Evolution of Molecular Interactions in the Interlayer of Na-Montmorillonite Swelling Clay with Increasing Hydration

Abstract

In this work, the swelling behavior of sodium (Na)-montmorillonite clay with increasing amounts of hydration is studied using molecular dynamics. The molecular models of the dry clay and the hydrated clays, consisting of 2, 4, 6, 8, and 10 monolayers of water in the interlayer, are used in this study. This work captures the evolution of interaction energies in the interlayer of Na-montmorillonite swelling clay with increasing hydration and provides insight into swelling mechanisms. This work shows the important role of bound water and clay-Na interactions during swelling to stabilize clay structure during hydration. Changes to water molecule conformations in the interlayer during swelling are also reported. The results and insight provided by this work will help in modeling and predicting exfoliation and resulting particle breakdown in swelling clays, in addition to expounding the key role of interlayer interactions on swelling in smectite clays.