| In recent years,the boilers were cleaned by citric acid solution in coal-fired power plants.The large amount of citric acid wastewater?CAW?was generated and caused serious environmental problems.A single chambered air cathode anaerobic fluidized bed microbial fuel cell?AFB-MFC?was used to dispose CAW.The operating conditions of AFB-MFC were optimized to improve the treatment efficacy and power density.The bioelectrochemical system of AFB-MFC improved the degradation reaction of organics.The reduced graphene oxide?RGO?supported platinum carbon nanoparticles?RGOPt-C?was modified the carbon cloth?CC?,the AFB-MFC with RGOPt-CCC improved the electricity generation.The AFB-MFC was applied to treat CAW containing high concentration of citric acid.The substrate concentration,flow rate and temperature on treatment process were investigated.The optimum conditions are that the flow rate of inlet wastewater is 5.22mL/s,the temperature is 40?and the COD contration is 2946.67 mg·L-1.The suitable operating conditions of AFB-MFC improved the treatment efficiency and electricity generation performance.The AFB-MFC/ABFBR was used to treat CAW.At the temperature of 40?,the removal efficiency and power density were improved in AFB-MFC with the platinum carbon?Pt-C?modified carbon cloth.When real CAW was employed as substrate,the COD removal efficiency in AFB-MFC was up to 90%,which was higher than in the anaerobic biological fluidized bed reactor?ABFBR?obtained the corresponding value of 84%.The maximum voltage(Umax)and the maximum power density(Pmax)were424.6 mV and 18.68 mW/m2,respectively,when the external resistance was 5000?.Furthermore,the Haldane inhibition model was well fitted with experiment data?R2=0.97-0.98?in AFB-MFC/ABFBR.The inhibition of citric acid degradation in ABFBR was stronger than that of AFB-MFC.The bioelectrochemical system not only improved the charge transfer but also accelerated the reaction rate of citric acid.The reduction of ferric ion and oxidation of ferrous ion in AFB-MFC played important roles of the critic acid degradation reaction.The AFB-MFC with three types of modified cathode was used to dispose CAW.The RGOPt-C/RGO/Pt-C was used to modify carbon cloth?CC?through the template method.The prepared cathodes were characterized by energy disperse spectroscopy?EDS?,scanning electron microscope?SEM?,Fourier transform infrared spectroscopy?FTIR?,cyclic voltammetry?CV?and electrochemical impedance spectroscopy?EIS?technology.The specific surface area of RGOPt-C,RGO and Pt-C respectively was589.61 m2/g,402.60 m2/g and 374.14 m2/g,and the charge transfer resistance(Rct)of RGOPt-CCC,RGOCC and Pt-CCC respectively was 26.56?,14.38?and 9.07?.The AFB-MFC with RGOPt-CCC achieved the highest voltage of 561.0 mV and produced the maximum power density of 232.90 mW/m2,which was 1.31 and 1.76times of that equipped with RGOCC cathode?429.4 mV,132.36 mW/m2 mW/m2?.However,the AFB-MFC with Pt-CCC produced Umaxax of 314.4 mV and Pmaxax of 79.80mW/m2,respectively.The results showed that RGOPt-C promoted the electron transfer and electrochemical activity on the surface of cathode.Therefore,the AFB-MFC with RGOPt-CCC produces higher treatment ability and electricity generation.The present study has successfully verified that a promising AFB-MFC technology can achieve high output power,revealing the enormous potential of scale-up AFB-MFC for treating CAW. |
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