Fabrication of CoFe2O4/Mn3O4 decorated ultrathin graphitic carbon nitride nanosheets membrane for persistent organic pollutants removal: Synergistic performance and mechanisms

Integration of sulfate radicals-based advanced oxidation processes (SR-AOPs) with separation membranes has enthralled considerable attentions because it can remove persistent toxic micropollutants in a low-energy and cost-effective manner. However, fabrication of such an integrated membrane simultaneously with excellent self-cleaning property, catalytic capability and long-term durability remains a challenge. Herein, for the first time, CoFe2O4 (CFO) and Mn3O4 (MO) nanoparticles were anchored on ultrathin graphitic carbon nitride (UCN) nanosheets via a solvothermal method to prepare heterogeneous Fenton-like catalysts (MO/CFOUCN). Systematic characterizations demonstrated the successful preparation of powder catalysts with favorable degradation ability. Notably, the optimal composite catalyst possessed satisfactory degradation (94.5 %) and kinetic rate (0.1367 min(-1)) for norfloxacin (NOR) within 30 min. Thereafter, an integrated MO/CFO/UCN@P membrane was fabricated by vacuum-assisted filtration of the catalyst on a supporting membrane surface. It was interestingly found that, benefiting from the synergistic effect of in-situ oxidation and membrane filtration, activating peroxymonosulfate (PMS) endowed the membrane with high removal rates (over 91.8 % for tetracycline, bisphenol A, humic acid (HA)) and high permeation flux (332.7 L.m(-2).h(-1)) driven solely by gravity. Significantly, the membrane achieved a flux recovery rate of 91.9 % with the assistance of PMS after filtering HA solution. Furthermore, quenching experiments and electron paramagnetic resonance (EPR) tests confirmed that both radical and nonradical pathways contributed to the mineralization of NOR. Based on the detection of intermediates in the degradation process, potential NOR degradation pathways were proposed. Overall, this study provided new ideas about integrating Fenton-like catalysts with membrane technology for removal of persistent organic pollutants.