An experimental study of the solubility and speciation of tungsten in NaCl-bearing aqueous solutions at 250, 300, and 350 °C
An experimental study of the solubility and speciation of tungsten in NaCl-bearing aqueous solutions at 250, 300, and 350 °C
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250、300和350℃含氯化钠水溶液中钨的溶解度和形态的实验研究
DOI：
10.1016/j.gca.2019.09.013
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发表时间：
2019-11
影响因子：
5
通讯作者：
Xian-Wu Bi
中科院分区：
文献类型：
--
作者：
Xin-Song Wang;Alex;er Timofeev;A.E. Williams-Jones;Lin-Bo Shang;Xian-Wu Bi
在250°C、300°C和350°C的蒸汽饱和水压力下，研究了三氧化钨固体在含nacl溶液中的溶解度和钨的形态。实验结果表明，温度和pH控制了三氧化钨的溶解度，而NaCl浓度除了影响溶液的离子强度外，对三氧化钨的溶解度没有影响。发现溶液中存在两种钨，即低pH时的H2WO40和高pH时的HWO4 -，这两种钨分别由WO3 + H2O = H2WO40和WO3 + H2O = HWO4 - + H+反应生成。这些反应的平衡常数的对数分别为- 5.18±0.26,- 4.97±0.25,- 4.69±0.10和- 7.91±0.30,- 7.67±0.29,- 7.52±0.18，分别为250、300和350℃。另外，在250°C、300°C和350°C条件下，H2WO40的第一和第二缔合常数的对数分别为2.72、2.71、2.83和5.59、6.49、8.07。这些值表明H2WO40仅在低pH值（<2.8）下才重要，而在自然界中常见的pH条件下，HWO4−是主要的钨种。本研究获得的数据被用来模拟白钨矿和铁素矿的溶解度。该模型表明，在盐度高、钙和铁含量低、ph值非常低或非常高的溶液中，钨的浓度在高温下最高。从流体中沉淀钨矿物的情况正好相反。
The solubility of tungsten trioxide solid and the speciation of tungsten in NaCl-bearing solutions have been investigated through experiments conducted at 250, 300, and 350 °C under vapour-saturated water pressure. Based on the results of these experiments, the solubility of tungsten trioxide was controlled by temperature and pH, whereas the NaCl concentration did not affect the solubility except through its influence on the ionic strength of the solution. Two tungsten species were found to be present in the solutions, namely H2WO40 at low pH and HWO4− at higher pH. These two species formed via the reactions WO3 + H2O = H2WO40 and WO3 + H2O = HWO4− + H+, respectively. The logarithms of the equilibrium constants for these reactions are −5.18 ± 0.26, −4.97 ± 0.25, −4.69 ± 0.10, and −7.91 ± 0.30, −7.67 ± 0.29, −7.52 ± 0.18 for 250, 300, and 350 °C, respectively. In addition, the logarithms of the first and second association constants of H2WO40 were determined to be 2.72, 2.71, 2.83, and 5.59, 6.49, 8.07 for 250, 300, and 350 °C, respectively. These values indicate that H2WO40 is only important at low pH values (<2.8), and that HWO4− is the dominant tungsten species at pH conditions commonly encountered in nature. The data obtained in this study were used to model the solubility of scheelite and ferberite. This modeling indicates that tungsten concentrations are highest at high temperature in solutions with high salinity, low contents of calcium and iron, and either very low or high pH. The opposite is true for tungsten mineral precipitation from a fluid.
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