Development of hydroxyapatite derived from Indian coral

A simple method of converting the calcium carbonate skeleton of the corals available in the Indian coast into hydroxyapatite granules has been developed. By heating the coral to 900 °C, the organic materials were eliminated. Powder X-ray diffraction analysis (XRD), Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA) were employed to characterize the coral and to optimize the processing parameters as well as to confirm the hydroxyapatite formation. The coral used exhibits the presence of both aragonite and calcite phases (dimorphism). At a temperature of 900 °C the coral was found to decompose all the carbonate phases. The pre-heated coral is converted into hydroxyapatite by a chemical exchange reaction with di-ammonium phosphate under hydrothermal conditions. The hydroxyapatite obtained was in powder form and does not contain any impurities. The in vitro solubility test of the apatite granules performed in Gomoris, Michalelis, Sorensens, Ringerʹs and phosphate buffer of pH 7.2 and de-ionized water indicated the stability of the coralline hydroxyapatite.