Experimental study on indirect mineral carbonation using five types of slag for production of high-purity calcium carbonate

Mineral carbonation is one of the known methods for carbon capture, utilization, and storage (CCUS). Slag from the steel industry is studied as a common source of CaCO₃ via mineral carbonation owing to its high Ca content. Despite numerous preliminary studies, the optimal factors governing the mineral carbonation of steelmaking slag, such as extraction and carbonation remain unexplored. In this study, we optimized the factors for Ca extraction and carbonation, as CaCO₃ produced under these optimized factors possesses commercial value due to its high purity. The extraction and carbonation experiments were performed on two types of slag samples, specifically non-magnetic steelmaking and pig iron slag, utilizing the chosen factors for each procedure. NH₄Cl was chosen as the extractant because of its high calcium selectivity and inhibition of gel formation. Precipitates with Ca content ≥ 98% were obtained by extracting and carbonating them. The crystalline form and particle size of CaCO₃ in the precipitates were determined by the pH control. The findings of this study will be used to improve the design of precipitated calcium carbonate (PCC) production processes and increase the economic value of their output.