Interpretation of Infrared Spectra of Oxidized and Reduced Nontronite*

J. W. Stucki and C. B. Roth
* Journal Paper 6252, Purdue University, Agricultural Experiment Station, West Lafayette, IN 47907, U.S.A.
Former Graduate Research Assistant, Purdue University, now Assistant Professor of Agronomy, University of Illinois.
Agronomy, Purdue University. West Lafayette, IN 47907, U.S.A.

Abstract: Infrared spectra of nontronite reveal shifts to lower wave, number in peaks located at 3570, 1030, and 821 cm−1, which are assigned to vibrational modes for O-H stretching, Si-Ob (basal oxygens) tetrahedral vibrations, and FeO-H deformation, respectively, as the Fe2+ content increases upon reduction. A pleochroic shoulder at 1110 cm−1 resulting from Si-Oa (apical oxygens) interactions appears to be unchanged with reduction. The absorption band at 848 cm−1 shifts to higher energy with reduction of structural iron, and persists at 840 cm−1 after complete deuteration of structural hydroxyls. The band is assigned to a Fe-OH mode where the OH moves as a unit. The shift in the Si-Ob mode to lower vibrational energy with reduction may indicate a decrease in stress forces between the tetrahedral and octahedral sheets.

Clays and Clay Minerals; December 1976 v. 24; no. 6; p. 293-296; DOI: 10.1346/CCMN.1976.0240604
© 1976, The Clay Minerals Society
Clay Minerals Society (www.clays.org)