Ultra-high adsorption capacity and selectivity of photo-enhanced sulfur-rich M2S3 (M--Bi and Sb) for gold recovery from electronic wastewater

Recycling gold efficiently from electronic waste (e-waste) not only facilitates the sustainable use of precious resources, but also mitigates environmental risks. In this work, two simple metal sulfides M2S3 (M--Bi and Sb) microspheres with extraordinary adsorption properties were prepared by a convenient hydrothermal technique for selectively recovering gold from e-waste water. The assistance of visible light significantly improved the gold adsorption performance of M2S3. Two sulfide materials exhibit excellent gold adsorption properties, and the maximum capacity for adsorption reaches 3615.45 mg g-1 for Bi2S3, and 1651.95 mg g-1 for Sb2S3 under optimal conditions and incandescent light irradiation. Gold adsorption on M2S3 materials follows Langmuir and pseudo-second order kinetic models, suggesting that the Au(III) adsorption is dominated by chemisorption in a monolayer adsorption mode. XRD and XPS analysis indicate that the strong sulfur affinity for gold and the photocatalytic reduction-oxidation reaction between Bi2S3 and gold are the main mechanisms for effective gold adsorption on metal sulfides. In addition, M2S3 exhibits excellent gold adsorption selectivity against coexisting ions including Zn(II), Co(II), Cu(II), Fe(III), Ni(II), Mg(II), Ca(II), Al(III) present in actual electronic wastewater. The gold loaded on Bi2S3 was efficiently eluted using acidic thiourea, and the excellent adsorption performance was maintained over five adsorption/desorption cycles. This work presents an effective and simple method for recovering gold(III) from the leachate of discarded electronic devices. Metal sulfides have high adsorption selectivity, ultra-high adsorption capacity, and excellent recyclability, making them a promising green adsorption material for recovering gold from electronic waste.