Rare earth elements (REEs) are a group of 17 metallic elements that are used in high-tech electronics, electric vehicle motors, defense systems, and other consumer goods, according to NETL. REEs can be extracted from coal waste by-products, but a very common element—aluminum—can interfere with such extraction. NETL researchers have developed a scalable method to detect aluminum using sensors. The solution could help inspire innovators to develop reliable domestic REE supplies.
Because the concentration of aluminum is often significantly higher than that of REEs in coal waste by-product feeds, its presence can interfere with the extraction and purification of REEs from some sources, NETL shared in a news release. NETL researchers Scott Crawford, John Baltrus, Ki-Joong Kim, and Nathan Diemler have devised an effective, renewable, technology that can detect aluminum in liquids for removal, clearing the way for more-effective REE recovery.
NETL’s new technology consists of a metal-organic framework thin film made of copper linked by 2-aminoterephthalic acid. "The high-quality film can be grown within 30 minutes using a metal oxide template at room temperature, which eliminates the need for external heating or specialized equipment," according to NETL.
Researchers tested the sensing films on three fly ash leachates. The film emits blue light in the presence of water and becomes significantly more intense in the presence of aluminum ions. During the testing, the film's fluorescence intensity correlated well with the aluminum concentration in the samples, highlighting the sensor's potential for real-world use, according to NETL. The same sensing film may also be recycled for multiple sensing cycles.
Domestic Mineral Sources Could Be Aided by the Metal-Organic Framework Thin Film
NETL points out that since January 2021, DOE has invested $25 million in 21 projects in Appalachia, the Gulf Coast, and other West and Midwest locations to support the production of REEs and critical minerals in traditional fossil fuel-producing communities. DOE also recently announced up to $156 million in funding from the Bipartisan Infrastructure Law for a first-of-a-kind facility to extract and separate REEs and critical minerals from unconventional sources like mining waste.
In addition to detecting an impurity in REE feedstocks, removing and refining aluminum from liquid sources can also provide an additional domestic source of common metal, which can be used in transportation, packaging, construction, consumer durables, electrical transmission lines, machinery, and other applications.