Specific adsorption at modulated liquid vertical bar liquid interfaces

Recently we derived an extension to the linear Gouy-Chapman theory, in orde r to describe the properties of a modulated liquid \ liquid interface betwe en two immiscible electrolyte solutions. In this work we extend our approac h to include specific adsorption of tons at the interface. Starting from a Hamiltonian which contains a singular part for the surface contributions, w e obtain, within the mean-field approach, a set of equations which allows u s to study the equilibrium between the diffuse and the singular part of the charge earners. It is shown that both adsorption and the roughness of the interface lead to a higher capacity compared with the prediction of the Gou y-Chapman theory. The correction introduced by the perturbation from a flat geometry involves the interplay beta een the two-point height-height corre lation function of the surface, the Debye lengths of the system, and a leng th characterizing the adsorption. Furthermore, we investigate the equilibri um distribution of an excess charge into an adsorbed and a diffuse part and show that the interface modulation shifts this equilibrium towards the ads orbed charge. (C) 1999 Published by Elsevier Science S.A. All rights reserv ed.