Experimental Study on Indirect CO₂ Mineralization of Industrial Solid Wastes: Electric Arc Furnace (EAF) Slag and Nickel Mine Tailings

CO₂ mineralization utilizing alkaline industrial wastes as feedstocks is a promising approach for long-term carbon sequestration. This study investigates the indirect carbonation of electric arc furnace (EAF) steel slag and nickel mine tailing using two leaching agents, inorganic hydrochloric acid (HCl) and waste-derived acid mine drainage (AMD). The efficiency of metal leaching and CO₂ sequestration capacity were evaluated under varying process conditions, including temperature and carbonation reaction acceleration by ultrasound cavitation. Results demonstrated that AMD can be a viable alternative to HCl, potentially reducing chemical costs while aiding in mine waste remediation. However, the effectiveness of both leaching and carbonation processes is strongly influenced by the mineralogical composition of the feedstocks. For serpentine-based feedstock rich in magnesium (nickel tailing), using AMD as a leaching agent resulted in a sequestration capacity of up to 65.12 g-CO₂ /kg-Ni-Tailing versus 18.28 g-CO₂ /kg-Ni-Tailing with HCl at room temperature. Conversely, for EAF steel slag rich in calcium, the trend was opposite, with HCl achieving a sequestration capacity of up to 154.76 g-CO₂/kg-EAF versus 63.58 g-CO₂/kg-EAF with AMD. The study further explores the impact of operating temperature and ultrasound process intensification on reaction kinetics, concluding that CO₂ sequestration efficiency was improved either by increasing the temperature or employing ultrasound processing. These findings contribute to the development of sustainable mineralization strategies for industrial waste valorization and greenhouse gas mitigation.