Singlet oxygen-dominated activation of peroxymonosulfate by CuO/MXene nanocomposites for efficient decontamination of carbamazepine under high salinity conditions: Performance and singlet oxygen evolution mechanism

The degradation of organic contaminants via traditional radical-dominated advanced oxidation processes (AOPs) under high salinity conditions was limited due to side reactions between coexisting inorganic anions and radicals. Herein, a nonradical oxidation process via peroxymonosulfate (PMS) activation by CuO/MXene for treating high-salinity organic wastewater was developed. Rapid removal efficiency of target pollutant carbamazepine (CBZ) was significantly enhanced to 95.88% within 20 min by CuO/MXene under high salinity conditions (NaCl, 200 mM), compared to the efficiency of 4.30% exhibited by PMS alone. Besides, CBZ maintained a higher removal efficiency of > 81.04% in complex highly saline wastewater composed of eight common inorganic anions. Radical quenching experiments and electron paramagnetic resonance (EPR) analysis confirmed that radical and nonradical oxidation processes were involved in the catalytic process. However, singlet oxygen (1O2) was identified as the primary reactive species, and its contribution rate to CBZ degradation was > 73.58% in a wide pH range (3.0-9.0). The oxygenated functional groups and the interaction between CuO/MXene and PMS facilitated the production of 1O2. The degradation pathway was proposed based on the detection of intermediates. This work provided a new inspiration for the decontamination of organic contaminants under high salinity conditions via a nonradical oxidation process.