Abstract
An investigation of diluent effect in the extraction of metals was carried out by examining the equilibrium distribution of copper and nickel in hydroxyoxime as extractant, using n-heptane, xylene, nitrobenzene and several oxygen-containing polar solvents as diluents. From a comparison in the shift of the infra-red absorption band of oxime and the extraction constant for each diluent, the strength of the interaction between the oxime and diluent molecules resulting from hydrogen-bonding can be used as a measure of the diluent effect.
Progressive replacement of n-heptane by an oxygen-containing polar solvent causes the extraction performance to be sharply reduced, without changing the molecular form of the extracted species. The extent of this reduction can be accounted for by the formation of an intermolecular complex between the oxime and polar solvent molecules, and the equilibrium constants of these complexes are reported. Identical treatment and analysis have been carried out for the combinations of xylene and polar solvents, and for n-heptane and xylene.
