Direct Aqueous Carbonation of Heat-Activated Lizardite; Effect of Particle Size and Solids Loading on Magnesite Yield

In this study, we investigated the effect of particle size and solids loading on the magnesite yield in the direct aqueous mineral carbonation of heat-activated lizardite. Experimentation was conducted under single-step reaction conditions (130 bar partial pressure of carbon dioxide (CO2) and 150 °C, with 0.64 M sodium bicarbonate (NaHCO3) and 15 wt% solids) as developed by the Albany Research Center (ARC). The objective of the study was to enhance the understanding of the direct aqueous mineral carbonation process in heat-activated lizardite. Furthermore, we aimed to shed light on how variations in particle size could affect the reaction rate, yield, and the development of protective silica layers. Our experimental data suggest that the extraction of magnesium from finer particles (sub 20 µm) is marginally more effective than from the larger size fractions. This difference likely stems from the larger surface area of fine particles (sub 20 µm) in both low and high solids loading experiments. The highest magnesite yield was 50% after 60 min, and this was achieved for both solids loadings (5 and 15 wt%), demonstrating that the solids loading had no impact on the yield. Our findings indicate rapid heat-activated lizardite reaction within 20 min, which achieved 34% and 40% conversion for 5 wt% and 15 wt% solids loading, respectively. This is followed by declining rates with increasing solids loading.