Bioelectrochemical Reduction of Fe(II)EDTA-NO in a Biofilm Electrode Reactor: Performance, Mechanism, and Kinetics.

A biofilm electrode reactor (BER) is proposed to effectively regenerate Fe(II)EDTA, a solvent for NOx removal from flue gas, from Fe(II)EDTA NO, a spent solution. In this study, the performance, mechanism, and kinetics of the bioelectrochemical reduction of Fe(II)EDTA NO were investigated. The pathways of Fe(II)EDTA NO reduction were investigated via determination of nitrogen element balance in the BER and an abiotic electrode reactor. The experimental results indicate that the chelated NO (Fe(II)EDTA NO) is reduced to N-2 with N2O as an intermediate. However, the oxidation of NO occurred in the absence of Fe(II)EDTA in abiotic reactors. Furthermore, the accumulation of N2O was suppressed with the help of electricity. The preponderant electron donor for reduction of Fe(II)EDTA NO was also confirmed via analysis of the electron conservation. About 87% of Fe(II)EDTA NO was reduced using Fe(II)EDTA as the electron donor in the presence of both glucose and cathode electrons while the cathode electrons were utilized for the reduction of Fe(III)EDTA to Fe(II)EDTA. Michaelis-Menten kinetic constants of bioelectrochemical reduction of Fe(II)EDTA NO were also calculated. The maximum reduction rate of Fe(II)EDTA NO was 13.04 mol m(-3) h(-1), which is 50% higher than that in a conventional biofilter.