Extraction of pure natural hydroxyapatite from the bovine bones bio waste by three different methods

In the present study, natural hydroxyapatite has been extracted from bio-waste; namely the bovine bones. Three different processes have been applied to extract the natural hydroxyapatite: thermal decomposition, subcritical water and alkaline hydrothermal processes. The results obtained by many physiochemical analyses have indicated that all the utilized methods have the ability to eliminate the organic compounds present in the bovine bones and produce pure hydroxyapatite bioceramic with average yield of 65%. Nanorod shape hydroxyapatite with an average length of 300 nm was obtained by the thermal process at temperature of 750 °C and holding time of 6 h. For the alkaline hydrothermal process, pure hydroxyapatite nanoparticles were produced at sodium hydroxide concentration of 25 wt%, temperature of 250 °C and holding time of 5 h. The subcritical water plucks out the collagen present in the bovine bones, so pure hydroxyapatite nanoflakes have been obtained at temperature of 275 °C and holding time 1 h. Selected area electron diffraction pattern images have signified that the thermal process produces good crystallinity hydroxyapatite. However, the subcritical water and alkaline processes produce small nanoparticles hydroxyapatite.