Europium exchange behaviour of synthetic smectites: spectroscopic and microcalorimetric studies of the influence of structural properties

Document available in extended abstract form only. Full text of publication follows: Among the various soils compounds, clays contribute largely to the transport of heavy metal cations, because of their high cation exchange capacity. The interaction of cations with clay sheets is strongly dependent on the structure of the latter and on the location of their charge deficit, thereby following the type of clays. The intention of the present work was to study the influence of structural properties of synthetic clays on their ion adsorption properties, and the interactions of the exchangeable cations in the interlayer space with water and with clay sheets. Homo-ionic Na-beidellites and Na-montmorillonite with various structural charges were synthesized and finely characterized. Adsorption capacity measurements of Eu(III) were determined. Special attention was paid to the control of the speciation diagram of Eu(III), the hydrolysis, and thus the control of the pH in aqueous suspension. The concentration of Eu(III) was determined with the aid of ionic chromatography analyzer, using UV detection, after optimizing the composition of the mobile phase and the post-column reagent. Time- Resolved Laser Spectroscopy was used to determine the hydration state of the free and the adsorbed species. Isotherm Titration Calorimetry measurements were carried out to determine the heat effect due to the exchange mechanisms. This work has been partially funded by the ANR (CILSAMES project (ANR-07-JCJC-0044) and the GNR Paris 1115. (authors)