SOLUBILITY OF HEMATITE, FE2O3(κ, α) AT 200°C AND THE STANDARD ENTROPY OF FE3+ ION IN AQUEOUS SOLUTION
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dc.contributor.author | Sergeeva E.I. | |
dc.contributor.author | Suleimenov O.M. | |
dc.contributor.author | Evstigneev A.V. | |
dc.contributor.author | Khodakovsky I.L. | |
dc.date.accessioned | 2021-01-16T07:39:46Z | |
dc.date.available | 2021-01-16T07:39:46Z | |
dc.date.issued | 1999 | |
dc.identifier | https://elibrary.ru/item.asp?id=35791593 | |
dc.identifier.citation | Geohimiya, 1999, 37, 11, 1218-1229 | |
dc.identifier.issn | 0016-7525 | |
dc.identifier.uri | https://repository.geologyscience.ru/handle/123456789/23205 | |
dc.description.abstract | The solubility of hematite, Fe2O3 (cr, α) in acidic (0.5 < pH < 2) and alkalic (12.7 < pH < 13.4) aqueous perchlorate solutions with ionic strengths of I = 0.1 and 0.316 was measured at 200°C and vapor saturation pressure. The measurements were carried out in solutions of perchloric acid and sodium hydroxide at concentrations of 0.01 < CHClO4 < 0.32 M and 0.112 < CNaOH < 0.301 M. The equilibrium constants of hematite dissolution reactions were calculated from the measured values at 200°C in acidic environments: 0.5Fe2O3(Cr, α + 2H+(sol) = FeOH2+(sol) + 0.5H2O(liq) logAr0(473.15 K) = -3.88 ± 0.36; 0.5Fe2O3(Cr, α) + 3H+(sol) = Fe3+(sol) + 1.5H2O(liq) logK0 (473.15 K) = -4.54 ± 0.36; and in alkalic environments: 0.5Fe2O3(Cr, α) + OH-(sol) + 1.5H2O(liq) = Fe(OH)-4 (sol) logK0(473.15 K) = -4.56 ± 0.10. Proceeding from the measured values and published data, thermodynamic properties were estimated for some iron-bearing compounds in the system Fe(III)-H2O at temperatures from 25-200°C. In particular, on the basis of hematite solubility measurements, we determined for the first time the standard entropy of Fe3+ ion in aqueous solution, S0 (298.15 K) Fe3+(Sol) = -275.0 ± 8.0 J/mol K and its standard free energy of formation, ΔfG0(298.15) Fe3+(Sol) = -16.5 ± 3.4 kJ/mol. The equilibrium constant of the hematite dissolution reaction (and Fe3+ ion formation) at 25°C in acidic environments was calculated: logK0(298.15 K) = 0.2 ± 0.4. The direct determination of this value by hematite dissolution at 25°C is hampered by kinetic problems. | |
dc.title | SOLUBILITY OF HEMATITE, FE2O3(κ, α) AT 200°C AND THE STANDARD ENTROPY OF FE3+ ION IN AQUEOUS SOLUTION | |
dc.type | Статья |
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