Role of Hydrodynamics, Li+ Addition and Transformation Kinetics on the Formation of Plate-Like {001} Calcite Crystals

Abstract

Plate-like calcite crystals with expressed unstable {001} planes are interesting research model for investigations of interfacial interactions of different additive molecules, but also the crystal growth mechanisms. The aim of this study is to reproducibly prepare a significant amount of well-defined plate-like calcite crystals and to investigate the critical experimental parameters. Thus, in precipitation system c(NaHCO3) = c(CaCl2) = 0.1 mol dm−3, the influence of hydrodynamic parameters (mode of mixing of the reaction components) and a presence of lithium ions Li+ within a wide range of concentrations, 0.0 mol dm−3 < c(Li+) < 1.0 mol dm−3, have been studied. In addition, the kinetics of the solution mediated transformation of the initially formed metastable polymorph, vaterite, were followed in order to reproducibly describe the formation of stable calcite with expressed unstable morphology. The results indicate that the plate-like calcite is formed predominantly when the ultrasound irradiation is applied at c(Li+) ≥ 0.3 mol dm−3. On the other hand, when the magnetic and mechanical stirring are applied at higher Li+ concentrations, truncated rhombohedral crystals in a mixture with plate-like crystals are obtained. It was also found that the Li+ addition significantly prolonged the transformation, mainly by inhibiting the crystal growth of calcite.