Application of the multi-site ion exchanger model to the sorption of Sr and Cs on natural clayey sandstone

Aubéry Wissocq (1, 2) , Catherine Beaucaire (1, 2) , Christelle Latrille (1)

1 CEA-DES (ex-DEN) - CEA-Direction des Energies (ex-Direction de l'Energie Nucléaire)
2 LAMBE - Laboratoire Analyse et Modélisation pour la Biologie et l'Environnement

To ensure the environmental monitoring of nuclear sites, sorption models enabling the prediction of contaminant migration (such as $^{90}$Sr and $^{137}$Cs) in soils, sediments and aquifers need to be developed. This paper aims 1) at developing a database containing the sorption properties of the pure mineral phases commonly encountered in natural environments and 2) at using this database in a multi-site ion exchange model to be applied on natural sediments. In addition to some raw adsorption data issued from literature, different sorption experiments of Sr and Cs, on pure illite and smectite, in competition with calcium were carried out, as a function of pH and as well as concentrations of Sr and Cs. These sorption data were interpreted using a multi-site ion-exchange model and contributed to the elaboration of a thermodynamic database gathering the retention properties of illite and smectite (site capacities and selectivity coefficients) towards Cs$^+$, Sr$^{2+}$, H$^+$ and Ca$^{2+}$. A multi-site ion exchange model based on the mixture of pure mineral phases (illite and smectite) was successfully applied to simulate the Sr and Cs behavior in a natural clayey sandstone, indicating that the additivity of retention properties of the minerals constituting the sediment can be verified.

Mots clés: cesium; strontium; smectite; sorption; ion exchange model; illite

Domaines: Physique Nucléaire Expérimentale [nucl-ex]; Physique Nucléaire Théorique [nucl-th]

Aubéry Wissocq, Catherine Beaucaire, Christelle Latrille. Application of the multi-site ion exchanger model to the sorption of Sr and Cs on natural clayey sandstone. Applied Geochemistry, 2018, 93, pp.167-177. ⟨10.1016/j.apgeochem.2017.12.010⟩. ⟨cea-02421720⟩