Kinetics of metal extraction in ionic liquids: Eu3+/HNO3//TODGA/[C1C4im][Tf2N] as a case study

Abstract

The kinetics of metal transfer in the system Eu³⁺/HNO₃//TODGA/[C₁C₄im][Tf₂N], where TODGA is N,N,N′,N′-tetraoctyl diglycolamide, is shown to depend on the chemical conditions (nitric acid and TODGA concentrations) and the time needed to reach equilibrium which may vary from less than 10 min to more than 4 h. At [HNO₃] = 4 M, a detailed kinetic study is performed for two different concentrations of TODGA. It is shown that the time required for water and acid solubilisation in the IL phase is very short, as is the time for IL solubilisation in the aqueous phase. By contrast, the extraction of Eu(III) takes more than 100 min to be completed and depends on the TODGA concentration. On the basis of these experimental facts, a simple kinetic model is proposed which is able to account for the data.