Interlayer Cation–Water Thermodynamics and Dynamics in Homoionic Alkali and Alkaline-Earth Exchanged Montmorillonites with Low Water Loadings

Dehydration enthalpy and dc conductivity obtained by means of thermogravimetric analysis and complex impedance spectroscopy respectively on three alkaline-earth, i.e. Mg2+, Ca2+, and Ba2+, exchanged montmorillonites with low water loading are reported. These data are compared with those previously reported on the same montmorillonite exchanged with the whole series of alkali cations, i.e. Li+, Na+, K+, Rb+, and Cs+. A comprehensive analysis of the interplay between the interlayer cations and the adsorbed water molecules is thus made possible regarding both the static, i.e. dehydration enthalpy, and dynamics, i.e. dc conductivity, points of view. It is pointed out that dehydration thermodynamics strongly depends on the cation electrostatic potential energy, whereas the dc conductivity temperature behavior, which turns out to be non-Arrhenian for the most hydrated samples can be remarkably well classified using the cation Jones-Dole viscosity B coefficient.