Carbide Slag Decontamination and Mineralization: A Circular Economy Approach to High-Purity CaCO3 and CO2 Storage

Calcium carbide slag is a highly alkaline solid waste generated during acetylene production, but its long-term accumulation causes land occupation and persistent environmental risks such as soil alkalinization and water pollution. To support circular economy and carbon emission reduction goals, in this study, we develop an integrated physical decontamination–mineralization process combining calcination, magnetic separation, sedimentation, and CO2 mineralization. After calcination, magnetic separation, and 8 h of gravity sedimentation, the removal efficiency of Si reaches about 67% (residual Si content reduces to 0.43%), while those of Fe and Al are 75.4% and 74.2%, respectively. The purified calcium-rich slurry is then used for CO2 mineralization. Under a solid-to-liquid ratio of 10% and a CO2 flow rate of 0.4 L/min, CO2 is fixed as carbonate solids, yielding calcite-type CaCO3 with 97.88% ± 0.35% purity. This process is centered on physical separation and uses no acids, alkalis, or ammonium salts, avoiding secondary pollution while achieving waste valorization and permanent CO2 sequestration. In this study, we provide a scalable, low-impact pathway for alkaline solid waste valorization and carbon emission reduction, contributing to sustainable consumption and production (SDG 12) and climate action (SDG 13).