The theoretical quantitative analysis of the temperature dependence and enthalpic effects of ion adsorption, developed in our earlier publications, was applied here to study the features of hematite/electrolyte interfaces. This is the first time that our set of experimental data could be used to carry out a simultaneous analysis of both the temperature dependence of the titration isotherm and directly measured enthalpic effects. To draw possible general conclusions about the features of the hematite/electrolyte interfaces, we considered two sets of experimental data measured in two laboratories, using the hematite samples prepared in different ways. The differences in sample preparations are manifested by substantially different values of the monitored surface charges and related calorimetric effects. The present quantitative analysis in Part I of this publication was carried out by using the model of an energetically homogeneous solid surface, which is still commonly accepted. Certain inconsistencies were found in the parameter values leading to a good fit of titration isotherms and those that are best to fit directly measured enthalpic effects. Thus, the general conclusion was drawn that this popular model is too crude for a quantitative analysis.

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The two hematite/KNO3 adsorption systems investigated in Part I are now subjected to a more refined quantitative analysis based on the models of an energetically heterogeneous oxide surface. The estimated parameters lead to a much more consistent, simultaneous fit of both titration isotherms and the related directly measured enthalpic effects. That quantitative analysis reveals that the differences in the preparation of these two hematite samples result in substantial differences in the heats accompanying ion adsorption. Generally, the more porous surface is, the lower are the heats of proton and cation adsorption, due probably to a deeper dehydratation of adsorbed ions. Our quantitative analysis also reveals substantial electrostatic contributions to the observed enthalpic effects, as well as contributions caused by surface energetic heterogeneity.