Sustainable gold leaching from refractory ores: MoS2-photocatalyzed leaching coupled with in situ utilization of mineral-sourced sulfur.

Gold (Au) has garnered significant attention due to its crucial applications in various fields, yet its green and sustainable recovery remains challenging. While cyanide has been the preferred leaching agent for over a century, its high toxicity and unsuitability for carbonaceous and high-copper ores limit its use. Thiosulfate shows potential for treating refractory gold ores, but its high consumption and low oxidation kinetics are obstacles. This study introduces a photocatalytic process that directly oxidizes gold by generating highly reactive free radicals via photocatalysis, while also oxidizing mineral sulfur to produce thiosulfate in situ. This enhances gold dissolution efficiency and reduces thiosulfate consumption. Electron paramagnetic resonance (EPR), time-of-flight secondary ion mass spectrometry (ToF-SIMS), and density functional theory (DFT) calculations elucidate the oxidation processes of Au and S by •OH and O2•-. Additionally, •OH directly participates in the cathodic reaction, significantly lowering the oxidation energy barrier of Au. The entire leaching process avoids strong acids, toxic compounds, and volatile reagents, enabling the direct extraction of insoluble gold ore by wet methods and offering a novel path for the green and sustainable development of precious metals.