Traditional batch configuration is not sustainable due to catalyst leaching and ineffective recovery. Herein, a novel membrane-based catalyst with oxygen vacancies is developed, which assembled metal-organic-framework cobalt ferrite nanocrystals (MOF-d CoxFe3-xO4) on polyvinylidene fluoride membrane to activate peroxymonosulfate (PMS) for catalytic degradation of emerging pollutants. MOF-d CoxFe3-xO4 are synthesized by one-step pyrolysis using Co/Fe bimetallic organic frameworks (CoxFe3-x bi-MOF) with tunable cobalt content as a template (x/3-x represented the molar ratio of Co and Fe in MOF). Intriguingly, MOF-d Co1.75Fe1.25O4 membrane exhibits excellent PMS activation efficiency as indicated by 95.12% removal of the probe chemical (bisphenol A) at 0.5 mM PMS (∼100 L m-2 h-1 at the loading of 10 mg), which is significantly higher than the traditional Co1.75Fe1.25O4 suspension system (34.16%). Experimental results show that the membrane has excellent anti-interference ability to anions and dissolved organic matter, and can effectively degrade a variety of emerging pollutants, and its performance is not inhibited by the change of solution pH (3-9) or the long-term (20 h) continuous flow operation. EPR and quenching experiments show that catalytic degradation is the result of the synergistic effect of radicals and non-radicals. The oxygen vacancy-mediated mechanism can explain the formation of active substances, and the formation of 1O2 plays an important role in the degradation of bisphenol A. This study provides a membrane-based strategy for effective and sustainable removal of emerging pollutants.
Keywords: Catalytic membrane; Fenton-like process; Metal-organic frameworks; Oxygen vacancy; Radical-nonradical coaction.
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