a b s t r a c tThe recovery of Zn(II) ions from chloride and sulfate solutions by the transport of a binary Zn(II)-Ni(II) and a quaternary Zn(II)-Cd(II)-Ni(II)-Pb(II) mixture ions through polymer inclusion membranes (PIMs) doped with 1-octyl-4-methylimidazole as an ion carrier was studied (c M(II) = 0.001 M; pH 6.0). The membranes were also used for the separation of metal ions from galvanic tailings. After 24 h, the separation efficiency of the ions from the tailings was higher than 95%, whereas that from the model chloride and sulfate solutions were 96% and 83%, respectively. The selectivity coefficients of Zn(II)/Ni(II) in the transport across PIMs doped with the imidazole derivative were higher for the o-nitrophenyloctyl ether (o-NPOE) than for the o-nitrophenylpentyl ether (o-NPPE) as plasticizers, due to an increased viscosity of the former. Membranes based on the o-NPOE plasticizer are characterized by higher porosity (23%) and lower roughness (7.7 nm), compared with those based on o-NPPE. Irrespective of the plasticizer used, the PIMs with 1-octyl-4-methylimidazole were characterized by high strengths and high thermal resistances (up to 200°C).

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The facilitated transport of Zn(II), Cd(II), Co(II), and Ni(II) ions from different aqueous chloride source phases (c Me = 0.001 mol/dm 3 , pH = 6.0) across supported (SLMs) and polymer inclusion membranes (PIMs) doped with 1-decyl-4-methylimidazole as ion carrier was reported. The membrane is characterized by means of atomic force microscopy (AFM). The results show that Zn(II) can be separated very effectively from other transition metal cations as Cd(II), Co(II), and Ni(II) from different equimolar mixtures of such ions. The higher initial fluxes for Zn(II) were found for PIM (3.62-4.10 µmol/m 2 .s), while the lower values were observed for SLM. However, after taking into account the morphology (porosity, tortuosity) of the membranes, the values of the initial flux of Zn(II) transport across the PIM are lower than those across the SLM. The recovery factor of Zn(II) ions during transport across PIM and SLM from different mixtures of cations is above 95% after 24 hrs. PIM containing 1-decyl-4-methylimidazole are stable for 120 hrs.Keywords polymer inclusion membrane (PIM); supported liquid membrane (SLM); separation of metal ions; imidazole derivatives INTRODUCTIONSupported liquid membranes (SLM) and polymer inclusion membranes (PIM) represent an attractive liquid-to-liquid extraction for the selective removal and concentration of nonferrous metal ions (Zn(II), Co(II), Ni(II), Cd(II), Cu(II), and Pb(II)) from aqueous solutions. The transport of such metal ions across SLM and PIM can be described as the simultaneous extraction and back-extraction operations combined in