Synthesis Route and Characterization of Hydroxyapatite Powder Prepared from Waste Egg Shells
Byline: FARZANA HABIB, SHAHZAD ALAM, NASEEM ZAHRA, MUHAMMAD IRFAN AND WAQAS IQBAL
A novel route is reported to prepare Hydroxyapatite powder (HAp) from egg shells. Eggshells were used as calcium precursor containing 94-97 % CaCO3. HAp was synthesized by reacting calcined egg shell powder with reagent grade phosphoric acid at room temperature by precipitation method followed by sintering at 900oC to get crystalline powder. Calcium and phosphorous were determined by Gravimetric and Spectrophotometric method respectively. The Ca/P molar ratio was found to be 1.63. Phase transformation was studied using powder XRD results showing characteristics diffraction peak for HAp and FTIR spectra show the characteristic peaks for phosphate and hydroxyl groups. Thermal analysis (DSC-TGA) was also carried out to investigate the thermal behavior of hydroxyapatite (HAp) powder.
Key Words: Hydroxyapatite, precipitation, egg shells, characterization
The interest in bioceramics has increased dramatically over the past two decades. The bioceramics can be used for many clinical applica- tions. Hydroxyapatite Ca10 (PO4)6 (OH)2 (HAp), is one of the most versatile bioceramic due to its excellent bioactive, biocompatible nature and bone bonding ability with surrounding tissues as it is widely used as in Tissue Engineering and Bone replacement . The interest in HAp arises from its similarity to bone apatite, the major component of the inorganic phase of the bone, which plays a key role in the calcification and resorption processes of bone.
Hydroxyapatite has been utilized as a dense, sintered ceramic (for middle ear implant applications and alveolar ridge reconstruction and augmentation) in porous form, as granules or filler for filling bony defects in dental and orthopedic surgery  and as coating on porous metal for producing an earlier and stronger fixation by enhancing bone in-growth and osseointegration. Many studies have indicated that HAp ceramics show no toxicity, inflammatory response, pyrogenetic response.
Several studies have been reported to synthesize HAp for implants or prosthesis purposes; there is an apparent need for inexpensive clinical grade HAp. Therefore, a simple cost-effective procedure is highly desirable to the researchers for the development of Hydroxyapatite. Various synthetic techniques including mechanochemical methods  slip casting techniques , precipitation method  and dry chemical methods  have been used to prepare hydroxyapatite powder (HAp) using various salts of calcium and phosphorous. Apart from standard calcium salts HAp can also be produced from some natural sources of calcium like sea corals , egg shells [8-9], sea shells  and also from body fluids . Utilization of calcium from natural source will minimize the chances of impurities like silica in the finished product. Moreover the cost of production can be reduced as there is no need to purify.
The egg shells and phosphoric acid were used and heating rate was varied and complicated filtration process was carried out . HAp from egg shells was synthesized via precipitation [8-12] method and low combustion method that was lengthy, complicated and require pH adjustment and control.
Egg shell consists of about 94-97% of CaCO3 and the other 3-6% is organic matter and egg...