Abstract: In this work, a novel biochar decorated Bi₄O₅Br₂/g-C₃N₄ S-scheme heterojunction was successfully prepared for Norfloxacin (NOR) degradation, and it was found that the 5 %-Bi₄O₅Br₂/g-C₃N₄/C heterojunction exhibited the excellent photocatalytic degradation activity toward NOR, degrading 92.5 % of NOR within 72 min under visible light irradiation. The effects of pH, dosage, and concentration of the NOR on the photocatalytic activity were also systematically investigated. The mechanism studies revealed that the active species like hole (h⁺), hydroxyl radical (·OH), and superoxide radical(·O₂^-) play a predominant role in the NOR degradation, and the enhanced removal rate of Bi₄O₅Br₂/g-C₃N₄/C heterojunction can be attributed to the synergistic effect of adsorption and photocatalytic process. In addition, an S-scheme transfer channel in the interface of the Bi₄O₅Br₂/g-C₃N₄/C heterojunction is proposed, which can effectively improve the separation of the photogenerated carriers and enhance the photocatalytic performance. This research provides inspiration for designing S-scheme heterojunction for wastewater treatment.

Key words: S-scheme heterojunction, g-C₃N₄, Biochar, Photocatalytic degradation, Norfloxacin