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Chemical Characteristics of Hydroxyapatite from Oyster Shell by Thermo-Chemical Process

Md.Hasan Mahmud,Kazi Abdus Salam, M.A.Gafur, Ashequl Alam Rana, Md. Rakibul Qadir, Shah Md. Masum, Mithun Sarker, and Mohammad Mainul Karim

Oyster shell is basically made of calcium carbonate. An attempt is made to convert calcium carbonate of oyster shell to hydroxyapatite (HA), a substitute material for bone and teeth in orthopedic and dentistry field due to their chemical and biological similarity to human hard tissue. In the present work, hydroxyapatite (HA) was successfully synthesized by wet precipitation method using Ca (NO3)2, and (NH4)2HPO4, and NH4OH as starting materials. The oyster shell was found to decompose within 10000C to all the carbonate phases. The calcined oyster shells were then treated with acids followed by different chemicals in ammoniacal media maintaining proper stoichiometry to produce fine hydroxyapatite (HA) as filter cake with a Ca/P molar ratio of 1.67. The dried HA powder was extremely pure. Different characterization techniques were adopted both for calcined oyster shell and HA by scanning electron microscopy (SEM), X-ray diffractometer (XRD), fourier transform infrared spectroscopy (FTIR) and thermo gravimetric analyzer (TGA). The absorption bands corresponding to phosphate and hydroxyl functional group which are characteristics of hydroxyapatite were confirmed by FTIR. Besides its effectiveness in bone substitution, the prepared HA holds great potential in the field of dental application.