A theoretical study of swelling and shrinking of hydrated Wyoming montmorillonite

Monte Carlo molecular modelling simulations were performed to investigate the swelling and shrinking behaviour of hydrated Wyoming-type montmorillonite (MMT) including different counterions. MCY, TIP4P, and SPC/E water and potential models were employed to Li- and Na-montmorillonite. The simulation data with the SPC/E water model fitted the experimental swelling curves. The agreement between our results and available experimental and/or preceding theoretical results allow us to predict the swelling and shrinking behaviour of MMT including other cations such as some heavy metal ions (Ni2+, Zn2+ and Pb2+). The hysteresis between swelling and shrinking is due to the different mechanism of adsorption and desorption by breaking and re-formation of hydrogen bonds between the water molecules.