Solid-waste-recycled CuO/C₃N₄ S-scheme heterojunctions for efficient photocatalytic antibiotic degradation

With the increasing severity of antibiotic pollution, the development of effective green photocatalysts for the degradation of organic pollutants in water has attracted extensive attention. Herein, we have prepared CuO/C₃N₄ S-scheme heterogeneous photocatalysts via recycling Cu resources from Cu-containing electroplating sludges. By mediating the acid leaching process, copper in electroplating sludges was dissolved selectively, while other metal species were retained in the residues. The CuO/C₃N₄ S-scheme heterojunction not only effectively suppressed the recombination of photogenerated charge carriers of C₃N₄, but also preserved the strong reducing electrons of C₃N₄ and the strong oxidizing holes of CuO, retaining the outstanding redox ability of CuO/C₃N₄. Therefore, CuO/C₃N₄ photocatalysts exhibited good catalytic performance in the degradation of tetracycline (over 95% in 2 h). In addition, CuO/C₃N₄ S-scheme heterojunctions achieved a high mineralization rate (45% in 2 hours), thus reducing secondary pollution during the degradation. This work provides a reliable direction for designing novel S-scheme heterojunction photocatalytic materials by using metal sources in solid waste.