Spontaneous precipitation of calcium carbonate in the presence of chondroitin sulfate

The kinetics of spontaneous precipitation of vaterite (CaCO3) from an aqueo us solution in the presence of chondroitin sulfates (CSA, CSB, CSC) was inv estigated by the constant composition method. The presence of chondroitin s ulfate in the supersaturated solution resulted in a reduction of the crysta l growth rate by 23-65%. Induction times preceding vaterite precipitation w ere inversely proportional to the solution's supersaturation and a surface energy of 52 mJ m(-2) was calculated according to the classical nucleation theory. Chondroitin sulfate influences the particle size distribution of th e vaterite crystals formed and stabilizing this mineral phase, preventing t he transformation to calcite. The apparent order found from kinetics data w as n > 2, thus suggesting a surface nucleation mechanism. (C) 2000 Elsevier Science B.V. All rights reserved.