Chemistry of soil minerals. Part IV. Synthetic alkylammonium montmorillonites and hectorites

Abstract

The syntheses of nitrogenous aluminosilicates of montmorillonite, mica, and zeolite groups first made in 1961 have been extended. Aluminosilicate and gallosilicate montmorillonites have been prepared above 200° in the presence of larger organic ions than previously, such as tetraethyl-, tetrapropyl-, and tetrabutyl-ammonium. The partial hydrolysis of the organic ions under hydrothermal conditions has been measured in the products, and it has been shown that the content of interlayer organic ions is comparable with that of inorganic ions in natural montmorillonoids. On the other hand the organic ions tend to behave more like fixed K⁺ ions in their exchange properties.

It has further been possible at about 100° to synthesise alkylammonium hectorites with unhydrolysed, interlayer quaternary ammonium ions. The organic cations were present in amounts comparable with but quantitatively less than the exchangeable ion content of natural hectorites. In magnesium silicate hectorites the organic ions were difficult to exchange, as compared with these ions in natural hectorites and montmorillonites prepared by ion exchange from the natural clays. Except for tetramethylammonium hectorite the basal spacings of the synthetic species were less than for corresponding ion-exchanged forms of the natural species. The natural and synthetic organohectorites also differed in the extent to which they swelled in liquids such as acetonitrile. Some synthetic organohectorites, however, behaved like their ion-exchanged counterparts from the natural clay in forming higharea sorbents.