Calorimetric effects of simple ion adsorption at the silica/electrolyte interface: Quantitative analysis of surface energetic heterogeneity

The equations developed by us for the triple layer surface complexation app roach, taking into account energetic heterogeneity of surface oxygens, are applied here to study the heterogeneity influences on the enthalpic effects accompanying ion adsorption at the silica/NaCl aqueous solution interface. That study is accompanied by the parallel experimental/theoretical study o f the energetic heterogeneity of surface oxygens for adsorption of argon mo lecules which are known to interact practically only with surface oxygens. Such studies provide a simpler interpretation for information of the surfac e energetic heterogeneity. That additional study confirms a proper choice o f the model of surface heterogeneity, accepted by us in our description of ion adsorption at the oxide/electrolyte interfaces. Our quantitative analys is also confirms quite different features of the silica/electrolyte interfa ce, compared to those formed by other metal oxides. Namely, in the case of the silica/electrolyte interface, the adsorption of water molecules on the surface oxygens SO- is a process highly competitive with proton adsorption leading to that of formation of the neutral surface complexes SOHO.