Enhanced performance of microbial fuel cells with enriched ferrous iron oxidation microflora at room temperatures

Abstract

Adding ferric ions (Fe3+) in catholyte can enhance performance of microbial fuel cells (MFCs). This work adopted biocathode with enriched Fe2+ oxidizing microflora to perform in situ Fe2+ oxidization so the MFC could operate with prolonged period with increased cell open circuit voltage (1037 mV) and maximum power density (71.8 Wm−3 at 154 Am−3) but with minimal needs for iron replenishment. The Fe2+-oxidizing microflora was very effective so the Fe3+/Fe2+ could reach high ratio, which was composed of Acidithiobacillus (73.8%), Acidiphilium (12.1%), Mycobacterium (6.92%), Sulfobacillus (2.66%), Ochrobactrum (1.30%), Alicyclobacillus (0.82%), and other minor species. The membrane transport and cell replication were shown to be their most important metabolic activities. The formation of jarosite and hydronium jarosite by Fe3+ and sulfate led to loss of iron ions, which should be minimized in operation.