Effective and selective extraction of Au(III) and Pd(II) from practical e-waste by tridentate thioether extractants

To address resources shortage and environmental degradation, noble metal recovery from e-waste is in desperate need. Herein, to achieve selective extraction of gold (Au) and palladium (Pd) from practical e-waste, a series of tridentate thioether extractants are designed with ester functional groups at both ends of the thioether. By varying the chain length of the ester alkyl, the relationship between extractant structure and performance is further explored. The results indicate that the as-introduced tridentate structure facilitate the Au(III) and Pd(II) extraction, demonstrating a complex mechanism involving both coordination substitution and ion association. Notably, the extractant with the shortest carbon chain length and smallest molecular weight delivers outstanding extraction capacities of 920.2 mg/g for Au(III) and 280.7 mg/g for Pd(II). More importantly, it exhibits superior selectivity (∼100 %) for Au(III) and Pd(II) in complex metal solutions. This work guides the design of thioether-based extractants for sustainable recovery of noble metal from practical e-waste.