Mechanistic insights into ultrasound‑ozone enhanced metallic dissolution: Radical evolution and interfacial electrochemistry from a model metallic system

This study systematically investigates the electrochemical dissolution behavior and underlying micro-mechanisms of copper-tellurium alloys in sulfuric acid solutions, enhanced by the synergistic effect of ultrasound and ozone. Focusing on Cu-Te alloys, we examined the effects of ultrasonic power, reaction temperature, and sulfuric acid concentration on dissolution kinetics, interfacial charge transfer, and reactive oxygen species (ROS) generation from the perspectives of electrochemical mechanisms and radical evolution. The results indicate that the corrosion current density of Cu-Te alloys is lowest in a pure sulfuric acid system due to significant surface passivation. The introduction of ozone markedly increases the corrosion current density. Under ultrasound-ozone synergy, the corrosion current exhibits a stepwise increase with rising ultrasonic power, reaching its maximum at 300 W. EPR spectra reveal that the characteristic signal intensity of DMPO-·OH continuously strengthens with increasing ultrasonic power, temperature, and sulfuric acid concentration, showing a high consistency with the electrochemical response. Furthermore, elevating the temperature and sulfuric acid concentration effectively boosts the oxidation peak current and significantly reduces the charge transfer resistance. SEM and AFM characterizations demonstrate a transition in the corrosion mode from localized pitting to uniform general dissolution, with the surface roughness decreasing from 100 nm to 77.4 nm. XRD and XPS results confirm that the ultrasound field accelerates the oxidation of Cu⁰ to Cu⁺/Cu 2 ⁺ and the transition of tellurium from lower to higher oxidation states, significantly improving the crystallinity of the products. Different from prior ultrasound-ozone hydrometallurgy studies that largely focused on leaching-process optimization for complex mineral feeds, this work delivering mechanistic foundations to guide ultrasound-assisted green hydrometallurgical extraction of critical metal resources.