Researchers at Rice University have developed a process to extract rare earth elements from discarded magnets using less energy and fewer chemicals than traditional methods. The technique, published in the Proceedings of the National Academy of Sciences, heats waste materials rapidly with electricity and employs chlorine gas to separate valuable elements. This approach could help meet growing demand for these critical materials by tapping into electronic waste.
Rare earth elements (REEs) are essential for electronics like phones and laptops, but recovering them from e-waste has been challenging. A team led by James Tour, a professor of materials science and nanoengineering at Rice University, has devised a method that addresses this by targeting waste magnets, such as those from neodymium-iron-boron and samarium-cobalt types.
The process builds on flash joule heating, discovered by Tour's group in 2018 for converting carbon sources into graphene. In 2023, they refined it with chlorine gas. Ground-up magnets, first heated to 800°C to demagnetize and soften them, are placed on a carbon platform inside a glass chamber. An electric current rapidly heats the material to thousands of degrees Celsius in seconds. Chlorine gas then reacts with non-REE components like iron, forming chlorides with low boiling points—iron chloride vaporizes at 315°C, compared to iron's 3,000°C—allowing them to deposit on the chamber walls. The REEs remain as oxides or oxychlorides on the platform, yielding over 90% purity and recovering more than 90% of the elements. The residue can be remagnetized by exposure to a magnet.
Tour emphasized the potential for the US: “The country’s scurrying to try to see how we can get these [REEs],” he said. “And, in our argument, it’s all in our waste… We have it right here, just pull it right back out of the waste.” Compared to hydrometallurgical extraction, which Tour calls “a messy, messy process” due to its heavy use of acids and solvents, this method cuts energy use by 87%, greenhouse gas emissions by 84%, and operating costs by 54%. With 66.2 million tonnes of e-waste produced globally in 2022—where REE concentrations exceed natural ores—and mining's environmental toll, Tour added: “You might as well just get it from waste.” The technique may extend to other e-waste forms.