Role of surrounding crystallization media in TiO2 polymorphs coexistence and the effect on AOPs performance

Abstract

Two TiO2 catalysts were prepared by sol-gel method, with the only singularity of the critical solvent removal step prior to heat-induced crystallization. Their different physico-chemical properties caused very distinct activity in the phenol degradation by several AOPs: heterogeneous photocatalysis and ozonation based processes (catalytic and photocatalytic). The remarkable differences found in structural, morphological and chemical surface properties, for both TiO2 catalysts, were ascribed to the differences in the crystallization environment, driving to diverse titania polymorphs. Titanium dioxide (TiEt-B) prepared with an exhaustive step for organics removal by dialysis, has given place to open-structured metastable brookite/anatase mixtures. This crystal structure has generated a texture governed by meso- and macroporosity with a large surface area, acidity and hydroxyl density. The lower hydrodynamic particle size in the aqueous media increased photo-exposed surface, which has led to higher mineralization degrees in phenol catalytic degradation performance, especially in all light-driven catalytic AOPs studied here.