Maximising CO2 sequestration via simultaneous milling and carbonation of steel slag: A Taguchi-driven optimisation approach

Steel slags, byproducts of the steelmaking industry, pose a significant environmental burden due to their large volume and limited reuse opportunities. CO 2 sequestration represents a promising utilisation route, enabled by their diverse mineral composition. However, conventional carbonation methods are often slow and require rigorous conditions. This study presents a rapid and intensified approach for carbon capture via simultaneous milling and carbonation of basic oxygen furnace (BOF) and argon oxygen decarburization (AOD) slags in the planetary ball mill. To optimise this complex process, a Taguchi design of experiments was employed, enabling the identification of key parameters for maximising CO 2 uptake. Optimal conditions, determined through signal-to-noise analysis and heatmaps, were found to be material-specific. Moreover, CO 2 uptake rates of 0.32 g CO 2 /g (AOD) and 0.25 g CO 2 /g (BOF) were achieved in just 6–8 minutes, meeting or exceeding values reported in the literature to date, 0.386 g CO 2 /g (AOD) and 0.188 g CO 2 /g (BOF) (Zhao Q. et al., 2025) (Santos M.R. et al., 2013). These results were obtained at impact energies of 110 J/g (AOD) and 152 J/g (BOF), demonstrating the system’s transferability across different mills, without the leaching of harmful metals. This work highlights a time-efficient and environmentally safe method for transforming steel slags into valuable carbon sinks. • High carbonation rates for steel slags after 6-8 minutes of milling and carbonation • CO 2 uptake rates of 0.32 g CO 2 /g (AOD) and 0.25 g CO 2 /g (BOF) • Low impact energies employed, enhancing scalability and industrial applicability • Leaching of harmful metals is not observed, ensuring environmental compliance