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

Ferrous chelates (Fe^IIEDTA) 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 Fe^IIEDTA 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 Fe^IIEDTA-NO and Fe^IIIEDTA could be used as the cathode electron acceptors in MFC. Low pH (pH = 5) was beneficial to electricity generation and Fe^IIIEDTA/Fe^IIEDTA-NO reduction by the abiotic cathode. The biocathode performed better in electricity generation and Fe^IIEDTA regeneration, and achieved a Fe^IIIEDTA reducing rate of 0.34 h⁻¹ and a Fe^IIEDTA-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 Fe^IIIEDTA, 0.44 L mmol⁻¹ h⁻¹ for Fe^IIEDTA-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.