A cavitation enabled green leaching of metals from spent lithium-ion batteries

As the world dabbles with increasing quantities of spent lithium-ion batteries (LIBs) and the need to recover valuable metals therein, sustainable approaches to achieving this need have become a necessity. In this work, we present the findings of an ultrasound-assisted intensification of a leaching process for the recovery of cobalt, nickel, manganese and lithium from spent LIBs. Molasses, methanesulfonic acid and ultrasonication were used together to enhance the leaching of the metals. The influence of ultrasonic modes, namely, sonication under isothermal and non-isothermal conditions, and leaching parameters, such as temperature, sonication amplitude, time, solid-liquid ratio, and reductant dosage, were evaluated. The leaching of metals was found to be strongly dependent on amplitude, temperature, and time. Compared to conventional mechanical stirring, the application of ultrasonic waves improves the leaching of metals by ∼22–74 %, with the degree of enhancement dependent on the temperature and the metal. The non-isothermal sonication mode (sonication without temperature control) has a lower energy input yet can yield a similar leaching performance as sonication under controlled temperature (isothermal mode). The results suggest that the introduction of ultrasonic waves created cavitation bubbles, which caused solid fragmentation, enhanced the mass transfer and diffusion of the reactants, and formed products that led to significant improvements in the leaching efficiency.