Extraction of Au(iii) from hydrochloric acid media using a novel amide-based ionic liquid

Abstract

Liquid–liquid extraction technology based on ionic liquids (ILs) is an efficient and environmentally friendly method to recover Au(III). This work aims to separate Au(III) from hydrochloric acid media using a novel IL [DBA-Pyr][NTf₂], which is a pyrrolidinium-based IL functionalized with amide groups. Firstly, experiments have been carried out under optimal conditions, including the concentration, acidity and temperature. It turns out that low concentrations of hydrochloric acid help in Au(III) extraction, while the increase of chloride ion concentrations has an adverse effect. Then, through Job's method, extraction complexes with a molar ratio of [DBA-Pyr][NTf₂]-to-Au(III) of 1 : 1 were determined. And, the anion exchange extraction mechanism was confirmed by FT-IR, UV-Vis, and ¹³C NMR spectroscopies and an electrostatic potential energy (ESP). Under the optimal extraction conditions, it has excellent selectivity to Au(III) compared to both base metal ions and platinum group metals (PGMs). Furthermore, Au(III) could also be recovered from the IL phase using an aqueous solution of thiourea in 95.6% with high selectivity. After 4 cycle experiments, an extraction efficiency of more than 90% is still maintained. The results show that [DBA-Pyr][NTf₂] has potential application prospects in Au(III) recovery from hydrochloric acid media.