Formation Of Electrochemical Active Biofilm And Its PH Distribution Inside Graphite Electrode Arrays

It is well known that, in the 21 st century, human beings are facing with two problems-energy crisis and environmental pollution, which has strongly restricted the sustainable development of the human society economy. With the rapid development of the social economy in recent years, the traditional fossil energy has been over-exploited and has been gradually exhausted. At the same time, environmental pollution, especially water pollution, has become more and more serious. But, the traditional wastewater treatment processes has always been high-input and zero-output. Hence it is necessary to find a new wastewater treatment craft to promote sustainable development for all. Against this background, MFC has attracted more and more attention due to the attractive benefits of degradation of organic matter in wastewater and simultaneous electricity recovery from wastewater.Unfortunately, the low power output of MFCs hindered its practical application. Among the factors that affect the MFCs performance, the anode performance is regarded as one of the key factors, especially the properties of biofilm on the anode with 3D structure. In this work, 3D anode array with different micro pore structure, based on the 2B pencil core unit, was fabricated. The transport of the substrate and product and the formation of biofilm as well as the pH distribution inside the micro pore structure of the anode was investigated. The main results were summarized below:(1) The different size of the graphite rods anode arrays with the fixed spacing at 0.5 mm, in which the pH distribution and the properties of biofilm was studied, were established. The results showed that, the electrochemical properties of anode biofilm attaching between the 2×2 graphite rods anode array and a single graphite rod anode had a slight difference. However, for the 6×6 graphite rods anode array, the pH value of anode central area was far lower than its outer area, causing the low electricity generation performance of the graphite rod in central area of the 6×6 graphite rods array due to the inhibiting function of the low-pH environment to the growth and the electrochemical activity of biofilm.(2) The different space of the graphite rods anode arrays under the constant volume at 196mm2 were established, in which the pH distribution and the properties of biofilm was studied. The results showed that, when the interspace of anode was larger than 3.4 mm, the proton transport had little influence on the formation of biofilm. On the contrary, the activity of anode biofilm was limited by the diffusion rate of proton when the interspace of anode was smaller than 3.4 mm. And when the interspace of anode was decreased to 1.66 mm, the power generation of different areas of the graphite rods array exhibited the significant differences because of the different pH distribution inside the graphite rods array.(3) The pH distribution and the properties of biofilm inside the 10×10 graphite rods anode were investigated. By compared with the experiments in chapter 3 and 4, when the number of graphite rod was more than 16, the increase in the number of graphite rod electrode had little effect on improving production performance. Meanwhile, with increasing the number of graphite rod electrode and decreasing of the interspace, the charge transfer resistance increased while the ohm resistance remained unchanged. In addition, the results also showed that, the distribution of biofilm on the anode surface was more uniform with the decrease in the difference of the pH value inside the graphite rods electrode array.