Charge heterogeneity in smectites

A - Papers appearing in refereed journals

Talibudeen, O. and Goulding, K. W. T. 1983. Charge heterogeneity in smectites. Clays and Clay Minerals. 31 (1), pp. 37-42.

AuthorsTalibudeen, O. and Goulding, K. W. T.
Abstract

The heterogeneity of sites for Ca>K exchange was examined by microcalorimetry in the <0.2-/zm fractions of some selected smectites. Six groups of sites, ranging in exothermic exchange enthalpy (-d(AHx)/dx) from 5.7 to 10.9 kJ/eq were identified. In Wyoming bentonites, only three groups with enthalpies of 5.7 to 7.5 kJ/eq were distinguished, although in the 0.2-1.0-p~m fraction, a 10.7-kJ/eq group was also observed. Redhill and Camp Berteau smectites contained, in addition, groups with enthalpies of 8.7-10.9 kJ/eq, but a New Mexico sample only had groups with the higher values. Thus, the exchange enthalpies of four main groups of sites (reclassified from those observed) appear to be inversely related to the extents of interlayer expansion in the samples by the adsorption of polar molecules. Consequently, a 'true montmorillonite,' such as a <0.2-/~m Wyoming bentonite, contains only fully expanding layers with -d(AHx)/dx values between 5.7 and 7.5 kJ/eq. As such, it is less heterogeneous and should have a much greater swelling capability than Camp Berteau montmorillonite which has, in addition, groups with exchange enthalpies of 8.7 and 10.3 kJ/eq.

KeywordsCation exchange; Enthalpy; Smectite; Surface charge; Swelling
Year of Publication1983
JournalClays and Clay Minerals
Journal citation31 (1), pp. 37-42
Digital Object Identifier (DOI)doi:10.1346/ccmn.1983.0310106
Web address (URL)http://www.clays.org/journal/archive/volume%2031/31-1-37.pdf
Open accessPublished as bronze (free) open access
Publisher's version
Output statusPublished
Publication dates
Print1982
Publication process dates
Accepted31 Jan 1982
Copyright licensePublisher copyright
ISSN0009-8604
PublisherClay Minerals Society

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