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 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.