Leaching mechanism of strategic metals from superalloy scrap under ultrasonic cavitation

To improve the recovery efficiency of strategic metals from superalloy scrap, an ultrasonic-assisted leaching method was proposed. During the ultrasonic-assisted leaching process, at 60 min, the leaching rates of Re, Ni, Co, Al, Cr, and W are 92.3%, 95.2%, 98.5%, 98.7%, 97.5%, and 27.2%, respectively, which are far superior to those in the normal leaching process at 120 min. The improvement in leaching efficiency can be attributed to the physical and chemical coupling effects of ultrasonic cavitation. The physical effect can prevent the formation of the impeded dissolution layer and encourage contact between solution and superalloy scrap, which improves the leaching rates of strategic metals. The chemical effect can promote the production of hydroxyl radicals in the HCl−H2O2 system, which can enhance the potential of the leaching system, resulting in stimulation of the chemical oxidation process of Re to ReO4−.