Crystal growth kinetics of calcite and its comparison with readily soluble salts

Abstract

The crystal growth kinetics of calcite was investigated in batch crystallizers of stirred tank and fluidized-bed type, which were maintained at a constant pH by an autotitrator. Rhombohedron seed crystals were prepared using different techniques, then the growth experiments were conducted in the metastable region, which was explored as part of this research, to suppress nucleation. The crystal growth rates were evaluated from the consumption rates of sodium carbonate and calcium ion for the stirred-tank and fluidized-bed experiments, respectively. Several operating variables were investigated and the crystal growth rate data of constant pH and ionic strength were analyzed by the two-step crystal growth model. The mass-transfer and surface-reaction coefficients were thus obtained and used to explain the growth behaviors of calcite crystals. Then, the crystal growth kinetics of this sparingly soluble salt was compared with that of readily soluble salts. Although the effects of pH and ionic strength on crystal growth were not reported for the readily soluble systems, these effects were significant to calcite growth.