Experiments on the stability of aqueous metal chloro complexes in supercritical hydrothermal solutions

水性金属氯配合物在超临界水热溶液中的稳定性实验

• 批准号: 07640647
• 负责人: UCHIDA Etsuo
• 金额: $ 1.41万
• 依托单位: Waseda University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 1995
• 资助国家: 日本
• 起止时间: 1995 至 1996
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-07640647/
• 关键词: Hydrothermal solution; chloro complex; supercritical; formation constant; Transition metal; alkaline earth metal.; 亜鉛; カドミウム; 平衡定数

In order to obtain the information on the aqueous speciation of metals under supercritical hydrothermal solutions, the effect of NaCl on the ion exchange equilibria between minerals and aqueous chloride solution under the coexistence of two phase minerals almost immiscible to each other. In the present study, experiments on the aqueous speciation for Mg^<2+>, Sr^<2->, Fe^<2+>, Mn^<2+>, Co^<2+> and Ni^<2+> were carried out using the CaWO_4-MeWO_4, system and for Zn^<2+> using the CaTiO_3MeTiO_3 system. The experimental conditions are mainly 600ﾟC and 1kb.As for Mg^<2+> and Sr^<2+>, the Ca/(Ca+Me)ratios of the aqueous chloride solution coexisting with the two solid phases are constant in spite of the increase of NaCl. This indicates that under supercritical hydrothermal solutions, Mg^<2+> and Sr^<2-> dissolve as neutral species, but not as higher-order chloro complexes. On the other hand, for Fe^<2+>, Mn^<2+>, Co^<2+>, Ni^<2+>, and Zn^<2+> the Ca/(Ca+Me) ratios decreased significantly with the increases of NaCl. This can be attributed to the formation of the higher-order chloro complexes of the metals. On the assumption that the metals exist as tri-chloro complexes under the experimental conditions, the formation constants of the tri-chloro complexes are in the order of Mn^<2+>>Co^<2+>>Fe^<2+>>Ni^<2+>. Based on the ligand field theory, it is supposed that the metals form tetrahedral chloro complexes with low-spin state under supercritical hydrothermal solutions.As for Zn^<2+>, the experiments were performed at 500 to 700ﾟC,1kb and 600ﾟC,0.5kb. As a result, it is clarified that the formation constant of the tri-chloro complex incerases with the increase of temperature but decreases with the increase of pressure. This suggests that transition metals can be leached effectively from magmas under higher tempearature and lower pressures.

为了获得超临界水热溶液中金属在水溶液中的形态信息，研究了NaCl对几乎不互溶的两相矿物共存条件下矿物与氯化物水溶液之间离子交换平衡的影响。本研究采用CaWO_4-MeWO_4体系对Mg^&lt;2+&gt;、Sr^<2->&lt;2+&gt;、Fe^&lt;2+&gt;、Mn^&lt;2+&gt;、Co^&lt;2+&gt;和Ni^&lt;2+&gt;进行了水溶液形态分析，采用CaTiO_3-MeTiO_3体系对Zn^&lt;2+&gt;进行了水溶液形态分析。实验条件主要为600 ℃、1 kb。对于Mg^&lt;2+&gt;和Sr^&lt;2+&gt;，两种固相共存的氯化物水溶液的Ca/（Ca+Me）比值随NaCl含量的增加而保持不变。这表明在超临界水热溶液中，Mg^2+和Sr^2<2->+以中性物种溶解，而不是以高级氯络合物溶解。而Fe^&lt;2+&gt;、Mn^&lt;2+&gt;、Co^&lt;2+&gt;、Ni^&lt;2+&gt;和Zn^&lt;2+&gt;的Ca/（Ca+Me）比值则随NaCl浓度的增加而显著降低。这可以归因于金属的高阶氯络合物的形成。在实验条件下，假设金属以三氯配合物形式存在，三氯配合物的形成常数顺序为Mn^&lt;2+&gt;Co^&lt;2+&gt;Fe^&lt;2+&gt;Ni^&lt;2+&gt;。根据配位场理论，推测金属离子在超临界水热溶液中形成四面体低自旋态的氯配合物，对Zn^（2+）在500 ~ 700 ℃，1 kb和600 ℃，0.5kb条件下进行了实验研究。结果表明，三氯配合物的生成常数随温度的升高而增大，随压力的升高而减小。这表明，在较高温度和较低压力下，过渡金属可以有效地从岩浆中浸出。

项目成果

E.Uchida,Y.Goryozono,M.Naito and M.Yamagami: "Agueous speciation of iron and manganose chlorides in supercritical hydrothermal solutions." Geochemical Journal. 29. 175-188 (1995)

E.Uchida、Y.Goryozono、M.Naito 和 M.Yamagami：“超临界热液中氯化铁和氯化锰的水形态”。