Insights into enhanced degradation of antibiotic trimethoprim in water using a novel K doped g-C3N4 photocatalyst under vacuum-UV irradiation: Performance and mechanisms

In this work, an innovative strategy combining vacuum ultraviolet (VUV) and K doping graphite carbon nitride (K-g-C3N4) was proposed for antibiotic removal in aqueous. The properties of K-g-C3N4 were systematically characterized by XRD, FT-IR, BET, SEM, UV-vis DRS, and XPS, showing that K-g-C3N4 possessed a larger specific surface and richer functional groups than g-C3N4. The catalytic efficiency of K-g-C3N4 was investigated for the trimethoprim (TMP) removal under VUV irradiation. Compared with UVC photolysis, VUV photolysis, UVC/g-C3N4, VUV/g-C3N4, and UVC/K-g-C3N4 processes, VUV/K-g-C3N4 enhanced the pseudo-first-order reaction rate constant of TMP removal by 2.0–19.7 times and the mineralization rate by 9.0%-38.2%. Electron paramagnetic resonance results and quenching experiments validated that O2•-, •OH, 1O2, h+, and e- were engaged in the VUV/K-g-C3N4 process. The fluorescent spectra of O2•--substituted and •OH-substituted products revealed that the K-g-C3N4 greatly enhanced the quantity of O2•- and •OH during VUV irradiation. The VUV/K-g-C3N4 system produced marginally more H2O2 and •OH than the UVC/K-g-C3N4 system, confirming that K-g-C3N4 predominantly utilized the UVC and other ultraviolet–visible light emitted by the VUV lamp, with VUV having a minor effect. Furthermore, K-g-C3N4 had exceptional stability and reusability, efficiently degrading various contaminants under VUV irradiation. This work offered a comprehensive insight into VUV/K-g-C3N4 process as a novel approach for antibiotic removal from water.