TY - JOUR
T1 - Enthalpy of formation of sulfate green rusts
AU - Mazeina, Lena
AU - Navrotsky, Alexandra
AU - Dyar, Darby
N1 - Funding Information:
We thank M. Kloster for detailed comments and discussions. We also acknowledge helpful discussions with D. Kessler, Q. Ouyang, L. Tang, and J. Widom. This research is supported by the NSF through Grants No. DMR-0211308 and No. MCB-0083704.
PY - 2008/2/15
Y1 - 2008/2/15
N2 - As a contribution to the systematic study of iron oxide thermodynamics, this work reports enthalpies of formation of green rust, a double layered (FeII, FeIII) hydroxide with the ideal stoichiometry FeII1 - x FeIIIx (OH)2 [Am -]y / m · n H2 O, with sulfate as the anion in the interlayer. Samples were characterized by X-ray powder diffraction, thermogravimetric analysis, infrared spectroscopy, and Mössbauer spectroscopy. Full chemical analysis was performed. Contents of FeII, FeIII, water, and sulfate were obtained. We report standard enthalpies of formation for green rust with different FeII/FeIII ratios. Enthalpies of formation from single cation compounds, namely, Fe(OH)2, Fe(OH)3, FeSO4 and H2O show reasonable agreement with Gibbs free energies of formation from single cation compounds recalculated from the reported literature values. These values show that green rust has little stabilization over a mechanical mixture of these single cation compounds and there is no thermodynamic preference for any particular FeII/FeIII ratio.
AB - As a contribution to the systematic study of iron oxide thermodynamics, this work reports enthalpies of formation of green rust, a double layered (FeII, FeIII) hydroxide with the ideal stoichiometry FeII1 - x FeIIIx (OH)2 [Am -]y / m · n H2 O, with sulfate as the anion in the interlayer. Samples were characterized by X-ray powder diffraction, thermogravimetric analysis, infrared spectroscopy, and Mössbauer spectroscopy. Full chemical analysis was performed. Contents of FeII, FeIII, water, and sulfate were obtained. We report standard enthalpies of formation for green rust with different FeII/FeIII ratios. Enthalpies of formation from single cation compounds, namely, Fe(OH)2, Fe(OH)3, FeSO4 and H2O show reasonable agreement with Gibbs free energies of formation from single cation compounds recalculated from the reported literature values. These values show that green rust has little stabilization over a mechanical mixture of these single cation compounds and there is no thermodynamic preference for any particular FeII/FeIII ratio.
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U2 - 10.1016/j.gca.2007.11.032
DO - 10.1016/j.gca.2007.11.032
M3 - Article
AN - SCOPUS:38749127199
SN - 0016-7037
VL - 72
SP - 1143
EP - 1153
JO - Geochimica et Cosmochimica Acta
JF - Geochimica et Cosmochimica Acta
IS - 4
ER -