In recent years, there is a huge interest in understanding the interactions of supercritical CO2 with clay minerals, particularly due to the potential of CO2 sequestration in deep geological formations. The intercalation of CO2 can occur both at the nano-confined interlayer regions of clay minerals and at the external pore spaces between two clay particles. However, the influence of the charge balancing cations in smectites on the incorporation of CO2 and the factors that dictate the intercalation process is not well explored on a fundamental molecular level. Grand canonical molecular dynamics simulations (GCMD) were performed to investigate the intercalation behavior of dry CO2 in dehydrated interlayers of smectite mineral, hectorite. A range of alkali and alkaline earth metal cations were examined to demonstrate their influence on the adsorption and dynamics of CO2. Our calculations clearly demonstrate that under anhydrous conditions, the intercalation of CO2 is higher with divalent cations than with monovalent ones, suggesting that both the size/charge ratio and the solvation energies play a critical role in determining the overall adsorption process. The outcomes of the simulations were compared with high pressure (P) and temperature (T) experimental XRD, IR and NMR data obtained under anhydrous conditions.

Intercalation of dry supercritical CO2 in smectite interlayers: A combined experimental and simulation study

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