Nitric oxide reduction in BioDeNOx reactors: Kinetics and mechanism

Abstract

Biological reduction of nitric oxide (NO) to di-nitrogen (N(2)) gas in aqueous Fe(II)EDTA(2-) solutions is a key reaction in BioDeNOx, a novel process for NOx removal from flue gases. The mechanism and kinetics of the first step of NO reduction, that is, the conversion of NO to N(2)O, was determined in batch experiments using various types of inocula. Experiments were performed in Fe(II)EDTA(2-) medium (5-25 mM) under BioDeNOx reactor conditions (55 degrees C, pH 7.2 +/- 0.2) with ethanol as external electron donor. BioDeNOx reactor mixed liquor gave the highest NO reduction rates (+/-0.34 nmol s(-1) mg(prot)(-1)) with an estimated K(m) value for NO lower than 10 nM. The specific NO (to N(2)O) reduction rate depended on the NO (aq) and Fe(II)EDTA(2-) concentration as well as the temperature. The experimental results, complemented with kinetic and thermodynamic considerations, show that Fe(II)EDTA(2-), and not ethanol, is the primary electron donor for NO reduction, that is, the BioDeNOx reactor medium (the redox system Fe(II)EDTA(2-)/Fe(III)EDTA(-)) interferes with the NO reduction electron transfer chain and thus enhances the NO denitrification rate.

Nitric oxide enhanced reduction in a rotating drum biofilter coupled with absorption by FeII(EDTA)

“…The inlet NO concentration increased from 340 mg m −3 to 430 mg m −3 , while the removal efficiency went up from 68.30% to 96.50% with an increase in the Fe II (EDTA) concentration from 50 mg L −1 to 500 mg L −1 . This strongly suggests that in the NO reduction system, that is, in aqueous Fe II (EDTA) solutions, the chelated Fe II was the direct electron donor for NO reduction . Though glucose is known to be an excellent electron donor for denitrification, and Fe II (EDTA) is not an energetically favorable electron donor for NO reduction, the debate on the primary donor electron between organic carbon and Fe II (EDTA) is undecided.…”

“…This strongly suggests that in the NO reduction system, that is, in aqueous Fe II (EDTA) solutions, the chelated Fe II was the direct electron donor for NO reduction. 19 Though glucose is known to be an excellent electron donor for denitrification, 20 and Fe II (EDTA) is not an energetically favorable electron donor for NO reduction, the debate on the primary donor electron between organic carbon and Fe II (EDTA) is undecided. The redox properties of FeEDTA and bacterial nitric oxide reductase (NOR), the denitrification enzyme that catalyzes NO reduction to N 2 O, allow Fe II (EDTA) to be directly involved in NOR reduction.…”

NO Removal with Efficient Recovery of N2O by Using Recyclable Fe3O4@EDTA@Fe(II) Complex: A Novel Approach toward Resource Recovery from Flue Gas

“…Obviously, the N 2 O recovery method described in this study can be operated at room temperature, which holds great benefit for energy saving compared to the existing method. Coal combustion products, with a typical NO x concentration in the range of 150–1000 ppm, have been suggested to be one of the major source of NO x emission . According to the annual consumption of coal as fuel (5.5 billion tons), the global NO emissions from coal combustion are estimated as 18.8 million tons (assuming that the NO x concentration is 500 ppm with 90% of NO content and that approximately 7600 m 3 of standard gas is produced from one ton of coal).…”

Simultaneous Biological and Chemical Removal of Sulfate and Fe(II)EDTA-NO in Anaerobic Conditions and Regulation of Sulfate Reduction Products

“…In the BioDeNOx process, the reduction of NO to N 2 was found to be biologically catalyzed with nitrous oxide (N 2 O) as an intermediate [43]. They found that the NO (aq) and Fe(II)EDTA concentration had an effect on the accumulation rate of N 2 O [44]. Other studies have shown that N 2 O accumulation was inhibited with a high C/N ratio, sufficient electron donor and a low sulfite concentration [45].…”