Electro-chemical re-utilisation of exhaust-gas-derived nitric oxide waste

Abstract

With rapid industrial development, the combustion of fossil fuels has also increased, and technologies for treating nitric oxide waste are being studied worldwide. Recently, an absorbent-based wet scrubber capable of selective and high-efficiency nitric oxide treatment has attracted increasing attention. In this study, a method of electro-chemically converting nitric oxide collected from wet scrubbers into valuable nitrate products has been developed. Ferrous ethylenediaminetetraacetate was selected for the proposed approach as a suitable metal chelate absorbent through screening. The absorbed nitric oxide was electro-chemically converted into nitrate, and synthesis efficiency was improved by studying parameters and related mechanisms. The optimal conditions were identified for oxidising the absorbed nitric oxide, and the nitrate concentration and absorbent re-use were confirmed. Nitric oxide was electrically desorbed from the absorbent, and nitrate was synthesised from the separated nitric oxide using a gas diffusion electrode-based system. The production efficiency was considerably increased by selecting the metal oxide catalyst, and the application potential of the process was demonstrated through long-term operation experiments. Therefore, the proposed strategies are promising for application to sustainable next-generation nitrogen cycling to synthesise valuable products while simultaneously treating air pollutants.