The Study Of Microbial Fuel Cells With Lake Bottom Sludge

Microbial fuel cell is an environmental friendly, recycled, new technology, whichcan transform bioenergy to electricity directly. Thus, it is very promising in waste watermanagement and new energy field. The electrochemical performances of the microbialfuel cells are mainly determined by their anode materials because of the importance ofbiocompatibility and the resistance of electron transfer between the electrode andmicroorganism. This paper is aimed to conduct researches on the dual chamber MFCequipment running under natural conditions with lake sludge as its bacteria source andits modification of anode materials by several electrochemical methods.First of all, the bacteria obtained from lake sludge were trained to the bacteria withelectrochemical activity through small intermittent current for5periods. Then, stainlesssteel mesh, foam nickel and carbon brush were chosen as anode materials to assemble a3-electrode system and a dual chamber microbial fuel cell system with proton exchangemembrane as the separator to evaluate the performances separately. Data analysisrevealed that, the open circuit potential became more negative with time increasing andat the same time, the anodic peak current of cyclic voltammetry kept rising for all3materials. This indicates that the electrochemical activity of the anodes was improvedwith running time increase. With time further extension, the peak current began todecrease because of the consumption of nutrients and the accumulation of metabolitesfrom the bacteria. In addition, the data of AC impedance of each electrode indicate thatboth of the polarization resistance and the diffusion resistance decrease with differentdegree during running. At last, the microbial fuel cell system with different anodematerials can generate open circuit voltage as300mV,380mV and460mV andgenerate power as0.071μW,7.284μW and41.82μW for stainless steel mesh, foamnickel and carbon brush, separately.Based on the results, pyrocatechol violet was used to modify the anodes. The cyclicvoltammetry and AC impedance tests revealed that the pyrocatechol violet can absorbon the electrode surface to strength the electron transfer, thus electrochemical activitieswere improved. Particulaly, the promotion for stainless steel mesh and foam Nickel isobvious, for carbon brush is limited even a slightly decrease of open circuit potentialwas obtained. Further tests were performed on the entire microbial fuel cell system, theopen circuit voltage and power of stainless steel mesh and foam nickel was improved 14%and60%after modification, while, for the carbon brush system, although the opencircuit voltage increase38%, the power decrease sharply for78%. Combine the analysisof cyclic voltammetry tests and morphology of failed carbon brush electrode, it isbelieved that the adsorption of pyrocatechol violet results in the aggregation andadhesion of carbon fibers, which decreases the porosity and the surface of the electrodefor low electrochemical activities.In summary, the dual chamber microbial fuel cell system assembled with lakesludge as the bacteria souce, with stainless steel mesh, foam nickel and carbon brush asanode materials and with proton exchange membrane as separator, running undernatural condition is effective in generating voltage and power. Modifications ofpyrocatechol violet on anode materials achieved initial success on stainless steel meshand foam nickel, while for carbon brush it is not suitable. Moreover, the chemicaloxygen demand of the anodic electrolyte decreases more than85%at most, indicatingthat the system has the potential of treating waste water.