Dissolution behavior of steelmaking slag for Ca extraction toward CO2 sequestration

The indirect steel slag (SS)-based carbon capture, utilization, and storage (SS-based CCUS) process is recognized as a promising way for simultaneous mitigation of CO2 emissions and valorization of wastes. Even so, much still needs to be done for sizeable and economic implementations of the SS-based CCUS process, such as enhancement of the selective extraction efficiency of Ca from SS, and a prior prediction of the Ca extraction potential of SS. It is necessary to simultaneously study mineralogy, morphology, solution chemistry, and passivation layer during the dissolution process of SS to improve the overall understanding of the Ca extraction behavior and dissolution mechanism. Therefore, in this work, three kinds of SS were investigated, such as basic oxygen steel slag (BOFS), electric arc furnace slag (EAFS), and ladle furnace slag (LFS). First, the mineral phase composition, and Ca distribution of various SS were identified and compared. In addition, the Ca extraction behavior and passivation mechanism of various SS were investigated by carrying out a series of leaching and corrosion tests in NH4Cl and CH3COOH solution. Results showed that whilst the Ca contents of the three SS samples were similar, the leaching behavior and the Ca extraction yield were significantly different. In addition, various passivation layers were observed, which was formed closely related to the dissolution manner of mineral phases in various solution environments, which was further assessed at atomic level. [Display omitted] •The mineralogical composition partly determined the distinct leaching behaviors of SS.•Various passivation layers were observed after leaching SSs in the different solvents.•The passivation layer formed may be related to the distinct dissolution manner of phases.•Roles of mineralogy and solvent on the dissolution of SS were assessed at the atom level.