(217g) Step-Wise Rare Earth Elements Recovery and CO2 Utilization Via pH Swing Carbonation of Alkaline Industrial Waste

Among the carbon capture, utilization, and storage (CCUS) technologies to achieve net-zero CO₂ emission, carbon mineralization that produces thermodynamically stable solid carbonates allows long-term CO₂ storage by reacting alkaline earth metals with CO₂. Furthermore, produced solid carbonates (e.g., CaCO₃, MgCO₃) can be applied to various industrial materials such as paper and plastic fillers offering economic benefits and allowing a circular carbon economy. Recently, industrial waste has been recognized as a desired feedstock because of its high reactivity with CO₂ and the environmental benefit of reduced landfill. In addition, alkaline industrial wastes often contain not only calcium or magnesium sources for carbon mineralization but also a significant quantity of valuable elements (e.g., Si, Al, and Fe) and rare earth elements (REEs) (e.g., La). In this study, we investigated the pH swing carbonation technology that consists of the extraction, precipitation, and carbonation steps, using the cast iron slag to stably store the CO₂ and produce valuable materials (i.e., REEs and CaCO₃). The physicochemical properties of industrial wastes were investigated by employing ICP-OES, PXRD, and XRF. The extraction, precipitation efficiency, and reaction kinetics were also examined. To selectively recover the REEs, the structured ligands were synthesized and its performance were evaluated. The physicochemical properties of precipitated CaCO₃ (PCC) were carefully examined for different applications of PCC .