On the selective separation of metal ions from hydrochloride aqueous solution by pertraction through supported ionic liquid membranes

Previously, we reported the use of imidazolium and ammonium based ionic liquids in the absence of chelating agents for the selective liquid-liquid extraction of Zn(II), Cd(II), Cu(II), and Fe(III) from hydrochloride aqueous solutions. It was found that the ionic liquid methyltrioctylammonium chloride, [MTOA+][Cl−], allowed the almost complete removal of Zn(II), Cd(II), Fe(III) and Cu(II) from the aqueous solutions. In this work, supported ionic liquid membranes based on methyltrioctylammonium chloride were used in an pertraction process for the selective extraction of Fe(III), Zn(II), Cd(II) and Cu(II). The influence of the composition of the receiving phase (milliQ water or Na2CO3, 0.1 M; or NH3,6 M) in the pertraction process was analyzed. It was found that Milli-Q water and Na2CO3 allowed the recovery of Zn(II), Fe(III), reaching pertraction factors (PFs), defined as the ratio between the concentration of the target metal ion in the receiving and the feed phase, of up to 373 for Zn(II), using Na2CO3 as receiving phase at 48 h and 9 for Fe(III), using Milli-Q water at 31 h. The use of NH3 (6 M) allowed the recovery of Cd(II), with a PF of 15.1 at 24 h. Therefore, by modifying the stripping composition, the selective separation of the target metal ions can be reached. It is worthy to highlight the remarkable stability of the obtained supported ionic liquid membranes.