Molecular dynamics simulation of the coupling and distribution patterns of CO₂ sequestration and slit pore media

The coupling and distribution patterns of CO2 and slit pore media are of great significance for CO2 sequestration, but urgency is needed to elucidate the occurrence state, displacement, and distribution patterns of CO2 in slit pores in different minerals, as well as the mineral adsorption and sequestration capacities. Molecular dynamics simulation is effective for studying the coupling between CO2 and minerals; hence, this study established molecular models highlighting the coupling between CO2 and minerals and performed molecular dynamics simulations. The simulation results revealed that (1) CO2 occurrence in gypsum slit pores is stable, with the distribution involving two adsorption layers. The CO2 occurrence in calcite slit pores stabilizes after 250 ps, involving two adsorption layers adjacent to the walls of the slit and an intermediate dissociation layer. The CO2 storage in quartz slit pores also stabilizes after 250 ps, involving two adsorption-diffusion layers adjoining the walls of the slit and an intermediate dissociation-diffusion layer. Finally, CO2 adsorption in illite slit pores is unstable and can be characterized by severe diffusion. (2) The adsorption capacities of CO2 for the studied minerals follow the order gypsum > calcite > quartz > illite. (3) The CO2 in the slit pores of gypsum and calcite, quartz, and illite can be characterized by minor, moderate, and major displacement, respectively. Overall, the results indicate that gypsum and calcite are suitable media for CO2 sequestration, whereas quartz and illite are unsuitable. This study not only supplements the literature of CO2 sequestration but also provides guidance for engineering.