An experimental study of the solubility and speciation of neodymium (III) fluoride in F-bearing aqueous solutions
An experimental study of the solubility and speciation of neodymium (III) fluoride in F-bearing aqueous solutions
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DOI：
10.1016/j.gca.2007.04.004
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发表时间：
2007-06
影响因子：
5
通讯作者：
Artashes A. Migdisov;A. Williams-Jones
中科院分区：
文献类型：
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作者：
Artashes A. Migdisov;A. Williams-Jones
在150、200和250 ° C的温度、饱和水蒸气压和总氟化物浓度（HF ° aq + F −）从2.0 × 10 − 3到0.23 mol/l的范围内研究了氟化钕（III）的溶解度。实验的结果表明，Nd3+和NdF2+是在溶液中的主要物种在调查的温度下，并用于推导NdF2+和NdF3的溶解度积的形成常数。在250、200和150 ° C时，NdF3的溶度积分别为− 24.4 ± 0.2、− 22.8 ± 0.1和− 21.5 ± 0.2;在250、200和150 ° C时，NdF3的生成常数分别为6.8 ± 0.1、6.2 ± 0.1和5.5 ± 0.2。这项研究的结果表明，已发表的理论预测显着高估了NdF2+的稳定性和NdF3的溶解度。对自然系统的潜在影响的结果进行了评估的一个假设的流体的组成类似的负责在新墨西哥州的Capitan岩体的稀土矿化。与使用哈斯[哈斯J.R.，休克E。L.，和Sassani D. C.（1995年）热液系统中的稀土元素：高压和高温下稀土元素水溶液络合物的标准偏摩尔热力学性质估计。地球化学。宇宙化学。Acta 59，4329 - 4350.]，这表明NdF2+是溶液中的主要物质，使用本文中提供的数据和先前公布的氯化物和硫酸盐物质的实验数据进行计算[Migdisov A.一、和Williams-Jones A. e.（2002）氯化物溶液中钕（III）络合作用的分光光度研究。地球化学。宇宙化学。Acta66，4311 - 4323; Migdisov A.一、Reukov V. V.，和Williams-Jones A. e.（2006）高温下硫酸盐溶液中钕（III）络合的分光光度研究。地球化学。宇宙化学。Acta 70，983 - 992.]表明氯化钕种类占优势，氟化钕种类相对不重要。这表明，可以接受的模式，稀土矿床调用氟化物络合热液稀土元素运输的方法可能需要重新评估。
The solubility of neodymium (III) fluoride was investigated at temperatures of 150, 200 and 250°C, saturated water vapor pressure, and a total fluoride concentration (HF°aq+F−) ranging from 2.0×10−3to 0.23mol/l. The results of the experiments show that Nd3+and NdF2+are the dominant species in solution at the temperatures investigated and were used to derive formation constants for NdF2+and a solubility product for NdF3. The solubility product of NdF3[Formula: see text] is −24.4±0.2, −22.8±0.1, and −21.5±0.2 at 250, 200 and 150°C, respectively, and the formation constant of [Formula: see text] is 6.8±0.1, 6.2±0.1, and 5.5±0.2 at 250, 200 and 150°C, respectively. The results of this study show that published theoretical predictions significantly overestimate the stability of NdF2+and the solubility of NdF3. The potential impact of the results on natural systems was evaluated for a hypothetical fluid with a composition similar to that responsible for REE mineralization in the Capitan pluton, New Mexico. In contrast to results obtained using the theoretical predictions of Haas [Haas J. R., Shock E. L., and Sassani D. C. (1995) Rare earth elements in hydrothermal systems: estimates of standard partial molal thermodynamic properties of aqueous complexes of the rare earth elements at high pressures and temperatures. Geochim. Cosmochim. Acta59, 4329–4350.], which indicate that NdF2+is the dominant species in solution, calculations employing the data presented in this paper and previously published experimental data for chloride and sulfate species [Migdisov A. A., and Williams-Jones A. E. (2002) A spectrophotometric study of neodymium(III) complexation in chloride solutions. Geochim. Cosmochim. Acta66, 4311–4323; Migdisov A. A., Reukov V. V., and Williams-Jones A. E. (2006) A spectrophotometric study of neodymium(III) complexation in sulfate solutions at elevated temperatures. Geochim. Cosmochim. Acta70, 983–992.] show that neodymium chloride species predominate and that neodymium fluoride species are relatively unimportant. This suggests that accepted models for REE deposits that invoke fluoride complexation as the method of hydrothermal REE transport may need to be re-evaluated.