Disinfection and Mechanistic Insights of Escherichia coli in Water by Bismuth Oxyhalide Photocatalysis

This study demonstrates the potential of a new BiOCl0.875Br0.125 photocatalyst to disinfect Escherichia coli in water under simulated solar irradiation. Photocatalytic efficiency was examined for different photocatalyst loadings, solar wavelengths, exposure times, photocatalyst concentration × contact time (Ct) concept and with the use of scavengers. To elucidate the inactivation mechanism, we examined DNA damage, membrane damage, lipid peroxidation and protein release. Both photolysis and photocatalysis were negligible under visible irradiation, but enhanced photocatalytic activity was observed under solar UVA (λ > 320 nm) and UVB (λ > 280 nm), with 1.5 and 3.6 log inactivation, respectively, after 40 min of irradiation. The log inactivation vs Ct curve for E. coli by UVA/BiOCl0.875Br0.125 was fairly linear, with Ct = 10 g L−1 × min, resulting in 2 log inactivation. Photocatalytic treatment led to membrane damage, but without lipid peroxidation. Accordingly, protein was released from the cells after UVA or UVA/BiOCl0.875Br0.125 treatment. Photocatalysis also increased endonuclease‐sensitive sites vs photolysis alone, by an unknown mechanism. Finally, E. coli inactivation was not influenced by the addition of tert‐butanol or l‐histidine, implying that neither hydroxyl radicals nor singlet oxygen reactive species are involved in the inactivation process. The use of a bismuth oxyhalide‐based photocatalyst for the disinfection of Escherichia coli in water under solar irradiation was demonstrated. Photocatalytic efficiency was examined for catalyst loadings, wavelengths, exposure times and concentration × time (Ct) concept and inactivation mechanism. We found that DNA is a possible target for bismuth oxyhalide using endonuclease‐sensitive sites assay. An increase in bacterial membrane permeability was observed, and however, no lipid peroxidation was detected. Finally, results showed that neither hydroxyl radicals nor singlet oxygen reactive species are involved in the inactivation process. The inactivation is attained mainly by the direct contribution of the photogenerated holes.