To improve power generation of microbial fuel cell, graphite anodes were modified electrochemically by polyaniline (PANI) and multi-walled carbon nanotubes (MWNTs). Commercial MWNTs were ultrasonically treated in a mixture solution of 3: 1 concentrated sulfuric and nitric acid for 3 h. Due to production of carboxylic acid groups at defect sites of MWNTs, its solubility in HC1 solution was improved. The film anodes were used in the anaerobic fluidized bed microbial fuel cell (AFBMFC) , and its performance of power production and the COD removal efficiency of wastewater were evaluated. It has been indicated that electrochemical method, including CV (cyclic voltammetry) and potentiostatic methods etc. , is of high-efficiency for preparation of electrode material, such as shorter preparation route and direct synthesis of composited film anodes as well as decrease of danger caused by use of poisonous reagents. Dopping of a small amount of MWNTs could increase significantly output electricity. Meanwhile, the optimal film anodes was prepared by potentiostatic method, containing 5% (mass) MWNT, whose maximum open-circuit voltage was 926. 5 mV and power density 112. 3 mW · m-2. For the optimal anodes, after running seven days, the COD removal efficiency of wastewater was 94. 5%. The photos from scanning electron microscope (SEM) showed that the surface of composite film anodes was of clavate and reticular structure, in favor of adhesion of microbe and formation of biological membrane. In addition, doping MWNT can reduce the start time of MFC to about one day and improve the stability of electrodes. The maximum open-circuit voltage was 735 mV for PANI film anodes, and the performance was also better for modified anodes than for graphite rods (no modified one). The optimal PANI film anode was prepared by cyclic voltammetry (CV) method, hydrochloric acid as proton acid and concentration 1 mol · L-1 , aniline 0. 1 mol · L-1 , the number of polymerization cycles 24. Furthermore, the major factor influencing output voltage is matrix concentration, when it is low the output voltage is dropped quickly and stabilized in a lower value.
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