Effect of temperature on the point of zero charge and surface charge of TiO2

Abstract

The point of zero charge, p.z.c._T, and surface charge, σ^T ₀, of titania over a wide pH range have been determined at various temperatures by potentiometric titration. It was found that a progressive increase in p.z.c._T can be achieved by increasing the temperature of aqueous suspensions from 10 to 45 °C. Therefore, an extension in the pH range in which titania can adsorb negative (positive) species is expected by increasing (decreasing) the impregnation temperature. The fact that the p.z.c._Tvs. 1/T curve does not obey the van't Hoff law, in disagreement with the literature, was explained considering two mechanisms for the charging of the titania surface, one for each phase (rutile and anatase). Morever, it was found that an increase (decrease) in the positive (negative) surface charge, proportional to the sites for adsorption of negative (positive) species, can be achieved by increasing the impregnation temperature.