Photocatalytic reduction of Se ions using suspended anatase powders

The photocatalytic reduction of aqueous Se(VI) solution was studied using t wo anatase type powders whose specific surface area and particle size were 145 m(2)/g and 1.0 mu m, and 47.6 m(2)/g and 0.2 mu m, respectively, and an HCOOH reductant. The principal reduction products were Se degrees and H2Se , but Se(IV) was not detected. The reduction rate of Se(VI) is mainly contr olled 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 redu ction of Se(VI) or Se degrees. Using a TiO2 catalyst having a high conversi on ratio, the time required for the reduction of Se(VI) to Se degrees and S e degrees to H2Se were in the ratios of 3 : 1, as expected theoretically. Although the reduction rates of Se(VI) can be approximately presumed knowin g the information of adsorption amount of Se(VI) onto TiO2 and energy conve rsion ratios of TiO2, pH of solution. amount of TiO2 and concentrations of Se(VI) and HCOOH were recognized another important factors.