Fast selective homogeneous extraction of UO with carboxyl-functionalised task-specific ionic liquids.

The carboxyl-functionalised task-specific ionic liquid of 1-carboxymethyl-3-methylimidazolium bis(trifluoromethyl-sulfonyl)imide ([HOOCmim][NTf]) was used as solvent and extractant for UO extraction from aqueous solution. A homogeneous phase of [HOOCmim][NTf]-HO system could be achieved at 75 °C, and 86.8 ± 4.8% of UO was separated from the aqueous solution after vibrating for only 1 min. Furthermore, nearly 97.3 ± 2.9% of UO was stripped from [HOOCmim][NTf] phase by 1 M HNO solution. K, Na, Mg, Dy, La, and Eu have little influence on the homogeneous extraction of UO, and the extraction efficiency of UO still remained at ca. 80%. Experimental and theoretical study on the selectivity of [HOOCmim][NTf]-HO system were performed for the first time. Density functional theory calculation indicates that the solvent effect plays a significant role on the selectivity of [HOOCmim][NTf]-HO.