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Structural Hydroxyls in Sepiolites

Published online by Cambridge University Press:  01 July 2024

J. L. Ahlrichs ,
C. Serna  and
J. M. Serratosa
J. L. Ahlrichs*
Affiliation:
Consejo Superior de Investigationes Cientificas, Madrid, Spain
C. Serna
Affiliation:
Consejo Superior de Investigationes Cientificas, Madrid, Spain
J. M. Serratosa
Affiliation:
Consejo Superior de Investigationes Cientificas, Madrid, Spain
*
*Visiting scientist from the Department of Agronomy, Purdue University, West Lafayette, Indiana 47907, U.S.A.
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Abstract

Three sepiolite clays studied showed evidence for the presence of structural hydroxyl groups in three to five different environments depending on the composition of the clay. A 3720 cm−1 i.r. frequency is shown to be characteristic of SiOH at crystal edges which are very abundant in sepiolites. This band has not been seen by most workers because the Nujol, fluorolube or KBr used in sample preparation perturb it sufficiently to obscure it under other OH stretching bands. The 3680 cm−1 band is confirmed as being from the (Mg)3OH and evidence of a very small band near 3640 cm−1 is suggested to arise from limited trioctahedral substitution. The very crystalline Ampandrandava sepiolite shows only the above three bands. The intermediately crystalline Vallecas shows a 3620 cm−1 band in addition which is characteristic of dioctahedral systems and is due to either some vacancy sites or to the presence of attapulgite. This dioctahedral band is greater in the less crystalline Salinelles sepiolite; in addition, it has a smaller 3585 cm−1 band. Mg-Al-vacancy and Mg-Fe‴-vacancy are suggested as the source of the 3620 cm−1 and 3585 cm−1 bands.

Type
Research Article
Information
Clays and Clay Minerals , Volume 23 , Issue 2 , April 1975 , pp. 119 - 124
Copyright
Copyright © 1975, The Clay Minerals Society

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