The synthesis of efficient and stable peroxymonosulfate (PMS) catalysts by doping naturally degradable and functional group-rich chitosan (CS) with nonmetallic atoms remains challenging. In this study, an environmentally friendly electron-rich S-doped CS ferrocarbon material (Fe-S-CN) was synthesized via the sol-gel method, and the resulting material exhibited excellent catalytic activity (up to 98.6 % diclofenac sodium (DCF) removal in 5 min), wide pH applicability, environmental tolerance and renewability. Moreover, Fe-S-CN synergistically activated PMS via both the radical pathway (superoxide radical (O2•-)) and the nonradical pathway (single-linear oxygen (1O2) and electron transfer processes (ETP)) to efficiently mineralize DCF. O2•- originates from the self-decomposition of PMS, whereas 1O2 is due to the oxidation of PMS and further conversion of O2•-. In addition, Fe species, graphitic N and thiophene S are the major active sites in Fe-S-CN. The susceptibility sites of DCF and its possible degradation pathways in the Fe-S-CN/PMS system were inferred in conjunction with density functional theory (DFT) calculation. The present study creates a promising scenario for the synergistic effect of easily overlooked heteroatom doping in chitosan iron-carbon materials in the removal of difficult-to-biodegrade organic matter from water bodies.
Keywords: Chitosan; Diclofenac sodium; Peroxomonosulfate activation; Sulfur dopant.
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