pH-Dependent selective extraction of gold(iii) from synthetic solution and computer motherboard leachate using a hybrid nanocomposite

Abstract

Recycling gold from electronic waste offers significant benefits for both environmental protection and resource sustainability. However, this process presents considerable challenges due to high costs, prolonged processing times, and interference from coexisting metals. In this study, we synthesized a hybrid mesoporous nanocomposite comprising platelets-like CoNi₂S₄ incorporated with g-C₃N₄ nanosheets (CoNi₂S₄@g-C₃N₄) for the selective recovery of gold (Au(III)) ions from spent computer motherboards. Comprehensive characterization of the CoNi₂S₄@g-C₃N₄ nanocomposite was conducted, including its physicochemical properties, textural and structural characteristics, morphology, and elemental composition. The CoNi₂S₄@g-C₃N₄ extractor demonstrated an exceptional adsorption capacity of 200.6 mg g⁻¹, with high selectivity at pH 2, rapid equilibrium time of 60 minutes, and satisfactory reusability for over ten cycles. Adsorption isotherm and kinetic studies revealed that the CoNi₂S₄@g-C₃N₄ nanocomposite adheres to the Langmuir adsorption model and the pseudo-second-order kinetic model for Au(III) ion adsorption. Overall, this study introduces a viable adsorbent that shows considerable promise for industrial-scale Au(III) extraction from e-waste.