The Performance Of MFCs With Ion Exchange Membranes As Separators

Microbial fuel cell (MFC) can degrade organic matters in water by microbes and produce electricity at the same time, which makes it receive widespread attentions in the fields of in water pollution control and resourcing. As a kind of important separating material between anode and cathode of dual chamber MFCs, ion exchange membrane plays an important role in MFC operations. However, there is no systematic studies on the performance difference and influencing factors of MFCs using ion exchange membrane as separator under different conditions (such as ion type of the membrane, cathodic conditions and structural parameters).Effect of ion type for the ion exchange membrane on MFC performance. The performances of MFCs constructed by carbon felt electrodes, potassium ferricyanide buffer solution as the cathodic electron acceptor, and ion exchange membrane separator were investigated and compared, where four types of ion exchange membranes including proton form cation exchange membrane (CEM-H), sodium form cation-exchange membrane (CEM-Na), hydroxide form anion exchange membranes (AEM-OH) and chloride were used. The results indicated that:the ion conductivity of CEM-Na and AEM-OH were far higher than those for CEM-H and AEM-Cl, respectively. During the initial operation stage of MFCs, CEM-H and AEM-OH both exhibited better electrochemical properties than the corresponding CEM-Na and AEM-Cl, including higher power outputs and lower internal resistances. Among the four MFCs, the one using CEM-H first reached the maximum voltage at 77 h, and its maximum power density (Pmax) achieved 899 mW/m2. The MFCs using AEM-OH and AEM-Cl both showed membrane pollution under the potassium ferricyanide buffer cathodic conditions, which resulted in the increase in mass transfer resistance and MFC performances reduction.Effect of cathodic conditions on MFC performance. The performances of MFCs operated under different cathodic conditions including potassium ferricyanide buffer solution cathode, aerated buffer solution cathode, aerated tap water cathode were investigated. The results indicated that:the MFC voltage polarization under potassium ferricyanide buffer solution cathode condition was mainly controlled by anodic polarization, while those under aerated cathode conditions were majorly controlled by cathodic polarization. For the MFC operated under aerated buffer solution cathode condition, the mass transfer resistance of the contaminated AEMs decreased from 29.06 Ω to 8.77 Ω after increasing the aeration rate from 0.9 mL/s to 1.8 mL/s. At the meantime, the cathodic over potential and the activation losses also decreased by increasing the aeration rate. On the other hand, the cathode ohmic resistance and limited diffusion resistance for the MFCs were enhanced by altering the cathode from aerated buffer solution cathode to aerated tap water cathode, which led to the deterioration in voltage and power output.Effect of the membrane area, membrane-anode distance on MFC performance. The results indicated that:MFC power density increased with the increase in the membrane area, while the internal resistances including the ohmic resistance and polarization resistance reduced with the with the increase in the membrane area. With the reduction in membrane-anode distance, the MFCs exhibited lower internal resistances, better anodic electrochemical activity as well as larger power outputs.