Recovery of magnesium from iron tailings: acid leaching kinetics and CO₂ mineralization

Aiming at the environmental problems caused by the accumulation of a large amount of iron tailings (IOT) and the status quo of low value added, this study proposes a new sulfuric acid leaching-mineralization process to recover magnesium from IOT. Combined with leaching experiments, kinetic equations, and reaction analysis, the leaching mechanism was explored, and the effects of reaction temperature, sulfuric acid concentration, and solid-liquid ratio on magnesium recovery were systematically investigated. And CO2 mineralization was carried out to synthesize anhydrous MgCO3. The results showed that the magnesium recovery was 55.75% under the optimal conditions (leaching temperature of 90℃, sulfuric acid concentration of 300 g/L, and solid-liquid ratio of 1:4). A kinetic equation describing this leaching process was established: 1-3(1-L)2/3+2(1-L) = kt (R²=0.9923), indicating that the product layer diffusion is the rate-limiting step. The apparent activation energy was calculated to be 22.14 kJ/mol. The mineralization stage produces anhydrous MgCO3 with a good degree of crystallinity, and each ton of IOT sequesters 0.38 tons of CO₂. This study establishes a synergistic technological pathway for high-value resource utilization and carbon capture, verifies its economic feasibility, and provides a new idea for sustainable tailings management.