Strengthening peroxymonosulfate activation via cotton-derived carbon: pathway transformation from radical to non-radical

Abstract

The application of metal-based catalysts derived from metal-organic frameworks (MOFs) to activate peroxymonosulfate (PMS) in wastewater decontamination has attracted enormous attention, but its common radical pathway extremely restricted its practical application due to the unavoidable quenching effect from water matrices. Herein, a biomass-derived carbon loading strategy was adopted to transform the reaction pathway from radical to non-radical. First, CuOx-C@CCDC (CCDC denotes the carboxylated cotton-derived carbon) was fabricated with Cu-MOFs/cotton as precursors. Serving as a PMS activator, CuOx-C@CCDC performs well for Fenton-like degradation of sulfoxazole (SIZ), attributing to the synergism between CuOx-C and CCDC, and its apparent rate constant (K_obs) for CuOx-C@CCDC was found to be 6.47 and 10.44 times higher than that of CuOx-C and CCDC, respectively. Mechanistic analysis by a series of characterization technologies including in-situ Raman spectroscopy, in-situ Fourier infrared spectroscopy, electron paramagnetic resonance spectroscopy, and electrochemical analysis unveiled that the radical pathway dominated by ^•OH made the main contribution in the CuOx-C/PMS system. In contrast, the electron-transfer-mediated nonradical pathway was responsible for SIZ degradation in the CuOx-C@CCDC/PMS system, wherein CuOx-C@CCDC functioned as the conductive mediator to transfer electron from SIZ to the surface-confined PMS*. Benefited from this, other electron-rich refractory organic pollutants including sulfamethoxazole, ciprofloxacin and tetracycline hydrochloride could also be efficiently eliminated. In addition, its superiorities including good recyclability, robustness, wide pH range, strong anti-interference against various inorganic anions and adaptability for actual wastewater display a promising prospect. Overall, this work provides a facile and feasible strategy to regulate the reaction pathways in PMS-based advanced oxidation processes.