PRECIPITATION OF CALCIUM AND MAGNESIUM CARBONATES FROM HOMOGENEOUS SUPERSATURATED SOLUTIONS

Homogeneous (unseeded) precipitation of calcium and magnesium carbonat es in the CaO-MgO-CO2-H2O system in supersaturated solutions was inves tigated. The induction period (tau) of spontaneous nucleation and the composition of precipitated solid phases were determined. The influenc e of saturation degree (chemical affinity) and Mg2+/Ca2+ activity rati o in solution on the kinetics of CaCO3 nucleation was studied. The ord er of CaCO3 homogeneous nucleation equals to 4. The surface energy of CaCO3 nucleus was measured to be 63 mJ/m(2). The main factor which con trols the Mg content in the solid phase being formed during unseeded p recipitation of carbonates is the saturation index of MgCO3 in solutio n. (C) 1998 Elsevier Science B.V. All rights reserved.