Efficient extraction of Au(Ⅲ) by a piperidine-based ionic liquid and exploration of the mechanism driving force

Abstract

Efficient gold extraction is of paramount importance, but how to improve the extraction efficiency and enhance the driving force of the extraction process is still to be explored. This study introduces an innovative approach using versatility ionic liquids (ILs) to overcome existing challenges. A tailored IL was synthesized and employed computational tools, including the Interaction Region Indicator, to predict its effectiveness in gold extraction. Quantum chemical calculations elucidated the interplay between hydrogen bonding capability and ion exchange properties of the ILs. Subsequent optimization of experimental conditions (0.1 mol/L HCl, 10.6 mg IL) yielded a remarkable 98.4 % extraction efficiency at 45 °C. Molecular dynamics simulations affirmed the IL's exceptional selectivity for Au(III) extraction, with analysis revealing that the extraction mechanism primarily hinged on electrostatic attraction and van der Waals interactions between ionic liquid cations and [AuCl4]−. This mechanism aligns with the established anion exchange mechanism, validated through Ultraviolet–visible spectrometer (UV–Vis), Nuclear Magnetic Resonance spectrometer (NMR), and Liquid Chromatograph Mass Spectrometer (LC-MS) analyzes. To complete the extraction cycle, 1.0 mol/L K2C2O4 was employed as a stripping agent for efficient Au(III) recovery from the loaded IL phase, facilitating repeated extraction cycles. This study underscores the sustainability of the IL-based Au(III) extraction process, maintaining consistently high extraction rates even after five cycles. In summary, this method does not use solvent, enabling environmentally friendly Au(III) extraction.