Performance Investigation And Application Extension For A Membrane-less Microbial Fuel Cell

A microbial fuel cel(lMFC)is an bioelectrochemical device which can recover the chemical energy containing in organic wastewater. The capability of simultaneous wastewater treatment and biological electricity generation makes MFCs an economical pathway to a sustainable energy future. Although an increase in power density of five orders of magnitude has been achieved in recent years, the practical application of MFCs has been limited by several challenging issues such as a lack of suitable cathodic electron acceptors, high electrolyte and electrode ohmic losses and pH differencesbetween the anode and cathode compartments. As one of the most important field of MFCs, membrane-less MFCs have attracted much attention worldwide. However, most of the studies focus on the effects of the cathode materials and electrolyte, and few researchers studied the effect of substrate transfer on the performance of the MFCs. Therefore, in this thesis, two types of flow fields, namely the interdigitated and serpentine anode flow fields, were used in a membrane-less MFC to investigate the effect of substrate transport on the performance of the MFC. On this basis, we have assessed the feasibility of using a membrane-less MFC with flow field as an effective way for the removal of volatile organic compounds (VOC). The main results of this thesis are as follows:â‘ A membrane-less MFC with different anode flow fields (serpentine and interdigitated) was designed to compare the effect of substrate transfer on the performance of the MFCs. It was demonstrated that the performance of the MFC with a serpentine flow field is superior to that with an interdigitated flow field when they were started up at a resistance of 100 ? and a substrate flow rate of 0.5mL/min. Compared with the interdigitated flow field membrane-less MFC, the serpentine flow field membrane-less MFC has a higher power density of 100 mW/m² and a current density of 500mA/m². The results indicated that the cathode surface and anode surface facing the chamber of membrane-less MFC using an interdigitated flow field was covered by a thicker biofilm than the serpentine flow field membrane-less MFC, resulting in an increase in the MFC ohmic resistance, poison of the cathode catalyst, and therefore the MFC performance.â‘¡MFC performance was strongly affected by the thickness of the chamber between the anode and cathode of a membrane-less MFC. It was found that the performance has an optimum performance when the thickness of the chamber between the anode and cathode was 2 cm. The thicker the chamber between the anode and cathode, the higher the membrane-less MFC resistance was. But when the thickness of the chamber between the anode and cathode decreased to a certain extent, oxygen diffusion from the cathode to the anode increased, causing the inhibition of the electrochemical active bacteria in the anode.â‘¢A new membrane-less MFC capable of simultaneous VOC treatment and electricity production was designed based on the above-mentioned MFC architecture. The feasibility of the MFC was verified by the existence of the anode biofilm for VOC treatment and electricity generation. Experiments also demonstrated that can be used as carbon sources for bacterial growth.â‘£It was shown that the performance of the membrane-less MFC capable of simultaneous VOC treatment and electricity production started up at a resistance of 100Ωhas a lower performance than that of 5000Ω. In detail, a open circuit voltage of 450 mV, a maximal power density of 4.5 mW/m², and a maximal current density of 40mA/m² can be achieved when the MFC was started up at a resistance of 5000 ?, while the MFC started up at a resistance of 100Ωonly has a open circuit voltage of 280 mV, a maximal power density of 0.55 mW/m², and a maximal current density of 12.5mA/m².⑤In this thesis, the effect of operational parameters on the performance of the MFC was also investigated. It was found that the flow rate and concentration of toluene had a great effect on the toluene degradation performance of the MFC. Based on the experimental results, it can be seen that the optimum toluene concentration and flow rate was 4g m^-3 and 10 mL/ min, respectively.