Visible-light-driven photocatalytic inactivation of Escherichia coli by magnetic Fe₂O₃-AgBr

Bacterial inactivation by magnetic photocatalyst receives increasing interests for the ease recovery and reuse of photocatalysts. This study investigated bacterial inactivation by a magnetic photocatalysts, Fe₂O₃-AgBr, under the irradiation of a commercially available light emitting diode lamp. The effects of different factors on the inactivation of Escherichia coli were also evaluated, in term of the efficiency in inactivation. The results showed that Fe₂O₃-AgBr was able to inactivate both Gram negative (E. coli) and Gram positive (Staphylococcus aureus) bacteria. Bacterial inactivation by Fe₂O₃-AgBr was more favorable under high temperature and alkaline pH. Presence of Ca²⁺ promoted the bacterial inactivation while the presence of SO₄^2- was inhibitory. The mechanisms of photocatalytic bacterial inactivation were systemically studied and the effects of the presence of various specific reactive species scavengers and argon suggest that Fe₂O₃-AgBr inactivate bacterial cells by the oxidation of H₂O₂ generated from the photo-generated electron and direct oxidation of photo-generated hole. The detection of different reactive species further supported the proposed mechanisms. The results provide information for the evaluation of bacterial inactivation performance of Fe₂O₃-AgBr under different conditions. More importantly, bacterial inactivation for five consecutive cycles demonstrated Fe₂O₃-AgBr exhibited highly stable bactericidal activity and suggest that the magnetic Fe₂O₃-AgBr has great potential for water disinfection.