Aug 28, 2009 - YINIAN ZHU, YUDAO CHEN, FEI LONG, JUNKANG LAN, NA HE, and MEIFANG QIAN. A series of arsenate-substituted fluorapatite (FA) was ...
Synthesis and Characterization of Arsenate/Phosphate Fluorapatite Solid Solutions YINIAN ZHU, YUDAO CHEN, FEI LONG, JUNKANG LAN, NA HE, and MEIFANG QIAN A series of arsenate-substituted fluorapatite (FA) was directly prepared through the aqueous precipitation method. Characterization studies from elemental analysis, X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectra, and scanning electron microscopy (SEM) have confirmed the formation of the arsenate/phosphate fluorapatite solid solutions (AsPFAs), i.e., Ca5(PxAs1–xO4)3F, which had a single phase of apatite structure. The analysis of the measurements indicated that the unit cell a and c parameters did not vary smoothly with the degree of substitution, as expected by Vegard’s law. The morphology was dependent of the arsenate/phosphate ratio. The solids with high As/(P + As) molar ratio of 0.29 to 1.0 were typically needlelike crystals, which developed along the c-axis; all apatites with the As/(P + As) molar ratio of 5 lm, which does not show the hexagonal or rod shape of the crystal characteristic of apatite.
IV.
CONCLUSIONS
The AsPFAs, i.e., Ca5(PxAs1–xO4)3F, are formed via a simple precipitation process; i.e., phosphate is added to the arsenic bearing solution in prescribed amounts to facilitate the formation of arsenate-phosphate apatite compounds. The prepared solid solutions show an apatite structure for the entire arsenate-phosphate series. With increasing arsenate content, the particles changed from smaller needlelike to large tabular crystals and the unit cell dimensions a and c increased, but not in fair agreement with Vegard’s law. The fundamental vibrational modes of PO43 are visible around 959 to 965 cm 1 (m2), 1041 to 1046, 1095 cm 1 (m3), 566 to 578, 602 to 606 cm 1 (m4), and 491 to 496 cm 1 (m1) for all the powders. The peaks of
METALLURGICAL AND MATERIALS TRANSACTIONS A
AsO43 appeared around 837 to 870 cm 1 (m3) and 422 to 430, 455 to 474 cm 1 (m4). The area of the phosphate peak decreased and that of the arsenate peak increased gradually as the As content of Ca5(PxAs1–xO4)3F solid solutions increased.
ACKNOWLEDGMENTS The manuscript has greatly benefited from insightful comments by two anonymous reviewers. The authors thank the Guangxi Key Laboratory of Environmental Engineering, Protection and Assessment for the research assistance (Grant No. GuiKeNeng0701K010) and the financial supports from the National Natural Science Foundation of China (Grant Nos. 40773059 and 40263001) and the Provincial Natural Science Foundation of Guangxi (Grant Nos. GuiKeZi0728222 and GuiKeGong0816003-1-1). Financial assistance for this research was also provided through the Program to Sponsor Teams for Innovation in the Construction of Talent Highlands in Guangxi Institutions of Higher Learning and the Special Research Program for Excellent Talents in Guangxi (Grant Nos. GuiKeRen 2007-71 and 2004217).
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