ADSORPTION FROM BINARY SOLUTIONS OF NON-ELECTROLYTES

A treatment of adsorption of binary regular solutions is presented using the Grand Partition Function and the Bragg-Williams approximation. Explicit solutions of the problem are found (1) when the surface makes a small perturbation of the solution composition (2) at the critical point for phase separation and (3) when adsorption is confined to the 1st or surface layer of the solution. The effect of the surface falls off exponentially and rapidly on entering the solution except near the critical point where a very slow fall-off is found. Case (3) is thus usually found experimentally; published experimental isotherms for the adsorption of benzene-cyclohexane on carbon blacks are analyzed, showing the degree of heterogeneity of these surfaces.