Construction Of Nitrogen Doped Biocathode And The Study On Antibiotic Resistant Genes In MFC

Microbial fuel cell(MFC)is a kind of sustainable energy utilization device that uses microorganisms to convert organic pollutants in wastewater into electric.Although Pt and other precious metals can effectively promote the oxygen reduction reaction(ORR)of cathode,it is difficult to be commercially available because of the high price.Looking for cheap catalysts or using a bio-cathode MFC(BCMFC)can effectively reduce the cost of MFC.The residues of antibiotics in the environment and their induced antibiotic resistant bacteria(ARB)and antibiotic resistant genes(ARGs)have posed a serious threat to the environment and human health.On the basis of the above problems,much attention has been paid in this paper to investigating the promotion of nitrogen doped(NCNT)and metal oxide doped carbon nanotubes on the bio-cathode ORR;On the other hand,the effect of cephalosporins on the MFC performance and the change rule of ARGs in the anode chamber were also mentioned.The effects of melamine and urea servesed as nitrogen sources to doped CNT on were compared.It was found that the nitrogen content was 2.32%and 1.30%,respectively,and the content of pyridine nitrogen in BM could reach 53.90%.Further electrochemical tests showed that the melamine doped electrode has better catalytic activity.Then the calcining temperature was optimized.The electrode had the best performance when the calcining temperature was 900?,and the maximum power density of BCMFC could reach 121.92 mW/m2.The effects of Fe3O4 and MnO2 doped NCNT on the performance of the bio-cathode were investigated.Cyclic voltammetry and Tafel curve data showed that Fe3O4-NCNT has a better ORR activity compared with the Mn02-NCNT bio-cathode.Fe3O4-NCNT has the highest power density of 216.05 mW/m2.At the same time,the electricity generation of Fe3O4-NCNT was less than NCNT,indicating that the nonmetal doped carbon materials has considerable promise for application.The addition of cefepime increased the internal resistance of the anode and reduces the power density generation of BCMFC.BCMFC was more tolerant to cefepime.When the concentration of cefepime in the influent was 0.6 mg/L and COD was 1000 mg/L,the efficiency of power production is the best.The traditional anaerobic biologic reactor(ABR)was more resistant to organic load.The degradation of cefepime in two systems was composed of fast adsorption and slow biodegradation(following first order kinetics).It revealed that the electron transfer mechanism in BCMFC anode is direct electron transfer.The change rule of ARGs in BCMFC was further discussed.Low concentration of cefepime stimulated microbial growth;high concentration inhibited growth and the number of bacteria decreased,but the relative abundance of ARGs remained at a higher level.When the concentration of FEP in the influent was changed at 0.2?1.0 mg/L(the concentration of COD was 1000 mg/L),the relative abundance of the total ARGs was 10-4.59?10-3.26,while the relative abundance of the total ARGs was 10-2.67?10-1.34 when the concentration of COD in the influent was changed at 200?1300 mg/L(the concentration of FEP was 0.6 mg/L).BCMFC affected horizontal transfer of ARGs due to its electrochemical effect,with the result that the transmission and replication of ARGs was not affected by the concentration of bacteria in the environment.There was no correlation between them in BCMFC,while it was significantly correlated in ABR(P<0.01).The negative correlation of ARGs in the aqueous phase and sludge phase in BCMFC was more than that of ABR,indicating that there was the reciprocal relationship between aqueous phase and sludge phase ARGs in BCMFC.