Effect of the interaction time of CO2–H2O on the alterations of coal pore morphologies and water migration during wetting

Abstract

CO2 geosequestration requires coal property examination for long-term storage sustainability. This study explores pore morphologies and water kinetic during wetting under interactions. Results showed that the CO2–H2O interaction induced intricate modifications in the coal pore architecture over time, causing a decrease in surface roughness and an increase in hydrophobicity of coal after long-term (10 days) and short-term (5 days) treatment. By setting a water intake, capillary force drives the transformation of free water to capillary water and adsorbed water. The adsorption kinetics of coal to water follows the linear driving force (LDF) mass transfer rate law, provided a good agreement with experimental data, validating its applicability to the studied system within the long time limits. As the reaction duration increased, the rate constant increased while the equilibrium adsorption capacity decreased. The modified Wenzel model of hydrophilic surface is proposed to interpret the temporal alterations, showing that untreated coal has substantial contact points on the rough surface, resulting in a smaller apparent contact area than the real contact area, hindering water retention and displaying enhanced wettability. The rule applied hydrophilic surface of both natural wettability adjusted by supercritical carbon dioxide (ScCO2).