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][NTf(2)]) was used as solvent and extractant for UO(2)(2+) extraction from aqueous solution. A homogeneous phase of [HOOCmim][NTf(2)]-H(2)O system could be achieved at 75 °C, and 86.8 ± 4.8% of UO(2)(2+) was separated from the aqueous solution after vibrating for only 1 min. Furthermore, nearly 97.3 ± 2.9% of UO(2)(2+) was stripped from [HOOCmim][NTf(2)] phase by 1 M HNO(3) solution. K(+), Na(+), Mg(2+), Dy(3+), La(3+), and Eu(3+) have little influence on the homogeneous extraction of UO(2)(2+), and the extraction efficiency of UO(2)(2+) still remained at ca. 80%. Experimental and theoretical study on the selectivity of [HOOCmim][NTf(2)]-H(2)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][NTf(2)]-H(2)O.