Enhanced heterogeneous degradation of sulfamethoxazole via peroxymonosulfate activation with novel magnetic MnFe2O4/GCNS nanocomposite

Abstract

A magnetic MnFe2O4/g-C3N4 nanosheet nanocomposite was fabricated and used as a heterogeneous catalyst for sulfamethoxazole (SMX) degradation with peroxymonosulfate. The physical and chemical features of the as-synthesized materials were characterized by various technologies. Compared with bare MnFe2O4, the MnFe2O4/g-C3N4 demonstrated better catalytic capacity and shown high catalytic efficiency with a wide initial pH range of 3–11. The activation energy was calculated for 40.47 KJ mol−1 to prove that the degradation was governed by the rate of intrinsic chemical reactions. The four consecutive cycles experiments indicated the excellent stability of as-synthesized catalyst. EPR analysis and quenching experiments demonstrated that SO4• and •OH were generated during the degradation process with SO4• acted as a predominant role. HPLC-MS/MS identified seven intermediate products produced in the degradation process. their ecotoxicity were estimated by ECOSAR model and displayed lower toxicity than SMX. Three relevant degradation pathways and possible degradation mechanism of SMX in the MnFe2O4/GCNS+system were proposed. The redox reaction between Mn2+/Mn3+ and Fe3+/Fe2+ were responsible for the SMX degradation. The g-C3N4 nanosheet was used as both the supporter of MnFe2O4 and the electron-transfer bridge between MnFe2O4 and PMS to accelerate the degradation efficiency.