Chromate Reduction on the Novel Hetero-system La2NiO4/TiO2 under Solar Light

The removal of hexavalent chromium Cr(VI) from aqueous solutions is successfully achieved over the new hetero-system La2NiO4/TiO2 at pH similar to 4 under solar light. La2NiO4 was found to be a direct band gap semiconductor with an optical transition of 1.30 eV. The photo-electrochemical characterization of the sensitizer La2NiO4 is undertaken to predict the electrons injection in TiO2 which acts as electrons Bridge to adsorbed HCrO4-. This compound presents a p-type semiconductor with a flat band potential of 0.18 V-SCE, more cathodic than that of TiO2. The photoactivity is strongly enhanced in the presence of oxalic acid as hole scavenger. The saturation is due to Cr3+ oxidation by photoholes and the competitive water reduction. The re-utilization shows a negligible deactivation effect and the hetero-system could be promising for increasing the quality of water.