Adsorption of gases and vapors on a solid surface

Abstract

The adsorption of gases and vapors on a planar surface is examined by a simple van der Waals-like theory and by the mean spherical approximation (MSA). For simplicity, the intermolecular potential of the gas molecules is assumed to be a hard-sphere potential with a Yukawa tail and the interaction of the molecules with the surface is assumed to be a hard repulsion with an exponential tail. If the gas molecules are strongly adsorbed, sharp positive maxima similar to the experimental results of Specovius and Findenegg are seen in the critical region in both the van der Waals and MSA calculations. For weakly adsorbed gases, the MSA predicts negative values for the adsorption including negative extreme in the critical region. Such isotherms have not been observed experimentally but might be seen in carefully chosen systems. © 1983 American Chemical Society.