A novel hydrothermal synthesis of nanohydroxyapatite from eggshell-calcium-oxide precursors

Hydroxyapatite (HA) is a material that has been widely applied to replace the damaged bone as a bone implant. Different types of HA have been successfully synthesized by a hydrothermal method based on calcium oxide (CaO) which was originated from chicken eggshells and diammonium hydrogen phosphate (DHP)/(NH₄)₂HPO₄ as their precursors. We present a novel approach to the hydrothermal synthesis of HA form eggshells as a new precursor via a one-step synthesis method. The influence of temperature was also observed to study the effect on the crystallinity, purity, and morphology of obtained HAs. The synthesis was carried out at two different temperatures, 200 °C (HA-200) and 230 °C (HA-230) for 48 h respectively. The structures, purities, and morphologies of hydroxyapatite were analyzed by X-ray Diffraction (XRD), Fourier Transform Infra-Red (FTIR), and Scanning Electron Microscopy- Energy Dispersive Spectroscopy (SEM-EDS), and Transmission electron microscopy (TEM). The XRD patterns show the HA main phase indicated the purity of 96.5% for HA-200 and 99.5% for HA-230. The TEM micrograph suggested a hexagonal-like of HA with an average particle size of 92.61 nm. Hexagonal-like of HAs are suitable for bone implants and further application.