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

¹ Unité de Science du Sol, INRA, Route de Saint Cyr, 78026 Versailles, and ² Laboratoire des Matériaux Minéraux, ENSCM, 3 rue Alfred Werner, 68093 Mulhouse, France

^* E-mail: prost{at}versailles.inra.fr

(Received 1 September 2000; revised 17 August 2001)

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 (V_K–V_Ca) 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.

KEYWORDS: exchange isotherms, FIR spectroscopy, selectivity, vermiculite, X-ray diffraction

This article has been cited by other articles:

				M. Diaz, V. Laperche, J. Harsh, and R. Prost Far infrared spectra of K+ in dioctahedral and trioctahedral mixed-layer minerals American Mineralogist, August 1, 2002; 87(8-9): 1207 - 1214. [Abstract] [Full Text] [PDF]

				R. BADREDDINE, R. LE DRED, and R. PROST Far infrared study of K+, Rb+ and Cs+ during their exchange with Na+ and Ca2+ in vermiculite Clay Minerals, March 1, 2002; 37(1): 71 - 81. [Abstract] [Full Text] [PDF]