A dimethyl ether-driven fractional crystallization process devised by researchers from U.S. Idaho National Laboratory and U.S. Ames Laboratory efficiently separates rare Earth elements (REEs) and transition metals from scrapped permanent magnets. This use of dimethyl ether, a gaseous compound that served as one of the first commercial refrigerants, was successfully demonstrated in the treatment of REE-bearing permanent magnet leachates as an atom-efficient, reagent-free separation method.

Shavings from discarded magnets are placed in a solution with lixiviants, a liquid used to selectively extractScheme depicting stages and passes in dimethyl ether-fractional crystallization. Source: C. Stetson et al.Scheme depicting stages and passes in dimethyl ether-fractional crystallization. Source: C. Stetson et al. metals from the material. Once the desired metals are leached from the material into the liquid, the new treatment scheme is applied.

The dimethyl ether-driven process uses far less energy and pressure than traditional methods, typically conducted at hundreds of degrees Celsius. Fractional crystallization can be carried out at ambient temperatures and requires only slightly elevated pressures of around five atmospheres. In comparison, the pressure in an unopened 12-ounce can of soda is 3.5 atmospheres. The lower energy and pressure requirements of the process translates into cost reductions as valuable REEs consumed in the manufacture of wind turbines, computer systems and other products are recovered.

Competing technologies also use added chemical “reagents” to drive precipitation and other separations, which inevitably become additional waste products with financial and environmental consequences. This is not the case for the dimethyl ether-based fractional crystallization described in Nature Communications.

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