Flue gas separation at organic-inorganic interface under geological conditions

Abstract

Injecting flue gas into geological reservoirs is a promising way to weaken greenhouse effects and achieve some additional benefits. However, for the effect of heterogeneous (organic-inorganic) interfaces on flue gas separation, it seems to be a lack of detailed theoretical and quantitative understanding, especially when metal ions are doped into organic matter. In this study, graphite-calcite (GC) interface was constructed to explore the adsorption behavior of flue gas by multiscale simulations. The adsorption structure, preferential orientation, relative concentration and diffusion coefficient of flue gas were calculated and compared at GC interface with and without calcium impurity. The results show that CO2 is preferentially adsorbed on heterogeneous surfaces, while N2 is squeezed into the central region of the interface. We highlight the importance of the number of Ca ions for flue gas separation. When Ca ion exists on graphite surface, CO2 adsorption capacity is remarkably enhanced. In practical applications, the selectivity parameter of GC interface containing calcium impurity has reached 21, so it has absolute advantages for flue gas separation. Our work affords new insights into flue gas adsorption in more realistic shale reservoirs.