Regeneration of the ionic liquid tetraoctylammonium oleate after metal extraction

Abstract

Ionic liquids (ILs) have been presented as suitable candidates for metal extraction in the hydrometallurgy. It has already been proven that they have an adjustable selectivity towards metal ions. However, industrial applications of ILs are often limited due to their high price. Therefore, regeneration and reuse of ILs is necessary. In this study the regeneration of the fatty acid based IL tetraoctylammonium oleate was investigated, because in previous study excellent metal salt extraction efficiencies were obtained with this benign IL. Two methods for regeneration were investigated, i.e. electro-deposition and chemical regeneration. Electro-deposition turned out to be unfeasible for this IL. Chemical regeneration showed that the metal ions (Zn, Co and Mn) can be selectively back-extracted, so that metals can also be separated from each other in this step. The best stripping solution was aqueous sodium oxalate, which allowed the IL to be reused with no further treatment.