Photocatalytic Reduction of Se Ions Using Suspended Anatase Powders

Abstract

The photocatalytic reduction of aqueous Se(VI) solution was studied using two types of TiO 2 powders with different specific surface areas and dispersed particle sizes as a catalyst, and HCOOH as a reductant. The principal reduction products were Se° and H 2 Se; Se(IV) was not detected. The reduction rate of Se(VI) was mainly controlled by the amount of Se(VI) adsorbed onto each type of the TiO 2 powders. When different TiO 2 powders were used, the energy conversion ratio of TiO 2 played the more important role in the photocatalytic reduction of Se(VI) or Se°. Using a TiO 2 catalyst with a high conversion ratio, the time required for the reductions of Se(VI) to Se° and of Se° to H 2 Se differed by a ratio of 3 : 1, as expected from reaction equations. The reduction rates for Se(VI) can be approximated from the amount of Se(VI) adsorbed onto TiO 2 powders and the energy conversion ratios. The pH of solution, amount of TiO 2 and concentrations of Se(VI) and HCOOH were additionaly recognized as important factors.