Synthesis and stability of hetaerolite, ZnMn/sub 2/O/sub 4/, at 25/sup 0/C
A precipitate of nearly pure hetaerolite, ZnMn/sub 2/O/sub 4/, a spinel-structured analog of hausmannite, Mn/sub 3/O/sub 4/, was prepared by an irreversible coprecipitation of zinc with manganese at 25/sup 0/C. The synthesis technique entailed constant slow addition of a dilute solution of Mn/sup 2 +/ and Zn/sup 2 +/ chlorides having a Mn/Zn ratio of 2:1 to a reaction vessel that initially contained distilled deionized water, maintained at a pH of 8.50 by addition of dilute NaOH by an automated pH stat, with continuous bubbling of CO/sub 2/-free air. The solid was identified by means of X-ray diffraction and transmission electron microscopy and consisted of bipyramidal crystals generally less than 0.10 ..mu..m in diameter. Zn/sup 2 +/ ions are able to substitute extensively for Mn/sup 2 +/ ions that occupy tetrahedral sites in the hausmannite structure. Hetaerolite appears to be more stable than hausmannite with respect to spontaneous conversion to ..gamma..MnOOH. The value of the standard free energy of formation of hetaerolite was estimated from the experimental data to be -289.4 +/- 0.8 kcal per mole. Solids intermediate in composition between hetaerolite and hausmannite can be prepared by altering the Mn/Zn ratio in the feed solution.
- Research Organization:
- Geological Survey, Menlo Park, CA (USA)
- OSTI ID:
- 6938644
- Journal Information:
- Geochim. Cosmochim. Acta; (United States), Journal Name: Geochim. Cosmochim. Acta; (United States) Vol. 51:6; ISSN GCACA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
580400* -- Geochemistry-- (-1989)
ACTIVATION ENERGY
ALKALINE EARTH METAL COMPOUNDS
ALUMINIUM COMPOUNDS
ALUMINIUM OXIDES
CHALCOGENIDES
CHEMISTRY
COHERENT SCATTERING
CONCENTRATION RATIO
CRYSTAL STRUCTURE
DIFFRACTION
ELECTRON MICROSCOPY
ENERGY
GEOCHEMISTRY
KINETICS
MAGNESIUM COMPOUNDS
MAGNESIUM OXIDES
MANGANESE COMPOUNDS
MICROSCOPY
MINERALS
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
PRECIPITATION
REACTION KINETICS
SCATTERING
SEPARATION PROCESSES
SPINELS
STABILITY
SYNTHESIS
TRANSITION ELEMENT COMPOUNDS
TRANSMISSION ELECTRON MICROSCOPY
X-RAY DIFFRACTION
ZINC COMPOUNDS