Effective degradation of 2,4,4′-trichlorodiphenyl by Fe3C@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 4 •– radical oxidation process was the effective technology in the last decades; however, there were few research focusing on removing PCBs by O 2 •– and 1 O 2 induced by PMS activation. In this work, 90.86% of 2,4,4-trichlorodiphenyl (PCB 28) was degraded by 0.3 g/L Fe 3 C@Fe-800 activated 0.5 mM PMS system under the synergistic action of O 2 •– and 1 O 2 . The structures of Fe 3 C@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 2 •– and 1 O 2 were the primary reactive species in Fe 3 C@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 Fe 3 C were the main active sites in Fe 3 C@Fe-800 for PMS activation to generate 1 O 2 . Unlike the reported •OH and SO 4 •– mediated degradation induced by the iron-based catalyst, both O 2 •– and 1 O 2 contributed to PCB 28 degradation： nucleophilic dichlorination reaction by O 2 •- and then ring-open oxidation process by 1 O 2 . Fe 3 C@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 Fe 3 C in PMS activation to generate O 2 •- and 1 O 2 for PCB 28 decontamination by nonradical way and provided a clue to design rationally catalysts in polychlorinated biphenyl pollution remediation.