Eco-friendly chitosan-based composite microspheres for efficient recovery of gold from electronic waste via adsorption-reduction cascade
Huan Xie, Jun Li, Yongmin Zhang
Abstract
With the growing demand for gold, recovering it from gold-containing solutions and electronic waste has emerged as a sustainable approach to mitigate environmental pollution and resource depletion. In this context, eco-friendly materials receive increasing attention due to their sustainability, non-toxicity, biodegradability. Here, a novel environmentally friendly porous bead material, CS-Fc@CD-TU, was developed using ferrocene-modified chitosan, oxidized cyclodextrin and thiourea , combining adsorption and reduction capabilities. Despite its moderate specific surface area (44.94 m 2 ·g −1 ), CS-Fc@CD-TU exhibited exceptional Au(III) adsorption, with a maximum adsorption capacity of 722.18 mg·g −1 , following pseudo-second-order kinetic and Langmuir isotherm models. The material maintained high removal efficiency (> 94 %) across temperatures (20–50 °C), Au(III) concentrations (50–200 mg·L −1 ), and pH levels (3–6), with excellent selectivity (distribution coefficient: 5.41 × 10 4 ) and interferences resistance. Notably, the adsorbed gold ions were rapidly reduced in situ to Au(0) due to the presence of ferrocene groups and C N bonds, thereby releasing the occupied adsorption sites for further gold ion capture. The reduced Au(0) further grow into Au nanoparticle (6–100 nm) with 99.8 % purity after calcination . When applied to electronic waste, CS-Fc@CD-TU effectively recovered gold ions at extremely low concentrations (1.23 ppm) and demonstrated high stability and reusability, retaining >97 % removal efficiency after five cycles. These results highlight CS-Fc@CD-TU as a promising, eco-friendly adsorbent for sustainable gold recovery.