The structure of Fe(iii) ions in strongly alkaline aqueous solutions from EXAFS and Mössbauer spectroscopy

P. Sipos, Dalma Zeller, E. Kuzmann, A. Vértes, Z. Homonnay, Monika Walczak, Sophie E. Canton

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Abstract

To establish the structure of ferric ions in strongly alkaline (pH > 13) environments, aqueous NaOH solutions supersaturated with respect to Fe(iii) and the solid ferric-hydroxo complex salts precipitating from them have been characterized with a variety of experimental techniques. From UV measurements, in solutions of pH > 13, only one kind of Fe(iii)-hydroxo complex species was found to be present. The micro crystals obtained from such solutions were proven to be a new, so far unidentified solid phase. Mössbauer spectra of the quick-frozen solution and that of the complex salt indicated a highly symmetrical ferric environment in both systems From the EXAFS and XANES spectra, the environment of the ferric ion in these solutions (both native and quick-frozen) and in the complex salt was found to be different. In the complex salt, the bond lengths are consistent with an octahedral coordination around the ferric centres. In solution, the coordination geometry of Fe(iii) is most probably tetrahedral. Our results demonstrate that in strongly alkaline aqueous solutions, ferric ions behave very similarly to other structurally related tervalent ions, like Al(iii) or Ga(iii).

Original languageEnglish
Pages (from-to)5603-5611
Number of pages9
JournalJournal of the Chemical Society. Dalton Transactions
Issue number41
DOIs
Publication statusPublished - aug. 27 2008

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Spectroscopy
Ions
Salts
Bond length
Crystals
Geometry

ASJC Scopus subject areas

  • Chemistry(all)

Cite this

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title = "The structure of Fe(iii) ions in strongly alkaline aqueous solutions from EXAFS and M{\"o}ssbauer spectroscopy",
abstract = "To establish the structure of ferric ions in strongly alkaline (pH > 13) environments, aqueous NaOH solutions supersaturated with respect to Fe(iii) and the solid ferric-hydroxo complex salts precipitating from them have been characterized with a variety of experimental techniques. From UV measurements, in solutions of pH > 13, only one kind of Fe(iii)-hydroxo complex species was found to be present. The micro crystals obtained from such solutions were proven to be a new, so far unidentified solid phase. M{\"o}ssbauer spectra of the quick-frozen solution and that of the complex salt indicated a highly symmetrical ferric environment in both systems From the EXAFS and XANES spectra, the environment of the ferric ion in these solutions (both native and quick-frozen) and in the complex salt was found to be different. In the complex salt, the bond lengths are consistent with an octahedral coordination around the ferric centres. In solution, the coordination geometry of Fe(iii) is most probably tetrahedral. Our results demonstrate that in strongly alkaline aqueous solutions, ferric ions behave very similarly to other structurally related tervalent ions, like Al(iii) or Ga(iii).",
author = "P. Sipos and Dalma Zeller and E. Kuzmann and A. V{\'e}rtes and Z. Homonnay and Monika Walczak and Canton, {Sophie E.}",
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T1 - The structure of Fe(iii) ions in strongly alkaline aqueous solutions from EXAFS and Mössbauer spectroscopy

AU - Sipos, P.

AU - Zeller, Dalma

AU - Kuzmann, E.

AU - Vértes, A.

AU - Homonnay, Z.

AU - Walczak, Monika

AU - Canton, Sophie E.

PY - 2008/8/27

Y1 - 2008/8/27

N2 - To establish the structure of ferric ions in strongly alkaline (pH > 13) environments, aqueous NaOH solutions supersaturated with respect to Fe(iii) and the solid ferric-hydroxo complex salts precipitating from them have been characterized with a variety of experimental techniques. From UV measurements, in solutions of pH > 13, only one kind of Fe(iii)-hydroxo complex species was found to be present. The micro crystals obtained from such solutions were proven to be a new, so far unidentified solid phase. Mössbauer spectra of the quick-frozen solution and that of the complex salt indicated a highly symmetrical ferric environment in both systems From the EXAFS and XANES spectra, the environment of the ferric ion in these solutions (both native and quick-frozen) and in the complex salt was found to be different. In the complex salt, the bond lengths are consistent with an octahedral coordination around the ferric centres. In solution, the coordination geometry of Fe(iii) is most probably tetrahedral. Our results demonstrate that in strongly alkaline aqueous solutions, ferric ions behave very similarly to other structurally related tervalent ions, like Al(iii) or Ga(iii).

AB - To establish the structure of ferric ions in strongly alkaline (pH > 13) environments, aqueous NaOH solutions supersaturated with respect to Fe(iii) and the solid ferric-hydroxo complex salts precipitating from them have been characterized with a variety of experimental techniques. From UV measurements, in solutions of pH > 13, only one kind of Fe(iii)-hydroxo complex species was found to be present. The micro crystals obtained from such solutions were proven to be a new, so far unidentified solid phase. Mössbauer spectra of the quick-frozen solution and that of the complex salt indicated a highly symmetrical ferric environment in both systems From the EXAFS and XANES spectra, the environment of the ferric ion in these solutions (both native and quick-frozen) and in the complex salt was found to be different. In the complex salt, the bond lengths are consistent with an octahedral coordination around the ferric centres. In solution, the coordination geometry of Fe(iii) is most probably tetrahedral. Our results demonstrate that in strongly alkaline aqueous solutions, ferric ions behave very similarly to other structurally related tervalent ions, like Al(iii) or Ga(iii).

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