Our modern life depends on rare earth elements, and one day soon we may not be able to meet the growing demand.
because their special attributesthese 17 metal elements are important components of computer screens, cell phones and other electronics, compact fluorescent lights, medical imaging machines, lasers, optical fibers, pigments, polishing powders, industrial catalysts – the list goes on (SN Online: 1/16/23). Notably, rare earths are important components of high-power magnets and rechargeable batteries in electric vehicles, as well as the renewable energy technologies needed to move the world to a low- or zero-carbon future.
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In 2021, the world 280,000 metric tons of rare earths mined — about 32 times the amount mined in the mid-1950s. Demand will only increase. Experts estimate that by 2040 we will need seven times as much rare earths as we do now.
It is not easy to satisfy this appetite. Rare earth elements are not present in concentrated deposits. Miners must excavate large quantities of ore, treat it physically and chemically to concentrate the rare earths, and then separate them. The transition is energy-intensive and dirty, requires toxic chemicals, and often produces small amounts of radioactive waste that must be disposed of safely. Another issue is access: China has a near monopoly on mining and processing; America has only one active mine (SN Online: 1/1/23).
There are no good substitutes for most of the work that rare earths do. So, to help meet future demand and diversify those who control supply—perhaps even making rare earth recycling “greener”—researchers are looking at alternatives to traditional mining.
Proposals include from Extraction of metals from coal waste Really standout ideas, like mining on the moon. But the method most likely to make an immediate impact is recycling. “Recycling is going to play a very important and central role,” said Ikenna Nlebedim, a materials scientist at Ames National Laboratory in Iowa and the Department of Energy’s Critical Materials Institute. “That’s not to say we’re going to get rid of the critical material challenge by recycling.”
Still, in the case of the rare-earth magnet market, recycling could meet as much as a quarter of rare-earth demand in about 10 years, according to some estimates. “That’s huge,” he said.
But there are technical, economic and logistical hurdles to overcome before rare earths in old laptops can be recycled as regularly as aluminum in empty soda cans.
Why is rare earth extraction so difficult?
Recycling seems like an obvious path to get more rare earths. Standard practice in the US and Europe is to recycle 15% to 70% of other metals such as iron, copper, aluminum, nickel and tin. Today, however, only about 1% of the rare earth elements in older products are recycled, says Simon Jowitt, an economic geologist at the University of Nevada, Las Vegas.
“Copper wire can be recycled into more copper wire. Steel can be recycled into more steel,” he said. But many rare earth products “are not very recyclable in nature”.
In touchscreens and similar products, rare earths are often mixed with other metals, making them difficult to remove. In some respects, recovering rare earths from waste items is similar to the challenge of extracting rare earths from ores and separating them from each other. Traditional rare earth recovery methods also require hazardous chemicals such as hydrochloric acid and a lot of heat, and therefore energy. In addition to the environmental footprint, the cost of recycling may not be worth the effort given the low production of rare earths. For example, a hard drive may only have a few grams; some products only provide milligrams.
Still, chemists and materials scientists are working to develop smarter recycling methods. Their technique puts microbes to work, doing away with acids in traditional methods or trying to bypass extraction and separation.
Microbial buddies could help recycle rare earths
One approach relies on microscopic partners. Gluconobacter Bacteria naturally produce organic acids that can extract rare earth elements such as lanthanum and cerium from spent catalysts used in petroleum refining or phosphors used in lighting. Yoshiko Fujita, a biogeochemist at the Idaho National Laboratory in Idaho Falls, says bacterial acid is less harmful to the environment than hydrochloric acid or other traditional metal-leaching acids. Fujita leads reuse and recycling research at the Institute for Critical Materials. “They also degrade naturally,” she said.
In experiments, bacterial acids recovered only about one-quarter to one-half of the rare earth elements from the spent catalyst and phosphorus. Hydrochloric acid can do a better job – in some cases as much as 99% extraction.but bioleaching may still be profitableFujita and colleagues in 2019 at ACS Sustainable Chemistry and Engineering.
Assuming a plant recycles 19,000 metric tons of spent catalyst per year, the team estimates annual revenue of about $1.75 million. But feeding the acid-producing bacteria on-site is quite an expense. With the bacteria fed refined sugar, the total cost of producing the rare earths is about $1.6 million per year, leaving only about $150,000 in profit. However, switching from sugar to corn stover, chaff and other harvest residues could cut costs by about $500,000 and boost profits to about $650,000.
Other microbes can also help extract rare earths and use them further. A few years ago, researchers discovered that some bacteria that metabolize rare earths produce a protein that preferentially grabs these metals. this protein, lanmodulin, isolatable rare earth Two components of a neodymium-rare earth magnet from each other, eg from dysprosium. A lanmodulin-based system could potentially eliminate the need for many of the chemical solvents commonly used in such separations. The waste products left behind – proteins – will be biodegradable. But whether the system will be successful on a commercial scale is unknown.
How to extract rare earths from discarded magnets
Another approach that has been commercialized skips acid and uses copper salts to extract rare earths from discarded magnets, a worthy goal. NdFeB magnets contain approximately 30% rare earths (by weight), the largest single-metal application in the world. One forecast suggests that recycling neodymium from US hard drive magnets alone could meet about 5% of global demand, excluding China, by the end of the decade.
A team led by Nlebedim developed a technique that uses copper salts to leach rare earths from e-scrap fragments that contain magnets. Soaking e-waste in a solution of copper salts at room temperature dissolves the rare earth elements in the magnets. Others can be dug up and recycled on their own, and the copper can be reused to make more brine. Next, the rare earths are solidified and, with the help of additional chemicals and heat, converted into powdered minerals called rare earth oxides. Nlebedim’s team has shown that the process can recover 90% to 98% of the rare earth elements, using the process also on leftover material from magnet manufacturing that would normally go to waste, and that the material is pure enough to make new magnets.
An economic analysis of the method shows that, in a best-case scenario, recycling 100 tons of surplus magnet material using this method could yield 32 tons of rare earth oxides, with a net profit of more than $1 million.
The study also assessed the environmental impact of the method.Compared to producing a kilogram of rare earth oxides through one of the main mining and processing methods currently used in China, the copper salt method has less than half the carbon footprint. Nlebedim’s team reported in 2021 that it produced an average of about 50 kilograms of carbon dioxide equivalent per kilogram of rare earth oxides, compared with 110 kilograms ACS Sustainable Chemistry and Engineering.
But it’s not necessarily greener than all forms of mining. One sticking point is that the process requires toxic ammonium hydroxide and roasting, which consumes a lot of energy and releases some carbon dioxide. Nlebedim’s group is now adapting the technique. “We want to decarbonize the process and make it safer,” he said.
In the meantime, the technology seems so promising that TdVib, an Iowa company that designs and manufactures magnetic materials and products, has licensed and built a pilot plant. TdVib president and chief executive Daniel Bina said the initial target was to produce two tons of rare earth oxides per month. The facility will recover rare earths from old hard drives in data centers.
Noveon Magnetics, based in San Marcos, Texas, already produces recycled NdFeB magnets. In typical magnet manufacturing, rare earths are mined, transformed into metal alloys, ground into a fine powder, magnetized and formed into magnets. Noveon eliminated the first two steps, said company CEO Scott Dunn.
After degaussing and cleaning discarded magnets, Noveon directly grinds them into powder before reassembling them into new magnets. Unlike other recycling methods, the rare earths do not need to be extracted and separated first. Dunn says the final product is more than 99 percent recycled magnets, with the addition of small amounts of virgin rare earth elements — what he calls a “secret recipe” — that allow the company to fine-tune the magnet’s properties.
Noveon’s method compared to traditional magnet mining and manufacturing Reduce energy use by approximately 90%Noveon’s CTO Miha Zakotnik, and other researchers report in 2016 Environmental Technology and InnovationAnother analysis in 2016 estimated that for every kilogram of magnets produced through Noveon’s method, about 12 kilograms of carbon dioxide equivalent are emitted.That is Greenhouse gas emissions are about half that of conventional magnets.
Dunn declined to say how many magnets Noveon currently produces or how much the magnets cost. But these magnets are being used in some industrial applications, such as pumps, fans and compressors, as well as some consumer power tools and other electronics.
Logistical obstacles to rare earth recycling
Even if researchers clear the technical hurdles, there are still logistical hurdles to recovery. “We don’t have a system for collecting end-of-life products that contain rare earths,” Fujita said, “and there’s a cost to dismantling them.” With a lot of e-waste, you have to find fragments that contain these precious metals before rare earth recycling can begin.
Noveon has a semi-automated process for removing magnets from hard drives and other electronic devices.
Apple is also trying to automate the recycling process. The company’s Daisy robot can disassemble iPhones. In 2022, Apple announced a pair of robots named Taz and Dave that could facilitate the recycling of rare earths. Taz can collect magnet-containing modules that are usually lost during shredding of electronic equipment. Dave can recycle magnets from the Haptic Engine, Apple’s technology that gives users tactile feedback when they tap the iPhone screen.
Even with robotic assistance, things would still be a lot easier if the company designed the product in a way that it could be easily recycled, Fujita said.
No matter how good recycling is, Jowitt sees no avoiding increasing mining to feed our rare earth-hungry society. But he agrees that recycling is necessary. “We’re dealing with an inherently finite resource,” he said. “We’re better off trying to extract what we can, rather than dumping it in landfill.”