The mechanisms of copper(II) solvent extraction by Cyanex 272, Cyanex 302 and Cyanex 301 are discussed. Extraction from sulfate media is strongly dependant upon sulfur substitution in the phosphinic acid and complete extraction of copper by Cyanex 302 and Cyanex 301 occurs below pH 0. Since conventional slope analysis is not possible under these conditions, the complex stoichiometries and geometries are inferred from analysis of the electronic, 31P-NMR and FAB-MS spectra of the complexed species. Cu(II) is reduced to Cu(I) on extraction by the sulfur-containing ligands, accompanied by the corresponding oxidation of the extractant. It is shown that copper combines in a 1:1 stoichiometric ratio with these ligands to form multinuclear oligomeric complexes, in which the ligands bridge between metal centers. The enhanced stabilities of the complexes formed with the sulfur-containing ligands are explained in terms of the Hard-Soft Acid-Base concept and pi bonding between the d orbitals of the metal center and the donor atoms.
ASJC Scopus subject areas
- Industrial and Manufacturing Engineering
- Metals and Alloys
- Materials Chemistry