Enhanced tetracycline antibiotic degradation by S-scheme Bi2MoO6/Bi/WO3 photocatalyst coupled with peroxymonosulfate activation

The residue of antibiotics damages ecosystems, destroys biological communities, causes immune damage and increased drug resistance in animals. The S-scheme Bi₂MoO₆/Bi/WO₃ was synthesized using a simple hydrothermal method to degrade Chlortetracycline hydrochloride (CTC), tetracycline hydrochloride (TCH) and oxytetracycline (OTC) under the combined conditions of visible light and PMS. Bi₂MoO₆/Bi/WO₃ heterojunction achieves a CTC, TCH and OTC removal efficiency of 94.08 %, 87.25 % and 90.36 % within 30 min under visible light and PMS. And Bi₂MoO₆/Bi/WO₃ has excellent resistance to cations and anions, stability and generalisability. Electrochemical measurements confirm effectively improved charge carrier separation in the composite system. The S-scheme charge transfer mechanism of Bi₂MoO₆/Bi/WO₃ composites is explained based on the results of energy band analysis and theoretical calculations. The S-scheme heterojunction Bi₂MoO₆/Bi/WO₃ synergistically enhances charge separation efficiency while enabling accelerated electron transport across the interfacial junctions. Additionally, the synergistic effect arising from the cyclic conversion between Bi^3 + and Bi⁰ significantly enhances PMS activation, leading to increased generation of reactive species (·SO₄^- and ¹O₂) and consequently improving the overall catalytic performance of the system. Moreover, Bi₂MoO₆/Bi/WO₃ has excellent reducibility, with Cr (VI) reduction and photocatalytic hydrogen production from water. This study provides a new approach for designing multifunctional heterogeneous catalysts that effectively degrade antibiotics, Cr (VI) reduction and photocatalytic hydrogen production in water under visible light.