The Effect of Feed Volumetric Flow Rate and NaCl Concentration on Microbial Fuel Cell Efficiency

Microbial fuel cell (MFC) is an electrochemical device which uses microorganisms to convert chemical energy of bio-fuel to electrical energy. One of the most important issues in the performance of microbial fuel cells is overcoming the internal resistance of the cell. The purpose of this study is to investigate the effect of inlet discharge and different concentrations of NaCl on microbial fuel cell performance. 

In this experimental study, 1 and 2 mL/min discharges as well as concentrations of 0.1, 0.5, and 1 M of NaCl were selected. We also used three continuous reactors, each with three main parts of anodes, cathodes, and polymer membranes, to investigate the effect of the above factors. The anode and cathode were carbon rods and the polymer membrane was Nafion 117. 

Compared to other concentrations, in 1 mL/min volumetric flow of feed and 0.5 M of NaCl concentration, MFC showed the best performance. However, in 2 mL/min volumetric flow, the best operation of MFC was in 1 M concentration of NaCl. With the change in discharge, the retention time changed, and with the change in concentration, the internal resistance of the cell as well as the process efficiency changed due to the change in the electrolyte conductivity. Changing the conductivity of the electrolyte alone did not decrease the internal resistance of the cell. Changes in discharge also showed that increasing the retention time did not result in higher efficiency. 

Both the electrolyte change and the retention time should be considered for optimal cell performance.