Toggle Main Menu Toggle Search

Open Access padlockePrints

Infrared study of reduced and reduced-reoxidized ferruginous smectite

Lookup NU author(s): Dr Claire Fialips


Full text for this publication is not currently held within this repository. Alternative links are provided below where available.


Oxidation-reduction processes within natural systems greatly influence the properties of sediments, soils and clays. The objective of this experimental study was to gather new evidence for the effects of changes in redox conditions (reduction and reoxidation) on structural properties of ferruginous smectite and to understand better the mechanisms involved. The <2 micrometer fraction of a ferruginous smectite (sample SWa-1), which contains 17.3 wt.% of total structural Fe, was studied by infrared (IR) spectroscopy. The pure Na-saturated clay was reduced by Na dithionite for 10 to 240 min to obtain various Fe(II):(total Fe) ratios ranging from 0 to 1.0. Selected reduced samples were then reoxidized completely by bubbling O2 gas through the suspensions for up to 12 h. Infrared spectra of the initially unaltered, reduced and reduced-reoxidized samples were collected. Reduction generated changes in the three studied spectral regions (O¡H stretching, M¡O¡H deformatio n, and Si¡O stretching) , indicating that major modifications occurred within the clay crystal beyond merely a change in Fe oxidation state. Partial dehydroxylation and redistribution of Fe, and perhaps Al, cations occurred upon reduction of SWa-1, changing the structural properties of its tetrahedral and octahedral sheets. Water molecules, probably generated by dehydroxylation within the octahedral sheet upon reduction, were tightly bound to the clay surface and were possibly trapped within the clay structure. Except for dehydroxylation and the Fe oxidation state, all these modifications were largely irreversible. The tightly bound water was not completely removed upon reoxidation and the cationic rearrangements generated during reduction were not reversed: either they were preserved as in the reduced state or cations were redistributed into a different configuration from the unreduced clay.

Publication metadata

Author(s): Fialips CI, Huo D, Yan L, Wu J, Stucki JW

Publication type: Article

Publication status: Published

Journal: Clays and Clay Minerals

Year: 2002

Volume: 50

Issue: 4

Pages: 455-469

Print publication date: 01/08/2002

ISSN (print): 0009-8604

ISSN (electronic): 1552-8367

Publisher: The Clay Minerals Society


DOI: 10.1346/000986002320514181


Altmetrics provided by Altmetric