Selective adsorption of metal cations onto AOT and dodecyl sulfate films at the air/solution interface

Abstract

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.