result still remains unexplained. To get a further insight into Barium-strontium hydroxyapatite solid solutions with different the mechanism of CO 2 adsorption various kinds of HAPs molar ratio Ba/(Ba / Sr) were synthesized by a wet method and with a wider range of cation/P ratio are required.
characterized by various means. The solid solution particles could
CaHAP can be synthesized in aqueous system at pH 8.5be prepared at molar ratios ranging from 0 to 1; however, Ba 2/ 9.5 (7, 8). Ca-deficient CaHAP forms at lower pH compared ions were more difficult to be incorporated into hydroxyapatite to the stoichiometric one (7, 9). However, Ca-rich CaHAP crystals compared to Sr 2/ ions. With increasing Ba 2/ content, the is hard to prepare, because Ca(OH) 2 is contained in the particles grew and finally turned into pure rod-shaped barium material formed at high pH (9). It has been reported that hydroxyapatite particles with a size of ca. 0.2 1 2 mm. The re-SrHAP and barium hydroxyapatite (BaHAP) containing no sulting particles were agglomerates consisted of primary fine particles except for strontium hydroxyapatite. The molar ratios (Ba / hydroxides as impurities are synthesized at higher pH than Sr)/P of all the particles were larger than the stoichiometric ratio CaHAP; SrHAP forms around pH 11 and BaHAP forms of 1.67, suggesting that CO 3 20 ions, OH 0 ions, and/or H 2 O moleabove pH 12 (10). Hence, in this study we tried to synthesize cules substitute for PO 4 30 ions in the crystal lattices. The amount barium-strontium hydroxyapatite (BaSrHAP) solid soluof CO 2 adsorbed irreversibly on the particles increased with intions to prepare the HAPs with cation/P ratios larger than creasing (Ba / Sr)/P except for strontium hydroxyapatite and , calcium-barium hydroxyapatite fitted a curve with a minimum at a cation/P ratio of ca. 1.56 as solid solution (16, 17) and barium-strontium fluorapatite well as other HAPs. ᭧ 1997 Academic Press solid solution (18) have been synthesized, but there is no