Aqueous speciation of magnesium, strontium, nickel and cobalt chlorides in hydrothermal solutions at 600°C and 1 kbar

Etsuo Uchida, Yuichi Goryozono, Masahiro Naito

    Research output: Contribution to journalArticle

    11 Citations (Scopus)

    Abstract

    The effect of NaCl on ion exchange equilibria in the system CaWO4-MeWO4-CaCl2-MeCl2-H 2O (Me: Mg, Sr, Ni and Co) was experimentally monitored at 600°C and 1 kbar. The Ca/(Ca + Me) ratio of the aqueous chloride solution in equilibrium with both CaWO4 and MeWO4 was constant for Mg and Sr in spite of the addition of NaCl, whereas the ratio decreased significantly for Ni and Co with the increase of NaCl. The experimental results indicate that both Ni2+ and Co2+ do form higher-order chloro-complexes such as NiCl3 - aq and CoCl3 - aq, whereas both Mg2+ and Sr2+ may not. The thermodynamic analysis of the experimental results gives 1.5 and 2.1 in logarithm units for the formation constants for NiCl3 - aq and CoCl3 - aq, respectively. By combining the results of Uchida et al. (1995), MeCl2aq tends to forms MeCl3 - aq in the order of SrCl2aq= CaCl2aq = MgCl2aq ≪ NiCl2aq < FeCl2aq < CoCl2aq < MnCl2aq at 600°C and 1 kbar. Based on ligand field theory, the above order may suggest that the transition metal cations exist as tetrahedral chloro-complexes with low-spin state in the supercritical hydrothermal solutions.

    Original languageEnglish
    Pages (from-to)99-109
    Number of pages11
    JournalGeochemical Journal
    Volume30
    Issue number2
    Publication statusPublished - 1996

    Fingerprint

    magnesium chlorides
    Magnesium Chloride
    strontium
    cobalt
    magnesium
    nickel
    chlorides
    chloride
    transition element
    logarithms
    ligand
    Transition metals
    Cations
    Chlorides
    ion exchange
    Ion exchange
    cation
    thermodynamics
    transition metals
    Thermodynamics

    ASJC Scopus subject areas

    • Geochemistry and Petrology
    • Geophysics

    Cite this

    Aqueous speciation of magnesium, strontium, nickel and cobalt chlorides in hydrothermal solutions at 600°C and 1 kbar. / Uchida, Etsuo; Goryozono, Yuichi; Naito, Masahiro.

    In: Geochemical Journal, Vol. 30, No. 2, 1996, p. 99-109.

    Research output: Contribution to journalArticle

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    AB - The effect of NaCl on ion exchange equilibria in the system CaWO4-MeWO4-CaCl2-MeCl2-H 2O (Me: Mg, Sr, Ni and Co) was experimentally monitored at 600°C and 1 kbar. The Ca/(Ca + Me) ratio of the aqueous chloride solution in equilibrium with both CaWO4 and MeWO4 was constant for Mg and Sr in spite of the addition of NaCl, whereas the ratio decreased significantly for Ni and Co with the increase of NaCl. The experimental results indicate that both Ni2+ and Co2+ do form higher-order chloro-complexes such as NiCl3 - aq and CoCl3 - aq, whereas both Mg2+ and Sr2+ may not. The thermodynamic analysis of the experimental results gives 1.5 and 2.1 in logarithm units for the formation constants for NiCl3 - aq and CoCl3 - aq, respectively. By combining the results of Uchida et al. (1995), MeCl2aq tends to forms MeCl3 - aq in the order of SrCl2aq= CaCl2aq = MgCl2aq ≪ NiCl2aq < FeCl2aq < CoCl2aq < MnCl2aq at 600°C and 1 kbar. Based on ligand field theory, the above order may suggest that the transition metal cations exist as tetrahedral chloro-complexes with low-spin state in the supercritical hydrothermal solutions.

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