Analysis of Surface Diffusion Phenomena in Liquid Phase Adsorption

Abstract

A model for surface diffusion was proposed on the basis of molecular diffusion. Surface diffusion was regarded as a molecular diffusion restricted due to the adsorptive interaction between adsorbate molecules and the surface of adsorbents. The restricted molecular diffusion model was formulated by applying the absolute rate theory. Experimental data of surface diffusion coefficient in reversed-phase liquid chromatography were analyzed by considering the influence of the adsorptive interaction. Though accurate specification of a frequency factor was not sufficient, characteristic features of the activation energy of surface diffusion could be quantitatively interpreted. The activation energy of surface diffusion was divided into two contributions of a hole-making step and a jumping one. The former was correlated with the evaporative energy of a solvent, not of an adsorbate, and the latter with the isosteric heat of adsorption of the adsorbate. The validity of the concept was proved by applying the model to...