The role of Mg~(2+) and Mg~(2+)/amino acid in controlling polymorph and morphology of calcium carbonate crystal

摘要

Mg~(2+) and the mixture of Mg~(2+)/DL-aspartic or L-tyrosine were used as effective crystal nucleation and growth modifiers to control the crystallization of CaCO_3. The polymorph and morphology of crystals were characterized using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD). The results demonstrated that various morphologies such as rod-shaped particles, spinose sphere particles, cauliflower-like crystals, and the spindly particles produced in above aqueous solutions. When the molar ratio of Mg~(2+) to Ca~(2+) was less than 8, the products were all the mixtures of calcite and aragonite. The ability of Mg~(2+) to induce the formation of aragonite was enhanced as the molar ratio of Mg~(2+) to Ca~(2+) increased. When the molar ratio reached 8, the crystals obtained were all aragonite. In the mixed systems of Mg~(2+)/amino acids, the presence of ammo acids was helpful for the formation of aragonite. The possible formation mechanisms of CaCO_3 in different systems were discussed in the paper.