Regulation of Microstructure of Calcium Carbonate Crystals by Egg White Protein

Crystal growth of calcium carbonate in biological simulation was investigated via egg white protein with different volume fractions, during which calcium carbonate was synthesized by calcium chloride and sodium carbonate. The morphology, thermal properties and microstructure of the calcium carbonate micro-to-nanoscale crystals were characterized by scanning electron microscopy(SEM), transmission electron microscopy(TEM), Fourier transform infrared spectroscopy(FTIR), thermogravimetric analysis(TG) and X-ray diffraction(XRD) analysis. The results show that the volume fraction of egg white protein has great influence on the shape, size and morphology of calcium carbonate crystals. The calcium carbonate crystals were the mixtures of calcite-vaterite-like crystals including spherical and rough surface, which are different from that formed in pure water. With the increase of egg white protein concentration, the diameter of calcium carbonate crystals changed, the amount of formed spherical calcium carbonate particles decreased and that of vaterite increased. These results indicate that the coordination and electrostatic interaction between egg white protein and Ca²⁺ significantly affect the calcium carbonate crystalization.