Surface Charge Density and Sorption of Water Vapour on Lithium Kaolinite

Abstract

KEENAN et al.¹ in an examination of adsorption of water vapour on several monoionic derivatives of kaolinite from Bath, South Carolina (Peerless No. 2, Vanderbilt Co., New York), found that—hysteresis being absent for all samples—lithium kaolinite showed the lowest water adsorption at any relative vapour pressure. Prior to the adsorption measurements (at 20° C), the samples were degassed under high vacuum at 70° C. Expressing the amount of water adsorbed per unit surface, these authors found identical values at any relative pressure for two samples of lithium kaolinite with different granulometric composition. They concluded that the adsorbed lithium ions have no effect on adsorption of water, and attributed this behaviour to the small ionic size of lithium, which permits the unhydrated ion to fit into the surface structure or to penetrate in the vacant octahedrally co-ordinated sites, thus becoming sterically hindered from interaction with water vapour.