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The Cr X-ray absorption K-edge structure of poorly crystalline Fe(III)-Cr(III)-oxyhydroxides

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Published/Copyright: April 2, 2015
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American Mineralogist
From the journal American Mineralogist Volume 95 Issue 8-9

Abstract

Poorly crystalline solids play an important role in many low-temperature geochemical processes, such as trace element speciation and biomineralization. Yet, the structures of many such naturally occurring phases are poorly understood. X-ray absorption spectroscopy is a powerful tool that permits chemically and spatially resolved investigations of poorly crystalline materials. In this study, we compare structural and electronic information derived from different regions of chromium K-edge X-ray absorption spectra for a series of poorly ordered iron(III)-chromium(III)-oxyhydroxides. These phases regularly form after the reduction of Cr(VI) by Fe(II) and often dictate the long-term fate of Cr in the environment. The distinct parts of the X-ray absorption spectrum, namely the pre-edge region, the near edge (XANES) region, and the extended (EXAFS) region, provide complementary information about the local chemical environment of Cr. Analysis of the XANES and EXAFS spectra showed that the structure around Cr in the Cr-poor sample is primarily composed of edge-sharing octahedra, whereas the octahedra in the Cr-rich samples are connected by edge-sharing and cornersharing linkages. The analysis of non-local transitions in the pre-edge spectra indicated the absence of Cr clustering at low Cr substitution. This study demonstrates the advantage of complementary pre-edge, XANES, and EXAFS analysis to deduce information on the medium-range environment around Cr in poorly ordered solids.

Keywords: XANES; EXAFS; pre-edge; chromium; iron; oxyhydroxides; poorly crystalline
Received: 2009-4-16
Accepted: 2010-4-2
Published Online: 2015-4-2
Published in Print: 2010-8-1

© 2015 by Walter de Gruyter Berlin/Boston

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https://doi.org/10.2138/am.2010.3274
Keywords for this article
XANES; EXAFS; pre-edge; chromium; iron; oxyhydroxides; poorly crystalline

Articles in the same Issue

  1. Resonant X-ray emission study of the lower-mantle ferropericlase at high pressures
  2. Uranyl phosphate sheet reconstruction during dehydration of metatorbernite [Cu(UO2)2(PO4)2·8H2O]
  3. Detection of structurally bound hydroxyl in fluorapatite from Apollo Mare basalt 15058,128 using TOF-SIMS
  4. Quantum-mechanical evaluation of Np-incorporation into studtite
  5. Electronic structure and local environment of substitutional V3+ in grossular garnet Ca3Al2(SiO4)3: K-edge X-ray absorption spectroscopy and first-principles modeling
  6. Elbrusite-(Zr)—A new uranian garnet from the Upper Chegem caldera, Kabardino-Balkaria, Northern Caucasus, Russia
  7. What drives the distribution in nature of 3T vs. 2M1 polytype in muscovites and phengites? A general assessment based on new data from metamorphic and igneous granitoid rocks
  8. Radiation damage and uranium concentration in zircon as assessed by Raman spectroscopy and neutron irradiation
  9. The Cr X-ray absorption K-edge structure of poorly crystalline Fe(III)-Cr(III)-oxyhydroxides
  10. Protracted oceanic subduction prior to continental subduction: New Lu-Hf and Sm-Nd geochronology of oceanic-type high-pressure eclogite in the western Dabie orogen
  11. Time-resolved in situ studies of apatite formation in aqueous solutions
  12. X-ray Rietveld and 57Fe Mössbauer studies of epidote and piemontite on the join Ca2Al2Fe3+Si3O12(OH)–Ca2Al2Mn3+Si3O12(OH) formed by hydrothermal synthesis
  13. Elastic behavior of zeolite boggsite in silicon oil and aqueous medium: A case of high-pressure-induced over-hydration
  14. Low-temperature infrared spectroscopic study of OH-stretching modes in kaolinite and dickite
  15. Stability field of the high-temperature orthorhombic phase in the enstatite-diopside system
  16. Unique crystal chemistry of two polymorphs of topaz-OH: A multi-nuclear NMR and Raman study
  17. Crystal chemistry of chromian pumpellyite from Osayama, Okayama Prefecture, Japan
  18. Toturite Ca3Sn2Fe2SiO12—A new mineral species of the garnet group
  19. The structure of schwertmannite, a nanocrystalline iron oxyhydroxysulfate
  20. Crystal chemistry of Cr-spinels from the lherzolite mantle peridotite of Ronda (Spain)
  21. Lead-tellurium oxysalts from Otto Mountain near Baker, California: I. Ottoite, Pb2TeO5, a new mineral with chains of tellurate octahedra
  22. Lead-tellurium oxysalts from Otto Mountain near Baker, California: II. Housleyite, Pb6CuTe4O18(OH)2, a new mineral with Cu-Te octahedral sheets
  23. The behavior of the Hf isotope system in radiation-damaged zircon during experimental hydrothermal alteration
  24. Letter. Crystal structure of a new high-pressure polymorph of topaz-OH
  25. Letter. In situ 238U-230Th disequilibrium dating of pyrochlore at sub-millennial precision
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