C vacancy and F decorated g-C3N4 for boosting photocatalytic ozonation of sodium p-perfluorinated nonoxybenzenesulfonate

Abstract

Photocatalytic ozonation (PCO) was a novel water treatment method, but the low photo-generated electron (e-) utilization and ambiguous ROS formation mechanism restrained its performance. Herein, C vacancy and F co-decorated g-C3N4 (FCN_Cv) was designed to accelerate the PCO performance with sodium p-perfluorinated nonoxybenzenesulfonate (OBS) acting as model pollutant. Comparative characterizations revealed that FCN_Cv remained the inherent structure of g-C3N4 (BCN), and had an enhanced conduction band potential, narrower band gap and longer e- lifetime. FCN_Cv exhibited the greater activity over BCN, with 99.3 % OBS removal in 30 min but only 78.3 % for BCN during PCO process. •OH was the main ROS for degrading OBS. The greater •OH yield was obtained by FCN_Cv PCO process because of the increase of e- utilization. On one hand, the two electrons reduction of O2 into H2O2 on FCN_Cv was accelerated, which triggered the peroxone reaction between photogenerated-H2O2 and O3. On the other hand, the direct one electron reduction of O3 by e- also accounted for •OH generation. 17 kinds of intermediates were detected and the OBS degradation routes were inferred, which was involved with hydroxylation, C-O cleavage and aromatic ring opening reactions. Overall, this study demonstrated the feasibility of decorating F element and C vacancy on g-C3N4 in enhancing e- utilization and •OH generation during PCO process as well as deepened the understanding of fate of OBS in PCO process.