Structural Design Of ZIF-67 Derived Catalytic Materials And Their Bisphenol A Degradation Performance And Mechanism

The advanced oxidation technology of persulfate based on heterogeneous catalysis has attracted much attention because of its advantages of mild reaction conditions,simple operation and strong oxidation.The research and development of high-performance catalytic materials is a key link to promote the technology to engineering applications.However,the existing catalytic materials still suffer many challenges such as poor catalytic efficiency,poor removal of target pollutants in complex substrates,and low stability during recycling.Based on above,this thesis takes the ZIF-67 derivative catalytic material as precursor,adopting the strategies of reaction kinetics regulation,tannic acid controllable etching,and in-situ growth to achieve the optimization of the catalyst structure and composition.Through the removal of bisphenol A,we explore the relationship between catalyst catalytic performance and structure and composition,and reveal the interface mechanism of pollutants and catalysts.The specific research content is as follows:（1）Based on the problems of poor catalytic activity and low stability of the current heterogeneous catalysts,Co₃O₄/C@Si O₂ nanoreactors（YSCCSs）with core-shell structure and graphitized carbon support（YSCCSs）were prepared by means of reaction kinetic control methods.In the removal of BPA,the efficiency of YSCCSs with a core-shell structure is 5.4times higher than that of Co₃O₄/C directly derived from ZIF-67(YSCCSs,0.75 min^-1,Co₃O₄/C,0.14 min^-1).At the same time,in the leaching test of cobalt ions,the maximum leaching amount of YSCCSs within 10 minutes was 0.093 mg/L,which was much lower than those of Co₃O₄/C with 0.35 mg/L and pure Co₃O₄ with 0.44 mg/L.The increase in catalytic efficiency and stability of the catalyst can be attributed to the existence of the core-shell structure and the supporting role of graphitized carbon to active sites.Radical quenching experiments and EPR results indicated that YSCCSs activates persulfate to degrade pollutants is a SO₄^·-dominated AOPs.（2）Based on the problem of metal ions leaching during the catalytic process,a nitrogen-doped,hierarchical porous carbon nanocatalyst（NDHC）was prepared using kinetic control and confined pyrolysis strategies.During the preparation process of the catalyst,most of the cobalt nanoparticles were removed by acid etching,therefore,only 0.012 mg/L of cobalt ions was detected,which is lower than YSCCSs（0.093 mg/L）,Co₃O₄/C（0.35 mg/L）and Co₃O₄（0.44mg/L）.The degradation experiment of BPA（20 mg/L）showed that NDHC could be optimized to achieve 97%removal within 5 minutes.This high efficiency can be attributed to the reasonable optimization of structure（grade porous）and composition（graphitization and nitrogen doping）.The quenching experiments and EPR test results show that NDHC activated PMS to degrade BPA is a singlet oxygen dominated non-radical advanced oxidation process.（3）Selective removal of organic pollutants from surface water with high efficiency is crucial in water purification.In this chapter,yolk-shell Co/C nanoreactors（YSCCNs）are facilely synthesized via pyrolysis of controllably etched ZIF-67 by tannic acid.Under HA and BPA condition,the reaction rate of YSCCNs is 0.32 min^-1,which is 23.1%and 45.4%higher than hollow structures（HCCNs）and solid structures（SCCNs）.This synergistic mechanism can be attributed to the size sieving effect of the nanoreactor shell:small molecules of BPA（1.07nm）can pass through the pores（1.5-3.0 nm）in the shell,while most of the humic acid（Average diameter>1μm）is intercepted on the shell.The size sieving effect enables YSCCNs to achieve rapid removal of target pollutants in complex pollutant systems of different sizes.（4）Using the strategy of in situ growth of ZIF-67 on the surface of cotton fibers,large-scale synthesis of catalyst precursor cotton@ZIF-67 was realized.The obtained composite catalyst CC@CNCo showed excellent performance in the removal of BPA.By optimizing the pyrolysis temperature,CC@CNCo-9 could achieve more than 97%BPA removal within 3 min,which is significantly better than traditional heterogeneous cobalt-based catalysts.This improvement may be due to the uniform loading of ZIF-67 nanoparticles on the cotton fiber,and the non-radical degradation process from the cotton fiber derived carbon.Finally,the catalyst CC@CNCo-9 was packed in the column and the continuous flow experiment was carried out.Compared with the pure non-radical process,it showed better stability.This thesis analyzes the properties of catalyst including catalyst activity,anti-interference ability,degradation mechanism,large-scale synthesis,and then discusses the advantages of MOF-based catalysts in the application of persulfate advanced oxidation processes and the existing problems and the possibility of large-scale synthesis.It aims to provide relevant theoretical and technical support by the design of high-performance catalytic materials to remove of trace organic pollutants.