The Adsorption and Desorption of Nitrogen Oxide by the Aqueous Dispersion of the Chelate Resin-Immobilized Iron(II) Complex

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Abstract
Aqueous dispersions of the chelate resin–iron(II) complex were prepared by ion-exchange in water from iron(II) sulfate and a chelate resin containing iminodiacetic acid moieties. The resulting dispersions in water (50 cm3) can adsorb 78% of the nitrogen oxide (NO) from 6 dm3 of nitrogen gas containing 1000 ppm of nitrogen oxide at 25 °C. The adsorption rate of NO by the dispersions depends greatly on both the particle size of the chelate resin used and the concentration of iron(II) in the supernatant. A fast adsorption of nitrogen oxide can be achieved by using small particles of the chelate resin and by dissolving a large amount of iron(II) ions in the aqueous part of the dispersions. The adsorption and desorption of nitrogen oxide can be understood in terms of a 1:1 reversible coordination of NO to the iron(II) ion immobilized on the chelate resin. The equilibrium constant, enthalpy change, and entropy change for the above adsorbing reaction were 3.11×104 dm3 mol−1, −45.6 kJ mol−1, and −68.2 J K−1 mol−1 respectively. Since the adsorbing reaction of NO in this system is reversible, the adsorbed NO can be released by heating the dispersions which have already adsorbed NO. The amount of the released NO can be predicted from the equilibrium constant at the releasing temperature. Moreover, a concentrated recovery of the NO can be achieved by the present aqueous dispersions system.