Subcritical CO₂ adsorption on geomaterials of coal-bearing strata in the context of geological carbon sequestration

This paper explores the adsorption behaviour of geomaterials in the framework of CO2 sequestration in shallow level coal seams. Manometric adsorption experiments were carried out on two anthracite coal samples, two rock samples from East Irish Sea, MX80-bentonite, Speswhite kaolinite, dry, wet and biofilm-laden (Bascillus mojavensis-laden) sand at subcritical pressure range (up to 6.4 MPa) of isothermal condition at 298.15 K. The experiments were aimed to investigate the influence of the biogeological conditions of coal and caprock constitutions on CO2 adsorption. At lower pressures, the moisture had an influence on the CO2 adsorption on coal resulted in reduced adsorption capacity. At elevated pressures, the volume expulsion behaviour and coal-water interaction had an influence on the adsorption capacities of moist coal sample and resulted in comparable adsorption capacities to dry sample. The disparity in the adsorption capacities between the wet powdered and wet intact core samples showed that the results obtained with powder samples may not reflect the field conditions. Wet conditions and Bascillus mojavensis bacteria influenced the adsorption capacity of sand and showed CO2 chemisorption capacity. The desorption isotherm pattern of wet and biofilm sand showed that the CO2 was continuously adsorbed independent of the gas phase pressure. Among the clay minerals, bentonite had greater affinity towards CO2. Despite the fact that the adsorption capacity of the cap rock is smaller than that of the coal samples, the experimental investigation with constituents of the cap rock provides insights into the effect of biogeological conditions of coal and rock sample constituents on CO2 storage in coal seams.