Thermodynamics of adsorption from solution: Part 2. - Imperfect systems

Abstract

This paper develops a consistent theoretical basis for the study of adsorption from solution by consideration of the effects of non-ideality of the surface and bulk phases on adsorption equilibrium. The definition and experimental determination of activity coefficients in surface phases is discussed and theoretical equations are given for adsorption from regular solutions and from solutions of molecules of different sizes. The equilibrium equations have been solved numerically and theoretical adsorption isotherms are given for regular solutions and for athermal solutions in which the molecules are oriented parallel to the surface. Equilibrium equations are given, but have not yet been solved numerically, for non-athermal solutions and for adsorption of molecules in an orientation normal to the surface. Equations are given for the heat of wetting of a solid by an imperfect solution, and a method is suggested for evaluation of the heat of mixing in a surface phase. A comparison is made with the limited experimental data in this field, and with other theoretical treatments.