Study On Synergistic Degradation Of Organic Wastewater By Novel Electrochemical-Fenton Oxidation System

With rapid development of the chemical industry,the wastewater contains high-concentration organic pollutants poses a serious threat to global water security,especially the recalcitrant organic matters.Whereas,these refractory organic contaminants can be hardly treated by conventional biological methods.Electrochemical-Fenton catalytic process is an advanced oxidation technology which is economical and efficient.At present,the theoretical research of electrochemical-Fenton catalytic process has matured.However,the disadvantages such as unsustainable efficiency,difficult to run in scale operation,high cost and poor stability are still exist in the practical applications.Therefore,it is significant to build a new system of electrochemical-Fenton catalytic process and explore its application in refractory chemical wastewater treatment.In this research,a sequential batch electrocatalytic Fenton-electrochemical oxidation system was first investigated,and tetramethyl piperidone as the target pollutant.The reactor design,assembly,and experimental procedure of the system were described step by step.Furthermore,the process of anodic oxidation of Fe²⁺generation,cathodic catalytic of H₂O₂generation and mechanism of Fenton and its oxidation were studied and verified.The operating parameters of the system were also investigated,including the influence of current density and p H on the H₂O₂production and COD_crremoval.The optimal operation parameters of the system were determined（p H=3,current density 20 m A/cm²）.Under this optimal operating condition,the maximum TOC removal rate of the tetramethyl piperidone simulated wastewater was 46.4%with 120 min reaction time,and the COD removal rate of actual wastewater reached 82.8%.Then,in order to achieve further improvement in oxidation efficiency of sequential batch system,a continuous flow electrocatalytic Fenton oxidation system with a gas diffusion electrode as a cathode was designed.The influence of the different current density,different flow rates and electrolyte changes on the yield of H₂O₂in this system were investigated.Using Benzotriazole（BTR）as the targeted pollutant,Benzotriazole and TOC of the simulated wastewater are continuously changed with time.The optimal operation parameters of the system were determined:current density was 20 m A/cm²,p H=3,flow rate was 2 L/h,Fe²⁺was 0.1 m M.Under this optimal operation condition,Benzotriazole can be completely removed in 40minutes,TOC removal rate was 58.3%and the toxicity of wastewater was also significantly reduced.Finally,the degradation of Benzotriazole in the secondary wastewater treatment plant was compared.Under this optimal condition,Benzotriazole was completely degraded within 40 min,and the TOC removal rate of Benzotriazole wastewater reached 40.8%.The novelty electrocatalytic Fenton oxidation system was based on this research,which exhibited advantages of higher efficiency and broad prospects in large-scale application.Furthermore,this study can also provide the reference and theoretical support in the future engineering applications of disposing chemical wastewater by using electrocatalytic Fenton oxidation processes.