Solvent extraction chemistry in ionic liquids: An overview of f-ions

Undoubtedly, ionic liquids (ILs) belong to the most investigated solvent systems in the last two decades not only in the field of liquid-liquid extraction and separation chemistry of metallic species. Nowadays, the academic research interest is still significantly growing with an increased focus on developing such "smart" reagents for very specific applications. Interesting from the research point of view are solvent extraction systems capable of discriminating between metal ions from within, or between 4f and 5f elements that will be reviewed and discussed herein including the design of new ionic liquid compounds. Most of the investigations have been done for the first time suggesting novel, unfamiliar cutting-edge research investigating ideas. This paper reviews previous literatures and our recent results adopting ILs in metal liquid-liquid extraction systems until the end of year 2020 with an emphasis on the synergistic effect, where possible, and task-specific ILs together with some accidentally established enhancements. Finally, a critical analysis on the lanthanoids intra-group selectivity versus the extraction performance in an ionic medium and, on the other hand, the nature of the water-immiscible ionic diluents used have also been carried out and is here presented, and critically addressed. (C) 2021 Elsevier B.V. All rights reserved.