Photocatalytic reduction of Cr(VI) in aqueous solutions by UV irradiation with the presence of titanium dioxide

The reduction of Cr(VI) in aqueous solution by UV/TiO2 reduction process was studied under various solution pH values, TiO2 dosages, light intensities, dissolved oxygen levels and other operating conditions. The reduction rates of Cr(VI) by photocatalytic-induced elections were significantly higher for acidic solutions than those for alkaline solutions. Increasing the light intensity would drastically increase the reduction rate of Cr(VI), but was ultimately influenced by the amount of TiO2 present in solutions. The presence of dissolved oxygen had minimum effect on the reduction of Cr(VI) by UV/TiO2 process in acidic solutions. The presence of ethanol might act as scavenger for holes and promoted the photocatalytic reduction of Cr(VI) by electrons. The Cr(VI) adsorbed on the surface of TiO2 particles was observed to be photoreduced to Cr(III) almost completely.