Rare earths: what they are and why they are important

BarcelonaFrom toothpaste to euro bills and mobile phones, most of the things we use every day are made from elements that come from underground. Furthermore, in recent years, the use of minerals has increased exponentially due to the energy transition and our increasingly technological society. Some of these materials are considered strategic and critical, with high added value and crucial for industry. And within this group are rare earths.

What are rare earths?

They are a group of 17 chemical elements, 15 of them from the lanthanide group, in addition to scandium and yttrium. They are called land Because, as Ramon Carbonell, CSIC research professor in Geosciences Barcelona (GEO3BCN-CSIC), points out, in the past this was the designation given to oxides. And the adjective rare This does not mean that they are present in low concentrations, because they are, in fact, quite abundant, but rather that they are very difficult to find in nature in isolation.

"There are many, but they're not pure, but rather mixed with chemically altered forms or other materials, which requires the application of chemical processes to separate them," Carbonell points out. Furthermore, they're not concentrated in deposits, but rather widely dispersed, which complicates their extraction. Therefore, although they began to be discovered in the 18th century, they didn't begin to be exploited on an industrial scale until the 20th century.

Why are they important?

Their magnetic, optical, and electrical properties currently make them irreplaceable in numerous advanced applications. For example, they have very high conductivity, making them crucial for fiber optics, LED displays, and electronic devices.

Where are they used?

To give you an idea, a single modern cell phone or computer contains at least 75 chemical elements obtained from at least 12 different minerals, which enable touchscreens, light emitting, and vibration, among other features. Rare earths are used in advanced chemical processes, defense, and aeronautics; to manufacture radars and sensors; in renewable energy and rechargeable batteries; space satellites and large telescopes; and in the medical industry.

Where are they found?

They are usually found in mountainous formations, associated with mineral deposits of any kind. They usually appear in small quantities mixed within other exploited minerals and in the form of oxides. They are often found in copper mines, for example. The world's largest deposit of rare earths is located in Bayan Obo, in northern China, from where around 50% of the world's production of these minerals is extracted. There are also reserves in Vietnam, Russia, the United States, Canada, Brazil, and Australia.

Kiruna, in Swedish Lapland, a major mining region in the Scandinavian country, houses the largest reserve of rare earths in Europe. They also exist in interesting abundances in Greenland. Hence, points out Patricia Córdoba, a senior scientist at the CSIC at the Institute for Environmental Diagnosis and Water Studies (IDAEA) in Barcelona, ​​​​the United States' interest in this country, which belongs to Denmark. However, this researcher points out, "there is a serious environmental problem there, because many rare earth deposits also contain uranium and thorium; both radioactive elements that could be released during the extraction process, which would pose serious risks to human health and the environment, contaminating soil and water."

They are also found in Río Tinto, in Huelva, although in small concentrations. In Catalonia, there had been explorations to search for critical minerals years ago, but now there is no exploitation of critical raw materials underway, largely due to social pressure, Córdoba points out. Likewise, Carbonell adds, "we have such small quantities that it is not feasible to extract them."

It has also been observed that some asteroids and moons of other planets contain high concentrations of metals that could contain rare earths. Therefore, missions to exploit these bodies could be considered in the future.

How are they extracted?

To obtain them, it is necessary to open mines, like traditional ones used to recover metals. Since rare earths are mixed with other minerals, very aggressive processes must be applied to separate the elements. Acids and other chemicals are used that release toxic substances in the process. "They have a huge environmental impact; it's clear that they are not sustainable in any way," Carbonell assures. Once separated, rare earths must be purified, also through aggressive chemical processes. "It is crucial to treat the waste generated properly so as not to contaminate the soil or groundwater deposits," emphasizes Córdoba, from Idaea-CSIC. Furthermore, some minerals release radioactive waste during the process, which further complicates their management.

Rare earths extracted around the world are shipped to China, which refines 85% of these materials. In the 1980s, this Asian country boosted their production as a national priority and built specialized facilities for separation and purification. Nowhere else are they as advanced. "Environmental regulations there have been very lax; things have been done that would have been unthinkable in Europe," Córdoba notes.

Where do the rare earths used in Europe come from?

On the European continent, social pressure during the 1980s and 1990s due to environmental and sustainability problems associated with mining led to the abandonment of the exploitation of high-value-added minerals for industry. "That makes us dependent on China," emphasizes Córdoba, who explains that after the European Commission recognized in 2008 that Europe was in a critical situation, it began legislating to reverse it. Thus, in 2011, it published a list of high-value-added metallic elements considered strategic, including rare earths. This list, which is updated every three years, has increased the number of metals included.

Furthermore, last year the law on critical raw materials was approved in the EU, which seeks to incentivize their extraction and proposes that 10% of the materials needed for European industry can be extracted in the EU by 2030. "There is a catch and it is that they do not say them, because they do not say how," highlights Córdoba, for whom "it would also be necessary to implement refineries and recycling plants for these metals in Europe; which would take at least one to two decades."

Are there alternatives to rare earths?

The high environmental impact caused by the extraction, recovery, and processing of these minerals, coupled with China's monopoly, has led experts to call for the search for alternative materials capable of providing the same characteristics. In this regard, nanomaterials, for example, are being researched. Recycling is also a desirable option, although current technology can barely recover critical materials to cover 20% of European demand. In part, this is because many materials cannot be fully recovered. Of lithium, for example, present in rechargeable batteries for electric vehicles, only around 1% can be recovered.

Therefore, there are growing calls for legislation to oblige manufacturers to implement eco-design in products and extend their useful life. "We are developing recycling technologies, but they still don't allow us to recover enough materials to meet current demand," says Córdoba, who leads the Recopps project for the recovery of critical materials. One of the main obstacles is that "recovering material from a cell phone, for example, requires more resources than buying it new." "They're not designed to be recycled; we need greater awareness and policies that promote recycling and eco-design," he claims.

And also, Carbonell recalls, a change as a society. The current consumption model and its constant growth makes these rare earths increasingly necessary to continue manufacturing objects. The impact is not only environmental, but also one of social justice. "As a society, we must decide where they come from, whether from China or Africa, where the laws are not as restrictive as at home, or we can exercise responsibility and try to extract them here, although it won't be able to meet Europe's current needs. The price we will pay is the impact on our environment," Carbonell argues, for whom "In countries like China or Senegal, the labor force that extracts these minerals, often children, works in very difficult conditions," he laments.

What are 10 of the most sought-after rare earths used for?

Praseodimi

Used for permanent magnets in electric vehicles. Also used in electric motors, especially in wind turbines and electric vehicles. Also used in drones. It makes the smallest and quietest magnets, like those in home refrigerators.

Scandium

It's found in aircraft structures in an alloy with aluminum; in tennis rackets; and in bicycles to make these objects harder. And as an additive in mercury vapor lamps.

Gadolini

It is used to make magnets, crystals, and high-refractive-index garnets; also in lasers, X-rays, computer memory, and as a contrast agent in MRIs.

Europium

Fundamental material in red and blue phosphors for television and computer screens.

Samari

Crucial to the development of modern electric motors.

Itri

It's found in objects such as LCD screens and energy-saving light bulbs. It allows for the fantastic red color of flat screens. It's also used to make high-temperature superconductors and yttrium iron garnet microwave filters.

Ytterbium and terbium

They allow computer data to be stored on increasingly smaller and larger devices due to their magnetic properties.

Neodymium

Used to make electric motors, especially in wind turbines and electric vehicles, and in drones. It allows magnets to be smaller and quieter, like those in home refrigerators, and also very powerful. It is key when space and weight are limiting factors, which is why they are used in computer hard drives. These magnets are also used in power steering, electric windows, and speakers. This rare earth is also used as a colorant in ceramic glazes and various types of glass, and in the manufacture of eyewear used by welders, as it absorbs the amber light from the electric arc flame.

Astronomers use it to calibrate devices called spectrometers and infrared radiation filters. And some crystals containing neodymium are used in the manufacture of synthetic rubies used in infrared radiation lasers. Neodymium lasers are used in dentistry and medicine.

Lantà

It constitutes up to 50% of digital camera lenses, including those in mobile phones. It is used in hybrid electric vehicle batteries; in steelmaking to remove impurities; and in the production of special alloys. It is used as a catalyst base for oil refining; in high-refractive-index glass, for hydrogen storage, and in battery electrodes.

Ceri

It is used as a chemical oxidant in lens polishing; as a yellow colorant for glass and ceramic objects; as a catalyst for self-cleaning furnaces and as catalysts for cracking in oil refineries. It is used in steelmaking to remove impurities and in the production of special alloys.