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Experiments and Thermodynamic Modeling of Chukanovite (Fe2(OH)2CO3) to High Ionic Strengths

Published online by Cambridge University Press:  20 March 2017

Sungtae Kim*
Affiliation:
Sandia National Laboratories, 4100 National Parks Highway, Carlsbad, NM 88220, U.S.A.
Justin Dean
Affiliation:
Sandia National Laboratories, 4100 National Parks Highway, Carlsbad, NM 88220, U.S.A.
Jandi Knox
Affiliation:
Sandia National Laboratories, 4100 National Parks Highway, Carlsbad, NM 88220, U.S.A.
Leslie Kirkes
Affiliation:
Sandia National Laboratories, 4100 National Parks Highway, Carlsbad, NM 88220, U.S.A.
Je-Hun Jang
Affiliation:
Sandia National Laboratories, 4100 National Parks Highway, Carlsbad, NM 88220, U.S.A.
*
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Abstract

While conducting siderite (FeCO3) solubility experiments in NaCl-Na2CO3 brines, evidence for a second phase was detected. Experiments, in which synthesized siderite was reacted with high ionic strength (0.18 – 7.5 m) solutions at room temperature and high pH (>10), were conducted in a glovebox. As the aging time of siderite-bearing experiments increased, the pH of the solution decreased, signaling formation of a hydroxyl-bearing phase. Decreasing pH values are interpreted to indicate that a hydroxyl-bearing phase, such as chukanovite, is the reaction controlling solid in the solid assemblage. Chukanovite was tentatively identified by XRD analysis. We set out, therefore, to determine the thermodynamic stability of chukanovite under the experimental conditions. Aqueous thermodynamic model parameters were determined with experimentally analyzed Fe(II) solubility data, and subsequently yielded a proposed formation free energy of chukanovite (-1149.8 kJ/mol).

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Articles
Copyright
Copyright © Materials Research Society 2017 

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References

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