Selective extraction of precious metals from urban mines plays a crucial role in mitigating the risk of depletion of precious metal resources and reducing waste pollution. However, a major obstacle in precious metal extraction lies in the difficulty of distinguishing the subtle differences in the physicochemical characteristics between them, especially gold and palladium. Herein, a proton-driven separation system was presented for cascade recovery of gold and palladium from waste-printed circuit boards (W-PCBs) leachate using poly(amidoxime) (PAO) hydrogel. This exhibits an ultra-high capacity, extra-fast rate, and excellent selectivity for the extraction of Au(Ⅲ) and Pd(Ⅱ). Notably, the separation of Au(Ⅲ) and Pd(Ⅱ) can be achieved with high selectivity at pH = 0, resulting in a remarkable separation factor of k_{Au(Ⅲ)/Pd(Ⅱ)} = 36.5. This was demonstrated to originate from the differential mechanism of PAO hydrogel for the capture of Au(Ⅲ) and Pd(Ⅱ) under proton-mediated conditions. Drawing inspiration from the mechanism, the proton-driven cascade recovery system demonstrates remarkable efficiency in sequentially recovering 99.92% of gold and 99.05% of palladium from W-PCBs acid leachate. This research opens up a strategy to precisely separate and recover precious metals from e-waste of urban mines.

The adsorbents–adsorbates interaction is critical for resourcelization in heavy metal wastewater treatment. Nevertheless, it is still indistinct to depict the impact of metal center effect on heavy metals removal performance in metal-organic frameworks (MOFs)-based adsorbents. Herein, a series of MOFs with different metal centers of Mg(II), La(III), and Zr(IV) are rationally designed, and the effect of electronic structure on the Sb(V) removal performance is systematically investigated. The obtained La-MGs achieve Sb(V) adsorption capacity of 897.6 mg/g, which is about 1.2 and 4.5 times above average than those of Zr-MGs and Mg-MGs, respectively. On account of more edge adsorption sites achieve, the sites utilization efficiency of La-MGs (92.1%) is much better than Zr-MGs (75.0%) and Mg-MGs (20.4%). Furthermore, density functional theory (DFT) calculations reveal that La-MGs are more active than Mg-MGs and Zr-MGs, owing to the lower adsorption energy, higher charge transfer, and stronger bonding interaction, which will promote the Sb(V) removal performance. The experimental results in practical water indicate that La-MGs effectively capture antimony at low concentration, reaching drinking water standard in samples from Ganjiang River. This study opens an avenue for atomic-level insight into high-efficient absorbents design for water treatment from electronic structure-modification of active centers.