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1 results

  • A far infrared study of K+ ions during K+ ⇋ Ca2+ exchange in vermiculite

  • R. Badreddine, R. Le Dred, R. Prost
  • Journal:
    Clay Minerals / Volume 37 / Issue 1 / March 2002
    Published online by Cambridge University Press:
    09 July 2018, pp. 59-70

  • K+ ⇋ Ca2+ exchange was performed on a mixed-layer (phlogopite-vermiculite) sample from Palabora, Republic of South Africa. Exchange isotherms, X-ray diffraction patterns and far infrared (FIR) spectra of the mineral were obtained. Different mineralogical phases were identified during the exchange process: K-vermiculite, Ca-vermiculite and a regular mixed-layer (VK–VCa) phase. Two types of exchange sites for K+ were identified by FIR during the exchange process. The first type, dominant in the K-vermiculite, gives an absorption band at 76 cm–1. The other, which was the most pronounced site in the mixed-layer phase, gives an absorption band at 72 cm–1. The mixed-layer phase was formed only when oxidation of Fe2+ resulted in the internal compensation of part of the negative charge of vermiculite. This study shows that the high selectivity displayed by vermiculite for K+ is enhanced by the formation of the mixed-layer phase.