Effects of NO2 - and NO3 - on the Fe(III)EDTA reduction in a chemical absorption-biological reduction integrated NO x removal system

The biological reduction of Fe(III) ethylenediaminetetraacetic acid (EDTA) is a key step for NO removal in a chemical absorption-biological reduction integrated process. Since typical flue gas contain oxygen, NO2 (-) and NO3 (-) would be present in the absorption solution after NO absorption. In this paper, the interaction of NO2 (-), NO3 (-), and Fe(III)EDTA reduction was investigated. The experimental results indicate that the Fe(III)EDTA reduction rate decrease with the increase of NO2 (-) or NO3 (-) addition. In the presence of 10 mM NO2 (-) or NO3 (-), the average reduction rate of Fe(III)EDTA during the first 6-h reaction was 0.076 and 0.17 mM h(-1), respectively, compared with 1.07 mM h(-1) in the absence of NO2 (-) and NO3 (-). Fe(III)EDTA and either NO2 (-) or NO3 (-) reduction occurred simultaneously. Interestingly, the reduction rate of NO2 (-) or NO3 (-) was enhanced in presence of Fe(III)EDTA. The inhibition patterns observed during the effect of NO2 (-) and NO3 (-) on the Fe(III)EDTA reduction experiments suggest that Escherichia coli can utilize NO2 (-), NO3 (-), and Fe(III)EDTA as terminal electron acceptors.