PREPARATION AND CHARACTERIZATION OF CALCIUM PHOSPHATE PARTICLES FROM FORCED HYDROLYSIS OF Ca(OH)2-TRIPHOSPHATE-K2S2O8 MIXED SOLUTION

The effects of potassium peroxodisulfate (K2S2O8) on the formation of calcium phosphate particles produced by aging Ca(OH)2 and sodium triphosphate (sodium tripolyphosphate, Natpp: Na5P3O10) mixed solution at 100~160 C for 18 h were examined. Spherical and monodispersed particles were produced at low K2S2O8 concentration ([K2S2O8]) region ([K2S2O8]≤4 mM) and their size was increased by increase in [K2S2O8]. On the contrary, fine irregular particles were produced at [K2S2O8]≥6 mM. The monodispersed spherical particles produced at [K2S2O8]≤4 mM were amorphous, though small irregular particles produced at [K2S2O8]≥6 mM were poorly crystallized calcium pyrophosphates (-Ca2P2O7). The Ca/P atomic ratios of these samples were 0.79~0.90, fairly closed to the Ca/P atomic ratio of 1.0 for -Ca2P2O7. A high adsorption selectivity of H2O was observed on amorphous monodispersed spherical particles. On the other hand, the -Ca2P2O7 particles with small amounts of hydrated H2O produced at [K2S2O8]≥6 mM exhibited no selective adsorption of H2O. With increase in the aging temperature, small numbers of transparent balloon-like hollow spheres were obtained at 120~140C. However, the fraction of hollow spheres was less than 5%. Aging above 150C, no balloon-like hollow sphere was precipitated but finally calcium hydroxyapatite (Ca10(PO4)6(OH)2, Hap) particles with small rod-like shape could be precipitated. These Hap particles produced at 150 and 160 C did not exhibit selective adsorption of H2O. (Received July 9, 2012; Accepted July 30, 2012)