Crystal growth of calcium carbonate with various morphologies in different amino acid systems

In our experiments, four kinds of amino acids, such as l -Cystine ( l -Cys), l -Tyrosine ( l -Tyr), dl -Aspartic Acid ( dl -Asp), l -Lysine ( l -Lys) and the mixed systems of l -Tyr (or l -Lys)/Mg 2+ , were used as effective modifiers to mediate the crystallization of CaCO 3 . The obtained crystals were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD). As the results have shown, calcite was formed in l -Cys system while both calcite and spherical vaterite with various morphologies were produced in the presence of l -Tyr, dl -Asp, and l -Lys whose ability to induce the formation of vaterite was enhanced in turn. It indicated that amino acids played an important role in the process of crystal growth of CaCO 3 , the addition of Mg 2+ was helpful for the formation of aragonite. The possible formation mechanism of CaCO 3 produced in different amino acid aqueous solutions was discussed in the end.