Photocatalytic reduction of Cr(VI) on TiO2 film formed by anodizing

Application of photocatalytic reduction to waste treatment of aqueous solutions is of interest comparing to the usage of chemical agents sometimes emanating a secondary waste. Photoreduction of dilute Cr(VI) ions less than 10 ppm in aqueous acidic solutions has been investigated using titanium oxide films formed by the anodizing process. Titanium plates with surface area of 5 cm2 were anodized in a sulfuric acid solution of pH 2 at 293 K. Photoreduction tests of Cr(VI) ions were carried out in 10 ppm K2Cr2O7 aqueous solution adjusted pH 2 by H2SO4, for 7 days, the change in the concentrations of Cr(VI) and Cr(III) ions was evaluated by capillary electrophoresis analysis. The TiO2 film prepared with anodization at 200 V was an anatase type. Concentration of Cr(VI) ions was reduced from 10 to 0.03 ppm and concentration of Cr(III) ions was increased to approximately 9 ppm, for 7 days by the reaction on TiO2 film under irradiation with 350 W Hg–Xe lamp.