Characterization of intermediate stages in the precipitation of hydroxyapatite ...

• Author(s): Castro, Filipa ; Ferreira, António ; Rocha, F. A. ; Vicente, A. A. ; Teixeira, J. A.
• Date: 2012
• Persistent ID: http://hdl.handle.net/1822/22209
• Origin: RepositóriUM - Universidade do Minho
• Subject(s): Precipitation; Batch; Calcium phosphate; Supersaturation; Morphology; Aggregation
• Document Type: Article
• Language: English

Description

Precipitation of hydroxyapatite Ca 5(PO 4) 3OH (HAp) was carried out by mixing a saturated calcium hydroxide aqueous solution with an orthophosphoric acid aqueous solution at 37°C. In order to promote optimal conditions for the production of HAp with high yields, mixing of the reaction medium was assured by a novel metal stirrer. Different experimental conditions were studied varying the mixing Ca/P molar ratio from 1 to 1.67. After process optimization, a suspension of HAp particles with pH close to 7 was obtained for a mixing molar ratio Ca/P=1.33. The precipitation process was then characterized as a function of pH and calcium concentration, revealing the existence of three different stages. The precipitate formed in each stage was characterized by scanning electron microscopy and X-ray diffraction.