Highly efficient and recyclable pyridinium-based poly(ionic liquid)s for selective gold recovery from electronic waste

Pyridinium PILs outperform quaternary ammonium ones for Au(III) adsorption. • Anion–π and H-bonding synergistically enhance Au(III) capture by pyridinium PILs. • Cl – -form PILs show higher Au uptake than Br – -form due to weaker dispersion forces. • PTPB-Cl achieves fast, selective Au recovery from waste CPU leachate. • PTPB-Cl maintains stable performance and structure over 10 adsorption cycles. A series of pyridinium- and quaternary ammonium-based poly(ionic liquid)s (PILs) with chloride (Cl − ) or bromide (Br − ) counter-anions were synthesized and evaluated for the adsorption of AuCl 4 − from aqueous solutions. The adsorption kinetics followed the pseudo-second-order model, and equilibrium data were well described by the Langmuir isotherm, indicating monolayer chemisorption. Pyridinium-based PILs exhibited significantly higher gold uptake than their quaternary ammonium analogues, attributable to the synergistic contribution of anion–π interactions, and C–H···Cl hydrogen bonding. Chloride-form PILs outperformed their bromide counterparts due to the lower polarizability of Cl⁻, which weakens dispersion interactions with the PIL backbone and facilitates anion exchange. The optimized PIL, PTPB-Cl, achieved efficient gold recovery from actual waste CPU leachate with negligible interference from coexisting metal ions. Moreover, PTPB-Cl maintained stable adsorption and desorption efficiencies over ten consecutive cycles, and post-recycling characterizations confirmed its structural integrity and complete gold desorption. Download: Download high-res image (265KB) Download: Download full-size image