Reduction and Oxidation of Fe3+ in Dioctahedral Smectites—III.* Oxidation of Octahedral Iron in Montmorillonite

I. Rozenson and L. Heller-Kallai
Department of Geology, The Hebrew University, Jerusalem, Israel
* Parts I and II: Clays & Clay Minerals, 1976, 24, 271; ibid. p. 283.

Abstract: Structural Fe2+ in montmorillonite is readily oxidized by contact with water, salt solutions or on mild heating. This is shown clearly by the Mössbauer spectra and is associated with a sharpening of the infrared absorption near 880 cm−1. It was inferred that this band comprises the Fe2+—OH—Al and Fe3+—OH—Al deformations. The rate at which oxidation occurs depends on the exchangeable cations. High acidity of the interlayers is conducive to oxidation, as is contact with Cu2+-containing solutions or concentrated H2O2 solutions.

The results show clearly that any chemical treatment of montmorillonite causes changes in the oxidation state of structural iron.

Key Words: Exchange • Iron • Oxidation • Reduction

Clays and Clay Minerals; April 1978 v. 26; no. 2; p. 88-92; DOI: 10.1346/CCMN.1978.0260202
© 1978, The Clay Minerals Society
Clay Minerals Society (www.clays.org)