Enhanced Reduction of Fe(II)EDTA-NO/Fe(III)EDTA in NO_x Scrubber Solution Using a Three-Dimensional Biofilm-Electrode Reactor

Abstract

A promising technique called chemical absorption-biological reduction (CABR) integrated approach has been developed recently for the nitrogen oxides (NO(x)) removal from flue gases. The major challenge for this approach is how to enhance the rate of the biological reduction step. To tackle the challenge, a three-dimensional biofilm-electrode reactor (3D-BER) was utilized. This reactor provides not only considerable amount of sites for biofilm, but also many electron donors for bioreduction. Factors affecting the performance of 3D-BER were optimized, including material of the third electrode (graphite), glucose concentration (1000 mg·L(-1)), and volume current density (30.53 A·m(-3) NCC). Experimental results clearly demonstrated that this method significantly promotes the bioreduction rate of Fe(II)EDTA-NO (0.313 mmol·L(-1)·h(-1)) and Fe(III)EDTA (0.564 mmol·L(-1)·h(-1)) simultaneously. Experiments on the mechanism showed that Fe(II)EDTA serves as the primary electron donor in the reduction of Fe(II)EDTA-NO, whereas the reduction of Fe(III)EDTA took advantage of both glucose and electrolysis-generated H(2) as electron donors. High concentration of Fe(II)EDTA-NO or Fe(III)EDTA interferes the bioreduction of the other one. The proposed methodology shows a promising prospect for NO(x) removal from flue gas.

A Biophysicochemical Model for NO Removal by the Chemical Absorption–Biological Reduction Integrated Process

“…It has been demonstrated that the CABR process features higher NO removal efficiency compared to the conventional biological denitrification, which showed over 90% in the long term operation under the typical CABR conditions . Parametric tests revealed that the gas residence time and the concentration of Fe­(II)­EDTA were critical to achieve a high NO removal efficiency. − It has been confirmed that the main end product of the NO reduction in the CABR system was nitrogen gas while N 2 O was an intermediate . Batch experimental results showed that the Fe­(III)­EDTA reduction rate was the limitation to achieving high NO removal capacity …”

Highly Efficient Heterogeneous Catalytic Reduction of Fe(II)EDTA-NO in Industrial Denitrification Solution over Pd/AC Catalyst

“…NO x , a typical component in flue gas streams, is recognized as another main pollutant that induces acid rain and greenhouse effects. , Compared with the various denitrification technologies, the liquid-phase denitrification characterized by Fe­(II)­EDTA has been demonstrated as a very promising research direction in controlling NO x emission because of its speedy capture ability for NO x . , However, the easy conversion of Fe­(II)­EDTA to Fe­(III)­EDTA causing a poor ability to absorb NO x and the regeneration of Fe­(II)­EDTA after absorbing NO have significantly restricted the large-scale application of the Fe­(II)­EDTA-based liquid-phase denitrification technique. In most studies, the simultaneous reductions of Fe­(II)­EDTA-NO and Fe­(III)­EDTA mainly focused on biological reduction.…”

A Mass-Transfer Model of Nitric Oxide Removal In a Rotating Drum Biofilter Coupled with FeII(EDTA) Absorption

“…The main reactions involved in the chemical absorption–biological reduction can be expressed as Surprisingly, Fe II (EDTA) and Fe III (EDTA) may be directly involved in the nitric oxide reductase (NOR) reduction during denitrification, based on the available midpoint potential between NO reductases and Fe II (EDTA)/Fe III (EDTA) system . However, according to some studies on biofilm-electrode reactors, Fe II (EDTA) is directly involved in the microbial reduction of chelate Fe II (EDTA)-NO as a dominant electron donor …”