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Sample records for adsorption isotherms modeling

  1. Modeling of Experimental Adsorption Isotherm Data

    Directory of Open Access Journals (Sweden)

    Xunjun Chen

    2015-01-01

    Full Text Available Adsorption is considered to be one of the most effective technologies widely used in global environmental protection areas. Modeling of experimental adsorption isotherm data is an essential way for predicting the mechanisms of adsorption, which will lead to an improvement in the area of adsorption science. In this paper, we employed three isotherm models, namely: Langmuir, Freundlich, and Dubinin-Radushkevich to correlate four sets of experimental adsorption isotherm data, which were obtained by batch tests in lab. The linearized and non-linearized isotherm models were compared and discussed. In order to determine the best fit isotherm model, the correlation coefficient (r2 and standard errors (S.E. for each parameter were used to evaluate the data. The modeling results showed that non-linear Langmuir model could fit the data better than others, with relatively higher r2 values and smaller S.E. The linear Langmuir model had the highest value of r2, however, the maximum adsorption capacities estimated from linear Langmuir model were deviated from the experimental data.

  2. A New Competitive Adsorption Isothermal Model of Heavy Metals in Soils

    Institute of Scientific and Technical Information of China (English)

    XUE Wen-Bo; YI Ai-Hua; ZHANG Zeng-Qiang; TANG Ci-Lai; ZHANG Xing-Chang; GAO Jin-Ming

    2009-01-01

    A new competitive adsorption isothermal model (CAIM) was developed for the coexistent and competitive binding of heavy metals to the soil surface.This model extended the earlier adsorption isothermal models by considering more than one kind of ion adsorption on the soil surface.It was compared with the Langmuir model using different conditions,and it was found that CAIM,which was suitable for competitive ion adsorption at the soil solid-liquid surface,had more advantages than the Langmuir model.The new competitive adsorption isothermal model was used to fit the data of heavy metal (Zn and Cd) competitive adsorption by a yellow soil at two temperatures.The results showed that CAIM was appropriate for the competitive adsorption of heavy metals on the soil surface at different temperatures.The fitted parameters of CAIM had explicit physical meaning.The model allowed for the calculation of the standard molar Gibbs free energy change,the standard molar enthalpy change,and the standard molar entropy change of the competitive adsorption of the heavy metals,Zn and Cd,by the yellow soil at two temperatures using the thermodynamic equilibrium constants.

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

    Science.gov (United States)

    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.

  4. Equilibrium isotherm and kinetics modeling of U(VI) adsorption by natural soil systems

    International Nuclear Information System (INIS)

    This research examined the adsorption capability of natural soils of different origin for U(VI) at soil-water interface and the mechanism involved. Adsorption kinetics study indicates that adsorption followed the pseudo-second order kinetics irrespective of soil types and was not solely controlled by the diffusion step rather surface complexation and ion-exchange plays major role. Study of adsorption isotherms indicates adsorption involves chemisorption and soil with high Fe and Mn content better fit to Langmuir model. The study provides a better insight for site selection for radioactive waste (uranium) disposal facilities as well as soil suitable for back fill or permeable reactive barrier to inhibit migration of U(VI). (author)

  5. Incorporating classic adsorption isotherms into modern surface complexation models: implications for sorption of radionuclides

    International Nuclear Information System (INIS)

    Full text of publication follows: Computer-aided surface complexation models (SCM) tend to replace the classic adsorption isotherm (AI) analysis in describing mineral-water interface reactions such as radionuclide sorption onto (hydr) oxides and clays. Any site-binding SCM based on the mole balance of surface sites, in fact, reproduces the (competitive) Langmuir isotherm, optionally amended with electrostatic Coulomb's non-ideal term. In most SCM implementations, it is difficult to incorporate real-surface phenomena (site heterogeneity, lateral interactions, surface condensation) described in classic AI approaches other than Langmuir's. Thermodynamic relations between SCMs and AIs that remained obscure in the past have been recently clarified using new definitions of standard and reference states of surface species [1,2]. On this basis, a method for separating the Langmuir AI into ideal (linear) and non-ideal parts [2] was applied to multi-dentate Langmuir, Frumkin, and BET isotherms. The aim of this work was to obtain the surface activity coefficient terms that make the SCM site mole balance constraints obsolete and, in this way, extend thermodynamic SCMs to cover sorption phenomena described by the respective AIs. The multi-dentate Langmuir term accounts for the site saturation with n-dentate surface species, as illustrated on modeling bi-dentate UVI complexes on goethite or SiO2 surfaces. The Frumkin term corrects for the lateral interactions of the mono-dentate surface species; in particular, it has the same form as the Coulombic term of the constant-capacitance EDL combined with the Langmuir term. The BET term (three parameters) accounts for more than a monolayer adsorption up to the surface condensation; it can potentially describe the surface precipitation of nickel and other cations on hydroxides and clay minerals. All three non-ideal terms (in GEM SCMs implementation [1,2]) by now are used for non-competing surface species only. Upon 'surface dilution

  6. How soil organic matter composition controls hexachlorobenzene–soil-interactions: Adsorption isotherms and quantum chemical modeling

    Energy Technology Data Exchange (ETDEWEB)

    Ahmed, Ashour A., E-mail: ashour.ahmed@uni-rostock.de [University of Rostock, Institute of Physics, D-18051 Rostock (Germany); University of Cairo, Faculty of Science, Department of Chemistry, 12613 Giza (Egypt); University of Rostock, Interdisciplinary Faculty, Department of Life, Light and Matter, D-18051 Rostock (Germany); Kühn, Oliver, E-mail: oliver.kuehn@uni-rostock.de [University of Rostock, Institute of Physics, D-18051 Rostock (Germany); University of Rostock, Interdisciplinary Faculty, Department of Life, Light and Matter, D-18051 Rostock (Germany); Aziz, Saadullah G., E-mail: saziz@kau.edu.sa [King Abdulaziz University, Faculty of Science, Chemistry Department, Jeddah 21589 (Saudi Arabia); Hilal, Rifaat H., E-mail: rhilal@kau.edu.sa [University of Cairo, Faculty of Science, Department of Chemistry, 12613 Giza (Egypt); King Abdulaziz University, Faculty of Science, Chemistry Department, Jeddah 21589 (Saudi Arabia); Leinweber, Peter, E-mail: peter.leinweber@uni-rostock.de [University of Rostock, Soil Science, D-18051 Rostock (Germany); University of Rostock, Interdisciplinary Faculty, Department of Life, Light and Matter, D-18051 Rostock (Germany)

    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 soil < original soil < soil + 3 HWE < soil + 6 HWE. For the latter three samples this order was also valid for the HCB adsorption. 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. - Highlights: • Conduction of adsorption experiment of different soil samples on HCB. • Development of a new SOM model for the study of the HCB

  7. How soil organic matter composition controls hexachlorobenzene–soil-interactions: Adsorption isotherms and quantum chemical modeling

    International Nuclear Information System (INIS)

    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 soil < original soil < soil + 3 HWE < soil + 6 HWE. For the latter three samples this order was also valid for the HCB adsorption. 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. - Highlights: • Conduction of adsorption experiment of different soil samples on HCB. • Development of a new SOM model for the study of the HCB

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

    Science.gov (United States)

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

    1998-01-01

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

  9. Adsorption Isotherms and Surface Reaction Kinetics

    Science.gov (United States)

    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)

  10. Modified Isothermal Adsorption Model of Shale Gas%修正的页岩气等温吸附模型

    Institute of Scientific and Technical Information of China (English)

    张跃磊; 李大华; 王青华; 郭东鑫

    2016-01-01

    When using Langmuir model and modified double Langmuir model on heterogeneity medium shale isotherm ad-sorption,the experimental data fitting accuracy and stability is not high. We launched a study on new isotherm adsorption equation. The study transforms the adsorption characteristics of different adsorption media within the adsorption system into the actual effect of system pressure,and corrects the pressure for double Langmuir model,getting a new P-Langmuir isotherm adsorption model,which is suitable for multi-adsorption-media system. The model is applied to fitting adsorption isotherm experimental data of 21 samples of Yuye 1 shale gas well in the Southeast of Chongqing and the result shows that average errors of Langmuir model are between-0.012 8 m3/t and 0.021 2 m3/t,D-Langmuir model between-0.003 64 m3/t and 0.021 2 m3/t, and all the values of the correlation coefficient R2 of the P-Langmuir model are between 0.992 5 and 0.999 8,and that average errors of 21 samples are between-0.003 25 m3/t and 0.003 21 m3/t. Compared to the Langmuir equation and double Lang-muir equation,P-Langmuir model is of higher fitting accuracy and better stability,has some practical significance for more accurately evaluating shale gas adsorption.%针对Langmuir等温吸附方程及修正的双朗格缪尔模型(D-Langmuir)在研究非均质吸附介质页岩等温吸附时,对实验数据拟合精度及稳定性不高的问题,展开了新的等温吸附方程研究,研究中将吸附系统内不同吸附介质的吸附特征转化为系统内压力的实际作用效果,对D-Langmuir模型进行压力修正,得到新的、适用于多吸附介质的P-Langmuir等温吸附模型。将以上模型应用于渝东南渝页1井共21个样品的等温吸附实验数据的拟合,结果表明:Langmuir模型平均误差在-0.0120∼80.0212 m3/t;D-Langmuir模型平均误差在-0.00364∼0.02120 m3/t;P-Langmuir等温吸附模型相关系数的平方0.9925≤R2≤0.9998

  11. Improved Isotherm Data for Adsorption of Methane on Activated Carbons

    KAUST Repository

    Loh, Wai Soong

    2010-08-12

    This article presents the adsorption isotherms of methane onto two different types of activated carbons, namely, Maxsorb III and ACF (A-20) at temperatures from (5 to 75) °C and pressures up to 2.5 MPa. The volumetric technique has been employed to measure the adsorption isotherms. The experimental results presented herein demonstrate the improved accuracy of the uptake values compared with previous measurement techniques for similar adsorbate-adsorbent combinations. The results are analyzed with various adsorption isotherm models. The heat of adsorption, which is concentration and temperature dependent, has been calculated from the measured isotherm data. Henry\\'s law coefficients for these adsorbent-methane pairs are also evaluated at various temperatures. © 2010 American Chemical Society.

  12. Adsorption isotherms of water on mica: redistribution and film growth.

    Science.gov (United States)

    Malani, Ateeque; Ayappa, K G

    2009-01-29

    Adsorption isotherms of water on muscovite mica are obtained using grand canonical Monte Carlo simulations over a wide range of relative vapor pressures, p/p(0) at 298 K. Three distinct stages are observed in the adsorption isotherm. A sharp rise in the water coverage occurs for 0 Clays Clay Miner. 2006 , 54 , 402 ), over the entire range of pressures investigated. Both SPC and extended simple point charge (SPC/E) water models were found to yield qualitatively similar adsorption and structural characteristics, with the SPC/E model predicting lower coverages than the SPC model for p/p(0) > 0.7. PMID:19123830

  13. How Soil Organic Matter Composition Controls Hexachlorobenzene-Soil-Interactions: Adsorption Isotherms and Quantum Chemical Modelling

    CERN Document Server

    Ahmed, Ashour; Kühn, Oliver

    2013-01-01

    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 soil < original soil < soil+3 HWE < soil+6 HWE. For the latter three samples this order was also valid for the HCB adsorption. 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 behaviour 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 HC...

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

    Science.gov (United States)

    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...

  15. How Soil Organic Matter Composition Controls Hexachlorobenzene-Soil-Interactions: Adsorption Isotherms and Quantum Chemical Modelling

    OpenAIRE

    Ahmed, Ashour; Leinweber, Peter; Kühn, Oliver

    2013-01-01

    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 soil < o...

  16. Modeling of iron adsorption on HTTA-loaded polyurethane foam using Freundlich, Langmuir and D-R isotherm expressions

    International Nuclear Information System (INIS)

    The sorption of Fe (III) at low pH range from 1 to 4.5 on open cell polyether type HTTA-loaded polyurethane foam has been carried out using batch technique. The optimum shaking time for 2.5 * 10-4M solution of Fe(III) was found to be 30 minutes. The concept of macropore and micropore nature of polyurethane foam sorbent offers unique advantages of adsorption. Freundlich and Langmuir adsorption isotherms are followed at low concentration range from 1 * 10-4 to 3 * 10 -4M solution of Fe(III). The Freundlich constant (1/n = 0.46 ± 0.013 and K = 9.16 ± 1.39 mg * g-1) and Langmuir isotherm constants (M = 21.78 mg * g-1 and b = 88.41 ± 9.731 * g-1) were established. The sorption mean free energy E = 12.22 ± 0.09 kJ * mol-1 and loading capacity Cm = 145.21 ± 6.1 mg * g-1 were evaluated using Dubinin-Radushkevich isotherm, which suggested that the adsorption mechanism was chemisorption. (author)

  17. The Calculation of Adsorption Isotherms from Chromatographic Peak Shapes

    Science.gov (United States)

    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)

  18. Adsorption isotherm special study. Final report

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    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.

  19. Adsorption isotherm special study. Final report

    International Nuclear Information System (INIS)

    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

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

    Science.gov (United States)

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

    2008-01-01

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

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

    Institute of Scientific and Technical Information of China (English)

    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 carded 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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Stanley, B.J.; Guiochon, G. [Tennessee Univ., Knoxville, TN (United States). Dept. of Chemistry]|[Oak Ridge National Lab., TN (United States)

    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.

  3. Estimating Uranium Partition Coefficients from Laboratory Adsorption Isotherms

    International Nuclear Information System (INIS)

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

  4. Determination of Differential Enthalpy and Isotherm by Adsorption Calorimetry

    Directory of Open Access Journals (Sweden)

    V. Garcia-Cuello

    2008-01-01

    Full Text Available An adsorption microcalorimeter for the simultaneous determination of the differential heat of adsorption and the adsorption isotherm for gas-solid systems are designed, built, and tested. For this purpose, a Calvet heat-conducting microcalorimeter is developed and is connected to a gas volumetric unit built in stainless steel to record adsorption isotherms. The microcalorimeter is electrically calibrated to establish its sensitivity and reproducibility, obtaining K=154.34±0.23 WV−1. The adsorption microcalorimeter is used to obtain adsorption isotherms and the corresponding differential heats for the adsorption of CO2 on a reference solid, such as a NaZSM-5 type zeolite. Results for the behavior of this system are compared with those obtained with commercial equipment and with other studies in the literature.

  5. Adsorption isotherm of uranyl ions by fish scales of corvina

    International Nuclear Information System (INIS)

    Fish scale is by-product of fishery. The scales are mainly formed by hydroxyapatite and collagen forming a kind of natural composite with a large specific surface area that intensifies the adsorption process. In this paper the potential of adsorption of scales of Corvina fish for uranyl ions from nitric solutions was studied. The scales were washed several times with faucet water, sun-dried, triturated and sieved. Equilibrium and kinetic studies in adsorption of uranyl ions in batch systems were carried out at room temperature. Equilibrium time was reached at 5 min for 0.1 g L-1 uranyl solution with removal efficiency over 82%, and at 1 min of contact was observed about 60% of removal. The equilibrium isotherm was obtained and the Langmuir model fitted best. These preliminary results are very promising, showing great perspectives of application of the fish scales as biosorbent for uranyl ions in radioactive wastewater treatment processes with a sustainable technology. (author)

  6. Adsorption isotherm of uranyl ions by fish scales of corvina

    Energy Technology Data Exchange (ETDEWEB)

    Costa, Caroline Hastenreiter; Santos, Bruno Zolotareff dos; Yamamura, Amanda Pongeluppe Gualberto; Yamaura, Mitiko, E-mail: hc.caroline@gmail.co, E-mail: bzsantos@gmail.co, E-mail: amandaifusp@yahoo.com.b, E-mail: myamaura@ipen.b [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2009-07-01

    Fish scale is by-product of fishery. The scales are mainly formed by hydroxyapatite and collagen forming a kind of natural composite with a large specific surface area that intensifies the adsorption process. In this paper the potential of adsorption of scales of Corvina fish for uranyl ions from nitric solutions was studied. The scales were washed several times with faucet water, sun-dried, triturated and sieved. Equilibrium and kinetic studies in adsorption of uranyl ions in batch systems were carried out at room temperature. Equilibrium time was reached at 5 min for 0.1 g L{sup -1} uranyl solution with removal efficiency over 82%, and at 1 min of contact was observed about 60% of removal. The equilibrium isotherm was obtained and the Langmuir model fitted best. These preliminary results are very promising, showing great perspectives of application of the fish scales as biosorbent for uranyl ions in radioactive wastewater treatment processes with a sustainable technology. (author)

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

    Science.gov (United States)

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

    2015-11-01

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

  8. Adsorption of Reactive Black 5 on Synthesized Titanium Dioxide Nanoparticles: Equilibrium Isotherm and Kinetic Studies

    OpenAIRE

    Majeed A. Shaheed; Falah H. Hussein

    2014-01-01

    The synthesized titanium dioxide nanoparticles (TiO2-NPs) were used as adsorbent to remove reactive black 5 (RB 5) in aqueous solution. Various factors affecting adsorption of RB 5 aqueous solutions such as pH, initial concentration, contact time, dose of nanoparticles, and temperature were analyzed at fixed solid/solution ratio. Langmuir and Freundlich isotherms were used as model adsorption equilibrium data. Langmuir isotherm was found to be the most adequate model. The pseudo-first-order, ...

  9. Derivation of the Freundlich Adsorption Isotherm from Kinetics

    Science.gov (United States)

    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. Isothermal Gaseous Detonation Model

    Science.gov (United States)

    Prokhorov, E. S.

    2015-05-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

    Medve, J.; Tjerneld, F. [Univ. of Lund (Sweden); Stahlberg, J. [Univ. of Uppsala (Sweden)

    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.

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

    Science.gov (United States)

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

    2015-11-01

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

  13. Calculation of Thermodynamic Parameters for Freundlich and Temkin Isotherm Models

    Institute of Scientific and Technical Information of China (English)

    ZHANGZENGQIANG; ZHANGYIPING; 等

    1999-01-01

    Derivation of the Freundlich and Temkin isotherm models from the kinetic adsorption/desorption equations was carried out to calculate their thermodynamic equilibrium constants.The calculation formulase of three thermodynamic parameters,the standard molar Gibbs free energy change,the standard molar enthalpy change and the standard molar entropy change,of isothermal adsorption processes for Freundlich and Temkin isotherm models were deduced according to the relationship between the thermodynamic equilibrium constants and the temperature.

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

    Institute of Scientific and Technical Information of China (English)

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

    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 Langrnuir isotherm revealed that the equilibrium constant derived from the Langmuir kinetic model,Ks-kinetic,is theoretically equivalent to the adsorption constant in Langrnuir 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 pH 3.2 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-Langrnuir were obtained.The values of Ks-kinetic and Ks-Langrnuir 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.

  15. Comparative Study of Adsorption Isotherms of Vitamin C on Multi wall and single wall Carbon Nanotube

    Directory of Open Access Journals (Sweden)

    Azin Dehmolaei

    2014-03-01

    Full Text Available We have studied the interaction of Vitamin C solution on multi-wall and single-wall carbon nanotubeAfter investigated comparative study and assigned to Vitamin C adsorption isotherm. The adsorption equilibrium isotherms were fitted by Freundlich, Langmuir, and Temkin models. It was found that the Langmuirmodel described the adsorption process better than other two isotherm models. The amount of Antioxidant drug(Vitamin C adsorbed on Multi wallcarbon nanotube surface increased with the increase of the initial Antioxidant concentration. Based on the results, under similar conditions the efficiency of adsorption of Vitamin C by Multi-wall carbon nanotube(MWCNTs was more thansingle-wall carbon nanotube.

  16. WATER ADSORPTION AND DESORPTION ISOTHERMS ON MILK POWDER: II. WHOLE MILK

    Directory of Open Access Journals (Sweden)

    Edgar M. Soteras

    2014-03-01

    Full Text Available The aim of this research was the determination of adsorption and desorption isotherms of cow whole milk powder. The experiments have been carried out at 15, 25 and 40 ºC, in ranges of moisture and water activity characteristic of normal conditions in which the processes of drying, packaging and storage are developed. By studying the influence of the temperature on the experimental plots, the isosteric adsorption heat was determined. Experimental data were correlated to the referential model of Guggenheim, Anderson and Boer (GAB. For both, adsorption and desorption, a good model fit was observed. The isotherms showed very similar shapes between them and, by comparing adsorption and desorption isotherms, the phenomenon of hysteresis was confirmed.

  17. 8-Hydroxyqunoline adsorption from aqueous solution using powdered orange peel: kinetic and isotherm study

    Directory of Open Access Journals (Sweden)

    Siraj Khalid

    2015-12-01

    Full Text Available Adsorption of 8-hydroxyquinoline (8HQ on powdered orange peel (POP, a locally available adsorbent, has been studied. Experiment was performed on different 8HQ concentration, particle size, and adsorbent dosage. The Langmuir and Freundlich adsorption isotherm model has been tested. The obtained results best fitted the Langmuir model, suggesting monolayer adsorption of 8HQ on POP. The kinetic studies for the adsorption process were also carried out using pseudo-first- and pseudo-second-order models, and the data obtained is best fitted to the pseudo-second-order kinetic model. Thermodynamic parameters were calculated for the adsorption process and the result showed that the values of ΔGads, ΔHads, and ΔSads are −1171.4J/mol, −140J/mol and −40.5 J/K at 303 K. Thus, it can be summarized that the adsorption of 8HQ is spontaneous, chemisorbed, monolayer, and exothermic

  18. Adsorption of Reactive Black 5 on Synthesized Titanium Dioxide Nanoparticles: Equilibrium Isotherm and Kinetic Studies

    Directory of Open Access Journals (Sweden)

    Majeed A. Shaheed

    2014-01-01

    Full Text Available The synthesized titanium dioxide nanoparticles (TiO2-NPs were used as adsorbent to remove reactive black 5 (RB 5 in aqueous solution. Various factors affecting adsorption of RB 5 aqueous solutions such as pH, initial concentration, contact time, dose of nanoparticles, and temperature were analyzed at fixed solid/solution ratio. Langmuir and Freundlich isotherms were used as model adsorption equilibrium data. Langmuir isotherm was found to be the most adequate model. The pseudo-first-order, pseudo-second-order, and intraparticle diffusion models were used to describe the adsorption kinetics. The experimental data was fitted to pseudo-second-order kinetics. The thermodynamic parameters such as Gibbs-free energy, enthalpy, and entropy changes were determined. These parameters indicated the endothermic and spontaneity nature of the adsorption. The results demonstrated the fact that the TiO2-NPs are promising adsorbent for the removal of RB 5 from aqueous solutions.

  19. Adsorption Isotherms of CH 4 on Activated Carbon from Indonesian Low Grade Coal

    KAUST Repository

    Martin, Awaludin

    2011-03-10

    This article presents an experimental approach for the determination of the adsorption isotherms of methane on activated carbon that is essential for methane storage purposes. The experiments incorporated a constant-volume- variable-pressure (CVVP) apparatus, and two types of activated carbon have been investigated, namely, activated carbon derived from the low rank coal of the East of Kalimantan, Indonesia, and a Carbotech activated carbon. The isotherm results which cover temperatures from (300 to 318) K and pressures up to 3.5 MPa are analyzed using the Langmuir, Tóth, and Dubinin-Astakhov (D-A) isotherm models. The heat of adsorption for the single component methane-activated carbon system, which is concentration- and temperature-dependent, is determined from the measured isotherm data. © 2011 American Chemical Society.

  20. FTIR spectrophotometry, kinetics and adsorption isotherms modeling, ion exchange, and EDX analysis for understanding the mechanism of Cd2+ and Pb2+ removal by mango peel waste

    International Nuclear Information System (INIS)

    Mango peel waste (MPW) was evaluated as a new sorbent for the removal of Cd2+ and Pb2+ from aqueous solution. The maximum sorption capacity of Cd2+ and Pb2+ was found to be 68.92 and 99.05 mg g-1, respectively. The kinetics of sorption of both metals was fast, reaching at equilibrium in 60 min. 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 Cd2+ and Pb2+. Chemical modification of MPW for blocking of carboxyl and hydroxyl groups showed that 72.46% and 76.26% removal of Cd2+ and Pb2+, 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 (Ca2+, Mg2+, Na+, K+) and proton H+ from MPW with the corresponding uptake of Cd2+ and Pb2+ 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 Cd2+ and Pb2+ from aqueous solution

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

    Science.gov (United States)

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

    2016-07-01

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

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

    Science.gov (United States)

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

    2016-02-01

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

  3. Adsorption isotherms of hog plum (Spondias mombin L. pulp powder obtained by spray dryer

    Directory of Open Access Journals (Sweden)

    Luís Gomes de Moura Neto

    2015-05-01

    Full Text Available Food sorption isotherms are highly important to predict drying time and storage conditions of a product. Current assay evaluates the behavior of adsorption isotherms of hog plum powder obtained by spray-dryer, through mathematical models. GAB, BET, Henderson and Oswin models were adjusted to the experimental data at 25, 30, 35 and 40ºC. The BET model best adjusted to the atomized hog plum for all temperatures tested, with an error ranging between 8.45 and 11.17%. The coefficient of determination (R2 had rates higher than 0.9900 for all the adjusted models. The behavior of hog plum powder adsorption isotherms was classified as Type III.

  4. Phosphorus isothermal adsorption characteristics of mulch of bioretention

    Directory of Open Access Journals (Sweden)

    Mei Ying

    2012-01-01

    Full Text Available This study aims to identify mulch of bioretention which has high phosphorus sorption capacity. The phosphorus adsorption characteristics of five types of mulch of bioretention are studied by three isothermal adsorption experiments. Results show that the Langmuir eqution is suitable for describing absorption characteristics of five types of mulch. The positive values of Gibbs free energy for phosphorus indicate that the phosphorus biosorption by five mulches is a non-spontaneous process, and the values of mean sorption free energy of mulch are less than 8 kJ/mol, which proves that the adsorption process can be dominated by physical forces. The vermiculite is the better mulch of bioretention based on high phosphorus removal capacity.

  5. A Poromechanical Model for Coal Seams Injected with Carbon Dioxide: From an Isotherm of Adsorption to a Swelling of the Reservoir Un modéle poromécanique pour l’injection de dioxyde de carbone dans des veines de charbon : d’une isotherme d’adsorption à un gonflement du réservoir

    Directory of Open Access Journals (Sweden)

    Nikoosokhan S.

    2012-11-01

    Full Text Available Injecting carbon dioxide into deep unminable coal seams can enhance the amount of methane recovered from the seam. This process is known as CO2-Enhanced Coal Bed Methane production (CO2-ECBM. The seam is a porous medium whose porous system is made of cleats (small natural fractures and of coal pores (whose radius can be as small as a few angström. During the injection process, the molecules of CO2 get adsorbed in the coal pores. Such an adsorption makes the coal swell, which, in the confined conditions that prevail underground, induces a closure of the cleat system of the coal bed reservoir and a loss of injectivity. In this work, we develop a poromechanical model which, starting from the knowledge of an adsorption isotherm and combined with reservoir simulations, enables to estimate the variations of injectivity of the coal bed reservoir over time during the process of injection. The model for the coal bed reservoir is based on poromechanical equations that explicitly take into account the effect of adsorption on the mechanical behavior of a microporous medium. We consider the coal bed reservoir as a dual porosity (cleats and coal porosity medium, for which we derive a set of linear constitutive equations. The model requires as an input the adsorption isotherm on coal of the fluid considered. Reversely, the model provides a way to upscale an adsorption isotherm into a meaningful swelling of the coal bed reservoir at the macroscopic scale. The parameters of the model are calibrated on data on coal samples available in the literature. Reservoir simulations of an injection of carbon dioxide in a coal seam are performed with an in-house finite volume and element code. The variations of injection rate over time during the process of injection are obtained from the simulations. The effect of the compressibility of the coal matrix on those variations is discussed. L’injection de dioxyde de carbone dans des veines de charbon profondes peut augmenter

  6. A new apparatus for the determination of adsorption isotherms and adsorption enthalpies on microporous and meso-porous media

    International Nuclear Information System (INIS)

    A specific thermostated experimental device comprising a differential heat flow calorimeter coupled with a home built manometric system has been built for the simultaneous determination of adsorption isotherms and adsorption enthalpies. The differential heat flow calorimeter is a Tian Calvet Setaram C80 model which measures the heat flux of a gas and can be operated isothermally, the manometric system is a stainless steel homemade apparatus. This coupled apparatus allows measurements for pressure up to 2.5 MPa and temperature up to 423.15 K. On the one hand, the apparatus and the experimental procedures are described. On the second hand the reliability and reproducibility were established by measuring adsorption isotherms on a benchmark (Filtrasorb F400) at 318.15 K. The gravimetric method has been used at higher pressure at various temperatures. These devices allowed us to study the adsorption of supercritical fluid (nitrogen N2, methane CH4, carbon dioxide CO2) in activated carbons and microporous or meso-porous silica. The adsorption of methane on a rock of type (TGR) was also studied. These experimental results are used for the study of the interactions fluid / solid that must be taken into account in molecular simulations or DFT theory. (author)

  7. Experimental Adsorption Isotherm of Methane onto Activated Carbon at Sub- and Supercritical Temperatures

    KAUST Repository

    Rahman, Kazi Afzalur

    2010-11-11

    This paper presents the experimentally measured adsorption isotherm data for methane onto the pitch-based activated carbon type Maxsorb III for temperatures ranging from (120 to 220) K and pressures up to 1.4 MPa. These data are useful to study adsorbed natural gas (ANG) storage systems when the low temperature natural gas regasified from the liquid phase is considered to charge in the storage chamber. Adsorption parameters were evaluated from the isotherm data using the Tóth and Dubinin-Astakhov models. The isosteric heat of adsorption, which is concentration- and temperature-dependent, is extracted from the data. The Henry\\'s law coefficients for the methane/Maxsorb III pairs are evaluated at various temperatures. © 2010 American Chemical Society.

  8. 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

    Science.gov (United States)

    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,...

  9. Isotherm and Kinetics of Arsenic (V Adsorption fromAqueous Solution Using Modified Wheat Straw

    Directory of Open Access Journals (Sweden)

    A Eslami

    2011-01-01

    Full Text Available "nBackgrounds and Objectives:Water contamination with arsenic has been recognized as a serious problem and its epidemiological problems to human health have been reported. The objective of this study was to explore the possibility modified wheat straw using sodium bicarbonate for removing arsenic from aqueous solution."nMaterials and Methods: Adsorption process was accomplished in a laboratory-scale batch with emphasis on the effect of various parameters such as pH, contact time, arsenic concentration and adsorbent dosage on adsorption efficiency. In order to understand the adsorption process, sorption kinetics and equilibrium isotherms were also determined."nResults: It was found that adsorption of the arsenic was influenced by several parameters such as arsenic initial concentration, adsorbent dosage and solution pH. Maximum absorption efficiency was achieved at pH 7. As expected the amount of arsenic adsorbed on wheat straw incresed as its concentration went up. Among the models tested, namely the Langmuir, Freundlich, and Dubinin Radushkevich isotherms, the adsorption equilibrium for arsenic was best described by the Langmuir and Freundlich models. It was also found that adsorption of arsenic by wheat straw followed pseudo second-order kinetics. Mean free energy of adsorption (15.8 kJ mol-1 indicates that adsorption of arsenic by wheat straw might follow a chemisorption mechanism. Desorption studies show that arsenic ions are strongly bounded with the adsorbent and exhibit low desorption."nConclusion: It is concluded that that adsorption by modified wheat straw is an efficient and reliable method for arsenic removal from liquid solutions.

  10. Kinetics and adsorption isotherm of C-phycocyanin from Spirulina platensis on ion-exchange resins

    Directory of Open Access Journals (Sweden)

    L. Sala

    2014-12-01

    Full Text Available C-phycocyanin is a natural blue dye extracted from Spirulina platensis, which has many applications in the food and pharmaceutical industries. In this paper the effect of pH and temperature on the adsorption of C-phycocyanin onto two different ion exchange resins (Streamline DEAE and Streamline Q XL for expanded bed adsorption chromatography was investigated. Moreover, the kinetics and adsorption isotherm were evaluated. The equilibrium for the Q XL matrix was reached after 60 min, while for DEAE it was only reached after 140 min. C-phycocyanin showed the highest partition coefficient at pH 7.5 for both resins at 25 ºC. The C-phycocyanin adsorption isotherm was very well represented by the Langmuir, Freundlich and Langmuir-Freundlich models, where the estimated values for Qm and Kd obtained by the Langmuir isotherm were, respectively, 33.92 mg.mL-1 and 0.123 mg.mL-1 for DEAE, and 28.12 mg.mL-1 and 0.082 mg.mL-1 for the Q XL matrix. A negative cooperativity was observed for C-phycocyanin binding when the Q XL matrix was used, while the cooperativity was purely independent using the DEAE matrix.

  11. Modeling and Prediction of Soil Water Vapor Sorption Isotherms

    DEFF Research Database (Denmark)

    Arthur, Emmanuel; Tuller, Markus; Moldrup, Per;

    2015-01-01

    Soil water vapor sorption isotherms describe the relationship between water activity (aw) and moisture content along adsorption and desorption paths. The isotherms are important for modeling numerous soil processes and are also used to estimate several soil (specific surface area, clay content...... wide range of soils; and (ii) develop and test regression models for estimating the isotherms from clay content. Preliminary results show reasonable fits of the majority of the investigated empirical and theoretical models to the measured data although some models were not capable to fit both sorption...

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

    Science.gov (United States)

    Hameed, B H; El-Khaiary, M I

    2008-06-15

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

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

    Energy Technology Data Exchange (ETDEWEB)

    Bera, Achinta; Kumar, T.; Ojha, Keka; Mandal, Ajay, E-mail: mandal_ajay@hotmail.com

    2013-11-01

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

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

    International Nuclear Information System (INIS)

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

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

    Science.gov (United States)

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

    2005-02-15

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

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

    Science.gov (United States)

    Vilvanathan, Sowmya; Shanthakumar, S

    2016-10-01

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

  17. An Adsorption Equilibria Model for Steady State Analysis

    KAUST Repository

    Ismail, Azhar Bin

    2016-02-29

    The investigation of adsorption isotherms is a prime factor in the ongoing development of adsorption cycles for a spectrum of advanced, thermally-driven engineering applications, including refrigeration, natural gas storage, and desalination processes. In this work, a novel semi-empirical mathematical model has been derived that significantly enhances the prediction of the steady state uptake in adsorbent surfaces. This model, a combination of classical Langmuir and a novel modern adsorption isotherm equation, allows for a higher degree of regression of both energetically homogenous and heterogeneous adsorbent surfaces compared to several isolated classical and modern isotherm models, and has the ability to regress isotherms for all six types under the IUPAC classification. Using a unified thermodynamic framework, a single asymmetrical energy distribution function (EDF) has also been proposed that directly relates the mathematical model to the adsorption isotherm types. This fits well with the statistical rate theory approach and offers mechanistic insights into adsorption isotherms.

  18. Adsorptive Removal of Reactive Black 5 from Wastewater Using Bentonite Clay: Isotherms, Kinetics and Thermodynamics

    Directory of Open Access Journals (Sweden)

    Muhammad Tahir Amin

    2015-11-01

    Full Text Available The studies of the kinetics and isotherms adsorption of the Reactive Black 5 (RB5 onto bentonite clay were explored in a batch study in a laboratory. The maximum RB5 adsorption conditions of bentonite clay were optimized such as shaking speed (100 rpm, temperature (323 K, pH (10, contact time (40 min, initial dye concentration (170 mg·L−1, and particle size (177 µm. The adsorbent surface was characterized using Fourier Transform Infrared Spectroscopy spectroscopy. The mechanisms and characteristic parameters of the adsorption process were analyzed using two parameter isotherm models which revealed the following order (based on the coefficient of determination: Harkin-Jura (0.9989 > Freundlich (0.9986 and Halsey (0.9986 > Langmuir (0.9915 > Temkin (0.9818 > Dubinin–Radushkevich (0.9678. This result suggests the heterogeneous nature of bentonite clay. Moreover, the adsorption process was chemisorption in nature because it follows the pseudo-second order reaction model with R2 value of 0.9998, 0.9933 and 0.9891 at 25, 75 and 100 mg·L−1 RB5 dye in the solution, respectively. Moreover, based on the values of standard enthalpy, Gibbs free energy change, and entropy, bentonite clay showed dual nature of exothermic and endothermic, spontaneous and non-spontaneous as well as increased and decreased randomness at solid–liquid interface at 303–313 K and 313–323 K temperature, respectively.

  19. A review of the thermodynamics of protein association to ligands, protein adsorption, and adsorption isotherms

    DEFF Research Database (Denmark)

    Mollerup, Jørgen

    2008-01-01

    The application of thermodynamic models in the development of chromatographic separation processes is discussed. The paper analyses the thermodynamic principles of protein adsorption. It can be modeled either as a reversible association between the adsorbate and the ligands or as a steady...... adsorption is discussed. Hydrophobic and reversed phase chromatography are useful techniques for measuring solute activity coefficients at infinite dilution....

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

    International Nuclear Information System (INIS)

    Highlights: • Cr(VI) can oxidize biological molecules and be one of the most harmful substance. • Magnetic seperation techniques are used on different applications in many fields. • Magnetic systems can be used for rapid and selective removal as a magnetic processor. • We investigate properties of both new material and other magnetic adsorbents reported in the literatures on the adsorption of Cr(VI) ions. • No researchments were reported on adsorption of Cr(VI) with magnetic vinylphenyl boronic acid microparticles. - Abstract: Magnetic vinylphenyl boronic acid microparticles, poly(ethylene glycol dimethacrylate(EG)–vinylphenyl boronic acid(VPBA)) [m-poly(EG–VPBA)], produced by suspension polymerization and characterized, was found to be an efficient solid polymer for Cr(VI) adsorption. The m-poly(EG–VPBA) microparticles were prepared by copolymerizing of ethylene glycol dimethylacrylate (EG) with 4-vinyl phenyl boronic acid (VPBA). The m-poly(EG–VPBA) microparticles were characterized by N2 adsorption/desorption isotherms, electron spin resonance (ESR), X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA), elemental analysis, scanning electron microscope (SEM) and swelling studies. The m-poly(EG–VPBA) microparticles were used at adsorbent/Cr(VI) ion ratios. The influence of pH, Cr(VI) initial concentration, temperature of the removal process was investigated. The maximum removal of Cr(VI) was observed at pH 2. Langmuir isotherm and Dubinin–Radushkvich isotherm were found to better fit the experiment data rather than Fruendlich isotherm. The kinetics of the adsorption process of Cr(VI) on the m-poly(EG–VPBA) microparticles were investigated using the pseudo first-order, pseudo-second-order, Ritch-second-order and intraparticle diffusion models, results showed that the pseudo-second order equation model provided the best correlation with the experimental results. The thermodynamic

  1. Study of Adsorption Isotherm Curves of Amino Acids on the Kaolinite

    Institute of Scientific and Technical Information of China (English)

    Liu Xiaolan; Zhang Zhengbin

    2002-01-01

    This paper studies the adsorption isotherm curves of four amino acids (glycine, aspartic acid, glutamic acid and lysine) and the effects of existences of different concentrations ot Cu(Ⅱ ) on them. Both the adsorption isotherm of the amino acids on the kaolinite and that when the copper ion Cu (Ⅱ) exists belong to the Langmuir type. The slopes of these adsorption isotherm increase with the increasing concentrations of Cu(Ⅱ) added. It can be explained in terms of formation of the type(Ⅰ) ternary surface complexes in these systems. The regular pattern of the effects of copper ion Cu(Ⅱ) on the adsorption isotherm of amino acids on the kaolinite is identical with that of its effects on the exchange and adsorption percentage E (%)-pH on the kaolinite in the same system.

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

    Science.gov (United States)

    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

  3. Adsorption isotherms and thermochemical data of FD&C Red n° 40 binding by Chitosan

    Directory of Open Access Journals (Sweden)

    J. S. Piccin

    2011-06-01

    Full Text Available Chitosan is a natural polymer that has been employed in dye adsorption. In this work, adsorption and thermodynamic data for the interaction of FD&C Red n° 40 food dye with chitosan in aqueous solutions were investigated. The equilibrium adsorption isotherms were determined by the batch method, from 298 to 338 K. Adsorption data were adjusted to five isotherm models: Langmuir, Freundlich, Redlich-Peterson, Temkin and Dubinin-Radushkevich, in order to determine which presented the best adjustment to the experimental data. Error analysis showed that the Langmuir isotherm model was the most appropriate for fitting the experimental data, with a maximum monolayer adsorption of 3065.8 µmol g-1 at 308 K. Negative enthalpy (-112.7 kJ mol-1, entropy (-0.338 kJ mol-1 K-1 and Gibbs free energy (-15.6 to 1.0 kJ mol-1 values demonstrated that the adsorption process is exothermic, spontaneous, favorable, and that randomness of the system decreases during the adsorption process.

  4. Isotherm and kinetic behavior of adsorption of anion polyacrylamide (APAM) from aqueous solution using two kinds of PVDF UF membranes

    International Nuclear Information System (INIS)

    To determine the isotherm parameters and kinetic parameters of adsorption of anion polyacrylamide (APAM) from aqueous solution on PVDF ultrafiltration membrane (PM) and modified PVDF ultrafiltration membrane (MPM) is important in understanding the adsorption mechanism of ultrafiltration processes. Effect of variables including adsorption time, initial solution concentration, and temperature were investigated. The Redlich-Peterson equation of the five different isotherm models we chose was the most fitted model, and the R2 was 0.9487, 0.9765 for PM and MPM, respectively; while, the pseudo-first-order model was the best choice among all the four kinetic models to describe the adsorption behavior of APAM onto membranes, suggesting that the adsorption mechanism was a chemical and physical combined adsorption on heterogeneous surface. The thermodynamic parameters were also calculated from the temperature dependence (ΔrGmθ,ΔrHmθ,ΔrSmθ), which showed that the process of adsorption is not spontaneous but endothermic process and high temperature favors the adsorption.

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

    Science.gov (United States)

    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.

  6. Removal of Bisphenol A from Aqueous solutions using Single walled carbon nanotubes: Investigation of adsorption isotherms

    Directory of Open Access Journals (Sweden)

    Elnaz Iravani

    2013-09-01

    Results: The maximum adsorption capacity was found to be 71.42 mg/g. The results of our experiments showed that maximum adsorption capacity at equilibrium was achieved at t = 60 min and pH = 9. Moreover, increasing the initial concentration is associated with an increase in adsorption capacity until it becomes constant. Conclusion: The BPA adsorption on SWCNT follows Freundlich-Langmuir isotherm.

  7. Simple and Efficient Synthesis of Iron Oxide-Coated Silica Gel Adsorbents for Arsenic Removal: Adsorption Isotherms and Kinetic Study

    International Nuclear Information System (INIS)

    Iron oxide (ferrihydrite, hematite, and magnetite) coated silica gels were prepared using a low-cost, easily-scalable and straightforward method as the adsorbent material for arsenic removal application. Adsorption of the anionic form of arsenic oxyacids, arsenite (AsO2-) and arsenate (AsO4-3), onto hematite coated silica gel was fitted against non-linear 3-parameter-model Sips isotherm and 2-parameter-model Langmuir and Freundlich isotherm. Adsorption kinetics of arsenic could be well described by pseudo-second-order kinetic model and value of adsorption energy derived from non-linear Dubinin-Radushkevich isotherm suggests chemical adsorption. Although arsenic adsorption process was not affected by the presence of sulfate, chloride, and nitrate anions, as expected, bicarbonate and silicate gave moderate negative effects while the presence of phosphate anions significantly inhibited adsorption process of both arsenite and arsenate. When the actual efficiency to remove arsenic was tested against 1 L of artificial arsenic-contaminated groundwater (0.6 mg/L) in the presence competing anions, the reasonable amount (20 g) of hematite coated silica gel could reduce arsenic concentration to below the WHO permissible safety limit of drinking water of 10 μg/L without adjusting pH and temperature, which would be highly advantageous for practical field application

  8. Use of Freundlich isotherm in the study of heavy metal adsorption in water

    International Nuclear Information System (INIS)

    It was studied the applicability of the Freundlich adsorption isotherm in cadmium, mercury, zinc, and copper extraction from water using activated carbon and cellulose as adsorbents. (author) 62 refs., 22 figs., 19 tabs

  9. Biosorption of the Copper and Cadmium Ions - a Study through Adsorption Isotherms Analysis

    Directory of Open Access Journals (Sweden)

    Marcia T. Veit

    2007-10-01

    Full Text Available In this work, the biosorption process of copper-cadmium ions binary mixture by using marine algae Sargassum filipendula was investigated. A set of experiments was performed to obtain equilibrium data for the given batch operational conditions - T=30°C, pH=5. The interpretation of equilibrium data was based on the binary adsorption isotherms models in the Langmuir and Freundlich forms. To evaluate the models parameters, nonlinear identification procedure was used based on the Least Square statistical method and SIMPLEX local optimizer. An analysis of the obtained results showed that the marine algae biomass has higher affinity to copper ions than to cadmium ones. The biomass maximum adsorption capacity for the binary system was about 1.16 meq/g.

  10. Adsorption of nuclides on hydrous oxides: Sorption isotherms on natural materials

    International Nuclear Information System (INIS)

    Hydrous oxides and minerals which have adsorbing groups that behave like hydrous oxides are ubiquitous components of geological formations and may dominate the adsorptive properties of the formations at conditions of natural groundwaters. An understanding of the adsorptive behavior of hydrous oxides is therefore necessary for reliable prediction of migration of nuclides through the formations. Various isotherms are derived from equilibrium ion-exchange theory for the sorption of non-hydrolyzed ions on hydrous oxides. These isotherms are compared with experimental isotherms for sorption of Cs/sup +/, Sr/sup 2+/, Eu/sup 3+/, and TcO/sub 4//sup -/ on several hydrous oxides. General features of these isotherms are predictable from ion-exchange equilibrium theory as applied to hydrous oxides. By combining isotherms for hydrous oxides with those for layer-type clay minerals, many unusual features of isotherms found on geological materials can be explained

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

    Energy Technology Data Exchange (ETDEWEB)

    Asgari, Ghorban [Department of Environmental Health Engineering, School of Health, Hamadan University of Medical Sciences, Hamadan (Iran, Islamic Republic of); Roshani, Babak, E-mail: babak.roshani@gmail.com [Department of Chemical and Biological Engineering, University of Saskatchewan, 57 Campus Drive, Saskatoon, SK, S7N 5A9 (Canada); Ghanizadeh, Ghader [Health Research Center and Health School, Baqiyatallah University of Medical Sciences, Tehran (Iran, Islamic Republic of)

    2012-05-30

    Highlights: Black-Right-Pointing-Pointer Removal of fluoride from drinking water. Black-Right-Pointing-Pointer Pumice as adsorbent functionalized by the cationic surfactant. Black-Right-Pointing-Pointer Effects of HDTMA loading. Black-Right-Pointing-Pointer Best fit of equilibrium expressions. Black-Right-Pointing-Pointer Maximum amount of adsorption. - Abstract: 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{sup -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{sup -1}, pH 6, and it adsorbs over 96% of fluoride from a solution containing 10 mg L{sup -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{sup 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{sub max}) was 41 mg g{sup -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

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

    Science.gov (United States)

    Naowanat, Nitiya; Thouchprasitchai, Nutthavich; Pongstabodee, Sangobtip

    2016-03-15

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

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

    Science.gov (United States)

    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)

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

    Energy Technology Data Exchange (ETDEWEB)

    Ramos-Ramirez, Esthela, E-mail: ramosre@quijote.ugto.mx [Centro de Investigaciones en Quimica Inorganica de la Universidad de Guanajuato, Noria Alta s/n, Col. Noria Alta, C.P. 36050, Guanajuato, Gto. (Mexico); Gutierrez Ortega, Norma L.; Conteras Soto, Cesar A. [Centro de Investigaciones en Quimica Inorganica de la Universidad de Guanajuato, Noria Alta s/n, Col. Noria Alta, C.P. 36050, Guanajuato, Gto. (Mexico); Instituto Nacional de Investigaciones Nucleares, Carretera Mexico-Toluca s/n, km 36.5, La Marquesa, Coyoacan Mexico, C.P. 52750 (Mexico); Olguin Gutierrez, Maria T. [Instituto Nacional de Investigaciones Nucleares, Carretera Mexico-Toluca s/n, km 36.5, La Marquesa, Coyoacan Mexico, C.P. 52750 (Mexico)

    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{sub 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.

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

    International Nuclear Information System (INIS)

    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 N2 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.

  16. The adsorption characteristics and porous structure of bentonite adsorbents as determined from the adsorption isotherms of benzene vapor

    Directory of Open Access Journals (Sweden)

    LEPA STOJANOVSKA

    2004-02-01

    Full Text Available The adsorption of benzene vapor on natural and acid activated bentonites was treated by the theory of volume filling of micropores. The micropore volume and characteristic values of the free energy of adsorption were determined from the adsorption isotherms. The Dubinin–Radushkevish–Stoeckli and Dubinin–Astakhov equations were used for this purpose. The results showed that natural bentonite has a more homogeneous micropore structure than the acid activated ones. The characteristic values of the free energy of adsorption for the natural bentonite were higher than those of the acid activated bentonite. This is due to differences in its structure and the pore size.

  17. Kinetics and adsorption isotherm of C-phycocyanin from Spirulina platensis on ion-exchange resins

    OpenAIRE

    Sala, L; F. S. Figueira; G. P. Cerveira; C. C. Moraes; S. J. Kalil

    2014-01-01

    C-phycocyanin is a natural blue dye extracted from Spirulina platensis, which has many applications in the food and pharmaceutical industries. In this paper the effect of pH and temperature on the adsorption of C-phycocyanin onto two different ion exchange resins (Streamline DEAE and Streamline Q XL) for expanded bed adsorption chromatography was investigated. Moreover, the kinetics and adsorption isotherm were evaluated. The equilibrium for the Q XL matrix was reached after 60 min, while for...

  18. Adsorption isotherms of hog plum (Spondias mombin L.) pulp powder obtained by spray dryer

    OpenAIRE

    Luís Gomes de Moura Neto; Érica Milô de Freitas Felipe Rocha; Marcos Rodrigues Amorim Afonso; José Maria Correia da Costa

    2015-01-01

    Food sorption isotherms are highly important to predict drying time and storage conditions of a product. Current assay evaluates the behavior of adsorption isotherms of hog plum powder obtained by spray-dryer, through mathematical models. GAB, BET, Henderson and Oswin models were adjusted to the experimental data at 25, 30, 35 and 40ºC. The BET model best adjusted to the atomized hog plum for all temperatures tested, with an error ranging between 8.45 and 11.17%. The coefficient of determinat...

  19. Biosorption of uranium (VI) and thorium (IV) onto Ulva gigantea (Kuetzing) bliding. Discussion of adsorption isotherms, kinetics and thermodynamic

    International Nuclear Information System (INIS)

    Ulva gigantea (Kuetzing) bliding (UGB) obtained from sea inlet of Izmir-Turkey has been studied as a biosorbent for removal of radioactive metals from water. In this study, unmodified UGB and modified UGB with glutaraldehyde (GUGB) characterized by FTIR spectroscopy were used as biosorbents for removal of U(VI) and Th(IV) ions from aqueous solution. Adsorption experiments performed under batch process with initial pH, contact time, adsorbent mass and temperature as variables. In order to determine the adsorption characteristics, Langmuir, Freundlich and Dubinin-Raduschkevich adsorption isotherms were applied to the adsorption data. Adsorption experiments showed that the adsorption isotherms correlated well with the Freundlich model. The sorption followed pseudo-second-order kinetics. The thermodynamic parameters such as variations of ΔH0, ΔG0 and ΔS0 were estimated as a function of temperature. The thermodynamics of the adsorption of U(VI) and Th(IV) onto UGB and GUGB indicates that the spontaneous and exothermic nature of the process. The results showed that UGB and GUGB were potential for application in removal of U(VI) and Th(IV) from aqueous solution. (author)

  20. Kinetics and Adsorption Isotherms Studies of Acridine Orange Dye from Aqueous Solution by Activated Charcoal

    Directory of Open Access Journals (Sweden)

    *N. Qamar

    2014-12-01

    Full Text Available The goal of this research is to evaluate the efficiency of charcoal as low coast and effective adsorbent for acridine orange (a cationic dye from aqueous solution at room temperature. Effect of initial pH (2-8, shaking time (5min. - 1hour, adsorbent dose (0.1gm- 0.9gm and dye concentration (37mg/30ml-185mg/30ml were investigated. Results demonstrated that charcoal act as good adsorbent for the removal AO where 99.15% of the dye was adsorbed within 30 minutes. For the maximum dye removal efficiency (100%, optimum conditions were obtained at pH 8 (99.24%, adsorbent dose of 0.9g and dye concentration of 185 mg with charcoal. Kinetics of adsorption was investigated as well as Langmuir and Freundlich isotherms were employed to describe equilibrium studies. The Langmuir adsorption isotherms models and pseudo second order kinetics fitted the experimental data best with high regression coefficient R2. The results of the present studies points to the potential of charcoal as an effective adsorbent for the removal of dye from contaminated water sources.

  1. Adsorption removal of Congo red from aqueous solution by polyhedral Cu2O nanoparticles: Kinetics, isotherms, thermodynamics and mechanism analysis

    International Nuclear Information System (INIS)

    Highlights: • Polyhedral Cu2O NPs with rough surfaces were prepared by a one-pot sonochemical precipitation method. • The Cu2O NPs show unprecedented adsorption capability toward Congo red. • CR adsorption onto Cu2O is a spontaneous, endothermic and chemisorption process. • The Cu2O adsorbent can be photocatalytically regenerated by visible light irradiation. - Abstract: Polyhedral cuprous oxide nanoparticles (Cu2O NPs) with rough surfaces were prepared by a one-pot sonochemical precipitation method. The products were characterized by SEM, XRD, EDS, XPS, and UV–Vis DRS, respectively. The adsorption behavior of Congo red (CR) from aqueous solution onto the as-prepared Cu2O NPs was systematically investigated. The equilibrium and kinetic studies suggested that the adsorption process followed Freundlich isotherm and pseudo-second order model, respectively. The as-prepared Cu2O NPs exhibited remarkable adsorption properties toward CR. The maximum adsorption capacity at 20 °C was 3904 mg g−1, which was the highest reported value so far in adsorption removal of CR. Together with the evaluation of the thermodynamic parameters such as Gibbs free energy, enthalpy and entropy change, our results show that the adsorption of CR onto Cu2O is a spontaneous, endothermic and chemisorption process. A putative interaction model between CR and Cu2O NPs was proposed. Moreover, the Cu2O adsorbent could be photocatalytically regenerated and reused without significant loss of its adsorption capability

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

    Science.gov (United States)

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

    2004-10-01

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

  3. Adsorption isotherms and kinetics for dibenzothiophene on activated carbon and carbon nanotube doped with nickel oxide nanoparticles

    Indian Academy of Sciences (India)

    MAZEN K NAZAL; GHASSAN A OWEIMREEN; MAZEN KHALED; MUATAZ A ATIEH; ISAM H ALJUNDI; ABDALLA M ABULKIBASH

    2016-04-01

    Activated carbon (AC) and multiwall carbon nanotubes (CNT) doped with 1, 5 and 10% Ni in the form of nickel oxide nanoparticles were prepared using the wetness impregnation method. These percentages were denoted by the endings NI1, NI5 and NI10 in the notations ACNI1, ACNI5, ACNI10 and CNTNI1, CNTNI5, CNTNIL10, respectively. The physicochemical properties for these adsorbents were characterized using N$_2$ adsorption–desorption surface area analyzer, thermal gravimetric analysis (TGA), scanning electron microscopy, energy-dispersive X-ray spectroscopy, field-emission transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectrometre. Adsorption isotherms were obtained and desulphurization kinetics were carried out on solutions of dibenzothiophene (DBT) and thiophene in a model fuel. The efficiencies of DBT and thiophene removal were reported. The adsorption isotherms fitted the Langmuir and Freundlich models. The highest adsorption capacity for DBT was $74\\pm 5$ mg g$^{−1}$ on ACNI5; the maximum adsorption capacities of the other adsorbents followed the trend ${\\rm ACNI1 > ACNI10 > AC > CNTNI5 > CNTNI1 > CNTNI10 > CNT}$. The adsorption rates for DBT and thiophene followed pseudo-second-order kinetics. The selective removal by these adsorbents of DBT relative to thiophene and naphthalene was evaluated. The adsorbents’ reusability and the effect of the percentage of aromaticcompounds on their adsorption capacity were also reported.

  4. Adsorption kinetics and isotherms of zeolite coatings directly crystallized on fibrous plates for heat pump applications

    International Nuclear Information System (INIS)

    Zeolite A coatings were grown on porous fibrous metal plates by using the substrate heating synthesis method. The coatings prepared were characterized by X-ray diffraction (XRD) and laser microscopy. Kinetic measurements were performed to determine the rates of adsorption of these materials while their adsorption isotherms were obtained by thermogravimetry (TG). The overall adsorption kinetics varied with the different samples investigated. The zeolite A coating grown on a copper fibrous support generally exhibited superior overall adsorption kinetics compared to a zeolite X coating with close mass, prepared previously on a stainless steel flat plate. The coating thickness as well as the support properties affected the performances of the samples. The inclusion of an additional polymer layer exhibited adverse impact on the kinetics especially after relatively high normalized loadings. The adsorption isotherms obtained for the zeolite coatings on fibrous supports were quite typical for zeolite A while the addition of polymer changed the isotherm type. -- Highlights: • Thick zeolite A coatings were grown on fibrous metal plates. • Use of fibrous supports improved heat transfer quality. • Coating thickness influenced adsorption kinetics notably. • Inclusion of an additional polymer layer changed kinetics and isotherm type

  5. Conceptual adsorption models and open issues pertaining to performance assessment

    International Nuclear Information System (INIS)

    Recently several articles have been published that question the appropriateness of the distribution coefficient, Rd, concept to quantify radionuclide migration. Several distinct issues surrounding the modeling of nuclide retardation. The first section defines adsorption terminology and discusses various adsorption processes. The next section describes five commonly used adsorption conceptual models, specifically emphasizing what attributes that affect adsorption are explicitly accommodated in each model. I also review efforts to incorporate each adsorption model into performance assessment transport computer codes. The five adsorption conceptual models are (1) the constant Rd model, (2) the parametric Rd model, (3) isotherm adsorption models, (4) mass action adsorption models, and (5) surface-complexation with electrostatics models. The final section discusses the adequacy of the distribution ratio concept, the adequacy of transport calculations that rely on constant retardation factors and the status of incorporating sophisticated adsorption models into transport codes. 86 refs., 1 fig., 1 tab

  6. Conceptual adsorption models and open issues pertaining to performance assessment

    International Nuclear Information System (INIS)

    Recently several articles have been published that question the appropriateness of the distribution coefficient, Rd, concept to quantify radionuclide migration. Several distinct issues are raised by various critics. In this paper I provide some perspective on issues surrounding the modeling of nuclide retardation. The first section defines adsorption terminology and discusses various adsorption processes. The next section describes five commonly used adsorption conceptual models, specifically emphasizing what attributes that affect adsorption are explicitly accommodated in each model. I also review efforts to incorporate each adsorption model into performance assessment transport computer codes. The five adsorption conceptual models are (1) the constant Rd model, (2) the parametric Rd model, (3) isotherm adsorption models, (4) mass-action adsorption models, and (5) surface-complexation with electrostatics models. The final section discusses the adequacy of the distribution ratio concept, the adequacy of transport calculations that rely on constant retardation factors and the status of incorporating sophisticated adsorption models into transport codes

  7. Effect of drying method on the adsorption isotherms and isosteric heat of passion fruit pulp powder

    Directory of Open Access Journals (Sweden)

    Maria Angélica Marques Pedro

    2010-12-01

    Full Text Available The sorption behavior of dry products is generally affected by the drying method. The sorption isotherms are useful to determine and compare thermodynamic properties of passion fruit pulp powder processed by different drying methods. The objective of this study is to analyze the effects of different drying methods on the sorption properties of passion fruit pulp powder. Passion fruit pulp powder was dehydrated using different dryers: vacuum, spray dryer, vibro-fluidized, and freeze dryer. The moisture equilibrium data of Passion Fruit Pulp (PFP powders with 55% of maltodextrin (MD were determined at 20, 30, 40 and 50 ºC. The behavior of the curves was type III, according to Brunauer's classification, and the GAB model was fitted to the experimental equilibrium data. The equilibrium moisture contents of the samples were little affected by temperature variation. The spray dryer provides a dry product with higher adsorption capacity than that of the other methods. The vibro-fluidized bed drying showed higher adsorption capacity than that of vacuum and freeze drying. The vacuum and freeze drying presented the same adsorption capacity. The isosteric heats of sorption were found to decrease with increasing moisture content. Considering the effect of drying methods, the highest isosteric heat of sorption was observed for powders produced by spray drying, whereas powders obtained by vacuum and freeze drying showed the lowest isosteric heats of sorption.

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

    Directory of Open Access Journals (Sweden)

    Roshanak Khandanlou

    Full Text Available 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.

  9. IN-VITRO KINETICS, ADSORPTION ISOTHERM, AND EFFECT OF PH ON ANTIDOTAL EFFECT OF ACTIVATED CHARCOAL IN TRAMADOL HYDROCHLORIDE INTOXICATION

    Directory of Open Access Journals (Sweden)

    Pandeya S

    2016-02-01

    Full Text Available Tramadol overdose has been one of the most frequent causes of drug poisoning in the recent years, especially in young adult males. In the current work, the in-vitro study on adsorption kinetics and the effect of pH on antidotal effect of activated charcoal (AC in tramadol hydrochloride intoxication were carried out. For adsorption study tramadol hydrochloride solutions of various concentrations were prepared in both simulated gastric fluid (SGF and simulated intestinal fluid (SIF and analyzed by UV spectrophotometer. For kinetics study tramadol hydrochloride and charcoal in ratio 1:5 was kept in 6 different flasks and sonicated for 5, 10, 15, 20, 25 and 30 minutes and analyzed spectrophotometrically. The data were plotted among two most commonly used adsorption isotherm, Langmuir isotherm and Freundlich isotherm and their coefficient of determination (R2 was compared to get the best adsorption isotherm equation. The kinetics study was done in both SGF and SIF. The result showed that AC 50 gm can adsorb 4802.692 mg tramadol hydrochloride at gastric environment and 8064.516 mg tramadol hydrochloride at intestinal environment. The R2 value in the current study is found to be more in SIF (0.986 than in SGF (0.985. In accordance to the value of R2, the pseudo second order kinetics model fit best for this study with R2 value of 0.9997 in SGF and 0.9994 in SIF. From the current study it can be concluded that 50g AC has the capacity to adsorb sufficient amount of tramadol hydrochloride and the kinetics followed during the adsorption was pseudo-second order.

  10. Non-isothermal adsorption of radioactive methyl iodide at high temperature

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Byung Seon; Park, Geun Il; Lee, Jung Won; Yoon, Ju Hyeon [KAERI, Taejon (Korea, Republic of); Yang, Ho Yeon [KHNPC, Taejon (Korea, Republic of); Ryu, Seung Kon [Chungnam National Univ., Taejon (Korea, Republic of)

    2003-07-01

    Although activated carbon has been successfully used in nuclear power plants, it cannot be considered as a primary adsorbent in a high temperature system, because of its low ignition temperature and its adverse reaction with nitrogen oxide. Therefore, activated carbon is virtually ruled out for high temperature operating systems. The adsorption and dynamic characteristics of gaseous methyl iodide for silver ion-exchanged zeolites at high temperatures up to 400 .deg. C was evaluated. In this study a simple nonisothermal and axially dispersed plug-flow was adopted to simulate the experimental breakthrough curves. The Langmuir-Freundlich isotherm model was used to represent the equilibrium relationship, and the linear driving force (LDF) approximation was used to represent the article uptake. From the viewpoint of silver utilization for the removal of methyl iodide, both the optimal operating temperature and the effective silver ion-exchange level were also determined.

  11. The Global Approach to TPD and Isothermal Adsorption - Desorption Kinetics

    Czech Academy of Sciences Publication Activity Database

    Galíková, Anna; Galík, Aftanas

    Bratislava: Slovak University of Technology , 2003 - (Markoš, J.; Štefuca, V.), s. 108 ISBN 80-227-1889-0. [International Conference of Slovak Society of Chemical Engineering /30./. Tatranské Matliare (SK), 26.05.2003-30.05.2003] R&D Projects: GA AV ČR IAA4072107 Institutional research plan: CEZ:AV0Z4072921 Keywords : adsorption * desorption * global fitting Subject RIV: CH - Nuclear ; Quantum Chemistry

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

    Science.gov (United States)

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

    2016-02-01

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

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

    Science.gov (United States)

    Jain, Rajeev; Sharma, Pooja; Sikarwar, Shalini

    2013-03-01

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

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

    Science.gov (United States)

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

    2016-01-01

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

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

    Science.gov (United States)

    Woitovich Valetti, Nadia; Picó, Guillermo

    2016-02-15

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

  16. Acid Blue 25 adsorption on base treated Shorea dasyphylla sawdust: Kinetic,isotherm, thermodynamic and spectroscopic analysis

    Institute of Scientific and Technical Information of China (English)

    Megat Ahmad Kamal Megat Hanafiah; Wan Saime Wan Ngah; Shahira Hilwani Zolkafly; Lee Ching Teong; Zafri Azran Abdul Majid

    2012-01-01

    The potential of base treated Shorea dasyphylla (BTSD) sawdust for Acid Blue 25 (AB 25) adsorption was investigated in a batch adsorption process.Various physiochemical parameters such as pH,stirring rate,dosage,concentration,contact time and temperature were studied.The adsorbent was characterized with Fourier transform infrared spectrophotometer,scanning electron microscope and Brunauer,Emmett and Teller analysis.The optimum conditions for AB 25 adsorption were pH 2,stirring rate 500 r/min,adsorbent dosage 0.10 g and contact time 60 min.The pseudo second-order model showed the best conformity to the kinetic,data.The equilibrium adsorption of AB 25 was described by Freundlich and Langmuir,with the latter found to agree well with the isotherm model.The maximum monolayer adsorption capacity of BTSD was 24.39 mg/g at 300 K,estimated from the Langmuir model.Thermodynamic parameters such as Gibbs free energy,enthalpy and entropy were determined.It was found that AB 25 adsorption was spontaneous and exothermic.

  17. Kinetic Isotherm of Amoxicillin Antibiotic through Adsorption and its Removal by Electrocoagulation

    Directory of Open Access Journals (Sweden)

    Jayati Chatterjee

    2014-06-01

    Full Text Available Antibiotics are emerging contaminants in the aquatic environment because they have adverse effects on the aquatic life and humans. The use of antibiotics in human and veterinary medicine has a significant effect on the quality of surface and groundwater. The relevance of an electrocoagulation (EC process for the removal of an antibiotic was selected because of its wide application, high solubility in water, high residual toxicity and an absence of biodegradability, was examined in this study. Metal hydroxides generated during EC were used to remove Amoxicillin (AMX from aqueous solution. The knowledge regarding the removal mechanism of this substance has not yet been investigated till now. Experiments were carried out in a batch electrochemical reactor using aluminum electrodes. The removal of AMX was relatively fast and equilibrium was reached within 20 min. The effects of the main operating parameters were examined and showed that irrespective of the initial concentration and for pH ranging from 3 to 10, maximum removal efficiency remained close to 95%; while a sharp decrease was recorded at pH 2 (8 % removal. The results of this study also showed that the removal of AMX from water was strongly affected by the current intensity. The mechanism of electrocoagulation was modeled using isotherm models and showed that the Sips isotherm matched satisfactorily the experimental data, suggesting monolayer coverage of adsorbed molecules and assumed a quasi-Gaussian distribution energy owing to the high correlation also found for the Toth model. In addition, adsorption kinetic studies showed that the EC process followed a pseudo-second-order kinetic model at the various current densities, as when the pH and initial antibiotic concentrations were considered.

  18. FTIR spectrophotometry, kinetics and adsorption isotherms modeling, ion exchange, and EDX analysis for understanding the mechanism of Cd{sup 2+} and Pb{sup 2+} removal by mango peel waste

    Energy Technology Data Exchange (ETDEWEB)

    Iqbal, Muhammad [Biotechnology Group, Centre for Environment Protection Studies, PCSIR Laboratories Complex, Ferozepur Road, Lahore 54600 (Pakistan)], E-mail: iqbalm@fulbrightweb.org; Saeed, Asma [Biotechnology Group, Centre for Environment Protection Studies, PCSIR Laboratories Complex, Ferozepur Road, Lahore 54600 (Pakistan); Zafar, Saeed Iqbal [School of Biological Sciences, University of Punjab, Lahore 54590 (Pakistan)

    2009-05-15

    Mango peel waste (MPW) was evaluated as a new sorbent for the removal of Cd{sup 2+} and Pb{sup 2+} from aqueous solution. The maximum sorption capacity of Cd{sup 2+} and Pb{sup 2+} was found to be 68.92 and 99.05 mg g{sup -1}, respectively. The kinetics of sorption of both metals was fast, reaching at equilibrium in 60 min. 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{sup 2+} and Pb{sup 2+}. Chemical modification of MPW for blocking of carboxyl and hydroxyl groups showed that 72.46% and 76.26% removal of Cd{sup 2+} and Pb{sup 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{sup 2+}, Mg{sup 2+}, Na{sup +}, K{sup +}) and proton H{sup +} from MPW with the corresponding uptake of Cd{sup 2+} and Pb{sup 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{sup 2+} and Pb{sup 2+} from aqueous solution.

  19. Equilibrium Isotherm Studies of Adsorption of Pigments Extracted from Kuduk-kuduk (Melastoma malabathricum L. Pulp onto TiO2 Nanoparticles

    Directory of Open Access Journals (Sweden)

    N. T. R. N. Kumara

    2014-01-01

    Full Text Available The adsorption of natural pigments onto TiO2 nanoparticles was investigated. The pigments were extracted from the dark purple colored pulp of the berry-like capsule of Kuduk-kuduk (Melastoma malabathricum L.. The Langmuir, Freundlich, Redlich-Peterson, and Sips isotherm models were used to analyze the equilibrium experimental data. Data correlated well with the Sips isotherm model, where the heterogeneity factor (n=0.24 indicated heterogeneous adsorption characteristics, with a maximum adsorption capacity of 0.0130 mg/g. The heterogeneous adsorption character was further supported by results obtained from zeta-potential measurements. When a dye-sensitized solar cell (DSSC was sensitized with the extracted pigment, the photo-energy conversion efficiency was measured to be 0.83%, thus proving the suitability of Kuduk-kuduk fruit pulp as a sensitizer in DSSCs.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

  2. Non-linear frequency response of non-isothermal adsorption controlled by micropore diffusion with variable diffusivity

    Directory of Open Access Journals (Sweden)

    MENKA PETKOVSKA

    2000-12-01

    Full Text Available The concept of higher order frequency response functions (FRFs is used for the analysis of non-linear adsorption kinetics on a particle scale, for the case of non-isothermal micropore diffusion with variable diffusivity. Six series of FRFs are defined for the general non-isothermal case. A non-linerar mathematical model is postulated and the first and second order FRFs derived and simulated. A variable diffusivity influences the shapes of the second order FRFs relating the sorbate concentration in the solid phase and t he gas pressure significantly, but they still keep their characteristics which can be used for discrimination of this from other kinetic mechanisms. It is also shown that first and second order particle FRFs offter sufficient information for an easy and fast estimation of all model parameters, including those defining the system non-linearity.

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

    International Nuclear Information System (INIS)

    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

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

    Science.gov (United States)

    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 298-318K. The FTIR results revealed that amine and carboxyl functional groups present on the surface of APSP. The SEM results show that APSP has an irregular and porous surface which is adequate morphology for dye adsorption. Desorption experiments were carried to explore the feasibility of adsorbent regeneration and the adsorbed MO from APSP was desorbed using 0.1M NaOH with an efficiency of 93.5%. Findings of the present study indicated that APSP can be successfully used for removal of MO from aqueous solution. PMID:26921544

  5. Evaluation of Theoretical and Empirical Water Vapor Sorption Isotherm Models for Soils

    DEFF Research Database (Denmark)

    Arthur, Emmanuel; Tuller, Markus; Moldrup, Per;

    2016-01-01

    The mathematical characterization of water vapor sorption isotherms of soils is crucial for modeling processes such as volatilization of pesticides and diffusive and convective water vapor transport. Although numerous physically-based and empirical models were previously proposed to describe...... sorption isotherms of building materials, food, and other industrial products, knowledge about the 24 applicability of these functions for soils is noticeably lacking. We present validation of nine models for characterizing adsorption/desorption isotherms for a water activity range from 0.03 to 0.93 for...

  6. Studies on the adsorption kinetics and isotherms for the removal and recovery of Methyl Orange from wastewaters using waste materials

    International Nuclear Information System (INIS)

    De-Oiled Soya a waste of Soya oil industries and Bottom Ash a waste of thermal power plants have been used as effective adsorbent for recovery and removal of hazardous dye Methyl Orange from wastewater. During the studies effects of amount of dye and adsorbents, pH, sieve sizes, column studies etc. have been carried out. Adsorption of the dye over both the adsorbents has been monitored through Langmuir and Freundlich adsorption isotherm models and feasibility of the process is predicted in both the cases. Different thermodynamic parameters like Gibb's free energy, enthalpy and entropy of the undergoing process are also evaluated through these adsorption models. The kinetic studies confirm the first order process for the adsorption reaction and also play an important role in finding out half-life of the adsorption process and rate constants for both the adsorbents. It is also found that over the entire concentration range the adsorption on Bottom Ash takes place via particle diffusion process, while that of De-Oiled Soya undergoes via film diffusion process. In order to establish the practical utility of the developed process, attempts have been made for the bulk removal of the dye through column operations. For the two columns saturation factors are found as 98.61 and 99.8%, respectively, for Bottom Ash and De-Oiled Soya with adsorption capacity of each adsorbent as 3.618 and 16.664 mg/g, respectively. The dye recovery has been achieved by eluting dil. NaOH through the exhausted columns

  7. Isothermal blast wave model of supernova remnants

    International Nuclear Information System (INIS)

    The validity of the ''adiabatic'' assumption in supernova remnant calculations is examined, and the alternative extreme of an isothermal blast wave is explored. It is concluded that, because of thermal conductivity, the large temperature gradients predicted by the adiabatic model probably are not maintained in nature. Self-similar solutions to the hydrodynamic equations for an isothermal blast wave have been found and studied. These solutions are then used to determine the relationship between X-ray observations and inferred parameters of supernova remnants. A comparison of the present results with those for the adiabatic model indicates differences which are less than present observational uncertainties. It is concluded that most parameters of supernova remnants inferred from X-ray measurements are relatively insensitive to the specifics of the blast wave model

  8. Isothermal blast wave model of supernova remnants

    Science.gov (United States)

    Solinger, A.; Buff, J.; Rappaport, S.

    1975-01-01

    The validity of the 'adiabatic' assumption in supernova-remnant calculations is examined, and the alternative extreme of an isothermal blast wave is explored. It is concluded that, because of thermal conductivity, the large temperature gradients predicted by the adiabatic model probably are not maintained in nature. Self-similar solutions to the hydrodynamic equations for an isothermal blast wave have been found and studied. These solutions are then used to determine the relationship between X-ray observations and inferred parameters of supernova remnants. A comparison of the present results with those for the adiabatic model indicates differences which are less than present observational uncertainties. It is concluded that most parameters of supernova remnants inferred from X-ray measurements are relatively insensitive to the specifics of the blast-wave model.

  9. A Linear Diffusion Model of Adsorption Kinetics at Fluid/Fluid Interfaces

    OpenAIRE

    Staszak, Maciej

    2016-01-01

    The paper presents a new model for kinetically controlled adsorption at the fluid/fluid interface. The main purpose of the presented approach is to relate easy to estimate bulk surfactant concentration with Gibbs surface excess. Two adsorption isotherms are involved in the new model development: Frumkin and Szyszkowski isotherms. Additionally the Johannsen time profile of concentration in the adsorption layer is assumed and estimated in the model derivation. The proposed approach assumes the ...

  10. Equilibrium adsorption isotherm of U(VI) at pH4 and pH5 onto synthetic magnetite nanoparticles

    International Nuclear Information System (INIS)

    The adsorption features of synthetic magnetite nanoparticles have been investigated for removal of uranyl ions from nitric solutions. These magnetic nanoparticles can be used to adsorb contaminants in wastewater and can subsequently be removed from the medium by a magnetic process because their superparamagnetic behavior. The magnetite nanoparticles were synthesized by simultaneous precipitating of Fe2+ and Fe3+ ions in a NaOH solution. Batch experiments were carried out to investigate the adsorption of UO22+ ions from nitric solution, pH 4 and 5, onto magnetic nanoparticles. The adsorption equilibrium was attained with 30 min of contact time. Two min of application of a magnetic field were sufficient for the removing of magnetite nanoparticles from the liquid medium. Equilibrium adsorption isotherm was evaluated using Freundlich and Langmuir models. The adsorption isotherm fitted well to the Langmuir equation with maximum adsorption capacity of 27 mg g-1. The adsorption was between 40% and 80% under conditions studied. The results showed that the nanoparticles of synthetic magnetite have high adsorption capacity for uranyl ions so they present good perspectives of application for the processes of uranium liquid waste treatment. (author)

  11. ADSORPTION OF Pb2+ IONS FROM AQUEOUS SOLUTIONS ONTO BAEL TREE LEAF POWDER: ISOTHERMS, KINETICS AND THERMODYNAMICS STUDY

    Directory of Open Access Journals (Sweden)

    P. SENTHIL KUMAR

    2009-12-01

    Full Text Available In this study, bael tree (BT leaf powder was used as an adsorbent for removal of Pb2+ ions from aqueous solutions through batch equilibrium technique. The influence of pH, equilibrium time, temperature, adsorbent dosage and initial concentration of metal ions on adsorbed amount of metals ions were investigated. Studies showed that the pH of aqueous solutions affected Pb2+ ions removal as a result of removal efficiency increased with increasing solution pH. The experimental isotherm data were analyzed using the Langmuir, Freundlich, Temkin and Dubinin-Radushkevich equations. The monolayer adsorption capacity is 4.065 mg/g with the correlation coefficient of 0.993. The experiments showed that highest removal rate was 84.93% at solution pH 5, contact time 60 min and initial concentration of 50 mg/L. Thermodynamic parameters such as Gibbs free energy, enthalpy, and entropy have also been evaluated and it has been found that the sorption process was feasible, spontaneous and exothermic in nature. Three simplified kinetic models including a pseudo-first-order equation, pseudo-second-order equation and intraparticle diffusion equation were selected to follow the adsorption process. Kinetic parameters, rate constants, equilibrium sorption capacities and related correlation coefficients, for each kinetic model were calculated and discussed. It was shown that the adsorption of Pb2+ ions could be described by the pseudo-second order equation, suggesting that the adsorption process is presumable a chemisorption.

  12. Adsorption of methylene blue onto poly(cyclotriphosphazene-co-4,4′-sulfonyldiphenol) nanotubes: Kinetics, isotherm and thermodynamics analysis

    International Nuclear Information System (INIS)

    Highlights: • Polyphosphazene nanotube as an adsorbent could be facilely synthesized. • The adsorbent owns numerous electron-rich N and P atoms and hydroxyl groups. • The adsorbent was an efficient and specific adsorbent for the removal of MB. • The pseudo-second-order model could be better to describe the adsorption of MB. • The MB adsorption onto PZS nanotubes was endothermic and spontaneous. - Abstract: 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 69.16 mg/g and the corresponding contact time of 15 min. Thermodynamic analyses showed that MB adsorption onto the PZS nanotubes was endothermic and spontaneous and it was also a physisorption process

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

    OpenAIRE

    Asif Naeem; Muhammad Akhtar; Waqar Ahmad

    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 sp...

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

    Science.gov (United States)

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

    2016-05-15

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

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

    Science.gov (United States)

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

    2012-03-30

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

  16. A family of lowered isothermal models

    CERN Document Server

    Gieles, Mark

    2015-01-01

    We present a family of self-consistent, spherical, lowered isothermal models, consisting of one or more mass components, with parameterised prescriptions for the energy truncation and for the amount of radially biased pressure anisotropy. The models are particularly suited to describe the phase-space density of stars in tidally limited, mass-segregated star clusters in all stages of their life-cycle. The models extend a family of isotropic, single-mass models by Gomez-Leyton and Velazquez, of which the well-known Woolley, King and Wilson (in the non-rotating and isotropic limit) models are members. We derive analytic expressions for the density and velocity dispersion components in terms of potential and radius, and introduce a fast model solver in PYTHON (LIMEPY), that can be used for data fitting or for generating discrete samples.

  17. A family of lowered isothermal models

    Science.gov (United States)

    Gieles, Mark; Zocchi, Alice

    2015-11-01

    We present a family of self-consistent, spherical, lowered isothermal models, consisting of one or more mass components, with parametrized prescriptions for the energy truncation and for the amount of radially biased pressure anisotropy. The models are particularly suited to describe the phase-space density of stars in tidally limited, mass-segregated star clusters in all stages of their life-cycle. The models extend a family of isotropic, single-mass models by Gomez-Leyton and Velazquez, of which the well-known Woolley, King and Wilson (in the non-rotating and isotropic limit) models are members. We derive analytic expressions for the density and velocity dispersion components in terms of potential and radius, and introduce a fast model solver in PYTHON (LIMEPY), that can be used for data fitting or for generating discrete samples.

  18. The influence of carbon surface oxygen groups on Dubinin-Astakhov equation parameters calculated from CO{sub 2} adsorption isotherm

    Energy Technology Data Exchange (ETDEWEB)

    Furmaniak, Sylwester; Terzyk, Artur P; Gauden, Piotr A [N Copernicus University, Department of Chemistry, Physicochemistry of Carbon Materials Research Group, Gagarin Street 7, 87-100 Torun (Poland); Harris, Peter J F [Centre for Advanced Microscopy, University of Reading, Whiteknights, Reading RG6 6AF (United Kingdom); Kowalczyk, Piotr, E-mail: aterzyk@chem.uni.torun.p, E-mail: p.j.f.harris@rdg.ac.u [Applied Physics, RMIT University, GPO Box 2476V, Victoria 3001 (Australia)

    2010-03-03

    We present the results of a systematic study of the influence of carbon surface oxidation on Dubinin-Astakhov isotherm parameters obtained from the fitting of CO{sub 2} adsorption data. Using GCMC simulations of adsorption on realistic VPC models differing in porosity and containing the most frequently occurring carbon surface functionalities (carboxyls, hydroxyls and carbonyls) and their mixtures, it is concluded that the maximum adsorption calculated from the DA model is not strongly affected by the presence of oxygen groups. Unfortunately, the same cannot be said of the remaining two parameters of this model i.e. the heterogeneity parameter (n) and the characteristic energy of adsorption (E{sub 0}). Since from the latter the pore diameters of carbons are usually calculated, by inverse-type relationships, it is concluded that they are questionable for carbons containing surface oxides, especially carboxyls.

  19. A Short Note on Non-isothermal Diffusion Models

    Directory of Open Access Journals (Sweden)

    T. Ficker

    2003-01-01

    Full Text Available Asymptotic behaviour of the DIAL and DRAL non-isothermal models, derived previously for the diffusion of water vapour through a porous building structure, is studied under the assumption that the initially non-isothermal structure becomes purely isothermal.

  20. Adsorption Model for Off-Gas Separation

    Energy Technology Data Exchange (ETDEWEB)

    Veronica J. Rutledge

    2011-03-01

    The absence of industrial scale nuclear fuel reprocessing in the U.S. has precluded the necessary driver for developing the advanced simulation capability now prevalent in so many other countries. Thus, it is essential to model complex series of unit operations to simulate, understand, and predict inherent transient behavior and feedback loops. A capability of accurately simulating the dynamic behavior of advanced fuel cycle separation processes will provide substantial cost savings and many technical benefits. The specific fuel cycle separation process discussed in this report is the off-gas treatment system. The off-gas separation consists of a series of scrubbers and adsorption beds to capture constituents of interest. Dynamic models are being developed to simulate each unit operation involved so each unit operation can be used as a stand-alone model and in series with multiple others. Currently, an adsorption model has been developed in gPROMS software. Inputs include gas stream constituents, sorbent, and column properties, equilibrium and kinetic data, and inlet conditions. It models dispersed plug flow in a packed bed under non-isothermal and non-isobaric conditions for a multiple component gas stream. The simulation outputs component concentrations along the column length as a function of time from which the breakthrough data is obtained. It also outputs temperature along the column length as a function of time and pressure drop along the column length. Experimental data will be input into the adsorption model to develop a model specific for iodine adsorption on silver mordenite as well as model(s) specific for krypton and xenon adsorption. The model will be validated with experimental breakthrough curves. Another future off-gas modeling goal is to develop a model for the unit operation absorption. The off-gas models will be made available via the server or web for evaluation by customers.

  1. Adsorption Model for Off-Gas Separation

    International Nuclear Information System (INIS)

    The absence of industrial scale nuclear fuel reprocessing in the U.S. has precluded the necessary driver for developing the advanced simulation capability now prevalent in so many other countries. Thus, it is essential to model complex series of unit operations to simulate, understand, and predict inherent transient behavior and feedback loops. A capability of accurately simulating the dynamic behavior of advanced fuel cycle separation processes will provide substantial cost savings and many technical benefits. The specific fuel cycle separation process discussed in this report is the off-gas treatment system. The off-gas separation consists of a series of scrubbers and adsorption beds to capture constituents of interest. Dynamic models are being developed to simulate each unit operation involved so each unit operation can be used as a stand-alone model and in series with multiple others. Currently, an adsorption model has been developed in gPROMS software. Inputs include gas stream constituents, sorbent, and column properties, equilibrium and kinetic data, and inlet conditions. It models dispersed plug flow in a packed bed under non-isothermal and non-isobaric conditions for a multiple component gas stream. The simulation outputs component concentrations along the column length as a function of time from which the breakthrough data is obtained. It also outputs temperature along the column length as a function of time and pressure drop along the column length. Experimental data will be input into the adsorption model to develop a model specific for iodine adsorption on silver mordenite as well as model(s) specific for krypton and xenon adsorption. The model will be validated with experimental breakthrough curves. Another future off-gas modeling goal is to develop a model for the unit operation absorption. The off-gas models will be made available via the server or web for evaluation by customers.

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

    International Nuclear Information System (INIS)

    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 (ΔHo), standard entropy (ΔSo), standard free energy (ΔGo) and activation energy were determined. The regeneration efficiency of the spent activated carbon was high, with TCP desorption of 99.6%.

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

    Science.gov (United States)

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

    2016-01-01

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

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

    Science.gov (United States)

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

    2016-11-01

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

  5. Modeling high adsorption capacity and kinetics of organic macromolecules on super-powdered activated carbon.

    Science.gov (United States)

    Matsui, Yoshihiko; Ando, Naoya; Yoshida, Tomoaki; Kurotobi, Ryuji; Matsushita, Taku; Ohno, Koichi

    2011-02-01

    The capacity to adsorb natural organic matter (NOM) and polystyrene sulfonates (PSSs) on small particle-size activated carbon (super-powdered activated carbon, SPAC) is higher than that on larger particle-size activated carbon (powdered-activated carbon, PAC). Increased adsorption capacity is likely attributable to the larger external surface area because the NOM and PSS molecules do not completely penetrate the adsorbent particle; they preferentially adsorb near the outer surface of the particle. In this study, we propose a new isotherm equation, the Shell Adsorption Model (SAM), to explain the higher adsorption capacity on smaller adsorbent particles and to describe quantitatively adsorption isotherms of activated carbons of different particle sizes: PAC and SPAC. The SAM was verified with the experimental data of PSS adsorption kinetics as well as equilibrium. SAM successfully characterized PSS adsorption isotherm data for SPACs and PAC simultaneously with the same model parameters. When SAM was incorporated into an adsorption kinetic model, kinetic decay curves for PSSs adsorbing onto activated carbons of different particle sizes could be simultaneously described with a single kinetics parameter value. On the other hand, when SAM was not incorporated into such an adsorption kinetic model and instead isotherms were described by the Freundlich model, the kinetic decay curves were not well described. The success of the SAM further supports the adsorption mechanism of PSSs preferentially adsorbing near the outer surface of activated carbon particles. PMID:21172719

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

    Directory of Open Access Journals (Sweden)

    Asif Naeem

    2013-01-01

    Full Text Available 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 % for 15 days. Freundlich adsorption isotherms ( 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 . Moreover, at all the levels of , 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 contents and quantity of fertilizer to other similar textured soils needs confirmation.

  7. Adsorption removal of Congo red from aqueous solution by polyhedral Cu{sub 2}O nanoparticles: Kinetics, isotherms, thermodynamics and mechanism analysis

    Energy Technology Data Exchange (ETDEWEB)

    Shu, Jinxia [Chemical Synthesis and Pollution Control Key Laboratory of Sichuan Province, College of Chemistry and Chemical Engineering, China West Normal University, Nanchong 637002 (China); Wang, Zhonghua, E-mail: zhwangs@163.com [Chemical Synthesis and Pollution Control Key Laboratory of Sichuan Province, College of Chemistry and Chemical Engineering, China West Normal University, Nanchong 637002 (China); Huang, Yijiang; Huang, Ni [Chemical Synthesis and Pollution Control Key Laboratory of Sichuan Province, College of Chemistry and Chemical Engineering, China West Normal University, Nanchong 637002 (China); Ren, Chunguang [Graduate School of Materials Science, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara 630-0192 (Japan); Zhang, Wei [College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123 (China)

    2015-06-05

    Highlights: • Polyhedral Cu{sub 2}O NPs with rough surfaces were prepared by a one-pot sonochemical precipitation method. • The Cu{sub 2}O NPs show unprecedented adsorption capability toward Congo red. • CR adsorption onto Cu{sub 2}O is a spontaneous, endothermic and chemisorption process. • The Cu{sub 2}O adsorbent can be photocatalytically regenerated by visible light irradiation. - Abstract: Polyhedral cuprous oxide nanoparticles (Cu{sub 2}O NPs) with rough surfaces were prepared by a one-pot sonochemical precipitation method. The products were characterized by SEM, XRD, EDS, XPS, and UV–Vis DRS, respectively. The adsorption behavior of Congo red (CR) from aqueous solution onto the as-prepared Cu{sub 2}O NPs was systematically investigated. The equilibrium and kinetic studies suggested that the adsorption process followed Freundlich isotherm and pseudo-second order model, respectively. The as-prepared Cu{sub 2}O NPs exhibited remarkable adsorption properties toward CR. The maximum adsorption capacity at 20 °C was 3904 mg g{sup −1}, which was the highest reported value so far in adsorption removal of CR. Together with the evaluation of the thermodynamic parameters such as Gibbs free energy, enthalpy and entropy change, our results show that the adsorption of CR onto Cu{sub 2}O is a spontaneous, endothermic and chemisorption process. A putative interaction model between CR and Cu{sub 2}O NPs was proposed. Moreover, the Cu{sub 2}O adsorbent could be photocatalytically regenerated and reused without significant loss of its adsorption capability.

  8. Servey Impact of Activated Alumina in Fluoride Concentration Peresent in Water and Appointment Adsorption Isotherm and Kinetics

    Directory of Open Access Journals (Sweden)

    Y Dadban Shahamat

    2009-11-01

    Full Text Available Backgrounds and Objectives: Determination of Fluoride in drinking water has received increasing interest, duo to its beneifical and detrimental effects on health. The aim of this research is investigation of Effect of  activated alumina in fluoride concentration reduction in drinking water."nMaterials and Methods: Expriment in batch system and with change effective parameters such as pH(5, 7,9, equilibration time (30, 60, 90, 120 minute, initial fluoride concentration(1.4, 2, 2.4 mg/l and activated Alumina dosage (0.1, 0.2, 0.3 gr/l was investigated. Also found data of this research were fited with Langmuir and Freundlich models, kinetic data with pseudo- first order, pseudo- second order and modifited pseudo- first order  models."nResults: The results showed that with increasing of pH of solution, removal efficiency was decreased and optimum pH was found to be in the range of 5 to 7. Also removal efficiency of fluoride was increased with increasing of adsorbent dosage and decreasing of initial concentration of fluoride. Adsorption isotherm data show that the fluoride sorption followed the Langmuir model (r2=0.98. Kinetics of sorption of fluoride onto Activated alumina was well described by pseudo- second order model."nConclusion: The concentration of Activated Alumina had significant effect on the reduction of fluoride ions concentration in water.The higher fluoride removals were observed for batch experiments at pH=5 because no free fluoride ion is present in the solutions, and it could be casued by electrostatic interactions between the surface of alumina and the dominant fluoride species in solution The kinetic model can adequately describe the removal behaviors of fluoride ion by alumina adsorption in the batch system.

  9. Investigation of non-isothermal and isothermal gasification process of coal char using different kinetic model

    Institute of Scientific and Technical Information of China (English)

    Wang Guangwei; Zhang Jianliang; Shao Jiugang; Li Kejiang; Zuo Haibin

    2015-01-01

    Isothermal and non-isothermal gasification kinetics of coal char were investigated by using thermogravi-metric analysis (TGA) in CO2 atmosphere, and the experimental data were interpreted with the aids of random pore model (RPM), unreacted shrinking core model (URCM) and volume model (VM). With the increase of heating rate, gasification curve moves into high temperature zone and peak rate of gasification increases;with the increase of gasification temperature, gasification rate increases and the total time of gasification is shortened. The increase of both heating rate and gasification temperature could improve gasification process of coal char. Kinetics analysis indicates that experimental data agree better with the RPM than with the other two models. The apparent activation energy of non-isothermal and isother-mal gasification of coal char using RPM is 193.9 kJ/mol and 212.6 kJ/mol respectively, which are in accor-dance with reported data. Gasification process of coal char under different heating rates and different temperatures are predicted by the RPM derived in this study, and it is found that the RPM predicts the reaction process satisfactorily.

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

    International Nuclear Information System (INIS)

    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 (ΔGo), change in enthalpy (ΔHo) and change in entropy (ΔSo) 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

  11. The isotherm slope. A criterion for studying the adsorption mechanism of benzotriazole on copper in sulphuric acid

    OpenAIRE

    Bastidas, D. M.; Gómez, R. R.; Cano, E.

    2005-01-01

    The adsorption of benzotriazole (BTA) on copper surfaces in 0.001, 0.005 and 0.01 M concentrations of sulphuric acid was investigated using gravimetric measurements. BTA was tested in concentrations from 1x10-5 to 1x10-1 M at temperatures from 298 to 328 K. The adsorption mechanism is discussed in terms of applicability of the conventional Frumkin, Bockris-Swinkels and Kastening-Holleck isotherms, among others. The best fit was obtained using the ...

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

    Science.gov (United States)

    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).

  13. Artificial neural network modeling of phase volume fraction of Ti alloy under isothermal and non-isothermal hot forging conditions

    International Nuclear Information System (INIS)

    An artificial neural network (ANN) model was applied to simulate the phase volume fraction of titanium alloy under isothermal and non-isothermal hot forging condition. For isothermal hot forging process, equilibrium phase volume fraction at specific temperature was predicted. For this purpose, chemical composition of six alloy elements (i.e. AI, Y, Fe, 0, N, and C) and specimen temperature were chosen as input parameter. After that, phase volume fraction under non-isothermal condition was simulated again. Input parameters consist of initial phase volume fraction, equilibrium phase volume fraction at specific temperature, cooling rate, and temperature.The ANN model was coupled with the FE simulation in order to predict the variation of phase volume fraction during non-isothermal forging. Ti-6AI-4Y alloy was forged under isothermal and non-isothermal condition and then, the resulting microstructures were compared with simulated data

  14. Statistical fractal adsorption isotherms, linear energy relations, and power-law trapping-time distributions in porous media

    International Nuclear Information System (INIS)

    Drazer and Zanette [Phys. Rev. E 60, 5858 (1999)] have reported on interesting experiments which show that trapping-time distributions in porous media obey a scaling law of the negative power-law type. Unfortunately, their theoretical interpretation of the experimental data has physical and mathematical inconsistencies and errors. Drazer and Zanette assume the existence of a distribution of local adsorption isotherms for which the random parameter is not a thermodynamic function, but a kinetic parameter, the trapping time. Moreover, they mistakenly identify the reciprocal value of a rate coefficient with the instantaneous (fluctuating) value of the trapping time. Their approach leads to mathematically inconsistent probability densities for the trapping times, which they find to be non-normalizable. We suggest a different theory, which is physically and mathematically consistent. We start with the classical patch approximation, which assumes the existence of a distribution of adsorption heats, and introduce two linear energy relationships between the activation energies of the adsorption and desorption processes and the adsorption heat. If the distribution of the adsorption heat obeys the exponential law of Zeldovich and Roghinsky, then both the adsorption isotherm and the probability density of trapping times can be evaluated analytically in terms of the incomplete beta and gamma functions, respectively. Our probability density of the trapping times is mathematically consistent; that is, it is non-negative and normalized to unity. For large times it has a long tail which obeys a scaling law of the negative power-law type, which is consistent with the experimental data of Drazer and Zanette. By using their data we can evaluate the numerical values of the proportionality coefficients in the linear energy relations. The theory suggests that experimental study of the temperature dependence of the fractal exponents helps to elucidate the mechanism of the adsorption

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

    Science.gov (United States)

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

    2015-12-15

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

  16. 采用空穴阻挡层提高有机太阳电池效率的研究%Adsorption Influencing Factors and Isotherms of Squid Melanin on Pb^2+ and Cr^6+

    Institute of Scientific and Technical Information of China (English)

    鲁婷婷; 林琳; 褚梦思; 汪盼盼; 黄乾; 宋茹

    2012-01-01

    为研究BCP对有机太阳电池的影响,制备了含BCP层的体相异质结电池,器件结构为:ITO/PEDOT:PSS/P3HT+PCBM/BCP/LiF/Al。结果表明:BCP层起到了空穴阻挡和电子传输的作用,器件性能随着BCP层厚度的不同而变化,当BCP厚度为6nm时,其性能最好。%In this study, squid melanin was used as adsorbent to remove of Pb^2+ and Cr^6+ from aqueous solutions, the adsorption factors including squid melanin content, adsorption time, adsorption temperature and solution pH were investigated, as well as the adsorption isotherms were analyzed. Results showed that the added squid melanin effectively adsorbed Pb^2+ and Cr^6+ in aqueous solutions. The removal rates of Pb^2+ and Cr^6+ were above 85.00% after adsorption of 15 min by squid melain. In addition, the removal rate of Pb^2+ decreased with the increased adsorption temperatures, whereas, the maximum adsorption of Cr^6+ was found at 35℃. The low adsorption capacity of squid melanin on Pb^2+ was observed at solution pH of 5.0, and the effective solution pH for Cr^6+ removal was in the range of 4.0 to 6.0. Furthermore, results of adsorption isotherms revealed that the adsorption characteristic of squid melanin on Cr^6+ fitted well to Langmuir and Freundlich models. By comparison, the adsorption behavior of squid melanin on Pb^2+ only had a good correlation with the Langmuir isotherm.

  17. Phase field modeling of dendritic coarsening during isothermal

    Directory of Open Access Journals (Sweden)

    Zhang Yutuo

    2011-08-01

    Full Text Available Dendritic coarsening in Al-2mol%Si alloy during isothermal solidification at 880K was investigated by phase field modeling. Three coarsening mechanisms operate in the alloy: (a melting of small dendrite arms; (b coalescence of dendrites near the tips leading to the entrapment of liquid droplets; (c smoothing of dendrites. Dendrite melting is found to be dominant in the stage of dendritic growth, whereas coalescence of dendrites and smoothing of dendrites are dominant during isothermal holding. The simulated results provide a better understanding of dendrite coarsening during isothermal solidification.

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

    International Nuclear Information System (INIS)

    Including sulfate adsorption improves the dynamic behavior of the SAFE model. - Sulfate adsorption was implemented in the dynamic, multi-layer soil chemistry model SAFE. The process is modeled by an isotherm in which sulfate adsorption is considered to be fully reversible and dependent on sulfate concentration as well as pH in soil solution. The isotherm was parameterized by a site-specific series of simple batch experiments at different pH (3.8-5.0) and sulfate concentration (10-260 μmol l-1) levels. Application of the model to the Lake Gaardsjoen roof covered site shows that including sulfate adsorption improves the dynamic behavior of the model and sulfate adsorption and desorption delay acidification and recovery of the soil. The modeled adsorbed pool of sulfate at the site reached a maximum level of 700 mmol/m2 in the late 1980s, well in line with experimental data

  19. Treatment of Wastewater from a Dairy Industry Using Rice Husk as Adsorbent: Treatment Efficiency, Isotherm, Thermodynamics, and Kinetics Modelling

    Directory of Open Access Journals (Sweden)

    Uttarini Pathak

    2016-01-01

    Full Text Available Effluent from milk processing unit contains soluble organics, suspended solids, and trace organics releasing gases, causing taste and odor, and imparting colour and turbidity produced as a result of high consumption of water from the manufacturing process, utilities and service section, chemicals, and residues of technological additives used in individual operations which makes it crucial matter to be treated for preserving the aesthetics of the environment. In this experimental study after determination of the initial parameters of the raw wastewater it was subjected to batch adsorption study using rice husk. The effects of contact time, initial wastewater concentration, pH, adsorbent dosage, solution temperature and the adsorption kinetics, isotherm, and thermodynamic parameters were investigated. The phenomenon of adsorption was favoured at a lower temperature and lower pH in this case. Maximum removal as high as 92.5% could be achieved using an adsorbent dosage of 5 g/L, pH of 2, and temperature of 30°C. The adsorption kinetics and the isotherm studies showed that the pseudo-second-order model and the Langmuir isotherm were the best choices to describe the adsorption behavior. The thermodynamic parameters suggested that not only was the adsorption by rice husk spontaneous and exothermic in nature but also the negative entropy change indicated enthalpy driven process.

  20. Off-Gas Adsorption Model Capabilities and Recommendations

    Energy Technology Data Exchange (ETDEWEB)

    Lyon, Kevin L. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Welty, Amy K. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Law, Jack [Idaho National Lab. (INL), Idaho Falls, ID (United States); Ladshaw, Austin [Georgia Inst. of Technology, Atlanta, GA (United States); Yiacoumi, Sotira [Georgia Inst. of Technology, Atlanta, GA (United States); Tsouris, Costas [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2016-03-01

    Off-gas treatment is required to reduce emissions from aqueous fuel reprocessing. Evaluating the products of innovative gas adsorption research requires increased computational simulation capability to more effectively transition from fundamental research to operational design. Early modeling efforts produced the Off-Gas SeParation and REcoverY (OSPREY) model that, while efficient in terms of computation time, was of limited value for complex systems. However, the computational and programming lessons learned in development of the initial model were used to develop Discontinuous Galerkin OSPREY (DGOSPREY), a more effective model. Initial comparisons between OSPREY and DGOSPREY show that, while OSPREY does reasonably well to capture the initial breakthrough time, it displays far too much numerical dispersion to accurately capture the real shape of the breakthrough curves. DGOSPREY is a much better tool as it utilizes a more stable set of numerical methods. In addition, DGOSPREY has shown the capability to capture complex, multispecies adsorption behavior, while OSPREY currently only works for a single adsorbing species. This capability makes DGOSPREY ultimately a more practical tool for real world simulations involving many different gas species. While DGOSPREY has initially performed very well, there is still need for improvement. The current state of DGOSPREY does not include any micro-scale adsorption kinetics and therefore assumes instantaneous adsorption. This is a major source of error in predicting water vapor breakthrough because the kinetics of that adsorption mechanism is particularly slow. However, this deficiency can be remedied by building kinetic kernels into DGOSPREY. Another source of error in DGOSPREY stems from data gaps in single species, such as Kr and Xe, isotherms. Since isotherm data for each gas is currently available at a single temperature, the model is unable to predict adsorption at temperatures outside of the set of data currently

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

    Science.gov (United States)

    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...

  2. 重金属生物吸附的吸附模型%Adsorption models for heavy metal biosorption

    Institute of Scientific and Technical Information of China (English)

    郑成; 虞启明; 尹平和

    2007-01-01

    Heavy metal biosorption is an effective process for the removal and recovery of heavy metal ions.Equilibrium isotherms obtained experimentally are usually correlated empirically with commonly used adsorption models, without considering the underlying mechanisms of biosorption.Commonly used models for correlating biosorption isotherm data are briefly reviewed and the use of the adsorption models in correlating the desorption processes is analysed.A set of biosorption/desorption experiments for a marine alga derived biosorbent are carried out to test the use of the adsorption models in the desorption process.Experimental data indicate that the amount of the heavy metal ions desorbed from the biomass could not be calculated with the adsorption models.This suggests that the empirical use of adsorption models in the correlation may not be valid when the reversibility of the biosorption equlibrium in the desorption process needs to be considered.Therefore, mechanism based biosorption models are needed for better correlation of equilibrium isotherm data.

  3. Absorption of calcium ions on oxidized graphene sheets and study its dynamic behavior by kinetic and isothermal models

    Science.gov (United States)

    Fathy, Mahmoud; Abdel Moghny, Th.; Mousa, Mahmoud Ahmed; El-Bellihi, Abdel-Hameed A.-A.; Awadallah, Ahmed E.

    2016-07-01

    Sorption of calcium ion from the hard underground water using novel oxidized graphene (GO) sheets was studied in this paper. Physicochemical properties and microstructure of graphene sheets were investigated using Raman spectrometer, thermogravimetry analyzer, transmission electron microscope, scanning electron microscope. The kinetics adsorption of calcium on graphene oxide sheets was examined using Lagergren first and second orders. The results show that the Lagergren second-order was the best-fit model that suggests the conception process of calcium ion adsorption on the Go sheets. For isothermal studies, the Langmuir and Freundlich isotherm models were used at temperatures ranging between 283 and 313 K. Thermodynamic parameters resolved at 283, 298 and 313 K indicating that the GO adsorption was exothermic spontaneous process. Finally, the graphene sheets show high partiality toward calcium particles and it will be useful in softening and treatment of hard water.

  4. Adsorption-desorption isotherms and heat of sorption of prickly pear fruit (Opuntia ficus indica)

    International Nuclear Information System (INIS)

    The equilibrium moisture contents were determined for prickly pear fruit using the gravimetric static method at t=30, 40 and 50 deg. C over a range of relative humidities from 0.05 to 0.9. The sorption curves of prickly pear fruit decreased with increase in temperature at constant relative humidity. The hysteresis effect was observed. The GAB, modified Halsey, modified Chung-Pfost, modified Oswin and modified Henderson models were tested to fit the experimental data. The GAB model was found to be the most suitable for describing the sorption curves. The monolayer moisture content values for the sorption at different temperatures are calculated using a modified BET equation. The isosteric heats of desorption and adsorption of water were determined from the equilibrium data at different temperatures

  5. Adsorption-desorption isotherms and heat of sorption of prickly pear fruit (Opuntia ficus indica)

    Energy Technology Data Exchange (ETDEWEB)

    Lahsasni, S.; Kouhila, M. E-mail: kouhila@hotmail.com; Mahrouz, M

    2004-01-01

    The equilibrium moisture contents were determined for prickly pear fruit using the gravimetric static method at t=30, 40 and 50 deg. C over a range of relative humidities from 0.05 to 0.9. The sorption curves of prickly pear fruit decreased with increase in temperature at constant relative humidity. The hysteresis effect was observed. The GAB, modified Halsey, modified Chung-Pfost, modified Oswin and modified Henderson models were tested to fit the experimental data. The GAB model was found to be the most suitable for describing the sorption curves. The monolayer moisture content values for the sorption at different temperatures are calculated using a modified BET equation. The isosteric heats of desorption and adsorption of water were determined from the equilibrium data at different temperatures.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    Shaker, Medhat A; Yakout, Amr A

    2016-02-01

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

  8. Characteristics of isothermal adsorption and desorption of aluminum ion to/from humic acids

    Institute of Scientific and Technical Information of China (English)

    WANG Qiang; WEI Shiqiang; HUANG Yuming; ZHANG Jinzhong

    2008-01-01

    The adsorption and desorption characteristics of Al3+ to/from humic acids at different pH, ionic strength, and temperature were studied by the C-25 glucosan-gel chromatography method. The results showed that the maximum adsorption amount (Qmax) and adsorption constant (k) increased, whereas, the absolute value of standard thermodynamic molar free energy change (AG0. m) decreased with the increase of pH at constant ionic strength and temperature. With ionic strength increasing from 0 to 0. 15 mol/L, Qmax and k increased and the absolute value of AG0. m decreased at constant pH and temperature. High temperature was unfavorable for the adsorption reaction, as indicated by the dramatic decrease of Qmax and the absolute value of AG0. m with an increase in temperature. The standard thermodynamic molar free energy change (AG0. m) and the standard thermodynamic enthalpy change (AH0. m) of the adsorption reaction were both negative, suggesting that adsorption reaction was spontaneous and exothermic. The desorption rate of HA-AI3+ complex accelerated with the decrease of pH, and a significant linear relationship could be obtained between pH and the desorption rates of Al3+ from humic acids. These results demonstrated that the Al3+ adsorption reaction was a "biphase" reaction, and adsorption occurred at both the interior and exterior adsorption sites of humic acids.

  9. Dependence of Elution Curve and Adsorption Isotherms of Insulin on composition of Mobile Phase of Frontal Analysis in Reversed Phase Liquid Chromatography

    Institute of Scientific and Technical Information of China (English)

    耿信笃; 弗莱德依瑞格涅尔

    2003-01-01

    With frontal analysis(FA),the dependence of adsorption isotherms of insulin on the composition of mobile phase in reversed phase liquid chromatography (RPLC) has been investigated,This is also a good example to employ the stoichiometric displacement theory (SDT) for ivestigating solute adsorption in physical chemistry.Six kinds of mobile phase in RPLC were employed to study the effects on the elution curves and adsorption isotherms of insulin.the key points of this paper are:(1) the stability of insulin due to delay time after preparing,the organic solvent concentration,the kind and the concentration of ion-pairing agent in mobile phase were found to affect both elution curve and adsorption isotherm very seriously.(2)To obtain a valid and comparable result,the composition of the mobile phase employed in FA must be as same as possible to that in usual RPLC of either analytical scale or preparative purpose.(3)Langmuir Equation and the SDT were employed to imitate these obtained adsorption isotherms.The expression for solute adsorption from solution of the SDT was found to have a better elucidation to the insulin adsorption from mobile phase in RPLC.

  10. Statistical mechanical lattice models of endohedral and exohedral xenon adsorption in carbon nanotubes and comparison with Monte-Carlo simulations

    International Nuclear Information System (INIS)

    Adsorption of xenon in carbon nanotubes has been investigated by Kuznetsova et al. [A. Kuznetsova, J.T. Yates Jr., J. Liu, R.E. Smalley, J. Chem. Phys. 112 (2000) 9590] and Simonyan et al. [V. Simonyan, J.K. Johnson, A Kuznetsova, J.T. Yates Jr., J. Chem. Phys. 114 (2001) 4180] where endohedral adsorption isotherms show a step-like structure. A matrix method is used for calculation of the statistical mechanics of a lattice model of xenon endohedral adsorption which reproduces the isotherm structure while exohedral adsorption is treated by mean-field theory

  11. Effect of temperature on the adsorption of short alkanes in the zeolite ssz-13-adapting adsorption isotherms to microporous materials

    NARCIS (Netherlands)

    Jiang, Tao; Göltl, Florian; Bulo, Rosa E.; Sautet, Philippe

    2014-01-01

    Understanding the diffusion and adsorption of hydrocarbons in zeolites is a highly important topic in the field of catalysis in micro-and mesoporous materials. Especially, the properties of alkanes in zeolites have been studied extensively. A theoretical description of these processes is challenging

  12. Investigation on adsorption capacity of TiO2-P25 nanoparticles in the removal of a mono-azo dye from aqueous solution: A comprehensive isotherm analysis

    Directory of Open Access Journals (Sweden)

    Behnajady Mohammad A.

    2014-01-01

    Full Text Available In this work TiO2-P25 nanoparticles with high surface area have been used as adsorbent for the removal of C.I Acid Red 27 (AR27, as an organic contaminant from aqueous solution. Characteristics of phases and crystallite size of TiO2-P25 nanoparticles were achieved from XRD and the surface area and pore size distribution were obtained from BET and BJH techniques. TiO2-P25 nanoparticles with almost 80% anatase and 20% rutile phases, the average crystallite size of 18 nm, have specific surface area of 56.82 m2 g-1. The effect of various parameters like initial AR27 concentration, pH, contact time and adsorbent dosage has been carried out in order to find desired adsorption conditions. The desired pH for adsorption of AR27 onto TiO2-P25 nanoparticles was 3. The equilibrium data were analyzed with various 2-, 3- and 4-parameter isotherm models. Equilibrium data fitted very well by the 4-parameter Fritz-Schluender model. Results of adsorption kinetics study indicated that the pseudo-second order kinetics provided the best fit with correlation coefficients close to unity.

  13. Batch kinetics, isotherm and thermodynamic studies of adsorption of strontium from aqueous solutions onto low cost rice-straw based carbons.

    Directory of Open Access Journals (Sweden)

    S. M. Yakout

    2010-09-01

    Full Text Available Present study explored the feasibility of using waste rice-straw based carbons as adsorbent for the removal of strontium under different experimental conditions. The batch sorption is studied with respect to solute concentration (2.8 - 110 mg/L, contact time, adsorbent dose (2.5 - 20 g/L and solution temperature (25 - 55oC. The Langmuir and Dubinin-Radushkevich adsorption models were applied to experimental equilibrium data and isotherm constants were calculated using linear regression analysis. A comparison of kinetic models applied to the adsorption of strontium on rice-straw carbon was evaluated for the pseudo-second-order, Elovich, intraparticle diffusion and Bangham’s kinetics models. The experimental data fitted very well the pseudosecond-order kinetic model and also followed by intra-particle diffusion model, whereas diffusion is not only the rate-controlling step. The results show that the sorption capacity increases with an increase in solution temperature from 25 to 55 oC. The thermodynamics parameters were evaluated. The positive value of ΔH (40.93 kJ indicated that the adsorption of strontium onto RS1 carbon was endothermic, which result was supported by the increasing adsorption of strontium with temperature. The positive value of ΔS (121.8 kJ/mol reflects good affinity of strontium ions towards the rice-straw based carbons. The results have establishedgood potentiality for the carbons particles to be used as a sorbent for the removal of strontium from wastewater.

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

    Science.gov (United States)

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

    2016-07-01

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

  15. Batch adsorption of iodo-butane on silver-zeolite with henry isotherm

    International Nuclear Information System (INIS)

    Adsorption of 1-iodo-butane in n-dodecane on silver zeolite (of Ionex Research Corp., U.S.A.) was carried out in a batch tank at 50, 60 and 70degC. The adsorbate bulk concentration-time data measured at various times before the equilibrium reached gave the values of surface diffusivity, particle-fluid mass transfer coefficient and the Henry's adsorption equilibrium constant. The mass transfer coefficient was found to be in terms of Sherwood number from 2∼∞, i.e., the same theoretical curve which agreed with the measured data was predicted with any Sherwood number greater than two. This indicated that the adsorption was controlled by the mass transfer within the adsorbent particle. The adsorption equilibrium constant and surface diffusivity were, respectively, expressed by the Arrhenius type equations. (author)

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

    Science.gov (United States)

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

    2015-12-01

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

  17. A mathematical model for isothermal heap and column leaching

    OpenAIRE

    L.R.P. de Andrade Lima

    2004-01-01

    Leaching occurs in metals recovery, in contaminated soil washing, and in many natural processes, such as fertilizer dissolution and rock weathering. This paper presents a model developed to simulate the transient evolution of the dissolved chemical species in the heap and column isothermal leaching processes. In this model, the solid bed is numerically divided into plane layers; the recovery of the chemical species, the enrichment of the pregnant leach solution, and the residual concentration...

  18. Characterization and adsorption modeling of silicon carbide-derived carbons.

    Science.gov (United States)

    Nguyen, T X; Bae, J-S; Bhatia, S K

    2009-02-17

    We present characterization results of silicon carbide-derived carbons (Si-CDCs) prepared from both nano- and micron-sized betaSiC particles by oxidation in pure chlorine atmosphere at various synthesis temperatures (600-1000 degrees C). Subsequently, the adsorption modeling study of simple gases (CH4 and CO2) in these Si-CDC samples for a wide range of pressures and temperatures using our Finite Wall Thickness model [Nguyen, T. X.; Bhatia, S. K. Langmuir 2004, 20, 3532] was also carried out. In general, characterization results showed that the core of Si-CDC particles contains predominantly amorphous material while minor graphitization was also observed on the surface of these particles for all the investigated synthesis temperatures (600-1000 degrees C). Furthermore, postsynthetic heat treatment at 1000 degrees C for 3 days, as well as particle size of precursor (betaSiC) were shown to have slight impact on the graphitization. In spite of the highly disordered nature of Si-CDC samples, the adsorption modeling results revealed that the Finite Wall Thickness model provides reasonably good prediction of experimental adsorption data of CO2 and CH4 in all the investigated Si-CDC samples at the temperatures of 273 K, 313 K, and 333 K for a wide range of pressure up to 200 bar. Furthermore, the impact of the difference in molecular size and geometry between analysis and probing gases on the prediction of the experimental adsorption isotherm in a disordered carbon using the slit-pore model is also found. Finally, the correlation between compressibility of the Si-CDC samples under high pressure adsorption and their synthesis temperature was deduced from the adsorption modeling. PMID:19123908

  19. Kinetic and isotherm studies of cadmium adsorption on manganese nodule residue

    International Nuclear Information System (INIS)

    The adsorption equilibrium and kinetics studies of cadmium (Cd) ions from aqueous solutions on manganese nodule residue were carried out by considering the influence of various parameters, such as contact time, solution pH and initial metal concentration in solution, temperature and adsorbent quantity. The adsorption of Cd increased with an increase in the concentrations of this metal in solution. Presence of manganese and iron content in manganese nodule residue (MNR) played a significant role in Cd(II) ions removal. The linear forms of the Langmuir and Freundlich equations were utilized for experiments with metal concentrations of 200 mg/L for Cd(II) as functions of solution pH (2.0-6.0). First-order rate equation and pseudo second-order rate equations were applied to study adsorption kinetics. Mass transfer study was also done to know the reaction rate. Thermodynamic parameters, such as standard Gibb's free energy (ΔGo), standard enthalpy (ΔHo) and standard entropy (ΔSo), were also evaluated by Van't Hoff equation. Thus, adsorption of Cd on this adsorbent was found to be spontaneous and exothermic thermodynamically. The adsorption capacity for Cd was found to be 19.8 mg/g of MNR. Under the optimised conditions, cadmium level was brought down from 100 mg/L to Cd less than detection limits and from 200 to 2 mg/L. Thus, the wastewater after cadmium removal could be safely disposed off on to land or sewage. Finally, the metal loaded adsorbent was subjected to desorption using different mineral acids and leaching by using toxicity characteristic leaching procedure (TCLP), synthetic precipitation leaching procedure (SPLP) tests for its further treatment or its safe disposal

  20. Combined Neutron Diffraction and Adsorption Isotherm Study of the Anomalous Wetting Properties of NH3 on Graphite

    International Nuclear Information System (INIS)

    The wetting properties of NH3 films on graphite have been examined over a temperature range of approximately 50K (centered about the bulk triple point of 195.4K) using a combination of high-resolution vapor pressure isotherms and elastic neutron diffraction. Between 172 and 215K, a single adsorption step appears at reduced pressures above 0.5. As the system is cooled, the position of this step (which is shown to be associated with the formation of a thin liquid film) increases smoothly between 0.5 and 0.95. Evidence is put forward that there is a transition from complete wetting to incomplete wetting to nonwetting. Also, the role of cluster formation and hydrogen bonding is discussed. copyright 1997 The American Physical Society

  1. Adsorption of acid and basic dyes by sludge-based activated carbon:Isotherm and kinetic studies

    Institute of Scientific and Technical Information of China (English)

    李鑫; 王广智; 李伟光; 王萍; 宿程远

    2015-01-01

    A batch experiment was conducted to investigate the adsorption of an acid dye (Acid Orange 51) and a basic dye (Safranine) from aqueous solutions by the sludge-based activated carbon (SBAC). The results show that the adsorption of Acid Orange 51 decreases at high pH values, whereas the uptake of Safranine is higher in neutral and alkaline solutions than that in acidic conditions. The adsorption time needed for Safranine to reach equilibrium is shorter than that for Acid Orange 51. The uptakes of the dyes both increase with temperature increasing, indicating that the adsorption process of the dyes onto SBAC is endothermic. The equilibrium data of the dyes are both best represented by the Redlich−Peterson model. At 25 °C, the maximum adsorption capacities of SBAC for Acid Orange 51 and Safranine are 248.70 mg/g and 525.84 mg/g, respectively. The Elovich model is found to best describe the adsorption process of both dyes, indicating that the rate-limiting step involves the chemisorption. It can be concluded that SBAC is a promising material for the removal of Acid Orange 51 and Safranine from aqueous solutions.

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

    International Nuclear Information System (INIS)

    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.

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

    Science.gov (United States)

    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.

  4. Modelling and understanding the competitive adsorption of microcystins and tannic acid.

    Science.gov (United States)

    Campinas, Margarida; Viegas, Rui M C; Rosa, Maria João

    2013-10-01

    A predictive model integrating adsorption kinetics and competitive isotherm models (Homogeneous Surface Diffusion Model, Freundlich-type and Fritz & Schlünder isotherms) was developed to describe and understand the competing mechanism(s) and the ionic strength (IS) role on microcystins (MC) and tannic acid (TA) competitive adsorption. The developed model showed good agreement with the experimental data obtained from batch adsorption tests and isotherms conducted with MC extracts and TA model solutions (single-solute and multicomponent, IS presence and absence) using a mesoporous powdered activated carbon (PAC). Results confirm that similar size molecules such as MC and TA are strong competitors and tannin-rich waters may severely affect MC residuals in the treated water. Unlike usually considered, both direct site and pore blockage mechanisms seem relevant. Competition effects appear to be more dependent on the competitor/contaminant molar ratio than on the initial concentrations. The IS affects the extent and the mechanisms of MC-TA competitive adsorption, reducing PAC dose for safe control of MC residuals. The developed model, including a Ds analysis, is an important tool to understand the competitive adsorption of similar size adsorbates. PMID:23880216

  5. Thermodynamics of hydrogen adsorption in MOF-177 at low temperatures: measurements and modelling

    International Nuclear Information System (INIS)

    Hydrogen adsorption measurements and modelling for the Zn-based microporous metal-organic framework (MOF) Zn4O(1,3,5-benzenetribenzoate)2, MOF-177, were performed over the 50-77 K and 0-40 bar ranges. The maximum excess adsorption measured under these conditions varies over about 105-70 mg g-1. An analysis of the isotherms near saturation shows that hydrogen is ultimately adsorbed in an incompressible phase whose density is comparable to that of the bulk liquid. These liquid state properties observed under supercritical conditions reveal a remarkable effect of nanoscale confinement. The entire set of adsorption isotherms can be well described using a micropore filling model. The latter is used, in particular, to determine the absolute amounts adsorbed and the adsorption enthalpy. When expressed in terms of absolute adsorption, the isotherms show considerable hydrogen storage capacities, reaching up to 125 mg g-1 at 50 K and 25 bar. The adsorption enthalpies are calculated as a function of fractional filling and range from 3 to 5 kJ mol-1 in magnitude, in accordance with physisorption. These results are discussed with respect to a similar analysis performed on another Zn-based MOF, Zn4O(1,4-benzenedicarboxylate)3, IRMOF-1, presented recently. It is found that both materials adsorb hydrogen by similar mechanisms.

  6. Isothermal dust models of Herschel-ATLAS galaxies

    CERN Document Server

    Smith, D J B; Jarvis, M J; Maddox, S J; Dunne, L; Bonfield, D G; Eales, S; Serjeant, S; Thompson, M A; Baes, M; Clements, D L; Cooray, A; De Zotti, G; Gonzàlez-Nuevo, J; van der Werf, P; Virdee, J; Bourne, N; Dariush, A; Hopwood, R; Ibar, E; Valiante, E

    2013-01-01

    We use galaxies from the Herschel-ATLAS survey, and a suite of ancillary simulations based on an isothermal dust model, to study our ability to determine the effective dust temperature, luminosity and emissivity index of 250um selected galaxies in the local Universe (z < 0.5). As well as simple far-infrared SED fitting of individual galaxies based on chi^2 minimisation, we attempt to derive the best global isothermal properties of 13,826 galaxies with reliable optical counterparts and spectroscopic redshifts. Using our simulations, we highlight the fact that applying traditional SED fitting techniques to noisy observational data in the Herschel Space Observatory bands introduces artificial anti-correlation between derived values of dust temperature and emissivity index. This is true even for galaxies with the most robust detections in our sample, making the results hard to interpret. We apply a method to determine the best-fit global values of isothermal effective temperature and emissivity index for z <...

  7. Isothermal crystallization kinetic modeling of poly(etherketoneketone) (PEKK)

    Science.gov (United States)

    Choupin, T.; Paris, C.; Cinquin, J.; Fayolle, B.; Régnier, G.

    2016-05-01

    Isothermal melt and cold crystallization kinetics of poly(etherketoneketone) (PEKK) have been investigated by differential scanning calorimetry. A modified Avrami model has been used to describe the two-stage crystallization of PEKK. The primary crystallization stage is assumed to be a two dimensional nucleation growth with an Avrami exponent of 2 whereas the secondary stage is assumed to be a one dimensional nucleation growth with an Avrami exponent of 1. The evolution of the crystallization constant rates depending on temperature has been modeled with the Hoffman and Lauritzen growth equation. The activation energy of nucleation constants Kg for both crystallizations are presented.

  8. Kinetics And Isotherm Studies On Cationic Dyes Adsorption Onto Annona Squmosa Seed Activated Carbon

    OpenAIRE

    Santhi, T.; S. Manonmani; Smitha, T

    2010-01-01

    The use of low - cost, locally available and eco-friendly adsorbents has been investigated as an ideal alternative to the current expensive methods of removing dyes from wastewater. This study investigates the potential use of activated carbon prepared from the Annona squmosa seed for the removal of methylene blue (MB) , methyl red (MR) and malachite green (MG) dyes from simulated wastewater. Adsorption of MB, MR and MG dyes on the Annona squmosa seed showed highest values at around pH 7.0, a...

  9. Tritium Specific Adsorption Simulation Utilizing the OSPREY Model

    Energy Technology Data Exchange (ETDEWEB)

    Veronica Rutledge; Lawrence Tavlarides; Ronghong Lin; Austin Ladshaw

    2013-09-01

    During the processing of used nuclear fuel, volatile radionuclides will be discharged to the atmosphere if no recovery processes are in place to limit their release. The volatile radionuclides of concern are 3H, 14C, 85Kr, and 129I. Methods are being developed, via adsorption and absorption unit operations, to capture these radionuclides. It is necessary to model these unit operations to aid in the evaluation of technologies and in the future development of an advanced used nuclear fuel processing plant. A collaboration between Fuel Cycle Research and Development Offgas Sigma Team member INL and a NEUP grant including ORNL, Syracuse University, and Georgia Institute of Technology has been formed to develop off gas models and support off gas research. This report is discusses the development of a tritium specific adsorption model. Using the OSPREY model and integrating it with a fundamental level isotherm model developed under and experimental data provided by the NEUP grant, the tritium specific adsorption model was developed.

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

    International Nuclear Information System (INIS)

    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.

  11. Modeling of the Adiabatic and Isothermal Methanation Process

    Science.gov (United States)

    Porubova, Jekaterina; Bazbauers, Gatis; Markova, Darja

    2011-01-01

    Increased use of biomass offers one of the ways to reduce anthropogenic impact on the environment. Using various biomass conversion processes, it is possible to obtain different types of fuels: • solid, e.g. bio-carbon; • liquid, e.g. biodiesel and ethanol; • gaseous, e.g. biomethane. Biomethane can be used in the transport and energy sector, and the total methane production efficiency can reach 65%. By modeling adiabatic and isothermal methanation processes, the most effective one from the methane production point of view is defined. Influence of the process parameters on the overall efficiency of the methane production is determined.

  12. Non-isothermal plasticity model for cyclic behaviour of soils.

    OpenAIRE

    Laloui, L.; Cekerevac, C.

    2008-01-01

    On the one hand, it has been observed that liquefaction- induced shear deformation of soils accumulates in a cycle- by-cycle pattern. On the other hand, it is known that heating could induce plastic hardening. This study deals with the constitutive modelling of the effect that heat may have on the cyclic mechanical properties of cohesive soils, a relatively new area of interest in soil mechanics. In this paper, after a presentation of the thermo-mechanical framework, a non-isothermal pl...

  13. Off-gas adsorption model and simulation - OSPREY

    International Nuclear Information System (INIS)

    A capability of accurately simulating the dynamic behavior of advanced fuel cycle separation processes is expected to provide substantial cost savings and many technical benefits. To support this capability, a modeling effort focused on the off-gas treatment system of a used nuclear fuel recycling facility is in progress. The off-gas separation consists of a series of scrubbers and adsorption beds to capture constituents of interest. Dynamic models are being developed to simulate each unit operation involved so each unit operation can be used as a stand-alone model and in series with multiple others. Currently, an adsorption model has been developed within Multi-physics Object Oriented Simulation Environment (MOOSE) developed at the Idaho National Laboratory (INL). Off-gas Separation and Recovery (OSPREY) models the adsorption of offgas constituents for dispersed plug flow in a packed bed under non-isothermal and non-isobaric conditions. Inputs to the model include gas composition, sorbent and column properties, equilibrium and kinetic data, and inlet conditions. The simulation outputs component concentrations along the column length as a function of time from which breakthrough data can be obtained. The breakthrough data can be used to determine bed capacity, which in turn can be used to size columns. In addition to concentration data, the model predicts temperature along the column length as a function of time and pressure drop along the column length. A description of the OSPREY model, results from krypton adsorption modeling and plans for modeling the behavior of iodine, xenon, and tritium will be discussed. (author)

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

    Science.gov (United States)

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

    2011-11-01

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

  15. Adsorption of Pentachlorophenol onto Oxide and Clay Minerals: Surface Reaction Model and Environmental Implications

    Institute of Scientific and Technical Information of China (English)

    WU Daqing; DIAO Guiyi; YUAN Peng; PENG Jinlian

    2006-01-01

    The adsorption of pentachlorophenol (PCP) onto quartz, kaolinite, illite, montmorillonite and iron oxides has been investigated by batch equilibrium techniques. The pH-dependent isotherms are curves with peak values, the position of which is at about pH= 5-6 depending on the mineral species. Based on distribution of both speciation of surface hydroxyls on minerals and PCP in solution a surface reaction model involving surface complexation and surface electrostatic attraction is presented to fit the pH-dependent isotherms, and both reaction constants are calculated. The results show that on quartz and phyllosilicate minerals the predominant adsorption reaction is surface complexation,meanwhile both of surface electrostatic attraction and surface complexation are involved on the iron oxide minerals. The reaction constants of surface electrostatic adsorption are usually one to three orders in magnitude, larger than that of surface complexation. The concentration-dependent isotherms can be well fitted by Langmuir equation with the correlation coefficient R>0.93 for kaolinite and iron oxides. The maximum adsorption is found in the order: hematite > lepidocrocite > goethite > kaolinite >quartz > montmorillonite ≈ illite, which can be interpreted by consideration of both reaction mechanism and surface hydroxyl density. The significant adsorption of PCP onto mineral surfaces suggests that clay and iron oxide minerals will play an important role as HIOCs are adsorbed in laterite or latertoid soil, which is widespread in South China.

  16. Modeling of the thermal effects of hydrogen adsorption on activated carbon

    Energy Technology Data Exchange (ETDEWEB)

    Richard, M.-A.; Chahine, R. [Univ. du Quebec a Trois-Rivieres, Inst. de recherche sur l' hydrogene, Trois-Rivieres, Quebec (Canada)]. E-mail: marc-andre.richard@uqtr.ca

    2006-07-01

    'Full text:' Heat management is one of the most critical issues for the design of efficient adsorption-based storage of hydrogen. We present simulations of mass and energy balance for hydrogen and nitrogen adsorption on activated carbon over wide temperature and pressure ranges. First, the Dubinin-Astakhov (DA) model is adapted to model excess hydrogen and nitrogen adsorption isotherms at high pressures and supercritical temperatures assuming a constant microporous adsorption volume. The five parameter modified D-A adsorption model is shown to fit the experimental data over the temperature range (35 K-293 K) for hydrogen and (93 K-298 K) for nitrogen and pressure range (0-6 MPa) within the experimental uncertainties of the measurement system. We derive the thermodynamic properties of the adsorbed phase from this analytical expression of the measured data. The mass and energy rate balance equations in a microporous adsorbent/adsorbate system are then presented and validated with nitrogen desorption experiments. Finally, simulations of adiabatic and isothermal filling of adsorption-based hydrogen storage are presented and discussed. (author)

  17. A transverse isotropic model for microporous solids: Application to coal matrix adsorption and swelling

    Science.gov (United States)

    Espinoza, D. N.; Vandamme, M.; Dangla, P.; Pereira, J.-M.; Vidal-Gilbert, S.

    2013-12-01

    Understanding the adsorption-induced swelling in coal is critical for predictable and enhanced coal bed methane production. The coal matrix is a natural anisotropic disordered microporous solid. We develop an elastic transverse isotropic poromechanical model for microporous solids which couples adsorption and strain through adsorption stress functions and expresses the adsorption isotherm as a multivariate function depending on fluid pressure and solid strains. Experimental data from the literature help invert the anisotropic adsorptive-mechanical properties of Brzeszcze coal samples exposed to CO2. The main findings include the following: (1) adsorption-induced swelling can be modeled by including fluid-specific and pressure-dependent adsorption stress functions into equilibrium equations, (2) modeling results suggest that swelling anisotropy is mostly caused by anisotropy of the solid mechanical properties, and (3) the total amount of adsorbed gas measured by immersing coal in the adsorbate overestimates adsorption amount compared to in situ conditions up to ˜20%. The developed fully coupled model can be upscaled to determine the coal seam permeability through permeability-stress relationships.

  18. Adsorption-transport modeling of anions through PVD membrane in the presence of the screen phenomenon

    Science.gov (United States)

    Madaeni, S. S.; Salehi, E.

    2009-01-01

    A mathematical model for transport and adsorption of chloride and sulphate ions through PVD membrane is presented at two pressures; 8 and 15 bar and 40 °C. The PVD membrane is negatively charged. Saturated brine containing NaCl with the concentration higher than 97% was challenged with the membrane as the feed. Other available ions in the solution were Fe 2+, Ca 2+, Mg 2+ and SO 42-. The screen effect of the cations on the membrane surface charge facilitates the passage of the anions through the membrane without any noticeable electrostatic repulsion. Hermia blocking laws combined with experimental results indicate that the internal pore closure of the membrane by anions and cake deposition on the membrane surface by cations are the separation mechanisms. The transmission of anions through the membrane may be predicted with a simple transport equation (convection and diffusion) combined with an adsorption isotherm. Both Langmuir and Freundlich adsorption isotherms were employed due to the simplicity and validity in liquid systems. The isotherm's parameters were determined at 10 bar during the unsteady state filtration. Under this condition, the permeate flux and concentration varied sharply due to adsorption. Finally, the model was compared with the experimental rejection data. An acceptable agreement around 95% at 8 bar and 92% at 15 bar was observed between theoretical model and experimental data.

  19. Isotermas de adsorção do pedúnculo seco do caju Adsorption isotherms of the dry cashew apple

    Directory of Open Access Journals (Sweden)

    Siumara R. Alcântara

    2009-02-01

    Full Text Available A atividade de água constitui um fator importante no processo de fermentação semi-sólida, haja vista sua relação com a quantidade de água disponível ao microrganismo responsável pelo metabolismo do produto, sendo necessário à obtenção de isotermas de sorção para caracterização do substrato. Ante o exposto, objetivou-se a construção das isotermas de adsorção do pedúnculo seco do caju (Anacardium occidentale L. nas temperaturas usuais de fermentação (25, 30, 35 e 40 ºC. Ajustaram-se as isotermas com os modelos de BET, GAB, Oswin, Henderson e Smith. Observou-se que o modelo de GAB apresentou melhor ajuste, de vez que, na faixa de atividade de água que maximiza a biossíntese do microrganismo, para produção de pectinases por Aspergillus niger, a umidade do substrato deve estar acima de 35% b.s.Water activity is a very important factor in a solid state fermentation process due to its relation with the water quantity available to the microorganism that will synthesize the product. Therefore, it is necessary to obtain the sorption isotherms for the characterization of the substrate. The objective of this study is to obtain adsorption isotherms of the dry cashew apple (Anacardium occidentale L. at normal temperatures of fermentation process (25, 30, 35 e 40 ºC. Five mathematical models were fitted to the experimental data: BET, GAB, Oswin, Henderson e Smith. The GAB model was better fitted to the product. The isotherms allowed the determination of the appropriate moisture content to obtain the water activities that maximize the biosynthesis of the microorganism for the pectin production by solid state fermentation process. The moisture content of the substrate should be above 35% d.b.

  20. A novel bio-adsorbent of mint waste for dyes remediation in aqueous environments: study and modeling of isotherms for removal of methylene Blue

    Directory of Open Access Journals (Sweden)

    Tarik Ainane

    2014-09-01

    Full Text Available The objective of this study was to investigate the possibility of using mint waste as a bioadsorbent for the removal of dye (Methylen Blue from aqueous solutions. Batch adsorption studies were carried out by monitoring the pH, the bio-adsorbent dose and the initial dye concentration. Attempts have also been made to monitor the adsorption process through Langmuir, Freundlich, Dubinin-Radushkevich, and Temkin adsorption isotherm models. These results have demonstrated the immense potential of mint waste as a bioadsorbent for dyes remediation in polluted water and wastewater. Finally followed by the process of adsorption phenomenon was achieved by fourier transform infrared spectrometer (FTIR, the results shows that the adsorption is mechanical trapping.

  1. Kinetic modeling of liquid-phase adsorption of Congo red dye using guava leaf-based activated carbon

    Science.gov (United States)

    Ojedokun, Adedamola Titi; Bello, Olugbenga Solomon

    2016-02-01

    Guava leaf, a waste material, was treated and activated to prepare adsorbent. The adsorbent was characterized using Scanning Electron Microscopy (SEM), Fourier Transform Infra Red (FTIR) and Energy-Dispersive X-ray (EDX) techniques. The carbonaceous adsorbent prepared from guava leaf had appreciable carbon content (86.84 %). The adsorption of Congo red dye onto guava leaf-based activated carbon (GLAC) was studied in this research. Experimental data were analyzed by four different model equations: Langmuir, Freundlich, Temkin and Dubinin-Radushkevich isotherms and it was found to fit Freundlich equation most. Adsorption rate constants were determined using pseudo-first-order, pseudo-second-order, Elovich and intraparticle diffusion model equations. The results clearly showed that the adsorption of CR dye onto GLAC followed pseudo-second-order kinetic model. Intraparticle diffusion was involved in the adsorption process. The mean energy of adsorption calculated from D-R isotherm confirmed the involvement of physical adsorption. Thermodynamic parameters were obtained and it was found that the adsorption of CR dye onto GLAC was an exothermic and spontaneous process at the temperatures under investigation. The maximum adsorption of CR dye by GLAC was found to be 47.62 mg/g. The study shows that GLAC is an effective adsorbent for the adsorption of CR dye from aqueous solution.

  2. 几种高油脂食品等温吸湿规律的研究%Study on isotherm adsorption of several kinds of high-fat food

    Institute of Scientific and Technical Information of China (English)

    杨琴; 范柳萍

    2012-01-01

    Four kinds of fatty food including vacuum fried lotus seed ,vacuum fried carrot chips, carrot chips fried at atmospheric conditions and potato chips fried at atmospheric conditions were employed to investigate the isotherm adsorption.The data of 4 kinds of fatty food were tested,according to the commonly used 5 kinds of isothermal adsorption model. The result showed that the most suitable isothermal adsorption model was the Peleg model and the order of the suitability was vacuum fried carrot chips,carrot chips fried at atmospheric conditions ,vacuum fried lotus seed ,and potato chips fried at atmospheric conditions.%研究了真空油炸莲子、真空油炸胡萝卜脆片、常压油炸胡萝卜脆片、常压油炸土豆脆片4种高脂食品的吸湿等温曲线。根据常用的5种等温吸附模型对4种物料的吸湿实验数据进行了拟合,比较了其拟合程度(R2)。结果表明,25℃条件下,4种高脂物料最适合的等温吸附模型都是Peleg模型,且拟合程度依次为真空油炸胡萝卜脆片、常压油炸胡萝卜脆片、真空油炸莲子、常压油炸土豆脆片。

  3. Determinación de la adsorción de cadmio mediante isotermas de adsorción en suelos agrícolas venezolanos Determination of the adsorption of cadmium by adsorption isotherms in agricultural soils venezuelans

    Directory of Open Access Journals (Sweden)

    Nereida Sánchez

    2011-04-01

    Full Text Available El cadmio es un metal pesado que tiende a acumularse en la superficie del suelo. En los últimos años, las actividades antropogénicas han ocasionado un incremento en los niveles de este metal en suelos agrícolas generando gran preocupación ambiental debido a su movilidad y lixiviación en el perfil del suelo y a la facilidad con que es absorbido por las plantas. El objetivo de este trabajo fue determinar la capacidad de adsorción de cadmio, de cuatro suelos venezolanos de uso agrícola con diferencias texturales. Para determinar la capacidad de adsorción del metal en cada suelo, inicialmente se determinó el tiempo óptimo de agitación; el cual fue de 2 horas y la relación suelo-solución enriquecedora de Cd; la cual fue de 1:50. Con estos parámetros se elaboraron las isotermas de adsorción para los suelos y se compararon los modelos de Freundlich y Langmuir. Los resultados mostraron que el modelo matemático de Freundlich es el que mejor describe la cinética de la reacción y la capacidad de adsorción de Cd por los suelos, siendo los que poseen mayores contenidos de arcilla, MO y pH ácidos los de mayor capacidad de adsorción.Cadmium is a heavy metal which tends to accumulate in the soil surface. In recent years, anthropogenic activities have caused an increase of the levels of this metal in agricultural soils causing great environmental concern due to their mobility and leaching in the soil profile and the ease way to be absorbed by plants. The purpose of this study was to determine the adsorption capacity of cadmium in four Venezuelan agricultural soils with different texture. To determine the adsorption capacity of Cd in each soil, first of all the optimal time of stirring was determined, which was two hours and the soilenriching solution of Cd, which was (1/50. With these parameters, cadmium adsorption isotherms for all soils were developed and compared with Freundlich and Langmuir models. The data showed that the Freundlich

  4. Isothermal CFD-model of Peirce-Smith converting process

    Energy Technology Data Exchange (ETDEWEB)

    Vaarno, J.; Pitkaelae, J.; Ahokainen, T.; Jokilaakso, A.

    1997-12-31

    The Peirce-Smith converter has been a dominating copper and nickel matte refining process since 1905. Due to extremely difficult process conditions, very little measured data has been available for studying interactions of the gas injection and molten sulphide matte. Detailed information on fluid dynamics of the gas injection is needed in solving gas injection related problems like refractory wear, accretion growth and tuyere blockage as well as optimising the efficiency of momentum and mass transfer created by the gas jets. A commercial CFD-code PHOENICS was used to solve isothermal flow field of gas and liquid in a Peirce-Smith converter. An Euler-Euler based algorithm was chosen for modelling fluid dynamics and evaluating controlling forces of a submerged gas injection generally. Predictions were made with a {kappa}-{epsilon} turbulence model in the body fitted co-ordinate system. The model has been verified with a 1/4 scale water model, and a parametric study with the mathematical model of submerged gas injection was made for the PS-process and the ladle injection processes. Limits of the modelling technique used were recognised, but calculated results indicates that the present model predicts the general flow field with reasonable accuracy and it can be used as input for more detailed mathematical models of gas plumes. Predicted bubble distribution, pattern of the flow field and magnitude of flow velocities were also used to evaluate scaling factors of physical models and general flow conditions of an industrial PS-converter. (orig.) 28 refs.

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

    International Nuclear Information System (INIS)

    Highlights: • βCD-BIMOTs-TDI exhibits macropore size (77.66 nm) with 1.254 m2 g−1 surface area. • Freundlich isotherm and pseudo-second order kinetics fit well the adsorption process. • Removal was optimum at pH 6 with 83% and reached equilibrium at 80 mg L−1. • Entropy (ΔS°) and heat of adsorption (ΔH°) estimated as −55.99 J/K mol and −18.10 J/mol. • Inclusion complex and π–π interaction were found to be dominant at pH 6. -- Abstract: 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 m2 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

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

    Energy Technology Data Exchange (ETDEWEB)

    Raoov, Muggundha [University of Malaya Centre for Ionic Liquids, Department of Chemistry, Faculty of Science, University of Malaya, Kuala Lumpur 50603 (Malaysia); Department of Chemistry, Faculty of Science, University of Malaya, Kuala Lumpur 50603 (Malaysia); Advanced Medical and Dental Institute, University of Science Malaysia, No. 1–8 (Lot 8), Persiaran Seksyen 4/1, Bandar Putra Bertam, Kepala Batas, Pulau Pinang 13200 (Malaysia); Mohamad, Sharifah, E-mail: sharifahm@um.edu.my [University of Malaya Centre for Ionic Liquids, Department of Chemistry, Faculty of Science, University of Malaya, Kuala Lumpur 50603 (Malaysia); Department of Chemistry, Faculty of Science, University of Malaya, Kuala Lumpur 50603 (Malaysia); Abas, Mohd Radzi [Department of Chemistry, Faculty of Science, University of Malaya, Kuala Lumpur 50603 (Malaysia)

    2013-12-15

    Highlights: • βCD-BIMOTs-TDI exhibits macropore size (77.66 nm) with 1.254 m{sup 2} g{sup −1} surface area. • Freundlich isotherm and pseudo-second order kinetics fit well the adsorption process. • Removal was optimum at pH 6 with 83% and reached equilibrium at 80 mg L{sup −1}. • Entropy (ΔS°) and heat of adsorption (ΔH°) estimated as −55.99 J/K mol and −18.10 J/mol. • Inclusion complex and π–π interaction were found to be dominant at pH 6. -- Abstract: 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{sup 2} g{sup −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. Isotermas de adsorção de cádmio em solos ácricos Cadmium adsorption isotherms in acric oxisols

    Directory of Open Access Journals (Sweden)

    Nivea M.P. Dias

    2001-05-01

    Anionic "Rhodic" Acrudox (RA and an Anionic "Xanthic" Acrudox (XA. In order to quantify the adsorbed cadmium, 2 g of oven-dried soil were stirred in polyethylene tubes, for 24 h, with 20 mL of a Ca(NO32 0.0025 mol L-1 solution containing different quantities of cadmium (5, 10, 15, 25, 50, 75, 100, 125, 150, 175 e 200 mg dm-3. Langmuir and Freundlich constants were estimated by nonlinear regressions. Cadmium adsorption was well described by both Langmuir and Freundlich models for all soils. RK exhibited the highest values of maximum cadmium adsorption, obtained from Langmuir isotherm, and the least values were from the subsurface layers of the Oxisols. Both equations described well the cadmium adsorption, mainly when the concentration of cadmium added was higher than 50 mg dm-3.

  8. Pressure swing adsorption modeling of acetone and toluene on activated carbon

    Institute of Scientific and Technical Information of China (English)

    唐琳; 李立清; 邢俊东; 刘峥; 姚小龙

    2013-01-01

    A five steps pressure swing adsorption process was designed for acetone and toluene mixtures separation and recovery. Dynamic distributions of gas phase content and temperature were investigated. Based on the theory of Soret and Dufour, a non-isothermal mathematical model was developed to simulate the PSA process. Effects of heat and mass transfer coefficients were studied. The coupled Soret and Dufour effects were also evaluated. It is found that the heat transfer coefficient has little effect on mass transfer in adsorption stage. However, it has some impacts in desorption stage. The maximum value of C/C0 increases by about 25% as heat transfer coefficient decreases. The temperature variation is less than 0.05 K with the change of mass transfer coefficient, so that the effect of mass transfer coefficient on heat transfer can be ignored. It is also concluded that the Soret and Dufour coupled effects are not obvious in pressure swing adsorption compared with fixed-bed adsorption.

  9. State of the art in establishing computed models of adsorption processes to serve as a basis of radionuclide migration assessment for safety analyses

    International Nuclear Information System (INIS)

    An important point in safety analysis of an underground repository is adsorption of radionuclides in the overlying cover. Adsorption may be judged according to experimental results or to model calculations. Because of the reliability aspired in safety analyses, it is necessary to strengthen experimental results by theoretical calculations. At the time, there is no single thermodynamic model of adsorption to be agreed on. Therefore, this work reviews existing equilibrium models of adsorption. Limitations of the Kd-concept and of adsorption-isotherms according to Freundlich and Langmuir are mentioned. The surface ionisation and complexation edl model is explained in full as is the criticism of this model. The application is stressed of simple surface complexation models to adsorption experiments in natural systems as is experimental and modelling work according to systems from Gorleben. Hints are given how to deal with modelling of adsorption related to Gorleben systems in the future. (orig.)

  10. Adsorption isotherm and inhibition effect of a synthesized di-(m-Formylphenol)-1,2-cyclohexandiimine on corrosion of steel X52 in HCl solution

    Institute of Scientific and Technical Information of China (English)

    A karimi; I Danaee; H Eskandari; M RashvanAvei

    2016-01-01

    The potential of di-(m-Formylphenol)-1,2-cyclohexandiimine as an environmentally friendly corrosion inhibitor for steel was investigated in 1 mol/L HCl using potentiodynamic polarization, electrochemical impedance spectroscopy and chronoamperometry measurements. All electrochemical measurements suggest that this compound is an excellent corrosion inhibitor for mild steel and the inhibition efficiency increases with the increase in inhibitor concentration. The effect of temperature on the corrosion behavior of mild steel with the addition of the Schiff base was studied in the temperature range from 25 °C to 65 °C. It is found that the adsorption of this inhibitor follows the Langmuir adsorption isotherms. The value of activation energy and the thermodynamic parameters such asΔHads,ΔSads,Kads andΔGads were calculated by the corrosion currents at different temperatures using the adsorption isotherm. The morphology of mild steel surface in the absence and presence of inhibitor was examined by scanning electron microscopy (SEM) images.

  11. Adsorptive removal of lead and cadmium ions using Cross -linked CMC Schiff base: Isotherm, Kinetics and Catalytic Activity

    Directory of Open Access Journals (Sweden)

    P. Moganavally

    2016-03-01

    Full Text Available Water plays a vital role to human and other living organisms. Due to the effluent coming from chemical industries, the industrial activity, contamination of ground water level is goes on increasing nowadays. Therefore, there is a need to develop technologies that can remove toxic pollutants in wastewater. Hence the cross linked Carboxymethyl chitosan(CMC/ 2,3-dimethoxy Benzaldehyde Schiff base complex has been synthesized and characterized by using FT-IR and SEM analysis. All these results revealed that cross linked Schiff base has formed with high adsorption capacity. The prepared effective adsorbent used for the removal of heavy metals like lead (II and cadmium (II ions from aqueous solution and the adsorption data follow the Freundlich model, which follows pseudo first order kinetics. Effect of various parameters like solution pH, adsorbent dose and contact time for the removal of heavy metals has been studied. The synthesized sample undergoes catalytic oxidation process significantly at 24 hrs. The results showed that cross linked Schiff base is an effective, eco-friendly, low-cost adsorbent.

  12. Isotherm-Based Thermodynamic Models for Solute Activities of Organic Acids with Consideration of Partial Dissociation.

    Science.gov (United States)

    Nandy, Lucy; Ohm, Peter B; Dutcher, Cari S

    2016-06-23

    Organic acids make up a significant fraction of the organic mass in atmospheric aerosol particles. The calculation of gas-liquid-solid equilibrium partitioning of the organic acid is therefore critical for accurate determination of atmospheric aerosol physicochemical properties and processes such as new particle formation and activation to cloud condensation nuclei. Previously, an adsorption isotherm-based statistical thermodynamic model was developed for capturing solute concentration-activity relationships for multicomponent aqueous solutions over the entire concentration range (Dutcher et al. J. Phys. Chem. C/A 2011, 2012, 2013), with model parameters for energies of adsorption successfully related to dipole-dipole electrostatic forces in solute-solvent and solvent-solvent interactions for both electrolytes and organics (Ohm et al. J. Phys. Chem. A 2015). However, careful attention is needed for weakly dissociating semivolatile organic acids. Dicarboxylic acids, such as malonic acid and glutaric acid are treated here as a mixture of nondissociated organic solute (HA) and dissociated solute (H(+) + A(-)). It was found that the apparent dissociation was greater than that predicted by known dissociation constants alone, emphasizing the effect of dissociation on osmotic and activity coefficient predictions. To avoid additional parametrization from the mixture approach, an expression was used to relate the Debye-Hückel hard-core collision diameter to the adjustable solute-solvent intermolecular distance. An improved reference state treatment for electrolyte-organic aqueous mixtures, such as that observed here with partial dissociation, has also been proposed. This work results in predictive correlations for estimation of organic acid and water activities for which there is little or no activity data. PMID:27222917

  13. Development of facile property calculation model for adsorption chillers based on equilibrium adsorption cycle

    Science.gov (United States)

    Yano, Masato; Hirose, Kenji; Yoshikawa, Minoru; Thermal management technology Team

    Facile property calculation model for adsorption chillers was developed based on equilibrium adsorption cycles. Adsorption chillers are one of promising systems that can use heat energy efficiently because adsorption chillers can generate cooling energy using relatively low temperature heat energy. Properties of adsorption chillers are determined by heat source temperatures, adsorption/desorption properties of adsorbent, and kinetics such as heat transfer rate and adsorption/desorption rate etc. In our model, dependence of adsorption chiller properties on heat source temperatures was represented using approximated equilibrium adsorption cycles instead of solving conventional time-dependent differential equations for temperature changes. In addition to equilibrium cycle calculations, we calculated time constants for temperature changes as functions of heat source temperatures, which represent differences between equilibrium cycles and real cycles that stemmed from kinetic adsorption processes. We found that the present approximated equilibrium model could calculate properties of adsorption chillers (driving energies, cooling energies, and COP etc.) under various driving conditions quickly and accurately within average errors of 6% compared to experimental data.

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

    Science.gov (United States)

    Feng, L; Andrade, J D

    1994-04-01

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

  15. Removal of Pyrethrin from Aqueous Effluents by Adsorptive Micellar Flocculation

    Directory of Open Access Journals (Sweden)

    Pardon K. Kuipa

    2015-01-01

    Full Text Available The equilibrium adsorption of pyrethrin onto aggregates formed by the flocculation of micelles of the surfactant sodium dodecyl sulphate (SDS with aluminium sulphate is reported. The experimental results were analysed using different adsorption isotherms (Langmuir, Freundlich, Redlich-Peterson, Sips, Radke-Prausnitz, Temkin, linear equilibrium, and the Dubin-Radushkevich isotherms. The Freundlich and linear equilibrium isotherms best describe the adsorption of pyrethrin onto SDS micellar flocs, with the Freundlich adsorption constant, KF, and the mass distribution coefficient, KD, of 64.266 ((mg/g(L/mg1/n and 119.65 L/g, respectively. Applicability of the Freundlich adsorption model suggests that heterogeneous surface adsorption affects the adsorption. The mean free energy value estimated using the Dubinin-Radushkevich isotherm was 0.136 kJ/mol indicating that physisorption may be predominant in the adsorption process.

  16. An experimental design approach for modeling As(V) adsorption from aqueous solution by activated carbon.

    Science.gov (United States)

    Bakkal Gula, C; Bilgin Simsek, E; Duranoglu, D; Beker, U

    2015-01-01

    The present paper discusses response surface methodology as an efficient approach for predictive model building and optimization of As(V) adsorption on activated carbon derived from a food industry waste: peach stones. The objectives of the study are application of a three-factor 2³ full factorial and central composite design technique for maximizing As(V) removal by produced activated carbon, and examination of the interactive effects of three independent variables (i.e., solution pH, temperature, and initial concentration) on As(V) adsorption capacity. Adsorption equilibrium was investigated by using Langmuir, Freundlich, and Dubinin-Radushkevich isotherm models. First-order and second-order kinetic equations were used for modeling of adsorption kinetics. Thermodynamic parameters (ΔG °, ΔH °, and ΔS °) were calculated and used to explain the As(V) adsorption mechanism. The negative value of ΔH (-7.778 kJ mol⁻¹) supported the exothermic nature of the sorption process and the Gibbs free energy values (ΔG°) were found to be negative, which indicates that the As(V) adsorption is feasible and spontaneous. PMID:25633943

  17. Simulations of isothermal processes in the semilocalized transition (SLT) model of thermoluminescence (TL)

    International Nuclear Information System (INIS)

    Semilocalized transition (SLT) kinetic models for thermoluminescence (TL) contain characteristics of both a localized transition (LT) and of a single trap model. TL glow curves within SLT models typically contain contain two TL peaks; the first peak corresponds to the intra-pair luminescence due to LTs and the second TL peak corresponds to delocalized transitions involving the conduction band (CB). The latter delocalized TL peak has also been found to exhibit non-typical double-peak structure, in which the main TL peak is accompanied by a smaller peak called the displacement peak. This paper describes the simulation of isothermal luminescence signals using a previously published SLT model. It is found that these simulated isothermal signals exhibit several unusual time characteristics. Isothermal signals associated with the LTs follow first order kinetics and are therefore described by single decaying exponentials. However, isothermal signals associated with delocalized transitions show a non-typical complex structure characterized by several time regions with different decay characteristics. For certain values of the parameters in the SLT model the isothermal signals can also exhibit non-monotonic behaviour as a function of time. Another notable result from the simulations is that isothermal currents (which are proportional to the concentration of electrons in the CB) can persist for very long periods of time, even after the apparent termination of the isothermal luminescence signals. It is concluded that isothermal processes described by the SLT model depend strongly on the presence of SLTs, in contrast to previous studies using Monte Carlo simulations, which showed a weak interdependence of these phenomena. The simulations in this paper suggest that isothermal experiments offer a sensitive method for detecting the presence of SLTs in a dosimetric material.

  18. Simulations of isothermal processes in the semilocalized transition (SLT) model of thermoluminescence (TL)

    Energy Technology Data Exchange (ETDEWEB)

    Pagonis, Vasilis [Physics Department, McDaniel College, Westminster, MD 21157 (United States); Kulp, Christopher, E-mail: vpagonis@mcdaniel.ed [Department of Astronomy and Physics, Lycoming College, Williamsport, PA 17701 (United States)

    2010-05-05

    Semilocalized transition (SLT) kinetic models for thermoluminescence (TL) contain characteristics of both a localized transition (LT) and of a single trap model. TL glow curves within SLT models typically contain contain two TL peaks; the first peak corresponds to the intra-pair luminescence due to LTs and the second TL peak corresponds to delocalized transitions involving the conduction band (CB). The latter delocalized TL peak has also been found to exhibit non-typical double-peak structure, in which the main TL peak is accompanied by a smaller peak called the displacement peak. This paper describes the simulation of isothermal luminescence signals using a previously published SLT model. It is found that these simulated isothermal signals exhibit several unusual time characteristics. Isothermal signals associated with the LTs follow first order kinetics and are therefore described by single decaying exponentials. However, isothermal signals associated with delocalized transitions show a non-typical complex structure characterized by several time regions with different decay characteristics. For certain values of the parameters in the SLT model the isothermal signals can also exhibit non-monotonic behaviour as a function of time. Another notable result from the simulations is that isothermal currents (which are proportional to the concentration of electrons in the CB) can persist for very long periods of time, even after the apparent termination of the isothermal luminescence signals. It is concluded that isothermal processes described by the SLT model depend strongly on the presence of SLTs, in contrast to previous studies using Monte Carlo simulations, which showed a weak interdependence of these phenomena. The simulations in this paper suggest that isothermal experiments offer a sensitive method for detecting the presence of SLTs in a dosimetric material.

  19. Modeling adsorption of liquid mixtures on porous materials

    DEFF Research Database (Denmark)

    Monsalvo, Matias Alfonso; Shapiro, Alexander

    2009-01-01

    of the MPTA onto liquids has been tested on experimental binary and ternary adsorption data. We show that, for the set of experimental data considered in this work, the MPTA model is capable of correlating binary adsorption equilibria. Based on binary adsorption data, the theory can then predict...... ternary adsorption equilibria. Good agreement with the theoretical predictions is achieved in most of the cases. Some limitations of the model are also discussed....

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

    Science.gov (United States)

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

    2011-09-16

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

  1. Isotherm of fluoride ion adsorption by zeolite andγ-alumina:comparison of linear and non-linear methods%沸石与γ-氧化铝吸附氟离子等温线的线性和非线性方法比较研究

    Institute of Scientific and Technical Information of China (English)

    陈安浩; 磨季云; 郝琨妍

    2014-01-01

    采用线性和非线性方法研究沸石与γ-氧化铝对水中氟离子吸附等温线的拟合形式,并分析比较了两种数据处理方法的优劣。结果表明,非线性方法提供了一种更准确的方法来确定最佳的吸附等温线模型;沸石吸附氟离子的实验数据与Redlich-Peterson、Langmiur等温线模型拟合较好;γ-氧化铝的吸附氟离子实验数据与Redlich-Peterson等温线模型拟合较好。%Linear and non-linear methods were adopted respectively to study the fitting degree of the adsorption of fluoride ions in water by zeolite and γ-alumina ,and the advantages as well as disadvan-tages of the two methods in data processing were compared .The results show that non-linear method is more accurate in determining the optimum adsorption isotherm model ,and the experimental data of zeolite adsorption of fluoride ions fits better with Redlich Peterson and Langmiur isotherm model , while the experimental data of γ-alumina adsorption of fluoride ions fits better with Redlich Peterson isotherm model .

  2. Adsorption hysteresis for a slit-like pore model

    Science.gov (United States)

    Kutarov, V. V.; Tarasevich, Yu. I.; Aksenenko, E. V.; Ivanova, Z. G.

    2011-07-01

    The Frenkel-Halsey-Hill equation is used to describe the adsorption branch of a hysteresis loop upon polylayer adsorption with an H3 loop according to IUPAC nomenclature. The equation for the desorption branch of a hysteresis loop is derived from a combined solution to the equation for the Gibbs potential change, given the adsorbent swelling and pore connectivity function, and the Laplace equation taken for the conditions of infinitely elongated meniscus. This equation is shown to connect the adsorbate relative pressure in a bulk phase for the desorption branch of a hysteresis loop with the key parameters of the adsorption system. The equation obtained was verified by a water adsorption isotherm on natural mineral schungite.

  3. 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

    International Nuclear Information System (INIS)

    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 1 h in both the cases, whereas, equilibrium establishment takes about 3-4 h. 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

  4. Finite Element Modeling of Adsorption Processes for Gas Separation and Purification

    International Nuclear Information System (INIS)

    Pacific Northwest National Laboratory (PNNL) has expertise in the design and fabrication of automated radioxenon collection systems for nuclear explosion monitoring. In developing new systems there is an ever present need to reduce size, power consumption and complexity. Most of these systems have used adsorption based techniques for gas collection and/or concentration and purification. These processes include pressure swing adsorption, vacuum swing adsorption, temperature swing adsorption, gas chromatography and hybrid processes that combine elements of these techniques. To better understand these processes, and help with the development of improved hardware, a finite element software package (COMSOL Multiphysics) has been used to develop complex models of these adsorption based operations. The partial differential equations used include a mass balance for each gas species and adsorbed species along with a convection conduction energy balance equation. These equations in conjunction with multicomponent temperature dependent isotherm models are capable of simulating separation processes ranging from complex multibed PSA processes, and multicomponent temperature programmed gas chromatography, to simple two component temperature swing adsorption. These numerical simulations have been a valuable tool for assessing the capability of proposed processes and optimizing hardware and process parameters.

  5. Modeling the Adsorption of Hydrophobic Ethoxylated Urethane (HEUR) Thickeners onto Latex Surfaces using Self-Consistent Field Theory

    Science.gov (United States)

    Ginzburg, Valeriy; van Dyk, Antony; Chatterjee, Tirtha; Wang, Shihu; Larson, Ronald

    2015-03-01

    Hydrophobic Ethoxylated Urethane (HEUR) polymers are widely used as rheology modifiers (thickeners) in waterborne latex paints. Recently, it has been shown that the thickening effect of HEURs in paints is largely determined by their adsorption onto latex surfaces, this adsorption being a function of polymer structure, latex surface chemistry, and total available latex surface. Here, we describe the application of Self-Consistent Field Theory (SCFT) to calculate adsorption isotherms of several model HEURs onto ideal hydrophobic latex surfaces. Unlike earlier SCFT studies of adsorption, we explicitly take into account the role of HEUR micelles and competition between adsorption and micellization. The results are compared with experimental data and coarse-grained molecular dynamic (CG-MD) simulations, and good qualitative and semi-quantitative agreement is found. This work was supported by The Dow Chemical Company.

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

    Science.gov (United States)

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

    2009-01-01

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

  7. Ordering kinetics in model systems with inhibited interfacial adsorption

    DEFF Research Database (Denmark)

    Willart, J.-F.; Mouritsen, Ole G.; Naudts, J.; Descamps, M.

    1992-01-01

    The ordering kinetics in two-dimensional Ising-like spin moels with inhibited interfacial adsorption are studied by computer-simulation calculations. The inhibited interfacial adsorption is modeled by a particular interfacial adsorption condition on the structure of the domain wall between...

  8. Generalized isothermal models with strange equation of state

    Indian Academy of Sciences (India)

    S D Maharaj; S Thirukkanesh

    2009-03-01

    We consider the linear equation of state for matter distributions that may be applied to strange stars with quark matter. In our general approach the compact relativistic body allows for anisotropic pressures in the presence of the electromagnetic field. New exact solutions are found to the Einstein–Maxwell system. A particular case is shown to be regular at the stellar centre. In the isotropic limit we regain the general relativistic isothermal Universe. We show that the mass corresponds to the values obtained previously for quark stars when anisotropy and charge are present.

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

    Science.gov (United States)

    Lazarevic, Natasa; Adnadjevic, Borivoj; Jovanovic, Jelena

    2011-07-01

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

  10. Optimization and Modeling of Hexavalent Chromium Removal from Aqueous Solution Via Adsorption on Multiwalled Carbon Nanotubes

    Directory of Open Access Journals (Sweden)

    Mina Gholipour

    2011-09-01

    Full Text Available Hexavalent chromium and its derivatives are potential pollutant due to their mortal affects. Therefore, It is essential to remove these components from wastewaters before disposal. Adsorption can be effective and versatile method for removing of hexavalent chromium. In this article, removal of hexavalent chromium via adsorption on multiwalled carbon nanotubes was investigated as a function of adsorbent dosage, initial solution pH, initial Cr(VI concentrations, contact time and temperature. The batch experiments were conducted at 3 different temperatures (17, 27 and 37ºC and shows that Cr (VI removal obeys pseudo-second order rate equation. Rate constant (K values in 3 temperatures, pre-exponential factor and adsorption activation energy (E was also obtained. The sorption data fitted well with Freundlich isotherm adsorption model. Thermodynamic parameters such as Gibbs free energy (ΔGº, enthalpy (ΔHº and entropy (ΔSº for Cr(VI adsorption were estimated and Results suggest that the adsorption process is a spontaneous and endothermic.

  11. Dynamic Evolution Model of Isothermal Voids and Shocks

    CERN Document Server

    Lou, Yu-Qing

    2009-01-01

    We explore self-similar hydrodynamic evolution of central voids embedded in an isothermal gas of spherical symmetry under the self-gravity. More specifically, we study voids expanding at constant radial speeds in an isothermal gas and construct all types of possible void solutions without or with shocks in surrounding envelopes. We examine properties of void boundaries and outer envelopes. Voids without shocks are all bounded by overdense shells and either inflows or outflows in the outer envelope may occur. These solutions, referred to as type $\\mathcal{X}$ void solutions, are further divided into subtypes $\\mathcal{X}_{\\rm I}$ and $\\mathcal{X}_{\\rm II}$ according to their characteristic behaviours across the sonic critical line (SCL). Void solutions with shocks in envelopes are referred to as type $\\mathcal{Z}$ voids and can have both dense and quasi-smooth edges. Asymptotically, outflows, breezes, inflows, accretions and static outer envelopes may all surround such type $\\mathcal{Z}$ voids. Both cases of c...

  12. Comparison of linear and non-linear models for the adsorption of fluoride onto geo-material: limonite.

    Science.gov (United States)

    Sahin, Rubina; Tapadia, Kavita

    2015-01-01

    The three widely used isotherms Langmuir, Freundlich and Temkin were examined in an experiment using fluoride (F⁻) ion adsorption on a geo-material (limonite) at four different temperatures by linear and non-linear models. Comparison of linear and non-linear regression models were given in selecting the optimum isotherm for the experimental results. The coefficient of determination, r², was used to select the best theoretical isotherm. The four Langmuir linear equations (1, 2, 3, and 4) are discussed. Langmuir isotherm parameters obtained from the four Langmuir linear equations using the linear model differed but they were the same when using the nonlinear model. Langmuir-2 isotherm is one of the linear forms, and it had the highest coefficient of determination (r² = 0.99) compared to the other Langmuir linear equations (1, 3 and 4) in linear form, whereas, for non-linear, Langmuir-4 fitted best among all the isotherms because it had the highest coefficient of determination (r² = 0.99). The results showed that the non-linear model may be a better way to obtain the parameters. In the present work, the thermodynamic parameters show that the absorption of fluoride onto limonite is both spontaneous (ΔG 0). Scanning electron microscope and X-ray diffraction images also confirm the adsorption of F⁻ ion onto limonite. The isotherm and kinetic study reveals that limonite can be used as an adsorbent for fluoride removal. In future we can develop new technology for fluoride removal in large scale by using limonite which is cost-effective, eco-friendly and is easily available in the study area. PMID:26676015

  13. A new adsorption isotherm for C5 hydrocarbons on metal–organic framework Cu3(BTC)2

    Czech Academy of Sciences Publication Activity Database

    Zukal, Arnošt; Kubů, Martin

    2015-01-01

    Roč. 21, 1-2 (2015), s. 99-105. ISSN 0929-5607 R&D Projects: GA ČR GA14-07101S Institutional support: RVO:61388955 Keywords : Cu3(BTC)2 * adsorption * C5 hydrocarbons Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 1.771, year: 2014

  14. A dynamic multi-level model for adsorptive solar cooling

    OpenAIRE

    Santori, Giulio; Sapienza, Alessio; Freni, Angelo

    2012-01-01

    This paper focuses on the development of a dynamic multi-level model for simulating of a solar cooling system adopting an adsorption chiller. The model integrates detailed simulation of the adsorption cycle (component level) into the transient simulation of the solar cooling system (system level). The chiller investigated was a standard two bed silica gel/water unit. The model was used to ascertain the feasibility of solar-driven adsorption cooling and for optimization purposes. In the base c...

  15. MATHEMATICAL MODELLING OF METHANE STEAM REFORMING IN A MEMBRANE REACTOR: AN ISOTHERMIC MODEL

    OpenAIRE

    ASSAF E.M.; JESUS C.D.F.; J.M. ASSAF

    1998-01-01

    A mathematical modelling of one-dimensional, stationary and isothermic membrane reactor for methane steam reforming was developed to compare the maximum yield for methane conversion in this reactor with that in a conventional fixed-bed reactor. Fick's first law was used to describe the mechanism of hydrogen permeation. The variables studied include: reaction temperature, hydrogen feed flow rate and membrane thickness. The results show that the membrane reactor presents a higher methane conver...

  16. MATHEMATICAL MODELLING OF METHANE STEAM REFORMING IN A MEMBRANE REACTOR : AN ISOTHERMIC MODEL

    OpenAIRE

    ASSAF E.M.; JESUS C.D.F.; J.M. ASSAF

    1998-01-01

    A mathematical modelling of one-dimensional, stationary and isothermic membrane reactor for methane steam reforming was developed to compare the maximum yield for methane conversion in this reactor with that in a conventional fixed-bed reactor. Fick's first law was used to describe the mechanism of hydrogen permeation. The variables studied include: reaction temperature, hydrogen feed flow rate and membrane thickness. The results show that the membrane reactor presents a higher methane conver...

  17. The use of laboratory adsorption data and models to predict radionuclide releases from a geological repository: A brief history

    International Nuclear Information System (INIS)

    Radionuclide (RN) adsorption has long been recognized as important to assure the isolation of nuclear wastes in a geological repository. Laboratory measured RN adsorption data have generally been expressed as distribution coefficient (Kd) values or adsorption isotherms. The surface complexation (SC) adsorption models were introduced in the late 1970''s. The best known of these models incorporate electrical double layer (EDL) theory. Their use requires that the water chemistry and surface properties of adsorbing rocks and minerals be fully characterized. Because the SC models are relatively mechanistic, they may allow extrapolation of adsorption results to repository conditions that lie outside the limited experimental range used to parameterize a given model. Turner has shown that the diffuse layer model (the simplest SC model) fits a wide range of RN adsorption data as well as the more complex models. Others have suggested ways to generalize and estimate SC model parameters for a variety of minerals, rocks and engineered materials. Degueldre and Werlni and Degueldre et al. have proposed a simplified SC model for RN adsorption that avoids EDL theory, in which the adsorption of RN species is estimated from linear free energy relationships. It is appropriate to ask how accurately RN adsorption behavior must be known or understood for total system performance analysis (TSPA). In most geological settings now being considered for repository development globally, it may suffice to select bounding Kd values for the different rock types. Use of the SC models to describe RN adsorption can provide one with increased confidence that minimum Kd''s and the distribution of Kd values the author might propose for TSPA are in fact conservative. 68 refs., 5 figs., 1 tab

  18. Synthesis of magnetic γ-Fe2O3-based nanomaterial for ultrasonic assisted dyes adsorption: Modeling and optimization.

    Science.gov (United States)

    Asfaram, Arash; Ghaedi, Mehrorang; Hajati, Shaaker; Goudarzi, Alireza

    2016-09-01

    γ-Fe2O3 nanoparticles were synthesized and loaded on activated carbon. The prepared nanomaterial was characterized by field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDX), Fourier transforms infrared spectroscopy (FT-IR) and X-ray diffraction (XRD). The γ-Fe2O3 nanoparticle-loaded activated carbon (γ-Fe2O3-NPs-AC) was used as novel adsorbent for the ultrasonic-assisted removal of methylene blue (MB) and malachite green (MG). Response surface methodology and artificial neural network were applied to model and optimize the adsorption of the MB and MG in their individual and binary solutions followed by the investigation on adsorption isotherm and kinetics. The individual effects of parameters such as pH, mass of adsorbent, ultrasonication time as well as MB and MG concentrations in addition to the effects of their possible interactions on the adsorption process were investigated. The numerical optimization revealed that the optimum adsorption (>99.5% for each dye) is obtained at 0.02g, 15mgL(-1), 4min and 7.0 corresponding to the adsorbent mass, each dye concentration, sonication time and pH, respectively. The Freundlich, Langmuir, Temkin and Dubinin-Radushkevich isotherms were studied. The Langmuir was found to be most applicable isotherm which predicted maximum monolayer adsorption capacities of 195.55 and 207.04mgg(-1) for the adsorption of MB and MG, respectively. The pseudo-second order model was found to be applicable for the adsorption kinetics. Blank experiments (without any adsorbent) were run to investigate the possible degradation of the dyes studied in presence of ultrasonication. No dyes degradation was observed. PMID:27150788

  19. Optimizing adsorption of fluoride from water by modified banana peel dust using response surface modelling approach

    Science.gov (United States)

    Bhaumik, Ria; Mondal, Naba Kumar

    2016-06-01

    The present work highlighted the effective application of banana peel dust (BPD) for removal of fluoride (F-) from aqueous solution. The effects of operating parameters such as pH, initial concentration, adsorbent dose, contact time, agitation speed and temperature were analysed using response surface methodology. The significance of independent variables and their interactions were tested by the analysis of variance and t test statistics. Experimental results revealed that BPD has higher F- adsorption capacity (17.43, 26.31 and 39.5 mg/g). Fluoride adsorption kinetics followed pseudo-second-order model with high correlation of coefficient value (0.998). On the other hand, thermodynamic data suggest that adsorption is favoured at lower temperature, exothermic in nature and enthalpy driven. The adsorbents were characterised through scanning electron microscope, Fourier transform infrared spectroscopy and point of zero charges (pHZPC) ranges from pH 6.2-8.2. Finally, error analysis clearly demonstrates that all three adsorbents are well fitted with Langmuir isotherm compared to the other isotherm models. The reusable properties of the material support further development for commercial application purpose.

  20. Modelling GAC adsorption of biologically pre-treated process water from hydrothermal carbonization.

    Science.gov (United States)

    Fettig, J; Liebe, H

    2015-01-01

    Granular-activated carbon (GAC) adsorption of biologically pre-treated process waters from hydrothermal carbonization (HTC) of different materials was investigated. Overall, isotherms showed that most of the dissolved organic substances are strongly adsorbable while the non-adsorbable fractions are small. The equilibrium data were modelled by using five fictive components to represent the organic matter. Mean film transfer coefficients and mean intraparticle diffusivities were derived from short-column and batch kinetic test data, respectively. Breakthrough curves in GAC columns could be predicted satisfactorily by applying the film-homogeneous diffusion model and using the equilibrium and kinetic parameters determined from batch tests. Thus, the approach is suited to model GAC adsorption of HTC process water under technical-scale conditions. PMID:26114274

  1. 天鹅湖沉积物对磷的吸附动力学及等温吸附特征%Characteristics of Adsorption Kinetics and Isotherms of Phosphate on Sediments in Swan Lake

    Institute of Scientific and Technical Information of China (English)

    高丽; 侯金枝; 宋鹏鹏

    2013-01-01

    以荣成天鹅湖这一天然泻湖为研究对象,研究了6个样点沉积物对磷的吸附动力学曲线和等温吸附方程,并分析了沉积物理化性质与磷吸附参数间的关系.结果表明,天鹅湖不同区域沉积物对磷的吸附动力学均符合二级动力学方程,吸附反应主要在前10h内完成,且0~2h内反应迅速.根据Langmuir模型,6个样点沉积物对磷的理论吸附容量(Qmax)的范围为294.12~1 111.11 mg/kg,其中湖区北部和中部沉积物的吸附能力高于南部.沉积物对水体中磷的吸附解吸平衡浓度(EPC0)的变幅为0.002 ~ 0.033 mg/L,其与沉积物本底吸附态磷(NAP)呈较弱的正相关关系.本研究条件下,大部分样点的EPC0小于上覆水中磷的浓度,其中湖区西北部和东南部沉积物中磷具有向上覆水体释放的趋势.沉积物的NAP与总氮、有机质、活性铝和黏粒间均呈显著正相关,Qmax与铁铝结合态磷、有机质、活性铝和粉粒间呈显著的正相关关系.活性铝、有机质和粒度是影响沉积物磷吸附的主要因素.%Adsorption kinetics and isotherms of phosphate on six sediments collected in Rongcheng Swan Lake (a nature lagoon) were determined in laboratory, and the relationship between the physical-chemical properties and the adsorption parameters of sediments was also discussed. The results indicated that the adsorption kinetics curve of phosphate at different sites all followed the second-order adsorption kinetic model. The adsorption reaction mainly occurred within 0-10 h, and the maximum adsorption rates occurred within 0-2 h. According to the Langmuir isotherm equation, phosphate adsorption capacity (Qmax) of surface sediments from Swan Lake varied from 294.12 mg/kg to 1 111.11 mg/kg. Phosphate sorption potential on the sediments from the northern and center areas was much higher than that from the south. The zero equilibrium phosphate concentration (EPC0) changed at the range of 0.002-0.033 mg/L, which

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

    Science.gov (United States)

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

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

  3. Modeling studies: Adsorption of aniline blue by using Prosopis Juliflora carbon/Ca/alginate polymer composite beads.

    Science.gov (United States)

    Kumar, M; Tamilarasan, R

    2013-02-15

    The research article describes the experimental and modeling study for the adsorptive removal of aniline blue dye (AB dye) from aqueous matrices using a Prosopis Juliflora modified carbon/Ca/alginate polymer bead as a low cost and eco-friendly adsorbent. The rate of adsorption was investigated under various experimental parameters such as contact time, adsorbent dose, dye concentration, pH and temperature. The kinetics, equilibrium and thermodynamic studies were assessed to find out the efficiency of the adsorption process. The equilibrium uptake capacity of the adsorption process was found with Freundlich and Langmuir adsorption isotherm equations and it was evaluated by dimensionless separation factor (R(L)). The dynamics of adsorption was predicted by pseudo-first order, pseudo-second order Lagergren's equation and intra particle diffusion model. Adsorption feasibility was assessed with thermodynamic parameters such as isosteric heat of adsorption (ΔH°), standard entropy (ΔS°) and Gibbs free energy (ΔG°) using VantHoff plot. The alginate bead was characterized with FTIR spectroscopy and Scanning Electron Microscopy (SEM). PMID:23399273

  4. Model-fitting approach to kinetic analysis of non-isothermal oxidation of molybdenite

    International Nuclear Information System (INIS)

    The kinetics of molybdenite oxidation was studied by non-isothermal TGA-DTA with heating rate 5degC.min-1. The model-fitting kinetic approach applied to TGA data. The Coats-Redfern method used of model fitting. The popular model-fitting gives excellent fit non-isothermal data in chemically controlled regime. The apparent activation energy was determined to be about 34.2 kcalmol-1 With pre-exponential factor about 108 sec-1 for extent of reaction less than 0.5

  5. Comparison of adsorption efficiency of Triton X-100 surfactant from industrial wastewater using synthetic and natural zeolites: isotherm and kinetic studies

    Directory of Open Access Journals (Sweden)

    A Shahbazi

    2016-01-01

    Full Text Available Background and Objectives: Rapid growing of Triton X-100 application in industries results in its appearance in effluents  and threaten the aqueous ecosystems. Triton X-100 is not biodegradable and can accumulate in food chain. Materials and Methods: In this study, sorption capacity of six synthesized zeolites with different regular porous structure was studied for triton X-100 (TX-100 surfactant and the results were compared with Clinoptilolite natural zeolite of Damavand region. Results: Within all zeolite studied, Beta(200 showed the highest sorption capacity (about 575 mg/g, which is due to its regular pore structure with large pore diameter, channel intersections, high SiO2/Al2O3 ratio and high surface area. Langmuir monolayer isotherm and pseudo-second-order kinetic equation could provide well-fitted to the experimental data in simulating adsorption behavior of TX-100 over Beta(200 zeolite. Conclusion: The adsorption feature was internal sorption and the intraparticle diffusion might be a rate-limiting control for Beta(200 zeolite. Results of experiments demonstrated that the hydrophobic zeolites with large pore diameter such as Beta(200 could be effective sorbents for industrial wastewater treatment features.

  6. Effects of 42-year long-term fertilizer management on soil phosphorus availability, fractionation, adsorption-desorption isotherm and plant uptake in flooded tropical rice

    Institute of Scientific and Technical Information of China (English)

    Pratap Bhattacharyya; Priyanka Gautam; Chinmaya Kumar Swain; Koushik Singha Roy; Pradeep Kumar Dash; Amaresh Kumar Nayak; Mohammad Shahid; Rahul Tripathi; Sangita Mohanty; Anjani Kumar; Rajagounder Raja; Bipin Bihari Panda; Banwari Lal

    2015-01-01

    Soil phosphorus (P) fractionation, adsorption, and desorption isotherm, and rice yield and P uptake were investigated in flooded tropical rice (Oryza sativa L.) following 42-year fertilizer and manure application. The treatments included low-input [unfertilized control without N, P, or K (C0N0)], farmyard manure (FYM) (C1N0), NP (C0NP), NPK (C0NPK), FYM+NP (C1NP), and high-input treatment, FYM+NPK (C1NPK). Grain yield was increased significantly by 74%over the control under the combined application of FYM+NPK. However, under low- and high-input treatments, yield as well as P uptake was maintained at constant levels for 35 years. During the same period, high yield levels and P uptake were maintained under the C0NP, C0NPK, and C1NPK treatments. These are unique characteristics of a tropical flooded ecosystem, which is a self-sustaining system for rice production. The Fe–P fraction was highest compared to the Ca–P and Al–P fractions after 42 years of fertilizer application and was significantly higher under FYM+NPK treatment. The P adsorption capacity of soil was highest under the low-input treatment and lowest under long-term balanced fertilization (FYM+NPK). In contrast, P desorption capacity was highest under NPK and lowest in the control treatment. Long-term balanced fertilization in the form of FYM+NPK for 42 years lowered the bonding energy and adsorption capacity for P in soil but increased its desorption potential, increasing P availability to the plant and leading to higher P uptake and yield maintenance.

  7. Development of a first-order kinetics-based model for the adsorption of nickel onto peat

    Institute of Scientific and Technical Information of China (English)

    LIU Zhi-rong; CHEN Xiao-song; ZHOU Li-min; WEI Peng

    2009-01-01

    The use of peat for the removal of nickel from aqueous solutions has been investigated at various pH values by means of static conditions. The present research shows that the ability of Ni to hind to peat increases as the pH value increases. The solutions reach adsorption equilibrium rapidly. A reasonable kinetic model, first-order in nickel concentration, has been developed and fitted to the adsorption of nickel (Ⅱ) onto peat. The first-order model provides a good correlation to the experimental data. The characteristic parameters of the Langmuir isotherm were determined at various temperatures. The relationship between kinetics and equilibrium isotherms was established through the forward- and backward-rate-constants, k and k2, and the equilibrium constant, K.

  8. Surface-complexation modeling of radionuclide adsorption in subsurface environments

    International Nuclear Information System (INIS)

    Requirements for applying the surface-complexation modeling approach to simulating radionuclide adsorption onto geologic materials are discussed. Accurate description of adsorption behavior requires that chemical properties of both adsorbent and adsorbate be characterized in conjunction with determinations of extent of adsorption. Critical chemical properties of adsorbents include dissolution and oxidation/reduction behavior, types and densities of adsorption sites, and interaction of sites with solution components. Important adsorbate properties include hydrolysis, complexation, oxidation/reduction, and oligomerization. Adsorption behavior is described by a set of chemical reactions and binding constants between: adsorption sites and solution components, adsorbate and solution components, and adsorbate and adsorption sites. Methods for implementing such an approach are discussed;examples based on solute adsorption onto oxides are presented. The approach currently used to simulate sorption onto geologic materials, i.e., the determination of distribution coefficients, yields estimates that are disparate and subject to large errors. Implementation of the surface-complexation modeling approach would greatly improve the predictability of the role of adsorption in regulating radionuclide transport in subsurface environments. Research efforts should be directed towards understanding radionuclide adsorption onto fixed-charge minerals (e.g., clays), carbonate minerals, and poly-mineralic assemblages representative of those present at potential repositories. 123 refs., 19 figs., 18 tabs

  9. Expanded bed adsorption of bromelain (E.C. 3.4.22.33) from Ananas comosus crude extract

    OpenAIRE

    Silveira, E.; M. E. Souza-Jr; J. C. C. Santana; A. C. Chaves; L. F. Porto; E. B. Tambourgi

    2009-01-01

    This work focuses on the adsorption of Bromelain in expanded bed conditions, such as the adsorption kinetics parameters. The adsorption kinetics parameters showed that after 40 minutes equilibrium was achieved and maximum adsorption capacity was 6.11 U per resin mL. However, the maximum adsorption capacity was only determined by measuring the adsorption isotherm. Only by the Langmuir model the maximum adsorption capacity, Qm, and dissociation constant, kd, values could be estimated as 9.18 U/...

  10. Thermodynamic Model Formulations for Inhomogeneous Solids with Application to Non-isothermal Phase Field Modelling

    Science.gov (United States)

    Gladkov, Svyatoslav; Kochmann, Julian; Reese, Stefanie; Hütter, Markus; Svendsen, Bob

    2016-04-01

    The purpose of the current work is the comparison of thermodynamic model formulations for chemically and structurally inhomogeneous solids at finite deformation based on "standard" non-equilibrium thermodynamics [SNET: e. g. S. de Groot and P. Mazur, Non-equilibrium Thermodynamics, North Holland, 1962] and the general equation for non-equilibrium reversible-irreversible coupling (GENERIC) [H. C. Öttinger, Beyond Equilibrium Thermodynamics, Wiley Interscience, 2005]. In the process, non-isothermal generalizations of standard isothermal conservative [e. g. J. W. Cahn and J. E. Hilliard, Free energy of a non-uniform system. I. Interfacial energy. J. Chem. Phys. 28 (1958), 258-267] and non-conservative [e. g. S. M. Allen and J. W. Cahn, A macroscopic theory for antiphase boundary motion and its application to antiphase domain coarsening. Acta Metall. 27 (1979), 1085-1095; A. G. Khachaturyan, Theory of Structural Transformations in Solids, Wiley, New York, 1983] diffuse interface or "phase-field" models [e. g. P. C. Hohenberg and B. I. Halperin, Theory of dynamic critical phenomena, Rev. Modern Phys. 49 (1977), 435-479; N. Provatas and K. Elder, Phase Field Methods in Material Science and Engineering, Wiley-VCH, 2010.] for solids are obtained. The current treatment is consistent with, and includes, previous works [e. g. O. Penrose and P. C. Fife, Thermodynamically consistent models of phase-field type for the kinetics of phase transitions, Phys. D 43 (1990), 44-62; O. Penrose and P. C. Fife, On the relation between the standard phase-field model and a "thermodynamically consistent" phase-field model. Phys. D 69 (1993), 107-113] on non-isothermal systems as a special case. In the context of no-flux boundary conditions, the SNET- and GENERIC-based approaches are shown to be completely consistent with each other and result in equivalent temperature evolution relations.

  11. APTES-modified mesoporous silicas as the carriers for poorly water-soluble drug. Modeling of diflunisal adsorption and release

    Science.gov (United States)

    Geszke-Moritz, Małgorzata; Moritz, Michał

    2016-04-01

    Four mesoporous siliceous materials such as SBA-16, SBA-15, PHTS and MCF functionalized with (3-aminopropyl)triethoxysilane were successfully prepared and applied as the carriers for poorly water-soluble drug diflunisal. Several techniques including nitrogen sorption analysis, XRD, TEM, FTIR and thermogravimetric analysis were employed to characterize mesoporous matrices. Adsorption isotherms were analyzed using Langmuir, Freundlich, Temkin and Dubinin-Radushkevich models. In order to find the best-fit isotherm for each model, both linear and nonlinear regressions were carried out. The equilibrium data were best fitted by the Langmuir isotherm model revealing maximum adsorption capacity of 217.4 mg/g for aminopropyl group-modified SBA-15. The negative values of Gibbs free energy change indicated that the adsorption of diflunisal is a spontaneous process. Weibull release model was employed to describe the dissolution profile of diflunisal. At pH 4.5 all prepared mesoporous matrices exhibited the improvement of drug dissolution kinetics as compared to the dissolution rate of pure diflunisal.

  12. Adsorption of amitraz on the clay

    Directory of Open Access Journals (Sweden)

    Jale Gülen

    2013-01-01

    Full Text Available Amitraz (AZ that is used as acaridies was tried to extract with a clay. The experimental data were modelled as using Langmuir and Freundlich isotherms. The adsorption data fit well with Langmuir isotherm that indicated the AZ adsorption is homogeneous and monolayer. The monolayer adsorption capacity was found to be 35.02 mg/g at 20 ºC temperature. Effect of the phases contact time, the initial solution pH and the initial pesticide concentration were investigated from the point of adsorption equilibrium and yield. The adsorption kinetics were investigated by applying pseudo first order, pseudo second order and intra particle diffusion laws. Adsorption of AZ was found to be best fitted by the pseudo second order model. The intra particle diffusion also plays an important role in adsorption phenomenon.

  13. A simplified adsorption model for water vapor adsorption on activated carbon

    Institute of Scientific and Technical Information of China (English)

    姚小龙; 李立清; 李海龙; 马卫武

    2014-01-01

    A simplified model was developed to describe the water vapor adsorption on activated carbon. The development of the simplified model was started from the original model proposed by DO and his co-workers. Two different kinds of carbon materials were prepared for water vapor adsorption, and the adsorption experiments were conducted at different temperatures (20-50 °C) and relative humidities (5%-99%) to test the model. It is shown that the amount of adsorbed water vapor in micropore decreases with the temperature increasing, and the water molecules form larger water clusters around the functional group as the temperature is up to a higher value. The simplified model describes reasonably well for all the experimental data. According to the fitted values, the parameters of simplified model were represented by the temperature and then the model was used to calculate the water vapor adsorption amount at 25 °C and 35 °C. The results show that the model can get relatively accurate values to calculate the water vapor adsorption on activated carbon.

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

    Science.gov (United States)

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

    2016-08-01

    Application of empirical models to adsorption of contaminants on natural heterogeneous sorbents is often challenging due to the uncertainty associated with fitting experimental data and determining adjustable parameters. Sediment samples from contaminated and uncontaminated portions of a study site in Maine, USA were collected and investigated for adsorption of arsenate [As(V)]. Two kinetic models were used to describe the results of single solute batch adsorption experiments. Piecewise linear regression of data linearized to fit pseudo-first order kinetic model resulted in two distinct rates and a cutoff time point of 14-19 h delineating the biphasic behavior of solute adsorption. During the initial rapid adsorption stage, an average of 60-80% of the total adsorption took place. Pseudo-second order kinetic models provided the best fit to the experimental data (R(2) > 0.99) and were capable of describing the adsorption over the entire range of experiments. Both Langmuir and Freundlich isotherms provided reasonable fits to the adsorption data at equilibrium. Langmuir-derived maximum adsorption capacity (St) of the studied sediments ranged between 29 and 97 mg/kg increasing from contaminated to uncontaminated sites. Solid phase As content of the sediments ranged from 3.8 to 10 mg/kg and the As/Fe ratios were highest in the amorphous phase. High-pH desorption experiments resulted in a greater percentage of solid phase As released into solution from experimentally-loaded sediments than from the unaltered samples suggesting that As(V) adsorption takes place on different reversible and irreversible surface sites. PMID:27218893

  15. MATHEMATICAL MODELLING OF METHANE STEAM REFORMING IN A MEMBRANE REACTOR: AN ISOTHERMIC MODEL

    Directory of Open Access Journals (Sweden)

    E.M. ASSAF

    1998-06-01

    Full Text Available A mathematical modelling of one-dimensional, stationary and isothermic membrane reactor for methane steam reforming was developed to compare the maximum yield for methane conversion in this reactor with that in a conventional fixed-bed reactor. Fick's first law was used to describe the mechanism of hydrogen permeation. The variables studied include: reaction temperature, hydrogen feed flow rate and membrane thickness. The results show that the membrane reactor presents a higher methane conversion yield than the conventional fixed-bed reactor.

  16. Surface complexation modeling calculation of Pb(II) adsorption onto the calcined diatomite

    Science.gov (United States)

    Ma, Shu-Cui; Zhang, Ji-Lin; Sun, De-Hui; Liu, Gui-Xia

    2015-12-01

    Removal of noxious heavy metal ions (e.g. Pb(II)) by surface adsorption of minerals (e.g. diatomite) is an important means in the environmental aqueous pollution control. Thus, it is very essential to understand the surface adsorptive behavior and mechanism. In this work, the Pb(II) apparent surface complexation reaction equilibrium constants on the calcined diatomite and distributions of Pb(II) surface species were investigated through modeling calculations of Pb(II) based on diffuse double layer model (DLM) with three amphoteric sites. Batch experiments were used to study the adsorption of Pb(II) onto the calcined diatomite as a function of pH (3.0-7.0) and different ionic strengths (0.05 and 0.1 mol L-1 NaCl) under ambient atmosphere. Adsorption of Pb(II) can be well described by Freundlich isotherm models. The apparent surface complexation equilibrium constants (log K) were obtained by fitting the batch experimental data using the PEST 13.0 together with PHREEQC 3.1.2 codes and there is good agreement between measured and predicted data. Distribution of Pb(II) surface species on the diatomite calculated by PHREEQC 3.1.2 program indicates that the impurity cations (e.g. Al3+, Fe3+, etc.) in the diatomite play a leading role in the Pb(II) adsorption and dominant formation of complexes and additional electrostatic interaction are the main adsorption mechanism of Pb(II) on the diatomite under weak acidic conditions.

  17. Parameterization of cloud droplet formation for global and regional models: including adsorption activation from insoluble CCN

    Directory of Open Access Journals (Sweden)

    P. Kumar

    2009-04-01

    Full Text Available Dust and black carbon aerosol have long been known to exert potentially important and diverse impacts on cloud droplet formation. Most studies to date focus on the soluble fraction of these particles, and overlook interactions of the insoluble fraction with water vapor (even if known to be hydrophilic. To address this gap, we developed a new parameterization that considers cloud droplet formation within an ascending air parcel containing insoluble (but wettable particles externally mixed with aerosol containing an appreciable soluble fraction. Activation of particles with a soluble fraction is described through well-established Köhler theory, while the activation of hydrophilic insoluble particles is treated by "adsorption-activation" theory. In the latter, water vapor is adsorbed onto insoluble particles, the activity of which is described by a multilayer Frenkel-Halsey-Hill (FHH adsorption isotherm modified to account for particle curvature. We further develop FHH activation theory to i find combinations of the adsorption parameters AFHH, BFHH which yield atmospherically-relevant behavior, and, ii express activation properties (critical supersaturation that follow a simple power law with respect to dry particle diameter.

    The new parameterization is tested by comparing the parameterized cloud droplet number concentration against predictions with a detailed numerical cloud model, considering a wide range of particle populations, cloud updraft conditions, water vapor condensation coefficient and FHH adsorption isotherm characteristics. The agreement between parameterization and parcel model is excellent, with an average error of 10% and R2~0.98. A preliminary sensitivity study suggests that the sublinear response of droplet number to Köhler particle concentration is not as strong for FHH particles.

  18. Parameterization of cloud droplet formation for global and regional models: including adsorption activation from insoluble CCN

    Directory of Open Access Journals (Sweden)

    P. Kumar

    2008-09-01

    Full Text Available Dust and black carbon aerosol have long been known to have potentially important and diverse impacts on cloud droplet formation. Most studies to date focus on the soluble fraction of such particles, and ignore interactions of the insoluble fraction with water vapor (even if known to be hydrophilic. To address this gap, we develop a new parameterization framework that considers cloud droplet formation within an ascending air parcel containing insoluble (but wettable particles mixed with aerosol containing an appreciable soluble fraction. Activation of particles with a soluble fraction is described through well-established Köhler Theory, while the activation of hydrophilic insoluble particles is treated by "adsorption-activation" theory. In the latter, water vapor is adsorbed onto insoluble particles, the activity of which is described by a multilayer Frankel-Halsey-Hill (FHH adsorption isotherm modified to account for particle curvature. We further develop FHH activation theory, and i find combinations of the adsorption parameters AFHH, BFHH for which activation into cloud droplets is not possible, and, ii express activation properties (critical supersaturation that follow a simple power law with respect to dry particle diameter.

    Parameterization formulations are developed for sectional and lognormal aerosol size distribution functions. The new parameterization is tested by comparing the parameterized cloud droplet number concentration against predictions with a detailed numerical cloud model, considering a wide range of particle populations, cloud updraft conditions, water vapor condensation coefficient and FHH adsorption isotherm characteristics. The agreement between parameterization and parcel model is excellent, with an average error of 10% and R2 ~0.98.

  19. Specific surface area effect on adsorption of chlorpyrifos and TCP by soils and modeling

    Science.gov (United States)

    The adsorption of chlorpyrifos and TCP (3,5,6, trichloro-2-pyridinol) was determined in four soils (Mollisol, Inceptisol, Entisol, Alfisol) having different specific surface areas (19–84 m2/g) but rather similar organic matter content (2.4–3.5%). Adsorption isotherms were derived from batch equilibr...

  20. Isotermas de adsorção de Freundlich para o crômio (III em Latossolos Freundlich adsorption isotherms for chromium (III in Oxisols

    Directory of Open Access Journals (Sweden)

    Marco Aurélio Kondracki de Alcântara

    2001-09-01

    the soil adsorptive capacity is exceeded and, potentially, the metals become available for leaching. The objectives of this study were to verify if the isotherm of Freundlich describes adequately the chromium adsorption by Oxisols, to study chromium adsorption considering different soils and horizons, as well as some chemical and physical attributes, and to evaluate the influence of the pH level on chromium adsorption. Samples of the A and B horizons of two soils were collected in the São Paulo State - Brazil: a Typic Eutrorthox (LVe and b Typic Haplorthox (LVd. The pH alteration of the surface horizons was performed with the addition of calcium carbonate to reach 70% base saturation. Samples were shaken with CrCl3 solutions (prepared in Ca(NO32 5 mmol L-1 as the support electrolyte of different initial chromium concentrations Co: 0; 0.5; 1.0; 2.5; 5.0; 10.0 and 50.0 mg L-1, using two replicates for each treatment. Freundlich isotherms were adjusted to describe the chromium adsorption by the soil. This isoterm fitted well to the experimental data. Chromium adsorption was higher in the Typic Eutrorthox than in the Typic Haplorthox. The adsorption was also favored by liming in both soils. There was no difference between chromium adsorption by the two horizons of the soils.

  1. Preparation and Characterization of Chitosan/Feldspar Biohybrid as an Adsorbent: Optimization of Adsorption Process via Response Surface Modeling

    Directory of Open Access Journals (Sweden)

    Maryam Yazdani

    2014-01-01

    Full Text Available Chitosan/feldspar biobased beads were synthesized, characterized, and tested for the removal of Acid Black 1 dye from aquatic phases. A four-factor central composite design (CCD accompanied by response surface modeling (RSM and optimization was used to optimize the dye adsorption by the adsorbent (chitosan/feldspar composite in 31 different batch experiments. Independent variables of temperature, pH, initial dye concentration, and adsorbent dose were used to change to coded values. To anticipate the responses, a quadratic model was applied. Analysis of variance (ANOVA tested the significance of the process factors and their interactions. The adequacy of the model was investigated by the correlation between experimental and predicted data of the adsorption and the calculation of prediction errors. The results showed that the predicted maximum adsorption amount of 21.63 mg/g under the optimum conditions (pH 3, temperature 15°C, initial dye concentration 125 mg/L, and dose 0.2 g/50 mL was close to the experimental value of 19.85 mg/g. In addition, the results of adsorption behaviors of the dye illustrated that the adsorption process followed the Langmuir isotherm model and the pseudo-second-order kinetic model. Langmuir sorption capacity was found to be 17.86 mg/g. Besides, thermodynamic parameters were evaluated and revealed that the adsorption process was exothermic and favourable.

  2. Multi-model attribution of upper-ocean temperature changes using an isothermal approach

    Science.gov (United States)

    Weller, Evan; Min, Seung-Ki; Palmer, Matthew D.; Lee, Donghyun; Yim, Bo Young; Yeh, Sang-Wook

    2016-06-01

    Both air-sea heat exchanges and changes in ocean advection have contributed to observed upper-ocean warming most evident in the late-twentieth century. However, it is predominantly via changes in air-sea heat fluxes that human-induced climate forcings, such as increasing greenhouse gases, and other natural factors such as volcanic aerosols, have influenced global ocean heat content. The present study builds on previous work using two different indicators of upper-ocean temperature changes for the detection of both anthropogenic and natural external climate forcings. Using simulations from phase 5 of the Coupled Model Intercomparison Project, we compare mean temperatures above a fixed isotherm with the more widely adopted approach of using a fixed depth. We present the first multi-model ensemble detection and attribution analysis using the fixed isotherm approach to robustly detect both anthropogenic and natural external influences on upper-ocean temperatures. Although contributions from multidecadal natural variability cannot be fully removed, both the large multi-model ensemble size and properties of the isotherm analysis reduce internal variability of the ocean, resulting in better observation-model comparison of temperature changes since the 1950s. We further show that the high temporal resolution afforded by the isotherm analysis is required to detect natural external influences such as volcanic cooling events in the upper-ocean because the radiative effect of volcanic forcings is short-lived.

  3. Selective adsorption of tannins onto hide collagen fibres

    Institute of Scientific and Technical Information of China (English)

    廖学品; 陆忠兵; 石碧

    2003-01-01

    Hide collagen of animals is used to prepare adsorbent material and its adsorption properties to tannins are investigated. It is indicated that the collagen fibres has excellent adsorption selectivity and high adsorption capacity to tannins. The adsorption rate of tannins is more than 90% whilst less than 10% of functional components are retained by the adsorbent. The adsorption mechanism of tannins onto hide collagen fibres is hydrogen-bonding association. Freundlich model can be used to describe the adsorption isotherms, and the pseudo-second-order rate model can be used to describe adsorption kinetics.

  4. Monte Carlo model of CO adsorption on supported Pt nanoparticle

    International Nuclear Information System (INIS)

    For molecular simulations with thousands of atoms it is desirable to use a lattice gas model because it is fast and easy-to-use for computations. Unfortunately, simulation of adsorption on heterogeneous surfaces within this model is rather complicated due to a large variety of available adsorption site types. We propose the combined model with lattice representation of adsorbent atoms and arbitrary location of adsorbate atoms. Using this model simulation of CO adsorption on supported Pt nanoparticles has been performed. With the proposed approach the above-mentioned difficulties were successfully overcome.

  5. Monte Carlo model of CO adsorption on supported Pt nanoparticle

    Energy Technology Data Exchange (ETDEWEB)

    Myshlyavtsev, A.V. [Omsk State Technical University, Omsk (Russian Federation); Institute of Hydrocarbons Processing SB RAS, Omsk (Russian Federation); Stishenko, P.V., E-mail: PVStishenko@omgtu.ru [Omsk State Technical University, Omsk (Russian Federation)

    2010-06-15

    For molecular simulations with thousands of atoms it is desirable to use a lattice gas model because it is fast and easy-to-use for computations. Unfortunately, simulation of adsorption on heterogeneous surfaces within this model is rather complicated due to a large variety of available adsorption site types. We propose the combined model with lattice representation of adsorbent atoms and arbitrary location of adsorbate atoms. Using this model simulation of CO adsorption on supported Pt nanoparticles has been performed. With the proposed approach the above-mentioned difficulties were successfully overcome.

  6. Adsorption of Pb(II) on mesoporous activated carbons fabricated from water hyacinth using H{sub 3}PO{sub 4} activation: Adsorption capacity, kinetic and isotherm studies

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Yang, E-mail: zzsfxyhy@163.com [Department of Chemistry and Environmental Science, Minnan Normal University, Zhangzhou 363000 (China); Fujian Province University Key Laboratory of Modern Analytical Science and Separation Technology, Minnan Normal University, Zhangzhou 363000 (China); Li, Shunxing; Chen, Jianhua; Zhang, Xueliang; Chen, Yiping [Department of Chemistry and Environmental Science, Minnan Normal University, Zhangzhou 363000 (China); Fujian Province University Key Laboratory of Modern Analytical Science and Separation Technology, Minnan Normal University, Zhangzhou 363000 (China)

    2014-02-28

    Activated carbons with high mesoporosity and abundant oxygen-containing functional groups were prepared from water hyacinth using H{sub 3}PO{sub 4} 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 m{sup 2}/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 (q{sub m}) 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.

  7. Modeling of Non-Isothermal Cryogenic Fluid Sloshing

    Science.gov (United States)

    Agui, Juan H.; Moder, Jeffrey P.

    2015-01-01

    A computational fluid dynamic model was used to simulate the thermal destratification in an upright self-pressurized cryostat approximately half-filled with liquid nitrogen and subjected to forced sinusoidal lateral shaking. A full three-dimensional computational grid was used to model the tank dynamics, fluid flow and thermodynamics using the ANSYS Fluent code. A non-inertial grid was used which required the addition of momentum and energy source terms to account for the inertial forces, energy transfer and wall reaction forces produced by the shaken tank. The kinetics-based Schrage mass transfer model provided the interfacial mass transfer due to evaporation and condensation at the sloshing interface. The dynamic behavior of the sloshing interface, its amplitude and transition to different wave modes, provided insight into the fluid process at the interface. The tank pressure evolution and temperature profiles compared relatively well with the shaken cryostat experimental test data provided by the Centre National D'Etudes Spatiales.

  8. Mathematical model of non-isothermal creep based anisotropic damage

    OpenAIRE

    Галаган, Ю. Н.; Лысенко, С. В.; Львов, Г. И.

    2008-01-01

    А mathematical model of nonisothermic creep for anisotropic damage case is considered. Constitutive relation of creep rate and kinematic equation of damage evolution are assumed temperature dependent. A second range tensor is used for description damage. A technique based on existing experimental curves for the identification of material creep constants is presented.

  9. NON-ISOTHERMAL MODELING AND SIMULATION FOR A SOLUBLE-LEAD ACID FLOW BATTERY

    OpenAIRE

    Amir A-K. Omran; Hassan. Al-Fetlawi; Falah K. Matlub

    2015-01-01

    Non-isothermal two-dimensional transient model for a soluble lead-acid flow battery is developed, including the negative electrode, positive electrode and the flow space between them. The model based on a comprehensive description of mass, charge, energy and momentum transport and conservation, and is combined with a global kinetic model for reactions involving lead species. The influence of the applied current density, operating temperature, inlet electrolyte velocity and initial concentrati...

  10. Modelling Gas Adsorption in Porous Solids: Roles of Surface Chemistry and Pore Architecture

    Indian Academy of Sciences (India)

    Satyanarayana Bonakala; Sundaram Balasubramanian

    2015-10-01

    Modelling the adsorption of small molecule gases such as N2 , CH4 and CO2 in porous solids can provide valuable insights for the development of next generation materials. Employing a grand canonical Monte Carlo simulation code developed in our group, the adsorption isotherms of CH4 and CO2 in many metal organic frameworks have been calculated and compared with experimental results. The isotherms computed within a force field approach are able to well reproduce the experimental data. Key functional groups in the solids which interact with gas molecules and the nature of their interactions have been identified. The most favorable interaction sites for CH4 and CO2 in the framework solids are located in the linkers which are directed towards the pores. The structure of a perfluorinated conjugated microporous polymer has been modelled and it is predicted to take up 10% more CO2 than its hydrogenated counterpart. In addition, the vibrational, orientational and diffusive properties of CO2 adsorbed in the solids have been examined using molecular dynamics simulations. Intermolecular modes of such adsorbed species exhibit a blue shift with increasing gas pressure.

  11. Adsorption of methylene blue from aqueous solution on zeolitic material for color and toxicity removal

    OpenAIRE

    Denise Alves Fungaro; Lucas Caetano Grosche; Alessandro Pinheiro; Juliana de Carvalho Izidoro; Sueli Ivone Borrely

    2011-01-01

    The adsorption of methylene blue (MB) from aqueous solution was carried out using zeolite. This adsorbent material was synthesized from fly ash as a low-cost adsorbent, allowing fly ash to become a recycled residue. Factors that affected adsorption were evaluated: initial dye concentration, contact time and temperature. The equilibrium of adsorption was modeled by Langmuir, Freundlich and Temkin models. The adsorption obtained data were well described by Temkin, the adsorption isotherm model....

  12. On a non-isothermal model for nematic liquid crystals

    International Nuclear Information System (INIS)

    A model describing the evolution of a liquid crystal substance in the nematic phase is investigated in terms of three basic state variables: the absolute temperature thetav, the velocity field u and the director field d, representing preferred orientation of molecules in a neighbourhood of any point of a reference domain. The time evolution of the velocity field is governed by the incompressible Navier–Stokes system, with a non-isotropic stress tensor depending on the gradients of the velocity and of the director field d, where the transport (viscosity) coefficients vary with temperature. The dynamics of d is described by means of a parabolic equation of Ginzburg–Landau type, with a suitable penalization term to relax the constraint |d| = 1. The system is supplemented by a heat equation, where the heat flux is given by a variant of Fourier's law, depending also on the director field d. The proposed model is shown to be compatible with first and second laws of thermodynamics, and the existence of global-in-time weak solutions for the resulting PDE system is established, without any essential restriction on the size of the data

  13. Adsorption of simazine on zeolite H-Y and sol-gel technique manufactured porous silica: A comparative study in model and natural waters.

    Science.gov (United States)

    Sannino, Filomena; Marocco, Antonello; Garrone, Edoardo; Esposito, Serena; Pansini, Michele

    2015-01-01

    In this work, we studied the removal of simazine from both a model and well water by adsorption on two different adsorbents: zeolite H-Y and a porous silica made in the laboratory by using the sol-gel technique. The pH dependence of the adsorption process and the isotherms and pseudo-isotherms of adsorption were studied. Moreover, an iterative process of simazine removal from both the model and well water, which allowed us to bring the residual simazine concentration below the maximum concentration (0.05 mg L(-1)) of agrochemicals in wastewater to be released in surface waters or in sink allowed by Italian laws, was proposed. The results obtained were very interesting and the conclusions drawn from them partly differed from what could reasonably be expected. PMID:26357888

  14. Dye adsorption behavior of Luffa cylindrica fibers.

    Science.gov (United States)

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

    2008-05-01

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

  15. Dye adsorption behavior of Luffa cylindrica fibers

    International Nuclear Information System (INIS)

    Using natural Luffa cylindrica fibers as adsorbent removal of methylene blue dye from aqueous solutions at different temperatures and dye concentrations was investigated in this study. Thermodynamics and kinetics of adsorption were also investigated. The adsorption isotherms could be well defined with Langmuir model instead of Freundlich model. The thermodynamic parameters of methylene blue (MB) adsorption indicated that the adsorption is exothermic and spontaneous. The average MB adsorption capacity was found out as 49 mg/g and average BET surface area of fibers was calculated as 123 m2/g

  16. Dye adsorption behavior of Luffa cylindrica fibers

    Energy Technology Data Exchange (ETDEWEB)

    Demir, H. [Izmir Institute of Technology, Faculty of Engineering, Department of Chemical Engineering, Guelbahce Campus, 35430 Urla Izmir (Turkey)], E-mail: hasandemir@iyte.edu.tr; Top, A.; Balkoese, D.; Ulkue, S. [Izmir Institute of Technology, Faculty of Engineering, Department of Chemical Engineering, Guelbahce Campus, 35430 Urla Izmir (Turkey)

    2008-05-01

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

  17. Isothermal crystallization of iPP in model glass‐fiber composites

    OpenAIRE

    Janevski, Aco; Bogoeva-Gaceva, Gordana

    1998-01-01

    : Isothermal crystallization of iPP in model glass-fiber composites is studied by DSC, and the basic energetic parameters of crystallization are determined. Unsized untreated and thermally treated glass fibers are used in model composites to determine the role of the surface on nucleation and crystallization processes. Thermally treated glass fibers are found to exhibit a predominant nucleating effect as compared to unsized untreated ones, and the crystallization proceeds faster, resulting in...

  18. MODELING OF ISOTHERMAL PRECIPITATION KINETICS IN HSLA STEELS AND ITS APPLICATION

    Institute of Scientific and Technical Information of China (English)

    X.M. Zhao; D. Wu; L.Z. Zhang; Z.Y. Liu

    2004-01-01

    Microalloying elements in high-strength low-alloy steels, such as Nb, Ti and V, precipitate during hot-rolling processes. On the basis of classical theory of nucleation and growth, quantitative modeling of isothermal precipitation was developed, which was tested by the stress relaxation method, the calculated precipitation-time-temperature curve is in good agreements with the measured results, then the model was applied to predict the precipitation behavior during continuous cooling.

  19. 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

    Science.gov (United States)

    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.

  20. A comparison of three turbulence models for axisymmetric isothermal swirling flows in the near burner zone

    Energy Technology Data Exchange (ETDEWEB)

    Ahlstedt, H. [Tampere Univ. of Technology (Finland). Energy and Process Engineering

    1997-12-31

    In this work three different turbulence models, the k - {epsilon}, RNG k - {epsilon} and Reynolds stress model, have been compared in the case of confined swirling flow. The flow geometries are the isothermal swirling flows measured by International Flame Research Foundation (IFRF). The inlet boundary profiles have been taken from the measurements. At the outlet the effect of furnace end contraction has been studied. The k - {epsilon} model falls to predict the correct flow field. The RNG k - {epsilon} model can provide improvements, although it has problems near the symmetry axis. The Reynolds stress model produces the best agreement with measured data. (author) 13 refs.

  1. A coordination chemistry approach for modeling trace element adsorption

    International Nuclear Information System (INIS)

    The traditional distribution coefficient, Kd, is highly dependent on the water chemistry and the surface properties of the geological system being studied and is therefore quite inappropriate for use in predictive models. Adsorption, one of the many processes included in Kd values, is described here using a coordination chemistry approach. The concept of adsorption of cationic trace elements by solid hydrous oxides can be applied to natural solids. The adsorption process is thus understood in terms of a classical complexation leading to the formation of surface (heterogeneous) ligands. Applications of this concept to some freshwater, estuarine and marine environments are discussed. (author)

  2. Numerical modeling of non-isothermal gas flow and NAPL vapor transport in soil

    Science.gov (United States)

    Pártl, Ondřej; Beneš, Michal; Frolkovič, Peter; Illangasekare, Tissa; Smits, Kathleen

    2016-05-01

    We introduce a mathematical model for the description of non-isothermal compressible flow of gas mixtures in heterogeneous porous media and we derive an efficient semi-implicit time-stepping numerical scheme for the solution of the governing equations. We experimentally estimate the order of convergence of the scheme in spatial variables and we present several computational studies that demonstrate the ability of the numerical scheme.

  3. A theoretical study of the validity of the isothermal model in internal ballistics

    Directory of Open Access Journals (Sweden)

    J. N. Kapur

    1961-01-01

    Full Text Available The effect of the neglect of the kinetic energy term in isothermal model internal ballistics has been discussed. The adjustments to be made in the parameters have been worked out. It has been shown that either M is to be increased by about 18.7%for tubular charges and by about 17.7%for cord charges or theta is to be decreased by about 16.0%.

  4. Adsorption of acid dyes on Natural wool yarns

    International Nuclear Information System (INIS)

    The adsorption isotherms have been developed for two acid dyes (red and yellow azo dyes) individually on natural wool yarns. The study revealed strong interactions between the effects of solution ph, temperature and initial dye concentration. Equilibrium uptake data were fitted to the Redlich- Peterson isotherm model. The adsorption behaviour approaches Langmuir model at favourable conditions of higher temperature and lower ph for yellow dye. (authors). 9 refs., 5 tabs., 8 figs

  5. Batch Sorption Experiments: Langmuir and Freundlich Isotherm Studies for the Adsorption of Textile Metal Ions onto Teff Straw (Eragrostis tef) Agricultural Waste

    OpenAIRE

    Mulu Berhe Desta

    2013-01-01

    Adsorption of heavy metals (Cr, Cd, Pb, Ni, and Cu) onto Activated Teff Straw (ATS) has been studied using batch-adsorption techniques. This study was carried out to examine the adsorption capacity of the low-cost adsorbent ATS for the removal of heavy metals from textile effluents. The influence of contact time, pH, Temperature, and adsorbent dose on the adsorption process was also studied. Results revealed that adsorption rate initially increased rapidly, and the optimal removal efficiency ...

  6. ADSORPTION OF Mg(II) ION FROM AQUEOUS SOLUTION ON CHITOSAN BEADS AND CHITOSAN POWDER

    OpenAIRE

    Sari Edi Cahyaningrum

    2010-01-01

    A basic investigation on the removal of Mg(II) ion from aqueous solution by chitosan beads wasconducted in a batch adsorption system. The influence of different experimental parameters; pH,agitation period and different concentration of Mg(II) ion was evaluated. A pH 7.0 was found to be anoptimum pH for Mg(II) adsorption onto chitosan powder and chitosan beads. The Langmuir andFreundlich adsorption isotherm models were applied to describe the isotherms and isotherm constantsfor the adsorption...

  7. Thermodynamic frameworks of adsorption kinetics modeling: Dynamic water uptakes on silica gel for adsorption cooling applications

    International Nuclear Information System (INIS)

    This paper presents the thermodynamic frameworks to describe the dynamic uptakes of water vapor on various sizes and layers of silica gels for adsorption cooling applications. The proposed kinetic formulation is developed from the rigor of the partition function of each adsorptive sites and the kinetics theory of adsorbate molecules with the analogy of Langmuir kinetics. The simulation results calculated from the proposed formulation are compared with experimentally measured kinetics data of various single and multi layers configuration of silica gels–water systems. An interesting and useful finding has been established that the proposed model is thermodynamically consistent from the Henry's region to the saturated pressure, and also is connected with the surface structural heterogeneity factors of adsorbents. - Highlights: • Thermodynamic frameworks of adsorption kinetics. • Statistical partition functions of adsorptive sites. • Valid from the Henry's region to the saturated pressure. • Dynamic uptakes of water vapor on silica gels. • Model is connected with the pore structure of adsorbents

  8. Modeling of combined high-temperature oxidation and nitridation under isothermal and thermal-cycling conditions

    International Nuclear Information System (INIS)

    A computer model was developed to simulate the oxidation and nitridation behavior of nickel-base alloys at high temperatures. The numerical model combines a commercial thermochemical software (ChemApp) with a two-dimensional finite-difference diffusion calculation. The growth of the external oxide scale and the dependence of the internal corrosion behavior on cracking and spalling of the oxide layer have been incorporated into the simulation. The model has been applied to reveal the mechanisms of several corrosion processes which have been investigated in air and oxygen-free nitrogen atmosphere under isothermal and thermal-cycling conditions. (orig.)

  9. (Amino acid + silica) adsorption thermodynamics: Effects of temperature

    International Nuclear Information System (INIS)

    Highlights: • High resolution, low concentration Gly, Lys and Glu solution adsorption isotherms. • All isotherms fitted with Langmuir–Freundlich isotherm model. • Gly, Lys and Glu show exothermic adsorption processes. • Isosteric heat analyses reveal changes in interaction strength with surface coverage. - Abstract: A thorough understanding of amino acid adsorption by mineral and oxide surfaces has a major impact on a variety of industrial and biomedical applications. Little information currently exists regarding temperature effects on most of these adsorption processes. Deeper thermodynamic analyses of their multiple temperature adsorption isotherms would aid the interpretation of the interfacial interactions. Low solution concentration adsorption isotherms for glycine, lysine and glutamic acid on a silica adsorbent were generated for T = (291, 298 and 310) K. Data analysis via the Clausius–Clapeyron method yielded the isosteric heat of adsorption as a function of fractional monolayer coverage for each adsorptive. Each amino acid showed an exothermic adsorption response. Glycine and lysine experienced a greater negative effect of increased temperature compared with glutamic acid, indicating a greater number of adsorbed molecules than glutamic acid, with the former undergoing intermolecular clustering within the adsorbed phase. Isosteric heat analyses suggest ionic interactions for lysine and hydrogen bonding for glutamic acid, both weakening with increased coverage. In contrast, initial hydrogen bonding led to ionic bonding for glycine with increasing coverage

  10. Adsorption of gaseous pollutants on activated carbon filters. Modelling of the coupled exchanges of heat and mass; Adsorption de polluants gazeux sur des filtres de charbon actif. Modelisation des echanges couples de matiere et de chaleur

    Energy Technology Data Exchange (ETDEWEB)

    Fiani, E.

    2000-01-27

    The aim of this work is to remove gasoline and odorous molecules vapors. Thermodynamics and kinetics studies have been carried out; they concern the fixation of representative gases on activated carbons. Hydrogen sulfide and n-butane are chosen to represent the odorous molecules. Different activated carbons are considered: only the adsorbent impregnated by KOH has satisfying performance. The adsorption of hydrocarbons on a granulated activated carbon is studied on four original devices specifically perfected for this work: gravimetry, calorimetry, thermal measurements and gaseous phase chromatography. The gravimetric measurements are coupled to thermal measurements inside the granulates. Strong temperature variations have then been observed inside a granulate during the adsorption. These experimental results have been taken into account to adapt the classical Langmuir kinetic model. This new model allows to predict all the curves: setting / internal temperature variation for the adsorption of the hydrocarbons alone. The competitive nature of the adsorption sites allows then to explain qualitatively the adsorption of binary mixtures of hydrocarbons. At last, the classical Langmuir model allows to explain correctly the thermodynamic results, for the hydrocarbons alone or in binary mixture. The proposed modelling allows then to treat both on a kinetic and thermodynamic way the case of a non isothermal adsorption at the scale of an activated carbon granulate and to predict the phenomena at the filter scale. (O.M.)

  11. Modeling and computational simulation of adsorption based chemical heat pumps

    International Nuclear Information System (INIS)

    In this study a methodology is developed for the design of a packed bed reactor to be used in a Chemical Heat Pump (CHP). Adsorption and desorption of ethanol on active carbon packing in the reactor are investigated. Depending on the cycle, i.e. adsorption or desorption, cooling or heating of the reactor material is modeled through transient energy equation. The parameters associated with the vapor-carbon adsorption kinetics are experimentally determined. Then spatial distribution of temperature and adsorbed vapor amount are obtained with respect to time in adsorption–desorption cycles. These profiles are used to predict heating or cooling powers and COP for different adsorbent bed geometries and adsorption/desorption cycle times. Strong effect of heat transfer resistance of the packing, hence reactor size, on the system performance is observed. - Highlights: ► Performance of a chemical pump reactor is investigated theoretically. ► Ethanol adsorption/desorption on active carbon packing is modeled and simulated. ► Adsorption/desorption kinetics and equilibrium relations are found experimentally.

  12. Speeds of sound and isothermal compressibility of ternary liquid systems: Application of Flory's statistical theory and hard sphere models

    Indian Academy of Sciences (India)

    Vimla Vyas

    2008-04-01

    Speeds of sound and densities of three ternary liquid systems namely, toluene + -heptane + -hexane (I), cyclohexane + -heptane + -hexane (II) and -hexane + - heptane + -decane (III) have been measured as a function of the composition at 298.15 K at atmospheric pressure. The experimental isothermal compressibility has been evaluated from measured values of speeds of sound and density. The isothermal compressibility of these mixtures has also been computed theoretically using different models for hard sphere equations of state and Flory's statistical theory. Computed values of isothermal compressibility have been compared with experimental findings. A satisfactory agreement has been observed. The superiority of Flory's statistical theory has been established quite reasonably over hard sphere models.

  13. Adsorption of uranyl ions in nanoparticles of magnetite

    International Nuclear Information System (INIS)

    This work studied the uranium (VI) adsorption, in the form of UO22+ ions, of the nitride solution by the syntetic magnetite. This solution was prepared by precipitation adding a solution of NaOH to the solution containing the ions Fe2+. The time of contact and the isothermal of equilibrium of ions UO22+ adsorption was verified. The isothermal of equilibrium presented more concordance with the Freundlich model, which characterized a heterogeneous adsorption surface of the magnetite. The great advantage of this technology is the combination of two separation techniques, by adsorption and magnetic, resulting in a highly efficient and reusable system

  14. Wall modeling for the simulation of highly non-isothermal unsteady flows; Modelisation de paroi pour la simulation d'ecoulements instationnaires non-isothermes

    Energy Technology Data Exchange (ETDEWEB)

    Devesa, A

    2006-12-15

    Nuclear industry flows are most of the time characterized by their high Reynolds number, density variations (at low Mach numbers) and a highly unsteady behaviour (low to moderate frequencies). High Reynolds numbers are un-affordable by direct simulation (DNS), and simulations must either be performed by solving averaged equations (RANS), or by solving only the large eddies (LES), both using a wall model. A first investigation of this thesis dealt with the derivation and test of two variable density wall models: an algebraic law (CWM) and a zonal approach dedicated to LES (TBLE-{rho}). These models were validated in quasi-isothermal cases, before being used in academic and industrial non-isothermal flows with satisfactory results. Then, a numerical experiment of pulsed passive scalars was performed by DNS, were two forcing conditions were considered: oscillations are imposed in the outer flow; oscillations come from the wall. Several frequencies and amplitudes of oscillations were taken into account in order to gain insights in unsteady effects in the boundary layer, and to create a database for validating wall models in such context. The temporal behaviour of two wall models (algebraic and zonal wall models) were studied and showed that a zonal model produced better results when used in the simulation of unsteady flows. (author)

  15. Wall modeling for the simulation of highly non-isothermal unsteady flows

    International Nuclear Information System (INIS)

    Nuclear industry flows are most of the time characterized by their high Reynolds number, density variations (at low Mach numbers) and a highly unsteady behaviour (low to moderate frequencies). High Reynolds numbers are un-affordable by direct simulation (DNS), and simulations must either be performed by solving averaged equations (RANS), or by solving only the large eddies (LES), both using a wall model. A first investigation of this thesis dealt with the derivation and test of two variable density wall models: an algebraic law (CWM) and a zonal approach dedicated to LES (TBLE-ρ). These models were validated in quasi-isothermal cases, before being used in academic and industrial non-isothermal flows with satisfactory results. Then, a numerical experiment of pulsed passive scalars was performed by DNS, were two forcing conditions were considered: oscillations are imposed in the outer flow; oscillations come from the wall. Several frequencies and amplitudes of oscillations were taken into account in order to gain insights in unsteady effects in the boundary layer, and to create a database for validating wall models in such context. The temporal behaviour of two wall models (algebraic and zonal wall models) were studied and showed that a zonal model produced better results when used in the simulation of unsteady flows. (author)

  16. Hyper-parallel tempering Monte Carlo simulations of Ar adsorption in new models of microporous non-graphitizing activated carbon: effect of microporosity

    Energy Technology Data Exchange (ETDEWEB)

    Terzyk, Artur P [Department of Chemistry, Physicochemistry of Carbon Materials Research Group, N Copernicus University, Gagarin Street 7, 87-100 Torun (Poland); Furmaniak, Sylwester [Department of Chemistry, Physicochemistry of Carbon Materials Research Group, N Copernicus University, Gagarin Street 7, 87-100 Torun (Poland); Gauden, Piotr A [Department of Chemistry, Physicochemistry of Carbon Materials Research Group, N Copernicus University, Gagarin Street 7, 87-100 Torun (Poland); Harris, Peter J F [Centre for Advanced Microscopy, University of Reading, Whiteknights, Reading RG6 6AF (United Kingdom); Wloch, Jerzy [Department of Chemistry, Synthesis and Modification of Carbon Materials Research Group, N Copernicus University, Gagarin Street 7, 87-100 Torun (Poland); Kowalczyk, Piotr [Division of Chemical Engineering, University of Queensland, Brisbane, QLD 4072 (Australia)

    2007-10-10

    The adsorption of gases on microporous carbons is still poorly understood, partly because the structure of these carbons is not well known. Here, a model of microporous carbons based on fullerene-like fragments is used as the basis for a theoretical study of Ar adsorption on carbon. First, a simulation box was constructed, containing a plausible arrangement of carbon fragments. Next, using a new Monte Carlo simulation algorithm, two types of carbon fragments were gradually placed into the initial structure to increase its microporosity. Thirty six different microporous carbon structures were generated in this way. Using the method proposed recently by Bhattacharya and Gubbins (BG), the micropore size distributions of the obtained carbon models and the average micropore diameters were calculated. For ten chosen structures, Ar adsorption isotherms (87 K) were simulated via the hyper-parallel tempering Monte Carlo simulation method. The isotherms obtained in this way were described by widely applied methods of microporous carbon characterisation, i.e. Nguyen and Do, Horvath-Kawazoe, high-resolution {alpha}{sub s} plots, adsorption potential distributions and the Dubinin-Astakhov (DA) equation. From simulated isotherms described by the DA equation, the average micropore diameters were calculated using empirical relationships proposed by different authors and they were compared with those from the BG method.

  17. Hyper-parallel tempering Monte Carlo simulations of Ar adsorption in new models of microporous non-graphitizing activated carbon: effect of microporosity

    International Nuclear Information System (INIS)

    The adsorption of gases on microporous carbons is still poorly understood, partly because the structure of these carbons is not well known. Here, a model of microporous carbons based on fullerene-like fragments is used as the basis for a theoretical study of Ar adsorption on carbon. First, a simulation box was constructed, containing a plausible arrangement of carbon fragments. Next, using a new Monte Carlo simulation algorithm, two types of carbon fragments were gradually placed into the initial structure to increase its microporosity. Thirty six different microporous carbon structures were generated in this way. Using the method proposed recently by Bhattacharya and Gubbins (BG), the micropore size distributions of the obtained carbon models and the average micropore diameters were calculated. For ten chosen structures, Ar adsorption isotherms (87 K) were simulated via the hyper-parallel tempering Monte Carlo simulation method. The isotherms obtained in this way were described by widely applied methods of microporous carbon characterisation, i.e. Nguyen and Do, Horvath-Kawazoe, high-resolution αs plots, adsorption potential distributions and the Dubinin-Astakhov (DA) equation. From simulated isotherms described by the DA equation, the average micropore diameters were calculated using empirical relationships proposed by different authors and they were compared with those from the BG method

  18. Proton adsorption onto alumina: extension of multisite complexation (MUSIC) theory

    Energy Technology Data Exchange (ETDEWEB)

    Nagashima, K.; Blum, F.D.

    1999-09-01

    The adsorption isotherm of protons onto a commercial {gamma}-alumina sample was determined in aqueous nitric acid with sodium nitrate as a background electrolyte. Three discrete regions could be discerned in the log-log plots of the proton isotherm determined at the solution pH 5 to 2. The multisite complexation (MUSIC) model was modified to analyze the simultaneous adsorption of protons onto various kinds of surface species.

  19. Proton Adsorption onto Alumina: Extension of Multisite Complexation (MUSIC) Theory.

    Science.gov (United States)

    Nagashima; Blum

    1999-09-01

    The adsorption isotherm of protons onto a commercial gamma-alumina sample was determined in aqueous nitric acid with sodium nitrate as a background electrolyte. Three discrete regions could be discerned in the log-log plots of the proton isotherm determined at the solution pH 5 to 2. The multisite complexation (MUSIC) model was modified to analyze the simultaneous adsorption of protons onto various kinds of surface species. Copyright 1999 Academic Press. PMID:10441408

  20. Desorption isotherms and mathematical modeling of thin layer drying kinetics of tomato

    Science.gov (United States)

    Belghith, Amira; Azzouz, Soufien; ElCafsi, Afif

    2016-03-01

    In recent years, there is an increased demand on the international market of dried fruits and vegetables with significant added value. Due to its important production, consumption and nutrient intake, drying of tomato has become a subject of extended and varied research works. The present work is focused on the drying behavior of thin-layer tomato and its mathematical modeling in order to optimize the drying processes. The moisture desorption isotherms of raw tomato were determined at four temperature levels namely 45, 50, 60 and 65 °C using the static gravimetric method. The experimental data obtained were modeled by five equations and the (GAB) model was found to be the best-describing these isotherms. The drying kinetics were experimentally investigated at 45, 55 and 65 °C and performed at air velocities of 0.5 and 2 m/s. In order to investigate the effect of the exchange surface on drying time, samples were dried into two different shapes: tomato halves and tomato quarters. The impact of various drying parameters was also studied (temperature, air velocity and air humidity). The drying curves showed only the preheating period and the falling drying rate period. In this study, attention was paid to the modeling of experimental thin-layer drying kinetics. The experimental results were fitted with four different models.

  1. Adsorption equilibria of butyl- and amylbenzene on monolithic silica-based columns.

    Science.gov (United States)

    Cavazzini, Alberto; Bardin, Gregory; Kaczmarski, Krzystof; Szabelski, Paweł; Al-Bokari, Majed; Guiochon, Georges

    2002-05-31

    The adsorption isotherms of butyl- and amylbenzene on silica monolithic columns were measured by frontal analysis. The external, internal and total porosities of these columns were determined by inverse size-exclusion chromatography. The adsorption isotherms are concave upward in the entire concentration range investigated. They were fitted to the anti-Langmuir model, an unusual model in liquid-solid and liquid-liquid phase equilibria. Band profiles under overloaded conditions were recorded. They were in good agreement with the profiles calculated using th,e lumped pore diffusion model of chromatography and these adsorption isotherms. PMID:12113336

  2. Modeling adsorption-desorption processes of Cd on montmorillonite

    OpenAIRE

    Undabeytia López, Tomás; Nir, Shlomo; Rytwo, Giora; Morillo González, Esmeralda; Maqueda Porras, Celia

    1998-01-01

    Adsorption-desorption of Cd to Ca montmorillonite (SAz-1) was studied at concentrations ranging from 44.5 to 266.8 IzM. An adsorption model was employed in the analysis of the data. The procedure consists of solving the electrostatic Gouy-Chapman equations and calculating adsorbed amounts of the cations as the sum of the cations residing in the double-layer region, and the cations chemically bound to the surface, in a closed system. The model also accounts explicitly for cation co...

  3. Adsorption of basic dye from aqueous solution onto fly ash

    Energy Technology Data Exchange (ETDEWEB)

    J.X. Lin; S.L. Zhan; M.H. Fang; X.Q. Qian; H. Yang [Zhejiang University, Hangzhou (China). College of Civil Engineering and Architecture

    2008-04-15

    The fly ash treated by H{sub 2}SO{sub 4} was used as a low-cost adsorbent for the removal of a typical dye, methylene blue, from aqueous solution. An increase in the specific surface area and dye-adsorption capacity was observed after the acid treatment. The adsorption isotherm and kinetics of the treated fly ash were studied. The experimental results were fitted using Langmuir and Freundlich isotherms. It shows that the Freundlich isotherm is better in describing the adsorption process. Two kinetic models, pseudo-first order and pseudo-second order, were employed to analyze the kinetic data. It was found that the pseudo-second-order model is the better choice to describe the adsorption behavior. The thermodynamic study reveals that the enthalpy ({Delta}H{sup 0}) value is positive (5.63 kJ/mol), suggesting an endothermic nature of the adsorption.

  4. Instabilities and the adiabatic and isothermal blast wave models for supernova remnants

    International Nuclear Information System (INIS)

    Isenberg as well as lerche and Vasyliunas proposed the existence of an instability to radial perturbations in adiabatic and isothermal models of self-similar supernova blast waves. Their derivations fail to impose the physical conservation laws at the shock (i.e., the Rankine-Hugoniot jump conditions) as boundary conditions, and their claim of an instability is unsubstantiated. Although as analytic demonstration of the stability of the adiabatic self-similar solution does not presently exist, the cumulative result of three decades of gas dynamic experimentation and numerical simulation provides unmistakable evidence for the stabilty of self-similar blast waves

  5. Phase field modeling of multiple dendrite growth of AI-Si binary alloy under isothermal solidification

    Institute of Scientific and Technical Information of China (English)

    Sun Qiang; Zhang Yutuo; Cui Haixia; Wang Chengzhi

    2008-01-01

    Phase field method offers the prospect of being able to perform realistic numerical experiments on dendrite growth in metallic systems. In this study, the growth process of multiple dendrites in Ai-2-mole-%-Si binary alloy under isothermal solidification was simulated using phase field model. The simulation results showed the impingement of arbitrarily oriented crystals and the competitive growth among the grains during solidification. With the increase of growing time, the grains begin to coalesce and impinge the adjacent grains. When the dendrites start to impinge, the dendrite growth is obviously inhibited.

  6. KINETIC MODELING AND ISOTHERM STUDIES ON A BATCH REMOVAL OF ACID RED 114 BY AN ACTIVATED PLANT BIOMASS

    Directory of Open Access Journals (Sweden)

    N. RAJAMOHAN

    2013-12-01

    Full Text Available In this paper, the dye Acid Red 114(AR 114 was removed from aqueous solutions using Acid-Activated Eichornia Crassipes (AAEC under batch conditions. The optimum conditions for AR 114 removal were found to be pH 1.5, adsorbent dosage = 1.25 g/L of solution and equilibrium time = 3 h. The equilibrium data were evaluated for compliance with Langmuir, Freundlich and Temkin isotherms and Langmuir isotherm was found to fit well. The maximum sorption capacity was estimated as 112.34 mg/g of adsorbent. Also, adsorption kinetics of the dye was studied and the rates of sorption were found to follow pseudo-second order kinetics with good correlation (R2 ≥ 0.997.The kinetic study at different temperatures revealed that the sorption was an endothermic process. The activation energy of the sorption process was estimated as 9.722 kJ/mol.

  7. Adsorption of U(VI) on sericite in the presence of Bacillus subtilis: A combined batch, EXAFS and modeling techniques

    Science.gov (United States)

    Sun, Yubing; Zhang, Rui; Ding, Congcong; Wang, Xiangxue; Cheng, Wencai; Chen, Changlun; Wang, Xiangke

    2016-05-01

    The effect of Bacillus subtilis (B. subtilis) on the adsorption of U(VI) onto sericite was investigated using batch, EXAFS and modeling techniques. The batch adsorption indicated that the increased adsorption of U(VI) on sericite + B. subtilis systems at pH 6.0 due to the combination of deprotonated carboxyl groups of B. subtilis with the hydroxyl of sericite. The slightly enhanced adsorption of U(VI) on sericite + B. subtilis with increasing CO2 contents at pH electrostatic attraction between positively charged U(VI) species (UO22+ species) and negatively charged surface of sericite + B. subtilis, whereas the U(VI) adsorption sharply decreased at pH > 7.0 owing to electrostatic repulsion between negatively charged sericite + B. subtilis and negatively charged U(VI) species such as UO2(OH)3- or UO2(CO3)22- species. According to EXAFS analysis, the increased adsorption mechanism of U(VI) on sericite + B. subtilis at pH 4.0 was attributed to the formation of U-P shell, whereas the bidentate inner-sphere surface complexes was also observed at pH 7.0 due to the formation of U-C shell (2.92 Å) and/or U-Si/Al (3.18 Å) shell. Under the range of allowable error, the pH-dependent and isothermal adsorption of U(VI) on sericite + B. subtilis can be fitted by surface complexation modeling using ion exchange and surface complexation reaction by using equilibrium parameters obtained from each binary systems. These findings are important to understand the fate and transport of U(VI) on the mineral-bacteria ternary systems in the near-surface environment.

  8. Phosphate adsorption on lanthanum loaded biochar.

    Science.gov (United States)

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

    2016-05-01

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

  9. Adsorption and desorption phenomena of PEO-PPO-PEO triblock copolymer systems on model surfaces

    Science.gov (United States)

    Brandani, Pietro

    This thesis reports on the kinetic and equilibrium behavior for the adsorption from solution of a family of copoly(ethyleneoxide-propyleneoxide-ethyleneoxide), PEO-PPO-PEO, triblock copolymers on gold surfaces modified by a methyl terminated self-assembled monolayer of a long chain alkanethiol (CH3(CH 2)10SH) and by a long chain mercaptoalkanoic acid (HOOC(CH 2)10SH). Events at the surface were monitored with a surface plasmon resonance technique with a high time resolution (0.1 s). Atomic force microscopy (AFM) in the liquid environment was conducted on a selected number of cases to discern the morphology of the copolymer coated surfaces. The data were analyzed in the context a mass transfer corrected Langmuir kinetics model. The model is only able to reproduce the observations for very dilute solutions, or for the initial stages of the process, but it allows to better discriminate the onset of the different mechanisms of adsorption. For the hydrophobic surface, the adsorbed amounts go through a maximum near the critical micelle concentration (CMC) and thus the process is not consistent with a Langmuir isotherm; in addition we the process is partially irreversible. The kinetics show that, for a series of compounds with the same length of the PPO block, the character of the adsorption process is affected by the relative balance of the hydrophilic and hydrophobic content within the copolymer: higher hydrophobic content leads to enhanced adsorption rates past the CMC. AFM observations confirm that globular micelle-like aggregates are present at the surface for the more hydrophobic species. In contrast, a uniform monolayer-like morphology is observed for the more hydrophilic species. For the hydrophilic surface, it is again found that the adsorbed amounts go through a maximum near the critical micelle concentration (CMC), however, in this case, the process is reversible. Enhanced adsorption rates past the CMC are observed irrespective of the relative balance of the

  10. ADSORPTION OF METHYLENE BLUE FROM AQUEOUS SOLUTION ON ACTIVATED CARBON PRODUCED FROM SOYBEAN OIL CAKE BY KOH ACTIVATION

    OpenAIRE

    Turgay Tay; Murat Erdem; Burak Ceylan,; Selhan Karagöz

    2012-01-01

    This study presents the adsorption behavior of the methylene blue (MB) dye onto the activated carbon produced from soybean oil cake by chemical activation with KOH at 800 °C. The adsorption isotherms, kinetic models, and thermodynamic parameters of the adsorption were studied. The Langmuir isotherm showed a better fit than the Freundlich isotherm. The adsorption rate was described by pseudo-second-order kinetics. The negative values of ΔG° and the positive values of ΔH° indicate that the adso...

  11. Modelling rheology of isothermal flow of carboxymethyl cellulose-alginate suspension in a horizontal conduit

    International Nuclear Information System (INIS)

    The rheology of isothermal flow of Carboxymethylcellulose (CMC) solution at 0.5 % mass concentration and, loaded with spherical alginate particles was modeled and analysed. A carrier fluid flow model of solid-liquid pseudoplastic Non-Newtonian suspension in a horizontal pipe governed by constitutive power law of Ostwald Wan der Waal was found not applicable to the range of experimental shearing rates of the flow regime of CMC alginate suspension. Therefore, a new model based on the effect of dynamic viscosity on concentration of the spherical particles in Newtonian flow regimes in relation to Brownian activated motion and hydrodynamics was developed to account for zero shear viscosity and resolve other physical limitations. Upon validation, the dynamic viscosity model fitted the experimental data of the shearing rates. (au)

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

    OpenAIRE

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

    2016-01-01

    International audience 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 mo...

  13. Biosorption of radiostrontium by alginate beads. Application of isotherm models and thermodynamic studies

    International Nuclear Information System (INIS)

    Radioactive strontium is one of the major radioactive contaminant and its contamination is a very serious concern. Therefore, there is a need for economic, effective, non-toxic, readily available and abundant adsorbent or biosorbent to remove strontium from solutions. In this study, biosorption of 85Sr as a surrogate for 90Sr onto alginate beads was investigated in a batch system. Alginate beads were prepared from Na-alginate via cross-linking with divalent calcium ions according to the egg box model. The effect of several parameters such as pH, initial strontium concentration, contact time, dosage of alginate beads and temperature were investigated. In order to optimize the design of biosorption system for the removal of strontium, it is important to establish the most appropriate correlation for equilibrium curves. The experimental isotherm data were described by 6 different biosorption isotherm models, namely Langmuir, Freundlich, Dubinin-Radushkevich, Temkin, Flory-Huggins and Brunauer, Emmer and Teller, with constants obtained from linear and non-linear regression methods. The thermodynamic parameters (ΔHdeg, ΔSdeg and ΔGdeg) for strontium biosorption were also determined. The results indicate that these alginate beads have a good potential for the biosorption of strontium from solutions. (author)

  14. Non-isothermal modelling of the all-vanadium redox flow battery

    International Nuclear Information System (INIS)

    An non-isothermal model for the all-vanadium redox flow battery (RFB) is presented. The two-dimensional model is based on a comprehensive description of mass, charge, energy and momentum transport and conservation, and is combined with a global kinetic model for reactions involving vanadium species. Heat is generated as a result of activation losses, electrochemical reaction and ohmic resistance. Numerical simulations demonstrate the effects of changes in the operating temperature on performance. It is shown that variations in the electrolyte flow rate and the magnitude of the applied current substantially alter the charge/discharge characteristics, the temperature rise and the distribution of temperature. The influence of heat losses on the charge/discharge behaviour and temperature distribution is investigated. Conditions for localised heating and membrane degradation are discussed.

  15. Adsorption of Lead Ions by Linde type F(K Zeolite

    Directory of Open Access Journals (Sweden)

    Han Chenghui

    2016-01-01

    Full Text Available The Test was to examine the adsorption property of Pb(II irons by Linde type F (K zeolite. The zeolite was synthesized by fly ash. The adsorbent dosage, pH, reaction temperature and reaction time were investigated. The adsorption isotherm and adsorption kinetics equation were studied. The results showed the adsorbent dosage, pH, reaction temperature and reaction time had significant effects on the adsorption of Pb(II irons. The removal rate was improved with the increasing of zeolite dosage. The saturated adsorption capacity was decreased gradually. The adsorption of Pb(II irons tended to saturate when initial pH was 6. With the increasing of temperature, the equilibration time of adsorption was shorter. Langmuir isotherm was more applicable to explain the monolayer adsorption procedure of Pb(II on Linde type F(K zeolite. For adsorption kinetics, pseudo-second order model showed better calculation results.

  16. The Grand Ensemble of Subsystems: Applications to Fitting Single-Component Adsorption Data

    CERN Document Server

    Mosquera, Martin A

    2009-01-01

    In this work, it is reviewed the cell model of adsorption by using the small system grand ensemble method. Under the common assumption that the adsorbate phase is divided into identical and weakly-interacting subsystems, it is suggested that the general multiparametric isotherm that arise from the theory may be used to fit the experimental data of adsorption of gases and vapours on microporous adorbents (type I isotherm), even though these present heterogeneties like pore size distribution. A simplified isotherm that reduces the number of adjustable parameters with respect to the general isotherm is proposed. Both isotherms, due to their relative high accuracy, can be used to estimate thermodynamical properties like isosteric and differential heats of adsorption. Also, a simple method is presented for systems that show an apparent variation in the coverage limit as function of temperature; for several systems, this method reduces the fitting deviations. Finally, several applications to fitting data of adsorpt...

  17. Adsorption of arsenic and boron by soil

    Energy Technology Data Exchange (ETDEWEB)

    Sakata, M.

    1986-01-01

    The author reports a study of the soil adsorption of As (trivalent) and B leached from coal ash. It has been found that the amount of adsorption is greatly affected by the pH of the solution. Maximum adsorption of As occurred from solutions with pH of about 8, while pH 8-9 resulted in maximum B adsorption. Furthermore, the As adsorption is related to the quantity of iron oxides and hydrated iron oxides in the soil, while the adsorption of B is related to the quantity of hydrated aluminium oxides and allophanes. Within the range of concentrations studied, the adsorption isotherm for As obeyed the Langmuir equation, and the B isotherm, that of Freundlich. At low concentrations, both elements conform to the Henry adsorption isotherm. The author also reports that the impact on ground water of elements such as As and B leached from coal ash can be conveniently predicted or evaluated by means of a diffusive flow model. 30 references, 14 figures, 3 tables.

  18. Adsorption of phenol on wood surfaces

    Science.gov (United States)

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

    2016-03-01

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

  19. Biosorption of Strontium from Simulated Nuclear Wastewater by Scenedesmus spinosus under Culture Conditions: Adsorption and Bioaccumulation Processes and Models

    Directory of Open Access Journals (Sweden)

    Mingxue Liu

    2014-06-01

    Full Text Available Algae biosorption is an ideal wastewater treatment method when coupled with algae growth and biosorption. The adsorption and bioaccumulation of strontium from simulated nuclear wastewater by Scenedesmus spinosus were investigated in this research. One hundred mL of cultured S. spinosus cells with a dry weight of 1.0 mg in simulated nuclear wastewater were used to analyze the effects on S. spinosus cell growth as well as the adsorption and bioaccumulation characters under conditions of 25 ± 1 °C with approximately 3,000 lux illumination. The results showed that S. spinosus had a highly selective biosorption capacity for strontium, with a maximum bioremoval ratio of 76%. The adsorbed strontium ion on cell walls was approximately 90% of the total adsorbed amount; the bioaccumulation in the cytoplasm varied by approximately10%. The adsorption quantity could be described with an equilibrium isotherm. The pseudo-second-order kinetic model suggested that adsorption was the rate-limiting step of the biosorption process. A new bioaccumulation model with three parameters was proposed and could give a good fit with the experiment data. The results suggested that S. spinosus may be a potential biosorbent for the treatment of nuclear wastewater in culture conditions.

  20. Modelling of the non isothermal cyclic behaviour of a polycrystalline Cu Zn Al shape memory alloy

    International Nuclear Information System (INIS)

    In this paper, a model describing the behaviour of Shape Memory Alloys (SMA) under constant applied stress and thermal cycling is developed. This is the first (and necessary) step to obtain a coherent modelling of the well-known Two Way Shape Memory Effect (TWSME) exhibited by SMA after a training process. Two different mechanisms characteristic to SMA are involved in the present description. The first one is related to training itself, whose macroscopic manifestation is the appearance of a permanent strain. The second one concerns the response of SMA to non-isothermal loading. It can be solved by the introduction of news variables in the internal variables set. There are the volume fraction of self-accommodating martensite (pure thermal effect) and the volume fraction of ''oriented'' martensite (thermo-mechanical effect). The comparison between simulation and our experimental results on Cu Zn Al polycrystals is fairly good. (orig.)

  1. Relationship between carbon microstructure, adsorption energy and hydrogen adsorption capacity at different temperatures

    International Nuclear Information System (INIS)

    observed for the CMS sample having micropores sizes of about 5 Angstroms. The SWNT sample shows a lower Qst due to its relatively wide PSD, and the non-porous carbon black is characterized by the lowest Qst values. The Qst values calculated from H2 adsorption isotherms measured at cryogenic temperatures below 1 atmosphere can be used to predict/estimate H2 adsorption at ambient temperatures under high pressures. Fig 3 shows the H2 adsorption isotherm on the SWNT sample calculated for 298 K from the low pressure and low temperature (77, 87 K) data using the Clausius-Clapeyron equation and assuming the temperature independence of the Qst values. A good agreement with high-pressure experimental data is observed. Predictions using DFT model will also be discussed during presentation. (authors)

  2. Modeling two-rate adsorption kinetics: Two-site, two-species, bilayer and rearrangement adsorption processes.

    Science.gov (United States)

    Tripathi, Sumit; Tabor, Rico F

    2016-08-15

    The adsorption kinetics of many systems show apparent two-rate processes, where there appears to be resolved fast and slow adsorption steps. Such non-standard adsorption processes cannot be accounted for by conventional modeling methods, motivating new approaches. In this work, we present four different models that can account for two-rate adsorption and are based upon physically realistic processes - two adsorbing species, two surface sites having different energies, bilayer formation and molecular rearrangement modes. Each model is tested using a range of conditions, and the characteristic behavior is explored and compared. In these models, the effects of mass transport and bulk concentration are also accounted for, making them applicable in systems which are transport-limited or attachment-limited, or intermediate between the two. The applicability of these models is demonstrated by fitting exemplar experimental data for each of the four models, selecting the model on the basis of the known physical behavior of the adsorption kinetics. These models can be applied in a wide range of systems, from stagnant adsorption in large volume water treatment to highly dynamic flow conditions relevant to printing, coating and processing applications. PMID:27209397

  3. A non-isothermal integrated model of coal-fired traveling grate boilers

    International Nuclear Information System (INIS)

    The aim of this study is to develop a mathematical model for coal combustion in traveling grate boilers. The model contains a 'bed-model' part and a 'furnace-model' part. Within the description of the 'bed-model', a non-isothermal particle model is proposed, in order to accommodate temperature gradients within combusting particles. The 'bed-model' is then coupled with the 'furnace-model' based on an integrated grid. To verify the model, an experimental fixed-bed furnace has been set up to simulate combustion in a real chain grate stoker. Concentrations of gas species at the bed surface have been measured. Predicted results are in reasonable agreement with experimental data. This has provided a basis for studying the effect of major parameters influencing boiler behavior, for optimizing combustion conditions. These factors have included the excess air ratio and particle diameter. The results show that there is an optimum excess air ratio required for optimized combustion and that smaller coal particle sizes (in the range of 0.02-0.04 m) enhance ignition and burnout properties of the fuel. It appears essential during operation to monitor and control excess air ratios and particle diameters carefully controlled.

  4. TWO-PARAMETER ISOTHERMS OF METHYL ORANGE SORPTION BY PINECONE DERIVED ACTIVATED CARBON

    Directory of Open Access Journals (Sweden)

    M. R. Samarghandi ، M. Hadi ، S. Moayedi ، F. Barjasteh Askari

    2009-10-01

    Full Text Available The adsorption of a mono azo dye methyl-orange (MeO onto granular pinecone derived activated carbon (GPAC, from aqueous solutions, was studied in a batch system. Seven two-parameter isotherm models Langmuir, Freundlich, Dubinin-Radushkevic, Temkin, Halsey, Jovanovic and Hurkins-Jura were used to fit the experimental data. The results revealed that the adsorption isotherm models fitted the data in the order of Jovanovic (X2=1.374 > Langmuir > Dubinin-Radushkevic > Temkin > Freundlich > Halsey > Hurkins-Jura isotherms. Adsorption isotherms modeling showed that the interaction of dye with activated carbon surface is localized monolayer adsorption. A comparison of kinetic models was evaluated for the pseudo-second order, Elovich and Lagergren kinetic models. Lagergren first order model was found to agree well with the experimental data (X2=9.231. In order to determine the best-fit isotherm and kinetic models, two error analysis methods of Residual Mean Square Error and Chi-square statistic (X2 were used to evaluate the data.

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

    International Nuclear Information System (INIS)

    Highlights: → Dolomite was used for adsorption of Sr (II) and Ba (II) for the first time. → The experiments were carried out to consider the effect of adsorption parameters. → We analyzed all experimental data using isotherm, kinetic and thermodynamic models. → The maximum adsorption capacity of dolomite was compared with other adsorbents. → Thermodynamic data indicate that the adsorption process was exothermic. - Abstract: 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 (ΔGo, ΔHo, and ΔSo) 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.

  6. Contribution to the study of chemical and physical properties of mineral coals and mineral active coals. New method of determination of adsorption isotherms

    International Nuclear Information System (INIS)

    For a better understanding of the influence of factors which influence the coal activation process, this research thesis aims at following, step by step, the evolution of texture and chemical properties of a mineral coal submitted to a series of treatments which allow its progressive transformation into an active coal. The first part reports sample preparation and the study of chemical properties, notably surface functions. The second part addresses physical properties of samples: study of porosity by electronic microscopy, apparatus used to study gas adsorption, helium adsorption by solid surfaces at room temperature, study of the porous texture by gas adsorption

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

    Science.gov (United States)

    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(-)models provide the best fit to the experimental points, indicating that the micropore volume filling theory is the best representation of the ion exchange processes under study among other 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. PMID:21497015

  8. Competitive adsorption of heavy metal ions on peat

    Institute of Scientific and Technical Information of China (English)

    LIU Zhi-rong; ZHOU Li-min; WEI Peng; ZENG Kai; WEN Chuan-xi; LAN Hui-hua

    2008-01-01

    The uptake capacities, and the adsorption kinetics, of copper, Cu(Ⅱ), nickel, Ni(Ⅱ), and cadmium, Cd(Ⅱ), on peat have been studied under static conditions. The results show that the adsorption rates are rapid: equilibrium is reached in twenty minutes. The adsorption of copper, nickel and cadmium is pH dependent over the pH range from 2 to 6. The adsorption kinetics can be excellently described by the Elovich kinetic equation. The adsorption isotherm fits a Langmuir model very well. The adsorption capacifies follow the order Cu2+>Ni2+>Cd2+ in single-component systems and the competitive adsorption capacities fall in the decreasing order Cu2+> Ni2+>Cd2+ in multi-component systems. The adsorption capacities of these three heavy metal ions on peat are consistent with their observed competitive adsorption capacities.

  9. Gallium adsorption on (0001) GaN surfaces

    OpenAIRE

    Adelmann, C.; Brault, J.; G. Mula; Daudin, B.; Lymperakis, L.; Neugebauer, J.

    2003-01-01

    We study the adsorption behavior of Ga on (0001) GaN surfaces combining experimental specular reflection high-energy electron diffraction with theoretical investigations in the framework of a kinetic model for adsorption and ab initio calculations of energy parameters. The measurement of a Ga/GaN adsorption isotherm allows the quantification of the equilibrium Ga surface coverage as a function of the impinging Ga flux. The temperature dependence is discussed within an {\\em ab initio} based gr...

  10. Modeling equilibrium adsorption of organic micropollutants onto activated carbon

    KAUST Repository

    De Ridder, David J.

    2010-05-01

    Solute hydrophobicity, polarizability, aromaticity and the presence of H-bond donor/acceptor groups have been identified as important solute properties that affect the adsorption on activated carbon. However, the adsorption mechanisms related to these properties occur in parallel, and their respective dominance depends on the solute properties as well as carbon characteristics. In this paper, a model based on multivariate linear regression is described that was developed to predict equilibrium carbon loading on a specific activated carbon (F400) for solutes reflecting a wide range of solute properties. In order to improve prediction accuracy, groups (bins) of solutes with similar solute properties were defined and solute removals were predicted for each bin separately. With these individual linear models, coefficients of determination (R2) values ranging from 0.61 to 0.84 were obtained. With the mechanistic approach used in developing this predictive model, a strong relation with adsorption mechanisms is established, improving the interpretation and, ultimately, acceptance of the model. © 2010 Elsevier Ltd.

  11. Adsorption and wetting.

    OpenAIRE

    Schlangen, L.J.M.

    1995-01-01

    Adsorption and wetting are related phenomena. In order to improve knowledge of both and their relations, experiments, thermodynamics and a theoretical interpretation have been connected, starring n-alkanes.Starting from the Gibbs adsorption equation thermodynamic relations between vapour adsorption and wetting are derived. The surface pressure of a film, formed by vapour adsorption on a solid surface, is calculated by integrating the vapour adsorption isotherm. The surface pressure at the sat...

  12. Cooperative sequential adsorption model with evaporation on Cayley tress

    Science.gov (United States)

    Banks, William; Schwen, Eric; Seredinski, Andrew; Simpson, Brian; Kim, Vincent; Zhao, Conan

    2014-03-01

    We present analytical results for a cooperative sequential adsorption model with evaporation on Cayley trees of coordination number three and four. This model can be applied to a variety of physical situations, such as ionic self-assembly of nanoparticles, or epidemic and voting problems. We first map our model onto an Ising model and use known results to characterize the steady state of the system. We derive the rate equations for the particle density and solve them numerically in the mean field approximation. We also discuss the role of the particle correlations and their relationship to external factors. Washington and Lee University, R. E. Lee Summer Scholars Program, The National Science Foundation.

  13. Adsorption of Nitrobenzene from Water onto High Silica Zeolites and Regeneration by Ozone

    OpenAIRE

    Reungoat, Julien; Pic, Jean-Stéphane; Manero, Marie-Hélène; Debellefontaine, Hubert

    2007-01-01

    This work investigates the removal of nitrobenzene (NB), a model pollutant from water, by combining adsorption onto zeolites and regeneration with ozone. The adsorption equilibrium isotherms of NB onto zeolites enabled the best adsorbent to be selected and zeolites with a high Si/Al ratio were the most efficient. The adsorption capacity depended on the Si/Al ratio and on the pore size. In a sequential process coupling adsorption and oxidation by ozone, NB was completely removed from water and...

  14. Sorption of Pb2+ from Aqueous Solution unto Modified Rice Husk: Isotherms Studies

    Directory of Open Access Journals (Sweden)

    A. O. Dada

    2013-01-01

    Full Text Available Investigation of the sorption potential of rice husk, an agricultural waste, as an adsorbent was carried out. The rice husk was modified with orthophosphoric acid and was used for adsorption of lead (II ions (Pb2+ from aqueous solution. Physicochemical properties of the modified rice husk were determined. Equilibrium sorption data were confirmed with Langmuir, Freundlich and Temkin adsorption isotherms. On the basis of adsorption isotherm graphs, R2 values were determined to be 0.995, 0.916, and 0.797 for Langmuir, Temkin, and Freundlich isotherms, respectively, indicating that the data fitted well into the adsorption isotherms, but Langmuir isotherm is a better model. The maximum monolayer coverage from Langmuir studies, Qmax=138.89 mg/g, Langmuir isotherm constant, KL=0.699 L/mg, and the separation factor, RL=1.41×10−2 at 100 mg/L of lead(II ions indicating that the sorption process, was favourable. The suitability of modified rice husk as an adsorbent for the removal of lead ions from aqueous solution and its potential for pollution control is established.

  15. Adsorption of Monobutyl Phthalate from Aqueous Phase onto Two Macroporous Anion-Exchange Resins

    Directory of Open Access Journals (Sweden)

    Zhengwen Xu

    2014-01-01

    Full Text Available As new emerging pollutants, phthalic acid monoesters (PAMs pose potential ecological and human health risks. In the present study, adsorption performance of monobutyl phthalate (MBP onto two macroporous base anion-exchange resins (D-201 and D-301 was discussed. It was found that the adsorption isotherms were best fitted by the Langmuir equation while the adsorption kinetics were well described by pseudo-first-order model. Analyses of sorption isotherms and thermodynamics proved that the adsorption mechanisms for DBP onto D-201 were ion exchange. However, the obtained enthalpy values indicate that the sorption process of MBP onto D-301 is physical adsorption. The equilibrium adsorption capacities and adsorption rates of DBP on two different resins increased with the increasing temperature of the solution. D-301 exhibited a higher adsorption capacity of MBP than D-201. These results proved that D-301, as an effective sorbent, can be used to remove phthalic acid monoesters from aqueous solution.

  16. Modeling and simulation of an isothermal reactor for methanol steam reforming

    Directory of Open Access Journals (Sweden)

    Raphael Menechini Neto

    2014-04-01

    Full Text Available Due to growing electricity demand, cheap renewable energy sources are needed. Fuel cells are an interesting alternative for generating electricity since they use hydrogen as their main fuel and release only water and heat to the environment. Although fuel cells show great flexibility in size and operating temperature (some models even operate at low temperatures, the technology has the drawback for hydrogen transportation and storage. However, hydrogen may be produced from methanol steam reforming obtained from renewable sources such as biomass. The use of methanol as raw material in hydrogen production process by steam reforming is highly interesting owing to the fact that alcohol has the best hydrogen carbon-1 ratio (4:1 and may be processed at low temperatures and atmospheric pressures. They are features which are desirable for its use in autonomous fuel cells. Current research develops a mathematical model of an isothermal methanol steam reforming reactor and validates it against experimental data from the literature. The mathematical model was solved numerically by MATLAB® and the comparison of its predictions for different experimental conditions indicated that the developed model and the methodology for its numerical solution were adequate. Further, a preliminary analysis was undertaken on methanol steam reforming reactor project for autonomous fuel cell.

  17. A k-{\\varepsilon} turbulence closure model of an isothermal dry granular dense matter

    Science.gov (United States)

    Fang, Chung

    2016-07-01

    The turbulent flow characteristics of an isothermal dry granular dense matter with incompressible grains are investigated by the proposed first-order k-{\\varepsilon} turbulence closure model. Reynolds-filter process is applied to obtain the balance equations of the mean fields with two kinematic equations describing the time evolutions of the turbulent kinetic energy and dissipation. The first and second laws of thermodynamics are used to derive the equilibrium closure relations satisfying turbulence realizability conditions, with the dynamic responses postulated by a quasi-linear theory. The established closure model is applied to analyses of a gravity-driven stationary flow down an inclined moving plane. While the mean velocity decreases monotonically from its value on the moving plane toward the free surface, the mean porosity increases exponentially; the turbulent kinetic energy and dissipation evolve, respectively, from their minimum and maximum values on the plane toward their maximum and minimum values on the free surface. The evaluated mean velocity and porosity correspond to the experimental outcomes, while the turbulent dissipation distribution demonstrates a similarity to that of Newtonian fluids in turbulent shear flows. When compared to the zero-order model, the turbulent eddy evolution tends to enhance the transfer of the turbulent kinetic energy and plane shearing across the flow layer, resulting in more intensive turbulent fluctuation in the upper part of the flow. Solid boundary as energy source and sink of the turbulent kinetic energy becomes more apparent in the established first-order model.

  18. A k-{\\varepsilon} turbulence closure model of an isothermal dry granular dense matter

    Science.gov (United States)

    Fang, Chung

    2015-07-01

    The turbulent flow characteristics of an isothermal dry granular dense matter with incompressible grains are investigated by the proposed first-order k-{\\varepsilon} turbulence closure model. Reynolds-filter process is applied to obtain the balance equations of the mean fields with two kinematic equations describing the time evolutions of the turbulent kinetic energy and dissipation. The first and second laws of thermodynamics are used to derive the equilibrium closure relations satisfying turbulence realizability conditions, with the dynamic responses postulated by a quasi-linear theory. The established closure model is applied to analyses of a gravity-driven stationary flow down an inclined moving plane. While the mean velocity decreases monotonically from its value on the moving plane toward the free surface, the mean porosity increases exponentially; the turbulent kinetic energy and dissipation evolve, respectively, from their minimum and maximum values on the plane toward their maximum and minimum values on the free surface. The evaluated mean velocity and porosity correspond to the experimental outcomes, while the turbulent dissipation distribution demonstrates a similarity to that of Newtonian fluids in turbulent shear flows. When compared to the zero-order model, the turbulent eddy evolution tends to enhance the transfer of the turbulent kinetic energy and plane shearing across the flow layer, resulting in more intensive turbulent fluctuation in the upper part of the flow. Solid boundary as energy source and sink of the turbulent kinetic energy becomes more apparent in the established first-order model.

  19. Precipitation model in microalloyed steels both isothermal and continuous cooling conditions

    Energy Technology Data Exchange (ETDEWEB)

    Medina, S. F.; Quispe, A.; Gomez, M.

    2015-07-01

    Niobium and vanadium precipitates (nitrides and carbides) can inhibit the static recrystallization of austenite but this does not happen for Ti, which form nitrides at high temperatures. RPTT diagrams show the interaction between recrystallization and precipitation allowing study the strain induced precipitation kinetics and precipitate coarsening. Based on Dutta and Sellars expression for the start of strain-induced precipitation in microalloyed steels, a new model has been constructed which takes into account the influence of variables such as microalloying element percentages, strain, temperature, strain rate and grain size. Recrystallization- Precipitation-Time-Temperature (RPTT) diagrams have been plotted thanks to a new experimental study carried out by means of hot torsion tests on approximately twenty microalloyed steels with different Nb, V and Ti contents. Mathematical analysis of the results recommends the modification of some parameters such as the supersaturation ratio (ks) and constant B, which is no longer a constant but a function of ks. The expressions are now more consistent and predict the Precipitation-Time-Temperature (PTT) curves with remarkable accuracy. The model for strain-induced precipitation kinetics is completed by means of Avramis equation. Finally, the model constructed in isothermal testing conditions, it has been converted to continuous cooling conditions in order to apply it in hot rolling. (Author)

  20. Predictions and measurements of isothermal airflow in a model once-through steam generator

    International Nuclear Information System (INIS)

    Once-Through Steam Generators (OTSGs) are used in the Nuclear Steam Supply Systems marketed by The Babcock and Wilcox Company (B and W). To analytically predict the three-dimensional, steady-state thermohydraulic conditions in the OTSG, B and W has developed a proprietary code THEDA-1 and is working in cooperation with EPRI to develop an improved version, THEDA-2. Confident application of THEDA requires experimental verification to demonstrate that the code can accurately describe the thermohydraulic conditions in geometries characteristic of the OTSG. The first step in the THEDA verification process is the subject of this report. A full-scale, partial-section model of two OTSG spans was constructed and tested using isothermal air as the working fluid. Model local velocities and pressure profiles were measured and compared to THEDA prediction for five model configurations. Over 3000 velocity measurements were taken and the results were compared to THEDA predictions. Agreement between measured and predicted velocity data was generally better than +-12.5%

  1. Adsorption characteristics of arsenic and boron by soil

    Energy Technology Data Exchange (ETDEWEB)

    Sakata, M.

    1986-01-01

    In order to obtain baseline data concerning the surface and ground water pollution caused by coal ash disposal, adsorption characteristics of arsenic (III) and boron by soil have been studied through laboratory experiments. The main results are as follows: (1) Arsenic (III) and boron adsorption on soil was strongly dependent on pH with adsorption maxima at pH 8 and 8-9, respectively. (2) Arsenic (III) and boron adsorption on soil over the entire concentration ranges investigated could be described by the Langmuir adsorption isotherm and the Freundlich adsorption isotherm, respectively. The Henry adsorption isotherm was also applicable over the lower concentration ranges of arsenic (III) and boron (As (III): < 0.1 deltag/ml; B: < 5deltag/ml.) (3) Arsenic (III) and boron adsorption on soil is controlled mainly by the contents of extractable Fe oxide and hydroxide for arsenic (III) and by the contents of extractable Al hydroxide and allophane (amorphous aluminium silicates) for boron. (4) Adsorption and movement of arsenic (III) and boron during the infiltration of coal ash leachate in soil layer were investigated by means of the unsteady-state, one-dimensional convective-diffusive mass transport model. This model is very useful for evaluation and prediction of the contamination of ground water by trace elements such as arsenic (III) and boron leached at coal ash disposal site.

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

    International Nuclear Information System (INIS)

    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

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

    Energy Technology Data Exchange (ETDEWEB)

    Gado, M, E-mail: parq28@yahoo.com; Zaki, S [Nuclear Materials Authority, P. O. Box 530 El Maadi, Cairo (Egypt)

    2016-01-01

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

  4. Isothermal calorimetry: a predictive tool to model drug-propellant interactions in pressurized metered dose systems.

    Science.gov (United States)

    Ooi, Jesslynn; Gaisford, Simon; Boyd, Ben J; Young, Paul M; Traini, Daniela

    2014-01-30

    The purpose of this work was to evaluate gas perfusion isothermal calorimetry (ITC) as a method to characterize the physicochemical changes of active pharmaceutical ingredients (APIs) intended to be formulated in pressurized metered dose inhalers (pMDIs) after exposure to a model propellant. Spray dried samples of beclomethasone dipropionate (BDP) and salbutamol sulphate (SS) were exposed to controlled quantities of 2H,3H-decafluoropentane (HPFP) to determine whether ITC could be used as a suitable analytical method for gathering data on the behavioural properties of the powders in real time. The crystallization kinetics of BDP and the physiochemical properties of SS were successfully characterized using ITC and supported by a variety of other analytical techniques. Correlations between real and model propellant systems were also established using hydrofluoroalkane (HFA-227) propellant. In summary, ITC was found to be suitable for gathering data on the crystallization kinetics of BDP and SS. In a wider context, this work will have implications on the use of ITC for stability testing of APIs in HFA-based pMDIs. PMID:24325938

  5. Kinetic Model of LiFePO4 Formation Using Non-Isothermal Thermogravimetric Analysis

    Directory of Open Access Journals (Sweden)

    Abdul Halim

    2014-03-01

    Full Text Available The formation reaction of LiFePO4 from decomposition of precursors LiOH, FeSO4.7H2O and (NH42HPO4 with mol ratio of Li:Fe:P=1:1:1 was investigated. The experiment was carried out by thermogravimetric differential thermal analysis (TG-DTA method using nitrogen as atmosfer at a constant heating rate to obtain kinetic constant parameters. Several heating rates were selected, there are 5, 7, 10, 15, 17.5, 22.5 and 25 °C/min. Activation energy, pre-exponential factor and reaction order were taken using Kissinger method and obtained respectively 56.086 kJ/mol, 6.95×108 min-1, and 1.058. Based on fitting result between reaction model and experiment were obtained that reaction obeyed the three dimension diffusion model. © 2014 BCREC UNDIP. All rights reservedReceived: 19th September 2013; Revised: 9th December 2013; Accepted: 23rd January 2014 [How to Cite: Halim, A., Widiyastuti, W., Setyawan, H., Winardi, S. (2014. Kinetic of LiFePO4 For-mation Using Non-isothermal Thermogravimetric Analysis. Bulletin of Chemical Reaction Engineering & Catalysis, 9 (1: 60-65. (doi:10.9767/bcrec.9.1.5508.60-65][Permalink/DOI: http://dx.doi.org/10.9767/bcrec.9.1.5508.60-65] 

  6. Non-isothermal electrochemical model for lithium-ion cells with composite cathodes

    Science.gov (United States)

    Basu, Suman; Patil, Rajkumar S.; Ramachandran, Sanoop; Hariharan, Krishnan S.; Kolake, Subramanya Mayya; Song, Taewon; Oh, Dukjin; Yeo, Taejung; Doo, Seokgwang

    2015-06-01

    Transition metal oxide cathodes for Li-ion batteries offer high energy density and high voltage. Composites of these materials have shown excellent life expectancy and improved thermal performance. In the present work, a comprehensive non-isothermal electrochemical model for a Lithium ion cell with a composite cathode is developed. The present work builds on lithium concentration-dependent diffusivity and thermal gradient of cathode potential, obtained from experiments. The model validation is performed for a wide range of temperature and discharge rates. Excellent agreement is found for high and room temperature with moderate success at low temperatures, which can be attributed to the low fidelity of material properties at low temperature. Although the cell operation is limited by electronic conductivity of NCA at room temperature, at low temperatures a shift in controlling process is seen, and operation is limited by electrolyte transport. At room temperature, the lithium transport in Cathode appears to be the main source of heat generation with entropic heat as the primary contributor at low discharge rates and ohmic heat at high discharge rates respectively. Improvement in electronic conductivity of the cathode is expected to improve the performance of these composite cathodes and pave way for its wider commercialization.

  7. Adsorption of rhodamine B by acid activated carbon-Kinetic, thermodynamic and equilibrium studies

    OpenAIRE

    Shanmugam Arivoli; M. Thenkuzhali; P. Martin Deva Prasath

    2009-01-01

    A carbonaceous adsorbent prepared from an indigenous waste by acid treatment was tested for its efficiency in removing Rhodamine B (RDB). The parameters studied include agitation time, initial dye concentration, carbon dose, pH and temperature. The adsorption followed first order kinetics and the rate is mainly controlled by intra-particle diffusion. Freundlich and Langmuir isotherm models were applied to the equilibrium data. The adsorption capacity (Qm) obtained from the Langmuir isotherm p...

  8. Adsorption of octylamine on titanium dioxide

    International Nuclear Information System (INIS)

    Processes of adsorption and desorption of a model active substance (octylamine) on the surface of unmodified titanium dioxide (E 171) have been performed. The effects of concentration of octylamine and time of the process on the character of adsorption have been studied and the efficiency of the adsorption/desorption has been determined. The samples obtained have been studied by X-ray diffraction. The nitrogen adsorption/desorption isotherms, particle size distribution and absorption capacities of water, dibutyl phthalate and paraffin oil have been determined. The efficiency of octylamine adsorption on the surface of the titanium dioxide has been found positively correlated with the concentration of octylamine in the initial solution. The desorption of octylamine has decreased with increasing concentration of this compound adsorbed. For octylamine in low concentrations the physical adsorption has been found to dominate, which is desirable when using TiO2 in the production of pharmaceuticals.

  9. U(VI) adsorption on natural iron-coated sands: comparison of approaches for modeling adsorption on heterogeneous environmental materials

    International Nuclear Information System (INIS)

    Adsorption of U(VI) on 6 samples of natural Fe-rich sands from Oyster, VA was studied over a range of U(VI) concentrations (0.1-100 μM), pH values (3-7.6), and dithionite-citrate-bicarbonate (DCB) extractable amounts of Fe (3.1-12.3 μmol/g). Four modeling approaches were applied to represent the U(VI) adsorption data. Model I was a two-site, diffuse double layer, surface complexation model based on data for synthetic ferrihydrite [Geochim. Cosmochim. Acta 58 (1994) 5465-5478]. Considering the magnitude of approximations necessary for application of the laboratory-based model to natural sands, Model I was surprisingly accurate, as determined by the goodness of fit parameter, χ2/N of 53.1-22.2. Model II was based on the reactions and diffuse double layer treatment of Model I, but was calibrated to a portion of U(VI) adsorption data for each sand, and then used to predict adsorption data for the same sand under different experimental conditions. Model II did not increase the accuracy of the predictions made with Model I, χ2/N of 42.4-27.6. Models III and IV were four-site affinity spectrum models, without an explicit electric double layer model or explicit surface hydrolysis reactions. Model III was based on a discrete log K spectrum approach, and Model IV was obtained from adjusting all surface stability constants and site concentrations for all surface sites. Models III and IV represented the U(VI) adsorption data with the greatest accuracy, χ2/N ranged from 13.8 to 4.4. Model I provides evidence supporting the practice of using pure phase thermodynamic reaction constants for describing the adsorption characteristics of environmentally important sorbents in certain simple cases. Yet, affinity spectrum approaches (Models III and IV) become increasingly important as more accurate interpolation of adsorption data is necessary, the sorbent becomes increasingly complex, or the range of experimental conditions expands

  10. A generalized adsorption-phase transition model to describe adsorption rates in flexible metal organic framework RPM3-Zn.

    Science.gov (United States)

    Lueking, Angela D; Wang, Cheng-Yu; Sircar, Sarmishtha; Malencia, Christopher; Wang, Hao; Li, Jing

    2016-03-14

    Flexible gate-opening metal organic frameworks (GO-MOFs) expand or contract to minimize the overall free energy of the system upon accommodation of an adsorbate. The thermodynamics of the GO process are well described by a number of models, but the kinetics of the process are relatively unexplored. A flexible GO-MOF, RPM3-Zn, exhibits a significant induction period for opening by N2 and Ar at low temperatures, both above and below the GO pressure. A similar induction period is not observed for H2 or O2 at comparable pressures and temperatures, suggesting the rate of opening is strongly influenced by the gas-surface interaction rather than an external stress. The induction period leads to severe mass transfer limitations for adsorption and over-prediction of the gate-opening pressure. After review of a number of existing adsorption rate models, we find that none adequately describe the experimental rate data and similar timescales for diffusion and opening invalidate prior reaction-diffusion models. Statistically, the rate data are best described by a compressed exponential function. The resulting fitted parameters exceed the expectations for adsorption but fall within those expected for phase transition. By treating adsorption as a phase transition, we generalize the Avrami theory of phase transition kinetics to describe adsorption in both rigid and flexible hosts. The generalized theory is consistent with observed experimental trends relating to induction period, temperature, pressure, and gas-substrate interaction. PMID:26563399

  11. Single and Tertiary System Dye Removal from Aqueous Solution Using Bottom Ash: Kinetic and Isotherm Studies

    Directory of Open Access Journals (Sweden)

    R. Gandhimathi

    2012-01-01

    Full Text Available This paper investigates the ability of Bottom ash to adsorb three cationic dyes from aqueous solution in single and tertiary systems. Crystal Violet (CV, Methylene Blue (MB and Malachite Green (MG were used as cationic dye models. The surface characteristics of Bottom ash were investigated using Fourier Transform Infrared (FTIR. Pseudo second order model was fitted better than Pseudo First order model for all system of MG, MB and CV. From the isotherm study, the adsorption capacity increased in the order of MB< MGadsorption capacity of Bottom ash decreases in tertiary system as compared to single system. Langmuir and Freundlich isotherm models were fitted for all system of dyes. Freundlich isotherm model found to be the best fit for all systems.

  12. Thiol-functionalized polysilsesquioxane as efficient adsorbent for adsorption of Hg(II) and Mn(II) from aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Niu, Yuzhong, E-mail: niuyuzhong@126.com; 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.

  13. Adsorption behaviour of aromatic in different activated carbon: (Frendlich and Langmuir models)

    International Nuclear Information System (INIS)

    Adsorption behavior of p-Cresol, Benzoic acid and nitrobenzene on the two different activated carbons was carried out at 301 K and at controlled ph conditions. In acidic conditions, well below the pKa of all solutes, it was observed that the adsorbate solubility and the electron density of its aromatic ring were the influencing factors on the extent of the adsorption by affecting the extent of London dispersion forces. In higher solution ph conditions, on the other hand, it was found that the electrostatic forces played a significant role on the extent on adsorption. The Effect of ph must be considered from its combined effects on the carbon surface and on the solute molecules. It was found that the uptake of the molecular form of the aromatic solute was dependent on the substituents of the aromatic ring. Adsorption of the solutes in higher ph values was found to be dependent on the concentration of anionic form of the solutes. All isotherms on the F 100 and S E I were fitted into Langmuir and Freundlich isotherm Equations, respectively to find the relative factors

  14. Erratum to 'Comments on: The phase-shift method for determining Langmuir adsorption isotherms of over-potentially deposited hydrogen for the cathodic H{sub 2} evolution reaction at poly-Re/aqueous electrolyte interfaces [International Journal of Hydrogen Energy (2005) 485-99]'

    Energy Technology Data Exchange (ETDEWEB)

    Lasia, Andrzej [Departement de Chimie, Universite de Sherbrooke, Que. (Canada)

    2005-12-01

    Erratum to 'The phase-shift method for determining Langmuir adsorption isotherms of over-potentially deposited hydrogen for the cathodic H2 evolution reaction at poly-Re/aqueous electrolyte interfaces, International Journal of Hydrogen Energy, Volume 30, Issue 5, April 2005, Pages 485-499'. (author)

  15. Seepage model and experiments of drag reduction by nanoparticle adsorption

    Institute of Scientific and Technical Information of China (English)

    龚玮; 狄勤丰; 王新亮; 华帅; 张任良; 叶峰

    2013-01-01

    The hydrophobic nanoparticle (HNP) adsorption is a new technique of drag reduction, which changes the wettability of the porous walls of the core, generates the slip-boundary of the fluid flow and consequently enhances the oil recovery. In the present work, a seepage model with consideration of the slip effect in the micro-channels and the influence of the equivalent pore radius mo- dified by the HNP adsorption is proposed based on the Darcy’s law. The permeability of the non-wetting phase in the porous media is calculated according to its dependence on the slip length, while the slip length is determined by a function of the contact angle and the equivalent pore radius. Numerical simulations are performed by use of the COMSOL multiphysics, and an acceptable agreement between experimental and simulation results is achieved (with an error less than 2.5%). The present model can then be used for the mechanism investigation and the prediction of the oilfield performance.

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

    Science.gov (United States)

    LeVan, M. Douglas; Finn, John E.

    1997-01-01

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

  17. Batch and continuous adsorption of strontium by plant root tissues

    Energy Technology Data Exchange (ETDEWEB)

    Jyhping Chen [Chang Gung Coll. of Medicience and Technology, Taoyuan, Taiwan (China). Dept. of Chemical Engineering

    1997-06-01

    Strontium (Sr) ions in aqueous solutions could be adsorbed by root tissue powders of Amaranthus spinosus, a common weed found in the fields. The adsorption isotherm could be fitted by either the Langmuir or the Freundlich model with the maximum adsorption capacity being 12.89 mg/g from the Langmuir isotherm. The maximum adsorption capacity of the biosorbent decreased with increasing temperature, whereas alkaline pretreatment enhanced the adsorption capacity 1.9 fold. Alginate gel beads (1 mm diameter) containing the root tissue powders were prepared and packed in a column for continuous adsorption/desorption of Sr in solution. Efficient desorption of Sr could be carried out with 0.1 M CaCl{sub 2} to give a concentrated Sr solution with 94% recovery. (author).

  18. Batch and continuous adsorption of strontium by plant root tissues

    International Nuclear Information System (INIS)

    Strontium (Sr) ions in aqueous solutions could be adsorbed by root tissue powders of Amaranthus spinosus, a common weed found in the fields. The adsorption isotherm could be fitted by either the Langmuir or the Freundlich model with the maximum adsorption capacity being 12.89 mg/g from the Langmuir isotherm. The maximum adsorption capacity of the biosorbent decreased with increasing temperature, whereas alkaline pretreatment enhanced the adsorption capacity 1.9 fold. Alginate gel beads (1 mm diameter) containing the root tissue powders were prepared and packed in a column for continuous adsorption/desorption of Sr in solution. Efficient desorption of Sr could be carried out with 0.1 M CaCl2 to give a concentrated Sr solution with 94% recovery. (author)

  19. Adsorption of EDTA on activated carbon from aqueous solutions

    International Nuclear Information System (INIS)

    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 R2 = 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 (Ea, ΔG0, ΔH0, ΔS0) obtained indicate the endothermic nature of EDTA adsorption on activated carbon.

  20. Binary Adsorption Equilibrium of Benzene—Water Vapor Mixtures on Activated Carbon

    Institute of Scientific and Technical Information of China (English)

    GAOHuasheng; YEYunchun; 等

    2002-01-01

    Adsorption equilibrium isotherms of benzene in the concentration range of 500-4000mg·m-3 on two commercial activated carbons were obtained using long-column method under 30℃ and different humidity conditions. Results show that the benzene and water vapors have depression effects upon the adsorption of each other and that the unfavorable effect of water vapor resembles its single-component isotherm on activated carbon.A competitive adsorption model was proposed to explore the depression mechanisms of the non-ideal,non-similar binary adsorption systems.A modified polanyi-Dubinin equation was set up to correlate the binary adsorption equilibrium and to calculte the isotherms of benzene on activated carbon in presence of water vapor with considerable precision.

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

    Science.gov (United States)

    Moreno-Piraján, Juan Carlos; Giraldo, Liliana

    2012-01-01

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

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

    Science.gov (United States)

    Moreno-Piraján, Juan Carlos; Giraldo, Liliana

    2012-01-01

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

  3. Simultaneous Adsorption of Cr(VI) and Phenol from Binary Mixture Using Iron Incorporated Rice Husk: Insight to Multicomponent Equilibrium Isotherm

    OpenAIRE

    Ankur Gupta; Chandrajit Balomajumder

    2016-01-01

    Fe modified rice husk was prepared as a low cost biosorbent for the removal of Cr(VI) and phenol both singly and in combination from single and binary simulated synthetic waste water. Rice husk was modified by treating with FeSO4·7H2O. The results showed that impregnation of iron onto the surface of rice husk improved the adsorption capability of both Cr(VI) and phenol. The effects of process parameters for multicomponent system such as pH, adsorbent dose, and contact time onto the percentage...

  4. Molecular thermodynamic modeling of ionic liquids using the perturbation-based linear Yukawa isotherm regularity.

    Science.gov (United States)

    Sohrabi Mahboub, Mahdi; Farrokhpour, Hossein

    2016-06-15

    In this paper, we present the results of an extensive study on a novel approach to the molecular modeling of pure ionic liquids (ILs) that incorporates the perturbed thermodynamic linear Yukawa isotherm regularity (LYIR), which is derived based on an effective nearest neighboring pair attractive interaction of the Yukawa potential. The LYIR was used to model the densities of ILs up to high pressures (35 MPa) and in the temperature range 293.15 to 393.15 K. To use the LYIR for ILs, a simple molecular model was proposed to describe their molecular structure, in which they were considered as a liquid consisting of the ion pairs moving together in the fluid, and each ion pair was assumed to be a one-center spherical united atom. The ILs under consideration contained one of the IL cations [C2mim](+), [C4mim](+), [C7mim](+), [C8mim](+), [C3mpy](+), [C3mpip](+), [C3mpyr](+) or [C4mpyr](+), and one of the IL anions [BF4](-), [C(CN)3](-), [CF3SO4](-) or [NTf2](-). The reliability and physical significance of the parameters as well as the proposed molecular model were tested by calculating the densities of pure imidazolium-, pyridinium-, piperidinium- and pyrrolidimium-based ILs. The results showed that the LYIR can be used to predict and reproduce the density of ILs in good agreement with the experimental data. In addition, the LYIR enabled us to determine the physical quantities, such as an effective Yukawa screening length, λ eff, the product of the effective energy well depth and the effective coordination number, (ε eff/k)z eff, the contribution of the non-reference thermal pressure and also the influence of the anionic and cationic structure on the λ eff parameter. The standard deviation of the IL densities predicted in this work is lower than those calculated by the one other important equation of state reported in the literature. PMID:27157142

  5. Molecular thermodynamic modeling of ionic liquids using the perturbation-based linear Yukawa isotherm regularity

    Science.gov (United States)

    Sohrabi Mahboub, Mahdi; Farrokhpour, Hossein

    2016-06-01

    In this paper, we present the results of an extensive study on a novel approach to the molecular modeling of pure ionic liquids (ILs) that incorporates the perturbed thermodynamic linear Yukawa isotherm regularity (LYIR), which is derived based on an effective nearest neighboring pair attractive interaction of the Yukawa potential. The LYIR was used to model the densities of ILs up to high pressures (35 MPa) and in the temperature range 293.15 to 393.15 K. To use the LYIR for ILs, a simple molecular model was proposed to describe their molecular structure, in which they were considered as a liquid consisting of the ion pairs moving together in the fluid, and each ion pair was assumed to be a one-center spherical united atom. The ILs under consideration contained one of the IL cations [C2mim]+, [C4mim]+, [C7mim]+, [C8mim]+, [C3mpy]+, [C3mpip]+, [C3mpyr]+ or [C4mpyr]+, and one of the IL anions [BF4]‑, [C(CN)3]‑, [CF3SO4]‑ or [NTf2]‑. The reliability and physical significance of the parameters as well as the proposed molecular model were tested by calculating the densities of pure imidazolium-, pyridinium-, piperidinium- and pyrrolidimium-based ILs. The results showed that the LYIR can be used to predict and reproduce the density of ILs in good agreement with the experimental data. In addition, the LYIR enabled us to determine the physical quantities, such as an effective Yukawa screening length, λ eff, the product of the effective energy well depth and the effective coordination number, (ε eff/k)z eff, the contribution of the non-reference thermal pressure and also the influence of the anionic and cationic structure on the λ eff parameter. The standard deviation of the IL densities predicted in this work is lower than those calculated by the one other important equation of state reported in the literature.

  6. Modelling of the isothermal replication of surface microstructures in polymer melts

    DEFF Research Database (Denmark)

    Rasmussen, Henrik Koblitz; Eriksson, Torbjörn Gerhard

    2005-01-01

    boundary condition. This allows an investigation of the effect of the rheological properties of the polymer melt on the ability of the material to fill small structures in a mould surface. Series of isothermal compression moulding experiments were performed with a polycarbonate (PC) and a polystyrene (PS...

  7. On pulsar-driven isothermal blast-wave models of supernova remnants

    International Nuclear Information System (INIS)

    The 'equilibrium' and stability of spherically-symmetric self-similar isothermal blast waves with a continuous post-shock flow velocity expanding into a medium whose density varies as rsup(-ω) ahead of the blast wave, and which are powered by a central source (a pulsar) whose power output varies with time as tsup(phi-3) are investigated. (Auth.)

  8. An improved single crystal adsorption calorimeter for determining gas adsorption and reaction energies on complex model catalysts.

    Science.gov (United States)

    Fischer-Wolfarth, Jan-Henrik; Hartmann, Jens; Farmer, Jason A; Flores-Camacho, J Manuel; Campbell, Charles T; Schauermann, Swetlana; Freund, Hans-Joachim

    2011-02-01

    A new ultrahigh vacuum microcalorimeter for measuring heats of adsorption and adsorption-induced surface reactions on complex single crystal-based model surfaces is described. It has been specifically designed to study the interaction of gaseous molecules with well-defined model catalysts consisting of metal nanoparticles supported on single crystal surfaces or epitaxial thin oxide films grown on single crystals. The detection principle is based on the previously described measurement of the temperature rise upon adsorption of gaseous molecules by use of a pyroelectric polymer ribbon, which is brought into mechanical∕thermal contact with the back side of the thin single crystal. The instrument includes (i) a preparation chamber providing the required equipment to prepare supported model catalysts involving well-defined nanoparticles on clean single crystal surfaces and to characterize them using surface analysis techniques and in situ reflectivity measurements and (ii) the adsorption∕reaction chamber containing a molecular beam, a pyroelectric heat detector, and calibration tools for determining the absolute reactant fluxes and adsorption heats. The molecular beam is produced by a differentially pumped source based on a multichannel array capable of providing variable fluxes of both high and low vapor pressure gaseous molecules in the range of 0.005-1.5 × 10(15) molecules cm(-2) s(-1) and is modulated by means of the computer-controlled chopper with the shortest pulse length of 150 ms. The calorimetric measurements of adsorption and reaction heats can be performed in a broad temperature range from 100 to 300 K. A novel vibrational isolation method for the pyroelectric detector is introduced for the reduction of acoustic noise. The detector shows a pulse-to-pulse standard deviation ≤15 nJ when heat pulses in the range of 190-3600 nJ are applied to the sample surface with a chopped laser. Particularly for CO adsorption on Pt(111), the energy input of 15 n

  9. Isothermal flow measurement using planar PIV in the 1/4 scaled model of CANDU reactor

    Energy Technology Data Exchange (ETDEWEB)

    Im, Sunghyuk; Sung, Hyung Jin [KAIST, Daejeon (Korea, Republic of); Seo, Han; Bang, In Cheol [UNIST, Ulsan (Korea, Republic of); Kim, Hyoung Tae [KAERI, Daejeon (Korea, Republic of)

    2015-05-15

    The local temperature of the moderator is a key parameter in determining the available subcooling. To predict the flow field and local temperature distribution in the calandria, Korea Atomic Energy Research Institute (KAERI) started the experimental research on moderator circulation as one of a national R and D research programs from 2012. This research program includes the construction of the Moderator Circulation Test (MCT) facility, production of the validation data for self-reliant CFD tools, and development of optical measurement system using the Particle Image Velocimetry (PIV) and Laser Induced Fluorescence (LIF) techniques. Small-scale 1/40 and 1/8 small-scale model tests were performed prior to installation of the main MCT facility to identify the potential problems of the flow visualization and measurement expected in the 1/4 scale MCT facility. In the 1/40 scale test, a flow field was measured with a PIV measurement technique under an iso-thermal state, and the temperature field was visualized using a LIF technique. In this experiment, the key point was to illuminate the region of interest as uniformly as possible since the velocity and temperature fields in the shadow regions were distorted and unphysical. In the 1/8 scale test, the flow patterns from the inlet nozzles to the top region of the tank were investigated using PIV measurement at two different positions of the inlet nozzle. For each position of laser beam exposure the measurement sections were divided to 7 groups to overcome the limitation of the laser power to cover the relatively large test section. The MCT facility is the large-scale facility designed to reproduce the important characteristics of moderator circulation in a CANDU6 calandria under a range of operating conditions. It is reduced in a 1/4 scale and a moderator test vessel is built to the specifications of the CANDU6 reactor design, where a working fluid is sub-cooled water with atmospheric pressure. Previous studies were

  10. Isothermal flow measurement using planar PIV in the 1/4 scaled model of CANDU reactor

    International Nuclear Information System (INIS)

    The local temperature of the moderator is a key parameter in determining the available subcooling. To predict the flow field and local temperature distribution in the calandria, Korea Atomic Energy Research Institute (KAERI) started the experimental research on moderator circulation as one of a national R and D research programs from 2012. This research program includes the construction of the Moderator Circulation Test (MCT) facility, production of the validation data for self-reliant CFD tools, and development of optical measurement system using the Particle Image Velocimetry (PIV) and Laser Induced Fluorescence (LIF) techniques. Small-scale 1/40 and 1/8 small-scale model tests were performed prior to installation of the main MCT facility to identify the potential problems of the flow visualization and measurement expected in the 1/4 scale MCT facility. In the 1/40 scale test, a flow field was measured with a PIV measurement technique under an iso-thermal state, and the temperature field was visualized using a LIF technique. In this experiment, the key point was to illuminate the region of interest as uniformly as possible since the velocity and temperature fields in the shadow regions were distorted and unphysical. In the 1/8 scale test, the flow patterns from the inlet nozzles to the top region of the tank were investigated using PIV measurement at two different positions of the inlet nozzle. For each position of laser beam exposure the measurement sections were divided to 7 groups to overcome the limitation of the laser power to cover the relatively large test section. The MCT facility is the large-scale facility designed to reproduce the important characteristics of moderator circulation in a CANDU6 calandria under a range of operating conditions. It is reduced in a 1/4 scale and a moderator test vessel is built to the specifications of the CANDU6 reactor design, where a working fluid is sub-cooled water with atmospheric pressure. Previous studies were

  11. Adsorption kinetics of propane on energetically heterogeneous activated carbon

    KAUST Repository

    Ismail, Azhar Bin

    2014-11-01

    The modeling of the adsorption isotherms and kinetics of the adsorbent+adsorbate pair is essential in simulating the performance of a pressurized adsorption chiller. In this work, the adsorption kinetics is analyzed from data measured using a magnetic suspension balance. The Statistical Rate Theory describes the Dubinin-Astakhov (DA) equation and extended to obtain an expression for transient analysis. Hence both the experimental excess equilibria data and the adsorption kinetics data may then be fitted to obtain the necessary parameters to fit the curves. The results fit the data very well within 6% of the error of regression. © 2014 Elsevier Ltd.

  12. Studies on the Physical Adsorption Equilibria of Gases on Porous Solids over a Wide Temperature Range Spanning the Critical Region——Adsorption on Microporous Activated Carbon

    Institute of Scientific and Technical Information of China (English)

    周亚平; 白书培; 周理; 杨斌

    2001-01-01

    Adsorption equilibria of nitrogen and methane on microporous (<2 nm) activated carbon were measured for a wide temperature range (103—298 K) spanning the critical region. Information relating to Henry constants, the isosteric heat of adsorption, and the amnount of limiting adsorption were evaluated. All isotherms show type-I features for both sub- and supercritical temperatures. A new isotherm equation and a consideration for the importance of the effect of the adsorbed phase volume allow this kind of isotherms to be modeled satisfactorily. The model parameter of the saturated amount of absolute adsorpaon (nt0) equals the limiting adsorption amount (nlim), leaving the physical meaning of the latter clarified, and the exponent parameter (q) proves to be an appropriate index of surface heterogeneity.

  13. 山西省典型土壤对重金属Cu、Zn和Pb等温吸附特征及应用%Isothermal adsorption characteristics and applications of Cu,Zn,and Pb in typical soil of Shanxi

    Institute of Scientific and Technical Information of China (English)

    秦俊梅; 刘奋武; 周俊; 卜玉山

    2013-01-01

    It was significant to find cheap and efficient adsorption materials to remove heavy metals from wastewater.In this study,the isothermal adsorption efficiencies of Cu,Zn,and Pb by calcareous clay soil,calcareous sandy soil,and alkaline bentonite were investigated through shake flask experiments.In addition,the removal efficiencies of Cu,Zn,and Pb from sewage treatment plant wastewater were studied by the above three adsorption material in the subsequent fixed bed adsorption process.Results showed that the isothermal adsorption characteristics of Cu,Zn,and Pb by calcareous clay soil,calcareous sandy soil,and alkaline bentonite was obviously correlated with Freundlich equation.The heavy metals adsorption forces of the calcareous clay soil,calcareous sandy soil,and alkaline bentonite were Zn>Cu > Pb,Cu> Zn> Pb,and Cu> Zn> Pb,respectively,while the heavy metals adsorption capacity of the calcareous clay soil,calcareous sandy soil,and alkaline bentonite were Cu>Zn>Pb,Pb>Cu>Zn,and Cu>Pb>Zn.Meanwhile,further fixed bed adsorption experiments revealed that the removal efficiency of Cu,Zn,and Pb from wastewater by calcareous clay soil adsorption were 79.9%,97.7%,and 73.4%,and the removal efficiency of Cu,Zn,and Pb by the alkaline bentonite adsorption were also reached to 70.3%,90.6%,and 90.6%,respectively.The results obtained from this study were helpful in choose of adsorbent to remove the heavy metals from wastewater.%寻求高效廉价重金属吸附材料在污水重金属去除领域具有重要意义.本研究采用摇瓶试验,研究了山西省石灰性黏壤土、石灰性砂壤土及碱性膨润土对Cu、Zn和Pb的等温吸附效果,并利用土柱吸附试验进一步研究了3类吸附材料对污水处理厂入厂污水中重金属的实际吸附去除能力.研究结果表明,石灰性黏壤土、石灰性砂壤土及碱性膨润土对污水中Cu、Zn和Pb的等温吸附行为均可用Freundlich吸附等温线显著拟合.

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

    Science.gov (United States)

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

    2016-01-20

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

  15. Sorption isotherms modeling approach of rice-based instant soup mix stored under controlled temperature and humidity

    Directory of Open Access Journals (Sweden)

    Yogender Singh

    2015-12-01

    Full Text Available Moisture sorption isotherms of rice-based instant soup mix at temperature range 15–45°C and relative humidity from 0.11 to 0.86 were determined using the standard gravimetric static method. The experimental sorption curves were fitted by five equations: Chung-Pfost, GAB, Henderson, Kuhn, and Oswin. The sorption isotherms of soup mix decreased with increasing temperature, exhibited type II behavior according to BET classification. The GAB, Henderson, Kuhn, and Oswin models were found to be the most suitable for describing the sorption curves. The isosteric heat of sorption of water was determined from the equilibrium data at different temperatures. It decreased as moisture content increased and was found to be a polynomial function of moisture content. The study has provided information and data useful in large-scale commercial production of soup and have great importance to combat the problem of protein-energy malnutrition in underdeveloped and developing countries.

  16. Competitive Adsorption: A Physical Model for Lung Surfactant Inactivation

    OpenAIRE

    Fernsler, Jonathan G.; Zasadzinski, Joseph A.

    2009-01-01

    Charged, surface-active serum proteins can severely reduce or eliminate the adsorption of lung surfactant from the subphase to the alveolar air-liquid interface via a kinetically controlled competitive adsorption process. The decreased surfactant concentration at the interface leads to higher surface tensions during the compression of the interface during breathing. The correspondence between the factors governing colloid stability and competitive adsorption is validated via a new method of m...

  17. Adsorption studies of polyelectrolytes and enzymes on lignocellulosic model surfaces

    OpenAIRE

    Saarinen, Terhi

    2008-01-01

    This thesis presents fundamental studies on the adsorption of polyelectrolytes and enzymes on solid surfaces. The overall objective of the research was to clarify the adsorption phenomena of polyelectrolytes and enzymes taking place in papermaking. The adsorption experiments were made with a quartz crystal microbalance with dissipation, QCM-D, and the enzyme-modified surfaces were characterised by atomic force microscopy, AFM. In order to study the interactions taking place at a molecula...

  18. Microwave synthesis and adsorption performance of a novel crosslinked starch microsphere

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Qintie, E-mail: qintlin@163.com [School of Environmental Science and Engineering, Guangdong University of Technology, Guangzhou 510006 (China); National Engineering Laboratory for Rice and By-Product Deep Processing, Center South University of Forestry and Technology, Changsha 41004 (China); Pan, Jianxin [School of Environmental Science and Engineering, Guangdong University of Technology, Guangzhou 510006 (China); Lin, Qinlu [National Engineering Laboratory for Rice and By-Product Deep Processing, Center South University of Forestry and Technology, Changsha 41004 (China); Liu, Qianjun [School of Environmental Science and Engineering, Guangdong University of Technology, Guangzhou 510006 (China)

    2013-12-15

    Highlights: • CSM was synthesized in a microwave-assisted inversed emulsion system. • The adsorption of methyl violet on CSM was exothermic and spontaneous. • The adsorption process followed the pseudo-second-order kinetics. • The isothermal data obeyed the Langmuir model. • pH variations did not significantly affect the adsorption of methyl violet onto CSM. -- Abstract: A new crosslinked starch microsphere (CSM) was synthesized in a microwave-assisted inversed emulsion system with soluble starch (ST) as a raw material, MBAA as a crosslinker, and K{sub 2}S{sub 2}O{sub 8}–NaHSO{sub 3} as an initiator. The synthesized starch microsphere was characterized and examined by scanning electron microscope (SEM), FTIR spectroscopy and adsorption isotherms of N{sub 2} at 77 K. Adsorption performance was investigated in methyl violet solution. The results showed that the maximum adsorption capacity for MV was 99.3 mg/g at 298 K, and the adsorption fitted pseudo-second-order kinetic model well with correlation coefficients greater than 0.99. The isothermal data obeyed the Langmuir model better compared to Freundlich model and Tempkin model, and the adsorption was exothermic and spontaneous. pH variations (2.0–10.0) did not significantly affect the adsorption of MV onto CSM.

  19. Isotopic composition of precipitations in Brazil: isothermic models and the influence of evapotranspiration in the Amazonic Basin

    International Nuclear Information System (INIS)

    The simplest theoretical models of the isotopic fractionation of water during equilibrium isothermical processes are analized in detail. The theoretical results are applied to the interpretation of the stable isotope concentrations in the precipitations of 11 Brazilian cities that belong to the international network of IAEA/WMO. The analysis shows that the experimental data are fairly consistent with such equilibrium models; no non-equilibrium processes need to be assumed. The study of the stable isotope content of precipitations in the Amazonic Basin suggests some modifications to the models in order that the evapotranspiration contribution to the vapour balance be taken into account

  20. Adsorption of ethanol onto activated carbon: Modeling and consequent interpretations based on statistical physics treatment

    Science.gov (United States)

    Bouzid, Mohamed; Sellaoui, Lotfi; Khalfaoui, Mohamed; Belmabrouk, Hafedh; Lamine, Abdelmottaleb Ben

    2016-02-01

    In this work, we studied the adsorption of ethanol on three types of activated carbon, namely parent Maxsorb III and two chemically modified activated carbons (H2-Maxsorb III and KOH-H2-Maxsorb III). This investigation has been conducted on the basis of the grand canonical formalism in statistical physics and on simplified assumptions. This led to three parameter equations describing the adsorption of ethanol onto the three types of activated carbon. There was a good correlation between experimental data and results obtained by the new proposed equation. The parameters characterizing the adsorption isotherm were the number of adsorbed molecules (s) per site n, the density of the receptor sites per unit mass of the adsorbent Nm, and the energetic parameter p1/2. They were estimated for the studied systems by a non linear least square regression. The results show that the ethanol molecules were adsorbed in perpendicular (or non parallel) position to the adsorbent surface. The magnitude of the calculated adsorption energies reveals that ethanol is physisorbed onto activated carbon. Both van der Waals and hydrogen interactions were involved in the adsorption process. The calculated values of the specific surface AS, proved that the three types of activated carbon have a highly microporous surface.

  1. Prediction of adsorption from multicomponent solutions by activated carbon using single-solute parameters. Part II—Proposed equation

    OpenAIRE

    Alkhamis, Khouloud A.; Wurster, Dale Eric

    2004-01-01

    Prediction of multicomponent adsorption is still one of the most challenging problems in the adsorption field. Many models have been proposed and employed to obtain multicomponent isotherms from single-component equilibrium data. However, most of these models were based on either unrealistic assumptions or on empirical equations with no apparent definition. The purpose of this investigation was to develop a multicomponent adsorption model based on a thermodynamically consistent equation, and ...

  2. Adsorption characteristics of water vapor on ferroaluminophosphate for desalination cycle

    KAUST Repository

    Kim, Youngdeuk

    2014-07-01

    The adsorption characteristics of microporous ferroaluminophosphate adsorbent (FAM-Z01, Mitsubishi Plastics) are evaluated for possible application in adsorption desalination and cooling (AD) cycles. A particular interest is its water vapor uptake behavior at assorted adsorption temperatures and pressures whilst comparing them to the commercial silica gels of AD plants. The surface characteristics are first carried out using N2 gas adsorption followed by the water vapor uptake analysis for temperature ranging from 20°C to 80°C. We propose a hybrid isotherm model, composing of the Henry and the Sips isotherms, which can be integrated to satisfactorily fit the experimental data of water adsorption on the FAM-Z01. The hybrid model is selected to fit the unusual isotherm shapes, that is, a low adsorption in the initial section and followed by a rapid vapor uptake leading to a likely micropore volume filling by hydrogen bonding and cooperative interaction in micropores. It is shown that the equilibrium adsorption capacity of FAM-Z01 can be up to 5 folds higher than that of conventional silica gels. Owing to the quantum increase in the adsorbate uptake, the FAM-Z01 has the potential to significantly reduce the footprint of an existing AD plant for the same output capacity. © 2014 Elsevier B.V.

  3. Adsorption of uranium(VI) from sulphate solutions using Amberlite IRA-402 resin: Equilibrium, kinetics and thermodynamics study

    International Nuclear Information System (INIS)

    Highlights: • Adsorption of uranium from sulphate solutions by an anion exchange resin. • The effects of pH, contact time and adsorbent dosage were investigated. • The adsorption equilibrium is well described by the Freundlich isotherm model. • The adsorption kinetics can be predicted by the pseudo second-order model. • The adsorption is a physical, spontaneous and endothermic process. - Abstract: In the present study, adsorption of uranium from sulphate solutions was evaluated using Amberlite IRA-402 resin. The variation of adsorption process was investigated in batch sorption mode. The parameters studied were pH, contact time and adsorbent dosage. Langmuir and Freundlich isotherm models were used in order to present a mathematical description of the equilibrium data at three different temperatures (25 °C, 35 °C and 45 °C). The final results confirmed that the equilibrium data tend to follow Freundlich isotherm model. The maximum adsorption capacity of Amberlite IRA-402 for uranium(VI) was evaluated to be 213 mg/g for the Langmuir model at 25 °C. The adsorption of uranium on the mentioned anion exchange resin was found to follow the pseudo-second order kinetic model, indicating that chemical adsorption was the rate limiting-step. The values of thermodynamic parameters proved that adsorption process of uranium onto Amberlite IRA-402 resin could be considered endothermic (ΔH > 0) and spontaneous (ΔG < 0)

  4. Gas adsorption on a single walled carbon nanotube-model simulation

    International Nuclear Information System (INIS)

    We simulate the conduction variation of a gas-adsorbed carbon nanotube by a hybridization model, which has been previously used to simulate the gas adsorption on a nanographite ribbon. Two energy parameters, hybridization interaction and orbital energy level, are employed to simulate and distinguish the adsorbed gases. Two mechanisms, carrier localization and charge distribution, coexist in the gas adsorption process and provide a qualitative explanation for the current increase or decrease in gas adsorption experiments for the carbon nanotube

  5. Effect of temperature and kinetic modelling of lignosulfonate adsorption onto powdered eggshell in batch systems

    OpenAIRE

    Muhammad Ali Zulfikar; Henry Setiyanto; Samitha Dewi Djajanti

    2013-01-01

    The sorption of lignosulfonate onto powdered eggshell under the influence of temperature has been studied. The rate of adsorption onto eggshell was investigated under a variety of adsorbent dosages. The kinetic data from these investigations were correlated to a number of adsorption models in an attempt to elucidate the mechanism of the adsorption processes. Thermodynamic parameter data indicated that the lignosulfonate sorption process was non-spontaneous and endothermic under the experiment...

  6. Study on the adsorption kinetics of orthophosphate anions on layer double hydroxide

    Institute of Scientific and Technical Information of China (English)

    PENG Shuchuan; L(U) Lü; WANG Jin; HAN Lu; CHEN Tianhu; JIANG Shaotong

    2009-01-01

    A kinetic study was conducted on the adsorption of orthophosphate anions on layer double hydroxide (LDH). The adsorption has proved itself to be a spontaneous endothermic process and is large in capacity and rate. The adsorption isotherm correlates well with the Freundlich model, and a rise in temperature will lead to an increase in adsorption efficiency. Additionally, the results suggested that the adsorption is an entropy-increasing process and is in good agreement with the pseudo-second order kinetics. The free energy (ΔG) of adsorption of orthophosphate onto LDH varies within the range of -1.75- -3.34 kJ/mol, the enthalpy (ΔH) varies by 7.96 kJ/mol and the entropy (ΔS) by 33.59 kJ/mol. The adsorption activation energy is 8.3 kJ/mol, showing that the adsorption of orthophosphate onto LDH is determined to be a physical adsorption.

  7. Novel sandwich structure adsorptive membranes for removal of 4-nitrotoluene from water.

    Science.gov (United States)

    Guo, Yuexin; Jia, Zhiqian

    2016-11-01

    Novel sandwich PES-SPES/PS-PDVB/PTFE adsorptive membranes were prepared by a filtration/immersion precipitation method and employed for the removal of 4-nitrotoluene from water. The static adsorption thermodynamics, kinetics, dynamic adsorption/desorption and membrane reusability were investigated. The results showed that the Freundlich model describes the adsorption isotherm satisfactorily. With increased PS-PDVB content, the maximum static adsorption capacity, partition coefficient, apparent adsorption rate constant, and dynamic adsorption capacity all significantly increased. The sandwich membranes showed much higher removal efficiency and adsorption capacity than those of mixed matrix membranes. With respect to dynamics adsorption/desorption, the sandwich membranes exhibited excellent reusability, with a removal efficiency greater than 95% even after five recycles. PMID:27322899

  8. Thermodynamic modeling of Cl(-), NO3(-) and SO4(2-) removal by an anion exchange resin and comparison with Dubinin-Astakhov isotherms.

    Science.gov (United States)

    Dron, Julien; Dodi, Alain

    2011-03-15

    The removal of chloride, nitrate, and sulfate ions from wastewaters by a macroporous ion-exchange resin is studied through the experimental results obtained for six ion exchange systems, OH(-)/Cl(-), OH(-)/NO3(-), OH(-)/SO4(2-), and HCO3(-)/Cl(-), Cl(-)/NO3(-), Cl(-)/SO4(2-). The results are described through thermodynamic modeling, considering either an ideal or a nonideal behavior of the ionic species in the liquid and solid phases. The nonidealities are determined by the Davies equation and Wilson equations in the liquid and solid phases, respectively. The results show that the resin has a strong affinity for all the target ions, and the order of affinity obtained is OH(-) < HCO3(-) < Cl(-) < NO3(-) < SO4(2-). The calculation of the changes in standard Gibbs free energies (ΔG(0)) shows that even though HCO3(-) has a lower affinity to the resin, it may affect the removal of Cl(-), and in the same way that Cl(-) may affect the removal of NO3(-) and SO4(2-). The application of nonidealities in the thermodynamic model leads to an improved fit of the model to the experimental data with average relative deviations below 1.5% except for the OH(-)/SO4(2-) system. On the other hand, considering ideal or nonideal behaviors has no significant impact on the determination of the selectivity coefficients. The thermodynamic modeling is also compared with the Dubinin-Astakhov adsorption isotherms obtained for the same ion exchange systems. Surprisingly, the latter performs significantly better than the ideal thermodynamic model and nearly as well as the nonideal thermodynamic model. PMID:21332215

  9. Nitrate Adsorption on Clay Kaolin: Batch Tests

    Directory of Open Access Journals (Sweden)

    Morteza Mohsenipour

    2015-01-01

    Full Text Available Soils possessing kaolin, gibbsite, goethite, and hematite particles have been found to have a natural capacity to attenuate pollution in aqueous phase. On the other hand, the hydroxyl group in soil increases anion exchange capacity under a low pH condition. The main objective of this paper was to evaluate effects of kaolin on nitrate reduction under acidic condition. In order to analyze the kaolin adsorption behaviour under various conditions, four different concentrations of nitrate, 45, 112.5, 225, and 450 mgNO3-/L, with a constant pH equal to 2, constant temperature equal to 25°C, and exposure period varying from 0 to 150 minutes were considered. The capacity of nitrate adsorption on kaolin has also been studied involving two well-known adsorption isotherm models, namely, Freundlich and Longmuir. The results revealed that approximately 25% of the nitrate present in the solution was adsorbed on clay kaolin. The laboratory experimental data revealed that Freundlich adsorption isotherm model was more accurate than Longmuir adsorption model in predicting of nitrate adsorption. Furthermore, the retardation factor of nitrate pollution in saturated zone has been found to be approximately 4 in presence of kaolin, which indicated that kaolin can be used for natural scavenger of pollution in the environment.

  10. Gyroidal nanoporous carbons - Adsorption and separation properties explored using computer simulations

    OpenAIRE

    Furmaniak, S.; Gauden, P. A.; Terzyk, A. P.; Kowalczyk, P.

    2016-01-01

    Adsorption and separation properties of gyroidal nanoporous carbons (GNCs) - a new class of exotic nanocarbon materials are studied for the first time using hyper parallel tempering Monte Carlo Simulation technique. Porous structure of GNC models is evaluated by the method proposed by Bhattacharya and Gubbins. All the studied structures are strictly microporous. Next, mechanisms of Ar adsorption are described basing on the analysis of adsorption isotherms, enthalpy plots, the values of Henry'...

  11. Investigating the thermodynamic stability of Bacillus subtilis spore-uranium(VI) adsorption though surface complexation modeling

    Science.gov (United States)

    Harrold, Z.; Hertel, M.; Gorman-Lewis, D.

    2012-12-01

    Dissolved uranium speciation, mobility, and remediation are increasingly important topics given continued and potential uranium (U) release from mining operations and nuclear waste. Vegetative bacterial cell surfaces are known to adsorb uranium and may influence uranium speciation in the environment. Previous investigations regarding U(VI) adsorption to bacterial spores, a differentiated and dormant cell type with a tough proteinaceous coat, include U adsorption affinity and XAFS data. We investigated the thermodynamic stability of aerobic, pH dependent uranium adsorption to bacterial spore surfaces using purified Bacillus subtilis spores in solution with 5ppm uranium. Adsorption reversibility and kinetic experiments indicate that uranium does not precipitate over the duration of the experiments and equilibrium is reached within 20 minutes. Uranium-spore adsorption edges exhibited adsorption at all pH measured between 2 and 10. Maximum adsorption was achieved around pH 7 and decreased as pH increased above 7. We used surface complexation modeling (SCM) to quantify uranium adsorption based on balanced chemical equations and derive thermodynamic stability constants for discrete uranium-spore adsorption reactions. Site specific thermodynamic stability constants provide insight on interactions occurring between aqueous uranium species and spore surface ligands. The uranium adsorption data and SCM parameters described herein, also provide a basis for predicting the influence of bacterial spores on uranium speciation in natural systems and investigating their potential as biosorption agents in engineered systems.

  12. Adsorption isotherms and selectivity of CO/N2/CO2 on MOF-74(Ni)%CO/N2/CO2在MOF-74(Ni)上吸附相平衡和选择性

    Institute of Scientific and Technical Information of China (English)

    刘有毅; 黄艳; 何嘉杰; 肖静; 夏启斌; 李忠

    2015-01-01

    This work investigates the adsorption performance of adsorbent MOF-74(Ni) for CO/N2 and CO2/CO2 binary gas mixtures. Adsorbent MOF-74(Ni) with high density of coordinatively unsaturated sites was synthesized by a hydrothermal method, and characterized with N2 adsorption, P-XRD, and SEM. The adsorption isotherms of CO, N2 and CO2 on MOF-74(Ni) were measured, and the selectivities for CO/N2 and CO/CO2 were calculated based on ideal adsorbed solution theory (IAST). Results showed that adsorbent MOF-74(Ni) achieved superior CO adsorption capacity of 6.15 mmol·g−1 at 298 K and 0.1 MPa, and as low as 0.86 mmol·g−1 for N2. In low pressure range of 0—40 kPa, MOF-74(Ni) showed significantly higher uptake for CO than that for CO2. Moreover, IAST-predicted CO/N2 selectivity of MOF-74(Ni) is above 1000, and its CO/CO2 selectivity is in the range of 4—9. It suggests that MOF-74(Ni) is more favorable for CO adsorption than N2and CO2 adsorption.%主要研究了MOF-74(Ni)材料对CO/N2/CO2的吸附分离性能。应用水热法合成制备MOF-74(Ni),分别采用全自动表面积吸附仪、P-XRD、扫描电子显微镜对材料的孔隙结构和晶体形貌进行了表征,应用静态吸附法测定了CO、N2和CO2在MOF-74(Ni)上的吸附等温线,应用DSLF方程模拟了3种气体MOF-74(Ni)上的吸附等温线,依据IAST理论模型计算了MOF-74(Ni)对CO/N2二元混合物和CO/CO2二元混合物的吸附选择性。研究结果表明:在0.1 MPa和常温条件下,MOF-74(Ni)材料对CO吸附容量高达6.15 mmol·g−1,而相同条件下N2的吸附量只有0.86 mmol·g−1。MOF-74(Ni)在低压下(0~40 kPa)对CO的吸附量明显高于其对CO2的吸附量。应用IAST模型估算MOF-74(Ni)对二元混合物吸附选择性的结果表明:MOF-74(Ni)对CO/N2混合物的吸附选择性在1000以上;MOF-74(Ni)对 CO/CO2的吸附选择性在4~9范围,在所研究的二元气体混合物吸附体系中,MOF-74(Ni)都能优先吸附CO。

  13. Precipitation model in microalloyed steels both isothermal and continuous cooling conditions

    Directory of Open Access Journals (Sweden)

    Medina, Sebastián F.

    2015-12-01

    Full Text Available Niobium and vanadium precipitates (nitrides and carbides can inhibit the static recrystallization of austenite but this does not happen for Ti, which form nitrides at high temperatures. RPTT diagrams show the interaction between recrystallization and precipitation allowing study the strain induced precipitation kinetics and precipitate coarsening. Based on Dutta and Sellars’s expression for the start of strain-induced precipitation in microalloyed steels, a new model has been constructed which takes into account the influence of variables such as microalloying element percentages, strain, temperature, strain rate and grain size. Recrystallization- Precipitation-Time-Temperature (RPTT diagrams have been plotted thanks to a new experimental study carried out by means of hot torsion tests on approximately twenty microalloyed steels with different Nb, V and Ti contents. Mathematical analysis of the results recommends the modification of some parameters such as the supersaturation ratio (ks and constant B, which is no longer a constant but a function of ks. The expressions are now more consistent and predict the Precipitation-Time-Temperature (PTT curves with remarkable accuracy. The model for strain-induced precipitation kinetics is completed by means of Avrami’s equation. Finally, the model constructed in isothermal testing conditions, it has been converted to continuous cooling conditions in order to apply it in hot rolling.Los precipitados de V y Nb (nitruros y carburos pueden inhibir la recristalización estática de la austenita, pero no sucede lo mismo con el Ti que forma nitruros a altas temperaturas. Los diagramas RPTT muestran la interacción entre la recristalización y la precipitación, permitiendo estudiar la cinética de la misma y el crecimiento de los precipitados. Partiendo de la expresión de Dutta y Sellars se ha construido un modelo para la precipitación inducida por la deformación en aceros microaleados. El nuevo modelo

  14. Gibbs adsorption and the compressibility equation

    International Nuclear Information System (INIS)

    A new approach for deriving the equation of state is developed. It is shown that the integral in the compressibility equation is identical to the isotherm for Gibbs adsorption in radial coordinates. The Henry, Langmuir, and Frumkin adsorption isotherms are converted into equations of state. It is shown that using Henry's law gives an expression for the second virial coefficient that is identical to the result from statistical mechanics. Using the Langmuir isotherm leads to a new analytic expression for the hard-sphere equation of state which can be explicit in either pressure or density. The Frumkin isotherm results in a new equation of state for the square-well potential fluid. Conversely, new adsorption isotherms can be derived from equations of state using the compressibility equation. It is shown that the van der Waals equation gives an adsorption isotherm equation that describes both polymolecular adsorption and the unusual adsorption behavior observed for supercritical fluids. copyright 1995 American Institute of Physics

  15. A Simple Adsorption Experiment

    Science.gov (United States)

    Guirado, Gonzalo; Ayllon, Jose A.

    2011-01-01

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

  16. Effect of temperature on equilibrium and thermodynamic parameters of Cd (II) adsorption onto turmeric powder

    International Nuclear Information System (INIS)

    Summary: Batch adsorption of Cd (II) onto turmeric powder was conducted as a function of temperature. Nonlinear Langmuir, Freundlich, Dubinin-Radushkevish (D-R) and Temkin equilibrium models were employed. In addition to R 2, five different error functions were used to determine best fit equilibrium isotherm model. It was found that Freundlich isotherm model provided better fit for adsorption data at 298 and 303 K and Langmuir model was suitable for the experimental data obtained at 310 and 313 K. It was found that increase in temperature decreased maximum adsorption capacities, showing that the adsorption of Cd (II) onto turmeric powder is exothermic. Enthalpy values also confirmed the same trend. Entropy values were negative which means that randomness decreased on increasing temperature. Gibbs free energies were non spontaneous at all the temperatures studied. E values were in the range of 2.73-3.23 kJ mol/sup -1/ which indicated that adsorption mechanism is essentially physical. (author)

  17. Adsorption Behaviors of Oxytetracycline onto Sediment in the Weihe River, Shaanxi, China

    Directory of Open Access Journals (Sweden)

    Dong-Hui Cheng

    2013-01-01

    Full Text Available Adsorption behaviors of oxytetracycline onto sediment in the Weihe River were described. The impact factors in the processes of adsorption, such as contact time, solution pH, temperature, and ionic strength, were determined by experiments. The experimental results were analyzed by kinetic and isotherm models. The adsorption kinetics was found to follow a pseudo-first-order model. The equilibrium adsorption data fitted well with the Langmuir and Freundlich isotherm models. However, the Langmuir isotherm was more suitable to describe the adsorption. Thermodynamics parameters such as Gibbs-free energy change (ΔG°, enthalpy change (ΔH°, and entropy change (ΔS° were calculated. Results showed that the adsorption was feasible, spontaneous, entropy increasing, and endothermic in nature, which reached equilibrium in about 24 hours. The adsorption capacity did not cause obvious change at solution pH 4.0–7.0, and both decreased in solution pH 7.0–10.0 and 4.0–2.0. The presence of electrolytes such as NaCl in aqueous solution had a significant negative effect on the adsorption. The mechanisms controlling the adsorption were supposed to be chemisorption.

  18. Adsorption of ferrous ions onto montmorillonites

    Energy Technology Data Exchange (ETDEWEB)

    Qin, Dawei, E-mail: qdw109@163.com [Qilu University of Technology, Jinan, 250353, Shandong (China); Niu, Xia [Qilu University of Technology, Jinan, 250353, Shandong (China); Qiao, Min; Liu, Gang; Li, Hongxin; Meng, Zhenxiao [Shandong SiBang pharmaceutical co., LTD, Jinan, Shandong, 250200 (China)

    2015-04-01

    Highlights: • Adsorption study of ferrous ions on montmorillonites. • Using ascorbic acid as antioxidants in adsorption process. • Fe (II)-MMT had good affinity for phosphate. - Abstract: The adsorption of Fe (II) onto montmorillonites was investigated through initial concentration, contact time, pH and temperature. During the whole adsorption process, the ascorbic acid (Vitamin C) was added as a kind of antioxidant, at the same time, deionized water (after boiling) and nitrogen protection were also used to avoid oxidation. The Fe{sup 2+}/Fe{sub total} ratio of the iron exists in the Fe-montmorillonites was found more than 95%. Two kinetic models, including pseudo-first-order and pseudo-second-order model, were used to analyze the adsorption process of Fe (II) on montmorillonites. The results of our study showed that adsorption process fitted with pseudo-second-order well. Adsorption isotherms showed that Langmuir model was better than Freundlich model. The thermodynamic parameters ΔG{sup 0} and ΔH{sup 0} were 3.696 kJ/mol and 6.689 kJ/mol (we just gave the values at 298 K), respectively. The positive values at different temperatures showed that the adsorption process was non-spontaneous and endothermic. The characteristics of materials were determined by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), Surface area and porosity analyzer, Thermogravimetric analysis (TGA), Differential scanning calorimeter (DSC) and Zeta potential distribution.

  19. General framework for adsorption processes on dynamic interfaces

    Science.gov (United States)

    Schmuck, Markus; Kalliadasis, Serafim

    2016-03-01

    We propose a novel and general variational framework modelling particle adsorption mechanisms on evolving immiscible fluid interfaces. A by-product of our thermodynamic approach is that we systematically obtain analytic adsorption isotherms for given equilibrium interfacial geometries. We validate computationally our mathematical methodology by demonstrating the fundamental properties of decreasing interfacial free energies by increasing interfacial particle densities and of decreasing surface pressure with increasing surface area.

  20. Methane adsorption behavior on coal having different pore structures

    Institute of Scientific and Technical Information of China (English)

    Zhao; Yi; Jiang; Chengfa; Chu; Wei

    2012-01-01

    The adsorption of methane onto five dry coal samples was measured at 298 K over the pressure range from 0 to 3.5 MPa using a volumetric method.The isotherm data were fitted to the Langmuir and the Freundlich equations.The kinetic data were fitted to a pseudo second order equation,the linear driving force equation(LDF),and an intra-particle diffusion model.These results showed that higher methane adsorption is correlated with larger micro-pore volumes and specific surface areas.The adsorption was related to the narrow micro-pore size distribution when the previous two parameters are large.The kinetics study showed that the kinetics of methane adsorption onto these five dry coal samples followed a pseudo second order model very well.Methane adsorption rates are controlled by intra-particle diffusion.The faster the intra-particle diffusion,the faster the methane adsorption rate will be.

  1. Methane adsorption behavior on coal having different pore structures

    Institute of Scientific and Technical Information of China (English)

    Zhao Yi; Jiang Chengfa; Chu Wei

    2012-01-01

    The adsorption of methane onto five dry coal samples was measured at 298 K over the pressure range from 0 to 3.5 MPa using a volumetric method.The isotherm data were fitted to the Langmuir and the Freundlich equations.The kinetic data were fitted to a pseudo second order equation,the linear driving force equation (LDF),and an intra-particle diffusion model.These results showed that higher methane adsorption is correlated with larger micro-pore volumes and specific surface areas.The adsorption was related to the narrow micro-pore size distribution when the previous two parameters are large.The kinetics study showed that the kinetics of methane adsorption onto these five dry coal samples followed a pseudo second order model very well.Methane adsorption rates are controlled by intra-particle diffusion.The faster the intra-particle diffusion,the faster the methane adsorption rate will be.

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

    Science.gov (United States)

    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.

  3. The adsorption of copper in a packed-bed of chitosan beads: modeling, multiple adsorption and regeneration.

    Science.gov (United States)

    Osifo, Peter O; Neomagus, Hein W J P; Everson, Raymond C; Webster, Athena; vd Gun, Marius A

    2009-08-15

    In this study, exoskeletons of Cape rock lobsters were used as raw material in the preparation of chitin that was successively deacetylated to chitosan flakes. The chitosan flakes were modified into chitosan beads and the beads were cross-linked with glutaraldehyde in order to study copper adsorption and regeneration in a packed-bed column. Five consecutive adsorption and desorption cycles were carried out and a chitosan mass loss of 25% was observed, after the last cycle. Despite the loss of chitosan material, an improved efficiency in the second and third cycles was observed with the adsorbent utilizing 97 and 74% of its adsorbent capacity in the second and third cycles, respectively. The fourth and fifth cycles, however, showed a decreased efficiency, and breakage of the beads was observed after the fifth cycle. In the desorption experiments, 91-99% of the adsorbed copper was regenerated in the first three cycles. It was also observed that the copper can be regenerated at a concentration of about a thousand fold the initial concentration. The first cycle of adsorption could be accurately described with a shrinking core particle model combined with a plug flow column model. The input parameters for this model were determined by batch characterization methods, with as only fitting parameter, the effective diffusion coefficient of copper in the bead. PMID:19321260

  4. The adsorption of copper in a packed-bed of chitosan beads: Modeling, multiple adsorption and regeneration

    International Nuclear Information System (INIS)

    In this study, exoskeletons of Cape rock lobsters were used as raw material in the preparation of chitin that was successively deacetylated to chitosan flakes. The chitosan flakes were modified into chitosan beads and the beads were cross-linked with glutaraldehyde in order to study copper adsorption and regeneration in a packed-bed column. Five consecutive adsorption and desorption cycles were carried out and a chitosan mass loss of 25% was observed, after the last cycle. Despite the loss of chitosan material, an improved efficiency in the second and third cycles was observed with the adsorbent utilizing 97 and 74% of its adsorbent capacity in the second and third cycles, respectively. The fourth and fifth cycles, however, showed a decreased efficiency, and breakage of the beads was observed after the fifth cycle. In the desorption experiments, 91-99% of the adsorbed copper was regenerated in the first three cycles. It was also observed that the copper can be regenerated at a concentration of about a thousand fold the initial concentration. The first cycle of adsorption could be accurately described with a shrinking core particle model combined with a plug flow column model. The input parameters for this model were determined by batch characterization methods, with as only fitting parameter, the effective diffusion coefficient of copper in the bead.

  5. The adsorption of copper in a packed-bed of chitosan beads: Modeling, multiple adsorption and regeneration

    Energy Technology Data Exchange (ETDEWEB)

    Osifo, Peter O., E-mail: petero@vut.ac.za [Department of Chemical Engineering, Vaal University of Technology, P/Bag X021, Vanderbijlpark 1900 (South Africa); Neomagus, Hein W.J.P.; Everson, Raymond C. [School of Chemical and Minerals Engineering, North-West University, P/Bag X6001, Potchefstroom 2520 (South Africa); Webster, Athena [University of Utah, Chemistry Department, Salt Lake City, UT 84112 (United States); Gun, Marius A. vd [Sulzer Elbar B.V., Spikweien 36, NL-5943 AD Lomm (Netherlands)

    2009-08-15

    In this study, exoskeletons of Cape rock lobsters were used as raw material in the preparation of chitin that was successively deacetylated to chitosan flakes. The chitosan flakes were modified into chitosan beads and the beads were cross-linked with glutaraldehyde in order to study copper adsorption and regeneration in a packed-bed column. Five consecutive adsorption and desorption cycles were carried out and a chitosan mass loss of 25% was observed, after the last cycle. Despite the loss of chitosan material, an improved efficiency in the second and third cycles was observed with the adsorbent utilizing 97 and 74% of its adsorbent capacity in the second and third cycles, respectively. The fourth and fifth cycles, however, showed a decreased efficiency, and breakage of the beads was observed after the fifth cycle. In the desorption experiments, 91-99% of the adsorbed copper was regenerated in the first three cycles. It was also observed that the copper can be regenerated at a concentration of about a thousand fold the initial concentration. The first cycle of adsorption could be accurately described with a shrinking core particle model combined with a plug flow column model. The input parameters for this model were determined by batch characterization methods, with as only fitting parameter, the effective diffusion coefficient of copper in the bead.

  6. Dynamics of CO 2 Adsorption on Amine Adsorbents. 1. Impact of Heat Effects

    KAUST Repository

    Bollini, Praveen

    2012-11-21

    The packed bed heat and mass transfer dynamics of CO2 adsorption onto a 3-aminopropylsilyl-functionalized SBA-15 silica material are reported. Concentration measurements at the outlet of the packed bed and temperature profiles inside the bed are measured simultaneously. Heat and mass transfer models in conjunction with the linear driving force rate model are used to simulate the concentration and temperature profiles in the bed. The heat and mass transfer processes in the amine adsorbent packed bed are successfully captured by the model, and comparison of isothermal and nonisothermal models reveals that isothermal models provide an accurate description of the dynamic mass transport behavior in the adsorption column under the experimental conditions used in this study. The results help establish that under certain experimental conditions, heat effects in amine adsorbent packed beds have a negligible effect on CO2 breakthrough, and simple isothermal models can be used to accurately assess adsorption kinetics. © 2012 American Chemical Society.

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

    International Nuclear Information System (INIS)

    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. - Highlights: • QDMAEMA-g-PE/PP fibers have high adsorption capacity for As(V) ions. • Adsorption of As(V) is independent on the solution pH over a wide range (4−10). • As(V) adsorption rate of QDMAEMA-g-PE/PP fibers is considerably fast. • The maximum adsorption capacity (qmax) was found to be 83.33 mg As(V)/g polymer

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

    Science.gov (United States)

    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. PMID:21179969

  9. Evaluation of Thermodynamic Parameters of 2, 4-Dichlorophenoxyacetic Acid (2, 4-D Adsorption

    Directory of Open Access Journals (Sweden)

    A. S. Ghatbandhe

    2013-01-01

    Full Text Available Thermodynamic parameters of 2, 4-Dichlorophenoxyacetic acid (2, 4-D adsorption were evaluated by studying the adsorption equilibrium and kinetics of 2, 4-D at different temperatures. Uptake capacity of activated carbon increases with temperature. Langmuir isotherm models were applied to experimental data of 2, 4-D adsorption. Equilibrium data fitted very well to the Langmuir equilibrium model. Adsorbent monolayer capacity , Langmuir constant and adsorption rate constant were evaluated at different temperatures for activated carbon adsorption. The activation energy of adsorption ( was determined using the Arrhenius equation. Using the thermodynamic equilibrium coefficients obtained at different temperatures, the thermodynamic constants of adsorption (, , and were evaluated. The obtained values of thermodynamic parameters show that the adsorption of 2, 4-D is an endothermic process.

  10. Equilibrium Isotherm Modeling, Kinetics and Thermodynamics Study for Removal of Lead from Waste Water

    OpenAIRE

    Chowdhury, Z.; S. M. Zain; Rashid, A K

    2011-01-01

    The low cost adsorbent palm oil fuel ash (POFA) derived from an agricultural waste material was investigated as a replacement of current expensive methods for treating wastewater contaminated by Pb(II) cation. Adsorption studies were carried out to delineate the effect of contact time, temperature, pH and initial metal ion concentration. The experimental data followed pseudo second order kinetics which confirms chemisorptions. The values of Langmuir dimensionless constant, RL and Freundlich c...

  11. Modeling adsorption and reactions of organic molecules at metal surfaces.

    Science.gov (United States)

    Liu, Wei; Tkatchenko, Alexandre; Scheffler, Matthias

    2014-11-18

    CONSPECTUS: The understanding of adsorption and reactions of (large) organic molecules at metal surfaces plays an increasingly important role in modern surface science and technology. Such hybrid inorganic/organic systems (HIOS) are relevant for many applications in catalysis, light-emitting diodes, single-molecule junctions, molecular sensors and switches, and photovoltaics. Obviously, the predictive modeling and understanding of the structure and stability of such hybrid systems is an essential prerequisite for tuning their electronic properties and functions. At present, density-functional theory (DFT) is the most promising approach to study the structure, stability, and electronic properties of complex systems, because it can be applied to both molecules and solids comprising thousands of atoms. However, state-of-the-art approximations to DFT do not provide a consistent and reliable description for HIOS, which is largely due to two issues: (i) the self-interaction of the electrons with themselves arising from the Hartree term of the total energy that is not fully compensated in approximate exchange-correlation functionals, and (ii) the lack of long-range part of the ubiquitous van der Waals (vdW) interactions. The self-interaction errors sometimes lead to incorrect description of charge transfer and electronic level alignment in HIOS, although for molecules adsorbed on metals these effects will often cancel out in total energy differences. Regarding vdW interactions, several promising vdW-inclusive DFT-based methods have been recently demonstrated to yield remarkable accuracy for intermolecular interactions in the gas phase. However, the majority of these approaches neglect the nonlocal collective electron response in the vdW energy tail, an effect that is particularly strong in condensed phases and at interfaces between different materials. Here we show that the recently developed DFT+vdW(surf) method that accurately accounts for the collective electronic

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

    International Nuclear Information System (INIS)

    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 1 h 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.

  13. Chemical modeling of boron adsorption by humic materials using the constant capacitance model

    Science.gov (United States)

    The constant capacitance surface complexation model was used to describe B adsorption behavior on reference Aldrich humic acid, humic acids from various soil environments, and dissolved organic matter extracted from sewage effluents. The reactive surface functional groups on the humic materials wer...

  14. Surface complexation modeling of uranyl adsorption on corrensite from the Waste Isolation Pilot Plant Site

    Energy Technology Data Exchange (ETDEWEB)

    Park, Sang-Won; Leckie, J.O. [Stanford Univ., CA (United States); Siegel, M.D. [Sandia National Labs., Albuquerque, NM (United States)

    1995-09-01

    Corrensite is the dominant clay mineral in the Culebra Dolomite at the Waste Isolation Pilot Plant. The surface characteristics of corrensite, a mixed chlorite/smectite clay mineral, have been studied. Zeta potential measurements and titration experiments suggest that the corrensite surface contains a mixture of permanent charge sites on the basal plane and SiOH and AlOH sites with a net pH-dependent charge at the edge of the clay platelets. Triple-layer model parameters were determined by the double extrapolation technique for use in chemical speciation calculations of adsorption reactions using the computer program HYDRAQL. Batch adsorption studies showed that corrensite is an effective adsorbent for uranyl. The pH-dependent adsorption behavior indicates that adsorption occurs at the edge sites. Adsorption studies were also conducted in the presence of competing cations and complexing ligands. The cations did not affect uranyl adsorption in the range studied. This observation lends support to the hypothesis that uranyl adsorption occurs at the edge sites. Uranyl adsorption was significantly hindered by carbonate. It is proposed that the formation of carbonate uranyl complexes inhibits uranyl adsorption and that only the carbonate-free species adsorb to the corrensite surface. The presence of the organic complexing agents EDTA and oxine also inhibits uranyl sorption.

  15. Surface complexation modeling of uranyl adsorption on corrensite from the Waste Isolation Pilot Plant Site

    International Nuclear Information System (INIS)

    Corrensite is the dominant clay mineral in the Culebra Dolomite at the Waste Isolation Pilot Plant. The surface characteristics of corrensite, a mixed chlorite/smectite clay mineral, have been studied. Zeta potential measurements and titration experiments suggest that the corrensite surface contains a mixture of permanent charge sites on the basal plane and SiOH and AlOH sites with a net pH-dependent charge at the edge of the clay platelets. Triple-layer model parameters were determined by the double extrapolation technique for use in chemical speciation calculations of adsorption reactions using the computer program HYDRAQL. Batch adsorption studies showed that corrensite is an effective adsorbent for uranyl. The pH-dependent adsorption behavior indicates that adsorption occurs at the edge sites. Adsorption studies were also conducted in the presence of competing cations and complexing ligands. The cations did not affect uranyl adsorption in the range studied. This observation lends support to the hypothesis that uranyl adsorption occurs at the edge sites. Uranyl adsorption was significantly hindered by carbonate. It is proposed that the formation of carbonate uranyl complexes inhibits uranyl adsorption and that only the carbonate-free species adsorb to the corrensite surface. The presence of the organic complexing agents EDTA and oxine also inhibits uranyl sorption

  16. Application of Zr/Ti-Pic in the adsorption process of Cu(II), Co(II) and Ni(II) using adsorption physico-chemical models and thermodynamics of the process; Aplicacao de Zr/Ti-PILC no processo de adsorcao de Cu(II), Co(II) e Ni(II) utilizando modelos fisico-quimicos de adsorcao e termodinamica do processo

    Energy Technology Data Exchange (ETDEWEB)

    Guerra, Denis Lima; Airoldi, Claudio [Universidade Estadual de Campinas (UNICAMP), SP (Brazil). Inst. de Quimica. Dept. de Quimica Inorganica]. E-mail: dlguerra@iqm.unicamp.br; Lemos, Vanda Porpino; Angelica, Romulo Simoes [Universidade Federal do Para (UFPa), Belem (Brazil); Viana, Rubia Ribeiro [Universidade Federal do Mato Grosso (UFMT), Cuiaba (Brazil). Inst. de Ciencias Exatas e da Terra. Dept. de Recursos Minerais

    2008-07-01

    The aim of this investigation is to study how Zr/Ti-Pic adsorbs metals. The physico-chemical proprieties of Zr/Ti-Pic have been optimized with pillarization processes and Cu(II), Ni(II) and Co(II) adsorption from aqueous solution has been carried out, with maximum adsorption values of 8.85, 8.30 and 7.78 x-1 mmol g{sup -1}, respectively. The Langmuir, Freundlich and Temkin adsorption isotherm models have been applied to fit the experimental data with a linear regression process. The energetic effect caused by metal interaction was determined through calorimetric titration at the solid-liquid interface and gave a net thermal effect that enabled the calculation of the exothermic values and the equilibrium constant. (author)

  17. Adsorption Properties of Chromium (VI by Chitosan Coated Montmorillonite

    Directory of Open Access Journals (Sweden)

    Dahe Fan

    2006-01-01

    Full Text Available The adsorption of chromium (VI by Chitosan Coated Montmorillonite (CCM from aqueous solution was studied. To evaluate the adsorption capacity, the effects of pH, initial concentration and temperature on the adsorption were investigated. The isothermal data was applied to Langmuir linear and the Freundlich linear isotherm equation and the thermodynamic parameters (ΔH, ΔG, ΔS were calculated according to the values of binding Langmuir constant, KL. Results indicated that the adsorption between CCM and chromium (VI was significantly physical, the negative ΔH constant at lower temperature confirmed that the more chromium (VI was adsorbed by chitosan coated montmorillonite at lower temperature. The kinetics of the sorption process of chromium (VI on chitosan coated montmorillonite were investigated using the pseudo-first order and pseudo-second order kinetics, results showed that the pseudo-second order equation model provided the best correlation with the experimental results.

  18. Manufactured solutions and the numerical verification of isothermal, nonlinear, three-dimensional Stokes ice-sheet models

    Directory of Open Access Journals (Sweden)

    W. Leng

    2012-07-01

    Full Text Available The technique of manufactured solutions is used for verification of computational models in many fields. In this paper we construct manufactured solutions for models of three-dimensional, isothermal, nonlinear Stokes flow in glaciers and ice sheets. The solution construction procedure starts with kinematic boundary conditions and is mainly based on the solution of a first-order partial differential equation for the ice velocity that satisfies the incompressibility condition. The manufactured solutions depend on the geometry of the ice sheet and other model parameters. Initial conditions are taken from the periodic geometry of a standard problem of the ISMIP-HOM benchmark tests and altered through the manufactured solution procedure to generate an analytic solution for the time-dependent flow problem. We then use this manufactured solution to verify a parallel, high-order accurate, finite element Stokes ice-sheet model. Results from the computational model show excellent agreement with the manufactured analytic solutions.

  19. Neutron diffraction and numerical modelling investigation of methane adsorption on bundles of carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, M.R.; Rols, S.; Wass, P.; Muris, M.; Bienfait, M.; Zeppenfeld, P.; Dupont-Pavlovsky, N

    2003-09-01

    Neutron diffraction measurements on a powder sample of bundles of single-walled carbon nanotubes are used to gain insight into adsorption sites for methane molecules. In parallel, numerical methods, based on empirical force-fields, are employed to calculate the adsorption of methane in bundles of nanotubes and neutron diffraction patterns based on these structures. Adsorption sites in grooves on the outer surface of bundles and on the curved surfaces of the nanotubes are characterised by their binding energy and relative abundance. Comparison with published adsorption isotherms indicate that the more stable groove sites must also be complemented by interstitial sites. Such sites are found to be energetically unfavourable in homogeneous bundles composed of average diameter nanotubes, but can become favourable in bundles made of bigger diameter tubes and in more realistic, heterogeneous bundles. Nanotube deformation is an important factor, limiting the size of interstitial channels, but also allowing the stabilisation of adsorbed methane molecules. Diffraction patterns calculated for methane-nanotube structures with partially occupied interstitial sites are in best agreement with the experimental diffraction data.

  20. Neutron diffraction and numerical modelling investigation of methane adsorption on bundles of carbon nanotubes

    International Nuclear Information System (INIS)

    Neutron diffraction measurements on a powder sample of bundles of single-walled carbon nanotubes are used to gain insight into adsorption sites for methane molecules. In parallel, numerical methods, based on empirical force-fields, are employed to calculate the adsorption of methane in bundles of nanotubes and neutron diffraction patterns based on these structures. Adsorption sites in grooves on the outer surface of bundles and on the curved surfaces of the nanotubes are characterised by their binding energy and relative abundance. Comparison with published adsorption isotherms indicate that the more stable groove sites must also be complemented by interstitial sites. Such sites are found to be energetically unfavourable in homogeneous bundles composed of average diameter nanotubes, but can become favourable in bundles made of bigger diameter tubes and in more realistic, heterogeneous bundles. Nanotube deformation is an important factor, limiting the size of interstitial channels, but also allowing the stabilisation of adsorbed methane molecules. Diffraction patterns calculated for methane-nanotube structures with partially occupied interstitial sites are in best agreement with the experimental diffraction data

  1. Mechanisms and modeling of halogenated aliphatic contaminant adsorption by carbon nanotubes.

    Science.gov (United States)

    Apul, Onur Guven; Zhou, Yang; Karanfil, Tanju

    2015-09-15

    This paper examines the adsorption of environmentally relevant halogenated aliphatic compounds using single-walled (SWCNT) and multi-walled carbon nanotubes (MWCNT), and the development of linear solvation-energy relationships (LSER) to examine those adsorption mechanisms. The poly-parameter LSER model was also compared to those previously generated for the adsorption of aromatic compounds by CNTs. The adsorption affinity of aliphatic compounds was greater on the SWCNT than MWCNT with similar oxygen contents. This was attributed to the pore-filling mechanism that was enhanced by higher micropore volume of the SWCNT bundles over the MWCNT bundles. LSER models showed that, at higher concentrations, B (the hydrogen bond accepting ability) was the most influential descriptor for both SWCNT and MWCNT. Other important descriptors were V followed by P, both of which exhibited a positive correlation with adsorption, indicating that their size and polarizability favors adsorption. The contribution of these descriptors to overall adsorption was 2-3 times less than the B. In comparison, V was the most important descriptor in the aromatic compound LSER models. This difference indicates that adsorbate hydrophobicity greatly affects the adsorption of aromatic compounds by CNTs, whereas, aliphatic compounds are affected by both the hydrophobic driving force and other interactions. PMID:25897695

  2. A preliminary study on the adsorptive removal of Cr(VI) using seaweed, Hydrilla verticillata

    International Nuclear Information System (INIS)

    The Cr(VI) adsorption efficiency of the seaweed, Hydrilla verticillata, was studied in batches. The adsorbent was characterized using SEM, BET surface area analyzer, Malvern particle size analyzer, EDAX and FT-IR. Cr(VI) removal efficiency of the adsorbent was studied as a function of different adsorption parameters such as contact time, stirring speed, pH, adsorbent dose, particle size, adsorbate concentration, and temperature. Langmuir, Freundlich, and Temkin adsorption isotherm equations were used in the equilibrium modeling. The adsorption process followed pseudo second-order kinetics and intra-particle diffusion was found to be the rate-controlling step. Experimental data follow Langmuir adsorption isotherm. Thermodynamic parameters such as Gibbs free energy and enthalpy of the adsorption process were evaluated to find out the feasibility of the adsorption process. The negative values of Gibb's free energy and positive enthalpy values show the feasibility and endothermic nature of the process. The significance of different adsorption parameters along with their combined effect on the adsorption process has been established through a full 24 factorial design. Among the different adsorption parameters, pH has the most influential effect on the adsorption process followed by adsorbate concentration and combined effects of all the four parameters were tested. The correlation among different adsorption parameters were studied using multi-variate analysis.

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

    International Nuclear Information System (INIS)

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

  4. Monte Carlo Simulation for the Adsorption of Symmetric Triblock Copolymers

    Institute of Scientific and Technical Information of China (English)

    彭昌军; 李健康; 刘洪来; 胡英

    2004-01-01

    The adsorption behavior of symmetric triblock copolymers, Am/2BnAm/2, from a nonselective solvent at solid-liquid interface has been studied by Monte Carlo simulations on a simple lattice model. Either segment A or segment B is attractive, while the other is non-attractive to the surface. Influences of the adsorption energy,bulk concentration, chain composition and chain length on the microstructure of adsorbed layers are presented.The results show that the total surface coverage and the adsorption amount increases monotonically as the bulk concentration increases. The larger the adsorption energy and the higher the fraction of adsorbing segments, the higher the total surface coverage is exhibited. The product of surface coverage and the proportion of non-attractive segments are nearly independent of the chain length, and the logarithm of the adsorption amount is a linear function of the reciprocal of the reduced temperature. When the adsorption energy is larger, the adsorption amount exhibits a maximum as the fraction of adsorbing segment increases. The adsorption isotherms of copolymers with different length of non-attractive segments can be mapped onto a single curve under given adsorption energy. The adsorption layer thickness decreases as the adsorption energy and the fraction of adsorbing segments increases, but it increhses as the length of non-attractive segments increases. The tails mainly govern the adsorption layer thickness.

  5. Thermodynamic Modeling of Surface Tension of Aqueous Electrolyte Solution by Competitive Adsorption Model

    OpenAIRE

    Mohamad Javad Kamali; Zakarya Kamali; Gholamhossein Vatankhah

    2015-01-01

    Thermodynamic modeling of surface tension of different electrolyte systems in presence of gas phase is studied. Using the solid-liquid equilibrium, Langmuir gas-solid adsorption, and ENRTL activity coefficient model, the surface tension of electrolyte solutions is calculated. The new model has two adjustable parameters which could be determined by fitting the experimental surface tension of binary aqueous electrolyte solution in single temperature. Then the values of surface tension for other...

  6. Adsorption of a textile dye from aqueous solutions by carbon nanotubes

    International Nuclear Information System (INIS)

    Multi-walled and single-walled carbon nanotubes were used as adsorbents for the removal of Reactive Blue 4 textile dye from aqueous solutions. The adsorbents were characterised using Raman spectroscopy, N2 adsorption/desorption isotherms and scanning and transmission electron microscopy. The effects of pH, agitation time and temperature on adsorption capacity were studied. In the acidic pH region, the adsorption of the dye was favourable using both adsorbents. The contact time to obtain equilibrium isotherms at 298-323 K was fixed at 4 hours for both adsorbents. For Reactive Blue 4 dye, Liu isotherm model gave the best fit for the equilibrium data. The maximum sorption capacity for adsorption of the dye occurred at 323 K, attaining values of 502.5 and 567.7 mg g-1 for MWCNT and SWCNT, respectively. (author)

  7. Adsorption of a textile dye from aqueous solutions by carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Machado, Fernando M.; Bergmann, Carlos P., E-mail: fernando.machado@hotmail.com.br [Universidade Federal do Rio Grande do Sul (UFRS), Porto Alegre, RS (Brazil). Dept. de Materiais; Lima, Eder C.; Adebayo, Matthew A. [Universidade Federal do Rio Grande do Sul (UFRS), Porto Alegre, RS (Brazil). Inst. de Quimica; Fagan, Solange B. [Centro Universitario Franciscano (UNIFRA), Santa Maria, RS (Brazil). Area de Ciencias Tecnologicas

    2014-08-15

    Multi-walled and single-walled carbon nanotubes were used as adsorbents for the removal of Reactive Blue 4 textile dye from aqueous solutions. The adsorbents were characterised using Raman spectroscopy, N{sub 2} adsorption/desorption isotherms and scanning and transmission electron microscopy. The effects of pH, agitation time and temperature on adsorption capacity were studied. In the acidic pH region, the adsorption of the dye was favourable using both adsorbents. The contact time to obtain equilibrium isotherms at 298-323 K was fixed at 4 hours for both adsorbents. For Reactive Blue 4 dye, Liu isotherm model gave the best fit for the equilibrium data. The maximum sorption capacity for adsorption of the dye occurred at 323 K, attaining values of 502.5 and 567.7 mg g{sup -1} for MWCNT and SWCNT, respectively. (author)

  8. Modelling of CO2 Adsorption from Exhaust Gases

    Science.gov (United States)

    Panowski, Marcin; Klainy, Roman; Sztelder, Karol

    World tendencies in environmental protection points out necessity of reduction of CO2 emission to atmosphere. The one of the main sources of CO2 emission is placed in energy sector where electric energy and heat are produced based on fossil fuels combustion. Therefore, it seems to be necessary to perform research on CO2 emission reduction in this sector. The main aim of work presented in this paper was focused on the analysis and assessment of CO2 separation from flue gases on the total efficiency of conventional power station. The paper shows the numerical calculations performed with IPSEpro simulation software by SimTech.For the CO2 separation the PTSA (pressure-Temperature Swing Adsorption) process was chosen and the numerical as well as simulation model of such process was formulated. The calculations were made for few different adsorbents taking into account varying values of such thermodynamic parameters of separation process like temperature or pressure. Results obtained from calculations point out that mixed PTSA technology is not very energy consuming process. Owing to utilisation of waste heat for sorbent regeneration, it does not decrease the total efficiency for more than 0.6%. However, that is caused by separation only, while after that CO2 must be compressed for further treatment.

  9. Error analysis of equilibrium studies for the almond shell activated carbon adsorption of Cr(VI) from aqueous solutions

    International Nuclear Information System (INIS)

    In this study, the preparation of activated carbon from almond shell with H2SO4 activation and its ability to remove toxic hexavalent chromium from aqueous solutions are reported. The influences of several operating parameters such as pH, particle size and temperature on the adsorption capacity were investigated. Adsorption of Cr(VI) is found to be highly pH, particle size and temperature dependent. Four adsorption isotherm models namely, Langmuir, Freundlich, Tempkin and Dubinin-Radushkevich were used to analyze the equilibrium data. The Langmuir isotherm provided the best correlation for Cr(VI) onto the almond shell activated carbon (ASC). Adsorption capacity was calculated from the Langmuir isotherm as 190.3 mg/g at 323 K. Thermodynamic parameters were evaluated and the adsorption was endothermic showing monolayer adsorption of Cr(VI). Five error functions were used to treat the equilibrium data using non-linear optimization techniques for evaluating the fit of the isotherm equations. The highest correlation for the isotherm equations in this system was obtained for the Freundlich isotherm. ASC is found to be inexpensive and effective adsorbent for removal of Cr(VI) from aqueous solutions

  10. Adsorption of mercury on lignin: Combined surface complexation modeling and X-ray absorption spectroscopy studies

    International Nuclear Information System (INIS)

    Adsorption of mercury (Hg) on lignin was studied at a range of pH values using a combination of batch adsorption experiments, a surface complexation model (SCM) and synchrotron X-ray absorption spectroscopy (XAS). Surface complexation modeling indicates that three types of acid sites on lignin surfaces, namely aliphatic carboxylic-, aromatic carboxylic- and phenolic-type surface groups, contributed to Hg(II) adsorption. The bond distance and coordination number of Hg(II) adsorption samples at pH 3.0, 4.0 and 5.5 were obtained from extended X-ray absorption fine structure (EXAFS) spectroscopy analysis. The results of SCM and XAS combined reveal that the predominant adsorption species of Hg(II) on lignin changes from HgCl20 to monodentate complex –C–O–HgCl and then bidentate complex –C–O–Hg–O–C– with increasing pH value from 2.0 to 6.0. The good agreement between SCM and XAS results provides new insight into understanding the mechanisms of Hg(II) adsorption on lignin. - Highlights: ► Lignin exhibits a high Hg(II) adsorption capability. ► Adsorption of Hg(II) on lignin is strongly pH-dependent. ► HgCl20, –C–O–HgCl and –C–O–Hg–O–C– are the main adsorption species of Hg(II). - Adsorption of Hg(II) on lignin is strongly pH-dependent, and the main adsorption Hg(II) species change from HgCl20 to –C–O–HgCl and –C–O–Hg–O–C– as pH increases from 2.0 to 6.0.

  11. A hybrid model of support vector regression with genetic algorithm for forecasting adsorption of malachite green onto multi-walled carbon nanotubes: central composite design optimization.

    Science.gov (United States)

    Ghaedi, M; Dashtian, K; Ghaedi, A M; Dehghanian, N

    2016-05-11

    The aim of this work is the study of the predictive ability of a hybrid model of support vector regression with genetic algorithm optimization (GA-SVR) for the adsorption of malachite green (MG) onto multi-walled carbon nanotubes (MWCNTs). Various factors were investigated by central composite design and optimum conditions was set as: pH 8, 0.018 g MWCNTs, 8 mg L(-1) dye mixed with 50 mL solution thoroughly for 10 min. The Langmuir, Freundlich, Temkin and D-R isothermal models are applied to fitting the experimental data, and the data was well explained by the Langmuir model with a maximum adsorption capacity of 62.11-80.64 mg g(-1) in a short time at 25 °C. Kinetic studies at various adsorbent dosages and the initial MG concentration show that maximum MG removal was achieved within 10 min of the start of every experiment under most conditions. The adsorption obeys the pseudo-second-order rate equation in addition to the intraparticle diffusion model. The optimal parameters (C of 0.2509, σ(2) of 0.1288 and ε of 0.2018) for the SVR model were obtained based on the GA. For the testing data set, MSE values of 0.0034 and the coefficient of determination (R(2)) values of 0.9195 were achieved. PMID:27119755

  12. A three-dimensional non-isothermal Ginzburg–Landau phase-field model for shape memory alloys

    International Nuclear Information System (INIS)

    In this paper, a macroscopic three-dimensional non-isothermal model is proposed for describing hysteresis phenomena and phase transformations in shape memory alloys (SMAs). The model is of phase-field type and is based on the Ginzburg–Landau theory. The hysteresis and phase transformations are governed by the kinetic phase evolution equation using the scalar order parameter, laws of conservation of the momentum and energy and a nonlinear coupling of the stress, the strain and the order parameter in a differential form. One of the important features of the model is that the phase transformation is governed by the stress tensor, as opposed to the transformation strain tensor typically used in the literature. The model takes into account different properties of austenite and martensite phases based on the compliance tensor as a function of the order parameter and stress. Representative numerical simulations on an SMA specimen reproduce hysteretic behaviors observed experimentally in the literature. (paper)

  13. Phase-field modeling of isothermal quasi-incompressible multicomponent liquids

    CERN Document Server

    Toth, Gyula I

    2016-01-01

    In this paper general dynamic equations describing the time evolution of isothermal quasi-incompressible multicomponent liquids are derived in the framework of the classical Ginzburg-Landau theory of first order phase transformations. Based on the fundamental continuum mechanical equations, a general convection-diffusion dynamics is set up first for compressible liquids. The constitutive relations for the diffusion fluxes and the capillary stress are determined in the framework of gradient theories. A mathematically precise definition of incompressibility is then given, which is taken into account by using the Lagrange multiplier method. To validate the theory, the general dynamic equations are solved numerically for the quaternary quasi-incompressible Cahn-Hilliard system. It is demonstrated that variable density (i) has no effect on equilibrium only in case of a suitably constructed free energy functional, while (ii) may influence non-equilibrium pattern formation significantly.

  14. Adsorption of naphthalene onto sonicated talc from aqueous solutions.

    Science.gov (United States)

    Sener, Savaş; Ozyilmaz, Azat

    2010-06-01

    The adsorption behavior of naphthalene onto naturally hydrophobic talc from aqueous solution was investigated in this study. The natural talc was first pretreated by sonication to improve the surface characteristics and enhance the uptake capacity by increasing the specific surface area (SSA) of talc. The naphthalene uptake of talc was found as 276 mg g(-1) and increased to 359 mg g(-1) after the sonication. Adsorption studies also showed that the adsorption of naphthalene onto the sonicated talc was not affected by changes in pH suggesting that the main driving forces for naphthalene adsorption onto talc was hydrophobic bonding rather than electrostatic force. The pseudo-first and pseudo-second orders and intraparticle diffusion equation were used to evaluate the kinetic data and the constants were determined. Adsorption process of naphthalene onto talc followed the pseudo-second-order rate expression for different initial naphthalene concentrations. The Langmuir and Freundlich isotherm models were used to model the isotherm data for their applicability. The Freundlich isotherm best fitted for the adsorption of naphthalene onto talc. PMID:20163977

  15. A two-phase flow and non-isothermal agglomerate model for a proton exchange membrane (PEM) fuel cell

    International Nuclear Information System (INIS)

    A two dimensional, across the channel, steady-state model for a proton exchange membrane fuel cell (PEMFC) is presented in which the non-isothermal model for temperature distribution, the two-phase flow model for liquid water transport and the agglomerate model for oxygen reduction reaction are fully coupled. This model is used to investigate thermal transport within the membrane electrode assembly (MEA) associated with the combinational water phase-transfer and transport mechanisms. Effective temperature distribution strategies are established aim to enhance the cell performance. Agglomerate assumption is adopted in which the ionomer and liquid water in turn cover the agglomerate to form the ionomer and liquid water films. Ionomer swelling is associated with the non-uniform distribution of the water content. The modelling results show that heat accumulates within the cathode catalyst layer under the channel. Higher operating temperature improves the cell performance by increasing the kinetics, reducing the liquid water saturation on the cathode and increasing the water carrying capacity of the anode gas. Applying higher temperature on the anode and enlarging the width ratio of the channel/rib could improve the cell performance. Higher cathode temperature decreases the oxygen mole fraction, resulting in an insufficient oxygen supply and a limitation of the cell performance. - Highlights: • The two-phase flow and non-isothermal model couple with the agglomerate model. • Oxygen diffusivity and solubility in Nafion® relate to water content and temperature. • Higher anode operating temperature improves the fuel cell performance. • Insufficient oxygen supply limits cell performance at higher current densities

  16. Ion adsorption components in liquid/solid systems

    Institute of Scientific and Technical Information of China (English)

    WU Xiao-fu; HU Yue-li; ZHAO Fang; HUANG Zhong-zi; LEI Dian

    2006-01-01

    Experiments on Zn2+ and Cd2+ adsorptions on vermiculite in aqueous solutions were conducted to investigate the widely observed adsorbent concentration effect on the traditionally defined adsorption isotherm in the adsorbate range 25-500 mg/L and adsorbent range 10-150 g/L. The results showed that the equilibrium ion adsorption density did not correspond to a unique equilibrium ion concentration in liquid phase. Three adsorbate/adsorbent ratios, the equilibrium adsorption density, the ratio of equilibrium adsorbate concentration in liquid phase to adsorbent concentration, and the ratio of initial adsorbate concentration to adsorbent concentration, were found to be related with unique values in the tested range. Based on the assumption that the equilibrium state of a liquid/solid adsorption system is determined by four mutually related components: adsorbate in liquid phase, adsorbate in solid phase, uncovered adsorption site and covered adsorption site, and that the equilibrium chemical potentials of these components should be equalized, a new model was presented for describing ion adsorption isotherm in liquid/solid systems. The proposed model fit well the experimental data obtained from the examined samples.

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

    Science.gov (United States)

    Javadian, Hamedreza; Taghavi, Mehdi

    2014-01-01

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

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

    International Nuclear Information System (INIS)

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

  19. Adsorptive removal of Cu(II) from aqueous solutions using collagen-tannin resin

    Energy Technology Data Exchange (ETDEWEB)

    Sun Xia; Huang Xin [Department of Biomass Chemistry and Engineering, Sichuan University, Chengdu 610065 (China); Liao Xuepin, E-mail: xpliao@scu.edu.cn [Department of Biomass Chemistry and Engineering, Sichuan University, Chengdu 610065 (China); National Engineering Laboratory for Clean Technology of Leather Manufacture, Sichuan University, Chengdu 610065 (China); Shi Bi, E-mail: shibi@scu.edu.cn [National Engineering Laboratory for Clean Technology of Leather Manufacture, Sichuan University, Chengdu 610065 (China)

    2011-02-28

    The collagen-tannin resin (CTR), as a novel adsorbent, was prepared via a reaction of collagen with black wattle tannin and aldehyde, and its adsorption properties to Cu(II) were systematically investigated, including pH effect, adsorption equilibrium, adsorption kinetics, and column adsorption. The adsorption capacity of Cu(II) on CTR was pH-dependent, and it increased with the increase of solution pH. The adsorption isotherms were well described by Langmuir isotherm model with correlating constant (R{sup 2}) higher than 0.99. The adsorption capacity determined at 303 K was high up to 0.26 mmol/g, which was close to the value (0.266 mmol/g) estimated from Langmuir equation. The adsorption capacity was increased with the increase of temperature, and thermodynamic calculations suggested that the adsorption of Cu(II) on CTR is an endothermic process. The adsorption kinetics were well fitted by the pseudo-second-order rate model. Further column studies suggested that CTR was effective for the removal of Cu(II) from solutions, and more than 99% of Cu(II) was desorbed from column using 0.1 mol/L HNO{sub 3} solution. The CTR column can be reused to adsorb Cu(II) without any loss of adsorption capacity.

  20. Adsorptive removal of Cu(II) from aqueous solutions using collagen-tannin resin

    International Nuclear Information System (INIS)

    The collagen-tannin resin (CTR), as a novel adsorbent, was prepared via a reaction of collagen with black wattle tannin and aldehyde, and its adsorption properties to Cu(II) were systematically investigated, including pH effect, adsorption equilibrium, adsorption kinetics, and column adsorption. The adsorption capacity of Cu(II) on CTR was pH-dependent, and it increased with the increase of solution pH. The adsorption isotherms were well described by Langmuir isotherm model with correlating constant (R2) higher than 0.99. The adsorption capacity determined at 303 K was high up to 0.26 mmol/g, which was close to the value (0.266 mmol/g) estimated from Langmuir equation. The adsorption capacity was increased with the increase of temperature, and thermodynamic calculations suggested that the adsorption of Cu(II) on CTR is an endothermic process. The adsorption kinetics were well fitted by the pseudo-second-order rate model. Further column studies suggested that CTR was effective for the removal of Cu(II) from solutions, and more than 99% of Cu(II) was desorbed from column using 0.1 mol/L HNO3 solution. The CTR column can be reused to adsorb Cu(II) without any loss of adsorption capacity.

  1. Kinetic and equilibrium study of adsorption of di-azo dyes on commercial activated carbon

    International Nuclear Information System (INIS)

    This research work is concerned with studying the adsorption of a number of di-azo dyes on commercial activated carbon (CAC). The synthesized dyes vary in their structures by the central parts. which are either ortho, meta or para phenvlene diamine. This variation affects the linearity of molecules, their spatial arrangement and electron movement throughout the molecule by resonance. Factors a fleeting adsorption process, such as the efiect of contact time, initial concentration, p1-I of the adsorption medium, adsorbent dose, effect of solvent and temperature were studied. The results indicated that, the adsorption process is fast in the first 10 mm, then gradually decreased with time and approaches maximum within 70-80 min for all the studied dyes. The increase of initial concentration and temperature decreased the adsorption efficiency. The results also shows that, the adsorption is found to be more efficient at low Ph value. The increase of the adsorbent dose increases the adsorption efficiency and decreases its capacity. The variation of solvent (ethanol-water ratio) indicates that the decrease of dielectric constant lowers the adsorption efficiency. The study included application of three adsorption isotherms, Freundlich, Langmuir and Tempkin on the experimental data of the studied systems. The results indicated that, Freundlich isotherm fits better the adsorption data. Kinetic analysis of the adsorption data was also conducted by employing 4 kinetic models; pseudo first order and pseudo second order, Elovich and intra particle diffusion equations. The results obtained conclude that, the studied systems follow the Pseudo second order model. (author)

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

    Science.gov (United States)

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

    2016-06-01

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

  3. Competitive adsorption of arsenate and phosphate onto calcite; experimental results and modeling with CCM and CD-MUSIC

    DEFF Research Database (Denmark)

    Sø, Helle Ugilt; Postma, Dieke; Jakobsen, Rasmus;

    2012-01-01

    adsorption of arsenate onto calcite is of minor importance in most groundwater aquifers, as phosphate is often present at concentration levels sufficient to significantly reduce arsenate adsorption. The CD-MUSIC model for calcite was used successfully to model adsorption of arsenate and phosphate separately...

  4. Isothermal gas chromatography of chlorides of Zr and Hf as Rf homologs

    International Nuclear Information System (INIS)

    An isothermal chromatographic apparatus was developed for the on-line experiments of super heavy elements in gas phase. As a model of Rf, we investigated the gas phase chemistry of Zr and Hf chlorides. The dependence of the reaction efficiency on temperature was examined. It was found that about 80% of Zr and Hf reacted with chlorinating gas at 900 deg C. Adsorption enthalpies of Zr and Hf chlorides were deduced from the isothermal chromatograph by the Monte Carlo simulation based on the microscopic model proposed by Zvara. (author)

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

    Science.gov (United States)

    Deng, Baolin; Kim, Eun-Sik

    2016-05-01

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

  6. A Study on Astrazon Black AFDL Dye Adsorption onto Vietnamese Diatomite

    Directory of Open Access Journals (Sweden)

    Bui Hai Dang Son

    2016-01-01

    Full Text Available In the present paper, the adsorption of Astrazon Black AFDL dye onto Vietnamese diatomite has been demonstrated. The diatomite was characterized by XRD, SEM, TEM, EDS, and nitrogen adsorption/desorption isotherms. The results show that diatomite mainly constituted centric type frustules characterized by pores as discs or as cylindrical shapes. The adsorption kinetics and isotherms of dye onto Vietnam diatomite were investigated. The experimental data were fitted well to both Freundlich and Langmuir in the initial concentration range of 400–1400 mg L−1. The average value of maximum adsorption capacity, qm, calculated from Freundlich equation is statistically similar to the average value of maximum monolayer adsorption capacity calculated from Langmuir equation. The thermodynamic parameters evaluated from the temperature dependent on adsorption isotherms in the range of 303–343 K show that the adsorption process was spontaneous and endothermic. The Webber and pseudo-first/second-order kinetic models were used to analyze the mechanism of adsorption. The piecewise linear regression and Akaike’s Information Criterion were used to analyze experimental data. The results show that the dye adsorption onto diatomite was film diffusion controlled and the goodness of fit of experimental data for kinetics modes was dependent on the initial concentration.

  7. Modeling of H2O adsorption-induced curvature of a metal/silicon nanocantilever

    International Nuclear Information System (INIS)

    A model to calculate the curvature of H2O adsorption-induced bending for a metal/silicon nanocantilever is proposed based on atomic and molecular interaction. Part of the potential of both adsorbates and substrate transfers to the elastic energy of the cantilever, and the total energy of the system reaches a minimum value when adsorption is stable. According to this principle the model is developed to calculate H2O adsorption-induced curvature of the nanocantilever. The model was tested with the molecular dynamics method using Material Studio software. The results agree with theoretical value. This model gives us a simple method to calculate adsorption-induced bending of the nanocantilever.

  8. Prediction of iodide adsorption on oxides by surface complexation modeling with spectroscopic confirmation.

    Science.gov (United States)

    Nagata, Takahiro; Fukushi, Keisuke; Takahashi, Yoshio

    2009-04-15

    A deficiency in environmental iodine can cause a number of health problems. Understanding how iodine is sequestered by materials is helpful for evaluating and developing methods for minimizing human health effects related to iodine. In addition, (129)I is considered to be strategically important for safety assessment of underground radioactive waste disposal. To assess the long-term stability of disposed radioactive waste, an understanding of (129)I adsorption on geologic materials is essential. Therefore, the adsorption of I(-) on naturally occurring oxides is of environmental concern. The surface charges of hydrous ferric oxide (HFO) in NaI electrolyte solutions were measured by potentiometric acid-base titration. The surface charge data were analyzed by means of an extended triple-layer model (ETLM) for surface complexation modeling to obtain the I(-) adsorption reaction and its equilibrium constant. The adsorption of I(-) was determined to be an outer-sphere process from ETLM analysis, which was consistent with independent X-ray absorption near-edge structure (XANES) observation of I(-) adsorbed on HFO. The adsorption equilibrium constants for I(-) on beta-TiO(2) and gamma-Al(2)O(3) were also evaluated by analyzing the surface charge data of these oxides in NaI solution as reported in the literature. Comparison of these adsorption equilibrium constants for HFO, beta-TiO(2), and gamma-Al(2)O(3) based on site-occupancy standard states permitted prediction of I(-) adsorption equilibrium constants for all oxides by means of the Born solvation theory. The batch adsorption data for I(-) on HFO and amorphous aluminum oxide were reasonably reproduced by ETLM with the predicted equilibrium constants, confirming the validity of the present approach. Using the predicted adsorption equilibrium constants, we calculated distribution coefficient (K(d)) values for I(-) adsorption on common soil minerals as a function of pH and ionic strength. PMID:19176225

  9. Carbonaceous solids as a model for adsorption by dispersion forces

    Energy Technology Data Exchange (ETDEWEB)

    Arnett, E.M.; Hutchinson, B.J.; Healy, M.H.

    1988-08-03

    Heats of adsorption of many liquids of widely varying structure are reported on several carbonaceous solids: graphite, anthracite coal, Ambersorb XE-348, and two graphitized carbon blacks, Carbopack B and F. Heats of adsorption on the two graphitized carbon black samples correlate closely with the polarizabilities of the adsorbate and the number of main group atoms in the molecules as might be expected for dispersion force interactions; there is no relationship to the basicities of the adsorbates. Except for the two graphitized carbon black samples, Carbopack B and F, correlation between the various type of carbonaceous solids is poor. 39 references, 6 figures, 3 tables.

  10. Evaluation of Various Water Models for Simulation of Adsorption in Hydrophobic Zeolites

    OpenAIRE

    Castillo, Juan Manuel; Dubbeldam, David; Vlugt, Thijs; Smit, Berend; Calero, Sofia

    2009-01-01

    Abstract We have performed a molecular simulation study on water adsorption in hydrophobic zeolites. The framework structures are truly periodic and therefore the Ewald summation is the natural choice for computing the Coulombic interactions. However, few water models have been parameterized using this method. The adsorption results are extremely sensitive to the water model used, the framework positions in the orthorhombic structure and the atomic charges of the zeolite framework....

  11. STOCHASTIC MODEL OF PERIODIC OPERATION PERFORMANCE FOR THE CONTINUOUS COUNTER—CURRENT ADSORPTION PROCESS

    Institute of Scientific and Technical Information of China (English)

    SunShuyi; NiuWengtai; 等

    1995-01-01

    A stochastic model is developed to predict the periodic operation per formance of the continuous counter-current adsorption process.The model takes into account the effects of random backmixing of particles,axial dispersion of liquid phase,liquid-film mass transfer,intraparticle diffusion and particle shape,and can reveal clearly the behavior of solid and liquid phase in adsorption process.The simulation results agree with the experimental data rather well.

  12. Surface structural ion adsorption modeling of competitive binding of oxyanions by metal (hydr)oxides

    Energy Technology Data Exchange (ETDEWEB)

    Hiemstra, T.; Riemsdijk, W.H. van [Wageningen Univ. and Research Centre (Netherlands)

    1999-02-01

    An important challenge in surface complexation models (SCM) is to connect the molecular microscopic reality to macroscopic adsorption phenomena. This study elucidates the primary factor controlling the adsorption process by analyzing the adsorption and competition of PO{sub 4}, AsO{sub 4}, and SeO{sub 3}. The authors show that the structure of the surface-complex acting in the dominant electrostatic field can be ascertained as the primary controlling adsorption factor. The surface species of arsenate are identical with those of phosphate and the adsorption behavior is very similar. On the basis of the selenite adsorption, The authors show that the commonly used 1pK models are incapable to incorporate in the adsorption modeling the correct bidentate binding mechanism found by spectroscopy. The use of the bidentate mechanism leads to a proton-oxyanion ratio and corresponding pH dependence that are too large. The inappropriate intrinsic charge attribution to the primary surface groups and the condensation of the inner sphere surface complex to a point charge are responsible for this behavior of commonly used 2pK models. Both key factors are differently defined in the charge distributed multi-site complexation (CD-MUSIC) model and are based in this model on a surface structural approach. The CD-MUSIC model can successfully describe the macroscopic adsorption phenomena using the surface speciation and binding mechanisms as found by spectroscopy. The model is also able to predict the anion competition well. The charge distribution in the interface is in agreement with the observed structure of surface complexes.

  13. Adsorption of organic matter contained in industrial phosphoric acid onto bentonite: Batch contact time and kinetic study

    International Nuclear Information System (INIS)

    The soluble organic matter present in industrial phosphoric acid can strongly affect the uranium recovery during its solvent extraction by forming stable foams and emulsions. The removal of these organics is an important step both for the production of decontaminated fertilizers and the successful recovery of uranium. The equilibrium isotherms of organic matter adsorption onto bentonite show that the data correlated well with freundlich's model and that the adsorption is physical in nature. the maximum monomolecular capacity (Qo) according to the Langmuir model is 153 mg/g for an initial organic matter concentration of 251.5 mg/1, at 30 oC. The operating parameters (agitation speed, solid/liquid ratio, temperature, particle size and initial organic matter concentration) influenced the rate of adsorption. The adsorption isotherm of uranium onto bentonite exhibits and anomalous shape similar to the Z-type isotherm reported by Giles et al

  14. Contribution of Ash Content Related to Methane Adsorption Behaviors of Bituminous Coals

    Directory of Open Access Journals (Sweden)

    Yanyan Feng

    2014-01-01

    Full Text Available Methane adsorption isotherms on coals with varying ash contents were investigated. The textural properties were characterized by N2 adsorption/desorption isotherm at 77 K, and methane adsorption characteristics were measured at pressures up to 4.0 MPa at 298 K, 313 K, and 328 K, respectively. The Dubinin-Astakhov model and the Polanyi potential theory were employed to fit the experimental data. As a result, ash content correlated strongly to methane adsorption capacity. Over the ash range studied, 9.35% to 21.24%, the average increase in methane adsorption capacity was 0.021 mmol/g for each 1.0% rise in ash content. With the increasing ash content range of 21.24%~43.47%, a reduction in the maximum adsorption capacities of coals was observed. In addition, there was a positive correlation between the saturated adsorption capacity and the specific surface area and micropore volume of samples. Further, this study presented the heat of adsorption, the isosteric heat of adsorption, and the adsorbed phase specific heat capacity for methane adsorption on various coals. Employing the proposed thermodynamic approaches, the thermodynamic maps of the adsorption processes of coalbed methane were conducive to the understanding of the coal and gas simultaneous extraction.

  15. Adsorption mechanisms of thallium (I) and thallium (III) by titanate nanotubes: Ion exchange and co-precipitation

    OpenAIRE

    Borthwick, Alistair; Liu, Wen; Zhang, Pan; Chen, Hao; Ni, Jinren

    2014-01-01

    Hydrothermally-synthesized titanate nanotubes (TNTs) are found to be excellent at adsorption of highly toxic thallium ions. Uptake of both thallium ions is very fast in the first 10 min. The adsorption isotherm of Tl(I) follows the Langmuir model with maximum adsorption capacity of 709.2 mg g1. Ion-exchange between Tl+ and Na+ in the interlayers of TNTs is the primary mechanism for Tl(I) adsorption. Excess Tl+ undergoes further exchange with H+. The adsorption mechanism is different for Tl(II...

  16. Dynamic analysis of the CTAR (constant temperature adsorption refrigeration) cycle

    International Nuclear Information System (INIS)

    The basic SAR (solar-driven adsorption refrigeration) machine is an intermittent cold production system. Recently, the CO-SAR (continuous operation solar-powered adsorption refrigeration) system is developed. The CO-SAR machine is based on the theoretical CTAR (constant temperature adsorption refrigeration) cycle in which the adsorption process takes place at a constant temperature that equals the ambient temperature. Practically, there should be a temperature gradient between the adsorption bed and the surrounding atmosphere to provide a driving potential for heat transfer. In the present study, the dynamic analysis of the CTAR cycle is developed. This analysis provides a comparison between the theoretical and the dynamic operation of the CTAR cycle. The developed dynamic model is based on the D-A adsorption equilibrium equation and the energy and mass balances in the adsorption reactor. Results obtained from the present work demonstrate that, the idealization of the constant temperature adsorption process in the theoretical CTAR cycle is not far from the real situation and can be approached. Furthermore, enhancing the heat transfer between the adsorption bed and the ambient during the bed pre-cooling process helps accelerating the heat rejection process from the adsorption reactor and therefore approaching the isothermal process. - Highlights: • The dynamic analysis of the CTAR (constant temperature adsorption refrigeration) cycle is developed. • The CTAR theoretical and dynamic cycles are compared. • The dynamic cycle approaches the ideal one by enhancing the bed precooling

  17. Adsorption Studies of Radish Leaf Powder

    Directory of Open Access Journals (Sweden)

    Ankita

    2016-01-01

    Full Text Available Radish leaves (Raphanus sativus powder fractions was subjected to moisture adsorption isotherms at different isothermal temperature conditions from 15-45°C with an equal interval of 10°C. The sorption data obtained in gravimetric static method under 0.11–0.90 water activity conditions were subjected for sorption isotherms and found to be typical sigmoid trend. Experimental data were assessed for the applicability in the prediction through sorption models fitting and found that Polynomial and GAB equations performed well over all fitted models in describing equilibrium moisture content – equilibrium relative humidity (EMC–ERH relationships for shelf stable dehydrated radish leaf powder, over the entire range of temperatures condition under study. The net isosteric heat of sorption, differential entropy and free energy were determined at different temperatures and their dependence was seen with respect to equilibrium moisture content.

  18. Model study of acid rain effect on adsorption of trace elements on soils using a multitracer

    International Nuclear Information System (INIS)

    Using a radioactive multitracer and model acid rain (HCl or H2SO4 solution), batch experiments were performed to examine the pH effect on the adsorption-desorption equilibrium of 16 elements on soils as a model study of an acid rain effect. Kaolin, black soil (original and with organic matter almost removed) and Kureha soil (original and with organic matter almost removed) were used as adsorbents. Characteristic dependence on the pH value of the suspension was observed for the adsorption of the elements on kaolin and the soils. The results of this model study indicate that acid rain decreases the retention of cations, while it increases or does not change the adsorption of anions on soils. Organic matter in soils has a positive effect on the extent of adsorption of most elements investigated. (author)

  19. Graphene Metal Adsorption as a Model Chemistry for Atmospheric Reactions

    OpenAIRE

    Ortiz, Y. P.; A. F. Jalbout

    2013-01-01

    We propose a mechanism by which chloromethane and dichloromethane decomposition reaction occurs on the surfaces of graphene. To this end we have performed calculations on the graphene surface with metal adsorption on the sheet on the opposite side of reactions to reduce the formation of free-radical intermediates.

  20. Multicomponent Adsorption Model for Polar and Associating Mixtures

    DEFF Research Database (Denmark)

    Nesterov, Igor; Shapiro, Alexander; Kontogeorgis, Georgios M.

    2015-01-01

    The multicomponent potential adsorption theory (MPTA) is revisited in this work for polar and associating systems. MPTA is used in combination with the CPA equation of state. Previous Studies have shown that both MPTA and other theories present difficulties for complex systems. Some of these...

  1. Systematic model behavior of adsorption on flat surfaces

    OpenAIRE

    Trasca, Raluca A.; Cole, Milton W.; Diehl, Renee D.

    2003-01-01

    A low density film on a flat surface is described by an expansion involving the first four virial coefficients. The first coefficient (alone) yields the Henry's law regime, while the next three correct for the effects of interactions. The results permit exploration of the idea of universal adsorption behavior, which is compared with experimental data for a number of systems.

  2. Water vapor adsorption on activated carbon preadsorbed with naphtalene.

    Science.gov (United States)

    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. PMID:15797395

  3. Investigating the potential of functionalized MCM-41 on adsorption of Remazol Red dye.

    Science.gov (United States)

    Santos, Danilo Oliveira; de Lourdes Nascimento Santos, Maria; Costa, José Arnaldo Santana; de Jesus, Roberta Anjos; Navickiene, Sandro; Sussuchi, Eliana Midori; de Mesquita, Maria Eliane

    2013-07-01

    The modification of MCM-41 was performed with 3-aminopropropyltrimethoxysilane. The structural order and textural properties of the synthesized materials were studied by X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetry/differential thermogravimetry, nitrogen adsorption, and desorption analysis. The adsorption capacity of NH2-MCM-41 was studied with Remazol Red dye. The following parameters were studied in the adsorption process: pH, temperature, adsorbent dosage, and initial concentration. The desorption process was studied in different concentrations of NaOH solutions. The Freundlich isotherm model was found to be fit with the equilibrium isotherm data. Kinetics of adsorption follows the modified Avrami rate equation. The maximum adsorption capacity was estimated to be 45.9 mg g(-1), with removal of the dye of 99.1%. The NH2-MCM-41 material exhibited high desorption capacity with 98.1%. PMID:23334547

  4. ADSORPTION OF CAFFEINE BY HYDROGEN DONATING ADSORBENTS BASED ON HYDROGEN BONDING

    Institute of Scientific and Technical Information of China (English)

    XUMancai; SHIZuoqing; 等

    2000-01-01

    The adsorption isotherms of caffeine from aqueous solution onto three hydrogen donating adsorbents-hydroxypolystyrene,polystryene-azo-pyrogallol,and D72 resin-were measured.The adsorption enthalpies calculated from the isotherms according to the Clausisu-Clapeyron equation were -24-36kJ/mol,-32-37kJ/mol,and -19-24kJ/mol respectively.These values implied that the adsorption processes were based on hydrogen bonding.Furthermore.the mechanism of the adsorption of caffeine onto D72 resin was studied by IR spectra and the small molecular model experiments,and the results showed that the adsorption of caffeine onto hydrogen donating adsorbents was based on hydrogen bonding.

  5. Kinetics and mechanism of the adsorption of methylene blue onto ACFs

    Institute of Scientific and Technical Information of China (English)

    YANG Zhi-yuan

    2008-01-01

    The kinetics and mechanism of methylene blue (MB) adsorption onto activated carbon fibers (ACFs) have been studied.The effects of various experimental parameters, such as the initial MB concentration and the ACF mass, on the adsorption rate were investigated. Equilibrium data were fit well by a Freundlich isotherm equation. Adsorption measurements show that the process is very fast. The adsorption data were modeled using first- and second-order kinetic equations and intra-particle diffusion models. It was found that the first-order kinetic equation could best describe the adsorption kinetics. The adsorption process was found to be complex and controlled by both surface and pore diffusion with surface diffusion at the earlier stages, followed by pore diffusion at the later stages. The thermodynamic parameters △G0, △S0 and △H0, have been calculated. The thermodynamics of the MB-ACF system indicate that the adsorption process is spontaneous.

  6. Enhanced adsorptive removal of toxic dyes using SiO2 nanofibers

    Science.gov (United States)

    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 ammonium dinitramide (ADN) from aqueous solutions. 1. Adsorption on powdered activated charcoal.

    Science.gov (United States)

    Santhosh, G; Venkatachalam, S; Ninan, K N; Sadhana, R; Alwan, S; Abarna, V; Joseph, M A

    2003-03-17

    Investigations on the adsorption of ammonium dinitramide (NH(4)N(NO(2))(2)) (ADN) from aqueous solutions on powdered activated charcoal (PAC) were carried out in order to find out an effective and easier method of separating ADN from aqueous solutions. The effectiveness of PAC in the selective adsorption of ADN from aqueous solutions of ADN (ADN-F) and ADN in presence of sulfate (SO(4)(2-)) and nitrate (NO(3)(-)) ions (ADN-PS) was examined and compared using batch and column methods. The adsorption process follows both Langmuir and Freundlich adsorption isotherms and the isotherm parameters for the models were determined. The observed data favor the formation of monolayer adsorption. The adsorption capacities were found to be 63.3, 119, 105.3 and 82 mg of ADN per g of PAC for ADN-F (batch), ADN-PS (batch), ADN-F (column) and ADN-PS (column), respectively. Break-through curves for ADN-F and ADN-PS were obtained for the optimization of separation of ADN from aqueous solutions. Elution curves were generated for the desorption of ADN from PAC using hot water as eluent. PMID:12628781

  8. A New FE Modeling Method for Isothermal Local Loading Process of Large-scale Complex Titanium Alloy Components Based on DEFORM-3D

    International Nuclear Information System (INIS)

    Isothermal local loading process provides a new way to form large-scale complex titanium alloy components. The forming process is characterized by an extreme size (large scale in global and compared small size in regional), multi-parameter effects, and complicated loading path. To establish a reasonable finite element model is one of the key problems urgently to be solved in the research and development of isothermal local loading forming process of large-scale complex titanium alloy components. In this paper, a new finite element model of the isothermal local loading process is developed under the DEFORM-3D environment based on the solution of some key techniques. The modeling method has the following features: (1) different meshing techniques are used in different loading areas and the number of meshed elements is determined according to the deformation characteristic in different local loading steps in order to improve computational efficiency; (2) the accurate magnitude of the friction factor under titanium alloy hot forming (isothermal forming) condition is adopted instead of the typical value for lubricated hot forming processes; (3) different FEM solvers are chosen at different stages according to the loading characteristic and the contact state; (4) in contrast to the local component model, a full 3D component is modeled to simulate the process. The 3D-FE model is validated by experimental data of a large-scale bulkhead forming under isothermal local loading. The model can describe the quantitative relationships between the forming conditions and the forming results. The results of the present study may provide a basis for studying the local deformation mechanism, selecting the reasonable parameters, optimizing the die design and the process control in isothermal local loading process of large-scale complex titanium alloy components.

  9. Adsorption of the enantiomers of 3-chloro-1-phenyl-propanol on silica-bonded chiral quinidine carbamate

    Energy Technology Data Exchange (ETDEWEB)

    Asnin, Leonid [University of Tennessee, Knoxville (UTK); Kaczmarski, Krzysztof [University of Tennessee and Rzeszow University of Technology, Poland; Felinger, Attila [ORNL; Gritti, Fabrice [University of Tennessee, Knoxville (UTK); Guiochon, Georges A [ORNL

    2005-10-01

    The interactions of 3-chloro-1-phenyl-propanol with a quinidine carbamate-bonded chiral stationary phase under NPLC conditions were studied by measuring the adsorption isotherm data of its enantiomers by frontal analysis, modeling these data with a suitable isotherm model, and comparing the experimental overloaded elution band profiles with those calculated with this isotherm and the equilibrium dispersive model of liquid chromatography. The affinity energy distribution was calculated from the adsorption isotherm data. The results show that the surface of the adsorbent is heterogeneous and exhibits a bimodal adsorption energy distribution. This fact is interpreted in terms of the presence of two different types of adsorption sites on the stationary phase, nonselective and enantioselective sites. Albeit the bi-Langmuir isotherm model successfully accounts for the single-component data corresponding to both enantiomers, the competitive bi-Langmuir isotherm model does not allow an accurate prediction of the overloaded band profiles of the racemic mixture. Thermodynamic data are drawn for explanation. Some aspects of the retention mechanism are discussed in the light of the data obtained.

  10. Adsorption of hexavalent chromium by graphite–chitosan binary composite

    Indian Academy of Sciences (India)

    RAJENDRA S DONGRE

    2016-06-01

    Graphite chitosan binary (GCB) composite was prepared for hexavalent chromium adsorption from studied water. GCB was characterized by TGA, FTIR, SEM and X-ray diffraction techniques.Wide porous sorptive surface of 3.89 m$^2$ g$^{−1}$ and absorptive functionalities of GCB was due to 20% (w/w) graphite support on chitosan evidenced from FTIR and SEM that impart maximum adsorption at pH 4, agitation with 200 rpm for 180 min. Adsorption studies revealed intraparticle diffusion models and best-fitted kinetics was pseudo 2nd order one. A wellfitted Langmuir isotherm model suggested monolayer adsorption with an adsorption capacity ($q_m$) of 105.6 mg g$^{−1}$ and $R^2 = 0.945$. Sorption mechanisms based on metal ionic interactions, intrusion/diffusion and chemisorptions onto composite. This graphite chitosan binary composite improve sorbent capacity for Cr(VI).

  11. Statistical optimization of adsorption processes for removal of 2,4-dichlorophenol by activated carbon derived from oil palm empty fruit bunches

    Institute of Scientific and Technical Information of China (English)

    Md. Zahangir ALAM; Suleyman A. MUYIBI; Juria TORAMAE

    2007-01-01

    The adsorption capacity of activated carbon produced from oil palm empty fruit bunches through removal of 2,4-dichlorophenol from aqueous solution was carried out in the laboratory. The activated carbon was produced by thermal activation at 800℃ with 30 min of activation time. The adsorption process conditions were determined with the statistical optimization followed by central composite design. A developed polynomial model for operating conditions of adsorption process indicated that the optimum conditions for maximum adsorption of phenolic compound were: agitation rate of 100 r/min, contact time of 8 h, initial adsorbate concentration of 250 mg/L and pH 4. Adsorption isotherms were conducted to evaluate biosorption process. Langmuir isotherm was more favorable (R2=0.93) for removal of 2,4-dichlorophenol by the activated carbon produced rather than the Freundlich isotherm (R2=0.88).

  12. Statistical optimization of adsorption processes for removal of 2,4-dichlorophenol by activated carbon derived from oil palm empty fruit bunches.

    Science.gov (United States)

    Alam, M Zahangir; Muyibi, Suleyman A; Toramae, Juria

    2007-01-01

    The adsorption capacity of activated carbon produced from oil palm empty fruit bunches through removal of 2,4-dichlorophenol from aqueous solution was carried out in the laboratory. The activated carbon was produced by thermal activation of activation time with 30 min at 800 degrees C. The adsorption process conditions were determined with the statistical optimization followed by central composite design. A developed polynomial model for operating conditions of adsorption process indicated that the optimum conditions for maximum adsorption of phenolic compound were: agitation rate of 100 r/min, contact time of 8 h, initial adsorbate concentration of 250 mg/L and pH 4. Adsorption isotherms were conducted to evaluate biosorption process. Langmuir isotherm was more favorable (R2 = 0.93) for removal of 2,4-dichlorophenol by the activated carbon rather than Freundlich isotherm (R2 = 0.88). PMID:17969639

  13. Adsorption and kinetic studies of seven different organic dyes onto magnetite nanoparticles loaded tea waste and removal of them from wastewater samples

    Science.gov (United States)

    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.

  14. Modeling and Optimization for Production of Rice Husk Activated Carbon and Adsorption of Phenol

    Directory of Open Access Journals (Sweden)

    Y. S. Mohammad

    2014-01-01

    Full Text Available Modeling of adsorption process establishes mathematical relationship between the interacting process variables and process optimization is important in determining the values of factors for which the response is at maximum. In this paper, response surface methodology was employed for the modeling and optimization of adsorption of phenol onto rice husk activated carbon. Among the action variables considered are activated carbon pretreatment temperature, adsorbent dosage, and initial concentration of phenol, while the response variables are removal efficiency and adsorption capacity. Regression analysis was used to analyze the models developed. The outcome of this research showed that 99.79% and 99.81% of the variations in removal efficiency and adsorption capacity, respectively, are attributed to the three process variables considered, that is, pretreatment temperature, adsorbent dosage, and initial phenol concentration. Therefore, the models can be used to predict the interaction of the process variables. Optimization tests showed that the optimum operating conditions for the adsorption process occurred at initial solute concentration of 40.61 mg/L, pretreatment temperature of 441.46°C, adsorbent dosage 4 g, adsorption capacity of 0.9595 mg/g, and removal efficiency of 97.16%. These optimum operating conditions were experimentally validated.

  15. MOISTURE ADSORPTION ISOTHERMS IN YELLOW PITAHAYA (Selenicereusmegalanthus

    Directory of Open Access Journals (Sweden)

    ALFREDO AYALA APONTE

    2011-01-01

    Full Text Available Se determinaron las isotermas de adsorción de humedad en pitahaya amarrilla a 15, 25, y 35ºC mediante el método gravímetro en el intervalo de actividad de agua (aw entre 0.111 y 0.901. Los valores experimentales de adsorción se ajustaron mediante los modelos de GAB, BET, Henderson, Smith, Caurie, y Peleg. El calor isostérico de adsorción (Qst se determinó mediante la ecuación de Clausius- Clapeyron. Los resultados mostraron que las isotermas fueron de tipo III. El contenido de humedad de equilibrio (CHE presentó dependencia con la temperatura, disminuyendo con el aumento de esta para un valor constante de aw. El modelo GAB fue el que presentó mejor ajuste de los valores experimentales. El Qst disminuyó con el aumento del CHE, variando de 57.154 a 45.79 kJ/mol para humedades de 0.05 y 0.4 (g agua/g ms, respectivamente. Estos resultados son de interés para establecer las mejores condiciones de almacenamiento de la pitahaya deshidratada, así como la predicción de la vida útil, y el diseño de empaque.

  16. Application of novel Polypyrrole/thiol-functionalized zeolite Beta/MCM-41 type mesoporous silica nanocomposite for adsorption of Hg{sup 2+} from aqueous solution and industrial wastewater: Kinetic, isotherm and thermodynamic studies

    Energy Technology Data Exchange (ETDEWEB)

    Javadian, Hamedreza, E-mail: Hamedreza.Javadian@yahoo.com [Department of Chemical Engineering, Shahrood Branch, Islamic Azad University, Shahrood, Islamic Republic of Iran (Iran, Islamic Republic of); Taghavi, Mehdi [Polymer Chemistry Research Laboratory, Department of Chemistry, University of Mazandaran, Babolsar, 47416-95447, Islamic Republic of Iran (Iran, Islamic Republic of)

    2014-01-15

    Hierarchical zeolite consists of both microporous and unordered mesoporous structures. A composite of Polypyrrole/thiol-functionalized Beta/MCM-41 (PPy/SH-Beta/MCM-41) was prepared, characterized by FE-SEM, FT-IR, XRD, TGA and BET analysis and applied in the investigation of its adsorption characteristics for the removal of Hg{sup 2+} ions from aqueous solutions. Thiol-functionalized Beta/MCM-41 (SH-Beta/MCM-41) was prepared by 3-mercaptopropyltrimethoxysilane (MPTMS) in the presence of aerosil-200 as a silica source by two-step hydrothermal crystallization procedure. Batch mode experiments were conducted and three kinetic models were used to describe the adsorption process. The experimental data fitted very well with the Pseudo-second-order kinetic model. The calculated thermodynamic parameters (ΔH, ΔS and ΔG) revealed that the adsorption of Hg{sup 2+} onto PPy/SH-Beta/MCM-41 is an endothermic and spontaneous process. It was found that temperature has a positive effect on the removal efficiency and that PPy/SH-Beta/MCM-41 is potentially able to remove Hg{sup 2+} ions from aqueous solutions at even high concentrations (400 mg L{sup −1}). The recovery of Hg{sup 2+} from the PPy/SH-Beta/MCM-41 adsorbent was found to be more than 90% using 0.5 M H{sub 2}SO{sub 4}, and the ability of the absorbent to be reused for removal of Hg{sup 2+} was investigated.

  17. Lead removal from aqueous solution by natural and pretreated clinoptilolite: Adsorption equilibrium and kinetics

    International Nuclear Information System (INIS)

    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 (o) indicates that adsorption of Pb(II) on clinoptilolite is spontaneous

  18. Non-isothermal Well Test Model and Its Application%温度试井模型及其应用

    Institute of Scientific and Technical Information of China (English)

    王威; 程时清

    2012-01-01

    试井是人们测取油气井不同工作制度下井底压力和温度的过程.但在常规的试井中,温度被假定为常数.但在实际测试中,温度是变化的.针对此情况,在能量守恒的基础上,根据傅里叶定律推导出产层处温度与地层热力学性质的关系,绘制了温度理论图版.通过选取不同的热力学参数值,得到了影响温度试井的热力学敏感性参数.在此基础上,根据建立的温度试井模型,反求有代表性的热力学参数.%The well test is a process that the bottom hole pressure and temperature will be measured in different work system. But in the conventional test, temperature was assumed to be constant. On fact, the temperature distributions in the reservoir and wellbore have been non-isothermal. According to Law of Energy conservation and Fourier law, deducing the relationship between formation temperature and the thermodynamic parameters and establishing a representative model for the temperature distribution in the reservoir, through choosing different thermody-namical parameters, the following parameters were tested for sensitivity of the solution to their values: the porosity of the formation, Joule-Thomson coefficient of the fluids, thermal conductivity of rock and fluid, permeability, thermal diffusivity length, in accordance with established non-isothermal well test model,some representative thermodynamic parameters have been obtained accurately.

  19. Continuous water treatment by adsorption and electrochemical regeneration.

    Science.gov (United States)

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

    2011-05-01

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

  20. Adsorptive desulfurization by activated alumina.

    Science.gov (United States)

    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. PMID:19523762

  1. Geochemical modelling of arsenic adsorption to oxide surfaces

    OpenAIRE

    Gustafsson, Jon Petter; Bhattacharya, Prosun

    2007-01-01

    In natural environments, arsenic chemistry is dominated by the reactions of its two predominant soluble forms, arsenate and arsenite. To predict the fate of As in the environment, it is necessary to consider processes that act to restrict its mobility. The mobility of As is strongly influenced by adsorption reactions to particle surfaces. Arsenate and arsenite may form surface complexes with a number of different oxides, including Fe-, Al-, Mn- and Ti oxides. The focus of this chapter is on t...

  2. Equilibrium and kinetic adsorption study of Basic Yellow 28 and Basic Red 46 by a boron industry waste

    International Nuclear Information System (INIS)

    In this study, the adsorption characteristics of Basic Yellow 28 (BY 28) and Basic Red 46 (BR 46) onto boron waste (BW), a waste produced from boron processing plant were investigated. The 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 two dyes could be described reasonably well by a generalized isotherm. Kinetic studies indicated that the kinetics of the adsorption of BY 28 and BR 46 onto BW follows a pseudo-second-order model. The result showed that the BW exhibited high-adsorption capacity for basic dyes and the capacity slightly decreased with increasing temperature. The maximum adsorption capacities of BY 28 and BR 46 are reported at 75.00 and 74.73 mg g-1, respectively. The dye adsorption depended on the initial pH of the solution with maximum uptake occurring at about pH 9 and electrokinetic behavior of BW. Activation energy of 15.23 kJ/mol for BY 28 and 18.15 kJ/mol for BR 46 were determined confirming the nature of the physisorption onto BW. These results indicate that BW could be employed as low-cost material for the removal of the textile dyes from effluents

  3. Theoretical and Experimental Study on the Adsorption and Desorption of Methane by Granular Activated Carbon at 25 ℃

    Institute of Scientific and Technical Information of China (English)

    E. Salehi; V. Taghikhani; C. Ghotbi; E. Nemati Lay; A. Shojaei

    2007-01-01

    A theoretical and experimental study was conducted to accurately determine the amount of adsorption and desorption of methane by various Granular Activated Carbon (GAC) under different physical conditions. To carry out the experiments, the volumetric method was used up to 500 psia at constant temperature of 25 ℃. In these experiments, adsorption as well as desorption capacities of four different GAC in the adsorption of methane, the major constituent of natural gas, at various equilibrium pressures and a constant temperature were studied. Also, various adsorption isotherm models were used to model the experimental data collected from the experiments. The accuracy of the results obtained from the adsorption isotherm models was compared and the values for the regressed parameters were reported. The results shows that the physical characteristics of activated carbons such as BET surface area, micropore volume, packing density, and pore size distribution play an important role in the amount of methane to be adsorbed and desorbed.

  4. Malachite green adsorption onto natural zeolite and reuse by microwave irradiation

    International Nuclear Information System (INIS)

    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.

  5. [Influences of cation species on adsorption and desorption of oxytetracycline in two typical soils of China].

    Science.gov (United States)

    Bao, Yan-Yu; Zhou, Qi-Xing; Zhang, Hao

    2009-02-15

    On the basis of the OECD Guideline 106, batch sorption methods were employed to reveal the effect of different cations (0.01 mol x L(-1) Ca2+, K+ and Na+) on oxytetracycline (OTC) adsorption and desorption process in two tested soils (cinnamon soil and red soil). Results show that the Freundlich model is the best isotherm to describe the experimental data of adsorption and desorption, and the average fitting correlation coefficient is 0.989. Except for the adsorption isotherm of cinnamon soil on OTC in 0.01 mol x L(-1) KCl, the other isotherms resemble the L-type curves. To the same cation, OTC adsorption capacity (lgKf) in the red soil (ranging from 2.907 to 3.173) is always higher than in the cinnamon soil (ranging from 2.577 to 2.885), and the adsorption strength (1/n) in the red soil (ranging from 0.672 to 0.825) is always lower than the cinnamon (ranging from 0.713 to 1.005). The dominant mechanism is physical adsorption in two soils. To the same soil, cation species don't affect OTC adsorption capacity (lgKf) (p > 0.05). And Ca2+ can reduce significantly the adsorption strength (p cinnamon soil, there is significantly HI difference (p < 0.01) between K+ and Ca2+, Na+. However, three cations have no significantly difference effect on HI in red soil. PMID:19402514

  6. Removal of Crystal Violet Dye from Aqueous Solutions onto Date Palm Fiber by Adsorption Technique

    OpenAIRE

    2013-01-01

    The adsorption of crystal violet (CV) onto date palm fibers (DPFs) was examined in aqueous solution at 25°C. The experimental maximum adsorption capacity value was 0.66×10−6. Langmuir, Freundlich, Elovich and Temkin models were applied to describe the equilibrium isotherms. The influence of pH and temperature on dye removal was evaluated. The percentage removal of CV dye by adsorption onto DPF at different pH and temperatures showed that these factors play a role in the adsorption process. Th...

  7. Isothermal Martensite Formation

    DEFF Research Database (Denmark)

    Villa, Matteo

    Isothermal (i.e. time dependent) martensite formation in steel was first observed in the 40ies of the XXth century and is still treated as an anomaly in the description of martensite formation which is considered as a-thermal (i.e. independent of time). Recently, the clarification of the mechanism...... leading to isothermal kinetics acquired new practical relevance because of the identification of isothermal martensite formation as the most likely process responsible for enhanced performances of sub-zero Celsius treated high carbon steel products. In the present work, different iron based alloys are...... chosen to investigate time dependent martensite formation. Among them, a Fe-11wt%Ni-0.6wt%C model alloy and Fe-1.6wt%Cr-1wt%C (AISI 52100), Fe-17wt%Cr-7wt%Ni (AISI 631) and Fe-16wt%Cr-5wt%Ni (AISI 630) commercial steels. The investigation was performed with in situ magnetometry, dilatometry, synchrotron...

  8. Removal of Ni2+ from Aqueous Solutions by Adsorption Onto Magnetic Multiwalled Carbon Nanotube Nanocomposite

    Directory of Open Access Journals (Sweden)

    Konicki Wojciech

    2014-06-01

    Full Text Available The removal of Ni2+ from aqueous solution by magnetic multiwalled carbon nanotube nanocomposite (MMWCNTs-C was investigated. MMWCNTs-C was characterized by X-ray Diffraction method (XRD, High-Resolution Transmission Electron Microscopy (HRTEM, surface area (BET, and Fourier Transform-Infrared Spectroscopy (FTIR. The effects of initial concentration, contact time, solution pH, and temperature on the Ni2+ adsorption onto MMWCNTs-C were studied. The Langmuir and Freundlich isotherm models were applied to fit the adsorption data. The results showed that the adsorption isotherm data were fitted well to the Langmuir isotherm model with the maximum monolayer adsorption capacity of 2.11 mg g–1. The adsorption kinetics was best described by the pseudo-second-order model. The thermodynamic parameters, such as ΔHo, ΔGo and ΔSo, were also determined and evaluated. The adsorption of Ni2+ is generally spontaneous and thermodynamically favorable. The values of ΔHo and ΔGo indicate that the adsorption of Ni2+ onto MMWCNTs-C was a physisorption process.

  9. Analysis of isothermal and cooling-rate-dependent immersion freezing by a unifying stochastic ice nucleation model

    Science.gov (United States)

    Alpert, Peter A.; Knopf, Daniel A.

    2016-02-01

    Immersion freezing is an important ice nucleation pathway involved in the formation of cirrus and mixed-phase clouds. Laboratory immersion freezing experiments are necessary to determine the range in temperature, T, and relative humidity, RH, at which ice nucleation occurs and to quantify the associated nucleation kinetics. Typically, isothermal (applying a constant temperature) and cooling-rate-dependent immersion freezing experiments are conducted. In these experiments it is usually assumed that the droplets containing ice nucleating particles (INPs) all have the same INP surface area (ISA); however, the validity of this assumption or the impact it may have on analysis and interpretation of the experimental data is rarely questioned. Descriptions of ice active sites and variability of contact angles have been successfully formulated to describe ice nucleation experimental data in previous research; however, we consider the ability of a stochastic freezing model founded on classical nucleation theory to reproduce previous results and to explain experimental uncertainties and data scatter. A stochastic immersion freezing model based on first principles of statistics is presented, which accounts for variable ISA per droplet and uses parameters including the total number of droplets, Ntot, and the heterogeneous ice nucleation rate coefficient, Jhet(T). This model is applied to address if (i) a time and ISA-dependent stochastic immersion freezing process can explain laboratory immersion freezing data for different experimental methods and (ii) the assumption that all droplets contain identical ISA is a valid conjecture with subsequent consequences for analysis and interpretation of immersion freezing. The simple stochastic model can reproduce the observed time and surface area dependence in immersion freezing experiments for a variety of methods such as: droplets on a cold-stage exposed to air or surrounded by an oil matrix, wind and acoustically levitated droplets

  10. Modeling adsorption rate of organic micropollutants present in landfill leachates onto granular activated carbon.

    Science.gov (United States)

    Ocampo-Pérez, Raúl; Abdel daiem, Mahmoud M; Rivera-Utrilla, José; Méndez-Díaz, José D; Sánchez-Polo, Manuel

    2012-11-01

    The overall adsorption rate of single micropollutants present in landfill leachates such as phthalic acid (PA), bisphenol A (BPA), diphenolic acid (DPA), 2,4-dichlorophenoxy-acetic acid (2,4-D), and 4-chloro-2-methylphenoxyacetic acid (MCPA) on two commercial activated carbons was studied. The experimental data obtained were interpreted by using a diffusional model (PVSDM) that considers external mass transport, intraparticle diffusion, and adsorption on an active site. Furthermore, the concentration decay data were interpreted by using kinetics models. Results revealed that PVSDM model satisfactorily fitted the experimental data of adsorption rate on activated carbon. The tortuosity factor of the activated carbons used ranged from 2 to 4. The contribution of pore volume diffusion represented more than 92% of intraparticle diffusion confirming that pore volume diffusion is the controlling mechanism of the overall rate of adsorption and surface diffusion can be neglected. The experimental data were satisfactorily fitted the kinetic models. The second-order kinetic model was better fitted the experimental adsorption data than the first-order model. PMID:22858399

  11. Adsorptive removal of Congo red, a carcinogenic textile dye, from aqueous solutions by maghemite nanoparticles

    International Nuclear Information System (INIS)

    The adsorption of Congo red (CR) onto maghemite nanoparticles (γ-Fe2O3) and its desorption was investigated. The adsorption capacity was evaluated using both the Langmuir and Freundlich adsorption isotherm models. Maghemite nanoparticles (γ-Fe2O3) were prepared easily in a surfactant-less microemulsion by co-precipitation method. The size of the produced maghemite nanoparticles was determined by X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM). Synthesized maghemite nanoparticles showed the highest adsorption capacities of CR compared to many other adsorbents and would be a good method to increase adsorption efficiency for the removal of CR in a wastewater treatment process. The maximum adsorption occurred at pH 5.9. The Langmuir adsorption capacity (qmax) was found to be 208.33 mg g-1 of the adsorbent.

  12. Adsorption of arsenate from aqueous solution by rice husk-based adsorbent

    Science.gov (United States)

    Khan, Taimur; Chaudhuri, Malay

    2013-06-01

    Rice husk-based adsorbent (RHBA) was prepared by burning rice husk in a muffle furnace at 400°C for 4 h and adsorption of arsenate by the RHBA from aqueous solution was examined. Batch adsorption test showed that extent of arsenate adsorption depended on contact time and pH. Equilibrium adsorption was attained in 60 min, with maximum adsorption occurring at pH 7. Equilibrium adsorption data were well described by the Freundlich isotherm model. Freundlich constants Kf and 1/n were 3.62 and 2, respectively. The RHBA is effective in the adsorption of arsenate from water and is a potentially suitable filter medium for removing arsenate from groundwater at wells or in households.

  13. Adsorption of arsenate from aqueous solution by rice husk-based adsorbent

    International Nuclear Information System (INIS)

    Rice husk-based adsorbent (RHBA) was prepared by burning rice husk in a muffle furnace at 400°C for 4 h and adsorption of arsenate by the RHBA from aqueous solution was examined. Batch adsorption test showed that extent of arsenate adsorption depended on contact time and pH. Equilibrium adsorption was attained in 60 min, with maximum adsorption occurring at pH 7. Equilibrium adsorption data were well described by the Freundlich isotherm model. Freundlich constants Kf and 1/n were 3.62 and 2, respectively. The RHBA is effective in the adsorption of arsenate from water and is a potentially suitable filter medium for removing arsenate from groundwater at wells or in households.

  14. Modeling the adsorption of weak organic acids on goethite: the ligand and charge distribution model

    OpenAIRE

    Filius, J.D.

    2001-01-01

    A detailed study is presented in which the CD-MUSIC modeling approach is used in a new modeling approach that can describe the binding of large organic molecules by metal (hydr)oxides taking the full speciation of the adsorbed molecule into account. Batch equilibration experiments were performed using the iron (hydr)oxide goethite to determine the adsorption of a series of weak organic acids (e.g. lactic acid, oxalic acid, malonic acid, phthalic acid, citric acid, and fulvic acid). In order t...

  15. Dynamic modeling of adsorption refrigerators for systm simulation; Dynamische Modellierung von Adsorptionskaelteanlagen fuer Systemsimulation

    Energy Technology Data Exchange (ETDEWEB)

    Dalibard, Antoine; Eicker, Ursula [Hochschule fuer Technik Stuttgart (Germany). Zentrum fuer nachhaltige Energietechnik; Ziegler, Felix [Technische Univ. Berlin (Germany). Inst. fuer Energietechnik, KT2

    2012-07-01

    The present paper deals with the dynamic modelling of two beds adsorption chillers with a special focus on the heat and mass recovery processes. A physical model able to calculate different heat recovery processes as well as mass recovery has been developed and implemented in the transient simulation environment TRNSYS. The main parameters required by the model and the modelling approach used are presented. Several concepts of heat recovery are presented and discussed. Also the concept of mass recovery is described. The model parameters have been adjusted to fit measurement data of an existing large capacity adsorption chiller (350 kW). This fitted model has been used to investigate the influence of the different heat recovery concepts on the chiller performance in steady state conditions. Depending on the concepts, the thermal COP can be increased by 10 to 30% in comparison with a cycle without heat recovery. Using mass recovery allows to increase the thermal COP by more than 10% and the cooling capacity by 2.5%. Combining both heat and mass recovery results in 35% COP improvement without reducing the cooling capacity. Comparing to other existing models, the model presents some advantages. It can simulate different heat recovery schemes and includes the possibility to calculate mass recovery between the two chambers. This model can be used for two beds adsorption chillers using different working pairs as silica-gel/water. Additionally, the model can be used for system simulation in order to investigate the influence of the transient behaviour of adsorption chillers on other components like cooling towers, solar collectors, buildings.. Further works will focus on the control optimization of adsorption chiller(s) at part load conditions. Also the primary energy savings potential of solar cooling systems equipped with adsorption chillers by using advanced controls will be investigated.

  16. Kinetics and thermodynamics of {beta}-carotene and chlorophyll adsorption onto acid-activated bentonite from Xinjiang in xylene solution

    Energy Technology Data Exchange (ETDEWEB)

    Wu Zhansheng [School of Life Science and Technology, Beijing Institute of Technology, Beijing 100081 (China); School of Chemistry and Chemical Engineering, Shihezi University, Shihezi, Xinjiang 832003 (China); Li Chun, E-mail: lichun@bit.edu.cn [School of Life Science and Technology, Beijing Institute of Technology, Beijing 100081 (China); School of Chemistry and Chemical Engineering, Shihezi University, Shihezi, Xinjiang 832003 (China)

    2009-11-15

    The kinetics and thermodynamics of {beta}-carotene and chlorophyll adsorption from xylene solution onto acid-activated bentonite (AAB) within the temperature range 65-95 deg. C were investigated. Adsorption of {beta}-carotene was described well with the Langmuir isotherm, whereas chlorophyll adsorption was determined well with the Freundlich isotherm, and the experimental data on chlorophyll adsorption were also fitted by the Langmuir isotherm to a certain extent, as reflected by correlation coefficients (R{sup 2}) over 0.9865. In addition, the adsorption of {beta}-carotene and chlorophyll onto AAB are favorable. The pseudo-second-order model was found to explain the kinetics of adsorption of both pigments more effectively. Increase of temperature enhanced the adsorption rate and equilibrium adsorption capacity of {beta}-carotene and chlorophyll on AAB. The activation energy for the sorption of {beta}-carotene and chlorophyll on AAB was 19.808 kJ/mol and 16.475 kJ/mol, respectively. The thermodynamic parameters {Delta}H{sup {theta}}, {Delta}S{sup {theta}} and {Delta}G{sup {theta}}, computed from K{sub F} of the adsorption isotherm constant, were 21.766 kJ/mol, 92.244 J/K mol and -9.554 kJ/mol respectively for the adsorption of {beta}-carotene on AAB at 65 deg. C, and for adsorption of chlorophyll on AAB at 65 deg. C were 31.051 kJ/mol, 93.549 J/K mol and -0.729 kJ/mol, respectively. The adsorption of {beta}-carotene and chlorophyll in xylene solution on AAB was a spontaneous and endothermic process with increasing in the randomness at the solid-solution interface.

  17. Determinação de isotermas de adsorção de Saccharomyces cerevisiae empregando acetato e sulfato de cádmio Cadmium adsorption isotherms by Saccharomyces cerevisiae using cadmiun acetate and sulphate

    Directory of Open Access Journals (Sweden)

    Silvana Albertini

    2007-06-01

    Full Text Available Para determinar as isotermas de adsorção de cádmio por Saccharomyces cerevisiae, foram utilizados os sais acetato e sulfato de cádmio, nas concentrações de 5; 10; 20; 40; 60; 80 e 100 mg.L-1. A biomassa foi produzida a partir de uma cultura "starter" de Saccharomyces cerevisiae IZ 1904. Após o contato de 16 horas entre o microrganismo em estudo e as soluções teste, a biomassa foi separada por centrifugação e o teor de cádmio residual foi determinado por espectrofotometria de absorção atômica diretamente no sobrenadante. Os dois sais testados demonstraram acúmulo crescente do metal nas concentrações de 5; 10; 20 e 40 mg.L-1. Porém, nas concentrações de 60; 80 e 100 mg.L-1, foi observado um acúmulo decrescente do metal, mostrando assim danos da parede celular, nem sempre evidenciados em nível de membrana citoplasmática, visualizados por microscopia eletrônica de varredura.To determine the isotherms of the adsorption of cadmium for Saccharomyces cerevisiae, acetate and sulphate salts were used at the concentrations of 5, 10, 20, 40, 60, 80, and 100 mg.L-1. The biomass was produced from a starter culture of Saccharomyces cerevisiae IZ 1904. After the contact of 16 hours among the microrganism study and the solution-test, the biomass was separated by a centrifugation and the cadmium residue content was determined directly in the supernatant by atomic absorption spectrophotometry. For the two salts which were used, a growing accumulation of cadmium was observed at concentrations of 5, 10, 20, and 40 mg.L-1. In the concentrations of 60; 80 and 100 mg.L-1 a decrease in the accumulation of the metal was observed, showing damage to the cellular wall, not always observed at the membrane citoplasmatic's level, visualized by a scanning electron microscopy.

  18. Adsorption characteristics of Ni2+ ion onto the diethylenetriaminepentaacetic acid-melamine / polyvinylidene fluoride blended resin

    Directory of Open Access Journals (Sweden)

    Xiaodan Zhao, Laizhou Song, Jun He, Tingying Wu, Ying Qin

    2010-01-01

    Full Text Available The polyvinylidene fluoride blended resin (DTPA-MA/PVDF adsorbent prepared by anchoring the chelating agent diethylenetriaminepentaacetic acid (DTPA to the resin via the amide covalent bond reaction between DTPA and melamine(MA, was used to remove nickel from aqueous solutions. The blended resin was prepared using the combination of solution blending technique and phase inversion process. The blended resin was characterized by Fourier transform infrared spectroscopy (FTIR, 13C nuclear magnetic resonance spectroscopy (13C NMR, environmental scanning electron microscopy (ESEM and N2 adsorption/desorption experiments. The sorption data was fit to linearized adsorption isotherms of the Langmuir, Freundlich, and D-R isotherms models. The batch sorption kinetics was evaluated using pseudo-first-order, pseudo-second-order, and intraparticle diffusion kinetic reaction models. ΔH° is less than 0, ΔG° is lower than 0, and ΔS° is greater than 0, which shows that the adsorption of Ni(II by the blended resin is a spontaneous, exothermic process. The adsorption isotherm fits better to the Langmuir isotherm model and the pseudo-second-order kinetics model gives a better fit to the batch sorption kinetics. The adsorption mechanism is assumed to be ion exchange between the nickel ion and the polyamino polycarboxylic acid chelating group of the blended resin.

  19. Removal of Bi(Ⅲ) with Adsorption Technique Using Coconut Shell Activated Carbon

    Institute of Scientific and Technical Information of China (English)

    SARTAPE Ashish; MANDHARE Aniruddha; SALVI Prathmesh; PAWAR Dattatraya; RAUT Prakash; ANUSE Mansing; KOLEKAR Sanjay

    2012-01-01

    In present study,we report the preparation of coconut shell activated carbon as adsorbent and its appli-cation for Bi(Ⅲ) removal from aqueous solutions.The developed adsorbent was characterized with scanning elec-tron microscope(SEM),Fourier Transform Infrared(FTIR),C,H,N,S analyzer,and BET surface area analyzer.The parameters examined include agitation time,initial concentration of Bi(Ⅲ),adsorbent dose and temperature.The maximum adsorption of Bi(Ⅲ)(98.72%) was observed at 250 mg·L-1 of Bi(Ⅲ) and adsorbent dose of 0.7 g when agitation was at 160 r·min-1 for 240 min at(299±2) K.The thermodynamic parameters such as Gibb's free energy(△Gθ),enthalpy(△Hθ) and entropy(△Sθ) were evaluated.For the isotherm models applied to adsorption study,the Langmuir isotherm model fits better than the Freundlich isotherm.The maximum adsorption capacity from the Langmuir isotherm was 54.35 mg?g?1 of Bi(Ⅲ).The kinetic study of the adsorption shows that the pseudo second order model is more appropriate than the pseudo first order model.The result shows that,coconut shell ac-tivated carbon is an effective adsorbent to remove Bi(Ⅲ) from aqueous solutions with good adsorption capacity.

  20. Effect of oxygen adsorption on surface tension of liquid copper: Experiments and thermodynamic models

    International Nuclear Information System (INIS)

    Highlights: • The effect of oxygen on the surface tension of liquid Cu was investigated. • The adsorption behavior of oxygen is presented with a thermodynamic model. • This model assumes a hypothetical binary system of Cu-“Cu2O”. • “Cu2O” is considered as an associate molecule. • Ideal adsorption model exhibits the best fit of the experimental results. - Abstract: The effect of oxygen adsorption on surface tension of liquid copper at two different temperatures (1390 and 1440 K) has been investigated. A combination of specially designed crucibles, He-Ne laser, and high-resolution photography in a highly controlled gas atmosphere was used for accurate measurements. Experimental data exhibits decreasing surface tension with increasing oxygen partial pressure. Discussion on the adsorption behavior of oxygen is presented based on thermodynamic models by assuming a hypothetical binary system of Cu-“Cu2O”, in which “Cu2O” is considered as an associate molecule. Ideal adsorption model which assumes insignificant interactions between Cu and Cu2O on the surface exhibits the best fit to the experimental results

  1. Adsorption of Acenaphthene unto Activated Carbon Produced from Agricultural Wastes

    Directory of Open Access Journals (Sweden)

    F.E. Adelowo

    2012-01-01

    Full Text Available The suitability and the performance of activated carbon produced from flamboyant pod back, milk bush kernel shell and rice husk for the effective removal of acenaphthene from simulated wastewater under the influence of carbonization temperature and initial concentration were investigated. The adsorption capacities of all the activated carbons obtained from the selected raw materials are influenced by increasing carbonization temperature. Activated carbons obtained from rice husk at carbonisation temperature of 600°C had the maximum adsorption capacity (5.554 mg g-1 while carbons produced from milk bush at carbonisation temperature of 300°C had the minimum adsorption capacity (1.386 mg g-1, for the adsorption of acenaphthene from the simulated wastewater. The removal efficiencies of the investigated adsorbents generally rank high and the highest value (80.56% was obtained for the adsorption of acenaphthene by rice husk carbonized at 600°C. Furthermore, the removal efficiencies obtained in the study decreased as the initial concentrations of the adsorbate increased. The four selected isotherm models; Freundlich, Langmuir, Temkin and Dubinin-Radushkevich described well the equilibrium adsorption of acenaphthene unto activated carbon derived from Flamboyant pod bark, milk bush kernel shell and rice husk. Sequence of suitability of the selected isotherms in the study was Temkin ≈ Freundlich >Dubinin-Radushkevich>Langmuir for adsorption of acenaphthene. It therefore shows that Temkin isotherm is the most suitable model for fitting experimental data obtained from adsorption of acenaphthene from simulated wastewater unto activated carbon produced from Flamboyant pod bark, milk bush kernel shell and rice husk.

  2. Influence of organobentonite structure on toluene adsorption from water solution

    Directory of Open Access Journals (Sweden)

    Nuria Vidal

    2012-12-01

    Full Text Available Due to increase water pollution by organic compound derived from hydrocarbons such as toluene, several alternative technologies for remediation of polluted water have been originated. In this work natural bentonites were modified with cetyltrimethylammonium (CTMA+ for obtaining organophilic bentonites. The obtained CTMA-bentonites would be suitable for use as adsorbents of toluene present in water. The influence of structural characteristics of CTMA-bentonites on their adsorption capacity was studied. It was shown that adsorption of toluene depended on homogeneous interlayer space associated with arrangements of CTMA+ paraffin-monolayer and bilayer models, accompanied by a high degree ordering of the carbon chain of organic cation in both arrangements. However, packing density would not have an evident influence on the retention capacity of these materials. The solids obtained were characterized by chemical analysis, X-ray diffractions and infrared spectroscopy. Toluene adsorption was measured by UV-visible spectrophotometer. Adsorption capacity was studied by determining adsorption isotherms and adsorption coefficient calculation. The adsorption isotherms were straight-line indicating a partition phenomenon of toluene between the aqueous and organic phase present in organophilic bentonites.

  3. Application of the 'bottom up' approach for the predictive modeling of sorption isotherms on Hungarian Boda clay

    International Nuclear Information System (INIS)

    Document available in extended abstract form only. Argillaceous rocks are being viewed with continuing interest in many waste management programmes as suitable host formations for the deep geological disposal of radioactive waste: Opalinus clay, Switzerland; Boom and Ypresian clays, Belgium, Callovo-Oxfordian clays, France. One of the options for disposal of radioactive waste in Hungary is the storage in the Boda Clay-stone Formation (BCF). Clay minerals such as illite, smectite, illite/smectite mixed layers and kaolinite are important components in such rock types and can often make up 50 or more wt.% of the total mass. Predicting the fate and transport of radionuclides (RNs) in the repository near- and far-fields is a key research issue in many radioactive waste management programmes, and is one of the main pillars upon which the safety cases for deep geological radioactive waste repositories are built. A broad variety of different types of sorption models i.e. empirical and mechanistic have been developed over the past few decades to describe the interaction of RNs at the clay-water interface over a wide range of conditions. Sorption edges and isotherms were measured for a large number of radionuclides with valences from II to VI on illite and montmorillonite and could be very well described by a relatively simple model, the 2 site proto-lysis non-electrostatic surface complexation and cation exchange (2SPNE SC/CE) sorption model. Cs sorption on illite was modelled in the past and was further developed to a generalised Cs sorption model. Sorption in most natural argillaceous rocks is inherently too complex and multi-faceted to be directly understood in terms of mechanisms and their associated parameters. The so-called 'bottom up' approach is based on the hypothesis that the uptake of RNs in complex mineral/groundwater systems can be quantitatively predicted from the understanding of the sorption processes on single minerals, and the models developed to describe

  4. Evaluation of flow models and pollutant retention isotherms for their application to rain garden bioretention

    OpenAIRE

    Quinn, Ruth

    2015-01-01

    The primary aims of this research was firstly to develop a computer modelling tool which could predict pollution retention in a rain garden and secondly to use the model and additional experiments to examine various aspects of rain garden design with respect to pollutant retention. Initially, the behaviour of all contaminants in urban runoff was examined including their retention and possible modelling methods. Heavy metals were then identified as the main focus of this project as this ch...

  5. Computer-aided model analysis for ionic strength-dependent effective charge of protein in ion-exchange chromatography

    DEFF Research Database (Denmark)

    Lim, Young-il; Jørgensen, Sten Bay; Kim, In-Ho

    2005-01-01

    A packed-bed chromatographic model developed in this study includes adsorption isotherms considering steric mass action (SMA) as well as non-linearity in liquid/solid phases, adsorption kinetics and mass transport. For solving the nonlinear and nonequilibrium adsorption model described by a partial...

  6. Effect of aniline on cadmium adsorption by sulfanilic acid-grafted magnetic graphene oxide sheets.

    Science.gov (United States)

    Hu, Xin-jiang; Liu, Yun-guo; Zeng, Guang-ming; Wang, Hui; Hu, Xi; Chen, An-wei; Wang, Ya-qin; Guo, Yi-Mming; Li, Ting-ting; Zhou, Lu; Liu, Shao-heng; Zeng, Xiao-xia

    2014-07-15

    Cd(II) has posed severe health risks worldwide. To remove this contaminant from aqueous solution, the sulfanilic acid-grafted magnetic graphene oxide sheets (MGOs/SA) were prepared and characterized. The mutual effects of Cd(II) and aniline adsorption on MGOs/SA were studied. The effects of operating parameters such as pH, ionic strength, contact time and temperature on the Cd(II) enrichment, as well as the adsorption kinetics and isotherm were also investigated. The results demonstrated that MGOs/SA could effectively remove Cd(II) and aniline from the aqueous solution and the two adsorption processes were strongly dependent on solution pH. The Cd(II) adsorption was reduced by the presence of aniline at pH5.4. The presence of Cd(II) diminished the adsorption capacity for aniline at pHadsorption at pH>7.8. The decontamination of Cd(II) by MGOs/SA was influenced by ionic strength. Besides, the adsorption process could be well described by pseudo-second-order kinetic model. The intraparticle diffusion study revealed that the intraparticle diffusion was not the only rate-limiting step for the adsorption process. Moreover, the experimental data of isotherm followed the Freundlich isotherm model. PMID:24863786

  7. Simulation and modeling of turbulent non isothermal vapor-droplet dispersed flow

    International Nuclear Information System (INIS)

    One of the reference accident that may occur in PWR (Pressurized Water Reactor) is LOCA (Loss of Coolant Accident). The LOCA is studied to design some emergency systems implemented in the basic nuclear installations. The LOCA corresponds to the break of a pipe in the primary loop. This accident is associated with a loss of pressure which leads to the vaporization of the water in the reactor core and then to the rise of the temperature of the assemblies. In this study, we focus on the area of vapor-droplet flow, where the cooling effectiveness of such a mixture is a major concern. The droplets act as heat sinks for the vapor and control the vapor temperature profile which, in turn, determines the wall heat transfer rate. Our general objective is to ameliorate the modeling of the vapor-droplet flow (i.e. at CFD scale). Particularly the estimation of the radial distribution of the droplets. The volume fraction distribution of the two phases depends on the size and dispersion of the droplets in the flow. The size of the droplets is controlled by the rupture and coalescence mechanisms and the interfacial mass transfer (evaporation/condensation). The distribution of the droplets is controlled by the transfer of momentum between the two phases. Our study focuses particularly on the latter point. We are restricted to flows where the liquid water flows under the form of non-deformable spherical droplets that do not interact with each other. Both phases are treated by a two-fluid approach Euler-Euler. In chapter 2, a description of two-phase flow model is presented, using separate mass, momentum, and energy equations for the two phases. These separate balance equations are obtained in an averaging process starting from the local instantaneous conservation equations of the individual phases. During the averaging process, important information on local flow processes are lost and, consequently, additional correlations are needed in order to close the system of equations. The

  8. Experimental and simulated propene isotherms on porous solids

    Science.gov (United States)

    Navarro, M. V.; Puértolas, B.; García, T.; Murillo, R.; Mastral, A. M.; Varela-Gandía, F. J.; Lozano-Castelló, D.; Cazorla-Amorós, D.; Bueno-López, A.

    2010-06-01

    The lack of treatment capacity of hydrocarbons by three-way catalysts during the "cold start" period creates an important environmental problem. During this period, the temperature of the three-way catalyst is too low for effective operation and cannot convert the hydrocarbons in the exhaust. 50-80% of the total hydrocarbon emissions are produced in this phase that accomplishes the first 60-120 s of the engine operation. In this study, the technology chosen to treat these emissions is the use of HC-traps, and molecular simulations are tested as a tool to reproduce the experimental adsorption behaviour of porous solids. Therefore, experimental and simulated adsorption isotherms of propene (model hydrocarbon) have been obtained for four different crystalline materials with distinctive framework structures (3D and 1D) and a variety of Si/Al ratios and cations (three zeolites: ZSM-5, BETA and Mordenite; and a silicoaluminophosphate molecular sieve: SAPO-5).

  9. MICRO-DESCRIPTION OF THE SOLUTE-FIELD AND THE PHASE-FIELD MODEL FOR ISOTHERMAL PHASE TRANSITION IN BINARY ALLOYS

    Institute of Scientific and Technical Information of China (English)

    H.M. Ding; L.L. Chen; R.X. Liu

    2004-01-01

    A new phase field method for two-dimensional simulations of binary alloy solidification was studied. A model basing on solute conservative in every unit was developed for solving the solute diffusion equation during solidification. Two-dimensional computations were performed for ideal solutions and Ni-Cu dendritic growth into an isothermal and highly supersaturated liquid phase.

  10. Simulation and modeling of turbulent non isothermal vapor-droplet dispersed flow

    Energy Technology Data Exchange (ETDEWEB)

    Baalbaki, Daoud

    2011-12-15

    One of the reference accident that may occur in PWR (Pressurized Water Reactor) is LOCA (Loss of Coolant Accident). The LOCA is studied to design some emergency systems implemented in the basic nuclear installations. The LOCA corresponds to the break of a pipe in the primary loop. This accident is associated with a loss of pressure which leads to the vaporization of the water in the reactor core and then to the rise of the temperature of the assemblies. In this study, we focus on the area of vapor-droplet flow, where the cooling effectiveness of such a mixture is a major concern. The droplets act as heat sinks for the vapor and control the vapor temperature profile which, in turn, determines the wall heat transfer rate. Our general objective is to ameliorate the modeling of the vapor-droplet flow (i.e. at CFD scale). Particularly the estimation of the radial distribution of the droplets. The volume fraction distribution of the two phases depends on the size and dispersion of the droplets in the flow. The size of the droplets is controlled by the rupture and coalescence mechanisms and the interfacial mass transfer (evaporation/condensation). The distribution of the droplets is controlled by the transfer of momentum between the two phases. Our study focuses particularly on the latter point. We are restricted to flows where the liquid water flows under the form of non-deformable spherical droplets that do not interact with each other. Both phases are treated by a two-fluid approach Euler-Euler. In chapter 2, a description of two-phase flow model is presented, using separate mass, momentum, and energy equations for the two phases. These separate balance equations are obtained in an averaging process starting from the local instantaneous conservation equations of the individual phases. During the averaging process, important information on local flow processes are lost and, consequently, additional correlations are needed in order to close the system of equations. The

  11. Testing lowered isothermal models with direct N-body simulations of globular clusters

    CERN Document Server

    Zocchi, Alice; Hénault-Brunet, Vincent; Varri, Anna Lisa

    2016-01-01

    Several self-consistent models have been proposed, aiming at describing the phase space distribution of stars in globular clusters. This study explores the ability of the recently proposed LIMEPY models (Gieles & Zocchi) to reproduce the dynamical properties of direct N-body models of a cluster in a tidal field, during its entire evolution. These dynamical models include prescriptions for the truncation and the degree of radially-biased anisotropy contained in the system, allowing us to explore the interplay between the role of anisotropy and tides in various stages of the life of star clusters. We show that the amount of anisotropy in an initially tidally underfilling cluster increases in the pre-collapse phase, and then decreases with time, due to the effect of the external tidal field on its spatial truncation. This is reflected in the correspondent model parameters, and the best-fit models reproduce the main properties of the cluster at all stages of its evolution, except for the phases immediately pr...

  12. ADSORPTION OF POLYCHLORINATED BIPHENYLS BY SOILS

    OpenAIRE

    Mihaela Preda; Radu Lăcătuşu; Dumitru Marian Motelică; Nicoleta Vrînceanu; Veronica Tănase

    2010-01-01

    The behavior of polychlorinated biphenyls (PCBs) in soil is determined by several factors including adsorption, mobility and degradation. Adsorption, directly or indirectly, influences the other factors. Adsorption process is generally evaluated by using adsorption isotherms representing the relationship between the quantity of substance adsorbed per unit weight and concentration of the substance in solution at equilibrium. They allow determination of the adsorption constant, which is directl...

  13. Thermodynamical and structural insights of orange II adsorption by MgRAlNO3 layered double hydroxides

    International Nuclear Information System (INIS)

    [Mg1-x Alx(OH)2][(NO3)x, nH2O] Layered Double Hydroxide (LDH) sorbents with variable Mg/Al molar (R=(1-x)/x) ratios were investigated for adsorption of azo dye, orange II (OII) at various pH and temperature conditions. Mg2AlNO3 displays the highest adsorption capacity with 3.611 mmol of OII per gram of Mg2AlNO3 at 40 oC. Adsorption isotherms have been fitted using the Langmuir model and free energy of adsorption (ΔGo), enthalpy (ΔHo) and entropy (ΔSo) were calculated. The experimental values for ΔGo in temperature range between 10 and 40 oC were found to be negative indicating that a spontaneous process occurred. Positive calculated enthalpy values, characteristic of an endothermic process were found. Characterization of solids (PXRD, FTIR, UV-vis, TGA/DTA, adsorption isotherm BET analysis, SEM and Zetametry) before and after adsorption showed that adsorption proceeds in two steps. First, adsorption occurs at the LDH surface, followed by intercalation via anion exchange. -- Graphical Abstract: Structural and thermodynamical insight of adsorption/Intercalation of OII in MgRAl LDH Display Omitted Highlights: → The nitrate containing hydrotalcite-like compounds (MgRAlNO3 LDH) were prepared by the coprecipitation method. → Adsorption of anionic orange dye(OII) is studied on LDHs at different temperatures. → The adsorption process is well described by the Langmuir isotherm model. → Mg2AlNO3 displays the highest adsorption capacity with 3.611 mmol of OII per gram of Mg2AlNO3 at 40 oC. → Adsorption process does not occur on the surface of the LDH only but an intercalation process is also occurring concomitantly according to the thermodynamical values.

  14. Effect of temperature and kinetic modelling of lignosulfonate adsorption onto powdered eggshell in batch systems

    Directory of Open Access Journals (Sweden)

    Muhammad Ali Zulfikar

    2013-06-01

    Full Text Available The sorption of lignosulfonate onto powdered eggshell under the influence of temperature has been studied. The rate of adsorption onto eggshell was investigated under a variety of adsorbent dosages. The kinetic data from these investigations were correlated to a number of adsorption models in an attempt to elucidate the mechanism of the adsorption processes. Thermodynamic parameter data indicated that the lignosulfonate sorption process was non-spontaneous and endothermic under the experimental conditions, with the Gibbs free energy (Go in the range of 1.83-1.07 kJ mol-1, enthalpy (Ho andentropy (So of 5.66 kJ mol-1 and 12.82 J mol-1, respectively and the activation energy of 18.17 kJ mol-1. The adsorption mechanism was found to follow a pseudo-second-order model, with the kinetic constants in the range of 0.689–1.430 g mg-1 min-1. Both the intra-particle diffusion and Boyd kinetic models indicated that boundary layer/film diffusion was the main rate determining step in lignosulfonate adsorption process.

  15. Modeling and Simulation of Fixed Bed Adsorption Column using Integrated CFD Approach

    Directory of Open Access Journals (Sweden)

    A.M. Shariff

    2010-01-01

    Full Text Available The understanding of detailed fluid flow in the fixed bed adsorption column is substantially crucial since the mass and heat transfer in the bed is influenced by the column hydrodynamics. In this study, an integrated CFD model was developed to model and simulate the adsorption dynamics and hydrodynamics of gaseous fluid (CH4 and CO2 mixture in the fixed bed adsorption column. The developed integrated model was used to determine the CO2 concentration factor at the column (which indicating the CO2 adsorption capacity as a function of time, based on different operating conditions. The simulated results were compared with experimental data and found to give a good agreement with error less than 2.5%. The effect of various influencing parameters such as feed velocity, bed porosity and feed concentration were studied to investigate their influences on the CO2 adsorption capacity. Besides, the effect of inlet CO2 concentration on the bed temperature profile was also studied in the present study.

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

    International Nuclear Information System (INIS)

    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 x 10-11 m/s and k = 3.1 x 10-12[exp( - t/τ) + 1/(t + 10-4)], for powder and pellet form adsorbents, respectively.

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

    Science.gov (United States)

    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.

  18. Validation of the Jarzynski relation for a system with strong thermal coupling: An isothermal ideal gas model

    Science.gov (United States)

    Baule, A.; Evans, R. M. L.; Olmsted, P. D.

    2006-12-01

    We revisit the paradigm of an ideal gas under isothermal conditions. A moving piston performs work on an ideal gas in a container that is strongly coupled to a heat reservoir. The thermal coupling is modeled by stochastic scattering at the boundaries. In contrast to recent studies of an adiabatic ideal gas with a piston [R.C. Lua and A.Y. Grosberg, J. Phys. Chem. B 109, 6805 (2005); I. Bena , Europhys. Lett. 71, 879 (2005)], the container and piston stay in contact with the heat bath during the work process. Under this condition the heat reservoir as well as the system depend on the work parameter λ and microscopic reversibility is broken for a moving piston. Our model is thus not included in the class of systems for which the nonequilibrium work theorem has been derived rigorously either by Hamiltonian [C. Jarzynski, J. Stat. Mech. (2004) P09005] or stochastic methods [G.E. Crooks, J. Stat. Phys. 90, 1481 (1998)]. Nevertheless the validity of the nonequilibrium work theorem is confirmed both numerically for a wide range of parameter values and analytically in the limit of a very fast moving piston, i.e., in the far nonequilibrium regime.

  19. Isothermal Kinetics Modelling of the Fischer-Tropsch Synthesis over the Spray-Dried Fe-Cu-K Catalyst

    Institute of Scientific and Technical Information of China (English)

    Xiaohui Guo; Ying Liu; Jie Chang; Liang Bai; Yuanyuan Xu; Hongwei Xiang; Yongwang Li

    2006-01-01

    The isothermal kinetics of the Fischer-Tropsch synthesis (FTS) over Fe-Cu-K spray-dried catalyst was studied in a spinning basket reactor. The experiments were carried out at a constant temperature of 523 K, n(H2)/n(CO) feed ratios of 0.8-2.0, reactor pressures of 1.1-2.5 MPa, and space velocity of 0.556× 10-3 Nm3/kgcat.s. Kinetic model for hydrocarbon formation was derived on the basis of simplified carbide mechanism to reduce the number of parameters. Two individual rate constants for methane and ethene were considered. Furthermore, the model was modified empirically by non-intrinsic effect, such as physisorption and fictitious olefin pressures that were taken into account, and the influences of secondary reaction of α-olefins on product distribution. The simulation results showed that the experimental phenomena of FTS and the deviations from ASF distribution, such as the relatively high yield of methane and low yield of ethene observed experimentally could be depicted basically.

  20. The influence of the carbon surface chemical composition on Dubinin-Astakhov equation parameters calculated from SF{sub 6} adsorption data-grand canonical Monte Carlo simulation

    Energy Technology Data Exchange (ETDEWEB)

    Furmaniak, Sylwester; Terzyk, Artur P; Gauden, Piotr A [Department of Chemistry, Physicochemistry of Carbon Materials Research Group, N Copernicus University, Gagarin Street 7, 87-100 Torun (Poland); Kowalczyk, Piotr [Nanochemistry Research Institute, Curtin University, PO Box U1987, Perth, WA 6845 (Australia); Harris, Peter J F, E-mail: aterzyk@chem.uni.torun.pl [Centre for Advanced Microscopy, University of Reading, Whiteknights, Reading RG6 6AF (United Kingdom)

    2011-10-05

    Using grand canonical Monte Carlo simulation we show, for the first time, the influence of the carbon porosity and surface oxidation on the parameters of the Dubinin-Astakhov (DA) adsorption isotherm equation. We conclude that upon carbon surface oxidation, the adsorption decreases for all carbons studied. Moreover, the parameters of the DA model depend on the number of surface oxygen groups. That is why in the case of carbons containing surface polar groups, SF{sub 6} adsorption isotherm data cannot be used for characterization of the porosity. (paper)