Optimization and mechanism insights into the sulfamethazine degradation by bimetallic ZVI/Cu nanoparticles coupled with H2O2

Zero-valent iron has been recognized as a promising catalyst for the degradation of micropollutants via Fenton-like reactions, however, the enhancement of its performance is insufficiently studied. In this feature, we investigate the activity of bimetallic copper/zero-valent iron nanoparticles (ZVI/Cu) as a heterogeneous catalyst for the degradation of sulfamethazine (SMZ), and intensively elucidate the reaction mechanism. The characterization of the catalyst by XRD, TEM, and EDS confirmed the growth of Cu degrees on the surface of the ZVI particles. Response surface methodology (RSM) coupled with a central composite design (CCD) optimized operating parameters such as pH, catalyst loading, H2O2 dose, and initial SMZ concentration. Under the optimum conditions (pH = 3.0, H2O2 concentration =2.0 g/L, ZVI/Cu loading =0.8 g/L), SMZ fell below the detection limit (0.036 mg/L) after 30 min of the reaction. The degradation mechanism revealed that hydroxyl radicals were the dominant oxidant species. However, the accumulated iron oxides on the shell of ZVI contributed to SMZ removal by adsorption. We propose a potential pathway for SMZ degradation based on the detected transformation products. This includes an early cleavage of the mediated sulfonamide group, which suggests an efficacious degradation into tentatively single-ring transformation compounds.