Efficient gold recovery from waste SIM cards by imidazolium-based ionic liquids: Insight into structure-performance relationship.

[Display omitted] • The structure-extraction performance relationship of ILs was systematically clarified. • ILs with lower solubility exhibited better extraction efficiency for Au(III). • The proposed structure-performance relationship demonstrated high universality. • [EB-IM][NTf 2 ] shows superior capacity (432.84 mg/g) and kinetics (1 min) for Au(III). • [EB-IM][NTf 2 ] possesses great practical application potential to e-waste. Ionic liquids (ILs) are regarded as an ideal candidate for recycling precious metals due to their green and tunable characteristics. However, the lack of understanding of structure-performance relationships still restricts the development and practical application of higher-performance ILs. Here, we aim to investigate the structure-extraction performance relationship, and develop a solvent-free extraction system for extracting gold from e-waste. The results demonstrate that the maximum loading capacity of imidazolium-based ILs follows the order of [EB-IM][NTf 2 ] (432.84 mg·g−1) > [EP-IM][NTf 2 ] (376.57 mg·g−1) > [EA-IM][NTf 2 ] (311.68 mg·g−1). The influence mechanism of substituents on extraction was examined through DFT calculation and quantitative NMR (q NMR). Our findings reveal that an increase in carbon chain length of ILs leads to a decrease in electrostatic potential (ESP) value, weaker binding energy, and reduced solubility. Remarkably, the decrease of solubility has a positive effect on improving extraction efficiency. Importantly, the proposed structure–activity relationship is universal. Moreover, [EB-IM][NTf 2 ] exhibited remarkable selectivity (β Au/Cu = 4.14 × 104, β Au/Ni = 2.46 × 103), recyclability (over 5 cycles) and good economic viability in waste SIM cards, obtaining high-purity gold with 23.78 karat. Overall, this study not only offers valuable guidance for the design of high-performance ILs, but also demonstrates the industrial prospect of ILs for recovering gold from e-waste. [ABSTRACT FROM AUTHOR]