Low-power LED lamp-driven dual-defect carbon nitride activated peroxydisulfate for bisphenol S degradation: Performance, DFT calculations, and mechanism

The heterogeneous photocatalytic activation of peroxydisulfate (PDS) has garnered significant research interest due to its high efficiency and environmentally friendly characteristics. Nonetheless, the effective activation of PDS using low-power light-emitting diode (LED) lamp presents challenges. This study focused on the controlled synthesis of carbon/nitrogen dual defects carbon nitride (VCN) by modifying the ratios of precursor and gas templating agents, which facilitated PDS activation under LED lamp to degrade bisphenol S (BPS). The VCN-2/ PDS/LED system achieved complete BPS degradation within 25 min, with a pseudo-first-order kinetic rate constant 11.15 times higher than that of the CN/PDS/LED system. This system demonstrated the capability to selectively degrade low ionization potential pollutants. Experiments involving quenching, probes, electrochemical methods, and electron spin resonance identified singlet oxygen as the primary reactive species. The improved catalytic performance was attributed to the redistribution of the conduction band and valence band in CN due to C/N double defects, which regulated the VCN energy levels. This configuration provided dual pathways for photogenerated electron transfer, allowing PDS to capture photogenerated electrons and enhancing the migration and separation of electron-hole pairs. Additionally, the effects of key experimental parameters (catalyst dosage, PDS dosage, initial pH, various inorganic ions, and humic acid) on BPS degradation were examined. The degradation intermediates of BPS were identified, degradation pathways were proposed, and their ecological toxicity was evaluated. This study clarifies the mechanism of PDS activation with VCN under low-power LED lamp and offers effective strategies for the remediation of emerging pollutants in aquatic environments.