Supercritical CO2 Confined in Palygorskite and Sepiolite Minerals: A Classical Molecular Dynamics Investigation

Abstract

We have investigated the ability of two modular phyllosilicates (palygorskite and sepiolite) to store CO2 molecules inside their structural channels by means of classical molecular dynamics. Several models containing an increasing supercritical-CO2/H2O ratio into the phyllosilicate channels have been built and the structural and dynamic properties of carbon dioxide and water molecules investigated in detail. We found that both clay minerals can achieve this goal, with sepiolite being able to store more carbon dioxide molecules (and more stably) than palygorskite, due to the larger channels of the former. Interestingly, with the increase of CO2 molecules inside the minerals, the diffusivity of both water and carbon dioxide drastically decreases and carbon dioxide molecules tend to arrange themselves in an ordered pattern.