Jamie C. Schulz and Gregory G. Warr
The selective binding of alkali and alkaline earth metal cations to adsorbed films of sodium bis(2,2′)ethylhexylsulfosuccinate (AOT) and sodium dodecyl sulfate (SDS) at air/solution interfaces has been studied by ion flotation. The selectivity orders obtained for both anionic surfactant films are Li+<Na+<K+<Rb+<Cs+ and Mg2+<Ca2+<Sr2+<Ba2+, although differences in absolute selectivities were found for the two surfactants. Selectivity was found to be determined by slight dehydration of the adsorbing ions.