Highly efficient and stable Ag–AgBr/TiO2 composites for destruction of Escherichia coli under visible light irradiation

Abstract

A series of Ag–AgBr/TiO2 composites were prepared by a sol–gel method followed by photoreduction. Effect of Ag–AgBr content on the physicochemical properties and antibacterial activities of the Ag–AgBr/TiO2 composites was investigated. These composites showed intrinsic antibacterial activities against Escherichia coli (E. coli) in the dark attributed to the Ag nanoparticles dispersed in the composites. Under visible light irradiation, inactivation of E. coli over these Ag–AgBr/TiO2 composites was attributed to both their photocatalytic disinfection activities and intrinsic antibacterial properties. The Ag–AgBr/TiO2 with an optimum Ti/Ag atomic ratio of 10 exhibited superior visible-light photocatalytic activities for ibuprofen degradation and mineralization as compared to the other Ag–AgBr/TiO2 composites and also Ag–AgBr/P25, Ag/TiO2 and TiO2. It is probably because of the coexistence of two visible-light active components (AgBr and Ag nanoparticles) and the most effective separation of photogenerated electrons and holes in this photocatalyst. Correspondingly, the photocatalyst achieved a much higher efficiency of E. coli destruction than Ag–AgBr/P25 and TiO2. E. coli was almost completely inactivated (7-log reduction) within 60 min by the photocatalyst with a rather low dosage of 0.05 g L−1 under white LED irradiation. Furthermore, the Ag–AgBr/TiO2 showed high stability for photocatalytic destruction of E. coli and the dark repair and photoreactivation did not occur after the photocatalytic process. Finally, the action spectrum of this photocatalyst for E. coli inactivation and the influence of several inorganic ions present in surface water were also investigated.