Pyridinium-based Task-specific Ionic Liquid with a Monothioether Group for Selective Extraction of Class b Metal Ions

A pyridinium-based task-specific ionic liquid (TSIL) with a monothioether group, [3-TPPy][NTf2], extracted typical class b metal ions, such as Ag(I), Cu(I), Pd(II), and Pt(II), in high selectivity. It was found that the composition ratio of the extracted Ag(I) and Cu(I) species depended on the TSIL concentration, and that TSIL extracted these metal ions through mono-S-coordinated complex formation at low TSIL concentrations. [3-TPPy][NTf2] can be recycled in the extraction–recovery process, which is of a great advantage for practical use in environmentally benign separation methods.