Nickel-decorated ZIF-67 (Co) MOF derived bi-metallic catalyst for efficient degradation of tetracycline under microwave irradiation through persulfate activation route: Performance assessment and predictive intermediate toxicity profile

In this study, tetracycline (TC) removal performance evaluation was accomplished alongside the prediction of the eco-toxicological effect of the generated intermediates. The polyhedron shaped nickel (Ni)-decorated ZIF-67 (Co) MOF derived bi-metallic catalyst was synthesized successfully by pyrolysis of the Ni-modified rhombic dodecahedron shaped ZIF-67 template. Therefore, under the following microwave (MW) based operation conditions: catalyst dose 0.6 g/L, initial concentration of TC 10 mg/L, MW input power 450 W, and at unchanged pH, Ni-decorated ZIF-67 (Co) derived catalyst Ni Co /C displayed ∼97.59 % TC removal within only 2 min of MW exposure. Magnetic (i.e., Ni and Co) and dielectric (i.e., carbon) counterparts enhanced better microwave absorption while reducing reflective loss. The absorbed microwave energy was dissipated to form localized ‘hotspots’ for direct decomposition of PS, H₂O, and TC molecules whereas conductive carbon matrix with Ni doping propagated electronic mobility for free reactive radical generation. The MW induced ‘photo-electric’ effect of electron-hole pair separation and electron transfer via redox couples (i.e., Co²⁺/Co³⁺ and Ni²⁺/Ni³⁺) encapsulated in carbon nanocage resulted in the generation of various reactive free radicals including sulfate (SO₄^•−), hydroxyl (^●OH), superoxide anion (^●O₂^–) radicals and singlet oxygen (¹O₂) which were confirmed by EPR. The theoretical eco-toxicological effects of intermediates were analyzed by ECOSAR and T.E.S.T. software, which may highlight the need for stringent rules in the future regarding the discharge of advanced oxidation process-treated wastewater and further research on the mitigation process. Moreover, the reusability study and evaluation of TC degradation in natural water showcased the calibre of this Ni-decorated ZIF-67 (Co) derived catalyst Ni Co /C to become a next-generation MW-responsive catalyst to tackle various emerging contaminants.