Mineralization mechanism of carbon dioxide with illite interlayer cations using molecular dynamics simulation and experiments

Abstract

Clay minerals can be identified as a prospective target for long-term CO2 sequestration due to their accessible interlayer cations and periodic sheet structure. Understanding the reactive motion of mineral and fluids has dual advantages of resources and environment. To clarify the storage mechanism, an alternative strategy for CO2 mineralization was investigated through molecular dynamics (MD) simulation and scCO2H2Oillite experiments. The MD simulation predicts the protonation of non-bridging oxygen (NBO) at the illite surface in the first picoseconds, resulting in HCO3- ion formations via the bonding between CO2 molecules and hydroxyl group dissociated from H2O molecules. Surface protonation leads to interlayer K+ cations hopping to the illite/fluids interface since the middle stage, mainly after 1 ns of the reaction. The leached K+ cations bond with the HCO3- ions and later interact with the hydroxyl groups, forming K2CO3 molecules at the interface. In accordance with the experimental results, the K+ cations’ concentration in the filtrates progressively increases throughout the reaction. Results of SEM-EDS, Raman and XPS measurements find that free CO2 clusters in contact with the leached interlayer cations can be converted into carbonate species through the mineralization reaction, precipitating at the surface and thus inducing interlayer swelling. These observations reveal that the clay-related mineralization is estimated to undergo an accumulated process, accessibly enhancing the amount of captured CO2. This is a new report that demonstrates the mechanism of CO2 mineralization in clay minerals, presenting a potential solution for CO2 sequestration enhancement. Insights into K+ cations leaching and mineralization kinetics and their underlying mechanisms during the scCO2H2Oillite reaction is a matter of generalization in clay minerals for CO2 storage.