Molecular simulation of CO2 adsorption on kaolinite: Insights into geological storage of CO2

Globally, the escalation of global warming, primarily attributed to anthropogenic carbon dioxide (CO2) 2 ) emissions, has been recognized as an urgent issue to address. Carbon dioxide capture and storage (CCS) technology has emerged as a critical and acknowledged strategy for mitigating atmospheric CO2 2 levels. During CO2 2 storage in geological formations, the gas undergoes several capture mechanisms, resulting in its storage within a porous medium. The adsorption of CO2 2 by kaolinite, a mineral prevalent in reservoirs and caprocks, and the interplay of various influencing factors, has become a central focus in research on the efficacy of geological CO2 2 storage. This study focuses on kaolinite, establishing a slit pore model and employing CO2 2 and H2O 2 O as fluid models, combines the potential energy parameters, constructs the molecular model required in the simulation study. We use molecular dynamics (MD) and Grand canonical Monte Carlo (GCMC) simulations to explore the configuration of CO2 2 adsorption and the microscopic adsorption mechanism of CO2 2 in kaolinite pores. Furthermore, this study examines the influence of various factors including pore size, temperature, pressure, water content and mineralogy on the adsorption characteristics of CO2 2 within kaolinite pores. The adsorption energy and capacity for CO2 2 in kaolinite are directly proportional to its pore size; larger pores correlate with higher absolute values of adsorption energy and enhanced adsorption capacity. The adsorption of CO2 2 within the pores of kaolinite intensifies as pressure increases, ultimately attaining equilibrium. Conversely, higher temperatures lead to a gradual decrease in CO2 2 adsorption and a reduction in the interaction force between the O atoms of CO2 2 and the H atoms on the kaolinite surface. An increase in water content corresponded with a decrease in both the quantity of CO2 2 adsorbed and the absolute value of adsorption energy. This implies that a higher initial water content in the pores of kaolinite impedes CO2 2 adsorption due to the occupation of available adsorption sites by H2O 2 O molecules. CO2 2 prefers to adsorb near the hydroxyl surface of kaolinite rather than the siloxane surface.