Synthesis of hydroxyapatite from waste egg-shell by Precipitation method

Abstract

In this study, precipitation method using orthophosphoric acid and incubated egg-shell as raw materials was used to prepare Hydroxyapatite (HAp) powder. The raw egg-shells powder consisting primarily: Monohydrocalcite : CaCO₃.H₂O (29-0306), Ikaite : CaCO₃. 6H₂O (37 - 0416) and Hydromagnesite  Mg₅(CO₃)₄(OH)₂.4H₂O (25 - 0513) were calcined to produce lime (CaO) and then reacted with distilled water to  form calcium-hydroxide ((Ca(OH)₂) which was used as precursors. The effect of calcinations at different temperatures (ranging from 300 – 600^o C) and particle sizes (ranging from 0.09 - 0.6 mm) were studied on the waste egg-shells. The as-heated powders and processed powders were characterized by photomicrographic analysis, X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). The influence of temperature on calcined egg-shell powder was investigated. Increasing temperature of the processed powder decreased the Ca/P ratio of the HAp powder and thus changed the surface morphology of the samples. At optimal conditions, calculated stoichiometric ratio of Ca/P of the synthesized HAp powder (74 - 0565) of 1.65 closed to the theoretical value of Ca/P ratio (1.67) and amenable to biomedical applications, was obtained.

 Keywords: Hydroxyapatite; Egg-shell; Precipitation Method, Ca/P Stoichiometric Ratio.