Aqueous Cr(VI) photo-reduction catalyzed by TiO 2 and sulfated TiO 2

Abstract

TiO 2 and sulfated TiO 2 (SO 4 2−/TiO 2) catalysts with different textural properties were prepared under different calcination temperatures and the photo-reduction of Cr(VI) to Cr(III) catalyzed by these catalysts was investigated. For the photocatalytic reduction of Cr(VI), the photocatalytic activities of the TiO 2 samples were found to be strongly dependent of the calcination temperature and TiO 2 calcined at 400 °C showed a higher catalytic activity compared to other TiO 2 catalysts. In contrast, sulfation of TiO 2 stabilized the catalytic activities of SO 4 2−/TiO 2 catalysts. At low calcination temperature, SO 4 2−/TiO 2 catalysts exhibited catalytic activities almost comparable with that of TiO 2 and the catalytic activities of SO 4 2−/TiO 2 catalysts were markedly higher than TiO 2 under high calcination temperature. In addition, the removal of surface SO 4 2− of SO 4 2−/TiO 2 catalyst led to a marked decrease of the catalytic activity for Cr(VI) photo-reduction, suggesting that the presence of surface SO 4 2− provided an acid environment over the catalyst surface and favored the photo-reduction of Cr(VI).