Preparation of high specific surface area hydroxyapatite for environmental applications

We report the preparation of hydroxyapatite in powdered form by aqueous reaction of calcium nitrate or hydroxide with phosphate ion at room temperature. With a slow maturation step of 48 h avoiding heat, the resulting products show large specific surface areas above 150 m²/g. The specific surface areas also depend on stirring speed with a maximum observed with gentle mixing. Ageing causes a decrease in specific surface area which tends to stabilize near 100 m²/g following a 1 year period. The hydroxyapatite may be spray dried and conserve interesting physical properties for environmental applications.