Swelling and diffusion behaviour of Na-vermiculite at different hydrated states

Monte Carlo and Molecular Dynamic simulation methods have been performed to study vermiculite, one of the swelling clay minerals. The evolution of the basal spacing of this clay mineral with increasing water content, as well as the evolution of this space of different hydrated states under the influence of temperature was investigated by means of Monte Carlo molecular simulation method. We found that the effect of temperature is much more important on the high hydrated clay and is negligible on low hydrated one. The diffusion behaviour of water and Na+ in the interlayer space of different hydrated vermiculite was also studied using the Molecular Dynamic simulation method. We found that the diffusion of water is much faster than Na+ at the same hydrated state. Moreover, the evolution of diffusion of water and cations shows a great increase on the thresholds of each hydrated state and then a decrease till the next hydrated state. (C) 2015 Elsevier B.V. All rights reserved.