Solvent extraction by selective ion solvation

Extraction reactions are identified, in which the main step is the replacement of the water that hydrates the ions in the aqueous phase by a solvation shell provided by the water-immiscible solvent. The change in solvation is measured by the standard molar Gibbs free energy of trans fer of the ion, which is related in a definite manner to certain properties of the solvent and of the ion and to the composition of the solvent, if it contains much water. Enthalpy or entropy changes may predominately control the transfer. These concepts are illustrated by the extraction of the halide anions into substituted phenols, of lithium, magnesium, and aluminium halides into (hydrous) 1-hexanol, and of dioxouranium (VI) and thorium or plutonium (IV) nitrates into neutral phosphoryl-group-containing solvents.