Experimental and Modeling Studies on the Absorption of NO in Aqueous Ferrous EDTA Solutions

This work describes an experimental and modeling study on an industrial relevant process (i.e., the absorption of NO in aqueous FeII(EDTA) solutions) to accurately determine the equilibrium constant of the reaction in the temperature range of 299-329 K. The experiments were carried out in a stirred cell contactor using a pH of 7 and an initial FeII(EDTA) concentration of 7-9 mol/m^3. A dynamic reactor model was developed to describe the experimental absorption profiles. Mass transfer effects were taken into account using the penetration theory for mass transfer. Excellent fits were obtained between measured and modeled profiles when assuming that the reaction takes place in the instantaneous regime. The following temperature dependence for the K value was obtained: K = exp((4702/T) - 8.534). Dynamic reactor modeling not only allowed calculation of the equilibrium constants of the reaction but also provided accurate values for the ratio of the diffusivity of FeII(EDTA) and NO (rP) at various temperatures. This ratio is of extreme importance for the design of a reactive NO absorption unit and could be expressed as: rP = -1.775 × 10^-4 T^2 + 0.11T - 16.93.