Selective and Efficient Gold Extraction from E-Waste by Pyrrolidinium-Based Ionic Liquids with Various N-Substituents

With environmental problems and a shortage of resources, it is urgent to recover gold from electronic waste (e-waste). Meanwhile, it is necessary to explore the relationships between the structures and extraction performances of ionic liquids (ILs) to further improve the extraction capacities of ILs for gold. Herein, three pyrrolidinium-based ILs with various N-substituents were synthesized for solvent-free extraction of Au(III). The three pyrrolidinium-based ILs exhibited ultrahigh extraction capacities for Au(III) with the order of [Pyr-EA][NTf2] (524.6 mg center dot g-1) > [Pyr-Bu][NTf2] (457.3 mg center dot g-1) > [Pyr-C2OC2][NTf2] (403.5 mg center dot g-1). The effects of N-substituents on extraction performances were quantitatively investigated by electrostatic potential (ESP) and quantitative NMR. Among them, the ester group (-COOR) is the most beneficial to the extraction process, which is associated with an increased ESP value and boosted hydrophobicity. Notably, [Pyr-EA][NTf2] displayed outstanding selectivity in multimetal solutions; especially, it could selectively and efficiently extract Au(III) from the actual CPU. Furthermore, [Pyr-EA][NTf2] possesses significant reuseability and can maintain superior extraction efficiency of 84.3% after five cycles. These excellent performances together with low cost ($0.44 center dot g-1 [Pyr-EA][NTf2]) and considerable profit ($29.72 center dot g-1 [Pyr-EA][NTf2]) confirmed that [Pyr-EA][NTf2] is a promising prospect for sustainable recovery of gold from e-waste.

Automated summary

In order to address environmental problems and resource shortage, the recovery of gold from e-waste is urgently needed. This study synthesized three pyrrolidinium-based ionic liquids (ILs) with different N-substituents for solvent-free extraction of Au(III) and found that [Pyr-EA][NTf2] exhibited the highest extraction capacity. The influence of N-substituents on extraction performance was quantitatively studied and it was determined that the ester group (-COOR) was the most beneficial. The IL [Pyr-EA][NTf2] demonstrated exceptional selectivity and reusability, making it a promising prospect for sustainable gold recovery from e-waste.