CO₂ mineralization by typical industrial solid wastes for preparing ultrafine CaCO₃: A review

Mineral carbonation is a promising CO₂ sequestration strategy that can utilize industrial wastes to convert CO₂ into high-value CaCO₃. This review summarizes the advancements in CO₂ mineralization using typical industrial wastes to prepare ultrafine CaCO₃. This work surveys the mechanisms of CO₂ mineralization using these wastes and its capacities to synthesize CaCO₃, evaluates the effects of carbonation pathways and operating parameters on the preparation of CaCO₃, analyzes the current industrial application status and economics of this technology. Due to the large amount of impurities in solid wastes, the purity of CaCO₃ prepared by indirect methods is greater than that prepared by direct methods. Crystalline CaCO₃ includes three polymorphs. The polymorph of CaCO₃ synthesized by carbonation process is determined the combined effects of various factors. These parameters essentially impact the nucleation and growth of CaCO₃ by altering the CO₂ supersaturation in the reaction system and the surface energy of CaCO₃ grains. Increasing the initial pH of the solution and the CO₂ flow rate favors the formation of vaterite, but calcite is formed under excessively high pH. Vaterite formation is favored at lower temperatures and residence time. With increased temperature and prolonged residence time, it passes through aragonite metastable phase and eventually transforms into calcite. Moreover, polymorph modifiers can decrease the surface energy of CaCO₃ grains, facilitating the synthesis of vaterite. However, the large-scale application of this technology still faces many problems, including high costs, high energy consumption, low calcium leaching rate, low carbonation efficiency, and low product yield. Therefore, it is necessary to investigate ways to accelerate carbonation, optimize operating parameters, develop cost-effective agents, and understand the kinetics of CaCO₃ nucleation and crystallization to obtain products with specific crystal forms. Furthermore, more studies on life cycle assessment (LCA) should be conducted to fully confirm the feasibility of the developed technologies.