Magnetite stability in aqueous sodium phosphate solutions at elevated temperatures

Conference · Sun Mar 01 00:00:00 EST 1992

OSTI ID:10140049

Ziemniak, S E; Opalka, E P

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
• Resource Relation: Conference: 9. international symposium on environmental degradation of materials in nuclear power systems,St. Louis, MO (United States),Aug 1993; Other Information: PBD: Mar 1992
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
36 MATERIALS SCIENCE
20 FOSSIL-FUELED POWER PLANTS
MAGNETITE
STABILITY
SODIUM PHOSPHATES
AQUEOUS SOLUTIONS
TEMPERATURE RANGE 0400-1000 K
EQUILIBRIUM
THERMODYNAMIC PROPERTIES
400201
360105
200104
CHEMICAL AND PHYSICOCHEMICAL PROPERTIES
CORROSION AND EROSION
COMPONENTS