Equilibrium adsorption diagram mixtures

The present paper deals with the threedimensional diagram for description of the equilibrium adsorption of O2/N2 mixtures on clinoptilolite. This diagram shows the dependence of the amount adsorbed on the total pressure, as well as the equilibrium concentration of the gas mixtures. Adsorption from binary mixtures involves theoretical and experimental problems. Ruthven s and Loughlin s works (7,8) provide much detail and they succeed in describing fully enough the complicated systems, but all at the expense of considerable characteristic constants used and elaborate computation. The experimental... 

Individuals of multicomponent mixtures compete for the limited space on the adsorbent. Equilibrium curves of binary mixtures, when plotted as x vs. y diagrams, resemble those of vapor-liquid mixtures, either for gases (Fig. 15.5) or liquids (Fig. 15.6). The shapes of adsorption curves of binary mixtures, Figure 15.7, are varied the total adsorptions of the components of the pairs of Figure 15.7 would be more nearly constant over the whole range of compositions in terms of liquid volume fractions rather than the mol fractions shown. 

In case of binaiy systems, co-adsorption was performed using three different initial mixtures - being equimolar (Z/ = Zz = O.S) and rich in component 1 and 2 (respectively Z/ = 0.85 and Z = 0.15) - whose molar ratio were formerly checked. The selectivity of adsorbent rn/2) was either directly represented in an X-Y isobaric equilibrium diagram, or determined using the following equation, where Xi and K are die adsorbed and gas phase molar fraction of f component, and plotted versus total amount adsorbed Qtad-... 

A threedimensional diagram, expressing the amount adsorbed as a function of sorbate equilibrium concentration and total pressure, is drawn using both direct experimental data and computed data for C /N- mixtures on K-clinoptilolite at room temperature. The real adsorption isotherms follow the Freundlich law for Nj and Henry s law for C>2 Freundlich and henry constants are computed and correlated to sorbate equilibrium concentration. Selectivity coefficients,, equilibrium constants, K, and the changes in the standard Gibbs free energy, aG°, are determined. Selectivity towards N. is satisfactory and K-clinoptilolite could be used for industrial air enrichment. 

The threedimensional diagram for N2 and O2, for various mixtures, is shown on Figure 3. Cuts at constant total pressure give isobars, an example of which is given in Figure 4, and represents ability of adsorption of each sorbate at different equilibrium con-... 

The Chreedimensional diagram obtained could serve both theoretical and technological computations concerning oxygen enrichment of air on K-clinoptilolite. It is a basis for determining of adsorption isobars, fictitious and real isotherms, as well as thermodynamic data for adsorption from binary C /Nj mixtures. Freundlich and Henry constants (for the real adsorption isotherms) correlated with the equilibrium concentration are useful for computation of the amounts adsorbed at arbitrary partial pressures and equilibrium concentrations. 

I Adsorption equilibrium data for the system oxygen/nitrogen/active carbon. Presented in a triangular diagram using mass fractions as the concentration scales i9= — 150°C, p = 1 bar). A, B State points of active carbon loaded with pure oxygen and pure nitrogen, respectively. Curve A.. E.. B Locus of the state points of active carbon loaded with gas mixture. 

FIG. 13 Adsorption equilibrium diagrams on solid/liquid interface in methanol-benzene mixtures at different equilibrium constants. Ki = 10, K2 = 10, = 10, = 1,... 

Let us now consider some experimental data on phase diagrams of filled polymer alloys. The effect of a solid surface on the equilibrium in ternary systems of polymer-polymer-solvent has been studied. This effect should be connected with the adsorption of one or both components of the pol5mier mixture at the interface with a solid. Figure 7.1 shows that introducing silica into ternary system PS-PBMA-benzene and PS-polycarbonate-chloroform results in the displacement of the binodal and change of its shape. For both polymer pairs investi-... 

FIG. 3 Adsorption equilibrium diagrams on S/L interlace in methanol-benzene mixtures at different... 

When both components of a binary gas or vapor mixture are separately adsorbed to roughly the same extent, the amount of either one adsorbed from the mixture will be affected by the presence of the other. Since such systems are composed of three components when the adsorbent is included, the equilibrium data are conveniently shown in the maimer used for ternary liquid equilibria in Chap. 10. For this purpose it is convenient to consider the solid adsorbent as being analogous to liquid solvent in extraction operations. However, adsorption is greatly influenced by both temperature and pressure, unlike liquid solubility, which is scarcely affected by pressure under ordinary circumstances. Equilibrium diagrams are consequently best plotted at constant temperature and constant total pressure, and they are therefore simultaneously isotherms and isobars. 

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