Crystallization kinetics of strontianite from Sr(HCO3)2 solutions

The kinetics of crystallization of strontium carbonate (strontianite) from strontium bicarbonate solutions were examined. CO2 was stripped from a slightly acidic solution of Sr(HCO3)2 by stirring resulting in critical supersaturation and precipitation of strontianite. The reduction of the Sr2+ concentration was recorded as a function of time by measuring the electrolytic conductivity and the pH value.Homogeneous primary nucleation is dominant at high supersaturations, whereas heterogeneous primary nucleation prevails at low supersaturations. The crystal growth rate increases with increasing supersaturation. This effect is less pronounced at higher supersaturations. The growth rate is mostly transport-controlled at high supersaturation. At lower supersaturation the crystal growth is mainly determined by integration of ions into the crystal lattice. These results may be used to explain the deposition of strontianite in natural systems.