Mass Transfer and Kinetics Study of Heterogeneous Semi-Batch Precipitation of Magnesium Carbonate

Precipitation kinetics and mass transfer of magnesium carbonate (MgCO₃) hydrates from a reaction of magnesium hydroxide (Mg(OH)₂) and CO₂ were analyzed. The effect of CO₂ flow rate and mixing intensity on precipitation was investigated under ambient temperature and atmospheric pressure. Raman spectroscopy was used to determine the composition of the solids during semi-batch crystallization. The obtained spectra revealed the dissolution of Mg(OH)₂ and the formation of MgCO₃. The precipitation rate increased with higher gas flow rate. The rotation speed of the stirrer had a significant effect on the dissolution of Mg(OH)₂. In the researched system, the main driver of the precipitation kinetics was the mass transfer of CO₂. Nesquehonite (MgCO₃·3H₂O), as needle-like crystals, was precipitated as the main product. Raman spectroscopy can serve as a potential tool to monitor the carbonation precipitation process.