INTERFACIAL PHASE-TRANSFER OF AMINO-COMPLEXED NI(II) CATIONS - A MODEL FOR SOLVENT-EXTRACTION OF TRANSITION-METALS

The Gibbs energy of interfacial transfer of Ni(II) complexed with some selected substituted ethylenediamines which differ in hydrophobicity, is measured voltammetrically and compared with the corresponding Gibbs energy of transfer of Ni(II) complexed with aromatic diazines. In the case of the ethylenediamino and alkyl ethylenediamino complexes, there exists clear evidence that the fast formation of the tris complexes in the reaction layer of both phases enhances the extraction of Ni(II) into the organic phase. The transfer of the protonated and unprotonated diamines is also studied. The collected thermodynamic data allow the calculation of the stability constants of the complexes in the organic phase which are higher by five orders of magnitude than in the aqueous phase. This kinetic and thermodynamic effect would strongly facilitate the solvent extraction of transition metals under technical conditions. © 1990.