Reduction Of Perchlorate And Nitrate And Electricity Production By Electrochemical Coupled Biological Cathode

Microbial fuel cell(MFC)is a device that can convert the chemical energy of the organic matter to electricity.Due to its advantages of transforming substrate into energy directly,normal operating temperature,low energy input and no waste gas output,it has been favored by the related researchers in electrochemical fields recently.Microbes attached to the cathode as catalyst and domesticated as autotrophic denitrification biocathode,can be used to reduce the perchlorate and nitrate in the groundwater.The MFC with biocathode not only removes the pollutants effectively,but also generates electricity simultaneously,so it rightly meets the requirement of environmental protection and social development at present.Perchlorate and nitrate are the most common oxygen inorganic anions in groundwater,and often mutually dependent.In a series of preliminary experiments,MFC was constructed,the microorganisms were domesticated and screened,the electrode materials were chose and the electrode distance was optimazed.Finally the 230 mL of cathode chamber volume,denitrifying bacteria acclimatized for 132 days,carbon felt electrode(3.0 cm×2.0 cm×O.3 cm)and 3 cm electrode spacing WERE determined as the starting condition of our MFC.In this study,an autotrophic denitrifying biocathode was investigated to achieve the combined of the nitrate or/and perchlorate reduction with electricity generation.Results showed that when the current density in MFC with sole perchlorate and sole nitrate as the substrate stabilized at 3.00 and 1.52 mA/m3,respectively.Meanwhile the perchlorate and nitrate removal efficiency reached the maximum of 53.14%and 87.05%.As influent molar ratio of NO3-/ClO4-was 1:1,the stable current density reached a peak value(3.10 A/m3)accompanied by the maximum integral mixed substrate removal(40.97%for ClO4-and 86.03%for NO3-).Open and close circuit experiments demonstrated that the nitrate and perchlorate removal should be ascribed to the biological reduction of autotrophic denitrifying biocathode.Cyclic voltammetry(CV)curves showed that all of biocathodes had strong electrochemical activity and there were few clear distinctions of redox potential between the biocathodes fed with different substrates.Results of 16S rRNA sequencing revealed a predominance of?-Proteobacteriain the autotrophic denitrifying biocathode,which is a well-known denitrifier.