Integrated Leaching and Separation of Metals Using Mixtures of Organic Acids and Ionic Liquids.

In this work, the aqueous phase diagram for the mixture of the hydrophilic tributyltetradecyl phosphonium ([P]Cl) ionic liquid with acetic acid (CHCOOH) is determined, and the temperature dependency of the biphasic region established. Molecular dynamic simulations of the [P]Cl + CHCOOH + HO system indicate that the occurrence of a closed "type 0" biphasic regime is due to a "washing-out" phenomenon upon addition of water, resulting in solvophobic segregation of the [P]Cl. The solubility of various metal oxides in the anhydrous [P]Cl + CHCOOH system was determined, with the system presenting a good selectivity for CoO. Integration of the separation step was demonstrated through the addition of water, yielding a biphasic regime. Finally, the [P]Cl + CHCOOH system was applied to the treatment of real waste, NiMH battery black mass, being shown that it allows an efficient separation of Co(II) from Ni(II), Fe(III) and the lanthanides in a single leaching and separation step.