Effect of Temperature on the Diffusion and Sorption of Cations in Clay Vermiculite

The MD method for modeling vermiculite containing Na⁺, Rb⁺, Cs⁺, Mg²⁺, and Ba²⁺ cations shows the following: With a weak swelling of clay, the temperature has no significant effect on the diffusion of water and cations through vermiculite. With a high content of water in vermiculite, the effect of temperature on the diffusion coefficient of water is greater than that of cations. We studied the structure of RDF ions in Na⁺-vermiculite, in which some of the cations are replaced by Rb⁺, Cs⁺, Mg²⁺, and Ba²⁺. Cations of alkali and alkaline earth metals compete with Na⁺ ions for adsorption sites on the surface of the clay layer. The alkaline earth metal cations are in the middle between the clay layers due to their higher charge and stronger hydration. In this case, Na⁺ is localized at the surface of the clay layer. Thus, cations of alkaline earth metals have little effect on the temperature dependence of the diffusion coefficient Na⁺.