Photocatalytic mineralisation of humic acids using TiO 2 modified by tungsten dioxide/ hydrogen peroxide

Abstract

TiO 2 of anatase structure was modified by tungsten dioxide and H 2O 2 in order to obtain WO 3-TiO 2 photocatalyst with enhanced photocatalytic activity under both, UV and artificial solar light irradiations. WO 2 was dissolved in 30% H 2O 2 and mixed with TiO 2 in a vacuum evaporator at 70°C. Such modified TiO 2 was dried and then calcinated at 400 and 600°C.The prepared samples and unmodified TiO 2 were used for the photocatalytic decomposition of humic acids (Leonardite standard IHSS) in the aqueous solution under irradiations of both, UV and artificial solar light. Modification of TiO 2 with tungsten dioxide and H 2O 2 improved separation of free carriers in TiO 2 which resulted in the increase of OH radicals formation. Calcination caused an increase of anatase crystals and higher yield in OH radicals. The uncalcined samples showed high abilities for the adsorption of HA. Combination of adsorption abilities and photocatalytic activity of photocatalyst caused that the uncalcined TiO 2 modified with WO 2/H 2O 2 showed the shortest time of HA mineralisation. The mineralisation of HA under the artificial solar light was much lower than under the UV. It was proved that, although OH radicals are powerful in the decomposition of HA, adsorption can facilitate the contact of the adsorbed molecules with the photocatalyst surface and accelerate their photocatalytic decomposition.