Synthesis of Hydroxyapatite by Using Calcium Carbonate and Phosphoric Acid in Various Water-Ethanol Solvent Systems

Abstract

The purpose of the present study is to synthesize hydroxyapatite by using CaCO(3) and H(3)PO(4) in various water-ethanol solvent systems. It was observed from experiments that formation of ammonium phosphate compounds hindered the formation of calcium phosphates in ethanol medium. Although the reactivity was better in aqueous medium, the carbonate contents of the products obtained were above 8.5%. Best results with a carbonate content as low as 3.82% was obtained in 50% ethanol containing mixed-aqueous medium at 80A degrees C and the FTIR analysis showed that the product was a carbonated apatite with a calculated composition of 14CaO center dot 4.2P(2)O(5)center dot CO(3)center dot 7.2H(2)O. The amorphous and porous phosphate compound obtained with a BET surface area of 106.6 m(2) g(-1) seems to be useful as adsorbent in wastewater treatment. Upon sintering of the amorphous product at 750A degrees C, crystalline hydroxyapatite with a BET surface area of 25.9 m(2) g(-1) is obtained that may be used in biomedical applications.