Processing of natural resourced hydroxyapatite from eggshell waste by wet precipitation method

In the present paper, synthesis of hydroxyapatite (HAp) powder from eggshell waste is produced through wet precipitation process at 50-55 degrees C. The thoroughly washed and dried eggshell powder is treated with dilute nitric acid followed by diammonium hydrogen phosphate under controlled reaction conditions such as pH, temperature, stirring time, etc. to obtain white HAp precipitate. The formation of the HAp phase and its thermal stability were identified through thermogravimetric/differential thermal analysis, Fourier transform infrared spectroscopy and X-ray diffraction studies at different calcined temperatures. The dried powder at 90-100 degrees C was wet ball milled for several hours and compacted to cylindrical shapes at a lower pressure of 850 kg cm(-2). The green compacts were sintered at different temperatures for 2 h in dry atmosphere. Average grain sizes of sintered samples are mostly in submicrometre range. The morphologies of the green as well as sintered compacts were observed by field emission scanning electron microscopy.