SYNERGISTIC EXTRACTION OF CADMIUM AND ZINC FROM NITRATE MEDIUM WITH 3-PHENYL-4-BENZOYLISOXAZOL-5-ONE IN THE PRESENCE OF METHYL-TRI-N-OCTYLAMMONIUM NITRATE IN CHLOROFORM AND TOLUENE

The synergistic extraction of cadmium and zinc, from 1M NaNO3 aqueous solutions, with the acidic chelating extractant 3-phenyl-4-benzoylisox azol-5-one (HPBI), in the presence of the nitrate salt of aliquat 336 (methyl-tri-n-octylammonium nitrate named TOMA . NO3), has been studie d in chloroform and toluene. The extracted species are TOMA.M(PBI)(3) with M = Cd, Zn. The synergistic extraction is described by the follow ing equilibria : M-aq(2+) + 2 HPBIorg + TOMA.PBIorg (K121) reversible arrow TOMA.M(PBI)(3,org) + 2 H-aq(+) with logK(121) = 2.62 (Cd), 4.16 (Zn) in chloroform and 4.26 (Cd), 5.54 (Zn) in toluene and HPBIorg + T OMA.NO3,org (Kexc) reversible arrow TOMA.PBIorg + H-aq(+) + NO3aq- wit h logK(exc) = -0.41 (chloroform) and 0.48 (toluene). The difference ob served between toluene and chloroform is mainly due to the higher dist ribution constant of HPBI in chloroform (logK(d) = 3.0) than in toluen e (logK(d) = 2.3). The Zn extraction is more enhanced by TOMA.NO3 than the Cd one, contrary to what is observed in the synergistic extractio n using 1-phenyl-3-methyl-4-benzoylpyrazol-5-one (HPMBP).