The photocatalytic reduction of aqueous solutions containing Se(VI) and Se(
IV) was studied using TiO2 powders and an HCOOH reductant. Without the addi
tion of a suitable reductant and UV irradiation, no significant reduction o
f Se(VI) and Se(IV) can proceed. The ability of Se ions to be adsorbed onto
TiO2 is an important factor in the ease of reduction of these ions, Elemen
tal Se is directly produced from both Se(VI) and Se(IV) solutions. The maxi
mum yield of elemental Se never reaches 100 pet, due to the initiation of H
2Se generation.