Magnetically recyclable spherical Cu2O@Fe3O4 S-scheme heterojunction for efficient tetracycline removal via visible light-activated peroxydisulfate

Abstract

The overuse of antibiotics in treating bacterial infections is a significant threat to the environment and human health. The utilization of visible-light-assisted peroxydisulfate (PDS) activation for eliminating organic pollutants is a promising approach. This study uses a straightforward hydrothermal method to prepare magnetically recyclable spherical Cu2O@Fe3O4. The efficacy of this material in removing antibiotic pollutants was assessed using simulated wastewater containing tetracycline (TC). TC removal was achieved by activating PDS with Cu2O@Fe3O4 as the visible light photocatalyst. Experimental findings revealed that under specific conditions—a pH of 9, a Cu2O@Fe3O4 concentration of 60 mg L−1, and a PDS concentration of 25 mg L−1—the removal rate of TC reached 97.67% after 30 min of irradiation. Moreover, Cu2O@Fe3O4 exhibited excellent recyclability, maintaining a removal rate of 93.33% after five recycling rounds. X-ray diffraction characterization of the Cu2O@Fe3O4 composite before and after cycling confirmed its robust stability and reusability. In situ X-ray photoelectron spectroscopy analysis showed that electrons migrated from Fe3O4 to Cu2O during the photocatalytic reaction, indicating the formation of an S-type heterojunction in Cu2O@Fe3O4. Free radical trapping experiments demonstrated the active involvement of ·OH, ·O2−, SO4˙− and h+ radicals in TC removal.