Effects of NO 2 − and NO 3 − 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, NO 2 − and NO 3 − would be present in the absorption solution after NO absorption. In this paper, the interaction of NO 2 − , NO 3 − , and Fe(III)EDTA reduction was investigated. The experimental results indicate that the Fe(III)EDTA reduction rate decrease with the increase of NO 2 − or NO 3 − addition. In the presence of 10 mM NO 2 − or NO 3 − , 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 NO 2 − and NO 3 − . Fe(III)EDTA and either NO 2 − or NO 3 − reduction occurred simultaneously. Interestingly, the reduction rate of NO 2 − or NO 3 − was enhanced in presence of Fe(III)EDTA. The inhibition patterns observed during the effect of NO 2 − and NO 3 − on the Fe(III)EDTA reduction experiments suggest that Escherichia coli can utilize NO 2 − , NO 3 − , and Fe(III)EDTA as terminal electron acceptors.