Thermodynamic stability of CoOOH and its coprecipitation with manganese |
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Authors: | John D. Hem Charles E. Roberson Carol J. Lind |
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Affiliation: | U.S. Geological Survey, 345 Middlefield Road, Menlo Park, California 94025 U.S.A. |
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Abstract: | A precipitate of cobalt oxyhydroxides formed by bubbling oxygen through a dilute solution of Co(NO3)2 held at pH 9.0 and 25°C was aged for 23 months in contact with the original solution, with access to atmospheric oxygen. Co3O4 and CoOOH were identified in the precipitate by X-ray diffraction. Chemical equilibria involving these solids were evaluated by measurements of solution pH and Co2+ activities and by redox potential measurements and gave a of . This value and other thermodynamic data show relative feasibility of hypothetical reaction steps and changes in reaction paths during automated coprecipitation titrations and subsequent aging of a precipitate that finally contained βMnOOH, MnO2 (birnessite) and CoOOH. |
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