Removal of copper ions by micelle-based separation processes. Electrochemical behavior of copper ions trapped in micellar particles

Micellar-based separation processes have been shown in the past few years to be especially attractive for the removal of metal ions from dilute aqueous solutions, when micellar extraction is combined with ultrafiltration. In the present paper we consider two ways of removing copper ions from micellar processes: the first is based on ion-exchange (anionic SDS micelles), the second on metal ion complexation by a micelle-solubilized extractant (CTAB/butanol/water/Kelex 100 microemulsions). The influence of the relative concentrations of the species involved and of the pH on the yield of extraction is investigated, and in the first case the results are compared with a theoretical prediction. In a second part we compare for the first time the electrochemical behavior of copper ions whether they are simply bound to the micelle surface or more deeply imbedded in the core of a microemulsion as a hydrophobic complex. The electroreduction of the copper ions is easily obtained when the metal ions are simply bound to the micellar surface, offering a way of recycling the micellar phase after the metal ions have been removed, The situation is more complicated when the copper ions form stable complexes solubilized in microemulsions, since the electroreduction is possible only once the complex has been destroyed in acidic media.