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A microstructural study of acid-activated montmorillonite from Choushan, China

Published online by Cambridge University Press:  09 July 2018

Hongping He*
Affiliation:
Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, WushanGuangzhou, 510640
Jiugao Guo
Affiliation:
Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, WushanGuangzhou, 510640
Xiande Xie
Affiliation:
Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, WushanGuangzhou, 510640
Hongfu Lin
Affiliation:
Zhejiang Foreign Trade Company for Industrial Minerals, Hangzhou 310000
Liyun Li
Affiliation:
Laboratory of Magnetic Resonance and Atom and Molecular Physics, Wuhan Institute of Physics, Chinese Academy of Sciences, Wuhan 430071, P. R. China
*

Abstract

Bentonite samples from Choushan treated at various acid concentrations were studied using chemical analysis, XRD, 29Si and 27Al MAS NMR to investigate the microstructure of the activated montmorillonites. Two types of structural units were formed during the activation: (1) (SiO)3SiOH, in which up to 15% of Si is bound; (2) Q4(0Al), a major building unit when the acid concentration is >10%. A significant 27Al signal at 55.0 ppm was recorded for both untreated montmorillonite and (to a much greater extent) in acid-treated montmorillonites. This was interpreted as arising from four-fold coordinated Al located in the ‘bulk’ octahedral sheet of montmorillonite. In the course of activation, the removal of one of a pair of octahedral Al ions from montmorillonite removes two hydroxyl groups and leaves the other Al of the pair in four-fold coordination.

Type
Research Article
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 2002

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