Prediction Of Multicomponent Adsorption Equilibria Research Articles

Experimental and modeling investigation of adsorption equilibrium of CH4, CO2, and N2 on activated carbon and prediction of multi-component adsorption equilibrium

In this study, the equilibrium adsorption isotherms of N2, CH4 and CO2 on two types of activated carbon adsorbents were measured. The experimental data of the equilibrium adsorption were fitted to the Sips isotherm model at different temperatures. It was found that the Sips model is appropriate to predict the behavior of gas adsorption. Moreover, a method based on the Gibbs energy of desorption of the solid adsorbent was used to estimate the amount of separation factor of binary mixtures at different temperatures. Also, the amount of gas adsorption on activated carbon was predicted by using the artificial neural network-genetic algorithm (ANN-GA) model. The results of the ANN-GA model indicated that the performance of the model for predicting the behavior of gas adsorption is acceptable. Finally, the extended Sips model was used to simulate the multi-component adsorption of three binary mixtures CO2/N2, CH4/N2 and CO2/CH4, and the results of this model were validated by experimental data.

A generalized procedure for the prediction of multicomponent adsorption equilibria

Prediction of multicomponent adsorption equilibria has been investigated for several decades. While there are theories available to predict the adsorption behavior of ideal mixtures, there are few purely predictive theories to account for nonidealities in real systems. Most models available for dealing with nonidealities contain interaction parameters that must be obtained through correlation with binary‐mixture data. However, as the number of components in a system grows, the number of parameters needed to be obtained increases exponentially. Here, a generalized procedure is proposed, as an extension of the predictive real adsorbed solution theory, for determining the parameters of any activity model, for any number of components, without correlation. This procedure is then combined with the adsorbed solution theory to predict the adsorption behavior of mixtures. As this method can be applied to any isotherm model and any activity model, it is referred to as the generalized predictive adsorbed solution theory. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2600–2610, 2015

Use of Adsorbed Solution theory to model competitive and co-operative sorption on elastic ion exchange resins

An Adsorbed Solution theory which takes into account non-idealities in both the adsorbed and the liquid phase was applied for the prediction of multi-component adsorption equilibria based on single component and binary mixture data. A novel non-iterative solution method was applied for the solution of the set of partly implicit model equations. The Pitzer activity coefficient model was used for the liquid phase and an empirical model for the adsorbed phase activity coefficients. Separation of concentrated acid lignocellulosic hydrolysates on an elastic strong acid cation exchange resin was used as a test system. The application is relevant in biorefineries when polysaccharides in wood are hydrolyzed to monosaccharides using concentrated sulfuric acid.It was found that the novel solution method for the equilibrium model can be applied successfully for complex multi-component systems; it is fast and easy to implement. The predictions of the thermodynamic model were validated with dynamic column experiments (pulse injections and loading/elution curves). Hereby, in the column mass balances, porosity fluctuations were taken explicitly into account. Satisfactory correlation between the calculated and experimental results was obtained. It was observed that the predictions of the model can be quite sensitive with respect to even minor inaccuracies in the calculated multi-component adsorption isotherms.

Adsorption of CO2, CH4, and N2in Activated Carbon Honeycomb Monolith

Biomethane generated from renewable sources can be used as a renewable fuel to achieve ambitious targets for biofuels. The development of adsorption-based technologies for purification of biogas requires knowledge of adsorption equilibria and kinetics of pure gases on a specific adsorbent material. In this work, we have measured adsorption equilibria of CO2, CH4, and N2 at (299, 323, 348, 373, and 423) K over a pressure range between (0 and 700) kPa on a carbon honeycomb monolith. The adsorption capacity of the activated carbon honeycomb monolith was CO2 > CH4 > N2. The multisite Langmuir model was employed to fit the data of the pure gases offering the possibility of direct prediction of multicomponent adsorption equilibria. The diffusion of single gases in the microporous structure of the activated carbon honeycomb monolith was studied by diluted breakthrough experiments. The experiments were performed over the same temperature range [(303 to 423) K]. A simplified 1D mathematical model was employed in t...

Measurement and prediction of adsorption equilibrium for a H2/N2/CH4/CO2 mixture

AbstractAdsorption equilibrium data for the pure gases, H2, N2, CH4, CO2, and a H2/N2/CH4/CO2 mixture on activated carbon JX101 were collected by static and dynamic methods, respectively. The tested range covered temperatures of 283–328 K and pressures up to 30 × 105 Pa. The difference in the adsorption mechanisms between the super‐ and sub‐critical components was considered for both correlation of pure gas adsorption and prediction of multicomponent adsorption equilibrium. The surface heterogeneity, interaction among the adsorbed molecules, and the non‐ideal behavior of the adsorbed phase were also accounted for. As a consequence, the pure gas adsorption data were accurately correlated, and the multicomponent adsorption equilibrium was satisfactorily predicted by a proposed model. Applicability of the new model was verified with the present experimental data and with literature values. In all cases, the new model produced better agreement between the predicted data and the experimentally measured data than previous models. This indicates that the new model is probably applicable to predict the adsorption equilibrium of gas mixtures either partially or totally composed of supercritical gases. © 2007 American Institute of Chemical Engineers AIChE J, 2007

Prediction of Adsorption of Nonideal Mixtures in Nanoporous Materials

The prediction of multicomponent adsorption equilibria from single-component adsorption experiments is a challenging and important problem. Predictions based upon the assumption of an ideal adsorbed solution (IAS) may give unacceptable errors, especially in the case of large differences in the size or the polarity of the adsorbate molecules. These differences in molecular properties generate differences in the chemical potential of the solid (ψ) that may be used to predict activity coefficients for nonideal adsorbed solutions (NIAS). The ψ plots for pure-gas isotherms identify ideal solutions and provide reliable predictions of mixture equilibria for nonideal adsorbed solutions.

Prediction of multicomponent adsorption equilibrium of gas mixtures including supercritical components

A new model to predict the adsorption equilibrium of mixtures containing supercritical components was presented. The difference in the adsorption mechanism between the supercritical components and the condensable components was accounted for in the new model. Lateral interaction in the adsorbed phase was also considered in the local isotherm. The new model was verified by the experimental data of the mixture CH 4/CO 2/C 2H 6 on activated carbon JX101 collected for 283–313 K and pressures up to 10 × 10 5 Pa . It was also verified with the experimental data published previously in literature. Considerable improvement in the prediction precision was achieved in using the new model to predict the adsorption of mixtures on activated carbon.

Theoretical Description of the Calorimetric Effects Accompanying the Mixed-Gas Adsorption Equilibria by Using the Ideal Adsorbed Solution Theory

The theoretical prediction of multicomponent adsorption equilibria from the single-component data is one of the most important problems in adsorption. The possibilities of the ideal adsorbed solution approach to study enthalpic effects accompanying the mixed-gas adsorption equilibria are presented. The obtained theoretical expressions for predicting isosteric heats of adsorption in a gas mixture are relatively simple and accurate. To predict phase diagrams and calorimetric effects in the mixed-gas adsorption, only the knowledge of single-gas adsorption isotherms and accompanying calorimetric effects is required.

Use of liquid phase adsorption for characterizing pore network connectivity in activated carbon

A simple percolation theory-based method for determination of the pore network connectivity using liquid phase adsorption isotherm data combined with a density functional theory (DFT)-based pore size distribution is presented in this article. The liquid phase adsorption experiments have been performed using eight different esters as adsorbates and microporous-mesoporous activated carbons Filtrasorb-400, Norit ROW 0.8 and Norit ROX 0.8 as adsorbents. The density functional theory (DFT)-based pore size distributions of the carbons were obtained using DFT analysis of argon adsorption data. The mean micropore network coordination numbers, Z, of the carbons were determined based on DR characteristic plots and fitted saturation capacities using percolation theory. Based on this method, the critical molecular sizes of the model compounds used in this study were also obtained. The incorporation of percolation concepts in the prediction of multicomponent adsorption equilibria is also investigated, and found to improve the performance of the ideal adsorbed solution theory (IAST) model for the large molecules utilized in this study.

Mixed‐gas adsorption

AbstractThe prediction of multicomponent adsorption equilibria from single‐component data is one of the most challenging and important problems in adsorption. The chief obstacle to progress is a scarcity of accurate and consistent experimental data over a wide range of temperature and loading for testing theories. Several binaries and one ternary system on two types of zeolites (silicalite and faujasite) were studied in a combination calorimeter‐volumetric apparatus. Activity coefficients and excess functions for enthalpy, free energy, and entropy were extracted from the binary data using a three‐constant equation to represent nonidealities. The successful correlation of binary excess functions with pure‐component properties for type I isotherms on zeolites is a first step toward predicting multicomponent adsorption from single‐gas adsorption and a major advancement over the theory of ideal adsorbed solutions.

Thermodynamic modeling of binary and ternary adsorption on silica gel

AbstractQualitative and quantitative characterization and prediction of multicomponent adsorption equilibria are essential for design of environmental remediation processes such as soil vapor extraction, bioventing, and thermal desorption. Single component, binary‐ and ternary‐mixture isotherms on silica gel were measured by the frontal analysis chromatography technique. Binary organic mixtures were composed of environmentally relevant VOCs, hexane/benzene (nonpolar/nonpolar), and hexane/trichloroethylene (nonpolar/slightly‐polar). Water binaries were water with hexane, benzene, or trichloethylene. Organic mixtures exhibited enhanced adsorption, where the adsorbed amount for each component was increased due to the second component. Water/hexane and water/benzene mixtures showed noncompetitive adsorption, where water adsorbed onto polar sites and n‐hexane or benzene adsorbed onto nonpolar sites. Competition for polar adsorption sites was observed for the trichloroethylene adsorption in water. Adsorption data of n‐hexane/benzene/water showed that n‐hexane and water were independently adsorbing onto different adsorption sites. Furthermore, n‐hexane and benzene with water showed the same adsorption behavior as without water. For the mixture of n‐hexane/trichloroethylene/water, only the amount of water adsorbed was reduced compared to the pure species adsorption of water. The adsorption equilibria of n‐hexane and trichloroethylene were not influenced in comparison to their pure species isotherms. Mixture isotherms were modeled with IAST, MSAM, and RAST. The nonideal adsorbed phase was characterized using activity coefficients.

On the performance of HIAST and IAST in the prediction of multicomponent adsorption equilibria

Abstract The performance of the heterogenous ideal absorbed solution theory (HIAST) using a uniform energy distribution and the global ideal adsorbed solution theory (IAST) is studied on their predictability f multicomponent adsorption equilibria along with experimental data of gases on two activated carbons. Results show that HIAST may not always provide better predictability than IAST if the energy distribution parameters are not properly chosen, although it is reported in the literature that in most cases HIAST is superior to IAST.

Application of IAST in the Prediction of Multicomponent Adsorption Equilibrium of Gases in Heterogeneous Solids: Micropore Size Distribution versus Energy Distribution

This article investigates the effect of surface heterogeneity and energy-matching scheme on the prediction of adsorption equilibria on activated carbon. The ideal adsorbed solution theory (IAST) is employed to evaluate the local adsorption equilibria on each energy site while the energetic heterogeneity of the system is represented by two forms: (1) uniform energy distribution, which employs the cumulative energy scheme to match different adsorbates in the adsorbed phase; and (2) micropore size distribution, which invokes the adsorbate-pore interaction matching scheme. The adsorption equilibria of hydrocarbon gas mixtures measured on two commercial activated carbons are used to compare the two models. It is found that uniform energy distribution can be insufficient in the prediction of multicomponent adsorption equilibria. On the other hand, the model assuming micropore size distribution as adsorption energetic heterogeneity and the adsorbate-pore interaction energy-matching scheme presents relatively stable prediction results.

New Model That Describes Adsorption of Laterally Interacting Gas Mixtures on Random Heterogeneous Surfaces. 2. Correlation of Complex Binary and Prediction of Multicomponent Adsorption Equilibria

The model developed in part 1 of this series for correlating single component and rather ideal binary adsorption equilibria demonstrated a remarkable ability for correlating complex binary adsorption equilibria, including adsorption azeotropes and sigmoidal-shaped x−y diagrams, using a single binary fitting parameter. This model was also extended successfully for predicting multicomponent adsorption equilibria on a heterogeneous adsorbent surface with a uniform distribution of Henry's law constant using single component adsorption isotherm parameters, along with one binary fitting parameter from each of the binary pairs in the multicomponent mixture. Overall, the results from this new model generally showed a marked improvement in the correlation of binary and prediction of multicomponent adsorption equilibria compared to that obtained with the multicomponent Langmuir model, which used only single component isotherm parameters, and compared to that obtained with two-dimensional fluid and loading ratio correlation models that also utilized binary fitting parameters.

Quaternary adsorption equilibria from aqueous systems onto decolourizing activated carbon

An experimental study has been conducted to obtain the adsorption isotherms of four typical pollutants from quaternary aqueous systems onto decolourizing activated carbon. The four materials investigated are: Phenol, 1,4-dihydroxybenzene, 4-amino-l-naphthalene sulfonic acid-sodium salt and Benzoic acid. The study has concentrated on the dilute region of concentrations which range from 10 to 165 ppm (mg/L) at an operating temperature of 30 °C. The quaternary adsorption equilibria have been modeled using the extended Langmuir predictive model and the ideal adsorbed solution (IAS) theory. In employing these models for the prediction of multicomponent adsorption equilibria, the single-solute isotherms are needed. These isotherms have been fitted to Langmuir, Freundlich, and Dubinin models and the resulting model parameters, which are needed for the prediction of multicomponent adsorption equilibria, are reported. Predictions obtained from the extended Langmuir predictive model and the ideal adsorbed solution (IAS) model are in agreement, however, they deviate to an appreciable extent from experimental observations.

Single-Component and Binary-Mixture Adsorption of Volatile Organic Contaminants on Silica Gel

Qualitative and quantitative characterization and prediction of multicomponent adsorption equilibria are essential for design of remediation processes such as soil vapor extraction, bioventing, and thermal desorption. The effects of physical properties of volatile organic components (VOCs) on adsorption equilibria were investigated by measuring single-component and binary-mixture adsorption isotherms on a polar adsorbent, silica gel, employing the frontal analysis chromatography technique. The binary mixtures were n-hexane/benzene (nonpolar/nonpolar), n-hexane/trichloroethylene (nonpolar/slightly polar), and chloroform/chlorobenzene (polar/polar). The adsorption isotherms for the single components were BET type II isotherms, indicating physical multilayer adsorption. The monolayer uptake increased with the increasing polarity of the components. The adsorption isotherms of the binary mixtures of n-hexane/benzene and n-hexane/trichloroethylene were BET-type II. For the chloroform/chlorobenzene mixture BET type III isotherms were observed. The coadsorption of the second adsorbate increased the uptake of the other adsorbate in all cases. Potential theory, the ideal adsorbed solution theory (IAS), and the multispace adsorbed solution model (MSAM) were used for the prediction of binary component isotherms from pure component isotherm data. Key words: Multicomponent adsorption equilibria; volatile organic contaminants; silica gel

Prediction of Multicomponent Adsorption Equilibrium Using a New Model of Adsorbed Phase Nonuniformity

We discuss the origin of adsorbed-phase nonuniformity and its implications for the prediction of a multicomponent adsorption equilibrium in microporous adsorbents. Current treatments of adsorbed phase nonuniformity are reviewed and a new model, the multispace adsorption model (MSAM), is presented. The MSAM multicomponent predictions have as inputs the pure-species adsorption isotherms and a single parameter characteristic of the adsorbent. We extend the original formulation of the model to include the temperature dependence of the parameters. Our model's performance is compared with that of the other thermodynamic models for multicomponent adsorption using our own experimental results and the literature data.

Theory for multicomponent adsorption equilibrium: Multispace adsorption model

AbstractA new theory for the prediction of multicomponent adsorption equilibrium in non‐crystalline porous solids is presented: the multispace adsorption model (MSAM). This theory allows for the inherent nonuniformity of the adsorbed phase by describing separately the adsorption in “spaces” close to, and far from, the adsorbent surface. The inputs to the calculation are the pure‐species adsorption isotherms and a single parameter characteristic of the adsorbent that can be obtained from very limited mixture data. We evaluate the theory by predicting multicomponent adsorption for a range of carbon adsorbents, making use of our own experimental results and literature data. The MSAM gives quantitative predictions for all the systems studied.

Vapor Phase Adsorption Equilibria of Toluene + 1-Propanol Mixtures on Y-Zeolites with Different Silicon to Aluminum Ratios

Zeolites with various silicon to aluminum ratios usually exhibit polar and nonpolar adsorption behavior depending on the degree of dealumination. The objective of the present study was to show the influence of the surface polarity on the adsorbate phase composition containing a polar and a nonpolar component: toluene and 1-propanol, respectively. Such systematic investigations should help to understand the significance of some adsorbent parameters, such as the surface heterogeneity. This basic knowledge is important for the development of improved models for the prediction of multicomponent adsorption equilibria.

MULTT-COMPONENT ADSORPTION OF ASPHALT FUNCTIONALITIES ON SILICA

ABSTRACT Single- and multi-component adsorption of compounds representing highly polar functional groups in asphalt onto SI-1000 silica has been performed at 25 °C using cyclohexane as a solvent. The asphalt functionalities used are benzoic acid (strong acid), 1-naphthol (weak acid), phenanthridine (strong base), and phenyisulfoxide (weak base). The bi-, tri-, and quadh-component adsorption behaviors demonstrated that the competitive adsorptive affinities of the asphalt functionalities for the silica are ranked as 1-naphthol < benzoic acid » phenanthridine < phenyisulfoxide. The prediction of multi-component adsorption equilibria has been made by applying the Langmuir Competitive Model (LCM) and the Ideal Adsorbed Solution Theory (LAST) to single-component adsorption data. Both the LCM and the LAST provided a good prediction for benzoic acid/1-naphthol and phenanthridine/phenyisulfoxide combinations. In the cases that involved acid-base combinations, however, both the LCM and the LAST yielded predictions ...