Ferrate (Fe(VI)) is an emerging green disinfectant and has received increasing attention nowadays. This study conducted systematic analyses of Fe(VI) disinfection on six typical bacteria in different water matrices. The results showed that Fe(VI) was more effective in inactivating Gram-negative (G-) bacteria than Gram-positive (G+) bacteria, and the disinfection performance of Fe(VI) was better in a phosphate buffer than that in a borate buffer and secondary effluent. The inactivation rate constants of G- bacteria were significantly higher than those of G+ bacteria. The cell membrane damage of G- bacteria was also more severe than that of G+ bacteria after Fe(VI) treatment. The cell wall structure, especially cell wall thickness, might account for the difference of the inactivation efficiency between G- bacteria and G+ bacteria. Moreover, it is revealed that Fe(VI) primarily reacted with proteins rather than other biological molecules (i.e., phospholipids, peptidoglycan, and lipopolysaccharide). This was further evidenced by the reduction of bacterial autofluorescence due to the destruction of bacterial proteins during Fe(VI) inactivation. Overall, this study advances the understanding of Fe(VI) disinfection mechanisms and provides valuable information for the Fe(VI) application in water disinfection.
Keywords: Bacterial inactivation kinetics; Biological molecules; Disinfection mechanisms; Ferrate; Reactivity.