Magnetic hollow microspheres encapsulated by MOFs for proficient gold capture from E-waste

A magnetic hollow MOF adsorbent encapsulated with polydopamine was fabricated. • The developed system for efficient and selective gold extraction from E -waste. • The maximum adsorption capacity for gold was 2293.97 mg g −1 at 318 K. • The adsorbent achieves a gold recovery rate of 95.68% from real samples. E -waste recycling has emerged as a sustainable route for gold recovery to alleviate resource shortages. Herein, a polydopamine-encapsulated magnetic hollow MOF (HM-UiO-DMSA) was fabricated via an in-situ growth strategy for selective gold extraction. The adsorbent achieves rapid equilibrium within 600 min and a high adsorption capacity of 1782.84 mg g −1 at pH 4, with adsorption behavior well fitted to the Freundlich isotherm. Benefiting from the abundant amino, thiol and carboxyl groups, HM-UiO-DMSA exhibits outstanding Au(III) selectivity and enrichment capacity. In simulated multi-metal E -waste leachate, the prominent Au(III) distribution coefficient (K d ) and concentration factor (CF) reach 235,258 mL g −1 and 4905.5 mL g −1 , respectively. Notably, benefiting from its intrinsic photothermal effect, HM-UiO-DMSA delivers an exceptional adsorption capacity of 2332.30 mg g −1 under UV irradiation, a value 27.73% greater than its nonmagnetic analogue (H-UiO-DMSA). A high gold recovery efficiency of 95.68% is realized for practical waste circuit board samples with ultra-low Au(III) concentrations, and the final recovered gold exhibits a high purity of 98.20% (23.6 K gold). The excellent gold separation performance originates from the synergistic coordination-reduction effect of heteroatoms and reductive polydopamine/DMSA groups. Furthermore, HM-UiO-DMSA possesses favorable recyclability over six cycles, enabling reliable gold recovery in complex acidic E -waste systems. Download: Download high-res image (115KB) Download: Download full-size image