A tailored nitrogen-rich polymer for highly efficient and selective capture of gold from waste printed circuit boards

Abstract

Achieving efficient and selective gold recovery from electronic waste is a desirable approach for the sustainable utilization of existing rare metal resources. In this study, an ingenious positively charged trap based on azole-functionalized polymer (CMCPS-IMZ) was strategically designed and synthesized via solvothermal method for the precise capture of gold complex ions. By incorporating nitrogen-containing heterocyclic groups onto the CMCPS surface, the porous structure and large surface area promoted the formation of gold-binding sites, thereby enhancing adsorption efficiency. Specifically, CMCPS-IMZ exhibited exceptional Au(III) adsorption performance, with a maximum loading capacity of 323.08 mg/g, following pseudo-first-order kinetics and Freundlich isotherm models. Theoretical calculations and experimental analysis suggested that the electrostatic interactions between the RNH⁺ group on CMCPS-IMZ and AuCl₄^- served as the primary driving force to realize the highly efficient gold recovery, as well as involved in weak intermolecular interactions. Furthermore, CMCPS-IMZ demonstrated remarkable stability over multiple adsorption–desorption cycles using 0.5 M SC(NH₂)₂ as the ideal eluent, underscoring its potential as a robust and sustainable platform for precious metals recovery. Notably, CMCPS-IMZ microspheres achieved a gold extraction efficiency exceeding 93.33 % even in the presence of high concentrations of interfering ions in actual e-waste leachate. This work provides valuable insights into the nature of ion affinity and selectivity, offering guidance for the rational design of advanced adsorbents with tailored binding sites for targeted ion capture.