The adsorption and displacement enthalpies of binary liquid mixtures have been investigated on silica gel. By application of the Gibbs surface model and the surface layer model, the displacement enthalpies measured by flow microcalorimetry were defined. Enthalpy isotherms were determined by studying benzene-n-heptane, methanol-benzene and methanol-n-heptane mixtures. A study was made of the extent to which the surface excess isotherms determine the displacement enthalpy isotherms. It was established that, assuming ideal behaviour of the adsorption layer (δHse = 0), the composition of the interfacial layer (ΦS1) is equal to the displacement enthalpy factor (ΨS1), i.e. the composition of the interfacial layer may be determined from calorimetric data alone. Differential displacement enthalpies were calculated and, from a combination of adsorption and calorimetric data, with the assumption of an ideal adsorption layer, adsorption equilibrium constants were also calculated. The relationships were also found to hold for the adsorption of partially miscible liquid mixtures.
ASJC Scopus subject areas