Negative-carbon recycling of copper from waste as secondary resources using deep eutectic solvents

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.

Tannic acid-assisted upcycling of Cu from waste printed circuit boards to an efficient peroxymonosulfate catalyst for the degradation of organic pollutants

The recovery of metals from solid waste for use as heterogeneous catalysts to activate peroxymonosulfate (PMS) for organic wastewater treatment is a promising, environmentally friendly and economical strategy. Herein, we present a facile and versatile strategy for upcycling copper (Cu) from waste printed circuit boards (PCBs) to Cu oxides supported on a three-dimensional carbon framework (10PCBs-Cu-TA) with the aid of tannic acid (TA). Compared to the PCBs-Cu synthesized without TA, introducing TA into 10PCBs-Cu-TA reduced Cu leaching, enhanced crystallinity, promoted electron transfer, and increased the number of oxygen vacancies. Moreover, 10PCBs-Cu-TA exhibited superior catalytic activity in activating PMS for the degradation of reactive brilliant blue KN-R, exceeding the activity of 10Cu-TA prepared using commercial Cu(NO3)2·3H2O. This enhanced performance may be attributed to the higher specific surface area and oxygen vacancies of 10PCBs-Cu-TA. The 10PCBs-Cu-TA/PMS system also exhibited broad catalytic universality and adaptability to various contaminants and water matrices. Quenching experiments, electron paramagnetic resonance analysis, and electrochemical measurements indicated that radical and non-radical processes jointly contributed to KN-R degradation. The proposed strategy for upcycling Cu from waste PCBs into functional materials provides novel insights into the utilization of solid waste and the development of PMS activators.