Preparation Of Heterogeneous Fenton Catalyst And Its Treatment Of Landfill Leachate

Landfill leachate is a typical organic wastewater with a high concentration of salt.It contains humic acid and other substances with complex molecular structure,which is extremely difficult to be degraded.Heterogeneous Fenton technology overcomes the shortcomings of traditional homogeneous Fenton technology and has the advantages of a wider p H threshold,less iron mud,and lower turbidity of effluent,which has attracted wide attention.In this study,the heterogeneous Fenton catalysts,including GAC-Fe₃O₄,GAC/α-Fe OOH,and GAC-Fe₂O₃,were prepared with granular activated carbons supported by iron oxides.The heterogeneous Fenton technology was used to treat landfill leachate and its membrane filtration concentrate.In this study,the optimum preparation conditions of three heterogeneous Fenton catalysts were investigated and the catalysts were characterized using SEM,EDS,FT-IR,and XRD.Heterogeneous Fenton catalyst was used to construct heterogeneous（electric）Fenton system to treat landfill leachate and membrane filtration concentrate.The reaction conditions were optimized by single factor experiment and orthogonal experiment,and the reaction mechanism was explored by comparing the reaction effects of different reaction systems combined with quenching experiment.The stability and reusability of heterogeneous Fenton catalysts were investigated.A heterogeneous Fenton fluidized bed reactor was designed to treat landfill leachate,the optimum conditions were investigated,and the stability of the reactor was evaluated.UV-Vis,FT-IR,GC-MS,and three-dimensional fluorescence spectra were used to characterize the water samples of landfill leachate and membrane filtration concentrate before and after treatment to analyze the degradation mechanism of organic matter.The conclusions are as follows:GAC-Fe₃O₄,GAC/α-Fe OOH,GAC-Fe₂O₃ showed their own characteristic peaks of iron oxides,indicating the successful preparation of heterogeneous Fenton catalyst.The optimal conditions of heterogeneous chemical Fenton treatment for landfill leachate were p H=4,H₂O₂ concentration of 10m L/L,GAC/α-Fe OOH dosage of 30g/L,and COD removal rate was 93.7%.The optimal conditions of membrane filtration concentrate were p H=5,H₂O₂ concentration of 30m L/L,GAC-Fe₃O₄dosage of 45g/L,and COD removal rate was 93.9%.The optimal treatment conditions of heterogeneous electro-Fenton treatment for landfill leachate were p H=5,GAC/α-Fe OOH dosage of 13.33g/L,applied voltage of 8V,reaction time of4h,the removal rates of COD,chroma,NH₃-N and TN were 97.4%,99%,100%and94.2%,respectively,and the energy consumption was 0.23k W·h（g COD）^-1.The optimal conditions of membrane filtration concentrate were p H=6,GAC-Fe₃O₄dosage of 11.67g/L,applied voltage of 8V,reaction time of 5h,the removal rates of COD,chroma and TN were 95.7%,99%and 94.9%,respectively,and the energy consumption was 0.098k W·h（g COD）^-1.The optimal reaction conditions for the treatment of landfill leachate in heterogeneous Fenton fluidized bed reactor were as follows:GAC/α-Fe OOH catalyst filler dosage of 30g/L,H₂O₂ concentration of12m L/L,HRT=3h.After continuous operation for 12h,the COD removal rate was still above 90%.The results of spectrum analysis showed that after Fenton treatment,the polycyclic aromatic hydrocarbons and long chain structure of landfill leachate and membrane filtration concentrate were reduced,and the vast majority of organic pollutants with complex structure were transformed into simple small molecules of alkane organic matter.·OH was produced by Fenton reaction of heterogeneous Fenton and heterogeneous electro-Fenton systems,which played an important role in the degradation of organic matter.In this study,heterogeneous Fenton iron catalyst was used to construct heterogeneous Fenton system for the treatment of landfill leachate and membrane filtration concentrate,which has a good removal effect on COD,chroma,ammonia nitrogen and total nitrogen,etc.,providing theoretical basis and experimental reference for the industrial application of the heterogeneous Fenton catalyst.