WorldWideScience

Sample records for adsorption isotherms modeling

  1. Modeling of Experimental Adsorption Isotherm Data

    OpenAIRE

    Xunjun Chen

    2015-01-01

    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...

  2. 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.

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

    Science.gov (United States)

    Jeppu, Gautham P.; Clement, T. Prabhakar

    2012-03-01

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

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

    Science.gov (United States)

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

    2016-01-01

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

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

    Science.gov (United States)

    Belhachemi, Meriem; Addoun, Fatima

    2011-12-01

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

  6. 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.

  7. Adsorption of Polycyclic Aromatic Hydrocarbons on Activated Carbons: Kinetic and Isotherm Curve Modeling

    Directory of Open Access Journals (Sweden)

    ROHADIN MORADI-RAD

    2015-10-01

    Full Text Available  The modeling of kinetic and isotherm curves acquired in adsorption of polycyclic aromatic hydrocarbons (PAHs as a model compound (phenanthrene on activated carbons in the organic solvent. All the runs were carried out in a batch system at atmospheric pressure, process temperature of 24±2°C, and using the 100 ml phenanthrene in cyclohexan. This experimental work was mainly focused on the study of how the variables properties such as adsorbent dosage, the initial phenanthrene concentration, contact time and pH of cyclohexane solutions influence the kinetic and isotherm of the adsorption process. The results indicated that pH did not play a key role in the process of phenanthrene adsorption. The considerable adsorption (8.34 mg/g was reached at pH 7, adsorbent dosage of 0.3 g/100 ml and agitation time of 11 h on activated carbons. The impact of adsorbent dose on phenanthrene concentration was not important after 0.3 g/100 ml. The results also showed that adsorption capacity became notably greater with an increase in contact time and initial phenanthrene concentration. Another important finding was that adsorption processes and equilibrium data well fitted by pseudo-second-order kinetic (R2=0.99 and Fraundlich adsorption models (R2=0.99. It can be concluded that there was a significant positive correlation between adsorption processes and the Freundlich isotherm model but Langmuir theory showed only a weak association.

  8. 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.

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

    Science.gov (United States)

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

    2016-01-15

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

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

    Science.gov (United States)

    Davis, Craig Warren; Di Toro, Dominic M

    2015-07-01

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

  11. Efficient adsorption of 4-Chloroguiacol from aqueous solution using optimal activated carbon: Equilibrium isotherms and kinetics modeling

    Directory of Open Access Journals (Sweden)

    Afidah Abdul Rahim

    2016-10-01

    Full Text Available The optimal activated carbon produced from Prosopis africana seed hulls (PASH-AC was obtained using the impregnation ratio of 3.19, activation temperature of 780 °C and activation time of 63 min with surface area of 1095.56 m2/g and monolayer adsorption capacity of 498.67 mg/g. The adsorption data were also modeled using five various forms of the linearized Langmuir equations as well as Freundlich and Temkin adsorption isotherms. In comparing the legitimacy of each isotherm model, chi square (χ2 was incorporated with the correlation coefficient (R2 to justify the basis for selecting the best adsorption model. Langmuir-2 > Freundlich > Temkin isotherms was the best order that described the equilibrium adsorption data. The results revealed pseudo-second-order to be the most ideal model in describing the kinetics data.

  12. 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

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

    Science.gov (United States)

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

    2016-06-01

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

  14. CO_2 isothermal adsorption models of coal in the Haishiwan Coalfield

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Since the capacity of CO2 adsorption of coal is a key factor in coal and CO2 outbursts,an experimental study was carried out on CO2 isothermal adsorption with high-pressure volumetry with dry coal samples from the No.2 coal seam in the Haishiwan Coalfield.Four different equations(Langmuir,BET,D-R and D-A) were used to fit the experimental data.We discuss adsorption mechanisms.The results show that the amount of CO2 adsorption increases rapidly under low relative pressure,i.e.,the ratio of equilibrium pressu...

  15. 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

  16. 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.

  17. COMPARATIVE STUDY OF LINEARIZED AND NON-LINEARIZED MODIFIED LANGMUIR ISOTHERM MODELS ON ADSORPTION OF ASPHALTENE ONTO MINERAL SURFACES

    OpenAIRE

    Mohammadi, M; AMERI SHAHRABI M.J.; Sedighi, M.

    2012-01-01

    In this paper, the Langmuir isotherm, originally derived for the adsorption of asphaltene extracted from shale oil and dissolved in toluene on Kaolin, Smectite, Fluorite and Hematite, was modified to fit the adsorption isotherm. The modified Langmuir isotherm parameters obtained from the four linear equations using the linear method differed. The aim of the proposed modification is based on the fact that direct application of the Langmuir isotherm often leads to poor data fitting. In the pres...

  18. Error Analysis of Adsorption Isotherm Models for Acid Dyes onto Bamboo Derived Activated Carbon

    Institute of Scientific and Technical Information of China (English)

    L.S. Chan; W.H. Cheung; S.J. Allen; G. McKay

    2012-01-01

    High surface area activated carbons were produced by thermal activation of waste bamboo scaffolding with phosphoric acid. Single component equilibrium dye adsorption was conducted on the carbons produced and comparedwith a commercially available carbon. Two acid dyes With different molecular sizes, namely Acid Yellow 117 (AY117) and Acid Blue 25 (AB25), were used to evaluate the adsorption capacity of the produced carbons. Itwas found that the dye with smaller molecular size, AB 25, was readily adsorbed onto the produced carbon, nearly three times, higher than a commercially available carbon, while the larger size dye, A.Y117, showed little adsorption.The experimental data were analyzed using isotherm equations including Langmuir, Freundlich, Tempkin,Toth, Redlich-Peterson and Sips equations. The equilibrium data were then analyzed using five different non-linear erroranalysis methods.

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

    Science.gov (United States)

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

    2016-09-01

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

  20. Adsorption from Experimental Isotherms of Supercritical Gases

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    A mathematical method was proposed for the determination of absolute adsorption from experimental isotherms. The method is based on the numerical equality of the absolute and the excess adsorption when either the gas phase density or the amount adsorbed is not quite considerable. The initial part of the experimental isotherms, which represents the absolute adsorption, became linear with some mathematical manipulations. The linear isotherms were reliably formulated. As consequence, either the volume or the density of the supercritical adsorbate could be determined by a non-empirical way. This method was illustrated by the adsorption data of supercritical hydrogen and methane on a superactivated carbon in large ranges of temperature and pressure.

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

    Science.gov (United States)

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

    2015-11-01

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

  2. 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)

  3. 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

  4. 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.

  5. 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...

  6. 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...

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

    Science.gov (United States)

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

    2016-01-01

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

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

    Science.gov (United States)

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

    2016-01-01

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

  9. 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...

  10. 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)

  11. Prediction of Pure Component Adsorption Equilibria Using an Adsorption Isotherm Equation Based on Vacancy Solution Theory

    DEFF Research Database (Denmark)

    Marcussen, Lis; Aasberg-Petersen, K.; Krøll, Annette Elisabeth

    2000-01-01

    An adsorption isotherm equation for nonideal pure component adsorption based on vacancy solution theory and the Non-Random-Two-Liquid (NRTL) equation is found to be useful for predicting pure component adsorption equilibria at a variety of conditions. The isotherm equation is evaluated successfully...... adsorption systems, spreading pressure and isosteric heat of adsorption are also calculated....

  12. 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)

  13. 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.

  14. 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.

  15. 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.

  16. Study of adsorption isotherms of green coconut pulp

    Directory of Open Access Journals (Sweden)

    Fábia Carolina Gonçalves Lavoyer

    2013-03-01

    Full Text Available Brazil is considered one of the largest producers and consumers of tropical fruits. Green coconut (Cocos nucifera L. stands out not only for its production and consumption, but also for the high amount of waste produced by coconut water industry and in natura consumption. Therefore, there is a need for utilization of this by-product. This study aims to study the adsorption isotherms of green coconut pulp and determine its isosteric heat of sorption. The adsorption isotherms at temperatures of 30, 40, 50, 60, and 70 °C were analyzed, and they exhibit type III behavior, typical of sugar rich foods. The experimental results of equilibrium moisture content were correlated by models present in the literature. The Guggenheim, Anderson and De Boer (GAB model proved particularly good overall agreement with the experimental data. The heat of sorption determined from the adsorption isotherms increased with the decrease in moisture content. The heat of sorption is considered as indicative of intermolecular attractive forces between the sorption sites and water vapor, which is an important factor to predict the shelf life of dried products.

  17. Adsorption isotherms for benzene on diatomites from China

    Institute of Scientific and Technical Information of China (English)

    YANG, Yu-Xianga; WU, Jie-Da; JIANG, Zhong-Liang; HUANG, Meng-Jian; CHEN, Rong-San; DAI, An-Bang

    2000-01-01

    In this paper, benzene adsorption isotherm and their hysteresis on two important local diatomites were determined at 25℃, ani their silicon hydroxyl group (SiOH) nunber was determined, their properties were reported, and the relationship between surface structure, surface SiOH number per nm2and adsorption isotherm with hysteresis was discussed. The specific surface was also calculated from the isotherms, and pore-size distribution was determined.

  18. 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

  19. Adsorption kinetics,isotherm,and thermodynamic studies of adsorption of pollutant from aqueous solutions onto humic acid

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    In the present study,humic acid was used as an adsorbent for the investigation of the adsorption kinetics,isotherms,and thermo-dynamic parameters of hexavalent chromium from aqueous solution at varying pH,temperatures,and concentrations.Adsorption isotherms and equilibrium adsorption capacities were determined by the fittings of the experimental data to three well-known iso-therm models:Langmuir,Freundlich,and Redlich-Peterson.The results showed that the Langmuir and Redlich-Peterson models appear to fit the adsorption better than did the Freundlich adsorption model for the adsorption of chromium onto humic acid.The equilibrium constants were used to calculate thermodynamic parameters such as the change of free energy,enthalpy,and entropy.The derived adsorption constants (logaL) and their temperature dependencies from Langmuir isotherm have been used to calculate the corresponding thermodynamic quantities such as the free energy of adsorption,heat,and entropy of adsorption.The thermo-dynamic data indicate that Cr (VI) adsorption onto humic acid is entropically driven and characterized by physical adsorption.

  20. 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.

  1. 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.

  2. 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)

  3. 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, ...

  4. 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.

  5. 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…

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

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

    Science.gov (United States)

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

    2013-04-01

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

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

    Directory of Open Access Journals (Sweden)

    Junsheng Liu

    2013-01-01

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

  13. A Modified Peng-Robinson Equation State for Prediction of Gas Adsorption Isotherm

    Institute of Scientific and Technical Information of China (English)

    Ali Akbar Amooey

    2014-01-01

    This research proposes a modified two-dimensional Peng-Robinson equation model to predict adsorp-tion isotherm in adsorbate-adsorbent systems. The parameters of the proposed model are calculated by using the op-timization of experimental data for the different single gas adsorption systems at various temperatures. The experi-mental adsorption equilibrium data of adsorbate-adsorbent systems was compared with the calculated results in our proposed model and the two-dimensional Hill-deBoer equation model. The proposed model as indicated in the re-sults shows a better prediction of the experimental results compared with two others.

  14. 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

  15. 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.

  16. 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.

  17. 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

  18. Multifractal characteristics of Nitrogen adsorption isotherms from tropical soils

    Science.gov (United States)

    Vidal Vázquez, Eva; Paz Ferreiro, Jorge

    2010-05-01

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

  19. 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.

  20. Relationship between breakthrough curve and adsorption isotherm of Ca(II) imprinted chitosan microspheres for metal adsorption

    Institute of Scientific and Technical Information of China (English)

    Yangcheng Lu; Jing He; Longwen Wu; Guangsheng Luo

    2016-01-01

    In this work, an equilibrium-dispersion model was successfully established to describe the breakthrough performance of Ca(II) imprinted chitosan (Ca(II)-CS) microspheres packed column for metal adsorption, and the assumptions of Langmuir isotherms and axial dispersion controlled mass transfer process were confirmed. The axial dispersion coefficient in Ca(II)-CS microspheres packed column was found to be almost proportional to the linear velocity and fit for prediction through single breakthrough test. Sensitivity analysis for breakthrough curve indicated the axial dispersion coefficient as well as Langmuir coefficient was sensitive variable for deep removal requirement. The retrieval of the adsorption isotherms of Ca(II)-CS microspheres from breakthrough curve was fulfilled by model ing calibration. A strategy based on the correlation between adsorption isotherms and breakthrough performance was further proposed to simplify the column adsorption design using absorbents with smal/uniform size and fast adsorption kinetics like Ca(II)-CS microspheres to cut down the gap between lab and industry.

  1. 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

  2. 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.

  3. Adsorption Isotherms of Quercetin and Catechin Compounds on Quercetin-MIP

    Institute of Scientific and Technical Information of China (English)

    JIN Yin-zhe; ROW Kyung Ho

    2007-01-01

    A molecular imprinted polymer(MIP) was prepared with quercetin as the template and methacrylic acid(MAA)as the functional monomer. Acetonitrile and methanol were used as the porogen with ethylene glycol dimethacrylate(EGDMA) as the crosslinker and 2,2'-azobis(isobutyronitrile) (AIBN) as the initiator. The experimental parameters of the equilibrium isotherms were estimated via linear and nonlinear regression analyses. The linear equation as the functions of the adsorption concentration of the single compound in its solution and the competitive adsorption of the single compound in its mixed compounds solution was then expressed, and the adsorption equilibrium data were correlated to Langmnir and Freundlich isotherm models. The mixture compounds show competitive adsorption on the specific binding sites of quercetin-MIP. Furthermore, the competitive Langmuir isotherms were applied to the mixture compounds. The adsorption concentrations of quercetin, ( + )catechin( + C), and ( - )epicatechin(EC) on the quercetin molecular imprinted polymer were compared. The quercetin-imprinted polymer shows extraordinarily higher adsorption ability for quercetin than for the two catechin compounds that were also assessed.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1986-08-01

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

  5. Accurate fit and thermochemical analysis of the adsorption isotherms of methane in zeolite 13X

    Energy Technology Data Exchange (ETDEWEB)

    Llano-Restrepo, M. [University of Valle, Valle (Colombia). School of Chemical Engineering

    2010-07-01

    The recovery of methane from landfill gases and coal mines has become of the utmost importance because methane has a global-climate warming potential much higher than that of carbon dioxide. Zeolite 13X is widely used for the separation of methane and carbon dioxide from such sources. Accurate fits of the adsorption isotherms of methane in zeolite 13X are required for the rigorous simulation of that separation. In this work, a generalized statistical thermodynamic adsorption (GSTA) model has been used to obtain a very accurate correlation of a published set of adsorption isotherms of methane in zeolite 13X that were measured from 120 K to 273 K over the pressure range 0.07 Pa to 12.2 MPa. In contrast, none of five traditional adsorption models was capable of fitting these isotherms. A thermochemical interpretation of the correlation is provided and predictions for the isosteric heat of adsorption are made, which turn out to be in excellent agreement with the available experimental data.

  6. 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.

  7. 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,...

  8. THE DETERMINATION OF ADSORPTION ISOTHERMS AND SOLID DIFFUSION COEFFICIENTS OF MANNITOL AND SORBITOL BY LIQUID CHROMATOGRAPHY TECHNIQUE

    Institute of Scientific and Technical Information of China (English)

    ZHAOYechun; XIHongxia; 等

    1999-01-01

    The parameter identification model is proposed for determining the linear adsorption isotherms and the solid diffusion coefficients by using adsorption chromatorgaphy.Axial dispersion coefficients is firstly determined by pulse-respond experiment technique with an inert substance as tracer,then the elution curves of chromatography separating the isomer mannitol and sorbitol are determined by the chromatographic measuring technique,and pinally the adsorption isotherms and the solid diffusion coefficients of mannitol and sorbitol on Ca2+ resins are estimated by using this model.The results show that the axial dispersion coefficients increase with fluid velocity increasing,The adsorption equilibrium constants decrease with temperature rising;and the solid diffusion coefficients increase with temperature rising.The theoretical elution curves are good agreement with the experimental elution curves of the liquid adsorption chromatography separating the mannitol and the sorbitol.The model provides a simple and reliable procedure to estimate the kinetic and thermodynamic parmeters of the adsorption.

  9. 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.......93) for a 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...

  10. 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.

  11. 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.

  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. 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

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

    Science.gov (United States)

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

    2013-04-01

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

  17. Isotherms for the adsorption of Cu(II onto lignin: Comparison of linear and non-linear methods

    Directory of Open Access Journals (Sweden)

    Brdar Mirjana M.

    2012-01-01

    Full Text Available Equilibrium studies were carried out for the adsorption of Cu(II onto Kraft lignin as an adsorbent. The experimental data were fitted to the Freundlich, Langmuir and Redlich-Peterson isotherms by linear and non-linear method. Comparison of linear and non-linear regression method was given in selecting the optimum isotherm for the experimental data. The coefficient of correlation r2 and Chi-square test χ2 was used to select the best linear theoretical isotherm. The best linear model is Redlich-Peterson isotherm model, where r2=0,985 and χ2=0,02. In order to predict the error ERRSQ, HYBRD, MPSD, ARE and EABS were used. Moreover, by minimizing these error functions the optimal values of parameters and also the optimum isotherm was found. The Redlich-Peterson isotherm was found to be the best representative for adsorption of Cu(II on the adsorbent in the cases when ERRSQ, HYBRD, MPSD functions were used. There coefficients of determination are 0.986, 0.985, 0.984, respectively and Chi-square is 0.02 in all cases. Freundlich isotherms which were obtained by minimization of the ERRSQ, HYBRD, MPSD, ARE and EABS function showed very good agreement with experimental data. In all cases the coefficients of determination are greater than 0.91. Besides, it was observed that non-linear isotherm models were better for representation of equilibrium data than linearized models.

  18. 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.

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

    Science.gov (United States)

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

    2016-10-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

    Munakata, K.; Nakamura, A. [Faculty of Engineering and Ressource Science, Akita University, Akita-shi, Akita (Japan); Kawamura, Y. [Japan Atomic Energy Agency -JAEA, Tokai, Ibaraki (Japan)

    2015-03-15

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

  1. 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.

  2. Tungsten removal from molybdate solutions using chelating ion-exchange resin:Equilibrium adsorption isotherm and kinetics

    Institute of Scientific and Technical Information of China (English)

    朱先正; 霍广生; 倪捷; 宋琼

    2016-01-01

    The equilibrium adsorption isotherm and kinetic of the sorption process for W and Mo on macro chelating resin D403 were investigated on single Na2MoO4 and Na2WO4 solutions. The sorption isotherm results show that the adsorption process of W obeys the Freundlich model very well whereas the exchange process with Mo approximately follows the Henry model. The kinetic experiments show that the intraparticle diffusion process was the rate-determining step for W sorption on the resin, and the corresponding activation energy is calculated to be 21.976 kJ/mol.

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

    Science.gov (United States)

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

    2014-05-01

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

  4. Available area isotherm

    NARCIS (Netherlands)

    Bosma, JC; Wesselingh, JA

    2004-01-01

    A new isotherm is presented for adsorption of proteins, the available area isotherm. This isotherm has a steric basis, unlike the (steric) mass action model. The shape of the available area isotherm is determined only by geometric exclusion. With the new isotherm, experimental results can be fitted

  5. ADSORPTION ISOTHERMS AND POTENTIAL DISTRIBUTIONS OF NITROGEN ON VARIOUS ACTIVATED CARBONS

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    The adsorption isotherms of four activated carbons (Norit RB1, Chemviron BPL, Monolit, and Ambersorb-572) have been examined by nitrogen adsorption at 77.5 K. A method for adsorption potential distribution calculation has been proposed based on the adsorption isotherms. This distribution provides information about possible changes in the Gibbs free energy caused by the energetic and geometrical heterogeneities of an activated carbon as well as by the adsorbate-related entropic effects. The general character of the adsorption potential distribution is clearly visible by its simple relation to the micropore and mesopore distribution.

  6. Adsorption modeling for macroscopic contaminant dispersal analysis

    Energy Technology Data Exchange (ETDEWEB)

    Axley, J.W.

    1990-05-01

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

  7. 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...... of adsorption is discussed. Hydrophobic and reversed phase chromatography are useful techniques for measuring solute activity coefficients at infinite dilution....

  8. The component fractionation effect in binary-component gas adsorption isotherm experiments on coal

    Institute of Scientific and Technical Information of China (English)

    TANG Shuheng; HAO Duohu; TANG Dazhen; LIU Dameng

    2005-01-01

    Different gas adsorption isotherm experiments were carried out on the coal samples from Jincheng district,including N2, CH4, CO2, as well as the binary-component gas of CH4-N2 and CH4-CO2 of three different concentrations. In the binary-component gas adsorption isotherm experiments,the gas component with higher adsorption ability is adsorbed firstly. Thus the result in its relative concentration in the free phase shows a trend of decrease first and then increase,whereas the relative concentration of the gas component with lower adsorption ability shows a trend of increase first and then decrease. In the adsorption phrase, the relative concentration of the gas component with higher adsorption ability increases gradually, and the relative concentration of the gas component with lower adsorption ability decreases gradually.In the adsorption competition of the binary-component gas,the adsorption rate of the gas component with higher adsorption ability shows a trend of rapidity at first then slowness, but the adsorption rate of the gas component with lower adsorption ability shows a trend of slowness at first then rapidity. The component fractionation effect in the binary-component gas adsorption isotherm experiments is caused by the difference of the adsorption ability of coal of different gas components.

  9. 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.

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

    Science.gov (United States)

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

    2014-10-01

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

  11. 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.

  12. 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.

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

    OpenAIRE

    Subramanyam, Busetty; Das, Ashutosh

    2014-01-01

    In adsorption study, to describe sorption process and evaluation of best-fitting isotherm model is a key analysis to investigate the theoretical hypothesis. Hence, numerous statistically analysis have been extensively used to estimate validity of the experimental equilibrium adsorption values with the predicted equilibrium values. Several statistical error analysis were carried out. In the present study, the following statistical analysis were carried out to evaluate the adsorption isotherm m...

  14. Adsorption Rate Models for Multicomponent Adsorption Systems

    Institute of Scientific and Technical Information of China (English)

    姚春才

    2004-01-01

    Three adsorption rate models are derived for multicomponent adsorption systems under either pore diffusion or surface diffusion control. The linear driving force (LDF) model is obtained by assuming a parabolic intraparticle concentration profile. Models I and Ⅱ are obtained from the parabolic concentration layer approximation. Examples are presented to demonstrate the usage and accuracy of these models. It is shown that Model I is suitable for batch adsorption calculations and Model Ⅱ provides a good approximation in fixed-bed adsorption processes while the LDF model should not be used in batch adsorption and may be considered acceptable in fixed-bed adsorption where the parameter Ti is relatively large.

  15. 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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Arifin, Eric; Lee, Jiukyu [Interdisciplinary Program in Nanoscience and Technology, Virginia (United States); Cha, Jinmyung [Seoul National Univ., Seoul (Korea, Republic of)

    2013-08-15

    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 (AsO{sup 2-}) and arsenate (AsO{sub 4}{sup -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.

  17. 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.

  18. 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.

  19. 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

  20. 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)

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

    Science.gov (United States)

    Kango, Sarita; Kumar, Rajesh

    2016-01-01

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

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

    Science.gov (United States)

    Kango, Sarita; Kumar, Rajesh

    2016-01-01

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

  3. 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.

  4. 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.

  5. Comparison of Frontal Analysis and Elution-Curve Method for Determining Adsorption Isotherms

    Institute of Scientific and Technical Information of China (English)

    Ju-Weon; LEE; Kyung; Ho; ROW

    2002-01-01

    Adsorption isotherm is the most fundamental information related to chromatography.To calculate the parameters of Langmuir adsorption isotherm of thymidine,fronal analysis(FA)and lution-curve method(ECM)were adopted in reversed-phase high performance liguid chromatography(RP-HPLC).In FA,tha concentration of stationary phase was measured from the elution curves and the isotherm was determined by regression analysis,while the parameters by ECM were obtained by parameter optimization.The adsorption isotherms of thymidine from the two methods were very similar.The superiority of ECM over FA was that the consumption of sample was less and only one or two in jections of sample were required.

  6. 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...

  7. 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...

  8. Adsorption modeling for off-gas treatment

    Energy Technology Data Exchange (ETDEWEB)

    Ladshaw, A.; Sharma, K.; Yiacoumi, S.; Tsouris, C. [Georgia Institute of Technology, Atlanta, GA 30332-0459 (United States); De Paoli, D.W. [Oak Ridge National Laboratory: Oak Ridge, TN 37831-6181 (United States)

    2013-07-01

    Off-gas generated from the reprocessing of used nuclear fuel contains a mixture of several radioactive gases including {sup 129}I{sub 2}, {sup 85}Kr, HTO, and {sup 14}CO{sub 2}. Over the past few decades, various separation and recovery processes have been studied for capturing these gases. Adsorption data for gaseous mixtures of species can be difficult to determine experimentally. Therefore, procedures capable of predicting the adsorption behavior of mixtures need to be developed from the individual isotherms of each of the pure species. A particular isotherm model of interest for the pure species is the Generalized Statistical Thermodynamic Adsorption isotherm. This model contains an adjustable number of parameters and will therefore describe a wide range of adsorption isotherms for a variety of components. A code has been developed in C++ to perform the non-linear regression analysis necessary for the determination of the isotherm parameters, as well as the least number of parameters needed to describe an entire set of data. (authors)

  9. ADSORPTION OF 1,2,4-ACID BY WEAKLY BASIC RESIN:ISOTHERMS,THERMODYNAMICS AND KINETICS

    Institute of Scientific and Technical Information of China (English)

    Fu-qiang Liu; Jin-long Chen; Chao Long; Ai-min Li; Guan-dao Gao; Quan-xing Zhang

    2004-01-01

    The adsorption properties, including the adsorption isotherms, thermodynamics and kinetics, of 1-arnino-2-naphthol-4-sulfonic acid (1,2,4-acid) onto weakly basic resin ND900 are investigated. Both the Langmuir and Freundlich equations can give a good fit to the adsorption isotherms, which indicates an endothermic and a favorable adsorption in our study range. A high yield in elimination of about 45.21%-97.28% is obtained for the tested adsorption systems. The capacity and affinity of the adsorption increase with temperature, due to the phenomena of "solvent-motivated" effects. The value of △H is 51.59 kJ/mol, which indicates a chemical adsorption and then expects the poor desorption property of ND900. The negative value of AG indicates the spontaneous nature of the adsorption process, and the positive value of △S shows the increased randomness at the solid/solution interface during the adsorption process. The value of the adsorption rate constant lower than 0.013 min-1 is indicative of a slow adsorption rate. The intra-particle diffusion must be one of the rate limiting steps.

  10. 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.

  11. 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.

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

    Science.gov (United States)

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

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

  13. 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

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

    Science.gov (United States)

    Mandal, Abhishek; Singh, Neera

    2016-01-01

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

  15. 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

  16. 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

  17. 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.

  18. 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.

  19. 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.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-08-01

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

  1. 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.

  2. 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.

  3. 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.

  4. 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

  5. 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.

  6. 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.

  7. 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.

  8. 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.

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

    Science.gov (United States)

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

    2002-11-01

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

  10. 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.

  11. 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.

  12. 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

    .93 for 207 soils, widely varying in texture and organic carbon content. 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...... and clay content and subsequent model application for prediction of measured isotherms showed promise for the majority of investigated soils. Only for soils with distinct kaolinitic and smectitic clay mineralogy predicted isotherms did not closely match the measurements.......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...

  13. Coal Adsorption Isotherms, Gas Content and Geological Controls of Bide-Santang Basin in China

    OpenAIRE

    Wu Caifang; Li Teng

    2013-01-01

    The adsorption isotherms of Bide-Santang Basin’s main coal seams is studied based on analyzing two Coalbed Methane (CBM) wells in Huale exploration region and testing the coal samples and the major geological factors are also discussed. A conclusion has been made that the adsorption capacity of Bide-Santang Basin’s main coal seams is high. The Langmuir volume (VL) of dry ash-free basis range from 17.69 m3/t to 21.38 m3/t and the average is 19.46 m3/t. The methane saturation of the coal reserv...

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

    Science.gov (United States)

    Subramanyam, Busetty; Das, Ashutosh

    2014-01-01

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

  15. 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.

  16. 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 298-318 K. The FTIR results revealed that amine and carboxyl functional groups present on the surface of APSP. The SEM results show that APSP has an irregular and porous surface which is adequate morphology for dye adsorption. Desorption experiments were carried to explore the feasibility of adsorbent regeneration and the adsorbed MO from APSP was desorbed using 0.1M NaOH with an efficiency of 93.5%. Findings of the present study indicated that APSP can be successfully used for removal of MO from aqueous solution. PMID:26921544

  17. Description of adsorption of hydrophobic organic compounds on sediment using multi-component adsorption model

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    A chemical sequential separation procedure for sediment bas been developed for the adsorptive investigation of hydrophobic organic compounds(HOCs) including four fractions: carbonate, hydrous metallic oxide(ferric oxide, manganese oxide and alumina), clay and organic matter. Adsorption isotherms of these hydrophobic solute probes, such as hexachloroethane, lindane and 1,2,4,5-tetrachlorobenzene were measured for model sorbents, model and natural sediment, and the latter of which was pretreated with the simplified sequential separation method. The linear and Langmuir models are applied to correlate the experimental data of humic substance and other model sorbents respectively. Multi-component Adsorptive Model (MCAM) was used to simulate adsorption isotherms of model and natural sediment. The results reveal that( 1 ) the separation efficiencies of carbonate, organic matter, ferric oxide, manganese oxide and alumina are 98. 1 % , 72.5% ,82.6%, 93.5% and 83.3%, respectively; (2) except for removing metallic oxide, the external structure of sediment is not changed greatly after separation; (3) the MCAM correlates the data of adsorption isotherm rather well with the maximal relative deviations of 9.76 % , 6.78 %and 9.53% for hexachloroethane, lindane and 1,2,4,5-tetrachlorobenaze in model sediment, respectively. The MCAM can clearly give expression to the different adsorptive mechanisms for HOCs in organic and inorganic matter, though the experimental data in each component are not very accurate due to the sequential separation efficiency.

  18. 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

  19. 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 ...

  20. 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.

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

    Science.gov (United States)

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

    2016-03-01

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

  2. 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.

  3. 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.

  4. 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...

  5. 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.

  6. Coal Adsorption Isotherms, Gas Content and Geological Controls of Bide-Santang Basin in China

    Directory of Open Access Journals (Sweden)

    Wu Caifang

    2013-12-01

    Full Text Available The adsorption isotherms of Bide-Santang Basin’s main coal seams is studied based on analyzing two Coalbed Methane (CBM wells in Huale exploration region and testing the coal samples and the major geological factors are also discussed. A conclusion has been made that the adsorption capacity of Bide-Santang Basin’s main coal seams is high. The Langmuir volume (VL of dry ash-free basis range from 17.69 m3/t to 21.38 m3/t and the average is 19.46 m3/t. The methane saturation of the coal reservoir is lower than 100%, commonly ranging from 75.04 to 105.55% and the average is 84.51%. It indicates that coal reservoir in the research area is undersaturation. The critical desorption pressures are between 1.22 MPa and 9.1 MPa and the average is 3.25 MPa. The coalbed methane theory recovery rates are between 19.96 and 46.15% with average of 34.51%. The main effect geology factors on the adsorption in this area are reservoir pressure, depth of burial, degree of coalification and characteristics of pores. The reservoir pressure and depth of burial are positively related with the gas content. The higher of the degree of metamorphism is, the stronger adsorbability of CBM is. The well-developed micropores and mesopores contribute to the adsorption capacity of CBM.

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

    Science.gov (United States)

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

    2016-02-26

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

  8. 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.

  9. 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.

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

    Directory of Open Access Journals (Sweden)

    Bastidas, D. M.

    2005-04-01

    Full Text Available 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 Frumkin isotherm model. The projected molecular area of BTA was calculated to elucidate inhibitor orientation in the adsorption process

    En el presente trabajo se estudia la adsorción del benzotriazol (BTA sobre el cobre en solución de ácido sulfúrico con concentraciones de 0,001, 0,005 y 0,01 M utilizando medidas gravimétricas. La concentración de BTA ensayada varió de 1x10-5 M a 1x10-1 M y la temperatura de 298 K a 328 K. El mecanismo de adsorción se analiza en términos de la aplicabilidad de las isotermas convencionales de Frumkin, Bockris-Swinkels y Kastening- Holleck, entre otras. La mejor descripción de los resultados se obtuvo utilizando la isoterma de Frumkin. Para analizar la orientación del BTA en el proceso de adsorción sobre el cobre, se calculó la superficie de la molécula de BTA.

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

    Directory of Open Access Journals (Sweden)

    Mulu Berhe Desta

    2013-01-01

    Full Text Available 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 was reached within about 1 hour. Further increase in contact time did not show significant change in equilibrium concentration; that is, the adsorption phase reached equilibrium. The adsorption isotherms could be fitted well by the Langmuir model. The value in the present investigation was less than one, indicating that the adsorption of the metal ion onto ATS is favorable. After treatment with ATS the levels of heavy metals were observed to decrease by 88% (Ni, 82.9% (Cd, 81.5% (Cu, 74.5% (Cr, and 68.9% (Pb. Results indicate that the freely abundant, locally available, low-cost adsorbent, Teff straw can be treated as economically viable for the removal of metal ions from textile effluents.

  12. Modeling adsorption with lattice Boltzmann equation.

    Science.gov (United States)

    Guo, Long; Xiao, Lizhi; Shan, Xiaowen; Zhang, Xiaoling

    2016-01-01

    The research of adsorption theory has recently gained renewed attention due to its critical relevance to a number of trending industrial applications, hydrogen storage and shale gas exploration for instance. The existing theoretical foundation, laid mostly in the early twentieth century, was largely based on simple heuristic molecular interaction models and static interaction potential which, although being insightful in illuminating the fundamental mechanisms, are insufficient for computations with realistic adsorbent structure and adsorbate hydrodynamics, both critical for real-life applications. Here we present and validate a novel lattice Boltzmann model incorporating both adsorbate-adsorbate and adsorbate-adsorbent interactions with hydrodynamics which, for the first time, allows adsorption to be computed with real-life details. Connection with the classic Ono-Kondo lattice theory is established and various adsorption isotherms, both within and beyond the IUPAC classification are observed as a pseudo-potential is varied. This new approach not only enables an important physical to be simulated for real-life applications, but also provides an enabling theoretical framework within which the fundamentals of adsorption can be studied. PMID:27256325

  13. Modeling adsorption with lattice Boltzmann equation

    Science.gov (United States)

    Guo, Long; Xiao, Lizhi; Shan, Xiaowen; Zhang, Xiaoling

    2016-01-01

    The research of adsorption theory has recently gained renewed attention due to its critical relevance to a number of trending industrial applications, hydrogen storage and shale gas exploration for instance. The existing theoretical foundation, laid mostly in the early twentieth century, was largely based on simple heuristic molecular interaction models and static interaction potential which, although being insightful in illuminating the fundamental mechanisms, are insufficient for computations with realistic adsorbent structure and adsorbate hydrodynamics, both critical for real-life applications. Here we present and validate a novel lattice Boltzmann model incorporating both adsorbate-adsorbate and adsorbate-adsorbent interactions with hydrodynamics which, for the first time, allows adsorption to be computed with real-life details. Connection with the classic Ono-Kondo lattice theory is established and various adsorption isotherms, both within and beyond the IUPAC classification are observed as a pseudo-potential is varied. This new approach not only enables an important physical to be simulated for real-life applications, but also provides an enabling theoretical framework within which the fundamentals of adsorption can be studied. PMID:27256325

  14. 用FA和ECM方法测定吸附等温线的比较%Comparison of Frontal Analysis and Elution-Curve Method for Determining Adsorption Isotherms

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Adsorption isotherm is the most fundamental information related to chromatography. To calculate the parameters of Langmuir adsorption isotherm of thymidine, frontal analysis (FA) and elution-curve method (ECM) were adopted in reversed-phase high performance liguid chromatography (RP-HPLC). In FA, the concentration of stationary phase was measured from the elution curves and the isotherm was determined by regression analysis, while the parameters by ECM were obtained by parameter optimization. The adsorption isotherms of thymidine from the two methods were very similar. The superiority of ECM over FA was that the consumption of sample was less and only one or two injections of sample were required.

  15. 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

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

    Science.gov (United States)

    Saleh, Tawfik A

    2015-11-01

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

  17. 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

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

    Science.gov (United States)

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

    2015-11-01

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

  19. 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.

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

    Science.gov (United States)

    Naeem, Asif; Akhtar, Muhammad; Ahmad, Waqar

    2013-01-01

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

  1. 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.

  2. Super-critical isothermal adsorption of gas in shale%页岩中气体的超临界等温吸附研究

    Institute of Scientific and Technical Information of China (English)

    刘圣鑫; 刘晓光; 钟建华; 马寅生; 尹成明; 刘成林; 李宗星; 李勇; 刘选; 毛毳

    2015-01-01

    Shale gas isothermal adsorption experiments are mostly experiments above the critical temperature, the adsorption quantity obtained from the experiments is excess adsorption. In order to study super-critical iso-thermal adsorption mechanism of the shale gas, the weighting method was used in this study, the high pressure isothermal adsorption experiment have been made for methane and carbon dioxide in shale above the critical tem-perature. Based on the analysis of the typical adsorption and super-critical adsorption difference, through modified super-critical isothermal adsorption model (Langmuir equation and pore filling (Dubinin Radushkevich D-R)), ex-perimental data were fitted . Study indicates that the simple Langmuir equation can approximately fit experimental data of methane adsorption, but the accuracy is not high, and can't fit carbon adsorption data. When the density of the adsorbed phase as parameter can be optimized, the modified microporous packing model and the Langmuir model can fit well adsorption data of methane and carbon dioxide, Fitting effect is the best with the modified mi-croporous packing model, the adsorption phase density of super-critical methane is consistent with literature reports, suggesting that adsorbed gas may exists in the form of pore filling.%页岩气等温吸附实验多为临界温度以上的吸附实验,其得到的吸附量为过剩吸附量。为了研究页岩气超临界等温吸附机理,运用重力法,在临界温度以上,分别进行了甲烷和二氧化碳在页岩中的高压等温吸附实验。在分析经典型吸附和超临界吸附区别的基础上,通过修改的超临界等温吸附模型(Langmuir方程和微孔充填(Dubinin Radushkevich,D-R))对实验数据进行了拟合。结果表明:简单的Langmuir方程可近似拟合甲烷吸附实验数据,但精度不高,且无法拟合二氧化碳的吸附数据;将吸附相密度作为可优化参数,修改的微孔充填模型

  3. 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.

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

    Science.gov (United States)

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

    2006-01-01

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

  5. Study of the adsorption of Cd (II from aqueous solution using zeolite-based geopolymer, synthesized from coal fly ash; kinetic, isotherm and thermodynamic studies

    Directory of Open Access Journals (Sweden)

    Hamedreza Javadian

    2015-11-01

    Full Text Available A specific type of zeolite, synthesized from coal fly ash, was used in our batch adsorption experiments in order to adsorb Cd (II ions from aqueous solution. Solid-state conversion of fly ash to an amorphous aluminosilicate adsorbent (geopolymer was investigated under specific conditions. The adsorbent ZFA was characterized using XRD, XRF, FT-IR, FE-SEM, LPS and BET surface area. The optimum conditions of sorption were found to be: a ZFA dose of 0.08 g in 25 mL of Cd (II with contact time of 7 h and pH 5. Four equations, namely Morris–Weber, Lagergren, Pseudo-second order and Elovich have been used in order to determine the kinetics of removal process. The collected kinetic data showed that pseudo-second order equations controlled the adsorption process. According to adsorption isotherm studies, the Langmuir isotherm was proved to be the best fit for our experimental data, in comparison to Freundlich, D–R and Tempkin models. The thermodynamic parameters ΔH, ΔS and ΔG are evaluated. Thermodynamic parameters showed that the adsorption of Cd (II onto ZFA was feasible, spontaneous and endothermic under studied conditions. To conduct desorption experiments, several solvents (including alkaline, bases and water have been employed. 84% of desorption efficiency was achieved using NaOH.

  6. 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.

  7. 二苯并呋喃在活性炭上的吸附相平衡和动力学%Adsorption Isotherm and Kinetics of Dibenzofuran on Granular Activated Carbons

    Institute of Scientific and Technical Information of China (English)

    李湘; 李忠; 罗灵爱

    2005-01-01

    The adsorption of dibenzofuran on three commercial granular activated carbons (ACs) was investigated by dynamic experiment to correlate the adsorption equilibrium and kinetics with the structure of activated carbons.Physical properties including surface area, average pore diameter, micropore area and micropore volume of the activated carbons were characterized by N2 adsorption experiment on ASAP2010. To calculate the adsorption parameters, adsorption isotherm data were fitted to the Langmuir equation, and adsorption kinetic data were fitted to the linear driving force (LDF) diffusion model. From the correlation results, it is concluded that the adsorption equilibrium and diffusion coefficient of dibenzofuran on activated carbon are controlled respectively by the total adsorbent surface area and the adsorbent pore diameter.

  8. Monte-Carlo simulations of methane/carbon dioxide and ethane/carbon dioxide mixture adsorption in zeolites and comparison with matrix treatment of statistical mechanical lattice model

    Science.gov (United States)

    Dunne, Lawrence J.; Furgani, Akrem; Jalili, Sayed; Manos, George

    2009-05-01

    Adsorption isotherms have been computed by Monte-Carlo simulation for methane/carbon dioxide and ethane/carbon dioxide mixtures adsorbed in the zeolite silicalite. These isotherms show remarkable differences with the ethane/carbon dioxide mixtures displaying strong adsorption preference reversal at high coverage. To explain the differences in the Monte-Carlo mixture isotherms an exact matrix calculation of the statistical mechanics of a lattice model of mixture adsorption in zeolites has been made. The lattice model reproduces the essential features of the Monte-Carlo isotherms, enabling us to understand the differing adsorption behaviour of methane/carbon dioxide and ethane/carbon dioxide mixtures in zeolites.

  9. Adsorption Behaviour of La(III and Eu(III Ions from Aqueous Solutions by Hydroxyapatite: Kinetic, Isotherm, and Thermodynamic Studies

    Directory of Open Access Journals (Sweden)

    F. Granados-Correa

    2013-01-01

    Full Text Available The hydroxyapatite was successfully synthesized, characterized, and used as an alternative low-cost adsorbent material to study the adsorption behavior of La(III and Eu(III ions from nitrate aqueous solutions as a function of contact time, initial metal ion concentration, pH, and temperature by using a bath technique. The kinetic data correspond very well to the pseudo-second-order equation, and in both cases the uptake was affected by intraparticle diffusion. Isotherm adsorption data were well fitted by the Freundlich model equation with 1/n>1, indicating a multilayer and cooperative-type adsorption. Thermodynamic parameters for the adsorption systems were determinated at 293, 303, 313, and 323 K. These parameters show that adsorptions of La(III and Eu(III ions on hydroxyapatite are endothermic and spontaneous processes. The adsorption was found to follow the order Eu(III > La(III and is dependent on ion concentration, pH, and temperature.

  10. 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

  11. 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

  12. 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.

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

    Science.gov (United States)

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

    2007-11-28

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

  14. 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

  15. 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.

  16. 壳聚糖金属离子印迹树脂的吸附模型%ADSORPTION MODEL OF METAL ION ON IMPRINTING CHITOSAN RESIN

    Institute of Scientific and Technical Information of China (English)

    谭天伟; 贺小进; 杜卫霞

    2001-01-01

    Adsorption model of metal ion on imprinting chitosan resin wasstudied. The chemical and the physical properties such as pore size distribution and heat stability were discussed and the imprinting chitosan resin can be used many times without losing adsorption capacity. The adsorption isotherms and adsorption mechanism were studied and a new model was suggested to correlate relation of adsorption with pH and metal ion concentration,which could explain mechanism of adsorption.

  17. 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

  18. 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.

  19. Protein adsorption on nanoparticles: model development using computer simulation

    Science.gov (United States)

    Shao, Qing; Hall, Carol K.

    2016-10-01

    The adsorption of proteins on nanoparticles results in the formation of the protein corona, the composition of which determines how nanoparticles influence their biological surroundings. We seek to better understand corona formation by developing models that describe protein adsorption on nanoparticles using computer simulation results as data. Using a coarse-grained protein model, discontinuous molecular dynamics simulations are conducted to investigate the adsorption of two small proteins (Trp-cage and WW domain) on a model nanoparticle of diameter 10.0 nm at protein concentrations ranging from 0.5 to 5 mM. The resulting adsorption isotherms are well described by the Langmuir, Freundlich, Temkin and Kiselev models, but not by the Elovich, Fowler-Guggenheim and Hill-de Boer models. We also try to develop a generalized model that can describe protein adsorption equilibrium on nanoparticles of different diameters in terms of dimensionless size parameters. The simulation results for three proteins (Trp-cage, WW domain, and GB3) on four nanoparticles (diameter  =  5.0, 10.0, 15.0, and 20.0 nm) illustrate both the promise and the challenge associated with developing generalized models of protein adsorption on nanoparticles.

  20. 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.

  1. 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

  2. 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.

  3. Dynamic modeling of fixed-bed adsorption of flue gas using a variable mass transfer model

    Energy Technology Data Exchange (ETDEWEB)

    Park, Jehun; Lee, Jae W. [Korea Advanced Institute of Science and Technology, Daejeon (Korea, Republic of)

    2016-02-15

    This study introduces a dynamic mass transfer model for the fixed-bed adsorption of a flue gas. The derivation of the variable mass transfer coefficient is based on pore diffusion theory and it is a function of effective porosity, temperature, and pressure as well as the adsorbate composition. Adsorption experiments were done at four different pressures (1.8, 5, 10 and 20 bars) and three different temperatures (30, 50 and 70 .deg. C) with zeolite 13X as the adsorbent. To explain the equilibrium adsorption capacity, the Langmuir-Freundlich isotherm model was adopted, and the parameters of the isotherm equation were fitted to the experimental data for a wide range of pressures and temperatures. Then, dynamic simulations were performed using the system equations for material and energy balance with the equilibrium adsorption isotherm data. The optimal mass transfer and heat transfer coefficients were determined after iterative calculations. As a result, the dynamic variable mass transfer model can estimate the adsorption rate for a wide range of concentrations and precisely simulate the fixed-bed adsorption process of a flue gas mixture of carbon dioxide and nitrogen.

  4. 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...

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

    Science.gov (United States)

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

    2013-01-01

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

  6. 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.

  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. 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.

  9. Modeling of boldine alkaloid adsorption onto pure and propyl-sulfonic acid-modified mesoporous silicas. A comparative study.

    Science.gov (United States)

    Geszke-Moritz, Małgorzata; Moritz, Michał

    2016-12-01

    The present study deals with the adsorption of boldine onto pure and propyl-sulfonic acid-functionalized SBA-15, SBA-16 and mesocellular foam (MCF) materials. Siliceous adsorbents were characterized by nitrogen sorption analysis, transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier-transform infrared (FT-IR) spectroscopy and thermogravimetric analysis. The equilibrium adsorption data were analyzed using the Langmuir, Freundlich, Redlich-Peterson, and Temkin isotherms. Moreover, the Dubinin-Radushkevich and Dubinin-Astakhov isotherm models based on the Polanyi adsorption potential were employed. The latter was calculated using two alternative formulas including solubility-normalized (S-model) and empirical C-model. In order to find the best-fit isotherm, both linear regression and nonlinear fitting analysis were carried out. The Dubinin-Astakhov (S-model) isotherm revealed the best fit to the experimental points for adsorption of boldine onto pure mesoporous materials using both linear and nonlinear fitting analysis. Meanwhile, the process of boldine sorption onto modified silicas was described the best by the Langmuir and Temkin isotherms using linear regression and nonlinear fitting analysis, respectively. The values of adsorption energy (below 8kJ/mol) indicate the physical nature of boldine adsorption onto unmodified silicas whereas the ionic interactions seem to be the main force of alkaloid adsorption onto functionalized sorbents (energy of adsorption above 8kJ/mol). PMID:27612776

  10. Simplified models for estimating isothermal operating characteristics of food extruders.

    Science.gov (United States)

    Levine, L; Rockwood, J

    1985-09-01

    A model of isothermal food extruder performance is described. Inferences about alternative extruder screw designs and their performance are drawn from the model. The model suggests that thread depth or diameter compression screws are superior in performance to a pitch compression screw. The advantage gained from using diameter compression screws is paid for with significantly higher rates of energy dissipation. The use of the model to characterize screws having both a compression zone and metering zone is described.

  11. 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.

  12. 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.

  13. 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

  14. 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.

  15. Modeling high-pressure adsorption of gas mixtures on activated carbon and coal using a simplified local-density model.

    Science.gov (United States)

    Fitzgerald, James E; Robinson, Robert L; Gasem, Khaled A M

    2006-11-01

    The simplified local-density (SLD) theory was investigated regarding its ability to provide accurate representations and predictions of high-pressure supercritical adsorption isotherms encountered in coalbed methane (CBM) recovery and CO2 sequestration. Attention was focused on the ability of the SLD theory to predict mixed-gas adsorption solely on the basis of information from pure gas isotherms using a modified Peng-Robinson (PR) equation of state (EOS). An extensive set of high-pressure adsorption measurements was used in this evaluation. These measurements included pure and binary mixture adsorption measurements for several gas compositions up to 14 MPa for Calgon F-400 activated carbon and three water-moistened coals. Also included were ternary measurements for the activated carbon and one coal. For the adsorption of methane, nitrogen, and CO2 on dry activated carbon, the SLD-PR can predict the component mixture adsorption within about 2.2 times the experimental uncertainty on average solely on the basis of pure-component adsorption isotherms. For the adsorption of methane, nitrogen, and CO2 on two of the three wet coals, the SLD-PR model can predict the component adsorption within the experimental uncertainties on average for all feed fractions (nominally molar compositions of 20/80, 40/60, 60/40, and 80/20) of the three binary gas mixture combinations, although predictions for some specific feed fractions are outside of their experimental uncertainties. PMID:17073487

  16. Modelling of adsorption of redox sensitive oxyanions on gibbsite

    Energy Technology Data Exchange (ETDEWEB)

    Miedaner, M.M.; Weerasooriya, R.; Tobschall, H.J. [Inst. fuer Geologie und Mineralogie, Friedrich Alexander Univ. Erlangen-Nuernberg, Erlangen (Germany)

    2004-06-01

    The adsorptive behaviour of minerals in natural soils has been the focus of many scientific investigations for a long time. Besides mineralogical studies, geochemists are also trying to determine the filter capacity with respect to waste-waters and to understand the buffering capacity for oxyanions (As, Se, Mo, P) in soils. The present work is part of an on-going project on developing a thermodynamically consistent database for the adsorption of oxyanions onto different Al-derived oxides / hydrooxides that are ubiquitous in nature. The experimental data are quantified by both 1-pK and 2-pK surface complexation models using charge distribution multi site ion complexation- (CD-MUSIC), double layer- (DLM) and triple layer- (TLM) mechanistic models explicitly accounting for the finite size of oxyanions. With this objective the adsorption of redox-sensitive oxyanions, e.g. As and Se on gibbsite was investigated as a function of solution pH, redox state e.g. arsenite and arsenate; selenate and selenite, and adsorbate loading. All experiments were carried out in batch systems to determine adsorption edges, isotherms and proton exchange ratios (r{sub anion/OH-}) upon oxyanions adsorption. Initial concentration of the adsorbates and the pH were ranged 1.34 - 13.4 {mu}mol/L and 4 - 9.2 respectively. Possible surface configurations were examined using both vibration spectroscopy and molecular modelling methods. (orig.)

  17. 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

  18. 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)

  19. Adsorption equilibrium and dynamics of lactase/CM-Sephadex system

    OpenAIRE

    Harsa, Hayriye Şebnem; Göksungur, Yekta; Güvenç, Ulgar

    1995-01-01

    Partitioning behaviour and adsorption isotherms of lactase/CM-Sephadex system at equilibrium were investigated together with the adsorption kinetics in this study. Maximum adsorption was obtained at the pH values between 5.5–6.0. Adsorption isotherm was a close fit to the Langmuir model.

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

    Science.gov (United States)

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

  1. Kinetic, isotherm and thermodynamics investigation on adsorption of divalent copper using agro-waste biomaterials, Musa acuminata, Casuarina equisetifolia L. and Sorghum bicolor

    Directory of Open Access Journals (Sweden)

    Mokkapati Ramya Prasanthi

    2016-06-01

    Full Text Available Three novel and distinct agricultural waste materials, viz., Casuarinas fruit powder (CFP, sorghum stem powder (SSP and banana stem powder (BSP were used as low cost adsorbents for the removal of toxic copper(II from aqueous solutions. Acid treated adsorbents were characterized by SEM, EDX and FTIR. Different factors effecting adsorption capacity were analyzed and the efficiency order was BSP>SSP>CFP. Based on the extent of compatibility to Freundlich/Langmuir/D-R/Temkin adsorption isotherm and different models (pseudo-first and second order, Boyd, Weber’s and Elovich, chemisorption primarily involved in the case of CFP and SSP, whereas, simultaneous occurrence of chemisorption and physisorption was proposed in the case of BSP. Based on the observations, it was proposed that three kinetic stages involve in adsorption process viz., diffusion of sorbate to sorbent, intra particle diffusion and then establishment of equilibrium. These adsorbents have promising role towards removal of Cu(II from industrial wastewater to contribute environmental protection.

  2. Dubinin-Astakhov model for acetylene adsorption on metal-organic frameworks

    Science.gov (United States)

    Cheng, Peifu; Hu, Yun Hang

    2016-07-01

    Acetylene (C2H2) is explosive at a pressure above 29 psi, causing a safety issue for its storage and applications. C2H2 adsorption on metal-organic frameworks (MOFs) has been explored to solve the issue. However, a suitable isotherm equation for C2H2 adsorption on various MOFs has not been found. In this paper, it was demonstrated that Dubinin-Astakhov equation can be exploited as a general isotherm model to depict C2H2 adsorption on MOF-5, ZIF-8, HKUST-1, and MIL-53. In contrast, commonly used Langmuir and BET models exhibited their inapplicability for C2H2 adsorption on those MOFs.

  3. Study of adsorption isotherms of green coconut pulp Estudo das isotermas de adsorção da polpa de coco verde

    Directory of Open Access Journals (Sweden)

    Fábia Carolina Gonçalves Lavoyer

    2013-03-01

    Full Text Available Brazil is considered one of the largest producers and consumers of tropical fruits. Green coconut (Cocos nucifera L. stands out not only for its production and consumption, but also for the high amount of waste produced by coconut water industry and in natura consumption. Therefore, there is a need for utilization of this by-product. This study aims to study the adsorption isotherms of green coconut pulp and determine its isosteric heat of sorption. The adsorption isotherms at temperatures of 30, 40, 50, 60, and 70 °C were analyzed, and they exhibit type III behavior, typical of sugar rich foods. The experimental results of equilibrium moisture content were correlated by models present in the literature. The Guggenheim, Anderson and De Boer (GAB model proved particularly good overall agreement with the experimental data. The heat of sorption determined from the adsorption isotherms increased with the decrease in moisture content. The heat of sorption is considered as indicative of intermolecular attractive forces between the sorption sites and water vapor, which is an important factor to predict the shelf life of dried products.O Brasil é considerado um dos maiores produtores e consumidores de frutas tropicais. O coco verde (Cocos nucifera L. se destaca tanto em termos de produção e consumo quanto em quantidade de resíduos gerada por indústrias de água de coco e pelo consumo in natura. Portanto, existe uma necessidade de aproveitamento deste subproduto. Este trabalho teve por objetivo estudar as isotermas de adsorção da polpa de coco verde e determinação do calor isostérico de sorção. As isotermas de adsorção para as temperaturas de 30, 40, 50, 60 e 70 °C foram analisadas e evidenciaram curvas do tipo III, típicas de alimentos ricos em açúcares. Os dados experimentais de umidade de equilíbrio foram correlacionados por modelos da literatura. O modelo de GAB apresentou melhor concordância com os dados experimentais, entre os

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

    Science.gov (United States)

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

    2013-02-01

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

  5. 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

  6. 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.

  7. 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 <...

  8. Adsorption Isotherms of Phenol and 4-Chlorophenol on Petroleum Asphaltenes Adsorption du phénol et du 4-chlorophénol sur les asphaltènes pétroliers

    Directory of Open Access Journals (Sweden)

    Jaoui M.

    2006-11-01

    Full Text Available The adsorption isotherms for phenol and 4-chlorophenol from water onto asphaltenes flocculated in bulk and asphaltenes deposited on silica were established by frontal analysis chromatography at 293, 298, 303, and 308 K. The adsorption was more important with asphaltenes flocculated in bulk and corresponded to a Freundlich isotherm mechanism. The high adsorbed amount of phenols suggests possible migration of phenols through the loose asphaltene structure. Isotherms observed with the silica coated by asphaltenes showed that adsorption occurs in two stages corresponding probably to two different organizations of solute molecules at the surface. Les isothermes d'adsorption du phénol et du 4-chlorophénol en solution dans l'eau sur des asphaltènes floculés en masse et sur des asphaltènes déposés sur de la silice ont été déterminés par analyse chromatographique frontale à 293, 298, 303 et 308 K. L'adsorption sur des asphaltènes floculés en masse était la plus importante avec des isothermes correspondant à un mécanisme de Freundlich. La quantité élevée de phénols adsorbés suggère une migration possible des molécules du phénol à travers la structure peu compacte des asphaltènes. Les isothermes observés dans le cas de silice tapissée d'asphaltènes ont montré que l'adsorption se produit en deux étapes correspondant probablement à deux organisations différentes des molécules de soluté à la surface.

  9. 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.

  10. 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

  11. Modeling Cavitation in ICE Pistons Made with Isothermal Forging

    Directory of Open Access Journals (Sweden)

    V.V. Astanin

    2014-07-01

    Full Text Available Possible causes for cavitations in parts made with an Al-Si eutectic alloy AK12D (AlSi12 were explored with mathematical and physical modeling with involved acoustic emission. Pores were formed from micro-cracks, which appear during the early stages of a deformation process, with the help of micro-stresses appearing at phase boundaries (Al/Si interface due to thermal expansion. At the design stage of isothermal forgings of such products it is recommended to provide a scheme of the deformed shape, which is under uniform compression, to compensate for the inter-phase stresses.

  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. 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.

  14. 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.

  15. 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.

  16. Exact matrix treatment of statistical mechanical lattice model of adsorption induced gate opening in metal-organic frameworks

    Science.gov (United States)

    Dunne, Lawrence J.; Manos, George

    2015-05-01

    Here we present a statistical mechanical lattice model which is exactly solvable using a matrix method and allows treatment of adsorption induced gate opening structural transformations of metal-organic frameworks which are nanoporous materials with exceptional adsorption properties. Modelling of these structural changes presents a serious theoretical challenge when the solid and gas species are treated in an even handed way. This exactly solvable model complements other simulation based approaches. The methodology presented here highlights the competition between the potential for adsorption and the energy required for structural transition as a driving force for the features in the adsorption isotherms.

  17. 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)

  18. Adsorption isotherms of H$_{2}$ and mixtures of H$_{2}$, CH$_{4}$, CO and CO$_{2}$ on copper plated stainless steel at 4.2 K

    CERN Document Server

    Wallén, E

    1996-01-01

    Adsorption isotherms in the pressure range 10$^{-11}$ to 10$^{-6} Torr have been measured for H$_2$ and mixtures of H$_2$ and CH$_4$, CO and CO$_2$ on copper plated stainless steel at 4.2 K. The measurements have been focused on the behaviour of the isotherms at low surface coverage, up to a few monolayers of adsorbed gas on the cold surface. The isotherms were measured in a static situation with a small amount of gas injected for each point on the isotherm. Co-adsorption measurements of H$_2$ with CH$_4$, CO and CO$_2$ as well as adsorption of H$_2$ on condensates of CH$_4$, CO and CO$_2$ have been made. A cryotrapping effect of H$_2$ is seen when co-adsorbing the gas mixtures, especially strong for the mixture of H$_2$ and CO$_2$. The measurements show that CO$_2$ condensed at 4.2 K may have a porous structure that H$_2$ can penetrate, while CO and CH$_4$ have rather dense structures when adsorbed at 4.2K. The measurements have been done within the framework of the Large Hadron Collider (LHC) project at CER...

  19. Fluid Flow and Mixing in Non-Isothermal Water Model of Continuous Casting Tundish

    Institute of Scientific and Technical Information of China (English)

    Mehdi ALIZADEH; Hossein EDRIS; Ali SHAFYEI

    2008-01-01

    Fluid flow and mixing of molten steel in a twin-slab-strand continuous casting tundish were investigated using a mixing model under non-isothermal conditions. This model led to a set of ordinary differential equations that were solved with a Runge-Kutta algorithm. Steady state water modeling was carried out under non-isothermal conditions. Experimental data obtained from the water model were used to calibrate the mixing model. Owing to the presence of a mixed convection in the non-isothermal conditions, a channelizing flow would be created in the fluid inside the tundish. A mixing model was designed that was capable of predicting RTD (residence time distribution) curves for different cases in non-isothermal conditions. The relationship between RTD parameters and the Tu (tundish Richardson number) was obtained for various cases under non-isothermal conditions. The results show that the RTD parameters were completely different under isothermal and non-isothermal conditions. The comparison of the RTD curves between the isothermal and non-isothermal conditions presents that the extent of mixing in the tundish in nonisothermal conditions is lower than the mixing extent in isothermal conditions.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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。

  5. Modelling of copper and zinc adsorption onto zeolite

    Directory of Open Access Journals (Sweden)

    H. Pavolová

    2016-10-01

    Full Text Available Adsorption of Cu(II and Zn(II ions from metallurgical solutions has been studied and the adsorption capacity of zeolite (Nižný Hrabovec, SK has been determined. Zeolites are characterized by relatively high sorption capacity, i.e. Cu(II and Zn(II can be removed even at relatively low concentrations. The experiments were realised in a batch system and evaluated using isotherms. According to the results of the experiments the adsorption equilibrium of Cu(II and Zn(II on zeolite was best described by Freundlich isotherm. The maximum sorption capacity was 1,48 and 1,49 mg/g for Cu(II and Zn(II, respectively. The experimental results of this study demonstrate that zeolite is suitable for adsorption of copper and zinc from aqueous solutions at low concentrations.

  6. 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

  7. 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

  8. 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.

  9. 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.

  10. 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.

  11. Analysis of statistical thermodynamic model for binary protein adsorption equilibria on cation exchange adsorbent

    Institute of Scientific and Technical Information of China (English)

    ZHOU Xiaopeng; SU Xueli; SUN Yan

    2007-01-01

    A study of nonlinear competitive adsorption equilibria of proteins is of fundamental importance in understanding the behavior of preparative chromatographic separation.This work describes the nonlinear binary protein adsorption equilibria on ion exchangers by the statistical thermodynamic (ST) model.The single-component and binary protein adsorption isotherms of bovine hemoglobin (Hb) and bovine serum albumin(BSA)on SP Sepharose FF were determined by batch adsorption experiments in 0.05 mol/L sodium acetate buffer at three pH values(4.5,5.0 and 5.5)and three NaCl concentrations(0.05,0.10 and 0.15 mol/L)at pH 5.0.The ST model was found to depict the effects of pH and ionic strength on the single-component equilibria well,with model parameters depending on the pH and ionic strength.Moreover,the ST model gave acceptable fitting to the binary adsorption data with the fltted singlecomponent model parameters,leading to the estimation of the binary ST model parameter.The effects of pH and ionic strength on the model parameters are reasonably interpreted by the electrostatic and thermodynamic theories.Results demonstrate the availability of the ST model for describing nonlinear competitive protein adsorption equilibria in the presence of two proteins.

  12. Modeling the Adsorption of Oxalate onto Montmorillonite.

    Science.gov (United States)

    Ramos, M Elena; Emiroglu, Caglayan; García, David; Sainz-Díaz, C Ignacio; Huertas, F Javier

    2015-11-01

    In this work, a multiscale modeling of the interaction of oxalate with clay mineral surfaces from macroscale thermodynamic equilibria simulations to atomistic calculations is presented. Previous results from macroscopic adsorption data of oxalate on montmorillonite in 0.01 M KNO3 media at 25 °C within the pH range from 2.5 to 9 have been used to develop a surface complexation model. The experimental adsorption edge data were fitted using the triple-layer model (TLM) with the aid of the FITEQL 4.0 computer program. Surface complexation of oxalate is described by two reactions: >AlOH + Ox(2-) + 2H(+) = >AlOxH + H2O (log K = 14.39) and >AlOH + Ox(2-) + H(+) = >AlOx(-) + H2O (log K = 10.39). The monodentate complex >AlOxH dominated adsorption below pH 4, and the bidentate complex >AlOx(-) was predominant at higher pH values. Both of the proposed inner-sphere oxalate species are qualitatively consistent with previously published diffuse reflectance FTIR spectroscopic results for oxalate on montmorillonite edge surface (Chem. Geol. 2014, 363, 283-292). Atomistic computational studies have been performed to understand the interactions at the molecular level between adsorbates and mineral surface, showing the atomic structures and IR frequency shifts of the adsorption complexes of oxalate with the edge surface of a periodic montmorillonite model. PMID:26444928

  13. 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

  14. 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.

  15. 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.

  16. Adsorption of Pb(Ⅱ) on Sediment of the Dianshan Lake:Adsorption Models and Kinetics

    Institute of Scientific and Technical Information of China (English)

    黄莉桦; 孙为民

    2004-01-01

    The adsorption characteristics of Pb on sediments of the Dianshan Lake in Shanghai was studied. The results show that (1)the relationship between the amount q of apparent equilibrium adsorption and the equilibrium concentration C conforms to the Freundlich isothermal adsorption equation; (2) the adsorption and desorption of Pb on sediments are not reversible, that is, adsorption/desorption of Pb exhibits hysteresis; (3) Pb adsorption behavior is initially fast, followed by a slow reaction, and the slow reaction conforms to a reversible first-order reaction; (4) by deducing the Pb adsorption kinetics, four kinetics parameters n, k1, k2, qmax independent of C could be worked out; (5) the equilibrium parameter (K) and the free energy change (ΔG) could also be determined,and the negative values of free energy change (ΔG) indicate the spontaneous nature of the adsorption.

  17. 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.

  18. 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.

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

    Science.gov (United States)

    Werner, Albert; Hackemann, Eva; Hasse, Hans

    2014-08-22

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

  20. Modeling the adsorption of mixed gases based on pure gas adsorption properties

    Science.gov (United States)

    Tzabar, N.; Holland, H. J.; Vermeer, C. H.; ter Brake, H. J. M.

    2015-12-01

    Sorption-based Joule-Thomson (JT) cryocoolers usually operate with pure gases. A sorption-based compressor has many benefits; however, it is limited by the pressure ratios it can provide. Using a mixed-refrigerant (MR) instead of a pure refrigerant in JT cryocoolers allows working at much lower pressure ratios. Therefore, it is attractive using MRs in sorption- based cryocoolers in order to reduce one of its main limitations. The adsorption of mixed gases is usually investigated under steady-state conditions, mainly for storage and separation processes. However, the process in a sorption compressor goes through various temperatures, pressures and adsorption concentrations; therefore, it differs from the common mixed gases adsorption applications. In order to simulate the sorption process in a compressor a numerical analysis for mixed gases is developed, based on pure gas adsorption characteristics. The pure gas adsorption properties have been measured for four gases (nitrogen, methane, ethane, and propane) with Norit-RB2 activated carbon. A single adsorption model is desired to describe the adsorption of all four gases. This model is further developed to a mixed-gas adsorption model. In future work more adsorbents will be tested using these four gases and the adsorption model will be verified against experimental results of mixed-gas adsorption measurements.

  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. Modeling and Experimental Studies of Mercury Oxidation and Adsorption in a Fixed-Bed Reactor

    Energy Technology Data Exchange (ETDEWEB)

    Buitrago, Paula A.; Morrill, Mike; Lighty, JoAnn S.; Silcox, Geoffrey D.

    2009-06-15

    This report presents experimental and modeling mercury oxidation and adsorption data. Fixed-bed and single-particle models of mercury adsorption were developed. The experimental data were obtained with two reactors: a 300-W, methane-fired, tubular, quartz-lined reactor for studying homogeneous oxidation reactions and a fixed-bed reactor, also of quartz, for studying heterogeneous reactions. The latter was attached to the exit of the former to provide realistic combustion gases. The fixed-bed reactor contained one gram of coconut-shell carbon and remained at a temperature of 150°C. All methane, air, SO2, and halogen species were introduced through the burner to produce a radical pool representative of real combustion systems. A Tekran 2537A Analyzer coupled with a wet conditioning system provided speciated mercury concentrations. At 150°C and in the absence of HCl or HBr, the mercury uptake was about 20%. The addition of 50 ppm HCl caused complete capture of all elemental and oxidized mercury species. In the absence of halogens, SO2 increased the mercury adsorption efficiency to up to 30 percent. The extent of adsorption decreased with increasing SO2 concentration when halogens were present. Increasing the HCl concentration to 100 ppm lessened the effect of SO2. The fixed-bed model incorporates Langmuir adsorption kinetics and was developed to predict adsorption of elemental mercury and the effect of multiple flue gas components. This model neglects intraparticle diffusional resistances and is only applicable to pulverized carbon sorbents. It roughly describes experimental data from the literature. The current version includes the ability to account for competitive adsorption between mercury, SO2, and NO2. The single particle model simulates in-flight sorbent capture of elemental mercury. This model was developed to include Langmuir and Freundlich isotherms, rate equations, sorbent feed rate, and

  3. 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

  4. 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.

  5. 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

  6. 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.

  7. 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.

  8. 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.

  9. Wide-range and accurate modeling of linear alkylbenzene sulfonate (LAS) adsorption/desorption on agricultural soil.

    Science.gov (United States)

    Oliver-Rodríguez, B; Zafra-Gómez, A; Reis, M S; Duarte, B P M; Verge, C; de Ferrer, J A; Pérez-Pascual, M; Vílchez, J L

    2015-11-01

    In this paper, rigorous data and adequate models about linear alkylbenzene sulfonate (LAS) adsorption/desorption on agricultural soil are presented, contributing with a substantial improvement over available adsorption works. The kinetics of the adsorption/desorption phenomenon and the adsorption/desorption equilibrium isotherms were determined through batch studies for total LAS amount and also for each homologue series: C10, C11, C12 and C13. The proposed multiple pseudo-first order kinetic model provides the best fit to the kinetic data, indicating the presence of two adsorption/desorption processes in the general phenomenon. Equilibrium adsorption and desorption data have been properly fitted by a model consisting of a Langmuir plus quadratic term, which provides a good integrated description of the experimental data over a wide range of concentrations. At low concentrations, the Langmuir term explains the adsorption of LAS on soil sites which are highly selective of the n-alkyl groups and cover a very small fraction of the soil surface area, whereas the quadratic term describes adsorption on the much larger part of the soil surface and on LAS retained at moderate to high concentrations. Since adsorption/desorption phenomenon plays a major role in the LAS behavior in soils, relevant conclusions can be drawn from the obtained results.

  10. Wide-range and accurate modeling of linear alkylbenzene sulfonate (LAS) adsorption/desorption on agricultural soil.

    Science.gov (United States)

    Oliver-Rodríguez, B; Zafra-Gómez, A; Reis, M S; Duarte, B P M; Verge, C; de Ferrer, J A; Pérez-Pascual, M; Vílchez, J L

    2015-11-01

    In this paper, rigorous data and adequate models about linear alkylbenzene sulfonate (LAS) adsorption/desorption on agricultural soil are presented, contributing with a substantial improvement over available adsorption works. The kinetics of the adsorption/desorption phenomenon and the adsorption/desorption equilibrium isotherms were determined through batch studies for total LAS amount and also for each homologue series: C10, C11, C12 and C13. The proposed multiple pseudo-first order kinetic model provides the best fit to the kinetic data, indicating the presence of two adsorption/desorption processes in the general phenomenon. Equilibrium adsorption and desorption data have been properly fitted by a model consisting of a Langmuir plus quadratic term, which provides a good integrated description of the experimental data over a wide range of concentrations. At low concentrations, the Langmuir term explains the adsorption of LAS on soil sites which are highly selective of the n-alkyl groups and cover a very small fraction of the soil surface area, whereas the quadratic term describes adsorption on the much larger part of the soil surface and on LAS retained at moderate to high concentrations. Since adsorption/desorption phenomenon plays a major role in the LAS behavior in soils, relevant conclusions can be drawn from the obtained results. PMID:26070080

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

    Science.gov (United States)

    Danielson, Thomas; Hin, Celine; Savara, Aditya

    2016-08-01

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

  12. Adsorption Models and Structural Characterization for Activated Carbon Fibers

    Institute of Scientific and Technical Information of China (English)

    CHEN Chuan-juan; WANG Ru-zhu; OLIVEIRA R.G.; HU Jin-qiang

    2009-01-01

    The nitrogen adsorption isotherms at 77.69 K were measured for two samples of activated carbon fibers and their microstructures were investigated. Among established isotherm equations, the Dubinin-Radushkevich equation showed the best agreement with the experimental data, while the Langmuir equation showed a large deviation when employed at low relative pressures. The MP method, t-method and αs-method were used to analyze the pore size distribution. The calculated average pore widths and BET (Brunauer-Emmett-Teller) surface areas for the sample A-13 were 0.86 nm and 1 286.60 m2/g, while for the sample A-16, they were 0.82 nm and 1 490.64 m2/g. The sample with larger pore width was more suitable to be used as additive in chemical heat pumps, while the other one could be used as adsorbent in adsorption refrigeration systems.

  13. Thermodynamic model for swelling of unconfined coal due to adsorption of mixed gases

    Science.gov (United States)

    Liu, Jinfeng; Peach, Colin; Spiers, Christopher

    2013-04-01

    gases, the adsorbed concentrations predicted reduce to the Langmuir isotherm for mixed gases. 3) Preferential adsorption sites model. This assumes adsorption sites show selectivity towards one gas, i.e. nsα adsorption sites can be occupied by both gases (cf. 2) while only (nsα -nsβ) adsorption sites can be occupied by gas β ( cf. 1). This model can be treated as a combination of Models 1 and 2. We compared these models to experimental measurements of swelling of an Australian sub-bituminous coal exposed to CH4, CO2 and to their mixtures at pressures up to 15 MPa, performed by Day et al. (2012, IJCG, 93, 40-48). Compared to other two models, the preferential adsorption sites model describes the experimental results best. This finding complies with the conventional view that CH4 is displaced by CO2 due to both depletion of CH4 partial pressure and preferential CO2 adsorption. However, our findings contradict the proposal by Day et al., based on their experiments, that CH4 and CO2 have access to all adsorption sites and that swelling solely depends on partial pressures. Additional experiments on different rank coals and gas species are underway to evaluate our models further.

  14. 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.

  15. Measurement and theoretical analysis of the adsorption of supercritical methane on superactivated carbon

    Institute of Scientific and Technical Information of China (English)

    周理; 李明; 周亚平

    2000-01-01

    Adsorption/desorption isotherms of supercritical methane on superactivated carbon have been measured in the range of 0-10 MPa and 233-333 K (20 K interval). The reversibility of the physical adsorption process is acknowledged. The heat of adsorption of 16.5 kJ/mol is determined from the isotherms, and a new modeling strategy for isotherms with maximum is presented. The model yields fits to the experimental isotherms with precision of ?%, maintaining the constancy of the characteristic energy of adsorption. The exponent of the model equation expresses the pore size distribution feature of the adsorbent. The density of the supercritical adsor-bate is evaluated as a parameter of the model. It is shown that the conventional isotherm theory works too at supercritical condition if the limit state of supercritical adsorption is introduced into isotherm modeling.

  16. Measurement and theoretical analysis of the adsorption of supercritical methane on superactivated carbon

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Adsorption/desorption isotherms of supercritical methane on superactivated carbon have been measured in the range of 0 10 MPa and 233 333 K (20 K interval). The reversibility of the physical adsorption process is acknowledged. The heat of adsorption of 16.5 kJ/mol is determined from the isotherms, and a new modeling strategy for isotherms with maximum is presented. The model yields fits to the experimental isotherms with precision of ±2%, maintaining the constancy of the characteristic energy of adsorption. The exponent of the model equation expresses the pore size distribution feature of the adsorbent. The density of the supercritical adsorbate is evaluated as a parameter of the model. It is shown that the conventional isotherm theory works too at supercritical condition if the limit state of supercritical adsorption is introduced into isotherm modeling.

  17. 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...

  18. 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...

  19. 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

  20. 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.

  1. 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

  2. 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.

  3. 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

  4. 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...

  5. 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

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

    Science.gov (United States)

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

    2012-10-30

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

  7. ADSORPTION MALACHITE GREEN ON NATURAL ZEOLITE

    Directory of Open Access Journals (Sweden)

    Eko Ariyanto

    2012-02-01

    Full Text Available A natural zeolite was employed as adsorbent for reducing of malachite green from aqueous solution. A batch system was applied to study the adsorption of malachite green in single system on natural zeolite. The adsorption studies indicate that malachite green in single component system follows the second-order kinetics and the adsorption is diffusion process with two stages for malachite green. Malachite green adsorption isotherm follows the Langmuir model.

  8. 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.

  9. 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

  10. 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).

  11. 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.

  12. 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.

  13. Monte Carlo simulation of hydrogen adsorption on Ni surfaces

    Institute of Scientific and Technical Information of China (English)

    WANG Rui; DENG Hui-qiu; YUAN Xiao-jian; HU Wang-yu

    2007-01-01

    In the present paper the adsorption kinetics of the hydrogen molecule on the(111)and(100)surfaces have been studied with the model proposed by Panczyk and the grand canonical Monte Carlo simulation method.The equilibrium adsorption isotherms are calculated at five different temperatures ranging from 314 K to 376 K and compared with the experimental equilibrium adsorption isotherms.The effects of temperature and pressure on coverage are also analyzed.

  14. Kinetic modeling of aldehyde adsorption rates on bare and aminopropylsilyl-modified silica gels by ultra-rapid-scanning fourier transform infrared spectrometry.

    Science.gov (United States)

    Yang, Husheng; Weinstock, Benjamin A; Hirsche, Blayne L; Griffiths, Peter R

    2005-04-26

    Enhancements of a model capable of precisely defining rates of adsorption in terms of a Langmuir isotherm and determined from infrared and pressure data collected in the millisecond time regime are described in detail. Rates of adsorption are determined for formaldehyde and acetaldehyde exposed to bare and aminopropylsilyl-derivatized silica gel. The model fits the collected data by varying the number of adsorption sites and the adsorption and desorption rate constants and determines the best fit based on the measured IR absorbance, partial pressure, exposure backpressure, number of adsorption sites, and time. The rate of adsorption onto irregular-shaped silica gel was faster than the rate onto the corresponding spherical silica gel. Formaldehyde was adsorbed more efficiently than acetaldehyde on APS silica gel than on bare silica gel, whereas acetaldehyde was adsorbed more efficiently than formaldehyde on underivatized silica, indicating the possibility that formaldehyde is adsorbed through the formation of a Schiff base.

  15. 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.

  16. 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/...

  17. 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.

  18. 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.

  19. Mathematical modelling of methane steam reforming in a membrane reactor: an isothermal model

    Energy Technology Data Exchange (ETDEWEB)

    Assaf, E.M. [Sao Paulo Univ., Sao Carlos, SP (Brazil). Dept. de Fisico-Quimica; Jesus, C.D.F.; Assaf, J.M. [Sao Carlos Univ., SP (Brazil). Dept. de Engenharia Quimica

    1998-06-01

    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 conversion yield than the conventional fixed-bed reactor. (author) 16 refs., 5 figs., 1 tab.; e-mail: eassaf at iqsc.sc.usp.br; mansur at power.ufscar.br

  20. 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.

  1. Application of HYDRUS 1D model for assessment of phenol-soil adsorption dynamics.

    Science.gov (United States)

    Pal, Supriya; Mukherjee, Somnath; Ghosh, Sudipta

    2014-04-01

    Laboratory-scale batch, vertical, and horizontal column experiments were conducted to investigate the attenuative capacity of a fine-grained clayey soil of local origin in the surrounding of a steel plant wastewater discharge site in West Bengal, India, for removal of phenol. Linear, Langmuir, and Freundlich isotherm plots from batch experimental data revealed that Freundlich isotherm model was reasonably fitted (R (2) = 0.94). The breakthrough column experiments were also carried out with different soil bed heights (5, 10, and 15 cm) under uniform flow to study the hydraulic movements of phenol by evaluating time concentration flow behavior using bromide as a tracer. The horizontal migration test was also conducted in the laboratory using adsorptive phenol and nonreactive bromide tracer to explore the movement of solute in a horizontal distance. The hydrodynamic dispersion coefficients (D) in the vertical and horizontal directions in the soil were estimated using nonlinear least-square parameter optimization method in CXTFIT model. In addition, the equilibrium convection dispersion model in HYDRUS 1D was also examined to simulate the fate and transport of phenol in vertical and horizontal directions using Freundlich isotherm constants and estimated hydrodynamic parameters as input in the model. The model efficacy and validation were examined through statistical parameters such as the coefficient of determination (R (2)), root mean square error and design of index (d). PMID:24407784

  2. 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.

  3. Unified water isotherms for clayey porous materials

    Science.gov (United States)

    Revil, A.; Lu, N.

    2013-09-01

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

  4. 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

    2016-01-01

    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.

  5. 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.

  6. 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

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

    Energy Technology Data Exchange (ETDEWEB)

    Akkaya, Recep, E-mail: rakkaya@cumhuriyet.edu.tr [Cumhuriyet University, Vocational School of Health Services, 58140 Sivas (Turkey); Akkaya, Birnur [Cumhuriyet University, Faculty of Science, Department of Molecular Biology and Genetics, 58140 Sivas (Turkey)

    2013-03-15

    Abstract: In this research, a novel composite, poly(2-hydroxyethylmethacrylate-expanded perlite) [P(HEMA-EP)], was synthesized and its adsorptive features were investigated. P(HEMA-EP)’s adsorptive features were evaluated for UO{sub 2}{sup 2+} and Th{sup 4+} ions in terms of the dependency upon the ion concentration, pH, temperature, and time. P(HEMA-EP) was able to bind UO{sub 2}{sup 2+} and Th{sup 4+} ions with strong chemical affinity. The adsorption results were fitted to the classical Langmuir, Freundlich, and Dubinin–Radushkevich (D–R) sorption models. P(HEMA-EP) was also used to study the removal of UO{sub 2}{sup 2+} and Th{sup 4+} ions from aqueous solutions in a batch system. The adsorption capacity (X{sub L}) of UO{sub 2}{sup 2+} and Th{sup 4+} ions was found to be 0.29 and 0.44 mol kg{sup −1}, respectively. The kinetic data corresponds well to the pseudo-second-order equation. Changes in the enthalpy and entropy values demonstrated that the overall adsorption process was spontaneous (ΔG < 0), endothermic (ΔH > 0), and had increased entropy (ΔS > 0), as expected. The reusability of the composites was confirmed for five sequential reuses.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

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

    OpenAIRE

    Al-Fetlawi, H.; A. A. Shah; Walsh, F.C.

    2009-01-01

    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 performa...

  13. 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...

  14. Selective adsorption of tannins onto hide collagen fibres

    Institute of Scientific and Technical Information of China (English)

    LIAO; Xuepin(廖学品); LU; Zhongbing(陆忠兵); SHI; Bi(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.

  15. 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.

  16. Modeling adsorption of binary and ternary mixtures on microporous media

    DEFF Research Database (Denmark)

    Monsalvo, Matias Alfonso; Shapiro, Alexander

    2007-01-01

    The goal of this work is to analyze the adsorption of binary and ternary mixtures on the basis of the multicomponent potential theory of adsorption (MPTA). In the MPTA, the adsorbate is considered as a segregated mixture in the external potential field emitted by the solid adsorbent. This makes...... it possible using the same equation of state to describe the thermodynamic properties of the segregated and the bulk phases. For comparison, we also used the ideal adsorbed solution theory (IAST) to describe adsorption equilibria. The main advantage of these two models is their capabilities to predict...... multicomponent adsorption equilibria on the basis of single-component adsorption data. We compare the MPTA and IAST models to a large set of experimental data, obtaining reasonable good agreement with experimental data and high degree of predictability. Some limitations of both models are also discussed....

  17. 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.

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

    Science.gov (United States)

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

  19. 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....

  20. 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.

  1. Adsorption of glucose, cellobiose, and cellotetraose onto cellulose model surfaces.

    Science.gov (United States)

    Hoja, Johannes; Maurer, Reinhard J; Sax, Alexander F

    2014-07-31

    Reliable simulation of molecular adsorption onto cellulose surfaces is essential for the design of new cellulose nanocomposite materials. However, the applicability of classical force field methods to such systems remains relatively unexplored. In this study, we present the adsorption of glucose, cellobiose, and cellotetraose on model surfaces of crystalline cellulose Iα and Iβ. The adsorption of the two large carbohydrates was simulated with the GLYCAM06 force field. To validate this approach, quantum theoretical calculations for the adsorption of glucose were performed: Equilibrium geometries were studied with density functional theory (DFT) and dispersion-corrected DFT, whereas the adsorption energies were calculated with two standard density functional approximations and five dispersion-containing DFT approaches. We find that GLYCAM06 gives a good account of geometries and, in most cases, accurate adsorption energies when compared to dispersion-corrected DFT energies. Adsorption onto the (100) surface of cellulose Iα is, in general, stronger than onto the (100) surface of cellulose Iβ. Contrary to intuition, the adsorption energy is not directly correlated with the number of hydrogen bonds; rather, it is dominated by dispersion interactions. Especially for bigger adsorbates, a neglect of these interactions leads to a dramatic underestimation of adsorption energies. PMID:25036217

  2. 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.

  3. 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

  4. 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.

  5. 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.

  6. Goethite surface reactivity: III. Unifying arsenate adsorption behavior through a variable crystal face - Site density model

    Science.gov (United States)

    Salazar-Camacho, Carlos; Villalobos, Mario

    2010-04-01

    We developed a model that describes quantitatively the arsenate adsorption behavior for any goethite preparation as a function of pH and ionic strength, by using one basic surface arsenate stoichiometry, with two affinity constants. The model combines a face distribution-crystallographic site density model for goethite with tenets of the Triple Layer and CD-MUSIC surface complexation models, and is self-consistent with its adsorption behavior towards protons, electrolytes, and other ions investigated previously. Five different systems of published arsenate adsorption data were used to calibrate the model spanning a wide range of chemical conditions, which included adsorption isotherms at different pH values, and adsorption pH-edges at different As(V) loadings, both at different ionic strengths and background electrolytes. Four additional goethite-arsenate systems reported with limited characterization and adsorption data were accurately described by the model developed. The adsorption reaction proposed is: lbond2 FeOH +lbond2 SOH +AsO43-+H→lbond2 FeOAsO3[2-]…SOH+HO where lbond2 SOH is an adjacent surface site to lbond2 FeOH; with log K = 21.6 ± 0.7 when lbond2 SOH is another lbond2 FeOH, and log K = 18.75 ± 0.9, when lbond2 SOH is lbond2 Fe 2OH. An additional small contribution of a protonated complex was required to describe data at low pH and very high arsenate loadings. The model considered goethites above 80 m 2/g as ideally composed of 70% face (1 0 1) and 30% face (0 0 1), resulting in a site density for lbond2 FeOH and for lbond2 Fe 3OH of 3.125/nm 2 each. Below 80 m 2/g surface capacity increases progressively with decreasing area, which was modeled by considering a progressively increasing proportion of faces (0 1 0)/(1 0 1), because face (0 1 0) shows a much higher site density of lbond2 FeOH groups. Computation of the specific proportion of faces, and thus of the site densities for the three types of crystallographic surface groups present in

  7. 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.

  8. Adsorption of thorium from aqueous solutions by perlite.

    Science.gov (United States)

    Talip, Z; Eral, M; Hiçsönmez, U

    2009-02-01

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

  9. 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.

  10. 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)

  11. LIQUID-PHASE ADSORPTION KINETICS OF ISOMALTOTRIOSE ON Ca2+ EXCHANGE RESIN

    Institute of Scientific and Technical Information of China (English)

    LI Xiang; GUO Haifu

    2006-01-01

    The adsorption of isomaltotriose from aqueous solution on Ca2+ resin was investigated.The adsorption isotherm and the rate curve were determined. The pseudo-first-order model,pseudo-second-order model and the intraparticle diffusion model were used to predict the rate constants of adsorption. The activation energy of adsorption has been also evaluated using the pseudo-second-order rate constants. The results showed that the adsorption of isomaltotriose onto Ca2+ resin is an exothermically activated process. The adsorption isotherm can be described by Langmuir equation. The pseudo-second-order model can fit well to the adsorption rate curve of isomaltotriose onto Ca2+ resin. It suggests that the adsorption of isomoltotriose onto Ca2+ resin involve chemical adsorption.

  12. 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)

  13. (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

  14. Kinetics and isotherm analysis of 2,4-dichlorophenoxyl acetic acid adsorption onto soil components under oxic and anoxic conditions.

    Science.gov (United States)

    Ololade, Isaac A; Alomaja, Folasade; Oladoja, Nurudeen A; Ololade, Oluwaranti O; Oloye, Femi F

    2015-01-01

    2,4-dichlorophenoxyl acetic acid (2,4-D, pKa = 2.8) is used extensively as a herbicide in agricultural practices. Its sorption behavior on both untreated and soils treated to significantly remove specific components (organic and iron and manganese [Fe-Mn] oxides and hydroxides phases) was investigated under oxic and anoxic conditions. The chemical and structural heterogeneity of the soil components were characterized by elemental analysis and X-ray diffraction (XRD). The coexistence of the various components seems to either mask sorption sites on the untreated soil surfaces or inhibit interlayer diffusion of 2,4-D. All sorption data conform to the Freundlich description and a pseudo-second-order kinetic model. There was a strong positive correlation between sorption capacity K(d), and surface area (r(2) ≤ 0.704), but a negative correlation was uncovered with both pH and organic carbon (r(2) ≤ -0.860). The results indicate that 2,4-D is preferably sorbed under oxic rather than anoxic conditions and it is greater on soils containing a high Fe content. There was incomplete 2,4-D sorption reversibility, with desorption occurring more rapidly under anoxic conditions. The study suggests that stimulation of Fe III reduction could be used for the bioremediation of a 2,4-D-contaminated site. PMID:25996813

  15. 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.)

  16. 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 adsorption was observed 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 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.

  17. Adsorption of phenol from water by ultrafine coal powders

    Institute of Scientific and Technical Information of China (English)

    LIU Zhuan-nian; ZHOU An-ning; YANG Fan; JIN Qi-ting

    2007-01-01

    Seven Shenfu coal powders different in particle size obtained by sieving and ball milling were used to probe their adsorption properties to phenol from water.The results show that the kinetics of phenol on coal powders follow the second-Order adsorption kinetic model well.Adsorption processes are governed by film diffusion and the kinetic parameters and the effective diffusion coefficients were calculated through plotting.Adsorption capacities to phenol increase exponentially with decreasing of diameter of coal described in terms of Freundlich isotherm,while for ultrafine coal powders with d50 of 4.28and 4.82 μm fit Langmuir isotherm well.

  18. 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.

  19. Competitive adsorption of heavy metals onto sesame straw biochar in aqueous solutions.

    Science.gov (United States)

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

    2016-01-01

    Objective of this research was to evaluate adsorption of heavy metals in mono and multimetal forms onto sesame straw biochar (SSB). Competitive sorption of metals by SSB has never been reported previously. The maximum adsorption capacities (mgg(-1)) of metals by SSB were in the order of Pb (102)≫Cd (86)≫Cr (65)>Cu (55)≫Zn (34) in the monometal adsorption isotherm and Pb (88)≫Cu (40)≫Cr (21)>Zn (7)⩾Cd (5) in the multimetal adsorption isotherm. Based on data obtained from the distribution coefficients, Freundlich and Langmuir adsorption models, and three-dimensional simulation, multimetal adsorption behaviors differed from monometal adsorption due to competition. Especially, during multimetal adsorption, Cd was easily exchanged and substituted by other metals. Further competitive adsorption studies are necessary in order to accurately estimate the heavy metal adsorption capacity of biochar in natural environments.

  20. 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.

  1. Adsorption Characteristics of Remazol Black B on Anoxic Sludge

    Institute of Scientific and Technical Information of China (English)

    HUANG Man-hong; CHEN Liang; CHEN Dong-hui; CHEN Chao-peng

    2009-01-01

    The adsorption characteristics of Remazol Black B on anoxic sludge were investigated. The parameters, such as initial pH, sulphate concentration, and temperature,affecting the dye adsorption were studied. The adsorption data were analyzed with three adsorption isotherm models,namely Langmuir, Freudlich, and linear partition. The results showed that adsorption of Remazol Black B on the sterilized sludge reached equilibrium in 4 h. It also indicated that pH had significant effect on anoxic sludge adsorption behavior. The adsorption capacity of anoxic sludge decreased with the increase of pH value and the maximum adsorption capacity of dyes occurred at pH = 3. The adsorptive capacities increased with the decrease of temperature and increase of sulphate concentration. Results also indicated that the adsorption equilibrium of Remazol Black B on anoxic sludge could be well fitted by Freundlich model.

  2. 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

  3. 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.

  4. Atomistic Modeling of Gas Adsorption in Nanocarbons

    Directory of Open Access Journals (Sweden)

    G. Zollo

    2012-01-01

    Full Text Available Carbon nanostructures are currently under investigation as possible ideal media for gas storage and mesoporous materials for gas sensors. The recent scientific literature concerning gas adsorption in nanocarbons, however, is affected by a significant variation in the experimental data, mainly due to the different characteristics of the investigated samples arising from the variety of the synthesis techniques used and their reproducibility. Atomistic simulations have turned out to be sometimes crucial to study the properties of these systems in order to support the experiments, to indicate the physical limits inherent in the investigated structures, and to suggest possible new routes for application purposes. In consideration of the extent of the theme, we have chosen to treat in this paper the results obtained within some of the most popular atomistic theoretical frameworks without any purpose of completeness. A significant part of this paper is dedicated to the hydrogen adsorption on C-based nanostructures for its obvious importance and the exceptional efforts devoted to it by the scientific community.

  5. 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.

  6. DECOLOURIZATION OF MALACHITE GREEN USING TAMARIND SEED: OPTIMIZATION, ISOTHERM AND KINETIC STUDIES

    Directory of Open Access Journals (Sweden)

    R. RAJESHKANNAN

    2011-03-01

    Full Text Available TIn this work, removal of malachite green (MG from aqueous solution using a low cost adsorbent, tamarind seed, was investigated. The adsorbent was characterized using SEM, BET surface area analyzer, and FT-IR. Decolourization of malachite green was studied as a function of different adsorption parameters such as temperature, adsorbent dose, contact time, adsorbent size and agitation speed. These parameters were optimized using response surface methodology (RSM. The significance of different adsorption parameters along with their combined effect on the adsorption process has been established through a full 50 factorial design. Langmuir, Freundlich, Redlich Petersen, Dubnin Redushkevich and Tempkin adsorption isotherm equations were used in the equilibrium modeling. Experimental data follows the Langmuir adsorption isotherm. The adsorption process follows a pseudo first order and intra-particle diffusion is found to be the rate-controlling step.

  7. An isothermal model of a hybrid Stirling/reverse-Brayton cryocooler

    Science.gov (United States)

    Nellis, G. F.; Maddocks, J. R.

    2003-01-01

    This paper presents a model of a cryogenic refrigerator that integrates a reverse-Brayton lower temperature stage with a 2-piston Stirling upper temperature stage using a rectification system of check valves and buffer volumes. The numerical model extends the isothermal Schmidt analysis of the Stirling cycle by deriving the additional dimensionless governing equations that characterize the recuperative system. Numerical errors are quantified and the results are verified against analytical solutions in the appropriate limits. The model is used to explore the effect of the rectification system's characteristics on the overall cycle's behavior. Finally, the model is used to optimize the hybrid system's design by varying the swept volume ratio and phase angle in order to maximize the refrigeration per unit of heat transfer in the recuperator and regenerator.

  8. 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)

  9. 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.

  10. Modeling of surfactant transport and adsorption in porous media

    Energy Technology Data Exchange (ETDEWEB)

    Chung, F.T.H.

    1991-04-01

    When surfactant solution is flowing in a reservoir formation, surfactants will be diluted by flow dispersion, retained in dead-end pores, adsorbed on rock surfaces, or precipitated due to ion exchange. The loss of surfactant will be detrimental to the performance of gas foam. Information of surfactant concentration profiles in reservoir formations is essential for gas foaming technique development. The major objective of this research is to investigate with mathematical models the transport and dynamic adsorption of surfactants in porous media. The mathematical models have taken into account the convection, dispersion, capacitance, and adsorption effects on concentrations of surfactants. Numerical methods and computer programs have been developed which can be used to match experimental results and to determine the characterization parameters in the models. The models can be included in foam simulation programs to calculate surfactant concentration profiles in porous media. A flow experimental method was developed to measure the effluent surfactant concentration, which will be used to determine the model parameters. Commercial foaming agent Alipal CD-128 was used in this study. Equilibrium adsorption and surfactant precipitation have been tested. Tracer solutions with a nonadsorbing solute such as dextrose and sucrose were used to determine the dispersion parameters for the experimental sandpack; thus, the adsorption of the surfactant in the test sand can be identified with an adequate model. 49 refs., 21 figs.

  11. 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...

  12. 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

  13. 多组分吸附过程的吸附速率模型%Adsorption Rate Models for Multicomponent Adsorption Systems

    Institute of Scientific and Technical Information of China (English)

    姚春才

    2004-01-01

    Three adsorption rate models are derived for multicomponent adsorption systems under either pore diffusion or surface diffusion control. The linear driving force (LDF) model is obtained by assuming a parabolic intraparticle concentration profile. Models I and Ⅱ are obtained from the parabolic concentration layer approximation. Examples are presented to demonstrate the usage and accuracy of these models. It is shown that Model I is suitable for batch adsorption calculations and Model H provides a good approximation in fixed-bed adsorption processes while the LDF model should not be used in batch adsorption and may be considered acceptable in fixed-bed adsorption where the parameter Ti is relatively large.

  14. Propylene/propane mixture adsorption on faujasite sorbents

    NARCIS (Netherlands)

    Van Miltenburg, A.; Gascon, J.; Zhu, W.; Kapteijn, F.; Moulijn, J.A.

    2008-01-01

    The adsorption of propylene and propane on zeolite NaX with and without a saturated (36 wt%) amount of CuCl have been investigated. The single component adsorption isotherms could be well described with a Dual-Site Langmuir model. The dispersion of CuCl results in a decrease of the maximum adsorptio

  15. 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...

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

    Science.gov (United States)

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

    2013-08-01

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

  17. 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...

  18. A physically based model for the isothermal martensitic transformation in a maraging steel

    Science.gov (United States)

    Kruijver, S. O.; Blaauw, H. S.; Beyer, J.; Post, J.

    2003-10-01

    Isothermal transformation from austenite to martensite in steel products during or after the production process often show residual stresses which can create unacceptable dimensional changes in the final product. Tn order to gain more insight in the effects infiuencing the isothermai transformation, the overall kinetics in a low Carbon-Nickel maraging steel is investigated. The influence of the austenitizing température, time and quenching rate on the transformation is measured magnetically and yields information about the transformation rate and final amount of transformation. A physically based model describing the nucleation and growth of martensite is used to explain the observed effects. The results show a very good fit of the experimental values and the model description of the transformation, within the limitations of the inhomogeneities (carbides and intermetallics, size and distribution in the material and stress state) and experimental conditions.

  19. 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.)

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  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. Interfacial adsorption of insulin - Conformational changes and reversibility of adsorption

    NARCIS (Netherlands)

    Mollmann, SH; Jorgensen, L; Bukrinsky, JT; Elofsson, U; Norde, W; Frokjaer, S

    2006-01-01

    The adsorption of human insulin to Teflon particles was studied with respect to conformational changes and the reversibility of adsorption was examined by total internal reflection fluorescence (TIRF). Adsorption isotherms for the adsorption of human insulin indicated high affinity adsorption, even

  6. Interfacial adsorption of insulin. Conformational changes and reversibility of adsorption

    NARCIS (Netherlands)

    Mollmann, S.H.; Bukrinsky, J.T.; Elofsson, U.; Norde, W.; Frokjaer, S.

    2006-01-01

    The adsorption of human insulin to Teflon particles was studied with respect to conformational changes and the reversibility of adsorption was examined by total internal reflection fluorescence (TIRF). Adsorption isotherms for the adsorption of human insulin indicated high affinity adsorption, even

  7. 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

  8. Analysis of isothermal and cooling rate dependent immersion freezing by a unifying stochastic ice nucleation model

    Science.gov (United States)

    Alpert, P. A.; Knopf, D. A.

    2015-05-01

    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 nuclei (IN) all have the same IN 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. A stochastic immersion freezing model based on first principles of statistics is presented, which accounts for variable ISA per droplet and uses physically observable 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, droplets in a continuous flow diffusion chamber (CFDC), the Leipzig aerosol cloud interaction simulator (LACIS), and the aerosol interaction and dynamics in the atmosphere (AIDA) cloud chamber. Observed time dependent isothermal frozen fractions exhibiting non-exponential behavior with time can be readily explained by this model considering varying ISA. An

  9. An Experimental Study on the Adsorption Behavior of Gases Crossing the Critical Temperature

    Institute of Scientific and Technical Information of China (English)

    ZHOULi; ZHOUYaping; 等

    2002-01-01

    Adsorption equilibria of CH4 and N2 on activated carbon and silica gel were measured for a wide temperature rang covering the critical point:158-298K for CH4,and 103-298K for N2.The determination of the compressibility factor is shown to have considerable effect on isotherm behavior at conditions after the isotherm maximum.A change in adsorption mechanisms on crossing the critical temperature was observed in all cases. The kind of adsorbents and how far the equilibrium temperature to the critical one are major factors affecting the transition of isotherms from sub-to supercritical.All continuous isotherms can be modeled by a unique model for the supercritical region.The satisfactory fitting of the model to the experimental isotherms proved the reliability of the absolute adsorption determined by the proposed method.

  10. Measuring and modeling the competitive adsorption of CO2, CH4, and N2 on a dry coal.

    Science.gov (United States)

    Ottiger, Stefan; Pini, Ronny; Storti, Giuseppe; Mazzotti, Marco

    2008-09-01

    Data on the adsorption behavior of CO 2, CH 4, and N 2 on coal are needed to develop enhanced coalbed methane (ECBM) recovery processes, a technology where the recovery of CH 4 is enhanced by injection of a gas stream consisting of either pure CO 2, pure N 2, or a mixture of both. The pure, binary, and ternary adsorption of these gases on a dry coal from the Sulcis Coal Province in Italy has been measured at pressures up to 180 bar and temperatures of 45 and 70 degrees C for the pure gases and of 45 degrees C for the mixtures. The experiments were performed in a system consisting of a magnetic suspension balance using a gravimetric-chromatographic technique. The excess adsorption isotherms are successfully described using a lattice density functional theory model based on the Ono-Kondo equations exploiting information about the structure of the coal, the adsorbed gases, and the interaction between them. The results clearly show preferential adsorption of CO 2 over CH 4 and N 2, which therefore indicate that ECBM may be a viable option for the permanent storage of CO 2. PMID:18680385

  11. 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.

  12. 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.

  13. Modeling of breakthrough curves of single and quaternary mixtures of ethanol, glucose, glycerol and acetic acid adsorption onto a microporous hyper-cross-linked resin.

    Science.gov (United States)

    Zhou, Jingwei; Wu, Jinglan; Liu, Yanan; Zou, Fengxia; Wu, Jian; Li, Kechun; Chen, Yong; Xie, Jingjing; Ying, Hanjie

    2013-09-01

    The adsorption of quaternary mixtures of ethanol/glycerol/glucose/acetic acid onto a microporous hyper-cross-linked resin HD-01 was studied in fixed beds. A mass transport model based on film solid linear driving force and the competitive Langmuir isotherm equation for the equilibrium relationship was used to develop theoretical fixed bed breakthrough curves. It was observed that the outlet concentration of glucose and glycerol exceeded the inlet concentration (c/c0>1), which is an evidence of competitive adsorption. This phenomenon can be explained by the displacement of glucose and glycerol by ethanol molecules, owing to more intensive interactions with the resin surface. The model proposed was validated using experimental data and can be capable of foresee reasonably the breakthrough curve of specific component under different operating conditions. The results show that HD-01 is a promising adsorbent for recovery of ethanol from the fermentation broth due to its large capacity, high selectivity, and rapid adsorption rate.

  14. Enzymatic degradation of plant cell wall polysaccharides: the kinetic effect of competitive adsorption

    DEFF Research Database (Denmark)

    Bergsøe, Merete Norsker; Bloch, Line; Adler-Nissen, Jens

    1999-01-01

    when any of the monocomponent enzymes are added. To describe the results a new model designated 'the competitive activity adsorption model' is proposed. The model is based on the fact that the enzymes are adsorbed to the substrate before action. A combination of the Langmuir adsorption isotherm...

  15. 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.

  16. Mathematical modeling of handmade recycled paper drying kinetics and sorption isotherms

    Directory of Open Access Journals (Sweden)

    M. G. A. Vieira

    2008-06-01

    Full Text Available The objective of this work is to analyze and compare the natural and forced convective drying of handmade recycled paper. Drying of recycled cellulose pulp was carried out under laboratory environment conditions and in a convective dryer with forced air circulation and controlled conditions of air temperature and velocity. The tests were conducted following a two-factor central composed factorial design of experiments, with six runs at the central point. The drying results were analyzed and fitted to mathematical models of Fick, Henderson and Pabis (Fick’s modified equation, Page and He (considering the nonlinear Fick effect. The model of Page represented best the experimental data and the one of Henderson and Pabis resulted in an adequate fit for the paper drying kinetics. Sorption isotherms were determined for the dried paper and the models of GAB (Guggenheim-Anderson-de Boer and GDW (Generalised D’Arcy and Watt resulted in excellent fits of the experimental data. The water sorption mechanism was suggested by the analysis of the calculated parameters of the GDW model.

  17. 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.

  18. 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.

  19. 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...

  20. The phase-shift method for determining Langmuir and Temkin adsorption isotherms of over-potentially deposited hydrogen for the cathodic H{sub 2} evolution reaction at the poly-Pt/H{sub 2}SO{sub 4} aqueous electrolyte interface

    Energy Technology Data Exchange (ETDEWEB)

    Chun, Jang H.; Jeon, Sang K.; Kim, Nam Y. [Department of Electronic Engineering, Kwangwoon University, Seoul 139-701 (Korea); Chun, Jin Y. [School of Chemical Engineering, Seoul National University, Seoul 151-744 (Korea)

    2005-11-01

    A linear relationship between the behavior (-f vs. E) of the phase shift (0{sup |}=<-f=<90{sup |}) for the optimum intermediate frequency and that ({theta} vs. E) of the fractional surface coverage (1>={theta}>=0) of over-potentially deposited hydrogen (OPD H) for the cathodic H{sub 2} evolution reaction (HER), i.e., the phase-shift method, at the poly-Pt/0.5M H{sub 2}SO{sub 4} aqueous electrolyte interface has been verified using cyclic voltammetric, differential pulse voltammetric, and ac impedance techniques. The phase-shift method for determining the suitable adsorption isotherm (Langmuir, Frumkin, Temkin) of OPD H for the cathodic HER at the interface also has been proposed. At the poly-Pt/0.5M H{sub 2}SO{sub 4} aqueous electrolyte interface, the Langmuir adsorption isotherm ({theta} vs. E) of OPD H, the equilibrium constant (K=1.3x10{sup -4}) for OPD H and the standard free energy ({delta}G{sub ads}{sup 0}=22.2kJ/mol) of OPD H are determined using the phase-shift method. At the same interface, the Temkin adsorption isotherm ({theta} vs. E) of OPD H, the equilibrium constant (1.3x10{sup -3}>=K>=1.3x10{sup -5} with {theta}, i.e., 0=<{theta}=<1) for OPD H, and the standard free energy (16.5=<{delta}G{sub {theta}}{sup 0}=<27.9kJ/mol with {theta}, i.e., 0=<{theta}=<1) of OPD H are also determined using the phase-shift method. At the intermediate values of {theta}, i.e., 0.2<{theta}<0.8, the Langmuir and Temkin adsorption isotherms of OPD H for the cathodic HER at the interface are converted to each other. The equilibrium constant (K{sub 0}) for the Temkin adsorption isotherm ({theta} vs. E) is ca. 10 times greater than that (K) for the corresponding Langmuir adsorption isotherm ({theta} vs. E). The interaction parameter (g) for the Temkin adsorption isotherm ({theta} vs. E) is ca. 4.6 greater than that (g) for the corresponding Langmuir adsorption isotherm ({theta} vs. E). These numbers (10 times and 4.6) can be taken as constant conversion factors between the

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

    Science.gov (United States)

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

    2016-01-01

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

  2. 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%

  3. 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)

  4. 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.

  5. Isotherms and kinetics of methanol vapor adsorption on carbon fibers and activated carbons%炭纤维和活性炭甲醇气相吸附动力学和等温线

    Institute of Scientific and Technical Information of China (English)

    C.Vagner; G.Finqueneisel; T.Zimny; J.V.Weber

    2003-01-01

    Adsorption of methanol vapor on two activated carbons with different origins and activation, and two carbon fibers (ex-PAN and ex-rayon) were investigated in static conditions. An original approach for diffusion problems by combining data from isotherms and adsorption kinetics is presented. It is found that the adsorption kinetics are influenced by temperature, the surface chemistry, the mesoporosity and the microtexture of the pores (shape and size) of the samples studied.%采用不同原料、不同活化过程的两种活性炭和两种炭纤维(PAN、Rayon基)进行了甲醇气相静态吸附,结合其吸附动力学和等温线的数据研究了有关扩散问题,发现温度与所用样品表面化学性质、中孔率、孔隙(形态与大小)微织构对其吸附动力学有影响.

  6. A kinetic model for corrosion and precipitation in non-isothermal LBE flow loop

    Science.gov (United States)

    He, By Xiaoyi; Li, Ning; Mineev, Mark

    2001-08-01

    A kinetic model was developed to estimate the corrosion/precipitation rate in a non-isothermal liquid lead-bismuth eutectic (LBE) flow loop. The model was based on solving the mass transport equation with the assumptions that convective transport dominates in the longitudinal flow direction and diffusion dominates in the transverse direction. The species concentration at wall is assumed to be determined either by the solubility of species in LBE in the absence of oxygen or by the reduction reaction of the protective oxide film when active oxygen control is applied. Analyses show that the corrosion/precipitation rate depends on the flow velocity, the species diffusion rate, the oxygen concentration in LBE, as well as the temperature distribution along a loop. Active oxygen control can significantly reduce the corrosion/precipitation of the structural materials. It is shown that the highest corrosion/precipitation does not necessarily locate at places with the highest/lowest temperature. For a material testing loop being constructed at the Los Alamos National Laboratory (LANL), the highest corrosion occurs at the end of the heater zone, while the highest precipitation occurs in the return flow in the recuperator.

  7. 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] 

  8. Removal of methyl violet dye by adsorption onto N-benzyltriazole derivatized dextran

    DEFF Research Database (Denmark)

    Cho, Eunae; Tahir, Muhammad Nazir; Kim, Hwanhee;

    2015-01-01

    was characterized by nuclear magnetic resonance spectroscopy, elemental analysis, and scanning electron microscopy. Dextran was substituted with a triazole-linked benzyl group. For decolorization of the dye effluent, adsorption is a very effective treatment; here, the driving force is based on hydrogen bonding, pi...... with equilibrium isotherms including the Langmuir, Freundlich, and Temkin models. Based on the Langmuir isotherm, the maximum adsorption capacity was determined to be 95.24 mg of dye per gram of the adsorbent. The adsorption obeyed pseudo-second order kinetics, and a negative Delta G(0) value indicated adsorption...

  9. 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.

  10. 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

  11. Contribution of Ash Content Related to Methane Adsorption Behaviors of Bituminous Coals

    OpenAIRE

    Yanyan Feng; Wen Yang; Wei Chu

    2014-01-01

    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 stu...

  12. 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.

  13. 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...

  14. 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, (ɛ 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.

  15. 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.

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

    Science.gov (United States)

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

    2011-05-01

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

  17. Removal of copper by modified chitosan adsorptive membrane

    Institute of Scientific and Technical Information of China (English)

    Xiaoshuai LIU; Zihong CHENG; Wei MA

    2009-01-01

    In this study, a novel adsorptive membrane was prepared from chitosan as the functional polymer and some additive blend solutions by solution casting method.The modified chitosan membrane was characterized by FTIR and its Water Swelling Ratio (WSR). The adsorption of copper ions on the adsorptive membrane was investi-gated in batch experiments. The results obtained from the experiments indicated that the membrane had a good adsorption capacity for copper ions, the optimal ionic strength and pH were 0.1 and 5-6, respectively. Compared with the Langmuir isotherm model, the experimental data were found to be following the Freundlich model.

  18. Adsorption behavior of bisphenol-A and diethyl phthalate onto bubble surface in nonfoaming adsorptive bubble separation

    OpenAIRE

    Maruyama, Hideo; Seki, Hideshi; Matsukawa, Yasuhiro; Suzuki, Akira; INOUE, Norio

    2008-01-01

    To clarify adsorption equilibrium relationship at liquid-atmosphere interface, adsorption behavior of bisphenol-A (BPA) and diethyl phthalate (DEP) onto bubble surface was studied by using nonfoaming adsorptive bubble separation (NFBS) technique. The adsorption isotherm of BPA and DEP were obtained experimentally. The experimental results showed that adsorption equilibrium of BPA and DEP on bubble surface followed Langmuir's adsorption isotherm. Two adsorption parameters, the adsorption equil...

  19. 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

  20. 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.

  1. Selective adsorption and separation of organic dyes from aqueous solution on polydopamine microspheres.

    Science.gov (United States)

    Fu, Jianwei; Xin, Qianqian; Wu, Xuechen; Chen, Zhonghui; Yan, Ya; Liu, Shujun; Wang, Minghuan; Xu, Qun

    2016-01-01

    Polydopamine (PDA) microspheres, synthesized by a facile oxidation polymerization route, were evaluated as a potential adsorbent for selective adsorption and separation of organic dyes. The adsorption processes towards nine water-soluble dyes (anionic dyes: methyl orange (MO), eosin-Y (EY), eosin-B (EB), acid chrome blue K (ACBK), neutral dye: neutral red (NR), and cationic dyes: rhodamine B (RhB), malachite green (MG), methylene blue (MB), safranine T (ST)) were thoroughly investigated. The adsorption selectivity of organic dyes onto PDA microspheres was successfully applied for the separation of dyes mixtures. Various influential factors such as solution pH, temperature, and contact time were employed to ascertain the optimal condition for adsorption of representative organic dyes including MB, MG and NR. The pseudo-first-order and pseudo-second-order kinetics models were used to fit the adsorption kinetics process. Five isothermal adsorption models (Langmuir, Dubnin-Radushkevich, Temkin, Freundlich and Harkins-Jura) were used to investigate the adsorption thermodynamics properties. The results showed that the PDA microspheres owned good selective adsorption ability towards cationic dyes. The adsorption kinetics process conformed to the pseudo-second-order kinetics model and the Langmuir isotherm model was more appropriate for tracing the adsorption behavior than other isotherm models. Thus, we can conclude PDA microspheres may be a high-efficiency selective adsorbent towards some cationic dyes.

  2. 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

  3. Adsorption-Induced Deformation of Mesoporous Solids

    CERN Document Server

    Gor, Gennady Yu

    2010-01-01

    The Derjaguin - Broekhoff - de Boer theory of capillary condensation is employed to describe deformation of mesoporous solids in the course of adsorption-desorption hysteretic cycles. We suggest a thermodynamic model, which relates the mechanical stress induced by adsorbed phase with the adsorption isotherm. Analytical expressions are derived for the dependence of the solvation pressure on the vapor pressure. The proposed method provides a semi-quantitative description of non-monotonic hysteretic deformation during capillary condensation without invoking any adjustable parameters. The method is showcased drawing on the examples of literature experimental data on adsorption deformation of porous glass and SBA-15 silica.

  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. 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

  7. 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).

  8. 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)

  9. 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.

  10. 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.

  11. 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.

  12. Adsorption of cationic surfactants on silica surface: 2. Comparison of theory with experiment

    NARCIS (Netherlands)

    Goloub, T.P.; Koopal, L.K.

    2004-01-01

    Possible application of the SCFA lattice model to describe the adsorption of ionic surfactants on the surface whose charge and potential can be changed under the effect of adsorbing surfactant was theoretically studied. Calculated isotherms of surfactant adsorption were compared with experimental ad

  13. Modification of porous starch for the adsorption of heavy metal ions from aqueous solution.

    Science.gov (United States)

    Ma, Xiaofei; Liu, Xueyuan; Anderson, Debbie P; Chang, Peter R

    2015-08-15

    Porous starch xanthate (PSX) and porous starch citrate (PSC) were prepared in anticipation of the attached xanthate and carboxylate groups respectively forming chelation and electrostatic interactions with heavy metal ions in the subsequent adsorption process. The lead(II) ion was selected as the model metal and its adsorption by PSX and PSC was characterized. The adsorption capacity was highly dependent on the carbon disulfide/starch and citric acid/starch mole ratios used during preparation. The adsorption behaviors of lead(II) ion on PSXs and PSCs fit both the pseudo-second-order kinetic model and the Langmuir isotherm model. The maximum adsorption capacity from the Langmuir isotherm equation reached 109.1 and 57.6 mg/g for PSX and PSC when preparation conditions were optimized, and the adsorption times were just 20 and 60 min, respectively. PSX and PSC may be used as effective adsorbents for removal of heavy metals from contaminated liquid. PMID:25794731

  14. Adsorption of Pb(Ⅱ) on Sediment of the Dianshan Lake:Adsorption Models and Kinetics%铅在淀山湖沉积物上的吸附模型及其动力学研究

    Institute of Scientific and Technical Information of China (English)

    黄莉桦; 孙为民

    2004-01-01

    The adsorption characteristics of Pb on sediments of the Dianshan Lake in Shanghai was studied. The results show that (1)the relationship between the amount q of apparent equilibrium adsorption and the equilibrium concentration C conforms to the Freundlich isothermal adsorption equation; (2) the adsorption and desorption of Pb on sediments are not reversible, that is, adsorption/desorption of Pb exhibits hysteresis; (3) Pb adsorption behavior is initially fast, followed by a slow reaction, and the slow reaction conforms to a reversible first-order reaction; (4) by deducing the Pb adsorption kinetics, four kinetics parameters n, k1, k2, qmax independent of C could be worked out; (5) the equilibrium parameter (K) and the free energy change (△G) could also be determined,and the negative values of free energy change (△G) indicate the spontaneous nature of the adsorption.

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

    Science.gov (United States)

    Kabiri, Maryam; Unsworth, Larry D

    2014-10-13

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

  16. 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).

  17. ADSORPTION OF PHENOL AND NITROPHENOLS ON A HYPERCROSSLINKED POLYMERIC ADSORBENT

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The adsorption of phenol and nitrophenols on hypercrosslinked polymeric adsorbent wasstudied as a function of the solution concentration and temperature. Adsorption isotherms of phenoland nitrophenols on hypercrosslinked resin were determined. These isotherms were modeledaccording to the Freundlich adsorption isotherm. The isotherms for phenol and nitrophenols onhypercrosslinked resin were assigned as L curves. Thermodynamic parameters were calculated for allphenol and nitrophenols. The kinetics experiment results showed that the adsorption rates were of thefirst-order kinetics. The rate constants at 303K were calculated.

  18. 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.

  19. Modeling lead adsorption on clays by models with and without electrostatic terms

    Energy Technology Data Exchange (ETDEWEB)

    Majone, M.; Papini, M.P.; Rolle, E. [Univ. of Rome La Sapienza (Italy)

    1996-05-10

    The research describes the adsorption of heavy metals (lead) on clay minerals (kaolinite) as function of different experimental conditions. The lead adsorption was investigated as function of pH and ionic strength at several initial lead concentrations. The adsorption of proton and sodium (obtained by titration curves and negative surface charge measurements, respectively) was also investigated as function of pH. All experimental variables were simultaneously accounted for by using the multivariate nonlinear regression of data, according to different models including or not including electrostatic interactions. The adsorption of lead, proton, and sodium on the clay was successfully described by a three-layer electrostatic model considering two discrete types of adsorption sites (with fixed and variable charge, respectively) and the additional effect of the heterogeneity of each site (in terms of continuous distribution of the affinity constants). Confident estimates were obtained for the site concentrations (adsorption maxima) and the heterogeneity parameters. The sites with fixed and variable charge were found to be 40 and 60% of the total, respectively. Both of them contribute to the lead adsorption in proportions which highly depend on the pH. The heterogeneity parameters of both sites have low values which underline the high influence of the continuous distribution of the affinity constants. The diffuse layer potential was also well estimated. It depends mainly on the ionic strength and it is quite different from the measured zeta potential (about one order of magnitude more negative). To consider simultaneously all experimental variables by a multivariate approach appeared to be very important for an accurate modeling. If only the lead adsorption was taken into account at a single ionic strength, the electrostatic effects could be neglected with no practical difference on the calculated behavior.

  20. 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.

  1. Solution of adsorption problems involving steep moving profiles

    DEFF Research Database (Denmark)

    Kiil, Søren; Bhatia, Suresh K.

    1998-01-01

    . Numerical solutions were found to match the analytical solution when it exists (i.e. when the adsorption isotherm is linear). Results of this application study show that the method is simple yet sufficiently accurate for use in adsorption problems with steep moving gradients, where global collocation......The moving finite element collocation method proposed by Kiil et al. (1995) for solution of problems with steep gradients is further developed to solve transient problems arising in the field of adsorption. The technique is applied to a model of adsorption in solids with bidisperse pore structures...

  2. 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.

  3. 基于热力学方法的煤岩吸附变形模型%A model of adsorption induced coal deformation based on thermodynamics approach

    Institute of Scientific and Technical Information of China (English)

    周军平; 鲜学福; 姜永东; 谷达圣; 王臣

    2011-01-01

    基于吸附过程的热动力学和能量守恒原理,建立了计算煤岩吸附气体引起的煤岩膨胀应变的理论模型,在获取煤岩对气体的吸附等温曲线的基础上,可通过模型得到煤岩吸附气体引起的吸附应变;利用已有的实验数据对模型的有效性进行了验证.结果表明,实验结果与模型预测的结果吻合较好,模型能够很好地描述煤岩吸附不同气体时产生的差异性膨胀现象;另外,模型可为预测CO2注入煤层后煤基质收缩/膨胀效应对储层渗透率的影响提供指导.%Based on the thermodynamics of adsorption and principal of energy balance, a theoretical model was developed to describe gas adsorption-induced coal deformation.This model was used to calculate the adsorption induced strain of coal through the gas adsorption isotherm,some experiment datas were used to validate the model.The results suggest that the model agrees well with experimental data of coal deformation induced by the gas adsorption, the model can describe the differential swelling phenomenon of coal caused by adsorption of different gas such as carbon dioxide,methane and nitrogen.Furthermore,this model provides a sound basis for estimating the dynamic change of coalbed permeability in response to swelling/shrinkage of coal matrix and can be applied to CO2-enhanced coalbed methane recovery and CO2 sequestration in deep,unminable coalbeds.

  4. Surface complexation modeling of the effects of phosphate on uranium(VI) adsorption

    Energy Technology Data Exchange (ETDEWEB)

    Romero-Gonzalez, M.R.; Cheng, T.; Barnett, M.O. [Auburn Univ., AL (United States). Dept. of Civil Engeneering; Roden, E.E. [Wisconsin Univ., Madison, WI (United States). Dept. of Geology and Geophysics

    2007-07-01

    Previous published data for the adsorption of U(VI) and/or phosphate onto amorphous Fe(III) oxides (hydrous ferric oxide, HFO) and crystalline Fe(III) oxides (goethite) was examined. These data were then used to test the ability of a commonly-used surface complexation model (SCM) to describe the adsorption of U(VI) and phosphate onto pure amorphous and crystalline Fe(III) oxides and synthetic goethite-coated sand, a surrogate for a natural Fe(III)-coated material, using the component additivity (CA) approach. Our modeling results show that this model was able to describe U(VI) adsorption onto both amorphous and crystalline Fe(III) oxides and also goethite-coated sand quite well in the absence of phosphate. However, because phosphate adsorption exhibits a stronger dependence on Fe(III) oxide type than U(VI) adsorption, we could not use this model to consistently describe phosphate adsorption onto both amorphous and crystalline Fe(III) oxides and goethite-coated sand. However, the effects of phosphate on U(VI) adsorption could be incorporated into the model to describe U(VI) adsorption to both amorphous and crystalline Fe(III) oxides and goethite-coated sand, at least for an initial approximation. These results illustrate both the potential and limitations of using surface complexation models developed from pure systems to describe metal/radionuclide adsorption under more complex conditions. (orig.)

  5. 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.

  6. Adsorption of Basic Brown and Chrysophenine from Water Solution by Magnesium Silicate Gel

    Directory of Open Access Journals (Sweden)

    Zhun Zhao

    2015-01-01

    Full Text Available Noncrystalline, high surface area magnesium silicate gel was successfully prepared by hydrothermal method. Such product was characterized by BET and XRD to determine surface area 576.4 m2·g−1, average pore width 2.76 nm, and amorphous surface. The adsorption behaviors of Basic Brown and Chrysophenine on magnesium silicate gel were investigated through changing initial concentration, adsorbent dosage, solution pH, contact time, and temperature. The experimental data was analyzed by the adsorption isotherms and kinetics. The results showed the adsorption progress was fast for Basic Brown, and the adsorption equilibrium was finished in 2 h, while the adsorption equilibrium of Chrysophenine was finished in 7 h. Freundlich isotherm model and second-order kinetic models described the adsorption process very well.

  7. 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.

  8. Adsorption of Geosmin and MIB on Activated Carbon Fibers-Single and Binary Solute System

    Energy Technology Data Exchange (ETDEWEB)

    Srinivasan, Rangesh; Sorial, George A., E-mail: george.sorial@uc.ed [University of Cincinnati, Department of Civil and Environmental Engineering (United States)

    2009-08-15

    The adsorption of two taste- and odor-causing compounds, namely MIB (2-methyl isoborneol-C{sub 11}H{sub 20}O) and geosmin (C{sub 12}H{sub 22}O) on activated carbon was investigated in this study. The impact of adsorbent pore size distribution on adsorption of MIB and geosmin was evaluated through single solute and multicomponent adsorption of these compounds on three types of activated carbon fibers (ACFs) and one granular activated carbon (GAC). The ACFs (ACC-15, ACC-20, and ACC-25) with different degrees of activation had narrow pore size distributions and specific critical pore diameters whereas the GAC (F-400) had a wider pore size distribution and lesser microporosity. The effect of the presence of natural organic matter (NOM) on MIB and geosmin adsorption was also studied for both the single solute and binary systems. The Myers equation was used to evaluate the single solute isotherms as it converges to Henry's law at low coverage and also serves as an input for predicting multicomponent adsorption. The single solute adsorption isotherms fit the Myers equation well and pore size distribution significantly influenced adsorption on the ACFs and GAC. The ideal adsorbed solute theory (IAST), which is a well-established thermodynamic model for multicomponent adsorption, was used to predict the binary adsorption of MIB and geosmin. The IAST predicted well the binary adsorption on the ACFs and GAC. Binary adsorption isotherms were also conducted in the presence of oxygen (oxic) and absence of oxygen (anoxic). There were no significant differences in the binary isotherm between the oxic and anoxic conditions, indicating that adsorption was purely through physical adsorption and no oligomerization was taking place. Binary adsorptions for the four adsorbents were also conducted in the presence of humic acid to determine the effect of NOM and to compare with IAST predictions. The presence of NOM interestingly resulted in deviation from IAST behavior in case of two

  9. ADSORPTION OF 2,4-DICHLOROBENZOXYACETIC ACID ONTO HYPERCROSSLINKED RESIN MODIFIED BY PHENOLIC HYDROXYL GROUP(AM-1)

    Institute of Scientific and Technical Information of China (English)

    Zheng-hao Fei; Jin-long Chen; Jian-guo Cai; Yu-ping Qiu; Ai-min Li; Quan-xing Zhang

    2004-01-01

    An experimental comparison of the adsorption properties of hypercrosslinked resin AM-1 modified by phenolic hydroxyl group with Amberlite XAD-4 toward 2,4-dichlorobenzoxyacetic acid was performed. This paper focuses on the static equilibrium adsorption behaviors and the adsorption thermodynamics. Two isotherm models were used to explain the results. It is seen that the Langmuir equation can give a perfect fit. The adsorption capacities from the different ranges of temperature, the adsorption enthalpy change value and the comparison of desorption conditions lead to the same conclusion that the adsorption of 2,4-dichlorobenzoxyacetic acid from water onto AM-1 is a type of physical and chemical transition.

  10. 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

  11. 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...

  12. 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.

  13. 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.

  14. Eu(III) adsorption on rutile:Batch experiments and modeling

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Eu(III) adsorption on rutile was investigated as a function of contact time,pH,ionic strength and Eu(III) concentration by using a batch experimental method.The effects of carbonate,sulfate,and phosphate were also studied.It was found that the kinetics of Eu(III) adsorption on rutile could be described by a pseudo-second-order model.The adsorption of Eu(III) on rutile is strongly pH-dependent,but relatively insensitive to ionic strength.A double layer model (DLM) with two inner-sphere Eu(III) surface complexes was applied to quantitatively interpret the adsorption of Eu(III) on rutile.There were no apparent effects of carbonate and sulfate on Eu(III) adsorption,whereas the presence of phosphate promoted Eu(III) adsorption on rutile.The surface complexes of Eu(III) on rutile were evidenced by X-ray photoelectron spectroscopy (XPS).

  15. Adsorption of cadmium from aqueous solutions by perlite.

    Science.gov (United States)

    Mathialagan, T; Viraraghavan, T

    2002-10-14

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

  16. Adsorption characteristics of Cu(II) and Pb(II) onto expanded perlite from aqueous solution.

    Science.gov (United States)

    Sari, Ahmet; Tuzen, Mustafa; Citak, Demirhan; Soylak, Mustafa

    2007-09-01

    The adsorption characteristics of Cu(II) and Pb(II) onto expanded perlite (EP) from aqueous solution were investigated with respect to the changes in pH of solution, adsorbent dosage, contact time and temperature of solution. For the adsorption of both metal ions, the Langmuir isotherm model fitted to equilibrium data better than the Freundlich isotherm model. Using the Langmuir model equation, the monolayer adsorption capacity of EP was found to be 8.62 and 13.39 mg/g for Cu(II) and Pb(II) ions, respectively. Dubinin-Radushkevich (D-R) isotherm model was also applied to the equilibrium data and the mean free energies of adsorption were found as 10.82 kJ/mol for Cu(II) and 9.12 kJ/mol for Pb(II) indicating that the adsorption of both metal ions onto EP was taken place by chemical ion-exchange. Thermodynamic functions, the change of free energy (DeltaG degrees ), enthalpy (DeltaH degrees ) and entropy (DeltaS degrees ) of adsorption were also calculated for each metal ions. These parameters showed that the adsorption of Cu(II) and Pb(II) ions onto EP was feasible, spontaneous and exothermic at 20-50 degrees C. Experimental data were also evaluated in terms of kinetic characteristics of adsorption and it was found that adsorption process for both metal ions followed well pseudo-second-order kinetics.

  17. 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'...

  18. 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.

  19. 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

  20. 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.

  1. 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...

  2. Adsorption-Desorption Characteristics of Chlorimuron-Ethyl in Soils

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The adsorption-desorption characteristics of chlorimuron-ethyl in soils were investigated to provide the basic data for evaluating the safety in field and the risk to water resource. The adsorption-desorption experiment was conducted by the batch equilibration and HPLC techniques; furthermore, data were analyzed with 5 mathematic models to describe the characteristics and mechanism of adsorption-desorption and translocation of the herbicide in soils. The results showed that the adsorption-desorption isotherms of chlorimuron-ethyl fitted for the Freundlich model well, and the physical reaction presents the main contribution during the adsorption-desorption process. The adsorption values (Kads-f) of chlorimuron-ethyl in 8 types of soil ranged from 0.798 to 6.891. The isotherms of 2# (Jiangxi clay) and 3# (Jiangxi sand loam)soils belong to the S-type curve, while the isotherms of another 6 type soils belong to the L-type isotherm. The results of desorption indicated that the hysteresis phenomena appeared during the desorption process, and the hysteresis coefficients(H) of the herbicides in 8 soils varied from 0.259-0.980. Furthermore, Kads-f and desorption values (Kdes-f) increased with the OM (%) and the clay content increasing, while the values decreased with the soils pH increasing. The H values decreased with the OM and the clay content increasing, and increased with the soils pH increasing. It can be concluded that the low adsorption abilities of chlorimuron-ethyl in test soils and un-reversible adsorption existed in the process, which will induce the great translocation of the herbicide after application in field. It can be transported to ground or groundwater causing risk to environments. The physical and chemical properties of soils, including the OM, the clay content, and the pH of soil were the dominating factors during the adsorption-desorption.

  3. 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

  4. 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。

  5. 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.

  6. Adsorption behaviors of acetaminophen onto sediment in the Weihe River, Shaanxi, China

    Institute of Scientific and Technical Information of China (English)

    Yue Zhao; Shengke Yang; Huihui Li; Di Wang

    2015-01-01

    abstract Adsorption behaviors of acetaminophen 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 (ΔG0), enthalpy change (ΔH0) and entropy change (ΔS0) 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 3.0–9.0, and decreased in solution pH 9.0–11.0. 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.

  7. 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…

  8. 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.

  9. 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.

  10. 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.

  11. Biosorptive uptake of Fe(2+), Cu(2+) and As(5+) by activated biochar derived from Colocasia esculenta: Isotherm, kinetics, thermodynamics, and cost estimation.

    Science.gov (United States)

    Banerjee, Soumya; Mukherjee, Shraboni; LaminKa-Ot, Augustine; Joshi, S R; Mandal, Tamal; Halder, Gopinath

    2016-09-01

    The adsorptive capability of superheated steam activated biochar (SSAB) produced from Colocasia esculenta was investigated for removal of Cu(2+), Fe(2+) and As(5+) from simulated coal mine wastewater. SSAB was characterized by scanning electron microscopy, Fourier transform infrared spectroscopy and Brunauer-Emmett-Teller analyser. Adsorption isotherm indicated monolayer adsorption which fitted best in Langmuir isotherm model. Thermodynamic study suggested the removal process to be exothermic, feasible and spontaneous in nature. Adsorption of Fe(2+), Cu(2+) and As(5+) on to SSAB was found to be governed by pseudo-second order kinetic model. Efficacy of SSAB in terms of metal desorption, regeneration and reusability for multiple cycles was studied. Regeneration of metal desorbed SSAB with 1 N sodium hydroxide maintained its effectiveness towards multiple metal adsorption cycles. Cost estimation of SSAB production substantiated its cost effectiveness as compared to commercially available activated carbon. Hence, SSAB could be a promising adsorbent for metal ions removal from aqueous solution.

  12. 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.

  13. 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.

  14. 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.

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

    Science.gov (United States)

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

    2015-11-01

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

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

    Science.gov (United States)

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

    2015-11-01

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

  17. Preparation of Adsorbent with Magnesium Sulfate and Straw Pulp Black Liquor and Its Phenol Adsorption Properties

    Institute of Scientific and Technical Information of China (English)

    GUO Lugang; WANG Haizeng

    2009-01-01

    A magnesia adsorbent was prepared from straw pulp black liquor and magnesium sulfate for the first time, and its adsorption of phenol from aqueous solution was examined. The characteristics of the adsorbent were tested through chemical analysis,surface analysis, X-ray diffraction and FT-IR spectroscopy. The effects of various factors, such as dose, adsorption time and adsorption temperature, on phenol adsorption behavior were studied. The results show that the adsorption processes can be fitted to the isotherm Langmuir model very well. It was found that the adsorption process was strongly influenced by temperature and the optimal temperature for phenol removal was 40 ℃. The optimum adsorption time was 10 min, and desorption would happen afterwards. Between the models of Langmuir and Freundlich, the adsorption process of phenol onto magnesia fitted the Langmuir equation better.

  18. 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.

  19. 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

  20. 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

  1. 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.

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

    Science.gov (United States)

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

    2014-10-01

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

  3. Applicable models for multi-component adsorption of dyes: A review

    Institute of Scientific and Technical Information of China (English)

    Babak Noroozi; George A.Sorial

    2013-01-01

    Adsorption is one of the several techniques that has been successfully used for dyes removal.Since most industrial colored effluents contain several components including dyes,having a strong knowledge about the scope of competitive adsorption process is a powerful key to design an appropriate system.This is mainly because of the complexity brought about by the increasing number of parameters needed for process description which complicates not only the process modeling but also the experimental data collection.A multicomponent adsorption model should be based on fundamental soundness,speed,and simplicity of calculation.For such systems,competition will change the adsorbent-adsorbate attractions.Thus,there is major concern to develop an accurate and reliable method to predict dye adsorption behavior in multi-component systems.This article covers topics such as the theory of dyes adsorption in multi-component systems along with applicable models according to the consistent theories presented by researchers.

  4. Adsorption of diethyl phthalate ester to clay minerals.

    Science.gov (United States)

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

    2015-01-01

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

  5. 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)

  6. 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

  7. 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

  8. 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...

  9. 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.

  10. Phase-field modeling of isothermal quasi-incompressible multicomponent liquids

    Science.gov (United States)

    Tóth, Gyula I.

    2016-09-01

    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 equations of continuum mechanics, 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. Next the general definition of incompressibility is given, which is taken into account in the derivation by using the Lagrange multiplier method. To validate the theory, the 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 (in case of a suitably constructed free energy functional) and (ii) can influence nonequilibrium pattern formation significantly.

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

    DEFF Research Database (Denmark)

    Rasmussen, Henrik Koblitz; Eriksson, Torbjörn Gerhard

    2005-01-01

    to the incoming molten plastic flow. Just before the flow-front of the melt reached the end of the inserts the polymer was frozen. The replicated PC and PS micro-structures were examined using a confocal laser scanning microscope. Uniaxial elongational viscosity and linear viscoelasticity were used...... 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......) melt. A round PC or PS plate with a thickness of 3 mm and a diameter of 59 mm was placed between and at the centre of two squared steel plate. The bottom plate is equipped with a microstructured nickel insert, positioned 46 mm from the middle of the steel plate. The insert contained 10 parallel...

  12. 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)

  13. 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

  14. 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

  15. Numerical Simulation of Temperature and Mixing Performances of Tri-screw Extruders with Non-isothermal Modeling

    Directory of Open Access Journals (Sweden)

    X.Z. Zhu

    2013-04-01

    Full Text Available Tri-screw extruders are new extrusion equipments for food and polymer processing. Especially, there is one special circumfluence exists in center region only at cross section. In this study, the 2D transient and non-isothermal modeling of a tri-screw extruder is established by using Finite Element Method (FEM with particle tracking technology to reduce the axial effects. The transient temperature and flow fields are calculated with a commercial code, Polyflow. Moreover, the effect of temperature rise due to viscous heating on the flow and mixing characteristics such as mixing index, segregation scale, mean and instantaneous time-averaged efficiency of mixing for the tri-screw extruder are carried out. The results show that in the special center region, the velocity and mixing index is small and viscosity and temperature are relatively big, indicating the poor mixing efficiency. When the heat transfers due to self-heating is considered, the dispersive mixing of the tri-screw extruder decreases, but the distributive mixing and stretching mixing efficiency all increase for the tri-screw extruder. In particular, the stretching effect of the fluid particles in the tri-screw extruder decreases due to the decrease of viscous dissipation when the non-isothermal model is employed.

  16. 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...

  17. 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 prob......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......-Radushkevich-Astakhov potentials and the potentials directly restored from experimental data by solving the inverse problem. Application of the latter potentials Clearly demonstrates the importance of the difference in adsorption capacities. However, the quality of prediction of binary adsorption is similar for both potentials...

  18. Adsorption of Carbon Dioxide on Activated Carbon

    Institute of Scientific and Technical Information of China (English)

    Bo Guo; Liping Chang; Kechang Xie

    2006-01-01

    The adsorption of CO2 on a raw activated carbon A and three modified activated carbon samples B, C, and D at temperatures ranging from 303 to 333 K and the thermodynamics of adsorption have been investigated using a vacuum adsorption apparatus in order to obtain more information about the effect of CO2 on removal of organic sulfur-containing compounds in industrial gases. The active ingredients impregnated in the carbon samples show significant influence on the adsorption for CO2 and its volumes adsorbed on modified carbon samples B, C, and D are all larger than that on the raw carbon sample A. On the other hand, the physical parameters such as surface area, pore volume, and micropore volume of carbon samples show no influence on the adsorbed amount of CO2. The Dubinin-Radushkevich (D-R) equation was the best model for fitting the adsorption data on carbon samples A and B, while the Freundlich equation was the best fit for the adsorption on carbon samples C and D. The isosteric heats of adsorption on carbon samples A, B, C, and D derived from the adsorption isotherms using the Clapeyron equation decreased slightly increasing surface loading. The heat of adsorption lay between 10.5 and 28.4 kJ/mol, with the carbon sample D having the highest value at all surface coverages that were studied. The observed entropy change associated with the adsorption for the carbon samples A, B, and C (above the surface coverage of 7 ml/g) was lower than the theoretical value for mobile adsorption. However, it was higher than the theoretical value for mobile adsorption but lower than the theoretical value for localized adsorption for carbon sample D.

  19. 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

  20. 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.

  1. 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)

  2. Fruit waste adsorbent for ammonia nitrogen removal from synthetic solution: Isotherms and kinetics

    Science.gov (United States)

    Zahrim, AY; Lija, Y.; Ricky, L. N. S.; Azreen, I.

    2016-06-01

    In this study, four types of watermelon rind (WR) adsorbents; fresh WR, modified WR with sodium hydroxide (NaOH), potassium hydroxide (KOH) and sulphuric acid (H2SO4) were used as a potential low-cost adsorbent to remove NH3-N from solution. The adsorption data were fitted with the adsorption isotherm and kinetic models to predict the mechanisms and kinetic characteristics of the adsorption process. The equilibrium data agreed well with Langmuir isotherm model with highest correlation (R2=1.00). As for kinetic modelling, the adsorption process follows pseudo-second order for all four types of adsorbents which has R2 value of 1.0 and calculated adsorption capacity, Qe of 1.2148mg/g. The calculated Qe for pseudo-second order has the smallest difference with the experimental Qe and thus suggest that this adsorption process is mainly governed by chemical process involving cations sharing or exchange between WR adsorbent and NH3-N in the solution.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. Thermodynamics and kinetics of cadmium adsorption onto oxidized granular activated carbon

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Cadmium sorption behavior of granular activated carbon oxidized with nitric acid was systematically studied by sets of the equilibrium and time-based experiments under various conditions. The cadmium adsorption capacity of oxidized granular activated carbon enlarged with an increase in pH, and reduced with an increase in ionic strength. Experimental data were evaluated to find out kinetic characteristics. Adsorption processes were found to follow pseudo-second order rate equation. Adsorption isotherms correlate well with the Langmuir isotherm model and the maximum sorption capacity of cadmium evaluated is 51.02 μmol/g. Thermodynamic parameters were calculated based on Van't Hoff equation. Equilibrium constant Kd was evaluated from Freundlich isotherm model constants, Langmuir isotherm model constants and isotherms, respectively. The average change of standard adsorption heat ΔHo is -25.29 kJ/mol. Negative ΔHo and ΔGo values indicate the adsorption process for cadmium onto the studied activated carbon is exothermic and spontaneous. The standard entropy ΔSo is also negative, which suggests a decrease in the freedom of the system.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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

  14. Modelling the crystal growth in highly undercooled alloy melts by non-isothermal phase-field method

    Institute of Scientific and Technical Information of China (English)

    Li Mei-E; Yang Gen-Cang; Zhou Yao-He

    2005-01-01

    A non-isothermal phase-field model is used to simulate the rapid solidification of highly undercooled alloy melts.The influence of undercooling on the solidification process is studied. It is indicated that with the increase of undercooling, the dendrite morphology changes from poorly developed dendrite, via the well-developed dendrite containing secondary and ternary arms, to the compact diamond-shaped grain. With increasing undercooling, the tip radius changes in the following rule: decrease → increase → decrease while the growth velocity increases constantly, which is consistent with the results predicted by the Boettinger-Coriell-Trivedi model. The thermal, solutal and kinetic undercooling contributions under different initial undercooling are also determined. It is shown that when the undercooling is increased beyond a certain value, the thermal undercooling contribution exceeds the solutal contribution and the dendrite growth transits from solutal diffusion controlled to thermal diffusion controlled one.

  15. An Experimental Study on the Adsorption Behavior of Gases Crossing the Critical Temperature%气体在临界温度附近吸附行为的实验研究

    Institute of Scientific and Technical Information of China (English)

    周理; 孙艳; 周亚平

    2002-01-01

    Adsorption equilibria of CH4 and N2 on activated carbon and silica gel were measured for a wide temperature range covering the critical point: 158-298 K for CH4, and 103-298 K for N2. The determination of the compressibility factor is shown to have considerable effect on isotherm behavior at conditions after the isotherm maximum. A change in adsorption mechanisms on crossing the critical temperature was observed in all cases.The kind of adsorbents and how far the equilibrium temperature to the critical one are major factors affecting the transition of isotherms from sub- to supercritical. All continuous isotherms can be modeled by a unique model for the supercritical region. The satisfactory fitting of the model to the experimental isotherms proved the reliability of the absolute adsorption determined by the proposed method.

  16. Removal of nitrobenzene from aqueous solution by a novel lipoid adsorption material (LAM)

    Energy Technology Data Exchange (ETDEWEB)

    Wen, Qinxue [State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology (SKLUWRE, HIT), Harbin 150090 (China); Chen, Zhiqiang, E-mail: czq0521@tom.com [State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology (SKLUWRE, HIT), Harbin 150090 (China); Lian, Jiaxiang; Feng, Yujie; Ren, Nanqi [State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology (SKLUWRE, HIT), Harbin 150090 (China)

    2012-03-30

    Highlights: Black-Right-Pointing-Pointer We synthesized a novel adsorbent-lipoid adsorption material (LAM). Black-Right-Pointing-Pointer We investigate the adsorption behavior isotherms of nitrobenzene on LAM. Black-Right-Pointing-Pointer We investigate the adsorption kinetics of nitrobenzene on LAM. Black-Right-Pointing-Pointer We proved that the reaction is spontaneous and is an exothermic reaction. Black-Right-Pointing-Pointer The removal efficiency of LAM was higher than that of GAC. - Abstract: In this study, a novel adsorbent referred to as a lipoid adsorption material (LAM) was synthesized with a hydrophobic nucleolus (triolein) and hydrophilic membrane structure (polyamide). The LAM was applied to the adsorption and removal of nitrobenzene from aqueous systems. Experiments were carried out to investigate the adsorption behavior of nitrobenzene on LAM, including the development of adsorption isotherms, the determination of adsorption kinetics, and to explore the influence of adsorbent dosage, contact time, temperature and the initial concentration of nitrobenzene on adsorption. The performance of LAM was compared with equal amounts of granular activated carbon (GAC) for adsorption. The adsorption isotherms for LAM were found to be described by the Linear equation, while the adsorption isotherms for granular activated carbon (GAC) were described by the Freundlich equation. Results indicated that the adsorption of nitrobenzene by LAM occurred mainly due to the partition function caused by the triolein nucleolus. Two kinetics models, pseudo-first-order and pseudo-second-order models were used to fit the experimental data for LAM adsorption. By comparing the correlation coefficients, it was found that the pseudo-first-order model was most suitable to describe the adsorption of nitrobenzene on LAM. The results also indicated that the factors that affect the adsorption rate would be either the nitrobenzene concentration or the character of the adsorbent

  17. Adsorption of Crystal Violet Dye onto Tamarind Seed Powder

    OpenAIRE

    Himanshu Patel; R. T. Vashi

    2010-01-01

    The present investigation describes adsorption of crystal violet dye from its aqueous solution onto tamarind (Tamarindus indica) fruit shell powder. Initial concentration, agitation speed and pH with various temperature have been studied, in which pH was found to be most effective. The adsorption data were mathematically analyzed using adsorption isotherm like Freundlich and Langmuir isotherm to study adsorption mechanism of crystal violet onto this seed powder. Freundlich isotherm was found ...

  18. 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.

  19. 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

  20. 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.

  1. 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.

  2. 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....

  3. Applicaiton of a Kinetic Multireaction Model for Studying Metolachlor Adsorption in Soil

    Institute of Scientific and Technical Information of China (English)

    ZHUHONGXIA; MALIWANG; 等

    1997-01-01

    Metolachlor retention on a Sharkey clay soil was quantified using a kinetic batch method for different initial solution concentrations.Time-dependent adsorption was carried out by monitoring solution concentration at different reaction times.Adsorption was kinetic multireaction model which includes reverible and irreversible retention processes of the equilibrium and kinetic types,The predictive capability of the model for the dexcription of experimental results for metolachlor retention was examined and proved to be adequate。

  4. 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.

  5. Branched pore kinetic model analysis of geosmin adsorption on super-powdered activated carbon.

    Science.gov (United States)

    Matsui, Yoshihiko; Ando, Naoya; Sasaki, Hiroshi; Matsushita, Taku; Ohno, Koichi

    2009-07-01

    Super-powdered activated carbon (S-PAC) is activated carbon of much finer particle size than powdered activated carbon (PAC). Geosmin is a naturally occurring taste and odor compound that impairs aesthetic quality in drinking water. Experiments on geosmin adsorption on S-PAC and PAC were conducted, and the results using adsorption kinetic models were analyzed. PAC pulverization, which produced the S-PAC, did not change geosmin adsorption capacity, and geosmin adsorption capacities did not differ between S-PAC and PAC. Geosmin adsorption kinetics, however, were much higher on S-PAC than on PAC. A solution to the branched pore kinetic model (BPKM) was developed, and experimental adsorption kinetic data were analyzed by BPKM and by a homogeneous surface diffusion model (HSDM). The HSDM describing the adsorption behavior of geosmin required different surface diffusivity values for S-PAC and PAC, which indicated a decrease in surface diffusivity apparently associated with activated carbon particle size. The BPKM, consisting of macropore diffusion followed by mass transfer from macropore to micropore, successfully described the batch adsorption kinetics on S-PAC and PAC with the same set of model parameter values, including surface diffusivity. The BPKM simulation clearly showed geosmin removal was improved as activated carbon particle size decreased. The simulation also implied that the rate-determining step in overall mass transfer shifted from intraparticle radial diffusion in macropores to local mass transfer from macropore to micropore. Sensitivity analysis showed that adsorptive removal of geosmin improved with decrease in activated carbon particle size down to 1microm, but further particle size reduction produced little improvement.

  6. 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.

  7. Heavy Metal Removal from Water by Adsorption Using Pillared Montmorillonite

    Institute of Scientific and Technical Information of China (English)

    LIU Yun; WU Pingxiao; DANG Zhi; YE Daiqi

    2006-01-01

    Removal of Cu2+, Cr3+ and Cd2+ from aqueous solutions by adsorption on montmorillonite modified by sodium dodecylsulfate (SDS) and hydroxy-alumino-silicate (HAS) was investigated.Experiments were carried out as a function of solution pH, solute concentration, and time. The Langmuir model was adopted to describe the single-solute adsorption isotherm, in which the Langmuir parameters were directly taken from those obtained in single-solute systems. The kinetics of metal ions adsorption was examined and the pseudo-first-order rate constant was finally evaluated.

  8. 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

  9. Particle concentration effect in adsorption/desorption of Zn(II) on anatase type nano TiO2

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Adsorption/desorption in a new Zn(II)-TiO2 adsorption system was investigated at different particle concentrations (Cp). TEM, SEM and XRD analyses revealed that the TiO2 particles were an aggregation of nano-sized (approximately 10 nm) pure anatase-type TiO2. Adsorption experiments were carried out with particle concentrations of 100, 400 and 1000 mg/L, and their adsorption isotherms were found to decline successively, showing an obvious Cp effect. Desorption experiments indicated that adsorption in this system was irreversible, and the irreversibility increased with increasing Cp. These phenomena could be explained by the MEA (metastable equilibrium adsorption) theory and the Cp effect could be modeled well with an MEA-Freundlich-type Cp effect isotherm equation. This study may help understand environmental behavior of contaminants on ultrafine natural particles.

  10. 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

  11. 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.

  12. Dynamic Adsorption/Desorption Process Model of Capacitive Deionization

    NARCIS (Netherlands)

    Biesheuvel, P.M.; Limpt, van B.; Wal, van der A.

    2009-01-01

    In capacitive deionization (CDI), an electrical potential difference is applied across oppositely placed electrodes, resulting in the adsorption of ions from aqueous solution and a partially ion-depleted product stream. CDI is a dynamic process which operates in a sequential mode; i.e., after a cert

  13. 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.

  14. 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.

  15. Removal of Cr(VI) from aqueous solution by adsorption onto activated carbon.

    Science.gov (United States)

    Selvi, K; Pattabhi, S; Kadirvelu, K

    2001-10-01

    Activated carbon (AC) prepared from coconut tree sawdust was used as an adsorbent for the removal of Cr(VI) from aqueous solution. Batch mode adsorption studies were carried out by varying agitation time, initial Cr(VI) concentration, carbon concentration and pH. Langmuir and Freundlich adsorption isotherms were applied to model the adsorption data. Adsorption capacity was calculated from the Langmuir isotherm and was 3.46 mg/g at an initial pH of 3.0 for the particle size 125-250 microm. The adsorption of Cr(VI) was pH dependent and maximum removal was observed in the acidic pH range. Desorption studies were carried out using 0.01-1 M NaOH solutions.

  16. 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

  17. 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.

  18. 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.

  19. 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).

  20. 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.