Influence of initial CaCl2 concentration on the phase and morphology of CaCO3 prepared by carbonation

Calcium carbonate particles were prepared by bubbling the mixed gas CO2/N-2 into CaCl2 solution. The effect of initial CaCl2 concentration on the morphology and phase of CaCO3 was discussed with the help of XRD and SEM measurements. The samples prepared at low CaCl2 concentration composed mainly of spherical vaterite. With the increase of CaCl2 concentration, more and more rhombic particles were formed and mixed with spherical particles. When the initial CaCl2 concentration increased to 0.3 mol/L, only rhombic calcite was formed in the final product. The change of CaCO3 morphology with the increase of CaCl2 concentration was attributed to the excess of Ca2+, which speeded the transformation of vaterite to calcite, thus more rhombic calcite was formed at higher CaCl2 concentration.