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Sample records for adsorption equilibrium isotherms

  1. Equilibrium isotherms, kinetics and thermodynamics studies of phenolic compounds adsorption on palm-tree fruit stones.

    PubMed

    Ahmed, Muthanna J; Theydan, Samar K

    2012-10-01

    Adsorption capacity of an agricultural waste, palm-tree fruit stones (date stones), for phenolic compounds such as phenol (Ph) and p-nitro phenol (PNPh) at different temperatures was investigated. The characteristics of such waste biomass were determined and found to have a surface area and iodine number of 495.71 m2/g and 475.88 mg/g, respectively. The effects of pH (2-12), adsorbent dose (0.6-0.8 g/L) and contact time (0-150 min) on the adsorptive removal process were studied. Maximum removal percentages of 89.95% and 92.11% were achieved for Ph and PNPh, respectively. Experimental equilibrium data for adsorption of both components were analyzed by the Langmuir, Freundlich and Tempkin isotherm models. The results show that the best fit was achieved with the Langmuir isotherm equation with maximum adsorption capacities of 132.37 and 161.44 mg/g for Ph and PNPh, respectively. The kinetic data were fitted to pseudo-first order, pseudo-second order and intraparticle diffusion models, and was found to follow closely the pseudo-second order model for both components. The calculated thermodynamic parameters, namely ΔG, ΔH, and ΔS showed that adsorption of Ph and PNPh was spontaneous and endothermic under examined conditions.

  2. 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.

  3. Adsorption of selected emerging contaminants onto PAC and GAC: Equilibrium isotherms, kinetics, and effect of the water matrix.

    PubMed

    Real, Francisco J; Benitez, F Javier; Acero, Juan L; Casas, Francisco

    2017-03-30

    The removal of three emerging contaminants (ECs) (amitriptyline hydrochloride (AH), methyl salicylate (MS) and 2-phenoxyethanol (PE)) dissolved in several water matrices by means of their adsorption onto powdered activated carbon (PAC) and granular activated carbon (GAC) has been investigated. When dissolved in ultrapure water, adsorption of the ECs followed the trend of AH > MS > PE, with a positive effect of the adsorbent dose. According to the analysis of the adsorption isotherms and adsorption kinetics, PAC showed strongly higher adsorption efficiency in both capacity and velocity of the adsorption, in agreement with its higher mesoporosity. Equilibrium isotherm data were fitted by Langmuir and Freundlich models. Pseudo-second order kinetics modeled very successfully the adsorption process. Finally, the effect of the presence of dissolved organic matter (DOM) in the water matrices (ultrapure water, surface water and two effluents from wastewater treatment plants) on the adsorption of the selected ECs onto PAC was established, as well as its performance on the removal of water quality parameters. Results show a negative effect of the DOM content on the adsorption efficiency. Over 50% of organic matter was removed with high PAC doses, revealing that adsorption onto PAC is an effective technology to remove both micro-pollutants and DOM from water matrices.

  4. 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.

  5. 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

  6. Equilibrium isotherms, kinetics, and thermodynamics studies for congo red adsorption using calcium alginate beads impregnated with nano-goethite.

    PubMed

    Munagapati, Venkata Subbaiah; Kim, Dong-Su

    2017-03-24

    The present study is concerned with the batch adsorption of congo red (CR) from an aqueous solution using calcium alginate beads impregnated with nano-goethite (CABI nano-goethite) as an adsorbent. The optimum conditions for CR removal were determined by studying operational variables viz. pH, adsorbent dose, contact time, initial dye ion concentration and temperature. The CABI nano-goethite was characterized by Fourier transform infrared spectroscopy (FTIR), X- ray diffraction (XRD) and Scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS) analysis. The CR sorption data onto CABI nano-goethite were described using Langmuir, Freundlich, Dubinin-Radushkevich and Temkin isotherm models. The results show that the best fit was achieved with the Langmuir isotherm model. The maximum adsorption capacity (181.1mg/g) of CR was occurred at pH 3.0. Kinetic studies showed that the adsorption followed a pseudo-second-order model. Desorption experiments were carried out to explore the feasibility of regenerating the adsorbent and the adsorbed CR from CABI nano-goethite. The best desorbing agent was 0.1M NaOH with an efficiency of 94% recovery. The thermodynamic parameters ΔG°, ΔH°, and ΔS° for the CR adsorption were determined by using adsorption capacities at five different temperatures (293, 303, 313, 323 and 303K). Results show that the adsorption process was endothermic and favoured at high temperature.

  7. Kinetic, equilibrium isotherm and thermodynamic studies of Cr(VI) adsorption onto low-cost adsorbent developed from peanut shell activated with phosphoric acid.

    PubMed

    ALOthman, Zeid A; Naushad, Mu; Ali, Rahmat

    2013-05-01

    A particular agricultural waste, peanut shell, has been used as precursor for activated carbon production by chemical activation with H₃PO₄. Unoxidized activated carbon was prepared in nitrogen atmosphere which was then heated in air at a desired temperature to get oxidized activated carbon. The prepared carbons were characterized for surface area, surface morphology, and pore volume and utilized for the removal of Cr(VI) from aqueous solution. Batch mode experiments were conducted to study the effects of pH, contact time, particle size, adsorbent dose, initial concentration of adsorbate, and temperature on the adsorption of Cr(VI). Cr(VI) adsorption was significantly dependent on solution pH, and the optimum adsorption was observed at pH 2. Pseudo-first-order, pseudo-second-order, and intraparticle diffusion models were used to analyze the kinetic data obtained at different initial Cr(VI) concentrations. The adsorption kinetic data were described very well by the pseudo-second-order model. Equilibrium isotherm data were analyzed by the Langmuir, Freundlich, and Temkin models. The results showed that the Langmuir adsorption isotherm model fitted the data better in the temperature range studied. The adsorption capacity which was found to increase with temperature showed the endothermic nature of Cr(VI) adsorption. The thermodynamic parameters, such as Gibb's Free energy change (ΔG°), standard enthalpy change (ΔH°), and standard entropy change (ΔS°) were evaluated.

  8. Adsorption isotherms of charged nanoparticles.

    PubMed

    Dos Santos, Alexandre P; Bakhshandeh, Amin; Diehl, Alexandre; Levin, Yan

    2016-10-19

    We present theory and simulations which allow us to quantitatively calculate the amount of surface adsorption excess of charged nanoparticles onto a charged surface. The theory is very accurate for weakly charged nanoparticles and can be used at physiological concentrations of salt. We have also developed an efficient simulation algorithm which can be used for dilute suspensions of nanoparticles of any charge, even at very large salt concentrations. With the help of the new simulation method, we are able to efficiently calculate the adsorption isotherms of highly charged nanoparticles in suspensions containing multivalent ions, for which there are no accurate theoretical methods available.

  9. 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.

  10. Experimental adsorption isotherms based on inverse gas chromatography.

    PubMed

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

    2002-09-06

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

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

  12. Characteristics of selective fluoride adsorption by biocarbon-Mg/Al layered double hydroxides composites from protein solutions: kinetics and equilibrium isotherms study.

    PubMed

    Ma, Wei; Lv, Tengfei; Song, Xiaoyan; Cheng, Zihong; Duan, Shibo; Xin, Gang; Liu, Fujun; Pan, Decong

    2014-03-15

    In the study, two novel applied biocarbon-Mg/Al layered double hydroxides composites (CPLDH and CPLDH-Ca) were successfully prepared and characterized by TEM, ICP-AES, XFS, EDS, FTIR, XRD, BET and pHpzc. The fluoride removal efficiency (RF) and protein recovery ratio (RP) of the adsorbents were studied in protein systems of lysozyme (LSZ) and bovine serum albumin (BSA). The results showed that the CPLDH-Ca presented remarkable performance for selective fluoride removal from protein solution. It reached the maximum RF of 92.1% and 94.8% at the CPLDH-Ca dose of 2.0g/L in LSZ and BSA system, respectively. The RP in both systems of LSZ and BSA were more than 90%. Additionally, the RP of CPLDH-Ca increased with the increase of ionic strengths, and it almost can be 100% with more than 93% RF. Fluoride adsorption by the CPLDH-Ca with different initial fluoride concentrations was found to obey the mixed surface reaction and diffusion controlled adsorption kinetic model, and the overall reaction rate is probably controlled by intra-particle diffusion, boundary layer diffusion and reaction process. The adsorption isotherms of fluoride in BSA system fit the Langmuir-Freundlich model well. The BSA has synergistic effect on fluoride adsorption and the degree increased with the increase of the initial BSA concentration.

  13. 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)

  14. 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.

  15. 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.

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

    DOE PAGES

    Lin, Ronghong; Ladshaw, Austin; Nan, Yue; ...

    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

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

    PubMed

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

    2008-01-01

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

  18. 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

  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 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)

  1. 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.

  2. Equilibrium sorption isotherms for nitrate on resin Amberlite IRA 400.

    PubMed

    Chabani, M; Amrane, A; Bensmaili, A

    2009-06-15

    The adsorption isotherms of nitrate on resin Amberlite IRA 400 at various pH, in the range 2-12, were experimentally determined by batch tests. The experimental data have been analysed using the Langmuir, Freundlich, Redlich-Peterson and Sips isotherms models. In order to determine the best fit isotherm, two error analysis methods were used to evaluate the data: the regression correlation coefficient, and the statistic Chi-square test. In the range of pH tested, the Sips model was found to give the best fit of the adsorption isotherm data. The maximum adsorption capacity can be deduced from the obtained correlation coefficients and was found to decrease for increasing pH.

  3. Correlation of ph dependant equilibrium isotherms of heavy metal biosorption with a modified Freundlich model.

    PubMed

    Liu, X; Goodfellow, M R; Yu, Q; Zheng, C

    2004-12-01

    Equilibrium isotherms of heavy metal biosorption are commonly correlated with adsorption models such as the Freundlich model. On the other hand, the adsorption properties of heavy metal biosorption are strongly influenced by the solution pH of the biosorption system. Therefore, standard adsorption models are limited to the correlation of equilibrium isotherms under constant pH values. In this paper, a modified Freundlich model was developed for the correlation of pH dependent equilibrium isotherms of heavy metal biosorption. The model was based on the mechanism that the functional groups for heavy metal interactions are weakly acidic groups and the uptake capacities of the biomass are affected through the association and dissociation equilibrium between two apparent ionic forms. Both the standard and the modified Freundlich models were tested with isotherm data for Cd2+, Cu2+ and Ni2+ biosorption onto pre-treated biomass of marine alga Durvillaea potatorum under various solution pH values. Regression analyses indicated that the developed model correlated the experimental data well.

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

    PubMed

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

    2015-11-01

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

  5. Adsorption characteristics of siloxanes in landfill gas by the adsorption equilibrium test

    SciTech Connect

    Nam, Sangchul; Namkoong, Wan; Kang, Jeong-Hee; Park, Jin-Kyu; Lee, Namhoon

    2013-10-15

    Highlights: • Equilibrium test was attempted to evaluate adsorption characteristics of siloxane. • L2 had higher removal efficiency in carbon compared to noncarbon adsorbents. • Total adsorption capacity of siloxane was 300 mg/g by coal activated carbon. • Adsorption characteristics rely on size of siloxane molecule and adsorbent pore. • Conversion of siloxane was caused by adsorption of noncarbon adsorbents. - Abstract: Due to the increase in energy cost by constantly high oil prices and the obligation to reduce greenhouse effect gases, landfill gas is frequently used as an alternative energy source for producing heat and electricity. Most of landfill gas utility facilities, however, are experiencing problems controlling siloxanes from landfill gas as their catalytic oxidizers are becoming fouled by silicon dioxide dust. To evaluate adsorption characteristics of siloxanes, an adsorption equilibrium test was conducted and parameters in the Freundlich and Langmuir isotherms were analyzed. Coconut activated carbon (CA1), coal activated carbon (CA2), impregnated activated carbon (CA3), silicagel (NCA1), and activated alumina (NCA2) were used for the adsorption of the mixed siloxane which contained hexamethyldisiloxane (L2), octamethylcyclotetrasiloxane (D4), and decamethylcyclopentasiloxane (D5). L2 had higher removal efficiency in noncarbon adsorbents compared to carbon adsorbents. The application of Langmuir and Freundlich adsorption isotherm demonstrated that coconut based CA1 and CA3 provided higher adsorption capacity on L2. And CA2 and NCA1 provided higher adsorption capacity on D4 and D5. Based on the experimental results, L2, D4, and D5 were converted by adsorption and desorption in noncarbon adsorbents. Adsorption affinity of siloxane is considered to be affect by the pore size distribution of the adsorbents and by the molecular size of each siloxane.

  6. Modeling of adsorption isotherms of phenol and chlorophenols onto granular activated carbon. Part II. Models with more than two parameters.

    PubMed

    Hamdaoui, Oualid; Naffrechoux, Emmanuel

    2007-08-17

    The adsorption equilibrium isotherms of five phenolic compounds, phenol, 2-chlorophenol, 4-chlorophenol, 2,4-dichlorophenol, and 2,4,6-trichlorophenol, from aqueous solutions onto granular activated carbon were studied and modeled. In order to determine the best-fit isotherm, the experimental equilibrium data were analyzed using thirteen adsorption isotherm models with more than two-parameter; nine three-parameter equations - the Redlich-Peterson, Sips, Langmuir-Freundlich, Fritz-Schlunder, Radke-Prasnitz (three models), Tóth, and Jossens isotherms - three four-parameter equation - the Weber-van Vliet, Fritz-Schlunder, and Baudu isotherms - and one five-parameter equation - the Fritz-Schlunder isotherm. The results reveal that the adsorption isotherm models fitted the experimental data in the order: Baudu (four-parameter)>Langmuir-Freundlich (three-parameter)>Sips (three-parameter)>Fritz-Schlunder (five-parameter)>Tóth (three-parameter)>Fritz-Schlunder (four-parameter)>Redlich-Peterson (three-parameter). The influence of solution pH on the adsorption isotherms of 4-CP was investigated. It was shown that the solution pH has not an effect on the adsorption isotherms for pHadsorptive pKa and the pH(PZC).

  7. Probing the mechanism of water adsorption in carbon micropores with multitemperature isotherms and water preadsorption experiments.

    PubMed

    Rutherford, S W

    2006-11-21

    The phenomenon of water adsorption in carbon micropores is examined through the study of water adsorption equilibrium in molecular sieving carbon. Adsorption and desorption isotherms are obtained over a wide range of concentrations from less than 0.1% to beyond 80% of the vapor pressure. Evidence is provided in support of a proposed bimodal water adsorption mechanism that involves the interaction of water molecules with functional groups at low relative pressures and the adsorption of water molecules between graphene layers at higher pressures. Decomposition of the equilibrium isotherm data through application of the extended cooperative multimolecular sorption theory, together with favorable quantitative comparison, provides support for the proposed adsorption mechanism. Additional support is obtained from a multitemperature study of water equilibrium. Temperatures of 20, 50, and 60 degrees C were probed in this investigation in order to provide isosteric heat of adsorption data for water interaction with the carbon molecular sieve. At low loading, the derived isosteric heat of adsorption is estimated to be 69 kJ/mol. This value is indicative of the adsorption of water to functional groups. At higher loading, the isosteric heat of adsorption decreases with increasing loading and approaches the heat of condensation, indicative of adsorption between graphene layers. Further support for the proposed adsorption mechanism is derived from carbon dioxide adsorption experiments on carbon molecular sieve that is preadsorbed with various amounts of water. Significant exclusion of carbon dioxide occurs, and a quantitative analysis that is based on the proposed bimodal water adsorption mechanism is employed in this investigation.

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

    PubMed

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

    2014-08-22

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

  9. 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…

  10. Adsorption of nitrophenol onto activated carbon: isotherms and breakthrough curves.

    PubMed

    Chern, Jia-Ming; Chien, Yi-Wen

    2002-02-01

    The adsorption isotherm of p-nitrophenol onto granular activated carbon in 25 degrees C aqueous solution was experimentally determined by batch tests. Both the Freundlich and the Redlich-Peterson models were found to fit the adsorption isotherm data well. A series of column tests were performed to determine the breakthrough curves with varying bed depths (3-6 cm) and water flow rates (21.6-86.4 cm3/h). Explicit equations for the breakthrough curves of the fixed-bed adsorption processes with the Langmuir and the Freundlich adsorption isotherms were developed by the constant-pattern wave approach using a constant driving force model in the liquid phase. The results show that the half breakthrough time increases proportionally with increasing bed depth but decreases inverse proportionally with increasing water flow rate. The constant-pattern wave approach using the Freundlich isotherm model fits the experimental breakthrough curves quite satisfactorily. A correlation was proposed to predict the volumetric mass-transfer coefficient in the liquid phase successfully. The effects of solution temperature and pH on the adsorption isotherm were also studied and the Tóth model was found to fit the isotherm data well at varying solution temperatures and pHs.

  11. Determination of the Surface Energy of Sand Using Adsorption Isotherm

    NASA Astrophysics Data System (ADS)

    Ma, Lianxi; Holste, James; Hall, Kenneth

    2003-03-01

    The BET isotherm equation for multiplayer adsorption was applied to hexane, methyl propyl ketone, and water adsorption by sand (particle size > 75 mm) at 25¡ãC and accordingly, specific surface area of sand was obtained. Spreading pressures and surface energies of sand were calculated from adsorption isotherms. Hysteresis loops were observed in all isotherms but desorption isotherms approach to original points at low vapor pressure. A modified Toth-Freundlich equation was developed, which agrees with experimental data well over a wider p/p0 range. Plots of Dubinin-Radushkevich show that at low-pressure linear relation was obtained therefore our sand sample can be treated as microporous materials.

  12. Adsorption of methylene blue onto bamboo-based activated carbon: kinetics and equilibrium studies.

    PubMed

    Hameed, B H; Din, A T M; Ahmad, A L

    2007-03-22

    Bamboo, an abundant and inexpensive natural resource in Malaysia was used to prepare activated carbon by physiochemical activation with potassium hydroxide (KOH) and carbon dioxide (CO(2)) as the activating agents at 850 degrees C for 2h. The adsorption equilibrium and kinetics of methylene blue dye on such carbon were then examined at 30 degrees C. Adsorption isotherm of the methylene blue (MB) on the activated carbon was determined and correlated with common isotherm equations. The equilibrium data for methylene blue adsorption well fitted to the Langmuir equation, with maximum monolayer adsorption capacity of 454.2mg/g. Two simplified kinetic models including pseudo-first-order and pseudo-second-order equation were selected to follow the adsorption processes. The adsorption of methylene blue could be best described by the pseudo-second-order equation. The kinetic parameters of this best-fit model were calculated and discussed.

  13. 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.

  14. Equilibrium and kinetic adsorption study of the adsorptive removal of Cr(VI) using modified wheat residue.

    PubMed

    Chen, Suhong; Yue, Qinyan; Gao, Baoyu; Xu, Xing

    2010-09-01

    A new adsorbent modified from wheat residue was synthesized after reaction with epichlorohydrin and triethylamine by using the modifying agents of diethylenetriamine in the presence of organic medium of N,N-dimethylformamide. The performance of the modified wheat straw (MWS) was characterized by Fourier transform infrared spectroscopy and point of zero charge analysis. The adsorption was investigated in a batch adsorption system, including both equilibrium adsorption isotherms and kinetics. Results showed that MWR had great anion-adsorbing capacity, due to the existence of a large number of introduced amino groups, and the value of pH(PZC) was around 5.0. Equilibrium data were analyzed using the Langmuir, Freundlich, and Temkin isotherm models and were found to be best represented by the Freundlich isotherm model. Evaluation of the adsorption process identified its endothermic nature. The maximum adsorption capacity of MWS for the removal of Cr(VI) was 322.58mg/g at 328K, indicating that MWS has high chromium removal efficiency, compared to other adsorbents reported. The kinetics of adsorption followed the pseudo-second-order kinetic equation. The mechanism of adsorption was investigated using the intraparticle diffusion model. Thermodynamic parameters (free energy change, enthalpy change, and entropy change) revealed that the adsorption of Cr(VI) onto MWS was endothermic and spontaneous; additionally, the adsorption can be characterized as an ion-exchange process. The results suggest that MWS is an inexpensive and efficient adsorbent for removing Cr(VI) ions from aqueous solution.

  15. 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

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

    PubMed

    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.

  17. 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.

  18. Kinetics and equilibrium adsorption studies of dimethylamine (DMA) onto ion-exchange resin.

    PubMed

    Hu, Qinhai; Meng, Yuanyuan; Sun, Tongxi; Mahmood, Qaisar; Wu, Donglei; Zhu, Jianhang; Lu, George

    2011-01-30

    The fine grained resin ZGSPC106 was used to adsorb dimethylamine (DMA) from aqueous solution in the present research. Batch experiments were performed to examine the effects of initial pH of solution and agitation time on the adsorption process. The thermodynamics and kinetics of adsorption were also analyzed. The maximum adsorption was found at natural pH of DMA solution and equilibrium could be attained within 12 min. The equilibrium adsorption data were conformed satisfactorily to the Langmuir equation. The evaluation based on Langmuir isotherm gave the maximal static saturated adsorption capacity of 138.89 mg/g at 293K. Various thermodynamic parameters such as free energy (ΔG°), enthalpy (ΔH°) and entropy (ΔS°) showed that the adsorption was spontaneous, endothermic and feasible. DMA adsorption on ZGSPC106 fitted well to the pseudo-second-order kinetic model. Furthermore, the adsorption mechanism was discussed by Fourier transform infrared spectroscopy (FT-IR) analysis.

  19. Pattern of adsorption isotherms in Ono-Kondo coordinates.

    PubMed

    Sumanatrakul, Panita; Abaza, Sarah; Aranovich, Gregory L; Sangwichien, Chayanoot; Donohue, Marc D

    2012-02-15

    The Ono-Kondo lattice density functional theory is used to analyze adsorbate-adsorbate interactions for supercritical systems. In prior work, this approach has been used to study intermolecular interactions in subcritical adsorbed phases, and this has included the study of adsorbate-adsorbate repulsions in the regime of adsorption compression. In this paper, we present the general pattern of adsorption isotherms in Ono-Kondo coordinates; this has not been done in the past. For this purpose, experimental isotherms for adsorption of supercritical fluids (including nitrogen, methane, and carbon dioxide) are plotted in Ono-Kondo coordinates. In addition, we performed Grand Canonical Monte Carlo simulations of adsorption for Lennard-Jones molecules and plotted isotherms in Ono-Kondo coordinates. Our results indicate a pattern of isotherms with regimes of adsorbate-adsorbate attractions at low surface coverage and adsorbate-adsorbate repulsions at high surface coverage. When the generalized Ono-Kondo model is used over a wide range of pressures - from low pressures of the Henry's law regime to supercritical pressures - the slope of the isotherm varies from positive at low pressures to negative at high pressures. The linear sections of these graphs show when the adsorbate-adsorbate interaction energies are approximately constant. When these linear sections have negative slopes, it indicates that the system is in a state of adsorption compression.

  20. A model for predicting contaminant removal by adsorption within the International Space Station water processor: 1. Multicomponent equilibrium modeling.

    PubMed

    Bulloch, J L; Hand, D W; Crittenden, J C

    1998-01-01

    A thermodynamic model is developed to predict adsorption equilibrium in the International Space Station water processor's multifiltration beds. The model predicts multicomponent adsorption equilibrium behavior using single-component isotherm parameters and fictitious components representing the background matrix. The fictitious components are determined by fitting total organic carbon and tracer isotherms with the ideal adsorbed solution theory. Multicomponent isotherms using a wastewater with high surfactant and organic compound concentrations are used to validate the equilibrium description on a coconut-shell-based granular activated carbon (GAC), coal-based GAC, and a polymeric adsorbent.

  1. Adsorption isotherms of 2,2,4-trimethylpentane and toluene vapors on hydrocarbon adsorber and light-off catalyst.

    PubMed

    Kim, Dae Jung

    2004-01-15

    Two monolithic hydrocarbon adsorbers and a monolithic light-off catalyst were selected as adsorbents, and the adsorptive capacity of a hydrocarbon for the adsorbents was measured by using a precise volumetric adsorption apparatus. 2,2,4-Trimethylpentane and toluene vapors were chosen as adsorbates. Equilibrium experiments were carried out at three different temperatures of 303.15, 323.15, and 343.15 K. Adsorption data of each hydrocarbon was fitted to the well-known isotherms such as the Langmuir equation and the Freundlich equation. The Freundlich isotherm predicted equilibrium data better than the Langmuir isotherm. Furthermore, the surface energetic heterogeneity of the adsorbents was evaluated using the isosteric heat of adsorption based on Clausius-Clapeyron equation. The surface energetic heterogeneity of the adsorbents depended on the precious metal (PM) loading and H-ZSM5 loading.

  2. Equilibrium and kinetics of water adsorption in carbon molecular sieve: theory and experiment.

    PubMed

    Rutherford, S W; Coons, J E

    2004-09-28

    Measurements of water adsorption equilibrium and kinetics in Takeda carbon molecular sieve (CMS) were undertaken in an effort to characterize fundamental mechanisms of adsorption and transport. Adsorption equilibrium revealed a type III isotherm that was characterized by cooperative multimolecular sorption theory. Water adsorption was found to be reversible and did not display hysteresis upon desorption over the conditions studied. Adsorption kinetics measurements revealed that a Fickian diffusion mechanism governed the uptake of water and that the rate of adsorption decreased with increasing relative pressure. Previous investigations have attributed the observed decreasing trend in the rate of adsorption to blocking of micropores. Here, it is proposed that the decrease is attributed to the thermodynamic correction to Fick's law which is formulated on the basis of the chemical potential as the driving force for transport. The thermodynamically corrected formulation accounted for observations of transport of water and other molecules in CMS.

  3. 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).

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

    PubMed

    Edwards, J Vincent; Castro, Nathan J; Condon, Brian; Costable, Carmen; Goheen, Steven C

    2012-05-01

    Albumin is the most abundant protein found in healing wounds. Traditional and chromatographic 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 dressings is adsorption and accumulation of proteins like albumin at the solid-liquid interface of the biological fluid and wound dressing fiber. To better understand the effect of fiber charge and molecular modifications in cellulose-containing fibers on the binding of serum albumin as observed in protease sequestrant dressings, albumin binding to modified cotton fibers was compared with traditional and chromatographic isotherms. Modified cotton including carboxymethylated, citrate-crosslinked, dialdehyde and phosphorylated cotton, which sequester elastase and collagenase, were compared for their albumin binding isotherms. Albumin isotherms on citrate-cellulose, cross-linked cotton demonstrated a two-fold increased binding affinity over untreated cotton. A comparison of albumin binding between traditional, solution isotherms and chromatographic isotherms on modified cellulose yielded similar equilibrium constants. Application of the binding affinity of albumin obtained in the in vitro protein isotherm to the in vivo wound dressing uptake of the protein is discussed. The chromatographic approach to assessment of albumin isotherms on modified cellulose offers a more rapid approach to evaluating protein binding on modified cellulose over traditional solution approaches.

  5. Determination of adsorption isotherms in supercritical fluid chromatography.

    PubMed

    Enmark, Martin; Forssén, Patrik; Samuelsson, Jörgen; Fornstedt, Torgny

    2013-10-18

    In this study we will demonstrate the potential of modern integrated commercial analytical SFC-systems for rapid and reliable acquisition of thermodynamic data. This will be done by transferring the following adsorption isotherm determination methods from liquid chromatography (LC) to supercritical fluid chromatography (SFC): Elution by Characteristic Points (ECP), the Retention Time Method (RTM), the Inverse Method (IM) and the Perturbation Peak (PP) method. In order to transfer these methods to SFC in a reliable, reproducible way we will demonstrate that careful system verification using external sensors of mass flow, temperature and pressure are needed first. The adsorption isotherm data generated by the different methods were analyzed and compared and the adsorption isotherms ability to predict new experimental elution profiles was verified by comparing experiments with simulations. It was found that adsorption isotherm data determined based on elution profiles, i.e., ECP, IM and RTM, were able to accurately predict overloaded experimental elution profiles while the more tedious and time-consuming PP method, based on small injections on concentration plateaus, failed in doing so.

  6. 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.

  7. Adsorption of leather dye onto activated carbon prepared from bottle gourd: equilibrium, kinetic and mechanism studies.

    PubMed

    Foletto, Edson Luiz; Weber, Caroline Trevisan; Paz, Diego Silva; Mazutti, Marcio Antonio; Meili, Lucas; Bassaco, Mariana Moro; Collazzo, Gabriela Carvalho

    2013-01-01

    Activated carbon prepared from bottle gourd has been used as adsorbent for removal of leather dye (Direct Black 38) from aqueous solution. The activated carbon obtained showed a mesoporous texture, with surface area of 556.16 m(2) g(-1), and a surface free of organic functional groups. The initial dye concentration, contact time and pH significantly influenced the adsorption capacity. In the acid region (pH 2.5) the adsorption of dye was more favorable. The adsorption equilibrium was attained after 60 min. Equilibrium data were analyzed by the Langmuir, Freundlich, Dubinin-Radushkevich and Temkin isotherm models. The equilibrium data were best described by the Langmuir isotherm, with maximum adsorption capacity of 94.9 mg g(-1). Adsorption kinetic data were fitted using the pseudo-first-order, pseudo-second-order, Elovich and intraparticle diffusion models. The adsorption kinetic was best described by the second-order kinetic equation. The adsorption process was controlled by both external mass transfer and intraparticle diffusion. Activated carbon prepared from bottle gourd was shown to be a promising material for adsorption of Direct Black 38 from aqueous solution.

  8. 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.

  9. 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.

  10. Equilibrium and kinetic adsorption study of a cationic dye by a natural adsorbent--silkworm pupa.

    PubMed

    Noroozi, B; Sorial, G A; Bahrami, H; Arami, M

    2007-01-02

    In this work the use of silkworm pupa, which is the waste of silk spinning industries has been investigated as an adsorbent for the removal of C.I. Basic Blue 41. The amino acid nature of the pupa provided a reasonable capability for dye removal. Equilibrium adsorption isotherms and kinetics were investigated. The adsorption equilibrium data were analyzed by using various adsorption isotherm models and the results have shown that adsorption behavior of the dye could be described reasonably well by either Langmuir or Freundlich models. The characteristic parameters for each isotherm have been determined. The monolayer adsorption capacity was determined to be 555 mg/g. Kinetic studies indicated that the adsorption follows pseudo-second-order kinetics with a rate constant of 0.0434 and 0.0572 g/min mg for initial dye concentration of 200 mg/l at 20 and 40 degrees C, respectively. Kinetic studies showed that film diffusion and intra-particle diffusion were simultaneously operating during the adsorption process. The rate constant for intra-particle diffusion was estimated to be 1.985 mg/g min(0.5).

  11. A comparative study of the adsorption equilibrium of progesterone by a carbon black and a commercial activated carbon

    NASA Astrophysics Data System (ADS)

    Valenzuela-Calahorro, Cristóbal; Navarrete-Guijosa, Antonio; Stitou, Mostafa; Cuerda-Correa, Eduardo M.

    2007-04-01

    In this paper the adsorption process of a natural steroid hormone (progesterone) by a carbon black and a commercial activated carbon has been studied. The corresponding equilibrium isotherms have been analyzed according to a previously proposed model which establishes a kinetic law satisfactorily fitting the C versus t isotherms. The analysis of the experimental data points out the existence of two well-defined sections in the equilibrium isotherms. A general equation including these two processes has been proposed, the global adsorption process being fitted to such equation. From the values of the kinetic equilibrium constant so obtained, values of standard average adsorption enthalpy ( ΔH°) and entropy ( ΔS°) have been calculated. Finally, information related to variations of differential adsorption enthalpy ( ΔH) and entropy ( ΔS) with the surface coverage fraction ( θ) was obtained by using the corresponding Clausius-Clapeyron equations.

  12. Competitive ion-exchange adsorption of proteins: competitive isotherms with controlled competitor concentration.

    PubMed

    Cano, Tony; Offringa, Natalie D; Willson, Richard C

    2005-06-24

    The competitive adsorption processes inevitably present in chromatographic separations of complex mixtures have not been extensively studied. This is partly due to the difficulty of measuring true competitive isotherms, in which all system parameters (including competitor concentrations) are held constant. We report a novel approach to determining competitive protein adsorption isotherms in which the competitor concentration is held constant across the entire isotherm. By using the heme prosthetic group in cytochrome b5 as a quantitative spectrophotometric label, competitive isotherms between cytochrome b5 and alpha-lactalbumin can be constructed. Similarly, manganese-substituted protoporphyrin IX heme replacement allows the non-perturbing labeling of individual cytochrome b5 conservative surface charge mutants by replacement of a single atom in the interior of the protein. This labeling allows the study of competition between cytochrome b5 charge mutants of identical size and shape, which differ only in charge arrangement. Using these techniques, the effect of competing species on equilibrium behavior and the apparent heterogeneity of anion-exchange adsorbents in the presence of competitors can be quantitatively studied by fitting the data to two popular single-component binding models, the Temkin and the Langmuir-Freundlich (L-F) isotherms.

  13. Adsorptive removal of chlorophenols from aqueous solution by low cost adsorbent--Kinetics and isotherm analysis.

    PubMed

    Radhika, M; Palanivelu, K

    2006-11-02

    Adsorptive removal of parachlorophenol (PCP) and 2,4,6-trichlorophenol (TCP) from aqueous solutions by activated carbon prepared from coconut shell was studied and compared with activated carbon of commercial grade (CAC). Various chemical agents in different concentrations were used (KOH, NaOH, CaCO(3), H(3)PO(4) and ZnCl(2)) for the preparation of coconut shell activated carbon. The coconut shell activated carbon (CSAC) prepared using KOH as chemical agent showed high surface area and best adsorption capacity and was chosen for further studies. Batch adsorption studies were conducted to evaluate the effect of various parameters such as pH, adsorbent dose, contact time and initial PCP and TCP concentration. Adsorption equilibrium reached earlier for CSAC than CAC for both PCP and TCP concentrations. Under optimized conditions the prepared activated carbon showed 99.9% and 99.8% removal efficiency for PCP and TCP, respectively, where as the commercially activated carbon had 97.7% and 95.5% removal for PCP and TCP, respectively, for a solution concentration of 50mg/L. Adsorption followed pseudo-second-order kinetics. The equilibrium adsorption data were analysed by Langmuir, Freundlich, Redlich-Peterson and Sips model using non-linear regression technique. Freundlich isotherms best fitted the data for adsorption equilibrium for both the compounds (PCP and TCP). Similarly, acidic pH was favorable for the adsorption of both PCP and TCP. Studies on pH effect and desorption revealed that chemisorption was involved in the adsorption process. The efficiency of the activated carbon prepared was also tested with real pulp and paper mill effluent. The removal efficiency using both the carbons were found highly satisfactory and was about 98.7% and 96.9% as phenol removal and 97.9% and 93.5% as AOX using CSAC and CAC, respectively.

  14. Adsorption of dyes using peat: equilibrium and kinetic studies.

    PubMed

    Sepúlveda, L; Fernández, K; Contreras, E; Palma, C

    2004-09-01

    In recent years, adsorption has been accepted as one of the most appropriate processes for decolorization of wastewaters. This paper presents experimental results on application of peat for removal of structurally diverse dyes (azo, oxazine, triphenylmethane, thiazine and others) with emphasis on relevant factors such as the adsorbate-adsorbent chemical properties and chemical interaction as well as adsorption conditions. The equilibrium experimental results were fitted to Langmuir and Freundlich isotherms to obtain the characteristic parameters of each model. According to the evaluation using the Langmuir equation, the maximum sorption capacity of basic dyes at 22 degrees C was 667 (mg g(-1)) for Basic Blue 24, 526 (mg g(-1)) for Basic Green 4 and 714 (mg g(-1)) for Basic Violet 4. On the other hand for Acid Black 1 it was only 25 (mg g(-1)). Batch kinetics studies were undertaken and the data evaluated in compliance with chemical sorption mechanisms. For all of the systems studied the pseudo-second order model provided the best correlation of the kinetic experimental data. A film-pore double resistance diffusion model for mass transfer has also been used in this study to determine the effective diffusivity, Deff, for the adsorption of basic dyes in to peat.

  15. Equilibrium isotherms of methane onto activated carbons using a static volumetric method.

    PubMed

    Kavitha, T; Kaliappan, S

    2009-07-01

    The aim of this research is to develop a technology for the storage of biogas. The present work pertains to the measurement of the adsorption capacity of methane onto activated carbons at room temperature at pressure range varying from 1 atm to 10 atm. The results were obtained with a static volumetric method. Adsorption isotherms for methane on Sorbonorit 4, Norit SX Plus, Sorbonorit B3, Norit PAC 200 XC were plotted. The equilibrium pressure data were analysed using Langmuir, Dubinin-Astakhov's (DA) and Dubinin-Radushkevich (DR) equations. The DA equation described the isotherm behavior better with the exponent n equals to 1.0 for Sorbonorit 4, Sorbonorit B3, Norit PAC 200 XC and 1.7 for Norit SX Plus than the other equations. The order of the adsorption capacity is as follows: Sorbonorit 4 (4.6 mmol/g) > Norit PAC 200 XC (3.81 mmol/g) > Sorbonorit B3 (3.52 mmol/g) > Norit SX Plus (3.51 mmol/g).

  16. Lead removal from aqueous solution by natural and pretreated clinoptilolite: adsorption equilibrium and kinetics.

    PubMed

    Günay, Ahmet; Arslankaya, Ertan; Tosun, Ismail

    2007-07-19

    Adsorption of Pb(II) ions from aqueous solution onto clinoptilolite has been investigated to evaluate the effects of contact time, initial concentration and pretreatment of clinoptilolite on the removal of Pb(II). Experimental data obtained from batch equilibrium tests have been analyzed by four two-parameter (Freundlich, Langmuir, Temkin and Dubinin-Radushkevich), four three-parameter (Redlich-Peterson, Sips, Toth and Khan) isotherm models, and kinetic models including the pseudo-first order, the pseudo-second order and Elovich equations using nonlinear regression technique. Of the two-parameter isotherms, Temkin isotherm was the best to describe the experimental data. Three-parameter isotherms have higher regression coefficients (>0.99) and lower relative errors (<5%) than two-parameter isotherms. The best fitting isotherm was the Sips followed by Toth and Redlich-Peterson isotherm equations. Maximum experimental adsorption capacity was found to be 80.933 and 122.400 mg/g for raw and pretreated clinoptilolite, respectively, for the initial concentration of 400 mg/L. Kinetic parameters; rate constants, equilibrium adsorption capacities and related coefficients for each kinetic model were evaluated according to relative errors and correlation coefficients. Results of the kinetic studies show that best fitted kinetic models are obtained to be in the order: the pseudo-first order, the pseudo-second order and Elovich equations. Using the thermodynamic equilibrium coefficients, Gibbs free energy of the Pb(II)-clinoptilolite system was evaluated. The negative value of change in Gibbs free energy (DeltaG degrees ) indicates that adsorption of Pb(II) on clinoptilolite is spontaneous.

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

    PubMed

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

    2013-10-01

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

  18. Adsorption of water vapor by poly(styrenesulfonic acid), sodium salt: isothermal and isobaric adsorption equilibria.

    PubMed

    Toribio, F; Bellat, J P; Nguyen, P H; Dupont, M

    2004-12-15

    Air conditioning and dehumidifying systems based on sorption on solids are of great interest, especially in humid climates, because they allow reduction of thermal loads and use of chlorofluorocarbons. Previous studies have shown that hydrophilic polymers such as sulfonic polymers can have very high performance in water adsorption from air. The aim of this study was to characterize the water vapor adsorption properties of fully sulfonated and monosulfonated poly(styrenesulfonic acid), sodium salt, and to elucidate the mechanism of adsorption on these materials. Adsorption isotherms have been determined by TGA between 298 and 317 K for pressures ranging from 0.1 to 45 hPa. They have type II of the IUPAC classification and a small hysteresis loop between adsorption and desorption processes was observed only for the monosulfonated sample. Water content is up to 80% weight at 80% relative humidity. Adsorption isotherms have been well fitted with the FHH model. Adsorption-desorption isobars have been determined by TGA under 37 hPa in the temperature range 298-373 K. They show that these polymers can be completely regenerated by heating at 313 K under humidified air. No degradation of the adsorption properties has been observed after several regenerations. Adsorption enthalpies and entropies have been deduced from the Clapeyron equation and from DSC measurements. A good agreement was found. A mechanism of adsorption is proposed considering two kinds of adsorbate: bounded water in electrostatic interaction with functional groups and free water resulting from condensation.

  19. Development of adsorbent from Teflon waste by radiation induced grafting: equilibrium and kinetic adsorption of dyes.

    PubMed

    Goel, N K; Kumar, Virendra; Pahan, S; Bhardwaj, Y K; Sabharwal, S

    2011-10-15

    Mutual radiation grafting technique was employed to graft polyacrylic acid (PAA) onto Polytetrafluoroethylene (Teflon) scrap using high energy gamma radiation. Polyacrylic acid-g-Teflon (PAA-g-Teflon) adsorbent was characterized by grafting extent measurement, FTIR spectroscopy, SEM and wet ability & surface energy analysis. The PAA-g-Teflon adsorbent was studied for dye adsorption from aqueous solution of basic dyes, namely, Basic red 29 (BR29) and Basic yellow 11 (BY11). The equilibrium adsorption data were analyzed by Langmuir and Freundlich adsorption isotherm models, whereas, adsorption kinetics was analyzed using pseudo-first order, pseudo-second order and intra-particle diffusion kinetic models. Equilibrium adsorption of BR29 was better explained by Langmuir adsorption model, while that of BY11 by Freundlich adsorption model. The adsorption capacity for BY11 was more than for BR29. Separation factor (R(L)) was found to be in the range 0 < R(L) < 1, indicating favorable adsorption of dyes. Higher coefficient of determination (r(2) > 0.99) and better agreement between the q(e,cal) and q(e,exp) values suggested that pseudo-second order kinetic model better represents the kinetic adsorption data. The non-linearity obtained for intra-particle diffusion plot indicated, more than one process is involved in the adsorption of basic dyes. The desorption studies showed that ~95% of the adsorbed dye could be eluted in suitable eluent.

  20. 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.

  1. Numerical estimation of adsorption energy distributions from adsorption isotherm data with the expectation-maximization method

    SciTech Connect

    Stanley, B.J.; Guiochon, G. |

    1993-08-01

    The expectation-maximization (EM) method of parameter estimation is used to calculate adsorption energy distributions of molecular probes from their adsorption isotherms. EM does not require prior knowledge of the distribution function or the isotherm, requires no smoothing of the isotherm data, and converges with high stability towards the maximum-likelihood estimate. The method is therefore robust and accurate at high iteration numbers. The EM algorithm is tested with simulated energy distributions corresponding to unimodal Gaussian, bimodal Gaussian, Poisson distributions, and the distributions resulting from Misra isotherms. Theoretical isotherms are generated from these distributions using the Langmuir model, and then chromatographic band profiles are computed using the ideal model of chromatography. Noise is then introduced in the theoretical band profiles comparable to those observed experimentally. The isotherm is then calculated using the elution-by-characteristic points method. The energy distribution given by the EM method is compared to the original one. Results are contrasted to those obtained with the House and Jaycock algorithm HILDA, and shown to be superior in terms of robustness, accuracy, and information theory. The effect of undersampling of the high-pressure/low-energy region of the adsorption is reported and discussed for the EM algorithm, as well as the effect of signal-to-noise ratio on the degree of heterogeneity that may be estimated experimentally.

  2. 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.

  3. 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

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

    PubMed

    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.

  5. Adsorption of cellulase Aspergillus niger on a commercial activated carbon: kinetics and equilibrium studies.

    PubMed

    Daoud, Fatima Boukraa-Oulad; Kaddour, Samia; Sadoun, Tahar

    2010-01-01

    The adsorption kinetics of cellulase Aspergillus niger on a commercial activated carbon has been performed using a batch-adsorption technique. The effect of various experimental parameters such as initial enzyme concentration, 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 and the rate constants were evaluated. The Langmuir and Freundlich adsorption isotherm models were applied to describe the equilibrium isotherms, and the isotherm constants were determined. It was found that Langmuir model was more suitable for our data. The activation energy of adsorption was also evaluated for the adsorption of enzyme onto activated carbon. It was found 11.37 kJ mol(-1). Thermodynamic parameters Delta G(0), Delta H(0) and DeltaS(0) were calculated, indicating that this process can be spontaneous and endothermic. The adsorption enthalpy and entropy were found 11.12 kJ mol(-1) and 0.084 kJ mol(-1)K(-1), respectively. At 30 degrees C and at pH 4.8, 1g activated carbon adsorbed about 1565 mg of cellulase, with a retention of 70% of the native enzyme activity up to five cycles of repeated batch enzyme reactions.

  6. Reliable prediction of adsorption isotherms via genetic algorithm molecular simulation.

    PubMed

    LoftiKatooli, L; Shahsavand, A

    2017-01-01

    Conventional molecular simulation techniques such as grand canonical Monte Carlo (GCMC) strictly rely on purely random search inside the simulation box for predicting the adsorption isotherms. This blind search is usually extremely time demanding for providing a faithful approximation of the real isotherm and in some cases may lead to non-optimal solutions. A novel approach is presented in this article which does not use any of the classical steps of the standard GCMC method, such as displacement, insertation, and removal. The new approach is based on the well-known genetic algorithm to find the optimal configuration for adsorption of any adsorbate on a structured adsorbent under prevailing pressure and temperature. The proposed approach considers the molecular simulation problem as a global optimization challenge. A detailed flow chart of our so-called genetic algorithm molecular simulation (GAMS) method is presented, which is entirely different from traditions molecular simulation approaches. Three real case studies (for adsorption of CO2 and H2 over various zeolites) are borrowed from literature to clearly illustrate the superior performances of the proposed method over the standard GCMC technique. For the present method, the average absolute values of percentage errors are around 11% (RHO-H2), 5% (CHA-CO2), and 16% (BEA-CO2), while they were about 70%, 15%, and 40% for the standard GCMC technique, respectively.

  7. Adsorptive removal of acrylonitrile by commercial grade activated carbon: kinetics, equilibrium and thermodynamics.

    PubMed

    Kumar, Arvind; Prasad, B; Mishra, I M

    2008-04-01

    The potential of activated carbons--powdered (PAC) and granular (GAC), for the adsorption of acrylonitrile (AN) at different initial AN concentrations (50adsorption was studied. The Langmuir, Freundlich, Tempkin, and Redlich-Peterson (R-P) isotherm equations were used to test their fit with the experimental data, and the model parameters were determined for different temperatures. The Langmuir and R-P models were found to be the best to describe the equilibrium isotherm data of AN adsorption on PAC and GAC, respectively. Error analysis also confirmed the efficacy of the R-P isotherm to best fit the experimental data. The pseudo-second order kinetic model best represents the kinetics of the adsorption of AN onto PAC and GAC. Maximum adsorption capacity of PAC and GAC at optimum conditions of AN removal (adsorbent dose approximately 20 g/l of solution, and equilibrium time approximately 5 h) was found to be 51.72 and 46.63 mg/g, respectively.

  8. 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.

  9. Binary adsorption equilibrium of carbon dioxide and water vapor on activated alumina.

    PubMed

    Li, Gang; Xiao, Penny; Webley, Paul

    2009-09-15

    Adsorption equilibria of a CO2/H2O binary mixture on activated alumina F-200 were measured at several temperatures and over a wide range of concentrations from 4% to around 90% of the saturated water vapor pressure. In comparison with the single-component data, the loading of CO2 was not reduced in the presence of H2O, whereas at low relative humidity the adsorption of H2O was depressed. The binary system was described by a competitive/cooperative adsorption model where the readily adsorbed water layers acted as secondary sites for further CO2 adsorption via hydrogen bonding or hydration reaction. The combination of kinetic models, namely, a Langmuir isotherm for characterizing pure CO2 adsorption and a BET isotherm for H2O, was extended to derive a binary adsorption equilibrium model for the CO2/H2O mixture. Models based on the ideal adsorbed solution theory of Myers and Prausnitz failed to characterize the data over the whole composition range, and a large deviation of binary CO2/H2O equilibrium from ideal solution behavior was observed. The extended Langmuir-BET (LBET) isotherm, analogous to the extended Langmuir equation, drastically underestimated the CO2 loading. By incorporating the interactions between CO2 and H2O molecules on the adsorbent surface and taking into account the effect of nonideality, the realistic interactive LBET (R-LBET) model was found to be in very good agreement with the experimental data. The derived binary isosteric heat of adsorption showed that the heat was reduced by competitive adsorption but promoted by cooperative adsorption.

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

    PubMed

    Vilvanathan, Sowmya; Shanthakumar, S

    2016-10-02

    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.

  11. 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.

  12. Adsorption of humic acid from aqueous solutions on crosslinked chitosan-epichlorohydrin beads: kinetics and isotherm studies.

    PubMed

    Wan Ngah, W S; Hanafiah, M A K M; Yong, S S

    2008-08-01

    The adsorption of humic acid on crosslinked chitosan-epichlorohydrin (chitosan-ECH) beads was investigated. Chitosan-ECH beads were characterized by Fourier transform infrared spectroscopy (FTIR), surface area and pore size analyses, and scanning electron microscopy (SEM). Batch adsorption experiments were carried out and optimum humic acid adsorption on chitosan-ECH beads occurred at pH 6.0, agitation rate of 300 rpm and contact time of 50 min. Adsorption equilibrium isotherms were analyzed by Langmuir and Freundlich models. Freundlich model was found to show the best fit for experimental data while the maximum adsorption capacity determined from Langmuir model was 44.84 mg g(-1). The adsorption of humic acid on chitosan-ECH beads was best described with pseudo-first-order kinetic model. For desorption study, more than 60% of humic acid could be desorbed from the adsorbent using 1.0M HCl for 180 min.

  13. 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.

  14. Equilibrium and heat of adsorption for organic vapors and activated carbons

    SciTech Connect

    David Ramirez; Shaoying Qi; Mark J. Rood; K. James Hay

    2005-08-01

    Determination of the adsorption properties of novel activated carbons is important to develop new air quality control technologies that can solve air quality problems in a more environmentally sustainable manner. Equilibrium adsorption capacities and heats of adsorption are important parameters for process analysis and design. Experimental adsorption isotherms were thus obtained for relevant organic vapors with activated carbon fiber cloth (ACFC) and coal-derived activated carbon adsorbents (CDAC). The Dubinin-Astakhov (DA) equation was used to describe the adsorption isotherms. The DA parameters were analytically and experimentally shown to be temperature independent. The resulting DA equations were used with the Clausius-Clapeyron equation to analytically determine the isosteric heat of adsorption ({Delta}H{sub s}) of the adsorbate-adsorbent systems studied here. ACFC showed higher adsorption capacities for organic vapors than CDAC. {Delta}H{sub s} values for the adsorbates were independent of the temperature for the conditions evaluated. {Delta}H{sub s} values for acetone and benzene obtained in this study are comparable with values reported in the literature. This is the first time that {Delta}H{sub s} values for organic vapors and these adsorbents are evaluated with an expression based on the Polanyi adsorption potential and the Clausius-Clapeyron equation. 28 refs., 5 figs., 5 tabs., 3 appends.

  15. Equilibrium and dynamic study on hexavalent chromium adsorption onto activated carbon.

    PubMed

    Di Natale, F; Erto, A; Lancia, A; Musmarra, D

    2015-01-08

    In this work, the results of equilibrium and dynamic adsorption tests of hexavalent chromium, Cr (VI), on activated carbon are presented. Adsorption isotherms were determined at different levels of pH and temperature. Dynamic tests were carried out in terms of breakthrough curves of lab-scale fixed bed column at different pH, inlet concentration and flow rate. Both the adsorption isotherms and the breakthrough curves showed non-linear and unconventional trends. The experimental results revealed that chromium speciation played a key role in the adsorption process, also for the occurrence of Cr(VI)-to-Cr(III) reduction reactions. Equilibrium tests were interpreted in light of a multi-component Langmuir model supported by ion speciation analysis. For the interpretation of the adsorption dynamic tests, a mass transfer model was proposed. Dynamic tests at pH 11 were well described considering the external mass transfer as the rate controlling step. Differently, for dynamic tests at pH 6 the same model provided a satisfying description of the experimental breakthrough curves only until a sorbent coverage around 1.6mgg(-1). Above this level, a marked reduction of the breakthrough curve slope was observed in response to a transition to an inter-particle adsorption mechanism.

  16. Thermodynamic modeling of solute adsorption equilibrium from near-critical carbon dioxide.

    PubMed

    Yang, Xiaoning

    2004-05-15

    Modeling of adsorption equilibrium for supercritical fluid mixtures, with as few parameters as possible, is important in applications of the technology of supercritical fluid adsorption. In this paper, a correlative model has been developed to represent the adsorption equilibria of solutes from the near-critical CO(2) fluid. A two-dimensional van der Waals equation of state and the three-dimensional P - R equation of state were used to describe the adsorbed and bulk phases, respectively. This model contains five parameters for adsorption equilibrium isotherms at finite concentrations and two parameters for adsorption equilibrium constants at infinite dilution. All the parameters are independent of temperature and pressure. By applying the model to the experimental data from the literature, it was shown that this model is capable of describing the adsorption behavior of solutes from supercritical carbon dioxide over relatively wide temperature and pressure ranges. In addition, the adsorption behavior of supercritical fluid mixtures was investigated at finite and infinite dilution conditions.

  17. Adsorption kinetics and isotherms of arsenite and arsenate on hematite nanoparticles and aggregates.

    PubMed

    Dickson, Dionne; Liu, Guangliang; Cai, Yong

    2017-01-15

    Iron (Fe) nanoparticles, e.g., zerovalent iron (ZVI) and iron oxide nanoparticles (IONP), have been used for remediation and environmental management of arsenic (As) contamination. These Fe nanoparticles, although originally nanosized, tend to form aggregates, in particular in the environment. The interactions of As with both nanoparticles and micron-sized aggregates should be considered when these Fe nanomaterials are used for mitigation of As issue. The objective of this study was to compare the adsorption kinetics and isotherm of arsenite (As(III)) and arsenate (As(V)) on bare hematite nanoparticles and aggregates and how this affects the fate of arsenic in the environment. The adsorption kinetic process was investigated with regards to the aggregation of the nanoparticles and the type of sorbed species. Kinetic data were best described by a pseudo second-order model. Both As species had similar rate constants, ranging from 3.82 to 6.45 × 10(-4) g/(μg·h), as rapid adsorption occurred within the first 8 h regardless of particle size. However, hematite nanoparticles and aggregates showed a higher affinity to adsorb larger amounts of As(V) (4122 ± 62.79 μg/g) than As(III) (2899 ± 71.09 μg/g) at equilibrium. We were able to show that aggregation and sedimentation of hematite nanoparticles occurs during the adsorption process and this might cause the immobilization and reduced bioavailability of arsenic. Isotherm studies were described by the Freundlich model and it confirmed that hematite nanoparticles have a significantly higher adsorption capacity for both As(V) and As(III) than hematite aggregates. This information is useful and can assist in predicting arsenic adsorption behavior and assessing the role of iron oxide nanoparticles in the biogeochemical cycling of arsenic.

  18. Theoretical study of the accuracy of the pulse method, frontal analysis, and frontal analysis by characteristic points for the determination of single component adsorption isotherms

    SciTech Connect

    Kaczmarski, Krzysztof; Guiochon, Georges A

    2009-01-01

    The adsorption isotherms of selected compounds are our main source of information on the mechanisms of adsorption processes. Thus, the selection of the methods used to determine adsorption isotherm data and to evaluate the errors made is critical. Three chromatographic methods were evaluated, frontal analysis (FA), frontal analysis by characteristic point (FACP), and the pulse or perturbation method (PM), and their accuracies were compared. Using the equilibrium-dispersive (ED) model of chromatography, breakthrough curves of single components were generated corresponding to three different adsorption isotherm models: the Langmuir, the bi-Langmuir, and the Moreau isotherms. For each breakthrough curve, the best conventional procedures of each method (FA, FACP, PM) were used to calculate the corresponding data point, using typical values of the parameters of each isotherm model, for four different values of the column efficiency (N = 500, 1000, 2000, and 10,000). Then, the data points were fitted to each isotherm model and the corresponding isotherm parameters were compared to those of the initial isotherm model. When isotherm data are derived with a chromatographic method, they may suffer from two types of errors: (1) the errors made in deriving the experimental data points from the chromatographic records; (2) the errors made in selecting an incorrect isotherm model and fitting to it the experimental data. Both errors decrease significantly with increasing column efficiency with FA and FACP, but not with PM.

  19. Equilibrium, kinetic and thermodynamic study of cesium adsorption onto nanocrystalline mordenite from high-salt solution.

    PubMed

    Lee, Keun-Young; Park, Minsung; Kim, Jimin; Oh, Maengkyo; Lee, Eil-Hee; Kim, Kwang-Wook; Chung, Dong-Yong; Moon, Jei-Kwon

    2016-05-01

    In this study, the equilibrium, kinetics and thermodynamics of cesium adsorption by nanocrystalline mordenite were investigated under cesium contamination with high-salt solution, simulating the case of an operation and decommissioning of nuclear facilities or an accident during the processes. The adsorption rate constants were determined using a pseudo second-order kinetic model. The kinetic results strongly demonstrated that the cesium adsorption rate of nano mordenite is extremely fast, even in a high-salt solution, and much faster than that of micro mordenite. In the equilibrium study, the Langmuir isotherm model fit the cesium adsorption data of nano mordenite better than the Freundlich model, which suggests that cesium adsorption onto nano mordenite is a monolayer homogeneous adsorption process. The obtained thermodynamic parameters indicated that the adsorption involved a very stable chemical reaction. In particular, the combination of rapid particle dispersion and rapid cesium adsorption of the nano mordenite in the solution resulted in a rapid and effective process for cesium removal without stirring, which may offer great advantages for low energy consumption and simple operation.

  20. Kinetics and equilibrium adsorption study of lead(II) onto activated carbon prepared from coconut shell.

    PubMed

    Sekar, M; Sakthi, V; Rengaraj, S

    2004-11-15

    Removal of lead from aqueous solutions by adsorption onto coconut-shell carbon was investigated. Batch adsorption experiments were performed to find out the effective lead removal at different metal ion concentrations. Adsorption of Pb2+ ion was strongly affected by pH. The coconut-shell carbon (CSC) exhibited the highest lead adsorption capacity at pH 4.5. Isotherms for the adsorption of lead on CSC were developed and the equilibrium data fitted well to the Langmuir, Freundlich, and Tempkin isotherm models. At pH 4.5, the maximum lead adsorption capacity of CSC estimated with the Langmuir model was 26.50 mg g(-1) adsorbent. Energy of activation (Ea) and thermodynamic parameters such as DeltaG, DeltaH, and DeltaS were evaluated by applying the Arrhenius and van't Hoff equations. The thermodynamics of Pb(II) on CSC indicates the spontaneous and endothermic nature of adsorption. Quantitative desorption of Pb(II) from CSC was found to be 75% which facilitates the sorption of metal by ion exchange.

  1. 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

    2012-11-07

    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.

  2. Equilibrium and kinetic aspects of sodium cromoglycate adsorption on chitosan: mass uptake and surface charging considerations.

    PubMed

    de Lima, C R M; Pereira, M R; Fonseca, J L C

    2013-09-01

    Chitosan has more and more been suggested as a material for use as adsorbent in the treatment of effluents as well as in the synthesis of drug-loaded nanoparticles for controlled release. In both cases, a good understanding of the process of adsorption, both kinetically and in terms of equilibrium, has an importance of its own. In this manuscript we study the interaction between sodium cromoglycate, a drug used in asthma treatment, and chitosan. Equilibrium experiments showed that Sips (or Freundlich-Langmuir) isotherm described well the resultant data and adsorption possibly occurred as in multilayers. A model based on ordinary reaction-rate theory, compounded of two processes, each one with a correlated velocity constant, described the kinetics of sorption. Kinetic and equilibrium data suggested the possibility of surface rearrangement, favored by the increase of temperature.

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

    SciTech Connect

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

    1983-01-01

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

  4. Methylene blue adsorption onto swede rape straw (Brassica napus L.) modified by tartaric acid: equilibrium, kinetic and adsorption mechanisms.

    PubMed

    Feng, Yanfang; Zhou, Hui; Liu, Guohua; Qiao, Jun; Wang, Jinhua; Lu, Haiying; Yang, Linzhang; Wu, Yonghong

    2012-12-01

    The aim of this study was to develop a promising and competitive bioadsorbent with the abundant of source, low price and environmentally friendly characters to remove cationic dye from wastewater. The swede rape straw (Brassica napus L.) modified by tartaric acid (SRSTA) was prepared, characterized and used to remove methylene blue (MB) from aqueous solution at varied operational conditions (including MB initial concentrations, adsorbent dose, etc.). Results demonstrated that the equilibrium data was well fitted by Langmuir isotherm model. The maximum MB adsorption capacity of SRSTA was 246.4 mg g(-1), which was comparable to the results of some previous studied activated carbons. The higher dye adsorption capacity could be attributed to the presence of more functional groups such as carboxyl group on the surface of SRSTA. The adsorption mechanism was also discussed. The results indicate that SRSTA is a promising and valuable absorbent to remove methylene blue from wastewater.

  5. Adsorption laboratory experiment for undergraduate chemical engineering: Introducing kinetic, equilibrium and thermodynamic concepts

    NASA Astrophysics Data System (ADS)

    Muryanto, S.; Djatmiko Hadi, S.

    2016-11-01

    Adsorption laboratory experiment for undergraduate chemical engineering program is discussed. The experiment demonstrated adsorption of copper ions commonly found in wastewater using bio-sorbent, i.e. agricultural wastes. The adsorption was performed in a batch mode under various parameters: adsorption time (up to 120 min), initial pH (2 to 6), adsorbent dose (2.0 to 12.0 g L-1), adsorbent size (50 to 170 mesh), initial Cu2+ concentration (25 to 100 ppm) and temperatures (room temp to 40°C). The equilibrium and kinetic data of the experiments were calculated using the two commonly used isotherms: Langmuir and Lagergren pseudo-first-order kinetics. The maximum adsorption capacity for Cu2+ was found as 94.34 mg g-1. Thermodynamically, the adsorption process was spontaneous and endothermic. The calculated activation energy for the adsorption was observed as high as 127.94 kJ mol-1. Pedagogically, the experiment was assumed to be important in increasing student understanding of kinetic, equilibrium and thermodynamic concepts.

  6. Moisture Adsorption Isotherms and Thermodynamic Characteristics of Tannic Acid

    NASA Astrophysics Data System (ADS)

    Červenka, L.; Cacková, L.

    2016-09-01

    Moisture adsorption isotherms of tannic acid were determined at 5, 15, and 35°C with the use of the static gravimetric method in the range 0.113-0.980 aw (aw is the water activity). It was shown that tannic acid adsorbed more water at 5°C. The experimental data fitted well to the Guggenheim-Anderson-de Boer and Yanniotis-Blahovec equations, giving the corresponding parameters by nonlinear regression. The monolayer moisture content, number of monolayers, and the surface area of sorption were demonstrated to decrease with increasing temperature. Mesopores dominated below the monolayer moisture content followed by the formation of macropores. The variation of the differential enthalpy and entropy with the moisture content showed that water was strongly bound to the surface of tannic acid below the moisture content 5.0 g water/100 g dry basis. The adsorption process was found to be enthalpy-driven; however, it was not spontaneous at a low moisture content, as follows from the enthalpy-entropy compensation theory. The variation of the net integral enthalpy and entropy (at a constant spreading pressure) with the moisture content exhibited maximum and minimum values, respectively. This behavior indicated that water molecules were strongly bound to the tannic acid surface at the moisture content up to its monolayer values.

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

    PubMed

    Kango, Sarita; Kumar, Rajesh

    2016-01-01

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

  8. Kinetics and equilibrium studies of malachite green adsorption on rice straw-derived char.

    PubMed

    Hameed, B H; El-Khaiary, M I

    2008-05-01

    In this work, the potential feasibility of rice straw-derived char (RSC) for removal of C.I. Basic Green 4 (malachite green (MG)), a cationic dye from aqueous solution was investigated. The isotherm parameters were estimated by non-linear regression analysis. The equilibrium process was described well by the Langmuir isotherm model. The maximum RSC sorption capacity was found to be 148.74 mg/L at 30 degrees C. The kinetics of MG sorption on RSC followed the Lagergren's pseudo-first-order model and the overall rate of dye uptake was found to be controlled by external mass transfer at the beginning of adsorption, while intraparticle diffusion controlled the overall rate of adsorption at a later stage. The results indicated that RSC was an attractive adsorbent for removing basic dye from aqueous solutions.

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

    PubMed

    Jeppu, Gautham P; Clement, T Prabhakar

    2012-03-15

    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.

  10. 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.

  11. 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.

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

    PubMed

    Ofomaja, Augustine E

    2010-07-01

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

  13. A new approach in regression analysis for modeling adsorption isotherms.

    PubMed

    Marković, Dana D; Lekić, Branislava M; Rajaković-Ognjanović, Vladana N; Onjia, Antonije E; Rajaković, Ljubinka V

    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.

  14. 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

  15. Application of water-activated carbon isotherm models to water adsorption isotherms of single-walled carbon nanotubes.

    PubMed

    Kim, Pyoungchung; Agnihotri, Sandeep

    2008-09-01

    The objective of this study is to understand the interactions of water with novel nanocarbons by implementing semiempirical models that were developed to interpret adsorption isotherms of water in common carbonaceous adsorbents. Water adsorption isotherms were gravimetrically determined on several single-walled carbon nanotube (SWNT) and activated carbon samples. Each isotherm was fitted to the Dubinin-Serpinsky (DS) equation, the Dubinin-Astakov equation, the cooperative multimolecular sorption theory, and the Do and Do equations. The applicability of these models was evaluated by high correlation coefficients and the significance of fitting parameters, especially those that delineate the concentration of hydrophilic functional groups, micropore volume, and the size of water clusters. Samples were also characterized by spectroscopic and adsorption techniques, and properties complementary to those quantified by the fitting parameters were extracted from the data collected. The comparison of fitting parameters with sample characterization results was used as the methodology for selecting the most informative and the best-fitting model. We conclude that the Do equation, as modified by Marban et al., is the most suitable semiempirical equation for predicting from experimental isotherms alone the size of molecular clusters that facilitate adsorption in SWNTs, deconvoluting the experimental isotherms into two subisotherms: adsorption onto hydrophilic groups and filling of micropores, and quantifying the concentration of hydrophilic functional groups, as well as determining the micropore volume explored by water. With the exception of the DS equation, the application of other water isotherm models to SWNTs is not computationally tractable. The findings from this research should aid studies of water adsorption in SWNTs by molecular simulation, which remains the most popular tool for understanding the microscopic behavior of water in nanocarbons.

  16. Adsorption and abiotic oxidation of arsenic by aged biofilter media: equilibrium and kinetics.

    PubMed

    Sahabi, Danladi Mahuta; Takeda, Minoru; Suzuki, Ichiro; Koizumi, Jun-ichi

    2009-09-15

    Removal of arsenic from groundwater by biological adsorptive filtration depends largely on its interaction with biogenic iron and manganese oxides surfaces. In the present study we investigated the arsenic adsorption and abiotic oxidation capacities of an aged biofilter medium (BM2) collected from a long time established groundwater treatment plant for removal of iron and manganese by biological filtration. Batch oxidation/adsorption kinetic experiments indicated that BM2 can easily oxidize As(III) to As(V) with the rate of oxidation less affected by pH-variations from 4 to 8.5. The adsorption capacity of the biofilter medium for the produced or added As(V), however, depends strongly on the pH of the solution. The kinetics results have shown that As(III) sorption followed pseudo-second order kinetics, whereas the sorption of As(V) was best described by the intra-particle diffusion model, indicating that adsorptions of As(III) and As(V) onto BM2 were governed by different mechanisms. Adsorption isotherms at 25 degrees C were measured for a range of arsenite and arsenate initial concentrations of 0.67-20 micromol/L and the pH range from 4 to 9. Adsorption maxima were highest at pH 4 and decrease steadily as the pH increases. The equilibrium data for both As(III) and As(V) fitted very well to the Freundlich and Sips isotherm equations and, in most cases, the two isotherms overlapped with the same correlation coefficients, indicating sorption to be multilayer on the heterogeneous surface of BM2. The implication of the data for arsenic removal from water by biological filtration has been discussed.

  17. 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

  18. Prediction of the competitive adsorption isotherms of 2-phenylethanol and 3-phenylpropanol by artificial neural networks.

    PubMed

    Wu, Xiuhong; Wang, Shaoyan; Zhang, Renzhuang; Gao, Zhiming

    2014-03-07

    Artificial neural networks (ANNs) were regarded as data-mapping networks with strong nonlinear fitting abilities. A 2-6-2 network was used to determine the competitive adsorption isotherm of 2-phenylethanol (PE) and 3-phenylpropanol (PP). The ANN results were forms of data mapping rather than theoretical mathematical model. The ANN architecture was established after training with a set of experimental data. The established ANN was applied to predict the adsorption isotherms of PE and PP. The selection of parameters for the ANN was discussed. The results indicate that ANN has excellent potential for use in non-linear chromatography for the prediction of adsorption isotherms.

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

    PubMed

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

    2009-04-09

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

  20. 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

  1. 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.

  2. Equilibrium CO2 adsorption on zeolite 13X prepared from natural clays

    NASA Astrophysics Data System (ADS)

    Garshasbi, Vahid; Jahangiri, Mansour; Anbia, Mansoor

    2017-01-01

    Zeolite 13X was successfully synthesized by hydrothermal treatment using natural clays extracted from Iranian resources. The preliminary natural materials and the final zeolite 13X samples were characterized by X-ray Diffraction (XRD), Fourier-Transfer Infrared (FTIR) spectroscopy, Scanning Electron Microscopy (SEM) and N2 adsorption-desorption isotherm. The effects of various factors such as NaOH addition amount and aging time on the crystalline products were studied during the synthesis process. The optimum conditions related to the synthesis of zeolite 13X were set. Accordingly, NaOH concentration was equal to 4 M. It was further crystallized at 65 °C for 72 h after its homogenization by agitation at room temperature for 120 h. In this study, the zeolite 13X prepared from natural kaolin (13X-K) showed a high BET surface area of 591 m2/g with higher micropore volume (0.250 cm3/g) than other materials. Adsorption equilibrium isotherms of CO2 were investigated using a static, volumetric method. In addition, pressures for the pure component data extended up to 20 bar. The adsorption equilibrium data of CO2 was fitted to Langmuir, Freundlich, Lamgmuir-Freundlich, Toth and BET isotherm models. It was found that the Langmuir-Freundlich model was more suitable than other models for CO2 description. The results showed that the synthetic zeolite has higher equilibrium selectivity for CO2. Also, the CO2 uptake by zeolite 13X-K was equal to 6.9 mmol/g.

  3. Adsorption kinetic and equilibrium study for removal of mercuric chloride by CuCl2-impregnated activated carbon sorbent.

    PubMed

    Li, Xin; Liu, Zhouyang; Lee, Joo-Youp

    2013-05-15

    The intrinsic adsorption kinetics of mercuric chloride (HgCl2) was studied for raw, 4% and 10% CuCl2-impregnated activated carbon (CuCl2-AC) sorbents in a fixed-bed system. An HgCl2 adsorption kinetic model was developed for the AC sorbents by taking into account the adsorption kinetics, equilibrium, and internal and external mass transfer. The adsorption kinetic constants determined from the comparisons between the simulation and experimental results were 0.2, 0.3, and 0.5m(3)/(gs) for DARCO-HG, 4%(wt), and 10%(wt) CuCl2-AC sorbents, respectively, at 140 °C. CuCl2 loading was found to slightly increase the adsorption kinetic constant or at least not to decrease it. The HgCl2 equilibrium adsorption data based on the Langmuir isotherm show that high CuCl2 loading can result in high binding energy of the HgCl2 adsorption onto the carbon surface. The adsorption equilibrium constant was found to increase by ~10 times when CuCl2 loading varied from 0 to 10%(wt), which led to a decrease in the desorption kinetic constant (k2) by ~10 times and subsequently the desorption rate by ~50 times. Intraparticle pore diffusion considered in the model showed good accuracy, allowing for the determination of intrinsic HgCl2 adsorption kinetics.

  4. Expanding the elution by characteristic point method for determination of various types of adsorption isotherms.

    PubMed

    Samuelsson, Jörgen; Undin, Torgny; Fornstedt, Torgny

    2011-06-17

    Important improvements have recently been made on the elution by characteristic point (ECP) method to increase the accuracy of the determined adsorption isotherms. However, the method has so far been limited/used for only type I adsorption isotherms (e.g. Langmuir, Tóth, bi-Langmuir). In this study, general strategies are developed to expand the ECP method for the determination of more complex adsorption isotherms including such containing inflection points. We will exemplify the methodology with type II, type III and type V isotherms. Guidelines are given for how to determine such isotherms using the ECP method and for the experimental considerations that must be taken into account or that may be eliminated in the particular case.

  5. 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

  6. Equilibrium and kinetic studies of adsorption of phosphate onto ZnCl2 activated coir pith carbon.

    PubMed

    Namasivayam, C; Sangeetha, D

    2004-12-15

    Phosphate removal from aqueous solution was investigated using ZnCl(2)-activated carbon developed from coir pith, an agricultural solid waste. Studies were conducted to delineate the effect of contact time, adsorbent dose, phosphate concentration, pH, and temperature. The adsorption equilibrium data followed both Langmuir and Freundlich isotherms. Langmuir adsorption capacity was found to be 5.1 mg/g. Adsorption followed second-order kinetics. The removal was maximum in the pH range 3-10. pH effect and desorption studies showed that adsorption occurred by both ion exchange and chemisorption mechanisms. Adsorption was found to be spontaneous and endothermic. Effect of foreign ions on adsorption shows that perchlorate, sulfate, and selenite decreased the percent removal of phosphate.

  7. 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.

  8. Freundlich and Langmuir adsorption isotherms and kinetics for the removal of Tartrazine from aqueous solutions using hen feathers.

    PubMed

    Mittal, Alok; Kurup, Lisha; Mittal, Jyoti

    2007-07-19

    Tartrazine, a yellow menace, is widely being used in cosmetics, foodstuffs, medicines and textile. It is carcinogenic and also catalyzes allergic problems. In the present work the ability to remove Tartrazine from aqueous solutions has been studied using waste material-hen feathers, as adsorbent. Effects of pH, concentration of the dye, temperature and adsorbent dosage have been studied. Equilibrium isotherms for the adsorption of the dye were measured experimentally. Results were analyzed by the Freundlich and Langmuir equation at different temperatures and determined the characteristic parameters for each adsorption isotherm. The adsorption process has been found endothermic in nature and thermodynamic parameters, Gibb's free energy (DeltaG degrees), change in enthalpy (DeltaH degrees) and change in entropy (DeltaS degrees) have been calculated. The paper also includes results on the kinetic measurements of adsorption of the dye on hen feathers at different temperatures. By rate expression and treatment of data it has been established that the adsorption of Tartrazine over hen feathers follows a first-order kinetics and a film diffusion mechanism operates at all the temperatures.

  9. 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.

  10. 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)

  11. Equilibrium adsorption studies of some aromatic pollutants from dilute aqueous solutions on activated carbon at different temperatures

    SciTech Connect

    Khan, A.R.; Ataullah, R.; Al-Haddad, A.

    1997-10-01

    Aqueous solutions of phenol, p-chlorophenol, and p-nitrophenol have been used to determine the adsorption isotherm for single solute systems on activated carbon at different temperatures. The experimental program has been conducted to investigate the influence of concentration and temperature. All the reported equilibrium isotherm equations have been tried on present and published experimental data. A generalized isotherm equation which was proposed by Khan et al. and tested for bi-solute adsorption data has been modified for single-solute system. The temperature dependency has also been incorporated into a generalized equation. It has been noticed that the Radke and Prausnitz and generalized isotherm equations could represent the entire data with a minimum average percentage error. The influence of different adsorbents, sorbate concentrations, and pH of aqueous solutions has also been discussed in detail. The temperature dependency has been investigated using both the Dubinin-Astakov and the modified generalized equation. The generalized equation describes the experimental and published data adequately and provides a single value of differential molar heat of adsorption, {Delta}H{sub ads}, for a single solute adsorption system. The Dubinin-Astakov isotherm equation has shown an increasing trend of {Delta}H{sub ads} as the loading of adsorbent has increased.

  12. Adsorption of Cd(II) and Pb(II) by a novel EGTA-modified chitosan material: kinetics and isotherms.

    PubMed

    Zhao, Feiping; Repo, Eveliina; Yin, Dulin; Sillanpää, Mika E T

    2013-11-01

    In this study, a novel adsorbent was synthesized by functionalizing chitosan with ethylene glycol-bis(2-aminoethylether)-N,N,N',N'-tetraacetic acid (EGTA) ligands. The adsorption capability of EGTA-modified chitosan was investigated by the removal of Cd(II) and Pb(II) from aqueous solutions. The adsorption and regeneration studies were performed by batch techniques. The effects of pH, contact time, and initial metal concentration were studied. Metal uptake by EGTA-chitosan was 0.74 mmol g(-1) for Cd(II) and 0.50 mmol g(-1) for Pb(II). The adsorption mechanism, that the adsorbent formed octahedral chelate structures with bivalent metal ions, was proposed tentatively based on the experimental results of FTIR and the theoretically calculated data of point charges. The kinetics of Cd(II) and Pb(II) on EGTA-chitosan complied with the pseudo-second-order model and the adsorption rate was also influenced by intra-particle diffusion. BiLangmuir isotherm model was well fitted to the experimental data of one-component adsorption suggesting the surface heterogeneity of the novel adsorbent. The extended form of the BiLangmuir model was tested for the modeling of two-component adsorption equilibrium of Cd(II) and Pb(II) on EGTA-chitosan. In the two-component solution, both competitive adsorption and positive synergy of chelation between metal ions occurred and the novel adsorbent showed higher affinity toward Cd(II).

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

    SciTech Connect

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

    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.

  14. Equilibrium and kinetic modeling of adsorption of reactive dye on cross-linked chitosan beads.

    PubMed

    Chiou, Ming Shen; Li, Hsing Ya

    2002-07-22

    The adsorption of reactive dye (Reactive Red 189) from aqueous solutions on cross-linked chitosan beads was studied in a batch system. The equilibrium isotherms at different particle sizes (2.3-2.5, 2.5-2.7 and 3.5-3.8mm) and the kinetics of adsorption with respect to the initial dye concentration (4320, 5760 and 7286 g/m(3)), temperature (30, 40 and 50 degrees C), pH (1.0, 3.0, 6.0 and 9.0), and cross-linking ratio (cross-linking agent/chitosan weight ratio: 0.2, 0.5, 0.7 and 1.0) were investigated. Langmuir and Freundlich adsorption models were applied to describe the experimental isotherms and isotherm constants. Equilibrium data fitted very well to the Langmuir model in the entire saturation concentration range (0-1800 g/m(3)). The maximum monolayer adsorption capacities obtained from the Langmuir model are very large, which are 1936, 1686 and 1642 g/kg for small, mediumand large particle sizes, respectively, at pH 3.0, 30 degrees C, and the cross-linking ratio of 0.2. The pseudo first- and second-order kinetic models were used to describe the kinetic data, and the rate constants were evaluated. The experimental data fitted well to the second-order kinetic model, which indicates that the chemical sorption is the rate-limiting step, instead of mass transfer. The initial dye concentration and the solution pH both significantly affect the adsorption capacity, but the temperature and the cross-linking ratio are relatively minor factors. An increase in initial dye concentration results in the increase of adsorption capacity, which also increases with decreasing pH. The activation energy is 43.0 kJ/mol for the adsorption of the dye on the cross-linked chitosan beads at pH 3.0 and initial dye concentration 3768 g/m(3).

  15. 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.

  16. Adsorption of crystal violet onto functionalised multi-walled carbon nanotubes: Equilibrium and kinetic studies.

    PubMed

    Sabna, V; Thampi, Santosh G; Chandrakaran, S

    2016-12-01

    Synthetic dyes present in effluent from textile, paper and paint industries contain crystal violet (CV), a known carcinogenic agent. This study investigates the modification of multiwalled carbon nanotubes by acid reflux method and equilibrium and kinetic behaviour of adsorption of CV onto functionalized multi-walled carbon nanotubes (fMWNTs) in batch system. High stability of the fMWNTs suspension in water indicates the hydrophilicity of fMWNTs induced due to the formation of functional groups that make hydrogen bonds with water molecules. fMWNTs were characterized by Fourier Transform Infra Red (FTIR) spectroscopy and the functional groups present on the fMWNTs were confirmed. Characteristic variation was observed in the FTIR spectra of fMWNTs after adsorption of crystal violet onto it. Adsorption characteristics were evaluated as a function of system variables such as contact time, dosage of fMWNTs and initial concentration and pH of the crystal violet solution. Adsorption capacity of fMWNTs and percentage removal of the dye increased with increase in contact time, adsorbent dosage and pH but declined with increase in initial concentration of the dye. fMWNTs showed higher adsorption capacity compared to that of pristine MWNTs. Data showed good fit with the Langmuir and Freundlich isotherm models and the pseudo-second order kinetic model; the maximum adsorption capacity was 90.52mg/g. Kinetic parameters such as rate constants, equilibrium adsorption capacities and regression coefficients were estimated. Results indicate that fMWNTs are an effective adsorbent for the removal of crystal violet from aqueous solution.

  17. 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.

  18. Adsorption equilibrium, kinetics and thermodynamics of dichloroacetic acid from aqueous solution using mesoporous carbon.

    PubMed

    Ding, Ying; Zhu, Jianzhong; Cao, Yang; Chen, Shenglu

    2014-08-01

    The presence of disinfection by-products, such as trihalomethanes and haloacetic acids in water, is believed to be harmful to human health. In this work, mesoporous carbon was synthesized with the evaporation-induced self-assembly method and employed to evaluate the effects of initial concentration, contact time, pH and temperature on the removal of dichloroacetic acid in batch experiments. Adsorption equilibrium was established in 480 min and the maximum adsorption (350mg/g) of dichloroacetic acid on the mesoporous carbon was observed to occur at 308 K and pH 3.0. Freundlich and Langmuir isotherms were used to analyse the equilibrium data at different temperatures; kinetic data were fitted to the pseudo-first-order and pseudo-second-order models and found that the adsorption capacity, mass transfer coefficient and diffusivity of dichloroacetic acid were directly affected by the physical and chemical parameters. In addition, the various thermodynamic parameters, such as Gibbs free energy (Delta G), enthalpy (Delta H = 54.35 kJmol-1) and entropy (Delta S = 258.36 Jmol-1 K-1) were calculated to analyse the adsorption process. The experimental results indicated that the mesoporous carbon was an excellent adsorbent for dichloroacetic acid removal from aqueous solutions.

  19. 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.

  20. Equilibrium modeling and kinetic studies on the adsorption of basic dye by a low-cost adsorbent: coconut (Cocos nucifera) bunch waste.

    PubMed

    Hameed, B H; Mahmoud, D K; Ahmad, A L

    2008-10-01

    In this paper, the ability of coconut bunch waste (CBW), an agricultural waste available in large quantity in Malaysia, to remove basic dye (methylene blue) from aqueous solution by adsorption was studied. Batch mode experiments were conducted at 30 degrees C to study the effects of pH and initial concentration of methylene blue (MB). Equilibrium adsorption isotherms and kinetics were investigated. The experimental data were analyzed by the Langmuir, Freundlich and Temkin models of adsorption. The adsorption isotherm data were fitted well to Langmuir isotherm and the monolayer adsorption capacity was found to be 70.92 mg/g at 30 degrees C. The kinetic data obtained at different concentrations have been analyzed using a pseudo-first-order, pseudo-second-order equation and intraparticle diffusion equation. The experimental data fitted very well the pseudo-second-order kinetic model.

  1. 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.

  2. On an isotherm thermodynamically consistent in Henry's region for describing gas adsorption in microporous materials.

    PubMed

    Pera-Titus, Marc

    2010-05-15

    The Dubinin-Astakhov and Dubinin-Radushkevich isotherms, originally formulated from the classical volume filling theory of micropores, constitute the most accepted models for describing gas adsorption in microporous materials. The most important weakness of these equations relies on the fact that they do not reduce to Henry's law at low pressures, not providing therefore a proper characterization of adsorbents in the early stage of adsorption. In this paper, we propose a way out of this inherent problem using the thermodynamic isotherm developed in a previous study [J. Llorens, M. Pera-Titus, J. Colloid Interface Sci. 331 (2009) 302]. This isotherm allows the generation of a series of equations that make available a comprehensive description of gas adsorption for the whole set of relative pressures (including Henry's region), also providing explicit information about energy heterogeneity of the adsorbent through the two characteristic m parameters of the thermodynamic isotherm (i.e., m(1) and m(2)). The obtained isotherm converges into the Dubinin-Astakhov isotherm for relative pressures higher than 0.1, the characteristic α parameter of this isotherm being expressed as α=m(2)-1 and the affinity coefficient (β) as a sole function of m(2). An expression differing from the Dubinin-Astakhov isotherm has been obtained for describing Henry's region, providing relevant information about confinement effects when applied to zeolites.

  3. Solutions for the equilibrium of static isothermal gas clouds with poloidal magnetic fields

    NASA Astrophysics Data System (ADS)

    Baureis, P.; Ebert, R.; Schmitz, F.

    1989-11-01

    A family of semi-analytical solutions for the equilibrium of magnetic self-gravitating gas clouds is presented. The configurations are isothermal and axially symmetric; the frozen-in magnetic field is poloidal. Formulating the equilibrium equations of such gas clouds in spherical polar coordinates, a separation of these equations provides simple representative solutions. The radial part of the density distribution is given by the characteristic inverse square of the radial coordinate. The angular parts are governed by a system of nonlinear ordinary differential equations which is solved numerically. The nonmagnetic limit is the isothermal gas sphere with infinite central density. With increasing field strength the configurations flatten. Besides the isothermal sound velocity the value of the magnetic field in the midplane is a free continuous parameter. In the limit of extremely strong fields a thin disk forms. The existence of bounded solutions is discussed, and the models are compared with configurations presented by other authors.

  4. 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.

  5. Water adsorption-desorption isotherms of two-dimensional hexagonal mesoporous silica around freezing point.

    PubMed

    Endo, Akira; Yamaura, Toshio; Yamashita, Kyohei; Matsuoka, Fumio; Hihara, Eiji; Daiguji, Hirofumi

    2012-02-01

    Zr-doped mesoporous silica with a diameter of approximately 3.8 nm was synthesized via an evaporation-induced self-assembly process, and the adsorption-desorption isotherms of water vapor were measured in the temperature range of 263-298 K. The measured adsorption-desorption isotherms below 273 K indicated that water confined in the mesopores did not freeze at any relative pressure. All isotherms had a steep curve, resulting from capillary condensation/evaporation, and a pronounced hysteresis. The hysteresis loop, which is associated with a delayed adsorption process, increased with a decrease in temperature. Furthermore, the curvature radius where capillary evaporation/condensation occurs was evaluated by the combined Kelvin and Gibbs-Tolman-Koening-Buff (GTKB) equations for the modification of the interfacial tension due to the interfacial curvature. The thickness of the water adsorption layer for capillary condensation was slightly larger, whereas that for capillary evaporation was slightly smaller than 0.7 nm.

  6. Isotherm, thermodynamic, kinetics and adsorption mechanism studies of methyl orange by surfactant modified silkworm exuviae.

    PubMed

    Chen, Hao; Zhao, Jie; Wu, Junyong; Dai, Guoliang

    2011-08-15

    This paper reports on the development of organo-modified silkworm exuviae (MSE) adsorbent prepared by using hexadecyltrimethylammonium bromide (HDTMAB) for removing methyl orange (MO), a model anionic dye, from aqueous solution. The natural and modified samples were characterized by scanning electron microscope (SEM), energy dispersive spectrometer (EDS) and Fourier transform infrared spectroscopy (FT-IR). Batch adsorption experiments were carried out to remove MO from its aqueous solutions using SE and MSE. It was observed that the adsorption capacity of MSE is 5-6 times of SE. The different parameters effecting on the adsorption capacity such as pH of the solution, initial dye concentration, temperature and contact time have been investigated. Analysis of adsorption results obtained at different temperatures showed that the adsorption pattern on the MSE can be described perfectly with Langmuir isotherm model compared with Freundlich and Dubinin-Radushkevich (D-R) isotherm models, and the characteristic parameters for each adsorption isotherm were also determined. The adsorption process has been found exothermic in nature and thermodynamic parameters have been calculated. The adsorption kinetic followed the pseudo-second order kinetic model. The results of FT-IR, EDS and desorption studies all suggest that methyl orange adsorption onto the MSE should be mainly controlled by the hydrophobic interaction mechanism, along with a considerable contribution of the anionic exchange mechanism. The results indicate that HDTMAB-modified silkworm exuviae could be employed as low-cost material for the removal of methyl orange anionic dye from wastewater.

  7. Single and binary adsorption of proteins on ion-exchange adsorbent: The effectiveness of isothermal models.

    PubMed

    Liang, Juan; Fieg, Georg; Shi, Qing-Hong; Sun, Yan

    2012-09-01

    Simultaneous and sequential adsorption equilibria of single and binary adsorption of bovine serum albumin and bovine hemoglobin on Q Sepharose FF were investigated in different buffer constituents and initial conditions. The results in simultaneous adsorption showed that both proteins underwent competitive adsorption onto the adsorbent following greatly by protein-surface interaction. Preferentially adsorbed albumin complied with the universal rule of ion-exchange adsorption whereas buffer had no marked influence on hemoglobin adsorption. Moreover, an increase in initial ratios of proteins was benefit to a growth of adsorption density. In sequential adsorption, hemoglobin had the same adsorption densities as single-component adsorption. It was attributed to the displacement of preadsorbed albumin and multiple layer adsorption of hemoglobin. Three isothermal models (i.e. extended Langmuir, steric mass-action, and statistical thermodynamic (ST) models) were introduced to describe the ion-exchange adsorption of albumin and hemoglobin mixtures. The results suggested that extended Langmuir model gave the lowest deviation in describing preferential adsorption of albumin at a given salt concentration while steric mass-action model could very well describe the salt effect in albumin adsorption. For weaker adsorbed hemoglobin, ST model was the preferred choice. In concert with breakthrough data, the research further revealed the complexity in ion-exchange adsorption of proteins.

  8. Kinetics and equilibrium adsorption of nano-TiO 2 particles on synthetic biofilm

    NASA Astrophysics Data System (ADS)

    Sahle-Demessie, Endalkachew; Tadesse, Haregewine

    2011-07-01

    Understanding the environmental behavior of nanoparticles includes their interaction with biofilms, which is a covering on the surface of a living or nonliving substrate composed of microorganisms. This study focuses on nano-TiO2 sorption mechanism by synthetic biofilm that was prepared as superporous spherical beads from agarose, using batch stirred flasks kept at room temperature. The pH plays an important part in these phenomena, by its influence on the nanoparticles and biofilm chemistry, where the biofilm nanoTiO2 uptake at neutral pH was enhanced over acidic conditions. Hydroxylation of TiO2 nanoparticles, dependent on pH and the salinity of the solution, influences the stability of colloids, the sorption kinetics via the nature of limiting phases: diffusion through the boundary layer or intrabiofilm mass transfer and the sorption mechanism. The sorption follows pseudo first-order adsorption kinetics with estimated average rate constants of 2.2 (min- 1). Equilibrium isotherms were evaluated using Langmuir and Freundlich isotherms to obtain the maximum uptake at different solution pH and the free energy of the adsorption. The adsorption is apparently irreversible because biofilm limits diffusion of particles out of the pores and the complexation active binding sites on the surface hydrated biofilm to the hydrophilic TiO2 nanoparticles.

  9. Adsorption equilibrium and kinetics of CO2, CH4, N2O, and NH3 on ordered mesoporous carbon.

    PubMed

    Saha, Dipendu; Deng, Shuguang

    2010-05-15

    Ordered mesoporous carbon was synthesized by a self-assembly technique and characterized with TEM, Raman spectroscopy, and nitrogen adsorption/desorption for its physical and pore textural properties. The high BET specific surface area (798 m(2)/g), uniform mesopore-size distribution with a median pore size of 62.6 Å, and large pore volume (0.87 cm(3)/g) make the ordered mesoporous carbon an ideal adsorbent for gas separation and purification applications. Adsorption equilibrium and kinetics of carbon dioxide, methane, nitrous oxide, and ammonia on the ordered mesoporous carbon were measured at 298 K and gas pressures up to 800 Torr. The adsorption equilibrium capacities on the ordered mesoporous carbon at 298 K and 800 Torr for ammonia, carbon dioxide, nitrous oxide, and methane were found to be 6.39, 2.39, 1.5, and 0.53 mmol/g, respectively. Higher adsorption uptakes of methane (3.26 mmol/g at 100 bar) and carbon dioxide (2.21 mmol/g at 13 bar) were also observed at 298 K and elevated pressures. Langmuir, Freundlich, and Toth adsorption equilibrium models were used to correlate all the adsorption isotherms, and a simplified gas diffusion model was applied to analyze the adsorption kinetics data collected at 298 K and four different gas pressures up to 800 Torr.

  10. 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.

  11. Isotherm and thermodynamic studies of Zn (II) adsorption on lignite and coconut shell-based activated carbon fiber.

    PubMed

    Shrestha, Sohan; Son, Guntae; Lee, Seung Hwan; Lee, Tae Gwan

    2013-08-01

    The Zn (II) adsorption capacity of lignite and coconut shell-based activated carbon fiber (ACF) was evaluated as a function of initial Zn (II) concentration, temperature and contact time in batch adsorption process in this study. Adsorption uptake increased with initial Zn (II) concentration and temperature. Optimal contact time for the adsorption of Zn (II) ions onto lignite and coconut shell-based ACF was found to be 50 min. Removal percentage decreased from 88.0% to 78.54% with the increment in initial Zn (II) concentration from 5 to 50 mg L(-1). Equilibrium data fit well with Langmuir-I isotherm indicating homogeneous monolayer coverage of Zn (II) ions on the adsorbent surface. Maximum monolayer adsorption capacity of Zn (II) ions on ACF was found to be 9.43 mg g(-1). Surface morphology and functionality of ACF prior to and after adsorption were characterized by electron microscopy and infrared spectroscopy. Various thermodynamic parameters such as standard Gibbs free energy (ΔG°), standard enthalpy (ΔH°), and standard entropy (ΔS°) were evaluated.

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

    PubMed

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

    2016-05-15

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

  13. Verification of selected relationships for fractally porous solids by using adsorption isotherms calculated from density functional theory

    NASA Astrophysics Data System (ADS)

    Jaroniec, Mietek; Kruk, Michal; Olivier, James

    1995-11-01

    Methods of calculating the fractal dimension (D) on the basis of single adsorption isotherms were critically tested by using argon composite adsorption isotherms for fractally porous solids. These isotherms were obtained from adsorption data for homogeneous slit-like pores calculated by employing the density functional theory (DFT). The composite adsorption isotherms were used to test the validity of the method based on the Frenkel-Halsey-Hill equation and so called "thermodynamic method" proposed by Neimark. The applicability of these methods was confirmed. However, our studies reveal new aspects of practical usage of both approaches, which need to be taken into consideration in analysis of experimental data.

  14. 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.

  15. Adsorption kinetics, isotherms and thermodynamics of atrazine on surface oxidized multiwalled carbon nanotubes.

    PubMed

    Chen, Guang-Cai; Shan, Xiao-Quan; Zhou, Yi-Quan; Shen, Xiu-e; Huang, Hong-Lin; Khan, Shahamat U

    2009-09-30

    The adsorption kinetics, isotherms and thermodynamic of atrazine on multiwalled carbon nanotubes (MWCNTs) containing 0.85%, 2.16%, and 7.07% oxygen was studied. Kinetic analyses were performed using pseudo-first-order, pseudo-second-order and intraparticle diffusion models. The regression results showed that the pseudo-second-order law fit the adsorption kinetics. The calculated thermodynamic parameters indicated that adsorption of atrazine on MWCNTs was spontaneous and exothermic. Standard free energy (DeltaG(0)) became less negative when the oxygen content of MWCNTs increased from 0.85% to 7.07% which is consistent with the low adsorption affinity of MWCNTs for atrazine.

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

    PubMed

    Goicochea, A Gama

    2007-11-06

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

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

    PubMed Central

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

    2013-01-01

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

  18. Kinetics and equilibrium adsorption study of p-nitrophenol onto activated carbon derived from walnut peel.

    PubMed

    Liu, Xiaohong; Wang, Fang; Bai, Song

    2015-01-01

    An original activated carbon prepared from walnut peel, which was activated by zinc chloride, was modified with ammonium hydroxide or sodium hydroxide in order to contrast the adsorption property of the three different activated carbons. The experiment used a static adsorption test for p-nitrophenol. The effects of parameters such as initial concentration, contact time and pH value on amount adsorbed and removal are discussed in depth. The thermodynamic data of adsorption were analyzed by Freundlich and Langmuir models. The kinetic data of adsorption were measured by the pseudo-first-order kinetics and the pseudo-second-order kinetics models. The results indicated that the alkalized carbon samples derived from walnut peel had a better performance than the original activated carbon treated with zinc chloride. It was found that adsorption equilibrium time was 6 h. The maximum removal rate of activated carbon treated with zinc chloride for p-nitrophenol was 87.3% at pH 3,whereas the maximum removal rate of the two modified activated carbon materials was found to be 90.8% (alkalized with ammonium hydroxide) and 92.0% (alkalized with sodium hydroxide) at the same pH. The adsorption data of the zinc chloride activated carbon were fitted to the Langmuir isotherm model. The two alkalized activated carbon samples were fitted well to the Freundlich model. The pseudo-second-order dynamics equation provided better explanation of the adsorption dynamics data of the three activated carbons than the pseudo-first-order dynamics equation.

  19. Adsorption of CO{sub 2} on activated carbon: Simultaneous determination of integral heat and isotherm of adsorption

    SciTech Connect

    Berlier, K.; Frere, M.

    1996-09-01

    Simultaneous measurements of isotherms and integral heats of adsorption of carbon dioxide (CO{sub 2}) at temperatures ranging from 278 K to 327 K (seven temperatures) and at pressures up to 110 kPa on activated carbon are presented.

  20. Adsorption equilibrium and dynamics of gasoline vapors onto polymeric adsorbents.

    PubMed

    Jia, Lijuan; Yu, Weihua; Long, Chao; Li, Aimin

    2014-03-01

    The emission of gasoline vapors is becoming a significant environmental problem especially for the population-dense area and also results in a significant economic loss. In this study, adsorption equilibrium and dynamics of gasoline vapors onto macroporous and hypercrosslinked polymeric resins at 308 K were investigated and compared with commercial activated carbon (NucharWV-A 1100). The results showed that the equilibrium and breakthrough adsorption capacities of virgin macroporous and hypercrosslinked polymeric resins were lower than virgin-activated carbon. Compared with origin adsorbents, however, the breakthrough adsorption capacities of the regenerated activated carbon for gasoline vapors decreased by 58.5 % and 61.3 % when the initial concentration of gasoline vapors were 700 and 1,400 mg/L, while those of macroporous and hypercrosslinked resins decreased by 17.4 % and 17.5 %, and 46.5 % and 45.5 %, respectively. Due to the specific bimodal property in the region of micropore (0.5-2.0 nm) and meso-macropore (30-70 nm), the regenerated hypercrosslinked polymeric resin exhibited the comparable breakthrough adsorption capacities with the regenerated activated carbon at the initial concentration of 700 mg/L, and even higher when the initial concentration of gasoline vapors was 1,400 mg/L. In addition, 90 % of relative humidity had ignorable effect on the adsorption of gasoline vapors on hypercrosslinked polymeric resin. Taken together, it is expected that hypercrosslinked polymeric adsorbent would be a promising adsorbent for the removal of gasoline vapors from gas streams.

  1. New theoretical expressions for the five adsorption type isotherms classified by BET based on statistical physics treatment.

    PubMed

    Khalfaoui, M; Knani, S; Hachicha, M A; Lamine, A Ben

    2003-07-15

    New theoretical expressions to model the five adsorption isotherm types have been established. Using the grand canonical ensemble in statistical physics, we give an analytical expression to each of five physical adsorption isotherm types classified by Brunauer, Emett, and Teller, often called BET isotherms. The establishment of these expressions is based on statistical physics and theoretical considerations. This method allowed estimation of all the mathematical parameters in the models. The physicochemical parameters intervening in the adsorption process that the models present could be deduced directly from the experimental adsorption isotherms by numerical simulation. We determine the adequate model for each type of isotherm, which fixes by direct numerical simulation the monolayer, multilayer, or condensation character. New equations are discussed and results obtained are verified for experimental data from the literature. The new theoretical expressions that we have proposed, based on statistical physics treatment, are rather powerful to better understand and interpret the various five physical adsorption type isotherms at a microscopic level.

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

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... colloid interfaces can be incorporated into this test. The ease of performing the isotherm test and mass... section served as the basis for this section. The soil and colloid chemistry literature and the analytical... using a chemical and/or physical treatment that does not alter or minimally alters the colloid...

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

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... colloid interfaces can be incorporated into this test. The ease of performing the isotherm test and mass... section served as the basis for this section. The soil and colloid chemistry literature and the analytical... using a chemical and/or physical treatment that does not alter or minimally alters the colloid...

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

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... colloid interfaces can be incorporated into this test. The ease of performing the isotherm test and mass... section served as the basis for this section. The soil and colloid chemistry literature and the analytical... using a chemical and/or physical treatment that does not alter or minimally alters the colloid...

  5. 40 CFR 796.2750 - Sediment and soil adsorption isotherm.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... colloid interfaces can be incorporated into this test. The ease of performing the isotherm test and mass... section served as the basis for this section. The soil and colloid chemistry literature and the analytical... using a chemical and/or physical treatment that does not alter or minimally alters the colloid...

  6. 40 CFR 796.2750 - Sediment and soil adsorption isotherm.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... colloid interfaces can be incorporated into this test. The ease of performing the isotherm test and mass... section served as the basis for this section. The soil and colloid chemistry literature and the analytical... using a chemical and/or physical treatment that does not alter or minimally alters the colloid...

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

    NASA Astrophysics Data System (ADS)

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

    2010-02-01

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

  8. Novel Silica-Based Hybrid Adsorbents: Lead(II) Adsorption Isotherms

    PubMed Central

    Wang, Xin

    2013-01-01

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

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

    PubMed

    Liu, Junsheng; Wang, Xin

    2013-01-01

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

  10. Equilibrium and kinetics study on hexavalent chromium adsorption onto diethylene triamine grafted glycidyl methacrylate based copolymers.

    PubMed

    Maksin, Danijela D; Nastasović, Aleksandra B; Milutinović-Nikolić, Aleksandra D; Suručić, Ljiljana T; Sandić, Zvjezdana P; Hercigonja, Radmila V; Onjia, Antonije E

    2012-03-30

    Two porous and one non-porous crosslinked poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate) [abbreviated PGME] were prepared by suspension copolymerization and functionalized with diethylene triamine [abbreviated PGME-deta]. Samples were characterized by elemental analysis, mercury porosimetry, scanning electron microscopy with energy-dispersive X-ray spectroscopy, and transmission electron microscopy. Kinetics of Cr(VI) sorption by PGME-deta were investigated in batch static experiments, in the temperature range 25-70°C. Sorption was rapid, with the uptake capacity higher than 80% after 30 min. Sorption behavior and rate-controlling mechanisms were analyzed using five kinetic models (pseudo-first order, pseudo-second order, Elovich, intraparticle diffusion and Bangham model). Kinetic studies showed that Cr(VI) adsorption adhered to the pseudo-second-order model, with definite influence of pore diffusion. Equilibrium data was tested with Langmuir, Freundlich and Tempkin adsorption isotherm models. Langmuir model was the most suitable indicating homogeneous distribution of active sites on PGME-deta and monolayer sorption. The maximum adsorption capacity from the Langmuir model, Q(max), at pH 1.8 and 25°C was 143 mg g(-1) for PGME2-deta (sample with the highest amino group concentration) while at 70°C Q(max) reached the high value of 198 mg g(-1). Thermodynamic parameters revealed spontaneous and endothermic nature of Cr(VI) adsorption onto PGME-deta.

  11. 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.

  12. Preparation of Ag/TiO2-zeolite adsorbents, their desulfurization performance, and benzothiophene adsorption isotherms

    NASA Astrophysics Data System (ADS)

    Song, Hua; Yang, Gang; Song, Hua-Lin; Wang, Deng; Wang, Xue-Qin

    2017-02-01

    A series of Ag/TiO2-NaY (TY) composite adsorbents were successfully prepared and characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, BET, scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) techniques. The effects of TiO2 and Ag contents on the structure and desulfurization performance of NaY zeolite were studied. The results show that anatase phase is the main form of TiO2 in AgTY adsorbent, and the Y-zeolite framework remained unchanged. AgTY with 6 wt % of Ag and 50 wt % of TiO2 exhibited the best desulfurization performance with the effluent volume of 63.2 mL/g at 10 mg/L sulfur breakthrough level (desulfurization rate of 95%). The benzothiophene (BT) removal performance of the various adsorbents follows the order: NaY < TiO2 < TY-50 < AgTY-50-6. The equilibrium data were modeled by Langmuir and Freundlich equations. The Langmuir model can describe well the adsorption isotherms of BT over AgTY.

  13. Equilibrium, kinetic and thermodynamic studies on the adsorption of the toxins of Bacillus thuringiensis subsp. kurstaki by clay minerals

    NASA Astrophysics Data System (ADS)

    Fu, Qingling; Deng, Yali; Li, Huishu; Liu, Jie; Hu, Hongqing; Chen, Shouwen; Sa, Tongmin

    2009-02-01

    The persistence of Bacillus thuringiensis ( Bt) toxins in soil is further enhanced through association with soil particles. Such persistence may improve the effectiveness of controlling target pests, but impose a hazard to non-target organisms in soil ecosystems. In this study, the equilibrium adsorption of the Bt toxin by four clay minerals (montmorillonite, kaolinite, goethite, and silicon dioxide) was investigated, and the kinetic and thermodynamic parameters were calculated. The results showed that Bt toxin could be adsorbed easily by minerals, and the adsorption was much easier at low temperature than at high temperature at the initial concentration varying from 0 to 1000 mg L -1. The adsorption fitted well to both Langmuir and Freundlich isotherm models, but the Freundlich equation was more suitable. The pseudo-second-order (PSO) was the best application model to describe the adsorption kinetic. The adsorption process appeared to be controlled by chemical process, and the intra-particle diffusion was not the only rate-controlling step. The negative standard free energy ( ΔGmθr) values of the adsorption indicated that the adsorption of the Bt toxin by the minerals was spontaneous, and the changes of the standard enthalpy ( ΔHmθr) showed that the adsorption of the Bt toxin by montmorillonite was endothermic while the adsorption by the other three minerals was exothermic.

  14. 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.

  15. 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.

  16. Effects of gas adsorption isotherm and liquid contact angle on capillary force for sphere-on-flat and cone-on-flat geometries.

    PubMed

    Hsiao, Erik; Marino, Matthew J; Kim, Seong H

    2010-12-15

    This paper explains the origin of the vapor pressure dependence of the asperity capillary force in vapor environments. A molecular adsorbate layer is readily formed on solid surface in ambient conditions unless the surface energy of the solid is low enough and unfavorable for vapor adsorption. Then, the capillary meniscus formed around the solid asperity contact should be in equilibrium with the adsorbate layer, not with the bare solid surface. A theoretical model incorporating the vapor adsorption isotherm into the solution of the Young-Laplace equation is developed. Two contact geometries--sphere-on-flat and cone-on-flat--are modeled. The calculation results show that the experimentally-observed strong vapor pressure dependence can be explained only when the adsorption isotherm of the vapor on the solid surface is taken into account. The large relative partial pressure dependence mainly comes from the change in the meniscus size due to the presence of the adsorbate layer.

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

    PubMed

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

    2014-01-01

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

  18. Removal of phenol from aqueous solutions by adsorption onto organomodified Tirebolu bentonite: equilibrium, kinetic and thermodynamic study.

    PubMed

    Senturk, Hasan Basri; Ozdes, Duygu; Gundogdu, Ali; Duran, Celal; Soylak, Mustafa

    2009-12-15

    A natural bentonite modified with a cationic surfactant, cetyl trimethylammonium bromide (CTAB), was used as an adsorbent for removal of phenol from aqueous solutions. The natural and modified bentonites (organobentonite) were characterized with some instrumental techniques (FTIR, XRD and SEM). Adsorption studies were performed in a batch system, and the effects of various experimental parameters such as solution pH, contact time, initial phenol concentration, organobentonite concentration, and temperature, etc. were evaluated upon the phenol adsorption onto organobentonite. Maximum phenol removal was observed at pH 9.0. Equilibrium was attained after contact of 1h only. The adsorption isotherms were described by Langmuir and Freundlich isotherm models, and both model fitted well. The monolayer adsorption capacity of organobentonite was found to be 333 mg g(-1). Desorption of phenol from the loaded adsorbent was achieved by using 20% acetone solution. The kinetic studies indicated that the adsorption process was best described by the pseudo-second-order kinetics (R(2) > 0.99). Thermodynamic parameters including the Gibbs free energy (DeltaG degrees), enthalpy (DeltaH degrees), and entropy (DeltaS degrees) were also calculated. These parameters indicated that adsorption of phenol onto organobentonite was feasible, spontaneous and exothermic in the temperature range of 0-40 degrees C.

  19. Adsorption of cesium from aqueous solution using agricultural residue--walnut shell: equilibrium, kinetic and thermodynamic modeling studies.

    PubMed

    Ding, Dahu; Zhao, Yingxin; Yang, Shengjiong; Shi, Wansheng; Zhang, Zhenya; Lei, Zhongfang; Yang, Yingnan

    2013-05-01

    A novel biosorbent derived from agricultural residue - walnut shell (WS) is reported to remove cesium from aqueous solution. Nickel hexacyanoferrate (NiHCF) was incorporated into this biosorbent, serving as a high selectivity trap agent for cesium. Field emission scanning electron microscope (FE-SEM) and thermogravimetric and differential thermal analysis (TG-DTA) were utilized for the evaluation of the developed biosorbent. Determination of kinetic parameters for adsorption was carried out using pseudo first-order, pseudo second-order kinetic models and intra-particle diffusion models. Adsorption equilibrium was examined using Langmuir, Freundlich and Dubinin-Radushkevich adsorption isotherms. A satisfactory correlation coefficient and relatively low chi-square analysis parameter χ(2) between the experimental and predicted values of the Freundlich isotherm demonstrate that cesium adsorption by NiHCF-WS is a multilayer chemical adsorption. Thermodynamic studies were conducted under different reaction temperatures and results indicate that cesium adsorption by NiHCF-WS is an endothermic (ΔH° > 0) and spontaneous (ΔG° < 0) process.

  20. 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.

  1. 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.

  2. A procedure to find thermodynamic equilibrium constants for CO2 and CH4 adsorption on activated carbon.

    PubMed

    Trinh, T T; van Erp, T S; Bedeaux, D; Kjelstrup, S; Grande, C A

    2015-03-28

    Thermodynamic equilibrium for adsorption means that the chemical potential of gas and adsorbed phase are equal. A precise knowledge of the chemical potential is, however, often lacking, because the activity coefficient of the adsorbate is not known. Adsorption isotherms are therefore commonly fitted to ideal models such as the Langmuir, Sips or Henry models. We propose here a new procedure to find the activity coefficient and the equilibrium constant for adsorption which uses the thermodynamic factor. Instead of fitting the data to a model, we calculate the thermodynamic factor and use this to find first the activity coefficient. We show, using published molecular simulation data, how this procedure gives the thermodynamic equilibrium constant and enthalpies of adsorption for CO2(g) on graphite. We also use published experimental data to find similar thermodynamic properties of CO2(g) and of CH4(g) adsorbed on activated carbon. The procedure gives a higher accuracy in the determination of enthalpies of adsorption than ideal models do.

  3. Establishing isothermal contact at a known temperature under thermal equilibrium in elevated temperature instrumented indentation testing

    NASA Astrophysics Data System (ADS)

    Hou, X. D.; Alvarez, C. L. M.; Jennett, N. M.

    2017-02-01

    Instrumented indentation testing (IIT) at elevated temperatures has proved to be a useful tool to study plastic and elastic deformation and understand the performance of material components at (or nearer to) the actual temperatures experienced in-service. The value of elevated temperature IIT data, however, depends on the ability not only to achieve a stable, isothermal indentation contact at thermal equilibrium when taking data, but to be able to assign a valid temperature to that contact (and so to the data). The most common method found in the current literature is to use the calculated thermal drift rate as an indicator, but this approach has never been properly validated. This study proves that using the thermal drift rate to determine isothermal contact may lead to large errors in the determination of the real contact temperature. Instead, a more sensitive and validated method is demonstrated, based upon using the indenter tip and the tip heater control thermocouple as a reproducible and calibrated contact temperature sensor. A simple calibration procedure is described, along with step by step guidance to establish an isothermal contact at a known temperature under thermal equilibrium when conducting elevated temperature IIT experiments.

  4. 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.

  5. Kinetics, equilibrium and thermodynamics of adsorption of 2-biphenylamine and dibenzylamine from aqueous solutions by Fe3O4/bentonite nanocomposite

    NASA Astrophysics Data System (ADS)

    Vasheghani F., B.; Rajabi, F. H.; Omidi, M. H.; Shabanian, S.

    2015-05-01

    Magnetic Fe3O4/bentonite nanocomposite is synthesized by chemical co-precipitation method. Experimental data are modelled by Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich isotherms. Freundlich and Langmuir isotherm model fitted the equilibrium data for the dibenzylamine (DBA) and 2-biphenylamine (BPA) respectively, compared to the other isotherm models. The calculated thermodynamic parameters, Δ G°, Δ H°, and Δ S° showed that the DBA and BPA adsorption on bentonite nanocomposite is spontaneous and endothermic under examined conditions. Experimental data were also modeled using the adsorption kinetic models. The results show that the adsorption processes of DBA and BPA followed well the pseudo-second-order kinetics. Results indicated that Fe3O4/bentonite nanocomposite could be an alternative for more costly adsorbents used for organic toxicants removal.

  6. Equilibrium and column adsorption studies of 2,4-dinitroanisole (DNAN) on surface modified granular activated carbons.

    PubMed

    Boddu, V M; Abburi, K; Fredricksen, A J; Maloney, S W; Damavarapu, R

    2009-02-01

    2,4-Dinitroanisole (DNAN) is used as a component extensively in the development of insensitive munitions. This may result in release of DNAN into the environment. Here, the results are reported of a study on the removal characteristics of DNAN through adsorption on granular activated carbon (GAC), chitosan coated granular activated carbon (CGAC), acid treated granular activated carbon (AGAC) and alkali treated granular activated carbon (BGAC) under equilibrium and column flow conditions. The effect of pH, contact time, concentration of DNAN, and presence of electrolytes on the uptake of DNAN by the adsorbents was investigated. The equilibrium data were fitted to different types of adsorption isotherms. The data were further analysed on the basis of Lagergren first-order, pseudo second-order and intraparticle diffusion kinetic models. Breakthrough curves were obtained based on column flow results. All the adsorbents were capable of removing about 99% of DNAN from aqueous media, except CGAC which adsorbed about 87% of DNAN.

  7. Adsorption behavior of activated carbon derived from pyrolusite-modified sewage sludge: equilibrium modeling, kinetic and thermodynamic studies.

    PubMed

    Chen, Yao; Jiang, Wenju; Jiang, Li; Ji, Xiujuan

    2011-01-01

    Activated carbon was developed from sewage sludge using pyrolusite as an additive. It was demonstrated that the removal efficiency of two synthetic dyes (Tracid orange GS and Direct fast turquoise blue GL) by the produced adsorbent was up to 97.6%. The activated carbon with pyrolusite addition had 38.2% higher surface area, 43.8% larger micropore and 54.4% larger mesopore production than ordinary sludge-based activated carbons. Equilibrium adsorption isotherms and kinetics were also investigated based on dyes adsorption tests. The experimental data were analyzed by the Langmuir and Freundlich models of adsorption, and the results fitted well to the Langmuir isotherm. The kinetic data have been analyzed using pseudo-first-order, pseudo-second-order and intraparticle diffusion equation. The experimental data fitted very well with pseudo-second-order kinetic model. Activation energies for the adsorption processes ranged between 8.7 and 19.1 kJ mol 1. Thermodynamic parameters such as standard free energy (deltaG0), standard enthalpy (deltaH0) and standard entropy (deltaS0) were evaluated. The adsorption of these two dyes on the activated carbon was found to be a spontaneous and endothermic process in nature.

  8. The adsorption of phloretin to lipid monolayers and bilayers cannot be explained by langmuir adsorption isotherms alone.

    PubMed Central

    Cseh, R; Benz, R

    1998-01-01

    Phloretin and its analogs adsorb to the surfaces of lipid monolayers and bilayers and decrease the dipole potential. This reduces the conductance for anions and increases that for cations on artificial and biological membranes. The relationship between the change in the dipole potential and the aqueous concentration of phloretin has been explained previously by a Langmuir adsorption isotherm and a weak and therefore negligible contribution of the dipole-dipole interactions in the lipid surface. We demonstrate here that the Langmuir adsorption isotherm alone is not able to properly describe the effects of dipole molecule binding to lipid surfaces--we found significant deviations between experimental data and the fit with the Langmuir adsorption isotherm. We present here an alternative theoretical treatment that takes into account the strong interaction between membrane (monolayer) dipole field and the dipole moment of the adsorbed molecule. This treatment provides a much better fit of the experimental results derived from the measurements of surface potentials of lipid monolayers in the presence of phloretin. Similarly, the theory provides a much better fit of the phloretin-induced changes in the dipole potential of lipid bilayers, as assessed by the transport kinetics of the lipophilic ion dipicrylamine. PMID:9512036

  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. Mean field lattice model for adsorption isotherms in zeolite NaA

    NASA Astrophysics Data System (ADS)

    Ayappa, K. G.; Kamala, C. R.; Abinandanan, T. A.

    1999-05-01

    Using a lattice model for adsorption in microporous materials, pure component adsorption isotherms are obtained within a mean field approximation for methane at 300 K and xenon at 300 and 360 K in zeolite NaA. It is argued that the increased repulsive adsorbate-adsorbate interactions at high coverages must play an important role in determining the adsorption behavior. Therefore, this feature is incorporated through a "coverage-dependent interaction" model, which introduces a free, adjustable parameter. Another important feature, the site volume reduction, has been treated in two ways: a van der Waal model and a 1D hard-rod theory [van Tassel et al., AIChE J. 40, 925 (1994)]; we have also generalized the latter to include all possible adsorbate overlap scenarios. In particular, the 1D hard-rod model, with our coverage-dependent interaction model, is shown to be in best quantitative agreement with the previous grand canonical Monte Carlo isotherms. The expressions for the isosteric heats of adsorption indicate that attractive and repulsive adsorbate-adsorbate interactions increase and decrease the heats of adsorption, respectively. It is concluded that within the mean field approximation, our simple model for repulsive interactions and the 1D hard-rod model for site volume reduction are able to capture most of the important features of adsorption in confined regions.

  11. Determination of competitive adsorption isotherms applying the nonlinear frequency response method. Part II. Experimental demonstration.

    PubMed

    Ilić, Milica; Petkovska, Menka; Seidel-Morgenstern, Andreas

    2009-08-14

    This paper demonstrates an experimental application of the nonlinear frequency response (FR) method extension to determine adsorption isotherms of binary mixtures. This method, based on the analysis of the response of a chromatographic column subjected to the sinusoidal inlet concentration changes, is shown to be an alternative for isotherm determination. The critical issue related to the successful application of the method is to reach experimentally the low frequency asymptotic behaviour of the corresponding frequency response functions (FRFs). Although, there are different possibilities to perform periodical inlet concentration changes, in this paper only simultaneous changes for both components were considered. The adsorption of phenol and 2-phenylethanol on octadecyl silica was analyzed experimentally using a mixture of methanol and water as a solvent. Parameters of competitive isotherms were also estimated for comparison using the classical perturbation method. Despite certain differences between competitive isotherms estimated with the two methods that were found, the obtained results show the potential of the nonlinear FR method for measuring competitive isotherms.

  12. Equilibrium, kinetic and thermodynamic studies on the adsorption of 2-nitroaniline onto activated carbon prepared from cotton stalk fibre.

    PubMed

    Li, Kunquan; Zheng, Zheng; Huang, Xingfa; Zhao, Guohua; Feng, Jingwei; Zhang, Jibiao

    2009-07-15

    Activated carbon prepared from cotton stalk fibre has been utilized as an adsorbent for the removal of 2-nitroaniline from aqueous solutions. The influence of adsorbent mass, contact time and temperature on the adsorption was investigated by conducting a series of batch adsorption experiments. The equilibrium data at different temperatures were fitted with the Langmuir, Freundlich, Tempkin, Redlich-Peterson and Langmuir-Freundlich models. The Langmuir-Freundlich isotherm was found to best describe the experimental data. The adsorption amount increased with increasing temperature. The maximum adsorption capacity of 2-nitroaniline was found to be 383 mg/g for initial 2-nitroaniline concentration of 200mg/L at 45 degrees C. The kinetic rates were modeled by using the Lagergren-first-order, pseudo-second-order and Elovich models. The pseudo-second-order model was found to explain the adsorption kinetics most effectively. It was also found that the pore diffusion played an important role in the adsorption, and intraparticle diffusion was the rate-limiting step at the first 30 min for the temperatures of 25, 35 and 45 degrees C. FTIR and (13)C NMR study revealed that the amino and isocyanate groups present on the surface of the adsorbent were involved in chemical interaction with 2-nitroaniline. The negative change in free energy (Delta G degrees) and positive change in enthalpy (Delta H degrees) indicated that the adsorption was a spontaneous and endothermic process.

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

    PubMed

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

    2012-03-30

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

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

    NASA Astrophysics Data System (ADS)

    Danielson, Thomas; Hin, Celine; Savara, Aditya

    2016-08-01

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

  15. 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)

    SciTech Connect

    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 calculated 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.

  17. Sb/Si(111) adsorption: hidden phase transitions behind Langmuir-like isotherms.

    PubMed

    Guesmi, H; Lapena, L; Ranguis, A; Müller, P; Tréglia, G

    2005-02-25

    The experimental study of the thermodynamic and kinetic properties of the Sb/Si(111) interface reveals a surprising behavior: a 2D phase condensates when the Sb coverage increases, indicating strong attractive Sb-Sb interactions, whereas the isotherms present a quasi-Langmuir shape, suggesting that these interactions should be negligible. Ab initio calculations raise this contradiction: while the adsorption site evolves from ternary towards the on-top position with increasing coverage, the character of the Sb-Sb effective interactions changes from repulsive towards attractive, resulting in an almost constant average adsorption energy. A simple (Langmuir) thermodynamic behavior can then be the consequence of a surface phase transition.

  18. Predicting adsorption isotherms using a two-dimensional statistical associating fluid theory

    NASA Astrophysics Data System (ADS)

    Martinez, Alejandro; Castro, Martin; McCabe, Clare; Gil-Villegas, Alejandro

    2007-02-01

    A molecular thermodynamics approach is developed in order to describe the adsorption of fluids on solid surfaces. The new theory is based on the statistical associating fluid theory for potentials of variable range [A. Gil-Villegas et al., J. Chem. Phys. 106, 4168 (1997)] and uses a quasi-two-dimensional approximation to describe the properties of adsorbed fluids. The theory is tested against Gibbs ensemble Monte Carlo simulations and excellent agreement with the theoretical predictions is achieved. Additionally the authors use the new approach to describe the adsorption isotherms for nitrogen and methane on dry activated carbon.

  19. Predicting adsorption isotherms using a two-dimensional statistical associating fluid theory.

    PubMed

    Martinez, Alejandro; Castro, Martin; McCabe, Clare; Gil-Villegas, Alejandro

    2007-02-21

    A molecular thermodynamics approach is developed in order to describe the adsorption of fluids on solid surfaces. The new theory is based on the statistical associating fluid theory for potentials of variable range [A. Gil-Villegas et al., J. Chem. Phys. 106, 4168 (1997)] and uses a quasi-two-dimensional approximation to describe the properties of adsorbed fluids. The theory is tested against Gibbs ensemble Monte Carlo simulations and excellent agreement with the theoretical predictions is achieved. Additionally the authors use the new approach to describe the adsorption isotherms for nitrogen and methane on dry activated carbon.

  20. Adsorption and desorption of arsenate on sandy sediments from contaminated and uncontaminated saturated zones: Kinetic and equilibrium modeling.

    PubMed

    Hafeznezami, Saeedreza; Zimmer-Faust, Amity G; Dunne, Aislinn; Tran, Tiffany; Yang, Chao; Lam, Jacquelyn R; Reynolds, Matthew D; Davis, James A; Jay, Jennifer A

    2016-08-01

    Application of empirical models to adsorption of contaminants on natural heterogeneous sorbents is often challenging due to the uncertainty associated with fitting experimental data and determining adjustable parameters. Sediment samples from contaminated and uncontaminated portions of a study site in Maine, USA were collected and investigated for adsorption of arsenate [As(V)]. Two kinetic models were used to describe the results of single solute batch adsorption experiments. Piecewise linear regression of data linearized to fit pseudo-first order kinetic model resulted in two distinct rates and a cutoff time point of 14-19 h delineating the biphasic behavior of solute adsorption. During the initial rapid adsorption stage, an average of 60-80% of the total adsorption took place. Pseudo-second order kinetic models provided the best fit to the experimental data (R(2) > 0.99) and were capable of describing the adsorption over the entire range of experiments. Both Langmuir and Freundlich isotherms provided reasonable fits to the adsorption data at equilibrium. Langmuir-derived maximum adsorption capacity (St) of the studied sediments ranged between 29 and 97 mg/kg increasing from contaminated to uncontaminated sites. Solid phase As content of the sediments ranged from 3.8 to 10 mg/kg and the As/Fe ratios were highest in the amorphous phase. High-pH desorption experiments resulted in a greater percentage of solid phase As released into solution from experimentally-loaded sediments than from the unaltered samples suggesting that As(V) adsorption takes place on different reversible and irreversible surface sites.

  1. Interaction of Pseudomonas putida with kaolinite and montmorillonite: a combination study by equilibrium adsorption, ITC, SEM and FTIR.

    PubMed

    Rong, Xingmin; Huang, Qiaoyun; He, Xiaomin; Chen, Hao; Cai, Peng; Liang, Wei

    2008-06-15

    Equilibrium adsorption along with isothermal titration calorimetry (ITC), Fourier transform infrared spectra (FTIR) and scanning electron microscopy (SEM) techniques were employed to investigate the adsorption of Pseudomonas putida on kaolinite and montmorillonite. A higher affinity as well as larger amounts of adsorption of P. putida was found on kaolinite. The majority of sorbed bacterial cells (88.7%) could be released by water from montmorillonite, while only a small proportion (9.3%) of bacteria desorbed from kaolinite surface. More bacterial cells were observed to form aggregates with kaolinite, while fewer cells were within the larger bacteria-montmorillonite particles. The sorption of bacteria on kaolinite was enthalpically more favorable than that on montmorillonite. Based on our findings, it is proposed that the non-electrostatic forces other than electrostatic force play a more important role in bacterial adsorption by kaolinite and montmorillonite. Adsorption of bacteria on clay minerals resulted in obvious shifts of infrared absorption bands of water molecules, showing the importance of hydrogen bonding in bacteria-clay mineral adsorption. The enthalpies of -4.1+/-2.1 x 10(-8) and -2.5+/-1.4 x 10(-8)mJ cell(-1) for the adsorption of bacteria on kaolinite and montmorillonite, respectively, at 25 degrees C and pH 7.0 were firstly reported in this paper. The enthalpy of bacteria-mineral adsorption was higher than that reported previously for bacteria-biomolecule interaction but lower than that of bacterial coaggregation. The bacteria-mineral adsorption enthalpies increased at higher temperature, suggesting that the enthalpy-entropy compensation mechanism could be involved in the adsorption of P. putida on clay minerals. Data obtained in this study would provide valuable information for a better understanding of the mechanisms of mineral-microorganism interactions in soil and associated environments.

  2. 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.

  3. The adsorption of basic dye (Astrazon Blue FGRL) from aqueous solutions onto sepiolite, fly ash and apricot shell activated carbon: kinetic and equilibrium studies.

    PubMed

    Karagozoglu, B; Tasdemir, M; Demirbas, E; Kobya, M

    2007-08-17

    In this study, sepiolite, fly ash and apricot stone activated carbon (ASAC) were used as adsorbents for the investigation of the adsorption kinetics, isotherms and thermodynamic parameters of the basic dye (Astrazon Blue FGRL) from aqueous solutions at various concentrations (100-300 mg/L), adsorbent doses (3-12 g/L) and temperatures (303-323 K). The result showed that the adsorption capacity of the dye increased with increasing initial dye concentration, adsorbent dose and temperature. Three kinetic models, the pseudo-first-order, second-order, intraparticle diffusion, were used to predict the adsorption rate constants. The kinetics of adsorption of the basic dye followed pseudo-second-order kinetics. Equations were developed using the pseudo-second-order model which predicts the amount of the basic dye adsorbed at any contact time, initial dye concentration and adsorbent dose within the given range accurately. The adsorption equilibrium data obeyed Langmuir isotherm. The adsorption capacities (Q0) calculated from the Langmuir isotherm were 181.5 mg/g for ASAC, 155.5 mg/g for sepiolite and 128.2 mg/g for fly ash at 303 K. Thermodynamical parameters were also evaluated for the dye-adsorbent systems and revealed that the adsorption process was endothermic in nature.

  4. Adsorption isotherms, kinetics, thermodynamics and desorption studies of 2,4,6-trichlorophenol on oil palm empty fruit bunch-based activated carbon.

    PubMed

    Tan, I A W; Ahmad, A L; Hameed, B H

    2009-05-30

    The adsorption characteristics of 2,4,6-trichlorophenol (TCP) on activated carbon prepared from oil palm empty fruit bunch (EFB) were evaluated. The effects of TCP initial concentration, agitation time, solution pH and temperature on TCP adsorption were investigated. TCP adsorption uptake was found to increase with increase in initial concentration, agitation time and solution temperature whereas adsorption of TCP was more favourable at acidic pH. The adsorption equilibrium data were best represented by the Freundlich and Redlich-Peterson isotherms. The adsorption kinetics was found to follow the pseudo-second-order kinetic model. The mechanism of the adsorption process was determined from the intraparticle diffusion model. Boyd plot revealed that the adsorption of TCP on the activated carbon was mainly governed by particle diffusion. Thermodynamic parameters such as standard enthalpy (DeltaH degrees ), standard entropy (DeltaS degrees ), standard free energy (DeltaG degrees ) and activation energy were determined. The regeneration efficiency of the spent activated carbon was high, with TCP desorption of 99.6%.

  5. Adsorption intrinsic kinetics and isotherms of lead ions on steel slag.

    PubMed

    Liu, Sheng-Yu; Gao, Jin; Yang, Yi-Jin; Yang, Ying-Chun; Ye, Zhi-Xiang

    2010-01-15

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

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

    PubMed

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

    2009-02-01

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

  7. Universal singularities of multilayer adsorption isotherms and determination of surface area of adsorbents

    SciTech Connect

    Aranovich, G.L.; Donohue, M.D.

    1996-07-15

    The singularity in the adsorption isotherm for macroporous and nonporous adsorbents is considered as a universal function that can be characterized with two parameters: a coefficient of proportionality, K, and an exponent, d. It is shown that the value of K is proportional to the adsorbent surface area but does not depend on the nature of the adsorbent. This leads to a new method to determine the surface area of an adsorbent, S, that is independent of the form of the adsorption isotherm at low and moderate reduced pressures. Comparison with the BET areas for nitrogen shows that the new method gives the values of S which are very close to the BET results if K = 1.47 {times} 10{sup {minus}5} mol/m{sup 2} (for nitrogen). Analysis of adsorption data for macroporous adsorbents shows that the BET isotherm gives systematic deviations and that the experimental amount adsorbed is smaller than the value predicted by the BET equation (even in the range of the best agreement with experiment). These deviations lead to systematic error in the values of S of about 43%. Using K equal to K{sub f} = 1/{sigma}N{sub A} (=1.025 {times} 10{sup {minus}5} mol/m{sup 2} for nitrogen), the authors are able to eliminate systematic error in the surface area determination. Here {sigma} is the area occupied by one molecule and N{sub A} is the Avogadro number.

  8. Equilibrium and kinetic studies of C.I. Basic Blue 41 adsorption onto N, F-codoped flower-like TiO2 microspheres

    NASA Astrophysics Data System (ADS)

    Jiang, Yinhua; Luo, Yingying; Zhang, Fumei; Guo, Leiqun; Ni, Liang

    2013-05-01

    Three-dimensional (3D) N, F-codoped flower-like TiO2 microspheres were successfully synthesized by a hydrothermal method combined with calcination process. The as-prepared samples were characterized by XRD, FE-SEM and EDS. The adsorption abilities of prepared samples were investigated for the removal of C.I. Basic Blue 41(CB41) from aqueous solution. The FE-SEM and adsorption results showed that doping amount of NH4F affected the morphologies of samples and sample NFT-1 with the structure of 3D flower-like microsphere had the highest adsorption amount of CB41. The effects of varying parameters such as pH, contact time, initial dye concentration and temperature on the CB41 adsorption onto NFT-1 were further examined. Equilibrium data correlated with Langmuir, Freundlich and Temkin isotherms. The Langmuir isotherm showed the best fit to the equilibrium data. The kinetic experimental data were analyzed by three kinetic models including the pseudo-first-order model, the pseudo-second-order model and the intraparticle diffusion model to access the adsorption mechanism and the potential rate-controlling step. The pseudo-second-order kinetic model described best for the adsorption of CB41 on NFT-1 and the intraparticle diffusion was not the only rate-controlling step. The thermodynamics parameters as positive values of ΔH° and negative values of ΔG° showed that the adsorption process was endothermic and spontaneous in nature.

  9. Characteristics of equilibrium, kinetics studies for adsorption of Hg(II), Cu(II), and Ni(II) ions by thiourea-modified magnetic chitosan microspheres.

    PubMed

    Zhou, Limin; Wang, Yiping; Liu, Zhirong; Huang, Qunwu

    2009-01-30

    Magnetic chitosan microspheres were prepared and chemically modified with thiourea (TMCS) for adsorption of metal ions. TMCS obtained were investigated by means of X-ray diffraction (XRD), IR, magnetic properties and thermogravimetric analysis (TGA). The adsorption properties of TMCS toward Hg(2+), Cu(2+), and Ni(2+) ions were evaluated. Various factors affecting the uptake behavior such as contact time, temperature, pH and initial concentration of the metal ions were investigated. The kinetics was evaluated utilizing the pseudo-first-order, pseudo-second-order, and the intra-particle diffusion models. The equilibrium data were analyzed using the Langmuir, Freundlich, and Tempkin isotherm models. The adsorption kinetics followed the mechanism of the pseudo-second-order equation for all systems studied, evidencing chemical sorption as the rate-limiting step of adsorption mechanism and not involving a mass transfer in solution. The best interpretation for the equilibrium data was given by Langmuir isotherm, and the maximum adsorption capacities were 625.2, 66.7, and 15.3mg/g for Hg(2+), Cu(2+), and Ni(2+) ions, respectively. TMCS displayed higher adsorption capacity for Hg(2+) in all pH ranges studied. The adsorption capacity of the metal ions decreased with increasing temperature. The metal ion-loaded TMCS with were regenerated with an efficiency of greater than 88% using 0.01-0.1M ethylendiamine tetraacetic acid (EDTA).

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

    PubMed

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

    2010-01-15

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

  11. Molecular simulation of excess isotherm and excess enthalpy change in gas-phase adsorption.

    PubMed

    Do, D D; Do, H D; Nicholson, D

    2009-01-29

    We present a new approach to calculating excess isotherm and differential enthalpy of adsorption on surfaces or in confined spaces by the Monte Carlo molecular simulation method. The approach is very general and, most importantly, is unambiguous in its application to any configuration of solid structure (crystalline, graphite layer or disordered porous glass), to any type of fluid (simple or complex molecule), and to any operating conditions (subcritical or supercritical). The behavior of the adsorbed phase is studied using the partial molar energy of the simulation box. However, to characterize adsorption for comparison with experimental data, the isotherm is best described by the excess amount, and the enthalpy of adsorption is defined as the change in the total enthalpy of the simulation box with the change in the excess amount, keeping the total number (gas + adsorbed phases) constant. The excess quantities (capacity and energy) require a choice of a reference gaseous phase, which is defined as the adsorptive gas phase occupying the accessible volume and having a density equal to the bulk gas density. The accessible volume is defined as the mean volume space accessible to the center of mass of the adsorbate under consideration. With this choice, the excess isotherm passes through a maximum but always remains positive. This is in stark contrast to the literature where helium void volume is used (which is always greater than the accessible volume) and the resulting excess can be negative. Our definition of enthalpy change is equivalent to the difference between the partial molar enthalpy of the gas phase and the partial molar enthalpy of the adsorbed phase. There is no need to assume ideal gas or negligible molar volume of the adsorbed phase as is traditionally done in the literature. We illustrate this new approach with adsorption of argon, nitrogen, and carbon dioxide under subcritical and supercritical conditions.

  12. A simple method for measuring excess adsorption isotherms of organic eluent components on reversed-phase packing materials.

    PubMed

    Ohashi, Junji; Harada, Makoto; Okada, Tetsuo

    2017-02-01

    A simple frontal analysis method has been developed for the reliable measurement of excess adsorption isotherms of an organic component on reversed-phase adsorbents in a series of programmed concentration steps. In the present method, a peak, which is produced by refractive index change in column eluate, is detected at 589 nm; it represents the elution volume of the boundary. The method is applied to the measurement of the excess adsorption isotherms of organic eluent components from water on commercially available reversed-phase stationary phases. The results are in good agreement with the previously reported isotherms. We also measure the excess adsorption isotherms of organic eluent components from solutions containing electrolytes. There are not any interference peaks on the elution traces. The method is thus reliably applicable to the evaluation of the excess adsorption of organic eluent components in practical systems.

  13. Adsorption equilibrium of organic vapors on single-walled carbon nanotubes

    USGS Publications Warehouse

    Agnihotri, S.; Rood, M.J.; Rostam-Abadi, M.

    2005-01-01

    Gravimetric techniques were employed to determine the adsorption capacities of commercially available purified electric arc and HiPco single-walled carbon nanotubes (SWNTs) for organic compounds (toluene, methyl ethyl ketone (MEK), hexane and cyclohexane) at relative pressures, p/p0, ranging from 1 ?? 10-4 to 0.95 and at isothermal conditions of 25, 37 and 50 ??C. The isotherms displayed both type I and type II characteristics. Adsorption isotherm modeling showed that SWNTs are heterogeneous adsorbents, and the Freundlich equation best describes the interaction between organic molecules and SWNTs. The heats of adsorption were 1-4 times the heats of vaporization, which is typical for physical adsorption of organic vapors on porous carbons. ?? 2005 Elsevier Ltd. All rights reserved.

  14. Kinetic and Isotherm Modelling of the Adsorption of
Phenolic Compounds from Olive Mill Wastewater onto Activated Carbon

    PubMed Central

    Casazza, Alessandro A.; Perego, Patrizia

    2015-01-01

    Summary The adsorption of phenolic compounds from olive oil wastewater by commercial activated carbon was studied as a function of adsorbent quantity and temperature. The sorption kinetics and the equilibrium isotherms were evaluated. Under optimum conditions (8 g of activated carbon per 100 mL), the maximum sorption capacity of activated carbon expressed as mg of caffeic acid equivalent per g of activated carbon was 35.8 at 10 °C, 35.4 at 25 °C and 36.1 at 40 °C. The pseudo-second-order model was considered as the most suitable for kinetic results, and Langmuir isotherm was chosen to better describe the sorption system. The results confirmed the efficiency of activated carbon to remove almost all phenolic compound fractions from olive mill effluent. The preliminary results obtained will be used in future studies. The carbohydrate fraction of this upgraded residue could be employed to produce bioethanol, and adsorbed phenolic compounds can be recovered and used in different industries. PMID:27904350

  15. Adsorption of reactive dyes from aqueous solutions by fly ash: kinetic and equilibrium studies.

    PubMed

    Dizge, N; Aydiner, C; Demirbas, E; Kobya, M; Kara, S

    2008-02-11

    Adsorption kinetic and equilibrium studies of three reactive dyes namely, Remazol Brillant Blue (RB), Remazol Red 133 (RR) and Rifacion Yellow HED (RY) from aqueous solutions at various initial dye concentration (100-500 mg/l), pH (2-8), particle size (45-112.5 microm) and temperature (293-323 K) on fly ash (FA) were studied in a batch mode operation. The adsorbent was characterized with using several methods such as SEM, XRD and FTIR. Adsorption of RB reactive dye was found to be pH dependent but both RR and RY reactive dyes were not. The result showed that the amount adsorbed of the reactive dyes increased with increasing initial dye concentration and contact time. Batch kinetic data from experimental investigations on the removal of reactive dyes from aqueous solutions using FA have been well described by external mass transfer and intraparticle diffusion models. It was found that external mass transfer and intraparticle diffusion had rate limiting affects on the removal process. This was attributed to the relatively simple macropore structure of FA particles. The adsorption data fitted well with Langmuir and Freundlich isotherm models. The optimum conditions for removal of the reactive dyes were 100mg/l initial dye concentration, 0.6g/100ml adsorbent dose, temperature of 293 K, 45 microm particle size, pH 6 and agitation speed of 250 rpm, respectively. The values of Langmuir and Freundlich constants were found to increase with increasing temperature in the range 135-180 and 15-34 mg/g for RB, 47-86 and 1.9-3.7 mg/g for RR and 37-61 and 3.0-3.6 mg/g for RY reactive dyes, respectively. Different thermodynamic parameters viz., changes in standard free energy, enthalpy and entropy were evaluated and it was found that the reaction was spontaneous and endothermic in nature.

  16. Kinetics of degradation and adsorption-desorption isotherms of thiobencarb and oxadiargyl in calcareous paddy fields.

    PubMed

    Mahmoudi, Mojtaba; Rahnemaie, Rasoul; Es-haghi, Ali; Malakouti, Mohammad J

    2013-05-01

    Herbicides are an important source of contamination in paddy fields. Monitoring their fate and chemical interactions is therefore imperative for sustaining the environment and human health. To meet this purpose, field experiments were conducted to investigate kinetics of thiobencarb and oxadiargyl dissipation in soil and water of two paddy fields. Their adsorption and desorption isotherms were also determined in the soil samples. Variation in concentration was monitored for 60d in soil solution phase and for 315d in soil solid phase. In soil solution, concentrations of both herbicides were rapidly reduced within 5d and reached steady state within 20-30d. Analysis of experimental data resolved a half-life ≈2-4d for both herbicides. In soil solid phase, adsorption reaction played a dominant role in the first 10d. Afterwards, degradation reactions regulated the process. Variation in concentration was minimized after about 150d for thiobencarb and 80d for oxadiargyl. The half-lives were calculated ≈50d for thiobencarb and ≈20d for oxadiargyl, indicating that association with soil particles protect them effectively against degradation reactions. Adsorption isotherms confirmed that both herbicides were strongly adsorbed on soil particles. Furthermore, desorption data indicated that after four successive desorption steps, less than 9% thiobencarb and 1% oxadiargyl were released. This denotes that electrolyte ions in solution cannot adequately compete with and replace adsorbed thiobencarb and oxadiargyl molecules. This would lead to a considerable hysteresis between adsorption and desorption isotherms as was observed experimentally. Overall, it was concluded that both herbicides are among non-persistent and immobile herbicides in the paddy soils.

  17. 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.

  18. 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

  19. Adsorption of Pb(II) ions from aqueous solution by native and activated bentonite: kinetic, equilibrium and thermodynamic study.

    PubMed

    Kul, Ali Riza; Koyuncu, Hülya

    2010-07-15

    In this study, the adsorption kinetics, equilibrium and thermodynamics of Pb(II) ions on native (NB) and acid activated (AAB) bentonites were examined. The specific surface areas, pore size and pore-size distributions of the samples were fully characterized. The adsorption efficiency of Pb(II) onto the NB and AAB was increased with increasing temperature. The kinetics of adsorption of Pb(II) ions was discussed using three kinetic models, the pseudo-first-order, the pseudo-second-order and the intra-particle diffusion model. The experimental data fitted very well the pseudo-second-order kinetic model. The initial sorption rate and the activation energy were also calculated. The activation energy of the sorption was calculated as 16.51 and 13.66 kJ mol(-1) for NB and AAB, respectively. Experimental results were also analysed by the Langmuir, Freundlich and Dubinin-Redushkevich (D-R) isotherm equations at different temperatures. R(L) separation factor for Langmuir and the n value for Freundlich isotherm show that Pb(II) ions are favorably adsorbed by NB and AAB. Thermodynamic quantities such as Gibbs free energy (DeltaG), the enthalpy (DeltaH) and the entropy change of sorption (DeltaS) were determined as about -5.06, 10.29 and 0.017 kJ mol(-1) K(-1), respectively for AAB. It was shown that the sorption processes were an endothermic reactions, controlled by physical mechanisms and spontaneously.

  20. Adsorption behavior of direct red 80 and congo red onto activated carbon/surfactant: process optimization, kinetics and equilibrium.

    PubMed

    Cheng, Zhengjun; Zhang, Lei; Guo, Xiao; Jiang, Xiaohui; Li, Tian

    2015-02-25

    Adsorptions of congo red and direct red 80 onto activated carbon/surfactant from aqueous solution were optimized. The Box-Behnken design (BBD) has been employed to analyze the effects of concentration of surfactant, temperature, pH, and initial concentration of the dye in the adsorption capacity. Their corresponding experimental data could be evaluated excellently by second order polynomial regression models and the two models were also examined based on the analysis of variance and t test statistics, respectively. The optimum conditions were obtained as follows: Cs=34.10 μM, T=50°C, pH=3.5, and CCR=160 mg/L for the congo red system, and Cs=34.10 μM, T=50°C, pH=6.1, and CDR80=110 mg/L for the direct red 80 system. And in these conditions, the measured experimental maximum adsorption capacities for the congo red and direct red 80 removals were 769.48 mg/g and 519.90 mg/g, which were consistent with their corresponding predicted values, with small relative errors of -2.81% and -0.67%, respectively. The adsorption equilibrium and kinetics for the two dye adsorptions onto AC/DDAC were also investigated. The experimental data were fitted by four isotherm models, and Langmuir model presented the best fit. The kinetic studies indicated that the kinetic data followed the pseudo-second-order model.

  1. Ab Initio Prediction of Adsorption Isotherms for Small Molecules in Metal-Organic Frameworks.

    PubMed

    Kundu, Arpan; Piccini, GiovanniMaria; Sillar, Kaido; Sauer, Joachim

    2016-10-17

    For CO and N2 on Mg(2+) sites of the metal-organic framework CPO-27-Mg (Mg-MOF-74), ab initio calculations of Gibbs free energies of adsorption have been performed. Combined with the Bragg-Williams/Langmuir model and taking into account the experimental site availability (76.5%), we obtained adsorption isotherms in close agreement with those in experiment. The remaining deviations in the Gibbs free energy (about 1 kJ/mol) are significantly smaller than the "chemical accuracy" limit of about 4 kJ/mol. The presented approach uses (i) a DFT dispersion method (PBE+D2) to optimize the structure and to calculate anharmonic frequencies for vibrational partition functions and (ii) a "hybrid MP2:(PBE+D2)+ΔCCSD(T)" method to determine electronic energies. With the achieved accuracy (estimated uncertainty ±1.4 kJ/mol), the ab initio energies become useful benchmarks for assessing different DFT + dispersion methods (PBE+D2, B3LYP+D*, and vdW-D2), whereas the ab initio heats, entropies, and Gibbs free energies of adsorption are used to assess the reliability of experimental values derived from fitting isotherms or from variable-temperature IR studies.

  2. Biosorption of food dyes onto Spirulina platensis nanoparticles: equilibrium isotherm and thermodynamic analysis.

    PubMed

    Dotto, G L; Lima, E C; Pinto, L A A

    2012-01-01

    The biosorption of food dyes FD&C red no. 40 and acid blue 9 onto Spirulina platensis nanoparticles was studied at different conditions of pH and temperature. Four isotherm models were used to evaluate the biosorption equilibrium and the thermodynamic parameters were estimated. Infra red analysis (FT-IR) and energy dispersive X-ray spectroscopy (EDS) were used to verify the biosorption behavior. The maximum biosorption capacities of FD&C red no. 40 and acid blue 9 were found at pH 4 and 298 K, and the values were 468.7 mg g(-1) and 1619.4 mg g(-1), respectively. The Sips model was more adequate to fit the equilibrium experimental data (R2>0.99 and ARE<5%). Thermodynamic study showed that the biosorption was exothermic, spontaneous and favorable. FT-IR and EDS analysis suggested that at pH 4 and 298 K, the biosorption of both dyes onto nanoparticles occurred by chemisorption.

  3. Sediment-air equilibrium partitioning of semi-volatile hydrophobic organic compounds. Part 1. Method development and water vapor sorption isotherm.

    PubMed

    de Seze, G; Valsaraj, K T; Reible, D D; Thibodeaux, L J

    2000-05-15

    Contaminated sediments that become exposed to air as a result of dredging and disposal in confined disposal facilities are potential sources of air pollution. A critical parameter to develop emission estimation models is the equilibrium partition coefficient of contaminants, between sediment and air. In this first of two articles, we present a method, based on gas saturation in a flowing stream, to study both the adsorption of water and semi-volatile organic compounds on a sediment from the Campus Lake, Baton Rouge, LA, USA. The experimental set-up was used to determine the adsorption isotherm for water partitioning between sediment and pore-air. A detailed characterization of the sediment surface area and pore volume was used to develop an adsorption-condensation model for predicting water sorption on sediment. The model was used to estimate the importance of water adsorption on mineral surfaces and condensation in pores. This information serves, in the accompanying second article in the series, as the basis for the modeling of the partitioning of phenanthrene, and dibenzofuran.

  4. Adsorptive potential of cationic Basic Yellow 2 (BY2) dye onto natural untreated clay (NUC) from aqueous phase: Mass transfer analysis, kinetic and equilibrium profile

    NASA Astrophysics Data System (ADS)

    Öztürk, A.; Malkoc, E.

    2014-04-01

    In this work, natural untreated clay (NUC) was studied for the removal of Basic Yellow 2 (BY2) from aqueous solution in batch system. The effects of initial BY2 concentration, contact time, solution temperature and solution pH on BY2 adsorption were investigated. Nitrogen sorption measurements were employed to investigate the variation in surface and pore properties after dye adsorption. The adsorbent was characterized by means of FTIR, PSD, TEM, XRD and BET analysis. The equilibrium adsorption data were analyzed by Langmuir, Freundlich, Temkin and Scatchard isotherm models. The maximum monolayer adsorption capacity was found to be 833.33 mg/g at 25 °C (at room temperature). The pseudo-second-order kinetic model provided the best fit to the experimental datas compared with pseudo-first-order kinetic adsorption models. To explain mass transfer mechanism of BY2 adsorption, obtained experimental datas were applied Weber and Morris model, Body and Frusawa and Smith models. The results show that the adsorption process is controlled by film diffusion. The thermodynamic parameters such as, Gibbs free energy changes (ΔG°), standard enthalpy change (ΔH°) and standard entropy change (ΔS°) were determined. Adsorption of BY2 on NUC is exothermic and spontaneous in nature. The calculated activation energy of adsorption was found to be 5.24 kJ/mol for BY2. This value indicates that the adsorption process is a physisorption.

  5. Adsorption of ammonium ion by coconut shell-activated carbon from aqueous solution: kinetic, isotherm, and thermodynamic studies.

    PubMed

    Boopathy, Ramasamy; Karthikeyan, Sekar; Mandal, Asit Baran; Sekaran, Ganesan

    2013-01-01

    Ammonium ions are one of the most encountered nitrogen species in polluted water bodies. High level of ammonium ion in aqueous solution imparts unpleasant taste and odor problems, which can interfere with the life of aquatics and human population when discharged. Many chemical methods are developed and being used for removal of ammonium ion from aqueous solution. Among various techniques, adsorption was found to be the most feasible and environmentally friendly with the use of natural-activated adsorbents. Hence, in this study, coconut shell-activated carbon (CSAC) was prepared and used for the removal of ammonium ion by adsorption techniques. Ammonium chloride (analytical grade) was purchased from Merck Chemicals for adsorption studies. The CSAC was used to adsorb ammonium ions under stirring at 100 rpm, using orbital shaker in batch experiments. The concentration of ammonium ion was estimated by ammonia distillate, using a Buchi distillation unit. The influence of process parameters such as pH, temperature, and contact time was studied for adsorption of ammonium ion, and kinetic, isotherm models were validated to understand the mechanism of adsorption of ammonium ion by CSAC. Thermodynamic properties such as ∆G, ∆H, and ∆S were determined for the ammonium adsorption, using van't Hoff equation. Further, the adsorption of ammonium ion was confirmed through instrumental analyses such as SEM, XRD, and FTIR. The optimum conditions for the effective adsorption of ammonium ion onto CSAC were found to be pH 9.0, temperature 283 K, and contact time 120 min. The experimental data was best followed by pseudosecond order equation, and the adsorption isotherm model obeyed the Freundlich isotherm. This explains the ammonium ion adsorption onto CSAC which was a multilayer adsorption with intraparticle diffusion. Negative enthalpy confirmed that this adsorption process was exothermic. The instrumental analyses confirmed the adsorption of ammonium ion onto CSAC.

  6. 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.

  7. Phenol adsorption on surface-functionalized iron oxide nanoparticles: modeling of the kinetics, isotherm, and mechanism

    NASA Astrophysics Data System (ADS)

    Yoon, Soon Uk; Mahanty, Biswanath; Ha, Hun Moon; Kim, Chang Gyun

    2016-06-01

    Phenol adsorption from aqueous solution was carried out using uncoated and methyl acrylic acid (MAA)-coated iron oxide nanoparticles (NPs), having size <10 nm, as adsorbents. Batch adsorption studies revealed that the phenol removal efficiency of MAA-coated NPs (950 mg g-1) is significantly higher than that of uncoated NPs (550 mg g-1) under neutral to acidic conditions. However, this improvement disappears above pH 9. The adsorption data under optimized conditions (pH 7) were modeled with pseudo-first- and pseudo-second-order kinetics and subjected to Freundlich and Langmuir isotherms. The analysis determined that pseudo-second-order kinetics and the Freundlich model are appropriate for both uncoated and MAA-coated NPs (all R 2 > 0.98). X-ray photoelectron spectroscopy analysis of pristine and phenol-adsorbed NPs revealed core-level binding energy and charge for Fe(2 s) and O(1 s) on the NP surfaces. The calculations suggest that phenol adsorption onto MAA-coated NPs is a charge transfer process, where the adsorbate (phenol) acts as an electron donor and the NP surface (Fe, O) as an electron acceptor. However, a physisorption process appears to be the relevant mechanism for uncoated NPs.

  8. 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.

  9. Characterizing particle-scale equilibrium adsorption and kinetics of uranium(VI) desorption from U-contaminated sediments

    SciTech Connect

    Stoliker, Deborah L.; Liu, Chongxuan; Kent, Douglas B.; Zachara, John M.

    2013-02-12

    Rates of contaminant U(VI) release from individual size fractions of a composite sediment from the seasonally saturated lower vadose zone of the Hanford 300-Area were examined in flow-through batch reactors to maintain quasi-constant chemical conditions. Variability in equilibrium adsorption among the various size fractions was determined in static batch reactors and analyzed using the surface complexation modeling approach. The estimated stoichiometric coefficients of U(VI) surface complexation reactions with respect to pH and carbonate concentrations varied with size fractions. This source of variability significantly increased the uncertainty in U(VI) conditional equilibrium constants over that estimated from experimental errors alone. A minimum difference between conditional equilibrium constants was established in order to evaluate statistically significant differences between sediment adsorption properties. A set of equilibrium and kinetic expressions for cation exchange, calcite dissolution, aerobic respiration, and silica dissolution were incorporated in a reaction-rate model to describe the temporal evolution of solute concentrations observed during the flow-through batch experiments. Parameters in the reaction-rate model, calibrated using experimental data for select size fractions, predicted the changes in solute concentrations for the bulk, <2 mm, sediment sample. Kinetic U(VI) desorption was well described using a multi-rate surface complexation model with an assumed lognormal distribution for the rate constants. The estimated mean and standard deviation were the same for all < 2mm size fractions, but differed in the 2-8mm size fraction. Micropore volumes in the varied size fractions were also similar as assessed using t-plots to analyze N2 desorption data. These findings provide further support for the link between microporosity and particle-scale mass transfer rates controlling kinetic U(VI) adsorption/desorption and for the utility of N2 desorption

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

    PubMed

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

    2015-06-01

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

  11. Adsorption of Zinc(II) on diatomite and manganese-oxide-modified diatomite: a kinetic and equilibrium study.

    PubMed

    Caliskan, Necla; Kul, Ali Riza; Alkan, Salih; Sogut, Eda Gokirmak; Alacabey, Ihsan

    2011-10-15

    The removal of Zn(II) ions from aqueous solution was studied using natural and MnO(2) modified diatomite samples at different temperatures. The linear Langmuir, Freundlich and Dubinin-Radushkevich (D-R) adsorption equations were applied to describe the equilibrium isotherms. From the D-R model, the mean adsorption energy was calculated as >8 kJ mol(-1), indicating that the adsorption of Zn(II) onto diatomite and Mn-diatomite was physically carried out. In addition, the pseudo-first-order, pseudo-second-order and intraparticle diffusion models were used to determine the kinetic data. The experimental data were well fitted by the pseudo-second-order kinetic model. Thermodynamic parameters such as the enthalpy (ΔH(0)), Gibbs' free energy (ΔG(0)) and entropy (ΔS(0)) were calculated for natural and MnO(2) modified diatomite. These values showed that the adsorption of Zn(II) ions onto diatomite samples was controlled by a physical mechanism and occurred spontaneously.

  12. 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.

  13. Adsorption kinetics, thermodynamics and isotherm of Hg(II) from aqueous solutions using buckwheat hulls from Jiaodong of China.

    PubMed

    Wang, Zengdi; Yin, Ping; Qu, Rongjun; Chen, Hou; Wang, Chunhua; Ren, Shuhua

    2013-02-15

    The adsorption kinetics and adsorption isotherms of buckwheat hulls in the region of Jiaodong, China (BHJC) for Hg(II) were investigated. Results revealed that the adsorption kinetics of BHJC for Hg(II) were well described by a pseudo second-order reaction model, and the adsorption thermodynamic parameters ΔG, ΔH and ΔS were -5.83 kJ mol(-1)(35°C), 73.1, and 256 JK(-1) mol(-1), respectively. Moreover, Langmuir, Freundlich and Redlich-Peterson isotherm models were applied to analyse the experimental data and to predict the relevant isotherm parameters. The best interpretation for the experimental data was given by the Langmuir isotherm equation, and the maximum adsorption capacity for Hg(II) is 243.90 mg/g at 35°C. Furthermore, investigation of the adsorption selectivity showed that BHJC displayed strong affinity for mercury in the aqueous solutions and exhibited 100% selectivity for mercury in the presence of Zn(II) and Cd(II).

  14. 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.

  15. On the 2D-transition, hysteresis and thermodynamic equilibrium of Kr adsorption on a graphite surface.

    PubMed

    Diao, Rui; Fan, Chunyan; Do, D D; Nicholson, D

    2015-12-15

    The adsorption and desorption of Kr on graphite at temperatures in the range 60-88K, was systematically investigated using a combination of several simulation techniques including: Grand Canonical Monte Carlo (GCMC), Canonical kinetic-Monte Carlo (C-kMC) and the Mid-Density Scheme (MDS). Particular emphasis was placed on the gas-solid, gas-liquid and liquid-solid 2D phase transitions. For temperatures below the bulk triple point, the transition from a 2D-liquid-like monolayer to a 2D-solid-like state is manifested as a sub-step in the isotherm. A further increase in the chemical potential leads to another rearrangement of the 2D-solid-like state from a disordered structure to an ordered structure that is signalled by (1) another sub-step in the monolayer region and (2) a spike in the plot of the isosteric heat versus density at loadings close to the dense monolayer coverage concentration. Whenever a 2D transition occurs in a grand canonical isotherm it is always associated with a hysteresis, a feature that is not widely recognised in the literature. We studied in details this hysteresis with the analysis of the canonical isotherm, obtained with C-kMC, which exhibits a van der Waals (vdW) type loop with a vertical segment in the middle. We complemented the hysteresis loop and the vdW curve with the analysis of the equilibrium transition obtained with the MDS, and found that the equilibrium transition coincides exactly with the vertical segment of the C-kMC isotherm, indicating the co-existence of two phases at equilibrium. We also analysed adsorption at higher layers and found that the 2D-coexistence is also observed, provided that the temperature is well below the triple point. Finally the 2D-critical temperatures were obtained for the first three layers and they are in good agreement with the experimental data in the literature.

  16. Determination of kinetic and equilibrium parameters of the batch adsorption of Mn(II), Co(II), Ni(II) and Cu(II) from aqueous solution by black carrot (Daucus carota L.) residues.

    PubMed

    Güzel, Fuat; Yakut, Hakan; Topal, Giray

    2008-05-30

    In this study, the effect of temperature on the adsorption of Mn(II), Ni(II), Co(II) and Cu(II) from aqueous solution by modified carrot residues (MCR) was investigated. The equilibrium contact times of adsorption process for each heavy metals-MCR systems were determined. Kinetic data obtained for each heavy metal by MCR at different temperatures were applied to the Lagergren equation, and adsorption rate constants (kads) at these temperatures were determined. These rate constants related to the adsorption of heavy metal by MCR were applied to the Arrhenius equation, and activation energies (Ea) were determined. In addition, the isotherms for adsorption of each heavy metal by MCR at different temperatures were also determined. These isothermal data were applied to linear forms of isotherm equations that they fit the Langmuir adsorption isotherm, and the Langmuir constants (qm and b) were calculated. b constants determined at different temperatures were applied to thermodynamic equations, and thermodynamic parameters such as enthalpy (Delta H), free energy (Delta G), and entropy (Delta S) were calculated and these values show that adsorption of heavy metal on MCR was an endothermic process and process of adsorption was favoured at high temperatures.

  17. 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.

  18. Evaluation of a predictive model for air/surface adsorption equilibrium constants and enthalpies.

    PubMed

    Arp, Hans Peter H; Goss, Kai-Uwe; Schwarzenbach, René P

    2006-01-01

    A model used to predict equilibrium adsorption to surfaces using a poly-parameter linear free-energy relationship as well as an empirical model used to predict enthalpies of adsorption of volatile compounds were evaluated with new experimental data to cover semivolatile compounds and a larger variability of compound classes. Equilibrium adsorption constants on a quartz surface ranging over seven orders of magnitude were measured for 142 compounds, and enthalpies of adsorption on a quartz surface from -33.7 to -99.8 kJ/mol were measured for 76 compounds. Agreement between experimental and predicted data was within a factor of two (82.1%) or three (100.0%) for the equilibrium adsorption constants and within 20% for the enthalpy of adsorption values. Thus, the scatter in the validation data sets reported here were practically the same as that for the calibration data sets used to derive the models. The few outliers that we identified in the prediction of equilibrium adsorption constants likely are caused by either shortcomings of the reported sorbate parameters or the occurrence of chemical speciation in the water layer on the surface of the quartz.

  19. Nonlinear isotherm and kinetics of adsorption of copper from aqueous solutions on bentonite

    NASA Astrophysics Data System (ADS)

    Sadeghalvad, Bahareh; Khosravi, Sara; Azadmehr, Amir Reza

    2016-11-01

    Bentonite is one of the most significant of clay minerals that has been studied extensively due to its potential applications in removal of various environmental pollutants. This ability is related to its high ionic exchange capacity and high specific surface area. Copper is one of the important elements of non-ferrous metals found in industrial waste waters. In the present work, the removal of copper from aqueous solutions with Iranian bentonite (from Birjand area, southeastern Iran) used without any chemical pretreatment, was studied. The experimental results were fitted by adsorption isotherms equations with two or three parameters, which include Langmuir, Freundlich, Dubinin-Radushkevich (D-R), Redlich-Peterson, Khan, and Toth models. The best correlation coefficient ( r 2) is 0.9879 observed for Langmuir model, maximum adsorption capacity of bentonite was 55.71 mg/g. The first-order and pseudo-second-order kinetic equations were used to describe the kinetics of adsorption. The experimental data were well fitted by the pseudo-second-order kinetics.

  20. Equilibrium isotherm studies for the uptake of cadmium and lead ions onto sugar beet pulp.

    PubMed

    Pehlivan, E; Yanik, B H; Ahmetli, G; Pehlivan, M

    2008-06-01

    The adsorption of Cd2+ and Pb2+ on sugar beet pulp (SBP), a low-cost material, has been studied. In the present work, the abilities of native (SBP) to remove cadmium (Cd2+) and lead (Pb2+) ions from aqueous solutions were compared. The (SBP) an industrial by product and solid waste of sugar industry were used for the removal of Cd2+ and Pb2+ ions from aqueous water. Batch adsorption studies were carried out to examine the influence of various parameters such as initial pH, adsorbent dose, initial metal ion concentration, and time on uptake. The sorption process was relatively fast and equilibrium was reached after about 70 min of contact. As much as 70-75% removal of Cd2+ and Pb2+ ions for (SBP) are possible in about 70 min, respectively, under the batch test conditions. Uptake of Cd2+ and Pb2+ ions on (SBP) showed a pH-dependent profile. The overall uptake for the (SBP) is at a maximum at pH 5.3 and gives up to 46.1 mg g(-1) for Cd2+ and at pH 5.0 and gives 43.5 mg g(-1) for Pb2+ for (SBP), which seems to be removed exclusively by ion exchange, physical sorption and chelation. A dose of 8 gL(-1) was sufficient for the optimum removal of both the metal ions. The Freundlich represented the sorption data for (SBP). In the presence of 0.1M NaNO3 the level of metal ion uptake was found to reach its maximum value very rapidly with the speed increasing both with the (SPB) concentration and with increasing initial pH of the suspension. The reversibility of the process was investigated. The desorption of Cd2+ and Pb2+ ions which were previously deposited on the (SBP) back into the deionised water was observed only in acidic pH values during one day study period and was generally rather low. The extent of adsorption for both metals increased along with an increase of the (SBP) dosage. (SBP), which is cheap and highly selective, therefore seems to be a promising substrate to entrap heavy metals in aqueous solutions.

  1. Equilibrium, kinetic and thermodynamic studies on the adsorption of phenol onto graphene

    SciTech Connect

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

    2012-08-15

    Graphical abstract: The effect of temperature on phenol adsorbed by graphene shows that the equilibrium adsorption capacity of phenol increases with the increase in temperature from 285 to 333 K. Increasing adsorption capacities with temperature indicates that the adsorption of phenol is controlled by an endothermic reaction. Highlights: ► The graphene has high phenol adsorption capacity. ► The graphene has a high specific surface area of 305 m{sup 2}/g. ► The adsorption capacity is high at acidic pH range. ► The graphene has rapid phenol adsorption rate. ► Phenol adsorption is a spontaneous and endothermic process. -- Abstract: Graphene, a new member of carbon family, has been prepared, characterized and used as adsorbent to remove phenol from aqueous solution. The effect parameters including pH, dosage, contact time, and temperature on the adsorption properties of phenol onto graphene were investigated. The results showed that the maximum adsorption capacity can reach 28.26 mg/g at the conditions of initial phenol concentration of 50 mg/L, pH 6.3 and 285 K. Adsorption data were well described by both Freundlich and Langmuir models. The kinetic study illustrated that the adsorption of phenol onto graphene fit the pseudo second-order model. The thermodynamic parameters indicated that the adsorption of phenol onto graphene was endothermic and spontaneous.

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

    NASA Astrophysics Data System (ADS)

    Ahmed, Salwa A.; Soliman, Ezzat M.

    2013-11-01

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

  3. Equilibrium models and kinetic for the adsorption of methylene blue on Co-hectorites.

    PubMed

    Ma, Jun; Jia, Yong-Zhong; Jing, Yan; Sun, Jin-He; Yao, Ying; Wang, Xiao-Hua

    2010-03-15

    The adsorption of methylene blue (MB) onto the surface of cobalt doping hectorite (Co-hectorite) was systematically studied. The physical properties of Co-hectorites were investigated, where characterizations were carried out by X-ray diffraction (XRD) and Electron Diffraction Spectrum (EDS) techniques, and morphology was examined by nitrogen adsorption. The sample with a Co content 5% (m/m) had a higher specific surface area than other Co-hectorites. The pore diameters were distributed between 2.5 and 5.0 nm. The adsorption results revealed that Co-hectorite surfaces possessed effective interactions with MB and bases, and greatest adsorption capacity achieved with Co content 5%, where the best-fit isotherm model was the Langmuir adsorption model. Kinetic studies were fitted to the pseudo-second-order kinetic model. The intraparticle diffusion was not the rate-limiting step for the whole reaction.

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

    PubMed

    Chaparadza, Allen; Hossenlopp, Jeanne M

    2012-01-01

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

  5. Adsorption of chromium (VI) by ethylenediamine-modified cross-linked magnetic chitosan resin: isotherms, kinetics and thermodynamics.

    PubMed

    Hu, Xin-jiang; Wang, Jing-song; Liu, Yun-guo; Li, Xin; Zeng, Guang-ming; Bao, Zheng-lei; Zeng, Xiao-xia; Chen, An-wei; Long, Fei

    2011-01-15

    The adsorption of chromium (VI) ions from aqueous solution by ethylenediamine-modified cross-linked magnetic chitosan resin (EMCMCR) was studied in a batch adsorption system. Chromium (VI) removal is pH dependent and the optimum adsorption was observed at pH 2.0. The adsorption rate was extremely fast and the equilibrium was established within 6-10min. The adsorption data could be well interpreted by the Langmuir and Temkin model. The maximum adsorption capacities obtained from the Langmuir model are 51.813mgg(-1), 48.780mgg(-1) and 45.872mgg(-1) at 293, 303 and 313K, respectively. The adsorption process could be described by pseudo-second-order kinetic model. The intraparticle diffusion study revealed that film diffusion might be involved in the present case. Thermodynamic parameters revealed the feasibility, spontaneity and exothermic nature of adsorption. The sorbents were successfully regenerated using 0.1N NaOH solutions.

  6. Non-equilibrium Thermodynamic Dissolution Theory for Multi-Component Solid/Liquid Surfaces Involving Surface Adsorption and Radiolysis Kinetics

    SciTech Connect

    Stout, R B

    2001-04-01

    A theoretical expression is developed for the dissolution rate response for multi-component radioactive materials that have surface adsorption kinetics and radiolysis kinetics when wetted by a multi-component aqueous solution. An application for this type of dissolution response is the performance evaluation of multi-component spent nuclear fuels (SNFs) for long term interim storage and for geological disposition. Typically, SNF compositions depend on initial composition, uranium oxide and metal alloys being most common, and on reactor burnup which results in a wide range of fission product and actinide concentrations that decay by alpha, beta, and gamma radiation. These compositional/burnup ranges of SNFs, whether placed in interim storage or emplaced in a geologic repository, will potentially be wetted by multi-component aqueous solutions, and these solutions may be further altered by radiolytic aqueous species due to three radiation fields. The solid states of the SNFs are not thermodynamically stable when wetted and will dissolve, with or without radiolysis. The following development of a dissolution theory is based on a non-equilibrium thermodynamic analysis of energy reactions and energy transport across a solid-liquid phase change discontinuity that propagates at a quasi-steady, dissolution velocity. The integral form of the energy balance equation is used for this spatial surface discontinuity analysis. The integral formulation contains internal energy functional of classical thermodynamics for both the SNFs' solid state and surface adsorption species, and the adjacent liquid state, which includes radiolytic chemical species. The steady-state concentrations of radiolytic chemical species are expressed by an approximate analysis of the decay radiation transport equation. For purposes of illustration a modified Temkin adsorption isotherm was assumed for the surface adsorption kinetics on an arbitrary, finite area of the solid-liquid dissolution interface. For

  7. Adsorption of methylene blue onto activated carbon produced from tea (Camellia sinensis L.) seed shells: kinetics, equilibrium, and thermodynamics studies.

    PubMed

    Gao, Jun-Jie; Qin, Ye-Bo; Zhou, Tao; Cao, Dong-Dong; Xu, Ping; Hochstetter, Danielle; Wang, Yue-Fei

    2013-07-01

    Tea (Camellia sinensis L.) seed shells, the main byproduct of the manufacture of tea seed oil, were used as precursors for the preparation of tea activated carbon (TAC) in the present study. A high yield (44.1%) of TAC was obtained from tea seed shells via a one-step chemical method using ZnCl2 as an agent. The Brunauer-Emmett-Teller (BET) surface area and the total pore volumes of the obtained TAC were found to be 1530.67 mg(2)/g and 0.7826 cm(3)/g, respectively. The equilibrium adsorption results were complied with Langmuir isotherm model and its maximum monolayer adsorption capacity was 324.7 mg/g for methylene blue. Adsorption kinetics studies indicated that the pseudo-second-order model yielded the best fit for the kinetic data. An intraparticle diffusion model suggested that the intraparticle diffusion was not the only rate-controlling step. Thermodynamics studies revealed the spontaneous and exothermic nature of the sorption process. These results indicate that tea seed shells could be utilized as a renewable resource to develop activated carbon which is a potential adsorbent for methylene blue.

  8. Adsorption of methylene blue onto activated carbon produced from tea (Camellia sinensis L.) seed shells: kinetics, equilibrium, and thermodynamics studies*

    PubMed Central

    Gao, Jun-jie; Qin, Ye-bo; Zhou, Tao; Cao, Dong-dong; Xu, Ping; Hochstetter, Danielle; Wang, Yue-fei

    2013-01-01

    Tea (Camellia sinensis L.) seed shells, the main byproduct of the manufacture of tea seed oil, were used as precursors for the preparation of tea activated carbon (TAC) in the present study. A high yield (44.1%) of TAC was obtained from tea seed shells via a one-step chemical method using ZnCl2 as an agent. The Brunauer-Emmett-Teller (BET) surface area and the total pore volumes of the obtained TAC were found to be 1 530.67 mg2/g and 0.782 6 cm3/g, respectively. The equilibrium adsorption results were complied with Langmuir isotherm model and its maximum monolayer adsorption capacity was 324.7 mg/g for methylene blue. Adsorption kinetics studies indicated that the pseudo-second-order model yielded the best fit for the kinetic data. An intraparticle diffusion model suggested that the intraparticle diffusion was not the only rate-controlling step. Thermodynamics studies revealed the spontaneous and exothermic nature of the sorption process. These results indicate that tea seed shells could be utilized as a renewable resource to develop activated carbon which is a potential adsorbent for methylene blue. PMID:23825151

  9. Characterizing size and porosity of hollow nanoparticles: SAXS, SANS, TEM, DLS, and adsorption isotherms compared.

    PubMed

    Chen, Zhi Hong; Kim, Chanhoi; Zeng, Xiang-bing; Hwang, Sun Hye; Jang, Jyongsik; Ungar, Goran

    2012-10-30

    A combination of experimental methods, including transmission and grazing incidence small-angle X-ray scattering (SAXS and GISAXS), small-angle neutron scattering (SANS), transmission electron microscopy (TEM), dynamic light scattering (DLS), and N(2) adsorption-desorption isotherms, was used to characterize SiO(2)/TiO(2) hollow nanoparticles (HNPs) of sizes between 25 and 100 nm. In the analysis of SAXS, SANS, and GISAXS data, the decoupling approximation and the Percus-Yevick structure factor approximation were used. Brunauer-Emmett-Teller, t-plot, and a spherical pore model based on Kelvin equation were applied in the treatment of N(2) isotherms. Extracted parameters from the scattering and TEM methods are the average outer and inner diameters and polydispersity. Good agreement was achieved between different methods for these extracted parameters. Merits, advantages, and disadvantages of the different methods are discussed. Furthermore, the combination of these methods provided us with information on the porosity of the shells of HNPs and the size of intrawall pores, which are critical to the applications of HNPs as drug delivery vehicles and catalyst supports.

  10. Characterization of CaF2 surfaces using Adsorption-Desorption Isotherms and Atomic Force Microscopy

    NASA Astrophysics Data System (ADS)

    Wadleigh, L. R.; Luhman, D. R.; Bumcrot, P. G.

    2012-02-01

    We are interested in using rough CaF2 films to study the superfluid transition in two-dimensional helium systems. These experiments require quantitative information regarding the topography of the CaF2 surfaces. The surface roughness of CaF2 films is known to increase with film thickness as has been shown with previous atomic force microscopy (AFM) measurements [1]. We have fabricated a series of CaF2 samples of different film thicknesses and thus different surface roughnesses. These surfaces were studied using AFM and adsorption-desorption isotherm measurements with liquid nitrogen at T=77 K. The isotherm measurements allow us to determine the pore size distribution of each CaF2 film thickness. We find the emergence of hysteretic capillary condensation due to deep pores in the CaF2 as the film thickness increases. The development of these deep pores is also seen in our AFM measurements. Our combined results provide a detailed description of CaF2 surface roughness which can be utilized in the planned superfluid experiment. [1] D.R. Luhman and R.B. Hallock, Phys Rev. E 70, 051606 (2004).

  11. 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.

  12. 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.

  13. 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.

  14. Heterogeneity of activated carbons in adsorption of phenols from aqueous solutions—Comparison of experimental isotherm data and simulation predictions

    NASA Astrophysics Data System (ADS)

    Podkościelny, P.; Nieszporek, K.

    2007-01-01

    Surface heterogeneity of activated carbons is usually characterized by adsorption energy distribution (AED) functions which can be estimated from the experimental adsorption isotherms by inverting integral equation. The experimental data of phenol adsorption from aqueous solution on activated carbons prepared from polyacrylonitrile (PAN) and polyethylene terephthalate (PET) have been taken from literature. AED functions for phenol adsorption, generated by application of regularization method have been verified. The Grand Canonical Monte Carlo (GCMC) simulation technique has been used as verification tool. The definitive stage of verification was comparison of experimental adsorption data and those obtained by utilization GCMC simulations. Necessary information for performing of simulations has been provided by parameters of AED functions calculated by regularization method.

  15. Equilibrium, kinetic and thermodynamic studies of mercury adsorption on almond shell.

    PubMed

    Khaloo, Shokooh Sadat; Matin, Amir Hossein; Sharifi, Sahar; Fadaeinia, Masoumeh; Kazempour, Narges; Mirzadeh, Shaghayegh

    2012-01-01

    The application of almond shell as a low cost natural adsorbent to remove Hg(2+) from aqueous solution was investigated. Batch experiments were carried out to evaluate the adsorption capacity of the material. The chemical and physical parameters such as pH, sorbent amount, initial ion concentration, and contact time were optimized for the maximum uptake of mercury onto the solid surface. Adsorption isotherms were expressed by Langmuir and Freundlich adsorption models, and the experimental data were found to fit the Langmuir model rather than the Freundlich. The maximum adsorption capacity obtained from the Langmuir isotherm was 135.13 mg/g. A kinetic study was carried out with pseudo-first-order and pseudo-second-order reaction equations and it was found that the Hg(2+) uptake process followed the pseudo-second-order rate expression. The thermodynamic values, ΔG(0), ΔH(0) and ΔS(0), indicated that adsorption was an endothermic and spontaneous process. The potential of this material for mercury elimination was demonstrated by efficient Hg(2+) removal from a synthetic effluent.

  16. Competitive adsorption of metal cations onto two gram positive bacteria: testing the chemical equilibrium model

    NASA Astrophysics Data System (ADS)

    Fowle, David A.; Fein, Jeremy B.

    1999-10-01

    In order to test the ability of a surface complexation approach to account for metal-bacteria interactions in near surface fluid-rock systems, we have conducted experiments that measure the extent of adsorption in mixed metal, mixed bacteria systems. This study tests the surface complexation approach by comparing estimated extents of adsorption based on surface complexation modeling to those we observed in the experimental systems. The batch adsorption experiments involved Ca, Cd, Cu, and Pb adsorption onto the surfaces of 2 g positive bacteria: Bacillus subtilis and Bacillus licheniformis. Three types of experiments were performed: 1. Single metal (Ca, Cu, Pb) adsorption onto a mixture of B. licheniformis and B. subtilis; 2. mixed metal (Cd, Cu, and Pb; Ca and Cd) adsorption onto either B. subtilis or B. licheniformis; and 3. mixed or single metal adsorption onto B. subtilis and B. licheniformis. %Independent of the experimental results, and based on the site specific stability constants for Ca, Cd, Cu, and Pb interactions with the carboxyl and phosphate sites on B. licheniformis and B. subtilis determined by Fein et al. (1997), by Daughney et al. (1998) and in this study, we estimate the extent of adsorption that is expected in the above experimental systems. Competitive cation adsorption experiments in both single and double bacteria systems exhibit little adsorption at pH values less than 4. With increasing pH above 4.0, the extent of Ca, Cu, Pb and Cd adsorption also increases due to the increased deprotonation of bacterial surface functional groups. In all cases studied, the estimated adsorption behavior is in excellent agreement with the observations, with only slight differences that were within the uncertainties of the estimation and experimental procedures. Therefore, the results indicate that the use of chemical equilibrium modeling of aqueous metal adsorption onto bacterial surfaces yields accurate predictions of the distribution of metals in complex

  17. Adsorption kinetics and equilibrium study of nitrogen species onto radiata pine (Pinus radiata) sawdust.

    PubMed

    Harmayani, Kadek D; Faisal Anwar, A H M

    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.

  18. Adsorption kinetics and equilibrium studies for removal of acid azo dyes by aniline formaldehyde condensate

    NASA Astrophysics Data System (ADS)

    Terangpi, Praisy; Chakraborty, Saswati

    2016-12-01

    Adsorption of two acid dyes named Acid orange 8 (AO8) and Acid violet 7 (AV7) by amine based polymer aniline formaldehyde condensate (AFC) was studied. Adsorption of both dyes was favored at acidic pH. Electrostatic attraction between protonated amine group (NH3 +) of AFC and anionic sulfonate group (SO3 -) of dye molecule along with hydrogen bond formation and interaction between aromatic group of dye and AFC were responsible mechanisms for dye uptake. Isotherm of AO8 was Type I and followed Langmuir isotherm model. AV7 isotherm on AFC was of Type III and followed Freundlich model. Kinetics study showed that external mass transfer was the rate limiting step followed by intraparticle diffusion. Maximum adsorption capacities of AO8 and AV7 were observed as 164 and 68 mg/g. AO8 dye being smaller in molecular size was adsorbed more due to higher diffusion rate and higher dye: AFC ratio, which enhanced the interaction between dye and polymer.

  19. 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.

  20. 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.

  1. 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

  2. Adsorption equilibrium and kinetics for SO2, NO, CO2 on zeolites FAU and LTA.

    PubMed

    Yi, Honghong; Deng, Hua; Tang, Xiaolong; Yu, Qiongfen; Zhou, Xuan; Liu, Haiyan

    2012-02-15

    In order to develop a single-step process for removing SO(2), NO, CO(2) in flue gas simultaneously by co-adsorption method. Pure component adsorption equilibrium and kinetics of SO(2), NO, and CO(2) on zeolite NaY, NaX, CaA were obtained respectively. Equilibrium data were analyzed by equilibrium model and Henry's law constant. The results suggest that Adsorption affinity follows the trend SO(2)>CO(2)>NO for the same adsorbent. Zeolite with stronger polar surface is a more promising adsorbent candidate. Kinetics behavior was investigated using the breakthrough curve method. The overall mass transfer coefficient and diffusivity factor were determined by a linear driving force model. The results are indicative of micropore diffusion controlling mechanism. NaY zeolite has the minimum resistance of mass transfer duo to the wide pore distribution and large pore amount. CaA zeolite exhibits the highest spatial hindered effect. Finally, co-adsorption effect of SO(2), NO, and CO(2) were investigated by multi-components breakthrough method. SO(2) and NO may form new adsorbed species, however, CO(2) presents a fast breakthrough. Chemical adsorption causes SO(2) transforms to SO(4)(2-), however, element N and C are not detected in adsorbed zeolites.

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

    PubMed

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

    2014-05-01

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

  4. Adsorption behavior of levulinic acid onto microporous hyper-cross-linked polymers in aqueous solution: Equilibrium, thermodynamic, kinetic simulation and fixed-bed column studies.

    PubMed

    Lin, Xiaoqing; Huang, Qianlin; Qi, Gaoxiang; Xiong, Lian; Huang, Chao; Chen, Xuefang; Li, Hailong; Chen, Xinde

    2017-03-01

    The recovery of levulinic acid (LA) from aqueous solution and actual biomass hydrolysate by a microporous hyper-cross-linked polymer, SY-01, was investigated for the first time under batch and fixed-bed column conditions. The results showed that the optimum pH should be in the acidic range (pH < 3.0) without adjusting the pH. In the single-component system equilibrium study, the Langmuir isotherm model fits the LA adsorption onto SY-01 resin better than the Freundlich isotherm model, indicating that LA adsorption onto SY-01 resin under the concentration range studied is a monolayer homogeneous adsorption process. The maximum adsorption capacity of LA onto SY-01 resin decreased with increasing temperature, ranging from 103.74 to 95.70 mg/g. The obtained thermodynamic parameters suggested that the adsorption of LA on SY-01 was spontaneous (ΔG(0)<-3.788 kJ/mol), and exothermic (ΔH(0) = -11.764 kJ/mol). For kinetic study, the adsorption of LA onto SY-01 resin at various operating conditions follows the pore diffusion model and the intraparticle diffusion is the rate-limiting step for the adsorption of LA onto SY-01 resin. The effective pore diffusivity was dependent upon temperature, but independent of initial LA concentration, and were 3.306 × 10(-10), 5.274 × 10(-10) and 7.707 × 10(-10) m(2)/s at 298, 318 and 338 K, respectively. In desorption process, the recovery efficiency of LA from SY-01 resin was 99.39%, and LA concentration in the eluent was raised 2.97-fold. In conclusion, our results show that the SY-01 resin has potential application in product recovery of LA from biomass hydrolysate.

  5. A review on zinc and nickel adsorption on natural and modified zeolite, bentonite and vermiculite: examination of process parameters, kinetics and isotherms.

    PubMed

    Malamis, S; Katsou, E

    2013-05-15

    Adsorption and ion exchange can be effectively employed for the treatment of metal-contaminated wastewater streams. The use of low-cost materials as sorbents increases the competitive advantage of the process. Natural and modified minerals have been extensively employed for the removal of nickel and zinc from water and wastewater. This work critically reviews existing knowledge and research on the uptake of nickel and zinc by natural and modified zeolite, bentonite and vermiculite. It focuses on the examination of different parameters affecting the process, system kinetics and equilibrium conditions. The process parameters under investigation are the initial metal concentration, ionic strength, solution pH, adsorbent type, grain size and concentration, temperature, agitation speed, presence of competing ions in the solution and type of adsorbate. The system's performance is evaluated with respect to the overall metal removal and the adsorption capacity. Furthermore, research works comparing the process kinetics with existing reaction kinetic and diffusion models are reviewed as well as works examining the performance of isotherm models against the experimental equilibrium data.

  6. Adsorption of direct dye on palm ash: kinetic and equilibrium modeling.

    PubMed

    Ahmad, A A; Hameed, B H; Aziz, N

    2007-03-06

    Palm ash, an agriculture waste residue from palm-oil industry in Malaysia, was investigated as a replacement for the current expensive methods of removing direct blue 71 dye from an aqueous solution. The experimental data were analyzed by the Langmuir and Freundlich models of adsorption. Equilibrium data fitted well with Freundlich model in the range of 50-600mg/L. The equilibrium adsorption capacity of the palm ash was determined with the Langmuir equation and found to be 400.01mg dye per gram adsorbent at 30 degrees C. The rates of adsorption were found to conform to the pseudo-second-order kinetics with good correlation. The results indicate that the palm ash could be employed as a low-cost alternative to commercial activated carbon.

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

    PubMed

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

    2016-01-20

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

  8. Equilibrium and kinetics study on the adsorption of perfluorooctanoic acid from aqueous solution onto powdered activated carbon.

    PubMed

    Qu, Yan; Zhang, Chaojie; Li, Fei; Bo, Xiaowen; Liu, Guangfu; Zhou, Qi

    2009-09-30

    Powdered activated carbon (PAC) was applied to remove perfluorooctanoic acid (PFOA) from the aqueous PFOA solution in this study. Contact time, adsorbent dose and temperature were analyzed as the effect factors in the adsorption reaction. The contact time of maximum PFOA uptake was around 1h while the sorption removal efficiency increased with the PAC concentrations. And the process of adsorption increased from 303 K to 313 K and then decreased from 313 K to 323 K. Among four applied models, the experimental isotherm data were discovered to follow Langmuir isotherm model more closely. Thermodynamically, adsorption was endothermic because enthalpy, entropy and Gibbs constants were 198.5 kJ/mol, 0.709 kJ/mol/K and negative, respectively, which also indicated that the adsorption process was spontaneous and feasible. From kinetic analysis, the adsorption was suggested to be pseudo-second-order model. The adsorption of PFOA on the PAC was mainly controlled by particle diffusion.

  9. Adsorption isotherm studies of Cu (II) and Co (II) in high concentration aqueous solutions on photocatalytically modified diatomaceous ceramic adsorbents

    NASA Astrophysics Data System (ADS)

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

    2017-01-01

    Photocatalytically modified ceramic adsorbents were synthesized for the removal of high concentration Cu (II) and Co (II) ions from their aqueous solutions. The raw material, diatomaceous aluminosilicate mineral was modified using silver and anatase titanium oxide nanoparticles. Batch adsorption experiment was carried out on the targeted metal ions and the results were analyzed by the Langmuir and Freundlich equation at different concentrations (100-1000 mg/l) and the characteristic parameters for each adsorption isotherm were determined. As-received raw materials do not exhibit any sorption capacity for high concentration Cu2+ and Co2+ adsorbates. However, the adsorption isotherms for modified diatomaceous ceramic adsorbents could be fitted well by the Langmuir model for both Cu2+ and Co2+ with correlation coefficient (R) of up to 0.99953. The highest and lowest monolayer coverage (q max) were 121.803 and 31.289 mg/g for Cu2+ and Co2+, respectively. The separation factor (R L) in the experiment was less than one (<1), indicating that the adsorption of metal ions on the Ag-TiO2-modified ceramic adsorbent is favorable. The highest adsorption capacity (K f) and intensity (n) constants obtained from Freundlich model are 38.832 (Cu2+ on ZEO-T) and 5.801 (Co2+ on STOX-Z).

  10. 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.

  11. Impact of the molecular structure and adsorption mode of D-π-A dye sensitizers with a pyridyl group in dye-sensitized solar cells on the adsorption equilibrium constant for dye-adsorption on TiO2 surface.

    PubMed

    Ooyama, Yousuke; Yamaguchi, Naoya; Ohshita, Joji; Harima, Yutaka

    2016-12-07

    D-π-A dyes NI-4 bearing a pyridyl group, YNI-1 bearing two pyridyl groups and YNI-2 bearing two thienylpyridyl groups as the anchoring group on the TiO2 surface have been developed as dye sensitizers for dye-sensitized solar cells (DSSCs), where NI-4 and YNI-2 can adsorb onto the TiO2 electrode through the formation of the coordinate bond between the pyridyl group of the dye and the Lewis acid site (exposed Ti(n+) cations) on the TiO2 surface, but YNI-1 is predominantly adsorbed on the TiO2 electrode through the formation of the hydrogen bond between the pyridyl group of the dye and the Brønsted acid sites (surface-bound hydroxyl groups, Ti-OH) on the TiO2 surface. The difference in the dye-adsorption mode among the three dyes on the TiO2 surface has been investigated from the adsorption equilibrium constant (Kad) based on the Langmuir adsorption isotherms. It was found that the Kad values of YNI-1 and YNI-2 are higher than that of NI-4, and more interestingly, the Kad value of YNI-2 is higher than that of YNI-1. This work demonstrates that that for the D-π-A dye sensitizers with the pyridyl group as the anchoring group to the TiO2 surface the number of pyridyl groups and the dye-adsorption mode on the TiO2 electrode as well as the molecular structure of the dye sensitizer affect the Kad value for the adsorption of the dye to the TiO2 electrode, that is, resulting in a difference in the Kad value among the D-π-A dye sensitizers NI-4, YNI-1 and YNI-2.

  12. 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.

  13. Application of a micromembrane chromatography module to the examination of protein adsorption equilibrium.

    PubMed

    Káňavová, Natália; Kosior, Anna; Antošová, Monika; Faber, René; Polakovič, Milan

    2012-11-01

    A micromembrane chromatography module based on a 96-well plate design and enabling fast and simple separation of small amounts of proteins was used for the determination of binding capacities of lysozyme, bovine serum albumin, ovalbumin, bovine γ-globulin, and human immunoglobulin G on a hydrophobic membrane Sartobind® Phenyl. Dependence of the binding capacity of the proteins on the ammonium sulfate concentration was examined in the salt concentration range of 0.5-2.0 mol L(-1). An exponential increase of the binding capacity was observed for all proteins. Simple Langmuir one-component isotherm was found suitable for the characterization of the effect of protein concentration in all cases. A combined effect of protein and salt concentrations was expressed via the Langmuir exponential isotherm and fitted the adsorption data for three of the investigated proteins well.

  14. Differential heat of adsorption of water vapor on silicified microcrystalline cellulose (SMCC): an investigation using isothermal microcalorimetry.

    PubMed

    Qian, Ken K; Bogner, Robin H

    2011-01-01

    A novel dual-shaft configuration in isothermal microcalorimetry was developed to study the interaction of water vapor with pharmaceutical excipients. An instrument performance test is suggested to validate the experimental data. Reliable experimental results can be collected using a single perfusion shaft; however, there was limitation of the dual-shaft configuration, which resulted deviation in the experimental results. A periodic performance test is recommended. Silicified microcrystalline cellulose (SMCC) was used as a model system to study the interaction using the dual-shaft method. Enthalpy of water vapor adsorption on SMCC was determined and compared to literature data. The data collected using the dual-shaft configuration did not reflect the actual physical system. The deviation was most likely due to the lack of flow control caused by viscous resistance. The enthalpy of adsorption was then calculated using isothermal microcalorimetry coupled with a dynamic vapor sorption apparatus. The results, -55 kJ/mol at low relative humidity (RH) to -22 kJ/mol at high RH, were consistent with the physical phenomenon of water vapor adsorption. Enthalpy of adsorption showed surface heterogeneity of SMCC and suggested multilayer condensation of water at approximately 60% RH. However, at high RH, the results showed the moisture-excipient interaction can be more complex than the proposed mechanism.

  15. 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.

  16. 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.

  17. Adsorption of methylene blue onto jute fiber carbon: kinetics and equilibrium studies.

    PubMed

    Senthilkumaar, S; Varadarajan, P R; Porkodi, K; Subbhuraam, C V

    2005-04-01

    Jute fiber obtained from the stem of a plant was used to prepare activated carbon using phosphoric acid. Feasibility of employing this jute fiber activated carbon (JFC) for the removal of Methylene blue (MB) from aqueous solution was investigated. The adsorption of MB on JFC has found to dependent on contact time, MB concentration and pH. Experimental result follows Langmuir isotherm model and the capacity was found to be 225.64 mg/g. The optimum pH for the MB removal was found to be 5-10. The kinetic data obtained at different concentrations have been analyzed using a pseudo-first-order, pseudo-second-order equation, intraparticle diffusion and Elovich equation. Among the kinetic models studied, the intraparticle diffusion was the best applicable model to describe the adsorption of MB onto JFC.

  18. Folding equilibrium constants of telomere G-quadruplexes in free state or associated with proteins determined by isothermal differential hybridization.

    PubMed

    Wang, Quan; Ma, Li; Hao, Yu-Hua; Tan, Zheng

    2010-11-15

    Guanine rich (G-rich) nucleic acids form G-quadruplex structures that are implicated in many biological processes, pharmaceutical applications, and molecular machinery. The folding equilibrium constant (K(F)) of the G-quadruplex not only determines its stability and competition against duplex formation in genomic DNA but also defines its recognition by proteins and drugs and technical specifications. The K(F) is most conveniently derived from thermal melting analysis that has so far yielded extremely diversified results for the human telomere G-quadruplex. Melting analysis cannot be used for nucleic acids associated with proteins, thus has difficulty to study how protein association affects the folding equilibrium of G-quadruplex structure. In this work, we established an isothermal differential hybridization (IDH) method that is able to determine the K(F) of G-quadruplex, either alone or associated with proteins. Using this method, we studied the folding equilibrium of the core sequence G(3)(T(2)AG(3))(3) from vertebrate telomere in K(+) and Na(+) solutions and how it is affected by proteins associated at its adjacent regions. Our results show that the K(F) obtained for the free G-quadruplex is within 1 order of magnitude of most of those obtained by melting analysis and protein binding beside a G-quadruplex can dramatically destabilize the G-quadruplex.

  19. 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.

  20. IgG adsorption on a new protein A adsorbent based on macroporous hydrophilic polymers. I. Adsorption equilibrium and kinetics.

    PubMed

    Perez-Almodovar, Ernie X; Carta, Giorgio

    2009-11-20

    Experimental determination and modeling of IgG binding on a new protein A adsorbent based on a macroporous resin were performed. The new adsorbent consists of polymeric beads based on hydrophilic acrylamido and vinyl monomers with a pore structure optimized to allow favorable interactions of IgG with recombinant protein A coupled to the resin. The particles have average diameter of 57 microm and a narrow particle size distribution. The IgG adsorption equilibrium capacity is 46 mg/cm(3) and the effective pore diffusivity determined from pulse response experiments for non-binding conditions is 8.0 x 10(-8) cm(2)/s. The IgG adsorption kinetics can be described with the same effective diffusivity by taking into account a heterogeneous binding mechanism with fast binding sites, for which adsorption is completely diffusion controlled, and slow binding sites for which adsorption is controlled by the binding kinetics. As a result of this mechanism, the breakthrough curve exhibits a tailing behavior, which appears to be associated with the slow binding sites. A detailed rate model taking into account intraparticle diffusion and binding kinetics is developed and is found capable of predicting both batch adsorption and breakthrough behavior over an ample range of experimental conditions. The corresponding effective diffusivity is independent of protein concentration in solution over the range 0.2-2 mg/cm(3) and of protein binding as a result of the large pore size of the support matrix. Overall, the small particle size and low diffusional hindrance allow capture of IgG with short residence times while attaining substantial dynamic binding capacities.

  1. Adsorption equilibrium and kinetics of monomer-dimer monoclonal antibody mixtures on a cation exchange resin.

    PubMed

    Reck, Jason M; Pabst, Timothy M; Hunter, Alan K; Wang, Xiangyang; Carta, Giorgio

    2015-07-10

    Adsorption equilibrium and kinetics are determined for a monoclonal antibody (mAb) monomer and dimer species, individually and in mixtures, on a macroporous cation exchange resin both under the dilute limit of salt gradient elution chromatography and at high protein loads and low salt based on batch adsorption equilibrium and confocal laser scanning microscopy (CLSM) experiments. In the dilute limit and weak binding conditions, the dimer/monomer selectivity in 10mM phosphate at pH 7 varies between 8.7 and 2.3 decreasing with salt concentration in the range of 170-230mM NaCl. At high protein loads and strong binding conditions (0-60mM NaCl), the selectivity in the same buffer is near unity with no NaCl added, but increases gradually with salt concentration reaching high values between 2 and 15 with 60mM added NaCl. For these conditions, the two-component adsorption kinetics is controlled by pore diffusion and is predicted approximately by a dual shrinking core model using parameters based on single component equilibrium and kinetics measurements.

  2. Equilibrium and kinetic modeling of adsorptive sulfur removal from gasoline by synthesized Ce-Y zeolite

    NASA Astrophysics Data System (ADS)

    Montazerolghaem, Maryam; Rahimi, Amir; Seyedeyn-Azad, Fakhry

    2010-11-01

    In this research, the adsorption of a model sulfur compound, thiophene, from a simulated gasoline onto Ce-Y zeolite in pellet and powder forms was investigated. For this purpose, zeolite Na-Y was synthesized, and Ce-Y zeolite was prepared via solid-state ion-exchanged (SSIE) method. Adsorptive desulfurization of model gasoline was conducted in a batch reactor at ambient conditions to evaluate the equilibrium and kinetics of thiophene adsorption onto Ce-Y zeolite. The equilibrium data were fitted to Langmuire and Toth models. Pseudo-n-order and modified n-order models, LDF-base model, and intra-particle diffusion model were evaluated to fit the kinetic of the adsorption process and to determine the mechanism of it. The corresponding parameters and/or correlation coefficients of each model were reported. The LDF-base model was used also to fit the mass transfer coefficient for both powder and pellet forms of the adsorbent. The best fit estimates for the mass transfer coefficient were obtained 4 × 10-11 m/s and k = 3.1 × 10-12[exp( - t/τ) + 1/(t + 10-4)], for powder and pellet form adsorbents, respectively.

  3. Liquid Phase adsorption kinetics and equilibrium of toluene by novel modified-diatomite.

    PubMed

    Sheshdeh, Reza Khalighi; Abbasizadeh, Saeed; Nikou, Mohammad Reza Khosravi; Badii, Khashayar; Sharafi, Mohammad Sadegh

    2014-01-01

    The adsorption equilibria of toluene from aqueous solutions on natural and modified diatomite were examined at different operation parameters such as pH, contact time, initial toluene concentration was evaluated and optimum experimental conditions were identified. The surface area and morphology of the nanoparticles were characterized by SEM, BET, XRD, FTIR and EDX analysis. It was found that in order to obtain the highest possible removal of toluene, the experiments can be carried out at pH 6, temperature 25°C, an agitation speed of 200 rpm, an initial toluene concentration of 150 mg/L, a centrifugal rate of 4000 rpm, adsorbent dosage = 0.1 g and a process time of 90 min. The results of this work show that the maximum percentage removal of toluene from aqueous solution in the optimum conditions for NONMD was 96.91% (145.36 mg/g). Furthermore, under same conditions, the maximum adsorption of natural diatomite was 71.45% (107.18 mg/g). Both adsorption kinetic and isotherm experiments were carried out. The experimental data showed that the adsorption follows the Langmuir model and Freundlich model on natural and modified diatomite respectively. The kinetics results were found to conform well to pseudo-second order kinetics model with good correlation. Thus, this study demonstrated that the modified diatomite could be used as potential adsorbent for removal of toluene from aqueous solution.

  4. 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...

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

    NASA Astrophysics Data System (ADS)

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

    2000-03-01

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

  6. Freundlich adsorption isotherms of agricultural by-product-based powdered activated carbons in a geosmin-water system.

    PubMed

    Ng, Chilton; Losso, Jack N; Marshall, Wayne E; Rao, Ramu M

    2002-11-01

    The present study was designed to model the adsorption of geosmin from water under laboratory conditions using the Freundlich isotherm model. This model was used to compare the efficiency of sugarcane bagasse and pecan shell-based powdered activated carbon to the efficiency of a coal-based commercial activated carbon (Calgon Filtrasorb 400). When data were generated from Freundlich isotherms, Calgon Filtrasorb 400 had greater geosmin adsorption at all geosmin concentrations studied than the laboratory produced steam-activated pecan shell carbon, steam-activated bagasse carbon, and the CO2-activated pecan shell carbon. At geosmin concentrations < 0.07 microg/l for the phosphoric acid-activated pecan shell carbon and below 0.08 microg/l for a commercially produced steam-activated pecan shell carbon obtained from Scientific Carbons, these two carbons had a higher calculated geosmin adsorption than Filtrasorb 400. While the commercial carbon was more efficient than some laboratory prepared carbons at most geosmin concentrations, the results indicate that when the amount of geosmin was below the threshold level of human taste (about 0.10 microg/l), the phosphoric acid-activated pecan shell carbon and the Scientific Carbons sample were more efficient than Filtrasorb 400 at geosmin removal.

  7. Kinetics and isotherm studies of Cd(II) adsorption from aqueous solution utilizing seeds of bottlebrush plant ( Callistemon chisholmii)

    NASA Astrophysics Data System (ADS)

    Rao, Rifaqat Ali Khan; Kashifuddin, Mohammad

    2014-12-01

    Seeds of bottlebrush, a novel plant material, were found to exhibit excellent adsorption capacity over a wide range of Cd(II) concentration. It was characterized by Fourier transform infrared spectroscopy and Scanning Electron Microscopy to support the adsorption of Cd(II) ions. Effect of various parameters like pH, contact time, initial concentration and different electrolytes was investigated using batch process to optimize conditions for maximum adsorption. The adsorbent data were analyzed using Langmuir, Freundlich, Temkin and Dubinin-Redushkeuich isotherm equations at 30°, 40° and 50 °C. Thermodynamic parameters such as standard enthalpy change (Δ H°), free energy change (Δ G°) and entropy change (Δ S°) were also evaluated and the results indicated that adsorption of Cd(II) are spontaneous and endothermic. Various kinetics models including the Pseudo-first-order kinetics, Pseudo-second-order kinetics and Intraparticle diffusion models have been applied to the experimental data to predict the adsorption kinetics. Kinetic study was carried out by varying initial concentration of Cd(II) at constant temperature and it was found that pseudo-second-order rate equation was better obeyed than pseudo-first-order equation supporting that chemisorption process was involved.

  8. 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.

  9. Adsorption isotherms of cellulose-based polymers onto cotton fibers determined by means of a direct method of fluorescence spectroscopy.

    PubMed

    Hoffmann, Ingo; Oppel, Claudia; Gernert, Ulrich; Barreleiro, Paula; von Rybinski, Wolfgang; Gradzielski, Michael

    2012-05-22

    We present a novel method for the measurement of polymer adsorption on fibers by employing fluorescently labeled polymers. The method itself can be used for any compound that either shows fluorescence or can be labeled with a fluorescent dye, which renders it ubiquitously applicable for adsorption studies. The main advantage of the method is that the choice of adsorbent is not limited to flat surfaces, thereby allowing the investigation of fibrous and porous systems. As an example of high interest for application we determined the adsorption isotherms of various polysaccharide-based polymers with different charges and different substituents on cotton fibers. These experiments show that the extent of adsorption depends not only on the charge conditions but also very much on the specific interactions between the polymer and fiber. For instance, the cationic hydroxyethyl cellulose can become bound to an extent similar to that of the anionic alginate, while the anionic carboxymethyl cellulose of similar charge density adsorbs much less under these conditions. This shows that the adsorption of polymers depends subtly on the details of the interaction between the polymer and fiber but can be determined with good precision with our direct fluorescence method.

  10. Adsorption of Toluene and Paraxylene from Aqueous Solution Using Pure and Iron Oxide Impregnated Carbon Nanotubes: Kinetics and Isotherms Study

    PubMed Central

    Abbas, Aamir; Ihsanullah; Al-Baghli, Nadhir A. H.

    2017-01-01

    Multiwall carbon nanotubes (CNTs) and iron oxide impregnated carbon nanotubes (CNTs-iron oxide) were investigated for the adsorption of hazardous toluene and paraxylene (p-xylene) from aqueous solution. Pure CNTs were impregnated with iron oxides nanoparticles using wet impregnation technique. Various characterization techniques including thermogravimetric analysis, scanning electron microscopy, elemental dispersion spectroscopy, X-ray diffraction, and nitrogen adsorption analysis were used to study the thermal degradation, surface morphology, purity, and surface area of the materials. Batch adsorption experiments show that iron oxide impregnated CNTs have higher degree of removal of p-xylene (i.e., 90%) compared with toluene (i.e., 70%), for soaking time 2 h, with pollutant initial concentration 100 ppm, at pH 6 and shaking speed of 200 rpm at 25°C. Pseudo-second-order model provides better fitting for the toluene and p-xylene adsorption. Langmuir and Freundlich isotherm models demonstrate good fitting for the adsorption data of toluene and p-xylene. PMID:28386208

  11. Water adsorption isotherms and hydration forces for lysolipids and diacyl phospholipids.

    PubMed Central

    Marsh, D.

    1989-01-01

    The repulsive forces in a wide range of diacyl and monoacyl phospholipid systems have been obtained from the adsorption isotherms for water. From the exponential dependence of the repulsive pressure on the water content, information has been deduced regarding the hydration force. For diacyl phosphatidylcholines the strength of the hydration force and its characteristic decay length are in good agreement with values previously obtained by x-ray diffraction methods. For natural and synthetic diacyl phosphatidylcholines in the fluid lamellar phase, the hydration force extrapolated to zero layer separation (Po) is in the range 4-5.10(8) N.m-2 and the decay length is approximately 0.3 nm. The results for dimyristoyl, dipalmitoyl, and distearoyl phosphatidylcholines in the gel phase are very similar with Po approximately 2.5.10(8) N.m-2 and decay length of approximately 0.2 nm. Egg monomethyl phosphatidylethanolamine is less strongly hydrated: Po = 2.3.10(9) N.m-2, with a decay length of 0.3 nm. Egg phosphatidylethanolamine and bovine phosphatidylserine hydrate even more weakly with Po approximately 1.3.10(8) N.m-2 and decay length of approximately 0.15 nm. Mixtures with cholesterol or phosphatidylcholine increase both Po and the decay length for phosphatidylethanolamine to values closer to those for phosphatidylcholine. The repulsive forces deduced for egg lysophosphatidylcholine at 40 degrees C display a biphasic water dependence, with the low water phase being similar to lamellar egg phosphatidylcholine, and the phase at higher water content having a smaller value of Po = 2.10(8) N.m-2 but a longer decay length of approximately 0.45 nm, corresponding to a nonlamellar configuration. Bovine lysophosphatidylserine similarly yields values of PO = 1.2.108 N.m-2 and an effective decay length of 0.64 nm. The hydration behavior of the various diacyl phospholipids has been interpreted in terms of the mean-field molecular force theory of lipid hydration, and values deduced for

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

    PubMed

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

    2016-07-01

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

  13. Adsorption Isotherms: North Caroline Apatite Induced Precipitation of Lead, Zinc, Manganese, and Cadmium from the Bunker Hill 4000 Soil

    DTIC Science & Technology

    1995-05-01

    Using the MINTEQ -A2 geochemical model, thermodynamic predictions for ^f0™«0™0? pyromorphytes (Pb5(POJ3 (OH, Cl)), hopeite (Zn3(POJ2 4H20...VERIFICATION OF PRECIPITATED METALS USING MINTEQ -A2 13 2.3.1 Experimental 2.3.2 Results ... 19 3.0 CONCLUSIONS 20 4.0...precipitated Pb-P04 complexes will be illustrated as sharp downward deviations from linearity of the adsorption isotherms, as predicted by MINTEQ -A2

  14. Bisphenol-A modified hyper-cross-linked polystyrene resin for salicylic acid removal from aqueous solution: adsorption equilibrium, kinetics and breakthrough studies.

    PubMed

    Hu, Huanxiao; Wang, Xiaomei; Li, Shengyong; Huang, Jianhan; Deng, Shuguang

    2012-04-15

    In this study, a series of bisphenol-A modified hyper-cross-linked polystyrene resins labeled as HJ-L00, HJ-L02, HJ-L04, HJ-L06 and HJ-L08 were synthesized, characterized and evaluated for adsorptive removal of salicylic acid from aqueous solutions. The structural characterization results indicated that the resins possessed predominant micropores/mesopores, moderate specific surface area and a few bisphenol-A groups on the surface. All the bisphenol-A modified hyper-cross-linked resins were effective for removing salicylic acid from aqueous solutions, and sample HJ-L02 had the largest adsorption capacity. The adsorption equilibrium data were correlated by the Freundlich isotherm model, and a positive adsorption enthalpy was obtained. The kinetic data were analyzed with two diffusion models and indicated that the intra-particle diffusion was the sole rate-controlling step in the first stage. The dynamic experimental results showed that the breakthrough point of the HJ-L02 adsorbent was at 90.2 BV (bed volume, 1 BV=10 mL) for a feed concentration of 500.0mg/L of salicylic acid, and 14.0 BV of 1% of sodium hydroxide could completely regenerate the HJ-L02 adsorbent column.

  15. Adsorption equilibrium and thermodynamics of CO2 and CH4 on carbon molecular sieves

    NASA Astrophysics Data System (ADS)

    Song, Xue; Wang, Li'ao; Ma, Xu; Zeng, Yunmin

    2017-02-01

    Carbon molecular sieves (CMS) are widely used in the separation of dioxide carbon and methane. In this research, three commercial CMS were utilized to analyze the pore structure and chemical properties. The adsorption isotherms of CO2 and CH4 were studied at 298 K, 308 K and 318 K over the pressure range of 0-1 MPa by an Intelligent Gravimetric analysis (IGA-100B, UK). Langmuir model was adopted to fit the experimental data. The working capacity and selectivity were employed to evaluate the adsorbents. The adsorption thermodynamics were discussed. The adsorbed amounts of both CO2 and CH4 are found to be highly related with the BET specific surface area and the volume of micropores, and also are interrelated with the total pore volume and micropore surface area. The standard enthalpy change (ΔHΘ), standard Gibbs free energy (ΔGΘ) and standard entropy change (ΔSΘ) at zero surface loading are negative, manifesting the adsorption process is exothermic and spontaneous, and the system tends to be ordered. With the increasing surface coverage, the absolute values of Gibbs free energy (ΔG) decrease whereas the absolute values of enthalpy change (ΔH) and entropy change(ΔS) increase. This indicates that as the adsorbed amount increases, the degree of the spontaneity reduces, the intermolecular forces among the adsorbate molecules increase, the orderliness of the system improves and the adsorbed amount approaches the maximum adsorbed capacity.

  16. Adsorptive removal of α-endosulfan from water by hydrophobic zeolites. An isothermal study.

    PubMed

    Yonli, Arsène H; Batonneau-Gener, Isabelle; Koulidiati, Jean

    2012-02-15

    This paper deals with the removal of α-endosulfan from water over HY and steamed HBEA zeolites. Experiments were performed to understand the adsorption mechanisms of α-endosulfan on zeolites and to determine the most efficient adsorbent for the purification of water contaminated by this pesticide. The experiments exhibit that α-endosulfan was adsorbed in the micropores. In the case of HY zeolites an adsorption of α-endosulfan molecules on BrØnsted sites was pointed out, due to a preferential water adsorption in mesopores. Moreover a physisorption of α-endosulfan occurred in micropores. For steamed HBEA zeolites physisorption in micropores was pointed out as the adsorption mode. For both types of zeolites a decrease of the adsorption capacities was noticed when the acidity of zeolites increased. There was also a linear relation between the adsorption capacities of α-endosulfan and the hydrophobicity (HI) of the samples and by determining the values of HI for a type of zeolite it was possible to deduce the uptake of α-endosulfan. The HY(40) sample was the most efficient for the removal of α-endosulfan from water because of preferential adsorption of water molecules in mesopores and lower acidity. For this sample the adsorption capacity for α-endosulfan was about 833.33 mg/g where for the most effective HBEA sample (St700(3)) the adsorption capacity was about 793.65 mg/g.

  17. Equilibrium and kinetic analysis of phosphorus adsorption from aqueous solution using waste alum sludge.

    PubMed

    Babatunde, A O; Zhao, Y Q

    2010-12-15

    Excess phosphorus (P) in wastewaters promotes eutrophication in receiving waterways. A cost-effective method such as use of novel low-cost adsorbents for its adsorptive removal would significantly reduce such impacts. Using batch experiments, the intrinsic dynamics of P adsorption by waste alum sludge (an inevitable by-product of drinking water treatment plants) was examined. Different models of adsorption were used to describe equilibrium and kinetic data, calculate rate constants and determine the adsorption capacity. Results indicate that the intraparticle rate constant increased from 0.0075 mg g(-1)min(-1) at 5 mg L(-1) to 0.1795 mg g(-1)min(-1) at 60 mg L(-1) indicating that more phosphate is adsorbed per g min at higher P concentration. Further analyses indicate involvement of film and particle diffusion mechanisms as rate controlling steps at lower and higher concentrations, respectively. Mass transfer coefficient obtained ranged from 1.7 × 10(-6) to 1.8 × 10(-8) indicating a rapid transportation of phosphate molecules onto the alum sludge. These results further demonstrates that alum sludge-hitherto thought of as undesirable waste, can be used as novel adsorbent for P removal from wastewater through various applications, thus offsetting a portion of the disposal costs while at the same time improving water quality in sensitive watersheds.

  18. Dye removal from textile industrial effluents by adsorption on exfoliated graphite nanoplatelets: kinetic and equilibrium studies.

    PubMed

    Carvallho, Marilda N; da Silva, Karolyne S; Sales, Deivson C S; Freire, Eleonora M P L; Sobrinho, Maurício A M; Ghislandi, Marcos G

    2016-01-01

    The concept of physical adsorption was applied for the removal of direct and reactive blue textile dyes from industrial effluents. Commercial graphite nanoplatelets were used as substrate, and the quality of the material was characterized by atomic force and transmission electron microscopies. Dye/graphite nanoplatelets water solutions were prepared varying their pH and initial dye concentration. Exceptionally high values (beyond 100 mg/L) for adsorptive capacity of graphite nanoplatelets could be achieved without complicated chemical modifications, and equilibrium and kinetic experiments were performed. Our findings were compared with the state of the art, and compared with theoretical models. Agreement between them was satisfactory, and allowed us to propose novel considerations describing the interactions of the dyes and the graphene planar structure. The work highlights the important role of these interactions, which can govern the mobility of the dye molecules and the amount of layers that can be stacked on the graphite nanoplatelets surface.

  19. 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,...

  20. Thermodynamic parameters for adsorption equilibrium of heavy metals and dyes from wastewaters: Research updated.

    PubMed

    Chang, Yingju; Lai, Juin-Yih; Lee, Duu-Jong

    2016-12-01

    The standard Gibbs free energy, enthalpy and entropy change data for adsorption equilibrium reported in biosorption literature during January 2013-May2016 were listed. Since the studied biosorption systems are all near-equilibrium processes, the enthalpy and entropy change data evaluated by fitting temperature-dependent free energy data using van Hoff's equation reveal a compensation artifact. Additional confusion is introduced with arbitrarily chosen adsorbate concentration unit in bulk solution that added free energy change of mixing into the reported free energy and enthalpy change data. Different standard states may be chosen for properly describing biosorption processes; however, this makes the general comparison between data from different systems inappropriate. No conclusion should be drawn based on unjustified thermodynamic parameters reported in biosorption studies.

  1. 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.

  2. Adsorption isotherms of some alkyl aromatic hydrocarbons and surface energies on partially dealuminated Y faujasite zeolite by inverse gas chromatography.

    PubMed

    Kondor, Anett; Dallos, András

    2014-10-03

    Adsorption isotherm data of some alkyl aromatic hydrocarbons (benzene, toluene, ethylbenzene, o-xylene, m-xylene and p-xylene) measured in the temperature range of 423-523K on a partially dealuminated faujasite type DAY F20 zeolite by inverse gas chromatography are presented in this work. The temperature dependent form of Tóth's equation has been fitted to the multiple temperature adsorption isotherms of benzene, toluene, ethylbenzene, o-xylene, m-xylene and p-xylene with standard deviations of 4.6, 5.0, 5.9, 4.3, 5.1 and 6.3mmolkg(-1) and coefficients of determinations (r(2)) of 0.977, 0.971, 0.974, 0.975, 0.991 and 0.991, respectively. The gas-solid equilibria and modeling were interpreted on the basis of the interfacial properties of the zeolite, by dispersive, specific and total surface energy heterogeneity profiles and distributions of the adsorbent measured by surface energy analysis.

  3. Bi-level optimizing control of a simulated moving bed process with nonlinear adsorption isotherms.

    PubMed

    Kim, Kiwoong; Kim, Jin-Il; Park, Hyukmin; Koo, Yoon-Mo; Lee, Kwang Soon

    2011-09-23

    A bi-level optimizing control scheme originally proposed for a simulated moving bed (SMB) with linear isotherms has been extended to an SMB with nonlinear isotherms. Cyclic steady state optimization is performed in the upper level to determine the optimum switching period and time-varying feed/desorbent flow rates, and repetitive model predictive control is run in the lower level for purity regulation, taking the decision variables from the upper level as feed-forward information. Experimental as well as numerical study for an SMB process separating a high-concentration mixture of aqueous L-ribose and L-arabinose solutions showed that the proposed scheme performs satisfactorily against various disturbances. In contrast, an alternative scheme based on an SMB model with linear isotherms showed a limitation in the control performance; this scheme was apt to fail in purity regulation.

  4. On the irreversibility of the adsorption isotherm in a closed-end pore.

    PubMed

    Nguyen, Phuong T M; Do, D D; Nicholson, D

    2013-03-05

    We present a simulation study of argon adsorption in a closed-end mesopore of uniform diameter in order to investigate the occurrence of hysteresis and propose two principal reasons for its existence: the variation in the shape and radius of curvature of the meniscus and the change in the packing of adsorbate during adsorption and desorption. This interpretation differs from classical theories that neglect both of these factors, and therefore find that adsorption-desorption in a closed-end pore is reversible. A detailed simulation study of the effects of temperature on the microscopic behavior of the adsorbate supports the interpretation proposed here.

  5. Kinetics and isotherm of fibronectin adsorption to three-dimensional porous chitosan scaffolds explored by 125I-radiolabelling

    PubMed Central

    Amaral, Isabel F.; Sousa, Susana R.; Neiva, Ismael; Marcos-Silva, Lara; Kirkpatrick, Charles J.; Barbosa, Mário A.; Pêgo, Ana P.

    2013-01-01

    In this study, 125I-radiolabelling was explored to follow the kinetics and isotherm of fibronectin (FN) adsorption to porous polymeric scaffolds, as well as to assess the elution and exchangeability of pre-adsorbed FN following incubation in serum-containing culture medium. Chitosan (CH) porous scaffolds with two different degrees of acetylation (DA 4% and 15%) were incubated in FN solutions with concentrations ranging from 5 to 50 µg/mL. The kinetic and isotherm of FN adsorption to CH were successfully followed using 125I-FN as a tracer molecule. While on DA 4% the levels of adsorbed FN increased linearly with FN solution concentration, on DA 15% a saturation plateau was attained, and FN adsorbed amounts were significantly lower. These findings were supported by immunofluorescent studies that revealed, for the same FN solution concentration, higher levels of exposed cell-binding domains on DA 4% as compared with DA 15%. Following incubation in serum containing medium, DA 4% also revealed higher ability to exchange pre-adsorbed FN by new FN molecules from serum than DA 15%. In accordance, when assessing the efficacy of passively adsorbed FN to promote endothelial cell (EC) adhesion to CH, ECs were found to adhere at higher levels to DA 4% as compared with DA 15%, 5 µg/mL of FN being already efficient in promoting cell adhesion and cytoskeletal organization on CH with DA 4%. Taken together the results show that protein radiolabelling can be used as an effective tool to study protein adsorption to porous polymeric scaffolds, both from single and complex protein solutions. PMID:23635535

  6. Measurement and modelling of adsorption equilibrium, adsorption kinetics and breakthrough curve of toluene at very low concentrations on to activated carbon.

    PubMed

    Réguer, Anne; Sochard, Sabine; Hort, Cécile; Platel, Vincent

    2011-01-01

    Indoor air pollution, characterized by many pollutants at very low concentrations, is nowadays known as a worrying problem for human health. Among physical treatments, adsorption is a widely used process, since porous materials offer high capacity for volatile organic chemicals. However, there are few studies in the literature that deal with adsorption as an indoor air pollution treatment. The aim of this study was to investigate the adsorption of toluene on to activated carbon at characteristic indoor air concentrations. Firstly, global kinetic parameters were determined by fitting Thomas's model to experimental data obtained with batch experiments. Then, these kinetic parameters led to the determination of Henry's coefficient, which was checked with experimental data of the adsorption isotherm. Secondly, we simulated a breakthrough curve made at an inlet concentration 10 times higher than the indoor air level. Even if the kinetic parameters in this experiment are different from those in batch experiments, it can be emphasized that the Henry coefficient stays the same.

  7. 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...

  8. 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...

  9. Arsenic (III) adsorption on iron acetate coated activated alumina: thermodynamic, kinetics and equilibrium approach

    PubMed Central

    2013-01-01

    The adsorption potential of iron acetate coated activated alumina (IACAA) for removal of arsenic [As (III)] as arsenite by batch sorption technique is described. IACAA was characterized by XRD, FTIR, EDAX and SEM instruments. Percentage adsorption on IACAA was determined as a function of pH, contact time and adsorbent dose. The study revealed that the removal of As (III) was best achieved at pH =7.4. The initial As (III) concentration (0.45 mg/L) came down to less than 0.01 mg/L at contact time 90 min with adsorbent dose of 1 g/100 mL. The sorption was reasonably explained with Langmuir and Freundlich isotherms. The thermodynamic parameters such as ΔG 0 , ΔH 0 , ΔS 0 and E a were calculated in order to understand the nature of sorption process. The sorption process was found to be controlled by pseudo-second order and intraparticle diffusion models. PMID:24359995

  10. Simultaneous adsorption of methyl red and methylene blue onto biochar and an equilibrium modeling at high concentration.

    PubMed

    Ding, Guanyu; Wang, Buyun; Chen, Lingyu; Zhao, Shuangjiao

    2016-11-01

    Methyl red, methylene blue and biochar were used to investigate simultaneous adsorption of dyes onto low-cost adsorbent at different concentrations combinations. Langmuir mixed model could describe the adsorption well at low concentrations. However, it could not describe the adsorption anymore when concentrations of methyl red and methylene blue were higher than 255 and 300 mg L(-1) respectively with 0.5 g L(-1) biochar loading. A new model on the interaction among adsorbed adsorbates at equilibrium was developed. It could describe the adsorption at high concentrations well. According to the experimental results, interaction among dyes molecules would replace the competition onto adsorbent to be the main factor influencing adsorption when amount of adsorbed adsorbates were higher than those required to form a monolayer on all the adsorbing sites of adsorbent. The model was further verified by adsorption with other solute such as glucose or NaCl in solution.

  11. FTIR spectrophotometry, kinetics and adsorption isotherms modeling, ion exchange, and EDX analysis for understanding the mechanism of Cd(2+) and Pb(2+) removal by mango peel waste.

    PubMed

    Iqbal, Muhammad; Saeed, Asma; Zafar, Saeed Iqbal

    2009-05-15

    Mango peel waste (MPW) was evaluated as a new sorbent for the removal of Cd(2+) and Pb(2+) from aqueous solution. The maximum sorption capacity of Cd(2+) and Pb(2+) was found to be 68.92 and 99.05mgg(-1), respectively. The kinetics of sorption of both metals was fast, reaching at equilibrium in 60min. Sorption kinetics and equilibria followed pseudo-second order and Langmuir adsorption isotherm models. FTIR analysis revealed that carboxyl and hydroxyl functional groups were mainly responsible for the sorption of Cd(2+) and Pb(2+). Chemical modification of MPW for blocking of carboxyl and hydroxyl groups showed that 72.46% and 76.26% removal of Cd(2+) and Pb(2+), respectively, was due to the involvement of carboxylic group, whereas 26.64% and 23.74% was due to the hydroxyl group. EDX analysis of MPW before and after metal sorption and release of cations (Ca(2+), Mg(2+), Na(+), K(+)) and proton H(+) from MPW with the corresponding uptake of Cd(2+) and Pb(2+) revealed that the main mechanism of sorption was ion exchange. The regeneration experiments showed that the MPW could be reused for five cycles without significant loss in its initial sorption capacity. The study points to the potential of new use of MPW as an effective sorbent for the removal of Cd(2+) and Pb(2+) from aqueous solution.

  12. Adsorption isotherms, kinetics and column operations for the removal of hazardous dye, Tartrazine from aqueous solutions using waste materials--Bottom Ash and De-Oiled Soya, as adsorbents.

    PubMed

    Mittal, Alok; Mittal, Jyoti; Kurup, Lisha

    2006-08-25

    Adsorbents, Bottom Ash (a power plant waste) and De-Oiled Soya (an agricultural waste) exhibit good efficacy to adsorb a highly toxic dye, Tartrazine. Through the batch technique equilibrium uptake of the dye is observed at different concentrations, pH of the solution, dosage of adsorbents and sieve size of adsorbents. Langmuir and Freundlich adsorption isotherms are successfully employed on both the adsorbents and on the basis of these models the thermodynamic parameters are evaluated. Kinetic investigations reveal that more than 50% adsorption of dye is achieved in about 1h in both the cases, whereas, equilibrium establishment takes about 3-4h. The linear plots obtained in rate constant and mass transfer studies further confirm the applicability of first order rate expression and mass transfer model, respectively. The kinetic data treated to identify rate controlling step of the ongoing adsorption processes indicate that for both the systems, particle diffusion process is predominant at higher concentrations, while film diffusion takes place at lower concentrations. The column studies reveal that about 96% saturation of both the columns is attained during their exhaustion, while about 88 and 84% of the dye material is recovered by eluting dilute NaOH solution through exhausted Bottom Ash and De-Oiled Soya columns, respectively.

  13. Adsorption of oxygen molecule in NaA zeolite: Isotherms and infrared measurements

    NASA Astrophysics Data System (ADS)

    Soussen-Jacob, Janine; Tsakiris, Jean; Cohen De Lara, Evelyne

    1989-08-01

    Isotherm and infrared induced band of O2 have been studied in the temperature range 93-193 K. At low temperature and low coverage, two components of the fundamental vibrational band appear on both sides of the gas frequency. Their intensities with respect to T and to the number of adsorbed molecules have been measured in order to understand the interaction of O2 with NaA zeolite. The frequency shift of each component has been related to the orientation of the molecule, from considerations about the interaction potential.

  14. 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.

  15. 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.

  16. Equilibrium model for biodegradation and adsorption of mixtures in GAC columns

    SciTech Connect

    Erlanson, B.C.; Dvorak, B.I.; Speitel, G.E. Jr.; Lawler, D.F.

    1997-05-01

    Microbial activity in granular activated carbon (GAC) columns has received much attention over the last 15 years because biodegradation of one or more chemicals might increase the GAC service life, thereby decreasing costs. An equilibrium model for simultaneous biodegradation and adsorption was developed and verified with existing data. For simplicity the model was restricted to only two components: one biodegradable and one not. The results from modeling over 300 hypothetical situations identified conditions where biodegradation significantly extends the service life of granular activated carbon (GAC) columns. When the nonbiodegradable chemical controls the service life, the only significant gains in service life occurred when the biodegradable and nonbiodegradable chemical had similar adsorbabilities. When the biodegradable chemical controls the service life, the service life was 1.2--7 times that with adsorption alone, depending on the relative adsorbability of the two chemicals. The increase in service life can be maximized by ensuring that biodegradation begins as soon as possible after start-up. The model provides a good screening tool for initial assessments of process feasibility, preliminary economic analyses, and planning of detailed experimental and computer modeling studies. Examples are presented using benzene and TCE to illustrate how the general trends presented apply to specific cases.

  17. Design of β-cyclodextrin modified TiO2 nanotubes for the adsorption of Cu(II): Isotherms and kinetics study.

    PubMed

    Triki, Mohamed; Tanazefti, Haythem; Kochkar, Hafedh

    2017-05-01

    This paper builds on previous literature showing the interesting adsorptive properties of TiO2 nanotubes. It further explores the positive effect of β-cyclodextrin on these properties. Hence, β-cyclodextrin modified TiO2 nanotubes were successfully prepared and characterized by XRD, N2 physisorption at 77K, Raman, FTIR-ATR, (1)H NMR, TEM and EPR. The adsorptive interaction of Cu(II) with materials was investigated in aqueous solution at pH 9.25 (NH4(+)/NH3). The main conclusion is that copper(II)-ammonia complexation equilibria play an important role in the adsorption process. The β-cyclodextrin was found to improve the Cu(NH3)4(2+) adsorption mainly by retarding its precipitation to high concentrations values (>400mgL(-1)). Adsorption experimental data showed good fit with the pseudo-second-order model and the Langmuir isotherm model.

  18. Surface heterogeneity of passively oxidized silicon carbide particles: vapor adsorption isotherms.

    PubMed

    Médout-Marère, V; Partyka, S; Dutartre, R; Chauveteau, G; Douillard, J M

    2003-06-15

    The surfaces of silicon carbide particles subjected to two different passive oxidation treatments have been characterized by immersion calorimetry and vapor adsorption techniques. Surface enthalpies and surface free energies have been computed using semiempirical models and are compared to theoretical estimations. The surface entropy term appears higher than in the case of other solids studied with the same analysis. The definition of the surface entropy term is discussed in order to explain the discrepancy between calculation and experiment. An explanation of results is proposed, which is related to the constitution of silicon oxide layers at the surface of silicon carbide, a fact demonstrated by previous XPS measurements.

  19. Quantifying differences in the impact of variable chemistry on equilibrium uranium(VI) adsorption properties of aquifer sediments

    USGS Publications Warehouse

    Stoliker, Deborah L.; Kent, Douglas B.; Zachara, John M.

    2011-01-01

    Uranium adsorption-desorption on sediment samples collected from the Hanford 300-Area, Richland, WA varied extensively over a range of field-relevant chemical conditions, complicating assessment of possible differences in equilibrium adsorption properties. Adsorption equilibrium was achieved in 500-1000 h although dissolved uranium concentrations increased over thousands of hours owing to changes in aqueous chemical composition driven by sediment-water reactions. A nonelectrostatic surface complexation reaction, >SOH + UO22+ + 2CO32- = >SOUO2(CO3HCO3)2-, provided the best fit to experimental data for each sediment sample resulting in a range of conditional equilibrium constants (logKc) from 21.49 to 21.76. Potential differences in uranium adsorption properties could be assessed in plots based on the generalized mass-action expressions yielding linear trends displaced vertically by differences in logKc values. Using this approach, logKc values for seven sediment samples were not significantly different. However, a significant difference in adsorption properties between one sediment sample and the fines (Kc uncertainty were improved by capturing all data points within experimental errors. The mass-action expression plots demonstrate that applying models outside the range of conditions used in model calibration greatly increases potential errors.

  20. Quantifying differences in the impact of variable chemistry on equilibrium uranium(VI) adsorption properties of aquifer sediments

    SciTech Connect

    Stoliker, Deborah L.; Kent, Douglas B.; Zachara, John M.

    2011-09-16

    Uranium adsorption-desorption on sediment samples collected from the Hanford 300-Area, Richland, WA varied extensively over a range of field-relevant chemical conditions, complicating assessment of possible differences in equilibrium adsorption properties. Adsorption equilibrium was achieved in 500-1000 hours although dissolved uranium concentrations increased over thousands of hours owing to changes in aqueous chemical composition driven by sediment-water reactions. A non-electrostatic surface complexation reaction, >SOH + UO22+ + 2CO32- = >SOUO2(CO3HCO3)2-, provided the best fit to experimental data for each sediment sample resulting in a range of conditional equilibrium constants (logKc) from 21.49 to 21.76. Potential differences in uranium adsorption properties could be assessed in plots based on the generalized mass-action expressions yielding linear trends displaced vertically by differences in logKc values. Using this approach, logKc values for seven sediment samples were not significantly different. However, a significant difference in adsorption properties between one sediment sample and the fines (<0.063 mm) of another could be demonstrated despite the fines requiring a different reaction stoichiometry. Estimates of logKc uncertainty were improved by capturing all data points within experimental errors. The mass-action expression plots demonstrate that applying models outside the range of conditions used in model calibration greatly increases potential errors.

  1. Equilibrium adsorption of caffeic, chlorogenic and rosmarinic acids on cationic cross-linked starch with quaternary ammonium groups.

    PubMed

    Simanaviciute, Deimante; Klimaviciute, Rima; Rutkaite, Ramune

    2017-02-01

    In the present study, the equilibrium adsorption of caffeic acid (CA) and its derivatives, namely, chlorogenic (CGA) and rosmarinic (RA) acids on cationic cross-linked starch (CCS) with degree of substitution of quaternary ammonium groups of 0.42 have been investigated in relation to the structure and acidity of phenolic acids. The Langmuir, Freundlich and Dubinin-Radushkevich adsorption models have been used to describe the equilibrium adsorption of CA, CGA and RA from their initial solutions and solutions having the equimolar amount of NaOH at different temperatures. In the case of adsorption from the initial solutions of acids the values of adsorption parameters were closely related to the dissociation constants of investigated acids. According to the increasing effectiveness of adsorption, phenolic acids could be arranged in the following order: CA

  2. Removal of Bisphenol A aqueous solution using surfactant-modified natural zeolite: Taguchi's experimental design, adsorption kinetic, equilibrium and thermodynamic study.

    PubMed

    Genç, Nevim; Kılıçoğlu, Ödül; Narci, Ali Oğuzhan

    2017-02-01

    In this study, surfactant-modified natural zeolite was used to remove Bisphenol A (BPA) from aqueous solutions. Kinetics, equilibrium and thermodynamics of BPA adsorption on the adsorbent surfaces were investigated. The experimental data were described with the Temkin isotherm and the pseudo-second- order kinetic model. Taguchi's robust design approach was used to optimize adsorption of BPA. Experimentation was planned as per Taguchi's L27 orthogonal array. Tests were conducted with different adsorbate amount, pH, time, initial concentration of BPA, temperature and agitation speed. The optimum levels of control factors for maximum total organic carbon removal were defined (adsorbate amount at 0.25 g, pH at 7, time at 30 min, initial concentration of BPA at 50 mg/L, temperature at 30°C and agitation speed at 200 rpm). The ANOVA analysis shown that the most effective control factor is adsorbent dosage; its contribution is 56.4%. Contribution of pH and mixing rate are 7.5% and 7.6%, respectively. A confirmation experiment was conducted to verify the feasibility and effectiveness of the optimal combination. The observed value of S/N (ηobs = 39) ratio is compared with that of the predicted value (ηopt = 48). The prediction error, that is, ηopt - ηobs = 9, is within CI value.

  3. Kinetic and equilibrium studies for the adsorption process of cadmium(II) and copper(II) onto Pseudomonas aeruginosa using square wave anodic stripping voltammetry method.

    PubMed

    Kong, Bo; Tang, Biyu; Liu, Xiaoying; Zeng, Xiandong; Duan, Haiyan; Luo, Shenglian; Wei, Wanzhi

    2009-08-15

    A novel method for the simultaneous determination of cadmium(II) and copper(II) during the adsorption process onto Pseudomonas aeruginosa was developed. The concentration of the free metal ions was successfully detected by square wave anodic stripping voltammetry (SWASV) on the mercaptoethane sulfonate (MES) modified gold electrode, while the P. aeruginosa was efficiently avoided approaching to the electrode surface by the MES monolayer. And the anodic stripping peaks of Cd(2+) and Cu(2+) appear at -0.13 and 0.34V respectively, at the concentration range of 5-50 microM, the peak currents of SWASV present linear relationships with the concentrations of cadmium and copper respectively. As the determination of Cd(2+) and Cu(2+) was in real time and without pretreatment, the kinetic characteristics of the adsorption process were studied and all the corresponding regression parameters were obtained by fitting the electrochemical experimental data to the pseudo-second-order kinetic model. Moreover, Langmuir and Freundlich models well described the biosorption isotherms. And there were some differences in the amount of metal ion adsorbed at equilibrium (q(e)) and other kinetics parameters when the two ions coexisted were compared with the unaccompanied condition, which were also discussed in this paper. The proposed electrode system provides excellent platform for the simultaneous determination of trace metals in complex biosorption process.

  4. Enhancing adsorption capacity of toxic malachite green dye through chemically modified breadnut peel: equilibrium, thermodynamics, kinetics and regeneration studies.

    PubMed

    Chieng, Hei Ing; Lim, Linda B L; Priyantha, Namal

    2015-01-01

    Breadnut skin, in both its unmodified (KS) and base-modified (BM-KS) forms, was investigated for its potential use as a low-cost adsorbent for the removal of toxic dye, malachite green (MG). Characterization of the adsorbents was carried out using scanning electron microscope, X-ray fluorescence and Fourier transform infra-red spectroscopy. Batch adsorption experiments, carried out under optimized conditions, for the adsorption of MG were fitted using five isotherm models (Langmuir, Freundlich, Dubinin-Radushkevich, Temkin and Sips) and six error functions to determine the best-fit model. The adsorption capacity was greatly enhanced when breadnut skin was chemically modified with NaOH, leading to an adsorption capacity of 353.0 mg g(-1), that was far superior to most reported adsorbents for the removal of MG. Thermodynamics studies indicated that the adsorption of MG was spontaneous on KS and BM-KS, and the reactions were endothermic and exothermic, respectively. Kinetics studies showed that both followed the pseudo-second order. Regeneration experiments on BM-KS indicated that its adsorption capacity was still maintained at>90% even after five cycles. It can be concluded that NaOH-modified breadfruit skin has great potential to be utilized in real-life application as a low-cost adsorbent for the removal of MG in wastewater treatment.

  5. Self-assembly in Nafion membranes upon hydration: water mobility and adsorption isotherms.

    PubMed

    Vishnyakov, Aleksey; Neimark, Alexander V

    2014-09-25

    By means of dissipative particle dynamics (DPD) and Monte Carlo (MC) simulations, we explored geometrical, transport, and sorption properties of hydrated Nafion-type polyelectrolyte membranes. Composed of a perfluorinated backbone with sulfonate side chains, Nafion self-assembles upon hydration and segregates into interpenetrating hydrophilic and hydrophobic subphases. This segregated morphology determines the transport properties of Nafion membranes that are widely used as compartment separators in fuel cells and other electrochemical devices, as well as permselective diffusion barriers in protective fabrics. We introduced a coarse-grained model of Nafion, which accounts explicitly for polymer rigidity and electrostatic interactions between anionic side chains and hydrated metal cations. In a series of DPD simulations with increasing content of water, a classical percolation transition from a system of isolated water clusters to a 3D network of hydrophilic channels was observed. The hydrophilic subphase connectivity and water diffusion were studied by constructing digitized replicas of self-assembled morphologies and performing random walk simulations. A non-monotonic dependence of the tracer diffusivity on the water content was found. This unexpected behavior was explained by the formation of large and mostly isolated water domains detected at high water content and high equivalent polymer weight. Using MC simulations, we calculated the chemical potential of water in the hydrated polymer and constructed the water sorption isotherms, which extended to the oversaturated conditions. We determined that the maximum diffusivity and the onset of formation of large water domains corresponded to the saturation conditions at 100% humidity. The oversaturated membrane morphologies generated in the canonical ensemble DPD simulations correspond to the metastable and unstable states of Nafion membrane that are not realized in the experiments.

  6. Equilibrium isotherm and kinetic studies for the simultaneous removal of phenol and cyanide by use of S. odorifera (MTCC 5700) immobilized on coconut shell activated carbon

    NASA Astrophysics Data System (ADS)

    Singh, Neetu; Balomajumder, Chandrajit

    2016-09-01

    In this study, simultaneous removal of phenol and cyanide by a microorganism S. odorifera (MTCC 5700) immobilized onto coconut shell activated carbon surface (CSAC) was studied in batch reactor from mono and binary component aqueous solution. Activated carbon was derived from coconut shell by chemical activation method. Ferric chloride (Fecl3), used as surface modification agents was applied to biomass. Optimum biosorption conditions were obtained as a function of biosorbent dosage, pH, temperature, contact time and initial phenol and cyanide concentration. To define the equilibrium isotherms, experimental data were analyzed by five mono component isotherm and six binary component isotherm models. The higher uptake capacity of phenol and cyanide onto CSAC biosorbent surface was 450.02 and 2.58 mg/g, respectively. Nonlinear regression analysis was used for determining the best fit model on the basis of error functions and also for calculating the parameters involved in kinetic and isotherm models. The kinetic study results revealed that Fractal-like mixed first second order model and Brouser-Weron-Sototlongo models for phenol and cyanide were capable to offer accurate explanation of biosorption kinetic. According to the experimental data results, CSAC with immobilization of bacterium S. odorifera (MTCC 5700) seems to be an alternative and effective biosorbent for the elimination of phenol and cyanide from binary component aqueous solution.

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

    PubMed

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

    2015-04-09

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

  8. Relative importance of column and adsorption parameters on the productivity in preparative liquid chromatography II: Investigation of separation systems with competitive Langmuir adsorption isotherms.

    PubMed

    Forssén, Patrik; Samuelsson, Jörgen; Fornstedt, Torgny

    2014-06-20

    In this study we investigated how the maximum productivity for commonly used, realistic separation system with a competitive Langmuir adsorption isotherm is affected by changes in column length, packing particle size, mobile phase viscosity, maximum allowed column pressure, column efficiency, sample concentration/solubility, selectivity, monolayer saturation capacity and retention factor of the first eluting compound. The study was performed by generating 1000 random separation systems whose optimal injection volume was determined, i.e., the injection volume that gives the largest achievable productivity. The relative changes in largest achievable productivity when one of the parameters above changes was then studied for each system and the productivity changes for all systems were presented as distributions. We found that it is almost always beneficial to use shorter columns with high pressure drops over the column and that the selectivity should be greater than 2. However, the sample concentration and column efficiency have very limited effect on the maximum productivity. The effect of packing particle size depends on the flow rate limiting factor. If the pumps maximum flow rate is the limiting factor use smaller packing, but if the pressure of the system is the limiting factor use larger packing up to about 40μm.

  9. Dye adsorption onto mesoporous materials: pH influence, kinetics and equilibrium in buffered and saline media.

    PubMed

    Gómez, J M; Galán, J; Rodríguez, A; Walker, G M

    2014-12-15

    Mesoporous materials were used as adsorbents for dye removal in different media: non-ionic, buffered and saline. The mesoporous materials used were commercial (silica gel) as well as as-synthesised materials (SBA-15 and a novel mesoporous carbon). Dye adsorption onto all the materials was very fast and the equilibrium was reached before 1 h. The pH has a significant influence on the adsorption capacity for the siliceous materials since the electrostatic interactions are the driving forces. However, the influence of the pH on the adsorption capacity of the carbonaceous material was lower, since the van der Waals interactions are the driving forces. The ionic strength has a great impact on the siliceous materials adsorption capacity, being their adsorption capacity in a buffered medium six times higher than the corresponding to a non-ionic medium. Nevertheless, ionic strength does not influence on the dye adsorption on the mesoporous carbon. Overall, the as-synthesised carbon material presents a clear potential to treat dye effluents, showing high adsorption capacity (q(e) ≈ 200 mg/g) in all the pH range studied (from 3 to 11); even at low concentrations (C(e) ≈ 10 mg/L) and at short contact times (t(e) < 30 min).

  10. Removal of direct blue-106 dye from aqueous solution using new activated carbons developed from pomegranate peel: adsorption equilibrium and kinetics.

    PubMed

    Amin, Nevine Kamal

    2009-06-15

    The use of cheap, high efficiency and ecofriendly adsorbent has been studied as an alternative source of activated carbon for the removal of dyes from wastewater. This study investigates the use of activated carbons prepared from pomegranate peel for the removal of direct blue dye from aqueous solution. A series of experiments were conducted in a batch system to assess the effect of the system variables, i.e. initial pH, temperature, initial dye concentration adsorbent dosage and contact time. The results showed that the adsorption of direct blue dye was maximal at pH 2, as the amount of adsorbent increased, the percentage of dye removal increased accordingly but it decreased with the increase in initial dye concentration and solution temperature. The adsorption kinetics was found to follow pseudo-second-order rate kinetic model, with a good correlation (R(2)>0.99) and intra-particle diffusion as one of the rate determining steps. Langmuir, Freundlich, Temkin, Dubinin-RadushKevich (D-R) and Harkins-Jura isotherms were used to analyze the equilibrium data at different temperatures. In addition, various thermodynamic parameters, such as standard Gibbs free energy (DeltaG degrees ), standard enthalpy (DeltaH degrees ), standard entropy (DeltaS degrees ), and the activation energy (E(a)) have been calculated. The adsorption process of direct blue dye onto different activated carbons prepared from pomegranate peel was found to be spontaneous and exothermic process. The findings of this investigation suggest that the physical sorption plays a role in controlling the sorption rate.

  11. 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

  12. Time evolution analysis of a 2D solid gas equilibrium: a model system for molecular adsorption and diffusion

    NASA Astrophysics Data System (ADS)

    Berner, S.; Brunner, M.; Ramoino, L.; Suzuki, H.; Güntherodt, H.-J.; Jung, T. A.

    2001-11-01

    The adsorption of sub-phthalocyanine molecules on Ag(1 1 1) has been studied by means of scanning tunneling microscopy (STM). The molecules are observed in different two-dimensional (2D) phases of adsorption which coexist in thermodynamic equilibrium. In the condensed phase the molecules form well-ordered islands with a honeycomb pattern. In the gas phase single molecules can be discriminated in single scan lines by characteristic tip excursions which occur randomly. The energy barrier for surface diffusion as well as the condensation energy to form 2D islands is estimated and discussed.

  13. Adsorption modeling for macroscopic contaminant dispersal analysis

    SciTech Connect

    Axley, J.W.

    1990-05-01

    Two families of macroscopic adsorption models are formulated, based on fundamental principles of adsorption science and technology, that may be used for macroscopic (such as whole-building) contaminant dispersal analysis. The first family of adsorption models - the Equilibrium Adsorption (EA) Models - are based upon the simple requirement of equilibrium between adsorbent and room air. The second family - the Boundary Layer Diffusion Controlled Adsorption (BLDC) Models - add to the equilibrium requirement a boundary layer model for diffusion of the adsorbate from the room air to the adsorbent surface. Two members of each of these families are explicitly discussed, one based on the linear adsorption isotherm model and the other on the Langmuir model. The linear variants of each family are applied to model the adsorption dynamics of formaldehyde in gypsum wall board and compared to measured data.

  14. 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.

  15. 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.

  16. The effect of water temperature on the adsorption equilibrium of dissolved organic matter and atrazine on granular activated carbon

    SciTech Connect

    Bernd Schreiber; Viktor Schmalz; Thomas Brinkmann; Eckhard Worch

    2007-09-15

    The influence of water temperature on the adsorption of natural dissolved organic matter (DOM) on activated carbon has not been investigated intensively yet. In this study, batch experiments with granular activated carbon (GAC) F300, from bituminous coal, have been carried out at three temperatures (5, 20, 35{sup o} C) using a humic acid model water and different types of surface water (lake, river, canal). Furthermore, the adsorption of an anthropogenic contaminant, atrazine, was quantified in the absence and presence of DOM. The results indicate a significant influence of water temperature on the adsorption equilibrium of DOM and atrazine. Contrary to expectations, DOM and atrazine adsorption in surface water tends to be increased with increasing water temperature, whereas the extent of this effect is dependent on the type and concentration of DOM. Furthermore, the temperature effect on atrazine adsorption is controlled by competition of DOM and atrazine on adsorption sites. Some assumptions are proposed and discussed for explaining the temperature effects observed in the batch studies. 39 refs., 4 figs., 2 tabs.

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

    SciTech Connect

    HASSAN, NEGUIBM

    2004-03-30

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

  18. Adsorption of Rhodamine B on two novel polar-modified post-cross-linked resins: Equilibrium and kinetics.

    PubMed

    Jiang, Xiangfu; Huang, Jianhan

    2016-04-01

    We employed two polar monomers, triallyl isocyanurate (TAIC) and butyl acrylate (BA), to copolymerize with divinylbenzene (DVB), and synthesized two starting copolymers labeled PDT and PDB. Then, the Friedel-Crafts alkylation reaction was performed for the two starting copolymers, and the residual pendent vinyl groups were consumed, and hence we obtained two novel polar-modified post-cross-linked resins PDTpc and PDBpc. The surface polarity greatly improved due to introduction of the polar monomers, and the Brunauer-Emmett-Teller (BET) surface area and pore volume significantly increased after the Friedel-Crafts alkylation reaction. Compared with the starting copolymers, the non-polar post-cross-linked resin PDVBpc and some other adsorbents in the references, PDTpc and PDBpc possessed a much enhanced adsorption to Rhodamine B, and the equilibrium capacity reached 578.2mg/g and 328.7mg/g, respectively, at an equilibrium concentration of 100mg/L, and the Freundlich model characterized the equilibrium data very well. The adsorption was a fast process and the kinetic data obeyed the micropore diffusion model. These results confirmed that PDTpc and PDBpc had the potential superiority in adsorptive removal of Rhodamine B from aqueous solution.

  19. Process development for removal and recovery of cadmium from wastewater by a low-cost adsorbent: Adsorption rates and equilibrium studies

    SciTech Connect

    Periasamy, K.; Namasivayam, C. . Dept. of Environmental Sciences)

    1994-02-01

    Activated carbon prepared from peanut hulls (PHC), an agricultural waste by-product, has been used for the adsorption of Cd(II) from synthetic wastewater. The adsorption data fit better with the Freundlich adsorption isotherm. The applicability of the Lagergren kinetic model has also been investigated. An almost quantitative removal of 20 mg/L Cd(II) by 0.7 g of PHC/L of aqueous solution was observed in the pH range 3.5--9.5. A comparative study with a commercial granular activated carbon (CAC) showed that the adsorption capacity (K[sub f]) of PHC was 31 times larger than that of CAC.

  20. Isotherm parameters and intraparticle mass transfer kinetics on molecularly imprinted polymers in acetonitrile/buffer mobile phases

    SciTech Connect

    Kim, Hyunjung; Kaczmarski, Krzysztof; Guiochon, Georges A

    2006-03-01

    The equilibrium isotherm and the intraparticle mass transfer kinetics of the enantiomers of the template were investigated on an Fmoc-L-tryptophan (Fmoc-L-Trp) imprinted polymer at different pHs and water concentrations in acetonitrile/aqueous buffer mobile phases. The equilibrium isotherm data were measured using frontal analysis at 25 {+-} 2 C. The adsorption energy distribution was found to be trimodal, with narrow modes. Consistent with this distribution, the adsorption data were modeled using a tri-Langmuir isotherm equation and the best estimates of the isotherm parameters were determined. The intraparticle mass transfer parameters were derived by comparing the profiles of experimental overloaded bands and the profiles calculated using the isotherm model and the lumped pore diffusion (POR) model of chromatography. These results showed that different adsorption and mass transfer mechanisms exist in mobile phases made of acetonitrile/aqueous buffer and of acetonitrile/acetic acid solutions.

  1. Non-equilibrium and equilibrium sorption with a linear-sorption isotherm during mass transport through an infinite, porous medium: some analytical solutions

    SciTech Connect

    Carnahan, C.L.; Remer, J.S.

    1981-04-01

    Analytical solutions have been developed for the problem of solute transport in a steady, three dimensional field of groundwater flow with non-equilibrium mass transfer of a radioactive species between fluid and solid phases and with anisotropic hydrodynamic dispersion. Interphase mass transport is described by a linear rate expression. Solutions are presented also for the case of equilibrium distribution of solute between fluid and solid phases. Three types of release from a point source were considered: instantaneous release of a finite mass of solute, continuous release at an exponentially decaying rate, and release for a finite period of time. Graphical displays of computational results for point-source solutions show the expected variation of sorptive retardation effects progressing from the case of no sorption, through several cases of non-equilibrium sorption, to the case of equilibrium sorption. The point-source solutions can be integrated over finite regions of a space to provide analytical solutions for regions of solute release having finite spatial extents and various geometrical shapes, thus considerably extending the utility of the point-source solutions.

  2. 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

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

    PubMed

    Rahman, Md Sayedur; Sathasivam, Kathiresan V

    2015-01-01

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

  4. Adsorption behaviour of direct yellow 50 onto cotton fiber: equilibrium, kinetic and thermodynamic profile.

    PubMed

    Ismail, L F M; Sallam, H B; Abo Farha, S A; Gamal, A M; Mahmoud, G E A

    2014-10-15

    This study investigated the adsorption of direct yellow 50 onto cotton fiber from aqueous solution by using parameters, such as pH, temperature, contact time, initial dye concentration and the effect of sodium sulphate, tetrasodium edate and trisodium citrate. The extent of dye adsorption increased with increasing contact time, temperature and solution concentration. The experimental data were analyzed by the Langmuir and Freundlich models of adsorption. It was found that the Langmuir equation fit better than the Freundlich equation. The results show that the presence of SE and SC significantly enhance the dye adsorption onto cotton fiber. In addition, the adsorption data obtained at different temperatures of DY50 onto cotton fiber were applied to pseudo first-order, pseudo second-order and intraparticle diffusion models. The rates of adsorption were found to conform to pseudo second-order kinetics with good correlation. Also, free energy of adsorption (ΔG(#)), enthalpy (ΔH(#)), and entropy (ΔS(#)) changes were determined to predict the nature of adsorption. The positive value of the enthalpy change indicated that the adsorption is endothermic process. The activation energy, Ea, is ranged between 1.9 and 3.9kJmol(-1) indicated that the adsorption process is a physisorption. This low value of Ea generally indicates diffusion controlled process.

  5. Adsorption behaviour of direct yellow 50 onto cotton fiber: Equilibrium, kinetic and thermodynamic profile

    NASA Astrophysics Data System (ADS)

    Ismail, L. F. M.; Sallam, H. B.; Abo Farha, S. A.; Gamal, A. M.; Mahmoud, G. E. A.

    2014-10-01

    This study investigated the adsorption of direct yellow 50 onto cotton fiber from aqueous solution by using parameters, such as pH, temperature, contact time, initial dye concentration and the effect of sodium sulphate, tetrasodium edate and trisodium citrate. The extent of dye adsorption increased with increasing contact time, temperature and solution concentration. The experimental data were analyzed by the Langmuir and Freundlich models of adsorption. It was found that the Langmuir equation fit better than the Freundlich equation. The results show that the presence of SE and SC significantly enhance the dye adsorption onto cotton fiber. In addition, the adsorption data obtained at different temperatures of DY50 onto cotton fiber were applied to pseudo first-order, pseudo second-order and intraparticle diffusion models. The rates of adsorption were found to conform to pseudo second-order kinetics with good correlation. Also, free energy of adsorption (ΔG#), enthalpy (ΔH#), and entropy (ΔS#) changes were determined to predict the nature of adsorption. The positive value of the enthalpy change indicated that the adsorption is endothermic process. The activation energy, Ea, is ranged between 1.9 and 3.9 kJ mol-1 indicated that the adsorption process is a physisorption. This low value of Ea generally indicates diffusion controlled process.

  6. Removal of 2,4-dichlorophenol using cyclodextrin-ionic liquid polymer as a macroporous material: characterization, adsorption isotherm, kinetic study, thermodynamics.

    PubMed

    Raoov, Muggundha; Mohamad, Sharifah; Abas, Mohd Radzi

    2013-12-15

    Cyclodextrin-ionic liquid polymer (βCD-BIMOTs-TDI) was firstly synthesized using functionalized β-Cyclodextrin (CD) with 1-benzylimidazole (BIM) to form monofunctionalized CD (βCD-BIMOTs) and was further polymerized using toluene diisocyanate (TDI) linker to form insoluble βCD-BIMOTs-TDI. SEM characterization result shows that βCD-BIMOTs-TDI exhibits macropore size while the BET result shows low surface area (1.254 m(2)g(-1)). The unique properties of the ILs allow us to produce materials with different morphologies. The adsorption isotherm and kinetics of 2,4-dichlorophenol (2,4-DCP) onto βCD-BIMOTs-TDI is studied. Freundlich isotherm and pseudo-second order kinetics are found to be the best to represent the data for 2,4-DCP adsorption on the βCD-BIMOTs-TDI. The presence of macropores decreases the mass transfer resistance and increases the adsorption process by reducing the diffusion distance. The change in entropy (ΔS°) and heat of adsorption (ΔH°) for 2,4-DCP on βCD-BIMOTs-TDI were estimated as -55.99 J/Kmol and -18.10 J/mol, respectively. The negative value of Gibbs free energy (ΔG°) indicates that the adsorption process is thermodynamically feasible, spontaneous and chemically controlled. Finally, the interactions between the cavity of βCD-BIMOTs and 2,4-DCP are investigated and the results shows that the inclusion of the complex formation and π-π interaction are the main processes involved in the adsorption process.

  7. Equilibrium, Kinetic, and Thermodynamic Studies on the Adsorption of Cadmium from Aqueous Solution by Modified Biomass Ash

    PubMed Central

    Zheng, Xuebo; Cui, Hongbiao; Zhu, Zhenqiu; Liang, Jiani

    2017-01-01

    Natural biomass ash of agricultural residuals was collected from a power plant and modified with hexagonal mesoporous silica and functionalized with 3-aminopropyltriethoxysilane. The physicochemical and morphological properties of the biomass ash were analyzed by ICP-OES, SEM, TEM-EDS, FTIR, and BET analysis. The adsorption behavior of the modified product for Cd2+ in aqueous solution was studied as a function of pH, initial metal concentration, equilibrium time, and temperature. Results showed that the specific surface area of the modified product was 9 times that of the natural biomass ash. The modified biomass ash exhibited high affinity for Cd2+ and its adsorption capacity increased sharply with increasing pH from 4.0 to 6.0. The maximum adsorption capacity was 23.95 mg/g in a pH 5 solution with an initial metal concentration of 50 mg/L and a contact time of 90 min. The adsorption of Cd2+ onto the modified biomass ash was well fitted to the Langmuir model and it followed pseudo-second-order kinetics. Thermodynamic analysis results showed that the adsorption of Cd2+ was spontaneous and endothermic in nature. The results suggest that the modified biomass ash is promising for use as an inexpensive and effective adsorbent for Cd2+ removal from aqueous solution. PMID:28348509

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

    NASA Astrophysics Data System (ADS)

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

    2014-06-01

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

  9. 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.

  10. 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.

  11. Adsorption studies of methylene blue and gentian violet on sugarcane bagasse modified with EDTA dianhydride (EDTAD) in aqueous solutions: kinetic and equilibrium aspects.

    PubMed

    Gusmão, Karla Aparecida Guimarães; Gurgel, Leandro Vinícius Alves; Melo, Tânia Márcia Sacramento; Gil, Laurent Frédéric

    2013-03-30

    In this study the adsorption of cationic dyes by modified sugarcane bagasse with EDTA dianhydride (EB) was examined using methylene blue (MB) and gentian violet (GV) as model compounds in aqueous single solutions. The synthesized adsorbent (EB) was characterized by FTIR, elemental analysis, and BET. The capacity of EB to adsorb dyes was evaluated at different contact times, pH values, and initial dye concentrations. According to the obtained results, the adsorption processes could be described by a pseudo-second-order kinetic model. The adsorption isotherms were well fitted by the Langmuir model. Maximum adsorption capacities for MB and GV on EB were found to be 202.43 and 327.83 mg/g, respectively. The free energy change during adsorption of MB and GV was found to be -22.50 and -24.21 kJ/mol, respectively, suggesting that chemisorption is the main mechanism controlling the adsorption process.

  12. Development, Construction, and Operation of a Multisample Volumetric Apparatus for the Study of Gas Adsorption Equilibrium

    ERIC Educational Resources Information Center

    Ribeiro, Rui P. P. L.; Silva, Ricardo J. S.; Esteves, Isabel A. A. C.; Mota, Jose´ P. B.

    2015-01-01

    The construction of a simple volumetric adsorption apparatus is highlighted. The setup is inexpensive and provides a clear demonstration of gas phase adsorption concepts. The topic is suitable for undergraduate chemistry and chemical engineering students. Moreover, this unit can also provide quantitative data that can be used by young researchers…

  13. Adsorption equilibrium, kinetics and thermodynamics of α-amylase on poly(DVB-VIM)-Cu(+2) magnetic metal-chelate affinity sorbent.

    PubMed

    Osman, Bilgen; Kara, Ali; Demirbel, Emel; Kök, Senay; Beşirli, Necati

    2012-09-01

    Designing an immobilised metal ion affinity process on large-scale demands that a thorough understanding be developed regarding the adsorption behaviour of proteins on metal-loaded gels and the characteristic adsorption parameters to be evaluated. In view of this requirement, interaction of α-amylase as a model protein with newly synthesised magnetic-poly(divinylbenzene-1-vinylimidazole) [m-poly(DVB-VIM)] microbeads (average diameter, 53-212 μm) was investigated. The m-poly(DVB-VIM) microbeads were prepared by copolymerising of divinylbenzene (DVB) with 1-vinylimidazole (VIM). The m-poly(DVB-VIM) microbeads were characterised by N(2) adsorption/desorption isotherms, electron spin resonance, elemental analysis, scanning electron microscope and swelling studies. Cu(2+) ions were chelated on the m-poly(DVB-VIM) beads and used in adsorption of α-amylase in a batch system. The maximum α-amylase adsorption capacity of the m-poly(DVB-VIM)-Cu(2+) beads was determined as 10.84 mg/g at pH 6.0, 25 °C. The adsorption data were analyzed using three isotherm models, which are the Langmuir, Freundlich and Dubinin-Radushkevich isotherm models. The pseudo-first-order, pseudo-second-order, modified Ritchie's-second-order and intraparticle diffusion models were used to test dynamic experimental data. The study of temperature effect was quantified by calculating various thermodynamic parameters such as Gibbs free energy, enthalpy and entropy changes.

  14. Pb(II) adsorption by a novel activated carbon - alginate composite material. A kinetic and equilibrium study.

    PubMed

    Cataldo, Salvatore; Gianguzza, Antonio; Milea, Demetrio; Muratore, Nicola; Pettignano, Alberto

    2016-11-01

    The adsorption capacity of an activated carbon - calcium alginate composite material (ACAA-Ca) has been tested with the aim of developing a new and more efficient adsorbent material to remove Pb(II) ion from aqueous solution. The study was carried out at pH=5, in NaCl medium and in the ionic strength range 0.1-0.75molL(-1). Differential Pulse Anodic Stripping Voltammetry (DP-ASV) technique was used to check the amount of Pb(II) ion removed during kinetic and equilibrium experiments. Different kinetic (pseudo first order, pseudo second order and Vermuelen) and equilibrium (Langmuir and Freundlich) models were used to fit experimental data, and were statistically compared. Calcium alginate (AA-Ca) improves the adsorption capacity (qm) of active carbon (AC) in the ACAA-Ca adsorbent material (e.g., qm=15.7 and 10.5mgg(-1) at I=0.25molL(-1), for ACAA-Ca and AC, respectively). SEM-EDX and thermogravimetric (TGA) measurements were carried out in order to characterize the composite material. The results of the speciation study on the Pb(II) solution and of the characterization of the ACAA-Ca and of the pristine AA-Ca and AC were evaluated in order to explain the specific contribution of AC and AA-Ca to the adsorption of the metal ion.

  15. Modeling, kinetic, and equilibrium characterization of paraquat adsorption onto polyurethane foam using the ion-pairing technique.

    PubMed

    Vinhal, Jonas O; Lage, Mateus R; Carneiro, José Walkimar M; Lima, Claudio F; Cassella, Ricardo J

    2015-06-01

    We studied the adsorption of paraquat onto polyurethane foam (PUF) when it was in a medium containing sodium dodecylsulfate (SDS). The adsorption efficiency was dependent on the concentration of SDS in solution, because the formation of an ion-associate between the cationic paraquat and the dodecylsulfate anion was found to be a fundamental step in the process. A computational study was carried out to identify the possible structure of the ion-associate in aqueous medium. The obtained data demonstrated that the structure is probably formed from four units of dodecylsulfate bonded to one paraquat moiety. The results showed that 94% of the paraquat present in 45 mL of a solution containing 3.90 × 10(-5) mol L(-1) could be retained by 300 mg of PUF, resulting in the removal of 2.20 mg of paraquat. The experimental data were reasonably adjusted to the Freundlich isotherm and to the pseudo-second-order kinetic model. Also, the application of Morris-Weber and Reichenberg models indicated that both film-diffusion and intraparticle-diffusion processes were active during the control of the adsorption kinetics.

  16. Kinetics and equilibrium of adsorption of dissolved organic matter fractions from secondary effluent by fly ash.

    PubMed

    Wei, Liangliang; Wang, Kun; Zhao, Qingliang; Xie, Chunmei; Qiu, Wei; Jia, Ting

    2011-01-01

    Fly ash was used as a low-cost adsorbent for removing dissolved organic matter (DOM) in secondary effluent. Batch experiments were conducted under various adsorbent dosages, pH, contact time, temperatures and DOM fractional characteristics. Under the optimum conditions of fly ash dosage of 15 g/L, temperature of 303 K and contact time of 180 min, a removal of 22.5% of the dissolved organic carbon (DOC), 23.7% of UV-254, 25.9% of the trihalomethanes precursors in secondary effluent was obtained. The adsorption of DOM fractions onto fly ash all followed the pseudo second-order kinetic model, and the hydrophilic fraction adsorption by fly ash also fitted the intraparticle diffusion model quite well. Freundlich and Langmuir models were applicable to the fly ash adsorption and their constants were evaluated. The maximum adsorption capacities of the adsorptions revealed that fly ash was more effective in adsorbing hydrophilic fraction than the acidic fractions. Structure changes of the DOM fractions after fly ash adsorption were also characterized via spectrum analyzing. Those mechanisms presented critical step toward improved efficiencies of fly ash adsorption via further surface-modification.

  17. Adsorptive removal of 2-chlorophenol by low-cost coir pith carbon.

    PubMed

    Namasivayam, C; Kavitha, D

    2003-03-17

    Adsorption of 2-chlorophenol (2-CP) by coir pith carbon was carried out by varying the parameters such as agitation time, 2-CP concentration, adsorbent dose, pH and temperature. Adsorption equilibrium reached at 40, 60, 80 and 100 min for 2-CP concentration of 10, 20, 30 and 40 mg/l, respectively. Adsorption followed second-order kinetics. The adsorption equilibrium data obeyed Freundlich isotherm. Acidic pH was favorable for the adsorption of 2-CP. Desorption studies showed that chemisorption plays a major role in the adsorption process.

  18. 2,4-D adsorption to biochars: effect of preparation conditions on equilibrium adsorption capacity and comparison with commercial activated carbon literature data.

    PubMed

    Kearns, J P; Wellborn, L S; Summers, R S; Knappe, D R U

    2014-10-01

    Batch isotherm experiments were conducted with chars to study adsorption of the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D). Chars generated from corncobs, bamboo and wood chips in a laboratory pyrolyzer at 400-700 °C were compared with traditional kiln charcoals collected from villages in S/SE Asia and with activated carbons (ACs). 2,4-D uptake by laboratory chars obtained from bamboo and wood chips after 14 h of pyrolysis at 700 °C, from wood chips after 96 h of pyrolysis at 600 °C, and one of the field-collected chars (basudha) was comparable to ACs. H:C and O:C ratios declined with pyrolysis temperature and duration while surface area increased to >500 m(2)/g. Increasing pyrolysis intensity by increasing temperature and/or duration of heating was found to positively influence adsorption capacity yield (mg(2,4-D/g(feedstock))) over the range of conditions studied. Economic analysis showed that high temperature chars can be a cost-effective alternative to ACs for water treatment applications.

  19. Biosorption of Acid Blue 25 by unmodified and CPC-modified biomass of Penicillium YW01: kinetic study, equilibrium isotherm and FTIR analysis.

    PubMed

    Yang, Yuyi; Jin, Danfeng; Wang, Guan; Liu, Danfeng; Jia, Xiaoming; Zhao, Yuhua

    2011-11-01

    The main objective of this work was to investigate the biosorption performance of unmodified and Cetylpyridinium chloride (CPC)-modified biomass of Penicillium YW 01 for Acid Blue 25 (AB 25). Maximum biosorption capacity of AB 25 onto CPC-modified biosorbent was 118.48 mg g(-1) under phosphoric-phosphate buffer with initial dye concentration of 200 mg L(-1) at 30°C. The biosorption pattern of AB 25 onto unmodified biosorbent in aqueous solution and phosphoric-phosphate buffer was well fitted with both Langmuir and Freundlich isotherm models. While the equilibrium data of CPC-modified biosorbent in aqueous solution and phosphoric-phosphate buffer failed to fit the Freundlich isotherm model, indicating the monolayer biosorption formed onto CPC-modified biosorbent. The values of initial biosorption rate of biosorbent in phosphoric-phosphate buffer were found to be higher than that of corresponding values in aqueous solution, indicating phosphoric-phosphate buffer enhanced the initial biosorption rate of biosorption process. Weber-Morris model analysis indicated that the boundary layer effect had more influence on the biosorption process in phosphoric-phosphate buffer. The BET surface area of CPC-modified biosorbent (0.5761 m(2) g(-1)) was larger than that of unmodified biomass (0.3081 m(2) g(-1)). Possible dye-biosorbent interactions were confirmed by Fourier transform infrared spectroscopy.

  20. Adsorption energies of mercury-containing species on CaO and temperature effects on equilibrium constants predicted by density functional theory calculations.

    PubMed

    Kim, Bo Gyeong; Li, Xinxin; Blowers, Paul

    2009-03-03

    The adsorption of Hg, HgCl, and HgCl2 on the CaO surface was investigated theoretically so the fundamental interactions between Hg species and this potential sorbent can be explored. Surface models of a 4 x 4 x 2 cluster, a 5 x 5 x 2 cluster, and a periodic structure using density functional theory calculations with LDA/PWC and GGA/BLYP functionals, as employed in the present work, offer a useful description for the thermodynamic properties of adsorption on metal oxides. The effect of temperature on the equilibrium constant for the adsorption of mercury-containing species on the CaO (0 0 1) surface was investigated with GGA/BLYP calculations in the temperature range of 250-600 K. Results show that, at low coverage of elemental mercury, adsorption on the surface is physisorption while the two forms of oxidized mercury adsorption undergo stronger adsorption. The adsorption energies decrease with increasing coverage for elemental mercury on the surfaces. The chlorine atom enhances the adsorption capacity and adsorbs mercury to the CaO surface more strongly. The adsorption energy is changed as the oxidation state varies, and the equilibrium constant decreases as the temperature increases, in good agreement with data for exothermic adsorption systems.

  1. Development of an isothermal titration microcalorimetric system with digital control and dynamic power peltier compensation. II. Characterization and operation mode. Myoglobin adsorption onto polymeric latex particles

    NASA Astrophysics Data System (ADS)

    Velázquez-Campoy, A.; López-Mayorga, O.; Cabrerizo-Vílchez, M. A.

    2000-04-01

    In a previous article a comprehensive description of an isothermal titration microcalorimeter with Peltier compensation was reported. This work deals with the characterization procedure and the operation mode. The transfer function parameters (time constants, calibration constants, and thermal properties of the system components) have been determined using a rigorous physical model for the microcalorimeter. To check the good performance of the instrument, titration experiments of cytidine and adenosine protonation have been carried out. Finally, as an example of the instrument applicability, differential heat measurements of myoglobin adsorption onto polymeric (polystyrene) latex particles are presented.

  2. Adsorption of aluminum and lead from wastewater by chitosan-tannic acid modified biopolymers: Isotherms, kinetics, thermodynamics and process mechanism.

    PubMed

    Badawi, M A; Negm, N A; Abou Kana, M T H; Hefni, H H; Abdel Moneem, M M

    2017-06-01

    Chitosan was reacted by tannic acid to obtain three modified chitosan biopolymer. Their chemical structures were characterized by FTIR and elemental analysis. The prepared biopolymers were used to adsorb Al(III) and Pb(II) metal ions from industrial wastewater. The factors affecting the adsorption process were biosorbent amount, initial concentration of metal ion and pH of the medium. The adsorption efficiency increased considerably with the increase of the biosorbent amount and pH of the medium. The adsorption process of biosorbent on different metal ions was fitted by Freundlich adsorption model. The adsorption kinetics was followed Pseudo-second-order kinetic model. The adsorption process occurred according to diffusion mechanism which was confirmed by the interparticle diffusion model. The modified biopolymers were efficient biosorbents for removal of Pb(II) and Al(III) metal ions from the medium.

  3. Mechanism of highly efficient adsorption of 2-chlorophenol onto ultrasonic graphene materials: Comparison and equilibrium.

    PubMed

    Soltani, Tayyebeh; Lee, Byeong-Kyu

    2016-11-01

    The deficiencies of the recently reported improved Hummers method for the synthesis of graphene oxide (GO), such as high reaction temperature (60°C) and long reaction time (10h), were successfully solved using a low-intensity ultrasonic bath for 30min at 40°C. Furthermore, compared to its conventional synthesis counterpart, a facile and fast, one-step ultrasonic method that excluded hydrazine hydrate was developed to synthesize reduced GO (rGO) from graphite (10min, 50°C) in the presence of hydrazine hydrate (rGO-C, 12h, 90°C). The adsorption characteristics of 2-chlorophenol (2-CP) from an aqueous solution were investigated using rGOs and GOs prepared by ultrasonic (rGO-Us/GO-Us) and conventional (rGO-C/GO-C) methods. Whereas 2-CP was completely removed with rGO-Us after 50min, only 40% of 2-CP was eliminated with rGO-C. The maximum adsorption capacity of 2-CP calculated by the Langmuir model onto rGO-Us (208.67mg/g) was much higher than that onto GO-Us (134.49mg/g). In addition, the ultrasonic graphene adsorption capacities were much higher than the corresponding values of rGO-C (49.9mg/g) and GO-C (32.06mg/g). The enhanced adsorption for rGO-Us and GO-Us is attributed to their greater surface areas, excellent oxygenated groups for GO-Us and superior π-electron-rich matrix for rGO-Us, compared to other adsorbents. The adsorption of 2-CP on the rGO materials increased with increasing solution pH to a maximum around its pKa (pKa=8.85), while the adsorption for the GO materials increased with decreasing solution pH. The adsorption mechanism proceeded via hydrogen bonding in neutral and acidic media, but via π-π electron donor-accepter (EDA) interactions between 2-CP and graphene materials in basic medium. The FTIR spectrum of GO-Us after adsorption indicates that the position and intensity of many peaks of GO-Us were affected due to the adsorption of different 2-CP groups at different pHs.

  4. Multilayer adsorption on fractal surfaces.

    PubMed

    Vajda, Péter; Felinger, Attila

    2014-01-10

    Multilayer adsorption is often observed in liquid chromatography. The most frequently employed model for multilayer adsorption is the BET isotherm equation. In this study we introduce an interpretation of multilayer adsorption measured on liquid chromatographic stationary phases based on the fractal theory. The fractal BET isotherm model was successfully used to determine the apparent fractal dimension of the adsorbent surface. The nonlinear fitting of the fractal BET equation gives us the estimation of the adsorption equilibrium constants and the monolayer saturation capacity of the adsorbent as well. In our experiments, aniline and proline were used as test molecules on reversed phase and normal phase columns, respectively. Our results suggest an apparent fractal dimension 2.88-2.99 in the case of reversed phase adsorbents, in the contrast with a bare silica column with a fractal dimension of 2.54.

  5. Adsorption of congo red by chitosan hydrogel beads impregnated with carbon nanotubes.

    PubMed

    Chatterjee, Sudipta; Lee, Min W; Woo, Seung H

    2010-03-01

    The adsorption performance of chitosan (CS) hydrogel beads was investigated after multiwalled carbon nanotubes (MWCNTs) impregnation for the removal of congo red (CR) as an anionic dye. The study of the adsorption capacity of CS/CNT beads as a function of the CNT concentration indicated that 0.01% CNT impregnation was the most useful for enhancing the adsorption capacity. The sulfur (%) in the CS/CNT beads measured by energy dispersive X-ray (EDX) was 2.5 times higher than that of normal CS beads after CR adsorption. Equilibrium adsorption isotherm data of the CS/CNT beads exhibited better fit to the Langmuir isotherm model than to the Freundlich isotherm model, and the heterogeneity factor (n) value of the CS/CNT beads calculated from the Sips isotherm model was close to unity (0.98). The maximum adsorption capacity of CS/CNT beads obtained from the Langmuir model was 450.4 mg g(-1).

  6. 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.

  7. ZnS:Cu nanoparticles loaded on activated carbon as novel adsorbent for kinetic, thermodynamic and isotherm studies of Reactive Orange 12 and Direct yellow 12 adsorption.

    PubMed

    Ghaedi, Mehrorang; Ansari, Amin; Sahraei, Reza

    2013-10-01

    The objective of this work is the study of adsorption of Reactive Orange 12 (RO-12) and Direct yellow 12 (DY 12) by zinc sulfide:copper (ZnS-Cu-NP-AC) nanoparticles loaded on activated carbon. This new material with high efficiency in a routine manner was synthesized in our laboratory and its surface properties viz surface area, pore volume and functional groups was characterized with different techniques such FT-IR, SEM, and BET analysis. Generally, in batch adsorption procedure variables including amount of adsorbent, initial dyes concentration, contact time, temperature on dyes removal percentage has great effect on removal percentage that their influence was optimized. The kinetic of proposed adsorption processes efficiently followed, pseudo-second-order, and intra-particle diffusion kinetic models. The equilibrium data the removal strongly follow Langmuir monolayer adsorption with high adsorption capacity in short time. This novel adsorbent by small amount (0.08 g) really is applicable for removal of high amount of both dyes (RO 12 and DY 12) in short time (<20 min). Based on the calculated thermodynamic parameters such as enthalpy (ΔH), entropy (ΔS), activation energy (Ea), sticking probability (S*) and Gibb's free energy changes (ΔG), it is noticeable that the sorption of both dyes onto ZnS:Cu-AC was spontaneous and endothermic process. At optimum values all variables the effect of contact time on adsorption was investigated and the dependency of adsorption data to different kinetic model such as pseudo-first-order, pseudo-second-order, Elovich and intra-particle diffusion was assessed and it was found that the removal processes follow pseudo second order kinetics and interparticle diffusion mechanism.

  8. Adsorption of radon and water vapor on commercial activated carbons

    SciTech Connect

    Hassan, N.M.; Ghosh, T.K.; Hines, A.L.; Loyalka, S.K.

    1995-02-01

    Equilibrium adsorption isotherms are reported for radon and water vapor on two commercial activated carbons: coconut shell Type PCB and hardwood Type BD. The isotherms of the water vapor were measured gravimetrically at 298 K. The isotherms of radon from dry nitrogen were obtained at 293, 298, and 308 K while the data for the mixture of radon and water vapor were measured at 298 K. The concentrations of radon in the gas and solid phases were measured simultaneously, once the adsorption equilibrium and the radioactive equilibrium between the radon and its daughter products were established. The shape of the isotherms was of Type III for the radon and Type V for the water vapor, according to Brunauer`s classification. The adsorption mechanism was similar for both the radon and the water vapor, being physical adsorption on the macropore surface area in the low pressure region and micropore filling near saturation pressure. The uptake capacity of radon decreased both with increasing temperature and relative humidity. The heat of adsorption data indicated that the PCB- and the BD-activated carbons provided a heterogeneous surface for radon adsorption. The equilibrium data for radon were correlated with a modified Freundlich equation.

  9. 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.

  10. 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

    2016-02-05

    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.

  11. 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.

  12. Characterizations of strontium(II) and barium(II) adsorption from aqueous solutions using dolomite powder.

    PubMed

    Ghaemi, Ahad; Torab-Mostaedi, Meisam; Ghannadi-Maragheh, Mohammad

    2011-06-15

    In this research, adsorption technique was applied for strontium and barium removal from aqueous solution using dolomite powder. The process has been investigated as a function of pH, contact time, temperature and adsorbate concentration. The experimental data was analyzed using equilibrium isotherm, kinetic and thermodynamic models. The isotherm data was well described by Langmuir isotherm model. The maximum adsorption capacity was found to be 1.172 and 3.958 mg/g for Sr(II) and Ba(II) from the Langmuir isotherm model at 293 K, respectively. The kinetic data was tested using first and pseudo-second order models. The results indicated that adsorption fitted well with the pseudo-second order kinetic model. The thermodynamic parameters (ΔG°, ΔH°, and ΔS°) were also determined using the equilibrium constant value obtained at different temperatures. The results showed that the adsorption for both ions was feasible and exothermic.

  13. Enhanced adsorptive removal of Safranine T from aqueous solutions by waste sea buckthorn branch powder modified with dopamine: Kinetics, equilibrium, and thermodynamics

    NASA Astrophysics Data System (ADS)

    Xu, Xiaohui; Bai, Bo; Wang, Honglun; Suo, Yourui

    2015-12-01

    Polydopamine coated sea buckthorn branch powder (PDA@SBP) was facilely synthesized via a one-pot bio-inspired dip-coating approach. The as-synthesized PDA@SBP was characterized using Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM). The adsorption progresses of Safranine T on the surface of PDA@SBP adsorbent were systematically investigated. More specifically, the effects of solution pH, contact time, initial concentration and temperature were evaluated, respectively. The experimental results showed the adsorption capacity of PDA@SBP at 293.15 K could reach up to 54.0 mg/g; the adsorption increased by 201.7% compared to that of native SBP (17.9 mg/g). Besides, kinetics studies showed that pseudo-second-order kinetic model adequately described the adsorption behavior. The adsorption experimental data could be fitted well a Freundlich isotherm model. Thermodynamic analyses showed that the ST adsorption was a physisorption endothermic process. Regeneration of the spent PDA@SBP adsorbent was conducted with 0.1 M HCl without significant reduction in adsorption capacity. On the basis of these investigations, it is believed that the PDA@SBP adsorbent could have potential applications in sewage disposal areas because of their considerable adsorption capacities, brilliant regeneration capability, and cost-effective and eco-friendly preparation and use.

  14. Testing isotherm models and recovering empirical relationships for adsorption in microporous carbons using virtual carbon models and grand canonical Monte Carlo simulations

    NASA Astrophysics Data System (ADS)

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

    2008-09-01

    Using the plausible model of activated carbon proposed by Harris and co-workers and grand canonical Monte Carlo simulations, we study the applicability of standard methods for describing adsorption data on microporous carbons widely used in adsorption science. Two carbon structures are studied, one with a small distribution of micropores in the range up to 1 nm, and the other with micropores covering a wide range of porosity. For both structures, adsorption isotherms of noble gases (from Ne to Xe), carbon tetrachloride and benzene are simulated. The data obtained are considered in terms of Dubinin-Radushkevich plots. Moreover, for benzene and carbon tetrachloride the temperature invariance of the characteristic curve is also studied. We show that using simulated data some empirical relationships obtained from experiment can be successfully recovered. Next we test the applicability of Dubinin's related models including the Dubinin-Izotova, Dubinin-Radushkevich-Stoeckli, and Jaroniec-Choma equations. The results obtained demonstrate the limits and applications of the models studied in the field of carbon porosity characterization.

  15. Kinetic Model for Surface-Active Enzymes Based on the Langmuir Adsorption Isotherm: Phospholipase C (Bacillus cereus) Activity toward Dimyristoyl Phosphatidylcholine/Detergent Micelles

    NASA Astrophysics Data System (ADS)

    Burns, Ramon A.; El-Sayed, Maha Y.; Roberts, Mary F.

    1982-08-01

    A simple kinetic model for the enzymatic activity of surface-active proteins against mixed micelles has been developed. This model uses the Langmuir adsorption isotherm, the classic equation for the binding of gas molecules to metal surfaces, to characterize enzyme adsorption to micelles. The number of available enzyme binding sites is equated with the number of substrate and inhibitor molecules attached to micelles; enzyme molecules are attracted to the micelle due to the affinity of the enzyme active site for the molecules in the micelle. Phospholipase C (Bacillus cereus) kinetics in a wide variety of dimyristoyl phosphatidylcholine/detergent micelles are readily explained by this model and the assumption of competitive binding of the detergent at the enzyme active site. Binding of phospholipase C to pure detergent micelles is demonstrated by gel filtration chromatography. The experimentally determined enzyme-detergent micelle binding constants are used directly in the rate equation. The Langmuir adsorption model predicts a variety of the characteristics observed for phospholipase kinetics, such as differential inhibition by various charged, uncharged, and zwitterionic detergents and surface-dilution inhibition. The essential idea of this model, that proteins can be attracted and bound to bilayers or micelles by possessing a binding site for the molecules composing the surface, may have wider application in the study of water-soluble (extrinsic) protein-membrane interactions.

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

    PubMed

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

    2011-07-15

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

  17. Experimental studies on equilibrium adsorption isosteres and determination of the thermodynamic quantities of polar media on alumina Al2O3

    NASA Astrophysics Data System (ADS)

    Yonova, Albena

    2017-03-01

    The present work is a revieif of theoretical and experimental study on the adsorption performance of the adsorbent Alumina (Al2O3) used in the adsorption system. An experimental investigation on the equilibrium adsorption isosteres at low pressure (< 1 atm) of working pairs Al2O3/H2O and Al2O3/C2H6O2 is carried out. The isovolume measurement method is adopted in the test setup to directly measure the saturated vapor pressures of working pairs at vapor-liquid equilibrium (dG=0 and dμi=0). Quantity adsorbed is determined from pressure, volume and temperature using gas law. The isosteric heat of adsorption is calculated from the slope of the plot of lnP versus 1/T different amounts of adsorbate onto adsorbent as follows: 0,01 vol% Al2O3/H2O; 0,03 vol% Al2O3/H2O; 0,1 vol% Al2O3/H2O; 0,01 vol% Al2O3/C2H6O2; 0,03 vol% Al2O3/C2H6O2; 0,1 vol% Al2O3/C2H6O2. This study shows that adsorption working pair Al2O3 C2H6O2 has better adsorption performances than those of the A2O3/H2O. Surface acidity! is a most important property! far both adsorption and catalysis and therefore is examined structure of active sites of alumina surface. Thermodynamic parameters such as isosteric heat of adsorption, isosteric enthalpy and entropy of adsorption are critical design variables in estimating the performance and predicting the mechanism of an adsorption process and are also one of the basic requirements for the characterization and optimization of an adsorption process

  18. Equilibrium fluctuations in the theory of surface processes on microparticles

    NASA Astrophysics Data System (ADS)

    Tovbin, Yu. K.

    2010-11-01

    The question of the role of equilibrium fluctuations in the adsorption theory and kinetics of surface processes occurring on the particles of the nanometer size range is discussed. Differences are put forward that need to be introduced to the fluctuation theory of surface processes on microparticles and that generalize Hill's approach to describing the thermodynamic properties of small systems. We show the importance of allowing for the discrete character of adsorption centers on the surfaces and their heterogeneity when describing adsorption isotherms and the rates of adsorption processes.

  19. BORONATE AFFINITY ADSORPTION OF RNA: POSSIBLE ROLE OF CONFORMATIONAL CHANGES. (R825354)

    EPA Science Inventory

    Batch equilibrium adsorption isotherm determination is used to characterize the adsorption of mixed yeast RNA on agarose-immobilized m-aminophenylboronic acid. It is shown that the affinity-enhancing influence of divalent cations depends strongly on the precise nature of t...

  20. Equilibrium and Heat of Adsorption for Organic Vapors and Activated Carbons

    DTIC Science & Technology

    2005-05-01

    Technol. 2005, 39, 5864-5871 5864 9 ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 39, NO. 15, 2005 10.1021/es048144r CCC: $30.25  2005 American Chemical...0.654 VOL. 39, NO. 15, 2005 / ENVIRONMENTAL SCIENCE & TECHNOLOGY 9 5865 have due to the drag force on the sample pan. In addition, the N2 flow prevented...results are provided as lines. 5866 9 ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 39, NO. 15, 2005 Increasing the adsorption temperature from 20 to 60 °C

  1. Characterizing particle-scale equilibrium adsorption and kinetics of uranium(VI) desorption from U-contaminated sediments

    USGS Publications Warehouse

    Stoliker, Deborah L.; Liu, Chongxuan; Kent, Douglas B.; Zachara, John M.

    2013-01-01

    Rates of U(VI) release from individual dry-sieved size fractions of a field-aggregated, field-contaminated composite sediment from the seasonally saturated lower vadose zone of the Hanford 300-Area were examined in flow-through reactors to maintain quasi-constant chemical conditions. The principal source of variability in equilibrium U(VI) adsorption properties of the various size fractions was the impact of variable chemistry on adsorption. This source of variability was represented using surface complexation models (SCMs) with different stoichiometric coefficients with respect to hydrogen ion and carbonate concentrations for the different size fractions. A reactive transport model incorporating equilibrium expressions for cation exchange and calcite dissolution, along with rate expressions for aerobic respiration and silica dissolution, described the temporal evolution of solute concentrations observed during the flow-through reactor experiments. Kinetic U(VI) desorption was well described using a multirate SCM with an assumed lognormal distribution for the mass-transfer rate coefficients. The estimated mean and standard deviation of the rate coefficients were the same for all <2 mm size fractions but differed for the 2–8 mm size fraction. Micropore volumes, assessed using t-plots to analyze N2 desorption data, were also the same for all dry-sieved <2 mm size fractions, indicating a link between micropore volumes and mass-transfer rate properties. Pore volumes for dry-sieved size fractions exceeded values for the corresponding wet-sieved fractions. We hypothesize that repeated field wetting and drying cycles lead to the formation of aggregates and/or coatings containing (micro)pore networks which provided an additional mass-transfer resistance over that associated with individual particles. The 2–8 mm fraction exhibited a larger average and standard deviation in the distribution of mass-transfer rate coefficients, possibly caused by the abundance of

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

    PubMed

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

    2015-09-21

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

  3. Adsorption of geosmin and 2-methylisoborneol onto powdered activated carbon at non-equilibrium conditions: influence of NOM and process modelling.

    PubMed

    Zoschke, Kristin; Engel, Christina; Börnick, Hilmar; Worch, Eckhard

    2011-10-01

    The adsorption of the taste and odour (T&O) compounds geosmin and 2-methylisoborneol (2-MIB) onto powdered activated carbon (PAC) has been studied under conditions which are typical for a drinking water treatment plant that uses reservoir water for drinking water production. The reservoir water as well as the pre-treated water (after flocculation) contains NOM that competes with the trace compounds for the adsorption sites on the carbon surface. Although the DOC concentrations in the reservoir water and in the pre-treated water were different, no differences in the competitive adsorption could be seen. By using two special characterisation methods for NOM (adsorption analysis, LC/OCD) it could be proved that flocculation removes only NOM fractions which are irrelevant for competitive adsorption. Different model approaches were applied to describe the competitive adsorption of the T&O compounds and NOM, the tracer model, the equivalent background compound model, and the simplified equivalent background compound model. All these models are equilibrium models but in practice the contact time in flow-through reactors is typically shorter than the time needed to establish the adsorption equilibrium. In this paper it is demonstrated that the established model approaches can be used to describe competitive adsorption of T&O compounds and NOM also under non-equilibrium conditions. The results of the model applications showed that in particular the simplified equivalent background compound model is a useful tool to determine the PAC dosage required to reduce the T&O compounds below the threshold concentration.

  4. Study on Adsorption of Cu(II) on Chitosan Nanofiber Membranes

    NASA Astrophysics Data System (ADS)

    Cao, Jianhua; Li, Dongzhou; Liang, Weihua; Wu, Dayong

    2014-12-01

    Chitosan nanofiber membranes by electrospinning technique were used to remove Cu(II) from aqueous solution. The adsorption kinetics, equilibrium isotherms, and pH effect were investigated in batch experiments. The Langmuir isotherm and pseudo second-order kinetic models agree well with the experimental data. The chitosan nanofiber membranes are effective for Cu(II) adsorption at pH6. Results showed that the maximum adsorption capacity of the chitosan nanofiber membranes with Cu(II) is 118.62 mg g-1. The chitosan nanofiber membranes can be used as an effective adsorbent for the removal of Cu(II) in aqueous solution due to high adsorption capacity.

  5. Studies on Thorium Adsorption Characteristics upon Activated Titanium Hydroxide Prepared from Rosetta Ilmenite Concentrate

    SciTech Connect

    Gado, M Zaki, S

    2016-01-01

    The titanium hydroxide prepared from Rosetta ilmenite concentrate has been applied for Th (IV) adsorption from its acid aqueous solutions. The prepared hydroxide is first characterized by both Fourier transform infrared (FT-IR) spectrum and thermogravimetric analysis. The relevant factors affecting the adsorption process have been studied. The obtained equilibrium data fits well with the Langmuir isotherm rather than Freundlich isotherm, while the adsorption kinetic data follow the pseudo-second order model. The different thermodynamic parameters have also been calculated and indicate that the adsorption process is spontaneous.

  6. Bromate adsorption using Fe-pillared bentonite.

    PubMed

    He, Shilong; Zhang, Dandan; Gu, Li; Zhang, Shenghua; Yu, Xin

    2012-01-01

    Bromate is an emerging hazardous substance in drinking water. In this study, the removal ofbromate by Fe-pillared bentonite was investigated using various experimental parameters: contact time, initial concentration (Co), temperature, initial pH and competing anions. The adsorption ofbromate followed the pseudo-second-order kinetic better than it followed other kinetic models, and the pseudo-second-order kinetic study showed that equilibrium could be achieved within 60 min. Equilibrium isotherms were analyzed by Freundlich, Langmuir, Redlich-Peterson and Toth isotherm models. The Toth and Redlich-Peterson models better represented the bromate adsorption. Results also indicated that, other than the competing anions and solution pH, temperature was a key parameter affecting adsorption. It was ultimately concluded that Fe-pillared bentonite was effective at removing bromate from water.

  7. 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.

  8. Comparative studies on removal of Erythrosine using ZnS and AgOH nanoparticles loaded on activated carbon as adsorbents: Kinetic and isotherm studies of adsorption

    NASA Astrophysics Data System (ADS)

    Ghaedi, M.; Rozkhoosh, Z.; Asfaram, A.; Mirtamizdoust, B.; Mahmoudi, Z.; Bazrafshan, A. A.

    2015-03-01

    Erythrosine adsorption (Er) onto ZnS and AgOH nanoparticle-loaded activated carbon (ZnS-NP-AC and AgOH-NP-AC) was studied and results were compared. Subsequent preparation were fully analyzed by different approach such as BET to obtain knowledge about surface area, pore volume, while FT-IR analysis give comprehensive information about functional group the dependency of removal percentage to adsorbent mass, initial Er concentration and contact time were investigated and optimum conditions for pH, adsorbent dosage, Er concentration and contact time was set as be 3.2, 0.016 g, 20 mg/L and 16 min and 3.2, 0.015 g, 19 mg/L and 2 min for ZnS-NP-AC and AgOH-NP-AC, respectively. The equilibrium data correspond to adsorption strongly follow Langmuir model by ZnS-NP-AC and Freundlich model for AgOH-NP-AC. High adsorption capacity for of 55.86-57.80 mg g-1 and 67.11-89.69 mg g-1 for ZnS-NP-AC and AgOH-NP-AC, respectively. The result of present study confirm the applicability of small amount of these adsorbent (<0.02 g) for efficient removal of Er (>95%) in short reasonable time (20 min).

  9. Comparative studies on removal of Erythrosine using ZnS and AgOH nanoparticles loaded on activated carbon as adsorbents: Kinetic and isotherm studies of adsorption.

    PubMed

    Ghaedi, M; Rozkhoosh, Z; Asfaram, A; Mirtamizdoust, B; Mahmoudi, Z; Bazrafshan, A A

    2015-03-05

    Erythrosine adsorption (Er) onto ZnS and AgOH nanoparticle-loaded activated carbon (ZnS-NP-AC and AgOH-NP-AC) was studied and results were compared. Subsequent preparation were fully analyzed by different approach such as BET to obtain knowledge about surface area, pore volume, while FT-IR analysis give comprehensive information about functional group the dependency of removal percentage to adsorbent mass, initial Er concentration and contact time were investigated and optimum conditions for pH, adsorbent dosage, Er concentration and contact time was set as be 3.2, 0.016g, 20mg/L and 16min and 3.2, 0.015g, 19mg/L and 2min for ZnS-NP-AC and AgOH-NP-AC, respectively. The equilibrium data correspond to adsorption strongly follow Langmuir model by ZnS-NP-AC and Freundlich model for AgOH-NP-AC. High adsorption capacity for of 55.86-57.80mgg(-1) and 67.11-89.69mgg(-1) for ZnS-NP-AC and AgOH-NP-AC, respectively. The result of present study confirm the applicability of small amount of these adsorbent (<0.02g) for efficient removal of Er (>95%) in short reasonable time (20min).

  10. Comparison of adsorption equilibrium models for the study of CL-, NO3- and SO4(2-) removal from aqueous solutions by an anion exchange resin.

    PubMed

    Dron, Julien; Dodi, Alain

    2011-06-15

    The removal of chloride, nitrate and sulfate ions from aqueous solutions by a macroporous resin is studied through the ion exchange systems OH(-)/Cl(-), OH(-)/NO(3)(-), OH(-)/SO(4)(2-), and HCO(3)(-)/Cl(-), Cl(-)/NO(3)(-), Cl(-)/SO(4)(2-). They are investigated by means of Langmuir, Freundlich, Dubinin-Radushkevitch (D-R) and Dubinin-Astakhov (D-A) single-component adsorption isotherms. The sorption parameters and the fitting of the models are determined by nonlinear regression and discussed. The Langmuir model provides a fair estimation of the sorption capacity whatever the system under study, on the contrary to Freundlich and D-R models. The adsorption energies deduced from Dubinin and Langmuir isotherms are in good agreement, and the surface parameter of the D-A isotherm appears consistent. All models agree on the order of affinity OH(-)adsorption isotherms. The nonlinear regression results are also compared with linear regressions. While the parameter values are not affected, the evaluation of the best fitting model is biased by linearization.

  11. Adsorption of pesticides on resins.

    PubMed

    Kyriakopoulos, Grigorios; Hourdakis, Adamadia; Doulia, Danae

    2003-03-01

    The objective of this work was to assess the capability of organic hydrophobic polymeric resins Amberlite XAD-4 and XAD-7 to remove the pesticides alachlor and amitrole from water. The pesticides adsorption on the two different adsorbents was measured by batch equilibrium technique and isotherm types and parameters were estimated. Two theoretical models were applied based on a Freundlich and a Langmuir isotherms. The effect of pesticides chemical composition and structure as well as the nature of solid surface on the efficiency of adsorption was evaluated. The influence of pH also was studied. In low pH solutions adsorption of amitrole was higher upon the nonionic aliphatic acrylic ester copolymer XAD-7 in comparison to the nonionic, crosslinked macroreticular copolymer of styrene divinylbenzene XAD-4. In neutral and intermediate pH solutions the polar acrylic ester copolymer XAD-7 was more effective to the retention of alachlor. The acrylic ester copolymer showed at pH 3 the lower effectiveness in alachlor removal from water. The data of the adsorption isotherms of pesticides upon the examined polymeric resins seemed to conform to both the Freundlich and the Langmuir isotherm models.

  12. 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.

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

    PubMed

    Subramanyam, Busetty; Das, Ashutosh

    2014-01-01

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

  14. Adsorption of Single and Binary Gases on Polystyrene and Carbon Adsorbents

    NASA Astrophysics Data System (ADS)

    Rothstein, Daniel P.

    Time-dependent transmissions of light organic gases at low concentrations through crosslinked polystyrene and activated carbon adsorbents were measured and analyzed to extract kinetic and equilibrium parameters and to evaluate these parameters in terms of several models of adsorption. Mass -balance in the adsorber bed allows calculation of the equilibrium adsorbed-phase concentration and the model-independent adsorption capacity. Adsorption isotherms are calculated from transmission curves for eight light organic gases adsorbed on polystyrene at several temperatures. The power-law forms of the Freundlich and Chakravarti-Dhar isotherms and the concentration-dependent adsorption capacities indicate heterogeneous adsorption well below monolayer coverage. The effects of heterogeneity increase as non-linearity of the isotherm increases. A mesopore structure is indicated for polystyrene. Characteristic curves are independent of temperature, but the use of an affinity coefficient is not able to demonstrate their independence of adsorbate. Isosteric hearts of adsorption are larger than the heats of vaporization and decrease with increasing surface coverage for three alkanes adsorbed on polystyrene. The transmission curves of several binary mixtures of gases with non-linear isotherms reveal adsorption interference, with adsorption capacities smaller than those from single -component experiments. The pairs with unequal adsorption capacities exhibit displacement, in qualitative agreement with adsorption interference models. The equilibrium adsorption of the binary mixtures cannot be reproduced by single-component isotherm parameters alone, but are described by modified Freundlich isotherms requiring binary experiments. Adsorption in a porous medium is described by a model including four dynamic processes: gas- and solid -phase diffusion, interfacial mass-transfer resistance, and a first-order chemical reaction. A new time-dependent solution to the differential equations of

  15. Application of activated carbon derived from 'waste' bamboo culms for the adsorption of azo disperse dye: kinetic, equilibrium and thermodynamic studies.

    PubMed

    Wang, Lianggui

    2012-07-15

    The utilization of activated carbon derived from 'waste' bamboo culms (BAC) for the removal of Disperse Red 167 (DR167), an azo disperse dye, was investigated. Studies of the properties of the adsorbent, the effect of contact time, the initial pH of the solution, the initial concentration of the dye solution and temperature indicated that a low initial pH or concentration of dye solution favors the adsorption process; temperature exerts a greater effect on the removal of azo disperse red 167 dye from aqueous solution. Kinetic and isotherm data were fitted to five non-linear kinetic and nine non-linear isotherm equations. In addition, the fits were evaluated in terms of the non-linear coefficient, Chi-square test, Marquardt's percent standard deviation error function and small-sample-corrected Akaike Information Criterion (AICc) methodology. The results showed that the AICc analysis was the best statistical tool for analyzing the data, the intra-particle diffusion and the pseudo-first-order models played important roles in the controlling rate step, and the Temkin equation best described the BAC isotherm data. Furthermore, the thermodynamic analysis indicated that the adsorption was a spontaneous, endothermic, entropy-increasing and physical process. Two types of commercial activated carbon, Filtrasorb 400 and Filtrasorb (F400 and F300), were used as contrast adsorbents. The contrast experiments revealed that BAC exhibits similar properties to F400 and F300. The utilization of bamboo wastes as carbon precursors is feasible.

  16. Adsorptive performance of un-calcined sodium exchanged and acid modified montmorillonite for Ni2+ removal: equilibrium, kinetics, thermodynamics and regeneration studies.

    PubMed

    Ijagbemi, Christianah Olakitan; Baek, Mi-Hwa; Kim, Dong-Su

    2010-02-15

    The efficacy of un-calcined sodium exchanged (Na-MMT) and acid modified montmorillonite (A-MMT) has been investigated for adsorptive removal of Ni(2+) from aqueous solution. Physico-chemical parameters such as pH, initial Ni(2+) concentration, and equilibrium contact time were studied in a series of batch adsorption experiments. The equilibrium time of contact for both adsorbents was about 230 min. The Redlich-Peterson model best described the equilibrium sorption of Ni(2+) onto Na-MMT and the Dubinin-Radushkevich model was the best model in predicting the equilibrium sorption of Ni(2+) onto A-MMT. The kinetics of Ni(2+) uptake by Na-MMT and A-MMT followed the pseudo second-order chemisorption mechanism. Sorptions of Ni(2+) onto Na-MMT and A-MMT were spontaneous and endothermic. Regeneration was tried for several cycles with a view to recover the adsorbed Ni(2+) and also to restore Na-MMT and A-MMT to their original states. The un-calcined Na-MMT and A-MMT have adsorptive potentials for removal of Ni(2+) from aqueous bodies.

  17. Methylene blue adsorption on graphene oxide/calcium alginate composites.

    PubMed

    Li, Yanhui; Du, Qiuju; Liu, Tonghao; Sun, Jiankun; Wang, Yonghao; Wu, Shaoling; Wang, Zonghua; Xia, Yanzhi; Xia, Linhua

    2013-06-05

    Graphene oxide has been used as an adsorbent in wastewater treatment. However, the dispersibility in aqueous solution and the biotoxicity to human cells of graphene oxide limits its practical application in environmental protection. In this research, a novel environmental friendly adsorbent, calcium alginate immobilized graphene oxide composites was prepared. The effects of pH, contact time, temperature and dosage on the adsorption properties of methylene blue onto calcium alginate immobilized graphene oxide composites were investigated. The equilibrium adsorption data were described by the Langmuir and Freundlich isotherms. The maximum adsorption capacity obtained from Langmuir isotherm equation was 181.81 mg/g. The pseudo-first order, pseudo-second order, and intraparticle diffusion equation were used to evaluate the kinetic data. Thermodynamic analysis of equilibriums indicated that the adsorption reaction of methylene blue onto calcium alginate immobilized graphene oxide composites was exothermic and spontaneous in nature.

  18. Removal of mercury(II) ions in aqueous solution using the peel biomass of Pachira aquatica Aubl: kinetics and adsorption equilibrium studies.

    PubMed

    Santana, Andrea J; dos Santos, Walter N L; Silva, Laiana O B; das Virgens, Cesário F

    2016-05-01

    Mercury is a highly toxic substance that is a health hazard to humans. This study aims to investigate powders obtained from the peel of the fruit of Pachira aquatica Aubl, in its in natura and/or acidified form, as an adsorbent for the removal of mercury ions in aqueous solution. The materials were characterized by Fourier transform infrared spectroscopy and thermogravimetric analysis. The infrared spectra showed bands corresponding to the axial deformation of carbonyls from carboxylic acids, the most important functional group responsible for fixing the metal species to the adsorbent material. The thermograms displayed mass losses related to the decomposition of three major components, i.e., hemicellulose, cellulose, and lignin. The adsorption process was evaluated using cold-vapor atomic fluorescence spectrometry (CV AFS) and cold-vapor atomic absorption spectrometry (CV AAS). Three isotherm models were employed. The adsorption isotherm model, Langmuir-Freundlich, best represented the adsorption process, and the maximum adsorption capacity was predicted to be 0.71 and 0.58 mg g(-1) at 25 °C in nature and acidified, respectively. Adsorption efficiencies were further tested on real aqueous wastewater samples, and removal of Hg(II) was recorded as 69.6 % for biomass acidified and 76.3 % for biomass in nature. Results obtained from sorption experiments on real aqueous wastewater samples revealed that recovery of the target metal ions was very satisfactory. The pseudo-second-order model showed the best correlation to the experimental data. The current findings showed that the investigated materials are potential adsorbents for mercury(II) ion removal in aqueous solution, with acidified P. aquatica Aubl being the most efficient adsorbent.

  19. Isotherm and kinetics study for acrylic acid removal using powdered activated carbon.

    PubMed

    Kumar, Arvind; Prasad, B; Mishra, I M

    2010-04-15

    The potential of powdered activated carbon (PAC) for the adsorption of acrylic acid (AA) from aqueous solution was studied at the initial concentration (C(0)) in the range of 50-500 mg/l over the temperature range of 303-348 K. The equilibrium adsorption studies were carried out to evaluate the effect of adsorbent dosage and contact time, change in pH by adding adsorbents and the initial concentration. Langmuir, Freundlich and Redlich-Peterson (R-P) equilibrium isotherm models were tested to represent the data. Error functions were used to test their validity to fit of the adsorption data with the isotherm and kinetic models. The Freundlich isotherm equation is found to best represent the equilibrium separation data in the temperature range of 303-348 K. The maximum adsorption capacity of AA onto PAC was obtained as q(m)=36.23 mg/g with an optimum PAC dosage w=20 g/l at 303 K for C(0)=100 mg/l. The pseudo-second-order kinetics is found to represent the experimental AA-PAC data. The negative value of DeltaG(ad)(o) (-16.60 to -18.18 kJ/mol K) indicate the feasibility and spontaneity of the adsorption process.

  20. Equilibrium, kinetic and sorber design studies on the adsorption of Aniline blue dye by sodium tetraborate-modified Kaolinite clay adsorbent.

    PubMed

    Unuabonah, Emmanuel I; Adebowale, Kayode O; Dawodu, Folasegun A

    2008-09-15

    Raw Kaolinite clay obtained Ubulu-Ukwu, Delta State of Nigeria and its sodium tetraborate (NTB)-modified analogue was used to adsorb Aniline blue dye. Fourier transformed infrared spectra of NTB-modified Kaolinite suggests that modification was effective on the surface of the Kaolinite clay with the strong presence of inner -OH functional group. The modification of Kaolinite clay raised its adsorption capacity from 1666 to 2000 mg/kg. Modeling adsorption data obtained from both unmodified and NTB-modified Kaolinite clay reveals that the adsorption of Aniline blue dye on unmodified Kaolinite clay is on heterogeneous adsorption sites because it followed strongly the Freundlich isotherm equation model while adsorption data from NTB-modified Kaolinite clay followed strongly the Langmuir isotherm equation model which suggest that Aniline blue dye was adsorb homogeneous adsorption sites on the NTB-modified adsorbent surface. There was an observed increase in the amount of Aniline blue adsorbed as initial dye concentration was increased from 10 to 30 mg/L. It was observed that kinetic data obtained generally gave better robust fit to the second-order kinetic model (SOM). The initial sorption rate was found to increased with increasing initial dye concentration (from 10 to 20 mg/L) for data obtained from 909 to 1111 mg kg(-1)min(-1) for unmodified and 3325-5000 mg kg(-1) min(-1) for NTB-modified adsorbents. Thereafter there was a decrease in initial sorption rate with further increase in dye concentration. The linearity of the plots of the pseudo-second-order model with very high-correlation coefficients indicates that chemisorption is involved in the adsorption process. From the design of a single-batch adsorber it is predicted that the NTB-modified Kaolinite clay adsorbent will require 50% less of the adsorbent to treat certain volumes of wastewater containing 30 mg/L of Aniline blue dye when it is compared with the unmodified adsorbent. This will be cost effective in

  1. 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.

  2. Lysozyme adsorption in pH-responsive hydrogel thin-films: the non-trivial role of acid-base equilibrium.

    PubMed

    Narambuena, Claudio F; Longo, Gabriel S; Szleifer, Igal

    2015-09-07

    We develop and apply a molecular theory to study the adsorption of lysozyme on weak polyacid hydrogel films. The theory explicitly accounts for the conformation of the network, the structure of the proteins, the size and shape of all the molecular species, their interactions as well as the chemical equilibrium of each titratable unit of both the protein and the polymer network. The driving forces for adsorption are the electrostatic attractions between the negatively charged network and the positively charged protein. The adsorption is a non-monotonic function of the solution pH, with a maximum in the region between pH 8 and 9 depending on the salt concentration of the solution. The non-monotonic adsorption is the result of increasing negative charge of the network with pH, while the positive charge of the protein decreases. At low pH the network is roughly electroneutral, while at sufficiently high pH the protein is negatively charged. Upon adsorption, the acid-base equilibrium of the different amino acids of the protein shifts in a nontrivial fashion that depends critically on the particular kind of residue and solution composition. Thus, the proteins regulate their charge and enhance adsorption under a wide range of conditions. In particular, adsorption is predicted above the protein isoelectric point where both the solution lysozyme and the polymer network are negatively charged. This behavior occurs because the pH in the interior of the gel is significantly lower than that in the bulk solution and it is also regulated by the adsorption of the protein in order to optimize protein-gel interactions. Under high pH conditions we predict that the protein changes its charge from negative in the solution to positive within the gel. The change occurs within a few nanometers at the interface of the hydrogel film. Our predictions show the non-trivial interplay between acid-base equilibrium, physical interactions and molecular organization under nanoconfined conditions

  3. 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

    2015-05-05

    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.

  4. 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.

  5. Adsorption studies of methylene blue dye on tunisian activated lignin

    NASA Astrophysics Data System (ADS)

    Kriaa, A.; Hamdi, N.; Srasra, E.

    2011-02-01

    Activated carbon prepared from natural lignin, providing from a geological deposit, was used as the adsorbent for the removal of methylene blue (MB) dye from aqueous solutions. Batch adsorption studies were conducted to evaluate various experimental parameters like pH and contact time for the removal of this dye. Effective pH for MB removal was 11. Kinetic study showed that the adsorption of dye was gradual process. Quasi equilibrium reached in 4 h. Pseudo-first-order, pseudo-second-order were used to fit the experimental data. Pseudo-second-order rate equation was able to provide realistic description of adsorption kinetics. The experimental isotherms data were also modelled by the Langmuir and Freundlich equation of adsorption. Equilibrium data fitted well with the Langmuir model with maximum monolayer adsorption capacity of 147 mg/g. Activated lignin was shown to be a promising material for adsorption of MB from aqueous solutions.

  6. Application of activated carbon derived from scrap tires for adsorption of Rhodamine B.

    PubMed

    Li, Li; Liu, Shuangxi; Zhu, Tan

    2010-01-01

    Activated carbon derived from solid hazardous waste scrap tires was evaluated as a potential adsorbent for cationic dye removal. The adsorption process with respect to operating parameters was investigated to evaluate the adsorption characteristics of the activated pyrolytic tire char (APTC) for Rhodamine B (RhB). Systematic research including equilibrium, kinetics and thermodynamic studies was performed. The results showed that APTC was a potential adsorbent for RhB with a higher adsorption capacity than most adsorbents. Solution pH and temperature exert significant influence while ionic strength showed little effect on the adsorption process. The adsorption equilibrium data obey Langmuir isotherm and the kinetic data were well described by the pseudo second-order kinetic model. The adsorption process followed intra-particle diffusion model with more than one process affecting the adsorption process. Thermodynamic study confirmed that the adsorption was a physisorption process with spontaneous, endothermic and random characteristics.

  7. A novel polar-modified post-cross-linked resin and its enhanced adsorption to salicylic acid: Equilibrium, kinetics and breakthrough studies.

    PubMed

    Wang, Xiaomei; Li, Guoqiang; Guo, Deping; Zhang, Yaling; Huang, Jianhan

    2016-05-15

    Improving the surface polarity is of significance for the post-cross-linked resins to enhance their adsorption to polar aromatic compounds. In the present study, we prepared a novel polar-modified post-cross-linked PDEpc_D by the Friedel-Crafts alkylation reaction and the amination reaction, the Brunauer-Emmett-Teller (BET) surface area and pore volume increased significantly after the Friedel-Crafts alkylation reaction and the surface polarity improved greatly after the amination reaction. Batch adsorption showed that PDEpc_D possessed a much enhanced adsorption to salicylic acid as compared the precursors PDE and PDEpc as well as the non-polar post-cross-linked PDVBpc. The equilibrium data was characterized by the Freundlich model, π-π stacking, hydrogen bonding and static interaction were the possible driving forces. The adsorption was a fast process and the kinetic data obeyed the micropore diffusion model. Column adsorption-desorption experiments suggested that PDEpc_D was a potential candidate for adsorptive removal of salicylic acid from aqueous solution.

  8. Role of the solvent in the adsorption-desorption equilibrium of cinchona alkaloids between solution and a platinum surface: correlations among solvent polarity, cinchona solubility, and catalytic performance.

    PubMed

    Ma, Zhen; Zaera, Francisco

    2005-01-13

    The role that the nature of the solvent plays in defining the extent of cinchona alkaloid adsorption-desorption equilibrium on platinum surfaces has been studied both by testing their solubility in 54 different solvents and by probing the stability of adsorbed cinchona in the presence of those solvents. The solubilities vary by as much as 5-6 orders of magnitude, display volcano-type correlations with solvent polarity and dielectric constant, and follow a cinchonine < cinchonidine < quinine, quinidine sequence. The adsorption-desorption equilibrium shifts toward the solution with increasing dissolving power of the solvent. The relevance of these results to the behavior of cinchona as chiral modifiers in hydrogenation catalysis is discussed.

  9. High adsorption capacity NaOH-activated carbon for dye removal from aqueous solution.

    PubMed

    Wu, Feng-Chin; Tseng, Ru-Ling

    2008-04-15

    In this study, the surface coverage ratio (Sc/Sp) and monolayer cover adsorption amount per unit surface area (qmon/Sp) were employed to investigate the adsorption isotherm equilibrium of the adsorption of dyes (AB74, BB1 and MB) on NaOH-activated carbons (FWNa2, FWNa3 and FWNa4); the adsorption rate of the Elovich equation (1/b) and the ratio of 1min adsorption amount of adsorbate to the monolayer cover amount of adsorbate (q1/qmon) were employed to investigate adsorption kinetics. The qmon/Sp of NaOH-activated carbons was better than that of KOH-activated carbons prepared from the same raw material (fir wood). The Sc/Sp values of the adsorption of all adsorbates on adsorbent FWNa3 in this study were found to be higher than those in related literature. Parameters 1/b and q1 of the adsorption of dyes on activated carbons in this study were higher than those on KOH-activated carbons; the q1/qmon value of FWNa3 was the highest. The pore structure and the TPD measurement of the surface oxide groups were employed to explain the superior adsorption performance of FWNa3. A high surface activated carbon (FWNa3) with excellent adsorption performance on dyes with relation to adsorption isotherm equilibrium and kinetics was obtained in this study. Several adsorption data processing methods were employed to describe the adsorption performance.

  10. 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.

  11. Removal of methylparaben from synthetic aqueous solutions using polyacrylonitrile beads: kinetic and equilibrium studies.

    PubMed

    Forte, Maurizio; Mita, Luigi; Perrone, Rosa; Rossi, Sergio; Argirò, Mario; Mita, Damiano Gustavo; Guida, Marco; Portaccio, Marianna; Godievargova, Tzonka; Ivanov, Yavour; Tamer, Mahmoud T; Omer, Ahmed M; Mohy Eldin, Mohamed S

    2017-01-01

    The removal of methylparaben (MP), a well-known endocrine disruptor, from aqueous solutions using polyacrylonitrile (PAN) beads has been studied under batch conditions, at room temperature and at different initial MP concentrations. The kinetic and equilibrium results have been analyzed. Kinetic modeling analysis has been carried out with three different types of adsorption models: pseudo-first-order, pseudo-second-order, and Elovich model. Kinetic data analysis indicated that the adsorption was a second-order process. The MP adsorption by PAN was also quantitatively evaluated by using the equilibrium adsorption isotherm models of Langmuir, Freundlich, Dubinin-Radushkevich (D-R), and Temkin and the applicability of the respective isotherm equations has been compared through the correlation coefficients. Adsorption data resulted well fitted by the Freundlich isotherm model. Data of MP adsorption have also been used to test different adsorption diffusion models. The diffusion rate equations inside particulate of Dumwald-Wagner and the intraparticle diffusion model have been used to calculate the diffusion rate. The actual rate-controlling step involved in the MB adsorption process was determined. The kinetic expression by Boyd gave the right indications. All together, our results indicate that PAN beads are a useful tool to remediate water bodies polluted by endocrine disruptors.

  12. Experimental comparison of adsorption characteristics of silica gel and zeolite in moist air

    NASA Astrophysics Data System (ADS)

    Xin, F.; Yuan, Z. X.; Wang, W. C.; Du, C. X.

    2017-02-01

    In this work, the macro adsorption characteristic of water vapor by the allochroic silica gel and the zeolite 5A and ZSM-5 were investigated experimentally. BET analysis method presented the difference of the porosity, the micro pore volume, and the specific surface area of the material. The dynamic and the equilibrium characteristics of the sample were measured thermo-gravimetrically in the moist air. In general, the ZSM-5 zeolite showed an inferior feature of the adsorption speed and the equilibrium concentration to the others. By comparison to the result of SAPO-34 zeolite in the open literature, the 5A zeolite showed some superiorities of the adsorption. The equilibrium concentration of the ZSM-5 zeolite was higher than that of the SAPO-34 calcined in the nitrogen, whereas it was lower than that calcined in the air. The adsorption isotherm was correlated and the relation of the isotherm to the microstructure of the material was discussed. With more mesopore volume involved, the zeolite presented an S-shaped isotherm in contrast to the exponential isotherm of the silica gel. In addition, the significance of the S-shaped isotherm for the application in adsorption heat pump has also been addressed.

  13. 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.

  14. High resolution N2 adsorption isotherms at 77.4 K and 87.3 K by carbon blacks and activated carbon fibers--analysis of porous texture of activated carbon fibers by αs-method.

    PubMed

    Nakai, Kazuyuki; Nakada, Yoko; Hakuman, Masako; Yoshida, Masayuki; Senda, Yousuke; Tateishi, Yuko; Sonoda, Joji; Naono, Hiromitsu

    2012-02-01

    The standard α(s)-data of N(2) at 87.3 K by graphitized and nongraphitized carbon black samples (GCB-I and NGCB) (cf.Figs. 3 and 4) have been determined on the basis of the high resolution adsorption isotherms of N(2) at 87.3 K, which were repeatedly measured in the pressure range of p/p(o)=5×10(-8)-0.4. The high resolution adsorption isotherms of N(2) by two kinds of activated carbon fibers (ACF-I and ACF-II) were measured from p/p(o)=10(-7) to p/p(o)=0.995 at 77.4 K and from p/p(o)=10(-7) to p/p(o)=0.4 at 87.3 K. Combination of the adsorption isotherms by ACF-I and ACF-II with the standard α(s)-data by NGCB at 77.4 K and 87.3 K make it possible to construct the high resolution α(s)-plots from very low filling (1%) to complete filling (100%). The high resolution α(s)-plots of N(2) at 77.4 K and 87.3 K were analyzed. On the basis of the analyzed result, the porous textures of ACF-I and ACF-II will be discussed.

  15. [Thermodynamics adsorption and its influencing factors of chlorpyrifos and triazophos on the bentonite and humus].

    PubMed

    Zhu, Li-Jun; Zhang, Wei; Zhang, Jin-Chi; Zai, De-Xin; Zhao, Rong

    2010-11-01

    The adsorption of chlorpyrifos and triazophos on bentonite and humus was investigated by using the equilibrium oscillometry. The adsorption capacity of chlorpyrifos and triazophos on humus was great higher than bentonite at the same concentration. Equilibrium data of Langmuir, Freundlich isotherms showed significant relationship to the adsorption of chlorpyrifos and triazophos on humus (chlorpyrifos: R2 0.996 4, 0.996 3; triazophos: R2 0.998 9, 0.992 4). Langmuir isotherm was the best for chlorpyrifos and triazophos on bentonite (chlorpyrifos: R2 = 0.995 7, triazophos: R2 = 0.998 9). The pH value, adsorption equilibrium time and temperature were the main factors affecting adsorption of chlorpyrifos and triazophos on bentonite and humus. The adsorption equilibrium time on mixed adsorbent was 12h for chlorpyrifos and 6h for triazophos respectively. The mass ratio of humus and bentonite was 12% and 14% respectively, the adsorption of chlorpyrifos and triazophos was the stronglest and tended to saturation. At different temperatures by calculating the thermodynamic parameters deltaG, deltaH and deltaS, confirmed that the adsorption reaction was a spontaneous exothermic process theoretically. The adsorption was the best when the pH value was 6.0 and the temperature was 15 degrees C.

  16. [Adsorption of Cd2+ on biochar from aqueous solution].

    PubMed

    Guo, Wen-juan; Liang, Xue-feng; Lin, Da-song; Xu, Ying-ming; Wang, Lin; Sun, Yue-bing; Qin, Xu

    2013-09-01

    Biomass-based materials such as biochar have a good performance in heavy metal adsorption. The adsorption of Cd2+ on biochar converted from cotton straw was studied. Adsorption isotherm, kinetics and effect factors such as temperature, pH and ionic strength were investigated. The adsorption of Cd2+ on biochar can be fitted by the Freundlich isotherm better than the Langmuir isotherm. The maximum adsorption amounts of Cd2+ at different temperatures were 9.738 mg x g(-1) (288.15 K), 10.14 mg x g(-1) (298.15 K), 10.40 mg x g(-1) (308.15 K) and 10.71 mg x g(-1) (318.15 K), respectively. The free energies AG(theta) were from -8.346 kJ x mol(-1) to -10.276 kJ x mol(-1) at different temperatures, indicating that the adsorption of Cd2+ onto biochar is spontaneous and is an endothermic process. The adsorption process can reach equilibrium within 40 minutes and can be fitted by the pseudo second order kinetic model. pH showed a significant effect on the adsorption of Cd2+ on biochar in the range of 2-8. The adsorption amount of Cd2+ on biochar shows a reducing trend with the increasing ionic strength.

  17. 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.

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

    PubMed

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

    2015-01-05

    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 (R(2)) 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.

  19. Investigation kinetics mechanisms of adsorption malachite green onto activated carbon.

    PubMed

    Onal, Y; Akmil-Başar, C; Sarici-Ozdemir, C

    2007-07-19

    Lignite was used to prepare activated carbon (T3K618) by chemical activation with KOH. Pore properties of the activated carbon such as BET surface area, pore volume, pore size distribution, and pore diameter were characterized by t-plot based on N2 adsorption isotherm. BET surface area of activated carbon is determined as 1000 m2/g. Adsorption capacity of malachite green (MG) onto T3K618 activated carbon was investigated in a batch system by considering the effects of various parameters like initial concentration (100, 150 and 200 mg/L) and temperature (25, 40 and 50 degrees C). The adsorption process was relatively fast and equilibrium was reached after about 20 min for 100, 150 mg/L at all adsorption temperature. Equilibrium time for 200 mg/L was determined as 20 min and 40 min at 298, 313 and 323 K, respectively. Simple mass and kinetic models were applied to the experimental data to examine the mechanisms of adsorption and potential rate controlling steps such as external mass transfer, intraparticle diffusion. Pseudo second-order model was found to explain the kinetics of MG adsorption most effectively. It was found that both mass transfer and pore diffusion are important in determining the adsorption rates. The intraparticle diffusion rate constant, external mass transfer coefficient, film and pore diffusion coefficient at various temperatures were evaluated. The activation energy (Ea) was determined as 48.56, 63.16, 67.93 kJ/mol for 100, 150, 200 mg/L, respectively. The Langmiur and Freundlich isotherm were used to describe the adsorption equilibrium studies at different temperatures. Langmiur isotherm shows better fit than Freundlich isotherm in the temperature range studied. The thermodynamic parameters, such as DeltaG degrees, DeltaS and DeltaH degrees were calculated. The thermodynamics of dyes-T3K618 system indicates endothermic process.

  20. Adsorption of EDTA on activated carbon from aqueous solutions.

    PubMed

    Zhu, Hai-song; Yang, Xiao-juan; Mao, Yan-peng; Chen, Yu; Long, Xiang-li; Yuan, Wei-kang

    2011-01-30

    In this study, the adsorption of EDTA on activated carbon from aqueous solutions has been investigated in a batch stirred cell. Experiments have been carried out to investigate the effects of temperature, EDTA concentration, pH, activated carbon mass and particle size on EDTA adsorption. The experimental results manifest that the EDTA adsorption rate increases with its concentration in the aqueous solutions. EDTA adsorption also increases with temperature. The EDTA removal from the solution increases as activated carbon mass increases. The Langmuir and Freundlich equilibrium isotherm models are found to provide a good fitting of the adsorption data, with R(2) = 0.9920 and 0.9982, respectively. The kinetic study shows that EDTA adsorption on the activated carbon is in good compliance with the pseudo-second-order kinetic model. The thermodynamic parameters (E(a), ΔG(0), ΔH(0), ΔS(0)) obtained indicate the endothermic nature of EDTA adsorption on activated carbon.

  1. Adsorption kinetics of Rhodamine-B on used black tea leaves

    PubMed Central

    2012-01-01

    Rhodamine B (Rh-B) is one of the most common pollutants in the effluents of textile industries effluents in developing countries. This study was carried out to evaluate the applicability of used black tea leaves (UBTL) for the adsorptive removal of Rh-B from aqueous system by investigating the adsorption kinetics in batch process. The effects of concentration and temperature on adsorption kinetics were examined. First-, second- and pseudo-second order kinetic equations were used to investigate the adsorption mechanism. The adsorption of Rh-B on UBTL followed pseudo-second order kinetics. The equilibrium amount adsorbed and the equilibrium concentration were calculated from pseudo-second-order kinetic plots for different initial concentrations of Rh-B to construct the adsorption isotherm. The adsorption isotherm was well expressed by Langmuir equation. The maximum adsorption capacity of UBTL to Rh-B was found to be 53.2 mg/g at pH = 2.0. The equilibrium amount adsorbed, calculated from pseudo-second-order kinetic plots, increased with temperature increase. The positive value of enthalpy of adsorption, ΔHads = 31.22 kJ/mol, suggested that the adsorption of Rh-B on UBTL at pH = 2.0 is an endothermic process. PMID:23369452

  2. Adsorption of natural organic matter and disinfection byproduct precursors from surface water onto TiO2 nanoparticles: pH effects, isotherm modelling and implications for using TiO2 for drinking water treatment.

    PubMed

    Gora, Stephanie L; Andrews, Susan A

    2017-05-01

    Titanium dioxide is a photocatalyst that can remove organic contaminants of interest to the drinking water treatment industry, including natural organic matter (NOM) and disinfection byproduct (DBP) precursors. The photocatalytic reaction occurs in two steps: adsorption of the contaminant followed by degradation of the adsorbed contaminant upon irradiation with UV light. The second part of this process can lead to the formation of reactive intermediates and negative impacts on treated water quality, such as increased DBP formation potential (DBPfp). Adsorption alone does not result in the formation of reactive intermediates and thus may prove to be a safe way to incorporate TiO2 into drinking water treatment processes. The goal of this study was to expand on the current understanding of NOM adsorption on TiO2 and examine it in a drinking water context by observing NOM adsorption from real water sources and evaluating the effects of the resulting reductions on the DBPfp of the treated water. Bottle point isotherm tests were conducted with raw water from two Canadian water treatment plants adjusted to pH 4, pH 6 and pH 8 and dosed with TiO2 nanoparticles. The DOC results were a good fit to a modified Freundlich isotherm. DBP precursors and liquid chromatography with organic carbon detection NOM fractions associated with DBP formation were removed to some extent at all pHs, but most effectively at pH 4.

  3. Polar modified post-cross-linked resin and its adsorption toward salicylic acid from aqueous solution: Equilibrium, kinetics and breakthrough studies.

    PubMed

    Fu, Zhenyu; He, Chunlian; Huang, Jianhan; Liu, You-Nian

    2015-08-01

    A novel polar modified post-cross-linked resin PDMPA was synthesized, characterized and evaluated for adsorption of salicylic acid from aqueous solution. PDMPA was prepared by a suspension polymerization of methyl acrylate (MA) and divinylbenzene (DVB), a Friedel-Crafts reaction and an amination reaction. After characterization of the chemical and pore structure of PDMPA, the adsorption behaviors of salicylic acid on PDMPA were determined in comparison with the precursor resins. The equilibrium adsorption capacity of salicylic acid on PDMPA was much larger than the precursor resins and the equilibrium data were correlated by both of the Langmuir and Freundlich models. The pseudo-second-order rate equation fitted the kinetic data better than the pseudo-first-order rate equation, and the micropore diffusion model could characterize the kinetic data very well. The dynamic experimental results showed that the breakthrough point and saturated point of salicylic acid on PDMPA were 40.3 and 92.4BV (1BV=10mL) at a feed concentration of 995.8mg/L and a flow rate of 1.4mL/min, and the resin column could be regenerated by 16.0BV of a mixture desorption solvent containing 0.01mol/L of NaOH (w/v) and 50% of ethanol (v/v).

  4. Adsorption behavior of methylene blue on carbon nanotubes.

    PubMed

    Yao, Yunjin; Xu, Feifei; Chen, Ming; Xu, Zhongxiao; Zhu, Zhiwen

    2010-05-01

    The effect of temperature on the equilibrium adsorption of methylene blue dye from aqueous solution using carbon nanotubes was investigated. The equilibrium adsorption data were analyzed using two widely applied isotherms: Langmuir and Freundlich. The results revealed that Langmuir isotherm fit the experimental results well. Kinetic analyses were conducted using pseudo-first and second-order models and the intraparticle diffusion model. The regression results showed that the adsorption kinetics were more accurately represented by pseudo-second-order model. The activation energy of system (Ea) was calculated as 18.54 kJ/mol. Standard free energy changes (DeltaG(0)), standard enthalpy change (DeltaH(0)), and standard entropy change (DeltaS(0)) were calculated using adsorption equilibrium constants obtained from the Langmuir isotherm at different temperatures. All DeltaG(0) values were negative; the DeltaH(0) values and DeltaS(0) values of CNTs were 7.29 kJ/mol and 64.6 J/mol K, respectively. Results suggested that the methylene blue adsorption on CNTs was a spontaneous and endothermic process.

  5. Biochars prepared from anaerobic digestion residue, palm bark, and eucalyptus for adsorption of cationic methylene blue dye: characterization, equilibrium, and kinetic studies.

    PubMed

    Sun, Lei; Wan, Shungang; Luo, Wensui

    2013-07-01

    Biochars prepared from anaerobic digestion residue (BC-R), palm bark (BC-PB) and eucalyptus (BC-E) were used as sorbents for removal of cationic methylene blue dye (MB). The FE-SEM images indicated that the biochars have a well-developed pore structure, and the Brunauer-Emmett-Teller surface areas of BC-R, BC-PB, and BC-E were 7.60, 2.46, and 10.35 m(2)g(-1), respectively. The efficiencies of MB removal in the samples with initial concentrations of 5 mg L(-1) at pH 7.0 and 40°C by BC-R, BC-PB, and BC-E after 2h were 99.5%, 99.3%, and 86.1%, respectively. Pseudo-second-order kinetics was the most suitable model for describing the adsorption of MB onto the biochars. The experimental data were best described by the Langmuir isotherm model, with a maximum monolayer adsorption capacity of 9.50 mg g(-1) at 40°C for BC-R. The biochars produced from the three types of solid waste showed considerable potential for adsorption.

  6. Utilization of powdered waste sludge (PWS) for removal of textile dyestuffs from wastewater by adsorption.

    PubMed

    Ozmihci, Serpil; Kargi, Fikret

    2006-11-01

    Acid pre-treated powdered waste sludge (PWS) was used for removal of textile dyestuffs from aqueous medium by adsorption as an alternative to the use of powdered activated carbon (PAC). The rate and extent of dysetuff removals were determined for four different dyestuffs at different PWS concentrations varying between 1 and 6 gl(-1). Biosorbed dyestuff concentrations at equilibrium decreased with increasing PWS concentration for all dyestuffs tested. PWS was more effective for adsorption of Remazol red RR and Chrisofonia direct yellow 12 as compared to the other dyestuffs tested. More than 80% percent dyestuff removal was obtained for all dyestuffs at PWS concentrations above 4 gl(-1) after 6h of incubation. Similar to percent dyestuff removal, the rate of adsorption was maximum at a PWS concentration of 4 gl(-1). Kinetics of adsorption of dyestuffs was investigated by using the first- and second-order kinetic models and the kinetic constants were determined. Second-order kinetics was found to fit the experimental data better than the first-order model for all dyestuffs tested. Adsorption isotherms were established for all dyestuffs used and the isotherm constants were determined by using the experimental data. Langmuir and the generalized adsorption isotherms were found to be more suitable than the Freundlich isotherm for correlation of equilibrium adsorption data. Acid pre-treated PWS was proven to be an effective adsorbent for dyestuff removal as compared to the other adsorbents reported in literature studies.

  7. Modeling high adsorption capacity and kinetics of organic macromolecules on super-powdered activated carbon.

    PubMed

    Matsui, Yoshihiko; Ando, Naoya; Yoshida, Tomoaki; Kurotobi, Ryuji; Matsushita, Taku; Ohno, Koichi

    2011-02-01

    The capacity to adsorb natural organic matter (NOM) and polystyrene sulfonates (PSSs) on small particle-size activated carbon (super-powdered activated carbon, SPAC) is higher than that on larger particle-size activated carbon (powdered-activated carbon, PAC). Increased adsorption capacity is likely attributable to the larger external surface area because the NOM and PSS molecules do not completely penetrate the adsorbent particle; they preferentially adsorb near the outer surface of the particle. In this study, we propose a new isotherm equation, the Shell Adsorption Model (SAM), to explain the higher adsorption capacity on smaller adsorbent particles and to describe quantitatively adsorption isotherms of activated carbons of different particle sizes: PAC and SPAC. The SAM was verified with the experimental data of PSS adsorption kinetics as well as equilibrium. SAM successfully characterized PSS adsorption isotherm data for SPACs and PAC simultaneously with the same model parameters. When SAM was incorporated into an adsorption kinetic model, kinetic decay curves for PSSs adsorbing onto activated carbons of different particle sizes could be simultaneously described with a single kinetics parameter value. On the other hand, when SAM was not incorporated into such an adsorption kinetic model and instead isotherms were described by the Freundlich model, the kinetic decay curves were not well described. The success of the SAM further supports the adsorption mechanism of PSSs preferentially adsorbing near the outer surface of activated carbon particles.

  8. Lysozyme immobilization via adsorption process using sulphonic acid functionalized silane grafted copolymer.

    PubMed

    Anirudhan, T S; Rauf, Tharun A

    2013-07-01

    A unique silane based adsorbent material, [stearyl alcohol (SA)-grafted-epichlorohydrin (E)]-grafted-aminoproypyl silanetriol (APST) was synthesized and functionalized with sulphonyl groups via sulphonation process [(SA-g-E)-g-APST/SO3H]. The adsorbent material characterization was done by FTIR, XRD, and TGA analysis. Immobilization of protein Lysozyme (LYZ) using batch adsorption process was carried out for studying the protein-particle interaction. The most suitable pH for maximum adsorption was found to be 7.0. Pseudo-second-order kinetic model was found to be the best fit and the adsorption equilibrium was attained within 3h. Studies on diffusion parameters explained that the adsorption mechanism was controlled by film diffusion mode. The adsorption process was then evaluated using the various isotherm models and the Sips isotherm model proved to be the best fit with a maximum adsorption capacity of 37.68 mg/g. The isotherm favorability of the adsorption process was calculated by calculating the separation factor (R(L)) and the values confirmed the favorability of the adsorption process. Studies on adsorption percentage with respect to temperature and thermodynamic studies revealed that adsorption process is exothermic, spontaneous with maximum entropy. Batch adsorption/desorption studies in acidic medium, for over six cycles showed the repeatability and regeneration capability of the adsorbent material (SA-g-E)-g-APST/SO3H.

  9. Equilibrium and kinetic studies on acid dye Acid Red 88 adsorption by magnetic ZnFe2O4 spinel ferrite nanoparticles.

    PubMed

    Konicki, Wojciech; Sibera, Daniel; Mijowska, Ewa; Lendzion-Bieluń, Zofia; Narkiewicz, Urszula

    2013-05-15

    A magnetic ZnFe2O4 (MNZnFe) was synthesized by microwave assisted hydrothermal method and was used as an adsorbent for the removal of acid dye Acid Red 88 (AR88) from aqueous solution. The effects of various parameters such as initial AR88 concentration (10-56 mg L(-1)), pH solution (3.2-10.7), and temperature (20-60°C) were investigated. Prepared magnetic ZnFe2O4 was characterized by XRD, SEM, HRTEM, ICP-AES, BET, FTIR, and measurements of the magnetic susceptibility. The experimental data were analyzed by the Langmuir and Freundlich models of adsorption. Equilibrium data fitted well with the Langmuir model. Pseudo-first-order and pseudo-second-order kinetic models and intraparticle diffusion model were used to examine the adsorption kinetic data. The adsorption kinetics was found to follow the pseudo-second-order kinetic model. Thermodynamics parameters, ΔG°, ΔH° and ΔS°, indicate that the adsorption of AR88 onto MNZnFe was spontaneous and exothermic in nature.

  10. Adsorption/desorption of Cd(II), Cu(II) and Pb(II) using chemically modified orange peel: Equilibrium and kinetic studies

    NASA Astrophysics Data System (ADS)

    Lasheen, Mohamed R.; Ammar, Nabila S.; Ibrahim, Hanan S.

    2012-02-01

    Waste materials from industries such as food processing may act as cost effective and efficient biosorbents to remove toxic contaminants from wastewater. This study aimed to establish an optimized condition and closed loop application of processed orange peel for metals removal. A comparative study of the adsorption capacity of the chemically modified orange peel was performed against environmentally problematic metal ions, namely, Cd 2+, Cu 2+ and Pb 2+, from aqueous solutions. Chemically modified orange peel (MOP) showed a significantly higher metal uptake capacity compared to original orange peel (OP). Fourier Transform Infrared (FTIR) Spectra of peel showed that the carboxylic group peak shifted from 1637 to 1644 cm -1 after Pb (II) ions binding, indicated the involvement of carboxyl groups in Pb(II) ions binding. The metals uptake by MOP was rapid and the equilibrium time was 30 min at constant temperature and pH. Sorption kinetics followed a second-order model. The mechanism of metal sorption by MOP gave good fits for Freundlich and Langmuir models. Desorption of metals and regeneration of the biosorbent was attained simultaneously by acid elution. Even after four cycles of adsorption-elution, the adsorption capacity was regained completely and adsorption efficiency of metal was maintained at around 90%.

  11. 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

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

    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 N(2) 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 C(18)-SH (coverage of 2.94 × 10(14) molecules cm(-2) based from the decomposition of the C(18)-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.

  12. Modeling of phase equilibrium and vapor adsorption on carbon black based on a combination of a lattice theory and equation of state.

    PubMed

    Ustinov, E A; Do, D D

    2002-09-15

    A thermodynamic approach is developed in this paper to describe the behavior of a subcritical fluid in the neighborhood of vapor-liquid interface and close to a graphite surface. The fluid is modeled as a system of parallel molecular layers. The Helmholtz free energy of the fluid is expressed as the sum of the intrinsic Helmholtz free energies of separate layers and the potential energy of their mutual interactions calculated by the 10-4 potential. This Helmholtz free energy is described by an equation of state (such as the Bender or Peng-Robinson equation), which allows us a convenient means to obtain the intrinsic Helmholtz free energy of each molecular layer as a function of its two-dimensional density. All molecular layers of the bulk fluid are in mechanical equilibrium corresponding to the minimum of the total potential energy. In the case of adsorption the external potential exerted by the graphite layers is added to the free energy. The state of the interface zone between the liquid and the vapor phases or the state of the adsorbed phase is determined by the minimum of the grand potential. In the case of phase equilibrium the approach leads to the distribution of density and pressure over the transition zone. The interrelation between the collision diameter and the potential well depth was determined by the surface tension. It was shown that the distance between neighboring molecular layers substantially changes in the vapor-liquid transition zone and in the adsorbed phase with loading. The approach is considered in this paper for the case of adsorption of argon and nitrogen on carbon black. In both cases an excellent agreement with the experimental data was achieved without additional assumptions and fitting parameters, except for the fluid-solid potential well depth. The approach has far-reaching consequences and can be readily extended to the model of adsorption in slit pores of carbonaceous materials and to the analysis of multicomponent adsorption

  13. Water vapor adsorption on activated carbon preadsorbed with naphtalene.

    PubMed

    Zimny, T; Finqueneisel, G; Cossarutto, L; Weber, J V

    2005-05-01

    The adsorption of water vapor on a microporous activated carbon derived from the carbonization of coconut shell has been studied. Preadsorption of naphthalene was used as a tool to determine the location and the influence of the primary adsorbing centers within the porous structure of active carbon. The adsorption was studied in the pressure range p/p0=0-0.95 in a static water vapor system, allowing the investigation of both kinetic and equilibrium experimental data. Modeling of the isotherms using the modified equation of Do and Do was applied to determine the effect of preadsorption on the mechanism of adsorption.

  14. Predicting protein dynamic binding capacity from batch adsorption tests.

    PubMed

    Carta, Giorgio

    2012-10-01

    The dynamic binding capacity (DBC) and its dependence on residence time influence the design and productivity of adsorption columns used in protein capture applications. This paper offers a very simple approach to predict the DBC of an adsorption column based on a measurement of the equilibrium binding capacity (EBC) and of the time needed to achieve one-half of the EBC in a batch adsorption test. The approach is based on a mass transfer kinetics model that assumes pore diffusion with a rectangular isotherm; however, the same approach is also shown to work for other systems where solute transport inside the particle occurs through other transport mechanisms.

  15. Enhancement of the adsorption capacity of the light-weight expanded clay aggregate surface for the metronidazole antibiotic by coating with MgO nanoparticles: Studies on the kinetic, isotherm, and effects of environmental parameters.

    PubMed

    Kalhori, Ebrahim Mohammadi; Al-Musawi, Tariq J; Ghahramani, Esmaeil; Kazemian, Hossein; Zarrabi, Mansur

    2017-02-09

    The synthesized MgO nanoparticles were used to coat the light-weight expanded clay aggregates (LECA) and as a metronidazole (MNZ) adsorbent. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Fourier-transformed infrared (FTIR) techniques were employed to study the surface morphology and characteristics of the adsorbents. MgO/LECA clearly revealed the advantages of the nanocomposite particles, showing high specific surface area (76.12 m(2)/g), significant adsorption sites and functional groups. Between pH 5 and 9, the MNZ sorption was not significantly affected. Kinetic studies revealed that the MNZ adsorption closely followed the Avrami model, with no dominant process controlling the sorption rate. The study of the effects of foreign ions revealed that the addition of carbonate raised the MNZ removal efficiency of LECA by 8% and the total removal of MNZ by MgO/LECA. Furthermore, nitrate and hardness only marginally influenced the MNZ removal efficiency and their effects can be ranked in the order of carbonate>nitrate>hardness. The isotherm adsorption of MNZ was best fitted with the Langmuir model enlighten the monolayer MNZ adsorption on the homogeneous LECA and MgO/LECA surfaces. The maximum adsorption capacity under optimum conditions was enhanced from 56.31 to 84.55 mg/g for LECA and MgO/LECA, respectively. These findings demonstrated that the MgO/LECA nanocomposite showed potential as an efficient adsorbent for MNZ removal.

  16. Thiol-functionalized polysilsesquioxane as efficient adsorbent for adsorption of Hg(II) and Mn(II) from aqueous solution

    SciTech Connect

    Niu, Yuzhong Qu, Rongjun; Liu, Xiguang; Mu, Lei; Bu, Baihui; Sun, Yuting; Chen, Hou; Meng, Yangfeng; Meng, Lina; Cheng, Lin

    2014-04-01

    Highlights: • PMPSQ was promising adsorbent for the removal of Hg(II) and Mn(II). • The adsorption kinetics followed the pseudo-second-order model. • The adsorption isotherms can be described by the monolayer Langmuir model. • The adsorption was controlled by film diffusion and chemical ion-exchange mechanism. - Abstract: Thiol-functionalized polysilsesquioxane was synthesized and used for the adsorption of Hg(II) and Mn(II) from aqueous solution. Results showed that the optimal pH was about 6 and 5 for Hg(II) and Mn(II), respectively. Adsorption kinetics showed that the adsorption equilibriums were established within 100 min and followed pseudo-second-order model. Adsorption isotherms revealed that the adsorption capacities increased with the increasing of temperature. The adsorption was found to be well described by the monolayer Langmuir isotherm model and took place by chemical ion-exchange mechanism. The thermodynamic properties indicated the adsorption processes were spontaneous and endothermic nature. Selectively adsorption showed that PMPSQ can selectively adsorb Hg(II) from binary ion systems in the presence of the coexistent ions Mn(II), Cu(II), Pb(II), Co(II), and Ni(II). Based on the results, it is concluded that PMPSQ had comparable high adsorption efficiency and could be potentially used for the removal of Hg(II) and Mn(II) from aqueous solution.

  17. Modeling of boldine alkaloid adsorption onto pure and propyl-sulfonic acid-modified mesoporous silicas. A comparative study.

    PubMed

    Geszke-Moritz, Małgorzata; Moritz, Michał

    2016-12-01

    The present study deals with the adsorption of boldine onto pure and propyl-sulfonic acid-functionalized SBA-15, SBA-16 and mesocellular foam (MCF) materials. Siliceous adsorbents were characterized by nitrogen sorption analysis, transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier-transform infrared (FT-IR) spectroscopy and thermogravimetric analysis. The equilibrium adsorption data were analyzed using the Langmuir, Freundlich, Redlich-Peterson, and Temkin isotherms. Moreover, the Dubinin-Radushkevich and Dubinin-Astakhov isotherm models based on the Polanyi adsorption potential were employed. The latter was calculated using two alternative formulas including solubility-normalized (S-model) and empirical C-model. In order to find the best-fit isotherm, both linear regression and nonlinear fitting analysis were carried out. The Dubinin-Astakhov (S-model) isotherm revealed the best fit to the experimental points for adsorption of boldine onto pure mesoporous materials using both linear and nonlinear fitting analysis. Meanwhile, the process of boldine sorption onto modified silicas was described the best by the Langmuir and Temkin isotherms using linear regression and nonlinear fitting analysis, respectively. The values of adsorption energy (below 8kJ/mol) indicate the physical nature of boldine adsorption onto unmodified silicas whereas the ionic interactions seem to be the main force of alkaloid adsorption onto functionalized sorbents (energy of adsorption above 8kJ/mol).

  18. Removal of ibuprofen, naproxen and carbamazepine in aqueous solution onto natural clay: equilibrium, kinetics, and thermodynamic study

    NASA Astrophysics Data System (ADS)

    Khazri, Hassen; Ghorbel-Abid, Ibtissem; Kalfat, Rafik; Trabelsi-Ayadi, Malika

    2016-04-01

    This study aimed to describe the adsorption of three pharmaceuticals compounds (ibuprofen, naproxen and carbamazepine) onto natural clay on the basis of equilibrium parameters such as a function of time, effect of pH, varying of the concentration and the temperature. Adsorption kinetic data were modeled using the Lagergren's first-order and the pseudo-second-order kinetic equations. The kinetic results of adsorption are described better using the pseudo-second order model. The isotherm results were tested in the Langmuir, Freundlich and Dubinin-Radushkevich models. The thermodynamic parameters obtained indicate that the adsorption of pharmaceuticals on the clay is a spontaneous and endothermic process.

  19. Adsorptive desulfurization by activated alumina.

    PubMed

    Srivastav, Ankur; Srivastava, Vimal Chandra

    2009-10-30

    This study reports usage of commercial grade activated alumina (aluminum oxide) as adsorbent for the removal of sulfur from model oil (dibenthiophene (DBT) dissolved in n-hexane). Bulk density of alumina was found to be 1177.77 kg/m(3). The BET surface area of alumina was found to decrease from 143.6 to 66.4 m(2)/g after the loading of DBT at optimum conditions. The carbon-oxygen functional groups present on the surface of alumina were found to be effective in the adsorption of DBT onto alumina. Optimum adsorbent dose was found to be 20 g/l. The adsorption of DBT on alumina was found to be gradual process, and quasi-equilibrium reached in 24 h. Langmuir isotherm best represented the equilibrium adsorption data. The heat of adsorption and change in entropy for DBT adsorption onto alumina was found to be 19.5 kJ/mol and 139.2 kJ/mol K, respectively.

  20. Influence of cationic surfactant on adsorption of Cr(VI) onto activated carbon.

    PubMed

    Choi, Hyun-Doc; Cho, Jung-Min; Baek, Kitae; Yang, Jung-Seok; Lee, Jae-Young

    2009-01-30

    The effect of a cationic surfactant on the adsorption of Cr(VI) on activated carbon was investigated using cetylpyridinium chloride (CPC). At a concentration below the critical micelle concentration (CMC) of CPC, the adsorption of CPC and Cr(VI) reached equilibrium within 60 min, while it took 180 min at the concentration above CMC. CPC decreased the adsorption rate of Cr(VI) and increased the adsorption amount of Cr(VI) onto activated carbon. To analyze adsorption phenomena of Cr(VI), adsorption kinetic and isotherm were used and fitted well with the pseudo-second order kinetic model and Langmuir adsorption model, respectively. CPC introduced a cationic functional group on the surface of activated carbon and provided an adsorption site for Cr(VI).

  1. 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.

  2. Batch study of liquid-phase adsorption of methylene blue using cedar sawdust and crushed brick.

    PubMed

    Hamdaoui, Oualid

    2006-07-31

    This paper presents a study on the batch adsorption of basic dye, methylene blue, from aqueous solution (40 mg L(-1)) onto cedar sawdust and crushed brick in order to explore their potential use as low-cost adsorbents for wastewater dye removal. Adsorption isotherms were determined at 20 degrees C and the experimental data obtained were modelled with the Langmuir, Freundlich, Elovich and Temkin isotherm equations. Adsorption kinetic data determined at a temperature of 20 degrees C were modelled using the pseudo-first and pseudo-second-order kinetic equations, liquid-film mass transfer and intra-particle diffusion models. By considering the experimental results and adsorption models applied in this study, it can be concluded that equilibrium data were represented well by a Langmuir isotherm equation with maximum adsorption capacities of 142.36 and 96.61 mg g(-1) for cedar sawdust and crushed brick, respectively. The second-order model best describes adsorption kinetic data. Analysis of adsorption kinetic results indicated that both film- and particle-diffusion are effective adsorption mechanisms. The Influence of temperature and pH of the solution on adsorption process were also studied. The extent of the dye removal decreased with increasing the solution temperature and optimum pH value for dye adsorption was observed at pH 7 for both adsorbents. The results indicate that cedar sawdust and crushed brick can be attractive options for dye removal from dilute industrial effluents.

  3. Removal of Reactofix Navy Blue 2 GFN from aqueous solutions using adsorption techniques.

    PubMed

    Gupta, Vinod Kumar; Jain, Rajeev; Varshney, Shaily; Saini, Vipin Kumar

    2007-03-15

    The wheat husk, an agricultural by-product, has been activated and used as an adsorbent for the adsorption of Reactofix Navy Blue 2 GFN from aqueous solution. In this work, adsorption of Reactofix Navy Blue 2 GFN on wheat husk and charcoal has been studied by using batch studies. The equilibrium adsorption level was determined to be a function of the solution pH, adsorbent dosage, dye concentration and contact time. The equilibrium adsorption capacities of wheat husk and charcoal for dye removal were obtained using Freundlich and Langmuir isotherms. Thermodynamic parameters such as the free energies, enthalpies and entropies of adsorption were also evaluated. Adsorption process is considered suitable for removing color, COD from waste water.

  4. Quantification of the effects of organic and carbonate buffers on arsenate and phosphate adsorption on a goethite-based granular porous adsorbent.

    PubMed

    Kanematsu, Masakazu; Young, Thomas M; Fukushi, Keisuke; Sverjensky, Dimitri A; Green, Peter G; Darby, Jeannie L

    2011-01-15

    Interest in the development of oxide-based materials for arsenate removal has led to a variety of experimental methods and conditions for determining arsenate adsorption isotherms, which hinders comparative evaluation of their adsorptive capacities. Here, we systematically investigate the effects of buffer (HEPES or carbonate), adsorbent dose, and solution pH on arsenate and phosphate adsorption isotherms for a previously well characterized goethite-based adsorbent (Bayoxide E33 (E33)). All adsorption isotherms obtained at different adsorbate/adsorbent concentrations were identical when 1 mM of HEPES (96 mg C/L) was used as a buffer. At low aqueous arsenate and phosphate concentration (∼1.3 μM), however, adsorption isotherms obtained using 10 mM of NaHCO(3) buffer, which is a reasonable carbonate concentration in groundwater, are significantly different from those obtained without buffer or with HEPES. The carbonate competitive effects were analyzed using the extended triple layer model (ETLM) with the adsorption equilibrium constant of carbonate calibrated using independent published carbonate adsorption data for pure goethite taking into consideration the different surface properties. The successful ETLM calculations of arsenate adsorption isotherms for E33 under various conditions allowed quantitative comparison of the arsenate adsorption capacity between E33 and other major adsorbents initially tested under varied experimental conditions in the literature.

  5. Adsorption mechanism of chloroacetanilide herbicides to modified montmorillonite.

    PubMed

    El-Nahhal, Yasser

    2003-09-01

    This study was undertaken to characterize the adsorption mechanism of alachlor and metolachlor on montmorillonite modified with cationic surfactants. Adsorbed amounts of cationic surfactant on montmorillonite surfaces were determined by CNHSO analyzer. Equilibrium concentrations of alachlor and metolachlor were determined by GC and adsorption results were fit to a linear regression equation. The slope of the isotherms (Kd) was normalized to the fraction of organic carbon on montmorillonite complexes to produce corresponding Koc. Adsorption of surfactants fit very well to Langmuir equation. Increased basal spacing indicates that surfactant molecules could penetrate through the interlayer spacing and arrange themselves in different ways. Equilibrium data of alachlor and metolachlor suggest that adsorption may occur via physical or chemical bonds. Koc values of alachlor or metolachlor decreased as the fraction of the organic carbon increased in montmorillonite complexes indicating independent adsorption process. Changes of the molar free energy of the adsorption reactions were in the range of physical adsorption, indicating that adsorption reactions are spontaneous and the molecules either adsorb on the surface or penetrate into the inter-layers of montmorillonite-surfactant complex. Careful investigation of the adsorption data suggests that interaction may occur via the active groups such as carbonyl group (-C=O), anilidic (C-N) group and/or phenyl rings. This information may provide better understanding on adsorption mechanism and be useful in designing ecologically acceptable herbicide formulations.

  6. Phosphate Adsorption using Modified Iron Oxide-based Sorbents in Lake Water: Kinetics, Equilibrium, and Column Tests

    EPA Science Inventory

    Adsorption behavior of Bayoxide ® E33 (E33) and three E33-modified sorbents for the removal of phosphate from lake water was investigated in this study. E33-modified sorbents were synthesized by coating with manganese (E33/Mn) and silver (E33/AgI and E33/AgII) nanoparticles. Adso...

  7. Neon and CO2 adsorption on open carbon nanohorns.

    PubMed

    Krungleviciute, Vaiva; Ziegler, Carl A; Banjara, Shree R; Yudasaka, Masako; Iijima, S; Migone, Aldo D

    2013-07-30

    We present the results of a thermodynamics and kinetics study of the adsorption of neon and carbon dioxide on aggregates of chemically opened carbon nanohorns. Both the equilibrium adsorption characteristics, as well as the dependence of the kinetic behavior on sorbent loading, are different for these two adsorbates. For neon the adsorption isotherms display two steps before reaching the saturated vapor pressure, corresponding to adsorption on strong and on weak binding sites; the isosteric heat of adsorption is a decreasing function of sorbent loading (this quantity varies by about a factor of 2 on the range of loadings studied), and the speed of the adsorption kinetics increases with increasing loading. By contrast, for carbon dioxide there are no substeps in the adsorption isotherms; the isosteric heat is a nonmonotonic function of loading, the value of the isosteric heat never differs from the bulk heat of sublimation by more than 15%, and the kinetic behavior is opposite to that of neon, with equilibration times increasing for higher sorbent loadings. We explain the difference in the equilibrium properties observed for neon and carbon dioxide in terms of differences in the relative strengths of adsorbate-adsorbate to adsorbate-sorbent interaction for these species.

  8. Removal of hazardous pharmaceutical dyes by adsorption onto papaya seeds.

    PubMed

    Weber, Caroline Trevisan; Collazzo, Gabriela Carvalho; Mazutti, Marcio Antonio; Foletto, Edson Luiz; Dotto, Guilherme Luiz

    2014-01-01

    Papaya (Carica papaya L.) seeds were used as adsorbent to remove toxic pharmaceutical dyes (tartrazine and amaranth) from aqueous solutions, in order to extend application range. The effects of pH, initial dye concentration, contact time and temperature were investigated. The kinetic data were evaluated by the pseudo first-order, pseudo second-order and Elovich models. The equilibrium was evaluated by the Langmuir, Freundlich and Temkin isotherm models. It was found that adsorption favored a pH of 2.5, temperature of 298 K and equilibrium was attained at 180-200 min. The adsorption kinetics followed the pseudo second-order model, and the equilibrium was well represented by the Langmuir model. The maximum adsorption capacities were 51.0 and 37.4 mg g(-1) for tartrazine and amaranth, respectively. These results revealed that papaya seeds can be used as an alternative adsorbent to remove pharmaceutical dyes from aqueous solutions.

  9. Adsorption behavior of some radionuclides on the Chinese weathered coal.

    PubMed

    Wu, Jianfeng; Xu, Qichu; Bai, Tao

    2007-08-01

    The equilibrium and kinetic properties of Am(III), Eu(III) and Cs(I) ions adsorption by three weathered coals (WCs) from China, have been investigated in batch stirred-tank experiments. The effects of contact time, solution acidity and initial sorbate concentration on the adsorption of Am(III), Eu(III) and Cs(I) by Yuxian(YX) Tongchuan (TC) and Pingxiang (PX) WC were evaluated. The radionuclide ions are able to form complex compounds with carboxylic and phenolic groups of WCs and they are also bounded with phenolic groups even at high acidity reaction solution (>0.1 mol/L). Mechanisms including ion exchange, complexation and adsorption to the coal surface are possible in the sorption process. The acidity of the solution played an important role in the adsorption. Even acidity as high as 0.1 mol/L, 60% of Am(III) or Eu(III), 40% of Cs(I) were found to be sorbed on the YX WC, which had the best adsorption capacity for Am(III) and Eu(III). Our batch adsorption studies showed the equilibrium adsorption data fit the linear Langmuir and Freundlich adsorption isotherm. The maximum equilibrium uptake of Eu(III) were 0.412, 3.701, 5.446 mmol/g for JXWC, TCWC and YXWC, respectively.

  10. Dynamics and thermodynamics of toxic metals adsorption onto soil-extracted humic acid.

    PubMed

    Shaker, Medhat A; albishri, Hassan M

    2014-09-01

    Humic acids, HA represent a large portion of natural organic matter in soils, sediments and waters. They are environmentally important materials due to their extensive ubiquity and strong complexation ability, which can influence heavy metal removal and transportation in waters. The thermodynamics and kinetics of the adsorption of Cd(II) and Cr(VI) onto solid soil-derived HA have been investigated at optimum conditions of pH (5.5±0.1), metal concentration (10-100mmolL(-1)) and different temperatures (293-323K). The suitability of adsorption models such as Freundlich and Langmuir to equilibrium data was investigated. The adsorption was well described by Langmuir isotherm model in multi-detectable steps. Adsorption sites, i (i=A, B, C) with different capacities, νi are characterized. The stoichiometric site capacity is independent of temperature and equilibrium constant, Ki. Adsorption sites A and B are selectively occupied by Cr(VI) cations while sites A and C are selectively occupied by Cd(II) cations. The thermodynamic parameters of adsorption systems are correlated for each adsorption step. The adsorption is endothermic, spontaneous and favorable. Different kinetic models are applied and the adsorption of these heavy metals onto HA follows pseudo-second-order kinetics and equilibrium is achieved within 24h. The adsorption reaction is controlled by diffusion processes and the type of the adsorption is physical.

  11. 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.

  12. 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

  13. Adsorption of globular proteins on locally planar surfaces. II. Models for the effect of multiple adsorbate conformations on adsorption equilibria and kinetics.

    PubMed Central

    Minton, A P

    1999-01-01

    Equilibrium and kinetic models for nonspecific adsorption of proteins to planar surfaces are presented. These models allow for the possibility of multiple interconvertible surface conformations of adsorbed protein. Steric repulsion resulting in area exclusion by adsorbed molecules is taken into account by treating the adsorbate as a thermodynamically nonideal two-dimensional fluid. In the equilibrium model, the possibility of attractive interactions between adsorbed molecules is taken into account in a limited fashion by permitting one of the adsorbed species to self-associate. Calculated equilibrium adsorption isotherms exhibit apparent high-affinity and low-affinity binding regions, corresponding respectively to adsorption of ligand at low fractional area occupancy in an energetically favorable side-on conformation and conversion at higher fractional area occupancy of the side-on conformation to an entropically favored end-on conformation. Adsorbate self-association may lead to considerable steepening of the adsorption isotherm, compensating to a variable extent for the broadening effect of steric repulsion. Kinetic calculations suggest that in the absence of attractive interactions between adsorbate molecules, the process of adsorption may be highly "stretched" along the time axis, rendering the attainment of adsorption equilibrium in the context of conventional experiments problematic. PMID:9876132

  14. 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.

  15. Adsorption and diffusion of carbon dioxide on metal-organic framework (MOF-5)

    SciTech Connect

    Zhao, Z.X.; Li, Z.; Lin, Y.S.

    2009-11-15

    Adsorption equilibrium and diffusion of CO{sub 2} on microporous metal-organic frameworks (MOF-5, or IRMOF-1) crystals were experimentally studied by the gravimetric method in the pressure range up to 1 atm. The MOF-5 crystal cubes of about 40-60 {mu} m in sizes were synthesized by the solvothermal method. Freundlich adsorption isotherm equation can fit well CO{sub 2} adsorption isotherms on MOF-5, with isosteric heat of adsorption of about 34 kJ/mol. Diffusion coefficient of CO{sub 2} in the MOF-5 is in the range of 8.1-11.5 x 10{sup -9} cm{sup 2}/s in 295-331K with activation energy of 7.61 kJ/mol. MOF-5 offers attractive adsorption properties as an adsorbent for separation of CO{sub 2} from flue gas.

  16. Adsorption and kinetic studies of seven different organic dyes onto magnetite nanoparticles loaded tea waste and removal of them from wastewater samples

    NASA Astrophysics Data System (ADS)

    Madrakian, Tayyebeh; Afkhami, Abbas; Ahmadi, Mazaher

    2012-12-01

    Adsorption of seven different organic dyes from aqueous solutions onto magnetite nanoparticles loaded tea waste (MNLTW) was studied. MNLTW was prepared via a simple method and was fully characterized. The properties of this magnetic adsorbent were characterized by scanning electron microscopy and X-ray diffraction. Adsorption characteristics of the MNLTW adsorbent was examined using Janus green, methylene blue, thionine, crystal violet, Congo red, neutral red and reactive blue 19 as adsorbates. Dyes adsorption process was thoroughly studied from both kinetic and equilibrium points of view for all adsorbents. The experimental isotherm data were analyzed using Langmuir, Freundlich, Sips, Redlich-Peterson, Brouers-Sotolongo and Temkin isotherms. The results from Langmuir isotherm indicated that the capacity of MNLTW for the adsorption of cationic dyes was higher than that for anionic dyes. The adsorption kinetics was tested for the pseudo-first order and pseudo-second order kinetic models at different experimental conditions.

  17. Malachite green adsorption onto natural zeolite and reuse by microwave irradiation.

    PubMed

    Han, Runping; Wang, Yu; Sun, Qing; Wang, Lulu; Song, Jiyun; He, Xiaotian; Dou, Chanchan

    2010-03-15

    Natural zeolite was used for the removal of malachite green (MG) from aqueous solution in batch mode and reused by microwave irradiation. The isotherm data were analyzed by the Langmuir, Freundlich, Redlich-Peterson, and Koble-Corrigan isotherm model. The better fit for the equilibrium process was Koble-Corrigan model. The kinetic studies indicated that the adsorption followed the pseudo-second-order kinetic. Thermodynamic calculations showed that the adsorption was spontaneous and endothermic process. Spent zeolite was treated by microwave irradiation and it was found that yield of regeneration was 85.8% in the case of microwave irradiated time 10 min at 160 W.

  18. H2S adsorption onto Cu-Zn-Ni nanoparticles loaded activated carbon and Ni-Co nanoparticles loaded γ-Al2O3: Optimization and adsorption isotherms.

    PubMed

    Daneshyar, A; Ghaedi, M; Sabzehmeidani, M M; Daneshyar, A

    2017-03-15

    The nanocomposites based on copper, zinc and nickel were loaded on activated carbon (Cu-Zn-Ni-NPs-AC) and cobalt and nickel nanoparticles was loaded on γ-alumina (Ni-Co-NPs-γAl2O3) and applied for removal of hydrogen sulfide (H2S) from natural gas and their efficiency were compared. Cu-Zn-Ni/AC and Ni-Co/γ-Al2O3 was characterized using different techniques such as energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM). The effects of variables such as amount of adsorbent, flow rate, temperature, pressure and volume of gas on H2S removal were examined and optimum values were found to be 0.3g adsorbent, and flow rate of 0.15L/min and 15°C and 7Psi for both adsorbent and also 5.5 and 6.5L of sample by Cu-Zn-Ni/C and Co-Ni/γ-Al2O3, respectively. Setting conditions at the above optimum conditions lead to achievement of maximum removal of H2S (94% and 91.6%) by Cu-Zn-Ni/AC and Co-Ni/γ-Al2O3. The negative value of ΔG° and its numerical value confirm physisorption nature of adsorption. The experimental equilibrium data with high efficiency were explained and represented by Langmuir model for both adsorbents with the highest correlation coefficients.

  19. Removal of azo dye by a highly graphitized and heteroatom doped carbon derived from fish waste: Adsorption equilibrium and kinetics.

    PubMed

    Liu, Zhengang; Zhang, Fang; Liu, Tingting; Peng, Nana; Gai, Chao

    2016-11-01

    A highly graphitized and heteroatom doped porous carbon was prepared from fish waste in the present study. The morphology and chemical composition of the resultant porous carbon were characterized by SEM-EDS, TEM, BET, XRD and Raman measurement. The prepared porous carbon was employed as an adsorbent for acid orange 7, a typical azo dye, removal from aqueous solution. The results showed that the porous carbon had ultrahigh surface area of 2146 m(2)/g, a high degree of graphitization structure and naturally doped with nitrogen and phosphorous. The maximum adsorption capacity of acid orange 7 reached 285.71 mg/g due to unique property of the prepared porous carbon. In addition, acid orange 7 adsorption onto the porous carbon well followed pseudo-second-order kinetics model and acid orange 7 diffusion in micropores was the potential rate controlling step.

  20. Adsorption equilibrium and transport kinetics for a range of probe gases in Takeda 3A carbon molecular sieve.

    PubMed

    Rutherford, S W; Coons, J E

    2005-04-15

    Measurements of adsorption equilibria and transport kinetics for argon, oxygen and nitrogen at 20, 50, and 80 degrees C on commercially derived Takeda carbon molecular sieve (CMS) employed for air separation have been undertaken in an effort to elucidate fundamental mechanisms of transport. Results indicate that micropore diffusion which is modeled by a Fickian diffusion process, governs the transport of oxygen molecules and the pore mouth barrier controls argon and nitrogen transport which is characterized by a linear driving force (LDF) model. For the three temperatures studied, the pressure dependence of the diffusivity and the LDF rate constant appear to be well characterized by a formulation based on the chemical potential as the driving force for transport. Isosteric heat of adsorption at zero loading and activation energy measurements are compared with predictions made from a previously proposed molecular model for characterizing CMS.

  1. Predicting Multicomponent Adsorption Isotherms in Open-Metal Site Materials Using Force Field Calculations Based on Energy Decomposed Density Functional Theory.

    PubMed

    Heinen, Jurn; Burtch, Nicholas C; Walton, Krista S; Fonseca Guerra, Célia; Dubbeldam, David

    2016-12-12

    For the design of adsorptive-separation units, knowledge is required of the multicomponent adsorption behavior. Ideal adsorbed solution theory (IAST) breaks down for olefin adsorption in open-metal site (OMS) materials due to non-ideal donor-acceptor interactions. Using a density-function-theory-based energy decomposition scheme, we develop a physically justifiable classical force field that incorporates the missing orbital interactions using an appropriate functional form. Our first-principles derived force field shows greatly improved quantitative agreement with the inflection points, initial uptake, saturation capacity, and enthalpies of adsorption obtained from our in-house adsorption experiments. While IAST fails to make accurate predictions, our improved force field model is able to correctly predict the multicomponent behavior. Our approach is also transferable to other OMS structures, allowing the accurate study of their separation performances for olefins/paraffins and further mixtures involving complex donor-acceptor interactions.

  2. Removal of Cd2+ from aqueous solution by adsorption using Fe-montmorillonite.

    PubMed

    Wu, Pingxiao; Wu, Weimin; Li, Shuzhen; Xing, Ning; Zhu, Nengwu; Li, Ping; Wu, Jinghua; Yang, Chen; Dang, Zhi

    2009-09-30

    Fe-montmorillonite (Fe-Mont.) is obtained by exchanging the original interlayer cations of montmorillonite by poly-hydroxyl ferric. In this paper, Fe-Mont. was synthesized by using Ca-montmorillonite (Ca-Mont.) directly under ultrasonic treatment with the aim to enhance the ability of removal of heavy metal ions from wastewater. The modified materials were characterized by X-ray diffraction (XRD) and Fourier transform infrared (FT-IR). Batch equilibrium experiments of Cd(II) ions (Cd(2+)) adsorption on the Fe-Mont. were performed. Effects of the initial pH of the solution and contact time on the adsorption of Cd(2+) were studied. Four types of adsorption isotherms were applied to describe the adsorption isotherms of Cd(2+) by Fe-Mont. The relationship between adsorbing capacity (q(e)) and equilibrium mass concentration (C(e)) is in accordance with the isothermal adsorption equation of Langmuir. Three kinetic models, including pseudo-first-order, pseudo-second-order and the Elovich equation model, were used to analyze the Cd(2+) adsorption process. The pseudo-second-order chemical reaction kinetics provide the best correlation of the experimental data, therefore the adsorption dynamics follows the laws of pseudo-second-order kinetics.

  3. [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.

  4. Adsorption of Pb(II) from aqueous solution by silica-gel supported hyperbranched polyamidoamine dendrimers.

    PubMed

    Niu, Yuzhong; Qu, Rongjun; Sun, Changmei; Wang, Chunhua; Chen, Hou; Ji, Chunnuan; Zhang, Ying; Shao, Xia; Bu, Fanling

    2013-01-15

    The adsorption properties of silica-gel supported hyperbranched polyamidoamine dendrimers (SiO(2)-G0-SiO(2)-G4.0) have been investigated by batch method. The effect of pH of the solution, contact time, initial Pb(II) ion concentration, temperature and coexisting metal ions have been demonstrated. The results indicated that the optimum pH value was 5. Adsorption kinetics was found to follow the pseudo-second-order model and controlled by film diffusion. The adsorption isotherms were fitted by Langmuir, Freundlich and Dubinin-Radushkevich (D-R) isotherm models. Langmuir isotherm model was found to be more suitable to describe the equilibrium data, suggesting the uptake of Pb(II) ions by monolayer adsorption. From D-R isotherm model, the calculated mean free energy E demonstrated the adsorption processes occurred by chemical ion-exchange mechanism. FTIR analysis revealed that amine groups were mainly responsible for the adsorption of Pb(II) by amino-terminated adsorbents, while CO of ester groups also participated in the adsorption process of ester-terminated ones. The adsorbents can selectively adsorb Pb(II) from binary ion systems in the presence of Mn(II), Cu(II), Co(II), and Ni(II). Based on the results, it is concluded that SiO(2)-G0-SiO(2)-G4.0 had great potential for the removal of Pb(II) from aqueous solution.

  5. Adsorption of methylene blue dye onto activated carbons based on agricultural by-products: equilibrium and kinetic studies.

    PubMed

    Ioannou, Z; Simitzis, J

    2013-01-01

    Mixtures of novolac resin and olive stone biomass (20/80 and 40/60 w/w) were cured, pyrolyzed up to 1,000 °C and activated with CO2 under a continuous flow operation (named N20B-cCa and N40B-cCa respectively). Commercial activated charcoal was similarly re-activated with CO2 and used for comparison reasons (AC-a). The characterization of these materials was performed by Fourier transform Infrared (FTIR) analysis and their specific surface area was determined according to DIN 66132. The materials were tested for their adsorption abilities at different temperatures (298, 333 K) and initial dye concentrations (0.01-0.35 g/L) using 1 L of methylene blue (MB) solution in 10 g of activated carbon. MB adsorption kinetic was also studied. The FTIR spectra of all activated carbons show absorption peaks which correspond to -OH, -CH, -C-O-C- groups and to aromatic ring. The presence of the absorption peak at about 1,400 cm(-1) for N20B-cCa, N40B-cCa indicates more acidic groups on them compared to the commercial AC-a. The specific surface area of N20B-cCa, N40B-cCa and AC-a has values equal to 352, 342 and 760 m(2)/g respectively. From the applied kinetic models, pseudo-second-order equation could best describe MB adsorption. Consequently, such adsorbents can be used as filters to adsorb dyes from wastewaters.

  6. Enhanced adsorptive removal of toxic dyes using SiO2 nanofibers

    NASA Astrophysics Data System (ADS)

    Batool, S. S.; Imran, Z.; Hassan, Safia; Rasool, Kamran; Ahmad, Mushtaq; Rafiq, M. A.

    2016-05-01

    Electrospinning method was used to synthesize porous SiO2 nanofibers. The adsorption of Methyl Orange and Safranin O by porous SiO2 nanofibers was carried out by varying the parameters such as pH, contact time, adsorbent dose, dye concentration, and temperature. Equilibrium adsorption data followed Langmuir isotherms. Kinetic adsorption followed second-order rate kinetics model. The maximum adsorption capacity for Methyl Orange and Safranin O was found to be 730.9 mg/g and 960.4 mg/g, respectively. Acidic pH was favorable for the adsorption of Methyl Orange while basic pH was favorable for the adsorptions of Safranin O. Modeling study suggested the major mode of adsorption, while thermodynamic study showed the endothermic reactions. This effort has pronounced impact on environmental applications of SiO2 nanofibers as auspicious adsorbent nanofibers for organic material from aqueous solution.

  7. [Adsorption of acid orange II from aqueous solution onto modified peat-resin particles].

    PubMed

    Sun, Qing-Ye; Yang, Lin-Zhang

    2007-06-01

    The adsorption of acid orange II onto modified peat-resin particles was examined in aqueous solution in a batch system. The Langmuir and Freundlich adsorption models were applied to describe the equilibrium isotherms. The pseudo-first-order, pseudo-second-order kinetic and the intraparticle diffusion models were used to describe the kinetic data. The results showed that both Langmuir and Freundlich adsorption models could be used to describe the adsorption of acid orange II onto modified peat-resin particles. The maximum adsorption capacity was 71.43 mg x g(-1). The data analysis indicated that the intraparticle diffusion model could fit the results of kinetic experiment well. The adsorption rate of acid orange II onto modified peat-resin particles is affected by the initial dye concentrations, sizes and doses of modified peat-resin particles and agitation rates. The surface of modified peat-resin particle is the major adsorption area.

  8. Adsorption potential of mercury(II) from aqueous solutions onto Romanian peat moss.

    PubMed

    Bulgariu, Laura; Ratoi, Mioara; Bulgariu, Dumitru; Macoveanu, Matei

    2009-06-01

    This study was undertaken to evaluate the adsorption potential of Romanian peat moss for the removal of mercury(II) from aqueous solutions. The batch system experiments carried out showed that this natural material was effective in removing mercury(II). The analysis of FT-IR spectra indicated that the mechanism involved in the adsorption can be mainly attributed to the binding of mercury(II) with the carboxylic groups of Romanian peat moss. Adsorption equilibrium approached within 60 min. The adsorption data fitted well the Langmuir isotherm model. The maximum adsorption capacity (qmax) was 98.94 mg g(-1). Pseudo-second-order kinetic model was applicable to the adsorption data. The thermodynamic parameters indicate that the adsorption process was spontaneous as the Gibbs free energy values were found to be negative (between -17.58 and -27.25 kJ mol(-1)) at the temperature range of 6-54 degrees C.

  9. Adsorption of binary mixtures of ethane and acetylene on activated carbon

    SciTech Connect

    Lee, T.V.; Huang, J.C.; Rothstein, D.; Madey, R.

    1984-01-01

    Dynamic measurement of the adsorption of binary mixtures of ethane and acetylene (and also of each gas alone) in a helium carrier gas were made on an (Columbia 4LXC 12/28) activated carbon adsorber bed at 25/sup 0/C. The adsorption capacities of the activated carbon for the pure gases and for each component in the mixtures are extracted from the transmission curves by the use of a mass balance equation. Transmission is the ratio of the concentration at the outlet of the adsorber bed to that at the inlet. The adsorption isotherms for pure ethane and acetylene can be presented by a modified Langmuir isotherm known as the Chakravarti-Dhar isotherm at gas concentrations up to at least 4.2 X 19/sup -7/ mol/cm/sup 3/ (viz., 7.8 mmHg). The gas-adsorbate equilibrium composition and the adsorption capacity of each component in the binary mixture of ethane and acetylene are estimated from the corresponding single-component isotherms by applying ideal adsorbed solution theory (IAST). The fact that the estimated values of the adsorption capacities and the gas-adsorbate equilibrium compositions are in good agreement with those extracted from the measurements for the binary mixtures of ethane and acetylene confirms that the ethane-acetylene system forms an ideal adsorbed phase on activated carbon at a pressure of about 7.3 mmHg and a temperature of 25/sup 0/C. 20 references, 4 figures, 4 tables.

  10. 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

  11. 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.

  12. Preparation of activated carbons from agricultural residues for pesticide adsorption.

    PubMed

    Ioannidou, Ourania A; Zabaniotou, Anastasia A; Stavropoulos, George G; Islam, Md Azharul; Albanis, Triantafyllos A

    2010-09-01

    Activated carbons (ACs) can be used not only for liquid but also for vapour phase applications, such as water treatment, deodorisation, gas purification and air treatment. In the present study, activated carbons produced from agricultural residues (olive kernel, corn cobs, rapeseed stalks and soya stalks) via physical steam activation were tested for the removal of Bromopropylate (BP) from water. For the characterization of the activated carbons ICP, SEM, FTIR and XRD analyses were performed. Adsorption kinetics and equilibrium isotherms were investigated for all biomass activated carbons in aqueous solutions. Experimental data of BP adsorption have fitted best to the pseudo 2nd-order kinetic model and Langmuir isotherm. The study resulted that corn cobs showed better adsorption capacity than the other biomass ACs. Comparison among ACs from biomass and commercial ones (F400 and Norit GL50) revealed that the first can be equally effective for the removal of BP from water with the latter.

  13. A Comparative Study of the Adsorption of Water and Methanol in Zeolite BEA: A Molecular Simulation Study

    SciTech Connect

    Nguyen, Van T.; Nguyen, Phuong T.; Dang, Liem X.; Mei, Donghai; Wick, Collin D.; Do, Duong D.

    2014-09-15

    Grand Canonical Monte Carlo (GCMC) simulations were carried out to study the equilibrium adsorption concentration of methanol and water in all-silica zeolite BEA over the wide temperature and pressure ranges. For both water and methanol, their adsorptive capacity increases with increasing pressure and decreasing temperature. The onset of methanol adsorption occurs at much lower pressures than water adsorption at all temperatures. Our GCMC simulation results also indicate that the adsorption isotherms of methanol exhibit a gradual change with pressure while water adsorption shows a sharp first-order phase transition at low temperatures. To explore the effects of Si/Al ratio on adsorption, a series of GCMC simulations of water and methanol adsorption in zeolites HBEA with Si/Al=7, 15, 31, 63 were performed. As the Si/Al ratio decreases, the onsets of both water and methanol adsorption dramatically shift to lower pressures. The type V isotherm obtained for water adsorption in hydrophobic BEA progressively changes to type I isotherm with decreasing Si/Al ratio in hydrophilic HBEA. This work was supported by the US Department of Energy, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences & Biosciences. Pacific Northwest National Laboratory (PNNL) is a multiprogram national laboratory operated for DOE by Battelle.

  14. Adsorption of humic acids and trace metals in natural waters

    NASA Technical Reports Server (NTRS)

    Leung, W. H.

    1982-01-01

    Studies concerning the interactions between suspended hydrous iron oxide and dissolved humic acids and trace metals are reported. As a major component of dissolved organic matters and its readiness for adsorption at the solid/water interface, humic acids may play a very important role in the organometallic geochemistry of suspended sediments and in determining the fate and distribution of trace metals, pesticides and anions in natural water systems. Most of the solid phases in natural waters contain oxides and hydroxides. The most simple promising theory to describe the interactions of hydrous iron oxide interface is the surface complex formation model. In this model, the adsorptions of humic acids on hydrous iron oxide may be interpreted as complex formation of the organic bases (humic acid oxyanions) with surface Fe ions. Measurements on adsorptions were made in both fresh water and seawater. Attempts have been made to fit our data to Langmuir adsorption isotherm. Adsorption equilibrium constants were determined.

  15. Modeling adsorption: Investigating adsorbate and adsorbent properties

    NASA Astrophysics Data System (ADS)

    Webster, Charles Edwin

    1999-12-01

    Surface catalyzed reactions play a major role in current chemical production technology. Currently, 90% of all chemicals are produced by heterogeneously catalyzed reactions. Most of these catalyzed reactions involve adsorption, concentrating the substrate(s) (the adsorbate) on the surface of the solid (the adsorbent). Pore volumes, accessible surface areas, and the thermodynamics of adsorption are essential in the understanding of solid surface characteristics fundamental to catalyst and adsorbent screening and selection. Molecular properties such as molecular volumes and projected molecular areas are needed in order to convert moles adsorbed to surface volumes and areas. Generally, these molecular properties have been estimated from bulk properties, but many assumptions are required. As a result, different literature values are employed for these essential molecular properties. Calculated molar volumes and excluded molecular areas are determined and tabulated for a variety of molecules. Molecular dimensions of molecules are important in the understanding of molecular exclusion as well as size and shape selectivity, diffusion, and adsorbent selection. Molecular dimensions can also be used in the determination of the effective catalytic pore size of a catalyst. Adsorption isotherms, on zeolites, (crystalline mineral oxides) and amorphous solids, can be analyzed with the Multiple Equilibrium Analysis (MEA) description of adsorption. The MEA produces equilibrium constants (Ki), capacities (ni), and thermodynamic parameters (enthalpies, ΔHi, and entropies, ΔSi) of adsorption for each process. Pore volumes and accessible surface areas are calculated from the process capacities. Adsorption isotherms can also be predicted for existing and new adsorbate-adsorbent systems with the MEA. The results show that MEA has the potential of becoming a standard characterization method for microporous solids that will lead to an increased understanding of their behavior in gas

  16. Potential Use of Molecular Sieves for the Removal of Ni2+ Metal Ion: Kinetics, Isotherms and Thermodynamic Studies

    NASA Astrophysics Data System (ADS)

    Gaddala, Babu Rao; Monditoka, Krishna Prasad; Challa, Venkata Ramachandra Murthy; Kadimpati, Kishore Kumar

    2016-10-01

    The potential of using molecular sieves as adsorbent for the removal of nickel from aqueous solution was investigated. The isotherms and kinetics of nickel adsorption using 3 Å molecular sieves were evaluated. The results indicated that equilibrium was established in about 5 h. The effect of the pH was examined in the range of 2-6. The maximum removal of nickel obtained is at pH value of 5. The effect of dosage also evaluated to get optimum adsorption of nickel. The maximum adsorption capacity at 25 °C is 18.25 mg/g. The effect of temperature has been carried out at 15, 25, 30, and 40 °C. The data obtained from adsorption isotherms of nickel at different temperatures fit to linear form of Freundlich adsorption equation followed by Langmuir equations. Adsorption kinetic data were modelled using the pseudo-first and pseudo-second-order equation models. The results indicated that the pseudo-second-order model was best described adsorption kinetic data. The thermodynamic parameters such as enthalpy (ΔH°), free energy (ΔG°), and entropy (ΔS°) were calculated. They show that adsorption of nickel onto molecular sieves is an exothermic process. These results show that molecular sieves are a good adsorbent for the removal of nickel from aqueous solutions and could be used as a purifier for water and wastewater.

  17. 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

    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.

  18. Adsorption Processes of Lead Ions on the Mixture Surface of Bentonite and Bottom Sediments.

    PubMed

    Hegedűsová, Alžbeta; Hegedűs, Ondrej; Tóth, Tomáš; Vollmannová, Alena; Andrejiová, Alena; Šlosár, Miroslav; Mezeyová, Ivana; Pernyeszi, Tímea

    2016-12-01

    The adsorption of contaminants plays an important role in the process of their elimination from a polluted environment. This work describes the issue of loading environment with lead Pb(II) and the resulting negative impact it has on plants and living organisms. It also focuses on bentonite as a natural adsorbent and on the adsorption process of Pb(II) ions on the mixture of bentonite and bottom sediment from the water reservoir in Kolíňany (SR). The equilibrium and kinetic experimental data were evaluated using Langmuir isotherm kinetic pseudo-first and pseudo-second-order rate equations the intraparticle and surface diffusion models. Langmuir isotherm model was successfully used to characterize the lead ions adsorption equilibrium on the mixture of bentonite and bottom sediment. The pseudo second-order model, the intraparticle and surface (film) diffusion models could be simultaneously fitted the experimental kinetic data.

  19. Removal of methylene blue from aqueous solution with magnetite loaded multi-wall carbon nanotube: kinetic, isotherm and mechanism analysis.

    PubMed

    Ai, Lunhong; Zhang, Chunying; Liao, Fang; Wang, Yao; Li, Ming; Meng, Lanying; Jiang, Jing

    2011-12-30

    In this study, we have demonstrated the efficient removal of cationic dye, methylene blue (MB), from aqueous solution with the one-pot solvothermal synthesized magnetite-loaded multi-walled carbon nanotubes (M-MWCNTs). The as-prepared M-MWCNTs were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared (FTIR) spectroscopy. The effects of contact time, initial dye concentration, and solution pH on the adsorption of MB onto M-MWCNTs were systematically studied. It was shown that the MB adsorption was pH-dependent. Adsorption kinetics was best described by the pseudo-second-order model. Equilibrium data were well fitted to the Langmuir isotherm model, yielding maximum monolayer adsorption capacity of 48.06 mg g(-1). FTIR analysis suggested that the adsorption mechanism was possibly attributed to the electrostatic attraction and π-π stacking interactions between MWCNTs and MB.

  20. Equilibrium, FTIR, scanning electron microscopy and small wide angle X-ray scattering studies of chromates adsorption on modified bentonite

    NASA Astrophysics Data System (ADS)

    Majdan, Marek; Maryuk, Oksana; Pikus, Stanisław; Olszewska, Elzbieta; Kwiatkowski, Ryszard; Skrzypek, Henryk

    2005-04-01

    The study presents a discussion about the adsorption mechanism of chromate anions on bentonite modified by hexadecyltrimethylammonium bromide (HDTMA-Br). The formation of alkylammonium chromates: HDTMAHCrO 4, (HDTMA) 2Cr 2O 7 and to the lesser extent (HDTMA) 2CrO 4 at the water-bentonite interface is examined based on the Scanning Electron Microscopy and surface tension measurements. The histograms of HDTMA/Cr(VI) molar ratio on the bentonite surface, found from Scanning Electron Microscopy (SEM) measurements, show that for the majority of points of bentonite surface the value of this ratio is in 1-2 range. FTIR spectra of modified bentonite samples show the change from gauche to trans conformation in the surfactant arrangement in the clay interlayer accompanying its concentration increase. In turn Small Wide Angle X-Ray Scattering (SWAXS) patterns evidently suggest incorporation of chromate anions into the interlamellar space of bentonite structure.

  1. Fruit waste adsorbent for ammonia nitrogen removal from synthetic solution: Isotherms and kinetics

    NASA Astrophysics Data System (ADS)

    Zahrim, AY; Lija, Y.; Ricky, L. N. S.; Azreen, I.

    2016-06-01

    In this study, four types of watermelon rind (WR) adsorbents; fresh WR, modified WR with sodium hydroxide (NaOH), potassium hydroxide (KOH) and sulphuric acid (H2SO4) were used as a potential low-cost adsorbent to remove NH3-N from solution. The adsorption data were fitted with the adsorption isotherm and kinetic models to predict the mechanisms and kinetic characteristics of the adsorption process. The equilibrium data agreed well with Langmuir isotherm model with highest correlation (R2=1.00). As for kinetic modelling, the adsorption process follows pseudo-second order for all four types of adsorbents which has R2 value of 1.0 and calculated adsorption capacity, Qe of 1.2148mg/g. The calculated Qe for pseudo-second order has the smallest difference with the experimental Qe and thus suggest that this adsorption process is mainly governed by chemical process involving cations sharing or exchange between WR adsorbent and NH3-N in the solution.

  2. Uptake of gaseous formaldehyde by soil surfaces: a combination of adsorption/desorption equilibrium and chemical reactions

    NASA Astrophysics Data System (ADS)

    Li, Guo; Su, Hang; Li, Xin; Kuhn, Uwe; Meusel, Hannah; Hoffmann, Thorsten; Ammann, Markus; Pöschl, Ulrich; Shao, Min; Cheng, Yafang

    2016-08-01

    Gaseous formaldehyde (HCHO) is an important precursor of OH radicals and a key intermediate molecule in the oxidation of atmospheric volatile organic compounds (VOCs). Budget analyses reveal large discrepancies between modeled and observed HCHO concentrations in the atmosphere. Here, we investigate the interactions of gaseous HCHO with soil surfaces through coated-wall flow tube experiments applying atmospherically relevant HCHO concentrations of ˜ 10 to 40 ppbv. For the determination of uptake coefficients (γ), we provide a Matlab code to account for the diffusion correction under laminar flow conditions. Under dry conditions (relative humidity = 0 %), an initial γ of (1.1 ± 0.05) × 10-4 is determined, which gradually drops to (5.5 ± 0.4) × 10-5 after 8 h experiments. Experiments under wet conditions show a smaller γ that drops faster over time until reaching a plateau. The drop of γ with increasing relative humidity as well as the drop over time can be explained by the adsorption theory in which high surface coverage leads to a reduced uptake rate. The fact that γ stabilizes at a non-zero plateau suggests the involvement of irreversible chemical reactions. Further back-flushing experiments show that two-thirds of the adsorbed HCHO can be re-emitted into the gas phase while the residual is retained by the soil. This partial reversibility confirms that HCHO uptake by soil is a complex process involving both adsorption/desorption and chemical reactions which must be considered in trace gas exchange (emission or deposition) at the atmosphere-soil interface. Our results suggest that soil and soil-derived airborne particles can either act as a source or a sink for HCHO, depending on ambient conditions and HCHO concentrations.

  3. Linear isotherm determination from linear gradient elution experiments.

    PubMed

    Pfister, David; Steinebach, Fabian; Morbidelli, Massimo

    2015-01-02

    A procedure to estimate equilibrium adsorption parameters as a function of the modifier concentration in linear gradient elution chromatography is proposed and its reliability is investigated by comparison with experimental data. Over the past decades, analytical solutions of the so-called equilibrium model under linear gradient elution conditions were derived assuming that proteins and modifier molecules access the same fraction of the pore size distribution of the porous particles. The present approach developed in this work accounts for the size exclusion effect resulting in different exclusions for proteins and modifier. A new analytical solution was derived by applying perturbation theory for differential equations, and the 1st-order approximated solution is presented in this work. Eventually, a turnkey and reliable procedure to efficiently estimate isotherm parameters as a function of modifier concentration from linear gradient elution experiments is proposed.

  4. Evaluation of surface excess isotherms in liquid chromatography.

    PubMed

    Vajda, Péter; Felinger, Attila; Guiochon, Georges

    2013-05-24

    Methods are proposed to calculate surface excess isotherms and to use them to derive adsorption isotherms in liquid chromatography. The consequences of these methods are discussed. The excess isotherm of isopropyl alcohol from its aqueous solutions on a C18 adsorbent was obtained using the minor disturbance method. The slope of the inflection tangent of the excess isotherm provides the position of the plane separating the adsorbed layer and the bulk phase, from which the adsorption isotherm was derived. At low concentrations of isopropyl alcohol, frontal analysis was used to derive the adsorption isotherm on the same adsorbent using an independent method. The isotherm was thus derived from both frontal analysis data and the minor disturbance method. The results obtained are compared. Our results show that the use of the same concentration unit for the calculation and the representation of the data is the only correct way to calculate the excess isotherms in practical applications of liquid chromatography.

  5. Application des modèles de Langmuir et Freundlich aux isothermes d'adsorption des métaux lourds par l'argile purifiée

    NASA Astrophysics Data System (ADS)

    Ayari, F.; Srasra, E.; Trabelsi-Ayadi, M.

    2004-12-01

    Bentonite, which consist essentially of clay minerals belonging to the smectite group, have a wide range of chemical and industrial uses. The structure chemical composition, exchangeable-ion type and small crystal size of smectite are responsible for several properties, including a large chemically active surface area, a high cation-exchange capacity and interlamellar surface having usual hydratation characteristics. A sample collected from Zaghouan (North East Tunisia, North Africa) is studied through some physico-chemical methods. Results from X-ray diffraction, chemical analysis, infrared spectroscopy, thermogravimetric analysis (TGA) and differential thermal analysis (DTA), cation exchange capacities, specific and total surfaces, confirm the general smectite character of the sample. The adsorption capacity of this clay was tested out using three metallic ions (Pb2+, Zn2+, Ni2+). The results showed that, in all cases, adsorption can be illustrated by Freundlich or Langmuir isotherms. However, for 10-3M Pb2+ the low value of the correlation coefficient (R2) indicated that the experimental data for the adsorption didn't fit to any linear form of the Langmuir equation. Metal adsorbed onto Zaghouan clay varied in the decreasing order PbPb2+ > Zn2+ > Ni2+ and fitted in satisfactorily with the uptake capacity. For Pb2+ the amount of adsorbed ions remained higher than the CEC (cation exchange capacity) of the clay fraction. This result may be due to adsorption of hydroxy lead complex in addition to sorption of bivalent lead form which explains the high amount of Pb2+ removed from aqueous solution.

  6. Ammonium Removal from Aqueous Solutions by Clinoptilolite: Determination of Isotherm and Thermodynamic Parameters and Comparison of Kinetics by the Double Exponential Model and Conventional Kinetic Models

    PubMed Central

    Tosun, İsmail

    2012-01-01

    The adsorption isotherm, the adsorption kinetics, and the thermodynamic parameters of ammonium removal from aqueous solution by using clinoptilolite in aqueous solution was investigated in this study. Experimental data obtained from batch equilibrium tests have been analyzed by four two-parameter (Freundlich, Langmuir, Tempkin and Dubinin-Radushkevich (D-R)) and four three-parameter (Redlich-Peterson (R-P), Sips, Toth and Khan) isotherm models. D-R and R-P isotherms were the models that best fitted to experimental data over the other two- and three-parameter models applied. The adsorption energy (E) from the D-R isotherm was found to be approximately 7 kJ/mol for the ammonium-clinoptilolite system, thereby indicating that ammonium is adsorbed on clinoptilolite by physisorption. Kinetic parameters were determined by analyzing the nth-order kinetic model, the modified second-order model and the double exponential model, and each model resulted in a coefficient of determination (R2) of above 0.989 with an average relative error lower than 5%. A Double Exponential Model (DEM) showed that the adsorption process develops in two stages as rapid and slow phase. Changes in standard free energy (∆G°), enthalpy (∆H°) and entropy (∆S°) of ammonium-clinoptilolite system were estimated by using the thermodynamic equilibrium coefficients. PMID:22690177

  7. Ammonium removal from aqueous solutions by clinoptilolite: determination of isotherm and thermodynamic parameters and comparison of kinetics by the double exponential model and conventional kinetic models.

    PubMed

    Tosun, Ismail

    2012-03-01

    The adsorption isotherm, the adsorption kinetics, and the thermodynamic parameters of ammonium removal from aqueous solution by using clinoptilolite in aqueous solution was investigated in this study. Experimental data obtained from batch equilibrium tests have been analyzed by four two-parameter (Freundlich, Langmuir, Tempkin and Dubinin-Radushkevich (D-R)) and four three-parameter (Redlich-Peterson (R-P), Sips, Toth and Khan) isotherm models. D-R and R-P isotherms were the models that best fitted to experimental data over the other two- and three-parameter models applied. The adsorption energy (E) from the D-R isotherm was found to be approximately 7 kJ/mol for the ammonium-clinoptilolite system, thereby indicating that ammonium is adsorbed on clinoptilolite by physisorption. Kinetic parameters were determined by analyzing the nth-order kinetic model, the modified second-order model and the double exponential model, and each model resulted in a coefficient of determination (R(2)) of above 0.989 with an average relative error lower than 5%. A Double Exponential Model (DEM) showed that the adsorption process develops in two stages as rapid and slow phase. Changes in standard free energy (∆G°), enthalpy (∆H°) and entropy (∆S°) of ammonium-clinoptilolite system were estimated by using the thermodynamic equilibrium coefficients.

  8. Removal of Pb(II) by adsorption onto Chinese walnut shell activated carbon.

    PubMed

    Yi, Zheng-ji; Yao, Jun; Kuang, Yun-fei; Chen, Hui-lun; Wang, Fei; Yuan, Zhi-min

    2015-01-01

    The excessive discharge of Pb(II) into the environment has increasingly aroused great concern. Adsorption is considered as the most effective method for heavy metal removal. Chinese walnut shell activated carbon (CWSAC) was used as an adsorbent for the removal of Pb(II) from aqueous solution. Batch experiments were conducted by varying contact time, temperature, pH, adsorbent dose and initial Pb(II) concentration. Adsorption equilibrium was established within 150 min. Although temperature effect was insignificant, the Pb(II) adsorption was strongly pH dependent and the maximum removal was observed at pH 5.5. The Pb(II) removal efficiency increased with increasing CWSAC dosage up to 2.0 g/L and reached a maximum of 94.12%. Langmuir and Freundlich adsorption isotherms were employed to fit the adsorption data. The results suggested that the equilibrium data could be well described by the Langmuir isotherm model, with a maximum adsorption capacity of 81.96 mg/g. Adsorption kinetics data were fitted by pseudo-first- and pseudo-second-order models. The result indicated that the pseudo-first-order model best describes the adsorption kinetic data. In summary, CWSAC could be a promising material for the removal of Pb(II) from wastewater.

  9. Adsorptive property of Cu2+-ZnO/cetylpyridinium-montmorillonite complexes for pathogenic bacterium in vitro.

    PubMed

    Ma, Yu-Long; Yang, Bo; Xie, Li

    2010-09-01

    Cu(2+)-ZnO/cetylpyridinium-montmorillonite (Cu(2+)-ZnO/CP-MMT) complexes were prepared using montmorillonite (MMT), Cu(2+), Zn(2+), and cetylpyridinium (CP). The goal was to assess comparatively the adsorption properties of Cu(2+)-ZnO/CP-MMT in vitro using pathogenic Escherichia coli. The results showed that Cu(2+)-ZnO/CP-MMT adsorbed significantly (P<0.05) more E. coli compared with the parent clay. The adsorption process of bacterial cells occurring on the modified MMT surface reached equilibrium after 90 min. The percentages of E. coli adsorbed onto the surfaces of Cu(2+)-ZnO/CP-MMT and MMT in adsorption equilibrium were 84.66% and 47.01%, respectively. Adsorption data from the bacteria-clay systems followed the Langmuir and Freundlich isotherms, but not the BET isotherm. Adsorption of E. coli in acidic medium was higher than in alkaline medium. The extent of bacteria adsorption onto the modified MMT increased with decreasing ionic strength, and with increasing temperature. The processes of E. coli adsorption onto the tested adsorbents were endothermic and spontaneous at the experimental temperature. The mechanism of adsorption of bacteria on Cu(2+)-ZnO/CP-MMT may involve enhanced hydrophobicity and the reversal of surface charge from negative to positive.

  10. Adsorption characteristics of brilliant green dye on kaolin.

    PubMed

    Nandi, B K; Goswami, A; Purkait, M K

    2009-01-15

    Experimental investigations were carried out to adsorb toxic brilliant green dye from aqueous medium using kaolin as an adsorbent. Characterization of kaolin is done by measuring: (i) particle size distribution using particle size analyzer, (ii) BET surface area using BET surface analyzer, and (iii) structural analysis using X-ray diffractometer. The effects of initial dye concentration, contact time, kaolin dose, stirring speed, pH and temperature were studied for the adsorption of brilliant green in batch mode. Adsorption experiments indicate that the extent of adsorption is strongly dependent on pH of solution. Free energy of adsorption (DeltaG0), enthalpy (DeltaH0) and entropy (DeltaS0) changes are calculated to know the nature of adsorption. The calculated values of DeltaG0 at 299K and 323K indicate that the adsorption process is spontaneous. The estimated values of DeltaH0 and DeltaS0 both show the negative sign, which indicate that the adsorption process is exothermic and the dye molecules are organized on the kaolin surface in less randomly fashion than in solution. The adsorption kinetic has been described by first-order, pseudo-second-order and intra-particle-diffusion models. It was observed that the rate of dye adsorption follows pseudo-second-order model for the dye concentration range studied in the present case. Standard adsorption isotherms were used to fit the experimental equilibrium data. It was found that the adsorption of brilliant green on kaolin follows the Langmuir adsorption isotherm.

  11. Batch studies of adsorption of copper and lead on activated carbon from Eucalyptus camaldulensis dehn. bark.

    PubMed

    Patnukao, Phussadee; Kongsuwan, Apipreeya; Pavasant, Prasert

    2008-01-01

    Powdered activated carbon (PAC) prepared from Eucalyptus camaldulensis Dehn. bark was tested for its adsorption capacity for Cu(II) and Pb(II). The experiment was conducted to investigate the effects of pH, contact time, initial metal concentration, and temperature. The best adsorption of both Cu(II) and Pb(II) occurred at pH 5, where the adsorption reached equilibrium within 45 min for the whole range of initial heavy metal concentrations (0.1-10 mmol/L). The adsorption kinetics was found to follow the pseudo-second order model where equilibrium adsorption capacities and adsorption rate constants increased with initial heavy metal concentrations. The adsorption isotherm followed Langmuir better than Freundlich models within the temperature range (25-60 degrees C). The maximum adsorption capacities (qm) occurred at 60 degrees C, where qm for Cu(II) and Pb(II) were 0.85 and 0.89 mmol/g, respectively. The enthalpies of Cu(II) and Pb(II) adsorption were 43.26 and 58.77 kJ/mol, respectively. The positive enthalpy of adsorption indicated an endothermic nature of the adsorption.

  12. A solvable model for localized adsorption in a Coulomb system

    SciTech Connect

    Rosinberg, M.L.; Blum, L.; Lebowitz, J.L.

    1986-07-01

    A model for an interface with localized adsorption is presented, in which the surface has a distribution of sticky adhesive sites in contact with a Coulomb fluid. Contrary to the current literature on the electrical double layer the surface charge is in dynamic equilibrium with the bulk fluid. The sum rules obeyed by the one- and two-body correlation functions are investigated. Explicit results are obtained for a solvable model, the two-dimensional one-component plasma at reduced temperature 2. The effect of the granularity of the adsorbed charge on the adsorption isotherm is discussed.

  13. Optimization of simultaneous ultrasound assisted toxic dyes adsorption conditions from single and multi-components using central composite design: Application of derivative spectrophotometry and evaluation of the kinetics and isotherms.

    PubMed

    Sharifpour, Ebrahim; Haddadi, Hedayat; Ghaedi, Mehrorang

    2017-05-01

    Present study is devoted on the efficient application of Sn (O, S)-NPs -AC for simultaneous sonicated accelerated adsorption of some dyes from single and multi-components systems. Sn (O, S) nanoparticles characterization by FESEM, EDX, EDX mapping and XRD revel its nano size structure with high purity of good crystallinity. Present adsorbent due to its nano spherical shape part