All of the world's discarded phones, broken laptops and other discarded electronics combine to be a treasure trove of rare earth elements (REEs). But isolating and recovering these increasingly sought-after materials is no easy task.
However, a team of researchers claims to have developed a way to separate REEs from waste (in this case using magnets) that is relatively simple, requires less energy, and is not nearly as emission- and pollution-intensive as current methods. The team published paper a description of this method in the Proceedings of the National Academy of Sciences.
In short, the process involves using an electric current to very quickly heat spent magnets to very high temperatures and using chlorine gas to react with the non-REEs in the mixture, holding them in the vapor phase. James Tour, one of the authors and a professor of materials science and nanoengineering at Rice University, says the research could help the United States meet the growing need for these elements.
“The country is rushing to see how we can get these [REEs]”,” he says. “And in our minds, it's all in our waste… We have it right here, just take it back out of the trash.”
It's getting hot in here
In 2018, Tur and his colleagues discovered that this rapid heating process, called flash Joule heating, can turn any source of carbon, including coal, biochar and mixed plastics, into graphene, a very thin, strong and conductive material.
Building on this, in 2023 they developed a method that uses instantaneous Joule heating and chlorine. In this work, they determined the Gibbs free energy, the reactivity of a material, for the oxide form of all 17 REEs and nine common oxides found in REE wastes.
The crushed waste magnets are placed on a carbon platform and surrounded by a glass chamber. A current passes through the platform, quickly producing enormous heat, reaching thousands of degrees Celsius in a matter of seconds. Chlorine gas is then released into the chamber, which creates chlorides of unwanted elements such as iron and lowers their boiling point.
