The Study Of Old Landfill Leachate By Electro-fenton Process Using Nano-Fe₃O₄@MOF As Catalyst

With the acceleration of urban development,the rate of garbage generation is also increasing.Currently,the most commonly used landfill method produces a large amount of landfill leachate.The leachate has high COD content,poor biodegradability,and a large number of toxic and harmful substances such as heavy metals,which pose a great threat to the environment.Conventional biological treatment process is not very effective in the treatment of landfill leachate,so it is necessary to develop more effective methods to improve the treatment effect and provid ideas for the pretreatment and deep treatment process application of leachate.In recent years,Heterogeneous electrofenton technology has achieved good results in the field of refractory wastewater degradation.It has the advantages of high reaction efficiency,low cost and no secondary pollution,and has a broad application prospect.However,the mass transfer efficiency of heterogeneous electrofenton method is generally low.Aiming at the difficulties in the treatment of the aged landfill leachate and the low efficiency of the catalyst in the electrofenton system,this study developed a kind of high-efficiency electrofenton catalyst and applied it in the treatment of the leachate,hoping to mineralize the organic matter in it to reduce COD,improve biodegradability and provide conditions for the subsequent biological treatment.In this paper,nano-Fe₃O₄ particles were prepared by solvothermal method,and then coated with a layer of Fe-MOFs.Finally,a nano-Fe₃O₄@MOF material with rough and porous surface was obtained.The shell-nucleus nanoparticles were analyzed by X-ray diffraction and observed by scanning electron microscopy and transmission electron microscopy.FT-IR indicates that the material has been modified with ligands of functional groups such as hydroxyl group and carboxyl group.The results showed that the specific surface area of the material was increased compared with that of nano-Fe₃O₄ particles,and the pores in the material were mainly mesoporous.A kind of electro-Fenton system was constructed to treat the leachate of aged landfill leachate,the leachate used in the experiment was taken from Zhengzhou comprehensive waste treatment plant,and the prepared nano-Fe₃O₄@MOF was used effluent.The results show that nano-Fe₃O₄@MOF material can achieve good treatment effect as catalyst,and the treatment cost can be reduced by magnetic separation and recovery.In the experiment,COD and UV₂₅₄ were used as indicators to investigate the influence factors of the system,and the best reaction conditions were obtained.When nano-Fe₃O₄@MOF dosage was 0.75 g/L,initial p H was 3,H₂O₂concentration was 0.1 mmol/L,current density was 15 m A/cm²,and electrode spacing was 1.5 cm,the removal rates of COD and UV₂₅₄ were as high as 70.8%and 80.11%respectively,the decolorization rate was 94.25%.The cyclic experiments and FT-IR spectra showed that the nano-Fe₃O₄@MOF has good reusability and structural stability.The three-dimensional fluorescence spectrum indicated that the landfill leachate contained a large amount of fulvic acid and humic acid,and can be almost completely removed by the catalytic electro-Fenton treatment,and the biodegradability was significantly improved,this is consistent with the results of biochemical analysis.By free radical quenching test,this paper argues that the·OH and·O₂^–are active factors that play a major role in the degradation of organic pollutants,·OH had better oxidation properties between them.Changes of substances in gas chromatography-mass spectrometry results and the uv-visible spectrum showed that during the reaction,macromolecular organic matter was open loop into small molecule organic compound,and then oxidized to CO₂ and H₂O to be removed from the system.Macromolecular organic matter in leachate ratio was reduced and the molecular weight of the overall was also reduced.