A novel mechanism for the extraction of metals from water to ionic liquids

We present a novel mechanism for the extraction of metals from aqueous phases to room-temperature ionic liquids (ILs) by use of a high-temperature salt as an extraction agent. The mechanism capitalizes on the fact that charged metal complexes are soluble in ILs; this allows for extraction of charged complexes rather than the neutral species, which are formed by conventional approaches. The use of a well-chosen extraction agent also suppresses the competing ion-exchange mechanism, thus preventing degradation of the ionic liquid. The approach permits the use of excess extractant to drive the recovery of metals in high yield. This work presents both a thermodynamic framework for understanding the approach and experimental verification of the process in a range of different ILs. The method has great potential value in the recovery of metals, water purification and nuclear materials processing. Out of phase: A novel mechanism for the extraction of charged metal complexes from aqueous phases to ionic liquids is presented (see picture). The thermodynamics of the reaction are explored, and it is shown that the use of a suitable co-extraction agent can suppress the competing ion-exchange process. This method serves to drive the recovery of metals in high yield under relatively mild conditions.