Application of polymer inclusion membranes doped with 1-hexyl-4-methylimidazole for pertraction of zinc(II) and other transition metal ions

Transport of Zn(II) from unary aqueous chloride solutions and from solutions which contain mixtures of Cd(II), Co(II) and Ni(II) ions in source phases (cMe = 0.001 mol/dm3, pH = 6.0) across polymer inclusion membranes (PIMs) doped with 1-hexyl-4-methylimidazole as ion carrier was studied. The use of 1-hexyl-4-methylimidazole enables the separation of 98.5% Zn(II) from a unary solution and 96.9% from a quaternary solution of Zn(II)-Cd(II)-Co(II)-Ni(II) after running the process for 24 hours. Using that ion carrier, the metals are transported in the following order: Zn(II) > Cd(II) > Ni(II) > Co(II), and the selectivity coefficients of Zn(II)/Cd(II), Zn(II)/Ni(II), and Zn(II)/Co(II) are 12.9, 23.4 and 40.8, respectively. Findings of atomic force microscopy (AFM) examinations as well as thermograms of a polymer inclusion membrane containing 1-hexyl-4-methylimidazole are also presented. A membrane with 1.0 mol/dm3 of carrier has a porosity of 15.8%, and roughness of 6.6 nm. The membranes remain thermally stable at temperatures up to 200oC. The findings were compared with earlier-reported results for 1-hexylimidazole.