Solvent extraction of lanthanides and yttrium from aqueous solution with methylimidazole in an ionic liquid

Abstract

1-Methylimidazole (1-MIM) and 2-methylimidazole (2-MIM) are miscible in water and imidazolium based ionic liquids (ILs), and can coordinate with soft metal ions. This paper reports a novel solvent extraction process for trivalent lanthanides and yttrium from aqueous solutions into ILs, which was promoted by a hydrophilic 1-MIM or 2-MIM. Slope analysis confirmed that MIM in ILs formed a 1 : 1 complex with La(3+) and Y(3+) and a 1 : 4 complex with Eu(3+) and Lu(3+), depending on the atomic number of the metal and the metal-ligand interactions that have been characterized by FTIR spectroscopy and ESI-MS. The effect of nitrate concentration on the extraction of lanthanides with 1-MIM in ILs was analysed. It indicated that nitrate anions were involved in the extraction process. Under the same conditions, the extraction of lanthanides with MIM into n-pentanol was carried out. The extractability was by far lower than that obtained in ILs. Both cationic exchange and neutral solvation mechanisms occurred in ILs and only the neutral solvation mechanism occurred in n-pentanol, which were demonstrated by the extraction tests and the structure of extracted species determined by ESI-MS. The competitive extraction in ILs showed good selectivity for lanthanides compared to alkali metals and alkaline earth cations. After extraction, lanthanides could be stripped very easily from the ionic liquid phase with dilute nitric acid. From the temperature dependence data, the thermodynamic parameter values (ΔH, ΔS and ΔG) were calculated. The results indicated that the extraction reactions were spontaneous and went through an endothermic process.

Characterization and Leaching of Neodymium Magnet Waste and Solvent Extraction of the Rare-Earth Elements Using TODGA

“…These have been widely utilized in industry for the solvent extraction separation of REEs [6]. The extracting agents mentioned have some disadvantages, such as poor selectivity, poor stripping of the metals from the organic phase, and a low rate of extraction.…”

Separating Rare-Earth Elements with Ionic Liquids

“…This was the first time the performance and mechanism of this extraction process have been reported [115]. This characterization entailed the investigation of several experimental parameters, such as (1) the nature of the IL, (2) the nature of the extractant, (3) contact time, (4) aqueous phase pH, and (5) effects of extractant concentration on the extraction behavior of metal ions [115]. Additionally, in order to compare the partitioning behavior of REEs in ILs, the extraction of La 3+ , Eu…”

“…Moreover, the imidazole structure, consisting of a five-membered heterocyclic ring with two N atoms, is amenable to selective coordinate to soft metal cations, such as REEs and Y [112][113][114][115][116]. In light of these advantageous qualities, we employed imidazole and its derivatives, 1-methylimidazole (1-MIM) and 2-methylimidazole (2-MIM), in REEs and Y extraction from an aqueous phase into imidazolium-based ILs [115]. This was the first time the performance and mechanism of this extraction process have been reported [115].…”

“…In light of these advantageous qualities, we employed imidazole and its derivatives, 1-methylimidazole (1-MIM) and 2-methylimidazole (2-MIM), in REEs and Y extraction from an aqueous phase into imidazolium-based ILs [115]. This was the first time the performance and mechanism of this extraction process have been reported [115]. This characterization entailed the investigation of several experimental parameters, such as (1) the nature of the IL, (2) the nature of the extractant, (3) contact time, (4) aqueous phase pH, and (5) effects of extractant concentration on the extraction behavior of metal ions [115].…”

Using Crystal Structures of Ionic Compounds to Explore Complexation and Extraction of Rare Earth Elements in Ionic Liquids

“…As extractants, N-heterocycles such as bis(triazine) pincer ligands are an important class of extractants in actinidelanthanide separations [57]. 1-and 2-methylimidazole have also been studied as extractants for lanthanides into ILs and show promise for intra-group separations [58].…”