Selective Emulsion Liquid Membrane Extraction of Cu(II) Mediated by a Schiff Base Ligand

This study concerns the application of a Schiff base ligand of type N3O2 as a carrier in a water-in-oil emulsion liquid membrane for the selective transport of copper ions. A hydrochloric acid solution formed the internal aqueous phase (receiving phase), and the membrane was composed of a Schiff base ligand called bis(1'-hydroxy-2'-acetonaphthone)-2,2'-diiminodiethylamine (L) in dichloromethane and the non-ionic surfactant Span® 80 in paraffin. By applying the optimum conditions, a quantitative uptake of copper ions (initial concentration 5 mg/L) from the aqueous feed phase (pH 5) into the receiving phase (hydrochloric acid 0.7 mol/L), after 10 min was attained. The optimal value determined for the treat ratio allows achieving a concentration factor of >6 for the copper ions in the receiving phase. The proposed emulsion liquid membrane provided an excellent selectivity towards copper ions with respect to some associated metal ions including Cd(II), Ni(II), Zn(II), Co(II), Fe(II), and Cr(III). However, such selectivity was not observed in the competition of Cd(II) and Pb(II) ions. The breakage of emulsions and recovery of the internal phase from the membrane was performed by freezing the internal solution. The expansion of the frozen internal phase volume results in the breakage of the emulsions. The applicability of the proposed procedure was appraised by employing the method for the recovery of copper from the leached solutions of the cobalt and nickel-cadmium filter cakes of a zinc production plant.