Preparation Of Electro-Fenton Cathode Modified With FeCo-ZIF Derivative And The Performance Of Degrading Antibiotics

Electro-Fenton technology uses oxygen reduction reaction（ORR）to generate H₂O₂in situ and is activated to generate hydroxyl radical（?OH）,thus realizing the advanced electrochemical oxidation technology for the efficient degradation of organic pollutants,while also realizing the characteristics of environmental protection.However,the homogeneous electro-Fenton system needs to be carried out under acid conditions,and the reaction process is accompanied by the formation of iron sludge,which limits its wide application.To overcome the shortcomings of homogeneous electro-Fenton,heterogeneous electro-Fenton system has attracted wide attention.The design of cathode directly affects the feasibility and efficiency of the system,so the preparation of cathode with high activity and high stability is very important in the electro-Fenton system.The combination of catalyst and carbon cathode can promote the in-situ utilization of H₂O₂and improve the recycling efficiency of catalyst.In this study,FeCo₂O₄catalyst was prepared using FeCo-ZIF as the precursor system.The catalyst was fixed on the carbon cathode by coating method as the catalytic layer,and the morphology composition and electro-chemical performance of the catalyst were characterized.Using ofloxacin（OFX）and sulfamemetrazole（SMX）as target pollutants,the heterogeneous electro-Fenton system was constructed to explore the influencing factors,degradation pathways and degradation mechanisms of target pollutants.The main work is as follows:（1）FeCo₂O₄-CF heterogeneous electro-Fenton cathode was prepared by calcination modification of carbon felt（CF）and combining with FeCo₂O₄.The thermal modification of CF improves the ORR selectivity of two electrons,and FeCo₂O₄is coated on CF as the catalytic layer of cathode.Scanning electron microscopy（SEM）,transmission electron microscopy（TEM）,X-ray diffraction（XRD）,X-ray photoelectron spectroscopy（XPS）and other characterization methods were used to characterize the catalytic layer of the prepared cathode.It was found that the catalytic layer of the prepared cathode had regular porous dodecahedron structure.Abundant micro-pores on the surface can provide more active sites to activate H₂O₂to?OH.The heterogeneous electro-Fenton system was constructed with boron-doped diamond electrode（BDD）and FeCo₂O₄-CF electrode as anode and cathode,and OFX as target pollutants,respectively.The catalytic activity experiment showed that the OFX removal rate reached 93%when the current was 30 m A,the oxygen flow rate was 50 m L/min,theCF calcination temperature was 500℃and the p H was 3,and the pollutant removal rate remained high after three consecutive runs.Radical quenching experiments and electron paramagnetic resonance（EPR）analysis of the types of free radicals in heterogeneous electro-Fenton system confirm that the high catalytic efficiency of heterogeneous electro-Fenton system is due to the synergistic effect of?OH and·O₂^-.（2）To realize the efficient utilization of O₂,improve the cathode formation rate of H₂O₂and the ability to generate?OH,the FeCo₂O₄/MWCNTs-C/PTFE air diffusion electrode was prepared by a simple mixing process.Using SEM,TEM,XRD,XPS and other characterization methods,the micro-morphology and phase structure of the prepared air diffusion electrode were characterized.It was found that the FeCo₂O₄nanoparticles were uniformly attached around the MWCNTs,and the abundant micro-pores on the surface of FeCo₂O₄could provide more active sites to activate H₂O₂to?OH.A heterogeneous electro-Fenton system was constructed with Pt sheet electrode,FeCo₂O₄/MWCNTs-C/PTFE air diffusion electrode and saturated calomel electrode（SCE）as anode,cathode and reference electrodes,respectively,and SMX as target pollutants.The catalytic activity experiments show that with the addition of different proportions of FeCo₂O₄,H₂O₂can decompose in situ in the presence of FeCo₂O₄,and 75%of SMX can be removed when the external voltage is-0.7V（V vs.SCE）,p H=3,and the ratio of FeCo₂O₄/MWCNTs is 3:1.In the range of p H=3,5,7,9,FeCo₂O₄/MWCNTs-C/PTFE air diffusion electrode has a high removal rate of SMX,which extends the range of application p H effectively.The degradation mechanism and pathway of SMX were proposed by EPR and LC-MS.The interconversion of Fe^2+/3+and Co^2+/3+in FeCo₂O₄effectively promoted the production of?OH,thus improving the cathodic catalytic degradation ability.In this paper,FeCo₂O₄derived from bimetallic FeCo-ZIF was used as the catalyst layer to design two kinds of heterogeneous cathodes for electro-Fenton system,and to explore the degradation mechanism of pollutants.The prepared cathodes have excellent electro-Fenton properties,which has important research significance and value for the development and design of new heterogeneous electro-Fenton cathodes.