Ultrasonic synergistic oxidation technology: Kinetics and mechanism of germanium leaching from high-sulfur germanium-bearing dust

To improve the low germanium leaching efficiency and lengthy leaching time in the current two-stage sulfuric acid leaching process for high-sulfur germanium-bearing dust, this study applies ultrasonic-assisted H₂O₂ oxidative leaching. Ultrasound and H₂O₂ are introduced in the first stage of leaching, while ultrasound is incorporated in the second stage. Analysis shows that the dust particles consist of an inner core and an outer shell, with PbS at the interface acting as the primary barrier to enhanced germanium leaching. After optimizing conditions, germanium leaching efficiency reached 94.10%, a 11.26% increase over conventional methods. During the oxidative leaching process, the intrinsic oxidizing capacity of H₂O₂ plays a dominant role. The introduction of ultrasound promotes the decomposition of H₂O₂, generating a greater quantity of hydroxyl radicals (OH•), enhancing mass transfer, refining the grain structure, and disrupting Si-Ge co-precipitation. Kinetic studies reveal that the first stage of germanium leaching conforms to the phenomenological model, involving rapid dissolution and slow diffusion. Ultrasound combined with H₂O₂ reduces dissolution activation energy by 43.15% and diffusion activation energy by 22.88%. This study is dedicated to proposing an efficient and environmentally friendly germanium extraction technology to achieve comprehensive recovery and utilization of germanium resources.