Charged surfaces and interfacial ions

Interfacial charge in a solid/liquid system is due to interactions of ions with surface sites affected by the electrostatic potential that is a conseq uence of their accumulation. The present theoretical approach is based on t he so-called Surface Complexation Model that has several modifications know n as either the 1-pK, the 2-pK, or the "MUSIC" model. These models assume d ifferent surface reactions and their equilibrium constants, taking into acc ount electrostatic interactions. For that purpose the relationships between potentials affecting the state of interfacial ions and their surface densi ties need to be known, so that a certain model of the electrical interfacia l layer should be introduced. The complexity of the problem results in the use of a variety of different theoretical approaches that cannot be disting uished experimentally. This article discusses several aspects of the proble m, such as counterion association, structure of the electrical interfacial layer, potential-charge relationships, surface potentials, the zero charge condition, enthalpy of surface reactions, and the influence of the interfac ial ionic equilibrium on the colloid stability. (C) 2000 Academic Press.