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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. 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…

  3. 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)

  4. 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.

  5. 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.

  6. Adsorption isotherm special study. Final report

    SciTech Connect

    1993-05-01

    The study was designed to identify methods to determine adsorption applicable to Uranium Mill Tailings Remedial Action (UMTRA) Project sites, and to determine how changes in aquifer conditions affect metal adsorption, resulting retardation factors, and estimated contaminant migration rates. EPA and ASTM procedures were used to estimate sediment sorption of U, As, and Mo under varying groundwater geochemical conditions. Aquifer matrix materials from three distinct locations at the DOE UMTRA Project site in Rifle, CO, were used as the adsorbents under different pH conditions; these conditions stimulated geochemical environments under the tailings, near the tailings, and downgradient from the tailings. Grain size, total surface area, bulk and clay mineralogy, and petrography of the sediments were characterized. U and Mo yielded linear isotherms, while As had nonlinear ones. U and Mo were adsorbed strongly on sediments acidified to levels similar to tailings leachate. Changes in pH had much less effect on As adsorption. Mo was adsorbed very little at pH 7-7.3, U was weakly sorbed, and As was moderately sorbed. Velocities were estimated for metal transport at different pHs. Results show that the aquifer materials must be characterized to estimate metal transport velocities in aquifers and to develop groundwater restoration strategies for the UMTRA project.

  7. The special features of protein adsorption isotherms on silica adsorbents

    NASA Astrophysics Data System (ADS)

    Chukhrai, E. S.; Atyaksheva, L. F.; Pilipenko, O. S.

    2011-05-01

    The adsorption isotherms of hemoglobin, peroxidase, and β-galactosidase on silochrome and mesoporous and biporous silicas were comparatively studied. Adsorption developed in two stages, including fast "reversible" protein adsorption (equilibrium was reached in t ≤ 1-2 h) and a "slow stage" of irreversible binding in t ≫ 24 h (multipoint adsorption). The corresponding equilibrium constants were determined. The mechanism of unlimited linear association of peroxidase in the adsorption layer on the surface of silochrome was established.

  8. 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.

  9. 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.

  10. 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.

  11. 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…

  12. 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.

  13. Experimental adsorption isotherms based on inverse gas chromatography.

    PubMed

    Kalogirou, E; Bassiotis, I; Artemiadi, Th; Margariti, S; Siokos, V; Roubani-Kalantzopoulou, F

    2002-09-01

    A new chromatographic perturbation method is used for studying the adsorption-desorption equilibrium in various gas-solid heterogeneous systems. It is the reversed-flow method giving accurate and precise values of many physicochemical constants including the basic and necessary adsorption isotherm values. For four inorganic oxides, namely, Cr2O3, Fe2O3, TiO2 and PbO, and two aromatic hydrocarbons (benzene, toluene) these adsorption isotherms have been determined through a non-linear model. PMID:12385379

  14. Adsorption Isotherm studies of Methyl Bromide adsorbed on Magnesium Oxide

    NASA Astrophysics Data System (ADS)

    Burns, Teresa; Sprung, Michael

    2005-03-01

    Understanding the interaction of polar molecules with ionic surfaces is technologically very important. Using high precision, volumetric adsorption isotherms the layering properties of methyl bromide on the MgO(100) surface were examined between 164 K and 179 K. Methyl bromide (Triple point = 179.49K) is found to exhibit two layering transitions within this temperature interval. Thermodynamic quantities derived from this study including the layering transition temperatures, the 2D compressibility, layer enthalpy and entropy of adsorption, and the isosteric enthalpy of adsorption will be presented. Comparisons with the adsorption properties of methyl chloride and methyl iodide will also be included.

  15. 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

  16. 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.

  17. 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

  18. The Langmuir isotherm: a commonly applied but misleading approach for the analysis of protein adsorption behavior.

    PubMed

    Latour, Robert A

    2015-03-01

    The Langmuir adsorption isotherm provides one of the simplest and most direct methods to quantify an adsorption process. Because isotherm data from protein adsorption studies often appear to be fit well by the Langmuir isotherm model, estimates of protein binding affinity have often been made from its use despite that fact that none of the conditions required for a Langmuir adsorption process may be satisfied for this type of application. The physical events that cause protein adsorption isotherms to often provide a Langmuir-shaped isotherm can be explained as being due to changes in adsorption-induced spreading, reorientation, clustering, and aggregation of the protein on a surface as a function of solution concentration in contrast to being due to a dynamic equilibrium adsorption process, which is required for Langmuir adsorption. Unless the requirements of the Langmuir adsorption process can be confirmed, fitting of the Langmuir model to protein adsorption isotherm data to obtain thermodynamic properties, such as the equilibrium constant for adsorption and adsorption free energy, may provide erroneous values that have little to do with the actual protein adsorption process, and should be avoided. In this article, a detailed analysis of the Langmuir isotherm model is presented along with a quantitative analysis of the level of error that can arise in derived parameters when the Langmuir isotherm is inappropriately applied to characterize a protein adsorption process.

  19. A model free method for estimation of complicated adsorption isotherms in liquid chromatography.

    PubMed

    Forssén, Patrik; Fornstedt, Torgny

    2015-08-28

    Here we show that even extremely small variations in the adsorption isotherm can have a tremendous effect on the shape of the overloaded elution profiles and that the earlier in the adsorption isotherms the variation take place, the larger its impact on the shape of the elution profile. These variations are so small that they can be "hidden" by the discretization and in the general experimental noise when using traditional experimental methods, such as frontal analysis, to measure adsorption isotherms. But as the effects of these variations are more clearly visible in the elution profiles, the Inverse Method (IM) of adsorption isotherm estimation is an option. However, IM usually requires that one selects an adsorption isotherm model prior to the estimation process. Here we show that even complicated models might not be able to estimate the adsorption isotherms with multiple inflection points that small variations might give rise to. We therefore developed a modified IM that, instead of fixed adsorption isotherm models, uses monotone piecewise interpolation. We first validated the method with synthetic data and showed that it can be used to estimate an adsorption isotherm, which accurately predicts an extremely "strange" elution profile. For this case it was impossible to estimate the adsorption isotherm using IM with a fixed adsorption model. Finally, we will give an example of a real chromatographic system where adsorption isotherm with inflection points is estimated by the modified IM.

  20. 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.

  1. 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

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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

  7. 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.

  8. A modified Langmuir-Freundlich isotherm model for simulating pH-dependent adsorption effects

    NASA Astrophysics Data System (ADS)

    Jeppu, Gautham P.; Clement, T. Prabhakar

    2012-03-01

    Analytical isotherm equations such as Langmuir and Freundlich isotherms are widely used for modeling adsorption data. However, these isotherms are primarily useful for simulating data collected at a fixed pH value and cannot be easily adapted to simulate pH-dependent adsorption effects. Therefore, most adsorption studies currently use numerical surface-complexation models (SCMs), which are more complex and time consuming than traditional analytical isotherm models. In this work, we propose a new analytical isotherm model, identified as the modified Langmuir-Freundlich (MLF) isotherm, which can be used to simulate pH-dependent adsorption. The MLF isotherm uses a linear correlation between pH and affinity coefficient values. We validated the proposed MLF isotherm by predicting arsenic adsorption onto two different types of sorbents: pure goethite and goethite-coated sand. The MLF model gave good predictions for both experimental and surface complexation-model predicted datasets for these two sorbents. The proposed analytical isotherm framework can help reduce modeling complexity, model development time, and computational efforts. One of the limitations of the proposed method is that it is currently valid only for single-component systems. Furthermore, the model requires a system-specific pH. vs. affinity coefficient relation. Despite these limitations, the approach provides a promising analytical framework for simulating pH-dependent adsorption effects.

  9. 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.

  10. 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

  11. Heterogeneous three-site lattice model for adsorption of aromatics in ZSM-5 zeolites: Temperature dependence of adsorption isotherms

    SciTech Connect

    Narkiewicz-Michalek, J.; Szabelski, P.; Rudzinski, W.; Chiang, A.S.T.

    1999-08-31

    The three-site lattice model of collective localized adsorption of aromatics in ZSM-5 zeolites, presented in previous publications, is extended by taking into account the effects of energetic heterogeneity of the sites of the same type. The appropriate theoretical equations are derived and used for simultaneous description of the experimental adsorption isotherms and heats of adsorption of benzene and p-xylene in silicalite at 303 K. It is shown that taking into account this additional level of heterogeneity leads to a much better description of both the adsorption isotherms and the related heats of adsorption in these systems. The extended model also allows one to predict correctly the adsorption isotherms of benzene and p-xylene in silicalite at different temperatures using the parameters found at one temperature.

  12. Ciprofloxacin adsorption on graphene and granular activated carbon: kinetics, isotherms, and effects of solution chemistry.

    PubMed

    Zhu, Xuan; Tsang, Daniel C W; Chen, Feng; Li, Shiyu; Yang, Xin

    2015-01-01

    Ciprofloxacin (CIP) is a commonly used antibiotic and widely detected in wastewaters and farmlands nowadays. This study evaluated the efficacy of next-generation adsorbent (graphene) and conventional adsorbent (granular activated carbon, GAC) for CIP removal. Batch experiments and characterization tests were conducted to investigate the adsorption kinetics, equilibrium isotherms, thermodynamic properties, and the influences of solution chemistry (pH, ionic strength, natural organic matter (NOM), and water sources). Compared to GAC, graphene showed significantly faster adsorption and reached equilibrium within 3 min, confirming the rapid access of CIP into the macroporous network of high surface area of graphene as revealed by the Brunner-Emmet-Teller measurements analysis. The kinetics was better described by a pseudo-second-order model, suggesting the importance of the initial CIP concentration related to surface site availability of graphene. The adsorption isotherm on graphene followed Langmuir model with a maximum adsorption capacity of 323 mg/g, which was higher than other reported carbonaceous adsorbents. The CIP adsorption was thermodynamically favourable on graphene and primarily occurred through π - π interaction, according to the FTIR spectroscopy. While the adsorption capacity of graphene decreased with increasing solution pH due to the speciation change of CIP, the adverse effects of ionic strength (0.01-0.5 mol L(-1)), presence of NOM (5 mg L⁻¹), and different water sources (river water or drinking water) were less significant on graphene than GAC. These results indicated that graphene can serve as an alternative adsorbent for CIP removal in commonly encountered field conditions, if proper separation and recovery is available in place. PMID:26050736

  13. 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

  14. Cadmium-109 Radioisotope Adsorption onto Polypyrrole Coated Sawdust of Dryobalanops aromatic: Kinetics and Adsorption Isotherms Modelling

    PubMed Central

    Olatunji, Michael Adekunle; Khandaker, Mayeen Uddin; Amin, Yusoff Mohd; Mahmud, Habibun Nabi Muhammad Ekramul

    2016-01-01

    A radiotracer study was conducted to investigate the removal characteristics of cadmium (109Cd) from aqueous solution by polypyrrole/ sawdust composite. Several factors such as solution pH, sorbent dosage, initial concentration, contact time, temperature and interfering metal ions were found to have influence on the adsorption process. The kinetics of adsorption was relatively fast, reaching equilibrium within 3 hours. A lowering of the solution pH reduced the removal efficiency from 99.3 to ~ 46.7% and an ambient temperature of 25°C was found to be optimum for maximum adsorption. The presence of sodium and potassium ions inhibited 109Cd removal from its aqueous solution. The experimental data for 109Cd adsorption showed a very good agreement with the Langmuir isotherm and a pseudo-first order kinetic model. The surface condition of the adsorbent before and after cadmium loading was investigated using BET, FESEM and FTIR. Considering the low cost of the precursor’s materials and the toxicity of 109Cd radioactive metal, polypyrrole synthesized on the sawdust of Dryobalanops aromatic could be used as an efficient adsorbent for the removal of 109Cd radioisotope from radionuclide-containing effluents. PMID:27706232

  15. Predicting the adsorption capacity and isotherm curvature of organic compounds onto activated carbons in natural waters.

    PubMed

    Hung, H W; Lin, T F

    2006-03-01

    A simple approach to predict the adsorption capacity and isotherm curvature of organic compounds onto activated carbon in natural water was investigated. A combination of the well-known equivalent background compound (EBC), and the simplified competitive adsorption model (SCAM) was employed to delineate the equilibrium capacity. This SCAM-EBC approach may reduce the numerical and experimental effort to obtain the parameters required to predict the adsorption capacity for a specific adsorption system. Several sets of experimental data, including weakly adsorbing (MTBE), strongly adsorbing compounds (TCP, atrazine, and chloroform), and two taste and odor causing compounds (MIB and geosmin) onto different activated carbons in three natural waters and a synthetic groundwater, were tested to verify the SCAM-EBC approach. Based on the approach, a parameter, called relative adsorptivity, describing the adsorption preference of the adsorbent between EBC and the target compound was employed to simulate the isotherm curvature in natural water. The relative adsorptivity of the SCAM-EBC approach is constant and can be directly obtained from the SCAM-EBC parameters in a specific adsorption system. The potential and extent of isotherm curvature can be simulated by only changing the parameter of relative adsorptivity. The marked isotherm curvature was found while the relative adsorptivity is larger than 2.0 to 4.0 for all the systems tested.

  16. 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.

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

    DOE PAGES

    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

  18. 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.

  19. Determination of gas phase adsorption isotherms--a simple constant volume method.

    PubMed

    Kim, Daekeun; Cai, Zhangli; Sorial, George A

    2006-08-01

    Single and ternary solute gas phase adsorption isotherms were conducted in this study to evaluate the effectiveness of a simple constant volume method, which was utilized by using Tedlar gas sampling bags as a constant volume batch reactor. For this purpose, gas phase adsorption of toluene, methyl ethyl ketone (MEK), and methyl isobutyl ketone (MIBK) on two types of activated carbons, BPL-bituminous base and OVC--coconut base, were investigated. For the single solute adsorption, the experimental adsorption data were found to be well correlated with Freundlich and Myers adsorption equations. The pore size distribution of adsorbents was found to affect their adsorption capacities; its effect was dependant on the solute concentration. The ternary adsorption experimental isotherms were accurately predicted by using the well-known model, i.e., ideal adsorbed solution theory (IAST).

  20. 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)

  1. 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

  2. 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.

  3. A New Approach in Regression Analysis for Modeling Adsorption Isotherms

    PubMed Central

    Onjia, Antonije E.

    2014-01-01

    Numerous regression approaches to isotherm parameters estimation appear in the literature. The real insight into the proper modeling pattern can be achieved only by testing methods on a very big number of cases. Experimentally, it cannot be done in a reasonable time, so the Monte Carlo simulation method was applied. The objective of this paper is to introduce and compare numerical approaches that involve different levels of knowledge about the noise structure of the analytical method used for initial and equilibrium concentration determination. Six levels of homoscedastic noise and five types of heteroscedastic noise precision models were considered. Performance of the methods was statistically evaluated based on median percentage error and mean absolute relative error in parameter estimates. The present study showed a clear distinction between two cases. When equilibrium experiments are performed only once, for the homoscedastic case, the winning error function is ordinary least squares, while for the case of heteroscedastic noise the use of orthogonal distance regression or Margart's percent standard deviation is suggested. It was found that in case when experiments are repeated three times the simple method of weighted least squares performed as well as more complicated orthogonal distance regression method. PMID:24672394

  4. Isotherms for adsorption of cellobiohydrolase I and II from Trichoderma reesei on microcrystalline cellulose

    SciTech Connect

    Medve, J.; Tjerneld, F.; Stahlberg, J.

    1997-04-01

    Adsorption to microcrystalline cellulose (Avicel) of pure cellobiohydrolase I and II (CBH I and CBH II) from Trichoderma reesei has been studied. Adsorption isotherms of the enzymes were measured at 4{degree}C using CBH I and CBH II alone and in reconstituted equimolar mixtures. Several models (Langmuir, Freundlich, Temkin, Jovanovic) were tested to describe the experimental adsorption isotherms. The isotherms did not follow the basic (one site) Langmuir equation that has often been used to describe adsorption isotherms of cellulases; correlation coefficients (R{sup 2}) were only 0.926 and 0.947, for CBH I and II, respectively. The experimental isotherms were best described by a model of Langmuir type with two adsorption sites and by a combined Langmuir-Freundlich model (analogous to the Hill equation); using these models the correlation coefficients were in most cases higher than 0.995. Apparent binding parameters derived from the two sites Langmuir model indicated stronger binding of CBH II compared to CBH I; the distribution coefficients were 20.7 and 3.7 L/g for the two enzymes, respectively. The binding capacity was higher for CBH I than for CBH II. The isotherms when analyzed with the combined model indicated presence of unequal binding sites on cellulose and/or negative cooperativity in the binding of the enzyme molecules. 39 refs., 3 figs., 3 tabs.

  5. Adsorption kinetics and isotherms of pesticides onto activated carbon-cloth.

    PubMed

    Ayranci, Erol; Hoda, Numan

    2005-09-01

    Adsorption of pesticides ametryn, aldicarb, dinoseb and diuron from aqueous solution onto high specific area activated carbon-cloth was studied. Kinetics of adsorption was followed by in situ UV-spectroscopy and the data were treated according to various rate models. The extent of adsorption was determined at the end of 125 min adsorption period. Rate constants and the extent of adsorption for the four pesticides were found to follow the order: dinoseb > ametryn > diuron > aldicarb. Adsorption isotherms were derived at 25 degrees C on the basis of batch analysis. Isotherm data were treated according to Langmuir and Freundlich models. The fits of experimental data to these equations were examined. The types of interactions between the surface and pesticide molecules were discussed. PMID:16083766

  6. A thermodynamically consistent explicit competitive adsorption isotherm model based on second-order single component behaviour.

    PubMed

    Ilić, Milica; Flockerzi, Dietrich; Seidel-Morgenstern, Andreas

    2010-04-01

    A competitive adsorption isotherm model is derived for binary mixtures of components characterized by single component isotherms which are second-order truncations of higher order equilibrium models suggested by multi-layer theory and statistical thermodynamics. The competitive isotherms are determined using the ideal adsorbed solution (IAS) theory which, in case of complex single component isotherms, does not generate explicit expressions to calculated equilibrium loadings and causes time consuming iterations in simulations of adsorption processes. The explicit model derived in this work is based on an analysis of the roots of a cubic polynomial resulting from the set of IAS equations. The suggested thermodynamically consistent and widely applicable competitive isotherm model can be recommended as a flexible tool for efficient simulations of fixed-bed adsorber dynamics.

  7. 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

  8. Study and numerical solution of a generalized mathematical model of isothermal adsorption

    SciTech Connect

    Komissarov, Yu.A.; Vetokhin, V.N.; Tsenev, V.A.; Gordeeva, E.L.

    1995-06-01

    A generalized mathematical model of isothermal adsorption that takes into account mass transfer on the surface of a particle, diffusion in micro- and macropores, and dispersion along the length of the apparatus is considered The parameters {lambda} and {var_phi}{sup 2} determine the dominating effect of any of the mass transfer mechanisms of the adsorption process. A numerical algorithm for solving the generalized adsorption model is suggested.

  9. Comparative adsorption isotherms and modeling of methylene blue onto activated carbons

    NASA Astrophysics Data System (ADS)

    Belhachemi, Meriem; Addoun, Fatima

    2011-12-01

    The adsorption of methylene blue (MB) on activated carbons prepared from date stones with different degree of activation has been investigated. Equilibrium adsorption data of MB was carried out at 298 K. Four isotherm models (Freundlich, Langmuir, Redlich-Peterson and Sips) were tested for modeling the adsorption isotherms by nonlinear method. The three-parameter equations (Redlich-Peterson and Sips) showed more applicability than the two-parameter equations (Freundlich and Langmuir), which can be explained by the fact that these have three adjustable parameters. The best fit was achieved with the Redlich-Peterson equation according to the high value of correlation coefficient. All the samples were capable of retaining the MB, with the best result being reached by the sample with higher burn-off. Date stones activated carbon showed high adsorption capacity of 460 mg/g, calculated from the Sips isotherm model.

  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. 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.

  12. Predicting heavy metals' adsorption edges and adsorption isotherms on MnO2 with the parameters determined from Langmuir kinetics.

    PubMed

    Hu, Qinghai; Xiao, Zhongjin; Xiong, Xinmei; Zhou, Gongming; Guan, Xiaohong

    2015-01-01

    Although surface complexation models have been widely used to describe the adsorption of heavy metals, few studies have verified the feasibility of modeling the adsorption kinetics, edge, and isotherm data with one pH-independent parameter. A close inspection of the derivation process of Langmuir isotherm revealed that the equilibrium constant derived from the Langmuir kinetic model, KS-kinetic, is theoretically equivalent to the adsorption constant in Langmuir isotherm, KS-Langmuir. The modified Langmuir kinetic model (MLK model) and modified Langmuir isotherm model (MLI model) incorporating pH factor were developed. The MLK model was employed to simulate the adsorption kinetics of Cu(II), Co(II), Cd(II), Zn(II) and Ni(II) on MnO2 at pH3.2 or 3.3 to get the values of KS-kinetic. The adsorption edges of heavy metals could be modeled with the modified metal partitioning model (MMP model), and the values of KS-Langmuir were obtained. The values of KS-kinetic and KS-Langmuir are very close to each other, validating that the constants obtained by these two methods are basically the same. The MMP model with KS-kinetic constants could predict the adsorption edges of heavy metals on MnO2 very well at different adsorbent/adsorbate concentrations. Moreover, the adsorption isotherms of heavy metals on MnO2 at various pH levels could be predicted reasonably well by the MLI model with the KS-kinetic constants.

  13. Characterization of nitrogen adsorption isotherms of thermally-treated organoclays using multifractal analysis

    NASA Astrophysics Data System (ADS)

    Lado, Marcos; Borisover, Mikhail; Paz-Gonzalez, Antonio

    2013-04-01

    Nitrogen adsorption isotherms of soils have been reported to exhibit multifractal behavior. In the present work, multifractal analysis is used to characterize changes in N2 adsorption isotherms of organoclays prepared with different cations and exposed to various thermal treatments. Wyoming bentonite was exchanged with benzyltrimethylammonium (BTMA-clay), tetraethylammonium (TEA-clay), and hexadecyltrimethylammonium exchanged at 41 and 90% of the cation exchange capacity of the clay (HDTMA41- and HDTMA90-clay). The resulting organoclays were exposed to temperatures ranging from 25 to 420°C during two hours, freeze-dried, and N2 adsorption isotherms were measured at 77°K. The obtained isotherms showed multifractal behavior, and parameters derived from Rényi and singularity spectra varied with changes in the organic cation and the treatment temperature. The type of cation was the dominant factor responsible for changes in spectra, and significant interactions were observed between type of cation and temperature for several parameters. Significant correlations were found between organic carbon content and multifractal parameters, indicating a relation between changes in N2 sorption sites and thermal transformations of the organic cations. Significant correlations were also found between some multifractal parameters and the heterogeneity exponent of a Freundlich model fitted to nitrobenzene isotherms measured in the organoclays, suggesting that multifractal analysis of N2 adsorption isotherms could be useful to analyze the heterogeneity of sorption sites when sorption determinations yield a limited amount of data.

  14. Adsorption of arsenite and arsenate onto ferrihydrite under competitive conditions : kinetics, isotherm, and pH effect

    NASA Astrophysics Data System (ADS)

    Qi, P.; Pichler, T.

    2014-12-01

    Competitive adsorption of As(III) and As(V) onto ferrihydrite was investigated in both single and bi-component systems using batch experiments. The adsorption of As(III) was inhibited by the presence of As(V) over the whole pH range when compared to As(III) only conditions. As(V) was adsorbed to a similar extent with As(III) at low pH under competitive conditions. Isotherm studies also showed that As(V) significantly decreased the adsorption of As(III) at pH 5, while the presence of As(III) had a small effect on As(V) adsorption. The Freundlich isotherm equation was successfully fitted to both single and bi-component adsorption scenarios of As(III) and As(V). At the same time intervals in the first 2 h under competitive conditions, kinetics studies suggested that the amount of As(III) adsorbed in the presence of As(V) was reduced compared to the single component system at low pH. The effect of As(III) on the adsorption rate of As(V) was negligible. A pseudo-second-order model could be fitted perfectly to each species under both single and competitive conditions. The spectra of ferrihydrite with adsorbed As(III), As(V) or both As species have a similar shape by ATR-FTIR, indicating that competition may be at play.

  15. Isothermal Adsorption Measurement for the Development of High Performance Solid Sorption Cooling System

    NASA Astrophysics Data System (ADS)

    Saha, Bidyut Baran; Koyama, Shigeru; Alam, K. C. Amanul; Hamamoto, Yoshinori; Akisawa, Atsushi; Kashiwagi, Takao; Ng, Kim Choon; Chua, Hui Tong

    Interest in low-grade thermal heat powered solid sorption system using natural refrigerants has been increased. However, the drawbacks of these adsorption systems are their poor performance. The objective of this paper is to improve the performance of thermally powered adsorption cooling system by selecting new adsorbent-refrigerant pairs. Adsorption capacity of adsorbent-refrigerant pair depends on the thermophysical properties (pore size, pore volume and pore diameter) of adsorbent and isothermal characteristics of the adsorbent-refrigerant pair. In this paper, the thermophysical properties of three types of silica gels and three types of pitch based activated carbon fibers are determined from the nitrogen adsorption isotherms. The standard nitrogen gas adsorption/desorption measurements on various adsorbents at liquid nitrogen of temperature 77.4 K were performed. Surface area of each adsorbent was determined by the Brunauer, Emmett and Teller (BET) plot of nitrogen adsorption data. Pore size distribution was measured by the Horvath and Kawazoe (HK) method. Adsorption/desorption isotherm results showed that all three carbon fibers have no hysteresis and had better adsorption capacity in comparison with those of silica gels.

  16. 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.

  17. 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.

  18. 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

  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.

  20. 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

  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.

  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. Rapid adsorption of copper(II) and lead(II) by rice straw/Fe₃O₄ nanocomposite: optimization, equilibrium isotherms, and adsorption kinetics study.

    PubMed

    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.

  4. 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.

  5. Electrochemically enhanced adsorption of nonylphenol on carbon nanotubes: Kinetics and isotherms study.

    PubMed

    Li, Xiaona; Chen, Shuo; Li, Liying; Quan, Xie; Zhao, Huimin

    2014-02-01

    Removal of nonylphenol (NP) from aqueous solution has attracted widely attention due to its aquatic toxicity and potential to disrupt the endocrine system. In an effort to develop the effective and environment-friendly treatment method for NP, adsorption of 4-n-nonylphenol (4-NP) on multi-walled carbon nanotubes (MWCNTs) under electrochemical assistance was studied. The adsorption kinetics and isotherms were investigated at different polarization potentials and compared with those of open circuit (OC) and powder MWCNTs adsorption. The adsorption kinetics was simulated by the model including pseudo-first-order model, pseudo-second-order model and intraparticle diffusion model. The isotherm was simulated with Langmuir model and Freudlich model, respectively. Experimental results indicated that 4-NP is able to be efficiently removed at a potential of -0.6V. Comparing with that of powder MWCNTs adsorption, the initial adsorption rate υ0 at -0.6V increased 7.9-fold according to pseudo-second-order model and the maximum adsorption capacity qm improved 1.7-fold according to Langmuir model. The improved adsorption effect at negative potential was ascribed to enhanced π-π electron-donor-acceptor (EDA) interaction between 4-NP and MWCNTs under electrochemical assistance.

  6. 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

  7. 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

  8. Evaluation of lead(II) immobilization by a vermicompost using adsorption isotherms and IR spectroscopy.

    PubMed

    Carrasquero-Durán, Armando; Flores, Iraima

    2009-02-01

    The immobilization of lead ions by a vermicompost with calcite added was evaluated by adsorption isotherms and the results were explained on basis of the pH dependent surface charge and by IR spectroscopy. The results showed maximum adsorption values between 113.6 mg g(-1) (33 degrees C) and 123.5mg g(-1) (50 degrees C). The point of zero net charge (PZC) was 7.5+/-0.1, indicating the presence of a positive surface charge at the pH of batch experiments. The differences in the IR spectra at pH 3.8 and 7.0 in the region from 1800 to 1300 cm(-1), were interpreted on the basis of the carboxyl acid ionization, that reduced the band intensity around 1725 cm(-1), producing signals at 1550 cm(-1) and 1390 cm(-1) of carboxylate groups. Similar changes were detected at pH 3.8 when Pb2+ was present suggesting that the ion complexation takes place by a cationic exchange equilibrium, between the protons and Pb2+ ions.

  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. 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

  11. 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.

  12. 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.

  13. Adsorption on heterogeneous surfaces: site energy distribution functions from Fritz-Schlüender isotherms.

    PubMed

    Kumar, Kannuchamy Vasanth; Monteiro de Castro, Mateus Carvalho; Martinez-Escandell, Manuel; Molina-Sabio, Miguel; Rodriguez-Reinoso, Francisco

    2010-08-23

    Different site energy distribution functions based on the condensation approximation method are proposed for the liquid-phase or gas-phase adsorption equilibrium data following the Fritz-Schlüender isotherm. Energy distribution functions for the four limiting cases of the Fritz-Schlüender isotherm are also discussed. The proposed models are successfully applied to the experimental equilibrium data of nitrogen molecules at 77 K on a pitch-based activated carbon (PA) and a pitch-based activated carbon containing boron (PBA). An energy distribution function based on FS isotherm containing five parameters suggest a unimodal distribution of binding sites for carbon PA, the binding site energies being distributed as exponential or unimodal, depending on the pressure, in the case of carbon PBA. The advantages of the proposed models are discussed.

  14. Chromatography Models with Langmuir and Steric Mass Action Adsorption Isotherms are of Differential Index One

    NASA Astrophysics Data System (ADS)

    von Lieres, Eric

    2010-09-01

    Chromatography is commonly applied for the separation of bio-molecules in pharmaceutical industry, and chromatography models are increasingly applied for rational process analysis and optimization. A rapid equilibrium assumption is often applied for the adsorption equation, which results in a non-linear system of partial differential-algebraic equations (PDAEs). In this contribution a proof is given, that these PDAEs are of differential index one for the two most prominent isotherm models, Langmuir and steric mass action (SMA).

  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. A regularization method for the reconstruction of adsorption isotherms in liquid chromatography

    NASA Astrophysics Data System (ADS)

    Zhang, Ye; Lin, Guang-Liang; Forssén, Patrik; Gulliksson, Mårten; Fornstedt, Torgny; Cheng, Xiao-Liang

    2016-10-01

    Determining competitive adsorption isotherms is an open problem in liquid chromatography. Since traditional experimental trial-and-error approaches are too complex and expensive, a modern technique of obtaining adsorption isotherms is to solve the inverse problem so that the simulated batch separation coincides with actual experimental results. This is a typical ill-posed problem. Moreover, in almost all cases the observed concentration at the outlet is the total response of all components, which makes the problem more difficult. In this work, we tackle the ill-posedness with a new regularization method, which is based on the fact that the adsorption isotherms do not depend on the injection profile. The proposed method transfers the original problem to an optimization problem with a time-dependent convection-diffusion equation constraint. Iterative algorithms for solving constraint optimization problems for both the equilibrium-dispersive and the transport-dispersive models are developed. The mass transfer resistance is also estimated by the proposed inverse method. A regularization parameter selection method and the convergence property of the proposed algorithm are discussed. Finally, numerical tests for both synthetic problems and real-world problems are given to show the efficiency and feasibility of the proposed regularization method.

  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.

  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. 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

  20. Suitability of adsorption isotherms for predicting the retention capacity of active slag filters removing phosphorus from wastewater.

    PubMed

    Pratt, C; Shilton, A

    2009-01-01

    Active slag filters are an emerging technology for removing phosphorus (P) from wastewater. A number of researchers have suggested that adsorption isotherms are a useful tool for predicting P retention capacity. However, to date the appropriateness of using isotherms for slag filter design remains unverified due to the absence of benchmark data from a full-scale, field filter operated to exhaustion. This investigation compared the isotherm-predicted P retention capacity of a melter slag with the P adsorption capacity determined from a full-scale, melter slag filter which had reached exhaustion after five years of successfully removing P from waste stabilization pond effluent. Results from the standard laboratory batch test showed that P adsorption correlated more strongly with the Freundlich Isotherm (R(2)=0.97, P<0.01) than the Langmuir Isotherm, a similar finding to previous studies. However, at a P concentration of 10 mg/L, typical of domestic effluent, the Freundlich equation predicted a retention capacity of 0.014 gP/kg slag; markedly lower than the 1.23 gP/kg slag adsorbed by the field filter. Clearly, the result generated by the isotherm bears no resemblance to actual field capacity. Scanning electron microscopy analysis revealed porous, reactive secondary minerals on the slag granule surfaces from the field filter which were likely created by weathering. This slow weathering effect, which generates substantial new adsorption sites, is not accounted for by adsorption isotherms rendering them ineffective in slag filter design. PMID:19403982

  1. Valorization of agricultural wastes as dye adsorbents: characterization and adsorption isotherms.

    PubMed

    Sepúlveda, Luisa A; Cuevas, Fernando A; Contreras, Elsa G

    2015-01-01

    The purpose of this work is to evaluate the valorization of agricultural waste, wheat straw (WS) and corn cob leaves (CCLs) as textile dye adsorbents. Physico-chemical and superficial characteristics of the agricultural wastes, together with the interactions with the CI Basic Violet 4 (BV4) dye, were investigated by means of the determination of the isotherm adsorption at different temperatures. The morphological characterization showed that the solid surface is coarse with a low pore level. However, through Fourier transformed infrared analysis, the presence of carboxylic and hydroxylic acid groups and hydrophobic methyl groups was detected. The concentration of acid groups is determined by the Boehm method and was found to be 1.00 and 0.89 meq/g for WS and CCLs, respectively. The point zero charge for each adsorbent was 5.76 and 4.08. Adsorption experimental data presented a better-fit Langmuir model, indicating that adsorption occurred in a monolayer with preferential interaction. The maximum adsorption capacity was determined to be 70.0-89.0 and 47.0-68.0 mg/g for CCLs and WS, respectively. The thermodynamic analysis of the Langmuir parameter b showed that the adsorption of the BV4 dye is spontaneous and exothermic with adsorption energies of 14.43 and 5.58 KJ/mol for CCLs and WS, respectively.

  2. Valorization of agricultural wastes as dye adsorbents: characterization and adsorption isotherms.

    PubMed

    Sepúlveda, Luisa A; Cuevas, Fernando A; Contreras, Elsa G

    2015-01-01

    The purpose of this work is to evaluate the valorization of agricultural waste, wheat straw (WS) and corn cob leaves (CCLs) as textile dye adsorbents. Physico-chemical and superficial characteristics of the agricultural wastes, together with the interactions with the CI Basic Violet 4 (BV4) dye, were investigated by means of the determination of the isotherm adsorption at different temperatures. The morphological characterization showed that the solid surface is coarse with a low pore level. However, through Fourier transformed infrared analysis, the presence of carboxylic and hydroxylic acid groups and hydrophobic methyl groups was detected. The concentration of acid groups is determined by the Boehm method and was found to be 1.00 and 0.89 meq/g for WS and CCLs, respectively. The point zero charge for each adsorbent was 5.76 and 4.08. Adsorption experimental data presented a better-fit Langmuir model, indicating that adsorption occurred in a monolayer with preferential interaction. The maximum adsorption capacity was determined to be 70.0-89.0 and 47.0-68.0 mg/g for CCLs and WS, respectively. The thermodynamic analysis of the Langmuir parameter b showed that the adsorption of the BV4 dye is spontaneous and exothermic with adsorption energies of 14.43 and 5.58 KJ/mol for CCLs and WS, respectively. PMID:25655393

  3. Water adsorption isotherms of carboxymethyl cellulose, guar, locust bean, tragacanth and xanthan gums.

    PubMed

    Torres, María D; Moreira, Ramón; Chenlo, Francisco; Vázquez, María J

    2012-06-20

    Water adsorption isotherms of carboxymethyl cellulose (CMC), guar gum (GG), locust bean gum (LBG), tragacanth gum (TG) and xanthan gum (XG) were determined at different temperatures (20, 35, 50, and 65°C) using a gravimetric method. Several saturated salt solutions were selected to obtain different water activities in the range from 0.09 to 0.91. Water adsorption isotherms of tested hydrocolloids were classified like type II isotherms. In all cases, equilibrium moisture content decreased with increasing temperature at each water activity value. Three-parameter Guggenheim-Anderson-de Boer (GAB) model was employed to fit the experimental data in the water activity range and statistical analysis indicated that this model gave satisfactory results. CMC and GG were the most and the least hygroscopic gums, respectively. Sorption heats decreased with increasing moisture content. Monolayer moisture content evaluated with GAB model was consistent with equilibrium conditions of maximum stability calculated from thermodynamic analysis of net integral entropy. Values of equilibrium relative humidity at 20°C are proposed to storage adequately the tested gums.

  4. 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.

  5. 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

  6. Modeling Nonlinear Adsorption to Carbon with a Single Chemical Parameter: A Lognormal Langmuir Isotherm.

    PubMed

    Davis, Craig Warren; Di Toro, Dominic M

    2015-07-01

    Predictive models for linear sorption of solutes onto various media, e.g., soil organic carbon, are well-established; however, methods for predicting parameters for nonlinear isotherm models, e.g., Freundlich and Langmuir models, are not. Predicting nonlinear partition coefficients is complicated by the number of model parameters to fit n isotherms (e.g., Freundlich (2n) or Polanyi-Manes (3n)). The purpose of this paper is to present a nonlinear adsorption model with only one chemically specific parameter. To accomplish this, several simplifications to a log-normal Langmuir (LNL) isotherm model with 3n parameters were explored. A single sorbate-specific binding constant, the median Langmuir binding constant, and two global sorbent parameters; the total site density and the standard deviation of the Langmuir binding constant were employed. This single-solute specific (ss-LNL) model (2 + n parameters) was demonstrated to fit adsorption data as well as the 2n parameter Freundlich model. The LNL isotherm model is fit to four data sets composed of various chemicals sorbed to graphite, charcoal, and activated carbon. The RMS errors for the 3-, 2-, and 1-chemical specific parameter models were 0.066, 0.068, 0.069, and 0.113, respectively. The median logarithmic parameter standard errors for the four models were 1.070, 0.4537, 0.382, and 0.201 respectively. Further, the single-parameter model was the only model for which there were no standard errors of estimated parameters greater than a factor of 3 (0.50 log units). The surprising result is that very little decrease in RMSE occurs when two of the three parameters, σκ and qmax, are sorbate independent. However, the large standard errors present in the other models are significantly reduced. This remarkable simplification yields the single sorbate-specific parameter (ss-LNL) model. PMID:26035092

  7. Modeling Nonlinear Adsorption to Carbon with a Single Chemical Parameter: A Lognormal Langmuir Isotherm.

    PubMed

    Davis, Craig Warren; Di Toro, Dominic M

    2015-07-01

    Predictive models for linear sorption of solutes onto various media, e.g., soil organic carbon, are well-established; however, methods for predicting parameters for nonlinear isotherm models, e.g., Freundlich and Langmuir models, are not. Predicting nonlinear partition coefficients is complicated by the number of model parameters to fit n isotherms (e.g., Freundlich (2n) or Polanyi-Manes (3n)). The purpose of this paper is to present a nonlinear adsorption model with only one chemically specific parameter. To accomplish this, several simplifications to a log-normal Langmuir (LNL) isotherm model with 3n parameters were explored. A single sorbate-specific binding constant, the median Langmuir binding constant, and two global sorbent parameters; the total site density and the standard deviation of the Langmuir binding constant were employed. This single-solute specific (ss-LNL) model (2 + n parameters) was demonstrated to fit adsorption data as well as the 2n parameter Freundlich model. The LNL isotherm model is fit to four data sets composed of various chemicals sorbed to graphite, charcoal, and activated carbon. The RMS errors for the 3-, 2-, and 1-chemical specific parameter models were 0.066, 0.068, 0.069, and 0.113, respectively. The median logarithmic parameter standard errors for the four models were 1.070, 0.4537, 0.382, and 0.201 respectively. Further, the single-parameter model was the only model for which there were no standard errors of estimated parameters greater than a factor of 3 (0.50 log units). The surprising result is that very little decrease in RMSE occurs when two of the three parameters, σκ and qmax, are sorbate independent. However, the large standard errors present in the other models are significantly reduced. This remarkable simplification yields the single sorbate-specific parameter (ss-LNL) model.

  8. 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

  9. 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.

  10. A site energy distribution function from Toth isotherm for adsorption of gases on heterogeneous surfaces.

    PubMed

    Kumar, K Vasanth; de Castro, M Monteiro; Martinez-Escandell, M; Molina-Sabio, M; Rodriguez-Reinoso, F

    2011-04-01

    A site energy distribution function based on a condensation approximation method is proposed for gas-phase adsorption systems following the Toth isotherm. The proposed model is successfully applied to estimate the site energy distribution of three pitch-based activated carbons (PA, PFeA and PBA) developed in our laboratory and also for other common adsorbent materials for different gas molecules. According to the proposed model the site energy distribution curves of the activated carbons are found to be exponential for hydrogen at 77 K. The site energy distribution of some of the activated carbon fibers, ambersorb, Dowex optipore, 13X Zeolite for different adsorbate molecules represents a quasi-Gaussian curve with a widened left hand side, indicating that most sites have adsorption energies lower than a statistical mean value.

  11. 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

  12. 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.

  13. 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.

  14. How soil organic matter composition controls hexachlorobenzene-soil-interactions: adsorption isotherms and quantum chemical modeling.

    PubMed

    Ahmed, Ashour A; Kühn, Oliver; Aziz, Saadullah G; Hilal, Rifaat H; Leinweber, Peter

    2014-04-01

    Hazardous persistent organic pollutants (POPs) interact in soil with the soil organic matter (SOM) but this interaction is insufficiently understood at the molecular level. We investigated the adsorption of hexachlorobenzene (HCB) on soil samples with systematically modified SOM. These samples included the original soil, the soil modified by adding a hot water extract (HWE) fraction (soil+3 HWE and soil+6 HWE), and the pyrolyzed soil. The SOM contents increased in the order pyrolyzed soiladsorption. The pyrolyzed soil adsorbed more HCB than the other samples at low initial concentrations, but at higher concentrations the HCB adsorption became weaker than in the samples with HWE addition. This adsorption combined with the differences in the chemical composition between the soil samples suggested that alkylated aromatic, phenol, and lignin monomer compounds contributed most to the HCB adsorption. To obtain a molecular level understanding, a test set has been developed on the basis of elemental analysis which comprises 32 representative soil constituents. The calculated binding energy for HCB with each representative system shows that HCB binds to SOM stronger than to soil minerals. For SOM, HCB binds to alkylated aromatic, phenols, lignin monomers, and hydrophobic aliphatic compounds stronger than to polar aliphatic compounds confirming the above adsorption isotherms. Moreover, quantitative structure-activity relationship (QSAR) of the binding energy with independent physical properties of the test set systems for the first time indicated that the polarizability, the partial charge on the carbon atoms, and the molar volume are the most important properties controlling HCB-SOM interactions.

  15. Multiscale analysis of nitrogen adsorption and desorption isotherms in soils developed over sandstone and basic parent materials with contrasting texture

    NASA Astrophysics Data System (ADS)

    Paz-Ferreiro, Jorge; Marinho, Mara de A.; de Abreu, Cleide A.

    2014-05-01

    Mono- and multifractal analysis of soil nitrogen adsorption isotherms (NAI) have been proven to be useful, allowing a better characterization of soil surface properties and soil porous system. Multiscale analysis of nitrogen desorption isotherms (NDI), which was less frequently performed, can also provide very valuable information. The multifractal theory was used to analyse both soil adsorption and desorption isotherms from soils developed over contrasting parent material and with different texture. We sampled 32 soil horizons from 6 soil profiles in neighbouring sites from São Paulo State, Brazil. Three of the profiles, developed over sandstone, were sandy loam or loamy, whereas the other three profiles, developed over weathered sediments or basic parent material, were clayey textured. Soil specific surface area (SSA) varied, from about 3.0 to 46 m2 g-1. Surface parameters showed a strong correlation with clay content, but they were not correlated with cation exchange capacity (CEC). The scaling properties of both nitrogen adsorption and desorption isotherms from all the studied soil horizons could be fitted reasonably well with multifractal models. Multifractal parameters from NAIs and NDIs showed great differences. The singularity spectra, f(α) of the desorption isotherms had an asymmetrically long left part and its asymmetry was in general higher compared with adsorption isotherms. Moreover, adsorption isotherms behaved like more clustered measures, showing lower entropy dimension, D1, smaller correlation dimension, D2, and higher heterogeneity than desorption isotherms. Differences in multifractal behaviour of NAIs and NDIs had been proven to be mainly related to the characteristics of the hysteretic loop measured at high relative pressures. Several multifractal parameters extracted from NAIs and NDIs also distinguished between sandy-loam and loam soils and clayey soils. Multifractal parameters calculated from NAIs and NDIs provide new insight to assess

  16. Modeling and CFD prediction for diffusion and adsorption within room with various adsorption isotherms.

    PubMed

    Murakami, S; Kato, S; Ito, K; Zhu, Q

    2003-01-01

    This paper presents physical models that are used for analyzing numerically the transportation of volatile organic compounds (VOCs) from building materials in a room. The models are based on fundamental physicochemical principles of their diffusion and adsorption/desorption (hereafter simply sorption) both in building materials and in room air. The performance of the proposed physical models is examined numerically in a test room with a technique supported by computational fluid dynamics (CFD). Two building materials are used in this study. One is a VOC emitting material for which the emission rate is mainly controlled by the internal diffusion of the material. The other is an adsorptive material that has no VOC source. It affects the room air concentration of VOCs with its sorption process. The floor is covered with an emission material made of polypropylene styrene-butadiene rubber (SBR). An adsorbent material made of coal-based activated carbon is spread over the sidewalls. The results of numerical prediction show that the physical models and their numerical simulations explain well the mechanism of the transportation of VOCs in a room.

  17. 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.

  18. Effect of 300 and 500 MPa pressure treatments on starch-water adsorption/desorption isotherms and hysteresis

    NASA Astrophysics Data System (ADS)

    Santos, Mauro D.; Cunha, Pedro; Queirós, Rui P.; Fidalgo, Liliana G.; Delgadillo, Ivonne; Saraiva, Jorge A.

    2014-10-01

    Pressure treatments of 300 and 500 MPa during 15 min were found to change starch-water sorption (adsorption and desorption) isotherms and the hysteresis effect, particularly the 500 MPa. This last treatment shifted the adsorption/desorption isotherms downward, compared with non-treated starch and starch treated at 300 MPa. The observed hysteresis effect decreased with the increase in pressure level in the whole aw range, indicating that adsorption and desorption isotherms became closer. Guggenheim-Anderson-De Boer and Brunauer-Emmett-Teller model parameters Cb, Cg, K and Mm also showed changes caused by pressure, the latter being lower in the pressure-processed samples, thus indicating possible changes on microbial and (bio)chemical stabilities of pressure-processed food products containing starch.

  19. Evaluation of gaseous fluorocarbon adsorption isotherms on porous adsorbents under high pressure

    SciTech Connect

    Kaliappan, S.; Furuya, E.G.; Noll, K.E.; Chang, H.T.; Wang, H.C.

    1996-11-01

    In this study data have been collected to aid in the design of a control system that will remove fluorocarbons by adsorbing onto porous adsorbents. A bench scale experimental adsorption system had been designed using high accuracy MKS pressure transducers of 10,000 torr (two nos.) and a 100 torr connected to digital readout units. Tetrafluoromethane (CF{sub 4}) one of the fluorinated carbon family has been selected to evaluate the adsorption characteristics on porous adsorbents. The CF{sub 4} was charged to a sample reservoir in the test system at 200 psig pressure and at 22 C was allowed into an adsorption chamber at small increment of pressure rise. The pressure drop, using a Valydine PS 309 differential pressure gauge from the sample reservoir and the pressure buildup in the adsorption chamber were measured and the amount of CF{sub 4} adsorbed onto the adsorbents was calculated using ideal gas law. Various adsorbents, molecular sieve 13X, Silicagel (14 x 20), Beads Activated Carbon, Granular Activated Carbons PCB 6 x 16, BPL 4 x 10, F300, and F400 had been studied. It has been found that GAC-PCB 6 x 16 has the highest adsorbing capacity of 0.51 gm/gm at the conditions established. GAC-F300 had the second highest adsorbing capacity of 0.413 gm/gm, among all the adsorbents tested. The isotherms were analyzed using several equations employing both two parameters and three parameters. The relationship between the constants and physical properties of adsorbent solids and adsorbate molecules is discussed. The result of this study will be utilized to design a pressure swing fluorocarbon adsorption system that can be economically (using recycle of the collected fluorocarbons) applied to fluorocarbon removal in the electronic industry.

  20. 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

  1. 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

  2. Adsorption of methylene blue onto poly(cyclotriphosphazene-co-4,4'-sulfonyldiphenol) nanotubes: kinetics, isotherm and thermodynamics analysis.

    PubMed

    Chen, Zhonghui; Zhang, Jianan; Fu, Jianwei; Wang, Minghuan; Wang, Xuzhe; Han, Runping; Xu, Qun

    2014-05-30

    Poly(cyclotriphosphazene-co-4,4'-sulfonyldiphenol) (PZS) nanotubes, an excellent adsorbent, were successfully synthesized by an in situ template method and used for the removal of methylene blue (MB) from aqueous solution. The morphology and structures of as-synthesized PZS nanotubes were characterized by scanning electron microscopy, transmission electron microscope, Fourier transform infrared spectroscopy and N2 adsorption/desorption isotherms. The effects of temperature, concentration, pH and contact time on MB adsorption were studied. It was favorable for adsorption under the condition of basic and high temperature. The pseudo-first-order, pseudo-second-order and intraparticle diffusion models were used to fit adsorption data in the kinetic studies. And results showed that the adsorption kinetics were more accurately described by the pseudo-second-order model. The equilibrium isotherms were conducted using Freundlich and Langmuir models. It has been demonstrated that the better agreement was Langmuir isotherm with correlation coefficient of 0.9933, equilibrium absorption capacity of 69.16mg/g and the corresponding contact time of 15min. Thermodynamic analyses showed that MB adsorption onto the PZS nanotubes was endothermic and spontaneous and it was also a physisorption process.

  3. 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

  4. 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.

  5. 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.

  6. 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

  7. Dextran-grafted cation exchanger based on superporous agarose gel: adsorption isotherms, uptake kinetics and dynamic protein adsorption performance.

    PubMed

    Shi, Qing-Hong; Jia, Guo-Dong; Sun, Yan

    2010-07-30

    A novel chromatographic medium for high-capacity protein adsorption was fabricated by grafting dextran (40kDa) onto the pore surfaces of superporous agarose (SA) beads. The bead was denoted as D-SA. D-SA, SA and homogeneous agarose (HA) beads were modified with sulfopropyl (SP) group to prepare cation exchangers, and the adsorption and uptake of lysozyme on all three cation-exchange chromatographic beads (SP-HA, SP-SA and SP-D-SA) were investigated at salt concentrations of 6-50mmol/L. Static adsorption experiments showed that the adsorption capacity of SP-D-SA (2.24mmol/g) was 78% higher than that of SP-SA (1.26mmol/g) and 54% higher than that of SP-HA (1.45mmol/g) at a salt concentration of 6mmol/L. Moreover, salt concentration had less influence on the adsorption capacity and dissociation constant of SP-D-SA than it did on SP-HA, suggesting that dextran-grafted superporous bead is a more potent architecture for chromatographic beads. In the dynamic uptake of lysozyme to the three cation-exchange beads, the D(e)/D(0) (the ratio of effective pore diffusivity to free solution diffusivity) values of 1.6-2.0 were obtained in SA-D-SA, indicating that effective pore diffusivities of SP-D-SA were about two times higher than free solution diffusivity for lysozyme. At 6mmol/L NaCl, the D(e) value in SA-D-SA (22.0x10(-11)m(2)/s) was 14.4-fold greater than that in SP-HA. Due to the superior uptake kinetics in SA-D-SA, the highest dynamic binding capacity (DBC) and adsorption efficiency (the ratio of DBC to static adsorption capacity) was likewise found in SP-D-SA. It is thus confirmed that SP-D-SA has combined the advantages of superporous matrix structure and drafted ligand chemistry in mass transport and offers a new opportunity for the development of high-performance protein chromatography.

  8. 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.

  9. Optimizing available phosphorus in calcareous soils fertilized with diammonium phosphate and phosphoric acid using Freundlich adsorption isotherm.

    PubMed

    Naeem, Asif; Akhtar, Muhammad; Ahmad, Waqar

    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 = aC(b/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

  10. 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

  11. 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

  12. 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.

  13. 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.

  14. Kinetics and isothermal modeling of liquid phase adsorption of rhodamine B onto urea modified Raphia hookerie epicarp

    NASA Astrophysics Data System (ADS)

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

    2016-09-01

    Epicarp of Raphia hookerie, a bioresource material, was modified with urea (UMRH) to adsorb Rhodamine B (RhB) from aqueous solution. Adsorbent morphology and surface chemistry were established by Brunauer-Emmett-Teller (BET) surface area determination, Fourier transform infrared spectroscopic (FTIR) analysis, scanning electron microscopy (SEM), as well as the pH point of zero charge (pHpzc) determination. Prepared material was subsequently utilized for the uptake of Rhodamine B (RhB). Operational parameters, such as adsorbent dosage, concentration, time, and temperature, were investigated. Evidence of effective urea modification was confirmed by vivid absorption bands at 1670 and 1472 cm-1 corresponding to C=O and C-N stretching vibrations, respectively. Optimum adsorption was obtained at pH 3. Freundlich adsorption isotherm best fits the equilibrium adsorption data, while evidence of adsorbate-adsorbate interaction was revealed by Temkin isotherm model. The maximum monolayer adsorption capacity (q max) was 434.78 mg/g. Kinetics of the adsorption process was best described by the pseudo-second-order kinetics model. Desorption efficiency was less than or equal to 25 % for all the eluents, and it follows the order HCl > H2O > CH3COOH.

  15. 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

  16. 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.

  17. Ab initio prediction of adsorption isotherms for small molecules in metal-organic frameworks: the effect of lateral interactions for methane/CPO-27-Mg.

    PubMed

    Sillar, Kaido; Sauer, Joachim

    2012-11-01

    A hybrid method that combines density functional theory for periodic structures with wave function-based electron correlation methods for finite-size models of adsorption sites is employed to calculate energies for adsorption of CH(4) onto different sites in the metal-organic framework (MOF) CPO-27-Mg (Mg-MOF-74) with chemical accuracy. The adsorption energies for the Mg(2+), linker, second layer sites are -27.8, -18.3, and -15.1 kJ/mol. Adsorbate-adsorbate interactions increase the average CH(4) adsorption energy by about 10% (2.4 kJ/mol). The free rotor-harmonic oscillator-ideal gas model is applied to calculate free energies/equilibrium constants for adsorption on the individual sites. This information is used in a multisite Langmuir model, augmented with a Bragg-Williams model for lateral interactions, to calculate adsorption isotherms. This ab initio approach yields the contributions of the individual sites to the final isotherms and also of the lateral interactions that contribute about 15% to the maximum excess adsorption capacity. Isotherms are calculated for both absolute amounts, for calculation of isosteric heats of adsorption as function of coverage, and excess amounts, for comparison with measured isotherms. Agreement with observed excess isotherms is reached if the experimentally determined limited accessibility of adsorption sites (78%) is taken into account.

  18. 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.

  19. Kinetic and isotherm error optimization studies for adsorption of atrazine and imidacloprid on bark of Eucalyptus tereticornis L.

    PubMed

    Mandal, Abhishek; Singh, Neera

    2016-01-01

    The aim of this study was to establish the bark of Eucalyptus tereticornis L. (EB) as a low cost bio-adsorbent for the removal of imidacloprid and atrazine from aqueous medium. The pseudo-first-order (PFO), pseudo-second-order (PSO), Elovich and intra-particle diffusion (IPD) models were used to describe the kinetic data and rate constants were evaluated. Adsorption data was analysed using ten 2-, 3- and 4-parameter models viz. Freundlich, Jovanovic, Langmuir, Temkin, Koble-Corrigan, Redlich-Peterson, Sips, Toth, Radke-Prausnitz, and Fritz-Schluender isotherms. Six error functions were used to compute the best fit single component isotherm parameters by nonlinear regression analysis. The results showed that the sorption of atrazine was better explained by PSO model, whereas the sorption of imidacloprid followed the PFO kinetic model. Isotherm model optimization analysis suggested that the Freundlich along with Koble-Corrigan, Toth and Fritz-Schluender were the best models to predict atrazine and imidacloprid adsorption onto EB. Error analysis suggested that minimization of chi-square (χ(2)) error function provided the best determination of optimum parameter sets for all the isotherms.

  20. Competitive adsorption and selectivity sequence of heavy metals by chicken bone-derived biochar: Batch and column experiment.

    PubMed

    Park, Jong-Hwan; Cho, Ju-Sik; Ok, Yong Sik; Kim, Seong-Heon; Kang, Se-Won; Choi, Ik-Won; Heo, Jong-Soo; DeLaune, Ronald D; Seo, Dong-Cheol

    2015-01-01

    The objective of this research was to evaluate adsorption of heavy metals in single- and ternary-metal forms onto chicken bone biochar (CBB). Competitive sorption of heavy metals by CBB has never been reported previously. The maximum adsorption capacities of metals by CBB were in the order of Cu (130 mg g(-1)) > Cd (109 mg g(-1)) > Zn (93 mg g(-1)) in the single-metal adsorption isotherm and Cu (108 mg g(-1)) > Cd (54 mg g(-1)) ≥ Zn (44 mg g(-1)) in the ternary-metal adsorption isotherm. Cu was the most retained cation, whereas Zn could be easily exchanged and substituted by Cu. Batch experimental data best fit the Langmuir model rather than the Freundlich isotherms. In the column experiments, the total adsorbed amounts of the metals were in the following order of Cu (210 mg g(-1)) > Cd (192 mg g(-1)) > Zn (178) in single-metal conditions, and Cu (156) > Cd (123) > Zn (92) in ternary-metal conditions. Results from both the batch and column experiments indicate that competitive adsorption among metals increases the mobility of these metals. Especially, Zn in single-metal conditions lost it adsorption capacity most significantly. Based on the 3D simulation graphs of heavy metals, adsorption patterns under single adsorption condition were different than under competitive adsorption condition. Results from both the batch and column experiments show that competitive adsorption among metals increases the mobility of these metals. The maximum metal adsorption capacity of the metals in the column experiments was higher than that in the batch experiment indicating other metal retention mechanisms rather than adsorption may be involved. Therefore, both column and batch experiments are needed for estimating retention capacities and removal efficiencies of metals in CBB.

  1. Temperature dependence of adsorption of PEGylated lysozyme and pure polyethylene glycol on a hydrophobic resin: comparison of isothermal titration calorimetry and van't Hoff data.

    PubMed

    Werner, Albert; Hackemann, Eva; Hasse, Hans

    2014-08-22

    The influence of temperature on the adsorption of PEGylated lysozyme and pure PEG on Toyopearl PPG-600M, a hydrophobic resin, is studied by batch equilibrium measurements and pulse response experiments. Differently PEGylated lysozymes are used for the studies, enabling a systematic variation of the solute properties. Either ammonium sulfate or sodium chloride are added. The enthalpy of adsorption is calculated from a van't Hoff analysis based on these data. It is also directly measured by Isothermal Titration Calorimetry. In the investigated temperature range from 5 °C to 35 °C adsorption is favored by higher temperatures and hence endothermic. The results of the van't Hoff analysis of the equilibrium and the pulse response data agree well. Discrepancies between enthalpies of adsorption obtained by calorimetry and van't Hoff analysis are found and discussed. We conclude that the most likely explanation is that thermodynamic equilibrium is not reached in the experiments even though they were carried out carefully and in the generally accepted way.

  2. 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.

  3. 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.

  4. 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

  5. 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

  6. Kinetic and isotherm modeling of Cd (II) adsorption by L-cysteine functionalized multi-walled carbon nanotubes as adsorbent.

    PubMed

    Taghavi, Mahmoud; Zazouli, Mohammad Ali; Yousefi, Zabihollah; Akbari-adergani, Behrouz

    2015-11-01

    In this study, multi-walled carbon nanotubes were functionalized by L-cysteine to show the kinetic and isotherm modeling of Cd (II) ions onto L-cysteine functionalized multi-walled carbon nanotubes. The adsorption behavior of Cd (II) ion was studied by varying parameters including dose of L-MWCNTs, contact time, and cadmium concentration. Equilibrium adsorption isotherms and kinetics were also investigated based on Cd (II) adsorption tests. The results showed that an increase in contact time and adsorbent dosage resulted in increase of the adsorption rate. The optimum condition of the Cd (II) removal process was found at pH=7.0, 15 mg/L L-MWCNTs dosage, 6 mg/L cadmium concentration, and contact time of 60 min. The removal percent was equal to 89.56 at optimum condition. Langmuir and Freundlich models were employed to analyze the experimental data. The data showed well fitting with the Langmuir model (R2=0.994) with q max of 43.47 mg/g. Analyzing the kinetic data by the pseudo-first-order and pseudo-second-order equations revealed that the adsorption of cadmium using L-MWSNTs following the pseudo-second-order kinetic model with correlation coefficients (R2) equals to 0.998, 0.992, and 0.998 for 3, 6, and 9 mg/L Cd (II) concentrations, respectively. The experimental data fitted very well with the pseudo-second-order. Overall, treatment of polluted solution to Cd (II) by adsorption process using L-MWCNT can be considered as an effective technology.

  7. 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...

  8. 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.

  9. Adsorption mechanism of sodium dodecyl benzene sulfonate on carbon blacks by adsorption isotherm and zeta potential determinations.

    PubMed

    Zhao, Yapei; Lu, Pei; Li, Caiting; Fan, Xiaopeng; Wen, Qingbo; Zhan, Qi; Shu, Xin; Xu, Tieliang; Zeng, Guangming

    2013-01-01

    Surfactant solutions were propounded to remove fine and hydrophobic carbon black particles from coal-fired flue gas. The adsorption mechanisms between sodium dodecyl benzene sulfonate (SDBS, an anionic surfactant) and carbon black particles in suspension were investigated. The influence of inorganic salt (NaCl) was also considered. As results showed, hydrophobic interactions contributed to the strong adsorption between SDBS and carbon black particles in the absence of NaCl, and adding NaCl affected the adsorption process. The adsorption amount of SDBS significantly increased when NaCl was added into the SDBS solution; however, when SDBS was in low concentration, the amount of adsorbed SDBS, which was responsible for the shift of zeta potentials, varied little under different concentrations of NaCl. This indicated that the adsorption of SDBS was mainly caused by hydrophobic interaction and Na+ could not change the adsorption of SDBS on adsorption site when SDBS was in low concentration. Moreover, the adsorbed SDBS and Na+ were retained in the Stern layer. PMID:23530331

  10. 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.

  11. Determination of adsorption isotherm parameters for minor whey proteins by gradient elution preparative liquid chromatography.

    PubMed

    Faraji, Naeimeh; Zhang, Yan; Ray, Ajay K

    2015-09-18

    Ion-Exchange Chromatography (IEC) techniques have been extensively investigated in protein purification processes, due to the more selective and milder separation steps. To date, existing studies of minor whey proteins fractionation in IEC have primarily been conducted as batch uptake studies, which require more experimental search space, time and materials. In this work, the selected resin's (SP Sepharose FF) equilibrium and dynamic binding capacity were first investigated. Next, adsorption of the pure binary mixture of lactoperoxidase and lactoferrin was studied to calibrate steric mass action (SMA) model using a simplified approach with data from single column experiments. The calibrated model was then verified by performing factorial-design based experiments for various process operating conditions assessing process performance on a larger bed height column. The model predicted results demonstrated a realistic agreement with the experiments providing reproducible column elution profile and reduced experimental work. Finally, whey protein isolate was used to evaluate model parameters in real conditions. Results obtained herein are suitable for future large scale applications.

  12. 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…

  13. Hemoglobin adsorption isotherm at the silica-water interface with evanescent wave cavity ring-down spectroscopy.

    PubMed

    Martin, W Blake; Mirov, Sergey; Martyshkin, Dmitri; Venugopalan, Ramakrishna; Shaw, Andrew M

    2005-01-01

    Evanescent wave cavity ring-down spectroscopy (EW-CRDS) is used to observe the adsorption isotherm for hemoglobin (Hb) from controlled urine samples to assess the potential for rapid diagnosis in hemoglobinuria. The absorbance of Hb at 425 nm is monitored using an alexandrite laser-pumped, room temperature, LiF:F2+** color-center pulsed laser. A minimum absorbance detection level of 2.57 x 10(-4) is achieved, corresponding to a minimum detectable concentration of Hb in urea of 5.8 nM. A multilayered Hb biofilm is formed, and a minimum of eight layers are required to model the adsorption isotherm, allowing for cooperative binding within the layers and extending 56 nm into the interface. A binding constant for Hb to silica 18.23+/-7.58 x 10(6) M is derived, and a binding constant for Hb to Hb in subsequent layers is determined to be 5.631+/-0.432 x 10(5) M. Stoichiometric binding coefficients of 1.530+/-0.981 for layer one and 1.792+/-0.162 for subsequent layers suggest that cooperative binding both to the silica surface and between the layers of the biofilm is important.

  14. 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.

  15. 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

  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.

  17. 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

  18. 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.

  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. 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...

  1. 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

  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.

  3. Predicting Phase Diagram of the CaCl2-H2O Binary System from the BET Adsorption Isotherm

    SciTech Connect

    Ally, Moonis Raza

    2008-01-01

    A recent publication in Fluid Phase Equilibria by Zeng (Zeng, Zhou et al. 2007) claimed remarkable accuracy in predicting the solubility of CaCl2-H2O solutions with the Brunaruer-Emett-Teller (BET) model parameters. Their approach necessarily requires prior knowledge of equilibrium water vapor pressures above saturated solutions as a function of temperature for the hydrates of CaCl2 that exist under those conditions. However, the intrinsic BET model does not require prior knowledge of such solubility data that the approach of (Zeng, Zhou et al. 2007) is dependent upon. This paper highlights the differences between the two approaches and covers a much wider range of compositions and temperatures than is done by (Zeng, Zhou et al. 2007). The statistical mechanical description of multilayer adsorption culminating in the BET adsorption isotherm for aqueous electrolytes as developed by Ally and Braunstein (Ally and Braunstein 1993) is used to predict the liquidus behavior of CaCl2-H2O across the entire composition range (from the melting point of pure water to the melting point of anhydrous calcium chloride), including possible metastable crystalline phases. The method requires as input the two BET parameters r, the statistically averaged number of adsorption sites and ε, the energy of adsorption of water in excess of the energy of condensation of pure water. Usually it suffices to keep r and ε constant, typically evaluated at 298.15 K, but in the case of CaCl2-H2O, it is found that both r and ε must be considered temperature dependent in order to predict the liquidus curve, eutectic and peritectic points with reasonable accuracy over the large temperature and compositional range for this binary system.

  4. 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.

  5. 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.

  6. 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

  7. Isotherm, kinetic, and thermodynamic studies on Hg(II) adsorption from aqueous solution by silica- multiwall carbon nanotubes.

    PubMed

    Saleh, Tawfik A

    2015-11-01

    Silica combined with 2% multiwall carbon nanotubes (SiO2-CNT) was synthesized and characterized. Its sorption efficacy was investigated for the Hg(II) removal from an aqueous solution. The effect of pH on the percentage removal by the prepared material was examined in the range from 3 to 7. The adsorption kinetics were well fitted by using a pseudo-second-order model at various initial Hg(II) concentrations with R (2) of >0.99. The experimental data were plotted using the interparticle diffusion model, which indicated that the interparticle diffusion is not the only rate-limiting step. The data is well described by the Freundlich isotherm equation. The activation energy (Ea) for adsorption was 12.7 kJ mol(-1), indicating the process is to be physisorption. Consistent with an endothermic process, an increase in the temperature resulted in increasing mercury removal with a ∆H(o) of 13.3 kJ/mol and a ∆S(o) 67.5 J/mol K. The experimental results demonstrate that the combining of silica and nanotubes is a promising alternative material, which can be used to remove the mercury from wastewaters. PMID:26087931

  8. Isotherm, kinetic, and thermodynamic studies on Hg(II) adsorption from aqueous solution by silica- multiwall carbon nanotubes.

    PubMed

    Saleh, Tawfik A

    2015-11-01

    Silica combined with 2% multiwall carbon nanotubes (SiO2-CNT) was synthesized and characterized. Its sorption efficacy was investigated for the Hg(II) removal from an aqueous solution. The effect of pH on the percentage removal by the prepared material was examined in the range from 3 to 7. The adsorption kinetics were well fitted by using a pseudo-second-order model at various initial Hg(II) concentrations with R (2) of >0.99. The experimental data were plotted using the interparticle diffusion model, which indicated that the interparticle diffusion is not the only rate-limiting step. The data is well described by the Freundlich isotherm equation. The activation energy (Ea) for adsorption was 12.7 kJ mol(-1), indicating the process is to be physisorption. Consistent with an endothermic process, an increase in the temperature resulted in increasing mercury removal with a ∆H(o) of 13.3 kJ/mol and a ∆S(o) 67.5 J/mol K. The experimental results demonstrate that the combining of silica and nanotubes is a promising alternative material, which can be used to remove the mercury from wastewaters.

  9. Multicomponent adsorption of alcohols onto silicalite-1 from aqueous solution: isotherms, structural analysis, and assessment of ideal adsorbed solution theory.

    PubMed

    Bai, Peng; Tsapatsis, Michael; Siepmann, J Ilja

    2012-11-01

    Configurational-bias Monte Carlo (CBMC) simulations in the isobaric-isothermal version of the Gibbs ensemble (GE) were carried out to probe the adsorption from aqueous solutions of methanol and/or ethanol onto silicalite-1. This methodology does require neither specification of the chemical potential nor any reference to activity models based on experimental data. The CBMC-GE methodology can be applied to the complete range of mixture compositions from pure water to pure alcohols and can also be used when multiple solute types are present at high concentration. The simulations demonstrate high selectivities for the alcohols (α(ethanol) > α(methanol)) almost over the entire composition range. The ideal adsorbed solution theory is found to substantially underpredict the amount of sorbed water and leads to very large errors for low alcohol solution concentrations. The simulations indicate that, at lower loadings, the adsorbed alcohol molecules can serve as seeds for water adsorption but, at higher loadings, alcohols displace water molecules from their preferred region.

  10. Adsorption of Pb(II) on mesoporous activated carbons fabricated from water hyacinth using H3PO4 activation: Adsorption capacity, kinetic and isotherm studies

    NASA Astrophysics Data System (ADS)

    Huang, Yang; Li, Shunxing; Chen, Jianhua; Zhang, Xueliang; Chen, Yiping

    2014-02-01

    Activated carbons with high mesoporosity and abundant oxygen-containing functional groups were prepared from water hyacinth using H3PO4 activation (WHAC) to eliminate Pb(II) in water. Characterizations of the WHAC were performed using Brunauer-Emmett-Teller (BET), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The BET analysis showed that WHAC possesses a high mesoporosity (93.9%) with a BET surface area of 423.6 m2/g. The presence of oxygen-containing functional groups including hydroxyl, carbonyl, carboxyl and phosphate groups renders the WHAC a favorable adsorbent for Pb(II) with the maximum monolayer capacity (qm) 118.8 mg/g. The adsorption behavior follows pseudo-first order kinetic and Langmuir isotherm. The desorption study demonstrated that the WHAC could be readily regenerated using 0.1 M HCl (pH = 1.0). The desorbed WHAC could be reused at least six times without significant adsorption capacity reduction. The adsorption process was spontaneous and endothermic with ΔG (-0.27, -1.13, -3.02, -3.62, -5.54, and -9.31 kJ/mol) and ΔH (38.72 kJ/mol). Under the optimized conditions, a small amount of the adsorbent (1.0 g/L) could remove as much as 90.1% of Pb(II) (50 mg/L) in 20 min at pH 6.0 and temperature of 298 K. Therefore, the WHAC has a great potential to be an economical and efficient adsorbent in the treatment of lead-contaminated water.

  11. 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.

  12. The study of non-linear kinetics and adsorption isotherm models for Acid Red 18 from aqueous solutions by magnetite nanoparticles and magnetite nanoparticles modified by sodium alginate.

    PubMed

    Berizi, Zohre; Hashemi, Seyed Yaser; Hadi, Mahdi; Azari, Ali; Mahvi, Amir Hosein

    2016-01-01

    Azo dyes are widely used in various industries. These substances produce toxic byproducts in aquatic environments in addition to their mutagenic and carcinogenic potential effects. In this study, the effect of magnetite nanoparticles and magnetite nanoparticles modified by sodium alginate in batch systems and nonlinear kinetic and adsorption isotherm models were investigated. Magnetite nanoparticles were synthesized by chemical co-precipitation method and then modified and used as adsorbent to adsorb Acid Red 18. After determining the optimum pH and adsorbent dose, non-equilibrium models for kinetic adsorption were tested with concentrations (25-100 mg/L) and at eight different periods of time (1-15 min) and the pseudo-first-order and pseudo-second-order non-linear models were used to describe the results. For adsorption isotherm, a contact time of 120 min was studied in different concentrations (25-100 mg/L) and the residual concentration of Acid Red 18 was obtained. The results are described by non-linear Langmuir, Freundlich and Dubinin-Radushkevich isotherm models. The optimum amounts of pH for magnetite nanoparticles and for modified ones were 3 and 5, respectively, the efficiencies were 0.75 and 0.2 g/L, respectively. According to the results sodium alginate has a high performance in adsorption of Acid Red 18. Adjusted correlation coefficients and chi-square test showed that Freundlich isotherm and then Langmuir isotherm can well describe the experimental results. In Freundlich, the value of (Kf) was 3.231 (L/g) for magnetite nanoparticles and 21.615 (L/g) for modified adsorbent. In Langmuir, the value of (qm) was 16.259 (mg/g) for magnetite nanoparticles and 73.464 (mg/g) for modified adsorbent. Comparing the Langmuir maximum calculated adsorption capacity indicated that modified adsorbent can adsorb the pollutants 6.5 times more than the other one.

  13. The study of non-linear kinetics and adsorption isotherm models for Acid Red 18 from aqueous solutions by magnetite nanoparticles and magnetite nanoparticles modified by sodium alginate.

    PubMed

    Berizi, Zohre; Hashemi, Seyed Yaser; Hadi, Mahdi; Azari, Ali; Mahvi, Amir Hosein

    2016-01-01

    Azo dyes are widely used in various industries. These substances produce toxic byproducts in aquatic environments in addition to their mutagenic and carcinogenic potential effects. In this study, the effect of magnetite nanoparticles and magnetite nanoparticles modified by sodium alginate in batch systems and nonlinear kinetic and adsorption isotherm models were investigated. Magnetite nanoparticles were synthesized by chemical co-precipitation method and then modified and used as adsorbent to adsorb Acid Red 18. After determining the optimum pH and adsorbent dose, non-equilibrium models for kinetic adsorption were tested with concentrations (25-100 mg/L) and at eight different periods of time (1-15 min) and the pseudo-first-order and pseudo-second-order non-linear models were used to describe the results. For adsorption isotherm, a contact time of 120 min was studied in different concentrations (25-100 mg/L) and the residual concentration of Acid Red 18 was obtained. The results are described by non-linear Langmuir, Freundlich and Dubinin-Radushkevich isotherm models. The optimum amounts of pH for magnetite nanoparticles and for modified ones were 3 and 5, respectively, the efficiencies were 0.75 and 0.2 g/L, respectively. According to the results sodium alginate has a high performance in adsorption of Acid Red 18. Adjusted correlation coefficients and chi-square test showed that Freundlich isotherm and then Langmuir isotherm can well describe the experimental results. In Freundlich, the value of (Kf) was 3.231 (L/g) for magnetite nanoparticles and 21.615 (L/g) for modified adsorbent. In Langmuir, the value of (qm) was 16.259 (mg/g) for magnetite nanoparticles and 73.464 (mg/g) for modified adsorbent. Comparing the Langmuir maximum calculated adsorption capacity indicated that modified adsorbent can adsorb the pollutants 6.5 times more than the other one. PMID:27642843

  14. The isothermal dendritic growth experiment: Scientific status of a USMP-2 space flight experiment

    NASA Astrophysics Data System (ADS)

    Glicksman, M. E.; Koss, M. B.; Hahn, R. C.; Rojas, A.; Karthikeyan, M.; Winsa, E. A.

    1993-07-01

    The Isothermal Dendritic Growth Experiment (IDGE), to be performed on three of the USMP flights, starting with United States Microgravity Payload-2 (USMP-2), is designed to provide microgravity data on dendritic growth for a critical test of theory. Ground based test data using succinontrile (SCN), from both a flight capable growth chamber and a laboratory growth chamber, are compared to theoretical estimates of dendritic tip radii and velocities at several microgravity levels. The comparison shows that the data from the flight chamber are consistent with the historical data and that dendritic growth in a microgravity environment of 10-3 g0 or lower should exhibit significant differences from the dendritic growth of SCN at go.

  15. 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.

  16. 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

  17. 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.

  18. 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.

  19. 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

  20. Use of lipophilic ion adsorption isotherms to determine the surface area and the monolayer capacity of a chromatographic packing, as well as the thermodynamic equilibrium constant for its adsorption.

    PubMed

    Cecchi, T

    2005-04-29

    A method that champions the approaches of two independent research groups, to quantitate the chromatographic stationary phase surface available for lipophilic ion adsorption, is presented. For the first time the non-approximated expression of the electrostatically modified Langmuir adsorption isotherm was used. The non approximated Gouy-Chapman (G-C) theory equation was used to give the rigorous surface potential. The method helps model makers, interested in ionic interactions, determine whether the potential modified Langmuir isotherm can be linearized, and, accordingly, whether simplified retention equations can be properly used. The theory cultivated here allows the estimates not only of the chromatographically accessible surface area, but also of the thermodynamic equilibrium constant for the adsorption of the amphiphile, the standard free energy of its adsorption, and the monolayer capacity of the packing. In addition, it establishes the limit between a theoretical and an empirical use of the Freundlich isotherm to determine the surface area. Estimates of the parameters characterising the chromatographic system are reliable from the physical point of view, and this greatly validates the present comprehensive approach.

  1. 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

  2. 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

  3. 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

  4. 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

  5. Interpretation of the excess adsorption isotherms of organic eluent components on the surface of reversed-phase adsorbents. Effect on the analyte retention.

    PubMed

    Kazakevich, Y V; LoBrutto, R; Chan, F; Patel, T

    2001-04-13

    The excess adsorption isotherms of acetonitrile, methanol and tetrahydrofuran from water on reversed-phase packings were studied, using 10 different columns packed with C1-C6, C8, C10, C12, and C18 monomeric phases, bonded on the same type of silica. The interpretation of isotherms on the basis of the theory of excess adsorption shows significant accumulation of the organic eluent component on the adsorbent surface on the top of "collapsed" bonded layer. The accumulated amount was shown to be practically independent of the length of alkyl chains bonded to the silica surface. A model that describes analyte retention on a reversed-phase column from a binary mobile phase is developed. The retention mechanism involves a combination of analyte distribution between the eluent and organic adsorbed layer, followed by analyte adsorption on the surface of the bonded phase. A general retention equation for the model is derived and methods for independent measurements of the involved parameters are suggested. The theory was tested by direct measurement of analyte retention from the eluents of varied composition and comparison of the values obtained with those theoretically calculated values. Experimental and theoretically calculated values are in good agreement.

  6. 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.

  7. 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.

  8. 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

  9. Adsorption of lead on multi-walled carbon nanotubes with different outer diameters and oxygen contents: kinetics, isotherms and thermodynamics.

    PubMed

    Yu, Fei; Wu, Yanqing; Ma, Jie; Zhang, Chi

    2013-01-01

    The effects of different outer diameters and surface oxygen contents on the adsorption of heavy metals onto six types of multi-walled carbon nanotubes (MWCNTs) were investigated in an aqueous solution and lead was chosen as a model metal ion. The results indicated that the percentage removal and adsorption capacity of lead remarkably increased with decreasing outer diameter due to larger specific surface area (SSA). The SSA-normalized maximum adsorption capacity (qmSSA) and SSA-normalized adsorption coefficient (Kd/SSA) were strongly positively correlated with surface oxygen content, implying that lead adsorption onto MWCNTs significantly increases with the rise of oxygen content and decreases with decreasing SSA. The calculated thermodynamic parameters indicated that adsorption of lead on MWCNTs was endothermic and spontaneous. When the oxygen content of MWCNTs increased from 2.0% to 5.9%, the standard free energy (deltaG0) became more negative, which implied that the oxygenated functional groups increased the adsorption affinity of MWCNTs for lead. Through calculation of enthalpy (deltaH0), deltaG0 and free energy of adsorption (Ea), lead adsorption onto MWCNTs was recognized as a chemisorption process. The chemical interaction between lead and the phenolic groups of MWCNTs could be one of the main adsorption mechanisms due to highly positive correlations between the phenolic groups and Kd/SSA or qm/SSA.

  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. How realistic is the pore size distribution calculated from adsorption isotherms if activated carbon is composed of fullerene-like fragments?

    PubMed

    Terzyk, Artur P; Furmaniak, Sylwester; Harris, Peter J F; Gauden, Piotr A; Włoch, Jerzy; Kowalczyk, Piotr; Rychlicki, Gerhard

    2007-11-28

    A plausible model for the structure of non-graphitizing carbon is one which consists of curved, fullerene-like fragments grouped together in a random arrangement. Although this model was proposed several years ago, there have been no attempts to calculate the properties of such a structure. Here, we determine the density, pore size distribution and adsorption properties of a model porous carbon constructed from fullerene-like elements. Using the method proposed recently by Bhattacharya and Gubbins (BG), which was tested in this study for ideal and defective carbon slits, the pore size distributions (PSDs) of the initial model and two related carbon models are calculated. The obtained PSD curves show that two structures are micro-mesoporous (with different ratio of micro/mesopores) and the third is strictly microporous. Using the grand canonical Monte Carlo (GCMC) method, adsorption isotherms of Ar (87 K) are simulated for all the structures. Finally PSD curves are calculated using the Horvath-Kawazoe, non-local density functional theory (NLDFT), Nguyen and Do, and Barrett-Joyner-Halenda (BJH) approaches, and compared with those predicted by the BG method. This is the first study in which different methods of calculation of PSDs for carbons from adsorption data can be really verified, since absolute (i.e. true) PSDs are obtained using the BG method. This is also the first study reporting the results of computer simulations of adsorption on fullerene-like carbon models.

  13. 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.

  14. Single-experiment displacement assay for quantifying high-affinity binding by isothermal titration calorimetry.

    PubMed

    Krainer, Georg; Keller, Sandro

    2015-04-01

    Isothermal titration calorimetry (ITC) is the gold standard for dissecting the thermodynamics of a biomolecular binding process within a single experiment. However, reliable determination of the dissociation constant (KD) from a single titration is typically limited to the range 100 μM>KD>1 nM. Interactions characterized by a lower KD can be assessed indirectly by so-called competition or displacement assays, provided that a suitable competitive ligand is available whose KD falls within the directly accessible window. However, this protocol is limited by the fact that it necessitates at least two titrations to characterize one high-affinity inhibitor, resulting in considerable consumption of both sample material and time. Here, we introduce a fast and efficient ITC displacement assay that allows for the simultaneous characterization of both a high-affinity ligand and a moderate-affinity ligand competing for the same binding site on a receptor within a single experiment. The protocol is based on a titration of the high-affinity ligand into a solution containing the moderate-affinity ligand bound to the receptor present in excess. The resulting biphasic binding isotherm enables accurate and precise determination of KD values and binding enthalpies (ΔH) of both ligands. We discuss the theoretical background underlying the approach, demonstrate its practical application to metal ion chelation, explore its potential and limitations with the aid of simulations and statistical analyses, and elaborate on potential applications to protein-inhibitor interactions.

  15. 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 PAGES

    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

  16. 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.

  17. Bioremoval of Basic Violet 3 and Acid Blue 93 by Pseudomonas putida and its adsorption isotherms and kinetics.

    PubMed

    Arunarani, A; Chandran, Preethy; Ranganathan, B V; Vasanthi, N S; Sudheer Khan, S

    2013-02-01

    Basic Violet 3 and Acid Blue 93 are the most important group of synthetic colourants extensively used in textile industries for dyeing cotton, wool, silk and nylon. Release of these dye pollutants in to the environment adversely affects the human health and aquatic organisms. The present study we used Pseudomonas putida MTCC 4910 for the adsorptive removal of Basic Violet 3 and Acid Blue 93 from the aqueous solutions. The pH (4-9) and NaCl concentrations (1mM-1M) did not influence the adsorption process. The equilibrium adsorption process fitted well to Freundlich model than Langmuir model. The kinetics of adsorption fitted well by pseudo-second-order. Thus in the present study an attempt has been made to exploit the dye removal capability of P. putida MTCC 4910, and it was found to be an efficient microbe that could be used for bio removal of dyes from textile effluents.

  18. 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.

  19. 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.

  20. 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

  1. [Impact of regional water chemistry on the phosphorus isothermal adsorption of the sediments in three subsidence waters of the Huainan Mine areas].

    PubMed

    Yi, Qi-Tao; Sun, Peng-Fei; Xie, Kai; Qu, Xi-Jie; Wang, Ting-Ting

    2013-10-01

    Three research sites of subsidence waters, including Panji (PJ), Guqiao (GQ) and Xieqiao (XQ) located in the Huainan "Panxie" Mine Area have been selected to address their phosphorus (P) adsorption behavior in the sediments considering the site-specific regional water chemistry. The P isothermal adsorption was measured in pure water and four different types of ion solutions, prepared through additions of sodium chloride (NaCl), calcium chloride (CaCl2), sodium bicarbonate (NaHCO3), and a mixture of sodium bicarbonate and calcium chloride (NaHCO3 + CaCI2). The first four settings were studied to analyze the individual impact of each solution on P adsorption while the last one was to study their combined effect. In general, Ca2 + could enhance P adsorption on sediment surfaces while weakly alkaline conditions caused by bicarbonates were unfavorable for its adsorption. As a comprehensive effect, the positive effect of the former was greater than the negative effect of the latter. The zero equilibrium phosphorus concentrations (EPC) in the three sites were 0. 059, 0. 032 and 0. 040 mg.L-1, respectively, showing trends of P releasing to the overlying water column. The site of PJ showed greater P releasing potential than those at the GQ and XQ sites, probably due to its higher nutrient level. Overall, P releasing risks in the researched sediments are weaker than those in eutrophic lakes, while they are very similar to lakes with lower trophic levels, because of their unique sedimentary environments from inundated agricultural soils.

  2. 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.

  3. 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.

  4. 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.

  5. Water adsorption isotherms on CH3-, OH-, and COOH-terminated organic surfaces at ambient conditions measured with PM-RAIRS.

    PubMed

    Tu, Aimee; Kwag, Hye Rin; Barnette, Anna L; Kim, Seong H

    2012-10-30

    The water adsorption isotherms on methyl (CH(3))-, hydroxyl (OH)-, and carboxylic acid (COOH)-terminated alkylthiol self-assembled monolayers (SAMs) on Au were studied at room temperature and ambient pressure with polarization modulation reflection-absorption infrared spectroscopy (PM-RAIRS). PM-RAIRS analysis showed that water does not adsorb at all on the CH(3)-SAM/Au at subsaturation humidity conditions. In a dry Ar environment, the OH-SAM/Au holds at least 2 layer thick strongly bound water molecules which exhibit a broad O-H stretch vibration peak centered at ∼3360 cm(-1). The peak position implies that the strongly bound water layer on the OH SAM is more like a liquid than an ice. The additional uptake of water in humid environments is relatively weak, and the peak position changes very little. Unlike the OH-SAM/Au, the COOH-SAM/Au does not have strongly bound water layer. This seems to be due to the strong hydrogen bonding between terminal COOH groups in dry conditions. The weak interactions between water and carboxyl groups at low relative humidity (RH) and the solvation of dissociated carboxylic groups in high RH lead to a type III isotherm behavior, based on the BET categories, for water adsorption on the COOH-SAM/Au. The water spectra on the COOH-SAM at RH > 45% are centered at ∼3430 cm(-1) and very broad, indicating that the hydrogen-bonding network of water on the COOH-SAM is much different from that on the OH-SAM.

  6. 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.

  7. Fractional Statistical Theory of Adsorption of Polyatomics

    NASA Astrophysics Data System (ADS)

    Riccardo, J. L.; Ramirez-Pastor, A. J.; Romá, F.

    2004-10-01

    A new theoretical description of fractional statistical theory of adsorption (FSTA) phenomena is presented based on Haldane’s statistics. Thermodynamic functions for adsorption of polyatomics are analytically developed. The entropy is characterized by an exclusion parameter g, which relates to the configuration of the admolecules and surface geometry. FSTA provides a simple framework to address a large class of complex adsorption systems. Comparisons of theoretical adsorption isotherms with experiments and simulations indicate that adsorption configuration and adsorption energy can accurately be assessed from this theory.

  8. Fractional statistical theory of adsorption of polyatomics.

    PubMed

    Riccardo, J L; Ramirez-Pastor, A J; Romá, F

    2004-10-29

    A new theoretical description of fractional statistical theory of adsorption (FSTA) phenomena is presented based on Haldane's statistics. Thermodynamic functions for adsorption of polyatomics are analytically developed. The entropy is characterized by an exclusion parameter g, which relates to the configuration of the admolecules and surface geometry. FSTA provides a simple framework to address a large class of complex adsorption systems. Comparisons of theoretical adsorption isotherms with experiments and simulations indicate that adsorption configuration and adsorption energy can accurately be assessed from this theory. PMID:15525184

  9. 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.

  10. 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...

  11. 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

  12. 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)

  13. 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

  14. 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.

  15. 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).

  16. 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.

  17. 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.

  18. Adsorption of thorium from aqueous solutions by perlite.

    PubMed

    Talip, Z; Eral, M; Hiçsönmez, U

    2009-02-01

    The use of expanded perlite for the adsorption of thorium from aqueous solution by batch technique is presented. The effects of particle size, pH of the solution, initial thorium concentration, shaking time, V/m ratio and temperature were determined. It was found that the adsorption capacity increases by the increase in the pH of the suspensions. The rate of thorium adsorption on expanded perlite was observed to be fast in the first hour of the reaction time. Adsorption isotherms were expressed by Langmuir and Freundlich adsorption models and the adsorption experiments conducted at 30 +/- 1 degrees C showed that the adsorption isotherms correlated well with the Langmuir model. From the adsorption data, thermodynamic parameters such as DeltaG(o), DeltaH(o) and DeltaS(o) were calculated as a function of temperature.

  19. 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…

  20. Theoretical consideration of the use of a Langmuir adsorption isotherm to describe the effect of light intensity on electron transfer in photosystem II.

    PubMed

    Fragata, Mário; Viruvuru, Venkataramanaiah; Dudekula, Subhan

    2007-03-29

    Electron transport through photosystem II (PSII), measured as oxygen evolution, was investigated in isolated PSII particles and thylakoid membranes irradiated with white light of intensities (I) of 20 to about 4000 micromol of photons/(m2.s). In steady-state conditions, the evolution of oxygen varies with I according to the hyperbolic expression OEth = OEth(max)I/(L1/2 + I) (eq i) where OEth is the theoretical oxygen evolution, OEth(max) is the maximum oxygen evolution, and L1/2 is the light intensity giving OEth(max)/2. In this work, the mathematical derivation of this relationship was performed by using the Langmuir adsorption isotherm and assuming that the photon interaction with the chlorophyll (Chl) in the PSII reaction center is a heterogeneous reaction in which the light is represented as a stream of particles instead of an electromagnetic wave (see discussion in Turro, N. J. Modern Molecular Photochemistry; University Science Books: Mill Valley, CA, 1991). In accordance with this approximation, the Chl molecules (P680) were taken as the adsorption surfaces (or heterogeneous catalysts), and the incident (or exciting) photons as the substrate, or the reagent. Using these notions, we demonstrated that eq i (Langmuir equation) is a reliable interpretation of the photon-P680 interaction and the subsequent electron transfer from the excited state P680, i.e., P680*, to the oxidized pheophytin (Phe), then from Phe- to the primary quinone QA. First, eq i contains specific functional and structural information that is apparent in the definition of OEth(max) as a measure of the maximal number of PSII reaction centers open for photochemistry, and L1/2 as the equilibrium between the electron transfer from Phe- to QA and the formation of reduced Phe in the PSII reaction center by electrons in provenance from P680*. Second, a physiological control mechanism in eq i is proved by the observation that the magnitudes of OEth(max) and L1/2 are affected differently by exogenous

  1. 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).

  2. 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).

  3. 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.

  4. 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)

  5. 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.

  6. 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

  7. 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.

  8. Adsorption selectivity: a way to homochirality? Computational experiments

    NASA Astrophysics Data System (ADS)

    Pauzat, F.; Ellinger, Y.; Markovits, A.

    2015-10-01

    Life, as we know it today, is inseparable from homochirality; standing within the panspermia hypothesis, we investigate computationally the still unknown origin of the enantiomeric excess present in the organic matter of well-defined families of meteorites [1,2,3] through the possibilities open by a selective adsorption of the enantiomers.

  9. 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.

  10. Adsorption of phenolic compound by aged-refuse.

    PubMed

    Xiaoli, Chai; Youcai, Zhao

    2006-09-01

    The adsorption of phenol, 2-chlorophenol, 4-chlorophenol and 2,4-dichlorophenol by aged-refuse has been studied. Adsorption isotherms have been determined for phenol, 2-chlorophenol, 4-chlorophenol and 2,4-dichlorophenol and the data fits well to the Freundlich equation. The chlorinated phenols are absorbed more strongly than the phenol and the adsorption capacity has an oblivious relationship with the numbers and the position of chlorine subsistent. The experiment data suggests that both the partition function and the chemical adsorption involve in the adsorption process. Pseudo-first-order and pseudo-second-order model were applied to investigate the kinetics of the adsorption and the results show that it fit the pseudo-second-order model. More than one step involves in the adsorption process and the overall rate of the adsorption process appears to be controlled by the chemical reaction. The thermodynamic analysis indicates that the adsorption is spontaneous and endothermic.

  11. Removal of microcystin-LR and microcystin-RR by graphene oxide: adsorption and kinetic experiments.

    PubMed

    Pavagadhi, Shruti; Tang, Ai Ling Lena; Sathishkumar, Muthuswamy; Loh, Kian Ping; Balasubramanian, Rajasekhar

    2013-09-01

    Graphene oxide (GO) was employed in the present study for removal of two commonly occurring algal toxins, microcystin-LR (MC-LR) and microcystin-RR (MC-RR), from water. The adsorption performance of GO was compared to that of commercially available activated carbon. Further, adsorption experiments were conducted in the presence of other environmental pollutants to understand the matrix effects of contaminated water on the selective adsorption of MC-LR and MC-RR onto GO. The environmental pollutants addressed in this study included different anions (nitrate NO3-, nitrite NO2-, sulphate SO4(2-), chloride (Cl(-)), phosphate PO4(3-) and fluoride (F(-))) and cations (sodium (Na(+)), potassium (K(+)), magnesium (Mg(2+)) and calcium (Ca(2+))). GO showed very a high adsorption capacity of 1700 μg/g for removal of MC-LR and 1878 μg/g for MC-RR while the maximum adsorption capacity obtained with the commercial activated carbon was 1481.7 μg/g and 1034.1 μg/g for MC-LR and MC-RR, respectively. The sorption kinetic experiments revealed that more than 90% removal of both MC-LR/RR was achieved within 5 min for all the doses studied (500, 700 and 900 μg/L). GO could be reused as an adsorbent following ten cycles of adsorption/desorption with no significant loss in its adsorption capacity.

  12. 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.

  13. Adsorptive removal of PPCPs by biomorphic HAP templated from cotton.

    PubMed

    Huang, Bin; Xiong, Dan; Zhao, Tingting; He, Huan; Pan, Xuejun

    2016-01-01

    Biomorphic nano-hydroxyapatite (HAP) was fabricated by a co-precipitation method using cotton as bio-templates and employed in adsorptive removal of ofloxacin (OFL) and triclosan (TCS) that are two representative pharmaceuticals and personal care products (PPCPs). The surface area and porosity, crystal phase, functional group, morphology and micro-structure of the synthesized HAP were characterized by Brunauer-Emmett-Teller isotherm, X-ray powder diffraction, Fourier transform infrared spectroscopy, scanning electron macroscopic and transmission electron microscopy. The effects of initial pH, ionic strength, initial concentration, contact time and temperature on the removal of PPCPs were studied in a batch experiment. The adsorption of OFL and TCS was rapid and almost accomplished within 50 min. Kinetic studies indicated that the adsorption process of OFL and TCS followed the pseudo-first-order and pseudo-second-order models, respectively. The Freundlich isotherm described the OFL adsorption process well but the adsorption of TCS fitted the Langmuir isotherm better. Thermodynamics and isotherm parameters suggested that both OFL and TCS adsorption were feasible and spontaneous. Hydrogen bond and Lewis acid-base reaction may be the dominating adsorption mechanism of OFL and TCS, respectively. Compared to other adsorbents, biomorphic HAP is environmentally friendly and has the advantages of high adsorption capacity, exhibiting potential application for PPCPs removal. PMID:27387006

  14. Surface area and pore size characteristics of nanoporous gold subjected to thermal, mechanical, or surface modification studied using gas adsorption isotherms, cyclic voltammetry, thermogravimetric analysis, and scanning electron microscopy

    PubMed Central

    Tan, Yih Horng; Davis, Jason A.; Fujikawa, Kohki; Ganesh, N. Vijaya; Demchenko, Alexei V.

    2012-01-01

    Nitrogen adsorption/desorption isotherms are used to investigate the Brunauer, Emmett, and Teller (BET) surface area and Barrett-Joyner-Halenda (BJH) pore size distribution of physically modified, thermally annealed, and octadecanethiol functionalized np-Au monoliths. We present the full adsorption-desorption isotherms for N2 gas on np-Au, and observe type IV isotherms and type H1 hysteresis loops. The evolution of the np-Au under various thermal annealing treatments was examined using scanning electron microscopy (SEM). The images of both the exterior and interior of the thermally annealed np-Au show that the porosity of all free standing np-Au structures decreases as the heat treatment temperature increases. The modification of the np-Au surface with a self-assembled monolayer (SAM) of C18-SH (coverage of 2.94 × 1014 molecules cm−2 based from the decomposition of the C18-SH using thermogravimetric analysis (TGA)), was found to reduce the strength of the interaction of nitrogen gas with the np-Au surface, as reflected by a decrease in the ‘C’ parameter of the BET equation. From cyclic voltammetry studies, we found that the surface area of the np-Au monoliths annealed at elevated temperatures followed the same trend with annealing temperature as found in the BET surface area study and SEM morphology characterization. The study highlights the ability to control free-standing nanoporous gold monoliths with high surface area, and well-defined, tunable pore morphology. PMID:22822294

  15. 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.

  16. 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,...

  17. 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.

  18. 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.

  19. Critical analysis of adsorption data statistically

    NASA Astrophysics Data System (ADS)

    Kaushal, Achla; Singh, S. K.

    2016-09-01

    Experimental data can be presented, computed, and critically analysed in a different way using statistics. A variety of statistical tests are used to make decisions about the significance and validity of the experimental data. In the present study, adsorption was carried out to remove zinc ions from contaminated aqueous solution using mango leaf powder. The experimental data was analysed statistically by hypothesis testing applying t test, paired t test and Chi-square test to (a) test the optimum value of the process pH, (b) verify the success of experiment and (c) study the effect of adsorbent dose in zinc ion removal from aqueous solutions. Comparison of calculated and tabulated values of t and χ 2 showed the results in favour of the data collected from the experiment and this has been shown on probability charts. K value for Langmuir isotherm was 0.8582 and m value for Freundlich adsorption isotherm obtained was 0.725, both are <1, indicating favourable isotherms. Karl Pearson's correlation coefficient values for Langmuir and Freundlich adsorption isotherms were obtained as 0.99 and 0.95 respectively, which show higher degree of correlation between the variables. This validates the data obtained for adsorption of zinc ions from the contaminated aqueous solution with the help of mango leaf powder.

  20. 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...

  1. Characteristics of PAHs adsorption on inorganic particles and activated sludge in domestic wastewater treatment.

    PubMed

    Liu, J J; Wang, X C; Fan, B

    2011-05-01

    The occurrence of polycyclic aromatic hydrocarbons (PAHs) in a domestic wastewater treatment plant (WWTP) was investigated in a 1 year period. In order to understand how PAHs were removed at different stages of the treatment process, adsorption experiments were conducted using quartz sand, kaolinite, and natural clay as inorganic adsorbents and activated sludge as organic adsorbent for adsorbing naphthalene, phenanthrene, and pyrene. As a result, the adsorption of PAHs by the inorganic adsorbents well followed the Langmuir isotherm while that by the activated sludge well followed the Freundlich isotherm. By bridging equilibrium partitioning coefficient with the parameters of adsorption isotherm, a set of mathematical models were developed. Under an assumption that in the primary settler PAHs removal was by adsorption onto inorganic particles and in the biological treatment unit it was by adsorption onto activated sludge, the model calculation results fairly reflected the practical condition in the WWTP.

  2. Kinetic and isotherm analyses for thorium (IV) adsorptive removal from aqueous solutions by modified magnetite nanoparticle using response surface methodology (RSM)

    NASA Astrophysics Data System (ADS)

    Karimi, Mohammad; Milani, Saeid Alamdar; Abolgashemi, Hossein

    2016-10-01

    In this study, the ability and the adsorption capacity of magnetite/aminopropyltriethoxysilane/glutaraldehyde (Fe3O4/APTES/GA) adsorbent were evaluated for the adsorption of thorium (IV) ions from aqueous solutions. The influence of the several variables such as pH (1-5), Th (IV) initial concentration (50-300 mg L-1) and adsorbent concentration (1-5 g L-1) on the Th (IV) adsorption were investigated by response surface methodology (RSM). The results showed that the highest absorption capacity (q) was 107.23 mg g-1 with respect to pH = 4.5, initial concentration of 250 mg L-1 and adsorbent concentration of 1 g L-1 for 90 min. Modeling equilibrium sorption data with the Langmuir, Freundlich and Dubinin-Radushkevich models pointed out that the results were in good agreement with Langmuir model. The experimental kinetic data were well fitted to pseudo-second-order equation with R2 = 0.9739. Also thermodynamic parameters (ΔGo, ΔHo, ΔSo) declared that the Th (IV) adsorption was endothermic and spontaneous.

  3. Cell wall reactivity of acidophilic and alkaliphilic bacteria determined by potentiometric titrations and Cd adsorption experiments.

    PubMed

    Kenney, Janice P L; Fein, Jeremy B

    2011-05-15

    In this study, we used potentiometric titrations and Cd adsorption experiments to determine the binding capacities of two acidophilic (A. cryptum and A. acidophilum) and two alkaliphilic (B. pseudofirmus and B. circulans) bacterial species in order to determine if any consistent trends could be observed relating bacterial growth environment to proton and Cd binding properties and to compare those binding behaviors to those of neutrophilic bacteria. All of the bacterial species studied exhibited significant proton buffering over the pH range in this study, with the alkaliphiles exhibiting significantly higher acidity constants than the acidophiles as well as the neutrophilic bacterial consortia. The calculated average site concentrations for each of the bacteria in this study are within 2σ experimental error of each other, with the exception of A. cryptum, which has a significantly higher Site 2 concentration than the other species. Despite differing acidity constants between the acidophiles and alkaliphiles, all bacteria except A. cryptum exhibited remarkably similar Cd adsorption behavior to each other, and the observed extent of adsorption was also similar to that predicted from a generalized model derived using neutrophilic bacterial consortia. This study demonstrates that bacteria that grow under extreme conditions exhibit similar proton and metal adsorption behavior to that of previously studied neutrophilic species and that a single set of proton and metal binding constants can be used to model the behavior of bacterial adsorption under a wide range of environmental conditions.

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

    DOE PAGES

    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

  5. Determination of Equilibrium and Kinetic Parameters of the Adsorption of Cr(III) and Cr(VI) from Aqueous Solutions to Agave Lechuguilla Biomass

    PubMed Central

    Romero-González, Jaime; Peralta-Videa, José R.; Rodríguez, Elena

    2005-01-01

    This investigation reveals the capability of Agave lechuguilla for trivalent and hexavalent chromium removal from aqueous solutions. Experimentation included pH profile, time dependence, adsorption capacity (KF and QL), adsorption intensity (n and RL) and saturation capacity (q s) studies. Batch experiments were conducted at 22∘C to characterize and model the adsorption equilibrium as well as biomass adsorption rates. pH 4 was the optimum for Cr(III) binding, while Cr(VI) optimum binding was at pH 2. Time profile experiments indicated that the adsorption of Cr(VI) by lechuguilla biomass was time-dependent and that of Cr(III) was not. Kinetic models demonstrated that a pseudo-second order reaction model best described the kinetic data for Cr(VI). The adsorption isotherms showed that the binding pattern for Cr(VI) followed the Freundlich isotherm model, while that for Cr(III) followed the Langmuir isotherm. PMID:18365089

  6. Adsorption of n-pentane on mesoporous silica and adsorbent deformation.

    PubMed

    Gor, Gennady Yu; Paris, Oskar; Prass, Johannes; Russo, Patrícia A; Ribeiro Carrott, M Manuela L; Neimark, Alexander V

    2013-07-01

    Development of quantitative theory of adsorption-induced deformation is important, e.g., for enhanced coalbed methane recovery by CO2 injection. It is also promising for the interpretation of experimental measurements of elastic properties of porous solids. We study deformation of mesoporous silica by n-pentane adsorption. The shape of experimental strain isotherms for this system differs from the shape predicted by thermodynamic theory of adsorption-induced deformation. We show that this difference can be attributed to the difference of disjoining pressure isotherm, responsible for the solid-fluid interactions. We suggest the disjoining pressure isotherm suitable for n-pentane adsorption on silica and derive the parameters for this isotherm from experimental data of n-pentane adsorption on nonporous silica. We use this isotherm in the formalism of macroscopic theory of adsorption-induced deformation of mesoporous materials, thus extending this theory for the case of weak solid-fluid interactions. We employ the extended theory to calculate solvation pressure and strain isotherms for SBA-15 and MCM-41 silica and compare it with experimental data obtained from small-angle X-ray scattering. Theoretical predictions for MCM-41 are in good agreement with the experiment, but for SBA-15 they are only qualitative. This deviation suggests that the elastic modulus of SBA-15 may change during pore filling.

  7. Quaternized dimethylaminoethyl methacrylate strong base anion exchange fibers for As(V) adsorption

    NASA Astrophysics Data System (ADS)

    Kavaklı, Cengiz; Akkaş Kavaklı, Pınar; Turan, Burcu Dila; Hamurcu, Aslı; Güven, Olgun

    2014-09-01

    N,N-Dimethylaminoethyl methacrylate (DMAEMA) grafted polyethylene/polypropylene (PE/PP) nonwoven fibers (DMAEMA-g-PE/PP) was prepared by radiation-induced graft polymerization. DMAEMA graft chains on nonwoven fibers were quaternized with dimethyl sulfate solution for the preparation of strong base anion exchange fibers (QDMAEMA-g-PE/PP). Fiber structures were characterized by FTIR, XPS and SEM techniques. The effect of solution pH, contact time, initial As(V) ion concentration and coexisting ions on the As(V) adsorption capacity of the QDMAEMA-g-PE/PP fibers were investigated by performing batch adsorption experiments. The adsorption of As(V) by QDMAEMA-g-PE/PP fibers was found to be independent on solution pH in the range 4.00-10.00. Kinetic experiments show that the As(V) adsorption rate was rapid and As(V) adsorption follows pseudo second-order kinetic model. As(V) adsorption equilibrium data were analyzed using Langmuir and Freundlich adsorption isotherm model equations. Langmuir and Freundlich adsorption isotherm models fitted the experimental data well. The maximum adsorption capacity (qmax) calculated from Langmuir isotherm was found to be 83.33 mg As(V)/g polymer at pH 7.00. The adsorbent was used for three cycles without significant loss of adsorption capacity. The adsorbed As(V) ions were desorbed effectively by a 0.1 M NaOH solution.

  8. Study of adsorption of Neon on open Carbon nanohorns aggregates

    NASA Astrophysics Data System (ADS)

    Ziegler, Carl Andrew

    Adsorption isotherms can be used to determine surface area of a substrate and the heat released when adsorption occurs. Our measurements are done determining the equilibrium pressures corresponding to a given amount of gas adsorbed on a substrate at constant temperature. The adsorption studies were done on aggregates of open dahlia-like carbon nanohorns. The nanohorns were oxidized for 9 hours at 550 °C to open them up and render their interior space accessible for adsorption. Volumetric adsorption measurements of Ne were performed at twelve different temperatures between 19 K and 48 K. The isotherms showed two substeps. The first substep corresponds to adsorption on the high energy binding sites in the interior of the nanohorns, near the tip. The second substep corresponds to low energy binding sites both on the outside of the nanotubes and inside the nanotube away from the tip. The isosteric heat measurements obtained from the isotherm data also shows these two distinct substeps. The effective surface area of the open nanotubes was determined from the isotherms using the point-B method. The isosteric heat and surface area data for neon on open nanohorns were compared to two similar experiments of neon adsorbed on aggregates of closed nanohorns.

  9. Heavy metal adsorption changes of EAF steel slag after phosphorus adsorption.

    PubMed

    Song, Guanling; Cao, Lijing; Chen, Xiao; Hou, Wenhua; Wang, Qunhui

    2012-01-01

    A kind of electric arc furnace (EAF) steel slag was phosphated, and its isothermal and dynamic adsorptions of copper, cadmium, and lead ions were measured to determine if heavy metal adsorption changes after phosphorus adsorption. The surface area increased greatly after the slag was phosphated. Isothermal adsorption experiments showed that the theoretical Q(max) of the EAF steel slag on Cu(2+), Cd(2+), and Pb(2+) improved 59, 50, and 89% respectively after it was phosphated. Dynamic adsorption results showed that the greatest adsorption capacities of unit volume of Cu(2+), Cd(2+), and Pb(2+) were 2.2, 1.8, and 1.8 times that of the column packed with original EAF steel slag when the column was packed with phosphate EAF steel slag at the same heavy metal ion concentration. The breakthrough time, the exhaustion time and elution efficiency of the column also increased when the column was packed with phosphated EAF steel slag compared with that packed with original EAF steel slag. Phosphorus adsorption could further improve the heavy metal ion adsorption of the EAF steel slag.

  10. Application of isothermal titration calorimetry for characterizing thermodynamic parameters of biomolecular interactions: peptide self-assembly and protein adsorption case studies.

    PubMed

    Kabiri, Maryam; Unsworth, Larry D

    2014-10-13

    The complex nature of macromolecular interactions usually makes it very hard to identify the molecular-level mechanisms that ultimately dictate the result of these interactions. This is especially evident in the case of biological systems, where the complex interaction of molecules in various situations may be responsible for driving biomolecular interactions themselves but also has a broader effect at the cell and/or tissue level. This review will endeavor to further the understanding of biomolecular interactions utilizing the isothermal titration calorimetry (ITC) technique for thermodynamic characterization of two extremely important biomaterial systems, viz., peptide self-assembly and nonfouling polymer-modified surfaces. The advantages and shortcomings of this technique will be presented along with a thorough review of the recent application of ITC to these two areas. Furthermore, the controversies associated with the enthalpy-entropy compensation effect as well as thermodynamic equilibrium state for such interactions will be discussed.

  11. Methylene blue adsorption from aqueous solution by activated carbon: effect of acidic and alkaline solution treatments.

    PubMed

    Ijagbemi, Christianah O; Chun, Ji I; Han, Da H; Cho, Hye Y; O, Se J; Kim, Dong S

    2010-01-01

    The removal of Methylene Blue (MB) from aqueous solution using activated carbon (AC) has been investigated. Adsorption experiments were conducted and the maximum adsorption capacity was determined. The effect of experimental parameters such as pH, dye concentration and temperature were studied on the adsorption process. Equilibrium data were mathematically modeled using the Langmuir and Freundlich adsorption models to describe the equilibrium isotherms at different dye concentrations and temperature. Parameters of best-fit model were calculated and discussed. To understand the mechanism of adsorption, kinetic models were employed to follow the adsorption processes; the pseudo-first-order best described the adsorption of MB onto AC. It was found that pH plays a major role in the adsorption process; adsorption capacity was influenced by the physical and surface chemical properties of carbon and the pH of the solution. 99.0% MB removal was achieved at equilibrium.

  12. 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.

  13. Preparation and properties of ion-imprinted hollow particles for the selective adsorption of silver ions.

    PubMed

    Hou, Hongbin; Yu, Demei; Hu, Guohe

    2015-02-01

    Four kinds of silver ion-imprinted particles (Ag-IIPs) with different morphologies were prepared by the surface ion-imprinting technology (SIIT) and were used for the selective removal and concentration of silver ions from wastewater. The favorable adsorptivity and selectivity of Ag-IIPs for Ag(+) were confirmed by a series of adsorption experiments at a suitable pH value. The adsorption mechanism was elucidated by analyzing the adsorption isotherms, adsorption thermodynamics, and adsorption kinetics systematically. The Ag(+) adsorption onto the Ag-IIPs was well-described by the Langmuir isotherm model, and it was likely to be a monolayer chemical adsorption. This conclusion was also confirmed by the thermodynamic parameters. Moreover, the adsorption kinetics indicated that the adsorption rate would be controlled jointly by the intraparticle diffusion and the inner surface adsorption process, and the latter process was generally associated with the formation and breaking of chemical bonds. Finally, the effects of different morphologies of the Ag-IIPs for Ag(+) adsorption were also investigated. In aqueous solution, the adsorptivity of the Ag(+) ion-imprinting single-hole hollow particles (Ag-IISHPs) for Ag(+) was highest (80.5 mg g(-1)) because of a specific morphology that features a single hole in the shell. In an oil-water mixture, Ag(+) in the water phase could be adsorbed efficiently by the Ag(+) ion-imprinting Janus hollow particles (Ag-IIJHPs), with emulsifiability originating from the Janus structure.

  14. 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

  15. 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.

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

    DOE PAGES

    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

  17. Adsorption and pressure swing desorption of NOx in Na-Y zeolite: experiments and modeling.

    PubMed

    Brilhac, J F; Sultana, A; Gilot, P; Martens, J A

    2002-03-01

    Pressure swing NOx adsorption-desorption cycles were performed in the temperature range 200-350 degrees C using a fixed adsorbent bed of compressed Na-Y pellets and using a honeycomb coated with Na-Y powder. The experiments were performed using a synthetic gas mixture mimicking exhaust from a lean burn internal combustion engine. Na-Y zeolite coadsorbs NO and NO2 as N2O3, which in the regeneration were displaced by competitively adsorbed water molecules from a hydrated air stream. The performance of the fixed bed in these NOx adsorption and displacement desorption processes were modeled with a one-dimensional model. The kinetic and thermodynamic parameters from the fixed bed model were implemented in a model for the operation of the monolith. The experimental adsorption and desorption NOx concentration profiles in the monolith were reasonably well reproduced by the model. The water content of the flushing stream and the stripping gas flow rate are key process parameters. Technically, both parameters can be optimized in a valveless system with rotating honeycomb adsorbent comprising a NOx adsorption, a water injection and a NOx evacuation section.

  18. [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

  19. [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.

  20. Artificial neural network (ANN) method for modeling of sunset yellow dye adsorption using zinc oxide nanorods loaded on activated carbon: Kinetic and isotherm study

    NASA Astrophysics Data System (ADS)

    Maghsoudi, M.; Ghaedi, M.; Zinali, A.; Ghaedi, A. M.; Habibi, M. H.

    2015-01-01

    In this research, ZnO nanoparticle loaded on activated carbon (ZnO-NPs-AC) was synthesized simply by a low cost and nontoxic procedure. The characterization and identification have been completed by different techniques such as SEM and XRD analysis. A three layer artificial neural network (ANN) model is applicable for accurate prediction of dye removal percentage from aqueous solution by ZnO-NRs-AC following conduction of 270 experimental data. The network was trained using the obtained experimental data at optimum pH with different ZnO-NRs-AC amount (0.005-0.015 g) and 5-40 mg/L of sunset yellow dye over contact time of 0.5-30 min. The ANN model was applied for prediction of the removal percentage of present systems with Levenberg-Marquardt algorithm (LMA), a linear transfer function (purelin) at output layer and a tangent sigmoid transfer function (tansig) in the hidden layer with 6 neurons. The minimum mean squared error (MSE) of 0.0008 and coefficient of determination (R2) of 0.998 were found for prediction and modeling of SY removal. The influence of parameters including adsorbent amount, initial dye concentration, pH and contact time on sunset yellow (SY) removal percentage were investigated and optimal experimental conditions were ascertained. Optimal conditions were set as follows: pH, 2.0; 10 min contact time; an adsorbent dose of 0.015 g. Equilibrium data fitted truly with the Langmuir model with maximum adsorption capacity of 142.85 mg/g for 0.005 g adsorbent. The adsorption of sunset yellow followed the pseudo-second-order rate equation.

  1. Combination of computational methods, adsorption isotherms and selectivity tests for the conception of a mixed non-covalent-semi-covalent molecularly imprinted polymer of vanillin.

    PubMed

    Puzio, Kinga; Delépée, Raphaël; Vidal, Richard; Agrofoglio, Luigi A

    2013-08-01

    A novel molecularly imprinted polymer (MIP) for vanillin was prepared by photo initiated polymerization in dichloromethane using a mixed semi-covalent and non-covalent imprinting strategy. Taking polymerisable syringaldehyde as "dummy" template, acrylamide was chosen as functional monomer on B3LYP/6-31+G(d,p) density functional theory computational method basis with counterpoise. The binding parameters for the recognition of vanillin on imprinted polymers were studied with three different isotherm models (Langmuir, bi-Langmuir and Langmuir-Freundlich) and compared. The results indicate an heterogeneity of binding sites. It was found and proved by DFT calculations that the specific binding of vanillin in the cavities is due to non-covalent interactions of the template with the hydroxyphenyl- and the amide-moieties. The binding geometry of vanillin in the MIP cavity was also modelled. The obtained MIP is highly specific for vanillin (with an imprinting factor of 7.4) and was successfully applied to the extraction of vanillin from vanilla pods, red wine spike with vanillin, natural and artificial vanilla sugar with a recovery of 80%.

  2. [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

  3. 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.

  4. 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.

  5. Adsorption characteristics of methylene blue onto agricultural wastes lotus leaf in bath and column modes.

    PubMed

    Han, Xiuli; Wang, Wei; Ma, Xiaojian

    2011-01-01

    The adsorption potential of lotus leaf to remove methylene blue (MB) from aqueous solution was investigated in batch and fixed-bed column experiments. Langmuir, Freundlich, Temkin and Koble-Corrigan isotherm models were employed to discuss the adsorption behavior. The results of analysis indicated that the equilibrium data were perfectly represented by Temkin isotherm and the Langmuir saturation adsorption capacity of lotus leaf was found to be 239.6 mg g(-1) at 303 K. In fixed-bed column experiments, the effects of flow rate, influent concentration and bed height on the breakthrough characteristics of adsorption were discussed. The Thomas and the bed-depth/service time (BDST) models were applied to the column experimental data to determine the characteristic parameters of the column adsorption. The two models were found to be suitable to describe the dynamic behavior of MB adsorbed onto the lotus leaf powder column.

  6. 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.

  7. 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.

  8. 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

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

    PubMed

    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

  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. 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

  12. 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.

  13. 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

  14. Adsorption of cadmium from aqueous solutions by perlite.

    PubMed

    Mathialagan, T; Viraraghavan, T

    2002-10-14

    The present study examined the use of perlite for the removal of cadmium from aqueous solutions. The effects of pH and contact time on the adsorption process were examined. The optimum pH for adsorption was found to be 6.0. Residual cadmium concentration reached equilibrium in 6h and the rate of cadmium adsorption by perlite was rapid in the first hour of the reaction time. Ho's pseudo-second-order model best described the kinetics of the reaction. Batch adsorption experiments conducted at room temperature (22+/-1 degrees C) showed that the adsorption pattern followed the Freundlich isotherm model. The maximum removal of cadmium obtained from batch studies was 55%. Thomas model was used to describe the adsorption data from column studies. The results generally showed that perlite could be considered as a potential adsorbent for cadmium removal from aqueous solutions.

  15. [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.

  16. Determination of binding capacity and adsorption enthalpy between Human Glutamate Receptor (GluR1) peptide fragments and kynurenic acid by surface plasmon resonance experiments.

    PubMed

    Csapó, E; Majláth, Z; Juhász, Á; Roósz, B; Hetényi, A; Tóth, G K; Tajti, J; Vécsei, L; Dékány, I

    2014-11-01

    The interaction between kynurenic acid (KYNA) and two peptide fragments (ca. 30 residues) of Human Glutamate Receptor 201-300 (GluR1) using surface plasmon resonance (SPR) spectroscopy was investigated. Because of the medical interest in the neuroscience, GluR1 is one of the important subunits of the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPAR). AMPARs are ionotoropic glutamate receptors, which are mediating fast synaptic transmission and are crucial for plasticity in the brain. On the other hand, KYNA has been suggested to have neuroprotective activity and it has been considered for apply in therapy in certain neurobiological disorders. In this article the adsorption of the GluR1201-230 and GluR1231-259 peptides were studied on gold biosensor chip. The peptides were chemically bonded onto the gold surface via thiol group of L-cysteine resulted in the formation of peptide monolayer on the SPR chip surface. Because the GluR1231-259 peptide does not contain L-cysteine the Val256 was replaced by Cys256. The cross sectional area and the surface orientation of the studied peptides were determined by SPR and theoretical calculations (LOMETS) as well. The binding capability of KYNA on the peptide monolayer was studied in the concentration range of 0.1-5.0 mM using 150 mM NaCl ionic strength at pH 7.4 (±0.02) in phosphate buffer solutions. In order to determine the binding enthalpy the experiments were carried out between +10°C and +40°C. The heat of adsorption was calculated by using adsorption isotherms at different surface loading of KYNA on the SPR chip.

  17. 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.

  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. 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.

  20. The role of Fe(III) modified montmorillonite on fluoride mobility: adsorption experiments and competition with phosphate.

    PubMed

    Bia, Gonzalo; De Pauli, Carlos P; Borgnino, Laura

    2012-06-15

    Fluoride adsorption onto Fe(III) modified montmorillonite was investigated using batch experiments. The effect of reaction time, pH, ionic strength and phosphate, as a competitive anion, was evaluated. Kinetics indicated that adsorption obeys a pseudo-first-order rate law which involves two steps. The fast one (bulk transport/surface reaction) occurs instantaneously. The slower (diffusion in pores) takes hours to complete. The adsorption rate increases by increasing the fluoride concentration and by decreasing pH. The presence of phosphate reduces fluoride adsorption and reveals that both ions are in competition for surface sites. The reduction in fluoride adsorption when phosphate is present depends on the order of adsorbate addition. The higher fluoride adsorption occurs when both anions are added simultaneously, whereas when either fluoride or phosphate is added first, the fluoride adsorption is lower. The presence of fluoride does not have a measurable effect on phosphate adsorption. The results obtained contribute to our understanding of the mobility of fluoride in surface water which has naturally high levels of fluoride, in both the presence and absence of phosphate.

  1. Adsorption thermodynamics of Methylene Blue onto bentonite.

    PubMed

    Hong, Song; Wen, Cheng; He, Jing; Gan, Fuxing; Ho, Yuh-Shan

    2009-08-15

    The effect of temperature on the equilibrium adsorption of Methylene Blue dye from aqueous solution using bentonite was investigated. The equilibrium adsorption data were analyzed using three widely applied isotherms: Langmuir, Freundlich, and Redlich-Peterson. A non-linear method was used for comparing the best fit of the isotherms. Best fit was found to be Redlich-Peterson isotherm. Thermodynamic parameters, such as DeltaG degrees, DeltaH degrees, and DeltaS degrees were calculated using adsorption equilibrium constant obtained from the Langmuir isotherm. Results suggested that the Methylene Blue adsorption on bentonite was a spontaneous and endothermic process.

  2. 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.

  3. 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

  4. Adsorption/electrosorption of catechol and resorcinol onto high area activated carbon cloth.

    PubMed

    Bayram, Edip; Hoda, Numan; Ayranci, Erol

    2009-09-15

    Removal of catechol and resorcinol from aqueous solutions by adsorption and electrosorption onto high area activated carbon cloth (ACC) was investigated. Kinetics of both adsorption and electrosorption were followed by in-situ UV-spectroscopic method and the data were treated according to pseudo-first-order, pseudo-second-order and intraparticle diffusion models. It was found that the adsorption and electrosorption of these compounds onto ACC follows pseudo-second-order model. pH changes during adsorption and electrosorption were followed and discussed with regard to the interaction between ACC and adsorbate molecules, utilizing the pH(pzc) value of ACC. An electrodesorption experiment was conducted to explore the possibility of regeneration of ACC. Adsorption isotherms were derived at 25 degrees C on the basis of batch analysis. The fits of experimental isotherm data to the well-known Freundlich, Langmuir and Tempkin models were examined. PMID:19345487

  5. 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.

  6. Adsorption-desorption behavior of thiram onto humic acid.

    PubMed

    Filipe, O M S; Vidal, M M; Duarte, A C; Santos, E B H

    2009-06-10

    The adsorption/desorption behavior of pure thiram (Thi-P) and formulated thiram (Thi-F) onto commercial humic acids (HA) was studied using a batch equilibration procedure. Results of adsorption kinetic experiments showed that thiram adsorption is a fast process since 85% of the equilibrium concentration is reached within two hours. Experimental K(D) values between 0.110 to 0.210 L g(-1) were obtained for the adsorption of both Thi-P and Thi-F onto HA, suggesting that thiram is strongly sorbed by humic acids. In general, for both Thi-P and Thi-F, the lower the initial thiram concentration, the stronger is its adsorption (higher K(D) and percentage adsorption values). The adsorption isotherms were found to match the BET model. The results show that thiram adsorption onto condensed humic acids cannot be explained only in terms of specific interactions, such as those identified in studies of adsorption of thiram with humic acids in solution. The comparison of sorption and desorption results allowed the observation of hysteresis phenomena. Desorption K(D) values were consistently higher than those for adsorption at the same equilibrium concentration. Hysteresis was lower for the formulated thiram suggesting that adsorption is more reversible in the presence of the formulation components turning the pesticide more susceptible to be leached.

  7. 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.

  8. 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.

  9. 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.

  10. Bridging the gap between batch and column experiments: A case study of Cs adsorption on granite.

    PubMed

    Wang, Tsing-Hai; Li, Ming-Hsu; Teng, Shi-Ping

    2009-01-15

    Both batch and column methods are conventionally utilized to determine some critical parameters for assessing the transport of contaminants of concern. The validity of using these parameters is somewhat confusing, however, since outputs such as distribution coefficient (Kd) from these two approaches are often discrepant. To bridge this gap, all possible factors that might contribute to this discrepancy were thoroughly investigated in this report by a case study of Cs sorption to crushed granite under various conditions. Our results confirm an important finding that solid/liquid (S/L) ratio is the dominant factor responsible for this discrepancy. As long as the S/L ratio exceeds 0.25, a consistent Kd value can be reached by the two methods. Under these conditions (S/L ratios>0.25), the sorption capacity of the solid is about an order of magnitude less than that in low S/L ratios (<0.25). Although low sorption capacity is observed in the cases of high S/L ratios, the sorption usually takes place preferentially on the most favorable (thermodynamically stable) sorption sites to form a stronger binding. This is verified by our desorption experiments in which a linear isotherm feature is shown either in deionized water or in 1M of ammonium acetate solutions. It may be concluded that batch experiment with an S/L ratio exceeding 0.25 is crucial to obtain convincing Kd values for safety assessment of radioactive waste repository.

  11. 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

  12. 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.

  13. Kinetics of salicylic acid adsorption on activated carbon.

    PubMed

    Polakovic, Milan; Gorner, Tatiana; Villiéras, Frédéric; de Donato, Philippe; Bersillon, Jean Luc

    2005-03-29

    The adsorption and desorption of salicylic acid from water solutions was investigated in HPLC microcolumns packed with activated carbon. The adsorption isotherm was obtained by the step-up frontal analysis method in a concentration range of 0-400 mg/L and was well fitted with the Langmuir equation. The investigation of rate aspects of salicylic acid adsorption was based on adsorption/desorption column experiments where different inlet concentrations of salicylic acid were applied in the adsorption phase and desorption was conducted with pure water. The concentration profiles of individual adsorption/desorption cycles data were fitted using several single-parameter models of the fixed-bed adsorption to assess the influence of different phenomena on the column behavior. It was found that the effects of axial dispersion and extraparticle mass transfer were negligible. A rate-determining factor of fixed-bed column dynamics was the kinetics of pore surface adsorption. A bimodal kinetic model reflecting the heterogeneous character of adsorbent pores was verified by a simultaneous fit of the column outlet concentration in four adsorption/desorption cycles. The fitted parameters were the fraction of mesopores and the adsorption rate constants in micropores and mesopores, respectively. It was shown that the former rate constant was an intrinsic one whereas the latter one was an apparent value due to the effects of pore blocking and diffusional hindrances in the micropores. PMID:15779975

  14. 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.

  15. 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

  16. Metal adsorption on mosses: Toward a universal adsorption model.

    PubMed

    González, A G; Pokrovsky, O S

    2014-02-01

    This study quantifies the adsorption of heavy metals on 4 typical moss species used for environmental monitoring in the moss bag technique. The adsorption of Cu(2+), Cd(2+), Ni(2+), Pb(2+) and Zn(2+) onto Hypnum sp., Sphagnum sp., Pseudoscleropodium purum and Brachytecium rutabulum has been investigated using a batch reactor in a wide range of pH (1.3-11.0) and metal concentrations in solution (1.6μM-3.8mM). A Linear Programming Model (LPM) was applied for the experimental data to derive equilibrium constants and the number of surface binding sites. The surface acid-base titration performed for 4 mosses at a pH range of 3-10 in 0.1M NaNO3 demonstrated that Sphagnum sp. is the most efficient adsorbent as it has the maximal number of proton-binding sites on the surface (0.65mmol g(-1)). The pKa computed for all the moss species suggested the presence of 5 major functional groups: phosphodiester, carboxyl, phosphoryl, amine and polyphenols. The results of pH-edge experiments demonstrated that B. rutabulum exhibits the highest percentage of metal adsorption and has the highest number of available sites for most of the metals studied. However, according to the results of the constant pH "Langmuirian" isotherm, Sphagnum sp. can be considered as the strongest adsorbent, although the relative difference from other mosses is within 20%. The LPM was found to satisfactorily fit the experimental data in the full range of the studied solution parameters. The results of this study demonstrate a rather similar pattern of five metal adsorptions on mosses, both as a function of pH and as a metal concentration, which is further corroborated by similar values of adsorption constants. Therefore, despite the species and geographic differences between the mosses, a universal adsorption edge and constant pH adsorption isotherm can be recommended for 4 studied mosses. The quantitative comparison of metal adsorption with other common natural organic and inorganic materials demonstrates

  17. Adsorption of organics from tar sand water by activated carbon in packed beds. Final report

    SciTech Connect

    Hines, A.L.; Pedram, E.O.

    1982-12-30

    The adsorption of TS-1S and TS-2C tar sand waters were studied at 278 and 298/sup 0/K on activated carbon in both batch and packed bed experiments. The isotherms were nonlinear over the entire liquid concentration ranges. Breakthrough curves were obtained in packed bed experiments as a function of bed lengths, particle size, and liquid velocity. A mechanistic approach was used to solve the mass transfer equations for the packed adsorber, the mass transfer coefficients and the rates of adsorption were calculated. Also the breakthrough curves were analyzed to establish the relative importance of the various individual mechanisms that contributed to the overall adsorption process.

  18. [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

  19. 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)…

  20. Isothermal vapour flow in extremely dry soils

    NASA Astrophysics Data System (ADS)

    Todman, L. C.; Ireson, A. M.; Butler, A. P.; Templeton, M. R.

    2012-04-01

    In dry soils hydraulic connectivity within the liquid water phase decreases and vapour flow becomes a significant transport mechanism for water. The temperature or solute concentration of the liquid phase affects the vapour pressure of the surrounding air, thus temperature or solute gradients can drive vapour flows. However, in extremely dry soils where water is retained by adsorptive forces rather than capillarity, vapour flows can also occur. In such soils tiny changes in water content significantly affect the equilibrium vapour pressure in the soil, and hence small differences in water content can initiate vapour pressure gradients. In many field conditions this effect may be negligible compared to vapour flows driven by other factors. However, flows of this type are particularly significant in a new type of subsurface irrigation system which uses pervaporation, via a polymer tubing, as the mechanism for water supply. In this system, water enters the soil in vapour phase. Experiments were performed in laboratory conditions using marine sand that had previously been oven dried and cooled. This dry sand was used to represent the desert conditions in which this irrigation system is intended for use. Experimental results show that isothermal vapour flows can significantly affect the performance of such irrigation systems due to the rapid transport of water through the soil via the vapour phase. When the irrigation pipe was buried at a depth of 10cm a vapour flow from the soil surface was observed in less than 2 hours. These flows therefore affect the loss of mass into the atmosphere and thus must be considered when evaluating the availability of water for the irrigated crop. The experiments also provide a rare opportunity to observe isothermal vapour flows initiating from a subsurface source. Such experiments allow the significance of these flows to be quantified and potentially applied to other areas of arid zone hydrology.

  1. IMPLICATION OF BIOSOLIDS ON ADSORPTION AND DESORPTION OF CD IN SOILS

    EPA Science Inventory

    Adsorption isotherms for soils from long-term biosolids-field experiments and their inorganic fractions were obtained by equilibration of the samples with cadmium nitrate. The cadmium nitrate solution was replaced with a calcium nitrate solution to obtain desorbed Cd. Results sho...

  2. 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.

  3. 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

  4. 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)

  5. 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

  6. 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.

  7. Applications and limits of theoretical adsorption models for predicting the adsorption properties of adsorbents.

    PubMed

    Park, Hyun Ju; Nguyen, Duc Canh; Na, Choon-Ki; Kim, Chung-il

    2015-01-01

    The objective of this study is to evaluate the applicability of adsorption models for predicting the properties of adsorbents. The kinetics of the adsorption of NO3- ions on a PP-g-AA-Am non-woven fabric have been investigated under equilibrium conditions in both batch and fixed bed column processes. The adsorption equilibrium experiments in the batch process were carried out under different adsorbate concentration and adsorbent dosage conditions and the results were analyzed using adsorption isotherm models, energy models, and kinetic models. The results of the analysis indicate that the adsorption occurring at a fixed adsorbate concentration with a varying adsorbent dosage occur more easily compared to those under a fixed adsorbent dosage with a varying adsorbate concentration. In the second part of the study, the experimental data obtained using fixed bed columns were fit to Bed Depth Service Time, Bohart-Adams, Clark, and Wolborska models, to predict the breakthrough curves and determine the column kinetic parameters. The adsorption properties of the NO3- ions on the PP-g-AA-Am non-woven fabric were differently described by different models for both the batch and fixed bed column process. Therefore, it appears reasonable to assume that the adsorption properties were dominated by multiple mechanisms, depending on the experimental conditions.

  8. Thermodynamic and kinetic parameters of ofloxacin adsorption from aqueous solution onto modified coal fly ash

    NASA Astrophysics Data System (ADS)

    Zhang, C.-L.; Zhao, F.; Wang, Y.

    2012-04-01

    Batch adsorption experiments were carried out for the removal of ofloxacin from aqueous solution using modified coal fly ash as adsorbent. The effects of various parameters such as contact time, initial solution concentration and temperature on the adsorption system were investigated. The optimum contact time was found to be 150 min. The adsorption isotherm data fit well with the Langmuir model, and the kinetic data fit well with the pseudo-second order and the intra-particle diffusion model. Intra-particle diffusion analysis demonstrates that ofloxacin diffuses quickly among the particles at the beginning of the adsorption process, and then the diffusion slows down and stabilizes. Thermodynamic parameters such as Δ G, Δ H, and Δ S were also calculated. The negative Gibbs free energy change and the positive enthalpy change indicated the spontaneous and endothermic nature of the adsorption, and the positive entropy change indicated that the adsorption process was aided by increased randomness.

  9. 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.

  10. Adsorption kinetic and thermodynamic studies of phosphate onto tantalum hydroxide.

    PubMed

    Yu, Shi-Hua; Dong, Xiao-Le; Gong, Hong; Jiang, Heng; Liu, Zhi-Gang

    2012-12-01

    Tantalum hydroxide exhibits the ability for the removal of phosphate from aqueous solution. The kinetic study, adsorption isotherm, thermodynamic study, desorption, and foreign anions effect were examined in batch experiments. The kinetic process was very well described by a pseudo-second-order rate model. The adsorption isotherms showed that phosphate uptake fitted with a Langmuir-type model very well, with an increase of PO4(3-) adsorption capacity from 78.5 to 97.0 mg/g when the temperature increased from 298 to 338 K. The negative values of deltaG(0) and the positive values of deltaH(0) indicated that the phosphate adsorption process was spontaneous and endothermic naturally. While the deltaS(0) values obtained were positive, indicating an increase in randomness at the solid-liquid interface during the adsorption. Foreign anions tests showed that the presence of competitive ions cause minimal interference with the adsorption of phosphate on tantalum hydroxide.

  11. [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

  12. [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

  13. Interpretation of dynamic frontal analysis data in solid/supercritical fluid adsorption systems. I: theory.

    PubMed

    Gritti, Fabrice; Tarafder, Abhijit; Guiochon, Georges

    2013-05-17

    A theory is proposed to relate the elution times of the adsorption front shocks of breakthrough curves recorded during classical dynamic frontal analysis (FA) experiments with selected compounds and their adsorption isotherms in solid/supercritical fluid adsorption systems. The actual density and viscosity of binary mixtures of CO2 and methanol were obtained from the NIST REPPROP software. Diluted solutions of S-naproxen were considered (<2% in mass) but the possible effects of the analyte concentration on the viscosity and the density of the eluent percolating through the column were neglected. This allows the determination of the excess adsorption isotherm (or Gibbs excess isotherm) of the adsorbed analyte in the whole column at constant mass and volumetric flow rate of pure CO2 and of the modifier solution. A local Langmuir adsorption isotherm and a constant saturation capacity were assumed in the calculations. The variation of the adsorption-desorption constant with the eluent density was taken from the experimental variation of the retention factor of S-naproxen on a chiral column packed with Whelk-O1 particles. The results show that the isotherm parameters obtained from the best adjustment of the Langmuir model to the SFC excess adsorption data deviates by less than 7% from the assumed saturation capacity and from the average of the equilibrium constant along the chromatographic column. In practice, this conclusion holds true provided that the precision of the measurement of elution times of front shocks of breakthrough curves is better than 1% and that the maximum surface coverage qexp,max/qS is at least equal to 20%.

  14. Comparison of batch, stirred flow chamber, and column experiments to study adsorption, desorption and transport of carbofuran within two acidic soils.

    PubMed

    Bermúdez-Couso, Alipio; Fernández-Calviño, David; Rodríguez-Salgado, Isabel; Nóvoa-Muñoz, Juan Carlos; Arias-Estévez, Manuel

    2012-06-01

    Different methods (batch, column and stirred flow chamber experiments) used for adsorption and desorption of carbofuran studies were compared. All tested methods showed that the carbofuran adsorption was higher in the soil with the higher organic matter content, whereas the opposite behaviour was observed for the percentage of carbofuran desorbed. However, different methods have revealed some discrepancies in carbofuran adsorption/desorption kinetics. Although batch method showed interesting data on equilibrium experiments, such as a low heterogeneity for the carbofuran adsorption sites independent of soil organic matter content, it had some disadvantages for carbofuran adsorption/desorption kinetic studies. The disadvantages were related with the excessive limitations of this method on kinetics, i.e., no difference could be detected between different soils. However, with column and stirred flow chamber methods the carbofuran adsorption/desorption kinetics of different soils could be compared. Moreover, the absolute values of carbofuran adsorption/desorption and its rate were higher in the stirred flow chamber than in the batch and column experiments. Using stirred flow chamber experiments the carbofuran desorption was significantly faster than its adsorption, whereas carbofuran using column experiments they were similar. These discrepancies should be considered when the results obtained only with one method is discussed.

  15. Pollutant dispersion in a large indoor space: Part 2 -Computational Fluid Dynamics (CFD) predictions and comparison with ascale model experiment for isothermal flow

    SciTech Connect

    Finlayson, Elizabeth U.; Gadgil, Ashok J.; Thatcher, Tracy L.; Sextro, Richard G.

    2002-10-01

    This paper reports on an investigation of the adequacy of Computational fluid dynamics (CFD), using a standard Reynolds Averaged Navier Stokes (RANS) model, for predicting dispersion of neutrally buoyant gas in a large indoor space. We used CFD to predict pollutant (dye) concentration profiles in a water filled scale model of an atrium with a continuous pollutant source. Predictions from the RANS formulation are comparable to an ensemble average of independent identical experiments. Model results were compared to pollutant concentration data in a horizontal plane from experiments in a scale model atrium. Predictions were made for steady-state (fully developed) and transient (developing) pollutant concentrations. Agreement between CFD predictions and ensemble averaged experimental measurements is quantified using the ratios of CFD-predicted and experimentally measured dye concentration at a large number of points in the measurement plane. Agreement is considered good if these ratios fall between 0.5 and 2.0 at all points in the plane. The standard k-epsilon two equation turbulence model obtains this level of agreement and predicts pollutant arrival time to the measurement plane within a few seconds. These results suggest that this modeling approach is adequate for predicting isothermal pollutant transport in a large room with simple geometry.

  16. 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.

  17. Unified water isotherms for clayey porous materials

    NASA Astrophysics Data System (ADS)

    Revil, A.; Lu, N.

    2013-09-01

    We provide a unified model for the soil-water retention function, including the effect of bound and capillary waters for all types of soils, including clayey media. The model combines a CEC-normalized isotherm describing the sorption of the bound water (and the filling of the trapped porosity) and the van Genuchten model to describe the capillary water sorption retention but ignore capillary condensation. For the CEC-normalized isotherm, we tested both the BET and Freundlich isotherms, and we found that the Freundlich is more suitable than the BET isotherm in fitting the data. It is also easier to combine the Freundlich isotherm with the van Genuchten model. The new model accounts for (1) the different types of clay minerals, (2) the different types of ions sorbed in the Stern layer and on the basal planes of 2:1 clays, and (3) the pore size distribution. The model is validated with different data sets, including mixtures of kaolinite and bentonite. The model parameters include two exponents (the pore size exponent of the van Genuchten model and the exponent of the Freundlich isotherm), the capillary entry pressure, and two critical water contents. The first critical water content is the water content at saturation (porosity), and the second is the maximum water content associated with adsorption forces, including the trapped nonbound water.

  18. [Adsorption and partition of PAHS on particles of the Yellow River].

    PubMed

    Meng, Li-hong; Xia, Xing-hui; Yu, Hui; Sha, Yu-juan

    2006-05-01

    Experiments were carried out to study the sorption of PAHs Benzo(a)pyrene, chrysene and Benzo(g, h, i)perylene on particles of the Yellow River. The contributions of adsorption and partition to the sorption of PAHs were investigated. Several significant results were obtained from the study: (1) The total sorption capacity increases with the particle content while the sorption capacity of unit weight particle decreases; the isotherms of Benzo(a)pyrene depend on the particle content. (2) Isotherms of Benzo(a) pyrene can be fitted with the Dual Adsorption-Partition model under different particle content; the measured value of the adsorption and partition are in accord with the theoretical value of the Dual Adsorption-Partition model. (3) The adsorption is predominant in the sorption of Benzo(a)pyrene. When the particle contents are 3, 8 and 15 g/L and the liquid equilibrium concentrations are 2.84, 2.35 and 3.4 microg/L, respectively, the contributions of adsorption are 67.8%, 65.6% and 62.69%, respectively. In addition, the contributions of adsorption have a decreasing trend with the increase of the particle content. (4) The sorption capacity of Benzo (a) pyrene being alone are bigger than that with other PAHs chrysene and Benzo(g, h, i)perylene coexisting in the water system, this also proves that the adsorption is predominant in the sorption of PAHs.

  19. 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.

  20. 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.

  1. Use of statistical design of experiments to evaluate the sorption capacity of 7-amine-4-azaheptylsilica and 10-amine- 4-azadecylsilica for Cu(II), Pb(II), and Fe(III) adsorption.

    PubMed

    Passos, Camila G; Ribaski, Fernanda S; Simon, Nathália M; dos Santos, Araci A; Vaghetti, Júlio C P; Benvenutti, Edilson V; Lima, Eder Cláudio

    2006-10-15

    7-Amine-4-azaheptylsilica (AAH Si) and 10-amine-4-azadecylsilica (AAD Si) were prepared and used for removal of Cu(II), Pb(II), and Fe(III) from aqueous solutions. Full 2(3) factorial designs with two pseudo-central points were carried out in order to achieve the best conditions of the batch adsorption procedure for metallic ion uptake by the adsorbents. To continue the optimizations, central composite surface design was also employed. These two independent statistical designs of experiments lead to the following conditions: m=30.0 mg of adsorbent; pH 6.0 for Cu(II) and Pb(II), pH 4.0 for Fe(III); t of contact 180 min to guarantee equilibration at higher adsorbate concentration. After optimization of the conditions, isotherms of the metallic ions adsorbed on the AAH Si and AAD Si adsorbents were obtained, which were fitted to nonlinear Langmuir and Freundlich isotherm models.

  2. [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.

  3. 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

  4. [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

  5. Adsorption of soluble oil from water to graphene.

    PubMed

    Wang, Na; Zhang, Yuchang; Zhu, Fuzhen; Li, Jingyi; Liu, Shuaishuai; Na, Ping

    2014-05-01

    The toxicity of soluble oil to the aquatic environment has started to attract wide attention in recent years. In the present work, we prepare graphene according to oxidation and thermal reduction methods for the removal of soluble oil from the solution. Characterization of the as-prepared graphene are performed by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Raman spectra, Brunauer-Emmett-Teller, X-ray photoelectron spectroscopy, and contact angle analysis. The adsorption behavior of soluble oil on graphene is examined, and the obtained adsorption data are modeled using conventional theoretical models. Adsorption experiments reveal that the adsorption rate of soluble oil on graphene is notably fast, especially for the soluble diesel oil, which could reach equilibrium within 30 min, and the kinetics of adsorption is perfectly consistent with a pseudo-second-order model. Furthermore, it is determined that the adsorption isotherm of soluble diesel oil with graphene fit the Freundlich model best, and graphene has a very strong adsorption capacity for soluble diesel oil in the solution. These results demonstrate that graphene is the material that provided both good adsorptive capacity and good kinetics, implying that it could be used as a promising sorbent for soluble oil removal from wastewater.

  6. [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.

  7. [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

  8. 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.

  9. Adsorption characteristics and preparative separation of chaetominine from Aspergillus fumigatus mycelia by macroporous resin.

    PubMed

    Liu, Changqing; Jiao, Ruihua; Yao, Lingyun; Zhang, Yupeng; Lu, Yanhua; Tan, Renxiang

    2016-03-15

    Chaetominine (CHA) is a quinazolinone alkaloid with strong anti-cancer activity produced by Aspergillus fumigatus CY018. For recovering CHA from A. fumigates efficiently, adsorption and desorption capacities of eight macroporous resins were tested in this work. Based on batch experiments, XAD-16 resin was revealed the best adsorption and desorption performance among all the tested resins. Then, adsorption kinetics and adsorption isotherms were constructed on XAD-16 resin, and the experimental data were fitted well to the pseudo first-order kinetics and Freundlick isotherm model. In the dynamic adsorption and desorption, the purity of CHA increased from 0.0314% (w/w) in the crude extract to 57.86% in the final product with recovery yield of 70.56% by a one-step treatment. Moreover, the experiments were also performed in a lab scale-up scale, in which the purity and recovery of CHA were 56.12% (w/w) and 68.02%, respectively. In addition, XAD-16 resin could be recycled 3 times for CHA separation after regeneration without adverse effects on adsorption/desorption performance. These results suggested that XAD-16 resin adsorption could act as a useful and economic method for recovering CHA from A. fumigatus.

  10. Adsorptive characterization of the ZIF-68 metal-organic framework: a complex structure with amphiphilic properties.

    PubMed

    Van der Perre, Stijn; Van Assche, Tom; Bozbiyik, Belgin; Lannoeye, Jeroen; De Vos, Dirk E; Baron, Gino V; Denayer, Joeri F M

    2014-07-22

    In this experimental study, the adsorption behavior of the ZIF-68 heterolinked zeolitic imidazolate framework has been explored. Vapor phase adsorption isotherms of linear C1-C6 alcohols, C6 alkane isomers, aromatics (benzene, toluene, xylene isomers, 1,3,5-trimethylbenzene, and 1,3,5-triisopropylbenzene), and polar adsorbates (water, acetonitrile, and acetone) are reported and discussed. The complex pore structure of ZIF-68, with two one-dimensional channels, each with a different polarity, displays an overall hydrophobic character. Its two-pore system results in S-shaped isotherms for small polar adsorbates (small alcohols, acetone, and acetonitrile), while longer alcohols and nonpolar molecules, such as aromatics and C6 alkane isomers, lead to type I adsorption isotherms. Bulky molecules, with a kinetic diameter significantly larger than the pore windows, are adsorbed in large amounts, which gave reason to think that this ZIF-68 material has a certain degree of framework flexibility to enlarge the free aperture of the channels. Besides, diffusion coefficients from vapor phase uptake and infrared experiments point to a different adsorption mechanism for polar and nonpolar adsorbates. Liquid phase adsorption experiments demonstrated the separation of alcohol mixtures (ethanol/1-butanol) at low concentration from water, with a clear preference for 1-butanol.

  11. 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.

  12. Isothermal and Adiabatic Measurements.

    ERIC Educational Resources Information Center

    McNairy, William W.

    1996-01-01

    Describes the working of the Adiabatic Gas Law Apparatus, a useful tool for measuring the pressure, temperature, and volume of a variety of gases undergoing compressions and expansions. Describes the adaptation of this apparatus to perform isothermal measurements and discusses the theory behind the adiabatic and isothermal processes. (JRH)

  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.

  14. 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.

  15. 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.

  16. 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...

  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. 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.

  19. Insight into the adsorption mechanisms of vanadium(V) on a high-efficiency biosorbent (Ti-doped chitosan bead).

    PubMed

    Liu, Xin; Zhang, Lingfan

    2015-08-01

    In this present study, a new chitosan bead modified with titanium ions (TiCB) was prepared and employed for the adsorption of vanadium ions from aqueous solutions. Batch adsorption experiments were performed to research the effect of various factors, including pH, temperature, contact time and initial concentration of vanadium(V) ions. The adsorption of vanadium was followed by the pseudo second-order kinetic and the Langmuir isotherm model, with a remarkable maximum adsorption capacity of 210 mg/g. The analysis of thermodynamic parameters (ΔG°, ΔH° and ΔS°) revealed that the nature of adsorption was feasible, spontaneous (ΔG°<0) and endothermic (ΔH°>0) process. FTIR, EDS, EMI and XPS studies suggested that the mechanisms of adsorption were possibly attributed to electrostatic attraction, ligand-exchange and redox reaction between TiCB and vanadium ions.

  20. Insight into the adsorption mechanisms of vanadium(V) on a high-efficiency biosorbent (Ti-doped chitosan bead).

    PubMed

    Liu, Xin; Zhang, Lingfan

    2015-08-01

    In this present study, a new chitosan bead modified with titanium ions (TiCB) was prepared and employed for the adsorption of vanadium ions from aqueous solutions. Batch adsorption experiments were performed to research the effect of various factors, including pH, temperature, contact time and initial concentration of vanadium(V) ions. The adsorption of vanadium was followed by the pseudo second-order kinetic and the Langmuir isotherm model, with a remarkable maximum adsorption capacity of 210 mg/g. The analysis of thermodynamic parameters (ΔG°, ΔH° and ΔS°) revealed that the nature of adsorption was feasible, spontaneous (ΔG°<0) and endothermic (ΔH°>0) process. FTIR, EDS, EMI and XPS studies suggested that the mechanisms of adsorption were possibly attributed to electrostatic attraction, ligand-exchange and redox reaction between TiCB and vanadium ions. PMID:25940529

  1. 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

  2. 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.

  3. Mechanical and dye adsorption properties of graphene oxide/chitosan composite fibers prepared by wet spinning.

    PubMed

    Li, Yanhui; Sun, Jiankun; Du, Qiuju; Zhang, Luhui; Yang, Xiaoxia; Wu, Shaoling; Xia, Yanzhi; Wang, Zonghua; Xia, Linhua; Cao, Anyuan

    2014-02-15

    Graphene oxide/chitosan composite fibers were prepared by a wet spinning method, and their mechanical properties were investigated. Experimental results showed that the introduction of graphene oxide at 4 wt% loading can improve the tensile strengths of chitosan fibers. Batch adsorption experiments were carried out to study the effect of various parameters, such as the initial pH value, adsorbent dosage, contact time and temperature on adsorption of fuchsin acid dye. The Langmuir model was used to fit the experimental data of adsorption isotherm, and kinetic studies showed that the adsorption data followed the pseudo-second order model. Thermodynamic studies indicated that the adsorption of fuchsin acid dye on graphene oxide/chitosan fibers was a spontaneous and exothermic process. Our results indicate that the graphene oxide/chitosan fibers have excellent mechanical properties and can serve as a promising adsorbent for the removal of dyes from aqueous solutions.

  4. 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.

  5. Photocatalytic degradation of phenol and phenolic compounds Part I. Adsorption and FTIR study.

    PubMed

    Araña, J; Pulido Melián, E; Rodríguez López, V M; Peña Alonso, A; Doña Rodríguez, J M; González Díaz, O; Pérez Peña, J

    2007-07-31

    With the goal of predicting the photocatalytic behaviour of different phenolic compounds (catechol, resorcinol, phenol, m-cresol and o-cresol), their adsorption and interaction types with the TiO(2) Degussa P-25 surface were studied. Langmuir and Freundlich isotherms were applied in the adsorption studies. The obtained results indicated that catechol adsorption is much higher than those of the other phenolics and its interaction occurs preferentially through the formation of a catecholate monodentate. Resorcinol and the cresols interact by means of hydrogen bonds through the hydroxyl group, and their adsorption is much lower than that of catechol. Finally, phenol showed an intermediate behaviour, with a Langmuir adsorption constant, K(L), much lower than that of catechol, but a similar interaction. The interaction of the selected molecules with the catalyst surface was evaluated by means of FTIR experiments, which allowed us to determine the probability of OH radical attack to the aromatic ring.

  6. 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

  7. 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

  8. Impact of sewage sludge spreading on nickel mobility in a calcareous soil: adsorption-desorption through column experiments.

    PubMed

    Mamindy-Pajany, Yannick; Sayen, Stéphanie; Guillon, Emmanuel

    2013-07-01

    A soil column adsorption-desorption study was performed on an agricultural calcareous soil to determine the impact of sewage sludge spreading on nickel mobility. Ni adsorption experiments were followed by desorption tests involving the following liquid extractants: water, calcium (100 mg/L), oxalic acid (525 mg/L equivalent to 100 mg carbon/L), and sludge extracts (0.5 and 2.5 g/L). Desorption tests were also conducted after sewage sludge spreading at three application rates (30, 75, and 150 t/ha). According to the breakthrough curve, Ni adsorption was irreversible and occurred mainly through interactions with calcite surface sites. Nickel desorption from the soil column was promoted in presence of significant dissolved organic carbon (DOC) concentration as observed with oxalic acid elution and sludge extract at 2.5 g/L. In sludge-amended soil columns, the maximum Ni levels occurred in first pore volumes, and they were positively correlated to the sludge application rate. The presence of DOC in leaching waters was the main factor controlling Ni desorption from the sludge-amended soil columns. This finding implies that DOC generated by sludge applied on calcareous soils might facilitate the leaching of Ni due to the formation of soluble Ni-organic complexes. Thus, sludge application can have potential environmental impacts in calcareous soils, since it promotes nickel transport by decreasing Ni retention by soil components.

  9. Collagen fiber immobilized Myrica rubra tannin and its adsorption to UO2(2+).

    PubMed

    Liao, Xuepin; Lu, Zhongbi; Du, Xiao; Liu, Xin; Shi, Bi

    2004-01-01

    Tannins, which are rich in ortho-hydroxyl groups, have a high affinity for UO2(2+). In this paper, Myrica rubra tannin was immobilized on collagen fiber by an aldehydic cross-linking reaction to prepare a novel adsorbent for uranium (UO2(2+)) recovery from wastewater. The adsorption equilibrium, the adsorption kinetics, and the effects of temperature and pH on the adsorption equilibrium were investigated in detail. It was found that the Myrica rubra tannin immobilized on collagen fiber exhibits an excellent adsorption capacity for UO2(2+). The adsorption capacity at 293 K and pH 5.0 was as high as 1.19 mmol UO2(2+)/g (283.3 mgU/g) when the initial concentration of UO2(2+) in solution was 7.5 mmol/L. The adsorption isotherms could be described by the Freundlich equation, and the increase of temperature promoted the adsorption to UO2(2+) . The adsorption kinetics data were fitted very well by the pseudosecond-order rate model, and the equilibrium adsorption capacity calculated by the pseudo-second-order rate model was almost the same as that determined by the actual measurement with the error < or = 4%. The pH has a significant effect on the adsorption process. According to our experiments, the suitable pH scope should be 5-8.

  10. 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

  11. Isothermal solidification in a binary alloy melt

    NASA Technical Reports Server (NTRS)

    Laxmanan, V.

    1988-01-01

    A space shuttle experiment employing the General Purpose (Rocket) Furnace (GPF) in its isothermal mode of operation is manifested on MSL-3, circa 1989. The central aim of this experiment is to investigate the effect of reduced gravity levels on the segregation behavior in a slowly, and isothermally, cooled sample of a binary Pb-15 wt percent Sn alloy. This experiment would thus be able to simulate, in a small laboratory sample, about 20 mm dia 60 mm high and weighing about 150 grams, some aspects of the segregation phenomena occurring in large industrial ingots. Ground-based experiments conducted in the single-cavity simulator of the GPF, located at Marshall Space Flight Center (MSFC), in support of the microgravity experiment are described in detail. The results of the MSFC experiments are compared with other related experiments conducted at Case Western Reserve University (CWRU), wherein the isothermal constraints were relaxed.

  12. 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

  13. Results of the HPT-experiment critical adsorption on EURECA I

    NASA Astrophysics Data System (ADS)

    Thommes, M.; Findenegg, G. H.

    1995-08-01

    The adsorption behavior of a near-critical fluid (SF_6) on a finely dispersed graphitic adsorbent (graphitized carbon black, Vulcan 3-G) has been studied. The surface excess concentration Gamma was measured as a function of temperature along near-critical isochores using a volumetric apparatus housed in a high-precision thermostat (HPT). Five experimental runs (each extending over ca. 30 days) were performed on the EURECA I space platform to avoid gravitational effects on the near-critical bulk fluid. In addition, complementary tests involving systematic changes of the experimental conditions were also performed by sequences of telecommands to test the reliability of the results in the near-critical region. The EURECA results confirm a novel critical adsorption phenomenon, which is probably due to the colloidal state of the adsorbent and is termed critical depletion.

  14. 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

  15. 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.

  16. 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.

  17. Adsorption Properties of Hydrogen and Carbon Dioxide in Prussian Blue Analogues M3[Co(CN)6]2, M ) Co, Zn

    SciTech Connect

    Natesakhawat, S.; Culp, J.T.; Matranga, C.S.; Bockrath, B.C.

    2007-01-18

    H2 and CO2 adsorption were studied in dehydrated Prussian blue analogues M3[Co(CN)6]2 (M ) Co, Zn) using volumetric isotherm measurements. Both materials adsorbed 1.2-1.3 wt % of H2 at 77 K and 760 Torr with isosteric heats of adsorption ranging from 5.9 to 6.8 kJ/mol. High-pressure H2 isotherms at 77 K showed that Co3[Co(CN)6]2 started to saturate well above 6 atm with a saturation coverage of ~1.9 wt %. These materials adsorbed approximately 17.6-19.7 wt % of CO2 at 253 K and 760 Torr with isosteric heats of adsorption of ~25-28 kJ/mol. The CO2 saturation coverages from high-pressure isotherms at 263 K and 15 atm were ~27.4-29.0 wt %. The displacement of CO2 by H2 in these compounds was investigated with Fourier transform infrared spectroscopy (FTIR). The FTIR experiments showed that CO2 physisorption at cryogenic temperatures produced an infrared peak at 2335 cm-1. Co-adsorption experiments revealed that H2 was able to displace preadsorbed CO2 if the PH2/PCO2 ratio was well above 100. The infrared results from the co-adsorption experiments also showed that H2 and CO2 competed for adsorption in the same pores under these conditions.

  18. Selective adsorption of uranium(VI) from aqueous solutions using the ion-imprinted magnetic chitosan resins.

    PubMed

    Zhou, Limin; Shang, Chao; Liu, Zhirong; Huang, Guolin; Adesina, Adesoji A

    2012-01-15

    The ion-imprinted magnetic chitosan resins (IMCR) prepared using U(VI) as a template and glutaraldehyde as a cross-linker showed higher adsorption capacity and selectivity for the U(VI) ions compared with the non-imprinted magnetic chitosan resins (NIMCR) without a template. The results showed that the adsorption of U(VI) on the magnetic chitosan resins was affected by the initial pH value, the initial U(VI) concentration, as well as the temperature. Both kinetics and thermodynamic parameters of the adsorption process were estimated. These data indicated an exothermic spontaneous adsorption process that kinetically followed the second-order adsorption process. Equilibrium experiments were fitted in Langmuir, Freundlich, and Dubinin-Radushkevich adsorption isotherm models to show very good fits with the Langmuir isotherm equation for the monolayer adsorption process. The monolayer adsorption capacity values of 187.26 mg/g for IMCR and 160.77 mg/g for NIMCR were very close to the maximum capacity values obtained at pH 5.0, temperature 298 K, adsorbent dose 50 mg, and contact time 3 h. The selectivity coefficient of uranyl ions and other metal ions on IMCR indicated an overall preference for uranyl ions. Furthermore, the IMCR could be regenerated through the desorption of the U(VI) ions using 0.5 M HNO(3) solution and could be reused to adsorb again.

  19. 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

  20. 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.

  1. 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.

  2. 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.

  3. 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

  4. 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

  5. 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.

  6. 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.

  7. 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

  8. Adsorption studies of azotetrazolate and 3,6-dihydrazinotetrazine on peat.

    PubMed

    Borkowski, Andrzej; Rydelek, Paweł; Szala, Mateusz

    2013-01-01

    The objective of our studies was the evaluation of the adsorption process of two high-nitrogen compounds-dihydrazinotetrazine (DHTz) and azotetrazolate ion (AZ)-on a chosen peat. The experiments were performed using a static method at three different temperatures (283, 298, and 333 K). The adsorption process of DHTz and AZ on peat was characterized by isotherms according to the Freundlich and Langmuir models. The obtained correlations between adsorption and equilibrium concentration were in good accordance with the Freundlich and Langmuir models, as confirmed by high values of the correlation coefficients (0.97-0.99). Adsorption of AZ on peat was less efficient than that of DHTz, and this inference was experimentally proven. The maximum surface coverages of peat particles with adsorbate according to the Langmuir model were calculated as 0.02 and 0.17 mol kg(-1) (at 298 K) for AZ and DHTz, respectively. The determined adsorption equilibrium constants confirmed greater adsorption of DHTz on the investigated peat. It can be concluded that adsorption of AZ occurred to a much lesser extent compared to that of DHTz, pointing to a potentially greater threat of migration of soluble azotetrazolates in soil. Standard enthalpies of adsorption estimated for AZ and DHTz were -11.1 and -23.7 kJ mol(-1), respectively. Based on these adsorption enthalpy values, it can be stated that both investigated compounds are adsorbed on peat by a physisorption process.

  9. 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

  10. 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.

  11. Determination of equilibrium and kinetic parameters of the adsorption of Cr(III) and Cr(VI) from aqueous solutions to Agave Lechuguilla biomass.

    PubMed

    Romero-González, Jaime; Gardea-Torresdey, Jorge L; Peralta-Videa, José R; Rodríguez, Elena

    2005-01-01

    This investigation reveals the capability of Agave lechuguilla for trivalent and hexavalent chromium removal from aqueous solutions. Experimentation included pH profile, time dependence, adsorption capacity (K(F) and Q(L)), adsorption intensity (n and R(L)) and saturation capacity (q(s)) studies. Batch experiments were conducted at 22( composite function)C to characterize and model the adsorption equilibrium as well as biomass adsorption rates. pH 4 was the optimum for Cr(III) binding, while Cr(VI) optimum binding was at pH 2. Time profile experiments indicated that the adsorption of Cr(VI) by lechuguilla biomass was time-dependent and that of Cr(III) was not. Kinetic models demonstrated that a pseudo-second order reaction model best described the kinetic data for Cr(VI). The adsorption isotherms showed that the binding pattern for Cr(VI) followed the Freundlich isotherm model, while that for Cr(III) followed the Langmuir isotherm. PMID:18365089

  12. Intestinal adsorption of levothyroxine by antacids and laxatives: case stories and in vitro experiments.

    PubMed

    Mersebach, H; Rasmussen, A K; Kirkegaard, L; Feldt-Rasmussen, U

    1999-03-01

    Two patients with hypothyroidism treated for upper dyspepsia and constipation with aluminum hydroxide and magnesium oxide, respectively, presented a marked increase in the serum concentration of thyroid stimulating hormone and low serum thyroxine on a fixed dosage of levothyroxine. After discontinuation of antacids/laxatives, thyroid stimulating hormone was again reduced indicating interaction between levothyroxine and antacids/laxatives. In vitro studies revealed a dose-related increased adsorption of levothyroxine by addition of a combination of aluminum hydroxide, magnesium hydroxide and magnesium carbonate, while no connection between levothyroxine and the addition of magnesium oxide, alone, was found. This finding has major clinical consequences since 1) many patients are treated with levothyroxine, 2) most patients do not tell physicians that they take antacids/laxatives, and 3) consumption of antacids/laxatives in patients with levothyroxine-treated hypothyroidism may lead to serious undersubstitution with levothyroxine.

  13. Critical analysis of the apoferritin adsorption at solid-liquid interfaces in the framework of a particular adsorption model

    NASA Astrophysics Data System (ADS)

    Lavalle, Ph.; Gergely, C.; Lustig, A.; Ball, V.

    2000-11-01

    The adsorption mechanism of horse spleen apoferritin on smooth Si(Ti)O2 surfaces was investigated by means of optical wave guide lightmode spectroscopy (OWLS) as well as with atomic force microscopy (AFM), for which images of high resolution were obtained on muscovite mica surfaces. By the use of both experimental methods, the adsorption process could be studied from a kinetic as well as from a statistical thermodynamics point of view. This approach allowed to test the hypothesis of the occurrence of a particular type of deposition mechanism, namely the random sequential adsorption (RSA), by evaluating all the requirements that should be fulfilled in such a process. Only the requirement relative to the kinetics of the adsorption process, and subsequently, the estimation of the surface coverage at saturation is fulfilled by our experiments. From the fit of the theoretical kinetic equations corresponding to the RSA model to the experimental adsorption kinetics we find that the apoferritin molecules occupy an area of 140±30 nm2, in agreement with the values found by counting the number of particles per unit area in the AFM experiments and also with the saturation level of the adsorption isotherm. From our experiments we found that the evolution of the surface coverage close to saturation did not follow the expected power law evolution with time in the framework of the RSA model. Moreover, the dependence of the density fluctuations on the sub-surface area in the AFM image is not consistent with the expected evolution obtained by computer simulations based on the RSA model. These results emphasize the difficulty to study the adsorption mechanism of proteins at solid—liquid interfaces in the framework of any given adsorption model.

  14. Performance, kinetics, and equilibrium of methylene blue adsorption on biochar derived from eucalyptus saw dust modified with citric, tartaric, and acetic acids.

    PubMed

    Sun, Lei; Chen, Dongmei; Wan, Shungang; Yu, Zebin

    2015-12-01

    Biochar derived from eucalyptus saw dust modified with citric, tartaric, and acetic acids at low temperatures was utilized as adsorbent to remove methylene blue (MB) from aqueous solutions. Fourier transform infrared spectroscopy analysis showed that the carboxyl group was introduced on the biochar surface. Adsorption experiment data indicated that eucalyptus saw dust modified with citric acid showed higher MB adsorption efficiency than that modified with tartaric and acetic acids. Pseudo-second-order kinetics was the most suitable model for describing MB adsorption on biochar compared with pseudo-first-order, Elovich, and intraparticle diffusion models. The calculated values of ΔG(0) and ΔH(0) indicated the spontaneous and endothermic nature of the adsorption process. MB adsorption on biochar followed the Langmuir isotherm. The maximum adsorption capacities for eucalyptus saw dust modified with citric, tartaric, and acetic acids were 178.57, 99.01, and 29.94 mg g(-1), respectively, at 35°C.

  15. Reduction of COD in refinery wastewater through adsorption on date-pit activated carbon.

    PubMed

    El-Naas, Muftah H; Al-Zuhair, Sulaiman; Abu Alhaija, Manal

    2010-01-15

    Experiments were carried out to evaluate the batch adsorption of COD from petroleum refinery wastewater on a locally prepared date-pit activated carbon (DP-AC), and its adsorption effectiveness was compared to that of commercially available BDH activated carbon (BDH-AC). Adsorption equilibrium and kinetic data were determined for both adsorbents and fitted to several adsorption isotherm and kinetics models, respectively. The Langmuir monolayer isotherm fitted well the equilibrium data of COD on both adsorbents; whereas, the kinetics data were best fitted by the pseudo-second order model. Modeling of the controlling mechanisms indicated that both intrinsic kinetics and mass transfer contributed to controlling the adsorption process. Mass transfer seemed to be the dominant mechanism at low COD content, while intrinsic kinetics dominates at high concentrations. In general, the adsorption effectiveness of locally prepared DP-AC was proven to be comparable to that of BDH-AC. Therefore, DP-AC can be utilized as an effective and less expensive adsorbent for the reduction of COD in refinery wastewater.

  16. Adsorption Behavior of Ferromagnetic Carbon Nanotubes for Methyl Orange from Aqueous Solution.

    PubMed

    Wang, Liping; Zhang, Mingyu; Zhao, Chenxi; Yang, Shan

    2016-03-01

    The ferromagnetic carbon nanotubes which can be easily separated from aqueous solution were prepared and characterized by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). Batch experiments were carried out to investigate the adsorption behavior of ferromagnetic carbon nanotubes for removing methyl orange (MO). The results showed that these ferromagnetic carbon nanotubes were richer in surface function groups than the carbon nanotubes did, furthermore, both γ-Fe2O3 and Fe with ferromagnetism were found on the surface of carbon nanotubes. The results also demonstrated that ferromagnetic carbon nanotubes possessed stronger adsorption ability for MO than carbon nanotubes did. The adsorption isotherms followed Langmuir isotherm equation and the adsorption kinetics could be well described with the pseudo second-order kinetic model. The adsorption process involved an intraparticle diffusion, while it was not the only rate-controlling step. The values of AG were negative and the value of ΔH is -12.37 kJ/mol, proving that the adsorption of MO onto ferromagnetic carbon nanotubes was a spontaneous and exothermic process.

  17. [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

  18. Adsorption Behavior of Ferromagnetic Carbon Nanotubes for Methyl Orange from Aqueous Solution.

    PubMed

    Wang, Liping; Zhang, Mingyu; Zhao, Chenxi; Yang, Shan

    2016-03-01

    The ferromagnetic carbon nanotubes which can be easily separated from aqueous solution were prepared and characterized by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). Batch experiments were carried out to investigate the adsorption behavior of ferromagnetic carbon nanotubes for removing methyl orange (MO). The results showed that these ferromagnetic carbon nanotubes were richer in surface function groups than the carbon nanotubes did, furthermore, both γ-Fe2O3 and Fe with ferromagnetism were found on the surface of carbon nanotubes. The results also demonstrated that ferromagnetic carbon nanotubes possessed stronger adsorption ability for MO than carbon nanotubes did. The adsorption isotherms followed Langmuir isotherm equation and the adsorption kinetics could be well described with the pseudo second-order kinetic model. The adsorption process involved an intraparticle diffusion, while it was not the only rate-controlling step. The values of AG were negative and the value of ΔH is -12.37 kJ/mol, proving that the adsorption of MO onto ferromagnetic carbon nanotubes was a spontaneous and exothermic process. PMID:27455713

  19. Tetracycline adsorption on chitosan: a mechanistic description based on mass uptake and zeta potential measurements.

    PubMed

    Caroni, A L P F; de Lima, C R M; Pereira, M R; Fonseca, J L C

    2012-12-01

    Adsorption phenomena occurring at the solid/liquid interface of chitosan particles are of extreme importance in the kinetics of drug release/upload as well as in effluent treatment by adsorption. In this work, equilibrium and kinetic aspects of protonated tetracycline adsorption on chitosan are explored using classic solution depletion method and zeta potential measurements. Equilibrium experiments showed that for solutions with tetracycline initial concentration of ca. 1.2 g L(-1), corresponding to a pH around 3, chitosan structure disrupted, as indicated by an increase in magnitude of tetracycline sorption. Adsorption and zeta potential isotherms before disruption suggested that the process of adsorption had a Langmuir character up to a point at which subsurface was exposed to adsorption; at this point, a second mode of sorption began: zeta potential tended to an equilibrium value, following Sips isotherm and tetracycline sorption had a linear dependence on its continuous phase concentration. The kinetics of tetracycline sorption suggested that sorption of tetracycline was divided between the sorption of protonated and non-protonated tetracycline; tetracycline in its non-protonated form seemed to rule the sorption of tetracycline.

  20. Adsorption of dyes onto activated carbon prepared from olive stones.

    PubMed

    Najar-Souissi, Souad; Ouederni, Abdelmottaleb; Ratel, Abdelhamid

    2005-01-01

    Activated carbon was produced from olive stones(OSAC) by a physical process in two steps. The adsorption character of this activated carbon was tested on three colour dyes molecules in aqueous solution: Methylene blue (MB), Rhodamine B (RB) and Congo Red(CR). The adsorption equilibrium was studied through isotherms construction at 30 degrees C, which were well described by Langmuir model. The adsorption capacity on the OSAC was estimated to be 303 mg/g, 217 mg/g and 167 mg/g respectively for MB, RB and CR. This activated carbon has a similar adsorption properties to that of commercial ones and show the same adsorption performances. The adsorption kinetics of the MB molecule in aqueous solution at different initial concentrations by OSAC was also studied. Kinetic experiments were well fitted by a simple intra-particle diffusion model. The measured kinetics constant was influenced by the initial concentration and we found the following correlation: Kid = 1.55 C0(0.51). PMID:16465895

  1. 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 ...

  2. 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

  3. Synthesized magnetic nanoparticles coated zeolite for the adsorption of pharmaceutical compounds from aqueous solution using batch and column studies.

    PubMed

    Salem Attia, Tamer Mohamed; Hu, Xia Lin; Yin, Da Qiang

    2013-11-01

    The contamination of fresh water with pharmaceutical and personal care products (PPCPs) has risen during the last few years. The adsorption of some PPCPs namely, Diclofenac-Na, Naproxen, Gemfibrozil and Ibuprofen from aqueous solution has been studied, magnetic nanoparticles coated zeolite (MNCZ) has been used as the adsorbent. Batch adsorption experiment was conducted to study the influences of different adsorption parameters such as contact time, solution pH and PPCPs concentrations in order to optimize the reaction conditions. The removal was favored at low pH values. Thus, as pH turns from acidic to basic conditions these compounds were less efficiently removed. The initial concentration does not appear to exert a noticeable effect on the removal efficiency of the studied PPCPs at low concentrations, but it showed less removal efficiency during high concentration of PPCPs especially for Ibuprofen. The removal of Diclofenac-Na was independent on time, while the contact time was of significant effect on the adsorption of Naproxen, Gemfibrozil and Ibuprofen even though these compounds were removed up to 95% during 10 min using MNCZ. From the isotherm adsorption study, the adsorption of PPCPs studied on MNCZ was best fitted with Freundlich isotherm equation. Pseudo-second order model providing the best fit model with the experimental data. Column adsorption study was conducted to compare the removal efficiency of MNCZ with other processes used at drinking water treatment plants (DWTPs), MNCZ showed high removal efficiency (>99%) than other used processes at DWTPs.

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

    PubMed

    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

  5. 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

  6. Thermodynamics of binary gas adsorption in nanopores.

    PubMed

    Dutta, Sujeet; Lefort, Ronan; Morineau, Denis; Mhanna, Ramona; Merdrignac-Conanec, Odile; Saint-Jalmes, Arnaud; Leclercq, Théo

    2016-09-21

    MCM-41 nanoporous silicas show a very high selectivity for monoalcohols over aprotic molecules during adsorption of a binary mixture in the gas phase. We present here an original use of gravimetric vapour sorption isotherms to characterize the role played by the alcohol hydrogen-bonding network in the adsorption process. Beyond simple selectivity, vapour sorption isotherms measured for various compositions help to completely unravel at the molecular level the step by step adsorption mechanism of the binary system in the nanoporous solid, from the first monolayers to the complete liquid condensation. PMID:27532892

  7. 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.

  8. 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.

  9. 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

  10. 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.

  11. Solvent vapor recovery by pressure swing adsorption. 3: Comparison of simulation with experiment for the butane-activated carbon system

    SciTech Connect

    Liu, J.; Holland, C.E.; Ritter, J.A.

    1999-06-01

    A fully predictive (no adjustable parameters), nonisothermal, multicomponent mathematical model was developed and used to simulate a pressure swing adsorption (PSA) process designed for the separation and recovery of concentrated butane vapor from nitrogen using BAX activated carbon. Nearly quantitative agreement with experiment was realized with this model over a wide range of process conditions, and for both the transient and periodic state process dynamics and the periodic state process performance. The model also verified some unique characteristics of this PSA process, and it revealed some of the subtleties associated with accurately simulating a PSA-solvent vapor recovery (SVR) process. These subtleties included the need to account for the adsorbate heat capacity and the temperature dependence of the gas-phase physical properties. No PSA models in the literature have included both of these features, which were critical to the accurate prediction of the heat effects in this PSA-SVR process.

  12. 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.

  13. Efficient Pb(II) removal using sodium alginate-carboxymethyl cellulose gel beads: Preparation, characterization, and adsorption mechanism.

    PubMed

    Ren, Huixue; Gao, Zhimin; Wu, Daoji; Jiang, Jiahui; Sun, Youmin; Luo, Congwei

    2016-02-10

    Alginate-carboxymethyl cellulose (CMC) gel beads were prepared in this study using sodium alginate (SA) and sodium CMC through blending and cross-linking. The specific surface area and aperture of the prepared SA-CMC gel beads were tested. The SA-CMC structure was characterized and analyzed via infrared spectroscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. Static adsorption experiment demonstrated that Pb(II) adsorption of SA-CMC exceeded 99% under the optimized conditions. In addition, experiments conducted under the same experimental conditions showed that the lead ion removal efficiency of SA-CMC was significantly higher than that of conventional adsorbents. The Pb(II) adsorption process of SA-CMC followed the Langmuir adsorption isotherm, and the dynamic adsorption model could be described through a pseudo-second-order rate equation. Pb(II) removal mechanisms of SA-CMC, including physical, chemical, and electrostatic adsorptions, were discussed based on microstructure analysis and adsorption kinetics. Chemical adsorption was the main adsorption method among these mechanisms. PMID:26686144

  14. 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…

  15. Dynamic technique for measuring adsorption in a gas chromatograph

    NASA Technical Reports Server (NTRS)

    Deuel, C. L.; Hultgren, N. W.; Mobert, M. L.

    1973-01-01

    Gas-chromatographic procedure, together with mathematical analysis of adsorption isotherm, allows relative surface areas and adsorptive powers for trace concentrations to be determined in a few minutes. Technique may be used to evaluate relative surface areas of different adsorbates, expressed as volume of adsorbent/gram of adsorbate, and to evaluate their relative adsorptive power.

  16. Adsorption of sodium diclofenac on graphene: a combined experimental and theoretical study.

    PubMed

    Jauris, I M; Matos, C F; Saucier, C; Lima, E C; Zarbin, A J G; Fagan, S B; Machado, F M; Zanella, I

    2016-01-21

    The interactions of sodium diclofenac drug (s-DCF) with different graphene species were investigated using both first principles calculations based on Density Functional Theory (DFT) and adsorption experiments. Through batch adsorption experiments, it was found that rGO was a good adsorbent for removing the s-DCF drug from aqueous solutions. The general-order kinetic model shows the best fit to the experimental data compared with pseudo-first order and pseudo-second order kinetic adsorption models. The equilibrium data (at 25 °C) were fitted to the Liu isotherm model. The maximum sorption capacity for adsorption of the s-DCF drug was 59.67 mg g(-1) for rGO. The s-DCF adsorption onto pristine graphene, graphene with a vacancy, reduced oxide graphene (rGO) and functionalized graphene nanoribbons were simulated providing a good understanding of the adsorption process of this molecule on graphene-family surfaces. The results predict a physisorption regime in all cases. Based on these results, the ab initio calculations and the adsorption experiments point out that the graphene-family are promising materials for extracting s-DCF from wastewater effluents.

  17. 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.

  18. 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

  19. 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.

  20. Adsorptive removal of phosphate from aqueous solutions using iron oxide tailings.

    PubMed

    Zeng, Le; Li, Xiaomei; Liu, Jindun

    2004-03-01

    This study explored the feasibility of utilizing industrial waste iron oxide tailings for phosphate removal in laboratory experiments. The experimental work emphasized on the evaluation of phosphate adsorption and desorption characteristics of the tailing material. The adsorption isotherm, kinetics, pH effect and desorption were examined in batch experiments. Five isotherm models were used for data fitting. The three-parameter equations (Redlich-Peterson and Langmuir-Freundlich) showed more applicability than the two-parameter equations (Freundlich, Langmuir and Temkin). A modified equation for calculation of the separation factor using the Langmuir-Freundlich equation constants was developed. The initial phosphate adsorption on the tailings was rapid. The adsorption kinetics can be best described by either the simple Elovich or power function equation. The phosphate adsorption on the tailings tended to decrease with an increase of pH. A phosphate desorbability of approximately 13-14% was observed, and this low desorbability likely resulted from a strong bonding between the adsorbed PO(4)(3-)and iron oxides in the tailings. Column flow-through tests using both synthetic phosphate solution and liquid hog manure confirmed the phosphate removal ability of the tailings. Due to their low cost and high capability, this type of iron oxide tailings has the potential to be utilized for cost-effective removal of phosphate from wastewater.

  1. [Preparation of surface molecularly imprinted polymers for penicilloic acid, and its adsorption properties].

    PubMed

    Zheng, Penglei; Luo, Zhimin; Chang, Ruimiao; Ge, Yanhui; Du, Wei; Chang, Chun; Fu, Qiang

    2015-09-01

    On account of the specificity and reproducibility for the determination of penicilloic acid in penicillin, this study aims to prepare penicilloic acid imprinted polymers (PEOA-MIPs) by surface polymerization method at the surface of modified silica particles by using penicilloic acid (PEOA) as the template molecule, methacrylic acid (MAA) as the functional monomer, ethylene glycol dimethacrylate ( EGDMA) as the cross linker, and methanol/acetonitrile as the solvents. The synthesis conditions were optimized, and PEOA-MIPs had the best adsorption capacity when the molar ratio of template molecule/functional monomer was 1 :4, cross linking degree was 85% and the solvent ratio of methanol/acetonitrile was 1 :1 (v/v). The adsorption properties were evaluated by adsorption experiments, including the adsorption isotherms, kinetics and selectivity. The adsorption process between PEOA-MIPs and PEOA fitted the Langmuir adsorption isotherm with the maximum adsorption capacity of 122. 78 mg/g and the pseudo-second-order reaction kinetics with fast adsorption kinetics (the equilibrium time of 45 min). The as-synthesized PEOA-MIPs were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), and thermal gravimetric analysis (TGA). The results indicated that the MIPs layer has been successfully grafted on the surface of SiO2 microparticles and the PEOA-MIPs had the excellent thermal stability. The PEOA-MIPs showed the highest selective recognition for PEOA. The PEOA-MIPs possess a high adsorption capacity, rapid mass-transfer rate and high selectivity to PEOA when compared with non-imprinted polymers (PEOA-NIPs). The PEOA-MIPs was expected to be used as the solid phase extraction medium and this study provides the potential applications for fast recognition and analysis of the penicilloic acid in penicillin. PMID:26753284

  2. 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

  3. Face-by-face growth of sucrose crystals from aqueous solutions in the presence of raffinose. I. Experiments and kinetic-adsorption model

    NASA Astrophysics Data System (ADS)

    Sgualdino, G.; Aquilano, D.; Cincotti, A.; Pastero, L.; Vaccari, G.

    2006-06-01

    Experimental growth kinetics of {1 0 0}, {1 0 1¯}, {1 1 0} and {1¯ 1¯ 0}, the four most important F (flat) forms of sucrose crystal, has been investigated within a range of low supersaturations ( 0.040⩽σ⩽0.080) and under varying raffinose concentrations (0.0 ⩽Craff⩽8.0% H 2O). The comparison with growth isotherms determined in pure solution confirms that raffinose dramatically slows down the growth rates of the first three forms, which still go on growing by the screw dislocation mechanism. Further, dead zones occur for both the {1 0 1¯} and {1 1 0} forms. On the contrary the {1¯ 1¯ 0} form is weakly affected, at least up to Craff≈3% H 2O, owing to the low structural compatibility between its surface sites and the adsorbed raffinose molecules. Both Cabrera-Vermilyea and Kubota-Mullin models, associated with Langmuir-type equilibrium isotherms, are tested to find the more suitable description of the kinetic behaviour in the presence of raffinose. The Kubota-Mullin model resulting the better one, we concluded that adsorption occurs at kink sites of all the interested forms. The predictive power of α h k l , the effectiveness coefficient of this model, is outlined as well. Finally, the disagreements between the model predictions and the experimental behaviour of the {1 0 0} form are attributed to the peculiar structure of its surface.

  4. Adsorptive separation of isobutene and isobutane on Cu3(BTC)2.

    PubMed

    Hartmann, Martin; Kunz, Sebastian; Himsl, Dieter; Tangermann, Oliver; Ernst, Stefan; Wagener, Alex

    2008-08-19

    The metal organic framework material Cu3(BTC)2 (BTC = 1,3,5-benzenetricarboxylate) has been synthesized using different routes: under solvothermal conditions in an autoclave, under atmospheric pressure and reflux, and by electrochemical reaction. Although the compounds display similar structural properties as evident from the powder X-ray diffraction (XRD) patterns, they differ largely in specific surface area and total pore volume. Thermogravimetric and chemical analysis support the assumption that pore blocking due to trimesic acid and/or methyltributylammoniummethylsulfate (MTBS) which has been captured in the pore system during reaction is a major problem for the electrochemically synthesized samples. Isobutane and isobutene adsorption has been studied for all samples at different temperatures in order to check the potential of Cu3(BTC)2 for the separation of small hydrocarbons. While the isobutene adsorption isotherms are of type I according to the IUPAC classification, the shape of the isobutane isotherm is markedly different and closer to type V. Adsorption experiments at different temperatures show that a somewhat higher amount of isobutene is adsorbed as compared to isobutane. Nevertheless, the differential enthalpies of adsorption are only different by about 5 kJ/mol, indicating that a strong interaction between the copper centers and isobutene does not drive the observed differences in adsorption capacity. The calculated breakthrough curves of isobutene and isobutane reveal that a low pressure separation is preferred due to the peculiar shape of the isobutane adsorption isotherms. This has been confirmed by preliminary breakthrough experiments using an equimolar mixture of isobutane and isobutene. PMID:18611044

  5. [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

  6. [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.

  7. 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.

  8. 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.

  9. Selective adsorption of silver ions from aqueous solution using polystyrene-supported trimercaptotriazine resin.

    PubMed

    Wang, Shiming; Li, Hongling; Chen, Xiaoya; Yang, Min; Qi, Yanxing

    2012-01-01

    Trimercaptotriazine-functionalized polystyrene chelating resin was prepared and employed for the adsorption of Ag(I) from aqueous solution. The adsorbent was characterized according to the following techniques: Fourier transform infrared spectroscopy, elemental analysis, scanning electron microscopy and the Brunauer-Emmet-Teller method. The effects of initial Ag(I) concentration, contact time, solution pH and coexisting ions on the adsorption capacity of Ag(I) were systematically investigated. The maximum adsorption capacity of Ag(I) was up to 187.1 mg/g resin at pH 0.0 and room temperature. The kinetic experiments indicated that the adsorption rate of Ag(I) onto the chelating resin was quite fast in the first 60 min and reached adsorption equilibrium after 360 min. The adsorption process can be well described by the pseudo second-order kinetic model and the equilibrium adsorption isotherm was closely fitted by the Langmuir model. Moreover, the chelating resin could selectively adsorb more Ag(I) ions than other heavy metal ions including: Cu(I), Zn(II), Ni(II), Pb(II) and Cr(III) during competitive adsorption in the binary metal species systems, which indicated that it was a highly selective adsorbent of Ag(I) from aqueous solution.

  10. 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

  11. 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.

  12. 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.

  13. Adsorption of Ag, Cu and Hg from aqueous solutions using expanded perlite.

    PubMed

    Ghassabzadeh, Hamid; Mohadespour, Ahmad; Torab-Mostaedi, Meisam; Zaheri, Parisa; Maragheh, Mohammad Ghannadi; Taheri, Hossein

    2010-05-15

    The aim of the present work was to investigate the ability of expanded perlite (EP) to remove of silver, copper and mercury ions from aqueous solutions. Batch adsorption experiments were carried out and the effect of pH, adsorbent dosage, contact time and temperature of solution on the removal process has been investigated. The optimum pH for the adsorption was found to be 6.5. Adsorption of these metal ions reached their equilibrium concentration in 120, 240 and 180 min for Ag (I), Cu (II) and Hg (II) ions, respectively. Experimental data were also evaluated in terms of kinetic characteristics of adsorption and it was found that adsorption process for these metal ions followed well pseudo-second-order kinetics. Using Langmuir isotherm model, maximum adsorption capacity of EP was found to be 8.46, 1.95 and 0.35 mg/g for Ag (I), Cu (II) and Hg (II) ions, respectively. Finally, the thermodynamic parameters including, the change of free energy (DeltaG degrees ), enthalpy (DeltaH degrees ) and entropy (DeltaS degrees ) of adsorption were calculated for each metal ion. The results showed that the adsorption of these metal ions on EP was feasible and exothermic at 20-50 degrees C.

  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 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

  16. 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

  17. Adsorption of organic chemicals in soils.

    PubMed

    Calvet, R

    1989-11-01

    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.

  18. 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…

  19. 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

  20. 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.

  1. [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.

  2. [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

  3. 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.

  4. A combined QCM and XPS investigation of asphaltene adsorption on metal surfaces.

    PubMed

    Rudrake, Amit; Karan, Kunal; Horton, J Hugh

    2009-04-01

    To investigate asphaltene-metal interactions, a combined quartz crystal microbalance (QCM) and X-ray photoelectron spectroscopy (XPS) study of asphaltene adsorption on a gold surface was conducted. Adsorption experiments were conducted at 25 degrees C with solutions of asphaltenes in toluene at concentrations ranging from 50 to 1500 ppm. QCM measurements yielded information on the kinetics of adsorption and further assessment of the data allowed the estimation of equilibrium adsorption levels. XPS analysis of adsorbed and bulk asphaltene demonstrated the presence of carboxylic, thiophenic, sulfide, pyridinic and pyrrolic type functional groups. The intensity of the main carbon (C-H) peak was related to surface coverage of adsorbed asphaltene as a function of asphaltene concentration by a simple mathematical model. The mass adsorption data from the QCM experiments also allowed estimation of the surface coverage, which was compared to those from XPS analyses. Surface coverage estimates as a function of asphaltene concentration could be described by a Langmuir (type-I) isotherm. The free energy of asphaltene adsorption was estimated to be -26.8+/-0.1 and -27.3+/-0.1 kJ/mol from QCM and XPS data, respectively assuming asphaltene molar mass of 750 g/gmol. QCM and XPS data was also analyzed to estimate adsorbed layer thickness after accounting for surface coverage. The thickness of the adsorbed asphaltene estimated from both XPS and QCM data analyses ranged from 6-8 nm over the entire range of adsorption concentrations investigated.

  5. 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

  6. 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.

  7. 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.

  8. 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.

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

    SciTech Connect

    Watanabe, Taku; Manz, Thomas A.; Sholl, David S.

    2011-02-28

    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 CO2 adsorption in four metal-organic frameworks (MOFs): IRMOF-1, ZIF-8, ZIF-90, and Zn(nicotinate)2. The resulting CO2 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 material for CO2 adsorption applications.

  10. [Effect of SDS on the adsorption of Cd2+ onto amphoteric modified bentonites].

    PubMed

    Wang, Jian-Tao; Meng, Zhao-Fu; Yang, Ya-Ti; Yang, Shu-Ying; Li, Bin; Xu, Shao-e

    2014-07-01

    Under different modified ratios, temperatures, pH and ionic strengths, the effect of sodium dodecyl sulfonate (SDS) on the adsorption of Cd2+ onto bentonites which modified with amphoteric modifier dodecyl dimethyl betaine (BS-12) was studied by batch experiments, and the adsorption mechanism was also discussed. Results showed that the adsorption of Cd2+ on amphoteric bentonites can be enhanced significantly by SDS combined modification, Cd2+ adsorption decreases in the order: BS + 150SDS (BS-12 + 150% SDS) > BS + 100SDS (BS-12 + 100% SDS) > BS +50SDS(BS-12 + 50% SDS) > BS + 25SDS (BS-12 + 25% SDS) > BS (BS-12) > CK (unmodified soil). The adsorption isotherm can be described by the Langmuir equation. The change of temperature effect from positive on CK and amphoteric bentonites to negative on BS + 150SDS bentonites is observed with an increase of SDS modified ratio. The pH has little influence on Cd2+ adsorption on bentonites. The adsorption of Cd2+ on bentonites decreases with ionic strength rise, but the effect of ionic strength can be reduced with an increase of SDS modified ratio also. The adsorption thermodynamic parameters demonstrated that the adsorption of Cd2+ on modified bentonites was spontaneously controlled by entropy increment. When the SDS modified ratio is lower than 100% CEC, the adsorption of Cd2+ on modified bentonites is a process with characteristics of both enthalpy increment and entropy increment, while the SDS modified ratio is equal to or higher than 100% CEC, the adsorption of Cd2+ on modified bentonites becomes a process of enthalpy decrement and entropy increment. PMID:25244843

  11. 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.

  12. Adsorption of Cd, Cu and Zn from aqueous solutions onto ferronickel slag under different potentially toxic metal combination.

    PubMed

    Park, Jong-Hwan; Kim, Seong-Heon; Kang, Se-Won; Kang, Byung-Hwa; Cho, Ju-Sik; Heo, Jong-Soo; Delaune, Ronald D; Ok, Yong Sik; Seo, Dong-Cheol

    2016-01-01

    Adsorption characteristics of potentially toxic metals in single- and multi-metal forms onto ferronickel slag were evaluated. Competitive sorption of metals by ferronickel slag has never been reported previously. The maximum adsorption capacities of toxic metals on ferronickel were in the order of Cd (10.2 mg g(-1)) > Cu (8.4 mg g(-1)) > Zn (4.4 mg g(-1)) in the single-metal adsorption isotherm and Cu (6.1 mg g(-1)) > Cd (2.3 mg g(-1)) > Zn (0.3 mg g(-1)) in the multi-metal adsorption isotherm. In comparison with single-metal adsorption isotherm, the reduction rates of maximum toxic metal adsorption capacity in the multi-metal adsorption isotherm were in the following order of Zn (93%) > Cd (78%) > Cu (27%). The Freundlich isotherm provides a slightly better fit than the Langmuir isotherm equation using ferronickel slag for potentially toxic metal adsorption. Multi-metal adsorption behaviors differed from single-metal adsorption due to competition, based on data obtained from Freundlich and Langmuir adsorption models and three-dimensional simulation. Especially, Cd and Zn were easily exchanged and substituted by Cu during multi-metal adsorption. Further competitive adsorption studies are necessary in order to accurately estimate adsorption capacity of ferronickel slag for potentially toxic metals in natural environments. PMID:26942519

  13. Adsorption of Cd, Cu and Zn from aqueous solutions onto ferronickel slag under different potentially toxic metal combination.

    PubMed

    Park, Jong-Hwan; Kim, Seong-Heon; Kang, Se-Won; Kang, Byung-Hwa; Cho, Ju-Sik; Heo, Jong-Soo; Delaune, Ronald D; Ok, Yong Sik; Seo, Dong-Cheol

    2016-01-01

    Adsorption characteristics of potentially toxic metals in single- and multi-metal forms onto ferronickel slag were evaluated. Competitive sorption of metals by ferronickel slag has never been reported previously. The maximum adsorption capacities of toxic metals on ferronickel were in the order of Cd (10.2 mg g(-1)) > Cu (8.4 mg g(-1)) > Zn (4.4 mg g(-1)) in the single-metal adsorption isotherm and Cu (6.1 mg g(-1)) > Cd (2.3 mg g(-1)) > Zn (0.3 mg g(-1)) in the multi-metal adsorption isotherm. In comparison with single-metal adsorption isotherm, the reduction rates of maximum toxic metal adsorption capacity in the multi-metal adsorption isotherm were in the following order of Zn (93%) > Cd (78%) > Cu (27%). The Freundlich isotherm provides a slightly better fit than the Langmuir isotherm equation using ferronickel slag for potentially toxic metal adsorption. Multi-metal adsorption behaviors differed from single-metal adsorption due to competition, based on data obtained from Freundlich and Langmuir adsorption models and three-dimensional simulation. Especially, Cd and Zn were easily exchanged and substituted by Cu during multi-metal adsorption. Further competitive adsorption studies are necessary in order to accurately estimate adsorption capacity of ferronickel slag for potentially toxic metals in natural environments.

  14. 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

  15. Isothermic hemodialysis and ultrafiltration.

    PubMed

    Rosales, L M; Schneditz, D; Morris, A T; Rahmati, S; Levin, N W

    2000-08-01

    The increase in patient temperature during hemodialysis is explained by hemodynamic compensation during ultrafiltration and hypovolemia that leads to peripheral vasoconstriction and reduced heat losses. We analyzed 51 stable high-efficiency hemodialysis treatments in 27 patients during isothermic dialysis in which body temperature was maintained at a constant level (+/-0.1 degrees C) using the temperature-control option of the Blood Temperature Monitor (BTM; Fresenius Medical Care, Bad Homburg, Germany). Hemodialysis was delivered using ultrapure water (limulus amebocyte lysate test < 0. 06 endotoxin units/mL) at mean blood flows of 410 +/- 40 mL/min. During treatments lasting 178 +/- 23 minutes, 4.8% +/- 1.4% of postdialysis body weight (W%) and 9.5% +/- 2.5% of postdialysis body water were removed using mean ultrafiltration rates of 1.1 +/- 0.3 L/h. Dialysate temperatures significantly decreased from 35.9 degrees C +/- 0.3 degrees C to 35.6 degrees C +/- 0.6 degrees C during hemodialysis. During these treatments, 187 +/- 69 kJ of thermal energy were removed from the patients through the extracorporeal circulation using cool dialysate. Extracorporeal heat flow was 17 +/- 6 W. Energy expenditure (H) estimated from anthropometric data was 65 +/- 12 W. Thus, 28% +/- 10% of estimated energy expenditure (H%) was removed during isothermic dialysis. A highly significant correlation was observed between H% and W% (H% = -5.6 * W%; r(2) = 0.91; P < 0.0001). This result is in support of the volume hypothesis of intradialytic heat accumulation and provides a rule of thumb to estimate extracorporeal cooling requirements for isothermic dialysis. Approximately 6% of H must be removed through the extracorporeal circulation for each percent of ultrafiltration-induced body-weight change. The importance of body temperature control during hemodialysis increases with increased ultrafiltration requirements.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. [Simulation study on the effect of salinity on the adsorption behavior of mercury in wastewater-irrigated area].

    PubMed

    Zheng, Shun-An; Li, Xiao-Hua; Xu, Zhi-Yu

    2014-05-01

    This study was designed to pinpoint the impact of salinity ( NaCl and Na2SO4, added at salinity levels of 0-5%, respectively) on the adsorption behavior of mercury in wastewater-irrigated areas of Tianjin City by batch and kinetic experiments. The results showed that, the Langmuir isotherm and the Elovich equation can well fitted batch and kinetic experimental data, respectively. As NaCI spiked in soil, Hg( II) adsorption capacity and strength had marked decreases, from 868.64 mgkg-1 and 1. 32 at control to 357.48 mgkg-1 and 0.63 at 5% salinity level of NaCI, respectively. As Na2SO4 spiked in soil, Hg(II) adsorption capacity (parameter qm in Langmuir isotherm) and strength (parameter k in Langmuir isotherm) changed slightly, from 868.64 mg kg-1 and 1.32 at control to 739.44 mg.kg-1 and 1. 18 at 5% salinity level of Na2 SO4, respectively. Kinetic data showed that, Hg( II) adsorption rate (parameter b in Elovich equation) in soil was not influenced by Na2SO, addition. However, the addition of NaC1 had a great effect on mercury adsorption rate. Hg(II ) adsorption capacity as a function of CI- or SO(2-)(4) content in soil could be simulated by the natural logarithm model, while Hg( II ) adsorption rate as a function of CI- content in soil could be simulated by the linear model. The study manifested that NaCI can significantly increase migration of Hg( II ) in the soil irrigated with wastewater, which may enhance Hg( II) bioavailability in the soil and cause a hazard to surface water. Especially, it will be harmful to human body through the food chain. PMID:25055690

  1. 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

  2. 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...

  3. 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

  4. Adsorption of methylene blue and methyl red dyes from aqueous solutions onto modified zeolites.

    PubMed

    Ioannou, Z; Karasavvidis, Ch; Dimirkou, A; Antoniadis, V

    2013-01-01

    Zeolite, hematite, modified zeolite and commercial activated charcoal were examined for their ability to remove methylene blue (MB) and methyl red (MR) from their aqueous solutions. Modified zeolite and hematite were produced according to the Schwertmann and Cornell method while zeolite and commercial activated charcoal were obtained from S&B and Fluka AG companies, respectively. Adsorption experiments were conducted at three different adsorbent-to-solution ratios, namely 8, 16 and 24 g/L under environmental conditions and continuous stirring. Equilibrium isotherms of MB and MR were studied at different initial concentrations (from 5 × 10(-4) to 5 × 10(-3) g/L). MB adsorption kinetics were also studied. The maximum adsorption of MB and MR from their aqueous solutions was achieved at 24 g/L (adsorbent-to-dye solution ratio) after 1 h and was equal to 100% (MB) on modified zeolite and 99% (MR) on commercial activated charcoal, respectively. All the other materials achieved intermediate values of dye adsorption. From the applied kinetic models, the pseudo-second-order equation best described the adsorption of MB and MR. Consequently, modified zeolite showed the highest adsorption capacity for MB, while commercial activated charcoal showed the highest adsorption capacity of MR. The studied adsorbents can be used as filters to remove dyes from wastewaters.

  5. 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

  6. First principles derived, transferable force fields for CO2 adsorption in Na-exchanged cationic zeolites.

    PubMed

    Fang, Hanjun; Kamakoti, Preeti; Ravikovitch, Peter I; Aronson, Matthew; Paur, Charanjit; Sholl, David S

    2013-08-21

    The development of accurate force fields is vital for predicting adsorption in porous materials. Previously, we introduced a first principles-based transferable force field for CO2 adsorption in siliceous zeolites (Fang et al., J. Phys. Chem. C, 2012, 116, 10692). In this study, we extend our approach to CO2 adsorption in cationic zeolites which possess more complex structures. Na-exchanged zeolites are chosen for demonstrating the approach. These methods account for several structural complexities including Al distribution, cation positions and cation mobility, all of which are important for predicting adsorption. The simulation results are validated with high-resolution experimental measurements of isotherms and microcalorimetric heats of adsorption on well-characterized materials. The choice of first-principles method has a significant influence on the ability of force fields to accurately describe CO2-zeolite interactions. The PBE-D2 derived force field, which performed well for CO2 adsorption in siliceous zeolites, does not do so for Na-exchanged zeolites; the PBE-D2 method overestimates CO2 adsorption energies on multi-cation sites that are common in cationic zeolites with low Si/Al ratios. In contrast, a force field derived from the DFT/CC method performed well. Agreement was obtained between simulation and experiment not only for LTA-4A on which the force field fitting is based, but for other two common adsorbents, NaX and NaY.

  7. 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

  8. 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.

  9. 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).

  10. Predicting mixed-gas adsorption equilibria on activated carbon for precombustion CO2 capture.

    PubMed

    García, S; Pis, J J; Rubiera, F; Pevida, C

    2013-05-21

    We present experimentally measured adsorption isotherms of CO2, H2, and N2 on a phenol-formaldehyde resin-based activated carbon, which had been previously synthesized for the separation of CO2 in a precombustion capture process. The single component adsorption isotherms were measured in a magnetic suspension balance at three different temperatures (298, 318, and 338 K) and over a large range of pressures (from 0 to 3000-4000 kPa). These values cover the temperature and pressure conditions likely to be found in a precombustion capture scenario, where CO2 needs to be separated from a CO2/H2/N2 gas stream at high pressure (~1000-1500 kPa) and with a high CO2 concentration (~20-40 vol %). Data on the pure component isotherms were correlated using the Langmuir, Sips, and dual-site Langmuir (DSL) models, i.e., a two-, three-, and four-parameter model, respectively. By using the pure component isotherm fitting parameters, adsorption equilibrium was then predicted for multicomponent gas mixtures by the extended models. The DSL model was formulated considering the energetic site-matching concept, recently addressed in the literature. Experimental gas-mixture adsorption equilibrium data were calculated from breakthrough experiments conducted in a lab-scale fixed-bed reactor and compared with the predictions from the models. Breakthrough experiments were carried out at a temperature of 318 K and five different pressures (300, 500, 1000, 1500, and 2000 kPa) where two different CO2/H2/N2 gas mixtures were used as the feed gas in the adsorption step. The DSL model was found to be the one that most accurately predicted the CO2 adsorption equilibrium in the multicomponent mixture. The results presented in this work highlight the importance of performing experimental measurements of mixture adsorption equilibria, as they are of utmost importance to discriminate between models and to correctly select the one that most closely reflects the actual process.

  11. 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

  12. 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.

  13. 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.

  14. Adsorption of organic dyes on TiO2 surfaces in dye-sensitized solar cells: interplay of theory and experiment.

    PubMed

    Anselmi, Chiara; Mosconi, Edoardo; Pastore, Mariachiara; Ronca, Enrico; De Angelis, Filippo

    2012-12-14

    /simulation and experiments appears to be the key to further DSCs progress, both concerning the design of new dye sensitizers and their interaction with the semiconductor and with the solution environment and/or an electrolyte upon adsorption onto the semiconductor. PMID:23108504

  15. 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.

  16. Proteins at fluid interfaces: adsorption layers and thin liquid films.

    PubMed

    Yampolskaya, Galina; Platikanov, Dimo

    2006-12-21

    A review in which many original published results of the authors as well as many other papers are discussed. The structure and some properties of the globular proteins are shortly presented, special accent being put on the alpha-chymotrypsin (alpha-ChT), lysozyme (LZ), human serum albumin (HSA), and bovine serum albumin (BSA) which have been used in the experiments with thin liquid films. The behaviour of protein adsorption layers (PAL) is extensively discussed. The dynamics of PAL formation, including the kinetics of adsorption as well as the time evolution of the surface tension of protein aqueous solutions, are considered. A considerable place is devoted to the surface tension and adsorption isotherms of the globular protein solutions, the simulation of PAL by interacting hard spheres, the experimental surface tension isotherms of the above mentioned proteins, and the interfacial tension isotherms for the protein aqueous solution/oil interface. The rheological properties of PAL at fluid interfaces are shortly reviewed. After a brief information about the experimental methods for investigation of protein thin liquid (foam or emulsion) films, the properties of the protein black foam films are extensively discussed: the conditions for their formation, the influence of the electrolytes and pH on the film type and stability, the thermodynamic properties of the black foam films, the contact angles film/bulk and their dynamic hysteresis. The next center of attention concerns some properties of the protein emulsion films: the conditions for formation of emulsion black films, the formation and development of a dimpling in microscopic, circular films. The protein-phospholipid mixed foam films are also briefly considered.

  17. 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)

  18. 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.

  19. Adsorption of phosphate from aqueous solution by hydroxy-aluminum, hydroxy-iron and hydroxy-iron-aluminum pillared bentonites.

    PubMed

    Yan, Liang-guo; Xu, Yuan-yuan; Yu, Hai-qin; Xin, Xiao-dong; Wei, Qin; Du, Bin

    2010-07-15

    Phosphorus removal is important for the control of eutrophication, and adsorption is an efficient treatment process. In this study, three modified inorganic-bentonites: hydroxy-aluminum pillared bentonite (Al-Bent), hydroxy-iron pillared bentonite (Fe-Bent), and mixed hydroxy-iron-aluminum pillared bentonite (Fe-Al-Bent), were prepared and characterized, and their phosphate adsorption capabilities were evaluated in batch experiments. The results showed a significant increase of interlayer spacing, BET surface area and total pore volume which were all beneficial to phosphate adsorption. Phosphate adsorption capacity followed the order: Al-Bent>Fe-Bent>Fe-Al-Bent. The adsorption rate of phosphate on the adsorbents fits pseudo-second-order kinetic models (R(2)=1.00, 0.99, 1.00, respectively). The Freundlich and Langmuir models both described the adsorption isotherm data well. Thermodynamic studies illustrated that the adsorption process was endothermic and spontaneous in nature. Finally, phosphate adsorption on the inorganic pillared bentonites significantly raised the pH, indicating an anion/OH(-) exchange reaction.

  20. 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.

  1. 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.

  2. 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.

  3. Adsorption of methylene blue from aqueous solution by graphene.

    PubMed

    Liu, Tonghao; Li, Yanhui; Du, Qiuju; Sun, Jiankun; Jiao, Yuqin; Yang, Guangming; Wang, Zonghua; Xia, Yanzhi; Zhang, Wei; Wang, Kunlin; Zhu, Hongwei; Wu, Dehai

    2012-02-01

    Graphene was prepared using a modified Hummers' method. The physico-chemical properties of graphene were characterized by TEM, BET specific surface area, FTIR, Raman and XRD measurements. The effect factors including pH, contact time, temperature and dosage on the adsorption properties of methylene blue onto graphene were investigated. The experimental data of isotherm followed the Langmuir isotherm model better than the Freundlich model. The maximum adsorption capacity obtained from Langmuir isotherm equation at 293 K was 153.85 mg/g, indicating graphene is a good adsorbent for the adsorption of MB. The kinetic study illustrated that the adsorption of methylene blue onto graphene fit the pseudo second-order model. The thermodynamic parameters indicated that the adsorption of methylene blue onto graphene was an endothermic and spontaneous process.

  4. 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.

  5. Sulfate adsorption on goethite

    SciTech Connect

    Rietra, R.P.J.J.; Hiemstra, T.; Riemsdijk, W.H. van

    1999-10-15

    Recent spectroscopic work has suggested that only one surface species of sulfate is dominant on hematite. Sulfate is therefore a very suitable anion to test and develop adsorption models for variable charge minerals. The authors have studied sulfate adsorption on goethite covering a large range of sulfate concentrations, surface coverages, pH values, and electrolyte concentrations. Four different techniques were used to cover the entire range of conditions. For characterization at low sulfate concentrations, below the detection limit of sulfate with ICP-AES, the authors used proton-sulfate titrations at constant pH. Adsorption isotherms were studied for the intermediate sulfate concentration range. Acid-base titrations in sodium sulfate and electromobility were used for high sulfate concentrations. All the data can be modeled with one adsorbed species if it is assumed that the charge of adsorbed sulfate is spatially distributed in the interface. The charge distribution of sulfate follows directly from modeling the proton-sulfate adsorption stoichoimemtry sine this stoichiometry is independent of the intrinsic affinity constant of sulfate. The charge distribution can be related to the structure of the surface complex by use of the Pauling bond valence concept and is in accordance with the microscopic structure found by spectroscopy. The intrinsic affinity constant follows from the other measurements. Modeling of the proton-ion stoichoimetry with the commonly used 2-pK models, where adsorbed ions are treated as point charges, is possible only if at least two surface species for sulfate are used.

  6. 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).

  7. 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.

  8. 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.

  9. 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

  10. Adsorption of Basic Violet 14 in aqueous solutions using KMnO4-modified activated carbon.

    PubMed

    Shi, Qianqian; Zhang, Jian; Zhang, Chenglu; Nie, Wei; Zhang, Bo; Zhang, Huayong

    2010-03-01

    In this paper, an activated carbon was prepared from Typha orientalis and then treated with KMnO(4) and used for the removal of Basic Violet 14 from aqueous solutions. KMnO(4) treatment influenced the physicochemical properties of the carbon and improved its adsorption capacity. Adsorption experiments were then conducted with KMnO(4)-modified activated carbon to study the effects of carbon dosage (250-1500 mg/L), pH (2-10), ion strength (0-0.5 mol/L), temperature, and contact time on the adsorption of Basic Violet 14 from aqueous solutions. The equilibrium data were analyzed by the Langmuir and Freundlich isotherms and fitted well with the Langmuir model. The pseudo-first-order, pseudo-second-order, and intraparticle diffusion models were used to evaluate the kinetic data and the pseudo-second-order kinetics was the best with good correlation.

  11. Kinetic adsorption of application of carbon nanotubes for Pb(II) removal from aqueous solution.

    PubMed

    Kabbashi, Nassereldeen A; Atieh, Muataz A; Al-Mamun, Abdullah; Mirghami, Mohamed E S; Alam, M D Z; Yahya, Noorahayu

    2009-01-01

    The capability of carbon nanotubes (CNTs) to adsorb lead (Pb) in aqueous solution was investigated. Batch mode adsorption experiment was conducted to determine the effects of pH, agitation speed, CNTs dosage and contact time. The removal of Pb(II) reached maximum value 85% or 83% at pH 5 or 40 mg/L of CNTs, respectively. Higher correlation coefficients from Langmuir isotherm model indicates the strong adsorptions of Pb(II) on the surface of CNTs (adsorption capacity Xm = 102.04 mg/g). The results indicates that the highest percentage removal of Pb (96.03%) can be achieved at pH 5, 40 mg/L of CNTs, contact time 80 min, and agitation speed 50 r/min.

  12. 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.

  13. 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

  14. 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.

  15. Isothermal Titration Calorimetry of Chiral Polymeric Nanoparticles.

    PubMed

    Werber, Liora; Preiss, Laura C; Landfester, Katharina; Muñoz-Espí, Rafael; Mastai, Yitzhak

    2015-09-01

    Chiral polymeric nanoparticles are of prime importance, mainly due to their enantioselective potential, for many applications such as catalysis and chiral separation in chromatography. In this article we report on the preparation of chiral polymeric nanoparticles by miniemulsion polymerization. In addition, we describe the use of isothermal titration calorimetry (ITC) to measure the chiral interactions and the energetics of the adsorption of enantiomers from aqueous solutions onto chiral polymeric nanoparticles. The characterization of chirality in nano-systems is a very challenging task; here, we demonstrate that ITC can be used to accurately determine the thermodynamic parameters associated with the chiral interactions of nanoparticles. The use of ITC to measure the energetics of chiral interactions and recognition at the surfaces of chiral nanoparticles can be applied to other nanoscale chiral systems and can provide further insight into the chiral discrimination processes of nanomaterials.

  16. 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

  17. 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.

  18. Protein Adsorption on Surfaces with Grafted Polymers

    PubMed Central

    Szleifer, I.

    1997-01-01

    A general theoretical framework for studying the adsorption of protein molecules on surfaces with grafted polymers is presented. The approach is a generalization of the single-chain mean-field theory, in which the grafted polymer-protein-solvent layer is assumed to be inhomogeneous in the direction perpendicular to the grafting surface. The theory enables the calculation of the adsorption isotherms of the protein as a function of the surface coverage of grafted polymers, concentration of protein in bulk, and type of solvent molecules. The potentials of mean force of the protein with the surface are calculated as a function of polymer surface coverage and amount of protein adsorbed. The theory is applied to model lysozyme on surfaces with grafted polyethylene oxide. The protein is modeled as spherical in solution, and it is assumed that the protein-polymer, protein-solvent, and polymer-solvent attractive interactions are all equal. Therefore, the interactions determining the structure of the layer (beyond the bare polymer-surface and protein-surface interactions) are purely repulsive. The bare surface-protein interaction is taken from atomistic calculations by Lee and Park. For surfaces that do not have preferential attractions with the grafted polymer segments, the adsorption isotherms of lysozyme are independent of the polymer length for chains with more than 50 ethylene oxide units. However, the potentials of mean force show strong variations with grafted polymer molecular weight. The competition between different conformations of the adsorbed protein is studied in detail. The adsorption isotherms change qualitatively for surfaces with attractive interactions with ethylene oxide monomers. The protein adsorption is a function of chain length—the longer the polymer the more effective it is in preventing protein adsorption. The structure of the layer and its deformation upon protein adsorption are very important in determining the adsorption isotherms and the

  19. Kinetics of Copper Adsorption from Effluent Stream by ZeoliteNaX

    NASA Astrophysics Data System (ADS)

    Singh, Surinder; Sambi, S. S.; Sharma, S. K.; Pandey, Pankaj Kumar

    2010-06-01

    The batch experiments were conducted to study the copper (II) removal by ZeoliteNaX at temperature of 288+1 K, adsorbent dose of 2 g/L and contact time of 24 hour. Effects of pH, temperature, contact time and Cu (II) ion concentration by the adsorbent were investigated. The data were analyzed using the Langmuir, Freundlich and Temkin isotherms. Freundlich isotherm was found to correlate the adsorption of Cu (II) better and the mono-layer adsorption capacity for Cu (II) removal was 41.6 mg/g. The adsorbed amounts of Cu (II) reached equilibrium within 150 minutes. The four adsorption kinetic models namely, the first order equation, second order equations, pseudo-first order equation and pseudo second-order equations were also tested to fit the data. The pseudo-first-order equation was found to fit best for the experimental data. Thermodynamic analysis indicated the spontaneous and endothermic nature of the adsorption of Cu (II) by ZeoliteNaX.

  20. [Fluoride adsorption form drinking water by granular lanthanum alginate].

    PubMed

    Huo, Ya-Kun; Ding, Wen-Ming; Huang, Xia

    2010-11-01

    Granular lanthanum alginate was prepared by dripping solved sodium alginate into lanthanum chloride solution. After washed and dried, sorbent with 1-1.5 mm diameter, 25% (mass fraction) La content was made and applied for fluoride removal from drinking test. Adsorption performance such as adsorption rate, adsorption isotherm, pH and disturbing ions effects were tested in batch adsorption. The changes of adsorbent surface and the solution composition before and after adsorption were also studied. Results showed that the adsorption rate was fast, fluoride concentration trend to stable after 2h reaction, and the adsorption rate fit for pseudo second order equation. The adsorption was significantly affected by pH and some disturbing ions, optimum pH = 4, phosphate and carbonate reduced adsorption. Adsorption isotherm fitted Langmuir equation well; the max adsorption capacity was 197.2 mg x g(-1). SEM photographs of sorbent before and after adsorption showed significantly different surface morphology; EDX composition analysis of sorbent surface and solution concentration changes before and after adsorption showed that ion exchange take placed between solution F- and sorbent surface Cl- and OH-.

  1. Adsorption of crude oil from aqueous solution by hydrogel of chitosan based polyacrylamide prepared by radiation induced graft polymerization.

    PubMed

    Sokker, H H; El-Sawy, Naeem M; Hassan, M A; El-Anadouli, Bahgat E

    2011-06-15

    The adsorption of crude oil (initial concentration 0.5-30 g/L) from aqueous solution using hydrogel of chitosan based polyacrylamide (PAM) prepared by radiation induced graft polymerization has been investigated. The prepared hydrogel was characterized by FTIR and SEM micrographs. The experiments were carried out as a function of different initial concentrations of oil residue, acrylamide concentration, contact time and pH to determine the optimum condition for the adsorption of residue oil from aqueous solution and sea water. The results obtained showed that the hydrogel prepared at concentration of 40% acrylamide (AAm) and at a radiation dose of 5 kGy has high removal efficiency of crude oil 2.3g/g at pH 3. Equilibrium studies have been carried out to determine the capacity of the hydrogel for adsorption of crude oil, Langmuir and Freundlich adsorption models were applied to describe the experimental isotherms and isotherms constants. Equilibrium data were found to fit very well with both Freundlich and Langmuir models. Also the adsorption of oil onto the hydrogel behaves as a pseudo-second-order kinetic models rather than the pseudo-first-order kinetic model.

  2. 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.

  3. 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

  4. 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.

  5. 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.

  6. 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

  7. Studies on preparing and adsorption property of grafting terpolymer microbeads of PEI-GMA/AM/MBA for bilirubin.

    PubMed

    Gao, Baojiao; Lei, Haibo; Jiang, Liding; Zhu, Yong

    2007-06-15

    Crosslinking copolymer microbeads with a diameter range of 100-150 microm were synthesized by suspension copolymerization of glycidyl methacrylate (GMA), acrylamide (AM) and N,N'-methylene bisacrylamide (MBA). Subsequently, polyethyleneimine (PEI) was grafted on the surfaces of the terpolymer microbeads GMA/AM/MBA via the ring-opening reaction of the epoxy groups, and the grafting microbeads PEI-GMA/AM/MBA were prepared. In this paper, the adsorption property of the grafting microbeads for bilirubin was mainly investigated, and the effects of various factors, such as pH value, ionic strength and grafting degree of PEI on the surface of grafting microbeads and the adsorption capacity of the grafting microbeads for bilirubin were examined. The batch adsorption experiment results show that by right of the action of grafted polyamine macromolecules PEI, the grafting microbeads PEI-GMA/AM/MBA have quite strong adsorption ability for bilirubin; the isotherm adsorption conforms to Freundlich equation. The pH value of the medium affects the adsorption capacity greatly, As in the nearly neutral solutions with pH 6, the grafting microbeads have the strongest adsorption ability for bilirubin, whereas in acidic and basic solutions their adsorption ability is weak. The ionic strength hardly affects the adsorption ability of the grafting microbeads. The grafting degree of PEI on the surfaces of the grafting microbeads also has a great effect on the adsorption capacity, and higher the grafting degree of PEI on the surface of the microbead PEI-GMA/AM/MBA, the stronger is the adsorption ability of the microbeads.

  8. 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...

  9. Discrete site surface complexation constants for lanthanide adsorption to bacteria as determined by experiments and linear free energy relationships.

    PubMed

    Ngwenya, Bryne T; Magennis, Marisa; Olive, Valerie; Mosselmans, J Fred W; Ellam, Robert M

    2010-01-15

    Bacteria are abundant in many natural and engineered environments where they are thought to exert important controls on the cycling, mobility, bioavailability, and toxicity of metal contaminants. In order to probe their role in moderating the behavior of lanthanides, pH-dependent adsorption edges of 13 individual lanthanides and yttrium to the Gram-negative bacterium Pantoea agglomerans were used to generate discrete site surface complexation constants. The calculated surface complexation constants were compared with stability constants estimated using linear free energy relationships based on a number of hydroxyl-containing ligands. The experimental data suggests that lanthanide adsorption edges below pH 6.5 are consistent with adsorption to phosphate groups for the light and some of the middle lanthanides (La to Gd), whereas some of the middle and heavy lanthanides appear to favor carboxyl co-ordination (Tb to Yb), although exceptions occur in each grouping. The experimentally derived surface complexation constants for carboxyl coordination were of similar magnitude to stability constants estimated from linear free energy correlations using fulvic acid stability constants. The implication is that the adsorption of lanthanides to bacterial surfaces could be modeled reasonably well using lanthanide stability constants for natural organic matter, except perhaps at low pH where phosphate binding dominates. PMID:20000843

  10. 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…

  11. 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.

  12. Phosphate removal from aqueous solution by adsorption on modified giant reed.

    PubMed

    Yue, Qin-Yan; Wang, Wen-Yi; Gao, Bao-Yu; Xu, Xing; Zhang, Jian; Li, Qian

    2010-04-01

    The use of modified giant reed (MGR) as an adsorbent to remove phosphate from an aqueous solution was investigated. The dosage of MGR, pH of the phosphate solution, thermodynamics, and the effects of several factors on kinetics (concentration of phosphate solution, solution temperature, and shaking speed) were studied in batch experiments. The results showed that MGR was particularly effective to remove phosphate and that the effective pH range for the phosphate removal was between 4 and 9. The adsorption process could reach equilibrium in 25 minutes. Three kinetic models have been evaluated to fit the experimental data. It was shown that the pseudo-second-order model best described the adsorption kinetics of phosphate on MGR. The low activation energy of the adsorption suggested a physisorption process for phosphate adsorption. The equilibrium isotherm showed that the adsorption system was consistent with the Langmuir equation. The negative values of standard free energy (AG) and enthalpy (AH) indicated that the adsorption of phosphate onto MGR was a spontaneous and exothermic process.

  13. 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

  14. 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.

  15. Liquid phase adsorption behavior of inulin-type fructan onto activated charcoal.

    PubMed

    Li, Kecheng; Liu, Song; Xing, Ronge; Yu, Huahua; Qin, Yukun; Li, Pengcheng

    2015-05-20

    This study describes liquid phase adsorption characteristics of inulin-type fructan onto activated charcoal. Batch mode experiments were conducted to study the effects of pH, contact time, temperature and initial concentration of inulin. Nearly neutral solution (pH 6-8) was favorable to the adsorption and the equilibrium was attained after 40 min with the maximum adsorption Qmax 0.182 g/g (adsorbate/adsorbent) at 298 K. The experimental data analysis indicated that the adsorption process fitted well with the pseudo-second-order kinetic model (R(2) = 1) and Langmuir isotherms model (R(2) > 0.99). Thermodynamic parameters revealed that the adsorption process was spontaneous and exothermic with a physical nature. Inulin desorption could reach 95.9% using 50% ethanol solution and activated charcoal could be reused without significant losses in adsorption capacity. These results are of practical significance for the application of activated charcoal in the production and purification of inulin-type fructan.

  16. Analysis of the statistical thermodynamic model for nonlinear binary protein adsorption equilibria.

    PubMed

    Zhou, Xiao-Peng; Su, Xue-Li; Sun, Yan

    2007-01-01

    The statistical thermodynamic (ST) model was used to study nonlinear binary protein adsorption equilibria on an anion exchanger. Single-component and binary protein adsorption isotherms of bovine hemoglobin (Hb) and bovine serum albumin (BSA) on DEAE Spherodex M were determined by batch adsorption experiments in 10 mM Tris-HCl buffer containing a specific NaCl concentration (0.05, 0.10, and 0.15 M) at pH 7.40. The ST model was found to depict the effect of ionic strength on the single-component equilibria well, with model parameters depending on ionic strength. Moreover, the ST model gave acceptable fitting to the binary adsorption data with the fitted single-component model parameters, leading to the estimation of the binary ST model parameter. The effects of ionic strength on the model parameters are reasonably interpreted by the electrostatic and thermodynamic theories. The effective charge of protein in adsorption phase can be separately calculated from the two categories of the model parameters, and the values obtained from the two methods are consistent. The results demonstrate the utility of the ST model for describing nonlinear binary protein adsorption equilibria.

  17. Removal of molybdate anions from water by adsorption on zeolite-supported magnetite.

    PubMed

    Verbinnen, Bram; Block, Chantal; Hannes, Dries; Lievens, Patrick; Vaclavikova, Miroslava; Stefusova, Katarina; Gallios, Georgios; Vandecasteele, Carlo

    2012-09-01

    Industrial wastewater may contain high molybdenum concentrations, making treatment before discharge necessary. In this paper, the removal of molybdate anions from water is presented, using clinoptilolite zeolite coated with magnetite nanoparticles. In batch experiments the influence of pH, ionic strength, possible interfering (oxy)anions, temperature and contact time is investigated. Besides determination of kinetic parameters and adsorption isotherms, thermodynamic modeling is performed to get better insight into the adsorption mechanism; molybdenum is assumed to be adsorbed as a FeOMoO2(OH).2H2O inner-sphere complex. At the optimum pH of 3, the adsorption capacity is around 18 mg molybdenum per gram adsorbent. The ionic strength of the solution has no influence on the adsorption capacity. Other anions, added to the molybdenum solution in at least a tenfold excess, only have a minor influence on the adsorption of molybdenum, with the exception of phosphate. Adsorption increases when temperature is increased. It is demonstrated that the adsorbent can be used to remove molybdenum from industrial wastewater streams, and that the limitations set by the World Health Organization (residual concentration of 70 microg/l Mo) can easily be met.

  18. 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

  19. Preparation of activated carbon from corn cob and its adsorption behavior on Cr(VI) removal.

    PubMed

    Tang, Shuxiong; Chen, Yao; Xie, Ruzhen; Jiang, Wenju; Jiang, Yanxin

    2016-01-01

    Operation experiments were conducted to optimize the preparation of activated carbons from corn cob. The Cr(VI) adsorption capacity of the produced activated carbons was also evaluated. The impact of the adsorbent dosage, contact time, initial solution pH and temperature was studied. The results showed that the produced corn cob activated carbon had a good Cr(VI) adsorptive capacity; the theoretical maximum adsorption was 34.48 mg g(-1) at 298 K. The Brunauer-Emmett-Teller and iodine adsorption value of the produced activated carbon could be 924.9 m(2) g(-1) and 1,188 mg g(-1), respectively. Under the initial Cr(VI) concentration of 10 mg L(-1) and the original solution pH of 5.8, an adsorption equilibrium was reached after 4 h, and Cr(VI) removal rate was from 78.9 to 100% with an adsorbent's dosage increased from 0.5 to 0.7 g L(-1). The kinetics and equilibrium data agreed well with the pseudo-second-order kinetics model and the Langmuir isotherm model. The equilibrium adsorption capacity improved with the increment of the temperature. PMID:27232401

  20. Hydrogen adsorption strength and sites in the metal organic framework MOF5: Comparing experiment and model calculations

    NASA Astrophysics Data System (ADS)

    Mulder, F. M.; Dingemans, T. J.; Schimmel, H. G.; Ramirez-Cuesta, A. J.; Kearley, G. J.

    2008-07-01

    Hydrogen adsorption in porous, high surface area, and stable metal organic frameworks (MOF's) appears a novel route towards hydrogen storage materials [N.L. Rosi, J. Eckert, M. Eddaoudi, D.T. Vodak, J. Kim, M. O'Keeffe, O.M. Yaghi, Science 300 (2003) 1127; J.L.C. Rowsell, A.R. Millward, K. Sung Park, O.M. Yaghi, J. Am. Chem. Soc. 126 (2004) 5666; G. Ferey, M. Latroche, C. Serre, F. Millange, T. Loiseau, A. Percheron-Guegan, Chem. Commun. (2003) 2976; T. Loiseau, C. Serre, C. Huguenard, G. Fink, F. Taulelle, M. Henry, T. Bataille, G. Férey, Chem. Eur. J. 10 (2004) 1373]. A prerequisite for such materials is sufficient adsorption interaction strength for hydrogen adsorbed on the adsorption sites of the material because this facilitates successful operation under moderate temperature and pressure conditions. Here we report detailed information on the geometry of the hydrogen adsorption sites, based on the analysis of inelastic neutron spectroscopy (INS). The adsorption energies for the metal organic framework MOF5 equal about 800 K for part of the different sites, which is significantly higher than for nanoporous carbon materials (˜550 K) [H.G. Schimmel, G.J. Kearley, M.G. Nijkamp, C.T. Visser, K.P. de Jong, F.M. Mulder, Chem. Eur. J. 9 (2003) 4764], and is in agreement with what is found in first principles calculations [T. Sagara, J. Klassen, E. Ganz, J. Chem. Phys. 121 (2004) 12543; F.M. Mulder, T.J. Dingemans, M. Wagemaker, G.J. Kearley, Chem. Phys. 317 (2005) 113]. Assignments of the INS spectra is realized using comparison with independently published model calculations [F.M. Mulder, T.J. Dingemans, M. Wagemaker, G.J. Kearley, Chem. Phys. 317 (2005) 113] and structural data [T. Yildirim, M.R. Hartman, Phys. Rev. Lett. 95 (2005) 215504].

  1. 40 CFR 796.2750 - Sediment and soil adsorption isotherm.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... Agricultural and Food Chemistry, 23:720-724 (1975). (2) Goring, C.A.I., Hamaker, J.W., (eds). Organic Chemicals... minerals and the amount present in a sediment or soil. (iii) “Organic matter” is the organic fraction of.... (vii) “Sediment” is the unconsolidated inorganic and organic material that is suspended in and...

  2. 40 CFR 796.2750 - Sediment and soil adsorption isotherm.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... Agricultural and Food Chemistry, 23:720-724 (1975). (2) Goring, C.A.I., Hamaker, J.W., (eds). Organic Chemicals... minerals and the amount present in a sediment or soil. (iii) “Organic matter” is the organic fraction of.... (vii) “Sediment” is the unconsolidated inorganic and organic material that is suspended in and...

  3. 40 CFR 796.2750 - Sediment and soil adsorption isotherm.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... Agricultural and Food Chemistry, 23:720-724 (1975). (2) Goring, C.A.I., Hamaker, J.W., (eds). Organic Chemicals... minerals and the amount present in a sediment or soil. (iii) “Organic matter” is the organic fraction of.... (vii) “Sediment” is the unconsolidated inorganic and organic material that is suspended in and...

  4. 40 CFR 796.2750 - Sediment and soil adsorption isotherm.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... Agricultural and Food Chemistry, 23:720-724 (1975). (2) Goring, C.A.I., Hamaker, J.W., (eds). Organic Chemicals... minerals and the amount present in a sediment or soil. (iii) “Organic matter” is the organic fraction of.... (vii) “Sediment” is the unconsolidated inorganic and organic mat