The Highly Efficient Photocatalytic System Coupling G-C₃N₄ With Persulfate For Degradation Of Organic Pollutants

With the rapid development of printing and dyeing,papermaking,pharmaceutical and other industries,a large number of traditional and emerging refractory organic pollutants are released into water bodies,resulting in the increasingly complex composition and increasing types of organic pollutants,which seriously threaten the survival of aquatic organisms and human health.The single water treatment technology cannot meet the needs of water organic pollution control due to the limitations of high energy consumption,low efficiency and high cost.The development of coupling technology for water treatment will become prevalent.The g-C3N4 and persulfate coupled photocatalytic technology is promising in water organic pollution control,while it still has some problems,such as low solar energy utilization,poor pollutant removal efficiency,lack of environmentally friendly catalysts and imperfect system construction.Therefore,it is urgent to improve the coupling photocatalytic technology of gC3N4 and persulfate,so as to develop an innovative green,cost-effective,efficient and widely applicable organic wastewater treatment technology.In order to meet the urgent needs of water pollution control,the main work of this study includes:(1)The synergistic effect and environmental application of coupled photocatalytic system(gCN-P)of g-C3N4 and persulfate(PDS)in the degradation of methyl orange(MO)under simulated sunlight were studied.The results showed that g-C3N4 and PDS have the best synergistic effect under simulated sunlight compared with visible light irradiation,and the synergistic index in the gCN-P system is 3.53.The gCN-P system performed well for the degradation of MO in tap water quality,and showed better removal effect on other typical pollutants such as macromolecular azo dyes,drugs,and endocrine disruptors.The main active substances for MO degradation and the stability of g-C3N4 in gCN-P system were confirmed by quenching and cycling experiments,respectively.The degradation mechanism and possible degradation pathway of MO in gCN-P under simulated sunlight were proposed by EPR and HPLC-MS.These results provided effective support for development of coupled photocatalytic technology of g-C3N4 and persulfate under simulated sunlight.(2)Based on the gCN-P system,a novel photocatalytic system(CNC-PDS)coupled gC3N4 non-metallic photocatalyst(CNC)with persulfate(PDS)was proposed to achieve highly efficient removal of organic pollutants.The chemical structure,morphology,photoelectric properties and specific surface area of CNC catalyst was characterized by XRD,UV-VIS,PL,EIS and BET.The photocatalytic degradation of paracetamol(PCM)by CNC-PDS photocatalytic system under simulated sunlight was investigated.The experimental results showed that the CNC-PDS system could completely treat 200 mL 10 mg/L PCM solution after 40 min of simulated sunlight irradiation,and the CNC catalyst had stable chemical structure verified by cycle experiments.The main active species of CNC-PDS system under simulated sunlight were explained by quenching experiment and EPR test,and the degradation mechanism of PCM was also proposed based on the results of quenching experiment and EPR test and Schottky curve.Based on the results of HPLC-MS,the possible degradation pathways of PCM were proposed.The CNC-PDS system is universal,which can efficiently degrade other typical organic pollutants such as azo dyes,antibiotics and endocrine disruptors under neutral conditions.The CNC-PDS system provides a new cost-effective and efficient technology for treatment of organic wastewater in an environmentally friendly way.