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- Author or Editor: K. Chalupská x
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Abstract
A surface complexation model, the so-called diffuse double layer model (DLM), was used in the description of the multicomponent system consisting of Czech sodium bentonite SABENYL and synthetic granitic water spiked with233U(VI). The experimental data were evaluated and the characteristic parameters, e.g., the equilibrium constants of all the reactions considered, were obtained and used for the numerical simulation of sorption selectivity of the uranium in relation to the total carbonate concentration. The values of separation factors indicate that the selectivity of uranium sorption in such multicomponent systems can depend not only on the pH and composition of both phases, but also on the phase ratio and starting concentrations of participating components.
Abstract
A general model, the so called Mean Molecular Weight Model (MMWM), of complexation of metal cations (Mez+) with macromolecular polyanions of humic acid (HAp-) is proposed. The model is based on the results of previous studies of the electrophoretic mobility of humate complexes and assumes that the complexation proceeds by consecutive neutralization of the dissociated carboxyl groups of the central polyanion HAp- with Mez+ cations. It reflects the macromolecular character of humic acid, applies molar concentrations of reacting components with equations for stability constants and incorporates also the mean charge of humic macromolecules. The model has been verified with experimental data obtained in the study of complexation of Eu(III) with Aldrich humic acid using ion exchange (Amberlite IR-120), over a broad range of [Eu] to [HA] ratio, at pH 4 and 7.
