Effect of Solid Ratio and Particle Size on Dissolution of Heat-Activated Lizardite at Elevated Pressures and Moderate Temperatures

This study investigates the effect of the particle size and solid-to-liquid ratio on the dissolution rate of magnesium (Mg) and silicon (Si) in heat-activated lizardite. The investigation was conducted under specific conditions: without the presence of sodium bicarbonate (NaHCO3), at a moderate temperature (40 °C), and under elevated CO2 pressure (100 bar). The aim was to isolate the dissolution reactions and enhance comprehension of the factors constraining the overall yields in the Albany Research Center (ARC) mineral carbonation process. Our study disclosed two distinct dissolution regimes: an initial stage with a rapid initial rate of Mg extraction, resulting in the fraction of Mg extracted ranging from 30 to 65% during the first 20 min of the experiment, following which the dissolution rate decreases dramatically. The initial rapid dissolution stage is primarily driven by the low pH of the supernatant solution, resulting from CO2 dissolution, leading to a higher concentration of protons that extract Mg2+ cations. However, as the heat-activated lizardite dissolution progresses, the pH increases due to the high level of leached Mg2+, and a diffusion barrier forms due to the precipitation of amorphous silica. This phenomenon ultimately slows down the mineral’s dissolution rate during the latter stages of particle dissolution.