Liquid CO2 to work for clean REE recovery

A team of researchers out of the University of Toronto has pioneered a method of separating critical minerals and metals from electronic waste, such as electric vehicle batteries and wind turbine magnets, by using captured carbon dioxide and a little pressure to provide the critical materials needed for a zero-carbon future.

While conventional rare earth ores typically contain 1 to 2% of these tech metals, recycling electronic waste provides an efficient avenue to obtain these vital resources in concentrations upwards of 20 to 40%.

Due to this potential urban mining effort, international investment in recycling is growing, especially as the capacity and technologies for recycling electronics improve.

"There are countries, and Canada is one of the leaders, that are really looking at this and they understand the importance of enabling recycling to our society," said Gisele Azimi, a professor at University of Toronto Engineering Professor and Canada Research Chair for Urban Mining Innovations

The recycling technique her team has honed involves heating and pressurizing carbon dioxide and transforming it into a supercritical fluid. In this state, it can then be used to dissolve and extract critical metals from target waste.

The biggest advantage of this CO2 method is that heating does not require much energy. In fact, the conversion occurs at roughly 30 degrees Celsius (86 degrees Fahrenheit).

Published in "Inorganic Chemistry," the U of T researcher teams' results were made in collaboration with the Canadian Light Source synchrotron – a system that produces different kinds of light in order to study the structural and chemical properties of materials at the molecular level – who was approached to help refine and better understand the supercritical fluid recycling process.

Currently able to extract metals from car batteries, wind turbine magnets, fluorescent bulbs, and many things in between, Azimi and her collaborators have been experimenting to see how far this new carbon-negative recycling method can take them.

Working with industry partners on piloting the technique, the work that is pushing the boundaries on known recycling practices is currently aimed at recovering gold and copper from circuit boards.

With various REE separation technologies popping up out of the woodwork these days, recycling technologies are still in their relative infancy before an industry standard emerges to close the circle from manufacturer to market.

Although a deluge of resources is available to recycle with the decades of electronic waste that have been produced, it will be some time before the newest EVs, wind turbines, battery storages, and other renewable technologies reach the end of their lives to be recycled, so there is still time to perfect the tech that will recover it efficiently and cleanly.