Capture and sequestration of CO2 in the interlayer space of hydrated calcium Montmorillonite clay under various geological burial depth

• CO2 diffuses more freely with the increase of depth and water content.
• The presence of interlayer CO2 inhibits the diffusion of all the mobile species.
• Hydrated clay system is an appropriate space capable of absorbing CO2 molecules.

We perform, at nanoscale level, the structure and dynamics of carbon dioxide molecules in hydrated Ca-montmorillonite clays. The swelling behaviour of hydrated Wyoming-type Montmorillonite including CO2 molecules and counterions is presented and analysed. In addition, the atom density profile, diffusion behaviours and radial distribution functions of CO2, interlayer water molecules and Calcium ions have been investigated at different geological burial depth of 0 km, 3 km and 6 km, which correspond to various temperature and pressure of simulation conditions. Furthermore, the influence of different hydration state on the dynamical behaviours of carbon dioxide is also explained. The calculated self-diffusion coefficient shows that the carbon dioxide species diffuse more freely with the increase of depth and water content. We also found that the presence of interlayer CO2 inhibits the diffusion of all the mobile species. These results mainly show that the hydrated clay system is an appropriate space capable of absorbing CO2 molecules.