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

Singlet oxygen (O-1(2)) is an effective reactive oxygen species in disinfection due to its long lifetime and sensitivity to bacteria. This study tried to develop a O-1(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 O-1(2) was the dominated ROS rather than OH center dot and SO4 center dot- 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 O-1(2) formation by aeration experiments and specific O-1(2) fluorescence probe. O-1(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.

Automated summary

This study developed an O-1(2)-dominated process for bacterial inactivation through visible light photocatalysis assisted by PMS. A novel CuS-modified MIL-101(Fe) photocatalyst was synthesized, which enhanced the photocatalytic performance. The results showed that O-1(2) attacked bacterial cell membranes and increased intracellular ROS levels, leading to irreversible cell death. Additionally, the developed system efficiently inactivated other bacteria in practical wastewater.