Elementos terras raras – o que são, aplicações e mercado mundial
Also known as the gold of the 21st century, Rare Earth Elements are widely used in high-tech equipment such as catalysts, solar cells, magnets, batteries, and lasers.
Because of this, government agencies in several countries have started to encourage the development of the production chain of this mineral commodity.
In Brazil, one of these initiatives is the National Mining Plan 2030, strategic tool to guide medium and long term policies that can contribute to the mineral sector being a foundation for the sustainable development of the Country.
Let’s learn a little more about these elements?
What are the Rare Earth Elements?
The Rare Earth Elements are a group of seventeen elements, fifteen of which belong to the lanthanide group [elements with atomic number (Z) between 57 and 71, i.e. from lanthanum – La to lutetium – Lu], which are joined by scandium (Z = 21) and yttrium (Z = 39), included because they have physical-chemical properties similar to the REEs.
Yttrium, Lanthanum and Neodymium. Source: Rocio et al. (2012).
REE do not occur as free metals in the earth’s crust, due to their behavior
The geochemical concentrations occur as a mixture of various REEs in minerals. These elements are found as components of accessory minerals, in the form of inclusions, filling fractures in other minerals and/or as replacement elements in the mineral.
The geochemical similarity of all the REEs allows for substitution between them in the structure crystalline mineral. This results in their wide distribution in the earth’s crust and the formation of minerals composed of several of the REE.
Despite these similarities in geochemical properties, the metallurgical, chemical, catalytic, electrical, magnetic, and optical properties vary subtly from one element to another.
REE minerals can be easily exploited, such as monazite from placer deposits. The separation of REEs from other elements is relatively easy, however their separation into individual oxides and/or metals are complex and expensive processes due to the small differences in their chemical behaviors.
Applications of Rare Earth Elements
REE are considered strategic elements because of their wide application in high-tech products. Its importance in modern industry is due to its numerous applications in metallurgy, wind and nuclear power, the oil industry, mining, and agriculture, among others.
Check out some applications of the Rare Earth Elements:
- NdFeB alloy – to produce super magnets, widely used in electric cars, power systems, and high-speed trains;
- Europium – on computer and television screens;
- Lutetium, cerium, scandium, lanthanum and neodymium – separation of components of Petroleum;
- Lanthanum – solar energy;
- Tulio – X-Ray devices.
World Rare Earth Market
Brazil was one of the largest producers of monazite (rare earth phosphate, uranium and thorium) until the middle of the last century, replaced by the US in the 1980s, which came to dominate the market.
Monazite crystal (João Torres Mine, Muqui, Espírito Santo). Source: Rob Lavinski & irocks.com.
Starting in 1984, China began producing REEs, sharing the world market with the US, and from 1990 on, gradually began to dominate the market.
Brazil currently has the world’s third largest known reserve of rare earths, but this wealth is not exploited due to the cost of extraction and separation technology, which forces the country to import these elements to use as raw material in the industries.
The world’s largest known reserves of REE are located in China, Vietnam, Brazil, Russia, and India, respectively.
|
Country |
Reserves (Million tons – Mt) |
|
China |
44 |
|
Vietnam |
22 |
|
Brazil |
21 |
|
Russia |
12 |
|
India |
6.9 |
The world’s largest reserves of REE. Source: U.S.GEOLOGICAL SURVEY, 2022
Regarding production, China continues to stand out and produced about 140 Mt in 2020.
It is worth mentioning that there is a worldwide effort to develop the production chain of
REE in view of its importance in high-tech productsand clean energy.
According to Fernando Landgraf (Escola Politécnica USP), the world market for rare earths is relatively small in financial terms, moving about $5 billion per year.
The viability of REE extraction projects depends on important points to be highlighted, such as: small market, high production costs, technological and environmental issues.
Rare Earth Deposits in Brazil
The known deposits and occurrences in the country are distributed nationwide. The most economically important are associated with the alkaline carbonate complexes, mainly of the Igneous Province of Alto do Paranaíba.
REE deposits occur in naturally rich rocks influenced by rock-forming processes, such as magmatic enrichment by hydrothermal fluids, magmatic segregation and/or redistribution and concentration by superficial processes.
Walters et al. (2010) proposes the simplified division of REE deposits into two main categories:
- primary – associated with igneous rocks and hydrothermal processes;
- secondary – formed by concentration through sedimentary and weathering processes.
The table below shows the Brazilian REE deposits and their classifications.
|
Primary |
Association |
Types |
Examples |
|
Carbonatite |
Magmatic / Veins and Stockworks |
Araxá (MG), Catalão (GO), Seis Lagos (AM) |
|
|
Peralkalkaline rocks subsaturated in silica |
Plutons/stocks and dikes |
Repartimento (RR), Morro do Ferro (MG) |
|
|
Granite Rocks |
Differentiated Granites |
Pitinga (AM), Serra Dourada (GO), Granitos Rondonianos (RO) |
|
|
Secondary |
Placer marinho |
Sedimentary |
Buena (RJ), Guarapari (ES), Cumuruxativa (BA) |
|
Placer fluvial |
Sedimentary |
São Gonçalo do Sapucaí (MG), Pitinga (AM) |
|
|
Clays with adsorbed ions |
Perfil laterítico |
Serra Dourada (GO) |
Classification of the Brazilian REE deposits. Source: Walters et al. (2010).
Challenges of rare earth elements production in Brazil
The Brazilian potential for RRE is great. Today, the country has the second largest reserve world with 21 Mt of mineable reserves of rare earth oxides (REO).
This scenario, however, does not put Brazil at an advantage in relation to the other countries, since there is a need for strong investment in the development of the technological routes of each deposit. This is because each mineralization requires routes appropriate to the type of ore in order to be economically viable, as they are expensive, low yielding and highly polluting processes.
Despite the growth in consumption of clean energy products and electric cars, which use REO in their manufacture, the demand for this mineral good will not show a significant increase in order to make the different projects that are underway in theworld.
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References
CODEMGE. http://recursomineralmg.codemge.com.br/substancias-minerais/terras-raras/
USGS. https://pubs.usgs.gov/periodicals/mcs2021/mcs2021-rare-earths.pdf
USGS. https://pubs.usgs.gov/pp/1802/o/pp1802o.pdf
Rare earths: current situation and perspectives. https://web.bndes.gov.br/bib/jspui/handle/1408/1527
Report: Evaluation of the Rare Earth Potential in Brazil – CETEM, CPRM
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