A lattice-gas model for ion pairing at liquid vertical bar liquid interfaces

The interface between two immiscible solutions is modeled as a phase bounda ry within a three-dimensional lattice gas. Pairing between ions on opposite sides of the interface is introduced through an attractive interaction pot ential. The profiles of the particle densities and of the electrostatic pot ential are obtained by Monte-Carlo simulations. In agreement with experimen tal findings, ion pairing is shown to enhance the interfacial capacity sign ificantly. There is no overshoot of the electrostatic potential at the inte rface; this indicates a fundamental difference between ion pairing and spec ific adsorption. (C) 2000 Elsevier Science S.A. All rights reserved.