Study Of Microbial Fuel Cell On Electricity Gerneration Performance And AZO Dye Wastewater Treatment

In recent years, microbial fuel cell (MFC) is a rapidly developed technology that can generateelectricity with simultaneous organic matter removal from domestic and industrial wastewaters. As a kindof revolutionary way for wastewater treatment, MFC has become the focus of researchers all over the world.However, the relatively low power output was considered as one of the main obstacles for its furtherapplication. Amongst many factors affecting the performance of MFC, the anode, which had greatinfluence on the growth and activities of microbes as well as on the electron transfer rates, was consideredas one of the key limiting factors. Traditionally, carbon materials which have been widely used as anodehave their drawbacks such as limited surface area and relatively small electrocatalytic activity. To increasethe anode performance, one promising approach is the modification of anode surface with certainelectroactive materials that can enhance the actual accessible area for bacteria to anchor and affect theinterfacial electron transfer resistance and subsequently improve the anode performance. The mainconclusions in the paper are as follows:(1) The gold colloids with20nm diameter were prepared via the reduction of HAuCl4by trisodiumcitrate. The gold nanoparticles (Au NPs) modified carbon paper electrode was successfully constructed bylayer-by-layer assembly technique for the first time. UV-vis spectroscopy was used to monitor the regularlayer growth of the {PEI/Au}10multilayer. The results of cyclic voltammetry (CV) and electrochemicalimpedance spectroscopy (EIS) in Fe(CN)63-/4-solution demonstrated that the Au NPs modified carbon paperelectrode exhibited better electrochemical behavior than the bare carbon paper electrode, includingrealtively high electroactive surface areas, increased electron transfer rate and decreased interfacial electron transfer resistance. A two-chambered MFC equipped with the modified anode achieved a maximum powerdensity of346mW m-2and a start time for the initial maximum stable voltage of175hours, which wererespectively50%higher and36%shorter than the corresponding values of the MFC with the unmodifiedanode. All the results indicated that the LBL assembly Au NPs-based modification on the anode was asimple but efficient method to incorporate Au NPs onto carbon paper electrodes and promoted theelectricity generation of MFC.(2) Graphene was synthesized by chemically reduction of graphene oxide (GO) to grapheme (GR). Weaimed to investigate whether modification of carbon paper (CP) anode with graphene (GR) vialayer-by-layer assembly technique is an effective approach to promote the electricity generation and methylorange (MO) removal in MFC. Using cyclic voltammetry (CV) and electrochemical impedancespectroscopy (EIS), the GR/CP electrode exhibited better electrochemical behavior. SEM results revealedthat the surface roughness of GR/CP increased, which was favorable for more bacterial to attach to theanode surface. The MFC equipped with GR/CP anode achieved a stable maximum power density of368mW m-2under1000external resistance and a start time for the initial maximum voltage of180hours,which were respectively51%higher and31%shorter than the corresponding values of the MFC with blankanode. The anode and cathode polarization curves revealed negligible difference in cathode potentials butobviously difference in anode potentials, indicating that the GR modified anode other than the cathode wasresponsible for the performance improvement of MFC. Meanwhile, compared with MFC with blank anode,11%higher decolorization efficiency and16%higher the COD removal rate were achieved in MFC withGR modified anode during electricity generation. This study might provide an effective way to modify theanode for enhanced electricity generation and efficient removal of azo dye in MFC.(3) Research on the decolorization of methyl orange (MO) simulated wastewater in the two-chambered cubic microbial fuel cells. Systemly studied the bioelectricity generation and decolorizationof MO in the anode chamber of MFC in wide concentration ranges of MO (from50to800mg L1) and ofco-substrate glucose (from0to2.0g L1). The microbial communities on the anode were revealed after theMFC was operated continuously for more than6months using MO-glucose mixtures as fuel. The resultsshowed that the added MO played an active role in production of electricity. The maximum voltage outputswere565,658,640,629,617and605mV for the1g L-1glucose with0,50,100,200,300and500mg L1MO, respectively. Moreover, accelerated decolorization efficiency of MO realized in MFC, increased57%compared to the open-circuit control during8hours. Co-substrate was necessary for the simultaneouselectricity generation and azo dye decolorization. Decolorization efficiency and COD removal rate bothincreased with the increase of the co-substrate concentration. The decolorization efficiency of300mg L-1MO in MFC without co-substrate was only7.5%，the maximum voltage output was only140mV。454high-throughput pyrosequencing revealed the microbial communities. Geobacter genus known to generateelectricity was detected. Bacteroidia class, Desulfovibrio and Trichococcus genus, which were most likelyresponsible for degrading methyl orange, were also detected.