The effect of weak acid anions on the selective catalytic wet air oxidation of aqueous ammonia to nitrogen

摘要

In this work, the effect of weak acid anions on the ammonia removal has been extensively studied for the process of selective catalytic wet air oxidation (CWAO) of ammonia to nitrogen. It is found that the presence of weak acid anions can effectively enhance the ammonia conversion and selectivity towards nitrogen. The combination between the weak acid anions and H⁺ to produce weak acid molecules is responsible for such enhancement. Firstly, the H⁺ consumption of weak acid anions can increase the NH3 concentration and thus the reactivity of ammonia oxidation, due to the shift to NH3 on the equilibrium of NH4 ⁺/NH3. Secondly, the competition combination with H⁺ between the weak acid anions and NO2 ⁻ can increase the concentration of NO2 ⁻ and thus boosts the disproportionation reaction between NH4 ⁺ and NO2 ⁻ to produce nitrogen.