Magnetite solubility and phase stability in alkaline media at elevated temperatures
- Knolls Atomic Power Lab., Schenetctady, NY (United States)
A platinum-lined, flowing autoclave facility was used to investigate the solubility behavior of magnetite (Fe{sub 3}O{sub 4}) in alkaline sodium phosphate and ammonium hydroxide solutions between 21 and 288{degrees}C. Measured iron solubilities were interpreted via via a Fe(II)/Fe(III) ion hydroxo-, phosphato-, and ammino-complexing model and thermodynamic functions for these equilibria were obtained from a least-squares analysis of the data. A total of 14 iron ion species were fitted. Complexing equilibria are reported for 8 new species: Fe(OH)(HPO{sub 4}){sup {minus}}, Fe(OH){sub 2}(HPO{sub 4}){sup 2{minus}}, Fe(OH){sub 3}(HPO{sub 4}){sup 2{minus}}, Fe(OH)(NH{sub 3}){sup +}, Fe(OH){sub 2}(PO{sub 4}){sup 3{minus}}, Fe(OH){sub 4}(HPO{sub 4}){sup 3{minus}}, Fe(OH){sub 2}(H{sub 2}PO{sub 4}){sup {minus}}, and Fe(OH){sub 3}(H{sub 2}PO{sub 4}){sup {minus}}. At elevated temperatures, hydrolysis and phosphato complexing tended to stabilize Fe(III) relative to Fe(II), as evidenced by free energy changes fitted to the oxidation reactions. For temperatures below 83{degrees}C and for a dissolved hydrogen concentration of 234 {mu}mol-kg{sup {minus}1}, the activity of ferrous iron in aqueous solution is controlled by a hydrous Fe(II) oxide solid phase rather than magnetite.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 255276
- Journal Information:
- Journal of Solution Chemistry, Vol. 24, Issue 9; Other Information: PBD: Sep 1995
- Country of Publication:
- United States
- Language:
- English
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