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EPR of VO2+ ions in Al-pillared montmorillonite

Published online by Cambridge University Press:  09 July 2018

O. Braddell ,
R. C. Barklie  and
D. H. Doff
O. Braddell
Affiliation:
Physics Department, Trinity College, Dublin 2, Ireland
R. C. Barklie
Affiliation:
Physics Department, Trinity College, Dublin 2, Ireland
D. H. Doff
Affiliation:
Geology Department, Trinity College, Dublin 2, Ireland
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Abstract

A pillared smectite clay has been formed by treating Na-montmorillonite with a hydroxy-aluminium solution with an OH/Al ratio of two. Heating the pillared clay for four h at 500°C reduces the interlayer spacing, measured at ambient humidity, from ∼ 9·4 to 8·0 Å. Hydrated VO2+ (and Mg2+) ions have been introduced into the region between the pillars by immersing the pillared clay in VOSO4-MgCl2 solutions and EPR measurements show that in general both immobile and mobile VO2+ ions are present. The immobile ion is probably VO2+(OH)x(H2O)5·x where x = 2–4, and is adsorbed on the pillars with a concentration that saturates at about 1 per 8 Al13 pillars in the unfired clay, and 1 per 4·3 pillars in the fired clay. The mobile species is VO2+(H2O)5 and for both fired and unfired clay in the wet state at room temperature it has a rotational correlation time of (9 ± 1) × 10−11s rad−1.

Type
Research Article
Information
Clay Minerals , Volume 25 , Issue 1 , March 1990 , pp. 15 - 25
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1990

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