Multiphase Monte Carlo and Molecular Dynamics Simulations of Water and CO2 Intercalation in Montmorillonite and Beidellite

摘要

Multiphase Gibbs ensemble Monte Carlo simulations were carried out to computethe free energy of swelling for Na-montmorillonite and Na-beidelliteinteracting with CO2 and H2O at pressure and temperature conditions relevantfor geological storage aquifers. The calculated swelling free energy curvesshow stable monolayer and bilayer configurations of the interlayer species forNa-montmorillonite, while only the monolayer structure is found to be stablefor Na-beidellite. The calculations show that CO2 is intercalated into hydratedclay phases at concentrations greatly exceeding its solubility in bulk water.This suggests that expandable clay minerals are good candidates for storingcarbon dioxide in interlayer regions. For Na-beidellite the CO2 moleculedistribution is mainly controlled by the position of the isomorphicsubstitutions, while for Na-montmorillonite the hydrated sodium ions play animportant role in establishing the CO2 distribution.