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Arsenate hydroxyapatite, Ca10(AsO4)6(OH)2 (AsHA), was synthesized by precipitation at 100°C, and characterized by X-ray studies, IR spectra, electron microscopy, and thermography (TGA, DTA and DTG). The solubility of AsHA was investigated between temperatures of 308 and 323 K, and in the pH range 4.0–8.0. It exhibited a retrograde solubility. The solubility behaviour can be explained on the basis of the chemical potential and free energy in solution. Standard thermodynamic parameters, ΔHθ, ΔSθ and ΔCpθ, are reported. The solubility products of AsHA were found to be 4.0 x 10−91, 2.7 x 10−91, 2.1 x 10−91 and 1.2 x 10−91 at temperatures of 3.08, 313, 318 and 323 K, respectively. |
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