Crystallization of Calcium Carbonate: Modeling Thermodynamic Equilibrium, Pathway, Nucleation, Growth, Agglomeration, and Dissolution Kinetics with the Presence of Mg<sup>2+</sup>, Ba<sup>2+</sup>, and Sr<sup>2+</sup>
Thiago Machado Neubauer, Fabiane Santos Serpa, Elton Franceschi, Cláudio Dariva, Cláudia Sayer, Pedro Henrique Hermes de Araújo, B. B. Castro, Wagner Aldeia, Cristiane da Costa
Abstract
Calcium carbonate (CaCO3) crystallization is a complex operation due to the diverse thermodynamic and kinetic factors involved during the particle formation of vaterite, aragonite, and calcite. This article involves the experimental and computational study of CaCO3 crystallization in the presence of Mg2+, Ba2+, and Sr2+. Crystallization experiments were performed varying the Mg2+, Ba2+, and Sr2+ concentration, monitored by dynamic light scattering, scanning electron microscopy, and X-ray diffractometry techniques. The crystallization model includes the thermodynamic equilibrium, pathway, and kinetic rates associated with a populational balance. It was obtained that the Mg2+ inhibited vaterite nucleation and accelerated its transformation to calcite. The Ba2+ and Sr2+ ions accelerate both calcite growth and vaterite-calcite transformation rates. All external ions produced an increase in crystal size and a decrease in the total crystalline mass, albeit in different proportions. Simulation results with the developed model presented a good agreement with experimental data with an error of 12% per variable. Thus, the proposed model framework may be helpful for the evaluation of the calcium carbonate crystallization process as a practical tool to provide insight into the extensively experimentally studied effects of external ions on CaCO3 crystal populations.