A singlet oxygen dominated process through photocatalysis of CuS-modified MIL-101(Fe) assisted by peroxymonosulfate for efficient water disinfection

Singlet oxygen ( 1 O 2 ) is an effective reactive oxygen species in disinfection due to its long lifetime and sensitivity to bacteria. This study tried to develop a 1 O 2 dominated process for bacterial inactivation by visible light (vis) photocatalysis assisted by PMS. A novel CuS-modified MIL-101(Fe) (CSMF) photocatalyst was synthesized for the first time. Compared with MIL-101(Fe), CuS-modified MIL-101(Fe) enhanced the photocatalytic performance by increasing absorption of visible light, narrowing down the bandgap and promoting photo carrier separation efficiency. 7.5-log Gram-negative Escherichia coli (E. coli) could be inactivated by Vis/CSMF/PMS system within 40 min, showing much better performance of 3.5-log E. coli inactivated by Vis/PMS system. The Vis/CSMF/PMS system is applicable in a broad pH range from 3.0 to 9.0, remaining quite steady disinfection efficiency after regenerations of the catalyst. Quenching experiments and electron paramagnetic resonance (EPR) analysis demonstrated 1 O 2 was the dominated ROS rather than OH • and SO 4 •− . Three pathways, including photo-generated electrons (e − ) and O 2 dependent pathway, photo-generated holes (h + ) dependent pathway and CSMF enhanced PMS dissociation pathway, were evidenced to responsible for 1 O 2 formation by aeration experiments and specific 1 O 2 fluorescence probe. 1 O 2 in water attacked the bacterial cell membranes first, got inside the cell and up-regulated the level of intracellular ROS, which further led to cell membrane damage and DNA degradation so as to irreversible cell death. In addition, the developed Vis/CSMF/PMS system could also efficiently inactivate gram-positive bacteria Staphylococcus aureus and fecal coliform bacteria in practical wastewater, suggesting its wide applicability as a promising alternative to conventional disinfection process.