Photocatalytic removal of elemental mercury on TiO2-BiOIO3 heterostructures: Mercury transformation, sulfur tolerance and SO2/SO3 conversion

Abstract

TiO2-BiOIO3 heterostructures were prepared to study the photocatalytic removal of elemental mercury, sulphur tolerance and SO2/SO3 conversion under UV irradiation. TiO2-BiOIO3 produced excellent photocatalytic performance with highest Hg0 adsorption and oxidation efficiencies of 58.5% and 36.5%. SO2 exhibited a negative effect on elemental mercury removal, and the oxidation efficiency of Hg0 and SO2 were also inhibited as H2O content increased. The conduction band of BiOIO3 trapped electrons from that of TiO2, the electrons reduced pre-adsorbed oxygen to superoxide radicals (O2−), which efficiently oxidize Hg0 and SO2, the generated Hg2+ and SO3 re-diffused into the gas. In the presence of H2O, photogenerated electrons flowed from the conduction band of BiOIO3 to the valence band of TiO2, I3−/I− acted as an electron transfer medium and prevented recombination of electrons and holes (h+), the gathered h+ reacted with H2O to form hydroxyl radicals (OH), which is oxidative species other than the oxidative site.