Unlocking efficient gold capture from electronic waste leachate with light weight hollow magnetic microspheres

Abstract

Developing magnetic adsorbents with superior adsorption capability has always been a massive challenge. Herein, an in-situ growth strategy was implemented to build polydopamine-encapsulated lightweight hollow magnetic microspheres and used to achieve selective recovery of gold from e-waste. The fabricated magnetic-dielectric microspheres, including hollow magnetic polydopamine microspheres (HMPM) and hollow magnetic polydopamine microspheres modified by allyl thiourea (HMPM&A), exhibited excellent gold adsorption capacities of 1205 mg g⁻¹ and 1766 mg g⁻¹, respectively at 298 K. The adsorption capacity was amazingly upsurged up to 1850 mg g⁻¹ and 2715 mg g⁻¹ under ultraviolet light, respectively, which is relatively enhanced compared to other reported magnetic adsorbents. The XPS survey and DFT calculations confirmed that Au(III) ions adsorption principally attributed to electrostatic interaction of N sites under acidic mediums and chelating interaction between Au(III) and S,N chelating site of thiourea groups, followed by subsequent reduction of Au(III) into to Au(0) with thiourea and dopamine units. The developed magnetic adsorbent showed impressive chemical stability for Au(III) adsorption up to eight consecutive adsorption-desorption cycles without any noticeable change in adsorption performance. The recovery rate of HMPM&A for Au(III) ions from actual samples was better up to 86.7 %. This work will broaden the construction strategy of magnetic adsorbents and promote the application of magnetic materials as an efficient functional material.