Performance On Visible-light Activation Of Persulfate By G-C₃N₄/TiO₂ Toward Degradation Of Micropollutants

A novel g-C₃N₄/TiO₂-Persulfate visible light catalytic system was proposed to efficiently remove micropollutant in water,which used heterojunction of g-C₃N₄/TiO₂ to generate a large of electrons to activate persulfate（PS）to enhance the removal effect of micropollutants under light irradiation.In this study,g-C₃N₄/TiO₂ photocatalyst was synthesized by calcining method.The physical and chemical properties of g-C₃N₄/TiO₂ catalyst were investigated by various materials characterization methods.The results showed that in g-C₃N₄/TiO₂ catalyst,TiO₂ particles were evenly distributed on g-C₃N₄ flake,the catalyst had certain visible light absorption performance,and the photogenerated electron-hole pairs had high separation efficiency.To investigate the application effect of catalysts,the removal characteristics of target pollutant acetaminophen（AAP）by g-C₃N₄/TiO₂-PS visible light catalytic system under various parameters were systematically studied.The results showed that g-C₃N₄/TiO₂ photocatalyst with mass ratio of 5%（TCN₅）showed the best dagradation effect;100 m L 5 mg/L acetaminophen solution with pH 7 was almost completely degraded within 30 min under the condition that the addition of catalyst and PS were respectively 0.5 g/L and 2 mM.Meanwhile,the mineralization of acetaminophen in 5%-g-C₃N₄/TiO₂-PS system was also very high,up to 80%,and its acute biological toxicity was significantly reduced after degradation reaction.In addition,the catalyst cycle experiments indicated that 5%-g-C₃N₄/TiO₂ had high stability.Through the free radical quenching experiments,electron paramagnetic resonance（EPR）confirmed that the oxidizing active species in 5%-g-C₃N₄/TiO₂ photocatalytic system were SO₄·^-,·OH and h⁺,in which h⁺played a leading role.The five intermediates produced during acetaminophen degradation were identified by time-of-light mass spectrometry,and inferred two degradation pathways.Besides acetaminophen,the degradation effects of other three common water micropollutants,carbamazepine,bisphenol A and phenol,were investigated,all of which reached high removal levels.Based on the results of characterization and the degradation experiments,the possible mechanism of action of g-C₃N₄/TiO₂-PS visible light catalytic system was proposed.