July 16, 2024
What are ETRs?
Rare earth elements (RTEs) are a group of 17 chemical elements that have similar physical and chemical properties. They are used in various technological applications, such as magnets, batteries, lasers, catalysts and screens. Despite their name, some ETRs are quite abundant in the earth's crust, such as cerium and neodymium. However, separating rare earth elements is difficult.
ETRs are divided into three groups: light, medium and heavy. The light ones have low atomic numbers (57 to 60) and are more common in nature. The medium ones have intermediate atomic numbers (61 to 65) and are less abundant. The heavy ones have higher atomic numbers (from 65 to 71) and are the rarest and most valuable.
Below are all the rare earth elements and their respective atomic numbers
Light:
Medium:
Heavy:
Of the 17 rare earth elements listed above, 15 are members of the lanthanide series. The remaining two, scandium and trio, are transition metals included in the rare earths, as they often appear mixed with lanthanides in the same deposits.
The main ETR-bearing minerals are: monazite, bastnasite, xenotime and loparite, as well as laterite clays that absorb ions. These minerals can be found in igneous, sedimentary and metamorphic rocks, as well as in alluvial and residual deposits.
According to the Natural Environment Research Council there are more than 200 minerals that contain Rare Earth elements. These elements can occur in a wide variety of mineral and structural classes. However, they are preferentially found in the form of carbonates, phosphates, silicates, fluorides and oxides.
Bastnasite is a rare earth fluorocarbon that contains approximately 75 per cent rare earth oxides in its composition, with the predominant elements being cerium (Ce), lanthanum (La), neodymium (Nd) and, to a lesser extent, praseodymium (Pr). On the other hand, monazite is a phosphate with a rare earth oxide content similar to bastnasite, but with significant thorium (0 to 20 per cent) and uranium (0 to 16 per cent) content, which makes it radioactive and difficult to extract.
Xenotime is a phosphate with a rare earth oxide content of 60 per cent and is considered the main source of heavy rare earths, along with ionic clays. In addition, some minerals such as apatite, pyrochlore and zircon can have significant levels of rare earths, even though they are not classified as sources of these elements.
Rare earth elements (RTE) are found in low concentrations in the earth's crust, but can be found in various geological environments, both endogenous and exogenous. Endogenous deposits originate in the Earth's interior. They are related to geothermal and tectonic activity. Examples include the formation of igneous and metamorphic rocks, as well as the creation of mineral deposits associated with magmatic intrusions and volcanic activity. Exogenous deposits originate on or near the Earth's surface and are caused by external forces such as climate, water and gravity. Examples include erosion, sedimentation and the formation of sedimentary rocks. Exogenous mineral deposits, such as placers (deposits of heavy minerals formed by the action of water currents), are formed by processes of weathering and sedimentary transport.
Below we highlight some deposits according to geological environment, and the image below shows the tectonic environments that form rare earth deposits and the associated rocks.
Endogenous environments: Mountain Pass (USA), Bayan Obo (China), Pitinga (AM).
Exogenous environments: Araxá (MG), Vitória (ES), São Gonçalo (MG).
Rare earth elements are essential components in various products with a wide variety of applications, especially in technological devices used in everyday life, such as smartphones, hard discs, computer monitors, televisions and electric vehicles. ETRs also have diverse applications in medicine, lasers, radar and sonar.
Although the amount of ETRs used in a product may be relatively small in terms of weight or volume, they are indispensable for the functioning of these devices and also, in some cases, can have a significant value in the composition of these materials. For example, magnets made of ETRs represent only a tiny fraction of the total weight, without which induction motors would not be possible. They are also used in agriculture and energy. For this reason, ETRs are considered strategic for the economic and scientific development of several countries. See below for the main markets that use Rare Earths:
1 - Nickel Metal Hydride (NiMH) batteries:
2 - Li-ion batteries:
Automotive: The automotive industry, especially in the hybrid and electric vehicle segment, depends significantly on ETRs for the production of efficient, high-capacity batteries.
In summary, the use of ETRs in batteries has significant value from both a technical and economic point of view, influencing various industries and global markets.
In Brazil, the presence of rare earths is identified in the monazite sands of the coast, and they are also found mainly in deposits near inactive volcanoes. The largest reserves identified in Brazil are located in Amazonas, in the Seis Lagos area, Araxá (MG) in the Barreiro Complex, Poços de Caldas (MG) in Morro do Ferro and Catalão (GO).
Despite having one of the world's largest reserves of rare earths, Brazil is not among the largest producers of these elements, due to the high cost of extraction and separation technology, forcing the country to import these elements for use as raw materials in industries. However, this scenario could change in the coming years due to high demand and high foreign investment in the sector.
According to the National Mining Agency there are currently 648 processes for Rare Earths in Brazil, of which 111 are research authorisations, 14 mining concessions and 523 applications. Most of these processes are from the last three years.
In 2022 there was a significant increase in the number of research requests filed by the National Mining Agency (ANM). The number jumped from 90 in 2021 to 154 in 2022. The number of approvals also increased from 1 in 2020 to 7 in 2022.
Major rare earth projects are already under development in Brazil. Among them, we can highlight the company Serra Verde Pesquisa e Mineração Ltda which has started commercial production of mixed rare earth concentrate in Minaçu (GO). The company began commissioning the first phase of operations in June 2023 and production in January 2024. The concentrate contains a combination of neodymium (Nd), praseodymium (Pr), terbium (Tb) and dysprosium (Dy). The company's goal is to achieve annual production of at least 5,000 tonnes of rare earth oxide over 25 years.
Several foreign companies have been paying attention to Brazil and are beginning to invest more and more in rare earths. The Canadian company Appia Rare Earths for example, has signed an agreement with 3S Ltda and Beko Invest to acquire up to a 70 per cent stake in the Cachoeirinha (GO) rare earths project.
The exploration of rare earth metals faces several challenges:
Complexity of Extraction and Processing: Rare earths are rarely found in high concentrations, making extraction and processing complex and expensive.
Environmental Impact: Mining and processing can cause significant environmental damage, including water and soil pollution.
Geopolitical dependence: Production is dominated by a few countries, such as China, which can create strategic vulnerabilities and dependencies.
Strict Strict: There are strict environmental regulations in many countries that can limit exploration and production.
Recycling Technology: Rare earth recycling is still limited and faces technical and economic challenges, making it difficult to reuse these metals.
These challenges make exploration of rare earth metals a complex and strategic field.
The world's main producers of rare earths are China, the United States and Australia. China is the world's largest producer, accounting for more than 60 per cent of global annual production in 2022 (Source: US Geological Survey - 2023). In addition to these countries, other major producers are: Burma, Vietnam, Thailand and India.
China is increasingly consolidating its position as the world's largest ETR producer, with 210,000 tonnes of rare earths extracted in 2022, 25% more than in 2021 (168,000 tonnes). According to the United States Geological Survey the world reserves of rare earths in 2022 total 130 million tonnes, and the countries with the largest reserves are: China, Vietnam, Russia and Brazil.
China's hegemony in the rare earths market places other countries in a position of dependence and vulnerability, especially in scenarios of geopolitical tension or supply shortages.
To meet this challenge, a team of researchers led by Victor Mougel, from the Laboratory of Inorganic Chemistry at ETH Zurich, has developed an innovative method for the efficient recycling of rare earth metals. Recently published in the journal Nature Communications, the study presents a process based on tetrathiometalates, inorganic molecules that have demonstrated unique redox properties. These compounds act as ligands that facilitate the separation of rare earth metals from complex mixtures, allowing for more efficient, rapid and sustainable recovery.
By prioritising recycling over mineral extraction, this approach not only preserves precious resources and reduces negative environmental impacts, but also offers a practical and cost-effective solution to address global challenges in the supply of strategic metals. The Swiss researchers' initiative not only represents a significant scientific breakthrough, but also promises to transform the current paradigm of consumption and disposal of technological products, towards a more sustainable and resilient future.