A research team has developed a process that uses a commercial refrigerant to separate rare earth elements and transition metals from magnet wastes.
The process uses a gas compound called dimethyl ether to create fractional crystallization.
“This process begins with a magnet that’s no longer useful, which is cut and ground into shavings,” says Caleb Stetson, experimental lead of the research project. “The magnet shavings are then put into a solution with lixiviants, a liquid used to selectively extract metals from the material. Once the desired metals are leached from the material into the liquid, we can then apply a treatment process.”
In an article published in Nature Communications, the researchers write: “Treatments at distinct temperatures ranging from 20-31° C enable crystallization of either lanthanide-rich or transition metal-rich products, with single-stage solute recovery of up to 95.9% and a separation factor as high as 704.”
“Upon completion of a crystallization, the solvent can be recovered with high efficiency at ambient pressure,” according to the researchers. “This separation process involves low energy and reagent requirements and does not contribute to waste generation.”
“It can be difficult to adjust temperatures for evaporative crystallization, but this fractional crystallization process eliminates all those challenges,” says Stetson. “For the process to separate distinct fractions from a metal-bearing solution, we only need to adjust the temperature by 10 degrees.”
Source: Idaho National Laboratory