Preparation Of Needle Coke-based Gas Diffusion Electro-Fenton Cathode And Treatment Of Coking Wastewater

With the rapid development of the coke industry,the production of coking wastewater is increasing,and the highly concentrated and toxic coking wastewater poses a serious threat to the safety of the water environment.With the progress of wastewater treatment technology,electro-Fenton advanced oxidation technology has a broad development space in the field of wastewater treatment,especially in the difficult biodegradable organic wastewater treatment.However,this technology still suffers from poor cathodic stability,easy to produce iron sludge,low current utilisation and other problems.The development of novel electro-Fenton cathodes and the improvement of cathode performance have become the key to breakthrough industrial application of this technology.In this study,the heterogeneous Fenton catalytic layer was prepared by loading Fe²⁺in needle coke with impregnating and calcining methods and the gas diffusion layer was prepared with the needle coke enhanced with hydrophobic function.The two layers were pressed on both sides of a titanium mesh to prepare a gas diffusion electro-Fenton cathode with which an electro-Fenton system was constructed to treat coking wastewater.The effect of the electrode prepared under different conditions on the removal of COD from coking wastewater was used as a characterization index to investigate the influence of the preparation conditions of needle coke-based gas diffusion electro-Fenton cathode on the electrode performance.The effectiveness of the preparation method and the catalytic activity of the electrodes were verified by characterising the apparent morphology and electrochemical properties of the electrode materials.The gas diffusion electro-Fenton cathode prepared under optimal conditions was used to treat coking wastewater,and the process parameters were optimized by response surface experiments based on single-factor experiments.Finally,a continuous flow electro-Fenton system was constructed to investigate the effects of hydraulic retention time,temperature and the initial concentration of pollutants on the treatment of coke wastewater to optimize the dynamic reaction conditions and verify the feasibility of the electro-Fenton process in practice.The experimental results show that:The impregnation calcination method could successfully load Fe²⁺inside the needle coke,making the electrode exhibit good redox performance.The optimum preparation conditions for the catalytic layer of the electrode were NaOH modification concentration of 1 mol/L,Fe²⁺loading of 2%,catalyst calcination temperature of 200°C,and catalyst-to-binder doping ratio of 3:1.The optimum preparation conditions for the gas diffusion layer were that the doping ratio of carbon material to binder was 1:2.5.The calcination temperature of the cathode was 300℃.The optimum conditions for coking wastewater treatment by electro-Fenton method were applied voltage=11 V,plate spacing=1 cm,and initial p H=2.8.The removal rates of COD,color,NH₃-N,SCN^-and S^2-from coking wastewater reached 91%,100%,100%,98.6%and 86%,respectively,and the biochemical properties increased from 0.181 to 0.418.The spectral analysis results showed that large amounts of aromatic compounds and small amounts of heterocyclic compounds were present in the coking wastewater,which gradually decreased,and even disappeared,during the reaction.The results of the quenching experiments of?OH confirmed that?OH was the main active substance in the electro-Fenton system which removed most of the COD and NH₃-N in the coking wastewater.Under the optimal reaction conditions of the continuous flow electro-Fenton system with a hydraulic retention time of 9h,temperature of 30℃,and initial COD concentration of 537 mg/L,the COD removal rate of coking wastewater reached 100%.The prepared electro-Fenton cathode is an electro-Fenton reaction cathode with excellent performance and green environmental characteristics,and the study can provide a solid theoretical basis and experimental basis for the application of the electro-Fenton cathode in practice.