Absorption of NO in Aqueous Solution of Co(II)-en: Determination of the Equilibrium Constant

Abstract

In a wet scrubbing process, the addition of ethylenediamine cobalt(II) (Co(II)-en) to enhance the solubility of NO in aqueous solution may provide a good environmental control technology (coordination catalysis reactions absorption) for removal of NO, after the use of a SO 2 scavenging process, that requires little capital when combined with a highly developed industrial wet desulfurization processes. Under anoxic conditions according to amount of time-dependent absorbed NO under different NO partial pressure, the mole ratio of reacted NO and Co(II)-en in the coordination reaction nNO + [Co(en) 3 ] 2+ ⇔ [Co(en) 3 (NO) n ] 2+ was determined to be 1:1, that is n = 1. From this, the formula of the formed nitrosyl metal complex is derived to be [Co(en) 3 (NO)] 2+ . For the development of this scrubbing technological process, knowledge of thermodynamic equilibrium data of the reaction NO + [Co(en) 3 ] 2+ ⇔ [Co(en) 3 (NO)] 2+ over a range of temperatures is of prime importance. In the temperature range from (30 to 90) °C, the equilibrium constant has been determined, and the experimental data fit the following equation well: Kp = (3.3153 ± 0.1160) x 10 -4 exp(4428.5 ± 96.2/T)/bar -1 where the reaction enthalpy is ∇H 0 = -(36.821 ± 0.800) kJ·mol -1 .