Photocatalytic Reduction of Se Ions Using Suspended Anatase Powders

Abstract

The photocatalytic reduction of aqueous Se(VI) solution was studied using two anatase type powders whose specific surface area and particle size were 145 m2/g and 1.0 μm, and 47.6 m²/g and 0.2 μm, respectively, and an HCOOH reductant. The principal reduction products were Se° and H₂Se, but Se(IV) was not detected. The reduction rate of Se(VI) is mainly controlled by the amount of Se(VI) adsorbed onto TiO₂ powder, as far as the same TiO₂ powders were used. When different TiO₂ powders were used, the energy conversion ratio of TiO₂ plays a more important role in photocatalytic reduction of Se(VI) or Se°. Using a TiO₂ catalyst having a high conversion ratio, the time required for the reduction of Se(VI) to Se° and Se° to H₂Se were in the ratios of 3:1, as expected theoretically.
Although the reduction rates of Se(VI) can be approximately presumed knowing the information of adsorption amount of Se(VI) onto TiO₂ and energy conversion ratios of TiO₂, pH of solution, amount of TiO₂ and concentrations of Se(VI) and HCOOH were recognized another important factors.