Experimental studies on mineral sequestration of CO₂ with buffer solution and fly ash in brines

Carbon dioxide sequestration using brines has emerged as a promising technology to mitigate the adverse impacts of climate change due to its large storage capacity and favourable chemistries. However, the permanent storage (mineral trapping) of CO₂ in brines takes significantly long periods of time as the formation of carbonates is very slow. The main parameters (brine composition, brine pH, system temperature and pressure) have been reported to affect significantly mineral trapping of CO₂ sequestration in brines. The precipitation of mineral carbonates is mostly dependent on brine pH. This study aims to promote the formation of carbonates by using additives that can enhance the brine pH. The pH effect of mixtures of a typical buffer solution (0.3M Tris) and coal fly ash (Class C) on promoting the precipitation of mineral carbonates (mainly calcium carbonates) for above-ground carbonation was evaluated in this study. The CO₂ binding capacity of the combination of tris buffer and fly ash was around 5.1 times larger than when only tris buffer was used and the combination had a synergistic effect on promoting the formation of mineral carbonates.