Multicomponent Adsorption Systems Research Articles

Binary Adsorption Isotherms of Water and Ethyl Acetate Vapor for Materials Contained in a Box of a Tobacco Product

ABSTRACT An experimental study has been carried out on the characteristics of binary adsorption isotherms of water and volatile flavor for typical materials used in a box of a tobacco product or cigarettes. Ethyl acetate chosen as a model for water–soluble volatile flavor. Binary adsorption isotherms for the tobacco, papers, filters, and activated carbons were measured with a flow–type multi–component adsorption system under the canstant conditions of temperature a t 303 K and vapor pressure of water a t 2.5 kPain the vapor pressure range of ethyl acetate from 0 to 4.2 kPa. A linear equation was applied to express the binary adsorption isotherms for the tobacco, papers and filters, while a Dubinin–Astakhov equation was applied for the activated carbons. The binary adsorption was characterized into three groups, depending on the selectivity as well as the mechanism of adsorption; i.e.(l) for tobacco and papers, water was adsorbed much greater rather than ethyl acetate, (2) for filters, ethyl acetate was ad...

Experimental determination of the binary equilibrium adsorption and desorption of propane-propylene mixtures on 13X molecular sieves by a differential sorption bed system and investigation of their equilibrium expressions

The experimental adsorption and desorption equilibrium data for propane, propylene, and propane-propylene mixtures on 13X molecular sieves are presented for different temperatures and compositions; these data were efficiently determined by using the differential sorption bed system described by Liapis et al. (Sep. Technol. 1992, 2, 141–154). The Toth equation was found to correlate with the experimental equilibrium single-component data very well. For the binary propane-propylene mixtures, propylene is the most preferentially adsorbed component. The feasibility of describing the experimental binary equilibrium data with the ideal adsorbed solution expressions, the heterogeneous ideal adsorbed solution expressions and the heterogeneous ideal adsorbed solution with specific gas-solid interactions expressions was examined. Comparison between these expressions and the experimental binary equilibrium data showed that none of the expressions could satisfactorily describe the experimental results for the binary mixtures for all temperatures and compositions studied in this work. For a given multicomponent adsorption system of interest, numerous sets of experimental equilibrium data of adsorption and desorption could be efficiently and accurately determined by using the differential sorption bed system and the experimental procedures described in this work; these results could be used in parameter estimation and model discrimination studies, as well as in process design.

Adsorption of phenols in a fixed-bed adsorber charged with polymeric sorbents

Adsorption of phenols onto a polymeric sorbent, SP206, was carried out in a fixed-bed adsorber and the saturated bed was regenerated by using 0.05 N sodium hydroxide solution to get information for a cyclic adsorption process as an alternative for the activated carbon process. Furthermore, a simple dynamic model for simulating the dynamic behavior of multicomponent adsorption systems was proposed based on both the ideal adsorbed solution theory (IAST) for multicomponent equilibria and the linear driving force approximation (LDFA) for intraparticle mass transport. In spite of its simplicity, the proposed dynamic model successfully simulated breakthrough curves up to a three-species mixture.

The interaction between organics and metal complexes in adsorption columns

The literature on the design of columns used for the adsorption of organics from waste-water is quite substantial. Many principles associated with the design of such columns can be applied in the design of adsorption columns for metal complexes. This study reports on the interaction between organics and dissolved metals in a column using activated carbon or ion-exchange resin as an absorbent. It will be shown here that many long-chain organics do not affect the equilibrium of adsorption of metal complexes, but have a profound effect on the kinetics of uptake of metal complexes. The kinetics of adsorption were described by a dual-rate kinetic model which was developed for a multi-component adsorption system. Furthermore, the intraparticle diffusivity which was associated with pore-blocking, decreased with an increase in the molecular mass of the organic species. In the case of the simultaneous adsorption between a metal cyanide and organic species, the Freundlich-type multi-component isotherm was found to be adequate to describe the equilibrium adsorption. A parametric sensitivity analysis was performed on the adsorption system to demonstrate the model flexibility for different operating conditions. Backmixing in the column seemed to be of minor importance.

Biospecific adsorption in fixed and periodic countercurrent beds

A mathematical model that describes the adsorption and wash stages of biospecific adsorption (affinity chromatography) in a packed column is presented. The model expressions account for film and pre diffusion mass transfer as well as for different mechanisms of interaction between the adsorbate(s) and the ligand. The model equations may be applicable to single and multi-component biospecific adsorption systems involving both monovalent and multivalent adsorbates.The results obtained from model simulations show that the breakthrough time of the adsorbate is significantly influenced by the rate of the interaction step between the adsorbate and the ligand. The results indicate that when short beds are employed, then the choice of ligand with respect to its rate of interaction with the adsorbate may be of paramount importance. In certain systems involving bivalent adsorbates, the adsorbate may be displaced from the one-site complex, reenter the flowing fluid stream, and increase the effluent adsorbate concentration above its inlet value. It is also shown that when a single column is divided into two beds operating in a periodic counter current mode, the ligand utilization can be almost four times higher than that obtained in a column of the same length operating in the fixed bed mode.The studies on the wash stage indicate that the reduction of the concentration of the contaminant to a specified low level may be accomplished for certain systems in a shorter time, if the direction of flow in the wash stage is opposite to that used in the adsorption stage. However, a larger amount of product will be lost, in general, when the direction of flow of the washing medium is opposite to that employed during the adsorption stage.

Multicomponent adsorption equilibria of phenols on activated carbon

Multicomponent adsorption equilibria of phenols on activated carbon were predicted by the ideal adsorbed solution (IAS) theory and results were compared with those calculated from two different Freundlich-type isotherms. Although some deviations between measured and calculated results are observed, the IAS theory permits rapid and relatively accurate predictions of adsorption equilibria for two-and three-component systems comparing with other isotherms. The results obtained show that the IAS theory is quite suitable for the extended application to multicomponent adsorption systems.

Parametric Sensitivity Study of Multicomponent Adsorption in Agitated Tanks

Abstract A comprehensive computer study of the most important physical, chemical; and geometric parameters on which the design of any multicomponent adsorption system relies was performed. In the analysis, the sensitivity of an adsorption model with respect to the model parameters was evaluated. The mathematical model utilized was developed by Mansour. The model takes into account internal and external diffusional resistances, and film resistance. The equilibrium between liquid and solid phases was described by a nonlinear Fritz-Schluender isotherm. The theoretical transient bath concentration profiles were obtained for the cases of adsorption of single, binary, and ternary systems. The numerical solution for the binary solute system was found to be in a very good agreement with previously published experimental results. The parametric study was applied to a binary solute system which has been shown to match corresponding experimental results. The parameters studied were: effect of competitive adsorption,...

Adsorption des acides humiques sur charbon active en poudre. Influence du triphosphate de sodium

The use of activated carbon beds for the removal of natural humic and fulvic substances found in water supplies, has recently received considerable attention in water treatment operation (Lee et al., 1980; Le Cloirec et al., 1983). Moreover, the use of carbon adsorption for the reduction of haloform precursors (Anderson et al., 1981) and trihalomethanes produced by chlorination process, has contributed to a comprehensive investigation of adsorption characteristics of natural organic compounds (McCreary and Snoeyink, 1981). Many recent works showed the influence of adsorption system characteristics, such as pH, salt type, salt concentration and ionic heterogeneity in multicomponent adsorption systems, on the removal efficiency of humic and fulvic substances by activated carbon (McCreary and Snoeyink, 1980; Randtke and Jepsen, 1982; Weber et al., 1983). The purpose of this study is to examine the effect of a main component of domestic detergents, sodium triphosphate (STP), on the adsorptive capacities of powdered activated carbon (PAC) for commercially supplied humic acids, at different pH values in distilled water. Also, the effect of STP concentration and pH on the adsorption affinity of the PAC for humic acids, is discussed in relation with electrokinetic properties of carbon particles (zeta potential measurements). A first batch equilibrium study (Figs 1 and 2), showed an effective enhancement of adsorption capacity for humic acids as a function of STP concentration, in a non buffered media (pH of distilled water, close to 5.0). For example, visible absorption analysis of humic acids indicates an increase of 93% (500 mg l −1 PAC) and 133% (1000 mg l −1 PAC) in the carbon adsorption efficiency for a STP concentration from 0.2 to 1.0mM. A second batch equilibrium study (Figs 3 and 4) led to adsorption isotherms for humic acids in distilled water, as a function of STP concentration and initial pH value of the non buffered multicomponent system. Freundlich isotherms showed an increase in the adsorption capacity of the PAC for humic acids, with a decrease in pH and an increase in STP concentration. However, the adsorption capacity for humic acids is quite reduced at high pH values in presence of STP, in comparison with results obtained with distilled water. Electrokinetic measurements on PAC suspensions (Fig. 5) indicates that both humic acids and STP induce a negative variation of the zeta potential of carbon particles. In such a binary system, the zeta potential is a linear function of the pH; the negative surface charge of the carbon increasing with an elevation of pH (Fig. 6). Therefore, it appears that some adsorption of triphosphate polyanion from solution could occur, contributing then to the apparent negative surface charge of PAC particles. It has been previously showed that the type of anion in sodium salts, had little effect on the enhancement of adsorptive capacities of activated carbon for humic substances (Lafrance and Mazet, 1985), due to Na + ions. However, adsorption of TP anions on the carbon surface may produce a source of repulsive charges, unfavourable to the co-adsorption of humic acids as the pH of the binary system reach more basic conditions. The influence of possible electrostatic interactions between adsorbates at the carbon surface, on the adsorption efficiency for humic acids, could then be studied by zeta potential measurements of PAC particles during the adsorption process.

Adsorption of multicomponent liquid mixtures on heterogeneous surfaces: Analysis of experimental data, measured at constant ratios of mole fractions of components in the bulk phase

On the basis of generalized integral equations, the adsorption from multicomponent ideal mixtures on heterogeneous solid surfaces has been discussed. Equations describing multicomponent liquid adsorption systems have been derived by assuming that (i) the adsorption data are measured by preserving constancy of the chosen ratios of mole fractions of the components in the bulk phase, and (ii) the heterogeneity parameters characterizing the adsorption of selected binary liquid mixtures are approximately equal. The equations were tested for three adsorption systems with ternary bulk phase.

Model for Design of Multicomponent Adsorption Systems

A predictive model for design of fixed-bed adsorbers for treatment of multicomponent waters and wastewaters is developed and compared to data from experimental systems. The model incorporates both liquid and solid phase resistances to mass transfer. The partial differential equations resulting from conceptual analysis of the model are solved numerically and the numeric algorithm is presented. Two bisolute systems, selected on the basis of providing a severe test of generality, are used for model verification. The components of one system exhibit substantially different affinities for adsorption as well as different intraparticle diffusion characteristics, while those of the second exhibit different adsorption affinities but similar microtransport characteristics. Satisfactory agreement is found between model predictions and experimental data under these rather broad conditions.

Grand ensemble Monte Carlo studies of physical adsorption

A grand canonical ensemble, Monte Carlo method has been used to simulate 12-6 argon-like molecules in the potential field of a plane, uniform homogeneous solid. The adsorbent field was assumed to be entirely due to dispersion forces, and parameters corresponding to graphite were used. Thermodynamic equations appropriate for a multicomponent adsorption system in the grand ensemble are discussed. The methods for realization of the various parameters in a single component system are presented. Results have been obtained for temperatures of 80 and 120 K and mainly for coverages above a statistical monolayer. Isotherms, isosteric heats and other thermodynamic properties are presented and where possible compared with nearby experimental data.