Simultaneous and efficient photocatalytic reduction of Cr(VI) and oxidation of trace sulfamethoxazole under LED light by rGO@CuO/BiVOp-n heterojunction composite.

Antibiotics and heavy metals often coexist in polluted environment, and the harm of combined pollution is greater than that of single pollution. In this study, a series of graphene supported p-n heterojunction rGO@CuO/BiVO composites are synthesized with different CuO doping for simultaneous detoxification of Cr(VI) and antibiotics. The obtained photocatalysts (rGO@CuO/BiVO) with proper loading amount of CuO shows the a high photocatalytic degradation activity for simultaneously efficient Cr(VI) reduction and sulfamethoxazole (SMZ) oxidation under LED light at neutral pH. The Cr(VI) was completely transformed to Cr(III) rather than simply Cr(VI) adsorbed on the surface of rGO@CuO/BiVO. The photocatalytic activity of composites can be attributed to excellent electrical conductivity of rGO and the p-n heterojunction between CuO and BiVO, which promotes the spatial separation of photogenerated charges at the heterojunction boundary and inhibits of the photogenerated h and e recombination. It's confirmed that h, O and OH are the main reactive species for the photocatalytic SMZ oxidation, and the most important reactive species is h. Finally, the tentative degradation pathways of SMZ are proposed based on the liquid chromatography-triple quadrupole mass spectrometry analysis. This work provides an effective approach for the treatment of water that contains SMZ and Cr(VI) under LED light.