A novel photocatalytic system coupling metal-free Carbon/g-C3N4 catalyst with persulfate for highly efficient degradation of organic pollutants

A variety of photocatalytic systems have emerged as the effective methods for the degradation of organic pol-lutants. In this research, a novel photocatalytic system, named CNC-PDS has been proposed, which couples a metal-free carbon/g-C3N4 (CNC) photocatalyst with persulfate (PDS), and applied for efficient degradation of paracetamol (PCM) under simulated sunlight. The CNC-PDS system exhibited excellent photocatalytic capability, where the PCM was completely degraded in 40 min under simulated sunlight. The degradation rate of CNC-PDS system was 9.5 times compared with the g-C3N4 and PDS coupled systems. The CNC-PDS system can efficiently degrade other representative pollutants in neutral solutions, such as pharmaceuticals, endocrine disrupting compounds (EDCs), azo dyes. The excellent catalytic activity of CNC-PDS system should be ascribed to the two aspects: a) the increased light absorption range led to more photo-induced electron-hole pairs generation compared with the original g-C3N4. Meanwhile, the charge separation efficiency of the CNC photocatalyst was drastically enhanced which was proved by the results of PL and EIS analysis. These results represented the carbon/g-C3N4 might offer more e(-) to promote PDS activation. b) The introduction of C=O and the improved specific surface area provided more active sites for PDS activation. In addition, the EPR analysis and quenching experiments indicated that O-2(center dot-), h(+) and O-1(2) were the main active species for PCM in the CNC-PDS system under simulated sunlight, and the contribution order was O-2(center dot-)>O-1(2)>h(+). The degradation pathways of PCM in the CNC-PDS system are proposed based on the results of HPLC-MS. The novel CNC-PDS photocatalytic system has provided a viable option for treatment of contaminated water by organic pollutants.