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Clays and Clay Minerals

, Volume 41, Issue 6, pp 662–667 | Cite as

The Chemical Form of Vanadium (IV) in Kaolinite

  • A. U. Gehring
  • I. V. Fry
  • J. Luster
  • Garrison Sposito
Article

Abstract

A combined application of electron paramagnetic resonance (EPR) and Fourier-transform infrared (FTIR) spectroscopies with thermal methods was used to determine the chemical form of V(IV) in a Georgia kaolinite (KGa-I). Precise values of the EPR spectroscopic g-values and hyperfine coupling constants were obtained for an untreated sample (g = 1.940, A = 18.71 mT; g = 1.966, A = 7.63 mT). Heating the sample to 1000°C in steps while monitoring phase changes with EPR and FTIR spectra led to the following structural interpretations: 1) Vanadium (IV) occurs almost entirely as an isomorphically substituted species in the octahedral sheet of KGa-1 kaolinite; 2) during the dehydroxylation of kaolinite at about 500°C and the subsequent formation of metakaolinite, V(IV)-substituted octahedral sites are readily converted into truncated octahedra exhibiting fourfold coordination; and 3) in these highly distorted four-coordinated sites, V(IV) is metastable, being completely oxidized at about 800°C.

Key Words

Electron paramagnetic resonance Isomorphic substitution Kaolinite Vanadium 

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Copyright information

© The Clay Minerals Society 1993

Authors and Affiliations

  • A. U. Gehring
    • 1
  • I. V. Fry
    • 2
  • J. Luster
    • 1
  • Garrison Sposito
    • 1
  1. 1.Department of Soil ScienceUniversity of California BerkeleyCaliforniaUSA
  2. 2.Department of Plant BiologyUniversity of California BerkeleyCaliforniaUSA

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