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Scandium and Beyond: Materials Science Allows for Harvesting of Mine Tailings

As nations and industries grapple with the global push towards net zero carbon emissions, researchers  from India’s Bengaluru Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR) have discovered a new material called “single-crystalline scandium nitride (ScN)” that is able to “emit, detect, and modulate infrared light with high efficiency making it useful for solar and thermal energy harvesting and for optical communication devices by effectively converting infrared light into renewable energy, according to a recent government press release.

The researchers find that the “exotic polaritons [i.e. quasi-particles] in the ScN can be utilized for solar and thermal energy harvesting.  Also, belonging to the same family of materials as gallium nitride (GaN), scandium nitride is compatible with modern complementary-metal-oxide-semiconductor (CMOS) or Si-chip technology and, therefore, could be easily integrated for on-chip optical communication devices.”

While discoveries like these in their initial stages are far from commercially viable, these findings once more underscore the importance of materials science, which has been yielding key breakthroughs at neck-breaking speeds, yielding new applications for many critical materials — in this case, and not for the first time in recent years, scandium.

Followers of ARPN may recall the “Light Rider,” a high-tech motorcycle, which, because it is held together by an intricate web of “Scalmalloy,” is perhaps the lightest motorcycle in the world. Scalmalloy is an “aluminum alloy powder ‘with almost the specific strength of titanium’ [used] to build incredible structures by fusing thin layers of the material together.” One of its key components is scandium – which explains the first syllable of its somewhat curious name, Aluminum being the middle-portion, with the “M” standing for Magnesium.

It is new applications like these that are making scandium an increasingly indispensable tech metal, particularly in the context of the lightweighting revolution – a development marked by the “growing imperative to lightweight transportation, buildings, and infrastructure systems.” 

Add to that the newly-found application for scandium in renewable energy, and we have another catalyst for the adoption rate of scandium, use of which was long limited to “niche Western products such as baseball bats and lacrosse sticks,” because of its classification as an “if” metal.  Writes the British Minor Metals Trade Association:

“Scandium has long been considered an ‘if’ metal. If only it were available in quantity, it could transform aircraft production and fuel consumption. If only it were available in quantity, it could speed the emerging hydrogen economy. If only it were available in quantity, it could accelerate the rollout of 5G technologies. And so on.

The view has been that scandium could be used in numerous large-volume applications, if only supplies were sufficient to meet the potential demand. Manufacturers regularly cited a lack of sufficient scandium supply as the reason why they did not roll out new uses and products containing scandium.”

Russia has long used scandium-aluminum alloys in its MIG fighter jets, but then Russia has long had commercial domestic scandium production.

While the same cannot be said for the United States, including the material on the U.S. Government Critical Minerals List, may be a sign that change is underway for North America’s scandium supplies. Writes Reuters’s Andy Home in regard to a long-standing mining operation in Quebec:

“It turns out, though, that Rio Tinto has been producing scandium all along at its titanium operations over the Canadian border. But the metal now deemed critical was going with other waste into a tailings pond.  The company has now worked out how to extract scandium oxide from the titanium processing stream, making it North America’s sole producer.”

In fact, harvesting mine tailings — again courtesy of materials science yielding research breakthroughs — is quickly becoming an important piece of the critical mineral resource supply puzzle, as mine waste tailings often “contain metals (such as rare earth elements) that were not considered worth extracting when the ores were initially processed, but which have since increased in value and use,” according to a 2017 research paper.

Reuters’s Home points to another Rio Tinto operation, its Kennecott copper smelter in Utah, where the company is converting the site’s anode slime waste stream into copper-tellurium, which is then sent on for refining and usage in photovoltaic solar panels.

Writes Home:

“[These] are examples of a new industry trend towards so called whole-concept mining, also known as total mining, broadening a historical focus on one or two primary products to potentially everything of metallic value in the ore being mined and processed.”

Pointing to other examples, including Russia’s Rusal harvesting aluminum tailings to recover scandium, he concludes:

“The USGS has been tasked with mapping and collecting data for areas containing mine waste ‘to increase understanding of above-ground critical mineral resources in previously disturbed areas’.

It’s not only a highly cost-effective way of closing the country’s critical minerals gaps, but also a way of closing the green-on-green divisions that cause every new energy transition metals mine to run into fierce environmental opposition.

The green future, it turns out, can be achieved at least in part by cleaning up the mining legacy of the past.”