Sonochemical synthesis of hydroxyapatite from H3PO4 solution with Ca(OH)2.

Ultrasound was irradiated to an aqueous suspension containing phosphoric acid (H3PO4) and calcium hydroxide (Ca(OH)2) to investigate the sonochemical effect on preparation of hydroxyapatite (Ca10(PO4)6(OH)2, HAp). HAp monophase could be synthesized from the suspension sonicated for 60 min. The reaction for HAp was promoted more effectively than that of the heating method conducted at the same conditions as those for the sonicating method. The equilibrium pH of the suspensions sonicated over 60 min was maintained neutral, suggesting that the synthesis reaction was almost completed. The ultrasonic irradiation played an important role to progress the heterogeneous reaction and the preparation of very fine HAp powder.