Schay-Nagy classification

In the case of adsorption of ideal or quasi-ideal mixtures on adsorbents with polar or apolar surfaces, usually U-shaped excess isotherms are obtained (type I according to the Schay-Nagy classification [46-49]. On adsorbents with polar surfaces, in the case of liquid pairs made up of components with a large difference in polarity (e.g., alcohol-benzene), the polar component is preferentially adsorbed on the surface (type II) and again U-shaped excess isotherms are obtained. Thus, in these systems the composition of the interfacial layer (< )f > or x]) increases monotonously as a function of equilibrium composition consequently, according to Eq. (8b), the enthalpy isotherm A // wiU also be a monotonously increasing function (Fig. 11a). 

FIGURE 3.10 Classification of composite isotherms. (After Nagy, L.G and Schay, G., Mag. Kem. Foly, 66, 31, 1960. With permission.)... 

---