Mechanistic studies on peroxymonosulfate activation by g-C3N4 under visible light for enhanced oxidation of light-inert dimethyl phthalate

Abstract

Excitation of metal-free graphitic carbon nitride (g-C3N4) under visible light can successfully achieve efficient activation of peroxymonosulfate (PMS). Synergistic effects and involved mechanism were systematically investigated using a light-inert endocrine disrupting compound, dimethyl phthalate (DMP), as the target pollutant. Under visible light irradiation, DMP could not be degraded by direct g-C3N4-mediated photocatalysis, while in the presence of PMS, the dominant radicals were converted from •O2 to SO4•- and •OH, resulting in effective DMP degradation and mineralization. Results showed that higher dosage of PMS or g-C3N4 could increase the activation amount of PMS and corresponding DMP degradation efficiency, but the latter approach was more productive in terms of making the most of PMS. High DMP concentration hindered effective contact between PMS and g-C3N4, but could provide efficient use of PMS. Higher DMP degradation efficiency was achieved at pH lower than the point of zero charge (5.4). Based on intermediates identification, the DMP degradation was found mainly through radical attack (•OH and SO4•-) of the benzene ring and oxidation of the aliphatic chains.