Dissolution characteristics of steel slag in aqueous solution and preparation of high purity CaCO3

Abstract

Steel slag (SS), a solid byproduct of the steel-making process, possesses high potential for value-added applications on account of its abundant content of CaO and MgO. These alkaline components make steel slag a viable candidate for carbonation and CO₂ fixation processes. This study investigated the hydration of steel slag, focusing on how variables such as particle size, reaction temperature, and reaction time influence the characteristics and efficiency of the resulting products. The findings revealed that hydration predominantly occurs through the dissolution of free calcium oxide (f-CaO), with an optimal total dissolution rate reaching 7.2 %. Notably, the dissolution rates of Ca, Si, and Mg were 10.7 %, 2.0 %, and 0.6 %, respectively, and the dissolution rate of Fe was almost zero. The surface covering model effectively described the interaction of steel slag in an aqueous solution. Under conditions of temperature at 25 ℃, a CO₂ flow rate of 200 mL/min, stirring speed at 600 rpm, and an aging time of 0 min, a pure calcium carbonate product with a purity level of 99.5 % and a particle size measuring 4.98 μm was successfully obtained. This study would offer a potential application approach for exploiting low-cost industrial solid waste steel slag to prepare calcite-type calcium carbonate, realizing the high-value utilization of steel slag and CO₂ fixation as well as emission reduction.