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Reduction and Reoxidation of Nontronite: Extent of Reduction and Reaction Rates

Published online by Cambridge University Press:  02 April 2024

Peter Komadel*
Affiliation:
Department of Agronomy, University of Illinois, Urbana, Illinois 61801
Paul R. Lear*
Affiliation:
Department of Agronomy, University of Illinois, Urbana, Illinois 61801
Joseph W. Stucki
Affiliation:
Department of Agronomy, University of Illinois, Urbana, Illinois 61801
*
1Current address: Institute of Inorganic Chemistry, CCR, Slovak Academy of Sciences, Bratislava, Czechoslovakia
2Current address: EPL Bioanalytical Services, Decatur, Illinois 62525
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Abstract

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The reduction and reoxidation of three nontronite samples, GAN (API H-33a, Garfield, Washington), SWa-1 (ferruginous Washington smectite), and NG-1 (Hohen Hagen, Federal Republic of Germany) were studied with visible absorption and Mössbauer spectroscopy. The intensity of the intervalence electron transfer (IT) band at 730 nm in these nontronites was monitored during reduction and reoxidation at 277, 294, and 348 K. The results showed that the intensity of the band followed the number of Fe(II)-O-Fe(III) groups in the clay crystal, increasing to a maximum at about Fe(II): total Fe = 0.4; upon complete reduction, the band decreased to about the intensity of the unaltered, oxidized sample. With reoxidation of the sample with O2, the intensity of the band increased sharply, followed by a gradual decay back to the original, oxidized intensity. The ultimate level of Fe reduction achieved was at least 92%. Concomitantly, the color changed from yellow through green, blue-green, dark blue, light blue, and light gray as the Fe(II) content increased. The GAN nontronite was more difficult to reduce than the SWa-1 or NG-1 samples. The rate and level of reduction increased with the amount of reducing agent added.

Type
Research Article
Copyright
Copyright © 1990, The Clay Minerals Society

References

Bonnin, D., Calas, G., Suquet, H. and Pezerat, H., 1985 Site occupancy of Fe5+ in Garfield nontronite: A spectroscopic study Phys. Chem. Minerals 12 5564.CrossRefGoogle Scholar
Chen, S. A., Low, P. F. and Roth, C. B., 1987 Relation between potassium fixation and the oxidation state of octahedral iron Soil Sci. Soc. Amer. J. 51 8286.CrossRefGoogle Scholar
Goodman, B. A., Russell, J. D., Fraser, A. R. and Woodhams, F. W. D., 1976 A Mössbauer and I.R. spectroscopic study of the structure of nontronite Clays & Clay Minerals 24 5359.CrossRefGoogle Scholar
Karickhoff, S. W. and Bailey, G. W., 1973 Optical absorption spectra of clay minerals Clays & Clay Minerals 21 5970.CrossRefGoogle Scholar
Komadel, P. and Stucki, J. W., 1988 The quantitative assay of minerals for Fe2+ and Fe3+ using 1,10-phenanthroline. III. A rapid photochemical method Clays & Clay Minerals 36 379381.CrossRefGoogle Scholar
Lear, P. R., Komadel, P. and Stucki, J. W., 1988 Möss-bauer spectroscopic identification of iron oxides in non-tronite from Hohen Hagen, Federal Republic of Germany Clays & Clay Minerals 36 376378.CrossRefGoogle Scholar
Lear, P. R. and Stucki, J. W., 1987 Intervalence electron transfer and magnetic exchange interactions in reduced nontronite Clays & Clay Minerals 35 373378.CrossRefGoogle Scholar
Lear, P. R. and Stucki, J. W. (1989) Effect of iron oxidation state on the surface area of smectites: Clays & Clay Minerals 37, (in press).CrossRefGoogle Scholar
Low, P. F., Roth, C. B. and Stucki, J. W. (1983) System and method for rapid beneficiation of bentonite clay: U.S. Patent 4,411,530, 4 pp.Google Scholar
Rozenson, I. and Heller-Kallai, L., 1976 Reduction and oxidation of Fe3+ in dioctahedral smectites— 1: Reduction with hydrazine and dithionite Clays & Clay Minerals 24 271282.CrossRefGoogle Scholar
Russell, J. D., Goodman, B. A. and Fraser, A. R., 1979 Infrared and Mössbauer studies of reduced nontronites Clays & Clay Minerals 27 6371.CrossRefGoogle Scholar
Sherman, D. and Vergo, N., 1988 Optical (diffuse reflectance) and Mössbauer spectroscopic study of nontronite and related Fe-bearing smectites Amer. Mineral. 73 13461354.Google Scholar
Stucki, J. W., Stucki, J. W., Goodman, B. A. and Schwertmann, U., 1988 Structural iron in smectites Iron in Soils and Clay Minerals The Netherlands D. Reidel, Dordrecht 625675.CrossRefGoogle Scholar
Stucki, J. W., Golden, D. C. and Roth, C. B., 1984 The preparation and handling of dithionite-reduced smectite suspensions Clays & Clay Minerals 32 191197.CrossRefGoogle Scholar
Stucki, J. W., Low, P. F., Roth, C. B. and Golden, D. C., 1984 Effect of iron oxidation state on clay swelling Clays & Clay Minerals 32 357362.CrossRefGoogle Scholar