Preparation and Ion Exchange Property of Needlelike Hydroxyapatite controlled Ca/P Ratios

本研究采用湿法制备针状hap。将化学计量量Ca/P摩尔比为1.67的CaCl_2 (A)和K_2HPO_4 (B)的水溶液在搅拌的同时缓慢滴入加热至-100℃的水中。沉淀产物经吸力过滤后，在-100 C条件下干燥24 ~ -48 h，干燥后在1200 C条件下烧结1 h，较长时间得到的HAp颗粒滴速较慢，在稀a、稀B溶液范围内（<0.3mol/dm^3）。通过电感耦合等离子体发射光谱（ICP）测定，针状颗粒仅是非化学计量的或缺钙的hap， Ca/P比为-1.54。目前还没有关于HAp的化学计量学、针状粒子的报道。为了便于在强酸性地区处理，采用博士叶片法研究了用于离子交换的烧结针状HAp过滤器的制备，结果表明：(1)带铸造的最佳水浆为：HAp质量为20 %，粘结剂质量为15 %，增塑剂质量为15 %，分散剂质量为1 %，水含有一定量的Ca (OH) _2或Ca (NO_3) _2。(2)各水泥浆均出现剪切减薄现象。(3)冷冻干燥后，在1200℃的温度下烧结1h，得到无裂纹的胶带。(4)将Pb^<2+>溶液通过烧结的针状HAp过滤器，在pH2下考察了Pb^<2+>离子的去除率，第一次运行时为-59%，重复5次运行后达到-100%。

Needlelike HAps were synhthesized by a wet method for the present study. Aqueous solutions of CaCl_2 (A) and K_2HPO_4 (B) with a stoichiometric Ca/P molar ratio (1.67) were slowly and simultaneously dropped, with stirring, into water heated to -100ﾟC.The precipitated products were filtered with suction and dried at -100ﾟC for 24 to -48 h. After drying, the obtained particles were sintered at 1200ﾟC for 1 h.Longer, needlelike particles of HAp were obtained at a slower dropping rate and in the range of the dilute A and B solutions (<0.3mol/dm^3). The needlelike particles were only nonstoichiometric or Ca-deficient HAps, with a Ca/P ratio of -1.54, as determined by inductively coupled plasma emission spectrometry (ICP). No stoichiometric, needlelike particles of HAp have yet reported.A preparation of sintered, needle-like HAp filters for an ion-exchange was examined by a doctor blade method in order to facilitate handling in the strongly acidic region, with the following results :(1) The best aqueous slurry for tape casting was the combination of HAp 20 mass%, binder 15 mass%, plasticizer 15 mass%, dispersant 1 mass% and water including specific amounts of Ca (OH) _2 or Ca (NO_3) _2.(2) A shear thinning behavior appeared at all aqueous slurries.(3) The tapes without cracks were obtained by sintering at 1200ﾟC for 1h after freeze-dried.(4) The removal of Pb^<2+> ions was investigated by passing through the Pb^<2+> solutions into the sintered, needle-like HAp filters at pH2, and was -59% at the first run and reached to -100% after repeated 5 runs with the same procedure as before.