Performance of Several Cobalt-Amine Denitration Solutions and Their Catalytic Regeneration by Graphene

Little attention has been focused on the use of cobalt(II)-amine chelates for the absorption of nitric oxide (NO) in flue gas, and research on the regeneration of cobalt denitration solutions is relatively rare. To supplement this research gap, several promising ethylenediamine derivatives were screened out. They are N-(2-hydroxyethyl)ethylenediamine, 1,2-propanediamine, and 1,2-cyclohexanediamine. These cobalt(II)-amine solutions are effective for denitration and have not been reported yet. However, they are also easily oxidized to the corresponding cobalt(III) species. In the presence of a nanocarbon material, cobalt(III) components are reduced to cobalt(II) components and release oxygen by reacting with acids. The effects of solution pH, temperature, and graphene dosage on the regeneration process were investigated. A proper addition of graphene as a catalyst contributes to the progress of regeneration. Catalytic mechanisms and regeneration performance have been discussed as much as possible. These mechanisms are related to the oxidation reactions and oxygenated species of cobalt complexes. The carbon material here acts as a catalyst for adsorbing cobalt chelates and accelerating charge transfer in the oxygen evolution reaction.