A Dual-Function Insoluble Ionic Liquid for the Selective Recovery of Gold and Copper from E-Waste

As natural resources for valuable metals diminish, the recovery of these metals from alternative sources is increasingly important. E-waste, containing higher concentrations of valuable metals compared to natural deposits, presents a promising solution. In this study, a carboxyl-functionalized imidazolium-based ionic liquid 1-carboxymethyl-3-dodecyl imidazolium bromide [C₁₂C₁COOHim]Br was employed for the selective recovery of gold (Au) and copper (Cu) from discarded CPU pins. Gold was efficiently adsorbed from aqua regia-leached solutions at room temperature, achieving a recovery rate of 96.7 % and a purity exceeding 97 %. Copper was selectively leached in an aqueous medium at 65 °C, with a recovery rate of 99.1 %. The maximum uptake capacity for gold and copper was obtained as 447 mg/g and 286 mg/g respectively. The dual-function ionic liquid acted as a sorbent for gold through anion exchange and as a leaching agent for copper via coordination with carboxylic acid groups. XPS analysis confirmed the binding interactions involved in both recovery processes. This work demonstrates an effective and sustainable methodology for recovering critical metals from e-waste, highlighting its potential for industrial applications in metal recycling.