Extraction of copper(II) ions from aqueous solutions with a methimazole-based ionic liquid

The recently synthesized ionic liquid (IL) 2-butylthiolonium bis(trifluoromethanesulfonypamide, 1NTf2], has been used for the extraction of copper(II) from aqueous solution. The pH of the aqueous phase decreases upon addition of [mimSBur, which is attributed to partial release of the hydrogen attached to the N(3) nitrogen atom of the imidazolium ring. The presence of sparingly soluble water in [mimSBu][NTf2] also is required in solvent extraction studies to promote the incorporation of Cu(II) into the knimSBul[NUJ ionic liquid phase. The labile copper(II) system formed by interacting with both the water and the IL cation component has been characterized by cyclic voltammetry as well as UV vis, Raman, and 111, 1 C, and 15N NMR spectroscopies. The extraction process does not require the addition of a complexing agent or p1.1 control of the aqueous phase. finimSBul[NTf2] can be recovered from the labile copper water IL interacting system by washing with a strong acid. High selectivity of copper(II) extraction is achieved relative to that of other divalent cobalt(II), iron(II), and nickel(II) transition-metal cations. The course of microextraction of Cu2+ from aqueous media into the [mimSBu][NTf2] IL phase was monitored in situ by cyclic voltammetry using a well-defined process in which specific interaction with copper is believed to switch from the ionic liquid cation component, bnimSBu], to the [NT1-2] anion during the course of electrochemical reduction from Cu(II) to Cu(I). The microextraction voltammetry technique provides a fast and convenient method to determine whether an IL is able to extract electroacfive metal ions from an aqueous solution.