SYNERGISTIC EXTRACTION OF NICKEL BY LIQUID SURFACTANT MEMBRANES

Synergistic extraction of NI(II) by a mixture of the active component in the commercial extractant LIX63, 5,8-dimethyl-7-hydroxydodecane-6-o xime, and di-oleylphosphoric acid (DOLPA) has been investigated by liq uid surfactant membranes (LSMs) containing a commercial surfactant, Sp an 80. Solvent extraction of Ni(II) with the mixture of LIX63 and an o rdinary extractant, di(2-ethylhexyl)-phosphoric acid (D2EHPA) was carr ied out. The results show that the LIX63-DOLPA mixture has a high syne rgistic effect on the extraction of Ni(II) in the LSM system compared with the LIX63-D2EHPA mixture. The synergistic effect of the LIX63-DOL PA mixture is attributed to a mixed ligand complex formation with the stoichiometry of Ni2+/LIX63/DOLPA = 1/2/2. Besides extractant synergis m, the effects of several operation factors in the LSMs were investiga ted: permeation of Ni(II), pH of external aqueous phase, and concentra tions of extractant and surfactant. The permeation mechanism of Ni(II) in LSMs has been elucidated by using the interfacial reaction model w hich takes into account the complex formation at the interface.