Visible-light-driven g-C3N4 doped CuFe2O4 floating catalyst enhanced peroxymonosulfate activation for sulfamethazine removal via singlet oxygen and high-valent metal-oxo species

In this study, floating carbon nitride incorporating copper ferrite catalyst (CNCFEp) was synthesized by a simple coprecipitation-calcination method. The prepared catalyst was applied to the catalytic activation of peroxymonosulfate (PMS) for the degradation of antibiotics under visible light irradiation (Vis/CNCFEp/PMS system). In the presence of CNCFEp (2.0 g/L) and PMS (0.1 g/L), 97.6 % of sulfamethazine (SMT, 10 mg/L) was degraded in 30 min under neutral conditions, whereas negligible influence was observed accompanied by water matrixes. The floating composite catalyst showed excellent stability after 5 times recycling experiments. Singlet oxygen (1O2) and high-valent oxo-metal species were unveiled to be the major reactive oxygen species (ROS), rather than conventional hydroxyl radicals or sulfate radicals. These nonradical species were produced by direct oxidation or the transformation of superoxide ions and metastable metal composite at neutral pH. SMT was broken down by four degradation pathways in this system and a remarkable reduction in toxicity has been demonstrated by the quantitative structure–activity relationship (QSAR) prediction. Likewise, the nonradical species were capable of inactivating the bacteria (E. coli). This work was the first study dedicated to the mechanism of PMS activation by CNCFEp and provides a novel catalytic system for removal of organic contaminants and bacteria in environmental waters.