Efficiency And Mechanism Of Uranium Removal In Microbial Fuel Cells Cathode

Uranium is stored through enrichment,concentration,or fixation,which is one of the essential methods to treat uranium-containing wastewater.Traditional uranium treatment methods have the defects of high energy consumption,high cost and easy to cause secondary pollution.However,Microbial Fuel Cell(MFC)is a kind of technology which can convert biomass energy into electricity and treat wastewater synchronously.It has many advantages,such as wide application range,high conversion efficiency,low running cost and no secondary pollution.Therefore,it has significant advantages to apply MFC technology to the treatment of uranium-containing wastewater efficiently.In this study,dual-chamber microbial fuel cell removal of uranium(VI)from solution and simultaneous electricity generation and mechanism were studied.Simulated domestic sewage was used as the anode substrate.Firstly,five kind of materials were used as cathode electrodes to construct dual-chamber MFC,respectively.The most advantageous cathode electrode material was selected by comparing the overall performance of MFC.Second,Glycine-hydrochloric acid buffer was introduce to improve the performance of MFC and obtained the best operating conditions.Finally,morphology,content and distribution of elements,valence of elements and phase analysis of the samples were studied by using modern detection techniques.Mechanism of the MFC system and the precipitation transformation mechanism were revealed.The screening results of materials showed:carbon brushes have the advantage of achieving high-energy bioelectricity from MFC.Used carbon brush as cathode electrode,MFC demonstrated better electrochemical performance and higher power generation.Power generation performance was improved with increase of initial uranium concentration,maximum power density was 91.8m W/m~2.Output power was stable,open circuit voltage could reach 996 m V.Glycine-hydrochloric acid buffer could improve performance of MFC with carbon brush as the cathode electrode.It turned out that:glycine-hydrochloric acid buffer could significantly improve uranium removal effect and electricity production of MFC,reduce internal resistance,increase reaction activity.Maximum uranium removal rate in the cathode chamber was over 99.5%,maximum power density was 269.5 m W/m~2.Open circuit voltage could reach 1.0V.The best operating conditions for MFC:anode substrate COD concentration was 800.0 mg/L,external circuit resistance was 600.0Ω,and the catholyte p H was 2.0.Under the condition of adding glycine-hydrochloric acid buffer,mechanism of removing uranium has been studied:H~+released by glycine-hydrochloric acid buffer and anode organic substrate were oxidized to produce concomitantly H~+and electrons,which reacted with hexavalent uranium in catholyte.U(VI)in catholyte obtained electrons generated by anode and transmitted to cathode through external circuit,and U(VI)was gradually converted to U(V).U(V)was converted to U(IV)by accepting electrons,continuously.Finally,U(IV)was removed by forming precipitate.This study had successfully applied acidic buffers to microbial fuel cells to improve the efficiency of power generation and uranium removal,and provide basic and theoretical support for MFC technology to treat actual wastewater.