The Fundamental Study Of Using Microbial Fuel Cells To Treat The Environmental Waste And Azo Dye Contaminant

Microbial fuel cells (MFCs) utilize the metabolism of bacteria to convert the chemical energy of compounds to electric energy directly, and oxidize the compounds simultaneously. The MFCs is not only a clean and recyclable new energy, but also is a newly device which can dispose the contaminant. At present, the study of using MFCs to treat environmental wastes and contaminants is still far from the real application. Most of the researches focus on how to improve the utilization of substrate and performance of the MFCs and to avoid some adverse factors.In this study, a dual-chamber MFCs has been used as the reactor with Ochrobactrum sp.575 or Shewanella putrefaciens as the anodic biocatalyst. The final electron acceptor is 50mM potassium ferricyanide and the carbon fiber brush electrodes are used as anode and cathode. The feasibility of electricity production when using xylose, Orange I and ortho-aminophenol (OAP) as the fuel of MFCs have been studied. The utilization of substrates in anodic chamber and the factors that affect the electricity production of MFCs are also discussed. The main conclusions are as follows:1. The MFCs catalyzed by pure strain cultures could degrade xylose, decolorize Orange I and oxidize OAP effectively and produce power at the same time. These MFCs could decompose substrates repetition and generate electricity for a long time, which provide an approach for dealing with the similar organic matter effectively and low energy consumption, and also offer scientific and technical basis for microbial fuel cell technology in real application.2. A new strain, Ochrobactrum sp.575, is applied as an anodic biocatalyst in a xylose MFCs. After long term electrochemical tension in the MFCs, the efficiency of biocatalyst could be improved and the output current density of MFCs also could be enhanced greatly. After evolving Ochrobactrum sp.575 three times, the 3nd-MFC could consume 97.16% xylose (the initial concentration was 100 mg/L) in a discharge cycle, and the maximum current density and power density were 3071.8 mA/m3 and 2625 mW/m3 respectively, which are higher than similar xylose MFCs reported before.We also found that fumaric acid is produced in anolyte after xylose metabolism by Ochrobactrum sp.575 in MFCs. However there is not fumaric acid in Ochrobactrum sp.575 suspension that cultured by aerobic condition. This indicates that the process of xylose digestion with Ochrobactrum sp.575 in MFCs depends on the succinate oxidation respiratory chain, which is quite different from the traditional NADH oxidation respiratory chain in other electroactive bacterial strains.3. The results of utilizing Shewanella putrefaciens as biocatalyst of MFCs to decolorize Orange I show that S. putrefaciens can decolorize Orange I quite well even the Orange I has negative effect on the growth of S. putrefaciens. The maximum power density and current density are 4070.6 mW/m3 and 10.86 A/m3 respectively and the internal resistance of MFCs is about 300 Ω when the initial concentration of Orange I is 100 mg/L. The final concentration of Orange I is only 6.91 mg/L, and the decolourization ratio is 95% in a discharge cycle.4. The result of utilizing S. putrefaciens as biocatalyst of MFCs to oxidize OAP indicate that although the OAP is hard to oxidize, about 46.6% OAP are oxidized by MFCs in a cycle, and the maximum power density and current density are 5871.3 mW/m3 and 6322 mA/m3 respectively.