Specific Ion Effects and Adsorption and Desorption at Liquid Surfaces

The adsorption or desorption at liquid surfaces is described by the Gibbs equation and derived from surface tension data. This thermodynamic concept, however, only allows for deriving the overall surface excess and is rather limited for determining the position of solutes relative to the outermost layer. Directly measuring concentration depth profiles provides this information. Concepts able to predict the adsorption of ions at liquids surfaces are so far only partially successful and seem to show that the mechanisms causing adsorption or desorption of ions at liquid surfaces are not yet understood.In this presentation a comprehensive study of the concentration depth profiles of ions of monovalent salts at the surface of various solvents will be shown. The results will be discussed in the context of the currently existing concepts prediction ions specific effects at liquid surfaces.