Investigation of Crystallization Mechanism of Solid Calcium Carbonate and its Thermodynamic Analysis for CO2 Storage and Utilization

Abstract

Carbon mineralization technology, which involves spontaneous reactions between carbon dioxide (CO2) and alkali earth metals such as calcium (Ca2+) and magnesium (Mg2+), is considered a promising method of both storage, which forms thermodynamically stable solid carbonate, and utilization, which has various potential applications in industrial areas. In particular, feedstocks such as natural minerals and industrial by-products are considered alkaline sources for carbon mineralization, but they contain low concentrations of Mg2+ depending on the type of feedstocks. Calcium carbonate (CaCO3) has three anhydrous crystals as calcite, aragonite, and vaterite due to different crystal structures. However, since Mg2+ has a higher enthalpy of dehydration than Ca2+, it is difficult to make high value-added CaCO3 by constraining the polymorph control and transformation of CaCO3. Here, the effect of Mg2+ in CaCO3 investigated the specific ratio of Ca2+ to Mg2+ such as 3:1, 4:1, and 5:1 and aging time. As increasing the Mg2+ ratio, it influenced in ways that lead to the formation of calcite, rather than aragonite and vaterite due to high enthalpy of dehydration. As the aging time increased, monohydrocalcite and hydromagnesite have appeared due to Mg2+ interrupted the dehydration process.