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Surface and intercalate chemistry of the layered silicates. Part VI. Tetrahydrofuran intercalates of a series of cation-exchanged montmorillonites
Journal article

Surface and intercalate chemistry of the layered silicates. Part VI. Tetrahydrofuran intercalates of a series of cation-exchanged montmorillonites

John M Adams, John M Thomas and Michael J Walters
Dalton Transactions, (2), pp 112-115
1976

Abstract

Intercalates of tetrahydrofuran (THF) with nine distinct cation-exchanged montmorillonites have been prepared and may be divided into two classes depending upon the magnitude of the basal spacing, d 001 . In one class (with NH 4 + , Na + , Co 2+ , Ni 2+ , and Cu 2+ ) d 001 lies close to 14.6 Å; in the other (with Ca 2+ , Sr 2+ and Ba 2+ ) the spacing is close to 19.0 Å, while Li + -exchanged montmorillonites are capable of forming both types of intercalate. The orientation and position of the organic molecules for six of the intercalates (NH 4 + , Na + , Co 2+ , Ni 2+ , Cu 2+ , and Sr 2+ ) have been determined form one-dimensional electron density maps constructed from the results of X -ray diffraction measurements. The lower-spacing intercalates have one layer of organic molecules in the interlamellar region with the THF perpendicular to the sheets. The number of THF molecules per formula unit [idealised, Al 4 Si 8 O 20 (OH) 4 ] ranges from 1.3 (NH 4 + ) to 2.3 (Ni 2+ ), the corresponding figures per exchanged cation being 2.6 (NH 4 + ) to 9.4 (Ni 2+ ). The higher spacing intercalates have a double layer of THF molecules inclined at ca . 55° to the sheets. There are, for example, 4.8 molecules per formula unit of the Sr 2+ -exchanged clay. Electron spectroscopy demonstrates that the copper-exchanged clay and intercalate change from Cu 2+ to Cu + under the influence of the incident, low energy, X -rays.

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