Study On The Construction And Degradation Mechanism Of Microbial Fuel Cell-Electro Fenton Coupling System

As an organic wastewater with high BOD,COD and ammonia nitrogen,swine wastewater will seriously pollute the environment and threaten human health if it is discharged into natural water and soil without effective treatment.Rhodamine B wastewater,as a typical dye wastewater,has the characteristics of large chroma,low removal rate of microorganisms,biological toxicity and complex material composition.If it is not treated correctly,it will threaten the natural environment and human life health.How to deal with the above-mentioned wastewater has gradually become the focus of today’s work.In recent years,microbial fuel cells and advanced oxidation methods have attracted the interest of water treatment workers.Microbial fuel cells can treat wastewater without additional energy and generate electricity at the same time.For advanced oxidation method,it can degrade refractory biodegradable organic matter by using strong oxidizing active substances such as hydroxyl radical（·OH）produced by itself.Based on this,this project combines the microbial fuel cell with the electro Fenton technology,constructs the Microbial fuel cell-electro Fenton coupling system,degrades the swine wastewater and rhodamine B wastewater（RhB）,respectively,thereby reducing the cost and providing the experimental basis for the engineering application.In this experiment,Fe@Fe ₂O₃/ACF was prepared by ultrasonic immersion in solution under the conditions of 2.9 g/L Fe Cl₃·6H₂O,20 minutes ultrasound and 14.6g/L Na BH₄.ACF was used as the anode,and the electricity-producing microorganisms was inoculated and domesticated in the anode chamber.The prepared composite cathode Fe@Fe ₂O₃/ACF has a good electrocatalytic function.After three cycles of domestication,the solution in anode chamber was replaced by 200 mL swine wastewater with pH of 10,and Rhodamine B solu tion with concentration of 10 mg/L and pH of 3 was added into cathode chamber,and the aeration rate was 0.3 L/min.Running the coupling system,the removal rates of BOD ₅,COD,TOC and NH₄⁺-N in anode chamber were 85.2%,75.1%,60.5%and 70.3%,respectively,and the maximum power density,current density and voltage were 16.7 W/m³,36 A/m³,900 mV,respectively,which proved that the coupling system had obvious power generation effect and better removal effect of pollutants in anode chamber.The degradation of Rhodamine B was studied by the above-mentioned Microbial fuel cell-electro Fenton coupling system.Through a series of comparative tests,the optimal reaction conditions of cathode chamber were found:pH 3,aeration rate 0.3L/min,initial concentration of Rhodamine B 10 mg/L and external resistance 120Ω.And under the condition,the removal rates of Rhodamine B and TOC in the cathode chamber were 95.0%and 90.2%,respectively,and the degradation law was in accordance with the first-order reaction kinetic model.The coulmbic efficiency and energy conversion efficiency of the Microbial fuel cell-Electro Fenton coupling system were 12.2%and 11.2%,respectively,and the mineralization current efficiency was 60.1%.Moreover,the composite cat hode Fe@Fe₂O₃/ACF could be recycled for 8times and had a good ability to degrade organic pollutants.Under the optimum conditions,benzoquinone（BQ）,tert butanol（TBA）and superoxide dismutase（SOD）were used as the capture agents of·O₂^-,·OH and H₂O₂,respectively,the degradation of Rhodamine B in the cathode chamber of the coupling system was investigated.In the presence of TBA,BQ and SOD,the degradation of Rhodamine B was about 30.1%,90.9%and 92.0%,which indicated that·OH was the main reactive oxide.In order to further prove that,the ESR spectrum analysis with DMPO as the spin trapping agent was carried out.From the DMPO-·OH spectrum,quartet lines with an intensity ratio of 1:2:2:1 were measured,which confirmed that·OH was the main contributor.Thus,·OH played a major role in the degradation of rhodamine B in the cathode chamber.Based on the determination of free radicals and the combination of biological,electrochemical and chemical effects,the reaction mechanism of Microbial fuel cell-Electro Fenton coupling system for the treatment of swine wastewater and rhodamine B wastewater was proposed.In the full-scan mode,the intermediate products in the degradation process of rhodamine B can be known by mass spectrometr y,and the possible degradation pathway of rhodamine B was proposed.In summary,the construction of Microbial fuel cell-electro Fenton coupling system successfully solves the problem of simultaneous treatment of two kinds of wastewater without consuming external energy.It is a promising and environmentally friendly wastewater treatment technology and provides experimental basis for future engineering applications.