STUDIES OF THE GROWTH AND DISSOLUTION KINETICS OF THE CACO3 POLYMORPHS CALCITE AND ARAGONITE .2. THE INFLUENCE OF DIVALENT-CATION ADDITIVESON THE GROWTH AND DISSOLUTION RATES

The influence of the divalent cations Fe2+, Cu2+, Zn2+, Mg2+, Sr2+, an d Ba2+ on the growth and dissolution rates of calcite and aragonite ha s been studied. In most cases the results can be interpreted by a reve rsible adsorption of the impurity ions at kinks sites according to the Langmuir-Volmer model. Ions of the transition metals show a stronger inhibition than earth alkaline ions. Mg2+ and Fe2+ have no influence o n growth and dissolution of aragonite. Further, Cu2+, and Zn2+ have a stronger effect on calcite, while Sr2+, and Ba2+ are more effective on aragonite. Results are used to show consequences for the polymorphic precipitation of CaCO3.