Constructing magnetic and high-efficiency AgI/CuFe2O4 photocatalysts for inactivation of Escherichia coli and Staphylococcus aureus under visible light: Inactivation performance and mechanism analysis

Highlights: • Novel AgI/CuFe₂O₄ catalysts with magnetic property were successfully fabricated. • AC-2 presented the best photo-inactivation rate both for Gram-negative E. coli and Gram-positive S. aureus. • The changes of E. coli morphology and inside contents were verified by TEM images. • Superoxide radical and holes were responsible for the high photo-disinfection efficiency. • Cycle experiments revealed the outstanding photo-stability and reusability of AgI/CuFe₂O₄. -- Abstract: Magnetic materials usually exhibit advanced performance in many areas for their easy separating and recycle ability. In this study, silver iodide/copper ferrite (AgI/CuFe₂O₄) catalysts with excellent magnetic property were successfully synthesized and characterized by a series of techniques. Two typical bacteria Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) were applied to estimate the photocatalytic inactivation performance of obtained AgI/CuFe₂O₄ catalysts. Results revealed that the AgI/CuFe₂O₄ (12.5% AgI) composite could absolutely inactivate 3 × 10⁹ CFU/mL E. coli and 2.7 × 10⁸ CFU/mL S. aureus cells severally in 50 min and 40 min under visible light irradiation, which showed a much higher photo-disinfection activity than monomers. Transmission electron microscopy was used to study the biocidal action of this nanocatalyst, the results confirmed that the treated E. coli cells were damaged, the nanocatalyst permeated into cells and resulting in death of cells. Besides, it was found that the destruction of bacterial membrane together with substantial leaked potassium ion (K⁺) which caused by the photo-generated reactive species superoxide radical (O₂⁻) and holes (h⁺) could be the direct disinfection principles. For a deep insight into practical applications, the influences of different catalyst concentrations and reaction pH were also taken into discussion in details. The overall results indicated the novel photocatalyst with strong redox capacity and outstanding reusability can be widely employed in bacteria elimination.