This work describes an experimental and modeling study on an industrial relevant process (i.e., the absorption of NO in aqueous Fe II (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 Fe II (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 Fe II (EDTA) and NO (r P ) at various temperatures. This ratio is of extreme importance for the design of a reactive NO absorption unit and could be expressed as: r P ) -1.775 ×

The kinetics of the reaction of oxygen with aqueous Fe II (EDTA) solutions has been determined in a range of process conditions (C Fe II (EDTA) ) 15-60 mol/m 3 , P O2 ) 5-20 kPa, pH ) 5-8, T ) 298-328 K, C NaCl ) 0-15 kg/m 3 ) using a gas-liquid stirred cell reactor. The oxygen absorption rates were modeled using an expression derived by De Coursey using the penetration theory of mass transfer. Within the range of process conditions applied, the reaction was shown to be first order in oxygen and second order in iron chelate. The temperature dependence of the kinetic constant may be expressed as (pH ) 7, no salt addition): k 12 ) 5.3 × 10 3 e -4098/T m 6 /(mol 2 ‚s). The kinetic constant is essentially independent of the pH in the range 5 < pH < 8. When applying a NaCl concentration of 15 kg/m 3 , the kinetic constant increases ∼35% (T ) 328 K). The oxidation of Fe II (EDTA) to Fe III (EDTA) is not the sole oxygen-consuming reaction. The extent of side reactions, possibly related to EDTA ligand degradation, is a function of the pH and the oxygen concentration. A remarkable, unprecedented step change in the selectivity of the reaction was observed when the reaction was performed at a higher oxygen concentration.

Reactive NO absorption in aqueous FeII(EDTA) solutions in the presence of denitrifying micro-organisms Gambardella, F.; Galán Sánchez, L.M.; Ganzeveld, K.J.; Winkelman, J.G.M.; Heeres, H.J. Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons the number of authors shown on this cover page is limited to 10 maximum. AbstractThe effect of the presence of denitrifying biomass on the reactive absorption of NO in aqueous Fe II (EDTA) solutions has been investigated (T = 303, 325 K, C Fe II (EDTA) = 30-35 mol/m 3 , C total solids = 0-7.5 kg/m 3 , C suspended solids = 0-1.2 kg/m 3 , C NO in = 250 vppm). The absorption rate of NO is affected by the presence of the biomass sludge and high sludge loadings resulted in reductions in the NO absorption rates. The decrease is likely due to partial blockage of the gas-liquid interface by inorganic and organic suspended solids and to a lesser extent to changes in the physical properties of the liquid. For one of the samples, an enhancement of the NO absorption rate was observed, presumably as a result of a shuttling effect due to the presence of small, adsorptive particles. A semi-empirical engineering model was developed based on the theory of mass transfer in combination with solid particles. The model includes both possible enhancement of mass transfer due to the presence of small adsorptive particles as well as reduction of the mass transfer rate due to the presence of particles adhering to the gas-liquid interface. The experimental profiles were modeled successfully using this approach.

No abstract

No abstract