Ultrasound-assisted processing (UAP) for enhancement of leaching and mineralization of electric arc furnace slag (EAFS) for CO2 sequestration: multiscale mechanistic insights

Official URL: https://dx.doi.org/10.1016/j.ces.2026.124840

As a major industrial solid waste stream, electric arc furnace slag (EAFS) represents a promising feedstock for CO2 mineralization, but its reactivity is extremely low under conventional processing conditions due to the presence of refractory phases such as åkermanite and brownmillerite. To address this challenge, this study developed a two-stage strategy: first, the ultrasound-assisted processing (UAP) synergistically coupled with mild acetic acid (HAc) was employed to enhance Ca2+ dissolution from EAFS, followed by UAP-enhanced carbonation of the leachate for efficient CO2 mineralization. Under the optimal operating conditions identified from the single-factor screening experiments (particle size 150–250 μm; ultrasonic power 480 W; temperature 60℃; solid-liquid ratio 50 g/L; acetic acid 0.5 mol·L−1; reaction time 100 min), a maximum Ca2+ leaching efficiency of 82.8% was achieved, representing a 33% increase over mechanical stirring. Notably, the Ca yield by UAP is tens of times higher than those reported in previous studies. UAP substantially modified the pore structure of EAFS, promoting mesopore development, increasing BET specific surface area by up to 45-fold, and enhancing pore-volume contribution below 2 nm, thereby improving pore-network formation, reactive-interface accessibility, and solid–liquid interactions during HAc leaching. During carbonation, UAP accelerated mineralization kinetics, achieving rapid Ca2+ conversion in the initial stage due to intensified mass transfer and enhanced nucleation. The resulting CaCO3 exhibits more uniform and dispersed morphologies than the agglomerated structures obtained under conventional stirring. These findings demonstrate that UAP can effectively couple slag valorization with CO2 mineralization, providing a viable pathway for process intensification in carbon capture and utilization.