Study On The Treatment Of Landfill Leachate Using Fe/Cu-needle Coke Three-dimensional Electro-Fenton Particle Electrodes

Landfill leachate is a hard-to-degrade organic wastewater,which will cause serious risks to human health and ecological environment if not treated correctly.The three-dimensional electro-Fenton（3DEF）technology has received much attention because of its high mass transfer efficiency and current utilization,and relatively low energy consumption.In this experiment,a novel particle electrode was developed to treat landfill leachate using a 3DEF system,providing a new solution to the environmental problem of landfill leachate pollution.In this study,Fe/Cu loaded needle coke particle electrode（Fe/Cu-NCPE）were prepare,in which Fe was extracted from iron tailings and doped with Cu-modified needle coke.A 3DEF system was constructed with Fe/Cu-NCPE to treat landfill leachate.The particle electrodes prepared under different conditions were used to treat landfill leachate,and the COD removal rate was used as the characterization index to investigate the effect of preparation conditions on the performance of Fe/Cu-NCPE.The Fe/Cu-NCPE before and after the reaction was analyzed by SEM,EDS,XRD,BET,XPS and Raman spectroscopy.The Fe/Cu-NCPE prepared under optimal conditions was used to treat the landfill leachate and bio-treated landfill leachate,respectively.The process parameters were optimized by single-factor experiments and response surface experiments to obtain the optimal treatment conditions for the landfill leachate and bio-treated landfill leachate,and the changes of pollutant indexes such as COD,nitrogen and color in the effluent under the optimal conditions were investigated.The pollutant removal mechanisms in the landfill leachate and bio-treated landfill leachate were investigated by spectral characterization.The experimental results show that:Fe oxides can be effectively extracted from iron tailings by acid leaching and alkali recovery.The optimal conditions for Fe/Cu-NCPE preparation are:doping ratio of 8:2 between needle coke and Fe oxides,particle size of 5±0.5 mm,Cu²⁺loading of3%,and binder ratio of 3:11.The impregnation calcination method can load Cu²⁺onto the surface of the needle coke material successfully.The main composition of the Fe oxide is Fe₃O₄,and the Fe/Cu-NCPEs are dominated by mesopores with well-developed pores with a high degree of graphitization and strong electrical conductivity.After the reaction,Fe and Cu still existed stably on Fe/Cu-NCPE,and the pore structure conductivity was almost unchanged.The 3DEF system can effectively treat landfill leachate water.Under the optimal conditions of initial pH2.52,applied voltage 9.62 V and particle electrode dosage 25.92 g/L,the removal rates of COD,NH₃-N,TN and color can reach 95.03%,93.8%,90.3%and 99%,respectively.In the 3DEF system,H₂O₂ generated on the surface of the cathode and polarized Fe/Cu-NCPE reacts with the loaded Fe²⁺and Cu⁺in a（like）Fenton reaction to generate·OH,so that large molecules of organic matter such as humic acid are effectively removed from the water,and the remaining ones are mostly alkanes.The optimal conditions for the treatment of bio-treated landfill leachate by the 3DEF system were that the applied voltage was 7.44 V,the initial pH was 2.86,and the particle electrode dosage was 19.7 g/L.The removal rates of COD,NH₃-N,NO₃-N,and color in bio-treated landfill leachate reached 91.36%,100%,93.3%,and 98%,respectively.The content of cyclic aromatic compounds,unsaturated aldehydes and ketones in the bio-treated landfill leachate was significantly reduced.The energy consumption of bio-treated landfill leachate treated with the 3DEF system was 66.96k Wh/m³,which was much less than the cost of two-dimensional electro-Fenton.The Fe/Cu-NCPE prepared in this study is of superior performance and good stability as 3DEF particle electrode,and the constructed 3DEF system can effectively degrade organic matter in landfill leachates,providing a theoretical and experimental basis for the treatment of landfill leachate by the 3DEF particle electrode.