Preparation And Application Of Transition Metal Oxide-based Catalytic Materials Based On Zeolitic Imidazole Framework

In recent years,more and more attention has been paid to the water environment caused by organic matter including BPA.Bisphenol A（BPA）is a very common industrial raw material,which is widely used in the industry of polycarbonate,epoxy resin and other chemicals.BPA also has endocrine disrupting effects.Even if a very low concentration of BPA appears in water,it will pose a huge threat to the environment and human health.Therefore,an effective solution to BPA is urgently needed.Advanced oxidation technology（AOPs）is a good method to efficiently solve the problem of organic pollution,which can degrade organic pollutants by activating persulfate（PMS）with high-performance catalysts.Due to the large specific surface area,ordered crystalline structure and tunable pore size characteristics of zeolite imidazole frameworks（ZIFs）,as well as the characteristics of high active centers of transition metal oxide-based materials,zeolitic imidazole frameworks and transition metal oxide-based materials have been widely used in recent years.In this study,we attempted to use advanced oxidation technology to solve BPA-containing pollutants,prepared transition metal oxide-based catalysts based on zeolite imidazole framework for AOPs,and also studied the performance and mechanism of the degradation of BPA with the combinational use of the catalysts and peroxymonosulfate（PMS）.First,a ZIF67@ZIF8-derived transition metal oxide/carbon nanofiber composite catalyst（CoO/Co@CNF）was successfully prepared by a three-step hybrid reaction,electrospinning,and heat treatment.The catalytic performance of the catalyst was determined by activating peroxymonosulfate（PMS）to degrade bisphenol A.The degradation degree and comprehensive degradation efficiency of CoO/Co@CNF were both higher than those of the catalyst prepared by single metal cobalt.For the simulated water sample containing 20 mg·L^-1of BPA,the removal rate of CoO/Co@CNF combined with PMS reached 99.8%within 5 min.CoO/Co@CNF showed very good recyclability and stability,and the catalytic activity of the catalyst remained above 88.9%after 9 cycles.The material characterization results show that the carbonized shell of CoO/Co@CNF forms a nanofiber structure with porous carbon coating,which effectively inhibits the agglomeration of catalyst particles,increases the specific surface area of??the catalyst and the exposure of the central active metal,and also elevates the the stability of the catalyst.Radical trapping experiments show that CoO/Co@CNF can effectively activate PMS to generate SO₄^-·,·OH and¹O₂together in degrading BPA.The results show that CoO/Co@CNF has potential application prospects in the field of advanced oxidation technology to treat organic wastewater.Second,ɑ-MnO₂（ɑ-MnO₂-40,ɑ-MnO₂-55,ɑ-MnO₂-70）andɑ-MnO₂-ZIF8（ɑ-MnO₂-ZIF8-40,ɑ-MnO₂-ZIF8-55,ɑ-MnO₂-ZIF8-70）at different temperatures were prepared by a three-step method of hydrothermal,heat treatment and standing at different temperatures.The experimental results show that the zeolite imidazole framework ZIF8 is uniformly supported on the surface of MnO₂,so as to increase the specific surface area and conductivity of the catalyst material.The performance of the catalysts was evaluated by experiments in whichɑ-MnO₂andɑ-MnO₂-ZIF8 were used for activating PMS to degrade bisphenol A.Within 20 min,theɑ-MnO₂-ZIF8-55/PMS system can degrade 99.4%of BPA.The excellent performance ofɑ-MnO₂-ZIF8-55 is mainly due to the presence of more oxygen vacancies on the surface of the material,and the surface-loaded zeolite imidazole framework ZIF8.The electron transfer ability of the catalyst is enhanced and the pollutants are enriched to a certain extent.ɑ-MnO₂-ZIF8-55 showed good recyclability and stability,and the degradation efficiency of BPA remained above 84.8%after 5 cycles of experiments.Therefore,ɑ-MnO₂-ZIF8 can be a promising catalyst in the field of BPA treatment by advanced oxidation technology based on sulfate radicals.In conclusion,combining zeolitic imidazole frameworks（ZIFs）with transition metal oxide-based materials is an effective strategy to obtain catalysts with high activity and high stability.