Application of the Theoretical 1-pK Approach to Analyzing Proton Adsorption Isotherm Derivatives on Heterogeneous Oxide Surfaces

The theory based on the complexation model has been used to derive the adsorption isotherm equation describing proton adsorption at the solid/electrolyte interface. The present equation applies to the 1-p K theory developed by Hiemstra and co-workers to describe oxide/electrolyte interfaces. Development has also been performed to take into account the local surface heterogeneity (i.e., the local p K distribution). It has then been shown that whatever the assumption, all the equations degenerate into a single derivative isotherm equation as the local surface potential and the heterogeneity parameters merge into one parameter. The obtained derivative equation has been used to model experimental high-resolution titration curves realized on anatase and goethite by using the titration derivative isotherm summation (TDIS) method proposed by Prelot and co-workers. The comparison between the fits obtained with this model and the Bragg−Williams−Temkin model shows that very similar quantitative results (peak position, adsorbed amounts) can be obtained. The present approach is, however, considered to be more realistic from a physical point of view.