Efficient photocatalytic degradation of sulfamethazine by Cu-Cu O/TiO2 composites: Performance, photocatalytic mechanism and degradation pathways

In this study, a novel Cu-CuxO/TiO2 composite photocatalyst was synthesized using combined sol–gel and impregnation methods. Several technologies were employed to characterize the morphology, crystalline structure, optical properties, and surface composition of the as-synthesized photocatalysts. The successful preparation of the Cu-CuxO/TiO2 composite was confirmed with superior properties compared to pure TiO2 and Cu-CuxO composite. The results for the degradation experiment employing sulfamethazine (SMZ) as the target pollutant indicated that the CT9 (the theoretical molar ratio of Cu(CH3COO)2 to TiO2 was 9:1) composite exhibits the best photocatalytic performance, and the degradation rate of SMZ reaches 98.2% after 60 min of irradiation. The good repeatability of CT9 was proved by five-cycle experiments. Radicals trapping experiments indicated that superoxide radicals and holes were primary oxidative species in photocatalytic degradation of SMZ. Eleven intermediates for SMZ degradation were identified employing LC-MS technology and the possible degradation pathways were proposed. ECOSAR models were used to predict the biotoxicity of the degradation intermediates. The present research exhibits a new opportunity for the construction of Cu-CuxO-based photocatalysts to remove contaminants from antibiotic wastewater.