Solvent Extraction of Yttrium by Task-specific Ionic Liquids Bearing Carboxylic Group

A new kind of hydrophobic ionic liquids [1-alkyl-3-(1-carboxylpropyl)im][PF6] has been synthesized, and their extraction properties for Y(III) in the nitric acid medium was also investigated. The effects of extractant concentration, equilibrium pH of aqueous phase, salt concentration, temperature etc. were discussed. The results show that this kind of Task-Specific Ionic Liquid (TSIL) needs to be saponified before being used for the Y(III) extraction, and the extraction is acid dependent, and the extraction efficiency increases with the aqueous phase acidity decreasing. Furthermore, the loaded organic phase is easy to be stripped; more than 95% Y(III) could be stripped from the loaded organic phase when the stripping acidity is higher than 0.07 mol·L−1. The slope analysis technique is used to investigate the extraction mechanism, and a possible cation-exchange extraction mechanism is proposed in the present extraction system.