Polyelectrolyte complex-derived adsorbent capsules capable of selective recovery of precious metal from multiple mixtures

Polyelectrolyte complexes (PECs) are valuable functional materials for many industrial applications, yet it is difficult to augment their morphologies for desired applications. Herewith, PEC capsules were strategically fabricated via salt-induced coacervation of poly(diallyldimethylammonium chloride) and poly(styrenesulfonate). The adsorbents showed Au(III) selectivity in multimetal mixtures of Au-Pt-Pd and Au-Cu-Co-Zn. The binding sites were offered by R₄N⁺ through electrostatic attraction, as elucidated with XPS. Selectivity was influenced by concentration, contact time and stirring speed. A new phenomenon of competing ion rejection was established to be caused by combined Au(III)/water penetration into the capsules, leading to decrease in bulk solution volume at equilibrium. The maximum Au(III) uptake was 176.63 ± 15.57 and 110.84 ± 2.32 mg/g for the Au-Pt-Pd and Au-Cu-Co-Zn systems, achievable within ∼ 1 and > 6 h, respectively. The loaded Au(III) was eluted with 0.1 M thiourea and regenerated for at least five cycles, making it practically feasible for resource recovery through urban mining.