Modification of the physicochemical properties of commercial TiO2 samples by soft mechanical activation

The modifications of the physicochemical properties, such as the crystalline phase composition, of two commercial TiO2 samples (Degussa P25 and Hombikat UV-100) by soft mechanical treatment have been studied. Original and modified TiO2 samples were widely characterized (XRD, BET surface area and pore size distribution, SEM/TEM, XPS and DR/UV-Vis). Certain structural and morphological differences were found after the mechanical treatment of the oxides, which depended on the initial phase composition of the oxide, and thus, on the kind of TiO2 sample. The photoactivities exhibited by original commercial (non-modified) TiO2 and the modified ones were tested for Cr(VI) photoreduction. Changes generated by soft mechanical treatment lead to a considerably modification in the intrinsic physicochemical properties of the non-modified TiO2 samples, inducing a decrease in their photoactivities. This loss of photoactivity could be a problem from the point of view of reutilization of the photocatalyst powder in big real collectors, where the photocatalyst particles are subjected to continuous collisions close to the soft mechanical activation conditions reported here. This is specially important for the TiO2 Degussa P25 sample, which after a short time of soft mechanical treatment shows a high alteration of its physicochemical properties and thus, in its photocatalytic activity. (C) 2002 Elsevier Science B.V. All rights reserved.