Green and efficient synthesis of Co-MOF-based/g-C3N4 composite catalysts to activate peroxymonosulfate for degradation of the antidepressant venlafaxine

Based on single metal–organic framework (MOF) composite catalyst ZIF-67/ g -C 3 N 4 (ZG), the composite catalysts ZIF-67/MOF-74(Ni)/ g -C 3 N 4 (ZNG) and ZIF-67/MIL-100(Fe)/ g -C 3 N 4 (ZMG) with double MOFs were synthesized, used to effectively activate peroxymonosulfate (PMS) for degrade venlafaxine (VEN). Various characterization methods (XRD, FT-IR, Raman, SEM , EDS, TEM and TG) showed that ZIF-67 and g -C 3 N 4 ; ZIF-67, MOF-74(Ni) and g -C 3 N 4 ; as well as ZIF-67, MIL-100(Fe) and g -C 3 N 4 successfully formed heterostructures . The series of catalytic degradation results showed that within 120 min, the degradation rate of VEN by ZMG achieved 100% and the mineralization rate reached 51.32%. The removal rate of VEN by ZNG was 91.38%, while that by ZG was only 27.75%. Free radical quenching tests and EPR further confirmed the production of OH and SO 4 − , which could be conducive to the degradation of VEN. The mechanism analysis of PMS activation confirmed that the interaction of Fe 2+ / Co 3+ was stronger than that of Ni 2+ / Co 3+ , and it was an important driving force to significantly enhance the synergistic effect. Finally, Gauss theory calculation and HPLC-MS/MS were used to analyze the intermediate products of VEN. It was verified that the main chemical reactions in the degradation process of VEN were hydroxylation , dehydration, demethylation and tertiary amine substitution.