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Sample records for equilibrium sorption isotherm

  1. Thermodynamic analysis of sorption isotherms of cassava (Manihot esculenta).

    PubMed

    Koua, Blaise Kamenan; Koffi, Paul Magloire Ekoun; Gbaha, Prosper; Toure, Siaka

    2014-09-01

    Sorption isotherms of cassava were determined experimentally using a static gravimetric method at 30, 45 and 60 °C and within the range of 0.10-0.90 water activity. At a constant water activity, equilibrium moisture content decreased with increasing temperature. The equilibrium moisture content increased with increasing water activity at a given temperature. The experimental results were modelled using seven sorption models using non-linear regression technique. Results demonstrated that the GAB model adequately predicted equilibrium moisture content of cassava for the range of temperatures and water activities studied. The thermodynamic functions such as net isosteric heat of sorption, differential entropy of sorption, net integral enthalpy and entropy were evaluated to provide an understanding of the properties of water and energy requirements associated with the sorption behaviour. Net isosteric heat and differential entropy decreased with increasing equilibrium moisture content. The net integral enthalpy decreased while net integral entropy increased with increasing equilibrium moisture content. Net integral entropy was negative in value. All thermodynamic functions were adequately characterised by a power law model. The point of maximum stability was found between 0.053 and 0.154 kg water/kg db for cassava. PMID:25190827

  2. Sorption isotherms and isosteric heats of sorption of Malaysian paddy.

    PubMed

    Mousa, Wael; Ghazali, Farinazleen Mohamad; Jinap, S; Ghazali, Hasanah Mohd; Radu, Son

    2014-10-01

    Understanding the water sorption characteristics of cereal is extremely essential for optimizing the drying process and ensuring storage stability. Water relation of rough rice was studied at 20, 30, 40 and 50 °C over relative humidity (RH.) between 0.113 and 0.976 using the gravimetric technique. The isotherms displayed the general sigmoid, Type II pattern and exhibited the phenomenon of hysteresis where it was more pronounced at lower temperatures. The sorption characteristics were temperature dependence where the sorption capacity of the paddy increased as the temperature was decreased at fixed (RH). Among the models assessed for their ability to fit the sorption data, Oswin equation was the best followed by the third order polynomial, GAB, Smith, Chung-Pfost, and Henderson models. The monolayer moisture content was higher for desorption than adsorption and tend to decrease with the increase in temperature. Given the temperature dependence of the sorption isotherms the isosteric heats of sorption were calculated using Claussius-Clapeyron equation. The net isosteric heats decreased as the moisture content was increased and heats of desorption were greater than that of adsorption. PMID:25328208

  3. Cr(VI) sorption by free and immobilised chromate-reducing bacterial cells in PVA-alginate matrix: equilibrium isotherms and kinetic studies.

    PubMed

    Rawat, Monica; Rawat, A P; Giri, Krishna; Rai, J P N

    2013-08-01

    Chromate-resistant bacterial strain isolated from the soil of tannery was studied for Cr(VI) bioaccumulation in free and immobilised cells to evaluate its applicability in chromium removal from aqueous solution. Based on the comparative analysis of the 16S rRNA gene, and phenotypic and biochemical characterization, this strain was identified as Paenibacillus xylanilyticus MR12. Mechanism of Cr adsorption was also ascertained by chemical modifications of the bacterial biomass followed by Fourier transform infrared spectroscopy analysis of the cell wall constituents. The equilibrium biosorption analysed using isotherms (Langmuir, Freundlich and Dubinin-Redushkevich) and kinetics models (pseudo-first-order, second-order and Weber-Morris) revealed that the Langmuir model best correlated to experimental data, and Weber-Morris equation well described Cr(VI) biosorption kinetics. Polyvinyl alcohol alginate immobilised cells had the highest Cr(VI) removal efficiency than that of free cells and could also be reused four times for Cr(VI) removal. Complete reduction of chromate in simulated effluent containing Cu(2+), Mg(2+), Mn(2+) and Zn(2+) by immobilised cells, demonstrated potential applications of a novel immobilised bacterial strain MR12, as a vital bioresource in Cr(VI) bioremediation technology. PMID:23361177

  4. Column Chromatography To Obtain Organic Cation Sorption Isotherms.

    PubMed

    Jolin, William C; Sullivan, James; Vasudevan, Dharni; MacKay, Allison A

    2016-08-01

    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. PMID:27379799

  5. Mathematical modeling of non-equilibrium sorption

    NASA Astrophysics Data System (ADS)

    Kaliev, Ibragim A.; Mukhambetzhanov, Saltanbek T.; Sabitova, Gulnara S.; Sakhit, Anghyz E.

    2016-08-01

    We consider the system of equations modeling the process of non-equilibrium sorption. Difference approximation of differential problem by the implicit scheme is formulated. The solution of the difference problem is constructed using the sweep method. Based on the numerical results we can conclude the following: when the relaxation time decreases to 0, then the solution of non-equilibrium problem tends with increasing time to solution of the equilibrium problem.

  6. Sorption of perfluorooctane sulfonate and perfluorooctanoate on activated carbons and resin: Kinetic and isotherm study.

    PubMed

    Yu, Qiang; Zhang, Ruiqi; Deng, Shubo; Huang, Jun; Yu, Gang

    2009-03-01

    Perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA) have increasingly attracted global concerns in recent years due to their global distribution, persistence, strong bioaccumulation and potential toxicity. The feasibility of using powder activated carbon (PAC), granular activated carbon (GAC) and anion-exchange resin (AI400) to remove PFOS and PFOA from water was investigated with regard to their sorption kinetics and isotherms. Sorption kinetic results show that the adsorbent size influenced greatly the sorption velocity, and both the GAC and AI400 required over 168h to achieve the equilibrium, much longer than 4h for the PAC. Two kinetic models were adopted to describe the experimental data, and the pseudo-second-order model well described the sorption of PFOS and PFOA on the three adsorbents. The sorption isotherms show that the GAC had the lowest sorption capacity both for PFOS and PFOA among the three adsorbents, while the PAC and AI400 possessed the highest sorption capacity of 1.04mmolg(-1) for PFOS and 2.92mmolg(-1) for PFOA according to the Langmuir fitting. Based on the sorption behaviors and the characteristics of the adsorbents and adsorbates, ion exchange and electrostatic interaction as well as hydrophobic interaction were deduced to be involved in the sorption, and some hemi-micelles and micelles possibly formed in the intraparticle pores. PMID:19095279

  7. Equilibrium sorption of cobalt, cesium, and strontium on Bandelier Tuff: analysis of alternative mathematical modeling

    SciTech Connect

    Polzer, W.L.; Fuentes, H.R.; Essington, E.H.; Roensch, F.R.

    1985-01-01

    Sorption isotherms are derived from batch equilibrium data for cobalt, cesium and strontium on Bandelier Tuff. Experiments were conducted at an average temperature of 23/sup 0/C and equilibrium was defined at 48 hours. The solute concentrations ranged from 0 to 500 mg/L. The radioactive isotopes /sup 60/Co, /sup 137/Cs, and /sup 85/Sr were used to trace the sorption of the stable solutes. The Linear, Langmuir, Freundlich and a Modified Freundlich isotherm equations are evaluated. The Modified Freundlich isotherm equation is validated as a preferred general mathematical tool for representing the sorption of the three solutes. The empirical constants derived from the Modified Freundlich isotherm equation indicate that under dynamic flow conditions strontium will move most rapidly and cobalt least rapidly. On the other hand, chemical dispersion will be greatest for cesium and least for strontium. Hill Plots of the sorption data suggest that in the region of low saturation sorption of all three solutes is impeded by interactions among sorption sites; cobalt exhibits the greatest effect of interactions and strontium shows only a minimal effect. In the saturation region of 50% or more, sorption of cobalt is enhanced slightly by interactions among sorption sites whereas sorption of cesium and strontium appears to be independent of site interactions. 9 references, 4 figures, 2 tables.

  8. COSOLVENT EFFECTS ON SORPTION ISOTHERM LINEARITY

    EPA Science Inventory

    Sorption-desorption hysteresis, slow desorption kinetics, and other nonideal phenomena have been attributed to the differing sorptive characteristics of the natural organic polymers associated with soils and sediments. In this study, aqueous and mixed solvent systems were used t...

  9. ISOT_Calc: A versatile tool for parameter estimation in sorption isotherms

    NASA Astrophysics Data System (ADS)

    Beltrán, José L.; Pignatello, Joseph J.; Teixidó, Marc

    2016-09-01

    Geochemists and soil chemists commonly use parametrized sorption data to assess transport and impact of pollutants in the environment. However, this evaluation is often hampered by a lack of detailed sorption data analysis, which implies further non-accurate transport modeling. To this end, we present a novel software tool to precisely analyze and interpret sorption isotherm data. Our developed tool, coded in Visual Basic for Applications (VBA), operates embedded within the Microsoft Excel™ environment. It consists of a user-defined function named ISOT_Calc, followed by a supplementary optimization Excel macro (Ref_GN_LM). The ISOT_Calc function estimates the solute equilibrium concentration in the aqueous and solid phases (Ce and q, respectively). Hence, it represents a very flexible way in the optimization of the sorption isotherm parameters, as it can be carried out over the residuals of q, Ce, or both simultaneously (i.e., orthogonal distance regression). The developed function includes the most usual sorption isotherm models, as predefined equations, as well as the possibility to easily introduce custom-defined ones. Regarding the Ref_GN_LM macro, it allows the parameter optimization by using a Levenberg-Marquardt modified Gauss-Newton iterative procedure. In order to evaluate the performance of the presented tool, both function and optimization macro have been applied to different sorption data examples described in the literature. Results showed that the optimization of the isotherm parameters was successfully achieved in all cases, indicating the robustness and reliability of the developed tool. Thus, the presented software tool, available to researchers and students for free, has proven to be a user-friendly and an interesting alternative to conventional fitting tools used in sorption data analysis.

  10. 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.

  11. Differential roles of humic acid and particulate organic matter in the equilibrium sorption of atrazine by soils.

    PubMed

    Yu, Zhiqiang; Sharma, Samriti; Huang, Weilin

    2006-08-01

    Recent studies have indicated that soil organic matter (SOM) may consist of physically and chemically different fractions, including particulate organic matter (POM), such as black carbon and unburned coal materials. The present study examined the differential roles of three different SOM fractions isolated from a peat and a topsoil in the equilibrium sorption of the herbicide atrazine (ATZ). The SOM fractions isolated from the two samples included humic acids (HAs), base-extracted humin (HM), and POM after demineralization of HM. A batch technique was employed to measure both the nonequilibrium ATZ sorption on the original and HA samples and the equilibrium ATZ sorption and desorption. The results showed that the phase-distribution relationships measured under nonequilibrium conditions were more linear and had lower sorption-capacity parameters compared with their respective isotherms measured under equilibrium conditions. The sorption isotherms were variously nonlinear, with POM exhibiting the greatest organic carbon-normalized sorption capacity. There existed apparent sorption-desorption hysteresis for each sorbent-sorbate system. It appeared that the extracted HAs could facilitate hydrolysis of ATZ when the reaction time extended to 4 d or longer. The equilibrium sorptive behavior of the HAs therefore was not examined. The present study indicated that both original samples showed lower organic carbon-normalized sorption distribution coefficients compared with their respective SOM fractions, suggesting that a fraction of sorption sites in soil aggregates were not accessed by ATZ. PMID:16916014

  12. ISOFIT - A PROGRAM FOR FITTING SORPTION ISOTHERMS TO EXPERIMENTAL DATA

    EPA Science Inventory

    Isotherm expressions are important for describing the partitioning of contaminants in environmental systems. ISOFIT (ISOtherm FItting Tool) is a software program that fits isotherm parameters to experimental data via the minimization of a weighted sum of squared error (WSSE) obje...

  13. SORPTION OF VOLATILE ORGANIC SOLVENTS FROM AQUEOUS SOLUTION ONTO SUBSURFACE SOLIDS

    EPA Science Inventory

    Sorption isotherms for tetrachloroethene on low-carbon subsurface core samples were linear to equilibrium solution concentrations of 2 mg L−1. Concentrations above this value produced pronounced curvature in the sorption isotherms. Sorption of tetrachloroethene, benzene, trichlor...

  14. 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)

  15. Effect of drying methods on the moisture sorption isotherms and thermodynamic properties of mint leaves.

    PubMed

    Dalgıç, Ali Coşkun; Pekmez, Hatice; Belibağlı, Kadir Bülent

    2012-08-01

    Mint leaves were dried by three different types of dryers, namely; tray, freeze and distributed (indirect)-type solar dryer. Sorption isotherms of fresh, solar, tray and freeze dried mint were determined at temperatures of 15 °C, 25 °C and 35 °C over a range of relative humidities (10-90%). The effect of drying method on the water sorption isotherms of dried mint samples was evaluated. Experimental data were used to determine the best models for predicting the moisture sorption content of mint. Among nine sorption models tested, Peleg, GAB, Lewicki and modified Mizrahi equations gave the best fit to experimental data. The sorption data were analyzed for determination of monolayer moisture content, density of sorbed water, number of adsorbed monolayers, percent bound water, and surface area of adsorbance. The experimental data were also used to determine some thermodynamic properties of mint. PMID:23904652

  16. Evaluation of theoretical and empirical water vapor sorption isotherm models for soils

    NASA Astrophysics Data System (ADS)

    Arthur, Emmanuel; Tuller, Markus; Moldrup, Per; de Jonge, Lis W.

    2016-01-01

    The mathematical characterization of water vapor sorption isotherms of soils is crucial for modeling processes such as volatilization of pesticides and diffusive and convective water vapor transport. Although numerous physically based and empirical models were previously proposed to describe sorption isotherms of building materials, food, and other industrial products, knowledge about the applicability of these functions for soils is noticeably lacking. We present an evaluation of nine models for characterizing adsorption/desorption isotherms for a water activity range from 0.03 to 0.93 based on measured data of 207 soils with widely varying textures, organic carbon contents, and clay mineralogy. In addition, the potential applicability of the models for prediction of sorption isotherms from known clay content was investigated. While in general, all investigated models described measured adsorption and desorption isotherms reasonably well, distinct differences were observed between physical and empirical models and due to the different degrees of freedom of the model equations. There were also considerable differences in model performance for adsorption and desorption data. While regression analysis relating model parameters and clay content and subsequent model application for prediction of measured isotherms showed promise for the majority of investigated soils, for soils with distinct kaolinitic and smectitic clay mineralogy predicted isotherms did not closely match the measurements.

  17. Kinetics and Equilibrium Sorption Models: Fitting Plutonium, Strontium, Uranium and Neptunium Loading on Monosodium Titanate (MST)

    SciTech Connect

    Fondeur, F

    2006-03-08

    The Dubinin-Astashov (DA) isotherm parameters for U, Pu, Sr and Np have been updated to include additional data obtained since the original derivation. The DA isotherms were modified to include a kinetic function derived by Rahn to describe sorbate loading from the beginning of sorption up to steady state. The final functions describe both kinetic and thermodynamic sorption.

  18. Determination of low levels of amorphous content in inhalation grade lactose by moisture sorption isotherms.

    PubMed

    Vollenbroek, Jasper; Hebbink, Gerald A; Ziffels, Susanne; Steckel, Hartwig

    2010-08-16

    Alpha-lactose monohydrate is widely used as an excipient in dry powder inhalers, and plays a very important role in the efficiency of the drug delivery. Due to the processing, low levels of amorphous lactose could be present in the blends. Varying amounts could have a strong effect on the efficiency of drug delivery of the powder blends. Therefore, the accurate measurement of low levels of amorphous lactose content is very important. A new method was developed to measure the amorphous content, based on dynamic vapour sorption (DVS). In contrast to the traditional re-crystallization approach of amorphous lactose, the new method is based on moisture sorption isotherms. Moisture sorption isotherms of blends of crystalline alpha-lactose and freeze-dried or spray-dried amorphous lactose were measured. By fitting the data with a Brunauer, Emmett, and Teller (BET) isotherm, a linear correlation was found between measured and actual amorphous content for the whole range of 0.1-100%. Differences between freeze-dried and spray-dried lactose, due to different molecular arrangements, could be removed by a preconditioning the samples at 35% RH prior to the isotherm measurement. It was shown that accurate determination of very low concentrations of amorphous lactose content is possible using moisture sorption isotherm analyses. PMID:20493937

  19. Soft computing modelling of moisture sorption isotherms of milk-foxtail millet powder and determination of thermodynamic properties.

    PubMed

    Simha, H V Vikram; Pushpadass, Heartwin A; Franklin, Magdaline Eljeeva Emerald; Kumar, P Arun; Manimala, K

    2016-06-01

    Moisture sorption isotherms of spray-dried milk-foxtail millet powder were determined at 10, 25 and 40 °C. Sorption data was fitted using classical and soft-computing approaches. The isotherms were of type II, and equilibrium moisture content (EMC) was temperature dependent. The BET monolayer moisture content decreased from 3.30 to 2.67 % as temperature increased from 10 to 40 °C. Amongst the classical models, Ferro-Fontan gave the best fit of EMC-aw data. However, the Sugeno-type adaptive neuro-fuzzy inference system (ANFIS) with generalized bell-shaped membership function performed better than artificial neural network and classical models with RMSE as low as 0.0099. The isosteric heat of sorption decreased from 150.32 kJ mol(-1) at 1 % moisture content to 44.11 kJ mol(-1) at 15 % moisture. The enthalpy-entropy compensation theory was validated, and the isokinetic and harmonic mean temperatures were determined as 333.1 and 297.5 K, respectively. PMID:27478226

  20. Methods for determining the CO2 sorption capacity of coal: Experimental and theoretical high pressure isotherms

    NASA Astrophysics Data System (ADS)

    Weishauptová, Zuzana; Přibyl, Oldřich

    2016-04-01

    One way to reduce CO2 emissions discharged into the atmosphere is by trapping it and storing it in suitable repositories, including coal-bearing strata. The history of coal mining in the Czech Republic is very rich but most of the mines have been closed down in recent years. However, the unmined coal seams are interesting for the purposes of CO2 storage, especially due the opportunities they offer for recovering coal-bed methane. Mine structures of this kind can be found in large parts of the Upper Silesian Basin, where the total storage capacity has been estimated at about 380 Mt CO2. This is an interesting storage potential. In order to identify a suitable high-capacity locality for CO2 storage within a coal seam, it is necessary to study not only the geological conditions within the seam, but also the textural properties of the coal, which control the mechanism and the extent of the storage. The major storage mechanism is by sorption processes that take place in the coal porous system (adsorption in micropores and on the surface of meso/macropores, and absorption in the macromolecular structure). The CO2 sorption capacity is generally indirectly determined in a laboratory by measuring the amount of carbon dioxide captured in a coal sample at a pressure and temperature corresponding to the in situ conditions, using high pressure sorption techniques. The low pressure sorption technique can be used, by setting the partial volumes of CO2 according to its binding and storage mode. The sorption capacity is determined by extrapolation to the saturation pressure as the sum of the individual partially sorbed volumes. The aim of the study was to determine the partial volumes of CO2 bound by different mechanisms in the individual parts of the porous system of the coal, and to compare the sum with the results obtained by the high pressure isotherm. The study was carried out with 3 samples from a borehole survey in the Czech part of the Upper Silesian Basin. A high pressure

  1. Sorption kinetics and equilibrium uptake for water vapor in soft-contact-lens hydrogels.

    PubMed

    Weinmüller, C; Langel, C; Fornasiero, F; Radke, C J; Prausnitz, J M

    2006-05-01

    A gravimetric-sorption technique was used to obtain kinetic and equilibrium adsorption/desorption data for water vapor in four different soft-contact-lens (SCL) polymers at 35 degrees C. The SCL materials are a conventional hydrogel (polymacon) with a low water content at saturation (<50 wt %); two conventional hydrogels (hilafilcon A and alphafilcon A) with a high water content at saturation (>50 wt %); and a siloxane hydrogel (balafilcon A). Absorption and desorption equilibrium isotherms (water activity versus water weight fraction) overlap at high water contents, whereas significant hysteresis is observed at low water contents. The hysteresis loop is likely due to trapping of water in the polymer during the desorption process because of a rubber-to-glass transition of the SCL-film surfaces. Sorption data were interpreted using Flory-Rehner theory. The positive Zimm and Lundberg cluster function suggests that water tends to cluster in these SCL materials, except at very low water content. For polymacon and hilafilcon A, Fickian diffusion is observed for all activities for both water sorption and desorption. However, for alphafilcon A and balafilcon A, non-Fickian features appear at intermediate/low activities, in particular during water desorption, suggesting coupling of the diffusion process with polymer-matrix relaxation. The diffusion coefficient increases significantly with water concentration for polymacon and hilafilcon A (from approximately 0.3 x 10(-8) to 4.0 x 10(-8) cm2/s) because of augmented mixture free volume induced by water sorption, whereas a more complex composition dependence is observed for alphafilcon A and balafilcon A probably as consequence of a combined effect of polymer relaxation, plasticization, and water clustering. PMID:16392136

  2. Summary report on the evaluation of a 1977--1985 edited sorption data base for isotherm modeling

    SciTech Connect

    Polzer, W.L.; Beckman, R.J.; Fuentes, H.R.; Yong, C.; Chan, P.; Rao, M.G.

    1993-09-01

    Sorption data bases collected by Los Alamos National Laboratory (LANL) from 1977 to 1985 for the Yucca Mountain Project.(YMP) have been inventoried and fitted with isotherm expressions. Effects of variables (e.g., particle size) on the isotherm were also evaluated. The sorption data are from laboratory batch measurements which were not designed specifically for isotherm modeling. However a limited number of data sets permitted such modeling. The analysis of those isotherm data can aid in the design of future sorption experiments and can provide expressions to be used in radionuclide transport modeling. Over 1200 experimental observations were inventoried for their adequacy to be modeled b isotherms and to evaluate the effects of variables on isotherms. About 15% of the observations provided suitable data sets for modeling. The data sets were obtained under conditions that include ambient temperature and two atmospheres, air and CO{sub 2}.

  3. Sorption of aniline derivatives on carbon fabric

    NASA Astrophysics Data System (ADS)

    Fazylova, G. F.; Valinurova, E. R.; Khamitov, E. M.; Kudasheva, F. Kh.

    2015-06-01

    The statistical adsorption of the chloro- and nitroderivatives of aniline on carbon fabric UVIS-AK was studied. The sorption isotherms of anilines on carbon fabric and coals were constructed at room temperature and a comparative analysis of their sorption activity was performed. The sorption isotherms were linearized in the coordinates of the Langmuir and Dubinin-Radushkevich equations. The main sorption parameters were calculated: the characteristic adsorption energies of anilines, changes in the Gibbs energies, monolayer capacities, and sorption equilibrium constants.

  4. Isotherms and thermodynamics for the sorption of heavy metal ions onto functionalized sporopollenin.

    PubMed

    Gubbuk, Ilkay Hilal

    2011-02-15

    In this study, sporopollenin of Lycopodium clavatum spores was used for the sorption experiment. Glutaraldehyde (GA) immobilized sporopollenin (Sp), is employed as a sorbent in sorption of selected heavy metal ions. The sorbent prepared by sequential treatment of sporopollenin by silanazing compound and glutaraldehyde is suggested for sorption of Cu(II), Zn(II) and Co(II) from aqueous solutions. Experimental conditions for effective sorption of heavy metal ions were optimized with respect to different experimental parameters using batch method in detail. Optimum pH range of Cu(II) has occurred at pH≥5.5 and Zn(II), Co(II) at pH≥5.0, for the batch method. All of the metal ions can be desorbed with 10 cm(3) of 0.5 mol dm(-3) of ethylenediaminetetraacetic acid (EDTA) solution. Langmuir, Freundlich and Dubinin-Radushkevich (D-R) isotherm equations were applied to the experimental data. Thermodynamic parameters such as free energy (ΔG(o)), entropy (ΔS(o)) and enthalpy (ΔH(o)) were also calculated from the sorption results used to explain the mechanism of the sorption. The results indicated that this sorbent is successfully employed in the separation of trace Cu(II), Zn(II) and Co(II) from the aqueous solutions. PMID:21144652

  5. Modeling of sorption isotherms of dried vegetable wastes from wholesale market

    SciTech Connect

    Lopez, A.; Iguaz, A.; Esnoz, A.; Virseda, P.

    2000-05-01

    The moisture sorption isotherms of dried vegetable wastes (based on green leaves and fruits) from wholesale market were determined at 25, 40, 60 and 90 C by the static gravimetric method. Experimental data were fit by using several mathematical models. The G.A.B. and the Halsey model gave the minimum mean square error. G.A.B. parameters were related with temperature by Arrhenius expressions.

  6. Comparison of high-pressure CO2 sorption isotherms on Eastern and Western US coals

    SciTech Connect

    Romanov, V; Hur, T -B; Fazio, J; Howard, B

    2013-10-01

    Accurate estimation of carbon dioxide (CO2) sorption capacity of coal is important for planning the CO2 sequestration efforts. In this work, we investigated sorption and swelling behavior of several Eastern and Western US coal samples from the Central Appalachian Basin and from San Juan Basin. The CO2 sorption isotherms have been completed at 55°C for as received and dried samples. The role of mineral components in coal, the coal swelling, the effects of temperature and moisture, and the error propagation have been analyzed. Changes in void volume due to dewatering and other factors such as temporary caging of carbon dioxide molecules in coal matrix were identified among the main factors affecting accuracy of the carbon dioxide sorption isotherms. The (helium) void volume in the sample cells was measured before and after the sorption isotherm experiments and was used to build the volume-corrected data plots.

  7. Comparative equilibrium studies of sorption of Pb(II) ions by sodium and calcium alginate.

    PubMed

    Khotimchenko, Maxim; Kovalev, Valeri; Khotimchenko, Yuri

    2008-01-01

    The absorption of Pb(II) ions from aqueous solution by different alginate compounds was studied in a batch sorption system. Water soluble sodium alginate and insoluble calcium alginate beads were investigated. The lead-binding capacity of both alginate compounds was highest within the pH range 6-8. The binding capacities and rates of Pb(II) ions by alginate compounds were evaluated. The Langmuir, Freundlich, and Bruneaur, Emmet and Teller (BET) sorption models were applied to describe the isotherms and isotherm constants. Sorption isothermal data could be well interpreted by the Langmuir model. The results obtained through the study suggest that alginate compounds are favorable sorbents. The largest amount of Pb(II) ions were bound by sodium alginate although the difference between two compounds was slight. Therefore, alginate substances may be considered as an alternative for sorption and removal of Pb(II) ions from wastewaters. PMID:18814578

  8. Sorption equilibrium of emerging and traditional organic contaminants in leafy rape, Chinese mustard, lettuce and Chinese cabbage.

    PubMed

    Yang, Chien-Ying; Chang, Meei-Ling; Wu, Siang Chen; Shih, Yang-Hsin

    2016-07-01

    Emerging and petroleum contaminants could transfer into food chains by plant uptake, potentially causing food security problems. To build a prediction model, the sorption equilibrium and uptake kinetics of toluene, p-xylene, naphthalene, bisphenol A, and 4-bromo-diphenyl ether in some common leafy vegetables including leafy rape, Chinese mustard, lettuce and Chinese cabbage were examined. The kinetic experiments revealed that high sorption rates were observed for these plants that had high lipid contents. For two emerging contaminants with polar functional groups, their resulting isotherms were strongly linear (R(2) = 0.92 to 1.00), indicating that the sorption was dominated by partitioning. Moreover, regression correlation showed that log Klip, the lipid-water partition coefficient, and log Kow, the octanol-water coefficient, for these organic chemicals were strongly linear-related, following the equation: log Klip = 0.894 × log Kow+0.219 (R(2) = 0.953). The correlation equation allows the prediction of the sorption capacity of plant species for an organic compound when the plant composition and the log Kow of the chemical are determined. This improved model containing different organic chemicals with a wide range of log Kow (2.73-4.80) and including emerging contaminants was established, which shows further utilization for predicting the sorption of organic contaminants by plants. PMID:27085315

  9. Beta-glucan rich composite flour biscuits: modelling of moisture sorption isotherms and determination of sorption heat.

    PubMed

    Panjagari, Narender Raju; Singh, Ashish Kumar; Ganguly, Sangita; Indumati, Kangampalayam Palaniswamy

    2015-09-01

    Moisture adsorption isotherms of beta-glucan rich composite flour biscuits were determined at 28, 37 and 45 °C. Experimental data were fitted to 12 mathematical models. A nonlinear regression analysis method was used to evaluate the constants of the sorption equations. Statistical testing of sorption models was carried out using multiple criteria such as coefficient of determination (R (2) ), reduced chi-square (χ (2) ), mean relative percent deviation modulus (P) and plotting of residuals. BET (R (2)  > 0.99; χ (2)  < 0.09; P < 7.52; RMS% < 9.22) was found suitable for predicting the M e -a w relationship in the a w range of 0.10-0.53. However, in the a w range of 0.10-0.85, although Ferro-Fontan and GAB models were found to have high R (2) values (>0.99), Peleg model was found to meet the multiple statistical criteion (R (2)  > 0.9996; χ (2)  < 0.04; P < 3.97; RMS% < 7.09). Properties of sorbed water were also determined. BET, GAB and Caurie monolayer moisture contents ranged from 2.64 to 3.36, 1.29-2.66 and 1.88-3.38 % d.b., respectively. Second-order regression equation was found to describe the relation between monolayer moisture content, M o and temperature, t (°C). The isosteric heat, calculated using Clausius-Clapeyron equation, was varied between 1.46 and 50.39 kJ g(-1) mol(-1) at moisture levels 1-12 % (d.b.). An exponential relationship was observed between the isosteric heat of sorption and moisture content. PMID:26344964

  10. Mechanistic investigation of non-ideal sorption behavior in natural organic matter. 1. Vapor phase equilibrium.

    PubMed

    Bell, Katherine Young; Leboeuf, Eugene J

    2012-06-19

    Results from an experimental and modeling investigation of the influence of thermodynamic properties of highly purified natural organic matter (NOM) on observed equilibrium sorption/desorption behaviors of vapor phase trichloroethylene (TCE) is presented. Identification of glass transition (T(g)) behavior in Leonardite humic acid and Organosolv lignin enabled evaluation of equilibrium and nonequilibrium sorption behavior in glassy and rubbery NOM. Specific differences in vapor phase equilibrium behavior in NOM above and below their T(g) were identified. In the glassy state (below T(g)), sorption of TCE is well-described by micropore models, with enthalpies of sorption characteristic of microporous, glassy macromolecules. Above T(g), sorptive behavior was well-described by Flory-Huggins theory, indicating that the mobility and structural configuration of rubbery NOM materials may be analogous to the characteristic sorption behavior observed in more mobile, rubbery macromolecules, including strong entropic changes during sorption. Results from this work provide further support that, at least for the samples employed in this study, NOM possesses macromolecular characteristics which display sorption behavior similar to synthetic macromolecules-an important assumption in conceptual sorption equilibrium models used in the analysis of the fate and transport of VOCs in the environment. PMID:22642948

  11. Phosphate sorption by three potential filter materials as assessed by isothermal titration calorimetry.

    PubMed

    Lyngsie, Gry; Penn, Chad J; Hansen, Hans C B; Borggaard, Ole K

    2014-10-01

    Phosphorus eutrophication of lakes and streams, coming from drained farmlands, is a serious problem in areas with intensive agriculture. Installation of phosphate (P) sorbing filters at drain outlets may be a solution. The aim of this study was to improve the understanding of reactions involved in P sorption by three commercial P sorbing materials, i.e. Ca/Mg oxide-based Filtralite-P, Fe oxide-based CFH-12 and Limestone in two particle sizes (2-1 mm and 1-0.5 mm), by means of isothermal titration calorimetry (ITC), sorption isotherms, sequential extractions and SEM-EDS. The results indicate that P retention by CFH is due to surface complexation by rapid formation of strong Fe-P bonds. In contrast, retention of P by Filtralite-P and Limestone strongly depends on pH and time and is interpreted due to formation of calcium phosphate precipitate(s). Consequently, CFH can unambiguously be recommended as P retention filter material in drain outlets, whereas the use of Filtralite-P and Limestone has certain (serious) limitations. Thus, Filtralite-P has high capacity to retain P but only at alkaline pH (pH ≥ 10) and P retention by Limestone requires long-time contact and a high ratio between sorbent and sorbate. PMID:24833525

  12. Idealized Shale Sorption Isotherm Measurements to Determine Pore Volume, Pore Size Distribution, and Surface Area

    NASA Astrophysics Data System (ADS)

    Holmes, R.; Wang, B.; Aljama, H.; Rupp, E.; Wilcox, J.

    2014-12-01

    One method for mitigating the impacts of anthropogenic CO2-related climate change is the sequestration of CO2 in depleted gas and oil reservoirs, including shale. The accurate characterization of the heterogeneous material properties of shale, including pore volume, surface area, pore size distributions (PSDs) and composition is needed to understand the interaction of CO2 with shale. Idealized powdered shale sorption isotherms were created by varying incremental amounts of four essential components by weight. The first two components, organic carbon and clay, have been shown to be the most important components for CO2 uptake in shales. Organic carbon was represented by kerogen isolated from a Silurian shale, and clay groups were represented by illite from the Green River shale formation. The rest of the idealized shale was composed of equal parts by weight of SiO2 to represent quartz and CaCO3 to represent carbonate components. Baltic, Eagle Ford, and Barnett shale sorption measurements were used to validate the idealized samples. The idealized and validation shale sorption isotherms were measured volumetrically using low pressure N2 (77K) and CO2 (273K) adsorbates on a Quantachrome Autosorb IQ2. Gravimetric isotherms were also produced for a subset of these samples using CO2 and CH4adsorbates under subsurface temperature and pressure conditions using a Rubotherm magnetic suspension balance. Preliminary analyses were inconclusive in validating the idealized samples. This could be a result of conflicting reports of total organic carbon (TOC) content in each sample, a problem stemming from the heterogeneity of the samples and different techniques used for measuring TOC content. The TOC content of the validation samples (Eagle Ford and Barnett) was measured by Rock-Eval pyrolysis at Weatherford Laboratories, while the TOC content in the Baltic validation samples was determined by LECO TOC. Development of a uniform process for measuring TOC in the validation samples is

  13. Stable carbon and hydrogen isotope fractionation of dissolved organic groundwater pollutants by equilibrium sorption

    NASA Astrophysics Data System (ADS)

    Höhener, Patrick; Yu, Xianjing

    2012-03-01

    Linear free energy relationships (LFERs) were established which relate equilibrium vapor-liquid isotope effects to stable carbon and hydrogen isotope enrichment factors for equilibrium sorption to geosorbents. The LFERs were established for normal, cyclic or branched alkanes, monoaromatic hydrocarbons, and chloroethenes. These LFERs predict that isotopic light compounds sorb more strongly than their heavy counterparts. Defining fractionation as in classical literature by "heavy divided by light", carbon enrichment factors for equilibrium sorption were derived which ranged from - 0.13 ± 0.04‰ (benzene) to - 0.52 ± 0.19‰ (trichloroethene at 5-15 °C). Hydrogen enrichment factors for sorption of 14 different compounds were between - 2.4 and - 9.2‰. For perdeuterated hydrocarbons the predicted enrichment factors ranged from - 19 ± 5.4‰ (benzene) to - 64 ± 30‰ (cyclohexane). Equilibrium sorption experiments with a soil and activated carbon as sorbents were performed in the laboratory for perdeuterocyclohexane and perdeuterotoluene. The measured D/H enrichments agreed with the LFER prediction for both compounds and both sorbents within the uncertainty estimate of the prediction. The results of this work suggest that equilibrium sorption does create only very small isotope shifts for 13C in groundwater pollutants in aquifers. It is also suggested that deuterium shifts are expected to be higher, especially for strongly sorbing pollutants.

  14. 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

    2015-04-01

    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. PMID:25576783

  15. CELL DENSITY AND NON-EQUILIBRIUM SORPTION EFFECTS ON BACTERIAL DISPERSAL IN GROUNDWATER MICROCOSMS

    EPA Science Inventory

    The relative importance of dispersion, physical straining, non-equilibrium sorption, and cell density on the dispersal of bacteria was examined in saturated, flow-dynamic sand columns. The bacterial breakthrough as a was followed by measuring the effluent concentration of 3H-aden...

  16. Influence of soil properties on heavy metal sequestration by biochar amendment: 1. Copper sorption isotherms and the release of cations.

    PubMed

    Uchimiya, Minori; Klasson, K Thomas; Wartelle, Lynda H; Lima, Isabel M

    2011-03-01

    The amendment of carbonaceous materials such as biochars and activated carbons is a promising in situ remediation strategy for both organic and inorganic contaminants in soils and sediments. Mechanistic understandings in sorption of heavy metals on amended soil are necessary for appropriate selection and application of carbonaceous materials for heavy metal sequestration in specific soil types. In this study, copper sorption isotherms were obtained for soils having distinct characteristics: clay-rich, alkaline San Joaquin soil with significant heavy metal sorption capacity, and eroded, acidic Norfolk sandy loam soil having low capacity to retain copper. The amendment of acidic pecan shell-derived activated carbon and basic broiler litter biochar lead to a greater enhancement of copper sorption in Norfolk soil than in San Joaquin soil. In Norfolk soil, the amendment of acidic activated carbon enhanced copper sorption primarily via cation exchange mechanism, i.e., release of proton, calcium, and aluminum, while acid dissolution of aluminum cannot be ruled out. For San Joaquin soil, enhanced copper retention by biochar amendment likely resulted from the following additional mechanisms: electrostatic interactions between copper and negatively charged soil and biochar surfaces, sorption on mineral (ash) components, complexation of copper by surface functional groups and delocalized π electrons of carbonaceous materials, and precipitation. Influence of biochar on the release of additional elements (e.g., Al, Ca) must be carefully considered when used as a soil amendment to sequester heavy metals. PMID:21147495

  17. Humidity scanning quartz crystal microbalance with dissipation monitoring setup for determination of sorption-desorption isotherms and rheological changes

    SciTech Connect

    Björklund, Sebastian Kocherbitov, Vitaly

    2015-05-15

    A new method to determine water sorption-desorption isotherms with high resolution in the complete range of water activities (relative humidities) is presented. The method is based on quartz crystal microbalance with dissipation monitoring (QCM-D). The QCM-D is equipped with a humidity module in which the sample film is kept in air with controlled humidity. The experimental setup allows for continuous scanning of the relative humidity from either dry to humid conditions or vice versa. The amount of water sorbed or desorbed from the sample is determined from the resonance frequencies of the coated quartz sensor, via analysis of the overtone dependence. In addition, the method allows for characterization of hydration induced changes of the rheological properties from the dissipation data, which is closely connected to the viscoelasticity of the film. The accuracy of the humidity scanning setup is confirmed in control experiments. Sorption-desorption isotherms of pig gastric mucin and lysozyme, obtained by the new method, show good agreement with previous results. Finally, we show that the deposition technique used to coat the quartz sensor influences the QCM-D data and how this issue can be used to obtain further information on the effect of hydration. In particular, we demonstrate that spin-coating represents an attractive alternative to obtain sorption-desorption isotherms, while drop-coating provides additional information on changes of the rheological properties during hydration.

  18. Isotherms and Kinetics of Water Vapor Sorption/Desorption for Surface Films of Polyion-Surfactant Ion Complex Salts.

    PubMed

    Gustavsson, Charlotte; Piculell, Lennart

    2016-07-14

    Thin films of "complex salts" (CS = ionic surfactants with polymeric counterions) have recently been shown to respond to humidity changes in ambient air by changing their liquid crystalline structure. We here report isotherms and kinetics of water sorption/desorption for ∼10-100 μm films of alkyltrimethylammonium polyacrylate CS, measured in a dynamic gravimetric vapor sorption instrument over a 0-95% relative humidity (RH) range. The sorption per ion pair was similar to that observed for common ionomers. A kinetic model for the water exchange is presented, assuming that the "external" transport between the vapor reservoir and the film surface is rate-determining. The model predicts that the water content, after a small stepwise change of the reservoir RH, should vary exponentially with time, with a time constant proportional to both the slope of the sorption isotherm and the film thickness. These predictions were confirmed for our films over large RH ranges, and the external mass transfer coefficient in our setup was calculated from the experimental data. Expressions derived for the Biot number (ratio of characteristic times for internal and external water transport) for the considered limiting case strongly indicate that external water transport should quite generally affect, or even dominate, the measured kinetics for similarly thin hydrated films. PMID:27327628

  19. Hydration and sorption characteristics of a polyfunctional weak-base anion exchanger after the sorption of vanillin and ethylvanillin

    NASA Astrophysics Data System (ADS)

    Rodionova, D. O.; Voronyuk, I. V.; Eliseeva, T. V.

    2016-07-01

    Features of the sorption of substituted aromatic aldehydes by a weak-base anion exchanger under equilibrium conditions are investigated using vanillin and ethylvanillin as examples. Analysis of the sorption isotherms of carbonyl compounds at different temperatures allows us to calculate the equilibrium characteristics of their sorption and assess the entropy and enthalpy contributions to the energy of the process. Hydration characteristics of the macroporous weak-base anion exchanger before and after the sorption of aromatic aldehydes are compared.

  20. Equilibrium theory-based design of simulated moving bed processes under reduced purity requirements linear isotherms.

    PubMed

    Rajendran, Arvind

    2008-03-28

    The design of simulated moving bed processes under reduced purity requirements for systems whose isotherm is linear is considered. Based on the equilibrium theory of chromatography, explicit equations to uniquely identify the separation region that will ensure specified extract and raffinate purities are derived. The identification of the region requires only the knowledge of Henry constants of the solutes, the concentration of the solutes in the feed and the purity specifications. These results are validated using numerical simulations. PMID:18281052

  1. Kinetics and equilibrium of the sorption of bisphenol A by carbon nanotubes from wastewater.

    PubMed

    Bohdziewicz, J; Kamińska, G

    2013-01-01

    The aim of this study was to determine the sorption potential of carbon nanotubes (CNTs) to bisphenol A (BPA) contained in synthetic wastewater whose composition corresponds to biologically treated effluents. These nanotubes differed in their outer diameter, the number of graphene layers and the presence of modifying functional groups. Based on the nitrogen adsorption-desorption isotherms, mensuration of the specific surface area and pore size distribution was undertaken. The porous structure of the CNTs was bidispersive; the majority consisted of micropores, there was an average fraction of mesopores, and macropores did not occur. On the basis of common kinetics models (pseudo-first-order and pseudo-second-order models), a trial of modelling the kinetics of BPA sorption onto nanotubes was undertaken. The experimental data were well fitted only to the pseudo-second-order models. The kinetics study indicated that adsorption of BPA on CNTs proceeded very fast, with the majority of the adsorbate being adsorbed in the first few seconds. The sorption capacity of nanotubes to BPA was the highest for single-walled CNTs. A decrease in the sorption potential of the nanotubes for higher pH values occurred as a result of the deprotonation of the BPA and formation of bisphenolate anions, consequently leading to a decrease of π-π (hydrophobic) interaction and enhancing electrostatic repulsion. Overall, these results unequivocally confirm the ideal performance and potential of nanotubes for removal of micropollutants from synthetic wastewater. Replicating the conditions occurring in real wastewater allows us to expect a high sorption of BPA in real competitive sorption systems. PMID:24056428

  2. A gel probe equilibrium sampler for measuring arsenic porewater profiles and sorption gradients in sediments: I. Laboratory development

    USGS Publications Warehouse

    Campbell, K.M.; Root, R.; O'Day, P. A.; Hering, J.G.

    2008-01-01

    A gel probe equilibrium sampler has been developed to study arsenic (As) geochemistry and sorption behavior in sediment porewater. The gels consist of a hydrated polyacrylamide polymer, which has a 92% water content. Two types of gels were used in this study. Undoped (clear) gels were used to measure concentrations of As and other elements in sediment porewater. The polyacrylamide gel was also doped with hydrous ferric oxide (HFO), an amorphous iron (Fe) oxyhydroxide. When deployed in the field, HFO-doped gels introduce a fresh sorbent into the subsurface thus allowing assessment of in situ sorption. In this study, clear and HFO-doped gels were tested under laboratory conditions to constrain the gel behavior prior to field deployment. Both types of gels were allowed to equilibrate with solutions of varying composition and re-equilibrated in acid for analysis. Clear gels accurately measured solution concentrations (??1%), and As was completely recovered from HFO-doped gels (??4%). Arsenic speciation was determined in clear gels through chromatographic separation of the re-equilibrated solution. For comparison to speciation in solution, mixtures of As(III) and As(V) adsorbed on HFO embedded in gel were measured in situ using X-ray absorption spectroscopy (XAS). Sorption densities for As(III) and As(V) on HFO embedded in gel were obtained from sorption isotherms at pH 7.1. When As and phosphate were simultaneously equilibrated (in up to 50-fold excess of As) with HFO-doped gels, phosphate inhibited As sorption by up to 85% and had a stronger inhibitory effect on As(V) than As(III). Natural organic matter (>200 ppm) decreased As adsorption by up to 50%, and had similar effects on As(V) and As(III). The laboratory results provide a basis for interpreting results obtained by deploying the gel probe in the field and elucidating the mechanisms controlling As partitioning between solid and dissolved phases in the environment. ?? 2008 American Chemical Society.

  3. Metal-anion sorption by chitosan beads: Equilibrium and kinetic studies

    SciTech Connect

    Guibal, E.; Milot, C.; Tobin, J.M.

    1998-04-01

    Chitosan is a well-known biopolymer, whose high nitrogen content confers remarkable ability for the sorption of metal ions from dilute effluents. However, its sorption performance in both equilibrium and kinetic terms is controlled by diffusion processes. Gel bead formation allows an expansion of the polymer network, which improves access to the internal sorption sites and enhances diffusion mechanisms. Molybdate and vanadate recovery using glutaraldehyde cross-linked chitosan beads reaches uptake capacities as high as 7--8 mmol/g, depending on the pH. The optimum pH (3--3.5) corresponded to the predominance range of hydrolyzed polynuclear metal forms and optimum electrostatic attraction. While for beads, particle size does not influence equilibrium, for flakes, increasing sorbent radius significantly decreases uptake capacities to 1.5 mmol/g. Sorption kinetics are mainly controlled by intraparticle diffusion for beads, while for flakes the controlling mechanisms are both external and intraparticle diffusion. The gel conditioning increases the intraparticle diffusivity by 3 orders of magnitude: intraparticle diffusivities range between 10{sup {minus}13} and 10{sup {minus}10} m{sup 2}/min, depending on the sorbent size and the conditioning.

  4. 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. PMID:27082255

  5. 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.

  6. 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, L.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.

  7. Thermodynamic analysis of water vapor sorption isotherms and mechanical properties of selected paper-based food packaging materials.

    PubMed

    Rhim, Jong-Whan; Lee, Jun Ho

    2009-01-01

    Adsorption isotherms of 3 selected paper-based packaging materials, that is, vegetable parchment (VP) paper, Kraft paper, and solid-bleached-sulfate (SBS) paperboard, were determined at 3 different temperatures (25, 40, and 50 degrees C). The GAB isotherm model was found to fit adequately for describing experimental adsorption isotherm data for the paper samples. The monolayer moisture content of the paper samples decreased with increase in temperature, which is in the range of 0.0345 to 0.0246, 0.0301 to 0.0238, and 0.0318 to 0.0243 g water/g solid for the MG paper, the Kraft paper, and the SBS paperboard, respectively. The net isosteric heats of sorption (q(st)) for the paper samples decreased exponentially with increase in moisture content after reaching the maximum values of 18.51, 27.39, and 26.80 kJ/mol for the VP paper, the Kraft paper, and the SBS paperboard, respectively, at low-moisture content. The differential enthalpy and entropy of 3 paper samples showed compensation phenomenon with the isokinetic temperature of 399.7 K indicating that water vapor had been adsorbed onto the paper samples with the same mechanism. Depending on the paper material, tensile strength of paper samples was affected by moisture content. PMID:20492112

  8. Sorption of methylene blue on treated agricultural adsorbents: equilibrium and kinetic studies

    NASA Astrophysics Data System (ADS)

    Tiwari, D. P.; Singh, S. K.; Sharma, Neetu

    2015-03-01

    Agricultural adsorbents are reported to have a remarkable performance for adsorption of dyes. In the present study, formaldehyde and sulphuric acid treated two agricultural adsorbents; potato peel and neem bark are used to adsorb methylene blue. On the whole, the acid-treated adsorbents are investigated to have high sorption efficiency compared to HCHO treated adsorbents. The percentage removal efficiency of H2SO4 treated potato peel (APP) increases considerably high from 75 to 100 % with increase in adsorbent dose, whereas the removal efficiency of H2SO4 treated neem bark (ANB) is found to be 98 % after adding the first dose only. The monolayer sorption behaviour of HCHO treated potato peel (PP) and APP is well defined by Langmuir, whereas the chemisorptions behaviour of HCHO treated neem bark (NB) and ANB is suggested by Temkin's isotherm model. The maximum adsorption capacity measured is highest in ANB followed by NB, PP and APP with the values of 1000, 90, 47.62 and 40.0 mg/g, respectively. The pseudo-second-order kinetic model fitted well with the observed data of all the four adsorbents. The results obtained reveal that NB and ANB both are good adsorbents compared to PP and APP.

  9. Sorption of Ochratoxin A from aqueous solutions using beta-cyclodextrin-polyurethane polymer

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The ability of a cyclodextrin-polyurethane polymer to remove ochratoxin A from aqueous solutions, including wine, was examined by batch rebinding assays and equilibrium sorption isotherms. The results were fit to two parameter models. Freundlich analysis of the sorption isotherm indicates the polyme...

  10. 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. PMID:26752149

  11. Thermal non-equilibrium analysis of porous annulus subjected to segmental isothermal heater - Part A

    NASA Astrophysics Data System (ADS)

    Al-Rashed, Abdullah A. A. A.; Salman, Ahmed N. J.; Khaleed, H. M. T.; Khan, T. M. Yunus; Kamangar, Sarfaraz

    2016-06-01

    The objective of present study is to evaluate the effect of the length and location of segmental heating of inner radius of annular cylinder containing porous medium between inner and outer radii. The fluid and solid matrix of porous medium are assumed to have temperature discrepancy subjected to isothermal heating of heater. The fluid is assumed to follow Darcy law and two separate equations are considered for energy transport to account for the thermal non-equilibrium condition. The boundary conditions are such that fluid and solid phase have different temperatures at the hot wall. The study is conducted for different lengths of heater corresponding to the 20%, 35% and 50% of the total height of the cylinder. The location of the heater is varied to three positions i.e. bottom section, mid-section and top of the cylinder.

  12. Mild hydration of didecyldimethylammonium chloride modified DNA by 1H-nuclear magnetic resonance and by sorption isotherm

    NASA Astrophysics Data System (ADS)

    Harańczyk, H.; Kobierski, J.; Nizioł, J.; Hebda, E.; Pielichowski, J.; Zalitacz, D.; Marzec, M.; El-Ghayoury, A.

    2013-01-01

    The gaseous phase hydration of deoxyribonucleic acid and didecyldimethylammonium chloride (C19H42ClN) complexes (DNA-DDCA) was observed using hydration kinetics, sorption isotherm, and high power nuclear magnetic resonance. Three bound water fractions were distinguished: (i) a very tightly bound water not removed by incubation over silica gel, (ii) a tightly bound water saturating with the hydration time t1h = (0.59 ± 0.04) h, and a loosely bound water fraction, (iii) with the hydration time t2h = (20.9 ± 1.3) h. Proton free induction decay was decomposed into the signal associated with the solid matrix of DNA-DDCA complex (T2S∗≈ 30 μs) and two liquid signal components coming from tightly bound (T2L1∗≈ 100 μs) and from loosely bound water fraction (T2L2∗≈ 1000 μs).

  13. Monte-Carlo sorption and neutron diffraction study of the filling isotherm in clathrate hydrates

    SciTech Connect

    Klapproth, Alice; Kuhs, Werner F.; Chazallon, Bertrand

    1999-06-15

    We are interested in the thermodynamics of the gas filling of clathrate hydrates. In order to determine the pressure-dependent filling of the cages, neutron powder diffraction experiments on N{sub 2} and CO{sub 2} clathrates were performed. Interaction potentials were refined by comparing the experimentally determined fillings with those generated by MC-sorption calculations. Unsatisfactory agreement between experiment and simulation is observed when using the widely employed SPC water-water interaction potential.

  14. Moisture sorption isotherms and thermodynamic properties of mexican mennonite-style cheese.

    PubMed

    Martinez-Monteagudo, Sergio I; Salais-Fierro, Fabiola

    2014-10-01

    Moisture adsorption isotherms of fresh and ripened Mexican Mennonite-style cheese were investigated using the static gravimetric method at 4, 8, and 12 °C in a water activity range (aw) of 0.08-0.96. These isotherms were modeled using GAB, BET, Oswin and Halsey equations through weighed non-linear regression. All isotherms were sigmoid in shape, showing a type II BET isotherm, and the data were best described by GAB model. GAB model coefficients revealed that water adsorption by cheese matrix is a multilayer process characterized by molecules that are strongly bound in the monolayer and molecules that are slightly structured in a multilayer. Using the GAB model, it was possible to estimate thermodynamic functions (net isosteric heat, differential entropy, integral enthalpy and entropy, and enthalpy-entropy compensation) as function of moisture content. For both samples, the isosteric heat and differential entropy decreased with moisture content in exponential fashion. The integral enthalpy gradually decreased with increasing moisture content after reached a maximum value, while the integral entropy decreased with increasing moisture content after reached a minimum value. A linear compensation was found between integral enthalpy and entropy suggesting enthalpy controlled adsorption. Determination of moisture content and aw relationship yields to important information of controlling the ripening, drying and storage operations as well as understanding of the water state within a cheese matrix. PMID:25328178

  15. Graphical representation for isothermal kinetics of non-equilibrium grain-boundary segregation

    SciTech Connect

    Wang Kai; Xu Tingdong; Song Shenhua; Shao Chong

    2011-06-15

    A model of non-equilibrium grain-boundary segregation of solute is expressed with graphs for the isothermal aging at various temperatures after quenching from a solution temperature. It is found from the graphical representations that when the samples are aged for a certain time at various temperatures there is a maximum value in the segregation concentration at a certain temperature. The aging time is equal or close to the critical time of non-equilibrium segregation corresponding to this temperature. This finding is experimentally confirmed with sulfur in an Ni-base superalloy with the aid of Auger electron spectroscopy. As an application of the new finding, a mechanism for intermediate temperature embrittlement of alloys is suggested and identified experimentally with tension tests of the superalloy. - Research Highlights: {yields} A peak of solute segregation emerges at a temperature when aging for a certain time at various temperatures after quenching. {yields} The aging time is equal or close to the critical time of segregation at this temperature. {yields} This finding is experimentally confirmed in an Ni-Cr-Fe superalloy. {yields} A mechanism for intermediate temperature embrittlement of alloys is proposed.

  16. Interaction of removal Ethidium Bromide with Carbon Nanotube: Equilibrium and Isotherm studies.

    PubMed

    Moradi, Omid; Norouzi, Mehdi; Fakhri, Ali; Naddafi, Kazem

    2014-01-01

    Drinking water resources may be contaminated with Ethidium Bromide (EtBr) which is commonly used in molecular biology laboratories for DNA identification in electrophoresis. Carbon nanotubes are expected to play an important role in sensing, pollution treatment and separation techniques. In this study adsorption of Ethidium Bromide on single-walled carbon nanotubes (SWCNTs) and carboxylate group functionalized single-walled carbon nanotube (SWCNT-COOH) surfaces have been investigated by UV-vis spectrophotometer. The effect of contact time, initial concentration and temperature were investigated. The adsorbents exhibits high efficiency for EtBr adsorption and equilibrium can be achieved in 6 and 3 min for SWCNTs and SWCNT-COOH, respectively. The effect of temperature on adsorption of EtBr by toward adsorbents shows the process in this research has been endothermic. The results showed that the equilibrium data were well described by the Langmuir isotherm model, with a maximum adsorption capacity of 0.770 and 0.830 mg/g for SWCNTs and SWCNT-COOH, respectively. The adsorption of EtBr on SWCNT-COOH is more than SWCNTs surfaces. A comparison of kinetic models was evaluated for the pseudo first-order, pseudo second-order models. Pseudo second-order was found to agree well with the experimental data. PMID:24401790

  17. Interaction of removal Ethidium Bromide with Carbon Nanotube: Equilibrium and Isotherm studies

    PubMed Central

    2014-01-01

    Drinking water resources may be contaminated with Ethidium Bromide (EtBr) which is commonly used in molecular biology laboratories for DNA identification in electrophoresis. Carbon nanotubes are expected to play an important role in sensing, pollution treatment and separation techniques. In this study adsorption of Ethidium Bromide on single-walled carbon nanotubes (SWCNTs) and carboxylate group functionalized single-walled carbon nanotube (SWCNT-COOH) surfaces have been investigated by UV–vis spectrophotometer. The effect of contact time, initial concentration and temperature were investigated. The adsorbents exhibits high efficiency for EtBr adsorption and equilibrium can be achieved in 6 and 3 min for SWCNTs and SWCNT-COOH, respectively. The effect of temperature on adsorption of EtBr by toward adsorbents shows the process in this research has been endothermic. The results showed that the equilibrium data were well described by the Langmuir isotherm model, with a maximum adsorption capacity of 0.770 and 0.830 mg/g for SWCNTs and SWCNT-COOH, respectively. The adsorption of EtBr on SWCNT-COOH is more than SWCNTs surfaces. A comparison of kinetic models was evaluated for the pseudo first-order, pseudo second-order models. Pseudo second-order was found to agree well with the experimental data. PMID:24401790

  18. Numerical simulation of advective-dispersive multisolute transport with sorption, ion exchange and equilibrium chemistry

    USGS Publications Warehouse

    Lewis, F.M.; Voss, C.I.; Rubin, Jacob

    1986-01-01

    A model was developed that can simulate the effect of certain chemical and sorption reactions simultaneously among solutes involved in advective-dispersive transport through porous media. The model is based on a methodology that utilizes physical-chemical relationships in the development of the basic solute mass-balance equations; however, the form of these equations allows their solution to be obtained by methods that do not depend on the chemical processes. The chemical environment is governed by the condition of local chemical equilibrium, and may be defined either by the linear sorption of a single species and two soluble complexation reactions which also involve that species, or binary ion exchange and one complexation reaction involving a common ion. Partial differential equations that describe solute mass balance entirely in the liquid phase are developed for each tenad (a chemical entity whose total mass is independent of the reaction process) in terms of their total dissolved concentration. These equations are solved numerically in two dimensions through the modification of an existing groundwater flow/transport computer code. (Author 's abstract)

  19. Moisture adsorption isotherms and glass transition temperature of pectin.

    PubMed

    Basu, Santanu; Shivhare, U S; Muley, S

    2013-06-01

    The moisture adsorption isotherms of low methoxyl pectin were determined at 30-70°C and water activity ranging from 0.11 to 0.94. The moisture adsorption isotherms revealed that the equilibrium moisture content increased with water activity. Increase in temperature, in general, resulted in decreased equilibrium moisture content. However in some cases, equilibrium moisture content values increased with temperature at higher water activities. Selected sorption models (GAB, Halsey, Henderson, Oswin, modified Oswin) were tested for describing the adsorption isotherms. Parameters of each sorption models were determined by nonlinear regression analysis. Oswin model gave the best fit for pectin sorption behaviour. Isosteric heat of sorption decreased with increase in moisture content and varied between 14.607 and 0.552 kJ/mol. Glass transition temperature decreased with increase in moisture content of pectin. PMID:24425957

  20. Solute transport with equilibrium aqueous complexation and either sorption or ion exchange: Simulation methodology and applications

    USGS Publications Warehouse

    Lewis, F.M.; Voss, C.I.; Rubin, J.

    1987-01-01

    Methodologies that account for specific types of chemical reactions in the simulation of solute transport can be developed so they are compatible with solution algorithms employed in existing transport codes. This enables the simulation of reactive transport in complex multidimensional flow regimes, and provides a means for existing codes to account for some of the fundamental chemical processes that occur among transported solutes. Two equilibrium-controlled reaction systems demonstrate a methodology for accommodating chemical interaction into models of solute transport. One system involves the sorption of a given chemical species, as well as two aqueous complexations in which the sorbing species is a participant. The other reaction set involves binary ion exchange coupled with aqueous complexation involving one of the exchanging species. The methodology accommodates these reaction systems through the addition of nonlinear terms to the transport equations for the sorbing species. Example simulation results show (1) the effect equilibrium chemical parameters have on the spatial distributions of concentration for complexing solutes; (2) that an interrelationship exists between mechanical dispersion and the various reaction processes; (3) that dispersive parameters of the porous media cannot be determined from reactive concentration distributions unless the reaction is accounted for or the influence of the reaction is negligible; (4) how the concentration of a chemical species may be significantly affected by its participation in an aqueous complex with a second species which also sorbs; and (5) that these coupled chemical processes influencing reactive transport can be demonstrated in two-dimensional flow regimes. ?? 1987.

  1. Dynamic sorption of ammonium by sandy soil in fixed bed columns: Evaluation of equilibrium and non-equilibrium transport processes.

    PubMed

    Jellali, S; Diamantopoulos, E; Kallali, H; Bennaceur, S; Anane, M; Jedidi, N

    2010-01-01

    The release of excess nitrogen-containing compounds into groundwater is a major concern in aquifer recharge by the Soil Aquifer Treatment (SAT) process. Ammonium (NH(4)(+)) is one of the most nocive and common nitrogen compounds in wastewaters. In order to assess the risk of wastewater use for aquifer recharge, NH(4)(+)adsorption onto Souhil wadi soil sampled from the SAT pilot plant (Nabeul, Tunisia) was studied using laboratory columns experiments. Several experiments were conducted using aqueous synthetic solutions under different aqueous ammonium concentrations and flow rates. Furthermore, a real wastewater solution was used to test the effect of competitive cations contents on NH(4)(+) adsorption. Afterwards, the Hydrus-1D model was used in inverse mode to simulate the ammonium transport through the Souhil wadi soil. For the synthetic solutions, the adsorbed ammonium amount varied from 1 to 30.7 mg kg(-1) for aqueous ammonium concentrations between 4.9 and 36.4 mg L(-1). The linear isotherm model was found to be the most suitable for describing this adsorption. The flow rate decrease from 45 to 15 mL min(-1) induced an increase in the ammonium adsorption capacity by 49%. Indeed, the lesser the flow rate is, the longer the residence time and the higher the exchange between the aqueous solution and soil matrix. The use of wastewater instead of aqueous synthetic solution decreased about 7 times the Souhil wadi adsorption capacity of ammonium because of its relatively high concentrations of competitive ions such as calcium and magnesium. The use of the Hydrus-1D model showed that the chemical non-equilibrium model was the best to simulate the ammonium transport through the laboratory soil columns. PMID:20034727

  2. Equilibrium metal concentration at zero net sorption (EMC{sub 0}): A new concept

    SciTech Connect

    Yuan, G.; Lavkulich, L.M.

    1995-12-31

    Heavy metals in soils and waters are of environmental concerns. Since total concentration of a metal in soil is not directly related to its bioavailability, soil tests rely on measurement of extractable or labile fractions of metals. However, reagents used in the measurements are significantly different from natural waters entering soils in terms of ionic strength, acidity, and heavy metal concentration, making the direct interpretation of test results difficult if correlation between chemical test data and plant response in the field is not available. It is suggested that EMC{sub 0} be used as an indicator of heavy metal status in soils. EMC{sub 0} can be determined as follows: solutions with various metal concentrations (C{sub 0}) in 0.005 M CaCl{sub 2} matrix are added to soil samples at a fixed soil/solution ratio. The suspensions are shaken 24 hrs to achieve equilibrium, and centrifuged. Metal concentrations in supernatants are analyzed and plotted against C{sub 0}. A regression line based on plotted data an da 1:1 line are drawn. The X-axis value corresponding t the intersection of the liens is EMC{sub 0}. At the intersection, metal concentration at equilibrium equals that in the initial solution; indicating net sorption of the metal is zero. A EMC{sub 0} value of 0.27 mg/kg Zn was determined in a soil sample from the Fraser Valley in British Columbia. The soil received heavy applications of poultry manure.This value is much greater than water soluble Zn (0.06 mg/kg) of the sample. The significance of EMC{sub 0} is when concentrations of a metal in natural waters are less than EMC{sub 0}, soil will release the metal to soil solution. EMC{sub 0} may be useful in comparing relative degrees of contamination in contaminated soils.

  3. Batch removal of malachite green from aqueous solutions by adsorption on oil palm trunk fibre: equilibrium isotherms and kinetic studies.

    PubMed

    Hameed, B H; El-Khaiary, M I

    2008-06-15

    Oil palm trunk fibre (OPTF)--an agricultural solid waste--was used as low-cost adsorbent to remove malachite green (MG) from aqueous solutions. The operating variables studied were contact time, initial dye concentration, and solution pH. Equilibrium adsorption data were analyzed by three isotherms, namely the Freundlich isotherm, the Langmuir isotherm, and the multilayer adsorption isotherm. The best fit to the data was obtained with the multilayer adsorption. The monolayer adsorption capacity of OPTF was found to be 149.35 mg/g at 30 degrees C. Adsorption kinetic data were modeled using the Lagergren pseudo-first-order, Ho's pseudo-second-order and Elovich models. It was found that the Lagergren's model could be used for the prediction of the system's kinetics. The overall rate of dye uptake was found to be controlled by external mass transfer at the beginning of adsorption, then for initial MG concentrations of 25, 50, 100, 150, and 300 mg/L the rate-control changed to intraparticle diffusion at a later stage, but for initial MG concentrations 200 and 250 mg/L no evidence was found of intraparticle diffusion at any period of adsorption. It was found that with increasing the initial concentration of MG, the pore-diffusion coefficient increased while the film-diffusion coefficient decreased. PMID:18022316

  4. 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. PMID:27101455

  5. [Sorption behaviors of BDE-28 on natural soils].

    PubMed

    Liu, Wen-Xin; Ling, Xi; Chen, Jiang-Lin; Li, Wei-Bo; Dou, Han; Tao, Shu

    2011-03-01

    The sorption kinetics and isotherms of BDE-28 on three natural soils with different soil organic matter fractions (f(oc)) were investigated. The results indicated that a two (fast and slow)-compartment first-order model was more appropriate for describing the sorption kinetic data, compared to a one-compartment first-order model, especially in the initial sorption stage within 25 h. The fast sorption was predominant during the whole sorption process from beginning to the apparent sorption equilibrium; while the contribution of the slow sorption to the total sorption amount gradually increased and then achieved a plateau at 49 h or 55 h. The approaching time to the individual sorption capacity for the fast sorption was much shorter than that for the slow sorption. The contribution of the fast sorption to the increase in the total sorption amount of BDE-28 was prevailing at the beginning of sorption process from 2.5 h to 4.5 h; whereas the fraction of the slow sorption became primary at the subsequent stage of sorption process. The fitting results by the Dubinin-Ashtakhov (DA) model were comparable with those by the Freundlich model in the range of apparent equilibrium concentration studied. As for the Freundlich model, the nonlinear exponent (n) values of BDE-28 for the two samples with lower f(oc) (0.72%) or higher f(oc) (7.90%) approached to 1.0 (1.03 +/- 0.05 and 1.00 +/- 0.05, respectively), suggesting the linear sorption characteristics in the studied range of apparent equilibrium concentrations of BDE-28; while the nonlinear behavior of BDE-28 for the left sample with medium f(oc) (4.42%) was indicated by its n value less than 1.0 (0.89 +/- 0.04). PMID:21634174

  6. Separation of (+)-catechin and quercetin on mesoporous MCM-41 composites: Dynamics of the sorption of flavonoids

    NASA Astrophysics Data System (ADS)

    Karpov, S. I.; Korabel'nikova, E. O.

    2015-06-01

    An analysis of conditions for chromatographic separation of quercetin and (+)-catechin based on experimental data and using the equations of an asymptotic model of sorption dynamics for substances characterized by convex isotherms of sorption is presented. The effects of the equilibrium (distribution coefficient) and kinetic (diffusion coefficient) factors on the dynamics of the sorption of flavonoids by ordered mesoporous material of the MCM-41 type and its composites with grafted organosilane groups is considered. The effects of kinetic and equilibrium parameters on the broadening of adsorption fronts is demonstrated with allowance for the inner and outer diffusion limitations of the sorption process.

  7. Transport and sorption of volatile organic compounds and water vapor in porous media

    SciTech Connect

    Lin, Tsair-Fuh

    1995-07-01

    To gain insight on the controlling mechanisms for VOC transport in porous media, the relations among sorbent properties, sorption equilibrium and intraparticle diffusion processes were studied at the level of individual sorbent particles and laboratory columns for soil and activated carbon systems. Transport and sorption of VOCs and water vapor were first elucidated within individual dry soil mineral grains. Soil properties, sorption capacity, and sorption rates were measured for 3 test soils; results suggest that the soil grains are porous, while the sorption isotherms are nonlinear and adsorption-desorption rates are slow and asymmetric. An intragranular pore diffusion model coupled with the nonlinear Freundlich isotherm was developed to describe the sorption kinetic curves. Transport of benzene and water vapor within peat was studied; partitioning and sorption kinetics were determined with an electrobalance. A dual diffusion model was developed. Transport of benzene in dry and moist soil columns was studied, followed by gaseous transport and sorption in activated carbon. The pore diffusion model provides good fits to sorption kinetics for VOCs to soil and VOC to granular activated carbon and activated carbon fibers. Results of this research indicate that: Intraparticle diffusion along with a nonlinea sorption isotherm are responsible for the slow, asymmetric sorption-desorption. Diffusion models are able to describe results for soil and activated carbon systems; when combined with mass transfer equations, they predict column breakthrough curves for several systems. Although the conditions are simplified, the mechanisms should provide insight on complex systems involving transport and sorption of vapors in porous media.

  8. Relationship between Crystal Thickness and Isothermal Crystallization Temperature for Determination of Equilibrium Melting Temperature for Syndiotatic Polypropylene

    NASA Astrophysics Data System (ADS)

    Wang, Zhi-Gang; Hsiao Hsiao, Benjamin; Srinivas, Srivatsan; Crist, Buckley

    2000-03-01

    Syndiotatic polypropylene (sPP) was used to investigate the relationship between isothermal crystallization temperature (Tc = 70-115^oC), crystal thickness and subsequent melting using simultaneous synchrotron small-angle X-ray scattering (SAXS) and wide-angle X-ray diffraction (WAXD) in conjunction with DSC. The thickest lamellar crystals melt at the end of the DSC endotherm. At this temperature, the SAXS intensity (corrected formelt scattering) showed a diffuse profile, and the crystalline feature in the WAXD pattern was completely absent. This crystal thickness was estimated using an approach based on the single lamella structure factor, which will also be compared to the value determined by the interface distribution function. The equilibrium melting temperature obtained this way will be contrasted by other methods such as the Hoffman-Weeks approach. Acknowledgement: This work was supported by by a NSF grant (DMR 9732653).

  9. Equilibrium studies of copper ion adsorption onto palm kernel fibre.

    PubMed

    Ofomaja, Augustine E

    2010-07-01

    The equilibrium sorption of copper ions from aqueous solution using a new adsorbent, palm kernel fibre, has been studied. Palm kernel fibre is obtained in large amounts as a waste product of palm oil production. Batch equilibrium studies were carried out and system variables such as solution pH, sorbent dose, and sorption temperature were varied. The equilibrium sorption data was then analyzed using the Langmuir, Freundlich, Dubinin-Radushkevich (D-R) and Temkin isotherms. The fit of these isotherm models to the equilibrium sorption data was determined, using the linear coefficient of determination, r(2), and the non-linear Chi-square, chi(2) error analysis. The results revealed that sorption was pH dependent and increased with increasing solution pH above the pH(PZC) of the palm kernel fibre with an optimum dose of 10g/dm(3). The equilibrium data were found to fit the Langmuir isotherm model best, with a monolayer capacity of 3.17 x 10(-4)mol/g at 339K. The sorption equilibrium constant, K(a), increased with increasing temperature, indicating that bond strength between sorbate and sorbent increased with temperature and sorption was endothermic. This was confirmed by the increase in the values of the Temkin isotherm constant, B(1), with increasing temperature. The Dubinin-Radushkevich (D-R) isotherm parameter, free energy, E, was in the range of 15.7-16.7kJ/mol suggesting that the sorption mechanism was ion exchange. Desorption studies showed that a high percentage of the copper was desorbed from the adsorbent using acid solutions (HCl, HNO(3) and CH(3)COOH) and the desorption percentage increased with acid concentration. The thermodynamics of the copper ions/palm kernel fibre system indicate that the process is spontaneous and endothermic. PMID:20346574

  10. Magnetohydrostatic equilibrium structure and mass of filamentary isothermal cloud threaded by lateral magnetic field

    SciTech Connect

    Tomisaka, Kohji

    2014-04-10

    Herschel observations have recently revealed that interstellar molecular clouds consist of many filaments. Polarization observations in optical and infrared wavelengths indicate that the magnetic field often runs perpendicular to the filament. In this article, we study the magnetohydrostatic configuration of isothermal gas in which the thermal pressure and the Lorentz force are balanced against the self-gravity, and the magnetic field is globally perpendicular to the axis of the filament. The model is controlled by three parameters: center-to-surface density ratio (ρ {sub c}/ρ {sub s}), plasma β of surrounding interstellar gas (β{sub 0}), and the radius of the hypothetical parent cloud normalized by the scale-height (R{sub 0}{sup ′}), although there remains freedom in how the mass is distributed against the magnetic flux (mass loading). In the case where R{sub 0}{sup ′} is small enough, the magnetic field plays a role in confining the gas. However, the magnetic field generally has the effect of supporting the cloud. There is a maximum line-mass (mass per unit length) above which the cloud is not supported against gravity. Compared with the maximum line-mass of a nonmagnetized cloud (2c{sub s}{sup 2}/G, where c{sub s} and G represent, respectively, the isothermal sound speed and the gravitational constant), that of the magnetized filament is larger than the nonmagnetized one. The maximum line-mass is numerically obtained as λ{sub max}≃0.24Φ{sub cl}/G{sup 1/2}+1.66c{sub s}{sup 2}/G, where Φ{sub cl} represents one half of the magnetic flux threading the filament per unit length. The maximum mass of the filamentary cloud is shown to be significantly affected by the magnetic field when the magnetic flux per unit length exceeds Φ{sub cl} ≳ 3 pc μG (c{sub s} /190 m s{sup –1}){sup 2}.

  11. Thermal non-equilibrium analysis of porous annulus subjected to segmental isothermal heater - Part B

    NASA Astrophysics Data System (ADS)

    Al-Rashed, Abdullah A. A. A.; Salman, Ahmed N. J.; Khaleed, H. M. T.; Khan, T. M. Yunus; Kamangar, Sarfaraz

    2016-06-01

    Investigation of heat transfer in an annular porous cylinder subjected to segmental heating is carried out. Thermal non-equilibrium condition is applied to porous medium. Finite element method is used to solve the governing partial differential equations. The fluid is assumed to follow Darcy law. The boundary conditions are such that the fluid and solid phase have different temperatures at the hot wall. The current study is an extension of the paper part-A in this conference but elaborating the results for heat transfer behavior in terms of Nusselt number.

  12. Thermoconvective instability and local thermal non-equilibrium in a porous layer with isoflux-isothermal boundary conditions

    NASA Astrophysics Data System (ADS)

    Celli, Michele; Barletta, Antonio; Storesletten, Leiv

    2014-04-01

    The effects of lack of local thermal equilibrium between the solid phase and the fluid phase are taken into account for the convective stability analysis of a horizontal porous layer. The layer is bounded by a pair of plane parallel walls which are impermeable and such that the lower wall is subject to a uniform flux heating, while the upper wall is isothermal. The local thermal non-equilibrium is modelled through a two-temperature formulation of the energy exchange between the phases, resulting in a pair of local energy balance equations: one for each phase. Small-amplitude disturbances of the basic rest state are envisaged to test the stability. Then, the standard normal mode procedure is adopted to detect the onset conditions of convective rolls. Beyond the Darcy-Rayleigh number, playing the role of order parameter for the transition to instability, the relevant dimensionless parameters are the inter-phase heat transfer parameter and the thermal conductivity ratio. The disturbance governing equations, formulated as an eigenvalue problem, are solved numerically by a shooting method. Results are reported for the neutral stability curves and for the critical values for the onset of instability.

  13. Optimization, equilibrium, kinetic, thermodynamic and desorption studies on the sorption of Cu(II) from an aqueous solution using marine green algae: Halimeda gracilis.

    PubMed

    Jayakumar, R; Rajasimman, M; Karthikeyan, C

    2015-11-01

    The aptitude of marine green algae Helimeda gracilis for sorption of Cu(II) ions from an aqueous solution was studied in batch experiments. The effect of relevant parameters such as function of pH, sorbent dosage, agitation speed and contact time was evaluated by using Response surface methodology (RSM). A maximum percentage removal of Cu (II) by Halimeda gracilis occurs at pH-4.49, sorbent dosage-1.98g/L, agitation speed-119.43rpm and contact time-60.21min. Further, the sorbent was characterized by using Fourier Transform Infrared Spectroscopy (FTIR) and Scanning electron microscope (SEM) analysis. Experimental data were analyzed in terms of pseudo-first order, pseudo-second order, intraparticle diffusion, power function and elovich kinetic models. The results showed that the sorption process of Cu(II) ions followed well pseudo-second order kinetics. The sorption data of Cu(II) ions at 308.15K are fitted to Langmuir, Freundlich, Dubinin-Radushkevich (D-R), Temkin, Sips and Toth isotherms. Sorption of Cu(II) onto marine green algae Helimeda gracilis followed the Langmuir and Toth isotherm models (R(2)=0.998 and R(2)=0.999) with the maximum sorption capacity of 38.46 and 38.07mg/g. The calculated thermodynamic parameters such as ΔG°, ΔH° and ΔS° showed that the sorption of Cu(II) ions onto Helimeda gracilis biomass was feasible, spontaneous and endothermic. Desorption study shows that the sorbent could be regenerated using 0.2M HCl solution, with up to 89% recovery. PMID:25866206

  14. Kinetics, equilibrium, and mechanisms of sorption and desorption of 17α-ethinyl estradiol in two natural soils and their organic fractions.

    PubMed

    Li, Jianzhong; Fu, Jing; Xiang, Xi; Wu, Miaomiao; Liu, Xiang

    2013-05-01

    A study was conducted on the kinetics, equilibrium, and mechanisms of sorption and desorption of 17α-ethinyl estradiol (EE2) in six sorbents, which were two natural soils (Bulk1 and Bulk2) and their fractions obtained by alkaline extraction, namely, humic acids (HA1 and HA2), and mineral-bond humins (MHU1 and MHU2). These sorbents, characterized by total organic carbon (TOC), black carbon (BC), gas adsorption and Fourier transform infrared spectra, were shown to be porous solids containing aromatic (hard carbon) and aliphatic carbon (soft carbon). The two-compartment first-order model fitted the kinetics of sorption very well (R(2)>0.990). The fast and slow sorption rate constants ranged from 1.110 h(-1) and 0.026 h(-1) to 2.063 h(-1) and 0.067 h(-1), respectively. The slow sorption was attributed to the diffusion of EE2 in micropores rather than organic matter. The Freundlich model fitted the equilibrium of sorption and desorption very well. The nonlinearity of sorption took the order MHU>bulk soil>HA and was positively related to BC/TOC (p<0.01). The hysteresis in MHU2 with higher BC/TOC was stronger than that in Bulk2 with lower BC/TOC, but a contrary observation was found in MHU1 and Bulk1. This contradictory phenomenon could be attributed to the location difference of hard carbon which greatly affected the desorption process. These findings could give an insight into the sorption mechanisms and promote an accurate model for the transport, fate and risk assessment of EE2 in the environment. PMID:23542434

  15. 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. PMID:25439731

  16. Assessing the effect of grain-scale sorption rate limitations on the fate of hydrophobic organic groundwater pollutants

    NASA Astrophysics Data System (ADS)

    Werner, David; Karapanagioti, Hrissi K.; Sabatini, David A.

    2012-03-01

    Subsurface pollutant transport models accounting for sorption rate limitations are computationally more demanding than those assuming local sorption equilibrium. We combine batch and column tests with modeling for a comparative assessment of different sorption models. For the relatively hydrophobic compound naphthalene, a model assuming local sorption equilibrium was unable to reproduce breakthrough curves in column studies with Canadian River Alluvium sediment which contains carbonaceous particles. Fully calibrated independent forward predictions of a first-order kinetic and two diffusion kinetic sorption models were in much better agreement with the experimental data. Predictions using a diffusion-limited kinetic sorption model assuming concentration-independent sorption coefficients performed equally well as a model using the Freundlich isotherm. Both diffusion-based kinetic sorption models were superior to the first-order rate approach. In the present study, the validity of the local sorption equilibrium assumption is discussed based on a Damköhler number and thus, the compound's sorption properties, the aquifer properties, and the scale of the process. Relatively high groundwater velocities in combination with a low sorption coefficient Kd and slow diffusion limited sorption kinetic rates are necessary conditions to justify the implementation of grain-scale sorption rate limitations in groundwater contaminant fate models. Such conditions exist when a low amount of carbonaceous particles is present in aquifers with high permeability.

  17. Sorption of Zn(II) in aqueous solutions by scoria.

    PubMed

    Kwon, Jang-Soon; Yun, Seong-Taek; Kim, Soon-Oh; Mayer, Bernhard; Hutcheon, Ian

    2005-09-01

    We conducted kinetic and equilibrium sorption experiments on removal of Zn(II) from aqueous solutions by scoria (a vesicular pyroclastic rock with basaltic composition) from Jeju Island, Korea, in order to examine its potential use as an efficient sorbent. The batch-type kinetic sorption tests under variable conditions indicated that the percentage of Zn(II) removal by scoria increases with decreasing initial Zn(II) concentration, particle size, and sorbate/sorbent ratio. However, the sorption capacity decreases with the decrease of the initial Zn(II) concentration and sorbate/sorbent ratio. Equilibrium sorption tests show that Jeju scoria has a larger capacity and affinity for Zn(II) sorption than commercial powdered activated carbon (PAC); at initial Zn(II) concentrations of more than 10mM, the sorption capacity of Jeju scoria is about 1.5 times higher than that of PAC. The acquired sorption data are better fitted to the Langmuir isotherm than the Freundlich isotherm. Careful examination of ionic concentrations in sorption batches suggests that the sorption behavior is mainly controlled by cation exchange and typically displays characteristics of 'cation sorption'. The Zn(II) removal capacity decreases when solution pH decreases because of the competition with hydrogen ions for sorption sites, while the Zn(II) removal capacity increases under higher pH conditions, likely due to hydroxide precipitation. At an initial Zn(II) concentration of 5.0mM, the removal increases from 70% to 96% with the increase of initial pH from 3.0 to 7.0. We recommend Jeju scoria as an economic and efficient sorbent for Zn(II) in contaminated water. PMID:16054911

  18. Sorption isotherms, thermodynamic properties and glass transition temperature of mucilage extracted from chia seeds (Salvia hispanica L.).

    PubMed

    Velázquez-Gutiérrez, Sandra Karina; Figueira, Ana Cristina; Rodríguez-Huezo, María Eva; Román-Guerrero, Angélica; Carrillo-Navas, Hector; Pérez-Alonso, César

    2015-05-01

    Freeze-dried chia mucilage adsorption isotherms were determined at 25, 35 and 40°C and fitted with the Guggenheim-Anderson-de Boer model. The integral thermodynamic properties (enthalpy and entropy) were estimated with the Clausius-Clapeyron equation. Pore radius of the mucilage, calculated with the Kelvin equation, varied from 0.87 to 6.44 nm in the temperature range studied. The point of maximum stability (minimum integral entropy) ranged between 7.56 and 7.63kg H2O per 100 kg of dry solids (d.s.) (water activity of 0.34-0.53). Enthalpy-entropy compensation for the mucilage showed two isokinetic temperatures: (i) one occurring at low moisture contents (0-7.56 kg H2O per 100 kg d.s.), controlled by changes in water entropy; and (ii) another happening in the moisture interval of 7.56-24 kg H2O per 100 kg d.s. and was enthalpy driven. The glass transition temperature Tg of the mucilage fluctuated between 42.93 and 57.93°C. PMID:25659716

  19. Moisture sorption characteristics of freeze dried whey-grape beverage mix.

    PubMed

    Varghese, K Shiby; Radhakrishna, K; Bawa, A S

    2014-10-01

    Moisture sorption isotherms of freeze dried whey-grape beverage powder were determined at 20, 30 and 40 °C. A gravimetric static method was used under 0.11-0.85 water activity range and the sorption isotherms were found to be Type II. Various mathematical models were fitted to experimental data and it was found that Peleg model suits best in describing the equilibrium moisture content-equilibrium relative humidity relationships of instant whey-grape beverage mix over the range of temperatures studied. The net isosteric heat of sorption varied between 5.22 and 1.12 KJ/mol at moisture level varying between 1 and 9 % db. At moisture content below 1 % (db) the isosteric heat of sorption increased sharply for freeze dried whey-grape beverage powder and value of 49.08 KJ/mol was estimated. PMID:25328219

  20. Mechanistic understanding and performance of biosorption of metal ions by grapefruit peel using FTIR spectroscopy, kinetics and adsorption isotherms modeling, alkali and alkaline metal displacement and EDX analysis

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The performance and mechanism of the sorptive removal of Ni2+ and Zn2+ from aqueous solution using grapefruit peel (GFP) as a new sorbent was investigated. The sorption process was fast, equilibrium was established in 60 min. The equilibrium process was described well by the Langmuir isotherm model,...

  1. Sorption of tylosin on clay minerals.

    PubMed

    Zhang, Qian; Yang, Chen; Huang, Weilin; Dang, Zhi; Shu, Xiaohua

    2013-11-01

    The equilibrium sorption of tylosin (TYL) on kaolinite and montmorillonite was measured at different solution pH using batch reactor systems. The results showed that all the sorption isotherms were nonlinear and that the nonlinearity decreased as the solution pH increased for a given clay. At a specific aqueous concentration, the single-point sorption distribution coefficient (KD) of TYL decreased rapidly as the solution pH increased. A speciation-dependent sorption model that accounted for the contributions of the cationic and neutral forms of TYL fit the data well, suggesting that the sorption may be dominated by both ion exchange and hydrophobic interactions. The isotherm data also fit well to a dual mode model that quantifies the contributions of a site-limiting Langmuir component (ion exchange) and a non-specific linear partitioning component (hydrophobic interactions). X-ray diffraction analyses revealed that the interlayers of montmorillonite were expanded due to the uptake of TYL. TYL molecules likely form a monolayer surface coverage. PMID:24007614

  2. Identical mechanism of isochronal and isothermal embrittlement in Ni(Bi) alloy: Thermo-induced non-equilibrium grain-boundary segregation of Bi

    NASA Astrophysics Data System (ADS)

    Zheng, Lei; Chellali, Reda; Schlesiger, Ralf; Meng, Ye; Baither, Dietmar; Schmitz, Guido

    2015-05-01

    Isochronal and isothermal plasticity after thermal pre-treatments are obtained by tensile tests to characterize the embrittling behaviors of Ni(Bi) alloy. Both isochronal and isothermal plasticity show evident minima. Fractography observed by scanning electron microscopy displays intergranular fracture for samples of low plasticity. The microstructure is found to be free of precipitates within grains and at grain boundaries by focused ion beam and transmission electron microscopy. Atom probe analysis indicates a strong tendency of Bi segregation to grain boundaries. By these results, the existing interpretations are discussed to be inadequate and both embrittlement are confirmed to be identical in mechanism, i.e. thermo-induced non-equilibrium grain-boundary segregation of Bi.

  3. Competitive sorption of cadmium and lead in acid soils of central Spain

    SciTech Connect

    Serrano, S.; Garrido, F.; Campbell, C.G.; Garcia-Gonzolez, Maria Teresa

    2004-01-30

    The bioavailability and ultimate fate of heavy metals in the environment are controlled by chemical sorption. To assess competitive sorption of Pb and Cd, batch equilibrium experiments (generating sorption isotherms) and kinetics sorption studies were performed using single and binary metal solutions in surface samples of four soils from central Spain. For comparisons between soils, as well as, single and binary metal solutions, soil chemical processes were characterized using the Langmuir equation, ionic strength, and an empirical power function for kinetic sorption. In addition, soil pH and clay mineralogy were used to explain observed sorption processes. Sorption isotherms were well described by the Langmuir equation and the sorption kinetics were well described by an empirical power function within the reaction times in this study. Soils with higher pH and clay content (characterized by having smectite) had the greatest sorption capacity as estimated by the maximum sorption parameter (Q) of the Langmuir equation. All soils exhibited greater sorption capacity for Pb than Cd and the presence of both metals reduced the tendency for either to be sorbed although Cd sorption was affected to a greater extent than that of Pb. The Langmuir binding strength parameter (k) was always greater for Pb than for Cd. However, these k values tended to increase as a result of the simultaneous presence of both metals, that may indicate competition for sorption sites promoting the retention of both metals on more specific sorption sites. The kinetic experiments showed that Pb sorption is initially faster than Cd sorption from both single and binary solutions although the simultaneous presence of both metals affected the sorption of Cd at short times while only a minor effect was observed on Pb. The estimated exponents of the kinetic function were in all cases smaller for Pb than for Cd, likely due to diffusion processes into micropores or interlayer space of the clay minerals which

  4. Sorption equilibrium of a wide spectrum of organic vapors in Leonardite humic acid: experimental setup and experimental data.

    PubMed

    Niederer, Christian; Goss, Kai-Uwe; Schwarzenbach, René P

    2006-09-01

    The environmental fate of volatile and semivolatile organic compounds is determined by their partitioning between air and soil constituents, in particular soil organic matter (SOM). While there are many studies on the partitioning of nonpolar compounds between water and SOM, data on sorption of polar compounds and data for sorption from the gas phase are rather limited. In this study, Leonardite humic acid/air partition coefficients for 188 polar and nonpolar organic compounds at temperatures between 5 and 75 degrees C and relative humidities between < 0.01% and 98% have been determined using a dynamic flow-through technique. To the best of our knowledge, this is by far the largest and most diverse and consistent data set for sorption into humic material published so far. The major results are as follows: the relative humidity affected the experimental partition coefficients by up to a factor of 3; polar compounds generally sorbed more strongly than nonpolar compounds due to H-bonding (electron donor/ acceptor interactions) with the humic acid; no glass transitions in the range of 5-75 degrees C that would be relevant with respect to the sorption behavior of hydrated Leonardite humic acid were observed; our experimental data agree well with experimental partition coefficients from various literature sources. PMID:16999112

  5. Sorption equilibrium of a wide spectrum of organic vapors in Leonardite humic acid: experimental setup and experimental data

    SciTech Connect

    Christian Niederer; Kai-Uwe Goss; Rene P. Schwarzenbach

    2006-09-01

    The environmental fate of volatile and semivolatile organic compounds is determined by their partitioning between air and soil constituents, in particular soil organic matter (SOM). While there are many studies on the partitioning of nonpolar compounds between water and SOM, data on sorption of polar compounds and data for sorption from the gas phase are rather limited. In this study, Leonardite humic acid/air partition coefficients for 188 polar and nonpolar organic compounds at temperatures between 5 and 75{sup o}C and relative humidities between {lt}0.01% and 98% have been determined using a dynamic flow-through technique. The Leonardite used is a standard humic acid produced by the natural oxidation of expose lignite originating from the Gascoyne Mine in North Dakota. To the best of our knowledge, this is by far the largest and most diverse and consistent data set for sorption into humic material published so far. The major results are as follows: the relative humidity affected the experimental partition coefficients by up to a factor of 3; polar compounds generally sorbed more strongly than nonpolar compounds due to H-bonding (electron donor/acceptor interactions) with the humic acid; no glass transitions in the range of 5-75{sup o}C that would be relevant with respect to the sorption behavior of hydrated Leonardite humic acid were observed; our experimental data agree well with experimental partition coefficients from various literature sources. 42 refs., 2 figs., 2 tabs.

  6. Arsenic sorption onto laterite iron concretions: temperature effect.

    PubMed

    Partey, Frederick; Norman, David; Ndur, Samuel; Nartey, Robert

    2008-05-15

    We investigated arsenate and arsenite sorption onto laterite iron concretions (LIC) to test its suitability for use in the low-tech treatment of arsenic-bearing drinking water. Batch experiments on crushed LIC from Prestea, Ghana were conducted at a series of temperatures, ionic strengths, and pHs. The point of zero net charge on laterite iron concretion was determined by potentiometric titrations yielding an average pHp(ZNC) around 8.64. Experiments show that sorption capacity for both arsenite and arsenate increase with temperature. The equilibrium sorption capacity for arsenite was larger than that for arsenate over the 25 to 60 degrees C temperature range. A Langmuir model satisfactorily fits the arsenite and arsenate sorption isotherm data. Both arsenite and arsenate sorbed over the pH range of natural waters. Arsenite sorption increases with increasing solution pH to a maximum at pH 7, then decreases with further increase in solution pH. Arsenate sorption, on the other hand, shows little change with increasing solution pH. Increasing solution ionic strength 10-fold results in a slight increase in sorption. Ionic strength experiments show that an inner-sphere sorption mechanism is responsible for As (V) sorption on LIC, while As (III) sorption is by an outer-sphere mechanism. Gibbs free energy (DeltaG degrees) for arsenite and arsenate sorption onto LIC was calculated from Langmuir isotherms; the negative values agree with reaction spontaneity. The positive values of the standard enthalpy (DeltaH degrees) show the endothermic nature of arsenite and arsenate sorption onto LIC. Positive entropy (DeltaS degrees) values suggest the affinity of LIC for the arsenic species in solution. Analysis of the arsenic sorption data suggests that LIC can be used for low-tech natural-materials arsenic water treatment. Laterite iron concretions have a number of advantages for this use over commercial materials, including the ability to remove arsenic from waters with a wide

  7. Sorption of aromatic organic pollutants to grasses from water

    USGS Publications Warehouse

    Barbour, J.P.; Smith, J.A.; Chiou, C.T.

    2005-01-01

    The influence of plant lipids on the equilibrium sorption of three aromatic solutes from water was studied. The plant-water sorption isotherms of benzene, 1,2-dichlorobenzene, and phenanthrene were measured over a large range of solute concentrations using sealed vessels containing water, dried plant material, and solute. The plant materials studied include the shoots of annual rye, tall fescue, red fescue, and spinach as well as the roots of annual rye. Seven out of eight sorption isotherms were linear with no evidence of competitive effects between the solutes. For a given plant type, the sorption coefficient increased with decreasing solute water solubility. For a given solute, sorption increased with increasing plant lipid content. The estimated lipid-water partition coefficients of individual solutes were found to be significantly greater than the corresponding octanol-water partition coefficients. This indicates that plant lipids are a more effective partition solvent than octanol for the studied aromatic compounds. As expected, the solute lipid-water partition coefficients were log-linearly related to the respective water solubilities. For the compounds studied, partitioning into the lipids is believed to be the primary sorption mechanism. ?? 2005 American Chemical Society.

  8. Thermodynamics of Cadmium Sorption on Different Soils of West Bengal, India

    PubMed Central

    Paul, Ranjit Kumar; Das, D. K.; Boruah, Romesh K.; Sonar, Indira

    2014-01-01

    A sorption study was conducted on different soils collected from five agroecological zones of West Bengal, India, to understand the soil environmental behavior and fate of cadmium. For this purpose batch adsorption experiments were carried out at the native soil pH and at three different temperatures (25°C, 35°C, and 45°C). The adsorption data fitted by a linear least squares technique to the different sorption isotherms. Most data obtained give the good fit to both Freundlich and modified Langmuir isotherms, but they are not consistent with the linear Langmuir adsorption model. Thermodynamic parameters, namely, thermodynamics equilibrium constant at a particular temperature T  (KT0), Gibbs free energy at a particular temperature T  (ΔGT0), and change of enthalpy (ΔH0) and change of entropy at temperature T  (ΔST0), were also determined by applying sorption value and concentrations of Cd in equilibrium solution within the temperature range. The thermodynamic parameters revealed that Cd sorption increases as the values of KT0, ΔGT0, ΔH0, and ΔST0 were increased on reaction temperatures. The spontaneous sorption reaction can be concluded due to high values of ΔGT0. The positive values of ΔH0 indicated that the Cd sorption is an endothermic one. Under these present conditions, the soil and its components possibly supply a number of sites having different adsorption energies for cadmium sorption. PMID:24683322

  9. Sorption kinetics and equilibrium of the herbicide diuron to carbon nanotubes or soot in absence and presence of algae.

    PubMed

    Schwab, Fabienne; Camenzuli, Louise; Knauer, Katja; Nowack, Bernd; Magrez, Arnaud; Sigg, Laura; Bucheli, Thomas D

    2014-09-01

    Carbon nanotubes (CNT) are strong sorbents for organic micropollutants, but changing environmental conditions may alter the distribution and bioavailability of the sorbed substances. Therefore, we investigated the effect of green algae (Chlorella vulgaris) on sorption of a model pollutant (diuron, synonyms: 3-(3,4-Dichlorophenyl)-1,1-dimethylurea, DCMU) to CNT (multi-walled purified, industrial grade, pristine, and oxidized; reference material: Diesel soot). In absence of algae, diuron sorption to CNT was fast, strong, and nonlinear (Freundlich coefficients: 10(5.79)-10(6.24) μg/kgCNT·(μg/L)(-n) and 0.62-0.70 for KF and n, respectively). Adding algae to equilibrated diuron-CNT mixtures led to 15-20% (median) diuron re-dissolution. The relatively high amorphous carbon content slowed down ad-/desorption to/from the high energy sorption sites for both industrial grade CNT and soot. The results suggest that diuron binds readily, but - particularly in presence of algae - partially reversibly to CNT, which is of relevance for environmental exposure and risk assessment. PMID:24949853

  10. 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

  11. Rapid Adsorption of Copper(II) and Lead(II) by Rice Straw/Fe3O4 Nanocomposite: Optimization, Equilibrium Isotherms, and Adsorption Kinetics Study

    PubMed Central

    Khandanlou, Roshanak; Ahmad, Mansor B.; Fard Masoumi, Hamid Reza; Shameli, Kamyar; Basri, Mahiran; Kalantari, Katayoon

    2015-01-01

    Rice straw/magnetic nanocomposites (RS/Fe3O4-NCs) were prepared via co-precipitation method for removal of Pb(II) and Cu(II) from aqueous solutions. Response surface methodology (RSM) was utilized to find the optimum conditions for removal of ions. The effects of three independent variables including initial ion concentration, removal time, and adsorbent dosage were investigated on the maximum adsorption of Pb (II) and Cu (II). The optimum conditions for the adsorption of Pb(II) and Cu(II) were obtained (100 and 60 mg/L) of initial ion concentration, (41.96 and 59.35 s) of removal time and 0.13 g of adsorbent for both ions, respectively. The maximum removal efficiencies of Pb(II) and Cu(II) were obtained 96.25% and 75.54%, respectively. In the equilibrium isotherm study, the adsorption data fitted well with the Langmuir isotherm model. The adsorption kinetics was best depicted by the pseudo-second order model. Desorption experiments showed adsorbent can be reused successfully for three adsorption-desorption cycles. PMID:25815470

  12. [Sorption Characteristics of Phenanthrene and 1, 1-Dichloroethene onto Reed Straw Biochar in Aquatic Solutions].

    PubMed

    Wu, Qing-wen; Meng, Liang; Zhang, Zhi-hao; Luo, Qi-shi; Yang, Jie

    2016-02-15

    The purpose of this study was to investigate the sorption characteristics of phenanthrene (PHE) and 1, 1-dichloroethene (1, 1-DCE) onto reed straw biochar at 500 degrees C in aquatic solutions. The sorption mechanisms and effects of solution pH and biochar mass on sorption intensity were discussed. The results showed that the time required to reach sorption equilibrium was 60 min and 480 min for PHE and 1, 1-DCE, respectively, with maximum removal rates of 81, 87% and 90.18%. The sorption kinetics of both PHE and 1, 1-DCE fitted the pseudo-second-order model well, but the pseudo-second-order reaction rate of PHE was higher than that of 1, 1-DCE. Furthermore, the sorption processes were controlled by both membrane diffusion and intra-particle diffusion, and the latter was found to be the rate-controlling step. Sorption isotherms of the two organic pollutants fitted well with the Freundlich equation, and the sorption affinity of 1, 1-DCE onto biochar was greater than that of PHE. The total sorption mechanism of biochar was the combination of partition and adsorption, and dominated by adsorption. The adsorption capacity of 1, 1-DCE was greater than that of PHE, but its partition capacity was much smaller, indicating that pollutants' molecular volume and relative polarity would mainly affect the total sorption. Analysis of Fourier transform infrared spectroscopy (FTIR) demonstrated that oxygen- and hydrogen-containing functional groups and pi--pi interaction were important for PHE and 1, 1-DCE sorption onto biochar. The solution pH value had no significant effect on the sorption intensity of PHE and 1, 1-DCE, however, with biochar mass increasing from 5 mg to 50 mg, the equilibrium sorption amount of PHE and 1, 1-DCE decreased by 6.78 times and 2.18 times, and the removal rate increased by 20.21% and 15.78%, respectively. PMID:27363160

  13. A gel probe equilibrium sampler for measuring arsenic porewater profiles and sorption gradients in sediments: II. Field application to Haiwee reservoir sediment

    USGS Publications Warehouse

    Campbell, K.M.; Root, R.; O'Day, P. A.; Hering, J.G.

    2008-01-01

    Arsenic (As) geochemistry and sorption behavior were measured in As- and iron (Fe)-rich sediments of Haiwee Reservoir by deploying undoped (clear) polyacrylamide gels and hydrous ferric oxide (HFO)-doped gels in a gel probe equilibrium sampler, which is a novel technique for directly measuring the effects of porewater composition on As adsorption to Fe oxides phases in situ. Arsenic is deposited at the sediment surface as As(V) and is reduced to As(III) in the upper layers of the sediment (0-8 cm), but the reduction of As(V) does not cause mobilization into the porewater. Dissolved As and Fe concentrations increased at depth in the sediment column driven by the reductive dissolution of amorphous Fe(III) oxyhydroxides and conversion to a mixed Fe(II, III) green rust-type phase. Adsorption of As and phosphorous (P) onto HFO-doped gels was inhibited at intermediate depths (10-20 cm), possibly due to dissolved organic or inorganic carbon, indicating that dissolved As concentrations were at least partially controlled by porewater composition rather than surface site availability. In sediments that had been recently exposed to air, the region of sorption inhibition was not observed, suggesting that prior exposure to air affected the extent of reductive dissolution, porewater chemistry, and As adsorption behavior. Arsenic adsorption onto the HFO-doped gels increased at depths >20 cm, and the extent of adsorption was most likely controlled by the competitive effects of dissolved phosphate. Sediment As adsorption capacity appeared to be controlled by changes in porewater composition and competitive effects at shallower depths, and by reductive dissolution and availability of sorption sites at greater burial depths. ?? 2008 American Chemical Society.

  14. Adsorption equilibrium of binary methane/ethane mixtures in BPL activated carbon: isotherms and calorimetric heats of adsorption.

    PubMed

    He, Yufeng; Yun, Jeong-Ho; Seaton, Nigel A

    2004-08-01

    The adsorption of pure methane and ethane in BPL activated carbon has been measured at temperatures between 264 and 373 K and at pressures up to 3.3 MPa with a bench-scale high-pressure open-flow apparatus. The same apparatus was used to measure the adsorption of binary methane/ethane mixtures in BPL at 301.4 K and at pressures up to 2.6 MPa. Thermodynamic consistency tests demonstrate that the data are thermodynamically consistent. In contrast to two sets of data previously published, we found that the adsorption of binary methane/ethane in BPL behaves ideally (in the sense of obeying ideal adsorbed solution theory, IAST) throughout the pressure and gas-phase composition range studied. A Tian-Calvet type microcalorimeter was used to measure low-pressure isotherms, the isosteric heats of adsorption of pure methane and ethane in BPL activated carbon, and the individual heats of adsorption in binary mixtures, at 297 K and at pressures up to 100 kPa. The mixture heats of adsorption were consistent with IAST. PMID:15274571

  15. Statistical Thermodynamics of an "Open" Hard Sphere System on the Equilibrium Fluid Isotherm: Study of Properties of the Freezing Transition Without Direct Involvement of the Equilibrium Solid Phase

    NASA Astrophysics Data System (ADS)

    Reiss, Howard; Manzanares, José A.

    2016-09-01

    Using several theoretical toolsldots (i) the nucleation theorem, (ii) an equivalent cavity, (iii) the reversible work of adding a cavity to an open hard sphere system, and (iv) the theory of "stability"... the authors estimated the density at which the hard sphere freezing transition occurs. No direct involvement of the equilibrium solid phase is involved. The reduced density \\uppi a^3ρ _f/6 (where a is the hard sphere diameter and ρ _f is the actual density at which freezing occurs) is found to be 0.4937 while the value obtained by computer simulation is 0.494. The agreement is good, but the new method still contains some approximation. However, the approximation is based on the idea that at a density just below ρ _f the fluid adopts a distorted structure resembling the solid, but different enough so that long-range order vanishes. Initial loss of stability may not be involved in every fluid-solid transition, but it may be an early step in the hard sphere and related systems.

  16. Least-Squares Analysis of Phosphorus Soil Sorption Data with Weighting from Variance Function Estimation: A Statistical Case for the Freundlich Isotherm

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Phosphorus sorption data for soil of the Pembroke classification are recorded at high replication — 10 experiments at each of 7 initial concentrations — for characterizing the data error structure through variance function estimation. The results permit the assignment of reliable weights for the su...

  17. Investigation and modeling of moisture sorption behaviour of rice starch/carboxymethyl chitosan blend films

    NASA Astrophysics Data System (ADS)

    Suriyatem, R.; Rachtanapun, C.; Raviyan, P.; Intipunya, P.; Rachtanapun, P.

    2015-07-01

    The biopolymer films from rice starch (RS) and carboxymethyl chitosan (CMCh) were developed by solution casting. The effect of the ratios of rice starch to CMCh (100:0, 88:12, 67:33, 50:50, 33:67, 12:88 and 0:100) on water barrier properties and moisture sorption isotherm of blend films was studied. Water vapor permeability of rice starch film and CMCh film were 4.8 and 9.1 g.mm/m2.mHg.day, respectively, while those of the RS/CMCh blend films ranged between 5.0 and 9.1 g.mm/m2.mHg.day. The sorption isotherm of RS/CMCh blend films was determined at 25°C. The sorption behaviour of RS/CMCh blend films could be categorized as type II and type III isotherms. The highest equilibrium moisture content (63.5 g water/100 g dry solid) was obtained in the CMCh film at aw of 0.87. For further application of sorption isotherm data, the moisture sorption characteristic of the films can be predicted using empirical models. Lewicki, Peleg, Guggenheim-Anderson-deBoer (GAB), Brunauer-Emmett-Teller (BET), and Oswin models were tested to fit the experimental data. The Peleg equation showed the best fit to the experimental data of the RS/CMCh blend films with r2 ∼ 0.997 and the lowest % RMS of 6.2-44.3.

  18. Pentachlorophenol sorption in nylon fiber and removal by immobilized Rhizopus oryzae ENHE.

    PubMed

    León-Santiestebán, Hugo; Meraz, Mónica; Wrobel, Kazimierz; Tomasini, Araceli

    2011-06-15

    This study describes pentachlophenol (PCP) sorption in nylon fiber in which Rhizopus oryzae ENHE was immobilized to remove the chemical compound. The experimental sorption data were analyzed using the Langmuir, Freundlich, and Redlich-Peterson isotherm models using non-linear error functions to fit the experimental data to the three models. Results showed that the isotherm obtained from the data fitted the three models used. However, the g parameter from Redlich-Peterson model showed that the isotherm obtained approaches the Freundlich model. This support reached the sorption equilibrium concentration at 3mg PCPg(-1)nylon. To study PCP removal capability by R. oryzae ENHE and to eliminate the error caused by PCP sorbed by the nylon fiber during its quantification, nylon fiber at PCP equilibrium sorption concentration was used to immobilize R. oryzae ENHE. It was found that this fungus grew within nylon fiber cubes in presence or not of PCP, even when PCP caused growth inhibition. Maximum biomass accumulated into nylon cubes without PCP was of 32 mg biomass g(-1)nylon and into nylon cubes at PCP equilibrium concentration was of 18 mg g(-1)nylon. The results showed that R. oryzae ENHE immobilized into nylon fiber removed 88.6% and 92% of PCP in cultures with 12.5 and 25 mg PCPL(-1), as initial concentration, respectively. This is the first work to report that a zygomycete, such as R. oryzae ENHE, immobilized into nylon fiber kept its potential to remove PCP. PMID:21514996

  19. Silica coated magnetic particles using microwave synthesis for removal of dyes from natural water samples: Synthesis, characterization, equilibrium, isotherm and kinetics studies

    NASA Astrophysics Data System (ADS)

    Ahmed, Salwa A.; Soliman, Ezzat M.

    2013-11-01

    Monitoring pollutants in water samples is a challenge to analysts. So, the removal of Napthol blue black (NBB) and Erichrome blue black R (EBBR) from aqueous solutions was investigated using magnetic chelated silica particles. Magnetic solids are widely used in detection and analytical systems because of the performance advantages they offer compared to similar solids that lack magnetic properties. In this context, a fast, simple and clean method for modification of magnetic particles (Fe3O4) with silica gel was developed using microwave technique to introduce silica gel coated magnetic particles (SG-MPs) sorbent. The magnetic sorbent was characterized by the FT-IR, X-ray diffraction (XRD), and scan electron microscope (SEM) analyses. The effects of pH, time, weight of sorbent and initial concentration of dye were evaluated. It was interesting to find from results that SG-MPs exhibits high percentage extraction of the studied dyes (100% for NBB and 98.75% for EBBR) from aqueous solutions. The Freundlich isotherm with r2 = 0.973 and 0.962 and Langmuir isotherms with r2 = 0.993 and 0.988 for NBB and EBBR, respectively were used to describe adsorption equilibrium. Also, adsorption kinetic experiments have been carried out and the data have been well fitted by a pseudo-second-order equation r2 = 1.0 for NBB and 0.999 for EBBR. The prepared sorbent with rapid adsorption rate and separation convenience was applied for removal of NBB and EBBR pollutants from natural water samples with good precision (RSD% = 0.05-0.3%).

  20. Equilibrium, Thermodynamics, and Kinetic Sorption Studies for the Removal of Coomassie Brilliant Blue on Wheat Bran as a Low-Cost Adsorbent

    PubMed Central

    Ata, Sadia; Imran Din, Muhammad; Rasool, Atta; Qasim, Imran; Ul Mohsin, Ijaz

    2012-01-01

    The sorption studies of coomassie brilliant blue (CBB) from aqueous solution have been carried out on wheat bran (WB). Coomassie brilliant blue on wheat bran was used to study the adsorption behavior under various parameters such as pH, dosage amount, and contact time. It was observed that under optimized conditions up to 95.70% dye could be removed from solution onto WB. Langmuir and Freundlich adsorption isotherms were used to elaborate the results. Freundlich model was found to be fitted well and favored multilayer adsorption. The Freundlich constants n and KF were determined as 0.53 and 2.5 × 10−4. Thermodynamic parameters such as ΔG, ΔH, and ΔS studied were taking into account, showed spontaneous and favorable reaction for coomassie brilliant blue on wheat bran. The maximum adsorption capacity qm was found to be 6.410 mg/g. The investigations show that non treated WB is a low-cost adsorbent for the removal of dyes from textile industry effluents. PMID:22567559

  1. Modeling of sorption characteristics of backfill materials

    SciTech Connect

    Chitra, S.; Sasidhar, P.; Lal, K.B.; Ahmed, J.

    1998-06-01

    Sorption data analysis was carried out using the Freundlich, Langmuir, and Modified Freundlich isotherms for the uptake of sodium and potassium in an initial concentration range of 10--100 mg/L on backfill materials, viz., bentonite, vermiculite, and soil samples. The soil samples were collected from a shallow land disposal facility at Kalpakkam. The Freundlich isotherm equation is validated as a preferred general mathematical tool for representing the sorption of K{sup +} by all the selected backfill materials. The Modified Freundlich isotherm equation is validated as a preferred mathematical tool for representing the sorption of Na{sup +} by the soil samples. Since a negative sorption was observed for the uptake of Na{sup +} by commercial clay minerals (vermiculite and bentonite clay in the laboratory experiments), sorption analysis could not be carried out using the above-mentioned isotherm equations. Hill plots of the sorption data suggest that in the region of low saturation (10--40 mg/L), sorption of K{sup +} by vermiculite is impeded by interaction among sorption sites. In the region of higher saturation (60--100 mg/L), sorption of K{sup +} by all three backfill materials is enhanced by interaction among sorption sites. The Hill plot of the sorption data for Na{sup +} by soil suggests that irrespective of Na{sup +} concentration, sorption of Na{sup +} at one exchange size enhances sorption at other exchange sites.

  2. Searching the best equilibrium moisture equation for lettuce seeds using measures of curvature and bias

    PubMed Central

    Bortolotti, Carolina T; Barrozo, Marcos A S

    2013-01-01

    In the present work, we performed a discrimination analysis of the nonlinear equations used to describe sorption isotherms of the lettuce seeds. The equilibrium data were obtained by the static method using saturated salt solutions. The best model to describe the equilibrium moisture of lettuce seeds was selected using measures of curvature and bias. The obtained results showed that the Copace equation was the best model in terms of nonsignificance for bias and nonlinearity measures. PMID:24804051

  3. Competitive sorption between 17alpha-ethinyl estradiol and bisphenol A/4-n-nonylphenol by soils.

    PubMed

    Li, Jianzhong; Jiang, Lu; Xiang, Xi; Xu, Shuang; Wen, Rou; Liu, Xiang

    2013-06-01

    The sorption of 17alpha-ethinyl estradiol (EE2), bisphenol A (BPA), and 4-n-nonylphenol (NP) in single systems and the sorption of EE2 with different initial aqueous concentrations of BPA or NP were examined using three soils. Results showed that all sorption isotherms were nonlinear and fit the Freundlich model. The degree of nonlinearity was in the order BPA (0.537-0.686) > EE2 (0.705-0.858) > NP (0.875-0.0.951) in single systems. The isotherm linearity index of EE2 sorption calculated by the Freundlich model for Loam, Silt Loam and Silt increased from 0.758, 0.705 and 0.858, to 0.889, 0.910 and 0.969, respectively, when BPA concentration increased from 0 to 1000 microg/L, but the effect of NP was comparably minimal. Additionally, EE2 significantly suppressed the sorption of BPA, but insignificantly suppressed that of NP. These findings can be attributed to the difference of sorption affinity of EE2, NP and BPA on the hard carbon (e.g., black carbon) of soil organic matter that dominated the sorption in the low equilibrium aqueous concentration range of endocrine-disrupting chemicals (EDCs). Competitive sorption among EDCs presents new challenges for predicting the transport and fate of EDCs under the influence of co-solutes. PMID:24191605

  4. Batch sorption dynamics, kinetics and equilibrium studies of Cr(VI), Ni(II) and Cu(II) from aqueous phase using agricultural residues

    NASA Astrophysics Data System (ADS)

    Kaur, Rajvinder; Singh, Joginder; Khare, Rajshree; Cameotra, Swaranjit Singh; Ali, Amjad

    2013-03-01

    In the present study, the agricultural residues viz., Syzygium cumini and Populus deltoides leaves powder have been used for the biosorption of Cu(II), Ni(II), and Cr(VI) from aqueous solutions. FTIR and SEM analysis of the biosorbents were performed to explore the type of functional groups available for metal binding and to study the surface morphology. Various physico-chemical parameters such as pH, adsorbent dosage, initial metal ion concentration, and equilibrium contact time were studied. Thermodynamic studies were carried out and the results demonstrated the spontaneous and endothermic nature of the biosorption process. The equilibrium data were tested using four isotherm models—Langmuir, Freundlich, Temkin and Dubinin-Radushkevich and the maximum biosorption capacities were evaluated. The Pseudo-first-order, pseudo-second-order, Elovich and intraparticle diffusion models were applied to study the reaction kinetics with pseudo-second order model giving the best fit ( R 2 = 0.99) to the experimental data.

  5. Sorption of biodegradation end products of nonylphenol polyethoxylates onto activated sludge.

    PubMed

    Hung, Nguyen Viet; Tateda, Masafumi; Ike, Michihiko; Fujita, Masanori; Tsunoi, Shinji; Tanaka, Minoru

    2004-01-01

    Nonylphenol(NP), nonylphenoxy acetic acid (NP1EC), nonylphenol monoethoxy acetic acid (NP2EC), nonylphenol monoethoxylate (NP1EO) and nonylphenol diethoxylate (NP2EO) are biodegradation end products (BEPs) of nonionic surfactant nonylphenolpolyethoxylates (NPnEO). In this research, sorption of these compounds onto model activated sludge was characterized. Sorption equilibrium experiments showed that NP, NP1EO and NP2EO reached equilibrium in about 12 h, while equilibrium of NP1EC and NP2EC were reached earlier, in about 4 h. In sorption isotherm experiments, obtained equilibrium data at 28 degrees C fitted well to Freundlich sorption model for all investigated compounds. For NP1EC, in addition to Freundlich, equilibrium data also fitted well to Langmuir model. Linear sorption model was also tried, and equilibrium data of all NP, NP1EO, NP2EO and NP2EC except NP1EC fitted well to this model. Calculated Freundlich coefficient (K(F)) and linear sorption coefficient (K(D)) showed that sorption capacity of the investigated compounds were in order NP > NP2EO > NP1EO > NP1EC approximately NP2EC. For NP, NP1EO and NP2EO, high values of calculated K(F) and K(D) indicated an easy uptake of these compounds from aqueous phase onto activated sludge. Whereas, NP1EC and NP2EC with low values of K(F) and K(D) absorbed weakly to activated sludge and tended to preferably remain in aqueous phase. PMID:15495957

  6. Effect of chemical treatments on water sorption and mechanical properties of flax fibres.

    PubMed

    Alix, S; Philippe, E; Bessadok, A; Lebrun, L; Morvan, C; Marais, S

    2009-10-01

    In this work, in order to improve the adhesion between a polyester matrix (unsaturated polyester resin) and flax fibres (Linum usitatissimum L.) and to increase their moisture resistance, chemical surface treatments have been used. These different treatments were performed with maleic anhydride (MA), acetic anhydride (Ac), silane (Si) and styrene (S). The modified flax fibres were characterized by means of infrared spectroscopy and surface energy analysis. The effect of these treatments on water sorption was investigated by using a gravimetric static equilibrium method. Water sorption isotherms were derived from kinetic data. The Park model based on the three sorption modes: Langmuir, Henry's law and clustering, was successfully used to simulate the experimental sorption data. It was found that the (Ac) and particularly (S) treatments reduced overall water uptake of flax fibres. We show that tensile modulus, breaking strength and breaking strain depend on the chemical treatment used. PMID:19477120

  7. Characterization of U(VI) Sorption-Desorption Processes and Model Upscaling

    SciTech Connect

    Bai, Jing; Dong, Wenming; Ball, William P.

    2006-10-12

    (VI) diffusion in silt/clay layers. Batch isotherm experiments were first used to confirm sorption isotherms under the intended test conditions and diffusion cell experiments were then conducted to explore the diffusion hypotheses. Important new information was obtained about the role of aqueous calcium and solid calcium carbonate in controlling sorption equilibrium with Hanford sediments. The retarded interparticle diffusion model with local sorption equilibrium was shown to very successfully simulate diffusion at high aqueous concentration of U(VI). By contrast, however, diffusion data obtained at low concentration suggested nonequilibrium of sorption even at diffusion time scales. Such nonequilibrium effects at low concentration are likely to be the result of sorption retarded intraparticle diffusion, and strong U(VI) sorption in the low concentration range.

  8. Sorption of perfluorochemicals to granular activated carbon in the presence of ultrasound.

    PubMed

    Zhao, Deming; Cheng, Jie; Vecitis, Chad D; Hoffmann, Michael R

    2011-03-24

    Perfluorochemicals (PFCs) are emerging pollutants of increasing public health and environmental concern due to their worldwide distribution, environmental persistence, and bioaccumulation potential. Activated carbon adsorption is an effective method to remove PFCs from water. Herein, we report on the sorption of four PFCs: perfluorooctane sulfonate (PFOS), perfluorooctanoate (PFOA), perfluorobutane sulfonate (PFBS), and perfluorobutanoate (PFBA), from deionized water (MQ) and landfill groundwater (GW) by granular activated carbon (GAC) in the absence and presence of 20 kHz ultrasound. In all cases, the adsorption kinetics were found to be well-represented by a pseudosecond-order model, with maximum monolayer sorption capacity and initial sorption rate values following the orders q(e)(PFOS) > q(e)(PFOA) > q(e)(PFBS) > q(e)(PFBA) and v(0)(PFOS) > v(0)(PFBS) > v(0)(PFOA) > v(0)(PFBA), respectively. The equilibrium adsorption was quantified by the BET multilayer absorption isotherm, and the monolayer sorption capacity increased with increasing PFC chain length: q(m)(PFOS) > q(m)(PFOA) > q(m)(PFBS) > q(m)(PFBA). The equilibrium PFC sorption constants, q(e) and q(m), and the sorption kinetic constants, v(0) and k(2), were greater in Milli-Q water than in landfill groundwater with or without pretreatment, indicating competition for sorption sites by natural and cocontaminant groundwater organics. Ultrasonic irradiation significantly increased the PFC-GAC sorption kinetics, 250-900%, and slightly increased the extent of PFC equilibrium adsorption, 5-50%. The ultrasonic PFC-GAC sorption kinetics enhancement increased with increasing PFC chain length, suggesting ultrasound acts to increase the PFC diffusion rate into GAC nanopores. PMID:21370832

  9. Sorption studies of Cr(VI) from aqueous solution using bio-char as an adsorbent.

    PubMed

    Hyder, A H M G; Begum, Shamim A; Egiebor, Nosa O

    2014-01-01

    The characteristics of sorption of hexavalent chromium (Cr(VI)) onto bio-char derived from wood chips (spruce, pine, and fir) were evaluated as a function of pH, initial Cr(VI) concentration and bio-char dosage using synthetic wastewater in batch tests. The initial Cr(VI) concentrations were varied between 10 and 500 mg/L to investigate equilibrium, kinetics, and isotherms of the sorption process. About 100% of Cr(VI) was removed at pH 2 with initial Cr(VI) concentration of 10 mg/L using 4 g of bio-char after 5 hours of sorption reaction. The maximum sorption capacity of the bio-char was 1.717 mg/g for an initial Cr(VI) concentration of 500 mg/L after 5 hours. The sorption kinetics of total Cr onto bio-char followed the second-order kinetic model. The Langmuir isotherm model provided the best fit for total Cr sorption onto bio-char. The bio-char used is a co-product of a down draft gasifier that uses the derived syngas to produce electricity. Bio-char as a low cost adsorbent demonstrated promising results for removal of Cr(VI) from aqueous solution. The findings of this study would be useful in designing a filtration unit with bio-char in a full-scale water and wastewater treatment plant for the Cr(VI) removal from contaminated waters. PMID:24901621

  10. [Sorption of 1-naphthol to plant cuticular waxes with different states].

    PubMed

    Chen, Bao-liang; Zhou, Dan-dan; Li, Yun-gui; Zhu, Li-zhong

    2008-06-01

    Wax components are ubiquitous in natural environments (such as plant and soil) and play a significant role in sorption of organic contaminants. To elucidate their sorption characteristics, cuticular waxes were isolated from the fruits of apple by organic solvent extraction method, and then the isolated-wax was reconstructed on montmorillonite with different loadings. Sorption behaviors of one polar organic pollutant, 1-naphthol, to isolated-wax, reconstructed-wax, and cuticle-associated-wax samples were compared by batch sorption method. Sorption properties of wax-montmorillonite complexes dependent on different wax-loadings were also investigated. Isotherms of 1-naphthol to wax samples were nonlinear, and fitted well with Freundlich equation. Although sorption of wax in the plant cuticle was weakened by other components of cuticle, its contribution to whole sorption of the cuticle increased with solute aqueous equilibrium concentration. Sorption coefficients at three equilibrium concentrations (1, 10, 100 microg/mL) were calculated, depending on solute concentrations and wax-loadings. Sorption coefficients normalized organic carbon contents (Koc) decreased with the increase of solute aqueous concentration. At low solute aqueous concentration, Koc values increased with the wax-loading increasing, reached maximum, and then decreased. At high solute aqueous concentration, Koc values were almost independent on wax-loadings. These observations indicated that partition was the dominant mechanism at high solute concentration, while specific interactions were involved as additional mechanisms at low solute concentration. Koc values of wax components in different states were in the order of reconstructed-wax (321.2) > isolated-wax (190.4) > cuticular-attached-wax (128.4), suggested that the sorption capability of wax was promoted once they were input into soil environment and then coated on mineral surface. PMID:18763521

  11. Determination of soil–water sorption coefficients of volatile methylsiloxanes

    PubMed Central

    Kozerski, Gary E; Xu, Shihe; Miller, Julie; Durham, Jeremy

    2014-01-01

    The sorption behaviors of 4 cyclic and linear volatile methyl siloxane (VMS) compounds between water and organic matter in 3 United Kingdom soils were studied by a batch equilibrium method using13C-enriched sorbates. Sorption and desorption kinetics and isotherms were determined for octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5), octamethyltrisiloxane (L3), and decamethyltetrasiloxane (L4). Concentrations of [13C]-VMS in the soil and aqueous phases were measured directly by extraction and gas chromatography–mass spectrometry techniques. All VMS compounds were sorbed rapidly, reaching constant distributions in all soils by 24 h. Desorption kinetics were very rapid, with reattainment of equilibrium within 1 h. In the main, linear isotherms were observed for aqueous concentrations at or below 4% of the solubility limits. The average sorption organic carbon partition coefficient (log KOC) values across soils were 4.23 for D4, 5.17 for D5, 4.32 for L3, and 5.13 for L4, with standard deviations of 0.09 to 0.34. Desorption KOC values were systematically greater by 0.1 log units to 0.3 log units. The linear isotherms and low variation in KOC values across soils suggested partitioning-dominated sorption of the VMS. Compared with traditional hydrophobic organic compounds, KOC values for the VMS compounds were significantly lower than expected on the basis of their octanol–water partition coefficients. A linear free energy relationship analysis showed that these differences could be rationalized quantitatively in terms of the inherent characteristics of the VMS compounds, combined with the differences in solvation properties of organic matter and octanol. Environ Toxicol Chem 2014; 33:1937–1945. PMID:24862578

  12. Sorbent Mass Variation Method: A New Possibility for the Determination of Binding Isotherms.

    PubMed

    Nagy, Miklós; Siegl, Zoltán; Szili, Krisztina; Fábos, Viktória; Kántor, Krisztina

    2016-06-28

    Measurement of equilibrium mass fraction of a surfactant as a function of the sorbent mass fraction was performed on gel sorbent-solution systems in order to determine binding isotherms and to calculate fundamental characteristics of the solvation layer. With application of this new method, it was possible to calculate specific solvation/sorption capacity and absolute average local composition of the solvation layer. It has been pointed out by systematic variation of the composition (hydrophobicity) and degree of cross-linking of the gel sorbents that the ratio of components in the solvation layer can be constant in a given range of equilibrium mass fraction of the sodium dodecyl sulfate (SDS) and that the specific solvation/sorption capacity of gel sorbents can be much greater than that of activated carbon type adsorbents. On the basis of a mixed sorbent model, it turned out from calculations that there is no preferential binding of SDS close to the chemical cross-links and that the surfactant molecules prefer vinyl acetate groups as binding sites. The density of cross-links regulates the aggregation number of the bound surfactant as well. For loose gels, both binding isotherms and swelling curves show that the surfactant-polymer interaction is a strongly cooperative process. The result of these experiments may influence the general concept of solvation/sorption isotherms and all related phenomena. PMID:27263864

  13. Nonlinear Chlorinated Solvent Sorption Impedes Remediation in Sedimentary Aquifers

    NASA Astrophysics Data System (ADS)

    Allen-King, R. M.; Rabideau, A. J.; Merlo, A.; Salvado i Estivill, J. A.; Barbarosa, V.; Matott, L. S.

    2014-12-01

    A 'tailing' pattern of rapid initial contaminant concentration decline followed by sustained release at a lower concentration is commonly produced by active remediation strategies. The ability of aquitard layers to cause this pattern is recognized. However, we hypothesize that nonlinear sorption combined with intragranular diffusion and mass storage within coarse, porous grains, can also cause tailing. Our project combines laboratory measurements of the equilibrium sorption isotherm for trichloroethene (TCE), release measurements from granular samples, and simulations of retarded intragranular diffusion. A novel aspect of our study is that we are examining a sample containing condensed kerogen as the primary form of organic matter on the impact of TCE mass storage, uptake and release rates. The kerogen-containing marine sedimentary rock used in our study is representative of the source rock of the surficial glacial aquifers in the southern Ontario, Canada region. The fact that energy producing shale units occur within the regional stratigraphic sequences indicates the high level of thermal maturation of the kerogen that comprises the sorbent for TCE in these samples. The equilibrium sorption isotherm spans nearly five orders of magnitude in aqueous concentration and is nonlinear. Preliminary comparisons between the mass release curve for grains equilibrated with a high TCE aqueous concentration (ca. 1000 mg/L) show that the physically-based model, which represents release controlled by intragranular diffusion with nonlinear local equilibrium sorption, provides a reasonable fit to the observed data with modest adjustment of the independently determined parameters. Additional experiments documenting TCE release from samples equilibrated at different initial aqueous concentrations and of different grain sizes will also be evaluated using the model and the results compared. Through extending simulations to the field scale, our results will contribute to a general

  14. Investigation of sulfonated aromatic compound (SAC) modification to nylon film. 2. Study of SAC sorption isotherm and atomic force microscopic characterization of nylon surfaces

    SciTech Connect

    Zhang, J.; Watson, B.A.; Keown, R.W.; Malone, C.P.; Barteau, M.A.

    1995-08-01

    Nylon 6 and nylon 66 films have been treated with aqueous sulfonated aromatic compound (SAC) solutions at concentrations ranging from 0.005 to 1.0 wt%. SAC uptakes at different treatment concentrations were measured and found to follow a BET isotherm. The surface morphologies of nylon film samples, including the original and SAC-treated films, have been characterized by atomic force microscopy (AFM). For untreated nylon 6 and nylon 66 films, AFM images show a randomly distributed fibrillar surface structure. Characteristic widths of fibrils in the nylon 66 and 6 films were 150-225 and 75-150 nm, respectively. For SAC-treated nylon films, the AFM images revealed that the surfaces of the films became covered with nodule-like features having a diameter range of 25-60 nm. AFM analysis provides evidence that SAC treatment deposited a surface coating on nylon films. AFM images of SAC-treated nylon films suggest a mechanism for stain resistance in which the SAC first forms a thin coating on the nylon via bondings between attractive groups in the SAC and nylon polymers. After treatment at increased SAC concentration, the surface is covered with nodule-like deposits which likely serve as a physical barrier to dye permeation. 20 refs., 8 figs.

  15. 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.

  16. Sorption mechanism of Cd(II) from water solution onto chicken eggshell

    NASA Astrophysics Data System (ADS)

    Flores-Cano, Jose Valente; Leyva-Ramos, Roberto; Mendoza-Barron, Jovita; Guerrero-Coronado, Rosa María; Aragón-Piña, Antonio; Labrada-Delgado, Gladis Judith

    2013-07-01

    The mechanism and capacity of eggshell for sorbing Cd(II) from aqueous solution was examined in detail. The eggshell was characterized by several techniques. The eggshell was mainly composed of Calcite (CaCO3). The surface charge distribution was determined by acid-base titration and the point of zero charge (PZC) of the eggshell was found to be 11.4. The sorption equilibrium data were obtained in a batch adsorber, and the adsorption isotherm of Langmuir fitted the data quite well. The sorption capacity of eggshell increased while raising the pH from 4 to 6, this tendency was attributed to the electrostatic interaction between the Cd2+ in solution and the surface of the eggshell. Furthermore, the sorption capacity was augmented by increasing the temperature from 15 to 35 °C because the sorption was endothermic. The sorption of Cd(II) occurred mainly onto the calcareous layer of the eggshell, but slightly on the membrane layer. It was demonstrated that the sorption of Cd(II) was not reversible, and the main sorption mechanisms were precipitation and ion exchange. The precipitation of (Cd,Ca)CO3 on the surface of the eggshell was corroborated by SEM and XRD analysis.

  17. The Influence of Temperature on the Sorption and Permeability of CO2 in poly(fluoroalkoxyphosphazene) membranes

    SciTech Connect

    Mayur Ostwal; JOshua M. Lau; Christopher J. Orme; Frederick F. Stewart; J. Douglas Way

    2009-11-01

    This paper reports the transport and sorption properties of poly(fluoroalkoxyphosphazene) (PFAP) membranes for carbon dioxide and nitrogen in both pure and mixed gas experiments. The CO2 permeability decreased from 336 to 142 Barrers with an increase in the CO2/N2 ideal separation factor from 12 to 21 as the membrane temperature was decreased from 303 K to 258 K at feed pressure of 2.9 bars. At lower feed pressure (1.5 bars) the CO2 permeability decreased from 327 to 140 Barrers, while the CO2/N2 ideal separation factor increased from 13 to 22 over the same temperature range. CO2 sorption isotherms were measured using the pressure decay equilibrium method. Solubility of CO2 was determined using the sorption isotherms and the diffusion coefficients were calculated from CO2 permeabilities and solubilities. Sorption isotherms were linear at each temperature for the pressure range studied and the enthalpy of sorption was -5.8 kcal/mol. The solubility coefficient values for CO2 increased from 0.95 to 5.43 cm3 CO2(STP)/cm3 polymer.atm whereas the diffusion coefficient decreased from 2.71 X 10-6 to 0.19 X 10-6 cm2/sec as the temperature decreased from 303 K to 258 K.

  18. Remediation of Rare Earth Element Pollutants by Sorption Process Using Organic Natural Sorbents

    PubMed Central

    Butnariu, Monica; Negrea, Petru; Lupa, Lavinia; Ciopec, Mihaela; Negrea, Adina; Pentea, Marius; Sarac, Ionut; Samfira, Ionel

    2015-01-01

    The effects of the sorption of environmental applications by various source materials of natural organic matter, i.e., bone powder, was examined. Sorption capacities and subsequent rare earth element retention characteristics of all metals tested were markedly increased by ionic task-specific. In this study, the abilities of three models’ isotherms widely were used for the equilibrium sorption data: Langmuir, Freundlich and Redlich-Peterson. For all studied metal ions the maximum adsorption capacity is close to those experimentally determined. The characteristic parameters for each isotherm and related coefficients of determination have been determined. The experimental data achieved excellent fits within the following isotherms in the order: Langmuir > Redlich-Peterson > Freundlich, based on their coefficient of determination values. The bone powder has developed higher adsorption performance in the removal process of Nd(III), Eu(III), La(III) from aqueous solutions than in the case of the removal process of Cs(I), Sr(II) and Tl(I) from aqueous solutions. The described relationships provide direct experimental evidence that the sorption-desorption properties of bone powder are closely related to their degree of the type of the metal. The results suggest a potential for obtaining efficient and cost-effective engineered natural organic sorbents for environmental applications. PMID:26378553

  19. Remediation of Rare Earth Element Pollutants by Sorption Process Using Organic Natural Sorbents.

    PubMed

    Butnariu, Monica; Negrea, Petru; Lupa, Lavinia; Ciopec, Mihaela; Negrea, Adina; Pentea, Marius; Sarac, Ionut; Samfira, Ionel

    2015-09-01

    The effects of the sorption of environmental applications by various source materials of natural organic matter, i.e., bone powder, was examined. Sorption capacities and subsequent rare earth element retention characteristics of all metals tested were markedly increased by ionic task-specific. In this study, the abilities of three models' isotherms widely were used for the equilibrium sorption data: Langmuir, Freundlich and Redlich-Peterson. For all studied metal ions the maximum adsorption capacity is close to those experimentally determined. The characteristic parameters for each isotherm and related coefficients of determination have been determined. The experimental data achieved excellent fits within the following isotherms in the order: Langmuir > Redlich-Peterson > Freundlich, based on their coefficient of determination values. The bone powder has developed higher adsorption performance in the removal process of Nd(III), Eu(III), La(III) from aqueous solutions than in the case of the removal process of Cs(I), Sr(II) and Tl(I) from aqueous solutions. The described relationships provide direct experimental evidence that the sorption-desorption properties of bone powder are closely related to their degree of the type of the metal. The results suggest a potential for obtaining efficient and cost-effective engineered natural organic sorbents for environmental applications. PMID:26378553

  20. Heterogeneous carbonaceous matter in sedimentary rock lithocomponents causes significant trichloroethylene (TCE) sorption in a low organic carbon content aquifer/aquitard system

    NASA Astrophysics Data System (ADS)

    Choung, Sungwook; Zimmerman, Lisa R.; Allen-King, Richelle M.; Ligouis, Bertrand; Feenstra, Stanley

    2014-10-01

    This study evaluated the effects of heterogeneous thermally altered carbonaceous matter (CM) on trichloroethylene (TCE) sorption for a low fraction organic carbon content (foc) alluvial sedimentary aquifer and aquitard system (foc = 0.046-0.105%). The equilibrium TCE sorption isotherms were highly nonlinear with Freundlich exponents of 0.46-0.58. Kerogen + black carbon was the dominant CM fraction extracted from the sediments and accounted for > 60% and 99% of the total in the sands and silt, respectively. Organic petrological examination determined that the kerogen included abundant amorphous organic matter (bituminite), likely of marine origin. The dark calcareous siltstone exhibited the greatest TCE sorption among aquifer lithocomponents and accounted for most sorption in the aquifer. The results suggest that the source of the thermally altered CM, which causes nonlinear sorption, was derived from parent Paleozoic marine carbonate rocks that outcrop throughout much of New York State. A synthetic aquifer-aquitard unit system (10% aquitard) was used to illustrate the effect of the observed nonlinear sorption on mass storage potential at equilibrium. The calculation showed that > 80% of TCE mass contained in the aquifer was sorbed on the aquifer sediment at aqueous concentration < 1000 μg L- 1. These results show that sorption is likely a significant contributor to the persistence of a TCE groundwater plume in the aquifer studied. It is implied that sorption may similarly contribute to TCE persistence in other glacial alluvial aquifers with similar geologic characteristics, i.e., comprised of sedimentary rock lithocomponents that contain thermally altered CM.

  1. Sorption of strontium on bentonite

    SciTech Connect

    Ali Khan, S.; Riaz-ur-Rehman; Ali Khan, M.

    1995-12-31

    Sorption of Sr on bentonite was studied using the batch technique. Distribution coefficients (K{sub d}) were determined as a function of contact time, pH, sorbent and sorbate concentration and temperature. The data were interpreted in terms of Freundlich, Langmuir and Dubinin-Radushkevich isotherms. Thermodynamic parameters for the sorption system were determined at three different temperatures. The positive value of the heat of sorption, {Delta}H{degree} = 30.62 kJ/mol at 295 K, shows that the sorption of strontium on bentonite is endothermic. The negative value of the free energy of sorption, {Delta}G{degree} = {minus}10.69 kJ/mol at 298 K, shows the spontaneity of the reaction. {Delta}G{degree} becomes more negative with increasing temperature, which shows that the sorption process is more favorable at higher temperatures. The mean free energy for sorption, E {approximately} 9 kJ/mol, suggests that ion exchange is the predominant mode of sorption in the Sr concentration range studies, i.e., 0.01--0.3 mol/dm{sup 3}. The presence of complementary cations depresses the sorption of strontium on bentonite in the order Ca{sup 2+}>Mg{sup 2+}>K{sup +}>Na{sup +}. Some organic complexing agents and natural ligands also affect the sorption of strontium. The desorption studies with ground water at low strontium loads on bentonite show that about 90% of Sr is irreversibly sorbed on the bentonite.

  2. Silica gel modified with N-(3-propyl)-O-phenylenediamine: functionalization, metal sorption equilibrium studies and application to metal enrichment prior to determination by flame atomic absorption spectrometry.

    PubMed

    Akl, Magda Ali Abd-elAziz; Kenawy, Ibraheim Mohamed; Lasheen, Rabab Ramadan

    2005-08-01

    The use of the chemically modified silica gel N-(3-propyl)-O-phenylenediamine (SiG-NPPDA) adsorbent, for the preconcentration and separation of trace heavy metals, was described. SiG-NPPDA sorbs quantitatively (90-100% recovery) trace amounts of nine heavy metals, viz., Cd(II), Zn(II), Fe(III), Cu(II), Pb(II), Mn(II), Cr(III), Co(II) and Ni(II) at pH 7-8. The sorption capacity varies from 350 to 450 micromol g(-1). Desorption was found to be quantitative with 1-2 M HNO3 or 0.05 M Na2EDTA. The distribution coefficient, Kd and the percentage concentration of the investigated metal ions on the adsorbent at equilibrium, C(M,eqm)% (Recovery, R%), were studied as a function of experimental parameters. The logarithmic values of the distribution coefficient, log Kd, ranges between 4.0 and 6.4. Some foreign ions caused little interference in the preconcentration and determination of the investigated nine metals by flame atomic absorption spectrometry (AAS). The adsorbent and its formed metal chelates were characterized by IR (absorbance and/or reflectance), potentiometric titrations and thermogravimetric analysis (TGA and DTG). The mode of chelation between the SiG-NPPDA adsorbent and the investigated metal ions is proposed to be due to the reaction of the investigated metal ions with the two nitrogen atoms of the SiG-NPPDA adsorbent. The present adsorbent coupled with flame AAS has been used to enrich and determine the nine metal ions in natural aqueous systems and in certified reference materials (RSD < or = 5%). The copper, iron, manganese and zinc present in some pharmaceutical vitamin samples were also preconcentrated on SiG-NPPDA adsorbent and determined by flame AAS (RSD < or = 4.2%). Nanogram concentrations (0.07-0.14 ng ml(-1)) of Cd(II), Zn(II), Fe(III), Pb(II), Cr(III), Mn(II), Cu(II), Co(II) and Ni(II) can be determined reliably with a preconcentration factor of 100. PMID:16122162

  3. Investigation of acetylated kapok fibers on the sorption of oil in water.

    PubMed

    Wang, Jintao; Zheng, Yian; Wang, Aiqin

    2013-02-01

    Kapok fibers have been acetylated for oil spill cleanup in the aqueous environment. The structures of raw and acetylated kapok fiber were characterized using Fourier transform infrared (FT-IR) spectroscopy and scanning electron microscopy (SEM). Without severe damage to the lumen structures, the kapok fibers were successfully acetylated and the resulting fibers exhibited a better oil sorption capacity than raw fibers for diesel and soybean oil. Compared with high viscosity soybean oil, low viscosity diesel shows a better affinity to the surface of acetylated fibers. Sorption kinetics is fitted well by the pseudo second-order model, and the equilibrium data can be described by the Freundlich isotherm model. The results implied that acetylated kapok fiber can be used as the substitute for non-biodegradable oil sorption materials. PMID:23596942

  4. Sorption reactivity of mineral surfaces: the model-free conversion of humidity effect on organic vapor sorption to the organic sorbate effect on water-sorbent interactions

    NASA Astrophysics Data System (ADS)

    Borisover, Mikhail

    2013-04-01

    Interaction of water with mineral surfaces is one of the key factors controlling their reactivity towards organic compounds in multiple physical and chemical processes, e.g., in sorption and catalysis. Specifically, water interactions with minerals (as well as with other naturally present sorbents) are of fundamental importance for distribution of organic compounds between different environmental phases. Therefore, it is of basic interest to learn about interrelations between organic sorbate - sorbent and water - sorbent interactions on a local scale, in a microenvironment specific for a given organic sorbate. The understanding of these interrelations can be approached by examining the effect of organic compounds on water - sorbent interactions. However, at environmentally relevant conditions associated with relatively low concentrations of organic compounds, it may be hardly possible to directly measure the effect of sorbed organic molecules on water sorption. This paper reports a thermodynamic approach in which the effect of organic compounds on sorbent-water interactions can be obtained, in a model-free way, from the equilibrium sorption isotherms of organic vapors on a variously hydrated surface (Borisover, M., Adsorption, DOI 10.1007/s10450-012-9446-7). The outcome of this conversion is a "differential" stoichiometry between changes in the amounts of water and organic compounds in the sorbed state. The analysis included the experimental sorption data for various organic vapors on such environmentally important sorbents as quartz, metal oxides, calcite, clay minerals and humic acid. So, based on sorption isotherms of organic compounds obtained at different relative air humidities, the number of water molecules expelled from a sorbent or co-sorbed, per an organic molecule sorbed, may easily be obtained for any humidity range. This "differential" stoichiometry was also examined by means of the Linear Free Energy Relationship (LFER). Based on the LFER analysis

  5. Adsorption of fluoride on synthetic iron (III), zirconium(IV) and binary iron(III)-zirconium (IV) oxides: comparative assessment on pH effect and isotherm.

    PubMed

    Biswas, Krishna; Bandhopadhyay, Durjoy; Ghosh, Uday Chand

    2008-04-01

    Fluoride is an accumulative poison at high dose of intake for humans and animals. In the present study, the sorption of fluoride from aqueous solution has been investigated on synthetic hydrous ferric oxide (HFO), hydrous zirconium oxide (HZO) and hydrous zirconium(IV)-iron(III) oxide (HZFO) by batch mode experiments. Both HFO and HZFO were crystalline and HZO was amorphous in nature. The parametes studied were the effect of pH and sorption equilibriums. The results showed increase in fluoride-sorption with increasing pH from nearly 2.0 to 5.0, 4.6 and 6.8 for HFO, HZO and HZFO, respectively. Analysis of temperature dependent sorption data obtained at equilibrium solution pH 6.8 (+/- 0.2) has been described by the Langmuir, Freundlich, Temkin and Redlich-Peterson isotherm model equations. The present sorption data fit, in general, found very well with the Langmuir and Redlich-Peterson models; and the data fit for HZFO and HFO found to increase, but for HZO the data found to decrease with increasing temperature. The computed thermodynamic parameters such as deltaG0, delltaH0 and deltaS0 from the Langmuir equilibrium constant (b, L/Umg) values show that the fluoride-sorption on HZFO was more spontaneous and endothermic process compared to HFO. The deltaH0 value obtained for fluoride adsorption on HZO indicates exothermic nature. PMID:19295101

  6. Sorption of selected veterinary antibiotics onto dairy farming soils of contrasting nature.

    PubMed

    Srinivasan, Prakash; Sarmah, Ajit K; Manley-Harris, Merilyn

    2014-02-15

    The sorption potential for three sulfonamides (SAs), sulfamethoxazole (SMO), sulfachloropyridazine (SCP) and sulfamethazine (SM) and a macrolide, tylosin tartrate (TT) was assessed on six New Zealand dairy farming soils of contrasting physico-chemical properties. Kinetics studies showed that the sorption was rapid in the first few hours of the contact time (0-2h for SA and 0-4h for TT) and thereafter apparent equilibrium was achieved. Batch sorption isotherm data revealed that the degree of isotherm linearity (N) for SCP and SM varied between 0.50 and 1.08 in the six soils. Isotherms of both TT and SMO were mostly non-linear with the degree of non-linearity for TT (N=0.38-0.71) being greater than for SMO (0.42-0.75) in all soils except Manawatu (TT) and Te Kowhai (SMO) where a linear pattern was observed. Concentration-dependent effective distribution coefficient (Kd(eff)) values for the SMO, SCP and SM antibiotics in the soils ranged from 0.85 to 16.35 L kg(-1), while that for TT was 1.6 to 1,042 L kg(-1). The sorption affinity for all soils followed an order: TT>SCP>SM>SMO. Remarkable high sorption for tylosin in Matawhero soil as compared to other soils was attributed to the presence of oxygen containing acidic polar functional groups as evident in the FT-IR spectra of the soil. Furthermore, it was hypothesised that sorption of TT onto soils was mostly driven by metal oxide-surface mediated transformations whereas for sulfonamides it was primarily due to hydrophobic interactions. PMID:24326064

  7. Manganese Nitride Sorption Joule-Thomson Refrigerator

    NASA Technical Reports Server (NTRS)

    Jones, Jack A.; Phillips, Wayne M.

    1992-01-01

    Proposed sorption refrigeration system of increased power efficiency combines MnxNy sorption refrigeration stage with systems described in "Regenerative Sorption Refrigerator" (NPO-17630). Measured pressure-vs-composition isotherms for reversible chemisorption of N2 in MnxNy suggest feasibility to incorporate MnxNy chemisorption stage in Joule-Thomson cryogenic system. Discovery represents first known reversible nitrogen chemisorption compression system. Has potential in nitrogen-isotope separation, nitrogen purification, or contamination-free nitrogen compression.

  8. Trihalomethane formation potential of aquatic and terrestrial fulvic and humic acids: Sorption on activated carbon.

    PubMed

    Abouleish, Mohamed Y Z; Wells, Martha J M

    2015-07-15

    Humic substances (HSs) are precursors for the formation of hazardous disinfection by-products (DBPs) during chlorination of water. Various surrogate parameters have been used to investigate the generation of DBPs by HS precursors and the removal of these precursors by activated carbon treatment. Dissolved organic carbon (DOC)- and ultraviolet absorbance (UVA254)-based isotherms are commonly reported and presumed to be good predictors of the trihalomethane formation potential (THMFP). However, THMFP-based isotherms are rarely published such that the three types of parameters have not been compared directly. Batch equilibrium experiments on activated carbon were used to generate constant-initial-concentration sorption isotherms for well-characterized samples obtained from the International Humic Substances Society (IHSS). HSs representing type (fulvic acid [FA], humic acid [HA]), origin (aquatic, terrestrial), and geographical source (Nordic, Suwannee, Peat, Soil) were examined at pH6 and pH9. THMFP-based isotherms were generated and compared to determine if DOC- and UVA254-based isotherms were good predictors of the THMFP. The sorption process depended on the composition of the HSs and the chemical nature of the activated carbon, both of which were influenced by pH. Activated carbon removal of THM-precursors was pH- and HS-dependent. In some instances, the THMFP existed after UVA254 was depleted. PMID:25847173

  9. SORPTION AND REEMISSION OF FORMALDEHYDE BY GYPSUM WALLBOARD

    EPA Science Inventory

    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. he sorption and desorption rate constants are determined by short-term experimental data. ong-term so...

  10. Sorption of carbamazepine from water by magnetic molecularly imprinted polymers based on chitosan-Fe₃O₄.

    PubMed

    Zhang, Ya-Lei; Zhang, Juan; Dai, Chao-Meng; Zhou, Xue-Fei; Liu, Shu-Guang

    2013-09-12

    A novel magnetic-molecularly imprinted polymer (MMIP) based on chitosan-Fe₃O₄ has been synthesized for fast separation of carbamazepine (CBZ) from water. During polymerization, the modified chitosan-Fe₃O₄ was used not only as supporter but also as functional monomer. The properties of obtained MMIP were characterized by scanning electron and transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectra, thermo-gravimetric analysis and so on. The sorption equilibrium data was well described by Freundlich isotherm model and the increase in the temperature generated an increase in the sorption amount, indicating endothermic nature of adsorption process. Sorption kinetics followed the pseudo-second-order model. The feasibility of selective sorption of CBZ from real water by the MMIP was analyzed by using spiked real water samples. The result showed that the sorption capacity of MMIP has no obvious decrease in different water samples whereas there was obvious decline in the sorption amount of the MNIP. PMID:23911519

  11. 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. PMID:26744934

  12. Linearised and non-linearised isotherm models optimization analysis by error functions and statistical means

    PubMed Central

    2014-01-01

    In adsorption study, to describe sorption process and evaluation of best-fitting isotherm model is a key analysis to investigate the theoretical hypothesis. Hence, numerous statistically analysis have been extensively used to estimate validity of the experimental equilibrium adsorption values with the predicted equilibrium values. Several statistical error analysis were carried out. In the present study, the following statistical analysis were carried out to evaluate the adsorption isotherm model fitness, like the Pearson correlation, the coefficient of determination and the Chi-square test, have been used. The ANOVA test was carried out for evaluating significance of various error functions and also coefficient of dispersion were evaluated for linearised and non-linearised models. The adsorption of phenol onto natural soil (Local name Kalathur soil) was carried out, in batch mode at 30 ± 20 C. For estimating the isotherm parameters, to get a holistic view of the analysis the models were compared between linear and non-linear isotherm models. The result reveled that, among above mentioned error functions and statistical functions were designed to determine the best fitting isotherm. PMID:25018878

  13. Production of activated carbon from biodiesel solid residues: An alternative for hazardous metal sorption from aqueous solution.

    PubMed

    Ribeiro, Rita F L; Soares, Vitor C; Costa, Letícia M; Nascentes, Clésia C

    2015-10-01

    In this study, the potential for the sorption of Pb(2+) and Cd(2+) from aqueous solutions using HNO3-treated activated carbon (TAC) obtained from radish press cake (Raphanus sativus L.), a solid residue from biodiesel production, was investigated. Activated carbon (AC) was obtained by physical activation with CO2(g). Chemical modification with HNO3 was employed to increase the sorption capability of the AC. The sorption of Pb(2+) and Cd(2+) was studied in monometallic systems in equilibrium with different metal-ion concentrations (10-400 mg L(-1)). The experimental sorption equilibrium data were fit to the Langmuir and Freundlich isotherm models. The maximum sorption capacity (qmax) obtained for AC from the Langmuir isotherm was 45.5 mg g(-1) for Cd(2+) and 250 mg g(-1) for Pb(2+). Moreover, TAC presented qmax of 166.7 mg g(-1) (1.48 mmol g(-1)) for Cd(2+) and 500.0 mg g(-1) (2.41 mmol g(-1)) for Pb(2+)showing the effect of chemical modification. Sorption-desorption studies showed that the interaction between metals and TAC is reversible and this sorbent can be reused for several consecutive cycles. Furthermore, the sorption of Cd(2+) and Pb(2+) by TAC was not affected by the presence of competing ions. The experimental data obtained in this study indicated that this solid residue is viable for the production of sorbents that remove metals, such as cadmium and lead, from wastewaters and thereby contribute to the sustainable development of the production of biodiesel. PMID:26233585

  14. Sorption of perfluoroalkyl substances in sewage sludge.

    PubMed

    Milinovic, Jelena; Lacorte, Silvia; Rigol, Anna; Vidal, Miquel

    2016-05-01

    The sorption behaviour of three perfluoroalkyl substances (PFASs) (perfluorooctanesulfonic acid (PFOS), perfluorooctanoic acid (PFOA) and perfluorobutanesulfonic acid (PFBS)) was studied in sewage sludge samples. Sorption isotherms were obtained by varying initial concentrations of PFOS, PFOA and PFBS. The maximum values of the sorption solid-liquid distribution coefficients (Kd,max) varied by almost two orders of magnitude among the target PFASs: 140-281 mL g(-1) for PFOS, 30-54 mL g(-1) for PFOA and 9-18 mL g(-1) for PFBS. Freundlich and linear fittings were appropriate for describing the sorption behaviour of PFASs in the sludge samples, and the derived KF and Kd,linear parameters correlated well. The hydrophobicity of the PFASs was the key parameter that influenced their sorption in sewage sludge. Sorption parameters and log(KOW) were correlated, and for PFOS (the most hydrophobic compound), pH and Ca + Mg status of the sludge controlled the variation in the sorption parameter values. Sorption reversibility was also tested from desorption isotherms, which were also linear. Desorption parameters were systematically higher than the corresponding sorption parameters (up to sixfold higher), thus indicating a significant degree of irreversible sorption, which decreased in the sequence PFOS > PFOA > PFBS. PMID:26780052

  15. Influence of soil properties on heavy metal sequestration by biochar amendment: 2. Copper desorption isotherms.

    PubMed

    Uchimiya, Minori; Klasson, K Thomas; Wartelle, Lynda H; Lima, Isabel M

    2011-03-01

    Contaminant desorption constrains the long-term effectiveness of remediation technologies, and is strongly influenced by dynamic non-equilibrium states of environmental and biological media. Information is currently lacking in the influence of biochar and activated carbon amendments on desorption of heavy metal contaminants from soil components. In this study, copper sorption-desorption isotherms were obtained for clay-rich, alkaline San Joaquin soil with significant heavy metal sorption capacity, and eroded, acidic Norfolk sandy loam soil having low capacity to retain copper. Acidic pecan shell-derived activated carbon and basic broiler litter biochar were employed in desorption experiments designed to address both leaching by rainfall and toxicity characteristics. For desorption in synthetic rain water, broiler litter biochar amendment diminished sorption-desorption hysteresis. In acetate buffer (pH 4.9), significant copper leaching was observed, unless acidic activated carbon (pH(pzc)=3.07) was present. Trends observed in soluble phosphorus and zinc concentrations for sorption and desorption equilibria suggested acid dissolution of particulate phases that can result in a concurrent release of copper and other sorbed elements. In contrast, sulfur and potassium became depleted as a result of supernatant replacements only when amended carbon (broiler litter biochar) or soil (San Joaquin) contained appreciable amounts. A positive correlation was observed between the equilibrium aluminum concentration and initial copper concentration in soils amended with acidic activated carbon but not basic biochar, suggesting the importance of cation exchange mechanism, while dissolution of aluminum oxides cannot be ruled out. PMID:21190718

  16. Typical agricultural diffuse herbicide sorption with agricultural waste-derived biochars amended soil of high organic matter content.

    PubMed

    Ouyang, Wei; Zhao, Xuchen; Tysklind, Mats; Hao, Fanghua

    2016-04-01

    Biochar application has been identified as the effective soil amendment and the materials to control the diffuse herbicide pollution. The atrazine was selected as the typical diffuse herbicide pollutant as the dominant proportion in applications. The biochar treated from four types of crops biomass were added to soil with high organic matter content. The basic sorption characteristics of biocahrs from corn cob (CC), corn stalk (CS), soybean straw (SS), rice straw (RS) and corn stalk paralyzed with 5% of ammonium dihydrogen phosphate (ACS) were analyzed, along with the comparison of the sorption difference of the raw soil and soil amended with biochars at four levels of ratio (0.5%, 1.0%, 3.0% and 5.0%). It was found that the linear distribution isotherm of raw soil was much effective due to the high organic matter background concentration. The addition of five types of biochars under two kinds of initial atrazine concentration (1 mg/L and 20 mg/L) demonstrated the sorption variances. Results showed the soil amended with RS and CS biochar had the biggest removal rate in four regular biochars and the removal rate of the ACS was the biggest. The sorption coefficient and the normalized sorption coefficient from Freundlich modeling presented the isothermal sorption characteristics of atrazine with soil of high organic matter content. The normalized sorption coefficient increased with the equilibrium concentration decreased in the biochar amended soil, which indicated the sorption performance will be better due to the low atrazine concentration in practice. Results showed that biochar amendment is the effective way to prevent leakage of diffuse herbicide loss. PMID:26852289

  17. Sorption kinetics of Cs and Sr in sediments of a Savannah River Site reservoir

    SciTech Connect

    Stephens, J.A.

    1997-07-01

    Laboratory measurements of the sorption and desorption of {sup 134}Cs and {sup 85}Sr to sediments were conducted. These sediments were sampled from the profundal zone of Par Pond at the Savannah River Site, Aiken, South Carolina. The isotopes {sup 134}Cs and {sup 85}Sr were used to trace the sorption properties of the main contaminants found in the reservoir which are {sup 137}Cs and {sup 90}Sr respectively. The sorption behavior of these two elements was studied using spiked sediment/water slurries of a known mass to volume ratio. The results reveal that Sr undergoes significant reversible sorption while a fraction of Cs irreversibly sorbs to the sediment. The calculated distribution coefficient Kd at equilibrium was (3 {+-} 0.6) x 10{sup 3} for {sup 134}Cs after 60 d and (1 {+-} 0.2) x 10{sup 3} for {sup 85}Sr after 7 d at pH {approx} 6 and slurry ratio of 1:1000 g/ml. The K{sub d} for {sup 134}Cs ranged from 2 x 10{sup 2} to 3 x 10{sup 4} depending on pH and conductivity. The {sup 85}Sr reached equilibrium in a few days, while {sup 134}Cs reached an apparent equilibrium in 1--2 months. The K{sub d} for {sup 134}Cs was a function of the slurry ratio, pH, conductivity, and contact time. These factors were interrelated since the sediments released ions to the slurry mixture which decreased the pH and increased the conductivity. A sorption isotherm measured for {sup 134}Cs was linear at water concentrations from 60 mBq/ml to 20 Bq/ml. A kinetic model was proposed to describe the basic sorption of {sup 134}Cs to Par Pond sediments under homogeneous laboratory conditions.

  18. Isothermal Gaseous Detonation Model

    NASA Astrophysics Data System (ADS)

    Prokhorov, E. S.

    2015-05-01

    We propose an isothermal gaseous detonation model taking into account the initial pressure of the explosive mixture that permits describing in a simplified form both the self-sustaining and the supercompressed and undercompressed detonation regimes. The exactness of this model has been estimated on the basis of a comparative analysis with the results of equilibrium calculations of the gas-dynamic parameters at the front of detonation waves.

  19. Isothermal Calorimeter

    NASA Technical Reports Server (NTRS)

    Rowlette, John J.

    1990-01-01

    Pressure-feedback signal indicates rate of heating. Improved isothermal calorimeter measures rate of heating in object under test. Called "isothermal" because chamber holding object and its environment maintained at or near constant temperature to minimize spurious tranfers of heat introducing errors into measurements. When item under test generates heat, rate of boiling and pressure in inner chamber increase. Servo-valve opens wider to maintain preset differential pressure. Valve-control voltage used as measure of rate of heating.

  20. Sorption kinetic studies of ammonium from aqueous solution on different inorganic and organic media.

    PubMed

    Kucić, Dajana; Cosić, Ivana; Vuković, Marija; Briski, Felicita

    2013-01-01

    In this study, the sorption of ammonium from aqueous solution onto activated carbon, natural zeolite, peat and potting soil was studied by performing batch kinetic sorption experiments. The activated carbon wasn't efficiently removing ammonium at concentrations higher than 50 mg L(-1). Sorption isotherms of ammonium on zeolite, peat and potting soil were determined at 25 degrees C and 200 rpm with the initial concentration of 50-7000 mg L(-1). Equilibrium data were fitted by Freundlich, Langmuir and Temkin isotherm and parameters were evaluated according these models. Langmuir model gives better fit to experimental data than Freundlich and Temkin models. Maximum adsorption capacities were for activated carbon 0.631 mg g(-1), zeolite 58 mg g(-1), peat 595 mg g(-1) and for potting soil 575 mg g(-1). The equilibrium kinetic data were analyzed using adsorption kinetic models: the pseudo-first and second-order equations and were found to follow the pseudo-second-order kinetic model. A comparison between linear and non-linear regression method for estimating the adsorption and kinetics parameters was examined. The obtained results showed that non-linear method may be a better way to determine the kinetic parameters. Thermodynamic studies showed exothermic and endothermic nature of the adsorption of NH4(+) on inorganic and organic adsorbents, respectively. From present results it can be seen that zeolite, peat and potting soil are good adsorbents for removal ammonium from aqueous solution. PMID:23841339

  1. USING METHANOL-WATER SYSTEMS TO INVESTIGATE PHENANTHRENE SORPTION-DESORPTION ON SEDIMENT

    EPA Science Inventory

    Sorption isotherm nonlinearity, sorption-desorption hysteresis, slow desorption kinetics, and other nonideal phenomena have been attributed to the differing sorptive characteristics of the natural organic matter (NOM) polymers associated with soils and sediments. A conceptualizat...

  2. EFFECTS OF BIOSOLIDS ON SORPTION AND DESORPTION BEHAVIOR OF CADMIUM IN BIOSOLIDS-AMENDED SOILS

    EPA Science Inventory

    Cadmium sorption and desorption experiments were conducted on different fractions of soils amended with different biosolids with varying chemical properties and unamended soil (control). Biosolids addition increased the slope of the Cd sorption isotherms compared to the control s...

  3. Thermodynamics of imidacloprid sorption in Croatian soils

    NASA Astrophysics Data System (ADS)

    Milin, Čedomila; Broznic, Dalibor

    2015-04-01

    Neonicotinoids are increasingly replacing the organophosphate and methylcarbamate acetylcholinesterase inhibitors which are losing their effectiveness because of selection for resistant pest populations. Imidacloprid is the most important neonicotinoid with low soil persistence, high insecticidal potency and relatively low mammalian toxicity. In Croatia, imidacloprid is most commonly used in olive growing areas, including Istria and Kvarner islands, as an effective means of olive fruit fly infestation control. Sorption-desorption behavior of imidacloprid in six soils collected from five coastal regions in Croatia at 20, 30 and 40°C was investigated using batch equilibrium technique. Isothermal data were applied to Freundlich, Langmuir and Temkin equation, and the thermodynamic parameters ΔH°, ΔG°, ΔS° were calculated. The sorption isotherm curves were of non-linear and may be classified as L-type suggesting a relatively high sorption capacity for imidacloprid. Our results showed that the KFsor values decreased for all the tested soils as the temperature increases, indicating that the temperature strongly influence the sorption. Values of ΔG° were negative (-4.65 to -2.00 kJ/mol) indicating that at all experimental temperatures the interactions of imidacloprid with soils were spontaneous process. The negative and small ΔH° values (-19.79 to -8.89 kJ/mol) were in the range of weak forces, such as H-bonds, consistent with interactions and par¬titioning of the imidacloprid molecules into soil organic matter. The ΔS° values followed the range of -57.12 to -14.51 J/molK, suggesting that imidacloprid molecules lose entropy during transition from the solution phase to soil surface. It was found that imidacloprid desorption from soil was concentration and temperature dependent, i.e. at lower imidacloprid concentrations and temperature, lower desorption percentage occurred. Desorption studies revealed that hysteretic behavior under different temperature

  4. Thermodynamics of water sorption in high performance glassy thermoplastic polymers

    PubMed Central

    Scherillo, Giuseppe; Petretta, Mauro; Galizia, Michele; La Manna, Pietro; Musto, Pellegrino; Mensitieri, Giuseppe

    2014-01-01

    Sorption thermodynamics of water in two glassy polymers, polyetherimide (PEI) and polyetheretherketone (PEEK), is investigated by coupling gravimetry and on line FTIR spectroscopy in order to gather information on the total amount of sorbed water as well as on the different species of water molecules absorbed within the polymers, addressing the issue of cross- and self-interactions occurring in the polymer/water systems. Water sorption isotherms have been determined at temperatures ranging from 30 to 70°C while FTIR spectroscopy has been performed only at 30°C. The experimental analysis provided information on the groups present on the polymer backbones involved in hydrogen bonding interactions with absorbed water molecules. Moreover, it also supplied qualitative indications about the different “populations” of water molecules present within the PEEK and a quantitative assessment of these “populations” in the case of PEI. The results of the experimental analysis have been interpreted using an equation of state theory based on a compressible lattice fluid model for the Gibbs energy of the polymer-water mixture, developed by extending to the case of out of equilibrium glassy polymers a previous model intended for equilibrium rubbery polymers. The model accounts for the non-equilibrium nature of glassy polymers as well as for mean field and for hydrogen bonding interactions, providing a satisfactory quantitative interpretation of the experimental data. PMID:24860802

  5. Equilibrium adsorption isotherm studies of Cu (II) and Co (II) in high concentration aqueous solutions on Ag-TiO2-modified kaolinite ceramic adsorbents

    NASA Astrophysics Data System (ADS)

    Ajenifuja, E.; Ajao, J. A.; Ajayi, E. O. B.

    2016-03-01

    Photocatalytic ceramic adsorbents were prepared from locally sourced kaolinite clay minerals for the removal of copper and cobalt ions from high concentration aqueous solutions. The minerals were treated with mild acid before modification using silver nanoparticles sources and titanium-oxide nanoparticles. Batch adsorption experiment was carried out on the targeted ions and the results were analyzed by Langmuir and Freundlich equation at different concentrations (100-1000 mg/l). As-received raw materials do not exhibit any adsorption capacity. However, the adsorption isotherms for modified kaolinite clay ceramic adsorbents could be fitted well by the Langmuir model for Cu2+ and Co2+ with correlation coefficient (R) of up to 0.99705. The highest and lowest monolayer coverage (q max) were 93.023 and 30.497 mg/g for Cu2+ and Co2+, respectively. The separation factor (R L ) was less than one (<1), indicating that the adsorption of metal ions on modified ceramic adsorbent is favorable. The highest adsorbent adsorption capacity (K f ) and intensity (n) constants obtained from Freundlich model are 14.401 (Cu2+ on KLN-T) and 6.057 (Co2+ on KLN-T).

  6. Thermodynamics of cationic surfactant sorption onto natural clinoptilolite

    SciTech Connect

    Sullivan, E.J.; Bowman, R.S.; Carey, J.W.

    1998-10-15

    Sorption enthalpies of hexadecyltrimethylammonium bromide (HDTMA) as monomers and micelles and tetraethylammonium bromide (TEA) were used with surfactant, counterion, and co-ion sorption isotherms to infer the conformation, sorption mechanism, and relative stability of the sorbed surfactants on natural clinoptilolite. The average value of the sorption enthalpy was {minus}10.38 kJ/mol for monomers, {minus}11.98 kJ/mol for micelles, and +3.03 kJ/mol for TEA. Sorption of monomers produced a lower sorption plateau than equivalent micelle sorption (maxima 145 mmol/kg, 225 mmol/kg). Analysis of the sorption data demonstrated a change in the sorption mechanism at the external cation exchange capacity (ECEC) of clinoptilolite. Sorption data from below and above the ECEC were fit to a simple polynomial model and the Gibbs free energy of sorption ({Delta} G{sub m}{sup 0}) and sorption entropies were calculated. Resultant values of {Delta} G{sub m}{sup 0} were {minus}9.27 and {minus}14.38 kJ/mol for HDTMA monomers and micelles, respectively, for sorption below the ECEC, and {minus}16.11 and {minus}23.10 kJ/mol, respectively, for sorption above the ECEC. The value for TEA was {minus}1.04 kJ/mol, indicating weaker sorption than for HDTMA. Monomer sorption to clinoptilolite exceeded the ECEC, even when the solution concentration was below the critical micelle concentration. Hydrophobic (tail-tail) components of {Delta} G{sub m}{sup 0} were the driving force for sorption of HDTMA, both below and above the ECEC. A significant kinetic effect was observed in the sorption isotherms with a period of rapid sorption followed by slow equilibration requiring 7 days to achieve steady state for HDTMA; TEA equilibration occurred within 24 h.

  7. Abamectin in soils: Analytical methods, kinetics, sorption and dissipation.

    PubMed

    Dionisio, Andreza Camilotti; Rath, Susanne

    2016-05-01

    Abamectin is a broad-spectrum antiparasitic agent that has been widely employed in veterinary medicine and has also been used as a pesticide in agriculture. Veterinary drugs may reach the soil and may be transported to surface and ground waters, posing risks to terrestrial and aquatic organisms. Sorption, transformation and transport processes are primarily responsible for the fate of these substances in the environment. In this study, the sorption and the aerobic dissipation of abamectin in Brazilian soils (sand, clay and sandy-clay) were evaluated. For sorption studies, batch equilibrium experiments were performed. Sorption and desorption isotherms were fitted to the Freundlich model. Abamectin showed a high affinity to soil particles, with Freundlich sorption and desorption coefficients ranging from 44 to 138 μg(1-1/n) (cm(3))(1/n) g(-1) and from 89 to 236 μg(1-1/n) (cm(3))(1/n) g(-1), respectively. Dissipation of abamectin was evaluated in sterile and non-sterile soils in an aerobic and dark environment under controlled temperature and humidity. The time required for a 50% reduction of the amount of abamectin present in non-sterile soils was up to 4 days, and the time period for 90% dissipation was up to 12 days. In sterilized soils, there was no reduction in the concentration of abamectin over 37 days of exposure, suggesting that aerobic microbial degradation must have been the primary mechanism responsible for the dissipation of abamectin in soils. PMID:26923238

  8. Removal of Direct Red 12B by garlic peel as a cheap adsorbent: Kinetics, thermodynamic and equilibrium isotherms study of removal

    NASA Astrophysics Data System (ADS)

    Asfaram, A.; Fathi, M. R.; Khodadoust, S.; Naraki, M.

    2014-06-01

    The removal of dyes from industrial waste is very important from health and hygiene point of view and for environmental protection. In this work, efficiency and performance of garlic peel (GP) adsorbent for the removal of Direct Red 12B (DR12B) from wastewater was investigated. The influence of variables including pH, concentration of the dye and amount of adsorbent, particle size, contact time and temperature on the dye removal has been investigated. It was observed that the pseudo-second-order kinetic model fits better with good correlation coefficient and the equilibrium data fitted well with the Langmuir model. More than 99% removal efficiency was obtained within 25 min at adsorbent dose of 0.2 g per 50 ml for initial dye concentration of 50 mg L-1. Calculation of various thermodynamic parameters such as, Gibb's free energy, entropy and enthalpy of the on-going adsorption process indicate feasibility and endothermic nature of DR12B adsorption.

  9. Sorption of biocides, triazine and phenylurea herbicides, and UV-filters onto secondary sludge.

    PubMed

    Wick, Arne; Marincas, Olivian; Moldovan, Zaharie; Ternes, Thomas A

    2011-06-01

    The sludge-water distribution of a total of 41 organic micropollutants (9 phenylurea herbicides, 11 triazines, 16 biocides and 5 UV-filters) was investigated in laboratory batch experiments with fresh secondary sludge taken from a municipal WWTP. Sorption kinetics as well as sorption isotherms were examined by analyzing the compound concentration in the aqueous and solid phase for mass balance control and quality assurance. The sorption kinetic experiments revealed a sorption equilibrium time of <2 h and adverse effects of sodium azide on the sludge-water distribution of several compounds. Sorption isotherms were constructed for 6 different spiking levels spanning 3 orders of magnitude (100 ng L(-1)-30,000 ng L(-1)) and were well described by the Freundlich model. For some compounds non-linear sorption with Freundlich exponents n < 1 revealed a decreased sorption affinity to the sludge flocs with increasing aqueous phase concentration. Therefore, sludge-water distribution coefficients (K(d,sec)) were calculated from the isotherm data for a constant concentration level of 1 μg L(-1). Based on the sludge dry weight (dw), the K(d,sec) values of phenylurea herbicides ranged from 9 L kg(dw sludge)(-1) (isoproturon) to 320 L kg(dw sludge)(-1) (neburon), those of triazines from 5 L kg(dw sludge)(-1) (atrazine) to 190 L kg(dw sludge)(-1) (terbutryn), those of biocides from 10 L kg(dw sludge)(-1) (N,N-dimethyl-N'-p-tolylsulfamide) to 40,000 L kg(dw sludge)(-1) (triclocarban) and those of UV-filters from 9 L kg(dw sludge)(-1) (phenylbenzimidazole sulfonic acid) to 720 L kg(dw sludge)(-1) (benzophenone-3). For most compounds K(d,sec) values were below 500 L kg(dw sludge)(-1) and thus removal in WWTPs by the withdrawal of excess sludge is expected to be negligible (<10%) except for the biocides triclocarban (80-95%), triclosan (55-85%), chlorophene (30-60%), imazalil (25-55%) and fenpropimorph (15-40%) as well as the UV-filter benzophenone-3

  10. Reductive transformation and sorption of cis- and trans-1,2-dichloroethene in a metallic iron-water system

    SciTech Connect

    Allen-King, R.M.; Halket, R.M.; Burris, D.R.

    1997-03-01

    Reductive transformation kinetic and sorption coefficients were determined for both cis- and trans-1,2-dichloroethene (DCE) in batch systems with zero-valent iron and water. Sorption quasi-equilibrium occurred rapidly for both compounds. Freundlich-type isotherms adequately described sorption over the measured concentration range. The magnitude of sorption was greater for trans-1,2-DCE than for the more soluble cis-1,2-DCE, indicating a possible influence of hydrophobicity. The trans-isomer was more reactive than the cis-isomer. The reaction order for trans-1,2-DCE was 1.22 and for cis-1,2-DCE was 1.77 and 1.64 in relatively high and low initial concentration experiments, respectively. The fact that the reaction order for the cis-isomer could not be reduced to unity by assuming that the bulk of observed sorption was to nonreactive sorption sites suggests that either the assumption may not be valid or that a more complex process exists for this isomer. Chloride was produced by the transformation reaction and chlorine mass balances for the batch systems were 80 to 85%. Other products observed were acetylene, ethene, ethane, C{sub 3}-C{sub 5} alkanes, and vinyl chloride.

  11. Plutonium(IV) and (V) Sorption to Goethite at Sub-Femtomolar to Micromolar Concentrations: Redox Transformations and Surface Precipitation.

    PubMed

    Zhao, Pihong; Begg, James D; Zavarin, Mavrik; Tumey, Scott J; Williams, Ross; Dai, Zurong R; Kips, Ruth; Kersting, Annie B

    2016-07-01

    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 the 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) Pu4O7 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. PMID:27268262

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

    SciTech Connect

    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 aqueous 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.

  13. Effects of plasticizers on sorption and optical properties of gum cordia based edible film.

    PubMed

    Haq, Muhammad Abdul; Jafri, Feroz Alam; Hasnain, Abid

    2016-06-01

    The present study aimed to characterize a biodegradable film produced from the polysaccharide of an indigenous plant Cordia myxa. Effect of plasticizer type (Glycerol, Sorbitol, PEG200 and PEG 400) and concentration (0-30 %) was studied on sorption and optical properties of the casted film. Increase in plasticizer concentration resulted in increase in equilibrium moisture content of the film and was supported by GAB model of sorption indicating that isotherms were of Type II. The monolayer value increased with the increase in plasticizer concentration with a peak of 0.93 g.g-1 for glycerol. Addition of plasticizers improved the total color (ΔE) with glycerol showing the highest effects. All films showed resistance to UV light in the range of 280-200 nm. The polysaccharide of the fruit of C.myxa can be used to prepare an edible film with improved properties as compared to other available edible coatings. PMID:27478216

  14. Degradation and sorption of atrazine, hexazinone and procymidone in coastal sand aquifer media.

    PubMed

    Pang, Liping; Close, Murray; Flintoft, Mark

    2005-02-01

    The degradation, sorption and transport of atrazine, hexazinone and procymidone in saturated coastal sand aquifer media were investigated in batch and column experiments. The pesticides were incubated with sterilised and non-sterilised groundwater or a mixture of groundwater and the aquifer material in the dark at 15 degrees C for 120 days. The estimated half-lives of the pesticides (and their ranges) in the mixture of groundwater and aquifer sand were 36 (31-40), 54 (40-77) and 84 (46-260) days for atrazine, procymidone and hexazinone, respectively. Compared with the relevant results for the groundwater-sand mixture phase, the estimated half-life of pesticides in the groundwater phase alone was shorter for procymidone (21 days) but longer for hexazinone (134 days); atrazine was not degraded in the groundwater phase. Chemical degradation appeared to have played the predominant role in the degradation of hexazinone and procymidone in the aquifer system, while both chemical and biological processes seemed to be important for the degradation of atrazine. Batch isothermal experiments were carried out at pH 4.6-4.7 to obtain sorption coefficients under equilibrium conditions. The isothermal data of the pesticides fitted well with the non-linear Freundlich function with an exponent of sorption coefficient that was greater than one. Contrary to reports in the literature, sorption of atrazine was the greatest, and procymidone was slightly more sorbed than hexazinone. A column experiment was conducted at a typical field-flow velocity of 0.5 m day(-1) over 60 days to study pesticide attenuation and transport in flow dynamic conditions. Retardation factors, R, derived from a two-site sorption/desorption model were 8.22, 1.76 and 1.63 for atrazine, procymidone and hexazinone, respectively. Atrazine displayed the lowest mobility and the mobility of procymidone was only slightly less than that of hexazinone, which is consistent with observations in the batch experiment. A

  15. Equilibrium uptake, sorption dynamics, process optimization, and column operations for the removal and recovery of malachite green from wastewater using activated carbon and activated slag

    SciTech Connect

    Gupta, V.K.; Srivastava, S.K.; Mohan, D.

    1997-06-01

    The waste slurry generated in fertilizer plants and slag (blast furnace waste) have been converted into low-cost adsorbents, activated carbon and activated slag, respectively, and these are utilized for the removal of malachite green (a basic dye) from wastewater. In the batch experiments, parameters studied include the effect of pH, sorbent dosage, adsorbate concentration, temperature, and contact time. Kinetic studies have been performed to have an idea of the mechanistic aspects and to obtain the thermodynamic parameters of the process. The uptake of the dye is greater on carbonaceous material than on activated slag. Sorption data have been correlated with both Langmuir and Freundlich adsorption models. The presence of anionic surfactants does not affect the uptake of dye significantly. The mass transfer kinetic approach has been applied for the determination of various parameters necessary for the designing of fixed-bed contactors. Chemical regeneration has been achieved with acetone in order to recover the loaded dye and restore the column to its original capacity without dismantling the same.

  16. Reversibility of strontium sorption on fracture fillings

    SciTech Connect

    Cui, D.; Eriksen, T.E.

    1995-12-31

    Granite has been chosen by several countries as a major candidate for deep geologic disposal of radioactive waste. The authors have carried out a comparative study of sorption and desorption of strontium in groundwater on separated size and magnetic fractions of fracture fillings from deep granite. Complete reversibility of the sorption process was demonstrated by identical Freundlich isotherms, isotopic exchangeability and pH dependence of the distribution coefficient R{sub d}.

  17. SORPTION ON WASTEWATER SOLIDS: ELIMINATION OF BIOLOGICAL ACTIVITY

    EPA Science Inventory

    Sorption was found to be greatly affected by the biological activity in wastewater solids. wo experimental techniques, cyanide treatment and pasteurization, were developed for eliminating the biological activity during isotherm measurements. oth methods are effective; however, pa...

  18. Simultaneous sorption and mechanical entrapment during polymer flow through porous media

    NASA Astrophysics Data System (ADS)

    Farajzadeh, R.; Bedrikovetsky, P.; Lotfollahi, M.; Lake, L. W.

    2016-03-01

    Physical adsorption and mechanical entrapment are two major causes of polymer retention in porous media. Physical adsorption is considered an equilibrium process and is often modeled by assuming a Langmuir isotherm. The outcome is a steady state pressure response because the permeability reduction is also accounted for by adsorption. However, some experimental data show gradual increase of pressure with time, implying that polymer retention is a time-dependent process. We discuss simultaneous effect of sorption and mechanical entrapment on the polymer retention in porous media. An exact solution for 1-D flow problem for the case of constant filtration coefficient and Langmuir-sorption isotherm, including explicit formulae for breakthrough concentration and pressure drop across the core is derived. The general model with a varying filtration coefficient was successfully matched with experimental data confirming the occurrence of simultaneous sorption with deep-bed filtration during polymer flow in porous media. In the absence of mechanical entrapment, the physical adsorption causes delay in the polymer front and does not affect the polymer concentration behind the front. Addition of mechanical entrapment results in slow recovery of the injected concentration at the outlet (for a varying filtration coefficient) or reaching to a steady state concentration, which is only a fraction of the injected concentration (for a constant filtration coefficient). Accurate assessment and quantification of the polymer retention requires both pressure and effluent concentration data at the outlet of the porous medium.

  19. Advances in Understanding Sorption and Transport Processes Affecting the Fate of Environmental Pollutants in the Subsurface

    NASA Astrophysics Data System (ADS)

    Karapanagioti, H. K.; Werner, D.; Werth, C.

    2012-04-01

    The results of a call for a special issue that is now in press by the Journal of Contaminant Hydrology will be presented. This special issue is edited by the authors and is entitled "Sorption and Transport Processes Affecting the Fate of Environmental Pollutants in the Subsurface". A short abstract of each paper will be presented along with the most interesting results. Nine papers were accepted. Pollutants studied include: biocolloids, metals (arsenic, chromium, nickel), organic compounds such as hydrocarbons, chlorinated hydrocarbons, micropollutants (PAHs, PCBs), pesticides (glyphosate, 2,4-D). Findings presented in the papers include a modified batch reactor system to study equilibrium-reactive transport problems of metals. Column studies along with theoretical approximations evaluate the combined effects of grain size and pore water velocity on the transport in water saturated porous media of three biocolloids. A polluted sediment remediation method is evaluated considering site-specific conditions through monitoring results and modelling. A field study points to glogging and also sorption as mechanisms affecting the effectiveness of sub-surface flow constructed wetlands. A new isotherm model combining modified traditionally used isotherms is proposed that can be used to simulate pH-dependent metal adsorption. Linear free energy relationships (LFERs) demonstrate ability to predict slight isotope shifts into the groundwater due to sorption. Possible modifications that improve the reliability of kinetic models and parameter values during the evaluation of experiments that assess the sorption of pesticides on soils are tested. Challenges in selecting groundwater pollutant fate and transport models that account for the effect of grain-scale sorption rate limitations are evaluated based on experimental results and are discussed based on the Damköhler number. Finally, a thorough review paper presents the impact of mineral micropores on the transport and fate of

  20. Removal of divalent heavy metals (Cd, Cu, Pb, and Zn) and arsenic(III) from aqueous solutions using scoria: kinetics and equilibria of sorption.

    PubMed

    Kwon, Jang-Soon; Yun, Seong-Taek; Lee, Jong-Hwa; Kim, Soon-Oh; Jo, Ho Young

    2010-02-15

    Kinetic and equilibrium sorption experiments were conducted on removal of divalent heavy metals (Pb(II), Cu(II), Zn(II), Cd(II)) and trivalent arsenic (As(III)) from aqueous solutions by scoria (a vesicular pyroclastic rock with basaltic composition) from Jeju Island, Korea, in order to examine its potential use as an efficient sorbent. The removal efficiencies of Pb, Cu, Zn, Cd, and As by the scoria (size=0.1-0.2mm, dose=60gL(-1)) were 94, 70, 63, 59, and 14%, respectively, after a reaction time of 24h under a sorbate concentration of 1mM and the solution pH of 5.0. A careful examination on ionic concentrations in sorption batches suggested that sorption behaviors of heavy metals onto scoria are mainly controlled by cation exchange. On the other hand, arsenic appeared to be sensitive to specific sorption onto hematite (a minor constituent of scoria). Equilibrium sorption tests indicated that the removal efficiency for heavy metals increases with increasing pH of aqueous solutions, which is resulted from precipitation as hydroxides. Similarly, multi-component systems containing heavy metals and arsenic showed that the arsenic removal increases with increasing pH of aqueous solutions, which can be attributed to coprecipitation with metal hydroxides. The empirically determined sorption kinetics were well fitted to a pseudo-second order model, while equilibrium sorption data for heavy metals and arsenic onto scoria were consistent with the Langmuir and Freundlich isotherms, respectively. Natural scoria studied in this work is an efficient sorbent for concurrent removal of divalent heavy metals and arsenic. PMID:19828237

  1. Heterogeneous carbonaceous matter in sedimentary rock lithocomponents causes significant trichloroethylene (TCE) sorption in a low organic carbon content aquifer/aquitard system.

    PubMed

    Choung, Sungwook; Zimmerman, Lisa R; Allen-King, Richelle M; Ligouis, Bertrand; Feenstra, Stanley

    2014-10-15

    This study evaluated the effects of heterogeneous thermally altered carbonaceous matter (CM) on trichloroethylene (TCE) sorption for a low fraction organic carbon content (foc) alluvial sedimentary aquifer and aquitard system (foc=0.046-0.105%). The equilibrium TCE sorption isotherms were highly nonlinear with Freundlich exponents of 0.46-0.58. Kerogen+black carbon was the dominant CM fraction extracted from the sediments and accounted for >60% and 99% of the total in the sands and silt, respectively. Organic petrological examination determined that the kerogen included abundant amorphous organic matter (bituminite), likely of marine origin. The dark calcareous siltstone exhibited the greatest TCE sorption among aquifer lithocomponents and accounted for most sorption in the aquifer. The results suggest that the source of the thermally altered CM, which causes nonlinear sorption, was derived from parent Paleozoic marine carbonate rocks that outcrop throughout much of New York State. A synthetic aquifer-aquitard unit system (10% aquitard) was used to illustrate the effect of the observed nonlinear sorption on mass storage potential at equilibrium. The calculation showed that >80% of TCE mass contained in the aquifer was sorbed on the aquifer sediment at aqueous concentration <1000 μgL(-1). These results show that sorption is likely a significant contributor to the persistence of a TCE groundwater plume in the aquifer studied. It is implied that sorption may similarly contribute to TCE persistence in other glacial alluvial aquifers with similar geologic characteristics, i.e., comprised of sedimentary rock lithocomponents that contain thermally altered CM. PMID:25168960

  2. Selective Sorption of Dissolved Organic Carbon Compounds by Temperate Soils

    PubMed Central

    Jagadamma, Sindhu; Mayes, Melanie A.; Phillips, Jana R.

    2012-01-01

    Background Physico-chemical sorption onto soil minerals is one of the major processes of dissolved organic carbon (OC) stabilization in deeper soils. The interaction of DOC on soil solids is related to the reactivity of soil minerals, the chemistry of sorbate functional groups, and the stability of sorbate to microbial degradation. This study was conducted to examine the sorption of diverse OC compounds (D-glucose, L-alanine, oxalic acid, salicylic acid, and sinapyl alcohol) on temperate climate soil orders (Mollisols, Ultisols and Alfisols). Methodology Equilibrium batch experiments were conducted using 0–100 mg C L−1 at a solid-solution ratio of 1∶60 for 48 hrs on natural soils and on soils sterilized by γ-irradiation. The maximum sorption capacity, Qmax and binding coefficient, k were calculated by fitting to the Langmuir model. Results Ultisols appeared to sorb more glucose, alanine, and salicylic acid than did Alfisols or Mollisols and the isotherms followed a non-linear pattern (higher k). Sterile experiments revealed that glucose and alanine were both readily degraded and/or incorporated into microbial biomass because the observed Qmax under sterile conditions decreased by 22–46% for glucose and 17–77% for alanine as compared to non-sterile conditions. Mollisols, in contrast, more readily reacted with oxalic acid (Qmax of 886 mg kg−1) and sinapyl alcohol (Qmax of 2031 mg kg−1), and no degradation was observed. The reactivity of Alfisols to DOC was intermediate to that of Ultisols and Mollisols, and degradation followed similar patterns as for Ultisols. Conclusion This study demonstrated that three common temperate soil orders experienced differential sorption and degradation of simple OC compounds, indicating that sorbate chemistry plays a significant role in the sorptive stabilization of DOC. PMID:23209742

  3. The sorption characteristics of mercury as affected by organic matter content and/or soil properties

    NASA Astrophysics Data System (ADS)

    Šípková, Adéla; Šillerová, Hana; Száková, Jiřina

    2014-05-01

    The determination and description of the mercury sorption extend on soil is significant for potential environmental toxic effects. The aim of this study was to assess the effectiveness of mercury sorption at different soil samples and vermicomposts. Mercury interactions with soil organic matter were studied using three soils with different physical-chemical properties - fluvisol, cambisol, and chernozem. Moreover, three different vermicomposts based on various bio-waste materials with high organic matter content were prepared in special fermentors. First was a digestate, second was represented by a mixture of bio-waste from housing estate and woodchips, and third was a garden bio-waste. In the case of vermicompost, the fractionation of organic matter was executed primarily using the resin SuperliteTM DAX-8. Therefore, the representation of individual fractions (humic acid, fulvic acid, hydrophilic compounds, and hydrophobic neutral organic matter) was known. The kinetics of mercury sorption onto materials of interest was studied by static sorption experiments. Samples were exposed to the solution with known Hg concentration of 12 mg kg-1 for the time from 10 minutes to 24 hours. Mercury content in the solutions was measured by the inductively coupled plasma mass spectrometry (ICP-MS). Based on this data, the optimum conditions for following sorption experiments were chosen. Subsequently, the batch sorption tests for all soil types and vermicomposts were performed in solution containing variable mercury concentrations between 1 and 12 mg kg-1. Equilibrium concentration values measured in the solution after sorption and calculated mercury content per kilogram of the soil or the vermi-compost were plotted. Two basic models of sorption isotherm - Langmuir and Freundlich, were used for the evaluation of the mercury sorption properties. The results showed that the best sorption properties from studied soil were identified in chernozem with highest cation exchange

  4. Competitive sorption of organic contaminants in chalk

    NASA Astrophysics Data System (ADS)

    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

  5. Linearity of iodine sorption and sorption capacities for seven soils

    SciTech Connect

    Sheppard, M.I.; Hawkins, J.L.; Smith, P.A.

    1996-11-01

    Iodine, a soluble and prevalent element in spent nuclear fuel and a pivotal element in the assessment of Canada`s nuclear fuel waste disposal option, sorbs to soils rich in organics and hydrous oxides. Biotic factors, such as microbes, enzymes and plant exudates, have been implicated in the retention of I to soils. Anion exchange of I{sup {minus}} or IO{sub 3}{sup {minus}} and chemical or biological oxidation to I{sub 2} followed by reactions with the soil organic matter are possible retention mechanisms. We have carried out sorption and desorption studies across a wide range of soil solution concentrations (10{sup {minus}7} to 10{sup 5} mg I/L, 10{sup {minus}12} to 1 M) for seven soils typical of upland and lowland soils of the Canadian Precambrian Shield. Soil solid-liquid partition values (K{sub d}), required for impact assessments, varied from 60 to 1800 L/kg and were significantly correlated with extractable Al oxide content, and background I and organic matter content. Freundlich isotherm fits show that sorption of I across our intentionally large concentration range is nonlinear; however, sorption of I across our intentionally large concentration range is nonlinear; however, sorption of I at environmental concentrations (<0.1 mg I/L soil solution) is linear and can be described by the K{sub d} model. Sorption of I was not related to peroxidase enzyme activity. Desorption percentages were small implying sorption was not easily reversed, even with a strong electrolyte, KNO{sub 3}. Desorption results and simple correlations of I sorption to soil properties suggest that the oxidation of I{sup {minus}} to I{sub 2} and complexation to organic functional groups or oxides are the major processes for I retention in Shield soils. 52 refs., 2 figs., 2 tabs.

  6. Synthesis of assorted metal ions anchored alginate bentonite biocomposites for Cr(VI) sorption.

    PubMed

    Gopalakannan, Venkatrajan; Periyasamy, Soodamani; Viswanathan, Natrayasamy

    2016-10-20

    Biocomposites were synthesized by dispersing bentonite (Bent) clay in a biopolymer namely alginate (Alg) and cross-linked with bi (Ca(2+)), tri (Ce(3+)) and tetravalent (Zr(4+)) metal ions viz., Ca@AlgBent, Ce@AlgBent and Zr@AlgBent composites respectively. The synthesized biocomposites were characterized by various instrumental techniques like FTIR, SEM and EDAX. Cr(VI) sorption capacities (SCs) of the biocomposites Ca@AlgBent, Ce@AlgBent and Zr@AlgBent were examined by batch process. Various adsorption influencing factors viz., contact time, dosage of the sorbent, pH of the medium, temperature, presence of common co-ions and initial Cr(VI) concentration were studied. Freundlich, Langmuir and Dubinin-Radushkevich (D-R) isotherm models were adopted to examine the adsorption equilibrium. Kinetics of the sorption process was carried out by pseudo-first-order and pseudo-second-order models. The nature of the sorption process was explained using thermodynamic parameters like ΔS°, ΔG° and ΔH° and a possible mechanism for the sorption of Cr(VI) onto the biocomposites was given. The application of the biocomposites at field conditions was also examined by testing it with industrial water. The regeneration studies were carried to know about the reusability of the biocomposites. PMID:27474660

  7. SORPTION OF ARSENATE AND ARSENITE ON RUO2.XH2O: A SPECTROSCOPIC AND MACROSCOPIC STUDY

    EPA Science Inventory

    The sorption of arsenate (As(V)) and arsenite (As(III)) on RuO2 xH2O was examined using macroscopic and microscopic techniques. Constant solid:solution ratio isotherms were constructed from batch sorption experiments to study the sorption of the inorganic arsenic species on RuO2...

  8. Reversible and irreversible sorption of perfluorinated compounds (PFCs) by sediments of an urban reservoir.

    PubMed

    Chen, Huiting; Reinhard, Martin; Nguyen, Viet Tung; Gin, Karina Yew-Hoong

    2016-02-01

    Uncertainty about the extent to which contaminant sorption by suspended solids and bed sediments is irreversible is a major impediment for modeling and managing the water quality of surface water resources. This study examined reversible and irreversible sorption of several perfluorinated compounds (PFCs) to bed sediments from an urban reservoir. PFCs investigated include C4, C6, C8, C9 and C10 perfluoroalkanoate homologues (PFBA, PFHxA, PFOA, PFNA and PFDA, respectively) and perfluorooctane and hexane sulfonate (PFOS and PFHxS, respectively). Although sorption branches of the PFOS, PFNA and PFDA isotherms were nearly linear (implying a partitioning-like process), desorption experiments indicated that a fraction of the sorbed PFCs were entrapped and resistant to desorption. The hysteretic desorption branches were approximately linear. Irreversibility increased with chain length and was nearly complete for PFDA (thermodynamic irreversibility index (TII) 0.98). For the weakly sorbing PFOA and PFHxS, sorption was largely reversible. Data suggest that (1) for the strongly sorbing PFCs, e.g. PFNA, PFDA and PFOS, bed sediments acted predominantly as irreversible sinks, (2) aqueous concentrations of the moderately sorbing PFCs (PFOA and PFHxS) are buffered by reversibly sorbing suspended solids, and (3) the short-chain PFCs (PFBA and PFHxA) are not significantly sorbed and therefore not expected to be significantly influenced by sediment transport. Situations in which highly contaminated particles entering relatively clean water bodies, equilibrium is approached from the reverse (desorption) direction. For irreversibly sorbed contaminants field-based K(D) values will be higher than the K(D) values derived from laboratory sorption data obtained from forward sorption experiments. PMID:26521093

  9. Sorption of acetochlor, S-metolachlor, and atrazine in surface and subsurface soil horizons of Argentina.

    PubMed

    Bedmar, Francisco; Daniel, Peter E; Costa, José L; Giménez, Daniel

    2011-09-01

    Understanding herbicide sorption within soil profiles is the first step to predicting their behavior and leaching potential. Laboratory studies were conducted to determine the influence of surface and subsurface soil properties on acetochlor, atrazine, and S-metolachlor sorption. Soil samples were taken from horizons A, B, and C of two loamy soils of the humid pampas of Argentina under no-till management; horizon A was divided into two layers, A(0) (0-5 cm) and A(1) (5 cm to the full thickness of an A horizon). Sorption isotherms were determined from each sampled horizon using the batch equilibrium method and seven concentrations (0, 0.1, 0.5, 2.0, 5.0, 10.0, and 20.0 mg L(-1)). Sorption affinity of herbicides was approximated by the Freundlich equation. The sorption strength K(f) (mg(1 - 1/n) kg(-1) L(1/n) ) over the soils and horizons studied followed the order S-metolachlor (16.51-29.19) > atrazine (4.85-12.34) ≥ acetochlor (5.17-11.97), which was closely related to the hydrophobicity of herbicides expressed as octanol-water partition coefficient (K(OW) ). The K(f) values of the three herbicides were positively correlated with soil organic carbon, with a significance of p < 0.01. Values of K(f) for the three herbicides decreased with depth in the two soils, indicating greater sorption onto surficial soil horizons and possibly a delayed transport toward subsurface soils and subsequent pollution of groundwater. PMID:21692102

  10. Fractionation of aquatic natural organic matter upon sorption to goethite and kaolinite

    USGS Publications Warehouse

    Meier, M.; Namjesnik-Dejanovic, K.; Maurice, P.A.; Chin, Y.-P.; Aiken, G.R.

    1999-01-01

    Natural organic matter (NOM) consists of a complex mixture of organic molecules; previous studies have suggested that preferential sorption of higher molecular weight, more hydrophobic, and more aromatic components may lead to fractionation of the NOM pool upon passage through porous media. Our work expands upon previous studies by quantifying the change in solution-phase weight average molecular weight (M(w)) upon sorption of bulk (rather than isolated) surface water NOM from the Suwannee River (SR) and the Great Dismal Swamp (GDS) to goethite and kaolinite at different sorption densities and at pH 4, 22??C. High pressure size exclusion chromatography (HPSEC) was used to quantify changes in M(w) upon sorption, and molar absorptivities at ?? = 280 nm were used to approximate changes in solution NOM aromaticity. Two SR water samples were used, with M(w) = 2320 and 2200 Da; a single GDS sample was used, with M(w) = 1890 Da. The SR NOM was slightly more hydrophobic and aromatic. These differences were reflected in greater sorption of SR NOM than GDS NOM. Both surface water NOMs showed a much greater affinity for goethite than for kaolinite. HPSEC analysis of the NOM remaining in solution after 24 h reaction time with geothite revealed that the largest changes in solution phase M(w)s (decreases by 900-1700 Da) occurred at relatively low equilibrium sorbate concentrations (approximately 5-20 mg C 1-1); the decrease in solution M(w) suggested that reactive surface sites were occupied disproportionately by large and intermediate size NOM moieties. At higher equilibrium NOM concentrations (>20 mg C 1-1), as percent adsorption decreased, M(w) in solution was similar to original samples. A smaller decrease in solution NOM M(w) (300-500 Da at 10-20 mg C 1-1 ~ 100 Da at > 20 mg) also occurred upon sorption to kaolinite. Overall, our results showed that factors (as related to NOM composition, clay mineral surface properties, and position along the sorption isotherm) which

  11. Equilibrium, kinetic and thermodynamic studies of acid Orange 52 dye biosorption by Paulownia tomentosa Steud. leaf powder as a low-cost natural biosorbent.

    PubMed

    Deniz, Fatih; Saygideger, Saadet D

    2010-07-01

    The biosorption of Acid Orange 52 onto the leaf powder of Paulownia tomentosa Steud. was studied in a batch adsorption system to estimate the equilibrium, kinetic and thermodynamic parameters as a function of solution pH, biosorbent concentration, dye concentration, biosorbent size, temperature and contact time. The Langmuir, Freundlich and Temkin isotherm models were used for modeling the biosorption equilibrium. The experimental equilibrium data could be well interpreted by the Temkin and Langmuir isotherms with maximum adsorption capacity of 10.5 mg g(-1). In order to state the sorption kinetics, the fits of pseudo-first order, pseudo-second order, Elovich and intraparticle diffusion kinetic models were investigated. It was obtained that the biosorption process followed the pseudo-second order rate kinetics. Thermodynamic studies indicated that this system was exothermic process. The results revealed that P. tomentosa leaf powder could be an efficient biosorbent for the treatment of wastewater containing Acid Orange 52. PMID:20194017

  12. 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. PMID:22022786

  13. Enhancement of phosphorus sorption onto light expanded clay aggregates by means of aluminum and iron oxide coatings.

    PubMed

    Yaghi, Nader; Hartikainen, Helinä

    2013-11-01

    Phosphorus (P) loading from non-point or point sources increases the eutrophication risk of natural waters. The functioning of constructed wetlands (CWs) used as natural water treatment systems can be improved by means of additional materials adsorbing soluble P. In this study, light expanded clay aggregates (LECA) and LECA coated with aluminum (Al) oxide (Al-LECA) or iron (Fe) oxide (Fe-LECA) were tested for their efficiency as P sorbents in the pH range 3-8. The oxide coatings duplicated the actual sorption capacity calculated from the sorption isotherms at the P concentration in the equilibrium solution of 20 μg L(-1), assumed to be the allowable P level in purified water. In the oxide-coated LECAs the sorption was fast and followed both the first- and second-order Lagergren kinetic models, suggesting that the formation of a binuclear surface complex was feasible. In LECA, sorption was markedly slower and followed the first-order kinetic model, indicating that retention occurred through a monodentate attachment. These findings were in harmony with the degree of P saturation (DPS) of the sorbent surfaces at the highest P addition level (200 μg L(-1)), DPS being decisively higher for LECA than for the oxide-coated sorbents. Accordingly, at higher pH values the competition by hydroxyl ions diminished the sorption in LECA relatively more than that in the coated sorbents. In agreement with the acidity of Al(3+) being 100 times lower than that of Fe(3+), at elevated pH the sorption by Al-LECA proved to be less reversible than that by Fe-LECA. The results provide evidence that in CWs Al-coated sorbents are superior to Fe-coated ones that are also redox-sensitive and may lose their sorption properties in anoxic conditions. PMID:23866174

  14. Understand rotating isothermal collapses yet

    SciTech Connect

    Tohline, J.E.

    1985-01-01

    A scalar virial equation is used to describe the dynamic properties of equilibrium gas clouds, taking into account the relative effects of surface pressure, rotation, self gravity and internal isothermal pressure. Details concerning the internal structure of the clouds are ignored in order to obtain a globalized analytical expression. The obtained solution to the equation is found to agree with the surface-pressure-dominated model of Stahler (1983), and the rotation-dominated model of Hayashi, Narita, and Miyama (1982). On the basis of the analytical expression of virial equilibrium in the clouds, some of the limiting properties of isothermal clouds are described, and a realistic starting model for cloud collapse is proposed. 18 references.

  15. 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

  16. An isotopic exchange method for the characterization of the irreversibility of pesticide sorption-desorption in soil.

    PubMed

    Celis, R; Koskinen, W C

    1999-02-01

    An isotopic exchange method is presented that characterizes the irreversibility of pesticide sorption-desorption by soil observed in batch equilibration experiments. The isotopic exchange of (12)C- and (14)C-labeled triadimefon [(1-(4-chlorophenoxy)-3,3-dimethyl-1-(1H-1, 2,4-triazol-1-yl)-2-butanone] and imidacloprid-guanidine [1-[(6-chloro-3-pyridinyl)methyl]-4,5-dihydro-1H-imidazol-2-amine] in Hanford sandy loam soil indicated that these systems can be described by a two-compartment model in which about 90% of sorption occurs on reversible, easily desorbable sites, whereas 10% of the sorbed molecules are irreversibly sorbed on soil and do not participate in the sorption-desorption equilibrium. This model closely predicted the hysteresis observed in the desorption isotherms from batch equilibration experiments. The isotopic exchange of triadimefon and imidacloprid-guanidine in Drummer silty clay loam soil indicated that there was a fraction of the sorbed (14)C-labeled pesticide that was resistant to desorption, which increased as pesticide concentration decreased and was higher for triadimefon than for imidacloprid-guanidine. In contrast, the batch equilibration method resulted in ill-defined desorption isotherms for the Drummer soil, which made accurate desorption characterization problematic. PMID:10563969

  17. Pyrolytic temperatures impact lead sorption mechanisms by bagasse biochars.

    PubMed

    Ding, Wenchuan; Dong, Xiaoling; Ime, Inyang Mandu; Gao, Bin; Ma, Lena Q

    2014-06-01

    The characteristics and mechanisms of Pb sorption by biochars produced from sugarcane bagasse at 250, 400, 500, and 600 °C were examined. The Pb sorption isotherms, kinetics and desorption were investigated. All biochars were effective in Pb sorption and were well described by Langmuir isotherm model and pseudo-second-order kinetic model. The maximum sorption capacity decreased from 21 to 6.1 mg g(-1) as temperature increased from 250 to 600 °C. The Pb sorption was rapid initially, probably controlled by cation exchange and complexation and then slowed down, which might be due to intraparticle diffusions. FTIR data and kinetic models suggested that oxygen functional groups were probably responsible for the high Pb sorption onto low temperature biochars (250 and 400 °C) whereas intraparticle diffusion was mainly responsible for low Pb sorption onto high temperature biochars (500 and 600 °C). Decreased phosphorus concentration indicated that P-induced Pb precipitation was also responsible for Pb sorption. Pyrolysis temperature significantly affected biochar properties and played an important role in Pb sorption capacity and mechanisms by biochars. PMID:24393563

  18. Sorption kinetics of hexadecyltrimethylammonium on natural clinoptilolite

    SciTech Connect

    Li, Z.

    1999-09-14

    Sorption kinetics of hexadecyltrimethylammonium (HDTMA) chloride on a natural clinoptilolite was studied in this research. The amount of HDTMA sorbed is a function of the initial HDTMA input and the sorption time. When the initial HDTMA input is less than the external cation-exchange capacity of the clinoptilolite, the HDTMA sorption is fast and equilibrium can be established in 1 h. As the initial HDTMA input is greater than the external cation-exchange capacity of clinoptilolite, which will result in more than a monolayer HDTMA surface coverage, the time for HDTMA sorption to reach equilibrium increases exponentially. The HDTMA sorption maximum on clinoptilolite increases logarithmically with mixing time. The counterion solution concentration data suggest that at the initial stage HDTMA molecules sorb on the zeolite via micelle forms, which is manifested by a decrease in chloride solution concentration with time. When HDTMA solution concentration is depleted to less than its critical micelle concentration, the adsorbed micelles (admicelles) rearrange themselves to a more stable monolayer or bilayer configuration, which is reflected by an increase in counterion solution concentration due to the desorption of chloride from admicelles. The time required for the surface rearrangement increases exponentially as the HDTMA input increases. The data of HDTMA sorption kinetics were fitted to different kinetic models, and the parabolic diffusion model fits the data best for the HDTMA sorption, counterion sorption at the initial stage and counterion desorption at the rearrangement stage. Thus, the sorption of HDTMA on clinoptilolite surfaces is diffusion controlled. The results also indicate that it is incomplete to discuss surfactant sorption without counterion concentration data.

  19. Impact of Sequential Ammonia Fiber Expansion (AFEX) Pretreatment and Pelletization on the Moisture Sorption Properties of Corn Stover

    SciTech Connect

    Bonner, Ian J.; Thompson, David N.; Teymouri, Farzaneh; Campbell, Timothy; Bals, Bryan; Tumuluru, Jaya Shankar

    2015-05-01

    Combining ammonia fiber expansion (AFEX™) pretreatment with a depot processing facility is a promising option for delivering high-value densified biomass to the emerging bioenergy industry. However, because the pretreatment process results in a high moisture material unsuitable for pelleting or storage (40% wet basis), the biomass must be immediately dried. If AFEX pretreatment results in a material that is difficult to dry, the economics of this already costly operation would be at risk. This work tests the nature of moisture sorption isotherms and thin-layer drying behavior of corn (Zea mays L.) stover at 20°C to 60°C before and after sequential AFEX pretreatment and pelletization to determine whether any negative impacts to material drying or storage may result from the AFEX process. The equilibrium moisture content to equilibrium relative humidity relationship for each of the materials was determined using dynamic vapor sorption isotherms and modeled with modified Chung-Pfost, modified Halsey, and modified Henderson temperature-dependent models as well as the Double Log Polynomial (DLP), Peleg, and Guggenheim Anderson de Boer (GAB) temperature-independent models. Drying kinetics were quantified under thin-layer laboratory testing and modeled using the Modified Page's equation. Water activity isotherms for non-pelleted biomass were best modeled with the Peleg temperature-independent equation while isotherms for the pelleted biomass were best modeled with the Double Log Polynomial equation. Thin-layer drying results were accurately modeled with the Modified Page's equation. The results of this work indicate that AFEX pretreatment results in drying properties more favorable than or equal to that of raw corn stover, and pellets of superior physical stability in storage.

  20. Sorption of triazoles to soil and iron minerals.

    PubMed

    Jia, Yu; Aagaard, Per; Breedveld, Gijs D

    2007-02-01

    Triazoles, additives in runway de-icers, are found in soil and groundwater at airport sites. To better understand the fate and transport of benzotriazole (BTA) and methylbenzotriazole (MeBTA) and to assess possible remediation options of contaminated groundwater, sorption to various soils and ferrous sorbents has been studied. In batch experiments, limited non-linear sorption of BTA to mineral subsoil from the Oslo International Airport, Gardermoen was observed. The sorption to soil could be described using a Freundlich isotherm. pH affected sorption of BTA to subsoil, although the effect was not strong. Increased sorption was observed to zerovalent iron (Fe(0)). MeBTA showed similar sorption behaviour as BTA although the sorption coefficient was generally higher. Sorption to Fe(0) seems to be controlled by multi-layer coverage. Our data suggest that sorption of triazoles to Fe(2)O(3) is negligible. However BTA sorption to 2-line and 6-line ferrihydrites showed strong sorption. The results demonstrate that triazoles are highly mobile in the subsurface environment, however zerovalent iron can be an effective medium for groundwater remediation. Without remediation, wide distribution of triazoles in the environment can be expected due to its extensive application and limited degradability. PMID:17123582

  1. Theoretical evidence of the difference in kinetics of water sorption and desorption in Nafion® membrane and experimental validation

    NASA Astrophysics Data System (ADS)

    Didierjean, S.; Perrin, J. C.; Xu, F.; Maranzana, G.; Klein, M.; Mainka, J.; Lottin, O.

    2015-12-01

    Water transport during sorption and desorption in Nafion® 117 samples is studied by means of dynamic model and experiments as a response of relative humidity step. The model takes into account a transfer resistance at the interface between the membrane and the surrounding medium, and considers that the water content of the membrane remains uniform at all times during sorption and desorption, which was confirmed using NMR imaging. Thus, its main hypothesis is that the membrane is in equilibrium with the humid gas located at the interface whose relative humidity is different than in the bulk. The calculated time-variations in the water content of a membrane sample (in acid form) during sorption and desorption show that desorption is faster than sorption due to the variations in the slope of the water uptake isotherm. The theoretical results and the experimental data show a good agreement which allows the determination of the mass transfer coefficient. The influence of diffusion and thermal effects are also discussed.

  2. Phosphorus sorption and buffering mechanisms in suspended sediments from the Yangtze Estuary and Hangzhou Bay, China

    NASA Astrophysics Data System (ADS)

    Li, M.; Whelan, M. J.; Wang, G. Q.; White, S. M.

    2013-05-01

    The adsorption isotherm and the mechanism of the buffering effect are important controls on phosphorus (P) behaviors in estuaries and are important for estimating phosphate concentrations in aquatic environments. In this paper, we derive phosphate adsorption isotherms in order to investigate sediment adsorption and buffering capacity for phosphorus discharged from sewage outfalls in the Yangtze Estuary and Hangzhou Bay near Shanghai, China. Experiments were also carried out at different temperatures in order to explore the buffering effects for phosphate. The results show that P sorption in sediments with low fine particle fractions was best described using exponential equations. Some P interactions between water and sediment may be caused by the precipitation of CaHPO4 from Ca2+ and HPO42- when the phosphate concentration in the liquid phase is high. Results from the buffering experiments suggest that the Zero Equilibrium Phosphate Concentrations (EPC0) vary from 0.014 mg L-1 to 0.061 mg L-1, which are consistent with measured phosphate concentrations in water samples collected at the same time as sediment sampling. Values of EPC0 and linear sorption coefficients (K) in sediments with high fine particle and organic matter contents are relatively high, which implies that they have high buffering capacity. Both EPC0 and K increase with increasing temperature, indicating a higher P buffering capacity at high temperatures.

  3. Phosphorus sorption and buffering mechanisms in suspended sediments from the Yangtze Estuary and Hangzhou Bay, China

    NASA Astrophysics Data System (ADS)

    Li, M.; Whelan, M. J.; Wang, G.; White, S. M.

    2012-12-01

    The adsorption isotherm and the mechanism of the buffering effect are important controls on phosphorus behaviors in estuaries and are important for estimating phosphate concentrations in aquatic environments. In this paper, we derive phosphate adsorption isotherms in order to investigate sediment adsorption and buffering capacity for phosphorus discharged from sewage outfalls in the Yangtze Estuary and Hangzhou Bay near Shanghai, China. Experiments were also carried out at different temperatures in order to explore the buffering effects for phosphate. The results show that P sorption in sediments with low fine particle fractions was best described using exponential equations. Some P interactions between water and sediment may be caused by the precipitation of CaHPO4 from Ca2+ and HPO42- when the phosphate concentration in the liquid phase is high. Results from the buffering experiments suggest that the Zero Equilibrium Phosphate Concentrations (EPC0) vary from 0.014 mg l-1 to 0.061 mg l-1, which are consistent with measured phosphate concentrations in water samples collected at the same time as sediment sampling. Values of EPC0 and linear sorption coefficients (K) in sediments with high fine particle and organic matter contents are relatively high, which implies that they have high buffering capacity. Both EPC0 and K increase with increasing temperature, indicating a higher P buffering capacity at high temperatures.

  4. Moisture sorption curves of fruit and nut cereal bar prepared with sugar and sugar substitutes.

    PubMed

    Pallavi, Byrappa Vasu; Chetana, Ramakrishna; Ravi, Ramaswamy; Reddy, Sunkireddy Yella

    2015-03-01

    Low sugar, low fat, dry fruit and nut cereal bars without sugar were prepared using cereals, nuts, and sugar substitutes. The sorption characteristics of the bars prepared with sugar substitutes in comparison with that of sugar were studied by keeping the bars at water activity (aw) from 0.1 to 0.9. The sorption isotherms of low sugar bars were practically identical below aw of 0.5 but above aw of 0.5, a clear differentiation in the isotherms could be observed compared to that of sugar counterpart. A sharp increase in moisture content was observed in the bars prepared with alternative sweeteners, above aw 0.6, whereas a gradual increase in aw was observed in the case of bar prepared with sugar. The ERH (Equilibrium relative humidity) value for bar with sugar was 50 %, and for bars prepared with alternative sweeteners, it was about 60 %. Low sugar cereal bar prepared with sorbitol + maltitol (SM) syrup scored higher sensory quality compared to other product prepared with sorbitol + nutriose (SN) as the former retained softness and chewiness on storage. Thus, it was observed that bars with alternative sweeteners will be more stable as their ERH is closer to normal ambient conditions compared to that prepared with sugar. PMID:25745238

  5. Plutonium sorption and desorption behavior on bentonite.

    PubMed

    Begg, James D; Zavarin, Mavrik; Tumey, Scott J; Kersting, Annie B

    2015-03-01

    Understanding plutonium (Pu) sorption to, and desorption from, mineral phases is key to understanding its subsurface transport. In this work we study Pu(IV) sorption to industrial grade FEBEX bentonite over the concentration range 10(-7)-10(-16) M to determine if sorption at typical environmental concentrations (≤10(-12) M) is the same as sorption at Pu concentrations used in most laboratory experiments (10(-7)-10(-11) M). Pu(IV) sorption was broadly linear over the 10(-7)-10(-16) M concentration range during the 120 d experimental period; however, it took up to 100 d to reach sorption equilibrium. At concentrations ≥10(-8) M, sorption was likely affected by additional Pu(IV) precipitation/polymerization reactions. The extent of sorption was similar to that previously reported for Pu(IV) sorption to SWy-1 Na-montmorillonite over a narrower range of Pu concentrations (10(-11)-10(-7) M). Sorption experiments with FEBEX bentonite and Pu(V) were also performed across a concentration range of 10(-11)-10(-7) M and over a 10 month period which allowed us to estimate the slow apparent rates of Pu(V) reduction on a smectite-rich clay. Finally, a flow cell experiment with Pu(IV) loaded on FEBEX bentonite demonstrated continued desorption of Pu over a 12 day flow period. Comparison with a desorption experiment performed with SWy-1 montmorillonite showed a strong similarity and suggested the importance of montorillonite phases in controlling Pu sorption/desorption reactions on FEBEX bentonite. PMID:25574607

  6. Metal adsorption by agricultural biosorbents: Adsorption isotherm, kinetic and biosorbents chemical structures.

    PubMed

    Sadeek, Sadeek A; Negm, Nabel A; Hefni, Hassan H H; Wahab, Mostafa M Abdel

    2015-11-01

    Biosorption of Cu(II), Co(II) and Fe(III) ions from aqueous solutions by rice husk, palm leaf and water hyacinth was investigated as a function of initial pH, initial heavy metal ions concentration and treatment time. The adsorption process was examined by two adsorption isotherms: Langmuir and Freundlich isotherms. The experimental data of biosorption process were analyzed using pseudo-first order, pseudo-second order kinetic models. The equilibrium biosorption isotherms showed that the three studied biosorbents possess high affinity and sorption capacity for Cu(II), Co(II) and Fe(III) ions. Rice husk showed more efficiency than palm leaf and water hyacinth. Adsorption of Cu(II) and Co(II) was more efficient in alkaline medium (pH 9) than neutral medium due to the high solubility of metal ion complexes. The metal removal efficiency of each biosorbent was correlated to its chemical structure. DTA studies showed formation of metal complex between the biosorbents and the metal ions. The obtained results showed that the tested biosorbents are efficient and alternate low-cost biosorbent for removal of heavy metal ions from aqueous media. PMID:26282929

  7. Efficient sorption of Cu(2+) by composite chelating sorbents based on potato starch-graft-polyamidoxime embedded in chitosan beads.

    PubMed

    Dragan, Ecaterina Stela; Apopei Loghin, Diana Felicia; Cocarta, Ana Irina

    2014-10-01

    Ionic composites based on cross-linked chitosan (CS) as matrix and poly(amidoxime) grafted on potato starch (AOX) as entrapped chelating resin were prepared as beads, for the first time in this work, by two strategies: (1) thorough mixing of previously prepared AOX in the CS solution followed by the bead formation and (2) thorough mixing of the potato starch-g-poly(acrylonitrile) (PS-g-PAN) copolymer in the initial CS solution, followed by bead formation, the amidoximation of the nitrile groups taking place inside the beads. Ionotropic gelation in tripolyphosphate was used to obtain the composite beads, and in situ covalent cross-linking by epichlorohydrin was carried out to stabilize the beads in the acidic pH range. Fourier transform infrared spectroscopy and the swelling ratio values in the acidic pH range confirmed the influence of the synthesis strategy on the structure of the CS/AOX composites. Scanning electron microscopy was employed to reveal the morphology of the novel composites, both before and after their loading with Cu(2+). The binding capacity of Cu(2+) ions as a function of sorbent composition, synthesis strategy, pH, sorbent dose, contact time, initial concentration of Cu(2+), and temperature was examined in batch mode. The main difference between the composites prepared with the two strategies consisted of the higher sorption capacity and the much faster settlement of the equilibrium sorption for the composite prepared by the in situ amidoximation of PS-g-PAN. The Langmuir, Freundlich, Temkin, Dubinin-Radushkevich, and Sips isotherms were applied to fit the sorption equilibrium data. The maximum equilibrium sorption capacity, qm, evaluated by the Langmuir model at 25 °C was 133.15 mg Cu(2+)/g for the CS/AOX composite beads prepared with the first strategy and 238.14 mg Cu(2+)/g for the CS/AOX composite beads prepared with the second strategy, at the same AOX content. The pseudo-second order kinetic model well fitted the sorption kinetics data

  8. Fe2+ sorption onto nontronite (NAu-2)

    SciTech Connect

    Jaisi, Deb P.; Liu, Chongxuan; Dong, Hailiang; Blake, Ruth E.; Fein, Jeremy B.

    2008-11-15

    The sorption of ferrous iron to a clay mineral, nontronite (NAu-2, a ferruginous smectite), was investigated under strictly anoxic conditions as a function of pH (3-10), Fe2+ concentration (0.01-50 mM), equilibration time (1 to 35 days), and ionic strength (0.01 to 0.5 M NaClO4). The surface properties of NAu-2 were independently characterized to determine its fixed charge and amphoteric site properties for the interpretation of Fe2+ sorption. Fe2+ sorption to NAu-2 was strongly dependent on pH and ionic strength, reflecting the coupled effects of Fe2+ sorption through ion exchange and surface complexation reactions. Fe2+ sorption to NAu-2 increased with increasing pH from pH 2.5 to 4.5, reached the first plateau from pH 4.5 to 7.0, increased again with increasing pH from pH 7.0 to 8.5, and reached the maximum (the second plateau) above pH 8.5. The Fe2+ sorption below pH 7.0 increased with decreasing ionic strength. The differences of Fe2+ sorption at different ionic strength, however, diminished with increasing equilibration time. The Fe2+ sorption from pH 4.5 to 7.0 increased with increasing equilibration time up to 35 days and showed stronger kinetic behavior in higher ionic strength solutions. Increasing Fe2+ concentration nonlinearly decreased Fe2+ sorption, resulting from the mass action and site saturation. An equilibrium model that integrated ion exchange, surface complexation and aqueous speciation reactions reasonably well described the Fe2+ sorption data as a function of pH, ionic strength, and Fe2+ concentration measured at 24 hours of equilibration. Model calculations showed that species Fe(OH)+ was required to describe Fe2+ sorption above pH 8.0. Model calculation also implied that the ion exchange reactions was responsible for the kinetic behavior of Fe2+ sorption. Overall, this study demonstrated that Fe2+ sorption to NAu-2 was complexly affected by equilibrium and kinetic processes.

  9. Sorption-desorption of aminocyclopyrachlor in selected Brazilian soils

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Aminocyclopyrachlor sorption and desorption was investigated in 14 soils from Brazil, representing a range of pH, and organic carbon (OC) and clay contents. Sorption kinetics demonstrated that soil-solution equilibrium was attained in a 24-h period. Freundlich equation adequately described behavior ...

  10. Sorption-desorption of indaziflam in selected agricultural soils

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Sorption and desorption of indaziflam in 6 soils from Brazil and 3 soils from the USA, with different physical chemical properties, were investigated using the batch equilibration method. Sorption kinetics demonstrated that soil-solution equilibrium was attained in a 24-h period. The Freundlich equa...

  11. Sorption and Transport of Diphenhydramine in Natural Soils

    NASA Astrophysics Data System (ADS)

    Rutherford, C. J.; Vulava, V. M.

    2013-12-01

    Pharmaceutical and related chemicals have been detected in streams and ground water sources throughout the world, as a result of sewage overflows, runoff, or sewage treatment facilities unequipped to remove trace levels of pharmaceuticals. Diphenhydramine- an antihistamine that is used to treat allergy and common cold symptoms, induce sleep, suppress cough, and treat motion sickness- is prominent among them. Diphenhydramine has a complex, highly polar organic structure including two benzene rings and an amine functional group. It has a solubility of 3.06 g/L and a pKa of 8.98. Recent studies have shown that diphenhydramine in streams disrupts the ecology by affecting the algal and bacterial biofilms present on the streambed. In streams, photosynthesis has been found to decrease by up to 99% and plant respiration has been inhibited. Diphenhydramine has also altered the types and numbers of bacteria found in streams. Its presence in contaminated stream bodies can result in contact with soils and sediment in the stream floodplain. The objective of this study is to measure sorption and transport behavior of diphenhydramine in natural soils and determine reactivity of soil components. These studies were conducted in the laboratory using natural soil collected from the Francis Marion National Forrest. Soil samples from A and B horizons of several soil series were characterized for physical and chemical properties: organic matter content ranged between 0.6-7.6%, clay content between 6-20%, and soil pH between 3.7-4.9. The B-horizon soils contain a higher amount of clay than the organic-rich A-horizon soils. Equilibrium sorption isotherms and reaction kinetic rates were measured using batch reactor experiments and chromatographic column experiments were conducted to measure transport behavior. Kinetic experiments showed that diphenhydramine sorbed more strongly to the clay-rich soils and reached equilibrium after seven days, compared to ten days in organic-rich soils. The

  12. Sorption of paracetamol onto biomaterials.

    PubMed

    Ferchichi, Maroua; Dhaouadi, Hatem

    2016-01-01

    Pharmaceutical residues released into the environment are posing more and more public health problems. It is worthwhile to study the retention of pharmaceuticals residues by adsorption on solid supports. Batch sorption experiments are intended to identify the adsorption isotherms of the pharmaceutically active ingredient on the biomaterials. The results obtained in this study have shown that the retention possibilities of these compounds by bio-adsorbents (clay and sand) are not significant. The negligible sorption for these media is explained by the low hydrophobicity of paracetamol (Log K(ow) = 0.46). The retention of paracetamol on the dehydrated sewage sludge and on Posidonia oceanica showed a relatively significant adsorption with a maximal quantity of 0.956 mg g(-1) and 1.638 mg g(-1) for the dehydrate sludge and P. oceanica, respectively. On the other hand, the study of paracetamol retention on the powdered activated carbon showed a high adsorption capacity of about 515.27 mg g(-1). Isotherm data show a good fit with Langmuir's model. An infrared analysis is carried out. It shows identical bands before and after adsorption, with some modifications. PMID:27387007

  13. Multifractal characteristics of Nitrogen adsorption isotherms from tropical soils

    NASA Astrophysics Data System (ADS)

    Vidal Vázquez, Eva; Paz Ferreiro, Jorge

    2010-05-01

    One of the primary methods used to characterize a wide range of porous materials, including soils, are gas adsorption isotherms. An adsorption isotherm is a function relating the amount of adsorbed gas or vapour to the respective equilibrium pressure, during pressure increase at constant temperature. Adsorption data allow easily estimates of specific surface area and also can provide a characterization of pore surface heterogeneity. Most of the properties and the reactivity of soil colloids are influenced by their specific surface area and by parameters describing the surface heterogeneity. For a restricted scale range, linearity between applied pressure and volume of adsorbate holds, which is the basis for current estimations of specific surface area. However, adsorption isotherms contain also non-linear segments of pressure versus volume so that evidence of multifractal scale has been demonstrated. The aim of this study was to analyze the multifractal behaviour of nitrogen adsorption isotherms from a set of tropical soils. Samples were collected form 54 horizons belonging to 19 soil profiles in the state of Minas Gerais, Brazil. The most frequent soil type was Oxisol, according to the Soil Survey Staff, equivalent to Latossolo in the Brazilian soil classification system. Nitrogen adsorption isotherms at standard 77 K were measured using a Thermo Finnigan Sorptomatic 1990 gas sorption analyzer (Thermo Scientific, Waltham, MA). From the raw data a distributions of mass along a support was obtained to perform multifractal analysis. The probability distribution was constructed by dividing the values of the measure in a given segment by the sum of the measure in the whole scale range. The box-counting method was employed to perform multifractal analysis. All the analyzed N2 adsorption isotherms behave like a multifractal system. The singularity spectra, f(α), showed asymmetric concave down parabolic shapes, with a greater tendency toward the left side, where moments

  14. Evaluating phenanthrene sorption on various wood chars

    USGS Publications Warehouse

    James, G.; Sabatini, D.A.; Chiou, C.T.; Rutherford, D.; Scott, A.C.; Karapanagioti, H.K.

    2005-01-01

    A certain amount of wood char or soot in a soil or sediment sample may cause the sorption of organic compounds to deviate significantly from the linear partitioning commonly observed with soil organic matter (SOM). Laboratory produced and field wood chars have been obtained and analyzed for their sorption isotherms of a model solute (phenanthrene) from water solution. The uptake capacities and nonlinear sorption effects with the laboratory wood chars are similar to those with the field wood chars. For phenanthrene aqueous concentrations of 1 ??gl-1, the organic carbon-normalized sorption coefficients (log Koc) ranging from 5.0 to 6.4 for field chars and 5.4-7.3 for laboratory wood chars, which is consistent with literature values (5.6-7.1). Data with artificial chars suggest that the variation in sorption potential can be attributed to heating temperature and starting material, and both the quantity and heterogeneity of surface-area impacts the sorption capacity. These results thus help to corroborate and explain the range of log Koc values reported in previous research for aquifer materials containing wood chars. ?? 2004 Elsevier Ltd. All rights reserved.

  15. Binary metal sorption by pine bark: Study of equilibria and mechanisms

    SciTech Connect

    Al-Asheh, S.; Duvnjak, Z.

    1998-06-01

    Pine bark was able to sorb cadmium, copper, and nickel ions from aqueous solutions. Binary equilibrium data from the combination of these metals were collected in this work using the sorbent. These data were modeled using three types of binary component equilibrium isotherms, all of which resulted in good fitting of the experimental data, with the Langmuir-Freundlich model resulting in their best representation. In general, the capacity of bark for each metal in the binary system was lower than in the single metal systems. The study also examined the mechanisms of metal biosorption by bark. Scanning electron microscopy (SEM) and energy-dispersive c-ray (EDX) microanalyses revealed that metal ions were sorbed mainly at the cell wall of the bark and only a small amount of ions diffused into the cytoplasm. Both the EDX analysis and the atomic absorption spectrophotometry (AAS) measurements showed that ion exchange was an important mechanism in this sorption process. Electron spin resonance (ESR) tests demonstrated that free radicals from the sorbent also have a significant role in the sorption processes.

  16. Ferrous iron sorption by hydrous metal oxides.

    PubMed

    Nano, Genevieve Villaseñor; Strathmann, Timothy J

    2006-05-15

    Ferrous iron is critical to a number of biogeochemical processes that occur in heterogeneous aquatic environments, including the abiotic reductive transformation of subsurface contaminants. The sorption of Fe(II) to ubiquitous soil minerals, particularly iron-free mineral phases, is not well understood. Colloidal TiO2, gamma-AlOOH, and gamma-Al2O2 were used as model hydrous oxides to investigate Fe(II) sorption to iron-free mineral surfaces. Rapid Fe(II) sorption during the first few hours is followed by a much slower uptake process that continues for extended periods (at least 30 days). For equivalent solution conditions, the extent of Fe(II) sorption decreases in the order TiO2 >gamma-Al2O3 >gamma-AlOOH. Short-term equilibrium sorption data measured over a wide range of conditions (pH, ionic strength, Fe(II)-to-sorbent ratio) are well described by the diffuse double layer model. Fe(II) sorption to TiO2 is best described by a single-site model that considers formation of two surface complexes, SOFe+ and SOFeOH0. For gamma-AlOOH and gamma-Al2O3, sorption data are best described by a two-site model that considers formation of SOFe+ complexes at weak- and strong-binding surface sites. Accurate description of sorption data for higher Fe(II) concentrations at alkaline pH conditions requires the inclusion of a Fe(II) surface precipitation reaction in the model formulation. The presence of common groundwater constituents (calcium, sulfate, bicarbonate, or fulvic acid) had no significant effect on Fe(II) sorption. These results demonstrate that iron-free soil minerals can exert a significant influence on Fe(II) sorption and speciation in heterogeneous aquatic systems. PMID:16337955

  17. Assessing the effect of humic acid redox state on organic pollutant sorption by combined electrochemical reduction and sorption experiments.

    PubMed

    Aeschbacher, Michael; Brunner, Sibyl H; Schwarzenbach, René P; Sander, Michael

    2012-04-01

    Natural Organic Matter (NOM) is a major sorbent for organic pollutants in soils and sediments. While sorption under oxic conditions has been well investigated, possible changes in the sorption capacity of a given NOM induced by reduction have not yet been studied. Reduction of quinones to hydroquinones, the major redox active moieties in NOM, increases the number of H-donor moieties and thus may affect sorption. This work compares the sorption of four nonionic organic pollutants of different polarities (naphthalene, acetophenone, quinoline, and 2-naphthol), and of the organocation paraquat to unreduced and electrochemically reduced Leonardite Humic Acid (LHA). The redox states of reduced and unreduced LHA in all sorption experiments were stable, as demonstrated by a spectrophotometric 2,6-dichlorophenol indophenol reduction assay. The sorption isotherms of the nonionic pollutants were highly linear, while paraquat sorption was strongly concentration dependent. LHA reduction did not result in significant changes in the sorption of all tested compounds, not even of the cationic paraquat at pH 7, 9, and 11. This work provides the first evidence that changes in NOM redox state do not largely affect organic pollutant sorption, suggesting that current sorption models are applicable both to unreduced and to reduced soil and sediment NOM. PMID:22372874

  18. Sorption of a nonionic surfactant Tween 80 by minerals and soils.

    PubMed

    Kang, Soyoung; Jeong, Hoon Young

    2015-03-01

    Batch experiments were conducted to evaluate Tween 80 sorption by oxides, aluminosilicates, and soils. For oxides, the sorption by silica and alumina follow linear isotherms, and that by hematite follows a Langmuir isotherm. Considering isotherm type and surface coverage, Tween 80 may partition into the silica/alumina-water interface, whereas it may bind to hematite surface sites. Among aluminosilicates, montmorillonite shows the greatest sorption due to the absorption of Tween 80 into interlayers. For other aluminosilicates, it sorbs to surfaces, with the sorption increasing as plagioclasesorption. The greater sorption by untreated soils than H2O2-treated soils indicates that soil organic matter is a vital sorbent. The sorption hysteresis, contributed to by clay minerals and soil organic matter, is characterized by the greater sorption during the desorption than the sorption stages. This suggests the potential difficulty in removing surfactants from soils. Also, sorption of surfactants can adversely affect surfactant-enhanced remediation by decreasing the aquifer permeability and the availability of surfactants for micellar solubilization. PMID:25463228

  19. Modeling Fission Product Sorption in Graphite Structures

    SciTech Connect

    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 distributions 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

  20. Sorption of cadmium and copper ions on natural and synthetic hydroxylapatite particles

    SciTech Connect

    Fernane, F.; Mecherri, M.O.; Sharrock, P. Hadioui, M.; Lounici, H.; Fedoroff, M.

    2008-05-15

    The sorption of divalent cadmium and copper ions from aqueous solutions on natural and synthetic hydroxyapatite was investigated by the batch method and under dynamic conditions in columns at 22 deg. C and pH 5. The effect of cadmium and copper concentration on sorption was studied. Both types of apatites are efficient, despite their different composition and morphology. The sorption mechanism involves an ion exchange for Cd(II), while Cu(II) leads to precipitation of a newly formed solid. Thus, the sorption efficiency depends on the experimental conditions and the specific physicochemical properties of the apatites used. The sorption isotherms were fitted to the Langmuir equation.

  1. The competitive effects of Ca(II) on Eu(III) sorption to goethite

    SciTech Connect

    Gall, E.J.; Snyder, L.I.; Bryce, A.L.

    1995-12-01

    Predictive modeling of the transport of trivalent rare earth and actinide elements in the geosphere is difficult as the mechanism of lanthanide sorption in natural systems is not well understood. Experimental data demonstrating rare earth sorption to soil components under environmentally realistic conditions is lacking. In this presentation, we report on the competitive effects of the presence of a major cation, Ca(II), on the sorption of Eu(III) to goethite. pH sorption edges and isotherms will be presented for both of these elements. Variables considered are ionic strength as well as Ca(II) and Eu(III) concentrations. Finally, mechanisms of lanthanide sorption will be discussed.

  2. Fate and transport with material response characterization of green sorption media for copper removal via desorption process.

    PubMed

    Chang, Ni-Bin; Houmann, Cameron; Lin, Kuen-Song; Wanielista, Martin

    2016-07-01

    Multiple adsorption and desorption cycles are required to achieve the reliable operation of copper removal and recovery. A green sorption media mixture composed of recycled tire chunk, expanded clay aggregate, and coconut coir was evaluated in this study for its desorptive characteristics as a companion study of the corresponding adsorption process in an earlier publication. We conducted a screening of potential desorbing agents, batch desorption equilibrium and kinetic studies, and batch tests through 3 adsorption/desorption cycles. The desorbing agent screening revealed that hydrochloric acid has good potential for copper desorption. Equilibrium data fit the Freundlich isotherm, whereas kinetic data had high correlation with the Lagergren pseudo second-order model and revealed a rapid desorption reaction. Batch equilibrium data over 3 adsorption/desorption cycles showed that the coconut coir and media mixture were the most resilient, demonstrating they could be used through 3 or more adsorption/desorption cycles. FE-SEM imaging, XRD, and EDS analyses supported the batch adsorption and desorption results showing significant surface sorption of CuO species in the media mixture and coconut coir, followed by partial desorption using 0.1 M HCl as a desorbing agent. PMID:27081796

  3. Sorption of copper(II) ion from aqueous solution by Tectona grandis l.f. (teak leaves powder).

    PubMed

    King, P; Srinivas, P; Kumar, Y Prasanna; Prasad, V S R K

    2006-08-25

    Studies on a batch sorption system using Tectona grandis l.f. as adsorbent was investigated to remove copper(II) from aqueous solutions. The adsorption experiments were performed under various conditions such as different initial concentrations, pH, adsorbent dosage and adsorbent particle size. The data showed that 0.1 g of Tectona grandis l.f. was found to remove 71.66% of 20 mg/L copper(II) from 30 mL aqueous solution in 180 min. The experimental equilibrium data were adjusted by the adsorption isotherms from Langmuir and Freundlich models and their equilibrium parameters were determined. The best-adjusted model to the experimental equilibrium data for Tectona grandis l.f. was the Langmuir model. Using the Langmuir model equation, the monolayer sorption capacity of Tectona grandis l.f. was evaluated and found to be 95.40 mg/g. The optimum pH value was found to be 5.5. The pseudo-first-order and pseudo-second-order kinetic models were used to describe the kinetic data. The dynamic data fitted the pseudo-second-order kinetic model. PMID:16443324

  4. Sorption of 3,3',4,4'-tetrachlorobiphenyl by microplastics: A case study of polypropylene.

    PubMed

    Zhan, Zhiwei; Wang, Jundong; Peng, Jinping; Xie, Qilai; Huang, Ying; Gao, Yifan

    2016-09-15

    Though plastics show good chemical inertness, they could sorb polychlorinated biphenyls (PCBs) and other toxic pollutants from the surrounding environment. Thus, ingestion of microplastics by marine organisms potentially enhances the transport and bioavailability of toxic chemicals. However, there is lack of studies on the sorption capacity, mechanism and factors affecting the sorption behavior. Here, sorption of PCBs by microplastics in the simulated seawater was studied using the batch oscillation equilibration technique, in which polypropylene (PP) and 3,3',4,4'-tetrachlorobiphenyl (PCB77) acted as model plastic and PCB, respectively. Factors including particle size, temperature and solution environment were investigated. Results showed that, equilibrium sorption time is about 8h and sorption capacity increase with decreasing particle size and temperature. Different sorption capacity in three solution environments was observed. Equilibrium data in three solution environments fitted very well to the Langmuir sorption model, indicating chemical sorption is the predominant mechanism. PMID:27230985

  5. Effect of natural organic materials on cadmium and neptunium sorption

    SciTech Connect

    Kung, K.S.; Triay, I.R.

    1994-10-01

    In a batch sorption study of the effect of naturally occurring organic materials on the sorption of cadmium and neptunium on oxides and tuff surfaces, the model sorbents were synthetic goethite, boehmite, amorphous silicon oxides, and a crushed tuff material from Yucca Mountain, Nevada. An amino acid, 3-(3,4-dihydroxypheny)-DL-alanine (DOPA), and an aquatic-originated fulvic material, Nordic aquatic fulvic acid (NAFA), were used as model organic chemicals. Sorption isotherm results showed that DOPA sorption followed the order aluminum oxide > iron oxide > silicon oxide and that the amount of DOAP sorption for a given sorbent increased as the solution pH was raised. The sorption of cadmium and neptunium on the iron oxide was about ten times higher than that on the aluminum oxide. The sorption of cadmium and neptunium on natural tuff material was much lower than that on aluminum and iron oxides. The sorption of cadmium on iron and aluminum oxides was found to be influenced by the presence of DOPA, and increasing the amount of DOPA coating resulted in higher cadmium sorption on aluminum oxide. However, for iron oxide, cadmium sorption decreased with increasing DOPA concentration. The presence of the model organic materials DOPA and NAFA did not affect the sorption of neptunium on tuff material or on the iron and aluminum oxides. Spectroscopic results indicate that cadmium complexes strongly with DOPA. Therefore, the effect of the organic material, DOPA, on the cadmium sorption is readily observed. However, neptunium is possibly complexed weakly with organic material. Thus, DOPA and NAFA have little effect on neptunium sorption on all sorbents selected for study.

  6. Isothermal Titration Calorimetry in the Student Laboratory

    ERIC Educational Resources Information Center

    Wadso, Lars; Li, Yujing; Li, Xi

    2011-01-01

    Isothermal titration calorimetry (ITC) is the measurement of the heat produced by the stepwise addition of one substance to another. It is a common experimental technique, for example, in pharmaceutical science, to measure equilibrium constants and reaction enthalpies. We describe a stirring device and an injection pump that can be used with a…

  7. Equilibrium and kinetic mechanisms of woody biochar on aqueous glyphosate removal.

    PubMed

    Mayakaduwa, S S; Kumarathilaka, Prasanna; Herath, Indika; Ahmad, Mahtab; Al-Wabel, Mohammed; Ok, Yong Sik; Usman, Adel; Abduljabbar, Adel; Vithanage, Meththika

    2016-02-01

    We investigated the removal of aqueous glyphosate using woody (dendro) biochar obtained as a waste by product from bioenergy industry. Equilibrium isotherms and kinetics data were obtained by adsorption experiments. Glyphosate adsorption was strongly pH dependent occurring maximum in the pH range of 5-6. The protonated amino moiety of the glyphosate molecule at this pH may interact with π electron rich biochar surface via π-π electron donor-acceptor interactions. Isotherm data were best fitted to the Freundlich and Temkin models indicating multilayer sorption of glyphosate. The maximum adsorption capacity of dendro biochar for glyphosate was determined by the isotherm modeling to be as 44 mg/g. Adsorption seemed to be quite fast, reaching the equilibrium <1 h. Pseudo-second order model was found to be the most effective in describing kinetics whereas the rate limiting step possibly be chemical adsorption involving valence forces through sharing or exchanging electrons between the adsorbent and sorbate. The FTIR spectral analysis indicated the involvement of functional groups such as phenolic, amine, carboxylic and phosphate in adsorption. Hence, a heterogeneous chemisorption process between adsorbate molecules and functional groups on biochar surface can be suggested as the mechanisms involved in glyphosate removal. PMID:26340852

  8. Sorption of Pseudomonas putida onto differently structured kaolinite minerals

    NASA Astrophysics Data System (ADS)

    Vasiliadou, I. A.; Papoulis, D.; Chrysikopoulos, C.; Panagiotaras, D.; Karakosta, E.; Fardis, M.; Papavassiliou, G.

    2010-12-01

    The presence of bio-colloids (e.g. bacteria and viruses) in the subsurface could be attributed to the release of particles from septic tanks, broken sewer lines or from artificial recharge with treated municipal wastewater. Bio-colloid transport in the subsurface is significantly affected by sorption onto the solid matrix. Bio-colloid attachment onto mobile or suspended in the aqueous phase soil particles (e.g. clay or other minerals) also may influence their fate and transport in the subsurface. The present study focuses on the investigation of Pseudomonas (Ps.) putida sorption onto well (KGa-1) and poorly (KGa-2) crystallized kaolinite minerals. Batch experiments were carried out to determine the sorption isotherms of Ps. putida onto both types of kaolinite particles. The sorption process of Ps. putida onto KGa-1 and KGa-2 is adequately described by a Langmuir isotherm. Attenuated Total Reflection Fourier Transform Infrared Spectroscopy as well as Nuclear Magnetic Resonance were employed to study the sorption mechanisms of Ps. putida. Experimental results indicated that KGa-2 presented higher affinity and sorption capacity than KGa-1. It was shown that electrostatic interactions and structural disorders can influence the sorption capacity of clay particles.

  9. Evaluation of pyrene sorption-desorption on tropical soils.

    PubMed

    Olu-Owolabi, Bamidele I; Diagboya, Paul N; Adebowale, Kayode O

    2014-05-01

    Sorption-desorption processes control soil-pollutant interactions. These processes determine the extent of pyrene transport in soils. Understanding sorption characteristics of pyrene is necessary in ascertaining its fate in soil. Laboratory batch experiments were conducted to study the sorptions-desorption of pyrene on eight soils from varying tropical agro-ecological zones (AEZs). The results showed that pyrene sorptions equilibria were attained within 720 min. Solution pH had a reciprocal effect on pyrene sorptions. Sorption was exothermic and increased with pyrene concentration in solution. The quantities of pyrene sorbed by each soil as well as the hysteresis were proportional to the percentage organic matter, and to some degree, the clay mineralogy. Sorption isotherms showed distributed reactivity involving several linear and non-linear isotherms. The present investigation showed that pyrene is likely to be more available to biota and reach the aquifer faster in low organic matter soils than those with relatively higher organic matter and more so in warmer climes. PMID:24584002

  10. SORPTION OF 2,3,7,8-TETRACHLORODIBENZO-P-DIOXIN FROM WATER BY SURFACE SOILS

    EPA Science Inventory

    The sorption of l4C-labeled 2,3,7,8-tetrachlorodibenzo- p-dioxin (TCDD) from water by two uncontaminated surface soils from the Times Beach, MO, area was evalu- ated by using batch shake testing. Sorption isotherm plots for the soil with the lower fraction organic carbon (f,) wer...

  11. Inhibition of Phosphorus Sorption to Goethite, Gibbsite, and Kaolin by Fresh and Decomposed Organic Matter

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The direct effects of dissolved organic matter (DOM) on the sorption of orthophosphate onto gibbsite, goethite, and kaolin were examined using an one-point phosphorus sorption index and the linear Tempkin isotherm model. Dissolved organic matter extracted from fresh and decomposed agricultural resi...

  12. SORPTION OF ARSENATE AND ARSENITE ON A RUTHENIUM COMPOUND: A MACROSCOPIC AND MICROSCOPIC STUDY

    EPA Science Inventory

    Sorption of arsenate and arsenite was examined on a ruthenium compound using macroscopic and microscopic techniques. Batch sorption experiments at pH 4,5,6, 7 and 8 were employed to construct constant solid solution ratio isotherms (CSI). After equilibration at the appropriate pH...

  13. Sorption of selenium(IV) and selenium(VI) onto magnetite

    NASA Astrophysics Data System (ADS)

    Martínez, M.; Giménez, J.; de Pablo, J.; Rovira, M.; Duro, L.

    2006-03-01

    In this work, we have studied the sorption of selenium ( 79Se is one of the main radionuclides in a spent nuclear fuel repository) on magnetite (Fe 3O 4), a mineral present in the near-field of a nuclear waste repository that might represent an important retardation factor for the mobility of many radionuclides. The sorption of both Se(IV) and Se(VI) onto magnetite has been fitted by a non-competitive Langmuir isotherm with Γmax = (3.13 ± 0.07) × 10 -6 mol m -2 and KL = (1.19 ± 0.07) × 10 6 dm 3 mol -1 for Se(IV) and Γmax = (3.5 ± 0.2) × 10 -6 mol m -2 and KL = (3.0 ± 0.1) × 10 5 dm 3 mol -1 for Se(VI). The variation of the sorption of selenium with pH has been modeled using the Triple Layer Surface Complexation Model and the equilibrium constants between selenium and magnetite have been obtained using the FITEQL program. For the case of Se(IV), the best fitting has been obtained using two inner-sphere complexes, lbond2 FeOHSeO 32- and lbond2 FeHSeO 3, while for Se(VI), the best fitting has been obtained considering only an outer-sphere complex, lbond2 FeOH 2+sbnd SeO 42-. The surface complexation reactions derived in this work are in agreement with those stated by other authors for sorption of Se(IV) and Se(VI) on hydrous iron oxides.

  14. Reliability analysis of nutrient removal from stormwater runoff with green sorption media under varying influent conditions.

    PubMed

    Jones, Jamie; Chang, Ni-Bin; Wanielista, Martin P

    2015-01-01

    To support nutrient removal, various stormwater treatment technologies have been developed via the use of green materials, such as sawdust, tire crumbs, sand, clay, sulfur, and limestone, as typical constituents of filter media mixes. These materials aid in the physiochemical sorption and precipitation of orthophosphates as well as in the biological transformation of ammonia, nitrates and nitrites. However, these processes are dependent upon influent conditions such as hydraulic residence time, influent orthophosphate concentrations, and other chemical species present in the inflow. This study aims to compare the physiochemical removal of orthophosphate by isotherm and column tests under differing influent conditions to realize the reliability of orthophosphate removal process with the aid of green sorption media. The green sorption media of interest in this study is composed of a 5:2:2:1 (by volume) mixture of cement sand, tire crumb, fine expanded clay, and limestone. Scenarios of manipulating the hydraulic residence time of the water from 18 min and 60 min, the influent dissolved phosphorus concentrations of 1.0 mg·L(-1) and 0.5 mg·L(-1), and influent water types of distilled and pond water, were all investigated in the column tests. Experimental data were compared with the outputs from the Thomas Model based on orthophosphate removal to shed light on the equilibrium condition versus kinetic situation. With ANOVA tests, significant differences were confirmed between the experimental data sets of the breakthrough curves in the column tests. SEM imaging analysis helps to deepen the understanding of pore structures and pore networks of meta-materials being used in the green sorption media. Life expectancy curves derived from the output of Thomas Model may be applicable for future system design of engineering processes. PMID:25278294

  15. Lanthanide sorption on smectitic clays in presence of cement leachates

    NASA Astrophysics Data System (ADS)

    Galunin, Evgeny; Alba, María D.; Santos, Maria J.; Abrão, Taufik; Vidal, Miquel

    2010-02-01

    Due to their potential retention capacity, clay minerals have been proposed for use in the engineered barriers for the storage of high-level radioactive actinides in deep geological waste repositories. However, there is still a lack of data on the sorption of actinides in clays in conditions simulating those of the repositories. The present article examines the sorption of two lanthanides (actinide analogues) in a set of smectitic clays (FEBEX bentonite, MX80 bentonite, hectorite, saponite, Otay montmorillonite, and Texas montmorillonite). Distribution coefficients ( Kd) were determined in two media: water and 0.02 mol L -1 Ca, the latter representing the cement leachates that may modify the chemical composition of the water in contact with the clay. The Kd values of the lanthanides used in the experiments (La and Lu) varied greatly (25-50 000 L kg -1) depending on the ionic medium (higher values in water than in the Ca medium), the initial lanthanide concentration (up to three orders of magnitude decrease inversely with lanthanide concentration), and the examined clay (up to one order of magnitude for the same lanthanide and sorption medium). Freundlich and Langmuir isotherms were used to fit sorption data to allow comparison of the sorption parameters among smectites. The model based on the two-site Langmuir isotherms provided the best fit of the sorption data, confirming the existence of sorption sites with different binding energies. The sites with higher sorption affinity were about 6% of the total sorption capacity in the water medium, and up to 17% in the Ca medium, although in this latter site sorption selectivity was lower. The wide range of Kd values obtained regarding the factors examined indicated that the retention properties of the clays should also be considered when selecting a suitable clay for engineered barriers.

  16. 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

    2013-07-01

    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. PMID:23711282

  17. A breakthrough biosorbent in removing heavy metals: Equilibrium, kinetic, thermodynamic and mechanism analyses in a lab-scale study.

    PubMed

    Abdolali, Atefeh; Ngo, Huu Hao; Guo, Wenshan; Lu, Shaoyong; Chen, Shiao-Shing; Nguyen, Nguyen Cong; Zhang, Xinbo; Wang, Jie; Wu, Yun

    2016-01-15

    A breakthrough biosorbent namely multi-metal binding biosorbent (MMBB) made from a combination of tea wastes, maple leaves and mandarin peels, was prepared to evaluate their biosorptive potential for removal of Cd(II), Cu(II), Pb(II) and Zn(II) from multi-metal aqueous solutions. FTIR and SEM were conducted, before and after biosorption, to explore the intensity and position of the available functional groups and changes in adsorbent surface morphology. Carboxylic, hydroxyl and amine groups were found to be the principal functional groups for the sorption of metals. MMBB exhibited best performance at pH 5.5 with maximum sorption capacities of 31.73, 41.06, 76.25 and 26.63 mg/g for Cd(II), Cu(II), Pb(II) and Zn(II), respectively. Pseudo-first and pseudo-second-order models represented the kinetic experimental data in different initial metal concentrations very well. Among two-parameter adsorption isotherm models, the Langmuir equation gave a better fit of the equilibrium data. For Cu(II) and Zn(II), the Khan isotherm describes better biosorption conditions while for Cd(II) and Pb(II), the Sips model was found to provide the best correlation of the biosorption equilibrium data. The calculated thermodynamic parameters indicated feasible, spontaneous and exothermic biosorption process. Overall, this novel MMBB can effectively be utilized as an adsorbent to remove heavy metal ions from aqueous solutions. PMID:26544889

  18. 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

  19. Pharmaceuticals' sorptions relative to properties of thirteen different soils.

    PubMed

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

    2015-04-01

    Transport of human and veterinary pharmaceuticals in soils and consequent ground-water contamination are influenced by many factors, including compound sorption on soil particles. Here we evaluate the sorption isotherms for 7 pharmaceuticals on 13 soils, described by Freundlich equations, and assess the impact of soil properties on various pharmaceuticals' sorption on soils. Sorption of ionizable pharmaceuticals was, in many cases, 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. The sorption coefficients for the remaining pharmaceuticals (trimethoprim, metoprolol, atenolol, and carbamazepine) were also positively correlated with the base cation saturation and cation exchange capacity. Positive correlations between sorption coefficients and clay content were found for clindamycin, clarithromycin, atenolol, and metoprolol. Positive correlations between sorption coefficients and organic carbon content were obtained for trimethoprim and carbamazepine. Pedotransfer rules for predicting sorption coefficients of various pharmaceuticals included hydrolytic acidity (sulfamethoxazole), organic carbon content (trimethoprimand carbamazepine), base cation saturation (atenolol and metoprolol), exchangeable acidity and clay content (clindamycin), and soil active pH and clay content (clarithromycin). Pedotransfer rules, predicting the Freundlich sorption coefficients, could be applied for prediction of pharmaceutical mobility in soils with similar soil properties. Predicted sorption coefficients together with pharmaceutical half-lives and other imputes (e.g., soil-hydraulic, geological, hydro-geological, climatic) may be used for

  20. [Desorption isotherms in amaranth flours].

    PubMed

    Alvarado, J D; Toaza, E; Coloma, G

    1990-09-01

    In milled seeds amaranth (Amaranthus hybridus) samples locally known as "ataco or sangoracha" and harvested in two consecutive years, the vapor pressure at four temperatures (15 degrees, 20 degrees, 25 degrees, 30 degrees C) was determined in samples obtained for drying in oven at different times, within a range between 60 g water/100 g dry matter for fresh seeds to 10 g water/100 g dry matter or below, as measured in a Brabender equipment. Vapor pressure of distilled water was also determined for water activity calculation. The isotherms for each temperature are presented. Application of the G.A.B. model (Guggenheim-Anderson-De Boer) allowed to establish the water content of greater stability within a range of 9.9 to 7.6 g/100 g. The third degree polynomial equations presented, adjust satisfactorily with the experimental data, and can be used to calculate equilibrium moisture content from 0.15 to 0.95 water activity values. Water desorption isotherms of foods are important to determine the equilibrium relationship between the moisture content of foods and the water activity, information which permits to establish likely physical, chemical or biological changes. It is considered that the results obtained are useful in drying, milling or storing amaranth flour. PMID:2134142

  1. Adsorption of methyl orange from aqueous solution by aminated pumpkin seed powder: Kinetics, isotherms, and thermodynamic studies.

    PubMed

    Subbaiah, Munagapati Venkata; Kim, Dong-Su

    2016-06-01

    Present research discussed the utilization of aminated pumpkin seed powder (APSP) as an adsorbent for methyl orange (MO) removal from aqueous solution. Batch sorption experiments were carried to evaluate the influence of pH, initial dye concentration, contact time, and temperature. The APSP was characterized by using Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM). The experimental equilibrium adsorption data were fitted using two two-parameter models (Langmuir and Freundlich) and two three-parameter models (Sips and Toth). Langmuir and Sips isotherms provided the best model for MO adsorption data. The maximum monolayer sorption capacity was found to be 200.3mg/g based on the Langmuir isotherm model. The pseudo-first-order and pseudo-second-order model equations were used to analyze the kinetic data of the adsorption process and the data was fitted well with the pseudo-second-order kinetic model (R(2)>0.97). The calculated thermodynamic parameters such as ΔG(0), ΔH(0) and ΔS(0) from experimental data showed that the sorption of MO onto APSP was feasible, spontaneous and endothermic in the temperature range 298-318 K. The FTIR results revealed that amine and carboxyl functional groups present on the surface of APSP. The SEM results show that APSP has an irregular and porous surface which is adequate morphology for dye adsorption. Desorption experiments were carried to explore the feasibility of adsorbent regeneration and the adsorbed MO from APSP was desorbed using 0.1M NaOH with an efficiency of 93.5%. Findings of the present study indicated that APSP can be successfully used for removal of MO from aqueous solution. PMID:26921544

  2. 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. PMID:25595537

  3. Sorption kinetics and its effects on retention and leaching.

    PubMed

    de Wilde, Tineke; Mertens, Jan; Spanoghe, Pieter; Ryckeboer, Jaak; Jaeken, Peter; Springael, Dirk

    2008-06-01

    Sorption of pesticides to substrates used in biopurification systems is important as it controls the system's efficiency. Ideally, pesticide sorption should occur fast so that leaching of the pesticide in the biopurification system is minimized. Although modeling of pesticide transport commonly assumes equilibrium, this may not always be true in practice. Sorption kinetics have to be taken into account. This study investigated the batch sorption kinetics of linuron, isoproturon, metalaxyl, isoxaben and lenacil on substrates commonly used in a biopurification system, i.e. cow manure, straw, willow chopping, sandy loam soil, coconut chips, garden waste compost and peat mix. The first-order sorption kinetics model was fitted to the observed pesticide concentrations versus time resulting in an estimated kinetic rate constant alpha. Sorption appeared to be fast for the pesticides linuron and isoxaben, pesticides which were classified as immobile, while less mobile pesticides displayed an overall slower sorption. However, the substrate does not seem to be the main parameter influencing the sorption kinetics. Coconut chips, which is a substrate with a high organic matter content showed slow sorption for most of the pesticides. The effect of different estimated alpha values on the breakthrough of pesticides through a biopurification system was evaluated using the HYDRUS 1D model. Significant differences in leaching behavior were observed as a result of the obtained differences in sorption kinetics. PMID:18413279

  4. Engineering a lignocellulosic biosorbent--coir pith for removal of cesium from aqueous solutions: equilibrium and kinetic studies.

    PubMed

    Parab, Harshala; Sudersanan, M

    2010-02-01

    A novel method of engineering lignocellulosic biosorbent- coir pith (CP) by incorporation of nickel hexacyanoferrate (NiHCF), also referred to as Prussian blue analogue (PBA) inside its porous matrix is reported. Structural characterization confirmed the successful synthesis of NiHCF in the coir pith matrix. Sorption capacity of coir pith (CP) before and after loading of NiHCF was investigated for cesium (Cs) in batch equilibrium studies. Kinetic studies showed that the sorption process was rapid and saturation was attained within 30 min. The applicability of non linear Langmuir, Freundlich and Redlich Peterson isotherms was examined for the experimental data. The present studies revealed that there was nearly 100% increase in the sorption capacity of CP after its surface modification with NiHCF. Owing to its low cost, fast sorption kinetics and high uptake capacity, coir pith loaded with NiHCF (CP-NiHCF) seems to be one of the most promising biosorbents for recovery of cesium from liquid nuclear wastes. PMID:19819515

  5. Seizure modeling of Pb(II) and Cd(II) from aqueous solution by chemically modified sugarcane bagasse fly ash: isotherms, kinetics, and column study.

    PubMed

    Shah, Bhavna; Mistry, Chirag; Shah, Ajay

    2013-04-01

    Heavy metal pollution is a common environmental problem all over the world. The purpose of the research is to examine the applicability of bagasse fly ash (BFA)-an agricultural waste of sugar industry used for the synthesis of zeolitic material. The zeolitic material are used for the uptake of Pb(II) and Cd(II) heavy metal. Bagasse fly ash is used as a native material for the synthesis of zeolitic materials by conventional hydrothermal treatment without (conventional zeolitic bagasse fly ash (CZBFA)) and with electrolyte (conventional zeolitic bagasse fly ash in electrolyte media (ECZBFA)) media. Heavy metal ions Pb(II) and Cd(II) were successfully seized from aqueous media using these synthesized zeolitic materials. In this study, the zeolitic materials were well characterized by different instrumental methods such as Brunauer-Emmett-Teller, XRF, Fourier transform infrared spectroscopy, powder X-ray diffraction, and scanning electron microscopic microphotographs. The presence of analcime, phillipsite, and zeolite P in adsorbents confirms successful conversion of native BFA into zeolitic materials. Seizure modeling of Pb(II) and Cd(II) was achieved by batch sorption experiments, isotherms, and kinetic studies. These data were used to compare and evaluate the zeolitic materials as potential sorbents for the uptake of heavy metal ions from an aqueous media. The Langmuir isotherm correlation coefficient parameters best fit the equilibrium data which indicate the physical sorption. Pseudo-second-order and intra-particle diffusion model matches best which indicates that the rate of sorption was controlled by film diffusion. The column studies were performed for the practical function of sorbents, and breakthrough curves were obtained, which revealed higher sorption capacity as compared to batch method. Synthesized zeolitic material (CZBFA and ECZBFA), a low-cost sorbent, was proven as potential sorbent for the uptake of Pb(II) and Cd(II) heavy metal ions. PMID:22739768

  6. Non-Equilibrium Water-Glassy Polymer Dynamics

    NASA Astrophysics Data System (ADS)

    Davis, Eric; Minelli, Matteo; Baschetti, Marco; Sarti, Giulio; Elabd, Yossef

    2012-02-01

    For many applications (e.g., medical implants, packaging), an accurate assessment and fundamental understanding of the dynamics of water-glassy polymer interactions is of great interest. In this study, sorption and diffusion of pure water in several glassy polymers films, such as poly(styrene) (PS), poly(methyl methacrylate) (PMMA), poly(lactide) (PLA), were measured over a wide range of vapor activities and temperatures using several experimental techniques, including quartz spring microbalance (QSM), quartz crystal microbalance (QCM), and time-resolved Fourier transform infrared-attenuated total reflectance (FTIR-ATR) spectroscopy. Non-Fickian behavior (diffusion-relaxation phenomena) was observed by all three techniques, while FTIR-ATR spectroscopy also provides information about the distribution of the states of water and water transport mechanisms on a molecular-level. Specifically, the states of water are significantly different in PS compared to PMMA and PLA. Additionally, a purely predictive non-equilibrium lattice fluid (NELF) model was applied to predict the sorption isotherms of water in these glassy polymers.

  7. Biosorption kinetics, thermodynamics and isosteric heat of sorption of Cu(II) onto Tamarindus indica seed powder.

    PubMed

    Chowdhury, Shamik; Saha, Papita Das

    2011-12-01

    Biosorption of Cu(II) by Tamarindus indica seed powder (TSP) was investigated as a function of temperature in a batch system. The Cu(II) biosorption potential of TSP increased with increasing temperature. The rate of the biosorption process followed pseudo second-order kinetics while the sorption equilibrium data well fitted to the Langmuir and Freundlich isotherm models. The maximum monolayer Cu(II) biosorption capacity increased from 82.97 mg g(-1) at 303 K to 133.24 mg g(-1) at 333 K. Thermodynamic study showed spontaneous and endothermic nature of the sorption process. Isosteric heat of sorption, determined using the Clausius-Clapeyron equation increased with increase in surface loading showing its strong dependence on surface coverage. The biosorbent was characterized by scanning electron microscopy (SEM), surface area and porosity analyzer, X-ray diffraction (XRD) spectrum and Fourier transform infrared (FTIR) spectroscopy. The results of FTIR analysis of unloaded and Cu(II)-loaded TSP revealed that -NH(2), -OH, -C=O and C-O functional groups on the biosorbent surface were involved in the biosorption process. The present study suggests that TSP can be used as a potential, alternative, low-cost biosorbent for removal of Cu(II) ions from aqueous media. PMID:21872453

  8. Estimation of soil sorption coefficients using QSARs

    SciTech Connect

    Doucette, W.J.

    1994-12-31

    Sorption coefficients quantitatively describe the extent to which an organic chemical distributes itself between an environmental solid and the aqueous phase that it is contact with at equilibrium. Because of the difficulty and expense associated with measuring sorption coefficients, estimated values are often used in place of site specific, experimental values for fate modeling. Most reported methods for estimating the sorption of organic chemicals onto environmental solids are based on observation that for many organic chemicals, and in particular neutral hydrophobic organics, sorption is directly proportional to the quantity of organic matter associated with the solid. Normalizing soil or sediment specific sorption coefficients to the organic carbon content of the sorbent yields a new ``constant``, Koc, that is considered unique property of the organic chemical being sorbed. Values of Koc are then typically estimated from correlations between Koc and various descriptors of hydrophobicity such as octanol/water partition coefficients (Kow), aqueous solubility (S), molecular connectivity indices (MCIs) and retention times or capacity factors generated by reverse phase high performance liquid chromatography (RP-HPLC). Group contribution methods have also been described. While the so-called ``Koc approach`` for estimating sorption coefficients is most appropriate for neutral, hydrophobic organic chemicals on environmental solids containing a significant amount of organic matter, it has been applied to a wide variety of chemical and soil types. This presentation will focus on a discussion of the Koc approach, its applicability and limitations. A comparison of several widely used methods for estimating Koc will be presented.

  9. SORPTION OF HEAVY METALS BY THE SOIL FUNGI ASPERGILLUS NIGER AND MUCOR ROUXII

    EPA Science Inventory

    Sorption of the nitrate salts of cadmium(II), copper (II), lanthanum(III) and silver (I) by two fungi, Aspergillus niger and Mucor rouxii, was evaluated using Fruendlich adsorption isotherms and energy dispersive X-ray electron microscopy. The linearized Freundlich isotherm descr...

  10. The use of a heterogeneity-based isotherm to interpret the transport of reactive radionuclides in volcanic tuff media

    SciTech Connect

    Polzer, W.L.; Fuentes, H.R.

    1987-12-31

    The sorption of cesium and strontium has been modeled with a heterogeneity-based isotherm equation for various tuff materials including those within a sequence of geologic stratigraphic units. The theory of the isotherm foresees the relative retardation and the chemical dispersion of the studied radionuclides during transport. The concepts of heterogeneity of sites and variability in the maximum number of sites available for sorption are incorporated into the model. 16 refs., 4 figs., 3 tabs.

  11. Sorption of polycyclic aromatic hydrocarbons to polystyrene nanoplastic.

    PubMed

    Liu, Lijing; Fokkink, Remco; Koelmans, Albert A

    2016-07-01

    Microplastic has become an emerging contaminant of global concern. Bulk plastic can degrade to form smaller particles down to the nanoscale (<100 nm), which are referred to as nanoplastics. Because of their high surface area, nanoplastic may bind hydrophobic chemicals very effectively, increasing their hazard when such nanoplastics are taken up by biota. The present study reports distribution coefficients for sorption of polycyclic aromatic hydrocarbons (PAHs) to 70 nm polystyrene in freshwater, and PAH adsorption isotherms spanning environmentally realistic aqueous concentrations of 10(-5)  μg/L to 1 μg/L. Nanopolystyrene aggregate state was assessed using dynamic light scattering. The adsorption isotherms were nonlinear, and the distribution coefficients at the lower ends of the isotherms were very high, with values up to 10(9) L/kg. The high and nonlinear sorption was explained from π-π interactions between the planar PAHs and the surface of the aromatic polymer polystyrene and was higher than for micrometer-sized polystyrene. Reduction of nanopolystyrene aggregate sizes had no significant effect on sorption, which suggests that the PAHs could reach the sorption sites on the pristine nanoparticles regardless of the aggregation state. Pre-extraction of the nanopolystyrene with C18 polydimethylsiloxane decreased sorption of PAHs, which could be explained by removal of the most hydrophobic fraction of the nanopolystyrene. Environ Toxicol Chem 2016;35:1650-1655. © 2015 SETAC. PMID:26588181

  12. Statistical physics studies of multilayer adsorption isotherm in food materials and pore size distribution

    NASA Astrophysics Data System (ADS)

    Aouaini, F.; Knani, S.; Ben Yahia, M.; Ben Lamine, A.

    2015-08-01

    Water sorption isotherms of foodstuffs are very important in different areas of food science engineering such as for design, modeling and optimization of many processes. The equilibrium moisture content is an important parameter in models used to predict changes in the moisture content of a product during storage. A formulation of multilayer model with two energy levels was based on statistical physics and theoretical considerations. Thanks to the grand canonical ensemble in statistical physics. Some physicochemical parameters related to the adsorption process were introduced in the analytical model expression. The data tabulated in literature of water adsorption at different temperatures on: chickpea seeds, lentil seeds, potato and on green peppers were described applying the most popular models applied in food science. We also extend the study to the newest proposed model. It is concluded that among studied models the proposed model seems to be the best for description of data in the whole range of relative humidity. By using our model, we were able to determine the thermodynamic functions. The measurement of desorption isotherms, in particular a gas over a solid porous, allows access to the distribution of pore size PSD.

  13. Sorption of organophosphate and triazine agrochemicals on biochars and soils

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Biochars are known to strongly sorb polar and nonpolar organic compounds, and biochar soil amendment can have counteracting impacts on the efficacy of, and runoff contamination by agrochemicals. This study investigated the sorption-desorption isotherms and kinetics of triazine (deisopropylatrazine)...

  14. Sorption of heavy metals by prepared bacterial cell surfaces

    SciTech Connect

    Churchill, S.A.; Walters, J.V.; Churchill, P.F.

    1995-10-01

    Prepared biomass from two Gram-negative and one Gram-positive bacterial strains was examined for single, binary, and quaternary mixtures of polyvalent metal cation binding to cell surfaces. The biosorption of {sub 24}Cr{sup 3+}, {sub 27}Co{sup 2+}, {sub 28}Ni{sup 2+}, and {sub 29}Cu{sup 2+} for each bacterial cell type was evaluated using a batch equilibrium method. The binding of each metal by all three bacterial cells could be described by the Freundlich sorption model. The isotherm binding constants suggest that E. coli cells are the most efficient at binding copper, chromium, and nickel; and M. luteus adsorbs cobalt most efficiently. The K-values for copper bound to P. aeruginosa and E. coli are > 2-fold and > 8-fold greater, respectively, than previous reported for intact cells. The general metal-affinity series observed was Cr{sup 3+} > Cu{sup 2+} > Ni{sup 2+} > Co{sup 2+}. There was a marked lower affinity of all biosorbents for Co{sup 2+} and Ni{sup 2+}. M. luteus and E. coli had a strong preference for Co{sup 2+} over Ni{sup 2+}. Metal-binding enhancement could be ascribed to increased cell barrier surface porosity to metal-bearing solutions.

  15. Sorption Charecterization of Radonuclides on Clays in Yucca Mountain Alluvium

    SciTech Connect

    M. Ding; P.W. Reimus; S. Chipera; C. Scism

    2006-03-17

    Sorption of {sup 237}Np(V) and {sup 233}U(VI) was measured on clays separated from Yucca Mountain alluvium as a function of solution pH and aqueous actinide concentrations. The results indicate that sorption of U and Np on the separated clay fraction depends strongly on solution pH. Np sorption on clays increases slowly with increasing pH from 3 to 7. Above pH 7, Np sorption on clays increases rapidly up to a pH of about 10. On the other hand, U sorption on clays reaches it maximum at a pH of about 6, with sorption decreasing as pH increases from 6 to 8 and then increasing again as pH increases further from 8 to about 10. The results suggest that a Freundlich isotherm can be used to describe U and Np sorption on clays at pH above 5.5. The results of this study indicate that clay minerals play a very important role in the sorption of U and Np on Yucca Mountain alluvium. Indeed, the clay content of the alluvium is probably considerably more important than water chemistry in predicting the ability of the alluvium to attenuate the transport of these radionuclides.

  16. “Multi-temperature” method for high-pressure sorption measurements on moist shales

    SciTech Connect

    Gasparik, Matus; Ghanizadeh, Amin; Gensterblum, Yves; Krooss, Bernhard M.

    2013-08-15

    A simple and effective experimental approach has been developed and tested to study the temperature dependence of high-pressure methane sorption in moist organic-rich shales. This method, denoted as “multi-temperature” (short “multi-T”) method, enables measuring multiple isotherms at varying temperatures in a single run. The measurement of individual sorption isotherms at different temperatures takes place in a closed system ensuring that the moisture content remains constant. The multi-T method was successfully tested for methane sorption on an organic-rich shale sample. Excess sorption isotherms for methane were measured at pressures of up to 25 MPa and at temperatures of 318.1 K, 338.1 K, and 348.1 K on dry and moisture-equilibrated samples. The measured isotherms were parameterized with a 3-parameter Langmuir-based excess sorption function, from which thermodynamic sorption parameters (enthalpy and entropy of adsorption) were obtained. Using these, we show that by taking explicitly into account water vapor as molecular species in the gas phase with temperature-dependent water vapor pressure during the experiment, more meaningful results are obtained with respect to thermodynamical considerations. The proposed method can be applied to any adsorbent system (coals, shales, industrial adsorbents) and any supercritical gas (e.g., CH{sub 4}, CO{sub 2}) and is particularly suitable for sorption measurements using the manometric (volumetric) method.

  17. Factors controlling alkylbenzene sorption to municipal solid waste.

    PubMed

    Wu, B; Taylor, C M; Knappe, D R; Nanny, M A; Barlaz, M A

    2001-11-15

    The sorption of toluene and o-xylene to individual municipal solid waste (MSW) constituents [office paper, newsprint, model food and yard waste, high density polyethylene, and poly(vinyl chloride) (PVC)] was evaluated. Effects of sorbent decomposition and solvent composition on alkylbenzene sorption were studied by evaluating biodegradable sorbents in both fresh and anaerobically decomposed form and by complementing single-solute isotherm tests with experiments conducted in acidogenic and methanogenic leachate. Alkylbenzene sorption to plastics was greaterthan to biopolymer composites, and differences in sorbate/sorbent solubility parameter compatibility explained this observation. Alkylbenzene sorption to biopolymer composites yielded linear isotherms, and sorption capacities [log(Koc/Kow)] decreased linearly with increasing sorbent polarity as expressed by the O-alkyl/alkyl ratio. Leachate composition had little effect on alkylbenzene sorption with one exception; volatile fatty acids in acidogenic leachate appeared to convert PVC from a glassy to a rubbery polymer. The results of this study showed that sorbent organic matter affinity for hydrophobic organic contaminants (HOCs) increases with increasing extent of MSW decomposition because of the recalcitrance of plastics and the preferential degradation of polar biopolymers. Furthermore, the plasticizing effect of volatile fatty acids in acidogenic leachate may enhance the bioavailability of HOCs sorbed to glassy organic matter in MSW or in soils contaminated with acidogenic leachate. PMID:11757618

  18. Sorption of norfloxacin onto humic acid extracted from weathered coal.

    PubMed

    Zhang, Qin; Zhao, Ling; Dong, Yuan-Hua; Huang, Guan-Yi

    2012-07-15

    Norfloxacin (NOR), is an ionizable and polar antimicrobial compound, and it may enter the environment in substantial amounts via the application of manure or sewage as a fertilizer. Sorption of NOR onto humic acid (HA) may affect its environmental fate. In this study, HA extracted from weathered coal was used to investigate the sorption of NOR at different solution chemistry conditions (pH, ionic strength) and temperatures. The sorption of NOR onto HA showed a two-stage sorption process with an equilibration time of 48 h. The sorption kinetic curve fitted well with a pseudo second-order kinetic model. Thermodynamic characteristics demonstrated that the sorption of NOR onto HA was a spontaneous and exothermic process predominated by physical sorption. All sorption isotherms fitted well with the Freundlich and Langmuir models and they were highly nonlinear with values of n between 0.4 and 0.5, suggesting the high heterogeneity of HA. Increasing Ca2+ concentration resulted in a considerable reduction in the K(d) values of NOR, hinting that Ca2+ had probably competed with NOR(+,0) for the cation exchange sites on the surfaces of HA. The sorption reached a maximum at pH 6.0 over the pH range of 2.0-8.0, implying that the primary sorption mechanism was cation exchange interaction between NOR(+,0) species and the negatively charged functional groups of HA. Spectroscopic evidence demonstrated that the piperazinyl moiety of NOR was responsible for sorption onto HA, while the carbonyl group and the aromatic structure of HA participated in adsorbing NOR. PMID:22459013

  19. Study of uranium(VI) and radium(II) sorption at trace level on kaolinite using a multisite ion exchange model.

    PubMed

    Reinoso-Maset, Estela; Ly, Jacques

    2016-06-01

    Uranium and the long-lived decay product radium-226 are abundantly present in mine wastes produced during uranium extraction activities. In the case of release to the surrounding environment, these radionuclides are at trace level compared to groundwater solutes, and the presence, content and properties of clay minerals in the host environment influence the extent of radionuclide sorption and, in turn, migration. Since clays are known to have the distinctive property of retaining ions, the aim of this work was to study the sorption of trace U(VI) and Ra(II) on a common phyllosilicate mineral, kaolinite, in the presence of excess K, a common groundwater cation, in order to obtain a thermodynamic database that describes the ion exchange equilibria occurring at the mineral-solution interface. Following a detailed experimental protocol using chemical and radiochemical analytical techniques, batch experiments over a wide pH range (from 2 to 11) and fixed concentration (ca. 10(-9) M), and additional adsorption isotherms at two different solution pH (6.2 and 10.4) over a concentration range (10(-10) to 10(-4) M) were carried out to measure the distribution coefficient (Kd) of U(VI) and Ra(II) sorption on kaolinite. The experimental sorption data was processed according to a general multisite sorbent/multispecies sorbate ion exchange model, which allowed deducing the charge of adsorbed species and the stoichiometry of the associated adsorption equilibria on kaolinite's surface sites. Aqueous speciation calculations predicted Ra(II) as Ra(2+) over the working pH range, and its adsorption curves and isotherms were explained using three sorption sites. Adsorption of U(VI) occurred on four sorption sites and was governed by its solution speciation, with positively charged hydroxylated (UO2(2+) and UO2(OH)(+)) and silicate (UO2(H3SiO4)(+)) species being adsorbed between pH 2 and 6, whereas its negatively charged forms (UO2(OH)3(-) and UO2(OH)4(2-)) dominated U(VI) sorption at

  20. Analysis and modeling of moisture sorption behavior for antimicrobial composite protein films.

    PubMed

    Lei, Qiao; Pan, Jiazhen; Bao, Jianqiang; Huang, Zhiying; Zhang, Yuting

    2014-01-01

    The WPI-NaCas-GLY antimicrobial film takes full advantage of the controlled release of active or antimicrobial agents as well as demonstrates a great potential for functioning as an alternative biodegradable polymer in practical applications. The moisture sorption kinetics of the film as an important carrier of active agents was investigated at various relative humidities (RH). The results indicated that the moisture sorption characterization and procedure of this film can be described well by the empirical Peleg model with higher confidence and concordance. The model could predict the film's moisture content at any time (Mt), the time to reach any given level of R (tR), the equilibrium moisture at any RH condition (Me), and isotherm trend based upon experimental data and modeled constants k(1), k(2), a, b, c, and d without giving consideration to their physical meaning. The water vapor transmission rate of the WPI-NaCas-GLY antimicrobial film increased exponentially with increasing RH due to its hydrophilicity, which was primarily caused by the presence of glycerol in a higher content. The results also suggested that aw predominately affects the film's Me values compared with the temperature factor by fixed nonlinear multiple regression analyses. PMID:25226893

  1. Hysteresis from Multiscale Porosity: Modeling Water Sorption and Shrinkage in Cement Paste

    NASA Astrophysics Data System (ADS)

    Pinson, Matthew B.; Masoero, Enrico; Bonnaud, Patrick A.; Manzano, Hegoi; Ji, Qing; Yip, Sidney; Thomas, Jeffrey J.; Bazant, Martin Z.; Van Vliet, Krystyn J.; Jennings, Hamlin M.

    2015-06-01

    Cement paste has a complex distribution of pores and molecular-scale spaces. This distribution controls the hysteresis of water sorption isotherms and associated bulk dimensional changes (shrinkage). We focus on two locations of evaporable water within the fine structure of pastes, each having unique properties, and we present applied physics models that capture the hysteresis by dividing drying and rewetting into two related regimes based on relative humidity (RH). We show that a continuum model, incorporating a pore-blocking mechanism for desorption and equilibrium thermodynamics for adsorption, explains well the sorption hysteresis for a paste that remains above approximately 20% RH. In addition, we show with molecular models and experiments that water in spaces of ≲1 nm width evaporates below approximately 20% RH but reenters throughout the entire RH range. This water is responsible for a drying shrinkage hysteresis similar to that of clays but opposite in direction to typical mesoporous glass. Combining the models of these two regimes allows the entire drying and rewetting hysteresis to be reproduced accurately and provides parameters to predict the corresponding dimensional changes. The resulting model can improve the engineering predictions of long-term drying shrinkage accounting also for the history dependence of strain induced by hysteresis. Alternative strategies for quantitative analyses of the microstructure of cement paste based on this mesoscale physical model of water content within porous spaces are discussed.

  2. Silylation of leached-vermiculites following reaction with imidazole and copper sorption behavior.

    PubMed

    Santos, Saloana S G; Pereira, Mariana B B; Almeida, Ramon K S; Souza, Antônio G; Fonseca, Maria G; Jaber, M

    2016-04-01

    Organically modified vermiculites were synthesized by previous silylation of three leached vermiculites, V0.3Cl, V0.5Cl and V0.8Cl, under anhydrous conditions following reaction with imidazole (Im), which acted as chelating agent for copper retention. Elemental analysis, X-ray diffraction, infrared spectroscopy, scanning electronic microscopy, transmission electron microscopy, (29)Si and (13)C NMR and nitrogen adsorption/desorption measurements were used to characterize pristine, leached and organofunctionalized solids. X-ray photoelectron spectroscopy (XPS) was used to evaluate the surface after copper sorption. Parameters such as contact time, pH and initial cation concentration for the adsorption of Cu(II) ions were investigated. The adsorption equilibrium data were fitted using the Langmuir isotherm model and the monolayer adsorption capacities were 2.38, 2.52 and 2.69mmolg(-1) for V0.5Cl-Im, V0.3Cl-Im and V0.8Cl-Im, respectively, at pH 6.0 and 298K for a time reaction of 80min. The sorption rates were described by pseudo-second-order kinetics. The chloropropyl imidazole vermiculites are promising adsorbents for the rapid removal of Cu(II) ions from aqueous solution. PMID:26844783

  3. Sorption of radionuclides by cement-based barrier materials

    SciTech Connect

    Li, Kefei 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 rapid 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.

  4. Kinetics and equilibrium studies of adsorption of chromium(VI) ion from industrial wastewater using Chrysophyllum albidum (Sapotaceae) seed shells.

    PubMed

    Amuda, O S; Adelowo, F E; Ologunde, M O

    2009-02-01

    A new biosorbent has been prepared by coating Chrysophyllum albidum (Sapotaceae) seed shells with chitosan and/or oxidizing agents such as sulfuric acid. This study investigated the technical feasibility of activated and modified activated C. albidum seed shells carbons for the adsorption of chromium(VI) from aqueous solution. The sorption process with respect to its equilibria and kinetics as well as the effects of pH, contact time, adsorbent mass, adsorbate concentration and particle size on adsorption was also studied. The most effective pH range was found to be between 4.5 and 5 for the sorption of the metal ion. The pseudo-first-order rate equation by Lagergren and pseudo-second-order rate equation were tested on the kinetic data, the adsorption process followed pseudo-second-order rate kinetics, also, isotherm data was analyzed for possible agreement with the Langmuir and Freundlich adsorption isotherms, the Freundlich and Langmuir models for dynamics of metal ion uptake proposed in this work fitted the experimental data reasonably well. However, equilibrium sorption data were better represented by Langmuir model than Freundlich. The adsorption capacity calculated from Langmuir isotherm was 84.31, 76.23 and 59.63mgCr(VI)/g at initial pH of 3.0 at 30 degrees C for the particle size of 1.00-1.25mm with the use of 12.5, 16.5 and 2.1g/L of CACASC, CCASC and ACASC adsorbent mass, respectively. This readily available adsorbent is efficient in the uptake of Cr(VI) ion in aqueous solution, thus, it could be an excellent alternative for the removal of heavy metals and organic matter from water and wastewater. PMID:19022632

  5. Regenerative Sorption Refrigerator

    NASA Technical Reports Server (NTRS)

    Jones, Jack A.; Wen, Liang-Chi; Bard, Steven

    1991-01-01

    Two-stage sorption refrigerator achieves increased efficiency via regenerative-heating concept in which waste heat from praseodymium/cerium oxide (PCO) chemisorption compressor runs charcoal/krypton (C/Kr) sorption compressor. Waste heat from each PCO sorption compressor used to power surrounding C/Kr sorption compressor. Flows of heat in two compressor modules controlled by gas-gap thermal switches. Has no wearing moving parts other than extremely long life, room-temperature check valves operating about twice per hour. Virtually no measurable vibration, and has potential operating life of at least ten years.

  6. Sorption behavior of mixtures of glycerol and starch.

    PubMed

    Enrione, Javier I; Hill, Sandra E; Mitchell, John R

    2007-04-18

    Glycerol is often added to starches to plasticize the product, but the presence of glycerol may also affect the water content of the samples. To evaluate the effect of glycerol on the sorption properties of starches, waxy maize, rice, and wheat starch were thermomechanically extruded in the presence of glycerol. Sorption isotherms of these extruded samples were ascertained using dynamic vapor sorption (DVS). BET and GAB modeling showed a monolayer (mo) significantly higher for waxy maize than for rice and wheat. Glycerol inclusion changed the model values, indicating reduction in sorption energy at the monolayer and restructuring of the multilayer. An interaction factor (xi) based on weight fraction models was calculated. Differences in xi were obtained when glycerol was added, varying from approximately 0.9 for 5% glycerol to approximately 0.8 for 20% glycerol, supporting the hypothesis of interactions between starch and this polyol. PMID:17362027

  7. Carbon Dioxide Transport and Sorption Behavior in Confined Coal Cores for Enhanced Coalbed Methane and CO2 Sequestration

    SciTech Connect

    Jikich, S.A.; McLendon, T.R.; Seshadri, K.S.; Irdi, G.A.; Smith, D.H.

    2007-11-01

    Measurements of sorption isotherms and transport properties of CO2 in coal cores are important for designing enhanced coalbed methane/CO2 sequestration field projects. Sorption isotherms measured in the lab can provide the upper limit on the amount of CO2 that might be sorbed in these projects. Because sequestration sites will most likely be in unmineable coals, many of the coals will be deep and under considerable lithostatic and hydrostatic pressures. These lithostatic pressures may significantly reduce the sorption capacities and/or transport rates. Consequently, we have studied apparent sorption and diffusion in a coal core under confining pressure. A core from the important bituminous coal Pittsburgh #8 was kept under a constant, three-dimensional external stress; the sample was scanned by X-ray computer tomography (CT) before, then while it sorbed, CO2. Increases in sample density due to sorption were calculated from the CT images. Moreover, density distributions for small volume elements inside the core were calculated and analyzed. Qualitatively, the computerized tomography showed that gas sorption advanced at different rates in different regions of the core, and that diffusion and sorption progressed slowly. The amounts of CO2 sorbed were plotted vs. position (at fixed times) and vs. time (for various locations in the sample). The resulting sorption isotherms were compared to isotherms obtained from powdered coal from the same Pittsburgh #8 extended sample. The results showed that for this single coal at specified times, the apparent sorption isotherms were dependent on position of the volume element in the core and the distance from the CO2 source. Also, the calculated isotherms showed that less CO2 was sorbed than by a powdered (and unconfined) sample of the coal. Changes in density distributions during the experiment were also observed. After desorption, the density distribution of calculated volume elements differed from the initial distribution

  8. Sorption studies of human keratinized tissues

    NASA Astrophysics Data System (ADS)

    Johnsen, G. K.; Martinsen, Ø. G.; Grimnes, Sverre

    2010-04-01

    Water content is known to be the most important single parameter for keratinized tissue to remain its vital functions. In that sense, a general knowledge of the water binding properties is of great interest, and a reliable measurement setup must be found. Also, revealing the sorption properties of human keratinized tissues is vital towards a calibration of susceptance based skin hydration measurements that already is an important diagnostic tool in clinical dermatology, and we will see that any hysteresis will complicate such a calibration further. In this study we investigated the sorption properties of keratinized tissues such as human epidermal stratum corneum (SC), hair and nail. The study was performed under controlled environmental conditions with a dynamic vapor sorption (DVS) instrument, and the water uptake of the keratinized test samples was measured as the relative humidity in the ambient air was altered step-wisely. In this study, vital and characteristic water sorption properties such as the isotherm, relative water uptake, and hysteresis were investigated and will be discussed.

  9. 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

  10. A thermodynamic model for gas adsorption isotherms

    SciTech Connect

    Riazi, M.R.; Khan, A.R.

    1999-02-15

    In this paper based on the principle of solution thermodynamics for gas-solid equilibrium, a relation is developed to express gas adsorption isotherms. An activity coefficient model based on weight fraction of sorbate in the solid phase has been derived that well describes the behavior of various gases on different types of adsorbents. The proposed model has been evaluated and compared with four other models commonly used for gas adsorption isotherms in the literature. For 12 different systems at various isotherms for the temperature range {minus}128 to 100 C and the pressure range 0.02 to 1219 kPa for 689 data points, the proposed model predicts equilibrium pressure with an average deviation of 5.3%, which is about half of the error obtained from other methods. The proposed model clearly outperforms other available methods such as the vacancy solution theory, the ideal adsorption solution model, and other various modified forms of the Langmuir isotherm. Unique features of the proposed model are its simplicity, generality, and accuracy over the entire pressure and temperature ranges.

  11. The sorption of quercetin by high-basicity anion exchangers

    NASA Astrophysics Data System (ADS)

    Udalova, N. A.; Karpov, S. I.; Selemenev, V. F.; Sharmar, I. A.

    2009-06-01

    The sorption of quercetin on anionites with various porosities in the OH- and Cl- forms was studied under static conditions. The equilibrium (distribution coefficients K p) and kinetic (effective diffusion coefficients D eff) parameters of quercetin sorption on AV-17-2P and AV-17-6M anionites in the Cl- and OH- forms were calculated. The mechanism of quercetin interactions with the anion exchangers was studied by electron microscopy and IR spectroscopy.

  12. Hydration of microcrystalline cellulose and milled cellulose studied by sorption calorimetry.

    PubMed

    Kocherbitov, Vitaly; Ulvenlund, Stefan; Kober, Maria; Jarring, Kjell; Arnebrant, Thomas

    2008-03-27

    The hydration of two different polymorphs of microcrystalline cellulose (cellulose I and II), as well as the hydration of amorphous cellulose was studied using water sorption calorimetry, gravimetric water vapor sorption, nitrogen sorption, and X-ray powder diffraction. Amorphous cellulose was prepared by means of ball-milling of microcrystalline cellulose (MCC). Whereas X-ray data showed the untreated MCC to consist of cellulose I, the amorphous cellulose was found to recrystallize into cellulose II after contact with water or water vapor at relative humidities (RHs) above 90%. Sorption isotherms show an increase of water sorption in the sequence cellulose Isorption becomes more exothermic in the same sequence. The specific area of cellulose is dramatically higher when calculated from the water adsorption than when calculated from nitrogen adsorption. A proposed mechanism of water sorption by MCC implies the adsorption of water molecules at solid-solid interfaces, i.e., between neighboring microfibrils, which explains the observed difference between water and nitrogen. The Brunauer-Emmett-Teller (BET) model is therefore not appropriate for the description of the hydration of cellulose. Rather, the Langmuir model represents a more accurate description of water sorption by MCC at low RH. At higher RH, the water adsorption competes with capillary condensation. The thickness of microfibrils, as calculated using the fitting of the sorption isotherm of MCC with the Langmuir equation, is about 4 nm. This value compares favorably with literature data. PMID:18307340

  13. Sorption of roxarsone onto soils with different physicochemical properties.

    PubMed

    Fu, Qing-Long; He, Jian-Zhou; Blaney, Lee; Zhou, Dong-Mei

    2016-09-01

    Elevated roxarsone (ROX) concentrations in soils, caused by land application of ROX-bearing poultry litter, mandate investigation of ROX sorption onto soils. Equilibrium and kinetic studies of ROX sorption onto five soils were carried out to explore the relationship between sorption parameters and soil properties, and to reveal the effects of coexisting humic acid (HA), P(V), As(V), and As(III) on ROX transport. Experimental results indicated that ROX sorption reached equilibrium within 24 h, with pseudo-second order rate constants of 5.74-5.26 × 10(2) g/(mg h); film and intra-particle diffusion were the rate-limiting processes. ROX sorption to soils involved partitioning and adsorption phenomena; however, their relative contributions varied for different soils. The maximum ROX sorption varied with soil type, ranging from 0.59 to 4.12 mg/g. Results from correlation analysis and multiple linear regressions revealed that the maximum sorption capacities, partition coefficients, and desorption percentages were correlated with soil properties, especially iron content, total organic carbon, and dissolved organic carbon. ROX sorption to soils was affected more by soil pH than the initial pH of ROX-containing solutions. Carboxylic and amide functional groups were determined to be responsible for ROX sorption to soils. ROX sorption capacities decreased in the presence of HA, P(V), As(V), and As(III), indicating that ROX mobility in soils was facilitated by dissolved organic matter (DOM) and competing anions. PMID:27281543

  14. Molecular Scale Assessment of Methylarsenic Sorption on Aluminum Oxide

    SciTech Connect

    Shimizu, M.; Ginder-Vogel, M; Parikh, S; Sparks, D

    2010-01-01

    Methylated forms of arsenic (As), monomethylarsenate (MMA) and dimethylarsenate (DMA), have historically been used as herbicides and pesticides. Because of their large application to agriculture fields and the toxicity of MMA and DMA, the sorption of methylated As to soil constituents requires investigation. MMA and DMA sorption on amorphous aluminum oxide (AAO) was investigated using both macroscopic batch sorption kinetics and molecular scale extended X-ray absorption fine structure (EXAFS) and Fourier transform infrared (FTIR) spectroscopic techniques. Sorption isotherm studies revealed sorption maxima of 0.183, 0.145, and 0.056 mmol As/mmol Al for arsenate (As{sup V}), MMA, and DMA, respectively. In the sorption kinetics studies, 100% of added As{sup V} was sorbed within 5 min, while 78% and 15% of added MMA and DMA were sorbed, respectively. Desorption experiments, using phosphate as a desorbing agent, resulted in 30% release of absorbed As{sup V}, while 48% and 62% of absorbed MMA and DMA, respectively, were released. FTIR and EXAFS studies revealed that MMA and DMA formed mainly bidentate binuclear complexes with AAO. On the basis of these results, it is proposed that increasing methyl group substitution results in decreased As sorption and increased As desorption on AAO.

  15. Sorption of lanthanum ions by natural clinoptilolite tuff

    NASA Astrophysics Data System (ADS)

    Dampilova, B. V.; Zonkhoeva, E. L.

    2013-08-01

    The equilibrium and kinetics of sorption of lanthanum ions on natural clinoptilolite tuff are studied. It is demonstrated that sorption of lanthanum ions from diluted solutions occurs in micropores of clinoptilolite, and from concentrated solutions in the mesoporous structure of tuff. The main capacity of zeolite tuff is found in the secondary porous structure. The sorption of lanthanum ions is limited by diffusion in tuff grains. Lanthanum ions are regularly distributed in the tuff phase and interact with the Brønsted centers of large clinoptilolite cavities.

  16. Studying the sorption properties of a clinoptilolite-containing tuff with respect to europium(III) ions

    NASA Astrophysics Data System (ADS)

    Kozhevnikova, N. M.

    2014-03-01

    The kinetic laws of sorption of europium(III) ions from sulfate solutions by a clinoptilolite-containing tuff are studied. The kinetic parameters of sorption process are determined and absorption isotherms are constructed for europium ions. It is found that both external and internal diffusion are rate-limiting steps, and europium is completely extracted from dilute solutions (<0.0025 m).

  17. Sorption testing and generalized composite surface complexation models for determining uranium sorption parameters at a proposed in-situ recovery site

    DOE PAGESBeta

    Johnson, Raymond H.; Truax, Ryan A.; Lankford, David A.; Stone, James J.

    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

  18. Removal of perfluorinated surfactants by sorption onto granular activated carbon, zeolite and sludge.

    PubMed

    Ochoa-Herrera, Valeria; Sierra-Alvarez, Reyes

    2008-08-01

    Perfluorinated surfactants are emerging pollutants of increasing public health and environmental concern due to recent reports of their world-wide distribution, environmental persistence and bioaccumulation potential. Treatment methods for the removal of anionic perfluorochemical (PFC) surfactants from industrial effluents are needed to minimize the environmental release of these pollutants. Removal of PFC surfactants from aqueous solutions by sorption onto various types of granular activated carbon was investigated. Three anionic PFC surfactants, i.e., perfluorooctane sulfonate (PFOS), perfluorooctanoic acid (PFOA) and perfluorobutane sulfonate (PFBS), were evaluated for the ability to adsorb onto activated carbon. Additionally, the sorptive capacity of zeolites and sludge for PFOS was compared to that of granular activated carbon. Adsorption isotherms were determined at constant ionic strength in a pH 7.2 phosphate buffer at 30 degrees C. Sorption of PFOS onto activated carbon was stronger than PFOA and PFBS, suggesting that the length of the fluorocarbon chain and the nature of the functional group influenced sorption of the anionic surfactants. Among all adsorbents evaluated in this study, activated carbon (Freundlich K(F) values=36.7-60.9) showed the highest affinity for PFOS at low aqueous equilibrium concentrations, followed by the hydrophobic, high-silica zeolite NaY (Si/Al 80, K(F)=31.8), and anaerobic sludge (K(F)=0.95-1.85). Activated carbon also displayed a superior sorptive capacity at high soluble concentrations of the surfactant (up to 80 mg l(-1)). These findings indicate that activated carbon adsorption is a promising treatment technique for the removal of PFOS from dilute aqueous streams. PMID:18511099

  19. 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 (Kdapp) 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 Kdapp while no obvious effect was observed at low HA levels; dissolved HA could inhibit phenanthrene sorption on the two sorbents. PMID:25147865

  20. As(V), Cr(III) and Cr(VI) sorption on biochars and soil

    NASA Astrophysics Data System (ADS)

    Diamadopoulos, Evan; Agrafioti, Evita; Kalderis, Dimitrios

    2014-05-01

    The use of biochar, as a cost effective sorbent for heavy metal removal from contaminated water and soils is becoming a very promising practice. In this study, rice husk, the organic fraction of solid wastes, as well as sewage sludge were used as precursors for biochar production. The first was chosen as one of the most abundant types of biomass worldwide and the other two in order to find alternative innovative uses of these wastes. A series of batch kinetic and equilibrium (sorption and desorption) experiments was conducted using As(V), Cr(III) and Cr(VI) as adsorbates. The specific heavy metals were chosen in order to assess biochars removal capacity towards both anionic and cationic metals. Apart from biochars, a sandy loam soil was also used as adsorbent for metal removal. Knowing the separate behavior of biochars and soil towards metal sorption, it could be the first step in explaining the fate of heavy metals in a biochar amended soil. The kinetic study showed that, for all adsorbents and metals examined, sorption can be well described by the pseudo-second order kinetic model. What is more, simulation of sorption isotherms gave a better fit for the Freundlich model, possibly due to the heterogeneous surface of the initial biomasses and the fine aggregates that soil consists of. Based on the equilibrium study, the materials examined removed more than 95% of the initial Cr(III). This is possibly related to the electrostatic interactions between adsorbents negative surface charge and Cr(III) cations. However, removal rates for As(V) and Cr(VI) anions were significantly lower. Biochar derived from sewage sludge was efficient in removing 89% of Cr(VI) and 53% of As(V). Its ash high Fe2O3 content may have enhanced metal adsorption via precipitation. Soil was the most effective material for the removal of As(V), yet it could not strongly retain metal anions compared to biochars, as a significant amount of the adsorbed metal was released during desorption

  1. Experimental study of water desorption isotherms and thin-layer convective drying kinetics of bay laurel leaves

    NASA Astrophysics Data System (ADS)

    Ghnimi, Thouraya; Hassini, Lamine; Bagane, Mohamed

    2016-02-01

    The aim of this work is to determine the desorption isotherms and the drying kinetics of bay laurel leaves (Laurus Nobilis L.). The desorption isotherms were performed at three temperature levels: 50, 60 and 70 °C and at water activity ranging from 0.057 to 0.88 using the statistic gravimetric method. Five sorption models were used to fit desorption experimental isotherm data. It was found that Kuhn model offers the best fitting of experimental moisture isotherms in the mentioned investigated ranges of temperature and water activity. The Net isosteric heat of water desorption was evaluated using The Clausius-Clapeyron equation and was then best correlated to equilibrium moisture content by the empirical Tsami's equation. Thin layer convective drying curves of bay laurel leaves were obtained for temperatures of 45, 50, 60 and 70 °C, relative humidity of 5, 15, 30 and 45 % and air velocities of 1, 1.5 and 2 m/s. A non linear regression procedure of Levenberg-Marquardt was used to fit drying curves with five semi empirical mathematical models available in the literature, The R2 and χ2 were used to evaluate the goodness of fit of models to data. Based on the experimental drying curves the drying characteristic curve (DCC) has been established and fitted with a third degree polynomial function. It was found that the Midilli Kucuk model was the best semi-empirical model describing thin layer drying kinetics of bay laurel leaves. The bay laurel leaves effective moisture diffusivity and activation energy were also identified.

  2. Sorption of non-polar organic compounds by micro-sized plastic particles in aqueous solution.

    PubMed

    Hüffer, Thorsten; Hofmann, Thilo

    2016-07-01

    The presence of microscale polymer particles (i.e., microplastics) in the environment has become a major concern in recent years. Sorption of organic compounds by microplastics may affect the phase distribution within both sediments and aqueous phases. To investigate this process, isotherms were determined for the sorption of seven aliphatic and aromatic organic probe sorbates by four polymers with different physico-chemical properties. Sorption increased in the order polyamide < polyethylene < polyvinylchloride < polystyrene. This order does not reflect the particle sizes of the investigated microplastics within the aqueous dispersions, indicating the influence of additional factors (e.g., π-π-interactions) on the sorption of aromatic compounds by polystyrene. Linear isotherms by polyethylene suggested that sorbate uptake was due to absorption into the bulk polymer. In contrast, non-linear isotherms for sorption by PS, PA, and PVC suggest a predominance of adsorption onto the polymer surface, which is supported by the best fit of these isotherms using the Polanyi-Manes model. A strong relationship between the sorption coefficients of the microplastics and the hydrophobicity of the sorbates suggests that hydrophobic interactions are of major importance. PMID:27086075

  3. Sorption Modeling and Verification for Off-Gas Treatment

    SciTech Connect

    Tavlarides, Lawrence L.; Lin, Ronghong; Nan, Yue; Yiacoumi, Sotira; Tsouris, Costas; Ladshaw, Austin; Sharma, Ketki; Gabitto, Jorge; DePaoli, David

    2015-04-29

    The project has made progress toward developing a comprehensive modeling capability for the capture of target species in off gas evolved during the reprocessing of nuclear fuel. The effort has integrated experimentation, model development, and computer code development for adsorption and absorption processes. For adsorption, a modeling library has been initiated to include (a) equilibrium models for uptake of off-gas components by adsorbents, (b) mass transfer models to describe mass transfer to a particle, diffusion through the pores of the particle and adsorption on the active sites of the particle, and (c) interconnection of these models to fixed bed adsorption modeling which includes advection through the bed. For single-component equilibria, a Generalized Statistical Thermodynamic Adsorption (GSTA) code was developed to represent experimental data from a broad range of isotherm types; this is equivalent to a Langmuir isotherm in the two-parameter case, and was demonstrated for Kr on INL-engineered sorbent HZ PAN, water sorption on molecular sieve A sorbent material (MS3A), and Kr and Xe capture on metal-organic framework (MOF) materials. The GSTA isotherm was extended to multicomponent systems through application of a modified spreading pressure surface activity model and generalized predictive adsorbed solution theory; the result is the capability to estimate multicomponent adsorption equilibria from single-component isotherms. This advance, which enhances the capability to simulate systems related to off-gas treatment, has been demonstrated for a range of real-gas systems in the literature and is ready for testing with data currently being collected for multicomponent systems of interest, including iodine and water on MS3A. A diffusion kinetic model for sorbent pellets involving pore and surface diffusion as well as external mass transfer has been established, and a methodology was developed for determining unknown diffusivity parameters from transient

  4. RESORCINOL-FORMALDEHYDE ADSORPTION OF CESIUM (Cs+) FROM HANFORD WASTE SOLUTIONS-PART I: BATCH EQUILIBRIUM STUDY

    SciTech Connect

    HASSAN, NEGUIBM

    2004-03-30

    Batch equilibrium measurements were conducted with a granular Resorcinol-Formaldehyde (RF) resin to determine the distribution coefficients (Kds) for cesium. In the tests, Hanford Site actual waste sample containing radioactive cesium and a pretreated waste sample that was spiked with non-radioactive cesium were used. Initial concentrations of non-radioactive cesium in the waste sample were varied to generate an equilibrium isotherm for cesium. Two additional tests were conducted using a liquid to solid phase ratio of 10 and a contact time of 120 hours. The measured distribution coefficient (Kd) for radioactive cesium (137Cs) was 948 mL/g; the Kd for non-radioactive cesium (133Cs) was 1039 mL/g. The Kd for non-radioactive cesium decreased from 1039 to 691 mL/g as the initial cesium concentration increased. Very little change of the Kd was observed at initial cesium concentrations above 64 mg/mL. The maximum sorption capacity for cesium on granular RF resin was 1.17 mmole/g dry resin. T his value was calculated from the fit of the equilibrium isotherm data to the Dubinin-Radushkevich equation. Previously, a total capacity of 2.84 mmole/g was calculated by Bibler and Wallace for air-dried RF resin.

  5. Sorption and transport of atrazine in an agricultural soil

    NASA Astrophysics Data System (ADS)

    Hakan Akyol, Nihat

    2014-05-01

    Sorption and transport of atrazine in an agricultural soil Atrazine is one of the most commonly used herbicides in large quantity worldwide. The objective of this study was to perform some batch and column experiments to examine the transport of atrazine in an agricultural soil from Turkey. Batch experiments indicated that sorption isotherm was nonlinear with a freundlich isotherm over a range of concentration (0.2-10 mg/L) examined. Column experiments showed that transport of atrazine in the soil was moderately retarded compared to non-reactive tracer (R = 2.9-4.0). The degree of retardation decreased with increasing atrazine concentration and residance time had negligable impact on degree of sorption. Flow interruption tests in the column experiments indicated that the rate-limited desorption of atrazine mainly controlled the non-ideal transport of atrazine due to the presence of organic matter fraction (0.83 %) in the soil. Sorption and desorption behavior of atrazine in such soils could have important impacts for risk assessment of atrazine-contaminated soil and should be taken into account in the regulation, management, and remediation of atrazine-contaminated sites. Keywords: Atrazine, Agricultural soil, Batch, Column, Desorption, Rate-limited desorption, Sorption, Transport.

  6. [Influence of SDBS on sorption behaviors of heavy oil on Jiaozhou Bay sediment].

    PubMed

    Cao, Xiao-Yan; Han, Hui; Yang, Gui-Peng

    2011-10-01

    Sorption behavior of heavy oil onto Jiaozhou Bay sediment in the presence of anionic surfactant sodium dodecylbenzene sulfonate (SDBS) in artificial seawater was studied. Batch method was used to investigate the kinetic and thermodynamic behaviors. The results showed that the sorption rate and sorption capacity increased with the increasing initial concentration of SDBS. The sorption rate equations could be described by the pseudo-second-order model. The sorption isotherms were in good agreement with the Freundlich model. Higher salinity and lower temperature of the medium were favorable to the process. In the temperature range of 283-308K, the values of thermodynamic parameters were estimated, such as the deltaG(theta), deltaH(theta), deltaS(theta) which had significantly negative values in the presence of SDBS than those without SDBS. The sorption process was a spontaneous and exothermic reaction, and the randomness was decreased during the process. PMID:22279917

  7. Competitive Sorption and Desorption of Chlorinated Organic Solvents (DNAPLs) in Engineered Natural Organic Matter

    SciTech Connect

    Tang, Jixin; Weber, Walter J., Jr.

    2004-03-31

    The effects of artificially accelerated geochemical condensation and maturation of natural organic matter on the sorption and desorption of trichloroethylene (TCE) and tetrachloroethylene (PCE) were studied. The sorption and desorption of TCE in the presence and absence of the competing PCE and 1,2-dichlorobenzene (DCB) were also examined. A sphagnum peat comprising geologically young organic matter was artificially ''aged'' using superheated water, thus increasing the aromaticity and the degree of condensation of its associated organic matter. The sorption of all solutes tested were increased remarkably and their respective desorptions reduced, by the aged peat. The sorption capacities and isotherm nonlinearities of the peat for both TCE and PCE were found to increase as treatment temperature increased. In the competitive sorption studies, both PCE and DCB were found to depress TCE sorption, with PCE having greater effects than DCB, presumably because the molecular structure o f the former is more similar to that of TCE.

  8. Sensitivity, Specificity, and the Hybridization Isotherms of DNA Chips

    PubMed Central

    Halperin, A.; Buhot, A.; Zhulina, E.B.

    2004-01-01

    Competitive hybridization, at the surface and in the bulk, lowers the sensitivity of DNA chips. Competitive surface hybridization occurs when different targets can hybridize with the same probe. Competitive bulk hybridization takes place when the targets can hybridize with free complementary chains in the solution. The effects of competitive hybridization on the thermodynamically attainable performance of DNA chips are quantified in terms of the hybridization isotherms of the spots. These relate the equilibrium degree of the hybridization to the bulk composition. The hybridization isotherm emerges as a Langmuir isotherm modified for electrostatic interactions within the probe layer. The sensitivity of the assay in equilibrium is directly related to the slope of the isotherm. A simpler description is possible, in terms of c50 values specifying the bulk composition corresponding to 50% hybridization at the surface. The effects of competitive hybridization are important for the quantitative analysis of DNA chip results, especially when used to study point mutations. PMID:14747310

  9. 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

  10. Sorption of Lincomycin by Manure-Derived Biochars from Water.

    PubMed

    Liu, Cheng-Hua; Chuang, Ya-Hui; Li, Hui; Teppen, Brian J; Boyd, Stephen A; Gonzalez, Javier M; Johnston, Cliff T; Lehmann, Johannes; Zhang, Wei

    2016-03-01

    The presence of antibiotics in agroecosystems raises concerns about the proliferation of antibiotic-resistant bacteria and adverse effects to human health. Soil amendment with biochars pyrolized from manures may be a win-win strategy for novel manure management and antibiotics abatement. In this study, lincomycin sorption by manure-derived biochars was examined using batch sorption experiments. Lincomycin sorption was characterized by two-stage kinetics with fast sorption reaching quasi-equilibrium in the first 2 d, followed by slow sorption over 180 d. The fast sorption was primarily attributed to surface adsorption, whereas the long-term slow sorption was controlled by slow diffusion of lincomycin into biochar pore structures. Two-day sorption experiments were performed to explore effects of biochar particle size, solid/water ratio, solution pH, and ionic strength. Lincomycin sorption to biochars was greater at solution pH 6.0 to 7.5 below the dissociation constant of lincomycin (7.6) than at pH 9.9 to 10.4 above its dissociation constant. The enhanced lincomycin sorption at lower pH likely resulted from electrostatic attraction between the positively charged lincomycin and the negatively charged biochar surfaces. This was corroborated by the observation that lincomycin sorption decreased with increasing ionic strength at lower pH (6.7) but remained constant at higher pH (10). The long-term lincomycin sequestration by biochars was largely due to pore diffusion plausibly independent of solution pH and ionic composition. Therefore, manure-derived biochars had lasting lincomycin sequestration capacity, implying that biochar soil amendment could significantly affect the distribution, transport, and bioavailability of lincomycin in agroecosystems. PMID:27065399

  11. Bacterial sorption of heavy metals.

    PubMed Central

    Mullen, M D; Wolf, D C; Ferris, F G; Beveridge, T J; Flemming, C A; Bailey, G W

    1989-01-01

    Four bacteria, Bacillus cereus, B. subtilis, Escherichia coli, and Pseudomonas aeruginosa, were examined for the ability to remove Ag+, Cd2+, Cu2+, and La3+ from solution by batch equilibration methods. Cd and Cu sorption over the concentration range 0.001 to 1 mM was described by Freundlich isotherms. At 1 mM concentrations of both Cd2+ and Cu2+, P. aeruginosa and B. cereus were the most and least efficient at metal removal, respectively. Freundlich K constants indicated that E. coli was most efficient at Cd2+ removal and B. subtilis removed the most Cu2+. Removal of Ag+ from solution by bacteria was very efficient; an average of 89% of the total Ag+ was removed from the 1 mM solution, while only 12, 29, and 27% of the total Cd2+, Cu2+, and La3+, respectively, were sorbed from 1 mM solutions. Electron microscopy indicated that La3+ accumulated at the cell surface as needlelike, crystalline precipitates. Silver precipitated as discrete colloidal aggregates at the cell surface and occasionally in the cytoplasm. Neither Cd2+ nor Cu2+ provided enough electron scattering to identify the location of sorption. The affinity series for bacterial removal of these metals decreased in the order Ag greater than La greater than Cu greater than Cd. The results indicate that bacterial cells are capable of binding large quantities of different metals. Adsorption equations may be useful for describing bacterium-metal interactions with metals such as Cd and Cu; however, this approach may not be adequate when precipitation of metals occurs. Images PMID:2515800

  12. Moisture Sorption and Thermodynamic Properties of Vacuum-Dried Capsosiphon fulvescens Powder

    PubMed Central

    Zuo, Li; Rhim, Jong-Whan; Lee, Jun Ho

    2015-01-01

    The moisture sorption isotherms of vacuum-dried edible green alga (Capsosiphon fulvescens) powders were determined at 25, 35, and 45°C and water activity (aw) in the range of 0.11~0.94. An inversion effect of temperature was found at high water activity (>0.75). Various mathematical models were fitted to the experimental data, and Brunauer, Emmett, and Teller model was found to be the most suitable model describing the relationship between equilibrium moisture content and water activity (<0.45). Henderson model could also provide excellent agreement between the experimental and predicted values despite of the intersection point. Net isosteric heat of adsorption decreased from 15.77 to 9.08 kJ/mol with an increase in equilibrium moisture content from 0.055 to 0.090 kg H2O/kg solids. The isokinetic temperature (Tβ) was 434.79 K, at which all the adsorption reactions took place at the same rate. The enthalpy-entropy compensation suggested that the mechanism of the adsorption process was shown to be enthalpy-driven. PMID:26451360

  13. Moisture Sorption and Thermodynamic Properties of Vacuum-Dried Capsosiphon fulvescens Powder.

    PubMed

    Zuo, Li; Rhim, Jong-Whan; Lee, Jun Ho

    2015-09-01

    The moisture sorption isotherms of vacuum-dried edible green alga (Capsosiphon fulvescens) powders were determined at 25, 35, and 45°C and water activity (a w) in the range of 0.11~0.94. An inversion effect of temperature was found at high water activity (>0.75). Various mathematical models were fitted to the experimental data, and Brunauer, Emmett, and Teller model was found to be the most suitable model describing the relationship between equilibrium moisture content and water activity (<0.45). Henderson model could also provide excellent agreement between the experimental and predicted values despite of the intersection point. Net isosteric heat of adsorption decreased from 15.77 to 9.08 kJ/mol with an increase in equilibrium moisture content from 0.055 to 0.090 kg H2O/kg solids. The isokinetic temperature (T β) was 434.79 K, at which all the adsorption reactions took place at the same rate. The enthalpy-entropy compensation suggested that the mechanism of the adsorption process was shown to be enthalpy-driven. PMID:26451360

  14. Investigation of the water sorption properties of Mars-relevant micro- and mesoporous minerals

    NASA Astrophysics Data System (ADS)

    Jänchen, Jochen; Bish, David L.; Möhlmann, Diedrich T. F.; Stach, Helmut

    2006-02-01

    Encouraged by recent results of the Mars Odyssey spacecraft mission and the OMEGA team (Mars Express) concerning water in equatorial latitudes between ±45° on Mars and the possible existence of hydrated minerals, we have investigated the water sorption properties of natural zeolites and clay minerals close to martian atmospheric surface conditions as well as the properties of Mg-sulfates and gypsum. To quantify the stability of hydrous minerals on the martian surface and their interaction with the martian atmosphere, the water adsorption and desorption properties of nontronite, montmorillonite, chabazite and clinoptilolite have been investigated using adsorption isotherms at low equilibrium water vapor pressures and temperatures, modeling of the adsorption equilibrium data, thermogravimetry (TG), differential scanning calorimetry (DSC), and proton magic angle spinning nuclear magnetic resonance measurements ( 1H MAS NMR). Mg-sulfate hydrates were also analyzed using TG/DSC methods to compare with clay mineral and zeolites. Our data show that these microporous minerals can remain hydrated under present martian atmospheric conditions and hold up to 2.5-25 wt% of water in their void volumes at a partial water vapor pressure of 0.001 mbar in a temperature range of 333-193 K. Results of the 1H MAS NMR measurements suggest that parts of the adsorbed water are liquid-like water and that the mobility of the adsorbed water might be of importance for adsorption-water-triggered chemistry and hypothetical exobiological activity on Mars.

  15. Equilibrium and kinetic models on the adsorption of Reactive Black 5 from aqueous solution using Eichhornia crassipes/chitosan composite.

    PubMed

    El-Zawahry, Manal M; Abdelghaffar, Fatma; Abdelghaffar, Rehab A; Hassabo, Ahmed G

    2016-01-20

    New natural biopolymer composite was prepared using extracted cellulose from an environmentally problematic water hyacinth Eichhornia crassipes (EC). The extracted cellulose was functionalized by chitosan and TiO2 nanoparticles to form EC/Chitosan (EC/Cs) composite network. Surface characterization of EC/Cs natural biopolymer composite was examined by spectrum analysis FT-IR, specific surface area, micropore volume, pore width and SEM. Furthermore, the sorption experiments were carried out as a function of pH, various initial dye concentration and contact time. Experiment results showed that the EC/Cs composite have high ability to remove C.I. Reactive Black 5 from its dye-bath effluent. The equilibrium sorption evaluation of RB5 conformed and fitted well to Langmuir adsorption isotherm models and the maximum sorption capacity was 0.606 mg/g. The kinetic adsorption models followed pseudo-second order model and the dye intra-particle diffusion may suggesting a chemical reaction mechanism. Further, it was obvious from the investigation that this composite could be applied as a promising low cost adsorbent for anionic dye removal from aqueous solutions. PMID:26572382

  16. Adsorption of Zn2+ ions onto NaA and NaX zeolites: kinetic, equilibrium and thermodynamic studies.

    PubMed

    Nibou, D; Mekatel, H; Amokrane, S; Barkat, M; Trari, M

    2010-01-15

    The adsorption of Zn(2+) onto NaA and NaX zeolites was investigated. The samples were synthesized according to a hydrothermal crystallization using aluminium isopropoxide (Al[OCH(CH(3))(2)](3)) as a new alumina source. The effects of pH, initial concentration, solid/liquid ratio and temperature were studied in batch experiments. The Freundlich and the Langmuir models were applied and the adsorption equilibrium followed Langmuir adsorption isotherm. The uptake distribution coefficient (K(d)) indicated that the Zn(2+) removal was the highest at minimum concentration. Thermodynamic parameters were calculated. The negative values of standard enthalpy of adsorption revealed the exothermic nature of the adsorption process whereas the negative activation entropies reflected that no significant change occurs in the internal structure of the zeolites solid matrix during the sorption of Zn(2+). The negative values of Gibbs free energy were indicative of the spontaneity of the adsorption process. Analysis of the kinetic and rate data revealed that the pseudo second-order sorption mechanism is predominant and the intra particle diffusion was the determining step for the sorption of zinc ions. The obtained optimal parameters have been applied to wastewater from the industrial zone (Algeria) in order to remove the contained zinc effluents. PMID:19773115

  17. Effects of biochar and clay amendment on nutrient sorption of an Arenosol in semi-arid NE-Brazil

    NASA Astrophysics Data System (ADS)

    Beusch, Christine; Kaupenjohann, Martin

    2014-05-01

    In the semi-arid Northeast of Brazil nutrient-poor Arenosol with a low capacity to retain water and nutrients is the predominant soil type. Our aim is to provide a long-term melioration of the soils with locally available and inexpensive materials. We hypothesize an increase in nutrient sorption by the addition of biochar and clay. We conducted adsorption experiments according to OECD 106 batch equilibrium method in order to test this hypothesis. Sandy Arenosol, locally produced pyrolized biochar made of Prosopis juliflora, and a clayey Vertisol with a clay content of 69.8 %, all from our project area in Pernambuco, NE-Brazil, were used. The percentage of biochar and Vertisol added were 0 % (pure Arenosol), 1 %, 2.5 %, 5 %, 10 %, 100 % (pure biochar respectively Vertisol). Samples were shaken for 24 hours in a 1:5 solid-solution ratio in six different concentrations of Ammonium-N, Nitrate-N (0 - 25 mg L-1 each), Phosphorus (0 - 19.8 mg L-1) and Potassium (0 - 50 mg L-1). These concentrations were chosen to represent a common range of nutrients in a prevalent quaternary fertilization scheme of N:P:K of 1:0.4:1, with half NH4-N and NO3-N each. Then, where possible, sorption isotherms according to Langmuir were derived. Addition of biochar and Vertisol only showed marginal effects on Ammonium sorption. We detected a high loss of Ammonium with pure biochar, we assume loss of gaseous NH3. High rates of biochar addition caused Nitrate retention. Biochar increased P sorption with a maximum adsorption capacity (qmax) of 27.35 mg kg-1 for the 5 % amendment, although some P was leached out (up to 1.58 mg kg-1 for the 10 % addition). Phosphate sorption on Vertisol was even higher with a qmax for the 5 % addition of 60.77 mg kg-1. Potassium did not sorb to biochar, but was strongly leached out (84.19 mg kg-1 out of the 5 % addition). For Vertisol we observed a strong Potassium sorption that is linear within the concentration range we tested. A possible enhancement of nutrient

  18. Comparative biosorption of Mn(II) and Pb(II) ions on raw and oxalic acid modified maize husk: kinetic, thermodynamic and isothermal studies

    NASA Astrophysics Data System (ADS)

    Adeogun, Abideen Idowu; Idowu, Mopelola Abidemi; Ofudje, Andrew Edwin; Kareem, Sarafadeen Olateju; Ahmed, Sikiru Akinyeye

    2013-03-01

    Maize husk, an abundant agricultural waste was used to prepare a biosorbent for the biosorption of Mn(II) and Pb(II) ions from aqueous solution in a batch process. Equilibrium and kinetics of biosorption of the metals ions were studied at 25 °C. The adsorbtion data were treated with common kinetic and isotherm models. The equilibrium data fitted well with Langmuir isotherm with maximum capacity of 8.52 and 7.38 mg g-1 for Mn(II) and Pb(II), respectively on raw biomass (UTCS). The capacity of 9.00 and 9.33 mg g-1 was observed for Mn(II) and Pb(II), respectively on acid modified biomass (ATCS). The study also revealed that the sorption process in both cases depend on biomass dosage, temperature, pH and initial metal ion concentration, respectively. The calculated thermodynamic parameters (∆ G o, ∆ H o and ∆ S o) showed that the biosorption of the metal ions onto maize husk is feasible, spontaneous and exothermic in nature.

  19. Sorption of isoflavones to river sediment and model sorbents and outcomes for larval fish exposed to contaminated sediment.

    PubMed

    Kelly, Megan M; Rearick, Daniel C; Overgaard, Camilla G; Schoenfuss, Heiko L; Arnold, William A

    2015-01-23

    Isoflavones are compounds whose presence in the aquatic environment is increasingly recognized and may be of concern due to their potential to act as endocrine disruptors. Sorption to particles may be a relevant removal mechanism for isoflavones. This work investigated the influence of pH, ionic strength, and sediment composition on sorption of genistein and daidzein, two key isoflavones, using sorption isotherms and edges. The effect of sorbed isoflavones on the survival, growth, and predator avoidance performance of larval fathead minnows (Pimephales promelas) was assessed. Sorption to goethite and kaolinite was pH-dependent, with a maximum near pH 7 for both compounds. Sorption to montmorillonite was ionic-strength dependent but largely pH-independent. Overall, sorption to sediments is likely to sequester less than 5% of isoflavones in a discharge. No statistically significant effects were observed for larvae exposed to sorbed isoflavones, suggesting that sorption to sediments reduces exposure to isoflavones. PMID:24792866

  20. Sorption of water by bidisperse mixtures of carbohydrates in glassy and rubbery states.

    PubMed

    Ubbink, Job; Giardiello, Maria-Isabelle; Limbach, Hans-Jörg

    2007-09-01

    Water sorption by bidisperse carbohydrate mixtures consisting of varying ratios of a narrow-molecular-weight distribution maltopolymer and the disaccharide maltose is investigated to establish a quantitative relation between the composition of the carbohydrate system and the water sorption isotherm. The sorption of water is approached from two limiting cases: the glassy state at low water content and the dilute aqueous carbohydrate solution. In the glassy state, the water content at a given water activity decreases with increasing maltose content of the matrix, whereas in the rubbery state it increases with increasing maltose content. The water sorption behavior in the glassy state is quantified using a variety of models, including the often-utilized but physically poorly founded Guggenheim-Anderson-de Boer model, several variants of the free-volume theory of sorption by glassy polymers, and a two-state sorption model introduced in the present paper. It is demonstrated that both the free-volume models and the two-state sorption model, which all encompass the Flory-Huggins theory for the rubbery-state sorption but which differ in their modeling of the glassy-state sorption, provide a physically consistent foundation for the analysis of water sorption by the carbohydrate matrixes. PMID:17691841

  1. Impact of coal structural heterogeneity on the nonideal sorption of organic contaminants.

    PubMed

    Shi, Xin; Fu, Heyun; Li, Yuan; Mao, Jingdong; Zheng, Shourong; Zhu, Dongqiang

    2011-06-01

    Carbonaceous geosorbents (black carbon, coal, and humin/kerogen) play a primary role in the nonideal sorption (isotherm nonlinearity, hysteresis, and multiphasic kinetics) of hydrophobic organic chemicals by soils and sediments. The present study investigated the impact of coal structural heterogeneity on sorption/desorption of two model monoaromatic compounds (1,3-dichlorobenzene and 1,3-dinitrobenzene). Due to the higher degree of aromaticity and condensation, anthracite showed stronger sorption affinity and nonlinearity and slower sorption kinetics than lignite. Removal of humic substances by alkali extraction and/or mineral fraction by acidification did not much affect organic carbon-normalized sorption coefficient to the coal, suggesting nearly complete accessibility of adsorption sites on the condensed organic carbon. However, the treatments greatly increased sorption kinetics and meanwhile alleviated hysteresis of 1,3-dinitrobenzene, as compared with the original lignite. These observations were attributed to the enhanced exposure of high-energy adsorption sites on the condensed organic carbon after exfoliating the surface coverage by humic substances and minerals. An empirical biphasic pseudo-second-order model consisting of a fast sorption phase and a slow sorption phase adequately quantified the overall sorption kinetics for the coal sorbents. The results indicated that the condensed organic carbon, in combination with other structural components, controls the nonideal sorption of unburned coal. PMID:21425302

  2. COSOLVENT EFFECTS ON SORPTION AND MOBILITY OF ORGANIC CONTAMINANTS IN SOILS

    EPA Science Inventory

    Batch equilibrium and column miscible displacement techniques were used to investigate the influence of an organic cosolvent (methanol) on the sorption and transport of three hydrophobic organic chemicals (HOCs) — naphthalene, phenanthrene, and diuron herbicide — in a sandy surfa...

  3. Water sorption by proteins: milk and whey proteins.

    PubMed

    Kinsella, J E; Fox, P F

    1986-01-01

    The content and physical state of water in foods influence their physical, chemical, quality, safety, and functional behavior. Information concerning the sorption behavior of dairy proteins, in the water activity (Aw) range 0 to 0.9, is collated in this paper. The sorption behavior of proteins in general, the kinetics of absorption, factors affecting water binding, the phenomenon of desorption hysteresis, and the chemical and physical nature of water/protein interactions are reviewed in general terms. This is followed by a discussion of thermodynamic aspects of sorption phenomena and the adequacy of the various equations for describing sorption isotherms of proteins. After a discussion of the methods available for measuring sorption by milk proteins, the sorption behavior of various milk protein preparations, i.e., nonfat dry milk, whey proteins, caseins, and milk powders is summarized. Finally, the water activity of cheese and its relationship to solute mobility and solvent water are discussed. Some of the unique features of protein behavior, i.e., conformational changes, swelling, and solubilization are cited as possible sources of disparities between various reports. PMID:3527564

  4. Sorption and degradation of bisphenol A by aerobic activated sludge.

    PubMed

    Zhao, Junming; Li, Yongmei; Zhang, Chaojie; Zeng, Qingling; Zhou, Qi

    2008-06-30

    Laboratory-scale batch experiments were conducted to investigate the sorption and degradation of bisphenol A (BPA) at microg/L range in an aerobic activated sludge system. The sorption isotherms and thermodynamics indicated that the sorption of BPA on sludge was mainly a physical process in which partitioning played a dominating role. The values of sorption coefficient Koc were between 621 and 736 L/kg in the temperature range of 10-30 degrees C. Both mixed liquor suspended solid (MLSS) and temperature influenced BPA sorption on sludge. The degradation of BPA by acclimated activated sludge could be described by first-order reaction equation with the first-order degradation rate constant of 0.80 h(-1) at 20 degrees C. The decrease of initial COD concentration and the increase of MLSS concentration and temperature enhanced BPA degradation rate. The removal of BPA in the activated sludge system was characterized by a quick sorption on the activated sludge and subsequent biodegradation. PMID:18179868

  5. Persistence and sorption of fipronil degradates in urban stream sediments.

    PubMed

    Lin, Kunde; Haver, Darren; Oki, Lorence; Gan, Jay

    2009-07-01

    Fipronil, an increasingly popular insecticide used for urban pest control, is known to readily transform into several degradates that generally have similar or greater toxicity to aquatic organisms than the parent compound. However, knowledge on the fate of these degradates in the environment is obscure. In the present study, degradation kinetics and sorption of desthiofipronil, fipronil sulfide, and fipronil sulfone were investigated in urban stream sediments. All degradates showed enhanced persistence in sediments compared to fipronil under facultative or anaerobic conditions. Under facultative conditions, the estimated half-lives of desthiofipronil, fipronil sulfide, and fipronil sulfone were 217 to 497, 195 to 352, and 502 to 589 d, respectively. Under anaerobic conditions, the corresponding half-lives were over one year in one sediment, while no detectable degradation occurred in the other two sediments after 280 d. Sorption isotherms of fipronil and its degradates in the sediments were linear, with mean K(OC) values of 802, 1,296, 3,684, and 3,543 L/kg for fipronil, desthiofipronil, fipronil sulfide, and fipronil sulfone, respectively, suggesting that the degradates generally have a higher sorption capacity than fipronil. Sorption coefficient K(d) increased up to fourfold over 280 d, suggesting an aging effect on sorption. The inherent toxicity, long persistence, and strong sorption potential highlight the importance for a better understanding of the sediment toxicity of fipronil degradates in surface water bodies. PMID:19215184

  6. Sorption of Cr(VI) by Amberlite XAD-7 resin impregnated with brilliant green and its determination by quercetin as a selective spectrophotometric reagent.

    PubMed

    Hosseini, Mohammad Saeid; Hosseini-Bandegharaei, Ahmad; Raissi, Haidar; Belador, Foroogh

    2009-09-30

    A new chelating polymeric sorbent as an extractant-impregnated resin (EIR) has been developed using brilliant green (BG) and Amberlite XAD-7 resin. The BG-impregnated resin showed superior binding affinity for Cr(VI) in the presence of many co-existing ions and no considerable interference was observed. The influence of various physicochemical parameters on the recovery of Cr(VI) were optimized by both static and dynamic methods. The Langmuir adsorption isotherm gave a satisfactory fit of the equilibrium data. The kinetic studies performed for Cr(VI) sorption revealed that <45 min was sufficient for reaching equilibrium metal ion sorption. A preconcentration factor of 100 was found for the column-mode extraction. The spectrophotometric determination of eluted Cr(VI) was carried out using quercetin as a selective reagent. The calibration graphs were linear in the range 5.0 x 10(-8) to 4.0 x 10(-7)M with a detection limit of 8 x 10(-9)M. The proposed method has been successfully employed for the analysis of natural water. The recoveries for the Cr(VI) amounts spiked to the samples were >93%, which confirmed accuracy of the measurements. PMID:19380195

  7. Impact of highly basic solutions on sorption of Cs + to subsurface sediments from the Hanford site, USA

    NASA Astrophysics Data System (ADS)

    Ainsworth, C. C.; Zachara, J. M.; Wagnon, K.; McKinley, S.; Liu, C.; Smith, S. C.; Schaef, H. T.; Gassman, P. L.

    2005-10-01

    The effect of caustic NaNO 3 solutions on the sorption of 137Cs to a Hanford site micaceous subsurface sediment was investigated as a function of base exposure time (up to 168 d), temperature (10°C or 50°C), and NaOH concentration (0.1 mol/L to 3 mol/L). At 10°C and 0.1 M NaOH, the slow evolution of [Al] aq was in stark contrast to the rapid increase and subsequent loss of [Al] aq observed at 50°C (regardless of base concentration). Exposure to 0.1 M NaOH at 10°C for up to 168 d exhibited little if any measurable effect on sediment mineralogy, Cs + sorption, or Cs + selectivity; sorption was well described with a two-site ion exchange model modified to include enthalpy effects. At 50°C, dissolution of phyllosilicate minerals increased with [OH]. A zeolite (tetranatrolite; Na 2Al 2Si 3O 10·2H 2O) precipitated in 0.1 M NaOH after about 7 days, while an unnamed mineral phase (Na 14Al 12Si 13O 51·6H 2O) precipitated after 4 and 2 days of exposure to 1 M and 3 M NaOH solutions, respectively. Short-term (16 h) Cs + sorption isotherms (10 -9-10 -2 mol/L) were measured on sediment after exposure to 0.1 M NaOH for 56, 112, and 168 days at 50°C. There was a trend toward slightly lower conditional equilibrium exchange constants (Δlog NaCsK c ˜ 0.25) over the entire range of surface coverage, and a slight loss of high affinity sites (15%) after 168 days of pretreatment with 0.1 M base solution. Cs + sorption to sediment over longer times was also measured at 50°C in the presence of NaOH (0.1 M, 1 M, and 3 M NaOH) at Cs + concentrations selected to probe a range of adsorption densities. Model simulations of Cs + sorption to the sediment in the presence of 0.1 M NaOH for 112 days slightly under-predicted sorption at the lower Cs + adsorption densities. At the higher adsorption densities, model simulations under-predicted sorption by 57%. This under-prediction was surmised to be the result of tetranatrolite precipitation, and subsequent slow Na → Cs exchange. At

  8. Lead sorption-desorption from organic residues.

    PubMed

    Duarte Zaragoza, Victor M; Carrillo, Rogelio; Gutierrez Castorena, Carmen M

    2011-01-01

    Sorption and desorption are mechanisms involved in the reduction of metal mobility and bioavailability in organic materials. Metal release from substrates is controlled by desorption. The capacity of coffee husk and pulp residues, vermicompost and cow manure to adsorb Pb2+ was evaluated. The mechanisms involved in the sorption process were also studied. Organic materials retained high concentrations of lead (up to 36,000 mg L(-1)); however, the mechanisms of sorption varied according to the characteristics of each material: degree of decomposition, pH, cation exchange capacity and percentage of organic matter. Vermicompost and manure removed 98% of the Pb from solution. Lead precipitated in manure and vermicompost, forming lead oxide (PbO) and lead ferrite (PbFe4O7). Adsorption isotherms did not fit to the typical Freundlich and Langmuir equations. Not only specific and non-specific adsorption was observed, but also precipitation and coprecipitation. Lead desorption from vermicompost and cow manure was less than 2%. For remediation of Pb-polluted sites, the application of vermicompost and manure is recommended in places with alkaline soils because Pb precipitation can be induced, whereas coffee pulp residue is recommended for acidic soils where Pb is adsorbed. PMID:21780703

  9. CO2 Sorption to Subsingle Hydration Layer Montmorillonite Clay Studied by Excess Sorption and Neutron Diffraction Measurements

    SciTech Connect

    Rother, Gernot; Ilton, Eugene S.; Wallacher, Dirk; Hauβ, Thomas; Schaef, Herbert T.; Qafoku, Odeta; Rosso, Kevin M.; Felmy, Andrew R.; Krukowski, Elizabeth G.; Stack, Andrew G.; Grimm, Nico; Bodnar, Robert J.

    2013-01-02

    Geologic storage of CO2 requires that the caprock sealing the storage rock is highly impermeable to CO2. Swelling clays, which are important components of caprocks, may interact with CO2 leading to volume change and potentially impacting the seal quality. The interactions of supercritical (sc) CO2 with Na saturated montmorillonite clay containing a subsingle layer of water in the interlayer region have been studied by sorption and neutron diffraction techniques. The excess sorption isotherms show maxima at bulk CO2 densities of ≈0.15 g/cm3, followed by an approximately linear decrease of excess sorption to zero and negative values with increasing CO2 bulk density. Neutron diffraction experiments on the same clay sample measured interlayer spacing and composition. The results show that limited amounts of CO2 are sorbed into the interlayer region, leading to depression of the interlayer peak intensity and an increase of the d(001) spacing by ca. 0.5 Å. The density of CO2 in the clay pores is relatively stable over a wide range of CO2 pressures at a given temperature, indicating the formation of a clay-CO2 phase. Finally, at the excess sorption maximum, increasing CO2 sorption with decreasing temperature is observed while the high-pressure sorption properties exhibit weak temperature dependence.

  10. CO2 sorption to subsingle hydration layer montmorillonite clay studied by excess sorption and neutron diffraction measurements.

    PubMed

    Rother, Gernot; Ilton, Eugene S; Wallacher, Dirk; Hauβ, Thomas; Schaef, Herbert T; Qafoku, Odeta; Rosso, Kevin M; Felmy, Andrew R; Krukowski, Elizabeth G; Stack, Andrew G; Grimm, Nico; Bodnar, Robert J

    2013-01-01

    Geologic storage of CO(2) requires that the caprock sealing the storage rock is highly impermeable to CO(2). Swelling clays, which are important components of caprocks, may interact with CO(2) leading to volume change and potentially impacting the seal quality. The interactions of supercritical (sc) CO(2) with Na saturated montmorillonite clay containing a subsingle layer of water in the interlayer region have been studied by sorption and neutron diffraction techniques. The excess sorption isotherms show maxima at bulk CO(2) densities of ≈ 0.15 g/cm(3), followed by an approximately linear decrease of excess sorption to zero and negative values with increasing CO(2) bulk density. Neutron diffraction experiments on the same clay sample measured interlayer spacing and composition. The results show that limited amounts of CO(2) are sorbed into the interlayer region, leading to depression of the interlayer peak intensity and an increase of the d(001) spacing by ca. 0.5 Å. The density of CO(2) in the clay pores is relatively stable over a wide range of CO(2) pressures at a given temperature, indicating the formation of a clay-CO(2) phase. At the excess sorption maximum, increasing CO(2) sorption with decreasing temperature is observed while the high-pressure sorption properties exhibit weak temperature dependence. PMID:22917276

  11. Hydrophobic conjugated microporous polymers for sorption of human serum albumin

    NASA Astrophysics Data System (ADS)

    Zheng, Chunli; Du, Miaomiao; Feng, Shanshan; Sun, Hanxue; Li, An; He, Chi; Zhang, TianCheng; Wang, Qiaorui; Wei, Wei

    2016-02-01

    This paper investigated the sorption of human serum albumin (HSA) from water by three kinds of conjugated microporous polymers (CMPs) with surface hydrophobicity and intrinsic porosity. It was found that the three CMPs captured HSA with fast sorption kinetics and good working capacity. Equilibrium was obtained at 80 min for all the tests, and the maximum sorption quantity (qm) ranged from 0.07 to 0.14 mg/mg. With the increase in the particle external surface area of the CMPs, a greater extent of HSA sorption was achieved. Moreover, promoting the dispersion of CMPs in HSA aqueous solution was also beneficial to the extraction. Attenuated Total Reflection Fourier Transform Infrared spectroscopy verified the interactions between the CMPs and the Nsbnd H, Cdbnd O, and Csbnd N groups of HSA. This paper might provide fundamental guidance for the practical application of CMPs to proteins separation and recovery.

  12. Sorption and desorption of sulfentrazone in Brazilian soils.

    PubMed

    Passos, Ana Beatriz R J; Freitas, Marco Antonio M; Torres, Lívia G; Silva, Antonio A; Queiroz, Maria Eliana L R; Lima, Cláudio F

    2013-01-01

    This study was undertaken to obtain information about the behavior of sulfentrazone in soil by evaluating the sorption and desorption of the herbicide in different Brazilian soils. Batch equilibrium method was used and the samples were analyzed by high performance liquid chromatography. Based on the results obtained from the values of Freundlich constants (Kf), we determined the order of sorption (Haplic Planosol < Red-Yellow Latosol < Red Argisol < Humic Cambisol < Regolitic Neosol) and desorption (Regolitic Neosol < Red Argisol < Humic Cambisol < Haplic Planosol < Red-Yellow Latosol) of sulfentrazone in the soils. The process of pesticide sorption in soils was dependent on the levels of organic matter and clay, while desorption was influenced by the organic matter content and soil pH. Thus, the use of sulfentrazone in soils with low clay content and organic matter (low sorption) increases the probability of contaminating future crops. PMID:23638891

  13. Carbon Dioxide Transport and Sorption Behavior in Confined Coal Cores for Carbon Sequestration

    SciTech Connect

    Jikich, Sinisha; McLendon, Robert; Seshadri, Kal; Irdi, Gino; Smith, Duane

    2009-01-01

    Measurements of sorption isotherms and transport properties of carbon dioxide (CO2) in coal cores are important for designing enhanced coalbed-methane/CO2-sequestration field projects. Sorption isotherms measured in the laboratory can provide the upper limit on the amount of CO2 that might be sorbed in these projects. Because sequestration sites will most likely be in unmineable coals, many of the coals will be deep and under considerable lithostatic and hydrostatic pressures. These lithostatic pressures may reduce the sorption capacities and/or transport rates significantly. Consequently, we have studied apparent sorption and diffusion in a coal core under confining pressure. A core from the important bituminous coal Pittsburgh #8 was kept under a constant, 3D effective stress; the sample was scanned by X-ray computer tomography (CT) before, then while, it sorbed CO2. Increases in sample density because of sorption were calculated from the CT images. Moreover, density distributions for small volume elements inside the core were calculated and analyzed. Qualitatively, the CT showed that gas sorption advanced at different rates in different regions of the core. and that diffusion and sorption progressed slowly. The amounts of CO2 sorbed were plotted vs. position (at fixed times) and vs. time (for various locations in the sample). The resulting sorption isotherms were compared to isotherms obtained from powdered coal from the same Pittsburgh #8 extended sample. The results showed that for this single coal at specified times, the apparent sorption isotherms were dependent on position of the volume element in the core and the distance from the CO2 source. Also, the calculated isotherms showed that less CO2 was sorbed than by a powdered (and unconfined) sample of the coal. Changes in density distributions during the experiment were also observed. After desorption, the density distribution of calculated

  14. Isothermally heatsunk diffusion cloud chamber refrigerator

    SciTech Connect

    Menocal, S.G.

    1987-05-05

    This patent describes a diffusion cloud chamber isothermally heatsunk refrigerator which comprises: a heatsink consisting of two phases of a saturated substance existing in thermodynamic equilibrium at constant pressure and therefore at constant temperature, contained in a reservoir; a means of pressure damping to maintain constant pressure, as the ratio of the two phases present changes and introduces volumetric changes in the substance; a cooling member which transfer heat from vapor in contact with the cooling member surface to the ''cold side'' of a Peltier thermoelectric element with which the cooling member is in thermal contact; a Peltier thermoelectric element which removes the heat supplied by the cooling member from its ''cold side'' and pumps it to the ''hot side'' when driven by an electric current; and a means of transferring heat from the ''hot side'' of the Peltier thermoelectric element to the two-phase isothermal substance in the reservoir.

  15. Study of sorption and swelling on block coals

    NASA Astrophysics Data System (ADS)

    Qu, Shijie; Chen, Guoqing; Yang, Jianli; Shen, Wenzhong; Li, Yunmei; Niu, Hongxian; Busch, Andreas

    2013-04-01

    Reducing CO2 emission into atmosphere is very important for the mitigation of global climate change. Many processes have been proposed for this purpose, including CO2 sequestration in un-minable coalbeds and enhance coalbed methane production (CO2-ECBM). Several theoretical studies and worldwide demonstration sites have illustrated the potential of the process.Most of these projects experienced permeability reduction of the coalbed with time, leading to operational difficulties because of the loss of injectability. The permeability reduction is generally considered to be caused by the coal swelling that is induced by gas sorption, because it can narrow or close the cleat of the coalbed. As a result, the migration of injected CO2 in coal pore or cleat becomes more difficult. Therefore, sorption and swelling characterizations are important issues for forecasting the performance of aimed coalbed. In this work, CO2/CH4sorption and swelling isotherms of two Chinese block coals (QS and YQ) were measured simultaneously under different temperature and pressure conditions. It was found that the swelling ratio of coal block by CO2 sorption increased with the increase of the gas sorption amount until it approached to a value of ~3 mmol-gas/g-coal and decreased slightly afterwards for both coals; while the swelling ratio of coal block by CH4 sorption increased with the increase of the gas sorption amount in the entire test region for both coals. By correlating the gas sorption amount and the corresponding swelling ratio, it was found that the swelling ratio of coal block is independent of temperature and coal type when the gas sorption amount is less than ~2mmol/g-coal. The differential profile of the swelling ratio with respect to sorption amount is appeared with a maximum value at ~1 mmol/g-coal for CH4 and at ~1.8 mmol/g-coal for CO2. Based on the theories related to gas sorption and solid surface energy, a mathematical model which correlates sorption and swelling behavior

  16. Sorption Properties of Iron-Magnesium and Nickel-Magnesium Mg2FeH6 and Mg2NiH4 Hydrides

    NASA Astrophysics Data System (ADS)

    Matysina, Z. A.; Zaginaichenko, S. Yu.; Shchur, D. V.; Gabdullin, M. T.

    2016-06-01

    Based on molecular-kinetic representations, theory of hydrogen absorption-desorption processes in binary Mg-Fe and Mg-Ni alloys is developed. Free energies of hydrides of these alloys are calculated. Equations of their thermodynamically equilibrium state determining the P-T-c diagrams are derived. A temperature dependence of the desorbed hydrogen concentration is established. A maximal desorption temperature is estimated. The state diagrams determining the concentration dependence of the maximal desorption temperature are constructed. Isopleths and isotherms of hydrogen solubility in the alloys are calculated. The possibility of manifestation of the hysteresis effect in hydrogen solubility isotherms is revealed and the decrease of the width and length of a hysteresis loop with increasing temperature is demonstrated together with the influence of the magnesium hydrate MgH2 in Mg2FeH6 samples and running of chemical reactions on the behavior of the isotherms and the occurrence of bends and jumps in them. All established functional dependences of the sorption properties of the examined alloys are compared with experimental data available from the literature.

  17. Sorption of heavy metals by the soil fungi 'Aspergillus niger' and Mucor rouxii

    SciTech Connect

    Mullen, M.D.; Wolf, D.C.; Beveridge, T.J.; Bailey, G.W.

    1992-01-01

    Sorption of the nitrate salts of cadmium(II), copper(II), lanthanum(III) and silver(I) by two fungi, Aspergillus niger and Mucor rouxii, was evaluated using Freundlich adsorption isotherms and energy dispersive X-ray electron microscopy. The linearized Freundlich isotherm described the metal sorption data well for metal concentrations of 5 microM-1 mM metal. Differences in metal binding were observed among metals, as well as between fungal species. Calculated Freundlich K values indicated that metal binding decreased in the order La(3+) > or = Ag(+) > Cu(2+) > Cd(2+). However, sorption of Ag(+) was greater than that of La(3+) from solutions of 0.1 and 1 mM metal and likely due to precipitation at the cell wall surface. At the 1 mM initial concentration, there were no significant differences between the two fungi in metal sorption, except for Ag(+) binding. At the 5 microM concentration, there was no difference between the fungi in their sorption capacities for the four metals. Electron microscopy-energy dispersive X-ray analysis indicated that silver precipitated onto cells as colloidal silver. The results indicate that Freundlich isotherms may be useful for describing short-term metal sorption by fungal biomass and for comparison with other soil constituents in standardized systems. (Copyright (c) 1992 Pergamon Press plc.)

  18. Hydrogen sorption rate by intermetallic compounds suitable for tritium storage

    SciTech Connect

    Penzhorn, R.D.; Sirch, M.; Perevezentsev, A.N.; Borisenko, A.N.

    1995-10-01

    The kinetics of the sorption of molecular hydrogen by ZrCo and Zr{sub 0.8}Ti{sub 0.3}Mn{sub 1.9} was investigated as function of temperature at several constant pressures of hydrogen. A comparison between the isothermal hydrogen sorption rates by ZrCo, Zr{sub 0.8}Ti{sub 0.3}Mn{sub 1.9} and LaNi{sub 4.7}Al{sub 0.3} is given and reaction mechanisms are discussed. From fittings of the experimental results to well known gas/solid reaction rate laws it was concluded that the reaction mechanisms of the reaction with ZrCo is complex and dependent upon the prevailing reaction conditions. The hydrogen sorption rate by the powder of all three IMC`s was found to be second order in hydrogen pressure. 8 refs., 7 figs., 1 tab.

  19. Carbon dioxide sorption capacities of coal gasification residues.

    PubMed

    Kempka, Thomas; Fernández-Steeger, Tomás; Li, Dong-Yong; Schulten, Marc; Schlüter, Ralph; Krooss, Bernhard M

    2011-02-15

    Underground coal gasification is currently being considered as an economically and environmentally sustainable option for development and utilization of coal deposits not mineable by conventional methods. This emerging technology in combination with carbon capture and sorptive CO2 storage on the residual coke as well as free-gas CO2 storage in the cavities generated in the coal seams after gasification could provide a relevant contribution to the development of Clean Coal Technologies. Three hard coals of different rank from German mining districts were gasified in a laboratory-scale reactor (200 g of coal at 800 °C subjected to 10 L/min air for 200 min). High-pressure CO2 excess sorption isotherms determined before and after gasification revealed an increase of sorption capacity by up to 42%. Thus, physical sorption represents a feasible option for CO2 storage in underground gasification cavities. PMID:21210659

  20. The sorption of Zectran on bottom sediments and peat moss

    SciTech Connect

    Matthews, E.W.; Faust, S.D.

    1981-01-01

    A modified analytical method employed to determine the insecticide Zectran in natural waters frequently has resulted in erroneous data. The errors have been attributed to interferences from particulate matter in these waters. In order to evaluate analytical interferences due to sorption of Zectran on particulates, a series of experiments was performed using bottom sediments and a peat moss in contact with aqueous solutions of zectran at a pH values of 6.0 and 20 degrees C. Isotherm studies confirmed that Zectran sorption occurs in a direct relation to the amount of chemically oxidizable carbon present in the bottom sediments or peat moss. However, the extent of sorption was limited, which suggested that particulates may not be the primary interference in the modified analytical method.

  1. Oxyanion sorption and surface anion exchange by surfactant-modified clay minerals

    SciTech Connect

    Li, Z.

    1999-10-01

    In this study the sorption of nitrate (NO{sub 2}{sup {minus}}) and chromate (CrO{sub 4}{sup 2{minus}}) from aqueous solution by surfactant-modified clay minerals was investigated. Both the sorption and desorption of oxyanions were found to follow a Langmuir sorption isotherm. In general, the sorption affinity is higher for chromate than for nitrate, reflecting that the interaction between the divalent anions and the surfactant bilayer is stronger than that between the monovalent anions and the surfactant bilayer. Surfactant-modified kaolinite has a higher sorption capacity for chromate. The sorption capacities for chromate and nitrate are equal for surfactant-modified illite while the sorption capacity for nitrate is higher for surfactant-modified smectite. Desorption by water revealed that chromate sorption was irreversible, while nitrate sorption was slightly reversible. In a mixed solution system, nitrate and chromate compete for the same sorption sites, resulting in a decrease in sorption capacity for each anion. Stoichiometric counterion desorption due to chromate and/or nitrate sorption further confirms that sorption of oxyanions by surfactant-modified clay minerals was due to surface anion exchange. The selectivity coefficients were higher for chromate to replace bromide than for nitrate to replace bromide for surfactant-modified kaolinite, but lower when surfactant-modified illite and smectite were the anion exchangers. The results indicate that surfactant-modified clay minerals are effective sorbents to remove anionic contaminants from water. However, the types of clay minerals should be correctly selected to maximize the contaminant removal efficiency.

  2. Kinetics of sorption of uranium(VI) compounds with zirconium-silica nanosorbents

    NASA Astrophysics Data System (ADS)

    Perlova, O. V.; Sazonova, V. F.; Perlova, N. A.; Yaroshenko, N. A.

    2014-06-01

    The kinetics of sorption of uranium(VI) compounds from sulfate and carbonate solutions using four samples of mesoporous zirconium-silica nanosorbents obtained by bitemplate (solubilization) synthesis was studied. The sorption equilibrium set-in time and the kinetic characteristics of sorption were shown to depend on the sorbent (its composition, specific surface area, dispersity, and pore size), the temperature, and the composition and pH of the solution from which uranium compounds are sorbed. The sorption kinetics was described by a first-order equation. The limiting stage of the process was found to be the external diffusion of uranium-containing particles to the sorbent surface.

  3. Partition Equilibrium

    NASA Astrophysics Data System (ADS)

    Feldman, Michal; Tennenholtz, Moshe

    We introduce partition equilibrium and study its existence in resource selection games (RSG). In partition equilibrium the agents are partitioned into coalitions, and only deviations by the prescribed coalitions are considered. This is in difference to the classical concept of strong equilibrium according to which any subset of the agents may deviate. In resource selection games, each agent selects a resource from a set of resources, and its payoff is an increasing (or non-decreasing) function of the number of agents selecting its resource. While it has been shown that strong equilibrium exists in resource selection games, these games do not possess super-strong equilibrium, in which a fruitful deviation benefits at least one deviator without hurting any other deviator, even in the case of two identical resources with increasing cost functions. Similarly, strong equilibrium does not exist for that restricted two identical resources setting when the game is played repeatedly. We prove that for any given partition there exists a super-strong equilibrium for resource selection games of identical resources with increasing cost functions; we also show similar existence results for a variety of other classes of resource selection games. For the case of repeated games we identify partitions that guarantee the existence of strong equilibrium. Together, our work introduces a natural concept, which turns out to lead to positive and applicable results in one of the basic domains studied in the literature.

  4. 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 ...

  5. Metal sorption on kaolinite

    SciTech Connect

    Westrich, H.R.; Brady, P.V.; Cygan, R.T.; Nagy, K.L.; Anderson, H.L.

    1997-03-01

    A key issue in performance assessment of low-level radioactive waste sites is predicting the transport and retardation of radionuclides through local soils under a variety of hydrologic and geochemical conditions. Improved transport codes should include a mechanistic model of radionuclide retardation. The authors have been investigating metal sorption (Cs{sup +}, Sr{sup 2+}, and Ba{sup 2+}) on a simple clay mineral (kaolinite) to better understand the geochemical interactions of common soil minerals with contaminated groundwaters. These studies include detailed characterizations of kaolinite surfaces, experimental adsorption measurements, surface complexation modeling, and theoretical simulations of cation sorption. The aluminol edge (010) site has been identified as the most likely site for metal sorption on kaolinite in natural solutions. Relative metal binding strengths decrease from Ba{sup 2+} to Sr{sup 2+} to Cs{sup +}, with some portion sorbed on both kaolinite edges and basal surfaces. Some Cs{sup +} also appears to be irreversibly sorbed on both sites. Molecular dynamics simulations suggest that Cs{sup +} is sorbed at aluminol (010) edge sites as an inner-sphere complex and weakly sorbed as an outer-sphere complex on (001) basal surfaces. These results provide the basis to understand and predict metal sorption onto kaolinite, and a framework to characterize sorption processes on more complex clay minerals.

  6. Adsorption of surfactants on sand surface in enhanced oil recovery: Isotherms, kinetics and thermodynamic studies

    NASA Astrophysics Data System (ADS)

    Bera, Achinta; Kumar, T.; Ojha, Keka; Mandal, Ajay

    2013-11-01

    Adsorption of surfactants onto reservoir rock surface may result in the loss and reduction of their concentrations in surfactant flooding, which may render them less efficient or ineffective in practical applications of enhanced oil recovery (EOR) techniques. Surfactant flooding for EOR received attraction due to its ability to increase the displacement efficiency by lowering the interfacial tension between oil and water and mobilizing the residual oil. This article highlights the adsorption of surfactants onto sand surface with variation of different influencing factors. It has been experimentally found that adsorption of cationic surfactant on sand surface is more and less for anionic surfactant, while non-ionic surfactant shows intermediate behaviour. X-ray diffraction (XRD) study of clean sand particles has been made to determine the main component present in the sand particles. The interaction between sand particles and surfactant has been studied by Fourier Transform Infrared (FTIR) Spectroscopy of the sand particles before and after aging with surfactant. Salinity plays an important role in adsorption of anionic surfactant. Batch experiments were also performed to understand the effects of pH and adsorbent dose on the sorption efficiency. The sand particles exhibited high adsorption efficiency at low pH for anionic and nonionic surfactants. But opposite trend was found for cationic surfactant. Adsorption data were analyzed by fitting with Langmuir, Freundlich, Redlich-Peterson, and Sips isotherm models. Results show that the Langmuir isotherm and pseudo-second order kinetics models suit the equilibrium and kinetics of adsorption on sand surface. Thermodynamics feasibility of the adsorption process was also studied to verify the spontaneity of the process.

  7. Adsorption isotherms and kinetics of activated carbons produced from coals of different ranks.

    PubMed

    Purevsuren, B; Lin, Chin-Jung; Davaajav, Y; Ariunaa, A; Batbileg, S; Avid, B; Jargalmaa, S; Huang, Yu; Liou, Sofia Ya-Hsuan

    2015-01-01

    Activated carbons (ACs) from six coals, ranging from low-rank lignite brown coal to high-rank stone coal, were utilized as adsorbents to remove basic methylene blue (MB) from an aqueous solution. The surface properties of the obtained ACs were characterized via thermal analysis, N2 isothermal sorption, scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and Boehm titration. As coal rank decreased, an increase in the heterogeneity of the pore structures and abundance of oxygen-containing functional groups increased MB coverage on its surface. The equilibrium data fitted well with the Langmuir model, and adsorption capacity of MB ranged from 51.8 to 344.8 mg g⁻¹. Good correlation coefficients were obtained using the intra-particle diffusion model, indicating that the adsorption of MB onto ACs is diffusion controlled. The values of the effective diffusion coefficient ranged from 0.61 × 10⁻¹⁰ to 7.1 × 10⁻¹⁰ m² s⁻¹, indicating that ACs from lower-rank coals have higher effective diffusivities. Among all the ACs obtained from selected coals, the AC from low-rank lignite brown coal was the most effective in removing MB from an aqueous solution. PMID:25909729

  8. 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). PMID:19799057

  9. Effect of humic acid on the sorption of perfluorooctane sulfonate (PFOS) and perfluorobutane sulfonate (PFBS) on boehmite.

    PubMed

    Wang, Fei; Shih, Kaimin; Leckie, James O

    2015-01-01

    The sorption of PFOS and PFBS on boehmite was significantly retarded by the competitive sorption of humic acid (HA), implying that PFOS and PFBS are likely more mobile in water and groundwater systems enriched with HA. The sorption behavior of PFOS and PFBS on the HA-modified boehmite surface were also found to differ due to their different chain lengths. For a partially HA-modified boehmite surface, the isotherm study showed that PFOS had a much higher maximum sorption capacity than PFBS and that PFOS might possess additional surface interactions besides electrostatic interaction. For a HA-saturated boehmite, a linear sorption isotherm was found for PFOS while nearly no PFBS sorption was observed. This indicates that sorption behavior between PFOS and the sorbed HA on boehmite was dominated by hydrophobic interactions, instead of electrostatic interaction. In addition, a conceptual model combining hydrophobic and electrostatic interaction was established to explain the sorption behavior of PFOS and PFBS on HA-modified boehmite. Finally, the results revealed that the sorption of PFOS and PFBS on HA-modified boehmite is pH-dependent. The neutralization of negative sites on HA-modified boehmite reduced the electrostatic repulsion and enhanced the partitioning of PFBS on the sorbed HA. PMID:25268321

  10. Kinetics of sorption of lead on bed sediments of River Hindon, India.

    PubMed

    Sharma, M K; Jain, C K; Singhal, D C; Choubey, V K

    2009-10-01

    A number of low cost waste sorbent have been used for removal of heavy metals, however, few studies have been carried out on the sorption process on riverbed sediments in their natural state of occurrence. Stream sediments adsorb certain solutes from streams, thereby significantly changing the solute composition, but little is known about quantitatively describing sorption phenomena and rates of these processes. In the present investigation, sorption of lead ions on river bed sediments of river Hindon, a tributary of river Yamuna, India has been studied to demonstrate the role of bed sediments in controlling metal pollution. The effect of various operating variables, viz., initial concentration, solution pH, sediment dose, contact time and particle size has been studied. The sorption of lead ions increased with respect to pH and sorbent dose and decreased with sorbent particle size. Two important geochemical phases, iron and manganese oxide, also play important role in the sorption process. The sorption data were analysed using Langmuir and Freundlich isotherm models to determine the mechanistic parameters related to the sorption process. Further, although lead ions have more affinity for the fine fraction of the sediment, but the overall contribution of coarser fraction to sorption is more as compared to clay and silt fraction. The kinetic data suggest that the sorption of lead on bed sediments is an endothermic process, which is spontaneous at low temperature. The uptake of lead is controlled by both bulk and intraparticle diffusion mechanism. PMID:18791802

  11. Capacity and mechanisms of ammonium and cadmium sorption on different wetland-plant derived biochars.

    PubMed

    Cui, Xiaoqiang; Hao, Hulin; Zhang, Changkuan; He, Zhenli; Yang, Xiaoe

    2016-01-01

    The objective of this study was to investigate the relationship between Cd(2+)/NH4(+) sorption and physicochemical properties of biochars produced from different wetland plants. Biochars from six species of wetland plants (i.e., Canna indica, Pennisetum purpureum Schum, Thalia dealbata, Zizania caduciflora, Phragmites australis and Vetiveria zizanioides) were obtained at 500°C and characterized, and their sorption for ammonium and cadmium was determined. There were significant differences in elemental composition, functional groups and specific surface area among the biochars derived from different wetland plant species. Sorption of ammonium and cadmium on the biochars could be described by a pseudo second order kinetic model, and the simple Langmuir model fits the isotherm data better than the Freundlich or Temkin model. The C. indica derived biochar had the largest sorption capacity for NH4(+) and Cd(2+), with a maximum sorption of 13.35 and 125.8mgg(-1), respectively. P. purpureum Schum derived biochar had a similar maximum sorption (119.3mgg(-1)) for Cd(2+). Ammonium sorption was mainly controlled by cation exchange, surface complexation with oxygen-containing functional groups and the formation of magnesium ammonium phosphate compounds, whereas for Cd(2+) sorption, the formation of cadmium phosphate precipitates, cation exchange and binding to oxygen-containing groups were the major possible mechanisms. In addition, the sorption of ammonium and cadmium was not affected by surface area and microporosity of the biochars. PMID:26386447

  12. Effect of fly ash on sorption behavior of metribuzin in agricultural soils.

    PubMed

    Singh, Neera; Raunaq; Singh, Shashi B

    2012-01-01

    This investigation was undertaken to determine the effect of two different fly ashes [Kota and Inderprastha (IP)] amendment on the sorption behavior of metribuzin in three Indian soil types. The IP fly ash was very effective in increasing the metribuzin sorption in the soils. The sorption with IP amendment was increased by 15-92%, whereas with the Kota fly ash an increase in sorption by 13-38% was noted. The adsorption isotherms fitted very well to the Freundlich adsorption equation and, in general, slope (1/n) values less then unity were observed. Although both the fly ashes significantly decreased metribuzin desorption, the IP fly ash was comparatively more effective in retaining metribuzin in the soils. Metribuzin sorption in the IP fly ash-amended soils showed strong correlation with the fly ash content and compared to K(f)/K(d) values, K(FA) values (sorption normalized to fly ash content) showed less variation. Metribuzin sorption-desorption did not correlate to the organic carbon content of the soil-fly ash mixture. The study demonstrates that all coal fly ashes may not be effective in enhancing the sorption of metribuzin in soils to the same extent. However, among the fly ashes used in this study, the IP fly ash was observed to be significantly effective in enhancing the sorption of metribuzin in soils. This may play an important role in reducing the run off and leaching losses of the herbicide by retaining it in the soil. PMID:22251208

  13. Effect of ten quaternary ammonium cations on tetrachloromethane sorption to clay from water

    USGS Publications Warehouse

    Smith, J.A.

    1990-01-01

    The mineral surface of Wyoming bentonite (clay) was modified by replacing inorganic ions by each of 10 quaternary ammonium compounds, and tetrachloromethane sorption to the modified sorbents from water was studied. Tetrachloromethane sorption from solution to clay modified with tetramethyl-, tetraethyl-, benzyltrimethyl-, or benzyltriethylammonium cations generally is characterized by relatively high solute uptake, isotherm nonlinearity, and competitive sorption (with trichloroethene as the competing sorbate). For these sorbents, the ethyl functional groups yield reduced sorptive capacity relative to methyl groups, whereas the benzyl group appears to have a similar effect on sorbent capacity as the methyl group. Sorption of tetrachloromethane to clay modified with dodecyldimethyl(2-phenoxyethyl)-, dodecyltrimethyl-, tetradecyltrimethyl-, hexadecyltrimethyl-, or benzyldimethylhexadecylammonium bromide is characterized by relatively low solute uptake, isotherm linearity, and noncompetitive sorption. For these sorbents, an increase in the size of the nonpolar functional group(s) causes an increase in the organic carbon normalized sorption coefficient (Koc). No measurable uptake of tetrachloromethane sorption by the unmodified clay or clay modified by ammonium bromide was observed. ?? 1990 American Chemical Society.

  14. Sorption of lead by settling pond soils after reclamation treatments

    NASA Astrophysics Data System (ADS)

    Asensio, Verónica; Forján, Rubén; Vega, Flora A.; Andrade, Luisa; Covelo, Emma F.

    2013-04-01

    The reclamation of degraded soils adding waste amendments can add significant concentrations of Pb. Because of this, it is important to know the sorption capacity of Pb by the soils where wastes with high concentrations of this metal are applied. To determine the sorption capacity of Pb by mine soils, before and after reclamation treatments, four different sites were selected at a settling pond mine zone: an untreated one as the control sample (B1), a vegetated one with pines for 21 years (B2v), a vegetated with eucalyptus for 6 years (B3v) and an amended with sewage sludges and paper mill residues for 5 months (B4w). All soils had one horizon except B4w, where twice were sampled (B4Aw and B4Bw). The B4Bw is considered analogous of the control soil. To evaluate the sorption capacity by the soils, sorption isotherms were constructed using single-metal solutions of Pb2+ nitrates (0.03, 0.05, 0.08, 0.1 and 0.5 mmol L-1) containing 0.01 M NaNO3 as background electrolyte (Vega et al., 2009). The overall capacity of the soil to sorb Pb was evaluated as the slope Kr (Vega et al., 2008). The obtained results show that the sorption isotherm of Pb by control soil (B1) and its analogous (B4Bw) are of L-type curve, whereas the sorption isotherms of the treated soils (B2v, B3v and B4Aw) are of H-type curve (Giles et al., 1974). The most of the obtained isotherms do not fit with the models of Langmuir or Freundlich, therefore sorption capacity was evaluated by Kr parameter. According to the obtained Kr parameter, B1 and B4Bw have the lowest Pb sorption capacity (Kr = 0.480 and 0.556, respectively), which increased two times after recently waste amending (B4Aw; Kr = 0.998). The vegetated sites (B2v and B3v) also have higher sorption capacity than B1, but lower than B4Aw (Kr = 0.692 and 0.725, respectively). The highest sorption capacity of Pb by the amended soil is due to its characteristics such as high pH and organic carbon content. This is corroborated by the significantly

  15. Helical equilibrium

    SciTech Connect

    Yoshikawa, S.

    1981-08-01

    A straight, helical plasma equilibrium equation is solved numerically for a plasma with a helical magnetic axis. As is expected, by a suitable choice of the plasma boundary, the vacuum configuration is made line ..integral.. dl/B stable. As the plasma pressure increases, the line ..integral.. dl/B criterion will improve (again as expected). There is apparently no limit on the plasma ..beta.. from the equilibrium consideration. Thus helical-axis stellarator ..beta.. will presumably be limited by MHD stability ..beta.., and not by equilibrium ..beta...

  16. CO2 Isotherms Measured on Moisture-Equilbrated Argonne Premium Coals at 550C and 15 Mpa

    SciTech Connect

    Goodman, A.L.

    2007-05-01

    Sorption isotherms, which describe the coal’s gas storage capacity, are important for estimating the carbon sequestration potential of coal seams. The DOE-NETL initiated a second inter-laboratory isotherm comparison of coals where CO2 sorption isotherms were collected on moisture-equilibrated coals at temperatures and pressures relevant to CO2 sequestration. Each laboratory used the same coal samples and followed the same general procedure; however, each laboratory used their own apparatus and isotherm measurement technique. This study investigated the inter-laboratory reproducibility of carbon dioxide isotherm measurements on moisture-equilibrated Argonne premium coal samples (Pocahontas #3, Illinois #6, and Beulah Zap). Six independent laboratories provided isotherm data on the three moisture-equilibrated coal samples at 55oC and pressures up to 15 MPa. Agreement among the laboratories was good up to 8 MPa. At the higher pressures, the data among the laboratories diverged significantly for two of the laboratories and coincided reasonably well for four of the laboratories. This work provides guidance for estimating the reproducibility that might be expected when comparing published sorption isotherms on moisture-equilibrated coals from different laboratories.

  17. Status Of Sorption Cryogenic Refrigeration

    NASA Technical Reports Server (NTRS)

    Jones, Jack A.

    1988-01-01

    Report reviews sorption refrigeration. Developed for cooling infrared detectors, cryogenic research, and other advanced applications, sorption refrigerators have few moving parts, little vibration, and lifetimes of 10 years or more. Describes types of sorption stages, multistage and hybrid refrigeration systems, power requirements, cooling capacities, and advantages and disadvantages of various stages and systems.

  18. When dissolved is not truly dissolved--the importance of colloids in studies of metal sorption on organic matter.

    PubMed

    Schijf, Johan; Zoll, Alison M

    2011-09-01

    In controlled metal sorption experiments, the equilibrium distribution coefficient is a key variable quantifying sorbate partitioning across the solid-solution interface. Separation of metals into 'dissolved' and 'particulate' fractions is commonly achieved with syringe filtration, where the boundary is somewhat arbitrarily dictated by the limited selection of available pore sizes. Investigations involving natural organic matter, such as bacterial cells or plant tissues, are especially prone to experimental artifacts if the substrate releases abundant colloidal compounds that contribute to sorption by binding free metal cations in a pH-dependent fashion yet pass through conventional filters, causing the truly dissolved fraction to be grossly overestimated. We observed this phenomenon during a study of lanthanide sorption on a marine macroalga, Ulva lactuca, as a function of pH. At low ionic strength, distribution coefficients calculated for a 0.22-μm size cutoff falsely imply that metal sorption reverses to gradual release above pH 4.6, instead of continuing to increase. Centrifuging the filtrates in Amicon® Ultra units (30 and 3 kDa molecular weight cutoff) revealed a mounting proportion of colloid-bound metal, constituting up to 95% of the 'dissolved' (<0.22 μm) fraction near pH 8. Measurements of DOC concentrations suggest this being due to pH-dependent binding of free metal cations to a fixed pool of organic colloids. The process is well described with a simple 2-site Langmuir isotherm in 0.05, 0.5, and 5.0M NaCl. Using this model to correct the original distribution coefficients not only removed the spurious reversal at low ionic strength, but also uncovered a prominent suppressive effect on the intermediate and high ionic strength data that had initially gone undetected. Ultra-filtration may thus be an essential analytical tool for proper characterization and interpretation of metal sorption on organic matter over a wide range of experimental conditions

  19. Effects of hydrodynamic conditions on the sorption behaviors of aniline on sediment with coexistence of nitrobenzene.

    PubMed

    Wang, Peng; Hua, Zulin; Cai, Yunjie; Shen, Xia; Li, Qiongqiong; Liu, Xiaoyuan

    2015-08-01

    The sorption behaviors of pollutants affected by hydrodynamic conditions were confirmed in natural water environment. The effects of hydrodynamic conditions on the sorption behaviors of aniline on sediment with coexistence of nitrobenzene were investigated. The particle entrainment simulator (PES) was used to simulate varied bottom shear stresses. The batch equilibrium method was applied to the experiments with the stress levels and the action time controlled at 0.2-0.5 N/m(2) and 24 h, respectively. The findings indicated that apparent partition coefficient of aniline on sediment increased with the shear stress significantly, while decreased with nitrobenzene concentration. On the contrary, both the sorption amount of aniline on suspended particulate matter (Q s) and the effect of nitrobenzene concentration on Q s declined as the shear stress increased. The sorption kinetic results showed that the sorption process followed the pseudo-second-order kinetics equation, and the process included two stages: fast sorption stage and slow sorption stage, among which the average sorption rate of fast stage was 7.5-9.5 times that of slow one. The effect of shear stress on the average sorption rate of aniline was enhanced with the increase of nitrobenzene concentration. And shear stress weakened the disturbance of cosolute on main solute sorption process. In addition, experiment results of sorption kinetic show that only the initial sorption rate was affected by shear stress and cosolute concentration. In the first 5 min, shear stress had positive effects on the sorption rate. After that, the sorption rate barely changed with shear stress and cosolute concentration. PMID:25843823

  20. Phenylurea herbicide sorption to biochars and agricultural soil

    PubMed Central

    WANG, DAOYUAN; MUKOME, FUNGAI N. D.; YAN, DENGHUA; WANG, HAO; SCOW, KATE M.; PARIKH, SANJAI J.

    2016-01-01

    Biochar is increasingly been used as a soil amendment to improve water holding capacity, reduce nutrient leaching, increase soil pH and also as a means to reduce contamination through sorption of heavy metals or organic pollutants. The sorption behavior of three phenylurea herbicides (monuron, diuron, linuron) on five biochars (Enhanced Biochar, Hog Waste, Turkey Litter, Walnut Shell and Wood Feedstock) and an agricultural soil (Yolo silt loam) was investigated using a batch equilibration method. Sorption isotherms of herbicides to biochars were well described by the Freundlich model (R2 = 0.93 -- 0.97). The adsorption KF values ranged from 6.94 to 1306.95 mg kg−1 and indicated the sorption of herbicides in the biochars and Yolo soil was in the sequence of linuron > diuron > monuron and walnut shell biochar > wood feedstock biochar > turkey litter biochar > enhanced biochar > hog waste biochar > Yolo soil. These data show that sorption of herbicides to biochar can have both positive (reduced off-site transport) and negative (reduced herbicide efficacy) implications and specific biochar properties, such as H/C ratio and surface area, should be considered together with soil type, agriculture chemical and climate condition in biochar application to agricultural soil to optimize the system for both agricultural and environmental benefits. PMID:26065514

  1. Arsenate sorption on monohydrocalcite by coprecipitation during transformation to aragonite.

    PubMed

    Fukushi, Keisuke; Sakai, Minoru; Munemoto, Takashi; Yokoyama, Yuka; Takahashi, Yoshio

    2016-03-01

    The metastability of monohydrocalcite (CaCO3·H2O: MHC) suggests high reactivity to dissolved trace elements. Using kinetic and isotherm sorption experiments with different reaction times (24h, 48h), As(V) sorption on MHC was examined to elucidate As(V) uptake by MHC. Although the MHC was transformed to aragonite with time, the MHC in higher As(V) loading conditions was able to persist longer than in lower loading conditions. Actually, As(V) uptake was negligible for samples in which the MHC remained. However, remarkable uptake of As(V) was observed for samples in which a complete transformation of MHC to aragonite occurred. Results of kinetic study confirmed that the timing of the MHC transformation coincided perfectly with that of As(V) removal from the solution. XAFS measurements showed that the local structure of As after the MHC transformation was almost identical to that of As in the As(V) coprecipitated aragonite. Sorption behavior of As(V) during the transformation is explainable theoretically by the substitution of As(V) into the aragonite structure. The distribution coefficient and (apparent) maximum sorption capacity of As(V) sorption on MHC after 48h at low-to-moderate As(V) concentrations are 500L/kg and 25μmol/g, respectively, which are much higher than those of simple adsorption of As(V) on calcite. PMID:26547619

  2. Moisture sorption characteristics of freeze-dried human platelets.

    PubMed

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

    2011-03-01

    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) m(2)/s when experimental data at initial time were used. These results would be helpful in choosing prehydration and storage condition for FDHPs. PMID:21370506

  3. Sorption of tributyltin onto a natural quartz sand.

    PubMed

    Behra, Philippe; Lecarme-Théobald, Emilie; Bueno, Maïté; Ehrhardt, Jean-Jacques

    2003-07-01

    The aim of this study is to understand the sorption of tributyltin (TBT) onto natural quartz sand by classical batch experiments and spectroscopic surface analyses. At pH<6, the major species of TBT is the cation TBT(+). Due to the presence of both the cationic part and the butyl chains, TBT should present amphiphilic properties. For concentrations lower than 40 microM, TBT sorption occurs as a homovalent 1:1 cation exchange between either H(+) or Na(+) and TBT(+). The increasing affinity of TBT with respect to the different materials follows the series kaolinitesorption, it seems that inner-sphere surface complexes could be formed due to the increase in the 3d-level binding energy. At TBT concentrations higher than 100 microM, we showed by flotation experiments and XPS analysis that the surface becomes hydrophobic. After one monolayer was formed, the TBT sorption could thus be due to hydrophobic interaction between the butyl chains of the sorbed TBT and those of the TBT still available from the bulk solution. This mechanism is consistent with surface condensation and the shape of the sorption isotherm. PMID:12804878

  4. Chitosan sorbents for platinum sorption from dilute solutions

    SciTech Connect

    Guibal, E.; Larkin, A.; Vincent, T.; Tobin, J.M.

    1999-10-01

    Chitosan has proved efficient at removing platinum in dilute effluents. The maximum uptake capacity reaches 300 mg/g (almost 1.5 mmol/g). The optimum pH for sorption is pH 2. A glutaraldehyde cross-linking pretreatment is necessary to stabilize the biopolymer in acidic solutions. Sorption isotherms have been studied as a function of pH, sorbent particle size, and the cross-linking ratio. Surprisingly, the extent of the cross-linking (determined by the concentration of the cross-linking agent in the treatment bath) has no significant influence on uptake capacity. Competitor anions such as chloride or nitrate induce a large decrease in the sorption efficiency. Sorption kinetics show also that uptake rate is not significantly changed by increasing either the cross-linking ratio or the particle size of the sorbent. Mass transfer rates are significantly affected by the initial platinum concentration and by the conditioning of the biopolymer. Gel-bead conditioning appears to reduce the sorption rate. While for molybdate and vanadate ions, mass transfer was governed by intraparticle mass transfer, for platinum, both external and intraparticle diffusion control the uptake rate. In contrast with the former ions, platinum does not form polynuclear hydrolyzed species, which are responsible for steric hindrance of diffusion into the polymer network.

  5. Biosorption of lead (II) from water using heartwood charcoal of Areca catechu: equilibrium and kinetics studies

    NASA Astrophysics Data System (ADS)

    Haloi, Nabanita; Sarma, H. P.; Chakravarty, P.

    2013-09-01

    Present study was conducted to investigate the removal of Pb(II) from water by using heartwood charcoal of Areca catechu (HCAC). Batch experiments were conducted to determine the adsorption properties at different contact times (5-30 min), concentrations (0.1-10 mg/L), amounts of adsorbents (0.1-0.6 g), and in a range of pH 2-7. Most favorable biosorption condition was found at pH 5.0, 0.5 g biomass dosage and at 25 min equilibrium time. The experimental results were fitted to the Langmuir and Freundlich isotherm models; the Freundlich isotherm was found to well represent the measured sorption data implying HCAC has heterogeneous surface. Lagergren first-order and pseudo-second-order kinetic model were used to analyze the biosorption data; it was observed that the pseudo-second-order model best represented the relationship. Scanning electron microscopy image and energy dispersive X-ray analysis were also incorporated in support of the study. The result shows that HCAC has the potentiality to remove Pb(II) from water.

  6. Sorption vacuum trap

    NASA Technical Reports Server (NTRS)

    Barrington, A. E.; Caruso, A. J.

    1970-01-01

    Modified sorption trap for use in high vacuum systems contains provisions for online regeneration of sorbent material. Trap is so constructed that it has a number of encapsulated resistance heaters and a valving and pumping device for removing gases from heated sorbing material. Excessive downtime is eliminated with this trap.

  7. Measurement techniques for carbon dioxide sorption capacity on various coal samples: critical review

    NASA Astrophysics Data System (ADS)

    Abunowara, M.; Bustam, M. A.; Sufian, S.; Eldemerdash, U.

    2016-06-01

    Underground carbon sequestration is proposed as a geologic disposal technique for the long-term storage of CO2 emissions to mitigate climate change and air pollution. Coal bed seams have large CO2 adsorption capacity, long time CO2 trapping and extra enhanced coal-bed methane recovery (CBM). However, CO2 sorption capacity is one of significant steps required to be determined accurately in any feasibility evaluation of carbon sequestration. Hence, in lab scale, there are three methods for CO2 adsorption capacity measurements namely manometric/volumetric, gravimetric and new capsule techniques for gas sorption on variety of sorbents. The manometric and volumetric methods require accurate determination of cell and void volumes and suitable equation of state (EoS). The gravimetric method requires a very accurate sensitive balance and less buoyancy effect and it is the best technique for small amounts (milligrams) of sorbents and the adsorption equilibrium can be mentored. Among all gas adsorption measurement techniques, the newly developed method “capsule method” exhibits the highest CO2 adsorption capacity on Polish coal by 4.08 mmol/g because capsule method that directly measures CO2 uptake of solid coal matrix cylinders, without the application of the equation of state (EoS) for CO2 or volumetric corrections. The main advantage of capsule method is that it is independent of any Equation of State (EoS), and it has no volumetric effects or impurities distort the shape of the gas adsorption isotherm. The disadvantage of capsule method is time-consuming and it is not easy to implement.

  8. Sorption of Cu(II) complexes with ligands tartrate, glycine and quadrol by chitosan.

    PubMed

    Gyliene, Ona; Binkiene, Rima; Butkiene, Rita

    2009-11-15

    The sorption by chitosan in Cu(II) solutions containing tartrate, glycine (amino acetic acid) and quadrol (N,N,N',N'-tetrakis(2-hydroxypropyl)ethylenediamine) as ligands has been investigated. The degree of sorbate removal strongly depends on pH. In solutions containing tartrate almost complete sorption of both Cu(II) and tartrate proceeds in mildly acidic and neutral solutions. The sorption of Cu(II) is also complete in alkaline solutions containing glycine; meanwhile a substantial sorption of glycine proceeds at pH approximately 6. The Cu(II) sorption in solutions containing quadrol is insignificant. Any sorption of quadrol does not proceed in the whole range of pH investigated. The investigations under equilibrium conditions showed that the Cu(II) sorption from tartrate containing solutions obeys Freundlich equation and in solutions containing glycine and quadrol it fits Langmuir equation. Supposedly, Cu(II) sorption onto chitosan proceeds with formation of amino complexes onto the surface of chitosan; the sorption of tartrate proceeds as electrostatic as well as with formation of amide bonds. Applying of electrolysis enables a complete removal of sorbed Cu(II) and ligands without changes in physical and chemical properties of chitosan. This is confirmed by sorption ability of regenerated chitosan, measurements of its molecular weight, the deacetylation degree and FT-IR spectra. PMID:19540041

  9. Sorption and desorption of arsenate and arsenite on calcite

    NASA Astrophysics Data System (ADS)

    Sø, Helle U.; Postma, Dieke; Jakobsen, Rasmus; Larsen, Flemming

    2008-12-01

    The adsorption and desorption of arsenate (As(V)) and arsenite (As(III)) on calcite was investigated in a series of batch experiments in calcite-equilibrated solutions. The solutions covered a broad range of pH, alkalinity, calcium concentration and ionic strength. The initial arsenic concentrations were kept low (<33 μM) to avoid surface precipitation. The results show that little or no arsenite sorbs on calcite within 24 h at an initial As concentration of 0.67 μM. In contrast, arsenate sorbs readily and quickly on calcite. Likewise, desorption of arsenate from calcite is fast and complete within hours, indicating that arsenate is not readily incorporated into the calcite crystal lattice. The degree of arsenate sorption depends on the solution chemistry. Sorption increases with decreasing alkalinity, indicating a competition for sorption sites between arsenate and (bi)carbonate. pH also affects the sorption behavior, likely in response to changes in arsenate speciation or protonation/deprotonation of the adsorbing arsenate ion. Finally, sorption is influenced by the ionic strength, possibly due to electrostatic effects. The sorption of arsenate on calcite was modeled successfully using a surface complexation model comprising strong and weak sites. In the model, the adsorbing arsenate species were HAsO4- and CaHAsO40. The model was able to correctly predict the adsorption of arsenate in the wide range of calcite-equilibrated solutions used in the batch experiments and to describe the non-linear shape of the sorption isotherms. Extrapolation of the experimental results to calcite bearing aquifers suggests a large variability in the mobility of arsenic. Under reduced conditions, arsenite, which does not sorb on calcite, will dominate and, hence, As will be highly mobile. In contrast, when conditions are oxidizing, arsenate is the predominant species and, because arsenate adsorbs strongly on calcite, As mobility will be significantly retarded. The estimated

  10. Sorption of tylosin and sulfamethazine on solid humic acid.

    PubMed

    Guo, Xuetao; Tu, Bei; Ge, Jianhua; Yang, Chen; Song, Xiaomei; Dang, Zhi

    2016-05-01

    Tylosin (TYL) and sulfamethazine (SMT) are ionizable and polar antimicrobial compounds, which have seeped into the environment in substantial amounts via fertilizing land with manure or sewage. Sorption of TYL and SMT onto humic acid (HA) may affect their environmental fate. In this study, the sorption of TYL and SMT on HA at different conditions (pH, ionic strength) was investigated. All sorption isotherms fitted well to the Henry and Freundlich models and they were highly nonlinear with values of n between 0.5 and 0.8, which suggested that the HA had high heterogeneity. The sorption of TYL and SMT on HA decreased with increasing pH (2.0-7.5), implying that the primary sorption mechanism could be due to cation exchange interactions between TYL(+)/SMT(+) species and the functional groups of HA. Increasing ionic strength resulted in a considerable reduction in the Kd values of TYL and SMT, hinting that interactions between H bonds and π-π EDA might be an important factor in the sorption of TYL and SMT on HA. Results of Fourier transform infrared (FT-IR) and (13)C-nuclear magnetic resonance (NMR) analysis further demonstrated that carboxyl groups and O-alkyl structures in the HA could interact with TYL and SMT via ionic interactions and H bonds, respectively. Overall, this work gives new insights into the mechanisms of sorption of TYL and SMT on HA and hence aids us in assessing the environmental risk of TYL and SMT under diverse conditions. PMID:27155426

  11. 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.

  12. Adsorption Properties of Tetracycline onto Graphene Oxide: Equilibrium, Kinetic and Thermodynamic Studies

    PubMed Central

    Ghadim, Ehsan Ezzatpour; Manouchehri, Firouzeh; Soleimani, Gholamreza; Hosseini, Hadi; Kimiagar, Salimeh; Nafisi, Shohreh

    2013-01-01

    Graphene oxide (GO) nanoparticle is a high potential effective absorbent. Tetracycline (TC) is a broad-spectrum antibiotic produced, indicated for use against many bacterial infections. In the present research, a systematic study of the adsorption and release process of tetracycline on GO was performed by varying pH, sorption time and temperature. The results of our studies showed that tetracycline strongly loads on the GO surface via π–π interaction and cation–π bonding. Investigation of TC adsorption kinetics showed that the equilibrium was reached within 15 min following the pseudo-second-order model with observed rate constants of k2 = 0.2742–0.5362 g/mg min (at different temperatures). The sorption data has interpreted by the Langmuir model with the maximum adsorption of 323 mg/g (298 K). The mean energy of adsorption was determined 1.83 kJ/mol (298 K) based on the Dubinin–Radushkevich (D–R) adsorption isotherm. Moreover, the thermodynamic parameters such as ΔH°, ΔS° and ΔG° values for the adsorption were estimated which indicated the endothermic and spontaneous nature of the sorption process. The electrochemistry approved an ideal reaction for the adsorption under electrodic process. Simulation of GO and TC was done by LAMMPS. Force studies in z direction showed that tetracycline comes close to GO sheet by C8 direction. Then it goes far and turns and again comes close from amine group to the GO sheet. PMID:24302989

  13. Selective Sorption of Dissolved Organic Carbon Compounds by Temperate Soils

    SciTech Connect

    Jagadamma, Sindhu; Mayes, Melanie; Phillips, Jana Randolph

    2012-01-01

    Physico-chemical sorption of dissolved organic carbon (DOC) on soil minerals is one of the major processes of organic carbon (OC) stabilization in soils, especially in deeper layers. The attachment of C on soil solids is related to the reactivity of the soil minerals and the chemistry of the sorbate functional groups, but the sorption studies conducted without controlling microbial activity may overestimate the sorption potential of soil. This study was conducted to examine the sorptive characteristics of a diverse functional groups of simple OC compounds (D-glucose, L-alanine, oxalic acid, salicylic acid, and sinapyl alcohol) on temperate climate soil orders (Mollisols, Ultisols and Alfisols) with and without biological degradative processes. Equilibrium batch experiments were conducted using 0-100 mg C L-1 at a solid-solution ratio of 1:60 for 48 hrs and the sorption parameters were calculated by Langmuir model fitting. The amount of added compounds that remained in the solution phase was detected by high performance liquid chromatography (HPLC) and total organic C (TOC) analysis. Soil sterilization was performed by -irradiation technique and experiments were repeated to determine the contribution of microbial degradation to apparent sorption. Overall, Ultisols did not show a marked preference for apparent sorption of any of the model compounds, as indicated by a narrower range of maximum sorption capacity (Smax) of 173-527 mg kg soil-1 across compounds. Mollisols exhibited a strong preference for apparent sorption of oxalic acid (Smax of 5290 mg kg soil-1) and sinapyl alcohol (Smax of 2031 mg kg soil-1) over the other compounds. The propensity for sorption of oxalic acid is mainly attributed to the precipitation of insoluble Ca-oxalate due to the calcareous nature of most Mollisol subsoils and its preference for sinapyl alcohol could be linked to the polymerization of this lignin monomer on 2:2 mineral dominated soils. The reactivity of Alfisols to DOC was in

  14. Amphiphilic hollow carbonaceous microspheres for the sorption of phenol from water.

    PubMed

    Guan, Zhengrong; Liu, Li; He, Lilu; Yang, Sen

    2011-11-30

    Amphiphilic porous hollow carbonaceous spheres (PHCSs) were synthesized via mild hydrothermal treatment of yeast cells and further pyrolyzing post treatment. The morphology, chemical composition, porosity, and structure of the carbonaceous materials were investigated. It is evident that the carbonaceous materials were composed of the carbonized organic matter (COM) and the noncarbonized organic matter (NOM), and the relative COM and NOM fractions could be adjusted through changing the temperature of hydrothermal and/or pyrolyzing treatment. The phenol sorption properties of the carbonaceous materials had been investigated and the sorption isotherms fit well to the modified Freundlich equation. It was found that the sorption isotherm of phenol onto PHCSs was practically linear even at extreme high concentrations, which was fewer reported for activated carbon or other inorganic materials. This type of sorption isothermals was assigned to a partition mechanism, and the largest value of the partition coefficient (K(f)) and carbon-normalized K(f) (K(oc)) is 56.7 and 91.5 mL g(-1), respectively. Moreover, PHCSs exhibit fast sorption kinetic and facile regeneration property. The results indicate PHCSs are potential effective sorbents for removal of undesirable organic chemicals in wastewater, especially at high concentrations. PMID:21943920

  15. SORPTION OF 2,3,7,8-TETRACHLORODIBENZO-P-DIOXIN FROM WATER BY SURFACE SOILS

    EPA Science Inventory

    The sorption of 14C-labelcd 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) from water by two uncontaminated surface soils from the Times Beach, MO, area was evaluated by using batch shake testing. orption isotherm plots for the soil with the lower fraction organic carbon (foc) were l...

  16. SORPTION OF ARSENITE AND ARSENATE ON A HIGH AFFINITY OXIDE: MACROSCOPIC AND MICROSCOPIC STUDIES

    EPA Science Inventory

    Sorption of arsenate and arsenite was examined on a Ru compound using macroscopic and microscopic techniques. Isotherms were constructed from batch studies at pH 4 through 8. Solution As was measured by ICAP. Samples of the Ru compound were equilibrated with arsenite and arsenate...

  17. Hydrogen sorption characteristics of nanostructured Pd–10Rh processed by cryomilling

    DOE PAGESBeta

    Yang, Nancy; Yee, Joshua K.; Zhang, Zhihui; Kurmanaeva, Lilia; Cappillino, Patrick; Stavila, Vitalie; Lavernia, Enrique J.; San Marchi, Chris

    2014-10-03

    Palladium and its alloys are model systems for studying solid-state storage of hydrogen. Mechanical milling is commonly used to process complex powder systems for solid-state hydrogen storage; however, milling can also be used to evolve nanostructured powder to modify hydrogen sorption characteristics. In the present study, cryomilling (mechanical attrition milling in a cryogenic liquid) is used to produce nanostructured palladium-rhodium alloy powder. Characterization of the cryomilled Pd-10Rh using electron microscopy, X-ray diffraction, and surface area analysis reveals that (i) particle morphology evolves from spherical to flattened disk-like particles; while the (ii) crystallite size decreases from several microns to less thanmore » 100 nm and (iii) dislocation density increases with increased cryomilling time. Hydrogen absorption and desorption isotherms as well as the time scales for absorption were measured for cryomilled Pd-10Rh, and correlated with observed microstructural changes induced by the cryomilling process. In short, as the microstructure of the Pd-10Rh alloy is refined by cryomilling: (i) the maximum hydrogen concentration in the α-phase increases, (ii) the pressure plateau becomes flatter, and (iii) the equilibrium hydrogen capacity at 760 Torr increases. In addition, the rate of hydrogen absorption was reduced by an order of magnitude compared to non-cryomilled (atomized) powder.« less

  18. Hydrogen sorption characteristics of nanostructured Pd–10Rh processed by cryomilling

    SciTech Connect

    Yang, Nancy; Yee, Joshua K.; Zhang, Zhihui; Kurmanaeva, Lilia; Cappillino, Patrick; Stavila, Vitalie; Lavernia, Enrique J.; San Marchi, Chris

    2014-10-03

    Palladium and its alloys are model systems for studying solid-state storage of hydrogen. Mechanical milling is commonly used to process complex powder systems for solid-state hydrogen storage; however, milling can also be used to evolve nanostructured powder to modify hydrogen sorption characteristics. In the present study, cryomilling (mechanical attrition milling in a cryogenic liquid) is used to produce nanostructured palladium-rhodium alloy powder. Characterization of the cryomilled Pd-10Rh using electron microscopy, X-ray diffraction, and surface area analysis reveals that (i) particle morphology evolves from spherical to flattened disk-like particles; while the (ii) crystallite size decreases from several microns to less than 100 nm and (iii) dislocation density increases with increased cryomilling time. Hydrogen absorption and desorption isotherms as well as the time scales for absorption were measured for cryomilled Pd-10Rh, and correlated with observed microstructural changes induced by the cryomilling process. In short, as the microstructure of the Pd-10Rh alloy is refined by cryomilling: (i) the maximum hydrogen concentration in the α-phase increases, (ii) the pressure plateau becomes flatter, and (iii) the equilibrium hydrogen capacity at 760 Torr increases. In addition, the rate of hydrogen absorption was reduced by an order of magnitude compared to non-cryomilled (atomized) powder.

  19. Moisture Sorption Behaviour and Mould Ecology of Trade Garri Sold in South Eastern Nigeria

    PubMed Central

    Samuel, Tochukwu; Ugwuanyi, J. Obeta

    2014-01-01

    Garri is a creamy white or yellow starchy grit produced by roasting to gelatinization and dryness of peeled, washed, mashed, and fermented dewatered cassava roots. It is the most important product of cassava in West and Central Africa. Mean moisture content of yellow and white garri was 11.11% and 10.81% within 24 hrs of sampling from the market, increasing to 17.27% and 16.14%, respectively, following 3 months of storage at room temperature. The water activity of samples varied from initial 0.587 to 0.934 following storage. Moisture sorption isotherms, determined by static gravimetric techniques at 20° and 30°C, showed temperature dependent BET Sigmoidal type II behaviour typical of carbohydrate rich foods but modulated very slightly by the content of palm oil. Equilibrium moisture content decreased with increase in temperature at constant water activity. A total of 10 fungal species belonging to the genera Mucor, Penicillium, Cephalosporium, Aspergillus, Scopulariopsis, Rhizopus, and Paecilomyces were identified, with range increasing with water activity of samples. PMID:26904621

  20. Isothermal separation processes

    NASA Technical Reports Server (NTRS)

    England, C.

    1982-01-01

    The isothermal processes of membrane separation, supercritical extraction and chromatography were examined using availability analysis. The general approach was to derive equations that identified where energy is consumed in these processes and how they compare with conventional separation methods. These separation methods are characterized by pure work inputs, chiefly in the form of a pressure drop which supplies the required energy. Equations were derived for the energy requirement in terms of regular solution theory. This approach is believed to accurately predict the work of separation in terms of the heat of solution and the entropy of mixing. It can form the basis of a convenient calculation method for optimizing membrane and solvent properties for particular applications. Calculations were made on the energy requirements for a membrane process separating air into its components.

  1. Importance of unburned coal carbon, black carbon, and amorphous organic carbon to phenanthrene sorption in sediments.

    PubMed

    Cornelissen, Gerard; Gustafsson, Orjan

    2005-02-01

    The aim of this paper was to estimate the contribution to total phenanthrene sorption from unburned coal and black carbon (BC; soot and charcoal) in sediment. We determined sorption isotherms for five Argonne Premium Coal standards over a wide concentration interval (0.01-10 000 ng/L). The coals showed strong and nonlinear sorption (carbon-normalized K(F) = 5.41-5.96; nF = 0.68-0.82). Coal sorption appeared to become more nonlinear with increasing coal maturity. The coal's specific surface area appeared to influence K(F). On the basis of the current coal sorption observations combined with earlier petrographic analyses and BC sorption experiments, we calculated for one particular sediment that coal, BC, and "other" OC were all important to PHE sorption in the environmentally relevant nanogram per liter range. This indicates that it is important to consider strong sorption to coal in the risk assessment of coal-impacted geosorbents (e.g., river beds) where coal is mined/shipped and manufactured gas plant sites. PMID:15757337

  2. Effect of organic and mineral soil fractions on sorption behaviour of chlorophenol and triazine micropollutants.

    PubMed

    Stipicević, Sanja; Fingler, Sanja; Drevenkar, Vlasta

    2009-03-01

    This article compares the sorption behaviour of 2,4,6-trichlorophenol, 2,3,4,6-tetrachlorophenol, pentachlorophenol, chlorotriazine atrazine, methylthiotriazine ametryn, methoxytriazine atratone, hydroxyatrazine, and didelakylated atrazine in a topsoil and an aquifer sediment before and after removal of sorbent organic matter and in humic acid. Freundlich isotherm coefficients Kf and 1/n and free energy change (deltaG degrees ) were calculated for all compounds in all sorbents. According to sorbent pH values, chlorophenolate anions and uncharged triazine species dominated in all sorption experiments with topsoil and aquifer sediment. In experiments with humic acid, chlorophenols, atrazine, and didealkylated atrazine existed almost completely as neutral species, whereas protonated species dominated for hydroxyatrazine, atratone, and ametryn. In addition to a hydrophobic partition, sorption of all compounds in native soil and sediment sorbents includes specific, more polar interactions, which greatly depend on sorbate acidity/basicity, specific properties of the sorbent organic matter and of mineral surface, as well as on the system pH. A significantly greater sorption intensity of all compounds in "organic-free" than in the native aquifer sediment confirmed the importance and possible dominance of mineral surface in the sorption process. Sorption intensity of chlorophenol and triazine compounds in humic acid was closely related to compound hydrophobicity. Greater sorption of almost completely protonated hydroxyatrazine than of the more hydropohobic but uncharged atrazine indicated different humic acid reaction sites for two compounds and consequently different sorption mechanisms. PMID:19329375

  3. Graphical determination of metal bioavailability to soil invertebrates utilizing the Langmuir sorption model

    SciTech Connect

    Donkin, S.G.

    1997-09-01

    A new method of performing soil toxicity tests with free-living nematodes exposed to several metals and soil types has been adapted to the Langmuir sorption model in an attempt at bridging the gap between physico-chemical and biological data gathered in the complex soil matrix. Pseudo-Langmuir sorption isotherms have been developed using nematode toxic responses (lethality, in this case) in place of measured solvated metal, in order to more accurately model bioavailability. This method allows the graphical determination of Langmuir coefficients describing maximum sorption capacities and sorption affinities of various metal-soil combinations in the context of real biological responses of indigenous organisms. Results from nematode mortality tests with zinc, cadmium, copper, and lead in four soil types and water were used for isotherm construction. The level of agreement between these results and available literature data on metal sorption behavior in soils suggests that biologically relevant data may be successfully fitted to sorption models such as the Langmuir. This would allow for accurate prediction of soil contaminant concentrations which have minimal effect on indigenous invertebrates.

  4. Contributions of a compost-biochar mixture to the metal sorption capacity of a mine tailing.

    PubMed

    Forján, R; Asensio, V; Rodríguez-Vila, A; Covelo, E F

    2016-02-01

    One technique applied to restore degraded or contaminated soils is to use amendments made of different types of waste materials, which in turn may contain metals such as Cu, Pb and Zn. For this reason, it is important to determine the capacity of the soil to retain these materials, and to compare the sorption capacity between an amended soil and another unamended soil. The aim of this study was to determine the mobility and availability of these metals in the soil after applying the amendment, and how it affected the soil's sorption capacity. Sorption isotherms were compared with the empirical models of Langmuir and Freundlich to estimate the sorption capacity. The overall capacity of the soils to sorb Cu, Pb or Zn was evaluated as the slope Kr. The amendments used in this study were a mixture made of compost and biochar in different proportions (20, 40, 60, 100 %), which were applied to the mine tailing from a settling pond from a copper mine. The mine tailing that were amended with the mixture of compost and biochar had a higher sorption capacity than the mine tailing from the unamended pond, and their sorption isotherms had a greater affinity towards Cu, Pb and Zn than the mine tailing that was studied. Therefore, the results obtained show that adding a mixture of compost and biochar favours the retention of Cu, Pb and Zn in mine tailing. PMID:26432263

  5. 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 ...

  6. TECHNETIUM SORPTION MEDIA REVIEW

    SciTech Connect

    DUNCAN JB; KELLY SE; ROBBINS RA; ADAMS RD; THORSON MA; HAASS CC

    2011-08-25

    This report presents information and references to aid in the selection of 99Tc sorption media for feasibility studies regarding the removal of 99Tc from Hanford's low activity waste. The report contains literature search material for sorption media (including ion exchange media) for the most tested media to date, including SuperLig 639, Reillex HPQ, TAM (Kruion), Purolite A520E and A530E, and Dowex 1X8. The U.S. Department of Energy (DOE), Office of River Protection (ORP) is responsible for management and completion of the River Protection Project (RPP) mission, which comprises both the Hanford Site tank farms and the Waste Treatment and Immobilization Plant (WTP). The RPP mission is to store, retrieve and treat Hanford's tank waste; store and dispose of treated wastes; and close the tank farm waste management areas and treatment facilities in a safe, environmentally compliant, cost-effective and energy-effective manner.

  7. 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. PMID:26437093

  8. Comparison of multifractal parameters form adsorption isotherms, desorption isotherms and mercury intrusion curves

    NASA Astrophysics Data System (ADS)

    Paz-Ferreiro, Jorge; Mon, Rodolfo; Vidal Vázquez, Eva

    2013-04-01

    The soil pore space is composed of a continuum of pores extremely variable in size, which range from equivalent diameter sizes smaller than nanometers to an upper limit of the order of centimeters. So, it is quite typical for soil pore space to display a size range of more than a factor of 106 in scale. Nitrogen sorption and mercury injection provide pores size distributions in the range from about 0.1 to 0.001 μm and 150 to 0.005 μm, respectively. The aims of this study were to evaluate the scaling properties of nitrogen adsorption isotherms (NAI), nitrogen desorption isotherms (NDI) and mercury intrusion porosimetry (MIP) curves of agricultural soils from "La Pampa húmeda", in the north of Buenos Aires and south of Santa Fé provinces, Argentina. Both NAIs, NDIs and MIPs exhibited multifractal behavior but its scaling properties were different so that the multifractality index, assessed by the width of the generalized dimension and the singularity spectra ranked as follows: NAI > NDI > MIP. Also, parameterization by the Hurst exponent indicates NAIs were less persistent than NDIs and in turn, these were less persistent than MIPs. The multfractal approach was useful to characterize the heterogeneity of various domains of the soil nano- micro- and mesopore system at the scale of small aggregates.

  9. Isothermal Amplification of Nucleic Acids.

    PubMed

    Zhao, Yongxi; Chen, Feng; Li, Qian; Wang, Lihua; Fan, Chunhai

    2015-11-25

    Isothermal amplification of nucleic acids is a simple process that rapidly and efficiently accumulates nucleic acid sequences at constant temperature. Since the early 1990s, various isothermal amplification techniques have been developed as alternatives to polymerase chain reaction (PCR). These isothermal amplification methods have been used for biosensing targets such as DNA, RNA, cells, proteins, small molecules, and ions. The applications of these techniques for in situ or intracellular bioimaging and sequencing have been amply demonstrated. Amplicons produced by isothermal amplification methods have also been utilized to construct versatile nucleic acid nanomaterials for promising applications in biomedicine, bioimaging, and biosensing. The integration of isothermal amplification into microsystems or portable devices improves nucleic acid-based on-site assays and confers high sensitivity. Single-cell and single-molecule analyses have also been implemented based on integrated microfluidic systems. In this review, we provide a comprehensive overview of the isothermal amplification of nucleic acids encompassing work published in the past two decades. First, different isothermal amplification techniques are classified into three types based on reaction kinetics. Then, we summarize the applications of isothermal amplification in bioanalysis, diagnostics, nanotechnology, materials science, and device integration. Finally, several challenges and perspectives in the field are discussed. PMID:26551336

  10. Sorption of copper onto low molecular weight chitosan derivative from aqueous solution.

    PubMed

    Boamah, Peter Osei; Huang, Yan; Hua, Mingqing; Onumah, Jacqueline; Sam-Amoah, Livingstone K; Boamah, Paul Osei; Qian, Yaao; Zhang, Qi

    2016-07-01

    In this study, sorption of copper onto low molecular weight chitosan derivative was studied. Experimental parameters such as pH of the solution (A), temperature (B), dose of the sorbent (C), and concentration of solution (D) were considered. The statistical results indicated that the dose of sorbent (C) and Cu (II) concentration (D) influenced removal efficiency at 5% significance level. Also, some interactions such as ABCD, ACD, ABC and AC affected the removal process. The sorbent was characterized with FTIR, SEM and TG/DSC. Freundlich isotherm model was the best isotherm model. The kinetic study results correlated well with the pseudo-second-order model. The thermodynamic studies revealed that the nature of copper sorption was spontaneous and endothermic. Strong affinity of the sorbent for copper (II) was revealed by the Isothermal Titration Calorimetry (ITC) technique. PMID:27039244

  11. Mechanisms of plutonium sorption to mineral oxide surfaces: new insights with implications for colloid-enhanced migration

    SciTech Connect

    Schwantes, J. M.; Santschi, Peter H.

    2010-11-01

    New equilibrium and kinetic models have been developed to describe rate-limited sorption and desorption of Pu onto and off of mineral oxide surfaces using a generic approach to estimate sorption constants that require minimal laboratory calibrations. Equilibrium reactions describing a total of six surface species were derived from a combination of empirical relationships previously described in the literature and generated as part of this work.

  12. Competitive sorption of cis-DCE and TCE in silica gel as a model porous mineral solid.

    PubMed

    Avila, Manuel Alejandro Salaices; Breiter, Roman

    2008-08-01

    The competitive sorption of 1,2-cis-dichloroethene (cis-DCE) and trichloroethene (TCE) was investigated by means of column experiments using a model porous mineral solid represented by silica gel. The experimental isotherms were obtained by employing a chromatographic method. The competitive sorption isotherms were modelled with the extended Freundlich and extended Langmuir isotherms, using the parameters from single-solute experiments. The breakthrough curves were modelled with the advection-dispersion transport equation coupled with the lumped pore diffusion model. The best results were obtained when the extended Freundlich isotherm was employed. The competitive sorption was revealed with the presence of an overshoot in the breakthrough curve of cis-DCE and a decrease in the degree of sorption of cis-DCE (20%) and TCE (12%). A linear dependency of the overshoot with an increase in the concentration of cis-DCE at a fixed concentration of TCE was observed, between 16% and 20%, and at least at concentrations <6 mg L(-1) in the liquid phase. The displaced molecules of cis-DCE by TCE were accumulated through the column causing its overshoot; thus short columns may hinder its observation. Thermodynamic analysis shows an exothermic adsorption process of -34 to -41 kJ mol(-1), which is enhanced by sorption in micropores. The Gibbs free energy is positive for cis-DCE in the multi-component case, due to its displacement by TCE. PMID:18541287

  13. Sorption behavior of bisphenol A on marine sediments.

    PubMed

    Xu, Xiangrong; Wang, Yuexing; Li, Xiaoyan

    2008-02-15

    Bisphenol A (BPA) is a known endocrine disrupting chemical (EDC) that has been widely used for the production of polycarbonate plastics and epoxy resins. In this experimental study, the sorption behavior of BPA on the marine sediments sampled from 6 different sites in the Mai Po Nature Reserve in Hong Kong was investigated. BPA sorption on the sediments can be well described by a linear sorption isotherm, suggesting a partition of BPA between the aqueous solution and the organic matter of the sediments. The BPA partition coefficient, K(d), for the raw sediment samples varied from 4.43 to 8.54 L/kg (R(2): 0.91-0.96) in nearly proportion to the organic content of the sediments. After the treatment of H(2)O(2) oxidation for organic removal, the sediments had the K(d) value reduced by more than 50%. However, the organic residue or black carbon of the sediments after the H(2)O(2) treatment had a much greater sorption capacity than the natural organic matter on the sediment which was oxidized by H(2)O(2). The organic normalized partition coefficients (K(oc)) averaged around 1355 L/kg for the H(2)O(2)-treated sediment, which was more than three times greater than the K(oc) value of 447 L/kg for the raw organic matter of the sediments. In addition to the organic content of the sediment, BPA sorption also was affected by a number of environmental factors. A pH drop, a temperature decrease and a reduction in salinity would increase the sorption of BPA on the sediment. The research findings are of significance to the description and assessment of the fate and transport of BPA and other similar EDCs in marine water-sediment systems. PMID:18205054

  14. Can soil drying affect the sorption of pesticides in soil?

    NASA Astrophysics Data System (ADS)

    Chaplain, Véronique; Saint, Philippe; Mamy, Laure; Barriuso, Enrique

    2010-05-01

    The sorption of pesticides in soils mainly controls their further dispersion into the environment. Sorption is usually related to the physico-chemical properties of molecules but it also depends on the hydrophobic features of soils. However, the hydrophobicity of soils changes with wetting and drying cycles and this can be enhanced with climate change. The objective of this study was to measure by using controlled artificial soils the influence of the hydrophobic characteristic of soils on the retention of a model pesticide. Artificial soils consisted in silica particles covered by synthetic cationic polymers. Polymers were characterized by the molar ratio of monomers bearing an alkyl chain of 12C. Two polymers were used, with 20 and 80 % ratios, and the same degree of polymerization. In addition, porous and non-porous particles were used to study the accessibility notion and to measure the influence of diffusion on pesticide sorption kinetics. Lindane was chosen as model molecule because its adsorption is supposed mainly due to hydrophobic interactions. Results on polymers adsorption on silica showed that it was governed by electrostatic interactions, without any dependency of the hydrophobic ratio. Polymers covered the entire surface of porous particles. Kinetic measurements showed that lindane sorption was slowed in porous particles due to the molecular diffusion inside the microporosity. The adsorption of lindane on covered silica particles corresponded to a partition mechanism described by linear isotherms. The slope was determined by the hydrophobic ratio of polymers: the sorption of lindane was highest in the most hydrophobic artificial soil. As a result, modification in soil hydrophobicity, that can happen with climate change, might affect the sorption and the fate of pesticides. However additional experiments are needed to confirm these first results. Such artificial soils should be used as reference materials to compare the reactivity of pesticides, to

  15. Sorption-capacity limited retardation of radionuclides transport in water-saturated packing materials

    SciTech Connect

    Pescatore, C.; Sullivan, T.

    1984-01-01

    Radionuclides breakthrough times as calculated through constant retardation factors obtained in dilute solutions are non-conservative. The constant retardation approach regards the solid as having infinite sorption capacity throughout the solid. However, as the solid becomes locally saturated, such as in the proximity of the waste form-packing materials interface, it will exhibit no retardation properties, and transport will take place as if the radionuclides were locally non-reactive. The magnitude of the effect of finite sorption capacity of the packing materials on radionuclide transport is discussed with reference to high-level waste package performance. An example based on literature sorption data indicates that the breakthrough time may be overpredicted by orders of magnitude using a constant retardation factor as compared to using the entire sorption isotherm to obtain a concentration-dependent retardation factor. 8 references, 3 figures, 3 tables.

  16. Sorption of PCE in a reactive zero-valent iron system

    SciTech Connect

    Campbell, T.J.; Burris, D.R.

    1995-12-01

    The degradation of the chlorinated solvents perchloroethylene (PCE) and trichloroethylene (TCE) by reduction on the surface of zero-valent iron has emerged in recent years as a potentially viable approach to the remediation of chlorinated solvent-contaminated groundwaters. The sorption of PCE in a batch reactive zero-valent iron system was examined in this study. Aqueous PCE concentrations and total system PCE masses were determined in batch time-series experiments used to ascertain degradation kinetics. Sorbed concentrations were calculated using the difference between the aqueous phase and total system masses. The results showed Langmuir isotherm behavior which is consistent with a model of a finite number of available sorption sites. The kinetics of sorption could not be determined since degradation was also occurring. Knowledge of sorption to reactive and non-reactive sites is of importance in gaining a thorough understanding of the performance-behavior of the flow-through reactive systems envisioned for remediation technologies.

  17. A general computer model for predicting the performance of gas sorption refrigerators

    NASA Technical Reports Server (NTRS)

    Sigurdson, K. B.

    1983-01-01

    Projected performance requirements for cryogenic spacecraft sensor cooling systems which demand higher reliability and longer lifetimes are outlined. The gas/solid sorption refrigerator is viewed as a potential solution to cryogenic cooling needs. A software model of an entire gas sorption refrigerator system was developed. The numerical model, evaluates almost any combination and order of refrigerator components and any sorbent-sorbate pair or which the sorption isotherm data are available. Parametric curves for predicting system performance were generated for two types of refrigerators, a LaNi5-H2 absorption cooler and a Charcoal-N2 adsorption cooler. It is found that precooling temperature and heat exchanger effectiveness affect the refrigerator performance. It is indicated that gas sorption refrigerators are feasible for a number of space applications.

  18. Modeling and Uncertainty Quantification of Vapor Sorption and Diffusion in Heterogeneous Polymers.

    PubMed

    Sun, Yunwei; Harley, Stephen J; Glascoe, Elizabeth A

    2015-10-01

    A high-fidelity model of kinetic and equilibrium sorption and diffusion is developed and exercised. The gas-diffusion model is coupled with a triple-sorption mechanism: Henry's law absorption, Langmuir adsorption, and pooling or clustering of molecules at higher partial pressures. Sorption experiments are conducted and span a range of relative humidities (0-95 %) and temperatures (30-60 °C). Kinetic and equilibrium sorption properties and effective diffusivity are determined by minimizing the absolute difference between measured and modeled uptakes. Uncertainty quantification and sensitivity analysis methods are described and exercised herein to demonstrate the capability of this modeling approach. Water uptake in silica-filled and unfilled poly(dimethylsiloxane) networks is investigated; however, the model is versatile enough to be used with a wide range of materials and vapors. PMID:26274619

  19. Modeling and Uncertainty Quantification of Vapor Sorption and Diffusion in Heterogeneous Polymers

    SciTech Connect

    Sun, Yunwei; Harley, Stephen J.; Glascoe, Elizabeth A.

    2015-08-13

    A high-fidelity model of kinetic and equilibrium sorption and diffusion is developed and exercised. The gas-diffusion model is coupled with a triple-sorption mechanism: Henry’s law absorption, Langmuir adsorption, and pooling or clustering of molecules at higher partial pressures. Sorption experiments are conducted and span a range of relative humidities (0-95 %) and temperatures (30-60 °C). Kinetic and equilibrium sorption properties and effective diffusivity are determined by minimizing the absolute difference between measured and modeled uptakes. Uncertainty quantification and sensitivity analysis methods are described and exercised herein to demonstrate the capability of this modeling approach. Water uptake in silica-filled and unfilled poly(dimethylsiloxane) networks is investigated; however, the model is versatile enough to be used with a wide range of materials and vapors.

  20. Phosphorus sorption characteristics of a light-weight aggregate.

    PubMed

    Zhu, T; Maehlum, T; Jenssen, P D; Krogstad, T

    2003-01-01

    A light-weight aggregate (LWA) made of expanded clay used as a filter media in wastewater treatment, was tested for sorption of phosphorus (P) in laboratory experiments. The objectives were to investigate the different P retention pools and how grain size, time, temperature and changed P concentration influenced the P binding mechanisms in this type of filter. Three different grain sizes (0-2 mm, 2-4 mm and 0-4 mm) were tested in a batch experiment. The isotherm for the P sorbed by the contact medium (including retention and fixation) was obtained under laboratory conditions. Fifty percent of the P sorption occurred in the first 4-8 hours. Temperature did not substantially influence P sorption for 0-2 mm grain size LWA. In the LWA suspension system, P desorption did not occur when the P content in the loading solution decreased. Fractionation analysis indicated that Ca-bound P, loosely-bound P, and Al-bound P were the predominant P retention pools. The loosely-bound P pool was determined primarily by the equilibrated P concentration in the system. Fe-bound P was negligible in the P sorption of LWA. PMID:14621152

  1. Rate of strontium sorption and the effects of variable aqueous concentrations of sodium and potassium on strontium distribution coefficients of a surficial sediment at the Idaho National Engineering Laboratory, Idaho

    USGS Publications Warehouse

    Bunde, R.L.; Rosentreter, J.J.; Liszewski, M.J.

    1998-01-01

    The rate of strontium sorption and the effects of variable aqueous concentrations of sodium and potassium on strontium sorption were measured as part of an investigation to determine strontium chemical transport properties of a surficial sediment at the Idaho National Engineering Laboratory (INEL), Idaho. Batch experimental techniques were used to determine the rate of strontium sorption and strontium distribution coefficients (K(d)s) between aqueous and solid phases. Rate experiments indicate that strontium in solution reached an apparent equilibrium with the sediment in 26 h. K(d)s were derived using the linear isotherm model at initial sodium concentrations from 100 to 5,000 mg/l and initial potassium concentrations from 2 to 150 mg/l. K(d)s ranged from 56 ?? 2 to 62 ?? 3 ml/g at initial aqueous concentrations of sodium and potassium equal to or less than 300 and 150 mg/l, respectively. K(d)s hinged from 4.7 ?? 0.2 to 19 ?? 1 ml/g with initial aqueous concentrations of sodium between 1,000 and 5,000 mg/l. These data indicate that sodium concentrations greater than 300 mg/l in wastewater increase the availability of strontium for transport beneath waste disposal ponds at the INEL by decreasing strontium sorption on the surficial sediment. Wastewater concentrations of sodium and potassium less than 300 and 150 mg/l, respectively, have little effect on the availability of strontium for transport.The rate of strontium sorption and the effects of variable aqueous concentrations of sodium and potassium on strontium sorption were measured as part of an investigation to determine strontium chemical transport properties of a surficial sediment at the Idaho National Engineering Laboratory (INEL), Idaho. Batch experimental techniques were used to determine the rate of strontium sorption and strontium distribution coefficients (Kds) between aqueous and solid phases. Rate experiments indicate that strontium in solution reached an apparent equilibrium with the sediment in 26

  2. Soil sorption of organic vapors and effects of humidity on sorptive mechanism and capacity

    USGS Publications Warehouse

    Chiou, C.T.; Shoup, T.D.

    1985-01-01

    Vapor sorption isotherms on dry Woodburn soil at 20-30??C were determined for benzene, chlorobenzene, p-dichlorobenzene, m-dichlorobenzene, 1,2,4-trichlorobenzene, and water as single vapors and for benzene, m-dichlorobenzene, and 1,2,4-trichlorobenzene as functions of relative humidity (RH). Isotherms for all compounds on dry soil samples are distinctively nonlinear, with water showing the greatest capacity. Water vapor sharply reduced the sorption capacities of organic compounds with the dry soil; on water-saturated soil, the reduction was about 2 orders of magnitude. The markedly higher sorption of organic vapors at subsaturation humidities is attributed to adsorption on the mineral matter, which predominates over the simultaneous uptake by partition into the organic matter. At about 90% RH, the sorption capacities of organic compounds become comparable to those in aqueous systems. The effect of humidity is attributed to adsorptive displacement by water of organics adsorbed on the mineral matter. A small residual uptake is attributed to the partition into the soil-organic phase that has been postulated in aqueous systems. The results are essentially in keeping with the model that was previously proposed for sorption on the soil from water and from organic solvents.Vapor sorption isotherms on dry Woodburn soil at 20-30 degree C were determined for benzene, chlorobenzene, p-dichlorobenzene, m-dichlorobenzene, 1,2,4-trichlorobenzene, and water as single vapors and for benzene, m-dichlorobenzene, and 1,2,4-trichlorobenzene as functions of relative humidity (RH). Isotherms for all compounds on dry soil samples are distinctively nonlinear, with water showing the greatest capacity. Water vapor sharply reduced the sorption capacities of organic compounds with the dry soil; on water-saturated soil, the reduction was about 2 orders of magnitude. The markedly higher sorption of organic vapors at subsaturation humidities is attributed to adsorption on the mineral matter

  3. Modeling and predicting competitive sorption of organic compounds in soil

    PubMed Central

    Faria, Isabel R.; Young, Thomas M.

    2011-01-01

    Binary systems consisting of 1,2-dichlorobenzene (12DCB) + competitor were investigated over a range of concentrations of competitor in three natural sorbents with distinct characteristics. Two models, the ideal adsorbed solution theory (IAST) and the Potential theory (Polanyi based multi-solute model), widely used in the prediction of multi-solute sorption equilibrium from single solute data were used to simulate competitive sorption in our systems. The goal was to determine which multi-solute model best represented the experimentally obtained multi-solute data in natural sorbents of varied properties. Results suggested that for the sorbents and sorbates studied the IAST model provided much better results. On average the IAST model provided lower errors (23%) than the Potential model (45%). The effect of competitor structure on the degree of competition was also investigated to identify any relationships between competition and structure using molecular descriptors. The competitors chlorobenzene, naphthalene, 1,4-dichlorobenzene, 1,2,4-trichlorobenzene all showed very similar degrees of competition, while benzene, phenanthrene and pyrene were the least effective competitors towards 12DCB across all sorbents. Different sorption sites or sorption mechanisms might be involved in the sorption of these molecules leading to a lack of competitive behavior. A significant relationship between competitor structure and the degree of competition was observed at environmentally relevant sorbed competitor concentrations for the soil containing the highest fraction of hard carbon (Forbes). PMID:21061392

  4. Modeling solute advection coupled with sorption kinetics in heterogeneous formations

    NASA Astrophysics Data System (ADS)

    Selroos, Jan-Olof; Cvetkovic, Vladimir

    1992-05-01

    A method for coupling sorption kinetics and solute advection in particle-tracking models is proposed; this method is efficient for the case where sorption rate coefficients can be assumed constant field scale parameters. A simulation example of reactive solute advection in two-dimensional heterogeneous porous media is presented. The effect of sorption kinetics on solute advection is investigated. Nonequilibrium effects are exhibited as enhanced tailing in the solute breakthrough. Because high variability in the hydraulic conductivity also yields enhanced tailing, the nonequilibrium effect is more pronounced for the case of low variability. Moreover, it may be difficult to distinguish cases of low variability with nonequilibrium sorption from cases of high variability with equilibrium sorption. A comparison of Monte Carlo ensemble results is made with an analytical model for the mass arrival of kinetically sorbing solute in heterogeneous porous media obtained using first-order perturbation. The comparison indicates that the analytical model provides reasonable approximations of the expected solute breakthrough if the variance of the natural logarithm of the hydraulic conductivity is smaller than 1.

  5. Application of the new thermodynamic approach to the description of superequivalent sorption by ion exchangers

    NASA Astrophysics Data System (ADS)

    Khokhlova, O. N.

    2014-08-01

    Using the example of sorption systems with the participation of amino acids, it is shown that the novel thermodynamic approach to describing superequivalent sorption as a combination of ion exchange and nonexchangeable absorption allows us to adequately describe such equilibria. Results from calculating the activity coefficients of components of a sorbent phase and the thermodynamic constants of ion exchange equilibrium and the superequivalent absorption of phenylalanine by AV-17-8 anion exchange resin are presented.

  6. Adsorption isotherm special study. Final report

    SciTech Connect

    1993-05-01

    The study was designed to identify methods to determine adsorption applicable to Uranium Mill Tailings Remedial Action (UMTRA) Project sites, and to determine how changes in aquifer conditions affect metal adsorption, resulting retardation factors, and estimated contaminant migration rates. EPA and ASTM procedures were used to estimate sediment sorption of U, As, and Mo under varying groundwater geochemical conditions. Aquifer matrix materials from three distinct locations at the DOE UMTRA Project site in Rifle, CO, were used as the adsorbents under different pH conditions; these conditions stimulated geochemical environments under the tailings, near the tailings, and downgradient from the tailings. Grain size, total surface area, bulk and clay mineralogy, and petrography of the sediments were characterized. U and Mo yielded linear isotherms, while As had nonlinear ones. U and Mo were adsorbed strongly on sediments acidified to levels similar to tailings leachate. Changes in pH had much less effect on As adsorption. Mo was adsorbed very little at pH 7-7.3, U was weakly sorbed, and As was moderately sorbed. Velocities were estimated for metal transport at different pHs. Results show that the aquifer materials must be characterized to estimate metal transport velocities in aquifers and to develop groundwater restoration strategies for the UMTRA project.

  7. Synthesis of hydrophobic cross-linked polyzwitterionic acid for simultaneous sorption of Eriochrome black T and chromium ions from binary hazardous waters.

    PubMed

    Saleh, Tawfik A; Muhammad, Auwal M; Ali, Shaikh A

    2016-04-15

    Hydrophobic cross-linked polyzwitterionic acid (HCPZA) containing long chain (C18) hydrophobes and residues of a glutamic acid having unquenched nitrogen valency was synthesized. Exploiting the chelating ability of the amino acid residues to scavenge toxic metals and the hydrophobic surface to scoop up the organic contaminants, the resin HCPZA was evaluated for simultaneous removal of chromium and Eriochrome black T (EBT) from wastewaters. The structure and morphology of the polymer before and after sorption were characterized by using FTIR, TGA, EDX and SEM. The effect of various parameters such as contact time, pH and initial concentrations were investigated to arrive at optimum conditions. The adsorption of Eriochrome black T and Cr (III) on HCPZA reached equilibrium in 30 min. The mechanism of adsorption was investigated using kinetic, diffusion and isotherm models. The adsorption kinetic data were described well by the pseudo-second order model and by the Freundlich isotherm model. EDX analysis confirmed the adsorption of Cr (III) and EBT on the polymer. The hydrophobic resin exhibited a remarkable simultaneous adsorption capacity for EBT and Cr (III) and thus demonstrated its potential to be a promising adsorbent for removal of dyes and heavy metal ions from wastewaters. PMID:26854746

  8. Water vapor sorption hysteresis of ceramic bricks

    NASA Astrophysics Data System (ADS)

    Koronthalyova, Olga

    2016-07-01

    A quantification of the hysteretic effects and their thorough analysis was carried out for three types of ceramic bricks. Water vapor adsorption/desorption isotherms were measured by the standard desiccator method. The desorption measurements were carried out from capillary moisture content as well as from equilibrium moisture content corresponding to the relative humidity of 98 %. For all three tested types of bricks the hysteretic effects were present but their significance differed depending on the particular type of brick. Significant differences were noticed also in desorption curves determined from capillary moisture content and from equilibrium moisture content corresponding to the relative humidity of 98 %. Based on the measured data a possible correlation between pore structure parameters and noticed hysteretic effects as well as relevance of the open pore model are discussed. The obtained adsorption/desorption curves were approximated by an analytical relation.

  9. Sorption of a fluorescent whitening agent (Tinopal CBS) onto modified cellulose fibers in the presence of surfactants and salt.

    PubMed

    Iamazaki, Eduardo T; Atvars, Teresa D Z

    2007-12-18

    The combined effect of salt (10 mmol L(-1)) and surfactants on the sorption of the fluorescent brightener 4,4'-distyrylbiphenyl sodium sulfonate (Tinopal CBS) onto modified cellulose fibers was studied. Sorption efficiencies with both cationic and anionic surfactants were evaluated. Emission spectroscopy was used for quantitative analysis since Tinopal has an intense fluorescence. The sorption efficiency of the brightener is greater for solutions containing a cationic surfactant (DTAC) below the critical micelle concentration (cmc), while for an anionic surfactant (SDS) above its cmc the efficiency is greater. The profile of the sorption isotherms were interpreted in terms of the evolution of surfactant aggregation at the fiber/solution interface. Salt influences the efficiency of the Tinopal sorption on the modified cellulose fibers either because it decreases the cmc of the surfactants or because the ions screen the surface charges of the fiber which decreases the electrostatic interaction among the charged headgroup of the surfactant and the charged fiber surface. PMID:18020381

  10. Sorption of graphites at high temperatures. Final report, February 1, 1977-June 30, 1978. [800 to 1100/sup 0/C; pseudo-isopiestic method

    SciTech Connect

    Kazi, N.I.; Pyecha, T.D.; Zumwalt, L.R.

    1980-06-30

    This report include: (1) corrected data and new data on cesium sorption by bulk graphite (H-451) with a discussion of anomalies and a comparison of the data; (2) a review of the exponential (Freundlich) isotherm theory and a derivation of the modified-exponential isotherm; (3) a report on a study by the pseudo-isopiestic method of cesium by H-451 graphite powder (size range 44 to 74 ..mu..m) of the type used in the Knudsen cell mass spectrometer method; (4) a comparison of the results on particulate graphite (powder) obtained by the Knudsen cell method and also a comparison of cesium sorption results obtained with the bulk graphite; (5) development of a theory for the kinetics of sorption of a system (cesium and graphite) which shows an exponential (Freundlich) type of sorption; (6) comparison of theoretical with observed kinetics for sorption of cesium by graphite (H-451) powder and a comparison of bulk graphite vs. particulate graphite sorption kinetics; (7) report of a study of the effects of barium on cesium sorption by H-451 graphite at 1000/sup 0/C; and (8) a thermodynamic treatment of mixed sorption and its application to mixed barium-cesium and strontium-cesium sorption by graphite.

  11. Surface complexation modeling of inositol hexaphosphate sorption onto gibbsite.

    PubMed

    Ruyter-Hooley, Maika; Larsson, Anna-Carin; Johnson, Bruce B; Antzutkin, Oleg N; Angove, Michael J

    2015-02-15

    The sorption of Inositol hexaphosphate (IP6) onto gibbsite was investigated using a combination of adsorption experiments, (31)P solid-state MAS NMR spectroscopy, and surface complexation modeling. Adsorption experiments conducted at four temperatures showed that IP6 sorption decreased with increasing pH. At pH 6, IP6 sorption increased with increasing temperature, while at pH 10 sorption decreased as the temperature was raised. (31)P MAS NMR measurements at pH 3, 6, 9 and 11 produced spectra with broad resonance lines that could be de-convoluted with up to five resonances (+5, 0, -6, -13 and -21ppm). The chemical shifts suggest the sorption process involves a combination of both outer- and inner-sphere complexation and surface precipitation. Relative intensities of the observed resonances indicate that outer-sphere complexation is important in the sorption process at higher pH, while inner-sphere complexation and surface precipitation are dominant at lower pH. Using the adsorption and (31)P MAS NMR data, IP6 sorption to gibbsite was modeled with an extended constant capacitance model (ECCM). The adsorption reactions that best described the sorption of IP6 to gibbsite included two inner-sphere surface complexes and one outer-sphere complex: ≡AlOH + IP₆¹²⁻ + 5H⁺ ↔ ≡Al(IP₆H₄)⁷⁻ + H₂O, ≡3AlOH + IP₆¹²⁻ + 6H⁺ ↔ ≡Al₃(IP₆H₃)⁶⁻ + 3H₂O, ≡2AlOH + IP₆¹²⁻ + 4H⁺ ↔ (≡AlOH₂)₂²⁺(IP₆H₂)¹⁰⁻. The inner-sphere complex involving three surface sites may be considered to be equivalent to a surface precipitate. Thermodynamic parameters were obtained from equilibrium constants derived from surface complexation modeling. Enthalpies for the formation of inner-sphere surface complexes were endothermic, while the enthalpy for the outer-sphere complex was exothermic. The entropies for the proposed sorption reactions were large and positive suggesting that changes in solvation of species play a major role in driving

  12. 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. PMID:26606188

  13. Streptococcus suis sorption on agricultural soils: role of soil physico-chemical properties.

    PubMed

    Zhao, Wenqiang; Liu, Xing; Huang, Qiaoyun; Cai, Peng

    2015-01-01

    Understanding pathogen sorption on natural soil particles is crucial to protect public health from soilborne and waterborne diseases. Sorption of pathogen Streptococcus suis on 10 agricultural soils was examined, and its correlations with soil physico-chemical properties were also elucidated. S. suis sorption isotherms conformed to the linear equation, with partition coefficients (Ks) ranging from 12.7 mL g(-1) to 100.1 mL g(-1). Bacteria were observed to sorb on the external surfaces of soil aggregates by scanning electron microscopy. Using Pearson correlation and linear regression analysis, solution pH was found to have significant negative correlations with Ks. Stepwise multiple regression and path analysis revealed that pH and cation exchange capacity (CEC) were the main factors influencing sorption behaviors. The obtained overall model (Ks=389.6-45.9×pH-1.3×CEC, R(2)=0.943, P<0.001) can accurately predict Ks values. However, the variability in Ks was less dependent on soil organic matter, specific surface area, soil texture and zeta potential, probably due to the internal-surface shielding phenomenon of soil aggregates. Additionally, the sorption trends cannot be interpreted by interaction energy barriers calculated using the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory, suggesting the limits of DLVO theory in describing pathogen sorption on natural soils. Our results also indicated soil pH and CEC should be preferentially considered when modeling S. suis sorption process. PMID:24968305

  14. Sorption of Cu(2+) on humic acids sequentially extracted from a sediment.

    PubMed

    Yang, Kun; Miao, Gangfen; Wu, Wenhao; Lin, Daohui; Pan, Bo; Wu, Fengchang; Xing, Baoshan

    2015-11-01

    In addition to the diverse properties of humic acids (HAs) extracted from different soils or sediments, chemical compositions, functional groups and structures of HAs extracted from a single soil or sediment could also be diverse and thus significantly affect sorption of heavy metals, which is a key process controlling the transfer, transformation and fate of heavy metals in the environment. In this study, we sequentially extracted four HA fractions from a single sediment and conducted the sorption experiments of Cu(2+) on these HA fractions. Our results showed that aromaticity and acidic group content of HA fraction decreased with increasing extraction. Earlier extracted HA fraction had higher sorption capacity and affinity for Cu(2+). There were two fractions of adsorbed Cu(2+) on HAs, i.e., ion exchanged fraction and surface bonded fraction, which can be captured mechanically by the bi-Langmuir model with good isotherm fitting. The ion exchanged fraction had larger sorption capacity but lower sorption affinity, compared with the surface bonded fraction. The dissociated carboxyl groups of HAs were responsible for both fractions of Cu(2+) sorption, due to the more Cu(2+) sorption on the earlier extracted HA fraction with more carboxyl groups and at higher pH. The intensive competition between H(+) and the exchangeable Cu(2+) could result in the decrease of ion exchanged capacity and affinity for Cu(2+) on HAs. PMID:26246274

  15. Sorption of basic and acid dyes from aqueous solutions onto oxihumolite.

    PubMed

    Janos, Pavel; Sedivý, Pavel; Rýznarová, Milena; Grötschelová, Sylvie

    2005-05-01

    Naturally occurring kind of weathered and oxidised young brown coal called oxihumolite was used for an adsorptive removal of basic (Methylene Blue, Malachite Green) as well as acid (Egacid Orange, Midlon Black) dyes from waters. It was shown that both kinds of dyes can be sorbed onto oxihumolite. The maximum sorption capacities determined from the parameters of Langmuir isotherms ranged from 0.070 mmol g-1 (for Midlon Black) to 0.278 mmol g-1 (for Malachite Green) and did not differ significantly for basic and acid dyes. The dye sorption (except of Midlon Black) increased in the presence of inorganic salt. Non-ionic surfactants, and surfactants bearing the same charge as the dye exhibited only a minor effect on the dye sorption, whereas oppositely charged surfactants enhanced the dye sorption to a certain extent. The pH value of the aqueous phase exhibited rather pronounced effect on the sorption of acid dyes causing a suppression of the sorption with increasing pH. The sorption of basic dyes, on the other hand, remained almost unchanged in the examined pH range. Oxihumolite is recommended for the treatment of acid wastewaters because of its limited stability in alkaline aqueous solutions. PMID:15811417

  16. Atrazine and metribuzin sorption in soils of the Argentinean humid pampas.

    PubMed

    Daniel, Peter E; Bedmar, Francisco; Costa, José L; Aparicio, Virginia C

    2002-12-01

    Laboratory studies were conducted to determine the influence of surface and subsurface properties of three representative soils of the humid pampas of Argentina on atrazine and metribuzin sorption. Atrazine and metribuzin sorption isotherms were constructed for each soil at four depths. Sorption affinity of herbicides was approximated by the Freundlich constant (K(f)), distribution coefficient (Kd), and the normalized Kd based on organic carbon content (K(oc)). Multiple regression of the sorption constants against selected soil properties indicated that organic carbon content (OC) and silt were related positively and negatively, respectively, to atrazine K(f) coefficient (r2 = 0.93), while Kd coefficient of atrazine was related positively to organic carbon content and negatively to both silt and cation exchange capacity (CEC) (r2 = 0.96). For metribuzin, only organic matter content was related positively to Kr coefficient (r2 = 0.51). Lower K(f) values for atrazine were obtained for all soils with increasing depth, indicating lesser sorption at greater depths. Metribuzin sorption was quite similar across all depths. Sorption constant K(f) of atrazine ranged from 2.06 to 7.82, while metribuzin K(f) values ranged from 1.8 to 3.52 and were lower than atrazine for all soils and depths, indicating a greater leaching potential across the soil profile. PMID:12463550

  17. Predicting the Sorption of Aromatic Acids to Noncarbonized and Carbonized Sorbents.

    PubMed

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

    2016-04-01

    Approaches based on the octanol-water partition coefficient are commonly used to describe sorption of neutral organic compounds in environmental systems, but they are not suitable for organic acids, which can dissociate to form anions. We here investigate the applicability of an alternative approach based on the pH-dependent distribution ratio (DOW) to describe sorption of aromatic acids to sorbents representing different degrees of carbonization. Sorption isotherms for four structurally similar acids ((2,4-dichlorophenoxy)acetic acid (2,4-D), 4-chloro-2-15 methylphenoxy)acetic acid (MCPA), 4-(2,4-dichlorophenoxy)butanoic16 acid (2,4-DB), and 5-chloro-2-(2,4-dichlorophenoxy)phenol (triclosan)) were measured for 15 sorbents: fresh and carbonized wood shavings, pig manure, sewage sludge, carbon nanotubes, and activated carbon. Dissociation greatly affected the sorption of all acids. Sorption coefficients measured in the high pH range indicated that sorption of the anions ranged over several orders of magnitude and should not be neglected. Sorption trends for all sorbates and carbonized sorbents could be very well described by a single regression equation that included DOW of the sorbate and the specific surface area of the sorbent (R(2) > 0.89). PMID:26949216

  18. Kinetics of histidine sorption and desorption on Fumasep® FTCM cation-exchange membranes

    NASA Astrophysics Data System (ADS)

    Maigurova, N. I.; Eliseeva, T. V.; Lantsuzskaya, E. V.; Sholokhova, A. Yu.

    2015-05-01

    The sorption of the basic amino acid histidine by Fumasep® FTCM membranes in different ionic forms is investigated over a wide range of solution concentrations. It is established that sorption limited by the stage of external diffusion. The time required for equilibrium to be established in the membrane-amino acid solution system is found to grow from 4 to 9 h when the initial concentration of the solution is reduced. The reversibility of histidine sorption is demonstrated, and the conditions of effective desorption are determined.

  19. On the fractality of the Freundlich adsorption isotherm in equilibrium and non-equilibrium cases.

    PubMed

    Borys, Przemysław; Grzywna, Zbigniew J

    2016-07-27

    We investigate the relationship between the Freundlich adsorption exponent and the fractal dimension of the adsorption sites for quasi-monolayer adsorption, and of the adsorbed aggregate for a simple case of multilayer adsorption. We further check whether the Freundlich adsorption mechanism may contribute to anomalous diffusion in the transport through porous materials. PMID:27414951

  20. Water sorption properties of HM-pectin and liposomes intended to alleviate dry mouth.

    PubMed

    Adamczak, Małgorzata I; Martinsen, Ørjan G; Smistad, Gro; Hiorth, Marianne

    2016-06-15

    Pharmaceutical formulations intended for treatment of xerostomia (dry mouth) should be able to keep the oral mucosa hydrated for a prolonged period of time. The products already existing on the market contain water-soluble polymers, however their ability to moisturize the oral mucosa for a longer period of time seems limited. In this paper the sorption properties of water vapor of high-methoxylated pectin (HM-pectin, a hydrophilic biopolymer) and phosphatidylcholine-based (Soya-PC) liposomes have been studied and compared using a gravimetric method. The kinetics of water desorption and sorption have been recorded over the relative humidity range RH=95-0-95%, at 35°C. The obtained isotherms were found to be well described by the n-layer Brunauer-Emmet-Teller (BET) adsorption model. The water isotherms on HM-pectin were Type II (IUPAC), while water isotherms on liposomes were Type III. The maximum water sorption capacity of liposomes (1.2mg water per mg of adsorbent at 95% RH) was found to be twice as high as for pectin. Due to the slower water release from the liposomes, as well as their high water sorption capacity, they seem to have great potential in relieving the symptoms of dry mouth syndrome. PMID:27109048

  1. Separation of water-ethanol mixtures by sorption

    SciTech Connect

    Schumacher, W.A.; Hwa, V.W.S.

    1980-01-01

    An experimental investigation was performed which examined sorption as a means for recovering anhydrous ethanol from water-ethanol mixtures. Adsorption isotherms were obtained at ambient temperature for two sorbents: a styrene-divinylbenzene copolymer manufactured by Rohm and Haas (Amberlite XAD-4) and Linde molecular sieve (No. 4966-77). Both sorbents appeared to reach a saturation level of ethanol on the sorbent for the range of ethanol concentration considered (0 to 12 wt % ethanol). The Linde sieve was more effective than the Rohm and Haas copolymer for the removal of ethanol from dilute solutions.

  2. Sorption selectivity of birnessite particle edges: a d-PDF analysis of Cd(ii) and Pb(ii) sorption by δ-MnO2 and ferrihydrite.

    PubMed

    van Genuchten, Case M; Peña, Jasquelin

    2016-08-10

    Birnessite minerals (layer-type MnO2), which bear both internal (cation vacancies) and external (particle edges) metal sorption sites, are important sinks of contaminants in soils and sediments. Although the particle edges of birnessite minerals often dominate the total reactive surface area, especially in the case of nanoscale crystallites, the metal sorption reactivity of birnessite particle edges remains elusive. In this study, we investigated the sorption selectivity of birnessite particle edges by combining Cd(ii) and Pb(ii) adsorption isotherms at pH 5.5 with surface structural characterization by differential pair distribution function (d-PDF) analysis. We compared the sorption reactivity of δ-MnO2 to that of the nanomineral, 2-line ferrihydrite, which exhibits only external surface sites. Our results show that, whereas Cd(ii) and Pb(ii) both bind to birnessite layer vacancies, only Pb(ii) binds extensively to birnessite particle edges. For ferrihydrite, significant Pb(ii) adsorption to external sites was observed (roughly 20 mol%), whereas Cd(ii) sorption was negligible. These results are supported by bond valence calculations that show comparable degrees of saturation of oxygen atoms on birnessite and ferrihydrite particle edges. Therefore, we propose that the sorption selectivity of birnessite edges follows the same order of that reported previously for ferrihydrite: Ca(ii) < Cd(ii) < Ni(ii) < Zn(ii) < Cu(ii) < Pb(ii). PMID:27183472

  3. Comparison of raw and modified activated carbon and rice industry wastes for methylene blue sorption

    NASA Astrophysics Data System (ADS)

    Befani, Maria; Manariotis, Ioannis D.; Karapanagioti, Hrissi K.; Quintero, César E.

    2015-04-01

    In Argentina the average paddy rice production was 1.3x106 tn/year in the last decade. Entre Ríos province (E.R.) accounts for 60% of national milling, resulting in a significant accumulation of waste in the local environment; husk and ashes are used as fuel in drying grain plants. The use of rice wastes, as low-cost sorbents for the removal of synthetic dyes and other contaminants may be a sustainable option. The aim of this work is the investigation of the removal capacity of methylene blue (MB) from aqueous solutions using: (a) rice husk from a rice mill located in E.R. of size between 0.15 to 1.18 mm (RH2), (b) ash from rice husk burned at 800°C in oven for the grain drying unit of the rice mill (RHA800), and (c) biochar obtained from pyrolysis of RH2 material at 850°C (RHA4). Commercial activated carbon (AC), which is a porous material of high sorption capacity, was also used to compare its sorption capacity with the rice husk products. Furthermore, the incorporation of iron in the AC was studied using two different AC/Fe weight-by-weight ratios (AC-Fe and AC-0.5 Fe). The solution pH effect was studied in a range from 2 to 6.9. The maximal MB removal was achieved at pH of 6.8 to 6.9 for all materials studied, and at pH of 6.4 for AC. Kinetic experiments were conducted for a period of 48 h at pH 7 and C0 = 50 mg MB/L. Equilibrium was reached after 24 h and the adsorption capacity was 156, 104, 90, 79, 26, and 9 mg/g for AC, AC-Fe, AC-0.5 Fe, RHA4, RH2 and RHA800, respectively. The pseudo-second-order model expressed better the sorption kinetics of MB for all adsorbent materials. The AC-based materials presented better performance. The experimental data were fitted with the Freundlich and Langmuir isotherm models. The Langmuir model fits the data better in all cases. The maximum adsorption capacity was 238, 125, 92, 91, 46 and 9 mg/g for AC, AC-Fe, AC-0.5 Fe, RHA4, RH2 and RHA800, respectively. Agricultural wastes can be considered low-cost sorbents, but

  4. Investigation of the carbon dioxide sorption capacity and structural deformation of coal

    SciTech Connect

    Hur, Tae-Bong; Fazio, James; Romanov, Vyacheslav; Harbert, William

    2010-01-01

    Due to increasing atmospheric CO2 concentrations causing the global energy and environmental crises, geological sequestration of carbon dioxide is now being actively considered as an attractive option to mitigate greenhouse gas emissions. One of the important strategies is to use deep unminable coal seams, for those generally contain significant quantities of coal bed methane that can be recovered by CO2 injection through enhanced coal bed natural gas production, as a method to safely store CO2. It has been well known that the adsorbing CO2 molecules introduce structural deformation, such as distortion, shrinkage, or swelling, of the adsorbent of coal organic matrix. The accurate investigations of CO2 sorption capacity as well as of adsorption behavior need to be performed under the conditions that coals deform. The U.S. Department of Energy-National Energy Technology Laboratory and Regional University Alliance are conducting carbon dioxide sorption isotherm experiments by using manometric analysis method for estimation of CO2 sorption capacity of various coal samples and are constructing a gravimetric apparatus which has a visual window cell. The gravimetric apparatus improves the accuracy of carbon dioxide sorption capacity and provides feasibility for the observation of structural deformation of coal sample while carbon dioxide molecules interact with coal organic matrix. The CO2 sorption isotherm measurements have been conducted for moist and dried samples of the Central Appalachian Basin (Russell County, VA) coal seam, received from the SECARB partnership, at the temperature of 55 C.

  5. Ion exchange during heavy metal bio-sorption from aqueous solution by dried biomass of macrophytes.

    PubMed

    Verma, V K; Tewari, Saumyata; Rai, J P N

    2008-04-01

    In this study, potentials of oven dried biomass of Eichhornia crassipes, Valisneria spiralis and Pistia stratiotes, were examined in terms of their heavy metal (Cd, Ni, Zn, Cu, Cr and Pb) sorption capacity, from individual-metal and multi-metal aqueous solutions at pH 6.0+/-0.1 (a popular pH of industrial effluent). V. spiralis was the most and E. crassipes was the least efficient for removal of all the metals. Cd, Pb and Zn were efficiently removed by all the three biomass. Cd was removed up to 98% by V. spiralis. Sorption data for Cr, Ni and Cd fitted better to Langmuir isotherm equation, while, the sorption data for Pb, Zn and Cu fitted better to Freundlich isotherm equation. In general, the presence of other metal ions did not influence significantly the targeted metal sorption capacity of the test plant biomasses. Ion exchange was proven the main mechanism involved in bio-sorption and there was a strong ionic balance between adsorbed (H(+) and M(2+)) to the released ions (Na(+) and K(+)) to and from the biomass. No significant difference was observed in the metal exchanged amount, by doubling of metal concentration (15-30 mg/l) in the solution and employing individual-metal and multi-metal solutions. PMID:17513104

  6. Binding Isotherms and Time Courses Readily from Magnetic Resonance

    PubMed Central

    2016-01-01

    Evidence is presented that binding isotherms, simple or biphasic, can be extracted directly from noninterpreted, complex 2D NMR spectra using principal component analysis (PCA) to reveal the largest trend(s) across the series. This approach renders peak picking unnecessary for tracking population changes. In 1:1 binding, the first principal component captures the binding isotherm from NMR-detected titrations in fast, slow, and even intermediate and mixed exchange regimes, as illustrated for phospholigand associations with proteins. Although the sigmoidal shifts and line broadening of intermediate exchange distorts binding isotherms constructed conventionally, applying PCA directly to these spectra along with Pareto scaling overcomes the distortion. Applying PCA to time-domain NMR data also yields binding isotherms from titrations in fast or slow exchange. The algorithm readily extracts from magnetic resonance imaging movie time courses such as breathing and heart rate in chest imaging. Similarly, two-step binding processes detected by NMR are easily captured by principal components 1 and 2. PCA obviates the customary focus on specific peaks or regions of images. Applying it directly to a series of complex data will easily delineate binding isotherms, equilibrium shifts, and time courses of reactions or fluctuations. PMID:27458657

  7. Binding Isotherms and Time Courses Readily from Magnetic Resonance.

    PubMed

    Xu, Jia; Van Doren, Steven R

    2016-08-16

    Evidence is presented that binding isotherms, simple or biphasic, can be extracted directly from noninterpreted, complex 2D NMR spectra using principal component analysis (PCA) to reveal the largest trend(s) across the series. This approach renders peak picking unnecessary for tracking population changes. In 1:1 binding, the first principal component captures the binding isotherm from NMR-detected titrations in fast, slow, and even intermediate and mixed exchange regimes, as illustrated for phospholigand associations with proteins. Although the sigmoidal shifts and line broadening of intermediate exchange distorts binding isotherms constructed conventionally, applying PCA directly to these spectra along with Pareto scaling overcomes the distortion. Applying PCA to time-domain NMR data also yields binding isotherms from titrations in fast or slow exchange. The algorithm readily extracts from magnetic resonance imaging movie time courses such as breathing and heart rate in chest imaging. Similarly, two-step binding processes detected by NMR are easily captured by principal components 1 and 2. PCA obviates the customary focus on specific peaks or regions of images. Applying it directly to a series of complex data will easily delineate binding isotherms, equilibrium shifts, and time courses of reactions or fluctuations. PMID:27458657

  8. Predictive modeling of an azo metal complex dye sorption by pumpkin husk.

    PubMed

    Çelekli, Abuzer; Bozkurt, Hüseyin

    2013-10-01

    Effective disposal of pumpkin husk (PH) as a redundant waste is a significant work for environmental protection and full utilization of resource. Predictive modeling of sorption of Lanaset Red (LR) G on PH was investigated in a batch system as functions of particle size, adsorbent dose, pH, temperature, and initial dye concentration. Fourier transform infrared spectroscopy attenuated total reflectance spectra of PH powders before and after the sorption of LR G were determined. Sorption process was found to be dependent on particle size, adsorbent dose, pH, temperature, initial dye concentration, and contact time. Amine and amide groups of PH had significant effect on the sorption process. The pHzpc of PH was found as 6.4. Sorption process was very fast initially and reached equilibrium within 60 min. Dynamic behavior of sorption was well represented by logistic and Avrami models. The sorption of LR G on PH was excellently described by Langmuir model, indicating a homogeneous phenomenon. Monolayer sorption capacity decreased from 440.78 to 436.28 mg g(-1) with increasing temperature. Activation energy, thermodynamic, and desorption studies showed that this process was physical character, exothermic, and spontaneous. This study confirmed that PH as an effective and low-cost adsorbent had a great potential for the removal of LR G as an alternative eco-friendly process. PMID:23625123

  9. Picloram and napropamide sorption as affected by polymer addition and salt concentration.

    PubMed

    Lu, Jianhang; Wu, Laosheng; Letey, John; Farmer, Walter J

    2002-01-01

    Polymer application to soil is a growing practice to improve soil physical properties and reduce soil erosion. Polymer addition can potentially influence herbicide and pesticide sorption in soil. The one-point distribution coefficient Kd values of two herbicides in the absence and presence of each of 10 polymers (7 polyacrylamides and 3 polysaccharides) were determined by the batch equilibrium method. The results showed that nonionic napropamide [2-(alpha-naphthoxy)-N,N-diethyl propionamide] sorption was essentially unaffected by the presence of any of the polymers. The influence of polymers on anionic picloram (4-amino-3,5,6-trichloropicolinic acid) sorption depends on the charge characteristics of polymers and salt concentrations in the solution. Electrostatic interaction and competition for sorption sites are two primary underlying mechanisms for the polymer influence. At low salt concentration, the increased picloram sorption in the presence of both cationic and anionic polymers was attributed to different electrostatic interactions and polymer partitioning between soil and solution phases. At high salt levels, the presence of polymers had either no influence or a slightly negative influence on the picloram sorption, which was attributed to competition for sorption sites. In field conditions, it is more likely that polymers have no or a slightly negative influence on herbicide sorption due to the presence of salts. PMID:12175041

  10. 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. PMID:25002191

  11. Equilibrium Shaping

    NASA Astrophysics Data System (ADS)

    Izzo, Dario; Petazzi, Lorenzo

    2006-08-01

    We present a satellite path planning technique able to make identical spacecraft aquire a given configuration. The technique exploits a behaviour-based approach to achieve an autonomous and distributed control over the relative geometry making use of limited sensorial information. A desired velocity is defined for each satellite as a sum of different contributions coming from generic high level behaviours: forcing the final desired configuration the behaviours are further defined by an inverse dynamic calculation dubbed Equilibrium Shaping. We show how considering only three different kind of behaviours it is possible to acquire a number of interesting formations and we set down the theoretical framework to find the entire set. We find that allowing a limited amount of communication the technique may be used also to form complex lattice structures. Several control feedbacks able to track the desired velocities are introduced and discussed. Our results suggest that sliding mode control is particularly appropriate in connection with the developed technique.

  12. 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

  13. Thermodynamic properties of adsorbed water on silica gel - Exergy losses in adiabatic sorption processes

    NASA Astrophysics Data System (ADS)

    Worek, W. M.; Zengh, W.; San, J.-Y.

    1991-09-01

    In order to perform exergy analyses to optimize the transient heat and mass transfer processes involving sorption by solid adsorbents, the thermodynamic properties of adsorbed water must be determined. In this paper, the integral enthalpy and entropy are determined directly from isotherm data of water adsorbed on silica gel particles and silica gel manufactured in the form of a felt with 25 percent cotton as a support and Teflon as a binder. These results are then used to evaluate the exergy losses, due to the sorption and the convective heat and mass transfer processes, that occur in each portion of an adiabatic desiccant dehumidificaton cycle.

  14. SORPTION BEHAVIOR OF MONOSODIUM TITANATE AND AMORPHOUS PEROXOTITANATE MATERIALS UNDER WEAKLY ACIDIC CONDITIONS

    SciTech Connect

    Hobbs, D.; Elvington, M.; Click, D.

    2009-11-11

    Inorganic, titanate-based sorbents are tested with respect to adsorption of a variety of sorbates under weakly acidic conditions (pH 3). Specifically, monosodium titanate (MST) and amorphous peroxotitanate (APT) sorption characteristics are initially probed through a screening process consisting of a pair of mixed metal solutions containing a total of 29 sorbates including alkali metals, alkaline earth metals, transition metals, metalloids and nonmetals. MST and APT sorption characteristics are further analyzed individually with chromium(III) and cadmium(II) using a batch method at ambient laboratory temperature, varying concentrations of the sorbents and sorbates and contact times. Maximum sorbate loadings are obtained from the respective adsorption isotherms.

  15. Sorption aspects for in situ matrix diffusion modeling at Palmottu natural analogue site, SW Finland

    SciTech Connect

    Rasilainen, K.; Suksi, J.; Hakanen, M.; Olin, M.

    1995-12-31

    Concentration profiles in rock matrix around water-carrying fissures were measured at Palmottu U deposit. The profiles were interpreted by the classical matrix diffusion concept. Site-specific sorption studies were performed for U using standard batch experiments and surface complexation modeling; the response of sorption isotherms was also tested. Site-specific matrix properties as well as initial and boundary conditions were used in simulations. The results indicate that matrix diffusion alone cannot explain the observed enrichment of U and its daughters in the rock matrix.

  16. Sorption of organic gases in a furnished room

    SciTech Connect

    Singer, Brett C.; Revzan, Kenneth L.; Hotchi, Toshifumi; Hodgson, Alfred T.; Brown, Nancy J.

    2003-11-30

    We present experimental data and semi-empirical models describing the sorption of organic gases in a simulated indoor residential environment. Two replicate experiments were conducted with 20 volatile organic compounds (VOCs) in a 50-m{sup 3} room finished with painted wallboard, carpet and cushion, draperies and furnishings. The VOCs span a wide volatility range and include ten Hazardous Air Pollutants. VOCs were introduced to the static chamber as a pulse and their gas-phase concentrations were measured during a net adsorption period and a subsequent net desorption period. Three sorption models were fit to the measured concentrations for each compound to determine the simplest formulation needed to adequately describe the observed behavior. Sorption parameter values were determined by fitting the models to adsorption period data then checked by comparing measured and predicted behavior during desorption. The adequacy of each model was evaluated using a goodness of fit parameter calculated for each period. Results indicate that sorption usually does not greatly affect indoor concentrations of methyl-tert-butyl ether, 2-butanone, isoprene and benzene. In contrast, sorption appears to be a relevant indoor process for many of the VOCs studied, including C{sub 8}-C{sub 10} aromatic hydrocarbons (HC), terpenes, and pyridine. These compounds sorbed at rates close to typical residential air change rates and exhibited substantial sorptive partitioning at equilibrium. Polycyclic aromatic HCs, aromatic alcohols, ethenylpyridine and nicotine initially adsorbed to surfaces at rates of 1.5 to >6 h{sup -1} and partitioned 95 to >99% in the sorbed phase at equilibrium.

  17. Sorption of selected organic compounds from water to a peat soil and its humic-acid and humin fractions: Potential sources of the sorption nonlinearity

    USGS Publications Warehouse

    Chiou, C.T.; Kile, D.E.; Rutherford, D.W.; Sheng, G.; Boyd, S.A.

    2000-01-01

    The sorption isotherms of ethylene dibromide (EDB), diuron (DUN), and 3,5-dichlorophenol (DCP) from water on the humic acid and humin fractions of a peat soil and on the humic-acid of a muck soil have been measured. The data were compared with those of the solutes with the whole peat from which the humic-acid (HA) and humin (HM) fractions were derived and on which the sorption of the solutes exhibited varying extents of nonlinear capacities at low relative concentrations (C(e)/S(w)). The HA fraction as prepared by the density-fractionated method is relatively pure and presumably free of high- surface-area carbonaceous material (HSACM) that is considered to be responsible for the observed nonlinear sorption for nonpolar solutes (e.g., EDB) on the peat; conversely, the base-insoluble HM fraction as prepared is presumed to be enriched with HSACM, as manifested by the greatly higher BET- (N2) surface area than that of the whole peat. The sorption of EDB on HA exhibits no visible nonlinear effect, whereas the sorption on HM shows an enhanced nonlinearity over that on the whole peat. The sorption of polar DUN and DCP on HA and HM display nonlinear effects comparable with those on the whole peat; the effects are much more significant than those with nonpolar EDB. These results conform to the hypothesis that adsorption onto a small amount of strongly adsorbing HSACM is largely responsible for the nonlinear sorption of nonpolar solutes on soils and that additional specific interactions with the active groups of soil organic matter are responsible for the generally higher nonlinear sorption of the polar solutes.

  18. 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

  19. 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

  20. Phosphorus sorption capacities and physicochemical properties of nine substrate materials for constructed wetland

    SciTech Connect

    Cui, L.H.; Zhu, X.Z.; Ma, M.; Ouyang, Y.; Dong, M.; Zhu, W.L.; Luo, S.M.

    2008-08-15

    Constructed wetland (CW) is a promising technique for removal of pollutants from wastewater and agricultural runoff. The performance of a CW to remove pollutants, however, hinges on the use of suitable substrate materials. This study examined the physicochemical properties and phosphorus (P) sorption capacities of nine different CW substrate materials using both batch experiments and the Freundlich as well as the Langmuir isotherm. The nine substrate materials used in this study were turf, topsoil, gravel, midsized sand (MSS), blast furnace slag (BFS), coal burn slag (CBS), blast furnace artificial slag (BFAS), coal burn artificial slag (CBAS), and midsized artificial sand (MSAS). Experimental data showed that sorption of P increased with initial solution P concentrations for all nine substrate materials. The maximum P sorption capacity of the substrate materials estimated by Langmuir isotherm was in the following order: turf (4243 mg/kg substrate) > BFAS (2116 mg/kg substrate) > BFS (1598 mg/kg substrate) > CBS (1449 mg/kg substrate) > top soil (1396 mg/kg substrate) > CBAS (1194 mg/kg substrate) > MSAS (519 mg/kg substrate) > gravel (494 mg/kg substrate) > MSS (403 mg/kg substrate). The specific gravity of eight substrate materials (except gravel) had very significant negative correlations with the P sorption, whereas the particle diameter of D-60 and uniformity coefficient (K-60) had positive correlations with the P sorption. The cation exchange capacity, organic matter, available ferrous, and exchangeable aluminum of the eight substrate materials also had very significant positive correlations with the P sorption, while the pH of the substrate materials showed a very significant negative correlation with the P sorption. Our study further suggests that turf and CBAS are the two relatively ideal substrate materials suitable for removal of P from a CW system.

  1. Phosphorus sorption capacities and physicochemical properties of nine substrate materials for constructed wetland.

    PubMed

    Cui, Lihua; Zhu, Xizhen; Ma, Mei; Ouyang, Ying; Dong, Mei; Zhu, Wenling; Luo, Shiming

    2008-08-01

    Constructed wetland (CW) is a promising technique for removal of pollutants from wastewater and agricultural runoff. The performance of a CW to remove pollutants, however, hinges on the use of suitable substrate materials. This study examined the physicochemical properties and phosphorus (P) sorption capacities of nine different CW substrate materials using both batch experiments and the Freundlich as well as the Langmuir isotherm. The nine substrate materials used in this study were turf, topsoil, gravel, midsized sand (MSS), blast furnace slag (BFS), coal burn slag (CBS), blast furnace artificial slag (BFAS), coal burn artificial slag (CBAS), and midsized artificial sand (MSAS). Experimental data showed that sorption of P increased with initial solution P concentrations for all nine substrate materials. The maximum P sorption capacity of the substrate materials estimated by Langmuir isotherm was in the following order: turf (4243 mg/kg substrate) > BFAS (2116 mg/kg substrate) > BFS (1598 mg/kg substrate) > CBS (1449 mg/kg substrate) > top soil (1396 mg/kg substrate) > CBAS (1194 mg/kg substrate) > MSAS (519 mg/kg substrate) > gravel (494 mg/kg substrate) > MSS (403 mg/kg substrate). The specific gravity of eight substrate materials (except gravel) had very significant negative correlations with the P sorption, whereas the particle diameter of D(60) and uniformity coefficient (K(60)) had positive correlations with the P sorption. The cation exchange capacity, organic matter, available ferrous, and exchangeable aluminum of the eight substrate materials also had very significant positive correlations with the P sorption, while the pH of the substrate materials showed a very significant negative correlation with the P sorption. Our study further suggests that turf and CBAS are the two relatively ideal substrate materials suitable for removal of P from a CW system. PMID:18175159

  2. Comparison of nonideal sorption formulations in modeling the transport of phthalate esters through packed soil columns

    NASA Astrophysics Data System (ADS)

    Maraqa, Munjed A.; Zhao, Xianda; Lee, Jae-ug; Allan, Fathi; Voice, Thomas C.

    2011-07-01

    Sorption of dimethyl phthalate (DMP), diethyl phthalate (DEP) and dipropyl phthalate (DPP) to two soil materials that vary in organic matter content was investigated using miscible displacement experiments under saturated flow conditions. Generated breakthrough curves (BTCs) were inversely simulated using linear, equilibrium sorption (LE), nonlinear, equilibrium sorption (NL), linear, first-order nonequilibrium sorption (LFO), linear, radial diffusion (LRD), and nonlinear, first-order nonequilibrium sorption (NFO) models. The Akaike information criterion was utilized to determine the preferred model. The LE model could not adequately describe phthalate ester (PE) BTCs in higher organic matter soil or for more hydrophobic PEs. The LFO and LRD models adequately described the BTCs but a slight improvement in curve-fitting was gained in some cases when the NFO model was used. However, none of the models could properly describe the desorptive tail of DPP for the high organic matter soil. Transport of DPP through this soil was adequately predicted when degradation or sorption hysteresis was considered. Using the optimized parameter values along with values reported by others it was shown that the organic carbon distribution coefficient ( Koc) of PEs correlates well with the octanol/water partition coefficient ( Kow). Also, a strong relationship was found between the first-order sorption rate coefficient normalized to injection pulse size and compound residence time. A similar trend of timescale dependence was found for the rate parameter in the radial diffusion model. Results also revealed that the fraction of instantaneous sorption sites is dependent on Kow and appears to decrease with the increase in the sorption rate parameter.

  3. Isotherm study of reactive Blue 19 adsorption by an alum sludge

    NASA Astrophysics Data System (ADS)

    Khim, Ong Keat; Nor, Mohd Asri Md; Mohamad, Syuriya; Nasaruddin, Nas Aulia Ahmad; Jamari, Nor Laili-Azua; Yunus, Wan Md Zin Wan

    2015-05-01

    This study investigates the adsorption of Reactive Blue 19 using dewatered alum sludge. The dewatered alum sludge was a sludge produced from drinking water treatment plant. Batch adsorption experiments were performed to investigate the mechanism of the dye adsorption. The adsorption was rapid at its initial stage but the rate decreased as it approached equilibrium. The adsorption data were evaluated by Langmuir and Freundlich isotherm models but was best described by the Langmuir isotherm model as it gave the highest correlation.

  4. Solution chemistry effects on sorption behavior of radionuclide 63Ni(II) in illite-water suspensions

    NASA Astrophysics Data System (ADS)

    Hu, Baowei; Cheng, Wen; Zhang, Hui; Yang, Shitong

    2010-11-01

    In this work, a naturally occurring illite was characterized by using FTIR and XRD to determine its chemical constituents and crystal structure. A series of batch experiments were carried out to investigate the effect of various environmental factors such as contact time, pH, ionic strength, foreign ions, coexisting humic substances and temperature on the sorption behavior of illite towards radionuclide 63Ni(II). The sorption of 63Ni(II) on illite was strongly dependent on pH and ionic strength. A positive effect of HA/FA on 63Ni(II) sorption was found at pH < 6.5, whereas a negative effect was observed at pH > 6.5. The Langmuir, Freundlich, and D-R models were used to simulate the sorption isotherms of 63Ni(II) at three different temperatures of 293, 313 and 333 K. The thermodynamic parameters (Δ H0, Δ S0 and Δ G0) of 63Ni(II) sorption on illite were calculated from the temperature dependent sorption isotherms, and the results indicated that the sorption of 63Ni(II) on illite was endothermic and spontaneous. At low pH, the sorption of 63Ni(II) was dominated by outer-sphere surface complexation and ion exchange with Na +/H + on illite surfaces, whereas inner-sphere surface complexation was the main sorption mechanism at high pH. From the experimental results, it is possible to conclude that illite has good potentialities for cost-effective treatments of 63Ni(II)-contaminated wastewaters.

  5. Silica Precipitation and Lithium Sorption

    SciTech Connect

    Jay Renew

    2015-09-20

    This file contains silica precipitation and lithium sorption data from the project. The silica removal data is corrected from the previous submission. The previous submission did not take into account the limit of detection of the ICP-MS procedure.

  6. Influence of organic matter type and medium composition on the sorption affinity of C12-benzalkonium cation.

    PubMed

    Chen, Yi; Hermens, Joop L M; Droge, Steven T J

    2013-08-01

    We used the 7-μm polyacrylate ion-exchange SPME fibers to investigate C12-benzalkonium sorption to 10 mg/L natural organic matter at concentrations well below the cation-exchange capacity. C12-BAC sorption at constant medium conditions differed within 0.4 log units for two humic acids (Aldrich, Leonardite) and peat (Sphagnum, Pahokee), with similar nonlinear sorption isotherms (KF ∼ 0.8). Sorption to the SPME fibers and Aldrich humic acid (AHA) was reduced at both low pH and high electrolyte concentration, and reduced more strongly by Ca²⁺ compared with Na⁺ at similar concentrations. Sorption isotherms for AHA (5-50-500 mM Na⁺, pH 6) was modeled successfully by the NICA-Donnan approach, resulting in an intrinsic sorption coefficient of 5.35 (Caq = 1 nM). The NICA-Donnan model further explained the stronger specific binding of Ca²⁺ compared to Na⁺ by differences in Boltzmann factors. This study provides relevant information to interpret bioavailability of quaternary ammonium compounds, and possibly for other organic cations. PMID:23676325

  7. Factors influencing sorption of ciprofloxacin onto activated sludge: experimental assessment and modelling implications.

    PubMed

    Polesel, Fabio; Lehnberg, Kai; Dott, Wolfgang; Trapp, Stefan; Thomas, Kevin V; Plósz, Benedek Gy

    2015-01-01

    Many of the pharmaceuticals and personal care products occurring in municipal sewage are ionizing substances, and their partitioning behaviour is affected by ionic interactions with solid matrices. In activated sludge systems, such interactions have currently not been adequately understood and described, particularly for zwitterionic chemicals. Here we present an assessment of the effects of pH and iron salt dosing on the sorption of ciprofloxacin onto activated sludge using laboratory experiments and full-scale fate modelling. Experimental results were described with Freundlich isotherms and showed that non-linear sorption occurred under all the conditions tested. The greatest sorption potential was measured at pH=7.4, at which ciprofloxacin is speciated mostly as zwitterion. Iron salt dosing increased sorption under aerobic and, to a lesser extent, anoxic conditions, whereas no effect was registered under anaerobic conditions. The activated sludge model for xenobiotics (ASM-X) was extended with Freundlich-based sorption kinetics and used to predict the fate of ciprofloxacin in a wastewater treatment plant (WWTP). Scenario simulations, using experimental Freundlich parameters, were used to identify whether the assessed factors caused a significant increase of aqueous ciprofloxacin concentration in full-scale bioreactors. Simulation results suggest that a pH increase, rather than a reduction in iron salt dosing, could be responsible for a systematic deterioration of sorption of ciprofloxacin in the WWTP. PMID:24972177

  8. Uranium sorption onto natural sands as a function of sediment characteristics and solution pH

    SciTech Connect

    Rosentreter, J.J.; Quarder, S.H.; Smith, R.W.; McLing, T.

    1996-10-01

    Uranium sorption studies were conducted on twenty-five sandy sediments obtained from Virginia`s Easter Shore Peninsula using batch contact methods. Distribution coefficient (Kd) and sorption isotherms have been determined as function of solution pH. All sediment samples strongly sorbed dissolved uranium species at pH values above 5. Sediments characterized by high iron, aluminum, and surface area, possessed the highest sorption characteristics. Both, Freundlich and Dubinin Radushkevich equations were able to describe the sorption behavior. From the Dubinin-Radushkevich equation, the solution-component-solid surface bounding energy and the sorption capacities, were estimated. Least square regression utilizing sediment characteristics provided an effective statistical method for Kd prediction. Predictions with relative errors of about 30% were obtained using only two sediment variables, such as, iron or aluminum content and surface area. In conclusion, the results support that ion exchange and surface complexation reactions with the ferric and aluminum oxide/oxyhydroxides groups are the predominant sorption mechanisms.

  9. Sorption characteristics of N-nitrosodimethylamine onto biochar from aqueous solution.

    PubMed

    Chen, Cuiping; Zhou, Wenjun; Lin, Daohui

    2015-03-01

    N-nitrosodimethylamine (NDMA) is an emerging carcinogenic disinfection by-product in water environment. Biochars utilized as sorbents for the removal of NDMA from aqueous solution, and the sorption characteristics and mechanism were investigate. Biochars were prepared from bamboo, rice straw and wood sawdust at 300-700°C. The pseudo-second-order model provided the best fit for the sorption kinetics of NDMA onto biochar and the sorption isotherms were described best with the Slips model. Biochar produced at 500°C removed NDMA from aqueous solution relatively efficiently, and the bamboo char demonstrated the best sorption potential among the three types of biochars. Solution chemistry such as pH and metal ions did not show obvious effect on NDMA removal. Three sorption mechanisms are suggested for NDMA sorption onto biochars, H-bond attraction between -N=O and the O-containing moieties, hydrophobic force between -CH3 and the ordered graphitic structure, and partition process of NDMA into the non-carbonization part of biochar. PMID:25553566

  10. Sorption of cadmium and lead by clays from municipal incinerator ash- water suspensions

    USGS Publications Warehouse

    Roy, W.R.; Krapac, I.G.; Steele, J.D.

    1993-01-01

    The effect of Cl complexation in extracts of a flue gas-scrubber incinerator fly ash sample on the sorption of Cd and Pb by kaolinite and illite was investigated using batch-sorption methods. In the pH range of 5 to 9, Cl complexation may reduce sorption and thus increase the mobility of these metals. When an ash-water suspension was acidified to pH 6.85, the dissolution of Cl and Ca essentially eliminated Cd sorption because of complexation and cationic competition. Cadmium would be considered as either mobile or very mobile under these conditions. Lead was not soluble in the pH- 6.85 suspension. At pH 12, the approximate pH of water in contact with flue gas-scrubber fly ash, Cd was essentially insoluble and Pb occurred as anionic Pb hydroxide. Anionic Pb was sorbed by the two clays, and the extent of sorption was not influenced by Cl or carbonate complexation. Sorption constants, derived from isotherms, suggested that Pb would be relatively immobile in saturated soil-water systems. The recent concern that highly alkaline, flue gas-scrubber fly ash may release environmentally significant concentrations of mobile Pb when placed in an ash-disposal site with a soil liner should be reevaluated in light of this study.

  11. Enhanced sorption of polycyclic aromatic hydrocarbons from aqueous solution by modified pine bark.

    PubMed

    Li, Yungui; Chen, Baoliang; Zhu, Lizhong

    2010-10-01

    To enhance removal efficiency of natural sorbent with polycyclic aromatic hydrocarbons (PAHs), single-solute and bi-solute sorption of phenanthrene and pyrene onto raw and modified pine bark were investigated. Pine bark was modified using Soxhlet extraction, saponification and acid hydrolysis, yielding six bark fractions with different chemical compositions. Raw pine bark exhibited high affinities with PAHs, and sorption was dominated by partitioning. The relatively nonlinear sorption isotherms of modified bark were attributed to the specific interaction between sorbate and aromatic core of sorbent. Comparison with lipid and suberin, lignin was the most powerful sorption medium, but which was almost completely suppressed by coexisting polysaccharide. After consuming polysaccharide by acid hydrolysis, sorption of pine bark fractions was notably increased (4-17 folds); and sorption of pyrene just decreased 16-34% with phenanthrene as a competitor. These observations suggest that pine bark is of great potential for PAHs removal and can be significantly promoted by acid hydrolysis for environmental application. PMID:20576561

  12. Enhanced sorption of polycyclic aromatic hydrocarbons from aqueous solution by modified pine bark.

    PubMed

    Li, Yungui; Chen, Baoliang; Zhu, Lizhong

    2010-10-01

    To enhance removal efficiency of natural sorbent with polycyclic aromatic hydrocarbons (PAHs), single-solute and bi-solute sorption of phenanthrene and pyrene onto raw and modified pine bark were investigated. Pine bark was modified using Soxhlet extraction, saponification and acid hydrolysis, yielding six bark fractions with different chemical compositions. Raw pine bark exhibited high affinities with PAHs, and sorption was dominated by partitioning. The relatively nonlinear sorption isotherms of modified bark were attributed to the specific interaction between sorbate and aromatic core of sorbent. Comparison with lipid and suberin, lignin was the most powerful sorption medium, but which was almost completely suppressed by coexisting polysaccharide. After consuming polysaccharide by acid hydrolysis, sorption of pine bark fractions was notably increased (4-17 folds); and sorption of pyrene just decreased 16-34% with phenanthrene as a competitor. These observations suggest that pine bark is of great potential for PAHs removal and can be significantly promoted by acid hydrolysis for environmental application. PMID:20578284

  13. Influence of molecular structure and adsorbent properties on sorption of organic compounds to a temperature series of wood chars.

    PubMed

    Lattao, Charisma; Cao, Xiaoyan; Mao, Jingdong; Schmidt-Rohr, Klaus; Pignatello, Joseph J

    2014-05-01

    Chars from wildfires and soil amendments (biochars) are strong adsorbents that can impact the fate of organic compounds in soil, yet the effects of solute and adsorbent properties on sorption are poorly understood. We studied sorption of benzene, naphthalene, and 1,4-dinitrobenzene from water to a series of wood chars made anaerobically at different heat treatment temperatures (HTT) from 300 to 700 °C, and to graphite as a nonporous, unfunctionalized reference adsorbent. Peak suppression in the NMR spectrum by sorption of the paramagnetic relaxation probe TEMPO indicated that only a small fraction of char C atoms lie near sorption sites. Sorption intensity for all solutes maximized with the 500 °C char, but failed to trend regularly with N2 or CO2 surface area, micropore volume, mesopore volume, H/C ratio, O/C ratio, aromatic fused ring size, or HTT. A model relating sorption intensity to a weighted sum of microporosity and mesoporosity was more successful. Sorption isotherm linearity declined progressively with carbonization of the char. Application of a thermodynamic model incorporating solvent-water and char-graphite partition coefficients permitted for the first time quantification of steric (size exclusion in pores) and π-π electron donor-acceptor (EDA) free energy contributions, relative to benzene. Steric hindrance for naphthalene increases exponentially from 9 to 16 kJ/mol (∼ 1.6-2.9 log units of sorption coefficient) with the fraction of porosity in small micropores. π-π EDA interactions of dinitrobenzene contribute -17 to -19 kJ/mol (3-3.4 log units of sorption coefficient) to sorption on graphite, but less on chars. π-π EDA interaction of naphthalene on graphite is small (-2 to 2 kJ/mol). The results show that sorption is a complex function of char properties and solute molecular structure, and not very predictable on the basis of readily determined char properties. PMID:24758543

  14. Spectroscopic study of dinitrophenol herbicide sorption on smectite.

    PubMed

    Johnston, C T; Sheng, G; Teppen, B J; Boyd, S A; de Oliveira, M F

    2002-12-01

    Sorption of two dinitrophenolic herbicides, 4,6-dinitro-o-cresol (DNOC) and 4,6-dinitro-2-sec-butylphenol (DINOSEB) to smectite was studied using FTIR, HPLC, and quantum chemical methods. The high affinity of DNOC and DINOSEB for smectite surfaces was attributed to site-specific interactions with exchangeable cations and nonspecific van der Waals interactions with the siloxane surface. The positions of the nu(asym)(NO) and nu(sym)(NO) vibrational modes were perturbed by the exchangeable cations with similar changes occurring for both alkali and alkaline earth cations as a function of ionic potential. The cation-induced changes to the vibrational bands of the NO2 groups indicate that exchangeable metal cations are coordinated to -NO2 groups. Quantum chemical methods predicted a red-shift of the nu(asym)(NO) band and a corresponding blue-shift of the nu(sym)(NO) modes, as was observed experimentally. The nature of the smectite surface itself did not strongly influence the vibrational modes of sorbed DNOC or DINOSEB on the basis of a comparison of DNOC sorbed to three different smectites (K-SWy-2, K-SAz-1, and K-SHCa-1). FTIR spectra of DNOC and DINOSEB sorbed to a K-SWy-2 smectite were studied quantitatively using a modified form of Beers law. The FTIR-derived sorption isotherm of DNOC sorbed to K-SWy-2 was in good agreement with the isotherm derived from HPLC measurements. The molar absorptivity value of DNOC sorbed to K-SWy-2 smectite was 1.43 x 10(7) cm2/mol in good agreement with literature values for nitroaromatics (average value of 1.72 x 10(7) +/- 0.3 cm2/mol). On the basis of this value, the limit of detection using the FTIR method of approximately 5 microgDNOC g(clay) was determined. These two observations (sorption isotherms and molar absorptivity) provide a direct link between the macroscopic sorption results and the FTIR spectra. PMID:12523422

  15. Kinetics of selenate sorption in soil as influenced by biotic and abiotic conditions: a stirred flow-through reactor study.

    PubMed

    Garcia-Sanchez, L; Loffredo, N; Mounier, S; Martin-Garin, A; Coppin, F

    2014-12-01

    This study (i) quantified the kinetics of selenate sorption and (ii) measured the influence of biotic processes in soil selenate stabilisation. Stirred flow-through reactor experiments were conducted on samples of a silty clay soil (pH = 8, Eh = 240-300 mV) from Bure (France) in both non-sterile and sterile conditions. Parameters of the proposed two-site sorption model (EK), adapted from van Genuchten and Wagenet (1989), were estimated by nonlinear regression. Fast selenate sorption on type-1 sites was moderate, with an equilibrium constant of 25.5 and 39.1 L/kg for non-sterile and sterile conditions. Rate-limited sorption on type-2 sites increased with time, and was predominant for longer periods of time in non-sterile conditions. At equilibrium, it would represent over 96% of the sorbed inventory, with mean sorption times of 17 h and 191 h for non-sterile and sterile conditions. Our results showed for Bure soil that (i) selenate sorption in flowing and mildly-oxidising conditions was strongly kinetically controlled, especially in non-sterile conditions, (ii) selenate desorption was much slower than sorption, which suggests its pseudo-irreversible stabilisation, and (iii) microbial activity increased the contribution of rate-limited sorption on type-2 sites, for which it increased sorption rate by a factor 7 but also facilitated its reversibility. This work stresses the limits of the Kd approach to represent selenate sorption in flowing conditions and supports an alternative formulation like the EK model, but also points out that biotic conditions are significant sources of variability for sorption parameters. PMID:25151638

  16. Kinetics of neptunium(V) sorption and desorption on goethite: An experimental and modeling study

    NASA Astrophysics Data System (ADS)

    Tinnacher, Ruth M.; Zavarin, Mavrik; Powell, Brian A.; Kersting, Annie B.

    2011-11-01

    Various sorption phenomena, such as aging, hysteresis and irreversible sorption, can cause differences between contaminant (ad)sorption and desorption behavior and lead to apparent sorption 'asymmetry'. We evaluate the relevance of these characteristics for neptunium(V) (Np(V)) sorption/desorption on goethite using a 34-day flow-cell experiment and kinetic modeling. Based on experimental results, the Np(V) desorption rate is much slower than the (ad)sorption rate, and appears to decrease over the course of the experiment. The best model fit with a minimum number of fitting parameters was achieved with a multi-reaction model including (1) an equilibrium Freundlich site (site 1), (2) a kinetically-controlled, consecutive, first-order site (site 2), and (3) a parameter ψ, which characterizes the desorption rate on site 2 based on a concept related to transition state theory (TST). This approach allows us to link differences in adsorption and desorption kinetics to changes in overall reaction pathways, without assuming different adsorption and desorption affinities (hysteresis) or irreversible sorption behavior a priori. Using modeling as a heuristic tool, we determined that aging processes are relevant. However, hysteresis and irreversible sorption behavior can be neglected within the time-frame (desorption over 32 days) and chemical solution conditions evaluated in the flow-cell experiment. In this system, desorption reactions are very slow, but they are not irreversible. Hence, our data do not justify an assumption of irreversible Np(V) sorption to goethite in transport models, which effectively limits the relevance of colloid-facilitated Np(V) transport to near-field environments. However, slow Np(V) desorption behavior may also lead to a continuous contaminant source term when metals are sorbed to bulk mineral phases. Additional long-term experiments are recommended to definitely rule out irreversible Np(V) sorption behavior at very low surface loadings and

  17. Effect of the adsorbate (Bromacil) equilibrium concentration in water on its adsorption on powdered activated carbon. Part 2: Kinetic parameters.

    PubMed

    Al Mardini, Fadi; Legube, Bernard

    2009-10-30

    The application of several monosolute equilibrium models has previously shown that Bromacil adsorption on SA-UF (Norit) powdered activated carbon (PAC) is probably effective on two types of sites. High reactivity sites were found to be 10-20 less present in a carbon surface than lower reactivity sites, according to the q(m) values calculated by isotherm models. The aims of this work were trying, primarily, to identify the kinetic-determinant stage of the sorption of Bromacil at a wide range of initial pesticide concentrations (approximately 5 to approximately 500 microg L(-1) at pH 7.8), and secondly, to specify the rate constants and other useful design parameters for the application in water treatment. It was therefore not possible to specify a priori whether the diffusion or surface reaction is the key step. It shows that many of the tested models which describe the stage of distribution or the surface reaction are correctly applied. However, the diffusivity values (D and D(0)) were found to be constant only constants for some specific experimental concentrations. The HSDM model of surface diffusion in pores was also applied but the values of the diffusion coefficient of surface (D(s)) were widely scattered and reduce significantly with the initial concentration or the equilibrium concentration in Bromacil. The model of surface reaction of pseudo-second order fitted particularly well and led to constant values which are independent of the equilibrium concentration, except for the low concentrations where the constants become significantly more important. This last observation confirms perfectly the hypothesis based on two types of sites as concluded by the equilibrium data (part 1). PMID:19560269

  18. Sorption and desorption of Cr(VI) ions from water by biochars in different environmental conditions.

    PubMed

    Tytłak, Aleksandra; Oleszczuk, Patryk; Dobrowolski, Ryszard

    2015-04-01

    In the present research, the potential of two biochars produced by the thermal decomposition of wheat straw (BCS) and wicker (BCW) for Cr(VI) ions removing from wastewater was investigated. The pH and the presence of chlorides and nitrates were also investigated. The Freundlich and Langmuir models were applied for the characterization of adsorption isotherms. The Langmuir model has better fitting of adsorption isotherms than the Freundlich model. The sorption process can be described by the pseudo second-order equation. The optimal adsorption capacities were obtained at pH 2 and were 24.6 and 23.6 mg/g for BCS and BCW, respectively. X-ray photoelectron spectroscopy (XPS) studies confirmed that Cr(III) ions were the most abundant chromium species on the biochars' surface. The results indicated that the sorption mechanism of Cr(VI) on biochar involves anionic and cationic adsorption combined with Cr(VI) species reduction. PMID:25378029

  19. Sorption behavior of U(VI) on phyllite: experiments and modeling.

    PubMed

    Arnold, T; Zorn, T; Zänker, H; Bernhard, G; Nitsche, H

    2001-02-01

    The sorption of U(VI) onto low-grade metamorphic rock phyllite was modeled with the diffuse double layer model (DDLM) using the primary mineralogical constituents of phyllite, i.e. quartz, chlorite, muscovite, and albite, as input components, and as additional component, the poorly ordered Fe oxide hydroxide mineral, ferrihydrite. Ferrihydrite forms during the batch sorption experiment as a weathering product of chlorite. In this process, Fe(II), leached from the chlorite, oxidizes to Fe(III), hydrolyses and precipitates as ferrihydrite. The formation of ferrihydrite during the batch sorption experiment was identified by Mössbauer spectroscopy, showing a 2.8% increase of Fe(III) in the phyllite powder. The ferrihydrite was present as Fe nanoparticles or agglomerates with diameters ranging from 6 to 25 nm, with indications for even smaller particles. These Fe colloids were detected in centrifugation experiments of a ground phyllite suspension using various centrifugal forces. The basis for the successful interpretation of the experimental sorption data of uranyl(VI) on phyllite were: (1) the determination of surface complex formation constants of uranyl with quartz, chlorite, muscovite, albite, and ferrihydrite in individual batch sorption experiments, (2) the determination of surface acidity constants of quartz, chlorite, muscovite, and albite obtained from separate acid-base titration, (3) the determination of surface site densities of quartz, chlorite, muscovite, and albite evaluated independently of each other with adsorption isotherms, and (4) the quantification of the secondary phase ferrihydrite, which formed during the batch sorption experiments with phyllite. The surface complex formation constants and the protolysis constants were optimized by using the experimentally obtained data sets and the computer code FITEQL. Surface site densities were evaluated from adsorption isotherms at pH 6.5. The uranyl(VI) sorption onto phyllite was accurately modeled with

  20. Polycyclic aromatic hydrocarbon (PAH) sorption process to the "black carbon" (BC) component in river sediments

    NASA Astrophysics Data System (ADS)

    Zhang, Jing; Séquaris, Jean-Marie; Narres, Hans-Dieter; Vereecken, Harry; Klumpp, Erwin

    2010-05-01

    The importance of BC for the long term sequestration of organic carbon is actually discussed for mitigating climate change. In this context, the role of BC as a filter or source of nutrients or toxic chemicals is questioned. The fate of polycyclic aromatic hydrocarbons (PAHs) is especially concerned. In this study, we have investigated the binding of PAH compounds, pyrene and phenanthrene, to Yangtze River sediments. For this purpose, the PAHs sorption to pristine and preheated sediments at 375°C was studied, which allow discriminating the contributions of amorphous organic carbon (AOC) and black carbon (BC) fractions to the PAH sorption extent. An analytical procedure for the determination of PAHs in the solution phase of the batch experiments has been developed with fluorescence spectroscopy. The PAHs sorption isotherms to pristine sediments were fitted by Freundlich and composite models as linear Langmuir model (LLM) and linear Polanyi-Dubinin-Manes model (LPDMM). The sequential application of composite models LLM and LPDMM to the sorption isotherms allows assessing the partition of PAHs into AOC and its nonlinear adsorption in the porous structure of BC. The modelling results indicate that the PAHs sorption to minor BC component of sediments (< 0.2 % TOC) is more effective than that to the major AOC component (< 1.3 % TOC). A similar sorption capacity of BC in pristine and preheated sediments is also calculated at high PAHs concentrations, which indicates that the AOC fraction does not block the micropore filling of BC. The microporous structure and the hydrophobic nature of BC component in sediments are thus factors, which create favourable energetic sites for the sorption of PAHs in the river sediments. It can also be shown that a BC molecular sieving plays an important role in the competitive PAHs sorption in a multi-solute system. J. Zhang, Ph.D. Dissertation, RWTH Aachen, Germany, 2010 J. Zhang et al., Effects of organic carbon and clay fractions on the

  1. Isotherm parameters and intraparticle mass transfer kinetics on molecularly imprinted polymers in acetonitrile/buffer mobile phases

    SciTech Connect

    Kim, Hyunjung; Kaczmarski, Krzysztof; Guiochon, Georges A

    2006-03-01

    The equilibrium isotherm and the intraparticle mass transfer kinetics of the enantiomers of the template were investigated on an Fmoc-L-tryptophan (Fmoc-L-Trp) imprinted polymer at different pHs and water concentrations in acetonitrile/aqueous buffer mobile phases. The equilibrium isotherm data were measured using frontal analysis at 25 {+-} 2 C. The adsorption energy distribution was found to be trimodal, with narrow modes. Consistent with this distribution, the adsorption data were modeled using a tri-Langmuir isotherm equation and the best estimates of the isotherm parameters were determined. The intraparticle mass transfer parameters were derived by comparing the profiles of experimental overloaded bands and the profiles calculated using the isotherm model and the lumped pore diffusion (POR) model of chromatography. These results showed that different adsorption and mass transfer mechanisms exist in mobile phases made of acetonitrile/aqueous buffer and of acetonitrile/acetic acid solutions.

  2. Isothermal-Gas-Transfer Program

    NASA Technical Reports Server (NTRS)

    Levine, Don I.

    1989-01-01

    Isothermal Gas Transfer program (GASXFER) solves variety of problems in which gas or gas mixture transferred between two containers. Special features of program include ease of entering data and ease of obtaining output. Program displays, prints, or graphs complete pressure history of each gas as function of time. Written in Lotus Symphony macrolanguage.

  3. Isothermal amplification of insect DNA

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The loop-mediated isothermal amplification of DNA (LAMP) method can amplify a target DNA sequence at a constant temperature in about 1 hour. LAMP has broad application in agriculture and medicine because of the need for rapid and inexpensive diagnoses. The power of LAMP is being used by researchers ...

  4. Scaling in Supersonic Isothermal Turbulence

    NASA Astrophysics Data System (ADS)

    Kritsuk, A. G.; Wagner, R.; Norman, M. L.

    2015-10-01

    An exact relation for third-order structure functions in isothermal compressible turbulence (Galtier & Banerjee 2011) is verified using numerical data from a simulation at Mach 6. The analysis supports a Kolmogorov-like cascade phenomenology and yields a reduced version of the relation for high Mach number turbulence.

  5. Isothermal Amplification of Insect DNA

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The loop-mediated isothermal amplification of DNA (LAMP) method can amplify a target DNA sequence at a constant temperature in about one hour. LAMP has broad application in agriculture and medicine because of the need for rapid and inexpensive diagnoses. LAMP eliminates the need for temperature cycl...

  6. Isothermal Dendritic Growth Experiment Video

    NASA Technical Reports Server (NTRS)

    1997-01-01

    This video, captured during the Isothermal Dendritic Growth Experiment (IDGE) flown on STS-87 as a part of the fourth United States Microgravity payload, shows the growth of a dendrite, and the surface solidification that occurred on the front and back windows of the growth chamber. Dendrites are tiny, tree like structures that form as metals solidify.

  7. Geochemical heterogeneity in a sand and gravel aquifer: Effect of sediment mineralogy and particle size on the sorption of chlorobenzenes

    USGS Publications Warehouse

    Barber, L.B., II; Thurman, E.M.; Runnells, D.R.

    1992-01-01

    The effect of particle size, mineralogy and sediment organic carbon (SOC) on solution of tetrachlorobenzene and pentachlorobenzene was evaluated using batch-isotherm experiments on sediment particle-size and mineralogical fractions from a sand and gravel aquifer, Cape Cod, Massachusetts. Concentration of SOC and sorption of chlorobenzenes increase with decreasing particle size. For a given particle size, the magnetic fraction has a higher SOC content and sorption capacity than the bulk or non-magnetic fractions. Sorption appears to be controlled by the magnetic minerals, which comprise only 5-25% of the bulk sediment. Although SOC content of the bulk sediment is < 0.1%, the observed sorption of chlorobenzenes is consistent with a partition mechanism and is adequately predicted by models relating sorption to the octanol/water partition coefficient of the solute and SOC content. A conceptual model based on preferential association of dissolved organic matter with positively-charged mineral surfaces is proposed to describe micro-scale, intergranular variability in sorption properties of the aquifer sediments.The effect of particle size, mineralogy and sediment organic carbon (SOC) on sorption of tetrachlorobenzene and pentachlorobenzene was evaluated using batch-isotherm experiments on sediment particle-size and mineralogical fractions from a sand and gravel aquifer, Cape Cod, Massachusetts. Concentration of SOC and sorption of chlorobenzenes increase with decreasing particle size. For a given particle size, the magnetic fraction has a higher SOC content and sorption capacity than the bulk or non-magnetic fractions. Sorption appears to be controlled by the magnetic minerals, which comprise only 5-25% of the bulk sediment. Although SOC content of the bulk sediment is <0.1%, the observed sorption of chlorobenzenes is consistent with a partition mechanism and is adequately predicted by models relating sorption to the octanol/water partition coefficient of the solute and

  8. Sorption-desorption of 1,2,4-trichlorobenzene on soil: Anionic surfactant and cationic polyelectrolyte effects

    SciTech Connect

    DiVincenzo, J.P.; Dentel, S.K.

    1996-11-01

    Anionic surfactants and cationic polymers are two classes of anthropogenic chemicals that are released to the environment in significant amounts. In particular, this occurs in the land disposal of sludges, potentially altering the terrestrial mobility of other contaminants such as hydrophobic organics. Thus, we examined the 1,2,4-trichlorobenzene (TCB) sorption-desorption on soil with sodium dodecyl sulfate (SDS) and/or a cationic polyelectrolyte (Percol 757) present. Initial experiments varying sorbent mass resulted in nonconstant partitioning and a nonlinear isotherm; a model of incomplete colloidal separation by centrifugation could not explain the nonlinearity. A proposed model quantifies this isotherm behavior with a BET isotherm equation related to the limiting sorption capacity of the organic matter phase, Q{sub om}{degrees}. Additions of SDS and/or polyelectrolyte led to significant changes in TCB sorption. The SDS decreased TCB sorption significantly, but only with SDS exceeding the critical micelle concentration (CMC). The CMC value itself varied with electrolyte and soil presence. Increasing the SDS concentration above the CMC caused TCB desorption from soil. The SDS also increased residual colloidal solids, but primarily below the CMC. Percol 757 slightly increased TCP sorption. With polymer added to soil containing SDS, TCB sorption was unaffected until charge equivalence was approached, whereupon sorption increased severalfold. This trend reversed when the SDS exceeded the sum of the polymer equivalence and the CMC. These results are explained in terms of polymer-surfactant interactions. Environmental implications include effects on transport of hydrophobic organics resulting form sludge disposal on land. 27 refs., 10 figs.

  9. Effects of temperature on trichloroethylene desorption from silica gel and natural sediments. 1. Isotherms

    SciTech Connect

    Werth, C.J.; Reinhard, M.

    1997-03-01

    Aqueous phase isotherms were calculated from vapor phase desorption isotherms measured at 15, 30, and 60{degree}C for trichloroethylene on a silica gel, an aquifer sediment, a soil, a sand fraction, and a clay and silt fraction, all at 100% relative humidity. Isosteric heats of adsorption (Q{sub st}(q)) were calculated as a function of the sorbed concentration, q, and examined with respect to the following mechanisms: adsorption on water wet mineral surfaces, sorption in amorphous organic matter (AOM), and adsorption in hydrophobic micropores. Silica gel, sand fraction, and clay and silt fraction 60{degree}C isotherms are characterized by a Freundlich region and a region at very low concentrations where isotherm points deviate from log-log linear behavior. The latter is designated the non-Freundlich region. For the silica gel, values of Q{sub st}(q) (9.5-45 kJ/mol) in both regions are consistent with adsorption in hydrophobic micropores. For the natural solids, values of Q{sub st}(q) in the Freundlich regions are less than or equal to zero and are consistent with sorption on water wet mineral surfaces and in AOM. In the non-Freundlich regions, diverging different temperature isotherms with decreasing q and Q{sub st}(q) value of 34 kJ/mol for the clay and silt fraction suggest that adsorption is occurring in hydrophobic micropores. The General Adsorption Isotherm is used to capture this adsorption heterogeneity. 57 refs., 5 figs., 2 tabs.

  10. Single-pellet dynamics for the soil organic matter effect on dichloromethane sorption

    SciTech Connect

    Cabbar, C.; Dogu, G.; Dogu, T.; McCoy, B.J.

    1996-07-01

    The migration of volatile organic compounds (VOCs) in soil is strongly influenced by soil composition, for example, amount and type of clay, organic matter, and moisture. Halogenated hydrocarbons are frequently detected in the soil gas, and thus the sorption of these VOCs in soils has become an active area of research. Recent studies reported sorption rates and equilibrium data for some chlorinated hydrocarbons and for benzene by means of a single-pellet moment technique. In low-moisture soils, sorption occurs mainly on mineral surfaces, but the influence of soil organic matter (SOM) can also be significant. In the current study the authors use the single-pellet moment method to determine the effect of SOM on dichloromethane sorption in a dry simulated soil.

  11. Assessment of metal sorption mechanisms by aquatic macrophytes using PIXE analysis.

    PubMed

    Módenes, A N; Espinoza-Quiñones, F R; Santos, G H F; Borba, C E; Rizzutto, M A

    2013-10-15

    In this work, a study of the metal sorption mechanism by dead biomass has been performed. All batch metal biosorption experiments were performed using the aquatic macrophyte Egeria densa as biosorbent. Divalent cadmium and zinc solutions were used to assess the sorption mechanisms involved. Using a suitable equilibrium time of 2h and a mixture of 300 mg biosorbent and 50 mL metal solution at pH 5, monocomponent sorption experiments were performed. In order to determine the residual amounts of metals in the aqueous solutions and the concentrations of removed metals in the dry biomass, Particle Induced X-ray Emission (PIXE) measurements in thin and thick target samples were carried out. Based on the strong experimental evidence from the mass balance among the major elements participating in the sorption processes, an ion exchange process was identified as the mechanism responsible for metal removal by the dry biomass. PMID:23921177

  12. Effect of dissolved organic matter from treated effluents on sorption of atrazine and prometryn by soils

    SciTech Connect

    Seol, Y.; Lee, L.S.

    2000-01-02

    The apparent enhanced transport of soil-applied atrazine following irrigation of treated effluents has been hypothesized to be from complexation of atrazine with effluent-borne dissolved organic matter (DOM). Under long-term effluent irrigation, even small DOM-induced decreases in pesticide sorption can result in significant enhanced pesticide movement due to cumulative effects. The effect of atrazine and prometryn association with DOM extracted from municipal wastewater (MW), swine-derived lagoon wastewater (SW), and dissolved Aldrich humic acid (HA) on sorption by two soils was measured in batch equilibration studies. Individual association of pesticides to DOM, sorption of DOM to soil, and pesticide sorption by soil were also quantified. Pesticide association to DOM normalized to organic carbon (OC) ranged from 30 to 1000 L/kg OC. DOM sorption by soil ranged from 1.5 to 10 L/kg with a silt loam having a higher affinity for the DOM than the sandy loam. DOM up to 150 mg OC/L did not significantly suppress sorption by soils of either atrazine or prometryne in agreement with predictions using the independently measured binary distribution coefficients in a model that assumed linear equilibrium behavior among pesticide, soil, and DOM. A sensitivity analysis was performed using the same model to identify what combination of soil, pesticide, and DOC variables may suppress sorption, resulting in facilitated transport. Results from the sensitivity analysis are presented and the potential for effluent properties other than DOM to facilitate pesticide transport is discussed.

  13. Determination of Chlorinated Solvent Sorption by Porous Material—Application to Trichloroethene Vapor on Cement Mortar

    PubMed Central

    Musielak, Marion; Brusseau, Mark L.; Marcoux, Manuel; Morrison, Candice; Quintard, Michel

    2014-01-01

    Experiments have been performed to investigate the sorption of trichloroethene (TCE) vapor by concrete material or, more specifically, the cement mortar component. Gas-flow experiments were conducted using columns packed with small pieces of cement mortar obtained from the grinding of typical concrete material. Transport and retardation of TCE at high vapor concentrations (500 mg L−1) was compared to that of a non-reactive gas tracer (Sulfur Hexafluoride, SF6). The results show a large magnitude of retardation (retardation factor = 23) and sorption (sorption coefficient = 10.6 cm3 g−1) for TCE, compared to negligible sorption for SF6. This magnitude of sorption obtained with pollutant vapor is much bigger than the one obtained for aqueous-flow experiments conducted for water-saturated systems. The considerable sorption exhibited for TCE under vapor-flow conditions is attributed to some combination of accumulation at the air-water interface and vapor-phase adsorption, both of which are anticipated to be significant for this system given the large surface area associated with the cement mortar. Transport of both SF6 and TCE was simulated successfully with a two-region physical non-equilibrium model, consistent with the dual-medium structure of the crushed cement mortar. This work emphasizes the importance of taking into account sorption phenomena when modeling transport of volatile organic compounds through concrete material, especially in regard to assessing vapor intrusion. PMID:25530647

  14. [Sorption of o-Phthalate onto Calcite in Open-System].

    PubMed

    Li, Zhen-xuan; Huang, Li-dong; Chen, Yan-fang; Miao, Ye; Liu, Da-gang; Xu, Zheng-wen

    2015-07-01

    The batch sorption methods were deployed to study the sorpti of p-phthalate on calcite in open-system. Results show that: (1) The o-phthalate sorption reached the equilibrium within 3 hours. Both pseudo first-order and pseudo second-order models described the kinetic characteristics well; (2) The o-phthalate sorption rate decreased with pH (7. 7-9.7). This phenomenon was due to the competition effect of HCO3- and CO(3)2-, and the electrostatic effect on the surface; (3) The o-phthalate sorption rate also decreased with the increase in ionic strength. This was due to the rise in concentration of HCO3- and CO(3)2- induced by salt effect; (4) Compared with m-phthalate and p-phthalate, o-phthalate sorption rate was much higher due to the proximity of its two carboxyl groups which easily formed a chelate ring of surface complex. By studying the factors that influence o-phthalate sorption onto calcite, the sorption mechanism can be well understood. This mechanism can be applied in the removal of o-phthalate from the environment. PMID:26489324

  15. Sorption of cesium and strontium on Savannah River soils impregnated with colloidal silica

    SciTech Connect

    Hakem, N.; Al Mahamid, I.; Apps, J.; Moridis, G.

    1997-01-01

    Colloidal silica (CS) is being considered as an injectable low viscosity fluid for creation of impermeable barrier containment of low level radioactive waste at the Savannah River Site (SRS), South Carolina. The sorption behavior of cesium and strontium on Savannah River Site Soils impregnated with Colloidal Silica was studied using a batch experimental method. The samples were prepared by addition of CS and an aqueous solution of CaCl{sub 2} to the soil materials. Sorption studies were conducted after the gelation of the CS samples had occurred. The variation of the sorption ratio, R, as a function of cesium or strontium concentration was examined. The Freundlich isotherm was used to fit the data and very good results were obtained.

  16. Transport and sorption behavior of individual phthalate esters in sandy aquifer: column experiments.

    PubMed

    Zakari, Sissou; Liu, Hui; Li, Yan-Xi; He, Xi; Tong, Lei

    2016-08-01

    This work aimed to quantify the transport and sorption behavior of four individual phthalate esters (PAEs) in sandy aquifer using column experiments so as to provide important parameters for the prediction and control of PAEs pollution plume in groundwater system. The transport curves of four individual PAEs were simulated with HYDRUS-1D through fitting linear and nonlinear equilibrium (LE/NO), linear and nonlinear, first-order, one-site non-equilibrium (LO/NO), linear and nonlinear, first-order, two-site non-equilibrium (LFO/NFO) sorption models. Simulation results showed that two-site models (LFO and NFO) displayed similar best fittings. The results from LFO model simulation showed that when water flowed 1000 m in sandy aquifer, PAEs with shorter carbon chains (DMP and DEP) transport 31.6 and 22.2 m, respectively. Unexpectedly for the same water transport distance, PAEs with longer carbon chains (DBP and DiBP) transported 40.2 and 60.7 m, respectively, which were faster than DMP and DEP, mainly due to the limited accessibility of type-2 sorption sites. The retardations were mainly caused by the sorption of PAEs on the time-dependent type-2 sites. DBP and DiBP exhibited higher mass transfer speed to and fro type-2 sites but showed lower total sorption coefficient (K) due to the limited accessibility of sorption sites. Coexistence of PAEs and smaller sorbent particles increased total K values of DBP and DiBP due to synergic development of more sorption sites with DMP and DEP. PMID:27146532

  17. 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

  18. The sorption capacity of boron on anionic-exchange resin

    SciTech Connect

    Lou, J.; Foutch, G.L.; Na, J.W.

    1999-11-01

    Boron sorption capacities on anionic-exchange resins vary with temperature, concentration, and resin crosslinkage. A semiempirical correlation, developed from boron solution chemistry, is presented to account for these variations. The relationship, based on boron chemistry and changes in Gibb's energy, can be stated approximately as Q = a{sub 1}C{sub B}{sup a{sub 2}}Z{sup a{sub 3}} exp[{minus}(a{sub 4}T + a{sub 5}T{sup 2} + a{sub 6}Z{sup 0.5})]. Correlation parameters, which vary with resin type, are evaluated experimentally. Parameter values for macroporous resin Diaion PA 300 and for gel-type resins Diaion SA10 and Amberlite IRN 78LC are presented. The resulting expression is used to determine boron sorption and desorption limitations on ion exchangers at various temperatures and concentrations, and to determine the interfacial boron concentration in equilibrium and rate models.

  19. 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. PMID:25014887

  20. Neptunium(V) sorption behavior on clinoptilolite, quartz and montmorillonite

    SciTech Connect

    Bertetti, F.P.; Pabalan, R.T.; Turner, D.R.; Almendarez, M.G.

    1996-08-01

    Performance assessment models have identified {sup 237}Np as a radionuclide of concern in meeting release limits established for the geologic disposal of high-level nuclear waste at the proposed repository at Yucca Mountain, Nevada. In this study, quartz, clinoptilolite, and montmorillonite, which are minerals representative of phases that occur both in the rock matrix and as fracture coatings at Yucca Mountain, were reacted with {sup 237}Np-bearing solutions to characterize the sorption behavior of Np(V) on these minerals. Batch experiments were conducted over a wide range of conditions in which pH of solution, surface loading, sorbent surface area, initial concentration of Np(V), and partial pressure of CO{sub 2} were varied. Initial Np(V) concentrations were between 1 {times} 10{sup {minus}7} and 1 {times} 10{sup {minus}6} M in electrolyte solutions of 0.1 or 0.01 M NaNO{sub 3}. The oxidation state of Np in solution was verified with NIR spectroscopy and by solvent extraction. Prior to the start of experiments, minerals were pretreated to eliminate impurities, and the clinoptilolite and montmorillonite were converted to Na-form by ion exchange with NaCl solutions. Results indicate that, for all three minerals, Np(V) sorption begins at pH values coincident with the start of hydrolysis in solution ({approximately}7). For solutions undersaturated with respect to atmospheric CO{sub 2}, sorption increases continuously with increasing pH. Under equilibrium with atmospheric CO{sub 2}, Np(V) sorption is important in the pH range (7--9.5) where NpO{sub 2}(OH){sup 0}(aq) is significant, whereas sorption is inhibited at higher pH where neptunyl carbonate complexes are the predominant species.

  1. Sorption of 17α-ethinyl estradiol, bisphenol A and phenanthrene to different size fractions of soil and sediment.

    PubMed

    Sun, Ke; Jin, Jie; Gao, Bo; Zhang, Zheyun; Wang, Ziying; Pan, Zezhen; Xu, Dongyu; Zhao, Ye

    2012-07-01

    The potential for negative effects caused by endocrine disrupting chemicals (EDCs) release into the environment is a prominent concern and numerous research projects have investigated possible environmental fate and toxicity. However, their sorption behavior by size fractions of soil and sediment has not been systematically represented. The sorption of bisphenol A (BPA), 17α-ethinyl estradiol (EE2) and phenanthrene (Phen) by different size fractions of soil and sediment were investigated. Sorption isotherms of EE2, BPA, and Phen by size fractions of soil (SL) and sediment (ST) were well fitted to the Freundlich model. The positive correlation between EE2, BPA and Phen sorption capacity (logK(d)) of size fractions and their organic carbon (OC) content suggests that OC of size fractions in SL and ST should regulate sorption, while the surface area (SA) of size fractions may not account for sorption of EE2, BPA and Phen. Each size fraction of ST had higher sorption capacity (K(d) or K(OC)) of EE2 and BPA than that of SL due to their difference in the polarity of organic matter (OM) between terrestrial and aquatic sources. Sorption capacity logK(d) for size fractions of SL and ST did not follow the order: clay>silt>sand due to the difference in OM abundance and composition between the size fractions. Large particle fractions of ST contributed about 80% to the overall sorption for any EE2, BPA, and Phen. This study was significant to evaluate size fractions of soil and sediment as well as their associated OM affecting EE2 and BPA sorption processes. PMID:22475149

  2. Sorption Characteristics of Aqueous Co(II) on Preformed Iron Ferrite Impregnated into Phenolsulphonic Formaldehyde Resin

    SciTech Connect

    Lee, K. J.; Kim, Y. K.

    2002-02-26

    A series of stepwise procedures to prepare a new organic-inorganic composite magnetic resin with phenolsulphonicformaldehyde and freshly formed iron ferrite was established, based upon wet-and-neutralization method for synthesizing iron ferrite and pearl-polymerization method for synthesizing rigid bead-type composite resin. The composite resin prepared by the above method shows stably high removal efficiency (maximally over 3.1 meq./gresin) to Co(II) species from wastewater in a wide range of solution pH. The wide range of applicable solution pH (i.e. pH 4.09 to 10.32) implies that the composite resin overcomes the limitations of the conventional ferrite process that is practically applicable only to alkaline conditions. It has been found that both ion exchange (by the organic resin constituent) and surface adsorption (by the inorganic adsorbent constituent) are major reaction mechanisms for removing Co(II) from wastewater, but surface precipitation results in the high sorption capacity to Co(II) beyond normal ion exchange capacity of the phenolsulphonic-formaldehyde resin. Standard enthalpy change derived from van't Hoff equation is 32.0 kJ{center_dot}mol-1 conforming to the typical range for chemisorption or ion exchange. In a wide range of equilibrium Co(II) concentration, the overall isotherm is qualitatively explained by the generalized adsorption isotherm concept proposed by McKinley. At the experimental conditions where the composite resin shows equivalent selectivity to Co(II) and other competing reagents (i.e. EDTA and Na), the ratios of Co(II) to other chemicals turn out to be 2:1 and 1:221, respectively. In addition, the selectivity of the PSF-F to Co(II) species is very high (about 72% of Co(II)-removal efficiency) even when the molar ratio of Co(II) to Ca(II) is 1:30. It is anticipated that the composite resin can also be used for column-operation with process-control by applying external magnetic field, since the rigid bead-type composite resin shows

  3. IDGE: Isothermal Dendritic Growth Experiment

    NASA Technical Reports Server (NTRS)

    1994-01-01

    The Isothermal Dendritic Growth Experiment (IDGE) flew on STS-62 to study the microscopic, tree-like structures (dendrites) that form within metals as they solidify from molten materials. The size, shape, and orientation of these dendrites affect the strength and usefulness of metals. Data from this experiment will be used to test and improve the mathematical models that support the industrial production of metals.

  4. Variation in sorption of propiconazole with biochars: The effect of temperature, mineral, molecular structure, and nano-porosity.

    PubMed

    Sun, Ke; Kang, Mingjie; Ro, Kyoung S; Libra, Judy A; Zhao, Ye; Xing, Baoshan

    2016-01-01

    Sorption behavior of propiconazole (PROPI) by plant-residue derived biochars (PLABs) and animal waste-derived biochars (ANIBs) obtained at three heating treatment temperatures (HTTs) (300, 450 and 600 °C) (e.g., BCs300, BCs450, and BCs600) and their corresponding de-ashed BCs450 was investigated. PLABs belonged to high- or medium-C biochars and ANIBs were low-C biochars. Surface C concentrations of the tested biochars were generally higher than their corresponding bulk C. Surface polar groups were mainly composed of O-containing groups of minerals within biochars. The nonlinearity coefficients (n) of propiconazole (PROPI) sorption isotherms ranged from 0.23 to 0.64, which was significantly and negatively related to organic carbon (OC)-normalized CO2-surface area (CO2-SA/OC) of biochars. This correlation along with the positive relationship between CO2-SA/OC and aromaticity indicates that pore-filling in nanopores within aromatic C dominate nonlinear PROPI sorption. HTTs or C contents do not necessarily regulate PROPI sorption. Removal of minerals from BCs450 elevated PROPI sorption because minerals may exert certain influence on sorption via impacting spatial arrangement of polar groups and/or organic matter (OM)-mineral interactions. This study helps to better understand sorption behavior of PROPI to biochars and evaluate the potential role of biochar in water treatment systems. PMID:26206746

  5. Application of headspace analysis to the study of sorption of hydrophobic organic chemicals to α-Al2O3

    USGS Publications Warehouse

    Pelinger, Judith A.; Eisenreich, Steven J.; Capel, Paul D.

    1993-01-01

    The sorption of hydrophobic organic chemicals (HOCs) to ??-Al2O3 was investigated with a headspace analysis method. The semiautomated headspace analyzer gave rapid, precise, and accurate results for a homologous series alkylbenzenes even at low percentages of solute mass sorbed (3-50%). Sorption experiments carried out with benzene alone indicated weak interactions with well-characterized aluminum oxide, and a solids concentration effect was observed. When the sorption coefficients for benzene alone obtained by headspace analysis were extrapolated up to the solids concentrations typically used in batch sorption experiments, the measured sorption coefficients agreed with reported sorption coefficients for HOCs and sediments of low fractional organic carbon content. Sorbed concentrations increased exponentially with aqueous concentration in isotherms with mixtures of alkylbenzenes, indicating solute-solute interactions at the mineral surface. Sorption was, however, greater than predicted for partitioning of a solute between its pure liquid phase and water, indicating additional influences of the surface and/or the structured liquid near the mineral surface. ?? 1993 American Chemical Society.

  6. Alginate and Algal-Based Beads for the Sorption of Metal Cations: Cu(II) and Pb(II).

    PubMed

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

    2016-01-01

    Alginate and algal-biomass (Laminaria digitata) beads were prepared by homogeneous Ca ionotropic gelation. In addition, glutaraldehyde-crosslinked poly (ethyleneimine) (PEI) was incorporated into algal beads. The three sorbents were characterized by scanning electron microscopy (SEM) coupled with energy dispersive X-ray analysis (EDX): the sorption occurs in the whole mass of the sorbents. Sorption experiments were conducted to evaluate the impact of pH, sorption isotherms, and uptake kinetics. A special attention was paid to the effect of drying (air-drying vs. freeze-drying) on the mass transfer properties. For alginate, freeze drying is required for maintaining the porosity of the hydrogel, while for algal-based sorbents the swelling of the material minimizes the impact of the drying procedure. The maximum sorption capacities observed from experiments were 415, 296 and 218 mg Pb g(-1) and 112, 77 and 67 mg Cu g(-1) for alginate, algal and algal/PEI beads respectively. Though the sorption capacities of algal-beads decreased slightly (compared to alginate beads), the greener and cheaper one-pot synthesis of algal beads makes this sorbent more competitive for environmental applications. PEI in algal beads decreases the sorption properties in the case of the sorption of metal cations under selected experimental conditions. PMID:27598128

  7. Modelling sorption of radionuclides on sorbent containing surface sites with variable charges: Ni-Sr-goethite system

    SciTech Connect

    Rao, M.G.; Halle, H.N.

    1996-02-01

    Results are presented on the retardation of radionuclides by sorption processes during host rock-ground water interactions. Studies are being performed at Yucca Mountain as part of a site selection for the underground disposal of high-level radioactive wastes. Tuff has a high sorption capacity for radionuclides. Several types of zeolites and montmorillonite, as well as goethite are known to occur in the tuff. Ion exchange phase equilibrium theory is used to describe sorption of mixtures of nickel and strontium ions in aqueous phase on goethite at a constant pH.

  8. Arbitrarily slow, non-quasistatic, isothermal transformations

    NASA Astrophysics Data System (ADS)

    Gavrilov, Momčilo; Bechhoefer, John

    2016-06-01

    For an overdamped colloidal particle diffusing in a fluid in a controllable, virtual potential, we show that arbitrarily slow transformations, produced by smooth deformations of a double-well potential, need not be reversible. The arbitrarily slow transformations do need to be fast compared to the barrier crossing time, but that time can be extremely long. We consider two types of cyclic, isothermal transformations of a double-well potential. Both start and end in the same equilibrium state, and both use the same basic operations —but in different order. By measuring the work for finite cycle times and extrapolating to infinite times, we found that one transformation required no work, while the other required a finite amount of work, no matter how slowly it was carried out. The difference traces back to the observation that when time is reversed, the two protocols have different outcomes, when carried out arbitrarily slowly. A recently derived formula relating work production to the relative entropy of forward and backward path probabilities predicts the observed work average.

  9. 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 (K2) 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

  10. 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.

  11. Sorption J-T refrigeration utilizing manganese nitride chemisorption

    NASA Technical Reports Server (NTRS)

    Jones, Jack; Lund, Alan

    1990-01-01

    The equilibrium pressures and compositions have been measured for a system of finely powdered manganese nitride and nitrogen gas at 650, 700, 800, and 850 C for various nitrogen loadings. Pressures ranged from less than 0.02 MPa at 650 C to 6.38 MPa at 850 C. Analysis of the test results has shown that under certain conditions Mn(x)N(y) could potentially be used in a triple regenerative sorption compressor refrigeration system, but the potential power savings are small compared to the increased complexity and reliability problems associated with very high temperature (above 950 C) pressurized systems.

  12. Characterization of carbons from olive cake by sorption of wastewater pollutants.

    PubMed

    Cimino, G; Cappello, R M; Caristi, C; Toscano, G

    2005-11-01

    Studies has been conducted to compare the sorption properties between raw carbons made from olive cake and commercial activated carbons to remove aquatic pollutant such as heavy metal (HM), phenol (Ph), dodecylbenzenesulfonic acid-sodium salt detergent (DBSNa) and methylene blue dye (MB). Effect of acidic treatments by H2SO4, HCl and HNO3 on the sorption properties of olive cake carbon (OCC) were studied by mass titration, SEM photographs, sorption isotherms. It is found that acidic treatment changes the surface properties of OCC but do not enhance its sorption capacity. Compared to commercial activated carbons the OCC derivatives generally are equally able to uptake HM and Ph from solution but MB and DBSNa are not. This different behaviour is to attribute to manufacturing and activation treatments so as surface groups of the precursor sorbent material. For the heavy metals, chromium and silver were removed effectively but to small extent cadmium. This may be because of the various charge densities of metal elements tested. The results of the multiple experiments indicate that sorption of cadmium ions can be significantly improved by the presence of complexing agents sorbed from the carbon. An empirical mathematical form is proposed to correlate experimental data and to compare the performance of the different sorbent materials. PMID:16257318

  13. Influence of clay minerals on sorption and bioreduction of arsenic under anoxic conditions.

    PubMed

    Ghorbanzadeh, Nasrin; Lakzian, Amir; Halajnia, Akram; Kabra, Akhil N; Kurade, Mayur B; Lee, Dae S; Jeon, Byong-Hun

    2015-12-01

    Adsorption of As(V) on various clay minerals including kaolinite (KGa-1), montmorillonite (SWy-1) and nontronites (NAU-1 and NAU-2), and subsequent bioreduction of sorbed As(V) to As(III) by bacterium Shewanella putrefaciens strain CN-32 were investigated. Nontronites showed relatively higher sorption capacity for As(V) primarily due to higher iron oxide content. Freundlich equation well described the sorption of As(V) on NAU-1, NAU-2 and SWy-1, while As(V) sorption isotherm with KGa-1 fitted well in the Langmuir model. The bacterium rapidly reduced 50% of dissolved As(V) to As(III) in 2 h, followed by its complete reduction (>ca. 98%) within 12 h. In contrast, sorption of As(V) to the mineral surfaces interferes with the activity of bacterium, resulting in low bioreduction of As(V) by 27% for 5 days of incubation. S. putrefaciens also promoted the reduction of Fe(III) present in the clay mineral to Fe(II). This study indicates that the sorption and subsequent bioreduction of As(V) on clay minerals can significantly influence the mobility of As(V) in subsurface environment. PMID:25971375

  14. Exceptionally strong sorption of infochemicals to activated carbon reduces their bioavailability to fish.

    PubMed

    Jonker, Michiel T O; van Mourik, Louise

    2014-03-01

    The addition of activated carbon (AC) to sediments is a relatively new approach to remediate contaminated sites. Activated carbon strongly sorbs hydrophobic organic contaminants, thereby reducing their bioavailability and uptake in organisms. Because of its high sorption capacity, AC might, however, also sorb other chemicals that are not contaminants but instead have ecological functions. Examples of such compounds are infochemicals or pheromones (i.e., compounds serving as chemical inter- and intraspecies information vectors). The present study investigated the sorption of 2 known infochemicals, hypoxanthine-3-N-oxide (H3NO) and pyridine-N-oxide (PNO), to 5 different powdered ACs. Sorption isotherms of these low-molecular-weight, polar fish kairomone substances appeared highly nonlinear, with logarithmic Freundlich sorption coefficients of up to 7.6. At physiologically relevant concentrations, sorption was up to 7 to 9 orders of magnitude stronger than expected on the basis of hydrophobic forces only (i.e., the compounds' log octanol-water partition coefficient, being approximately -1), indicating exceptionally strong binding to specific sites. This binding effectively reduced the bioavailability of H3NO to Sarasa goldfish, as was shown in a behavioral assay. The present study demonstrates the previously unrecognized potential of AC to sorb ecologically relevant chemicals. Whether this potential may lead to subtle, unwanted ecological effects in the field will have to be investigated in more detail during future research. PMID:24272993

  15. Cationic amphiphilic microfibrillated cellulose (MFC) for potential use for bile acid sorption.

    PubMed

    Zhu, Xuhai; Wen, Yangbing; Cheng, Dong; Li, Changmo; An, Xingye; Ni, Yonghao

    2015-11-01

    In this work, Micro-fibrillated Cellulose (MFC) was cationically modified by quaternary ammonium groups with different chemical structures aiming to improve the sorption capacity to bile acid. The in-vitro bile acid sorption was performed by investigating various factors, such as quaternary ammonium group content and length of its alkyl substituent of the modified cationic MFC (CMFC), ionic strength, initial concentration and hydrophobicity of bile acid. The results showed that the sorption behavior of the modified CMFC was strongly influenced by the quaternary ammonium group content and the lengths of its alkyl substituent, the sorption capacity for the modified CMFC with a C18 alkyl substituent, was approximately 50% of that of Cholestyramine. The experimental isotherm results were well fitted into the Temkin model. The effect of salts in the solution was smaller for the bile acid sorption onto the hydrophobic CMFC than the CMFC. It was also found that the binding capacity of CMFC was higher for more hydrophobic deoxycholate in comparison with cholate. PMID:26256387

  16. 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. PMID:22659728

  17. ISOTHERMAL PHASE TRANSFORMATION CYCLING IN STEEL BY APPLICATION OF A HIGH MAGNETIC FIELD

    SciTech Connect

    Ludtka, Gerard Michael; Jaramillo, Roger A; Ludtka, Gail Mackiewicz-; Kisner, Roger A; Wilgen, John B

    2007-01-01

    A phase transformation reversal via the application and removal of a large magnetic field was investigated. Because a large magnetic field can alter the phase equilibrium between paramagnetic austenite and ferromagnetic ferrite, volume fractions for each phase constituent can be modified at constant temperature by changing the magnetic field strength. In this research elevated temperature isothermal hold experiments were performed for 5160 steel. During the isothermal hold, the magnetic field was cycled between 0 and 30 Tesla. As companion experiments, temperature cycling and isothermal holds were performed without magnetic fields. The resulting microstructures were examined using optical and SEM metallography. These microstructures indicate that a portion of the microstructure experiences isothermal transformation cycling between austenite and ferrite due to the application and removal of the 30T (Tesla) magnetic field.

  18. BACTERIAL SORPTION OF HEAVY METALS

    EPA Science Inventory

    Four bacteria, Bacillus cereus, B. subtilis, Escherichia coli, and Pseudomonas aeruginosa, were examined for the ability to remove Ag+, Cd2+, Cu2+, and La3+ from solution by batch equilibration methods. d and Cu sorption over the concentration range 0.001 to 1 mM was described by...

  19. 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. PMID:25561259

  20. Sorption and degradation of pharmaceuticals and personal care products (PPCPs) in soils.

    PubMed

    Yu, Yong; Liu, Yin; Wu, Laosheng

    2013-06-01

    Pharmaceuticals and personal care products (PPCPs) are one class of the most urgent emerging contaminants, which have drawn much public and scientific concern due to widespread contamination in aquatic environment. Most studies on the environmental fate and behavior of PPCPs have focused on nonsteroidal anti-inflammatory drugs. Some other compounds with high concentrations were less mentioned. In this study, sorption and degradation of five selected PPCPs, including bisphenol A (BPA), carbamazepine (CBZ), gemfibrozil (GFB), octylphenol (OP), and triclosan (TCS) have been investigated using three different soils. Sorption isotherms of all tested PPCPs in soils were well described by Freundlich equation. TCS and OP showed moderate to strong sorption, while the sorption of GFB and CBZ in soils was negligible. Degradation of PPCPs in three soils was generally fitted first-order exponential decay model, with half-lives (t 1/2) varying from 9.8 to 39.1 days. Sterilization could prolong the t 1/2 of PPCPs in soil, indicating that microbial activity played an important role in the degradation of these chemicals in soils. Degradation of PPCPs in soils was also influenced by the soil organic carbon (f oc) contents. Results from our data show that sorption to the soils varied among the different PPCPs, and their sorption affinity on soil followed the order of TCS > OP > BPA > GFB > CBZ. The degradation of the selected PPCPs in soil was influenced by the microbial activity and soil type. The poor sorption and relative persistence of CBZ suggest that it may pose a high leaching risk for groundwater contamination when recycled for irrigation. PMID:23292228

  1. Sorption of a branched nonylphenol and perfluorooctanoic acid on Yangtze River sediments and their model components.

    PubMed

    Li, Chengliang; Ji, Rong; Schäffer, Andreas; Sequaris, Jean-Marie; Amelung, Wulf; Vereecken, Harry; Klumpp, Erwin

    2012-10-26

    Many metabolites of organic surfactants such as nonylphenol (NP) and perfluorooctanoic acid (PFOA) are ubiquitously found in the environment and are toxic if not sorbed on soils and sediments. In this study, we quantified the sorption of the NP isomer with the highest endocrine activity, [4-(1-ethyl-1,3-dimethylpentyl) phenol] (NP111), and that of PFOA on Yangtze River sediments and its model components illite, goethite and natural organic matter. The sorption experiments were performed with (14)C-labeled NP111 and PFOA by batch or dialysis techniques. The results showed that the sorption isotherms of NP111 and PFOA on the sediments were fitted well by the linear adsorption model. The sorption of NP111 depended largely on the organic carbon content of the sediments. The K(OC) values of NP111 ranged from 6 × 10(3) to 1.1 × 10(4) L kg(-1) indicating that hydrophobic interaction between NP and organic carbon is the main mechanism of sorption. The sorption of NP111 on illite was poor. The sorption of PFOA on the sediments was significantly lower than that of NP111. The affinity of PFOA to adsorb on goethite was slightly higher than on the sediments, but was moderate on illite and negligible on a reference natural organic matter. Principal axis component analysis confirmed that various sediment parameters control the binding of PFOA. This analysis grouped the respective K(d) values to the contents of black carbon, iron oxides and clay, and, hence, to the specific surface area of the sediments. PMID:22892466

  2. Studies on sorption of some geomaterials for fluoride removal from aqueous solutions.

    PubMed

    Sujana, M G; Pradhan, H K; Anand, S

    2009-01-15

    In the present study the defluoridation capacities of some of the naturally occurring materials like low and high iron containing lateritic ores, overburden from chromite mines of Orissa Mining Corporation (OMC) and Tata Steel have been estimated. The various experimental parameters studied for fluoride sorption from aqueous solutions were: time, pH, initial fluoride concentration, sorbent dose and temperature. The three geomaterials, namely chromite overburden from Orissa Mining Corporation, both low and high iron containing lateritic ores sorbed fluoride effectively. The sorption kinetics for these samples was found to follow first order rate expression and the experimental equilibrium sorption data fitted reasonably well to both Langmuir and Freundlich models. The negative values of DeltaG degrees suggest the sorption of fluoride onto three samples to be spontaneous and the exothermic nature of sorption is confirmed by the -DeltaH degrees values. The negative DeltaS degrees values for these sorbents point towards decreased randomness at the solid/solution interface. The sorption studies were also carried out at natural pH conditions for fluoride removal from ground water samples and the fluoride level could be reduced from 10.25 to <1.0mgL(-1) by multistage adsorption process using OMC and NH samples. PMID:18450373

  3. Long-term experiments to investigate irreversibility in sorption of pesticides to soil.

    PubMed

    Suddaby, L A; Beulke, S; van Beinum, W; Oliver, R G; Kuet, S; Brown, C D

    2016-11-01

    Experiments investigated irreversibility in pesticide sorption to soil. Sorption behaviour under abiotic conditions was quantified for chlorotoluron, prometryn and hexaconazole in three soils over periods of up to 274 days. An isotope-exchange procedure was used whereby sorption of (12)C- and (14)C-pesticide isotopes in shaken suspensions of three soils (56-168 days shaking) was followed by substitution of the isotopes in the liquid phase and a 14-day exchange phase. This was followed by forced isotope exchange where the sorbed (14)C material was exchanged by adding an excess of non-radiolabelled compound. Experiments were concluded with solvent extraction and soil combustion to determine remaining radioactivity. Under conditions of continuous shaking, the pesticide-soil systems took around four months to approach sorption equilibrium, resulting in strong asymmetry between the profiles of exchange for isotopes of all three compounds. Physically entrapped residues were released back into solution under the steep concentration gradient of forced isotope exchange and small amounts of radioactivity were still being released at the termination of the experiment. The profiles of exchange did not deviate markedly from ideal behaviour based on the assumption that sorption is fully reversible. Whilst the timescales for release of sorbed residues back into solution were very long, soil combustion at study termination only yielded <1-2% of applied radioactivity; this confirms that sorption processes under abiotic soil conditions were overwhelmingly reversible for this set of compounds and soils. PMID:27479454

  4. Experimental study of uranium(6+) sorption of the zeolite mineral clinoptilolite

    SciTech Connect

    Pabalan, R.T.; Prikryl, J.D.; Muller, P.M.; Dietrich, T.B.

    1993-12-31

    Experiments on the sorption of uranium(6+) on clinoptilolite from solutions in equilibrium with atmospheric CO{sub 2}(g) were conducted to understand the fundamental controls on uranium sorption on zeolite minerals, including the effects of pH, aqueous uranium speciation, and uranium concentration in solution. The results indicate that uranium(6+) species are strongly sorbed on the zeolite mineral clinoptilolite at near-neutral pH. The amount of uranium sorbed is strongly dependent on pH and, to some extent, on the total concentration of uranium. Uranium sorption on clinoptilolite is important in the pH range where UO{sub 2}(OH){sub 2}{degrees}(aq) is the predominant uranium aqueous species, whereas sorption is inhibited at pH`s where carbonate- and hydroxy-carbonate-complexes are the primary uranyl species. Surface adsorption appears to be the main sorption mechanism, although at pH<4 the results suggest ion exchange may occur between the UO{sub 2}{sup 2+} ions in solution and the cations in the intracrystalline cation exchange sites of clinoptilolite. The effectiveness of zeolite-rich horizons underneath Yucca Mountain, Nevada, as barriers to actinide transport through sorption processes will depend strongly on groundwater chemistry. Reliable predictions of radionuclide transport through these horizons will need to properly account for changes in solution chemistry.

  5. Stuies of neptunium(V) sorption on montmorillonite, clinoptilolite, quartz and {alpha}-alumina

    SciTech Connect

    Bertetti, F.P.; Pabalan, R.T.; Turner, D.R.; Almendarez, M.G.

    1996-10-01

    {sup 237}Np is a particular concern to the safety suitability of Yucca Mountain, Nevada, as a geologic repository for high-level nuclear wastes. In this study, montmorillonite, clinoptilolite, quartz, and {alpha}-alumina were reacted with {sup 237}Np-bearing solutions to characterize the sorption behavior of Np(V) on these minerals. Batch experiments were conducted at room temperature (20{plus_minus}2{degrees}C) over a range of conditions in which solution pH, sorbent surface area, initial concentration of N(V), ionic strength, and partial pressure of CO{sub 2} were varied. For all the minerals studied, Np(V) sorption begins at pH values coincident with the start of Np hydrolysis in solution ({approximately}6.5-7). For solutions undersaturated with respect to atmospheric CO{sub 2}, sorption increases continuously with increasing pH. For solutions at equilibrium with atmospheric CO{sub 2}, the {open_quotes}sorption envelope{close_quotes} is coincident with the calculated predominance field (pH {approximately}7-9.5) of the NpO{sub 2}(OH){sup 0}(aq) species, and sorption is inhibited at higher pH where neptunyl carbonate complexes predominate. Modeling of the sorption behavior of Np(V) was performed using a surface complexation-approach (Diffuse-Layer Model).

  6. New method for quantification of dye sorption using SBA mesoporous silica as a target sorbent.

    PubMed

    Nesic, Aleksandra R; Kokunesoski, Maja J; Volkov-Husovic, Tatjana D; Velickovic, Sava J

    2016-03-01

    In this work, a new method for the quantification of methyl violet cationic dye sorption onto SBA-15 mesoporous silica was developed. This method related the intensity of coloration of SBA-15 samples (after reached equilibrium sorption) within dye concentration in aqueous solution using Image-Pro Plus software. The sorption process of methyl violet dye onto SBA-15 was analyzed varying different initial parameters (dye concentration, mass of sorbent, pH of dye solution, and contact sorption time). SBA-15 proved as efficient sorbent for removal of methyl violet dye in contact time of 5 min, with maximum percentage of dye removal 99% at pH 8. The results obtained from Image-Pro Plus showed to be in good agreement with the sorption parameters obtained by UV/Vis spectroscopy, which has been the most commonly used instrument for quantification of dye sorption. The image analysis method proved well prediction of dye concentrations with maximum relative error of 1.83%. The advantages of this method are low cost and reliable quantitative evaluation with minimum of time. PMID:26875074

  7. Isothermal compressors for process gases

    SciTech Connect

    Wiederuh, E.; Meinhart, D. )

    1992-09-01

    This paper reports on isothermal compressors which are more efficient for all gases. The study of several representative gases considered stage efficiencies, pressure ratios and pressure losses of the intercoolers. Generally there are two ways to reduce power consumption of a gas compression process: minimize losses of the compressor or improve the thermodynamics of the process. But there are some new ways to reduce losses of turbocompressors. Losses of the impeller labyrinth seals and the balance piston labyrinth seal can be reduced by optimizing the labyrinth geometry and minimizing labyrinth clearances. Therefore, conventional labyrinth seals are still being studied and will be improved.

  8. p-Nitrophenol, phenol and aniline sorption by organo-clays.

    PubMed

    Ko, Chun Han; Fan, Chihhao; Chiang, Po Neng; Wang, Ming Kuang; Lin, Kuo Chuan

    2007-10-22

    The aims of this study were to make use of organo-clays (i.e., Cloisite-10A, Cloisite-15A, Cloisite-30B and Cloisite-93A), to remove p-nitrophenol, phenol and aniline of organic pollutants. The organo-clays were characterized by X-ray diffraction (XRD). Sorption isotherm, kinetic and pH effect of p-nitrophenol, phenol and aniline sorbed by four organo-clays were evaluated. The d-spacings (001) of the XRD peak of Cloisite-10A, Cloisite-15A, Cloisite-30B and Cloisite-93A are 1.98, 2.76, 1.93 and 2.64 nm, respectively. The d(001)-spacings of XRD indicated that these p-nitropheno, phenol and aniline could penetrate into the interlayer of clays and expand the d(001)-spacings. The linear sorption isotherm of constant partition was employed to describe the sorption isotherms of phenols sorbed by organo-clays through hydrophobic-hydrophobic chemical reactions. The parabolic diffusion and power-function of kinetic models were employed to describe properly the kinetic experiments. The rate limiting step of the p-nitrophenol sorption reactions on organo-clays were diffusion-controlled processes (i.e., 15A, 30B, 93A) and chemical-controlled process for 10A organo-clays. The pre-exponential factor of the p-nitrophenol sorbed by four organo-clays showed the trend as follows: 10A> 30B> 93A> 15A. The efficiency of these organo-clays in removing phenol compounds in water treatments merit further study. PMID:17478038

  9. Sorption characteristics of fluoride on to magnesium oxide-rich phases calcined at different temperatures.

    PubMed

    Sasaki, Keiko; Fukumoto, Naoyuki; Moriyama, Sayo; Hirajima, Tsuyoshi

    2011-07-15

    The effect of calcination temperature during production of magnesium oxide-rich phases from MgCO(3) on the sorption of F(-) ions in the aqueous phase has been investigated. Magnesium oxide-rich phases were formed by calcination at over 873 K for 1h. Higher calcination temperatures produced more crystalline MgO with smaller specific surface area and provided larger values of the total basicity per unit surface area. The higher calcination temperatures lead to slower F(-) removal rate, and lower equilibrium F(-) concentrations, when the equilibrium F(-) concentrations are less than 1 mmol dm(-3). Larger total basicity per unit surface area made the reactivity with F(-) ions in aqueous phase more feasible, resulting in a greater degree of F(-) sorption. For equilibrium F(-) concentrations more than 1 mmol dm(-3), lower calcination temperatures favored the co-precipitation of F(-) with Mg(OH)(2), probably leading to the formation of Mg(OH)(2-x)F(x), and the achievement of larger sorption density. This is the first paper which describes the relationship between the solid base characteristics obtained by CO(2)-TPD for MgO with different calcination temperatures as a function of the reactivity of F(-) sorption in the aqueous phase. PMID:21571430

  10. Synthesis of a novel magnetic zeolite nanocomposite for removal of Cs+ and Sr2+ from aqueous solution: kinetic, equilibrium, and thermodynamic studies.

    PubMed

    Faghihian, Hossein; Moayed, Mohammad; Firooz, Alireza; Iravani, Mozhgan

    2013-03-01

    In this study, a novel magnetic zeolite nanocomposite (MZNC) was prepared by nanozeolite A and iron oxide. Nanocrystalline zeolite A was synthesized, and then, iron oxide nanocrystals were prepared in the presence of nanozeolite. The prepared nanocomposite was characterized by XRD, XRF, FT-IR, DTG, VSM, and TEM methods. The applicability of the synthesized nanocomposite for removal of Cs(+) and Sr(2+) from aqueous solutions was assessed, and the effective parameters such as initial concentration, initial pH, contact time, and temperature on the sorption process were studied and optimized. The composite was able to remove 95.2% and 81.4% of Sr(+2) and Cs(+1) from 0.01 N aqueous solutions, respectively. The kinetic studies showed that the process was quite rapid, and 90% of equilibrium capacity was achieved within 30 min. Experimental kinetic data were found to be well fitted with pseudo-second-order kinetic model with rate constant of 0.2845 and 0.2722 g mmol(-1) min(-1) for Cs(+) and Sr(2+), respectively. The Langmuir, Freundlich, and D-R isotherm models were used to describe the equilibrium data. The saturation magnetization of nanocomposite was measured as 19.50 emu g(-1), which facilitated magnetic separation of the sample after adsorption process. PMID:23266030

  11. Irreversibility of 2,4-Dichlorophenoxyacetic Acid Sorption onto a Volcanic Ash Soil

    NASA Astrophysics Data System (ADS)

    Mon, E.; Kawamoto, K.; Komatsu, T.; Moldrup, P.

    2008-12-01

    Pesticide sorption and desorption in soils are key processes governing fate and transport of pesticides in the soil environment. The irreversibility (or hysteresis) in the processes of pesticide sorption and desorption needs to be known to accurately predict behavior of pesticides in soil systems. 2,4-dichlorophenoxyacetic acid (2,4-D) is a widely used pesticide in agriculture fields. However, only few studies of 2,4-D adsorption onto Andosols (volcanic ash soils) have been published, and the knowledge of 2,4-D desorption onto Andosols is very limited. In this study, a volcanic ash soil sampled from a pasture site in Nishi-Tokyo, Japan was used as a sorbent in order to investigate the irreversibility of 2,4-D sorption. For comparison, a pure clay mineral (kaolinite) obtained from Clay Science Society of Japan (CSSJ) was also used. 2,4-D solutions with three concentrations (0.011, 0.022 and 0.045 mmol/L) were prepared in artificial rain water (ARW= 0.085mM NaCl + 0.015mM CaCl2) to simulate field conditions. To prepare the sample solutions, the solid mass/liquid volume ratio of 1:10 was used for both sorbents (volcanic ash soil and kaolinite). The experiments were conducted in triplicate using a batch method under different pH conditions to examine the effect of pH. Desorption was measured during a equilibration procedure: After removal of 7 mL of supernatant in the sorption step, 7 mL of ARW excluding 2,4-D was added to the sample solution after which, it was equilibrated and centrifuged. The procedure was performed sequentially three or four times to obtain a desorption isotherm. Sorption and desorption generally followed Freundlich isotherms. The results showed markedly effects of pH on 2,4-D sorption and desorption in both the soil and kaolinite, with the percentage of sorption increasing with decreasing pH whereas the percentage of desorption decreased. There was a larger adsorption-desorption hysteresis in the volcanic ash soil as compared to kaolinite

  12. Deviations from sorption linearity on soils of polar and nonpolar organic compounds at low relative concentrations

    USGS Publications Warehouse

    Chiou, C.T.; Kile, D.E.

    1998-01-01

    A series of single-solute and binary-solute sorption data have been obtained on representative samples of polar compounds (substituted ureas and phenolic compounds) and of nonpolar compounds (e.g., EDB and TCE) on a peat soil and a mineral (Woodburn) soil; the data extend to low relative solute concentrations (C(e)/S(w)). At relatively low C(e)/S(w), both the nonpolar and the polar solutes exhibit nonlinear sorption. The sorption nonlinearity approaches apparent saturation at about C(e)/S(w) = 0.010-0.015 for the nonpolar solutes and at about C(e)/S(w) = 0.10-0.13 for the polar solutes; above these C(e)/S(w) regions, the isotherms are practically linear. The nonlinear sorption capacities are greater for polar solutes than for nonpolar solutes and the peat soil shows a greater effect than the Woodburn soil. The small nonlinear sorption capacity for a nonpolar solute is suppressed indiscriminately by either a nonpolar or a polar cosolute at relatively low C(e)/S(w) of the cosolute. By contrast, the abilities of different cosolutes to suppress the nonlinear capacity of a nominal polar solute differ drastically. For polar solutes, a nonpolar cosolute exhibits a limited suppression even at high cosolute C(e)/S(w); effective suppression occurs when the cosolute is relatively polar and at various C(e)/S(w). These differences suggest that more than a single mechanism is required to account for the nonlinear sorption of both nonpolar and polar compounds at low C(e)/S(w). Mechanistic processes consistent with these observations and with soil surface areas are discussed along with other suggested models. Some important consequences of the nonlinear competitive sorption to the behavior of contaminants in natural systems are discussed.A number of conceptual models was postulated to account for the nonlinear solute sorption on soils of significant soil organic matter. A series of single-solute and binary-route sorption data was obtained representing samples of polar compounds of

  13. An unusual H2 sorption mechanism in PCN-14: insights from molecular simulation.

    PubMed

    Pham, Tony; Forrest, Katherine A; Space, Brian

    2016-08-01

    Simulations of H2 sorption were performed in PCN-14, a metal-organic framework (MOF) that consists of Cu(2+) ions coordinated to 5,5'-(9,10-anthracenediyl)diisophthalate (adip) linkers. This MOF displays an excess H2 uptake of 2.70 wt% at 77 K and 1.0 atm and an initial H2Qst value of 8.6 kJ mol(-1) according to previous experimental measurements. The experimental H2 sorption isotherms and Qst values in PCN-14 were reproduced in simulations using well-known H2 potentials that have been widely used for MOF-H2 theoretical studies. H2 sorption in PCN-14 was dominated by repulsion/dispersion energetics; this allowed the experimental observables to be reproduced by a model that includes only Lennard-Jones parameters. The most energetically favorable H2 sorption site in PCN-14 corresponds to sorption within a small cage that is enclosed by three [Cu2(O2CR)4] units and three adip linkers. The anthracenyl rings of the adip linkers represent the secondary sorption sites within the MOF. In contrast to expectations, sorption of H2 onto the Cu(2+) ions of the copper paddlewheels was not observed within the simulations at low loading. The simulations revealed that the open-metal sites in PCN-14 were occupied at high loading. Control simulations of H2 sorption in PCN-14 for different cases in which the partial positive charge of one of the paddlewheel Cu(2+) ions was increased relative to the other revealed that sorption onto the open-metal sites can be captured if there is a very high positive charge on the metal. Otherwise, the calculated partial charge for the Cu(2+) ions in PCN-14 in this work was not high enough in magnitude to facilitate strong H2-metal interactions in simulation. This study shows the power of using molecular simulations to elucidate an unusual H2 sorption behavior in a MOF. PMID:27426916

  14. Sorption Enhanced Reaction Process (SERP) for production of hydrogen

    SciTech Connect

    Anand, M.; Hufton, J.; Mayorga, S.

    1996-10-01

    Sorption Enhanced Reaction Process (SERP) is a novel process that is being developed for the production of lower cost hydrogen by steam-methane reforming (SMR). In this process the reaction of methane with steam is carried out in the presence of an admixture of a catalyst and a selective adsorbent for carbon dioxide. The key consequences of SERP are: (i) reformation reaction is carried out at a significantly lower temperature (300-500{degrees}C) than that in a conventional SMR reactor (800-1100{degrees}C), while achieving the same conversion of methane to hydrogen, (ii) the product hydrogen is obtained at reactor pressure (200-400 psig) and at 98+% purity directly from the reactor (compared to only 70-75% H{sub 2} from conventional SMR reactor), (iii) downstream hydrogen purification step is either eliminated or significantly reduced in size. The first phase of the program has focused on the development of a sorbent for CO{sub 2} which has (a) reversible CO{sub 2} capacity >0.3 mmol/g at low partial pressures of CO{sub 2} (0.1 - 1.0 atm) in the presence of excess steam (pH{sub 2}O/pCO{sub 2}>20) at 400-500{degrees}C and (b) fast sorption-desorption kinetics for CO{sub 2}, at 400-500{degrees}C. Several families of supported sorbents have been identified that meet the target CO{sub 2} capacity. A few of these sorbents have been tested under repeated sorption/desorption cycles and extended exposure to high pressure steam at 400-500{degrees}C. One sorbent has been scaled up to larger quantities (2-3 kg) and tested in the laboratory process equipment for sorption and desorption kinetics of CO{sub 2}. The CO{sub 2}, sorption and desorption kinetics are desirably fast. This was a critical path item for the first phase of the program and now has been successfully demonstrated. A reactor has been designed that will allow nearly isothermal operation for SERP-SMR. This reactor was integrated into an overall process flow diagram for the SERP-SMR process.

  15. 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.

  16. Application of the method of temporal moments to interpret solute transport with sorption and degradation.

    PubMed

    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. PMID:12498577

  17. Sorption of tetravalent thorium on muscovite

    NASA Astrophysics Data System (ADS)

    Schmidt, M.; Lee, S. S.; Wilson, R. E.; Soderholm, L.; Fenter, P.

    2012-07-01

    Adsorption of tetravalent thorium to the (0 0 1) basal surface of the phyllosilicate muscovite from an aqueous solution (1 × 10-4 mol/L Th(IV) in 1 × 10-1 mol/L NaCl, pH = 3.2) was studied by crystal truncation rod (CTR) and resonant anomalous X-ray reflectivity (RAXR) measurements. Th uptake to the muscovite surface from solutions with total Th concentrations [Th]tot = 1 × 10-6-4.88 × 10-3 mol/L and 1 × 10-1 mol/L NaCl, pH = 3.2 was quantified by alpha-spectrometry. The uptake measurements showed that Th adsorption to the muscovite surface follows a Langmuir isotherm with an apparent adsorption constant Kapp = 2 × 104 L/mol up to [Th]tot = 1.02 × 10-3 mol/L. The CTR and RAXR results identified one dominant Th species with a very broad distribution centered ∼10 Å above the surface, in agreement with strongly hydrated extended outer sphere sorption. The findings indicate that the large energy of hydration (ΔGhyd = -5815 kJ/mol (Marcus, 1991)) for the small and highly-charged Th4+ cation is a controlling parameter in its surface speciation. The surface occupancy (0.4 Th per unit cell area, AUC) measured by RAXR exceeds the expected level for surface charge compensation by tetravalent Th (0.25 Th/AUC). However, the radiometric uptake measurements show smaller occupancies (0.21 Th/AUC) after rinsing by deionized water, indicating a partial removability of sorbed thorium. Thorium oligomerization was observed at total Th concentrations [Th]tot ⩾ 2.0 × 10-3 mol/L in presence of the surface, although solubility studies suggest that Th is soluble under these solution conditions.

  18. Characterization of carbonated tricalcium silicate and its sorption capacity for heavy metals: a micron-scale composite adsorbent of active silicate gel and calcite.

    PubMed

    Chen, Quanyuan; Hills, Colin D; Yuan, Menghong; Liu, Huanhuan; Tyrer, Mark

    2008-05-01

    Adsorption-based processes are widely used in the treatment of dilute metal-bearing wastewaters. The development of versatile, low-cost adsorbents is the subject of continuing interest. This paper examines the preparation, characterization and performance of a micro-scale composite adsorbent composed of silica gel (15.9 w/w%), calcium silicate hydrate gel (8.2 w/w%) and calcite (75.9 w/w%), produced by the accelerated carbonation of tricalcium silicate (C(3)S, Ca(3)SiO(5)). The Ca/Si ratio of calcium silicate hydrate gel (C-S-H) was determined at 0.12 (DTA/TG), 0.17 ((29)Si solid-state MAS/NMR) and 0.18 (SEM/EDS). The metals-retention capacity for selected Cu(II), Pb(II), Zn(II) and Cr(III) was determined by batch and column sorption experiments utilizing nitrate solutions. The effects of metal ion concentration, pH and contact time on binding ability was investigated by kinetic and equilibrium adsorption isotherm studies. The adsorption capacity for Pb(II), Cr(III), Zn(II) and Cu(II) was found to be 94.4 mg/g, 83.0 mg/g, 52.1 mg/g and 31.4 mg/g, respectively. It is concluded that the composite adsorbent has considerable potential for the treatment of industrial wastewater containing heavy metals. PMID:17950999

  19. Relative effects of advection, sorption and diffusion on transport and tailing of chlorinated solvents

    NASA Astrophysics Data System (ADS)

    Maghrebi, M.; Jankovic, I.; Rabideau, A. J.; Allen-King, R. M.; Weissmann, G. S.

    2011-12-01

    Effects of three key transport mechanisms (advection, diffusion and sorption) on transport and contaminant tailing of chlorinated solvents have been investigated using a numerical model. Thousands of model simulations have been conducted for various combinations of transport parameters that govern three key mechanisms in order to quantify tailing and relative importance of each mechanism. Hydraulic conductivity model contains a single inclusion of constant conductivity K embedded in a homogeneous anisotropic background of conductivity Kh,Kv. The inclusion is shaped as an oblate ellipsoid and subject to uniform flow. The background represents "average" conductivity of a heterogeneous formation while inclusion is used to represent geologic units that are more or less conductive than the background. The ratio of long to short semi-axis of the inclusion (a/b) models the ratio of horizontal to vertical integral scales (Ih/Iv) of different geologic units, where integral scales can be obtained, for example, using indicator variograms. The flow solution for present problem is obtained analytically as a closed form solution with exact expressions for Darcy velocity valid both inside and outside the inclusion. Sorption is modeled as an equilibrium process governed by a linear isotherm. The effects on transport and tailing are accounted for using retardation factors. Sorption heterogeneity is created by allowing different values of retardation factor for the interior (Ri) and the exterior of the inclusion (Rb). Diffusive displacements have been added to retarded advective displacements using random walk method. Peclet number, defined as Pe=U Ih/D (U is the groundwater velocity, D is the molecular diffusion coefficient for chlorinated solvents), is used to quantify the diffusion process. Very large numbers of particles (hundreds of thousands) have been tracked using very small time steps (as small as a/10,000) to provide sufficient resolution to breakthrough curves and to

  20. Sorption Characteristics of Organic Powder Sorption Material in Fluidized Bed with a Cooling Pipe

    NASA Astrophysics Data System (ADS)

    Horibe, Akihiko; Husain, Syahrul; Inaba, Hideo; Haruki, Naoto

    The dynamic sorption characteristics of organic sorbent materials have been studied by using fluidized bed with a cooling pipe. The organic powder type sorbent made from a bridged complex of sodium polyacrylate which is one of the sorption polymers is adopted in this study. Sorption rate of water vapor and the variation of temperature in the sorbent bed with time were measured under various conditions. As a result, sorption ratio increases and the completion time for the sorption process decreases by using a cooling pipe. Furthermore, the non-dimensional correlation equations were obtained for water vapor mass transfer under sorption process in terms of relevant non-dimensional parameters.