Variable thickness of the liquid sorption layers on solid surfaces

Calculations of the adsorption capacity and the thickness of the adsorption layer are of primary importance for studies of the adsorption of binary mixtures. Earlier methods were applicable to the determination of real adsorption capacity only in the case of monolayers and/or layers of constant thickness, independent even of mixture composition. In the case of the adsorption isotherms of binary mixtures of non-electrolytes these conditions are often not fulfilled, and neither the Schay-Nagy extrapolation method nor reciprocal isotherm representations can be used for the determination of adsorption capacity on the basis of adsorption isotherms. Here we present a method of calculation suitable for the computation of surface composition and adsorption layer thickness in the whole composition range. Thus, instead of a single value of adsorption capacity, the system is characterized by the layer thickness isotherm given as a function of the composition of the bulk phase. (C) 1998 Elsevier Science B.V. All rights reserved.