Evaluation of equilibrium parameters characterizing metal oxide/electrolyte solution interface

According to the surface complexation model (SCM), charging of a metal oxide surface in aqueous environment is due to interactions of active surface groups with ions from the bulk of the solution. Several models for mechanism of surface reactions were proposed. Interfacial equilibrium is determined by corresponding equilibrium constants, but also with the structure of the electrical interfacial layer (EIL). Therefore, evaluation of equilibrium parameters is not a simple task. Traditionally, the measurements of pH dependency of surface charge density was used for that purpose. This article shows that introduction of electrokinetic data produces more reliable results, especially in the case of specific adsorption. If surface charge density and/or adsorption data are not available, one may still deduce interfacial equilibrium constants from electrokinetic results combined with measurements of the surface potential.