Influence of electrolyte ion adsorption on the derivative of potentiometric titration curve of oxide suspension – theoretical analysis

The theory based on the 1-pK triple layer model of the oxide/electrolyte interface is used to obtain the derivative of a proton adsorption isotherm. The present approach is much more rigorous and complex from a physical point of view compared to our previous paper [J. Phys. Chem. B. 106 (2002) 13280]. In the present work we take into account adsorption of inert electrolyte ions. Also, the present approach takes into consideration the local surface heterogeneity. The aim of this work is not to propose new surface model, but to develop a theoretical basis for obtaining of proton affinity distribution from the derivatives of a potentiometric titration curve. We demonstrate how including of electrolyte ion adsorption influences on the shape and behavior of the local derivatives of potentiometric titration curves. The influence of the other parameters is also thoroughly investigated. It was found that complete description of the derivative of surface charging curve requires a high number of parameters. Therefore, it is difficult to adopt the obtained peaks for unambiguous decomposition of experimental derivative of a titration curve onto the parts coming from different patches of the surface.