Effect of Liquid Electron Mediators on Continuous N2O Gas Removal at Room Temperature: Electrochemical and Electroscrubbing Analysis

Abstract

Many techniques used for N2O abatement involve high temperature catalytic removal with the synthesis of relatively non-valuable products. In the present attempt, N2O degradation was achieved at ambient temperature using different electron mediators during electroscrubbing to form a high value product, NH3. A combination of mediator precursors, such as Fe(III)[Ni(II)(CN)4]1+, Fe(III)[Co(II)(CN)5], and [Ni(II)(CN)4]2−•[Co(II)(CN)5]1−, were added to a 10 M KOH solution to generate the electron mediators. The oxidation/reduction potential (ORP) of the electrolyzed solutions of each complex and the UV-visible spectra confirmed the formation of Fe(II)[Ni(II)(CN)4], Fe(II)[Co(II)(CN)5]1−, and [Ni(I)(CN)4]3−•[Co(II)(CN)5]3− at the cathodic half-cell. N2O degradation was confirmed to occur via a mediated electrochemical reduction (MER) process from the change in reduction efficiency from 4% to 2% (Fe(II)-Ni) and 15% to 12.5% (Ni(I)-Co(II)). Online FTIR gas analysis confirmed that NH3 formed from the degradation of N2O. Although the reduction efficiency was lower for Fe(III)[Ni(II)(CN)4]1+, a high NH3 concentration formed (4.39 mg/hr.) when it was used as an electron mediator. The presence of the [Co(II)(CN)5]3− complex in the mixed complex reduced the level of NH3 formation. The developed method can degrade N2O to NH3 efficiently at ambient temperature.