Fast selective homogeneous extraction of UO 2 2+ with carboxyl-functionalised task-specific ionic liquids.

The carboxyl-functionalised task-specific ionic liquid of 1-carboxymethyl-3-methylimidazolium bis(trifluoromethyl-sulfonyl)imide ([HOOCmim][NTf2 ]) was used as solvent and extractant for UO2 2+ extraction from aqueous solution. A homogeneous phase of [HOOCmim][NTf2 ]-H2 O system could be achieved at 75 °C, and 86.8 ± 4.8% of UO2 2+ was separated from the aqueous solution after vibrating for only 1 min. Furthermore, nearly 97.3 ± 2.9% of UO2 2+ was stripped from [HOOCmim][NTf2 ] phase by 1 M HNO3 solution. K+ , Na+ , Mg2+ , Dy3+ , La3+ , and Eu3+ have little influence on the homogeneous extraction of UO2 2+ , and the extraction efficiency of UO2 2+ still remained at ca. 80%. Experimental and theoretical study on the selectivity of [HOOCmim][NTf2 ]-H2 O 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][NTf2 ]-H2 O.