On one hand, pyrometallurgy, which uses extremely high temperatures, produces greenhouse gas emissions. On the other hand, hydrometallurgy, which uses acids and reducing agents for extraction, creates wastewater that needs to be processed and handled.
In contrast, the U of T group is using supercritical fluid extraction to recover metals from end-of-life Li-ion batteries. This process separates one component from another by using an extracting solvent at a temperature and pressure above its critical point — where it adopts the properties of both a liquid and a gas.
To recover the metals, the scientists used carbon dioxide as a solvent, which was brought to the supercritical phase by increasing the temperature above 31 Celsius, and the pressure up to 7 megapascals.
They were able to show that this process matched the extraction efficiency of lithium, nickel, cobalt and manganese to 90% when compared to the conventional…
