Effects of NO2− and NO3− on the Fe(III)EDTA reduction in a chemical absorption–biological reduction integrated NOx removal system

Abstract

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.