Two cation exchange models for direct and inverse modelling of solution major cation composition in equilibrium with illite surfacesReport as inadecuate




Two cation exchange models for direct and inverse modelling of solution major cation composition in equilibrium with illite surfaces - Download this document for free, or read online. Document in PDF available to download.

* Corresponding author 1 BRGM - Bureau de Recherches Géologiques et Minières 2 Modélisation de l-impact des stockages profonds BRGM - Bureau de Recherches Géologiques et Minières

Abstract : Na-K, Na-Ca and Na-Mg exchange isotherms were performed on the fine fraction < 2 µm of Imt-2 illite samples at a total normality of about 0.005 mol-L in anionic chloride medium. The derived selectivity coefficients for Na-K, Na-Ca and Na-Mg were found to vary as a function of the exchanger composition and compared well with the data collected in the literature for similar experimental conditions. Two models were built to reproduce the data: the first was a multi2-site model with constant Gaines and Thomas selectivity coefficients; the second was a one-site model taking into account surface species activity coefficients. The results of the models were in rather good agreement with both our data and literature data. The multi-site model proved to be efficient in predicting the exchanger composition as a function of the Na-Ca-Mg-K concentrations in solution, whereas the one-site model proved to be a better approach to derive the Na-Ca-Mg-K concentrations in solution based on the knowledge of the exchanger composition and the total normality of the solution. The interest of this approach is illustrated by the need for major cation solute concentration predictions in compacted clay for the characterization of nuclear deep disposal host rock repositories.





Author: Christophe Tournassat - Hélène Gailhanou - Catherine Crouzet - Gilles Braibant - Anne Gautier - Arnault Lassin - Philippe Blanc

Source: https://hal.archives-ouvertes.fr/



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