Construction of g/C₃N₄-ZnO composites with enhanced visible-light photocatalytic activity for degradation of amoxicillin

Abstract

g/C₃N₄-ZnO composite catalysts were synthesized through surface hybridization of the delocalized conjugated-π structure of g/C₃N₄ with the closely contacted surface of ZnO via a successive and simultaneous calcination procedure, and two kinds of photocatalysts, g/C₃N₄-ZnO1 and g/C₃N₄-ZnO2, were obtained. Heterojunctions were formed between the two components, which promote the separation of photogenerated carriers efficiently, and then enhanced the degradation of 100 mg/L of AMX The degradation rate of g/C₃N₄-ZnO1 was 1.54, 11.33, and 2.52-fold that of g/C₃N₄-ZnO2, g/C₃N₄ and ZnO, respectively, at a 3.5-h reaction period, with the dosage of 0.3 g/L, and solution pH at 7.0±0.2. The recycle and reuse ability was excellent and 90.5% of AMX mitigation was achieved in the fifth cycle. For g/C₃N₄-ZnO1, electrons migrated from the conduction band of g/C₃N₄ to that of ZnO via the heterojunction. ·OH and h⁺ were the main active species for AMX degradation, compared to ·O ⁻₂ dominated for g/C₃N₄. Twelve intermediate products were identified, and two degradation pathways were inferred for g/C₃N₄-ZnO1 and g/C₃N₄-ZnO2, respectively. Finally, transformation products without lactam rings were achieved, which lost most of the antibacterial potencies, and the ecotoxicity was also dramatically decreased as indicated by the ECOSAR program.