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

Copper-nickel tailings (CNTs), consisting of more than 80% magnesium-bearing silicate minerals, offer great potential for mineral sequestration of carbon dioxide (CO2). The dissolution kinetics of CNTs in hydrochloric acid (HCl) solution was investigated from aspects of leaching experiment and kinetic modeling, while the effects of reaction time, HCl concentration, solid-to-liquid ratio, and reaction temperature on the leaching rate of magnesium were comprehensively studied in this work. Results show that the suitable leaching conditions for magnesium in CNTs are 2 M HCl, 50 g/L and 90 ℃, 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 the combination of chemical reaction and product layer diffusion, with a calculated apparent activation energy of 77.51 kJ·mol-1. This study demonstrates the great feasibility of CNTs as a medium for CO2 mineral sequestration.