Extraction of copper(II) from aqueous solutions with the ionic liquid 3-butylpyridinium bis(trifluoromethanesulfonyl)imide

The new room temperature protic ionic liquid 3-butylpyridinium bis(trifluoromethanesulfonyl)imide, [3-BuPyr][NTf2], was used for the extraction of copper(II) ions from aqueous solutions without addition of a complexing agent or pH control of the aqueous phase. During the extraction process the hydrogen atom attached to the N atom of the pyridine ring is released by water to form H3O+ ions in the aqueous phase. This N atom can be re-protonated by other molecules of water or interact with copper(II) to form a labile complex system. The solubility of [3-BuPyr][NTf2] in the aqueous phase does not increase during extraction and it can be recovered from the formed complex by washing it with a strong acid. The extracted phase was characterized by cyclic voltammetry (CV) as well as UV–vis and NMR spectroscopies. Copper can be electrodeposited from the formed complex on glassy carbon (GC) or platinum (Pt) electrodes at room temperature. The resultant electrodeposits were characterized by CV and energy dispersive X-ray (EDX) analysis.

► Cu2+ extraction from aqueous solutions with the ionic liquid [3-BuPyr][NTf2].
► Complex formation between [3-BuPyr][NTf2] and Cu2+ during the extraction process.
► Copper electrodeposition on glassy carbon electrodes from the formed complex.
► Recovery and reuse of [3-BuPyr][NTf2] after extraction.