Effect of aqueous acetic, oxalic and carbonic acids on the adsorption of americium onto alpha-alumina

摘要

The prediction of the migration for radionuclides in geologic media requires a quantitative knowledge of retardation phenomena. For this purpose, the sorption of Am(III) onto a model mineral - alpha-alumina - is studied here, including the effects of groundwater chemistry: pH and concentrations of small organic ligands (acetate, oxalate and carbonate anions). This work presents some experimental evidences for the synergic sorption mechanism of americium-ligand cationic complexes onto the alumina. As its anionic complexes were not sorbed, Am(III) cations were desorbed as a result of the formation of anionic complexes in the aqueous phase. By using the ion-exchange theory, and a corresponding restricted set of parameters - exchange capacities and thermodynamic equilibrium constants - the whole set of sorption experiments of Am(III) cationic species onto the a-alumina was modelled in various chemical conditions.