An Analytical Model for Probing Ion Dynamics in Clays with Broadband Dielectric Spectroscopy

Benjamin Rotenberg (1) , Anthony Cadene (1) , Jean-François Dufrêche (1) , Serge Durand-Vidal (1) , Jean-Claude Badot (2) , Pierre Turq (1)

1 LI2C - Liquides Ioniques et Interfaces Chargées
2 LCAES - Laboratoire de Chimie Appliquée de l'État Solide

A simple two-state model is proposed to explicitly derive the ionic contribution to the frequency-dependent dielectric permittivity of clay. This model is based on a separation of time scales and accounts for two possible solvation modes (inner/outer-sphere complexes) for ions in the interlayer spacing and a possible chemical exchange between both forms. The influence on the permittivity of thermodynamic (distribution constant Kd) and dynamic (diffusion coefficient, chemical relaxation rate) parameters is discussed. In turn, this model is used to analyze experimental data obtained with Na-montmorillonite for two relative humidities. The values of the parameters extracted from these measurements, and their variation with water content, show that the proposed model is at least reasonable.

Domaines: Matériaux; Chimie théorique et/ou physique

Benjamin Rotenberg, Anthony Cadene, Jean-François Dufrêche, Serge Durand-Vidal, Jean-Claude Badot, et al.. An Analytical Model for Probing Ion Dynamics in Clays with Broadband Dielectric Spectroscopy. Journal of Physical Chemistry B, 2005, 109, pp.15548-15557. ⟨10.1021/jp051586k⟩. ⟨hal-00166966⟩