Leveraging metal sites and hydroxyl groups in bimetal-organic framework for effective gold extraction from e-waste leachate

The exponential growth in electronic waste (e-waste) poses a serious environmental threat, while also serving as a valuable source of precious metals (e.g., gold). However, developing efficient and highly selective adsorbent materials for gold extraction remains a significant challenge. Herein, we present a synergistic adsorption-reduction-nucleation strategy for gold recovery from e-waste leachate leveraging the metal sites and hydroxyl groups. The synthesized FeM-MOF-74 (M = Co, Ni, Cu) composites demonstrate exceptional adsorption capacity (3078 mg g(-1)) and rapid kinetics (97% within 3 min) for Au(III), maintaining a distribution coefficient of 1.25 x 10(7) mL g(-1) even in the presence of high concentrations of interfering ions, which surpass the performance of previously reported adsorbents. Impressively, FeM-MOF-74 composites exhibit a promising gold extraction efficiency of over 98% with high-purity gold recovery (similar to 23.9 K) in undiluted actual e-waste leachate. The proposed FeM-MOF-74-based gold recovery process offers significant cost advantages, as evidenced by a technoeconomic analysis showing a remarkable input-output ratio of 1909%. The gold recovery mechanisms are further elucidated through spectroscopic analysis and theoretical calculations, revealing a synergistic effect where metal sites promote the efficient reduction of Au(III) while hydroxyl groups serve as the nucleation sites for gold nanoparticles. This work is expected to provide a promising strategy for the treatment of electronic waste and the recovery of precious metals from leachate.