Hydration forces between mica surfaces in electrolyte solutions

✍ Scribed by R.M. Pashley

• Publisher: Elsevier Science
• Year: 1982
• Tongue: English
• Weight: 343 KB
• Volume: 16
• Category: Article
• ISSN: 0001-8686
• DOI: 10.1016/0001-8686(82)85006-9

✦ Synopsis

The forces between two molecularly smooth mica surfaces were measured over a range of concentrations in aqueous Li -+, Na+, Kf and Cs* chloride solutions. Deviations from DLVO forces in the form of additional short-range repulsive "hydration" forces were observed only above some critical bulk concentration, which was different for each electrolyte_ These observations are internreted in terms of the corresponding ion exchange oroperties at the mica surface. "Hydration" forces apparently arise when hydrated cations adsorbed on mica are prevented from desorbing as two interacting surfaces approach-Dehydration of the cations leads to a repulsive hydration force. A simple site-binding model was successfully applied to describe the charging behavior of interacting mica surfaces_ By subtraction of the DLVOregulation theory frcm the total measured force the net hydration force was obtained for mica surfaces apparently fully covered with adsorbed cations. The magnitude of this extra force followed the series Naf> Li c >Kf> cs + and,in each case, could be described by a double-exoonential decay.

-_ II.