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Sample records for adsorption isotherm experiments

  1. The Calculation of Adsorption Isotherms from Chromatographic Peak Shapes

    ERIC Educational Resources Information Center

    Neumann, M. G.

    1976-01-01

    Discusses the relationship between adsorption isotherms and elution peak shapes in gas chromatography, and describes a laboratory experiment which involves the adsorption of hexane, cyclohexane, and benzene on alumina at different temperatures. (MLH)

  2. Adsorption Isotherms and Surface Reaction Kinetics

    ERIC Educational Resources Information Center

    Lobo, L. S.; Bernardo, C. A.

    1974-01-01

    Explains an error that occurs in calculating the conditions for a maximum value of a rate expression for a bimolecular reaction. The rate expression is derived using the Langmuir adsorption isotherm to relate gas pressures and corresponding surface coverages. (GS)

  3. A Simple Adsorption Experiment

    ERIC Educational Resources Information Center

    Guirado, Gonzalo; Ayllon, Jose A.

    2011-01-01

    The study of adsorption phenomenon is one of the most relevant and traditional physical chemistry experiments performed by chemistry undergraduate students in laboratory courses. In this article, we describe an easy, inexpensive, and straightforward way to experimentally determine adsorption isotherms using pieces of filter paper as the adsorbent…

  4. CARBON ADSORPTION ISOTHERMS FOR TOXIC ORGANICS

    EPA Science Inventory

    An experimental protocol for measuring the activated carbon adsorption isotherm was developed and applied to a wide range of organic compounds. Methods for treatment of the isotherm data and a standard format for presentation of results are shown. In the early phase of the study ...

  5. 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.

  6. 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.

  7. Adsorption isotherm of non-azeotropic solution onto porous adsorbents

    NASA Astrophysics Data System (ADS)

    Bono, A.; Ramlan, N. A.; Anisuzzaman, S. M.; Chu, C. M.; Farm, Y. Y.

    2016-06-01

    Adsorption isotherm is essential component in the understanding of the adsorption process. Several methods of the measurements, analysis and interpretation of adsorption from solution have been reported in the literature. Most of the measurements of adsorption isotherm from solution were involved the measurement of excess isotherm conducted at low region of sorbates concentration. Direct interpretation of excess adsorption isotherm as adsorption isotherm is always been practice. Therefore, in this work a study on the measurement of the adsorption isotherm from solution of non-azeotropic organic solvent mixture onto porous adsorbents for whole range of liquid concentration was conducted. The study included the measurement of excess adsorption isotherm using conventional technique. Theoretical analysis and interpretation of adsorption isotherm from the excess isotherm were conducted using Pseudo Ideal Adsorption, Gibbs Dividing Plane Model and Langmuir-Fruendlich binary isotherm model. For organic solvents, acetone and propanol were chosen as the adsorbates due to the non-azeotropic properties in the mixture. Activated carbon and silicalite were chosen as adsorbents due to the different in their porosity such as macro porous and micro porous structure. The result of the study has revealed that the adsorption isotherm of non-azeotropic mixture onto activated carbon and silicalite can be interpreted as monolayer type of adsorption.

  8. 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.

  9. Kinetics and isotherms of Neutral Red adsorption on peanut husk.

    PubMed

    Han, Runping; Han, Pan; Cai, Zhaohui; Zhao, Zhenhui; Tang, Mingsheng

    2008-01-01

    Adsorption of Neutral Red (NR) onto peanut husk in aqueous solutions was investigated at 295 K. Experiments were carried out as function of pH, adsorbent dosage, contact time, and initial concentration. The equilibrium adsorption data were analyzed by Langmuir, Freundlich, Temkin, Dubinin-Radushkevich, and Toth isotherm models. The results indicated that the Toth and Langmuir models provided the best correlation of the experimental data. The adsorption capacity of peanut husk for the removal of NR was determined with the Langmuir and found to be 37.5 mg/g at 295 K. The adsorption kinetic data were modeled using the pseudo-first order, pseudo-second order, and intra-particle diffusion kinetic equations. It was seen that the pseudo-first order and pseudo-second order kinetic equations could describe the adsorption kinetics. The intraparticle diffusion model was also used to express the adsorption process at the two-step stage. It was implied that peanut husk may be suitable as adsorbent material for adsorption of NR from aqueous solutions. PMID:19143308

  10. 40 CFR 796.2750 - Sediment and soil adsorption isotherm.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 31 2010-07-01 2010-07-01 true Sediment and soil adsorption isotherm. 796.2750 Section 796.2750 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) TOXIC SUBSTANCES CONTROL ACT (CONTINUED) CHEMICAL FATE TESTING GUIDELINES Transport Processes § 796.2750 Sediment and soil adsorption isotherm....

  11. The Effect of Pore Connectivity on Water Adsorption Isotherms in Non-activated Graphitic Nanopores

    SciTech Connect

    StrioloDr., A; Gubbins, Dr. K. E.; Chialvo, Ariel A; Cummings, Peter T

    2005-01-01

    The adsorption of water in graphitic carbons is usually simulated via a weighted average of the adsorption isotherms simulated in carbon-slit pore of different widths. By following this procedure, details about pore morphology and pore connectivity may be overlooked. Towards a better match between virtual and real experiments, we present simulated adsorption isotherms for SPC/E model water in porous carbons composed by interconnected carbon-slit pores. The pores are separated from each other by one graphene layer. Imperfections (lack of carbon atoms) in the graphene layers result in interconnections between pores. The grand canonical Monte Carlo algorithm is used here to simulate water adsorption. Our results show that while the qualitative features obtained in the simulation of independent slit-shaped pores are reproduced when interconnected pores are considered, the adsorption isotherms rise more gradually and the adsorption/desorption hysteresis loops are narrower in the latter case.

  12. Effect of moisture on adsorption isotherms and adsorption capacities of CO{sub 2} on coals

    SciTech Connect

    Ekrem Ozdemir; Karl Schroeder

    2009-05-15

    The effect of moisture on the adsorption isotherms and adsorption capacities of CO{sub 2} on Argonne Premium coals has been investigated. In some experiments a small hysteresis was observed between the adsorption and desorption isotherms. The hysteresis was absent or negligible for high-rank and as-received coals but was discernible for lower rank and dried coals. An equation that accounted for the volumetric changes when an adsorbate alters the structure of an adsorbent was employed to interpret the data. The best-fit solutions indicate that the coal volume decreases upon drying. The microscopic shrinkage estimated using helium expansion was greater than the shrinkage reported using the bed-height technique. The microscopic shrinkage was 5-10% for low-moisture medium and high-rank coals and up to 40% for low-rank coals having higher moisture contents. The CO{sub 2} swelling of coals during adsorption isotherm measurements was estimated to be about the same as the shrinkage that occurred during the moisture loss. The adsorption capacity, isosteric heat of adsorption, average pore size, and surface area of the as-received (moist) and dried Argonne coals were estimated after accounting for the volume changes. The isosteric heat of adsorption of CO{sub 2} was found to be between 23 and 25 kJ/mol for as-received coals and between 25 and 27 kJ/mol for dried coals, regardless of the rank. The degree of drying was shown to affect the adsorption capacity and the calculated surface area. For dried coals, the adsorption capacity showed the typical 'U-shape' dependence on rank whereas the as-received coals displayed a more linear dependence. A relationship is proposed to quantify the effect of moisture on the adsorption capacity. The mechanism of CO{sub 2} adsorption on moist coals and the implications of the lower adsorption capacity of wet coals to coal seam sequestration of CO{sub 2} are presented. 70 refs., 12 figs., 2 tabs.

  13. Derivation of the Freundlich Adsorption Isotherm from Kinetics

    ERIC Educational Resources Information Center

    Skopp, Joseph

    2009-01-01

    The Freundlich adsorption isotherm is a useful description of adsorption phenomena. It is frequently presented as an empirical equation with little theoretical basis. In fact, a variety of derivations exist. Here a new derivation is presented using the concepts of fractal reaction kinetics. This derivation provides an alternative basis for…

  14. 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.

  15. Simulated Water Adsorption Isotherms in Hydrophilic and Hydrophobic Cylinderical Nanopores

    SciTech Connect

    StrioloDr., A; Naicker, P. K.; Chialvo, Ariel A; Cummings, Peter T; Gubbins, Dr. K. E.

    2005-01-01

    Grand canonical Monte Carlo simulations are performed to study the adsorption of water in single-walled carbon nanotubes (SWCNs). At room temperature the resulting adsorption isotherms in (10:10) and wider SWCNs are characterized by negligible amount of water uptake at low pressures, sudden and complete pore filling once a threshold pressure is reached, and wide adsorption/desorption hysteresis loops. The width of these loops decreases as pore diameter narrows. Adsorption/desorption hysteresis loops are not observed for water adsorption in (6:6) SWCNs. When the nanotubes are doped with small amounts of oxygenated sites it is possible to obtain adsorption isotherms in which the water uptake increases gradually as the pressure increases. Simulated X-ray diffraction patterns for confined water are also reported.

  16. 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.

  17. 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

  18. The effects of Concentration and Salinity on Polymer Adsorption Isotherm at Sandstone Rock Surface

    NASA Astrophysics Data System (ADS)

    Ali, M.; Ben Mahmud, H.

    2015-04-01

    Adsorption of hydrolyzed polyacrylamide (HPAM) polymers on sandstone rock surface was studied by static adsorption experiments. Total of 10 Runs of static experiments were conducted in test tubes by mixing the desired solution with crushed rock sample, at temperature of 25 °C, and salinity range from 0-4 wt%. The results are in conformity with Langmuir's isotherm. Ten different isotherms were generated at each Run. The initial polymer concentration was varied from 0.3-2.1 g/l. The effects of salinity have been studied by observation on Langmuir adsorption coefficients (Y and K). The results show that the adsorption coefficient (Y) was found to have linear relationship with salinity. The adsorption coefficient (K) was found to be related to salinity by a quadratic relationship.

  19. Microscopic Perspective on the Adsorption Isotherm of a Heterogeneous Surface

    PubMed Central

    Carr, Rogan; Comer, Jeffrey; Ginsberg, Mark D.; Aksimentiev, Aleksei

    2012-01-01

    Adsorption of dissolved molecules onto solid surfaces can be extremely sensitive to the atomic-scale properties of the solute and surface, causing difficulties for the design of fluidic systems in industrial, medical and technological applications. In this communication, we show that the Langmuir isotherm for adsorption of a small molecule to a realistic, heterogeneous surface can be predicted from atomic structures of the molecule and surface through molecular dynamics (MD) simulations. We highlight the method by studying the adsorption of dimethyl-methylphosphonate (DMMP) to amorphous silica substrates and show that subtle differences in the atomic-scale surface properties can have drastic effects on the Langmuir isotherm. The sensitivity of the method presented is sufficient to permit the optimization of fluidic devices and to determine fundamental design rules for controlling adsorption at the nanoscale. PMID:22611479

  20. Enthalpy of adsorption and isotherms for adsorption of naphthenic acid onto clays

    SciTech Connect

    Zou, L.; Han, B.; Yan, H.; Kasperski, K.L.; Xu, Y.; Hepler, L.G.

    1997-06-15

    The enthalpies of adsorption and the isotherms for adsorption of naphthenic acid onto Na-montmorillonite, Na-kaolinite, and Na-illite were studied by means of calorimetry and the static method at 298.15 K. The results show that the enthalpies of adsorption and saturated adsorption amounts of naphthenic acid on different clays change in the order Na-montmorillonite > Na-illite > Na-kaolinite. The interaction between naphthenic acid and clays is discussed.

  1. Adsorption and disjoining pressure isotherms of confined polymers using dissipative particle dynamics.

    PubMed

    Goicochea, A Gama

    2007-11-01

    The adsorption and disjoining pressure isotherms of polymers confined by planar walls are obtained using Monte Carlo (MC) simulations in the Grand Canonical (GC) ensemble in combination with the mesoscopic technique known as dissipative particle dynamics (DPD). Two models of effective potentials for the confining surfaces are used: one with both an attractive and a repulsive term and one with a purely repulsive term. As for the polymer, seven-bead linear model of polyethylene glycol (PEG) dissolved in water is used. The results indicate remarkably good agreement between the trends shown by our adsorption isotherms and those obtained from experiments of PEG on oxide surfaces. Additionally, the disjoining pressure isotherm of water shows oscillations, while those of PEG display the same trend for both wall models. Moreover, it is found that the disjoining pressure isotherms are in qualitative agreement with those from experiments on confined linear polymers. PMID:17914849

  2. 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

  3. ISOTHERMAL AIR INGRESS VALIDATION EXPERIMENTS

    SciTech Connect

    Chang H Oh; Eung S Kim

    2011-09-01

    Idaho National Laboratory carried out air ingress experiments as part of validating computational fluid dynamics (CFD) calculations. An isothermal test loop was designed and set to understand the stratified-flow phenomenon, which is important as the initial air flow into the lower plenum of the very high temperature gas cooled reactor (VHTR) when a large break loss-of-coolant accident occurs. The unique flow characteristics were focused on the VHTR air-ingress accident, in particular, the flow visualization of the stratified flow in the inlet pipe to the vessel lower plenum of the General Atomic’s Gas Turbine-Modular Helium Reactor (GT-MHR). Brine and sucrose were used as heavy fluids, and water was used to represent a light fluid, which mimics a counter current flow due to the density difference between the stimulant fluids. The density ratios were changed between 0.87 and 0.98. This experiment clearly showed that a stratified flow between simulant fluids was established even for very small density differences. The CFD calculations were compared with experimental data. A grid sensitivity study on CFD models was also performed using the Richardson extrapolation and the grid convergence index method for the numerical accuracy of CFD calculations . As a result, the calculated current speed showed very good agreement with the experimental data, indicating that the current CFD methods are suitable for predicting density gradient stratified flow phenomena in the air-ingress accident.

  4. Estimating Uranium Partition Coefficients from Laboratory Adsorption Isotherms

    SciTech Connect

    Hull, Laurence Charles; Grossman, Christopher; Fjeld, R. A.; Coates, C.J.; Elzerman, A.

    2002-08-01

    An estimated 330 metric tons of uranium have been buried in the radioactive waste Subsurface Disposal Area (SDA) at the Idaho National Engineering and Environmental Laboratory (INEEL). An assessment of uranium transport parameters is being performed to decrease the uncertainty in risk and dose predictions derived from computer simulations of uranium fate and transport to the underlying Snake River Plain Aquifer. Uranium adsorption isotherms have been measured in the laboratory and fit with a Freundlich isotherm. The Freundlich n parameter was statistically identical for 14 sediment samples. The Freundlich Kf for seven samples, where material properties have been measured, is correlated to sediment surface area. Based on these empirical observations, a model has been derived for adsorption of uranium on INEEL sedimentary materials using surface complexation theory. The model was then used to predict the range of adsorption conditions to be expected at the SDA. Adsorption in the deep vadose zone is predicted to be stronger than in near-surface sediments because the total dissolved carbonate decreases with depth.

  5. Estimating Uranium Partition Coefficients from Laboratory Adsorption Isotherms

    SciTech Connect

    Hull, L.C.; Grossman, C.; Fjeld, R.A.; Coates, J.T.; Elzerman, A.W.

    2002-05-10

    An estimated 330 metric tons of uranium have been buried in the radioactive waste Subsurface Disposal Area (SDA) at the Idaho National Engineering and Environmental Laboratory (INEEL). An assessment of uranium transport parameters is being performed to decrease the uncertainty in risk and dose predictions derived from computer simulations of uranium fate and transport to the underlying Snake River Plain Aquifer. Uranium adsorption isotherms have been measured in the laboratory and fit with a Freundlich isotherm. The Freundlich n parameter was statistically identical for 14 sediment samples. The Freundlich Kf for seven samples, where material properties have been measured, is correlated to sediment surface area. Based on these empirical observations, a model has been derived for adsorption of uranium on INEEL sedimentary materials using surface complexation theory. The model was then used to predict the range of adsorption conditions to be expected at the SDA. Adsorption in the deep vadose zone is predicted to be stronger than in near-surface sediments because the total dissolved carbonate decreases with depth.

  6. Removal Rate of Organic Matter Using Natural Cellulose via Adsorption Isotherm and Kinetic Studies.

    PubMed

    Din, Mohd Fadhil Md; Ponraj, Mohanadoss; Low, Wen-Pei; Fulazzaky, Mohamad Ali; Iwao, Kenzo; Songip, Ahmad Rahman; Chelliapan, Shreeshivadasan; Ismail, Zulhilmi; Jamal, Mohamad Hidayat

    2016-02-01

    In this study, the removal of natural organic matter (NOM) using coconut fiber (CF) and palm oil fiber (POF) was investigated. Preliminary analysis was performed using a jar test for the selection of optimal medium before the fabricated column model experiment. The equilibrium studies on isotherms and kinetic models for NOM adsorption were analyzed using linearized correlation coefficient. Results showed that the equilibrium data were fitted to Langmuir isotherm model for both CF and POF. The most suitable adsorption model was the pseudo-first-order kinetic model for POF and pseudo-second-order kinetic model for CF. The adsorption capacities achieved by the CF and POF were 15.67 and 30.8 mg/g respectively. Based on this investigation, it can be concluded that the POF is the most suitable material for the removal of NOM in semi polluted river water. PMID:26803100

  7. Immobilization of Acetobacter aceti on cellulose ion exchangers: adsorption isotherms

    SciTech Connect

    Bar, R.; Gainer, J.L.; Kirwan, D.J.

    1986-08-01

    The adsorptive behavior of cells of Acetobacter aceti, ATCC 23746, on DEAE-, TEAE-, and DEHPAE-cellulose ion exchangers in a modified Hoyer's medium at 30 degrees Centigrade was investigated. The maximum observed adsorption capacities varied from 46 to 64 mg dry wt/g resin. The Langmuir isotherm form was used to fit the data, since the cells formed a monolayer on the resin and exhibited saturation. The equilibrium constant in the Langmuir expression was qualitatively correlated with the surface charge density of the resin. The adsorption was also ''normalized'' by considering the ionic capacities of the resins. The exceptionally high normalized adsorption capacity of ECTEOLA-cellulose, 261 mg dry/meq, may be explained by an interaction between the cell wall and the polyglyceryl chains of the exchanging groups in addition to the electrostatic effects. The effect of pH on the bacterial adsorption capacity of ECTEOLA-, TEAE-, and phosphate-cellulose resins was studied and the pH of the bacteria was estimated to be 3.0. 17 references.

  8. Effect of pore blockage on adsorption isotherms and dynamics: Anomalous adsorption of iodine on activated carbon

    SciTech Connect

    Bhatia, S.K.; Liu, F.; Arvind, G.

    2000-04-18

    Isotherm hysteresis and pore-clocking effects of trapped molecules on adsorption dynamics is studied here, using the iodine-carbon system in the 300--343 K temperature range. It is found that a portion of the iodine is strongly adsorbed, and does not desorb, even over very long time scales, while the remainder adsorbs reversibly as a homogeneous monolayer with a Langmuirian isotherm in mesopores. The strongly adsorbed iodine appears to adsorb in micropores and at the mesopore mouths, hindering uptake of the reversible iodine. The uptake data for the adsorption and desorption dynamics of the reversible part is found to be best explained by means of a pore mouth resistance control mechanism. it is concluded that the dynamics of the adsorption and desorption at the pore mouth is important at early stages of the process.

  9. Enhanced fluoride adsorption by nano crystalline γ-alumina: adsorption kinetics, isotherm modeling and thermodynamic studies

    NASA Astrophysics Data System (ADS)

    Chinnakoti, Prathibha; Chunduri, Avinash L. A.; Vankayala, Ranganayakulu K.; Patnaik, Sandeep; Kamisetti, Venkataramaniah

    2016-06-01

    Nano materials in particular nano oxides with enhanced surface area and an excellent catalytic surface serve as potential adsorbents for defluoridation of water. In the present study nano γ-alumina was synthesized through a simple and low cost, surfactant assisted solution combustion method. As synthesized material was characterized by XRD and FESEM for its phase, size and morphological characteristics. Surface properties have been investigated by BET method. Nano γ-alumina was further used for a detailed adsorption study to remove fluoride from water. Batches of experiments were performed at various experimental conditions such as solution pH, adsorbent dose, initial fluoride concentration and contact time to test the defluoridation ability of γ-alumina. Fluoride Adsorption by nano sized γ-alumina was rapid and reached equilibrium within two hours. The adsorption worked well at pH 4.0, where ˜96 % of fluoride was found to be adsorbed on adsorbent. It was possible to reduce fluoride levels to as low as 0.3 mg/L (within the safe limit of WHO: ≤1.5 mg/L) from an initial fluoride levels of 10 mg/L. This could be achieved using a very small quantity, 1 g/L of γ-alumina at pH 4 within 1 h of contact time. Defluoridation capacity of nano γ-alumina was further investigated by fitting the equilibrium data to various isotherm as well as kinetic models. The present study revealed that γ-alumina could be an efficient adsorbent for treating fluoride contaminated water.

  10. 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.

  11. Optimal smoothing of site-energy distributions from adsorption isotherms

    SciTech Connect

    Brown, L.F.; Travis, B.J.

    1983-01-01

    The equation for the adsorption isotherm on a heterogeneous surface is a Fredholm integral equation. In solving it for the site-energy distribution (SED), some sort of smoothing must be carried out. The optimal amount of smoothing will give the most information that is possible without introducing nonexistent structure into the SED. Recently, Butler, Reeds, and Dawson proposed a criterion (the BRD criterion) for choosing the optimal smoothing parameter when using regularization to solve Fredholm equations. The BRD criterion is tested for its suitability in obtaining optimal SED's. This criterion is found to be too conservative. While using it never introduces nonexistent structure into the SED, significant information is often lost. At present, no simple criterion for choosing the optimal smoothing parameter exists, and a modeling approach is recommended.

  12. 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

  13. Magnetic vinylphenyl boronic acid microparticles for Cr(VI) adsorption: kinetic, isotherm and thermodynamic studies.

    PubMed

    Kara, Ali; Demirbel, Emel; Tekin, Nalan; Osman, Bilgen; Beşirli, Necati

    2015-04-01

    Magnetic vinylphenyl boronic acid microparticles, poly(ethylene glycol dimethacrylate(EG)-vinylphenyl boronic acid(VPBA)) [m-poly(EG-VPBA)], produced by suspension polymerization and characterized, was found to be an efficient solid polymer for Cr(VI) adsorption. The m-poly(EG-VPBA) microparticles were prepared by copolymerizing of ethylene glycol dimethylacrylate (EG) with 4-vinyl phenyl boronic acid (VPBA). The m-poly(EG-VPBA) microparticles were characterized by N2 adsorption/desorption isotherms, electron spin resonance (ESR), X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA), elemental analysis, scanning electron microscope (SEM) and swelling studies. The m-poly(EG-VPBA) microparticles were used at adsorbent/Cr(VI) ion ratios. The influence of pH, Cr(VI) initial concentration, temperature of the removal process was investigated. The maximum removal of Cr(VI) was observed at pH 2. Langmuir isotherm and Dubinin-Radushkvich isotherm were found to better fit the experiment data rather than Fruendlich isotherm. The kinetics of the adsorption process of Cr(VI) on the m-poly(EG-VPBA) microparticles were investigated using the pseudo first-order, pseudo-second-order, Ritch-second-order and intraparticle diffusion models, results showed that the pseudo-second order equation model provided the best correlation with the experimental results. The thermodynamic parameters (free energy change, ΔG(0) enthalpy change, ΔH(0); and entropy change, ΔS(0)) for the adsorption have been evaluated. PMID:25666882

  14. 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.

  15. Kinetic and isotherms studies of phosphorus adsorption onto natural riparian wetland sediments: linear and non-linear methods.

    PubMed

    Zhang, Liang; Du, Chao; Du, Yun; Xu, Meng; Chen, Shijian; Liu, Hongbin

    2015-06-01

    Riparian wetlands provide critical functions for the improvement of surface water quality and storage of nutrients. Correspondingly, investigation of the adsorption characteristic and capacity of nutrients onto its sediments is benefit for utilizing and protecting the ecosystem services provided by riparian areas. The Langmuir and Freundlich isotherms and pseudo-second-order kinetic model were applied by using both linear least-squares and trial-and-error non-linear regression methods based on the batch experiments data. The results indicated that the transformations of non-linear isotherms to linear forms would affect the determination process significantly, but the non-linear regression method could prevent such errors. Non-linear Langmuir and Freundlich isotherms both fitted well with the phosphorus adsorption process (r (2) > 0.94). Moreover, the influences of temperature and ionic strength on the adsorption of phosphorus onto natural riparian wetland sediments were also studied. Higher temperatures were suitable for phosphorus uptake from aqueous solution using the present riparian wetland sediments. The adsorption capacity increased with the enhancement of ionic strength in agreement with the formation of inner-sphere complexes. The quick adsorption of phosphorus by the sediments mainly occurred within 10 min. The adsorption kinetic was well-fitted by pseudo-second-order kinetic model (r (2) > 0.99). The scanning electron microscopy (SEM) and Fourier transformation infrared (FT-IR) spectra analyses before and after phosphorus adsorption revealed the main adsorption mechanisms in the present system. PMID:26017810

  16. Ni (II) adsorption onto Chrysanthemum indicum: Influencing factors, isotherms, kinetics, and thermodynamics.

    PubMed

    Vilvanathan, Sowmya; Shanthakumar, S

    2016-10-01

    The study explores the adsorption potential of Chrysanthemum indicum biomass for nickel ion removal from aqueous solution. C. indicum flowers in raw (CIF-I) and biochar (CIF-II) forms were used as adsorbents in this study. Batch experiments were conducted to ascertain the optimum conditions of solution pH, adsorbent dosage, contact time, and temperature for varying initial Ni(II) ion concentrations. Surface area, surface morphology, and functionality of the adsorbents were characterized by Brunauer, Emmett, and Teller (BET) surface analysis, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and Fourier transform infrared spectroscopy (FTIR). Adsorption kinetics were modeled using pseudo-first order, pseudo-second order, Elovich, intraparticle diffusion, Bangham's, and Boyd's plot. The equilibrium data were modeled using Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich (D-R) isotherm models. Experimental data provided the best fit to pseudo-second-order kinetic model and Langmuir isotherm model for the adsorption of Ni(II) ion on both CIF-I and CIF-II with maximum adsorption capacities of 23.97 and 44.02 mg g(-1), respectively. Thermodynamic analysis of the data proved the process to be spontaneous and endothermic in nature. Desorption studies were conducted to evaluate the possibility of reusing the adsorbents. Findings of the present study provide substantial evidence for the use of C. indicum flower as an eco-friendly and potential adsorbent for the removal of Ni(II) ions from aqueous solution. PMID:27185382

  17. Correlation of adsorption isotherms of hydrogen isotopes on mordenite adsorbents using reactive vacancy solution theory

    SciTech Connect

    Munakata, K.; Nakamura, A.; Kawamura, Y.

    2015-03-15

    The authors have applied the isotherm equations derived from the reactive vacancy solution theory (RVST) to correlation of experimental and highly non-ideal adsorption isotherms of hydrogen and deuterium on a mordenite adsorbent, and have examined the ability of the isotherm equations to match this correlation. Several isotherm equations such as Langmuir, Freundlich, Toth, Vacancy Solution Theory and so forth were also tested, but they did not work. For the Langmuir-Freundlich equation tests have indicated that its 'ability to correlate' of the adsorption isotherms is not satisfactory. For the multi-site Langmuir-Freundlich (MSLF) equation the correlation of the isotherms appears to be somewhat improved but remains unsatisfactory. The results show that the isotherm equations derived from RVST can better correlate the experimental isotherms.

  18. [Application of classical isothermal adsorption models in heavy metal ions/ diatomite system and related problems].

    PubMed

    Zhu, Jian; Wu, Qing-Ding; Wang, Ping; Li, Ke-Lin; Lei, Ming-Jing; Zhang, Wei-Li

    2013-11-01

    In order to fully understand adsorption nature of Cu2+, Zn2+, Pb2+, Cd2+, Mn2+, Fe3+ onto natural diatomite, and to find problems of classical isothermal adsorption models' application in liquid/solid system, a series of isothermal adsorption tests were conducted. As results indicate, the most suitable isotherm models for describing adsorption of Pb2+, Cd2+, Cu2+, Zn2+, Mn2+, Fe3+ onto natural diatomite are Tenkin, Tenkin, Langmuir, Tenkin, Freundlich and Freundlich, respectively, the adsorption of each ion onto natural diatomite is mainly a physical process, and the adsorption reaction is favorable. It also can be found that, when using classical isothermal adsorption models to fit the experimental data in liquid/solid system, the equilibrium adsorption amount q(e) is not a single function of ion equilibrium concentration c(e), while is a function of two variables, namely c(e) and the adsorbent concentration W0, q(e) only depends on c(e)/W(0). Results also show that the classical isothermal adsorption models have a significant adsorbent effect, and their parameter values are unstable, the simulation values of parameter differ greatly from the measured values, which is unhelpful for practical use. The tests prove that four-adsorption-components model can be used for describing adsorption behavior of single ion in nature diatomite-liquid system, its parameters k and q(m) have constant values, which is favorable for practical quantitative calculation in a given system. PMID:24455943

  19. Colloidal stability dependence on polymer adsorption through disjoining pressure isotherms.

    PubMed

    Goicochea, A Gama; Nahmad-Achar, E; Pérez, E

    2009-04-01

    The disjoining pressure of polymers confined by colloidal walls was computed using dissipative particle dynamics simulations at constant chemical potential, volume, and temperature. The polymers are able to adsorb on the surfaces according to two models. In the so-called surface-modifying polymers, all monomers composing the chains have the same affinity for the substrate, whereas for the end-grafted polymer only the monomer at one of the ends of the polymer molecule adsorbs on the colloidal surface, resembling the behavior of dispersing agents. We find that these adsorption models yield markedly different disjoining pressure isotherms, which in turn predict different stability conditions for the colloidal dispersion. Our results show that for end-grafted polymers, a larger degree of polymerization at the same monomer concentration leads to better stability than for the surface-modifying ones. But also the unbound monomers of the surface-modifying type dominate over both kinds of polymers at large surface distances. The origin of these differences when the chemical nature of monomers is the same, and molecular weight and polymer concentration are used to characterize colloidal stability, is found to be mainly entropic. PMID:19228014

  20. Characterizing Nitrogen adsorption and desorption isotherms in soils using multifractal analysis

    NASA Astrophysics Data System (ADS)

    Paz Ferreiro, Jorge; Miranda, José G. V.; Vidal Vázquez, Eva

    2010-05-01

    The specific surface area is an attribute known to characterize the soil ability to retain and transport nutrients and water. A number of studies have shown that specific surface area correlates cation exchange capacity, organic matter content, water retention, aggregate stability and clay swelling. In the past fractal theory has been widely used to study different gas adsorption isotherms like water vapour and nitrogen adsorption isotherms. More recently we have shown that nitrogen adsorption isotherms showed multifractal nature. In this work, both N2 adsorption and desorption isotherms measured in a Mollisol were examined as a probability measure using the multifractal formalism in order to determinate its possible multifractal behaviour. Soil samples were collected in two different series of an Argiudoll located in the north of Buenos Aires and in the south of Santa Fe provinces, Argentina. Two treatments of each soil series were sampled at three depths, without replication, resulting in six samples per soil series and a total of twelve samples analyzed. Multifractal analysis was performed using the box counting method. Both, the N2 adsorption and desorption isotherms exhibited a well defined scaling behaviour indicating a fully developed multifractal structure of each isotherm branch. The singularity spectra and Rényi dimension spectra obtained for adsorption and also for desorption isotherms had shapes similar to the spectra of multifractal measures and several parameters were extracted from these spectra. The capacity dimension, D0, for both N2 adsorption and desorption data sets were not significantly different from 1.00. However, nitrogen adsorption and desorption data showed significantly different values of entropy dimension, D1, and correlation dimension, D2. For instance, entropy dimension values extracted from multifractal spectra of adsorption isotherms were on average 0.578 and varied from 0.501 to 0.666. In contrast, the corresponding figures for

  1. Isothermal dendritic growth - A low gravity experiment

    NASA Technical Reports Server (NTRS)

    Glicksman, M. E.; Hahn, R. C.; Lograsso, T. A.; Rubinstein, E. R.; Winsa, E.

    1987-01-01

    The Isothermal Dendritic Growth Experiment has been designed to test dendritic growth theory at low undercoolings, under microgravity conditions in the Space Shuttle Cargo Bay-borne Material Science Laboratory. The experiment will be essentially autonomous, although limited in-flight interaction through a computer interface is planned. A crystal growth chamber able to yield oriented single-crystal dendritic growth will be incorporated; 'seeding' the chamber with a crystal of the requisite orientation will not in itself meet this requirement.

  2. Isotherms for Water Adsorption on Molecular Sieve 3A: Influence of Cation Composition

    DOE PAGESBeta

    Lin, Ronghong; Ladshaw, Austin; Nan, Yue; Liu, Jiuxu; Yiacoumi, Sotira; Tsouris, Costas; DePaoli, David W.; Tavlarides, Lawrence L.

    2015-06-16

    This study is part of our continuing efforts to address engineering issues related to the removal of tritiated water from off-gases produced in used nuclear fuel reprocessing facilities. In the current study, adsorption equilibrium of water on molecular sieve 3A beads was investigated. Adsorption isotherms for water on the UOP molecular sieve 3A were measured by a continuous-flow adsorption system at 298, 313, 333, and 353 K. Experimental data collected were analyzed by the Generalized Statistical Thermodynamic Adsorption (GSTA) isotherm model. The K+/Na+ molar ratio of this particular type of molecular sieve 3A was ~4:6. Our results showed that themore » GSTA isotherm model worked very well to describe the equilibrium behavior of water adsorption on molecular sieve 3A. The optimum number of parameters for the current experimental data was determined to be a set of four equilibrium parameters. This result suggests that the adsorbent crystals contain four energetically distinct adsorption sites. In addition, it was found that water adsorption on molecular sieve 3A follows a three-stage adsorption process. This three-stage adsorption process confirmed different water adsorption sites in molecular sieve crystals. In addition, the second adsorption stage is significantly affected by the K+/Na+ molar ratio. In this stage, the equilibrium adsorption capacity at a given water vapor pressure increases as the K+/Na+ molar ratio increases.« less

  3. Isotherms for Water Adsorption on Molecular Sieve 3A: Influence of Cation Composition

    SciTech Connect

    Lin, Ronghong; Ladshaw, Austin; Nan, Yue; Liu, Jiuxu; Yiacoumi, Sotira; Tsouris, Costas; DePaoli, David W.; Tavlarides, Lawrence L.

    2015-06-16

    This study is part of our continuing efforts to address engineering issues related to the removal of tritiated water from off-gases produced in used nuclear fuel reprocessing facilities. In the current study, adsorption equilibrium of water on molecular sieve 3A beads was investigated. Adsorption isotherms for water on the UOP molecular sieve 3A were measured by a continuous-flow adsorption system at 298, 313, 333, and 353 K. Experimental data collected were analyzed by the Generalized Statistical Thermodynamic Adsorption (GSTA) isotherm model. The K+/Na+ molar ratio of this particular type of molecular sieve 3A was ~4:6. Our results showed that the GSTA isotherm model worked very well to describe the equilibrium behavior of water adsorption on molecular sieve 3A. The optimum number of parameters for the current experimental data was determined to be a set of four equilibrium parameters. This result suggests that the adsorbent crystals contain four energetically distinct adsorption sites. In addition, it was found that water adsorption on molecular sieve 3A follows a three-stage adsorption process. This three-stage adsorption process confirmed different water adsorption sites in molecular sieve crystals. In addition, the second adsorption stage is significantly affected by the K+/Na+ molar ratio. In this stage, the equilibrium adsorption capacity at a given water vapor pressure increases as the K+/Na+ molar ratio increases.

  4. Grand canonical Monte Carlo simulation of the adsorption isotherms of water molecules on model soot particles

    NASA Astrophysics Data System (ADS)

    Moulin, F.; Picaud, S.; Hoang, P. N. M.; Jedlovszky, P.

    2007-10-01

    The grand canonical Monte Carlo method is used to simulate the adsorption isotherms of water molecules on different types of model soot particles. The soot particles are modeled by graphite-type layers arranged in an onionlike structure that contains randomly distributed hydrophilic sites, such as OH and COOH groups. The calculated water adsorption isotherm at 298K exhibits different characteristic shapes depending both on the type and the location of the hydrophilic sites and also on the size of the pores inside the soot particle. The different shapes of the adsorption isotherms result from different ways of water aggregation in or/and around the soot particle. The present results show the very weak influence of the OH sites on the water adsorption process when compared to the COOH sites. The results of these simulations can help in interpreting the experimental isotherms of water adsorbed on aircraft soot.

  5. Application of zeolite-activated carbon macrocomposite for the adsorption of Acid Orange 7: isotherm, kinetic and thermodynamic studies.

    PubMed

    Lim, Chi Kim; Bay, Hui Han; Neoh, Chin Hong; Aris, Azmi; Abdul Majid, Zaiton; Ibrahim, Zaharah

    2013-10-01

    In this study, the adsorption behavior of azo dye Acid Orange 7 (AO7) from aqueous solution onto macrocomposite (MC) was investigated under various experimental conditions. The adsorbent, MC, which consists of a mixture of zeolite and activated carbon, was found to be effective in removing AO7. The MC were characterized by scanning electron microscopy (SEM), energy dispersive X-ray, point of zero charge, and Brunauer-Emmett-Teller surface area analysis. A series of experiments were performed via batch adsorption technique to examine the effect of the process variables, namely, contact time, initial dye concentration, and solution pH. The dye equilibrium adsorption was investigated, and the equilibrium data were fitted to Langmuir, Freundlich, and Tempkin isotherm models. The Langmuir isotherm model fits the equilibrium data better than the Freundlich isotherm model. For the kinetic study, pseudo-first-order, pseudo-second-order, and intraparticle diffusion model were used to fit the experimental data. The adsorption kinetic was found to be well described by the pseudo-second-order model. Thermodynamic analysis indicated that the adsorption process is a spontaneous and endothermic process. The SEM, Fourier transform infrared spectroscopy, ultraviolet-visible spectral and high performance liquid chromatography analysis were carried out before and after the adsorption process. For the phytotoxicity test, treated AO7 was found to be less toxic. Thus, the study indicated that MC has good potential use as an adsorbent for the removal of azo dye from aqueous solution. PMID:23653315

  6. A Sixth-Form Teaching Unit on the Langmuir Adsorption Isotherm

    ERIC Educational Resources Information Center

    Walkley, G. H.

    1973-01-01

    Presents a teaching unit on the Langmuir absorption isotherm suitable for advanced secondary school chemistry classes. Describes the experimental investigation of the isothermal adsorption of sulfur dioxide on charcoal, and discusses the derivation of the Langmuir equation and some applications. (JR)

  7. Low-cost magnetic adsorbent for As(III) removal from water: adsorption kinetics and isotherms.

    PubMed

    Kango, Sarita; Kumar, Rajesh

    2016-01-01

    Magnetite nanoparticles as adsorbent for arsenic (As) were coated on sand particles. The coated sand was used for the removal of highly toxic element 'As(III)' from drinking water. Here, batch experiments were performed with the variation of solution pH, adsorbent dose, contact time and initial arsenic concentration. The adsorbent showed significant removal efficiency around 99.6 % for As(III). Analysis of adsorption kinetics revealed that the adsorbent follows pseudo-second-order kinetics model showing R (2) = 0.999, whereas for pseudo-first-order kinetics model, the value of R (2) was 0.978. In the case of adsorption equilibrium, the data is well fitted with Langmuir adsorption isotherm model (R (2) > 0.99), indicating monolayer adsorption of As(III) on the surface of adsorbent. The existence of commonly present ions in water influences the removal efficiency of As(III) minutely in the following order PO4 (3-) > HCO3 (-) > Cl(-) > SO4 (2-). The obtained adsorbent can be used to overcome the problem of water filtration in rural areas. Moreover, as the nano-magnetite is coated on the sand, it avoids the problem of extraction of nanoparticles from treated water and can easily be removed by a simple filtration process. PMID:26711813

  8. Kafirin adsorption on ion-exchange resins: isotherm and kinetic studies.

    PubMed

    Kumar, Prashant; Lau, Pei Wen; Kale, Sandeep; Johnson, Stuart; Pareek, Vishnu; Utikar, Ranjeet; Lali, Arvind

    2014-08-22

    Kafirin is a natural, hydrophobic and celiac safe prolamin protein obtained from sorghum seeds. Today kafirin is found to be useful in designing delayed delivery systems and coatings of pharmaceuticals and nutraceuticals where its purity is important and this can be obtained by adsorptive chromatography. This study is the first scientific insight into the isotherm and kinetic studies of kafirin adsorption on anion- and cation-exchange resins for practical applications in preparative scale chromatography. Adsorption isotherms of kafirin were determined for five anion- and two cation-exchange resins in batch systems. Isotherm parameters such as maximum binding capacity and dissociation constant were determined from Langmuir isotherm, and adsorptive capacity and affinity constant from Freundlich isotherm. Langmuir isotherm was found to fit the adsorption equilibrium data well. Batch uptake kinetics for kafirin adsorption on these resins was also carried out and critical parameters including the diffusion coefficient, film mass transfer coefficient, and Biot number for film-pore diffusion model were calculated. Both the isotherm and the kinetic parameters were considered for selection of appropriate resin for kafirin purification. UNOsphere Q (78.26 mg/ml) and Toyopearl SP-650M (57.4 mg/ml) were found to offer better kafirin binding capacities and interaction strength with excellent uptake kinetics under moderate operating conditions. With these adsorbents, film diffusion resistance was found to be major governing factor for adsorption (Bi<10 and δ<1). Based on designer objective function, UNOsphere Q was found be best adsorbent for binding of kafirin. The data presented is valuable for designing large scale preparative adsorptive chromatographic kafirin purification systems. PMID:25022481

  9. Isothermal dendritic growth: A low gravity experiment

    NASA Technical Reports Server (NTRS)

    Glicksman, M. E.; Hahn, R. C.; Lograsso, T. A.; Rubinstein, E. R.; Selleck, M. E.; Winsa, E.

    1988-01-01

    The Isothermal Dendritic Growth Experiment is an active crystal growth experiment designed to test dendritic growth theory at low undercoolings where convection prohibits such studies at 1 g. The experiment will be essentially autonomous, though limited in-flight interaction through a computer interface is planned. One of the key components of the apparatus will be a crystal growth chamber capable of achieving oriented single crystal dendritic growth. Recent work indicates that seeding the chamber with a crystal of the proper orientation will not, in and of itself, be sufficient to meet this requirement. Additional flight hardware and software required for the STS flight experiment are currently being developed at NASA Lewis Research Center and at Rensselaer Polytechnic Institute.

  10. Adsorption of emulsified oil from metalworking fluid on activated bleaching earth-chitosan-SDS composites: Optimization, kinetics, isotherms.

    PubMed

    Naowanat, Nitiya; Thouchprasitchai, Nutthavich; Pongstabodee, Sangobtip

    2016-03-15

    The adsorption of emulsified oil from metalworking fluid (MWF) on activated bleaching earth (BE)-chitosan-sodium dodecyl sulfate (SDS) composites (BE/MCS) was investigated under a statistical design of experiments at a 95% confidence interval to identify the critical factors and to optimize the adsorption capacity. The BE/MCS adsorbents were characterized by means of X-ray diffraction, Fourier transform infrared spectroscopy, Brunauer-Emmett-Teller adsorption/desorption isotherms, contact angle analysis (sessile drop technique) and their zeta potential. From the results of a full 2(5) factorial design with three center points, the adsorbent weight and initial pH of the MWF had a significant antagonistic effect on the adsorption capacity while the initial MWF concentration and BE:chitosan:SDS weight ratio had a synergistic influence. Temperature factor has no discernible effect on the capacity. From the FCCC-RSM design, the optimal capacity range of 2840-2922.5 mg g(-1) was achieved at sorbent weight of 1.6-1.9 g, pH of 5.5-6.5, initial MWF concentration of 52-55 g l(-1) and BE:chitosan:SDS (w/w/w) ratio of 4.7:1:1-6.2:1:1. To test the validation and sensitivity of RSM model, the results showed that the estimated adsorption capacity was close to the experimental capacity within an error range of ±3%, suggesting that the RSM model was acceptable and satisfied. From three kinetics models (pseudo-first-order, pseudo-second-order model and Avrami's equation) and two adsorption isotherms (Langmuir model and Freundlich model), assessed using an error function (Err) and the coefficient of determination (R(2)), Avrami's equation and Freundlich isotherm model provided a good fitting for the data, suggesting the presence of more than one reaction pathway in the MWF adsorption process and the heterogeneous surface adsorption of the BC/ABE-5.5 composite. PMID:26731309

  11. 40 CFR 796.2750 - Sediment and soil adsorption isotherm.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... to sediments and soils is an important process that affects a chemical's distribution in the.... “Adsorption, desorption of parathion as affected by soil organic matter,” Journal of Agricultural and Food... 40 Protection of Environment 32 2014-07-01 2014-07-01 false Sediment and soil adsorption...

  12. 40 CFR 796.2750 - Sediment and soil adsorption isotherm.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... to sediments and soils is an important process that affects a chemical's distribution in the.... “Adsorption, desorption of parathion as affected by soil organic matter,” Journal of Agricultural and Food... 40 Protection of Environment 33 2012-07-01 2012-07-01 false Sediment and soil adsorption...

  13. 40 CFR 796.2750 - Sediment and soil adsorption isotherm.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... to sediments and soils is an important process that affects a chemical's distribution in the.... “Adsorption, desorption of parathion as affected by soil organic matter,” Journal of Agricultural and Food... 40 Protection of Environment 32 2011-07-01 2011-07-01 false Sediment and soil adsorption...

  14. Kinetic Interpretation of Water Vapor Adsorption-Desorption Behavior of a Desiccant Rotor Showing S-shaped Adsorption Isotherm

    NASA Astrophysics Data System (ADS)

    Okamoto, Kumiko; Oshima, Kazunori; Takewaki, Takahiko; Kodama, Akio

    Adsorption / desorption behavior of water vapor in a desiccant rotor containing an iron aluminophosphate type zeolite FAM-Z01 (Functional Adsorbent Material Zeolite 01) was experimentally investigated for humidity swing. This rotor exhibited an S-shaped adsorption isotherm with its temperature dependence. Humidity swing, using a small piece of the rotor, could be usefully applied to interpret adsorption / desorption mechanisms by observing their rates. The most significant finding was that the adsorption / desorption rates in humidity swing could be described by the amount of adsorption, temperature and amplitude of the humidity swing, not by cycle time. Also, using the liner driving force (LDF) model, the overall mass transfer coefficient changed with the elapse of time or with the amount of adsorbed water. This implied that the LDF model, considering constant value of the overall mass transfer coefficient, was probably unable to explain the water adsorption / desorption behavior of FAM-Z01 desiccant rotor.

  15. Isothermal Dendritic Growth Experiment - SCN Dendrites

    NASA Technical Reports Server (NTRS)

    1995-01-01

    The Isothermal Dendritic Growth Experiment (IDGE), flown on three Space Shuttle missions, is yielding new insights into virtually all industrially relevant metal and alloy forming operations. IDGE used transparent organic liquids that form dendrites (treelike structures) similar to the crystals that form inside metal alloys. Comparing Earth-based and space-based dentrite growth velocity, tip size and shape provid a better understanding of the fundamentals of dentritic growth, including gravity's effects. These shadowgraphic images show succinonitrile (SCN) dentrites growing in a melt (liquid). The space-grown crystals also have cleaner, better defined sidebranches. IDGE was developed by Rensselaer Polytechnic Institude (RPI) and NASA/ Glenn Research Center(GRC). Advanced follow-on experiments are being developed for flight on the International Space Station. Photo gredit: NASA/Glenn Research Center

  16. Adsorption of di-2-pyridyl ketone salicyloylhydrazone on silica gel: characteristics and isotherms.

    PubMed

    Antonio, P; Iha, K; Suárez-Iha, M E V

    2004-10-01

    The adsorption of DPKSH onto silica gel was investigated, at 25+/-1 degrees C and pH 1, 4.7 and 12. For the same DPKSH concentration interval, the minimum required time of contact for adsorption maximum at pH 4.7 was smaller than at pH 1 and the maximum amount of DPKSH adsorbed per gram of silica at pH 1 is smaller than at pH 4.7. At pH 12 the DPKSH adsorption onto silica gel was not significant. The adsorption data followed Langmuir, Freundlich and Dubinin-Radushkevich (D-R) isotherms. The maximum amount of solute adsorbed (m(ads)(max)) and the adsorption constant, K(L), were derived from Langmuir isotherm. The Freundlich constants 1/n and K(F) related, respectively, to the energetic heterogeneity of adsorption sites and an empirical constant were evaluated. The mean sorption free energy (E) of DPKSH adsorption onto silica gel was calculated from D-R isotherm indicating a physical adsorption mode. Finally, conductimetric titrations showed the silica particle basicity and acidity as 0.002 and 0.3mmolg(-1), respectively. PMID:18969629

  17. VOCs isotherms on day zeolite by static and dynamic methods: experiments and modelling.

    PubMed

    El Brihi, T; Jaubert, J N; Barth, D; Perrin, L

    2003-10-01

    A dynamic method and a static gravimetric method are respectively used to measure the adsorption equilibria of m-xylene and n-butyl acetate on Wessalith DAY zeolite F20. The equilibrium experiments are performed at different temperatures for both volatile organic compounds (VOCs). The m-xylene isotherms obtained in this study by the dynamic method are compared to our recently published data in which the static gravimetric method was used in order to test the influence of the experimental technique. Because the adsorption isotherms of m-xylene were correlated in our previous paper, in this study only the n-butyl acetate experimental data are correlated with various adsorption isotherm models: Langmuir, Toth and Dubinin equations. PMID:14669800

  18. Modeling of adsorption isotherms of water vapor on Tunisian olive leaves using statistical mechanical formulation

    NASA Astrophysics Data System (ADS)

    Knani, S.; Aouaini, F.; Bahloul, N.; Khalfaoui, M.; Hachicha, M. A.; Ben Lamine, A.; Kechaou, N.

    2014-04-01

    Analytical expression for modeling water adsorption isotherms of food or agricultural products is developed using the statistical mechanics formalism. The model developed in this paper is further used to fit and interpret the isotherms of four varieties of Tunisian olive leaves called “Chemlali, Chemchali, Chetoui and Zarrazi”. The parameters involved in the model such as the number of adsorbed water molecules per site, n, the receptor sites density, NM, and the energetic parameters, a1 and a2, were determined by fitting the experimental adsorption isotherms at temperatures ranging from 303 to 323 K. We interpret the results of fitting. After that, the model is further applied to calculate thermodynamic functions which govern the adsorption mechanism such as entropy, the free enthalpy of Gibbs and the internal energy.

  19. Eriobotrya japonica seed biocomposite efficiency for copper adsorption: Isotherms, kinetics, thermodynamic and desorption studies.

    PubMed

    Mushtaq, Mehwish; Bhatti, Haq Nawaz; Iqbal, Munawar; Noreen, Saima

    2016-07-01

    Adsorption techniques are widely used to remove pollutants from wastewater; however, composites are gaining more importance due to their excellent adsorption properties. Bentonite composite with Eriobotrya japonica seed was prepared and used for the adsorption of copper (Cu) metal from aqueous media. The process variables such as pH, Cu(II) ions initial concentration, adsorbent dose, contact time and temperature were optimized for maximum Cu(II) adsorption. At pH 5, adsorbent dose 0.1 g, contact time 45 min, Cu(II) ions initial concentration 75 mg/L and temperature 45 °C, maximum Cu(II) adsorption was achieved. Desorption studies revealed that biocomposite is recyclable. Langmuir, Freundlich and Harkins-Jura isotherms as well as pseudo-first and pseudo-second-order kinetics models were applied to understand the adsorption mechanism. Thermodynamic parameters (ΔG(0), ΔH(0) and ΔS(0)) suggest that the adsorption process was spontaneous and endothermic in nature. The pseudo-second-order kinetic model and Langmuir isotherm fitted well to the adsorption data. Results showed that biocomposite was more efficient for Cu(II) adsorption in comparison to individuals native Eriobotrya japonica seed biomass and Na-bentonite. PMID:27039361

  20. Novel silica-based hybrid adsorbents: lead(II) adsorption isotherms.

    PubMed

    Liu, Junsheng; Wang, Xin

    2013-01-01

    Water pollution caused by the lead(II) from the spent liquor has caught much attention. The research from the theoretical model to application fundaments is of vital importance. In this study, lead(II) adsorption isotherms are investigated using a series of hybrid membranes containing mercapto groups (-SH groups) as the hybrid adsorbents. To determine the best fitting equation, the experimental data were analyzed using six two-parameter isotherm equations (i.e., Langmuir, Freundlich, Dubinin-Radushkevich (D-R), Temkin, Harkins-Jura, and Halsey isotherm models). It was found that the lead(II) adsorption on these samples followed the Freundlich, Dubinin-Radushkevich (D-R), and Halsey isotherm models. Moreover, the mean free energy of adsorption was calculated using Dubinin-Radushkevich (D-R) isotherm model and it was confirmed that the adsorption process was physical in nature. These findings are very meaningful in the removal of lead(II) ions from water using the hybrid membranes as adsorbents. PMID:24302877

  1. Adsorption kinetics and isotherm of anionic dyes onto organo-bentonite from single and multisolute systems.

    PubMed

    Shen, Dazhong; Fan, Jianxin; Zhou, Weizhi; Gao, Baoyu; Yue, Qinyan; Kang, Qi

    2009-12-15

    The performances of polydiallydimethylammonium modified bentonite (PDADMA-bentonite) as an adsorbent to remove anionic dyes, namely Acid Scarlet GR (AS-GR), Acid Turquoise Blue 2G (ATB-2G) and Indigo Carmine (IC), were investigated in single, binary and ternary dye systems. In adsorption from single dye solutions with initial concentration of 100 micromol/L, the dosage of PDADMA-bentonite needed to remove 95% dye was 0.42, 0.68 and 0.75 g/L for AS-GR, ATB-2G and IC, respectively. The adsorption isotherms of the three dyes obeyed the Langmuir isotherm model with the equilibrium constants of 0.372, 0.629 and 4.31 L/micromol, the saturation adsorption amount of 176.3, 149.2 and 228.7 micromol/g for ATB-2G, IC and AS-GR, respectively. In adsorption from mixed dye solutions, the isotherm of each individual dye followed an expanded Langmuir isotherm model and the relationship between the total amount of dyes adsorbed and the total equilibrium dye concentration was interpreted well by Langmuir isotherm model. In the region of insufficient dosage of PDADMA-bentonite, the dye with a larger affinity was preferentially removed by adsorption. Desorption was observed in the kinetic curve of the dye with lower affinity on PDADMA-bentonite surface by the competitive adsorption. The kinetics in single dye solution and the total adsorption of dyes in binary and ternary dye systems nicely followed pseudo-second-order kinetic model. PMID:19631461

  2. 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

  3. Adsorption Isotherms for Xenon and Krypton using INL HZ-PAN and AgZ-PAN Sorbents

    SciTech Connect

    Troy G. Garn; Mitchell Greenhalgh; Veronica J. Rutledge; Jack D. Law

    2014-08-01

    The generation of adsorption isotherms compliments the scale-up of off-gas processes used to control the emission of encapsulated radioactive volatile fission and activation products released during Used Nuclear Fuel (UNF) reprocessing activities. A series of experiments were conducted to obtain capacity results for varying Kr and Xe gas concentrations using HZ-PAN and AgZ-PAN engineered form sorbents. Gas compositions for Kr ranged from 150-40,000 ppmv and 250-5020 ppmv for Xe in a helium balance. The experiments were all performed at 220 K at a flowrate of 50 sccm. Acquired capacities were then respectively fit to the Langmuir equation using the Langmuir linear regression method to obtain the equilibrium parameters Qmax and Keq. Generated experimental adsorption isotherms were then plotted with the Langmuir predicted isotherms to illustrate agreement between the two. The Langmuir parameters were provided for input into the OSPREY model to predict breakthrough of single component adsorption of Kr and Xe on HZ-PAN and AgZ-PAN sorbents at the experimental conditions tested. Kr and Xe capacities resulting from model breakthrough predictions were then compared to experimental capacities for model validation.

  4. ISOTHERMAL AIR-INGRESS VALIDATION EXPERIMENTS

    SciTech Connect

    Chang H. Oh; Eung S. Kim

    2013-01-01

    Idaho National Laboratory has conducted airingress experiments as part of a campaign to validate computational fluid dynamics (CFD) calculations for very high-temperature gas-cooled reactor (VHTR) analysis. An isothermal test loop was designed to recreate exchange or stratified flow that occurs in the lower plenum of VHTR after a break in the primary loop allows helium to leak out and reactor building air to enter the reactor core. The experiment was designed to measure stratified flow in the inlet pipe connecting to the lower plenum of the General Atomics gas turbine–modular helium reactor (GT-MHR). Instead of helium and air, brine and sucrose were used as heavy fluids, and water was used as the lighter fluid to create, using scaling laws, the appropriate flow characteristics of the lower plenum immediately after depressurization. These results clearly indicate that stratified flow is established even for very small density differences. Corresponding CFD results were validated with the experimental data. A grid sensitivity study on CFD models was also performed using the Richardson extrapolation and the grid convergence index method for the numerical accuracy of CFD calculations. The calculated current speed showed very good agreement with the experimental data, indicating that current CFD methods are suitable for simulating density gradient stratified flow phenomena in an air-ingress accident.

  5. Isothermal Dendritic Growth Experiment - PVA Dendrites

    NASA Technical Reports Server (NTRS)

    1997-01-01

    The Isothermal Dendritic Growth Experiment (IDGE), flown on three Space Shuttle missions, is yielding new insights into virtually all industrially relevant metal and alloy forming operations. IDGE used transparent organic liquids that form dendrites (treelike structures) similar to those inside metal alloys. Comparing Earth-based and space-based dendrite growth velocity, tip size and shape provides a better understanding of the fundamentals of dentritic growth, including gravity's effects. Shalowgraphic images of pivalic acid (PVA) dendrites forming from the melt show the subtle but distinct effects of gravity-driven heat convection on dentritic growth. In orbit, the dendrite grows as its latent heat is liberated by heat conduction. This yields a blunt dendrite tip. On Earth, heat is carried away by both conduction and gravity-driven convection. This yields a sharper dendrite tip. In addition, under terrestrial conditions, the sidebranches growing in the direction of gravity are augmented as gravity helps carry heat out of the way of the growing sidebranches as opposed to microgravity conditions where no augmentation takes place. IDGE was developed by Rensselaer Polytechnic Institute and NASA/Glenn Research Center. Advanced follow-on experiments are being developed for flight on the International Space Station. Photo Credit: NASA/Glenn Research Center

  6. Adsorption of pharmaceuticals onto activated carbon fiber cloths - Modeling and extrapolation of adsorption isotherms at very low concentrations.

    PubMed

    Fallou, Hélène; Cimetière, Nicolas; Giraudet, Sylvain; Wolbert, Dominique; Le Cloirec, Pierre

    2016-01-15

    Activated carbon fiber cloths (ACFC) have shown promising results when applied to water treatment, especially for removing organic micropollutants such as pharmaceutical compounds. Nevertheless, further investigations are required, especially considering trace concentrations, which are found in current water treatment. Until now, most studies have been carried out at relatively high concentrations (mg L(-1)), since the experimental and analytical methodologies are more difficult and more expensive when dealing with lower concentrations (ng L(-1)). Therefore, the objective of this study was to validate an extrapolation procedure from high to low concentrations, for four compounds (Carbamazepine, Diclofenac, Caffeine and Acetaminophen). For this purpose, the reliability of the usual adsorption isotherm models, when extrapolated from high (mg L(-1)) to low concentrations (ng L(-1)), was assessed as well as the influence of numerous error functions. Some isotherm models (Freundlich, Toth) and error functions (RSS, ARE) show weaknesses to be used as an adsorption isotherms at low concentrations. However, from these results, the pairing of the Langmuir-Freundlich isotherm model with Marquardt's percent standard of deviation was evidenced as the best combination model, enabling the extrapolation of adsorption capacities by orders of magnitude. PMID:26606322

  7. Monte Carlo simulations of phase transitions and adsorption isotherm discontinuities on surface compression.

    PubMed

    Charniak, C L; Wetzel, T E; Aranovich, G L; Donohue, M D

    2008-08-01

    Low temperature, Grand Canonical Monte Carlo simulations were used to study the adsorption of fluid layers on cubic, hexagonal, and atomically smooth substrates to determine the effects of registry and surface compression on the system. The size of the fluid molecules was fixed to be 20% larger than the substrate molecules in order to observe the transition from an expanded to commensurate and finally to an incommensurate monolayer. For relatively weak fluid-substrate interactions, the cubic system underwent a first-order phase transition. As the strength of the fluid-substrate interactions increased, the molecules became fixed at commensurate locations and the transition from low density to commensurate packing became continuous. The strong fluid-substrate interactions lead to the development of a kink in the adsorption isotherm that showed the increased stability of the commensurate phase. This kink became more pronounced as the system temperature was decreased. The hexagonal system showed less dramatic results due to a decrease in the substrate well depth of the relative to the cubic system. The system did experience a first-order phase transition for a weak fluid-substrate interactions and the transition became much more gradual as the fluid-substrate interaction increased. The molecules became fixed to commensurate substrate locations, but the surface was not corrugated sufficiently to have a stable commensurate phase. The atomically smooth substrate showed the first-order phase transition expected of a low temperature system with no effects of registry. PMID:18513735

  8. The Isothermal Dendritic Growth Experiment (IDGE)

    NASA Technical Reports Server (NTRS)

    Glicksman, Martin E.; Koss, M. B.; Lupulescu, A. O.; LaCombe, J. C.; Frei, J. E.; Malarik, D. C.

    1999-01-01

    The Isothermal Dendritic Growth Experiment (IDGE) constituted a series of three NASA-supported microgravity experiments, all of which flew aboard the space shuttle, Columbia. This experimental space flight series was designed and operated to grow and record dendrite solidification in the absence of gravity-induced convective heat transfer, and thereby produce a wealth of benchmark-quality data for testing solidification scaling laws. The data and analysis performed on the dendritic growth speed and tip size in Succinontrie (SCN) demonstrates that although the theory yields predictions that are reasonably in agreement with experiment, there are significant discrepancies. However, some of these discrepancies can be explained by accurately describing the diffusion of heat. The key finding involves recognition that the actual three-dimensional shape of dendrites includes time-dependent side-branching and a tip region that is not a paraboloid of revolution. Thus, the role of heat transfer in dendritic growth is validated, with the caveat that a more realistic model of the dendrite then a paraboloid is needed to account for heat flow in an experimentally observed dendrite. We are currently conducting additional analysis to further confirm and demonstrate these conclusions. The data and analyses for the growth selection physics remain much less definitive. From the first flight, the data indicated that the selection parameter, sigma*, is not exactly a constant, but exhibits a slight dependence on the supercooling. Additional data from the second flight are being examined to investigate the selection of a unique dendrite speed, tip size and shape. The IDGE flight series is now complete. We are currently completing analyses and moving towards final data archiving. It is gratifying to see that the IDGE published results and archived data sets are being used actively by other scientists and engineers. In addition, we are also pleased to report that the techniques and IDGE

  9. Experimental studies of hydrogen on boron nitride: I. Adsorption isotherms of HD

    SciTech Connect

    Evans, M.D.; Sullivan, N.S.

    1995-09-01

    The authors report the results of measurements of adsorption isotherms of deuterium hydride (HD) adsorbed onto boron nitride. From this data they derive both the two-dimensional critical point temperatures (using Larher`s method) and the heat of adsorption for the first few layers of this system. These results are compared with similar measurements of HD adsorbed onto graphite and MgO. While substantial substeps within some adlayer steps are evident in the adsorption isotherms of HD on graphite and MgO and have been shown to indicate a two-dimensional liquid-solid transition within the layer, no substep is evident at the level of one percent of a step level for HD adsorbed onto BN.

  10. 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

  11. Adsorption isotherms of phenolic compounds from aqueous solutions onto activated carbon fibers

    SciTech Connect

    Juang, R.S.; Wu, F.C.; Tseng, R.L.

    1996-05-01

    Phenolic compounds exist widely in the industrial effluents such as those from oil refineries and the coal tar, plastics, leather, paint, pharmaceutical, and steel industries. Since they are highly toxic and are, in general, not amenable to biological degradation, methods of treatment are continuously being modified and developed. Liquid-phase adsorption equilibria of eight phenolic compounds onto activated carbon fibers were measured in the concentration range 40--500 g/m{sup 3} at 303 K. High adsorption capacities were observed for the chlorinated phenols compared to the methyl-substituted phenols. Several two- and three-parameter isotherm equations were tested. Among the equations tried, the three-parameter equation of Jossens et al. based on a heterogeneous surface adsorption theory was found to be the most satisfactory over the entire range of concentration. The widely used two-parameter equations of Langmuir and Freundlich were not applicable to the present adsorption systems.

  12. Water adsorption isotherms on porous onionlike carbonaceous particles. Simulations with the grand canonical Monte Carlo method

    NASA Astrophysics Data System (ADS)

    Hantal, György; Picaud, Sylvain; Hoang, Paul N. M.; Voloshin, Vladimir P.; Medvedev, Nikolai N.; Jedlovszky, Pál

    2010-10-01

    The grand canonical Monte Carlo method is used to simulate the adsorption isotherms of water molecules on different types of model soot particles. These soot models are constructed by first removing atoms from onion-fullerene structures in order to create randomly distributed pores inside the soot, and then performing molecular dynamics simulations, based on the reactive adaptive intermolecular reactive empirical bond order (AIREBO) description of the interaction between carbon atoms, to optimize the resulting structures. The obtained results clearly show that the main driving force of water adsorption on soot is the possibility of the formation of new water-water hydrogen bonds with the already adsorbed water molecules. The shape of the calculated water adsorption isotherms at 298 K strongly depends on the possible confinement of the water molecules in pores of the carbonaceous structure. We found that there are two important factors influencing the adsorption ability of soot. The first of these factors, dominating at low pressures, is the ability of the soot of accommodating the first adsorbed water molecules at strongly hydrophilic sites. The second factor concerns the size and shape of the pores, which should be such that the hydrogen bonding network of the water molecules filling them should be optimal. This second factor determines the adsorption properties at higher pressures.

  13. Water adsorption isotherms on porous onionlike carbonaceous particles. Simulations with the grand canonical Monte Carlo method.

    PubMed

    Hantal, György; Picaud, Sylvain; Hoang, Paul N M; Voloshin, Vladimir P; Medvedev, Nikolai N; Jedlovszky, Pál

    2010-10-14

    The grand canonical Monte Carlo method is used to simulate the adsorption isotherms of water molecules on different types of model soot particles. These soot models are constructed by first removing atoms from onion-fullerene structures in order to create randomly distributed pores inside the soot, and then performing molecular dynamics simulations, based on the reactive adaptive intermolecular reactive empirical bond order (AIREBO) description of the interaction between carbon atoms, to optimize the resulting structures. The obtained results clearly show that the main driving force of water adsorption on soot is the possibility of the formation of new water-water hydrogen bonds with the already adsorbed water molecules. The shape of the calculated water adsorption isotherms at 298 K strongly depends on the possible confinement of the water molecules in pores of the carbonaceous structure. We found that there are two important factors influencing the adsorption ability of soot. The first of these factors, dominating at low pressures, is the ability of the soot of accommodating the first adsorbed water molecules at strongly hydrophilic sites. The second factor concerns the size and shape of the pores, which should be such that the hydrogen bonding network of the water molecules filling them should be optimal. This second factor determines the adsorption properties at higher pressures. PMID:20950025

  14. Relation between Water Vapor Adsorption Isotherms and Dynamic Dehumidification Performances of Desiccant Rotor

    NASA Astrophysics Data System (ADS)

    Inoue, Koji; Matsuguma, Shingo; Jin, Wei-Li; Okano, Hiroshi; Teraoka, Yasutake; Hirose, Tsutomu

    Desiccant rotors with different water vapor adsorption properties were fabricated by the synthesis of silica gels inside the honeycomb matrices. Dynamic dehumidification performances of the rotors were measured under different conditions and they were discussed in relation to water vapor adsorption isotherms. At the reactivation air temperatures of 80 and 140 oC, the best dynamic performance was observed with the rotor on which the adsorbed amount of water vapor at lower relative humidity was highest. When the reactivation air temperature was 50 oC, on the other hand, the rotor of which the isotherm exhibited monotonic and nearly linear increase up to higher relative humidity was the most suitable. The normalized changes of absolute humidity and adsorbed amount were defined, and these phenomena were analyzed. When the dependences of both parameters against the relative humidity were similar, the rotor showed the best dehumidification performance.

  15. Oxygen chemisorption on V/sub 2/O/sub 5/: isotherms and isobars of adsorption

    SciTech Connect

    Rey, L.; Gambaro, L.A.; Thomas, H.J.

    1984-06-01

    Experimental results of oxygen adsorption on V/sub 2/O/sub 5/ (isotherms and isobars) are reported. In its normal state V/sub 2/O/sub 5/ is a nonstoichiometric oxide that shows oxygen vacancies with the subsequent formation of V/sup 4 +/ ions. A model is developed for the interaction between oxygen (gaseous, adsorbed, and bulk) and the solid phase (V/sub 2/O/sub 5/). 12 references, 4 figures, 1 table.

  16. Adsorption of metal ions onto Moroccan stevensite: kinetic and isotherm studies.

    PubMed

    Benhammou, A; Yaacoubi, A; Nibou, L; Tanouti, B

    2005-02-15

    The aim of this paper is to study the adsorption of the heavy metals (Cd(II), Cu(II), Mn(II), Pb(II), and Zn(II)) from aqueous solutions by a natural Moroccan stevensite called locally rhassoul. We carried out, first, a mineralogical and physicochemical characterization of stevensite. The surface area is 134 m2/g and the cation exchange capacity (CEC) is 76.5 meq/100 g. The chemical formula of stevensite is Si3.78Al0.22Mg2.92Fe0.09Na0.08K0.08O10(OH)2.4H2O. Adsorption tests of Cd(II), Cu(II), Mn(II), Pb(II), and Zn(II) in batch reactors were carried out at ambient temperature and at constant pH. Two simplified models including pseudo-first-order and pseudo-second- order were used to test the adsorption kinetics. The equilibrium time and adsorption rate of adsorption were determined. The increasing order of the adsorption rates follows the sequence Mn(II) > Pb(II) > Zn(II) > Cu(II) > Cd(II). The Dubinin-Radushkevich (D-R), Langmuir, and Redlich-Peterson (R-P) models were adopted to describe the adsorption isotherms. The maximal adsorption capacities at pH 4.0 determined from the D-R and Langmuir models vary in the following order: Cu(II) > Mn(II) > Cd(II) > Zn(II) > Pb(II). The equilibrium data fitted well with the three-parameter Redlich-Peterson model. The values of mean energy of adsorption show mainly an ion-exchange mechanism. Also, the influence of solution pH on the adsorption onto stevensite was studied in the pH range 1.5-7.0. PMID:15589536

  17. The investigation of kinetic and isotherm of fluoride adsorption onto functionalize pumice stone.

    PubMed

    Asgari, Ghorban; Roshani, Babak; Ghanizadeh, Ghader

    2012-05-30

    In this research work, pumice that is functionalized by the cationic surfactant, hexadecyltrimethyl ammonium (HDTMA), is used as an adsorbent for the removal of fluoride from drinking water. This work was carried out in two parts. The effects of HDTMA loading, pH (3-10), reaction time (5-60 min) and the adsorbent dosage (0.15-2.5 g L(-1)) were investigated on the removal of fluoride as a target contaminate from water through the design of different experimental sets in the first part. The results from this first part revealed that surfactant-modified pumice (SMP) exhibited the best performance at dose 0.5 g L(-1), pH 6, and it adsorbs over 96% of fluoride from a solution containing 10 mg L(-1) fluoride after 30 min of mixing time. The four linear forms of the Langmuir, Freundlich, Temkin and Dubinin-Radushkevich isotherms model were applied to determine the best fit of equilibrium expressions. Apart from the regression coefficient (R(2)), four error functions were used to validate the isotherm and kinetics data. The experimental adsorption isotherm complies with Langmuir equation model type 1. The maximum amount of adsorption (Q(max)) was 41 mg g(-1). The kinetic studies indicated that the adsorption of fluoride best fitted with the pseudo-second-order kinetic type 1. Thermodynamic parameters evaluation of fluoride adsorption on SMP showed that the adsorption process under the selected conditions was spontaneous and endothermic. The suitability of SMP in defluoridation at field condition was investigated with natural groundwater samples collected from a nearby fluoride endemic area in the second part of this study. Based on this study's results, SMP was shown to be an affordable and a promising option for the removal of fluoride in drinking water. PMID:22476092

  18. Removal of water and iodine by solid sorbents: adsorption isotherms and kinetics

    SciTech Connect

    Lin, R.; Tavlarides, L.L.

    2013-07-01

    Tritium and iodine-129 are two major radioactive elements that are present in off-gases from spent fuel reprocessing plants. Adsorption by solid sorbents is the state-of-the-art technique for removal of these species from off-gases. Modeling and simulating adsorption processes require accurate adsorption equilibrium and kinetic data to permit reasonable estimates of process parameters. We have developed a continuous flow single-pellet adsorption system to gather accurate adsorption equilibrium and kinetic data for adsorption of water by molecular sieve 3A and for adsorption of iodine by silver exchanged mordenite. In this paper, the design of the water and iodine adsorption experimental systems are briefly described and results of water adsorption experiments are presented and discussed. Water uptake curves are fitted with the linear-driving force (LDF) model and the shrinking-core model to determine kinetic parameters. It is shown that the kinetics of water adsorption on zeolite 3A under current experimental conditions is controlled by both the external film resistance and the macro-pore diffusion and can be predicted by both the LDF model and the shrinking-core model with the former one performing slightly better. Preliminary results from iodine adsorption experiments will be presented in the conference.

  19. Isotherm for Adsorption of Agrobacterium tumefaciens to Susceptible Potato (Solanum tuberosum L.) Tissues.

    PubMed

    Kluepfel, D A; Pueppke, S G

    1985-06-01

    Potato tuber disks were submerged in suspensions containing 10 to 10 cells of Agrobacterium tumefaciens B6 per ml. After 60 min, the disks were rinsed and homogenized, and portions of the homogenates were plated to measure the number of adsorbed bacteria. At low initial bacterial concentrations (10/ml), 5 to 23% of the bacteria adsorbed. At higher bacterial concentrations, the corresponding value was approximately 1.2%. Adsorption was a reversible equilibrium process. Binding saturation was not achieved, and adsorbed bacteria were confined to monolayers on the surfaces of tissue prepared for scanning electron microscopy. Adsorption of strain B6 to potato tuber tissues is described accurately by the Freundlich adsorption isotherm and may be a nonspecific phenomenon. PMID:16346800

  20. 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

  1. Determination of the adsorptive capacity and adsorption isotherm of vapor-phase mercury chloride on powdered activated carbon using thermogravimetric analysis

    SciTech Connect

    Hsun-Yu Lin; Chung-Shin Yuan; Wei-Ching Chen; Chung-Hsuang Hung

    2006-11-15

    This study investigated the use of thermogravimetric analysis (TGA) to determine the adsorptive capacity and adsorption isotherm of vapor-phase mercury chloride on powdered activated carbon (PAC). The technique is commonly applied to remove mercury-containing air pollutants from gas streams emitted from municipal solid waste incinerators. An alternative form of powdered activated carbon derived from a pyrolyzed tire char was prepared for use herein. The capacity of waste tire-derived PAC to adsorb vapor-phase HgCl{sub 2} was successfully measured using a self-designed TGA adsorption system. Experimental results showed that the maximum adsorptive capacities of HgCl{sub 2} were 1.75, 0.688, and 0.230 mg of HgCl{sub 2} per gram of powdered activated carbon derived from carbon black at 30, 70, and 150{sup o} for 500 {mu}g/m{sup 3} of HgCl{sub 2}, respectively. Four adsorption isotherms obtained using the Langmuir, Freundlich, Redlich-Peterson, and Brunauer-Emmett-eller (BET) models were used to simulate the adsorption of HgCl{sub 2}. The comparison of experimental data associated with the four adsorption isotherms indicated that BET fit the experimental results better than did the other isotherms at 30{sup o}, whereas the Freundlich isotherm fit the experimental results better at 70 and 150{sup o}. Furthermore, the calculations of the parameters associated with Langmuir and Freundlich isotherms revealed that the adsorption of HgCl{sub 2} by PAC-derived carbon black favored adsorption at various HgCl{sub 2} concentrations and temperatures. 35 refs., 7 figs., 3 tabs.

  2. Adsorption of Phenol from Aqueous Solution Using Lantana camara, Forest Waste: Kinetics, Isotherm, and Thermodynamic Studies

    PubMed Central

    Girish, C. R.; Ramachandra Murty, V.

    2014-01-01

    The present work investigates the potential of Lantana camara, a forest waste, as an adsorbent for the phenol reduction in wastewater. Batch studies were conducted with adsorbent treated with HCl and KOH to determine the influence of various experimental parameters such as pH, contact time, adsorbent dosage, and phenol concentration. The experimental conditions were optimized for the removal of phenol from wastewater. Equilibrium isotherms for the adsorption of phenol were analyzed by Freundlich, Langmuir, Temkin, and Dubinin-Radushkevich isotherm models. Thermodynamic parameters like the Gibbs free energy (ΔG°), enthalpy (ΔH°), and entropy (ΔS°) were also determined and they showed that the adsorption process was feasible, spontaneous, and exothermic in the temperature range of 298–328 K. The kinetic data were fitted with pseudo-second-order model. The equilibrium data that followed Langmuir model with the monolayer adsorption capacity was found to be 112.5 mg/g and 91.07 mg/g for adsorbent treated with HCl and KOH, respectively, for the concentration of phenol ranging from 25 to 250 mg/L. This indicates that the Lantana camara was a promising adsorbent for the removal of phenol from aqueous solutions. PMID:27350997

  3. Adsorption isotherm predicted from a lattice gas with general lateral interactions in a single-phase regime

    NASA Astrophysics Data System (ADS)

    Medved', I.; Trník, A.; Černý, Robert

    2014-12-01

    We investigate which isotherm equation arises when a lattice gas with rather general lateral interactions is used to model an adsorption of particles on a solid surface at subcritical temperatures. For simplicity, an energetically homogeneous surface is considered, and only a single phase is assumed to be stable in the system. We show that, up to a constant, the result is a sum of terms that have the same form as the Hill isotherm or, less accurately, as the Freundlich isotherm. Each of these terms contains three types of microscopic parameters whose relation to the details of the considered lattice gas, such as its lateral interactions, is provided. We also provide a formula for the heat of adsorption and discuss the phenomenon of adsorption compression. We illustrate the results for a simple lattice gas on a triangular lattice with pair and triple interactions. Possible extensions to inhomogeneous surfaces, multi-component adsorption, and phase coexistence regions are pointed out.

  4. 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

  5. Single time point isothermal drug stability experiments at constant humidity.

    PubMed

    Tao, Jian-Lin; Zhan, Xian-Cheng; Li, Lin-Li; Lin, Bing; Jiang, Lu

    2009-03-01

    A single time point isothermal drug stability experiments at constant humidity is introduced. In the new method, kinetic parameters related to both moisture and temperature were obtained by a single pair of experiments: these related to moisture by one with a group of testing humidities and a fixed temperature, those related to temperature by the other with a group of testing temperatures and a constant humidity. By a simulation, the estimates for the kinetic parameters (E(a), m, A) obtained by the proposed method and the reported programmed humidifying and heating method were statistically evaluated and were compared with those obtained by the isothermal measurements at constant humidity. Results indicated that under the same experimental conditions, the estimates obtained by the proposed method were significantly more precise than those obtained by the reported programmed humidifying and heating method. The estimates obtained by the isothermal method at constant humidity were somewhat more precise than those obtained by the proposed method. However, the experimental period needed by the isothermal method at constant humidity was greatly longer than that needed by the proposed method. The stability of dicloxacillin sodium, as a solid state model, was investigated by the single time point isothermal drug stability experiments at constant humidity. The results indicated that the kinetic parameters obtained by the proposed method were comparable to those from the reported. PMID:19252391

  6. Adsorption on molecularly imprinted polymers of structural analogues of a template. Single-component adsorption isotherm data

    SciTech Connect

    Kim, Hyunjung; Guiochon, Georges A

    2005-10-01

    The equilibrium adsorption isotherms on two otherwise identical polymers, one imprinted with Fmoc-L-tryptophan (Fmoc-L-Trp) (MIP), the other nonimprinted (NIP), of compounds that are structural analogues of the template were acquired by frontal analysis (FA) in an acetonitrile/acetic acid (99/1 v/v) mobile phase, over a wide concentration range (from 0.005 to 50 mM). These analogues were Fmoc-L-tyrosine, Fmoc-L-serine, Fmoc-L-phenyalanine, Fmoc-glycine (Fmoc-Gly), Fmoc-L-tryptophan pentafluorophenyl ester (Fmoc-L-Trp(OPfp)), and their antipodes. These substrates have different numbers of functional groups able to interact with the 4-vinylpyridine groups of the polymer. For a given number of the functional groups, these substrates have different hydrophobicities of their side groups (as indicated by their partition coefficients (log P{sub ow}) in the octanol-water system (e.g., from 4.74 for Fmoc-Trp to 2.53 for Fmoc-Gly)). Statistical results from the fitting of the FA data to Langmuirian isotherm models, the calculation of the affinity energy distribution, and the comparison of calculated and experimental band profiles show that all these sets of FA data are best accounted for by a tri-Langmuir isotherm model, except for the data of Fmoc-L-Trp(OPfp) that are best modeled by a simple Langmuir isotherm. So, all compounds but Fmoc-L-Trp(OPfp) find three different types of adsorption sites on both the MIP and the NIP. The properties of these different types of sites were studied systematically. The results show that the affinity of the structural analogues for the NIP is controlled mostly by the number of the functional groups on the substrates and somewhat by the hydrophobicity of their side groups. These two factors control also the MIP affinity toward the enantiomers of the structural analogues that have a stereochemistry different from that of the template. In contrast, the affinity of the highest affinity sites of the MIP toward the enantiomers of these

  7. A comparative examination of the adsorption mechanism of an anionic textile dye (RBY 3GL) onto the powdered activated carbon (PAC) using various the isotherm models and kinetics equations with linear and non-linear methods

    NASA Astrophysics Data System (ADS)

    Açıkyıldız, Metin; Gürses, Ahmet; Güneş, Kübra; Yalvaç, Duygu

    2015-11-01

    The present study was designed to compare the linear and non-linear methods used to check the compliance of the experimental data corresponding to the isotherm models (Langmuir, Freundlich, and Redlich-Peterson) and kinetics equations (pseudo-first order and pseudo-second order). In this context, adsorption experiments were carried out to remove an anionic dye, Remazol Brillant Yellow 3GL (RBY), from its aqueous solutions using a commercial activated carbon as a sorbent. The effects of contact time, initial RBY concentration, and temperature onto adsorbed amount were investigated. The amount of dye adsorbed increased with increased adsorption time and the adsorption equilibrium was attained after 240 min. The amount of dye adsorbed enhanced with increased temperature, suggesting that the adsorption process is endothermic. The experimental data was analyzed using the Langmuir, Freundlich, and Redlich-Peterson isotherm equations in order to predict adsorption isotherm. It was determined that the isotherm data were fitted to the Langmuir and Redlich-Peterson isotherms. The adsorption process was also found to follow a pseudo second-order kinetic model. According to the kinetic and isotherm data, it was found that the determination coefficients obtained from linear method were higher than those obtained from non-linear method.

  8. Adsorption of malachite green by polyaniline-nickel ferrite magnetic nanocomposite: an isotherm and kinetic study

    NASA Astrophysics Data System (ADS)

    Patil, Manohar R.; Shrivastava, V. S.

    2014-11-01

    This work deals with the development of an efficient method for the removal of a MG (malachite green) dye from aqueous solution using polyaniline (PANI)-Nickel ferrite (NiFe2O4) magnetic nanocomposite. It is successfully synthesised in situ through self polymerisation of monomer aniline. Adsorptive removal studies are carried out for water soluble MG dye using PANI-Nickel ferrite magnetic nanocomposite in aqueous solution. Different parameters like dose of adsorbent, contact time, different initial conc., and pH have been studied to optimise reaction condition. It is concluded that adsorptive removal by PANI-Nickel ferrite magnetic nanocomposite is an efficient method for removing a MG dye from aqueous solution than work done before. The optimum conditions for the removal of the dye are initial concentration 30 mg l-1, adsorbent dose 5gm l-1 and pH 7. The adsorption capacity is found 4.09 mg g-1 at optimum condition 30 mg l-1. The adsorption followed pseudo-second-order kinetics. The experimental isotherm is found to fit with Langmuir equation. The prepared adsorbent is characterised by techniques SEM, EDS, XRD and VSM.

  9. 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.

  10. The Isothermal Dendritic Growth Experiment Archive

    NASA Astrophysics Data System (ADS)

    Koss, Matthew

    2009-03-01

    The growth of dendrites is governed by the interplay between two simple and familiar processes---the irreversible diffusion of energy, and the reversible work done in the formation of new surface area. To advance our understanding of these processes, NASA sponsored a project that flew on the Space Shuttle Columbia is 1994, 1996, and 1997 to record and analyze benchmark data in an apparent-microgravity ``laboratory.'' In this laboratory, energy transfer by gravity driven convection was essentially eliminated and one could test independently, for the first time, both components of dendritic growth theory. The analysis of this data shows that although the diffusion of energy can be properly accounted for, the results from interfacial physics appear to be in disagreement and alternate models should receive increased attention. Unfortunately, currently and for the foreseeable future, there is no access or financial support to develop and conduct additional experiments of this type. However, the benchmark data of 35mm photonegatives, video, and all supporting instrument data are now available at the IDGE Archive at the College of the Holy Cross. This data may still have considerable relevance to researchers working specifically with dendritic growth, and more generally those working in the synthesis, growth & processing of materials, multiscale computational modeling, pattern formation, and systems far from equilibrium.

  11. Study of the kinetics and the adsorption isotherm of cadmium(II) from aqueous solution using green algae (Ulva lactuca) biomass.

    PubMed

    Asnaoui, H; Laaziri, A; Khalis, M

    2015-01-01

    Batch experiments were conducted to study the adsorption of hazardous cadmium onto low-cost algae biomass in aqueous solution with respect to concentration of adsorbate, adsorbent dosage, contact time, solution pH and temperature. Langmuir and Freundlich adsorption models were applied to describe the equilibrium isotherms and the isotherm constants were determined. The activation energy of adsorption was also evaluated for the adsorption of cadmium onto Ulva lactuca biomass. Experimental data were tested in terms of biosorption kinetics using pseudo-first-order and pseudo-second-order kinetic models. The results showed that the biosorption processes of Cd(II) followed well pseudo-second-order kinetics. Langmuir and Freundlich models were applied to describe the biosorption isotherm of the metal ions by Ulva lactuca biomass. Langmuir model fitted the equilibrium data better than the Freundlich isotherm. The biosorption capacity of Ulva lactuca biomass for cadmium was found to be 3.02 mg/g at pH 5.60 min equilibrium time and 20 °C. The mean free energy which was calculated was 6.24 kJ/mol for Cd(II) biosorption, which shows that the adsorption is physical. The calculated thermodynamic parameters (ΔG0, ΔH0 and ΔS0) showed that the biosorption of Cd(II) onto Ulva lactuca biomass was feasible, spontaneous and exothermic under examined conditions. The results indicate that algae Ulva lactuca could be employed as a low-cost material for the removal of metal ions from aqueous solution. PMID:26524441

  12. Simultaneous removal of potent cyanotoxins from water using magnetophoretic nanoparticle of polypyrrole: adsorption kinetic and isotherm study.

    PubMed

    Hena, S; Rozi, R; Tabassum, S; Huda, A

    2016-08-01

    Cyanotoxins, microcystins and cylindrospermopsin, are potent toxins produced by cyanobacteria in potable water supplies. This study investigated the removal of cyanotoxins from aqueous media by magnetophoretic nanoparticle of polypyrrole adsorbent. The adsorption process was pH dependent with maximum adsorption occurring at pH 7 for microcystin-LA, LR, and YR and at pH 9 for microcystin-RR and cylindrospermopsin (CYN). Kinetic studies and adsorption isotherms reflected better fit for pseudo-second-order rate and Langmuir isotherm model, respectively. Thermodynamic calculations showed that the cyanotoxin adsorption process is endothermic and spontaneous in nature. The regenerated adsorbent can be successfully reused without appreciable loss of its original capacity. PMID:27072032

  13. Adsorption of fluoride to UiO-66-NH2 in water: Stability, kinetic, isotherm and thermodynamic studies.

    PubMed

    Lin, Kun-Yi Andrew; Liu, Yu-Ting; Chen, Shen-Yi

    2016-01-01

    To provide safe drinking water, fluoride in water must be removed and adsorption processes appear to be the most widely used method. Metal organic frameworks (MOFs) represent a new class of adsorbents that have been used in various adsorption applications. To study the adsorption mechanism of fluoride to MOFs in water and obtain related adsorption parameters, we synthesized a zirconium-based MOF with a primary amine group on its ligand, named UiO-66-NH2. The kinetics, adsorption isotherm and thermodynamics of fluoride adsorption to UiO-66-NH2 were investigated. The crystalline structure of UiO-66-NH2 remained intact and the local structure of zirconium in UiO-66-NH2 did not change significantly after being exposed to fluoride. The kinetics of the fluoride adsorption in UiO-66-NH2 could be well represented by the pseudo second order rate law. The enthalpy of the adsorption indicates that the F(-) adsorption to UiO-66-NH2 was classified as a physical adsorption. However, the comparison between the adsorption capacities of UiO-66-NH2 and UiO-66 suggests that the fluoride adsorption to UiO-66-NH2 might primarily involve a strong interaction between F(-) and the metal site. The fluoride adsorption capacity of UiO-66-NH2 was found to decrease when pH>7. While the presence of chloride/bromide ions did not noticeably change the adsorption capacity of UiO-66-NH2, the ionic surfactants slightly affected the adsorption capacity of UiO-66-NH2. These findings provide insights to further optimize the adsorption process for removal of fluoride using zirconium-based MOFs. PMID:26397913

  14. Numerical determination of non-Langmuirian adsorption isotherms of ibuprofen enantiomers on Chiralcel OD column using ultraviolet-circular dichroism dual detector.

    PubMed

    Li, Hui; Jiang, Xiaoxiao; Xu, Wei; Chen, Yongtao; Yu, Weifang; Xu, Jin

    2016-02-26

    Competitive adsorption isotherm of ibuprofen enantiomers on Chiralcel OD stationary phase at 298K was determined by the application of inverse method. Transport dispersive (TD) chromatography model was used to describe mass balances of the enatiomers. Axial dispersion and mass transfer coefficients were estimated from a series of linear pulse experiments. It was found that the overloaded elution profile of total concentration of racemic ibuprofen cannot be satisfactorily fitted by substituting bi-Langmuir model, the most widely used isotherm model for enantiomers, into TD model and tuning the isotherm parameters. UV-CD dual detector setup was then applied to obtain the individual overloaded elution profiles of both enantiomers. The more informative experimental data revealed non-Langmuirian adsorption behavior of ibuprofen enantiomers on chiralcel OD stationary phase. Two analytical binary isotherm models, both accounting for adsorbate-adsorbate interactions and having the feature of inflection points, were then evaluated. A comparison between quadratic model and Moreau model showed that the former gives better fitting results. The six parameters involved in quadratic model were determined stepwisely. Three of them were first obtained by fitting overloaded elution profiles of S-ibuprofen. The other three were then acquired by fitting overloaded elution profiles of both enantiomers recorded by UV-CD dual detector for racemic ibuprofen. A further attempt was also made at reducing the number of quadratic model parameters. PMID:26846132

  15. Adsorption isotherm studies of chromium (VI) from aqueous solutions using sol-gel hydrotalcite-like compounds.

    PubMed

    Ramos-Ramírez, Esthela; Ortega, Norma L Gutiérrez; Soto, Cesar A Contreras; Gutiérrez, Maria T Olguín

    2009-12-30

    In under-developed countries, industries such as paint and pigment manufacturing, leather tanning, chrome plating and textile processing, usually discharge effluents containing Cr(VI) and Cr(III) into municipal sanitary sewers. It has been reported that Cr(VI) acts as a powerful epithelial irritant and as a human carcinogen. In the present work, hydrotalcite-like compounds with a Mg/Al ratio=2 were synthesized by the sol-gel method. The hydrotalcite-like compounds and their corresponding thermally treated products were characterized by powder X-ray diffraction, infrared spectroscopy and N(2) adsorption. The hydrotalcite-like compounds and the heated solids were used as adsorbents for Cr(VI) in aqueous solutions. Adsorption isotherm studies of Cr(VI) from aqueous solution are described. The adsorbent capacity was determined using the Langmuir, Freundlich and Dubinin-Radushkevich adsorption isotherm models. The Cr(VI) adsorption isotherm data fit best to the Langmuir isotherm model. The maximum Cr(VI) uptake by hydrotalcite and the heated solids was determined using the Langmuir equation and was found to range between 26 and 29 mg Cr(VI)/g adsorbent. PMID:19744787

  16. 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

  17. Predicting CH4 adsorption capacity of microporous carbon using N2 isotherm and a new analytical model

    USGS Publications Warehouse

    Sun, Jielun; Chen, S.; Rostam-Abadi, M.; Rood, M.J.

    1998-01-01

    A new analytical pore size distribution (PSD) model was developed to predict CH4 adsorption (storage) capacity of microporous adsorbent carbon. The model is based on a 3-D adsorption isotherm equation, derived from statistical mechanical principles. Least squares error minimization is used to solve the PSD without any pre-assumed distribution function. In comparison with several well-accepted analytical methods from the literature, this 3-D model offers relatively realistic PSD description for select reference materials, including activated carbon fibers. N2 and CH4 adsorption data were correlated using the 3-D model for commercial carbons BPL and AX-21. Predicted CH4 adsorption isotherms, based on N2 adsorption at 77 K, were in reasonable agreement with the experimental CH4 isotherms. Modeling results indicate that not all the pores contribute the same percentage Vm/Vs for CH4 storage due to different adsorbed CH4 densities. Pores near 8-9 A?? shows higher Vm/Vs on the equivalent volume basis than does larger pores.

  18. Optimizing Available Phosphorus in Calcareous Soils Fertilized with Diammonium Phosphate and Phosphoric Acid Using Freundlich Adsorption Isotherm

    PubMed Central

    Akhtar, Muhammad

    2013-01-01

    In calcareous soils, phosphorus (P) retention and immobilization take place due to precipitation and adsorption. Since soil pH is considered a major soil variable affecting the P sorption, an acidic P fertilizer could result in low P adsorption compared to alkaline one. Therefore, P adsorption from DAP and phosphoric acid (PA) required to produce desired soil solution P concentration was estimated using Freundlich sorption isotherms. Two soils from Faisalabad and T. T. Singh districts were spiked with 0, 10, and 20 % CaCO3 for 15 days. Freundlich adsorption isotherms (P = aCb/a) were constructed, and theoretical doses of PA and DAP to develop a desired soil solution P level (i.e., 0.20 mg L−1) were calculated. It was observed that P adsorption in soil increased with CaCO3. Moreover, at all the levels of CaCO3, P adsorption from PA was lower compared to that from DAP in both the soils. Consequently, lesser quantity of PA was required to produce desired solution P, 0.2 mg L−1, compared to DAP. However, extrapolating the developed relationship between soil CaCO3 contents and quantity of fertilizer to other similar textured soils needs confirmation. PMID:24307878

  19. The Republic of the Philippines coalbed methane assessment: based on seventeen high pressure methane adsorption isotherms

    USGS Publications Warehouse

    Flores, Romeo M.; Stricker, Gary D.; Papasin, Ramon F.; Pendon, Ronaldo R.; del Rosario, Rogelio A.; Malapitan, Ruel T.; Pastor, Michael S.; Altomea, Elmer A.; Cuaresma, Federico; Malapitan, Armando S.; Mortos, Benjamin R.; Tilos, Elizabeth N.

    2006-01-01

    Introduction: The Republic of the Philippines has some 19 coal districts that contain coal deposits ranging from Eocene to Pleistocene in age. These coal districts include: (1) Catanduanes (Eocene); (2) Cebu, Zamboanga Sibuguey, Bukidnon, Maguindanao, Sarangani, and Surigao (Oligocene to Miocene); (3) Batan Island, Masbate, Semirara (including Mindoro), and Quezon-Polilio (lower-upper Miocene); (4) Davao, Negros, and Sorsogon (middle-upper Miocene); (5) Cotabato (lower Miocene-lower Pliocene), Cagayan-Isabella, and Quirino (upper Miocene-Pliocene); (6) Sultan Kudarat (upper Miocene-Pleistocene); and (7) Samar-Leyte (lower Pliocene-Pleistocene). In general, coal rank is directly related to the age of the deposits - for example, the Eocene coal is semi-anthracite and the Pliocene-Pleistocene coal is lignite. Total coal resources in these 19 coal districts, which are compiled by the Geothermal and Coal Resources Development Division (GCRDD) of the Department of Energy of the Philippines, are estimated at a minimum of 2,268.4 million metric tonnes (MMT) (approximately 2.3 billion metric tones). The largest resource (550 MMT) is the subbituminous coal in the Semirara (including Mindoro) coal district, and the smallest (0.7 MMT) is the lignite-subbituminous coal in the Quirino coal district. The combined lignite and subbituminous coal resources, using the classification by GCRDD and including Semirara and Surigao coal districts, are about 1,899.2 MMT, which make up about 84 percent of the total coal resources of the Philippines. The remaining resources are composed of bituminous and semi-anthracite coal. The subbituminous coal of Semirara Island in the Mindoro- Semirara coal district (fig. 2) is known to contain coalbed methane (CBM), with the coal being comparable in gas content and adsorption isotherms to the coal of the Paleocene Fort Union Formation in the Powder River Basin in Wyoming, USA (Flores and others, 2005). As a consequence, the presence of CBM in the

  20. Adsorption kinetics, isotherms and thermodynamics of atrazine removal using a banana peel based sorbent.

    PubMed

    Chaparadza, Allen; Hossenlopp, Jeanne M

    2012-01-01

    Atrazine removal from water by treated banana peels was studied. The effect of pH, contact time, initial atrazine concentration, and temperature were investigated. Batch experiments demonstrated that 15 g L(-1) adsorbent dosage removed 90-99% of atrazine from 1-150 ppm aqueous solutions. The removal was both pH and temperature dependent with the most atrazine removed between pH 7 and 8.2 and increased with increasing temperature. Equilibrium data fitted well to the Langmuir and Redlich-Peterson models in the concentration and temperature ranges investigated, with a maximum adsorption capacity of 14 mg g(-1). Simple mass transfer models were applied to the experimental data to examine the adsorption mechanism and it was found that both external mass transfer and intraparticle diffusion played important roles in the adsorption mechanisms. The enthalpy of atrazine adsorption was evaluated to be 67.8 ± 6.3 kJ mol(-l) with a Gibbs free energy of -5.7 ± 1.2 kJ mol(-1). PMID:22339031

  1. 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

  2. Adsorption isotherms for hydrogen chloride (HCl) on ice surfaces between 190 and 220 K.

    PubMed

    Zimmermann, S; Kippenberger, M; Schuster, G; Crowley, J N

    2016-05-18

    The interaction of hydrogen chloride (HCl) with ice surfaces at temperatures between 190 and 220 K was investigated using a coated-wall flow-tube connected to a chemical ionization mass spectrometer. Equilibrium surface coverages of HCl were determined at gas phase concentrations as low as 2 × 10(9) molecules cm(-3) (∼4 × 10(-8) Torr at 200 K) to derive Langmuir adsorption isotherms. The data are described by a temperature independent partition coefficient: KLang = (3.7 ± 0.2) × 10(-11) cm(3) molecule(-1) with a saturation surface coverage Nmax = (2.0 ± 0.2) × 10(14) molecules cm(-2). The lack of a systematic dependence of KLang on temperature contrasts the behaviour of numerous trace gases which adsorb onto ice via hydrogen bonding and is most likely related to the ionization of HCl at the surface. The results are compared to previous laboratory studies, and the equilibrium partitioning of HCl to ice surfaces under conditions relevant to the atmosphere is evaluated. PMID:27142478

  3. Effect of the endcapping of reversed-phase high-performance liquid chromatography adsorbents on the adsorption isotherm

    SciTech Connect

    Gritti, Fabrice; Guiochon, Georges A

    2005-09-01

    The retention mechanisms of n-propylbenzoate, 4-t ert-butylphenol, and caffeine on the endcapped Symmetry-C{sub 18} and the non-endcapped Resolve-C{sub 18} are compared. The adsorption isotherms were measured by frontal analysis (FA), using as the mobile phase mixtures of methanol or acetonitrile and water of various compositions. The isotherm data were modeled and the adsorption energy distributions calculated. The surface heterogeneity increases faster with decreasing methanol concentration on the non-endcapped than on the endcapped adsorbent. For instance, for methanol concentrations exceeding 30% (v/v), the adsorption of caffeine is accounted for by assuming three and two different types of adsorption sites on Resolve-C{sub 18} and Symmetry-C{sub 18}, respectively. This is explained by the effect of the mobile phase composition on the structure of the C{sub 18}-bonded layer. The bare surface of bonded silica appears more accessible to solute molecules at high water contents in the mobile phase. On the other hand, replacing methanol by a stronger organic modifier like acetonitrile dampens the differences between non-endcapped and endcapped stationary phase and decreases the degree of surface heterogeneity of the adsorbent. For instance, at acetonitrile concentrations exceeding 20%, the surface appears nearly homogeneous for the adsorption of caffeine.

  4. Effect of humic acid on the adsorption/desorption behavior of glyphosate on goethite. Isotherms and kinetics.

    PubMed

    Arroyave, Jeison Manuel; Waiman, Carolina C; Zanini, Graciela P; Avena, Marcelo J

    2016-02-01

    The effects of humic acid (HA) on the adsorption/desorption of glyphosate (Gly) on goethite were investigated under pseudo equilibrium conditions by adsorption isotherms and under kinetic conditions by ATR-FTIR spectroscopy. Isotherms reveal that the attachment of Gly is almost completely inhibited by HA molecules. The opposite effect is not observed: HA adsorption is not affected by the presence of Gly. ATR-FTIR allowed the simultaneous detection of adsorbed HA and Gly during kinetic runs, revealing that HA at the surface decreases markedly the adsorption rate of Gly likely as a result of a decreased availability of sites for Gly adsorption and because of electrostatic repulsion. In addition, HA in solution increases the desorption rate of Gly. The rate law for Gly desorption could be determined giving important insights on the desorption mechanism. The herbicide is desorbed by two parallel processes: i) a direct detachment from the surface, which is first order in adsorbed Gly; and ii) a ligand exchange with HA molecules, which is first order in adsorbed Gly and first order in dissolved HA. Rate constants for both processes were quantified, leading to half-lives of 3.7 h for the first process, and 1.4 h for the second process in a 400 mg L(-1) HA solution. These data are important for modeling the dynamics of glyphosate in environmentally relevant systems, such as soils and surface waters. PMID:26657085

  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. The removal of arsenate from water using iron-modified diatomite (D-Fe): isotherm and column experiments.

    PubMed

    Pantoja, M L; Jones, H; Garelick, H; Mohamedbakr, H G; Burkitbayev, M

    2014-01-01

    Iron hydroxide supported onto porous diatomite (D-Fe) is a low-cost material with potential to remove arsenic from contaminated water due to its affinity for the arsenate ion. This affinity was tested under varying conditions of pH, contact time, iron content in D-Fe and the presence of competitive ions, silicate and phosphate. Batch and column experiments were conducted to derive adsorption isotherms and breakthrough behaviours (50 μg L(-1)) for an initial concentration of 1,000 μg L(-1). Maximum capacity at pH 4 and 17% iron was 18.12-40.82 mg of arsenic/g of D-Fe and at pH 4 and 10% iron was 18.48-29.07 mg of arsenic/g of D-Fe. Adsorption decreased in the presence of phosphate and silicate ions. The difference in column adsorption behaviour between 10% and 17% iron was very pronounced, outweighing the impact of all other measured parameters. There was insufficient evidence of a correlation between iron content and arsenic content in isotherm experiments, suggesting that ion exchange is a negligible process occurring in arsenate adsorption using D-Fe nor is there co-precipitation of arsenate by rising iron content of the solute above saturation. PMID:23807557

  7. Kinetic, isotherm and thermodynamic investigations of phosphate adsorption onto core-shell Fe₃O₄@LDHs composites with easy magnetic separation assistance.

    PubMed

    Yan, Liang-guo; Yang, Kun; Shan, Ran-ran; Yan, Tao; Wei, Jing; Yu, Shu-jun; Yu, Hai-qin; Du, Bin

    2015-06-15

    In this study, three different magnetic core-shell Fe3O4@LDHs composites, Fe3O4@Zn-Al-, Fe3O4@Mg-Al-, and Fe3O4@Ni-Al-LDH were prepared via a rapid coprecipitation method for phosphate adsorptive removal. The composites were characterized by XRD, FTIR, TEM, VSM and BET analyses. Characterization results proved the successful synthesis of core-shell Fe3O4@LDHs composites with good superparamagnetisms. Batch experiments were conducted to study the adsorption efficiency of phosphate. Optimal conditions for the phosphate adsorption were obtained: 0.05 g of adsorbent, solution pH of 3, and contact time of 60 min. Proposed mechanisms for the removal of phosphate species onto Fe3O4@LDHs composites at different initial solution pH were showed. The kinetic data were described better by the pseudo-second-order kinetic equation and KASRA model. The adsorption isotherm curves showed a three-region behavior in the ARIAN model. It had a good fit with Langmuir model and the maximum adsorption capacity followed the order of Fe3O4@Zn-Al-LDH>Fe3O4@Mg-Al-LDH>Fe3O4@Ni-Al-LDH. Thermodynamic analyses indicated that the phosphate adsorption process was endothermic and spontaneous in nature. The three Fe3O4@LDHs composites could be easily separated from aqueous solution by the external magnetic field in 10s. These novel magnetic core-shell Fe3O4@LDHs adsorbents may offer a simple single step adsorption treatment option to remove phosphate from water without the requirement of pre-/post-treatment for current industrial practice. PMID:25778739

  8. Kinetics and isotherm analysis of Tropaeoline 000 adsorption onto unsaturated polyester resin (UPR): a non-carbon adsorbent.

    PubMed

    Jain, Rajeev; Sharma, Pooja; Sikarwar, Shalini

    2013-03-01

    The presence of dyes in water is undesirable due to the toxicological impact of their entrance into the food chain. Owing to the recalcitrant nature of dyes to biological oxidation, a tertiary treatment like adsorption is required. In the present study, unsaturated polyester resin (UPR) has been used as a sorbent in the treatment of dye-contaminated water. Different concentrations of Tropaeoline 000 containing water were treated with UPR. The preliminary investigations were carried out by batch adsorption to examine the effects of pH, adsorbate concentration, adsorbent dosage, contact time, and temperature. A plausible mechanism for the ongoing adsorption process and thermodynamic parameters have also been obtained from Langmuir and Freundlich adsorption isotherm models. Thermodynamic parameter showed that the sorption process of Tropaeoline 000 onto activated carbon (AC) and UPR were feasible, spontaneous, and endothermic under studied conditions. The estimated values for (ΔG) are -10.48 × 10(3) and -6.098 × 10(3) kJ mol(-1) over AC and UPR at 303 K (30 °C), indicating towards a spontaneous process. The adsorption process followed pseudo-first-order model. The mass transfer property of the sorption process was studied using Lagergren pseudo-first-order kinetic models. The values of % removal and k (ad) for dye systems were calculated at different temperatures (303-323 K). The mechanism of the adsorption process was determined from the intraparticle diffusion model. PMID:22689095

  9. Activated carbon derived from carbon residue from biomass gasification and its application for dye adsorption: Kinetics, isotherms and thermodynamic studies.

    PubMed

    Maneerung, Thawatchai; Liew, Johan; Dai, Yanjun; Kawi, Sibudjing; Chong, Clive; Wang, Chi-Hwa

    2016-01-01

    In this work, activated carbon (AC) as an effective and low-cost adsorbent was successfully prepared from carbon residue (or char, one of the by-products from woody biomass gasification) via physical activation. The surface area of char was significantly increased from 172.24 to 776.46m(2)/g after steam activation at 900°C. The obtained activated carbons were then employed for the adsorption of dye (Rhodamine B) and it was found that activated carbon obtained from steam activation exhibited the highest adsorption capability, which is mainly attributed to the higher surface area and the abundance of hydroxyl (-OH) and carboxyl (-COOH) groups on the activated carbon surface. Moreover, it was also found that the adsorption capability significantly increased under the basic condition, which can be attributed to the increased electrostatic interaction between the deprotonated (negatively charged) activated carbon and dye molecules. Furthermore, the equilibrium data were fitted into different adsorption isotherms and found to fit well with Langmuir model (indicating that dye molecules form monolayer coverage on activated carbon) with a maximum monolayer adsorption capability of 189.83mg/g, whereas the adsorption kinetics followed the pseudo-second-order kinetics. PMID:26512858

  10. Investigation of adsorption kinetics and isotherm of cellulase and B-Glucosidase on lignocellulosic substrates

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Clear understanding of enzyme adsorption during enzymatic hydrolysis of lignocellulosic biomass is essential to enhance the cost-efficiency of hydrolysis. However, conclusions from literatures often contradicted each other because enzyme adsorption is enzyme, biomass/pretreatment and experimental co...

  11. Adsorption and isothermal models of atrazine by zeolite prepared from Egyptian kaolin

    NASA Astrophysics Data System (ADS)

    Jamil, Tarek S.; Gad-Allah, Tarek A.; Ibrahim, Hanan S.; Saleh, Tamer S.

    2011-01-01

    The adsorption behavior of Atrazine on zeolites, prepared from Egyptian kaolin, has been studied in order to consider the application of these types of zeolites in water purification. The batch mode has been employed, using atrazine solution of concentration ranging from 2 to 10 mg /l. The adsorption capacity and distribution coefficients ( Kd) were determined for the adsorption system as a function of sorbate concentration. It was found that, under the studies concentrations, the percent of adsorbed atrazine on both zeolites match to Langmuir and Freundlich adsorption models. The constants of each model were calculated to assess the adsorption behavior of atrazine on each type of zeolite. According to the equilibrium studies, adsorption of atrazine on zeolite X at lower concentrations is much better than that on zeolite A. The application of Dublin-Kaganer-Radushkevich model revealed physisorption endothermic adsorption process for both zeolites. These results show that natural zeolites hold great potential to remove hazardous materials such as atrazine from water.

  12. Liquid phase adsorptions of Rhodamine B dye onto raw and chitosan supported mesoporous adsorbents: isotherms and kinetics studies

    NASA Astrophysics Data System (ADS)

    Inyinbor, A. A.; Adekola, F. A.; Olatunji, G. A.

    2016-04-01

    Irvingia gabonensis endocarp waste was charred (DNc) and subsequently coated with chitosan (CCDNc). Physicochemical characteristics of the two adsorbents were established, while Fourier transform infrared (FTIR), Scanning electron microscopy (SEM) and Brunauer-Emmett-Teller (BET) surface area methods were further employed for characterization. Efficiencies of the prepared adsorbents in the uptake of Rhodamine B (RhB) from aqueous effluent were investigated and adsorption data were tested using four isotherms and four kinetics models. The BET surface areas of the prepared adsorbent were 0.0092 and 4.99 m2/g for DNc and CCDNc, respectively, and maximum adsorption was recorded at pH between 3 and 4, respectively. While monolayer adsorption dominates the uptake of RhB onto DNc, uptake of RhB onto CCDNc was onto heterogeneous surface. The maximum monolayer adsorption capacities (q max) obtained from the Langmuir equation are 52.90 and 217.39 mg/g for DNc and CCDNc, respectively. Pseudo second order and Elovich kinetic models well described the kinetics of the two adsorption processes. The mean sorption energy (E) calculated from the D-R model and desorption efficiencies suggests that while the uptake of RhB onto DNc was physical in nature, for RhB-CCDNc system chemisorption dominates.

  13. Adsorption of probe molecules in pillared interlayered clays: Experiment and computer simulation

    SciTech Connect

    Gallardo, A. Guil, J. M.; Lomba, E.; Almarza, N. G.; Khatib, S. J.; Cabrillo, C.; Sanz, A.; Pires, J.

    2014-06-14

    In this paper we investigate the adsorption of various probe molecules in order to characterize the porous structure of a series of pillared interlayered clays (PILC). To that aim, volumetric and microcalorimetric adsorption experiments were performed on various Zr PILC samples using nitrogen, toluene, and mesitylene as probe molecules. For one of the samples, neutron scattering experiments were also performed using toluene as adsorbate. Various structural models are proposed and tested by means of a comprehensive computer simulation study, using both geometric and percolation analysis in combination with Grand Canonical Monte Carlo simulations in order to model the volumetric and microcalorimetric isotherms. On the basis of this analysis, we propose a series of structural models that aim at accounting for the adsorption experimental behavior, and make possible a microscopic interpretation of the role played by the different interactions and steric effects in the adsorption processes in these rather complex disordered microporous systems.

  14. Recombinant protein purification using gradient-assisted simulated moving bed hydrophobic interaction chromatography. Part I: selection of chromatographic system and estimation of adsorption isotherms.

    PubMed

    Palani, Sivakumar; Gueorguieva, Ludmila; Rinas, Ursula; Seidel-Morgenstern, Andreas; Jayaraman, Guhan

    2011-09-16

    The design of gradient simulated moving bed (SMB) chromatographic processes requires an appropriate selection of the chromatographic system followed by the determination of adsorption isotherm parameters in the relevant range of mobile phase conditions. The determination of these parameters can be quite difficult for recombinant target proteins present in complex protein mixtures. The first part of this work includes the estimation of adsorption isotherm parameters for streptokinase and a lumped impurity fraction present in an Escherichia coli cell lysate for a hydrophobic interaction chromatography (HIC) matrix. Perturbation experiments were carried out using a Butyl Sepharose matrix with purified recombinant protein on buffer equilibrated columns as well as with crude cell lysate saturated columns. The Henry constants estimated for streptokinase were found to exhibit in a wide range a linear dependence on the salt concentration in the mobile phase. These parameters were applied in subsequent investigations to design a simulated moving bed (SMB) process capable to purify in a continuous manner recombinant streptokinase from the E. coli cell lysate. PMID:21816402

  15. Description of Chemically and Thermally Treated Multi-Walled Carbon Nanotubes Using Sequential Decomposition of Adsorption Isotherms

    NASA Astrophysics Data System (ADS)

    Albesa, Alberto G.; Rafti, Matías; Vicente, José Luis

    2016-03-01

    The effect of wet acid oxidation by means of sulfuric/nitric acid mixtures, and high-temperature treatment of commercial arc-discharge synthesized multi-walled carbon nanotubes (MWCNTs) was studied. In order to analyze the adsorption capacities of differently treated MWCNTs, we employed a multistep method that considers separately different pressure ranges (zones) on the experimentally obtained isotherms. The method is based on simple gas isotherm measurements (N2, CO2, CH4, etc.). Low pressure ranges can be described using Dubinin’s model, while high pressure regimes can be fitted using different models such as BET multilayer and Freundlich equations. This analysis allows to elucidate how different substrate treatments (chemical and thermal) can affect the adsorbate-adsorbent interactions; moreover, theoretical description of adsorbate-adsorbate interactions can be improved if a combination of adsorption mechanisms are used instead of a unique model. The results hereby presented also show that, while MWCNTs are a promising material for storage applications, gas separation applications should carefully consider the effect of wide nanotube size distribution present on samples after activation procedures.

  16. Adsorption isotherms, kinetics and thermodynamic studies towards understanding the interaction between cross-linked alginate-guar gum matrix and chymotrypsin.

    PubMed

    Woitovich Valetti, Nadia; Picó, Guillermo

    2016-02-15

    The adsorption kinetics of chymotrypsin, a pancreatic serine protease, onto an alginate-gum guar matrix cross-linked with epichlorohydrin has been performed using a batch-adsorption technique. The effect of various experimental parameters such as pH, salt presence, contact time and temperature were investigated. The pseudo-first-order and pseudo-second-order kinetic models were used to describe the kinetic data which shows that the adsorption of the enzyme followed the pseudo-second-order rate expression. The Langmuir, Freundlich and Hill adsorption isotherm models were applied to describe the equilibrium isotherms, and the isotherm constants were determined. It was found that Hill model was more suitable for our data because the isotherm data showed a sigmoidal behavior with the free enzyme concentration increasing in equilibrium. At 8°C and at pH 5.0, 1g hydrate matrix adsorbed about 7mg of chymotrypsin. In the desorption process 80% of the biological activity of chymotrypsin was recovered under the condition of 50mM phosphate buffer, pH 7.00-500mM NaCl. When successive cycles of adsorption/washing/desorption were performed, it was observed that the matrix remained functional until the fourth cycle of repeated batch enzyme adsorption. These results are important in terms of diminishing of cost and waste generation. PMID:26849187

  17. Adsorption of heavy metal ions using hierarchical CaCO3-maltose meso/macroporous hybrid materials: adsorption isotherms and kinetic studies.

    PubMed

    Ma, Xiaoming; Li, Liping; Yang, Lin; Su, Caiyun; Wang, Kui; Yuan, Shibao; Zhou, Jianguo

    2012-03-30

    Highly ordered hierarchical calcium carbonate is an important phase and has technological interest in the development of functional materials. The work describes hierarchical CaCO(3)-maltose meso/macroporous hybrid materials were synthesized using a simple gas-diffusion method. The uniform hexagonal-shaped CaCO(3)-maltose hybrid materials are formed by the hierarchical assembly of nanoparticles. The pore structure analysis indicates that the sample possesses the macroporous structure of mesoporous framework. The distinguishing features of the hierarchical CaCO(3)-maltose materials in water treatment involve not only high removal capacities, but also decontamination of trace metal ions. Langmuir model fitted the equilibrium data better than the Freundlich isotherm. The maximum removal capacity of the CaCO(3)-maltose hybrid materials for Pb(2+), Cd(2+), Cu(2+), Co(2+), Mn(2+) and Ni(2+) ions was 3242.48, 487.80, 628.93, 393.70, 558.66 and 769.23 mg/g, respectively. Adsorption data were modeled using the pseudo-first-order, pseudo-second-order and intra-particle diffusion kinetics equations. The results indicate that pseudo-second-order kinetic equation and intra-particle diffusion model can better describe the adsorption kinetics. The adsorption and precipitation transformation mechanism can be considered due to hierarchical meso/macroporous structure, rich organic ligands of the CaCO(3)-maltose hybrid materials and the larger solubility product of CaCO(3). PMID:22326246

  18. Bayesian and Frequentist Methods for Estimating Joint Uncertainty of Freundlich Adsorption Isotherm Fitting Parameters

    EPA Science Inventory

    In this paper, we present methods for estimating Freundlich isotherm fitting parameters (K and N) and their joint uncertainty, which have been implemented into the freeware software platforms R and WinBUGS. These estimates were determined by both Frequentist and Bayesian analyse...

  19. Chromatographic and traditional albumin isotherms on cellulose: a model for wound protein adsorption on modified cotton

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Albumin is the most abundant protein found in healing wounds. Traditional and chromatogrpahic protein isotherms of albumin binding on modified cotton fibers are useful in understanding albumin binding to cellulose wound dressings. An important consideration in the design of cellulosic wound dressin...

  20. Using Compression Isotherms of Phospholipid Monolayers to Explore Critical Phenomena: A Biophysical Chemistry Experiment

    ERIC Educational Resources Information Center

    Gragson, Derek E.; Beaman, Dan; Porter, Rhiannon

    2008-01-01

    Two experiments are described in which students explore phase transitions and critical phenomena by obtaining compression isotherms of phospholipid monolayers using a Langmuir trough. Through relatively simple analysis of their data students gain a better understanding of compression isotherms, the application of the Clapeyron equation, the…

  1. Adsorption of HMF from water/DMSO solutions onto hydrophobic zeolites: experiment and simulation.

    PubMed

    Xiong, Ruichang; León, Marta; Nikolakis, Vladimiros; Sandler, Stanley I; Vlachos, Dionisios G

    2014-01-01

    The adsorption of 5-hydroxymethylfurfural (HMF), DMSO, and water from binary and ternary mixtures in hydrophobic silicalite-1 and dealuminated Y (DAY) zeolites at ambient conditions was studied by experiments and molecular modeling. HMF and DMSO adsorption isotherms were measured and compared to those calculated using a combination of grand canonical Monte Carlo and expanded ensemble (GCMC-EE) simulations. A method based on GCMC-EE simulations for dilute solutions combined with the Redlich-Kister (RK) expansion (GCMC-EE-RK) is introduced to calculate the isotherms over a wide range of concentrations. The simulations, using literature force fields, are in reasonable agreement with experimental data. In HMF/water binary mixtures, large-pore hydrophobic zeolites are much more effective for HMF adsorption but less selective because large pores allow water adsorption because of H2 O-HMF attraction. In ternary HMF/DMSO/water mixtures, HMF loading decreases with increasing DMSO fraction, rendering the separation of HMF from water/DMSO mixtures by adsorption difficult. The ratio of the energetic interaction in the zeolite to the solvation free energy is a key factor in controlling separation from liquid mixtures. Overall, our findings could have an impact on the separation and catalytic conversion of HMF and the rational design of nanoporous adsorbents for liquid-phase separations in biomass processing. PMID:24106213

  2. Dye adsorption of cotton fabric grafted with PPI dendrimers: Isotherm and kinetic studies.

    PubMed

    Salimpour Abkenar, Samera; Malek, Reza Mohammad Ali; Mazaheri, Firouzmehr

    2015-11-01

    In this research, the cotton fabrics grafted with two generations of the poly(propylene imine) dendrimers were applied to adsorb textile dyes from aqueous solutions. Direct Red 80 (anionic dye), Disperse Yellow 42 (nonionic dye) and Basic Blue 9 (cationic dye) were selected as model dyes. The effect of various experimental parameters such as initial concentration of dyes, charge of dyes molecule, salt and pH was investigated on the adsorption process. Furthermore, kinetics and equilibrium of the adsorption process on the grafted samples were studied. It was found that maximum adsorption of anionic and disperse dyes took place at around pH 3, while cationic dye could be adsorbed at around pH 11. The Langmuir equation was able to describe the mechanism of dyes adsorption. In addition, the second-order equation was found to be fit with the kinetics data. Interestingly, it seems that the dye adsorption of the grafted fabrics is strongly pH dependent. PMID:26292774

  3. Effect of cation type, alkyl chain length, adsorbate size on adsorption kinetics and isotherms of bromide ionic liquids from aqueous solutions onto microporous fabric and granulated activated carbons.

    PubMed

    Hassan, Safia; Duclaux, Laurent; Lévêque, Jean-Marc; Reinert, Laurence; Farooq, Amjad; Yasin, Tariq

    2014-11-01

    The adsorption from aqueous solution of imidazolium, pyrrolidinium and pyridinium based bromide ionic liquids (ILs) having different alkyl chain lengths was investigated on two types of microporous activated carbons: a fabric and a granulated one, well characterized in terms of surface chemistry by "Boehm" titrations and pH of point of zero charge measurements and of porosity by N2 adsorption at 77 K and CO2 adsorption at 273 K. The influence of cation type, alkyl chain length and adsorbate size on the adsorption properties was analyzed by studying kinetics and isotherms of eight different ILs using conductivity measurements. Equilibrium studies were carried out at different temperatures in the range [25-55 °C]. The incorporation of ILs on the AC porosity was studied by N2 adsorption-desorption measurements at 77 K. The experimental adsorption isotherms data showed a good correlation with the Langmuir model. Thermodynamic studies indicated that the adsorption of ILs onto activated carbons was an exothermic process, and that the removal efficiency increased with increase in alkyl chain length, due to the increase in hydrophobicity of long chain ILs cations determined with the evolution of the calculated octanol-water constant (Kow). The negative values of free energies indicated that adsorption of ILs with long chain lengths having hydrophobic cations was more spontaneous at the investigated temperatures. PMID:24929502

  4. Interactions between lignosulphonates and the components of the lead-acid battery. Part 1. Adsorption isotherms

    NASA Astrophysics Data System (ADS)

    Myrvold, Bernt O.

    The expander performs at least five different tasks in the battery. It is a fluidiser for the negative paste. It controls the formation stage of the battery. It controls the shape and size of the lead sulphate crystals formed upon discharge, and thus prevents the sintering of the active mass. It controls the rate of the lead to lead sulphate oxidation during discharge. Finally, it affects the charge acceptance. To gain more understanding of these different effects the interaction between lead, lead(II) oxide, lead(IV) oxide, lead sulphate, barium sulphate and carbon black and the experimental lignosulphonate (LS) expander UP-414 has been investigated. We also compared with Vanisperse A and several other lignosulphonates, to elucidate the mechanisms operating. In most cases, we have studied concentration ranges that are both higher and lower than those normally encountered in batteries. There is no adsorption of lignosulphonates to pure lead surfaces. Adsorption to lead sulphate is a slow process. In the presence of lead ions lignosulphonates will also adsorb to lead. The adsorption to lead(II) oxide is a fast process, and a strong adsorption occurs. In all these cases, it is preferably the high molecular weight fraction that interacts with the solid surfaces. Lead ions leaching from the surface complexes with lignosulphonates to give a more hydrophobic species. This allows the normally negatively charged lignosulphonate to adsorb to the negatively charged substrates. The lignosulphonates have an ability to complex lead ions and keep them solvated. This confirms previous observations of the lignosulphonates ability to promote the dissolution-precipitation mechanism for lead sulphate formation on the expense of the solid-state reaction.

  5. Kinetic and isotherm studies of adsorption and biosorption processes in the removal of phenolic compounds from aqueous solutions: comparative study

    PubMed Central

    2013-01-01

    The phenolic compounds are known by their carcinogenicity and high toxicity as well as creating unpleasant taste and odor in water resources. The present study develops a cost-effective technology for the treatment of water contaminated with phenolic compounds, including Phenol (Ph), 2-chlorophenol (2-CP), and 4-chlorophenol (4-CP). So, two sorbents, rice bran ash (RBA) and biomass of brown algae, Cystoseiraindica, were used and results were compared with the commercially granular activated carbon (GAC). The phenolic compounds were determined using a high performance liquid chromatography (HPLC) under batch equilibrium conditions. The effects of contact time, pH, initial adsorbate concentration, and adsorbent dosages on the removal efficiency were studied. The adsorption data were simulated by isotherm and kinetic models. Results indicated that RBA and GAC had the lowest efficiency for the removal of 2-CP, while the order of removal efficiency for C. indica biomass was as follows: 2-CP > 4-CP > phenol. The efficiency of GAC was higher than those of other adsorbents for all of the phenolic compounds. Furthermore, the adsorption capacity of RBA was found to be higher than that of C. indica biomass. The optimal initial pH for the removal of phenol, 2-CP and 4-CP was determined to be 5, 7, and 7 for RBA, GAC, and algal biomass, respectively. Kinetic studies suggested that the pseudo-second order best fitted the kinetic data. PMID:24355013

  6. Adsorption isotherms and kinetics of methylene blue on a low-cost adsorbent recovered from a spent catalyst of vinyl acetate synthesis

    NASA Astrophysics Data System (ADS)

    Zhang, Zhengyong; Zhang, Zebiao; Fernández, Y.; Menéndez, J. A.; Niu, Hao; Peng, Jinhui; Zhang, Libo; Guo, Shenghui

    2010-02-01

    A regenerated activated carbon used as catalyst support in the synthesis of vinyl acetate has been tested as a low-cost adsorbent for the removal of dyes. After a thorough textural characterization of the regenerated activated carbon, its adsorption isotherms and kinetics were determined using methylene blue as model compound at different initial concentrations. Both Langmuir and Freundlich isotherm models were developed and then compared. It was found that the equilibrium data were best represented by the Langmuir isotherm model. The kinetic data were fitted to pseudo-first-order, pseudo-second-order and intraparticle diffusion models, and it was found that the best fitting corresponded to the pseudo-second-order kinetic model. The results showed that this novel adsorbent had a high adsorption capacity, making it suitable for use in the treatment of methylene blue enriched wastewater.

  7. Solvothermal synthesis of different phase N-TiO2 and their kinetics, isotherm and thermodynamic studies on the adsorption of methyl orange.

    PubMed

    Fan, Jimin; Zhao, Zhihuan; Liu, Wenhui; Xue, Yongqiang; Yin, Shu

    2016-05-15

    The different crystal forms of nitrogen doped-titanium oxide (N-TiO2) with different particle sizes were produced by precipitation-solvothermal method and their adsorption mechanism were also investigated. The adsorption kinetics showed that rutile N-TiO2 displayed higher adsorption capacity than anatase for methyl orange (MO) and its adsorption behavior followed the pseudo-second-order kinetics. The equilibrium adsorption rate of N-TiO2 for MO was well fitted by the Langmuir isotherm model and the adsorption process was monolayer adsorption. The adsorption capacity decreased with increasing temperature. The average correlation coefficient was beyond 97%. The thermodynamic parameters (ΔaGm(ө), ΔaHm(ө), and ΔaSm(ө)) were calculated. It was found that anatase and rutile N-TiO2 had different adsorption enthalpy and entropy. The smaller the particle size, the greater the surface area and surface energy was, then ΔaGm(ө) decreased and the standard equilibrium constant increased at the same time. The adsorption process onto different crystalline phase N-TiO2 was exothermic and non-spontaneous. PMID:26945716

  8. Preparation To Minimize Buffer Mismatch in Isothermal Titration Calorimetry Experiments.

    PubMed

    Bian, Xuelin; Lockless, Steve W

    2016-05-17

    There is a growing need to study ligand binding to proteins in native or complex solution using isothermal titration calorimetry (ITC). For example, it is desirable to measure ligand binding to membrane proteins in more native lipid-like environments such as bicelles, where ligands can access both sides of the membrane in a homogeneous environment. A critical step to obtain high signal-to-noise is matching the reaction chamber solution to the ligand solution, typically through a final dialysis or gel filtration step. However, to obtain reproducible bicelles, the lipid concentrations must be carefully controlled which eliminates the use of dialysis that can disrupt these parameters. Here, we report and validate a rapid preparation ITC (RP-ITC) approach to measure ligand binding without the need for a dialysis step. This general approach is used to quantify ion binding to a K(+) channel embedded in bicelles and can be applied to complex, less defined systems. PMID:27092566

  9. Investigation of simultaneous biosorption of copper(II) and chromium(VI) on dried Chlorella vulgaris from binary metal mixtures: Application of multicomponent adsorption isotherms

    SciTech Connect

    Aksu, Z.; Acikel, U.; Kutsal, T.

    1999-02-01

    Although the biosorption of single metal ions to various kinds of microorganisms has been extensively studied and the adsorption isotherms have been developed for only the single metal ion situation, very little attention has been given to the bioremoval and expression of adsorption isotherms of multimetal ions systems. In this study the simultaneous biosorption of copper(II) and chromium(VI) to Chlorella vulgaris from a binary metal mixture was studied and compared with the single metal ion situation in a batch stirred system. The effects of pH and single- and dual-metal ion concentrations on the equilibrium uptakes were investigated. In previous studies the optimum biosorption pH had been determined as 4.0 for copper(II) and as 2.0 for chromium(VI). Multimetal ion biosorption studies were performed at these two pH values. It was observed that the equilibrium uptakes of copper(II) or chromium(VI) ions were changed due to the biosorption pH and the presence of other metal ions. Adsorption isotherms were developed for both single- and dual-metal ions systems at these two pH values, and expressed by the mono- and multicomponent Langmuir and Freundlich adsorption models. Model parameters were estimated by nonlinear regression. It was seen that the adsorption equilibrium data fitted very well to the competitive Freundlich model in the concentration ranges studied.

  10. Structure regulation of silica nanotubes and their adsorption behaviors for heavy metal ions: pH effect, kinetics, isotherms and mechanism.

    PubMed

    Wang, Pan; Du, Mingliang; Zhu, Han; Bao, Shiyong; Yang, Tingting; Zou, Meiling

    2015-04-01

    Silica nanotubes (SNTs) with controlled nanotubular structure were synthesized via an electrospinning and calcination process. In this regard, SNTs were found to be ideal adsorbents for Pb(II) removal with a higher adsorption capacity, and surface modification of the SNTs by sym-diphenylcarbazide (SD-SNTs) markedly enhanced the adsorption ability due to the chelating interaction between imino groups and Pb(II). The pH effect, kinetics, isotherms and adsorption mechanism of SNTs and SD-SNTs on Pb(II) adsorption were investigated and discussed detailedly. The adsorption capacity for Pb(II) removal was found to be significantly improved with the decrease of pH value. The Langmuir adsorption model agreed well with the experimental data. As for kinetic study, the adsorption onto SNTs and SD-SNTs could be fitted to pseudo-first-order and pseudo-second-order model, respectively. In addition, the as-prepared SNTs and SD-SNTs also exhibit high adsorption ability for Cd(II) and Co(II). The experimental results demonstrate that the SNTs and SD-SNTs are potential adsorbents and can be used effectively for the treatment of heavy-metal-ions-containing wastewater. PMID:25615696

  11. Thermodynamics, interfacial pressure isotherms and dilational rheology of mixed protein-surfactant adsorption layers.

    PubMed

    Fainerman, V B; Aksenenko, E V; Krägel, J; Miller, R

    2016-07-01

    Proteins and their mixtures with surfactants are widely used in many applications. The knowledge of their solution bulk behavior and its impact on the properties of interfacial layers made great progress in the recent years. Different mechanisms apply to the formation process of protein/surfactant complexes for ionic and non-ionic surfactants, which are governed mainly by electrostatic and hydrophobic interactions. The surface activity of these complexes is often remarkably different from that of the individual protein and has to be considered in respective theoretical models. At very low protein concentration, small amounts of added surfactants can change the surface activity of proteins remarkably, even though no strongly interfacial active complexes are observed. Also small added amounts of non-ionic surfactants change the surface activity of proteins in the range of small bulk concentrations or surface coverages. The modeling of the equilibrium adsorption behavior of proteins and their mixtures with surfactants has reached a rather high level. These models are suitable also to describe the high frequency limits of the dilational viscoelasticity of the interfacial layers. Depending on the nature of the protein/surfactant interactions and the changes in the interfacial layer composition rather complex dilational viscoelasticities can be observed and described by the available models. The differences in the interfacial behavior, often observed in literature for studies using different experimental methods, are at least partially explained by a depletion of proteins, surfactants and their complexes in the range of low concentrations. A correction of these depletion effects typically provides good agreement between the data obtained with different methods, such as drop and bubble profile tensiometry. PMID:26198014

  12. Adsorption isotherms and structure of cationic surfactants adsorbed on mineral oxide surfaces prepared by atomic layer deposition.

    PubMed

    Wangchareansak, Thipvaree; Craig, Vincent S J; Notley, Shannon M

    2013-12-01

    The adsorption isotherms and aggregate structures of adsorbed surfactants on smooth thin-film surfaces of mineral oxides have been studied by optical reflectometry and atomic force microscopy (AFM). Films of the mineral oxides of titania, alumina, hafnia, and zirconia were produced by atomic layer deposition (ALD) with low roughness. We find that the surface strongly influences the admicelle organization on the surface. At high concentrations (2 × cmc) of cetyltrimethylammonium bromide (CTAB), the surfactant aggregates on a titania surface exhibit a flattened admicelle structure with an average repeat distance of 8.0 ± 1.0 nm whereas aggregates on alumina substrates exhibit a larger admicelle with an average separation distance of 10.5 ± 1.0 nm. A wormlike admicelle structure with an average separation distance of 7.0 ± 1.0 nm can be observed on zirconia substrates whereas a bilayered aggregate structure on hafnia substrates was observed. The change in the surface aggregate structure can be related to an increase in the critical packing parameter through a reduction in the effective headgroup area of the surfactant. The templating strength of the surfaces are found to be hafnia > alumina > zirconia > titania. Weakly templating surfaces are expected to have superior biocompatibility. PMID:24224944

  13. Isotherm and kinetics study of malachite green adsorption onto copper nanowires loaded on activated carbon: artificial neural network modeling and genetic algorithm optimization.

    PubMed

    Ghaedi, M; Shojaeipour, E; Ghaedi, A M; Sahraei, Reza

    2015-05-01

    In this study, copper nanowires loaded on activated carbon (Cu-NWs-AC) was used as novel efficient adsorbent for the removal of malachite green (MG) from aqueous solution. This new material was synthesized through simple protocol and its surface properties such as surface area, pore volume and functional groups were characterized with different techniques such XRD, BET and FESEM analysis. The relation between removal percentages with variables such as solution pH, adsorbent dosage (0.005, 0.01, 0.015, 0.02 and 0.1g), contact time (1-40min) and initial MG concentration (5, 10, 20, 70 and 100mg/L) was investigated and optimized. A three-layer artificial neural network (ANN) model was utilized to predict the malachite green dye removal (%) by Cu-NWs-AC following conduction of 248 experiments. When the training of the ANN was performed, the parameters of ANN model were as follows: linear transfer function (purelin) at output layer, Levenberg-Marquardt algorithm (LMA), and a tangent sigmoid transfer function (tansig) at the hidden layer with 11 neurons. The minimum mean squared error (MSE) of 0.0017 and coefficient of determination (R(2)) of 0.9658 were found for prediction and modeling of dye removal using testing data set. A good agreement between experimental data and predicted data using the ANN model was obtained. Fitting the experimental data on previously optimized condition confirm the suitability of Langmuir isotherm models for their explanation with maximum adsorption capacity of 434.8mg/g at 25°C. Kinetic studies at various adsorbent mass and initial MG concentration show that the MG maximum removal percentage was achieved within 20min. The adsorption of MG follows the pseudo-second-order with a combination of intraparticle diffusion model. PMID:25699703

  14. Isotherm and kinetics study of malachite green adsorption onto copper nanowires loaded on activated carbon: Artificial neural network modeling and genetic algorithm optimization

    NASA Astrophysics Data System (ADS)

    Ghaedi, M.; Shojaeipour, E.; Ghaedi, A. M.; Sahraei, Reza

    2015-05-01

    In this study, copper nanowires loaded on activated carbon (Cu-NWs-AC) was used as novel efficient adsorbent for the removal of malachite green (MG) from aqueous solution. This new material was synthesized through simple protocol and its surface properties such as surface area, pore volume and functional groups were characterized with different techniques such XRD, BET and FESEM analysis. The relation between removal percentages with variables such as solution pH, adsorbent dosage (0.005, 0.01, 0.015, 0.02 and 0.1 g), contact time (1-40 min) and initial MG concentration (5, 10, 20, 70 and 100 mg/L) was investigated and optimized. A three-layer artificial neural network (ANN) model was utilized to predict the malachite green dye removal (%) by Cu-NWs-AC following conduction of 248 experiments. When the training of the ANN was performed, the parameters of ANN model were as follows: linear transfer function (purelin) at output layer, Levenberg-Marquardt algorithm (LMA), and a tangent sigmoid transfer function (tansig) at the hidden layer with 11 neurons. The minimum mean squared error (MSE) of 0.0017 and coefficient of determination (R2) of 0.9658 were found for prediction and modeling of dye removal using testing data set. A good agreement between experimental data and predicted data using the ANN model was obtained. Fitting the experimental data on previously optimized condition confirm the suitability of Langmuir isotherm models for their explanation with maximum adsorption capacity of 434.8 mg/g at 25 °C. Kinetic studies at various adsorbent mass and initial MG concentration show that the MG maximum removal percentage was achieved within 20 min. The adsorption of MG follows the pseudo-second-order with a combination of intraparticle diffusion model.

  15. Highly efficient ultrasonic-assisted removal of Hg(II) ions on graphene oxide modified with 2-pyridinecarboxaldehyde thiosemicarbazone: Adsorption isotherms and kinetics studies.

    PubMed

    Tadjarodi, Azadeh; Moazen Ferdowsi, Somayeh; Zare-Dorabei, Rouholah; Barzin, Ahmad

    2016-11-01

    A novel adsorbent, based on modifying graphene oxide (GO) chemically with 2-pyridinecarboxaldehyde thiosemicarbazone (2-PTSC) as ligand, was designed by facile process for removal of Hg(II) from aqueous solution. Characterization of the adsorbent was performed using various techniques, such as FT-IR, XRD, XPS, SEM and AFM analysis. The adsorption capacity was affected by variables such as adsorbent dosage, pH solution, Hg(2+) initial concentration and sonicating time. These variables were optimized by rotatable central composite design (CCD) under response surface methodology (RSM). The predictive model for Hg(II) adsorption was constructed and applied to find the best conditions at which the responses were maximized. In this conditions, the adsorption capacity of this adsorbent for Hg(2+) ions was calculated to be 309mgg(-1) that was higher than that of GO. Appling the ultrasound power combined with adsorption method was very efficient in shortening the removal time of Hg(2+) ions by enhancing the dispersion of adsorbent and metal ions in solution and effective interactions among them. The adsorption process was well described by second-order kinetic and Langmuir isotherm model in which the maximum adsorption capacity (Qm) was found to be 555mgg(-1) for adsorption of Hg(2+) ions over the obtained adsorbent. The performance of adsorbent was examined on the real wastewaters and confirmed the applicability of adsorbent for practical applications. PMID:27245963

  16. 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

  17. Heavy Metal Adsorption onto Kappaphycus sp. from Aqueous Solutions: The Use of Error Functions for Validation of Isotherm and Kinetics Models.

    PubMed

    Rahman, Md Sayedur; Sathasivam, Kathiresan V

    2015-01-01

    Biosorption process is a promising technology for the removal of heavy metals from industrial wastes and effluents using low-cost and effective biosorbents. In the present study, adsorption of Pb(2+), Cu(2+), Fe(2+), and Zn(2+) onto dried biomass of red seaweed Kappaphycus sp. was investigated as a function of pH, contact time, initial metal ion concentration, and temperature. The experimental data were evaluated by four isotherm models (Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich) and four kinetic models (pseudo-first-order, pseudo-second-order, Elovich, and intraparticle diffusion models). The adsorption process was feasible, spontaneous, and endothermic in nature. Functional groups in the biomass involved in metal adsorption process were revealed as carboxylic and sulfonic acids and sulfonate by Fourier transform infrared analysis. A total of nine error functions were applied to validate the models. We strongly suggest the analysis of error functions for validating adsorption isotherm and kinetic models using linear methods. The present work shows that the red seaweed Kappaphycus sp. can be used as a potentially low-cost biosorbent for the removal of heavy metal ions from aqueous solutions. Further study is warranted to evaluate its feasibility for the removal of heavy metals from the real environment. PMID:26295032

  18. Removal of uranium(VI) from aqueous solutions by manganese oxide coated zeolite: discussion of adsorption isotherms and pH effect.

    PubMed

    Han, Runping; Zou, Weihua; Wang, Yi; Zhu, Lu

    2007-01-01

    This paper discusses the adsorption properties for uranium(VI) by manganese oxide coated zeolite (MOCZ). The removal of uranium(VI) from aqueous solution by adsorption onto MOCZ in a single-component system with various contact times, pH, competitive ions, temperatures and initial concentrations of uranium(VI) was investigated. The experimental results were fitted to the Langmuir, Freundlich and the three-parameter Redlich-Peterson model isotherms to obtain the characteristic parameters of each model. Both the Langmuir and Redlich-Peterson isotherms were found to best represent the measured adsorption data. According to the evaluation using the Langmuir equation, the maximum adsorption capacity of uranium(VI) ions onto MOCZ was 15.1 mg g(-1) at 293K and pH 4.0. Using the thermodynamic equilibrium constants obtained at different temperatures, various thermodynamic parameters, such as DeltaG(0), DeltaH(0) and DeltaS(0), have been calculated. The thermodynamics of uranium(VI) ion/MOCZ system indicates the spontaneous and endothermic nature of the process. It was noted that an increase in temperature resulted in a higher uranium loading per unit weight of the adsorbent. PMID:17258360

  19. Heavy Metal Adsorption onto Kappaphycus sp. from Aqueous Solutions: The Use of Error Functions for Validation of Isotherm and Kinetics Models

    PubMed Central

    Rahman, Md. Sayedur; Sathasivam, Kathiresan V.

    2015-01-01

    Biosorption process is a promising technology for the removal of heavy metals from industrial wastes and effluents using low-cost and effective biosorbents. In the present study, adsorption of Pb2+, Cu2+, Fe2+, and Zn2+ onto dried biomass of red seaweed Kappaphycus sp. was investigated as a function of pH, contact time, initial metal ion concentration, and temperature. The experimental data were evaluated by four isotherm models (Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich) and four kinetic models (pseudo-first-order, pseudo-second-order, Elovich, and intraparticle diffusion models). The adsorption process was feasible, spontaneous, and endothermic in nature. Functional groups in the biomass involved in metal adsorption process were revealed as carboxylic and sulfonic acids and sulfonate by Fourier transform infrared analysis. A total of nine error functions were applied to validate the models. We strongly suggest the analysis of error functions for validating adsorption isotherm and kinetic models using linear methods. The present work shows that the red seaweed Kappaphycus sp. can be used as a potentially low-cost biosorbent for the removal of heavy metal ions from aqueous solutions. Further study is warranted to evaluate its feasibility for the removal of heavy metals from the real environment. PMID:26295032

  20. CO2 adsorption isotherm on clay minerals and the CO2 accessibility into the clay interlayer

    NASA Astrophysics Data System (ADS)

    Gensterblum, Yves; Bertier, Pieter; Busch, Andreas; Rother, Gernot; Krooß, Bernhard

    2013-04-01

    Large-scale CO2 storage in porous rock formations at 1-3 km depth is seen as a global warming mitigation strategy. In this process, CO2 is separated from the flue gas of coal or gas power plants, compressed, and pumped into porous subsurface reservoirs with overlying caprocks (seals). Good seals are mechanically and chemically stable caprocks with low porosity and permeability. They prevent leakage of buoyant CO2 from the reservoir. Caprocks are generally comprised of thick layers of shale, and thus mainly consist of clay minerals. These clays can be affected by CO2-induced processes, such as swelling or dissolution. The interactions of CO2 with clay minerals in shales are at present poorly understood. Sorption measurements in combination scattering techniques could provide fundamental insight into the mechanisms governing CO2-clay interaction. Volumetric sorption techniques have assessed the sorption of supercritical CO2 onto coal (Gensterblum et al., 2010; Gensterblum et al., 2009), porous silica (Rother et al., 2012a) and clays as a means of exploring the potential of large-scale storage of anthropogenic CO2 in geological reservoirs (Busch et al., 2008). On different clay minerals and shales, positive values of excess sorption were measured at gas pressures up to 6 MPa, where the interfacial fluid is assumed to be denser than the bulk fluid. However, zero and negative values were obtained at higher densities, which suggests the adsorbed fluid becomes equal to and eventually less dense than the corresponding bulk fluid, or that the clay minerals expand on CO2 charging. Using a combination of neutron diffraction and excess sorption measurements, we recently deduced the interlayer density of scCO2 in Na-montmorillonite clay in its single-layer hydration state (Rother et al., 2012b), and confirmed its low density, as well as the expansion of the basal spacings. We performed neutron diffraction experiments at the FRMII diffractometer on smectite, kaolinite and illite

  1. Evaluating the long-term performance of low-cost adsorbents using small-scale adsorption column experiments.

    PubMed

    Callery, O; Healy, M G; Rognard, F; Barthelemy, L; Brennan, R B

    2016-09-15

    This study investigated a novel method of predicting the long-term phosphorus removal performance of large-scale adsorption filters, using data derived from short-term, small-scale column experiments. The filter media investigated were low-cost adsorbents such as aluminum sulfate drinking water treatment residual, ferric sulfate drinking water treatment residual, and fine and coarse crushed concretes. Small-bore adsorption columns were loaded with synthetic wastewater, and treated column effluent volume was plotted against the mass of phosphorus adsorbed per unit mass of filter media. It was observed that the curve described by the data strongly resembled that of a standard adsorption isotherm created from batch adsorption data. Consequently, it was hypothesized that an equation following the form of the Freundlich isotherm would describe the relationship between filter loading and media saturation. Moreover, the relationship between filter loading and effluent concentration could also be derived from this equation. The proposed model was demonstrated to accurately predict the performance of large-scale adsorption filters over a period of up to three months with a very high degree of accuracy. Furthermore, the coefficients necessary to produce said model could be determined from just 24 h of small-scale experimental data. PMID:27295617

  2. Ethane adsorption on aggregates of dahlia-like nanohorns: experiments and computer simulations.

    PubMed

    Russell, Brice A; Migone, Aldo D; Petucci, Justin; Mercedes Calbi, M; Yudasaka, Masako; Iijima, Sumio

    2016-06-01

    This is a report on a study of the adsorption characteristics of ethane on aggregates of unopened dahlia-like carbon nanohorns. This sorbent presents two main groups of adsorption sites: the outside surface of individual nanohorns and deep, interstitial spaces between neighbouring nanohorns towards the interior of the aggregates. We have explored the equilibrium properties of the adsorbed ethane films by determining the adsorption isotherms and isosteric heat of adsorption. Computer simulations performed on different model structures indicate that the majority of ethane adsorption occurs on the outer region of the aggregates, near the ends of the nanohorns. We have also measured the kinetics of adsorption of ethane on this sorbent. The measurements and simulations were conducted along several isotherms spanning the range between 120 K and 220 K. PMID:27218414

  3. Use of solid waste for chemical stabilization: Adsorption isotherms and {sup 13}C solid-state NMR study of hazardous organic compounds sorbed on coal fly ash

    SciTech Connect

    Netzel, D.A.; Lane, D.C.; Rovani, J.F.; Cox, J.D.; Clark, J.A.; Miknis, F.P.

    1993-09-01

    Adsorption of hazardous organic compounds on the Dave Johnston plant fly ash is described. Fly ash from Dave Johnston and Laramie River power plants were characterized using elemental, x-ray, and {sup 29}Si NMR; the Dave Johnston (DJ) fly ash had higher quartz contents, while the Laramie River fly ash had more monomeric silicate anions. Adsorption data for hydroaromatics and chlorobenzenes indicate that the adsorption capacity of DJ coal fly ash is much less than that of activated carbon by a factor of >3000; but it is needed to confirm that solid-gas and solid-liquid equilibrium isotherms can indeed be compared. However, for pyridine, pentachlorophenol, naphthalene, and 1,1,2,2-tetrachloroethane, the DJ fly ash appears to adsorb these compounds nearly as well as activated carbon. {sup 13}C NMR was used to study the adsorption of hazardous org. cpds on coal fly ash; the nuclear spin relaxation times often were very long, resulting in long experimental times to obtain a spectrum. Using a jumbo probe, low concentrations of some hazardous org. cpds could be detected; for pentachlorophenol adsorbed onto fly ash, the chemical shift of the phenolic carbon was changed. Use of NMR to study the adsorption needs further study.

  4. Silicate liquid immiscibility in isothermal crystallization experiments. [lunar-evolution simulation

    NASA Technical Reports Server (NTRS)

    Longhi, J.

    1990-01-01

    The role of silicate liquid immiscibility (SLI) in the petrogenesis of lunar granites was investigated in experiments in which four glasses were synthesized from reagent-grade oxides and carbonates with the compositions of two of the sets of coexisting liquids reported by Hess et al. (1975): a KREEP basalt derivative and a mare basalt derivative. Isothermal crystallization experiments showed that SLI is a stable phenomenon in residual lunar liquids saturated with plagioclase, and is likely to produce large compositional separations. The results indicate that controlled-cooling-rate experiments of Rutherford et al. (1974), and Hess et al. (1975, 1978) were substantially correct analogs of the natural process of liquid immiscibility.

  5. Can carbon surface oxidation shift the pore size distribution curve calculated from Ar, N2 and CO2 adsorption isotherms? Simulation results for a realistic carbon model

    NASA Astrophysics Data System (ADS)

    Furmaniak, Sylwester; Terzyk, Artur P.; Gauden, Piotr A.; Harris, Peter J. F.; Kowalczyk, Piotr

    2009-08-01

    Using the virtual porous carbon model proposed by Harris et al, we study the effect of carbon surface oxidation on the pore size distribution (PSD) curve determined from simulated Ar, N2 and CO2 isotherms. It is assumed that surface oxidation is not destructive for the carbon skeleton, and that all pores are accessible for studied molecules (i.e., only the effect of the change of surface chemical composition is studied). The results obtained show two important things, i.e., oxidation of the carbon surface very slightly changes the absolute porosity (calculated from the geometric method of Bhattacharya and Gubbins (BG)); however, PSD curves calculated from simulated isotherms are to a greater or lesser extent affected by the presence of surface oxides. The most reliable results are obtained from Ar adsorption data. Not only is adsorption of this adsorbate practically independent from the presence of surface oxides, but, more importantly, for this molecule one can apply the slit-like model of pores as the first approach to recover the average pore diameter of a real carbon structure. For nitrogen, the effect of carbon surface chemical composition is observed due to the quadrupole moment of this molecule, and this effect shifts the PSD curves compared to Ar. The largest differences are seen for CO2, and it is clearly demonstrated that the PSD curves obtained from adsorption isotherms of this molecule contain artificial peaks and the average pore diameter is strongly influenced by the presence of electrostatic adsorbate-adsorbate as well as adsorbate-adsorbent interactions.

  6. Can carbon surface oxidation shift the pore size distribution curve calculated from Ar, N(2) and CO(2) adsorption isotherms? Simulation results for a realistic carbon model.

    PubMed

    Furmaniak, Sylwester; Terzyk, Artur P; Gauden, Piotr A; Harris, Peter J F; Kowalczyk, Piotr

    2009-08-01

    Using the virtual porous carbon model proposed by Harris et al, we study the effect of carbon surface oxidation on the pore size distribution (PSD) curve determined from simulated Ar, N(2) and CO(2) isotherms. It is assumed that surface oxidation is not destructive for the carbon skeleton, and that all pores are accessible for studied molecules (i.e., only the effect of the change of surface chemical composition is studied). The results obtained show two important things, i.e., oxidation of the carbon surface very slightly changes the absolute porosity (calculated from the geometric method of Bhattacharya and Gubbins (BG)); however, PSD curves calculated from simulated isotherms are to a greater or lesser extent affected by the presence of surface oxides. The most reliable results are obtained from Ar adsorption data. Not only is adsorption of this adsorbate practically independent from the presence of surface oxides, but, more importantly, for this molecule one can apply the slit-like model of pores as the first approach to recover the average pore diameter of a real carbon structure. For nitrogen, the effect of carbon surface chemical composition is observed due to the quadrupole moment of this molecule, and this effect shifts the PSD curves compared to Ar. The largest differences are seen for CO(2), and it is clearly demonstrated that the PSD curves obtained from adsorption isotherms of this molecule contain artificial peaks and the average pore diameter is strongly influenced by the presence of electrostatic adsorbate-adsorbate as well as adsorbate-adsorbent interactions. PMID:21828590

  7. Protein adsorption and interfacial rheology interfering in dilatational experiment

    NASA Astrophysics Data System (ADS)

    Rühs, P. A.; Scheuble, N.; Windhab, E. J.; Fischer, P.

    2013-05-01

    The static and dilatational response of β-lactoglobulin fibrils and native β-lactoglobulin (monomers) at water-air and water-oil interfaces (pH 2) was measured using the pendant drop method. The resulting adsorption behavior and viscoelasticity is dependent of concentration and adsorption time. The interfacial pressure of the β-lactoglobulin fibrils obtained in static measurements was 16-18 mN/m (against air) and 7 mN/m (against oil) for all concentrations. With higher concentrations, faster adsorption kinetics and slightly higher interfacial and surface pressure is achieved but did not lead to higher viscoelastic moduli. The transient saturation of the interface is similar for both the fibril solution and the monomers, however the fibril solution forms a strong viscoelastic network. To evaluate the superimposed adsorption behavior and rheological properties, the formed interfacial layer was subjected to dilatational experiments, which were performed by oscillating the surface area of the drop in sinusoidal and sawtooth (diagonal) deformation manner. The sinusoidal oscillations (time depended area deformation rate) result in a complex interfacial tension behavior against air and oil interfaces and show remarkable differences during compression and expansion as emphasized by Lissajous figures. For diagonal (constant area deformation rate) experiments, a slight bending of the interfacial tension response was observed at low frequencies emphasizing the influence of protein adsorption during rheological measurements.

  8. Protein adsorption on low temperature isotropic carbon. III. Isotherms, competitivity, desorption and exchange of human albumin and fibrinogen.

    PubMed

    Feng, L; Andrade, J D

    1994-04-01

    In this paper we consider the adsorption of albumin and fibrinogen on low temperature isotropic carbon (LTIC). A subsequent paper considers the adsorption of other plasma proteins [Feng L, Andrade JD, Colloids and Surfaces (in press)]. Carbon fragments and silica plates were used as adsorbents. Adsorption was carried out by incubating the adsorbents in solutions of 125I-labelled and unlabelled proteins (single component system), or with buffer-diluted human plasma (multicomponent system). Adsorbed proteins then underwent displacement by buffer, by single protein solutions or by dilute plasma. Results show that the LTIC substrate adsorbs a large amount of proteins before saturation, which may be due to multilayer adsorption. LTIC also irreversibly holds adsorbed proteins against the exchange agents used; little adsorbed proteins can be displaced, even after a very short adsorption time. There is no preferential adsorption for either albumin or fibrinogen on LTIC from their binary solutions, suggesting that both proteins have high affinities for the surface. Such strong interactions between LTIC and proteins are not attributed to electrostatic interactions. On the other hand, protein adsorption on the silica surface is selective and reversible, with a much higher affinity for fibrinogen than albumin and an even higher affinity for some other plasma proteins. The paper also discusses the effect of sequential protein addition to a solution on the surface concentration and suppression of adsorption of both proteins in the presence of other plasma proteins. A very important conclusion is that the LTIC surface is very active towards proteins adsorption. PMID:8061122

  9. Isothermal Dendritic Growth Experiment (IDGE) Is the First United States Microgravity Experiment Controlled From the Principal Investigator's University

    NASA Technical Reports Server (NTRS)

    Malarik, Diane C.; Glicksman, Martin E.

    1997-01-01

    The scientific objective of the Isothermal Dendritic Growth Experiment (IDGE) is to test fundamental assumptions about dendritic solidification of molten materials. IDGE is a microgravity materials science experiment using apparatus that was designed, built, tested, and operated by people from the NASA Lewis Research Center. The IDGE experiment was conceived by the principal investigator, Professor Martin E. Glicksman from Rensselaer Polytechnic Institute in Troy, New York. This experiment was a team effort of civil servants from the NASA Lewis Research Center, contractors from Aerospace Design & Fabrication, Inc. (ADF), and personnel at Rensselaer.

  10. Non-isothermal infiltration and tracer transport experiments on large soil columns

    NASA Astrophysics Data System (ADS)

    Sobotkova, Martina; Snehota, Michal; Cejkova, Eva; Tesar, Miroslav

    2016-04-01

    Isothermal and non-isothermal infiltration experiments were carried out in the laboratory on large undisturbed soil columns (19 cm in diameter, 25 cm high) taken at the experimental catchments Roklan (Sumava Mountains, Czech Republic) and Uhlirska (Jizera Mountains, Czech republic). The aim of the study was twofold. The first goal was to obtain water flow and heat transport data for indirect parameter estimation of thermal and hydraulic properties of soils from two sites by inverse modelling. The second aim was to investigate the extent of impact of the temperature on saturated hydraulic conductivity (Ksat) and dispersity of solute transport. The temperature of infiltrating water in isothermal experiment (20 °C) was equal to the initial temperature of the sample. For non-isothermal experiment water temperature was 5°C, while the initial temperature of the sample was 20°C as in previous case. The experiment was started by flooding the sample surface. Then water level was maintained at constant level throughout the infiltration run using the optical sensor and peristaltic pump. Concentration pulse of deuterium was applied at the top of the soil sample, during the steady state flow. Initial pressure head in the sample was close to field capacity. Two tensiometers and two temperature sensors were inserted in the soil sample in two depths (9 and 15 cm below the top of the sample). Two additional temperature sensors monitored the temperature entering and leaving the samples. Water drained freely through the perforated plate at the bottom of sample by gravity. Inflow and outflow water flux densities, water pressure heads and soil temperatures were monitored continuously during experiments. Effluent was sampled in regular time intervals and samples were analysed for deuterium concentrations by laser spectroscopy to develop breakthrough curves. The outcome of experiments are the series of measured water fluxes, pressure heads and temperatures ready for inverse modelling

  11. ISOTHERMAL AIR INGRESS VALIDATION EXPERIMENTS AT IDAHO NATIONAL LABORATORY: DESCRIPTION AND SUMMARY OF DATA

    SciTech Connect

    Chang H. Oh; Eung S. Kim

    2010-09-01

    Idaho National Laboratory performed air ingress experiments as part of validating computational fluid dynamics code (CFD). An isothermal stratified flow experiment was designed and set to understand stratified flow phenomena in the very high temperature gas cooled reactor (VHTR) and to provide experimental data for validating computer codes. The isothermal experiment focused on three flow characteristics unique in the VHTR air-ingress accident: stratified flow in the horizontal pipe, stratified flow expansion at the pipe and vessel junction, and stratified flow around supporting structures. Brine and sucrose were used as heavy fluids and water was used as light fluids. The density ratios were changed between 0.87 and 0.98. This experiment clearly showed that a stratified flow between heavy and light fluids is generated even for very small density differences. The code was validated by conducting blind CFD simulations and comparing the results to the experimental data. A grid sensitivity study was also performed based on the Richardson extrapolation and the grid convergence index method for modeling confidence. As a result, the calculated current speed showed very good agreement with the experimental data, indicating that the current CFD methods are suitable for predicting density gradient stratified flow phenomena in the air-ingress accident.

  12. Glyphosate and AMPA adsorption in soils: laboratory experiments and pedotransfer rules.

    PubMed

    Sidoli, Pauline; Baran, Nicole; Angulo-Jaramillo, Rafael

    2016-03-01

    Adsorption of the herbicide glyphosate and its main metabolite AMPA (aminomethylphosphonic acid) was investigated on 17 different agricultural soils. Batch equilibration adsorption data are shown by Freundlich adsorption isotherms. Glyphosate adsorption is clearly affected by equilibration concentrations, but the nonlinear AMPA adsorption isotherms indicate saturation of the adsorption sites with increasing equilibrium concentrations. pHCaCl2 (i.e. experimental pH) is the major parameter governing glyphosate and AMPA adsorption in soils. However, considering pHCaCl2 values, available phosphate amount, and amorphous iron and aluminium oxide contents by using a nonlinear multiple regression equation, obtains the most accurate and powerful pedotransfer rule for predicting the adsorption constants for these two molecules. As amorphous iron and aluminium oxide contents in soil are not systematically determined, we also propose a pedotransfer rule with two variables-pHCaCl2 values and available phosphate amount-that remains acceptable for both molecules. Moreover, the use of the commonly measured pHwater or pHKCl values gives less accurate results compared to pHCaCl2 measurements. To our knowledge, this study is the first AMPA adsorption characterization for a significant number of temperate climate soils. PMID:26581693

  13. Generalized adsorption isotherms for molecular and dissociative adsorption of a polar molecular species on two polar surface geometries: Perovskite (100) (Pm-3m) and fluorite (111) (Fm-3m)

    DOE PAGESBeta

    Danielson, Thomas; Hin, Celine; Savara, Aditya

    2016-08-10

    Lattice based kinetic Monte Carlo (KMC) simulations have been used to determine a functional form for the second order adsorption isotherms on two commonly investigated crystal surfaces: the (111) fluorite surface and the (100) perovskite surface which has the same geometric symmetry as the NaCl (100) surface. The functional form is generalized to be applicable to all values of the equilibrium constant by a shift along the pressure axis. Functions have been determined for estimating the pressure at which a desired coverage would be achieved and for estimating the coverage at a certain pressure. The generalized form has been calculatedmore » by investigating the surface adsorbate coverage across a range of thermodynamic equilibrium constants that span the range 10-26 to 1013. Finally, the equations have been shown to be general for any value of the adsorption equilibrium constant.« less

  14. Generalized adsorption isotherms for molecular and dissociative adsorption of a polar molecular species on two polar surface geometries: Perovskite (100) (Pm-3m) and fluorite (111) (Fm-3m)

    NASA Astrophysics Data System (ADS)

    Danielson, Thomas; Hin, Celine; Savara, Aditya

    2016-08-01

    Lattice based kinetic Monte Carlo simulations have been used to determine a functional form for the second order adsorption isotherms on two commonly investigated crystal surfaces: the (111) fluorite surface and the (100) perovskite surface which has the same geometric symmetry as the NaCl (100) surface. The functional form is generalized to be applicable to all values of the equilibrium constant by a shift along the pressure axis. Functions have been determined for estimating the pressure at which a desired coverage would be achieved and, conversely, for estimating the coverage at a certain pressure. The generalized form has been calculated by investigating the surface adsorbate coverage across a range of thermodynamic equilibrium constants that span the range 10-26 to 1013. The equations have been shown to be general for any value of the adsorption equilibrium constant.

  15. Optimization, isotherm, kinetic and thermodynamic studies of Pb(II) ions adsorption onto N-maleated chitosan-immobilized TiO₂ nanoparticles from aqueous media.

    PubMed

    Shaker, Medhat A; Yakout, Amr A

    2016-02-01

    Chitosan, CS was chemically engineered by maleic anhydride via simple protocol to produce N-maleated chitosan, MCS which immobilized on anatase TiO2 to synthesize novel eco-friendly nanosorbent (51±3.8 nm), MCS@TiO2 for cost-effective and efficient removal of Pb(II) ions from aqueous media. The chemical structure, surface properties and morphology of MCS@TiO2 were recognized by FTIR, (1)H NMR, XRD, TEM, DLS and zeta-potential techniques. The relations between %removal of Pb(II) and different analytical parameters such as solution acidity (pH), MCS@TiO2 dosage, time of contact and initial Pb(II) concentration were optimized using response surface methodology (RSM) and Box-Behnken design (BBD) statistical procedures. The fitting of the experimental data to four different isotherm models at optimized conditions was carried out by various statistical treatments including the correlation coefficient (r), coefficient of determination (r(2)) and non-linear Chi-square (χ(2)) test analyses which all confirm the suitability of Langmuir model to explain the adsorption isotherm data. Also, statistics predicted that the pseudo-second-order model is the optimum kinetic model among four applied kinetic models to closely describe the rate equation of the adsorption process. Thermodynamics viewed the adsorption as endothermic and feasible physical process. EDTA could release the sorbed Pb(II) ions from MCS@TiO2 with a recovery above 92% after three sorption-desorption cycles. The novel synthesized nanosorbent is evidenced to be an excellent solid phase extractor for Pb(II) ions from wastewaters. PMID:26520475

  16. Optimization, isotherm, kinetic and thermodynamic studies of Pb(II) ions adsorption onto N-maleated chitosan-immobilized TiO2 nanoparticles from aqueous media

    NASA Astrophysics Data System (ADS)

    Shaker, Medhat A.; Yakout, Amr A.

    2016-02-01

    Chitosan, CS was chemically engineered by maleic anhydride via simple protocol to produce N-maleated chitosan, MCS which immobilized on anatase TiO2 to synthesize novel eco-friendly nanosorbent (51 ± 3.8 nm), MCS@TiO2 for cost-effective and efficient removal of Pb(II) ions from aqueous media. The chemical structure, surface properties and morphology of MCS@TiO2 were recognized by FTIR, 1H NMR, XRD, TEM, DLS and zeta-potential techniques. The relations between %removal of Pb(II) and different analytical parameters such as solution acidity (pH), MCS@TiO2 dosage, time of contact and initial Pb(II) concentration were optimized using response surface methodology (RSM) and Box-Behnken design (BBD) statistical procedures. The fitting of the experimental data to four different isotherm models at optimized conditions was carried out by various statistical treatments including the correlation coefficient (r), coefficient of determination (r2) and non-linear Chi-square (χ2) test analyses which all confirm the suitability of Langmuir model to explain the adsorption isotherm data. Also, statistics predicted that the pseudo-second-order model is the optimum kinetic model among four applied kinetic models to closely describe the rate equation of the adsorption process. Thermodynamics viewed the adsorption as endothermic and feasible physical process. EDTA could release the sorbed Pb(II) ions from MCS@TiO2 with a recovery above 92% after three sorption-desorption cycles. The novel synthesized nanosorbent is evidenced to be an excellent solid phase extractor for Pb(II) ions from wastewaters.

  17. Follow-on Research Activities for the Rensselaer Isothermal Dendritic Growth Experiment (RIDGE)

    NASA Technical Reports Server (NTRS)

    LaCombe, J. C.; Koss, M. B.; Lupulescu, A. O.; Frei, J. E.; Giummarra, C.; Glicksman, M. E.

    2001-01-01

    The RIDGE effort continues the aegis of the earlier, NASA-sponsored, Isothermal Dendritic Growth Experiment (IDGE) series of experiments through the continued analysis of microgravity data acquired during these earlier space flights. The preliminary observations presented here demonstrate that there are significant differences between SCN and the more anisotropic PVA dendrites. The side branch structure becomes amplified only further behind the tip, and the interface shape is generally wider (i.e. more hyperbolic than parabolic) in PVA than in SCN. These characteristics are seen to affect the process of heat transport. Additionally, the dendrites grown during the fourth United States Microgravity Payload (USMP-4) exhibit time-dependent growth characteristics and may not always have reached steady-state growth during the experiment.

  18. Adsorption of Cd(II) by Mg-Al-CO3- and magnetic Fe3O4/Mg-Al-CO3-layered double hydroxides: Kinetic, isothermal, thermodynamic and mechanistic studies.

    PubMed

    Shan, Ran-ran; Yan, Liang-guo; Yang, Kun; Hao, Yuan-feng; Du, Bin

    2015-12-15

    Understanding the adsorption mechanisms of metal cations on the surfaces of solids is important for determining the fate of these metals in water and wastewater treatment. The adsorption kinetic, isothermal, thermodynamic and mechanistic properties of cadmium (Cd(II)) in an aqueous solution containing Mg-Al-CO3- and magnetic Fe3O4/Mg-Al-CO3-layered double hydroxide (LDH) were studied. The results demonstrated that the adsorption kinetic and isotherm data followed the pseudo-second-order model and the Langmuir equation, respectively. The adsorption process of Cd(II) was feasible, spontaneous and endothermic in nature. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy were used to explain the adsorption mechanisms. The characteristic XRD peaks and FTIR bands of CdCO3 emerged in the LDH spectra after Cd(II) adsorption, which indicated that the adsorption of Cd(II) by LDHs occurred mainly via CdCO3 precipitation, surface adsorption and surface complexation. Furthermore, the magnetic Fe3O4/Mg-Al-CO3-LDH can be quickly and easily separated using a magnet before and after the adsorption process. PMID:26073520

  19. Precipitation and surface adsorption of metal complexes during electropolishing. Theory and characterization with X-ray nanotomography and surface tension isotherms.

    PubMed

    Nave, Maryana I; Chen-Wiegart, Yu-chen Karen; Wang, Jun; Kornev, Konstantin G

    2015-09-21

    Electropolishing of metals often leads to supersaturation conditions resulting in precipitation of complex compounds. The solubility diagrams and Gibbs adsorption isotherms of the electropolishing products are thus very important to understand the thermodynamic mechanism of precipitation of reaction products. Electropolishing of tungsten wires in aqueous solutions of potassium hydroxide is used as an example illustrating the different thermodynamic scenarios of electropolishing. Electropolishing products are able to form highly viscous films immiscible with the surrounding electrolyte or porous shells adhered to the wire surface. Using X-ray nanotomography, we discovered a gel-like phase formed at the tungsten surface during electropolishing. The results of these studies suggest that the electropolishing products can form a rich library of compounds. The surface tension of the electrolyte depends on the metal oxide ions and alkali-metal complexes. PMID:26279498

  20. Near-isothermal furnace for in situ and real time X-ray radiography solidification experiments

    NASA Astrophysics Data System (ADS)

    Becker, M.; Dreißigacker, C.; Klein, S.; Kargl, F.

    2015-06-01

    In this paper, we present a newly developed near-isothermal X-ray transparent furnace for in situ imaging of solidification processes in thin metallic samples. We show that the furnace is ideally suited to study equiaxed microstructure evolution and grain interaction. To observe the growth dynamics of equiaxed dendritic structures, a minimal temperature gradient across the sample is required. A uniform thermal profile inside a circular sample is achieved by positioning the sample in the center of a cylindrical furnace body surrounded by a circular heater arrangement. Performance tests with the hypo-eutectic Al-15wt.%Cu and the near-eutectic Al-33wt.%Cu alloys validate the near-isothermal character of the sample environment. Controlled cooling rates of less than 0.5 K min-1 up to 10 K min-1 can be achieved in a temperature range of 720 K-1220 K. Integrated in our rotatable laboratory X-ray facility, X-RISE, the furnace provides a large field of view of 10.5 mm in diameter and a high spatial resolution of ˜4 μm. With the here presented furnace, equiaxed dendrite growth models can be rigorously tested against experiments on metal alloys by, e.g., enabling dendrite growth velocities to be determined as a function of undercooling or solutal fields in front of the growing dendrite to be measured.

  1. Near-isothermal furnace for in situ and real time X-ray radiography solidification experiments

    SciTech Connect

    Becker, M. Dreißigacker, C.; Klein, S.; Kargl, F.

    2015-06-15

    In this paper, we present a newly developed near-isothermal X-ray transparent furnace for in situ imaging of solidification processes in thin metallic samples. We show that the furnace is ideally suited to study equiaxed microstructure evolution and grain interaction. To observe the growth dynamics of equiaxed dendritic structures, a minimal temperature gradient across the sample is required. A uniform thermal profile inside a circular sample is achieved by positioning the sample in the center of a cylindrical furnace body surrounded by a circular heater arrangement. Performance tests with the hypo-eutectic Al-15wt.%Cu and the near-eutectic Al-33wt.%Cu alloys validate the near-isothermal character of the sample environment. Controlled cooling rates of less than 0.5 K min{sup −1} up to 10 K min{sup −1} can be achieved in a temperature range of 720 K–1220 K. Integrated in our rotatable laboratory X-ray facility, X-RISE, the furnace provides a large field of view of 10.5 mm in diameter and a high spatial resolution of ∼4 μm. With the here presented furnace, equiaxed dendrite growth models can be rigorously tested against experiments on metal alloys by, e.g., enabling dendrite growth velocities to be determined as a function of undercooling or solutal fields in front of the growing dendrite to be measured.

  2. Near-isothermal furnace for in situ and real time X-ray radiography solidification experiments.

    PubMed

    Becker, M; Dreißigacker, C; Klein, S; Kargl, F

    2015-06-01

    In this paper, we present a newly developed near-isothermal X-ray transparent furnace for in situ imaging of solidification processes in thin metallic samples. We show that the furnace is ideally suited to study equiaxed microstructure evolution and grain interaction. To observe the growth dynamics of equiaxed dendritic structures, a minimal temperature gradient across the sample is required. A uniform thermal profile inside a circular sample is achieved by positioning the sample in the center of a cylindrical furnace body surrounded by a circular heater arrangement. Performance tests with the hypo-eutectic Al-15wt.%Cu and the near-eutectic Al-33wt.%Cu alloys validate the near-isothermal character of the sample environment. Controlled cooling rates of less than 0.5 K min(-1) up to 10 K min(-1) can be achieved in a temperature range of 720 K-1220 K. Integrated in our rotatable laboratory X-ray facility, X-RISE, the furnace provides a large field of view of 10.5 mm in diameter and a high spatial resolution of ∼4 μm. With the here presented furnace, equiaxed dendrite growth models can be rigorously tested against experiments on metal alloys by, e.g., enabling dendrite growth velocities to be determined as a function of undercooling or solutal fields in front of the growing dendrite to be measured. PMID:26133847

  3. A study of the adsorption of the amphiphilic penicillins cloxacillin and dicloxacillin onto human serum albumin using surface tension isotherms

    NASA Astrophysics Data System (ADS)

    Barbosa, Silvia; Leis, David; Taboada, Pablo; Attwood, David; Mosquera, Victor

    The interaction of human serum albumin (HSA) with two structurally similar anionic amphiphilic penicillins, cloxacillin and dicloxacillin, at 25°C has been examined by surface tension measurements under conditions at which the HSA molecule was positively (pH 4.5) or negatively charged (pH 7.4). Measurements were at fixed HSA concentrations (0.0125 and 0.125% w/v) and at drug concentrations over a range including, where possible, the critical micelle concentration (cmc). Interaction between anionic drugs and positively charged HSA at pH 7.4 resulted in an increase of the cmc of each drug as a consequence of its removal from solution by adsorption. Limited data for cloxacillin at pH 4.5 indicated an apparent decrease of the cmc in the presence of HSA suggesting a facilitation of the aggregation by association with the protein. Changes in the surface tension-log (drug concentration) plots in the presence of HSA have been discussed in terms of the adsorption of drug at the air-solution and protein-solution interfaces. Standard free energy changes associated with the micellization of both drugs and their adsorption at the air-solution interface have been calculated and compared.

  4. Isothermal Dendritic Growth Experiment - Science, engineering, and hardware development for USMP space flights

    NASA Technical Reports Server (NTRS)

    Glicksman, M. E.; Hahn, R. C.; Koss, M. B.; Tirmizi, S. H.; Selleck, M. E.; Velosa, A.; Winsa, E.

    1991-01-01

    The Isothermal Dendritic Growth Experiment (IDGE) has been designed to provide microgravity data on dendritic growth for a critical test of theory. This paper updates progress on constructing a crystal growth chamber suitable for space flight. The IDGE chamber is constructed from glass and stainless steel and is hermetically sealed by electron beam welds and glass-metal seals. Initial tests of the chambers sample's melting point plateau show that the new chamber design is capable of preserving the 99.9995 percent purity of succinonitrile. Dendrite growth can be initiated in the center of the IDGE chamber by means of thermo-electric coolers and a capillary injector tube (stinger). The new IDGE chamber is ready for fully integrated tests with the prototype IDGE engineering hardware at NASA's Lewis Research Center.

  5. Successful Isothermal Dendritic Growth Experiment (IDGE) Proves Current Theories of Dendritic Solidification are Flawed

    NASA Technical Reports Server (NTRS)

    1996-01-01

    The scientific objective of the Isothermal Dendritic Growth Experiment (IDGE) is to test fundamental assumptions about dendritic solidification of molten materials. "Dendrites"-- from the ancient Greek word for tree--are tiny branching structures that form inside molten metal alloys when they solidify during manufacturing. The size, shape, and orientation of the dendrites have a major effect on the strength, ductility (ability to be molded or shaped), and usefulness of an alloy. Nearly all of the cast metal alloys used in everyday products (such as automobiles and airplanes) are composed of thousands to millions of tiny dendrites. Gravity, present on Earth, causes convection currents in molten alloys that disturb dendritic solidification and make its precise study impossible. In space, gravity is negated by the orbiting of the space shuttle. Consequently, IDGE (which was conducted on the space shuttle) gathered the first precise data regarding undisturbed dendritic solidification. IDGE is a microgravity materials science experiment that uses an apparatus which was designed, built, tested, and operated by people from the NASA Lewis Research Center. This experiment was conceived by the principal investigator, Professor Martin E. Glicksman, from Rensselaer Polytechnic Institute in Troy, New York. The experiment was a team effort of Lewis civil servants, contractors from Aerospace Design & Fabrication Inc. (ADF), and personnel at Rensselaer.

  6. Phycoremediation and adsorption isotherms of cadmium and copper ions by Merismopedia tenuissima and their effect on growth and metabolism.

    PubMed

    Fawzy, Mustafa A

    2016-09-01

    The current study tends to investigate the removal of cadmium and copper ions by Merismopedia tenuissima, grown in different concentrations of cadmium and copper ions, as well to investigate their effects on growth and metabolism. Sorption isotherms of Langmuir and Freundlich were obtained for the quantitative description of cadmium and copper uptake by M. tenuissima. Langmuir model adequately to describe the data of biosorption for these metals. However, the Freundlich model could work well in case of Cu(2+) only. M. tenuissima appears to be more efficient for removing Cd(2+) ions than Cu(2+). However, the affinity constant of Cu(2+) on the biomass of M. tenuissima was higher than Cd(2+) indicating that M. tenuissima is more tolerant to Cd(2+) phytotoxicity than Cu(2+). FTIR analysis of algae with and without biosorption revealed the presence of carboxyl, amino, amide and hydroxyl groups, which were responsible for biosorption of Cd(+2) and Cu(+2) ions. PMID:27458699

  7. Comparative Study on the Implication of Three Nanoparticles on the Removal of Trichloroethylene by Adsorption - The Pilot and Rapid Small-Scale Column Tests

    EPA Science Inventory

    The impact of three commercially-available nanoparticles (NPs) on trichloroethylene (TCE) adsorption onto granular activated carbon (GAC) was investigated. TCE Adsorption isotherm and column breakthrough experiments were conducted in the presence and absence of silicon dioxide (S...

  8. The Freundlich adsorption isotherm constants and prediction of phosphorus bioavailability as affected by different phosphorus sources in two Kansas soils.

    PubMed

    Shafqat, Mustafa N; Pierzynski, Gary M

    2014-03-01

    Phosphorus (P) adsorption onto soil constituents influences P bioavailability from both agronomic and environmental perspectives. In this study, the P availability from different P sources along with utility of Freundlich adsorption coefficients on the predictability of various crop growth parameters were assessed. Two soils were amended with 150mgPkg(-1) each from six different P sources comprised of manures from two types of ruminants animals, three types of monogastric animals, and inorganic P fertilizer. Corn (Zea mays) was grown and harvested seven times under greenhouse conditions to remove P from the P amended treatments. The application of all P sources reduced the value of Freundlich K and increased the value of Freundlich 1/n and equilibrium P concentration (EPC0) in both soils compared to the un-amended control before cropping. The swine (Sus scrofa) manure (HM) resulted in significant smaller values of Freundlich K and larger values of 1/n in the P deficient Eram-Lebo soil compared to other P sources while, the opposite was true for the turkey (Meleagris gallopava) litter (TL) in the Ulysses soil. The corn biomass, tissue P concentration and P uptake were significantly influenced by all P sources during the first harvest and the total P uptake during seven harvests in both soils compared to the control treatment. Both Freundlich coefficients had strong relationships with the aforementioned corn parameters in the P deficient Eram-Lebo soil while, strength of the association was weak or missing in the Ulysses soil which had optimum levels of antecedent P. PMID:24238913

  9. Non-Isothermic Chemical Kinetics in the Undergraduate Laboratory: Arrhenius Parameters from Experiments with Hyperbolic Temperature Variation.

    ERIC Educational Resources Information Center

    Salvador, F.; And Others

    1984-01-01

    Describes a method which adapts itself to the characteristics of the kinetics of a chemical reaction in solution, enabling students to determine the Arrhenius parameters with satisfactory accuracy by means of a single non-isothermic experiment. Both activation energy and the preexponential factor values can be obtained by the method. (JN)

  10. Adsorption in single-walled carbon nanotubes by experiments and molecular simulation II: Effect of morphology and temperature on organic adsorption

    USGS Publications Warehouse

    Agnihotri, S.; Rostam-Abadi, M.; Mota, J.P.B.; Rood, M.J.

    2005-01-01

    Hexane adsorption on single-walled carbon nanotube (SWNT) bundles was studied. Hexane adsorption capacities of two purified SWNT samples was gravimetrically determined at isothermal conditions of 25??, 37??, and 50??C for 10-4 < p/po < 0.9, where p/po is hexane vapor pressure relative to its saturation pressure. Simulation of hexane adsorption under similar temperature and pressure conditions were performed on the external and internal sites of nanotube bundles of diameters same as those in experimental samples. The simulations could predict isotherms for a hypothetical scenario where all nanotubes in a sample would be open. This is an abstract of a paper presented at the AIChE Annual Meeting and Fall Showcase (Cincinnati, OH 10/30/2005-11/4/2005).

  11. Effects of Humidity Swings on Adsorption Columns for Air Revitalization: Modeling and Experiments

    NASA Technical Reports Server (NTRS)

    LeVan, M. Douglas; Finn, John E.

    1997-01-01

    Air purification systems are necessary to provide clean air in the closed environments aboard spacecraft. Trace contaminants are removed using adsorption. One major factor concerning the removal of trace contaminants is relative humidity. Water can reduce adsorption capacity and, due to constant fluctuations, its presence is difficult to incorporate into adsorption column designs. The purpose of the research was to allow for better design techniques in trace contaminant adsorption systems, especially for feeds with water present. Experiments and mathematical modeling research on effects of humidity swings on adsorption columns for air revitalization were carried out.

  12. Isotherms and kinetic study of dihydrogen and hydrogen phosphate ions (H{2}PO{4}- and HPO{4}2-) adsorption onto crushed plant matter of the semi-arid zones of Morocco: Asphodelus microcarpus, Asparagus albus and Senecio anthophorbium

    NASA Astrophysics Data System (ADS)

    Chiban, M.; Benhima, H.; Saadi, B.; Nounah, A.; Sinan, F.

    2005-03-01

    In the present work H{2}PO4- and HPO42- ions adsorption onto organic matter (OM) obtained from ground dried three plants growing in arid zones of Morocco has been studied. The adsorption process is affected by various parameters such as contact time, particle size and initial concentration of phosphate solution (Ci ≤ 30 mg/l). The uptake of both ions is increased by increasing the concentration of them selves. The retention of phosphate ions by Asphodelus microcarpus, Asparagus albus are well defined by several isotherms such as the Langmuir, Temkin and Freundlich.

  13. Evaluating protocols and analytical methods for peptide adsorption experiments.

    PubMed

    Fears, Kenan P; Petrovykh, Dmitri Y; Clark, Thomas D

    2013-12-01

    This paper evaluates analytical techniques that are relevant for performing reliable quantitative analysis of peptide adsorption on surfaces. Two salient problems are addressed: determining the solution concentrations of model GG-X-GG, X5, and X10 oligopeptides (G = glycine, X = a natural amino acid), and quantitative analysis of these peptides following adsorption on surfaces. To establish a uniform methodology for measuring peptide concentrations in water across the entire GG-X-GG and X n series, three methods were assessed: UV spectroscopy of peptides having a C-terminal tyrosine, the bicinchoninic acid (BCA) protein assay, and amino acid (AA) analysis. Due to shortcomings or caveats associated with each of the different methods, none were effective at measuring concentrations across the entire range of representative model peptides. In general, reliable measurements were within 30% of the nominal concentration based on the weight of as-received lyophilized peptide. In quantitative analysis of model peptides adsorbed on surfaces, X-ray photoelectron spectroscopy (XPS) data for a series of lysine-based peptides (GGKGG, K5, and K10) on Au substrates, and for controls incubated in buffer in the absence of peptides, suggested a significant presence of aliphatic carbon species. Detailed analysis indicated that this carbonaceous contamination adsorbed from the atmosphere after the peptide deposition. The inferred adventitious nature of the observed aliphatic carbon was supported by control experiments in which substrates were sputter-cleaned by Ar(+) ions under ultra-high vacuum (UHV) then re-exposed to ambient air. In contrast to carbon contamination, no adventitious nitrogen species were detected on the controls; therefore, the relative surface densities of irreversibly-adsorbed peptides were calculated by normalizing the N/Au ratios by the average number of nitrogen atoms per residue. PMID:24706133

  14. Effect of grain size on uranium(VI) surface complexation kinetics and adsorption additivity.

    PubMed

    Shang, Jianying; Liu, Chongxuan; Wang, Zheming; Zachara, John M

    2011-07-15

    The contribution of variable grain sizes to uranium adsorption/desorption was studied using a sediment from the US DOE Hanford site. The sediment was wet sieved into four size fractions: coarse sand (1-2 mm), medium sand (0.2-1 mm), fine sand (0.053-0.2 mm), and clay/silt fraction (<0.053 mm). For each size fraction and their composite (sediment), batch and flow-cell experiments were performed to determine uranium adsorption isotherms and kinetic uranium adsorption and subsequent desorption. The results showed that uranium adsorption isotherms and adsorption/desorption kinetics were size specific, reflecting the effects of size-specific adsorption site concentration and kinetic rate constants. The larger-size fraction had a larger mass percentage in the sediment but with a smaller adsorption site concentration and generally a slower uranium adsorption/desorption rate. The same equilibrium surface complexation reaction and reaction constant could describe uranium adsorption isotherms for all size fractions and the composite after accounting for the effect of adsorption site concentration. Mass-weighted, linear additivity was observed for both uranium adsorption isotherms and adsorption/desorption kinetics in the composite. One important implication of this study is that grain-size distribution may be used to estimate uranium adsorption site and adsorption/desorption kinetic rates in heterogeneous sediments from a common location. PMID:21648458

  15. Combined Yamamoto approach for simultaneous estimation of adsorption isotherm and kinetic parameters in ion-exchange chromatography.

    PubMed

    Rüdt, Matthias; Gillet, Florian; Heege, Stefanie; Hitzler, Julian; Kalbfuss, Bernd; Guélat, Bertrand

    2015-09-25

    Application of model-based design is appealing to support the development of protein chromatography in the biopharmaceutical industry. However, the required efforts for parameter estimation are frequently perceived as time-consuming and expensive. In order to speed-up this work, a new parameter estimation approach for modelling ion-exchange chromatography in linear conditions was developed. It aims at reducing the time and protein demand for the model calibration. The method combines the estimation of kinetic and thermodynamic parameters based on the simultaneous variation of the gradient slope and the residence time in a set of five linear gradient elutions. The parameters are estimated from a Yamamoto plot and a gradient-adjusted Van Deemter plot. The combined approach increases the information extracted per experiment compared to the individual methods. As a proof of concept, the combined approach was successfully applied for a monoclonal antibody on a cation-exchanger and for a Fc-fusion protein on an anion-exchange resin. The individual parameter estimations for the mAb confirmed that the new approach maintained the accuracy of the usual Yamamoto and Van Deemter plots. In the second case, offline size-exclusion chromatography was performed in order to estimate the thermodynamic parameters of an impurity (high molecular weight species) simultaneously with the main product. Finally, the parameters obtained from the combined approach were used in a lumped kinetic model to simulate the chromatography runs. The simulated chromatograms obtained for a wide range of gradient lengths and residence times showed only small deviations compared to the experimental data. PMID:26306913

  16. A Simple Rate Law Experiment Using a Custom-Built Isothermal Heat Conduction Calorimeter

    ERIC Educational Resources Information Center

    Wadso, Lars; Li, Xi.

    2008-01-01

    Most processes (whether physical, chemical, or biological) produce or consume heat: measuring thermal power (the heat production rate) is therefore a typical method of studying processes. Here we describe the design of a simple isothermal heat conduction calorimeter built for use in teaching; we also provide an example of its use in simultaneously…

  17. HIGH TEMPERATURE SULFATION STUDIES IN AN ISOTHERMAL REACTOR: A COMPARISON OF THEORY AND EXPERIMENT

    EPA Science Inventory

    The paper gives high-temperature isothermal data on sulfur dioxide (SO2) capture, obtained as a function of temperature, SO2 partial pressure, and Ca/S molar ratio for a pulverized dolomite (34 micrometer mean size) and a high-purity calcite (11 micrometer mean size). The experim...

  18. Design, construction, and calibration of an isothermal titration calorimeter and its application in the study of the adsorption of phenolic compounds

    NASA Astrophysics Data System (ADS)

    Moreno-Piraján, Juan Carlos; Giraldo, Liliana

    2012-01-01

    An isothermal calorimetric titration was designed and built, and some of the results obtained are presented here. For this purpose, a Calvet heat-conducting microcalorimeter was developed and connected to a titration unit built for this experiment to record titration thermograms. The microcalorimeter was electrically calibrated to establish its sensitivity and reproducibility, obtaining K = 13.56 ± 0.21 W V-1. Additionally, the equipment was tested using the heat of neutralisation for the tris-hydroxymethyl-aminomethane-HCl (THAM-HCl) system, obtaining ΔH = -30.92 ± 0.03 kJ mol-1. The unit was assembled to obtain titration heats and the corresponding thermodynamic variables (ΔH, ΔG, ΔS, and Ke) with a system of phenolic derivatives-activated carbon (synthesised from potato peel).

  19. Design, construction, and calibration of an isothermal titration calorimeter and its application in the study of the adsorption of phenolic compounds.

    PubMed

    Moreno-Piraján, Juan Carlos; Giraldo, Liliana

    2012-01-01

    An isothermal calorimetric titration was designed and built, and some of the results obtained are presented here. For this purpose, a Calvet heat-conducting microcalorimeter was developed and connected to a titration unit built for this experiment to record titration thermograms. The microcalorimeter was electrically calibrated to establish its sensitivity and reproducibility, obtaining K = 13.56 ± 0.21 W V(-1). Additionally, the equipment was tested using the heat of neutralisation for the tris-hydroxymethyl-aminomethane-HCl (THAM-HCl) system, obtaining ΔH = -30.92 ± 0.03 kJ mol(-1). The unit was assembled to obtain titration heats and the corresponding thermodynamic variables (ΔH, ΔG, ΔS, and K(e)) with a system of phenolic derivatives-activated carbon (synthesised from potato peel). PMID:22299996

  20. Removal of phenol from aqueous solutions by adsorption.

    PubMed

    Roostaei, Nadia; Tezel, F Handan

    2004-02-01

    Experiments have been conducted to examine the liquid-phase adsorption of phenol from water by silica gel, HiSiv 3000, activated alumina, activated carbon, Filtrasorb-400, and HiSiv 1000. Experiments were carried out for the analysis of adsorption equilibrium capacities and kinetics. The adsorption isotherm model of the Langmuir-Freundlich type was the best to describe adsorption equilibrium data for phenol for the adsorbents studied. Results of kinetic experiments indicated that HiSiv 1000 had the highest rate of adsorption among the adsorbents studied and therefore more detailed studies were carried out with this adsorbent. The influence of particle size, temperature, and thermal regeneration on adsorption of phenol by HiSiv 1000 was evaluated. From particle size experiments it appeared that adsorption capacity of HiSiv 1000 did not change by changing the particle size, but the rate of adsorption decreased considerably by increasing the particle size. The effect of temperature on adsorption was studied by determining equilibrium isotherms for HiSiv 1000 at 25, 40, and 55 degrees C. The results showed that adsorption capacity decreased with increasing temperature. Thermal regeneration of HiSiv 1000 was performed at 360 degrees C. It was observed that adsorption capacity of HiSiv 1000 did not change after 14 regeneration cycles. Equilibrium experiments showed that the adsorption capacities of activated carbon and Filtrasorb-400 were several times higher than that of HiSiv 1000. PMID:15160741

  1. A Biomedical Application of Activated Carbon Adsorption: An Experiment Using Acetaminophen and N-Acetylcysteine.

    ERIC Educational Resources Information Center

    Rybolt, Thomas R.; And Others

    1988-01-01

    Illustrates an interesting biomedical application of adsorption from solution and demonstrates some of the factors that influence the in vivo adsorption of drug molecules onto activated charcoal. Uses acetaminophen and N-acetylcysteine for the determination. Suggests several related experiments. (MVL)

  2. Insights into tetracycline adsorption onto kaolinite and montmorillonite: experiments and modeling.

    PubMed

    Zhao, Yanping; Gu, Xueyuan; Li, Shiyin; Han, Ruiming; Wang, Guoxiang

    2015-11-01

    Adsorption of tetracycline (TC) on kaolinite and montmorillonite was investigated using batch adsorption experiments with different pH, ionic strength, and surface coverage. As a result, pH and ionic strength-dependent adsorption of TC was observed for the two clay minerals. The adsorption of TC decreased with the increase of pH and ionic strength, and high initial TC concentration had high adsorption. In addition, a triple-layer model was used to predict the adsorption and surface speciation of TC on the two minerals. As a result, four complex species on kaolinite (≡X(-)∙H3TC(+), ≡X(-)∙H2TC(±), ≡SOH(0)∙H2TC(±), and ≡SOH(0)∙HTC(-)) and three species on montmorillonite (≡X(-)∙H3TC(+), ≡X(-)∙H2TC(±), and ≡SOH(0)∙HTC(-)) were structurally constrained by spectroscopy, and these species were also successfully fitted to the adsorption edges of TC. Three functional groups of TC were involved in these adsorption reactions, including the positively charged dimethylamino group, the C=O amide I group, and the C=O group at the C ring. Combining adsorption experiments and model in this study, the adsorption of TC on kaolinite and montmorillonite was mainly attributed to cation exchange on the surface sites (≡X(-)) compared to surface complexation on the edge sites (≡SOH) at natural soil pH condition. Moreover, the surface adsorption species, the corresponding adsorption modes, and the binding constants for the surface reactions were also estimated. PMID:26122570

  3. Effect of Grain Size on Uranium(VI) Surface Complexation Kinetics and Adsorption Additivity

    SciTech Connect

    Shang, Jianying; Liu, Chongxuan; Wang, Zheming; Zachara, John M.

    2011-07-27

    Laboratory experiments were performed to investigate the contribution of variable grain sizes to uranium adsorption/desorption in a sediment collected from the US DOE Hanford site. The sediment was wet-sieved into four size fractions: coarse sand (1-2 mm), medium sand (0.2-1 mm), fine sand (0.05-0.2 mm), and clay/silt fraction (< 0.05mm). For each size fraction and their composite (sediment), batch experiments were performed to determine uranium adsorption isotherms, and stirred flow-cell experiments were conducted to derive kinetic data of uranium adsorption and subsequent desorption. The results showed that uranium adsorption isotherms and adsorption/desorption kinetics were size-specific, reflecting the effects of size-specific adsorption site concentration and kinetic rate constants. The larger-size fraction had a larger mass percentage in the sediment, but with a smaller adsorption site concentration and generally a slower uranium adsorption/desorption rate. The same equilibrium surface complexation reaction and reaction constant could describe uranium adsorption isotherms for all size fractions and the composite after accounting for the effect of adsorption site concentration. Mass-weighted, linear additivity was observed for both uranium adsorption isotherms and adsorption/desorption kinetics in the composite. Our analysis also showed that uranium adsorption site concentration estimated from the adsorption isotherms was 3 orders of magnitude less than a site concentration estimated from sediment surface area and generic site density. One important implication of this study is that grain size distribution may be used to estimate uranium adsorption site, and adsorption/desorption kinetic rates in heterogeneous sediments from a common location.

  4. Calcium lignosulfonate adsorption and desorption on Berea sandstone.

    PubMed

    Grigg, Reid B; Bai, Baojun

    2004-11-01

    This paper describes adsorption and desorption studies carried out with calcium lignosulfonate (CLS) on Berea sandstone. Circulation experiments were performed to determine CLS adsorption isotherms and the effects of CLS concentration, temperature, salinity, brine hardness, and injection rate on adsorption density. Flow-through experiments were performed to assess the reversibility of CLS adsorption and the influence of postflush rate, brine concentration, brine hardness, brine pH, and temperature on the desorption process. Results indicate that CLS adsorption isotherms on Berea sandstone follow the Freundlich isotherm law. The results presented in this paper on the effects of CLS adsorption and desorption on Berea sandstone show that: (1) increasing CLS concentration and salinity increases CLS adsorption density; (2) increasing temperature will decrease adsorption density; (3) increasing injection rate of CLS solution will slightly decrease CLS adsorption density; (4) postflush rate and salinity of brine have a large impact on the CLS desorption process; (5) the adsorption and desorption process are not completely reversible; and (5) temperature and pH of the postflush brine have little effect on desorption. PMID:15380409

  5. Response surface methodology approach for optimization of simultaneous dye and metal ion ultrasound-assisted adsorption onto Mn doped Fe3O4-NPs loaded on AC: kinetic and isothermal studies.

    PubMed

    Asfaram, Arash; Ghaedi, Mehrorang; Goudarzi, Alireza; Rajabi, Maryam

    2015-09-01

    In the present work, the usefulness of ultrasonic power as a dispersion and mixing tool to accelerate the adsorption of Safranin O (SO), methylene blue (MB), Pb(2+) ions and Cr(3+) ions onto the novel composite Fe3O4-NPs-AC adsorbent was investigated. This new material was extensively characterized and analyzed by different techniques such as XRD, FESEM, Raman spectroscopy and FT-IR. Central composite design (CCD) based on designed runs revealed that adsorbent mass, sonication time, MB concentration, SO concentration, Pb(2+) ion and Cr(3+) ion concentration and some of their interactions have significant contributions to the target compounds removal percentages. A combination of response surface methodology and Design-Expert software was used to qualify and estimate the influence and magnitude of each terms contribution to the response. An optimization study using the following investigated increments of the effective variables, adsorbent mass (0.01-0.03 g), sonication time (2-6 min), initial dye concentration (5-25 mg L(-1)), and initial metal ion concentration (20-60 mg L(-1)), revealed that fixing the experimental variables at 0.025 g of Mn-Fe3O4-NPs-AC, with a 3 min sonication time, and 20 mg L(-1) of MB, 10 mg L(-1) of SO, 38 mg L(-1) of Pb(2+) ions and 42 mg L(-1) of Cr(3+) ions at room temperature lead to the achievement of the best characteristics and performance. Conduction of 32 experiments according to the limitations of CCD and a subsequent analysis of variance (ANOVA) gave useful information about the significant and also approximate contributions of each term (main and interaction of variables) in an empirical equation for the expected response. The results indicate that the R(2) values are more than 0.988 and the adjusted R(2) values are in reasonable agreement with R(2). Under the optimal conditions, the MB, SO, Pb(2+) ion and Cr(3+) ion removal efficiencies reached 99.54%, 98.87%, 80.25% and 99.54% after 3 min, while their equilibrium data with

  6. [Virus adsorption from batch experiments as influenced by air-water interface].

    PubMed

    Zhang, Hui; Zhao, Bing-zi; Zhang, Jia-bao; Zhang, Cong-zhi; Wang, Qiu-ying; Chen, Ji

    2007-12-01

    The presence of air-water interface in batch sorption experiments may result in inaccurate estimation of virus adsorption onto various soils. A batch sorption experiment was conducted to compare the adsorption results of MS2 in different soils under presence/absence of air-water interface. Soils with sterilization/nonterilization treatment were used. Virus recovery efficiency in a blank experiment (no soil) was also evaluated as affected by different amount of air-water interface. The presence of air-water interface altered the results of virus adsorption in different soils with different extent, with Sandy fluvo-aquic soil being the most considerably affected, followed by Red loam soil, and the least being Red clay soil, probably because of different soil properties associated with virus adsorption/inactivation. Soil sterilization resulted in more significant difference of virus adsorption onto the Sandy fluvo-aquic soil between the presence and absence of air-water interface, while a reduced difference was observed in the Red loam soil. The presence of air-water interface significantly decreased virus recovery efficiency, with the values being decreased with increase in the amount of air-water interface. Soil particles likely prohibit viruses from reaching the air-water interface or alter the forces at the solid-water-air interface so that the results from the blank experiment did not truly represent results from control blank, which probably resulted in adsorption difference between presence and absence of the air-water interface. PMID:18290440

  7. Thermal Cycling and Isothermal Deformation Response of Polycrystalline NiTi: Simulations vs. Experiment

    NASA Technical Reports Server (NTRS)

    Manchiraju, Sivom; Gaydosh, Darrell; Benafan, Othmane; Noebe, Ronald; Vaidyanathan, Raj; Anderson, Peter M.

    2011-01-01

    A recent microstructure-based FEM model that couples crystal-based plasticity, the B2<-> MB190 phase transformation and anisotropic elasticity at the grain scale is calibrated to recent data for polycrystalline NiTi (49.9 at.% Ni). Inputs include anisotropic elastic properties, texture and differential scanning calorimetry data, as well as a subset of recent isothermal deformation and load-biased thermal cycling data. The model is assessed against additional experimental data. Several experimental trends are captured - in particular, the transformation strain during thermal cycling monotonically increases and reaches a peak with increasing bias stress. This is achieved, in part, by modifying the martensite hardening matrix proposed by Patoor et al. [Patoor E, Eberhardt A, Berveiller M. J Phys IV 1996;6:277]. Some experimental trends are underestimated - in particular, the ratcheting of macrostrain during thermal cycling. This may reflect a model limitation that transformation-plasticity coupling is captured on a coarse (grain) scale but not on a fine (martensitic plate) scale.

  8. Unified superresolution experiments and stochastic theory provide mechanistic insight into protein ion-exchange adsorptive separations

    PubMed Central

    Kisley, Lydia; Chen, Jixin; Mansur, Andrea P.; Shuang, Bo; Kourentzi, Katerina; Poongavanam, Mohan-Vivekanandan; Chen, Wen-Hsiang; Dhamane, Sagar; Willson, Richard C.; Landes, Christy F.

    2014-01-01

    Chromatographic protein separations, immunoassays, and biosensing all typically involve the adsorption of proteins to surfaces decorated with charged, hydrophobic, or affinity ligands. Despite increasingly widespread use throughout the pharmaceutical industry, mechanistic detail about the interactions of proteins with individual chromatographic adsorbent sites is available only via inference from ensemble measurements such as binding isotherms, calorimetry, and chromatography. In this work, we present the direct superresolution mapping and kinetic characterization of functional sites on ion-exchange ligands based on agarose, a support matrix routinely used in protein chromatography. By quantifying the interactions of single proteins with individual charged ligands, we demonstrate that clusters of charges are necessary to create detectable adsorption sites and that even chemically identical ligands create adsorption sites of varying kinetic properties that depend on steric availability at the interface. Additionally, we relate experimental results to the stochastic theory of chromatography. Simulated elution profiles calculated from the molecular-scale data suggest that, if it were possible to engineer uniform optimal interactions into ion-exchange systems, separation efficiencies could be improved by as much as a factor of five by deliberately exploiting clustered interactions that currently dominate the ion-exchange process only accidentally. PMID:24459184

  9. 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,...

  10. 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.

  11. Thermodynamic characterization of polymeric materials subjected to non-isothermal flows: Experiment, theory and simulation

    NASA Astrophysics Data System (ADS)

    Ionescu, Tudor Constantin

    Frictional or viscous heating phenomena are found in virtually every industrial operation dealing with processing of polymeric materials. This work is aimed at addressing some of the existing shortcomings in modeling non-isothermal polymer flowing processes. Specifically, existing theories suggest that when a polymer melt is subjected to deformation, its internal energy changes very little compared to its conformational entropy. This statement forms the definition of the Theory of Purely Entropic Elasticity (PEE) applied to polymer melts. Under the auspices of this theory, the temperature evolution equation for modeling the polymer melt under an applied deformation is greatly simplified. In this study, using a combination of experimental measurements, continuum-based computer modeling and molecular simulation techniques, the validity of this theory is tested for a wide range of processing conditions. First, we present experimental evidence that this theory is only valid for low deformation regimes. Furthermore, using molecular theory, a direct correlation is found between the relaxation characteristics of the polymer and the flow regime where this theory stops being valid. We present a new and improved form of the temperature equation containing an extra term previously neglected under the PEE assumption, followed by a recipe for evaluating the extra term. The corrected temperature equation is found to give more accurate predictions for the temperature profiles in the high flow rate regimes, in excellent agreement with our experimental measurements. Next, in order to gain a molecular-level understanding of our experimental findings, a series of polydisperse linear alkane systems with average chain lengths between 24 and 78 carbon atoms are modeled with an applied "orienting field" using a highly efficient non-equilibrium Monte Carlo scheme. Our simulation results appear to substantiate our experimental findings. The internal energy change of the oriented

  12. Adsorption isotherms, kinetics, thermodynamics and desorption studies for uranium and thorium ions from aqueous solution by novel microporous composite P(HEMA-EP)

    NASA Astrophysics Data System (ADS)

    Akkaya, Recep; Akkaya, Birnur

    2013-03-01

    In this research, a novel composite, poly(2-hydroxyethylmethacrylate-expanded perlite) [P(HEMA-EP)], was synthesized and its adsorptive features were investigated. P(HEMA-EP)'s adsorptive features were evaluated for UO22+ and Th4+ ions in terms of the dependency upon the ion concentration, pH, temperature, and time. P(HEMA-EP) was able to bind UO22+ and Th4+ ions with strong chemical affinity. The adsorption results were fitted to the classical Langmuir, Freundlich, and Dubinin-Radushkevich (D-R) sorption models. P(HEMA-EP) was also used to study the removal of UO22+ and Th4+ ions from aqueous solutions in a batch system. The adsorption capacity (XL) of UO22+ and Th4+ ions was found to be 0.29 and 0.44 mol kg-1, respectively. The kinetic data corresponds well to the pseudo-second-order equation. Changes in the enthalpy and entropy values demonstrated that the overall adsorption process was spontaneous (ΔG < 0), endothermic (ΔH > 0), and had increased entropy (ΔS > 0), as expected. The reusability of the composites was confirmed for five sequential reuses.

  13. The adsorption of amino acids and cations onto goethite: a prebiotic chemistry experiment.

    PubMed

    Farias, Ana Paula S F; Carneiro, Cristine E A; de Batista Fonseca, Inês C; Zaia, Cássia T B V; Zaia, Dimas A M

    2016-06-01

    Few prebiotic chemistry experiments have assessed the adsorption of biomolecules by iron oxide-hydroxides. The present work investigated the effects of cations in artificial seawaters on the adsorption of Gly, α-Ala and β-Ala onto goethite, and vice versa. Goethite served to concentrate K and Mg cations from solution; these effects could have played important roles in peptide nucleoside formation. Goethite showed low adsorption of Gly and α-Ala. On the other hand, β-Ala (a non-protein amino acid) was highly adsorbed by goethite. Because Gly and α-Ala are the most common amino acids in living beings, and iron oxide-hydroxides are widespread on Earth, additional iron oxides should be studied. Increased ionic strength in artificial seawaters decreased the adsorption of amino acids by goethite. Because Na was highly abundant in the artificial seawater, it showed the highest effect on amino acid adsorption. β-Ala increased the adsorption of K and Ca by goethite, this effect could have been important for peptide synthesis. PMID:26984319

  14. A method for the calculation of the adsorbed phase volume and pseudo-saturation pressure from adsorption isotherm data on activated carbon.

    PubMed

    Srinivasan, Kandadai; Saha, Bidyut Baran; Ng, Kim Choon; Dutta, Pradip; Prasad, Madhu

    2011-07-21

    We propose a new method for evaluating the adsorbed phase volume during physisorption of several gases on activated carbon specimens. We treat the adsorbed phase as another equilibrium phase which satisfies the Gibbs equation and hence assume that the law of rectilinear diameters is applicable. Since invariably the bulk gas phase densities are known along measured isotherms, the constants of the adsorbed phase volume can be regressed from the experimental data. We take the Dubinin-Astakhov isotherm as the model for verifying our hypothesis since it is one of the few equations that accounts for adsorbed phase volume changes. In addition, the pseudo-saturation pressure in the supercritical region is calculated by letting the index of the temperature term in Dubinin's equation to be temperature dependent. Based on over 50 combinations of activated carbons and adsorbates (nitrogen, oxygen, argon, carbon dioxide, hydrocarbons and halocarbon refrigerants) it is observed that the proposed changes fit experimental data quite well. PMID:21670804

  15. Argon and nitrogen adsorption in disordered nanoporous carbons: simulation and experiment.

    PubMed

    Pikunic, Jorge; Llewellyn, Philip; Pellenq, Roland; Gubbins, Keith E

    2005-05-10

    We report experimental measurements of the isosteric heats of adsorption for argon and nitrogen in two microporous saccharose-based carbons, using a Tian-Calvet microcalorimeter. These data are used to test recently developed molecular models of these carbons, obtained by a constrained reverse Monte Carlo method. Grand canonical Monte Carlo simulation is used to calculate the adsorption isotherms and isosteric heats for these systems, and the results for the latter are compared to the experimental data. For argon, excellent quantitative agreement is obtained over the entire range of pore filling. In the case of nitrogen, very good agreement is obtained over the range of coverage 0.25 < or = gamma/gamma 0 < or = 0.85, but discrepancies are observed at lower and higher coverages. The discrepancy at low coverage may be due to the presence of oxygenated groups on the pore surfaces, which are not taken into account in the model. The differences at high coverage are believed to arise from the presence of a few mesopores, which again are not included in the model. Pair correlation functions (argon-carbon and argon-argon) are determined from the simulations and are discussed as a function of pore filling. Snapshots of the simulations are presented and provide a picture of the pore filling process. PMID:16032857

  16. Impact of Nanoparticles and Natural Organic Matter on the Removal of Organic Pollutants by Activated Carbon Adsorption

    EPA Science Inventory

    Isotherm experiments evaluating trichloroethylene (TCE) adsorption onto powdered activated carbon (PAC) were conducted in the presence and absence of three commercially available nanomaterials— iron oxide (Fe2O3), titanium dioxide (TiO2), and silicon dioxide (SiO2). Isotherm exp...

  17. Third and Final Shuttle Mission of the Isothermal Dendritic Growth Experiment Conducted: Highest Supercooling Ever Recorded Achieved

    NASA Technical Reports Server (NTRS)

    Glicksman, Martin E.; Malarik, Diane C.

    1999-01-01

    Dendrites describe the treelike crystal morphology commonly assumed in metals and alloys that freeze from supercooled or supersaturated melts. There remains a high level of engineering interest in dendritic solidification because the size, shape, and orientation of the dendrites determine the final microstructure of a material. It is the microstructure that then determines the physical properties of cast or welded products. Although it is well known that dendritic growth is controlled by the transport of latent heat from the moving solid-liquid interface, an accurate and predictive model has not yet been developed. The effects of gravity-induced convection on the transfer of heat from the interface have prevented adequate testing, under terrestrial conditions, of solidification models. The Isothermal Dendritic Growth Experiment (IDGE) constituted a series of three microgravity experiments flown aboard the Space Shuttle Columbia. The apparatus was used to grow and record dendrite solidification in the absence of gravity-induced convective heat transfer, thereby producing a wealth of benchmark-quality data for testing solidification models and theories.

  18. Adsorption of iodine on hydrogen-reduced silver-exchanged mordenite: Experiments and modeling

    DOE PAGESBeta

    Nan, Yue; Tavlarides, Lawrence L.; DePaoli, David W.

    2016-08-03

    The adsorption process of iodine, a major volatile radionuclide in the off-gas streams of spent nuclear fuel reprocessing, on hydrogen-reduced silver-exchanged mordenite (Ag0Z) was studied at the micro-scale. The gas-solid mass transfer and reaction involved in the adsorption process were investigated and evaluated with appropriate models. Optimal conditions for reducing the silver-exchanged mordenite (AgZ) in a hydrogen stream were determined. Kinetic and equilibrium data of iodine adsorption on Ag0Z were obtained by performing single-layer adsorption experiments with experimental systems of high precision at 373–473 K over various iodine concentrations. Results indicate approximately 91% to 97% of the iodine adsorption wasmore » through the silver-iodine reaction. The effect of temperature on the iodine loading capacity of Ag0Z was discussed. In conclusion, the Shrinking Core model describes the data well, and the primary rate controlling mechanisms were macro-pore diffusion and silver-iodine reaction. © 2016 American Institute of Chemical Engineers AIChE J, 2016« less

  19. Non-isothermal model experiments and numerical simulations for directional solidification of multicrystalline silicon in a traveling magnetic field

    NASA Astrophysics Data System (ADS)

    Dadzis, K.; Niemietz, K.; Pätzold, O.; Wunderwald, U.; Friedrich, J.

    2013-06-01

    A new experimental setup containing a GaInSn melt with a square horizontal cross section of 10×10 cm2 and a variable melt height up to 10 cm has been developed. The melt is positioned in the center of a coil system generating a traveling magnetic field (TMF). Using a cooling system at the bottom and a heating system at the top of the melt, a vertical temperature difference up to approximately 50 K can be applied to the melt, imitating the thermal conditions during the directional solidification of multicrystalline silicon. Direct measurements of the time-dependent velocity and the temperature profiles were performed using ultrasonic Doppler velocimetry and thermocouples, respectively. Complementary three-dimensional (3D) numerical simulations of the model experiments were used to validate the numerical tools and to gain a deeper insight into the characteristics of TMF flows in square melts. The classical toroidal flow structure known from isothermal cylindrical melts is shown to obtain a large horizontal central vortex at a small height of the square melt, whereas a distinct 3D asymmetry appears at a large height. A vertical temperature gradient tends to suppress the vertical melt motion and leads to new complex horizontal flow structures.

  20. A molecular model for adsorption of water on activated carbon: Comparison of simulation and experiment

    SciTech Connect

    McCallum, C.L.; McGrother, S.C.; Bandosz, T.J.; Mueller, E.A.; Gubbins, K.E.

    1999-01-19

    Experimental and molecular simulation results are presented for the adsorption of water onto activated carbons. The pore size distribution for the carbon studied was determined from nitrogen adsorption data using density functional theory, and the density of acidic and basic surface sites was found using Boehm and potentiometric titration. The total surface site density was 0.675 site/nm{sup 2}. Water adsorption was measured for relative pressures P/P{sub 0} down to 10{sup {minus}3}. A new molecular model for the water/activated carbon system is presented, which the authors term the effective single group model, and grand canonical Monte Carlo simulations are reported for the range of pressures covered in the experiments. A comparison of these simulations with the experiments show generally good agreement, although some discrepancies are attributed to the simplification of using a single surface group species, while those at high pressure are believed to arise from uncertainties in the pore size distribution. The simulation results throw new light on the adsorption mechanism for water at low pressures. The influence of varying both the density of surface sites and the size of the graphite microcrystals is studied using molecular simulation.

  1. Interlamellar adsorption of organic pollutants from water on hydrophobic clay minerals

    SciTech Connect

    Dekany, I.; Farkas, A.; Kiraly, Z.; Klumpp, E.; Narres, H.D.

    1995-12-01

    The adsorption excess isotherms of n-pentanol and nitrobenzene were determined with surfactant-modified (hexadecylanimonium ions) layered silicates. Both liquids intercalate into the silicate layers and increase the basal spacing, determined by X-ray diffraction measurements, depending on the equilibrium concentration in the bulk phase. To control the entropy change due to the intercalation, flow microcalorimetric experiments were made and enthalpy of displacement isotherms (adsorption and desorption) were determined. The information obtained from these three different measurements permitted the assessment of the composition of the interlarnellar space (in volume fraction of the intercalated molecules) and the thermodynamics of adsorption.

  2. Adsorption efficiency of natural materials for low-concentration cesium in solution.

    PubMed

    Miura, A; Kubota, T; Hamada, K; Hitomi, T

    2016-01-01

    In this study, several natural materials were investigated in order to clarify their potential use as cesium (Cs) adsorbents in situ. Four materials--carbonized rice hull, beech sawdust, oak sawdust, and charcoal (Japanese cedar)--which were previously shown to have Cs adsorption capabilities, were examined. Cs adsorption experiments were conducted using different initial Cs and adsorbent concentrations. The physical properties, adsorption isotherms, and adsorption processes were then examined, so as to exploit the Cs adsorption characteristics in the field. Based on these findings, carbonized rice hull and beech sawdust were selected as effective Cs adsorbents. It was found that these materials show continuous and stable Cs adsorption rates for different initial Cs concentrations. The adsorption efficiency of these two adsorption materials in combination was considered, and it was shown that the adsorption isotherms for carbonized rice hull and beech sawdust follow the Freundlich model. Furthermore, the beech sawdust adsorption process exhibited better agreement with the calculated values obtained via the adsorption rate model and the adsorption kinetics model than did the carbonized rice hull adsorption. PMID:27191567

  3. [Adsorption and Desorption Characteristics of Endosulfan in Purple Soil].

    PubMed

    Zhao, Yan; Zheng, Guo-can; Zhu, Heng; Zhang, Jin-zhong; Zhu, Xiu-ying; Hu, Shu-chun; Wu, Ya-lin

    2015-09-01

    In order to reveal the residual process of endosulfan in purple soil and protect soil ecological environment, the adsorption and desorption characteristics of endosulfan in purple soil were investigated, and effects of temperature, adsorbent amount, and initial pH of adsorption solution on the adsorption capacity were also examined by static adsorption and desorption experiments. The results showed that the adsorption kinetic process could be well described by the second-order kinetic equation with the initial rate constants of α-, β-endosulfan as 0. 157 and 0. 115 mg.(g.min)-1, respectively. The adsorption thermodynamic process could be well described by the Langmuir isotherm with the maximum adsorption capacities of α-, β-endosulfan as 0. 257 mg . g -1 and 0. 155 mg . g -1, respectively. The adsorption process of endosulfan in purple soil may be an exothermic physicochemical process, and is dominated by physical adsorption. Under the experimental conditions examined in this study, the initial pH of adsorption solution had a relative great influence on the adsorption capacity, whereas the temperature and adsorbent amount had no significant influence. The desorption experiments found that the maximum desorption capacities of α-, β-endosulfan adsorbed in purple soil were 0. 029 mg . g -1 and 0. 017 mg . g -1 at 6 and 4 h, and accounted for 10. 5% and 16. 1% in the maximum adsorption capacities, respectively. PMID:26717711

  4. Experiments and Modeling of Uranium Adsorption in the Presence of Other Ions in Simulated Seawater

    DOE PAGESBeta

    Ladshaw, Austin; Das, Sadananda; Liao, Wei-Po; Yiacoumi, Sotira; Janke, Christopher James; Mayes, Richard T.; Dai, Sheng; Tsouris, Costas

    2015-11-19

    Seawater contains uranium at an average concentration of 3.3 ppb, as well as a variety of other ions at either overwhelmingly higher or similar concentrations, which complicate the recovery of uranium. This report describes an investigation of the effects of various factors such as uranium speciation and presence of salts including sodium, calcium, magnesium, and bicarbonate, as well as trace elements such as vanadium on uranium adsorption kinetics in laboratory experiments. Adsorption models are also developed to describe the experimental data of uranium extraction from seawater. Results show that the presence of calcium and magnesium significantly slows down the uraniummore » adsorption kinetics. Vanadium can replace uranium from amidoxime-based adsorbent in the presence of sodium in the solution. Results also show that bicarbonate in the solution strongly competes with amidoxime for binding uranium, and thus slows down the uranium adsorption kinetics. Developed on the basis of the experimental findings, the model is capable of describing the effects of pH, ionic strength, temperature, and concentration of various species. The results of this work are useful in the understanding of the important factors that control the adsorbent capacity and kinetics of uranium uptake by amidoxime-based adsorbents.« less

  5. Experiments and Modeling of Uranium Adsorption in the Presence of Other Ions in Simulated Seawater

    SciTech Connect

    Ladshaw, Austin; Das, Sadananda; Liao, Wei-Po; Yiacoumi, Sotira; Janke, Christopher James; Mayes, Richard T.; Dai, Sheng; Tsouris, Costas

    2015-11-19

    Seawater contains uranium at an average concentration of 3.3 ppb, as well as a variety of other ions at either overwhelmingly higher or similar concentrations, which complicate the recovery of uranium. This report describes an investigation of the effects of various factors such as uranium speciation and presence of salts including sodium, calcium, magnesium, and bicarbonate, as well as trace elements such as vanadium on uranium adsorption kinetics in laboratory experiments. Adsorption models are also developed to describe the experimental data of uranium extraction from seawater. Results show that the presence of calcium and magnesium significantly slows down the uranium adsorption kinetics. Vanadium can replace uranium from amidoxime-based adsorbent in the presence of sodium in the solution. Results also show that bicarbonate in the solution strongly competes with amidoxime for binding uranium, and thus slows down the uranium adsorption kinetics. Developed on the basis of the experimental findings, the model is capable of describing the effects of pH, ionic strength, temperature, and concentration of various species. The results of this work are useful in the understanding of the important factors that control the adsorbent capacity and kinetics of uranium uptake by amidoxime-based adsorbents.

  6. Molecular mechanism of the hydration of Candida antarctica lipase B in the gas phase: Water adsorption isotherms and molecular dynamics simulations.

    PubMed

    Branco, Ricardo J F; Graber, Marianne; Denis, Vinciane; Pleiss, Jürgen

    2009-12-14

    Hydration is a major determinant of activity and selectivity of enzymes in organic solvents or in gas phase. The molecular mechanism of the hydration of Candida antarctica lipase B (CALB) and its dependence on the thermodynamic activity of water (a(w)) was studied by molecular dynamics simulations and compared to experimentally determined water sorption isotherms. Hydration occurred in two phases. At low water activity, single water molecules bound to specific water binding sites at the protein surface. As the water activity increased, water networks gradually developed. The number of protein-bound water molecules increased linearly with a(w), until at a(w)=0.5 a spanning water network was formed consisting of 311 water molecules, which covered the hydrophilic surface of CALB, with the exception of the hydrophobic substrate-binding site. At higher water activity, the thickness of the hydration shell increased up to 10 A close to a(w)=1. Above a limit of 1600 protein-bound water molecules the hydration shell becomes unstable and the formation of pure water droplets occurs in these oversaturated simulation conditions. While the structure and the overall flexibility of CALB was independent of the hydration state, the flexibility of individual loops was sensitive to hydration: some loops, such as those part of the substrate-binding site, became more flexible, while other parts of the protein became more rigid upon hydration. However, the molecular mechanism of how flexibility is related to activity and selectivity is still elusive. PMID:19847841

  7. [Adsorption of Cr (VI) on magnetic graphene from aqueous solution].

    PubMed

    Liu, Wei; Yang, Qi; Li, Bo; Chen, Hai; Nie, Lan-Yu

    2015-02-01

    Chemical deposition method was applied to prepare magnetic graphene composites using graphite oxide and ferric salt (FeCl2 - 4H2O and FeCl3 x 6H2O) as starting materials. The static experiments were performed to study kinetics, thermodynamic, adsorption isotherm and effects of various parameters, such as pH, temperature and time on Cr(VI) adsorption. The results showed that adsorption kinetics followed the pseudo-second-order model. Compared with Freundlich isotherm, Langmuir isotherm could better describe the adsorption process. The parameters of thermodynamics were ΔHθ = 33.89 kJ x mol(-1), ΔSθ = 120.15 J x (mol x K)(-1), ΔGθ = -2.51 kJ x mol(-1) (303 K), it demonstrated that the adsorption was a spontaneously endothermic process. It also indicated that the optimal pH was 2. Higher temperature and extension of time were in favor of adsorption. When used repeatedly for three times, the adsorption capacity decreased from 3.9 mg x g(-1) to 2.1 mg x g(-1) with an initial concentration of 5 mg x L(-1). By using a permanent magnet, the recycling process of adsorbent was easy to be operated and adsorbent could be regenerated by sodium hydrate solution. Hence, the composites is a promising adsorbent for efficient removal of Cr(VI) from wastewater. PMID:26031080

  8. Adsorption of diethyl phthalate ester to clay minerals.

    PubMed

    Wu, Yanhua; Si, Youbin; Zhou, Dongmei; Gao, Juan

    2015-01-01

    Phthalate esters are a group of plasticizers, which have been widely detected in China's agricultural and industrial soils. In this study, batch adsorption experiments were conducted to investigate the environmental effects on the adsorption of diethyl phthalate ester (DEP) to clay minerals. The results showed that DEP adsorption isotherms were well fitted with the Freundlich model; the interlayer spacing of K(+) saturated montmorillonite (K-mont) was the most important adsorption area for DEP, and di-n-butyl ester (DnBP) was limited to intercalate into the interlayer of K-mont due to the bigger molecular size; there was no significant effect of pH and ionic strength on DEP adsorption to K-mont/Ca-mont, but to Na-mont clay. The adsorption to kaolinite was very limited. Data of X-ray diffraction and FTIR spectra further proved that DEP molecules could intercalate into K-/Ca-mont interlayer, and might interact with clay through H-bonding between carbonyl groups and clay adsorbed water. Coated humic acid on clay surface would enhance DEP adsorption at low concentration, but not at high concentration (eg. Ce>0.26 mM). The calculated adsorption enthalpy (ΔHobs) and adsorption isotherms at varied temperatures showed that DEP could be adsorbed easier as more adsorbed. This study implied that clay type, compound structure, exchangeable cation, soil organic matter and temperature played important roles in phthalate ester's transport in soil. PMID:25150972

  9. Adsorption structures and energetics of molecules on metal surfaces: Bridging experiment and theory

    NASA Astrophysics Data System (ADS)

    Maurer, Reinhard J.; Ruiz, Victor G.; Camarillo-Cisneros, Javier; Liu, Wei; Ferri, Nicola; Reuter, Karsten; Tkatchenko, Alexandre

    2016-05-01

    Adsorption geometry and stability of organic molecules on surfaces are key parameters that determine the observable properties and functions of hybrid inorganic/organic systems (HIOSs). Despite many recent advances in precise experimental characterization and improvements in first-principles electronic structure methods, reliable databases of structures and energetics for large adsorbed molecules are largely amiss. In this review, we present such a database for a range of molecules adsorbed on metal single-crystal surfaces. The systems we analyze include noble-gas atoms, conjugated aromatic molecules, carbon nanostructures, and heteroaromatic compounds adsorbed on five different metal surfaces. The overall objective is to establish a diverse benchmark dataset that enables an assessment of current and future electronic structure methods, and motivates further experimental studies that provide ever more reliable data. Specifically, the benchmark structures and energetics from experiment are here compared with the recently developed van der Waals (vdW) inclusive density-functional theory (DFT) method, DFT + vdWsurf. In comparison to 23 adsorption heights and 17 adsorption energies from experiment we find a mean average deviation of 0.06 Å and 0.16 eV, respectively. This confirms the DFT + vdWsurf method as an accurate and efficient approach to treat HIOSs. A detailed discussion identifies remaining challenges to be addressed in future development of electronic structure methods, for which the here presented benchmark database may serve as an important reference.

  10. Adsorptive Removal and Adsorption Kinetics of Fluoroquinolone by Nano-Hydroxyapatite

    PubMed Central

    Chen, Yajun; Lan, Tao; Duan, Lunchao; Wang, Fenghe; Zhao, Bin; Zhang, Shengtian; Wei, Wei

    2015-01-01

    Various kinds of antibiotics, especially fluoroquinolone antibiotics (FQs) have been widely used for the therapy of infectious diseases in human and livestock. For their poorly absorbed by living organisms, large-scale misuse or abuse of FQs will foster drug resistance among pathogenic bacteria, as well as a variety of environmental problems when they were released in the environment. In this work, the adsorption properties of two FQs, namely norfloxacin (NOR) and ciprofloxacin (CIP), by nano-hydroxyapatite (n-HAP) were studied by batch adsorption experiments. The adsorption curves of FQs by n-HAP were simulated by Langmuir and Freundlich isotherms. The results shown that NOR and CIP can be adsorbed effectively by the adsorbent of n-HAP, and the adsorption capacity of FQs increase with increasing dosage of n-HAP. The optimum dosage of n-HAP for FQs removal was 20 g·L-1, in which the removal efficiencies is 51.6% and 47.3%, and an adsorption equilibrium time is 20 min. The maximum removal efficiency occurred when pH is 6 for both FQs. The adsorption isotherm of FQs fits well for both Langmuir and Freundlich equations. The adsorption of both FQs by n-HAP follows second-order kinetics. PMID:26698573

  11. A pressure-amplifying framework material with negative gas adsorption transitions.

    PubMed

    Krause, Simon; Bon, Volodymyr; Senkovska, Irena; Stoeck, Ulrich; Wallacher, Dirk; Többens, Daniel M; Zander, Stefan; Pillai, Renjith S; Maurin, Guillaume; Coudert, François-Xavier; Kaskel, Stefan

    2016-04-21

    Adsorption-based phenomena are important in gas separations, such as the treatment of greenhouse-gas and toxic-gas pollutants, and in water-adsorption-based heat pumps for solar cooling systems. The ability to tune the pore size, shape and functionality of crystalline porous coordination polymers--or metal-organic frameworks (MOFs)--has made them attractive materials for such adsorption-based applications. The flexibility and guest-molecule-dependent response of MOFs give rise to unexpected and often desirable adsorption phenomena. Common to all isothermal gas adsorption phenomena, however, is increased gas uptake with increased pressure. Here we report adsorption transitions in the isotherms of a MOF (DUT-49) that exhibits a negative gas adsorption; that is, spontaneous desorption of gas (methane and n-butane) occurs during pressure increase in a defined temperature and pressure range. A combination of in situ powder X-ray diffraction, gas adsorption experiments and simulations shows that this adsorption behaviour is controlled by a sudden hysteretic structural deformation and pore contraction of the MOF, which releases guest molecules. These findings may enable technologies using frameworks capable of negative gas adsorption for pressure amplification in micro- and macroscopic system engineering. Negative gas adsorption extends the series of counterintuitive phenomena such as negative thermal expansion and negative refractive indices and may be interpreted as an adsorptive analogue of force-amplifying negative compressibility transitions proposed for metamaterials. PMID:27049950

  12. A pressure-amplifying framework material with negative gas adsorption transitions

    NASA Astrophysics Data System (ADS)

    Krause, Simon; Bon, Volodymyr; Senkovska, Irena; Stoeck, Ulrich; Wallacher, Dirk; Többens, Daniel M.; Zander, Stefan; Pillai, Renjith S.; Maurin, Guillaume; Coudert, François-Xavier; Kaskel, Stefan

    2016-04-01

    Adsorption-based phenomena are important in gas separations, such as the treatment of greenhouse-gas and toxic-gas pollutants, and in water-adsorption-based heat pumps for solar cooling systems. The ability to tune the pore size, shape and functionality of crystalline porous coordination polymers—or metal–organic frameworks (MOFs)—has made them attractive materials for such adsorption-based applications. The flexibility and guest-molecule-dependent response of MOFs give rise to unexpected and often desirable adsorption phenomena. Common to all isothermal gas adsorption phenomena, however, is increased gas uptake with increased pressure. Here we report adsorption transitions in the isotherms of a MOF (DUT-49) that exhibits a negative gas adsorption; that is, spontaneous desorption of gas (methane and n-butane) occurs during pressure increase in a defined temperature and pressure range. A combination of in situ powder X-ray diffraction, gas adsorption experiments and simulations shows that this adsorption behaviour is controlled by a sudden hysteretic structural deformation and pore contraction of the MOF, which releases guest molecules. These findings may enable technologies using frameworks capable of negative gas adsorption for pressure amplification in micro- and macroscopic system engineering. Negative gas adsorption extends the series of counterintuitive phenomena such as negative thermal expansion and negative refractive indices and may be interpreted as an adsorptive analogue of force-amplifying negative compressibility transitions proposed for metamaterials.

  13. Studies of gas adsorption in flexible Metal-Organic frameworks

    NASA Astrophysics Data System (ADS)

    Sircar, Sarmishtha

    Flexible Metal-Organic frameworks that exhibit a gate-opening (GO) adsorption mechanism have potential for gas separations and gas storage. The GO phenomenon occurs when molecular gates in the structure expand/contract in response to the activation/de-activation of a system variable e.g. temperature, pressure or gas. Sharp discontinuities in the isotherm leading to S-shapes and large adsorption-desorption hysteresis are typical of this phenomenon. This study investigates the kinetics and thermodynamics of the GO behavior by combining adsorption measurements and analytical modeling of adsorption kinetics and capacity as a function of adsorbate, GO pressure, and temperature. Basic understanding of GO mechanism will help harness GO-MOF's as adsorbents for gas separations and storage. Experiments were performed on two precharacterized MOFs with verified GO behavior. These are (1) Zn2(bpdc)2(bpee), which expands from a relative amorphous to crystalline structure and (2) Cu[(dhbc) 2(4,4f-bpy)]H2O, a mutually interdigitated 2-D structure (bpdc = biphenyldicarboxylate, bpee = 1,2]bipyridylethene; DMF = N,N-dimethyl formamide, dhbc= 2,5-dihydroxybenzoic acid, bpy=bipyridine). Both sub- and super-critical adsorption data were collected using three adsorption units: a standard low-pressure volumetric adsorption unit, a commercial high-pressure gravimetric analyzer and a custom-built high-pressure differential volumetric unit. Collected laboratory data were combined with published adsorption rate and isotherm data for analysis to broaden the range of data collection. The accuracy of the high-pressure differential unit was improved by over 300-fold by changing analytical methods of processing data to establish a reliable null correction. A pronounced effect of the allowed experimental time was found at cryogenic temperatures on (1). Tightening the stability criteria used by the adsorption equipment to determine equilibration increased the experimental time from the order of

  14. Adsorption of a multicomponent rhamnolipid surfactant to soil

    SciTech Connect

    Noordmann, W.H.; Brusseau, M.L.; Janssen, D.B.

    2000-03-01

    The adsorption of rhamnolipid, a multicomponent biosurfactant with potential application in soil remediation, to two sandy soils was investigated using batch and column studies. The surfactant mixture contained six anionic components differing in lipid chain length and number of rhamnose moieties. Batch adsorption experiments indicated that the overall adsorption isotherms of total surfactant and of the individual components leveled off above a concentration at which micelles were formed. Column experiments showed that the retardation factors for the total surfactant and for the individual components decreased with increasing influent concentration. Extended tailing was observed in the distal portion of the surfactant breakthrough curve. The concentration-dependent retardation factors and the extended tailing are in accordance with the nonlinear (concave) adsorption isotherms found in the batch adsorption studies. The more hydrophobic rhamnolipid components were preferentially adsorbed, but adsorption was not correlated with the organic carbon content of the soil. This suggests that adsorption of rhamnolipid to soil is not a partitioning process but mainly an interfacial adsorption process.

  15. Molecular structure-adsorption study on current textile dyes.

    PubMed

    Örücü, E; Tugcu, G; Saçan, M T

    2014-01-01

    This study was performed to investigate the adsorption of a diverse set of textile dyes onto granulated activated carbon (GAC). The adsorption experiments were carried out in a batch system. The Langmuir and Freundlich isotherm models were applied to experimental data and the isotherm constants were calculated for 33 anthraquinone and azo dyes. The adsorption equilibrium data fitted more adequately to the Langmuir isotherm model than the Freundlich isotherm model. Added to a qualitative analysis of experimental results, multiple linear regression (MLR), support vector regression (SVR) and back propagation neural network (BPNN) methods were used to develop quantitative structure-property relationship (QSPR) models with the novel adsorption data. The data were divided randomly into training and test sets. The predictive ability of all models was evaluated using the test set. Descriptors were selected with a genetic algorithm (GA) using QSARINS software. Results related to QSPR models on the adsorption capacity of GAC showed that molecular structure of dyes was represented by ionization potential based on two-dimensional topological distances, chromophoric features and a property filter index. Comparison of the performance of the models demonstrated the superiority of the BPNN over GA-MLR and SVR models. PMID:25529487

  16. [Adsorption characteristics of f2 bacteriophages by four substrates in constructed wetland].

    PubMed

    Chen, Di; Zheng, Xiang; Wei, Yuan-Song; Yang, Yong

    2013-10-01

    Performance of f2 phages adsorption by four substrates including anthracite coal, steel slag, zeolite and forsterite was investigated through batch and dynamic experiments. Results of batch experiments showed that the removal efficiency of f2 phages by these four substrates was in the order of anthracite > steel slag > forsterite approximately zeolite. The adsorption of f2 phages by anthracite experienced fast, medium and slow stages, and the removal efficiency of f2 phages increased gradually with the increase of anthracite dosage, e. g. the optimized dosage of anthracite was 8.0 g at a solid/liquid ratio of 1:12.5 (m/V). The isothermal adsorption of all four substrates was described with Freundlich and Langmuir isothermal adsorption equation very well, and the adsorption of f2 phages by both anthracite and steel slag fitted pseudo-second order adsorption kinetics at their theoretical adsorption capacities of 3. 35 x 10(8) PFU.g-1 and 2.56 x 10(8) PFU.g-1, respectively, nearly the same as the equilibrium adsorption capacities obtained under the experiment conditions. And the liquid diffusion process was a rate-limiting step of the adsorption of f2 phage by both anthracite and steel slag, but not the only one. The results of dynamic adsorption experiments showed that the adsorption process of f2 phages in the three adsorption columns including anthracite, steel slag and zeolite experienced four stages of adaption, adsorption, pulse adsorption and adsorption equilibrium, and the total removal rates of f2 phages were more than 2. 55 Ig. PMID:24364309

  17. Arsenic Adsorption Equilibrium Concentration and Adsorption Rate of Activated Carbon Coated with Ferric-Aluminum Hydroxides

    NASA Astrophysics Data System (ADS)

    Zhang, M.; Sugita, H.; Oguma, T.; Hara, J.; Takahashi, S.

    2015-12-01

    In some areas of developing countries, ground or well water contaminated with arsenic has been reluctantly used as drinking water. It is highly desirable that effective and inexpensive arsenic removal agents should be developed and provided to reduce the potential health risk. Previous studies demonstrated that activated carbon coated with ferric-aluminum hydroxides (Fe-Al-C) has high adsorptive potential for removal of arsenic. In this study, a series of experiments using Fe-Al-C were carried to discuss adsorption equilibrium time, adsorption equilibrium concentration and adsorption rate of arsenic for Fe-Al-C. Fe-Al-C used in this study was provided by Astec Co., Ltd. Powder reagent of disodium hydrogen arsenate heptahydrate was dissolved into ion-exchanged water. The solution was then further diluted with ion-exchanged water to be 1 and 10 mg/L as arsenic concentration. The pH of the solution was adjusted to be around 7 by adding HCl and/or NaOH. The solution was used as artificial arsenic contaminated water in two types of experiments (arsenic adsorption equilibrium and arsenic adsorption rate tests). The results of the arsenic equilibrium tests were showed that a time period of about 3 days to reach apparent adsorption equilibrium for arsenic. The apparent adsorption equilibrium concentration and adsorbed amount of arsenic on Fe-Al-C adsorbent could be estimated by application of various adsorption isotherms, but the distribution coefficient of arsenic between solid and liquid varies with experimental conditions such as initial concentration of arsenic and addition concentration of adsorbent. An adsorption rate equation that takes into account the reduction in the number of effective adsorption sites on the adsorbent caused by the arsenic adsorption reaction was derived based on the data obtained from the arsenic adsorption rate tests.

  18. Co-adsorption of Trichloroethylene and Arsenate by Iron-Impregnated Granular Activated Carbon.

    PubMed

    Deng, Baolin; Kim, Eun-Sik

    2016-05-01

    Co-adsorption of trichloroethylene (TCE) and arsenate [As(V)] was investigated using modified granular activated carbons (GAC): untreated, sodium hypochlorite-treated (NaClO-GAC), and NaClO with iron-treated GAC (NaClO/Fe-GAC). Batch experiments of single- [TCE or As(V)] and binary- [TCE and As(V)] components solutions are evaluated through Langmuir and Freundlich isotherm models and adsorption kinetic tests. In the single-component system, the adsorption capacity of As(V) was increased by the NaClO-GAC and the NaClO/Fe-GAC. The untreated GAC showed a low adsorption capacity for As(V). Adsorption of TCE by the NaClO/Fe-GAC was maximized, with an increased Freundlich constant. Removal of TCE in the binary-component system was decreased 15% by the untreated GAC, and NaClO- and NaClO/Fe-GAC showed similar efficiency to the single-component system because of the different chemical status of the GAC surfaces. Results of the adsorption isotherms of As(V) in the binary-component system were similar to adsorption isotherms of the single-component system. The adsorption affinities of single- and binary-component systems corresponded with electron transfer, competitive adsorption, and physicochemical properties. PMID:27131303

  19. Application of novel Polypyrrole/thiol-functionalized zeolite Beta/MCM-41 type mesoporous silica nanocomposite for adsorption of Hg2+ from aqueous solution and industrial wastewater: Kinetic, isotherm and thermodynamic studies

    NASA Astrophysics Data System (ADS)

    Javadian, Hamedreza; Taghavi, Mehdi

    2014-01-01

    Hierarchical zeolite consists of both microporous and unordered mesoporous structures. A composite of Polypyrrole/thiol-functionalized Beta/MCM-41 (PPy/SH-Beta/MCM-41) was prepared, characterized by FE-SEM, FT-IR, XRD, TGA and BET analysis and applied in the investigation of its adsorption characteristics for the removal of Hg2+ ions from aqueous solutions. Thiol-functionalized Beta/MCM-41 (SH-Beta/MCM-41) was prepared by 3-mercaptopropyltrimethoxysilane (MPTMS) in the presence of aerosil-200 as a silica source by two-step hydrothermal crystallization procedure. Batch mode experiments were conducted and three kinetic models were used to describe the adsorption process. The experimental data fitted very well with the Pseudo-second-order kinetic model. The calculated thermodynamic parameters (ΔH, ΔS and ΔG) revealed that the adsorption of Hg2+ onto PPy/SH-Beta/MCM-41 is an endothermic and spontaneous process. It was found that temperature has a positive effect on the removal efficiency and that PPy/SH-Beta/MCM-41 is potentially able to remove Hg2+ ions from aqueous solutions at even high concentrations (400 mg L-1). The recovery of Hg2+ from the PPy/SH-Beta/MCM-41 adsorbent was found to be more than 90% using 0.5 M H2SO4, and the ability of the absorbent to be reused for removal of Hg2+ was investigated.

  20. Adsorption of clofibric acid and ketoprofen onto powdered activated carbon: effect of natural organic matter.

    PubMed

    Gao, Yaohuan; Deshusses, Marc A

    2011-12-01

    The adsorption of two acidic pharmaceutically active compounds (PhACs), clofibric acid and ketoprofen, onto powdered activated carbon (PAC) was investigated with a particular focus on the influence of natural organic matter (NOM) on the adsorption of the PhACs. Suwannee River humic acids (SRHAs) were used as a substitute for NOM. Batch adsorption experiments were conducted to obtain adsorption kinetics and adsorption isotherms with and without SRHAs in the system. The adsorption isotherms and adsorption kinetics showed that the adsorption ofclofibric acid was not significantly affected by the presence of SRHAs at a concentration of 5 mg (as carbon) L(-1). An adsorption capacity of 70 to 140 mg g(-1) was observed and equilibrium was reached within 48 h. In contrast, the adsorption of ketoprofen was markedly decreased (from about 120 mg g(-1) to 70-100 mg g(-1)) in the presence of SRHAs. Higher initial concentrations of clofibric acid than ketoprofen during testing may explain the different behaviours that were observed. Also, the more hydrophobic ketoprofen molecules may have less affinity for PAC when humic acids (which are hydrophilic) are present. The possible intermolecular forces that could account for the different behaviour of clofibric acid and ketoprofen adsorption onto PAC are discussed. In particular, the relevance of electrostatic forces, electron donor-acceptor interaction, hydrogen bonding and London dispersion forces are discussed PMID:22439557

  1. Detailed characterization and preliminary adsorption model for materials for an intermediate-scale reactive-transport experiment

    SciTech Connect

    Ward, D.B.; Bryan, C.R.; Siegel, M.D.

    1994-12-31

    An experiment involving migration of fluid and tracers (Li, Br, Ni) through a 6-m-high x 3-m-dia caisson Wedron 510 sand, is being carried out for Yucca Mountain Site Characterization Project. Sand`s surface chemistry of the sand was studied and a preliminary surface-complexation model of Ni adsorption formulated for transport calculations. XPS and leaching suggest that surface of the quartz sand is partially covered by thin layers of Fe-oxyhydroxide and Ca-Mg carbonate and by flakes of kaolinite. Ni adsorption by the sand is strongly pH-dependent, showing no adsorption at pH 5 and near-total adsorption at pH 7. Location of adsorption edge is independent of ionic strength and dissolved Ni concentration; it is shifted to slightly lower pH with higher pCO2 and to slightly higher pH by competition with Li. Diminished adsorption at alkiline pH with higher pCO2 implies formation of dissolved Ni-carbonato complexes. Ni adsorption edges for goethite and quartz, two components of the sand were also measured. Ni adsorption on pure quartz is only moderately pH-dependent and differs in shape and location from that of the sand, whereas Ni adsorption by goethite is strongly pH-dependent. A triple-layer surface-complexation model developed for goethite provides a good fit to the Ni-adsorption curve of the sand. Based on this model, the apparent surface area of the Fe-oxyhydroxide coating is estimated to be 560 m{sup 2}/g, compatible with its occurrence as amorphous Fe-oxyhydroxide. Potentiometric titrations on sand also differ from pure quartz and suggest that effective surface area of sand may be much greater than that measured by N{sub 2}-BET gas adsorption. Attempts to model the adsorption of bulk sand in terms of properties of pure end member components suggest that much of the sand surface is inert. Although the exact Ni adsorption mechanisms remain ambiguous, this preliminary adsorption model provides an initial set of parameters that can be used in transport calculations.

  2. Effect of Ultrasound on Bisphenol A Adsorption on the Granular Activated Carbon

    NASA Astrophysics Data System (ADS)

    Myunghee Lim,; Younggyu Son,; Mingcan Cui,; Jeehyeong Khim,

    2010-07-01

    The aim of this study is to investigate the effects of ultrasound (power, frequency) on bisphenol A (BPA) adsorption on granular activated carbon (GAC). The result of adsorption isotherm in a BPA solution, using sonicated GAC (at 35 kHz) can more successfully adsorb BPA than sonicated GAC (at 300 kHz) and the original GAC. At low frequency GAC has a high cavitation effect. Therefore, the amount of adsorbed BPA at a low frequency was higher than at a high frequency. In isotherm experiments, ultrasound can enhance the adsorption process in GAC in both frequencies (35 and 300 kHz). These results agree with other previous researches. The effect of power intensity in the adsorption of BPA is increased the adsorption of BPA with increasing power. The optimum power exists and differs from frequencies because the cavitation effect is not the same with different frequencies.

  3. Effects of Humidity Swings on Adsorption Columns for Air Revitalization: Modeling and Experiments

    NASA Technical Reports Server (NTRS)

    LeVan, M. Douglas; Finn, John E.

    1997-01-01

    The goal of this research was to develop a dynamic model which can predict the effect of humidity swings on activated carbon adsorption beds used to remove trace contaminants from the atmosphere in spacecraft. Specifically, the model was to be incorporated into a computer simulation to predict contaminant concentrations exiting the bed as a function of time after a humidity swing occurs. Predicted breakthrough curves were to be compared to experimentally measured results. In all respects the research was successful. The two major aspects of this research were the mathematical model and the experiments. Experiments were conducted by Mr. Appel using a fixed-bed apparatus at NASA-Ames Research Center during the summers of 1994 and 1995 and during the first 8 months of 1996. Mr. Appel conducted most of his mathematical modeling work at the University of Virginia. The simulation code was used to predict breakthrough curves using adsorption equilibrium correlations developed previously by M. D. LeVan's research group at the University of Virginia. These predictions were compared with the experimental measurements, and this led to improvements in both the simulation code and the apparatus.

  4. Adsorption of lead at variable pH onto a natural porous medium: Modeling of batch and column experiments

    SciTech Connect

    Papini, M.P.; Kahie, Y.D.; Troia, B.; Majone, M.

    1999-12-15

    The surface complexation approach has been applied to describe the adsorption of lead and proton onto a heterogeneous natural porous medium at constant ionic strength. Acid-base titration experiments were used to determine the minimum number of sites needed to describe the surface heterogeneity. Lead adsorption tests at several pH and total lead concentration were used to complete the model structure, whose adjustable parameters (site concentration and apparent formation constants) were determined by nonlinear multivariate regression of titration and adsorption data. The final model represents the acid-base properties of the surface by the presence of two amphoteric sites, SOH and TOH, and a monoprotic one, MOH; whereas lead adsorption is considered only onto SOH and MOH sites. The model allows a good representation of the experimental behavior in the whole experimental range. Theoretical surface speciation shows that lead adsorption occurs mostly onto site MOH at low pH level and on both SOH and MOH sites at higher values. The model was independently validated by simulating Pb and pH breakthrough experiments performed in small chromatographic columns. Experimental breakthroughs are well predicted by an advection-dispersion transport model coupled with the chemical equilibrium routine (IMPACT), without any parameter adjustment. A large spreading of Pb and pH breakthroughs was calculated and experimentally observed, even in the absence of any kinetic effect. That spreading is explained in terms of the concomitant presence of competitive adsorption and surface heterogeneity.

  5. Water adsorption on O(2x2)/Ru(0001) from STM experiments andfirst-principles calculations

    SciTech Connect

    Cabrera-Sanfelix, P.; Sanchez-Portal, D.; Mugarza, A.; Shimizu,T.K.; Salmeron, M.; Arnau, A.

    2007-10-15

    We present a combined theoretical and experimental study of water adsorption on Ru(0001) pre-covered with 0.25 monolayers (ML) of oxygen forming a (2 x 2) structure. Several structures were analyzed by means of Density Functional Theory calculations for which STM simulations were performed and compared with experimental data. Up to 0.25 monolayers the molecules bind to the exposed Ru atoms of the 2 x 2 unit cell via the lone pair orbitals. The molecular plane is almost parallel to the surface with its H atoms pointing towards the chemisorbed O atoms of the 2 x 2 unit cell forming hydrogen bonds. The existence of these additional hydrogen bonds increases the adsorption energy of the water molecule to approximately 616 meV, which is {approx}220 meV more stable than on the clean Ru(0001) surface with a similar configuration. The binding energy shows only a weak dependence on water coverage, with a shallow minimum for a row structure at 0.125 ML. This is consistent with the STM experiments that show a tendency of the molecules to form linear rows at intermediate coverage. Our calculations also suggest the possible formation of water dimers near 0.25 ML.

  6. Kinetic models for the adsorption of lead ions by steel slag.

    PubMed

    Liu, Sheng-Yu; Gao, Jin; Qu, Bin; Yang, Yi-Jin; Xin, Xin

    2010-08-01

    Batch experiments were carried out to investigate the kinetics of adsorption of lead ions by steel slag on the basis of the external diffusion, intraparticle diffusion and adsorption reaction model (pseudo-first-order, pseudo-second-order). The results showed that the controlling step for the adsorption kinetics changed with experimental parameters varied. When the particle size of steel slag was larger than 120 mesh, intraparticle diffusion of Pb(2+) was the controlling step; when the initial concentration of Pb(2+) was less than 150 mg L(-1) or the shaking rate was lower than 150 rpm, external diffusion of Pb(2+) was promoted. Contrary to the former experimental conditions, the adsorption reaction was the controlling step, and the adsorption followed second-order kinetics, with an adsorption rate constant of 13.26 g mg(-1) min(- 1). The adsorption isotherm of Pb(2+) with steel slag followed the Langmuir model, with a correlation coefficient of 0.99. PMID:19808736

  7. Laboratory column experiments for radionuclide adsorption studies of the Culebra dolomite member of the Rustler Formation

    SciTech Connect

    Lucero, D.A.; Heath, C.E.; Brown, G.O.

    1998-04-01

    Radionuclide transport experiments were carried out using intact cores obtained from the Culebra member of the Rustler Formation inside the Waste Isolation Pilot Plant, Air Intake Shaft. Twenty-seven separate tests are reported here and include experiments with {sup 3}H, {sup 22}Na, {sup 241}Am, {sup 239}Np, {sup 228}Th, {sup 232}U and {sup 241}Pu, and two brine types, AIS and ERDA 6. The {sup 3}H was bound as water and provides a measure of advection, dispersion, and water self-diffusion. The other tracers were injected as dissolved ions at concentrations below solubility limits, except for americium. The objective of the intact rock column flow experiments is to demonstrate and quantify transport retardation coefficients, (R) for the actinides Pu, Am, U, Th and Np, in intact core samples of the Culebra Dolomite. The measured R values are used to estimate partition coefficients, (kd) for the solute species. Those kd values may be compared to values obtained from empirical and mechanistic adsorption batch experiments, to provide predictions of actinide retardation in the Culebra. Three parameters that may influence actinide R values were varied in the experiments; core, brine and flow rate. Testing five separate core samples from four different core borings provided an indication of sample variability. While most testing was performed with Culebra brine, limited tests were carried out with a Salado brine to evaluate the effect of intrusion of those lower waters. Varying flow rate provided an indication of rate dependent solute interactions such as sorption kinetics.

  8. Characteristics of simultaneous ammonium and phosphate adsorption from hydrolysis urine onto natural loess.

    PubMed

    Jiang, Shanqing; Wang, Xiaochang; Yang, Shengjiong; Shi, Honglei

    2016-02-01

    Nutrient recovery from human urine is a promising pretreatment of domestic wastewater and provides a sustainable recyclability of N and P. In this study, batch experiments were conducted to identify the characteristics of natural loess (NL) for the adsorption and recovery of ammonium and phosphate from hydrolysis urine (HU). The adsorption mechanisms, the adsorption kinetics and isotherms, as well as the major influencing factors, such as pH and temperature, were investigated. Results revealed that adsorption of ammonium occurred by means of ion exchange and molecule adsorption with the ≡ Si-OH groups, while phosphate adsorption was based on the calcium phosphate precipitation reaction and formation of inner-sphere complexes with ≡ M-OH groups. The adsorption processes of ammonium and phosphate were well described by the pseudo-second-order kinetic model and the Freundlich isotherm model. Adsorption of phosphate was endothermic, while ammonium adsorption was exothermic. Furthermore, the maximum ammonium and phosphate adsorption capacities of NL was 23.24 mg N g(-1) and 4.01 mg P g(-1) at an initial pH of 9 and 10, respectively. Results demonstrated that nutrient-adsorbed NL used as compound fertilizer or conventional fertilizer superaddition was feasible for its high contents of N and P as well as its environmental friendliness. PMID:26432267

  9. Continuous water treatment by adsorption and electrochemical regeneration.

    PubMed

    Mohammed, F M; Roberts, E P L; Hill, A; Campen, A K; Brown, N W

    2011-05-01

    This study describes a process for water treatment by continuous adsorption and electrochemical regeneration using an air-lift reactor. The process is based on the adsorption of dissolved organic pollutants onto an adsorbent material (a graphite intercalation compound, Nyex(®)1000) and subsequent electrochemical regeneration of the adsorbent leading to oxidation of the adsorbed pollutant. Batch experiments were carried out to determine the adsorption kinetics and equilibrium isotherm for adsorption of a sample contaminant, the organic dye Acid Violet 17. The adsorbent circulation rate, the residence time distribution (RTD) of the reactor, and treatment by continuous adsorption and electrochemical regeneration were studied to investigate the process performance. The RTD behaviour could be approximated as a continuously stirred tank. It was found that greater than 98% removal could be achieved for continuous treatment by adsorption and electrochemical regeneration for feed concentrations of up to 300 mg L(-1). A steady state model has been developed for the process performance, assuming full regeneration of the adsorbent in the electrochemical cell. Experimental data and modelled predictions (using parameters for the adsorbent circulation rate, adsorption kinetics and isotherm obtained experimentally) of the dye removal achieved were found to be in good agreement. PMID:21511325

  10. Adsorptive removal of methylene blue by CuO-acid modified sepiolite as effective adsorbent and its regeneration with high-temperature gas stream.

    PubMed

    Su, Chengyuan; Wang, Liang; Chen, Menglin; Huang, Zhi; Lin, Xiangfeng

    2016-01-01

    In this study, the dynamic adsorption of methylene blue dye onto CuO-acid modified sepiolite was investigated. Meanwhile, the equilibrium and kinetic data of the adsorption process were studied to understand the adsorption mechanism. Furthermore, a high-temperature gas stream was applied to regenerate the adsorbent. The results showed that the Langmuir isotherm model was applied to describe the adsorption process. The positive value of enthalpy change indicated that the adsorption process was endothermic in nature. In the dynamic adsorption process, the best adsorption performance was achieved when the ratio of column height to diameter was 2.56 and the treatment capacity was 6 BV/h. The optimal scenario for regeneration experiments was the regeneration temperature of 550-650 °C, the space velocity of 100 min(-1) and the regeneration time of 10 min. The effective adsorption of CuO-acid modified sepiolite was kept for 12 cycles of adsorption and regeneration. PMID:27533859

  11. The adsorptivity of organic substances with various physico-chemical properties

    SciTech Connect

    Baikova, T.V.; Gubkina, M.L.; Nikolaev, K.M.

    1994-02-01

    The adsorption isotherms of benzene, n-hexane, cyclohexane, and 1,2-dibromo- 1,1,2,2-tetrafluoroethane on a nonporous carbon adsorbent, carbon black, were calculated from the results of a gas-chromatographic experiment at 373 K. A general equation of adsorption isotherm for vapors of organic substances on nonporous sorbents that was proposed earlier is shown to be valid in the range of relative pressures, p/p{sub s}, of 10{sup -7}-1 and temperatures of 293-373 K.

  12. [Characteristic of ammonia nitrogen adsorption on karst underground river sediments].

    PubMed

    Guo, Fang; Chen, Kun-Kun; Jiang, Guang-Hui

    2011-02-01

    Karst aquifers are one of the most important aquifers in Southwestern China. One of the characteristics of karst aquifers is the enhanced permeability permits high flow velocities are capable of transporting suspended and bedload sediments. Mobile sediment in karst may act as a vector for the transport of contaminates. 14 sediment samples were collected from two underground rivers in two typical karst areas in Liuzhou city, Guangxi Autonomous Region, China. According to simulated experiment methods, characteristic of adsorption of ammonia nitrogen on sediment was studied. The results of ammonia nitrogen adsorption dynamics on sediments showed that the maximum adsorption velocity was less than 2 h. The adsorption balance quantity in 5 h accounted for 71% - 98% of the maximum adsorption quantity. The maximum adsorption quantity of ammonia nitrogen was 385.5 mg/kg, which was sediment from a cave in the middle areas of Guancun underground river system. The study of isotherm adsorption indicated adsorption quantity of NH4+ increase followed by incremental balance concentration of NH4+ in the aquatic phase. Adsorption quantity of ammonia nitrogen in sediments has a relative linear relationship with adsorption balance concentrations. Adsorption-desorption balance concentrations were all low, indicating sediments from underground rivers have great adsorption potential. Under the condition of low and high concentrations of ammonia nitrogen in overlying water, Langmuir and Tempkin couldn't simulate or simulate results couldn't reach remarkable level, whilst Linear and Freundlich models could simulate well. Research on different type sediments, sampling times and depths from two underground rivers shows characteristic of ammonia nitrogen adsorption on karst underground river sediments doesn't have good correspondence with the type of sediments. One of the reasons is there is no big difference between sediments in the development of climate, geology, hydrological conditions

  13. Exploring the Stability of Gold Nanoparticles by Experimenting with Adsorption Interactions of Nanomaterials in an Undergraduate Lab

    ERIC Educational Resources Information Center

    Lee, Chi-Feng; You, Pei-Yun; Lin, Ying-Chiao; Hsu, Tsai-Ling; Cheng, Pi-Yun; Wu, Yu-Xuan; Tseng, Chi-Shun; Chen, Sheng-Wen; Chang, Huey-Por; Lin, Yang-Wei

    2015-01-01

    The proposed experiment can help students to understand the factors involved in the stability of gold nanoparticles (Au NPs) by exploring the adsorption interaction between Au NPs and various substances. The students in this study found that the surface plasmon resonance band of Au NP solutions underwent a red shift (i.e., from 520 to 650 nm)…

  14. Parameterization and evaluation of sulfate adsorption in a dynamic soil chemistry model.

    PubMed

    Martinson, Liisa; Alveteg, Mattias; Warfvinge, Per

    2003-01-01

    Sulfate adsorption was implemented in the dynamic, multi-layer soil chemistry model SAFE. The process is modeled by an isotherm in which sulfate adsorption is considered to be fully reversible and dependent on sulfate concentration as well as pH in soil solution. The isotherm was parameterized by a site-specific series of simple batch experiments at different pH (3.8-5.0) and sulfate concentration (10-260 micromol 1(-1)) levels. Application of the model to the Lake Gardsj6n roof covered site shows that including sulfate adsorption improves the dynamic behavior of the model and sulfate adsorption and desorption delay acidification and recovery of the soil. The modeled adsorbed pool of sulfate at the site reached a maximum level of 700 mmol/m(2) in the late 1980s, well in line with experimental data. PMID:12683988

  15. Adsorption behavior of perfluorooctanesulfonate (PFOS) and perfluorooctanoate (PFOA) on boehmite.

    PubMed

    Wang, Fei; Liu, Chengshuai; Shih, Kaimin

    2012-11-01

    Understanding the interaction of perfluorochemicals, persistent pollutants with known human health effects, with mineral compounds in surface water and groundwater environments is essential to determining their fate and transport. Kinetic experiments showed that adsorption equilibrium can be achieved within 48 h and the boehmite (AlOOH) surface is receptive to perfluorooctanesulfonate (PFOS) and perfluorooctanoate (PFOA) adsorption. The adsorption isotherms estimated the maximum adsorption capacities of PFOS and PFOA on boehmite as 0.877 μg m(-2) and 0.633 μg m(-2), respectively. Compared to the adsorption capacity on γ-alumina, the abundant hydroxyl groups on boehmite surfaces resulted in the 2-3 times higher adsorption of PFOS and PFOA. Increasing solution pH led to a moderate decrease in PFOS and PFOA adsorption, owing to an increase in ligand exchange reactions and the decrease of electrostatic interactions. The presence of NaCl and CaCl(2) in solution demonstrated negative effects for PFOS and PFOA adsorption on boehmite surfaces, with potential mechanisms being electrical double layer compression, competitive adsorption of chloride, and the Ca(2+) bridging effect between perfluorochemicals. PMID:22897837

  16. Fixed-bed adsorption of toluene on high silica zeolites: experiments and mathematical modelling using LDF approximation and a multisite model.

    PubMed

    Brodu, Nicolas; Sochard, Sabine; Andriantsiferana, Caroline; Pic, Jean-Stéphane; Manero, Marie-Hélène

    2015-01-01

    The adsorption of toluene (TOL) as a target volatile organic compound has been studied experimentally and modelled on various hydrophobic zeolites: Faujasite (FAU), ZSM-5 (Z) and Mordenite (MOR). The influence of the nature of the compensating cation (H+ or Na+) has also been investigated for ZSM-5 zeolite, which is known to possess three kinds of adsorption sites (sinusoidal channels, straight channels and intersections). Type I isotherms observed on FAU, Na-Z and MOR fitted well with the Langmuir model. A deviation from a type I isotherm was observed for H-Z, because of the structure of this zeolite. The Successive Langmuir Model was more successful to fit the 'bump' of the experimental curve than the Double Langmuir. Classical shapes were found for MOR, FAU and Na-Z breakthrough curves that were fitted with good accuracy using the Linear Driving Force (LDF) approximation. In the case of H-Z, a change of profile was observed during the dynamic adsorption and the differences seen between the Na-Z and H-Z behaviours were explained by the strong interactions between Na+ and adsorbed TOL at the intersection sites. The Na+ cations prevented reorientation of TOL molecules at the intersection and thereby avoided the filling of the sinusoidal channel segments. Thus, a specific model was developed for fitting the breakthrough curve of H-Z. The model developed took into account these two types of adsorption sites with the overall uptake for each site being given by an LDF approximation. PMID:25624172

  17. Kinetic Study of Adsorption Processes in Solution: An Undergraduate Physical Chemistry Experiment.

    ERIC Educational Resources Information Center

    Casado, Julio; And Others

    1985-01-01

    Background information, apparatus needed, procedures used, and results obtained are provided for a simple kinetic method for the monitoring of adsorption processes. The method, which involved adsorption of crystal violet onto activated carbon, is suitable for classroom and/or research purposes. (JN)

  18. Batch and column studies of adsorption of Li, Ni and Br by a reference sand for contaminant transport experiments

    SciTech Connect

    Seigel, M.D.; Ward, D.B.; Bryan, C.R.

    1995-09-01

    A processed quartz sand (Wedron 510), mined from the St. Peter sandstone, has been characterized by a variety of chemical and physical methods for use as a reference porous media in transport model validation experiments. Wedron 510 sand was used in an intermediate-scale experiment involving migration of Ni, Li and Br through a 6-m high x 3-m diameter caisson. Ni and Li adsorption/desorption, and Li/Ni site-competition experiments yielded information on the importance of the trace mineral phases to adsorption of Li and Ni by the sand. The presence of an iron hydroxide coating similar to goethite on the sand grains is suggested by visual observation and leaching experiments. Kaolinite was identified by SEM and XRD as a significant trace mineral phase in the sand and occurs as small particles coating the sand grains. Quartz, the predominant constituent of the sand by weight, does not appear to contribute significantly to the adsorption properties of the sand. Qualitatively, the adsorption properties of the sand can be adequately modeled as a two-mineral system (goethite and kaolinite). The studies described in this report should provide a basis for understanding transport of Ni, Li and Br through porous media similar to the reference sand. Techniques were developed for obtaining parameter values for surface complexation and kinetic adsorption models for the sand and its mineral components. These constants can be used directly in coupled hydrogeochemical transport codes. The techniques should be useful for characterization of other natural materials and elements in high-level nuclear waste in support of coupled hydrogeochemical transport calculations for Yucca Mountain.

  19. [Adsorption-desorption Characteristics of Fermented Rice Husk for Ferrous and Sulfur Ions].

    PubMed

    Xie, Xiao-mei; Liao, Min; Hua, Jia-yuan; Chen, Na; Zhang, Nan; Xu, Pei-zhi; Xie Kai-zhi; XU, Chang-xu; Liu, Guang-rong

    2015-10-01

    To understand the potential of rice husk to fix Fe2+ and S2- ions, the sorption of Fe2+ and S2- by fermented rice husk was studied by using batch incubation experiments in the present study. The effects of adsorption time, Fe2+ and S2- concentration, pH, the temperature and ionic strength in adsorption reaction solution on the sorption were investigated. Therefore, the stability of Fe2+ and S2- adsorbed by fermented rice husk was further validated by desorption experiments performed under similar conditions as adsorption. The results showed that, the adsorption kinetics of Fe2+ (r = 0.912 1) and S2- (r = 0.901 1) by fermented rice husk fits the Elovich kinetics equation, and Freundlich isotherm model could simulate the isotherm adsorption processes of Fe2+ (R2 = 0.965 1) and S2- (R2 = 0.936 6) on fermented rice husk was better than other models. The adsorption processes on fermented rice husk were non- preferential adsorption for Fe2+ and S2, while the adsorption process of Fe2+ on fermented rice husk was spontaneous reaction and the adsorption process of S2- was non-spontaneous reaction. The adsorption processes of Fe2+ and S2- on fermented rice husk were endothermic process since high temperature could benefit to the adsorption. The adsorption mechanism of Fe2+ on fermented rice husk was mainly controlled by coordination adsorption, the adsorption mechanism of S2- on fermented rice husk was mainly controlled by ligand exchange adsorption. The adsorption processes of Fe2+ and S2- on fermented rice husk showed greater pH adaptability which ranged from 1.50 to 11.50. With the increasing of ionic strength, the amount of adsorbed Fe2+ on fermented rice husk wasincreased in some extent, the amount of adsorbed S2- on fermented rice husk was slightly decreased, which further proved the adsorption of Fe2+ was major in inner sphere complexation and the adsorption of S2- was major in outer complexation. The desorption rates of Fe2+ and S2- which was adsorbed by fermented

  20. Adsorption of 1,1,1,2-tetrafluoroethane by various adsorbents

    SciTech Connect

    Lin, S.H.; Lin, R.C.

    1999-11-01

    Experiments have been conducted to investigate gas-phase adsorption characteristics of 1,1,1,2-tetrafluoroethane (HFC-134a) by activated carbon fiber, extruded activated carbon, granular activated carbon, activated alumina, and molecular sieve. HGC-134a is currently regarded as an excellent replacement for chlorofluorocarbon-12, a refrigerating and cooling agent extensively used previously in all automobiles and many cooling systems. Performances of HFC-134a adsorption were characterized by the equilibrium adsorption capacity, time to reach equilibrium, and desorption efficiency of exhausted adsorbent. A simple thermal treatment process with proper operating temperature and treatment duration was found to be effective for the regeneration of exhausted absorbents. Adsorption isotherms of the empirical Freundlich and Hossens types were observed to adequately represent the equilibrium adsorption data. A mass transfer model based on the pseudo steady state squared driving force was adopted to describe the mass transfer process of HFC-134a adsorption.

  1. Gas adsorption on microporous carbon thin films

    SciTech Connect

    O'Shea, S.; Pailthorpe, B.A.; Collins, R.E.; Furlong, D.N. )

    1992-05-01

    A gas adsorption study was performed on amorphous hydrogenated carbon thin films which are deposited by reactive magnetron sputtering using acetylene gas. It is found that the films are highly microporous. Annealing significantly increases the adsorption capacity of the films and decreases the effects of low-pressure hysteresis in the adsorption isotherms. The general gas adsorption behavior closely resembles that of powdered activated carbons. The Dubinin-Radushkevich equation can be used to model the submonolayer adsorption isotherm for a variety of gases. 38 refs., 9 figs., 3 tabs.

  2. Nanoscale elastic properties of montmorillonite upon water adsorption.

    PubMed

    Ebrahimi, Davoud; Pellenq, Roland J-M; Whittle, Andrew J

    2012-12-11

    Smectites are an important group of clay minerals that experience swelling upon water adsorption. This paper uses molecular dynamics with the CLAYFF force field to simulate isothermal isobaric water adsorption of interlayer Wyoming Na-montmorillonite, a member of the smectite group. Nanoscale elastic properties of the clay-interlayer water system are calculated from the potential energy of the model system. The transverse isotropic symmetry of the elastic constant matrix was assessed by calculating Euclidean and Riemannian distance metrics. Simulated elastic constants of the clay mineral are compared with available results from acoustic and nanoindentation measurements. PMID:23181550

  3. Radiation synthesis of spherical cellulose-based adsorbent for efficient adsorption and detoxification of Cr(VI)

    NASA Astrophysics Data System (ADS)

    Dong, Zhen; Zhao, Jing; Du, Jifu; Li, Cancan; Zhao, Long

    2016-09-01

    Spherical cellulose-based adsorbent (2-AMPR) with 2-aminomethyl pyridine was synthesized by radiation method. The adsorption behaviors of 2-AMPR for Cr(VI) removal were evaluated through batch and column experiments. The results presented that the adsorption kinetics well obeyed pseudo-second-order mode and the adsorption isotherm of Cr(VI) followed the Langmuir model with adsorption capacity of 209.6 mg/g at optimal pH 2.0. Dynamical experiments revealed that the 2-AMPR could selectively and simultaneously separate and detoxify trace amount of Cr(VI) even from simulated electroplating wastewater including high concentration of Cu(II), Ni(II) and Zn(II) ions. Additionally, FTIR and XPS analysis verified that part of Cr(VI) was reduced to Cr(III) during adsorption process by adsorption-reduction mechanism.

  4. Arsenate adsorption mechanisms at the allophane - Water interface

    USGS Publications Warehouse

    Arai, Y.; Sparks, D.L.; Davis, J.A.

    2005-01-01

    We investigated arsenate (As(V)) reactivity and surface speciation on amorphous aluminosilicate mineral (synthetic allophane) surfaces using batch adsorption experiments, powder X-ray diffraction (XRD), and X-ray absorption spectroscopy (XAS). The adsorption isotherm experiments indicated that As(V) uptake increased with increasing [As(V)]0 from 50 to 1000 ??M (i.e., Langmuir type adsorption isotherm) and that the total As adsorption slightly decreased with increasing NaCl concentrations from 0.01 to 0.1 M. Arsenate adsorption was initially (0-10 h) rapid followed by a slow continuum uptake, and the adsorption processes reached the steady state after 720 h. X-ray absorption spectroscopic analyses suggest that As(V) predominantly forms bidentate binuclear surface species on aluminum octahedral structures, and these species are stable up to 11 months. Solubility calculations and powder XRD analyses indicate no evidence of crystalline AI-As(V) precipitates in the experimental systems. Overall, macroscopic and spectroscopic evidence suggest that the As(V) adsorption mechanisms at the allophane-water interface are attributable to ligand exchange reactions between As(V) and surface-coordinated water molecules and hydroxyl and silicate ions. The research findings imply that dissolved tetrahedral oxyanions (e.g., H2PO42- and H2AsO42-) are readily retained on amorphous aluminosilicate minerals in aquifer and soils at near neutral pH. The innersphere adsorption mechanisms might be important in controlling dissolved arsenate and phosphate in amorphous aluminosilicate-rich low-temperature geochemical environments. ?? 2005 American Chemical Society.

  5. Adsorption of cadmium from aqueous solution onto untreated coffee grounds: equilibrium, kinetics and thermodynamics.

    PubMed

    Azouaou, N; Sadaoui, Z; Djaafri, A; Mokaddem, H

    2010-12-15

    Adsorption can be used as a cost effective and efficient technique for the removal of toxic heavy metals from wastewater. Waste materials with no further treatment such as coffee grounds from cafeterias may act as adsorbents for the removal of cadmium. Batch kinetic and equilibrium experiments were conducted to study the effects of contact time, adsorbent dose, initial pH, particle size, initial concentration of cadmium and temperature. Three adsorption isotherm models namely, Langmuir, Freundlich and Dubinin-Radushkevich were used to analyse the equilibrium data. The Langmuir isotherm which provided the best correlation for Cd(2+) adsorption onto coffee grounds, shows that the adsorption was favourable and the adsorption capacity found was equal to 15.65 mg g(-1). Thermodynamic parameters were evaluated and the adsorption was exothermic. The equilibrium was achieved less than 120 min. The adsorption kinetic data was fitted with first and second order kinetic models. Finally it was concluded that the cadmium adsorption kinetic onto coffee grounds was well fitted by second order kinetic model rather than first order model. The results suggest that coffee grounds have high possibility to be used as effective and economical adsorbent for Cd(2+) removal. PMID:20817346

  6. [Adsorption of Congo red from aqueous solution on hydroxyapatite].

    PubMed

    Zhan, Yan-Hui; Lin, Jian-Wei

    2013-08-01

    The adsorption of Congo red (CR) from aqueous solution on hydroxyapatite was investigated using batch experiments. The hydroxyapatite was effective for CR removal from aqueous solution. The adsorption kinetics of CR on hydroxyapatite well followed a pseudo-second-order model. The equilibrium adsorption data of CR on hydroxyapatite could be described by the Langmuir, Freundlich and Dubinin-Radushkevich (D-R) isotherm models. Thermodynamic parameters such as Gibbs free energy change, enthalpy change and entropy change were calculated and showed that the adsorption of CR on hydroxyapatite was spontaneous and exothermic in nature. The CR adsorption capacity for hydroxyapatite decreased significantly with increasing pH from 8 to 10. Thermal regeneration showed that hydroxyapatite could be used for six desorption-adsorption cycles with high removal efficiency for CR in each cycle. The mechanisms for CR adsorption on hydroxyapatite with pH value below the pH at point of zero charge (pH(PZC)) include electrostatic attraction, hydrogen bonding and Lewis acid-base interaction. The mechanisms for CR adsorption on hydroxyapatite with pH value above its pH(PZC) include hydrogen bonding and Lewis acid-base interaction. Results of this work indicate that hydroxyapatite is a promising adsorbent for CR removal from aqueous solution. PMID:24191561

  7. Adsorption of oleic acid at sillimanite/water interface.

    PubMed

    Kumar, T V Vijaya; Prabhakar, S; Raju, G Bhaskar

    2002-03-15

    The interaction of oleic acid at sillimanite-water interface was studied by adsorption, FT-IR, and zeta potential measurements. The isoelectric point (IEP) of sillimanite obtained at pH 8.0 was found to shift in the presence of oleic acid. This shift in IEP was attributed to chemisorption of oleic acid on sillimanite. Adsorption experiments were conducted at pH 8.0, where the sillimanite surface is neutral. The adsorption isotherm exhibited a plateau around 5 micromol/m2 that correspond to a monolayer formation. Adsorption of oleic acid on sillimanite, alumina, and aluminum hydroxide was studied by FT-IR. Chemisorption of oleic acid on the above substrates was confirmed by FT-IR studies. Hydroxylation of mineral surface was found to be essential for the adsorption of oleic acid molecules. These surface hydroxyl sites were observed to facilitate deprotonation of oleic acid and its subsequent adsorption. Thus protons from oleic acid react with surface hydroxyl groups and form water molecules. Based on the experimental results, the mechanism of oleic acid adsorption on mineral substrate was proposed. Free energy of adsorption was estimated using the Stern-Graham equation for a sillimanite-oleate system. PMID:16290466

  8. A Robust Metal-Organic Framework with An Octatopic Ligand for Gas Adsorption and Separation: A Combined Characterization by Experiments and Molecular Simulations

    SciTech Connect

    Zhuang, Wenjuan; Yuan, Daqiang; Liu, Dahuan; Zhong, Chongli; Li, Jian-Rong; Zhou, Hong-Cai

    2012-01-10

    A newly designed octatopic carboxylate ligand, tetrakis[(3,5-dicarboxyphenyl)oxamethyl]methane (TDM8–) has been used to connect a dicopper paddlewheel building unit affording a metal–organic framework (MOF), Cu₄(H₂O)₄(TDM)·xS (PCN-26·xS, S represents noncoordinated solvent molecules, PCN = porous coordination network) with novel structure, high gas uptake, and interesting gas adsorption selectivity. PCN-26 contains two different types of cages, octahedral and cuboctahedral, to form a polyhedron-stacked three-dimensional framework with open channels in three orthogonal directions. Gas adsorption studies of N₂, Ar, and H₂ on an activated PCN-26 at 77 K, 1 bar, reveals a Langmuir surface area of 2545 m²/g, a Brunauer–Emmett–Teller (BET) surface area of 1854 m²/g, a total pore volume of 0.84 cm³/g, and a H₂ uptake capacity of 2.57 wt %. Additionally, PCN-26 exhibits a CO₂/N₂ selectivity of 49:1 and CO₂/CH₄ selectivity of 8.4:1 at 273 K. To investigate properties of gas adsorption and the adsorption sites for CO₂ in activated PCN-26, theoretical simulations of the adsorption isotherms of CO₂, CH₄, and N₂ at different temperatures were carried out. Experimental results corroborate very well with those of molecular simulations.

  9. [Adsorption Characteristics of Norfloxacin by Biochars Derived from Reed Straw and Municipal Sludge].

    PubMed

    Zhang, Han-yu; Wang, Zhao-wei; Gao, Jun-hong; Zhu, Jun-min; Xie, Chao-ran; Xie, Xiao-yun

    2016-02-15

    Two types of biochars were prepared by pyrolyzing reed straw and municipal sludge at the temperature of 500 degrees C. The structure and properties of biochars were characterized by BET, scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and fourier transform infrared spectroscopy ( FTIR ). The effects of pH value, adsorption time, temperature and initial concentration of norfloxacin (NOR) on the adsorption behaviors were determined by single factor experiments, which were used to preliminarily discuss adsorption mechanism. The results showed that the adsorption of NOR onto biochars derived from reed straw and municipal sludge could reach 70% and 60% of the total adsorption within 12 h, respectively; the maximum adsorption capacities of the two biochars were 2.13 mg x g(-1) (biochar derived from reed straw) and 2.09 mg x g(-1) (biochar derived from municipal sludge). The quantities of both absorptions increased with the decreasing solution pH. The two adsorption kinetics of NOR onto biochars followed the pseudo second order kinetic equations, and adsorption isotherms fitted well with the Langmuir equations. Adsorption thermodynamics parameters such as Gibbs free energy (AG), enthalpy (AH) and entropy (AS) indicated that the two adsorptions were endothermic reactions. Infrared spectroscopy analysis indicated that oxygen-containing functional groups on biochars provided NOR molecules with adsorptive sites, which facilitated the formation of hydrogen bonds between NOR and the biochars. PMID:27363161

  10. Isosteric heat of hydrogen adsorption on MOFs: comparison between adsorption calorimetry, sorption isosteric method, and analytical models

    NASA Astrophysics Data System (ADS)

    Kloutse, A. F.; Zacharia, R.; Cossement, D.; Chahine, R.; Balderas-Xicohténcatl, R.; Oh, H.; Streppel, B.; Schlichtenmayer, M.; Hirscher, M.

    2015-12-01

    Isosteric heat of adsorption is an important parameter required to describe the thermal performance of adsorptive storage systems. It is most frequently calculated from adsorption isotherms measured over wide ranges of pressure and temperature, using the so-called adsorption isosteric method. Direct quantitative estimation of isosteric heats on the other hand is possible using the coupled calorimetric-volumetric method, which involves simultaneous measurement of heat and adsorption. In this work, we compare the isosteric heats of hydrogen adsorption on microporous materials measured by both methods. Furthermore, the experimental data are compared with the isosteric heats obtained using the modified Dubinin-Astakhov, Tóth, and Unilan adsorption analytical models to establish the reliability and limitations of simpler methods and assumptions. To this end, we measure the hydrogen isosteric heats on five prototypical metal-organic frameworks: MOF-5, Cu-BTC, Fe-BTC, MIL-53, and MOF-177 using both experimental methods. For all MOFs, we find a very good agreement between the isosteric heats measured using the calorimetric and isosteric methods throughout the range of loading studied. Models' prediction on the other hand deviates from both experiments depending on the MOF studied and the range of loading. Under low-loadings of less than 5 mol kg-1, the isosteric heat of hydrogen adsorption decreases in the order Cu-BTC > MIL-53 > MOF-5 > Fe-BTC > MOF-177. The order of isosteric heats is coherent with the strength of hydrogen interaction revealed from previous thermal desorption spectroscopy measurements.

  11. Adsorption mechanisms for fatty acids on DLC and steel studied by AFM and tribological experiments

    NASA Astrophysics Data System (ADS)

    Simič, R.; Kalin, M.

    2013-10-01

    Fatty acids are known to affect the friction and wear of steel contacts via adsorption onto the surface, which is one of the fundamental boundary-lubrication mechanisms. The understanding of the lubrication mechanisms of polar molecules on diamond-like carbon (DLC) is, however, still insufficient. In this work we aimed to find out whether such molecules have a similar effect on DLC coatings as they do on steel. The adsorption of hexadecanoic acid in various concentrations (2-20 mmol/l) on DLC was studied under static conditions using an atomic force microscope (AFM). The amount of surface coverage of the adsorbed fatty-acid molecules was analysed. In addition, tribological tests were performed to correlate the wear and friction behaviours in tribological contacts with the adsorption of molecules on the surface under static conditions. A good correlation between the AFM results and the tribological behaviour was observed. We confirmed that fatty acids can adsorb onto the DLC surfaces and are, therefore, potential boundary-lubrication agents for DLC coatings. The adsorption of the fatty acid onto the DLC surfaces reduces the wear of the coatings, but it is less effective in reducing the friction. Tentative adsorption mechanisms that include an environmental species effect, a temperature effect and a tribochemical effect are proposed for DLC and steel surfaces based on our results and few potential mechanisms found in literature.

  12. Impact of biochar produced from post-harvest residue on the adsorption behavior of diesel oil on loess soil.

    PubMed

    Jiang, Yu Feng; Sun, Hang; Yves, Uwamungu J; Li, Hong; Hu, Xue Fei

    2016-02-01

    The primary objective of this study was to investigate the effect of biochar, produced from wheat residue at different temperatures, on the adsorption of diesel oil by loess soil. Kinetic and equilibrium data were processed to understand the adsorption mechanism of diesel by biochar-affected loess soil; dynamic and thermodynamic adsorption experiments were conducted to characterize this adsorption. The surface features and chemical structure of biochar, modified at varying pyrolytic temperatures, were investigated using surface scanning electron microscopy and Fourier transform infrared analysis. The kinetic data showed that the adsorption of diesel oil onto loess soil could be described by a pseudo-second-order kinetic model, with the rate-controlling step being intraparticle diffusion. However, in the presence of biochar, boundary layer control and intraparticle diffusion were both involved in the adsorption. Besides, the adsorption equilibrium data were well described by the Freundlich isothermal model. The saturated adsorption capacity weakened as temperature increased, suggesting a spontaneous exothermic process. Thermodynamic parameter analysis showed that adsorption was mainly a physical process and was enhanced by chemical adsorption. The adsorption capacity of loess soil for diesel oil was weakened with increasing pH. The biochar produced by pyrolytic wheat residue increased the adsorption behavior of petroleum pollutants in loess soil. PMID:25980560

  13. A comparative adsorption study: 17β-estradiol onto aerobic granular sludge and activated sludge.

    PubMed

    Zheng, Xiao-ying; He, Yu-jie; Chen, Wei; Wang, Ming-yang; Cao, Su-lan; Ni, Ming; Chen, Yu

    2016-01-01

    Adsorption plays a significant role in removing hydrophobic 17β-estradiol (E2) from wastewater. Batch experiments were conducted to compare the adsorption of E2 onto activated aerobic granular sludge (AGS) and activated sludge (AS), and features evaluated included the adsorption kinetics, thermodynamics, and influence of other environmental factors. By using a non-chemical wet-heat technique, both AGS and AS were treated to inactivated status. Then, after loading E2, the adsorption equilibrium capacity of the AGS was found to be greater than that of the AS at the same initial concentration of E2. Moreover, both the adsorption processes corresponded to a pseudo-second-order kinetic model; the adsorption rate constant of AGS was found to be higher and the half-adsorption time was shorter than that of AS. Next, evaluations of adsorption isotherms and thermodynamics indicated that the adsorption process was mainly a physical process. Lower temperatures facilitated a higher equilibrium adsorption capacity. However, the adsorption binding sites of AGS were distributed more uniformly at higher temperature, in contrast to the distribution found for AS. Finally, acidic conditions and an appropriate ionic strength (0.4 mol/L) were found to be particularly conducive to the adsorption process. Overall, the results showed that AGS has the potential to adsorb E2 with significant efficiency, thereby offering a new and more efficient means of treating E2 and trace oestrogens in wastewater. PMID:26209151

  14. Models of pure CO2 and pure CH4 adsorption on the late paleozoic coals from the Kailuan Coalfield, Hebei, China

    USGS Publications Warehouse

    Dai, S.; Zhang, B.; Peng, S.; Zhang, X.; Chou, C.

    2009-01-01

    Isothermal adsorption experiments of pure CO2 and CH4 on different coals in rank (the No. 11 Coal from the Linnancang Mine and the No. 9 Coal from the Majiagou Mine) from the Kailuan Coalfield of Hebei Province, China, have been studied. Four different models (Langmuir, BET, D-R, and D-A) were used to fit the experimental data of CO2 and CH4 adsorption and their fitting degree were investigated. The results showed that the adsorption capacity of the Majiagou coal(Ro, ran = 1. 21%) is higher than that of the Linnancang coal (Ro, ran = 0. 58%). The adsorption capacity of CO2 is higher than that of CH4 on the same coal under the same pressure. The adsorption isotherms of pure CO 2 and pure CH4 on the Majiagou coal can be classified as Type I and their fitting errors of curves are very weak; thus the experimental data can be presented using the Langmuir isotherm. However, the adsorption of Linnancang coal is more complicated, and can be presented using D-A model because of its minimum error. Monolayer adsorption occurs during the adsorption of pure CO2 and pure CH4 on the No. 11 Coal and that of pure CH4 on the No. 9 Coal.

  15. Adsorption and desorption of phosphate on limestone in experiments simulating seawater intrusion

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The absorption and desorption of phosphorus on a large block of limestone was investigated using deionized water (DIW) and seawater. The limestone had a high affinity to adsorb phosphorus in DIW. Phosphate adsorption was significantly less in seawater, and more phosphorus was desorbed in the seawate...

  16. A Prebiotic Chemistry Experiment on the Adsorption of Nucleic Acids Bases onto a Natural Zeolite

    NASA Astrophysics Data System (ADS)

    Anizelli, Pedro R.; Baú, João Paulo T.; Gomes, Frederico P.; da Costa, Antonio Carlos S.; Carneiro, Cristine E. A.; Zaia, Cássia Thaïs B. V.; Zaia, Dimas A. M.

    2015-09-01

    There are currently few mechanisms that can explain how nucleic acid bases were synthesized, concentrated from dilute solutions, and/or protected against degradation by UV radiation or hydrolysis on the prebiotic Earth. A natural zeolite exhibited the potential to adsorb adenine, cytosine, thymine, and uracil over a range of pH, with greater adsorption of adenine and cytosine at acidic pH. Adsorption of all nucleic acid bases was decreased in artificial seawater compared to water, likely due to cation complexation. Furthermore, adsorption of adenine appeared to protect natural zeolite from thermal degradation. The C=O groups from thymine, cytosine and uracil appeared to assist the dissolution of the mineral while the NH2 group from adenine had no effect. As shown by FT-IR spectroscopy, adenine interacted with a natural zeolite through the NH2 group, and cytosine through the C=O group. A pseudo-second-order model best described the kinetics of adenine adsorption, which occurred faster in artificial seawaters.

  17. A Prebiotic Chemistry Experiment on the Adsorption of Nucleic Acids Bases onto a Natural Zeolite.

    PubMed

    Anizelli, Pedro R; Baú, João Paulo T; Gomes, Frederico P; da Costa, Antonio Carlos S; Carneiro, Cristine E A; Zaia, Cássia Thaïs B V; Zaia, Dimas A M

    2015-09-01

    There are currently few mechanisms that can explain how nucleic acid bases were synthesized, concentrated from dilute solutions, and/or protected against degradation by UV radiation or hydrolysis on the prebiotic Earth. A natural zeolite exhibited the potential to adsorb adenine, cytosine, thymine, and uracil over a range of pH, with greater adsorption of adenine and cytosine at acidic pH. Adsorption of all nucleic acid bases was decreased in artificial seawater compared to water, likely due to cation complexation. Furthermore, adsorption of adenine appeared to protect natural zeolite from thermal degradation. The C=O groups from thymine, cytosine and uracil appeared to assist the dissolution of the mineral while the NH2 group from adenine had no effect. As shown by FT-IR spectroscopy, adenine interacted with a natural zeolite through the NH2 group, and cytosine through the C=O group. A pseudo-second-order model best described the kinetics of adenine adsorption, which occurred faster in artificial seawaters. PMID:25754589

  18. Adsorption and transport of polymaleic acid on Callovo-Oxfordian clay stone: Batch and transport experiments

    NASA Astrophysics Data System (ADS)

    Durce, Delphine; Landesman, Catherine; Grambow, Bernd; Ribet, Solange; Giffaut, Eric

    2014-08-01

    Dissolved Organic Matter (DOM) can affect the mobility of radionuclides in pore water of clay-rich geological formations, such as those intended to be used for nuclear waste disposal. The present work studies the adsorption and transport properties of a polycarboxylic acid, polymaleic acid (PMA, Mw = 1.9 kDa), on Callovo-Oxfordian argillite samples (COx). Even though this molecule is rather different from the natural organic matter found in clay rock, the study of its retention properties on both dispersed and intact samples allows assessing to which extent organic acids may undergo sorption under natural conditions (pH 7) and what could be the impact on their mobility. PMA sorption and desorption were investigated in dispersed systems. The degree of sorption was measured after 1, 8 and 21 days and for a range of PMA initial concentrations from 4.5 × 10- 7 to 1.4 × 10- 3 mol.L- 1. The reversibility of the sorption process was estimated by desorption experiments performed after the sorption experiments. At the sorption steady state, the sorption was described by a two-site Langmuir model. A total sorption capacity of COx for PMA was found to be 1.01×10- 2 mol.kg- 1 distributed on two sorption sites, one weak and one strong. The desorption of PMA was incomplete, independently of the duration of the sorption phase. The amount of desorbable PMA even appeared to decrease for sorption phases from 1 to 21 days. To describe the apparent desorption hysteresis, two conceptual models were applied. The two-box diffusion model accounted for intraparticle diffusion and more generally for nonequilibrium processes. The two-box first-order non-reversible model accounted for a first-order non-reversible sorption and more generally for kinetically-controlled irreversible sorption processes. The use of the two models revealed that desorption hysteresis was not the result of nonequilibrium processes but was due to irreversible sorption. Irreversible sorption on the strong site was

  19. Surface modification of activated carbon for enhanced adsorption of perfluoroalkyl acids from aqueous solutions.

    PubMed

    Zhi, Yue; Liu, Jinxia

    2016-02-01

    The objective of the research was to examine the effect of increasing carbon surface basicity on uptake of perfluorooctane sulfonic (PFOS) and carboxylic acids (PFOA) by activated carbon. Granular activated carbons made from coal, coconut shell, wood, and phenolic-polymer-based activated carbon fibers were modified through high-temperature and ammonia gas treatments to facilitate systematical evaluation of the impact of basicity of different origins. Comparison of adsorption isotherms and adsorption distribution coefficients showed that the ammonia gas treatment was more effective than the high-temperature treatment in enhancing surface basicity. The resultant higher point of zero charges and total basicity (measured by total HCl uptake) correlated with improved adsorption affinity for PFOS and PFOA. The effectiveness of surface modification to enhance adsorption varied with carbon raw material. Wood-based carbons and activated carbon fibers showed enhancement by one to three orders of magnitudes while other materials could experience reduction in adsorption towards either PFOS or PFOA. PMID:26469934

  20. Fundamentals of high pressure adsorption

    SciTech Connect

    Zhou, Y.P.; Zhou, L.

    2009-12-15

    High-pressure adsorption attracts research interests following the world's attention to alternative fuels, and it exerts essential effect on the study of hydrogen/methane storage and the development of novel materials addressing to the storage. However, theoretical puzzles in high-pressure adsorption hindered the progress of application studies. Therefore, the present paper addresses the major theoretical problems that challenged researchers: i.e., how to model the isotherms with maximum observed in high-pressure adsorption; what is the adsorption mechanism at high pressures; how do we determine the quantity of absolute adsorption based on experimental data. Ideology and methods to tackle these problems are elucidated, which lead to new insights into the nature of high-pressure adsorption and progress in application studies, for example, in modeling multicomponent adsorption, hydrogen storage, natural gas storage, and coalbed methane enrichment, was achieved.

  1. Adsorption characteristics of haloacetonitriles on functionalized silica-based porous materials in aqueous solution.

    PubMed

    Prarat, Panida; Ngamcharussrivichai, Chawalit; Khaodhiar, Sutha; Punyapalakul, Patiparn

    2011-09-15

    The effect of the surface functional group on the removal and mechanism of dichloroacetonitrile (DCAN) adsorption over silica-based porous materials was evaluated in comparison with powdered activated carbon (PAC). Hexagonal mesoporous silicate (HMS) was synthesized and functionalized by three different types of organosilanes (3-aminopropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane and n-octyldimethysilane). Adsorption kinetics and isotherm models were used to determine the adsorption mechanism. The selective adsorption of five haloacetonitriles (HANs) in the single and mixed solute systems was also studied. The experiments revealed that the surface functional groups of the adsorbents largely affected the DCAN adsorption capacities. 3-Mercaptopropyl-grafted HMS had a high DCAN adsorption capacity compared to PAC. The adsorption mechanism is believed to occur via an ion-dipole electrostatic interaction in which water interference is inevitable at low concentrations of DCAN. In addition, the adsorption of DCAN strongly depended on the pH of the solution as this related to the charge density of the adsorbents. The selective adsorption of the five HANs over PAC was not observed, while the molecular structure of different HANs obviously influenced the adsorption capacity and selectivity over 3-mercaptopropyl-grafted HMS. PMID:21752539

  2. Negligible effects of tryptophan on the aflatoxin adsorption of sodium bentonite.

    PubMed

    Magnoli, A P; Copia, P; Monge, M P; Magnoli, C E; Dalcero, A M; Chiacchiera, S M

    2014-01-01

    The main objective of this study was to determine if the competitive adsorption of tryptophan (Trp) and aflatoxin B₁ (AFB₁) could potentially affect the ability of a sodium bentonite (NaB) to prevent aflatoxicosis in monogastric animals. The adsorption of Trp and AFB₁ on this adsorbent is fast and could be operating on the same time-scale making competition feasible. In vitro competitive adsorption experiments under simulated gastrointestinal conditions were performed. A high affinity of the clay for Trp and NaB was observed. The effect of an excess of KCl to mimic the ionic strength of the physiological conditions were also investigated. A six-times decrease in the Trp surface excess at saturation was observed. A similar behaviour was previously found for AFB₁ adsorption. Taking into account the amount of Trp adsorbed by the clay and the usual adsorbent supplementation level in diets, a decrease in Trp bioavailability is not expected to occur. Tryptophan adsorption isotherms on NaB were 'S'-shaped and were adjusted by the Frumkin-Fowler-Guggenheim model. The reversibility of the adsorption processes was investigated in order to check a potential decrease in the ability of NaB to protect birds against chronic aflatoxicoses. Adsorption processes were completely reversible for Trp, while almost irreversible for AFB₁. In spite of the high affinity of the NaB for Trp, probably due to the reversible character of Trp adsorption, no changes in the AFB₁ adsorption isotherm were observed when an excess of the amino acid was added to the adsorption medium. As a consequence of the preferential and irreversible AFB₁ adsorption and the reversible weak binding of Trp to the NaB, no changes in the aflatoxin sorption ability of the clay are expected to occur in the gastrointestinal tract of birds. PMID:25363215

  3. Kinetic and equilibrium studies of adsorptive removal of phenol onto eggshell waste.

    PubMed

    Daraei, H; Mittal, A; Noorisepehr, M; Daraei, F

    2013-07-01

    The aim of the present research is to develop economic, fast, and versatile method for the removal of toxic organic pollutant phenol from wastewater using eggshell. The batch experiments are conducted to evaluate the effect of pH, phenol concentration, dosage of adsorbent, and contact time on the removal of phenol. The paper includes in-depth kinetic studies of the ongoing adsorption process. Attempts have also been made to verify Langmuir and Freundlich adsorption isotherms. The morphology and characteristics of eggshell have also been studied using scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, and X-ray fluorescence analysis. At ambient temperature, the maximum adsorption of phenol onto eggshells has been achieved at pH 9 and the contact time, 90 min. The experimental data give best-fitted straight lines for pseudo-first-order as well as pseudo-second-order kinetic models. Furthermore, the adsorption process verifies Freundlich and Langmuir adsorption isotherms, and on the basis of mathematical expressions of these models, various necessary adsorption constants have been calculated. Using adsorption data, various thermodynamic parameters like change in enthalpy (∆H(0)), change in entropy (∆S(0)), and change in free energy ∆G(0) have also been evaluated. Results clearly reveal that the solid waste material eggshell acts as an effective adsorbent for the removal of phenol from aqueous solutions. PMID:23274804

  4. Facile synthesis of boehmite/PVA composite membrane with enhanced adsorption performance towards Cr(VI).

    PubMed

    Luo, Lei; Cai, Weiquan; Zhou, Jiabin; Li, Yuanzhi

    2016-11-15

    A novel boehmite/PVA composite membrane (BPCM) with remarkably enhanced adsorption performance towards Cr(VI) was successfully synthesized from Al(NO3)3·9H2O using HAc as the peptizing agent via a facile sol-gel method. The physicochemical properties of the BPCM, the boehmite powder (BP) without PVA and a commercial boehmite powder (CBP) were comparatively characterized by XRD, TGA-DSC, FT-IR and XPS. Batch adsorption experiments showed that the adsorption performance of the BPCM is much better than those of BP and CBP. Its adsorption process was well described by the pseudo-second-order kinetic model, and its equilibrium data fit the Langmuir isotherm well with a maximum adsorption capacity of 36.41mgg(-1). Its interference adsorption experiment in presence of coexisting anions showed that SO4(2-) and HPO4(2-) have greater effect than those of the Cl(-), F(-), C2O4(2-) and HCO3(-). A three step action mechanism including adsorption of Cr(VI) anions, complexation between Cr(VI) anions and the functional groups on the surface of BPCM, and the reduction of Cr(VI) to Cr(III) was proposed to illustrate the adsorption process. This efficient film could be easily separated after adsorption, exhibiting great potential for the removal of Cr(VI) from aqueous solution, and other fields of environmental remediation. PMID:27450337

  5. Physico-chemical processes for landfill leachate treatment: Experiments and mathematical models

    SciTech Connect

    Xing, W.; Ngo, H.H.; Kim, S.H.; Guo, W.S.; Hagare, P.

    2008-07-01

    In this study, the adsorption of synthetic landfill leachate onto four kinds of activated carbon has been investigated. From the equilibrium and kinetics experiments, it was observed that coal based PAC presented the highest organic pollutants removal efficiency (54%), followed by coal based GAC (50%), wood based GAC (33%) and wood based PAC (14%). The adsorption equilibrium of PAC and GAC was successfully predicted by Henry-Freundlich adsorption model whilst LDFA + Dual isotherm Kinetics model could describe well the batch adsorption kinetics. The flocculation and flocculation-adsorption experiments were also conducted. The results indicated that flocculation did not perform well on organics removal because of the dominance of low molecular weight organic compounds in synthetic landfill leachate. Consequently, flocculation as pretreatment to adsorption and a combination of flocculation-adsorption could not improve much the organic removal efficiency for the single adsorption process.

  6. Potential soluble, reactive, adsorptive and particulate tracers for source-receptor experiments in MATEX

    SciTech Connect

    Senum, G.I.; Dietz, R.N.

    1985-07-01

    A survey of potential non-conservative tracers for use in source-receptor studies in acid deposition is presented. Classes of tracers considered were water soluble tracers, chemically reactive tracers, adsorptive tracers and particulate tracers. A criterion used for the selection of compounds for nonconservative tracers is that they be as reasonably compatible in the analytical detection system used for the conservative perfluorocarbon tracers. For each class of non-conservative tracers several example compounds are given and discussed, along with the research needed to develop these tracers. A reasonable development time for these tracers is as follows; adsorptive tracers, 2 years; particulate tracers, 2 1/2 years; soluble tracers, 3 years and reactive tracers, 3 1/2 years. By development, it is meant that 1 or 2 tracers have been developed and at least demonstrated in a small field test. 6 refs., 2 tabs.

  7. Adsorption of atrazine on soils: model study.

    PubMed

    Kovaios, Ilias D; Paraskeva, Christakis A; Koutsoukos, Petros G; Payatakes, Alkiviades Ch

    2006-07-01

    The adsorption of the widely used herbicide atrazine onto three model inorganic soil components (silica gel, gamma-alumina, and calcite (CaCO(3)) was investigated in a series of batch experiments in which the aqueous phase equilibrated with the solid, under different solution conditions. Atrazine did not show discernible adsorption on gamma-alumina (theta=25 degrees C, 3.8adsorption from solutions was found for silica gel suspensions. The adsorption isotherms obtained for atrazine uptake on silica gel particles were best fitted with the Freundlich model. An increase of the ionic strength of the electrolytic solution induced an increase of the surface concentration of atrazine on silica gel, indicating significant electrostatic interactions between atrazine and silica gel particles, possibly through interaction with the surface silanol groups of the solid substrate. Increase of the pH value of the electrolyte solution from 6 to 9 considerably decreased the amount of atrazine adsorbed on the silica gel substrate. Decrease of the solution pH from 6 to 3 had only a slight effect on the surface concentration of the adsorbed atrazine. The adsorption of atrazine on silica gel increased when the temperature was decreased from 40 to 25 degrees C, an indication that the adsorption is exothermic. The calculated enthalpy of adsorption ( approximately 10 kJ/mol) indicates that the uptake at the solid-liquid equilibrium pH (6.1) was largely due to physisorption. PMID:16556447

  8. Reversible adsorption of hydrogen chloride to ice surfaces

    NASA Astrophysics Data System (ADS)

    Zimmermann, Stefan; Kippenberger, Matthias; Crowley, John

    2015-04-01

    Hydrogen chloride is the most important reservoir of gaseous, reactive chlorine in the atmosphere. Although several laboratory investigations of the interaction of HCl with ice surfaces have been conducted, there is still great uncertainty associated with the adsorption isotherms of HCl on ice, which is largely a consequence of most previous studies being unable to work at concentrations relevant for the atmosphere and to explore the non-saturated part of the isotherm at sub-monolayer coverage. We have conducted experiments on HCl uptake on ice surfaces at temperatures between 190 and 220 K, using a coated wall flow tube. HCl at concentrations as low as 2 × 109 molecule cm3 (~10-8 Torr) was detected using a chemical-ionization, quadrupole mass spectrometer. The equilibrium surface coverage of HCl on ice could be interpreted using the Langmuir-model to derive partition coefficients (KLang). We find that the dissociative Langmuir isotherm describes our data significantly better than the non-dissociative type. Surprisingly, and in contrast to the behavior of the majority of traces-gases which adsorb reversibly on ice surfaces, the partition-coefficients we derive for HCl do not show a systematic dependence on temperature, precluding the simple derivation of an adsorption enthalpy and indicating the presence of more complex adsorption and desorption mechanisms for strong acids ionizing on the surface compared to H-bonded trace gases.

  9. Surface pressure isotherm for a monolayer of charged colloidal particles at a water/nonpolar-fluid interface: experiment and theoretical model.

    PubMed

    Petkov, Plamen V; Danov, Krassimir D; Kralchevsky, Peter A

    2014-03-18

    Monolayers from electrically charged micrometer-sized silica particles, spread on the air/water interface, are investigated. Because of the electrostatic repulsion, the distances between the particles are considerably greater than their diameters, i.e., we are dealing with nondensely packed interfacial layers. The electrostatic repulsion between the particles occurs through the air phase. Surface pressure vs area isotherms were measured by Langmuir trough, and the monolayers' morphology was monitored by microscope. The mean area per particle is determined by Delaunay triangulation and Voronoi diagrams. In terms of mean area, the surface pressure for monolayers from polydisperse and monodisperse particles obeys the same law. The experiments show that Π ∝ L(-3) at large L, where Π is the surface pressure and L is the mean interparticle distance. A theoretical cell model is developed, which predicts not only the aforementioned asymptotic law but also the whole Π(L) dependence. The model presumes a periodic distribution of the surface charge density, which induces a corresponding electric field in the air phase. Then, the Maxwell pressure tensor of the electric field in the air phase is calculated and integrated according to the Bakker's formula to determine the surface pressure. Thus, all collective effects from the electrostatic interparticle interactions are taken into account as well as the effects from the particle finite size. By evaporation of water, the particle monolayers are deposited on a solid substrate placed on the bottom of the trough. The electrostatic interparticle repulsion is strong enough to withstand the attractive lateral capillary immersion forces that are operative during the drying of the monolayer on the substrate. The obtained experimental results and the developed theoretical model can be useful for prediction and control of the properties of nondensely packed interfacial monolayers from charged particles that find applications for

  10. Adsorption of nicotine from aqueous solution onto hydrophobic zeolite type USY

    NASA Astrophysics Data System (ADS)

    Lazarevic, Natasa; Adnadjevic, Borivoj; Jovanovic, Jelena

    2011-07-01

    The isothermal adsorption of nicotine from an aqueous solution onto zeolite type USY was investigated. The adsorption isotherms of nicotine onto the zeolite at different temperatures ranging from 298 to 322 K were determined. It was found that the adsorption isotherms can be described by the model of Freundlich adsorption isotherm. Based on the adsorption isotherms the changes of adsorption heat, free energy and entropy with adsorption degree were determined. The determined decrease of adsorption heat with adsorption degree can be explained by the presence of the adsorption centers of different energy and concentration on interface of zeolite-nicotine solution. It was found that the probability function of density distribution of the heat of adsorption (DDF) has exponential form. It was concluded that the possibility of fitting the adsorption isotherms of nicotine onto the zeolite by Freundlich adsorption isotherm was a direct consequence of that. The determined increase in entropy with the increase in adsorption degree can be explained with the change of phase state of adsorbed nicotine.

  11. Fibrinogen adsorption onto 316L stainless steel, Nitinol and titanium

    NASA Astrophysics Data System (ADS)

    Bai, Zhijun; Filiaggi, M. J.; Dahn, J. R.

    2009-03-01

    Fibrinogen adsorption onto mechanically polished biomedical grade 316L stainless steel (316LSS), nickel titanium alloy (Nitinol) and commercially pure titanium (CpTi) surfaces were studied by measurements of adsorption isotherms and adsorption kinetics using an ex-situ wavelength dispersive spectroscopy technique (WDS). Surface composition, roughness and wettability of these materials were characterized by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and water contact angle (WCA) measurements. Adsorption isotherm results showed that surface protein concentration on these materials increased with increasing concentration of fibrinogen in phosphate buffer solution. The fibrinogen adsorption isotherms were modeled by both the monolayer Langmuir isotherm and the multilayer Brunauer-Emmett-Teller (BET) isotherm. The results strongly suggest that fibrinogen forms multilayer structures on these materials when the concentration in solution is high. Complementary measurements on the absorbed fibrinogen films by spectroscopic ellipsometry (SE) support this view.

  12. Adsorption of Ar on individual carbon nanotubes, graphene, and graphite

    NASA Astrophysics Data System (ADS)

    Dzyubenko, Boris; Kahn, Joshua; Vilches, Oscar; Cobden, David

    2015-03-01

    We compare and contrast results of adsorption measurements of Ar on single-walled carbon nanotubes, graphene, and graphite. Adsorption isotherms on individual suspended nanotubes were obtained using both the mechanical resonance frequency shift (sensitive to mass adsorption) and the electrical conductance. Isotherms on graphene mounted on hexagonal boron nitride were obtained using only the conductance. New volumetric adsorption isotherms on bulk exfoliated graphite were also obtained, paying special attention to the very low coverage region (less than 2% of a monolayer). This allowed us to compare the degree of heterogeneity on the three substrate types, the binding energies, and the van der Waals 2D parameters. Research supported by NSF DMR 1206208.

  13. Adsorption and transformation of ammonium ion in a loose-pore geothermal reservoir: Batch and column experiments

    NASA Astrophysics Data System (ADS)

    Zhao, Li; Li, Yanli; Wang, Shidong; Wang, Xinyi; Meng, Hongqi; Luo, Shaohe

    2016-09-01

    Adsorption kinetics and transformation process of ammonium ion (NH4+) were investigated to advance the understanding of N cycle in a low-temperature loose-pore geothermal reservoir. Firstly, batch experiments were performed in order to determine the sorption capacity and the kinetic mechanism of NH4+ onto a loose-pore geothermal reservoir matrix. Then column experiments were carried out at temperatures from 20 °C to 60 °C in order to determine the transport parameters and transformation mechanism of NH4+ in the studied matrix. The results showed that the adsorption process of NH4+ onto the porous media well followed the pseudo-second-order model. No obvious variation of hydrodynamic dispersion coefficient (D) and retardation factor (R) was observed at different transport distances at a Darcy's flux of 2.27 cm/h, at which nitrification could be neglected. The simulated D obtained by the CDE model in CXTFIT2.1 increased with temperature while R decreased with temperature, indicating that the adsorption capacity of NH4+ onto the matrix decreased with the increasing of temperature. When the Darcy's flux was decreased to 0.014 cm/h, only a little part of NH4+ could be transformed to nitrate, suggesting that low density of nitrifiers existed in the simulated loose-pore geothermal reservoir. Although nitrification rate increased with temperature in the range of 20 °C to 60 °C, it was extremely low and no accumulation of nitrite was observed under the simulated low-temperature geothermal conditions without addition of biomass and oxygen.

  14. Adsorption and transformation of ammonium ion in a loose-pore geothermal reservoir: Batch and column experiments.

    PubMed

    Zhao, Li; Li, Yanli; Wang, Shidong; Wang, Xinyi; Meng, Hongqi; Luo, Shaohe

    2016-09-01

    Adsorption kinetics and transformation process of ammonium ion (NH4(+)) were investigated to advance the understanding of N cycle in a low-temperature loose-pore geothermal reservoir. Firstly, batch experiments were performed in order to determine the sorption capacity and the kinetic mechanism of NH4(+) onto a loose-pore geothermal reservoir matrix. Then column experiments were carried out at temperatures from 20°C to 60°C in order to determine the transport parameters and transformation mechanism of NH4(+) in the studied matrix. The results showed that the adsorption process of NH4(+) onto the porous media well followed the pseudo-second-order model. No obvious variation of hydrodynamic dispersion coefficient (D) and retardation factor (R) was observed at different transport distances at a Darcy's flux of 2.27cm/h, at which nitrification could be neglected. The simulated D obtained by the CDE model in CXTFIT2.1 increased with temperature while R decreased with temperature, indicating that the adsorption capacity of NH4(+) onto the matrix decreased with the increasing of temperature. When the Darcy's flux was decreased to 0.014cm/h, only a little part of NH4(+) could be transformed to nitrate, suggesting that low density of nitrifiers existed in the simulated loose-pore geothermal reservoir. Although nitrification rate increased with temperature in the range of 20°C to 60°C, it was extremely low and no accumulation of nitrite was observed under the simulated low-temperature geothermal conditions without addition of biomass and oxygen. PMID:27356192

  15. Adsorption of methyl violet from aqueous solutions by the biochars derived from crop residues.

    PubMed

    Xu, Ren-kou; Xiao, Shuang-cheng; Yuan, Jin-hua; Zhao, An-zhen

    2011-11-01

    The adsorption of methyl violet by the biochars from crop residues was investigated with batch and leaching experiments--adsorption capacity varied with their feedstock in the following order: canola straw char>peanut straw char>soybean straw char>rice hull char. This order was generally consistent with the amount of negative charge of the biochars. Zeta potentials and Fourier transform infrared photoacoustic spectroscopy, combined with adsorption isotherms and effect of ionic strength, indicated that adsorption of methyl violet on biochars involved electrostatic attraction, specific interaction between the dye and carboxylate and phenolic hydroxyl groups on the biochars, and surface precipitation. Leaching experiments showed that 156 g of rice hull char almost completely removed methyl violet from 18.2 L of water containing 1.0 mmol/L of methyl violet. The biochars had high removal efficiency for methyl violet and could be effective adsorbents for removal of methyl violet from wastewater. PMID:21924897

  16. Response surface methodology approach for optimization of adsorption of Janus Green B from aqueous solution onto ZnO/Zn(OH)2-NP-AC: Kinetic and isotherm study

    NASA Astrophysics Data System (ADS)

    Ghaedi, M.; Khafri, H. Zare; Asfaram, A.; Goudarzi, A.

    2016-01-01

    The Janus Green B (JGB) adsorption onto homemade ZnO/Zn(OH)2 nanoparticles loaded on activated carbon (AC) which characterized by FESEM and XRD analysis has been reported. Combination of response surface methodology (RSM) and central composite design (CCD) has been employed to model and optimize variables using STATISTICA 10.0 software. The influence of parameters over pH (2.0-8.0), adsorbent (0.004-0.012 g), sonication time (4-8 min) and JGB concentration (3-21 mg L-1) on JGB removal percentage was investigated and their main and interaction contribution was examined. It was revealed that 21 mg L-1 JGB, 0.012 g ZnO/Zn(OH)2-NP-AC at pH 7.0 and 7 min sonication time permit to achieve removal percentage more than 99%. Finally, a good agreement between experimental and predicted values after 7 min was achieved using pseudo-second-order rate equation. The Langmuir adsorption is appropriate for correlation of equilibrium data. The small amount of adsorbent (0.008-0.015 g) is applicable for successful removal of JGB (RE > 99%) in short time (7 min) with high adsorption capacity (81.3-98.03 mg g-1).

  17. Studies of gas adsorption in flexible Metal-Organic frameworks

    NASA Astrophysics Data System (ADS)

    Sircar, Sarmishtha

    Flexible Metal-Organic frameworks that exhibit a gate-opening (GO) adsorption mechanism have potential for gas separations and gas storage. The GO phenomenon occurs when molecular gates in the structure expand/contract in response to the activation/de-activation of a system variable e.g. temperature, pressure or gas. Sharp discontinuities in the isotherm leading to S-shapes and large adsorption-desorption hysteresis are typical of this phenomenon. This study investigates the kinetics and thermodynamics of the GO behavior by combining adsorption measurements and analytical modeling of adsorption kinetics and capacity as a function of adsorbate, GO pressure, and temperature. Basic understanding of GO mechanism will help harness GO-MOF's as adsorbents for gas separations and storage. Experiments were performed on two precharacterized MOFs with verified GO behavior. These are (1) Zn2(bpdc)2(bpee), which expands from a relative amorphous to crystalline structure and (2) Cu[(dhbc) 2(4,4f-bpy)]H2O, a mutually interdigitated 2-D structure (bpdc = biphenyldicarboxylate, bpee = 1,2]bipyridylethene; DMF = N,N-dimethyl formamide, dhbc= 2,5-dihydroxybenzoic acid, bpy=bipyridine). Both sub- and super-critical adsorption data were collected using three adsorption units: a standard low-pressure volumetric adsorption unit, a commercial high-pressure gravimetric analyzer and a custom-built high-pressure differential volumetric unit. Collected laboratory data were combined with published adsorption rate and isotherm data for analysis to broaden the range of data collection. The accuracy of the high-pressure differential unit was improved by over 300-fold by changing analytical methods of processing data to establish a reliable null correction. A pronounced effect of the allowed experimental time was found at cryogenic temperatures on (1). Tightening the stability criteria used by the adsorption equipment to determine equilibration increased the experimental time from the order of

  18. Modeling investigation of membrane biofouling phenomena by considering the adsorption of protein, polysaccharide and humic acid.

    PubMed

    Demneh, Seyedeh Marzieh Ghasemi; Nasernejad, Bahram; Modarres, Hamid

    2011-11-01

    The importance of solute adsorption in the biofouling membrane has been clearly verified for the performance of membrane bioreactor (MBR). In order to quantify the mechanism of static adsorption in biofouling during of MBR process, we characterize membrane biofouling caused by model solutions containing a protein (bovine serum albumin, BSA), a humic substance (humic acid, HA) and a polysaccharide (alginic acid, Alg) on commercial hydrophilic polyethersulfone (PES) membrane. For static adsorption experiments, membranes were immersed in well-defined model solutions in three temperatures (298, 308 and 318 K) to obtain equilibrium data. To determine the characteristic parameters for this process, 7 isotherm models were applied to the experimental data. Three error analysis methods; the coefficient of nonlinear regression (R(2)), the sum of the squared errors (SSE) and standard deviation of residuals (S(yx)), were used to evaluate the data and determine the best fit isotherm for each model solutions. The error values demonstrated that the Sips isotherm model provided the best fit to the experimental data. AFM images were used for determination of changes in membrane surface after adsorption. These images confirmed the results obtained from adsorption isotherm study. Thermodynamic parameters such as standard free energy (Δ(r)G(θ)), enthalpy (Δ(r)H(θ)) and entropy (Δ(r)S(θ)) changes were determined; these adsorption processes were found to be feasible and endothermic but not spontaneous. The distribution of the substances adsorbed on PES surface were more chaotic than that in the aqueous solutions. Parameters obtained in this study can be used to determine the "fouling potential" of a given feed stream and a membrane. PMID:21798726

  19. Protein nanoparticle interaction: A spectrophotometric approach for adsorption kinetics and binding studies

    NASA Astrophysics Data System (ADS)

    Vaishanav, Sandeep K.; Chandraker, Kumudini; Korram, Jyoti; Nagwanshi, Rekha; Ghosh, Kallol K.; Satnami, Manmohan L.

    2016-08-01

    Investigating the protein nanoparticle interaction is crucial to understand how to control the biological interactions of nanoparticles. In this work, Model protein Bovine serum albumin (BSA) was used to evaluate the process of protein adsorption to the gold nanoparticles (GNPs) surface. The binding of a model protein (BSA) to GNPs was investigated through fluorescence quenching measurements. The strong affinities of BSA for GNPs were confirmed by the high value of binding constant (Ks) which was calculated to be 2.2 × 1011 L/mol. In this consequence, we also investigated the adsorption behavior of BSA on GNPs surface via UV-Vis spectroscopy. The effect of various operational parameters such as pH, contact time, initial BSA concentration, and temperature on adsorption of BSA was investigated using batch adsorption experiments. Kinetics of adsorption was found to follow the pseudo-second order rate equation. The suitability of Freundlich and Langmuir adsorption models to the equilibrium data was investigated. The equilibrium adsorption was well described by the Freundlich isotherm model. The maximum adsorption capacity for BSA adsorbed on GNPs was 58.71 mg/g and equilibrium constant was 0.0058 calculated by the Langmuir model at 298 K and pH = 11.0. Thermodynamic parameters showed that the adsorption of BSA onto GNPs was feasible, spontaneous, and exothermic.

  20. Kinetics and Thermodynamics of Reserpine Adsorption onto Strong Acidic Cationic Exchange Fiber

    PubMed Central

    Guo, Zhanjing; Liu, Xiongmin; Huang, Hongmiao

    2015-01-01

    The kinetics and thermodynamics of the adsorption process of reserpine adsorbed onto the strong acidic cationic exchange fiber (SACEF) were studied by batch adsorption experiments. The adsorption capacity strongly depended on pH values, and the optimum reserpine adsorption onto the SACEF occurred at pH = 5 of reserpine solution. With the increase of temperature and initial concentration, the adsorption capacity increased. The equilibrium was attained within 20 mins. The adsorption process could be better described by the pseudo-second-order model and the Freundlich isotherm model. The calculated activation energy Ea was 4.35 kJ/mol. And the thermodynamic parameters were: 4.97<ΔH<7.44 kJ/mol, -15.29<ΔG<-11.87 kJ/mol and 41.97<ΔS<47.35 J/mol·K. The thermodynamic parameters demonstrated that the adsorption was an endothermic, spontaneous and feasible process of physisorption within the temperature range between 283 K and 323 K and the initial concentration range between 100 mg/L and 300 mg/L. All the results showed that the SACEF had a good adsorption performance for the adsorption of reserpine from alcoholic solution. PMID:26422265

  1. Adsorption of a cationic surfactant by a magsorbent based on magnetic alginate beads.

    PubMed

    Obeid, Layaly; El Kolli, Nadia; Dali, Noëlle; Talbot, Delphine; Abramson, Sébastien; Welschbillig, Mathias; Cabuil, Valérie; Bée, Agnès

    2014-10-15

    Adsorption of cetylpyridinium chloride (CPC), a cationic surfactant, by magnetic alginate beads (MagAlgbeads) was investigated. The magnetic adsorbent (called magsorbent) was prepared by encapsulation of magnetic functionalized nanoparticles in an alginate gel. The influence on CPC adsorption of several parameters such as contact time, pH and initial surfactant concentration was studied. The equilibrium isotherm shows that adsorption occurs through both electrostatic interactions with charge neutralization of the carboxylate groups of the beads and hydrophobic interactions inducing the formation of surfactant aggregates in the beads. The dosage of calcium ions released in the solution turns out to be a useful tool for understanding the adsorption mechanisms. Adsorption is accompanied by a shrinking of the beads that corresponds to a 45% reduction of the volume. Adsorption kinetic experiments show that equilibrium time is strongly dependent on the surfactant concentration, which monitors the nature of the interactions. On the other hand, since the pH affects the ionization state of adsorption sites, adsorption depends on the pH solution, maximum adsorption being obtained in a large pH range (3.2-12) in agreement with the pKa value of alginate (pKa=3.4-4.2). Finally, due to the formation of micelle-like surfactants aggregates in the magnetic alginate beads, they could be used as a new efficient magsorbent for hydrophobic pollutants. PMID:25086393

  2. Kinetic Batch Soil Adsorption Studies of 2, 4-dinitroanisole (DNAN)

    NASA Astrophysics Data System (ADS)

    Arthur, J.; Mark, N. W.; Taylor, S.; Brusseau, M. L.; Dontsova, K.

    2014-12-01

    Currently the explosive 2, 4, 6- trinitrotoluene (TNT) is used as a main ingredient in munitions; however the compound has failed to meet sensitivity requirements. The replacement compound being tested is 2, 4-dinitroanisole (DNAN). DNAN is less sensitive to shock, high temperatures, and has good detonation characteristics. However, DNAN is more soluble than TNT, which can influence transport and fate behavior and thus bioavailability and exposure potential. DNAN has been shown to have some human and environmental toxicity. The objective of this study was to investigate the environmental fate of DNAN in soil, with a specific focus on sorption processes. Batch experiments were conducted using 11 soils collected from military installations located across the United States. The soils were characterized for pH, specific surface area, electrical conductivity, cation exchange capacity, and organic carbon content. Adsorption kinetic data determined at room temperature were fitted using the first order kinetic equation. Adsorption isotherms were fitted with linear and Freundlich isotherm equations. The magnitudes of the linear adsorption coefficients ranged from 0.6 to 6 cm3/g. Results indicated that the adsorption of DNAN is strongly dependent on the amount of organic carbon present in the soil.

  3. Adsorption / Desorption Behavior of Water Vapor in an Adsorbent Desiccant Rotor

    NASA Astrophysics Data System (ADS)

    Tsujiguchi, Takuya; Kodama, Akio

    Adsorption / desorption behavior of water vapor onto desiccant rotor has been investigated to improve the desiccant cooling system by means of computer simulation. In this paper, we paid attention to the relationship between the equilibrium amount of water adsorbed onto the desiccant material and the relative humidity, that is adsorption isotherm as a principal characteristic feature of adsorbent. Considering actual adsorbents, five types of adsorption isotherms were assumed to clarify the influence of adsorption isotherm on the dehumidifying performance. After the investigation on the influences of some operating conditions on the dehumidifying performance at each selected adsorption isotherm, it was found that higher dehumidifying performance and reduction of length of desiccant rotor could be achieved by selecting appropriate adsorption isotherm. It was also predicted that S-shaped adsorption isotherm which is raised sharply at relative humidity around 15 % could produce the lowest air humidity at regeneration air temperature 80 °C. Moreover influence of the intraparticle diffusion coefficient which significantly influence on the adsorption / desorption rate was discussed choosing two adsorption isotherm from the above five isotherms. It seems that effective range of the intraparticle diffusion coefficient for the significant improvement of the dehumidifying performance was strongly influenced by the shape of adsorption isotherm.

  4. Size dependent adsorption on nanocrystal surfaces

    NASA Astrophysics Data System (ADS)

    Lu, H. M.; Wen, Z.; Jiang, Q.

    2005-03-01

    A quantitative thermodynamic correlation method to describe the size dependent Langmuir adsorption isotherm is developed. According to the model, the equilibrium adsorption constant increases as material size decreases, which is in agreement with the literature data of acetic acid, valeric acid, oxalic acid, and adipic acid on anatase nanoparticles.

  5. [Preparation of magnetic quaternary chitosan salt and its adsorption of methyl orange from water].

    PubMed

    Zhang, Cong-lu; Hu, Xiao-min; Ying, Shi-ying; Wang, Fang

    2013-05-01

    First, quaternary chitosan salts with different substitution degrees were prepared in glycine hydrochloride ([Gly]Cl) ionic liquid. Nano-sized Fe3O4 powder was obtained through chemical co-precipitation method. And then, magnetic quaternary chitosan particles were prepared through inverse suspension cross-linking using Fe3O4 was the nucleus and glutaraldehyde as the cross-linking agent. The influence of different reaction conditions on adsorption was discussed. Adsorption of methyl orange (MO) by magnetic quaternary chitosan particles was studied through the static adsorption method. The results showed that at pH 3.0 and 25 degrees C the adsorption capacity varied from 37.45 mg x g(-1) to 277.5 mg x g(-1) with the MO concentration ranging from 20 mg x L(-1) to 150 mg x L(-1). The adsorption isotherm was fitted to the Freundlich model and the adsorption kinetics was fitted to the pseudo-second order kinetic isotherms capacity experiment. It was found that after the adsorbent was used for four times, its removal rate still exceeded 90%. PMID:23914533

  6. Fe(II) adsorption onto natural polymers derived from low-grade lignites

    SciTech Connect

    Tarlan, E.; Ahmetli, G.

    2007-09-15

    In comparison with conventional chemical treatment methods for Fe(II) ions, adsorption and ion exchange are considered more easily applicable and economical, depending on the material used. Polymeric rnaterials are the examples used in these commonly applied removal processes. In this study, the adsorption of Fe(II) ions from aqueous solutions onto two different natural polymers, insoluble humic acids (IHAs) extracted from low-grade lignites from Beysehir and Ermenek (in the central Anatolia region, Konya, Turkey), was investigated. The IHAs were synthesized through a series of acid-base reactions, and the obtained precipitates were chemically stable and had about 40% humic matter together with functional carboxyl and hydroxyl groups. The effects of the time and initial metal concentration on the effectiveness of the IHAs for Fe(II) adsorption were determined through batch experiments; the adsorption isotherms and capacities were calculated. The IHAs were effective, with capacities of 59 mg/g for the Beysehir IHA and 57 mg/g for the Ermenek IHA, for Fe removal under neutral pH conditions. The adsorption followed mainly a Freundlich isotherm for both IHAs, and the calculated adsorption rates were 0.86 for the Beysehir IHA and 0.81 for the Ermenek IHA. This indicated that the effectiveness of the Beysehir IHA was slightly higher than that of the Ermenek IHA. The results confirmed the real possibility of the practical application of IHAs for the separation of Fe(II) in aqueous systems.

  7. Effect of humic acids on the adsorption of paraquat by goethite.

    PubMed

    Brigante, Maximiliano; Zanini, Graciela; Avena, Marcelo

    2010-12-15

    The adsorption of the herbicide paraquat (PQ(2+)) on goethite and on the binary system humic acid-goethite has been studied in batch experiments by performing adsorption isotherms under different conditions of pH, supporting electrolyte concentration and temperature. The results were completed with capillary electrophoresis (CE) in order to measure the binding isotherm between PQ(2+) and humic acid (HA) molecules in solution. PQ(2+) adsorption is negligible on the bare goethite surface but important on the HA-goethite adsorbent. In this last case, the adsorption increases by increasing pH and decreasing electrolyte concentration. There are no significant effects of temperature on the adsorption. The adsorption takes place by direct binding of PQ(2+) to adsorbed HA molecules leading to the formation of surface species of the type goethite-HA-PQ(2+). The results are consistent with a mechanism where PQ(2+) binds negatively charged groups of HA (carboxylates and phenolates) forming ionic pairs or outer-sphere complexes. Since goethite in nature usually contains adsorbed HA molecules, it may act as a good adsorbent for cationic herbicides. This will not only benefit the deactivation of the herbicides but also reduce their leaching and transport through groundwater. PMID:20828932

  8. Influence of elastic strains on the adsorption process in porous materials. Thermodynamics and experiment

    NASA Astrophysics Data System (ADS)

    Grosman, A.; Ortega, C.

    2010-06-01

    If we disregard the shape of the boundary hysteresis loop, H1 for SBA-15, MCM-41 and KIT-6, H2 for p +-type porous silicon and porous glass, the hysteretic features inside the loop are qualitatively the same for all these systems and show that none of them are composed of independent pores whether the pores are interconnected or not. We hence believe that the physical parameter which couples the pores is not the interconnectivity but the elastic deformation of the porous matrix. The thermodynamic approach we develop includes the elastic energy of the solid. We show that the variation of the surface free energy, which is proportional to the deformation of the porous matrix, is an important component of the total free energy. With porous silicon, we experimentally show that a stress external to the porous matrix exerted by the substrate on which it is supported significantly increases the total free energy and the adsorbed amount and decreases the condensation pressure compared to that of the same porous matrix detached from its substrate which is the relaxed state of the supported layer. This stress can be partly relaxed by making thicker porous layers due to the breaking of Si-Si bonds. This results in the shift of the isotherms towards that of the membrane. We propose a new interaction mechanism occurring through the pore wall elastic deformation in which the external mechanical stress is imposed on a given pore by its neighbours.

  9. Adsorption of phenolic compounds on fly ash

    SciTech Connect

    Akgerman, A.; Zardkoohi, M.

    1996-03-01

    Adsorption isotherms for adsorption of phenol, 3-chlorophenol, and 2,4-dichlorophenol from water onto fly ash were determined. These isotherms were modeled by the Freundlich isotherm. The fly ash adsorbed 67, 20, and 22 mg/g for phenol, chlorophenol, and 2,4-dichlorophenol, respectively, for the highest water phase concentrations used. The affinity of phenolic compounds for fly ash is above the expected amount corresponding to a monolayer coverage considering that the surface area of fly ash is only 1.87 m{sup 2}/g. The isotherms for contaminants studied were unfavorable, indicating that adsorption becomes progressively easier as more solutes are taken up. Phenol displayed a much higher affinity for fly ash than 3-chlorophenol and 2,4-dichlorophenol.

  10. Adsorption Behaviors of 17α-Ethinylestradiol in Sediment-Water System in Northern Taihu Lake, China

    PubMed Central

    Wang, Yonghua; Hu, Liangfeng; Wang, Qiuying; Lu, Guanghua; Li, Yi

    2014-01-01

    Adsorption behavior of 17α-ethinylestradiol (EE2) in northern Taihu Lake sediment was analyzed by using batch equilibrium experiment. Freundlich isotherm could describe the adsorption thermodynamic behavior of EE2 in sediment. Sediment organic matter (SOM) contents had important impacts on the adsorption capacity for EE2. The pH values also influenced the adsorption capacity for EE2. Increase of pH value could decrease the EE2 adsorption, which might be due to the electrostatic repulsion between the anionic form of EE2 and sediments with negative charge under high pH values. Competitive effects of bisphenol A (BPA) on EE2 adsorption were further analyzed. The results showed that low concentration BPA did not have significant influences on EE2 adsorption. However, high concentration BPA could reduce EE2 adsorption, which might be due to the similar molecular diameter of BPA with adsorption sites and one more benzene ring with a hydroxyl group in BPA. These results provide primary information of EE2 adsorption in sediment-water system in Taihu Lake, which is useful for the environmental risk assessment and management of EE2 in studied area. PMID:25152910

  11. Dye adsorption behavior of Luffa cylindrica fibers.

    PubMed

    Demir, H; Top, A; Balköse, D; Ulkü, S

    2008-05-01

    Using natural Luffa cylindrica fibers as adsorbent removal of methylene blue dye from aqueous solutions at different temperatures and dye concentrations was investigated in this study. Thermodynamics and kinetics of adsorption were also investigated. The adsorption isotherms could be well defined with Langmuir model instead of Freundlich model. The thermodynamic parameters of methylene blue (MB) adsorption indicated that the adsorption is exothermic and spontaneous. The average MB adsorption capacity was found out as 49 mg/g and average BET surface area of fibers was calculated as 123 m(2)/g. PMID:17919814

  12. Adsorption in sparse networks. 2: Silica aerogels

    SciTech Connect

    Scherer, G.W.; Calas, S.; Sempere, R.

    1998-06-15

    The model developed in Part 1 is applied to nitrogen adsorption isotherms obtained for a series of silica aerogels whose densities are varied by partial sintering. The isotherms are adequately described by a cubic network model, with all of the pores falling in the mesopore range; the adsorption and desorption branches are fit by the same pore size distribution. For the least dense gels, a substantial portion of the pore volume is not detected by condensation. The model attributes this effect to the shape of the adsorbate/adsorptive interface, which can adopt zero curvature even in mesopores, because of the shape of the network.

  13. A Study of Adsorptive Characteristics of Australian Coals

    NASA Astrophysics Data System (ADS)

    Lan, Y. P.; Tsai, L. L.

    2012-04-01

    Ever since the Kyoto Protocol, controlling carbon dioxide emission and reducing its content in atmosphere are very important environmental issues up to today. One of the effective methods for permanent sequestration of anthropogenic CO2 is to inject CO2 into deep, unminable coal seams and recover coal bed methane at the same time. CO2-ECBM technology had been proved to be very promising to meet the needs of both environment and energy. Beside other external environment factors, capacity of CO2 adsorption and CH4 desorption are the most influencing factors in selection of sites for the geological storage of CO2. Therefore, the objective of this study is to understand the relationship between gas adsorption and CO2 sequestration, by various experiments for the characterization of Australian of coals. Generally speaking, coal seam gas comprises mostly of CH4, CO2, C2H6, and N2. However, some of the Australian coals were reported with significant amount of CO2 up to 90%, which might strongly affect their capacity of CO2 capture and storage (CCS). High to medium volatile bituminous coals from Sydney Basin and Bowen Basin, southeast Australia were selected in this study. Experiments include maceral composition and vitrinite reflectance measurements, petrographic analysis, Proximate analysis, Ultimate analysis, specific surface area analysis as well as CO2 and CH4 adsorption experiments were performed. Parameters for difference adsorption functions (Langmuir, BET, D-R and D-A) were then calculated to fit their adsorption isotherms the best fitting curve can then be found. Among these adsorption functions, Langmuir is the most basic and commonly used function theory. The results of all experiments were synthesized to discuss the relations among each other, so as to establish the relationship between gas adsorption and coal characteristics.

  14. Adsorption Removal of Environmental Hormones of Dimethyl Phthalate Using Novel Magnetic Adsorbent

    PubMed Central

    Chang, Chia-Chi; Tseng, Jyi-Yeong; Ji, Dar-Ren; Chiu, Chun-Yu; Lu, De-Sheng; Chang, Ching-Yuan; Yuan, Min-Hao; Chang, Chiung-Fen; Chiou, Chyow-San; Chen, Yi-Hung; Shie, Je-Lueng

    2015-01-01

    Magnetic polyvinyl alcohol adsorbent M-PVAL was employed to remove and concentrate dimethyl phthalate DMP. The M-PVAL was prepared after sequential syntheses of magnetic Fe3O4 (M) and polyvinyl acetate (M-PVAC). The saturated magnetizations of M, M-PVAC, and M-PVAL are 57.2, 26.0, and 43.2 emu g−1 with superparamagnetism, respectively. The average size of M-PVAL by number is 0.75 μm in micro size. Adsorption experiments include three cases: (1) adjustment of initial pH (pH0) of solution to 5, (2) no adjustment of pH0 with value in 6.04–6.64, and (3) adjusted pH0 = 7. The corresponding saturated amounts of adsorption of unimolecular layer of Langmuir isotherm are 4.01, 5.21, and 4.22 mg g−1, respectively. Values of heterogeneity factor of Freundlich isotherm are 2.59, 2.19, and 2.59 which are greater than 1, revealing the favorable adsorption of DMP/M-PVAL system. Values of adsorption activation energy per mole of Dubinin-Radushkevich isotherm are, respectively, of low values of 7.04, 6.48, and 7.19 kJ mol−1, indicating the natural occurring of the adsorption process studied. The tiny size of adsorbent makes the adsorption take place easily while its superparamagnetism is beneficial for the separation and recovery of micro adsorbent from liquid by applying magnetic field after completion of adsorption. PMID:26258169

  15. Visualizing Gas Adsorption on Porous Solids: Four Simple, Effective Demonstrations

    ERIC Educational Resources Information Center

    Cheung, Ocean

    2014-01-01

    Gas adsorption on porous solids is a topic that is often discussed in an undergraduate chemistry or chemical engineering course. The idea of porosity and gas adsorption on a porous solid is usually discussed with adsorption isotherms recorded using commercially available equipment. This discussion can be rather abstract and can be difficult for…

  16. Adsorption of mercury in coal-fired power plants gypsum slurry on TiO2/chitosan composite material

    NASA Astrophysics Data System (ADS)

    Gao, P.; Gao, B. B.; Gao, J. Q.; Zhang, K.; Chen, Y. J.; Yang, Y. P.; Chen, H. W.

    2016-07-01

    In this study, a simple method was used to prepare a chitosan adsorbent to mix with KI and TiO2. Gravimetric analysis (TG), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) were used to characterize the samples before and after adsorption of Hg2+. A mercury adsorption experiment was also conducted in the gypsum slurry. The results show that using hydrobromic acid as a solvent of adsorbent resulted in a better adsorption effect than using acetic acid alone. Also, the sample (CS-KI/TiO2-HBr) had a maximum mercury adsorption capacity when the pH=5 and the t=50°C. The characterization experiments showed that the thermal stability of composite materials declined and the TiO2 uniformly dispersed in the surface of the samples with a lamellar structure, generating a lot of cracks and recesses that increased the reactive sites. Furthermore, when the TiO2 reacted with CS, it resulted in Ti-C, Ti-O and Ti-N bonds. The Br- can prevent the growth of TiO2 crystal grains and strengthen the ability of I- to remove mercury. The adsorption isotherm and kinetic results indicated that the adsorption behaviour of CS-KI/TiO2-HBr as it removes Hg2+ is an inhomogeneous multilayer adsorption process. The surface adsorption and intraparticle diffusion effects are both important in the Hg2+ adsorption process.

  17. Removal of semivolatiles from soils by steam stripping. IV. Effects of adsorption/desorption kinetics

    SciTech Connect

    Rodriguez-Maroto, J.M.; Gomez-Lahoz, C.; Wilson, D.J.

    1995-07-01

    A mathematical model is developed for in-situ steam stripping of semivolatile organic compounds (SVOCs) in which the adsorption isotherm of the SVOCs on the soil is nonlinear and in which desorption kinetics may be rate limiting. Severe tailing, similar to that found with diffusion-limited steam stripping, is readily produced by the model, even under situations in which adsorption-desorption kinetics are rapid. The results also indicate that field experiments alone are not likely to be able to distinguish between limitations imposed on the rate of steam-stripping remediation by diffusion kinetics and those imposed by desorption kinetics.

  18. Molecular simulations of the adsorption of cycloalkanes in MFI-type silica.

    PubMed

    Schenk, Merijn; Smit, Berend; Maesen, Theo L M; Vlugt, Thijs J H

    2005-07-01

    A new force field for the simulation of the adsorption of cycloalkanes in nanoporous silica affords a significant improvement over any previously employed force field. The simulated isotherms reproduce the most salient features in the experimental isotherms extremely well. The study of cyclo-pentane, -hexane, and -heptane adsorption in MFI-type silica indicates an inflection for cyclopentane but not for cyclohexane at intermediate pressure. If corroborated by experiments, such an inflection point would afford an excellent calibration point for further force field developments. At low pressures, mixture isotherms of cyclohexane and n-hexane show a temperature dependence on the selectivity in accordance with recent results by J. P. Fox and S. P. Bates, J. Phys. Chem., 2004, 108, 17136. This dependence is caused by a difference in temperature dependence of the Henry coefficient for both molecules. At high pressures entropy effects due to packing always favor the sorption of n-hexane. Furthermore, the influence of the flexibility of the zeolite framework on the adsorption of these rather bulky molecules is investigated. It is found that this influence of the flexibility on the adsorption of cyclohexane is as small as with n-alkanes. PMID:16189573

  19. Effect of gas adsorption on acoustic wave propagation in MFI zeolite membrane materials: experiment and molecular simulation.

    PubMed

    Manga, Etoungh D; Blasco, Hugues; Da-Costa, Philippe; Drobek, Martin; Ayral, André; Le Clezio, Emmanuel; Despaux, Gilles; Coasne, Benoit; Julbe, Anne

    2014-09-01

    The present study reports on the development of a characterization method of porous membrane materials which consists of considering their acoustic properties upon gas adsorption. Using acoustic microscopy experiments and atomistic molecular simulations for helium adsorbed in a silicalite-1 zeolite membrane layer, we showed that acoustic wave propagation could be used, in principle, for controlling the membranes operando. Molecular simulations, which were found to fit experimental data, showed that the compressional modulus of the composite system consisting of silicalite-1 with adsorbed He increases linearly with the He adsorbed amount while its shear modulus remains constant in a large range of applied pressures. These results suggest that the longitudinal and Rayleigh wave velocities (VL and VR) depend on the He adsorbed amount whereas the transverse wave velocity VT remains constant. PMID:25089584

  20. Revisiting Isotherm Analyses Using R: Comparison of Linear, Non-linear, and Bayesian Techniques

    EPA Science Inventory

    Extensive adsorption isotherm data exist for an array of chemicals of concern on a variety of engineered and natural sorbents. Several isotherm models exist that can accurately describe these data from which the resultant fitting parameters may subsequently be used in numerical ...

  1. Adsorption experiment of toxic micro-pollutants derived from automobiles using red soil.

    PubMed

    Kawai, Takahiro; Ichiki, Atsushi; Sawada, Yasunori

    2015-01-01

    In some countries, non-point source pollution derived from a city's economic activities tends to be a barrier to the improvement of water quality. Roadway runoff is known to contain toxic micro-pollutants such as polycyclic aromatic hydrocarbons (PAHs). Conversely, red soil is known to adsorb some organic matter. In this study, artificial roadway runoff water containing toxic micro-pollutants was made using roadway dust collected from a highway, and used for both batch-type tests and soil column tests with red soil in order to understand adsorption ability of the red soil on such toxic micro-pollutants, especially PAHs. In the batch-type tests, PAHs could be removed by approximately 40% when the contact time was 90 minutes. In the soil column tests, PAHs were removed by more than 80% while suspended solids were removed by more than 90%. Notably, PAHs with a high molecular weight were removed more readily in the tests than PAHs with a low molecular weight. PMID:26606103

  2. The mechanism of Zn sup 2+ adsorption on calcite

    SciTech Connect

    Zachara, J.M. ); Kittrick, J.A.; Harsh, J.B. )

    1988-09-01

    The adsorption of Zn{sup 2+} on calcite (CaCO{sub 3(s)}) was investigated from aqueous solutions in equilibrium with CaCO{sub 3(s)} and undersaturated with respect to Zn{sub 5}(OH){sub 6}(CO{sub 3}){sub 2(s)}. Zinc adsorption occurred via exchange with Ca{sub 2+} in a surface-adsorbed layer on calcite. The validity of this exchange reaction was supported by adsorption isotherm and constant concentration experiments, where Ca{sup 2+}{sub aq} was varied by systematically changing the pH and CO{sub 2(g)}. Greater adsorption of Zn{sup 2+} occurred at higher pH and Co{sub 2(g)} levels, where Ca{sup 2+} activities were lowest. Sites available for Zn{sup 2+} sorption were less than 10% of Ca{sup 2+} sites on the calcite surface. Surface exchange of Zn{sup 2+} did not affect the solubility of calcite. Zinc sorption was apparently independent of surface charge, which suggested that the surface complex had covalent character. Desorption and isotopic exchange experiments indicated that the surface complex remained hydrated and labile as Zn{sup 2+} was rapidly exchangeable with Ca{sup 2+}. Careful analysis of the adsorption data showed that Zn{sup 2+} and ZnOH{sup +} were the sorbing species.

  3. Adsorption on ordered and disordered duplex layers of porous anodic alumina.

    PubMed

    Bruschi, Lorenzo; Mistura, Giampaolo; Phadungbut, Poomiwat; Do, D D; Nicholson, D; Mayamei, Yashar; Lee, Woo

    2015-05-01

    We have carried out systematic experiments and numerical simulations of the adsorption on porous anodic aluminum oxide (AAO) duplex layers presenting either an ordered or a disordered interconnecting interface between the large (cavity) and small (constriction) sections of the structured pores. Selective blocking of the pore openings resulted in three different pore topologies: open structured pores, funnel pores, and ink-bottle pores. In the case of the structured pores having an ordered interface, the adsorption isotherms present a rich phenomenology characterized by the presence of two steps in the condensation branch and the opening of one (two) hysteresis loops during evaporation for the ink-bottle (open and funnel) pores. The isotherms can be obtained by summing the isotherms measured on uniform pores having the dimensions of the constrictions or of the cavities. The numerical analysis of the three different pore topologies indicates that the shape of the junction between the two pore sections is only important for the adsorption branch. In particular, a conic junction which resembles that of the AAO pores represents the experimental isotherms for the open and funnel pores better, but the shape of the junction in the ink bottle pores does not matter. The isotherms for the duplex layers with a disordered interface display the same general features found for the ordered duplex layers. In both cases, the adsorption branches coincide and have two steps which are shifted to lower relative pressures compared to those for the ordered duplex. Furthermore, the desorption branches comprise hysteresis loops much wider than those of the ordered duplex layers. Overall, this study highlights the important role played by morphologies where there are interconnections between large and small pores. PMID:25871845

  4. [Study on treatment of methylene blue wastewater by fly ash adsorption-Fenton and thermal regeneration].

    PubMed

    Bai, Yu-Jie; Zhang, Ai-Li; Zhou, Ji-Ti

    2012-07-01

    The physicochemical properties of water-washed fly ash (FA) and acid modified fly ash (M-FA) were investigated. The adsorption of methylene blue by FA and M-FA were studied by batch experiments. Two methods, Fenton-drive oxidation regeneration and thermal regeneration, were used for regeneration of the used FA and M-FA. The result showed that the rate of adsorption process followed the second order kinetics and the adsorption followed Langmuir isotherms. The adsorption equilibrium time was 30 min, and the equilibrium adsorption capacity of FA and M-FA were 4.22 mg x g(-1) and 5.98 mg x g(-1) respectively. The adsorption capability of M-FA was higher than that of FA. In the range of pH 2-12, the adsorption capacity of M-FA increased with the increase of pH, whereas the adsorption capacity of FA decreased slowly until the pH 8 and then increased. Electrostatic adsorption was the major factor on the adsorption capacity. Around 61% and 55% percentage regeneration (PR) were obtained for FA and M-FA respectively when 78.4 mmol x L(-1) H2O2 and 0.72 mmol x L(-1) Fe2+ were used. When the condition of thermal regeneration was 400 degrees C and 2 h, a positive correlation can be found between the PRs of FA and regeneration times, the PRs were 102%, 104% and 107% in three cycles of adsorption-thermal regeneration process. However a negative correlation can be found between the PRs of M-FA and regeneration times, the PRs were 82%, 75% and 74% in three cycles of adsorption-thermal regeneration process. The PR of FA was higher than that of M-FA, and thermal regeneration was superior to Fenton-drive regeneration. PMID:23002621

  5. Effect of organic matter and calcium carbonate on behaviors of cadmium adsorption-desorption on/from purple paddy soils.

    PubMed

    Zhao, Xiulan; Jiang, Tao; Du, Bin

    2014-03-01

    Batch experiments and sequential extraction analysis were employed to investigate the effects of soil organic matter and CaCO3 on the adsorption and desorption of cadmium (Cd(2+)) onto and from two purple paddy soils, an acidic purple paddy soil (APPS) and a calcareous purple paddy soil (CPPS). The Cd(2+) adsorption isotherms on both soils could be well-described by the Langmuir and Freundlich equations. CPPS had a higher capacity and a stronger affinity for Cd(2+) adsorption compared with APPS. The adsorption process of Cd(2+) on APPS was dominated by electrostatic attractions, whereas the adsorption mechanism varied depending on the Cd(2+) concentrations in equilibrium solutions on CPPS. At low equilibrium concentrations, the adsorption process was primarily specific adsorption, but nonspecific adsorption dominated at high equilibrium concentrations. Removal of organic matter decreased the amount of Cd(2+) adsorption on both of the soils, slightly affected the Cd(2+) desorption rate and exchangeable Cd (EXC-Cd) in APPS and increased the desorption rate and EXC-Cd in CPPS, suggesting that the effect of organic matter on Cd(2+) adsorption-desorption depends on the soils. CPPS and APPS containing CaCO3 exhibited higher adsorption amounts but lower desorption rates and lower proportions of EXC-Cd than those of their corresponding soils without CaCO3, demonstrating that CaCO3 played an important role in Cd(2+) specific adsorption on soil. The changes in the thermodynamic parameters, including free energy (ΔG(0)), enthalpy (ΔH(0)) and entropy (ΔS(0)), as evaluated by the Van't Hoff equations, indicated that the adsorption was a spontaneous and endothermic process with the primary interaction forces of dipole interactions and hydrogen bonds on APPS, whereas both physical and chemical interactions dominated the adsorption on CPPS. PMID:24289979

  6. Phosphate adsorption performance of a novel filter substrate made from drinking water treatment residuals.

    PubMed

    Wang, Wendong; Ma, Cui; Zhang, Yinting; Yang, Shengjiong; Shao, Yue; Wang, Xiaochang

    2016-07-01

    Phosphate is one of the most predominant pollutants in natural waters. Laboratory experiments were conducted to investigate the phosphate adsorption performance of a (NFS) made from drinking water treatment residuals. The adsorption of phosphate on the NFS fitted well with the Freundlich isotherm and pseudo second-order kinetic models. At pH7.0, the maximum adsorption capacity of 1.03mg/g was achieved at 15°C corresponding to the wastewater temperature in cold months, and increased notably to 1.31mg/g at 35°C. Under both acidic conditions (part of the adsorption sites was consumed) and basic conditions (negative charges formed on the surface of NFS, which led to a static repulsion of PO4(3-) and HPO4(2-)), the adsorption of phosphate was slightly inhibited. Further study showed that part of the adsorption sites could be recovered by 0.25mol/L NaOH. The activation energy was calculated to be above 8.0kJ/mol, indicating that the adsorption of phosphate on NFS was probably a chemical process. Considering the strong phosphate adsorption capacity and recoverability, NFS showed great promise on enhancing phosphate removal from the secondary treated wastewater in the filtration process. PMID:27372133

  7. Adsorption of Cd(II) by two variable-charge soils in the presence of pectin.

    PubMed

    Wang, Ru-Hai; Zhu, Xiao-Fang; Qian, Wei; Zhao, Min-Hua; Xu, Ren-Kou; Yu, Yuan-Chun

    2016-07-01

    Batch experiments were conducted to investigate cadmium(II) (Cd(II)) adsorption by two variable-charge soils (an Oxisol and an Ultisol) as influenced by the presence of pectin. When pectin dosage was less than 30 g kg(-1), the increase in Cd(II) adsorption with the increasing dose of pectin was greater than that when the pectin dosage was >30 g kg(-1). Although both Langmuir and Freundlich equations fitted the adsorption isotherms of Cd(II) and electrostatic adsorption data of Cd(II) by the two soils well, the Langmuir equation showed a better fit. The increase in the maximum total adsorption of Cd(II) induced by pectin was almost equal in both the soils, whereas the increase in the maximum electrostatic adsorption of Cd(II) was greater in the Oxisol than in the Ultisol because the former contained greater amounts of free Fe/Al oxides than the latter, which, in turn, led to a greater increase in the negative charge on the Oxisol. Therefore, the presence of pectin induced the increase in Cd(II) adsorption by the variable-charge soils mainly through the electrostatic mechanism. Pectin increased the adsorption of Cd(II) by the variable-charge soils and thus decreased the activity and mobility of Cd(II) in these soils. PMID:26996909

  8. Isothermal titration calorimetry of RNA.

    PubMed

    Salim, Nilshad N; Feig, Andrew L

    2009-03-01

    Isothermal titration calorimetry (ITC) is a fast and robust method to study the physical basis of molecular interactions. A single well-designed experiment can provide complete thermodynamic characterization of a binding reaction, including K(a), DeltaG, DeltaH, DeltaS and reaction stoichiometry (n). Repeating the experiment at different temperatures allows determination of the heat capacity change (DeltaC(P)) of the interaction. Modern calorimeters are sensitive enough to probe even weak biological interactions making ITC a very popular method among biochemists. Although ITC has been applied to protein studies for many years, it is becoming widely applicable in RNA biochemistry as well, especially in studies which involve RNA folding and RNA interactions with small molecules, proteins and with other RNAs. This review focuses on best practices for planning, designing and executing effective ITC experiments when one or more of the reactants is an RNA. PMID:18835447

  9. Adsorption of lipase on polypropylene powder.

    PubMed

    Gitlesen, T; Bauer, M; Adlercreutz, P

    1997-04-01

    Adsorption of different lipases by EP-100 polypropylene powder from crude and pure lipase preparations was studied. Langmuir isotherms described the adsorption equilibria well both for protein and lipase activity adsorption. Adsorption isotherms for five different proteins all gave a similar saturation level of 220 mg protein per g carrier. Twelve commercial lipase preparations were tested for selectivity in the adsorption of lipase. For all preparations the selectivity factor was larger than one. In a crude lipase preparation from Pseudomonas fluorescence, the specific activity in solution decreased by two orders of magnitude after adsorption. The adsorption was not significantly influenced by pH changes in the adsorption buffer, indicating that hydrophobic and not electrostatic interactions are the dominating adsorption forces. Adsorption of a crude lipase from Candida rugosa (Sigma) was fast and equilibrium was reached in 30 and 100 min for protein and lipase activity adsorption respectively. Desorption in aqueous solution was negligible. Investigations with seven different lipases showed no correlation between the specific lipolytic activity of dissolved enzyme in aqueous solution and the specific activity of adsorbed enzyme in an esterification reaction in organic solvent. PMID:9106498

  10. Adsorption of organic chemicals in soils.

    PubMed Central

    Calvet, R

    1989-01-01

    This paper presents a review on adsorption of organic chemicals on soils sediments and their constituents. The first part of this review deals with adsorption from gas and liquid phases and gives a discussion on the physical meaning of the shape of adsorption isotherms. Results show that no general rules can be proposed to describe univocally the relation between the shape of isotherms and the nature of adsorbate-adsorbent system. Kinetics of adsorption is discussed through the description of various models. Theoretical developments exist both for the thermodynamics and the kinetics of adsorption, but there is a strong need for experimental results. Possible adsorption mechanisms are ion exchange, interaction with metallic cations, hydrogen bonds, charge transfers, and London-van der Waals dispersion forces/hydrophobic effect. However, direct proofs of a given mechanism are rare. Several factors influence adsorption behavior. Electronic structure of adsorbed molecules, properties of adsorbents, and characteristics of the liquid phase are discussed in relation to adsorption. Such properties as water solubility, organic carbon content of adsorbing materials, and the composition of the liquid phase are particularly important. Evaluation of adsorption can be obtained through either laboratory measurements or use of several correlations. Adsorption measurements must be interpreted, taking into account treatment of adsorbent materials, experimental conditions, and secondary phenomena such as degradations. Correlations between adsorption coefficients and water-octanol partition coefficient or water solubility are numerous. They may be useful tools for prediction purposes. Relations with transport, bioavailability, and degradation are described. PMID:2695323

  11. Phosphate adsorption on lanthanum loaded biochar.

    PubMed

    Wang, Zhanghong; Shen, Dekui; Shen, Fei; Li, Tianyu

    2016-05-01

    To attain a low-cost and high-efficient phosphate adsorbent, lanthanum (La) loaded biochar (La-BC) prepared by a chemical precipitation method was developed. La-BC and its pristine biochar (CK-BC) were comparatively characterized using zeta potential, BET surface area, scanning electron microscopy/energy dispersive spectrometer (SEM-EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FT-IR). The adsorption ability and the mechanisms during adsorption process for the La-BC samples were also investigated. La loaded on the surface of biochar can be termed as La-composites (such as LaOOH, LaONO3 and La(OH)3), leading to the decrease of negative charge and surface area of biochar. La-BC exhibited the high adsorption capacity to phosphate compared to CK-BC. Adsorption isotherm and adsorption kinetic studies showed that the Langmuir isotherm and second order model could well describe the adsorption process of La-BC, indicating that the adsorption was dominated by a homogeneous and chemical process. The calculated maximum adsorption capacity was as high as 46.37 mg g(-1) (computed in P). Thermodynamic analysis revealed that the adsorption was spontaneous and endothermic. SEM, XRD, XPS and FT-IR analysis suggested that the multi-adsorption mechanisms including precipitation, ligand exchange and complexation interactions can be evidenced during the phosphate adsorption process by La-composites in La-BC. PMID:26871732

  12. Three model space experiments on chemical reactions. [Gibbs adsorption, equilibrium shift and electrodeposition

    NASA Technical Reports Server (NTRS)

    Grodzka, P.; Facemire, B.

    1977-01-01

    Three investigations conducted aboard Skylab IV and Apollo-Soyuz involved phenomena that are of interest to the biochemistry community. The formaldehyde clock reaction and the equilibrium shift reaction experiments conducted aboard Apollo Soyuz demonstrate the effect of low-g foams or air/liquid dispersions on reaction rate and chemical equilibrium. The electrodeposition reaction experiment conducted aboard Skylab IV demonstrate the effect of a low-g environment on an electrochemical displacement reaction. The implications of the three space experiments for various applications are considered.

  13. Sonochemical assisted hydrothermal synthesis of ZnO: Cr nanoparticles loaded activated carbon for simultaneous ultrasound-assisted adsorption of ternary toxic organic dye: Derivative spectrophotometric, optimization, kinetic and isotherm study.

    PubMed

    Jamshidi, M; Ghaedi, M; Dashtian, K; Hajati, S; Bazrafshan, A A

    2016-09-01

    Chromium doped zinc oxide nanoparticles (ZnO: Cr-NPs) was synthesized by ultrasonically assisted hydrothermal method and characterized by FE-SEM, XRD and TEM analysis. Subsequently, this composite ultrasonically assisted was deposited on activated carbon (ZnO: Cr-NPs-AC) and used for simultaneous ultrasound-assisted removal of three toxic organic dye namely of malachite green (MG), eosin yellow (EY) and Auramine O (AO). Dyes spectra overlap in mixture (major problem for simultaneous investigation) of this systems was extensively resolved by derivative spectrophotometric method. The magnitude of variables like initial dyes concentration, adsorbent mass and sonication time influence on dyes removal was optimized using small central composite design (CCD) combined with desirability function (DF) approach, while pH was studied by one-a-time approach. The maximized removal percentages at desirability of 0.9740 was set as follow: pH 6.0, 0.019g ZnO: Cr-NPs-AC, 3.9min sonication at 4.5, 4.8 and 4.7mgL(-1) of MG, EY and AO, respectively. Above optimized points lead to achievement of removal percentage of 98.36%, 97.24%, and 99.26% correspond to MG, EY and AO, respectively. ANOVA for each dyes based p-value less than (<0.0001) suggest highly efficiency of CCD model for prediction of data concern to simultaneous removal of these dyes within 95% confidence interval, while their F-value for MG, EY and AO is 935, 800.2, and 551.3, respectively, that confirm low participation of this them in signal. The value of multiple correlation coefficient R(2), adjusted and predicted R(2) for simultaneous removal of MG is 0.9982, 0.9972 and 0.9940, EY is 0.9979, 0.9967 and 0.9930 and for AO is 0.9970, 0.9952 and 0.9939. The adsorption rate well fitted by pseudo second-order and Langmuir model via high, economic and profitable adsorption capacity of 214.0, 189.7 and 211.6mgg(-1) for MG, EY and AO, respectively. PMID:27150752

  14. Comparative evaluation of adsorption kinetics of diclofenac and isoproturon by activated carbon.

    PubMed

    Torrellas, Silvia A; Rodriguez, Araceli R; Escudero, Gabriel O; Martín, José María G; Rodriguez, Juan G

    2015-01-01

    Adsorption mechanism of diclofenac and isoproturon onto activated carbon has been proposed using Langmuir and Freundlich isotherms. Adsorption capacity and optimum adsorption isotherms were predicted by nonlinear regression method. Different kinetic equations, pseudo-first-order, pseudo-second-order, intraparticle diffusion model and Bangham kinetic model, were applied to study the adsorption kinetics of emerging contaminants on activated carbon in two aqueous matrices. PMID:26301850

  15. Adsorption of a Textile Dye on Commercial Activated Carbon: A Simple Experiment to Explore the Role of Surface Chemistry and Ionic Strength

    ERIC Educational Resources Information Center

    Martins, Angela; Nunes, Nelson

    2015-01-01

    In this study, an adsorption experiment is proposed using commercial activated carbon as adsorbent and a textile azo dye, Mordant Blue-9, as adsorbate. The surface chemistry of the activated carbon is changed through a simple oxidation treatment and the ionic strength of the dye solution is also modified, simulating distinct conditions of water…

  16. Adsorption of divalent metal ions from aqueous solutions using graphene oxide.

    PubMed

    Sitko, Rafal; Turek, Edyta; Zawisza, Beata; Malicka, Ewa; Talik, Ewa; Heimann, Jan; Gagor, Anna; Feist, Barbara; Wrzalik, Roman

    2013-04-28

    The adsorptive properties of graphene oxide (GO) towards divalent metal ions (copper, zinc, cadmium and lead) were investigated. GO prepared through the oxidation of graphite using potassium dichromate was characterized by scanning electron microscopy (SEM), powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and infrared spectroscopy (FT-IR). The results of batch experiments and measurements by flame atomic absorption spectrometry (F-AAS) indicate that maximum adsorption can be achieved in broad pH ranges: 3-7 for Cu(II), 5-8 for Zn(II), 4-8 for Cd(II), 3-7 for Pb(II). The maximum adsorption capacities of Cu(II), Zn(II), Cd(II) and Pb(II) on GO at pH = 5 are 294, 345, 530, 1119 mg g(-1), respectively. The competitive adsorption experiments showed the affinity in the order of Pb(II) > Cu(II) ≫ Cd(II) > Zn(II). Adsorption isotherms and kinetic studies suggest that sorption of metal ions on GO nanosheets is monolayer coverage and adsorption is controlled by chemical adsorption involving the strong surface complexation of metal ions with the oxygen-containing groups on the surface of GO. Chemisorption was confirmed by XPS (binding energy and shape of O1s and C1s peaks) of GO with adsorbed metal ions. The adsorption experiments show that the dispersibility of GO in water changes remarkably after complexation of metal ions. After adsorption, the tendency to agglomerate and precipitate is observed. Excellent dispersibility of GO and strong tendency of GO-Me(II) to precipitate open the path to removal of heavy metals from water solution. Potential application of GO in analytical chemistry as a solid sorbent for preconcentration of trace elements and in heavy metal ion pollution cleanup results from its maximum adsorption capacities that are much higher than those of any of the currently reported sorbents. PMID:23443993

  17. [Adsorption of methylene blue from water by the biochars generated from crop residues].

    PubMed

    Xu, Ren-Kou; Zhao, An-Zhen; Xiao, Shuang-Cheng; Yuan, Jin-Hua

    2012-01-01

    Biochars were prepared from straws of rice, peanut and soybean and rice hull using a low temperature pyrolysis method and adsorption of methylene blue by these biochars were investigated with batch and leaching experiments. Results indicated that biochars have high adsorption capacity for methylene blue and followed the order: rice straw char > soybean straw char > peanut straw char > rice hull char. This order is generally consistent with the amount of negative charge and specific surface area of these biochars. While methylene blue was mainly adsorbed specifically by the biochars, because the adsorption of methylene blue increased with the increase of ionic strength and the adsorption led to the shift of zeta potential of biochar particles to positive value direction. Langmuir equation fitted the adsorption isotherms well and can be used to describe the adsorption behaviors of methylene blue by the biochars. The maximum adsorption capacity of methylene blue predicted by langmuir equation was 196.1, 169.5, 129.9 and 89.3 mmol x kg(-1) for rice straw char, soybean straw char, peanut straw char and rice hull char, respectively. Leaching experiments show that rice hull char of 156 g can remove methylene blue from 30 L water containing 0.3 mmol x L(-1) of methylene blue completely and the cumulative amount of methylene blue absorbed by the biochar reaches 57.7 mmol x kg(-1). The biochars can be used as efficient adsorbents to remove methylene blue from waste water of dye. PMID:22452202

  18. Evaluation of vermicompost as a raw natural adsorbent for adsorption of pesticide methylparathion.

    PubMed

    Mendes, Camila Bitencourt; Lima, Giovana de Fátima; Alves, Vanessa Nunes; Coelho, Nívia Maria Melo; Dragunski, Douglas Cardoso; Tarley, César Ricardo Teixeira

    2012-01-01

    The assessment of vermicompost (VC) as a low-cost and alternative adsorbent for the removal of the pesticide methylparathion (MP) from an aqueous medium has been investigated by batch and column experiments. Parameters related to MP adsorption, i.e. equilibrium time (61.5 min) and adsorption pH (6.8) were optimized by using Doehlert design. The initial and final MP concentrations after adsorption assays were determined by square-wave adsorptive cathodic stripping voltammetry using an electrode composed of a multiwalled carbon nanotube dispersed in mineral oil. Batch adsorption experimental data were fitted to the Langmuir and Freundlich isotherm adsorptions, and a very good fit to the Langmuir linear model, giving a maximum adsorption capacity (MAC) of 0.17 mg g(-1). This result was very similar to that obtained with the column experiments. In order to evaluate the MP desorption from column packed VC, 100.0 ml of nitric acid solution (pH 3.0) has been percolated through material. No leaching of MP was observed, thus confirming the strong interaction between MP and VC. The satisfactory MAC obtained and low cost makes the VC a reliable natural material for the removal of MP from aqueous effluents. PMID:22519100

  19. Highly enhanced adsorption for the removal of Hg(II) from aqueous solution by Mercaptoethylamine/Mercaptopropyltrimethoxysilane functionalized vermiculites.

    PubMed

    Tran, Lytuong; Wu, Pingxiao; Zhu, Yajie; Yang, Lin; Zhu, Nengwu

    2015-05-01

    Vermiculites modified with Mercaptoethylamine (MEA) and 3-Mercaptopropyltrimethoxysilane (MPTMS) were used as effective adsorbents for the removal of Hg(II) from aqueous solution. The physicochemical characteristics of the pristine and functionalized vermiculites were analyzed by XRD, BET, FTIR, SEM, TEM and Zeta potentials, confirming that the vermiculite was successfully functionalized by the organic ligands containing the thiol (SH) metal-chelating groups. Batch adsorption experiments demonstrated that the factors such as initial pH, contact time, temperature, coexisting cations and initial Hg(II) concentration could significantly influence the adsorption behaviors typically for VER and MEA-VER, whereas the adsorption capacity of MPTMS-VER showed negligible dependence on such factors. The maximum adsorption capacity of Hg(II) ions was greatly improved after functionalization, which was in the order of MPTMS-VER>MEA-VER>VER (286.29 μg g(-1), 176.33 μg g(-1), 99.95 μg g(-1), respectively). The adsorption isotherm could be well described with Langmuir model and the kinetic studies indicated that the adsorption process fitted well with the pseudo-second-order model. The calculated thermodynamic parameters suggested that the adsorption process was feasible and spontaneous. The adsorption mechanism of Hg(II) on thiol groups was studied through XPS analysis. Considering the favorable adsorption capacities, thiol-functionalized vermiculites show a promising application in the removal of Hg(II) from wastewater. PMID:25643962

  20. 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.

  1. Comparing the removal of perchlorate when using single-walled carbon nanotubes (SWCNTs) or granular activated carbon: adsorption kinetics and thermodynamics.

    PubMed

    Lou, Jie C; Hsu, Yung S; Hsu, Kai L; Chou, Ming S; Han, Jia Y

    2014-01-01

    This study aims to remove perchlorate using single-walled carbon nanotubes (SWCNTs) or granular activated carbon (GAC). Dynamic and equilibrium adsorption experiments were performed to evaluate the thermodynamic behavior of perchlorate on SWCNTs and GAC. Key parameters affecting the adsorption, such as pH, ionic strength, and temperature were studied. The experimental results showed that the dynamic adsorption experiment achieved equilibrium in approximately eight hours. The adsorption capacity increased as the concentration of perchlorate increased or as the ionic strength decreased. The selected adsorption models were the modified Freundlich, the pseudo-1st-order, and the pseudo-2nd-order equations. The results showed that the modified Freundlich equation best described the kinetic adsorption processes. The maximal adsorption capacities of GAC and SWCNTs were 33.87-28.21 mg/g and 13.64 - 10.03 mg/g, respectively, at a constant temperature between 5°C and 45°C. The thermodynamic parameters, such as the equilibrium constant (K0 ), the standard free energy changes (ΔG°), the standard enthalpy change (ΔH°) and the standard entropy change (ΔS°), were obtained. The results of the isothermal equilibrium adsorption experiment showed that low pH levels, low ionic strength, and low-temperature conditions facilitated the perchlorate adsorption, indicating that GAC and SWCNTs are potential absorbents for water treatment. PMID:24410681

  2. Adsorption of heavy metal cations by Na-clinoptilolite: equilibrium and selectivity studies.

    PubMed

    Mihaly-Cozmuta, L; Mihaly-Cozmuta, A; Peter, A; Nicula, C; Tutu, H; Silipas, Dan; Indrea, Emil

    2014-05-01

    This paper summarizes the conclusions of experiments conducted on the adsorption of Cd(2+), Co(2+), Cu(2+), Mn(2+), Ni(2+), Pb(2+) and Zn(2+) onto zeolite. The focus of the experiments was to establish the influence of the initial pH of the contact solution as well as the selectivity of zeolite on the efficiency of the adsorption process. To this end, experimental adsorption isotherms were established for the pH values ranging from 1 to 4 by using the Na-form of clinoptilolite (particle size range 0.5-1 mm) as an adsorbent. Langmuir, Freundlich and Dubinin-Raduschkevich isotherm models were used to validate the experimental data and the Gibbs free energy was calculated based on the distribution coefficient. From the Langmuir model, correlations between the maximum adsorption capacity and selected physical-chemical parameters of the cations studied were established. The results of the experiments suggest that the selectivity of zeolite is strongly influenced by the pH of the contact solution, dehydration energy of cations, diffusion coefficient and the pH at which the precipitation of hydroxides occurs. PMID:24603029

  3. Protein adsorption using novel carboxymethyl-curdlan microspheres.

    PubMed

    Rafigh, Sayyid Mahdi; Vaziri Yazdi, Ali; Safekordi, Ali Akbar; Heydari Nasab, Amir; Ardjmand, Mehdi; Naderi, Fereshteh; Mozafari, Hamid

    2016-06-01

    Carboxymethyl-curdlan as a water soluble curdlan derivative, was synthesized in an aqueous alkaline medium using monochloroacetic acid. Novel carboxymethyl-curdlan (CC) microspheres were prepared by the method of W/O/W emulsion. The chemical and morphological structures of CC microspheres were investigated by scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR) and particle size analysis. The CC microspheres were spherical, free flowing, non-aggregated and uniform mono-disperse with diameter of 260μm. The prepared CC microspheres were applied to adsorbing Bovine serum albumin (BSA) as model protein. Factors influencing the adsorption of BSA such as solution pH, temperature, initial BSA concentration and ionic strength were examined by batch experiments. The maximum adsorption capacity was calculated as 168mg/g under optimal conditions including BSA initial concentration (4mg/mL), pH (4.7), adsorption time (9h) and temperature (35°C). The adsorption isotherm followed the Langmuir model and the adsorption kinetics fitted the pseudo-second-order model. In addition, the CC microspheres can be also regenerated and re-used. PMID:26964526

  4. Adsorption of CO2, N2, and CH4 in Cs-exchanged chabazite: A combination of van der Waals density functional theory calculations and experiment study

    NASA Astrophysics Data System (ADS)

    Shang, Jin; Li, Gang; Singh, Ranjeet; Xiao, Penny; Danaci, David; Liu, Jefferson Z.; Webley, Paul A.

    2014-02-01

    The crucial role of dispersion force in correctly describing the adsorption of some typical small-size gas molecules (e.g., CO2, N2, and CH4) in ion-exchanged chabazites has been investigated at different levels of theory, including the standard density functional theory calculation using the Perdew, Burke, and Ernzerhof (PBE) exchange-correlation functional and van der Waals density functional theory (vdWDFT) calculations using different exchange-correlation models - vdW_DF2, optB86b, optB88, and optPBE. Our results show that the usage of different vdWDFT functionals does not significantly change the adsorption configuration or the profile of static charge rearrangement of the gas-chabazite complexes, in comparison with the results obtained using the PBE. The calculated values of adsorption enthalpy using different functionals are compared with our experimental results. We conclude that the incorporation of dispersion interaction is imperative to correctly predict the trend of adsorption enthalpy values, in terms of different gas molecules and Cs+ cation densities in the adsorbents, even though the absolute values of adsorption enthalpy are overestimated by approximate 10 kJ/mol compared with experiments.

  5. Mesoporous carbon adsorbents from melamine-formaldehyde resin using nanocasting technique for CO2 adsorption.

    PubMed

    Goel, Chitrakshi; Bhunia, Haripada; Bajpai, Pramod K

    2015-06-01

    Mesoporous carbon adsorbents, having high nitrogen content, were synthesized via nanocasting technique with melamine-formaldehyde resin as precursor and mesoporous silica as template. A series of adsorbents were prepared by varying the carbonization temperature from 400 to 700°C. Adsorbents were characterized thoroughly by nitrogen sorption, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), elemental (CHN) analysis, Fourier transform infrared (FTIR) spectroscopy and Boehm titration. Carbonization temperature controlled the properties of the synthesized adsorbents ranging from surface area to their nitrogen content, which play major role in their application as adsorbents for CO2 capture. The nanostructure of these materials was confirmed by XRD and TEM. Their nitrogen content decreased with an increase in carbonization temperature while other properties like surface area, pore volume, thermal stability and surface basicity increased with the carbonization temperature. These materials were evaluated for CO2 adsorption by fixed-bed column adsorption experiments. Adsorbent synthesized at 700°C was found to have the highest surface area and surface basicity along with maximum CO2 adsorption capacity among the synthesized adsorbents. Breakthrough time and CO2 equilibrium adsorption capacity were investigated from the breakthrough curves and were found to decrease with increase in adsorption temperature. Adsorption process for carbon adsorbent-CO2 system was found to be reversible with stable adsorption capacity over four consecutive adsorption-desorption cycles. From three isotherm models used to analyze the equilibrium data, Temkin isotherm model presented a nearly perfect fit implying the heterogeneous adsorbent surface. PMID:26040750

  6. Mechanisms of chromium and arsenite adsorption by amino-functionalized SBA-15.

    PubMed

    Wu, Yunhai; Zhou, Jianxin; Jin, Yanping; Cao, Julin; Yilihan, Palizhati; Wen, Yajun; Wu, Yunying

    2014-02-01

    The adsorption of Cr(VI) and As(III) by amino-functionalized SBA-15 (NH2-SBA-15) from single and binary systems were investigated in this work. The effects of pH and temperature on the adsorption of NH2-SBA-15 were studied. Adsorption kinetics, isotherm model, and thermodynamics were studied to analyze the experimental data. pH 2 was the optimum condition for the adsorption of Cr(VI) and pH 4 for As(III) adsorption. Increasing temperature had a positive effect on the removal of both Cr(VI) and As(III). The Freundlich isotherm model can depict the adsorption process best. The pseudo-second-order kinetic model fitted well with the kinetic data of Cr(VI) and As(III) in the single-component system. In the binary system, the adsorption of As(III) by NH2-SBA-15 was slightly enhanced with the presence of Cr(VI); however, As(III) had no obvious effect on the removal of Cr(VI). Regeneration experiments indicated that 0.1 mol/L NaHCO3 was an efficient desorbent for the recovery of Cr(VI) and As(III) from NH2-SBA-15; the desorption rates for Cr(VI) and As(III) were 91.6 and 33.59 %, respectively. After five recycling cycles, the removal rates were 88 and 7 % for Cr(VI) and As(III) adsorption by NH2-SBA-15, respectively. PMID:23990259

  7. Competitive adsorption of furfural and phenolic compounds onto activated carbon in fixed bed column.

    PubMed

    Sulaymon, Abbas H; Ahmed, Kawther W

    2008-01-15

    For a multicomponent competitive adsorption of furfural and phenolic compounds, a mathematical model was builtto describe the mass transfer kinetics in a fixed bed column with activated carbon. The effects of competitive adsorption equilibrium constant, axial dispersion, external mass transfer, and intraparticle diffusion resistance on the breakthrough curve were studied for weakly adsorbed compound (furfural) and strongly adsorbed compounds (parachlorophenol and phenol). Experiments were carried out to remove the furfural and phenolic compound from aqueous solution. The equilibrium data and intraparticle diffusion coefficients obtained from separate experiments in a batch adsorber, by fitting the experimental data with theoretical model. The results show that the mathematical model includes external mass transfer and pore diffusion using nonlinear isotherms and provides a good description of the adsorption process for furfural and phenolic compounds in a fixed bed adsorber. PMID:18284136

  8. Excellent adsorption and desorption characteristics of polypyrrole/TiO2 composite for Methylene Blue

    NASA Astrophysics Data System (ADS)

    Li, Jingjing; Feng, Jiangtao; Yan, Wei

    2013-08-01

    P25 or self-prepared TiO2 coated polypyrrole (PPy/P25 or PPy/TiO2) composites as novel adsorbents were prepared. Their adsorption-desorption characteristics for Methylene Blue (MB) were comparatively investigated. X-ray photoelectron spectroscopy (XPS) showed that PPy/TiO2 possessed higher doping level than PPy/P25. Thermogravimetric analysis (TGA) indicated that PPy/TiO2 contained more PPy than PPy/P25. The results of water vapor adsorption suggested that the PPy/TiO2 composite was more hydrophobic than PPy/P25. The adsorption results revealed that the composites pretreated in the solution with higher pH value exhibited larger adsorption capacities. The ionic concentration in MB solution slightly impacted the removal of MB by the PPy/TiO2 composite. The adsorption equilibrium results showed that the adsorption of MB was completed in a short time of 30 min. Pseudo-second-order and Langmuir isotherm models were effectively employed to describe the adsorption behavior of MB. PPy/TiO2 and PPy/P25 were found to have better removal ability for MB compared with pure PPy; especially PPy/TiO2, on which the maximum adsorption amount was about 3.6 or 5.5 times higher than that of PPy/P25 or pure PPy, respectively. The thermodynamic analysis indicated that the adsorption of MB was spontaneous and endothermic in nature. The regeneration experiments exhibited that PPy/TiO2 can be reused at least seven times without obvious loss of its original adsorption capacity. Electrostatic interaction, hydrogen bonding and hydrophobic interaction played the roles in MB adsorption performance. It is expected that the PPy/TiO2 composite can be considered as a stable adsorbent for dye removal.

  9. Accurate Treatment of Electrostatics during Molecular Adsorption in Nanoporous Crystals without Assigning Point Charges to Framework Atoms

    SciTech Connect

    Watanabe, T; Manz, TA; Sholl, DS

    2011-03-24

    Molecular simulations have become an important complement to experiments for studying gas adsorption and separation in crystalline nanoporous materials. Conventionally, these simulations use force fields that model adsorbate-pore interactions by assigning point charges to the atoms of the adsorbent. The assignment of framework charges always introduces ambiguity because there are many different choices for defining point charges, even when the true electron density of a material is known. We show how to completely avoid such ambiguity by using the electrostatic potential energy surface (EPES) calculated from plane wave density functional theory (DFT). We illustrate this approach by simulating CO(2) adsorption in four metal-organic frameworks (MOFs): IRMOF-1, ZIE-8, ZIE-90, and Zn(nicotinate)(2). The resulting CO(2) adsorption isotherms are insensitive to the exchange-correlation functional used in the DFT calculation of the EPES but are sensitive to changes in the crystal structure and lattice parameters. Isotherms computed from the DFT EPES are compared to those computed from several point charge models. This comparison makes possible, for the first time, an unbiased assessment of the accuracy of these point charge models for describing adsorption in MOFs. We find an unusually high Henry's constant (109 mmol/g.bar) and intermediate isosteric heat of adsorption (34.9 kJ/mol) for Zn(nicotinate)(2), which makes it a potentially attractive mateiial for CO(2) adsorption applications.

  10. Prediction of equilibrium parameters of adsorption of lead (II) ions onto diatomite

    NASA Astrophysics Data System (ADS)

    Salman, Taylan; Ardalı, Yüksel; Gamze Turan, N.

    2013-04-01

    Heavy metals from industrial wastewaters are one of the most important environmental issues to be solved today. Due to their toxicity and nonbiodegradable nature, heavy metals cause environmental and public health problems. Various techniques have been developed to remove heavy metals from aqueous solutions. These include chemical precipitation, reverse osmosis, ion Exchange and adsorption. Among them, adsorption is considered to be a particularly competitive and effective process for the removal of heavy metals from aqueous solutions. There is growing interest in using low cost, commercially available materials for the adsorption of heavy metals. Diatomite is a siliceous sedimentary rock having an amorphous form of silica (SiO2. nH2O) containing a small amount of microcrystalline material. It has unique combination of physical and chemical properties such as high porosity, high permeability, small particle size, large surface area, and low thermal conductivity. In addition, it is available in Turkey and in various locations around the world. Therefore, diatomite has been successfully used as adsorbent for the removal of heavy metals. The aim of the study is to investigate the adsorption properties of diatomite. The equilibrium adsorption data were applied to the Langmuir, Freundlich and Dubinin-Radushkevic (D-R) isotherm models. Adsorption experiments were performed under batch process, using Pb (II) initial concentration, pH of solution and contact time as variables. The results demonstrated that the adsorption of Pb (II) was strongly dependent on pH of solution. The effect of pH on adsorption of Pb(II) on diatomite was conducted by varying pH from 2 to 12 at 20 oC. In the pH range of 2.0-4.0, the adsorption percentage increases slightly as the pH increasing. At pH>4, the adsorption percentage decreases with increasing pH because hydrolysis product and the precipitation begin to play an important role in the sorption of Pb (II). At pH4, the maximum adsorption

  11. Bovine Serum Albumin Adsorption in Mesoporous Titanium Dioxide: Pore Size and Pore Chemistry Effect.

    PubMed

    Liu, Chang; Guo, Yanhua; Hong, Qiliang; Rao, Chao; Zhang, Haijuan; Dong, Yihui; Huang, Liangliang; Lu, Xiaohua; Bao, Ningzhong

    2016-04-26

    Understanding the mechanism of protein adsorption and designing materials with high sensitivity, high specificity and fast response are critical to develop the next-generation biosensing and diagnostic platforms. Mesoporous materials with high surface area, tunable pores, and good thermal/hydrostatic stabilities are promising candidates in this field. Because of the excellent biocompatibility, titanium dioxide has received an increasing interest in the past decade for biomedical applications. In this work, we synthesized mesoporous titanium dioxide with controlled pore sizes (7.2-28.0 nm) and explored their application for bovine serum albumin (BSA) adsorption. Scanning electron microscopy (SEM), X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and nitrogen adsorption/desorption experiments were performed to characterize the mesoporous TiO2 samples before and after BSA adsorption. Isothermal microcalorimetry was applied to measure both the adsorption heat and conformation rearrangement heat of BSA in those mesopores. We also carried out thermogravimetry measurements to qualitatively estimate the concentration of hydroxyl groups, which plays an important role in stabilizing BSA in-pore adsorption. The adsorption stability was also examined by leaching experiments. The results showed that TiO2 mesopores can host BSA adsorption when their diameters are larger than the hydrodynamic size of BSA (∼9.5 nm). In larger mesopores studied, two BSA molecules were adsorbed in the same pores. In contrast to the general understanding that large mesopores demonstrate poor stabilities for protein adsorptions, the synthesized mesoporous TiO2 samples demonstrated good leaching stabilities for BSA adsorption. This is probably due to the combination of the mesoporous confinement and the in-pore hydroxyl groups. PMID:27048991

  12. Dynamic behaviour of Cd2+ adsorption in equilibrium batch studies by CaCO3(-)-rich Corbicula fluminea shell.

    PubMed

    Ismail, Farhah Amalya; Aris, Ahmad Zaharin; Latif, Puziah Abdul

    2014-01-01

    This work presents the structural and adsorption properties of the CaCO3(-)-rich Corbicula fluminea shell as a natural and economic adsorbent to remove Cd ions from aqueous solutions under batch studies. Experiments were conducted with different contact times, various initial concentrations, initial solution pH and serial biosorbent dosage to examine the dynamic characterization of the adsorption and its influence on Cd uptake capacity. The characterization of the C. fluminea shell using SEM/EDX revealed that the adsorbent surface is mostly impregnated by small particles of potentially calcium salts. The dominant Cd adsorption mechanism is strongly pH and concentration dependent. A maximum Cd removal efficiency of 96.20% was obtained at pH 7 while the optimum adsorbent dosage was observed as 5 g/L. The Langmuir isotherm was discovered to be more suitable to represent the experimental equilibrium isotherm results with higher correlation coefficients (R(2) > 0.98) than Freundlich (R(2) < 0.97).The correlation coefficient values (p < 0.01) indicated the superiority of the Langmuir isotherm over the Freundlich isotherm. PMID:23771443

  13. Adsorption of phenol on wood surfaces

    NASA Astrophysics Data System (ADS)

    Mamleeva, N. A.; Lunin, V. V.

    2016-03-01

    Adsorption of phenol on aspen and pine wood is investigated. It is shown that adsorption isotherms are described by the Langmuir model. The woods' specific surface areas and adsorption interaction constants are determined. It is found that the sorption of phenol on surfaces of aspen and pine is due to Van der Waals interactions ( S sp = 45 m2/godw for aspen and 85 m2/godw for pine). The difference between the adsorption characteristics is explained by properties of the wood samples' microstructures.

  14. Understanding H isotope adsorption and absorption of Al-alloys using modeling and experiments (LDRD: #165724)

    SciTech Connect

    Ward, Donald K.; Zhou, Xiaowang; Karnesky, Richard A.; Kolasinski, Robert; Foster, Michael E.; Thurmer, Konrad; Chao, Paul; Epperly, Ethan Nicholas; Zimmerman, Jonathan A.; Wong, Bryan M.; Sills, Ryan B.

    2015-09-01

    Current austenitic stainless steel storage reservoirs for hydrogen isotopes (e.g. deuterium and tritium) have performance and operational life-limiting interactions (e.g. embrittlement) with H-isotopes. Aluminum alloys (e.g.AA2219), alternatively, have very low H-isotope solubilities, suggesting high resistance towards aging vulnerabilities. This report summarizes the work performed during the life of the Lab Directed Research and Development in the Nuclear Weapons investment area (165724), and provides invaluable modeling and experimental insights into the interactions of H isotopes with surfaces and bulk AlCu-alloys. The modeling work establishes and builds a multi-scale framework which includes: a density functional theory informed bond-order potential for classical molecular dynamics (MD), and subsequent use of MD simulations to inform defect level dislocation dynamics models. Furthermore, low energy ion scattering and thermal desorption spectroscopy experiments are performed to validate these models and add greater physical understanding to them.

  15. Adsorption of DNA on biomimetic apatites: Toward the understanding of the role of bone and tooth mineral on the preservation of ancient DNA

    NASA Astrophysics Data System (ADS)

    Grunenwald, A.; Keyser, C.; Sautereau, A. M.; Crubézy, E.; Ludes, B.; Drouet, C.

    2014-02-01

    In order to shed some light on DNA preservation over time in skeletal remains from a physicochemical viewpoint, adsorption and desorption of DNA on a well characterized synthetic apatite mimicking bone and dentin biominerals were studied. Batch adsorption experiments have been carried out to determine the effect of contact time (kinetics), DNA concentration (isotherms) and environmentally relevant factors such as temperature, ionic strength and pH on the adsorption behavior. The analogy of the nanocrystalline carbonated apatite used in this work with biological apatite was first demonstrated by XRD, FTIR, and chemical analyses. Then, DNA adsorption kinetics was fitted with the pseudo-first order, pseudo-second order, Elovich, Ritchie and double exponential models. The best results were achieved with the Elovich kinetic model. The adsorption isotherms of partially sheared calf thymus DNA conformed satisfactorily to Temkin's equation which is often used to describe heterogeneous adsorption behavior involving polyelectrolytes. For the first time, the irreversibility of DNA adsorption toward dilution and significant phosphate-promoted DNA desorption were evidenced, suggesting that a concomitant ion exchange process between phosphate anionic groups of DNA backbone and labile non-apatitic hydrogenphosphate ions potentially released from the hydrated layer of apatite crystals. This work should prove helpful for a better understanding of diagenetic processes related to DNA preservation in calcified tissues.

  16. Synthesis of magnetic γ-Fe2O3-based nanomaterial for ultrasonic assisted dyes adsorption: Modeling and optimization.

    PubMed

    Asfaram, Arash; Ghaedi, Mehrorang; Hajati, Shaaker; Goudarzi, Alireza

    2016-09-01

    γ-Fe2O3 nanoparticles were synthesized and loaded on activated carbon. The prepared nanomaterial was characterized by field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDX), Fourier transforms infrared spectroscopy (FT-IR) and X-ray diffraction (XRD). The γ-Fe2O3 nanoparticle-loaded activated carbon (γ-Fe2O3-NPs-AC) was used as novel adsorbent for the ultrasonic-assisted removal of methylene blue (MB) and malachite green (MG). Response surface methodology and artificial neural network were applied to model and optimize the adsorption of the MB and MG in their individual and binary solutions followed by the investigation on adsorption isotherm and kinetics. The individual effects of parameters such as pH, mass of adsorbent, ultrasonication time as well as MB and MG concentrations in addition to the effects of their possible interactions on the adsorption process were investigated. The numerical optimization revealed that the optimum adsorption (>99.5% for each dye) is obtained at 0.02g, 15mgL(-1), 4min and 7.0 corresponding to the adsorbent mass, each dye concentration, sonication time and pH, respectively. The Freundlich, Langmuir, Temkin and Dubinin-Radushkevich isotherms were studied. The Langmuir was found to be most applicable isotherm which predicted maximum monolayer adsorption capacities of 195.55 and 207.04mgg(-1) for the adsorption of MB and MG, respectively. The pseudo-second order model was found to be applicable for the adsorption kinetics. Blank experiments (without any adsorbent) were run to investigate the possible degradation of the dyes studied in presence of ultrasonication. No dyes degradation was observed. PMID:27150788

  17. ADSORPTION OF POLYCYCLIC AROMATIC HYDROCARBONS IN AGED HARBOR SEDIMENTS

    EPA Science Inventory

    Polycyclic aromatic hydrocarbons (PAHs) are a group of hydrophobic organic contaminants which have low aqueous solubilities and are common pollutants in harbor sediments. Adsorption and desorption isotherms for PAHs are conducted to study the abiotic sorption of PAHs in uncontami...

  18. Liquid-Phase Adsorption of Phenol onto Activated Carbons Prepared with Different Activation Levels.

    PubMed

    Hsieh; Teng

    2000-10-01

    The influence of the pore size distribution of activated carbon on the adsorption of phenol from aqueous solutions was explored. Activated carbons with different porous structures were prepared by gasifying a bituminous coal char to different extents of burn-off. The results of adsorption experiments show that the phenol capacity of these carbons does not proportionally increase with their BET surface area. This reflects the heterogeneity of the carbon surface for adsorption. The pore size distributions of these carbons, determined according to the Dubinin-Stoeckli equation, were found to vary with the burn-off level. By incorporating the distribution with the Dubinin-Radushkevich equation using an inverse proportionality between the micropore size and the adsorption energy, the isotherms for the adsorption of phenol onto these carbons can be well predicted. The present study has demonstrated that the heterogeneity of carbon surface for the phenol adsorption can be attributed to the different energies required for adsorption in different-size micropores. Copyright 2000 Academic Press. PMID:10998301

  19. Adsorption kinetics and equilibrium study of nitrogen species onto radiata pine (Pinus radiata) sawdust.

    PubMed

    Harmayani, Kadek D; Faisal Anwar, A H M

    2016-01-01

    Nitrogen species (NH3-N, NO3-N, and NO2-N) are found as one of the major dissolved constituents in wastewater or stormwater runoff. In this research, laboratory experiments were conducted to remove these pollutants from the water environment using radiata pine (Pinus radiata) sawdust. A series of batch tests was conducted by varying initial concentration, dosage, particle size, pH, and contact time to check the removal performance. Test results confirmed the effectiveness of radiata pine sawdust for removing these contaminants from the aqueous phase (100% removal of NO3-N, and NO2-N; 55% removal of NH3-N). The adsorbent dosage and initial concentration showed a significantly greater effect on the removal process over pH or particle sizes. The optimum dosage for contaminant removal on a laboratory scale was found to be 12 g. Next, the adsorption kinetics were studied using intraparticle diffusion, liquid-film diffusion, and a pseudo-first order and pseudo-second order model. The adsorption of all species followed a pseudo-second order model but NO2-N adsorption followed both models. In addition, the kinetics of NO2-N adsorption showed two-step adsorption following intraparticle diffusion and liquid-film diffusion. The isotherm study showed that NO3-N and NO2-N adsorption fitted slightly better with the Freundlich model but that NH3-N adsorption followed both Freundlich and Langmuir models. PMID:27438245

  20. Simultaneous oxidation and adsorption of As(III) from water by cerium modified chitosan ultrafine nanobiosorbent.

    PubMed

    Zhang, Lingfan; Zhu, Tianyi; Liu, Xin; Zhang, Wenqing

    2016-05-01

    Since most existing arsenic removal adsorbents are difficult to effectively remove arsenite (As(III)), an urgent need is to develop an efficient adsorbent for removing As(III) from contaminated water. In this study, a novel ultrafine nanobiosorbent of cerium modified chitosan (Ce-CNB) with simultaneous oxidation and adsorption As(III) performance has been successfully developed. The resulting Ce-CNB with or without As(III) adsorption was characterized by FTIR, XRD, SEM, EDS, TEM, EMI and XPS analysis. Batch of adsorption experiments were performed to investigate the effects of various conditions on the As(III) adsorption. The adsorption behaviors were well described by the Langmuir isotherm and the pseudo-second-order kinetic model, with the maximum adsorption capacities of 57.5 mg g(-1). The adsorption mechanisms for As(III) were (i) formed monodentate and bidentate complexes between hydroxyl groups and arsenite; and (ii) partial As(III) oxidized to As(V) followed by simultaneously adsorbed on the surface of Ce-CNB. This novel nanocomposite can be reused while maintaining a high removal efficiency and can be applied to treat 5.8L of As(III)-polluted water with the effluent concentration lower than the World Health Organization standard, which suggests its great potential to remove As(III) from contaminated water. PMID:26808237

  1. Adsorption and desorption of arsenic to aquifer sediment on the Red River floodplain at Nam Du, Vietnam

    NASA Astrophysics Data System (ADS)

    Thi Hoa Mai, Nguyen; Postma, Dieke; Thi Kim Trang, Pham; Jessen, Søren; Hung Viet, Pham; Larsen, Flemming

    2014-10-01

    The adsorption of arsenic onto aquifer sediment from the Red River floodplain, Vietnam, was determined in a series of batch experiments. Due to water supply pumping, river water infiltrates into the aquifer at the field site and has leached the uppermost aquifer sediments. The leached sediments remain anoxic but contain little reactive arsenic and iron, and are used in our experiments. The adsorption and desorption experiments were carried out by addition or removal of arsenic from the aqueous phase in sediment suspensions under strictly anoxic conditions. Also the effects of HCO3, Fe(II), PO4 and Si on arsenic adsorption were explored. The results show much stronger adsorption of As(V) as compared to As(III), full reversibility for As(III) adsorption and less so for As(V). The presence or absence of HCO3 did not influence arsenic adsorption. Fe(II) enhanced As(V) sorption but did not influence the adsorption of As(III) in any way. During simultaneous adsorption of As(III) and Fe(II), As(III) was found to be fully desorbable while Fe(II) was completely irreversibly adsorbed and clearly the two sorption processes are uncoupled. Phosphate was the only solute that significantly could displace As(III) from the sediment surface. Compiling literature data on arsenic adsorption to aquifer sediment in Vietnam and Bangladesh revealed As(III) isotherms to be almost identical regardless of the nature of the sediment or the site of sampling. In contrast, there was a large variation in As(V) adsorption isotherms between studies. A tentative conclusion is that As(III) and As(V) are not adsorbing onto the same sediment surface sites. The adsorption behavior of arsenic onto aquifer sediments and synthetic Fe-oxides is compared. Particularly, the much stronger adsorption of As(V) than of As(III) onto Red River as well as on most Bangladesh aquifer sediments, indicates that the perception that arsenic, phosphate and other species compete for the same surface sites of iron oxides in

  2. Physical Adsorption of Gases on Heterogeneous Solids and Equilibrium Studies of the Pressure Swing Adsorption Process.

    NASA Astrophysics Data System (ADS)

    Lu, Xiaochun

    1990-01-01

    Adsorption isotherms of ethane, propane, and n -butane on two polystyrene adsorbents and two activated carbons were measured at 0, 25, and 40^ circC. A dynamic chromatographic experimental system was used to measure the transmission curves of gases through a packed bed. The transmission is defined as the ratio of the adsorbate concentration at the bed outlet to that at the bed inlet. A mass-balance equation was used to calculate the solid-phase concentration and the dimensionless adsorption capacity. The structural and energetic heterogeneities of microporous adsorbents were explored by means of Dubinin's Theory of Volume Filling of Micropores (TVFM) and by a modified TVFM. The structural heterogeneity of a microporous adsorbent refers to the non-uniformity of the pore sizes and pore shapes. In polystyrene adsorbents, these non -uniform pores were formed by different copolymerization of monomers; while in activated carbons, these non-uniform pores were formed in the processes of carbonization and activation. The energetic heterogeneities of a microporous adsorbent comes from the structural heterogeneity as well as from the various atoms and functional groups exposed at the pore surface, the impurities strongly bound to the surface, and the irregularities in the crystallographical structure of the surface. Dubinin's original TVFM applies well in structurally homogeneous or weakly-heterogeneous microporous activated carbons; however, fits of experimental isotherms to the Dubinin-Radushkevich equation reveal deviations for structurally -heterogeneous adsorbents. We extended Dubinin's TVFM to the case of structurally-heterogeneous adsorbents by using an overall integral isotherm equation. A gamma-function type micropore-size distribution was used and a three-parameter isotherm equation was obtained. The experimental isotherms on activated carbons were fitted well by this isotherm equation. We characterized eight different activated carbons with the three

  3. Nickel adsorption on single and dual site clay surfaces; Effect of pH and nickel loadings

    NASA Astrophysics Data System (ADS)

    Rajapaksha, A. U.; Vithanage, M. S.; Bandara, A.; Weerasooriya, R.

    2011-12-01

    We examined Ni sorption to single and dual site clays (Al dominant, Fe dominant and both Al and Fe rich sorbents) as adsorbents for removal of Ni from aqueous solutions to (i) compare the capacities, (ii) study the effect of solution pH, (iii) examine the effect of ionic strength on adsorption (iv) determine the adsorption capacity through isotherm models. Gibbsite and goethite were selected as the single site sorbent for Al and Fe while Natural Red Earth (NRE) and laterite, were used as the sorbents with dual sites for this study. The effect of pH on the sorption was studied by adjusting the pH in the range of 4-10. In these experiments, the adsorbent concentration was kept at 5 g/l of solution containing 10 mg/l Ni(II) at 25 0C. Adsorption isotherms were conducted in 0.01 M NaNO3 solution, at pH ≈ 7.5. Both single and dual site clay minerals have exhibited no dependence on ionic strength indicating inner-sphere surface complexation. However, gibbsite demonstrated highest adsorption. Adsorption increased 4-5 folds with the pH increase from 6.0 to 8.5 with maximum adsorption at pH > 8.0. Elemental mapping demonstrated the distribution of elements on the grain including sorbed Ni. These results indicate that > AlO- sites attract Ni better than >FeO- sites. Adsorption shows decrease from gibbsite > laterite > goethite > NRE. Gibbsite showed best fit for the Langmuir equation with r2 around 0.98. This indicates homogeneous adsorption. Maximum adsorption capacity for gibbsite is reported as 5.08x10-4 mol/kg. Therefore, gibbsite and laterite have a good potential to be used to remove nickel from aqueous solutions. Key words : Gibbsite, Geothite, Laterite, Natural Red Earth, Ni sorption

  4. Proton adsorption onto alumina: extension of multisite complexation (MUSIC) theory

    SciTech Connect

    Nagashima, K.; Blum, F.D.

    1999-09-01

    The adsorption isotherm of protons onto a commercial {gamma}-alumina sample was determined in aqueous nitric acid with sodium nitrate as a background electrolyte. Three discrete regions could be discerned in the log-log plots of the proton isotherm determined at the solution pH 5 to 2. The multisite complexation (MUSIC) model was modified to analyze the simultaneous adsorption of protons onto various kinds of surface species.

  5. Proton Adsorption onto Alumina: Extension of Multisite Complexation (MUSIC) Theory.

    PubMed

    Nagashima; Blum

    1999-09-01

    The adsorption isotherm of protons onto a commercial gamma-alumina sample was determined in aqueous nitric acid with sodium nitrate as a background electrolyte. Three discrete regions could be discerned in the log-log plots of the proton isotherm determined at the solution pH 5 to 2. The multisite complexation (MUSIC) model was modified to analyze the simultaneous adsorption of protons onto various kinds of surface species. Copyright 1999 Academic Press. PMID:10441408

  6. 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.

  7. Low-pressure equilibrium binary argon-methane gas mixture adsorption on exfoliated graphite: Experiments and simulations

    NASA Astrophysics Data System (ADS)

    Albesa, Alberto; Russell, Brice; Vicente, José Luis; Rafti, Matías

    2016-04-01

    Adsorption equilibrium measurements of pure methane, pure argon, and binary mixtures over exfoliated graphite were carried for different initial compositions, temperatures, and total pressures in the range of 0.1-1.5 Torr using the volumetric static method. Diagrams for gas and adsorbed phase compositions were constructed for the conditions explored, and isosteric heats of adsorption were calculated. Experimental results were compared with predictions obtained with Monte Carlo simulations and using the Ideal Adsorbed Solution Theory (IAST).

  8. Adsorption modeling for off-gas treatment

    SciTech Connect

    Ladshaw, A.; Sharma, K.; Yiacoumi, S.; Tsouris, C.; De Paoli, D.W.

    2013-07-01

    Off-gas generated from the reprocessing of used nuclear fuel contains a mixture of several radioactive gases including {sup 129}I{sub 2}, {sup 85}Kr, HTO, and {sup 14}CO{sub 2}. Over the past few decades, various separation and recovery processes have been studied for capturing these gases. Adsorption data for gaseous mixtures of species can be difficult to determine experimentally. Therefore, procedures capable of predicting the adsorption behavior of mixtures need to be developed from the individual isotherms of each of the pure species. A particular isotherm model of interest for the pure species is the Generalized Statistical Thermodynamic Adsorption isotherm. This model contains an adjustable number of parameters and will therefore describe a wide range of adsorption isotherms for a variety of components. A code has been developed in C++ to perform the non-linear regression analysis necessary for the determination of the isotherm parameters, as well as the least number of parameters needed to describe an entire set of data. (authors)

  9. Lysozyme adsorption at a silica surface using simulation and experiment: effects of pH on protein layer structure.

    PubMed

    Kubiak-Ossowska, Karina; Cwieka, Monika; Kaczynska, Agnieszka; Jachimska, Barbara; Mulheran, Paul A

    2015-10-01

    Hen Egg White Lysozyme (HEWL) is a widely used exemplar to study protein adsorption on surfaces and interfaces. Here we use fully atomistic Molecular Dynamics (MD) simulations, Multi-Parametric Surface Plasmon Resonance (MP-SPR), contact angle and zeta potential measurements to study HEWL adsorption at a silica surface. The simulations provide a detailed description of the adsorption mechanism and indicate that at pH7 the main adsorption driving force is electrostatics, supplemented by weaker hydrophobic forces. Moreover, they reveal the preferred orientation of the adsorbed protein and show that its structure is only slightly altered at the interface with the surface. This provides the basis for interpreting the experimental results, which indicate the surface adsorbs a close-packed monolayer at about pH10 where the surface has a large negative zeta potential and the HEWL is positively charged. At higher pH, the adsorption amount of the protein layer is greatly reduced due to the loss of charge on the protein. At lower pH, the smaller zeta potential of the surface leads to lower HEWL adsorption. These interpretations are complemented by the contact angle measurements that show how the hydrophobicity of the surface is greatest when the surface coverage is highest. The simulations provide details of the hydrophobic residues exposed to solution by the adsorbed HEWL, completing the picture of the protein layer structure. PMID:26315945

  10. Competitive adsorption/desorption of tetracycline, oxytetracycline and chlortetracycline on two acid soils: Stirred flow chamber experiments.

    PubMed

    Fernández-Calviño, David; Bermúdez-Couso, Alipio; Arias-Estévez, Manuel; Nóvoa-Muñoz, Juan Carlos; Fernández-Sanjurjo, Maria J; Álvarez-Rodríguez, Esperanza; Núñez-Delgado, Avelino

    2015-09-01

    The objective of this work was to study the competitive adsorption/desorption of tetracycline (TC), oxytetracycline (OTC) and chlortetracycline (CTC) on two acid soils. We used the stirred flow chamber technique to obtain experimental data on rapid kinetic processes affecting the retention/release of the antibiotics. Both adsorption and desorption were higher on soil 1 (which showed the highest carbon, clay and Al and Fe oxides content) than on soil 2. Moreover, hysteresis affected the adsorption/desorption processes. Experimental data were fitted to a pseudo-first order equation, resulting qamax (adsorption maximum) values that were higher for soil 1 than for soil 2, and indicating that CTC competed with TC more intensely than OTC in soil 1. Regarding soil 2, the values corresponding to the adsorption kinetics constants (ka) and desorption kinetics constants for fast sites (kd1), followed a trend inverse to qamax and qdmax respectively. In conclusion, competition affected adsorption/desorption kinetics for the three antibiotics assayed, and thus retention/release and subsequent transport processes in soil and water environments. PMID:25973861

  11. Sulfate adsorption and surface precipitation on a volcanic ash soil (allophanic andisol).

    PubMed

    Ishiguro, Munehide; Makino, Tomoyuki; Hattori, Yasunobu

    2006-08-15

    Sulfate strongly adsorbs on metal oxides and soils with variable charges. However, its surface precipitation has not been clearly evaluated and its adsorption mechanism has been in dispute. In the present study, an allophanic andisol, a typical volcanic ash soil having both negative and positive variable charges, was used to identify the adsorption mechanism of sulfate. Sulfate adsorption isotherms were obtained by a batch method at pH values of 4, 5, 6, and 7 in a wide range of concentrations in an Na-H-SO(4)-OH system. Theoretical isotherms were applied to the measured values for the evaluation. The surface precipitation was detected by the measured adsorption isotherms, and the BET isotherm confirmed the presence of multilayer adsorption. Stronger and weaker adsorption sites were suggested by using the Langmuir isotherm for the monolayer adsorption. The adsorption energies obtained from the Langmuir equation and recent spectroscopic analysis suggested that the stronger adsorption corresponded to an inner-sphere surface complex and that the weaker adsorption corresponded to outer-sphere surface complexation. The BET and Langmuir equations showed three types of adsorption mechanisms for the sulfate adsorption on the soil. PMID:16750540

  12. Adsorptive removal of nitrilotris(methylenephosphonic acid) antiscalant from membrane concentrates by iron-coated waste filtration sand.

    PubMed

    Boels, L; Tervahauta, T; Witkamp, G J

    2010-10-15

    Iron-coated waste filtration sand was investigated as a low-cost adsorbent for the removal of nitrilotris(methylenephosphonic acid) (NTMP) from membrane concentrates. The adsorption of this phosphonate-based antiscalant on this material was measured and compared with two commercially available anion exchange resins and activated carbon. Comprehensive adsorption experiments were conducted in several synthetic concentrate solutions and in a concentrate collected from a full scale nano-filtration brackish water desalination plant. The effect of pH, ionic strength and the presence of competitive anions on the equilibrium adsorption were investigated. The results showed that, in contrast to the anion exchange resins, the adsorption on coated filtration sand is not suppressed at increasing ionic strength and is much less affected by the competitive anions carbonate and sulphate. The adsorption decreased slightly when the pH was raised from 7.0 to 8.0. The adsorption isotherms in the real nano-filtration concentrate, measured in the concentration interval of 5-50 mg dm(-1) NTMP, showed that the maximum adsorption capacity of coated filtration sand was 4.06 mg g(-1). The adsorption capacity per unit mass of the adsorbents at low NTMP concentration (12.5 mg dm(-3)) followed the decreasing order Amberlite IRA-410>coated filtration sand>Amberlite IRA-900>Norit SAE Super. This demonstrates that the use of iron-coated waste filtration sand offers a promising means for the removal of NTMP from membrane concentrates. PMID:20667427

  13. A comparative study and evaluation of sulfamethoxazole adsorption onto organo-montmorillonites.

    PubMed

    Lu, Laifu; Gao, Manglai; Gu, Zheng; Yang, Senfeng; Liu, Yuening

    2014-12-01

    Three organo-montmorillonites were prepared using surfactants, and their adsorption behaviors toward sulfamethoxazole (SMX) were investigated. The surfactants used were cetyltrimethyl ammonium bromide (CTMAB), 3-(N,N-dimethylhexadecylammonio) propane sulfonate (HDAPS) and 1,3-bis(hexadecyldimethylammonio)-propane dibromide (BHDAP). The properties of the organo-montmorillonites were characterized by X-ray diffraction, scanning electron microscopy and N2 adsorption-desorption isotherm measurements. Results showed that the interlayer spacing of montmorillonite was increased and the surface area as well as the morphology were changed. Batch adsorption experiments showed that the surfactant loading amount had a great effect on the adsorption of SMX. The adsorption process was pH dependent and the maximum adsorption capacity was obtained at pH3 for HDAPS-Mt, while CTMAB-Mt and BHDAP-Mt showed a high removal efficiency at 3-11. The adsorption capacity increased with the initial SMX concentration and contact time but decreased with increasing solution ionic strength. Kinetic data were best described by the pseudo second-order model. Equilibrium data were best represented by the Langmuir model, and the Freundlich constant (n) indicated a favorable adsorption process. The maximum adsorption capacity of SMX was 235.29 mg/g for CTMAB-Mt, 155.28 mg/g for HDAPS-Mt and 242.72 mg/g for BHDAP-Mt. Thermodynamic parameters were calculated to evaluate the spontaneity and endothermic or exothermic nature. The adsorption mechanism was found to be dominated by electrostatic interaction, while hydrophobic interaction played a secondary role. PMID:25499502

  14. Adsorption behavior of anionic polyelectrolyte for chemical mechanical polishing (CMP).

    PubMed

    Kim, Sarah; So, Jae-Hyun; Lee, Dong-Jun; Yang, Seung-Man

    2008-03-01

    In this work, we investigated the adsorption characteristics of anionic polyelectrolytes, which are used in shallow trench isolation chemical mechanical polishing with ceria abrasives. Specifically, the adsorption isotherms and chain conformation of anionic polyelectrolytes were studied in order to elucidate the difference in removal rates of silicon dioxide (SiO2) and silicon nitride (Si3N4) layers and the high selectivity characteristics of ceria slurry. Adsorption isotherms, FT-IR spectroscopy and contact angle measurements revealed that the anionic polyelectrolyte additives had much better adsorption affinities for the Si3N4 surface than for the SiO2 surface. Moreover, blanket wafer polishing results were successfully correlated with the adsorption isotherms of polyelectrolytes on the oxide particle suspensions. PMID:18078949

  15. Multilayer adsorption of Cu(II) and Cd(II) over Brazilian Orchid Tree (Pata-de-vaca) and its adsorptive properties

    NASA Astrophysics Data System (ADS)

    Jorgetto, Alexandre de O.; da Silva, Adrielli C. P.; Wondracek, Marcos H. P.; Silva, Rafael I. V.; Velini, Edivaldo D.; Saeki, Margarida J.; Pedrosa, Valber A.; Castro, Gustavo R.

    2015-08-01

    Through very simple and inexpensive processes, pata-de-vaca leaves were turned into a powder and applied as an adsorbent for the uptake of Cu(II) and Cd(II) from water. The material was characterized through SEM, EDX, FTIR and surface area measurement. The material had its point of zero charge determined (5.24), and its adsorption capacity was evaluated as a function of time, pH and metal concentration. The material presented fast adsorption kinetics, reaching adsorption equilibrium in less than 5 min and it had a good correlation with the pseudo-second order kinetic model. Optimum pH for the adsorption of Cu(II) and Cd(II) were found to be in the range from 4 to 5, approximately. In the experiment as a function of the analyte concentration, analogously to gas adsorption, the material presented a type II isotherm, indicating the formation of multilayers for both species. Such behavior was explained with basis in the alternation between cations and anions over the material's surface, and the maximum adsorption capacity, considering the formation of the multilayers were found to be 0.238 mmol L-1 for Cu(II) and 0.113 mmol L-1 for Cd(II).

  16. Non isothermal drying process optimisation - Drying of clay tiles

    NASA Astrophysics Data System (ADS)

    Vasić, M.; Radojević, Z.

    2015-11-01

    In our previous studies we have developed a model for determination of the variable effective diffusivity and identification of the exact transition points between possible drying mechanisms. The next goal was to develop a drying regime which could in advance characterize the real non isothermal process of drying clay tiles. In order to do this four isothermal experiments were recorded. Temperature and humidity were maintained at 350C / 75%; 450C / 70%; 450C / 60% and 500C / 60%; respectively in each experiment. All experimentally collected data were analyzed and the exact transition points between possible drying mechanisms were detected. Characteristic drying period (time) for each isothermal drying mechanism was also detected. The real, non-isothermal drying process was approximated by 5 segments. In each of these segments approximately isothermal drying condition were maintained. Temperature and humidity of the drying air, in the first four segments, was maintained on the same level as in recorded isothermal experiments while in the fifth segment, it were maintained at 700C / 40%. The duration of the first four segments were calculated from the diagrams Deff - t respectively for each experiment. The clay tile in experiment five was dried without cracking using the proposed non isothermal drying regime.

  17. Adsorption of alkenyl succinic anhydride from solutions in carbon tetrachloride on a fine magnetite surface

    NASA Astrophysics Data System (ADS)

    Balmasova, O. V.; Ramazanova, A. G.; Korolev, V. V.

    2016-06-01

    The adsorption of alkenyl succinic anhydride from a solution in carbon tetrachloride on a fine magnetite surface at a temperature of 298.15 K is studied using fine magnetite, which forms the basis of magnetic fluids, as the adsorbent. An adsorption isotherm is recorded and interpreted in terms of the theory of the volume filling of micropores (TVFM). Adsorption process parameters are calculated on the basis of the isotherm. It is shown that at low equilibrium concentrations, the experimental adsorption isotherm is linear in the TVFM equation coordinates.

  18. A quantitative method evaluating the selective adsorption of molecularly imprinted polymer.

    PubMed

    Zhang, Z B; Hu, J Y

    2012-01-01

    Adsorption isotherms of 4 estrogenic compounds, estrone, 17β-estradiol, 17α-ethinylestradiol and Bisphenol A, using molecularly imprinted polymer were studied. The isotherms can be simulated by Langmuir model. According to the adsorption isotherms and the template's mass balance, an experimental concept, selective adsorption ratio, SAR, was proposed to assess how many template molecules extracted out of MIP could create selective binding sites. The SAR of the molecularly imprinted polymer was 74.3% for E2. This concept could be used to evaluate quantitatively the selective adsorption. PMID:22423989

  19. Adsorption of H2, Ne, and N2 on Activated Charcoal

    NASA Technical Reports Server (NTRS)

    Chang, C. K.; Tward, E.; Boudaie, K. I.

    1986-01-01

    9-page report presents measured adsorption isotherms of hydrogen, neon, and nitrogen on activated charcoal for temperatures from 77 to 400 K and pressures from 1 to 80 atmospheres (0.1 to 8.1 MPa). Heats of adsorption calculated from isotherms also presented. Report gives expressions, based on ideal-gas law, which show relationship between different definitions of volume of gas adsorbed and used in describing low-pressure isotherms.

  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. 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.

  2. Adsorption of Nickel (II) from Aqueous Solution by Bicarbonate Modified Coconut Oilcake Residue Carbon.

    PubMed

    Vijayakumari, N; Srinivasan, K

    2014-07-01

    The adsorption of Ni (II) on modified coconut oilcake residue carbon (bicarbonate treated coconut oilcake residue carbon-BCORC) was employed for the removal of Ni (II) from water and wastewater. The influence of various factors such as agitation time, pH and carbon dosage on the adsorption capacity has been studied. Adsorption isothermal data could be interpreted by Langmuir and Freundlich equations. In order to understand the reaction mechanism, kinetic data has been studied using reversible first order rate equation. Similar studies were carried out using commercially available activated carbon--CAC, for comparison purposes. Column studies were conducted to obtain breakthrough capacities of BCORC and CAC. Common anions and cations affecting the removal of Ni (II) on both the carbons were also studied. Experiments were also done with wastewater containing Ni (II), to assess the potential of these carbons. PMID:26563074

  3. Comparison of linear and non-linear models for the adsorption of fluoride onto geo-material: limonite.

    PubMed

    Sahin, Rubina; Tapadia, Kavita

    2015-01-01

    The three widely used isotherms Langmuir, Freundlich and Temkin were examined in an experiment using fluoride (F⁻) ion adsorption on a geo-material (limonite) at four different temperatures by linear and non-linear models. Comparison of linear and non-linear regression models were given in selecting the optimum isotherm for the experimental results. The coefficient of determination, r², was used to select the best theoretical isotherm. The four Langmuir linear equations (1, 2, 3, and 4) are discussed. Langmuir isotherm parameters obtained from the four Langmuir linear equations using the linear model differed but they were the same when using the nonlinear model. Langmuir-2 isotherm is one of the linear forms, and it had the highest coefficient of determination (r² = 0.99) compared to the other Langmuir linear equations (1, 3 and 4) in linear form, whereas, for non-linear, Langmuir-4 fitted best among all the isotherms because it had the highest coefficient of determination (r² = 0.99). The results showed that the non-linear model may be a better way to obtain the parameters. In the present work, the thermodynamic parameters show that the absorption of fluoride onto limonite is both spontaneous (ΔG < 0) and endothermic (ΔH > 0). Scanning electron microscope and X-ray diffraction images also confirm the adsorption of F⁻ ion onto limonite. The isotherm and kinetic study reveals that limonite can be used as an adsorbent for fluoride removal. In future we can develop new technology for fluoride removal in large scale by using limonite which is cost-effective, eco-friendly and is easily available in the study area. PMID:26676015

  4. Adsorption and desorption of arsenate on sandy sediments from contaminated and uncontaminated saturated zones: Kinetic and equilibrium modeling.

    PubMed

    Hafeznezami, Saeedreza; Zimmer-Faust, Amity G; Dunne, Aislinn; Tran, Tiffany; Yang, Chao; Lam, Jacquelyn R; Reynolds, Matthew D; Davis, James A; Jay, Jennifer A

    2016-08-01

    Application of empirical models to adsorption of contaminants on natural heterogeneous sorbents is often challenging due to the uncertainty associated with fitting experimental data and determining adjustable parameters. Sediment samples from contaminated and uncontaminated portions of a study site in Maine, USA were collected and investigated for adsorption of arsenate [As(V)]. Two kinetic models were used to describe the results of single solute batch adsorption experiments. Piecewise linear regression of data linearized to fit pseudo-first order kinetic model resulted in two distinct rates and a cutoff time point of 14-19 h delineating the biphasic behavior of solute adsorption. During the initial rapid adsorption stage, an average of 60-80% of the total adsorption took place. Pseudo-second order kinetic models provided the best fit to the experimental data (R(2) > 0.99) and were capable of describing the adsorption over the entire range of experiments. Both Langmuir and Freundlich isotherms provided reasonable fits to the adsorption data at equilibrium. Langmuir-derived maximum adsorption capacity (St) of the studied sediments ranged between 29 and 97 mg/kg increasing from contaminated to uncontaminated sites. Solid phase As content of the sediments ranged from 3.8 to 10 mg/kg and the As/Fe ratios were highest in the amorphous phase. High-pH desorption experiments resulted in a greater percentage of solid phase As released into solution from experimentally-loaded sediments than from the unaltered samples suggesting that As(V) adsorption takes place on different reversible and irreversible surface sites. PMID:27218893

  5. 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.

  6. Competitive adsorption of heavy metals onto sesame straw biochar in aqueous solutions.

    PubMed

    Park, Jong-Hwan; Ok, Yong Sik; Kim, Seong-Heon; Cho, Ju-Sik; Heo, Jong-Soo; Delaune, Ronald D; Seo, Dong-Cheol

    2016-01-01

    Objective of this research was to evaluate adsorption of heavy metals in mono and multimetal forms onto sesame straw biochar (SSB). Competitive sorption of metals by SSB has never been reported previously. The maximum adsorption capacities (mgg(-1)) of metals by SSB were in the order of Pb (102)≫Cd (86)≫Cr (65)>Cu (55)≫Zn (34) in the monometal adsorption isotherm and Pb (88)≫Cu (40)≫Cr (21)>Zn (7)⩾Cd (5) in the multimetal adsorption isotherm. Based on data obtained from the distribution coefficients, Freundlich and Langmuir adsorption models, and three-dimensional simulation, multimetal adsorption behaviors differed from monometal adsorption due to competition. Especially, during multimetal adsorption, Cd was easily exchanged and substituted by other metals. Further competitive adsorption studies are necessary in order to accurately estimate the heavy metal adsorption capacity of biochar in natural environments. PMID:26082184

  7. Separation of toxic rhodamine B from aqueous solution using an efficient low-cost material, Azolla pinnata, by adsorption method.

    PubMed

    Kooh, Muhammad Raziq Rahimi; Lim, Linda B L; Lim, Lee Hoon; Dahri, Muhammad Khairud

    2016-02-01

    This study investigated the potential of untreated Azolla pinnata (AP) to remove toxic rhodamine B (RB) dye. The effects of adsorbent dosage, pH, ionic strength, contact time, and concentration were studied. Experiments involving the effects of pH and ionic strength indicated that hydrophobic-hydrophobic interactions might be the dominant force of attraction for the RB-AP adsorption system. The kinetics modelling of the kinetics experiment showed that pseudo-second-order best represented the adsorption process. The Weber-Morris intraparticle diffusion model showed that intraparticle diffusion is not the rate-limiting step, while the Boyd model suggested that film diffusion might be rate-limiting. The adsorption isotherm model, Langmuir, best represented the adsorption process, and the maximum adsorption capacity was predicted to be 72.2 and 199.7 mg g(-1) at 25 and 65 °C, respectively. Thermodynamics study indicates spontaneity, endothermic and physisorption-dominant adsorption process. The adsorbents were regenerated to satisfactory level with distilled water, HNO3 and NaOH. Pre-treatment of adsorbent with oxalic acid, citric acid, NaOH, HCl and phosphoric acid was investigated but the adsorption capacity was less than the untreated AP. PMID:26797814

  8. Adsorption of octylamine on titanium dioxide

    NASA Astrophysics Data System (ADS)

    Siwińska, Daria; Kołodziejczak-Radzimska, Agnieszka; Krysztafkiewicz, Andrzej; Jesionowski, Teofil

    2009-05-01

    Processes of adsorption and desorption of a model active substance (octylamine) on the surface of unmodified titanium dioxide (E 171) have been performed. The effects of concentration of octylamine and time of the process on the character of adsorption have been studied and the efficiency of the adsorption/desorption has been determined. The samples obtained have been studied by X-ray diffraction. The nitrogen adsorption/desorption isotherms, particle size distribution and absorption capacities of water, dibutyl phthalate and paraffin oil have been determined. The efficiency of octylamine adsorption on the surface of the titanium dioxide has been found positively correlated with the concentration of octylamine in the initial solution. The desorption of octylamine has decreased with increasing concentration of this compound adsorbed. For octylamine in low concentrations the physical adsorption has been found to dominate, which is desirable when using TiO 2 in the production of pharmaceuticals.

  9. Adsorption of Pb(II), Cr(III), Cu(II), Cd(II) and Ni(II) onto a vanadium mine tailing from aqueous solution.

    PubMed

    Shi, Taihong; Jia, Shiguo; Chen, Ying; Wen, Yinghong; Du, Changming; Guo, Huilin; Wang, Zhuochao

    2009-09-30

    The adsorption of heavy metal cations Pb(II), Cr(III), Cu(II), Cd(II) and Ni(II) from aqueous solution by a mine tailing which mainly contains muscovite was investigated. The property of the mineral was investigated by using SEM, FT-IR, XRD and BET analysis. pH(pzc) was measured by an titration technique to give a value of 5.4+/-0.1. Kinetics experiments indicated that the processes can be simulated by pseudo-second-order model. Total adsorption amounts of the heavy metal increased, while the adsorption density decreased when the solid-to-liquid ratio (S/L) increased. Grain size did not affect the adsorption capacity significantly. The resulting isotherms can be described by Frendlich relationship. And the maximum adsorption capacity (molar basis) followed the order of Cr(III)>Pb(II)>Cu(II)>Ni(II)>Cd(II). Thermodynamic analysis showed that the adsorption processed were endothermic and may be chemical in nature with positive DeltaH(0). The positive DeltaS(0) suggested that dissociative processed were involved. Small positive DeltaG(0) suggested that the adsorption processes required a small amount of energy. Adsorption processes were slightly affected by electrolyte ion concentration but strongly dependent on pH value. The most possible mechanism of the adsorption processes involve the inner-sphere-complexions by the aluminol or silanol groups on the surface of the mineral. PMID:19427115

  10. Adsorption of pyridine by combusted oil shale

    NASA Astrophysics Data System (ADS)

    Essington, M. E.

    1992-03-01

    Large volumes of solid waste material will be produced during the commercial production of shale oil. An alternative to the disposal of the solid waste product is utilization. One potential use of spent oil shale is for the stabilization of hazardous organic compounds. The objective of this study was to examine the adsorption of pyridine, commonly found in oil shale process water, by spent oil shale. The adsorption of pyridine by fresh and weathered samples of combusted New Albany Shale and Green River Formation oil shale was examined. In general, pyridine adsorption can be classified as L-type and the isotherms modeled with the Langmuir and Freundlich equations. For the combusted New Albany Shale, weathering reduced the predicted pyridine adsorption maximum and increased the amount of pyridine adsorbed at low solution concentrations. For the combusted Green River Formation oil shales, weathering increased the predicted pyridine adsorption maximum. The pyridine adsorption isotherms were similar to those produced for a combusted Australian oil shale. Although adsorption can be mathematically described by empirical models, the reduction in solution concentrations of pyridine was generally less than 10 mg/l at an initial concentration of 100 mg/l. Clearly, the observed reduction in solution pyridine concentrations does not sufficiently justify using spent oil shale as a stabilizing medium. However, data in the literature suggest that other organic compounds can be effectively removed from solution by spent oil shale and that adsorption is dependent on process conditions and organic compound type.

  11. 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

  12. Development of a sodium alginate-based organic/inorganic superabsorbent composite hydrogel for adsorption of methylene blue.

    PubMed

    Thakur, Sourbh; Pandey, Sadanand; Arotiba, Omotayo A

    2016-11-20

    Batch adsorption experiments were carried out for the removal of methylene blue (MB) cationic dye from aqueous solution using organic/inorganic hydrogel nanocomposite of titania incorporated sodium alginate crosslinked polyacrylic acid (SA-cl-poly(AA)-TiO2). The hydrogel was prepared by graft copolymerization of acrylic acid (AA) onto sodium alginate (SA) biopolymer in the presence of a crosslinking agent, a free radical initiator and TiO2 nanoparticles. The hydrogel exhibited a high swelling capacity of 412.98g/g. The factors influencing adsorption capacity of the absorbents such as pH of the dye solutions, initial concentration of the dye, amount of absorbents, and temperature were investigated and used to propose a possible mechanism of adsorption. The adsorption process concurs with a pseudo-second-order kinetics and with Langmuir isotherm equation. A very high adsorption capacity (Qmax=2257.36 (mg/g)) and a correlation coefficient of 0.998 calculated from isotherm equations show the high efficiency of the absorbent and thus expected to be a good candidate as an absorbent for water treatment. PMID:27561469

  13. Adsorption of Hg(II) from aqueous solutions using TiO2 and titanate nanotube adsorbents

    NASA Astrophysics Data System (ADS)

    López-Muñoz, María-José; Arencibia, Amaya; Cerro, Luis; Pascual, Raquel; Melgar, Álvaro

    2016-03-01

    Titania and titanate nanotubes were evaluated as adsorbents for the removal of Hg(II) from aqueous solution. Commercial titanium dioxide (TiO2-P25, Evonik), a synthesized anatase sample obtained by the sol-gel method (TiO2-SG) and titanate nanotubes (TNT) prepared via hydrothermal treatment were compared. Mercury adsorption was analysed by kinetic and equilibrium experiments, studying the influence of pH and the type of adsorbents. The kinetics of Hg(II) adsorption on titania and titanate nanotubes could be well described by the pseudo-second order model. It was found that the process is generally fast with small differences between adsorbents, which cannot be explained by their dissimilarities in textural properties. Equilibrium isotherm data were best fitted with the Sips isotherm model. The maximum adsorption capacities of Hg(II) were achieved with titanate nanotubes sample, whereas between both titania samples, TiO2-SG exhibited the highest mercury uptake. For all adsorbents, adsorption capacities were enhanced as pH was increased, achieving at pH 10 Hg(II) adsorption capacities of 100, 121, and 140 mg g-1 for TiO2-P25, TiO2-SG, and TNT, respectively. Differences between samples were discussed in terms of their crystalline phase composition and chemical nature of both, mercury species and surface active sites.

  14. Adsorption of organic molecules on silica surface.

    PubMed

    Parida, Sudam K; Dash, Sukalyan; Patel, Sabita; Mishra, B K

    2006-09-13

    The adsorption behaviour of various organic adsorbates on silica surface is reviewed. Most of the structural information on silica is obtained from IR spectral data and from the characteristics of water present at the silica surface. Silica surface is generally embedded with hydroxy groups and ethereal linkages, and hence considered to have a negative charged surface prone to adsorption of electron deficient species. Adsorption isotherms of the adsorbates delineate the nature of binding of the adsorbate with silica. Aromatic compounds are found to involve the pi-cloud in hydrogen bonding with silanol OH group during adsorption. Cationic and nonionic surfactants adsorb on silica surface involving hydrogen bonding. Sometimes, a polar part of the surfactants also contributes to the adsorption process. Styryl pyridinium dyes are found to anchor on silica surface in flat-on position. On modification of the silica by treating with alkali, the adsorption behaviour of cationic surfactant or polyethylene glycol changes due to change in the characteristics of silica or modified silica surface. In case of PEG-modified silica, adsolubilization of the adsorbate is observed. By using a modified adsorption equation, hemimicellization is proposed for these dyes. Adsorptions of some natural macromolecules like proteins and nucleic acids are investigated to study the hydrophobic and hydrophilic binding sites of silica. Artificial macromolecules like synthetic polymers are found to be adsorbed on silica surface due to the interaction of the multifunctional groups of the polymers with silanols. Preferential adsorption of polar adsorbates is observed in case of adsorbate mixtures. When surfactant mixtures are considered to study competitive adsorption on silica surface, critical micelle concentration of individual surfactant also contributes to the adsorption isotherm. The structural study of adsorbed surface and the thermodynamics of adsorption are given some importance in this review

  15. Studies of adsorption equilibria and kinetics in the systems: Aqueous solution of dyes-mesoporous carbons

    NASA Astrophysics Data System (ADS)

    Derylo-Marczewska, A.; Marczewski, A. W.; Winter, Sz.; Sternik, D.

    2010-06-01

    Two carbonaceous materials were synthesized by using the method of impregnation of mesoporous silicas obtained by applying the Pluronic copolymers as pore-creating agents. The isotherms of adsorption of methylene blue and methyl orange from aqueous solutions were measured by the static method. The profiles of adsorbate concentration change in time were obtained from the UV-vis spectra. The adsorption isotherms and kinetic dependence were discussed in the terms of theory of adsorption on heterogeneous surfaces.

  16. Adsorption and reactions of O2 and D2 on small free palladium clusters in a cluster-molecule scattering experiment

    NASA Astrophysics Data System (ADS)

    Andersson, Mats; Rosén, Arne

    2010-08-01

    The adsorption of oxygen and hydrogen (deuterium) on small neutral palladium clusters was investigated in a cluster beam experiment. The beam passes through two low-pressure reaction cells, and the clusters, with and without adsorbed molecules, are detected using laser ionization and mass spectrometry. Both H2 and O2 adsorb efficiently on the palladium clusters with only moderate variations with cluster size in the investigated range, i.e. between 8 and 28 atoms. The co-adsorption of H2 and O2 results in the formation of H2O, detected as a decrease in the number of adsorbed oxygen atoms with an increasing number of collisions with H2 molecules. A comparison is done with an earlier similar study of clusters of Pt. Furthermore a comparison is done with what is known for sticking and reactivity of surfaces.

  17. EFFECT OF GAC CHARACTERISTICS ON ADSORPTION OF ORGANIC POLLUTANTS

    EPA Science Inventory

    The impact of the characteristics of granular activated carbon (GAC) on adsorption capacity and on the potential for polymerization of phenolic compounds on the surface of GAC in the presence of molecular oxygen is evaluated in this study. Adsorption isotherm data were collected...

  18. Adsorption behavior of copper and zinc in soils: Influence of pH on adsorption characteristics

    SciTech Connect

    Msaky, J.J. ); Calvet, R. )

    1990-08-01

    The authors studied adsorption of copper and zinc on three different soils: a brown silty soil, an Oxisol, and a Podzol. They determined the amounts adsorbed and the shapes of adsorption isotherms as a function of the pH of the adsorbing medium at a constant ionic strength. The adsorbed amount-pH relationship depended strongly on the natures of the metallic cation and of the soil. The pH greatly influenced the characteristics of adsorption isotherms. They based interpretation on the variations with the pH of both adsorbent affinity for the metal in relation to the surface electric charge and chemical speciation in solution. The adsorption mechanism in the Oxisol probably involves monohydroxylated cations but is more determined by bivalent cations in the brown silty soil and the Podzol. From a general point of view, adsorption of copper and zinc cannot be represented with a single adsorption constant, but should be described by adsorption isotherms obtained at various pH values.

  19. Rapid adsorptive removal of toxic Pb(2+) ion from aqueous solution using recyclable, biodegradable nanocomposite derived from templated partially hydrolyzed xanthan gum and nanosilica.

    PubMed

    Ghorai, Soumitra; Sarkar, Amit Kumar; Pal, Sagar

    2014-10-01

    This work studied the application of a novel biodegradable nanocomposite based on partially hydrolyzed polyacrylamide grafted xanthan gum and nanosilica (h-XG/SiO2) towards efficient and rapid removal of toxic Pb(2+) ions from aqueous environment. The uptake ability of Pb(2+) using h-XG/SiO2 has been studied in batch adsorption experiments with variation of adsorption parameters. The excellent removal rate (99.54% adsorption within 25min) and superior adsorption capacity (Qmax=1012.15mgg(-1)) of the composite material have been explained on the basis of synergistic and chelating effects of h-XG/SiO2 with Pb(2+) ion through electrostatic interactions. The kinetics, isotherm and thermodynamics studies reveal that Pb(2+) adsorb rapidly on nanocomposite surface, which is in agreement with pseudo-second-order kinetics and Langmuir adsorption isotherm models. In consequence of excellent adsorption as well as regeneration characteristics of nanocomposite, it has been found to be a promising adsorbent towards removal of Pb(2+) ions from battery industry wastewater. PMID:25164955

  20. Comparative studies on adsorptive removal of heavy metal ions by biosorbent, bio-char and activated carbon obtained from low cost agro-residue.

    PubMed

    Kırbıyık, Çisem; Pütün, Ayşe Eren; Pütün, Ersan

    2016-01-01

    In this study, Fe(III) and Cr(III) metal ion adsorption processes were carried out with three adsorbents in batch experiments and their adsorption performance was compared. These adsorbents were sesame stalk without pretreatment, bio-char derived from thermal decomposition of biomass, and activated carbon which was obtained from chemical activation of biomass. Scanning electron microscopy and Fourier transform-infrared techniques were used for characterization of adsorbents. The optimum conditions for the adsorption process were obtained by observing the influences of solution pH, adsorbent dosage, initial solution concentration, contact time and temperature. The optimum adsorption efficiencies were determined at pH 2.8 and pH 4.0 for Fe(III) and Cr(III) metal ion solutions, respectively. The experimental data were modelled by different isotherm models and the equilibriums were well described by the Langmuir adsorption isotherm model. The pseudo-first-order, pseudo-second-order kinetic, intra-particle diffusion and Elovich models were applied to analyze the kinetic data and to evaluate rate constants. The pseudo-second-order kinetic model gave a better fit than the others. The thermodynamic parameters, such as Gibbs free energy change ΔG°, standard enthalpy change ΔH° and standard entropy change ΔS° were evaluated. The thermodynamic study showed the adsorption was a spontaneous endothermic process. PMID:26819399

  1. Adsorption of dye from wastewater using chitosan-CTAB modified bentonites.

    PubMed

    Guo, Jianzhong; Chen, Shunwei; Liu, Li; Li, Bing; Yang, Ping; Zhang, Lijun; Feng, Yanlong

    2012-09-15

    Dyeing wastewater removal is important for the water treatment, and adsorption is an efficient treatment process. In this study, three modified bentonites, chitosan modified bentonite (CTS-Bent), hexadecyl trimethyl ammonium bromide (CTAB) modified bentonite (CTAB-Bent), and both chitosan and hexadecyl trimethyl ammonium bromide modified bentonite (CTS-CTAB-Bent) were prepared and characterized by FTIR and XRD analysis. Batch experiments were conducted to evaluate the adsorptive removal of weak acid scarlet from aqueous phase using modified bentonites under different conditions. The results show that the adsorption capacity of weak acid scarlet onto natural bentonite was low (4.9%), but higher for 1CTS-Bent and 1CTS-10CTAB-Bent. The optimal conditions for weak acid scarlet adsorption were 1% chitosan, 10% CTAB, at 80°C and reaction time 2.5h. The best removal efficiency was ∼85%, and the adsorption capacity of weak acid scarlet was around 102.0mg g(-1), much higher than that of commercial activated carbon (27.2mg g(-1)). These results suggest that 1CTS-10CTAB-Bent is an excellent adsorbent for effective weak acid scarlet removal from water. The adsorption isotherms of weak acid scarlet were investigated. It was found that Langmuir and Temkin models fitted the data very well (R(2)>0.99). PMID:22738850

  2. Fluoride adsorption onto amorphous aluminum hydroxide: Roles of the surface acetate anions.

    PubMed

    Zhang, Yong-Xing; Jia, Yong

    2016-12-01

    Amorphous aluminum hydroxide with hydroxyl groups, acetate anions and chlorine anions enriched surface was synthesized, and was characterized by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, and nitrogen adsorption-desorption isotherms. Batch experiments were performed to study the influence of various experimental parameters such as contact time, initial fluoride concentration, temperature, pH value and the presence of competing anions on the adsorption of fluoride on amorphous aluminum hydroxide. The kinetic data was well fitted to pseudo-second-order model. The fluoride adsorption on the amorphous aluminum hydroxide can be well described by the Langmuir model, and the maximum adsorption capacity was 63.94mgg(-1) at pH 7.0. Thermodynamic parameters including the Gibbs free energy, standard enthalpy and standard entropy were calculated, and the results suggested that the adsorption of fluoride on the amorphous aluminum hydroxide was a feasible, spontaneous and exothermic process. The adsorption mechanism was revealed by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy analysis. The results suggested that the surface acetate anions and surface chlorine anions played important roles in the fluoride removal process. PMID:27565961

  3. Adsorption of Procion Red MX 8B using spent tea leaves as adsorbent

    NASA Astrophysics Data System (ADS)

    Heraldy, Eddy; Osa, Riesta Ramdhaniyati; Suryanti, Venty

    2016-02-01

    The adsorption of Procion Red MX 8B using spent tea leaves (STL) as adsorbent, has been studied by batch adsorption technique. The adsorbent was activated by NaOH 4% for 24 hours for delignification process. The adsorbent was characterized using FTIR to indetify the functional groups of cellulose was shown by uptake -OH, C-H and C-O. The optimum conditions of adsorption experiments were achieved when pH was set as 6 with contact time of 75 minutes and capacity of adsorption was 3.28 mg/g. The equilibrium data were fitted to Langmuir and Isotherm Freundlichs. The kinetic models, pseudo first order and pseudo second order were employed to describe the adsorption mechanism. The experimental results showed that the pseudo second order equation was the best model that described the adsorption behavior with the coefficient of correlation (R2) was equal higher than 0.99 The results suggested that STL had high potential to be used as effective adsorbent for Procion Red MX 8B removal.

  4. Adsorption studies of Cu(II) onto biopolymer chitosan and its nanocomposite 5%bentonite/chitosan.

    PubMed

    Moussout, Hamou; Ahlafi, Hammou; Aazza, Mustapha; Zegaoui, Omar; El Akili, Charaf

    2016-01-01

    Chitosan (CS) and nanocomposite 5%bentonite/chitosan (5%Bt/CS) prepared from the natural biopolymer CS were tested to remove Cu(II) ions using a batch adsorption experiment at various temperatures (25, 35 and 45°C). X-ray diffraction, Fourier transform infrared spectroscopy, and thermogravimetric analysis/differential thermal analysis (TGA/DTA) were used in CS and the nanocomposite characterisation. This confirmed the exfoliation of bentonite (Bt) to form the nanocomposite. The adsorption kinetics of copper on both solids was found to follow a pseudo-second-order law at each studied temperature. The Cu(II) adsorption capacity increased as the temperature increased from 25 to 45°C for nanocomposite adsorbent but slightly increased for CS. The data were confronted to the nonlinear Langmuir, Freundlich and Redlich-Peterson models. It was found that the experimental data fitted very well the Langmuir isotherm over the whole temperature and concentration ranges. The maximum monolayer adsorption capacity for the Cu(II) was 404-422 mg/g for CS and 282-337 mg/g for 5%Bt/CS at 25-45°C. The thermodynamic study showed that the adsorption process was spontaneous and endothermic. The complexation of Cu(II) with NH(2) and C = O groups as active sites was found to be the main mechanism in the adsorption processes. PMID:27148722

  5. 40 CFR 796.2750 - Sediment and soil adsorption isotherm.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... and tissues of soil organisms, and substances synthesized by the microbial population. (iv) “Particle... growth of land plants. Its formation and properties are determined by various factors such as parent... during sieving, crush and grind dried soil very gently. (C) Eliminate microbial growth during the...

  6. Direct injection method for HPLC/MS/MS analysis of acrylamide in aqueous solutions: application to adsorption experiments.

    PubMed

    Mnif, Ines; Hurel, Charlotte; Marmier, Nicolas

    2015-05-01

    Polyacrylamides are polymers used in many fields and represent the main source of release of the highly toxic acrylamide in the environment. In this work, a simple, rapid, and sensitive analytical method was developed with HPLC/MS/MS and direct injection for acrylamide analysis in water and adsorption samples. AFNOR standards NF T90-210 and NF T90-220 were used for the analytical method validation and uncertainty estimation. Limit of quantification (LOQ) for acrylamide was 1 μg/L, and accuracy was checked at three acrylamide levels (1, 6, and 10 μg/L). Uncertainties were estimated at 34.2, 22, and 12.4 % for acrylamide concentrations at LOQ, 6 μg/L, and 10 μg/L, respectively. Acrylamide adsorption on clays (kaolinite, illite) and sludge was then studied as a function of pH, time, and acrylamide concentrations. Acrylamide adsorption on kaolinite, illite, and sludge was found to be very weak since adsorption percentages were inferior to 10 %, whatever the pH value and the initial acrylamide concentration. The low affinity of acrylamide for clays and sludge is likely due to its hydrophilic property, small size, and charge neutrality. PMID:25388555

  7. ATR-FTIR Spectroscopy in the Undergraduate Chemistry Laboratory: Part II--A Physical Chemistry Laboratory Experiment on Surface Adsorption

    ERIC Educational Resources Information Center

    Schuttlefield, Jennifer D.; Larsen, Sarah C.; Grassian, Vicki H.

    2008-01-01

    Attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy is a useful technique for measuring the infrared spectra of solids and liquids as well as probing adsorption on particle surfaces. The use of FTIR-ATR spectroscopy in organic and inorganic chemistry laboratory courses as well as in undergraduate research was presented…

  8. Protein Adsorption in Microengraving Immunoassays

    PubMed Central

    Song, Qing

    2015-01-01

    Microengraving is a novel immunoassay forcharacterizing multiple protein secretions from single cells. During the immunoassay, characteristic diffusion and kinetic time scales τD and τK determine the time for molecular diffusion of proteins secreted from the activated single lymphocytes and subsequent binding onto the glass slide surface respectively. Our results demonstrate that molecular diffusion plays important roles in the early stage of protein adsorption dynamics which shifts to a kinetic controlled mechanism in the later stage. Similar dynamic pathways are observed for protein adsorption with significantly fast rates and rapid shifts in transport mechanisms when C0* is increased a hundred times from 0.313 to 31.3. Theoretical adsorption isotherms follow the trend of experimentally obtained data. Adsorption isotherms indicate that amount of proteins secreted from individual cells and subsequently captured on a clean glass slide surface increases monotonically with time. Our study directly validates that protein secretion rates can be quantified by the microengraving immunoassay. This will enable us to apply microengraving immunoassays to quantify secretion rates from 104–105 single cells in parallel, screen antigen-specific cells with the highest secretion rate for clonal expansion and quantitatively reveal cellular heterogeneity within a small cell sample. PMID:26501282

  9. Adsorption of isopropanol and cyclohexane on zinc oxide

    NASA Astrophysics Data System (ADS)

    Bratchikova, I. G.; Pylinina, A. I.; Platonov, E. A.; Danilova, M. N.; Isaeva, N. Yu.; Yagodovskii, V. D.

    2015-01-01

    Adsorption isotherms of isopropanol and cyclohexane are obtained in the range of 234-303 K on an initial surface of zinc oxide and after its treatment with glow-discharge plasma in O2 and high-frequency plasma in Ar. The values of isosteric heat and adsorption entropy are shown to be only slightly affected by these treatments. It is found that the acidity of the surface increases by 38 and 97%, respectively, and the acidic sites are not adsorption sites for either adsorbate. At low degrees of occupation, the adsorption isotherms of (CH3)2CHOH are described by an equation of induced adsorption whose parameters are dependent on the plasma-chemical treatments. It is concluded that adsorbed isopropanol particles exist in positively and negatively charged forms. The adsorption of cyclohexane is described by the Hill-de Boer equation for the initial ZnO surface, and by the Langmuir equation after plasma-chemical treatments.

  10. Uranium Adsorption to A Hanford Sediment Sample: Effects of Suspended Particle Concentration at High pH

    NASA Astrophysics Data System (ADS)

    Bai, J.; Ball, W. P.

    2006-05-01

    Adsorption (surface complexation) is an important retardation process involved in the transport of uranium(VI) in the subsurface environment at the Hanford, WA DOE site. Accurate evaluation of adsorption equilibrium by means of adsorption isotherm experiments is a prerequisite for understanding and modeling uranium(VI) transport and fate. In this study, several series of batch adsorption experiments were performed at controlled pH (8.0, 8.5 and 9.5) on replicate samples of a silt/clay-size fraction of sediment culled from core borings located roughly 43 meters below the SX Tank farm at the Hanford site. At pH 8.0 and 8.5, the adsorption isotherm was found to be reversible and independent of the concentration of suspended sediment particles, and to be well described by a Freundlich model. At pH 9.5, however, the observed adsorption was found to depend on the experimental conditions of particle concentration - 100g/L, 200g/L and 400g/L were tested. Stronger adsorption was observed for lower particle concentrations, and desorption was less complete under these conditions. Various hypotheses, including colloidal effects, solid aggregation, and surface precipitation, are being explored as explanation of these observations. Centrifugation and ultra-filtration results suggest that colloidal effects are unlikely, and flow-through columns are currently being conducted (with re-circulated stock uranium solution) to investigate whether physical phenomena (e.g. effects of particle-particle contact) are a possible cause. It is also possible that surface precipitation may be occurring under some conditions, and on- going investigations will explore this possibility.

  11. U(VI) adsorption on aquifer sediments at the Hanford Site.

    PubMed

    Um, Wooyong; Serne, R Jeffrey; Brown, Christopher F; Last, George V

    2007-08-15

    Aquifer sediments collected via split-spoon sampling in two new groundwater wells in the 200-UP-1 operable unit at the Hanford Site were characterized and showed typical Ringold Unit E Formation properties dominated by gravel and sand. High iron-oxide content in Fe oxide/clay coatings caused the highest U(VI) adsorption as quantified by batch K(d) values, indicating iron oxides are the key solid adsorbent in the 200-UP-1 sediments that affect U(VI) fate and mobility. Even though U(VI) adsorption on the gravel-sized fraction of the sediments is considered to be negligible, careful characterization should be conducted to determine U(VI) adsorption on gravel, because of presence of Fe oxides coatings and diffusion-controlled adsorption into the gravel particles' interior surfaces. A linear adsorption isotherm was observed up to 10(-6) M (238 microg/L) of total U(VI) concentration in batch U(VI) adsorption tests with varying total U(VI) concentrations in spiked groundwater. U(VI) adsorption decreased with increasing concentrations of dissolved carbonate, because strong anionic aqueous uranium-carbonate complexes formed at high pH and high alkalinity conditions. Noticeable uranium desorption hysteresis was observed in a flow-through column experiment, suggesting that desorption K(d) values for aged uranium-contaminated sediments at the Hanford Site can be larger than adsorption K(d) values determined in short-term laboratory experiments and slow uranium release from contaminated sediments into the groundwater is expected. PMID:17499879

  12. U(VI) adsorption on aquifer sediments at the Hanford Site

    NASA Astrophysics Data System (ADS)

    Um, Wooyong; Serne, R. Jeffrey; Brown, Christopher F.; Last, George V.

    2007-08-01

    Aquifer sediments collected via split-spoon sampling in two new groundwater wells in the 200-UP-1 operable unit at the Hanford Site were characterized and showed typical Ringold Unit E Formation properties dominated by gravel and sand. High iron-oxide content in Fe oxide/clay coatings caused the highest U(VI) adsorption as quantified by batch Kd values, indicating iron oxides are the key solid adsorbent in the 200-UP-1 sediments that affect U(VI) fate and mobility. Even though U(VI) adsorption on the gravel-sized fraction of the sediments is considered to be negligible, careful characterization should be conducted to determine U(VI) adsorption on gravel, because of presence of Fe oxides coatings and diffusion-controlled adsorption into the gravel particles' interior surfaces. A linear adsorption isotherm was observed up to 10 - 6 M (238 μg/L) of total U(VI) concentration in batch U(VI) adsorption tests with varying total U(VI) concentrations in spiked groundwater. U(VI) adsorption decreased with increasing concentrations of dissolved carbonate, because strong anionic aqueous uranium-carbonate complexes formed at high pH and high alkalinity conditions. Noticeable uranium desorption hysteresis was observed in a flow-through column experiment, suggesting that desorption Kd values for aged uranium-contaminated sediments at the Hanford Site can be larger than adsorption Kd values determined in short-term laboratory experiments and slow uranium release from contaminated sediments into the groundwater is expected.

  13. Hydrogen adsorption on functionalized nanoporous activated carbons.

    PubMed

    Zhao, X B; Xiao, B; Fletcher, A J; Thomas, K M

    2005-05-12

    There is considerable interest in hydrogen adsorption on carbon nanotubes and porous carbons as a method of storage for transport and related energy applications. This investigation has involved a systematic investigation of the role of functional groups and porous structure characteristics in determining the hydrogen adsorption characteristics of porous carbons. Suites of carbons were prepared with a wide range of nitrogen and oxygen contents and types of functional groups to investigate their effect on hydrogen adsorption. The porous structures of the carbons were characterized by nitrogen (77 K) and carbon dioxide (273 K) adsorption methods. Hydrogen adsorption isotherms were studied at 77 K and pressure up to 100 kPa. All the isotherms were Type I in the IUPAC classification scheme. Hydrogen isobars indicated that the adsorption of hydrogen is very temperature dependent with little or no hydrogen adsorption above 195 K. The isosteric enthalpies of adsorption at zero surface coverage were obtained using a virial equation, while the values at various surface coverages were obtained from the van't Hoff isochore. The values were in the range 3.9-5.2 kJ mol(-1) for the carbons studied. The thermodynamics of the adsorption process are discussed in relation to temperature limitations for hydrogen storage applications. The maximum amounts of hydrogen adsorbed correlated with the micropore volume obtained from extrapolation of the Dubinin-Radushkevich equation for carbon dioxide adsorption. Functional groups have a small detrimental effect on hydrogen adsorption, and this is related to decreased adsorbate-adsorbent and increased adsorbate-adsorbate interactions. PMID:16852056

  14. Effect of low-concentration rhamnolipid on adsorption of Pseudomonas aeruginosa ATCC 9027 on hydrophilic and hydrophobic surfaces.

    PubMed

    Zhong, Hua; Jiang, Yongbing; Zeng, Guangming; Liu, Zhifeng; Liu, Liuxia; Liu, Yang; Yang, Xin; Lai, Mingyong; He, Yibin

    2015-03-21

    The effects of low-concentration monorhamnolipid (monoRL) on the adsorption of Pseudomonas aeruginosa ATCC 9027 grown on glucose or hexadecane to glass beads with hydrophobic or hydrophilic surfaces was investigated using batch adsorption experiments. Results showed that adsorption isotherms of the cells on both types of glass beads fitted the Freundlich equation better than the Langmuir equation. The Kf of the Freundlich equation for adsorption of hexadecane-grown cell to glass beads with hydrophobic surface was remarkably higher than that for adsorption of hexadecane-grown cell to glass beads with hydrophilic surface, or glucose-grown cell to glass beads with either hydrophilic or hydrophobic surface. Furthermore, it decreased with the increasing monoRL concentration. For both groups of cells, the zeta potential was close to each other and stable with the increase of monoRL concentration. The surface hydrophobicity of hexadecane-grown cells, however, was significantly higher than that of the glucose-grown cells and it decreased with the increase of monoRL concentration. The results indicate the importance of hydrophobic interaction on adsorption of bacterial cells to surfaces and monoRL plays a role in reducing the bacterial adsorption by affecting cell surface hydrophobicity. PMID:25528238

  15. Influence of pH on the adsorption of uranium ions by oxidized activated carbon and chitosan

    SciTech Connect

    Park, G.I.; Park, H.S.; Woo, S.I.

    1999-03-01

    The adsorption characteristics of uranyl ions on surface-oxidized carbon were compared with those of powdered chitosan over a wide pH range. In particular, an extensive analysis was made on solution pH variation during the adsorption process or after adsorption equilibrium. Uranium adsorption on the two adsorbents was revealed to be strongly dependent on the initial pH of the solution. A quantitative comparison of the adsorption capacities of the two adsorbents was made, based on the isotherm data obtained at initial pH 3, 4, and 5. In order to analyze the adsorption kinetics incorporated with pH effects, batch experiments at various initial pH values were carried out, and solution pH profiles with the adsorption time were also evaluated. The breakthrough behavior in a column packed with oxidized carbon was also characterized with respect to the variation of effluent pH. Based on these experimental results, the practical applicability of oxidized carbon for uranium removal from acidic radioactive liquid waste was suggested.

  16. Preparation, characterization and dye adsorption properties of γ-Fe 2O 3/SiO 2/chitosan composite

    NASA Astrophysics Data System (ADS)

    Zhu, H. Y.; Jiang, R.; Fu, Y.-Q.; Jiang, J.-H.; Xiao, L.; Zeng, G.-M.

    2011-12-01

    A γ-Fe2O3/SiO2/chitosan composite was prepared by water-in-oil emulsification, and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM). Effects of various factors, including adsorbent dosage, initial dye concentration, solution pH, and competing anions, on the adsorption of methyl orange from aqueous solutions by the resulting composite were studied by batch adsorption experiments. The adsorption kinetics was found to follow the pseudo-second-order kinetic model, and intraparticle diffusion was related to the adsorption, but not as a sole rate-controlling step. The equilibrium adsorption data were well described by the Freundlich isotherm model. Evaluation of the thermodynamic parameters ΔG°, ΔH°, and ΔS° revealed that the adsorption process was naturally feasible, spontaneous, and exothermic. The composite was proven to be efficient, suitable and promising for the removal of methyl orange from aqueous solutions since it has a relatively higher adsorption capacity than other low-cost adsorbents.

  17. 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

  18. A batch adsorption study on bentonite clay Pertinence to transport modeling?

    NASA Astrophysics Data System (ADS)

    BOURG, I.; BOURG, A. C.; SPOSITO, G.

    2001-12-01

    Bentonite clay is often used as a component of engineered barriers for the isolation of high-level toxic wastes. This swelling clay is used for its physical (impermeability, self-healing) but also for its chemical properties, mostly a high cation exchange capacity (CEC). The adsorbed cations being temporarily immobilized, this should slow down the release of cations from the waste to the surrounding environment. In order to assess the performance of the engineered barrier, the partitioning of solutes between the liquid and solid phases needs to be quantified for use in transport models. The usual method for characterizing the adsorption is through batch adsorption experiments on dispersed suspensions of the solid, yielding an adsorption isotherm (adsorbed concentration vs. dissolved concentration). This isotherm however should be a function of various environmental variables (e.g., pH, ionic strength, concentrations of various ligands and competing adsorbents), so that extrapolation of lab data to performance assessment in the field is problematic. We present results from a study of the adsorption of cesium, strontium, cadmium and lead on dispersed suspensions of the standard BX-80 bentonite. Through a wide range of experimental parameters (pH, ionic strength, reaction time, reactor open or closed to the atmosphere, study of a range of cations of differing properties), we seek a mechanistic interpretation of the results instead of an empirical determination of adsorption parameters. Depending on the mechanisms that control the adsorption in different experimental ranges, we discuss the degree to which the partitioning coefficient (Kd) obtained in the lab can be extrapolated to a transport model through compacted bentonite in a natural environment.

  19. Adsorption of L-glutamic acid and L-aspartic acid to γ-Al2O3

    NASA Astrophysics Data System (ADS)

    Greiner, Edward; Kumar, Kartik; Sumit, Madhuresh; Giuffre, Anthony; Zhao, Weilong; Pedersen, Joel; Sahai, Nita

    2014-05-01

    The interactions of amino acids with mineral surfaces have potential relevance for processes ranging from pre-biotic chemistry to biomineralization to protein adsorption on biomedical implants in vivo. Here, we report the results of experiments investigating the adsorption of L-glutamic (Glu) and L-aspartic (Asp) acids to γ-Al2O3. We examined the extent of Glu and Asp coverage as a function of pH and solution concentration (pH edges and isotherms) in solution-depletion experiments and used in situ Attenuated Total Refkectance Fourier Transform Infrared (ATR-FTIR) spectroscopy to estimate the molecular conformations of the adsorbed molecules. Glu and Asp exhibited similar adsorption behavior on γ-Al2O3 with respect to pH and solution concentration. In general, adsorption decreased as pH increased. At low and high amino acid concentrations, the isotherms exhibited two apparent saturation coverages, which could be interpreted as 1:4 or 1:2 ratios of adsorbed molecule/surface Al sites. Tetradentate tetranuclear and bidentate binuclear species were the dominant conformations inferred independently from FTIR spectra. In these conformations, both carboxylate groups are involved in bonding to either four or to two Al surface atoms, through direct covalent bonds or via H-bonds. An outer sphere species, in which one carboxylate group interacts with a surface Al atom, could not be ruled out based on the FTIR spectra.

  20. An Experimental-Theoretical Analysis of Protein Adsorption on Peptidomimetic Polymer Brushes

    PubMed Central

    Lau, K.H. Aaron; Ren, Chunlai; Park, Sung Hyun; Szleifer, Igal; Messersmith, Phillip B.

    2012-01-01

    Surface-grafted water soluble polymer brushes are being intensely investigated for preventing protein adsorption to improve biomedical device function, prevent marine fouling, and enable applications in biosensing and tissue engineering. In this contribution, we present an experimental-theoretical analysis of a peptidomimetic polymer brush system with regard to the critical brush density required for preventing protein adsorption at varying chain lengths. A mussel adhesive-inspired DOPA-Lys pentapeptide surface grafting motif enabled aqueous deposition of our peptidomimetic polypeptoid brushes over a wide range of chain densities. Critical densities of 0.88 nm−2 for a relatively short polypeptoid 10-mer to 0.42 nm−2 for a 50-mer were identified from measurements of protein adsorption. The experiments were also compared with the protein adsorption isotherms predicted by a molecular theory. Excellent agreements in terms of both the polymer brush structure and the critical chain density were obtained. Furthermore, atomic force microscopy (AFM) imaging is shown to be useful in verifying the critical brush density for preventing protein adsorption. The present co-analysis of experimental and theoretical results demonstrates the significance of characterizing the critical brush density in evaluating the performance of an anti-fouling polymer brush system. The high fidelity of the agreement between the experiments and molecular theory also indicate that the theoretical approach presented can aid in the practical design of antifouling polymer brush systems. PMID:22107438

  1. Argon Adsorption on Open Carbon Nanohorns

    NASA Astrophysics Data System (ADS)

    Russell, Brice; Calvillo, Angel; Khanal, Pravin; Migone, Aldo; Iijima, Sumio; Yudasaka, Masako

    We have measured adsorption isotherms for argon adsorbed on a 0.1692 g sample of chemically-opened carbon nanohorns. Two clear substeps are visible in the adsorption data, corresponding to groups of stronger binding sites (lower pressure substep) and weaker binding sites (higher pressure substep). We have measured adsorption at eight different temperatures in the range between approximately 70 and 110 K. The space at the interior of the individual nanohorns is accessible to sorbates in these chemically opened nanohorns. Consequently, higher loadings are obtained on these samples when compared to those measured on unopened (as-produced) nanohorns. Results for the kinetics of adsorption, the effective specific surface area, and the isosteric heat of adsorption as a function of sorbent loading will be presented and compared to results from other gases adsorbed on nanohorns. This work was supported by the NSF through Grant DMR-1006428.

  2. Enhancing adsorption capacity of toxic malachite green dye through chemically modified breadnut peel: equilibrium, thermodynamics, kinetics and regeneration studies.

    PubMed

    Chieng, Hei Ing; Lim, Linda B L; Priyantha, Namal

    2015-01-01

    Breadnut skin, in both its unmodified (KS) and base-modified (BM-KS) forms, was investigated for its potential use as a low-cost adsorbent for the removal of toxic dye, malachite green (MG). Characterization of the adsorbents was carried out using scanning electron microscope, X-ray fluorescence and Fourier transform infra-red spectroscopy. Batch adsorption experiments, carried out under optimized conditions, for the adsorption of MG were fitted using five isotherm models (Langmuir, Freundlich, Dubinin-Radushkevich, Temkin and Sips) and six error functions to determine the best-fit model. The adsorption capacity was greatly enhanced when breadnut skin was chemically modified with NaOH, leading to an adsorption capacity of 353.0 mg g(-1), that was far superior to most reported adsorbents for the removal of MG. Thermodynamics studies indicated that the adsorption of MG was spontaneous on KS and BM-KS, and the reactions were endothermic and exothermic, respectively. Kinetics studies showed that both followed the pseudo-second order. Regeneration experiments on BM-KS indicated that its adsorption capacity was still maintained at>90% even after five cycles. It can be concluded that NaOH-modified breadfruit skin has great potential to be utilized in real-life application as a low-cost adsorbent for the removal of MG in wastewater treatment. PMID:25409587

  3. Studies on chelating adsorption properties of novel composite material polyethyleneimine/silica gel for heavy-metal ions

    NASA Astrophysics Data System (ADS)

    Gao, Baojiao; An, Fuqiang; Liu, Kangkai

    2006-12-01

    Firstly, the coordination processes of line-type polyethyleneimine with Cu 2+, Cd 2+ and Zn 2+ were studied by using visible light absorption spectroscopy and chelation conductivity titration method, and the structures of the chelates were determined. Afterwards, polyethyleneimine (PEI) was grafted onto the surface of silica gel particles via the coupling effect of γ-chloropropyl trimethoxysilane (CP), and the novel composite adsorption material PEI/SiO 2 with strong adsorption ability towards heavy-metal ions was prepared. The chelating adsorption properties of PEI/SiO 2 for Cu 2+, Cd 2+ and Zn 2+ were researched by both static (batch) and dynamic (flow) methods. The experiment results show that water-soluble polyamine PEI with line-type structure reacts with Cu 2+, Cd 2+ and Zn 2+ easily and quantitatively, and water-soluble chelates with four ligands are formed. The composite material PEI/SiO 2 possesses very strong chelating adsorption ability for heavy-metal ions, and the saturated adsorption amount can reach 25.94 mg g -1 and 50.01 mg g -1 for Cu 2+ under static and dynamic conditions, respectively. The isothermal adsorption data fit to Langmuir equation, and the adsorption is typical chemical adsorption with monomolecular layer. The adsorbing ability of PEI/SiO 2 towards the three kinds of the ions follows the order of Cu 2+ > Cd 2+ > Zn 2+. The pH value has great influence on the sorption, and at pH 6-7, the adsorption capacity is the greatest. The fact that adsorption capacity increases with temperature rising indicates the adsorbing process of PEI/SiO 2 for metal ions is endothermic. As diluted hydrochloric acid is used as eluent, the adsorbed heavy-metal ions are eluted easily from PEI/SiO 2, and the regeneration and reuse without decreasing sorption for PEI/SiO 2 are demonstrated.

  4. Adsorption interference in mixtures of trace contaminants flowing through activated carbon adsorber beds

    NASA Technical Reports Server (NTRS)

    Madey, R.; Photinos, P. J.

    1980-01-01

    Adsorption interference in binary and ternary mixtures of trace contaminants in a helium carrier gas flowing through activated carbon adsorber beds are studied. The isothermal transmission, which is the ratio of the outlet to the inlet concentration, of each component is measured. Interference between co-adsorbing gases occurs when the components are adsorbed strongly. Displacement of one component by another is manifested by a transmission greater than unity for the displaced component over some range of eluted volume. Interference is evidenced not only by a reduction of the adsorption capacity of each component in the mixture in comparison with the value obtained in a single-component experiment, but also by a change in the slope of the transmission curve of each component experiment.

  5. Adsorption characteristics of siloxanes in landfill gas by the adsorption equilibrium test

    SciTech Connect

    Nam, Sangchul; Namkoong, Wan; Kang, Jeong-Hee; Park, Jin-Kyu; Lee, Namhoon

    2013-10-15

    Highlights: • Equilibrium test was attempted to evaluate adsorption characteristics of siloxane. • L2 had higher removal efficiency in carbon compared to noncarbon adsorbents. • Total adsorption capacity of siloxane was 300 mg/g by coal activated carbon. • Adsorption characteristics rely on size of siloxane molecule and adsorbent pore. • Conversion of siloxane was caused by adsorption of noncarbon adsorbents. - Abstract: Due to the increase in energy cost by constantly high oil prices and the obligation to reduce greenhouse effect gases, landfill gas is frequently used as an alternative energy source for producing heat and electricity. Most of landfill gas utility facilities, however, are experiencing problems controlling siloxanes from landfill gas as their catalytic oxidizers are becoming fouled by silicon dioxide dust. To evaluate adsorption characteristics of siloxanes, an adsorption equilibrium test was conducted and parameters in the Freundlich and Langmuir isotherms were analyzed. Coconut activated carbon (CA1), coal activated carbon (CA2), impregnated activated carbon (CA3), silicagel (NCA1), and activated alumina (NCA2) were used for the adsorption of the mixed siloxane which contained hexamethyldisiloxane (L2), octamethylcyclotetrasiloxane (D4), and decamethylcyclopentasiloxane (D5). L2 had higher removal efficiency in noncarbon adsorbents compared to carbon adsorbents. The application of Langmuir and Freundlich adsorption isotherm demonstrated that coconut based CA1 and CA3 provided higher adsorption capacity on L2. And CA2 and NCA1 provided higher adsorption capacity on D4 and D5. Based on the experimental results, L2, D4, and D5 were converted by adsorption and desorption in noncarbon adsorbents. Adsorption affinity of siloxane is considered to be affect by the pore size distribution of the adsorbents and by the molecular size of each siloxane.

  6. Use of Activated Charcoal for {sup 220}Rn Adsorption for Operations Associated with the Uranium Deposit in the Auxiliary Charcoal Bed at the Molten Salt Reactor Experiment Facility

    SciTech Connect

    Coleman, R.L.

    1999-03-01

    Measurements have been collected with the purpose of evaluating the effectiveness of activated charcoal for the removal of {sup 220}Rn from process off-gas at the Molten Salt Reactor Experiment (MSRE) at Oak Ridge National Laboratory. A series of bench-scale tests were performed at superficial flow velocities of 10, 18, 24, and 33 cm/s (20, 35, 47, and 65 ft/min) with a continuous input concentration of {sup 220}Rn in the range of 9 x 10{sup 3} pCi/L. In addition, two tests were performed at the MSRE facility by flowing helium through the auxiliary charcoal bed uranium deposit. These tests were performed so that the adsorptive effectiveness could be evaluated with a relatively high concentration of {sup 220}Rn. In addition to measuring the effectiveness of activated charcoal as a {sup 220}Rn adsorption media, the source term for available {sup 220}Rn in the deposit is actually available for removal and that the relative activity of fission gases is very small when compared to {sup 220}Rn. The measurement data were then used to evaluate the expected effectiveness of a proposed charcoal adsorption bed consisting of a right circular cylinder having a diameter of 43 cm and a length of 91 cm (17 in. I.D. x 3 ft.). The majority of the measurement data predicts an overall 220Rn activity reduction factor of about 1 x 10{sup 9} for such a design; however, two measurements collected at a flow velocity of 18 cm/s (35 ft/min) indicated that the reduction factor could be as low as 1 x 10{sup 6}. The adsorptive capacity of the proposed trap was also evaluated to determine the expected life prior to degradation of performance. Taking a conservative vantage point during analysis, it was estimated that the adsorption effectiveness should not begin to deteriorate until a {sup 220}Rn activity on the order of 10{sup 10} Ci has been processed. It was therefore concluded that degradation of performance would likely occur as the result of causes other than filling by radon progeny.

  7. Use of Activated Charcoal for Rn-220 Adsorption for Operations Associated with the Uranium Deposit in the Auxiliary Charcoal Bed at the Molten Salt Reactor Experiment Facility

    SciTech Connect

    Coleman, R.L.

    1999-03-17

    Measurements have been collected with the purpose of evaluating the effectiveness of activated charcoal for the removal of {sup 220}Rn from process off-gas at the Molten Salt Reactor Experiment (MSRE) at Oak Ridge National Laboratory. A series of bench-scale tests were performed at superficial flow velocities of 10, 18, 24, and 33 cm s{sup -1} (20, 35, 47, and 65 ft min{sup -1}) with a continuous input concentration of {sup 220}Rn in the range of 9 x 10{sup 3} pCi L{sup -1}. In addition, two tests were performed at the MSRE facility by flowing helium through the auxiliary charcoal bed uranium deposit. These tests were performed so that the adsorptive effectiveness could be evaluated with a relatively high concentration of {sup 220}Rn. In addition to measuring the effectiveness of activated charcoal as a {sup 220}Rn adsorption media, the source term for available {sup 220}Rn and gaseous fission products was evaluated and compared to what is believed to be present in the deposit. The results indicate that only a few percent of the total {sup 220}Rn in the deposit is actually available for removal and that the relative activity of fission gases is very small when compared to {sup 220}Rn. The measurement data were then used to evaluate the expected effectiveness of a proposed charcoal adsorption bed consisting of a right circular cylinder having a diameter of 43 cm and a length of 91 cm (17 in. I.D. x 3 ft.). The majority of the measurement data predicts an overall {sup 220}Rn activity reduction factor of about 1 x 10{sup 9} for such a design; however, two measurements collected at a flow velocity of 18 cm s{sup -1} (35 ft min{sup -1}) indicated that the reduction factor could be as low as 1 x 10{sup 6}. The adsorptive capacity of the proposed trap was also evaluated to determine the expected life prior to degradation of performance. Taking a conservative vantage point during analysis, it was estimated that the adsorption effectiveness should not begin to deteriorate

  8. Chromium adsorption by lignin

    SciTech Connect

    Lalvani, S.B.; Huebner, A.; Wiltowski, T.S.

    2000-01-01

    Hexavalent chromium is a known carcinogen, and its maximum contamination level in drinking water is determined by the US Environmental Protection Agency (EPA). Chromium in the wastewaters from plating and metal finishing, tanning, and photographic industries poses environmental problems. A commercially available lignin was used for the removal of hexavalent as well as trivalent chromium from aqueous solution. It is known that hexavalent chromium is present as an anionic species in the solution. It was found that lignin can remove up to 63% hexavalent and 100% trivalent chromium from aqueous solutions. The removal of chromium ions was also investigated using a commercially available activated carbon. This absorbent facilitated very little hexavalent and almost complete trivalent chromium removal. Adsorption isotherms and kinetics data on the metal removal by lignin and activated carbon are presented and discussed.

  9. Adsorption characteristics of hexavalent chromium on HCB/TiO2

    NASA Astrophysics Data System (ADS)

    Zhang, Li; Zhang, Yonggang

    2014-10-01

    Sol-gel method was adopted to prepare HCB/TiO2 and its adsorption ability of hexavalent chromium, Cr(VI), and removal from aqueous solution were investigated. The samples were characterized by Power X-ray diffraction (XRD) and a transmission electron microscope (TEM) which showed that the TiO2 was deposited on the surface of HCB. FTIR was used to identify the changes of the surface functional groups before and after adsorption. Potentiometric titration method was used to characterize the zero charge (pHpzc) characteristics of the surface of HCB/TiO2 which showed more acidic functional groups containing. Batch experiments showed that initial pH, absorbent dosage, contact time and initial concentration of Cr(VI) were important parameters for the Cr(VI) adsorption studies. The Freundlich isotherm model better reflected the experimental data better. Cr(VI) adsorption process followed the pseudo-second order kinetic model, which illustrated chemical adsorption. The thermodynamic parameters, such as Gibbs free energy (ΔG), changes in enthalpy change (ΔH) and changes in entropy change (ΔS) were also evaluated. Negative value of free energy occurred at temperature range of 25-45 °C, so Cr(VI) adsorption by HCB/TiO2 is spontaneous. Desorption results showed that the adsorption capacity could maintain 80% after five cycles. The maximum adsorption capacity for Cr(VI) was at 27.33 mg g-1 in an acidic medium, of which the value is worth comparable with other low-cost adsorbents.

  10. Optimization of mesoporous carbons for efficient adsorption of berberine hydrochloride from aqueous solutions.

    PubMed

    Li, Yin; Fu, Jie; Deng, Shuguang; Lu, Xiuyang

    2014-06-15

    Sixteen mesoporous carbon adsorbents were synthesized by varying the ratio of soft to hard templates in order to optimize the pore textural properties of these adsorbents. The mesoporous carbon adsorbents have a high BET specific surface area (1590.3-2193.5 m(2)/g), large pore volume (1.72-2.56 cm(3)/g), and uniform pore size distribution with a median pore diameter ranging from 3.51 nm to 4.52 nm. It was observed that pore textural properties of the carbon adsorbents critically depend on the molar ratio of carbon sources to templates, and the hard template plays a more important role than the soft template in manipulating the pore textures. Adsorption isotherms of berberine hydrochloride at 303 K were measured to evaluate the adsorption efficacy of these adsorbents. The adsorption of berberine hydrochloride from aqueous solutions on the sixteen mesoporous carbon adsorbents synthesized in this work is very efficient, and the adsorption equilibrium capacities on all samples are more than double the adsorption capacities of berberine hydrochloride of the benchmark adsorbents (polymer resins and spherical activated carbons) at similar conditions. It was observed from the adsorption experiments that the equilibrium adsorption amounts of berberine hydrochloride are strongly correlated with the BET specific surface area and pore volume of the adsorbents. The adsorbent with the highest BET of 2193.5 m(2)/g displayed the largest adsorption capacity of 574 mg/g at an equilibrium concentration of 0.10mg/mL of berberine hydrochloride in an aqueous solution. PMID:24767505

  11. Liquid-Phase Adsorption Fundamentals.

    ERIC Educational Resources Information Center

    Cooney, David O.

    1987-01-01

    Describes an experiment developed and used in the unit operations laboratory course at the University of Wyoming. Involves the liquid-phase adsorption of an organic compound from aqueous solution on activated carbon, and is relevant to adsorption processes in general. (TW)

  12. Experimental study of water adsorption on activated carbons

    SciTech Connect

    Salame, I.I.; Bandosz, T.J. |

    1999-01-19

    Two carbons of different origins (wood and coal) were oxidized with nitric acid. The materials were characterized using sorption of nitrogen. Boehm titration, and potentiometric titration. The water adsorption isotherms were measured at various temperatures close to ambient (relative pressure from 0.001 to 0.3). From these isotherms heats of adsorption were calculated using virial equation. The results showed that the isosteric heats of water adsorption are affected by surface chemical heterogeneity only at low surface coverage. The shapes of heats obtained indicate strong water-water interactions as a result of adsorption on secondary sites and cluster formation. In all cases the limiting heat of adsorption equal to the heat of water condensation (45 kJ/mol) was obtained.

  13. Lattice Boltzmann simulations of the permeability and capillary adsorption of cement model microstructures

    SciTech Connect

    Zalzale, M.; McDonald, P.J.

    2012-12-15

    The lattice Boltzmann method is used to investigate the permeability of microstructures of cement pastes generated using the numerical models CEMHYD3D (Bentz, 1997) and {mu}IC (Bishnoi and Scrivener, 2009). Results are reported as a function of paste water-to-cement ratio and degree of hydration. The permeability decreases with increasing hydration and decreasing water-to-cement ratio in agreement with experiment. However the permeability is larger than the experimental data recorded using beam bending methods (Vichit-Vadakan and Scherer, 2002). Notwithstanding, the lattice Boltzmann results compare favourably with alternate numerical methods of permeability calculation for cement model microstructures. In addition, we show early results for the liquid/vapour capillary adsorption and desorption isotherms in the same model {mu}IC structures. The broad features of the experimental capillary porosity isotherm are reproduced, although further work is required to adequately parameterise the model.

  14. Adsorption of heavy metal ions from aqueous solutions by bio-char, a by-product of pyrolysis

    NASA Astrophysics Data System (ADS)

    Kılıç, Murat; Kırbıyık, Çisem; Çepelioğullar, Özge; Pütün, Ayşe E.

    2013-10-01

    Bio-char, a by-product of almond shell pyrolysis, was used as an alternative adsorbent precursor for the removal of heavy metal ions from aqueous solutions. The adsorption potential of almond shell bio-char for Ni(II) and Co(II) removal was investigated. Adsorption experiments were carried out by varying pH, adsorbent dosage, initial metal ion concentrations, contact time and temperature to determine the optimum conditions. To describe the equilibrium isotherms the experimental data were analyzed by the Langmuir, Freundlich, Dubinin-Radushkevich (D-R) and Temkin isotherm models. Pseudo-first order, pseudo-second order, and intraparticle diffusion kinetic models were used to find out the kinetic parameters and mechanism of adsorption process. The thermodynamic parameters such as ΔG°, ΔH° and ΔS° were calculated for predicting the nature of adsorption. The results showed that bio-char derived from pyrolysis of biomass can be used as a low-cost and effective adsorbent for removal of heavy metal ions from aqueous solutions.

  15. The behavior of the adsorption of cytochrome C on lipid monolayers: A study by the Langmuir-Blodgett technique and theoretical analysis.

    PubMed

    Li, Junhua; Sun, Runguang; Hao, Changchun; He, Guangxiao; Zhang, Lei; Wang, Juan

    2015-10-01

    Cytochrome c (Cyt c) is an essential component of the inner mitochondrial respiratory chain because of its function of transferring electrons. The feature is closely related to the interaction between Cyt c and membrane lipids. We used Langmuir-Blodgett monolayer technique combined with AFM to study the interaction of Cyt c with lipid monolayers at air-buffer interface. In our work, by comparing the mixed Cyt c-anionic (DPPS) and Cyt c-zwitterionic (DPPC/DPPE) monolayers, the adsorption capacity of Cyt c on lipid monolayers is DPPS>DPPE>DPPC, which is attributed to their different headgroup structures. π-A isothermal data show that Cyt c (v=2.5 μL) molecules are at maximum adsorption quantity on lipid monolayer. Moreover, Cyt c molecules would form aggregations and drag some lipids with them into subphase if the protein exceeds the maximum adsorption quantity. π-T curve indicates that it takes more time for Cyt c molecular conformation to rearrange on DPPE monolayer than on DPPC. The compressibility study reveals that the adsorption or intermolecular aggregation of Cyt c molecules on lipid monolayer will change the membrane fluidization. In order to quantitatively estimate Cyt c molecular adsorption properties on lipid monolayers, we fit the experimental isotherm with a simple surface state equation. A theoretical model is also introduced to analyze the liquid expanded (LE) to liquid condensed (LC) phase transition of DPPC monolayer. The results of theoretical analysis are in good agreement with the experiment. PMID:26071844

  16. Adsorption behavior and mechanism of Cr(VI) using Sakura waste from aqueous solution

    NASA Astrophysics Data System (ADS)

    Qi, Wenfang; Zhao, Yingxin; Zheng, Xinyi; Ji, Min; Zhang, Zhenya

    2016-01-01

    A forestall waste, Sakura leave, has been studied for the adsorption of Cr(VI) from aqueous solution. The materials before and after adsorption were characterized by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). To investigate the adsorption performance of Sakura waste, batch experiments were conducted under different adsorbent dosage, contact time, initial concentration of Cr(VI), and co-existing ions. Results showed the data fitted pseudo-second-order better than pseudo-first-order kinetic model. Equilibrium data was analyzed with Langmuir, Freundlich and Redlich-Peterson isotherm models at temperature ranges from 25 °C to 45 °C. The maximum adsorption capacity from the Langmuir model was 435.25 mg g-1 at pH 1.0. The presence of Cl-, SO42- and PO43- would lead to an obvious negative effect on Cr(VI) adsorption, and their influence order follows PO43- > SO42- > Cl-. The study developed a new way to reutilize wastes and showed a great potential for resource recycling.

  17. Effect of surface acidity and basicity of aluminas on asphaltene adsorption and oxidation.

    PubMed

    Nassar, Nashaat N; Hassan, Azfar; Pereira-Almao, Pedro

    2011-08-01

    This study investigates the effect of surface acidity and basicity of aluminas on asphaltene adsorption followed by air oxidation. Equilibrium batch adsorption experiments were conducted at 25°C with solutions of asphaltenes in toluene at concentrations ranging from 100 to 3000 g/L using three conventional alumina adsorbents with different surface acidity. Data were found to better fit to the Freundlich isotherm model showing a multilayer adsorption. Results showed that asphaltene adsorption is strongly affected by the surface acidity, and the adsorption capacities of asphaltenes onto the three aluminas followed the order acidic>basic and neutral. Asphaltenes adsorbed over aluminas were subjected to oxidation in air up to 600°C in a thermogravimetric analyzer to study the catalytic effect of aluminas with different surface acidity. A correlation was found between Freundlich affinity constant (1/n) and the catalytic activity. Basic alumina that has the lowest 1/n value, depicting strongest interactions, has the highest catalytic activity, followed by neutral and acidic aluminas, respectively. PMID:21571295

  18. Effects of a manganese oxide-modified biochar composite on adsorption of arsenic in red soil.

    PubMed

    Yu, Zhihong; Zhou, Li; Huang, Yifan; Song, Zhengguo; Qiu, Weiwen

    2015-11-01

    The arsenic adsorption capacity of a manganese oxide-modified biochar composite (MBC), prepared by pyrolysis of a mixture of potassium permanganate and biochar, was investigated in red soil. Adsorption experiments using batch procedures were used to estimate the arsenic adsorption capacities of the absorbent materials. Adsorption and desorption isotherms, Fourier-transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) were used to characterise the prepared adsorbent materials, and a plausible mechanism for arsenic removal by MBC was proposed. Arsenic in red soil-MBC mixtures exhibited lower mobility than that in soils amended with pristine biochar. The improved removal performance of soil-MBC mixtures was attributed to a lower H/C ratio, higher O/C ratio, higher surface hydrophilicity, and higher surface sorption capacity, even though the impregnation of manganese oxide decreased the specific surface area of the biochar. Arsenic retention increased as the biochar content increased, mainly owing to an increase in soil pH. Several oxygenated functional groups, especially O-H, CO, Mn-O, and Si-O, participated in the adsorption process, and manganese oxides played a significant role in the oxidation of arsenic. This study highlights the potential of MBC as an absorbent to immobilise arsenic for use in contaminated land remediation in the red soils region. PMID:26320008

  19. Dependence of the adsorption of chiral compounds on their enantiomeric composition

    NASA Astrophysics Data System (ADS)

    Gordon, Alexander D.; Karakalos, Stavros; Zaera, Francisco

    2014-11-01

    The adsorption of two different chiral molecules on platinum surfaces has been explored as a function of enantiomeric composition. In the first case, the saturation monolayers obtained by the adsorption of 1-(naphthyl)ethylamine (NEA) from CCl4 solutions were characterized in situ by reflection-absorption infrared spectroscopy (RAIRS). It was found that racemic mixtures yield different IR spectra than those obtained from enantiopure monolayers, a behavior that was interpreted as the result of the formation of racemate pairs via hydrogen bonding at the amine moiety also responsible for bonding to the surface. NEA adsorption under these conditions is reversible and can be modified by subsequent exposures to solutions of different chiral compositions, but that appears to take place only via changes in the relative fractions of enantiopure versus racemic domains on the surface; no other enantiomeric ratios are apparent in the IR data. The second study focused on the uptake of propylene oxide (PO) on Pt(111) under ultrahigh vacuum (UHV) conditions. In that case, racemic monolayers show densities up to ~ 20% lower than those obtained with one single enantiomer. This can be explained by kinetic arguments, since data from isothermal molecular-beam experiments indicated that the PO sticking coefficient depends on the chirality of the incoming PO molecules relative to that of the neighboring adsorbed PO species. Monte Carlo simulations could reproduce the experimental data by assuming adsorbate-assisted adsorption and enantiospecific adsorption geometries for molecules impinging on sites adjacent to previously adsorbed surface species.

  20. Adsorption studies of cadmium ions on alginate-calcium carbonate composite beads

    NASA Astrophysics Data System (ADS)

    Mahmood, Zahid; Amin, Athar; Zafar, Uzma; Raza, Muhammad Amir; Hafeez, Irfan; Akram, Adnan

    2015-07-01

    Alginate-calcium carbonate composite material was prepared in the form of beads and characterized using Fourier transform infra red (FT-IR) spectroscopy and scanning electron microscope (SEM) techniques. The adsorption of Cd2+ ions was studied through batch experiments. The adsorption parameters such as contact time (120 min), adsorbent dose (1.5 g), initial metal ion concentration(10 mg/L), pH (6) and agitation speed (150 rpm) were optimized at room temperature. Langmuir and Freundlich isotherms were applied to the data and it was noted that the adsorption of Cd2+ ions is better explained by Freundlich model. The kinetic studies showed that the adsorption of Cd2+ ions followed pseudo-first order kinetics. Thermodynamic parameters like ∆G 0, ∆H 0 and ∆S 0 were calculated and on the basis of these values it was established that the adsorption process is feasible and endothermic in nature. It was concluded from the study that the composite material of alginate and calcium carbonate can effectively be used to recover Cd2+ ions from wastewater.

  1. 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

  2. Arsenic (V) adsorption on Fe3O4 nanoparticle-coated boron nitride nanotubes.

    PubMed

    Chen, Rongzhi; Zhi, Chunyi; Yang, Huang; Bando, Yoshio; Zhang, Zhenya; Sugiur, Norio; Golberg, Dmitri

    2011-07-01

    Multiwalled boron nitride nanotubes (BNNTs) functionalized with Fe(3)O(4) nanoparticles (NPs) were used for arsenic removal from water solutions. Sonication followed by a heating process was developed to in situ functionalize Fe(3)O(4) NPs onto a tube surface. A batch of adsorption experiments conducted at neutral pH (6.9) and room temperature (25 °C) and using the developed nanocomposites revealed effective arsenic (V) removal. The Langmuir, Freundlich, and Dubinin-Radushkevich adsorption isotherms were measured for a range of As(V) initial concentrations from 1 to 40 mg/L under the same conditions. The equilibrium data well fitted all isotherms, indicating that the mechanism for As(V) adsorption was a combination of chemical complexation and physical electrostatic attraction with a slight preference for chemisorption. The magnetite NPs functionalized on BNNTs led to a simple and rapid separation of magnetic metal-loaded adsorbents from the treated water under an external magnetic field. PMID:21507418

  3. Investigation on the adsorption of phosphorus by Fe-loaded ceramic adsorbent.

    PubMed

    Wang, Di; Chen, Nan; Yu, Yang; Hu, Weiwu; Feng, Chuanping

    2016-02-15

    This aim of this study was to remove phosphorus from aqueous solution using a Fe-loaded ceramic (Fe-LC) adsorbent prepared by mixing dolomite, montmorillonite, FeSO4·7H2O and starch. Simplex-centroid mixture design method was used to determine the optimum mixture proportions by evaluating both phosphorus adsorption efficiency and adsorbent hardness. The study found that the optimum adsorption capacity and the strength can be achieved with the composition of 3.87g dolomite, 3.00g starch, 2.13g montmorillonite and 1.00g FeSO4·7H2O (10g in total). The optimized Fe-LC was evaluated in the batch and the fixed bed experiments. The point of zero charge, pHpzc was found to be 6.0. The adsorption kinetic and isotherm data well agreed with the pseudo-second-order kinetic and the Langmuir isotherm models, respectively. The breakthrough time increased with increasing in the bed depth, whereas inverse relationship was observed with the initial phosphorus concentration in the fixed bed studies. The co-existing anions (SO4(2-), NO3(-) and Cl(-)) had negligible influence on phosphorus removal. The BDST and Thomas model explained the breakthrough behavior for phosphorus removal with a high degree of correlation. PMID:26624533

  4. A GCMC simulation and experimental study of krypton adsorption/desorption hysteresis on a graphite surface.

    PubMed

    Prasetyo, Luisa; Horikawa, Toshihide; Phadungbut, Poomiwat; Johnathan Tan, Shiliang; Do, D D; Nicholson, D

    2016-09-15

    Adsorption isotherms and isosteric heats of krypton on a highly graphitized carbon black, Carbopack F, have been studied with a combination of Monte Carlo simulation and high-resolution experiments at 77K and 87K. Our investigation sheds light on the microscopic origin of the experimentally observed, horizontal hysteresis loop in the first layer, and the vertical hysteresis-loop in the second layer, and is found to be in agreement with our recent Monte Carlo simulation study (Diao et al., 2015). From detailed analysis of the adsorption isotherm, the latter is attributed to the compression of an imperfect solid-like state in the first layer, to form a hexagonally packed, solid-like state, immediately following the first order condensation of the second layer. To ensure that capillary condensation in the confined spaces between microcrystallites of Carbopack F does not interfere with these hysteresis loops, we carried out simulations of krypton adsorption in the confined space of a wedge-shaped pore that mimics the interstices between particles. These simulations show that, up to the third layer, any such interference is negligible. PMID:27343464

  5. Adsorptive desulphurization study of liquid fuels using Tin (Sn) impregnated activated charcoal.

    PubMed

    Shah, Syed Sikandar; Ahmad, Imtiaz; Ahmad, Waqas

    2016-03-01

    Keeping in view the growing concern regarding desulphurization of petroleum products, the present study was under taken to investigate the efficiency of tin impregnated activated charcoal (Sn-AC) as a potential adsorbent for the desulphurization of model and real commercial straight run kerosene and diesel oil samples. The adsorbent Sn-AC was prepared by wet impregnation process in the laboratory and characterized by SEM, EDX and surface area analysis. Initial experiments were carried out using model oil, which was prepared by dissolving dibenzothiophene (DBT) in cyclohexane, the optimum conditions for desulfurization were found to be, 60°C temperature, 1h contact time and adsorbent dosage of 0.8g, under which about 99.4% of DBT removal was attained. Under optimized conditions the desulfurization of real oil i.e., kerosene and diesel oil was also investigated. Kinetic studies revealed that DBT adsorption followed pseudo second order kinetics and the data best fits in the Langmuir adsorption isotherm as compared to Freundlich adsorption isotherm model. The adsorbent could be easily regenerated simply by washing with toluene for a multiple cycles and reused without losing its efficiency. PMID:26551224

  6. Adsorption of Pb(2+) from aqueous solution using spinel ferrite prepared from steel pickling sludge.

    PubMed

    Fang, Binbin; Yan, Yubo; Yang, Yang; Wang, Fenglian; Chu, Zhen; Sun, Xiuyun; Li, Jiansheng; Wang, Lianjun

    2016-01-01

    In this paper, spinel ferrite with high crystallinity and high saturation magnetization was successfully prepared from steel pickling sludge by adding iron source and precipitator in the hydrothermal condition. The obtained spinel ferrite was characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), vibrating sample magnetometer (VSM), and Zeta potential methods and investigated as an adsorbent for removal of Pb(2+) from aqueous solution. Batch experiments were performed by varying the pH values, contact time, temperature and initial metal concentration. The result of pH impact showed that the adsorption of Pb(2+) was a pH dependent process, and the pH 5.8 ± 0.2 was found to be the optimum condition. The achieved experimental data were analyzed with various kinetic and isotherm models. The kinetic studies revealed that Pb(2+) adsorption onto spinel ferrite followed a pseudo-second order model, and the Langmuir isotherm model provided the perfect fit to the equilibrium experimental data. At different temperatures, the maximum Pb(2+) adsorption capacities calculated from the Langmuir equation were in the range of 126.5-175.4 mg/g, which can be in competition with other adsorbents. The thermodynamic results showed that the spinel ferrite could spontaneously and endothermically adsorb Pb(2+) from aqueous solution. The regeneration studies showed that spinel ferrite could be used five times (removal efficiency (%) >90%) by desorption with HNO3 reagent. PMID:26942534

  7. Adsorption-desorption of 2,4,6-trinitrotoluene and hexahydro-1,3,5-trinitro-1,3,5-triazine in soils

    SciTech Connect

    Xue, S.K.; Selim, H.M.; Iskandar, I.K.

    1995-11-01

    This study studied the adsorption-desorption behavior of TNT (2, 4, 6-trinitrotoluene) and RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine) in a bentonite/sand reference material (Swy-1 montmorillonite clay mixed with acid-washed sand) and two selected soils (Norwood and Kolin). Release of TNT,RDX, and other compounds from a contaminated soil obtained from the Louisiana Army Ammunition Plant (AAP) site was also investigated. The kinetics of TNT and RDX retention were measured using batch methods for a range of input concentrations. For RDX, the adsorption isotherms were distinctly linear. The TNT adsorption isotherm for bentonite/sand mixture appeared linear and was described equally well using linear, Freundlich, Langmuir, and a modified Langmuir model. For the Norwood and Kolin soils, TNT adsorption isotherms exhibited distinct nonlinearity and the Freundlich model provided the best fit. As indicated by the K{sub d} values, TNT exhibited stronger retention or affinity to all soils and the bentonite/sand mixture than for RDX. The RDX retention data indicated little time-dependent behavior. The TNT retention data indicated a continued decrease in TNT concentration with time in the Norwood and Kolin soils. This was possibly caused by the formation and subsequent adsorption of transformation products because transformation products, such as amino nitro toluene compounds, were identified during batch experiments. For the bentonite/sand mixture, TNT retention was rapid initially and reached apparent equilibrium within 1 day. Unlike Kolin and Norwood soils, there was no hysteretic behavior of TNT adsorption-desorption by the bentonite/sand mixture and a mass balance suggested fully reversible retention mechanisms. 15 refs., 13 figs., 2 tabs.

  8. Adsorption of nucleotides onto ferromagnesian phyllosilicates: Significance for the origin of life

    NASA Astrophysics Data System (ADS)

    Pedreira-Segade, Ulysse; Feuillie, Cécile; Pelletier, Manuel; Michot, Laurent J.; Daniel, Isabelle

    2016-03-01

    The concentration of prebiotic organic building blocks may have promoted the formation of biopolymers in the environment of the early Earth. We therefore studied the adsorption of RNA monomers AMP, GMP, CMP, and UMP, and DNA monomers dGMP, dCMP, and TMP, on minerals that were abundant in the early Earth environment as the result of aqueous or hydrothermal alteration of the primitive oceanic crust. We focused our study on swelling clays, i.e. nontronite and montmorillonite, and non-swelling phyllosilicates, i.e. pyrophyllite, chlorite, lizardite and chrysotile suspended in an aqueous saline solution analog to seawater. In this reference study, adsorption experiments were carried out under standard conditions of pressure and temperature and controlled pH. Under such conditions, this work is also relevant to the preservation of nucleic acids in Fe-Mg-rich terrestrial and Martian soils. We compared the adsorption of the different monomers on individual minerals, as well as the adsorption of single monomers on the whole suite of minerals. We found that DNA monomers adsorb much more strongly than RNA monomers, and that any monomer containing the G nucleobase adsorbed more strongly than one containing the C nucleobase. At high surface loadings (greater than about 1 mM monomer in aqueous solution) we also found a dramatic increase in the slope of adsorption isotherm on the swelling clays, leading to large increases in the amounts adsorbed. Data were processed in order to understand the adsorption mechanism of nucleotides onto mineral surfaces. We infer that all nucleotides behave as homologous molecules in regard to their adsorption onto the studied mineral surfaces. At low to moderate surface loadings, their adsorption is best explained by a single mechanism common to the suite of minerals of the present study. At pH 7, adsorption certainly proceeds by ligand exchange between the phosphate group and the hydroxyls of the broken edges of phyllosilicates leading to the

  9. [Adsorption of Phosphate by Lanthanum Hydroxide/Natural Zeolite Composites from Low Concentration Phosphate Solution].

    PubMed

    Lin, Jian-wei; Wang, Hong; Zhan, Yan-hui; Chen, Dong-mei

    2016-01-15

    A series of composites of lanthanum hydroxide/natural zeolite ( La( OH) 3/NZ composites) were prepared by co-precipitation method, and these composites were used as adsorbents to remove phosphate from aqueous solution. The phosphate adsorption capacities of different composites prepared with different precipitated pH values were compared in batch mode. The adsorption characteristics of phosphate from aqueous solution on the La(OH)3/NZ composite prepared with the precipitated pH value of 11 was investigated using batch experiments. The results showed that the La(OH)3/NZ composite prepared with the precipitated pH values of 5-7 and 13 had a low adsorption capacity for phosphate in aqueous solution, while the La( OH) 3/NZ composites prepared with the precipitated pH values of 9-12 exhibited much higher phosphate adsorption capacity. The phosphate adsorption capacity of the La (OH)3/NZ composite increased with the increase of the precipitated pH value from 9 to 11, but remained basically unchanged with the increase of the precipitated pH value from 11 to 12. The equilibrium adsorption data of phosphate from aqueous solution on the La ( OH ) 3/NZ composite prepared with the precipitated pH value of 11 could be described by the Langmuir isotherm model with the predicted maximum phosphate adsorption of 44 mg x g(-1) (phosphate solution pH 7 and 30 degrees C). The kinetic data of phosphate adsorption from low concentration phosphate solution on the La(OH)3/NZ composite prepared with the precipitated pH value of 11 well followed a pseudo-second-order model. The presence of Cl- and SO4(2-) in low concentration phosphate solution had no negative effect on phosphate adsorption onto the La(OH)3/NZ composite prepared with the precipitated pH value of 11, while the presence of HCO3- slightly inhibited the adsorption of phosphate. Coexisting humic acid had a negative effect on the adsorption of phosphate at low concentration on the La(OH)3/NZ composite prepared with the

  10. Impact of carbon nanotube morphology on phenanthrene adsorption.

    PubMed

    Apul, Onur Guven; Shao, Ting; Zhang, Shujuan; Karanfil, Tanju

    2012-01-01

    The present study examined the roles of the specific surface area (SSA), diameter, and length of carbon nanotubes (CNT) on the adsorption of phenanthrene (PNT) by analyzing the adsorption isotherms obtained with several single-walled carbon nanotubes (SWNT) and multiwalled carbon nanotubes (MWNT). At low equilibrium concentrations (e.g., 1 ppb), MWNTs with larger outer diameters exhibited higher PNT adsorption capacity on an SSA basis than those with smaller diameters. With increasing equilibrium concentration, adsorption on an SSA basis became independent of MWNT diameter, and the total surface area controlled maximum adsorption capacity. A similar analysis for the adsorption of naphthalene, a planar molecule with one less benzene ring but 20 times higher solubility than PNT, showed no correlation with respect to MWNT outer diameter. The results indicated that the surface curvature of MWNT was more important on the adsorption of PNT than on the adsorption of naphthalene. Specific surface area normalized isotherms did not show a correlation between PNT adsorption and lengths of SWNTs and MWNTs. Characterization results indicated that the morphology of CNTs plays an important role on the SSA and pore volume. Data from the manufacturer may not always represent the characteristics of CNTs in a particular batch. Therefore, accurate characterization of CNTs is critical to systematically examine the behavior of CNTs, such as adsorption and transport, in environmental systems. PMID:22002628

  11. Evaluation of the isosteric heat of adsorption at zero coverage for hydrogen on activated carbons

    NASA Astrophysics Data System (ADS)

    Dohnke, E.; Beckner, M.; Romanos, J.; Olsen, R.; Wexler, C.; Pfeifer, P.

    2011-03-01

    Activated carbons made from corn cob show promise as materials for high-capacity hydrogen storage. As part of our characterization of these materials, we are interested in learning how different production methods affect the adsorption energies. In this talk, we will show how hydrogen adsorption isotherms may be used to calculate these adsorption energies at zero coverage using Henry's law. We will additionally discuss differences between the binding energy and the isosteric heat of adsorption by applying this analysis at different temperatures.

  12. Potential failure of life detection experiments on Mars resulting from adsorption of organic compounds on to common instrument materials

    NASA Astrophysics Data System (ADS)

    Court, Richard W.; Sims, Mark R.; Cullen, David C.; Sephton, Mark A.

    2012-12-01

    Some life detection instruments under development for operation on Mars use solvents to extract organic compounds from samples of Martian regolith and rock and to transfer the extracts to dedicated detectors. However, it is possible that organic compounds extracted from Martian samples and dissolved in the solvent could adsorb to instrument surfaces, potentially resulting in a failure to detect organic matter that could have been avoided by using more appropriate instrument materials. If successful detection and characterisation is to take place it is therefore essential to understand the interactions between dissolved organic targets and the surfaces of space instrument components. One such life detection instrument is the Life Marker Chip (LMC) being developed for the ExoMars mission, which relies on a novel surfactant-based solvent system and antibody-based detectors. We have tested the ability of a range of materials, including titanium, stainless steel, aluminium, the fluoropolymer Viton™, polytetrafluoroethylene (PTFE), nylon, polypropylene, polyethersulfone and cellulose acetate to adsorb a range of organic standards from the surfactant solution intended to be used by the LMC. Results indicate that aromatic hydrocarbons, specifically anthracene, are more prone to adsorption than straight chain, branched and cyclic aliphatic species. Titanium, aluminium and stainless steel show little adsorption ability and are suitable for larger-area applications. PTFE and Viton™ are suitable for use in small-area applications such as seals and filters. Nylon, polypropylene, polyethersulfone and cellulose acetate show stronger adsorption characteristics and should be avoided in the forms employed here. The ability of some materials to selectively adsorb organic compounds from solvent extracts can lower the sensitivity of life detection instruments. In future, it would be prudent to test all space instrument materials for their ability to adsorb target organic compounds

  13. Adsorption of radon and water vapor on commercial activated carbons

    SciTech Connect

    Hassan, N.M.; Ghosh, T.K.; Hines, A.L.; Loyalka, S.K.

    1995-02-01

    Equilibrium adsorption isotherms are reported for radon and water vapor on two commercial activated carbons: coconut shell Type PCB and hardwood Type BD. The isotherms of the water vapor were measured gravimetrically at 298 K. The isotherms of radon from dry nitrogen were obtained at 293, 298, and 308 K while the data for the mixture of radon and water vapor were measured at 298 K. The concentrations of radon in the gas and solid phases were measured simultaneously, once the adsorption equilibrium and the radioactive equilibrium between the radon and its daughter products were established. The shape of the isotherms was of Type III for the radon and Type V for the water vapor, according to Brunauer`s classification. The adsorption mechanism was similar for both the radon and the water vapor, being physical adsorption on the macropore surface area in the low pressure region and micropore filling near saturation pressure. The uptake capacity of radon decreased both with increasing temperature and relative humidity. The heat of adsorption data indicated that the PCB- and the BD-activated carbons provided a heterogeneous surface for radon adsorption. The equilibrium data for radon were correlated with a modified Freundlich equation.

  14. [Adsorption Behaviors of Lead on Multi-Walled Carbon Nanotube-Hydroxyapatite Composites].

    PubMed

    Zhang, Jin-li; Li, Yu

    2015-07-01

    Multi-walled carbon nanotube-hydroxyapatite composites (MWCNT-HAP) were employed as the sorbent to study the sorption characteristic of Pb (II) using batch experiments. Effects of dosage of adsorbent, pH, ionic strength, contact time, initial concentration of lead and temperature were investigated. The results indicated that the removal of lead to MWCNT-HAP composites was strongly dependent on dosage of adsorbent, pH, temperature, and independent of ionic strength. The maximum adsorption capacity of lead was about 716. 13 mg.g-1 at 20°C, with a solid/liquid ratio of 0.08 g.L-1, pH0 = 5.5 and an initial concentration of 100 mg.L-1. The adsorption of Pb(II) on MWCNT-HAP composites was a fast process and could reach the equilibrium within 60 minutes. Ninety percent of the maximum adsorption capacity could be reached in 30 minutes. The kinetic data were fitted to pseudo-second-order kinetic model reasonably well. The kinetic sorption of Pb(II) on MWCNT-HAP was well described by pseudo-second-order kinetic model. The negative free energy calculated from the temperature dependent sorption isotherms suggested that the sorption of Pb(II) on MWCNT-HAP composites was a spontaneous process, and high temperature favored the adsorption process. The higher correlation coefficient values (R2 = 0. 999 8 - 1. 000 0) of Langmuir isotherm model at different temperatures suggested that Langmuir model could be used to simulate the sorption of Pb(II) on MWCNT-HAP. The adsorption mechanism mainly involves surface complexation between the lead ions and the surface oxygen-containing functional groups of the MWCNT-HAP, dissolution of HAP and precipitation of pyromorphite [Pb10 (PO4)6 (OH) 2], ion exchange reaction between Pb2+ and Ca2+ of hydroxyapatite. PMID:26489325

  15. Synthesis of Fe3O4/Polyacrylonitrile Composite Electrospun Nanofiber Mat for Effective Adsorption of Tetracycline.

    PubMed

    Liu, Qing; Zhong, Lu-Bin; Zhao, Quan-Bao; Frear, Craig; Zheng, Yu-Ming

    2015-07-15

    Novel Fe3O4/polyacrylonitrile (PAN) composite nanofibers (NFs) were prepared by a simple two-step process, an electrospinning and solvothermal method. Characterization by field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) demonstrated formation of a uniform nanoparticles coating (about 20 nm in thickness) on the PAN nanofiber backbone. The coating was constructed by well-crystallized cubic phase Fe3O4 nanoparticles as examined by X-ray diffraction spectroscopy (XRD). The coating doubled the specific surface area of NFs, from 8.4 to 17.8 m2 g(-1), as confirmed by nitrogen sorption isotherm analysis. To evaluate the feasibility of Fe3O4/PAN composite NFs as a potential adsorbent for antibiotic removal, batch adsorption experiments were conducted using tetracycline (TC) as the model antibiotic molecule. The results showed that Fe3O4/PAN composite NFs were effective in removing TC with no impactful loss of Fe in the pH regime of environmental interest (5-8). The adsorption of TC onto Fe3O4/PAN composite NFs better fitted the pseudo-second-order kinetics model, and the maximum adsorption capacity calculated from Langmuir isotherm model was 257.07 mg g(-1) at pH 6. The composite NFs also exhibited good regenerability over repeated adsorption/desorption cycles. Surface complexation between TC and the composite NFs contributed most to the adsorption as elucidated by X-ray photoelectron spectroscopy (XPS). This highly effective and novel adsorbent can be easily modularized and separated, promising its huge potential in drinking and wastewater treatment for antibiotic removal. PMID:26079116

  16. Biocomposite fiber of calcium alginate/multi-walled carbon nanotubes with enhanced adsorption properties for ionic dyes.

    PubMed

    Sui, Kunyan; Li, Yujin; Liu, Rongzhan; Zhang, Yang; Zhao, Xin; Liang, Hongchao; Xia, Yanzhi

    2012-09-01

    A bioadsorbent of calcium alginate/multi-walled carbon nanotubes (CA/MWCNTs) composite fiber was fabricated by wet spinning and was characterized. Adsorptions of methylene blue (MB) and methyl orange (MO) ionic dyes onto CA/MWCNT composite fibers were investigated with different MWCNTs content and pH values. The results showed that introduction of MWCNTs of CA/MWCNTs composite fiber could not only sharply increase the adsorption capacity of MO onto bioadsorbent by 3 times, but enhanced the adsorption rate for MB compared to that of native CA fiber. Adsorption kinetics was determined by fitting pseudo-first, second-order and the intra-particle diffusion models to the experimental data, with the second-order model providing the best description of MB and MO adsorption onto CA/MWCNT fibers. The equilibrium adsorption data were analyzed by two widely applied isotherms: Langmuir and Freundlich. The desorption experiments showed the percentage of desorption were found to be 79.7% and 80.2% for MB and MO, respectively. PMID:24751058

  17. Adsorption of toxic carbamate pesticide oxamyl from liquid phase by newly synthesized and characterized graphene quantum dots nanomaterials.

    PubMed

    Agarwal, Shilpi; Sadeghi, Nima; Tyagi, Inderjeet; Gupta, Vinod Kumar; Fakhri, Ali

    2016-09-15

    Graphene quantum dots have been synthesized using the microwave-assisted hydrothermal route. The surface textural and morphological structure of synthesized adsorbent i.e. graphene quantum dots was analyzed using various analytical techniques such as X-ray diffraction, Transmission electron Microscopy, Atomic Force Microscopy and N2 adsorption-desorption instrumental techniques. The application of graphene quantum dots as an adsorbent for the removal of noxious pesticide compound i.e. oxamyl from aqueous solutions was well investigated and elucidated. The impact of several effective parameters such as effect of agitation speed, pH, adsorbent dose, contact time, temperature and initial concentration on sorption efficiency was studied and optimized using batch adsorption experiments. The optimized pH for maximum oxamyl adsorption was found to be 8.0 and for the maximum adsorption rates the adsorbent dose of 0.6g was found to be optimum to carry out the adsorption with in less than 25min of contact time. From the results obtained, it is clear that for all contact times, an increase in oxamyl concentration resulted in increase in the percent oxamyl removal. The adsorption equilibrium and kinetic data were well fitted and found to be in good agreement with the Langmuir isotherm and pseudo-second-order kinetic model. PMID:27362399

  18. Arsenite adsorption on cryogels embedded with iron-aluminium double hydrous oxides: possible polishing step for smelting wastewater?

    PubMed

    Kumar, Prashanth Suresh; Onnby, Linda; Kirsebom, Harald

    2013-04-15

    Arsenic is among the most toxic elements and it commonly exists in water as arsenite (As(III)) and arsenate (As(V)) ions. As(III) removal often requires a pre-oxidation or pH adjustment step and it is a challenge to adsorb As(III) at circumneutral pH. In this study, iron-aluminium double hydrous oxides were synthesized and incorporated into cryogels. The resulting composite cryogels were evaluated for As(III) adsorption. Initial experiments indicated that the adsorbent showed similar adsorption kinetics for both As(V) and As(III) ions. The adsorption of As(III) best fit the Langmuir isotherm and the maximum adsorption capacity was 24.6 mg/g. Kinetic modeling indicated that the mechanism of adsorption was chemisorption, making the adsorbent-adsorbate interactions independent of charge and hence allowing the adsorbent to function equally efficient across pH 4-11. A Swedish smelting wastewater was used to evaluate the adsorption performance in continuous mode. The studies showed that the adsorbent was successful in reducing the arsenic concentrations below the European Union emission limit (0.15 mg/l) in a smelting wastewater collected after two precipitation processes. The arsenic removal was obtained without requiring a pH adjustment or a pre-oxidation step, making it a potential choice as an adsorbent for As(III) removal from industrial wastewaters. PMID:23500428

  19. [Study of adsorption and desorption of behaviors of Pb2+ on thiol-modified bentonite by flame atomic absorption spectrometry].

    PubMed

    Chen, Wen; Xiong, Qiong-Xian; Pang, Xiao-Feng; Zhu, Xia-Ping; Han, Mei; Zhao, Qiu-Xiang; Liu, Wen-Hua

    2013-03-01

    A comparative analysis of the functional groups and surface structure of the Ca-bentonite (RB) and thiol-modified bentonite (TMB) were characterized by means of FTIR and SEM. The absorptive property of Pb2+ on TMB and RB and its influential factors was studied and the conditions for the adsorption were optimized by using FAAS method. Then the conditions for desorption of Pb2+ from the TMB by using simulated acid rain were studied and the contrast analysis of absorptive stability of Pb2+ on TMB and RB was given. The results showed that the adsorption rate of Pb2+ by TMB could reach more than 98%, when the initial Pb2+ concentration was 100 mg.L-1, the liquid-solid ratio was 5 g.L-1, pH was 6. 0, KNO3 ionic strength was 0. 1 mol.L-1 and adsorption period was 60min at 25 C. The saturated adsorption capacity of TMB was 67.27 mg.g-1; it's much more than that of RB (9.667 mg.g-1). The adsorption of Pb2+ on TMB follows Langmuir and Freundlich isotherm models well. Desorption experiments of Pb2+ from TMB with simulated acid rain (pH 3. 50) were done, and the desorption rate was 0. The results showed that TMB has a strong adsorption and fixation capacity for PbZ+; it is adapted to lead contaminated soil for chemical remediation. PMID:23705461

  20. Preparation and Characterization of Chitosan/Feldspar Biohybrid as an Adsorbent: Optimization of Adsorption Process via Response Surface Modeling

    PubMed Central

    Yazdani, Maryam; Bahrami, Hajir; Arami, Mokhtar

    2014-01-01

    Chitosan/feldspar biobased beads were synthesized, characterized, and tested for the removal of Acid Black 1 dye from aquatic phases. A four-factor central composite design (CCD) accompanied by response surface modeling (RSM) and optimization was used to optimize the dye adsorption by the adsorbent (chitosan/feldspar composite) in 31 different batch experiments. Independent variables of temperature, pH, initial dye concentration, and adsorbent dose were used to change to coded values. To anticipate the responses, a quadratic model was applied. Analysis of variance (ANOVA) tested the significance of the process factors and their interactions. The adequacy of the model was investigated by the correlation between experimental and predicted data of the adsorption and the calculation of prediction errors. The results showed that the predicted maximum adsorption amount of 21.63 mg/g under the optimum conditions (pH 3, temperature 15°C, initial dye concentration 125 mg/L, and dose 0.2 g/50 mL) was close to the experimental value of 19.85 mg/g. In addition, the results of adsorption behaviors of the dye illustrated that the adsorption process followed the Langmuir isotherm model and the pseudo-second-order kinetic model. Langmuir sorption capacity was found to be 17.86 mg/g. Besides, thermodynamic parameters were evaluated and revealed that the adsorption process was exothermic and favourable. PMID:24587722

  1. 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

  2. Adsorption of Cu2+ ions using chitosan-modified magnetic Mn ferrite nanoparticles synthesized by microwave-assisted hydrothermal method

    NASA Astrophysics Data System (ADS)

    Meng, Yuying; Chen, Deyang; Sun, Yitao; Jiao, Dongling; Zeng, Dechang; Liu, Zhongwu

    2015-01-01

    Chitosan-modified Mn ferrite nanoparticles were synthesized by a one-step microwave-assisted hydrothermal method. These Mn ferrite magnetic composite nanoparticles were employed to absorb Cu2+ ions in water. XRD verified the spinel structure of the MnFe2O4 nanoparticles. Chitosan modification does not result in any phase change of MnFe2O4. FTIR and zeta potentials curves for all samples suggest that chitosan can be successfully coated on the Mn ferrites. TEM characterization showed that the modified MnFe2O4 nanoparticles have a cubic shape with a mean diameter of ∼100 nm. For adsorption behavior, the effects of experiment parameters such as solution pH value, contact time and initial Cu2+ ions concentration on the adsorption efficiency were systematically investigated. The results showed that increasing solution pH value and extending contact time are favorable for improving adsorption efficiency. Especially, adsorption efficiency can reach up to 100% and 96.7% after 500 min adsorption at pH 6.5 for the solutions with initial Cu2+ ions concentration of 50 mg/L and 100 mg/L. Adsorption data fits well with the Langmuir isotherm models with a maximum adsorption capacity (qm) and a Langmuir adsorption equilibrium constant (K) of 65.1 mg/g and 0.090 L/mg, respectively. The adsorption kinetic agrees well with pseudo second order model with the pseudo second rate constants (K2) of 0.0468 and 0.00189 g/mg/min for solutions with initial Cu2+ ions of 50 and 100 mg/L, respectively.

  3. Studies on Thorium Adsorption Characteristics upon Activated Titanium Hydroxide Prepared from Rosetta Ilmenite Concentrate

    SciTech Connect

    Gado, M Zaki, S

    2016-01-01

    The titanium hydroxide prepared from Rosetta ilmenite concentrate has been applied for Th (IV) adsorption from its acid aqueous solutions. The prepared hydroxide is first characterized by both Fourier transform infrared (FT-IR) spectrum and thermogravimetric analysis. The relevant factors affecting the adsorption process have been studied. The obtained equilibrium data fits well with the Langmuir isotherm rather than Freundlich isotherm, while the adsorption kinetic data follow the pseudo-second order model. The different thermodynamic parameters have also been calculated and indicate that the adsorption process is spontaneous.

  4. Competitive adsorption and transport of phthalate esters in the clay layer of JiangHan plain, China.

    PubMed

    Liu, Hui; Zhang, Dan; Li, Minjing; Tong, Lei; Feng, Liang

    2013-09-01

    This study aimed to investigate the adsorption behavior of phthalate esters (PAEs) in the clay layer of JiangHan Plain, China, so as to make better understanding about the source and control of PAEs in groundwater. Adsorption kinetics, isotherms, and miscible displacement experiments were conducted, and different models were used to simulate the experiment data. Results showed that the adsorption kinetics followed pseudo-second-order model. The kinetic parameters showed quantitative relationships with straight and branched chain carbon numbers of PAEs. These relationships were simulated and carefully discussed. The adsorption isotherms followed linear model better. And partition coefficient (Kd) increased with the carbon chain length of PAEs. Miscible displacement experiments showed that DEHP could not flow out of the column in 100d. HYDRUS-1D and two-site sorption model (linear, first order nonequilibrium adsorption) were used for the simulation of the breakthrough and transport curves of DMP, DEP, DBP, and DiBP. Results showed that the dispersion coefficients (D) and partition coefficient (Kd(')) increased with the carbon chain length. About 10% DBP and DiBP and 1% DMP and DEP were absorbed on the type-1 sites. DMP and DEP were much easier to transfer into the type-2 sites than DBP and DiBP. DBP and DiBP might aggregate in micro-pores of the sorbent. Retardation coefficient and Damkohler number were also calculated and discussed. It was proved that clay layer is an important retarder for PAEs downward transport. However, it can be passed through if the time is sufficient. PMID:23706400

  5. 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.

  6. 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 ...

  7. 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.

  8. 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...

  9. Adsorption characteristics of rocks from vapor-dominated geothermal reservoir at the Geysers, CA

    SciTech Connect

    Satik, Cengiz; Walters, Mark; Horne, Roland N.

    1996-01-24

    This paper reports on a continuing experimental effort to characterize the adsorption behavior of rocks from The Geysers steam field in California. We show adsorption results obtained for 36 rock samples. All of the adsorption isotherms plotted on the same graph exhibit an envelope of isotherms. The minimum and the maximum values of the slope (or rate of adsorption) and of the magnitude within this envelope of isotherms belonged to the UOC-1 (felsite) and NCPA B-5 (serpentine) samples. The values of surface area and porosity, and pore size distribution for 19 of the samples indicated a very weak correlation with adsorption. An interpretation of the pore size distributions and the liquid saturation isotherms suggests that the change in the slope and the magnitude of the adsorption isotherms within the envelope is controlled primarily by the physical adsorption mechanism instead of capillary condensation. Grain-size and framework grain to matrix ratio are found to be insufficient to characterize this adsorption behavior. An accurate identification of the mineralogy of the samples will be essential to complete this analysis.

  10. Adsorption of organic solvent vapors on hydrophobic Y-type zeolite

    SciTech Connect

    Yun, J.H.; Choi, D.K.; Kim, S.H.

    1998-06-01

    Experimental isotherms and prediction results for adsorption of benzene, toluene, dichloromethane and 1,1-dichloro-1-fluoroethane on hydrophobic Y-type zeolite are reported. Isotherm shows the type-V shape according to the classification by Brunauer et al. A simple thermodynamic method is employed to predict the experimental equilibrium data at various temperatures simultaneously. This plain method is based on the assumption that the value of the isosteric heat of adsorption does not depend on temperature for a certain surface loading. The Clausius-Clapeyron equation was used to calculate the isosteric heat of adsorption. To apply the method, only two sets of the experimental isotherm data at two different temperatures are needed. The Clausius-Clapeyron equation with two isotherms provided simple and reliable prediction of adsorption equilibrium relationships at various temperatures. Results with this method showed that the predicted value agrees well with the experimental data in the range of temperatures for the system tested.

  11. Protein Adsorption and Deposition onto Microfiltration Membranes: The Role of Solute-Solid Interactions.

    PubMed

    Martínez; Martín; Prádanos; Calvo; Palacio; Hernández

    2000-01-15

    The mass of gamma-globulin fouling an Anodisc alumina membrane with a nominal pore diameter of 0.1 µm has been measured at several concentrations and pHs. This fouling resulted from filtering through the membrane in a continuous recirculation device. The low-concentration fouling can be attributed mainly to adsorption. The complete concentration dependence of fouling mass has been obtained and fitted to a Freundlich heterogeneous isotherm, from which the pH dependence of active fouling sites and energies has been also obtained. Adsorption is studied as a function of the electrostatic forces between the solute and the membrane. A sharp maximum in the adsorbed mass for zero electrostatic force is observed. At high concentrations, accumulation plays a relevant role at alkaline pH, as confirmed by flux decay experiments, retention measurements, and AFM (atomic force microscopy) pictures. Copyright 2000 Academic Press. PMID:10631028

  12. Experimental and simulated propene isotherms on porous solids

    NASA Astrophysics Data System (ADS)

    Navarro, M. V.; Puértolas, B.; García, T.; Murillo, R.; Mastral, A. M.; Varela-Gandía, F. J.; Lozano-Castelló, D.; Cazorla-Amorós, D.; Bueno-López, A.

    2010-06-01

    The lack of treatment capacity of hydrocarbons by three-way catalysts during the "cold start" period creates an important environmental problem. During this period, the temperature of the three-way catalyst is too low for effective operation and cannot convert the hydrocarbons in the exhaust. 50-80% of the total hydrocarbon emissions are produced in this phase that accomplishes the first 60-120 s of the engine operation. In this study, the technology chosen to treat these emissions is the use of HC-traps, and molecular simulations are tested as a tool to reproduce the experimental adsorption behaviour of porous solids. Therefore, experimental and simulated adsorption isotherms of propene (model hydrocarbon) have been obtained for four different crystalline materials with distinctive framework structures (3D and 1D) and a variety of Si/Al ratios and cations (three zeolites: ZSM-5, BETA and Mordenite; and a silicoaluminophosphate molecular sieve: SAPO-5).

  13. Nanoporous chalcogenides for adsorption and gas separation.

    PubMed

    Ori, Guido; Massobrio, Carlo; Pradel, Annie; Ribes, Michel; Coasne, Benoit

    2016-05-21

    The adsorption and gas separation properties of amorphous porous chalcogenides such as GeS2 are investigated using statistical mechanics molecular simulation. Using a realistic molecular model of such amorphous adsorbents, we show that they can be used efficiently to separate different gases relevant to environmental and energy applications (H2, CO2, CH4, N2). In addition to shedding light on the microscopic adsorption mechanisms, we show that coadsorption in this novel class of porous materials can be described using the ideal adsorbed solution theory (IAST). Such a simple thermodynamic model, which allows avoiding complex coadsorption measurements, describes the adsorption of mixture from pure component adsorption isotherms. Our results, which are found to be in good agreement with available experimental data, paves the way for the design of gas separation membranes using the large family of porous chalcogenides. PMID:27126718

  14. Thermodynamic investigation of trichloroethylene adsorption in water-saturated microporous adsorbents

    SciTech Connect

    Farrell, J.; Hauck, B.; Jones, M.

    1999-08-01

    Adsorption of trichloroethylene (TCE) in adsorbents containing hydrophilic and hydrophobic micropores was investigated in order to determine the mechanisms responsible for TCE adsorption on mineral solids. A high-pressure liquid chromatography method was used to measure TCE adsorption isotherms on three microporous adsorbents. Silica gel and zeolite type NaX were used as hydrophilic model adsorbents, and hexamethyldisilazane (HMDS)-treated silica gel was used as a model hydrophobic adsorbent. Batch uptake and desorption isotherms were also measured on the hydrophilic silica gel. Uptake of TCE by all three adsorbents was linear over the concentration range investigated. However, the silica gel desorption isotherm was highly nonlinear, as indicated by its Freundlich isotherm exponent of 0.58. Capillary phase separation into hydrophobic micropores was postulated as being responsible for the isotherm hysteresis. Supporting this hypothesis was the conformance of the TCE adsorption isotherm to Dubinin-Radushkevitch volume filling of micropores theory. The enthalpies for TCE adsorption on all three solids were determined by van't Hoff analysis of distribution coefficients measured over a temperature range from 5 to 90 C. The TCE adsorption enthalpies on the silica gel and HMDS silica gel were exothermic, but on the zeolite adsorption was endothermic. High exothermic adsorption enthalpies on the silica gel adsorbents indicated that TCE adsorption was occurring in hydrophobic micropores, and that adsorption on surfaces with large radii of curvature contributed only minimally to the total uptake. This indicates that the predominant mechanism for TCE adsorption on these mineral solids is not partitioning into the vicinal water layer.

  15. Adsorptive removal of 2-chlorophenol by low-cost coir pith carbon.

    PubMed

    Namasivayam, C; Kavitha, D

    2003-03-17

    Adsorption of 2-chlorophenol (2-CP) by coir pith carbon was carried out by varying the parameters such as agitation time, 2-CP concentration, adsorbent dose, pH and temperature. Adsorption equilibrium reached at 40, 60, 80 and 100 min for 2-CP concentration of 10, 20, 30 and 40 mg/l, respectively. Adsorption followed second-order kinetics. The adsorption equilibrium data obeyed Freundlich isotherm. Acidic pH was favorable for the adsorption of 2-CP. Desorption studies showed that chemisorption plays a major role in the adsorption process. PMID:12628792

  16. Characteristics of phosphate adsorption onto granulated coal ash in seawater.

    PubMed

    Asaoka, Satoshi; Yamamoto, Tamiji

    2010-08-01

    The deterioration of sediments is a serious environmental problem. Controlling nutrient release fluxes from sediments is important to alleviating eutrophication and to reducing terrigenous nutrient loads. The purpose of this study was to evaluate the phosphate removal performance of granulated coal ash (GCA) from seawater, which is produced from coal thermal electric power generation. Batch experiments were carried out to investigate the removal kinetics of phosphate from seawater under both oxic and anoxic conditions. Phosphate was removed well from seawater under both oxic and anoxic conditions. The adsorption isotherm for phosphate revealed that GCA could remove phosphate effectively from seawater above a concentration of 1.7micromolL(-1). GCA can reduce the concentration of phosphate in seawater effectively under anoxic conditions where iron type adsorbents cannot be applied. Therefore, GCA could potentially be used to adsorb phosphate in the organically-enriched sediment, which generally occurs under highly reductive conditions. PMID:20403625

  17. Adsorptive removal of methylene blue by rhamnolipid-functionalized graphene oxide from wastewater.

    PubMed

    Wu, Zhibin; Zhong, Hua; Yuan, Xingzhong; Wang, Hou; Wang, Lele; Chen, Xiaohong; Zeng, Guangming; Wu, Yan

    2014-12-15

    In this article, a rhamnolipid-functionalized graphene oxide (RL-GO) hybrid was prepared by one-step ultrasonication and adsorptive removal of methylene blue (MB) from both artificial and real wastewater by the RL-GO was investigated. The Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), Fourier transform infrared spectrum (FT-IR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller (BET) area and Zeta potential analysis were used to characterize the adsorbent. The results showed that RL-GO had abundant functional groups and a mesopores feature. MB adsorption by the RL-GO increased with increase in adsorbent dose, pH, temperature and initial MB concentration, while it was insensitive to ionic strength variation. The adsorption kinetics fitted well to the pseudo-second-order model with correlation coefficients greater than 0.999. The Intra-particle diffusion and Boyd's film-diffusion models showed that the rate-controlled step was dominated by film-diffusion in the beginning and then followed by intra-particle diffusion. The adsorption isotherm was fitted by adsorption models with the suitability in order of BET > Freundlich > Langmuir > Temkin, based on comparison between correlation coefficients. Thermodynamic analysis of equilibriums suggested that the adsorption MB on RL-GO was spontaneous and endothermic. The adsorption mechanism was also proposed to be electrostatic attraction, π-π interaction and hydrogen bond. In addition, the real wastewater experiment, the regeneration study and the comparative cost analysis showed that the RL-GO composites could be a cost-effective and promising sorbent for MB wastewater treatment owing to its high efficiency and excellent reusability. PMID:25314573

  18. Adsorption studies of chromium (VI) removal from water by lanthanum diethanolamine hybrid material.

    PubMed

    Mandal, Sandip; Sahu, Manoj Kumar; Giri, Anil Kumar; Patel, Raj Kishore

    2014-01-01

    In the present research work, lanthanum diethanolamine hybrid material is synthesized by co-precipitation method and used for the removal of Cr(VI) from synthetic dichromate solution and hand pump water sample. The sorption experiments were carried out in batch mode to optimize various influencing parameters such as adsorbent dose, contact time, pH, competitive anions and temperature. The characterization of the material and mechanism of Cr(VI) adsorption on the material was studied by using scanning electron microscope, Fourier transform infrared, X-ray diffraction, Brunauer-Emmett-Teller and thermogravimetric analysis-differential thermal analysis. Adsorption kinetics studies reveal that the adsorption process followed first-order kinetics and intraparticle diffusion model with correlation coefficients (R2) of 0.96 and 0.97, respectively. The adsorption data were best fitted to linearly transformed Langmuir isotherm with correlation coefficient (R2) of 0.997. The maximum removal of Cr(VI) is found to be 99.31% at optimal condition: pH = 5.6 of the solution, adsorbent dose of 8 g L(-1) with initial concentration of 10mgL(-1) of Cr(VI) solution and an equilibrium time of 50 min. The maximum adsorption capacity of the material is 357.1 mg g(-1). Thermodynamic parameters were evaluated to study the effect of temperature on the removal process. The study shows that the adsorption process is feasible and endothermic in nature. The value of E (260.6 kJ mol(-1)) indicates the chemisorption nature of the adsorption process. The material is difficult to be regenerated. The above studies indicate that the hybrid material is capable of removing Cr(VI) from water. PMID:24645464

  19. Peat and coconut fiber as biofilters for chromium adsorption from contaminated wastewaters.

    PubMed

    Henryk, Kołoczek; Jarosław, Chwastowski; Witold, Żukowski

    2016-01-01

    Batch adsorption experiments were performed for the removal of chromium (III) and chromium (VI) ions from aqueous solutions using Canadian peat and coconut fiber. The Langmuir model was used to describe the adsorption isotherm. The maximum adsorption for peat reached 18.75 mg/g for Cr(III) and 8.02 mg/g for Cr(VI), whereas the value for fiber was slightly higher and reached 19.21 mg/g for Cr(III) and 9.54 mg/g for Cr(VI). Both chromium forms could be easily eluted from the materials. The adsorption of chromium forms to organic matter could be explained in terms of formation of donor-acceptor chemical covalent bound with hydroxyl groups as ligands and chromium as the central atom in the formed complex. The chromate-reducing activities were monitored with the use of electron paramagnetic resonance spectroscopy. The results showed that both adsorption and reduction occurred simultaneously and the maximum adsorption capacity of hexavalent chromium being equal to 95% for fiber and 92% for peat was obtained at pH 1.5. The reduction of Cr(VI) in wastewaters began immediately and disappeared after 20 h. Both materials contained yeast and fungi species which can be responsible for reduction of chromium compounds, due to their enzymatic activity (Chwastowski and Koloczek (Acta Biochim Pol 60: 829-834, 2013)). The reduction of Cr(VI) is a two-phase process, the first phase being rapid and based on chemical reaction and the second phase having biological features. After the recovery step, both types of organic materials can be used again for chromium adsorption without any loss in the metal uptake. Both of the materials could be used as biofilters in the wastewater treatment plants. PMID:26315594

  20. Kinetics and equilibrium adsorption study of p-nitrophenol onto activated carbon derived from walnut peel.

    PubMed

    Liu, Xiaohong; Wang, Fang; Bai, Song

    2015-01-01

    An original activated carbon prepared from walnut peel, which was activated by zinc chloride, was modified with ammonium hydroxide or sodium hydroxide in order to contrast the adsorption property of the three different activated carbons. The experiment used a static adsorption test for p-nitrophenol. The effects of parameters such as initial concentration, contact time and pH value on amount adsorbed and removal are discussed in depth. The thermodynamic data of adsorption were analyzed by Freundlich and Langmuir models. The kinetic data of adsorption were measured by the pseudo-first-order kinetics and the pseudo-second-order kinetics models. The results indicated that the alkalized carbon samples derived from walnut peel had a better performance than the original activated carbon treated with zinc chloride. It was found that adsorption equilibrium time was 6 h. The maximum removal rate of activated carbon treated with zinc chloride for p-nitrophenol was 87.3% at pH 3,whereas the maximum removal rate of the two modified activated carbon materials was found to be 90.8% (alkalized with ammonium hydroxide) and 92.0% (alkalized with sodium hydroxide) at the same pH. The adsorption data of the zinc chloride activated carbon were fitted to the Langmuir isotherm model. The two alkalized activated carbon samples were fitted well to the Freundlich model. The pseudo-second-order dynamics equation provided better explanation of the adsorption dynamics data of the three activated carbons than the pseudo-first-order dynamics equation. PMID:26676011

  1. Studies of liquid adsorption, condensation and surface conductivity in porous media

    NASA Astrophysics Data System (ADS)

    Qi, Hao

    In the petroleum industry, accurate estimates of hydrocarbon reserve and its producibility are without a doubt among the most important issues. Quantitative estimates require the knowledge of three basic parameters of the rock formation: the porosity φ, the water saturation S w and the permeability k. Electrical conductivity is one of the most commonly made measurements used to deduce these quantities. Some empirical relationships used to make such estimates are quite well established and understood, however, many still lack a sound scientific foundation. Systematic laboratory investigation and theoretical understanding of the underlying petrophysics are much needed. This dissertation consists of three projects aimed at understanding both the surface conductivity observed in shaly sandstone, and the related phenomena of molecular adsorption on heterogeneous surfaces. In the first project, we carried out nitrogen adsorption experiments on three shale samples whose fractal dimensions had been previously characterized by small angle scattering (SANS). We found that analyzing the adsorption isotherm data according to the available theoretical predictions always resulted in D values that are lower than those obtained by SANS. The second project, a numerical simulation of adsorption on fractal surfaces, was designed to understand the origin of discrepancies revealed in the first project. We found that the interplay between van der Waals adsorption and capillary condensation always leads to a crossover between the two theoretical limits. The simulated isotherms exhibit the same general features we observed in our experimental data. The third project was aimed at understanding the surface conduction in porous media. We isolated the surface conductivity by growing water layers on the surface with water adsorption isotherm technique. Some of our results indicate that AC impedance measurement could let us determine the surface conductivity and separate it from that of the

  2. Evaluation of Fuller's earth for the adsorption of mercury from aqueous solutions: a comparative study with activated carbon.

    PubMed

    Oubagaranadin, John U Kennedy; Sathyamurthy, N; Murthy, Z V P

    2007-04-01

    Fuller's earth (FE) has been used as an adsorbent in this work to remove mercury from aqueous solutions. For the purpose of comparison, simultaneous experiments using activated carbon (AC) have also been done. The aim of the work is to test how best FE can be used as an adsorbent for mercury. Equilibrium isotherms, such as Freundlich, Langmuir, Dubinin-Redushkevich, Temkin, Harkins-Jura, Halsey and Henderson have been tested. Kinetic studies based on Lagergren first-order, pseudo-second-order rate expressions and intra-particle diffusion studies have been done. The batch experiments were conducted at room temperature (30 degrees C) and at the normal pH (6.7+/-0.2) of the solution. It has been observed that Hg(II) removal rate is better for FE than AC, due to large dosage requirement, whereas the adsorption capacity of AC is found to be much better than FE. Hence, although FE can be used as an adsorbent, a high dosage is required, when compared to AC. Hybrid fractional error function analysis shows that the best-fit for the adsorption equilibrium data is represented by Freundlich isotherm. Kinetic and film diffusion studies show that the adsorption of mercury on FE and AC is both intra-particle diffusion and film diffusion controlled. PMID:16987602

  3. Assessing the Adsorption Properties of Shales

    NASA Astrophysics Data System (ADS)

    Pini, R.

    2014-12-01

    Fine-grained rocks, such as shales, contain a significant amount of nanopores that can significantly contribute to their storage capacity through the mechanism of adsorption. The current ability to extract natural gas that is adsorbed in the rock's matrix is limited and current technology focuses primarily on the free gas in the fractures, thus leading to very low recovery efficiencies. Shales constitute also a great portion of so-called caprocks above potential CO2 sequestration sites; hereby, the adsorption process may limit the CO2 mobility within the cap-rock, thus minimizing leakage phenomena. Whether it is a reservoir or a caprock, understanding and quantifying the mechanisms of adsorption in these natural materials is key to improve the engineering design of subsurface operations. Results will be presented from a laboratory study that combines conventional techniques for the measurement of adsorption isotherms with novel methods that allows for the imaging of adsorption using x-rays. Various nanoporous materials are considered, thus including rocks, such as shales and coals, pure clay minerals and engineered adsorbents with well-defined nanopore structures, such as zeolites. Supercritical CO2 adsorption isotherms have been measured with a Rubotherm Magnetic Suspension balance by covering the pressure range 0.1-20~MPa. A medical x-ray CT scanner has been used to identify three-dimensional patterns of the adsorption properties of a packed-bed of adsorbent, thus enabling to assess the spatial variability of the adsorption isotherm. The data are analyzed by using thermodynamically rigorous measures of adsorption and a graphical method is applied for their interpretation. The density of the adsorbed phase is estimated and compared to data reported in the literature; the latter is key to disclose gas-reserves and/or potential storage capacity estimates. When evaluated against classic adsorbent materials, the adsorption mechanism in shales is further complicated by

  4. Predicting helium and neon adsorption and separation on carbon nanotubes by Monte Carlo simulation.

    PubMed

    Bolboli Nojini, Zabiollah; Abbas Rafati, Amir; Majid Hashemianzadeh, Seyed; Samiee, Sepideh

    2011-04-01

    The adsorption of helium and neon mixtures on single-walled carbon nanotubes (SWCNTs) was investigated at various temperatures (subcritical and supercritical) and pressures using canonical Monte Carlo (CMC) simulation. Adsorption isotherms were obtained at different temperatures (4, 40, 77 and 130 K) and pressures ranging from 1 to 16 MPa. Separation factors and isosteric enthalpies of adsorption were also calculated. Moreover, the adsorption isotherms were obtained at constant specific temperatures (4 and 40 K) and pressures (0.2 and 1.0 MPa) as a function of the amount adsorbed. All of the adsorption isotherms for an equimolar mixture of helium and neon have a Langmuir shape, indicating that no capillary condensation occurs. Both the helium and the neon adsorption isotherms exhibit similar behavior, and slightly more of the helium and neon mixture is adsorbed on the inner surfaces of the SWCNTs than on their outer surfaces. More neon is adsorbed than helium within the specified pressure range. The data obtained show that the isosteric enthalpies for the adsorption of neon are higher than those for helium under the same conditions, which means that adsorption of neon preferentially occurs by (15, 15) SWCNTs. Furthermore, the isosteric enthalpies of adsorption of both gases decrease with increasing temperature. PMID:20559855

  5. Modeling high adsorption capacity and kinetics of organic macromolecules on super-powdered activated carbon.

    PubMed

    Matsui, Yoshihiko; Ando, Naoya; Yoshida, Tomoaki; Kurotobi, Ryuji; Matsushita, Taku; Ohno, Koichi

    2011-02-01

    The capacity to adsorb natural organic matter (NOM) and polystyrene sulfonates (PSSs) on small particle-size activated carbon (super-powdered activated carbon, SPAC) is higher than that on larger particle-size activated carbon (powdered-activated carbon, PAC). Increased adsorption capacity is likely attributable to the larger external surface area because the NOM and PSS molecules do not completely penetrate the adsorbent particle; they preferentially adsorb near the outer surface of the particle. In this study, we propose a new isotherm equation, the Shell Adsorption Model (SAM), to explain the higher adsorption capacity on smaller adsorbent particles and to describe quantitatively adsorption isotherms of activated carbons of different particle sizes: PAC and SPAC. The SAM was verified with the experimental data of PSS adsorption kinetics as well as equilibrium. SAM successfully characterized PSS adsorption isotherm data for SPACs and PAC simultaneously with the same model parameters. When SAM was incorporated into an adsorption kinetic model, kinetic decay curves for PSSs adsorbing onto activated carbons of different particle sizes could be simultaneously described with a single kinetics parameter value. On the other hand, when SAM was not incorporated into such an adsorption kinetic model and instead isotherms were described by the Freundlich model, the kinetic decay curves were not well described. The success of the SAM further supports the adsorption mechanism of PSSs preferentially adsorbing near the outer surface of activated carbon particles. PMID:21172719

  6. Fundamental studies of methyl iodide adsorption in DABCO impregnated activated carbons.

    PubMed

    Herdes, Carmelo; Prosenjak, Claudia; Román, Silvia; Müller, Erich A

    2013-06-11

    Methyl iodide capture from a water vapor stream using 1,4-diazabicyclo[2.2.2]octane (DABCO)-impregnated activated carbons is, for the first time, fundamentally described here on the atomic level by means of both molecular dynamics and grand canonical Monte Carlo simulations. A molecular dynamics annealing strategy was adopted to mimic the DABCO experimental impregnation procedure in a selected slitlike carbon pore. Predictions, restricted to the micropore region, are made about the adsorption isotherms of methyl iodide, water, and nitrogen on both impregnated and bare activated carbon models. Experimental and simulated nitrogen adsorption isotherms are compared for the validation of the impregnation strategy. Selectivity analyses of the preferential adsorption toward methyl iodide over water are also reported. These simulated adsorption isotherms sum up to previous experimental studies to provide an enhanced picture for this adsorption system of widespread use at nuclear plant HVAC facilities for the capture of radioactive iodine compounds. PMID:23679202

  7. Equilibrium and kinetic data and process design for adsorption of Congo Red onto bentonite.

    PubMed

    Bulut, Emrah; Ozacar, Mahmut; Sengil, I Ayhan

    2008-06-15

    The adsorption of Congo Red onto bentonite in a batch adsorber has been studied. Four kinetic models, the pseudo first- and second-order equations, the Elovich equation and the intraparticle diffusion equation, were selected to follow the adsorption process. Kinetic parameters; rate constants, equilibrium adsorption capacities and correlation coefficients, for each kinetic equation were calculated and discussed. It was shown that the adsorption of Congo Red onto bentonite could be described by the pseudo second-order equation. The experimental isotherm data were analyzed using the Langmuir, Freundlich and Temkin equations. Adsorption of Congo Red onto bentonite followed the Langmuir isotherm. A single stage batch adsorber was designed for different adsorbent mass/treated effluent volume ratios using the Langmuir isotherm. PMID:18055111

  8. Adsorption of ammonium dinitramide (ADN) from aqueous solutions. 1. Adsorption on powdered activated charcoal.

    PubMed

    Santhosh, G; Venkatachalam, S; Ninan, K N; Sadhana, R; Alwan, S; Abarna, V; Joseph, M A

    2003-03-17

    Investigations on the adsorption of ammonium dinitramide (NH(4)N(NO(2))(2)) (ADN) from aqueous solutions on powdered activated charcoal (PAC) were carried out in order to find out an effective and easier method of separating ADN from aqueous solutions. The effectiveness of PAC in the selective adsorption of ADN from aqueous solutions of ADN (ADN-F) and ADN in presence of sulfate (SO(4)(2-)) and nitrate (NO(3)(-)) ions (ADN-PS) was examined and compared using batch and column methods. The adsorption process follows both Langmuir and Freundlich adsorption isotherms and the isotherm parameters for the models were determined. The observed data favor the formation of monolayer adsorption. The adsorption capacities were found to be 63.3, 119, 105.3 and 82 mg of ADN per g of PAC for ADN-F (batch), ADN-PS (batch), ADN-F (column) and ADN-PS (column), respectively. Break-through curves for ADN-F and ADN-PS were obtained for the optimization of separation of ADN from aqueous solutions. Elution curves were generated for the desorption of ADN from PAC using hot water as eluent. PMID:12628781

  9. 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.

  10. 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

  11. Fruit waste adsorbent for ammonia nitrogen removal from synthetic solution: Isotherms and kinetics

    NASA Astrophysics Data System (ADS)

    Zahrim, AY; Lija, Y.; Ricky, L. N. S.; Azreen, I.

    2016-06-01

    In this study, four types of watermelon rind (WR) adsorbents; fresh WR, modified WR with sodium hydroxide (NaOH), potassium hydroxide (KOH) and sulphuric acid (H2SO4) were used as a potential low-cost adsorbent to remove NH3-N from solution. The adsorption data were fitted with the adsorption isotherm and kinetic models to predict the mechanisms and kinetic characteristics of the adsorption process. The equilibrium data agreed well with Langmuir isotherm model with highest correlation (R2=1.00). As for kinetic modelling, the adsorption process follows pseudo-second order for all four types of adsorbents which has R2 value of 1.0 and calculated adsorption capacity, Qe of 1.2148mg/g. The calculated Qe for pseudo-second order has the smallest difference with the experimental Qe and thus suggest that this adsorption process is mainly governed by chemical process involving cations sharing or exchange between WR adsorbent and NH3-N in the solution.

  12. Arsenic(V) adsorption-desorption in agricultural and mine soils: Effects of organic matter addition and phosphate competition.

    PubMed

    Arco-Lázaro, Elena; Agudo, Inés; Clemente, Rafael; Bernal, M Pilar

    2016-09-01

    High total and bioavailable concentrations of As in soils represent a potential risk for groundwater contamination and entry in the food chain. The use of organic amendments in the remediation of As-contaminated soils has been found to produce distinct effects on the solubility of As in the soil. Therefore, knowledge about As adsorption-desorption processes that govern its solubility in soil is of relevance in order to predict the behaviour of this element during these processes. In this paper, the objective was to determine As adsorption and desorption in four different soils, with and without compost addition, and also in competition with phosphate, through the determination of sorption isotherms. Batch experiments were carried out using three soils affected differently by previous mining activity of the Sierra Minera of La Unión-Cartagena (SE Spain) and an agricultural soil from Segovia province (central Spain). Adsorption was higher in the mining soils (and highest in the acidic one) than in the agricultural soils, although the latter were not affected negatively by organic matter or phosphate competition for sorption sites. The results show that As adsorption in most soils, both with and without compost, fitted better a multimolecular layer model (Freundlich), whereas As adsorption in competition with P fitted a monolayer model (Langmuir). Moreover, the use of compost and phosphate reduced the adsorption of As in the mining soils, while in the agricultural soils compost increased their low adsorption capacity. Therefore, the use of compost can be a good option to favour As immobilisation in soils of low adsorption, but knowledge of the soil composition will be crucial to predict the effects of organic amendments on As solubility in soils and its associated environmental risk. PMID:27239690

  13. 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

  14. 3D Finite Element Analysis of Spider Non-isothermal Forging Process

    NASA Astrophysics Data System (ADS)

    Niu, Ling; Wei, Wei; Wei, Kun Xia; Alexandrov, Igor V.; Hu, Jing

    2016-05-01

    The differences of effective stress, effective strain, velocity field, and the load-time curves between the spider isothermal and non-isothermal forging processes are investigated by making full use of 3D FEA, and verified by the production experiment of spider forging. Effective stress is mainly concentrated on the pin, and becomes lower closer to the front of the pin. The maximum effective strain in the non-isothermal forging is lower than that in the isothermal. The great majority of strain in the non-isothermal forging process is 1.76, which is larger than the strain of 1.31 in the isothermal forging. The maximum load required in the isothermal forging is higher than that in the non-isothermal. The maximum experimental load and deformation temperature in the spider production are in good agreement with those in the non-isothermal FEA. The results indicate that the non-isothermal 3D FEA results can guide the design of the spider forging process.

  15. 3D Finite Element Analysis of Spider Non-isothermal Forging Process

    NASA Astrophysics Data System (ADS)

    Niu, Ling; Wei, Wei; Wei, Kun Xia; Alexandrov, Igor V.; Hu, Jing

    2016-06-01

    The differences of effective stress, effective strain, velocity field, and the load-time curves between the spider isothermal and non-isothermal forging processes are investigated by making full use of 3D FEA, and verified by the production experiment of spider forging. Effective stress is mainly concentrated on the pin, and becomes lower closer to the front of the pin. The maximum effective strain in the non-isothermal forging is lower than that in the isothermal. The great majority of strain in the non-isothermal forging process is 1.76, which is larger than the strain of 1.31 in the isothermal forging. The maximum load required in the isothermal forging is higher than that in the non-isothermal. The maximum experimental load and deformation temperature in the spider production are in good agreement with those in the non-isothermal FEA. The results indicate that the non-isothermal 3D FEA results can guide the design of the spider forging process.

  16. Adsorption studies of methylene blue dye on tunisian activated lignin

    NASA Astrophysics Data System (ADS)

    Kriaa, A.; Hamdi, N.; Srasra, E.

    2011-02-01

    Activated carbon prepared from natural lignin, providing from a geological deposit, was used as the adsorbent for the removal of methylene blue (MB) dye from aqueous solutions. Batch adsorption studies were conducted to evaluate various experimental parameters like pH and contact time for the removal of this dye. Effective pH for MB removal was 11. Kinetic study showed that the adsorption of dye was gradual process. Quasi equilibrium reached in 4 h. Pseudo-first-order, pseudo-second-order were used to fit the experimental data. Pseudo-second-order rate equation was able to provide realistic description of adsorption kinetics. The experimental isotherms data were also modelled by the Langmuir and Freundlich equation of adsorption. Equilibrium data fitted well with the Langmuir model with maximum monolayer adsorption capacity of 147 mg/g. Activated lignin was shown to be a promising material for adsorption of MB from aqueous solutions.

  17. Application of HYDRUS 1D model for assessment of phenol-soil adsorption dynamics.

    PubMed

    Pal, Supriya; Mukherjee, Somnath; Ghosh, Sudipta

    2014-04-01

    Laboratory-scale batch, vertical, and horizontal column experiments were conducted to investigate the attenuative capacity of a fine-grained clayey soil of local origin in the surrounding of a steel plant wastewater discharge site in West Bengal, India, for removal of phenol. Linear, Langmuir, and Freundlich isotherm plots from batch experimental data revealed that Freundlich isotherm model was reasonably fitted (R (2) = 0.94). The breakthrough column experiments were also carried out with different soil bed heights (5, 10, and 15 cm) under uniform flow to study the hydraulic movements of phenol by evaluating time concentration flow behavior using bromide as a tracer. The horizontal migration test was also conducted in the laboratory using adsorptive phenol and nonreactive bromide tracer to explore the movement of solute in a horizontal distance. The hydrodynamic dispersion coefficients (D) in the vertical and horizontal directions in the soil were estimated using nonlinear least-square parameter optimization method in CXTFIT model. In addition, the equilibrium convection dispersion model in HYDRUS 1D was also examined to simulate the fate and transport of phenol in vertical and horizontal directions using Freundlich isotherm constants and estimated hydrodynamic parameters as input in the model. The model efficacy and validation were examined through statistical parameters such as the coefficient of determination (R (2)), root mean square error and design of index (d). PMID:24407784

  18. The adsorption/desorption of phosphorus in freshwater sediments from buffer zones: the effects of sediment concentration and pH.

    PubMed

    Zhang, Liang; Du, Yun; Du, Chao; Xu, Meng; Loáiciga, Hugo A

    2016-01-01

    Riparian buffer zones adjacent to reservoirs and lakes protect aquatic ecosystems from polluted surface runoff. Sediments, collected from the buffer zones of Danjiangkou Reservoir (SR) and Honghu Lake (SL) in an ecologically fragile region in central China, were evaluated to reveal their phosphorus-adsorbing/desorbing properties and storage capacities. A nonlinear regression method was used to fit the pseudo-second-order kinetic and the modified crossover-type Langmuir isotherm models to the experimental data. It is shown that the adsorption of phosphorus onto the studied sediments followed the pseudo-second-order kinetic expression. The modified crossover-type Langmuir isotherm model was found to be a suitable method for describing adsorption/desorption processes in the experimental sediments. The maximum adsorption capacities (Q m), partitioning coefficients (K p), native adsorbed exchangeable phosphorus (NAP), and equilibrium phosphorus concentration (EPC0) were subsequently obtained for the experimental sediments. The effects of sediment concentration and pH were also investigated by batch experiments and Fourier transformation infrared and scanning electron microscopy analyses. The adsorption/desorption characteristics of different phosphate species on the sediments from reservoir and lake buffer zones were identified. PMID:26638155

  19. Design of a hybrid advective-diffusive microfluidic system with ellipsometric detection for studying adsorption.

    PubMed

    Wang, Lei; Zhao, Cunlu; Wijnperlé, Daniel; Duits, Michel H G; Mugele, Frieder

    2016-05-01

    Establishing and maintaining concentration gradients that are stable in space and time is critical for applications that require screening the adsorption behavior of organic or inorganic species onto solid surfaces for wide ranges of fluid compositions. In this work, we present a design of a simple and compact microfluidic device based on steady-state diffusion of the analyte, between two control channels where liquid is pumped through. The device generates a near-linear distribution of concentrations. We demonstrate this via experiments with dye solutions and comparison to finite-element numerical simulations. In a subsequent step, the device is combined with total internal reflection ellipsometry to study the adsorption of (cat)ions on silica surfaces from CsCl solutions at variable pH. Such a combined setup permits a fast determination of an adsorption isotherm. The measured optical thickness is compared to calculations from a triple layer model for the ion distribution, where surface complexation reactions of the silica are taken into account. Our results show a clear enhancement of the ion adsorption with increasing pH, which can be well described with reasonable values for the equilibrium constants of the surface reactions. PMID:27375818

  20. Preparation of bioinorganic fertilizing media by adsorption of humates on glassy aluminosilicates.

    PubMed

    Chassapis, Konstantinos; Roulia, Maria; Vrettou, Evangelia; Parassiris, Anastassios

    2010-11-01

    Surface-modified expanded perlite was synthesized using humic substances from the Megalopolis peaty lignite. Adsorption is efficient and increases at higher temperatures and lower pHs. The preparation can be carried out under mild conditions leading to an eco-friendly, bioinorganic material useful as soil conditioner and biofertilizer. Six adsorption models were applied; the Klotz, Freundlich and Redlich-Peterson isotherms fit more successfully to the experimental data. The obeying of the theoretical models was correlated with the heterogeneity and non-uniform distribution of the adsorption sites, host-guest attraction forces as well as the formation of self-assembled aggregates and self-organized multilayers of humic substances onto the aluminosilicate adsorbent, consistent with changes in micromorphology. Thermodynamic quantities revealing distinct physicochemical characteristics of the adsorption phenomena, i.e., enthalpy, entropy and free energy change, were calculated. Desorption experiments and cultivation of microorganisms demonstrated that perlite may act successfully as host material for microbial populations upgrading the humic-loaded perlite for soil applications. PMID:20692818

  1. Adsorption and desorption characteristics of methamphetamine, 3,4-methylenedioxymethamphetamine, and pseudoephedrine in soils.

    PubMed

    Pal, Raktim; Megharaj, Mallavarapu; Kirkbride, K Paul; Naidu, Ravi

    2015-06-01

    This work presents, for the first time, information on the adsorption-desorption characteristics of illicit drugs and precursors in soils and an estimation of their potential bioavailability. The experiment was conducted using a batch equilibrium technique for the parent drugs methamphetamine and 3,4-methylenedioxymethamphetamine (MDMA) and the precursor pseudoephedrine in three South Australian soils varying in physiochemical properties. The individual compounds exhibited different adsorption mechanisms in the test soils, and the results fitted better with the Freundlich isotherm model (r (2) ≥ 0.99). The maximum adsorption capacity was recorded for pseudoephedrine (2,000 μg g(-1)). However, pseudoephedrine recorded lower organic carbon normalized adsorption coefficient values (<250 mL g(-1)), lower magnitudes of Gibb's free energy change, and higher percent desorption (73-92 %) compared to methamphetamine and MDMA. The results thus showed pseudoephedrine to be the most mobile compound in the soils under study, to have the highest availability for degradation of the three compounds, and to have the highest susceptibility to biotic degradation in test soils. PMID:24838127

  2. Deactivation model for the adsorption of trichloroethylene vapor on an activated carbon bed

    SciTech Connect

    Suyadal, Y.; Erol, M.; Oguz, H.

    2000-03-01

    In this work, the adsorption of trichloroethylene (TCE) vapor was investigated in a laboratory-scale packed-bed adsorber by using granular activated carbon (GAC) at constant pressure (101.3 kPa). The packed-bed adsorber (PBA) was operated batchwise with the charges of GAC particles in the ranges of 2.5--10.0 g for obtaining TCE breakthrough curves. Experiments were carried out at different temperatures (25.6 {le} T({degree}C) {le} 35.8) and TCE feedstock concentrations (6,350 {le} C (ppm TCE) {le} 7,950) within the range of space velocity (5,000 {le} {var_theta} (h{sup {minus}1}) {le} 17,000). The effects of TCE inlet concentration, operating temperature, and mass of adsorbent (m{sub Ads}) on the TCE breakthrough curves were investigated, respectively. The deactivation model (DM) was tested for these curves by using the analogy between the adsorption of TCE and the deactivation of catalyst particles. Observed adsorption rate constants (k{sub S}) and first-order deactivation rate constants (k{sub d}) were obtained from the model. It was found that the deactivation model describes the experimental breakthrough curves more accurately compared to the adsorption isotherms given in the literature.

  3. Nitrate adsorption from aqueous solution using granular chitosan-Fe3+ complex

    NASA Astrophysics Data System (ADS)

    Hu, Qili; Chen, Nan; Feng, Chuanping; Hu, WeiWu

    2015-08-01

    In the present study, In order to efficiently remove nitrate, granular chitosan-Fe3+ complex with high chemical stability and good environmental adaptation was synthesized through precipitation method and characterized using SEM, XRD, BET and FTIR. The nitrate adsorption performance was evaluated by batch experiments. The results indicated that granular chitosan-Fe3+ complex was an amorphous and mesoporous material. The BET specific surface area and average pore size were 8.98 m2 g-1 and 56.94 Å, respectively. The point of zero charge was obtained at pH 5. The maximum adsorption capacity reached 8.35 mg NO3--N g-1 based on Langmuir-Freundlich model. Moreover, no significant change in the nitrate removal efficiency was observed in the pH range of 3.0-10.0. The adverse influence of sulphate on nitrate removal was the most significant, followed by bicarbonate and fluoride, whereas chloride had slightly adverse effect. Adsorption process followed the pseudo-second-order kinetic model, and the experimental equilibrium data were fitted well with the Langmuir-Freundlich and D-R isotherm models. Thermodynamic parameters revealed that nitrate adsorption was a spontaneous and exothermic process. Granular chitosan-Fe3+ complex could be effectively regenerated by NaCl solution.

  4. Adsorption of sodium lauryl sulfate onto arsenic-bearing ferrihydrite.

    PubMed

    Quan, C; Khoe, G; Bagster, D

    2001-02-01

    Ferrihydrite is an excellent adsorbent for binding trace toxic contaminants such as arsenic, and precipitate flotation of the arsenic-bearing ferrihydrite has been studied. Anionic surfactants such as sodium lauryl sulfate (SLS) and sodium oleate (NaOL) are suitable collectors for the flotation. The adsorption of SLS both alone and after the subsequent addition of NaOL on these precipitates at pH 4-5 was measured. It has been shown that the synergistic effect of the two surfactants on flotation is dependent on their addition order. The presence of NaOL before SLS in the conditioning stage can prevent the adsorption of SLS because of the electrostatic shielding of adsorption sites on the precipitates. The post addition of NaOL to the SLS-bearing precipitates can promote the flocculation of the precipitates and enhance entrainment of SLS for better flotation. The SLS adsorption data fit better with the modified Frumkin isotherm than the Langmuir isotherm. Thermodynamic parameters (-delta Gads0,delta Hads0, and delta Sads0) have been derived from the analysis of the adsorption isotherms. The results suggest that the adsorption of SLS on AFH is physical and exothermic. PMID:11229002

  5. Adsorption of naphthalene onto sonicated talc from aqueous solutions.

    PubMed

    Sener, Savaş; Ozyilmaz, Azat

    2010-06-01

    The adsorption behavior of naphthalene onto naturally hydrophobic talc from aqueous solution was investigated in this study. The natural talc was first pretreated by sonication to improve the surface characteristics and enhance the uptake capacity by increasing the specific surface area (SSA) of talc. The naphthalene uptake of talc was found as 276 mg g(-1) and increased to 359 mg g(-1) after the sonication. Adsorption studies also showed that the adsorption of naphthalene onto the sonicated talc was not affected by changes in pH suggesting that the main driving forces for naphthalene adsorption onto talc was hydrophobic bonding rather than electrostatic force. The pseudo-first and pseudo-second orders and intraparticle diffusion equation were used to evaluate the kinetic data and the constants were determined. Adsorption process of naphthalene onto talc followed the pseudo-second-order rate expression for different initial naphthalene concentrations. The Langmuir and Freundlich isotherm models were used to model the isotherm data for their applicability. The Freundlich isotherm best fitted for the adsorption of naphthalene onto talc. PMID:20163977

  6. Adsorption of Cd(II) and Cu(II) from aqueous solution by carbonate hydroxylapatite derived from eggshell waste.

    PubMed

    Zheng, Wei; Li, Xiao-ming; Yang, Qi; Zeng, Guang-ming; Shen, Xiang-xin; Zhang, Ying; Liu, Jing-jin

    2007-08-17

    Carbonate hydroxylapatite (CHAP) synthesized by using eggshell waste as raw material has been investigated as metal adsorption for Cd(II) and Cu(II) from aqueous solutions. The effect of various parameters on adsorption process such as contact time, solution pH, amount of CHAP and initial concentration of metal ions was studied at room temperature to optimize the conditions for maximum adsorption. The results showed that the removal efficiency of Cd(II) and Cu(II) by CHAP could reach 94 and 93.17%, respectively, when the initial Cd(II) concentration 80 mg/L and Cu(II) 60 mg/L and the liquid/solid ratio was 2.5 g/L. The equilibrium sorption data for single metal systems at room temperature could be described by the Langmuir and Freundlich isotherm models. The highest value of Langmuir maximum uptake, (b), was found for cadmium (111.1mg/g) and copper (142.86 mg/g). Similar Freundlich empirical constants, K, were obtained for cadmium (2.224) and copper (7.925). Ion exchange and surface adsorption might be involved in the adsorption process of cadmium and copper. Desorption experiments showed that CaCl2, NaCl, acetic acid and ultrasonic were not efficient enough to desorb substantial amount of metal ions from the CHAP. The results obtained show that CHAP has a high affinity to cadmium and copper. PMID:17368932

  7. Adsorption characteristics of multiple microcystins and cylindrospermopsin on sediment: Implications for toxin monitoring and drinking water treatment.

    PubMed

    Maghsoudi, Ehsan; Prévost, Michèle; Vo Duy, Sung; Sauvé, Sébastien; Dorner, Sarah

    2015-09-01

    Adsorption of mixtures of cyanotoxins onto sediment as a dominant mechanism in the elimination of cyanotoxins from the aqueous phase has not been extensively investigated. The aim of this study was to investigate adsorption and desorption behavior of six microcystins including microcystin (MC)-LR, RR, YR, LY, LW and LF and cylindrospermopsin (CYN) on natural sediment. Freundlich and Langmuir isotherms could be fitted for MC-LR, RR, YR and CYN. Sorption kinetics showed immediate rapid adsorption for all cyanotoxins: CYN, MCLW and MCLF were adsorbed 72.6%, 56.7% and 55.3% respectively within 2 h. Results of desorption experiments demonstrated that less than 9% of cyanotoxins desorbed from sediment within 96 h. Adsorption of cyanotoxins onto three fractionated sediments particles, clay-silt (<75 μm), find sand (75-315 μm) and coarse sand (315-2000 μm) demonstrated that adsorption capacity of coarse sand fraction for all the tested cyanotoxins was less than 4% of the clay-silt fraction. Results of this study revealed that there is a potential for cyanotoxins to accumulate in the sediments of lakes, as well as in drinking water treatment plants. Monitoring programs must consider cyanotoxins in the particulate phase to avoid largely underestimating toxin concentrations following their release from blooms. PMID:26091872

  8. Mobility of pharmaceutical compounds in the terrestrial environment: Adsorption kinetics of the macrocyclic lactone eprinomectin in soils.

    PubMed

    Vassilis, Litskas D; George, Batzias C; Charalampos, Paraskevas G; Athina, Pavlatou-Ve; Xanthippos, Karamanlis N

    2016-02-01

    Avermectins, such as eprinomectin (EPM), are antiparasitic drugs widely and globally used. There is undisputed evidence that they could be a threat for the terrestrial ecosystem. Despite their global use, data for avermectins behaviour and fate in soils are scarce. The objectives of this research were to conduct adsorption experiments in the soil to determine kinetics and isotherms as well as to explore the EPM adsorption mechanism. Accordingly, various models were employed to study the adsorption behaviour and kinetics as well as the adsorption mechanism of EPM in soils. The results showed that the degree of EPM adsorption to soils is determined by the soils' physicochemical properties and the EPM initial concentration. It is possible that dissolved EPM concentration will be higher in soils that contain low amounts of clay minerals and organic matter, resulting in higher toxicity risk for the soil biota and shallow groundwater aquifers contamination. The results of this study are crucial for impact assessment of EPM and in the design of environmental fate or ecotoxicological studies. PMID:26469933

  9. Kinetic studies of the sucrose adsorption onto an alumina interface

    NASA Astrophysics Data System (ADS)

    Singh, Kaman; Mohan, Sudhanshu

    2004-01-01

    An account is given of an experimental kinetic study of adsorption of analar reagent sucrose (ARS) onto an alumina interface spectrometrically ( λmax=570 nm) at pH 8.0 and at room temperature. The adsorption isotherm is a typical Langmuirian isotherm (S-type) and adsorption parameters have been deduced according to the Langmuir's model. The adsorption coefficient evaluated from the Langmuir's equation was found to be 2.52×10 2 l mol -1. Adsorption mechanism has been interpreted on the basis of metal-saccharide interaction as found in organometallic compounds and interaction due to negatively charged ends on the disaccharide molecules and positively charge groups on the surface on alumina which depends on the pH value. The effects of variation in experimental conditions of the adsorption system have also been investigated. The adsorption exhibited a typical response to the pH effect and on going towards the PZC the net charge decreases and any reaction making dependence on charge and maximum adsorption (amount) was found near the isoelectric point of alumina (pH 9.0). The presence of ions like Cl -, SO 42- and PO 43- affect the adsorbed amount quantitatively and it seems that these anions compete with sucrose for the positively charged surface sites. The addition of similar concentration of cations was found to reduce the adsorbed amount. The temperature was found to have an inverse effect on adsorption. The additions of catonic and anionic detergents influence both the adsorbed amount and the adsorption rate. The thermodynamics of the titled adsorption model indicates the spontaneous and exothermic nature. The negative value of entropy is an indication of probability of favorable and complex nature of the adsorption.

  10. Removal of fluoride from groundwater by adsorption onto La(III)- Al(III) loaded scoria adsorbent

    NASA Astrophysics Data System (ADS)

    Zhang, Shengyu; Lu, Ying; Lin, Xueyu; Su, Xiaosi; Zhang, Yuling

    2014-06-01

    The La3+-Al3+ loaded scoria (La-Al-Scoria) was prepared as adsorbent for the fluoride removal from groundwater. The connecting time experiment indicated that the fluoride adsorption process reached equilibrium within 5 hours. The kinetics of fluoride ion adsorption onto La-Al-Scoria was followed the pseudo-second order with correlation coefficient value (R2) of 0.997. The isotherm data was well fitted to both of the Freundlich and Langmuir isotherm models, the R2 of Freundlich and Langmuir were 0.98 and 0.97, respectively. Subsequently, the adsorbent was characterized by scanning electron microscope (SEM), Energy dispersive analysis of X-ray (EDX), X-ray diffraction analysis (XRD) and X-ray Photoelectron Spectroscopy (XPS) measurements. SEM visual expressed that the dense canal surface structure of natural scoria appeared a large amount of rod-like composite after modification. The XRD and XPS instrumental studies revealed that the La3+ and Al3+ were loaded on the surface of modified scoria and the fluoride ion was adsorbed on the La-Al-Scoria. The large amount of La-Al-O composite oxide existed onto the surface of La-Al-Scoria was the immanent cause for the excellent adsorption capacity of fluoride ion.

  11. Column Experiments for Radionuclide Adsorption Studies of the Culebra Dolomite: Retardation Parameter Estimation for Non-Eluted Actinide Species

    SciTech Connect

    Brown, G.O.; Lucero, D.A.; Perkins, W.G.

    1999-01-01

    The U.S. Department of Energy (DOE) has been developing a nuclear waste disposal facility, the Waste Isolation Pilot Plant (WIPP), located approximately 42 km east of Carlsbad, New Mexico. The WIPP is designed to demonstrate the safe disposal of transuranic wastes produced by the defense nuclear-weapons program. Performance assessment analyses (U.S. DOE, 1996) indicate that human intrusion by inadvertent and intermittent drilling for resources provide the only credible mechanisms for significant releases of radionuclides horn the disposal system. These releases may occur by five mechanisms: (1) cuttings, (2) cavings, (3) spallings, (4) direct brine releases, and (5) long-term brine releases. The first four mechanisms could result in immediate release of contaminant to the accessible environment. For the last mechanism, migration pathways through the permeable layers of rock above the Salado are important, and major emphasis is placed on the Culebra Member of the Rustler Formation because this is the most transmissive geologic layer in the disposal system. For reasons of initial quantity, half-life, and specific radioactivity, certain isotopes of Th, U, Am, and Pu would dominate calculated releases from the WIPP. In order to help quanti~ parameters for the calculated releases, radionuclide transport experiments have been carried out using five intact-core columns obtained from the Culebra dolomite member of the Rustler Formation within the Waste Isolation Pilot Plant (WIPP) site in southeastern New Mexico. This report deals primarily with results of mathematical analyses related to the retardation of %J%, 24%, and 24'Am in two of these cores (B-Core - VPX26-11A and C-Core - VPX28-6C). All B-Core transport experiments were done using Culebra-simukmt brine relevant to the core recovery location (the WIPP air-intake shaft - AIS). Most experiments with C-Core were done with AIS brine with some admixture of a brine composition (ERDA-6) that simulated deeper formation

  12. Novel sandwich structure adsorptive membranes for removal of 4-nitrotoluene from water.

    PubMed

    Guo, Yuexin; Jia, Zhiqian

    2016-11-01