Construction And Power Generation Of Auto-feeding Microbial Fuel Cell

Microbial fuel cell(MFC)is an emerging wastewater treatment technology which can convert organic chemical energy into electrical energy directly by using electroactive microorganisms as catalysts.However,the application of MFC for partical in wastewater treatment is limited due to economic and amplification issues.As a new type of portable energy technology,the small-size MFC may have more practical application prospects in some special occasions.However,the practical application of small-sized MFCs still faces the following problems.(i)Generally,the small-size MFC requires the assist of additional equipment and power to achieve continuous feeding of substrate solution,such as peristaltic pumps and pipes.(ii)When the small-sized MFC is moved or shaken,the hydraulic disturbance of the electrolyte solution would break the established electroactive biofilm on the anode thus decrease the electrochemical stability of the anode.Inspired by the transpiration process of plant,auto-feeding microbial fuel cells(AF-MFC)were constructed in this paper.The required nutrient of the biofilms in the MFC like was auto-fed by a process like the transpiration in plant.This dissertation includes following two parts:In the first part,an auto-feeding hydrogel-electrolyte microbial fuel cell(AF-HE-MFC)was constructed by using the carbon black/stainless steel mesh composite material as anode,an air diffusion electrolyte as cathode,sodium polyacrylate(SPA)superabsorbent polymer as hydrogel electrolyte(HE)and hydrogel-filled capillary as the transport channel.The balance of the electrolyte in AF-SE-MFC was investigated.It was found that the auto-feeding rate of solution in the AF-HE-MFC was about 0.17 g/h.The capillary parameters have slight effect on the auto-feeding rate,but the temperature and air flow of the environment have a significant effect on the evaporation rate of water from the air-cathode.The electrical performance shows that the AF-HE-MFC achieves a stable power output when hydrogel electrolyte was used in the MFC.When the concentration of sodium acetate substrate was 40 mM,the AF-HE-MFC exhibited the best electrochemical performance with a maximum power density of 1180±115 mW/m~2(295.6±28.8W/m~3),which was 79.5%of the liquid electrolyte MFC.Low or high substrate concentration is not conducive to the power output of AF-HE-MFC.Although the AF-HE-MFC achieves the auto-deeding of the substrate and shows good electrical performance,the running time is limited,and the voltage drops after about ten days,mainly due to the changes of internal environment(such as salt accumulation,etc.)of the HE as the running time increases,which resulting in the influence of electroactive microbial.In view of the limited running time of the AF-HE-MFC,another electrolyte replaceable AF-MFC was constructed in this paper.An auto-feeding sponge-electrolyte microbial fuel cell(AF-SE-MFC)was constructed by using the graphite felt as anode,air diffusion electrolyte as cathode,melamine foam swollen with phosphate buffer solution as sponge electrolyte and hydrogel-filled capillary as the transport channel.The feeding balance tests show that the electrolyte solution can achieve auto-feeding and the sponge electrolyte can maintain the stability of water content.Electrical performance tests showed that the AF-SE-MFC had a high performance and long-term stability.When the substrate concentration of the feeding solution is 80 mM and the sponge thickness is 8 mm,the maximum power density reaches 1650 mW/m~2(206 W/m~3).Furthermore,the AF-SE-MFC performance can be restored by replacing the sponge electrolyte when the electrical performance decreased.Therefore,the AH-SE-MFC is a kind of portable energy device with a long-term operation stability,which can be used for a long time by replacing the sponge electrolyte.