Regeneration of Fe II /Fe III complex from NO chelating absorption by microbial fuel cell.

Ferrous chelates (FeIIEDTA) can effectively absorb NO, but the regeneration of them usually consumes large amounts of organic matter or energy. In this study, a new approach to regenerate NO absorbed ferrous chelates with simultaneous electricity generation was investigated by a microbial fuel cell (MFC). The performance and mechanisms of FeIIEDTA regeneration were evaluated in the cathode of MFC reactor with and without the presence of microorganisms (referring to biocathode and abiotic cathode), respectively. It was found that FeIIEDTA-NO and FeIIIEDTA could be used as the cathode electron acceptors in MFC. Low pH (pH = 5) was beneficial to electricity generation and FeIIIEDTA/FeIIEDTA-NO reduction by the abiotic cathode. The biocathode performed better in electricity generation and FeIIEDTA regeneration, and achieved a FeIIIEDTA reducing rate of 0.34 h-1 and a FeIIEDTA-NO reducing rate of 0.97 L mmol-1 h-1, which are much higher that than those for the abiotic cathode (0.23 h-1 for FeIIIEDTA, 0.44 L mmol-1 h-1 for FeIIEDTA-NO). This was likely because the activation polarization loss and over cathode potential were reduced as a result of the catalytic activity of NO and iron reducing bacteria.