Insights into the dissolution kinetics of copper–nickel tailings for CO₂ mineral sequestration

Copper–nickel tailings (CNTs), consisting of more than 80wt% magnesium-bearing silicate minerals, show great potential for CO₂ mineral sequestration. The dissolution kinetics of CNTs in HCl solution was investigated through a leaching experiment and kinetic modeling, and the effects of reaction time, HCl concentration, solid-to-liquid ratio, and reaction temperature on the leaching rate of magnesium were comprehensively studied. Results show that the suitable leaching conditions for magnesium in CNTs are 2 M HCl, a solid-to-liquid ratio of 50 g·L⁻¹, and 90°C, at which the maximum leaching rate of magnesium is as high as 83.88%. A modified shrinking core model can well describe the leaching kinetics of magnesium. The dissolution of magnesium was dominated by a combination of chemical reaction and product layer diffusion, with a calculated apparent activation energy of 77.51 kJ·mol⁻¹. This study demonstrates the feasibility of using CNTs as a media for CO₂ mineral sequestration.