Enhancing the economic feasibility of vaterite production using calcium hydroxide in pH-swing processes

The challenge of cost-effective and efficient indirect carbonation processes is significant. This study aimed to address the limitations associated with alkaline additives, which are among the primary factors negatively affecting the economic viability of the indirect carbonation process. Specifically, we evaluated the feasibility of replacing NaOH, a commonly used alkaline additive, with Ca(OH)₂, a more cost-effective and safer alternative. Particular emphasis was placed on the potential production of fine-particle vaterite CaCO₃, which, despite its high industrial applicability, poses production challenges owing to its inherent instability. Experiments were conducted to evaluate the impact of using Ca(OH)₂, with and without sucrose, on the production yield, morphology, particle size, and purity of CaCO₃, in comparison to NaOH. Despite the low solubility of Ca(OH)₂, its combination with sucrose effectively stabilized pH levels and significantly enhanced CaCO₃ yields. The addition of sucrose further increased supersaturation, aiding vaterite formation. Using Ca(OH)₂ with sucrose resulted in a vaterite content exceeding 95%, similar to that achieved with NaOH. A cost analysis revealed that producing vaterite-type CaCO₃ using Ca(OH)₂ combined with sucrose required only 53% of the cost associated with NaOH, demonstrating its superior economic feasibility. These findings establish Ca(OH)₂, particularly in combination with sucrose, as a viable alternative to NaOH in the pH swing process, providing cost savings, improved safety, and high-purity vaterite-type CaCO₃ suitable for various industrial applications.