Study On The Electrical Properties Of Straw And Its Components In Microbial Fuel Cell

The development and demand of energy is a topic that will never change from ancient times to the present.Environmental protection is also a problem that has been paid special attention to in recent years.The shortage of energy and the pollution of environment and atmosphere will affect the future development of human beings.A large number of straws are burned every year in China.If it can be combined with energy,the balance between economic growth and ecological environment will be realized.Nowadays,microbial fuel cell(MFC)is an ideal device to produce electric energy by using the chemical energy of biomass.If it can use straw and its components to efficiently convert into electric energy in MFC,it not only expands the new mode of straw utilization,but also widens the field of MFC.It has important research significance and value.In this paper,two chamber microbial fuel cell(MFC)was used as the reactor and Bacillus subtilis as the starter to study the effect of different cathode liquid components on the electrical performance of straw hydrolysate.When potassium ferricyanide solution,potassium ferricyanide mixed with sodium chloride solution and sodium chloride solution were used as cathode solution respectively,the experimental results showed that when potassium ferricyanide was used as cathode solution 4450 minutes before MFC operation,the maximum power output was 38 m V,density was 0.023 W/m~2,the current density was 0.077 A/m~2,and the internal resistance was 2.7248 Ω.After 4450 minutes of operation,when the mixed solution is cathode liquid,the maximum electric capacity is 42 m V,the maximum power density is 0.013 W/m~2,the current density is 0.058 A/m~2,and the internal resistance is 3.1409 Ω.During the experiment,when sodium chloride was used as cathode liquid,the maximum electric capacity was 14 m V,the maximum power density was 0.002 W/m~2,the current density was 0.018 A/m~2,and the internal resistance was 5.4762 Ω.The results show that the system is more stable when potassium ferricyanide solution is used as cathode solution.The power density is related to the internal resistance.It was found by scanning electron microscope that the biomass of anode carbon felt was large in the experiment with potassium ferricyanide as the solution,and most of them were enriched with rod-shaped microorganisms.Based on the sodium methyl cellulose component in straw,the effect of sodium methylene cellulose on the electrical properties of MFC was studied,and the stable voltage of the battery was 104,107,100,147,45 m V when the concentration of sodium methylene cellulose was 10.0,2.5,1.0,0.5,0.1 g/L.The results show that: CMC-Na concentration was 0.5 g/L,the maximum power output was 147 m V,the maximum power density was 0.106 W/m~2,and the internal resistance was 0.3312 Ω.The results show that when the substrate concentration is too high or too low,it is not conducive to the decomposition and utilization of microorganisms.The research of using cellulose component in straw as substrate is lower than that of using straw as substrate,and its electricity output accounts for about 59% of the electricity output of using straw as substrate,which is similar to the proportion of cellulose in straw about 45%.With the main components of hemicellulose(L-arabinose and D-xylose)in the straw as the substrate,the concentration of hemicellulose(L-arabinose and D-xylose)in the straw was changed.When the concentration was 1.0 g/L,the maximum electricity production was 51 m V and the maximum power density was 0.013 W/m~2.The substrate concentration will also be used in subsequent experiments.This experiment shows that the straw components(L-arabinose and D-xylose)account for about 20% of the electricity output when straw is used as the substrate,which is not much different from the proportion of hemicellulose in the straw of about 35%,which is related to the proportion of hemicellulose in the straw of less.By changing the species,stirring method,p H value and concentration of the cathode liquid,the following conclusions are obtained: the electricity production performance of Bacillus subtilis as the starter is better than that of the mixed bacteria,and the mixed bacteria system is more complex,and the dominant species is not necessarily the one needed by the anode chamber to get the electricity production bacteria.When the stirring mode is appropriate,the electricity production effect is better than that without stirring.It can be seen from the observation of the microbial morphology of the anode carbon felt after reaction that the microorganism is better enriched on the carbon felt in the stirring state.When the p H = 6.4 concentration is 25 m M,potassium ferricyanide solution is the cathode solution,More conducive to increasing the power of electricity production.