Photocatalytic degradation of oily wastewater over ZnO-CuO/rGO photocatalyst under visible light

Metal oxide composites integrating with carbon materials have attracted a great deal of attention as the potential photocatalysts for environmental treatment. The ZnO-CuO composites intergrated with reduced graphene oxide (rGO) were successfully prepared via co-precipitation method. The crystalline structure of the ZnO-CuO/rGO ternary composites was examined by the X-ray diffraction analysis. Field emission scanning electron microscopy analysis shows the distribution of metal oxides onto the plate-like graphene. The calculated band gap values of the ZnO nanoparticles (3.16 eV) were decreased to 2.62 eV in the prepared (ZnO/CuO)/rGO ternary composites. In this work, the photocatalytic activity of the ZnO-CuO/rGO with 15 % rGO photocatalyst was evaluated for the chemical oxygen demand (COD) of oily wastewater treatment process, which showed COD removal reaching 95 % after 6 h exposure to visible light irradiation. Moreover, the recycle and recovery test revealed the relatively good stability and repetitive use of ZnO-CuO/rGO for high COD removal of oily wastewater.