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MIT process (from 36) tion to separate out economically impor-
tant metals like cobalt in recycled lithium-
“We are looking at very well-established ion batteries.
materials in conditions that are uncommon
compared to what has been done before,” Separating dysprosium
Allanore explains, “and that is why we are They also used their techniques to sepa-
finding new applications or new realities.” rate dysprosium — a rare-earth element
used in applications ranging from data
In the process of synthetizing high-tem- storage devices to optoelectronics — from
perature sulfide materials to support elec- rare-earth-boron magnets, or from the
trochemical production, Stinn says, “we typical mixture of oxides available from
learned we could be very selective and mining minerals such as bastnaesite.
very controlled about what products we
made. And it was with that understand- Metals like cobalt and rare earths are only
ing that we realized, ‘OK, maybe there’s found in small amounts in mined materi-
an opportunity for selectivity in separation als, so industries must process large vol-
here.’” umes of material to retrieve or recycle
enough of these metals to be economically
A mix of metal oxides viable, Allanore explains.
The chemical reaction exploited by the
researchers reacts a material containing By eliminating the need for liquid separa-
a mix of metal oxides to form new metal- tion and the extra steps and materials it
sulfur compounds or sulfides. requires to dissolve and then reprecipitate
individual elements, the MIT research-
By altering factors like temperature, gas ers’ process significantly reduces the costs
pressure, and the addition of carbon in incurred and emissions produced during
the reaction process, Stinn and Allanore separation.
found that they could selectively create a
variety of sulfide solids that can be physi- Adapting to large amounts
cally separated by a variety of methods, The next step is to show that the process
including crushing the material and sorting can work for large amounts of raw mate-
different-sized sulfides or using magnets rial — separating out 16 elements from
to separate different sulfides from one rare-earth mining streams, for example.
another.
“Now we have shown that we can handle
Current methods three or four or five of them together,
Current methods of rare metal separation but we have not yet processed an actual
rely on large quantities of energy, water, stream from an existing mine at a scale
acids, and organic solvents which have to match what’s required for deployment,”
costly environmental impacts, says Stinn. Allanore says.
“We are trying to use materials that are Stinn and colleagues have built a reactor
abundant, economical, and readily avail- that can process about 10 kilograms of
able for sustainable materials separation, raw material per day, and the research-
and we have expanded that domain to ers are starting conversations with several
now include sulfur and sulfides.” corporations with a view toward commer-
cializing the process. — Becky Ham
Stinn and Allanore used selective sulfida- mit.edu
