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On the mechanisms of apophyllite alteration in aqueous solutions; a combined AFM, XPS and MAS NMR study

Kirill Aldushin, Guntram Jordan, Michael Fechtelkord, Wolfgang W. Schmahl, Hans-Werner Becker and Werner Rammensee
On the mechanisms of apophyllite alteration in aqueous solutions; a combined AFM, XPS and MAS NMR study
Clays and Clay Minerals (August 2004) 52 (4): 432-442

Abstract

Apophyllite, a hydrous K-Ca-phyllosilicate, reacts with acidic aqueous solutions at room temperature. Various analytical methods have been applied to study the mechanism of the reaction and its characteristics, i.e. the changes in chemical composition, modifications in crystal structure and alterations in surface morphology. In contact with acidic solution, protonation of the terminal, non-bridging oxygen at the silicate tetrahedra takes place and the interlayer cations K (super +) and Ca (super 2+) are removed. The protonation and ion removal causes the interlayer spacing to increase. Atomic force microscopy shows that the increase takes place discontinuously and, therefore, reflects a discontinuous reaction that comprises a two-or three-step protonation. Additionally, three structurally different protonation sites have been detected by nuclear magnetic resonance spectroscopy which also differ in the amount of close-by hydrogen, although in pristine apophyllite all terminal oxygen positions at silicate tetrahedra are structurally equivalent. In many clay minerals such structurally different protonation sites have not been detected so far. Thus, the multistep protonation process in apophyllite clearly demonstrates the vast sensitivity of the protonation reaction on small structural variations in phyllosilicates.


ISSN: 0009-8604
EISSN: 1552-8367
Coden: CLCMAB
Serial Title: Clays and Clay Minerals
Serial Volume: 52
Serial Issue: 4
Title: On the mechanisms of apophyllite alteration in aqueous solutions; a combined AFM, XPS and MAS NMR study
Affiliation: Ruhr-Universitaet Bochum, Institute fuer Geologie, Mineralogie und Geophysik, Bochum, Federal Republic of Germany
Pages: 432-442
Published: 200408
Text Language: English
Publisher: Clay Minerals Society, Clarkson, NY, United States
References: 41
Accession Number: 2005-000638
Categories: Mineralogy of silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 1 table
Secondary Affiliation: Universitaet zu Koeln, DEU, Federal Republic of Germany
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute.
Update Code: 200501
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