The Study On Power Generation And NO_x Removal Performance Of Multi-electrode MFC

Microbial Fuel Cell（MFC）is a technology that can degrade pollutants by biochemical and electrochemical reactions,and generate electricity simultaneously.Because of the energy crisis,a large of researchers have been attracted and focused on this area.So far,improving the power output was still an important task for MFC.The cell voltage of a single MFC is normally limited to 0.2～0.5V,which cannot provide enough energy for actual power equipment.In addition,oxygen in air was usually used as electron acceptor at cathode of MFC in previous studies.Few studies have focused on other gasous electron acceptors,especially the harmful waste gas.NO is the main pollutant in exhaust gas.If NO can be reduced to harmless N₂ at the cathode of MFC,this kind of MFC will combine three important functions in one.The three functions are wastewater treatment,exhaust gas purification and electric power output.This paper focuses on the following work:on the one hand,we reconstruct the configuration of the traditional single-electrode MFC by increasing the number of anodes or cathodes and adding a three-dimensional cathode with an activated carbon layer.On the other hand,the mixed gas of NO and O₂ was used as the cathode electron acceptor,and the NOx removal and the power output of MFC was tested.To improve the power output,the number of cathode was increased from one to six.The results showed that the maximum power density of an MFC with six cathodes was almost 6 times that of an MFC with 2 cathodes.During the process of gradually decreasing the external resistance,the anode potential of the multi-cathode MFC（MFC-DTS）is stable,and no power overshoot occur during the entire process.During charging and discharging,the maximum power density of MFC-DTS can reach 8.5 W/m³.The removal efficiency of TOC of synthetic wastewater was 78.9%and 88.8%after 24h and 48h treatment by MFC respectively.Even for TOC of actual wastewater,the removal efficiency was more than 70%after 24h treatment.On the basis of MFC-DTS,we constructed a multi-anode MFC（MFC-XTS）and a three-dimensional cathode MFC（MFC-HXT）with activated carbon added to the cathode catalytic layer side.It was found that the internal resistance of MFC-XTS and MFC-HXT was reduced by 35.6%and 65.8%respectively,compared to that of MFC-DTS.During charging and discharging,the maximum pulse power of MFC-XTS and MFC-HXT is 18.6%and 34%higher than MFC-DTS,respectively.In addition,the TOC removal of three MFCs was tested.The results showed that MFC-XTS and MFC-HXT had better TOC removal rate than that of MFC-DTS for both synthetic wastewater and actual wastewater.More interestingly,MFC-XTS and MFC-HXT can suppress voltage inversion in series.When two MFCs are connected in series,the addition of MFC-XTS extends the voltage cycle from 13.5hours to 44 hours,and the addition of MFC-HXT extends the voltage cycle to 42 hours.The electric charge number of the serial MFC-XTS or MFC-HXT is 56.9%and 46.2%more than that of the serial MFC-DTS.The NO and O₂was mixed as synthetic pollutant gas and used as cathodic electron acceptor in MFC.The results showed that the removal efficiency of NOx by MFC was improved with the increase of NO and O₂ concentration.When the gas flow rate increased the removal efficiency of NO_xdropped down.The best NOx removal efficiency by MFC reached 65.29%under NO of 0.1%and O₂of 10%with the gas flow rate of 30ml/min.The power generation ability of MFC was tested,and the results showed that the maximum power of MFC with O₂（20%）as the cathode electron acceptor was 4.04W/m³,and the maximum power of MFC under NO of 0.1%and O₂ of 20%was 3.85W/m³.After 4h treatment,MFC under NO（0.1%）and O₂（20%）removed 54%of TOC of synthetic wastewater,which was72%higher than that of MFC using O₂（20%）as cathode electron acceptor.In addition,the MFC showed good stability for NOx purification.The cathode and anode also stayed good performance during a long-term stability test.