Enriched Nitrogen Vacancies Co-C3n5 as Peroxymonosulfate Activator Under Visible Light Irradiation for Tetracycline Degradation Via Enhanced Multiple Electron Transfer Mechanisms

Heterogeneous photocatalytic activation coupled with peroxymonosulfate (PMS) for emerging organic contaminates degradation is considered as an advanced water purification technology. In this study, a novel Co-C3N5photocatalyst with tailored nitrogen vacancies was synthesized by one-step thermal polymerization for PMS activation and tetracycline removal. The photo-chemical oxidation (0.4% Co-C3N5/PMS/light) system displayed superior advantage, in which the observed rate constant of TC degradation (0.1488 min-1) was 10.86 and 1.82 times higher than that of photooxidation and chemical oxidation systems. The main active species including h+, 1O2 and Co(IV) were identified by quenching experiments, electron paramagnetic resonance and chemical probe method using phenyl methyl sulfoxide (PMSO). Moreover, the density functional theory calculation results further verified the reconstruction of local charge distribution during photo-chemical oxidation synergism, indicating Co doping not only introduced nitrogen vacancies to promote photoelectrons capture, but also boosted electron transfer from C-N framework to PMS and the generation of active species. Three possible pathways of TC degradation were proposed and the reduced toxicity of the intermediates were evaluated. Overall, this study proposed unique multiple electron transfer mechanisms for the enhanced tetracycline degradation in Co-C3N5/PMS/light system and provided a novel strategy for developing high-efficient photocatalyst and rapid degradation of organic pollutants.