Thermodynamics of adsorption from binary liquid mixtures on heterogeneous adsorbents

Abstract

The surface excess isotherms for adsorption of n-heptane–cyclohexane mixtures on graphon and benzene–cyclohexane mixtures on silica gel at three different temperatures have been analysed by a simple analytical model which accounts for the effects of the liquid-phase non-ideality, the dissimilarity of the adsorbate sizes and the adsorbent heterogeneity on the isotherm. The adsorbents are found to be substantially heterogenous for these mixtures. An analytical expression for the heat of immersion of the heterogeneous adsorbent as a function of the equilibrium liquid-phase composition has been derived. It is shown that the adsorbent heterogeneity has a much more pronounced effect on the shape of the surface excess isotherm than on the heat of immersion.