Chromate Reduction on the Novel Hetero-system La 2 NiO 4 /TiO 2 under Solar Light

The removal of hexavalent chromium Cr(VI) from aqueous solutions is successfully achieved over the new hetero-system La 2 NiO 4 /TiO 2 at pH~4 under solar light. La 2 NiO 4 was found to be a direct band gap semiconductor with an optical transition of 1.30 eV. The photo-electrochemical characterization of the sensitizer La 2 NiO 4 is undertaken to predict the electrons injection in TiO 2 which acts as electrons Bridge to adsorbed HCrO 4 − . This compound presents a p-type semiconductor with a flat band potential of 0.18 V SCE - more cathodic than that of TiO 2 . The photoactivity is strongly enhanced in the presence of oxalic acid as hole scavenger. The saturation is due to Cr 3+ oxidation by photoholes and the competitive water reduction. The reutilization shows a negligible deactivation effect and the hetero-system could be promising for increasing the quality of water.