Kinetics for the simultaneous removal of NO and SO2 with cobalt ethylenediamine solution

Abstract NO can be removed from exhaust gas streams by using a basic solution of cobalt ethylenediamine (H 2 NCH 2 CH 2 NH 2 ). The cobalt ethylenediamine acts as a homogeneous catalyst to oxidize NO into soluble nitrogen dioxide and realize the oxidation and absorption of nitric oxide simultaneously. The dissolved oxygen in equilibrium with the residual oxygen in the exhaust gas stream acts as the oxidant. SO 2 can also be removed by the Co(en) 3 3+ (en stands for ethylenediamine) solution. A double-stirred reactor with a plane gas–liquid interface that was planar to close approximation was used to measure the absorption rates of NO into the Co(en) 3 3+ solutions. The experiments demonstrate that the gas–liquid reaction becomes gas film controlling as the cobalt ethylenediamine concentration exceeds 0.03 mol l −1 when there is 1200 ppm SO 2 in the gas phase. The NO absorption rate decreases as SO 2 concentration increases. Oxygen in the gas phase accelerates the NO absorption rate into the cobalt ethylenediamine solution. The optimal temperature for nitric oxide absorption is 50 °C. The NO absorption rate increases as the pH of the Co(en) 3 3+ solutions rises.