Quaternary amine-functionalized electrospun nanofibers for selective gold capture: Experimental and DFT calculation study

Developing efficient adsorbent materials for gold recovery from e-waste holds critical importance for sustainable resource management and conservation. In this study, GA-PVA/PEI-Cl nanofibers are prepared using the electrospinning technique combined with quaternization modification, and the material shows fast and efficient adsorption properties. It was revealed that the kinetic equilibrium of Au(III) adsorption by GA-PVA/PEI-Cl took only 6 h, and the theoretical maximum adsorption capacity was 949.48 mg/g, which is better than most of the reported adsorbents in terms of both adsorption rate and capacity. In the simulated wastewater, GA-PVA/PEI-Cl showed excellent selectivity for Au(III) with a distribution coefficient as high as 49,249.6 mL/g. The adsorption isotherm and kinetic model fitting showed that the process was consistent with the Langmuir model and pseudo-second-order kinetic model, which belongs to the monolayer adsorption mechanism dominated by chemisorption. It was found that stable performance of the adsorbent was maintained after five adsorption–desorption cycles. Combined with DFT calculations and XPS analysis, the adsorption mechanism involves the synergistic action of multiple mechanisms: protonated amine groups (–NH 3 + , –NH 2 + ) and quaternized amine groups (−R 4 N + ) decrease the distance to AuCl 4 − through electrostatic interactions, followed by coordination of the nitrogen/oxygen groups to Au(III) and the in situ reduction of Au(III) to Au(0) via electron transfer. GA-PVA/PEI-Cl demonstrates potential as an efficient material for gold recovery from e-waste, owing to its rapid adsorption kinetics, high selectivity, and stable regeneration properties.