Tungsten-doped TiO2 vs pure TiO2 photocatalysts:: Effects on photobleaching kinetics and mechanism

Sol gel prepared tungsten (VI) doped TiO2 powders were evaluated as photocatalysts for crystal violet (CV) bleaching under UV irradiation, in the presence of oxygen. The incorporation of the hexavalent cation affects both surface and bulk properties. The optimum activity observed results from the competition between higher surface areas and lower specific activities per adsorption site. At pH 4.0, doped particles share a common photodegradation mechanism, where the relative contribution of the aromatic structure rupture over the loss of terminal methyl groups (N-demethylation) is more relevant than in the case of non-doped titania. This behavior can be minimized shifting the pH into basic condition.