A Thermodynamic Analysis of Ion Adsorption in the Metal Oxide/Electrolyte Systems in which PZC and CIP do not Coincide

A theoretical-numerical analysis of two adsorption systems composed of the same kind of oxide- TiO₂, and of two different electrolytes, NaCl and CsCl is presented. For one kind of the electrolyte (NaCl), PZC and CIP coincide, whereas they are different for the other (CsCl) electrolyte. The analysis is carried out by applying the popular TLM model, and by drawing formal-mathematical consequences of CIP existence in both kinds of adsorption systems. The values of the adsorption parameters are found by fitting simultaneously the obtained theoretical expressions to both experimental titration isotherms, and to the individual isotherms of cation adsorption measured using radiometric methods. That theoretical-numerical analysis suggests, that the inequality PZC (pK ^int _a1 + pK ^int _a2) may be a general feature of the oxide/electrolyte systems including the systems in which PZC and CIP coincide.