Advances in hydrometallurgy recovery of critical metals from urban mines: Ultrasonic applications and intensified mechanisms

The recovery of critical metals from urban mines will advance the construction of “zero-waste cities” and the transition toward a circular economy. However, for complex systems such as electronic, industrial auxiliary, and industrial processing wastes, conventional recovery methods often struggle to overcome challenges such as sluggish leaching kinetics and mass transfer limitations, which severely constrain their large-scale industrial application. The application of ultrasonic fields in hydrometallurgy has demonstrated significant advantages as a promising process intensification technique. This review systematically summarizes the current research on ultrasound-intensified valuable metals recovery from urban mines, focusing on both direct and auxiliary synergistic mechanisms throughout the metal recovery process. This study elucidates the transient interfacial evolution laws of interactions between complex solid wastes and ultrasound, and re-examines the process intensification logic of hydrometallurgy from the perspective of multifield coupling. This study aims to provide a theoretical foundation and technical reference for establishing green, efficient, and low-energy recovery pathways for critical metals in urban mines. This study also holds significant academic and practical value for deepening the application of process intensification theory in the field of solid waste resource utilization.