Synergistic CO2mineralization using coal fly ash and red mud as a composite system

CO2mineralization plays a critical role in the storage and utilization of CO2. Coal fly ash (CFA) and red mud (RM) are widely utilized as CO2mineralizers. However, the inert calcium species in CFA limit its carbonation capacity, meanwhile the substantial Ca2+releasing of RM is hindered by a covering layer of calcium carbonate. In this study, CO2mineralization in a composite system of CFA and RM was investigated to enhance the carbonation capacity. Multiple analyzers were employed to characterize the raw materials and resulting mineralization products. The results demonstrated that a synergistic effect existed in the composite system of CFA and RM, resulting in improving CO2mineralization rate and efficiency. The produced calcium carbonate was ectopically attached the surface of CFA in the composite system, thus slowing down its coverage on the surface of RM. This phenomenon facilitated further releasing Ca2+from the internal RM, thereby enhancing CO2mineralization efficiency. Meanwhile, the inclusion of RM significantly improved the alkalinity of the composite system, which not only promoted the dissolution of Ca2+of the inert CaSO4(H2O)2in CFA, but also accelerated CO2mineralization rate. The investigation would be beneficial to CO2mineralization using industrial solid wastes.