Simultaneous Degradation Of Azo Dye And Bioelectricity Generation Using Air-cathode Single Chamber Microbial Fuel Cell

The world-wide aggravations of energy crisis and water pollution are inspiring the search for renewable economy and efficient technology of wastewater treatment and exploitation for sustainable and clean energy. Microbial fuel cell (MFC) has been proved able to generate electrical currents via oxidizing organic compounds by using microorganisms as the bio-catalysts. Nowadays MFC technology is drawing attention of international environmentalists and energy sector. Currently MFC is still in its infant because of the difficulty to degrade complex organic compounds. This study attempted to use easy-degradation organics as co-substrate to degrade complex contamination and provided the basis for a new way to treat azo dye by MFC.In this thesis, an air-cathode microbial fuel cell with Congo red as characteristic pollutant was constructed to investigate the effect of different ready biodegradable organic carbon sources on simultaneous decolorization of Congo red and bioelectricity generation. And the key factors to affect the process and the connection of degradation and electricity generation were investigated. The pathway and intermediates of Congo red were also analyzed.Anaerobic and aerobic sludge can be used as inoculating source, which formed an active biofilm in anode. The voltage and power density gradually increased to highest, however the impedance decreased. High-coverage and abundant microorganism were observed after MFC start-up.In co-substrate, MFC can decolorize Congo red at 98% upwards. However, the decolorization rate was different with the organic carbon sources used, the fastest was obtained with glucose followed by ethanol and sodium acetate. The maximum power density produced followed the order of glucose (103 mW·m-2) > sodium acetate(85.9mW·m-2) > ethanol(63.2mW·m-2).In MFC of 400 ml, anode area in 72cm2 was more available for decolorization and electricity generation than 18cm2. But power density decreased with the anode area increased. The electricity generation and decolorization were all affected by Congo red concentration improved. The decolorization rate and maximum power density were all increased as glucose concentration up.Decolorization of Congo red attributed to microorganism degradation in co-substrate. Azo bonds destroyed and accumulated intermediates which can not be degraded further were observed during Congo red biodegradation. During LC-MS, the structure of four main products can be speculated: Benzidine,2-((4'-aminobiphenyl-4yl)diazenyl)naphthanlen -1-amine,1-(biphenyl-4-yl)-2-(naphthalene-2-yl)diazene and 4,6-diaminonaphthalene-1- sulfonate.Compared with conventional anaerobic method, MFC gained a better kinetic for decolorization. Degradation of Congo red decreased the voltage and prolonged electrical cycle time. Increasing quantity of co-substrate can adjust electron competition between electricity-generating and decolorization bacteria.