Efficient removal of metal ions from the ionic liquid aqueous solution by selective electrodialysis

Abstract

In this work, due to the fact that the simulate spinning solution containing [Emim]Dep ILs, Mg2+, Ca2+, K+ and Na+, the selective electrodialysis (SED) method was chosen to achieve the separation of ILs and metal ions by the discrepancy of electrostatic action, pore size, hydration energy and etc. Various operating parameters, including the applied voltage drop, pH, ILs concentration, Mg2+/[Emim]+ ratio, type of anions (SO42- and Cl-) were investigated to evaluate the separation ability. What’s more, the separation mechanism of [Emim]+ and metal ions was revealed under different initial concentration of ILs. The critical aggregation concentration of ILs decreased with an increase in the concentration of Mg2+ ion. The transmembrane rate of monovalent ion ([Emim]+, K+ and Na+) was faster than that of divalent metal ions (Mg2+, Ca2+). In the natural spinning solution, PIL, RMg2+ and RCa2+ reached up to 90%, 98% and 96%, respectively. The spectra of FT-IR, 1H NMR and 13C NMR proved that the recycled ILs by the SED method was electrochemically stable. These results demonstrated that the SED process can be employed to separate the metal ions from the IL aqueous solution.