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 NO ₂ ^- 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.