Characterization of aqueous interactions of copper-doped phosphate-based glasses by vapour sorption.

PubMed

Stähli, Christoph; Shah Mohammadi, Maziar; Waters, Kristian E; Nazhat, Showan N

2014-07-01

Owing to their adjustable dissolution properties, phosphate-based glasses (PGs) are promising materials for the controlled release of bioinorganics, such as copper ions. This study describes a vapour sorption method that allowed for the investigation of the kinetics and mechanisms of aqueous interactions of PGs of the formulation 50P2O5-30CaO-(20-x)Na2O-xCuO (x=0, 1, 5 and 10mol.%). Initial characterization was performed using (31)P magic angle spinning nuclear magnetic resonance and attenuated total reflectance-Fourier transform infrared spectroscopy. Increasing CuO content resulted in chemical shifts of the predominant Q(2) NMR peak and of the (POP)as and (PO(-)) Fourier transform infrared absorptions, owing to the higher strength of the POCu bond compared to PONa. Vapour sorption and desorption were gravimetrically measured in PG powders exposed to variable relative humidity (RH). Sorption was negligible below 70% RH and increased exponentially with RH from 70 to 90%, where it exhibited a negative correlation with CuO content. Vapour sorption in 0% and 1% CuO glasses resulted in phosphate chain hydration and hydrolysis, as evidenced by protonated Q(0)(1H) and Q(1)(1H) species. Dissolution rates in deionized water showed a linear correlation (R(2)>0.99) with vapour sorption. Furthermore, cation release rates could be predicted based on dissolution rates and PG composition. The release of orthophosphate and short polyphosphate species corroborates the action of hydrolysis and was correlated with pH changes. In conclusion, the agreement between vapour sorption and routine characterization techniques in water demonstrates the potential of this method for the study of PG aqueous reactions. Copyright © 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Combined performance of biochar sorption and magnetic separation processes for treatment of chromium-contained electroplating wastewater.

PubMed

Wang, Sheng-ye; Tang, Yan-kui; Li, Kun; Mo, Ya-yuan; Li, Hao-feng; Gu, Zhan-qi

2014-12-01

Magnetic biochar was prepared with eucalyptus leaf residue remained after essential oil being extracted. Batch experiments were conducted to examine the capacity of the magnetic biochar to remove Cr (VI) from electroplating wastewater and to be separated by an external magnetic field. The results show that the initial solution pH plays an important role on both sorption and separation. The removal rates of Cr (VI), total Cr, Cu (II), and Ni (II) were 97.11%, 97.63%, 100% and 100%, respectively. The turbidity of the sorption-treated solution was reduced to 21.8NTU from 4075NTU after 10min magnetic separation. The study also confirms that the magnetic biochar still retains the original magnetic separation performance after the sorption process. Copyright © 2014 Elsevier Ltd. All rights reserved.

Cadmium removal by bioclastic granules (Lithothamnium calcareum): batch and fixed-bed column systems sorption studies.

PubMed

Veneu, Diego Macedo; Schneider, Claudio Luiz; de Mello Monte, Marisa Bezerra; Cunha, Osvaldo Galvão Caldas; Yokoyama, Lídia

2018-07-01

The potential of Bioclastic Granules - BG (calcium-carbonate-based material) using the algae Lithothamnium calcareum as sorbent for the removal of Cd(II) from aqueous solutions by sorption was evaluated through batch and continuous systems tests using a fixed-bed column. Sorption process variables, in particular pH (2-7), particle size (<38-300 μm), initial BG concentration (0.1-1.0 g L -1 ), initial Cd(II) concentrations (5-400 mg L -1 ) and contact time (5-240 min), were evaluated. Adsorption isotherm profiles of Cd(II) per BG were similar to an L-type, or Langmuir type, with the adsorption forming a monolayer of approximately 0.61 μm, with a q max of 188.74 mg g -1 and k L of 0.710 L mg -1 . Thomas's model considers that sorption is not limited to a chemical reaction but is controlled by mass transfer at the interface. In the present study, the obtained value of k Th was 0.895 mL h -1  mg -1 , reaching a sorption capacity q o of 124.4 mg g -1 . For the Yoon-Nelson model, it was possible to obtain two important parameters to describe the behavior of the column, the rate constant (k YN ), obtaining a value of 0.09 h -1 and an τ of 82.12 h corresponding to the time required for sorption to occur of 50% of the solute in the rupture curve. X-ray diffraction and scanning electron microscopy analyses coupled to the X-ray dispersive energy system (SEM/EDS) of the BG after the Cd(II) ion sorption tests evidenced the formation of crystals with the prevalence of a new mineral phase (otavite).

Effect of experimental variables onto Co(2+) and Sr(2+) sorption behavior in red mud-water suspensions.

PubMed

Milenković, Aleksandra S; Smičiklas, Ivana D; Šljivić-Ivanović, Marija Z; Živković, Ljiljana S; Vukelić, Nikola S

2016-07-02

The prospects of rinsed red mud (alumina production residue) utilization for liquid radioactive waste treatment have been investigated, with Co(2+) and Sr(2+) as model cations of radioactive elements. To evaluate the sorption effectiveness and corresponding binding mechanisms, the process was analyzed in batch conditions, by varying experimental conditions (pH, Co(2+) and Sr(2+) concentrations in single solutions and binary mixtures, contact time, and the concentration of competing cations and ligands common in liquid radioactive waste). Comparison of the Co(2+) and Sr(2+) sorption pH edges with the red mud isoelectric point has revealed that Co(2+) removal took place at both positive and negative red mud surface, while Sr(2+) sorption abruptly increased when the surface became negatively charged. The increase of initial cation content and pH resulted in increased equilibrium times and sorption capacity and decreased rate constants. From single metal solutions and various binary mixtures, Co(2+) was sorbed more efficiently and selectively than Sr(2+). While Sr(2+) sorption was reduced by coexisting cations in the order Al(3+) ≥ Ca(2+) >Na(+) ≥Cs(+), removal of Co(2+) was affected by Al(3+) species and complexing agents (EDTA and citrate). Desorption of Co(2+) was negligible in Ca(2+) and Sr(2+) containing media and in solutions with initial pH 4-7. Sr(2+) desorption was generally more pronounced, especially at low pH and in the presence of Co(2+). Collected macroscopic data signify that Co(2+) sorption by red mud minerals occurred via strong chemical bonds, while Sr(2+) was retained mainly by weaker ion-exchange or electrostatic interactions. Results indicate that the rinsed red mud represent an efficient, low-cost sorbent for Co(2+) and Sr(2+) immobilization.

The influence of clay surface modification with berberine on the sorption of anthocyanins

NASA Astrophysics Data System (ADS)

Chulkov, A. N.; Deineka, V. I.; Tikhova, A. A.; Vesentzev, A. I.; Deineka, L. A.

2012-03-01

The influence of preliminary sorption of berberine on the sorption of anthocyanins by bentonite clay was studied. The cation exchange sorption mechanism was found to be replaced by hydrophobic sorption of these compounds after clay modification with berberine. The enthalpy of sorption along the initial isotherm part changed from endothermic to exothermic.

The role of external and internal mass transfer in the process of Cu2+ removal by natural mineral sorbents.

PubMed

Sljivić, M; Smiciklas, I; Plećas, I; Pejanović, S

2011-07-01

The kinetics of Cu2+ sorption on to zeolite, clay and diatomite was investigated as a function of initial metal concentrations. For consideration of the mass transfer phenomena, single resistance models based on both film and intraparticle diffusion were tested and compared. The obtained results suggested that the rate-limiting step in Cu2+ sorption strongly depended on the sorbent type, as well as on initial cation concentration. The decrease in external mass transfer coefficients with the increase in initial metal concentrations was in excellent agreement with expressions based on Sherwood and Schmidt dimensionless numbers. The internal diffusivities through zeolite particles were in the range 1.0 x 10(-11) to 1.0 x 10(-13) m2/min, depending on the Cu2+ concentration and the applied theoretical model.

Gypsum-wallboard formaldehyde-sorption model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Silberstein, S.

1989-11-01

Gypsum wallboard was shown to absorb formaldehyde in a prototype house and in a measuring chamber, as reported previously by researchers at Oak Ridge National Laboratory (ORNL). Also as reported previously, formaldehyde concentrations attained equilibrium in two phases in response to a change in the air exchange rate or to the removal of the formaldehyde source. A rapid initial phase was followed by a slow phase lasting several days. A formaldehyde sorption model that accounts for the biphasic concentration pattern is presented here. Experiments for testing the predictability of the model are proposed.

Enhancement of soil retention for phenanthrene in binary cationic gemini and nonionic surfactant mixtures: characterizing two-step adsorption and partition processes through experimental and modeling approaches.

PubMed

Zhao, Shan; Huang, Gordon; An, Chunjiang; Wei, Jia; Yao, Yao

2015-04-09

The enhancement of soil retention for phenanthrene (PHE) through the addition of a binary mixture of cationic gemini (12-2-12) and nonionic surfactants (C12E10) was investigated. The maximum apparent sorption coefficient Kd(*) reached 4247.8 mL/g through the addition of mixed 12-2-12 gemini and C12E10 surfactants, which was markedly higher than the summed individual results in the presence of individual 12-2-12 gemini (1148.6 mL/g) or C12E10 (210.0 mL/g) surfactant. However, the sorption of 12-2-12 gemini was inhibited by the increasing C12E10 dose; and a higher initial 12-2-12 gemini dose showed a higher "desorption" rate. The present study also addressed the sorption behavior of the single 12-2-12 gemini surfactant at the soil/aqueous interface. The sorption isotherm was divided into two steps to elucidate the sorption process; and the sorption schematics were proposed to elaborate the growth of surfactant aggregates corresponding to the various steps of the sorption isotherm. Finally, a two-step adsorption and partition model (TAPM) was developed to simulate the sorption process. Analysis of the equilibrium data indicated that the sorption isotherms of 12-2-12 gemini fitted the TAPM model better. Thermodynamic calculations confirmed that the 12-2-12 gemini sorption at the soil/aqueous interface was spontaneous and exothermic from 288 to 308K. Copyright © 2014 Elsevier B.V. All rights reserved.

Experimental and modeling studies of sorption of ceria nanoparticle on microbial biofilms.

PubMed

Jing, Hengye; Mezgebe, Bineyam; Aly Hassan, Ashraf; Sahle-Demessie, Endalkachew; Sorial, George A; Bennett-Stamper, Christina

2014-06-01

This study focuses on the interaction of ceria nanoparticles (CeO2-NPs) with Pseudomonas fluorescens and Mycobacterium smegmatis biofilms. Confocal laser microscopy and transmission electron microscopy determined the distribution of NPs in the complex structures of biofilm at molecular levels. Visual data showed that most of the adsorption takes place on the bacterial cell walls and spores. The interaction of nanoparticles (NPs) with biofilms reached equilibrium after the initial high adsorption rate regardless of biofilm heterogeneity and different nanoparticle concentrations in the bulk liquid. Physical processes may dominate this sorption phenomenon. Pseudo first order sorption kinetics was used to estimate adsorption and desorption rate of CeO2-NPs onto biofilms. When biofilms got exposed to CeO2-NPs, a self-protecting mechanism was observed. Cells moved away from the bulk solution in the biofilm matrix, and portions of biofilm outer layer were detached, hence releasing some CeO2-NPs back to the bulk phase. Published by Elsevier Ltd.

Equilibrium, kinetic and thermodynamic studies of uranium biosorption by calcium alginate beads.

PubMed

Bai, Jing; Fan, Fangli; Wu, Xiaolei; Tian, Wei; Zhao, Liang; Yin, Xiaojie; Fan, Fuyou; Li, Zhan; Tian, Longlong; Wang, Yang; Qin, Zhi; Guo, Junsheng

2013-12-01

Calcium alginate beads are potential biosorbent for radionuclides removal as they contain carboxyl groups. However, until now limited information is available concerning the uptake behavior of uranium by this polymer gel, especially when sorption equilibrium, kinetics and thermodynamics are concerned. In present work, batch experiments were carried out to study the equilibrium, kinetics and thermodynamics of uranium sorption by calcium alginate beads. The effects of initial solution pH, sorbent amount, initial uranium concentration and temperature on uranium sorption were also investigated. The determined optimal conditions were: initial solution pH of 3.0, added sorbent amount of 40 mg, and uranium sorption capacity increased with increasing initial uranium concentration and temperature. Equilibrium data obtained under different temperatures were fitted better with Langmuir model than Freundlich model, uranium sorption was dominated by a monolayer way. The kinetic data can be well depicted by the pseudo-second-order kinetic model. The activation energy derived from Arrhenius equation was 30.0 kJ/mol and the sorption process had a chemical nature. Thermodynamic constants such as ΔH(0), ΔS(0) and ΔG(0) were also evaluated, results of thermodynamic study showed that the sorption process was endothermic and spontaneous. Copyright © 2013 Elsevier Ltd. All rights reserved.

Effect of plasticizer on moisture sorption isotherm of sugar palm (Arenga Pinnata) starch film

NASA Astrophysics Data System (ADS)

Jatmiko, Tri Hadi; Poeloengasih, Crescentiana D.; Prasetyo, Dwi Joko; Rosyida, Vita Taufika

2016-02-01

The effect of plasticizer type (glycerol, sorbitol) and plasticizer concentrations (30, 35, 40, 45% w/w polymer) on the moisture sorption isotherm characteristics of sugar palm (Arenga pinnata) starch films were investigated. Moisture affinity of sugar palm starch films was influenced by the plasticizer type and plasticizer concentration. The affinity of the glycerol plasticized film is stronger than that of sorbitol plasticized film. Sugar palm starch film with a higher concentration of glycerol absorbs more moisture with higher initial absorption rate than that of with sorbitol. Films with higher plasticizer concentration of glycerol and sorbitol show higher equilibrium moisture contents at the given relative humidity. The moisture sorption isotherm characteristic of sugar palm starch films can be described very well with the semi empirical 4 parameter Peleg's model.

Sorption of DNA by diatomite-Zn(II) embedded supermacroporous monolithic p(HEMA) cryogels.

PubMed

Tozak, Kabil Özcan; Erzengin, Mahmut; Sargin, Idris; Ünlü, Nuri

2013-01-01

In this study, the DNA sorption performance of diatomite-Zn(II) embedded supermacroporous monolithic p(HEMA) cryogels were investigated for the purpose of designing a novel adsorbent that can be utilized for DNA purification, separation and immunoadsorption studies such as removal of anti-dsDNA antibodies from systemic lupus erythematosus (SLE) patient plasma. Poly(2-hydroxyethyl methacrylate) [p(HEMA)]-based monolithic cryogel column embedded with Zn(2+)-diatomite particles was prepared by free radical cryo-copolymerization of 2-hydroxyethyl methacrylate (HEMA) with N,N'-methylene-bis-acrylamide (MBAAm). The polymerization reaction was initiated by N,N,N',N'-tetramethylene diamine (TEMED) and ammonium persulfate (APS) pair in an ice bath. After thawing, the monolithic composite cryogels were used for affinity sorption and then subsequent desorption of DNA molecules from aqueous solutions. Diatomite (DA) particles were characterized by XRF and BET method. The characterization of composite cryogel was done through SEM imaging. The effects of pH of the solution, initial DNA concentration, ionic strength, temperature and flow rates on adsorption were investigated to determine the optimum conditions for adsorption/desorption experiments. The particle embedding procedure was shown to yield significantly enhanced adsorption of DNA on the adsorbent. Furthermore, considering its excellent bio-compatibility, p(HEMA) cryogels are promising a candidate for further DNA sorption studies.

Sorption of DNA by diatomite-Zn(II) embedded supermacroporous monolithic p(HEMA) cryogels

PubMed Central

Tozak, Kabil Özcan; Erzengin, Mahmut; Sargin, Idris; Ünlü, Nuri

2013-01-01

In this study, the DNA sorption performance of diatomite-Zn(II) embedded supermacroporous monolithic p(HEMA) cryogels were investigated for the purpose of designing a novel adsorbent that can be utilized for DNA purification, separation and immunoadsorption studies such as removal of anti-dsDNA antibodies from systemic lupus erythematosus (SLE) patient plasma. Poly(2-hydroxyethyl methacrylate) [p(HEMA)]-based monolithic cryogel column embedded with Zn2+-diatomite particles was prepared by free radical cryo-copolymerization of 2-hydroxyethyl methacrylate (HEMA) with N,N'-methylene-bis-acrylamide (MBAAm). The polymerization reaction was initiated by N,N,N',N'-tetramethylene diamine (TEMED) and ammonium persulfate (APS) pair in an ice bath. After thawing, the monolithic composite cryogels were used for affinity sorption and then subsequent desorption of DNA molecules from aqueous solutions. Diatomite (DA) particles were characterized by XRF and BET method. The characterization of composite cryogel was done through SEM imaging. The effects of pH of the solution, initial DNA concentration, ionic strength, temperature and flow rates on adsorption were investigated to determine the optimum conditions for adsorption/desorption experiments. The particle embedding procedure was shown to yield significantly enhanced adsorption of DNA on the adsorbent. Furthermore, considering its excellent bio-compatibility, p(HEMA) cryogels are promising a candidate for further DNA sorption studies. PMID:26600734

Sorptive removal of nickel onto weathered basaltic andesite products: kinetics and isotherms.

PubMed

Shah, Bhavna A; Shah, Ajay V; Singh, Rajesh R; Patel, Nayan B

2009-07-15

The suitability of weathered basaltic andesite products (WBAP) as a potential sorbent was assessed for the removal of Ni (II) from electroplating industrial wastewater. A model study based on the batch mode of operation was carried out for Ni (II) removal from aqueous solution. The effect of various parameters such as hydronium ion concentration, shaking time, sorbent dose, initial Ni (II) concentration, and temperature on the sorption process was studied. At optimised conditions of the various parameters, the industrial wastewater loaded with Ni (II) was sorbed onto WBAP. Thermodynamic parameters for the sorption process were evaluated. Freundlich, Langmuir, Temkin, and Dubinin-Kaganer-Radushkevich isotherms were applied to the sorption pattern on the WBAP. The sorption dynamics of the process was evaluated by applying Lagergren, Bangham, and Weber & Morris equations. The sorption process follows Pseudo-second-order rate of surface diffusion which is identified as the predominating mechanism. The sorption process was found to be reversible by the recovery of sorbed Ni (II) upon extraction with 0.5 MHNO3. The sorbent before and after sorption, was characterized by Fourier transform infrared (FTIR), Powder X-Ray diffraction PXRD), and Thermogravimetric analysis (TGA) methods. The change in surface morphology and crystallanity of the mineral after sorption was analyzed by Scanning electron microscopy (SEM) and Transmission electron microscopy (TEM). Based on the previous model study, an electroplating industrial effluent was successfully treated with WBAP to minimize the pollution load caused by Ni (II).

Toxic substances in surface waters and sediments--A study to assess the effects of arsenic-contaminated alluvial sediment in Whitewood Creek, South Dakota

USGS Publications Warehouse

Kuwabara, James S.; Fuller, Christopher C.

2003-01-01

Field measurements and bioassay experiments were done to investigate the effects of arsenic and phosphorus interactions on sorption of these solutes by the benthic flora (periphyton and submerged macrophytes) in Whitewood Creek, a stream in western South Dakota. Short-term (24-hour) sorption experiments were used to determine arsenic transport characteristics for algae (first-order rate constants for solute sorption, biomass, and accumulation factors) collected in the creek along a transect beginning upstream from a mine discharge point and downgradient through a 57-kilometer reach. Temporal changes in biomass differed significantly between and within sampling sites. Arsenic concentrations in plant tissue increased with distance downstream, but temporal changes in concentrations in tissues differed considerably from site to site. Cultures of Achnanthes minutissima (Bacillariophyceae) and Stichococcus sp. (Chlorophyceae) were isolated from four sites along a longitudinal concentration gradient of dissolved arsenic within the study reach and were maintained at ambient solute concentrations. Arsenic accumulation factors and sorption-rate constants for these isolates were determined as a function of dissolved arsenate and orthophosphate. Cell surfaces of algal isolates exhibited preferential orthophosphate sorption over arsenate. Initial sorption of both arsenate and orthophosphate followed first-order mass transfer for each culturing condition. Although sorption-rate constants increased slightly with increased dissolved-arsenate concentration, algae, isolated from a site with elevated dissolved arsenic in the stream channel, had a significantly slower rate of arsenic sorption compared with the same species isolated from an uncontaminated site upstream. In diel studies, amplitudes of the pH cycles increased with measured biomass except at a site immediately downstream from water-treatment-plant discharge. Inorganic pentavalent arsenic dominated arsenic speciation at all sites?not a surprising result for the well-oxygenated water column along this reach. Concentration fluctuations in dissolved-arsenic species lagged pH fluctuations by approximately 3 hours at the most downstream site, but no discernible lag was observed at an artificially pooled area with an order of magnitude higher biomass. Furthermore, the amplitudes of diel fluctuations in arsenic species were greater at the pooled area than at the most downstream site. Lack of correspondence between changes in dissolved-orthophosphate concentrations and arsenic species may have resulted from preferential sorption of orthophosphate over arsenate by the biomass. Based on carbon-fixation estimates, the phosphorus demand from photosynthetic activity required water-column concentrations to be supplemented by another source such as phosphate regeneration within the benthic community or desorption of particle-bound phosphate.

Sorption and desorption of carbamazepine, naproxen and triclosan in a soil irrigated with raw wastewater: estimation of the sorption parameters by considering the initial mass of the compounds in the soil.

PubMed

Durán-Álvarez, Juan C; Prado-Pano, Blanca; Jiménez-Cisneros, Blanca

2012-06-01

In conventional sorption studies, the prior presence of contaminants in the soil is not considered when estimating the sorption parameters because this is only a transient state. However, this parameter should be considered in order to avoid the under/overestimation of the soil sorption capacity. In this study, the sorption of naproxen, carbamazepine and triclosan was determined in a wastewater irrigated soil, considering the initial mass of the compounds. Batch sorption-desorption tests were carried out at two soil depths (0-10 cm and 30-40 cm), using either 10 mM CaCl(2) solution or untreated wastewater as the liquid phase. Data were satisfactorily fitted to the initial mass model. For the two soils, release of naproxen and carbamazepine was observed when the CaCl(2) solution was used, but not in the soil/wastewater system. The compounds' release was higher in the topsoil than in the 30-40 cm soil. Sorption coefficients (K(d)) for CaCl(2) solution tests showed that in the topsoil, triclosan (64.9 L kg(-1)) is sorbed to a higher extent than carbamazepine and naproxen (5.81 and 2.39 L kg(-1), respectively). In the 30-40 cm soil, carbamazepine and naproxen K(d) values (11.4 and 4.41 L kg(-1), respectively) were higher than those obtained for the topsoil, while the triclosan K(d) value was significantly lower than in the topsoil (19.2 L kg(-1)). Differences in K(d) values were found when comparing the results obtained for the two liquid phases. Sorption of naproxen and carbamazepine was reversible for both soils, while sorption of triclosan was found to be irreversible. This study shows the sorption behavior of three pharmaceuticals in a wastewater irrigated soil, as well as the importance of considering the initial mass of target pollutants in the estimation of their sorption parameters. Copyright © 2012 Elsevier Ltd. All rights reserved.

A nonequilibrium model for reactive contaminant transport through fractured porous media: Model development and semianalytical solution

NASA Astrophysics Data System (ADS)

Joshi, Nitin; Ojha, C. S. P.; Sharma, P. K.

2012-10-01

In this study a conceptual model that accounts for the effects of nonequilibrium contaminant transport in a fractured porous media is developed. Present model accounts for both physical and sorption nonequilibrium. Analytical solution was developed using the Laplace transform technique, which was then numerically inverted to obtain solute concentration in the fracture matrix system. The semianalytical solution developed here can incorporate both semi-infinite and finite fracture matrix extent. In addition, the model can account for flexible boundary conditions and nonzero initial condition in the fracture matrix system. The present semianalytical solution was validated against the existing analytical solutions for the fracture matrix system. In order to differentiate between various sorption/transport mechanism different cases of sorption and mass transfer were analyzed by comparing the breakthrough curves and temporal moments. It was found that significant differences in the signature of sorption and mass transfer exists. Applicability of the developed model was evaluated by simulating the published experimental data of Calcium and Strontium transport in a single fracture. The present model simulated the experimental data reasonably well in comparison to the model based on equilibrium sorption assumption in fracture matrix system, and multi rate mass transfer model.

[Bromate reduction by granular activated carbon].

PubMed

Huang, Xin; Gao, Nai-yun; Lu, Pin-pin

2007-10-01

Batch experiments were conducted to evaluate the kinetics of reducing bromate to bromide by granular activated carbon. Solution conditions were studied in details, such as pH, ionic strength, temperature and initial bromate concentration. The results showed the removal capacity of GAC was positively relevant to surface basic functional groups. The whole process was inhibited by other anions in solution and the inhibition sequence was NO3(-) > SO4(2-) > Cl(-). Pseudo-second order rate equation and intraparticle diffusion model were applied to fit the process of bromate reduction and the process of bromide formation, respectively, with regression coefficients higher than 0.97 at most cases. Bromate removal was found to be favored under conditions with low pH value and low ionic strength. Both sorption rate of bromate and formation rate of bromide were decreased, and then increased along with the increase of temperature during 15-42 degree C. In this experiment, the maximum adsorption capacity of GAC is 769.23 micromol/g (98.4 mg/g), whereas the sorption process is slow and easily influenced. It is concluded that the sorption of bromate by the micropore portion of GAC was influenced by the release of bromide.

Ni(II) biosorption by Cassia fistula (Golden Shower) biomass.

PubMed

Hanif, Muhammad Asif; Nadeem, Raziya; Bhatti, Haq Nawaz; Ahmad, Najum Rashid; Ansari, Tariq Mehmood

2007-01-10

Cassia fistula is a fast-growing, medium-sized, deciduous tree which is now widely cultivated worldwide as an ornamental tree for its beautiful showy yellow flowers. Methods are required to reuse fallen leaves, branches, stem bark and pods when they start getting all over lawn. This investigation studies the use of these non-useful parts of C. fistula as naturally occurring biosorbent for the batch removal of Ni(II) in a well stirred system under different experimental conditions. The data showed that the maximum pH (pHmax) for efficient sorption of Ni(II) was 6 at which evaluated biosorbent dosage, biosorbent particle size, initial concentrations of Ni(II) and sorption time were 0.1 g/100 mL, <0.255 mm, up to 200 mg/L and 720 min, respectively. The experimental results were analyzed in terms of Langmuir and Freundlich isotherms. The Langmuir isotherm model fitted well to data of Ni(II) biosorption by C. fistula biomass as compared to the model of Freundlich. The kinetic studies showed that the sorption rates could be described better by a second order expression than by a more commonly applied Lagergren equation. The magnitude of the Gibbs free energy values indicates spontaneous nature of the sorption process. The sorption ability of C. fistula biomass for Ni(II) removal tends to be in the order: leaves

Sorption of Groundwater Dissolved Organic Carbon onto Minerals

NASA Astrophysics Data System (ADS)

Rutlidge, H.; Oudone, P.; McDonough, L.; Meredith, K.; Andersen, M. S.; O'Carrol, D. M.; Baker, A.

2017-12-01

Our understanding of groundwater organic matter (OM) as a carbon source or sink in the environmental carbon cycle is limited. The dynamics of groundwater OM is mainly governed by biological processing and its sorption to minerals. In saturated groundwaters, dissolved OM (DOM) represents one part of the groundwater organic carbon pool. Without consideration of the DOM sorption, it is not possible to quantify governing groundwater OM processes. This research explores the rate and extent of DOM sorption on different minerals. Groundwater DOM samples, and International Humic Substances Society (IHSS) standard solutions, were analysed. Each was mixed with a range of masses of iron coated quartz, clean quartz, and calcium carbonate, and shaken for 2 hours to reach equilibrium before being filtered through 0.2 μm for total dissolved organic carbon (DOC) and composition analysis by size-exclusion chromatography-organic carbon detection (LC-OCD). Sorption isotherms were constructed and groundwater DOM sorption were compared to the sorption of IHSS standards. Initial results suggest that for the IHSS standards, the operationally-defined humic substances fraction had the strongest sorption compared to the other LC-OCD fractions and total DOC. Some samples exhibited a small increase in the low molecular weight neutral (LMW-N) aqueous concentration with increasing humic substances sorption. This gradual increase observed could be the result of humic substances desorbing or their breakdown during the experiment. Further results comparing these IHSS standards with groundwater samples will be presented. In conjunction with complementary studies, these results can help provide more accurate prediction of whether groundwater OM is a carbon source or sink, which will enable the management of the groundwater resources as part of the carbon economy.

Plutonium(IV) and (V) sorption to goethite at sub-femtomolar to micromolar concentrations: Redox transformations and surface precipitation

DOE PAGES

Zhao, Pihong; Begg, James D.; Zavarin, Mavrik; ...

2016-06-06

Here, Pu(IV) and Pu(V) sorption to goethite was investigated over a concentration range of 10 –15–10 –5 M at pH 8. Experiments with initial Pu concentrations of 10 –15 – 10 –8 M produced linear Pu sorption isotherms, demonstrating that Pu sorption to goethite is not concentration-dependent across this concentration range. Equivalent Pu(IV) and Pu(V) sorption Kd values obtained at 1 and 2-week sampling time points indicated that Pu(V) is rapidly reduced to Pu(IV) on the goethite surface. Further, it suggested that Pu surface redox transformations are sufficiently rapid to achieve an equilibrium state within 1 week, regardless of themore » initial Pu oxidation state. At initial concentrations >10 –8 M, both Pu oxidation states exhibited deviations from linear sorption behavior and less Pu was adsorbed than at lower concentrations. NanoSIMS and HRTEM analysis of samples with initial Pu concentrations of 10 –8 – 10 –6 M indicated that Pu surface and/or bulk precipitation was likely responsible for this deviation. In 10 –6 M Pu(IV) and Pu(V) samples, HRTEM analysis showed the formation of a body centered cubic (bcc) Pu 4O 7 structure on the goethite surface, confirming that reduction of Pu(V) had occurred on the mineral surface and that epitaxial distortion previously observed for Pu(IV) sorption occurs with Pu(V) as well.« less

Equilibrium and kinetic modelling of chromium(III) sorption by animal bones.

PubMed

Chojnacka, Katarzyna

2005-04-01

The paper discusses sorption of Cr(III) ions from aqueous solutions by animal bones. Animal bones were found to be an efficient sorbent with the maximum experimentally determined sorption capacity in the range 29-194 mg g(-1) that depended on pH and temperature. The maximum experimentally determined sorption capacity was obtained at 50 degrees C, pH 5. Batch kinetics and equilibrium experiments were performed in order to investigate the influence of contact time, initial concentration of sorbate and sorbent, temperature and pH. It was found that sorption capacity increased with increase of Cr(III) concentration, temperature and initial pH of metal solution. Mathematical models describing kinetics and statics of sorption were proposed. It was found that process kinetics followed the pseudo-second-order pattern. The influence of sorbent concentration was described with Langmuir-type equation and the influence of sorbate concentration was described with empirical dependence. The models were positively verified.

Impact of the organic coating on nanoparticles stability and reactivity

NASA Astrophysics Data System (ADS)

Gelabert, A.; Sivry, Y.; Ould Boualy, L.; Roselyne, F.; Juillot, F.; Menguy, N.; Benedetti, M. F.

2010-12-01

The strong increase in the use of engineered nanoparticles (NPs) during the last decade may ultimately result in their release in environmental settings, as predicted for different types of NPs by Gottshalk et al.. Most of these NPs incorporate functionalized coatings to gain industrial benefits, which in turn may play a critical rule for the whole NPs reactivity. Thus, along with stability studies focusing on the fate of NPs in natural systems, an accurate understanding of the coating impacts on the NPs behaviour and reactivity is highly required. This study aims to estimate the impact of three different coatings on the NPs dissolution rates in natural water (Seine river water), and their sorption properties onto a model mineral substrate. In this work, ZnO NPs have been coated, either with triethoxycaprylylsilane (hydrophobic), methacryloxypropyltrimethoxysilane (hydrophilic), or aminopropyltriethoxusilane (cationic). The dissolution rates were determined using two protocols: the Donnan Membrane Technique to measure the remaining free metal concentration in solution, and a 1 kDa ultrafiltration procedure to access both the free metal and small organic complexes part. For all three coating types, a fast dissolution step is reached in less than one day, followed by a slow precipitation of new mineral phases to finally reach a steady state. No major differences in the dissolution rates and profiles have been observed. Sorption studies on synthetic microsized goethite have been conducted at pH 7.5. The sorption ratio has been estimated as a function of initial NPs concentrations (from 10-7 M to 10-3 M), and follows a Langmuir shape for the hydrophobic and hydrophilic coatings at concentrations lower than 2.10-4 M. Interestingly, those two NPs exhibit high sorption capacities (10 times higher) compared to free Zn2+ sorption. On the other hand, at those concentrations, the cationic coating only induces a weak sorption without any defined trend. Moreover, for the hydrophobic-coated NPs at higher concentrations, the isotherm sorption shape shifts from a Langmuir type to a linear increase, thus indicating an important change in the sorption mechanism. To explain these differences in sorption as a function of the coating properties, the NPs aggregation state has been investigated for all three suspensions, and this parameter appears to be one of the major controls for the coated NPs sorbing properties. These physico-chemical aspects of manufactured NPs behaviour in natural systems constitute an essential step with great implications for ecotoxicological studies. Gottshalk F., Sonderer T., Scholz R.W., and Nowack B., Environmental Science and Technology, 2009, 43, 9216-9222

Kinetic sorption of contaminants of emerging concern by a palygorskite-montmorillonite filter medium.

PubMed

Berhane, Tedros M; Levy, Jonathan; Krekeler, Mark P S; Danielson, Neil D

2017-06-01

Kinetic sorption of bisphenol A (BPA), carbamazepine (CMZ) and ciprofloxacin (CIP) by three palygorskite-montmorillonite (Pal-Mt) granule sizes was studied. For BPA, CMZ and CIP, apparent sorption equilibrium was reached within about 3, 5 and 16 h, respectively. The highest and the lowest sorption capacities were by the small and the large granule sizes, respectively. Experimental results were compared to various sorption kinetics models to gain insights regarding the sorption processes and achieve a predictive capacity. The pseudo-second order (PSO) and the Elovich models performed the best while the pseudo-first order (PFO) model was only adequate for CMZ. The intraparticle-diffusion (IPD) model showed a two-step linear plot of BPA, CMZ and CIP sorption versus square root of time that was indicative of surface-sorption followed by IPD as a rate-limiting process before equilibrium was reached. Using the pseudo-first order (PFO) and the pseudo-second order (PSO) rate constants combined with previously-established Langmuir equilibrium sorption models, the kinetic sorption (k a ) and desorption (k d ) Langmuir kinetic rate constants were theoretically calculated for BPA and CIP. Kinetic sorption was then simulated using these theoretically calculated k a and k d values, and the simulations were compared to the observed behavior. The simulations fit the observed sorbed concentrations better during the early part of the experiments; the observed sorption during later times occurred more slowly than expected, supporting the hypothesis that IPD becomes a rate-limiting process during the course of the experiment. Copyright © 2017 Elsevier Ltd. All rights reserved.

Factors Effecting the Fate and Transport of CL-20 in the Vadose Zone and Groundwater: Final Report 2002 - 2004 SERDP Project CP-1255

DOE Office of Scientific and Technical Information (OSTI.GOV)

Szecsody, James E.; Riley, Robert G.; Devary, Brooks J.

2005-06-01

This SERDP-funded project was initiated to investigate the fate of CL-20 in the subsurface environment, with a focus on identification and quantification of geochemical and microbial reactions of CL-20. CL-20 can be released to the surface and subsurface terrestrial environment by: a) manufacturing processes, b) munition storage, and c) use with low order detonation or unexploded ordnance. The risk of far-field subsurface migration was assessed through labora-tory experiments with a variety of sediments and subsurface materials to quantify processes that control CL-20 sorption-limited migration and degradation. Results of this study show that CL-20 will exhibit differing behavior in the subsurfacemore » terrestrial environment: 1. CL-20 on the sediment surface will photodegrade and interact with plants/animals (described in other SERDP projects CU 1254, 1256). CL-20 will exhibit greater sorption in humid sediments to organic matter. Transport will be solubility limited (i.e., low CL-20 aqueous solubility). 2. CL-20 infiltration into soils (<2 m) from spills will be subject to sorption to soil organic matter (if present), and low to high biodegradation rates (weeks to years) depending on the microbial population (greater in humid environment). 3. CL-20 in the vadose zone (>2 m) will be, in most cases, subject to low sorption and low degradation rates, so would persist in the subsurface environment and be at risk for deep migration. Low water content in arid regions will result in a decrease in both sorption and the degradation rate. Measured degradation rates in unsaturated sediments of years would result in significant subsurface migration distances. 4. CL-20 in groundwater will be subject to some sorption but likely very slow degradation rates. CL-20 sorption will be greater than RDX. Most CL-20 degradation will be abiotic (ferrous iron and other transition metals), because most deep subsurface systems have extremely low natural microbial populations. Degradation rates will range from weeks (iron reducing systems) to years. Although CL-20 will move rapidly through most sediments in the terrestrial environment, subsurface remediation can be utilized for cleanup. Transformation of CL-20 to intermediates can be rapidly accomplished under: a) reducing conditions (CL-20 4.1 min. half-life, RDX 18 min. half-life), b) alkaline (pH >10) conditions, and c) bioremediation with added nutrients. CL-20 degradation to intermediates may be insufficient to mitigate environmental impact, as the toxicity of many of these compounds is unknown. Biostimulation in oxic to reducing systems by carbon and nutrient addition can mineralize CL-20, with the most rapid rates occurring under reducing conditions.« less

Effect of biochar particle size on hydrophobic organic compound sorption kinetics: Applicability of using representative size.

PubMed

Kang, Seju; Jung, Jihyeun; Choe, Jong Kwon; Ok, Yong Sik; Choi, Yongju

2018-04-01

Particle size of biochar may strongly affect the kinetics of hydrophobic organic compound (HOC) sorption. However, challenges exist in characterizing the effect of biochar particle size on the sorption kinetics because of the wide size range of biochar. The present study suggests a novel method to determine a representative value that can be used to show the dependence of HOC sorption kinetics to biochar particle size on the basis of an intra-particle diffusion model. Biochars derived from three different feedstocks are ground and sieved to obtain three daughter products each having different size distributions. Phenanthrene sorption kinetics to the biochars are well described by the intra-particle diffusion model with significantly greater sorption rates observed for finer grained biochars. The time to reach 95% of equilibrium for phenanthrene sorption to biochar is reduced from 4.6-17.9days for the original biochars to <1-4.6days for the powdered biochars with <125μm in size. A moderate linear correlation is found between the inverse square of the representative biochar particle radius obtained using particle size distribution analysis and the apparent phenanthrene sorption rates determined by the sorption kinetics experiments and normalized to account for the variation of the sorption rate-determining factors other than the biochar particle radius. The results suggest that the representative biochar particle radius reasonably describes the dependence of HOC sorption rates on biochar particle size. Copyright © 2017 Elsevier B.V. All rights reserved.

Equilibrium and Kinetic Studies of Cd2+ Biosorption by the Brown Algae Sargassum fusiforme

PubMed Central

Zou, Hui-Xi; Li, Nan; Wang, Li-Hua; Yu, Ping; Yan, Xiu-Feng

2014-01-01

A fundamental investigation of the biosorption of Cd2+ from aqueous solution by the edible seaweed Sargassum fusiforme was performed under batch conditions. The influences of experimental parameters, such as the initial pH, sorption time, temperature, and initial Cd2+ concentration, on Cd2+ uptake by S. fusiforme were evaluated. The results indicated that the biosorption of Cd2+ depended on the initial Cd2+ concentration, as well as the pH. The uptake of Cd2+ could be described by the Langmuir isotherm model, and both the Langmuir biosorption equilibrium constant and the maximum biosorption capacity of the monolayer decreased with increasing temperature, thereby confirming the exothermic character of the sorption process. The biosorption kinetics follows the pseudo-second-order kinetic model, and intraparticle diffusion is the sole rate-limiting step for the entire biosorption period. These fundamental equilibrium and kinetic results can support further studies to the removal of cadmium from S. fusiforme harvested from cadmium-polluted waters. PMID:24736449

Biodegradation of sorbed chemicals in soil

DOE Office of Scientific and Technical Information (OSTI.GOV)

Scow, K.M.; Fan, S.; Johnson, C.

Rates of biodegradation of sorbed chemicals are usually lower in soil than in aqueous systems, in part because sorption reduces the availability of the chemical to microorganisms. Biodegradation, sorption, and diffusion occur simultaneously and are tightly coupled. In soil, the rate of biodegradation is a function of a chemical`s diffusion coefficient, sorption partition coefficient, the distance it must diffuse from the site of sorption to microbial populations that can degrade it, and its biodegradation rate constant. A model (DSB model) was developed that describes biodegradation of chemicals limited in the availability by sorption and diffusion. Different kinetics expressions describe biodegradationmore » depending on whether the reaction is controlled by mass transfer (diffusion and sorption) or the intrinsic biodegradation rate, and whether biodegradation begins during or after the majority of sorption has occurred. We tested the hypothesis that there is a direct relationship between how strongly a chemical is sorbed and the chemical`s biodegradation rate. In six soils with different organic carbon contents, there was no relationship between the extent or rate of biodegradation and the sorption partition coefficient for phenanthrene. Aging of phenanthrene residues in soil led to a substantial reduction in the rate of biodegradation compared to biodegradation rates of recently added phenanthrene. Considerable research has focused on identification and development of techniques for enhancing in situ biodegradation of sorbed chemicals. Development of such techniques, especially those involving inoculation with microbial strains, should consider physical mass transfer limitations and potential decreases in bioavailability over time. 4 refs., 3 figs., 1 tab.« less

Solid phase extraction of uranium(VI) onto benzoylthiourea-anchored activated carbon.

PubMed

Zhao, Yongsheng; Liu, Chunxia; Feng, Miao; Chen, Zhen; Li, Shuqiong; Tian, Gan; Wang, Li; Huang, Jingbo; Li, Shoujian

2010-04-15

A new solid phase extractant selective for uranium(VI) based on benzoylthiourea anchored to activated carbon was developed via hydroxylation, amidation and reaction with benzoyl isothiocyanate in sequence. Fourier transform infrared spectroscopy and total element analysis proved that benzoylthiourea had been successfully grafted to the surface of the activated carbon, with a loading capacity of 1.2 mmol benzoylthiourea per gram of activated carbon. The parameters that affect the uranium(VI) sorption, such as contact time, solution pH, initial uranium(VI) concentration, adsorbent dose and temperature, have been investigated. Results have been analyzed by Langmuir and Freundlich isotherm; the former was more suitable to describe the sorption process. The maximum sorption capacity (82 mg/g) for uranium(VI) was obtained at experimental conditions. The rate constant for the uranium sorption by the as-synthesized extractant was 0.441 min(-1) from the first order rate equation. Thermodynamic parameters (DeltaH(0)=-46.2 kJ/mol; DeltaS(0)=-98.0 J/mol K; DeltaG(0)=-17.5 kJ/mol) showed the adsorption of an exothermic process and spontaneous nature, respectively. Additional studies indicated that the benzoylthiourea-anchored activated carbon (BT-AC) selectively sorbed uranyl ions in the presence of competing ions, Na(+), Co(2+), Sr(2+), Cs(+) and La(3+). 2009 Elsevier B.V. All rights reserved.

Praseodymium sorption on Laminaria digitata algal beads and foams.

PubMed

Wang, Shengye; Hamza, Mohammed F; Vincent, Thierry; Faur, Catherine; Guibal, Eric

2017-10-15

Algal (Laminaria digitata) beads and algal foams have been prepared by a new synthesis mode and the sorbents were tested for praseodymium sorption in batch and fixed-bed like systems (recirculation or one-pass modes), respectively. Metal binding occurs through ion-exchange with Ca(II) ions used for ionotropic gelation of alginate contained in the algal biomass and eventually with protons. Sorption isotherms at pH 4 are described by the Langmuir and the Sips equations with maximum sorption capacities close to 110-120mgPrg -1 . Uptake kinetics are fitted by the pseudo-second order reaction rate equation for both beads and foams; in the case of beads the Crank equation also gives good fit of experimental data. Metal is successfully desorbed using 2M HCl/0.05M CaCl 2 solutions and the sorbent can be efficiently re-used for a minimum of 5 cycles with negligible decrease in sorption/desorption properties and appreciable concentrating effect (around 8-10 times the initial metal concentration). Tested in continuous mode, the algal foam shows typical breakthrough curves that are fitted by the Yan method; desorption is also efficient and allows under the best conditions to achieve a concentration factor close to 8. Copyright © 2017 Elsevier Inc. All rights reserved.

Transport of bisphenol-A in sandy aquifer sediment: Column experiment.

PubMed

Zakari, Sissou; Liu, Hui; Tong, Lei; Wang, Yan; Liu, Jianfeng

2016-02-01

The present paper aims to study the transport behavior of bisphenol-A (BPA) in sandy aquifer so as to provide important parameters for the prediction and control of contaminant plume in aquifer. Miscible displacement experiments were conducted and the breakthrough curves (BTCs) were simulated using HYDRUS-1D software. The effects of pore-water velocity (10-52 cm h(-1)) and initial concentration (2.5-40 mg L(-1)) on the sorption were also investigated. The BTCs of BPA fit the linear first-order non-equilibrium two-site model. The parameters such as partition coefficient (K(d)), the fraction of instantaneous adsorption on "Type-1" sites (F), the first order sorption rate coefficient for the kinetic non-equilibrium (type-2) sites (α), the retardation coefficient (R), and sorption capacity (q(column)) were computed. Results showed that BPA transported 0.11-0.83 m with various pore water velocity in sandy sediment column when water flowed 1 m. The sorption of BPA was mainly caused by the instantaneous surface adsorption as F varied from 0.596 to 0.908. The transport velocity of BPA was affected by pore water velocity (v) and followed the linear equation 1/R = 0.0600 + 0.0110v (r(2) = 0.9724). The parameter K(d) were also closely related to v and followed the equation LnK(d) = 1.0023-0.0482v (r(2) = 0.9690). The sorption capacity was more related to the initial BPA concentration (C0) and followed the linear equation q(column) = 0.265 + 0.253C0 (r(2) = 0.9727). The parameter α was affected by both v and C0 whereas F was not dramatically affected by both. Copyright © 2015 Elsevier Ltd. All rights reserved.

Lead and vanadium removal from a real industrial wastewater by gravitational settling/sedimentation and sorption onto Pinus sylvestris sawdust.

PubMed

Kaczala, F; Marques, M; Hogland, W

2009-01-01

Batch sorption with untreated Pinus sylvestris sawdust after settling/sedimentation phase to remove vanadium and lead from a real industrial wastewater was investigated using different adsorbent doses, initial pH, and contact time. The development of pH along the sorption test and a parallel investigation of metals release from sawdust in distilled water were carried out. In order to evaluate kinetic parameters and equilibrium isotherms, Lagergren first-order, pseudo-second-order, intra-particle diffusion and Freundlich models were explored. When the initial pH was reduced from 7.4 to 4.0, the sorption efficiency increased from 32% to 99% for Pb and from 43% to 95% for V. Whereas, V removal was positively correlated with the adsorbent dose, Pb removal was not. The sorption process was best described by pseudo-second-order kinetics. According to Freundlich parameters (K(f) and n) sawdust presented unfavourable intensity for sorption of V.

Steady-state equation of water vapor sorption for CaCl2-based chemical sorbents and its application

PubMed Central

Zhang, Haiquan; Yuan, Yanping; Sun, Qingrong; Cao, Xiaoling; Sun, Liangliang

2016-01-01

Green CaCl2-based chemical sorbent has been widely used in sorption refrigeration, air purification and air desiccation. Methods to improve the sorption rate have been extensively investigated, but the corresponding theoretical formulations have not been reported. In this paper, a sorption system of solid-liquid coexistence is established based on the hypothesis of steady-state sorption. The combination of theoretical analysis and experimental results indicates that the system can be described by steady-state sorption process. The steady-state sorption equation, μ = (η − γT) , was obtained in consideration of humidity, temperature and the surface area. Based on engineering applications and this equation, two methods including an increase of specific surface area and adjustment of the critical relative humidity (γ) for chemical sorbents, have been proposed to increase the sorption rate. The results indicate that the CaCl2/CNTs composite with a large specific surface area can be obtained by coating CaCl2 powder on the surface of carbon nanotubes (CNTs). The composite reached sorption equilibrium within only 4 h, and the sorption capacity was improved by 75% compared with pure CaCl2 powder. Furthermore, the addition of NaCl powder to saturated CaCl2 solution could significantly lower the solution’s γ. The sorption rate was improved by 30% under the same environment. PMID:27682811

Steady-state equation of water vapor sorption for CaCl2-based chemical sorbents and its application

NASA Astrophysics Data System (ADS)

Zhang, Haiquan; Yuan, Yanping; Sun, Qingrong; Cao, Xiaoling; Sun, Liangliang

2016-09-01

Green CaCl2-based chemical sorbent has been widely used in sorption refrigeration, air purification and air desiccation. Methods to improve the sorption rate have been extensively investigated, but the corresponding theoretical formulations have not been reported. In this paper, a sorption system of solid-liquid coexistence is established based on the hypothesis of steady-state sorption. The combination of theoretical analysis and experimental results indicates that the system can be described by steady-state sorption process. The steady-state sorption equation, μ = (η - γT) , was obtained in consideration of humidity, temperature and the surface area. Based on engineering applications and this equation, two methods including an increase of specific surface area and adjustment of the critical relative humidity (γ) for chemical sorbents, have been proposed to increase the sorption rate. The results indicate that the CaCl2/CNTs composite with a large specific surface area can be obtained by coating CaCl2 powder on the surface of carbon nanotubes (CNTs). The composite reached sorption equilibrium within only 4 h, and the sorption capacity was improved by 75% compared with pure CaCl2 powder. Furthermore, the addition of NaCl powder to saturated CaCl2 solution could significantly lower the solution’s γ. The sorption rate was improved by 30% under the same environment.

Rates and equilibria of perfluorooctanoate (PFOA) sorption on soils from different regions of China.

PubMed

Miao, Yu; Guo, Xuetao; Dan Peng; Fan, Tingyu; Yang, Chen

2017-05-01

Understanding sorption of PFOA on soil particles is crucial to evaluate its environmental risk. Here, sorption of PFOA onto ten agricultural soils was examined. The influence of soil physico-chemical properties on PFOA sorption was investigated. The sorption rate of PFOA followed a pseudo-second-order kinetics. Isotherm data of PFOA sorption was fitted with both Freundlich and linear models and the latter fitted better. The sorption-desorption of PFOA onto ten soil samples depended on soil organic carbon content and composition of soil minerals. The sorption and desorption isotherms of PFOA on ten soils were linear, except for the sorption of PFOA onto a few soils, which was described by the Freundlich equation with the parameter N >1. The main sorption mechanism of PFOA was hydrophobic interaction between the perfluorinated carbon chain and the organic matter of soil, as evidenced by the correlation between the solid-liquid distribution coefficient and the fraction of soil organic carbon. The sorption of PFOA in soils was highly irreversible. Copyright © 2017 Elsevier Inc. All rights reserved.

Spatial Moment Equations for a Groundwater Plume with Degradation and Rate-Limited Sorption

EPA Science Inventory

In this note, we analytically derive the solution for the spatial moments of groundwater solute concentration distributions simulated by a one-dimensional model that assumes advective-dispersive transport with first-order degradation and rate-limited sorption. Sorption kinetics...

Fate and transport of uranium (VI) in weathered saprolite

DOE PAGES

Kim, Young-Jin; Brooks, Scott C.; Zhang, Fan; ...

2014-11-09

We conducted batch and column experiments to investigate sorption and transport of uranium (U) in the presence of saprolite derived from interbedded shale, limestone, and sandstone sequences. Sorption kinetics were measured at two initial concentrations (C0; 1, 10 mM) and three soil:solution ratios (Rs/w; 0.005, 0.25, 2 kg/L) at pH 4.5 (pH of the saprolite). The rate of U loss from solution (mmole/L/h) increased with increasing Rs/w. Uranium sorption exhibited a fast phase with 80% sorption in the first eight hours for all C0 and Rs/w values and a slow phase during which the reaction slowly approached (pseudo) equilibrium overmore » the next seven days. The pH-dependency of U sorption was apparent in pH sorption edges. U(VI) sorption increased over the pH range 4e6, then decreased sharply at pH > 7.5. U(VI) sorption edges were well described by a surface complexation model using calibrated parameters and the reaction network proposed by Waite et al. (1994). Sorption isotherms measured using the same Rs/w and pH values showed a solids concentration effect where U(VI) sorption capacity and affinity decreased with increasing solids concentration. Moreover, this effect may have been due to either particle aggregation or competition between U(VI) and exchangeable cations for sorption sites. The surface complexation model with calibrated parameters was able to predict the general sorption behavior relatively well, but failed to reproduce solid concentration effects, implying the importance of appropriate design if batch experiments are to be utilized for dynamic systems. Transport of U(VI) through the packed column was significantly retarded. We also conducted transport simulations using the reactive transport model HydroGeoChem (HGC) v5.0 that incorporated the surface complexation reaction network used to model the batch data. Model parameters reported by Waite et al. (1994) provided a better prediction of U transport than optimized parameters derived from our sorption edges. The results presented in this study highlight the challenges in defining appropriate conditions for batch-type experiments used to extrapolate parameters for transport models, and also underline a gap in our ability to transfer batch results to transport simulations.« less

Effect of organic complexing agents on the interactions of Cs(+), Sr(2+) and UO(2)(2+) with silica and natural sand.

PubMed

Reinoso-Maset, Estela; Worsfold, Paul J; Keith-Roach, Miranda J

2013-05-01

Sorption processes play a key role in controlling radionuclide migration through subsurface environments and can be affected by the presence of anthropogenic organic complexing agents found at contaminated sites. The effect of these complexing agents on radionuclide-solid phase interactions is not well known. Therefore the aim of this study was to examine the processes by which EDTA, NTA and picolinate affect the sorption kinetics and equilibria of Cs(+), Sr(2+) and UO2(2+) onto natural sand. The caesium sorption rate and equilibrium were unaffected by the complexing agents. Strontium however showed greater interaction with EDTA and NTA in the presence of desorbed matrix cations than geochemical modelling predicted, with SrNTA(-) enhancing sorption and SrEDTA(2-) showing lower sorption than Sr(2+). Complexing agents reduced UO2(2+) sorption to silica and enhanced the sorption rate in the natural sand system. Elevated concentrations of picolinate reduced the sorption of Sr(2+) and increased the sorption rate of UO2(2+), demonstrating the potential importance of this complexing agent. These experiments provide a direct comparison of the sorption behaviour of Cs(+), Sr(2+) and UO2(2+)onto natural sand and an assessment of the relative effects of EDTA, NTA and picolinate on the selected elements. Copyright © 2013 Elsevier Ltd. All rights reserved.

Removal of perfluorinated surfactants from wastewater by adsorption and ion exchange - Influence of material properties, sorption mechanism and modeling.

PubMed

Schuricht, Falk; Borovinskaya, Ekaterina S; Reschetilowski, Wladimir

2017-04-01

Perfluorooctane sulfonate (PFOS) has attracted increasing concern in recent years due to its world-wide distribution, persistence, bioaccumulation and potential toxicity. The influence of sorbent properties on the adsorptive elimination of PFOS from wastewater by activated carbons, polymer adsorbents and anion exchange resins was investigated with regard to their isotherms and kinetics. The batch and column tests were combined with physicochemical characterization methods, e.g., N 2 physisorption, mercury porosimetry, infrared spectroscopy, differential scanning calorimetry, titrations, as well as modeling. Sorption kinetics was successfully modelled applying the linear driving force (LDF) approach for surface diffusion after introducing a load dependency of the mass transfer coefficient β s . The big difference in the initial mass transfer coefficient β s,0 , when non-functionalized adsorbents and ion-exchange resins are compared, suggests that the presence of functional groups impedes the intraparticle mass transport. The more functional groups a resin possesses and the longer the alkyl moieties are the bigger is the decrease in sorption rate. But the selectivity for PFOS sorption is increasing when the character of the functional groups becomes more hydrophobic. Accordingly, ion exchange and hydrophobic interaction were found to be involved in the sorption processes on resins, while PFOS is only physisorptively bound to activated carbons and polymer adsorbents. In agreement with the different adsorption mechanisms, resins possess higher total sorption capacities than adsorbents. Hence, the latter ones are rendered more effective in PFOS elimination at concentrations in the low μg/L range, due to a less pronounced convex curvature of the sorption isotherm in this concentration range. Copyright © 2016. Published by Elsevier B.V.

Analysis of sorption into single ODS-silica gel microparticles in acetonitrile-water.

PubMed

Nakatani, Kiyoharu; Kakizaki, Hiroshi

2003-08-01

Intraparticle mass transfer processes of Phenol Blue (PB) in single octadecylsilyl (ODS)-silica gel microparticles in acetonitrile-water were analyzed by microcapillary manipulation and microabsorption methods. An absorption maximum of PB, the sorption isotherm parameters, and the sorption rate in the microparticle system were highly dependent on the percentage of acetonitrile in solution. The results are discussed in terms of the microscopic polarity surrounding PB in the ODS phase and the relationship between the isotherm parameters and the sorption rate.

Computational Identification and Analysis of the Key Biosorbent Characteristics for the Biosorption Process of Reactive Black 5 onto Fungal Biomass

PubMed Central

Yang, Yu-Yi; Li, Ze-Li; Wang, Guan; Zhao, Xiao-Ping; Crowley, David E.; Zhao, Yu-Hua

2012-01-01

The performances of nine biosorbents derived from dead fungal biomass were investigated for their ability to remove Reactive Black 5 from aqueous solution. The biosorption data for removal of Reactive Black 5 were readily modeled using the Langmuir adsorption isotherm. Kinetic analysis based on both pseudo-second-order and Weber-Morris models indicated intraparticle diffusion was the rate limiting step for biosorption of Reactive Black 5 on to the biosorbents. Sorption capacities of the biosorbents were not correlated with the initial biosorption rates. Sensitivity analysis of the factors affecting biosorption examined by an artificial neural network model showed that pH was the most important parameter, explaining 22%, followed by nitrogen content of biosorbents (16%), initial dye concentration (15%) and carbon content of biosorbents (10%). The biosorption capacities were not proportional to surface areas of the sorbents, but were instead influenced by their chemical element composition. The main functional groups contributing to dye sorption were amine, carboxylic, and alcohol moieties. The data further suggest that differences in carbon and nitrogen contents of biosorbents may be used as a selection index for identifying effective biosorbents from dead fungal biomass. PMID:22442697

Removal of copper by oxygenated pyrolytic tire char: kinetics and mechanistic insights.

PubMed

Quek, Augustine; Balasubramanian, Rajashekhar

2011-04-01

The kinetics of copper ion (Cu(II)) removal from aqueous solution by pyrolytic tire char was modeled using five different conventional models. A modification to these models was also developed through a modified equation that accounts for precipitation. Conventional first- and second-order reaction models did not fit the copper sorption kinetics well, indicating a lack of simple rate-order dependency on solute concentration. Instead, a reversible first-order rate reaction showed the best fit to the data, indicating a dependence on surface functional groups. Due to the varying solution pH during the sorption process, modified external and internal mass transfer models were employed. Results showed that the sorption of copper onto oxygenated chars was limited by external mass transfer and internal resistance with and without the modification. However, the modification of the sorption process produced very different results for unoxygenated chars, which showed neither internal nor external limitation to sorption. Instead, its slow sorption rate indicates a lack of surface functional groups. The sorption of Cu(II) by oxygenated and unoxygenated chars was also found to occur via three and two distinct stages, respectively. Copyright © 2010 Elsevier Inc. All rights reserved.

Investigation of metal ions sorption of brown peat moss powder

NASA Astrophysics Data System (ADS)

Kelus, Nadezhda; Blokhina, Elena; Novikov, Dmitry; Novikova, Yaroslavna; Chuchalin, Vladimir

2017-11-01

For regularities research of sorptive extraction of heavy metal ions by cellulose and its derivates from aquatic solution of electrolytes it is necessary to find possible mechanism of sorption process and to choice a model describing this process. The present article investigates the regularities of aliovalent metals sorption on brown peat moss powder. The results show that sorption isotherm of Al3+ ions is described by Freundlich isotherm and sorption isotherms of Na+ i Ni2+ are described by Langmuir isotherm. To identify the mechanisms of brown peat moss powder sorption the IR-spectra of the initial brown peat moss powder samples and brown peat moss powder samples after Ni (II) sorption were studied. Metal ion binding mechanisms by brown peat moss powder points to ion exchange, physical adsorption, and complex formation with hydroxyl and carboxyl groups.

Experimental study of Pb (II) solution sorption behavior onto Coffee Husk Bioactivated Carbon

NASA Astrophysics Data System (ADS)

Fona, Z.; Habibah, U.

2018-04-01

Coffee husk which is abundantly produced in the coffee plantations is potential to be a challenging adsorbent. The fate of Pb (II) solution in the sorption mechanism onto the adsorbent has been investigated. This paper aimed to study the efficiency of Pb (II) aqueous solution removal using activated carbon from coffee husk (CAC). The sorption characteristics were using two isotherm models, Langmuir and Freundlich, were also reported. The coffee husk from local plantations in Middle Aceh was carbonized and sieved to 120/140 mesh. The charcoal was activated using hydrochloric acid before contacted with the different initial concentrations of Pb (II) solution. The remaining concentrations of the metal in the specified contact times were determined using Atomic Adsorption Spectrophotometer at 283.3 wavelength. The result showed that the equilibrium concentrations were obtained in about 30 minutes which depended on the initial concentration. The sorption mechanism followed Freundlich isotherm model where the adsorption constant and capacity were accordingly 1.353 and 1.195 mgg‑1. The iodine sorption was up to 1,053 mgg‑1. Based on the ash and moisture content, as well as iodine sorption, the activated carbon met the national standard.

Stabilization of the initial electrochemical potential for a metal-based potentiometric titration study of a biosorption process.

PubMed

Naja, Ghinwa; Mustin, Christian; Volesky, Bohumil; Berthelin, Jacques

2006-01-01

An interactive metal-based potentiometric titration method has been developed using an ion selective electrode for studying the sorption of metal cations. The accuracy of this technique was verified by analyzing the metal sorption mechanism for the biomass of Rhizopus arrhizus fungus and diatomite, two dissimilar materials (organic and mineral, strong sorbent and weak sorbent) of a different order of cation exchange capacity. The problem of the initial electrochemical potential was addressed identifying the usefulness of a Na-sulfonic resin as a strong chelating agent applied before the beginning of sorption titration experiments so that the titration curves and the sorption uptake could be quantitatively compared. The resin stabilized the initial electrochemical potential to -405+/-5 mV corresponding to 2 micro gl(-1) of lead concentration in solution. The amounts of lead sorbed by R. arrhizus biomass and diatomite were 0.9 mmol g(-1) (C(e)=5.16 x 10(-2)mM) and 0.052 mmol g(-1) (C(e)=5.97 x 10(-2) mM), respectively. Lead sorption by the fungal biomass was pinpointed to at least two types of chemical active sites. The first type was distinguished by high reactivity and a low number of sites whereas the other was characterized by their higher number and lower reactivity.

Cs sorption to potential host rock of low-level radioactive waste repository in Taiwan: experiments and numerical fitting study.

PubMed

Wang, Tsing-Hai; Chen, Chin-Lung; Ou, Lu-Yen; Wei, Yuan-Yaw; Chang, Fu-Lin; Teng, Shi-Ping

2011-09-15

A reliable performance assessment of radioactive waste repository depends on better knowledge of interactions between nuclides and geological substances. Numerical fitting of acquired experimental results by the surface complexation model enables us to interpret sorption behavior at molecular scale and thus to build a solid basis for simulation study. A lack of consensus on a standard set of assessment criteria (such as determination of sorption site concentration, reaction formula) during numerical fitting, on the other hand, makes lower case comparison between various studies difficult. In this study we explored the sorption of cesium to argillite by conducting experiments under different pH and solid/liquid ratio (s/l) with two specific initial Cs concentrations (100mg/L, 7.5 × 10(-4)mol/L and 0.01 mg/L, 7.5 × 10(-8)mol/L). After this, numerical fitting was performed, focusing on assessment criteria and their consequences. It was found that both ion exchange and electrostatic interactions governed Cs sorption on argillite. At higher initial Cs concentration the Cs sorption showed an increasing dependence on pH as the solid/liquid ratio was lowered. In contrast at trace Cs levels, the Cs sorption was neither s/l dependent nor pH sensitive. It is therefore proposed that ion exchange mechanism dominates Cs sorption when the concentration of surface sorption site exceeds that of Cs, whereas surface complexation is attributed to Cs uptake under alkaline environments. Numerical fitting was conducted using two different strategies to determine concentration of surface sorption sites: the clay model (based on the cation exchange capacity plus surface titration results) and the iron oxide model (where the concentration of sorption sites is proportional to the surface area of argillite). It was found that the clay model led to better fitting than the iron oxide model, which is attributed to more amenable sorption sites (two specific sorption sites along with larger site density) when using clay model. Moreover, increasing s/l ratio would produce more sorption sites, which helps to suppress the impact of heterogeneous surface on Cs sorption behavior under high pH environments. Copyright © 2011 Elsevier B.V. All rights reserved.

Effects of resident water and non-equilibrium adsorption on the primary and enhanced coalbed methane gas recovery

NASA Astrophysics Data System (ADS)

Jahediesfanjani, Hossein

The major part of the gas in coalbed methane and shale gas reservoirs is stored as the adsorbed gas in the coal and organic materials of the black shale internal surfaces. The sorption sites in both reservoirs are composed of several macropores that contain very small pore sizes. Therefore, the adsorption/desorption is very slow process and follows a non-equilibrium trend. The time-dependency of the sorption process is further affected by the reservoir resident water. Water can diffuse into the matrix and adsorption sites, plug the pores and affect the reservoir gas production. This study presents an experimental and theoretical procedure to investigate the effects of the resident water and time-dependency of the sorption process on coalbed and shale gas primary and enhanced recovery by simultaneous CO 2/N2 injection. Series of the experiments are conducted to construct both equilibrium and non-equilibrium single and multi-component isotherms with the presence of water. A novel and rapid data interpretation technique is developed based on the nonequilibrium adsorption/desorption thermodynamics, mass conservation law, and volume filling adsorption theory. The developed technique is implemented to construct both equilibrium and non-equilibrium multi-component multi-phase isotherms from the early time experimental measurements. The non-equilibrium isotherms are incorporated in the coalbed methane/shale gas reservoir simulations to account for the time-dependency of the sorption process. The experimental results indicate that the presence of water in the sorption system reduces both carbon dioxide and nitrogen adsorption rates. Reduction in the adsorption rate for carbon dioxide is more than nitrogen. The results also indicate that the resident water reduces the adsorption ability of low rank coals more than high rank ones. The results of the multi-component sorption tests indicate that increasing the initial mole fraction of the nitrogen gas in the injected CO2/N2 mixture will increase the net carbon dioxide sequestration rate on coals in the presence of water. The optimum CO2/N2 ratio that can result in the maximum carbon dioxide sequestration rate can be obtained by conducting the experiments for various CO2/N2 ratios. The results of applying the developed non-equilibrium interpretation technique for several literature and in-house data indicate that both the equilibrium and non-equilibrium isotherms can be constructed in shorter time period (around 70 times less than the time required with the equilibrium techniques) and with higher accuracy using this method. (Abstract shortened by UMI.)

Sorption of VX to Clay Minerals and Soils: Thermodynamic and Kinetic Studies

DTIC Science & Technology

2012-12-01

Suspengel 200, humus , and soil substrates for use in this study. In addition, the authors gratefully acknowledge the support of the ECBC Technical...sorption profiles for VX with clay substrates ..................................55 30. Initial kinetic sorption profiles for VX with humus ...naturally derived garden soil amendment, identified as humus , was purchased from Frey Brothers (Quarryville, PA). Two natural soils, identified as MCL lot

Sorption and desorption studies of a reactive azo dye on effective disposal of redundant material.

PubMed

Çelekli, Abuzer; Bozkurt, Hüseyin

2013-07-01

The effective disposal of redundant elephant dung (ED) is important for environmental protection and utilization of resource. The aim of this study was to remove a toxic-azo dye, Reactive Red (RR) 120, using this relatively cheap material as a new adsorbent. The FTIR-ATR spectra of ED powders before and after the sorption of RR 120 and zero point charge (pHzpc) of ED were determined. The sorption capacity of ED for removing of RR 120 were carried out as functions of particle size, adsorbent dose, pH, temperature, ionic strength, initial dye concentration, and contact time. Sorption isotherm, kinetic, activation energy, thermodynamic, and desorption parameters of RR 120 on ED were studied. The sorption process was found to be dependent on particle size, adsorbent dose, pH, temperature, ionic strength, initial dye concentration, and contact time. FTIR-ATR spectroscopy indicated that amine and amide groups have significant role on the sorption of RR 120 on ED. The pHzpc of ED was found to be 7.3. Sorption kinetic of RR 120 on ED was well described by sigmoidal Logistic model. The Langmuir isotherm was well fitted to the equilibrium data. The maximum sorption capacity was 95.71 mg g(-1). The sorption of RR 120 on ED was mainly physical and exothermic according to results of D-R isotherm, Arrhenius equation, thermodynamic, and desorption studies. The thermodynamic parameters showed that this process was feasible and spontaneous. This study showed that ED as a low-cost adsorbent had a great potential for the removal of RR 120 as an alternative eco-friendly process.

Effect made by the colloids to the sorption behavior of strontium on granite fracture-fillings

NASA Astrophysics Data System (ADS)

Wang, L.; Zuo, R.

2017-12-01

The objective of this study was to investigate the effects made by the colloid to the sorption capacity of colloids in granite fracture-fillings in aqueous solutions. The granite fracture-fillings were collected from three different depth of the research mine in Gansu province. According to the composition of the local soil and groundwater, two colloids were chosen to investigate this sorption process. Batch tests had been investigated at 27° under the air atmosphere as a function of pH(3 11), initial uranium concentration(5 400 mg/L) and water-rock ratio on the sorption of Sr on granite fracture-fillings. The batch experimental results showed that the sorption capacity presented a positive relationship with pH value, which may be caused by the hydrolytic adsorption raised by the reaction between Sr(OH)+ and OH- groups on the surface on the adsorbent. Initial strontium concentration also showed a positive relationship with sorption capacity when the concentration was lower than 200mg/mL, when the concentration was higher than 200mg/ml sorption reached the equilibrium. Sorption percentage showed a positive relationship with water/solid ratios, when the ratio was lower than 1:100 the system got equilibrium. When other experiment parameters were fixed and only the solid-liquid ratio changed, the adsorption capacity increased with the increasing solid-water ratio. The reason was that the total amount of Sr in the adsorption system remained unchanged, the adsorption sites increased with the solid-liquid ratio, and the adsorption capacity increased gradually with the increasing adsorption sites. The experiments data were interpreted in terms of Freundlich and Langmuir isotherms and the data fitted the former better. Equilibrium isotherm studies were used to evaluate the maximum sorption capacity of colloid.

A method to simultaneously determine sorption isotherms and sorption enthalpies with a double twin microcalorimeter

NASA Astrophysics Data System (ADS)

Wadso, Lars; Markova, Natalia

2002-07-01

Sorption of vapors of water, ethanol, and other liquids on solids like pharmaceuticals, textiles and food stuffs are of both practical and theoretical importance. In this article we present a technique to simultaneously measure sorption isotherms and sorption enthalpies. The sample is contained in one end of a sorption vessel. In the other end a vaporizable liquid is introduced to start the measurement. Mass transfer from the liquid to the sample is by vapor diffusion and the rate of mass transfer is calculated from the measured thermal power of vaporization. Simultaneously, the thermal power of sorption is measured and from this one may calculate the differential enthalpy of sorption. The thermal power measurements are made by inserting the sorption vessel in an isothermal double twin microcalorimeter.

Turbulent coagulation of particles smaller than the length scales of turbulence and equilibrium sorption of phenanthrene to clay: Implications for pollutant transport in the estuarine water column

NASA Astrophysics Data System (ADS)

Brunk, Brett Kenneth

1997-11-01

Pollutant and particle transport in estuaries is affected by a multitude of physical, chemical and biological processes. In this research the importance of equilibrium sorption and turbulent coagulation were studied. Sorption in estuaries was modeled using phenanthrene, bacterial extracellular polymer and kaolinite clay as surrogates for a hydrophobic organic pollutant, dissolved organic matter and inorganic suspended sediment, respectively. Experiments over a range of estuarine salinities showed that ionic strength had the largest effect on the extent of sorption, while the effect of extracellular polymer coatings on the mineral surfaces was insignificant. Further calculations using typical estuarine suspended sediment concentrations indicated that equilibrium sorption could not fully account for the solid/solution phase distribution of hydrophobic organic compounds in the estuarine water column. For particles that are small compared to the length scales of turbulence, the rate of coagulation is related to the dynamics of the smallest turbulent eddies since they have the highest shear rate. Experimental and theoretical effort focused on determining the coagulation rate of spherical particles in isotropic turbulence. A pair diffusion approximation valid for rapidly fluctuating flows was used to calculate the rate of coagulation in a randomly varying isotropic linear flow field. Dynamic simulations of particle coagulation in Gaussian turbulence were computed over a range of representative values of particle-particle interactions (i.e, hydrodynamic interactions and van der Waals attraction) and total strain (i.e., the product of the strain rate and its time scale). The computed coagulation rates for isotropic turbulence differed from analytical approximations valid at large and small total strain. As expected, particle interactions were found to be significant. Experimental measurements of coagulation in grid-generated turbulence were obtained by measuring the loss of singlet particles from an initially monodisperse suspension as a function of turbulence intensity. Model predictions based on the particle Hamaker constant and spatial distribution of turbulence in the reactor agreed well with the experiments without the use of any fitting parameters. The close agreement of simulations and observations indicate the numerical model has successfully captured the relevant physics that governs the aggregation of colloidal particles in turbulent flows. This work is the first successful description of turbulent coagulation. Given the ubiquity of turbulent suspensions in engineered and natural systems, the ability to quantitatively describe particle behavior under these conditions is expected to have considerable utility.

Sorption of lead from aqueous solution by chemically modified carbon adsorbents.

PubMed

Nadeem, Muhammad; Mahmood, A; Shahid, S A; Shah, S S; Khalid, A M; McKay, G

2006-12-01

An indigenously prepared, steam activated and chemically modified carbon from husk and pods of Moringa oleifera (M. oleifera), an agricultural waste, was comparatively examined as an adsorbent for the removal of lead from aqueous solutions. Studies were conducted as a function of contact time, initial metal concentration, dose of adsorbent, agitation speed, particle size and pH. Maximum uptake capacities were found to be, 98.89, 96.58, 91.8, 88.63, 79.43% for cetyltrimethyl ammonium bromide (CTAB), phosphoric, sulfuric, hydrochloric acid treated and untreated carbon adsorbents, respectively. Bangham, pseudo-first- and second-order, intra-particle diffusion equations were implemented to express the sorption mechanism by utilized adsorbents. Adsorption rate of lead ions was found to be considerably faster for chemically modified adsorbents than unmodified. The results of adsorption were fitted to both the Langmuir and Freundlich models. Satisfactory agreement between the metal uptake capacities by the adsorbents at different time intervals was expressed by the correlation coefficient (R(2)). The Langmuir model represented the sorption process better than the Freundlich one, with R(2) values ranging from 0.994 to 0.998.

The Study of Blocking Agent on Lengkeng (Euphoria Logan Lour) Fruit Shell and Seed for Adsorption of Pb (II) from Aqueous Solution

NASA Astrophysics Data System (ADS)

Kurniawati, D.; Zein, R.; Chaidir, Z.; Aziz, H.

2018-04-01

The study focuses on the roles played by mayor functional groups(carboxyl) in the lengkeng shell for sorption of Pb (II). The biosorbent was characterized by FTIR and elemental analyses. The parameters such as pH, initial concentration, particle sizes, adsorbent dose and flow rate were also studied. The results showed that the optimum condition was at pH = 3, concentration 400 mg/l, 250 μm particle sizes, adsorbent dose 0,5 g and 2 ml/min flow rate with adsorption capacity 4,8933 mg/g(shell) and 5,2720 mg/g(seed). It is show that ion exchange play as a more important role in the sorption of Pb (II) on lengkeng shell and seed. Blocking of COOH groups by chemical esterification resulted in Pb important reduction in metal binding.The result showed that adsorption capacity of lengkeng shell uncreases until 63.67 % and lengkeng seed uncreases 98.70%.

Sorption of perfluorooctanoic acid, perfluorooctane sulfonate and perfluoroheptanoic acid on granular activated carbon.

PubMed

Zhang, Di; Luo, Qi; Gao, Bin; Chiang, Sheau-Yun Dora; Woodward, David; Huang, Qingguo

2016-02-01

The sorption of perfluorooctane sulfonate (PFOS), perfluorooctanoic acid (PFOA), and perfluoroheptanoic acid (PFHpA) on granular activated carbon (GAC) was characterized and compared to explore the underlying mechanisms. Sorption of the three perfluoroalkyl acids (PFAAs) on GAC appeared to be a rapid intra-particle diffusion process, which were well represented by the pseudo-second-order rate model with the sorption rate following the order PFOS > PFOA > PFHpA. Sorption isotherm data were well fitted by the Freundlich model with the sorption capacity (Kf) of PFOS, PFOA and PFHpA being 4.45, 2.42 and 1.66 respectively. This suggests that the hydrophilic head group on PFAAs, i.e. sulfonate vs carboxylic, has a strong influence on their sorption. Comparison between PFOA and PFHpA revealed that hydrophobicity could also play a role in the sorption of PFAAs on GAC when the fluorocarbon chain length is different. Analyses using Attenuated Total Reflection (ATR)-Fourier Transform Infrared (FTIR) spectroscopy suggested possible formation of a negative charge-assisted H-bond between PFAAs and the functionalities on GAC surfaces, including non-aromatic ketones, sulfides, and halogenated hydrocarbons. Copyright © 2015 Elsevier Ltd. All rights reserved.

Isotherm, kinetic, and thermodynamic study of ciprofloxacin sorption on sediments.

PubMed

Mutavdžić Pavlović, Dragana; Ćurković, Lidija; Grčić, Ivana; Šimić, Iva; Župan, Josip

2017-04-01

In this study, equilibrium isotherms, kinetics and thermodynamics of ciprofloxacin on seven sediments in a batch sorption process were examined. The effects of contact time, initial ciprofloxacin concentration, temperature and ionic strength on the sorption process were studied. The K d parameter from linear sorption model was determined by linear regression analysis, while the Freundlich and Dubinin-Radushkevich (D-R) sorption models were applied to describe the equilibrium isotherms by linear and nonlinear methods. The estimated K d values varied from 171 to 37,347 mL/g. The obtained values of E (free energy estimated from D-R isotherm model) were between 3.51 and 8.64 kJ/mol, which indicated a physical nature of ciprofloxacin sorption on studied sediments. According to obtained n values as measure of intensity of sorption estimate from Freundlich isotherm model (from 0.69 to 1.442), ciprofloxacin sorption on sediments can be categorized from poor to moderately difficult sorption characteristics. Kinetics data were best fitted by the pseudo-second-order model (R 2  > 0.999). Thermodynamic parameters including the Gibbs free energy (ΔG°), enthalpy (ΔH°) and entropy (ΔS°) were calculated to estimate the nature of ciprofloxacin sorption. Results suggested that sorption on sediments was a spontaneous exothermic process.

Modeling of batch sorber system: kinetic, mechanistic, and thermodynamic modeling

NASA Astrophysics Data System (ADS)

Mishra, Vishal

2017-10-01

The present investigation has dealt with the biosorption of copper and zinc ions on the surface of egg-shell particles in the liquid phase. Various rate models were evaluated to elucidate the kinetics of copper and zinc biosorptions, and the results indicated that the pseudo-second-order model was more appropriate than the pseudo-first-order model. The curve of the initial sorption rate versus the initial concentration of copper and zinc ions also complemented the results of the pseudo-second-order model. Models used for the mechanistic modeling were the intra-particle model of pore diffusion and Bangham's model of film diffusion. The results of the mechanistic modeling together with the values of pore and film diffusivities indicated that the preferential mode of the biosorption of copper and zinc ions on the surface of egg-shell particles in the liquid phase was film diffusion. The results of the intra-particle model showed that the biosorption of the copper and zinc ions was not dominated by the pore diffusion, which was due to macro-pores with open-void spaces present on the surface of egg-shell particles. The thermodynamic modeling reproduced the fact that the sorption of copper and zinc was spontaneous, exothermic with the increased order of the randomness at the solid-liquid interface.

Adsorptive removal of direct azo dye from aqueous phase onto coal based sorbents: a kinetic and mechanistic study.

PubMed

Venkata Mohan, S; Chandrasekhar Rao, N; Karthikeyan, J

2002-03-01

This communication presents the results pertaining to the investigation conducted on color removal of trisazo direct dye, C.I. Direct Brown 1:1 by adsorption onto coal based sorbents viz. charfines, lignite coal, bituminous coal and comparing results with activated carbon (Filtrasorb-400). The kinetic sorption data indicated the sorption capacity of the different coal based sorbents. The sorption interaction of direct dye on to coal based sorbents obeys first-order irreversible rate equation and activated carbon fits with the first-order reversible rate equation. Intraparticle diffusion studies revealed the dye sorption interaction was complex and intraparticle diffusion was not only the rate limiting step. Isothermal data fit well with the rearranged Langmuir adsorption model. R(L) factor revealed the favorable nature of the isotherm of the dye-coal system. Neutral solution pH yielded maximum dye color removal. Desorption and interruption studies further indicated that the coal based sorbents facilitated chemisorption in the process of dye sorption while, activated carbon resulted in physisorption interaction.

INFLUENCE OF ORGANIC COSOLVENTS ON THE SORPTION KINETICS OF HYDROPHOBIC ORGANIC CHEMICALS

EPA Science Inventory

A quantitative examination of the kinetics of sorption of hydrophobic organic chemicals by soils from mixed solvents reveals that the reverse sorption rate constant (k2) increases log-linearly with increasing volume fraction of organic cosolvent (fc). This relationship was expec...

A model for trace metal sorption processes at the calcite surface: Adsorption of Cd2+ and subsequent solid solution formation

USGS Publications Warehouse

Davis, J.A.; Fuller, C.C.; Cook, A.D.

1987-01-01

The rate of Cd2+ sorption by calcite was determined as a function of pH and Mg2+ in aqueous solutions saturated with respect to calcite but undersaturated with respect to CdCO3. The sorption is characterized by two reaction steps, with the first reaching completion within 24 hours. The second step proceeded at a slow and nearly constant rate for at least 7 days. The rate of calcite recrystallization was also studied, using a Ca2+ isotopic exchange technique. Both the recrystallization rate of calcite and the rate of slow Cd2+ sorption decrease with increasing pH or with increasing Mg2+. The recrystallization rate could be predicted from the number of moles of Ca present in the hydrated surface layer. A model is presented which is consistent with the rates of Cd2+ sorption and Ca2+ isotopic exchange. In the model, the first step in Cd2+ sorption involves a fast adsorption reaction that is followed by diffusion of Cd2+ into a surface layer of hydrated CaCO3 that overlies crystalline calcite. Desorption of Cd2+ from the hydrated layer is slow. The second step is solid solution formation in new crystalline material, which grows from the disordered mixture of Cd and Ca carbonate in the hydrated surface layer. Calculated distribution coefficients for solid solutions formed at the surface are slightly greater than the ratio of equilibrium constants for dissolution of calcite and CdCO3, which is the value that would be expected for an ideal solid solution in equilibrium with the aqueous solution. ?? 1987.

Cadmium sorption and extractability in tropical soils with variable charge.

PubMed

Colzato, Marina; Alleoni, Luís Reynaldo Ferracciú; Kamogawa, Marcos Yassuo

2018-05-14

The availability of cadmium (Cd) for plants and its impact in the environment depends on Cd sorption in soil colloids. The study of Cd sorption in soil and its fractionation is an interesting tool for the evaluation of Cd affinity with soil pools. The objective with this study was to evaluate Cd sorption and desorption in tropical soils with variable charge (three Oxisols), in a Mollisol and in two Entisols with diverse physical, chemical, and mineralogical attributes. We used a thermodynamic approach to evaluate Cd sorption and performed a chemical fractionation of Cd in the six soils. Data from Cd sorption fit the Langmuir model (r > 0.94), and the sorption capacity ranged from 0.33 to 11.5 mmol kg -1 . The Gibbs standard free energy was positively correlated to Cd sorption capacity (r = 0.74, except for the Quartzipsamments), and it was more favorable in soils with great sorption capacity. Distribution of Cd among fractions was not affected (t test, α = 0.05) by initial concentration, and there was a predominance of Cd extractable in 0.1 mol L -1 CaCl 2 .

Interactions among K+-Ca2+ exchange, sorption of m-dinitrobenzene, and smectite quasicrystal dynamics.

PubMed

Chatterjee, Ritushree; Laird, David A; Thompson, Michael L

2008-12-15

The fate of organic contaminants in soils and sediments is influenced by sorption of the compounds to surfaces of soil materials. We investigated the interaction among sorption of an organic compound, cation exchange reactions, and both the size and swelling of smectite quasicrystals. Two reference smectites that vary in location and amount of layer charge, SPV (a Wyoming bentonite) and SAz-1 were initially Ca- and K-saturated and then equilibrated with mixed 0.01 M KCl and 0.005 M CaCl2 salt solutions both with and without the presence of 200 mg L(-1) m-dinitrobenzene (m-DNB). In general, sorption of m-DNB increased with the amount of K+ in the system for both clays, and the SPV sorbed more m-DNB than the SAz-1. Sorption of m-DNB increased the preference of Ca-SPV for K+ relative to Ca2+ but had little effect on K+-Ca2+ selectivity for K-SPV. Selectivity for K+ relative to Ca2+ was slightly higher for both K-SAz-1 and Ca-SAz-1 in the presence of m-DNB than in its absence. Distinct hysteresis loops were observed for the K+-Ca2+ cation exchange reactions for both clays, and the legacy of having been initially Ca- or K-saturated influenced sorption of m-DNB by SPV but had little effect for SAz-1. Suspension X-ray diffraction was used to measure changes in d-spacing and the relative thickness of smectite quasicrystals during the cation exchange and m-DNB sorption reactions. The results suggest that interactions among cation exchange and organic sorption reactions are controlled byan inherently hysteretic complex feedback process that is regulated by changes in the size and extent of swelling of smectite quasicrystals.

Rapid removal of uranium from aqueous solutions using magnetic Fe3O4@SiO2 composite particles.

PubMed

Fan, Fang-Li; Qin, Zhi; Bai, Jing; Rong, Wei-Dong; Fan, Fu-You; Tian, Wei; Wu, Xiao-Lei; Wang, Yang; Zhao, Liang

2012-04-01

Rapid removal of U(VI) from aqueous solutions was investigated using magnetic Fe(3)O(4)@SiO(2) composite particles as the novel adsorbent. Batch experiments were conducted to study the effects of initial pH, amount of adsorbent, shaking time and initial U(VI) concentrations on uranium sorption efficiency as well as the desorbing of U(VI). The sorption of uranium on Fe(3)O(4)@SiO(2) composite particles was pH-dependent, and the optimal pH was 6.0. In kinetics studies, the sorption equilibrium can be reached within 180 min, and the experimental data were well fitted by the pseudo-second-order model, and the equilibrium sorption capacities calculated by the model were almost the same as those determined by experiments. The Langmuir sorption isotherm model correlates well with the uranium sorption equilibrium data for the concentration range of 20-200 mg/L. The maximum uranium sorption capacity onto magnetic Fe(3)O(4)@SiO(2) composite particles was estimated to be about 52 mg/g at 25 °C. The highest values of uranium desorption (98%) was achieved using 0.01 M HCl as the desorbing agent. Fe(3)O(4)@SiO(2) composite particles showed a good selectivity for uranium from aqueous solution with other interfering cation ions. Present study suggested that magnetic Fe(3)O(4)@SiO(2) composite particles can be used as a potential adsorbent for sorption uranium and also provided a simple, fast separation method for removal of heavy metal ion from aqueous solution. Copyright © 2011 Elsevier Ltd. All rights reserved.

The role of sorption and biodegradation in the removal of acetaminophen, carbamazepine, caffeine, naproxen and sulfamethoxazole during soil contact: A kinetics study.

PubMed

Martínez-Hernández, Virtudes; Meffe, Raffaella; Herrera López, Sonia; de Bustamante, Irene

2016-07-15

In countries like Spain, where water is a limited resource, reusing effluents from wastewater treatment plants may imply the introduction of incompletely eliminated pollutants into the environment. Therefore, this work identified the role of sorption and biodegradation in attenuating pharmaceutical compounds (acetaminophen, carbamazepine, caffeine, naproxen and sulfamethoxazole) in natural soil. It also determined which sorption and removal ("sorption+biodegradation") kinetics models describe the behaviour of these substances in the water-soil system. Presence of potential transformation products (TPs) as a result of pharmaceuticals biodegradation was also studied. To this end, serial batch-type experiments were performed with a soil:water ratio of 1:4 and an initial pharmaceutical concentration of 100μgL(-1). Despite results are dependent on soil characteristics, they revealed that, for those substances with a higher affinity to the soil used (loamy sand), sorption seems to play a key role during the first 48h of contact with soil, and gives way to biodegradation afterwards. The sorption of the pharmaceuticals studied follows a pseudo second-order kinetics. Caffeine and sulfamethoxazole displayed the fastest initial sorption velocities (h=2055 and h=228μgkg(-1)h(-1), respectively). The removal kinetics experiments, satisfactorily simulated by the first-order kinetics model, indicated the presence of potential microbial adaptation to degradation. Indeed, half-lives decreased from 1.6- to 11.7-fold with respect to initial values. The microbial capacity to degrade sulfamethoxazole could be a matter of concern if bacteria have developed resistance to this antibiotic. Caffeine, acetaminophen and sulfamethoxazole were mitigated to a greater extent, whereas the removal of naproxen and carbamazepine was more limited. The appearance of epoxy-carbamazepine and N4-acetyl-sulfamethoxazole as possible TPs of carbamazepine and sulfamethoxazole, respectively, indicated that biodegradation was incomplete and showed the capacity of soil microbes to transform these substances. Copyright © 2016 Elsevier B.V. All rights reserved.

Use of carbonised beet pulp carbon for removal of Remazol Turquoise Blue-G 133 from aqueous solution.

PubMed

Dursun, Arzu Y; Tepe, Ozlem; Dursun, Gülbeyi

2013-01-01

Carbonised beet pulp (BPC) produced from agricultural solid waste by-product in sugar industry was used as adsorbent for the removal of Remazol Turquoise Blue-G 133 (RTB-G 133) dye in this study. The kinetics and equilibrium of sorption process were investigated with respect to pH, temperature and initial dye concentration. Adsorption studies with real textile wastewater were also performed. The results showed that adsorption was a strongly pH-dependent process, and optimum pH was determined as 1.0. The maximum dye adsorption capacity was obtained as 47.0 mg g(-1)at the temperature of 25 °C at this pH value. The Freundlich and Langmuir adsorption models were used for describing the adsorption equilibrium data of the dye, and isotherm constants were evaluated depending on sorption temperature. Equilibrium data of RTB-G 133 sorption fitted very well to the Freundlich isotherm. Mass transfer and kinetic models were applied to the experimental data to examine the mechanisms of adsorption and potential rate-controlling steps. It was found that both external mass transfer and intra-particle diffusion played an important role in the adsorption mechanisms of dye and adsorption kinetics followed the pseudo second-order type kinetic model. The thermodynamic analysis indicated that the sorption process was exothermic and spontaneous in nature.

Removal of ammonia nitrogen from leachate of Muribeca municipal solid waste landfill, Pernambuco, Brazil, using natural zeolite as part of a biochemical system.

PubMed

Lins, Cecilia Maria M S; Alves, Maria Cristina M; Campos, Juacyara C; Silva, Fabrícia Maria S; Jucá, José Fernando T; Lins, Eduardo Antonio M

2015-01-01

The inadequate disposal of leachate is one of the key factors in the environmental impact of urban solid waste landfills in Brazil. Among the compounds present in the leachates from Brazilian landfills, ammonia nitrogen is notable for its high concentrations. The purpose of this study was to assess the efficiency of a permeable reactive barrier filled with a natural zeolite, which is part of a biochemical system for the tertiary treatment of the leachate from Muribeca Municipal Solid Waste Landfill in Pernambuco, Brazil, to reduce its ammonia nitrogen concentration. This investigation initially consisted of kinetic studies and batch equilibrium tests on the natural zeolite to construct the sorption isotherms, which showed a high sorption capacity, with an average of 12.4 mg NH4+.L(-1), a value close to the sorption rates found for the aqueous ammonium chloride solution. A permeable reactive barrier consisting of natural zeolite, as simulated by the column test, was efficient in removing the ammonia nitrogen present in the leachate pretreated with calcium hydroxide. Nevertheless, the regenerated zeolite did not satisfactorily maintain the sorption properties of the natural zeolite, and an analysis of their cation-exchange properties showed a reduced capacity of 54 meq per 100 g for the regenerated zeolite compared to 150 meq per 100 g for the natural zeolite.

Mini-columns for Conducting Breakthrough Experiments. Design and Construction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dittrich, Timothy M.; Reimus, Paul William; Ware, Stuart Douglas

Experiments with moderately and strongly sorbing radionuclides (i.e., U, Cs, Am) have shown that sorption between experimental solutions and traditional column materials must be accounted for to accurately determine stationary phase or porous media sorption properties (i.e., sorption site density, sorption site reaction rate coefficients, and partition coefficients or K d values). This report details the materials and construction of mini-columns for use in breakthrough columns to allow for accurate measurement and modeling of sorption parameters. Material selection, construction techniques, wet packing of columns, tubing connections, and lessons learned are addressed.

SOLUBILITY, SORPTION AND TRANSPORT OF HYDROPHOBIC ORGANIC CHEMICALS IN COMPLEX MIXTURES

EPA Science Inventory

The research summarized in this report focuses on the effects which organic cosolvents have on the sorption and mobility of organic contaminants. This work was initiated In an effort to improve our understanding of the environmental consequences associated with complex mixtur...

Kinetics of the sorption of triterpene saponin by hypercrosslinked polystyrene

NASA Astrophysics Data System (ADS)

Mironenko, N. V.; Brezhneva, T. A.; Selemenev, V. F.

2013-03-01

The kinetics of sorption of triterpene saponin by the polymer sorbent NM-200 is considered. The influence of the surface activity of glycoside on the rate of formation and structure of the adsorption layer on the sorbent's surface is established. The rate-determining step of sorption is found to be diffusion into the sorbent grain. The value of the activation energy demonstrates the determining role of dispersion forces in the interaction between triterpene saponin and the polymer sorbent MN-200.

Batch and fixed-bed assessment of sulphate removal by the weak base ion exchange resin Amberlyst A21.

PubMed

Guimarães, Damaris; Leão, Versiane A

2014-09-15

This paper investigated sulphate removal from aqueous solutions by Amberlyst A21, a polystyrene weak base ion exchange resin. Both the pH and initial sulphate concentration were observed to strongly affect sorption yields, which were largest in acidic environments. Working under optimum operational conditions, sulphate sorption by Amberlyst A21 was relatively fast and reached equilibrium after 45 min of contact between the solid and liquid phases. Sorption kinetics could be described by either the pseudo-first order (k1=3.05 × 10(-5)s(-1)) or pseudo-second order model (k2=1.67 × 10(-4)s(-1)), and both the Freundlich and Langmuir models successfully fitted the equilibrium data. Sulphate uptake by Amberlyst A21 was a physisorption process (ΔH=-25.06 kJ mol(-1)) that occurred with entropy reduction (ΔS=-0.042 kJ mol(-1)K(-1)). Elution experiments showed that sulphate is easily desorbed (∼ 100%) from the resin by sodium hydroxide solutions at pH 10 or pH 12. Fixed-bed experiments assessed the effects of the initial sulphate concentration, bed height and flow rate on the breakthrough curves and the efficiency of the Amberlyst A21 in the treatment of a real effluent. In all studied conditions, the maximum sulphate loading resin varied between 8 and 40 mg(SO4(2-))mL(resin)(-1). Copyright © 2014 Elsevier B.V. All rights reserved.

Kinetic and mechanism studies of the adsorption of lead onto waste cow bone powder (WCBP) surfaces.

PubMed

Cha, Jihoon; Cui, Mingcan; Jang, Min; Cho, Sang-Hyun; Moon, Deok Hyun; Khim, Jeehyeong

2011-01-01

This study examines the adsorption isotherms, kinetics and mechanisms of Pb²(+) sorption onto waste cow bone powder (WCBP) surfaces. The concentrations of Pb²(+) in the study range from 10 to 90 mg/L. Although the sorption data follow the Langmuir and Freundlich isotherm, a detailed examination reveals that surface sorption or complexation and co-precipitation are the most important mechanisms, along with possibly ion exchange and solid diffusion also contributing to the overall sorption process. The co-precipitation of Pb²(+) with the calcium hydroxyapatite (Ca-HAP) is implied by significant changes in Ca²(+) and PO₄³⁻ concentrations during the metal sorption processes. The Pb²(+) sorption onto the WCBP surface by metal complexation with surface functional groups such as ≡ POH. The major metal surface species are likely to be ≡ POPb(+). The sorption isotherm results indicated that Pb²(+) sorption onto the Langmuir and Freundlich constant q(max) and K( F ) is 9.52 and 8.18 mg g⁻¹, respectively. Sorption kinetics results indicated that Pb²(+) sorption onto WCBP was pseudo-second-order rate constants K₂ was 1.12 g mg⁻¹ h⁻¹. The main mechanism is adsorption or surface complexation (≡POPb(+): 61.6%), co-precipitation or ion exchange [Ca₃(.)₉₃ Pb₁(.)₀₇ (PO₄)₃ (OH): 21.4%] and other precipitation [Pb 50 mg L⁻¹ and natural pH: 17%). Sorption isotherms showed that WCBP has a much higher Pb²(+) removal rate in an aqueous solution; the greater capability of WCBP to remove aqueous Pb²(+) indicates its potential as another promising way to remediate Pb²(+)-contaminated media.

The power of power: electrokinetic control of PAH interactions with exfoliated graphite.

PubMed

Qin, Jinyi; Moustafa, Ahmed; Harms, Hauke; El-Din, Mohamed Gamal; Wick, Lukas Y

2015-05-15

Exfoliated graphite (EG) exhibits exceptional sorption capacity for petroleum and dissolved hydrocarbons owing to its highly hydrophobic surface and wide pore size distribution. The high price of preparing EG, however, restricts its application. Methods which increase the rate or extent of sorption to EG even further are thus longed for. Here, we assess the effects of weak direct current (DC) fields on the sorption of the polycyclic aromatic hydrocarbon phenanthrene (PHE) to EG. DC applied to an ionic solution in a solid matrix invokes electroosmotic flow (EOF), i.e., the surface charge-induced movement of the solution. EG was exposed to weak DC fields in the presence of dissolved PHE to test if EOF increases transport of PHE to poorly accessible sorption sites. DC fields increased PHE sorption rates in EG sevenfold and reduced the desorption rate of sorbed PHE by >99%. EOF thus appeared to be highly effective in translocating PHE into pores, which contribute most of the sorption sites, but are difficult to access in the absence of EOF by molecular diffusion only. The observed 'power of power' may be used to kinetically regulate the interaction of sorbates with EG or other porous sorbents in environmental (bio-) technology. Copyright © 2015 Elsevier B.V. All rights reserved.

Characterization of the atrazine sorption process on Andisol and Ultisol volcanic ash-derived soils: kinetic parameters and the contribution of humic fractions.

PubMed

Báez, María E; Fuentes, Edwar; Espinoza, Jeannette

2013-07-03

Atrazine sorption was studied in six Andisol and Ultisol soils. Humic and fulvic acids and humin contributions were established. Sorption on soils was well described by the Freundlich model. Kf values ranged from 2.2-15.6 μg(1-1/n)mL(1/n)g⁻¹. The relevance of humic acid and humin was deduced from isotherm and kinetics experiments. KOC values varied between 221 and 679 mLg⁻¹ for these fractions. Fulvic acid presented low binding capacity. Sorption was controlled by instantaneous equilibrium followed by a time-dependent phase. The Elovich equation, intraparticle diffusion model, and a two-site nonequilibrium model allowed us to conclude that (i) there are two rate-limited phases in Andisols related to intrasorbent diffusion in organic matter and retarded intraparticle diffusion in the organo-mineral complex and that (ii) there is one rate-limited phase in Ultisols attributed to the mineral composition. The lower organic matter content of Ultisols and the slower sorption rate and mechanisms involved must be considered to assess the leaching behavior of atrazine.

ATRAZINE DESORPTION KINETICS FROM A FRESH-WATER SEDIMENT

EPA Science Inventory

Research has shown that the sorption and desorption of neutral organic compounds to soils and sediments occurs in two stages, with an initial rapid sorption/desorption phase (usually less than an hour) followed by a slower phase that can last for several months to years for very ...

Algal Foams Applied in Fixed-Bed Process for Lead(II) Removal Using Recirculation or One-Pass Modes

PubMed Central

Wang, Shengye; Vincent, Thierry; Faur, Catherine; Guibal, Eric

2017-01-01

The incorporation of brown algae into biopolymer beads or foams for metal sorption has been previously reported. However, the direct use of these biomasses for preparing foams is a new approach. In this study, two kinds of porous foams were prepared by ionotropic gelation using algal biomass (AB, Laminaria digitata) or alginate (as the reference) and applied for Pb(II) sorption. These foams (manufactured as macroporous discs) were packed in filtration holders (simulating fixed-bed column) and the system was operated in either a recirculation or a one-pass mode. Sorption isotherms, uptake kinetics and sorbent reuse were studied in the recirculation mode (analogous to batch system). In the one-pass mode (continuous fixed-bed system), the influence of parameters such as flow rate, feed metal concentration and bed height were investigated on both sorption and desorption. In addition, the effect of Cu(II) on Pb(II) recovery from binary solutions was also studied in terms of both sorption and desorption. Sorption isotherms are well fitted by the Langmuir equation while the pseudo-second order rate equation described well both sorption and desorption kinetic profiles. The study of material regeneration confirms that the reuse of the foams was feasible with a small mass loss, even after 9 cycles. In the one-pass mode, for alginate foams, a slower flow rate led to a smaller saturation volume, while the effect of flow rate was less marked for AB foams. Competitive study suggests that the foams have a preference for Pb(II) over Cu(II) but cannot selectively remove Pb(II) from the binary solution. PMID:29039806

Equilibrium sorption and diffusion rate studies with halogenated organic chemical and sandy aquifer material

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ball, W.P.

1990-01-01

Concepts for rate limitation of sorptive uptake of hydrophobic organic solutes by aquifer solids are reviewed, emphasizing physical diffusion models and in the context of effects on contaminant transport. Data for the sorption of tetrachloroethene (PCE) and 1,2,4,5-tetrachlorobenzene (TeCB) on Borden sand are presented, showing that equilibrium is attained very slowly, requiring equilibration times on the order of tens of days for PCE and hundreds of days for TeCB. The rate of approach to equilibrium decreased with increasing particle size and sorption distribution coefficient, in accordance with retarded intragranular diffusion models. Pulverization of the samples significantly decreased the required timemore » to equilibrium without changing the sorption capacity of the solids. Batch sorption methodology was refined to allow accurate measurement of long-term distribution coefficients, using purified {sup 14}C-labelled solute spikes and sealed glass ampules. Sorption isotherms for PCE and TeCB were conducted with size fractions of Borden sand over four to five orders of magnitude in aqueous concentration, and were found to be slightly nonlinear (Freundlich exponent = 0.8). A concentrated set of data in the low concentration range (<50 ug/L) revealed that sorption in this range could be equally well described by a linear isotherm. Distribution coefficients of the two solutes with seven size fractions of Borden sand, measured at low concentration and at full equilibrium, were between seven and sixty times the value predicted on the basis of recent correlations with organic carbon content. Rate results for coarse size fractions support a simple pore diffusion model, with pore diffusion coefficients estimated to be approximately 3 {times} 10{sup {minus}8} cm{sup 2}/sec, more than 200{times} lower than the aqueous diffusivities.« less

QSAR ANALYSIS OF SORPTION-CORRECTED RATE CONSTANTS FOR REDUCTIVE BIOTRANSFORMATION OF HALOGENATED AROMATICS

EPA Science Inventory

The inherent coupling among geochemical and microbial reactions may have significant effects on the environmental fate of a containinant. For example, sorption processes may decrease the concentration of an organic compound in solution, thereby reducing the biodegradation rate of...

Surfactant-enhanced remediation of a trichloroethene-contaminated aquifer. 1. Transport of triton X-100

USGS Publications Warehouse

Smith, J.A.; Sahoo, D.; Mclellan, H.M.; Imbrigiotta, T.E.

1997-01-01

Transport of a nonionic surfactant (Triton X-100) at aqueous concentrations less than 400 mg/L through a trichloroethene-contaminated sand-and-gravel aquifer at Picatinny Arsenal, NJ, has been studied through a series of laboratory and field experiments. In the laboratory, batch and column experiments were conducted to quantify the rate and amount of Triton X-100 sorption to the aquifer sediments. In the field, a 400 mg/L aqueous Triton X-100 solution was injected into the aquifer at a rate of 26.5 L/min for a 35-d period. The transport of Triton X-100 was monitored by sampling and analysis of groundwater at six locations surrounding the injection well. Equilibrium batch sorption experiments showed that Triton X-100 sorbs strongly and nonlinearly to the field soil with the sharpest inflection point of the isotherm occurring at an equilibrium aqueous Triton X-100 concentration close to critical micelle concentration. Batch, soil column, and field experimental data were analyzed with zero-, one-, and two- dimensional (respectively) transient solute transport models with either equilibrium or rate-limited sorption. These analyses reveal that Triton X- 100 sorption to the aquifer solids is slow relative to advective and dispersive transport and that an equilibrium sorption model cannot simulate accurately the observed soil column and field data. Comparison of kinetic sorption parameters from batch, column, and field transport data indicate that both physical heterogeneities and Triton X-100 mass transfer between water and soil contribute to the kinetic transport effects.Transport of a nonionic surfactant (Triton X-100) at aqueous concentrations less than 400 mg/L through a trichloroethene-contaminated sand-and-gravel aquifer was studied. Equilibrium batch sorption experiments showed that Triton X-100 sorbs strongly and nonlinearly to the field soil with the sharpest inflection point of the isotherm occurring at an equilibrium aqueous Triton X-100 concentration close to critical micelle concentration. Batch, soil column, and field experimental data were analyzed with zero-, one-, and two-dimensional transient solute transport models with either equilibrium or rate-limited sorption. These analyses revealed that Triton X-100 sorption to the aquifer solids was slow relative to advective and dispersive transport.

Sorption of lambda-cyhalothrin, cypermethrin, deltamethrin and fenvalerate to quartz, corundum, kaolinite and montmorillonite.

PubMed

Oudou, H Chaaieri; Hansen, H C Bruun

2002-12-01

Sorption to mineral surfaces may be important for retention and degradation of hydrophobic pesticides in subsoils and aquifers poor in organic matter. In this work the title pyrethroids have been used to investigate selective interactions with the surfaces of four minerals. Sorption of the four pyrethroids was quantified in batch experiments with initial pyrethroid concentrations of 1-100 microg/l. Sorption to centrifuge tubes used in the batch experiments accounted for 25-60% of total sorption. Net sorption was obtained from total sorption after subtracting the amounts of pyrethroids sorbed to centrifuge tubes used. All isotherms could be fitted by the Freundlich equation with n ranging between 0.9 and 1.1. Bonding affinities per unit surface area decreased in the order: corundum > quartz > montmorillonite approximately equal kaolinite. A similar sequence as found for the total surface tension of the minerals. All minerals showed the same selectivity order with respect to sorption affinity of the four pyrethroids: lambda-cyhalothrin > deltamethrin > cypermethrin > fenvalerate, which shows that the most hydrophobic compound is sorbed most strongly. Stereochemical properties of the four pyrethroid formulations may also contribute to the selectivity pattern.

Colloid-Facilitated Transport of 137Cs in Fracture-Fill Material. Experiments and Modeling

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dittrich, Timothy M.; Reimus, Paul William

2015-10-29

In this study, we demonstrate how a combination of batch sorption/desorption experiments and column transport experiments were used to effectively parameterize a model describing the colloid-facilitated transport of Cs in the Grimsel granodiorite/FFM system. Cs partition coefficient estimates onto both the colloids and the stationary media obtained from the batch experiments were used as initial estimates of partition coefficients in the column experiments, and then the column experiment results were used to obtain refined estimates of the number of different sorption sites and the adsorption and desorption rate constants of the sites. The desorption portion of the column breakthrough curvesmore » highlighted the importance of accounting for adsorption-desorption hysteresis (or a very nonlinear adsorption isotherm) of the Cs on the FFM in the model, and this portion of the breakthrough curves also dictated that there be at least two different types of sorption sites on the FFM. In the end, the two-site model parameters estimated from the column experiments provided excellent matches to the batch adsorption/desorption data, which provided a measure of assurance in the validity of the model.« less

Unrefined humic substances as a potential low-cost amendment for the management of acidic groundwater contamination.

PubMed

Gonzalez-Raymat, Hansell; Anagnostopoulos, Vasileios; Denham, Miles; Cai, Yong; Katsenovich, Yelena P

2018-04-15

The present study explores a novel application of Huma-K, a commercially available, unrefined humic substance, as a promising low-cost source of organic matter for in situ remediation of contaminated acidic groundwater plumes. This can be achieved by creating a humic-rich coating on the surface of minerals which can enhance the sorption of contaminants from groundwater. Huma-K was characterized by means of scanning electron microscopy equipped with energy dispersive spectroscopy, Fourier-transform infrared analysis, and potentiometric titrations. Batch experiments were performed to investigate the sorption-desorption behavior of Huma-K and to evaluate what conditions (pH, contact time, and initial Huma-K concentration) affect these processes upon injection into aquifer sediments. As evidenced by potentiometric titrations, Huma-K possesses functional groups that have an acidic nature, with pK values in the range of 4-6 (carboxylic) and 9-10 (phenolic). Sorption, homogeneous precipitation, and surface-induced precipitation seem to be favored in the presence of sediment at pH 4, where there is less deprotonation of acidic functional groups. As the pH is increased, functional groups become negatively charged, leading to electrostatic repulsion and dissolution of Huma-K from sediment. Kinetic experiments indicate that Huma-K sorption is a slow-rate process, most likely governed by film diffusion. The enhanced sorption of Huma-K in acidic conditions suggests that it may be used to create a subsurface treatment zone in acidic aquifers for the sequestration of contaminants such as uranium. The treatment zone will persist as long as the pH does not increase sufficiently to cause soil-bound Huma-K to be released, remobilizing aqueous contaminants. Copyright © 2018 Elsevier Ltd. All rights reserved.

Time-dependent phosphate dynamics in reclaimed lignite-mine soils under Robinia pseudoacacia L.

NASA Astrophysics Data System (ADS)

Freese, Dirk; Slazak, Anna

2017-04-01

As a consequence of the opencast lignite mining activities in Lusatia/Germany, the cultivation of Short Rotation Coppice plantations (SRC) has been considered as a viable option for reclamation purposes. In this region an area of about 1000 km2 has been degraded. Owing to the unfavourable biotic and abiotic properties of the overburden mining substrate, the biogeochemical processes associated with the soil ecosystem development are in the initial phase. The substrate contains very low amount of nutrients, mainly very low total Phosphate (P) content nearly equal to zero. The lack of P is one of the main issues in reclamation of this marginal site. Therefore, the cultivation of perennial SRC with Robinia pseudoacacia L. is considered as a supporting measurement for effective soil reclamation. In this context, it is important to understand the dynamics of P in this "initial substrate" to describe the P availability and P sorption/desorption.. Iron/aluminium oxides and organic matter are the soil constituents most strongly affecting the reactions and rate of P sorption and desorption, also in post-mining soils. Therefore the interaction of these oxides and organic matter with P is essential with regard to developing effective nutrient management strategies for marginal sites. The study focused on P sorption and desorption with regard to different development stages of R. pseudoacacia L. established in a short rotation coppices on the post mining soils. to describe the P availability (Pav) in relation to total P mobility. The hypothesis is that SRC would cause significant changes in soil P dynamics over time in post lignite mining soils. The trees has been planted in between 1995 and 2007, which means that R. pseudoacacia L. was in a range of 2 to 20 years old at different sampling times. Soil was sampled in 2008 and 2015 at three depths of: 0-3cm, 3-10 cm and 10-30 cm. To characterize the P dynamics different P forms and P sorption/desorption kinetics were analysed. With increasing age of trees the ratio of available P to total P decreased in tendency for all soil layers. The total P content increased slightly over time in all soil layers. But the amount of Fe and Al oxides increased also over time and therefore the overall P sorption capacity increased, too. Hence, the ratio between available P and total P shifted more to the less available forms of P in soil. Within a period of 20 years, R. pseudoacacia L. cultivation on post mining sites increased the contents of available P and total P, repectively. The P sorption increased with time of soil development showing the maximum at the oldest site. Nevertheless, P sorption of these initial post mining soils is still rather low. The results suggest, that the SRC of R. pseudoacacia L. on post mining sites have a positive influence on the P dynamics. References Freese, D., Van Riemsdijk, W.H., Van Der Zee, S.E.A.T.M., 1995. Modelling phosphate-sorption kinetics in acid soils. European Journal of Soil Science 46(2), 239-245. Matos, E.S., Freese, D., Böhm, C., Quinkenstein, A., Hüttl, R.F., 2012. Organic Matter Dynamics in Reclaimed Lignite Mine Soils under Robinia pseudoacacia L. Plantations of Different Ages in Germany. Communications in Soil Science and Plant Analysis 43(5), 745-755.

Competitive sorption of organic contaminants in chalk.

PubMed

Graber, E R; Borisover, M

2003-12-01

In the Negev desert, Israel, a chemical industrial complex is located over fractured Eocene chalk formations where transfer of water and solutes between fracture voids and matrix pores affects migration of contaminants in the fractures due to diffusion into the chalk matrix. This study tests sorption and sorption competition between contaminants in the chalk matrix to make it possible to evaluate the potential for contaminant attenuation during transport in fractures. Single solute sorption isotherms on chalk matrix material for five common contaminants (m-xylene, ametryn, 1,2-dichloroethane, phenanthrene, and 2,4,6-tribromophenol) were found to be nonlinear, as confirmed in plots of Kd versus initial solution concentration. Over the studied concentration ranges, m-xylene Kd varied by more than a factor of 100, ametryn Kd by a factor of 4, 1,2-dichloroethane Kd by more than a factor of 3, phenanthrene Kd by about a factor of 2, and 2,4,6-tribromophenol Kd by a factor of 10. It was earlier found that sorption is to the organic matter component of the chalk matrix and not to the mineral phases (Chemosphere 44 (2001) 1121). Nonlinear sorption isotherms indicate that there is at least some finite sorption domain. Bi-solute competition experiments with 2,4,6-tribromophenol as the competitor were designed to explore the nature of the finite sorption domain. All of the isotherms in the bi-solute experiments are more linear than in the single solute experiments, as confirmed by smaller variations in Kd as a function of initial solution concentration. For both m-xylene and ametryn, there is a small nonlinear component or domain that was apparently not susceptible to competition by 2,4,6-tribromophenol. The nonlinear sorption domain(s) is best expressed at low solution concentrations. Inert-solvent-normalized single and bi-solute sorption isotherms demonstrate that ametryn undergoes specific force interactions with the chalk sorbent. The volume percent of phenanthrene sorbed at the liquid solubility limit is calculated to be 13% v:v in both the single and bi-solute experiments. This value exceeds what may be reasonably interpreted as partitioning of phenanthrene into organic matter, despite the relative linearity of the phenanthrene sorption isotherm (compared with other compounds) in both single and bi-solute systems.

Examination of Technetium Transport Through Soils Under Contrasting Redox Conditions: Batch and Column Work

NASA Astrophysics Data System (ADS)

Dozier, R.; Montgomery, D.; Wylie, E. M.; Dogan, M.; Moysey, S. M.; Powell, B. A.; Martinez, N. E.

2015-12-01

Experiments were performed under various reducing conditions to evaluate the transport behavior of technetium-99 (99Tc) in the presence of sandy clay loam soil from the Savannah River Site (SRS) and goethite, magnetite, and iron sulfide, which were selected for their increasing reducing potential. The experiments were conducted to investigate how redox reaction equilibria and rates affect the overall mobility of 99Tc as it transitions between the mobile Tc(VII) and immobile Tc(IV). Under oxygen-rich conditions, batch sorption isotherms measured for TcO4- across the concentration range 0.5 to 50 μg/L were linear with distribution coefficients (Kd) of 0.78 mL/g or lower, with decreasing sorption for goethite, magnetite, and iron sulfide, respectively. Addition of Na2S resulted in a marked increase in apparent 99Tc sorption to the solid phase, with Kd of 43 mL/g, 35 mL/g, and 29 mL/g, following the same mineral trend as previously. The increased Kd values are possibly due to reduction of Tc(VII) to Tc(IV), resulting in the formation of TcO2(s). SRS soil batch sorption isotherms measured for TcO4- across the same concentration range were also linear, with Kd of 0.7 mL/g for unadjusted pH, 5.1 mL/g for pH of around 6, and 6.7 mL/g for pH of around 4. Kinetic batch sorption tests showed less than 10% 99Tc sorption in an oxidizing environment and greater than 95% sorption in a reducing environment, with both reactions occurring on the order of minutes. In contrast, desorption experiments initiated by transferring the samples from a reducing environment (0.1% H2(g)/99.9% N2(g)) to atmospheric conditions resulted in a slow desorption step on the order of days. Column experiments conducted with the SRS sands indicate a retardation factor of 1.17 for 99Tc under oxygen rich conditions. Additional column experiments are being conducted to evaluate 99Tc transport dependencies on transitions between oxygen rich and poor conditions.

Sorption kinetics of zinc and nickel on modified chitosan.

PubMed

Tripathi, Nimisha; Choppala, Girish; Singh, Raj S; Srivastava, Prashant; Seshadri, Balaji

2016-09-01

This study was conducted to evaluate the effect of equilibration time on adsorption of zinc [Zn(II)] and nickel [Ni(II)] on pure and modified chitosan beads. The initial adsorption of Zn(II) was high on molybdenum (Mo)-impregnated chitosan beads (MoCB) during the initial 60 min. However, after 240 min, Zn(II) adsorption occurred more on single super phosphate chitosan beads (SSPCB), followed by monocalcium phosphate chitosan beads (MCPCB), untreated pure chitosan beads (UCB), and MoCB. Similarly, Ni(II) adsorption was greatest on MoCB during the initial 60 min. At the conclusion of the experiment (at 240 min), the greatest adsorption was occurred on MCPCB, followed by MoCB, UCB, and SSPCB. Chemical sorption and intra-particle diffusion were probably the dominant processes responsible for Zn(II) and Ni(II) sorption onto chitosan beads. The results demonstrated that modified chitosan beads were effective in adsorbing Zn and Ni and hence, could be used for the removal of these toxic metals from soil.

Characterization of banana peel by scanning electron microscopy and FT-IR spectroscopy and its use for cadmium removal.

PubMed

Memon, Jamil R; Memon, Saima Q; Bhanger, M I; Memon, G Zuhra; El-Turki, A; Allen, Geoffrey C

2008-10-15

This study describes the use of banana peel, a commonly produced fruit waste, for the removal of Cd(II) from environmental and industrial wastewater. The banana peel was characterized by FT-IR and scanning electron microscopy (SEM) coupled with energy dispersive X-ray (EDX) analysis. The parameters pH, contact time, initial metal ion concentration and temperature were investigated and found to be rapid ( approximately 97% within 10 min). The Langmuir adsorption isotherm was used to describe partitioning behavior for the system at room temperature. The value of Q(L) was found to be (35.52 mg g(-1)) higher than the previously reported materials. The binding of metal ions was found to be pH-dependent with the optimal sorption occurring at pH 8. The retained species were eluted with 5 mL of 5 x 10(-3)M HNO(3) with the detection limit of 1.7 x 10(-3)mg L(-1). Kinetics of sorption followed the pseudo-first-order rate equation with the rate constant k, equal to 0.13+/-0.01 min(-1). Thermodynamic parameters such as Gibbs free energy at 303K (-7.41+/-0.13 kJ mol(-1)) and enthalpy (40.56+/-2.34 kJ mol(-1)) indicated the spontaneous and endothermic nature of the sorption process. The developed method was utilized for the removal of Cd(II) ions from environmental and industrial wastewater samples using flame atomic absorption spectrophotometer (FAAS).

Phosphorus immobilization in micropores of drinking-water treatment residuals: implications for long-term stability.

PubMed

Makris, Konstantinos C; Harris, Willie G; O'Connor, George A; Obreza, Thomas A

2004-12-15

Drinking-water treatment residuals (WTRs) can immobilize excess soil phosphorus (P), but little is known about the long-term P retention by WTRs. To evaluate the long-term P sorption characteristics of one Fe- and one Al-based WTR, physicochemical properties pertinent to time-dependency and hysteresis of P sorption were assessed. This study also investigated the P sorption mechanisms that could affect the long-term stability of sorbed P by WTRs. Phosphorus sorption kinetics by the WTRs exhibited a slow phase that followed an initial rapid phase, as typically occurs with metal hydroxides. Phosphorus sorption maxima for both Fe- and Al-based WTRs exceeded 9100 mg of P kg(-1) and required a greater specific surface area (SSA) than would be available based on BET-N2 calculations. Electron microprobe analyses of cross-sectional, P-treated particles showed three-dimensional P sorption by WTRs. Carbon dioxide gas sorption was greater than N2, suggesting steric restriction of N2 diffusion by narrow micropore openings. Phosphorus-treated Co2 SSAs were reduced by P treatment, suggesting P sorption by micropores (5-20 A). Mercury intrusion porosimetry indicated negligible macroporosity (pores > 500 A). Slow P sorption kinetics by WTRs may be explained by intraparticle P diffusion in micropores. Micropore-bound P should be stable and immobilized over long periods.

Infrared study of CO{sub 2} sorption over 'molecular basket' sorbent consisting of polyethylenimine-modified mesoporous molecular sieve

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, X.X.; Schwartz, V.; Clark, J.C.

2009-04-15

An infrared study has been conducted on CO{sub 2} sorption into nanoporous CO{sub 2} 'molecular basket' sorbents prepared by loading polyethylenimine (PEI) into mesoporous molecular sieve SBA-15. IR results from DRIFTS showed that a part of loaded PEI is anchored on the surface of SBA-15 through the interaction between amine groups and isolated surface silanol groups. Raising the temperature from 25 to 75{sup o}C increased the molecular flexibility of PEI loaded in the mesopore channels, which may partly contribute to the increase of CO{sub 2} sorption capacity at higher temperatures. CO{sub 2} sorption/desorption behavior studied by in situ transmission FTIRmore » showed that CO{sub 2} is sorbed on amine sites through the formation of alkylammonium carbamates and absorbed into the multiple layers of PEI located in mesopores of SBA-15. A new observation by in situ IR is that two broad IR bands emerged at 2450 and 2160 cm{sup -1} with CO{sub 2} flowing over PEI(50)/SBA-15, which could be attributed to chemically sorbed CO{sub 2} species on PEI molecules inside the mesopores of SBA-15. The intensities of these two bands also increased with increasing CO{sub 2} exposure time and with raising CO{sub 2} sorption temperature. By comparison of the CO{sub 2} sorption rate at 25 and 75{sup o}C in terms of differential IR intensities, it was found that CO{sub 2} sorption over molecular basket sorbent includes two rate regimes which suggest two distinct steps: rapid sorption on exposed outer surface layers of PEI (controlled by sorption affinity or thermodynamics) and the diffusion and sorption inside the bulk of multiple layers of PEI (controlled by diffusion). The sorption of CO{sub 2} is reversible at 75{sup o}C.« less

RATES OF IRON OXIDATION AND ARSENIC SORPTION DURING GROUND WATER-SURFACE WATER MIXING AT A HAZARDOUS WASTE SITE

EPA Science Inventory

The fate of arsenic discharged from contaminated ground water to a pond at a hazardous waste site is controlled, in part, by the rate of ferrous iron oxidation-precipitation and arsenic sorption. Laboratory experiments were conducted using site-derived water to assess the impact...

Sorption characteristics of cadmium in a clay soil of Mae Ku creek, Tak Province, Thailand

NASA Astrophysics Data System (ADS)

Thunyawatcharakul, P.; Chotpantarat, S.

2018-05-01

Mae Sot is a district in Tak province, the northern part of Thailand where has encountered with cadmium (Cd) contaminated in soils. Exposure of Cd can lead to severe health effect, for examples, bone softening, osteoporosis, renal dysfunction, and Itai-Itai disease. This study aims at elucidating sorption behavior of Cd in the contaminated soil collected from Mae Ku creek, Mae Sot district, Thailand. Batch sorption experiment was conducted in order to investigate sorption characteristics of Cd onto the contaminated soil. The soil sample taken from the study area consists of 26% sand, 16% silt 58% clay, which categorized as a clay soil, based on USDA classification. Soil pH is slightly alkaline (pH∼7.7) and organic matter in the soil is 2.93%. The initial concentration in the batch sorption experiment was in the range from 0- 200 ppm. The result from the batch sorption experiment showed that soil sample can adsorb Cd up to 173.5 ppm and the sorption behavior of the soil sample can be well described by Freundlich isotherm, indicating the multilayer sorption (R2 = 0.9964), with Freundlich constants of 0.312 and 1.760 L g-1 for 1/n and Kf, respectively.

Removal of lindane from an aqueous solution by using aminopropyl silica gel-immobilized calix[6]arene.

PubMed

Tor, Ali; Aydin, Mehmet Emin; Aydin, Senar; Tabakci, Mustafa; Beduk, Fatma

2013-11-15

An aminopropyl silica gel-immobilized calix[6]arene (C[6]APS) has been used for the removal of lindane from an aqueous solution in batch sorption technique. The C[6]APS was synthesized with p-tert-butylcalix[6]arene hexacarboxylate derivative and aminopropyl silica gel in the presence of N,N'-diisopropyl carbodiimide coupling reagent. The sorption study was carried out as functions of solution pH, contact time, initial lindane concentration, C[6]APS dosage and ionic strength of solution. The matrix effect of natural water samples on the sorption efficiency of C[6]APS was also investigated. Maximum lindane removal was obtained at a wide pH range of 2-8 and sorption equilibrium was achieved in 2h. The isotherm analysis indicated that the sorption data can be represented by both Langmuir and Freundlich isotherm models. Increasing ionic strength of the solutions increased the sorption efficiency and matrix of natural water samples had no effect on the sorption of lindane. By using multilinear regression model, regression equation was also developed to explain the effects of the experimental variables. Copyright © 2013 Elsevier B.V. All rights reserved.

Parameter and observation importance in modelling virus transport in saturated porous media - Investigations in a homogenous system

USGS Publications Warehouse

Barth, Gilbert R.; Hill, M.C.

2005-01-01

This paper evaluates the importance of seven types of parameters to virus transport: hydraulic conductivity, porosity, dispersivity, sorption rate and distribution coefficient (representing physical-chemical filtration), and in-solution and adsorbed inactivation (representing virus inactivation). The first three parameters relate to subsurface transport in general while the last four, the sorption rate, distribution coefficient, and in-solution and adsorbed inactivation rates, represent the interaction of viruses with the porous medium and their ability to persist. The importance of four types of observations to estimate the virus-transport parameters are evaluated: hydraulic heads, flow, temporal moments of conservative-transport concentrations, and virus concentrations. The evaluations are conducted using one- and two-dimensional homogeneous simulations, designed from published field experiments, and recently developed sensitivity-analysis methods. Sensitivity to the transport-simulation time-step size is used to evaluate the importance of numerical solution difficulties. Results suggest that hydraulic conductivity, porosity, and sorption are most important to virus-transport predictions. Most observation types provide substantial information about hydraulic conductivity and porosity; only virus-concentration observations provide information about sorption and inactivation. The observations are not sufficient to estimate these important parameters uniquely. Even with all observation types, there is extreme parameter correlation between porosity and hydraulic conductivity and between the sorption rate and in-solution inactivation. Parameter estimation was accomplished by fixing values of porosity and in-solution inactivation.

Indoor sorption of surrogates for sarin and related nerve agents.

PubMed

Singer, Brett C; Hodgson, Alfred T; Destaillats, Hugo; Hotchi, Toshifumi; Revzan, Kenneth L; Sextro, Richard G

2005-05-01

Sorption rate parameters were determined for three organophosphorus (OP) compounds [dimethyl methylphosphonate (DMMP), diethyl ethylphosphonate (DEEP), and triethyl phosphate (TEP)] as surrogates for the G-type nerve agents sarin (GB), soman (GD), and tabun (GA). OP surrogates were injected and vaporized with additional volatile organic compounds into a 50 m3 chamber finished with painted wallboard. Experiments were conducted at two furnishing levels: (i) chamber containing only hard surfaces including a desk, a bookcase, tables, and chairs and (ii) with the addition of plush materials including carpet with cushion, draperies, and upholstered furniture. Each furnishing level was studied with aged and new painted wallboard. Gas-phase concentrations were measured during sealed chamber adsorb and desorb phases and then fit to three mathematical variations of a previously proposed sorption model having a surface sink and allowing for an embedded sink. A four-parameter model allowing unequal transport rates between surface and embedded sinks provided excellent fits for all conditions. To evaluate the potential effect of sorption, this model was incorporated into an indoor air quality simulation model to predict indoor concentrations of a G-type agent and a nonsorbing agent for hypothetical outdoor releases with shelter-in-place (SIP) response. Sorption was simulated using a range of parameters obtained experimentally. Simulations considered outdoor Gaussian plumes of 1- and 5-h duration and infiltration rates of 0.1, 0.3, and 0.9 h(-1). Indoor toxic loads (TL) for a 10-h SIP were calculated as integral C2 dt for a G-type agent. For the 5-h plume, sheltering reduced TLs for the nonsorbing agent to approximately 10-65% of outdoor levels. Analogous TLs for a G-type agent were 2-31% or 0.3-12% of outdoor levels assuming slow or moderate sorption. The relative effect of sorption was more pronounced for the longer plume and higher infiltration rates.

Infrared Study of CO2 Sorption over ?Molecular Basket? Sorbent Consisting of Polyethylenimine-Modified Mesoporous Molecular Sieve

DOE Office of Scientific and Technical Information (OSTI.GOV)

Overbury, Steven; Wang, Xiaoxing; Clark, Jason

2009-01-01

An infrared study has been conducted on CO{sub 2} sorption into nanoporous CO{sub 2} 'molecular basket' sorbents prepared by loading polyethylenimine (PEI) into mesoporous molecular sieve SBA-15. IR results from DRIFTS showed that a part of loaded PEI is anchored on the surface of SBA-15 through the interaction between amine groups and isolated surface silanol groups. Raising the temperature from 25 to 75 C increased the molecular flexibility of PEI loaded in the mesopore channels, which may partly contribute to the increase of CO{sub 2} sorption capacity at higher temperatures. CO{sub 2} sorption/desorption behavior studied by in situ transmission FTIRmore » showed that CO{sub 2} is sorbed on amine sites through the formation of alkylammonium carbamates and absorbed into the multiple layers of PEI located in mesopores of SBA-15. A new observation by in situ IR is that two broad IR bands emerged at 2450 and 2160 cm{sup -1} with CO{sub 2} flowing over PEI(50)/SBA-15, which could be attributed to chemically sorbed CO{sub 2} species on PEI molecules inside the mesopores of SBA-15. The intensities of these two bands also increased with increasing CO{sub 2} exposure time and with raising CO{sub 2} sorption temperature. By comparison of the CO{sub 2} sorption rate at 25 and 75 C in terms of differential IR intensities, it was found that CO{sub 2} sorption over molecular basket sorbent includes two rate regimes which suggest two distinct steps: rapid sorption on exposed outer surface layers of PEI (controlled by sorption affinity or thermodynamics) and the diffusion and sorption inside the bulk of multiple layers of PEI (controlled by diffusion). The sorption of CO{sub 2} is reversible at 75 C. Comparative IR examination of the CO{sub 2} sorption/desorption spectra on dry and prewetted PEI/SBA-15 sorbent revealed that presorbed water does not significantly affect the CO{sub 2}-amine interaction patterns.« less

Physicochemical properties related to long-term phosphorus retention by drinking-water treatment residuals.

PubMed

Makris, Konstantinos C; Harris, Willie G; O'Connor, George A; Obreza, Thomas A; Elliott, Herschel A

2005-06-01

Drinking-water treatment residuals (WTRs) are nonhazardous materials that can be obtained free-of-charge from drinking-water treatment plants to reduce soluble phosphorus (P) concentrations in poorly P sorbing soils. Phosphorus sorption capacities of WTRs can vary 1-2 orders of magnitude, on the basis of short-term equilibration times (up to 7 d), but studies dealing with long-term (weeks to months) P retention by WTRs are lacking. Properties that most affect long-term P sorption capacities are pertinent to the efficacy of WTRs as amendments to stabilize P in soils. This research addressed the long-term (up to 80 d) P sorption/desorption characteristics and kinetics for seven WTRs, including the influence of specific surface area (SSA), porosity, and total C content on the overall magnitude of P sorption by seven WTRs. The data confirm a strong but variable affinity for P by WTRs. Aluminum-based WTRs tended to have higher P sorption capacity than Fe-based WTRs. Phosphorus sorption with time was biphasic in nature for most samples and best fit to a second-order rate model. The P sorption rate dependency was strongly correlated with a hysteretic P desorption, consistent with kinetic limitations on P desorption from micropores. Oxalate-extractable Al + Fe concentrations of the WTRs did not effectively explain long-term (80 d) P sorption capacities of the WTRs. Micropore (CO2-based) SSAs were greater than BET-N2 SSAs for most WTRs, except those with the lowest (<80 g kg(-1)) total C content. There was a significant negative linear correlation between the total C content and the CO2/N2 SSA ratio. The data suggest that C in WTRs increases microporosity, but reduces P sorption per unit pore volume or surface area. Hence, variability in C content confounds direct relations among SSA, porosity, and P sorption. Total C, N2-based SSA, and CO2-based SSAs explained 82% of the variability in the long-term P sorption capacities of the WTRs. Prediction of long-term P sorption capacities for different WTRs may be achieved by taking into account the three proposed variables.

Kinetics of sorption of polyaromatic hydrocarbons onto granular activated carbon and Macronet hyper-cross-linked polymers (MN200).

PubMed

Valderrama, C; Cortina, J L; Farran, A; Gamisans, X; Lao, C

2007-06-01

Polymeric supports are presented as an alternative to granular activated carbon (GAC) for organic contaminant removal from groundwater using permeable reactive barriers (PRB). The search for suitable polymeric sorbents for hydrocarbon extraction from aqueous streams has prompted the synthesis of new resins incorporating new functionalities or modifying the polymer network properties that solve many of the existing problems. Between them, the new type of polymeric sorbents Macronet Hypersol containing a styrene-divinylbenzene macroporous hyperreticulated network has been evaluated. Because of their potential sorptive properties, tests were conducted to determine the feasibility of using them as a low-cost reactive material for groundwater applications. The present work describes the sorption of six polycyclic hydrocarbons (PAHs) from aqueous solution onto both Macronet polymeric sorbent MN200 and granular activated carbon. Batch experiments were performed to determine loading rates of a family of PAHs (naphthalene, fluorene, anthracene, acenaphthene, pyrene, and fluoranthene), from a simple two-rings PAH (naphthalene) up to a four-ring PAH (pyrene). The behavior of a non-functionalized Macronet support (MN200) was compared with the behavior of a recognized material, granular activated carbon (GAC). Analyses of the respective rate data with three theoretical models (pseudo-first- and pseudo-second-order reaction models and the Elovich model) were used to describe the PAH sorption kinetics. Sorption rate constants were determined by graphical analysis of the proposed models. The study showed that sorption systems followed a pseudo-first-order reaction model, although the pseudo-second-order reaction model provides an acceptable description of the sorption process. Graphical analysis showed that the sorption process with activated carbon is a more complex process than the one observed for hyper-cross-linked polymers (MN200). A simulation of the barrier thickness needed to treat a PAH-polluted plume showed that 0.1-1 m of sorption media is enough even for high water fluxes such as 0.1-2 m(3)/m(2)/day for both sorbents.

Application potential of grapefruit peel as dye sorbent: kinetics, equilibrium and mechanism of crystal violet adsorption.

PubMed

Saeed, Asma; Sharif, Mehwish; Iqbal, Muhammad

2010-07-15

This study reports the sorption of crystal violet (CV) dye by grapefruit peel (GFP), which has application potential in the remediation of dye-contaminated wastewaters using a solid waste generated by the citrus fruit juice industry. Batch adsorption of CV was conducted to evaluate the effect of initial pH, contact time, temperature, initial dye concentration, GFP adsorbent dose, and removal of the adsorbate CV dye from aqueous solution to understand the mechanism of sorption involved. Sorption equilibrium reached rapidly with 96% CV removal in 60 min. Fit of the sorption experimental data was tested on the pseudo-first and pseudo-second-order kinetics mathematical equations, which was noted to follow the pseudo-second-order kinetics better, with coefficient of correlation > or = 0.992. The equilibrium process was well described by the Langmuir isotherm model, with maximum sorption capacity of 254.16 mg g(-1). The GFP was regenerated using 1 M NaOH, with up to 98.25% recovery of CV and could be reused as a dye sorbent in repeated cycles. GFP was also shown to be highly effective in removing CV from aqueous solution in continuous-flow fixed-bed column reactors. The study shows that GFP has the potential of application as an efficient sorbent for the removal of CV from aqueous solutions. 2010 Elsevier B.V. All rights reserved.

Phosphate removal from aqueous solutions using raw and activated red mud and fly ash.

PubMed

Li, Yanzhong; Liu, Changjun; Luan, Zhaokun; Peng, Xianjia; Zhu, Chunlei; Chen, Zhaoyang; Zhang, Zhongguo; Fan, Jinghua; Jia, Zhiping

2006-09-01

The effect of acidification and heat treatment of raw red mud (RM) and fly ash (FA) on the sorption of phosphate was studied in parallel experiments. The result shows that a higher efficiency of phosphate removal was acquired by the activated samples than by the raw ones. The sample prepared by using the RM stirred with 0.25 M HCl for 2h (RM0.25), as well as another sample prepared by heating the RM at 700 degrees C for 2h (RM700), registered the maximum removal of phosphate (99% removal of phosphate). This occurred when they were used in the phosphate sorption studies conducted at pH 7.0 and 25 degrees C with the initial PO(4)(3-) concentration of 155 mg P/l. The FA samples treated in the same way described above can achieve 7.0 and 8.2 mg P/l phosphate removal for FA0.25 and FA700 respectively, corresponding to 45.2% and 52.9% removal. The activated materials performed higher phosphate removal over broader pH range compared with the raw ones. The influences of various factors, such as initial pH and initial phosphate concentration on the sorption capacity were also studied in batch equilibration technique. Solution pH significantly influenced the sorption. Each sample achieved the maximal removal of phosphate at pH 7.0. The amount of phosphate removal increased with the solute concentration. The Freundlich and Langmuir models were used to simulate the sorption equilibrium. The results indicate that the Langmuir model has a better correlation with the experimental data than the Freundlich model.

Metals sorption from aqueous solutions by Kluyveromyces marxianus: process optimization, equilibrium modeling and chemical characterization.

PubMed

Pal, Rama; Tewari, Saumyata; Rai, Jai P N

2009-10-01

The dead Kluyveromyces marxianus biomass, a fermentation industry waste, was used to explore its sorption potential for lead, mercury, arsenic, cobalt, and cadmium as a function of pH, biosorbent dosage, contact time, agitation speed, and initial metal concentration. The equilibrium data fitted the Langmuir model better for cobalt and cadmium, but Freundlich isotherm for all metals tested. At equilibrium, the maximum uptake capacity (Qmax) was highest for lead followed by mercury, arsenic, cobalt, and cadmium. The RL values ranged between 0-1, indicating favorable sorption of all test metals by the biosorbent. The maximum Kf value of Pb showed its efficient removal from the solution. However, multi-metal analysis depicted that sorption of all metals decreased except Pb. The potentiometric titration of biosorbent revealed the presence of functional groups viz. amines, carboxylic acids, phosphates, and sulfhydryl group involved in heavy metal sorption. The extent of contribution of functional groups and lipids to biosorption was in the order: carboxylic>lipids>amines>phosphates. Blocking of sulfhydryl group did not have any significant effect on metal sorption.

Kinetic characteristic of phenanthrene sorption in aged soil amended with biochar

NASA Astrophysics Data System (ADS)

Kim, Chanyang; Kim, Yong-Seong; Hyun, Seunghun

2015-04-01

Biochar has been recently highlighted as an amendment that affects yield of the crops by increasing pH, cation exchange capacity and water retention, and reduces the lability of contaminants by increasing sorption capacity in the soil system. Biochar's physico-chemical properties, high CEC, surfaces containing abundant micropores and macropores, and various types of functional groups, play important roles in enhancing sorption capacity of contaminants. Aging through a natural weathering process might change physico-chemical properties of biochar amended in soils, which can affect the sorption behavior of contaminants. Thus, in this study, the sorption characteristics of phenanthrene (PHE) on biochar-amended soils were studied with various types of chars depending on aging time. To do this, 1) soil was amended with sludge waste char (SWC), wood char (WC), and municipal waste char (MWC) during 0, 6, and 12 month. Chars were applied to soil at 1% and 2.5% (w/w) ratio. 2) Several batch kinetic and equilibrium studies were conducted. One-compartment first order and two-compartment first order model apportioning the fraction of fast and slow sorbing were selected for kinetic models. Where, qt is PHE concentration in biochar-amended soils at each time t, qeis PHE concentration in biochar-amended soils at equilibrium. ff is fastly sorbing fraction and (1-ff) is slowly sorbing fraction. k is sorption rate constant from one-compartment first order model, k1 and k2 are sorption rate constant from two-compartment first order model, t is time (hr). The equilibrium sorption data were fitted with Fruendlich and Langmuir equation. 3) Change in physico-chemical properties of biochar-amended soils was investigated with aging time. Batch equilibrium sorption results suggested that sorbed amount of PHE on WC was greater than SWC and MWC. The more char contents added to soil, the greater sorption capacity of PHE. Sorption equilibrium was reached after 4 hours and equilibrium pH ranged from 6.5 to 8.0. Sorption capacity was reduced with aging time. From kinetic results, two-compartment first order model was more suitable than one-compartment first order model. Fast sorption site of biochar-amended soils dominated total sorption process (i.e., Fraction of fast sorption site ranged from 0.55 to 0.96). Reduced sorption capacity with aging time could be attributed to changes in physico-chemical properties of biochar-amended soils (e.g., reduced pores and increased hydrophilic carboxyl and carbonyl functional groups). Verification is FI-IR and SSA. It is assumed that biochar is a suitable material for PHE contaminated soil in order to reduce the lability of PHE. However, aging effects would lessen biochar benefit for reducing the sorption capacity of PHE by forming hydrophilic functional group and reducing pores.

Sorption-desorption of imidacloprid onto a lacustrine Egyptian soil and its clay and humic acid fractions.

PubMed

Kandil, Mahrous M; El-Aswad, Ahmed F; Koskinen, William C

2015-01-01

Sorption-desorption of the insecticide imidacloprid 1-[(6-chloro-3-pyridinyl)-methyl]-N-nitro-2-imidazolidinimine onto a lacustrine sandy clay loam Egyptian soil and its clay and humic acid (HA) fractions was investigated in 24-h batch equilibrium experiments. Imidacloprid (IMDA) sorption-desorption isotherms onto the three sorbents were found to belong to a non-linear L-type and were best described by the Freundlich model. The value of the IMDA adsorption distribution coefficient, Kd(ads), varied according to its initial concentration and was ranged 40-84 for HA, 14-58 for clay and 1.85-4.15 for bulk soil. Freundlich sorption coefficient, Kf(ads), values were 63.0, 39.7 and 4.0 for HA, clay and bulk soil, respectively. The normalized soil Koc value for imidacloprid sorption was ∼800 indicating its slight mobility in soils. Nonlinear sorption isotherms were indicated by 1/n(ads) values <1 for all sorbents. Values of the hysteresis index (H) were <1, indicating the irreversibility of imidacloprid sorption process with all tested sorbents. Gibbs free energy (ΔG) values indicated a spontaneous and physicosorption process for IMDA and a more favorable sorption to HA than clay and soil. In conclusion, although the humic acid fraction showed the highest capacity and affinity for imidacloprid sorption, the clay fraction contributed to approximately 95% of soil-sorbed insecticide. Clay and humic acid fractions were found to be the major two factors controlling IMDA sorption in soils. The slight mobility of IMDA in soils and the hysteresis phenomenon associated with the irreversibility of its sorption onto, mainly, clay and organic matter of soils make its leachability unlikely to occur.

Micropore clogging by leachable pyrogenic organic carbon: A new perspective on sorption irreversibility and kinetics of hydrophobic organic contaminants to black carbon.

PubMed

Wang, Bingyu; Zhang, Wei; Li, Hui; Fu, Heyun; Qu, Xiaolei; Zhu, Dongqiang

2017-01-01

Black carbon (BC) plays a crucial role in sequestering hydrophobic organic contaminants in the environment. This study investigated key factors and mechanisms controlling nonideal sorption (e.g., sorption irreversibility and slow kinetics) of model hydrophobic organic contaminants (nitrobenzene, naphthalene, and atrazine) by rice-straw-derived BC. After removing the fraction of leachable pyrogenic organic carbon (LPyOC) (referring to composites of dissoluble non-condensed organic carbon and associated mineral components) with deionized water or 0.5 M NaOH, sorption of these sorbates to BC was enhanced. The sorption enhancement was positively correlated with sorbate molecular size in the order of atrazine > naphthalene > nitrobenzene. The removal of LPyOC also accelerated sorption kinetics and reduced sorption irreversibility. These observations were attributed to increased accessibility of BC micropores initially clogged by the LPyOC. Comparison of BC pore size distributions before and after atrazine sorption further suggested that the sorbate molecules preferred to access the micropores that were more open, and the micropore accessibility was enhanced by the removal of LPyOC. Consistently, the sorption of nitrobenzene and atrazine to template-synthesized mesoporous carbon (CMK3), a model sorbent with homogeneous pore structures, showed decreased kinetics, but increased irreversibility by impregnating sorbent pores with surface-grafted alkylamino groups and by subsequent loading of humic acid. These findings indicated an important and previously unrecognized role of LPyOC (i.e., micropore clogging) in the nonideal sorption of organic contaminants to BC. Copyright © 2016 Elsevier Ltd. All rights reserved.

Novel kinetic model of the removal of divalent heavy metal ions from aqueous solutions by natural clinoptilolite.

PubMed

Jovanovic, Mina; Rajic, Nevenka; Obradovic, Bojana

2012-09-30

Removal of heavy metal ions from aqueous solutions using zeolites is widely described by pseudo-second order kinetics although this model may not be valid under all conditions. In this work, we have extended approaches used for derivation of this model in order to develop a novel kinetic model that is related to the ion exchange mechanism underlying sorption of metal ions in zeolites. The novel model assumed two reversible steps, i.e. release of sodium ions from the zeolite lattice followed by bonding of the metal ion. The model was applied to experimental results of Cu(II) sorption by natural clinoptilolite-rich zeolitic tuff at different initial concentrations and temperatures and then validated by predictions of ion exchange kinetics of other divalent heavy metal ions (i.e. Mn(II), Zn(II) and Pb(II)). Model predictions were in excellent agreements with experimental data for all investigated systems. In regard to the proposed mechanism, modeling results implied that the sodium ion release rate was constant for all investigated metals while the overall rate was mainly determined by the rate of heavy metal ion bonding to the lattice. In addition, prediction capabilities of the novel model were demonstrated requiring one experimentally determined parameter, only. Copyright © 2012 Elsevier B.V. All rights reserved.

Sorption of Heterotrophic and Enteric Bacteria to Glass Surfaces in the Continuous Culture of River Water

PubMed Central

Hendricks, Charles W.

1974-01-01

A natural population of heterotrophic bacteria, including enterics, was observed to sorb to glass surfaces and multiply during the continuous culture of river water. An initial rate of attachment equivalent to a doubling time of about 2 h was observed with a corresponding increase in the suspended population. After 24 h both the sorbed and suspended populations stabilized with a mass doubling time approximating 100 h at a dilution rate of 0.012/h. On the basis of respiration and degradative enzymatic data, the sorbed microorganisms appeared to be somewhat more metabolically active than the organisms in suspension. PMID:4424694

Testosterone sorption and desorption: effects of soil particle size.

PubMed

Qi, Yong; Zhang, Tian C; Ren, Yongzheng

2014-08-30

Soils contain a wide range of particles of different diameters with different mobility during rainfall events. Effects of soil particles on sorption and desorption behaviors of steroid hormones have not been investigated. In this study, wet sieve washing and repeated sedimentation methods were used to fractionate the soils into five ranges. The sorption and desorption properties and related mechanisms of testosterone in batch reactors filled with fractionated soil particles were evaluated. Results of sorption and desorption kinetics indicate that small soil particles have higher sorption and lower desorption rates than that of big ones. Thermodynamic results show the sorption processes are spontaneous and exothermal. The sorption capacity ranks as clay>silt>sand, depending mainly on specific surface area and surface functional groups. The urea control test shows that hydrogen bonding contributes to testosterone sorption onto clay and silt but not on sand. Desorption tests indicate sorption is 36-65% irreversible from clay to sand. Clays have highest desorption hysteresis among these five soil fractions, indicating small particles like clays have less potential for desorption. The results provide indirect evidence on the colloid (clay)-facilitated transport of hormones (micro-pollutants) in soil environments. Copyright © 2014 Elsevier B.V. All rights reserved.

Sorption behavior of nano-TiO2 for the removal of selenium ions from aqueous solution.

PubMed

Zhang, Lei; Liu, Na; Yang, Lijun; Lin, Qing

2009-10-30

Titanium dioxide nanoparticles were employed for the sorption of selenium ions from aqueous solution. The process was studied in detail by varying the sorption time, pH, and temperature. The sorption was found to be fast, and to reach equilibrium basically within 5.0 min. The sorption has been optimized with respect to the pH, maximum sorption has been achieved from solution of pH 2-6. Sorbed Se(IV) and Se(VI) were desorbed with 2.0 mL 0.1 mol L(-1) NaOH. The kinetics and thermodynamics of the sorption of Se(IV) onto nano-TiO2 have been studied. The kinetic experimental data properly correlate with the second-order kinetic model (k(2)=0.69 g mg(-1) min(-1), 293 K). The overall rate process appears to be influenced by both boundary layer diffusion and intraparticle diffusion. The sorption data could be well interpreted by the Langmuir sorption isotherm. The mean energy of adsorption (14.46 kJ mol(-1)) was calculated from the Dubinin-Radushkevich (D-R) adsorption isotherm at room temperature. The thermodynamic parameters for the sorption were also determined, and the DeltaH(0) and DeltaG(0) values indicate exothermic behavior.

Sorption equilibria of ethanol on cork.

PubMed

Lequin, Sonia; Chassagne, David; Karbowiak, Thomas; Bellat, Jean-Pierre

2013-06-05

We report here for the first time a thermodynamic study of gaseous ethanol sorption on raw cork powder and plate. Our study aims at a better understanding of the reactivity of this material when used as a stopper under enological conditions, thus in close contact with a hydroethanolic solution, wine. Sorption−desorption isotherms were accurately measured by thermogravimetry at 298 K in a large range of relative pressures. Sorption enthalpies were determined by calorimetry as a function of loading. Sorption−desorption isotherms exhibit a hysteresis loop probably due to the swelling of the material and the absorption of ethanol. Surprisingly, the sorption enthalpy of ethanol becomes lower than the liquefaction enthalpy as the filling increases. This result could be attributed to the swelling of the material, which would generate endothermic effects. Sorption of SO₂ on cork containing ethanol was also studied. When the ethanol content in cork is 2 wt %, the amount of SO₂ sorbed is divided by 2. Thus, ethanol does not enhance the sorption rate for SO₂ but, on the contrary, decreases the SO₂ sorption activity onto cork, probably because of competitive sorption mechanisms.

Competitive sorption of atenolol, trimetoprim, carbamazepine and sulfamethoxazole in three soil types

NASA Astrophysics Data System (ADS)

Kočárek, Martin; Kodešová, Radka; Klement, Aleš; Golovko, Oksana; Fér, Miroslav; Nikodem, Antonín; Vondráčková, Lenka; Jakšík, Ondřej; Grabic, Roman

2016-04-01

Transport of human and veterinary pharmaceuticals in soils and consequent ground-water contamination are influenced by many factors, including compound sorption on soil particles and dissipation. Batch sorption experiment for 9 soils (3 soil types with 3 (Greyic Phaeozem on loess), 4 (Haplic Luvisol on loess) and 2 (Haplic Cambisol on gneiss) horizons) and mixture of 4 pharmaceuticals (atenolol, trimetoprim, carbamazepine and sulfamethoxazole) was performed to study competitive sorption of compounds in each soil sample. Sorption affinities and dissipation half-lives of all compounds in topsoils were previously studied by Kodešová et al. (2015 and 2016). Ten grams of dry soil was placed directly into the plastic centrifuge tubes and 20 ml of solution of a known pharmaceutical concentration was added. The same concentrations (0.5, 1, 2.5, 5 and 10 mg/l) were used for all compounds. Three replicates of each concentration were applied for each soil. Tube was shaken for 24 h using the shaking apparatus at 20 C. After shaking, the analyzed soil suspension was centrifuged for 10 min at 6,000 rotations per minute. The actual initial and final equilibrium pharmaceutical concentrations were measured using two-dimensional liquid chromatography-tandem mass spectrometry LC/LC-MS/MS using isotope dilution and internal standard methods. The pharmaceutical concentration adsorbed on soil particles was calculated using the initial and final (i.e. after incubation) pharmaceutical concentrations. The Freundlich equations were used to fit data points of the measured adsorption isotherms. In the case of carbamazepine (neutral form) and sulfamethoxazole (partly negatively charged) sorption affinity of compounds decrease with soil depth. On the other hand in the case of atenolol and trimethoprim (both positively charged) compound sorption affinity was not depth dependent. Data obtained for top soils were compared with sorption affinities for single compounds published by (Kodešová et al., 2015). While sorption affinities of atenolol, trimethoprim and carbamazepine due to compound competition decrease, sorption affinity of sulfamethoxazole increased. Pearson product moment correlation coefficient and p-value were used to evaluate relationships between sorption coefficients and soil properties. Kodešová, R., Grabic, R., Kočárek, M., Klement, A., Golovko, O., Fér, M., Nikodem, A., Jakšík, O. (2015a): Pharmaceuticals' sorptions relative to properties of thirteen different soils. Science of the Total Environment, 511, 435-443. Kodešová, R., Kočárek, M., Klement, A., Golovko, O., Koba, O., Fér, M., Nikodem, A., Vondráčková, L., Jakšík, O., Grabic, R. (2016): An analysis of the dissipation of pharmaceuticals under thirteen different soil conditions. Science of the Total Environment, 544, 369-381.

Comparative evaluation of sorption kinetics and isotherms of pyrene onto microplastics.

PubMed

Wang, Wenfeng; Wang, Jun

2018-02-01

Concerns regarding microplastics pollution and their potential to concentrate and transport organic contaminants in aquatic environments are growing in recent years. Sorption of organic chemicals by microplastics may affect the distribution and bioavailability of the chemicals. Here sorption process of pyrene (Pyr), a frequently encountered polycyclic aromatic hydrocarbon in aquatic environments, on three types of mass-produced plastic particles (high-density polyethylene (PE), polystyrene (PS) and polyvinylchloride (PVC)), was investigated by comparative analysis of different sorption kinetic and isotherm models. Optimum kinetic and isotherm models were predicted by the linear least-squares regression method. The pseudo-second-order kinetic model was more appropriate in describing the entire sorption process (R 2  > 0.99). Sorption rates of Pyr onto microplastics were mainly controlled by intraparticle diffusion. PE exhibited the highest affinity for Pyr, followed by PS and PVC. The sorption equilibrium data were best fitted to the Langmuir isotherm (R 2  > 0.99), indicating monolayer coverage of Pyr onto the microplastics. Copyright © 2017 Elsevier Ltd. All rights reserved.

Sorption Equilibria of Vapor Phase Organic Pollutants on Unsaturated Soils and Soil Minerals

DTIC Science & Technology

1990-04-01

Sorbent Characterization .. ........ .......... 6 a. Description of Inorganic Solids and Soils. .... ........ 6 b. Moisture Content...compounds (TCE and toluene) is compared for a cored depth profile obtained from an unsaturated soil and for simulated profiles using inorganic solids. The...Sorbent Characterization a. Description of Inorganic Solids and Soils Inorganic solids were used for initial sorption studies to develop experimental

Immobilization of Iodate and Iodide using Iron Oxides through Sorption and Co-precipitation at Hanford Site

NASA Astrophysics Data System (ADS)

Wang, G.; Qafoku, N. P.; Truex, M. J.; Strickland, C. E.; Freedman, V. L.

2017-12-01

Isotopes of iodine were generated during plutonium production at the U.S. Department of Energy (DOE) Hanford Site. The long half-life 129I generated during reactor operations has been released into the subsurface, resulting in several large plumes at the Hanford subsurface. We studied the interaction of iodate (IO3-) and iodide (I-) with Fe oxides. A series of batch experiments were conducted to investigate adsorption and co-precipitation of iodine species in the presence of a variety of Fe oxides, such as ferrihydrite, goethite, hematite and magnetite. In the sorption experiments, each Fe oxide was added to an artificial groundwater containing either iodate or iodide, and reacted at room temperature. The sorption batch experiments for each mineral were conducted at varied initial iodate or iodide concentrations under 3 different pH conditions (pH 5, 7, and 9). In the co-precipitation batch experiments, the initial Fe-mineral-forming solutions were prepared in artificial groundwater containing iodate or iodide. Our results indicate that both sorption and co-precipitation are viable mechanisms of the attenuation of the liquid phase iodine. Species Fe oxides could serve as hosts of iodate and iodide that are present at the Hanford subsurface.

The availability of diltiazem: a study on the sorption by intravenous delivery systems and on the stability of the drug.

PubMed

De Vroe, C; De Muynck, C; Remon, J P; Scheldewaert, R; Colardyn, F

1989-04-01

The stability and the sorption by intravenous delivery systems of the calcium antagonist diltiazem dissolved into either 5% dextrose or 0.9% sodium chloride solutions have been investigated, under conditions simulating current clinical practice. Static experiments showed an excellent stability and no sorption after 48 h. Dynamic experiments, at a perfusion rate of 20 mg h-1, showed no sorption of the drug by infusion fluid containers, burettes or administration sets. For end-line filters a temporary decrease of the recovered amount of diltiazem was observed but only with the 0.9% NaCl solution. It is concluded that the stability and the sorption of diltiazem offers no problem with regard to clinical efficacy.

Kinetics of Molybdenum Adsorption and Desorption in Soils.

PubMed

Sun, Wenguang; Selim, H Magdi

2018-05-01

Much uncertainty exists in mechanisms and kinetics controlling the adsorption and desorption of molybdenum (Mo) in the soil environment. To investigate the characteristics of Mo adsorption and desorption and predict Mo behavior in the vadose zone, kinetic batch experiments were performed using three soils: Webster loam, Windsor sand and Mahan sand. Adsorption isotherms for Mo were strongly nonlinear for all three soils. Strong kinetic adsorption of Mo by all soils was also observed, where the rate of retention was rapid initially and was followed by slow retention behavior with time. The time-dependent Mo sorption rate was not influenced when constant pH was maintained. Desorption or release results indicated that there were significant fractions of Mo that appeared to be irreversible or slowly reversibly sorbed by Windsor and Mahan. X-ray absorption near edge structure (XANES) analysis for Windsor and Mahan soils indicated that most of Mo had been bound to kaolinite, whereas Webster had similar XANES features to those of Mo sorbed to montmorillonite. A sequential extraction procedure provided evidence that a significant amount of Mo was irreversibly sorbed. A multireaction model (MRM) with nonlinear equilibrium and kinetic sorption parameters was used to describe the adsorption-desorption kinetics of Mo on soils. Our results demonstrated that a formulation of MRM with two sorption sites (equilibrium and reversible) successfully described Mo adsorption-desorption data for Webster loam, and an additional irreversible reaction phase was recommended to describe Mo desorption or release with time for Windsor and Mahan soils. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

Evaluation of Sorption Mechanism of Pb (II) and Ni (II) onto Pea (Pisum sativum) Peels.

PubMed

Haq, Atta Ul; Saeed, Muhammad; Anjum, Salma; Bokhari, Tanveer Hussain; Usman, Muhammad; Tubbsum, Saiqa

2017-07-01

The present study was carried out to know the sorption mechanism of Pb (II) and Ni (II) in aqueous solution using pea peels under the influence of sorbent dose, pH, temperature, initial metal ion concentration and contact time. SEM and FTIR were used for characterization of pea peels. The study showed that solution pH affects sorption process and the optimum pH for Pb (II) was 6.0 while for that of Ni (II) was 7.0. Pseudo-second order kinetic model was found to be the most suitable one to explain the kinetic data not only due to high value of R 2 (>0.99) but also due to the closeness of the experimental sorption capacity values to that of calculated sorption capacity values of pseudo second order kinetic model. It can be seen from the results that Freundlich isotherm explains well the equilibrium data (R 2 >0.99). Sorption capacity of pea peels was 140.84 and 32.36 for Pb (II) and Ni (II) mg g -1 respectively. The positive value of ΔH° and negative values of ΔG° suggest that sorption of Pb (II) and Ni (II) onto pea peels is an endothermic and spontaneous process respectively.

Thermodynamic, Kinetic, and Equilibrium Parameters for the Removal of Lead and Cadmium from Aqueous Solutions with Calcium Alginate Beads

PubMed Central

Alfaro-Cuevas-Villanueva, Ruth; Hidalgo-Vázquez, Aura Roxana; Cortés Penagos, Consuelo de Jesús; Cortés-Martínez, Raúl

2014-01-01

The sorption of cadmium (Cd) and lead (Pb) by calcium alginate beads (CAB) from aqueous solutions in batch systems was investigated. The kinetic and thermodynamic parameters, as well as the sorption capacities of CAB in each system at different temperatures, were evaluated. The rate of sorption for both metals was rapid in the first 10 minutes and reached a maximum in 50 minutes. Sorption kinetic data were fitted to Lagergren, pseudo-second-order and Elovich models and it was found that the second-order kinetic model describes these data for the two metals; comparing kinetic parameters for Cd and Pb sorption a higher kinetic rate (K 2) for Pb was observed, indicating that the interaction between lead cations and alginate beads was faster than for cadmium. Similarly, isotherm data were fitted to different models reported in literature and it was found that the Langmuir-Freundlich (L-F) and Dubinin-Radushkevich (D-R) models describe the isotherms in all cases. CAB sorption capacity for cadmium was 27.4 mg/g and 150.4 mg/g for lead, at 25°C. Sorption capacities of Cd and Pb increase as temperature rises. According to the thermodynamic parameters, the cadmium and lead adsorption process was spontaneous and endothermic. It was also found that pH has an important effect on the adsorption of these metals by CAB, as more were removed at pH values between 6 and 7. PMID:24587740

Sorption isotherm and kinetic modeling of aniline on Cr-bentonite.

PubMed

Zheng, Hong; Liu, Donghong; Zheng, Yan; Liang, Shuping; Liu, Zhe

2009-08-15

In this paper, the sorption characteristics of aniline on Cr-bentonite prepared using synthetic wastewater containing chromium was investigated in a batch system at 30 degrees C. The effects of relevant parameters, such as pH value of solution, adsorbent dosage and initial aniline concentration were examined. The experimental data were analyzed by the Langmuir and Freundlich, and Temkin models of sorption. The sorption isotherm data were fitted well to Langmuir isotherm and the monolayer sorption capacity was found to be 21.60 mg/g at 30 degrees C. Dubinin-Redushkevich (D-R) isotherm was applied to describe the nature of aniline uptake and it was found that it occurred chemically. The kinetic data obtained at different concentrations were analyzed using a pseudo first-order, pseudo second-order kinetic equation and intraparticle diffusion model. The experimental data fitted very well the pseudo second-order kinetic model. Intraparticle diffusion affects aniline uptake. The results indicate that there is significant potential for Cr-bentonite as an adsorbent material for aniline removal from aqueous solutions.

Ammonia-nitrogen sorptional properties of banana peels.

PubMed

Chen, Yunnen; Ding, Lichao; Fan, Jingbiao

2011-04-01

Using modified banana peel as a biosorbent to treat water containing ammonia-nitrogen (NH4(+)-N) was studied. Related parameters in the sorptional process, such as chemical modification, pH, and contact time were investigated. The experimental results showed that banana peel modified by 30% sodium hydroxide (NaOH) and mesothermal microwaves (NMBPs) can greatly improve the sorption removal for NH4(+)-N. The kinetics study revealed that the sorption behavior better fit the pseudo-second-order equation than the Lagergren first-order equation. Fourier transform infrared absorption spectrum analysis of banana peels and NMBPs before and after NH4(+)-N sorption revealed that the activity of hydroxyl groups at the surface of the banana peels was strengthened after modification, and nitrogenous groups appeared after biosorpting the NH4(+)-N. In the end, metallurgical wastewater containing a low concentration of NH4(+)-N was treated by NMBPs. The initial NH4(+)-N concentration of 138 mg/L was reduced to 13 mg/L in 25 minutes by 4 g/L NMBPs at pH 10.

Enhancement of the bentonite sorption properties.

PubMed

Mockovciaková, Annamária; Orolínová, Zuzana; Skvarla, Jirí

2010-08-15

The almost monomineral fraction of bentonite rock-montmorillonite was modified by magnetic particles to enhance its sorption properties. The method of clay modification consists in the precipitation of magnetic nanoparticles, often used in preparing of ferrofluids, on the surface of clay. The influence of the synthesis temperature (20 and 85 degrees C) and the weight ratio of bentonite/iron oxides (1:1 and 5:1) on the composite materials properties were investigated. The obtained materials were characterized by the X-ray diffraction method and Mössbauer spectroscopy. Changes in the surface and pore properties of the magnetic composites were studied by the low nitrogen adsorption method and the electrokinetic measurements. The natural bentonite and magnetic composites were used in sorption experiments. The sorption of toxic metals (zinc, cadmium and nickel) from the model solutions was well described by the linearized Langmuir and Freundlich sorption model. The results show that the magnetic bentonite is better sorbent than the unmodified bentonite if the initial concentration of studied metals is very low. Copyright 2010 Elsevier B.V. All rights reserved.

The role of sorption processes in the removal of pharmaceuticals by fungal treatment of wastewater.

PubMed

Lucas, D; Castellet-Rovira, F; Villagrasa, M; Badia-Fabregat, M; Barceló, D; Vicent, T; Caminal, G; Sarrà, M; Rodríguez-Mozaz, S

2018-01-01

The contribution of the sorption processes in the elimination of pharmaceuticals (PhACs) during the fungal treatment of wastewater has been evaluated in this work. The sorption of four PhACs (carbamazepine, diclofenac, iopromide and venlafaxine) by 6 different fungi was first evaluated in batch experiments. Concentrations of PhACs in both liquid and solid (biomass) matrices from the fungal treatment were measured. Contribution of the sorption to the total removal of pollutants ranged between 3% and 13% in relation to the initial amount. The sorption of 47 PhACs in fungi was also evaluated in a fungal treatment performed in 26days in a continuous bioreactor treating wastewater from a veterinary hospital. PhACs levels measured in the fungal biomass were similar to those detected in conventional wastewater treatment (WWTP) sludge. This may suggest the necessity of manage fungal biomass as waste in the same manner that the WWTP sludge is managed. Copyright © 2017 Elsevier B.V. All rights reserved.

Sorption of Perfluorinated Compounds onto different types of sewage sludge and assessment of its importance during wastewater treatment.

PubMed

Arvaniti, Olga S; Andersen, Henrik R; Thomaidis, Nikolaos S; Stasinakis, Athanasios S

2014-09-01

The distribution coefficient (Kd) and the organic carbon distribution coefficient (KOC) were determined for four Perfluorinated Compounds (PFCs) to three different types of sludge taken from a conventional Sewage Treatment Plant (STP). Batch experiments were performed in six different environmental relevant concentrations (200ngL(-1)to 5μgL(-1)) containing 1gL(-1) sludge. Kd values ranged from 330 to 6015, 329 to 17432 and 162 to 11770Lkg(-1) for primary, secondary and digested sludge, respectively. The effects of solution's pH, ionic strength and cation types on PFCs sorption were also evaluated. Sorption capacities of PFCs significantly decreased with increased pH values from 6 to 8. Furthermore, the divalent cation (Ca(2+)) enhanced PFCs sorption to a higher degree in comparison with the monovalent cation (Na(+)) at the same ionic strength. The obtained Kd values were applied to estimate the sorbed fractions of each PFC in different stages of a typical STP and to calculate their removal through treated wastewater and sludge. In primary settling tank, the predicted sorbed fractions ranged from 3% for Perfluorooctanoic Acid (PFOA) to 55% for Perfluoroundecanoic acid (PFUdA), while in activated sludge tank and anaerobic digester sorption was more than 50% for all target compounds. Almost 86% of initial PFOA load is expected to be detected in treated wastewater; while Perfluorodecanoic acid (PFDA), PFUdA and Perfluorooctanesulfonate (PFOS) can be significantly removed (>49%) via sorption to primary and excess secondary sludge. In anaerobic digester, the major part (>76%) of target PFCs is expected to be sorbed to sludge, while almost 3% of initial PFOA load will be detected in sludge leachates. Copyright © 2014 Elsevier Ltd. All rights reserved.

Phosphorus sorption-desorption and effects of temperature, pH and salinity on phosphorus sorption in marsh soils from coastal wetlands with different flooding conditions.

PubMed

Bai, Junhong; Ye, Xiaofei; Jia, Jia; Zhang, Guangliang; Zhao, Qingqing; Cui, Baoshan; Liu, Xinhui

2017-12-01

Wetland soils act as a sink or source of phosphorus (P) to the overlaying water due to phosphorus sorption-desorption processes. Litter information is available on sorption and desorption behaviors of phosphorus in coastal wetlands with different flooding conditions. Laboratory experiments were conducted to investigate phosphorus sorption-desorption processes, fractions of adsorbed phosphorus, and the effects of salinity, pH and temperature on phosphorus sorption on soils in tidal-flooding wetlands (TW), freshwater-flooding wetlands (FW) and seasonal-flooding wetlands (SW) in the Yellow River Delta. Our results showed that the freshly adsorbed phosphorus dominantly exists in Occluded-P and Fe/AlP and their percentages increased with increasing phosphorus adsorbed. Phosphorus sorption isotherms could be better described by the modified Langmuir model than by the modified Freundlich model. A binomial equation could be properly used to describe the effects of salinity, pH, and temperature on phosphorus sorption. Phosphorus sorption generally increased with increasing salinity, pH, and temperature at lower ranges, while decreased in excess of some threshold values. The maximum phosphorus sorption capacity (Q max ) was larger for FW soils (256 mg/kg) compared with TW (218 mg/kg) and SW soils (235 mg/kg) (p < 0.05). The percentage of phosphorus desorption (P des ) in the FW soils (7.5-63.5%) was much lower than those in TW (27.7-124.9%) and SW soils (19.2-108.5%). The initial soil organic matter, pH and the exchangeable Al, Fe and Cd contents were important factors influencing P sorption and desorption. The findings of this study indicate that freshwater restoration can contribute to controlling the eutrophication status of water bodies through increasing P sorption. Copyright © 2017 Elsevier Ltd. All rights reserved.

Sludge-Derived Biochar for Arsenic(III) Immobilization: Effects of Solution Chemistry on Sorption Behavior.

PubMed

Zhang, Weihua; Zheng, Juan; Zheng, Pingping; Tsang, Daniel C W; Qiu, Rongliang

2015-07-01

Recycling sewage sludge by pyrolysis has attracted increasing attention for pollutant removal from wastewater and soils. This study scrutinized As(III) sorption behavior on sludge-derived biochar (SDBC) under different pyrolysis conditions and solution chemistry. The SDBC pyrolyzed at a higher temperature showed a lower As(III) sorption capacity and increasingly nonlinear isotherm due to loss of surface sites and deoxygenation-dehydrogenation. The Langmuir sorption capacity on SDBC (3.08-6.04 mg g) was comparable to other waste-derived sorbents, with the highest As(III) sorption on SDBC pyrolyzed at 400°C for 2 h. The As(III) sorption kinetics best fit with the pseudo-second-order equation, thus suggesting the significance of the availability of surface sites and initial concentration. Sorption of As(III) was faster than that of Cr(VI) but slower than that of Pb(II), which was attributed to their differences in molar volume (correlated to diffusion coefficients) and sorption mechanisms. The X-ray photoelectron spectra revealed an increase of oxide oxygen (O) with a decrease of sorbed water, indicative of ligand exchange with hydroxyl groups on SDBC surfaces. The As(III) sorption was not pH dependent in acidic-neutral range (pH < 8) due to the buffering capacity and surface characteristics of the SDBC; however, sorption was promoted by increasing pH in the alkaline range (pH > 8) because of As(III) speciation in solution. An increasing ionic strength (0.001-0.1 mol L) facilitated As(III) sorption, indicating the predominance of ligand exchange over electrostatic interactions, while high concentrations (0.1 mol L) of competing anions (fluoride, sulfate, carbonate, and phosphate) inhibited As(III) sorption. These results suggest that SDBC is applicable for As(III) immobilization in most environmentally relevant conditions. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

Modeling the rate-controlled sorption of hexavalent chromium

USGS Publications Warehouse

Grove, D.B.; Stollenwerk, K.G.

1985-01-01

Sorption of chromium VI on the iron-oxide- and hydroxide-coated surface of alluvial material was numerically simulated with rate-controlled reactions. Reaction kinetics and diffusional processes, in the form of film, pore, and particle diffusion, were simulated and compared with experimental results. The use of empirically calculated rate coefficients for diffusion through the reacting surface was found to simulate experimental data; pore or particle diffusion is believed to be a possible rate-controlling mechanism. The use of rate equations to predict conservative transport and rate- and local-equilibrium-controlled reactions was shown to be feasible.

Arsenic sorption to nanoparticulate mackinawite (FeS): An examination of phosphate competition.

PubMed

Niazi, Nabeel Khan; Burton, Edward D

2016-11-01

Nanoparticulate mackinawite (FeS) can be an important host-phase for arsenic (As) in sulfidic, subsurface environments. Although not previously investigated, phosphate (PO 4 3- ) may compete with As for available sorption sites on FeS, thereby enhancing As mobility in FeS-bearing soils, sediments and groundwater systems. In this study, we examine the effect of PO 4 3- on sorption of arsenate (As(V)) and arsenite (As(III)) to nanoparticulate FeS at pH 6, 7 and 9. Results show that PO 4 3- (at 0.01-1.0 mM P) did not significantly affect sorption of either As(V) or As(III) to nanoparticulate FeS at initial aqueous As concentrations ranging from 0.01 to 1.0 mM. At pH 9 and 7, sorption of both As(III) and As(V) to nanoparticulate FeS was similar, with distribution coefficient (K d ) values spanning 0.76-15 L g -1 (which corresponds to removal of 87-98% of initial aqueous As(III) and As(V) concentrations). Conversely, at pH 6, the sorption of As(III) was characterized by substantially higher K d values (6.3-93.4 L g -1 ) than those for As(V) (K d  = 0.21-0.96 L g -1 ). Arsenic K-edge X-ray absorption near edge structure (XANES) spectroscopy indicated that up to 52% of the added As(V) was reduced to As(III) in As(V) sorption experiments, as well as the formation of minor amounts of an As 2 S 3 -like species. In As(III) sorption experiments, XANES spectroscopy also demonstrated the formation of an As 2 S 3 -like species and the partial oxidation of As(III) to As(V) (despite the strictly O 2 -free experimental conditions). Overall, the XANES data indicate that As sorption to nanoparticulate FeS involves several redox transformations and various sorbed species, which display a complex dependency on pH and As loading but that are not influenced by the co-occurrence of PO 4 3- . This study shows that nanoparticulate FeS can help to immobilize As(III) and As(V) in sulfidic subsurface environments where As co-exists with PO 4 3- . Copyright © 2016 Elsevier Ltd. All rights reserved.

Temperature and chemical composition controls on sorption of DOC to iron hydroxides under dynamic flow conditions

NASA Astrophysics Data System (ADS)

Daugherty, E.; Lobo, G.; Pallud, C. E.; Borch, T.

2017-12-01

Mineral-organic associations contribute substantially to the long-term preservation of soil organic matter (SOM) and carbon sequestration. Iron-organic associations are especially important because iron (hydr)oxide minerals and surface coatings are prevalent and effective sorbents of SOM. While mineral-organic associations, and iron-organic associations in particular have been studied extensively, it remains unclear how the abiotic interactions between these soil components will be affected by shifting climate. Will DOM adsorption increase or decrease with rising temperature? Does the adsorption response to temperature depend on the type of DOM? To answer these questions, we investigated the impacts of temperature (7, 25, and 45˚C) and dissolved organic matter (DOM) type on DOM sorption to ferrihydrite-coated sand in a fixed bed column at neutral pH. Breakthrough curves of the standard humic substances at 25˚C indicated that humic acids were in general retained less than fulvic acids. Response to temperature varied from no effect to a marked increase in the quantity adsorbed. Modeling of DOM breakthrough curves using the advection-diffusion equation with a linear adsorption isotherm showed that the equilibrium distribution coefficient increased over time, with retardation factors increasing 4 to 10 times for every simulation. This suggests that the DOM adsorbed to the ferrihydrite-coated sand acts as a sorbent that is 4 to 10 times more powerful than the coated sand alone. Differences in breakthrough due to DOM type and temperature became less pronounced at slower flow rates, and breakthrough occurred at nearly half as many pore volumes at a flow rate of 0.01 mL min-1 vs. 0.05 mL min-1. These results suggest DOM adsorption was diffusion controlled at low flow rates and kinetically controlled at high flow rates, which may explain the increased temperature sensitivity at high flow rates. Analyses to determine adsorptive fractionation are ongoing, but preliminary data suggest that aromatic moieties may be selectively retained during initial contact between DOM and ferrihydrite. Our results suggest that water flow rate is likely to play an important role in determining the relative effects of temperature on DOM sorption to iron minerals.

Studies of anions sorption on natural zeolites.

PubMed

Barczyk, K; Mozgawa, W; Król, M

2014-12-10

This work presents results of FT-IR spectroscopic studies of anions-chromate, phosphate and arsenate - sorbed from aqueous solutions (different concentrations of anions) on zeolites. The sorption has been conducted on natural zeolites from different structural groups, i.e. chabazite, mordenite, ferrierite and clinoptilolite. The Na-forms of sorbents were exchanged with hexadecyltrimethylammonium cations (HDTMA(+)) and organo-zeolites were obtained. External cation exchange capacities (ECEC) of organo-zeolites were measured. Their values are 17mmol/100g for chabazite, 4mmol/100g for mordenite and ferrierite and 10mmol/100g for clinoptilolite. The used initial inputs of HDTMA correspond to 100% and 200% ECEC of the minerals. Organo-modificated sorbents were subsequently used for immobilization of mentioned anions. It was proven that aforementioned anions' sorption causes changes in IR spectra of the HDTMA-zeolites. These alterations are dependent on the kind of anions that were sorbed. In all cases, variations are due to bands corresponding to the characteristic Si-O(Si,Al) vibrations (occurring in alumino- and silicooxygen tetrahedra building spatial framework of zeolites). Alkylammonium surfactant vibrations have also been observed. Systematic changes in the spectra connected with the anion concentration in the initial solution have been revealed. The amounts of sorbed CrO4(2-), AsO4(3-) and PO4(3-) ions were calculated from the difference between their concentrations in solutions before (initial concentration) and after (equilibrium concentration) sorption experiments. Concentrations of anions were determined by spectrophotometric method. Copyright © 2014 Elsevier B.V. All rights reserved.

Fundamental aspects related to batch and fixed-bed sulfate sorption by the macroporous type 1 strong base ion exchange resin Purolite A500.

PubMed

Guimarães, Damaris; Leão, Versiane A

2014-12-01

Acid mine drainage is a natural process occurring when sulfide minerals such as pyrite are exposed to water and oxygen. The bacterially catalyzed oxidation of pyrite is particularly common in coal mining operations and usually results in a low-pH water polluted with toxic metals and sulfate. Although high sulfate concentrations can be reduced by gypsum precipitation, removing lower concentrations (below 1200 mg/L) remains a challenge. Therefore, this work sought to investigate the application of ion exchange resins for sulfate sorption. The macroporous type 1 strong base IX resin Purolite A500 was selected for bath and fixed-bed sorption experiments using synthetic sulfate solutions. Equilibrium experiments showed that sulfate loading on the resin can be described by the Langmuir isotherm with a maximum uptake of 59 mg mL-resin(-1). The enthalpy of sorption was determined as +2.83 kJ mol(-1), implying an endothermic physisorption process that occurred with decreasing entropy (-15.5 J mol(-1).K(-1)). Fixed-bed experiments were performed at different bed depths, flow rates, and initial sulfate concentrations. The Miura and Hashimoto model predicted a maximum bed loading of 25-30 g L-bed(-1) and indicated that both film diffusion (3.2 × 10(-3) cm s(-1) to 22.6 × 10(-3) cm s(-1)) and surface diffusion (1.46 × 10(-7) cm(2) s(-1) to 5.64 × 10(-7) cm(2) s(-1)) resistances control the sorption process. It was shown that IX resins are an alternative for the removal of sulfate from mine waters; they ensure very low residual concentrations, particularly in effluents where the sulfate concentration is below the gypsum solubility threshold. Copyright © 2014 Elsevier Ltd. All rights reserved.

The fate of bisphenol A, 4-tert-octylphenol and 4-nonylphenol leached from plastic debris into marine water--experimental studies on biodegradation and sorption on suspended particulate matter and nano-TiO2.

PubMed

Staniszewska, Marta; Graca, Bożena; Nehring, Iga

2016-02-01

Experiments were carried out, the aim of which was to determine the leaching rates for bisphenol A (4,4'-(propane-2,2-diyl)diphenol - BPA), 4-tert-octylphenol (OP), 4-nonylphenol (NP) from polycarbonate and recycled tyre granules into the seawater. Additionally biodegradation, sorption on marine suspended particulate matter and sorption on various types of nano-TiO2 of BPA, OP, NP were studied. Experiments were carried out on plastics at various stages of degradation. The conducted experiment confirmed the flux of BPA, OP and NP from the studied plastics into seawater. The initial photodegradation of the plastic had a significant influence on the amount of the studied components released into water. During the first days of the experiment leaching was weaker from aged materials. After 60 days leaching of BPA and OP was higher for aged plastic compared to unaged. On average, suspension adsorbed OP, BPA and NP from seawater at respective levels of 37%, 75% and 100%. On the other hand, during biodegradation on average 25%, 9% and 2% of OP, BPA and NP respectively are removed from water. Nano-TiO2 of 21 nm pore size diameter adsorbed all the compounds more strongly than nano-TiO2 of 15 nm pores sized coated with Al and stearic acid. The strongest sorption (100%) on different types of nano-TiO2 was that of the most hydrophobic and more linear structured NP with just one phenol group. The weakest sorption was observed in the case of BPA, which is the least hydrophobic, and characterized by higher compared to NP and OP steric hindrance and electrostatic repulsion. Copyright © 2015 Elsevier Ltd. All rights reserved.

Moisture Sorption-desorption Characteristics and the Corresponding Thermodynamic Properties of Carvedilol Phosphate.

PubMed

Allada, Ravikiran; Maruthapillai, Arthanareeswari; Palanisamy, Kamaraj; Chappa, Praveen

2017-01-01

Carvedilol phosphate (CDP) is a nonselective beta-blocker used for the treatment of heart failures and hypertension. In this work, moisture sorption-desorption characteristics and thermodynamic properties of CDP have been investigated. The isotherms were determined using dynamic vapor sorption analyzer at different humidity conditions (0%-90% relative humidity) and three pharmaceutically relevant temperatures (20°C, 30°C, and 40°C). The experimental sorption data determined were fitted to various models, namely, Brunauer-Emmett-Teller; Guggenheim-Anderson-De Boer (GAB); Peleg; and modified GAB. Isosteric heats of sorption were evaluated through the direct use of sorption isotherms by means of the Clausius-Clapeyron equation. The sorption model parameters were determined from the experimental sorption data using nonlinear regression analysis, and mean relative percentage deviation (P), correlation (Correl), root mean square error, and model efficiency were considered as the criteria to select the best fit model. The sorption-desorption isotherms have sigmoidal shape - confirming to Type II isotherms. Based on the statistical data analysis, modified GAB model was found to be more adequate to explain sorption characteristics of CDP. It is noted that the rate of adsorption and desorption is specific to the temperature at which it was being studied. It is observed that isosteric heat of sorption decreased with increasing equilibrium moisture content. The calculation of the thermodynamic properties was further used to draw an understanding of the properties of water and energy requirements associated with the sorption behavior. The sorption-desorption data and the set of equations are useful in the simulation of processing, handling, and storage of CDP and further behavior during manufacture and storage of CDP formulations.

Adsorptive behaviour of mercury on algal biomass: competition with divalent cations and organic compounds.

PubMed

Carro, Leticia; Barriada, José L; Herrero, Roberto; Sastre de Vicente, Manuel E

2011-08-15

Biosorption processes constitute an effective technique for mercury elimination. Sorption properties of native and acid-treated Sargassum muticum have been studied. Effect of pH, initial mercury concentration and contact time studies provided fundamental information about the sorption process. This information was used as the reference values to analyse mercury sorption under competition conditions. Saline effect has shown little influence in sorption, when only electrostatic modifications took place upon salt addition. On the contrary, if mercury speciation dramatically changed owing to the addition of an electrolyte, such as in the case of chloride salt, very large modifications in mercury sorption were observed. Competition with other divalent cations or organic compounds has shown little or none effect on mercury, indicating that a different mechanism is taking place during the removal of these pollutants. Finally, continuous flow experiments have clearly shown that a reduction process is also taking place during mercury removal. This fact is not obvious to elucidate under batch sorption experiments. Scanning Electron Microscopy analysis of the surface of the materials show deposits of mercury(I) and metallic mercury which is indicative of the reduction process proposed. Copyright © 2011 Elsevier B.V. All rights reserved.

Sorption of small molecules in polymeric media

NASA Astrophysics Data System (ADS)

Camboni, Federico; Sokolov, Igor M.

2016-12-01

We discuss the sorption of penetrant molecules from the gas phase by a polymeric medium within a model which is very close in spirit to the dual sorption mode model: the penetrant molecules are partly dissolved within the polymeric matrix, partly fill the preexisting voids. The only difference with the initial dual sorption mode situation is the assumption that the two populations of molecules are in equilibrium with each other. Applying basic thermodynamics principles we obtain the dependence of the penetrant concentration on the pressure in the gas phase and find that this is expressed via the Lambert W-function, a different functional form than the one proposed by dual sorption mode model. The Lambert-like isotherms appear universally at low and moderate pressures and originate from the assumption that the internal energy in a polymer-penetrant-void ternary mixture is (in the lowest order) a bilinear form in the concentrations of the three components. Fitting the existing data shows that in the domain of parameters where the dual sorption mode model is typically applied, the Lambert function, which describes the same behavior as the one proposed by the gas-polymer matrix model, fits the data equally well.

Moisture sorption characteristics of freeze-dried human platelets*

PubMed Central

Xu, Meng-jie; Chen, Guang-ming; Fan, Ju-li; Liu, Jin-hui; Xu, Xian-guo; Zhang, Shao-zhi

2011-01-01

Freeze-drying is a promising method for a long-term storage of human platelets. The moisture sorption characteristics of freeze-dried human platelets (FDHPs) were studied in this paper. The moisture sorption isotherms of FDHPs and freeze-dried lyophilization buffer (FDLB) were measured at 4, 25, and 37 °C. The experimental data were fitted to Brunauer-Emmett-Teller (BET) and Guggenheim-Anderson-de Boer (GAB) equations. There were no significant statistical differences (P>0.05) between the sorption characteristics of FDHPs and FDLB at 4 and 25 °C, while FDHPs absorbed more water at 37 °C. The net isosteric heat of sorption was derived. The heat for FDHPs showed an abnormal negative value at low moisture contents when 25 and 37 °C data were used. Dynamic sorption experiments were carried out at 25 °C with environmental water activity controlled at 0.75, 0.85, and 0.90. The moisture diffusion coefficient was fitted to be 8.24×10−12 m2/s when experimental data at initial time were used. These results would be helpful in choosing prehydration and storage condition for FDHPs. PMID:21370506

SORPTION KINETICS OF PAHS IN METHANOL-WATER SYSTEMS

EPA Science Inventory

The objectives of this study were to evaluate the relationships between the equilibrium sorption constant (Kp), the first-order desorption rate coefficient (k2), and the volumetric fraction of water miscible solvent (fc); and to utilize SPARC-calculated (SPARC Performs Automatic ...

Biotransformation and sorption of trace organic compounds in biological nutrient removal treatment systems.

PubMed

Lakshminarasimman, Narasimman; Quiñones, Oscar; Vanderford, Brett J; Campo-Moreno, Pablo; Dickenson, Eric V; McAvoy, Drew C

2018-05-28

This study determined biotransformation rates (k bio ) and sorption-distribution coefficients (K d ) for a select group of trace organic compounds (TOrCs) in anaerobic, anoxic, and aerobic activated sludge collected from two different biological nutrient removal (BNR) treatment systems located in Nevada (NV) and Ohio (OH) in the United States (US). The NV and OH facilities operated at solids retention times (SRTs) of 8 and 23 days, respectively. Using microwave-assisted extraction, the biotransformation rates of the chosen TOrCs were measured in the total mixed liquor. Sulfamethoxazole, trimethoprim, and atenolol biotransformed in all three redox regimes irrespective of the activated sludge source. The biotransformation of N, N-diethyl-3-methylbenzamide (DEET), triclosan, and benzotriazole was observed in aerobic activated sludge from both treatment plants; however, anoxic biotransformation of these three compounds was seen only in anoxic activated sludge from NV. Carbamazepine was recalcitrant in all three redox regimes and both sources of activated sludge. Atenolol and DEET had greater biotransformation rates in activated sludge with a higher SRT (23 days), while trimethoprim had a higher biotransformation rate in activated sludge with a lower SRT (8 days). The remaining compounds did not show any dependence on SRT. Lyophilized, heat inactivated sludge solids were used to determine the sorption-distribution coefficients. Triclosan was the most sorptive compound followed by carbamazepine, sulfamethoxazole, DEET, and benzotriazole. The sorption-distribution coefficients were similar across redox conditions and sludge sources. The biotransformation rates and sorption-distribution coefficients determined in this study can be used to improve fate prediction of the target TOrCs in BNR treatment systems. Copyright © 2018. Published by Elsevier B.V.

Nitrogen transport and transformations in a shallow aquifer receiving wastewater discharge: A mass balance approach

USGS Publications Warehouse

Desimone, Leslie A.; Howes, Brian L.

1998-01-01

Nitrogen transport and transformations were followed over the initial 3 years of development of a plume of wastewater-contaminated groundwater in Cape Cod, Massachusetts. Ammonification and nitrification in the unsaturated zone and ammonium sorption in the saturated zone were predominant, while loss of fixed nitrogen through denitrification was minor. The major effect of transport was the oxidation of discharged organic and inorganic forms to nitrate, which was the dominant nitrogen form in transit to receiving systems. Ammonification and nitrification in the unsaturated zone transformed 16–19% and 50–70%, respectively, of the total nitrogen mass discharged to the land surface during the study but did not attenuate the nitrogen loading. Nitrification in the unsaturated zone also contributed to pH decrease of 2 standard units and to an N2O increase (46–660 µg N/L in the plume). Other processes in the unsaturated zone had little net effect: Ammonium sorption removed <1% of the total discharged nitrogen mass; filtering of particulate organic nitrogen was less than 3%; ammonium and nitrate assimilation was less than 6%; and ammonia volatilization was less than 0.25%. In the saturated zone a central zone of anoxic groundwater (DO ≤ 0.05 mg/L) was first detected 17 months after effluent discharge to the aquifer began, which expanded at about the groundwater-flow velocity. Although nitrate was dominant at the water table, the low, carbon-limited rates of denitrification in the anoxic zone (3.0–9.6 (ng N/cm3)/d) reduced only about 2% of the recharged nitrogen mass to N2. In contrast, ammonium sorption in the saturated zone removed about 16% of the recharged nitrogen mass from the groundwater. Ammonium sorption was primarily limited to anoxic zone, where nitrification was prevented, and was best described by a Langmuir isotherm in which effluent ionic concentrations were simulated. The initial nitrogen load discharged from the groundwater system may depend largely on the growth and stability of the sorbed ammonium pool, which in turn depends on effluent-loading practices, subsurface microbial processes, and saturation of available exchange sites.

Kinetic, equilibrium and thermodynamic studies on sorption of uranium and thorium from aqueous solutions by a selective impregnated resin containing carminic acid.

PubMed

Rahmani-Sani, Abolfazl; Hosseini-Bandegharaei, Ahmad; Hosseini, Seyyed-Hossein; Kharghani, Keivan; Zarei, Hossein; Rastegar, Ayoob

2015-04-09

In this work, the removal of uranium and thorium ions from aqueous solutions was studied by solid-liquid extraction using an advantageous extractant-impregnated resin (EIR) prepared by loading carminic acid (CA) onto Amberlite XAD-16 resin beads. Batch sorption experiments using CA/XAD-16 beads for the removal of U(VI) and Th(IV) ions were carried out as a function of several parameters, like equilibration time, metal ion concentration, etc. The equilibrium data obtained from the sorption experiments were adjusted to the Langmuir isotherm model and the calculated maximum sorption capacities in terms of monolayer sorption were in agreement with those obtained from the experiments. The experimental data on the sorption behavior of both metal ions onto the EIR beads fitted well in both Bangham and intra-particle diffusion kinetic models, indicating that the intra-particle diffusion is the rate-controlling step. The thermodynamic studies at different temperatures revealed the feasibility and the spontaneous nature of the sorption process for both uranium and thorium ions. Copyright © 2014 Elsevier B.V. All rights reserved.

Cadmium mobility in sediments and soils from a coal mining area on Tibagi River watershed: environmental risk assessment.

PubMed

Galunin, Evgeny; Ferreti, Jeferson; Zapelini, Iago; Vieira, Isadora; Ricardo Teixeira Tarley, César; Abrão, Taufik; Santos, Maria Josefa

2014-01-30

The risk of cadmium contamination in the Tibagi River watershed (Parana State, Brazil) affected by past coal mining activities was assessed through sorption-desorption modeling for sediment and soil samples. The acidic character of the samples resulted in more competition between the cadmium ions and protons, thereby influencing the cadmium sorption-desorption. The sorption isotherms were fitted to the Langmuir and Freundlich single models and to the dual-site Langmuir-Freundlich (or Sips) model. The single-site models indicated a low-energy character of sorption sites on the sample sorption sites, whereas the dual-site model explained the availability of higher-affinity and lower-affinity non-specific sites. The correlation of the sorption and desorption constants with the physicochemical and mineralogical characteristics of the samples showed that the cadmium sorption behavior was significantly affected by the pH, point of zero charge, and also by the magnesium, aluminum, calcium and manganese amounts. Besides, the desorption rate and hysteresis index suggested a high risk of cadmium mobilization along the Tibagi River basin. Copyright © 2013 Elsevier B.V. All rights reserved.

Competitive sorption of persistent organic pollutants onto microplastics in the marine environment.

PubMed

Bakir, Adil; Rowland, Steven J; Thompson, Richard C

2012-12-01

Plastics are known to sorb persistent organic pollutants from seawater. However, studies to quantify sorption rates have only considered the affinity of chemicals in isolation, unlike the conditions in the environment where contaminants are present as complex mixtures. Here we examine whether phenanthrene and 4,4'-DDT, in a mixture, compete for sorption sites onto PVC with no added additives (unplasticised PVC or uPVC) and Ultra-High Molecular Weight polyethylene. Interactions were investigated by exposing particles of uPVC and UHMW PE to mixtures of 3H and 14C radiolabelled Phe and DDT. Changes in sorption capacity were modelled by applying a Freundlich binding sorption isotherms. An Extended Langmuir Model and an Interaction Factor Model were also applied to predict equilibrium concentrations of pollutants onto plastic. This study showed that in a bi-solute system, DDT exhibited no significantly different sorption behaviour than in single solute systems. However, DDT did appear to interfere with the sorption of Phe onto plastic, indicating an antagonistic effect. Copyright © 2012 Elsevier Ltd. All rights reserved.

The modeling of reactive solute transport with sorption to mobile and immobile sorbents 1. Experimental evidence and model development

NASA Astrophysics Data System (ADS)

Knabner, P.; Totsche, K. U.; Kögel-Knabner, I.

Modeling carrier-influenced transport needs to take into account the reactivity of the carrier itself. This paper presents a mathematical model of reactive solute transport with sorption to mobile and immobile sorbents. The mobile sorbent is also considered to be reactive. To justify the assumptions and generality of our modeling approach, experimental findings are reviewed and analyzed. A transformation of the model in terms of total concentrations of solute and mobile sorbents is presented which simplifies the mathematical formulations. Breakthrough data on dissolved organic carbon are presented to exemplify the need to take into account the reactivity of the mobile sorbent. Data on hexachlorobiphenyl and cadmium are presented to demonstrate carrier-introduced increased mobility, whereas data on anthracene and pyrene are presented to demonstrate carrier-introduced reduced mobility. The experimental conditions leading to the different findings are pointed out. The sorption processes considered in the model are both equilibrium and nonequilibrium processes, allowing for different sorption sites and nonlinear isotherms and rate functions. Effective isotherms, which describe the sorption to the immobile sorbent in the presence of a mobile sorbent and rate functions, are introduced and their properties are discussed.

Characterization of nicosulfuron availability in aged soils.

PubMed

Regitano, Jussara B; Koskinen, William C

2008-07-23

Sorption-desorption interactions of pesticides with soil determine their availability for transport, plant uptake, and microbial degradation. These interactions are affected by the physical-chemical properties of the pesticide and soil, and for some pesticides, their residence time in the soil. This research evaluated changes in sorption/availability of nicosulfuron (2-[[[[(4,6-dimethoxy-2-pyrimidinyl]amino]carbonyl]amino]sulfonyl]-N,N-dimethyl-3-pyridinecarboxamide) herbicide with aging in different soils, using a radiolabeled ((14)C) tracer. Aging significantly increased sorption. For instance, after the 41-day incubation, calculated K d,app increased by a factor of 2 to 3 in Mollisols from the Midwestern United States and by a factor of 5 to 9 in Oxisols from Brazil and Hawaii, as compared to freshly treated soils. In view of this outcome, potential transport of nicosulfuron would be overpredicted if freshly treated soil K d values were used to predict transport. The fact that the nicosulfuron solution concentration decreased faster than the soil concentration with time suggested that the increase in sorption was because the rate of degradation in solution and on labile sites was faster than the rate of desorption of the neutral species from the soil particles. It may have also been due to nicosulfuron anion diffusion to less accessible sites with time, leaving the more strongly bound neutral molecules for the sorption characterization. Regardless of the mechanism, these results are further evidence that increases in sorption during pesticide aging should be taken into account during the characterization of the sorption process for mathematical models of pesticide degradation and transport.

An efficient phosphorus scavenging from aqueous solution using magnesiothermally modified bio-calcite.

PubMed

Ahmad, Munir; Ahmad, Mahtab; Usman, Adel R A; Al-Faraj, Abdullah S; Ok, Yong Sik; Hussain, Qaiser; Abduljabbar, Adel S; Al-Wabel, Mohammad I

2018-07-01

Bio-calcite (BC) derived from waste hen eggshell was subjected to thermal treatments (calcined bio-calcite (CBC)). The BC and CBC were further modified via magnesiothermal treatments to produce modified bio-calcite (MBC) and modified calcined bio-calcite (MCBC), respectively, and evaluated as a novel green sorbent for P removal from aqueous solutions in the batch experiments. Modified BC exhibited improved structural and chemical properties, such as porosity, surface area, thermal stability, mineralogy and functional groups, than pristine material. Langmuir and Freundlich models well described the P sorption onto both thermally and magnesiothermally sorbents, respectively, suggesting mono- and multi-layer sorption. Langmuir predicted highest P sorption capacities were in the order of: MCBC (43.33 mg g -1 ) > MBC (35.63 mg g- 1 ) > CBC (34.38 mg g -1 ) > BC (30.68 mg g -1 ). The MBC and MCBC removed 100% P up to 50 mg P L -1 , which reduced to 35.43 and 39.96%, respectively, when P concentration was increased up to 1000 mg L -1 . Dynamics of P sorption was well explained by the pseudo-second-order rate equation, with the highest sorption rate of 4.32 mg g -1  min -1 for the MCBC. Hydroxylapatite [Ca 10 (PO 4 ) 6 (OH) 2 ] and brushite [CaH(PO 4 )·2H 2 O] were detected after P sorption onto the modified sorbents by X-ray diffraction analysis, suggesting chemisorption as the operating sorption mechanism.

Use of natural clinoptilolite for the removal of lead, copper and zinc in fixed bed column.

PubMed

Stylianou, Marinos A; Hadjiconstantinou, Michalis P; Inglezakis, Vasilis J; Moustakas, Konstantinos G; Loizidou, Maria D

2007-05-08

This work deals with the removal of lead, copper and zinc from aqueous solutions by using natural zeolite (clinoptilolite). Fixed bed experiments were performed, using three different volumetric flow rates of 5, 7 and 10bed volume/h, under a total normality of 0.01N, at initial pH of 4 and ambient temperature (25 degrees C). The removal efficiency increased when decreasing the flow rate and the following selectivity series was found: Pb(2+)>Zn(2+)> or =Cu(2+). Conductivity measurements showed that lead removal follows mainly ion exchange mechanism, while copper and zinc removal follows ion exchange and sorption mechanism as well.

Application of Empirical Peleg Model to Study the Water Adsorption of Full Cream Milk in Drying Process

NASA Astrophysics Data System (ADS)

Hashib, S. Abd; Rosli, H.; Suzihaque, M. U. H.; Zaki, N. A. Md; Ibrahim, U. K.

2017-06-01

The ability of spray dryer in producing full cream milk at different inlet temperatures and the effectiveness of empirical model used in order to interpret the drying process data is evaluated in this study. In this study, a lab-scale spray dryer was used to dry full cream milk into powder with inlet temperature from 100 to 160°C with a constant pump speed 4rpm. Peleg empirical model was chosen in order to manipulate the drying data into the mathematical equation. This research was carry out specifically to determine the equilibrium moisture content of full cream milk powder at various inlet temperature and to evaluate the effectiveness of Peleg empirical model equation in order to describe the moisture sorption curves for full cream milk. There were two conditions set for this experiments; in the first condition (C1), further drying process of milk powder in the oven at 98°C to 100°C while the second condition (C2) is mixing the milk powder with different salt solutions like Magnesium Chloride (MgCl), Potassium Nitrite (KNO2), Sodium Nitrite (NaNO2) and Ammonium Sulfate ((NH4)2SO4). For C1, the optimum temperature were 160°C with equilibrium moisture content at 3.16 weight dry basis and slowest sorption rates (dM/dt) at 0.0743 weight dry basis/hr. For C2, the best temperature for the mixture of dry samples with MgCl is at 115°C with equilibrium moisture content and sorption rates is -78.079 weight dry basis and 0.01 weight dry basis/hr. The best temperature for the mixture of milk powder with KNO2 is also at 115°C with equilibrium moisture content and sorption rates at -83.9645 weight dry basis and 0.0008 weight dry basis/hr respectively. For mixture of dry samples with NaNO2, the best temperature is 160°C with equilibrium moisture content and sorption rates at 84.1306 weight dry basis and 0.0013 weight dry basis/hr respectively. Lastly, the mixture of dry samples with ((NH4)2SO4 where the best temperature is at 115°C with equilibrium moisture content -83.8778 weight dry basis and sorption rates at 0.0021 weight dry basis/hr. The best temperature selected best on the lowest moisture content formed and also the slowest sorption rates.

Mobility and bioavailability reduction of soil TNT via sorption enhancement using monopotassium phosphate.

PubMed

Jung, Jae-Woong; Nam, Kyoungphile

2014-06-30

In this study, the effect of monopotassium phosphate (MKP) on the reduction in mobility and bioavailability of 2,4,6-trinitrotoluene (TNT) was tested. In the test soil, collected from an active firing range, of which cation binding sites were mostly exchanged with H(+) or Al(3+), potassium ions in MKP exchanged the existing cations and hence significantly increased TNT sorption. In addition, a competitive sorption experiment with hexafluorobenzene and 2,4-dinitrotoluene suggests that TNT was specifically sorbed through cation-polar interaction in the test soil. The unit-equivalent Freundlich sorption coefficient of TNT in MKP-amended soil (1370.96 mg-TNT/kg-soil) was about 13 times higher than that in untreated soil (106.23 mg-TNT/kg-soil). Finally, modified synthetic precipitation leaching procedure and hydroxypropyl-β-cyclodextrin extraction result revealed that MKP application could reduce both the leachability and bioavailability of soil TNT. The leachable and extractable fraction of TNT in untreated soil were 87.63% and 94.47% of the initial TNT, respectively, whereas these fractions decreased to 49.15% and 54.85% of the initial TNT in the presence of MKP, respectively. MKP application can be a benign technology which can reduce both mobility and bioavailability of TNT in soil. Copyright © 2014. Published by Elsevier B.V.

Sorption of atrazine and ametryn by carbonatic and non-carbonatic soils of varied origin.

PubMed

Kasozi, G N; Nkedi-Kizza, P; Li, Y; Zimmerman, A R

2012-10-01

Sorption of two s-triazines, atrazine and ametryn, by carbonatic soils, Histosols, Spodosols and Oxisols was examined. Linear isotherms were observed and sorption coefficients (K(d)) of both compounds were significantly lower (α = 0.05) onto carbonatic soils compared to non-carbonatic soils. Furthermore, among carbonatic soil types, the marl-carbonatic soils had the lowest sorption affinities. K(d) and organic carbon content were highly correlated, suggesting predominant influence of organic carbon in the sorption of the s-triazine, except in Oxisols and Spodosols where variations suggest other factors. Upon removal of organic matter (OM) using sodium hypochlorite and hydrogen peroxide, the K(d) values were reduced by ~90%, indicating minimal contribution of mineral surfaces. Thus OM compositional differences likely explain the large variation in s-triazine sorption within and between soil orders. This study highlights the need to consider OM composition in addition to quantity when determining pesticide applications rates, particularly for carbonatic soils. Copyright © 2012 Elsevier Ltd. All rights reserved.

Sorption and reemission of formaldehyde by gypsum wallboard. Report for June 1990-August 1992

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chang, J.C.S.

1993-01-01

The paper gives results of an analysis of the sorption and desorption of formaldehyde by unpainted wallboard, using a mass transfer model based on the Langmuir sorption isotherm. The sorption and desorption rate constants are determined by short-term experimental data. Long-term sorption and desorption curves are developed by the mass transfer model without any adjustable parameters. Compared with other empirically developed models, the mass transfer model has more extensive applicability and provides an elucidation of the sorption and desorption mechanism that empirical models cannot. The mass transfer model is also more feasible and accurate than empirical models for applications suchmore » as scale-up and exposure assessment. For a typical indoor environment, the model predicts that gypsum wallboard is a much stronger sink for formaldehyde than for other indoor air pollutants such as tetrachloroethylene and ethylbenzene. The strong sink effects are reflected by the high equilibrium capacity and slow decay of the desorption curve.« less

Radionuclide sorption in Yucca Mountain tuffs with J-13 well water: Neptunium, uranium, and plutonium. Yucca Mountain site characterization program milestone 3338

DOE Office of Scientific and Technical Information (OSTI.GOV)

Triay, I.R.; Cotter, C.R.; Kraus, S.M.

1996-08-01

We studied the retardation of actinides (neptunium, uranium, and plutonium) by sorption as a function of radionuclide concentration in water from Well J-13 and of tuffs from Yucca Mountain. Three major tuff types were examined: devitrified, vitric, and zeolitic. To identify the sorbing minerals in the tuffs, we conducted batch sorption experiments with pure mineral separates. These experiments were performed with water from Well J-13 (a sodium bicarbonate groundwater) under oxidizing conditions in the pH range from 7 to 8.5. The results indicate that all actinides studied sorb strongly to synthetic hematite and also that Np(V) and U(VI) do notmore » sorb appreciably to devitrified or vitric tuffs, albite, or quartz. The sorption of neptunium onto clinoptilolite-rich tuffs and pure clinoptilolite can be fitted with a sorption distribution coefficient in the concentration range from 1 X 10{sup -7} to 3 X 10{sup -5} M. The sorption of uranium onto clinoptilolite-rich tuffs and pure clinoptilolite is not linear in the concentration range from 8 X 10{sup -8} to 1 X 10{sup -4} M, and it can be fitted with nonlinear isotherm models (such as the Langmuir or the Freundlich Isotherms). The sorption of neptunium and uranium onto clinoptilolite in J-13 well water increases with decreasing pH in the range from 7 to 8.5. The sorption of plutonium (initially in the Pu(V) oxidation state) onto tuffs and pure mineral separates in J-13 well water at pH 7 is significant. Plutonium sorption decreases as a function of tuff type in the order: zeolitic > vitric > devitrified; and as a function of mineralogy in the order: hematite > clinoptilolite > albite > quartz.« less

Sorption behaviour of nonylphenol and nonylphenol monoethoxylate in soils.

PubMed

Milinovic, J; Lacorte, S; Rigol, A; Vidal, M

2015-11-01

Sorption behaviour of two alkylphenolic compounds (APCs), nonylphenol (NP) and nonylphenol monoethoxylate (NP1EO), was studied in five soils with contrasting characteristics. Sorption isotherms were obtained by equilibrating the soil samples with 0.01 mol L(-1) CaCl2 solutions containing different initial concentrations of NP or NP1EO. Linear fitting was generally appropriate for describing the sorption behaviour of NP and NP1EO in the soils, with the exception of two cases, for which the Freundlich model was more suitable for describing the sorption pattern of NP1EO. Solid-liquid distribution coefficients derived from sorption isotherms (Kd) varied from 24 to 1059 mL g(-1) for NP and from 51 to 740 mL g(-1) for NP1EO. For most soils, sorption Kd values were higher for NP than for NP1EO due to the higher hydrophobicity of NP. Sorption reversibility of NP and NP1EO was also tested from desorption isotherms. Desorption solid-liquid distribution coefficients (Kd,des), obtained from linear fitting, were between 130 and 1467 mL g(-1) for NP and between 24 and 1285 mL g(-1) for NP1EO. Kd,des values were higher than Kd values, which demonstrated that target compounds were irreversibly sorbed into soils, with the exception of the high desorption yield (45%) of NP1EO in the soil with the lowest content of organic matter. The fraction of soil organic carbon (FOC) was a key parameter that influenced the sorption of NP and NP1EO in soils, with logKOC values of 4.0 and 3.8, respectively. Copyright © 2014 Elsevier Ltd. All rights reserved.

Multi-component sorption of Pb(II), Cu(II) and Zn(II) onto low-cost mineral adsorbent.

PubMed

Prasad, Murari; Xu, Huan-yan; Saxena, Sona

2008-06-15

Multi-component sorption studies were carried out for attenuation of divalent heavy metal cations (Pb2+, Cu2+ and Zn2+) by a low-cost mineral adsorbent from the aqueous solution. Kinetic and equilibrium batch-type sorption experiments were conducted under variable conditions for multi-component using low-grade (<12%P2O5) phosphate rock. Percentage of multiple heavy metal species removal increases with decreasing initial metals concentration and particle size. The equilibrium data were well described to a lesser extent by Freundlich model but Langmuir model seemed to be more appropriate with the fixation capacity obtained at room temperature for Pb2+, Cu2+ and Zn2+ was 227.2, 769.2 and 666.6 micromol g(-1), respectively. Two simple kinetic models were tested to investigate the adsorption mechanism. Rate constants have been found nearly constant at all metal concentrations for first order. The comparison of adsorption capacity of low-grade phosphate rock decreases in multi-component system as compared to single component due to ionic interactions. X-ray powder diffraction (XRPD) technique was used to ascertain the formation of new metal phases followed by surface complexation. Used adsorbents have been converted into a value added product by utilizing innovative Zero-waste concept to solve the used adsorbents disposal problem and thus protecting the environment.

Transformations of TNT and related aminotoluenes in groundwater aquifer slurries under different electron-accepting conditions

USGS Publications Warehouse

Krumholz, L.R.; Li, J.; Clarkson, W.W.; Wilber, G.G.; Suflita, J.M.

1997-01-01

The transport and fate of pollutants is often governed by both their tendency to sorb as well as their susceptibility to biodegradation. We have evaluated these parameters for 2,4,6-trinitrotoluene (TNT) and several biodegradation products. Slurries of aquifer sediment and groundwater depleted TNT at rates of 27, 7.7 and 5.9 μM day−1 under methanogenic, sulfate-reducing and nitrate-reducing conditions, respectively. Abiotic losses of TNT were determined in autoclaved controls. Abiotic TNT loss and subsequent transformation of the products was also observed. These transformations were especially important during the first step in the reduction of TNT. Subsequent abiotic reactions could account for all of the transformations observed in bottles which were initially nitrate-reducing. Other controls removed TNT reduction products at much slower rates than slurries containing live organisms. 2-Amino-4,6-dinitrotoluene was produced in all slurries but disappeared in methanogenic and in sulfate-reducing slurries within several weeks. This compound was converted to 2,4-diamino-6-nitrotoluene in all slurries with subsequent removal of the latter from methanogenic and sulfate-reducing slurries, while it persisted in autoclaved controls and in the nitrate-reducing slurries. Aquifer slurries incubated with either 2,4- or 2,6-diaminotoluene showed losses of these compounds relative to autoclaved controls under nitrate-reducing conditions but not under sulfate-reducing or methanogenic conditions. These latter compounds are important as reduced intermediates in the biodegradation of dinitrotoluenes and as industrial chemicals. In experiments to examine sorption, exposure to landfill sediment resulted in losses of approximately 15% of diaminotoluene isomers and 25% of aminodinitrotoluene isomers from initial solution concentrations within 24 h. Isotherms confirmed that the diaminotoluenes were least strongly sorbed and the amino-dinitrotoluenes most strongly sorbed to this sediment, while TNT sorption capacity was intermediate. In our studies, 2,4,6-triaminotoluene sorption capacity was indeterminate due to its chemical instability. Coupled with biodegradation information, isotherms help describe the likelihood of contaminant removal, persistence, and movement at impacted sites.

Computer model of one-dimensional equilibrium controlled sorption processes

USGS Publications Warehouse

Grove, D.B.; Stollenwerk, K.G.

1984-01-01

A numerical solution to the one-dimensional solute-transport equation with equilibrium-controlled sorption and a first-order irreversible-rate reaction is presented. The computer code is written in FORTRAN language, with a variety of options for input and output for user ease. Sorption reactions include Langmuir, Freundlich, and ion-exchange, with or without equal valance. General equations describing transport and reaction processes are solved by finite-difference methods, with nonlinearities accounted for by iteration. Complete documentation of the code, with examples, is included. (USGS)

Enhancing oil removal from water by immobilizing multi-wall carbon nanotubes on the surface of polyurethane foam.

PubMed

Keshavarz, Alireza; Zilouei, Hamid; Abdolmaleki, Amir; Asadinezhad, Ahmad

2015-07-01

A surface modification method was carried out to enhance the light crude oil sorption capacity of polyurethane foam (PUF) through immobilization of multi-walled carbon nanotube (MWCNT) on the foam surface at various concentrations. The developed sorbent was characterized using scanning electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, and tensile elongation test. The results obtained from thermogravimetric and tensile elongation tests showed the improvement of thermal and mechanical resistance of surface-modified foam. The experimental data also revealed that the immobilization of MWCNT on PUF surface enhanced the sorption capacity of light crude oil and reduced water sorption. The highest oil removal capacity was obtained for 1 wt% MWCNT on PUF surface which was 21.44% enhancement in light crude oil sorption compared to the blank PUF. The reusability of surface modified PUF was determined through four cycles of chemical regeneration using petroleum ether. The adsorption of light crude oil with 30 g initial mass showed that 85.45% of the initial oil sorption capacity of this modified sorbent was remained after four regeneration cycles. Equilibrium isotherms for adsorption of oil were analyzed by the Freundlich, Langmuir, Temkin, and Redlich-Peterson models through linear and non-linear regression methods. Results of equilibrium revealed that Langmuir isotherm is the best fitting model and non-linear method is a more accurate way to predict the parameters involved in the isotherms. The overall findings suggested the promising potentials of the developed sorbent in order to be efficiently used in large-scale oil spill cleanup. Copyright © 2015 Elsevier Ltd. All rights reserved.

Effects of Radiation and Temperature on Iodide Sorption by Surfactant-Modified Bentonite

DOE Office of Scientific and Technical Information (OSTI.GOV)

Choung, Sungwook; Kim, Min Kyung; Yang, Jungseok

2014-08-04

Bentonite, which is used as an engineered barrier in geological repositories, is ineffective for sorbing anionic radionuclides because of its negatively charged surface. This study modified raw bentonite using a cationic surfactant (i.e., hexadecyltrimethylammonium [HDTMA]-Br) to improve its sorption capability for radioactive iodide. The effects of temperature and radiation on the iodide sorption of surfactant-modified bentonite (SMB) were evaluated under alkaline pH condition similar to that found in repository environments. Different amounts of surfactant, equivalent to the 50, 100, and 200% cation-exchange capacity of the bentonite, were used to produce the HDTMA-SMB for iodide sorption. The sorption reaction of themore » SMB with iodide reached equilibrium rapidly within 10 min regardless of temperature and radiation conditions. The rate of iodide sorption increased as the amount of the added surfactant was increased and nonlinear sorption behavior was exhibited. However, high temperature and γ-irradiation (60Co) resulted in significantly (~2–10 times) lower iodide Kd values for the SMB. The results of Fourier transform infrared spectroscopy analysis suggested that the decrease in iodide sorption may be caused by weakened physical electrostatic force between the HDTMA and iodide, and by the surfactant becoming detached from the SMB during the heating and irradiation processes.« less

Analytical Modeling of Aquifer Decontamination by Pulsed Pumping When Contaminant Transport is Affected by Rate-Limited Sorption and Desorption

DTIC Science & Technology

1993-09-01

CONTAMINANT TRANSPORT IS AFFECTED BY RATE-LIMITED SORPTION AND DESORPTION IgIntroduction Groundwater is the source of drinking water for...depend upon groundwater as their drinking water source [Wentz, 1989:271] . Historically, groundwater has been considered an unlimited and safe source...of drinking water. However, the widespread contamination of groundwater due to years of accidental or deliberate dumping of various synthetic organic

Comparative study of Se oxyanions retention on three argillaceous rocks: Upper Toarcian (Tournemire, France), Black Shales (Tournemire, France) and Opalinus Clay (Mont Terri, Switzerland).

PubMed

Frasca, B; Savoye, S; Wittebroodt, C; Leupin, O X; Michelot, J-L

2014-01-01

A comparative study of selenium oxyanion sorption was carried out by means of batch sorption experiments on three argillaceous rocks that differ in their mineralogical compositions and textural properties. The results show no selenate (Se(VI)) sorption onto the argillaceous rocks after 60 days, but clear sorption of selenite (Se(IV)), the extent being closely related to the initial Se(IV) concentration. At the lowest concentration ([Se(IV)]eq < 10(-8) mol L(-1)), the ranking of rock affinity for Se(IV) is Black Shales > Opalinus Clay (OPA) > Upper Toarcian, with Rd values of 910 ± 70, 600 ± 65 and 470 ± 70 mL g(-1) respectively. The Se(IV) sorption isotherms acquired for the three argillaceous rocks can be reproduced well by means of Langmuir formalism, particularly with a two-site Langmuir model. The comparison of the Se(IV) sorption isotherms obtained for these three rocks led to identification of pyrite associated with natural organic matter (NOM) as one of the main phases involved in selenium retention. While the desorption results suggested a significant Se(IV) reduction in the Upper Toarcian samples, the reversible sorption shown on the Black Shales and OPA samples was correlated with a sulfate increase, symptomatic of surface oxidation of pyrite which could limit the Se(IV) reduction in favor of sorption. Copyright © 2013 Elsevier Ltd. All rights reserved.

The impacts of effective stress and CO 2 sorption on the matrix permeability of shale reservoir rocks [The impacts of CO 2 sorption and effective stress on the matrix permeability of shale reservoir rocks

DOE PAGES

Wu, Wei; Zoback, Mark D.; Kohli, Arjun H.

2017-05-02

We assess the impacts of effective stress and CO 2 sorption on the bedding-parallel matrix permeability of the Utica shale through pressure pulse-decay experiments. We first measure permeability using argon at relatively high (14.6 MPa) and low (2.8 MPa) effective stresses to assess both pressure dependence and recoverability. We subsequently measure permeability using supercritical CO 2 and again using argon to assess changes due to CO 2 sorption. We find that injection of both argon and supercritical CO 2 reduces matrix permeability in distinct fashion. Samples with permeability higher than 10 –20 m 2 experience a large permeability reduction aftermore » treatment with argon, but a minor change after treatment with supercritical CO 2. However, samples with permeability lower than this threshold undergo a slight change after treatment with argon, but a dramatic reduction after treatment with supercritical CO 2. These results indicate that effective stress plays an important role in the evolution of relatively permeable facies, while CO 2 sorption dominates the change of ultra-low permeability facies. The permeability reduction due to CO 2 sorption varies inversely with initial permeability, which suggests that increased surface area from hydraulic stimulation with CO 2 may be counteracted by sorption effects in ultra-low permeability facies. As a result, we develop a conceptual model to explain how CO 2 sorption induces porosity reduction and volumetric expansion to constrict fluid flow pathways in shale reservoir rocks.« less

The impacts of effective stress and CO 2 sorption on the matrix permeability of shale reservoir rocks [The impacts of CO 2 sorption and effective stress on the matrix permeability of shale reservoir rocks

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, Wei; Zoback, Mark D.; Kohli, Arjun H.

We assess the impacts of effective stress and CO 2 sorption on the bedding-parallel matrix permeability of the Utica shale through pressure pulse-decay experiments. We first measure permeability using argon at relatively high (14.6 MPa) and low (2.8 MPa) effective stresses to assess both pressure dependence and recoverability. We subsequently measure permeability using supercritical CO 2 and again using argon to assess changes due to CO 2 sorption. We find that injection of both argon and supercritical CO 2 reduces matrix permeability in distinct fashion. Samples with permeability higher than 10 –20 m 2 experience a large permeability reduction aftermore » treatment with argon, but a minor change after treatment with supercritical CO 2. However, samples with permeability lower than this threshold undergo a slight change after treatment with argon, but a dramatic reduction after treatment with supercritical CO 2. These results indicate that effective stress plays an important role in the evolution of relatively permeable facies, while CO 2 sorption dominates the change of ultra-low permeability facies. The permeability reduction due to CO 2 sorption varies inversely with initial permeability, which suggests that increased surface area from hydraulic stimulation with CO 2 may be counteracted by sorption effects in ultra-low permeability facies. As a result, we develop a conceptual model to explain how CO 2 sorption induces porosity reduction and volumetric expansion to constrict fluid flow pathways in shale reservoir rocks.« less

Sorption and speciation of selenium in boreal forest soil.

PubMed

Söderlund, Mervi; Virkanen, Juhani; Holgersson, Stellan; Lehto, Jukka

2016-11-01

Sorption and speciation of selenium in the initial chemical forms of selenite and selenate were investigated in batch experiments on humus and mineral soil samples taken from a 4-m deep boreal forest soil excavator pit on Olkiluoto Island, on the Baltic Sea coast in southwestern Finland. The HPLC-ICP-MS technique was used to monitor any possible transformations in the selenium liquid phase speciation and to determine the concentrations of selenite and selenate in the samples for calculation of the mass distribution coefficient, K d , for both species. Both SeO 3 2- and SeO 4 2- proved to be resistant forms in the prevailing soil conditions and no changes in selenium liquid phase speciation were seen in the sorption experiments in spite of variations in the initial selenium species, incubation time or conditions, pH, temperature or microbial activity. Selenite sorption on the mineral soil increased with time in aerobic conditions whilst the opposite trend was seen for the anaerobic soil samples. Selenite retention correlated with the contents of organic matter and weakly crystalline oxides of aluminum and iron, solution pH and the specific surface area. Selenate exhibited poorer sorption on soil than selenite and on average the K d values were 27-times lower. Mineral soil was more efficient in retaining selenite and selenate than humus, implicating the possible importance of weakly crystalline aluminum and iron oxides for the retention of oxyanions in Olkiluoto soil. Sterilization of the soil samples decreased the retention of selenite, thus implying some involvement of soil microbes in the sorption processes or a change in sample composition, but it produced no effect for selenate. There was no sorption of selenite by quartz, potassium feldspar, hornblende or muscovite. Biotite showed the best retentive properties for selenite in the model soil solution at about pH 8, followed by hematite, plagioclase and chlorite. The K d values for these minerals were 18, 14, 8 and 7 L/kg, respectively. It is proposed that selenite sorption is affected by the structural Fe(II) in biotite, which is capable of inducing the reduction of SeO 3 2- to Se(0). Selenite probably forms a surface complex with Fe(III) atoms on the surface of hematite, thus explaining its retention on this mineral. None of the minerals retained selenate to any extent. Copyright © 2016 Elsevier Ltd. All rights reserved.

Chemically modified biochar produced from conocarpus waste increases NO3 removal from aqueous solutions.

PubMed

Usman, Adel R A; Ahmad, Mahtab; El-Mahrouky, Mohamed; Al-Omran, Abdulrasoul; Ok, Yong Sik; Sallam, Abdelazeem Sh; El-Naggar, Ahmed H; Al-Wabel, Mohammad I

2016-04-01

Biochar has emerged as a universal sorbent for the removal of contaminants from water and soil. However, its efficiency is lower than that of commercially available sorbents. Engineering biochar by chemical modification may improve its sorption efficiency. In this study, conocarpus green waste was chemically modified with magnesium and iron oxides and then subjected to thermal pyrolysis to produce biochar. These chemically modified biochars were tested for NO3 removal efficiency from aqueous solutions in batch sorption isothermal and kinetic experiments. The results revealed that MgO-biochar outperformed other biochars with a maximum NO3 sorption capacity of 45.36 mmol kg(-1) predicted by the Langmuir sorption model. The kinetics data were well described by the Type 1 pseudo-second-order model, indicating chemisorption as the dominating mechanism of NO3 sorption onto biochars. Greater efficiency of MgO-biochar was related to its high specific surface area (391.8 m(2) g(-1)) and formation of strong ionic complexes with NO3. At an initial pH of 2, more than 89 % NO3 removal efficiency was observed for all of the biochars. We conclude that chemical modification can alter the surface chemistry of biochar, thereby leading to enhanced sorption capacity compared with simple biochar.

Kinetic studies on phosphorus sorption by selected soil amendments for septic tank effluent renovation.

PubMed

Cheung, K C; Venkitachalam, T H

2006-01-01

A systematic kinetic study of phosphorus (P) sorption by various materials in the soil infiltration system of septic tanks was undertaken by following the time course of P sorption by sorbents in contact with various P solutions over periods up to 360 days. Uptake of P seemed to consist of two distinct stages. Initial uptake was very rapid and this phase was completed in 4 days or less. A slower removal stage followed for some materials over many months. Phosphorus sorption during the fast reaction stage appeared to be associated with the soluble Ca content of the materials. The fast reaction of calcareous materials accounted for the bulk (>70%) of the total P removed. Merribrook loamy sand exhibited the highest proportion of P sorption during the slow phase. It should be noted, however, that for solution P concentrations in the range found in typical effluents (approximately 20 mg L(-1)) the fast reaction phase seemed to be responsible for virtually all P removed. None of the six kinetic formulae examined possessed the sophistication and detail needed to portray accurately the time course of P sorption for all the sorbents investigated. The Elovich equation and the kinetic modification of the Freundlich isotherm expression appeared to provide a reasonable fit of the experimental data.

The sorption of silver by poorly crystallized manganese oxides

USGS Publications Warehouse

Anderson, B.J.; Jenne, E.A.; Chao, T.T.

1973-01-01

The sorption of silver by poorly crystallized manganese oxides was studied using synthesized samples of three members of the manganous manganite (birnessite) group, of different chemical composition and crystallinity, and a poorly organized ??-MnO2. All four oxides sorbed significant quantities of silver. The manganous manganites showed the greatest sorption (up to 0.5 moles silver/mole MnOx at pH 7) while the ??-MnO2 showed the least (0.3 moles silver/ mole MnOx at pH 7). Sorption of silver was adequately described by the Langmuir equation over a considerable concentration range. The relationship failed at low pH values and high equilibrium silver concentrations. The sorption capacity showed a direct relationship with pH. However, the rate of increase of sorption capacity decreased at the higher pH values. Silver sorption maxima. were not directly related to surface area but appeared to vary with the amount of occluded sodium and potassium present in the manganese oxide. The important processes involved in the uptake of silver by the four poorly crystallized manganese oxides ara considered to be surface exchange for manganese, potassium and sodium as well as exchange for structural manganese, potassium and sodium. ?? 1973.

Sorbed atrazine shifts into non-desorbable sites of soil organic matter during aging.

PubMed

Park, Jeong-Hun; Feng, Yucheng; Cho, Sung Yong; Voice, Thomas C; Boyd, Stephen A

2004-11-01

Soil-chemical contact time (aging) is an important determinant of the sorption and desorption characteristics of the organic contaminants and pesticides in the environment. The effects of aging on mechanism-specific sorption and desorption of atrazine were studied in soil and clay slurries. Sorption isotherm and desorption kinetic experiments were performed, and soil-water distribution coefficients and desorption rate parameters were evaluated using linear and non-linear sorption equations and a three-site desorption model, respectively. Aging time for sorption of atrazine in sterilized soil and clay slurries ranged from 2 days to 8 months. Atrazine sorption isotherms were nearly linear (r(2)>0.97) and sorption coefficients were strongly correlated to soil organic carbon content. Sorption distribution coefficients (K(d)) increased with increase in age in all five soils studied, but not for K-montmorillonite. Sorption non-linearity did not increase with increase in age except for the Houghton muck soil. Desorption profiles were well described by the three-site desorption model. The equilibrium site fraction (f(eq)) decreased and the non-desorbable site fraction (f(nd)) increased as a function of aging time in all soils. For K-montmorillonite, f(nd) approximately 0 regardless of aging, showing that aging phenomena are sorbent/mechanism specific. In all soils, it was found that when normalized to soil organic matter content, the concentration of atrazine in desorbable sites was relatively constant, whereas that in non-desorbable site increased. This, and the lack of aging effects on desorption from montmorillonite, suggests that sorption into non-desorbable sites of soil organic matter is primary source of increased atrazine sorption in soils during aging.

Sorption-desorption and transport of trimethoprim and sulfonamide antibiotics in agricultural soil: effect of soil type, dissolved organic matter, and pH.

PubMed

Zhang, Ya-Lei; Lin, Shuang-Shuang; Dai, Chao-Meng; Shi, Lu; Zhou, Xue-Fei

2014-05-01

Use of animal manure is a main source of veterinary pharmaceuticals (VPs) in soil and groundwater through a series of migration processes. The sorption-desorption and transport of four commonly used VPs including trimethoprim (TMP), sulfapyridine, sulfameter, and sulfadimethoxine were investigated in three soil layers taken from an agricultural field in Chongming Island China and two types of aqueous solution (0.01 M CaCl2 solution and wastewater treatment plant effluent). Results from sorption-desorption experiments showed that the sorption behavior of selected VPs conformed to the Freundlich isotherm equation. TMP exhibited higher distribution coefficients (K d = 6.73-9.21) than other sulfonamides (K d = 0.03-0.47), indicating a much stronger adsorption capacity of TMP. The percentage of desorption for TMP in a range of 8-12 % is not so high to be considered significant. Low pH (

Fate of the antibiotic sulfadiazine in natural soils: Experimental and numerical investigations.

PubMed

Engelhardt, Irina; Sittig, Stephan; Šimůnek, Jirka; Groeneweg, Joost; Pütz, Thomas; Vereecken, Harry

2015-01-01

Based on small-scale laboratory and field-scale lysimeter experiments, the sorption and biodegradation of sulfonamide sulfadiazine (SDZ) were investigated in unsaturated sandy and silty-clay soils. Sorption and biodegradation were low in the laboratory, while the highest leaching rates were observed when SDZ was mixed with manure. The leaching rate decreased when SDZ was mixed with pure water, and was smallest with the highest SDZ concentrations. In the laboratory, three transformation products (TPs) developed after an initial lag phase. However, the amount of TPs was different for different mixing-scenarios. The TP 2-aminopyrimidine was not observed in the laboratory, but was the most prevalent TP at the field scale. Sorption was within the same range at the laboratory and field scales. However, distinctive differences occurred with respect to biodegradation, which was higher in the field lysimeters than at the laboratory scale. While the silty-clay soil favored sorption of SDZ, the sandy, and thus highly permeable, soil was characterized by short half-lives and thus a quick biodegradation of SDZ. For 2-aminopyrimidine, half-lives of only a few days were observed. Increased field-scale biodegradation in the sandy soil resulted from a higher water and air permeability that enhanced oxygen transport and limited oxygen depletion. Furthermore, low pH was more important than the organic matter and clay content for increasing the biodegradation of SDZ. A numerical analysis of breakthrough curves of bromide, SDZ, and its TPs showed that preferential flow pathways strongly affected the solute transport within shallow parts of the soil profile at the field scale. However, this effect was reduced in deeper parts of the soil profile. Due to high field-scale biodegradation in several layers of both soils, neither SDZ nor 2-aminopyrimidine was detected in the discharge of the lysimeter at a depth of 1m. Synthetic 50 year long simulations, which considered the application of manure with SDZ for general agricultural practices in Germany and humid climate conditions, showed that the concentration of SDZ decreased below 0.1 μg/L in both soils below the depth of 50 cm. Copyright © 2015 Elsevier B.V. All rights reserved.

Fate of the antibiotic sulfadiazine in natural soils: Experimental and numerical investigations

NASA Astrophysics Data System (ADS)

Engelhardt, Irina; Sittig, Stephan; Šimůnek, Jirka; Groeneweg, Joost; Pütz, Thomas; Vereecken, Harry

2015-06-01

Based on small-scale laboratory and field-scale lysimeter experiments, the sorption and biodegradation of sulfonamide sulfadiazine (SDZ) were investigated in unsaturated sandy and silty-clay soils. Sorption and biodegradation were low in the laboratory, while the highest leaching rates were observed when SDZ was mixed with manure. The leaching rate decreased when SDZ was mixed with pure water, and was smallest with the highest SDZ concentrations. In the laboratory, three transformation products (TPs) developed after an initial lag phase. However, the amount of TPs was different for different mixing-scenarios. The TP 2-aminopyrimidine was not observed in the laboratory, but was the most prevalent TP at the field scale. Sorption was within the same range at the laboratory and field scales. However, distinctive differences occurred with respect to biodegradation, which was higher in the field lysimeters than at the laboratory scale. While the silty-clay soil favored sorption of SDZ, the sandy, and thus highly permeable, soil was characterized by short half-lives and thus a quick biodegradation of SDZ. For 2-aminopyrimidine, half-lives of only a few days were observed. Increased field-scale biodegradation in the sandy soil resulted from a higher water and air permeability that enhanced oxygen transport and limited oxygen depletion. Furthermore, low pH was more important than the organic matter and clay content for increasing the biodegradation of SDZ. A numerical analysis of breakthrough curves of bromide, SDZ, and its TPs showed that preferential flow pathways strongly affected the solute transport within shallow parts of the soil profile at the field scale. However, this effect was reduced in deeper parts of the soil profile. Due to high field-scale biodegradation in several layers of both soils, neither SDZ nor 2-aminopyrimidine was detected in the discharge of the lysimeter at a depth of 1 m. Synthetic 50 year long simulations, which considered the application of manure with SDZ for general agricultural practices in Germany and humid climate conditions, showed that the concentration of SDZ decreased below 0.1 μg/L in both soils below the depth of 50 cm.

POLANYI-BASED MODELS FOR THE COMPETITIVE SORPTION OF LOW-POLARITY ORGANIC CONTAMINANTS ON A NATURAL SORBENT. (R825406)

EPA Science Inventory

The development of appropriate equilibrium sorption relationships for anthropogenic organic contaminants with soils and sediments is essential to predicting the extents and rates of solid-water interactions in the environment. In this context, we previously reported results that ...

NONEQUILIBRIUM SORPTION DURING DISPLACEMENT OF HYRDOPHOBIC ORGANIC CHEMICALS AND 45CA THROUGH SOIL COLUMNS WITH AQUEOUS AND MIXED SOLVENTS

EPA Science Inventory

A series of miscible displacement experiments was conducted to investigate the significance of intraorganic matter diffusion (IOMD) as the rate-limiting step in sorption of organic and inorganic solutes during steady water flow in soil columns. Displacement studies were performed...

Evaluating agricultural management effects on alachlor availability: Tillage, green manure, and biochar

USDA-ARS?s Scientific Manuscript database

Agricultural and soil management practices have been reported to affect alachlor sorption-desorption and degradation rates. The objectives of this study were to: (a) assess differences in alachlor sorption due to tillage treatments (chisel plow and ridge tillage) on soils from three Midwestern U.S. ...

Impact of soil organic carbon on monosodium methyl arsenate (MSMA) sorption and species transformation.

PubMed

Ou, Ling; Gannon, Travis W; Polizzotto, Matthew L

2017-11-01

Monosodium methyl arsenate (MSMA), a common arsenical herbicide, is a major contributor of anthropogenic arsenic (As) to the environment. Uncertainty about controls on MSMA fate and the rates and products of MSMA species transformation limits effective MSMA regulation and management. The main objectives of this research were to quantify the kinetics and mechanistic drivers of MSMA species transformation and removal from solution by soil. Laboratory MSMA incubation studies with two soils and varying soil organic carbon (SOC) levels were conducted. Arsenic removal from solution was more extensive and faster in sandy clay loam incubations than sand incubations, but for both systems, As removal was biphasic, with initially fast removal governed by sorption, followed by slower As removal limited by species transformation. Dimethylarsinic acid was the dominant product of species transformation at first, but inorganic As(V) was the ultimate transformation product by experiment ends. SOC decreased As removal and enhanced As species transformation, and SOC content had linear relationships with As removal rates (R 2  = 0.59-0.95) for each soil and reaction phase. These results reveal the importance of edaphic conditions on inorganic As production and overall mobility of As following MSMA use, and such information should be considered in MSMA management and regulatory decisions. Copyright © 2017 Elsevier Ltd. All rights reserved.

Characteristics of and sorption to biochars derived from waste material

NASA Astrophysics Data System (ADS)

Sun, Huichao; Kah, Melanie; Sigmund, Gabriel; Hofmann, Thilo

2015-04-01

Biochars can exhibit a high sorption potential towards heavy metals and organic contaminants in various environmental matrices (e.g., water, soil). They have therefore been proposed for environmental remediation purposes to sequester contaminants. To date, most studies have focused on the physicochemical and sorption properties of mineral phases poor biochars, which are typically produced from plant residues. Only little knowledge is available for biochars derived from human and animal waste material, which are typically characterized by high mineral contents (e.g., sewage sludge, manure). Using human and animal waste as source material to produce biochars would support the development of attractive combined strategies for waste management and remediation. The potential impact of mineral phases on the physicochemical and sorption properties of biochars requires further studies so that the potential as sorbent material can be evaluated. With this purpose, different source material biochars were produced at 200°C, 350°C and 500°C, to yield a series of biochars representing a range of mineral content. The derived biochars from wood shavings (<1% ash), sewage sludge (50-70% ash) and pig manure (30-60% ash), as well as a commercial biochar derived from grain husks (40% ash), were extensively characterized (e.g., element composition, surface area, porosity, Fourier transform infrared spectroscopy). The contents of potentially toxic elements (i.e., heavy metals and polycyclic aromatic hydrocarbons) of all materials were within the guidelines values proposed by the International Biochar Initiative, indicating their suitability for environmental application. Single point sorption coefficients for the model sorbate pyrene were measured to investigate the effect of mineral content, feedstock, pyrolysis temperature, particle size fractions and acid demineralization on sorption behavior. Overall, sorption of pyrene was strong for all materials (4 < Log Kd < 6.5 L/kg). Sorption generally increased with increasing pyrolysis temperature but there was no effect of particle size on sorption affinity. For mineral phase rich biochars, sorption generally increased after acid demineralization. When considering all materials together, the sorbent aromaticity (hydrogen-carbon ratio) was the most important factor controlling sorption of pyrene. Overall, the study demonstrates that biochars derived from human and animal waste material and exhibiting high mineral contents have potential for remediation applications.

Curing of Composites: An Integrated Multiscale Process Description Toward Tailored Structures and Properties

DTIC Science & Technology

2004-11-01

surface prox- Experimental studies𔃼-l4 have shown that the ad- imity of the fiber changes the structure of the resin in sorption of an epoxy system... sorption layer to the ith bulk layer, and RdE(i + 1, The adsorbed state exchanges mass with the bulk i) is the rate term of the desorption of epoxy mole...thickness from -y = 0 to a ;5 nonzero value was primarily due to the shift in the 7 contribution to the interphase gradient from that of ad- 40 sorption

Sorption of Organophosphorus Flame Retardants (OPFRs) on ...

EPA Pesticide Factsheets

Organophosphorus flame retardants (OPFRs) are widely used as additives in industrial and consumer products such as electrical and electronic products, furniture, plastics, textiles, and building/construction materials. Due to human exposure and potential health effects, OPFRs including tris(2-chloroethyl) phosphate (TCEP), tris(1-chloro-2-propyl) phosphate (TCPP), and tris(1,3-dichloro-2-propyl) phosphate (TDCPP) are EPA Action Plan chemicals for chemical assessments under the Toxic Substances Control Act (TSCA). This work investigated the sorption of these three compounds from the air to settled Arizona Test Dust (ATD) and house dust (HD) in a dual small chamber system. The OPFR exposed dust was analyzed to determine the sorption concentration and sorption rate of OPFRs on the dust. The effect of the composition of the dust on OPFR sorption was evaluated. The results showed that ATD and HD have varied sorption capacity for OPFRs from air. This work explores the relationship between OPFR concentrations in settled dust and air. The data can be used to determine partitioning of OPFRs between the gas phase and settled dust indoors and to inform strategies to reduce exposure and risk.

Sorption of chlorophenols from aqueous solution by granular activated carbon, filter coal, pine and hardwood.

PubMed

Hossain, G S M; McLaughlan, R G

2012-09-01

Wood and coal, as low-cost sorbents, have been evaluated as an alternative to commercial granular activated carbon (GAC) for chlorophenol removal. Kinetic experiments indicated that filter coal had a significantly lower rate of uptake (approximately 10% of final uptake was achieved after three hours) than the other sorbents, owing to intra-particle diffusion limitations. The data fitted a pseudo-second-order model. Sorption capacity data showed that GAC had a high sorption capacity (294-467 mg g(-1)) compared with other sorbents (3.2-7.5 mg(g-1)). However, wood and coal had a greater sorption capacity per unit surface area than GAC. Sorption equilibrium data was best predicted using a Freundlich adsorption model. The sorption capacity for all sorbents was 2-chlorophenol < 4-chlorophenol < 2, 4-dichlorophenol, which correlates well with solute hydrophobicity, although the relative differences were much less for coal than the other sorbents. The results showed that pine, hardwood and filter coal can be used as sorbent materials for the removal of chlorophenol from water; however, kinetic considerations may limit the application of filter coal.

Sorption of Cr(VI), Cu(II) and Pb(II) by growing and non-growing cells of a bacterial consortium.

PubMed

Sannasi, P; Kader, J; Ismail, B S; Salmijah, S

2006-03-01

This paper reports the sorption of three metallic ions, namely Cr(VI), Cu(II) and Pb(II) in aqueous solution by a consortium culture (CC) comprising an acclimatised mixed bacterial culture collected from point and non-point sources. Metal sorption capability of growing and non-growing cells at initial pH of between 3 and 8 in the 1-100mg/L concentration range were studied based on Q(max) and K(f) values of the Langmuir and linearised Freundlich isotherm models, respectively. Maximal metal loading was generally observed to be dependent on the initial pH. Growing cells displayed significant maximal loading (Q(max)) for Pb(II) (238.09 mg/g) and Cu(II) (178.87 mg/g) at pH 6 and at pH 7 for Cr(VI) (90.91 mg/g) compared to non-growing cells (p < 0.05). At the pH range of 6-8, growing cells showed higher loading capacity compared to non-growing cells i.e. 38-52% for Cr, 17-28% for Cu and 3-17% for Pb. At lower metal concentrations and at more acidic pH (3-4) however, non-growing cells had higher metal loading capacity than growing cells. The metal sorption capacity for both populations were as follows: Pb(II) > Cu(II) > Cr(VI).

Sorption-desorption and biosorption of bisphenol A, triclosan, and 17α-ethinylestradiol to sewage sludge.

PubMed

Banihashemi, Bahman; Droste, Ronald L

2014-07-15

To better understand the fate of microconstituents (MCs) in an activated sludge (AS) system, sorption, biosorption, and desorption studies were investigated at μg/L range for 17α-ethinylestradiol (EE2), bisphenol A (BPA), and triclosan (TCS). Batch experiments with activated and deactivated sludge originating from continuous flow porous pot reactors operating at solid retention times (SRTs) of 5, 10, and 15 days were conducted in order to investigate the sorption kinetics and distinguish physicochemical sorption and biosorption. The effect of SRT and the biomass concentration on sorption kinetics were also studied. Selected MCs showed high sorption affinity to the non-viable biomass during the first 30 min of the experiment, which was gradually reduced until equilibrium was reached. Desorption results showed two distinct stages, a very rapid desorption within 20 min followed by a slow desorption stage. Biosorption study indicated that the soluble concentrations of target compounds decreased rapidly for selected MCs similar to the sorption study; however, the soluble and solid phase concentrations continued to decrease slowly during the length of the experiment which indicates the possible biodegradation of these compounds in both phases. Finally, mathematical models were applied to describe the sorption mechanism and Freundlich sorption isotherms with values of 1/n close to 1 were found to best fit the results which demonstrate that all tested concentrations result on the linear part of the Freundlich isotherm. Calculation of the Freundlich constant, KF and distribution coefficient, Kd exhibited the greater tendency of EE2 and TCS for sorption, compared to BPA. The results of this study indicated that the SRT had a clear effect on the sorption kinetics where the highest sorption rate constant was achieved for a SRT of 10 days for all three target substances. This could be due to change of the morphology of the biomass from reactors operating at different SRTs. Copyright © 2014 Elsevier B.V. All rights reserved.

Sulfamethazine Sorption to Soil: Vegetative Management, pH, and Dissolved Organic Matter Effects.

PubMed

Chu, Bei; Goyne, Keith W; Anderson, Stephen H; Lin, Chung-Ho; Lerch, Robert N

2013-01-01

Elucidating veterinary antibiotic interactions with soil is important for assessing and mitigating possible environmental hazards. The objectives of this study were to investigate the effects of vegetative management, soil properties, and >1000 Da dissolved organic matter (DOM) on sulfamethazine (SMZ) behavior in soil. Sorption experiments were performed over a range of SMZ concentrations (2.5-50 μmol L) using samples from three soils (Armstrong, Huntington, and Menfro), each planted to one of three vegetation treatments: agroforestry buffers strips (ABS), grass buffer strips (GBS), and row crops (RC). Our results show that SMZ sorption isotherms are well fitted by the Freundlich isotherm model (log = 0.44-0.93; Freundlich nonlinearity parameter = 0.59-0.79). Further investigation of solid-to-solution distribution coefficients () demonstrated that vegetative management significantly ( < 0.05) influences SMZ sorption (ABS > GBS > RC). Multiple linear regression analyses indicated that organic carbon (OC) content, pH, and initial SMZ concentration were important properties controlling SMZ sorption. Study of the two most contrasting soils in our sample set revealed that increasing solution pH (pH 6.0-7.5) reduced SMZ sorption to the Armstrong GBS soil, but little pH effect was observed for the Huntington GBS soil containing 50% kaolinite in the clay fraction. The presence of DOM (150 mg L OC) had little significant effect on the Freundlich nonlinearity parameter; however, DOM slightly reduced SMZ values overall. Our results support the use of vegetative buffers to mitigate veterinary antibiotic loss from agroecosystems, provide guidance for properly managing vegetative buffer strips to increase SMZ sorption, and enhance understanding of SMZ sorption to soil. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

Effect of mineral surface properties (alumina, kaolinite) on the sorptive fractionation mechanisms of soil fulvic acids: Molecular-scale ESI-MS studies

NASA Astrophysics Data System (ADS)

Fleury, Guillaume; Del Nero, Mirella; Barillon, Rémi

2017-01-01

We addressed the effects of mineral surface properties (kaolinite versus Al-oxide) on the sorption-driven fractionation of a soil fulvic acid (FA) at acidic pH, mainly by means of ESI(-)-FTMS analysis of initial and supernatant solutions of FA sorption batch experiments. The MS data provided clear molecular-scale evidence of distinct mechanisms and molecular parameters controlling the FA fractionation upon its sorption on clay and oxide surfaces, respectively. Identification of sorbing and not-sorbing FA compounds in kaolinite-solution systems revealed a weak fractionation among members of sbnd CO2 series of aliphatics or not-condensed aromatics (NCAs) at pH 3.8, and almost no sorption of poorly-oxygenated polycyclic aromatic compounds (PACs) and NCAs. This first molecular-scale description of a FA fractionation in a clay-solution system suggests that H-bonding with low affinity sites (aluminol/silanol) on the basal planes of the clay particles is the main mechanism of sorption. Due to the predominance of such weak and poorly-selective mechanism, the sorption of aliphatic and NCA molecules bearing oxygenated functionalities was prevented at pH 5, due to dissolved Al competing successfully for their coordination. In contrast, a strong FA fractionation was observed onto alumina, with a preferential retention of PACs and highly-oxygenated aliphatics and NCAs. The major part of the poorly oxygenated aliphatics was left in solution. The sorption degree of NCAs and aliphatics was strongly correlated with molecular acidity. For PACs and poorly-oxygenated NCAs, the sorption was driven by reactions of surface ligand exchange (for the most oxygenated compounds) or by hydrophobic interactions (for the least oxygenated compounds).

Bio sorption of strontium from aqueous solution by New Strain Bacillus sp. GTG-83

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tajer Mohammad Ghazvini, P.; Ghorbanzadeh Mashkani, S.; Ghafourian, H.

Attempt was made to isolate bacterial strains capable of removing Sr biologically. In this study we collected ten different water samples from naturally radioactive spring Neydasht in Iran and bacterial strains samples isolated. Initial screening of a total of 50 bacterial isolates resulted in selection of one strain. The strain showed maximum adsorption capacity with 55 mg Sr/g dry wt. It was tentatively identified as Bacillus sp. according to morphological and biochemical properties and called strain GTG-83. Studies indicated that Bacillus sp. GTG-83 was able to grow aerobically in the presence of 50 mM SrCl{sub 2} but showed severe growthmore » inhibition at levels above that concentration. The bio-sorption capacity of Bacillus sp. GTG-83 strongly depends on solution pH, and the maximum Sr sorption capacity of Bacillus sp. GTG-83 were obtained at pH 10 independent of the absence or the presence of increasing concentrations of salt (MgCl{sub 2}). Sr-salt bio-sorption studies were also performed at this pH values. Equilibrium uptakes of Sr increased with increasing Sr concentrations up to 250 mg/l for Bacillus sp. GTG-83. Maximum bio-sorption of Sr was obtained at temperatures in the range of 30-35 deg. C. Bacillus sp. GTG-83 bio-sorbed 97 mg Sr/g dry wt at 100 mg/l initial Sr concentration without salt medium (MgCl{sub 2}). When salt concentration (MgCl{sub 2}) increased to 15% (w/v), these values dropped to 23.6 mg Sr/g dry wt at the same conditions. Uptake of Sr within 5 min of incubation was relatively rapid and the absorption continued slowly thereafter. (authors)« less

Investigating the Influence of the Initial Biomass Distribution and Injection Strategies on Biofilm-Mediated Calcite Precipitation in Porous Media

DOE PAGES

Hommel, Johannes; Lauchnor, Ellen; Gerlach, Robin; ...

2015-12-16

Attachment of bacteria in porous media is a complex mixture of processes resulting in the transfer and immobilization of suspended cells onto a solid surface within the porous medium. However, quantifying the rate of attachment is difficult due to the many simultaneous processes possibly involved in attachment, including straining, sorption, and sedimentation, and the difficulties in measuring metabolically active cells attached to porous media. Preliminary experiments confirmed the difficulty associated with measuring active Sporosarcina pasteurii cells attached to porous media. However, attachment is a key process in applications of biofilm-mediated reactions in the subsurface such as microbially induced calcite precipitation.more » Independent of the exact processes involved, attachment determines both the distribution and the initial amount of attached biomass and as such the initial reaction rate. As direct experimental investigations are difficult, this study is limited to a numerical investigation of the effect of various initial biomass distributions and initial amounts of attached biomass. This is performed for various injection strategies, changing the injection rate as well as alternating between continuous and pulsed injections. The results of this study indicate that, for the selected scenarios, both the initial amount and the distribution of attached biomass have minor influence on the Ca 2+ precipitation efficiency as well as the distribution of the precipitates compared to the influence of the injection strategy. The influence of the initial biomass distribution on the resulting final distribution of the precipitated calcite is limited, except for the continuous injection at intermediate injection rate. But even for this injection strategy, the Ca 2+ precipitation efficiency shows no significant dependence on the initial biomass distribution.« less

Investigating the Influence of the Initial Biomass Distribution and Injection Strategies on Biofilm-Mediated Calcite Precipitation in Porous Media

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hommel, Johannes; Lauchnor, Ellen; Gerlach, Robin

Attachment of bacteria in porous media is a complex mixture of processes resulting in the transfer and immobilization of suspended cells onto a solid surface within the porous medium. However, quantifying the rate of attachment is difficult due to the many simultaneous processes possibly involved in attachment, including straining, sorption, and sedimentation, and the difficulties in measuring metabolically active cells attached to porous media. Preliminary experiments confirmed the difficulty associated with measuring active Sporosarcina pasteurii cells attached to porous media. However, attachment is a key process in applications of biofilm-mediated reactions in the subsurface such as microbially induced calcite precipitation.more » Independent of the exact processes involved, attachment determines both the distribution and the initial amount of attached biomass and as such the initial reaction rate. As direct experimental investigations are difficult, this study is limited to a numerical investigation of the effect of various initial biomass distributions and initial amounts of attached biomass. This is performed for various injection strategies, changing the injection rate as well as alternating between continuous and pulsed injections. The results of this study indicate that, for the selected scenarios, both the initial amount and the distribution of attached biomass have minor influence on the Ca 2+ precipitation efficiency as well as the distribution of the precipitates compared to the influence of the injection strategy. The influence of the initial biomass distribution on the resulting final distribution of the precipitated calcite is limited, except for the continuous injection at intermediate injection rate. But even for this injection strategy, the Ca 2+ precipitation efficiency shows no significant dependence on the initial biomass distribution.« less

Carbon Sorption Cryogenic Regenerator

NASA Technical Reports Server (NTRS)

Jones, Jack A.; Petrick, S. Walter; Britcliffe, Michael J.

1989-01-01

Liquid-helium refrigerator includes regenerator filled with carbon sorbent made from Saran polyvinylidene chloride. Material results in lower operating temperatures and longer times between maintenance than comparable refrigerators containing other regenerators. Sorbent material machined to various configurations to fit inside cylindrical regenerator can. Configuration chosen with regard to heat capacity, pressure drop, and rate of sorption.

Sorption, desorption, and surface oxidative fate of nicotine.

PubMed

Petrick, Lauren; Destaillats, Hugo; Zouev, Irena; Sabach, Sara; Dubowski, Yael

2010-09-21

Nicotine dynamics in an indoor environment can be greatly affected by building parameters (e.g. relative humidity (RH), air exchange rate (AER), and presence of ozone), as well as surface parameters (e.g. surface area (SA) and polarity). To better understand the indoor fate of nicotine, these parameter effects on its sorption, desorption, and oxidation rates were investigated on model indoor surfaces that included fabrics, wallboard paper, and wood materials. Nicotine sorption under dry conditions was enhanced by higher SA and higher polarity of the substrate. Interestingly, nicotine sorption to cotton and nylon was facilitated by increased RH, while sorption to polyester was hindered by it. Desorption was affected by RH, AER, and surface type. Heterogeneous nicotine-ozone reaction was investigated by Fourier transform infrared spectrometry with attenuated total reflection (FTIR-ATR), and revealed a pseudo first-order surface reaction rate of 0.035 +/- 0.015 min(-1) (at [O(3)] = 6 +/- 0.3 x 10(15) molecules cm(-3)) that was partially inhibited at high RH. Extrapolation to a lower ozone level ([O(3)] = 42 ppb) showed oxidation on the order of 10(-5) min(-1) corresponding to a half-life of 1 week. In addition, similar surface products were identified in dry and high RH using gas chromatography-mass spectrometry (GC-MS). However, FTIR analysis revealed different product spectra for these conditions, suggesting additional unidentified products and association with surface water. Knowing the indoor fate of condensed and gas phase nicotine and its oxidation products will provide a better understanding of nicotine's impact on personal exposures as well as overall indoor air quality.

Kinetics of Methylmercury Production Revisited

DOE PAGES

Olsen, Todd A.; Muller, Katherine A.; Painter, Scott L.; ...

2018-01-27

Laboratory measurements of the biologically mediated methylation of mercury (Hg) to the neurotoxin monomethylmercury (MMHg) often exhibit kinetics that are inconsistent with first-order kinetic models. Using time-resolved measurements of filter passing Hg and MMHg during methylation/demethylation assays, a multisite kinetic sorption model, and reanalyses of previous assays, we show in this paper that competing kinetic sorption reactions can lead to time-varying availability and apparent non-first-order kinetics in Hg methylation and MMHg demethylation. The new model employing a multisite kinetic sorption model for Hg and MMHg can describe the range of behaviors for time-resolved methylation/demethylation data reported in the literature includingmore » those that exhibit non-first-order kinetics. Additionally, we show that neglecting competing sorption processes can confound analyses of methylation/demethylation assays, resulting in rate constant estimates that are systematically biased low. Finally, simulations of MMHg production and transport in a hypothetical periphyton biofilm bed illustrate the implications of our new model and demonstrate that methylmercury production may be significantly different than projected by single-rate first-order models.« less

Removal of Organophosphorus Pesticides from Aqueous Solution by Magnetic Fe3O4/Red Mud-Nanoparticles.

PubMed

Aydin, Senar

2016-12-01

  The aim of this study was to investigate the usability of magnetic Fe3O4/red mud nanoparticles (NPs) for the removal of organophosphorus pesticides from water samples. The effect of various experimental parameters such as red mud amount in Fe3O4/red mud-NPs, pH, contact time, initial pesticide concentrations and adsorbent dose was studied in order to find the optimum conditions for their removal in a batch process. The Fe3O4/red mud-NPs were characterized by using TGA, SEM, XRD, VSM, and determination of the BET surface area. After the regenerated Fe3O4/red mud-NPs were used three times, the sorption capacity and the magnetic separability were observed to be unaffected. Freundlich model described the sorption process better than Langmuir isotherm and the pseudo second-order kinetic model was determined as the best-fit model. The film diffusion mechanism was found to be a main rate control mechanism. The Fe3O4/red mud-NPs satisfactorily removed the OPPS from real water samples.

Water-sensitive positron trapping modes in nanoporous magnesium aluminate ceramics

NASA Astrophysics Data System (ADS)

Filipecki, J.; Ingram, A.; Klym, H.; Shpotyuk, O.; Vakiv, M.

2007-08-01

The water-sensitive positron trapping modes in nanoporous MgAl2O4 ceramics with a spinel structure are studied. It is shown that water-sorption processes in magnesium aluminate ceramics leads to corresponding increase in positron trapping rates of extended defects located near intergranual boundaries. This catalytic affect has reversible nature, being strongly dependent on sorption water fluxes in ceramics. The fixation of all water-dependent positron trapping inputs allow to refine the most significant changes in positron trapping rate of extended defects.

Titanium Pyrophosphate for Removal of Trivalent Heavy Metals and Actinides Simulated by Retention of Europium

PubMed Central

Flores-Espinosa, Rosa María; Ordoñez-Regil, Eduardo; Fernández-Valverde, Suilma Marisela

2017-01-01

This work addresses the synthesis of titanium pyrophosphate, as well as the characterization and evaluation of the sorption process of europium, for removal of trivalent heavy metals and actinides simulate. The evaluation of the surface properties of titanium pyrophosphate was carried out determining the surface roughness and surface acidity constants. The values obtained from the determination of the surface roughness of the synthesized solid indicate that the surface of the material presents itself as slightly smooth. The FITEQL program was used to fit the experimental titration curves to obtain the surface acidity constants: log⁡K+ = 3.59 ± 0.06 and log⁡K− = −3.90 ± 0.05. The results of sorption kinetics evidenced that the pseudo-order model explains the retention process of europium, in which the initial sorption velocity was 8.3 × 10−4 mg g−1 min−1 and kinetic constant was 1.8 × 10−3 g mg min−1. The maximum sorption capacity was 0.6 mg g−1. The results obtained from sorption edge showed the existence of two bidentate complexes on the surface. PMID:28785720

Inhibitory effect on the uptake and diffusion of Cd(2+) onto soybean hull sorbent in Cd-Pb binary sorption systems.

PubMed

Módenes, Aparecido N; Espinoza-Quiñones, Fernando R; Colombo, Andréia; Geraldi, Claudinéia L; Trigueros, Daniela E G

2015-05-01

The uptake of Cd(2+) and Pb(2+) ions by a soybean hull (SH) biosorbent in single and binary systems has been investigated. Sorption tests regarding SH in natura and chemically treated were carried out testing a suitable value range of solution pH, sorption temperature and shaking velocity. Sorption capacity is improved at pH 4, 30 °C temperature and 100 rpm. When a strong base is applied, a related-to-untreated SH increasing of 20% in the sorption capacity of Pb(2+) ions was observed, but with poor results for Cd(2+) uptake. Additionally, a relatively strong decreasing in both sorption capacities of Pb(2+) and Cd(2+) ions was evidenced for all acidic treatments. Regarding untreated SH, kinetic sorption data of both metals were well-interpreted by a pseudo second-order model and a rate-limiting step on the basis of an intra-particle diffusion model was suggested to occur. An inhibitory effect of Pb(2+) diffusion over Cd(2+) one was observed, limiting to reach the obtained maximum sorption capacity in single system. Maximum adsorption capacities of 0.49 and 0.67mequivg(-1) for Cd(2+) and Pb(2+), respectively, were predicted by the Langmuir isotherm model that reproduced well the equilibrium sorption data for single systems. The inhibitory effect of one metal over the other one was verified in equilibrium sorption data for binary systems interpreted on the basis of a modified extended Langmuir isotherm model, predicting changes in metal affinity onto the SH surface. Finally, SH is an alternative biosorbent with a great potential for the wastewater treatment containing cadmium and lead ions. Copyright © 2015 Elsevier Ltd. All rights reserved.

Identifiability of sorption parameters in stirred flow-through reactor experiments and their identification with a Bayesian approach.

PubMed

Nicoulaud-Gouin, V; Garcia-Sanchez, L; Giacalone, M; Attard, J C; Martin-Garin, A; Bois, F Y

2016-10-01

This paper addresses the methodological conditions -particularly experimental design and statistical inference- ensuring the identifiability of sorption parameters from breakthrough curves measured during stirred flow-through reactor experiments also known as continuous flow stirred-tank reactor (CSTR) experiments. The equilibrium-kinetic (EK) sorption model was selected as nonequilibrium parameterization embedding the K d approach. Parameter identifiability was studied formally on the equations governing outlet concentrations. It was also studied numerically on 6 simulated CSTR experiments on a soil with known equilibrium-kinetic sorption parameters. EK sorption parameters can not be identified from a single breakthrough curve of a CSTR experiment, because K d,1 and k - were diagnosed collinear. For pairs of CSTR experiments, Bayesian inference allowed to select the correct models of sorption and error among sorption alternatives. Bayesian inference was conducted with SAMCAT software (Sensitivity Analysis and Markov Chain simulations Applied to Transfer models) which launched the simulations through the embedded simulation engine GNU-MCSim, and automated their configuration and post-processing. Experimental designs consisting in varying flow rates between experiments reaching equilibrium at contamination stage were found optimal, because they simultaneously gave accurate sorption parameters and predictions. Bayesian results were comparable to maximum likehood method but they avoided convergence problems, the marginal likelihood allowed to compare all models, and credible interval gave directly the uncertainty of sorption parameters θ. Although these findings are limited to the specific conditions studied here, in particular the considered sorption model, the chosen parameter values and error structure, they help in the conception and analysis of future CSTR experiments with radionuclides whose kinetic behaviour is suspected. Copyright © 2016 Elsevier Ltd. All rights reserved.

Sorption and degradation of selected pharmaceuticals in representative soils of the Czech Republic

NASA Astrophysics Data System (ADS)

Kodesova, Radka; Kocarek, Martin; Klement, Ales; Golovko, Oksana; Grabic, Roman; Fer, Miroslav; Nikodem, Antonin; Jaksik, Ondrej

2015-04-01

Knowledge of contaminant behavior (e.g. its sorption onto soil particle, degradation etc.) is essential when assessing contaminant migration in soil and groundwater environment. This study was focused on evaluating sorption isotherms and half-lives for 7 pharmaceuticals (clarithromycin, trimethoprim, metoprolol, atenolol, clindamycin, carbamazepine, sulfamethoxazole) on 13 soils of different soil properties. Sorption of ionizable compounds was highly affected by soil pH. The sorption coefficient of sulfamethoxazole was negatively correlated to soil pH and thus positively related to hydrolytic acidity and exchangeable acidity. Sorption coefficients for clindamycin and clarithromycin were positively related to soil pH and thus negatively related to hydrolytic acidity and exchangeable acidity and positively related to base cation saturation. Sorption coefficients for the remaining pharmaceuticals (trimethoprim, metoprolol, atenolol, and carbamazepine) were also positively correlated with the base cation saturation and cation exchange capacity. Degradation rates in some degree reflected sorption of studied pharmaceuticals on soil particles and increased with decreasing sorption. The highest mobility in studied soils was observed for sulfamethoxazole, but this pharmaceutical was relatively quickly degraded. The second highest mobility was found for carbamazepine, which mostly did not noticeably degrade during our experiments. Thus this pharmaceutical has the highest potential to migrate in water environment. The lowest mobility was observed for clarithromycin. However, this pharmaceutical due to its stability may be retained in an environment for a long time. Acknowledgement: The authors acknowledge the financial support of the Czech Science Foundation (Project No. 13-12477S, Transport of pharmaceuticals in soils). References: Kodesova, R., Grabic, R., Kocarek, M., Klement, A., Golovko, O., Fer, M., Nikodem, A., Jaksik, O., Pharmaceuticals' sorptions relative to properties of thirteen different soils. Science of the Total Environment 511 (2015) 435-443.

Sorption of phenanthrene and benzene on differently structural kerogen: important role of micropore-filling.

PubMed

Zhang, Yulong; Ma, Xiaoxuan; Ran, Yong

2014-02-01

Shale was thermally treated to obtain a series of kerogen with varied maturation. Their chemical, structural and porous properties were related to the sorption and/or desorption behaviors of phenanthrene and benzene. As the treatment temperature increases, aliphatic and carbonyl carbon of the kerogen samples decrease, while their aromaticity and maturation increase. Meanwhile, the isothermal nonlinearity of phenanthrene and benzene increases whereas the sorption capacity and micropore adsorption volumes (Vo,d) initially increase and then decrease. The Vo,d of benzene is significantly correlated with, but higher than that of phenanthrene, suggesting similar micropore filling mechanism and molecular sieve effect. The benzene desorption exhibits hysteresis, which is related to the pore deformation of the kerogen and the entrapment of solute in the kerogen matrix. The Vo,d of phenanthrene and benzene on the kerogen samples accounts for 23-46% and 36-65% of the maximum sorption volumes, respectively, displaying the importance of the micropore filling. Copyright © 2013 Elsevier Ltd. All rights reserved.

Sorption and transport of iodine species in sediments from the Savannah River and Hanford Sites.

PubMed

Hu, Qinhong; Zhao, Pihong; Moran, Jean E; Seaman, John C

2005-07-01

Iodine is an important element in studies of environmental protection and human health, global-scale hydrologic processes and nuclear nonproliferation. Biogeochemical cycling of iodine is complex, because iodine occurs in multiple oxidation states and as inorganic and organic species that may be hydrophilic, atmophilic, and biophilic. In this study, we applied new analytical techniques to study the sorption and transport behavior of iodine species (iodide, iodate, and 4-iodoaniline) in sediments collected at the Savannah River and Hanford Sites, where anthropogenic (129)I from prior nuclear fuel processing activities poses an environmental risk. We conducted integrated column and batch experiments to investigate the interconversion, sorption and transport of iodine species, and the sediments we examined exhibit a wide range in organic matter, clay mineralogy, soil pH, and texture. The results of our experiments illustrate complex behavior with various processes occurring, including iodate reduction, irreversible retention or mass loss of iodide, and rate-limited and nonlinear sorption. There was an appreciable iodate reduction to iodide, presumably mediated by the structural Fe(II) in some clay minerals; therefore, careful attention must be given to potential interconversion among species when interpreting the biogeochemical behavior of iodine in the environment. The different iodine species exhibited dramatically different sorption and transport behavior in three sediment samples, possessing different physico-chemical properties, collected from different depths at the Savannah River Site. Our study yielded additional insight into processes and mechanisms affecting the geochemical cycling of iodine in the environment, and provided quantitative estimates of key parameters (e.g., extent and rate of sorption) for risk assessment at these sites.

Retention and Migration of Chlorpyrifos in Aquatic Sediments and Soils

NASA Astrophysics Data System (ADS)

Gebremariam, S. Y.; Beutel, M.; Yonge, D.; Flury, M.; Harsh, J. B.

2010-12-01

The accurate description of the fate and transport of potentially toxic agricultural pesticides in sediments and soils is of great interest to environmental scientists and regulators. Of particular concern is the widely documented detection of agricultural pesticides and their byproducts in drinking water wells. This presentation discusses results of a study of the fate and transport of chlorpyrifos, a strongly hydrophobic organophosphate-pesticide, in sediments and soils collected from a range of aquatic environments. Using radio-labeled chlorpyrifos, this study is unique in its comprehensive nature and focus on aquatic sediments, for which studies involving pesticide fate and transport are limited. Study components include: (1) batch equilibrium experiments to evaluate sorption/desorption parameters; (2) kinetic and non-equilibrium sorption experiments using miniaturized flow-cells; (3) column experiments to understand patterns of pesticide break through; and (4) numerical modeling of chlorpyrifos transport through aquatic sediments and soils. Initial results show that chlorpyrifos sorption, when corrected for reversible sorption to container walls, exhibited two component sorption, a large irreversible fraction and a smaller reversible fraction that can act as a secondary source. In addition, of a wide range of soil parameters measured, organic carbon content exhibited the highest correlation with chlorpyrifos retention in cranberry field soils. Simulation models developed in this study, which account for hysteretic and nonlinear sorption, will help to better predict the fate of chlorpyrifos and other hydrophobic chemicals in sediments and soils.

Biosorption of lead, cadmium, and zinc by Citrobacter strain MCM B-181: Characterization studies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Puranik, P.R.; Paknikar, K.M.

1999-03-01

The biosorption process for removal of lead, cadmium, and zinc by Citrobacter strain MCM B-181, a laboratory isolate, was characterized. Effects of environmental factors and growth conditions on metal uptake capacity were studied. Pretreatment of biomass with chemical agents increased cadmium sorption efficiency; however, there was no significant enhancement in lead and zinc sorption capacity. Metal sorption by Citrobacter strain MCM B-181 was found to be influenced by the pH of the solution, initial metal concentration, biomass concentration, and type of growth medium. The metal sorption process was not affected by the age of the culture or change in temperature.more » Equilibrium metal sorption was found to fit the Langmuir adsorption model. Kinetic studies showed that metal uptake by Citrobacter strain MCm B-181 was a fast process, requiring < 20 min to achieve > 90% adsorption efficiency. The presence of cations reduced lead, zinc, and cadmium sorption to the extent of 11.8%, 84.3%, and 33.4%, respectively. When biomass was exposed to multimetal solutions, metals were adsorbed in the order Co{sup 2+} < Ni{sup 2+} < Cd{sup 2+} < Cu{sup 2+}, Zn{sup 2+} < Pb{sup 2+}. A new mathematical model used for batch kinetic studies was found to be highly useful in prediction of experimentally obtained metal concentration profiles as a function of time.« less

Pressure impact of autoclave treatment on water sorption and pectin composition of flax cellulosic-fibres.

PubMed

Alix, S; Colasse, L; Morvan, C; Lebrun, L; Marais, S

2014-02-15

The tensile properties of flax fibres might permit them to be used in composites as reinforcement in organic resin, as long as their mechanical properties are reproducible and their water sorption are reduced. In this study, to minimise the variability of mechanical properties, several samples of flax fibres were blended as a non-woven fabric. In order to reduce the water absorption of this non-woven technical fibres, an autoclave treatment was performed which was expected to remove the pectins and then to reduce the water sorption on their negative charges. The impact of autoclave pressure (0.5, 1 and 2 bars) on water sorption was investigated by using a gravimetric static equilibrium method. The Park model based on the three sorption modes: Langmuir, Henry's law and clustering, was successfully used to simulate the experimental sorption data. The lowest pressure treatments impacted only the Langmuir contribution while the 2 bar autoclave-treatment positively impacted the water resistance in the core of fibres by reducing Henry's absorption rate. This was shown to be related to the chemical modifications at the surface and in the core of fibres. A schematic model is presented relating the water sorption and the pectic composition of the fabric. Copyright © 2013 Elsevier Ltd. All rights reserved.

Sorption and biodegradation characteristics of the selected pharmaceuticals and personal care products onto tropical soil.

PubMed

Foolad, Mahsa; Hu, Jiangyong; Tran, Ngoc Han; Ong, Say Leong

2016-01-01

In the present study, the sorption and biodegradation characteristics of five pharmaceutical and personal care products (PPCPs), including acetaminophen (ACT), carbamazepine (CBZ), crotamiton (CTMT), diethyltoluamide (DEET) and salicylic acid (SA), were studied in laboratory-batch experiments. Sorption kinetics experimental data showed that sorption systems under this study were more appropriately described by the pseudo second-order kinetics with a correlation coefficient (R2)>0.98. Sorption equilibrium data of almost all target compounds onto soil could be better described by the Freundlich sorption isotherm model. The adsorption results showed higher soil affinity for SA, following by ACT. Results also indicated a slight effect of pH on PPCP adsorption with lower pH causing lower adsorption of compounds onto the soil except for SA at pH 12. Moreover, adsorption of PPCPs onto the soil was influenced by natural organic matter (NOM) since the higher amount of NOM caused lower adsorption to the soil. Biodegradation studies of selected PPCPs by indigenous microbial community present in soil appeared that the removal rates of ACT, SA and DEET increased with time while no effect had been observed for the rest. This study suggests that the CBZ and CTMT can be considered as suitable chemical sewage indicators based on their low sorption affinity and high resistance to biodegradation.

Detailed sorption characteristics of the anti-diabetic drug metformin and its transformation product guanylurea in agricultural soils.

PubMed

Briones, Rowena M; Sarmah, Ajit K

2018-07-15

Detection of metformin, an antidiabetic drug and its transformation product guanylurea in various environmental matrices such as surface water and groundwater, coupled with their effects on aquatic organisms warrant an understanding of the compounds fate and behaviour in the environment. Batch studies were conducted with the aim of evaluating the sorption of these two emerging contaminants in six New Zealand agricultural soils of contrasting physico-chemical properties. Kinetic studies revealed that metformin and guanylurea sorption in Te Kowhai soil was very rapid initially achieving 90% sorption within the first 4 and 13h, respectively. Fit of several isotherm models to the measured batch sorption data showed that the hybrid models Langmuir-Freundlich and Redlich-Peterson best described the isotherms. Freundlich isotherm showed higher linearity for guanylurea (n F =0.58-0.93) in all soils compared to metformin (n F =0.25-0.71). A linear isotherm was fitted at environmentally relevant low concentrations (< 3mg/L) of target compounds and calculated values of sorption distribution coefficient (K d ) were in the range of 8.97 to 53.49L/kg for metformin and between 10.6 and 37.51L/kg for guanylurea. Sorption of both metformin and guanylurea was dependent on the soil characteristics, however, no generalisation could be made as to which had higher affinity to soils studied. Pearson's correlation and multiple regression analyses indicate that Si/Al (p=0.042) and clay (p=0.015) significantly influenced metformin K d values, whereas the soil's cation exchange capacity (p=0.024) is the single most significant factor determining guanylurea sorption in soils. It is likely that the type of minerals present in soils and its ion-exchange capacity could play an important role in metformin and guanylurea sorption, respectively. Copyright © 2018. Published by Elsevier B.V.

Chromium(VI) sorption efficiency of acid-activated banana peel over organo-montmorillonite in aqueous solutions.

PubMed

Ashraf, Anam; Bibi, Irshad; Niazi, Nabeel Khan; Ok, Yong Sik; Murtaza, Ghulam; Shahid, Muhammad; Kunhikrishnan, Anitha; Li, Dongwei; Mahmood, Tariq

2017-07-03

In the present study, we examined sorption of chromate (Cr(VI)) to acid-activated banana peel (AABP) and organo-montmorillonite (O-mont) as a function of pH, initial Cr(VI) concentration at a sorbent dose of 4 g L -1 and at 20 ± 1°C in aqueous solutions. In sorption edge experiments, maximum Cr(VI) removal was obtained at pH 3 after 2 hours by AABP and O-mont (88% and 69%). Sorption isotherm data showed that the sorption capacity of AABP was higher than O-mont (15.1 vs. 6.67 mg g -1 , respectively, at pH 4). Freundlich and Langmuir models provided the best fits to describe Cr(VI) sorption onto AABP (R 2 = 0.97) and O-mont (R 2 = 0.96). Fourier transform infrared spectroscopy elucidated that for AABP mainly the -OH, -COOH, -NH 2 , and for O-mont intercalated amines and -OH surface functional groups were involved in Cr(VI) sorption. The scanning electron microscopy combined with energy dispersive X-ray spectroscopy (SEM-EDX) analyses, although partly, indicate that the (wt. %) proportion of cations (e.g., Ca, Mg) in AABP decreased after Cr(VI) sorption. This may be due to ion exchange of chromite (Cr(III)) (produced from Cr(VI) reduction) with cationic elements in AABP. Also, Cr(VI) desorption (using phosphate solution) from AABP was lower (29%) than that from O-mont (51%) up to the third regeneration cycle. This bench scale comparative study highlights that the utilization of widely available and low-cost acid-activated biomaterials has a greater potential than organo-clays for Cr(VI) removal in aqueous media. However, future studies are warranted to precisely delineate different mechanisms of Cr(VI) sorption/reduction by acid-activated biomaterials and organo-clays.

Selenium(IV) and (VI) sorption by soils surrounding fly ash management facilities

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hyun, S.; Burns, P.E.; Murarka, I.

2006-11-15

Leachate derived from unlined coal ash disposal facilities is one of the most significant anthropogenic sources of selenium to the environment. To establish a practical framework for predicting transport of selenium in ash leachate, sorption of Se(IV) and Se(VI) from 1 mM CaSO{sub 4} was measured for 18 soils obtained down-gradient from three ash landfill sites and evaluated with respect to several soil properties. Furthermore, soil attenuation from lab-generated ash leachate and the effect of Ca{sup 2+} and SO{sub 4}{sup 2-} concentrations as well as pH on both Se(IV) and Se(VI) was quantified for a subset of soils. For bothmore » Se(IV) and Se(VI), pH combined with either percentage clay or dithionite-citrate-bicarbonate (DCB)-extractable Fe described {gt} 80% of the differences in sorption across all soils, yielding an easy approach for making initial predictions regarding site-specific selenium transport to sensitive water bodies. Se(IV) consistently exhibited an order of magnitude greater sorption than Se(VI). Selenium sorption was highest at lower pH values, with Se(IV) sorption decreasing at pH values above 6, whereas Se(VI) decreased over the entire pH range (2.5-10). Using these pH adsorption envelopes, the likely effect of ash leachate-induced changes in soil pore water pH with time on selenium attenuation by down gradient soils can be predicted. Selenium sorption increased with increasing Ca{sup 2+} concentrations while SO{sub 4}2- suppressed sorption well above enhancements by Ca{sup 2+}. Soil attenuation of selenium from ash leachates agreed well with sorption measured from 1 mM CaSO{sub 4}, indicating that 1 mM CaSO{sub 4} is a reasonable synthetic leachate for assessing selenium behavior at ash landfill sites.« less

Kinetics of zero-valent iron reductive transformation of the anthraquinone dye Reactive Blue 4.

PubMed

Epolito, William J; Yang, Hanbae; Bottomley, Lawrence A; Pavlostathis, Spyros G

2008-12-30

The effect of operational conditions and initial dye concentration on the reductive transformation (decolorization) of the textile dye Reactive Blue 4 (RB4) using zero-valent iron (ZVI) filings was evaluated in batch assays. The decolorization rate increased with decreasing pH and increasing temperature, mixing intensity, and addition of salt (100gL(-1) NaCl) and base (3gL(-1) Na2CO3 and 1gL(-1) NaOH), conditions typical of textile reactive dyebaths. ZVI RB4 decolorization kinetics at a single initial dye concentration were evaluated using a pseudo first-order model. Under dyebath conditions and at an initial RB4 concentration of 1000mgL(-1), the pseudo first-order rate constant (kobs) was 0.029+/-0.006h(-1), corresponding to a half-life of 24.2h and a ZVI surface area-normalized rate constant (kSA) of 2.9x10(-4)Lm(-2)h(-1). However, as the initial dye concentration increased, the kobs decreased, suggesting saturation of ZVI surface reactive sites. Non-linear regression of initial decolorization rate values as a function of initial dye concentration, based on a reactive sites saturation model, resulted in a maximum decolorization rate (Vm) of 720+/-88mgL(-1)h(-1) and a half-saturation constant (K) of 1299+/-273mgL(-1). Decolorization of RB4 via a reductive transformation, which was essentially irreversible (2-5% re-oxidation), is believed to be the dominant decolorization mechanism. However, some degree of RB4 irreversible sorption cannot be completely discounted. The results of this study show that ZVI treatment is a promising technology for the decolorization of commercial, anthraquinone-bearing, spent reactive dyebaths.

Comparison of amphiphilic polyurethane nanoparticles to nonionic surfactants for flushing phenanthrene from soil.

PubMed

Kim, Ju-Young; Shim, Sun-Bo; Shim, Jin-Kie

2004-12-31

Amphiphilic polyurethane (APU) nanoparticles were synthesized through crosslinking polymerization of nano-aggregates of urethane acrylate nonionomer (UAN). The efficiency of in situ extraction of sorbed phenanthrene from aquifer material was tested using soil columns and compared with that of surfactants such as Triton X-100, Brij 30, and Tween 80. The extraction efficiency of those washing materials strongly depended on their concentration, flow rate, and the degree of sorption within soil column. That is, the extraction efficiency increased with the decrease of flow rate and the degree of sorption and the increase of the concentration. Even though the surfactants are superior to APU nanoparticles at solubilizing phenanthrene, at the same flow rate (0.02 mL/min) and concentration (4000 mg/L), the effectiveness of in situ soil washing of APU nanoparticles was about two times higher than those of surfactants. This is because, at the lower flow rates, the degree of sorption of APU nanoparticles was lower than that of surfactants, owing to the chemically crosslinked nature of APU nanoparticles.

Modeling the Impact of Heterogeneous Spatial Distribution of Soil Microbes on Pesticide Biodegradation at the Centimeter Scale

NASA Astrophysics Data System (ADS)

Babey, T.; De Dreuzy, J. R.; Pinheiro, M.; Garnier, P.; Vieublé-Gonod, L.; Rapaport, A.

2015-12-01

Micro-organisms and substrates may be heterogeneously distributed in soils. This repartition as well as transport mechanisms bringing them into contact are expected to impact the biodegradation rates. Pinheiro et al [2015] have measured in cm-large reconstructed soil cores the fate of an injection of 2,4-D pesticide for different injection conditions and initial distributions of soil pesticide degraders. Through the calibration of a reactive transport model of these experiments, we show that: i) biodegradation of diffusion-controlled pesticide fluxes is favored by a high Damköhler number (high reaction rate compared to flux rate); ii) abiotic sorption processes are negligible and do not interact strongly with biodegradation; iii) biodegradation is primarily governed by the initial repartition of pesticide and degraders for diffusion-controlled transport, as diffusion greatly limits the flux of pesticide reaching the microbial hotspot due to dilution. These results suggest that for biodegradation to be substantial, a spatial heterogeneity in the repartition of microbes and substrate has to be associated with intermittent and fast transport processes to mix them.

Heavy metals binding properties of esterified lemon.

PubMed

Arslanoglu, Hasan; Altundogan, Hamdi Soner; Tumen, Fikret

2009-05-30

Sorption of Cd(2+), Cr(3+), Cu(2+), Ni(2+), Pb(2+) and Zn(2+) onto a carboxyl groups-rich material prepared from lemon was investigated in batch systems. The results revealed that the sorption is highly pH dependent. Sorption kinetic data indicated that the equilibrium was achieved in the range of 30-240 min for different metal ions and sorption kinetics followed the pseudo-second-order model for all metals studied. Relative sorption rate of various metal cations was found to be in the general order of Ni(2+)>Cd(2+)>Cu(2+)>Pb(2+)>Zn(2+)>Cr(3+). The binding characteristics of the sorbent for heavy metal ions were analyzed under various conditions and isotherm data was accurately fitted to the Langmuir equation. The metal binding capacity order calculated from Langmuir isotherm was Pb(2+)>Cu(2+)>Ni(2+)>Cd(2+)>Zn(2+)>Cr(3+). The mean free energy of metal sorption process calculated from Dubinin-Radushkevich parameter and the Polanyi potential was found to be in the range of 8-11 kJ mol(-1) for the metals studied showing that the main mechanism governing the sorption process seems to be ion exchange. The basic thermodynamic parameters of metals ion sorption process were calculated by using the Langmuir constants obtained from equilibration study. The DeltaG degrees and DeltaH degrees values for metals ion sorption on the lemon sorbent showed the process to be spontaneous and exothermic in nature. Relatively low DeltaH degrees values revealed that physical adsorption significantly contributed to the mechanism.

Surface reactions kinetics between nanocrystalline magnetite and uranyl.

PubMed

Missana, Tiziana; Maffiotte, César; García-Gutiérrez, Miguel

2003-05-01

Magnetite is the most important end member of iron corrosion products under reducing environment, which is the condition expected in a deep geological high level radioactive waste disposal. Nanocrystalline magnetite was synthesized in the laboratory and its physicochemical properties were analyzed in detail. The kinetics of the adsorption of U(VI) and the kinetics of the actinide reduction to a lower oxidation state, in presence of the oxide, were studied by means of batch sorption techniques and X-ray photoelectron spectroscopy (XPS) analysis. The results showed that the uranium sorption and reduction processes on the magnetite surface have very fast kinetics (hours), the reduction process being triggered by sorption. XPS measurements showed that the speciation of uranium at the surface does not show significant changes with time (from 1 day to 3 months), as well as the quantity of uranium detected at the surface. The surface speciation depended on the initial pH of the contact solution. Considering that the Eh of equilibrium between magnetite and the solution, under our experimental conditions, is slightly positive (50-100 mV), the uranium reduction would also be thermodynamically possible within the liquid phase. However, the kinetics of reduction in the liquid occur at a much slower rate which, in turn, has to depend on the attainment of the magnetite/solution equilibrium. The decrease of uranium in solution, observed after the uranyl adsorption stage, and particularly at acidic pH, is most probably due to the precipitation of U(IV) formed in the solution.

Cadmium biosorption rate in protonated Sargassum biomass

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, J.; Volesky, B.

1999-03-01

Biosorption of the heavy metal ion Cd{sup 2+} by protonated nonliving brown alga Sargassum fluitans biomass was accompanied by the release of hydrogen protons from the biomass. The uptake of cadmium and the release of proton matched each other throughout the biosorption process. The end-point titration methodology was used to maintain the constant pH 4.0 for developing the dynamic sorption rate. The sorption isotherm could be well represented by the Langmuir sorption model. A mass transfer model assuming the intraparticle diffusion in a one-dimensional thin plate as a controlling step was developed to describe the overall biosorption rate of cadmiummore » ions in flat seaweed biomass particles. The overall biosorption mathematical model equations were solved numerically yielding the effective diffusion coefficient D{sub e} about 3.5 {times} 10{sup {minus}6} cm{sup 2}/s. This value matches that obtained for the desorption process and is approximately half of that of the molecular diffusion coefficient for cadmium ions in aqueous solution.« less

Quaternized wood as sorbent for hexavalent chromium.

PubMed

Low, K S; Lee, C K; Lee, C Y

2001-01-01

The potential of quaternized wood (QW) chips in removing hexavalent chromium from synthetic solution and chrome waste under both batch and continuous-flow conditions was investigated. Sorption was found to be dependent on pH, metal concentration, and temperature. QW chips provide higher sorption capacity and wider pH range compared with untreated wood chips. The equilibrium data could be fitted into the Langmuir isotherm model, and maximum sorption capacities were calculated to be 27.03 and 25.77 mg/g in synthetic chromate solution and chrome waste, respectively. The presence of sulfate in high concentration appeared to suppress the uptake of chromium by QW chips. Column studies showed that bed depth influenced the breakthrough time greatly whereas flow rate of influent had little effect on its sorption on the column.

Adsorption of As(III), As(V) and Cu(II) on zirconium oxide immobilized alginate beads in aqueous phase.

PubMed

Kwon, Oh-Hun; Kim, Jong-Oh; Cho, Dong-Wan; Kumar, Rahul; Baek, Seung Han; Kurade, Mayur B; Jeon, Byong-Hun

2016-10-01

A composite adsorbent to remove arsenite [As(III)], arsenate [As(V)], and copper [Cu(II)] from aqueous phase was synthesized by immobilizing zirconium oxide on alginate beads (ZOAB). The composition (wt%) of ZOAB (Zr-34.0; O-32.7; C-21.3; Ca-1.0) was confirmed by energy dispersive X-ray (EDX) analysis. Sorption studies were conducted on single and binary sorbate systems, and the effects of contact time, initial adsorbate concentration, and pH on the adsorption performance of ZOAB (pHPZC = 4.3) were monitored. The sorption process for As(III)/As(V) and Cu(II) reached an equilibrium state within 240 h and 24 h, respectively, with maximum sorption capacities of 32.3, 28.5, and 69.9 mg g(-1), respectively. The addition of Cu(II) was favorable for As(V) sorption in contrast to As(III). In the presence of 48.6 mg L(-1) Cu(II), the sorption capacity of As(V) increased from 1.5 to 3.8 mg g(-1) after 240 h. The sorption data for As(III)/As(V) and Cu(II) conformed the Freundlich and Langmuir isotherm models, respectively. The adsorption of As(III), As(V), and Cu(II) followed pseudo second order kinetics. The effect of arsenic species on Cu(II) sorption was insignificant. The results of present study demonstrated that the synthesized sorbent could be useful for the simultaneous removal of both anionic and cationic contaminants from wastewaters. Copyright © 2016 Elsevier Ltd. All rights reserved.

Sensitivity of Deep Soil Organic Carbon Age to Sorption, Transport and Microbial Interactions - Insights from a Calibrated Process Model

NASA Astrophysics Data System (ADS)

Ahrens, B.; Schrumpf, M.; Reichstein, M.

2013-12-01

Subsoil soil organic carbon (SOC) is characterized by conventional radiocarbon ages on the order of centuries to millennia. Most vertically explicit SOC turnover models represent this persistence of deep SOC by one pool that has millennial turnover times. This approach lumps different stabilizing mechanisms such as chemical recalcitrance, sorptive stabilization and energy limitation into a single rate constant. As an alternative, we present a continuous, vertically explicit SOC decomposition model that allows for stabilization via sorption and microbial interactions (COMISSION model). We compare the COMISSION model with the SOC profile of a Haplic Podzol under a Norway spruce forest. In the COMISSION model two pools receive aboveground litter input and vertically distributed root litter input. The readily leachable and soluble fraction of litter input enters a dissolved organic carbon pool (DOC), while the rest enters the residue pool which represents polymeric, non-soluble SOC. The residue pool is depolymerized with extracellular enzymes produced by a microbial pool to enter the DOC pool which represents SOC potentially available for assimilation by microbes. The adsorption/desorption of DOC from/to mineral surfaces controls the availability of carbon in the DOC pool for assimilatory uptake by microbes. The sorption of DOC is modeled with dynamic Langmuir equations. The desorbed part of the DOC pool not only constitutes the substrate for the microbial pool, but is also transported via advection. Interactions of microbes with the residue and DOC pool are modeled with Michaelis-Menten kinetics - this not only allows representing ';priming', but also the retardation of decomposition via energy limitation in the deep soil where substrate is scarce. Further, soil organic matter is recycled within the soil profile through microbial processing - dead microbes either enter the DOC or the residue pool, and thereby also contribute to longer residence times with soil depth. First results of a calibration against SOC, SO14C, MOC and MO14C profiles (mineral associated organic carbon, density fraction >1.6 g cm-3) of a Haplic Podzol of the Waldstein site (Germany) show that we can use the maximum sorption capacity (qmax) estimated from batch sorption experiments to parameterize the dynamic Langmuir sorption equation. qmax could potentially be extrapolated to other soil profiles based on relations to iron and aluminum oxide contents. Although we are able to capture the secondary maximum of SOC contents in the Bh horizon with qmax from batch sorption experiments, our results indicate that the adsorption and desorption rates retrieved from batch sorption experiments are too fast to explain the low Δ14C values of the MOC. This could point to other processes apart from DOC sorption that trigger stabilization by organo-mineral associations with a stronger apparent irreversibility (e.g. inclusion in small pores). Alternatively, the conditions of batch sorption experiments (constant shaking in centrifuge tubes) might not be representative for in situ sorption conditions. Overall, we show how effective decomposition rates and 14C ages readily emerge from a combination of known stabilizing and destabilizing mechanisms and we discuss how to identify these processes with a model-data fusion framework.

Sorption and oxic degradation of the explosive CL-20 during transport in subsurface sediments.

PubMed

Szecsody, J E; Girvin, D C; Devary, B J; Campbell, J A

2004-08-01

The abiotic sorption and oxic degradation processes that control the fate of the explosive CL-20, Hexanitrohexaazaisowurtzitane, in the subsurface environment were investigated to determine the potential for vadose and groundwater contamination. Sorption of aqueous CL-20 is relatively small (K(d) = 0.02-3.83 cm3 g(-1) for 7 sediments and 12 minerals), which results in only slight retardation relative to water movement. Thus, CL-20 could move quickly through unsaturated and saturated sediments of comparable composition to groundwater, similar to the subsurface behavior of RDX. CL-20 sorption was mainly to mineral surfaces of the sediments, and the resulting isotherm was nonlinear. CL-20 abiotically degrades in oxic environments at slow rates (i.e., 10s to 100s of hours) with a wide variety of minerals, but at fast rates (i.e., minutes) in the presence of 2:1 phyllosilicate clays (hectorite, montmorillonite, nontronite), micas (biotite, illite), and specific oxides (MnO2 and the ferrous-ferric iron oxide magnetite). High concentrations of surface ferrous iron in a dithionite reduced sediment degraded CL-20 the fastest (half-life < 0.05 h), but 2:1 clays containing no structural or adsorbed ferrous iron (hectorite) could also quickly degrade CL-20 (half-life < 0.2 h). CL-20 degradation rates were slower in natural sediments (half-life 3-800 h) compared to minerals. Sediments with slow degradation rates and small sorption would exhibit the highest potential for deep subsurface migration. Products of CL-20 oxic degradation included three high molecular weight compounds and anions (nitrite and formate). The 2-3.5 moles of nitrite produced suggest CL-20 nitro-groups are degraded, and the amount of formate produced (0.2-1.2 moles) suggests the CL-20 cage structure is broken in some sediments. Identification of further degradation products and CL-20 mineralization rates is needed to fully assess the impact of these CL-20 transformation rates on the risk of CL-20 (and degradation product) subsurface movement.

Sorption-induced effects of humic substances on mass transfer of organic pollutants through aqueous diffusion boundary layers: the example of water/air exchange.

PubMed

Ramus, Ksenia; Kopinke, Frank-Dieter; Georgi, Anett

2012-02-21

This study examines the effect of dissolved humic substances (DHS) on the rate of water-gas exchange of organic compounds under conditions where diffusion through the aqueous boundary layer is rate-determining. A synthetic surfactant was applied for comparison. Mass-transfer coefficients were determined from the rate of depletion of the model compounds by means of an apparatus containing a stirred aqueous solution with continuous purging of the headspace above the solution. In addition, experiments with continuous passive dosing of analytes into the water phase were conducted to simulate a system where thermodynamic activity of the chemical in the aqueous phase is identical in the presence and absence of DHS. The experimental results show that DHS and surfactants can affect water-gas exchange rates by the superposition of two mechanisms: (1) hydrodynamic effects due to surface film formation ("surface smoothing"), and (2) sorption-induced effects. Whether sorption accelerates or retards mass transfer depends on its effect on the thermodynamic activity of the pollutant in the aqueous phase. Mass transfer will be retarded if the activity (or freely dissolved concentration) of the pollutant is decreased due to sorption. If it remains unchanged (e.g., due to fast equilibration with a sediment acting as a large source phase), then DHS and surfactant micelles can act as an additional shuttle for the pollutants, enhancing the flux through the boundary layer.

Lead and cadmium sorption mechanisms on magnetically modified biochars.

PubMed

Trakal, Lukáš; Veselská, Veronika; Šafařík, Ivo; Vítková, Martina; Číhalová, Sylva; Komárek, Michael

2016-03-01

This paper discusses Cd(II) and Pb(II) sorption efficiency of biochars modified by impregnation with magnetic particles. All selected biochar characteristics were significantly affected after the modification. More specifically, the cation exchange capacity increased after the modification, except for grape stalk biochar. However, the changes in the pH value, PZC, and BET surface after modification process were less pronounced. The metal loading rate was also significantly improved, especially for Cd(II) sorption on/in nut shield and plum stone biochars (10- and 16-times increase, respectively). The results indicated that cation exchange (as a metal sorption mechanism) was strengthened after Fe oxide impregnation, which limited the desorbed amount of tested metals. In contrast, the magnetization of grape stalk biochar reduced Pb(II) sorption in comparison with that of pristine biochar. Magnetic modification is, therefore, more efficient for biochars with well-developed structure and for more mobile metals, such as Cd(II). Copyright © 2015 Elsevier Ltd. All rights reserved.

Sorption interactions of heavy metals with biochar in soil remediation studies

NASA Astrophysics Data System (ADS)

Fristak, Vladimir; Friesl-Hanl, Wolfgang; Wawra, Anna; Soja, Gerhard

2015-04-01

The search for new materials in soil remediation applications has led to new conversion technologies such as carbonization and pyrolysis. Biochar represents the pyrolytic product of different biomass input materials processed at 350-1000°C and anoxic conditions. The pyrolysis temperature and feedstock have a considerable influence on the quality of the charred product and also its main physico-chemical properties. Biochar as porous material with large specific surface and C-stability is utilized in various environmental and agricultural technologies. Carbon sequestration, increase of soil water-holding capacity and pH as well as sorption of different xenobiotics present only a fraction of the multitude of biochar application possibilities. Heavy metals as potential sources of ecotoxicological risks are characterized by their non-degradability and the potential transfer into the food chain. Carbonaceous materials have been used for a long time as sorbents for heavy metals and organic contaminants in soil and water technologies. The similarity of biochar with activated carbon predetermines this material as remediation tool which plays an important role in heavy metal immobilization and retention with a parallel reduction in the risk of ground water and food crop contamination. In all this processes the element-specific sorption behaviour of biochar creates new conditions for pollutant binding. Sorption interaction and separation of contaminants from soil solution or waste effluent can be affected by wide-ranging parameters. In detail, our study was based on batch-sorption comparisons of two biochars produced from wood chips and green waste residues. We observed that sorption efficiency of biochar for model bivalent heavy metals (Cd, Zn, Cu) can be influenced by equilibrium parameters such as pH, contact time, initial concentration of metal in reaction solutions, presence of surfactants and chemical modification by acid hydrolysis, esterification and methylation. The study of sorption mechanisms showed differences in the sorption of the targeted heavy metals in relation to the contribution of ion-exchange and precipitation processes. We confirmed the effectivity of physico-chemical artificial aging on sorption capacity of biochar in terms of changes in surface structure. Based on these results, the application potential of biochar as sorption material for stabilizing heavy metals in soils is discussed.

Sorption--desorption studies on granite. I. Initial studies of strontium, technetium, cesium, barium, cerium, europium, uranium, plutonium, and americium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Erdal, B.R.; Aguilar, R.D.; Bayhurst, B.P.

Distribution ratios were determined for sorption--desorption of radioactive tracers between the Climax Stock granite (quartz monzonite porphyry) obtained at Nevada Test Site and a water prepared to be resonably representative of the natural composition of water in equilibrium with the Climax Stock granite. The measurements were performed at 22 and 70{sup 0}C under atmospheric oxygen conditions. Elements given in order of increasing distribution coefficient at ambient temperature are: U(VI), Sr, Tc(VII), Ba, Ce(III), Cs, Eu(III), Pu, and Am. At 70{sup 0}C the order is: Tc(VII), Sr, Ce(III), Eu(III), Ba, Cs, Pu, and Am. The effects of surface area and mineralogymore » on sorption were also investigated.« less

Bio-based thermosetting epoxy foam: Tannic acid valorization toward dye-decontaminating and thermo-protecting applications.

PubMed

Esmaeili, N; Salimi, A; Zohuriaan-Mehr, M J; Vafayan, M; Meyer, W

2018-05-23

Bio-resourced thermosetting epoxy foam was synthesized from tannic acid toward two different applications e.g., dye-decontaminating and thermo-insulating. Epoxidized tannic acid (ETA) foam was produced without using of organic volatile compounds or flammable foaming gases. The foam density, thermal conductivity and closed-cell content were studied. Besides, TGA showed high char yield (49% in N 2 and 48.3% in air) at 600 °C accompanied by high LOI (37.1 in N 2 and 36.8 in air). The high thermo-stability and intumescent char yield along with low thermal conductivity recommends the foam suitability for being used as an insulating material. Additionally, sorption of methylene blue onto ETA foam was kinetically investigated. The study of contact time, ionic strength, solution pH, initial sorbate concentration and desorption revealed the dependency of the sorption process to pH and initial sorbate concentration. The experimental data fitted well with the Langmuir isotherm (R 2  = 0.997), yielding maximum sorption capacity of 36.25 mg/g (ETA foam = 0.05 g, pH = 7, MB concentration = 50 ppm, Volume = 25 mL). The kinetic data verified that MB sorption could be represented by the pseudo second-order model. Overall, the ETA foam can be introduced as a candidate for removing cationic pollutants, thermal insulator, and self-extinguishing/intumescent materials. Copyright © 2018 Elsevier B.V. All rights reserved.

Sorption of chromium with struvite during phosphorus recovery.

PubMed

Rouff, Ashaki A

2012-11-20

Struvite (MgNH(4)PO(4)·6H(2)O; MAP) precipitation is a viable means of phosphorus (P) recovery from animal and human wastes. The behavior of metal contaminants such as chromium (Cr) during struvite precipitation, however, requires consideration. Here the influence of both Cr concentration and oxidation state on sorption is assessed. The Cr content of struvite precipitated in the presence of 1-100 μM Cr as Cr(III) (22.3-3030.1 mg/kg) was higher than that of solids from Cr(VI) (4.5-5.1 mg/kg) solutions. For 1-20 μM Cr(III) solids, scanning electron microscopy (SEM) revealed etch pit formation on struvite crystal surfaces, indicative of a surface interaction. The formation of an adsorbate was confirmed by X-ray absorption fine structure spectroscopy (XAFS). At initial concentrations ≥20 μM Cr(III), XAFS confirmed the formation of a Cr(OH)(3)·nH(2)O(am) precipitate. Fourier transform infrared (FT-IR) spectroscopy revealed that both Cr(III) and Cr(VI) sorption resulted in distortion of the PO(4)(3-) tetrahedra in the mineral structure. This, combined with SEM results revealed that even at low sorbed concentrations, the Cr impurity can affect the mineral surface and structure. Thus, the initial Cr concentration and oxidation state in wastes targeted for P recovery will dictate the final Cr content, the mechanism of sorption, and impact on the struvite structure.

Ferrihydrite-impregnated granular activated carbon (FH@GAC) for efficient phosphorus removal from wastewater secondary effluent.

PubMed

Mahardika, Dedy; Park, Hak-Soon; Choo, Kwang-Ho

2018-05-23

Adsorptive removal of phosphorus from wastewater effluents has attracted attention because of its reduced sludge production and potential P recovery. In this study, we investigated granular activated carbons (GACs) impregnated with amorphous ferrihydrite (FH@GAC) for the sorption of phosphorus from aqueous solutions. Preoxidation of intact GAC surfaces using an oxidant (e.g., hypochlorite) and strong acids (e.g., HNO 3 /H 2 SO 4 ) was performed to create active functional groups (e.g., carboxyl or phenolic) for enhanced iron binding, leading to greater phosphorus uptake. Both the rate and the capacity of phosphorus sorption onto FH@GAC had significant, positive relationships (Pearson correlation coefficient r > 0.9) with the product of surface area and Fe content. The pseudo-second-order reaction kinetics explained the P sorption rate better than the pseudo-first-order reaction kinetics, whereas the Langmuir model fit the P sorption isotherm better than the Freundlich model. The iron content in the FH@GAC increased significantly (>10 mg/g) when GAC (e.g., BMC1050) was preoxidized by a 1:1 (w/w) concentrated HNO 3 /H 2 SO 4 mixture. The Langmuir maximum P sorption capacity of a functionalized FH@BMC1050 adsorbent prepared with acid pretreatment was estimated to be substantial (5.73 mg P/g GAC corresponding to 526 mg P/g Fe). This sorption capacity was superior to that of a FH slurry, possibly because the nano-sized FH formed inside the GAC pores (<2.5 nm) can bind phosphate ions more effectively than FH aggregates. Fixed-bed column reactor operation with bicarbonate regeneration showed potential for efficient, continuous phosphorus removal by FH@GAC media. Copyright © 2018 Elsevier Ltd. All rights reserved.

Synthesis optimization of oil palm empty fruit bunch and rice husk biochars for removal of imazapic and imazapyr herbicides.

PubMed

Yavari, Saba; Malakahmad, Amirhossein; Sapari, Nasiman B; Yavari, Sara

2017-05-15

Imidazolinones are a family of herbicides that are used to control a broad range of weeds. Their high persistence and leaching potential make them probable risk to the ecosystems. In this study, biochar, the biomass-derived solid material, was produced from oil palm empty fruit bunches (EFB) and rice husk (RH) through pyrolysis process. Feedstock and pyrolysis variables can control biochar sorption capacity. Therefore, the present study attempts to evaluate effects of three pyrolysis variables (temperature, heating rate and retention time) on abilities of biochars for removal of imazapic and imazapyr herbicides from soil. Response surface methodology (RSM) was used for optimizing the variables to achieve maximum sorption performance of the biochars. Experimental data were interpreted accurately by quadratic models. Based on the results, sorption capacities of both biochars raised when temperature decreased to 300 °C, mainly because of increased biochars effective functionality in sorption of polar molecules. Heating rate of 3°C/min provided optimum conditions to maximize the sorption capacities of both biochars. Retention time of about 1 h and 3 h were found to be the best for EFB and RH biochars, respectively. EFB biochar was more efficient in removal of the herbicides, especially imazapyr due to its chemical composition and higher polarity index (0.42) rather than RH biochar (0.39). Besides, higher cation exchange capacity (CEC) values of EFB biochar (83.90 cmol c /kg) in comparison with RH biochar (70.73 cmol c /kg) represented its higher surface polarity effective in sorption of the polar herbicides. Copyright © 2017 Elsevier Ltd. All rights reserved.

Moisture Sorption–desorption Characteristics and the Corresponding Thermodynamic Properties of Carvedilol Phosphate

PubMed Central

Allada, Ravikiran; Maruthapillai, Arthanareeswari; Palanisamy, Kamaraj; Chappa, Praveen

2017-01-01

Aims: Carvedilol phosphate (CDP) is a nonselective beta-blocker used for the treatment of heart failures and hypertension. In this work, moisture sorption–desorption characteristics and thermodynamic properties of CDP have been investigated. Materials and Methods: The isotherms were determined using dynamic vapor sorption analyzer at different humidity conditions (0%–90% relative humidity) and three pharmaceutically relevant temperatures (20°C, 30°C, and 40°C). The experimental sorption data determined were fitted to various models, namely, Brunauer–Emmett–Teller; Guggenheim-Anderson-De Boer (GAB); Peleg; and modified GAB. Isosteric heats of sorption were evaluated through the direct use of sorption isotherms by means of the Clausius-Clapeyron equation. Statistical Analysis Used: The sorption model parameters were determined from the experimental sorption data using nonlinear regression analysis, and mean relative percentage deviation (P), correlation (Correl), root mean square error, and model efficiency were considered as the criteria to select the best fit model. Results: The sorption–desorption isotherms have sigmoidal shape – confirming to Type II isotherms. Based on the statistical data analysis, modified GAB model was found to be more adequate to explain sorption characteristics of CDP. It is noted that the rate of adsorption and desorption is specific to the temperature at which it was being studied. It is observed that isosteric heat of sorption decreased with increasing equilibrium moisture content. Conclusions: The calculation of the thermodynamic properties was further used to draw an understanding of the properties of water and energy requirements associated with the sorption behavior. The sorption–desorption data and the set of equations are useful in the simulation of processing, handling, and storage of CDP and further behavior during manufacture and storage of CDP formulations. PMID:28584488

Contribution of extracellular polymeric substances from Shewanella sp. HRCR-1 biofilms to U(VI) immobilization.

PubMed

Cao, Bin; Ahmed, Bulbul; Kennedy, David W; Wang, Zheming; Shi, Liang; Marshall, Matthew J; Fredrickson, Jim K; Isern, Nancy G; Majors, Paul D; Beyenal, Haluk

2011-07-01

The goal of this study was to quantify the contribution of extracellular polymeric substances (EPS) to U(VI) immobilization by Shewanella sp. HRCR-1. Through comparison of U(VI) immobilization using cells with bound EPS (bEPS) and cells with minimal EPS, we show that (i) bEPS from Shewanella sp. HRCR-1 biofilms contribute significantly to U(VI) immobilization, especially at low initial U(VI) concentrations, through both sorption and reduction; (ii) bEPS can be considered a functional extension of the cells for U(VI) immobilization and they likely play more important roles at lower initial U(VI) concentrations; and (iii) the U(VI) reduction efficiency is dependent upon the initial U(VI) concentration and decreases at lower concentrations. To quantify the relative contributions of sorption and reduction to U(VI) immobilization by EPS fractions, we isolated loosely associated EPS (laEPS) and bEPS from Shewanella sp. HRCR-1 biofilms grown in a hollow fiber membrane biofilm reactor and tested their reactivity with U(VI). We found that, when reduced, the isolated cell-free EPS fractions could reduce U(VI). Polysaccharides in the EPS likely contributed to U(VI) sorption and dominated the reactivity of laEPS, while redox active components (e.g., outer membrane c-type cytochromes), especially in bEPS, possibly facilitated U(VI) reduction.

Contribution of Extracellular Polymeric Substances from Shewanella sp. HRCR-1 Biofilms to U(VI) Immobilization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cao, Bin; Ahmed, B.; Kennedy, David W.

2011-06-05

The goal of this study was to quantify the contribution of extracellular polymeric substances (EPS) in U(VI) immobilization by Shewanella sp. HRCR-1. Through comparison of U(VI) immobilization using cells with bound EPS (bEPS) and cells without EPS, we showed that i) bEPS from Shewanella sp. HRCR-1 biofilms contributed significantly to U(VI) immobilization, especially at low initial U(VI) concentrations, through both sorption and reduction; ii) bEPS could be considered as a functional extension of the cells for U(VI) immobilization and they likely play more important roles at initial U(VI) concentrations; and iii) U(VI) reduction efficiency was found to be dependent uponmore » initial U(VI) concentration and the efficiency decreased at lower concentrations. To quantify relative contribution of sorption and reduction in U(VI) immobilization by EPS fractions, we isolated loosely associated EPS (laEPS) and bEPS from Shewanella sp. HRCR-1 biofilms grown in a hollow fiber membrane biofilm reactor and tested their reactivity with U(V). We found that, when in reduced form, the isolated cell-free EPS fractions could reduce U(VI). Polysaccharides in the EPS likely contributed to U(VI) sorption and dominated reactivity of laEPS while redox active components (e.g., outer membrane c-type cytochromes), especially in bEPS, might facilitate U(VI) reduction.« less

Structural characteristics and sorption properties of lithium-selective composite materials based on TiO2 and MnO2

NASA Astrophysics Data System (ADS)

Chaban, M. O.; Rozhdestvenska, L. M.; Palchyk, O. V.; Dzyazko, Y. S.; Dzyazko, O. G.

2018-04-01

A number of nanomaterials containing titanium dioxide and manganese dioxide were synthesized. The effect of synthesis conditions on structural and sorption characteristics for the selective extraction of lithium ions from solutions was studied. The ion-exchange materials were investigated with the methods of electron microscopy, thermogravimetric and X-ray analyses. During thermal synthesis phases of lithium manganese titanium spinel and TiO2 are being formed. Replacing a part of manganese with titanium ions leads to a decrease in the dissolution of Mn and to an increase in chemical stability. Composites with optimal values of selectivity and sorption rates were used to remove lithium ions from solutions with high salt background. The recovery degree of lithium ions under dynamic conditions reached 99%, the highest sorption capacity was found at pH 10.

Radionuclide desorption kinetics on synthetic Zn/Ni-labeled montmorillonite nanoparticles

NASA Astrophysics Data System (ADS)

Huber, F. M.; Heck, S.; Truche, L.; Bouby, M.; Brendlé, J.; Hoess, P.; Schäfer, T.

2015-01-01

Sorption/desorption kinetics for selected radionuclides (99Tc(VII), 232Th(IV), 233U(VI), 237Np(V), 242Pu and 243Am(III)) under Grimsel (Switzerland) ground water conditions (pH 9.7 and ionic strength of ∼1 mM) in the presence of synthetic Zn or Ni containing montmorillonite nanoparticles and granodiorite fracture filling material (FFM) from Grimsel were examined in batch studies. The structurally bound Zn or Ni in the octahedral sheet of the synthetic colloids rendered them suitable as colloid markers. Only a weak interaction of the montmorillonite colloids with the fracture filling material occurs over the experimental duration of 10,000 h (∼13 months). The tri- and tetravalent radionuclides are initially strongly associated with nanoparticles in contrast to 99Tc(VII), 233U(VI) and 237Np(V) which showed no sorption to the montmorillonite colloids. Radionuclide desorption of the nanoparticles followed by sorption to the fracture filling material is observed for 232Th(IV), 242Pu and 243Am(III). Based on the conceptual model that the driving force for the kinetically controlled radionuclide desorption from nanoparticles and subsequent association to the FFM is the excess in surface area offered by the FFM, the observed desorption kinetics are related to the colloid/FFM surface area ratio. The observed decrease in concentration of the redox sensitive elements 99Tc(VII), 233U(VI) and 237Np(V) may be explained by reduction to lower oxidation states in line with Eh-pH conditions prevailing in the experiments and thermodynamic considerations leading to (i) precipitation of a sparingly soluble phase, (ii) sorption to the fracture filling material, (iii) possible formation of eigencolloids and/or (iv) sorption to the montmorillonite colloids. Subsequent to the sorption/desorption kinetics study, an additional experiment was conducted investigating the potential remobilization of radionuclides/colloids attached to the FFM used in the sorption/desorption kinetic experiments by contacting this FFM with pure Grimsel groundwater for 7 days. A positive correlation of 242Pu, 232Th(IV) and 237Np was observed with the Zn and Ni concentrations in the desorption experiments indicating a remobilization of sorbed montmorillonite colloids. The results of the study in hand highlight (i) the novel use of structural labeled colloids to decrease the uncertainties in the determination of nanoparticle attachment providing more confidence in the derived radionuclide desorption rates. Moreover, the data illustrate (ii) the importance of radionuclide colloid desorption to be considered in the analysis and application of colloid facilitated transport both in laboratory or in-situ experiments and numerical model simulations and (iii) a possible remobilization of sorbed colloids and associated radionuclides by desorption from the matrix material (FFM) under non-equilibrium conditions.

Experimental determination of sorption in fractured flow systems

NASA Astrophysics Data System (ADS)

Zimmerman, Mitchell D.; Bennett, Philip C.; Sharp, John M.; Choi, Wan-Joo

2002-09-01

Fracture "skins" are alteration zones on fracture surfaces created by a variety of biological, chemical, and physical processes. Skins increase surface area, where sorption occurs, compared to the unaltered rock matrix. This study examines the sorption of organic solutes on altered fracture surfaces in an experimental fracture-flow apparatus. Fracture skins containing abundant metal oxides, clays, and organic material from the Breathitt Formation (Kentucky, USA) were collected in a manner such that skin surface integrity was maintained. The samples were reassembled in the lab in a flow-through apparatus that simulated ˜2.7 m of a linear fracture "conduit." A dual-tracer injection scheme was utilized with the sorbing or reactive tracer compared to a non-reactive tracer (chloride) injected simultaneously. Sorption was assessed from the ratio of the first temporal moments of the breakthrough curves and from the loss of reactive tracer mass and evaluated as a function of flow velocity and solute type. The breakthrough curves suggest dual-flow regimes in the fracture with both sorbing and non-sorbing flow fields. Significant sorption occurs for the reactive components, and sorption increased with decreasing flow rate and decreasing compound solubility. Based on moment analysis, however, there was little retardation of the center of solute mass. These data suggest that non-equilibrium sorption processes dominate and that slow desorption and boundary layer diffusion cause extensive tailing in the breakthrough curves.

Formation and Release of Cobalt(II) Sorption and Precipitation Products in Aging Kaolinite-Water Slurries.

PubMed

Thompson; Parks; Brown

2000-02-15

The uptake and release behavior of cobalt(II) was studied over thousands of hours in CO(2)-free aqueous suspensions of kaolinite under three pairs of total cobalt concentration (Co(T)) and near-neutral pH (7.5-7.8) conditions. Dissolved cobalt, aluminum, and silicon concentrations were monitored by ICPMS, and cobalt-containing products were identified by EXAFS spectroscopy. In each uptake experiment, cobalt sorbed to kaolinite as a mixture of surface-adsorbed monomers or polymers and hydrotalcite-like precipitates of the approximate composition Co(x)Al(OH)(2x+2)(A(n-))(1/n), where 2

Effects of N-vinylcaprolactam containing polyelectrolytes on hardness, fluoride release and water sorption of conventional glass ionomers.

PubMed

Moshaverinia, Alireza; Ansari, Sahar; Roohpour, Nima; Reshad, Mamaly; Schricker, Scott R; Chee, Winston Wl

2011-05-01

N-vinylcaprolactam (NVC) containing glass ionomers are promising dental restorative materials with improved mechanical properties; however, little information is available on other physical properties of this type of modified glass ionomer, especially their water sorption, fluoride releasing properties and microhardness. The purpose of this study was to investigate the effects of NVC-containing polyelectrolytes on microhardness, fluoride release and water sorption of conventional glass ionomer cements (GIC). The terpolymer of acrylic acid (AA), itaconic acid (IA) and N-vinylcaprolactam (NVC) with 8:1:1 and 7:1:2 (AA: IA: NVC) molar ratios was synthesized by free radical polymerization and characterized using 1H-NMR and FTIR. Experimental GIC specimens were made from a 50% solution of the synthesized terpolymer with Fuji IX powder in a 3.6:1 P/L ratio. Specimens were mixed and fabricated at room temperature. Vickers hardness was determined using a microhardness tester. Water sorption and fluoride releasing properties were also investigated. Commercial Fuji IX was used as the control group. All specimens were first conditioned in distilled water at 37°C for 1 day up to 1 month. Results for the experimental GIC were compared with the control group, using 1-way and 2-way ANOVA and the Tukey multiple range test (α=.05). The NVC-modified GIC exhibited higher mean values of Vickers hardness numbers (VHN). However, the data exhibited no statistically significant differences between the experimental and control groups. The experimental cement (TP2) absorbed significantly more water than the control group (P<.034). Additionally, NVC-containing specimens showed comparable fluoride releasing properties with almost the same fluoride burst and continued fluoride release from the bulk of the material. It was concluded that a hydrophilic monomer such as NVC might be able to increase the water sorption and decrease the amount of initial fluoride release of the glass ionomers. Hydrophilic monomer such as NVC might be able to increase the water sorption and decrease the amount of initial fluoride release of the glass ionomers. Copyright © 2011 The Editorial Council of the Journal of Prosthetic Dentistry. Published by Mosby, Inc. All rights reserved.

Better Gas-Gap Thermal Switches For Sorption Compressors

NASA Technical Reports Server (NTRS)

Bhandari, Pradeep; Rodriguez, Jose

1995-01-01

Gas-gap thermal switches associated with sorption compressors of some heat pumps and cryogenic systems designed for higher performance, according to proposal, by introducing controlled turbulent flows into gas gaps. Utilizes convection in turbulent flow to transfer heat at greater rate. Design takes advantage of flow of working fluid. Working fluid also serve as heat transfer medium in gas gap.

X-ray absorption spectroscopy as a tool investigating arsenic(III) and arsenic(V) sorption by an aluminum-based drinking-water treatment residual.

PubMed

Makris, Konstantinos C; Sarkar, Dibyendu; Parsons, Jason G; Datta, Rupali; Gardea-Torresdey, Jorge L

2009-11-15

Historic applications of arsenical pesticides to agricultural land have resulted in accumulation of residual arsenic (As) in such soils. In situ immobilization represents a cost-effective and least ecological disrupting treatment technology for soil As. Earlier work in our laboratory showed that drinking-water treatment residuals (WTRs), a low-cost, waste by-product of the drinking-water treatment process exhibit a high affinity for As. Wet chemical experiments (sorption kinetics and desorption) were coupled with X-ray absorption spectroscopy measurements to elucidate the bonding strength and type of As(V) and As(III) sorption by an aluminum-based WTR. A fast (1h), followed by a slower sorption stage resulted in As(V) and As(III) sorption capacities of 96% and 77%, respectively. Arsenic desorption with a 5mM oxalate from the WTR was minimal, being always <4%. X-ray absorption spectroscopy data showed inner-sphere complexation between As and surface hydroxyls. Reaction time (up to 48h) had no effect on the initial As oxidation state for sorbed As(V) and As(III). A combination of inner-sphere bonding types occurred between As and Al on the WTR surface because mixed surface geometries and interatomic distances were observed.

Effects of human management on black carbon sorption/desorption during a water transfer project: Recognizing impacts and identifying mitigation possibilities.

PubMed

Hao, Rong; Zhang, Jinliang; Wang, Peichao; Hu, Ronggui; Song, Yantun; Wu, Yupeng; Qiu, Guohong

2018-05-15

Water resources management is an important public concern. In this study, we examined the extent of sorption/desorption of trace pollutants to soil black carbon (BC) in the water level fluctuation zone (WLFZ) of the middle route of the South to North Water Transfer Project in China. In addition, we investigated the main management measures affecting these processes during the project. The results showed that the pseudo second-order model adequately describes the sorption/desorption of phenanthrene on the soil BC in the WLFZ. Water level fluctuation may indirectly influenced BC sorption/desorption by altering water chemistry. Water level residence time had negative effects on BC sorption in short-term experiments (days to months), but the impact gradually diminished with increased residence time. The results suggested that long-term field monitoring of water chemistry is urgent. During the initial period of water transfer, delaying the water supplies as drinking water source or directly irrigating crops could mitigate the adverse impacts. Future research should focus on the water-soluble products of BC degradation. The findings of this study should be useful in improving sustainable management of water resources for water transfer projects. Copyright © 2018 Elsevier Ltd. All rights reserved.

A conversion of CO2-ECBM related lab observations to reservoir requirements

NASA Astrophysics Data System (ADS)

Gensterblum, Yves; Merkel, Alexej; Busch, Andreas; Krooß, Bernhard

2013-04-01

To predict a CBM production profile either during primary or secondary production, aspects like coal permeability and porosity, density, ash and moisture content, initial gas-in-place (GIP) (from canister desorption tests), gas sorption capacity from laboratory isotherms (to obtain gas saturations and desorption pressure), gas diffusivities, coal volumetrics (thickness and areal extent) need to be understood as a minimum requirement. When dealing with CO2-ECBM selective adsorption, counter diffusion in the coal matrix, or coal shrinkage and swelling (from CH4 desorption and CO2 adsorption, respectively) and the influence of moisture need to be investigated in addition to the parameters above. During CO2-ECBM processes, the areal distribution of the CO2 injected is accomplished by flow through the cleat network. When CO2 is entering the coal matrix by a combined sorption/diffusion process it will adsorb to the coal inner surface and at the same time replace part of the CH4. This replacement occurs either by a reduction in the CH4 partial pressure or by a higher selective sorption of CO2 over CH4. Because of a concentration gradient between CH4 in the matrix compared to the cleat system, CH4 diffuses from the coal matrix into the cleat system where, by pressure drawdown towards a production well, it can be produced. In this context this presentation summarizes gas (CO2, CH4) and water sorption on coal and specifically addresses the following topics: • CH4 and CO2 sorption capacity as a function depth and rank • CO2 and CH4 sorption on natural coals and its dependence on coal specific parameters like coal rank, maceral composition or ash content (Busch and Gensterblum, 2011). • Water sorption on coal, its dependence on coal properties such as rank and coal chemistry and gas sorption in the presence of water (Busch and Gensterblum, 2011). • Uncertainties in reservoir characterisation (Gensterblum et al., 2010; Gensterblum et al., 2009) • Sorption uptake kinetic as a function of surface coverage and the influence of moisture on the kinetic Busch, A. and Gensterblum, Y., 2011. CBM and CO2-ECBM related sorption processes in coal: A review. International Journal of Coal Geology, 87: 49-71. Gensterblum, Y. et al., 2010. European inter-laboratory comparison of high pressure CO2 sorption isotherms II: Natural coals. International Journal of Coal Geology, 84(2): 115-124. Gensterblum, Y. et al., 2009. European inter-laboratory comparison of high pressure CO2 sorption isotherms. I: Activated carbon. Carbon, 47(13): 2958-2969.

High-pressure sorption of nitrogen, carbon dioxide, and their mixtures on Argonne Premium Coals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Andreas Busch; Yves Gensterblum; Bernhard M. Krooss

2007-06-15

Gas sorption isotherms have been measured for carbon dioxide and nitrogen and their binary mixture (N{sub 2}/CO{sub 2} {approximately} 80/20) on three different moisture-equilibrated coals from the Argonne Premium Coal Sample Program by the U.S. Department of Energy, varying in rank from 0.25 to 1.68% vitrinite reflectance (VR{sub r}). The measurements were conducted at 55 C and at pressures up to 27 MPa for the pure gases and up to 10 MPa for the gas mixture. The effects of the large differences in equilibrium moisture contents (0.8 to 32.2%) on sorption capacity were estimated on the basis of the aqueousmore » solubility of CO{sub 2} and N{sub 2} at experimental conditions. Especially for the Beulah-Zap coal with an equilibrium moisture content of {approximately} 32%, the amount of dissolved CO{sub 2} contributes significantly to the overall storage capacity, whereas the amounts of N{sub 2} dissolved in the moisture water are low and can be neglected. Sorption measurements with nitrogen/carbon dioxide mixtures showed very low capacities for N{sub 2}. For Illinois coal, these excess sorption values were even slightly negative, probably due to small volumetric effects (changes in condensed phase volume). The evolution of the composition of the free gas phase in contact with the coal sample has been monitored continuously during each pressure step of the sorption tests. This composition changed strongly over time. Apparently, CO{sub 2} reaches sorption sites very quickly initially and is subsequently partly replaced by N{sub 2} molecules until concentration equilibration is reached. 18 refs., 10 figs., 2 tabs.« less

Assessment of bioavailability of soil-sorbed atrazine.

PubMed

Park, Jeong-Hun; Feng, Yucheng; Ji, Pingsheng; Voice, Thomas C; Boyd, Stephen A

2003-06-01

Bioavailability of pesticides sorbed to soils is an important determinant of their environmental fate and impact. Mineralization of sorbed atrazine was studied in soil and clay slurries, and a desorption-biodegradation-mineralization (DBM) model was developed to quantitatively evaluate the bioavailability of sorbed atrazine. Three atrazine-degrading bacteria that utilized atrazine as a sole N source (Pseudomonas sp. strain ADP, Agrobacterium radiobacter strain J14a, and Ralstonia sp. strain M91-3) were used in the bioavailability assays. Assays involved establishing sorption equilibrium in sterile soil slurries, inoculating the system with organisms, and measuring the CO(2) production over time. Sorption and desorption isotherm analyses were performed to evaluate distribution coefficients and desorption parameters, which consisted of three desorption site fractions and desorption rate coefficients. Atrazine sorption isotherms were linear for mineral and organic soils but displayed some nonlinearity for K-saturated montmorillonite. The desorption profiles were well described by the three-site desorption model. In many instances, the mineralization of atrazine was accurately predicted by the DBM model, which accounts for the extents and rates of sorption/desorption processes and assumes biodegradation of liquid-phase, but not sorbed, atrazine. However, for the Houghton muck soil, which manifested the highest sorbed atrazine concentrations, enhanced mineralization rates, i.e., greater than those expected on the basis of aqueous-phase atrazine concentration, were observed. Even the assumption of instantaneous desorption could not account for the elevated rates. A plausible explanation for enhanced bioavailability is that bacteria access the localized regions where atrazine is sorbed and that the concentrations found support higher mineralization rates than predicted on the basis of aqueous-phase concentrations. Characteristics of high sorbed-phase concentration, chemotaxis, and attachment of cells to soil particles seem to contribute to the bioavailability of soil-sorbed atrazine.

Assessment of Bioavailability of Soil-Sorbed Atrazine

PubMed Central

Park, Jeong-Hun; Feng, Yucheng; Ji, Pingsheng; Voice, Thomas C.; Boyd, Stephen A.

2003-01-01

Bioavailability of pesticides sorbed to soils is an important determinant of their environmental fate and impact. Mineralization of sorbed atrazine was studied in soil and clay slurries, and a desorption-biodegradation-mineralization (DBM) model was developed to quantitatively evaluate the bioavailability of sorbed atrazine. Three atrazine-degrading bacteria that utilized atrazine as a sole N source (Pseudomonas sp. strain ADP, Agrobacterium radiobacter strain J14a, and Ralstonia sp. strain M91-3) were used in the bioavailability assays. Assays involved establishing sorption equilibrium in sterile soil slurries, inoculating the system with organisms, and measuring the CO2 production over time. Sorption and desorption isotherm analyses were performed to evaluate distribution coefficients and desorption parameters, which consisted of three desorption site fractions and desorption rate coefficients. Atrazine sorption isotherms were linear for mineral and organic soils but displayed some nonlinearity for K-saturated montmorillonite. The desorption profiles were well described by the three-site desorption model. In many instances, the mineralization of atrazine was accurately predicted by the DBM model, which accounts for the extents and rates of sorption/desorption processes and assumes biodegradation of liquid-phase, but not sorbed, atrazine. However, for the Houghton muck soil, which manifested the highest sorbed atrazine concentrations, enhanced mineralization rates, i.e., greater than those expected on the basis of aqueous-phase atrazine concentration, were observed. Even the assumption of instantaneous desorption could not account for the elevated rates. A plausible explanation for enhanced bioavailability is that bacteria access the localized regions where atrazine is sorbed and that the concentrations found support higher mineralization rates than predicted on the basis of aqueous-phase concentrations. Characteristics of high sorbed-phase concentration, chemotaxis, and attachment of cells to soil particles seem to contribute to the bioavailability of soil-sorbed atrazine. PMID:12788728

Fate and transport of phenol in a packed bed reactor containing simulated solid waste

DOE Office of Scientific and Technical Information (OSTI.GOV)

Saquing, Jovita M., E-mail: jmsaquing@gmail.com; Knappe, Detlef R.U., E-mail: knappe@ncsu.edu; Barlaz, Morton A., E-mail: barlaz@ncsu.edu

Highlights: Black-Right-Pointing-Pointer Anaerobic column experiments were conducted at 37 Degree-Sign C using a simulated waste mixture. Black-Right-Pointing-Pointer Sorption and biodegradation model parameters were determined from batch tests. Black-Right-Pointing-Pointer HYDRUS simulated well the fate and transport of phenol in a fully saturated waste column. Black-Right-Pointing-Pointer The batch biodegradation rate and the rate obtained by inverse modeling differed by a factor of {approx}2. Black-Right-Pointing-Pointer Tracer tests showed the importance of hydrodynamic parameters to improve model estimates. - Abstract: An assessment of the risk to human health and the environment associated with the presence of organic contaminants (OCs) in landfills necessitates reliable predictivemore » models. The overall objectives of this study were to (1) conduct column experiments to measure the fate and transport of an OC in a simulated solid waste mixture, (2) compare the results of column experiments to model predictions using HYDRUS-1D (version 4.13), a contaminant fate and transport model that can be parameterized to simulate the laboratory experimental system, and (3) determine model input parameters from independently conducted batch experiments. Experiments were conducted in which sorption only and sorption plus biodegradation influenced OC transport. HYDRUS-1D can reasonably simulate the fate and transport of phenol in an anaerobic and fully saturated waste column in which biodegradation and sorption are the prevailing fate processes. The agreement between model predictions and column data was imperfect (i.e., within a factor of two) for the sorption plus biodegradation test and the error almost certainly lies in the difficulty of measuring a biodegradation rate that is applicable to the column conditions. Nevertheless, a biodegradation rate estimate that is within a factor of two or even five may be adequate in the context of a landfill, given the extended retention time and the fact that leachate release will be controlled by the infiltration rate which can be minimized by engineering controls.« less

Lead sorption by waste biomass of hazelnut and almond shell.

PubMed

Pehlivan, Erol; Altun, Türkan; Cetin, Serpil; Iqbal Bhanger, M

2009-08-15

The potential to remove Pb(2+) ion from aqueous solutions using the shells of hazelnut (HNS) (Corylus avellana) and almond (AS) (Prunus dulcis) through biosorption was investigated in batch experiments. The main parameters influencing Pb(2+) ion sorption on HNS and AS were: initial metal ion concentration, amount of adsorbent, contact time and pH value of solution. The influences of initial Pb(2+) ion concentration (0.1-1.0mM), pH (2-9), contact time (10-240 min) and adsorbent amount (0.1-1.0 g) have been investigated. Equilibrium isotherms have been measured and modelled. Adsorption of Pb(2+) ions was in all cases pH-dependent showing a maximum at equilibrium pH values between 6.0 and 7.0, depending on the biomaterial, that corresponded to equilibrium pH values of 6.0 for HNS and 7.0 for AS. The equilibrium sorption capacities of HNS and AS were 28.18 and 8.08 mg/g for lead, respectively after equilibrium time of 2h. The adsorption data fit well with the Langmuir isotherm model and the experimental result inferred that adsorption, chelation and ion exchange are major adsorption mechanisms for binding Pb(2+) ion to the sorbents.

Cobalt sorption onto anaerobic granular sludge: isotherm and spatial localization analysis.

PubMed

van Hullebusch, Eric D; Gieteling, Jarno; Zhang, Min; Zandvoort, Marcel H; Daele, Wim Van; Defrancq, Jacques; Lens, Piet N L

2006-01-24

This study investigated the effect of different feeding regimes on the cobalt sorption capacity of anaerobic granular sludge from a full-scale bioreactor treating paper mill wastewater. Adsorption experiments were done with non-fed granules in monometal (only Co) and competitive conditions (Co and Ni in equimolar concentrations). In order to modify the extracellular polymeric substances and sulfides content of the granules, the sludge was fed for 30 days with glucose (pH 7, 30 degrees C, organic loading rate=1.2 g glucose l(-1) day-1) in the presence (COD/SO4(2-)=1) or absence of sulfate. The partitioning of the sorbed cobalt between the exchangeable, carbonates, organic matter/sulfides and residual fractions was determined using a sequential extraction procedure (modified Tessier). Experimental equilibrium sorption data for cobalt were analysed by the Langmuir, Freundlich and Redlich-Peterson isotherm equations. The total Langmuir maximal sorption capacity of the sludge fed with glucose and sulfate loaded with cobalt alone displayed a significantly higher maximal cobalt sorption (Qmax =18.76 mg g-1 TSS) than the sludge fed with glucose alone (Qmax =13.21 mg g-1 TSS), essentially due to an increased sorption capacity of the exchangeable (30-107%) and organic/sulfides fractions (70-30%). Environmental scanning electron microscopy coupled with an energy dispersive X-ray analysis of granular cross-sections showed that mainly iron minerals (i.e. iron sulfides) were involved in the cobalt accumulation. Moreover, the sorbed cobalt was mainly located at the edge of the granules. The sorption characteristics of the exchangeable and carbonates fractions fitted well to the Redlich-Peterson model (intermediate multi-layer sorption behaviour), whereas the sorption characteristics of the organic matter/sulfides and residual fractions fitted well to the Langmuir model (monolayer sorption behaviour). The organic matter/sulfides fraction displayed the highest affinity for cobalt for the three sludge types investigated.

Prediction of the sorption capacities and affinities of organic chemicals by XAD-7.

PubMed

Yang, Kun; Qi, Long; Wei, Wei; Wu, Wenhao; Lin, Daohui

2016-01-01

Macro-porous resins are widely used as adsorbents for the treatment of organic contaminants in wastewater and for the pre-concentration of organic solutes from water. However, the sorption mechanisms for organic contaminants on such adsorbents have not been systematically investigated so far. Therefore, in this study, the sorption capacities and affinities of 24 organic chemicals by XAD-7 were investigated and the experimentally obtained sorption isotherms were fitted to the Dubinin-Ashtakhov model. Linear positive correlations were observed between the sorption capacities and the solubilities (SW) of the chemicals in water or octanol and between the sorption affinities and the solvatochromic parameters of the chemicals, indicating that the sorption of various organic compounds by XAD-7 occurred by non-linear partitioning into XAD-7, rather than by adsorption on XAD-7 surfaces. Both specific interactions (i.e., hydrogen-bonding interactions) as well as nonspecific interactions were considered to be responsible for the non-linear partitioning. The correlation equations obtained in this study allow the prediction of non-linear partitioning using well-known chemical parameters, namely SW, octanol-water partition coefficients (KOW), and the hydrogen-bonding donor parameter (αm). The effect of pH on the sorption of ionizable organic compounds (IOCs) could also be predicted by combining the correlation equations with additional equations developed from the estimation of IOC dissociation rates. The prediction equations developed in this study and the proposed non-linear partition mechanism shed new light on the selective removal and pre-concentration of organic solutes from water and on the regeneration of exhausted XAD-7 using solvent extraction.

Strong adsorbability of mercury ions on aniline/sulfoanisidine copolymer nanosorbents.

PubMed

Li, Xin-Gui; Feng, Hao; Huang, Mei-Rong

2009-01-01

The highest Hg-ion adsorbance so far, namely up to 2063 mg g(-1), has been achieved by poly(aniline-co-5-sulfo-2-anisidine) nanosorbents. Sorption of Hg ions occurs mainly by redox and chelation mechanisms (see scheme), but also by ion exchange and physisorption.Poly(aniline (AN)-co-5-sulfo-2-anisidine (SA)) nanoparticles were synthesized by chemical oxidative copolymerization of AN and SA monomers, and their extremely strong adsorption of mercury ions in aqueous solution was demonstrated. The reactivity ratios of AN and SA comonomers were found to be 2.05 and 0.02, respectively. While AN monomer tends to homopolymerize, SA monomer tends to copolymerize with AN monomer because of the great steric hindrance and electron-attracting effect of the sulfo groups, despite the effect of conjugation of the methoxyl group with the benzene ring. The effects of initial mercury(II) concentration, sorption time, sorption temperature, ultrasonic treatment, and sorbent dosage on mercury-ion sorption onto AN/SA (50/50) copolymer nanoparticles with a number-average diameter of around 120 nm were significantly optimized. The results show that the maximum Hg-ion sorption capacity on the particulate nanosorbents can even reach 2063 mg of Hg per gram of sorbent, which would be the highest Hg-ion adsorbance so far. The sorption data fit to the Langmuir isotherm, and the process obeys pseudo-second-order kinetics. The IR and UV/Vis spectral data of the Hg-loaded copolymer particles suggest that some mercury(II) was directly reduced by the copolymer to mercury(I) and even mercury(0). A mechanism of sorption between the particles and Hg ions in aqueous solution is proposed, and a physical/ion exchange/chelation/redox sorption ratio of around 2/3/45/50 was found. Copolymer nanoparticles may be one of the most powerful and cost-effective sorbents of mercury ions, with a wide range of potential applications for the efficient removal and even recovery of the mercury ions from aqueous solution.

Sorption and degradation of selected organic UV filters (BM-DBM, 4-MBC, and OD-PABA) in laboratory water-sediment systems.

PubMed

Li, Sheng; Lu, Guanghua; Xie, Zhengxin; Ding, Jiannan; Liu, Jianchao; Li, Yi

2016-05-01

Organic UV filters that have been widely used in sunscreens and other personal care products have drawn much public concern because of their widespread contamination in the environment and their potential ecological risks to ecosystems. We selected three UV filters with high frequency of detection in the environment, namely butyl methoxy dibenzoylmethane (BM-DBM), ethylhexyl dimethyl p-aminobenzoate (OD-PABA), and 4-methylbenzylidene camphor (4-MBC), to investigate the sorption and degradation behaviors of these compounds in lab-scale water-sediment systems set up with natural water and sediment samples collected from different rivers and lakes (i.e., Yangtze River, Qinhuai River, Xuanwu Lake, and Mochou Lake) in Nanjing, East China. The sorption isotherms of these UV filters were well described by the Freundlich equation (C s   = K f  × C w (n) ). The sorption of three UV filters in four sediments was all linear or close to it, with n values between 0.92 and 1.13. A moderate to strong sorption affinity was observed for these compounds, and the sorption appears to be irreversible. For the combined sorption and degradation studies, sorption was found to be a primary mechanism for the disappearance of these UV filters from the water phase, and biotransformation appears to be the predominant factor for the degradation of the target compounds in the water-sediment systems. All three UV filters were found to be slightly resistant to the microbes in these systems, with DT50total and DT90total values-the disappearance time (DT) describes the time in which the initial total mass of the UV filters in the whole system is reduced by 50 and 90 %-ranging between 18 and 31 days and 68 and 101 days, respectively.

Redox Sorption of Oxygen Dissolved in Water on Copper Nanoparticles in an Ion Exchange Matrix

NASA Astrophysics Data System (ADS)

Vakhnin, D. D.; Pridorogina, V. E.; Polyanskii, L. N.; Kravchenko, T. A.; Gorshkov, V. S.

2018-01-01

The redox sorption of molecular oxygen from water by a thin granular layer of a copper-ion exchanger nanocomposite in the currentless mode and under cathodic polarization is studied. The speed of propagation of the boundaries of the chemical reaction of stepwise oxidation of copper nanoparticles under the conditions of polarization slows considerably. At the same time, the amount of electrochemically regenerated copper from the resulting oxides that is capable of interacting with oxygen again grows. The stationarity of the redox sorption of oxygen is due to the equality of the rates of oxidation and reduction of the metallic component of the composite.

Iodine sorption study on the proposed use of Viton A in a shuttle galley water accumulator

NASA Technical Reports Server (NTRS)

Gibbons, Randall E.; Schultz, John R.; Sauer, Richard L.

1988-01-01

The installation of a Viton A accumulator in the Shuttle galley has been proposed to prevent overpressurization of the hot water supply system. A laboratory study has been conducted to determine if there would be any interaction between the Viton A material and the iodine used to disinfect the water. Coupons of Viton A were exposed for 24 hours to aqueous iodine solutions similar in quality to the Shuttle's potable water. Changes in the iodine residual were monitored to determine the rate of iodine sorption by the coupon. Total organic carbon (TOC) was monitored to determine the rate of desorption of organic materials from the Viton A. The same coupons were then soaked in reagent-grade water for 24 hours, and iodine was monitored to determine the rate of iodine desorption. The coupons were again exposed to iodine solutions for 24 hours and iodine and TOC were monitored. No significant change in the iodine sorption rate was detected between the first and second exposures. A triangle taste test indicated at a 1 percent confidence level that the water exposed to Viton A had a different taste which was less acceptable to the panelists.

Sorption properties of algae Spirogyra sp. and their use for determination of heavy metal ions concentrations in surface water.

PubMed

Rajfur, Małgorzata; Kłos, Andrzej; Wacławek, Maria

2010-11-01

Kinetics of heavy-metal ions sorption by alga Spirogyra sp. was evaluated experimentally in the laboratory, using both the static and the dynamic approach. The metal ions--Mn(2+), Cu(2+), Zn(2+) and Cd(2+)--were sorbed from aqueous solutions of their salts. The static experiments showed that the sorption equilibria were attained in 30 min, with 90-95% of metal ions sorbed in first 10 min of each process. The sorption equilibria were approximated with the Langmuir isotherm model. The algae sorbed each heavy metal ions proportionally to the amount of this metal ions in solution. The experiments confirmed that after 30 min of exposition to contaminated water, the concentration of heavy metal ions in the algae, which initially contained small amounts of these metal ions, increased proportionally to the concentration of metal ions in solution. The presented results can be used for elaboration of a method for classification of surface waters that complies with the legal regulations. Copyright © 2010 Elsevier B.V. All rights reserved.

Water sorption-desorption in conifer cuticles: The role of lignin.

PubMed

Reina, José J.; Domínguez, Eva; Heredia, Antonio

2001-07-01

Current information on the type and amount of biopolymers present in the epidermis of conifer species is still insufficient. This work presents the detailed morphology and chemical composition of Araucaria bidwillii cuticle after selective treatments to remove the different types of biopolymers. After removal of the waxes, cutin and polar hydrolyzable components, a lignin-like fraction, which makes up 25% of the initial cuticle weight, was identified by GC-MS and infrared spectroscopy. The isolated lignin is of G type, mainly formed by guaiacyl units. This composition indicates that the conifer cuticle investigated here has similar composition to other conifer-isolated cuticles. Water sorption and desorption by the isolated cuticle and the different cuticle fractions, including lignin, were studied. The analysis of the isotherms, following distinct physicochemical models, gave useful information on the structural and physiological role of the different biopolymers present in the cuticle. Lignin fraction showed both a high water sorption and capability of retaining it in comparision to other cuticle components. Hysteresis effect on water sorption-desorption cycle and water cluster formations has also been studied, and their physiological role discussed.

Lithium sorption properties of HMnO in seawater and wastewater.

PubMed

Park, HyunJu; Singhal, Naresh; Jho, Eun Hea

2015-12-15

The lithium concentration in seawater is 0.17 mg/L, which is very low, but the overall quantity is approximately 2.5 × 10(14) kg. Therefore, seawater, which contains a vast amount of lithium, could be a major alternative source that might supply the rising demand for lithium. This research was undertaken to evaluate the feasibility of a manganese oxide (HMnO) adsorbent, which was produced after leaching lithium from lithium manganese oxide, for lithium collection from seawater. The HMnO was synthesized and deformed to a plastic after wet blending of manganese oxide and lithium hydroxide, and subsequently, the influence of pH, sorption isotherms, sorption rates, sorption energies, and effects of the co-ions were measured. Thermodynamic parameters such as ΔG°, ΔH°, and ΔS° indicated that the nature of the lithium sorption was both spontaneous and endothermic. The used HMnO could be regenerated by washing it with an HCl solution. The results demonstrated that HMnO could be effectively used for the collection of lithium from seawater with good selectivity. Copyright © 2015 Elsevier Ltd. All rights reserved.

Removal of toxic heavy metal ions in runoffs by modified alfalfa and juniper

Treesearch

J.S. Han; J.K. Park; S.H. Min

2000-01-01

A series of batch isotherm tests was performed with alfalfa and juniper fibers to evaluate the effectiveness in filtering toxic heavy metals from stormwater. The adsorption of the heavy metal ions on the alfalfa and juniper fibers was strongly dependent on the equilibrium pH value of the solution. The change in sorption rate over time showed that two different sorption...

The Geochemical Behavior and Transport Characteristics of Xenoestrogens

NASA Astrophysics Data System (ADS)

Wallace, T. C.; Bennett, P. C.

2003-12-01

Xenoestrogens are estrogenic active synthetic chemicals that mimic the actions of female sex hormones. Xenoestrogens can be produced synthetically and naturally, and exposure can occur from a variety of sources- food additives, plastics, pesticides, or pharmaceuticals. These environmental chemicals are also known as endocrine disruptors because exposure to low doses (ng/L) have been linked to adverse effects in the reproductive and developmental stages in aquatic species (i.e. reproductive anomalies, feminization, infertility, alterations in growth during life cycles, and changes in community structures). Determining the exposure risks of these toxicological compounds, however, requires a better understanding of the geochemical behavior and transport of synthetic estrogens it is discharged to. Estrogen and its metabolites are also useful tracers because of their specific medical usage (sources from birth control pills, estrogen replacement therapy, and livestock farming), slow degradation before excretion, and unique physiochemical properties (low volatility, hydrophobicity, and high Kow). Estradiol concentrations analyzed by an enzyme-linked immunoassay (ELISA) show that <2-55 ng/L are discharged to Walnut Creek, a stream that also connects to the Colorado River(TX). The bioavailability of these compounds is affected by sorption processes, where xenoestrogens become associated with solid phases. A series of batch sorption experiments using sediment collected from Walnut Creek downstream of an Austin waste water treatment plant and synthetic estrogen standards (Simga@ Estrone, 17B-Estradiol, and Estriol), examined the distribution of estrogen between solid and aqueous phases. Analysis of the concentrations sorbed to sediment result in Freundlich sorption isotherms using HPLC/UV techniques (High Performance Liquid Chromatography with UV detectors- 220 and 280nm). Sorption occurs rapidly with 98% of 17B-Estradiol sorbed within 30 minutes (Estriol=80%, Estrone=95%), which is compared to photolysis degradation rates under UV and a broader spectrum sun lamp. Ultraviolet/Visible (UV/VIS) spectroscopy of the estrogen standards with dilute fulvic acid may indicate complexing with organic material. The hydrophobic nature of estrogen molecules due to a phenolic group seem to play a large role in the sorption rate. This sorption may alter direct photolysis decay rates, thereby acting as both a `sunscreen' and a carrier by increasing the exposure distance and bioavailability of xenoestrogens in the aquatic environment.

Mercury Sorption and Desorption on Gold: A Comparative Analysis of Surface Acoustic Wave and Quartz Crystal Microbalance-Based Sensors.

PubMed

Kabir, K M Mohibul; Sabri, Ylias M; Esmaielzadeh Kandjani, Ahmad; Matthews, Glenn I; Field, Matthew; Jones, Lathe A; Nafady, Ayman; Ippolito, Samuel J; Bhargava, Suresh K

2015-08-04

Microelectromechanical sensors based on surface acoustic wave (SAW) and quartz crystal microbalance (QCM) transducers possess substantial potential as online elemental mercury (Hg(0)) vapor detectors in industrial stack effluents. In this study, a comparison of SAW- and QCM-based sensors is performed for the detection of low concentrations of Hg(0) vapor (ranging from 24 to 365 ppbv). Experimental measurements and finite element method (FEM) simulations allow the comparison of these sensors with regard to their sensitivity, sorption and desorption characteristics, and response time following Hg(0) vapor exposure at various operating temperatures ranging from 35 to 75 °C. Both of the sensors were fabricated on quartz substrates (ST and AT cut quartz for SAW and QCM devices, respectively) and employed thin gold (Au) layers as the electrodes. The SAW-based sensor exhibited up to ∼111 and ∼39 times higher response magnitudes than did the QCM-based sensor at 35 and 55 °C, respectively, when exposed to Hg(0) vapor concentrations ranging from 24 to 365 ppbv. The Hg(0) sorption and desorption calibration curves of both sensors were found to fit well with the Langmuir extension isotherm at different operating temperatures. Furthermore, the Hg(0) sorption and desorption rate demonstrated by the SAW-based sensor was found to decrease as the operating temperature increased, while the opposite trend was observed for the QCM-based sensor. However, the SAW-based sensor reached the maximum Hg(0) sorption rate faster than the QCM-based sensor regardless of operating temperature, whereas both sensors showed similar response times (t90) at various temperatures. Additionally, the sorption rate data was utilized in this study in order to obtain a faster response time from the sensor upon exposure to Hg(0) vapor. Furthermore, comparative analysis of the developed sensors' selectivity showed that the SAW-based sensor had a higher overall selectivity (90%) than did the QCM counterpart (84%) while Hg(0) vapor was measured in the presence of ammonia (NH3), humidity, and a number of volatile organic compounds at the chosen operating temperature of 55 °C.

Effect of gaseous ammonia on nicotine sorption

DOE Office of Scientific and Technical Information (OSTI.GOV)

Webb, A.M.; Singer, B.C.; Nazaroff, W.W.

2002-06-01

Nicotine is a major constituent of environmental tobacco smoke. Sorptive interactions of nicotine with indoor surfaces can substantially alter indoor concentrations. The phenomenon is poorly understood, including whether sorption is fully reversible or partially irreversible. They hypothesize that acid-base chemistry on indoor surfaces might contribute to the apparent irreversibility of nicotine sorption under some circumstances. Specifically, they suggest that nicotine may become protonated on surfaces, markedly reducing its vapor pressure. If so, subsequent exposure of the surface to gaseous ammonia, a common base, could raise the surface pH, causing deprotonation and desorption of nicotine from surfaces. A series of experimentsmore » was conducted to explore the effect of ammonia on nicotine sorption to and reemission from surfaces. The results indicate that, under some conditions, exposure to gaseous ammonia can substantially increase the rate of desorption of previously sorbed nicotine from common indoor surface materials.« less

Cysteine-Functionalized Chitosan Magnetic Nano-Based Particles for the Recovery of Light and Heavy Rare Earth Metals: Uptake Kinetics and Sorption Isotherms

PubMed Central

Galhoum, Ahmed A.; Mafhouz, Mohammad G.; Abdel-Rehem, Sayed T.; Gomaa, Nabawia A.; Atia, Asem A.; Vincent, Thierry; Guibal, Eric

2015-01-01

Cysteine-functionalized chitosan magnetic nano-based particles were synthesized for the sorption of light and heavy rare earth (RE) metal ions (La(III), Nd(III) and Yb(III)). The structural, surface, and magnetic properties of nano-sized sorbent were investigated by elemental analysis, FTIR, XRD, TEM and VSM (vibrating sample magnetometry). Experimental data show that the pseudo second-order rate equation fits the kinetic profiles well, while sorption isotherms are described by the Langmuir model. Thermodynamic constants (ΔG°, ΔH°) demonstrate the spontaneous and endothermic nature of sorption. Yb(III) (heavy RE) was selectively sorbed while light RE metal ions La(III) and Nd(III) were concentrated/enriched in the solution. Cationic species RE(III) in aqueous solution can be adsorbed by the combination of chelating and anion-exchange mechanisms. The sorbent can be efficiently regenerated using acidified thiourea. PMID:28347004

Cadmium removal in a biosorption column

DOE Office of Scientific and Technical Information (OSTI.GOV)

Volesky, B.; Prasetyo, I.

New biosorbent material derived from a ubiquitous brown marine alga Ascophyllum nodosum has been examined in packed-bed flow-through sorption columns. It effectively removed 10 mg/L of cadmium down to 1.5 ppb levels in the effluent, representing 99.985% removal. The experimental methodology used was based on the early Bohart and Adams sorption model, resulting in quantitative determination of the characteristic process parameters which can be used for performance comparison and process design. An average metal loading of the biosorbent (N[sub 0]) determined was 30 mg Cd/g, corresponding closely to that observed for the batch equilibrium metal concentration of 10 mg Cd/L.more » The critical bed depth (D[sub min]) for the potable water effluent quality standard varied with the column feed flow rate from 20 to 50 cm. The sorption column mass transfer and dispersion coefficients were determined, which are also required for solving the sorption model equations.« less

Virus transport during infiltration of a wetting front into initially unsaturated sand columns.

PubMed

Kenst, Andrew B; Perfect, Edmund; Wilhelm, Steven W; Zhuang, Jie; McCarthy, John F; McKay, Larry D

2008-02-15

We investigated the effect of different flow conditions on the transport of bacteriophage phiX174 in Memphis aquifer sand. Virus transport associated with a wetting front moving into an initially unsaturated horizontal sand column was experimentally compared with that observed under steady-state saturated vertical flow. Results obtained by sectioning the sand columns showthattotal (retained and free) resident virus concentrations decreased approximately exponentially with the travel distance. The rate of decline was similar under both transient unsaturated flow and steady-state saturated flow conditions. Total resident virus concentrations near the inlet were an order of magnitude greater than the virus concentration of the influent solution in both experiments, indicating continuous virus sorption during flow through this zone. Virus retardation was quantified using the ratio of the centroids of the relative saturation and virus concentration versus relative distance functions. The mean retardation factors were 6.43 (coefficient of variation, CV = 14.4%) and 8.22 (CV = 8.22%) for the transient unsaturated and steady-state saturated flow experiments, respectively. Attest indicated no significant difference between these values at P < 0.05. Air-water and air-water-solid interfaces are thought to enhance virus inactivation and sorption to solid particles. The similar retardation factors obtained may be attributable to the reduced presence of these interfaces in the two flow systems investigated as compared to steady-state unsaturated flow experiments in which these interfaces occur throughout the entire column.

Cr(VI)-contaminated groundwater remediation with simulated permeable reactive barrier (PRB) filled with natural pyrite as reactive material: Environmental factors and effectiveness.

PubMed

Liu, Yuanyuan; Mou, Haiyan; Chen, Liqun; Mirza, Zakaria A; Liu, Li

2015-11-15

Permeable reactive barriers (PRBs) are efficient technologies for in situ remediation of contaminated groundwater, the effectiveness of which greatly depends on the reactive media filled. Natural pyrite is an iron sulfide material with a very low content of iron and sulfur, and a mining waste which is a potential material for Cr(VI) immobilization. In this study, we conducted a series of batch tests to research the effects of typical environmental factors on Cr(VI) removal and also simulated PRB filled with natural pyrite to investigate its effectiveness, in order to find a both environmentally and economically fine method for groundwater remediation. Batch tests showed that pH had the significant impact on Cr(VI) removal with an apparently higher efficiency under acidic conditions, and dissolved oxygen (DO) would inhibit Cr(VI) reduction; a relatively high initial Cr(VI) concentration would decrease the rate of Cr(VI) sorption; ionic strength and natural organic matter resulted in no significant effects on Cr(VI) removal. Column tests demonstrated that the simulated PRB with natural pyrite as the reactive media was considerably effective for removing Cr(VI) from groundwater, with a sorption capability of 0.6222 mg Cr per gram of natural pyrite at an initial Cr(VI) concentration of 10mg/L at pH 5.5 in an anoxic environment. Copyright © 2015 Elsevier B.V. All rights reserved.

Time-dependent sorption of two novel fungicides in soils within a regulatory framework.

PubMed

Gulkowska, Anna; Buerge, Ignaz J; Poiger, Thomas; Kasteel, Roy

2016-12-01

Convincing experimental evidence suggests increased sorption of pesticides on soil over time, which, so far, has not been considered in the regulatory assessment of leaching to groundwater. Recently, Beulke and van Beinum (2012) proposed a guidance on how to conduct, analyse and use time-dependent sorption studies in pesticide registration. The applicability of the recommended experimental set-up and fitting procedure was examined for two fungicides, penflufen and fluxapyroxad, in four soils during a 170 day incubation experiment. The apparent distribution coefficient increased by a factor of 2.5-4.5 for penflufen and by a factor of 2.5-2.8 for fluxapyroxad. The recommended two-site, one-rate sorption model adequately described measurements of total mass and liquid phase concentration in the calcium chloride suspension and the calculated apparent distribution coefficient, passing all prescribed quality criteria for model fit and parameter reliability. The guidance is technically mature regarding the experimental set-up and parameterisation of the sorption model for the two moderately mobile and relatively persistent fungicides under investigation. These parameters can be used for transport modelling in soil, thereby recognising the existence of the experimentally observed, but in the regulatory leaching assessment of pesticides not yet routinely considered phenomenon of time-dependent sorption. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry.

Oxygen sorption and desorption properties of selected lanthanum manganites and lanthanum ferrite manganites.

PubMed

Nielsen, Jimmi; Skou, Eivind M; Jacobsen, Torben

2015-06-08

Temperature-programmed desorption (TPD) with a carrier gas was used to study the oxygen sorption and desorption properties of oxidation catalysts and solid-oxide fuel cell (SOFC) cathode materials (La(0.85) Sr(0.15)0.95 MnO(3+δ) (LSM) and La(0.60) Sr(0.40) Fe(0.80) Mn(0.20) O(3-δ) (LSFM). The powders were characterized by X-ray diffractometry, atomic force microscopy (AFM), and BET surface adsorption. Sorbed oxygen could be distinguished from oxygen originating from stoichiometry changes. The results indicated that there is one main site for oxygen sorption/desorption. The amount of sorbed oxygen was monitored over time at different temperatures. Furthermore, through data analysis it was shown that the desorption peak associated with oxygen sorption is described well by second-order desorption kinetics. This indicates that oxygen molecules dissociate upon adsorption and that the rate-determining step for the desorption reaction is a recombination of monatomic oxygen. Typical problems with re-adsorption in this kind of TPD setup were revealed to be insignificant by using simulations. Finally, different key parameters of sorption and desorption were determined, such as desorption activation energies, density of sorption sites, and adsorption and desorption reaction order. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Controlling risks of P water pollution by sorption on soils, pyritic material, granitic material, and different by-products: effects of pH and incubation time.

PubMed

Romar-Gasalla, Aurora; Nóvoa-Muñoz, Juan Carlos; Arias-Estévez, Manuel; Fernández-Sanjurjo, María J; Álvarez-Rodríguez, Esperanza; Núñez-Delgado, Avelino

2018-05-13

Batch experiments were used to test P sorbent potential of soil samples, pyritic and granitic materials, mussel shell, mussel shell ash, sawdust, and slate waste fines for different pH and incubation times. Maximum P sorption varied in a wide range of pH: < 4 for pyritic material, 4-6 for forest soil, > 5 for slate fines, > 6 for shell ash, and pH 6-8 for mussel shell. P sorption was rapid (< 24 h) for forest soil, shell ash, pyritic material, and fine shell. On the opposite side, it was clearly slower for vineyard soil, granitic material, slate fines, pine sawdust, and coarse shell, with increased P sorption even 1 month later. For any incubation time, P sorption was > 90% in shell ash, whereas forest soil, pyritic material, and fine shell showed sorption rates approaching 100% within 24 h of incubation. These results could be useful to manage and/or recycle the sorbents tested when focusing on P immobilization or removal, in circumstances where pH changes and where contact time may vary from hours to days, thus aiding to diminish P pollution and subsequent eutrophication risks, promoting conservation and sustainability.

Removal of Cesium From Acidic Radioactive Tank Waste Using IONSIV IE-911 (CST)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mann, Nicholas Robert; Todd, Terry Allen

2004-10-01

IONSIV IE-911, or the engineered form of crystalline silicotitanate (CST), manufactured by UOP Molecular Sieves, has been evaluated for the removal of cesium from Idaho National Engineering and Environmental Laboratory (INEEL) acidic radioactive tank waste. A series of batch contacts and column tests were performed by using three separate batches of CST. Batch contacts were performed to evaluate the concentration effects of nitric acid, sodium, and potassium ions on cesium sorption. Additional batch tests were performed to determine if americium, mercury, and plutonium would sorb onto IONSIV IE-911. An equilibrium isotherm was generated by using a concentrated tank waste simulant.more » Column tests using a 1.5 cm 3 column and flow rates of 3, 5, 10, 20, and 30 bed volumes (BV)/hr were performed to elucidate dynamic cesium sorption capacities and sorption kinetics. Additional experiments investigated the effect of CST batch and pretreatment on cesium sorption. The thermal stability of IONSIV IE-911 was evaluated by performing thermal gravimetric analysis/differential thermal analysis. Overall, IONSIV IE-911 was shown to be effective for cesium sorption from complex, highly acidic solutions; however, sorbent stability in these solutions may have a deleterious effect on cesium sorption.« less

Adsorptive removal of Auramine-O: kinetic and equilibrium study.

PubMed

Mall, Indra Deo; Srivastava, Vimal Chandra; Agarwal, Nitin Kumar

2007-05-08

Present study deals with the adsorption of Auramine-O (AO) dye by bagasse fly ash (BFA) and activated carbon-commercial grade (ACC) and laboratory grade (ACL). BFA is a solid waste obtained from the particulate collection equipment attached to the flue gas line of the bagasse fired boilers of cane sugar mills. Batch studies were performed to evaluate the influences of various experimental parameters like initial pH (pH(0)), contact time, adsorbent dose and initial concentration (C(0)) for the removal of AO. Optimum conditions for AO removal were found to be pH(0) approximately 7.0 and equilibrium time approximately 30 min for BFA and approximately 120 min for activated carbons. Optimum BFA, ACC and ACL dosages were found to be 1, 20 and 2g/l, respectively. Adsorption of AO followed pseudo-second order kinetics with the initial sorption rate for adsorption on BFA being the highest followed by those on ACL and ACC. The sorption process was found to be controlled by both film and pore diffusion with film diffusion at the earlier stages followed by pore diffusion at the later stages. Equilibrium isotherms for the adsorption of AO on BFA, ACC and ACL were analyzed by Freundlich, Langmuir, Dubinin-Radushkevich, and Temkin isotherm equations using linear correlation coefficient. Langmuir isotherm gave the best correlation of adsorption for all the adsorbents studied. Thermodynamic study showed that adsorption of AO on ACC (with a more negative Gibbs free energy value) is more favoured. BFA which was used without any pretreatment showed high surface area, pore volume and pore size exhibiting its potential to be used as an adsorbent for the removal of AO.

Conceptual models governing leaching behavior and their long-term predictive capability

USGS Publications Warehouse

Claassen, Hans C.

1981-01-01

Six models that may be used to describe the interaction of radioactive waste solids with aqueous solutions are as follows:Simple linear mass transfer;Simple parabolic mass transfer;Parabolic mass transfer with the formation of a diffusion-limiting surface layer at an arbitrary time;Initial parabolic mass transfer followed by linear mass transfer at an arbitrary time;Parabolic (or linear) mass transfer and concomitant surface sorption; andParabolic (or linear) mass transfer and concomitant chemical precipitation.Some of these models lead to either illogical or unrealistic predictions when published data are extrapolated to long times. These predictions result because most data result from short-term experimentation. Probably for longer times, processes will occur that have not been observed in the shorter experiments. This hypothesis has been verified by mass-transfer data from laboratory experiments using natural volcanic glass to predict the composition of groundwater. That such rate-limiting mechanisms do occur is reassuring, although now it is not possible to deduce a single mass-transfer limiting mechanism that could control the solution concentration of all components of all waste forms being investigated. Probably the most reasonable mechanisms are surface sorption and chemical precipitation of the species of interest. Another is limiting of mass transfer by chemical precipitation on the waste form surface of a substance not containing the species of interest, that is, presence of a diffusion-limiting layer. The presence of sorption and chemical precipitation as factors limiting mass transfer has been verified in natural groundwater systems, whereas the diffusion-limiting mechanism has not been verified yet.

Kinetic and thermodynamic studies of the Co(II) and Ni(II) ions removal from aqueous solutions by Ca-Mg phosphates.

PubMed

Ivanets, A I; Srivastava, V; Kitikova, N V; Shashkova, I L; Sillanpää, M

2017-03-01

The aim of this work was to study the sorption kinetics and thermodynamics of Co(II) and Ni(II) from aqueous solutions by sorbents on the basis of hydrogen (PD-1) and tertiary (PD-2) Ca-Mg phosphates depending on the solution temperature and sorbents chemical composition. Kinetic studies of adsorption of Co(II) and Ni(II) ions onto samples of phosphate sorbents were performed in batch experiment at the temperatures 288, 303, 318 and 333 K. The sorbent dose was fixed at 10 g L -1 , initial pH value 2.6, and contact time varied from 5 to 600 min. The kinetics of Co(II) and Ni(II) adsorption were analyzed by using pseudo-first order, pseudo-second order and intraparticle diffusion models. Thermodynamic parameters (ΔG°, ΔH° and ΔS°) for the sorption of Co(II) and Ni(II) were determined using the Gibbs-Helmholtz equation. The calculated kinetic parameters and corresponding correlation coefficients revealed that Co(II) and Ni(II) uptake process followed the pseudo-second order rate expression. Thermodynamic studies confirmed the spontaneous and endothermic nature of removal process which indicate that sorption of Co(II) and Ni(II) ions onto both phosphate sorbents is favoured at higher temperatures and has the chemisorptive mechanism. The data thus obtained would be useful for practical application of the low cost and highly effective Ca-Mg phosphate sorbents. Copyright © 2016 Elsevier Ltd. All rights reserved.

Hierarchical porous membrane via electrospinning PIM-1 for micropollutants removal

NASA Astrophysics Data System (ADS)

Pan, Ying; Zhang, Lijie; Li, Zhaojing; Ma, Liujia; Zhang, Yufeng; Wang, Jun; Meng, Jianqiang

2018-06-01

Ideal adsorbents are featured by both high adsorption capacity and high adsorption rate. Current adsorptive membranes enjoy good mass transfer performance but have limited sorption capacity. Microporous organic polymer has superiorities of small pore size and high surface area which is conductive to high adsorption capacity, but usually suffers from high mass transfer resistance. In this work, the polymer of intrinsic microporosity PIM-1 was fabricated into microfiber membranes by electrospinning for carbendazim and phenol adsorption. The PIM-1 and its electrospun membranes were characterized by 1H NMR, GPC, ATR-FTIR, FESEM, TG and BET measurements. The electrospun PIM-1 membrane was demonstrated to have hierarchical porous structure with high surface area. The equilibrium adsorption capacity for carbendazim and phenol was 0.084 mmol/g and 0.804 mmol/g, respectively. The adsorption isotherm fits well with Langmuir model and the adsorption kinetic can be described by film diffusion and chemical reaction model. The membrane can retain 95% of its initial capacity after cycling 10 times. Both the sorption capacity and kinetic coefficients are high when comparing with other sorbents for either carbendazim or phenol, demonstrating that the electrospun PIM-1 is a good adsorbent.

Functionalization of Magnetic Chitosan Particles for the Sorption of U(VI), Cu(II) and Zn(II)—Hydrazide Derivative of Glycine-Grafted Chitosan

PubMed Central

Hamza, Mohammed F.; Aly, Mohsen M.; Abdel-Rahman, Adel A.-H.; Ramadan, Samar; Raslan, Heba; Wang, Shengye; Vincent, Thierry; Guibal, Eric

2017-01-01

A new magnetic functionalized derivative of chitosan is synthesized and characterized for the sorption of metal ions (environmental applications and metal valorization). The chemical modification of the glycine derivative of chitosan consists of: activation of the magnetic support with epichlorohydrin, followed by reaction with either glycine to produce the reference material (i.e., Gly sorbent) or glycine ester hydrochloride, followed by hydrazinolysis to synthesize the hydrazide functionalized sorbent (i.e., HGly sorbent). The materials are characterized by titration, elemental analysis, FTIR analysis (Fourrier-transform infrared spectrometry), TGA analysis (thermogravimetric analysis) and with SEM-EDX (scanning electron microscopy coupled to energy dispersive X-ray analysis). The sorption performances for U(VI), Cu(II), and Zn(II) are tested in batch systems. The sorption performances are compared for Gly and HGly taking into account the effect of pH, the uptake kinetics (fitted by the pseudo-second order rate equation), and the sorption isotherms (described by the Langmuir and the Sips equations). The sorption capacities of the modified sorbent reach up to 1.14 mmol U g−1, 1.69 mmol Cu g−1, and 0.85 mmol Zn g−1. In multi-metal solutions of equimolar concentration, the chemical modification changes the preferences for given metal ions. Metal ions are desorbed using 0.2 M HCl solutions and the sorbents are re-used for five cycles of sorption/desorption without significant loss in performances. PMID:28772896

Removal of nitrate and phosphate using chitosan/Al2O3/Fe3O4 composite nanofibrous adsorbent: Comparison with chitosan/Al2O3/Fe3O4 beads.

PubMed

Bozorgpour, Farahnaz; Ramandi, Hossein Fasih; Jafari, Pooya; Samadi, Saman; Yazd, Shabnam Sharif; Aliabadi, Majid

2016-12-01

In the present study the chitosan/Al 2 O 3 /Fe 3 O 4 composite nanofibrous adsorbent was prepared by electrospinning process and its application for the removal of nitrate and phosphate were compared with chitosan/Al 2 O 3 /Fe 3 O 4 composite bead adsorbent. The influence of Al 2 O 3 /Fe 3 O 4 composite content, pH, contact time, nitrate and phosphate initial concentrations and temperature on the nitrate and phosphate sorption using synthesized bead and nanofibrous adsorbents was investigated in a single system. The reusability of chitosan/Al 2 O 3 /Fe 3 O 4 composite beads and nanofibers after five sorption-desorption cycles were carried out. The Box-Behnken design was used to investigate the interaction effects of adsorbent dosage, nitrate and phosphate initial concentrations on the nitrate and phosphate removal efficiency. The pseudo-second-order kinetic model and known Freundlich and Langmuir isotherm models were used to describe the kinetic and equilibrium data of nitrate and phosphate sorption using chitosan/Al 2 O 3 /Fe 3 O 4 composite beads and nanofibers. The influence of other anions including chloride, fluoride and sulphate on the sorption efficiency of nitrate and phosphate was examined. The obtained results revealed the higher potential of chitosan/Al 2 O 3 /Fe 3 O 4 composite nanofibers for nitrate and phosphate compared with chitosan/Al 2 O 3 /Fe 3 O 4 composite beads. Copyright © 2016 Elsevier B.V. All rights reserved.

Atrazine and Diuron partitioning within a soil-water-surfactant system

NASA Astrophysics Data System (ADS)

Wang, P.; Keller, A.

2006-12-01

The interaction between pesticide and soil and water is even more complex in the presence of surfactants. In this study, batch equilibrium was employed to study the sorption of surfactants and the partitioning behaviors of Atrazine and Diuron within a soil-water-surfactant system. Five soils and four surfactants (nonionic Triton- 100, cationic Benzalkonium Chloride (BC), anionic Linear Alkylbenzenesulfonate (LAS), and anionic Sodium Dodecyl Sulfate (SDS)) were used. All surfactant sorption isotherms exhibited an initial linear increase at low surfactant concentrations but reached an asymptotic value as the surfactant concentrations increased. Among the surfactants, BC had the highest sorption onto all soils, followed by Triton-100 and then by LAS and SDS, implying that the nature of the charge significantly influences surfactant sorption. Sorption of either Triton-100 or BC was highly correlated with soil Cation Exchange Capacity (CEC) while that of LAS and SDS was complicated by the presence of Ca2+ and Mg2+ in the aqueous phase and the CEC sites. Both LAS and SDS formed complexes with Ca2+ and Mg2+, resulting in a significant decrease in the detergency of the surfactants. At high surfactant concentrations and with micelles present in the aqueous phase, the micelles formed a more competitive partitioning site for the pesticides, resulting in less pesticide sorbed to the soil. At low Triton-100 and BC concentration, the sorption of the surfactants first resulted in less Atrazine sorption but more Diuron sorption, implying competition between the surfactants and Atrazine, which serves as an indirect evidence that there is a different sorption mechanism for Atrazine. Atrazine is a weak base and it protonates and becomes positively charged near particle surfaces where the pH is much lower than in the bulk solution. The protonated Atrazine may then be held on the CEC sites via electrostatic attraction. Triton-100, LAS and SDS sorbed on the soil showed similar sequestration efficiency for Atrazine and Diuron while BC sorbed on the soils with lower CECs showed much higher Atrazine and Diuron sequestration efficiency than the other surfactants, suggesting that the sorbed BC on these soils with less CEC forms bulk-like partitioning media more easily than the soils with higher CECs. These results significantly improve our understanding of partitioning of pesticides within soil-water-surfactant systems. These findings can serve to improve the pesticide removal efficiency of soil washing systems. Also, our results show that by studying the effect of surfactants on pesticide sorption can serve as a new method to study pesticide sorption mechanisms.

Behavior of technetium-99 in soils and plants. Final report, April 1, 1974--December 31, 1978

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gast, R.G.; Landa, E.R.; Thorvig, L.J.

Studies described in this report were aimed at establishing the magnitude and mechanisms of /sup 99/Tc sorption by soils and uptake by plants. Results show that /sup 99/Tc was sorbed from solution over a period to two to five weeks by 8 of 11 soils studies. The slow rate of sorption, the lack of sorption by low organic matter soils, the elimination of sorption following sterilization and increased sorption following addition of dextrose all point to a microbial role in the sorption process. However, it has not been established whether this is a direct or indirect role nor is itmore » possible to clearly predict the conditions under which sorption will occur. Results of plant uptake studies show that /sup 99/Tc can be taken up and translocated into the photosynthetic tissue of higher plants with concentrations in seeds being much less than in vegetative tissue. Technetium-99 was also shown to be toxic to plants at low concentrations and evidence suggests that this is a chemically rather than radiologically induced toxicity. However, this remains to be completely resolved as well as whether there is a threshold level of /sup 99/Tc required before toxicity occurs. Studies of short-term, dynamic, aerobic systems indicated that /sup 99/Tc moves through the soil as a relatively large anion exhibiting characteristic miscible displacement with some asymmetric tailing. /sup 99/Tc exhibits greater retention that C1/sup -/, which may be attributed statistically to weak complexion by organic matter. It is unlikely that this retention phenomenon is related to the static sorption activity reported in the first part of this study.« less

Sorption characteristics and separation of tellurium ions from aqueous solutions using nano-TiO2.

PubMed

Zhang, Lei; Zhang, Min; Guo, Xingjia; Liu, Xueyan; Kang, Pingli; Chen, Xia

2010-12-15

Titanium dioxide nanoparticles (nano-TiO(2)) were employed for the sorption of Te(IV) ions from aqueous solution. A detailed study of the process was performed by varying the sorption time, pH, and temperature. The sorption was found to be fast, equilibrium was reached within 8 min. When the concentration of Te(IV) was below 40 mg L(-1), at least 97% of tellurium was adsorbed by nano-TiO(2) in the pH range of 1-2 and 8-9. The sorbed Te(IV) ions were desorbed with 2.0 mL of 0.5 mol L(-1) NaOH. The sorption data could be well interpreted by the Langmuir model with the maximum adsorption capacity of 32.75 mg g(-1) (20 ± 0.1 °C) of Te(IV) on nano-TiO(2). The kinetics and thermodynamics of the sorption of Te(IV) onto nano-TiO(2) were also studied. The kinetic experimental data properly correlated with the second-order kinetic model (k(2)=0.0368 g mg(-1)min(-1), 293 K). The overall rate process appeared to be influenced by both boundary layer diffusion and intra-particle diffusion. The mean energy of adsorption was calculated to be 17.41 kJ mol(-1) from the Dubinin-Radushkevich (D-R) adsorption isotherm at room temperature. Moreover, the thermodynamic parameters for the sorption were estimated, and the ΔH(0) and ΔG(0) values indicated the exothermic and spontaneous nature of the sorption process, respectively. Finally, Nano-TiO(2) as sorbent was successfully applied to the separation of Te(IV) from the environmental samples with satisfactory results (recoveries >95%, relative standard deviations was 2.0%). Copyright © 2010 Elsevier B.V. All rights reserved.

Impact of long-term wastewater irrigation on sorption and transport of atrazine in Mexican agricultural soils.

PubMed

Müller, K; Duwig, C; Prado, B; Siebe, C; Hidalgo, C; Etchevers, J

2012-01-01

In the Mezquital Valley, Mexico, crops have been irrigated with untreated municipal wastewater for more than a century. Atrazine has been applied to maize and alfalfa grown in the area for weed control for 15 years. Our objectives were to analyse (i) how wastewater irrigation affects the filtering of atrazine, and (ii) if the length of irrigation has a significant impact. We compared atrazine sorption to Phaeozems that have been irrigated with raw wastewater for 35 (P35) and 85 (P85) years with sorption to a non-irrigated (P0) Phaeozem soil under rainfed agriculture. The use of bromide as an inert water tracer in column experiments and the subsequent analysis of the tracers' breakthrough curves allowed the calibration of the hydrodynamic parameters of a two-site non equilibrium convection-dispersion model. The quality of the irrigation water significantly altered the soils' hydrodynamic properties (hydraulic conductivity, dispersivity and the size of pores that are hydraulically active). The impacts on soil chemical properties (total organic carbon content and pH) were not significant, while the sodium adsorption ratio was significantly increased. Sorption and desorption isotherms, determined in batch and column experiments, showed enhanced atrazine sorption and reduced and slower desorption in wastewater-irrigated soils. These effects increased with the length of irrigation. The intensified sorption-desorption hysteresis in wastewater-irrigated soils indicated that the soil organic matter developed in these soils had fewer high-energy, easily accessible sorption sites available, leading to lower and slower atrazine desorption rates. This study leads to the conclusion that wastewater irrigation decreases atrazine mobility in the Mezquital valley Phaeozems by decreasing the hydraulic conductivity and increasing the soil's sorption capacity.

Surface Engineering of PAMAM-SDB Chelating Resin with Diglycolamic Acid (DGA) Functional Group for Efficient Sorption of U(VI) and Th(IV) from Aqueous Medium.

PubMed

Ilaiyaraja, P; Deb, A K Singha; Ponraju, D; Ali, Sk Musharaf; Venkatraman, B

2017-04-15

A novel chelating resin obtained via growth of PAMAM dendron on surface of styrene divinyl benzene resin beads, followed by diglycolamic acid functionalization of the dendrimer terminal. Batch experiments were conducted to study the effects of pH, nitric acid concentration, amount of adsorbent, shaking time, initial metal ion concentration and temperature on U(VI) and Th(IV) adsorption efficiency. Diglycolamic acid terminated PAMAM dendrimer functionalized styrene divinylbenzene chelating resin (DGA-PAMAM-SDB) is found to be an efficient candidate for the removal of U(VI) and Th(IV) ions from aqueous (pH >4) and nitric acid media (>3M). The sorption equilibrium could be reached within 60min, and the experimental data fits with pseudo-second-order model. Langmuir sorption isotherm model correlates well with sorption equilibrium data. The maximum U(VI) and Th(IV) sorption capacity onto DGA-PAMAMG 5 -SDB was estimated to be about 682 and 544.2mgg -1 respectively at 25°C. The interaction of actinides and chelating resin is reversible and hence, the resin can be regenerated and reused. DFT calculation on the interaction of U(VI) and Th(IV) ions with chelating resin validates the experimental findings. Copyright © 2017 Elsevier B.V. All rights reserved.

Influence of chemical and mechanical polishing on water sorption and solubility of denture base acrylic resins.

PubMed

Rahal, Juliana Saab; Mesquita, Marcelo Ferraz; Henriques, Guilherme Elias Pessanha; Nóbilo, Mauro Antonio Arruda

2004-01-01

Influence of polishing methods on water sorption and solubility of denture base acrylic resins was studied. Eighty samples were divided into groups: Classico (CL), and QC 20 (QC) - hot water bath cured; Acron MC (AC), and Onda Cryl (ON) - microwave cured; and submitted to mechanical polishing (MP) - pumice slurry, chalk powder, soft brush and felt cone in a bench vise; or chemical polishing (CP) - heated monomer fluid in a chemical polisher. The first desiccation process was followed by storage in distilled water at 37 +/- 1 degrees C for 1 h, 1 day, 1, 2, 3 and 4 weeks. Concluding each period, water sorption was measured. After the fourth week, a second desiccation process was done to calculate solubility. Data were submitted to analysis of variance, followed by Tukey test (p

Sequestration of hydrophobic organic contaminants by geosorbents

USGS Publications Warehouse

Luthy, Richard G.; Aiken, George R.; Brusseau, Mark L.; Cunningham, Scott D.; Gschwend, Philip M.; Pignatello, Joseph J.; Reinhard, Martin; Traina, Samuel J.; Weber, Walter J.; Westall, John C.

1997-01-01

The chemical interactions of hydrophobic organic contaminants (HOCs) with soils and sediments (geosorbents) may result in strong binding and slow subsequent release rates that significantly affect remediation rates and endpoints. The underlying physical and chemical phenomena potentially responsible for this apparent sequestration of HOCs by geosorbents are not well understood. This challenges our concepts for assessing exposure and toxicity and for setting environmental quality criteria. Currently there are no direct observational data revealing the molecular-scale locations in which nonpolar organic compounds accumulate when associated with natural soils or sediments. Hence macroscopic observations are used to make inferences about sorption mechanisms and the chemical factors affecting the sequestration of HOCs by geosorbents. Recent observations suggest that HOC interactions with geosorbents comprise different inorganic and organic surfaces and matrices, and distinctions may be drawn along these lines, particularly with regard to the roles of inorganic micropores, natural sorbent organic matter components, combustion residue particulate carbon, and spilled organic liquids. Certain manipulations of sorbates or sorbent media may help reveal sorption mechanisms, but mixed sorption phenomena complicate the interpretation of macroscopic data regarding diffusion of HOCs into and out of different matrices and the hysteretic sorption and aging effects commonly observed for geosorbents. Analytical characterizations at the microscale, and mechanistic models derived therefrom, are needed to advance scientific knowledge of HOC sequestration, release, and environmental risk.

A conversion of CO2-ECBM related lab observations to reservoir requirements

NASA Astrophysics Data System (ADS)

Gensterblum, Y.; Merkel, A.; Busch, A.; Krooss, B. M.

2012-04-01

To predict a CBM production profile either during primary or secondary production, aspects like coal permeability and porosity, density, ash and moisture content, initial gas-in-place (GIP) (from canister desorption tests), gas sorption capacity from laboratory isotherms (to obtain gas saturations and desorption pressure), gas diffusivities, coal volumetrics (thickness and areal extent) need to be understood as a minimum requirement. When dealing with CO2-ECBM selective adsorption, counter diffusion in the coal matrix, or coal shrinkage and swelling (from CH4 desorption and CO2 adsorption, respectively) and the influence of moisture need to be investigated in addition to the parameters above. During CO2-ECBM processes, the areal distribution of the CO2 injected is accomplished by flow through the cleat network. When CO2 is entering the coal matrix by a combined sorption/diffusion process it will adsorb to the coal inner surface and at the same time replace part of the CH4. This replacement occurs either by a reduction in the CH4 partial pressure or by a higher selective sorption of CO2 over CH4. Because of a concentration gradient between CH4 in the matrix compared to the cleat system, CH4 diffuses from the coal matrix into the cleat system where, by pressure drawdown towards a production well, it can be produced. In this context this presentation summarizes gas (CO2, CH4) and water sorption on coal and specifically addresses the following topics: • CH4 and CO2 sorption capacity as a function depth and rank • CO2 and CH4 sorption on natural coals and its dependence on coal specific parameters like coal rank, maceral composition or ash content (Busch and Gensterblum, 2011). • Water sorption on coal, its dependence on coal properties such as rank and coal chemistry and gas sorption in the presence of water (Busch and Gensterblum, 2011). • N2, CH4, CO2 displacement experiments and the volumetric response of the coal on the present gas type (sorbing or inert) in the pore system • Uncertainties in reservoir characterisation (Gensterblum et al., 2010; Gensterblum et al., 2009) • Sorption uptake kinetic as a function of surface coverage and the influence of moisture on the kinetic Busch, A. and Gensterblum, Y., 2011. CBM and CO2-ECBM related sorption processes in coal: A review. International Journal of Coal Geology, 87: 49-71. Gensterblum, Y. et al., 2010. European inter-laboratory comparison of high pressure CO2 sorption isotherms II: Natural coals. International Journal of Coal Geology, 84(2): 115-124. Gensterblum, Y. et al., 2009. European inter-laboratory comparison of high pressure CO2 sorption isotherms. I: Activated carbon. Carbon, 47(13): 2958-2969.

Interaction of Se{sup 0} nanoparticles stabilized by poly(vinylpyrrolidone) with gel films of cellulose Acetobacter xylinum

DOE Office of Scientific and Technical Information (OSTI.GOV)

Baklagina, Yu. G.; Khripunov, A. K.; Tkachenko, A. A.

2006-07-15

The sorption and desorption of poly(vinylpyrrolidone)-Se{sup 0} (PVP-Se{sup 0}) nanoparticles on gel films of cellulose Acetobacter xylinum (CAX) are investigated. It is revealed that the hydrodynamic radius R{sub h} of PVP-Se{sup 0} nanoparticles decreases from 57 nm in the initial solution (without CAX gel films) to 25 nm after the sorption of nanostructures on gel films and then increases to approximately 100 nm after the desorption of nanoparticles with water from dry samples of the CAX gel film-PVP-Se{sup 0} nanocomposite. It is found that selenium atoms do not penetrate into crystallites of the cellulose nanofibrils and replace water molecules sorbedmore » by the primary hydroxyl groups of their walls. Poly(vinylpyrrolidone)-Se{sup 0} nanoclusters differ in the number and size upon their sorption inside the cellulose gel film and on the film surface.« less

Retainment of the antimicrobial agent triclosan in a septic tank.

PubMed

Kirjanova, Ala; Rimeika, Mindaugas; Vollertsen, Jes; Nielsen, Asbjørn Haaning

2014-01-01

Laboratory experiments were conducted to investigate the fate of the antimicrobial agent triclosan (TCS) in a conventional septic tank. The main mechanism of TCS removal from wastewater was identified to be rapid TCS sorption to suspended particles followed by settling of these particles to the bottom of the septic tank. Sorption to particles was completed within minutes while the settling took several days. Therefore, in a septic tank the removal of TCS from wastewater is mainly determined by the removal of suspended particles by sedimentation. Over 5 days of hydraulic residence time the initial dissolved TCS concentration of 100 μg L(-1) was reduced by 87 ± 8%. During the first 24 hours, 66-86% of all removed TCS was retained, whereas during the remainder of the experiment a slight but steady decrease in TCS concentration was observed. This was most likely caused by TCS diffusion and its subsequent sorption onto the septic sludge.

Adsorption and desorption of oxytetracycline and carbamazepine by multiwalled carbon nanotubes.

PubMed

Oleszczuk, Patryk; Pan, Bo; Xing, Baoshan

2009-12-15

We investigated the adsorption-desorption by multiwalled carbon nanotubes (MWCNTs) of two pharmaceuticals, oxytetracycline (OTC) and carbamazepine (CBZ). The pharmaceuticals demonstrated relatively fast sorption kinetics on MWCNTs. All adsorption isotherms were nonlinear and fit the Polanyi-Manes model (PMM). The single point adsorption coefficient (K) values for OTC were more than 1 order of magnitude higher than those for CBZ on corresponding MWCNTs. The adsorbed volume capacity (Q(0)) and K values of PMM showed a significant relationship with surface areas and the meso- and micropore volume of MWCNTs for both chemicals. Depending on the MWCNT outer diameter, 13.8-25.2% and 62.7-90.6% of initially adsorbed OTC and CBZ, respectively, were desorbed after 200 h. The rate of desorption of both OTC and CBZ depended upon pH and the quantity of initially adsorbed pharmaceuticals, as well as aggregation in the case of OTC.

Reactive Radial Diffusion Model for the Aging/Sequestration Process

NASA Astrophysics Data System (ADS)

Ginn, T. R.; Basagaoglu, H.; McCoy, B. J.; Scow, K. M.

2001-12-01

A radial diffusion model has been formulated to simulate age-dependent bioavailability of chemical compounds to micro-organisms residing outside (and/or inside) the porous soil particles. Experimental findings in the literature indicate that the sequestration and reduction in bioavailability of contaminants are controlled presumably by the diffusion-limited sorption kinetics and the time-variant desorption process. Here we combine radial-diffusion mass transfer modeling with the exposure-time concept to generate mass-balance equations for the intra- and extra-particle concentrations. The model accomodates reversible sorption kinetics involving sorption time-dependence of the rate coefficients, distinct intra- and extra-particle biodegradation rates; and a dynamic mass interaction between the intra- and extra-particle concentrations arising from the radial diffusion concept. The model explicitly treats multiple particle classes distributed in size and chemical properties in a bulk aquifer or soil volume, which allows the simulation of the sequestration and bioavailability of contaminants in different particle size classes that have distinct diffusion, reaction, and aging properties.

Aminopyridine modified Spirulina platensis biomass for chromium(VI) adsorption in aqueous solution.

PubMed

Bayramoglu, Gulay; Akbulut, Aydin; Arica, M Yakup

Chemical modification of Spirulina platensis biomass was realized by sequential treatment of algal surface with epichlorohydrin and aminopyridine. Adsorptive properties of Cr(VI) ions on native and aminopyridine modified algal biomass were investigated by varying pH, contact time, ionic strength, initial Cr(VI) concentration, and temperature. FTIR and analytical analysis indicated that carboxyl and amino groups were the major functional groups for Cr(VI) ions adsorption. The optimum adsorption was observed at pH 3.0 for native and modified algal biomasses. The adsorption capacity was found to be 79.6 and 158.7 mg g(-1), for native and modified algal biomasses, respectively. For continuous system studies, the experiments were conducted to study the effect of important design parameters such as flow rate and initial concentration of metal ions, and the maximum sorption capacity was observed at a flow rate of 50 mL h(-1), and Cr(VI) ions concentration 200 mg L(-1) with modified biomass. Experimental data fitted a pseudo-second-order equation. The regeneration performance was observed to be 89.6% and 94.3% for native and modified algal biomass, respectively.

Processes and kinetics of Cd2+ sorption by a calcareous aquifer sand

USGS Publications Warehouse

Fuller, C.C.; Davis, J.A.

1987-01-01

The rate of Cd2+ sorption by a calcareous aquifer sand was characterized by two reaction steps, with the first step reaching completion in 24 hours. The second step proceeded at a slow and nearly constant rate for at least seven days. The first step includes a fast adsorption reaction which is followed by diffusive transport into either a disordered surface film of hydrated calcium carbonate or into pore spaces. After 24 hours the rate of Cd2+ sorption was constant and controlled by the rate of surface coprecipitation, as a solid solution of CdCO3 in CaCO3 formed in recrystallizing material. Desorption of Cd2+ from the sand was slow. Clean grains of primary minerals, e.g. quartz and aluminosilicates. sorbed much less Cd2+ than grains which had surface patches of secondary minerals, e.g. carbonates, iron and manganese oxides. Calcite grains sorbed the greatest amount of Cd2+ on a weight-normalized basis despite the greater abundance of quartz. A method is illustrated for determining empirical binding constants for trace metals at in situ pH values without introducing the experimental problem of supersaturation. The binding constants are useful for solute transport models which include a computation of aqueous speciation. ?? 1987.

Influence of Manufacturing Parameters on Microstructure and Hydrogen Sorption Behavior of Electron Beam Melted Titanium Ti-6Al-4V Alloy

PubMed Central

Pushilina, Natalia; Syrtanov, Maxim; Murashkina, Tatyana; Kudiiarov, Viktor; Lider, Andrey; Koptyug, Andrey

2018-01-01

Influence of manufacturing parameters (beam current from 13 to 17 mA, speed function 98 and 85) on microstructure and hydrogen sorption behavior of electron beam melted (EBM) Ti-6Al-4V parts was investigated. Optical and scanning electron microscopies as well as X-ray diffraction were used to investigate the microstructure and phase composition of EBM Ti-6Al-4V parts. The average α lath width decreases with the increase of the speed function at the fixed beam current (17 mA). Finer microstructure was formed at the beam current 17 mA and speed function 98. The hydrogenation of EBM Ti-6Al-4V parts was performed at the temperatures 500 and 650 °С at the constant pressure of 1 atm up to 0.3 wt %. The correlation between the microstructure and hydrogen sorption kinetics by EBM Ti-6Al-4V parts was demonstrated. Lower average hydrogen sorption rate at 500 °C was in the sample with coarser microstructure manufactured at the beam current 17 mA and speed function 85. The difference of hydrogen sorption kinetics between the manufactured samples at 650 °C was insignificant. The shape of the kinetics curves of hydrogen sorption indicates the phase transition αH + βH→βH. PMID:29747471

Sorption reaction mechanism of some hazardous radionuclides from mixed waste by impregnated crown ether onto polymeric resin.

PubMed

Shehata, F A; Attallah, M F; Borai, E H; Hilal, M A; Abo-Aly, M M

2010-02-01

A novel impregnated polymeric resin was practically tested as adsorbent material for removal of some hazardous radionuclides from radioactive liquid waste. The applicability for the treatment of low-level liquid radioactive waste was investigated. The material was prepared by loading 4,4'(5')di-t-butylbenzo 18 crown 6 (DtBB18C6) onto poly(acrylamide-acrylic acid-acrylonitril)-N, N'-methylenediacrylamide (P(AM-AA-AN)-DAM). The removal of (134)Cs, (60)Co, (65)Zn , and ((152+154))Eu onto P(AM-AA-AN)-DAM/DtBB18C6 was investigated using a batch equilibrium technique with respect to the pH, contact time, and temperature. Kinetic models are used to determine the rate of sorption and to investigate the mechanism of sorption process. Five kinetics models, pseudo-first-order, pseudo-second-order, intra-particle diffusion, homogeneous particle diffusion (HPDM), and Elovich models, were used to investigate the sorption process. The obtained results of kinetic models predicted that, pseudo-second-order is applicable; the sorption is controlled by particle diffusion mechanism and the process is chemisorption. The obtained values of thermodynamics parameters, DeltaH degrees , DeltaS degrees , and DeltaG degrees indicated that the endothermic nature, increased randomness at the solid/solution interface and the spontaneous nature of the sorption processes. Copyright (c) 2009 Elsevier Ltd. All rights reserved.

Influence of Manufacturing Parameters on Microstructure and Hydrogen Sorption Behavior of Electron Beam Melted Titanium Ti-6Al-4V Alloy.

PubMed

Pushilina, Natalia; Syrtanov, Maxim; Kashkarov, Egor; Murashkina, Tatyana; Kudiiarov, Viktor; Laptev, Roman; Lider, Andrey; Koptyug, Andrey

2018-05-10

Influence of manufacturing parameters (beam current from 13 to 17 mA, speed function 98 and 85) on microstructure and hydrogen sorption behavior of electron beam melted (EBM) Ti-6Al-4V parts was investigated. Optical and scanning electron microscopies as well as X-ray diffraction were used to investigate the microstructure and phase composition of EBM Ti-6Al-4V parts. The average α lath width decreases with the increase of the speed function at the fixed beam current (17 mA). Finer microstructure was formed at the beam current 17 mA and speed function 98. The hydrogenation of EBM Ti-6Al-4V parts was performed at the temperatures 500 and 650 °С at the constant pressure of 1 atm up to 0.3 wt %. The correlation between the microstructure and hydrogen sorption kinetics by EBM Ti-6Al-4V parts was demonstrated. Lower average hydrogen sorption rate at 500 °C was in the sample with coarser microstructure manufactured at the beam current 17 mA and speed function 85. The difference of hydrogen sorption kinetics between the manufactured samples at 650 °C was insignificant. The shape of the kinetics curves of hydrogen sorption indicates the phase transition α H + β H →β H .

Sorption kinetics and leachability of heavy metal from the contaminated soil amended with immobilizing agent (humus soil and hydroxyapatite).

PubMed

Chaturvedi, Pranav Kumar; Seth, Chandra Shekhar; Misra, Virendra

2006-08-01

Release of heavy metals onto the soil as a result of agricultural and industrial activities may pose a serious threat to the environment. This study investigated the kinetics of sorption of heavy metals on the non-humus soil amended with (1:3) humus soil and 1% hydroxyapatite used for in situ immobilization and leachability of heavy metals from these soils. For this, a batch equilibrium experiment was performed to evaluate metal sorption in the presence of 0.05 M KNO(3) background electrolyte solutions. The Langmuir isotherms applied for sorption studies showed that the amount of metal sorbed on the amended soil decreased in the order of Pb(2+)>Zn(2+)>Cd(2+). The data suggested the possibility of immobilization of Pb due to sorption process and immobilization of Zn and Cd by other processes like co-precipitation and ion exchange. The sorption kinetics data showed the pseudo-second-order reaction kinetics rather than pseudo-first-order kinetics. Leachability study was performed at various pHs (ranging from 3 to 10). Leachability rate was slowest for the Pb(2+) followed by Zn(2+) and Cd(2+). Out of the metal adsorbed on the soil only 6.1-21.6% of Pb, 7.3-39% of Zn and 9.3-44.3% of Cd leached out from the amended soil.

Characterizing redox conditions and monitoring attenuation of selected pharmaceuticals during artificial recharge through a reactive layer.

PubMed

Valhondo, Cristina; Carrera, Jesús; Ayora, Carlos; Tubau, Isabel; Martinez-Landa, Lurdes; Nödler, Karsten; Licha, Tobias

2015-04-15

A permeable reactive layer was installed at the floor of an infiltration basin. The reactive layer comprised 1) vegetable compost to provide a sorption surface for neutral organic compounds and to release easily degradable organic matter, thus generating a sequence of redox states, and 2) minor amounts of clay and iron oxide to increase sorption of cationic and anionic species, respectively. Field application of this design was successful in generating denitrification, and manganese-, and iron-reducing conditions beneath the basin. This, together with the increase in types of sorption sites, may explain the improved removal of three of the four selected pharmaceuticals compared with their behavior prior to installation of the layer. After installation of the reactive layer, atenolol concentrations were below the detection limits in the vadose zone. Moreover, concentrations of gemfibrozil and cetirizine were reduced to 20% and 40% of their initial concentrations, respectively, after 200 h of residence time. In contrast, prior to installation of the reactive layer, the concentrations of these three pharmaceuticals in both the vadose zone and the aquifer were more than 60% of the initial concentration. Carbamazepine exhibited recalcitrant behavior both prior to and after the reactive barrier installation. Copyright © 2015 Elsevier B.V. All rights reserved.

Adsorptive removal of Cu(II) from aqueous solution and industrial effluent using natural/agricultural wastes.

PubMed

Singha, Biswajit; Das, Sudip Kumar

2013-07-01

The potentiality of low cost natural/agricultural waste biomasses for the removal of Cu(II) ion from aqueous solution has been investigated in batch experiments. The effect of various physico-chemical parameters such as initial pH, initial Cu(II) concentration, adsorbent dosage, contact time and temperature has been studied. The optimum pH for adsorption was found to be 6 for all adsorbents used. Kinetics data were best described by the pseudo-2nd-order model. The experimental data were fitted well with Freundlich and Halsey isotherm models. The diffusion coefficient and sorption energy indicated that the adsorption process was chemical in nature. Thermodynamic parameters such as ΔG°, ΔH° and ΔS° were calculated, and it was observed that the adsorption process was spontaneous and endothermic. The mean sorption energy was calculated using Dubinin-Radushkevich isotherm model and it confirmed that the sorption process was chemical in nature. Different active functional groups were identified by FTIR studies which were responsible for Cu(II) ion adsorption process. Application study using electroplating industrial waste water and regeneration experiment of the adsorbent were also investigated. Design procedure for the batch process was also reported. Copyright © 2013 Elsevier B.V. All rights reserved.

Carbonate component reduces o,oEDDHA/Fe sorption on two-line ferrihydrite

NASA Astrophysics Data System (ADS)

Yunta, F.; Lucena, J. J.; Smolders, E.

2012-04-01

The o,oEDDHA/Fe is the most common and effective iron chelate used as fertilizer in calcareous soils. Several authors have reported that the anionic o,oEDDHA/Fe complex is adsorbed to soil components such as ferrihydrite. The bicarbonate anion may be a competing ion for this sorption, however no studies have yet identified the extent and mechanism of this interaction. The aim of this work was to study the carbonate (bicarbonate + carbonate) effect on EDDHA/Fe adsorption on two-line ferrihydrite. Two-line ferrihydrite was synthetized adding NaOH on a nitrate iron (III) solution up to a final pH to be 8.0 and allowing to age for 22 hours at 20°C. Dialyzed ferrihydrite was characterized by determining specific parameters such as Fe/OH ratio, BET surface, point zero of charge and x-ray diffraction. The sorption was performed at three pH levels (5, 7.5 and 9.5) and three initial carbonate concentrations (from 0 to 2 mM). Initial EDDHA/Fe, ferrihydrite and ionic strength concentrations were adjusted to 0.18 mM, 10 g L-1 and 5 mM respectively. Total dissolved FeEDDHA concentrations were quantified at 480 nm. The o,oEDDHA/Fe isomers (rac-o,oEDDHA/Fe and meso-o,oEDDHA/Fe) were separated and quantified by High Performance Liquid Chromatography (HPLC) fitting a photodiode array detector (PDA). Distribution factor (KD) and sorbed o,oEDDHA/Fe concentration were determined. Actual carbonate concentration was determined using a multi N/C analyzer. Ferrihydrite samples showed a typical XRD pattern of two-line ferrihydrite, two broad peaks at about 35 and 62° respectively. The BET surfaces (two replicates) were 259.2 ± 3.1 m2/g and 256.0 ± 2.5 m2/g. The Point Zero of Salt Effect (PZSE) was 7.9 ± 0.2 as bibliographically supported for all fresh and thus not rigorously de-carbonated ferrihydrite samples. The KD of the o,oEDDHA/Fe increased from 27.4 ± 0.6 to 304 ± 6 l/kg by decreasing pH from 9.5 and 5.0 when no carbonate was added. Increasing equilibrium carbonate concentrations between 8.6 10-2 and 76 10-2 mM decreased the KD about two-fold at pH 7.5. The KD values from meso-o,oEDDHA/Fe were up to 1000 fold larger than those of rac-o,oEDDHA/Fe at highest carbonate concentration at pH 7.5 and pH dependency suggests that former binds as inner sphere whereas latter binds as outer sphere. Despite the carbonate competition is unlikely to largely affect the net sorption of the chelate in soil, clear differences between meso-o,oEDDHA/Fe and rac-o,oEDDHA/Fe sorption rate on ferrihydrite in presence of carbonate were found.

Removal of chromium (VI) using poly(methylacrylate) functionalized guar gum.

PubMed

Singh, Vandana; Kumari, Premlata; Pandey, Sadanand; Narayan, Tripti

2009-03-01

Using persulfate/ascorbic acid redox pair, poly(methylacrylate) was grafted on to guar gum and the conditions for the grafting were optimized. The copolymer sample having maximum %G was evaluated for the removal of Cr(VI) and the sorption conditions were optimized. The sorption was found pH dependent, pH 1.0 being the optimum value. Sorption data at pH 1.0 were modeled using both the Langmuir and Freundlich isotherms where the data fitted better to Freundlich isotherm. The equilibrium sorption capacity of 29.67mg/g was determined from the Langmuir isotherm. The sorption followed a pseudo-second-order kinetics with a rate constant 2.5x10(-4)gmg(-1) min(-1). The grafted product was also evaluated for Cr(VI) removal from local electroplating industrial waste water. The regeneration experiments revealed that the guar-graft-poly(methylacrylate) could be successfully reused for five cycles. In the present study conductivity measurements were used instead of conventional photometric method for determining Cr(VI) concentration in the equilibrium solutions and the results obtained have been compared with photometric method. Optimum Cr(VI) binding under highly acidic conditions indicated significant contribution of non electrostatic forces in the adsorption process.

Boron removal by a composite sorbent: Polyethylenimine/tannic acid derivative immobilized in alginate hydrogel beads.

PubMed

Bertagnolli, Caroline; Grishin, Andrey; Vincent, Thierry; Guibal, Eric

2017-03-21

A novel composite material was prepared by the grafting of tannic acid on polyethylenimine (PEI), which allows an efficient sorption of boron (sorption capacity close to 0.89 mmol B g -1 ). The encapsulation of this chelating sorbent (finely crushed) facilitates its use (readily solid/liquid separation, use in fixed-bed columns) at the expense of a loss in sorption capacity (proportionally decreased by the introduction of alginate having poor efficiency for boron uptake). Sorption isotherms are modeled using the Langmuir equation, while the kinetic profiles are presented a good fit by pseudo-second order rate equation. In addition, the encapsulating matrix introduces supplementary resistance to intraparticle diffusion, especially when the resin is dried without control: freeze-drying partially limits this effect. The stability (at long-term storage) of the sorbent is improved when the sorbent is stored under nitrogen atmosphere. The presence of an excess of NaCl was investigated. The degradation of the hydrogel (by ion-exchange of Ca(II) with Na(I)) leads to a decrease in the sorption performance of composite material but the action of Ca(II) ions in the solutions re-stabilizes the hydrogel.

How to examine soil sorption of ionizable organic compounds and avoid varying pH?

NASA Astrophysics Data System (ADS)

Borisover, Mikhail

2017-04-01

Multiple natural and anthropogenic organic compounds including new and emerging pollutants undergo ionization in aqueous solutions, and their sorption by soils and sediments is contributed by presence of both molecular and ionized species. Better understanding of environmental fate of organic chemicals requires taking into account interactions of molecular and ionized species with environmental sorbents. A "standard" (and undoubtedly important) procedure for differentiating contributions of molecular and ionized species into the overall soil sorption of an organic compound involves varying pH of solution in batch sorption experiments. However, varying pH is (1) often not possible, without destroying a sorbent, e.g., due to the buffer capacity of soils containing carbonates, (2) difficult for further interpretation, since it changes not only the ionization status of a solute in a solution but also the sorbent structure, e.g., a conformation of organic matter, and/or ionization of surface functional groups, (3) making difficult (or even impossible) to explicitly evaluate the role of dissolved species-bulk water interactions, directly affecting the affinity of a sorbate to distribute between water and a sorbent. Indeed, both molecular and ionized species undergo interactions with the solvent bulk and, at least in the case of the ionized ones, there was no a simple way to quantify organic ion-water interactions and their role in organic ion distribution between soil and water phases. This paper presents a "counter-intuitive" approach to examine sorption interactions of an ionizable compound, without experimenting with varied pH. The approach is based on an idea of replacing an initial state in sorption transfer of an ionizable compound from the solvent bulk to a solvated (hydrated) sorbed state: a traditional coefficient describing distribution of a partially ionized compound between a hydrated sorbent and a co-equilibrated aqueous phase is converted to the coefficient describing the transfer of the sorbing compound from its initial molecular (non-ionized) state (in a solution or in the gas phase) to the final hydrated sorbed state equilibrated with the actual aqueous solution of this ionizable compound. In this way, any contributions from the bulk solvent-organic ion interactions into the sorption transfer may be excluded; in addition, further any solute-solvent interactions may be taken out of the consideration. Therefore, compound's sorption characteristics "cleared" of solute-solvent interactions may be obtained, and a better understanding of relations between interactions in a sorbed phase and a molecular structure of organic sorbates can be reached. The approach is illustrated by examining sorption of variously ionized organic compounds, i.e., those belonging to the pharmaceuticals and personal care products (triclosan, gemfibrozil, galaxolide), and aliphatic organic acids on natural and organic amendment-enriched soils. Specifically, it is demonstrated how the greater H-donating ability of trifluoroacetic acid, as compared with acetic acid, strengthens the acid interactions in the soil phase. In another series of examples, it is shown how hydrophobic and non-ionizing galaxolide interacts weakly with soils, as compared with partially ionized triclosan and almost fully ionized gemfibrozil, i.e., leading to the conclusions not reachable based only on the direct comparison of experimentally measured distribution coefficients.

Synthesis and applications of eco-magnetic nano-hydroxyapatite chitosan composite for enhanced fluoride sorption.

PubMed

Pandi, Kalimuthu; Viswanathan, Natrayasamy

2015-12-10

Adsorption is a significant reaction occurs between adsorbent/water interface for controlling the pollutants in the aqueous environment. In this regard, an eco-magnetic biosorbent was prepared by uniform deposition of magnetic Fe3O4 particles on the surface of nano-hydroxyapatite (n-HAp)/chitosan (CS) nanocomposite namely Fe3O4@n-HApCS composite as versatile sorbent for fluoride sorption. The resulting Fe3O4@n-HApCS nanocomposite was characterized by FTIR and SEM with EDAX techniques. The defluoridation capacity (DC) was found to depend on the contact time, pH, co-existing anions, initial fluoride concentration and temperature. The sorption isotherm was investigated by Freundlich, Langmuir and Temkin isotherm models using the batch method. The thermodynamic parameters revealed the feasibility, spontaneity and endothermic nature of fluoride sorption. The results of this research work designated that Fe3O4@n-HApCS composite having the excellent defluoridation capacity than the individual components and interesting to note that the easy magnetic separation of Fe3O4@n-HApCS composite from aqueous medium. Copyright © 2015 Elsevier Ltd. All rights reserved.

Treatment of radioactive liquid waste (Co-60) by sorption on Zeolite Na-A prepared from Iraqi kaolin.

PubMed

Mustafa, Yasmen A; Zaiter, Maysoon J

2011-11-30

Iraqi synthetic zeolite type Na-A has been suggested as ion exchange material to treat cobalt-60 in radioactive liquid waste which came from neutron activation for corrosion products. Batch experiments were conducted to find out the equilibrium isotherm for source sample. The equilibrium isotherm for radioactive cobalt in the source sample showed unfavorable type, while the equilibrium isotherm for the total cobalt (the radioactive and nonradioactive cobalt) in the source sample showed a favorable type. The ability of Na-A zeolite to remove cobalt from wastewater was checked for high cobalt concentration (822 mg/L) in addition to low cobalt concentration in the source sample (0.093 mg/L). A good fitting for the experimental data with Langmuir equilibrium model was observed. Langmuir constant qm which is related to monolayer adsorption capacity for low and high cobalt concentration was determined to be 0.021 and 140 mg/g(zeolite). The effects of important design variables on the zeolite column performance were studied these include initial concentration, flow rate, and bed depth. The experimental results have shown that high sorption capacity can be obtained at high influent concentration, low flow rate, and high bed depth. Higher column performance was obtained at higher bed depth. Thomas model was employed to predict the breakthrough carves for the above variables. A good fitting was observed with correlation coefficients between 0.915 and 0.985. Copyright © 2011 Elsevier B.V. All rights reserved.

Colloid transport in model fracture filling materials

NASA Astrophysics Data System (ADS)

Wold, S.; Garcia-Garcia, S.; Jonsson, M.

2010-12-01

Colloid transport in model fracture filling materials Susanna Wold*, Sandra García-García and Mats Jonsson KTH Chemical Science and Engineering Royal Institute of Technology, SE-100 44 Stockholm, Sweden *Corresponding author: E-mail: wold@kth.se Phone: +46 8 790 6295 In colloid transport in water-bearing fractures, the retardation depends on interactions with the fracture surface by sorption or filtration. These mechanisms are difficult to separate. A rougher surface will give a larger area available for sorption, and also when a particle is physically hindered, it approaches the surface and enables further sorption. Sorption can be explained by electrostatics were the strongest sorption on minerals always is observed at pH below pHpzc (Filby et al., 2008). The adhesion of colloids to mineral surfaces is related to the surface roughness according to a recent study (Darbha et al., 2010). There is a large variation in the characteristics of water-bearing fractures in bedrock in terms of aperture distribution, flow velocity, surface roughness, mineral distributions, presence of fracture filling material, and biological and organic material, which is hard to implement in modeling. The aim of this work was to study the transport of negatively charged colloids in model fracture filling material in relation to flow, porosity, mineral type, colloid size, and surface charge distribution. In addition, the impact on transport of colloids of mixing model fracture filling materials with different retention and immobilization capacities, determined by batch sorption experiments, was investigated. The transport of Na-montmorillonite colloids and well-defined negatively charged latex microspheres of 50, 100, and 200 nm diameter were studied in either columns containing quartz or quartz mixed with biotite. The ionic strength in the solution was exclusively 0.001 and pH 6 or 8.5. The flow rates used were 0.002, 0.03, and 0.6 mL min-1. Sorption of the colloids on the model fracture minerals was studied prior to the transport experiments under the same conditions. By varying the amount of solid substrate, it was possible to determine an interaction constant from a linear expression. Complementary zeta potential measurements and scanning electron microscopy (SEM) imaging were performed to examine the mineral surfaces after exposure to colloids. In experiments with low flow rates the retention of the colloids in the transport experiments were attributed to the interaction constants including both physical filtration and sorption. At higher flow rate the interactions between colloids and mineral surfaces were also significant but not as pronounced. Immobilization and retardation of the colloids were reflected by the interaction constants, which included both an irreversible and a reversible component of physical filtration and sorption. References Darbha, G.K., Schaefer, T., Heberling, F., Lüttge, A. and Fisher, C. 2010. Retention of Latex Colloids on Calcite as a Function of Surface Roughness and Topography. Langmuir, 26(7), 4743-4752. Filby, A., Plaschke, M., Geckeis, H., Fanghänel, Th. 2008. Interaction of latex colloids with mineral surfaces and Grimsel granodiorite. J. Contam. Hydrol., 102, 273-284.

Nonideal transport of reactive solutes in heterogeneous porous media: 4. Analysis of the Cape Cod Natural‐Gradient Field Experiment

USGS Publications Warehouse

Brusseau, Mark L.; Srivastava, Rajesh

1999-01-01

One of the largest field studies of reactive‐solute transport is the natural‐gradient experiment conducted at Cape Cod from 1985 to 1988. Major findings regarding the transport behavior of the reactive solute (lithium) were that the rate of plume displacement decreased with time (temporal increase in effective retardation), the degree of longitudinal spreading was much greater than that observed for bromide for an equivalent travel distance, and the plume was asymmetric, with maximum concentrations located near the leading edges. The objective of our work was to quantitatively analyze the transport of lithium and to attempt to identify the factor or factors that contributed significantly to its observed nonideal transport. We used a mathematical model that accounted for several transport factors, including spatially variable hydraulic conductivity and spatially variable, nonlinear, rate‐limited sorption, with all parameter values obtained independently. The transport behavior observed during the first 250 days, corresponding to a transport distance of 60 m, was predicted reasonably well by the simulation that incorporated spatially variable hydraulic conductivity; nonlinear, rate‐limited, spatially variable sorption; and uniform water chemistry. However, the larger degree of deceleration observed during the latter stage of the experiment (the filial 20 m) was not. The larger deceleration was successfully simulated by increasing 3‐fold the mean sorption capacity of the latter portion of the transport domain. Such a change in sorption capacity is consistent with the potential impact on lithium sorption of measured changes in water chemistry (e.g.,pH increase, reduction in resident Zn)at occur in the zone through which the lithium plume traversed. The results of the analyses suggest that nonlinear sorption and variable water chemistry may have btors responsible for the nonuniform displacement of the lithium plume, with rate‐limited sorption/desorption having minimal impact. In addition, the asymmetry of the plume appears to have been caused primarily by nonlinear sorption, whereas the enhanced longitudinal spreading appears to have been caused by the combined influences of spatially variable hydraulic conductivity and sorption, nonlinear sorption, and rate‐limited sorption/desorption. A comparison of the results of this analysis to those we obtained from an analysis of the Borden natural‐gradient study reveals several similarities regarding the transport of reactive contaminants at the field scale.

Diffusion and sorption of organic micropollutants in biofilms with varying thicknesses.

PubMed

Torresi, Elena; Polesel, Fabio; Bester, Kai; Christensson, Magnus; Smets, Barth F; Trapp, Stefan; Andersen, Henrik R; Plósz, Benedek Gy

2017-10-15

Solid-liquid partitioning is one of the main fate processes determining the removal of micropollutants in wastewater. Little is known on the sorption of micropollutants in biofilms, where molecular diffusion may significantly influence partitioning kinetics. In this study, the diffusion and the sorption of 23 micropollutants were investigated in novel moving bed biofilm reactor (MBBR) carriers with controlled biofilm thickness (50, 200 and 500 μm) using targeted batch experiments (initial concentration = 1 μg L -1 , for X-ray contrast media 15 μg L -1 ) and mathematical modelling. We assessed the influence of biofilm thickness and density on the dimensionless effective diffusivity coefficient f (equal to the biofilm-to-aqueous diffusivity ratio) and the distribution coefficient K d,eq (L g -1 ). Sorption was significant only for eight positively charged micropollutants (atenolol, metoprolol, propranolol, citalopram, venlafaxine, erythromycin, clarithromycin and roxithromycin), revealing the importance of electrostatic interactions with solids. Sorption equilibria were likely not reached within the duration of batch experiments (4 h), particularly for the thickest biofilm, requiring the calculation of the distribution coefficient K d,eq based on the approximation of the asymptotic equilibrium concentration (t > 4 h). K d,eq values increased with increasing biofilm thickness for all sorptive micropollutants (except atenolol), possibly due to higher porosity and accessible surface area in the thickest biofilm. Positive correlations between K d,eq and micropollutant properties (polarity and molecular size descriptors) were identified but not for all biofilm thicknesses, thus confirming the challenge of improving predictive sorption models for positively charged compounds. A diffusion-sorption model was developed and calibrated against experimental data, and estimated f values also increased with increasing biofilm thickness. This indicates that diffusion in thin biofilms may be strongly limited (f ≪ 0.1) by the high biomass density (reduced porosity). Copyright © 2017 Elsevier Ltd. All rights reserved.

An evaluation of fluid bed drying of aqueous granulations.

PubMed

Hlinak, A J; Saleki-Gerhardt, A

2000-01-01

The purpose of the work described was twofold: (a) to apply heat and mass balance approaches to evaluate the fluid bed drying cycle of an aqueous granulation, and (b) to determine the effect of the temperature and relative humidity of the drying air on the ability to meet a predetermined moisture content specification. Water content determinations were performed using Karl Fischer titration, and Computrac and Mark 1 moisture analyzers. The water vapor sorption isotherms were measured using a gravimetric moisture sorption apparatus with vacuum-drying capability. Temperature, relative humidity, and air flow were measured during the drying cycle of a production-scale fluid bed dryer. Heat and mass balance equations were used to calculate the evaporation rates. Evaporation rates calculated from heat and mass balance equations agreed well with the experimental data, whereas equilibrium moisture content values provided useful information for determination of the upper limit for inlet air humidity. Increasing the air flow rate and inlet temperature reduced the drying time through the effect on the primary driving force. As expected, additional drying of granules during the equilibration period did not show a significant impact on reducing the final moisture content of granules. Reducing the drying temperature resulted in measurement of higher equilibrium moisture content for the granules, which was in good agreement with the water vapor sorption data. Heat and mass balance equations can be used to successfully model the fluid bed drying cycle of aqueous granulations. The water vapor sorption characteristics of granules dictate the final moisture content at a given temperature and relative humidity.

Study of the mechanisms of cadmium biosorption by dealginated seaweed waste.

PubMed

Romero-Gonzalez, M E; Williams, C J; Gardiner, P H

2001-07-15

The ability of dealginated seaweed waste, a waste material derived from the commercial processing of seaweed for alginate production, to remove cadmium from solution was determined. Cadmium sorption was found to be rapid (91% removal within 5 min), achieving a residual concentration of 0.8 mg L-1 after 1-h contact time from an initial solution concentration of 10 mg L-1. The binding of cadmium by dealginate was found to be pH dependent, optimal sorption occurring at around pH 6-8. The mechanism of cadmium ion binding by dealginate was investigated by a number of techniques. Potentiometric titration of the dealginate revealed two distinct pKa values, the first having a value similar to carboxyl groups and the second comparable with that of saturated thiols and amines. Esterification of the dealginate resulted in the subsequent reduction in cadmium sorption (95% to 17%), indicating that carboxyl groups are largely responsible for sorption. Evidence from FT-IR spectra confirmed the presence of carboxyl groups in untreated dealginate, while the number of carboxyl groups was markedly reduced in the esterified sample. Furthermore, the FT-IR spectrum for dealginate was found to be similar to that previously reported for mannuronic acid-rich calcium alginate. Determination of a molar ratio in the displacement of calcium by cadmium on dealginate further supported the presence of an ion-exchange relationship. The ion-exchange constant was calculated to be 0.329 x 10(-6). The speciation of cadmium in solution both before and after sorption was determined by an ion-selective electrode (ISE) technique. The findings of this study suggest that the sorption of cadmium by dealginate is mainly due to an ion-exchange mechanism.

Ion reactivity of calcium-deficient hydroxyapatite in standard cell culture media.

PubMed

Gustavsson, J; Ginebra, M P; Engel, E; Planell, J

2011-12-01

Solution-mediated surface reactions occur for most calcium phosphate-based biomaterials and may influence cellular response. A reasonable extrapolation of such processes observed in vitro to in vivo performance requires a deep understanding of the underlying mechanisms. We therefore systematically investigated the nature of ion reactivity of calcium-deficient hydroxyapatite (CDHA) by exposing it for different periods of time to standard cell culture media of different chemical composition (DMEM and McCoy medium, with and without osteogenic supplements and serum proteins). Kinetic ion interaction studies of principal extracellular ions revealed non-linear sorption of Ca²⁺ (∼50% sorption) and K⁺ (∼8%) as well as acidification of all media during initial contact with CDHA (48h). Interestingly, inorganic phosphorus (P(i)) was sorbed from McCoy medium (∼50%) or when using osteogenic media containing β-glycerophosphate, but not from DMEM medium. Non-linear sorption data could be perfectly described by pseudo-first-order and pseudo-second-order sorption models. At longer contact time (21 days), and with frequent renewal of culture medium, sorption of Ca²⁺ remained constant throughout the experiment, while sorption of P(i) gradually decreased in McCoy medium. In great contrast, CDHA began to release P(i) slowly with time when using DMEM medium. Infrared spectra showed that CDHA exposed to culture media had a carbonated surface chemistry, suggesting that carbonate plays a key role in the ion reactivity of CDHA. Our data show that different compositions of the aqueous environment may provoke opposite ion reactivity of CDHA, and this must be carefully considered when evaluating the osteoinductive potential of the material. Copyright © 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Transient solute transport with sorption in Poiseuille flow

NASA Astrophysics Data System (ADS)

Hesse, M. A.; Zhang, L.; Wang, M.

2016-12-01

Sorption onto the wall has been observed to both increase [Lungu and Moffatt, 1982] and decrease the average solute transport velocity [Golay, 1958], relative to the mean flow velocity. Similarly, opposite conclusion have been reached for the effect of sorption on dispersion. In this work, we study transient solute transport in Poiseuille flow with sorptive boundary and initial transversely uniform distribution (linear release) to reconcile the two different views on solute transport (figure 1) with sorption. Two-dimensional simulations in figure 2 show that there is a transition from fast transport dominated by a fast-moving pulse in the middle of the channel at early times, to slow transport at late times once desorption from the walls becomes important. A set of series solutions for zeroth, first and second longitudinal moment have been derived and we show that the zeroth-order term in the solution corresponds to the slow transport in the late regime, while the first-order term corresponds to the fast transport in the early regime (figure 3). Based on the analytical solution, the time scales for early regime and late regimes of both the velocity and the dispersion coefficient have been determined for an equilibrium sorption model and a kinetic linear sorption model. Furthermore, we give approximated analytical solution when both adsorption and desorption are slow. References M.J.E. Golay. Theory of chromatography in open and coated tubular columns iwth round and rectangular cross-sections. In D.H.Desty, editor, Gas Chromatography, pages 36-53, New York, 1958. Academic Press Inc. E.M. Lungu and H.K. Moffatt. the effect of wall conductance on heat diffusion in duct flow. Journal of Engineering Mathematics, 1692 ;121-136, 1982.

Modification of a method-of-characteristics solute-transport model to incorporate decay and equilibrium-controlled sorption or ion exchange

USGS Publications Warehouse

Goode, D.J.; Konikow, Leonard F.

1989-01-01

The U.S. Geological Survey computer model of two-dimensional solute transport and dispersion in ground water (Konikow and Bredehoeft, 1978) has been modified to incorporate the following types of chemical reactions: (1) first-order irreversible rate-reaction, such as radioactive decay; (2) reversible equilibrium-controlled sorption with linear, Freundlich, or Langmuir isotherms; and (3) reversible equilibrium-controlled ion exchange for monovalent or divalent ions. Numerical procedures are developed to incorporate these processes in the general solution scheme that uses method-of- characteristics with particle tracking for advection and finite-difference methods for dispersion. The first type of reaction is accounted for by an exponential decay term applied directly to the particle concentration. The second and third types of reactions are incorporated through a retardation factor, which is a function of concentration for nonlinear cases. The model is evaluated and verified by comparison with analytical solutions for linear sorption and decay, and by comparison with other numerical solutions for nonlinear sorption and ion exchange.

Kinetic modeling of antimony(III) oxidation and sorption in soils.

PubMed

Cai, Yongbing; Mi, Yuting; Zhang, Hua

2016-10-05

Kinetic batch and saturated column experiments were performed to study the oxidation, adsorption and transport of Sb(III) in two soils with contrasting properties. Kinetic and column experiment results clearly demonstrated the extensive oxidation of Sb(III) in soils, and this can in return influence the adsorption and transport of Sb. Both sorption capacity and kinetic oxidation rate were much higher in calcareous Huanjiang soil than in acid red Yingtan soil. The results indicate that soil serve as a catalyst in promoting oxidation of Sb(III) even under anaerobic conditions. A PHREEQC model with kinetic formulations was developed to simulate the oxidation, sorption and transport of Sb(III) in soils. The model successfully described Sb(III) oxidation and sorption data in kinetic batch experiment. It was less successful in simulating the reactive transport of Sb(III) in soil columns. Additional processes such as colloid facilitated transport need to be quantified and considered in the model. Copyright © 2016 Elsevier B.V. All rights reserved.

Waste-Heat-Driven Cooling Using Complex Compound Sorbents

NASA Technical Reports Server (NTRS)

Rocketfeller, Uwe; Kirol, Lance; Khalili, Kaveh

2004-01-01

Improved complex-compound sorption pumps are undergoing development for use as prime movers in heat-pump systems for cooling and dehumidification of habitats for humans on the Moon and for residential and commercial cooling on Earth. Among the advantages of sorption heat-pump systems are that they contain no moving parts except for check valves and they can be driven by heat from diverse sources: examples include waste heat from generation of electric power, solar heat, or heat from combustion of natural gas. The use of complex compound sorbents in cooling cycles is not new in itself: Marketing of residential refrigerators using SrCl2 was attempted in the 1920s and 30s and was abandoned because heat- and mass-transfer rates of the sorbents were too low. Addressing the issue that gave rise to the prior abandonment of complex compound sorption heat pumps, the primary accomplishment of the present development program thus far has been the characterization of many candidate sorption media, leading to large increases in achievable heat- and mass-transfer rates. In particular, two complex compounds (called "CC260-1260" and "CC260-2000") were found to be capable of functioning over the temperature range of interest for the lunar-habitat application and to offer heat- and mass-transfer rates and a temperature-lift capability adequate for that application. Regarding the temperature range: A heat pump based on either of these compounds is capable of providing a 95-K lift from a habitable temperature to a heat-rejection (radiator) temperature when driven by waste heat at an input temperature .500 K. Regarding the heat- and mass-transfer rates or, more precisely, the power densities made possible by these rates: Power densities observed in tests were 0.3 kilowatt of cooling per kilogram of sorbent and 2 kilowatts of heating per kilogram of sorbent. A prototype 1-kilowatt heat pump based on CC260-2000 has been built and demonstrated to function successfully.

Adsorptive removal of phthalate ester (Di-ethyl phthalate) from aqueous phase by activated carbon: a kinetic study.

PubMed

Venkata Mohan, S; Shailaja, S; Rama Krishna, M; Sarma, P N

2007-07-19

Adsorptive studies were carried out on Di-ethyl phthalate (DEP) removal from aqueous phase onto activated carbon. Batch sorption studies were performed and the results revealed that activated carbon demonstrated ability to adsorb DEP. Influence of varying experimental conditions such as DEP concentration, pH of aqueous solution, and dosage of adsorbent were investigated on the adsorption process. Sorption interaction of DEP onto activated carbon obeyed the pseudo second order rate equation. Experimental data showed good fit with both the Langmuir and Freundlich adsorption isotherm models. DEP sorption was found to be dependent on the aqueous phase pH and the uptake was observed to be greater at acidic pH.

Phosphorus sorption capacity of biochars varies with biochar type and salinity level.

PubMed

Dugdug, Abdelhafid Ahmed; Chang, Scott X; Ok, Yong Sik; Rajapaksha, Anushka Upamali; Anyia, Anthony

2018-02-10

Biochar is recognized as an effective material for recovering excess nutrients, including phosphorus (P), from aqueous solutions. Practically, that benefits the environment through reducing P losses from biochar-amended soils; however, how salinity influences P sorption by biochar is poorly understood and there has been no direct comparison on P sorption capacity between biochars derived from different feedstock types under non-saline and saline conditions. In this study, biochars derived from wheat straw, hardwood, and willow wood were used to compare P sorption at three levels of electrical conductivity (EC) (0, 4, and 8 dS m -1 ) to represent a wide range of salinity conditions. Phosphorus sorption by wheat straw and hardwood biochars increased as aqueous solution P concentration increased, with willow wood biochar exhibiting an opposite trend for P sorption. However, the pattern for P sorption became the same as the other biochars after the willow wood biochar was de-ashed with 1 M HCl and 0.05 M HF. Willow wood biochar had the highest P sorption (1.93 mg g -1 ) followed by hardwood (1.20 mg g -1 ) and wheat straw biochars (1.06 mg g -1 ) in a 25 mg L -1 P solution. Although the pH in the equilibrium solution was higher with willow wood biochar (~ 9.5) than with the other two biochars (~ 6.5), solution pH had no or minor effects on P sorption by willow wood biochar. The high sorption rate of P by willow wood biochar could be attributed to the higher concentrations of salt and other elements (i.e., Ca and Mg) in the biochar in comparison to that in wheat straw and hardwood biochars; the EC values were 2.27, 0.53, and 0.27 dS m -1 for willow wood, wheat straw, and hardwood biochars, respectively. A portion of P desorbed from the willow wood biochar; and that desorption increased with the decreasing P concentration in the aqueous solution. Salinity in the aqueous solution influenced P sorption by hardwood and willow wood but not by wheat straw biochar. We conclude that the P sorption capacity of the studied biochars is dependent on the concentration of the soluble element in the biochar, which is dependent on the biochar type, as well as the salinity level in the aqueous solution.

Anaerobic degradation of aircraft deicing fluid (ADF) in upflow anaerobic sludge blanket (UASB) reactors and the fate of ADF additives

NASA Astrophysics Data System (ADS)

Pham, Thi Tham

2002-11-01

A central composite design was employed to methodically investigate anaerobic treatment of aircraft deicing fluid (ADF) in bench-scale Upflow Anaerobic Sludge Blanket (UASB) reactors. A total of 23 runs at 17 different operating conditions were conducted in continuous mode. The development of four empirical models describing process responses (i.e., chemical oxygen demand (COD) removal efficiency, biomass specific acetoclastic activity, methane production rate, and methane production potential) as functions of ADF concentration, hydraulic retention time (HRT), and biomass concentration is presented. Model verification indicated that predicted responses (COD removal efficiencies, biomass specific acetoclastic activity, and methane production rates and potential) were in good agreement with experimental results. Biomass specific acetoclastic activity was improved by almost two-fold during ADF treatment in UASB reactors. For the design window, COD removal efficiencies were higher than 90%. Predicted methane production potentials were close to theoretical values, and methane production rates increased as the organic loading rate (OLR) was increased. ADF toxicity effects were evident for 1.6% ADF at medium specific organic loadings (SOLR above 0.5 g COD/g VSS/d). In contrast, good reactor stability and excellent removal efficiencies were achieved at 1.2% ADF for reactor loadings approaching that of highly loaded systems (0.73 g COD/g VSS/d). Acclimation to ADF resulted in an initial reduction in the biomass settling velocity. The fate of ADF additives was also investigated. There was minimal sorption of benzotriazole (BT), 5-methyl-1 H-benzotriazole (MeBT), and 5,6-dimethyl-1 H-benzotriazole (DiMeBT) to anaerobic granules. A higher sorption capacity was measured for NP. Active transport may be one of the mechanisms for NP sorption. Ethylene glycol degradation experiments indicated that BT, MeBT, DiMeBT, and the nonionic surfactant Tergitol NP-4 had no significant effects on acidogenesis and methanogenesis at the concentration levels studied. A significant inhibition of acetoclastic activity was observed for NP at 100 mg/L, with acetic acid consumption rate at 38% of that for controls. No evidence for anaerobic degradation of benzotriazole and its derivatives was observed; however, both batch and continuous experiments suggested that anaerobic degradation of NP occurred. Kinetic analysis of operational data obtained for the anaerobic treatment of ADF in UASB reactors indicated that the substrate utilization rate was independent of the reactor biomass concentration. The maximum rate of substrate utilization and the half-velocity constants for ADF treatment were 28.4 g COD/L/d and 648 mg COD/L, respectively. For 1.2% ADF, the biomass yield and endogenous decay coefficients were 0.027 g VSS/g COD and 0.012 d-1 , respectively.

Ad-/desorption behavior of Sulfadiazine on soil and soil components

NASA Astrophysics Data System (ADS)

Meng, N.; Lewandowski, H.; Kasteel, R.; Narres, H.-D.; Klumpp, E.; Vereecken, H.

2009-04-01

Sulfadiazine [4-amino-N-(2-pyrimidinyl)benzene sulfonamide, SDZ] belongs to the widely used antibacterial veterinary pharmaceuticals which reach the environment by the application of manure. Therefore the adsorption and desorption behavior of 14C labeled sulfadiazine was investigated with different inorganic soil components including Al2O3, goethite, illite and compared with air-dried topsoil. The batch sorption experiments with Al2O3and soil were performed in natural pH-values (8.2 and 7.5, negatively charged SDZ). Experiments with illite and goethite were done with pH-values of 4.2 and 6.8 (natural pH of illite and goethite, neutral and partly negatively charged SDZ) and also done in buffer solution about pH 8 for comparing the adsorption on all adsorbents in same pH range. The adsorption isotherms on all sorbents are strongly nonlinear and can be fitted well by the Freundlich equation. From the initial slope of the isotherm the partition coefficient Kd could be determined. The adsorption of SDZ on illite at pH 4.2 and on goethite at pH 6.8 has higher Kd-values than at pH 8, which demonstrates that the negative charge of SDZ obstructs the adsorption. The desorption isotherms show hysteresis effects for all adsorbents. The strong hysteresis was found for goethite and soil indicates strongly physical or chemical binding. On the other hand, the low hysteresis effect for Al2O3 and illite indicates the weak binding of the adsorbed SDZ. The properties of the inorganic matrix and especially the charges of the inorganic compounds in relation to the charge of SDZ are important parameters for the sorption process. The data could be described by modeling with different sorption rates and sites.

Multi-podant diglycolamides and room temperature ionic liquid impregnated resins: An excellent combination for extraction chromatography of actinides.

PubMed

Gujar, R B; Ansari, S A; Verboom, W; Mohapatra, P K

2016-05-27

Extraction chromatography resins, prepared by impregnating two multi-podant diglycolamide ligands, viz. diglycolamide-functionalized calix[4]arene (C4DGA) and tripodal diglycolamide (T-DGA) dissolved in the room temperature ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide (RTIL: C4mimTf2N) on Chromosorb-W (an inert solid support), gave excellent results for the removal of trivalent actinides from acidic waste solutions. Distribution coefficient measurements on several metal ions showed selective sorption of Am(III) over hexavalent uranyl ions and other fission product elements such as strontium and cesium. The sorbed metal ions could be efficiently desorbed with a complexing solution containing guanidine carbonate and EDTA buffer. The sorption of Am(III) on both resins followed pseudo-second order rate kinetics with rate constants of 1.37×10(-6) and 6.88×10(-7)g/cpmmin for T-DGA and C4DGA resins, respectively. The metal sorption on both resins indicated the Langmuir monolayer chemisorption phenomenon with Eu(III) sorption capacities of 4.83±0.21 and 0.52±0.05mg per g of T-DGA and C4DGA resins, respectively. The results of column studies show that these resins are of interest for a possible application for the recovery of hazardous trivalent actinides from dilute aqueous solutions. Copyright © 2016 Elsevier B.V. All rights reserved.

Potassium-based sorbents from fly ash for high-temperature CO2 capture.

PubMed

Sanna, Aimaro; Maroto-Valer, M Mercedes

2016-11-01

Potassium-fly ash (K-FA) sorbents were investigated for high-temperature CO 2 sorption. K-FAs were synthesised using coal fly ash as source of silica and aluminium. The synthesised materials were also mixed with Li 2 CO 3 and Ca(OH) 2 to evaluate their effect on CO 2 capture. Temperature strongly affected the performance of the K-FA sorbents, resulting in a CO 2 uptake of 1.45 mmol CO 2 /g sorbent for K-FA 1:1 at 700 °C. The CO 2 sorption was enhanced by the presence of Li 2 CO 3 (10 wt%), with the K-FA 1:1 capturing 2.38 mmol CO 2 /g sorbent at 700 °C in 5 min. This sorption was found to be similar to previously developed Li-Na-FA (2.54 mmol/g) and Li-FA (2.4 mmol/g) sorbents. The presence of 10 % Li 2 CO 3 also accelerated sorption and desorption. The results suggest that the increased uptake of CO 2 and faster reaction rates in presence of K-FA can be ascribed to the formation of K-Li eutectic phase, which favours the diffusion of potassium and CO 2 in the material matrix. The cyclic experiments showed that the K-FA materials maintained stable CO 2 uptake and reaction rates over 10 cycles.

Dynamic behavior of semivolatile organic compounds in indoor air. 2. Nicotine and phenanthrene with carpet and wallboard.

PubMed

Van Loy, M D; Riley, W J; Daisey, J M; Nazaroff, W W

2001-02-01

The surface interactions of nicotine and phenanthrene with carpet, painted wallboard, and stainless steel were investigated in a room-sized environmental test chamber. Adsorption kinetics were tested by flash evaporating a known mass of each compound into a sealed 20 m3 chamber containing one or more of the tested sorbents. In each experiment, one or more emissions were performed after the gas-phase concentration had reached an apparent plateau. At the end of each experiment, the chamber was ventilated and resealed to monitor reemission of the compound from the sorbents. Kinetic sorption parameters were determined by fitting a mass-balance model to the experimental results. The sorption capacity of stainless steel was of similar magnitude for nicotine and phenanthrene. Sorption of nicotine on carpet and wallboard was much stronger, with equilibrium partitioning values 2-3 orders of magnitude higher. The sorption capacities of phenanthrene on carpet and wallboard were smaller, approximately 10-20% of the stainless steel values. The rates of uptake are of similar magnitude for all sorbate--sorbent pairs and are consistent with the limit imposed by gas-phase boundary-layer mass transport. The rates of desorption are much faster for phenanthrene than for nicotine. Model simulations predict average nicotine levels in a typical smoking residence that are consistent with published data.

Adsorption and degradation of sulfadiazine and sulfamethoxazole in an agricultural soil system under an anaerobic condition: Kinetics and environmental risks.

PubMed

Shen, Genxiang; Zhang, Yu; Hu, Shuangqing; Zhang, Hongchang; Yuan, Zhejun; Zhang, Wei

2018-03-01

Sulfonamides, one of the commonest antibiotics, were widely used on humans and livestock to control pathema and bacterial infections resulting in further environmental risks. The present study evaluated the adsorption and degradation of sulfadiazine (SDZ) and sulfamethoxazole (SMX) in an agricultural soil system under an anaerobic condition. Low sorption coefficients (K d , 1.22 L kg -1 for SDZ and 1.23 L kg -1 for SMX) obtained from Freundlich isotherms experiment indicated that poor sorption of both antibiotics may pose a high risk to environment due to their high mobility and possibility of entering surface and ground water. Degradation occurred at a lower rate under the anaerobic environment, where both two antibiotics had higher persistence in sterile and non-sterile soils with degradation ratio <75% and DT50 > 20 d. Additionally, the addition of manure slightly increased degradation rates of SDZ and SMX, but there were no significant differences between single and repeated manure application at a later stage (p > 0.05), which suggested that the degradation was affected by both biotic and abiotic factors. Degradation rates would be slower at a higher concentration, indicating that degradation kinetics of SDZ and SMX were dependent on initial concentrations. During the degradation period, the antibiotics removal may change temperature, pH, sulfate and nitrate in soil, which suggested that the variation of antibiotics concentrations was related to the changes of soil physicochemical properties. An equation was proposed to elucidate the link between adsorption and degradation under different conditions, and to predict potential environmental risks of antibiotics. Copyright © 2017 Elsevier Ltd. All rights reserved.

Comparative Study of Molecular Basket Sorbents Consisting of Polyallylamine and Polyethylenimine Functionalized SBA-15 for CO2 Capture from Flue Gas.

PubMed

Wang, Dongxiang; Wang, Xiaoxing; Song, Chunshan

2017-11-17

Polyallylamine (PAA)-based molecular basket sorbents (MBS) have been studied for CO 2 capture in comparison with polyethylenimine (PEI)-based MBS. The characterizations including N 2 physisorption, diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), and thermogravimetric analysis (TGA) showed that PAA (M n =15 000) is more rigid and has more steric hindrance inside SBA-15 pores than PEI owing mainly to its different polymer structure. The effects of temperature and PAA loading on the CO 2 sorption capacity of PAA-based MBS have been examined by TGA by using 100 % CO 2 gas stream and compared with PEI/SBA-15. It was found that the capacity of the PAA/SBA-15 sorbent increased with increasing temperature. The optimum capacity of 88 mg CO2  g sorb -1 was obtained at 140 °C for PAA(50)/SBA-15 whereas the optimum sorption temperature was 75 and 90 °C for PEI-I(50)/SBA-15 (PEI-I, M n =423) and PEI-II(50)/SBA-15 (PEI-II, M n =25 000), respectively. The capacity initially increased with the increase of PAA loading and then dropped at high amine contents, owing to the increased diffusion barrier. The highest CO 2 capacity of 109 mg CO2  g sorb -1 was obtained at a PAA loading of 65 wt %, whereas the PAA(50)/SBA-15 sorbent gave the best amine efficiency of 0.23 mol CO2  mol N -1 . The effect of moisture was examined in a fixed-bed flow system with simulated flue gas containing 15 % CO 2 and 4.5 % O 2 in N 2 . It was found that the presence of moisture significantly enhanced CO 2 sorption over PAA(50)/SBA-15 and greatly improved its cyclic stability and regenerability. Compared with PEI/SBA-15, PAA/SBA-15 possesses a better thermal stability and higher resistance to oxidative degradation. However, the CO 2 sorption rate over the PAA(50)/SBA-15 sorbent was much slower. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Persistence and partitioning of eight selected pharmaceuticals in the aquatic environment: laboratory photolysis, biodegradation, and sorption experiments.

PubMed

Yamamoto, Hiroshi; Nakamura, Yudai; Moriguchi, Shigemi; Nakamura, Yuki; Honda, Yuta; Tamura, Ikumi; Hirata, Yoshiko; Hayashi, Akihide; Sekizawa, Jun

2009-02-01

We selected eight pharmaceuticals with relatively high potential ecological risk and high consumption-namely, acetaminophen, atenolol, carbamazepine, ibuprofen, ifenprodil, indomethacin, mefenamic acid, and propranolol-and conducted laboratory experiments to examine the persistence and partitioning of these compounds in the aquatic environment. In the results of batch sunlight photolysis experiments, three out of eight pharmaceuticals-propranolol, indomethacin, and ifenprodil-were relatively easily photodegraded (i.e., half-life<24h), whereas the other five pharmaceuticals were relatively stable against sunlight. The results of batch biodegradation experiments using river water suggested relatively slow biodegradation (i.e., half-life>24h) for all eight pharmaceuticals, but the rate constant was dependent on sampling site and time. Batch sorption experiments were also conducted to determine the sorption coefficients to river sediments and a model soil sample. The determined coefficients (K(d) values) were much higher for three amines (atenolol, ifenprodil, and propranolol) than for neutral compounds or carboxylic acids; the K(d) values of the amines were comparable to those of a four-ring polycyclic aromatic hydrocarbon (PAH) pyrene. The coefficients were also higher for sediment/soil with higher organic content, and the organic carbon-based sorption coefficient (logK(oc)) showed a poor linear correlation with the octanol-water distribution coefficient (logD(ow)) at neutral pH. These results suggest other sorption mechanisms-such as electrochemical affinity, in addition to hydrophobic interaction-play an important role in sorption to sediment/soil at neutral pH.

Effects of aged sorption on pesticide leaching to groundwater simulated with PEARL.

PubMed

Boesten, Jos J T I

2017-01-15

Leaching to groundwater is an important element of the regulatory risk assessment of pesticides in western countries. Including aged sorption in this assessment is relevant because there is ample evidence of this process and because it leads to a decrease in simulated leaching. This work assesses the likely magnitude of this decrease for four groundwater scenarios used for regulatory purpose in the EU (from the UK, Portugal, Austria and Greece) and for ranges of aged-sorption parameters and substance properties using the PEARL model. Three aged-sorption parameters sets were derived from literature, representing approximately 5th, 50th and 95th percentile cases for the magnitude of the effect of aged sorption on leaching concentrations (called S, M and L, respectively). The selection of these percentile cases was based only on the f NE parameter (i.e. the ratio of the aged sorption and the equilibrium sorption coefficients) because leaching was much more affected by the uncertainty in this parameter than by the uncertainty in the desorption rate coefficient of these sites (k d ). For the UK scenario, the annual flux concentration of pesticide leaching at 1m depth decreased by typically a factor of 5, 30 and >1000 for the S, M and L parameter sets, respectively. This decrease by a factor of 30 for the M parameter set appeared to be approximately valid also for the other three scenarios. Decreasing the Freundlich exponent N from 0.9 into 0.7 for the M parameter set, increased this factor of 30 into a factor of typically 1000, considering all four scenarios. The aged-sorption sites were close to their equilibrium conditions during the leaching simulations for two of the four scenarios (for all substances considered and the M parameter set), but this was not the case for the other two scenarios. Copyright © 2016 Elsevier B.V. All rights reserved.

Equilibrium and kinetic studies of sorption of 2.4-dichlorophenol onto 2 mixtures: bamboo biochar plus calcium sulphate (BC) and hydroxyapatite plus bamboo biochar plus calcium sulphate (HBC), in a fluidized bed circulation column

DOE PAGES

Alamin, Ahmed Hassan; Kaewsichan, Lupong

2016-06-30

Sorption studies were carried out to investigate removal of 2.4-dichlorophenol (2.4-DCP) from aqueous solution in a fluidized bed by two types of adsorbent mixtures: BC (Bamboo char plus Calcium sulphate), and HBC (Hydroxyapatite plus Bamboo char plus Calcium sulphate); both manufactured in ball shape. The main material bamboo char was characterized by FTIR, DTA and SEM. The adsorption experiments were conducted in a fluidized bed circulation column. Adsorption, isotherms and kinetic studies were established under 180 min operating process time, at different initial 2.4-DCP solution concentrations ranging from 5–10 mg/L, and at different flow rates ranging from 0.25–0.75 L/min. Themore » data obtained fitted well for both the Langmuir and Freundlich isotherm models; indicating favorable condition of monolayer adsorption. The kinetics of both adsorbents complies with the pseudo second-order kinetic model. BC was proven a new effective composite and low cost adsorbent which can be applied in the field of wastewater treatment, and it can also play an important role in industry water treatment« less

Equilibrium and kinetic studies of sorption of 2.4-dichlorophenol onto 2 mixtures: bamboo biochar plus calcium sulphate (BC) and hydroxyapatite plus bamboo biochar plus calcium sulphate (HBC), in a fluidized bed circulation column

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alamin, Ahmed Hassan; Kaewsichan, Lupong

Sorption studies were carried out to investigate removal of 2.4-dichlorophenol (2.4-DCP) from aqueous solution in a fluidized bed by two types of adsorbent mixtures: BC (Bamboo char plus Calcium sulphate), and HBC (Hydroxyapatite plus Bamboo char plus Calcium sulphate); both manufactured in ball shape. The main material bamboo char was characterized by FTIR, DTA and SEM. The adsorption experiments were conducted in a fluidized bed circulation column. Adsorption, isotherms and kinetic studies were established under 180 min operating process time, at different initial 2.4-DCP solution concentrations ranging from 5–10 mg/L, and at different flow rates ranging from 0.25–0.75 L/min. Themore » data obtained fitted well for both the Langmuir and Freundlich isotherm models; indicating favorable condition of monolayer adsorption. The kinetics of both adsorbents complies with the pseudo second-order kinetic model. BC was proven a new effective composite and low cost adsorbent which can be applied in the field of wastewater treatment, and it can also play an important role in industry water treatment« less

Design and development of a four-cell sorption compressor based J-T cooler using R134a as working fluid

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mehta, R. N.; Bapat, S. L.; Atrey, M. D.

The need of a cooler with no electromagnetic interference and practically zero vibration has led to sorption compressor based Joule-Thomson (J-T) coolers. These are useful for sophisticated electronic, ground based and space borne systems. In a Sorption compressor, adsorbed gases are desorbed into a confined volume by raising temperature of the sorption bed resulting in an increase in pressure of the liberated gas. In order to have the system (compressor) functioning on a continuous basis, with almost a constant gas flow rate, multiple cells are used with the adaptation of Temperature Swing Adsorption (TSA) process. As the mass of themore » desorbed gas dictates the compressor throughput, a combination of sorbent material with high adsorption capacity for a chosen gas or gas mixture has to be selected for efficient operation of the compressor. Commercially available (coconut-shell base) activated carbon has been selected for the present application. The characterization study for variation of discharge pressure is used to design the Four-cell sorption compressor based cryocooler with a desired output. Apart from compressor, the system includes a) After cooler b) Return gas heat exchanger c) capillary tube as the J-T expansion device and d) Evaporator.« less

Design and development of a four-cell sorption compressor based J-T cooler using R134a as working fluid

NASA Astrophysics Data System (ADS)

Mehta, R. N.; Bapat, S. L.; Atrey, M. D.

2014-01-01

The need of a cooler with no electromagnetic interference and practically zero vibration has led to sorption compressor based Joule-Thomson (J-T) coolers. These are useful for sophisticated electronic, ground based and space borne systems. In a Sorption compressor, adsorbed gases are desorbed into a confined volume by raising temperature of the sorption bed resulting in an increase in pressure of the liberated gas. In order to have the system (compressor) functioning on a continuous basis, with almost a constant gas flow rate, multiple cells are used with the adaptation of Temperature Swing Adsorption (TSA) process. As the mass of the desorbed gas dictates the compressor throughput, a combination of sorbent material with high adsorption capacity for a chosen gas or gas mixture has to be selected for efficient operation of the compressor. Commercially available (coconut-shell base) activated carbon has been selected for the present application. The characterization study for variation of discharge pressure is used to design the Four-cell sorption compressor based cryocooler with a desired output. Apart from compressor, the system includes a) After cooler b) Return gas heat exchanger c) capillary tube as the J-T expansion device and d) Evaporator.

Adsorption and chemical reaction of gaseous mixtures of hydrogen chloride and water on aluminum oxide and application to solid-propellant rocket exhaust clouds

NASA Technical Reports Server (NTRS)

Cofer, W. R., III; Pellett, G. L.

1978-01-01

Hydrogen chloride (HCl) and aluminum oxide (Al2O3) are major exhaust products of solid rocket motors (SRM). Samples of calcination-produced alumina were exposed to continuously flowing mixtures of gaseous HCl/H2O in nitrogen. Transient sorption rates, as well as maximum sorptive capacities, were found to be largely controlled by specific surface area for samples of alpha, theta, and gamma alumina. Sorption rates for small samples were characterized linearly with an empirical relationship that accounted for specific area and logarithmic time. Chemisorption occurred on all aluminas studied and appeared to form from the sorption of about a 2/5 HCl-to-H2O mole ratio. The chemisorbed phase was predominantly water soluble, yielding chloride/aluminum III ion mole ratios of about 3.3/1 suggestive of dissolved surface chlorides and/or oxychlorides. Isopiestic experiments in hydrochloric acid indicated that dissolution of alumina led to an increase in water-vapor pressure. Dissolution in aqueous SRM acid aerosol droplets, therefore, might be expected to promote evaporation.

Non-enzymatic browning kinetics analysed through water-solids interactions and water mobility in dehydrated potato.

PubMed

Acevedo, Nuria C; Schebor, Carolina; Buera, Pilar

2008-06-01

Non-enzymatic browning (NEB) development was studied in dehydrated potato at 70°C. It was related to the macroscopic and molecular properties and to water-solid interactions over a wide range of water activities. Time resolved (1)H NMR, thermal transitions and water sorption isotherms were evaluated. Although non-enzymatic browning could be detected in the glassy state; colour development was higher in the supercooled state. The reaction rate increased up to a water content of 26g/100g of solids (aw=0.84) and then decreased at higher water contents, concomitantly with the increase of water proton mobility. The joint analyses of NEB kinetics, water sorption isotherm and proton relaxation behaviour made it evident that the point at which the reaction rate decreased, after a maximum value, could be related to the appearance of highly mobile water. The results obtained in this work indicate that the prediction of chemical reaction kinetics can be performed through the integrated analysis of water sorption, water and solids mobility and the physical state of the matrix. Copyright © 2007 Elsevier Ltd. All rights reserved.

Characterization of Sweetmeat Waste and Its Suitability for Sorption of As(III) in Aqueous Media.

PubMed

Islam, Md Mirajul; Adak, Asok; Paul, Prabir K

2017-04-01

  Presence of arsenic in effluents from mining, mineral processing, and metal plating industries pose a serious health hazard to human beings. In this research, suitability of cheap sweetmeat waste (SMW), which is sweet industry byproduct, was investigated for the treatment of As(III). The physicochemical properties of the sorbent were characterized. The SEM images revealed highly heterogeneous sorbent surface. XRD analysis showed the presence of different polysaccharides mainly containing hydroxyl functional group. FTIR analysis was also performed to confirm the functional groups present in the sorbent. Batch experiments were conducted for kinetic analysis, effect of initial As(III) concentration, sorbent dose, electrolytes, pH, and temperature in order to understand sorption behavior. Presence of electrolyte, solution pH, and temperature were found to affect the performance of the sorbent. The sorption followed pseudo-second order reaction and Langmuir isotherm model best. The studies revealed SMW to be an efficient media for removal of As(III) from aqueous environment.

Surface Changes in Well Casing Pipe Exposed to High Concentrations of Organics in Aqueous Solution

DTIC Science & Technology

1990-03-01

chloride (PVC) was the most resins (FEP, TFE and PFA ) are listed as unaffected by commonly used well casing material for ground water 99% of the...of its sample variation, all six of the test, control and un- apparent preferential rate of sorption (Miller 1982). Its treated SS304 and PVC samples...materials. In Grudtaecna~nto:Fieldinctlt- (1986) Sorption of organics by monitoring well con- ods (A.G. Collins and A.I. Johnson. Ed.). American

Increasing ion sorption and desorption rates of conductive electrodes

DOEpatents

DePaoli, David William; Kiggans, Jr., James O; Tsouris, Costas; Bourcier, William; Campbell, Robert; Mayes, Richard T

2014-12-30

An electrolyte system includes a reactor having a pair of electrodes that may sorb ions from an electrolyte. The electrolyte system also includes at least one power supply in electrical communication with the reactor. The at least one power supply may supply a DC signal and an AC signal to the pair of electrodes during sorption of the ions. In addition, the power supply may supply only the AC signal to the pair of electrodes during desorption of the ions.

Influences on the H2-sorption properties of Mg of Co (with various sizes) and CoO addition by reactive grinding and their thermodynamic stabilities

NASA Astrophysics Data System (ADS)

Song, Myoung Youp; Lee, DongSub; Kwon, IkHyun

2004-02-01

We attempted to improve the H2-sorption properties of Mg by mechanical grinding under H2 (reactive grinding) with Co (with various particle sizes) and with CoO. The thermodynamic stabilities of the added Co and CoO were also investigated. CoO addition has the best influence and addition of smaller particles of Co (0.5-1.5 μm) has a better effect than the addition of larger particles of Co on the H2-sorption properties of Mg. The activated Mg+10 wt.% CoO sample has about 5.54 wt% hydrogen-storage capacity at 598 K and the highest hydriding rate, showing an Ha value of 2.39 wt.% after 60 min at 598 K, 11.2 bar H2. The order of the hydriding rates after activation is the same as that of the specific surface areas of the samples. The reactive grinding of Mg with Co or CoO and hydriding-dehydriding cycling increase the H2-sorption rates by facilitating nucleation of magnesium hydride or α solid solution of Mg and H (by creating defects on the surface of the Mg particles and by the additive), and by making cracks on the surface of Mg particles and reducing the particle size of Mg, thus shortening the diffusion distances of hydrogen atoms. The cobalt oxide is stable even after 14 hydriding cycles at 598 K under 11.2 bar H2. Discharge capacities are measured for the sampple Mg+10 wt.%CoO and Mg+10wt.%Co (0.5-1.5 μm) with good hydrogen-storage properties.

Sorption and biodegradation of organic micropollutants during river bank filtration: a laboratory column study.

PubMed

Bertelkamp, C; Reungoat, J; Cornelissen, E R; Singhal, N; Reynisson, J; Cabo, A J; van der Hoek, J P; Verliefde, A R D

2014-04-01

This study investigated sorption and biodegradation behaviour of 14 organic micropollutants (OMP) in soil columns representative of the first metre (oxic conditions) of the river bank filtration (RBF) process. Breakthrough curves were modelled to differentiate between OMP sorption and biodegradation. The main objective of this study was to investigate if the OMP biodegradation rate could be related to the physico-chemical properties (charge, hydrophobicity and molecular weight) or functional groups of the OMPs. Although trends were observed between charge or hydrophobicity and the biodegradation rate for charged compounds, a statistically significant linear relationship for the complete OMP mixture could not be obtained using these physico-chemical properties. However, a statistically significant relationship was obtained between biological degradation rates and the OMP functional groups. The presence of ethers and carbonyl groups will increase biodegradability, while the presence of amines, ring structures, aliphatic ethers and sulphur will decrease biodegradability. This predictive model based on functional groups can be used by drinking water companies to make a first estimate whether a newly detected compound will be biodegraded during the first metre of RBF or that additional treatment is required. In addition, the influence of active and inactive biomass (biosorption), sand grains and the water matrix on OMP sorption was found to be negligible under the conditions investigated in this study. Retardation factors for most compounds were close to 1, indicating mobile behaviour of these compounds during soil passage. Adaptation of the biomass towards the dosed OMPs was not observed for a 6 month period, implying that new developed RBF sites might not be able to biodegrade compounds such as atrazine and sulfamethoxazole in the first few months of operation. Copyright © 2013 Elsevier Ltd. All rights reserved.

Characterization of sorption processes for the development of low-cost pesticide decontamination techniques.

PubMed

Rojas, Raquel; Vanderlinden, Eva; Morillo, José; Usero, José; El Bakouri, Hicham

2014-08-01

The adsorption/desorption behavior of four pesticides (atrazine, alachlor, endosulfan sulfate and trifluralin) in aqueous solutions onto four adsorbents (sunflower seed shells, rice husk, composted sewage sludge and soil) was investigated. Pesticide determination was carried out using stir bar sorptive extraction and gas chromatography coupled with mass spectroscopy. Maximum removal efficiency (73.9%) was reached using 1 g of rice husk and 50 mL of pesticide solution (200 μg L(-1)). The pseudo adsorption equilibrium was reached with 0.6 g organic residue, which was used in subsequent experiments. The pseudo-first-order, pseudo-second-order kinetics and the intra-particle diffusion models were used to describe the kinetic data and rate constants were evaluated. The first model was more suitable for the sorption of atrazine and alachlor while the pseudo-second-order best described endosulfan sulfate and trifluralin adsorption, which showed the fastest sorption rates. 4h was considered as the equilibrium time for determining adsorption isotherms. Experimental data were modeled by Langmuir and Freundlich models. In most of the studied cases both models can describe the adsorption process, although the Freundlich model was applicable in all cases. The sorption capacity increased with the hydrophobic character of the pesticides and decreased with their water solubility. Rice husk was revealed as the best adsorbent for three of the four studied pesticides (atrazine, alachlor and endosulfan sulfate), while better results were obtained with composted sewage sludge and sunflower seed shell for the removal of trifluralin. Although desorption percentages were not high (with the exception of alachlor, which reached a desorption rate of 57%), the Kfd values were lower than the Kf values for adsorption and all H values were below 100, indicating that the adsorption was weak. Copyright © 2014 Elsevier B.V. All rights reserved.

Sorption isotherm studies of Cd(II) ions using living cells of the marine microalga Tetraselmis suecica (Kylin) Butch.

PubMed

Pérez-Rama, M; Torres, E; Suárez, C; Herrero, C; Abalde, J

2010-10-01

The present work reports the use of living cells of the marine microalga Tetraselmis suecica for the biosorption of cadmium ions. For a better understanding of the biosorption characteristics, three fractions of removed cadmium (total, bioadsorbed and intracellular) were measured in the cells after 24 and 72 h of exposure to different initial cadmium concentrations (0.6-45 mg L(-1)). Both the Langmuir and Freundlich models were suitable for describing the sorption of cadmium ions by this microalga. The maximum sorption capacity was estimated to be 40.22 mg Cd g(-1) after 72 h using the Langmuir sorption model. In the lower cadmium concentrations, metal removed intracellularly was higher than that removed on the microalgal cell surface. Therefore, the intracellular fraction contributed more to the total removed cadmium than the fraction bioadsorbed to the cellular surface. The results showed that the cadmium removal capacity using living biomass could be much more effective than with non-living biomass due to the intracellular bioaccumulation. According to the microorganism selected and its tolerance to the toxic effect of the metal, the cadmium content in the intracellular fraction can become very significant, just like it happened with Tetraselmis. Copyright (c) 2010 Elsevier Ltd. All rights reserved.

Organic pollutants removal from 2,4,6-trinitrotoluene (TNT) red water using low cost activated coke.

PubMed

Zhang, Mohe; Zhao, Quanlin; Ye, Zhengfang

2011-01-01

We treated 2,4,6-trinitrotoluene (TNT) red water from the Chinese explosive industry with activated coke (AC) from lignite. Since the composition of TNT red water was very complicated, chemical oxygen demand (COD) was used as the index for evaluating treatment efficiency. This study focused on sorption kinetics and equilibrium sorption isotherms of AC for the removal of COD from TNT red water, and the changes of water quality before and after adsorption were evaluated using high performance liquid chromatography, UV-Vis spectra and gas chromatography/mass spectroscopy. The results showed that the sorption kinetics of COD removal from TNT red water onto AC fitted well with the pseudo second-order model. The adsorption process was an exothermic and physical process. The sorption isotherm was in good agreement with Redlich-Peterson isotherm. At the conditions of initial pH = 6.28, 20 degrees C and 3 hr of agitation, under 160 g/L AC, 64.8% of COD was removed. The removal efficiencies of 2,4-dinitrotoluene-3-sulfonate (2,4-DNT-3-SO3-) and 2,4-dinitrotoluene-5-sulfonate (2,4-DNT-5-SO3-) were 80.5% and 84.3%, respectively. After adsorption, the acute toxicity of TNT red water reduced greatly, compared with that of unprocessed TNT red water.

Sorption of fluoride using chemically modified Moringa oleifera leaves

NASA Astrophysics Data System (ADS)

Dan, Shabnam; Chattree, Amit

2018-05-01

Contamination of drinking water due to fluoride is a severe health hazard problem. Excess of fluoride (> 1.5 mg/L) in drinking water is harmful to human health. Various treatment technologies for removing fluoride from groundwater have been investigated. The present study showed that the leaves of Moringa oleifera, a herbal plant is an effective adsorbent for the removal of fluoride from aqueous solution. Acid treated Moringa oleifera leaves powder showed good adsorption capacity than alkali treated Moringa oleifera leaves powder. Batch sorptive defluoridation was conducted under the variable experimental condition such as pH, contact time, adsorbent dose and initial fluoride ion concentration. Maximum defluoridation was achieved at pH 1. The percentage of fluoride removal increases with adsorbent dose. The equilibrium sorption data were fitted into Langmuir, Freundlich and Temkin isotherms. Of the three adsorption isotherms, the R 2 value of Langmuir isotherm model was the highest. The maximum monolayer coverage ( Q max) from Langmuir isotherm model was determined to be 1.1441 mg/g, the separation factor indicating a favorable sorption experiment is 0.035. It was also discovered that the adsorption did not conform to the Freundlich adsorption isotherm. The heat of sorption process was estimated from Temkin Isotherm model to be - 0.042 J/mol which vividly proved that the adsorption experiment followed a physical process.

Graphene oxide-facilitated transport of levofloxacin and ciprofloxacin in saturated and unsaturated porous media.

PubMed

Sun, Kaixuan; Dong, Shunan; Sun, Yuanyuan; Gao, Bin; Du, Wenchao; Xu, Hongxia; Wu, Jichun

2018-04-15

In this work, effects of graphene oxide (GO) on the co-transport of the two typical Fluoroquinolones (FQs) - levofloxacin (LEV) and ciprofloxacin (CIP) in saturated and unsaturated quartz sand media were studied. The adsorption isotherms showed that GO had much larger sorption capacities to LEV and CIP than sand with the largest Langmuir adsorption capacity of 409 mg g -1 (CIP-GO); while the sorption affinity of the two FQs onto the two adsorbents might follow the order of CIP-sand > LEV-sand > LEV-GO > CIP-GO. GO promoted the mobility of the two FQs in both saturated and unsaturated porous media due to its strong mobility and sorption capacity. The GO-bound LEV/CIP was responsible for the LEV/CIP transport in the porous media, and transport of GO-bound FQs increased with the increasing of initial GO concentration. Under unsaturated conditions, moisture showed little effect on the transport of GO-bound CIP; however, the mobility of GO-bound LEV reduced with the decreasing of moisture content, suggesting the transport of adsorbed LEV from GO to air-water interface. GO sorption reduced the antibacterial ability of the two FQs, but they were still effective in inhibiting E. coli growth. Copyright © 2018 Elsevier B.V. All rights reserved.

Optimal design of active spreading systems to remediate sorbing groundwater contaminants in situ

NASA Astrophysics Data System (ADS)

Piscopo, Amy N.; Neupauer, Roseanna M.; Kasprzyk, Joseph R.

2016-07-01

The effectiveness of in situ remediation to treat contaminated aquifers is limited by the degree of contact between the injected treatment chemical and the groundwater contaminant. In this study, candidate designs that actively spread the treatment chemical into the contaminant are generated using a multi-objective evolutionary algorithm. Design parameters pertaining to the amount of treatment chemical and the duration and rate of its injection are optimized according to objectives established for the remediation - maximizing contaminant degradation while minimizing energy and material requirements. Because groundwater contaminants have different reaction and sorption properties that influence their ability to be degraded with in situ remediation, optimization was conducted for six different combinations of reaction rate coefficients and sorption rates constants to represent remediation of the common groundwater contaminants, trichloroethene, tetrachloroethene, and toluene, using the treatment chemical, permanganate. Results indicate that active spreading for contaminants with low reaction rate coefficients should be conducted by using greater amounts of treatment chemical mass and longer injection durations relative to contaminants with high reaction rate coefficients. For contaminants with slow sorption or contaminants in heterogeneous aquifers, two different design strategies are acceptable - one that injects high concentrations of treatment chemical mass over a short duration or one that injects lower concentrations of treatment chemical mass over a long duration. Thus, decision-makers can select a strategy according to their preference for material or energy use. Finally, for scenarios with high ambient groundwater velocities, the injection rate used for active spreading should be high enough for the groundwater divide to encompass the entire contaminant plume.

Gas-phase organics in environmental tobacco smoke. 1. Effects of smoking rate, ventilation, and furnishing level on emission factors.

PubMed

Singer, Brett C; Hodgson, Alfred T; Guevarra, Karla S; Hawley, Elisabeth L; Nazaroff, William W

2002-03-01

We measured the emissions of 26 gas-phase organic compounds in environmental tobacco smoke (ETS) using a model room that simulates realistic conditions in residences and offices. Exposure-relevant emission factors (EREFs), which include the effects of sorption and re-emission over a 24-h period, were calculated by mass balance from measured compound concentrations and chamber ventilation rates in a 50-m3 room constructed and furnished with typical materials. Experiments were conducted at three smoking rates (5, 10, and 20 cigarettes day(-1)), three ventilation rates (0.3, 0.6, and 2 h(-1)), and three furnishing levels (wallboard with aluminum flooring, wallboard with carpet, and full furnishings). Smoking rate did not affect EREFs, suggesting that sorption was linearly related to gas-phase concentration. Furnishing level and ventilation rate in the model room had little effect on EREFs of several ETS compounds including 1,3-butadiene, acrolein, acrylonitrile, benzene, toluene, and styrene. However, sorptive losses at low ventilation with full furnishings reduced EREFs for the ETS tracers nicotine and 3-ethenylpyridine by as much as 90 and 65% as compared to high ventilation, wallboard/aluminum experiments. Likewise, sorptive losses were 40-70% for phenol, cresols, naphthalene, and methylnaphthalenes. Sorption persisted for many compounds; for example, almost all of the sorbed nicotine and most of the sorbed cresol remained sorbed 3 days after smoking. EREFs can be used in models and with ETS tracer-based methods to refine and improve estimates of exposures to ETS constituents.

A novel biosorbent for dye removal: extracellular polymeric substance (EPS) of Proteus mirabilis TJ-1.

PubMed

Zhang, Zhiqiang; Xia, Siqing; Wang, Xuejiang; Yang, Aming; Xu, Bin; Chen, Ling; Zhu, Zhiliang; Zhao, Jianfu; Jaffrezic-Renault, Nicole; Leonard, Didier

2009-04-15

This paper deals with the extracellular polymeric substance (EPS) of Proteus mirabilis TJ-1 used as a novel biosorbent to remove dye from aqueous solution in batch systems. As a widely used and hazardous dye, basic blue 54 (BB54) was chosen as the model dye to examine the adsorption performance of the EPS. The effects of pH, initial dye concentration, contact time and temperature on the sorption of BB54 to the EPS were examined. At various initial dye concentrations (50-400 mg/L), the batch sorption equilibrium can be obtained in only 5 min. Kinetic studies suggested that the sorption followed the internal transport mechanism. According to the Langmuir model, the maximum BB54 uptake of 2.005 g/g was obtained. Chemical analysis of the EPS indicated the presence of protein (30.9%, w/w) and acid polysaccharide (63.1%, w/w). Scanning electron microscopy (SEM) images showed that the EPS with a crystal-linear structure was whole enwrapped by adsorbed dye molecules. FTIR spectrum result revealed the presence of adsorbing groups such as carboxyl, hydroxyl and amino groups in the EPS. High-molecular weight of the EPS with more binding-sites and stronger van der Waals forces together with its specific construct leads to the excellent performance of dye adsorption. The EPS shows potential board application as a biosorbent for both environmental protection and dye recovery.

Biosorption of neodymium on Chlorella vulgaris in aqueous solution obtained from hard disk drive magnets

PubMed Central

Kucuker, Mehmet Ali; Wieczorek, Nils; Kuchta, Kerstin; Copty, Nadim K.

2017-01-01

In recent years, biosorption is being considered as an environmental friendly technology for the recovery of rare earth metals (REE). This study investigates the optimal conditions for the biosorption of neodymium (Nd) from an aqueous solution derived from hard drive disk magnets using green microalgae (Chlorella vulgaris). The parameters considered include solution pH, temperature and biosorbent dosage. Best-fit equilibrium as well as kinetic biosorption models were also developed. At the optimal pH of 5, the maximum experimental Nd uptakes at 21, 35 and 50°C and an initial Nd concentration of 250 mg/L were 126.13, 157.40 and 77.10 mg/g, respectively. Analysis of the optimal equilibrium sorption data showed that the data fitted well (R2 = 0.98) to the Langmuir isotherm model, with maximum monolayer coverage capacity (qmax) of 188.68 mg/g, and Langmuir isotherm constant (KL) of 0.029 L/mg. The corresponding separation factor (RL) is 0.12 indicating that the equilibrium sorption was favorable. The sorption kinetics of Nd ion follows well a pseudo-second order model (R2>0.99), even at low initial concentrations. These results show that Chlorella vulgaris has greater biosorption affinity for Nd than activated carbon and other algae types such as: A. Gracilis, Sargassum sp. and A. Densus. PMID:28388641

Sorption and Transport of Sildenafil in Natural Soils

NASA Astrophysics Data System (ADS)

Boudinot, F. G.; Vulava, V. M.

2013-12-01

Pharmaceutical Chemicals (PCs) mainly enter our ecosystems from discharges of treated wastewater and have direct effects on the ecological health of that area. Sildenafil citrate (Viagra) is one such PC, whose presence has been reported in stream waters. Although one study has shown that sildenafil is not harmful in bacterial and fungal environments, there remains much unknown about its fate elsewhere in ecosystems. Sildenafil is a complex organic molecule with two amino functional groups that result in pKa's of 7.27 and 5.97. It also has a high solubility of 3.5 g/L. Given that sildenafil consumption (and concurrently disposal) is on the rise, it is essential that its behavior in the natural environment be better understood. The goal of this study was to quantify the sorption and transport behavior of sildenafil in differing natural soils with varying compositions. Pristine A- and B- horizon soil samples from several soil series were collected in a managed forest near Charleston, SC and used for these studies. The soils were characterized for physical and chemical properties: soil organic matter content ranged between 0.6-7.6%, clay content between 6-20%, and soil pH between 4-5. These soils were then used to perform kinetic reaction, sorption, and column transport experiments. Batch kinetic experiments showed a fast reaction rate in both clay-rich and organic-rich soils and an equilibration time of less than 24 hours. Batch reactor sorption experiments provided data for sorption isotherms (plot of sildenafil in solution, C vs. sildenafil sorbed in soil, q) which were nonlinear. The isotherms were fit using Freundlich model (q=KfCn, where Kf and n are fitting parameters). Sildenafil sorbed more strongly to clay-rich soils compared with organic-rich soils with less clay. It is hypothesized that permanent negative charge on clay mineral surfaces form ionic bonds with positively charged amines in sildenafil in acidic pHs. Transport experiments were conducted using glass chromatography columns, homogenously packed with soil, saturated with 5 mM CaCl2 solution, and injected with 100 mg/L sildenafil. The effluent solution concentrations were plotted as a function of time to plot breakthrough curves. Sildenafil was significantly retarded in clay-rich soil column experiments confirming trends observed in sorption experiments. Overall data indicate very strong sorption of sildenafil to both organic- rich and clay-rich soils, but stronger sorption to clay-rich soils. Strong soil sorption acts as a filter for water, leaving the PC behind in the soils. These results suggest that little sildenafil will reside in groundwater once exposed to natural soils. Further research is needed to better understand how sildenafil's metabolites respond in ecosystems. Given the high metabolic rate and long shelf life of sildenafil, these metabolites may be more prevalent in natural soils.

Transport of polar and non-polar volatile compounds in polystyrene foam and oriented strand board

NASA Astrophysics Data System (ADS)

Yuan, Huali; Little, John C.; Hodgson, Alfred T.

Transport of hexanal and styrene in polystyrene foam (PSF) and oriented strand board (OSB) was characterized. A microbalance was used to measure sorption/desorption kinetics and equilibrium data. While styrene transport in PSF can be described by Fickian diffusion with a symmetrical and reversible sorption/desorption process, hexanal transport in both PSF and OSB exhibited significant hysteresis, with desorption being much slower than sorption. A porous media diffusion model that assumes instantaneous local equilibrium governed by a nonlinear Freundlich isotherm was found to explain the hysteresis in hexanal transport. A new nonlinear sorption and porous diffusion emissions model was, therefore, developed and partially validated using independent chamber data. The results were also compared to the more conventional linear Fickian-diffusion emissions model. While the linear emissions model predicts styrene emissions from PSF with reasonable accuracy, it substantially underestimates the rate of hexanal emissions from OSB. Although further research and more rigorous validation is needed, the new nonlinear emissions model holds promise for predicting emissions of polar VOCs such as hexanal from porous building materials.

Aluminum drinking water treatment residuals (Al-WTRs) as sorbent for mercury: Implications for soil remediation.

PubMed

Hovsepyan, Anna; Bonzongo, Jean-Claude J

2009-05-15

The potential of readily available and non-hazardous waste material, aluminum drinking water treatment residuals (Al-WTRs), to efficiently sorb and immobilize mercury (Hg) from aqueous solutions was evaluated. Al-WTR samples with average specific surface area of 48m(2)/g and internal micropore surface area of 120m(2)/g were used in a series of batch sorption experiments. Obtained sorption isotherms indicated a strong affinity of Hg for Al-WTRs. Using the Langmuir adsorption model, a relatively high maximum sorption capacity of 79mg Hg/g Al-WTRs was determined. Sorption kinetic data was best fit to a pseudo-first-order model, while the use of the Weber-Morris and Bangham models suggested that the intraparticle diffusion could be the rate-limiting step. Also, Al-WTRs effectively immoblized Hg in the pH range of 3-8. The results from these short-term experiments demonstrate that Al-WTRs can be effectively used to remove Hg from aqueous solutions. This ability points to the potential of Al-WTRs as a sorbent in soil remediation techniques based on Hg-immobilization.

Synthesis of 3D iron and carbon-based composite as a bifunctional sorbent and catalyst for remediation of organic pollutants

NASA Astrophysics Data System (ADS)

Li, Ling; Shen, Yi; Wang, Zhaomei

2017-07-01

We prepared a 3D monolith by integrating graphite nanosheet encapsulated iron nanoparticles (Fe@GNS) into graphite felt (GF) supports. The structural properties of the resulting Fe@GNS/GF monolith are characterized by x-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, x-ray photoelectron spectroscopy and N2 adsorption-desorption isotherms. The Fe@GNS/GF monoliths are utilized as a bifunctional sorbent and catalyst for water remediation. Using Congo red and methyl violet 2B as model pollutants, the sorption and catalytic performance of the Fe@GNS/GF composite are examined. The Fe@GNS/GF monolith possesses maximum sorption capacities of 177 and 142 mg g-1 for the sorption of CR and MV-2B, respectively. It also exhibits rate constants of 0.0563 and 0.0464 min-1 for the catalytic degradation of CR and MV-2B, respectively. As a proof of concept, the Fe@GNS/GF is successfully utilized to decontaminate simulated organic waste water via a combination of sorption and catalytic degradation processes.

Interaction between Silver Nanoparticles and Spinach Leaf

NASA Astrophysics Data System (ADS)

Tian, Y.; Li, H.; Zhang, Y.; Riser, E.; He, S.; Zhang, W.

2013-12-01

Interactions of engineered nanoparticles (ENPs) with plant surfaces are critical to assessing the bioavailability of ENPs to edible plants and to further evaluating impacts of ENPs on ecological health and food safety. Silver nanoparticles (i.e., nanoAg) could enter the agroecosystems either as an active ingredient in pesticides or from other industrial and consumer applications. Thus, in the events of pesticide application, rainfall, and irrigation, vegetable leaves could become in contact and then interact with nanoAg. The present study was to assess whether the interaction of nanoAg with spinach leaves can be described by classical sorption models and to what extent it depends on and varies with dispersion methods, environmental temperature, and ion release. We investigated the stability and ion release of nanoAg dispersed by sodium dodecyl sulfate (SDS, 1%) and humic acid (HA, 10 mg C/L) solutions, as well as sorption and desorption of nanoAg on and from the fresh spinach leaf. Results showed SDS-nanoAg released about 2%-8% more Ag ion than HA-nanoAg. The sorption of Ag ion, described by the Freundlich model in the initial concentration range of 0.6-50 mg/L, was 2-4 times higher than that of nanoAg. The sorption of nanoAg on spinach leaf can be fitted by the Langmuir model, and the maximum sorption amount of HA-nanoAg and SDS-nanoAg was 0.21 and 0.41 mg/g, respectively. The higher sorption of SDS-nanoAg relative to that of HA-nanoAg could be partially resulted from the higher release of Ag ion from the former. The maximum desorption amount of HA-nanoAg and SDS-nanoAg in 1% SDS solution was 0.08 and 0.10 mg/g, respectively. NanoAg attachment on and its penetration to the spinach leaf was visualized by the Scanning Electron Microscope equipped with an Energy Dispersive Spectrometer (SEM-EDS). It is equally important that the less sorption of nanoAg under low environmental temperature could be partially due to the closure of stomata, as verified by SEM-EDS. CytoViva Hyperspectral Imaging System was also employed to map the distribution of nanoAg in the leaf profile. Significant sorption of nanoAg on spinach leaf should urge the precaution with potential widespread use of ENPs in agriculture.

Results of a European interlaboratory comparison on CO2 sorption on activated carbon and coals

NASA Astrophysics Data System (ADS)

Gensterblum, Yves; Busch, Andreas; Krooss, Bernhard; de Weireld, Guy; Billemont, Pierre; van Hemert, Patrick; Wolf, Karl-Heinz

2013-04-01

For the assessment of CO2 storage in coal seams or enhanced coalbed methane production (ECBM), the sorption properties of natural coals are important parameters. Since more and more laboratories worldwide are concerned with measurements of gas sorption on coal it is indispensable to establish quality standards for such experiments. The first two interlaboratory studies on CO2 sorption on coal (Goodman et al. 2004, 2007) revealed a poor agreement of sorption isotherms among the participating laboratories, particularly in the high-pressure range. During the MOVECBM (http://www.movecbm.eu/) project funded by the European Commission (6th framework), an interlaboratory comparison of CO2 sorption on selected coals and activated carbon was initiated. Measurements were performed on dry samples at 45° C using the manometric and the gravimetric method. up to a final pressure of 15 MPa. The first set of high-pressure sorption measurements was performed on a Filtrasorb 400 activated carbon sample in order to minimise heterogeneity effects and to optimize the experimental procedures for the individual (manometric or gravimetric) methods (Gensterblum et al. 2009). Since comparability for the activated carbon was excellent, the measurements were continued using natural coals of various rank (anthracite, bituminous coal and lignite) to study the influence of heterogeneities and varying starting conditions on the CO2 sorption properties (Gensterblum et al. 2010). Compared to the poor reproducibility observed in previous interlaboratory studies (Goodman et al., 2004, 2007) this European study showed excellent agreement (<5 % deviation) among the participating laboratories with good repeatability. The sorption data and technical information on the different experimental setups have been used to investigate errors and potential pitfalls in the assessment of high-pressure CO2 sorption isotherms. References Gensterblum Y., P. van Hemert, P. Billemont, A. Busch, B.M. Krooss, G. de Weireld, D. Prinz , K.-H.A.A. Wolf, "European inter-laboratory comparison of high pressure CO2 sorption isotherms. II: natural coals" IJCG, 2010, 84, 115-124 Gensterblum Y., P. van Hemert, P. Billemont, A. Busch, D. Charriére, D. Li, B.M. Krooss, G. de Weireld, D. Prinz , K.-H.A.A. Wolf, "European inter-laboratory comparison of high pressure CO2 sorption isotherms. I: Activated carbon" Carbon 47 ( 2009 ) 2958 -2969 Goodman, A.L., Busch, A., Duffy, G., Fitzgerald, J.E., Gasem, K.A.M., Gensterblum, Y., Krooss, B.M., Levy, J., Ozdemir, E., Pan, Z., Robinson, Jr., R.L., Schroeder, K., Sudibandriyo, M., White, C. (2004). An Inter-laboratory Comparison of CO2 Isotherms Measured on Argonne Premium Coal Samples. Energy and Fuels 18, 1175-1182. Goodman, A.L., Busch, A., Day, S., Duffy, G.J., Fitzgerald, J.E., Gasem, K.A.M., Gensterblum, Y., Hartman, C., Krooss, B.M., Pan, Z., Pratt, T., Robinson, Jr., R.L., Romanov, V., Sakurovs, R., Schroeder, K., Sudibandriyo, M., White, C.M. (2007) "Inter-laboratory Comparison II: CO2 Isotherms Measured on Moisture-Equilibrated Argonne Premium Coals at 55oC and 15 MPa", International Journal of Coal Geology 72, 153-164.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Goltz, M.N.; Oxley, M.E.

Aquifer cleanup efforts at contaminated sites frequently involve operation of a system of extraction wells. It has been found that contaminant load discharged by extraction wells typically declines with time, asymptotically approaching a residual level. Such behavior could be due to rate-limited desorption of an organic contaminant from aquifer solids. An analytical model is presented which accounts for rate-limited desorption of an organic solute during cleanup of a contaminated site. Model equations are presented which describe transport of a sorbing contaminant in a converging radial flow field, with sorption described by (1) equilibrium, (2) first-order rate, and (3) Fickian diffusionmore » expressions. The model equations are solved in the Laplace domain and numerically inverted to simulate contaminant concentrations at an extraction well. A Laplace domain solution for the total contaminant mass remaining in the aquifer is also derived. It is shown that rate-limited sorption can have a significant impact upon aquifer remediation. Approximate equivalence among the various rate-limited models is also demonstrated.« less

Modelling the diffusive transport and remobilisation of 137Cs in sediments: The effects of sorption kinetics and reversibility

NASA Astrophysics Data System (ADS)

Smith, J. T.; Comans, R. N. J.

1996-03-01

In determining the mobility of ions in sediments it is important to take account of the solid phase sorption and speciation. Measurements were made of activity depth profiles of 137Cs from fallout from Nuclear Weapons Testing and from the Chernobyl accident in two lake sediments. The fraction of 137Cs in the aqueous, exchangeably sorbed and "fixed" phases was determined at each depth interval. A model was developed to simulate the transport of 137Cs in these sediments, taking account of changes in sorption properties as the concentration of the competing ammonium ion changes with depth, as well as transfers of activity to less-exchangeable sites on the solids. The model simulations give reasonable agreement with experimental data, and the fitted rate constant for slow transfers to less-exchangeable sites ( T1/2 = 50-125 d) is in agreement with independent measurements. The modelling gave evidence for a reverse reaction from less-exchangeable to exchangeable sites with a half-life of order 10 y. Model results were compared with those generated by a physical mixing model and the standard molecular diffusion model assuming equilibrium sorption to the solid phase. Estimates were made of the remobilisation of Chernobyl 137Cs from these sediments to the water column: predicted rates vary from around 3% of the inventory per year 2 years after the fallout event to 0.04% per year 30 years after the fallout.

Removal of dissolved organic carbon by aquifer material: Correlations between column parameters, sorption isotherms and octanol-water partition coefficient.

PubMed

Pradhan, Snigdhendubala; Boernick, Hilmar; Kumar, Pradeep; Mehrotra, Indu

2016-07-15

The correlation between octanol-water partition coefficient (KOW) and the transport of aqueous samples containing single organic compound is well documented. The concept of the KOW of river water containing the mixture of organics was evolved by Pradhan et al. (2015). The present study aims at determining the KOW and sorption parameters of synthetic aqueous samples and river water to finding out the correlation, if any. The laboratory scale columns packed with aquifer materials were fed with synthetic and river water samples. Under the operating conditions, the compounds in the samples did not separate, and all the samples that contain more than one organic compound yielded a single breakthrough curve. Breakthrough curves simulated from sorption isotherms were compared with those from the column runs. The sorption parameters such as retardation factor (Rf), height of mass transfer zone (HMTZ), rate of mass transfer zone (RMTZ), breakpoint column capacity (qb) and maximum column capacity (qx) estimated from column runs, sorption isotherms and models developed by Yoon-Nelson, Bohart-Adam and Thomas were in agreement. The empirical correlations were found between the KOW and sorption parameters. The transport of the organics measured as dissolved organic carbon (DOC) through the aquifer can be predicted from the KOW of the river water and other water samples. The novelty of the study is to measure KOW and to envisage the fate of the DOC of the river water, particularly during riverbank filtration. Statistical analysis of the results revealed a fair agreement between the observed and computed values. Copyright © 2016 Elsevier Ltd. All rights reserved.

Relation of organic contaminant equilibrium sorption and kinetic uptake in plants

USGS Publications Warehouse

Li, H.; Sheng, G.; Chiou, C.T.; Xu, O.

2005-01-01

Plant uptake is one of the environmental processes that influence contaminant fate. Understanding the magnitude and rate of plant uptake is critical to assessing potential crop contamination and the development of phytoremediation technologies. We determined (1) the partition-dominated equilibrium sorption of lindane (LDN) and hexachlorobenzene (HCB) by roots and shoots of wheat seedlings, (2) the kinetic uptake of LDN and HCB by roots and shoots of wheat seedlings, (3) the kinetic uptake of HCB, tetrachloroethylene (PCE), and trichloroethylene (TCE) by roots and shoots of ryegrass seedlings, and (4) the lipid, carbohydrate, and water contents of the plants. Although the determined sorption and the plant composition together suggest the predominant role of plant lipids for the sorption of LDN and HCB, the predicted partition with lipids of LDN and HCB using the octanol-water partition coefficients is notably lower than the measured sorption, due presumably to underestimation of the plant lipid contents and to the fact that octanol is less effective as a partition medium than plant lipids. The equilibrium sorption or the estimated partition can be viewed as the kinetic uptake limits. The uptakes of LDN, PCE, and TCE from water at fixed concentrations increased with exposure time in approach to steady states. The uptake of HCB did not reach a plateau within the tested time because of its exceptionally high partition coefficient. In all of the cases, the observed uptakes were lower than their respective limits, due presumably to contaminant dissipation in and limited water transpiration by the plants. ?? 2005 American Chemical Society.

Superhydrophobic graphene-based sponge as a novel sorbent for crude oil removal under various environmental conditions.

PubMed

Shiu, Ruei-Feng; Lee, Chon-Lin; Hsieh, Ping-Yen; Chen, Chi-Shuo; Kang, Yun-Yi; Chin, Wei-Chun; Tai, Nyan-Hwa

2018-05-15

Mechanical recovery of oils using oil sorbents is one of the most important approaches to manage marine oil spills. However, the properties of the oils spilled into sea are influenced by external environmental conditions. In this study, we present a graphene-based (GB) sponge as a novel sorbent for crude oil removal and compare its performance with that of a commercial sorbent sheet under various environmental parameters. The GB sponge with excellent superhydrophobic and superoleophilic characteristics is demonstrated to be an efficient sorbent for crude oils, with high sorption capacity (up to 85-95 times its weight) and good reusability. The crude-oil-sorption capacity of our GB sponge is remarkably higher (about 4-5 times) than that of the commercial sheet and most other previously reported sponge sorbents. Moreover, several challenging environmental conditions were examined for their effects on the sorption performance, including the weathering time of oils, seawater temperature, and turbulence (wave effect). The results show that the viscosity of the oil increased with increasing weathering time or decreasing temperature; therefore, the sorption rate seemed to decrease with longer weathering times and lower temperatures. Turbulence can facilitate inner sorption and promote higher oil sorption. Our results indicate that the extent of the effects of weather and other environmental factors on crude oil should be considered in the assessment of the effective adsorption capacity and efficiency of sorbents. The present work also highlights the widespread potential applications of our GB sponge in marine spilled-oil cleanup and hydrophobic solvent removal. Copyright © 2018 Elsevier Ltd. All rights reserved.

Application of the method of temporal moments to interpret solute transport with sorption and degradation

NASA Astrophysics Data System (ADS)

Pang, Liping; Goltz, Mark; Close, Murray

2003-01-01

In this note, we applied the temporal moment solutions of [Das and Kluitenberg, 1996. Soil Sci. Am. J. 60, 1724] for one-dimensional advective-dispersive solute transport with linear equilibrium sorption and first-order degradation for time pulse sources to analyse soil column experimental data. Unlike most other moment solutions, these solutions consider the interplay of degradation and sorption. This permits estimation of a first-order degradation rate constant using the zeroth moment of column breakthrough data, as well as estimation of the retardation factor or sorption distribution coefficient of a degrading solute using the first moment. The method of temporal moment (MOM) formulae was applied to analyse breakthrough data from a laboratory column study of atrazine, hexazinone and rhodamine WT transport in volcanic pumice sand, as well as experimental data from the literature. Transport and degradation parameters obtained using the MOM were compared to parameters obtained by fitting breakthrough data from an advective-dispersive transport model with equilibrium sorption and first-order degradation, using the nonlinear least-square curve-fitting program CXTFIT. The results derived from using the literature data were also compared with estimates reported in the literature using different equilibrium models. The good agreement suggests that the MOM could provide an additional useful means of parameter estimation for transport involving equilibrium sorption and first-order degradation. We found that the MOM fitted breakthrough curves with tailing better than curve fitting. However, the MOM analysis requires complete breakthrough curves and relatively frequent data collection to ensure the accuracy of the moments obtained from the breakthrough data.

Transport of four pharmaceuticals in different horizons of three soil types

NASA Astrophysics Data System (ADS)

Kodesova, Radka; Svatkova, Paula; Klement, Ales; Jaksik, Ondrej; Golovko, Oksana; Fer, Miroslav; Kocarek, Martin; Nikodem, Antonin; Grabic, Roman

2015-04-01

Soil structure, which varies in different soil types and the horizons of these soil types, has a significant impact on water flow and contaminant transport in soils. Transport of many contaminants is in addition strongly influenced by their sorption on soil particles. Transport of four pharmaceuticals (sulfamethoxazole, trimethoprim, atenolol and carbamazepine) was studied in soil columns (a diameter of 10.5 cm and a height of 13 cm) taken from all diagnostic horizons of three different soil types (Haplic Luvisol, Greyic Phaeozem and Haplic Cambisol). The irrigation by water contaminated by a mixture of all four compounds followed by ponding infiltration of distilled water was simulated and water outflow and solute concentrations from the bottom of the soil sample was monitored in time. The highest infiltration rates were observed for soil samples from the Bt horizons of the Greyic Phaeozem that exhibited prismatic structure, followed by rates observed in the Ap horizons of the Haplic Luvisol, Greyic Phaeozem and Haplic Cambisol (due to their granular soil structure and presence of root channels). The lowest infiltration rate was measured for the Bw horizon of the Haplic Cambisol, which had a poorly developed soil structure and a low fraction of macropores. Compound discharge was however also highly affected by their sorption on solids. The highest mobility was observed for sulfamethoxazole followed by carbamazepine atenolol and trimethoprim, which corresponds to measured sorption isotherms. Mobility of ionizable compounds in different soil samples was influenced by pH (i.e. degree and form of their ionization) and sites available for absorption. Mobility of sulfamethoxazole decreased with decreasing pH (i.e. the largest sorption measured in horizons of the Haplic Cambisol). While mobility of atenolol and trimethoprim decreased with increasing base cation saturation, and with increasing organic matter content for carbamazepine. As result of both affects (i.e. soil structure and compounds' sorption) the highest discharge of all compounds was observed from the Ap horizon of the Greyic Phaeozem followed by compound discharge from the C horizons of the Greyic Phaeozem and the C and Bt2 horizons of the Haplic Luvisol. Acknowledgement: The authors acknowledge the financial support of the Czech Science Foundation (Project No. 13-12477S, Transport of pharmaceuticals in soils). References: Kodesova, R., Grabic, R., Kocarek, M., Klement, A., Golovko, O., Fer, M., Nikodem, A., Jaksik, O., Pharmaceuticals' sorptions relative to properties of thirteen different soils. Science of the Total Environment 511 (2015) 435-443.

On the possibility of controlling the hydrophilic/hydrophobic characteristics of toroid Mo138 nanocluster polyoxometalates

NASA Astrophysics Data System (ADS)

Grzhegorzhevskii, K. V.; Adamova, L. V.; Eremina, E. V.; Ostroushko, A. A.

2017-03-01

The possibility of changing the hydrophilic (polar) surfaces of toroid nanocluster polyoxomolibdates to hydrophobic (nonpolar) surfaces via the modification of Mo138 nanoclusters by surfactant molecules (dodecylpyridinium chloride) as a result of the interaction between these compounds in solutions is demonstrated. Benzene and methanol are used as molecular probes (indicators of the condition of nanocluster surfaces). Comparative characteristics of the equilibrium sorption of benzene and methanol vapors on the initial and modified surfaces of the solid polyoxometalate, and data on the sorption of organic molecules on the surfaces of Rhodamine B-modified nanoclusters of the toroid (Mo138) and keplerate (Mo132) types are obtained.

Sorption of atmospheric gases by bulk lithium metal

DOE PAGES

Hart, C. A.; Skinner, C. H.; Capece, A. M.; ...

2016-01-01

Lithium conditioning of plasma facing components has enhanced the performance of several fusion devices. Elemental lithium will react with air during maintenance activities and with residual gases (H 2O, CO, CO 2) in the vacuum vessel during operations. We have used a mass balance (microgram sensitivity) to measure the mass gain of lithium samples during exposure of a ~1 cm 2 surface to ambient and dry synthetic air. For ambient air, we found an initial mass gain of several mg/h declining to less than 1 mg/h after an hour and decreasing by an order of magnitude after 24 h. Amore » 9 mg sample achieved a final mass gain corresponding to complete conversion to Li 2CO 3 after 5 days. Exposure to dry air resulted in a 30 times lower initial rate of mass gain. The results have implications for the chemical state of lithium plasma facing surfaces and for safe handling of lithium coated components.« less

Preparation of carbon coated Fe3O4 nanoparticles for magnetic separation of uranium

NASA Astrophysics Data System (ADS)

Zhang, Xiaofei; Wang, Jun

2018-01-01

Uranium(VI) was removed from aqueous solutions using carbon coated Fe3O4 nanoparticles (Fe3O4@C). Batch experiments were conducted to study the effects of initial pH, shaking time and temperature on uranium sorption efficiency. It was found that the maximum adsorption capacity of the Fe3O4@C toward uranium(VI) was ∼120.20 mg g-1 when the initial uranium(VI) concentration was 100 mg L-1, displaying a high efficiency for the removal of uranium(VI) ions. Kinetics of the uranium(VI) removal is found to follow pseudo-second-order rate equation. In addition, the uranium(VI)-loaded Fe3O4@C nanoparticles can be recovered easily from aqueous solution by magnetic separation and regenerated by acid treatment. Present study suggested that magnetic Fe3O4@C composite particles can be used as an effective and recyclable adsorbent for the removal of uranium(VI) from aqueous solutions.

i-SVOC -- A simulation program for indoor SVOCs (Version 1.0)

EPA Science Inventory

Program i-SVOC estimates the emissions, transport, and sorption of semivolatile organic compounds (SVOCs) in the indoor environment as functions of time when a series of initial conditions is given. This program implements a framework for dynamic modeling of indoor SVOCs develope...

Simulation Program i-SVOC User’s Guide

EPA Science Inventory

This document is the User’s Guide for computer program i-SVOC, which estimates the emissions, transport, and sorption of semivolatile organic compounds (SVOCs) in the indoor environment as a function of time when a series of initial conditions is given. This program implements a ...

Waste isolation safety assessment program. Task 4. Collection and generation of transport data theoretical and experimental evaluation of waste transport in selected rocks. Annual progress report, October 1, 1978-September 30, 1979

DOE Office of Scientific and Technical Information (OSTI.GOV)

Silva, R.J.; Benson, L.V.; Yee, A.W.

1979-09-30

The objective of the program is to establish a basis for the prediction of radionuclide sorption in geologic environments. In FY 79, experimental and theoretical efforts were concentrated on a study of the sorption of cesium on the solid substrates Min-u-sil (quartz) and Belle Fourche clay (montmorillonite). Cesium sorption isotherms were obtained for the two substrates at 26/sup 0/C as a function of initial Cs concentration in solution (10/sup -3/M to 10/sup -9/M), pH (5 to 10) and supporting electrolyte concentration (0.002M, 0.01M, 0.1M, and 1M) NaCl and a simulated basalt groundwater in batch-type experiments using crushed material. Characterization ofmore » the solid phases included measurements of chemical compositions, particle sizes, surface areas, and cation-exchange capacities. In addition, potentiometric acid/base titrations of the solid phases were conducted in order to determine the acid dissociation and electrolyte exchange constants of the surfaces. Preliminary analysis of the sorption data indicate that while the clay data could be explained by simple mass-action expressions, the quartz data could not. Theoretical efforts were aimed at developing and testing an electrolyte binding electrical double-layer model to predict sorption isotherms. A computerized version of the model, MINEQL, which simultaneously considers surface and solution chemical equilibria, was brought to operational status. Input parameters required by MINEQL were determined and sorption isotherms for Cs on the Belle Fourche clay were calculated over the same range of parameters as the experimental measurements. Comparisons showed that the model was able to simulate the isotherms quite well except at the lowest pH values for the 0.002M and 0.01M NaCl solutions.« less

Cr(VI) Sorption by Nanosized FeS-Coated Sand

NASA Astrophysics Data System (ADS)

Park, M.; Jeong, H. Y.; Lee, S.; Kang, N.; Kim, K. H.; Choi, H. J.

2015-12-01

Cr(VI) sorption experiments were conducted as a function of pH (4.7, 7.0 and 9.7) using nanosized FeS-coated sand under anoxic environments. Under the experimental conditions, the sand used, with the FeS content of 0.068 mmol per 1 g sand, completely reduced the initially added Cr(VI) to Cr(III) over the pH range examined. The sorption of the once-reduced Cr(III) varied greatly with the solution pH. By the solution-phase analysis, significant amounts of Cr(III) remained as dissolved species at pH 4.7. On the other hands, dissolved Cr was below the detection limit (0.2 μM) at pH 7.0 and 9.7, indicating the greater sorption of Cr(III) at neutral to basic pH than acidic pH. From Cr-K edge X-ray absorption spectroscopy (XAS) analysis of the solid products, the sorbed Cr was shown to be present predominantly as trivalent state in all samples. Regardless of pH, the second coordination shell around Cr (i.e., the Cr-Cr(Fe) shell) was shown to be located at ~2.6 Å, which was far shorter than those in Cr(III)-bearing model compounds such as Cr(OH)3(s) and [Cr, Fe](OH)3(s). Furthermore, the coordination numbers of the second and third shells in the sorption samples (N = 0.7-1.8) were much lower than those in Cr(OH)3(s) and [Cr, Fe](OH)3(s). Taken together, the sorption of the once-reduced Cr(III) was likely to occur via surface-mediated processes (e.g., surface complexation and/or surface precipitation) rather than the bulk-phase precipitation. Financial support was provided by the "R&D Project on Environmental Management of Geologic CO2 Storage" from the KEITI (Project Number: 2014001810003).

The fate of silver nanoparticles in soil solution--Sorption of solutes and aggregation.

PubMed

Klitzke, Sondra; Metreveli, George; Peters, Andre; Schaumann, Gabriele E; Lang, Friederike

2015-12-01

Nanoparticles enter soils through various pathways. In the soil, they undergo various interactions with the solution and the solid phase. We tested the following hypotheses using batch experiments: i) the colloidal stability of Ag NP increases through sorption of soil-borne dissolved organic matter (DOM) and thus inhibits aggregation; ii) the presence of DOM suppresses Ag oxidation; iii) the surface charge of Ag NP governs sorption onto soil particles. Citrate-stabilized and bare Ag NPs were equilibrated with (colloid-free) soil solution extracted from a floodplain soil for 24h. Nanoparticles were removed through centrifugation. Concentrations of free Ag ions and DOC, the specific UV absorbance at a wavelength of 254 nm, and the absorption ratio α254/α410 were determined in the supernatant. Nanoparticle aggregation was studied using time-resolved dynamic light scattering (DLS) measurement following the addition of soil solution and 1.5mM Ca(2+) solution. To study the effect of surface charge on the adsorption of Ag NP onto soil particles, bare and citrate-stabilized Ag NP, differing in the zeta potential, were equilibrated with silt at a solid-to-solution ratio of 1:10 and an initial Ag concentration range of 30 to 320 μg/L. Results showed that bare Ag NPs sorb organic matter, with short-chained organic matter being preferentially adsorbed over long-chained, aromatic organic matter. Stabilizing effects of organic matter only come into play at higher Ag NP concentrations. Soil solution inhibits the release of Ag(+) ions, presumably due to organic matter coatings. Sorption to silt particles was very similar for the two particle types, suggesting that the surface charge does not control Ag NP sorption. Besides, sorption was much lower than in comparable studies with sand and glass surfaces. Copyright © 2014. Published by Elsevier B.V.

Biosorption of Nickel from Industrial Wastewater using Zygnema sp.

NASA Astrophysics Data System (ADS)

Sivaprakash, Kanchana; Blessi T. L., Adlin; Madhavan, Jeyanthi

2015-12-01

Contamination of water sources with heavy metals is a very important pollution problem in the current scenario. Biosorption is an effective method for the removal of heavy metal ions from wastewaters. In this study, the removal of Nickel(II) ions from electroplating industrial wastewater using biosorbent prepared from fresh water algal biomass Zygnema was investigated under batch mode. The sorption efficiency of nickel on Zygnema sp. was evaluated as a function of time, pH and sorbent dosage. The Nickel(II) uptake was dependent on initial pH with pH 3 being the optimum value. For 100 mg/L initial Nickel(II) concentration, sorption equilibrium was attained at a contact time of 100 min. The sorbent dosage affected the biosorption efficiency and maximum removal of 76.4 % was obtained at a dosage of 7.5 g/L. From the performance studies, algal biosorbent Zygnema is found to be a valuable material for the removal of Nickel from industrial wastewater and a better substitute for the conventional adsorbents.

Assessing microbial utilization of free versus sorbed Alanine by using position-specific 13C labeling and 13C-PLFA analysis

NASA Astrophysics Data System (ADS)

Herschbach, Jennifer; Apostel, Carolin; Spielvogel, Sandra; Kuzyakov, Yakov; Dippold, Michaela

2016-04-01

Microbial utilization is a key transformation process of soil organic matter (SOM). Sorption of low molecular weight organic substances (LMWOS) to soil mineral surfaces blocks or delays microbial uptake and therefore mineralization of LMWOS to CO2, as well as all other biochemical transformations. We used position-specific labeling, a tool of isotope applications novel to soil science, combined with 13C-phospholipid fatty acid (PLFA) analysis, to assess microbial utilization of sorbed and non-sorbed Alanine in soil. Alanine has various functional groups enabling different sorption mechanisms via its positive charge (e.g. to clay minerals by cation exchange), as well as via its negative charge (e.g. to iron oxides by ligand exchange). To assess changes in the transformation pathways caused by sorption, we added uniformly and position-specifically 13C and 14C labeled Alanine to the Ap of a loamy Luvisol in a short-term (10 days) incubation experiment. To allow for sorption of the tracer solution to an aliquot of this soil, microbial activity was minimized in this subsample by sterilizing the soil by γ-radiation. After shaking, the remaining solutions were filtered and the non-sorbed Alanine was removed with Millipore water and then added to non-sterilized soil. For the free Alanine treatment, solutions with Alanine of similar amount and isotopic composition were prepared, added to the soil and incubated as well. The respired CO2 was trapped in NaOH and its 14C-activity was determined at increasing times intervals. Microbial utilization of Alanine's individual C positions was evaluated in distinct microbial groups classified by 13C-PLFA analysis. Sorption to soil minerals delayed respiration to CO2 and reduced initial respiration rate by 80%. Irrespective of sorption, the highest amount was respired from the carboxylic position (C-1), whereas the amino-bound (C-2) and the methylic position (C-3) were preferentially incorporated into PLFA of microorganisms due to the basic microbial metabolism of C3 molecules in glycolysis. Reconstruction of microbial transformation pathways showed that the C-2 position of Alanine was lost as CO2 faster than its C-3 position regardless of whether the molecule was used ana- or catabolically. The highest incorporations of all positions in PLFA were accomplished by Gram negatives. Free Alanine was preferentially used by highly competitive prokaryotes, while sorbed Alanine was preferred by filamentous microorganisms. In detail, the free living osmotrophic Gram negative bacteria utilize more easily accessible dissolved substances. The utilization of sorbed substances are achieved by less mobile microorganisms, e.g. eukaryotic fungi and Actinomycetes, which form biofilms. None of these findings could have been achieved without the position-specific labeling approach, therefore this method will strongly improve our understanding of stabilization processes and soil C fluxes.

Synthetic coprecipitates of exopolysaccharides and ferrihydrite. Part II: Siderophore-promoted dissolution

NASA Astrophysics Data System (ADS)

Mikutta, Christian; Kretzschmar, Ruben

2008-02-01

Ferrihydrite (Fh) coprecipitated with exopolymers of plants and microbes may differ in its geochemical reactivity from its abiotic counterpart. We synthesized Fh in the presence and absence of acid polysaccharides (polygalacturonic acid (PGA), alginate, xanthan) and characterized the physical and structural properties of the precipitates formed [Mikutta C., Mikutta R., Bonneville S., Wagner F., Voegelin A., Christl I. and Kretzschmar R. (2008) Synthetic coprecipitates of exopolysaccharides and ferrihydrite. Part I: Characterization. Geochim. Cosmochim. Acta]. In this paper, we focus on the reactivity of PGA and alginate coprecipitates and pure Fh, and studied their interaction with the microbial siderophore desferrioxamine B (DFOB) in the presence and absence of low molecular weight organic (LMWO) acid anions (malate, citrate). Batch adsorption and dissolution experiments were performed in the dark at pH 7 in 10 mM NaClO 4 background electrolyte. In the dissolution experiments, different modes of ligand addition were applied (single, simultaneous, stepwise). With an estimated Langmuir sorption maximum of 15 mmol/mol Fe, a PGA coprecipitate with 11% C org sorbed about four times as much DFOB as pure Fh, and the amount of DFOB sorbed was ˜4-fold larger than estimated from the sum of DFOB sorption to pure Fh and PGA alone. The apparent initial dissolution rates, Rapp-initial, and pseudo-first order rate coefficients, k, of the coprecipitates exceeded those of pure Fh by up to two orders of magnitude. Citrate and malate exerted a strong synergistic effect on the DFOB-promoted dissolution of pure Fh, whereas synergistic effects of both anions were absent or negligible for the coprecipitates. Rapp-initial of the citrate and DFOB-promoted dissolution of PGA coprecipitates increased with increasing molar C/Fe ratio of the coprecipitates, independent of the charge of the LMWO ligand. Our results indicate that polyuronates stabilize Fh particles sterically and /or electrostatically, thus increasing the mineral surface area accessible to LMWO ligands. In contrast, pure Fh was coagulated at pH 7 (pH iep of Fh = 7.1), and hence only a small fraction of the Fh surface underwent dissolution. The increase in ligand-accessible surface area of Fh upon coprecipitation with acid polysaccharides seems to primarily control the kinetics of the ligand-promoted dissolution at neutral pH. In pH environments where the solubility of Fe(III) is very low, dissolution rates of Fe(III) (hydr)oxides in such coprecipitates may therefore exceed those of pure minerals by several orders of magnitude, despite a similar crystallinity of the minerals.

Modeling study of natural emissions, source apportionment, and emission control of atmospheric mercury

NASA Astrophysics Data System (ADS)

Shetty, Suraj K.

Mercury (Hg) is a toxic pollutant and is important to understand its cycling in the environment. In this dissertation, a number of modeling investigations were conducted to better understand the emission from natural surfaces, the source-receptor relationship of the emissions, and emission reduction of atmospheric mercury. The first part of this work estimates mercury emissions from vegetation, soil and water surfaces using a number of natural emission processors and detailed (LAI) Leaf Area Index data from GIS (Geographic Information System) satellite products. East Asian domain was chosen as it contributes nearly 50% of the global anthropogenic mercury emissions into the atmosphere. The estimated annual natural mercury emissions (gaseous elemental mercury) in the domain are 834 Mg yr-1 with 462 Mg yr-1 contributing from China. Compared to anthropogenic sources, natural sources show greater seasonal variability (highest in simmer). The emissions are significant, sometimes dominant, contributors to total mercury emission in the regions. The estimates provide possible explanation for the gaps between the anthropogenic emission estimates based on activity data and the emission inferred from field observations in the regions. To understand the contribution of domestic emissions to mercury deposition in the United States, the second part of the work applies the mercury model of Community Multi-scale Air Quality Modeling system (CMAQ-Hg v4.6) to apportion the various emission sources attributing to the mercury wet and dry deposition in the 6 United States receptor regions. Contributions to mercury deposition from electric generating units (EGU), iron and steel industry (IRST), industrial point sources excluding EGU and IRST (OIPM), the remaining anthropogenic sources (RA), natural processes (NAT), and out-of-boundary transport (BC) in domain was estimated. The model results for 2005 compared reasonably well to field observations made by MDN (Mercury Deposition Network) and CAMNet (Canadian Atmospheric Mercury Measurement Network). The model estimated a total deposition of 474 Mg yr-1 to the CONUS (Contiguous United States) domain, with two-thirds being dry deposited. Reactive gaseous mercury contributed the most to 60% of deposition. Emission speciation distribution is a key factor for local deposition as contribution from large point sources can be as high as 75% near (< 100 km) the emission sources, indicating that emission reduction may result in direct deposition decrease near the source locations. Among the sources, BC contributes to about 68% to 91% of total deposition. Excluding the BC's contribution, EGU contributes to nearly 50% of deposition caused by CONUS emissions in the Northeast, Southeast and East Central regions, while emissions from natural processes are more important in the Pacific and West Central regions (contributing up to 40% of deposition). The modeling results implies that implementation of the new emission standards proposed by USEPA (United States Environmental Protection Agency) would significantly benefit regions that have larger contributions from EGU sources. Control of mercury emissions from coal combustion processes has attracted great attention due to its toxicity and the emission-control regulations and has lead to advancement in state-of-the-art control technologies that alleviate the impact of mercury on ecosystem and human health. This part of the work applies a sorption model to simulate adsorption of mercury in flue gases, onto a confined-bed of activated carbon. The model's performances were studied at various flue gas flow rates, inlet mercury concentrations and adsorption bed temperatures. The process simulated a flue gas, with inlet mercury concentration of 300 ppb, entering at a velocity of 0.3 m s-1 from the bottom into a fixed bed (inside bed diameter of 1 m and 3 m bed height; bed temperature of 25 °C) of activated carbon (particle size of 0.004 m with density of 0.5 g cm-3 and surface area of 90.25 cm2 g -1). The model result demonstrated that a batch of activated carbon bed was capable of controlling mercury emission for approximately 275 days after which further mercury uptake starts to decrease till it reaches about 500 days when additional control ceases. An increase in bed temperature significantly reduces mercury sorption capacity of the activated carbon. Increase in flue gas flow rate may result in faster consumption of sorption capacity initially but at a later stage, the sorption rate decreases due to reduced sorption capacity. Thus, overall sorption rate remains unaffected. The activated carbon's effective life (time to reach saturation) is not affected by inlet mercury concentration, implying that the designing and operation of a mercury sorption process can be done independently. The results provide quantitative indication for designing efficient confined-bed process to remove mercury from flue gases.

Optimal design of active spreading systems to remediate sorbing groundwater contaminants in situ.

PubMed

Piscopo, Amy N; Neupauer, Roseanna M; Kasprzyk, Joseph R

2016-07-01

The effectiveness of in situ remediation to treat contaminated aquifers is limited by the degree of contact between the injected treatment chemical and the groundwater contaminant. In this study, candidate designs that actively spread the treatment chemical into the contaminant are generated using a multi-objective evolutionary algorithm. Design parameters pertaining to the amount of treatment chemical and the duration and rate of its injection are optimized according to objectives established for the remediation - maximizing contaminant degradation while minimizing energy and material requirements. Because groundwater contaminants have different reaction and sorption properties that influence their ability to be degraded with in situ remediation, optimization was conducted for six different combinations of reaction rate coefficients and sorption rates constants to represent remediation of the common groundwater contaminants, trichloroethene, tetrachloroethene, and toluene, using the treatment chemical, permanganate. Results indicate that active spreading for contaminants with low reaction rate coefficients should be conducted by using greater amounts of treatment chemical mass and longer injection durations relative to contaminants with high reaction rate coefficients. For contaminants with slow sorption or contaminants in heterogeneous aquifers, two different design strategies are acceptable - one that injects high concentrations of treatment chemical mass over a short duration or one that injects lower concentrations of treatment chemical mass over a long duration. Thus, decision-makers can select a strategy according to their preference for material or energy use. Finally, for scenarios with high ambient groundwater velocities, the injection rate used for active spreading should be high enough for the groundwater divide to encompass the entire contaminant plume. Copyright © 2016 Elsevier B.V. All rights reserved.

Fate and mobility of pharmaceuticals in solid matrices.

PubMed

Drillia, Panagiota; Stamatelatou, Katerina; Lyberatos, Gerasimos

2005-08-01

The sorption and mobility of six pharmaceuticals were investigated in two soil types with different organic carbon and clay content, and in bacterial biomass (aerobic and anaerobic). The pharmaceuticals examined were carbamazepine, propranolol, diclofenac sodium, clofibric acid, sulfamethoxazole and ofloxacin. The sorption experiments were performed according to the OECD test Guideline 106. The distribution coefficients determined by this batch equilibrium method varied with the pharmaceutical tested and the solid matrix type. Ofloxacin was particularly strongly adsorbed (except of the case of using anaerobic biomass for the solid matrix) while clofibric acid was found to be weakly adsorbed. The fate of pharmaceuticals in soil was also assessed using lysimeters. Important parameters that were studied were: the pharmaceutical loading rate and the hydraulic loading rate for adsorption and the rate and duration of a "rain" event for desorption. Major differences in the mobility of the six pharmaceuticals were observed and correlated with the adsorption/desorption properties of the compounds.

Effects of natural organic matter on PCB-activated carbon sorption kinetics: implications for sediment capping applications.

PubMed

Fairey, Julian L; Wahman, David G; Lowry, Gregory V

2010-01-01

In situ capping of polychlorinated biphenyl (PCB)-contaminated sediments with a layer of activated carbon has been proposed, but several questions remain regarding the long-term effectiveness of this remediation strategy. Here, we assess the degree to which kinetic limitations, size exclusion effects, and electrostatic repulsions impaired PCB sorption to activated carbon. Sorption of 11 PCB congeners with activated carbon was studied in fixed bed reactors with organic-free water (OFW) and Suwannee River natural organic matter (SR-NOM), made by reconstituting freeze-dried SR-NOM at a concentration of 10 mg L(-1) as carbon. In the OFW test, no PCBs were detected in the column effluent over the 390-d study, indicating that PCB-activated carbon equilibrium sorption capacities may be achieved before breakthrough even at the relatively high hydraulic loading rate (HLR) of 3.1 m h(-1). However, in the SR-NOM fixed-bed test, partial PCB breakthrough occurred over the entire 320-d test (HLRs of 3.1-, 1.5-, and 0.8 m h(-1)). Simulations from a modified pore and surface diffusion model indicated that external (film diffusion) mass transfer was the dominant rate-limiting step but that internal (pore diffusion) mass transfer limitations were also present. The external mass transfer limitation was likely caused by formation of PCB-NOM complexes that reduced PCB sorption through a combination of (i) increased film diffusion resistance; (ii) size exclusion effects; and (iii) electrostatic repulsive forces between the PCBs and the NOM-coated activated carbon. However, the seepage velocities in the SR-NOM fixed bed test were about 1000 times higher than would be expected in a sediment cap. Therefore, additional studies are needed to assess whether the mass transfer limitations described here would be likely to manifest themselves at the lower seepage velocities observed in practice.

The novel kinetics expression of Cadmium (II) removal using green adsorbent horse dung humic acid (Hd-Ha)

NASA Astrophysics Data System (ADS)

Basuki, Rahmat; Santosa, Sri Juari; Rusdiarso, Bambang

2017-03-01

Humic acid from dry horse dung powder has been prepared and this horse dung humic acid (HD-HA) was then applied as a sorbent to adsorb Cadmium(II) from a solution. Characterization of HD-HA was conducted by detection of its functional group, UV-Vis spectra, ash level, and total acidity. Result of the work showed that HD-HA had similar character compared with peat soil humic acid (PS-HA) and previous researchers. The adsorption study of this work was investigated by batch experiment in pH 5. The thermodynamics parameters in this work were determined by the Langmuir isotherm model for monolayer sorption and Freundlich isotherm model multilayer sorption. Monolayer sorption capacity (b) for HD-HA was 1.329 × 10-3 mol g-1, equilibrium constant (K) was 5.651 (mol/L)-1, and multilayer sorption capacity was 2.646 × 10-2 mol g-1. The kinetics parameters investigated in this work were determined by the novel kinetics expression resulted from the mathematical derivation the availability of binding sites of sorbent. Adsorption rate constant (ka) from this novel expression was 43.178 min-1 (mol/L)-1 and desorption rate constant (kd) was 1.250 × 10-2 min-1. Application of the kinetics model on sorption Cd(II) onto HD-HA showed the nearly all of models gave a good linearity. However, only this proposed kinetics expression has good relation with Langmuir model. The novel kinetics expression proposed in this paper seems to be more realistic and reasonable and close to the experimental real condition because the value of ka/kd (3452 (mol/L)-1) was fairly close with K from Langmuir isotherm model (5651 (mol/L)-1). Comparison of this novel kinetics expression with well-known Lagergren pseudo-first order kinetics and Ho pseudo-second order kinetics was also critically discussed in this paper.

TNT transport and fate in contaminated soil

DOE Office of Scientific and Technical Information (OSTI.GOV)

Comfort, S.D.; Shea, P.J.; Hundal, L.S.

1995-11-01

Past disposal practices at munitions production plants have contaminated terrestrial and aquatk ecosystems with 2,4,6-trinitrotoluene (TNT). We determined TNT transport, degradation, and long-term sorption characteristics in soil. Transport experiments were conducted with repacked, unsaturated soil columns containing uncontaminated soil or layers of contaminated and uncontaminated soil. Uncontaminated soil columns received multiple pore volumes (22-50) of a TNT-{sup 3}H{sub 2}O pulse, containing 70 or 6.3 mg TNT L{sup -1} at a constant pore water velocity. TNT breakthrough curves (BTCs) never reached initial solute pulse concentrations. Apex concentrations (C/C{sub o}) were between 0.6 and 0.8 for an initial pulse of 70 mgmore » TNT L{sup -1} and 0.2 to 0.3 for the 6.3 mg TNT L{sup -1} pulse. Earlier TNT breakthrough was observed at the higher pulse concentration. This mobility difference was predicted from the nonlinear adsorption isotherm determined for TNT sorption. In all experiments, a significant fraction of added TNT was recovered as amino degradates of TNT. Mass balance estimates indicated 81% of the added TNT was recovered (as TNT and amino degradates) from columns receiving the 70 mg TNT L{sup -1} pulse compared to 35% from columns receiving the 6.3 mg TNT L{sup -1} pulse. Most of the unaccountable TNT was hypothesized to be unextractable. This was supported by a 168-d sorption experiment, which found that within 14d, 80% of {sup 14}C activity (added as {sup 14}C-TNT) was adsorbed and roughly 40% unextractable. Our observations illustrate that TNT sorption and degradation are concentration-dependent and the assumptions of linear adsorption and adsorption-desorption singularity commonly used in transport modeling, may not be valid for predicting TNT transport in munitions-contaminated soils. 29 refs., 6 figs., 7 tabs.« less

Methodological interference of biochar in the determination of extracellular enzyme activities in composting samples

NASA Astrophysics Data System (ADS)

Jindo, K.; Matsumoto, K.; García Izquierdo, C.; Sonoki, T.; Sanchez-Monedero, M. A.

2014-07-01

Biochar application has received increasing attention as a means to trap recalcitrant carbon and enhance soil fertility. Hydrolytic enzymatic assays, such as β-glucosidase and phosphatase activities, are used for the assessment of soil quality and composting process, which are based on use of p-nitrophenol (PNP) derivatives as substrate. However, sorption capacity of biochar can interfere with colorimetric determination of the hydrolysed PNP, either by the sorption of the substrate or the reaction product of hydrolysis into biochar surface. The aim of the present work is to study the biochar sorption capacity for PNP in biochar-blended composting mixtures in order to assess its impact on the estimation of the colorimetric-based enzymatic assays. A retention test was conducted by adding a solution of known amounts of PNP in universal buffer solution (pH = 5, 6.5 and 11, corresponding to the β-glucosidase, acid and alkaline phosphatase activity assays, respectively), in samples taken at the initial stage and after maturation stage from four different composting piles (two manure composting piles; PM: poultry manure, CM: cow manure and two other similar piles containing 10% of additional biochar (PM + B, CM + B)). The results show that biochar-blended composts (PM + B, CM + B) generally exhibited low enzymatic activities, compared to manure compost without biochar (PM, CM). In terms of the difference between the initial and maturation stage of composting process, the PNP retention in biochar was shown higher at maturation stage, caused most probably by an enlarged proportion of biochar inside compost mixture after the selective degradation of easily decomposable organic matter. TThe retention of PNP on biochar was influenced by pH dependency of sorption capacity of biochar and/or PNP solubility, since PNP was more efficiently retained by biochar at low pH values (5 and 6.5) than at high pH values (11).

Methodological interference of biochar in the determination of extracellular enzyme activities in composting samples

NASA Astrophysics Data System (ADS)

Jindo, K.; Matsumoto, K.; García Izquierdo, C.; Sonoki, T.; Sanchez-Monedero, M. A.

2014-03-01

Biochar application has received increasing attention as a means to trap recalcitrant carbon and enhance soil fertility. Hydrolytic enzymatic assays, such as β-glucosidase and phosphatase activities, are used for the assessment of soil quality and composting process, which are based on use of p-nitrophenol (PNP) derivatives as substrate. However, sorption capacity of biochar can interfere colorimetric determination of the hydrolysed PNP, either by the sorption of the substrate or the reaction-product of hydrolysis into biochar surface. The aim of the present work is to study the biochar sorption capacity for PNP in biochar-blended composting mixtures in order to assess its impact on the estimation of the colorimetric-based enzymatic assays. A retention test was conducted by adding a solution of known amounts of PNP in universal buffer solution (pH = 5, 6.5 and 11, corresponding to the β-glucosidase, acid and alkaline phosphatase activity assays, respectively), in samples taken at the initial stage and after maturation stage from 4 different composting piles (two manure composting piles (PM: poultry manure, CM: cow manure) and two other similar piles containing 10% of additional biochar (PM + B, CM + B)). The results show that biochar blended composts (PM + B, CM + B) generally exhibited low enzymatic activities, compared to manure compost without biochar (PM, CM). In terms of the difference between the initial and maturation stage of composting process, the PNP retention in biochar was shown more clearly at maturation stage, caused by an enlarged proportion of biochar inside compost mixture after the selective degradation of easily decomposable organic matter. The retention of PNP was more pronounced at low pH (5 and 6.5) than at high pH (11), 3 reflecting on pH dependency of sorption 49 capacity of biochar and/or PNP 50 solubility.

Heavy metals removal from aqueous solutions and wastewaters by using various byproducts.

PubMed

Shaheen, Sabry M; Eissa, Fawzy I; Ghanem, Khaled M; Gamal El-Din, Hala M; Al Anany, Fathia S

2013-10-15

Water contamination with heavy metals (HM) represents a potential threat to humans, animals and plants, and thus removal of these metals from contaminated waters has received increasing attention. The present study aimed to assess the efficiency of some low cost sorbents i.e., chitosan (CH), egg shell (ES), humate potassium (HK), and sugar beet factory lime (SBFL) for removal of cadmium (Cd), copper (Cu), lead (Pb) and zinc (Zn) from wastewaters. For this purpose batch equilibrium experiments were conducted with aqueous solutions containing various concentrations of the metals and sorbents in a mono-metal and competitive sorption system. Sorption isotherms were developed, and sorption parameters were determined. The potential applicability of the tested sorbents in the removal of Cd, Cu, and Zn from contaminated wastewaters was also investigated by equilibrating different sorbents and water ratios. Chitosan expressed the highest affinity for the metals followed by SBFL, ES, and HK. Nearly 100% of the metals were removed from aqueous solutions with the lowest initial metal concentrations by the sorbents especially CH and SBFL. However, the sorption efficiency decreased as the initial metal concentrations increased. Competition among the four metals changed significantly their distribution coefficient (Kd) values with the sorbents. The selectivity sequence of the metals was: Pb > Cu > Zn > Cd. The metal removal from the wastewaters varied from 72, 69, and 60 to nearly 100% for Cd, Cu and Zn, respectively. The efficiency of the studied byproducts in removing metals from the wastewaters differed based on the source of contamination and metal concentrations. Cadmium removal percentages by HK and CH were higher than SBFL and ES. The HK and CH exhibited the highest removal percentage of Cu from water with high concentrations. The SBFL and ES revealed the highest removal percentage of Zn from water with high concentrations. The results, demonstrate a high potential of CH, SBFL, HK, and ES for the remediation of HM contaminated wastewaters. Copyright © 2013 Elsevier Ltd. All rights reserved.

Sustainable Soil Washing: Shredded Card Filtration of Potentially Toxic Elements after Leaching from Soil Using Organic Acid Solutions

PubMed Central

Ash, Christopher; Drábek, Ondřej; Tejnecký, Václav; Jehlička, Jan; Michon, Ninon; Borůvka, Luboš

2016-01-01

Shredded card (SC) was assessed for use as a sorbent of potentially toxic elements (PTE) carried from contaminated soil in various leachates (oxalic acid, formic acid, CaCl2, water). We further assessed SC for retention of PTE, using acidified water (pH 3.4). Vertical columns and a peristaltic pump were used to leach PTE from soils (O and A/B horizons) before passing through SC. Sorption onto SC was studied by comparing leachates, and by monitoring total PTE contents on SC before and after leaching. SC buffers against acidic soil conditions that promote metals solubility; considerable increases in solution pH (+4.49) were observed. Greatest differences in solution PTE content after leaching with/without SC occurred for Pb. In oxalic acid, As, Cd, Pb showed a high level of sorption (25, 15, and 58x more of the respective PTE in leachates without SC). In formic acid, Pb sorption was highly efficient (219x more Pb in leachate without SC). In water, only Pb showed high sorption (191x more Pb in leachate without SC). In desorption experiments, release of PTE from SC varied according to the source of PTE (organic/mineral soil), and type of solvent used. Arsenic was the PTE most readily leached in desorption experiments. Low As sorption from water was followed by fast release (70% As released from SC). A high rate of Cd sorption from organic acid solutions was followed by strong retention (~12% Cd desorption). SC also retained Pb after sorption from water, with subsequent losses of ≤8.5% of total bound Pb. The proposed use of this material is for the filtration of PTE from extract solution following soil washing. Low-molecular-mass organic acids offer a less destructive, biodegradable alternative to strong inorganic acids for soil washing. PMID:26900684

Imidacloprid sorption and transport in cropland, grass buffer and riparian buffer soils

USGS Publications Warehouse

Satkowski, Laura E.; Goyne, Keith W.; Anderson, Stephen H.; Lerch, Robert N.; Allen, Craig R.; Snow, Daniel D.

2018-01-01

An understanding of neonicotinoid sorption and transport in soil is critical for determining and mitigating environmental risk associated with the most widely used class of insecticides. The objective of this study was to evaluate mobility and transport of the neonicotinoid imidacloprid (ICD) in soils collected from cropland, grass vegetative buffer strip (VBS), and riparian VBS soils. Soils were collected at six randomly chosen sites within grids that encompassed all three land uses. Single-point equilibrium batch sorption experiments were conducted using radio-labeled (14C) ICD to determine solid–solution partition coefficients (Kd). Column experiments were conducted using soils collected from the three vegetation treatments at one site by packing soil into glass columns. Water flow was characterized by applying Br− as a nonreactive tracer. A single pulse of 14C-ICD was then applied, and ICD leaching was monitored for up to 45 d. Bromide and ICD breakthrough curves for each column were simulated using CXTFIT and HYDRUS-1D models. Sorption results indicated that ICD sorbs more strongly to riparian VBS (Kd = 22.6 L kg−1) than crop (Kd = 11.3 L kg−1) soils. Soil organic C was the strongest predictor of ICD sorption (p < 0.0001). The column transport study found mean peak concentrations of ICD at 5.83, 10.84, and 23.8 pore volumes for crop, grass VBS, and riparian VBS soils, respectively. HYDRUS-1D results indicated that the two-site, one-rate linear reversible model best described results of the breakthrough curves, indicating the complexity of ICD sorption and demonstrating its mobility in soil. Greater sorption and longer retention by the grass and riparian VBS soils than the cropland soil suggests that VBS may be a viable means to mitigate ICD loss from agroecosystems, thereby preventing ICD transport into surface water, groundwater, or drinking water resources.

Scaling Effects of Cr(VI) Reduction Kinetics. The Role of Geochemical Heterogeneity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Li; Li, Li

2015-10-22

The natural subsurface is highly heterogeneous with minerals distributed in different spatial patterns. Fundamental understanding of how mineral spatial distribution patterns regulate sorption process is important for predicting the transport and fate of chemicals. Existing studies about the sorption was carried out in well-mixed batch reactors or uniformly packed columns, with few data available on the effects of spatial heterogeneities. As a result, there is a lack of data and understanding on how spatial heterogeneities control sorption processes. In this project, we aim to understand and develop modeling capabilities to predict the sorption of Cr(VI), an omnipresent contaminant in naturalmore » systems due to its natural occurrence and industrial utilization. We systematically examine the role of spatial patterns of illite, a common clay, in determining the extent of transport limitation and scaling effects associated with Cr(VI) sorption capacity and kinetics using column experiments and reactive transport modeling. Our results showed that the sorbed mass and rates can differ by an order of magnitude due to of the illite spatial heterogeneities and transport limitation. With constraints from data, we also developed the capabilities of modeling Cr(VI) in heterogeneous media. The developed model is then utilized to understand the general principles that govern the relationship between sorption and connectivity, a key measure of the spatial pattern characteristics. This correlation can be used to estimate Cr(VI) sorption characteristics in heterogeneous porous media. Insights gained here bridge gaps between laboratory and field application in hydrogeology and geochemical field, and advance predictive understanding of reactive transport processes in the natural heterogeneous subsurface. We believe that these findings will be of interest to a large number of environmental geochemists and engineers, hydrogeologists, and those interested in contaminant fate and transport, water quality and water composition, and natural attenuation processes in natural systems.« less

Sorption kinetics and isotherm studies of a cationic dye using agricultural waste: broad bean peels.

PubMed

Hameed, B H; El-Khaiary, M I

2008-06-15

In this paper, broad bean peels (BBP), an agricultural waste, was evaluated for its ability to remove cationic dye (methylene blue) from aqueous solutions. Batch mode experiments were conducted at 30 degrees C. Equilibrium sorption isotherms and kinetics were investigated. The kinetic data obtained at different concentrations have been analyzed using pseudo-first-order, pseudo-second-order and intraparticle diffusion equations. The experimental data fitted very well the pseudo-first-order kinetic model. Analysis of the temportal change of q indicates that at the beginning of the process the overall rate of adsorption is controlled by film-diffusion, then at later stage intraparticle-diffusion controls the rate. Diffusion coefficients and times of transition from film to pore-diffusion control were estimated by piecewise linear regression. The experimental data were analyzed by the Langmuir and Freundlich models. The sorption isotherm data fitted well to Langmuir isotherm and the monolayer adsorption capacity was found to be 192.7 mg/g and the equilibrium adsorption constant Ka is 0.07145 l/mg at 30 degrees C. The results revealed that BBP was a promising sorbent for the removal of methylene blue from aqueous solutions.

Removal of PPCPs from the sludge supernatant in a one stage nitritation/anammox process.

PubMed

Alvarino, T; Suarez, S; Katsou, E; Vazquez-Padin, J; Lema, J M; Omil, F

2015-01-01

Pharmaceutical and personal care products (PPCPs) are extensively used and can therefore find their way into surface, groundwater and municipal and industrial effluents. In this work, the occurrence, fate and removal mechanisms of 19 selected PPCPs was investigated in an 'ELiminación Autótrofa de Nitrógeno' (ELAN) reactor of 200 L. In this configuration, ammonium oxidation to nitrite and the anoxic ammonium oxidation (anammox)processes occur simultaneously in a single-stage reactor under oxygen limited conditions. The ELAN process achieved high removal (>80%) of the studied hormones, naproxen, ibuprofen, bisphenol A and celestolide, while it was not effective in the removal of carbamazepine (<7%), diazepam (<7%) and fluoxetine (<30%). Biodegradation was the dominant removal mechanism, while sorption was only observed for musk fragrances, fluoxetine and triclosan. The sorption was strongly dependent on the granule size, with smaller granules facilitating the sorption of the target compounds. Increased hydraulic retention time enhanced the intramolecular diffusion of the PPCPs into the granules, and thus increased the solid phase concentration. The increase of nitritation rate favored the removal of ibuprofen, bisphenol A and triclosan, while the removal of erythromycin was strongly correlated to the anammox reaction rate.

DEVELOPMENT OF TRANSITION METAL OXIDE-ZEOLITE CATALYSTS TO CONTROL CHLORINATED VOC AIR EMISSIONS

EPA Science Inventory

The paper discusses the development of transition metal oxide (TMO)-zeolite oxidation catalysts to control chlorinated volatile organic compound (CVOC) air emissions. esearch has been initiated to enhance the utility of these catalysts by the development of a sorption-catalyst sy...

In situ arsenic oxidation and sorption by a Fe-Mn binary oxide waste in soil.

PubMed

McCann, Clare M; Peacock, Caroline L; Hudson-Edwards, Karen A; Shrimpton, Thomas; Gray, Neil D; Johnson, Karen L

2018-01-15

The ability of a Fe-Mn binary oxide waste to adsorb arsenic (As) in a historically contaminated soil was investigated. Initial laboratory sorption experiments indicated that arsenite [As(III)] was oxidized to arsenate [As(V)] by the Mn oxide component, with concurrent As(V) sorption to the Fe oxide. The binary oxide waste had As(III) and As(V) adsorption capacities of 70mgg -1 and 32mgg -1 respectively. X-ray Absorption Near-Edge Structure and Extended X-ray Absorption Fine Structure at the As K-edge confirmed that all binary oxide waste surface complexes were As(V) sorbed by mononuclear bidentate corner-sharing, with 2 Fe at ∼3.27Ǻ. The ability of the waste to perform this coupled oxidation-sorption reaction in real soils was investigated with a 10% by weight addition of the waste to an industrially As contaminated soil. Electron probe microanalysis showed As accumulation onto the Fe oxide component of the binary oxide waste, which had no As innately. The bioaccessibility of As was also significantly reduced by 7.80% (p<0.01) with binary oxide waste addition. The results indicate that Fe-Mn binary oxide wastes could provide a potential in situ remediation strategy for As and Pb immobilization in contaminated soils. Crown Copyright © 2017. Published by Elsevier B.V. All rights reserved.

Investigations of Heavy Metal Ion Sorption Using Nanocomposites of Iron-Modified Biochar

NASA Astrophysics Data System (ADS)

Kołodyńska, D.; Bąk, J.; Kozioł, M.; Pylypchuk, L. V.

2017-06-01

Magnetic biochar nanocomposites were obtained by modification of biochar by zero-valent iron. The article provides information on the impact of contact time, initial Cd(II), Co(II), Zn(II), and Pb(II) ion concentrations, dose of the sorbents, solution pH and temperature on the adsorption capacity. On the basis of experiments, it was found that the optimum parameters for the sorption process are phase contact time 360 min (after this time, the equilibrium of all concentrations is reached), the dose of sorbent equal to 5 g/dm3, pH 5 and the temperature 295 K. The values of parameters calculated from the kinetic models and isotherms present the best match to the pseudo second order and Langmuir isotherm models. The calculated thermodynamic parameters ΔH 0, ΔS 0 and ΔG 0 indicate that the sorption of heavy metal ions is an exothermic and spontaneous process as well as favoured at lower temperatures, suggesting the physical character of sorption. The solution of nitric acid(V) at the concentration 0.1 mol/dm3 was the best acidic desorbing agent used for regeneration of metal-loaded magnetic sorbents. The physicochemical properties of synthesized composites were characterized by FTIR, SEM, XRD, XPS and TG analyses. The point characteristics of the double layer for biochar pHPZC and pHIEP were designated.

Low effect of phenanthrene bioaccessibility on its biodegradation in diffusely contaminated soil.

PubMed

Crampon, M; Cébron, A; Portet-Koltalo, F; Uroz, S; Le Derf, F; Bodilis, J

2017-06-01

This study focused on the role of bioaccessibility in the phenanthrene (PHE) biodegradation in diffusely contaminated soil, by combining chemical and microbiological approaches. First, we determined PHE dissipation rates and PHE sorption/desorption isotherms for two soils (PPY and Pv) presenting similar chronic PAH contamination, but different physico-chemical properties. Our results revealed that the PHE dissipation rate was significantly higher in the Pv soil compared to the PPY soil, while PHE sorption/desorption isotherms were similar. Interestingly, increases of PHE desorption and potentially of PHE bioaccessibility were observed for both soils when adding rhamnolipids (biosurfactants produced by Pseudomonas aeruginosa). Second, using 13 C-PHE incubated in the same soils, we analyzed the PHE degrading bacterial communities. The combination of stable isotope probing (DNA-SIP) and 16S rRNA gene pyrosequencing revealed that Betaproteobacteria were the main PHE degraders in the Pv soil, while a higher bacterial diversity (Alpha-, Beta-, Gammaproteobacteria and Actinobacteria) was involved in PHE degradation in the PPY soil. The amendment of biosurfactants commonly used in biostimulation methods (i.e. rhamnolipids) to the two soils clearly modified the PHE sorption/desorption isotherms, but had no significant impact on PHE degradation rates and PHE-degraders identity. These results demonstrated that increasing the bioaccessibility of PHE has a low impact on its degradation and on the functional populations involved in this degradation. Copyright © 2017 Elsevier Ltd. All rights reserved.

Enhanced Indirect Photochemical Transformation of Histidine and Histamine through Association with Chromophoric Dissolved Organic Matter.

PubMed

Chu, Chiheng; Lundeen, Rachel A; Remucal, Christina K; Sander, Michael; McNeill, Kristopher

2015-05-05

Photochemical transformations greatly affect the stability and fate of amino acids (AAs) in sunlit aquatic ecosystems. Whereas the direct phototransformation of dissolved AAs is well investigated, their indirect photolysis in the presence of chromophoric dissolved organic matter (CDOM) is poorly understood. In aquatic systems, CDOM may act both as sorbent for AAs and as photosensitizer, creating microenvironments with high concentrations of photochemically produced reactive intermediates, such as singlet oxygen (1O2). This study provides a systematic investigation of the indirect photochemical transformation of histidine (His) and histamine by 1O2 in solutions containing CDOM as a function of solution pH. Both His and histamine showed pH-dependent enhanced phototransformation in the CDOM systems as compared to systems in which model, low-molecular-weight 1O2 sensitizers were used. Enhanced reactivity resulted from sorption of His and histamine to CDOM and thus exposure to elevated 1O2 concentrations in the CDOM microenvironment. The extent of reactivity enhancement depended on solution pH via its effects on the protonation state of His, histamine, and CDOM. Sorption-enhanced reactivity was independently supported by depressed rate enhancements in the presence of a cosorbate that competitively displaced His and histamine from CDOM. Incorporating sorption and photochemical transformation processes into a reaction rate prediction model improved the description of the abiotic photochemical transformation rates of His in the presence of CDOM.

Role of biotransformation, sorption and mineralization of (14)C-labelled sulfamethoxazole under different redox conditions.

PubMed

Alvarino, T; Nastold, P; Suarez, S; Omil, F; Corvini, P F X; Bouju, H

2016-01-15

(14)C-sulfamethoxazole biotransformation, sorption and mineralization was studied with heterotrophic and autotrophic biomass under aerobic and anoxic conditions, as well as with anaerobic biomass. The (14)C-radiolabelled residues distribution in the solid, liquid and gas phases was closely monitored along a total incubation time of 190 h. Biotransformation was the main removal mechanism, mineralization and sorption remaining below 5% in all the cases, although the presence of a carbon source exerted a positive effect on the mineralization rate by the aerobic heterotrophic bacteria. In fact, an influence of the type of primary substrate and the redox potential was observed in all cases on the biotransformation and mineralization rates, since an enhancement of the removal rate was observed when an external carbon source was used as a primary substrate under aerobic conditions, while a negligible effect was observed under nitrifying conditions. In the liquid phases collected from all assays, up to three additional peaks corresponding to (14)C-radiolabelled residues were detected. The highest concentration was observed under anaerobic conditions, where two radioactive metabolites were detected representing each around 15% of the total applied radioactivity after 180 h incubation. One of the metabolites detected under anoxic and anaerobic conditions, is probably resulting from ring cleavage of the isoxazole ring. Copyright © 2015 Elsevier B.V. All rights reserved.

Modelling of Pesticide Transport During An Injection Experiment In A Physical and Geochemical Heterogeneous Aquifer

NASA Astrophysics Data System (ADS)

Hojberg, A. L.; Engesgaard, P.; Bjerg, P. L.

The fate of selected pesticides under natural groundwater conditions was studied by natural gradient short and long term injection experiments in a shallow uncon- fined aerobic aquifer. Bentazone, DNOC, MCPP, dichlorprop, isoproturon, and BAM (dichlobenil metabolite) were injected in aqueous solution with bromide as a nonre- active tracer. The Bromide and pesticide plumes were sampled during the initial 25 m of migration in a dense monitoring net of multilevel samplers. The aquifer was physical and geochemical heterogeneous, which affected transport of several of the pesticides. A 3D reactive transport code was developed including one- and two-site linear/nonlinear equilibrium/nonequilibrium sorption and first-order as well as single Monod degradation kinetic coupled to microbial growth. Model simulations demon- strated that microbial growth was likely supported by the phenoxy acids MCPP and dichlorprop, while degradation of DNOC was adequately described by first-order degradation with no initial lag time. An observed vertical increase in pH was observed at the site and implemented in the transport code. The numerical analysis indicated that degradation of the three degradable pesticides may have been affected by vertical pH variations. Spatial variability in observed DNOC sorption was similarly suspected to be an effect of varying pH. pH dependency on DNOC sorption was confirmed by the model recognized by a match to observed breakthrough at the individual sampling points, when pH variation was included in the simulations.

Microbial Reduction of Fe(III) and U(VI) in Aquifers: Simulations Exploring Coupled Effects of Heterogeneity and Fe(II) Sorption

NASA Astrophysics Data System (ADS)

Scheibe, T. D.; Fang, Y.; Roden, E. E.; Brooks, S. C.; Chien, Y.; Murray, C. J.

2004-05-01

Uranium is a significant groundwater contaminant at many former mining and processing sites. In its oxidized state, U(VI) is soluble and mobile, although strongly retarded by sorption to natural iron oxide surfaces. It has been demonstrated that commonly occurring subsurface microorganisms can reduce uranium and other metals when provided sufficient carbon as an electron donor. Reduced U(IV) precipitates as a solid phase; therefore biostimulation provides a potential strategy for in situ removal from contaminated groundwater. However, these biogeochemical reactions occur in the context of a complex heterogeneous environment in which flow and transport dynamics and abiotic reactions can have significant impacts. We have constructed a high-resolution numerical model of groundwater flow and multicomponent reactive transport that incorporates heterogeneity in hydraulic conductivity and initial Fe(III) distribution, microbial growth and transport dynamics, and effects of sorption or precipitation of biogenic Fe(II) on availability of Fe(III) as an electron acceptor. The biogeochemical reaction models and their parameters are based on laboratory experiments; the heterogeneous field-scale property distributions are based on interpretations of geophysical and other observations at a highly characterized field site. The model is being run in Monte Carlo mode to examine the controls that these factors exert on 1) the initial distribution of sorbed uranium in an oxic environment and 2) the reduction and immobilization of uranium upon introduction of a soluble electron donor.

Large-Pore 3D Cubic Mesoporous (KIT-6) Hybrid Bearing a Hard-Soft Donor Combined Ligand for Enhancing U(VI) Capture: An Experimental and Theoretical Investigation.

PubMed

Yuan, Li-Yong; Zhu, Lin; Xiao, Cheng-Liang; Wu, Qun-Yan; Zhang, Nan; Yu, Ji-Pan; Chai, Zhi-Fang; Shi, Wei-Qun

2017-02-01

A preorganized tetradentate phenanthrolineamide (DAPhen) ligand with hard and soft donors combined in the same molecule has been found to possess high extraction ability toward actinides over lanthanides from acidic aqueous solution in our previous work. Herein we grafted phenanthrolineamide groups onto a large-pore three-dimensional cubic silica support by the reaction of DAPhen siloxane with KIT-6 substrate to prepare a novel uranium-selective sorbent, KIT-6-DAPhen. The as-synthesized sorbent was well-characterized by scanning electron microscopy, high-resolution transmission electron microscopy, N 2 adsorption/desorption, X-ray diffraction, FT-IR, 13 C cross-polarization magic-angle spinning NMR, and TGA techniques, which confirmed the consummation of the functionalization. Subsequently, the effects of contact time, solution pH, initial U(VI) concentration, and the presence of competing metal ions on the U(VI) sorption onto KIT-6-DAPhen sorbent were investigated in detail. It was found that KIT-6-DAPhen showed largely enhanced sorption capacity and excellent selectivity toward U(VI). The maximum sorption capacity of KIT-6-DAPhen at pH 5.0 reaches 328 mg of U/g of sorbent, which is superior to most of functionalized mesoporous silica materials. Density functional theory coupled with quasi-relativistic small-core pseudopotentials was used to explore the sorption interaction between U(VI) and KIT-6-DAPhen, which gives a sorption reaction of KIT-6-DAPhen + [UO 2 (H 2 O) 5 ] 2+ + NO 3 - ⇄ [UO 2 (KIT-6-DAPhen)(NO 3 )] + + 5H 2 O. The findings of the present work provide new clues for developing new actinide sorbents by combining new ligands with various mesoporous matrixes.

Effect of coexisting Al(III) ions on Pb(II) sorption on biochars: Role of pH buffer and competition.

PubMed

Yang, Yuxi; Zhang, Weihua; Qiu, Hao; Tsang, Daniel C W; Morel, Jean-Louis; Qiu, Rongliang

2016-10-01

Biochar is being widely considered as a promising amendment agent for immobilizing heavy metals in contaminated acidic soils, where plenty of soluble Al(III) ions exist. In view of uncertain significance of the effects of coexisting Al(III) on Pb(II) sorption by biochars, this study used kenaf core biochar (KB550; high carbon, low ash) and sewage sludge biochar (SB550; low carbon, high ash) pyrolyzed at 550 °C to elucidate the influence of coexisting Al(III) species and biochars' mineral components on Pb(II) immobilization conducted in aqueous solution with initial pHs of 3.0-4.5. Results showed that Al(III) reduced Pb(II) sorption on KB550 primarily via pH buffering against biochar alkalinity, thus inhibiting lead carbonate formation. In contrast, the reduction on SB550 mainly resulted from direct competition for sorption sites, especially on Fe-rich phengite 2M1 and metakaolinite. Because of Pb-P precipitation and Pb-K interlayer exchange, the residual Pb(II) adsorption capacity resistant to coexisting Al(III) was 3-5 times higher on SB550 than on KB550. The Pb-K interlayer exchange was enhanced by lower pH and coexisting Al(III), while Pb-P precipitation was the dominant Pb(II) sorption mechanism on SB550 resistant to Al(III) buffering and competition at higher pH. Application of these two biochars as amendments confirmed that the mineral-rich SB550 was more suitable for Pb(II) immobilization in acidic soils with high levels of extractable Al(III). Copyright © 2016 Elsevier Ltd. All rights reserved.

Water sorption and solubility of different calcium hydroxide cements.

PubMed

Francisconi, Luciana Fávaro; de Freitas, Anderson Pinheiro; Scaffa, Polliana Mendes Candia; Mondelli, Rafael Francisco Lia; Francisconi, Paulo Afonso Silveira

2009-01-01

Calcium hydroxide cements have been largely used in deep cavities due to their abilities to stimulate dentin formation. However, their resistance can be relatively low and their solubility relatively high, in many instances. This study evaluated water sorption and solubility of different calcium hydroxide cements, in order to show alterations that may reduce their effectiveness. Five discs (20 mm in diameter and 1.5 mm thick) of three different materials (Biocal, Dycal and Hidro C) were prepared with the aid of a ring-shaped metallic matrix. After being stored at 37 degrees C for 24 h, the discs were weighed on a precision weight scale, dehydrated and weighed again. Immediately after weighing, discs were stored for a week in 50 mL of distilled water at 37 degrees C and, then, weighed again, dehydrated and submitted to a new weighing. The loss of soluble material and its water sorption was obtained from the difference between the initial and the final dry mass of each disc, after 1 week of immersion in water. Data were analyzed for significant differences by two-way ANOVA and Tukey's test (p<0.05). Mean water sorption values (g) +/- standard deviation and percentage (%), for each evaluated cement, were: Biocal (0.006 +/- 0.001 / 2.15); Dycal (0.016 +/- 0.004 / 5.49); and Hidro C (0.025 +/- 0.003 / 8.27). Mean solubility values (g) +/- standard deviation and percentage (%), for each evaluated cement, were: Biocal (0.002 +/- 0.001 / 0.72); Dycal (0.013 +/- 0.004 / 4.21); and Hidro C (0.023 +/- 0.004 / 7.65). Biocal absorbed less water and was less soluble than the other evaluated cements; Hidro C exhibited the highest water sorption and solubility values; and there were significant differences among all evaluated experimental groups.

Removal of hexavalent chromium upon interaction with biochar under acidic conditions: mechanistic insights and application.

PubMed

Choudhary, Bharat; Paul, Debajyoti; Singh, Abhas; Gupta, Tarun

2017-07-01

Chromium pollution of soil and water is a serious environmental concern due to potential carcinogenicity of hexavalent chromium [Cr(VI)] when ingested. Eucalyptus bark biochar (EBB), a carbonaceous black porous material obtained by pyrolysis of biomass at 500 °C under oxygen-free atmosphere, was used to investigate the removal of aqueous Cr(VI) upon interaction with the EBB, the dominant Cr(VI) removal mechanism(s), and the applicability to treat Cr(VI)-contaminated wastewater. Batch experiments showed complete removal of aqueous Cr(VI) at pH 1-2; sorption was negligible at pH 1, but ~55% of total Cr was sorbed onto the EBB surface at pH 2. Detailed investigations on unreacted and reacted EBB through Fourier transform infrared spectroscopy and X-ray photoelectron spectrometry (XPS) indicate that the carboxylic groups in biochar played a dominant role in Cr(VI) sorption, whereas the phenolic groups were responsible for Cr(VI) reduction. The predominance of sorption-reduction mechanism was confirmed by XPS studies that indicated ~82% as Cr(III) and ~18% as Cr(VI) sorbed on the EBB surface. Significantly, Cr(VI) reduction was also facilitated by dissolved organic matter (DOM) extracted from biochar. This reduction was enhanced by the presence of biochar. Overall, the removal of Cr(VI) in the presence of biochar was affected by sorption due to electrostatic attraction, sorption-reduction mediated by surface organic complexes, and aqueous reduction by DOM. Relative dominance of the aqueous reduction mechanism depended on a critical biochar dosage for a given electrolyte pH and initial Cr(VI) concentration. The low-cost EBB developed here successfully removed all Cr(VI) in chrome tanning acidic wastewater and Cr(VI)-contaminated groundwater after pH adjustment, highlighting its potential applicability in effective Cr(VI) remediation.

Characterization of potassium hydroxide (KOH) modified hydrochars from different feedstocks for enhanced removal of heavy metals from water.

PubMed

Sun, Kejing; Tang, Jingchun; Gong, Yanyan; Zhang, Hairong

2015-11-01

Hydrochars produced from different feedstocks (sawdust, wheat straw, and corn stalk) via hydrothermal carbonization (HTC) and KOH modification were used as alternative adsorbents for aqueous heavy metals remediation. The chemical and physical properties of the hydrochars and KOH-treated hydrochars were characterized, and the ability of hydrochars for removal of heavy metals from aqueous solutions as a function of reaction time, pH, and initial contaminant concentration was tested. The results showed that KOH modification of hydrochars might have increased the aromatic and oxygen-containing functional groups, such as carboxyl groups, resulting in about 2-3 times increase of cadmium sorption capacity (30.40-40.78 mg/g) compared to that of unmodified hydrochars (13.92-14.52 mg/g). The sorption ability among different feedstocks after modification was as the following: sawdust > wheat straw > corn stack. Cadmium sorption kinetics on modified hydrochars could be interpreted with a pseudo-second order, and sorption isotherm was simulated with Langmuir adsorption model. High cadmium uptake on modified hydrochars was observed over the pH range of 4.0-8.0, while for other heavy metals (Pb(2+), Cu(2+), and Zn(2+)) the range was 4.0-6.0. In a multi-metal system, the sorption capacity of heavy metals by modified hydrochars was also higher than that by unmodified ones and followed the order of Pb(II) > Cu(II) > Cd(II) > Zn(II). The results suggest that KOH-modified hydrochars can be used as a low cost, environmental-friendly, and effective adsorbent for heavy metal removal from aqueous solutions.

Role of soil sorption and microbial degradation on dissipation of mesotrione in plant-available soil water.

PubMed

Shaner, Dale; Brunk, Galen; Nissen, Scott; Westra, Phil; Chen, Wenlin

2012-01-01

Mesotrione is a carotenoid biosynthesis-inhibiting herbicide labeled for pre-emergence and postemergence weed control in corn production. Understanding the factors that influence the dissipation of mesotrione in soil and in the plant-available water (PAW) is important for the environmental fate assessment and optimal weed management practices. The present research investigated the role of soil properties and microbial activities on the interrelated sorption and degradation processes of mesotrione in four soils by direct measurements of PAW. We found that mesotrione bound to the soils time dependently, with approximately 14 d to reach equilibrium. The 24-h batch-slurry equilibrium experiments provided the sorption partition coefficient ranging from 0.26 to 3.53 L kg(-1), depending on soil organic carbon and pH. The dissipation of mesotrione in the soil-bound phase was primarily attributed to desorption to the PAW. Degradation in the PAW was rapid and primarily dependent on microbial actions, with half-degradation time (DT(50)) <3 d in all four soils tested. The rapid degradation in the PAW became rate limited by sorption as more available molecules were depleted in the soil pore water, resulting in a more slowed overall process for the total soil-water system (DT(50) <26 d). The dissipation of mesotrione in the PAW was due to microbial metabolism and time-dependent sorption to the soils. A coupled kinetics model calibrated with the data from the laboratory centrifugation technique provided an effective approach to investigate the interrelated processes of sorption and degradation in realistic soil moisture conditions. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

Phosphorus Sorption Capacity of Gray Forest Soil as Dependent on Fertilization System

NASA Astrophysics Data System (ADS)

Rogova, O. B.; Kolobova, N. A.; Ivanov, A. L.

2018-05-01

In this paper, the results of the study of changes in the phosphorus sorption capacity of gray forest soils of Vladimir opolie under the impact of different fertilization systems are discussed. The quantitative parameters of the potential buffer capacity of soils for phosphorus (PBCP) and Langmuir sorption isotherms have been calculated. It is shown that the application of organic fertilizers results in a stronger decrease in PBCP than the application of mineral fertilizers. The portion of phosphorus of mineral compounds considerably increases, and the high content of available phosphates is maintained. In the variants with application of mineral phosphorus in combination with manure, the portions of organic and mineral phosphorus are at the level typical of unfertilized soils. The energy of phosphate bonds with the soil is minimal upon the application of a double rate of mineral phosphorus at the maximum capacity in relation to phosphate ions.

In situ precipitation of nano-hydroxyapatite in gelatin polymatrix towards specific fluoride sorption.

PubMed

Pandi, Kalimuthu; Viswanathan, Natrayasamy

2015-03-01

This study investigates the synthesis of nano-hydroxyapatite (n-HAp) incorporated gelatin (Gel) biocomposite namely n-HAp@Gel composite for efficient removal of fluoride from aqueous solution. The results demonstrated that, the developed n-HAp@Gel biocomposite possess an enhanced defluoridation capacity (DC) of 4157 mgF-/kg. The batch experiments were optimized as a function of various influencing parameters like contact time, pH, co-ions, temperature and initial fluoride concentration. The physicochemical characteristics of n-HAp@Gel composite was examined by using different instrumental techniques like FTIR, XRD, TGA-DSC and SEM with EDAX analysis. The sorption data were fitted with various isotherm models. The acquired thermodynamic parameters showed that the sorption of fluoride onto the sorbent was endothermic and spontaneous in nature. The reaction-based and diffusion-based models were used to identify the kinetics of the reaction. At field conditions, n-HAp@Gel composite reduce the fluoride concentration below the tolerance limit. A regeneration technique was proposed in order to reuse the sorbent. Copyright © 2014 Elsevier B.V. All rights reserved.

Adsorption of Congo red dye onto antimicrobial terephthaloyl thiourea cross-linked chitosan hydrogels.

PubMed

El-Harby, Nouf F; Ibrahim, Shaimaa M A; Mohamed, Nadia A

2017-11-01

Adsorption capacity of three antimicrobial terephthaloyl thiourea cross-linked chitosan hydrogels for Congo red dye removal from its aqueous solution has been investigated for the first time in this work. These hydrogels were prepared by reacting chitosan with various amounts of terephthaloyl diisothiocyanate cross-linker. The effect of the hydrogel structural variations and several dye adsorption processing parameters to achieve the best adsorption capacity were investigated. The hydrogels' structural variations were obtained by varying their terephthaloyl thiourea moieties content. The processing variables included initial concentration of the dye solution, temperature and time of exposure to the dye. The adsorption kinetics and isotherms showed that the sorption processes were better fitted by the pseudo-second-order equation and the Langmuir equation, respectively. On the basis of the Langmuir analysis Congo red dye gave the maximum sorption capacity of 44.248 mg/g. The results obtained confirmed that the sorption phenomena are most likely to be controlled by chemisorption process. The adsorption reaction was endothermic and spontaneous according to the calculated results of adsorption thermodynamics.

Structural and Kinetic Hydrogen Sorption Properties of Zr0.8Ti0.2Co Alloy Prepared by Ball Milling

PubMed Central

He, Hui; Tang, Tao; Huang, Zhiyong; Sang, Ge; Zhang, Guanghui; Ba, Jingwen; Liu, Meng

2018-01-01

The effects of ball milling on the hydrogen sorption kinetics and microstructure of Zr0.8Ti0.2Co have been systematically studied. Kinetic measurements show that the hydrogenation rate and amount of Zr0.8Ti0.2Co decrease with increasing the ball milling time. However, the dehydrogenation rate accelerates as the ball milling time increases. Meanwhile, the disproportionation of Zr0.8Ti0.2Co speeds up after ball milling and the disproportionation kinetics is clearly inclined to be linear with time at 500°C. It is found from X-ray powder diffraction (XRD) results that the lattice parameter of Zr0.8Ti0.2Co gradually decreases from 3.164 Å to 3.153 Å when the ball milling time extends from 0 h to 8 h, which is mainly responsible for the hydrogen absorption/desorption behaviors. In addition, scanning electron microscope (SEM) images demonstrate that the morphology of Zr0.8Ti0.2Co has obviously changed after ball milling, which is closely related to the hydrogen absorption kinetics. Besides, high-resolution transmission electron microscopy (HRTEM) images show that a large number of disordered microstructures including amorphous regions and defects exist after ball milling, which also play an important role in hydrogen sorption performances. This work will provide some insights into the principles of how to further improve the hydrogen sorption kinetics and disproportionation property of Zr0.8Ti0.2Co. PMID:29721128

Volatilization of pesticides from the bare soil surface: evaluation of the humidity effect.

PubMed

Schneider, Martina; Endo, Satoshi; Goss, Kai-Uwe

2013-01-01

Volatilization of pesticides from soils under dry conditions (water content below the permanent wilting point) can be significantly influenced by sorption to hydrated mineral surfaces. This sorption process strongly depends on the water activity, expressed as equilibrium relative humidity in the pore space of the soil, and on the available surface area of the hydrated minerals. In this study, the influence of different humidity regimes on the volatilization of two pesticides (triallate and trifluralin) was demonstrated with a bench-scale wind tunnel system that allowed the establishment of well controlled humidity conditions within the soil. In the experiment starting with very dry conditions, increasing the relative humidity in the adjacent air from 60 to 85% resulted in an up to 8 times higher volatilization rate of the pesticides. An additional strong increase in volatilization (up to 3 times higher) was caused by a simulated rain event, which eliminates all sorption sites associated to mineral surfaces. In agreement with this interpretation, the comparison of two soils suggested that mineral surface area was the soil property that governs the volatilization under dry conditions, whereas soil organic matter was the controlling variable under wet conditions. In contrast to expectations, the use of a novel capsulated suspension for triallate showed the same humidity effects and no substantially lower volatilization rates in comparison to the regular formulation. This study demonstrated that humidity effects on pesticide volatilization can be interpreted via the mechanism of sorption to mineral surfaces under dry conditions. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

Derived and thiourea-functionalized silica for cadmium removal: isotherm, kinetic and thermodynamic studies

NASA Astrophysics Data System (ADS)

Omotunde, Iyanu; Okoronkwo, Afamefuna; Oluwashina, Olugbenga

2018-03-01

The present study explored the feasibility of using derived and thiourea-functionalized silica as adsorbent for the removal of cadmium under different experimental conditions. Effects of various parameters such as function of point of zero charge (pHPZC), solution pH, sorbent-sorbate resident time and ratio, concentration and temperature were investigated. The sorption of cadmium followed the pseudo-second-order rate kinetics. Thermodynamic studies revealed that the sorption of cadmium was endothermic and spontaneous, with good affinity toward the sorbent. Various isotherm models, viz. Langmuir, Freundlich, Temkin, Dubinin-Radushkevich, Harkins-Jura, and Halsey isotherms were used to analyze the equilibrium data at different temperatures. The Freundlich, Halsey, Langmuir, and Temkin models were found to be in good agreement with the experimental data with high R 2, low RMSE, and low χ 2 values. The results show that the sorption capacity increases with an increase in solution temperature from 28 to 65 °C. The maximum sorption capacity calculated from Langmuir isotherm was 27.55 and 28.41 mg g-1 for derived and thiourea-functionalized silica, respectively, at optimum condition of pH 5 and contact time of 120 min.

Evaluation of physicochemical and biological properties of chitosan/poly (vinyl alcohol) polymer blend membranes and their correlation for Vero cell growth.

PubMed

Sharma, Parul; Mathur, Garima; Dhakate, Sanjay R; Chand, Subhash; Goswami, Navendu; Sharma, Sanjeev K; Mathur, Ashwani

2016-02-10

The blend membranes with varying weight ratios of chitosan/poly (vinyl alcohol) (CS/PVA) (1:0, 1:1, 1:2.5, 1.5:1, 1.5: 2.5) were prepared using solvent casting method and were evaluated for their potential application in single-use membrane bioreactors (MBRs). The physicochemical properties of the prepared membranes were investigated for chemical interactions (FTIR), surface morphology (SEM), water uptake, protein sorption (qe), ammonia sorption and growth kinetics of Vero cells. CS/PVA blend membrane having weight ratio of 1.5:1 had shown enhanced membrane flexibility, reduced water uptake, less protein sorption and no ammonium sorption compared to CS membrane. This blend membrane also showed comparatively enhanced higher specific growth rate (0.82/day) of Vero cells. Improved physicochemical properties and growth kinetics obtrude CS/PVA (1.5:1) as a potential surface for adhesion and proliferation with possible application in single use membrane bioreactors. Additionally, new insight explaining correlation between water holding (%) of CS/PVA (1.5:1) blend membrane and doubling time (td) of Vero cells is proposed. Copyright © 2015 Elsevier Ltd. All rights reserved.

Maize, switchgrass, and ponderosa pine biochar added to soil increased herbicide sorption and decreased herbicide efficacy.

PubMed

Clay, Sharon A; Krack, Kaitlynn K; Bruggeman, Stephanie A; Papiernik, Sharon; Schumacher, Thomas E

2016-08-02

Biochar, a by-product of pyrolysis made from a wide array of plant biomass when producing biofuels, is a proposed soil amendment to improve soil health. This study measured herbicide sorption and efficacy when soils were treated with low (1% w/w) or high (10% w/w) amounts of biochar manufactured from different feedstocks [maize (Zea mays) stover, switchgrass (Panicum vigatum), and ponderosa pine (Pinus ponderosa)], and treated with different post-processing techniques. Twenty-four hour batch equilibration measured sorption of (14)C-labelled atrazine or 2,4-D to two soil types with and without biochar amendments. Herbicide efficacy was measured with and without biochar using speed of seed germination tests of sensitive species. Biochar amended soils sorbed more herbicide than untreated soils, with major differences due to biochar application rate but minor differences due to biochar type or post-process handling technique. Biochar presence increased the speed of seed germination compared with herbicide alone addition. These data indicate that biochar addition to soil can increase herbicide sorption and reduce efficacy. Evaluation for site-specific biochar applications may be warranted to obtain maximal benefits without compromising other agronomic practices.

Biodegradation, sorption, and transport of 2,4-dichlorophenoxyacetic acid in saturated and unsaturated soils.

PubMed Central

Estrella, M R; Brusseau, M L; Maier, R S; Pepper, I L; Wierenga, P J; Miller, R M

1993-01-01

The fate of an organic contaminant in soil depends on many factors, including sorption, biodegradation, and transport. The herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) was used as a model compound to illustrate the impact of these interacting factors on the fate of an organic contaminant. Batch and column experiments performed with a sandy loam soil mixture under saturated and unsaturated conditions were used to determine the effects of sorption and biodegradation on the fate and transport of 2,4-D. Sorption of 2,4-D was found to have a slight but significant effect on transport of 2,4-D under saturated conditions (retardation factor, 1.8) and unsaturated conditions (retardation factor, 3.4). Biodegradation of 2,4-D was extensive under both batch and column conditions and was found to have a significant impact on 2,4-D transport in column experiments. In batch experiments, complete mineralization of 2,4-D (100 mg kg-1) occurred over a 4-day period following a 3-day lag phase under both saturated and unsaturated conditions. The biodegradation rate parameters calculated for batch experiments were found to be significantly different from those estimated for column experiments. PMID:8285717

Sorption, photodegradation, and chemical transformation of naproxen and ibuprofen in soils and water.

PubMed

Vulava, Vijay M; Cory, Wendy C; Murphey, Virginia L; Ulmer, Candice Z

2016-09-15

Pharmaceutically active compounds (PhACs) are released into the environment where they undergo soil sorption, photodegradation, and chemical transformation into structurally similar compounds. Here we report on studies of naproxen (NAP) and ibuprofen (IBP), two widely-used nonsteroidal anti-inflammatory drugs (NSAIDS), in soils and water. Organic matter (OM) was observed to play an important role in each of these processes. Sorption was observed to be stronger and nonlinear in higher OM soils while weaker but still significant in lower OM, higher clay soils; the amphiphilic nature of these two PhACs combined with the complex charged and nonpolar surfaces available in the soil was observed to control the sorption behavior. Simulated solar photodegradation rates of NAP and IBP in water were observed to change in the presence of humic acid or fulvic acid. Structural analogs of each compound were observed as the result of chemical transformation in both photoexposed aqueous solutions and non-photoexposed soil. Two of these transformation products were detected as both soil and photo transformation products for both PhACs. OM was observed to influence the chemical transformation of both pharmaceuticals. Copyright © 2016 Elsevier B.V. All rights reserved.

Water Sorption and Vapor-Phase Deuterium Exchange Studies on Methemoglobin CC, SC, SS, AS, and AA

PubMed Central

Killion, Philip J.; Cameron, Bruce F.

1972-01-01

Five hemoglobins whose genetic relationship to one another involves one set of alleles, hemoglobins CC, SC, SS, AS, and AA, were studied in the Met form. Two different investigations were conducted at 28°C on these methemoglobins within a McBain gravimetric sorption system: sorption of H2O vapor and vapor-phase deuterium-hydrogen exchange. For each of the five samples there was close agreement between the per cent hydration of polar sites as determined from sorption studies and the maximum per cent of labile hydrogens that were exchanged during the vapor-phase deuterium exchange study. Both studies measured a slight increase in the number of polar sites accessible to H2O or D2O vapor for those samples in which the substituent in the sixth position from the N-terminus of the two β-chains had a positively charged side chain and a slight decrease for those in which the substituent had a negatively charged side chain. The in-exchange of deuterium for hydrogen occurred at a faster observed rate than the out-exchange of hydrogen for deuterium. PMID:5030563

Ultrafast Carbon Dioxide Sorption Kinetics Using Lithium Silicate Nanowires.

PubMed

Nambo, Apolo; He, Juan; Nguyen, Tu Quang; Atla, Veerendra; Druffel, Thad; Sunkara, Mahendra

2017-06-14

In this paper, the Li 4 SiO 4 nanowires (NWs) were shown to be promising for CO 2 capture with ultrafast kinetics. Specifically, the nanowire powders exhibited an uptake of 0.35 g g -1 of CO 2 at an ultrafast adsorption rate of 0.22 g g -1 min -1 at 650-700 °C. Lithium silicate (Li 4 SiO 4 ) nanowires and nanopowders were synthesized using a "solvo-plasma" technique involving plasma oxidation of silicon precursors mixed with lithium hydroxide. The kinetic parameter values (k) extracted from sorption kinetics obtained using NW powders are 1 order of magnitude higher than those previously reported for the Li 4 SiO 4 -CO 2 reaction system. The time scales for CO 2 sorption using nanowires are approximately 3 min and two orders magnitude faster compared to those obtained using lithium silicate powders with spherical morphologies and aggregates. Furthermore, Li 4 SiO 4 nanowire powders showed reversibility through sorption-desorption cycles indicating their suitability for CO 2 capture applications. All of the morphologies of Li 4 SiO 4 powders exhibited a double exponential behavior in the adsorption kinetics indicating two distinct time constants for kinetic and the mass transfer limited regimes.

Bioremediation of arsenic from water with citric acid cross-linked water hyacinth (E. crassipes) root powder.

PubMed

Gogoi, Pankaj; Adhikari, Pooja; Maji, Tarun K

2017-08-01

A green and novel approach was demonstrated for successful remediation of arsenic from contaminated water by citric acid (CA) cross-linked water hyacinth root powder (RP). Different analytical techniques were used to investigate the binding and structural properties of prepared materials. Titanium dioxide played a significant role in the cross-linking process. Incorporation of CA into RP enhanced its integrity, and thus removal efficiency remained unaffected after several cyclic runs. Also the turbidity which formed due to treatment with uncross-linked RP was reduced to below the permissible limit. Effect of the amount of CA, material dose, treatment time, initial ion concentration, and pH were investigated. Use of 10% (w/w) CA was found to be sufficient to bring down the turbidity of the treated water below 2.5 nephelometric turbidity unit (NTU) without hampering the removal capacity/rate. A material dose of 5 g/L removed successfully total inorganic arsenic concentration to below 10 μg/L. The sorption process could be reasonably explained by Langmuir isotherm, and the maximum adsorption capacity was found to be 28 μg of arsenic/g. The material was found to be more efficient at acidic pH (pH ZPC  = 6.72). The sorption process was governed by a pseudo-second-order kinetic model.

Desorption kinetics of cesium from Fukushima soils.

PubMed

Murota, Kento; Saito, Takumi; Tanaka, Satoru

2016-03-01

Understanding the behaviors of Cs(+) in soils is crucial for evaluation of the impacts of disposal of soils contaminated by radiocesium, (137)Cs. The desorption rate of Cs(+) evaluated in relatively short periods of time may not be adequate for such a purpose. In this study, we investigated long-term desorption kinetics of (137)Cs and (133)Cs from soils collected in Fukushima Prefecture by batch desorption experiments in the presence of cation exchange resin as a sorbent. The sorbent can keep the concentration of Cs(+) in the aqueous phase low and prevent re-sorption of desorbed Cs(+). Up to 60% of (137)Cs was desorbed after 139 d in dilute KCl media, which was larger than the desorption by conventional short-term extraction with 1 M ammonium acetate. Desorption of (137)Cs continued even after this period. It was also found that high concentration of K(+) prevented desorption of Cs(+) in the initial stage of desorption, but the effect was alleviated with time. The desorbed fraction of stable Cs was smaller than that of (137)Cs. This indicated that (137)Cs may gradually move to more stable states in soils. The half-life of (137)Cs desorption from the slowest sorption site was estimated to be at least two years by a three-site desorption model. Copyright © 2015 Elsevier Ltd. All rights reserved.

Hydrogen storage materials discovery via high throughput ball milling and gas sorption.

PubMed

Li, Bin; Kaye, Steven S; Riley, Conor; Greenberg, Doron; Galang, Daniel; Bailey, Mark S

2012-06-11

The lack of a high capacity hydrogen storage material is a major barrier to the implementation of the hydrogen economy. To accelerate discovery of such materials, we have developed a high-throughput workflow for screening of hydrogen storage materials in which candidate materials are synthesized and characterized via highly parallel ball mills and volumetric gas sorption instruments, respectively. The workflow was used to identify mixed imides with significantly enhanced absorption rates relative to Li2Mg(NH)2. The most promising material, 2LiNH2:MgH2 + 5 atom % LiBH4 + 0.5 atom % La, exhibits the best balance of absorption rate, capacity, and cycle-life, absorbing >4 wt % H2 in 1 h at 120 °C after 11 absorption-desorption cycles.

Polychlorinated Biphenyl Sources, Emissions, and Environmental Levels in school Buildings (PCB Workshop presentation)

EPA Science Inventory

Measure PCB emission rates from primary sources in laboratory chambersMeasure transport and sorption by materials and dust in laboratory chambersCharacterize PCBs in school building materialsEstimate PCB emission rates from sources in schoolsExamine congener patterns in sources a...

Modeling Np and Pu transport with a surface complexation model and spatially variant sorption capacities: Implications for reactive transport modeling and performance assessments of nuclear waste disposal sites

USGS Publications Warehouse

Glynn, P.D.

2003-01-01

One-dimensional (1D) geochemical transport modeling is used to demonstrate the effects of speciation and sorption reactions on the ground-water transport of Np and Pu, two redox-sensitive elements. Earlier 1D simulations (Reardon, 1981) considered the kinetically limited dissolution of calcite and its effect on ion-exchange reactions (involving 90Sr, Ca, Na, Mg and K), and documented the spatial variation of a 90Sr partition coefficient under both transient and steady-state chemical conditions. In contrast, the simulations presented here assume local equilibrium for all reactions, and consider sorption on constant potential, rather than constant charge, surfaces. Reardon's (1981) seminal findings on the spatial and temporal variability of partitioning (of 90Sr) are reexamined and found partially caused by his assumption of a kinetically limited reaction. In the present work, sorption is assumed the predominant retardation process controlling Pu and Np transport, and is simulated using a diffuse-double-layer-surface-complexation (DDLSC) model. Transport simulations consider the infiltration of Np- and Pu-contaminated waters into an initially uncontaminated environment, followed by the cleanup of the resultant contamination with uncontaminated water. Simulations are conducted using different spatial distributions of sorption capacities (with the same total potential sorption capacity, but with different variances and spatial correlation structures). Results obtained differ markedly from those that would be obtained in transport simulations using constant Kd, Langmuir or Freundlich sorption models. When possible, simulation results (breakthrough curves) are fitted to a constant K d advection-dispersion transport model and compared. Functional differences often are great enough that they prevent a meaningful fit of the simulation results with a constant K d (or even a Langmuir or Freundlich) model, even in the case of Np, a weakly sorbed radionuclide under the simulation conditions. Functional behaviors that cannot be fit include concentration trend reversals and radionuclide desorption spikes. Other simulation results are fit successfully but the fitted parameters (Kd and dispersivity) vary significantly depending on simulation conditions (e.g. "infiltration" vs. "cleanup" conditions). Notably, an increase in the variance of the specified sorption capacities results in a marked increase in the dispersion of the radionuclides. The results presented have implications for the simulation of radionuclide migration in performance assessments of nuclear waste-disposal sites, for the future monitoring of those sites, and more generally for modeling contaminant transport in ground-water environments. ?? 2003 Published by Elsevier Science Ltd.

Bioremediation of surface water co-contaminated with zinc (II) and linear alkylbenzene sulfonates by Spirulina platensis

NASA Astrophysics Data System (ADS)

Meng, Huijuan; Xia, Yunfeng; Chen, Hong

Potential remediation of surface water contaminated with linear alkylbenzene sulfonates (LAS) and zinc (Zn (II)) by sorption on Spirulina platensis was studied using batch techniques. Results show that LAS can be biodegraded by Spirulina platensis, and its biodegradation rate after 5 days was 87%, 80%, and 70.5% when its initial concentration was 0.5, 1, and 2 mg/L, respectively. The maximum Zn (II) uptake capacity of Spirulina platensis was found to be 30.96 mg/g. LAS may enhance the maximum Zn (II) uptake capacity of Spirulina platensis, which can be attributed to an increase in bioavailability due to the presence of LAS. The biodegradation rates of LAS by Spirulina platensis increased with Zn (II) and reached the maximum when Zn (II) was 4 mg/L. The joint toxicity test showed that the combined effect of LAS and Zn (II) was Synergistic. LAS can enhance the biosorption of Zn (II), and reciprocally, Zn (II) can enhance LAS biodegradation.

Multi-process herbicide transport in structured soil columns: Experiments and model analysis

NASA Astrophysics Data System (ADS)

Köhne, J. Maximilian; Köhne, Sigrid; Šimůnek, Jirka

2006-05-01

Model predictions of pesticide transport in structured soils are complicated by multiple processes acting concurrently. In this study, the hydraulic, physical, and chemical nonequilibrium (HNE, PNE, and CNE, respectively) processes governing herbicide transport under variably saturated flow conditions were studied. Bromide (Br -), isoproturon (IPU, 3-(4-isoprpylphenyl)-1,1-dimethylurea) and terbuthylazine (TER, N2-tert-butyl-6-chloro- N4-ethyl-1,3,5-triazine-2,4-diamine) were applied to two soil columns. An aggregated Ap soil column and a macroporous, aggregated Ah soil column were irrigated at a rate of 1 cm h - 1 for 3 h. Two more irrigations at the same rate and duration followed in weekly intervals. Nonlinear (Freundlich) equilibrium and two-site kinetic sorption parameters were determined for IPU and TER using batch experiments. The observed water flow and Br - transport were inversely simulated using mobile-immobile (MIM), dual-permeability (DPM), and combined triple-porosity (DP-MIM) numerical models implemented in HYDRUS-1D, with improving correspondence between empirical data and model results. Using the estimated HNE and PNE parameters together with batch-test derived equilibrium sorption parameters, the preferential breakthrough of the weakly adsorbed IPU in the Ah soil could be reasonably well predicted with the DPM approach, whereas leaching of the strongly adsorbed TER was predicted less well. The transport of IPU and TER through the aggregated Ap soil could be described consistently only when HNE, PNE, and CNE were simultaneously accounted for using the DPM. Inverse parameter estimation suggested that two-site kinetic sorption in inter-aggregate flow paths was reduced as compared to within aggregates, and that large values for the first-order degradation rate were an artifact caused by irreversible sorption. Overall, our results should be helpful to enhance the understanding and modeling of multi-process pesticide transport through structured soils during variably saturated water flow.

Tracking the Fate of Explosive-Trinitrotriazine (RDX) in Coastal Marine Ecosystems Using Stable Isotopic Tracer

NASA Astrophysics Data System (ADS)

Ariyarathna, T. S.; Ballentine, M.; Vlahos, P.; Smith, R. W.; Bohlke, J. K.; Tobias, C. R.; Fallis, S.; Groshens, T.; Cooper, C.

2017-12-01

It has been estimated that there are hundreds of explosive-contaminated sites all over the world and managing these contaminated sites is an international challenge. As coastal zones and estuaries are commonly impacted zones, it is vital to understand the fate and transport of munition compounds in these environments. The demand for data on sorption, biodegradation and mineralization of trinitrotriazine (RDX) in coastal ecosystems is the impetus for this study using stable nitrogen isotopes to track its metabolic pathways. Mesocosm experiments representing subtidal vegetated, subtidal unvegetated and intertidal marsh ecocosms were conducted. Steady state concentrations of RDX were maintained in the systems throughout two-week time duration of experiments. Sediment, pore-water and overlying water samples were analyzed for RDX and degradation products. Isotope analysis of the bulk sediments revealed an initial rising inventory of 15N followed by a decay illustrating the role of sediments on sorption and degradation of RDX in anaerobic sediments respectively. Both pore-water and overlying water samples were analyzed for 15N inventories of different inorganic nitrogen pools including ammonium, nitrate, nitrite, nitrous oxide and nitrogen gases. RDX is mineralized to nitrogen gas through a series of intermediates leaving nitrous oxide as the prominent metabolite of RDX. Significant differences in RDX metabolism were observed in the three different ecosystems based on sediment characteristics and redox conditions in the systems. Fine grained organic carbon rich sediments show notably higher mineralization rates of RDX in terms of production of its metabolites. Quantification of degradation and transformation rates leads to mass balances of RDX in the systems. Further analysis of results provides insights for mineralization pathways of RDX into both organic and inorganic nitrogen pools entering the marine nitrogen cycle.

A METHOD FOR ESTIMATING DISTRIBUTIONS OF MASS TRANSFER RATE COEFFICIENTS WITH APPLICATION TO PURGING AND BATCH EXPERIMENTS. (R825825)

EPA Science Inventory

Mass transfer between aquifer material and groundwater is often modeled as first-order rate-limited sorption or diffusive exchange between mobile zones and immobile zones with idealized geometries. Recent improvements in experimental techniques and advances in our understanding o...

Do Vertical Gradients in Soil Environmental Conditions Regulate Exudation Rates from Peatland Vegetation?

NASA Astrophysics Data System (ADS)

Proctor, C.; He, Y.

2017-12-01

Deposition of carbon belowground via the root exudation pathway is the net of root-borne efflux and influx processes. For select exudates, root have a remarkable ability to actively recapture lost compounds, suggesting that influx mechanisms regulate exudation. However, roots are not the sole sink for root effluxed carbon. Roots compete with solute sorption and microbial uptake, whom are regulated by a unique set of soil environmental conditions. Peatland soil features stark vertical gradients in their physical, chemical, biological, and hydrological properties, which has downstream implications for the relative competitive ability of each actor in root-soil-microbial interactions. This study developed a single root exudate model using the Barber-Cushman approach to examine the radial accumulation of exudates in simulated peatland soil with vertical gradients. The model simulated efflux, influx, solute diffusion, solute mineralization and solid phase sorption mechanisms as depth dependent on bulk density, porosity, tortuosity, buffer power, temperature, and microbial biomass. Deeper peat soil reduced the porosity that permits solute transport, increased tortuosity which lowered the effective diffusion rate, increased solute-solid sorption, and reduced microbial mineralization of effluxed compounds. Slower mineralization rates were partially juxtaposed by increases in sorption, albeit the net removal of effluxed compounds was lower, leading to a larger amount of exudates to remain in the rhizosphere around deeper roots. Increase in the solid phase, and its subsequent constriction of solute migration, lead to a higher accumulation of effluxed compounds on the rhizoplane, up to 1.23x higher than shallow soil. Subsequently, influx mechanisms captured a larger fraction of effluxed compounds (69.06% at -10cm versus 84.8% at -80 cm), reducing net exudation rates from 0.641 to 0.315 nmol cm-1 hr-1 between -10 and -80cm depths. These results suggest that localized environmental conditions around roots can be a considerable influence on root influx and competition for root exudates. The insights provided by this model help provide a better understanding of exudate regulation in peatlands and the quantity and quality of carbon deposited to the methanogen community.

Pesticide interactions with soils affected by olive oil mill wastewater

NASA Astrophysics Data System (ADS)

Keren, Yonatan; Bukhanovsky, Nadezhda; Borisover, Mikhail

2013-04-01

Soil pesticide sorption is well known to affect the fate of pesticides, their bioavailability and the potential to contaminate air and water. Soil - pesticide interactions may be strongly influenced by soil organic matter (SOM) and organic matter (OM)-rich soil amendments. One special OM source in soils is related to olive oil production residues that may include both solid and liquid wastes. In the Mediterranean area, the olive oil production is considered as an important field in the agricultural sector. Due to the significant rise in olive oil production, the amount of wastes is growing respectively. Olive oil mill waste water (OMWW) is the liquid byproduct in the so-called "three phase" technological process. Features of OMWW include the high content of fatty aliphatic components and polyphenols and their often-considered toxicity. One way of OMWW disposal is the land spreading, e.g., in olive orchards. The land application of OMWW (either controlled or not) is supposed to affect the multiple soil properties, including hydrophobicity and the potential of soils to interact with pesticides. Therefore, there is both basic and applied interest in elucidating the interactions between organic compounds and soils affected by OMWW. However, little is known about the impact of OMWW - soil interactions on sorption of organic compounds, and specifically, on sorption of agrochemicals. This paper reports an experimental study of sorption interactions of a series of organic compounds including widely used herbicides such as diuron and simazine, in a range of soils that were affected by OMWW (i) historically or (ii) in the controlled land disposal experiments. It is demonstrated that there is a distinct increase in apparent sorption of organic chemicals in soils affected by OMWW. In selected systems, this increase may be explained by increase in SOM content. However, the SOM quality places a role: the rise in organic compound - soil interactions may both exceed the SOM content increase and be less than that. Sorption interactions of herbicides with soils demonstrate a strong hysteresis (which is not expected to be related to a biodegradation). The data suggests that the OMWW - soil interaction seems to change the shape of the apparent sorption isotherms of organic sorbates, and, possibly, their sorption mechanisms: from a Langmuir-like sorption isotherm (describing the adsorptive interactions with a saturation of sorption sites) in the native soils to the sigmoidal or linear isotherms (expected for a partitioning into the bulk OM phases and their swelling) in the OMWW-amended soils. These results may have a significant impact on multiple agricultural and hydrological aspects, e.g., such as the application rate of herbicides in the field, and their possible release and the long term effect on groundwater. The authors acknowledge the support from the OLIVEOIL project (SCHA849/13) funded by DFG.

[Sorption mechanism of ofloxacin by carbon nanotubes].

PubMed

Zhao, Xing-Xing; Yu, Shui-Li; Wang, Zhe

2014-02-01

Sorption of ofloxacin (OFL) by carbon nanotubes is an effective method to control its fate in aquatic environment. The sorption process of OFL by mixed acid-treated and non-treated multi-walled carbon nanotubes was discussed. Sorption kinetics, sorption isotherm, desorption, sorption thermodynamics and effect of pH were investigated. The results indicated that the sorption kinetics followed the pseudo-second order kinetics model. The equilibrium sorption capacity of OFL on MWCNTs-O was higher. The sorption isotherm could be fitted by both the Langmuir and Freundlich models. The equilibrium sorption capacity dropped when the pH of aqueous solution was in the range of 6.0 to 10.0. Obvious desorption hysteresis was observed during the desorption experiments, especially on MWCNTs-O. Sorption thermodynamics analysis showed that the interactions between the OFL and sorbents were mainly between molecules. More oxygen-containing functional groups introduced on MWCNTs provided OFL molecules with more sorptive sites, which facilitated the generation of hydrogen bonds, a relatively strong interaction. The hydrogen bonds dominated the sorption process of OFL by MWCNTs/MWCNTs-O, explaining the experimental phenomena.

[Impact of biochar amendment on the sorption and dissipation of chlorantraniliprole in soils].

PubMed

Wang, Ting-Ting; Yu, Xiang-Yang; Shen, Yaen; Zhang, Chao-Lan; Liu, Xian-Jin

2012-04-01

The effects of biochar amendment on sorption and dissipation of chlorantraniliprole (CAP) in 5 different agricultural soils were studied. Red gum wood (Eucalyptus spp.) derived biochar was amended into a black soil, a yellow soil, a red soil, a purplish soil, and a fluvo-aquic soil at the rate of 0.5% (by weight). The sorption and dissipation behaviors of CAP in soils with and without biochar amendment were measured by batch equilibration technique and dissipation kinetic experiment, respectively. The objective was to investigate the impact of biochar application on the environmental fate of pesticides in agricultural soils with different physical-chemical properties, and evaluate the potential ecological impacts of field application of biochar materials. The results showed that biochar application in soils could enhance the sorption of CAP, but the magnitudes were varied among soils with different properties. Amendment of 0.5% (by weight) biochar in the black soil, which have high content of organic matter (4.59%), resulted in an increase of sorption coefficient (K(d)) by 2.17%; while for the fluvo-aquic soil with organic matter content of 1.16%, amendment of biochar at the same level led to an increase of 139.13%. The sorption capacity of biochar was partially suppressed when biochar was mixed with soils. The calculated K(Fbiochar) of biochar after mixed in the black soil, yellow soil, red soil, purplish soil, and fluvo-aquic soil were decreased by 96.94%, 90.6%, 91.31%, 68.26%, and 34.59%, respectively, compared to that of the original biochar. The half-lives of CAP in black soil, yellow soil, red soil, purplish soil, and fluvo-aquic soil were 115.52, 133.30, 154.03, 144.41 and 169.06 d, respectively. In soils amended with biochar, the corresponding half-lives of CAP were extended by 20.39, 35.76, 38.51, 79.19, and 119.75 d, respectively. Similar to the effects of biochar on CAP sorption, in soil with higher content of organic matter, the retardation of CAP dissipation by amending biochar was smaller than that in soil with lower content of organic matter. Our results suggested that application of biochar in soils could enhance the sorption and sequestration of CAP, and retard its soil dissipation, but the magnitudes depended on the organic matter content of the soils.

Cation-Pi Interaction: A Key Force for Sorption of Fluoroquinolone Antibiotics on Pyrogenic Carbonaceous Materials.

PubMed

Zhao, Qing; Zhang, Siyu; Zhang, Xuejiao; Lei, Lei; Ma, Wei; Ma, Chuanxin; Song, Lei; Chen, Jingwen; Pan, Bo; Xing, Baoshan

2017-12-05

Cation-pi attraction is a major force that determines macromolecular structures and drug-receptor interactions. However, the role of the cation-pi interaction in sorption of fluoroquinolone antibiotics by pyrogenic carbonaceous materials (PCMs) has not been addressed. We studied sorption of ciprofloxacin (CIP) on graphite to quantify the contribution of the cation-pi interaction. Through competition experiments, the decreased amount of sorbed CIP by sequential treatment with hexadecane, phenanthrene and benzylamine represents the contribution of hydrophobic, pi-pi and cation-pi interactions, respectively. Benzylamine competed more strongly with CIP than n-hexadecane and phenanthrene, indicating that cation-pi is a major force. Cation-pi interactions accounted for up to 72.6% of the total sorption at an initial CIP concentration of 0.000015 mmol/L. Importantly, species transformation (CIP(0) captures H + from water to form CIP(+1)) induced by cation-pi interactions was verified both experimentally and theoretically and can be used to explain the environmental behavior of other fluoroquinolone antibiotics and biochemical processes of amino acids that interact with aromatic moieties. Because of the significant role of cation-pi interactions, CIP desorption increased up to 2.32 times when Na + increased from 0.01 mM to 0.45 mM, which is an environmentally relevant scenario at river estuaries. Hence, behaviors of fluoroquinolone antibiotics that are affected by ionic strength changes need to be carefully evaluated, especially in river estuaries.

Comparative study of differently treated animal bones for Co(2+) removal.

PubMed

Dimović, S; Smiciklas, I; Plećas, I; Antonović, D; Mitrić, M

2009-05-15

The objective of the present study was the evaluation of differently treated bovine bones for Co(2+) removal from aqueous media. Powdered bones (B), as well as samples prepared by H(2)O(2) oxidation (BH(2)O(2)) and annealing at 400-1000 degrees C (B400-B1000), were tested as sorbent materials. A combination of XRD, FTIR spectroscopies, DTA/TGA analyses, specific surface area (S(p)) and point of zero charge (pH(PZC)) measurements was utilized for physicochemical characterization of sorbents. Sorption of Co(2+) was studied in batch conditions as a function of pH, contact time and Co(2+) concentration. Initial pH values in the range 4-8 were found optimal for sorption experiments. Equilibrium time of 24h was required in all investigated systems. The maximum sorption capacities differ significantly from 0.078 to 0.495mmol/g, whereas the affinity towards Co(2+) decreased in the order: B400>BH(2)O(2)>B600>B>B800>B1000. The pseudo-second-order model and Langmuir theoretical equation were used for fitting the kinetic and equilibrium data, respectively. Ion-exchange with Ca(2+) and specific cation sorption were identified as main removal mechanisms. The amounts of Co(2+) desorbed from loaded bone sorbents increased with the decrease of pH as well as with the increase of Ca(2+) concentration. Heating at 400 degrees C was found to be an optimal treatment for the production of the Co(2+) removal agent.

Cysteine-functionalized silica-coated magnetite nanoparticles as potential nanoadsorbents

NASA Astrophysics Data System (ADS)

Enache, Daniela F.; Vasile, Eugenia; Simonescu, Claudia M.; Răzvan, Anca; Nicolescu, Alina; Nechifor, Aurelia-Cristina; Oprea, Ovidiu; Pătescu, Rodica-Elena; Onose, Cristian; Dumitru, Florina

2017-09-01

Fe3O4, Fe3O4@SiO2, and Fe3O4@SiO2@ICPTES-cysteine MNPs have been prepared by the deposition of silica onto magnetite nanoparticles via controlled hydrolysis of TEOS. The new formed silica surface has been functionalized by grafting 3-(triethoxysilyl) propyl isocyanate (ICPTES) and, subsequently, by condensation of isocyanate moiety with cysteine. The morphology of magnetic silica nanoparticles has been investigated by FTIR, PXRD, TEM-HRTEM/SEM/EDX as well as TG experiments. HRTEM microscopy revealed that the Fe3O4, Fe3O4@SiO2 and Fe3O4@SiO2@ICPTES-cysteine nanoparticles are all of spherical shape with particle of ca. 10-30 nm diameters and the silica-coated magnetites have a core-shell structure. Fe3O4, Fe3O4@SiO2, and Fe3O4@SiO2@ICPTES-cysteine MNPs have been tested for their sorption capacity of Pb(II) from synthetic aqueous solutions and the influence of pH solution, contact time, initial heavy metal ion concentrations, and adsorption isotherms on the sorption behavior were also studied. The kinetic studies revealed that the Pb(II) sorption process is mainly controlled by chemical mechanisms. Fe3O4@SiO2@ICPTES-cysteine, with a sorption capacity of 81.8 mg Pb(II)/g, has the potential to be an efficient Pb(II) adsorbent.

Influence of carbon and metal oxide nanomaterials on aqueous concentrations of the munition constituents cyclotrimethylenetrinitramine (RDX) and tungsten.

PubMed

Brame, Jonathon A; Kennedy, Alan J; Lounds, Christopher D; Bednar, Anthony J; Alvarez, Pedro J J; Scott, Andrea M; Stanley, Jacob K

2014-05-01

There is an increasing likelihood of interactions between nanomaterials and munitions constituents in the environment resulting from the use of nanomaterials as additives to energetic formulations and potential contact in waste streams from production facilities and runoff from training ranges. The purpose of the present research was to determine the ability of nano-aluminum oxide (Al(2)O(3)) and multiwalled carbon nanotubes (MWCNTs) to adsorb the munitions constituents cyclotrimethylenetrinitramine (RDX) and tungsten (W) from aqueous solution as a first step in determining the long-term exposure, transport, and bioavailability implications of such interactions. The results indicate significant adsorption of RDX by MWCNTs and of W by nano-Al(2)O(3) (but not between W and MWCNT or RDX and nano-Al(2)O(3)). Kinetic sorption and desorption investigations indicated that the most sorption occurs nearly instantaneously (<5 min), with a relatively slower, secondary binding leading to statistically significant but relatively smaller increases in adsorption over 30 d. The RDX sorption that occurred during the initial interaction was irreversible, with long-term, reversible sorption likely the result of a secondary interaction; as interaction time increased, however, the portion of W irreversibly sorbed onto nano-Al(2)O(3) also increased. The present study shows that strong interactions between some munitions constituents and nanomaterials following environmental release are likely. Time-dependent binding has implications for the bioavailability, migration, transport, and fate of munitions constituents in the environment. © 2014 SETAC.

Use of modified pine bark for removal of pesticides from stormwater runoff

Treesearch

Mandla A. Tshabalala

2003-01-01

Pesticide entrainment in stormwater runoff can contribute to non-point source pollution of surface waters. Granular activated carbon has been successfully used for removing pesticides from wastewater. However, implementation of granular activated carbon sorption media in stormwater filtration systems comes with high initial capital investment and operating costs....

Alginate-immobilized bentonite clay: adsorption efficacy and reusability for Cu(II) removal from aqueous solution.

PubMed

Tan, Wei Shang; Ting, Adeline Su Yien

2014-05-01

This study evaluated the use of alginate-immobilized bentonite to remove Cu(II) as an alternative to mitigate clogging problems. The adsorption efficacy (under the influence of time, pH and initial Cu(II) concentration) and reusability of immobilized-bentonite (1% w/v bentonite) was tested against plain alginate beads. Results revealed that immobilized bentonite demonstrated significantly higher sorption efficacy compared to plain alginate beads with 114.70 and 94.04 mg Cu(II) adsorbed g(-1) adsorbent, respectively. Both sorbents were comparable in other aspects where sorption equilibrium was achieved within 6 h, with optimum pH between pH 4 and 5 for adsorption, displayed maximum adsorption capacity at initial Cu(II) concentrations of 400 mg l(-1), and demonstrated excellent reusability potential with desorption greater than 90% throughout three consecutive adsorption-desorption cycles. Both sorbents also conformed to Langmuir isotherm and pseudo-second order kinetic model. Immobilized bentonite is therefore recommended for use in water treatments to remove Cu(II) without clogging the system. Copyright © 2013 Elsevier Ltd. All rights reserved.

Sorption testing and generalized composite surface complexation models for determining uranium sorption parameters at a proposed in-situ recovery site

DOE Office of Scientific and Technical Information (OSTI.GOV)

Johnson, Raymond H.; Truax, Ryan A.; Lankford, David A.

Solid-phase iron concentrations and generalized composite surface complexation models were used to evaluate procedures in determining uranium sorption on oxidized aquifer material at a proposed U in situ recovery (ISR) site. At the proposed Dewey Burdock ISR site in South Dakota, USA, oxidized aquifer material occurs downgradient of the U ore zones. Solid-phase Fe concentrations did not explain our batch sorption test results,though total extracted Fe appeared to be positively correlated with overall measured U sorption. Batch sorption test results were used to develop generalized composite surface complexation models that incorporated the full genericsorption potential of each sample, without detailedmore » mineralogiccharacterization. The resultant models provide U sorption parameters (site densities and equilibrium constants) for reactive transport modeling. The generalized composite surface complexation sorption models were calibrated to batch sorption data from three oxidized core samples using inverse modeling, and gave larger sorption parameters than just U sorption on the measured solidphase Fe. These larger sorption parameters can significantly influence reactive transport modeling, potentially increasing U attenuation. Because of the limited number of calibration points, inverse modeling required the reduction of estimated parameters by fixing two parameters. The best-fit models used fixed values for equilibrium constants, with the sorption site densities being estimated by the inversion process. While these inverse routines did provide best-fit sorption parameters, local minima and correlated parameters might require further evaluation. Despite our limited number of proxy samples, the procedures presented provide a valuable methodology to consider for sites where metal sorption parameters are required. Furthermore, these sorption parameters can be used in reactive transport modeling to assess downgradient metal attenuation, especially when no other calibration data are available, such as at proposed U ISR sites.« less

Sorption testing and generalized composite surface complexation models for determining uranium sorption parameters at a proposed in-situ recovery site

DOE PAGES

Johnson, Raymond H.; Truax, Ryan A.; Lankford, David A.; ...

2016-02-03

Solid-phase iron concentrations and generalized composite surface complexation models were used to evaluate procedures in determining uranium sorption on oxidized aquifer material at a proposed U in situ recovery (ISR) site. At the proposed Dewey Burdock ISR site in South Dakota, USA, oxidized aquifer material occurs downgradient of the U ore zones. Solid-phase Fe concentrations did not explain our batch sorption test results,though total extracted Fe appeared to be positively correlated with overall measured U sorption. Batch sorption test results were used to develop generalized composite surface complexation models that incorporated the full genericsorption potential of each sample, without detailedmore » mineralogiccharacterization. The resultant models provide U sorption parameters (site densities and equilibrium constants) for reactive transport modeling. The generalized composite surface complexation sorption models were calibrated to batch sorption data from three oxidized core samples using inverse modeling, and gave larger sorption parameters than just U sorption on the measured solidphase Fe. These larger sorption parameters can significantly influence reactive transport modeling, potentially increasing U attenuation. Because of the limited number of calibration points, inverse modeling required the reduction of estimated parameters by fixing two parameters. The best-fit models used fixed values for equilibrium constants, with the sorption site densities being estimated by the inversion process. While these inverse routines did provide best-fit sorption parameters, local minima and correlated parameters might require further evaluation. Despite our limited number of proxy samples, the procedures presented provide a valuable methodology to consider for sites where metal sorption parameters are required. Furthermore, these sorption parameters can be used in reactive transport modeling to assess downgradient metal attenuation, especially when no other calibration data are available, such as at proposed U ISR sites.« less

Phosphorus retention and sorption by constructed wetland soils in Southeast Ireland.

PubMed

Dunne, E J; Culleton, N; O'Donovan, G; Harrington, R; Daly, K

2005-11-01

It may be necessary to use constructed wetlands as a land use practice to mitigate phosphorus (P) loss from agriculture in Ireland. The objectives of this study were to determine the ability of two constructed wetland site soils to retain and sorb P. Intact soil/water column studies were used to determine P release/retention rates during a 30-day incubation period. Soil columns flooded with distilled water released P during the first 2 days; however, soluble reactive P (SRP) concentrations in overlying floodwaters decreased thereafter. Soils with overlying floodwaters spiked at 5 and 15 mg SRP L(-1) retained highest amounts of P (p < 0.05) with retention at these concentrations controlled by SRP in overlying waters. Retention rates by soils ranged between 0.3 and 60.9 mg Pm(-2) d(-1). Maximum P sorption capacity (Smax) was higher for wetland soils at Dunhill, Waterford (1464 mg P kg(-1)) in comparison to soils at Johnstown Castle, Wexford (618 mg P kg(-1)). Equilibrium P concentrations (EPC0) were low (in the microg SRP L(-1) range), indicating a high capacity of these soils to sorb P. Phosphorus sorption parameters were significantly related to ammonium oxalate extractable aluminium (Al) and iron (Fe) content of soils.

Kinetic studies for Ni(II) biosorption from industrial wastewater by Cassia fistula (Golden Shower) biomass.

PubMed

Hanif, Muhammad Asif; Nadeem, Raziya; Zafar, Muhammad Nadeem; Akhtar, Kalsoom; Bhatti, Haq Nawaz

2007-07-16

The present study explores the ability of Cassia fistula waste biomass to remove Ni(II) from industrial effluents. C. fistula biomass was found very effective for Ni(II) removal from wastewater of Ghee Industry (GI), Nickel Chrome Plating Industry (Ni-Cr PI), Battery Manufacturing Industry (BMI), Tanner Industry: Lower Heat Unit (TILHU), Tannery Industry: Higher Heat Unit (TIHHU), Textile Industry: Dying Unit (TIDU) and Textile Industry: Finishing Unit (TIFU). The initial Ni(II) concentration in industrial effluents was found to be 34.89+/-0.01, 183.56+/-0.08, 21.19+/-0.01, 43.29+/-0.03, 47.26+/-0.02, 31.38+/-0.01 and 31.09+/-0.01mg/L in GI, Ni-Cr PI, BMI, TILHU, TIHHU, TIDU and TIFU, respectively. After biosorption the final Ni(II) concentration in industrial effluents was found to be 0.05+/-0.01, 17.26+/-0.08, 0.03+/-0.01, 0.05+/-0.01, 0.1+/-0.01, 0.07+/-0.01 and 0.06+/-0.01mg/L in GI, Ni-Cr PI, BMI, TILHU, TIHHU, TIDU and TIFU, respectively. The % sorption Ni(II) ability of C. fistula from seven industries included in present study tend to be in following order: TILHU (99.88)>GI (99.85) approximately BMI (99.85)>TIFU (99.80)>TIHHU (99.78)>TIDU (99.77)>Ni-Cr PI (90.59). Sorption kinetic experiments were performed in order to investigate proper sorption time for Ni(II) removal from wastewater. Batch metal ion uptake capacity experiments indicated that sorption equilibrium reached much faster in case of industrial wastewater samples (480min) in comparison to synthetic wastewater (1440min) using same biosorbent. The kinetic data were analyzed in term of pseudo-first-order and pseudo-second-order expressions. Pseudo-second-order model described well the sorption kinetics of Ni(II) onto C. fistula biomass from industrial effluents in comparison to pseudo-first-order kinetic model. Due to unique high Ni(II) sorption capacity of C. fistula waste biomass it can be concluded that it is an excellent biosorbent for Ni(II) uptake from industrial effluents.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Parker, Kent E.; Golovich, Elizabeth C.; Wellman, Dawn M.

Iodine sorption onto seven resins and six carbon materials was evaluated using water from well 299-W19-36 on the Hanford Site. These materials were tested using a range of solution-to-solid ratios. The test results are as follows. The efficacy of the resin and granular activated carbon materials was less than predicted based on manufacturers’ performance data. It is hypothesized that this is due to the differences in speciation previously determined for Hanford groundwater. The sorption of iodine is affected by the iodine species in the source water. Iodine loading on resins using source water ranged from 1.47 to 1.70 µg/g withmore » the corresponding K d values from 189.9 to 227.0 mL/g. The sorption values when the iodine is converted to iodide ranged from 2.75 to 5.90 µg/g with the corresponding K d values from 536.3 to 2979.6 mL/g. It is recommended that methods to convert iodine to iodide be investigated in fiscal year (FY) 2015. The chemicals used to convert iodine to iodate adversely affected the sorption of iodine onto the carbon materials. Using as-received source water, loading and K d values ranged from 1.47 to 1.70 µg/g and 189.8 to 226.3 mL/g respectively. After treatment, loading and K d values could not be calculated because there was little change between the initial and final iodine concentration. It is recommended the cause of the decrease in iodine sorption be investigated in FY15. In direct support of CH2M HILL Plateau Remediation Company, Pacific Northwest National Laboratory has evaluated samples from within the 200W pump and treat bioreactors. As part of this analysis, pictures taken within the bioreactor reveal a precipitate that, based on physical properties and known aqueous chemistry, is hypothesized to be iron pyrite or chalcopyrite, which could affect iodine adsorption. It is recommended these materials be tested at different solution-to-solid ratios in FY15 to determine their effect on iodine sorption.« less

Theoretical Investigations of CO2 and CH4 Sorption in an Interpenetrated Diamondoid Metal–Organic Material

PubMed Central

2015-01-01

Grand canonical Monte Carlo (GCMC) simulations of CO2 and CH4 sorption and separation were performed in dia-7i-1-Co, a metal–organic material (MOM) consisting of a 7-fold interpenetrated net of Co2+ ions coordinated to 4-(2-(4-pyridyl)ethenyl)benzoate linkers. This MOM shows high affinity toward CH4 at low loading due to the presence of narrow, close fitting, one-dimensional hydrophobic channels—this makes the MOM relevant for applications in low-pressure methane storage. The calculated CO2 and CH4 sorption isotherms and isosteric heat of adsorption, Qst, values in dia-7i-1-Co are in good agreement with the corresponding experimental results for all state points considered. The experimental initial Qst value for CH4 in dia-7i-1-Co is currently the highest of reported MOM materials, and this was further validated by the simulations performed herein. The simulations predict relatively constant Qst values for CO2 and CH4 sorption across all loadings in dia-7i-1-Co, consistent with the one type of binding site identified for the respective sorbate molecules in this MOM. Examination of the three-dimensional histogram showing the sites of CO2 and CH4 sorption in dia-7i-1-Co confirmed this finding. Inspection of the modeled structure revealed that the sorbate molecules form a strong interaction with the organic linkers within the constricted hydrophobic channels. Ideal adsorbed solution theory (IAST) calculations and GCMC binary mixture simulations predict that the selectivity of CO2 over CH4 in dia-7i-1-Co is quite low, which is a direct consequence of the MOM’s high affinity toward both CO2 and CH4 as well as the nonspecific mechanism shown here. This study provides theoretical insights into the effects of pore size on CO2 and CH4 sorption in porous MOMs and its effect upon selectivity, including postulating design strategies to distinguish between sorbates of similar size and hydrophobicity. PMID:24835550

Influence of smectite hydration and swelling on atrazine sorption behavior.

PubMed

Chappell, Mark A; Laird, David A; Thompson, Michael L; Li, Hui; Teppen, Brian J; Aggarwal, Vaneet; Johnston, Cliff T; Boyd, Stephen A

2005-05-01

Smectites, clay minerals commonly found in soils and sediments, vary widely in their ability to adsorb organic chemicals. Recent research has demonstrated the importance of surface charge density and properties of exchangeable cations in controlling the affinity of smectites for organic molecules. In this study, we induced hysteresis in the crystalline swelling of smectites to test the hypothesis that the extent of crystalline swelling (or interlayer hydration status) has a large influence on the ability of smectites to adsorb atrazine from aqueous systems. Air-dried K-saturated Panther Creek (PC) smectite swelled less (d(001) = 1.38 nm) than never-dried K-PC (d(001) = 1.7 nm) when rehydrated in 20 mM KCl. Correspondingly, the air-dried-rehydrated K-PC had an order of magnitude greater affinity for atrazine relative to the never-dried K-PC. Both air-dried-rehydrated and never-dried Ca-PC expanded to approximately 2.0 nm in 10 mM CaCl2 and both samples had similar affinities for atrazine that were slightly lower than that of never-dried K-PC. The importance of interlayer hydration status in controlling sorption affinity was confirmed by molecular modeling, which revealed much greater interaction between interlayer water molecules and atrazine in a three-layer hydrate relative to a one-layer hydrate. The entropy change on moving atrazine from a fully hydrated state in the bulk solution to a partially hydrated state in the smectite interlayers is believed to be a major factor influencing sorption affinity. In an application test, choice of background solution (20 mM KCl versus 10 mM CaCl2) and air-drying treatments significantly affected atrazine sorption affinities for three-smectitic soils; however, the trends were not consistent with those observed for the reference smectite. Further, extending the initial rehydration time from 24 to 240 h (prior to adding atrazine) significantly decreased the soil's sorption affinity for atrazine. We conclude that interlayer hydration status has a large influence on the affinity of smectites for atrazine and that air-drying treatments have the potential to modify the sorption affinity of smectitic soils for organic molecules such as atrazine.

Consideration of grain packing in granular iron treatability studies

NASA Astrophysics Data System (ADS)

Firdous, R.; Devlin, J. F.

2014-08-01

Commercial granular iron (GI) is light steel that is used in Permeable Reactive Barriers (PRBs). Investigations into the reactivity of GI have focused on its chemical nature and relatively little direct work has been done to account for the effects of grain shape and packing. Both of these factors are expected to influence available grain surface area, which is known to correlate to reactivity. Commercial granular iron grains are platy and therefore pack in preferential orientations that could affect solution access to the surface. Three packing variations were investigated using Connelly Iron and trichloroethylene (TCE). Experimental kinetic data showed reaction rates 2-4 times higher when grains were packed with long axes preferentially parallel to flow (VP) compared to packings with long axes preferentially perpendicular to flow (HP) or randomly arranged (RP). The variations were found to be explainable by variations in reactive sorption capacities, i.e., sorption to sites where chemical transformations took place. The possibility that the different reactive sorption capacities were related to physical pore-scale differences was assessed by conducting an image analysis of the pore structure of sectioned columns. The analyses suggested that pore-scale factors - in particular the grain surface availability, reflected in the sorption capacity terms of the kinetic model used - could only account for a fraction of the observed reactivity differences between packing types. It is concluded that packing does affect observable reaction rates but that micro-scale features on the grain surfaces, rather than the pore scale characteristics, account for most of the apparent reactivity differences. This result suggests that treatability tests should consider the packing of columns carefully if they are to mimic field performance of PRBs to the greatest extent possible.

BEARKIMPE-2: A VBA Excel program for characterizing granular iron in treatability studies

NASA Astrophysics Data System (ADS)

Firdous, R.; Devlin, J. F.

2014-02-01

The selection of a suitable kinetic model to investigate the reaction rate of a contaminant with granular iron (GI) is essential to optimize the permeable reactive barrier (PRB) performance in terms of its reactivity. The newly developed Kinetic Iron Model (KIM) determines the surface rate constant (k) and sorption parameters (Cmax &J) which were not possible to uniquely identify previously. The code was written in Visual Basic (VBA), within Microsoft Excel, was adapted from earlier command line FORTRAN codes, BEARPE and KIMPE. The program is organized with several user interface screens (UserForms) that guide the user step by step through the analysis. BEARKIMPE-2 uses a non-linear optimization algorithm to calculate transport and chemical kinetic parameters. Both reactive and non-reactive sites are considered. A demonstration of the functionality of BEARKIMPE-2, with three nitroaromatic compounds showed that the differences in reaction rates for these compounds could be attributed to differences in their sorption behavior rather than their propensities to accept electrons in the reduction process.

Uncertainty analysis of multi-rate kinetics of uranium desorption from sediments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Xiaoying; Liu, Chongxuan; Hu, Bill X.

2014-01-01

A multi-rate expression for uranyl [U(VI)] surface complexation reactions has been proposed to describe diffusion-limited U(VI) sorption/desorption in heterogeneous subsurface sediments. An important assumption in the rate expression is that its rate constants follow a certain type probability distribution. In this paper, a Bayes-based, Differential Evolution Markov Chain method was used to assess the distribution assumption and to analyze parameter and model structure uncertainties. U(VI) desorption from a contaminated sediment at the US Hanford 300 Area, Washington was used as an example for detail analysis. The results indicated that: 1) the rate constants in the multi-rate expression contain uneven uncertaintiesmore » with slower rate constants having relative larger uncertainties; 2) the lognormal distribution is an effective assumption for the rate constants in the multi-rate model to simualte U(VI) desorption; 3) however, long-term prediction and its uncertainty may be significantly biased by the lognormal assumption for the smaller rate constants; and 4) both parameter and model structure uncertainties can affect the extrapolation of the multi-rate model with a larger uncertainty from the model structure. The results provide important insights into the factors contributing to the uncertainties of the multi-rate expression commonly used to describe the diffusion or mixing-limited sorption/desorption of both organic and inorganic contaminants in subsurface sediments.« less

Sorption of Hydrophobic Organic Compounds on Natural Sorbents and Organoclays from Aqueous and Non-Aqueous Solutions: A Mini-Review

PubMed Central

Moyo, Francis; Tandlich, Roman; Wilhelmi, Brendan S.; Balaz, Stefan

2014-01-01

Renewed focus on the sorption of hydrophobic organic chemicals (HOCs) onto mineral surfaces and soil components is required due to the increased and wider range of organic pollutants being released into the environment. This mini-review examines the possibility of the contribution and mechanism of HOC sorption onto clay mineral sorbents such as kaolinite, and soil organic matter and the possible role of both in the prevention of environmental contamination by HOCs. Literature data indicates that certain siloxane surfaces can be hydrophobic. Therefore soils can retain HOCs even at low soil organic levels and the extent will depend on the structure of the pollutant and the type and concentration of clay minerals in the sorbent. Clay minerals are wettable by nonpolar solvents and so sorption of HOCs onto them from aqueous and non-aqueous solutions is possible. This is important for two reasons: firstly, the movement and remediation of soil environments will be a function of the concentration and type of clay minerals in the soil. Secondly, low-cost sorbents such as kaolinite and expandable clays can be added to soils or contaminated environments as temporary retention barriers for HOCs. Inorganic cations sorbed onto the kaolinite have a strong influence on the rate and extent of sorption of hydrophobic organic pollutants onto kaolinite. Structural sorbate classes that can be retained by the kaolinite matrix are limited by hydrogen bonding between hydroxyl groups of the octahedral alumosilicate sheet and the tetrahedral sheet with silicon. Soil organic carbon plays a key role in the sorption of HOCs onto soils, but the extent will be strongly affected by the structure of the organic soil matter and the presence of soot. Structural characterisation of soil organic matter in a particular soil should be conducted during a particular contamination event. Contamination by mining extractants and antibiotics will require renewed focus on the use of the QSAR approaches in the context of the sorption of HOCs onto clay minerals from aqueous and non-aqueous solutions. PMID:24821385

Defluoridation by Bacteriogenic Iron Oxides: Sorption Studies

NASA Astrophysics Data System (ADS)

Evans, K.; Ferris, F.

2009-05-01

At concentrations above 1 mg/L, fluoride in drinking water can lead to dental and skeletal fluorosis, a disease that causes mottling of the teeth, calcification of ligaments, crippling bone deformities and many other physiological disorders that can, ultimately, lead to death. Conservative estimates are that fluorosis afflicts tens of millions of people worldwide. As there is no treatment for fluorosis, prevention is the only means of controlling the disease. While numerous defluoridation techniques have been explored, no single method has been found to be both effective and inexpensive enough to implement widely. Our research began in India, with a large-scale geochemical study of the groundwater in a fluoride-contaminated region of Orissa. Having developed a better understanding of the geochemical relationships that exist between fluoride and other parameters present in an affected area, as well as the complex relationships that arise among those parameters that can impact the presence of fluoride, we began investigating certain remediation scenarios involving iron oxides. A common approach to remediation involves the partitioning of fluoride from groundwater by sorption onto a variety of materials, one of the most effective of which is iron oxide whose surface area acts as a scavenger for fluoride. In the presence of iron oxidizing bacteria, the oxidation rate of iron has been shown to be ˜6 times greater than in their absence; fluoride should, therefore, be removed from an aqueous environment by bacteriogenic iron oxides (BIOS) much more quickly than by abiotic iron oxides. Most recently, sorption studies have been conducted using both BIOS and synthetic hydrous ferric oxides in order to compare the behavior between biotic and abiotic sorbents. These studies have provided sorption isotherms that allow comparison of fluoride removed by sorption to BIOS versus synthetic iron oxides. Sorption affinity constants have also been determined, which allow for the prediction of fluoride removal in a wide variety of groundwater systems. Sorption isotherms and affinity constants show the use of BIOS to be a promising technique for the remediation of fluoride in groundwater.

Phosphorus fraction and phosphate sorption-release characteristics of the wetland sediments in the Yellow River Delta

NASA Astrophysics Data System (ADS)

Cui, Yuan; Xiao, Rong; Xie, Ying; Zhang, Mingxiang

2018-02-01

The aim of this study was to investigate phosphorus (P) fractions and phosphate sorption-release characteristics of the surface sediments regarding the wetland restoration in the Yellow River Delta (YRD). Sediments samples were collected from three typical sample plots: Phragmites australis community (p), Suaeda salsa community (s), and bare land (b) both in natural wetland (N) and restored wetland (R). The results showed that the mean content of TP was 541.58 mg/kg, and the rank order of P fractions were: inorganic phosphorus (IP) (65.6%) > residual phosphorus (RP) (24.9%) > organic phosphorus (OP) (9.5%). For sediments under the same land cover, TP and OP contents were significantly higher in natural wetlands than those in restored wetlands. This indicated that the restoration project really made a difference in TP content of sediments, and the decreased TP might result from decreased OP. For P kinetics sorption, a quick sorption mainly occurred within 0.5 h. The maximum phosphorus adsorption capacities (Qmax) ranging from 139.40 mg/kg to 224.06 mg/kg and the bonding energy constant (K) ranging from 0.33 mg/L to 1.37 mg/L were both obtained using a Langmuir model. In addition, Qmax, P release (Pr) and P release rates (Prr) were in the order of Nb > Np > Ns > Rb > Rp > Rs, Np > Rp > Ns > Rs = Nb > Rb and Rp > Ns > Rs > Rb > Np > Nb, respectively. This indicated that sediments from natural wetland could adsorb more P as well as release more P into overlying water, moreover, more content of P were left in sediments comparing to restored wetland. Sediments from bare land were more likely to retain P as a pool because of the highest sorption capacity while lowest release potential. Our study showed that P sorption-release and the quick sorption processes were mainly affected by sediment moisture, amorphous iron and aluminum oxides (Feox and Alox). Besides, Qmax was related to background value of sediments P. OP was the major P fraction adsorbed by sediments, and the P adsorbed by sediments was mainly adsorbed on Feox and Alox.

Interfacial Interaction of Titania Nanoparticles and Ligated Uranyl Species: A Relativistic DFT Investigation.

PubMed

Zhao, Hong-Bo; Zheng, Ming; Schreckenbach, Georg; Pan, Qing-Jiang

2017-03-06

To understand interfacial behavior of actinides adsorbed onto mineral surfaces and unravel their structure-property relationship, the structures, electronic properties, and energetics of various ligated uranyl species adsorbed onto TiO 2 surface nanoparticle clusters (SNCs) were examined using relativistic density functional theory. Rutile (110) and anatase (101) titania surfaces, experimentally known to be stable, were fully optimized. For the former, models studied include clean and water-free Ti 27 O 64 H 20 (dry), partially hydrated (Ti 27 O 64 H 20 )(H 2 O) 8 (sol) and proton-saturated [(Ti 27 O 64 H 20 )(H 2 O) 8 (H) 2 ] 2+ (sat), while defect-free and defected anatase SNCs involving more than 38 TiO 2 units were considered. The aquouranyl sorption onto rutile SNCs is energetically preferred, with interaction energies of -8.54, -10.36, and -2.39 eV, respectively. Energy decomposition demonstrates that the sorption is dominated by orbital attractive interactions and modified by steric effects. Greater hydrogen-bonding involvement leads to increased orbital interactions (i.e., more negative energy) from dry to sol/sat complexes, while much larger steric interaction in the sat complex significantly reduces the sorption interaction (i.e., more positive energy). For dry SNC, adsorbates were varied from aquo to aquo-carbonato, to carbonato, to hydroxo uranyl species. Longer U-O surf /U-Ti distances and more positive sorption energies were calculated upon introducing carbonato and hydroxo ligands, indicative of weaker uranyl sorption onto the substrate. This is consistent with experimental observations that the uranyl sorption rate decreases upon raising solution pH value or adding carbon dioxide. Anatase SNCs adsorbing aquouranyl are even more exothermic, because more bonds are formed than in the case of rutile. Moreover, the anatase sorption can be tuned by surface defects as well as its Ti and O stoichiometry. All the aquouranyl-SNC complexes show similar character of molecular orbitals and energetic order although differing in highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) gaps and orbital energy levels, but changes can be accomplished by adding carbonato and hydroxo ligands.

Biosorption of Azo dyes by spent Rhizopus arrhizus biomass

NASA Astrophysics Data System (ADS)

Salvi, Neeta A.; Chattopadhyay, S.

2017-10-01

In the present study, spent Rhizopus arrhizus biomass was used for the removal of six azo dyes from aqueous solutions. The dye removal capacity of the biomass was evaluated by conducting batch tests as a function of contact time, biomass dosage, pH and initial dye concentrations. The pseudo-second-order kinetic model fitted well with the experimental data with correlation coefficients greater than 0.999, suggesting that chemisorptions might be the rate limiting step. The equilibrium sorption data showed good fit to the Langmuir isotherm model. Among the six dyes tested, the maximum monolayer adsorption capacity for fast red A and metanil yellow was found to be 108.8 and 128.5 mg/g, respectively. These encouraging results suggest that dead Rhizopus arrhizus biomass could be a potential biomaterial for the removal of azo dyes from aqueous dye solution.

Physical aging of linear and network epoxy resins

NASA Technical Reports Server (NTRS)

Kong, E. S.-W.; Wilkes, G. L.; Mcgrath, J. E.; Banthia, A. K.; Mohajer, Y.; Tant, M. R.

1981-01-01

Network and linear epoxy resins principally based on the diglycidyl ether of bisphenol-A and its oligomers are prepared and studied using diamine and anhydride crosslinking agents. Rubber modified epoxies and a carbon fiber reinforced composite are also investigated. All materials display time-dependent changes when stored at temperatures below the glass transition temperature after quenching (sub-T/g/ annealing). Solvent sorption experiments initiated after different sub-T(g) annealing times demonstrate that the rate of solvent uptake can be indirectly related to the free volume of the epoxy resins. Residual thermal stresses and water are found to have little effect on the physical aging process, which affects the sub-T(g) properties of uniaxial carbon fiber reinforced epoxy material. Finally, the importance of the recovery phenomenon which affects the durability of epoxy glasses is considered.

Use of biomass sorbents for oil removal from gas station runoff.

PubMed

Khan, Eakalak; Virojnagud, Wanpen; Ratpukdi, Thunyalux

2004-11-01

The use of biomass sorbents, which are less expensive and more biodegradable than synthetic sorbents, for oil removal from gas station runoff was investigated. A bench-scale flume experiment was conducted to evaluate the oil removal and retention capabilities of the biomass sorbents which included kapok fiber, cattail fiber, Salvinia sp., wood chip, rice husk, coconut husk, and bagasse. Polyester fiber, a commercial synthetic sorbent, was also experimented for comparison purpose. Oil sorption and desorption tests were performed at a water flow rate of 20 lmin-1. In the oil sorption tests, a 50 mgl(-1) of used engine oil-water mixture was synthesized to simulate the gas station runoff. The mass of oil sorbed for all sorbents, except coconut husk and bagasse, was greater than 70%. Cattail fiber and polyester fiber were the sorbents that provided the least average effluent oil concentrations. Oil selectivity (hydrophobic properties) and physical characteristics of the sorbents are the two main factors that influence the oil sorption capability. The used sorbents from the sorption tests were employed in the desorption tests. Results indicated that oil leached out of all the sorbents tested. Polyester fiber released the highest amount of oil, approximately 4% (mass basis) of the oil sorbed. copyright 2004 Elsevier Ltd.

Sorption of water alkalinity and hardness from high-strength wastewater on bifunctional activated carbon: process optimization, kinetics and equilibrium studies.

PubMed

Amosa, Mutiu K

2016-08-01

Sorption optimization and mechanism of hardness and alkalinity on bifunctional empty fruit bunch-based powdered activation carbon (PAC) were studied. The PAC possessed both high surface area and ion-exchange properties, and it was utilized in the treatment of biotreated palm oil mill effluent. Batch adsorption experiments designed with Design Expert(®) were conducted in correlating the singular and interactive effects of the three adsorption parameters: PAC dosage, agitation speed and contact time. The sorption trends of the two contaminants were sequentially assessed through a full factorial design with three factor interaction models and a central composite design with polynomial models of quadratic order. Analysis of variance revealed the significant factors on each design response with very high R(2) values indicating good agreement between model and experimental values. The optimum operating conditions of the two contaminants differed due to their different regions of operating interests, thus necessitating the utility of desirability factor to get consolidated optimum operation conditions. The equilibrium data for alkalinity and hardness sorption were better represented by the Langmuir isotherm, while the pseudo-second-order kinetic model described the adsorption rates and behavior better. It was concluded that chemisorption contributed majorly to the adsorption process.

Sorption and retention of diclofenac on zeolite in the presence of cationic surfactant.

PubMed

Sun, Ken; Shi, Yan; Wang, Xiaoyu; Li, Zhaohui

2017-02-05

Diclofenac (DC) is one of the most widely prescribed non-steroidal anti-inflammatory drugs and one of the commonly found pharmaceuticals in aquatic environments and wastewater treatment plants. It possesses negative charges when solution pH is greater than its pKa value, while most of the soil components and sediment minerals bear negative charges, too, resulting in a net repulsion between the soil minerals and DC. Surfactant-modified zeolite (SMZ) has been studied extensively over the last 20 years for its effective removal of anionic contaminants tested under different experimental scales. However, its application for the removal of anionic drugs, such as DC, was less reported. This study focused on the sorption of DC by SMZ under different physic-chemical conditions, supplemented with instrumental analyses, in order to elucidate the mechanism of DC sorption by SMZ and to expand the SMZ application further. The results showed that the retention of DC was on the external surfaces of SMZ with extremely fast removal rate. Both anion exchange and partitioning of DC into the adsorbed surfactant micelles (admicelles) were responsible for the extended DC sorption. Interactions of DC with SMZ were facilitated with the benzene ring, the CO, and the CH 2 CH 3 functional groups. Copyright © 2016 Elsevier B.V. All rights reserved.

Transport of sulfadiazine in soil columns — Experiments and modelling approaches

NASA Astrophysics Data System (ADS)

Wehrhan, Anne; Kasteel, Roy; Simunek, Jirka; Groeneweg, Joost; Vereecken, Harry

2007-01-01

Antibiotics, such as sulfadiazine, reach agricultural soils directly through manure of grazing livestock or indirectly through the spreading of manure or sewage sludge on the field. Knowledge about the fate of antibiotics in soils is crucial for assessing the environmental risk of these compounds, including possible transport to the groundwater. Transport of 14C-labelled sulfadiazine was investigated in disturbed soil columns at a constant flow rate of 0.26 cm h - 1 near saturation. Sulfadiazine was applied in different concentrations for either a short or a long pulse duration. Breakthrough curves of sulfadiazine and the non-reactive tracer chloride were measured. At the end of the leaching period the soil concentration profiles were determined. The peak maxima of the breakthrough curves were delayed by a factor of 2 to 5 compared to chloride and the decreasing limbs are characterized by an extended tailing. However, the maximum relative concentrations differed as well as the eluted mass fractions, ranging from 18 to 83% after 500 h of leaching. To identify relevant sorption processes, breakthrough curves of sulfadiazine were fitted with a convective-dispersive transport model, considering different sorption concepts with one, two and three sorption sites. Breakthrough curves can be fitted best with a three-site sorption model, which includes two reversible kinetic and one irreversible sorption site. However, the simulated soil concentration profiles did not match the observations for all of the used models. Despite this incomplete process description, the obtained results have implications for the transport behavior of sulfadiazine in the field. Its leaching may be enhanced if it is frequently applied at higher concentrations.

Raw or incubated olive-mill wastes and its biotransformed products as agricultural soil amendments-effect on sorption-desorption of triazine herbicides.

PubMed

Delgado-Moreno, Laura; Almendros, Gonzalo; Peña, Aránzazu

2007-02-07

Raw olive-mill waste and soil amendments obtained from their traditional composting or vermicomposting were added, at rates equivalent to 200 Mg ha-1, to a calcareous silty clay loam soil in a laboratory test, in order to improve its fertility and physicochemical characteristics. In particular, the effects on the sorption-desorption processes of four triazine herbicides have been examined. We found that comparatively hydrophobic herbicides terbuthylazine and prometryn increased their retention on amended soil whereas the more polar herbicides simazine and cyanazine were less affected. Soil application of olive cake, without transformation, resulted in the highest herbicide retention. Its relatively high content in aliphatic fractions and lipids could explain the increased herbicide retention through hydrophobic bonding and herbicide diffusion favored by poorly condensed macromolecular structures. On the other hand, the condensed aromatic structure of the compost and vermicompost from olive cake could hinder diffusion processes, resulting in lower herbicide sorption. In fact, the progressive humification in soil of olive-mill solid waste led to a decrease of sorption capacity, which suggested important changes in organic matter quality and interactions during the mineralization process. When soil amended with vermicompost was incubated for different periods of time, the enhanced herbicide sorption capacity persisted for 2 months. Pesticide desorption was reduced by the addition of fresh amendments but was enhanced during the transformation process of amendments in soil. Our results indicate the potential of soil amendments based on olive-mill wastes in the controlled, selective release of triazine herbicides, which varies depending on the maturity achieved by their biological transformation.

Selectivity sequences and sorption capacities of phosphatic clay and humus rich soil towards the heavy metals present in zinc mine tailing.

PubMed

Chaturvedi, Pranav Kumar; Seth, Chandra Shekhar; Misra, Virendra

2007-08-25

Sorption efficacy of phosphatic clay and humus rich soil alone and on combination were tested towards heavy metals present in zinc mine tailing (Zawar Zinc Mine), Udaipur (India). Characterization of the zinc mine tailing sample indicated the presence of Pb, Cu, Zn and Mn in the concentration of 637, 186, 720 and 577microg(-1), respectively. For sorption efficacy, the zinc mine tailing soil were properly amended with phosphatic clay and humus rich soil separately and in combination and leachability study was performed by batch experiment at different pH range from 3 to 9. The data showed that the percent leachability of heavy metal in non-amended soil was 75-90%. After amendment with phosphatic clay percent leachability of heavy metals became 35-45%. Further, the addition of humus soil to phosphatic clay decreased the percent leachability up to 5-15% at all tested pH. Column leachability experiment was performed to evaluate the rate of leachability. The shape of cumulative curves of Pb, Cu, Zn and Mn showed an increase in its concavity in following order: PbCu>Zn>Mn. Further, Langmuir isotherms applied for the sorption studies indicated that phosphatic clay in the presence of humus soil had high affinity for Pb followed by Cu, Zn and Mn, with sorption capacities (b) 139.94, 97.02, 83.32 and 67.58microgg(-1), respectively.

pH-dependent biotransformation of ionizable organic micropollutants in activated sludge.

PubMed

Gulde, Rebekka; Helbling, Damian E; Scheidegger, Andreas; Fenner, Kathrin

2014-12-02

Removal of micropollutants (MPs) during activated sludge treatment can mainly be attributed to biotransformation and sorption to sludge flocs, whereby the latter process is known to be of minor importance for polar organic micropollutants. In this work, we investigated the influence of pH on the biotransformation of MPs with cationic-neutral speciation in an activated sludge microbial community. We performed batch biotransformation, sorption control, and abiotic control experiments for 15 MPs with cationic-neutral speciation, one control MP with neutral-anionic speciation, and two neutral MPs at pHs 6, 7, and 8. Biotransformation rate constants corrected for sorption and abiotic processes were estimated from measured concentration time series with Bayesian inference. We found that biotransformation is pH-dependent and correlates qualitatively with the neutral fraction of the ionizable MPs. However, a simple speciation model based on the assumption that only the neutral species is efficiently taken up and biotransformed by the cells tends to overpredict the effect of speciation. Therefore, additional mechanisms such as uptake of the ionic species and other more complex attenutation mechanisms are discussed. Finally, we observed that the sorption coefficients derived from our control experiments were small and showed no notable pH-dependence. From this we conclude that pH-dependent removal of polar, ionizable organic MPs in activated sludge systems is less likely an effect of pH-dependent sorption but rather of pH-dependent biotransformation. The latter has the potential to cause marked differences in the removal of polar, ionizable MPs at different operational pHs during activated sludge treatment.

The use of inverse gas chromatography and gravimetric vapour sorption to study transitions in amorphous lactose.

PubMed

Ambarkhane, Ameet V; Pincott, Kim; Buckton, Graham

2005-04-27

The aim of this study was to measure the glass transition of amorphous lactose under well-controlled temperature and humidity, using inverse gas chromatography (IGC) and to relate these data to gravimetric vapour sorption experiments. Amorphous lactose (spray-dried) was exposed to a stepwise increment in the relative humidity (%RH) under isothermal conditions in an IGC. At the end of each conditioning step a decane injection was made, and the retention volumes were calculated using the maximum peak height (V(max)) method. The pressure drop across the column was recorded using the pressure transducers. These measurements were performed at various temperatures from 25 to 40 degrees C. The extent of water sorption at identical humidity (%RH) and temperature conditions was determined gravimetrically using dynamic vapour sorption (DVS). At each T, it was possible to determine: (1) a transition at low RH relating to the onset of mobility; (2) changes in retention volume relating to the point, where T(g) = T; (3) changes in pressure drop, which were related to the sample collapse. The rate and extent of water sorption was seen to alter at T(g) and also at a collapse point. Combinations of temperature and critical %RH (%cRH required to lower the dry glass transition temperature to the experimental temperature) obtained from IGC were comparable to those obtained from DVS. It was shown that at each T, the sample spontaneously crystallised, when T(g) was 32 degrees C below T. Inverse gas chromatograph can be used in this novel way to reveal the series of transitions that occur in amorphous materials.

Sorption-desorption of carbamazepine by palygorskite-montmorillonite (PM) filter medium.

PubMed

Berhane, Tedros M; Levy, Jonathan; Krekeler, Mark P S; Danielson, Neil D; Stalcup, Apryll

2015-01-23

Palygorskite-montmorillonite (PM) was studied as a potential sewage treatment effluent filter material for carbamazepine. Batch sorption experiments were conducted as a function of granule size (0.3-0.6, 1.7-2.0 and 2.8mm) and different sewage effluent conditions (pH, ionic strength and temperature). Results showed PM had a mix of fibrous and plate-like morphologies. Sorption and desorption isotherms were fitted to the Freundlich model. Sorption is granule size-dependent and the medium granule size would be an appropriate size for optimizing both flow and carbamazepine retention. Highest and lowest sorption capacities corresponded to the smallest and the largest granule sizes, respectively. The lowest and the highest equilibrium aqueous (Ce) and sorbed (qe) carbamazepine concentrations were 0.4 mg L(-1) and 4.5 mg L(-1), and 0.6 mg kg(-1) and 411.8 mg kg(-1), respectively. Observed higher relative sorption at elevated concentrations with a Freundlich exponent greater than one, indicated cooperative sorption. The sorption-desorption hysteresis (isotherm non-singularity) indicated irreversible sorption. Higher sorption observed at higher rather than at lower ionic strength conditions is likely due to a salting-out effect. Negative free energy and the inverse sorption capacity-temperature relationship indicated the carbamazepine sorption process was favorable or spontaneous. Solution pH had little effect on sorption. Copyright © 2014 Elsevier B.V. All rights reserved.

Sorption and Release of Organics by Primary, Anaerobic, and Aerobic Activated Sludge Mixed with Raw Municipal Wastewater

PubMed Central

Modin, Oskar; Saheb Alam, Soroush; Persson, Frank; Wilén, Britt-Marie

2015-01-01

New activated sludge processes that utilize sorption as a major mechanism for organics removal are being developed to maximize energy recovery from wastewater organics, or as enhanced primary treatment technologies. To model and optimize sorption-based activated sludge processes, further knowledge about sorption of organics onto sludge is needed. This study compared primary-, anaerobic-, and aerobic activated sludge as sorbents, determined sorption capacity and kinetics, and investigated some characteristics of the organics being sorbed. Batch sorption assays were carried out without aeration at a mixing velocity of 200 rpm. Only aerobic activated sludge showed net sorption of organics. Sorption of dissolved organics occurred by a near-instantaneous sorption event followed by a slower process that obeyed 1st order kinetics. Sorption of particulates also followed 1st order kinetics but there was no instantaneous sorption event; instead there was a release of particles upon mixing. The 5-min sorption capacity of activated sludge was 6.5±10.8 mg total organic carbon (TOC) per g volatile suspend solids (VSS) for particulate organics and 5.0±4.7 mgTOC/gVSS for dissolved organics. The observed instantaneous sorption appeared to be mainly due to organics larger than 20 kDa in size being sorbed, although molecules with a size of about 200 Da with strong UV absorbance at 215–230 nm were also rapidly removed. PMID:25768429

Unraveling adsorption behavior and mechanism of perfluorooctane sulfonate (PFOS) on aging aquatic sediments contaminated with engineered nano-TiO2.

PubMed

Qian, Jin; Li, Kun; Wang, Peifang; Wang, Chao; Liu, Jingjing; Tian, Xin; Lu, Bianhe; Guan, Wenyi

2018-04-20

Engineered nano-TiO 2 (Enano-TiO 2 ) have inevitably discharged into aquatic sediments that resulted from their widespread use. The physicochemical characteristics of sediments might be changed because of remarkable properties of Enano-TiO 2 and affected by the aging of sediments, thereby altering the environmental behavior and bioavailability of other pollutants such as perfluorooctane sulfonate (PFOS) in sediments. Here, adsorption behavior and mechanism of PFOS on aging aquatic sediments spiked with Enano-TiO 2 at a weight ratio of 5.0% were investigated. The results showed that Enano-TiO 2 significantly altered zero points of charge (pH zpc ) and pore surface properties of sediments, manifested as pH zpc , the total surface area (S BET ), the micro-pore surface area (S micro ), and the external surface area (S ext ) of sediment particles contaminated with Enano-TiO 2 clearly increased, instead average pore size decreased. Rapid intra-particle diffusion processes were well fitted by the pseudo-second-order rate model with the sorption rate (K 2 ) following the order single (5.764 mg/(g·h)) > binary systems (3.393 mg/(g·h)). Freundlich model best described the sorption isotherm data with the larger sorption capacity (K F ) and sorption affinity (1/n) of sediments spiked with Enano-TiO 2 than that of sediments only. Additionally, Enano-TiO 2 changed the adsorption thermodynamics of PFOS on the sediments with the absolute value of ∆G 0 , ∆H 0 , and ∆S 0 increased. Fourier transform infrared (FT-IR) spectroscopy suggested possible formation of a negative charge-assisted H-bond between PFOS and the functionalities on sediment surfaces, including O-H of carboxyl, alcohol, phenols, and chemisorbed H 2 O as well as carbonyl groups (C=O) of ketone groups. Furthermore, the multilayer sorption of PFOS on sediments contaminated with Enano-TiO 2 is plausible because of bridging effect of Cu 2+ and Pb 2+ .

Polyvinyl alcohol-based nanocomposite hydrogels containing magnetic laponite RD to remove cadmium.

PubMed

Mola Ali Abasiyan, Sara; Mahdavinia, Gholam Reza

2018-05-01

In this study, magnetic nanocomposite hydrogels based on polyvinyl alcohol were synthesized. Magnetic polyvinyl alcohol/laponite RD (PVA-mLap) nanocomposites were characterized by scanning electron microscopy, X-ray diffraction, transmission electron microscopy, and Fourier transform infrared spectroscopy. The results indicated that PVA-mLap had desirable magnetic-sorption properties and magnetic-laponite nanoparticles were successfully synthesized and added to polyvinyl alcohol. The present nanocomposites were applied to remove Cd 2+ from aqueous solution. The influence of initial Cd 2+ concentration, magnetic-laponite concentration, pH, and ionic strength on adsorption isotherm was investigated. Heterogeneity of adsorption sites was intensified by increasing magnetic concentration of adsorbents and by rising pH value. Results of ionic strength studies indicated that by increasing ionic strength more than four times, the adsorption of Cd 2+ has only decreased around 15%. According to the results, the dominant mechanism of Cd 2+ sorption by the present adsorbents was determined chemical and specific sorption. Therefore, the use of the present nanocomposites as a powerful adsorbent of Cd 2+ in the wastewater treatment is suggested. Isotherm data were described by using Freundlich and Langmuir models, and better fitting was introduced Langmuir model.

Banana peel: a green and economical sorbent for the selective removal of Cr(VI) from industrial wastewater.

PubMed

Memon, Jamil R; Memon, Saima Q; Bhanger, Muhammad I; El-Turki, Adel; Hallam, Keith R; Allen, Geoffrey C

2009-05-01

This study describes the use of banana peel, a commonly produced fruit waste, for the removal of Cr(VI) from industrial wastewater. The parameters pH, contact time, initial metal ion concentration, and temperature were investigated and the conditions resulting in rapid and efficient adsorption (95% within 10 min) were determined. The binding of metal ions was found to be pH dependent with the optimal sorption occurring at pH 2. The retained species were eluted with 5 mL of 2M H(2)SO(4). To elucidate the mechanism of the process, total amounts of chromium and Cr(VI) were analyzed using flame atomic absorption and ultraviolet-visible (UV-vis) spectroscopic techniques, respectively. The Langmuir and Dubinin-Radushkevich (D-R) isotherms were used to describe the partitioning behavior for the system at different temperatures. Kinetics and thermodynamics of Cr(VI) removal by banana peel were also studied. The influence of diverse ions on the sorption behavior revealed that only Fe(II) ions (of those tested) suppressed the sorption of Cr(VI) ions to some extent. The method was applied for the removal of Cr(VI) from industrial wastewater.

Effect of Time-Dependent Sorption on the Dissipation of Water-Extractable Pesticides in Soils.

PubMed

Motoki, Yutaka; Iwafune, Takashi; Seike, Nobuyasu; Inao, Keiya; Otani, Takashi

2016-06-08

The dissipation behavior of water-extractable pesticides in soils is important when assessing the phytoavailability of pesticides in soils. This process is less understood than pesticide extraction with organic solvents. To elucidate the dissipation behavior of water-extractable pesticides in soils, we conducted an incubation study using 27 pesticides and five Japanese soils. The rate of decrease of the level of pesticides in water extracts was faster in soils than that of total extracts (water extracts and acetone extracts). This suggests that time-dependent sorption contributed to the difference in the dissipation between the pesticides in water and total extracts from soils. Increased apparent sorption coefficients (Kd,app) with time were positively and significantly correlated with Kd,app values of a 0 day incubation [Kd,app(t0)]. This empirical relationship suggests that Kd,app(t0) values can predict the time-dependent increase in Kd,app and the dissipation of water-extractable pesticides in soils.

Conservative and reactive solute transport in constructed wetlands

USGS Publications Warehouse

Keefe, Steffanie H.; Barber, Larry B.; Runkel, Robert L.; Ryan, Joseph N.; McKnight, Diane M.; Wass, Roland D.

2004-01-01

The transport of bromide, a conservative tracer, and rhodamine WT (RWT), a photodegrading tracer, was evaluated in three wastewater‐dependent wetlands near Phoenix, Arizona, using a solute transport model with transient storage. Coupled sodium bromide and RWT tracer tests were performed to establish conservative transport and reactive parameters in constructed wetlands with water losses ranging from (1) relatively impermeable (15%), (2) moderately leaky (45%), and (3) significantly leaky (76%). RWT first‐order photolysis rates and sorption coefficients were determined from independent field and laboratory experiments. Individual wetland hydraulic profiles influenced the extent of transient storage interaction in stagnant water areas and consequently RWT removal. Solute mixing and transient storage interaction occurred in the impermeable wetland, resulting in 21% RWT mass loss from main channel and storage zone photolysis (10%) and sorption (11%) reactions. Advection and dispersion governed solute transport in the leaky wetland, limiting RWT photolysis removal (1.2%) and favoring main channel sorption (3.6%). The moderately leaky wetland contained islands parallel to flow, producing channel flow and minimizing RWT losses (1.6%).

On the role of humic acids' carboxyl groups in the binding of charged organic compounds.

PubMed

Smilek, Jiří; Sedláček, Petr; Kalina, Michal; Klučáková, Martina

2015-11-01

Interactions of humic acids (HAs) with two cationic dyes (methylene blue and rhodamine 6G) were studied using a unique combination of diffusion and partitioning studies in HAs, containing hydrogels and batch sorption experiments. In order to investigate the involvement of carboxyl groups of HAs in these interactions, all experiments were performed for both, the original lignite HAs and HAs with selectively methylated carboxyls. The results of the diffusion experiments confirm that the interactions between the solute and humic substances have a strong impact on the rate of diffusion process. Surprisingly, the effect is almost equally approved for original and methylated HAs. On the other hand, the results of batch sorption experiments show strong improvement of the sorption capacity (methylated HAs), which is explained by changed morphology of alkylated HAs. The comparison of the results of diffusion and adsorption experiments shows that the diffusion experiments simulate the transport of solutes in natural humics containing environment more reasonably. Copyright © 2015 Elsevier Ltd. All rights reserved.

Sorption of radionuclides by cement-based barrier materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Kefei, E-mail: likefei@tsinghua.edu.cn; Pang, Xiaoyun

2014-11-15

This paper investigates the sorption of radionuclide ions, {sup 137}Cs{sup +} and {sup 90}Sr{sup 2+}, by cement-based barrier materials for radioactive waste disposal. A mortar with ternary binder is prepared and powder samples are ground from the hardened material following a predetermined granulometry. After pre-equilibrium with an artificial pore solution, the sorption behaviors of powder samples are investigated through single sorption and blended sorption. The results show that: (1) no systematic difference is observed for single and blended sorptions thus the interaction between {sup 137}Cs{sup +} and {sup 90}Sr{sup 2+} sorptions must be weak; (2) the sorption kinetics is rapidmore » and all characteristic times are less than 1d; (3) the sorption capacity is enhanced by C–A–S–H hydrates and the measured K{sub d} values can be predicted from C–S–H sorption data with Ca/Si ratio equal to Ca/(Si + Al) ratio.« less

Novel biosynthesized silver nanoparticles from cobweb as adsorbent for Rhodamine B: equilibrium isotherm, kinetic and thermodynamic studies

NASA Astrophysics Data System (ADS)

Azeez, Luqmon; Lateef, Agbaje; Adebisi, Segun A.; Oyedeji, Abdulrasaq O.

2018-03-01

This study has investigated the adsorption of Rhodamine B (Rh-B) dye on novel biosynthesized silver nanoparticles (AgNPs) from cobweb. The effects of contact time, initial pH, initial dye concentration, adsorbent dosage and temperature were studied on the removal of Rh-B and they significantly affected its uptake. Adsorption isotherms were evaluated using Langmuir, Freundlich, Temkin and Dubinin-Radushkevich isotherm models. The adsorption process was best described by Langmuir isotherm with R 2 of 0.9901, indicating monolayer adsorption. The maximum adsorption capacity ( q max) of 59.85 mg/g showed that it has relatively high performance, while adsorption intensity showed a favourable adsorption process. Pseudo-second-order kinetics fitted best the rate of adsorption and intra-particle diffusion revealed both surface adsorption and intra-particle diffusion-controlled adsorption process. Negative values of thermodynamic parameters (Δ H°, Δ S° and Δ G°) indicated an exothermic and spontaneous adsorption process. The mean sorption energy ( E) and activation energy ( E a) suggested the uptake of Rh-B onto AgNPs was chemical in nature (chemosorption).

Biosorption of Cd(II) and Cs(I) from aqueous solution by live and dead cells of Saccharomyces carlsbergensis PTCC 5051.

PubMed

Sayyadi, Shayan; Ahmady-Asbchin, Salman; Kamali, Kasra

2018-02-01

The biosorption characteristics of Cd(II) and Cs(I) using live and dead cells of Saccharomyces carlsbergensis PTCC 5051 as biosorbents have been investigated in the present research. The influence of different experimental parameters such as initial pH (pHi), shaking rate, sorption time and initial metal concentration was evaluated. The optimum pH was obtained as 4 for Cd(II) and 7 for Cs(I). The experimental adsorption data were fitted to the Langmuir linear equation adsorption model. The highest metal uptake values of 0.593 and 0.473 mmol g -1 were calculated for Cd(II) and Cs(I), respectively. The results of Fourier transform infrared analysis suggested the involvement of amine, carboxyl and hydroxyl groups during the biosorption process and also indicated that more functional groups were involved in the biosorption process of live adsorbents, compared with those linked to dead biomass. The results showed that the biomass of S. carlsbergensis PTCC 5051 is a suitable biosorbent for the removal of Cd(II) and Cs(I) from the aqueous solutions.

Effect of Cosolutes on the Sorption of Phenanthrene onto Mineral Surface of River Sediments and Kaolinite

PubMed Central

2014-01-01

Sorption of phenanthrene onto the natural sediment with low organic carbon content (OC%), organic-free sediment, and kaolinite was investigated through isotherm experiments. Effects of cosolutes (pyrene, 4-n-nonyphenol (NP), and humic acid (HA)) on phenanthrene sorption were also studied by comparing apparent solid-water distribution coefficients (K d app) of phenanthrene. Two addition sequences, including “cosolute added prior to phenanthrene” and “cosolute and phenanthrene added simultaneously,” were adopted. The Freundlich model fits phenanthrene sorption on all 3 sorbents well. The sorption coefficients on these sorbents were similar, suggesting that mineral surface plays an important role in the sorption of hydrophobic organic contaminants on low OC% sediments. Cosolutes could affect phenanthrene sorption on the sorbents, which depended on their properties, concentrations, and addition sequences. Pyrene inhibited phenanthrene sorption. Sorbed NP inhibited phenanthrene sorption at low levels and promoted sorption at high levels. Similar to NP, effect of HA on phenanthrene sorption onto the natural sediment depended on its concentrations, whereas, for the organic-free sediment and kaolinite, preloading of HA at high levels led to an enhancement in phenanthrene K d app while no obvious effect was observed at low HA levels; dissolved HA could inhibit phenanthrene sorption on the two sorbents. PMID:25147865

The Effect of Pressure and Organic Constituents on the Cesium Ion Exchange Performance of IONSIV IE-911

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fondeur, F.F.

2000-07-18

This study examined cesium ({sup 137}Cs) ion exchange of crystalline silicotitanate (CST) in simulated waste solution. In particular, the study focused on the effect of CST pretreatment on the kinetics and extent of cesium adsorption. The test used IONSIV{reg_sign}IE-911 (UOP LLC, Molecular Sieves Division, Des Plaines, IL), the engineered form of CST. Pretreatment steps examined include: soaking CST in 2M NaOH solution for three days, exposing CST to 50% relative humidity for one week, flowing organic-containing (saturated) salt solution through a CST packed bed (at 5 cm/min. superficial velocity), or drying CST in air at 100 C for three days.more » Some tests occurred under 50 and 25 psig of argon. The following conclusions summarize the results. Pretreatment of IE-911 in organic-containing (e.g., tri-n-butyl phosphate, dibutylphosphate, butanol, paraffin and Dow Corning H-10 defoamer) simulated waste or simulated waste yielded a 83% slower rate of cesium adsorption and 56% lower cesium capacity after one week. Pretreatment of IE-911 in 2M caustic solution for 48 hours yielded a slower approach to equilibrium cesium distribution in batch contact tests--7.7 mL/(g*h) during the first 48 hours and 2.4 ml/(g*h) thereafter. Carboxylates and adsorbed carbonates inside the pores likely affect the cesium transport by either increasing the path-length or reducing mass transfer rate. Heating IE-911 as received from the vendor at 100 C for 24 hours significantly degraded its cesium removal performance by a 40.7% reduction in capacity and 43% reduction in sorption rate over one week of testing. Testing determined nearly identical distribution coefficients K{sub d} between lot {number_sign} 9990-9681-0004 and 9990-9881-0005 (i.e., difference of only 5.6%). Tests measuring water insertion rates into IE-911 show that hydration of the IE-911 does not appear to limit the rate of cesium sorption. Increasing the atmospheric pressure from 0 to 50 psig had no effect on cesium sorption. Note that lower apparent capacity or slower cesium sorption rate in these limited-duration batch contact tests as a result of pretreatment do not necessarily imply reduced dynamic performance in a flowing ion-exchange application. The experiments that provided the bases for the currently proposed facility design used caustic-pretreated IE-911. Another report will assess whether the presence of the organic compounds in the waste solution impeded column performance.« less

Sorption of Metal Ions on Clay Minerals.

PubMed

Schlegel; Charlet; Manceau

1999-12-15

The mechanism of Co uptake from aqueous solution onto hectorite (a magnesian smectite) and its impact on the stability of this clay mineral were investigated as a function of Co concentration (TotCo = 20 to 200 µM, 0.3 M NaNO(3)) and ionic strength (0.3 and 0.01 M NaNO(3), TotCo = 100 µM) by combining kinetics measurements and Co K-edge extended X-ray absorption fine structure (EXAFS) spectroscopy. The morphology of the sorbent phase was characterized by atomic force microscopy (AFM) and consists of lath-type particles bounded by large basal planes and layer edges. At low ionic strength (0.01 M NaNO(3)), important Co uptake occurred within the first 5 min of reaction, consistent with Co adsorption on exchange sites of hectorite basal planes. Thereafter, the sorption rate dramatically decreased. In contrast, at high ionic strength (0.3 M NaNO(3)), Co uptake rate was much slower within the first 5 min and afterward higher than at 0.01 M NaNO(3), consistent with Co adsorption on specific surface sites located on the edges of hectorite. Time-dependent isotherms for Co uptake at high ionic strength indicated the existence of several sorption mechanisms having distinct equilibration times. The dissolution of hectorite was monitored before and after Co addition. A congruent dissolution regime was observed prior to Co addition. Just after Co addition, an excess release of Mg relatively to congruent dissolution rates occurred at both high and low ionic strengths. At high ionic strength, this excess release nearly equaled the amount of sorbed Co. The dissolution rate of hectorite then decreased at longer Co sorption times. EXAFS spectra of hectorite reacted with Co at high and low ionic strengths and for reaction times longer than 6 h, exhibited similar features, suggesting that the local structural environments of Co atoms are similar. Spectral simulations revealed the occurrence of approximately 2 Mg and approximately 2 Si neighboring cations at interatomic distances characteristic of edge-sharing linkages between Co and Mg octahedra and corner-sharing linkages between Co octahedra and Si tetrahedra, respectively. This local structure is characteristic of inner sphere mononuclear surface complexes at layer edges of hectorite platelets. The occurrence of these complexes even at low ionic strength apparently conflicts with kinetics results, as exchangeable divalent cations are known to form outer sphere surface complexes. To clarify this issue, the amount of Co adsorbed on exchange sites was calculated from the solute Co concentration, assuming that cation exchange was always at equilibrium. These calculations showed that sorbed Co was transferred within 48 h from exchange sites to edge sorption sites. Copyright 1999 Academic Press.

Modeling Fission Product Sorption in Graphite Structures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Szlufarska, Izabela; Morgan, Dane; Allen, Todd

2013-04-08

The goal of this project is to determine changes in adsorption and desorption of fission products to/from nuclear-grade graphite in response to a changing chemical environment. First, the project team will employ principle calculations and thermodynamic analysis to predict stability of fission products on graphite in the presence of structural defects commonly observed in very high- temperature reactor (VHTR) graphites. Desorption rates will be determined as a function of partial pressure of oxygen and iodine, relative humidity, and temperature. They will then carry out experimental characterization to determine the statistical distribution of structural features. This structural information will yield distributionsmore » of binding sites to be used as an input for a sorption model. Sorption isotherms calculated under this project will contribute to understanding of the physical bases of the source terms that are used in higher-level codes that model fission product transport and retention in graphite. The project will include the following tasks: Perform structural characterization of the VHTR graphite to determine crystallographic phases, defect structures and their distribution, volume fraction of coke, and amount of sp2 versus sp3 bonding. This information will be used as guidance for ab initio modeling and as input for sorptivity models; Perform ab initio calculations of binding energies to determine stability of fission products on the different sorption sites present in nuclear graphite microstructures. The project will use density functional theory (DFT) methods to calculate binding energies in vacuum and in oxidizing environments. The team will also calculate stability of iodine complexes with fission products on graphite sorption sites; Model graphite sorption isotherms to quantify concentration of fission products in graphite. The binding energies will be combined with a Langmuir isotherm statistical model to predict the sorbed concentration of fission products on each type of graphite site. The model will include multiple simultaneous adsorbing species, which will allow for competitive adsorption effects between different fission product species and O and OH (for modeling accident conditions).« less

Fixed bed sorption of phosphorus from wastewater using iron oxide-based media derived from acid mine drainage

USGS Publications Warehouse

Sibrell, Philip L.; Tucker, T.W.

2012-01-01

Phosphorus (P) releases to the environment have been implicated in the eutrophication of important water bodies worldwide. Current technology for the removal of P from wastewaters consists of treatment with aluminum (Al) or iron (Fe) salts, but is expensive. The neutralization of acid mine drainage (AMD) generates sludge rich in Fe and Al oxides that has hitherto been considered a waste product, but these sludges could serve as an economical adsorption media for the removal of P from wastewaters. Therefore, we have evaluated an AMD-derived media as a sorbent for P in fixed bed sorption systems. The homogenous surface diffusion model (HSDM) was used to analyze fixed bed test data and to determine the value of related sorption parameters. The surface diffusion modulus Ed was found to be a useful predictor of sorption kinetics. Values of Ed < 0.2 were associated with early breakthrough of P, while more desirable S-shaped breakthrough curves resulted when 0.2 < Ed < 0.5. Computer simulations of the fixed bed process with the HSDM confirmed that if Ed was known, the shape of the breakthrough curve could be calculated. The surface diffusion coefficient D s was a critical factor in the calculation of Ed and could be estimated based on the sorption test conditions such as media characteristics, and influent flow rate and concentration. Optimal test results were obtained with a relatively small media particle size (average particle radius 0.028 cm) and resulted in 96 % removal of P from the influent over 46 days of continuous operation. These results indicate that fixed bed sorption of P would be a feasible option for the utilization of AMD residues, thus helping to decrease AMD treatment costs while at the same time ameliorating the impacts of P contamination.

Estimation of biotransformation and sorption of emerging organic compounds (EOCs) during artificial recharge through a reactive barrier.

NASA Astrophysics Data System (ADS)

Valhondo, C.; Martinez-Landa, L.; Carrera, J.; Hidalgo, J. J.; Ayora, C.

2016-12-01

The reuse of lesser quality water such as effluents from wastewater treatment plants or effluent-receiving water bodies has been promoted due to the water shortages affecting many regions of the world. Artificial recharge through infiltration basins is known to improve several water quality parameters including the attenuation of emerging organic compounds (EOCs). Many of these contaminants exhibit redox dependent biotransformation because the redox state is one of the factors controlling microbial community development. Together with biotransformation, sorption also affects the behavior of EOCs in their passage through the soil. We studied EOCs attenuation in an infiltration system is located in Sant Vicenç dells Horts on the Llobregat delta (Barcelona, Spain), where the local water agency has an artificial recharge pilot project . The Llobregat river water used for the artificial recharge is affected by treatment plant effluents which contain EOCs. A reactive barrier consisting of vegetable compost, clay, and iron oxide was installed in the bottom of the infiltration basin to enhance biotransformation and sorption of EOCs. The barrier releases dissolved organic carbon, which favors the development of a broad range of redox environments, and supplies neutral, cationic, and anionic surfaces to favor sorption of different types of contaminants. Results were excellent, but quantitative evaluation of the EOCs attenuation requires knowledge of the residence time distribution of infiltrated water. A tracer test was performed by adding tracers to the infiltration water and interpreting the breakthrough curves at diverse monitoring points with a 2D multilayer numerical model. The calibrated model quantify degradation, as a first order law, and sorption through a linear distribution coefficient for ten selected EOCs. Results indicate higher degradation rates and sorption coefficients in the reactive barrier than in the rest of the aquifer for nine and eight of the ten studied EOCs, respectively, which demonstrates the efficiency of the reactive barrier to enhance the removal of EOCs.

Fate and Tranport of MTBE in Clay-Rich Materials

NASA Astrophysics Data System (ADS)

lenczewski, m e

2001-12-01

A recent report by the U.S. Geological Survey identified methyl tert-butyl ether (MTBE), a constituent of reformulated gasoline, as the most common contaminant of urban aquifers in the United States. MTBE has been released into groundwater supplies by leaking underground fuel tanks. In Illinois, it has been found in 26 of the 1,800 public water supplies and although detection was intermittent, levels were high enough to be offensive to users in some Illinois communities. MTBE is also being used in Mexico to solve the problem of air quality; however, it has the potential to harm the drinking water quality in the process. Early research on MTBE considered it resistant to biodegradation and unable to adsorb to soils and sediments. However, recent evidence indicates that biodegradation does occur under certain conditions and that sorption can occur to organic materials. This research project will investigate the biodegradation of MTBE and its sorption to the clay-rich glacial till found in northern Illinois and lacustrine clays found in the Chalco Basin, Mexico City, Mexico whose interaction with MTBE has not previously been studied. The principal hypothesis of this research is that the microorganisms and environmental factors in clay-rich materials will increase the biodegradation and sorption of MTBE as compared to sandy materials. The experiments will simulate a spill of MTBE or downgradient from a gasoline spill. Microcosms and batch isotherm experiments will be used to demonstrate the potential for biodegradation and sorption in these materials; however, laboratory results are not considered reliable estimates of actual field sorption and biodegradation rates. Therefore long-term column experiments will also be conducted in which large sample volumes of material that simulate the heterogeneities naturally observed in the environment. This research will increase understanding of the biodegradation and sorption of MTBE and lay the necessary groundwork to implement the optimal remediation method for sites contaminated by MTBE, helping to ensure a sustainable groundwater resource.

Simultaneous determination of the heat and the quantity of vapor sorption using a novel microcalorimetric method.

PubMed

Lehto, V P; Laine, E

2000-06-01

In this study, instrumentation for measuring vapor sorption enthalpies and sorption uptakes simultaneously with an isothermal microcalorimeter is introduced. Various pharmaceutical model substances undergoing phase transitions when exposed to humid conditions (25 degrees C), were employed to evaluate the usefulness and sensitivity of the constructed experimental method. The sample is placed in the sample vessel of a RH cell and the moisture content of the air flow is controlled. From the RH cell the air flow is conducted into a subsequent perfusion cell in which a saturated salt solution has been loaded. The RH cell and perfusion cells are positioned in the sample sides of two twin calorimetric units. Depending on the moisture content in the outlet flow leaving the preceding RH cell, the heat flow signal from the subsequent perfusion cell will vary. By means of blank measurement with identical settings, the rate of water sorption can be calculated and, by integration, the amount of sorbed water is obtained. Amorphous lactose and cefadroxil undergo recrystallization when the moisture level in the surroundings exceeds the threshold values specific to each compound. During the sorption phase, heat is evolved fairly linearly as a function of consumed moisture, and also after the recrystallization, the heats indicate linear behavior. The heat values for the desorption phase of amorphous lactose and the adsorption of crystalline lactose coincide. With the different anhydrous forms of theophylline, the hydration takes place more rapidly in the metastable form 1, and generally, the process is more energetic in form 1. In all cases, the gravimetric results agree with the water sorption uptakes calculated from the calorimetric data. The technique introduced offers a rapid and sensitive method to gain new insights into the transitions in which vapors are involved. In addition, different kinds of surfaces with various energetics can now be studied more closely.

Geochemical Fate and Transport of Diphenhydramine and Cetirizine in Soil

NASA Astrophysics Data System (ADS)

Wireman, R.; Rutherford, C. J.; Vulava, V. M.; Cory, W. C.

2015-12-01

Pharmaceuticals compounds presence in natural soils and water around the world has become a growing concern. These compounds are being discharged into the environment through treated wastewater or municipal sludge applications. The main goal of this study is determine their geochemical fate in natural soils. In this study we investigated sorption and transport behavior of diphenhydramine (DPH) and cetirizine (CTZ) in natural soils. These two commonly-used antihistamines are complex aromatic hydrocarbons with polar functional groups. Two clean acidic soils (pH~4.5) were used for these studies - an A-horizon soil that had higher organic matter content (OM, 7.6%) and a B-horizon soil that had lower OM (1.6%), but higher clay content (5.1%). Sorption isotherms were measured using batch reactor experiments. Data indicated that sorption was nonlinear and that it was stronger in clay-rich soils. The pKa's of DPH and CTZ are 8.98 and 8.27 respectively, i.e., these compounds are predominantly in cationic form at soil pH. In these forms, they preferentially sorb to negatively charged mineral surfaces (e.g., clay) present in the soils. Soil clay mineral characterization indicated that kaolinite was the dominant clay mineral present along with small amount of montmorillonite. The nonlinear sorption isotherms were fitted with Freundlich model. Transport behavior of both compounds was measured using glass chromatography columns. As expected both DPH and CTZ were strongly retained in the clay-rich soil as compared with OM-rich soil. The asymmetrical shape of the breakthrough curves indicated that there were likely two separate sorption sites in the soil, each with different reaction rates with each compound. A two-region advection-dispersion transport code was used to model the transport breakthrough curves. There was no evidence of transformation or degradation of the compounds during our sorption and transport studies.

Removal of selected pharmaceuticals from aqueous solution using magnetic chitosan: sorption behavior and mechanism.

PubMed

Zhang, Yalei; Shen, Zhe; Dai, Chaomeng; Zhou, Xuefei

2014-11-01

A novel-modified magnetic chitosan adsorbent was used to remove selected pharmaceuticals, i.e., diclofenac (DCF) and clofibric acid (CA) and carbamazepine (CBZ), from aqueous solutions. The characterization of magnetic chitosan was achieved by scanning electron and transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, vibrating sample magnetometer, and nitrogen sorption analysis. The magnetic chitosan had effective sorption affinity for DCF and CA but no sorption of CBZ was observed. The sorption capacities of CA and DCF in the individual solutions were 191.2 and 57.5 mg/g, respectively. While in mixed solution, DCF showed higher sorption affinity. Sorption kinetics indicated a quick equilibrium reached within 2 min. Lower solution pH values were found to be advantageous for the adsorption process. The sorption efficacy of CA declined significantly with increasing inorganic salt concentration. However, sorption performance of DCF was stable under different ionic strength conditions.

Soil-adjusted sorption isotherms for arsenic(V) and vanadium(V)

NASA Astrophysics Data System (ADS)

Rückamp, Daniel; Utermann, Jens; Florian Stange, Claus

2017-04-01

The sorption characteristic of a soil is usually determined by fitting a sorption isotherm model to laboratory data. However, such sorption isotherms are only valid for the studied soil and cannot be transferred to other soils. For this reason, a soil-adjusted sorption isotherm can be calculated by using the data of several soils. Such soil-adjusted sorption isotherms exist for cationic heavy metals, but are lacking for heavy metal oxyanions. Hence, the aim of this study is to establish soil-adjusted sorption isotherms for the oxyanions arsenate (arsenic(V)) and vanadate (vanadium(V)). For the laboratory experiment, 119 soils (samples from top- and subsoils) typical for Germany were chosen. The batch experiments were conducted with six concentrations of arsenic(V) and vanadium(V), respectively. By using the laboratory data, sorption isotherms for each soil were derived. Then, the soil-adjusted sorption isotherms were calculated by non-linear regression of the sorption isotherms with additional soil parameters. The results indicated a correlation between the sorption strength and oxalate-extractable iron, organic carbon, clay, and electrical conductivity for both, arsenic and vanadium. However, organic carbon had a negative regression coefficient. As total organic carbon was correlated with dissolved organic carbon; we attribute this observation to an effect of higher amounts of dissolved organic substances. We conclude that these soil-adjusted sorption isotherms can be used to assess the potential of soils to adsorb arsenic(V) and vanadium(V) without performing time-consuming sorption experiments.

Metal Ions Removal Using Nano Oxide Pyrolox™ Material

NASA Astrophysics Data System (ADS)

Gładysz-Płaska, A.; Skwarek, E.; Budnyak, T. M.; Kołodyńska, D.

2017-02-01

The paper presents the use of Pyrolox™ containing manganese nano oxides used for the removal of Cu(II), Zn(II), Cd(II), and Pb(II) as well as U(VI) ions. Their concentrations were analyzed using the atomic absorption spectrometer SpectrAA 240 FS (Varian) as well as UV-vis method. For this purpose the static kinetic and equilibrium studies were carried out using the batch technique. The effect of solution pH, shaking time, initial metal ion concentrations, sorbent dosage, and temperature was investigated. The equilibrium data were analyzed using the sorption isotherm models proposed by Freundlich, Langmuir-Freundlich, Temkin, and Dubinin-Radushkevich. The kinetic results showed that the pseudo second order kinetic model was found to correlate the experimental data well. The results indicate that adsorption of Cu(II), Zn(II), Cd(II), and Pb(II) as well as U(VI) ions is strongly dependent on pH. The value of pH 4-7 was optimal adsorption. The time to reach the equilibrium was found to be 24 h, and after this time, the sorption percentage reached about 70%. Kinetics of Cu(II), Zn(II), Cd(II), Pb(II), and U(VI) adsorption on the adsorbent can be described by the pseudo second order rate equation. Nitrogen adsorption/desorption, infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) measurements for adsorbent characterization were performed. Characteristic points of the double layer determined for the studied Pyrolox™ sample in 0.001 mol/dm3 NaCl solution are pHPZC = 4 and pHIEP < 2.

Assessing effects of aerobic and anaerobic conditions on phosphorus sorption and retention capacity of water treatment residuals.

PubMed

Oliver, Ian W; Grant, Cameron D; Murray, Robert S

2011-03-01

Water treatment residuals (WTRs) are the by-products of drinking water clarification processes, whereby chemical flocculants such as alum or ferric chloride are added to raw water to remove suspended clay particles, organic matter and other materials and impurities. Previous studies have identified a strong phosphorus (P) fixing capacity of WTRs which has led to experimentation with their use as P-sorbing materials for controlling P discharges from agricultural and forestry land. However, the P-fixing capacity of WTRs and its capacity to retain sorbed P under anaerobic conditions have yet to be fully demonstrated, which is an issue that must be addressed for WTR field applications. This study therefore examined the capacity of WTRs to retain sorbed P and sorb further additional P from aqueous solution under both aerobic and anaerobic conditions. An innovative, low cost apparatus was constructed and successfully used to rapidly establish anoxic conditions in anaerobic treatments. The results showed that even in treatments with initial solution P concentrations set at 100 mg l(-1), soluble reactive P concentrations rapidly fell to negligible levels (due to sorption by WTRs), while total P (i.e. dissolved + particulate and colloidal P) was less than 3 mg l(-1). This equated to an added P retention rate of >98% regardless of anaerobic or aerobic status, indicating that WTRs are able to sorb and retain P in both aerobic and anaerobic conditions. Copyright © 2010 Elsevier Ltd. All rights reserved.

The effect of the type of HA on the degradation of PLGA/HA composites.

PubMed

Naik, Ashutosh; Shepherd, David V; Shepherd, Jennifer H; Best, Serena M; Cameron, Ruth E

2017-01-01

The aim of this study is to explore the importance of the potentially competing effects of buffering effects of the calcium phosphate filler and particle-mediated water sorption on the degradation products of poly(d,l lactide-co-glycolide (50:50))(PLGA)/hydroxyapatite(HA) composites. Further the influence of type of HA on the mechanical properties of the composites was investigated. Phase pure HA was synthesised via a reaction between aqueous solutions of calcium hydroxide and orthophosphoric acid. The powder produced was either used as produced (uncalcined) or calcined in air or calcined in a humidified argon atmosphere. An in-vitro degradation study was carried out in phosphate buffered saline (PBS). The results obtained indicated that the degradation rate of the composite might be better understood if both the buffering effects and the rate of water sorption by the composites are considered. Copyright © 2016 Elsevier B.V. All rights reserved.

A Comparative Evaluation of Sorption, Solubility, and Compressive Strength of Three Different Glass Ionomer Cements in Artificial Saliva: An in vitro Study

PubMed Central

Bhatia, Hind P; Sood, Shveta; Sharma, Naresh

2017-01-01

Aim To evaluate and compare the sorption, solubility, and compressive strength of three different glass ionomer cements in artificial saliva - type IX glass ionomer cement, silver-reinforced glass ionomer cement, and zirconia-reinforced glass ionomer cement, so as to determine the material of choice for stress-bearing areas. Materials and methods A total of 90 cylindrical specimens (4 mm diameter and 6 mm height) were prepared for each material following the manufacturer’s instructions. After subjecting the specimens to thermocycling, 45 specimens were immersed in artificial saliva for 24 hours for compressive strength testing under a universal testing machine, and the other 45 were evaluated for sorption and solubility, by first weighing them by a precision weighing scale (W1), then immersing them in artificial saliva for 28 days and weighing them (W2), and finally dehydrating in an oven for 24 hours and weighing them (W3). Results Group III (zirconomer) shows the highest compressive strength followed by group II (Miracle Mix) and least compressive strength is seen in group I (glass ionomer cement type IX-Extra) with statistically significant differences between the groups. The sorption and solubility values in artificial saliva were highest for glass ionomer cement type IX - Extra-GC (group I) followed by zirconomer-Shofu (group III), and the least value was seen for Miracle Mix-GC (group II). Conclusion Zirconia-reinforced glass ionomer cement is a promising dental material and can be used as a restoration in stress-bearing areas due to its high strength and low solubility and sorption rate. It may be a substitute for silver-reinforced glass ionomer cement due to the added advantage of esthetics. Clinical significance This study provides vital information to pediatric dental surgeons on relatively new restorative materials as physical and mechanical properties of the new material are compared with conventional materials to determine the best suited material in terms of durability, strength and dimensional stability. This study will boost confidence among dental surgeons in terms of handling characteristics, cost effectiveness and success rate. This study will help clinically and scientifically; pediatric dental surgeons to use this material in stress-bearing areas in pediatric patients. How to cite this article Bhatia HP, Singh S, Sood S, Sharma N. A Comparative Evaluation of Sorption, Solubility, and Com-pressive Strength of Three Different Glass Ionomer Cements in Artificial Saliva: An in vitro Study. Int J Clin Pediatr Dent 2017;10(1):49-54. PMID:28377656

WATER SORPTION AND SOLUBILITY OF DIFFERENT CALCIUM HYDROXIDE CEMENTS

PubMed Central

Francisconi, Luciana Fávaro; de Freitas, Anderson Pinheiro; Scaffa, Polliana Mendes Candia; Mondelli, Rafael Francisco Lia; Francisconi, Paulo Afonso Silveira

2009-01-01

Objectives: Calcium hydroxide cements have been largely used in deep cavities due to their abilities to stimulate dentin formation. However, their resistance can be relatively low and their solubility relatively high, in many instances. This study evaluated water sorption and solubility of different calcium hydroxide cements, in order to show alterations that may reduce their effectiveness. Material and methods: Five discs (20 mm in diameter and 1.5 mm thick) of three different materials (Biocal®, Dycal® and Hidro C®) were prepared with the aid of a ring-shaped metallic matrix. After being stored at 37°C for 24 h, the discs were weighed on a precision weight scale, dehydrated and weighed again. Immediately after weighing, discs were stored for a week in 50 mL of distilled water at 37°C and, then, weighed again, dehydrated and submitted to a new weighing. The loss of soluble material and its water sorption was obtained from the difference between the initial and the final dry mass of each disc, after 1 week of immersion in water. Data were analyzed for significant differences by two-way ANOVA and Tukey's test (p<0.05). Results: Mean water sorption values (g) ± standard deviation and percentage (%), for each evaluated cement, were: Biocal® (0.006 ± 0.001 / 2.15); Dycal® (0.016 ± 0.004 / 5.49); and Hidro C® (0.025 ± 0.003 / 8.27). Mean solubility values (g) ± standard deviation and percentage (%), for each evaluated cement, were: Biocal® (0.002 ± 0.001 / 0.72); Dycal® (0.013 ± 0.004 / 4.21); and Hidro C® (0.023 ± 0.004 / 7.65). Conclusions: Biocal® absorbed less water and was less soluble than the other evaluated cements; Hidro C® exhibited the highest water sorption and solubility values; and there were significant differences among all evaluated experimental groups. PMID:19936520

Sorption and Transport of Ranitidine in Natural Soils

NASA Astrophysics Data System (ADS)

Gaynor, A. J.; Vulava, V. M.

2013-12-01

Increasing levels of pharmaceuticals and their degradants are being discovered in natural water systems all over the world. These chemicals are reported to be discharged from wastewater treatment plants, sewage overflow, and leaking septic tanks. Ranitidine is an example of one such pharmaceutical chemical found in municipal drinking water, streams, and streambed sediments. It is a histamine H2-receptor antagonist, which inhibits the production of stomach acid and is commonly used to treat peptic ulcers and gastro esophageal reflux disease. Ranitidine is a complex organic compound; it is acidic, highly polar, and has two pKa values of approximately 8.2 and 2.7 because of the amine functional groups. When administered orally 25 - 30% of unchanged ranitidine has been shown to expel through urine. The objective of this research is to establish sorption and transport patterns of ranitidine in natural soils and to determine which soil properties influence these patterns the most. Laboratory experiments were preformed on A-horizon and B-horizon soil samples collected from the relatively undisturbed Francis Marion National Forest, a managed forest near Charleston, SC. The soils were characterized for chemical and physical properties: ranges of clay content = 6-20%, total organic content = 1-8%, and pH = 3.6-4.9. Kinetic reaction rates and equilibrium sorption isotherms were measured using batch experiments, whereas column experiments were used to quantify transport behavior. The reaction rates were -0.22/day and -0.33/day for organic-rich and clay-rich soils, respectively. The kinetic reaction rates were used to determine equilibration times for further equilibrium batch reactor experiments, which have soil solutions spiked with concentrations of ranitidine ranging from 0.1 mg/L to 100 mg/L. The concentration remaining in solution (C, mg/L) was plotted against the concentration in the soil (q, mg/kg) to create sorption isotherms. Ranitidine was more strongly sorbed to B-horizon than to A-horizon soils, implying a strong preference for soils higher in clay content. Freundlich model (q = Kf Cn, where Kf and n are fitting parameters) fit the sorption isotherms. Glass chromatography columns packed with soil were used for column experiments. Ranitidine tracer was injected into saturated soil columns and the breakthrough tracer concentrations were plotted as a function of time. The shape of these breakthrough curves indicated that there were two distinct sorption sites on soils - organic matter and clay minerals - which influenced tracer transport. A two-region, nonequilibrium transport code was used to model the breakthrough curves. These experiments indicate that ranitidine sorbs more strongly to clay-rich soils than to organic-rich soils. The presence of amine functional groups in ranitidine's chemical structure results in its acidic behavior in the soil solution. In acidic solutions, the cationic form of ranitidine likely forms ionic bonds with negatively charged clay surfaces. Other components of ranitidine are likely to form covalent bonds with organic matter. The data shows the complex nature of ranitidine in interactions with environmental surfaces.

The analysis of isotherms of radionuclides sorption by inorganic sorbents

NASA Astrophysics Data System (ADS)

Bykova, E. P.; Nedobukh, T. A.

2017-09-01

The isotherm of cesium sorption by an inorganic sorbent based on granulated glauconite obtained in a wide cesium concentrations range was mathematically treated using Langmuir, Freundlich and Redlich-Peterson sorption models. The algorithms of mathematical treatment of experimental data using these models were described; parameters of all isotherms were determined. It was shown that estimating the correctness of various sorption models relies not only on the correlation coefficient values but also on the closeness of the calculated and experimental data. Various types of sorption sites were found as a result of mathematical treatment of the isotherm of cesium sorption. The algorithm was described and calculation of parameters of the isotherm was performed under the assumption that simultaneous sorption on all three types of sorption sites occurs in accordance with Langmuir isotherm.

Role of the Ca-pectates on the accumulation of heavy metals in the root apoplasm.

PubMed

Castaldi, Paola; Lauro, Giampaolo; Senette, Caterina; Deiana, Salvatore

2010-12-01

In order to better understand the processes that regulate the accumulation in the apoplasm of heavy metals and their mobilization by the plant metabolites it is essential to study the mechanisms that regulate the interactions between metal ions and pectins. In such a context, the sorption of Cd(II), Zn(II), Cu(II) and Pb(II) from single and multi-metal solutions, by a Ca-polygalacturonate gel with a degree of esterification of 18.0 (PGAM(1)) and 65.5% (PGAM(2)) was studied in the 3.0-6.0 pH range in the presence of CaCl(2) 2.5mM. The sorption of Cr(III) from single metal solution was also considered. The results show that the amount of each metal ion sorbed increases with increasing the initial metal ion concentration and pH. The data from the single metal solution tests show that at pH 6.0 the affinity of the metal ions towards the PGAM(1) matrix follows the order: Cr(III)>Cu(II)≅Pb(II)≫Zn(II)≅Cd(II). The simultaneous sorption of the bivalent metal ions by the PGAM(1) gels indicates that Pb(II) is selectively sorbed. The FT-IR spectra show that the carboxylate groups are mainly responsible for the metal ion coordination. The ability of PGAM(2) to accumulate Cr(III), Cu(II), and Pb(II) was lower than that found in the PGAM(1) systems whereas the sorption of Zn(II) and Cd(II) was negligible. Copyright © 2010 Elsevier Masson SAS. All rights reserved.

Influence of calcite and dissolved calcium on uranium(VI) sorption to a hanford subsurface sediment.

PubMed

Dong, Wenming; Ball, William P; Liu, Chongxuan; Wang, Zheming; Stone, Alan T; Bai, Jing; Zachara, John M

2005-10-15

The influence of calcite and dissolved calcium on U(VI) adsorption was investigated using a calcite-containing sandy silt/clay sediment from the U. S. Department of Energy Hanford site. U(VI) adsorption to sediment, treated sediment, and sediment size fractions was studied in solutions that both had and had not been preequilibrated with calcite, at initial [U(VI)] = 10(-7)-10(-5) mol/L and final pH = 6.0-10.0. Kinetic and reversibility studies (pH 8.4) showed rapid sorption (30 min), with reasonable reversibility in the 3-day reaction time. Sorption from solutions equilibrated with calcite showed maximum U(VI) adsorption at pH 8.4 +/- 0.1. In contrast, calcium-free systems showed the greatest adsorption at pH 6.0-7.2. At pH > 8.4, U(VI) adsorption was identical from calcium-free and calcium-containing solutions. For calcite-presaturated systems, both speciation calculations and laser-induced fluorescence spectroscopic analyses indicated that aqueous U(VI) was increasingly dominated by Ca2UO2(CO3)3(0)(aq) at pH < 8.4 and thatformation of Ca2UO2(CO3)3(0)(aq) is what suppresses U(VI) adsorption. Above pH 8.4, aqueous U(VI) speciation was dominated by UO2(CO3)3(4-) in all solutions. Finally, results also showed that U(VI) adsorption was additive in regard to size fraction but not in regard to mineral mass: Carbonate minerals may have blocked U(VI) access to surfaces of higher sorption affinity.

Uptake of Cr3+ from aqueous solution by lignite-based humic acids.

PubMed

Arslan, G; Pehlivan, E

2008-11-01

Humic acid (HA) produced from brown coal, a relatively abundant and inexpensive material is currently being investigated as an adsorbent to remove toxic metals from aqueous solution. The influence of five parameters (contact time, solution pH, initial metal concentration, temperature and amount of adsorbent) on the removal at 20+/-1 degrees C was studied. HAs were prepared from lignites by using alkaline extraction, sedimentation and acidic precipitation. Adsorption equilibrium was achieved in about 60 min for Cr3+ ion. The Langmuir adsorption isotherm was used to describe observed sorption phenomena. The maximum adsorption capacity of 0.17 mmol for Ilgin (HA1), 0.29 mmol for Beysehir (HA2) and 0.18 mmol Ermenek (HA3) and 0.17 mmol of Cr3+/g for activated carbon (AC) was achieved, respectively at pH of 4.1. More than 84% of Cr3+ was removed by HA2, 54% by HA3 and 51% by HA1 and 50% by AC from aqueous solution. The adsorption was strongly dependent on pH but independent of ionic strength and metal ions. The adsorption of Cr3+ was higher between pH 4.1 and 5.1 for all HAs and maximum sorption was observed at pH 4.1. The rise in temperature caused a slight decrease in the value of the equilibrium constant (Kc) for the sorption of Cr3+ ion. Complex mechanisms including ion exchange, complexation and adsorption and size exclusion are possible for sorption of Cr3+ ion on HAs.

Fate of Nutrients in Shallow Groundwater Receiving Treated Septage, Malibu, CA

PubMed Central

Izbicki, John A

2014-01-01

Treated wastewater discharged from more than 400 onsite wastewater treatment systems (OWTS) near the Civic Center area of Malibu, California, 40 km west of downtown Los Angeles, composes 28% of the recharge to a 3.4 km2 alluvial aquifer. On the basis of δ18O and δD data, the fraction of wastewater in some samples was >70%. Ammonium and nitrate concentrations in water from 15 water-table wells sampled in July 2009 and April 2010 ranged from <0.01 to 12 milligrams per liter as nitrogen (mg/L as N), and from <0.01 to 11 mg/L as N, respectively. Chemical and isotopic data (δ15N of ammonium and nitrate, and δ18O of nitrate) show two processes remove nitrogen discharged from OWTS. Where groundwater was reducing, sorption of ammonium resulted in 30 to 50% nitrogen removal. Where groundwater was initially oxic, nitrification with subsequent denitrification as reducing conditions developed, resulted in up to 60% nitrogen removal. Nitrogen removal through sorption dominated during the cooler April sample period, and denitrification dominated during the warmer July sample period. The combination of mixing and nitrogen removal due to denitrification, sorption, and volatilization produces a δ15N apparent fractionation factor (εapp = −5), that can be explained using laboratory-derived fractionation factors (ε) for the individual processes. Phosphate concentrations ranged from < 0.04 to 2 mg/L as phosphorous. Sorption to iron oxides on the surfaces of mineral grains at near-neutral pH's removed some phosphate; however, little removal occurred at more alkaline pH's (>7.3). PMID:24902718

Investigation of sorption/desorption equilibria of heavy metal ions on/from quartz using rhamnolipid biosurfactant.

PubMed

Aşçi, Yeliz; Nurbaş, Macid; Sağ Açikel, Yeşim

2010-01-01

In the present study, the sorption characteristics of Cd(II) and Zn(II) ions on quartz, a representative soil-component, and the desorption of these metal ions from quartz using rhamnolipid biosurfactant were investigated. In the first part of the studies, the effects of initial metal ion concentration and pH on sorption of Cd(II) and Zn(II) ions by a fixed amount of quartz (1.5g) were studied in laboratory batch mode. The equilibrium sorption capacity for Cd(II) and Zn(II) ions was measured and the best correlation between experimental and model predicted equilibrium uptake was obtained using the Freundlich model. Although investigations on the desorption of heavy metal ions from the main soil-components are crucial to better understand the mobility and bioavailability of metals in the environment, studies on the description of desorption equilibrium were performed rarely. In the second part, the desorption of Cd(II) and Zn(II) from quartz using rhamnolipid biosurfactant was investigated as a function of pH, rhamnolipid concentration, and the amounts of sorbed Cd(II) and Zn(II) ions by quartz. The Freundlich model was also well fitted to the obtained desorption isotherms. Several indexes were calculated based on the differences of the quantity of Cd-Zn sorbed and desorbed. A desorption hysteresis (irreversibility) index based on the Freundlich exponent, concentration-dependent metal distribution coefficients, and the irreversibility index based on the metal distribution coefficient were used to quantify hysteretic behavior observed in the systems. 2009 Elsevier Ltd. All rights reserved.

Fate of nutrients in shallow groundwater receiving treated septage, Malibu, CA

USGS Publications Warehouse

Izbicki, John

2014-01-01

Treated wastewater discharged from more than 400 onsite wastewater treatment systems (OWTS) near the Civic Center area of Malibu, California, 40 km west of downtown Los Angeles, composes 28% of the recharge to a 3.4 km2 alluvial aquifer. On the basis of δ18O and δD data, the fraction of wastewater in some samples was >70%. Ammonium and nitrate concentrations in water from 15 water-table wells sampled in July 2009 and April 2010 ranged from <0.01 to 12 milligrams per liter as nitrogen (mg/L as N), and from <0.01 to 11 mg/L as N, respectively. Chemical and isotopic data (δ15N of ammonium and nitrate, and δ18O of nitrate) show two processes remove nitrogen discharged from OWTS. Where groundwater was reducing, sorption of ammonium resulted in 30 to 50% nitrogen removal. Where groundwater was initially oxic, nitrification with subsequent denitrification as reducing conditions developed, resulted in up to 60% nitrogen removal. Nitrogen removal through sorption dominated during the cooler April sample period, and denitrification dominated during the warmer July sample period. The combination of mixing and nitrogen removal due to denitrification, sorption, and volatilization produces a δ15N apparent fractionation factor (εapp= -5), that can be explained using laboratory-derived fractionation factors (ε) for the individual processes. Phosphate concentrations ranged from <0.04 to 2 mg/L as phosphorous. Sorption to iron oxides on the surfaces of mineral grains at near-neutral pH's removed some phosphate; however, little removal occurred at more alkaline pH's (>7.3).

Differences in sorption behavior of the herbicide 4-chloro-2-methylphenoxyacetic acid on artificial soils as a function of soil pre-aging.

PubMed

Waldner, Georg; Friesl-Hanl, Wolfgang; Haberhauer, Georg; Gerzabek, Martin H

The sorption behavior of the herbicide 4-chloro-2-methylphenoxyacetic acid (MCPA) to three different artificial soil mixtures was investigated. Artificial soils serve as model systems for improving understanding of sorption phenomena. The soils consisted of quartz, ferrihydrite, illite, montmorillonite, and charcoal. In a previous study, several selected mixtures had been inoculated with organic matter, and microbial aging (incubation) had been performed for different periods of time (3, 12, and 18 months) before conducting the sorption experiments. The effect of this pre-incubation time on the sorption behavior was determined. Interaction of MCPA with soil surfaces was monitored by aqueous phase sorption experiments, using high-performance liquid chromatography/ultraviolet and in selected cases Fourier-transformed infrared spectroscopy. The sorption behavior showed large differences between differently aged soils; Freundlich and linear sorption model fits (with sorption constants K f , 1/ n exponents, and K d values, respectively) were given for pH = 3 and the unbuffered pH of ∼7. The largest extent of sorption from diluted solutions was found on the surfaces with a pre-incubation time of 3 months. Sorption increased at acidic pH values. Regarding the influence of aging of artificial soils, the following conclusions were drawn: young artificial soils exhibit stronger sorption at lower concentrations, with a larger K f value than aged soils. A correlation with organic carbon content was not confirmed. Thus, the sorption characteristics of the soils are more influenced by the aging of the organic carbon than by the organic carbon content itself.

Potential for biodegradation and sorption of acetaminophen, caffeine, propranolol and acebutolol in lab-scale aqueous environments.

PubMed

Lin, Angela Yu-Chen; Lin, Chih-Ann; Tung, Hsin-Hsin; Chary, N Sridhara

2010-11-15

Sorption and combined sorption-biodegradation experiments were conducted in laboratory batch studies with 100 g soil/sediments and 500 mL water to investigate the fates in aqueous environments of acetaminophen, caffeine, propranolol, and acebutolol, four frequently used and often-detected pharmaceuticals. All four compounds have demonstrated significant potential for degradation and sorption in natural aqueous systems. For acetaminophen, biodegradation was found to be a primary mechanism for degradation, with a half-life (t(1/2)) for combined sorption-biodegradation of 2.1 days; in contrast, sorption alone was responsible only for a 30% loss of aqueous-phase acetaminophen after 15 days. For caffeine, both biodegradation and sorption were important (t(1/2) for combined sorption-biodegradation was 1.5 days). However, for propranolol and acebutolol, sorption was found to be the most significant removal mechanism and was not affected by biodegradation. Desorption experiments revealed that the sorption process was mostly irreversible. High values were found for K(d) for caffeine, propranolol, and acebutolol, ranging from 250 to 1900 L kg(-1), which explained their greater tendency for sorption onto sediments, compared to the more hydrophilic acetaminophen. Experimentally derived values for logK(oc) differed markedly from values calculated from correlation equations. This discrepancy was attributed to the fact that these equations are well suited for hydrophobic interactions but may fail to predict the sorption of polar and ionic compounds. These results suggest that mechanisms other than hydrophobic interactions played an important role in the sorption process. Copyright © 2010 Elsevier B.V. All rights reserved.

Removal of chromium from aqueous solutions by diatomite treated with microemulsion.

PubMed

Dantas, T N; Dantas Neto, A A; Moura, M C

2001-06-01

In order to evaluate the sorption of heavy metals, a crude diatomite was impregnated with a microemulsion which showed remarkable increase in chromium sorption capacity as compared to untreated diatomite. Samples with two different granulometries were investigated, both yielding practically complete adsorption. The adsorption process is pH dependent and the best results for the initial Cr (III) concentration of 1.5 g/L were obtained at pH 2.95. The effect of the concentration of the chromium synthetic solution was also investigated. The adsorption isotherms were obtained (30. 40 and 50 degrees C) and the Freundlich and Langmuir models were used to determine the adsorption capacity of the adsorbent. Following the adsorption step, a desorption process was carried out using several eluant solutions. The best results were obtained using hydrochloric acid (100%) as eluant.

Sorption-desorption of antimony species onto calcined hydrotalcite: Surface structure and control of competitive anions.

PubMed

Constantino, Leonel Vinicius; Quirino, Juliana Nunes; Abrão, Taufik; Parreira, Paulo Sérgio; Urbano, Alexandre; Santos, Maria Josefa

2018-02-15

Calcined hydrotalcite can be applied to remove anionic contaminants from aqueous systems such as antimony species due to its great anion exchange capacity and high surface area. Hence, this study evaluated antimonite and antimonate sorption-desorption processes onto calcined hydrotalcite in the presence of nitrate, sulfate and phosphate. Sorption and desorption experiments of antimonite and antimonate were carried out in batch equilibrium and the post-sorption solids were analyzed by X-ray fluorescence (EDXRF). Sorption data were better fitted by dual-mode Langmuir-Freundlich model (R 2 >0.99) and desorption data by Langmuir model. High maximum sorption capacities were found for the calcined hydrotalcite, ranging from 617 to 790meqkg -1 . The competing anions strongly affected the antimony sorption. EDXRF analysis and mathematical modelling showed that sulfate and phosphate presented higher effect on antimonite and antimonate sorption, respectively. High values for sorption efficiency (SE=99%) and sorption capacity were attributed to the sorbent small particles and the large surface area. Positive hysteresis indexes and low mobilization factors (MF>3%) suggest very low desorption capacity to antimony species from LDH. These calcined hydrotalcite characteristics are desirable for sorption of antimony species from aqueous solutions. Copyright © 2017. Published by Elsevier B.V.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Clausen, J.L.; Sturchio, N.C.; Heraty, L.J.

NA processes such as biodegradation, sorption, dilution dispersion, advection, and possibly sorption and diffusion are occurring in the Northeast and Northwest plumes. However, the overall biological attenuation rate for TCE within the plumes is not sufficiently rapid to utilize as remedial option. The mobility and toxicity of {sup 99}Tc is not being reduced by attenuating processes within the Northwest Plume. The current EPA position is that NA is not a viable remedial approach unless destructive processes are present or processes are active which reduce the toxicity and mobility of a contaminant. Therefore, active remediation of the dissolved phase plumes willmore » be necessary to reduce contaminant concentrations before an NA approach could be justified at PGDP for either plume. Possible treatment methods for the reduction of dissolved phase concentrations within the plumes are pump-and-treat bioaugmentation, biostimulation, or multiple reactive barriers. Another possibility is the use of a regulatory instrument such as an Alternate Concentration Limit (ACL) petition. Biodegradation of TCE is occurring in both plumes and several hypothesis are possible to explain the apparent conflicts with some of the geochemical data. The first hypothesis is active intrinsic bioremediation is negligible or so slow to be nonmeasurable. In this scenario, the D.O., chloride, TCE, and isotopic results are indicative of past microbiological reactions. It is surmised in this scenario, that when the initial TCE release occurred, sufficient energy sources were available for microorganisms to drive aerobic reduction of TCE, but these energy sources were rapidly depleted. The initial degraded TCE has since migrated to downgradient locations. In the second scenario, TCE anaerobic degradation occurs in organic-rich micro-environments within a generally aerobic aquifer. TCE maybe strongly absorbed to organic-rich materials in the aquifer matrix and degraded by local Immunities of microbes, perhaps even under anaerobic conditions. Chloride, generated by degradation in such microenvironment is released rapidly into the water, as is CO{sub 2}, from respiration of the microorganisms. TCE and its organic degradation products are retained on the aquifer matrix by sorption, and released more slowly into the groundwater. In this process, chloride produced from the microbial reaction may become separated in the plume from the residual TCE. This may explain why the chloride isotope ratio and dissolved TCE do not correlate with the DIC isotope ratio. The relationship between the {delta}{sup 37}Cl values of TCE and dissolved inorganic chloride is consistent with what would be expected from the degradation of TCE, but is complicated by the elevated levels of background chloride, presumably due to agriculture practice, and complex behavior of TCE in the aquifer.« less

SPECTROSCOPIC ANALYSIS OF METALS IN BIOSOLIDS

EPA Science Inventory

The results of decades of research illustrate that metals in biosolids-amended soils are retained at a higher rate than soils without biosolids-amendments indicating that either an individual or combination of constituents within biosolids is responsible for the elevated sorption...

Poly(vinyl alcohol)/hydroxyapatite Monolithic In-Needle Extraction (MINE) device: Preparation and examination of drug affinity.

PubMed

Pietrzyńska, Monika; Czerwiński, Michał; Voelkel, Adam

2017-07-15

Polymer-ceramic materials based on poly(vinyl alcohol) (PVA) and hydroxyapatite were applied as sorption material in Monolithic In-Needle Extraction (MINE) device. The presented device provides new possibilities for the examination of bisphosphonates affinity for bone and will be a helpful tool in evaluation of potential antiresorptive drugs suitability. A ceramic part of monoliths was prepared by incorporation of hydroxyapatite (HA) into the reaction mixture or by using a soaking method (mineralization of HA on the PVA). The parameters of synthesis conditions were optimized to achieve a monolithic material having the appropriate dimensions after the soaking process enabling placing of the monolithic material inside the needle. Furthermore, the material must have had optimal dimensions after the re-soaking process to fit perfectly to the needle. Among the sixteen monolithic materials, eight of them were selected for further study, and then four of them were selected as a sorbent material for the MINE device. The material properties were examined on the basis of several parameters: swelling ratio, initial mass reversion and initial diameter reversion, mass growth due to the HA formation, and antiresorptive drug sorption. The MINE device might be then used as a tool for examination of interactions between bisphosphonate and bone. The simulated body fluid containing sodium risedronate (RSD) as a standard compound was passed through the MINE device. The obtained device allowed for sorption about 0.38mg of RSD. The desorption process was carried out in five steps allowing insightful analysis. The MINE device turned out to be a helpful tool for determination of the bisphosphonates affinity to the ceramic part of sorbent (hydroxyapatite) and to assess the usefulness of them as antiresorptive drugs in the future. Copyright © 2017 Elsevier B.V. All rights reserved.

Simultaneous removal of aqueous Zn2+, Cu2+, Cd2+, and Pb2+ by zeolites synthesized from low-calcium and high-calcium fly ash.

PubMed

Ji, X D; Ma, Y Y; Peng, S H; Gong, Y Y; Zhang, F

2017-10-01

In this study, zeolites were synthesized from low-calcium (LCZ) and high-calcium (HCZ) fly ash, respectively. Subsequently, the zeolites were tested for their removal effectiveness for four aqueous cations, namely, Zn 2+ , Cu 2+ , Cd 2+ , and Pb 2+ , as a function of contact time, pH value, adsorbent dosage, and initial concentration of heavy metals. Both zeolites were characterized by X-ray diffraction, X-ray fluorescence spectrometry, scanning electron microscopy, specific surface area, and cation exchange capacity. The results show that HCZ mainly consists of an unnamed zeolite (Na 6 [AlSiO 4 ] 6 ·4H 2 O), whereas LCZ mainly consists of faujasite-type zeolite. The optimum sorption conditions were pH = 6.0; adsorbent dosage = 1.0 g·L -1 ; temperature = 25 °C; contact time = 100 min; and initial heavy metal concentration = 100 mg·L -1 . The sorption kinetics of the four aqueous cations on both LCZ and HCZ followed the pseudo-second-order kinetic model, and the sorption isotherm data fitted well with the Langmuir isotherm model. For LCZ, the maximum adsorption capacities of Zn 2+ , Cu 2+ , Cd 2+ , and Pb 2+ were 155.76, 197.86, 123.76, and 186.22 mg·g -1 , respectively. For HCZ, the values were 154.08, 183.15, 118.91, and 191.94 mg·g -1 , respectively. The zeolites were regenerated by NaCl solution (1 mol·L -1 ) and showed high removal efficiency. In conclusion, zeolites produced by fly ash are promising materials for removing Zn 2+ , Cu 2+ , Cd 2+ , and Pb 2+ from wastewater.

Study on the sorption behaviour of estrone on marine sediments.

PubMed

Zhang, Jing; Yang, Gui-Peng; Li, Quan; Cao, Xiaoyan; Liu, Guangxing

2013-11-15

The sorption behaviour of estrone (E1) on marine sediments treated by different methods was systematically investigated. About 22 h was required for sorption equilibrium of E1. Sorption isotherms of E1 were well fitted with Freundlich model. The sorption behaviour of E1 on HCl-treatment and H2O-treatment sediments related significantly with the sediment organic carbon contents. Additionally, clay minerals and surface areas of sediments played dominant roles in the sorption of E1 on H2O2-treatment sediments. Some external factors which could affect sorption behaviour of E1 were also investigated. Our results showed that the sorption capacity of E1 on the sediments increased with the increasing concentrations of cationic surfactant cetyltrimethylammonium bromide (CTAB), nonionic surfactant polyoxyethylene (80) sorbitan esters (Tween 80) and salinity of seawater. In contrast, the sorption capacity of E1 decreased with the increasing concentration of anionic surfactant sodium dodecylbenzene sulfonate (SDBS), pH value and temperature of seawater. Copyright © 2013 Elsevier Ltd. All rights reserved.

Sorption of dodecyltrimethylammonium chloride (DTAC) to agricultural soils.

PubMed

Xiang, Lei; Sun, Teng-Fei; Zheng, Mei-Jie; Li, Yan-Wen; Li, Hui; Wong, Ming-Hung; Cai, Quan-Ying; Mo, Ce-Hui

2016-08-01

Quaternary ammonium compounds (QACs) used as cationic surfactants are intensively released into environment to be pollutants receiving more and more concerns. Sorption of dodecyltrimethylammonium chloride (DTAC), one of commonly used alkyl QACs, to five types of agricultural soils at low concentrations (1-50mg/L) was investigated using batch experiments. DTAC sorption followed pseudo-second-order kinetics and reached reaction equilibrium within 120min. Both Freundlich model and Langmuir model fitted well with DTAC isotherm data with the latter better. DTAC sorption was spontaneous and favorable, presenting a physical sorption dominated by ion exchanges. Sorption distribution coefficient and sorption affinity demonstrated that soil clay contents acted as a predominant phase of DTAC sorption. DTAC could display a higher mobility and potential accumulation in crops in the soils with lower clay contents and lower pH values. Sorption of DTAC was heavily affected by ions in solution with anion promotion and cation inhibition. Copyright © 2016. Published by Elsevier B.V.

Column Chromatography To Obtain Organic Cation Sorption Isotherms.

PubMed

Jolin, William C; Sullivan, James; Vasudevan, Dharni; MacKay, Allison A

2016-08-02

Column chromatography was evaluated as a method to obtain organic cation sorption isotherms for environmental solids while using the peak skewness to identify the linear range of the sorption isotherm. Custom packed HPLC columns and standard batch sorption techniques were used to intercompare sorption isotherms and solid-water sorption coefficients (Kd) for four organic cations (benzylamine, 2,4-dichlorobenzylamine, phenyltrimethylammonium, oxytetracycline) with two aluminosilicate clay minerals and one soil. A comparison of Freundlich isotherm parameters revealed isotherm linearity or nonlinearity was not significantly different between column chromatography and traditional batch experiments. Importantly, skewness (a metric of eluting peak symmetry) analysis of eluting peaks can establish isotherm linearity, thereby enabling a less labor intensive means to generate the extensive data sets of linear Kd values required for the development of predictive sorption models. Our findings clearly show that column chromatography can reproduce sorption measures from conventional batch experiments with the benefit of lower labor-intensity, faster analysis times, and allow for consistent sorption measures across laboratories with distinct chromatography instrumentation.