Synthesis of Hydroxyapatite by Interfacial Reaction in a Multiple Emulsion

Interfacial reaction in a multiple emulsion, which is one of methods forproducing inorganic microspheres, was applied to synthesize hydroxyapatite. Themultiple emulsion was a W/O/W emulsion, made of dipotassium hydrogen phosphatesolution as an inner aqueous phase, benzene as an oil phase, and calcium nitrate solutionas an outer aqueous phase. The reaction was carried out in the multiple emulsion for 24 hours at 323 K. The crystalline phase was varied with an initial pH of the inner aqueousphase, and single phase hydroxyapatite was synthesized at an initial pH of 12. Theproducts were composed of porous microspheres of less than 3 μm in size. The microspheres were composed of nanospheres of less than 120 nm in size. Byconsidering the mass balance, it was suggested that each nanosphere was formed in aninner aqueous phase droplet