Effective degradation of 2,4,4'-trichlorodiphenyl by FeC@Fe-800 activated peroxymonosulfate: Superoxide radical and singlet oxygen-dominated advanced oxidation process.

Polychlorinated biphenyls (PCBs) degradation by peroxymonosulfate (PMS) activation through •OH and SO radical oxidation process was the effective technology in the last decades; however, there were few research focusing on removing PCBs by O and O induced by PMS activation. In this work, 90.86% of 2,4,4-trichlorodiphenyl (PCB 28) was degraded by 0.3 g/L FeC@Fe-800 activated 0.5 mM PMS system under the synergistic action of O and O. The structures of FeC@Fe-800 were identified by Scanning electron microscope (SEM), High resolution-transmission electron microscopy (HR-TEM), X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller (BET), Raman spectra and Fourier transform infrared (FT-IR) spectra. Electron paramagnetic resonance (EPR) measurements and quenching tests verified that O and O were the primary reactive species in FeC@Fe-800/PMS/PCB 28 ternary reaction system. Density functional theory (DFT), Linear sweep voltammetry (LSV), and chronoamperometry test revealed that electron-deficient Fe atoms on FeC were the main active sites in FeC@Fe-800 for PMS activation to generate O. Unlike the reported •OH and SO mediated degradation induced by the iron-based catalyst, both O and O contributed to PCB 28 degradation： nucleophilic dichlorination reaction by O and then ring-open oxidation process by O. FeC@Fe-800/PMS system had excellent catalytic performance under different reaction conditions and possessed desirable inorganic salt and natural organic matter resistance. This work elucidated the important role of FeC in PMS activation to generate O and O for PCB 28 decontamination by nonradical way and provided a clue to design rationally catalysts in polychlorinated biphenyl pollution remediation.