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:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- AC12-76SN00052
- OSTI ID:
- 10140049
- Report Number(s):
- KAPL--4735; CONF-930821--1; ON: DE92016359
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
200104
36 MATERIALS SCIENCE
360105
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201
AQUEOUS SOLUTIONS
CHEMICAL AND PHYSICOCHEMICAL PROPERTIES
COMPONENTS
CORROSION AND EROSION
EQUILIBRIUM
MAGNETITE
SODIUM PHOSPHATES
STABILITY
TEMPERATURE RANGE 0400-1000 K
THERMODYNAMIC PROPERTIES