Parametric study and mechanism analysis of NO removal by cobalt ethylenediamine

Abstract

Nitrogen oxides (NOx) are one of the major air pollutants, causing many environmental problems, NO being the main component of NOx. In the present work, the solution of cobalt ethylenediamine was used to removal NO via the wet denitrification method. For industrial applications, this experiments was carried out in the packing tower and the influence of CO2 and SO2 on the removal rate of NO also was analyzed. It found that the concentration of [Co(en)3]2+, pH, gas flow rate, the liquid-gas ration, the concentration of NO and O2 strongly affected the denitrification efficiency at a different rate. More precisely, the concentration of 0.025 mol/L of [Co(en)3]2+, pH of 13.0, low gas flow rate, high liquid-gas ratio, and high concentration of NO and O2 was proved to be recommendable for the highest efficiency. Furthermore, a reduced amount of CO2 and SO2 in the flue gas would be a recommended method for NO removal. Although three different reaction paths have been proposed by previous studies, they are still controversial. To determine which is the most accurate, three different reaction paths were checked by experiments in this work. The results implied that the cobalt ethylenediamine was complexed with NO and O2 to produce [Co(en)2(NO)(OH−)]+ and [Co2(en)4O2(OH)]3+, and then these products reacted each other to regenerate the [Co(en)3]2+. As a summary, we can affirm that the present work can guide toward the industrialization of wet denitrification using cobalt ethylenediamine.