Investigation On The Extraction Of Lanthanides And Actinides With Methylimidazole And Derivatives

A novel solvent extraction process to trivalent lanthanides, actinides and yttrium from aqueous solutions into ionic liquids (ILs) or organic solvent was studied in this thesis, that was promoted by hydrophilic methylimidazole (MIM) and derivatives which are miscible in water and imidazolium based ILs and can coordinate with soft metal ions. Under the same conditions, the extraction of lanthanides and actinides with MIM into ILs and n-pentanol were both carried out, and related experimental results revealed the extractability of MIM in n-pentanol was by far lower than that obtained in ILs. The effect of nitrate concentration on the extraction of lanthanides or actinides with MIM was carried out and the results indicated that nitrate anions were involved in extraction process. Slope analysis confirmed that MIM in ILs formed 1:1 complexes with La3+, Y3+and UO22+, and 1: 4 complexes with Eu3+, Lu3+and Th4+. The complexes were characterized by FTIR spectroscopy and ESI-MS, and the results revealed both a cationic exchange and neutral solvation mechanism occurred in ILs and only a neutral solvation mechanism occurred in n-pentanol. The competitive extraction showed good selectivity for lanthanides and actinides compared to alkali metals and alkaline earth cations, and it also showed good selectivity for Th4+compared to lanthanides (Ⅲ) and UO22+. After extraction, lanthanides and actinides can be stripped very easily from the ionic liquid phase with dilute nitric acid. From the temperature dependence data, the thermodynamic parameters values (△H, AS and AG) were calculated, and the results indicated the extraction reactions are spontaneous and go through endothermic process.In view of the disadvantages of MIM just as unrepeatability and weak extractability under high acid, we synthesized a type of solid-phase extraction agent by means of chemical modification of 2-methyl-2-oxazoline which has the same extraction mechanism with MIM. The solid-phase extraction agent can effectively overcome the disadvantages of MIM and has a great significance in the extraction of lanthanides and actinides.