Thenoyltrifluoroacetone: Preferable Molecule for Solvent Extraction of Metals—Ancient Twists to New Approaches

A review of the investigations devoted to the solvent extraction processes of metal ions with a chelating ligand thenoyltrifluoroacetone (HTTA) is presented herein. It seems that this molecule has been preferred in the field for more than half a century, and that it is used very often as an extractant for almost all metals. The main objective of the present review is also to provide an overview of the synergistic solvent extraction of lanthanoids, particularly with the use of a β-diketone−neutral mixture. Based on the previous published results in the open literature, the extraction efficiency has been examined in detail and discussed further mainly in terms of the corresponding equilibrium constants among other outlined, so-important parameters. Major conclusions on the role of ligating groups of extractants towards the mechanism, an improved extraction enhancement, and selectivity are additionally provided. The fact that ionic liquids (ILs) appear to be replacing volatile diluents in the field of the liquid–liquid extraction of metals, again with the participation of this β-diketone, is not surprising. As is well known, a very efficient and simple way to determine the stoichiometry of the extracted species in the organic phase is by the simple use of the slope analysis method; however, it is sometimes difficult to perform, either because it somehow requests good solubility of the ligand or because obtained slopes are quite often far from integer values in ILs.