Dissimilatory reduction of Fe^III (EDTA) with microorganisms in the system of nitric oxide removal from the flue gas by metal chelate absorption

In the system of nitric oxide removal from the flue gas by metal chelate absorption, it is an obstacle that ferrous absorbents are easily oxidized by oxygen in the flue gas to ferric counterparts, which are not capable of binding NO. By adding iron metal or electrochemical method, Fe^III (EDTA) can be reduced to Fe^II (EDTA). However, there are various drawbacks associated with these techniques. The dissimilatory reduction of Fe^III (EDTA) with microorganisms in the system of nitric oxide removal by metal chelate absorption was investigated. Ammonium salt instead of nitrate was used as the nitrogen source, as nitrates inhibited the reduction of Fe^III due to the competition between the two electron acceptors. Supplemental glucose and lactate stimulated the formation of Fe^II more than ethanol as the carbon sources. The microorganisms cultured at 50°C were not very sensitive to the other experimental temperature, the reduction percentage of Fe^III varied little with the temperature range of 30-50°C. Concentrated Na₂CO₃ solution was added to adjust the solution pH to an optimal pH range of 6-7. The overall results revealed that the dissimilatory ferric reducing microorganisms present in the mix-culture are probably neutrophilic, moderately thermophilic Fe^III reducers.