Selective gold extraction from e-waste leachate via sulfur-redox mechanisms using sulfhydryl-functionalized MOFs

Urban mining of precious metals from electronic waste (e-waste) offers a dual advantage by addressing solid waste management challenges and supplying high-value metals for diverse applications. However, traditional extraction methods generally suffer from poor selectivity and limited capacity in complex acidic leachate. Herein, we present a sulfhydryl-functionalized zirconium-based metal-organic framework (Zr-MSA-AA) as a recyclable and highly selective adsorbent for efficient gold recovery. Specifically, the Zr-MSA-AA exhibits high recovery capacity (1021 mg g-1), remarkable pH-universal, and superb selectivity (Kd of 2.2 x 107 mL g-1) for gold ions across wide pH range and competitive conditions. Comprehensive mechanistic investigations highlight the pivotal role of sulfhydryl groups in selectively capturing gold ions. The redox-transformation of sulfhydryl and sulfonic acid groups mediated the reduction of Au(III) to Au(0) through the nucleation of chlorine-stabilized gold clusters. This unique mechanism, driven by the redox activity of designed sulfhydryl sites, not only mitigates interference from competing cations but also facilitates rapid adsorption kinetics (kf of 1.17 x 10-7 m s-1) for gold ions, surpassing the performance of previous adsorbents. Consequently, Zr-MSA-AA demonstrates exceptional practical applicability, achieving high-purity gold recovery (23.8 Karat) from real e-waste leachate through straightforward physical separation methods. This study introduces an alternative practical strategy for utilizing sulfur's redox activity in adsorbent design, advancing the sustainable recycling of non-renewable metal resources while contributing to environmental conservation.