Preparation and microelectrophoresis characterisation of calcium carbonate particles in the presence of anionic polyelectrolyte

Calcium carbonate (CaCO3) crystal growth experiments in the presence of the polystyrene sulfonate were made at ambient temperature. This polyelectrolyte inhibits the crystal growth in all directions and modifies the crystal structure and morphology. Further, the unstable vaterite CaCO3 crystalline structure was stabilized in the precipitation medium in the presence of the polyelectrolyte. Thus, at moderate polyelectrolyte concentration, spherical CaCO3 particles are obtained having a smaller size compared to the rhombohedral. particles obtained in the absence of the polyelectrolyte. By increasing the polyelectrolyte concentration, the CaCO3 particles mean size and size-polydispersity index decrease. The microelectrophoresis studies indicate that in the presence of the anionic polyelectrolyte, the CaCO3 particles are negatively surface charged. The results obtained indicate a correlation between the CaCO3 particle sizes, their surface charges and the equilibrium pH of the aqueous CaCO3 dispersion. Finally, the data obtained was used to throw light on the mechanism by which polymeric additives affect the morphology, size and crystalline structure of calcium carbonate CaCO3. (C) 2003 Elsevier Science B.V. All rights reserved.