Efficient removal of drug-resistant Providencia alcalifaciens and its associated QnrS2 antibiotic-resistance genes by carbon-doped polymer carbon nitride

Pathogenic bacteria posed a serious threat to water ecosystems and might even have triggered disease outbreaks. In this study, a carbon-doped polymer carbon nitride (C-PCN) composed of numerous interwoven and stacked ultrathin lamellar units was fabricated via a simple stepwise calcination strategy. Compared with the polymer carbon nitride (PCN), C-PCN exhibited more remarkable photocatalytic performance for the Providencia alcalifaciens (P. alcalifaciens) isolated from a local hospital's waste water. C-PCN with a concentration of 0.4 mg mL⁻¹ killed 7.07 log P. alcalifaciens within 100 min, whereas PCN could only inactivate 2.38 log P. alcaliphilus under the same conditions. Moreover, C-PCN could remove 99.87% antibiotic-resistance genes (ARGs) QnrS2 within 6 h. We addressed the gap in the existing research on inactivated P. alcalifaciens, and the fragmentation pathway of circular plasmids during photocatalysis reaction was observed via atomic force microscopy (AFM). The incorporation of carbon enhanced the visible light absorption capability of C-PCN and promoted more efficient charge separation. Mechanism investigation revealed that ˙O₂⁻ and ˙OH were the vital reactive oxygen species (ROS) for antibiotic-resistance bacteria (ARB) inactivation and ARG degradation. ROS could induce cell rupture by damaging cellular membranes and disrupt metabolic processes by affecting enzyme activity. Additionally, a small-scale continuous-flow device could inactivate bacteria in hospital wastewater in 2.5 h under natural light irradiation, thus laying a foundation for advanced hospital wastewater treatment.