Persulfate-mediated catalytic and photocatalytic bacterial inactivation by magnetic natural ilmenite

In this study, a natural occurring ilmenite was successfully developed as an efficient catalyst/photocatalyst for bacterial inactivation coupling with persulfate (PS) under visible light (Vis) irradiation. The excellent bacterial inactivation is demonstrated by the result that the bactericidal efficiency in the ilmenite/PS/Vis process reached 6 log10 cfu/mL within 30 min as compared to that of 1.5 log10 cfu/mL for the ilmenite/Vis process and 4 log10 cfu/mL for the ilmenite/PS under same conditions. Integrated with the electron paramagnetic resonance analysis, electrochemical measurements and photoluminescence spectroscopic analysis, the enhanced performance was attributed to the accelerated capture of photo-generated electrons by PS and ≡Fe(II) of ilmenite promoted PS activation vice versa to collectively generate more radicals for E. coli inactivation in the ilmenite/PS/Vis process. For the first time, the generation of singlet oxygen (1O2) was proved to be the primary bactericidal agent other than SO4− and O2−, which caused leakage and mineralization of E. coli intracellular components. Impressively, the 1O2-mediated ilmenite/PS/Vis system showed good inactivation performance in authentic water body and maintained good reusability in the pilot-scale 25 L reactor. This work highlights the great potential of natural ilmenite as catalyst and elucidated a new opportunity for persulfate remediation of controlling microbial water contaminants.