Efficient extraction of Au(Ⅲ) used morpholine-based ionic liquids in acidic medium from wasted CPU leachate

Two types of ionic liquids, Ethyl 2-(4-methylmorpholin-4-ium-4-yl)acetate bis(trifluoromethanesulfonyl)imide ([EMMi][NTf 2 ]) and Ethyl 6-(4-methylmorpholin-4-ium-4-yl)hexanoate bis(trifluoromethanesulfonyl)imide ([EHMMi][NTf 2 ]), which have exceptional extraction capabilities, were designed and synthesized. A solvent-free extraction system was established. By using only 16   mg of [EMMi][NTf 2 ], controlling the upper critical solution temperature (UCST) temperature to 333   K, and increasing the reaction time to 10   min, the Au(III) extraction efficiency can reach 98.6%. The theoretical calculations provided insight into the potential efficacy of utilizing ionic liquids for the extraction of Au(III), whereas the molecular dynamics simulations revealed the fundamental factors driving this extraction process, primarily attributed to the electrostatic interaction and van der Waals interaction interplay between the cations of the ionic liquid and Au(III). The anion exchange mechanism can be discerned from UV Vis and 13 C-NMR spectra. [EMMi][NTf 2 ] demonstrated an extraction efficiency of 97.31% and effectively extracted Au(III) from the CPU diluent solutions. [EMMi][NTf₂] exhibited remarkable stability (>89% efficiency after 5 cycles) and exceptional profitability (output–input ratio: 2006%), making it a sustainable and economically viable extractant.