Magnesium leaching from dunite slurry and CO2 mineralization to form hydrated MgCO3 with different morphologies

Abstract

This study investigates the leaching and purification processes for dunite slurry, a common mining waste material, and the carbonation processes for the mineralization of CO₂ with

. Results indicate that HCl is a promising leaching agent, and pH and temperature are major factors in controlling the efficiency of the leaching process, with leaching efficiencies of 82% achieved after 4 h using 2 M HCl solution at 75 °C. The removal of other ions like

,

, and

through the purification of the leachate using ammonium hydroxide was also proven to be effective, completely removing iron and aluminum from the leachate from starting concentrations of 3.10 and 0.40 g/L, respectively. The carbonation of magnesium at room temperature was investigated with both purified leachate and pure MgCl₂ aqueous solution. Nesquehonite crystals began to form after 1.5 h with a conversion of

to nesquehonite of approximately 5%. The produced crystals possess a needle-like shape, which could be modified using the biopolymers pectin and xanthan. Pectin had a limited influence on the length of the crystals, reducing the needle length with increasing pectin concentration. Xanthan, on the other hand, shortened and widened the needle-like structure into a column shape as more xanthan was added. This study demonstrates the potential for this process to utilize mining wastes and sequester CO₂, producing useful mineral products in the process.