Magnetite stability in aqueous sodium phosphate solutions at elevated temperatures
Magnetite (Fe[sub 3]O[sub 4]) is shown to transform to a sodium ferric hydroxy-phosphate compound in concentrated, alkaline sodium phosphate solutions at elevated temperatures via 1/3 Fe[sub 3]O[sub 4](s) + 13/3 Na[sup +] + 2 HPO[sub 4][sup =] [r reversible] Na[sub 4]Fe(OH)(PO[sub 4])[sub 2][center dot]1/3NaOH(s) + 1/3 H[sup +] + 1/6 H[sub 2](g). The thermodynamic equilibrium for this reaction was defined in the system Na[sub 2]O-P[sub 2]O[sub 5]Fe[sub 3]O[sub 4]-H[sub 2]O for Na/P molar ratios between 2.1 and 3. Quantitative chemical, infrared and Mossbauer spectroscopic, and X-ray diffraction analyses are employed to verify that the precipitated solid was a single phase having the non-whole number stoichiometric Na/P ratio 2.15 [plus minus] 0.02. Standard entropy and free energy of formation for sodium ferric hydroxyphosphate were calculated to be 729.2 J/mol-K and [minus]3550.3 kJ/mol, respectively.
- Research Organization:
- Knolls Atomic Power Lab., Schenectady, NY (United States)
- Sponsoring Organization:
- DOE; USDOE, Washington, DC (United States)
- DOE Contract Number:
- AC12-76SN00052
- OSTI ID:
- 6443144
- Report Number(s):
- KAPL-4735; CONF-930821--1; ON: DE92016359
- Country of Publication:
- United States
- Language:
- English
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400201* -- Chemical & Physicochemical Properties
ALKALI METAL COMPOUNDS
AQUEOUS SOLUTIONS
DISPERSIONS
EQUILIBRIUM
IRON ORES
MAGNETITE
MINERALS
MIXTURES
ORES
OXIDE MINERALS
OXYGEN COMPOUNDS
PHOSPHATES
PHOSPHORUS COMPOUNDS
PHYSICAL PROPERTIES
SODIUM COMPOUNDS
SODIUM PHOSPHATES
SOLUTIONS
STABILITY
TEMPERATURE RANGE
TEMPERATURE RANGE 0400-1000 K
THERMODYNAMIC PROPERTIES