Mechanism of Ag-enhanced CuBi₂O₄ inactivation of Escherichia coli in a photocatalytic Fenton system

In this work, Ag/CuBi₂O₄ composite photocatalyst films with excellent photocatalytic sterilization properties were prepared by photodeposition. The photocatalytic activity of silver-modified CuBi₂O₄ (Ag/CuBi₂O₄) under the photocatalytic-Fenton coupling system was verified by its inactivation rate of Escherichia coli in seawater. The results showed that the photocatalytic sterilizing performance of CuBi₂O₄ loaded with Ag in the presence of trace amounts of H₂O₂ was significantly improved. 15Ag/CuBi₂O₄ possessed the optimal photocatalytic activity, and its sterilizing rate in 30 min could reach 96.6%. Its sterilization rate in 30 min could reach 96.6%, which is about 70% higher than that of pure CuBi₂O₄. Meanwhile, the mechanism of the enhanced sterilization performance of Ag/CuBi₂O₄ in the photocatalytic-Fenton coupled system was investigated. Firstly, according to the electrochemical results, the loading of Ag can significantly improve the charge separation efficiency of CuBi₂O₄. And promotes the conversion of H₂O₂ to hydroxyl radicals(·OH); Secondly, the valence band potential of 15Ag/CuBi₂O₄ is more positive than that of CuBi₂O₄, which suggests that Ag loading can enhance the oxidation of CuBi₂O₄ cavities. Comprehensive radical trapping experiments demonstrate that ·OH and holes (h⁺) are the main active species for inactivating Escherichia coli (E. coli). In this work, effective conversion of H₂O₂ to ·OH in a wide spectral range was achieved by loading Ag nanoparticles on the surface of CuBi₂O₄, which provides a new idea for the development of photocatalytic-Fenton coupling technology and ballast water treatment.