University of São Paulo: Valuable and versatile: research with rare earths shows the way to create a productive chain in Brazil

THERare earths are a group of chemical elements, normally found in nature mixed with ores, difficult to extract – hence the name -, but with peculiar characteristics, such as intense magnetism and absorption and emission of light. These special properties make them used in a multitude of technological applications, such as LED lamps, lasers, supermagnets present in computer hard drives and electric car engines, and in the separation of petroleum components. Currently, Brazil has the world’s second 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 industries, mainly from China, the largest producer in the world.

At USP, research groups carry out studies with rare earths, obtaining promising results, such as a non-polluting separation method, based on nanotechnology, in addition to applications in lighting, lasers, steel production, solar cells, ultraviolet ray filters and automotive catalysts . The University also coordinates a National Institute of Science and Technology (INCT) returning to mastery of all stages of the production chain of manufacturing rare earth supermagnets, from mine to magnet, and is currently collaborating with the installation of a magnet factory in Minas Gerais.

The world’s largest proven reserves of rare earths are in China, with 44 million tons. Brazil comes right behind, with 22 million, the same amount as Vietnam, but ahead of Russia, with 12 million, India, with 6.9 million, and Australia, with 3.4 million, according to data from 2018 of the United States Geological Service (USGS).

“In Brazil, rare earths are found in monazite sands on the coast and mainly in deposits close to extinct volcanoes, such as in the cities of Araxá and Poços de Caldas, in Minas Gerais, and Catalão, in Goiás, and also in Pitinga, in Amazonas . It is likely that the Brazilian reserves are much larger than what is currently proven, especially in the Amazon”, reports Professor Fernando Landgraf, from USP’s Polytechnic School (Poli) , to Jornal da USP. “However, in the rare earths production chain, Brazil has the ore, it has the final consumption, as it imports supermagnets for wind generators and electric motors, but it does not master the intermediate steps of the process, that is, the separation of the elements and the manufacture of supermagnets.”

Professor Henrique Elsi Toma, from the Institute of Chemistry (IQ) at USP, reports that Brazil came to play a leading role in the field, by developing separation and purification technology. “The first deposit was discovered in 1886, on Cumuruxatiba beach, in Bahia, and in 1915 Brazil was the world’s largest supplier of monazite, a mineral extracted from sand that contains rare earths, and at the time was used to produce incandescent blankets, that allow gas lanterns to emit white light.” In 1946, chemist Pawell Krumholz, who later became a professor at USP, created the technique for separating rare earths from monazite and applied it at the company Orquima, which he had founded five years earlier. “In 1957, a line of research on rare earth chemistry was created at USP, coordinated by Professor Ernesto Giesbrecht”, he reports.

In the 1950s, the focus of monazite exploration became the extraction of thorium and uranium, used in the production of nuclear energy. “Brazil dominated the technology for extracting rare earths, but they had few significant technological applications. The situation changed with the advent of color television at the end of that decade, when screens were painted with europium to produce color images. Later, the main applications of rare earths became high-power magnets and lasers, using neodymium extracted from monazite, but by then Brazil had already lost space in the world market”, explains Toma. “In 1962, Usina Santo Amaro (USAM), which belongs to Orquima, was nationalized and became part of the Nuclemon company, whose name was changed in 1992 to Indústrias Nucleares do Brasil (INB). In 2004, the country stopped producing rare earths and, in 2012, monazite exports to China were interrupted, which began to monopolize the world market with its internal production. Although Brazil is considered a ‘mineral country’ due to the abundance of deposits, the focus is on the export of raw ore, especially iron, which does not require sophisticated or very costly extraction technologies.”

According to Fernando Landgraf, the world market for rare earths is relatively small in financial terms, moving around 5 billion dollars a year, but its strategic importance is enormous. “For example, rare earth magnets are indispensable for electric cars. China has invested in the entire production chain of rare earths, starting with extraction, passing through separation, production of magnets and finally the production of electric cars. It is obvious that she will want to sell the car, not the magnet”, he says. “Today, in Brazil, there is no one who extracts the rare earth concentrate separated from other elements, therefore, they are not commercialized. The cost of obtaining it is not compensating compared to the imported product. There are plans for Mineração Serra Verde, in Minaçu, in the State of Goiás, start producing and exporting the concentrate, but only from next year.” USGS data indicate that China is the world’s largest producer of rare earths, with 120 thousand tons extracted in 2018, followed by Australia, with 20 thousand tons, and the United States, with 15 thousand.

Art by Rebeca Alencar with images from Flaticon
Extraction and production chair
At IQ, Professor Henrique Toma’s research group, specialized in nanotechnology, developed a technique called magnetic hydrometallurgy for the separation of rare earths, simplifying and making the process cheaper. “The method uses magnetic nanoparticles modified with a chemical agent that captures the rare earths that are mixed with the ore, placed in a small reactor. After the nanoparticles are rescued with a neodymium magnet, their acidity is modified, releasing the rare earths”, he describes. “In the traditional process, carried out in gigantic reactors, this separation requires thousands of liters of solvent, which can only be used once and pollute the environment. With nanoparticles, once the rare earths are separated, they can be used again.”

According to Toma, the process is automated, non-polluting, facilitates the separation of different chemical elements and can be used in the recovery of rare earths from electronic waste. “To clean the environment, the ideal is not to explore, but just to recycle the ores, as happens with aluminum cans. For example, an electric car is estimated to contain a kilo of neodymium. When the vehicle becomes scrap metal, if it is not recycled, the neodymium becomes a pollutant. For this reason, it is essential to develop advanced techniques that will allow recycling in the future”, he emphasizes. “This is still a new technique, which has been producing publications and scientific works, but it needs support to reach the market – the research almost stopped due to lack of resources. Brazil has rare earths and technology, it could go a long way, but the companies do not have a tradition of technological development, almost everything is imported”, he says. The research was supported by the National Council for Scientific and Technological Development (CNPq) and one of the articles describing the magnetic hydrometallurgy technique was published in 2019, in the scientific journal Hidrometallurgy , and can be accessed at this link .

Together with the Technological Research Institute of São Paulo (IPT), USP coordinates the National Institute of Science and Technology Processing and Applications of Rare-Earth Magnets for High-Tech Industry (INCT Patria), which has collaborated with the installation of a laboratory-factory of rare earth magnets in Minas Gerais, LabFabITR. The factory, an initiative of the Minas Gerais Development Company (Codemge), will be installed in the municipality of Lagoa Santa, in Greater Belo Horizonte, based on a project prepared by a group from the Federal University of Santa Catarina (UFSC).

“The first two stages of the process, the concentration and separation of rare earths to obtain the neodymium oxide used in magnets, were coordinated by the Federal Government’s Mineral Technology Center (Cetem) and the Nuclear Technology Development Center (CDTN). , with the collaboration of Poli and the mining company CDMM, which supplies the rare earths used in the project”, describes Landgraf. “Researchers from IPT and Poli conducted the next steps, the transformation of neodymium oxide into metallic neodymium, used in the production of a metallic alloy with boron and iron. These elements are cast and undergo a controlled solidification process, from which very thin strips are obtained, for better control of the alloy structure. The strips are ground and the resulting powder is used to make the magnet.”

IPT also collaborated with studies on the protection of the magnet against corrosion. The factory’s equipment has already been purchased and the facilities should start producing in April of next year. “With LabFabITR, a production chain will be formed, from the extraction of neodymium to the manufacture of magnets for companies that produce electric motors and generators”, observes the professor at Poli. “The idea is that, in ten years, the factory will produce 100 tons of magnets per year. This number is lower than the demand in the Brazilian market, which is 2,000 tons per year, but there is an expectation that, when production is consolidated, companies will enter the project, allowing an increase in the number of magnets produced”. INCT Patria’s research involving LabFabITR is supported by the Coordination for the Improvement of Higher Education Personnel (Capes),

One light, several applications
Also at IQ, the group coordinated by Professor Hermi Felinto de Brito is researching luminescent materials that convert light, containing rare earths, which act both as efficient light emitters and can be applied as optical markers. “Rare earths have been used as light converters in lasers, displays, fluorescent lamps, LEDs and OLEDs”, says the professor. “We have developed new luminescent materials as emitting centers, whose applications have grown significantly in recent years, in advanced studies of photonics, optoelectronic devices, fluorescent biological markers, white light emitting devices, multicolor pigments and transparent emitting films. These elements are of great importance in the field of biomedicine, for example. USP Journal .

Brito exemplifies the activity of the group’s researchers, described in articles published in international scientific journals, such as the Journal of Material Chemistry and ACS Applied Material & Interfaces, with the recent development of rare earth compounds that act as optical markers on documents such as ID, passport, diploma, driver’s license and stamps, as well as on banknotes. “The main objective of these markers is to prove the authenticity through the luminescence of the material”, he highlights. The professor recalls that Brazil has always contributed to research on rare earths in the world, dominating the separation process and even exporting pure europium oxide in the middle of the last century. “However, in the 1970s and 1980s, Brazil had already lost its competitiveness in the market. Today, despite the country having huge reserves of rare earths, one of the biggest bottlenecks in production is the need for new technologies to separate these elements, because rare earths have similar chemical properties, making it difficult to produce them on a large scale and with high purity.” The research on optical markers has the collaboration of the Energy and Nuclear Research Institute, the Federal Universities of Pernambuco (UFPE) and Paraíba (UFPB) and the National Synchrotron Light Laboratory (LNLS), in addition to financial support from Capes, CNPq and Fapesp.

“Our group is currently developing research in automotive soot catalysis, photocatalysis for the decomposition of antibiotics and pollutants in water, recovery of rare earths from exhausted lamps and catalysts, and inorganic polymers for physiological range thermometers”, reports Professor Osvaldo Antônio Serra, coordinator from the Rare Earth Laboratory of the Faculty of Philosophy, Sciences and Letters of Ribeirão Preto (FFCLRP). “We use several rare earths, such as cerium for catalysis, europium and terbium for luminescence, neodymium and ytterbium for thermometry. There are some companies in Brazil that mine rare earths, in Minas Gerais and Goiás, but the quantity is small and production costs are high, compared to China. Furthermore, there is the environmental problem, which arises when opening the ore with concentrated acids and bases;

Recently, FFCLRP researchers managed to develop a method that uses luminescent materials to detect firearm residues, in collaboration with Professor Marcelo Firmino de Oliveira, from the Forensic Chemistry area of ​​the FFCLRP Chemistry Department. “Our group has also been working for 15 years with the development of sunscreens based on rare earths, specifically with cerium. We have a licensed patent and several scientific articles on the subject”, observes Serra. “In new collaborations with the Federal University of Pernambuco (UFPE), we started skin toxicity tests. It is hoped that in the future this formulation may be in sunscreens available on the market.”

The emission of light through rare earths is also being researched by the group of professor Euclydes Marega Junior, from the São Carlos Institute of Physics (IFSC) at USP. The most studied elements are erbium, ytterbium and thulium, which emit different colored lights. “Often, the presence of rare earths in everyday life is not even noticed. Do you know what the similarity is between a gas lamp and an LED lamp?”, asks the professor. “They don’t produce white light, only blue. In the lamp, an incandescent blanket receives blue light and turns it into white, actually a combination of lights of the three basic colors, blue, green and red, emitted by rare earths. The LED lamp is covered with a layer of cerium oxide, a rare earth, with the same function of emitting white light.”

Using a combination of erbium, terbium and thulium, the IFSC researchers created an LED that produces white light. “This LED emits infrared light, which is not visible. Rare earths are part of a conversion mechanism inside the LED, they absorb the infrared and turn it into visible light. Each material emits light of a different basic color, and because they are together, they form white light”. Marega Júnior points out that, without rare earths, it would be impossible to have low consumption lighting sources. “An LED bulb consumes 90% less energy than incandescent bulbs, which demonstrates the importance of rare earths. The great challenge for Brazil is to purify rare earths on a large scale, but there is no policy to encourage the industry, everything is bought ready-made; if there is an import problem, the factories stop.”

Lasers, solar cells, steel, catalysts
In addition to magnets, neodymium is used in the production of laser devices as it allows for light emissions with greater quality and color purity. “Most lasers emit a beam of light in only one direction, but today a new class is being studied, that of random lasers, in which light propagates in several directions, and which can, for example, increase the lighting power of light bulbs or the efficiency of cancer treatments, when reaching various points of the diseased tissue”, says engineer Josivanir Gomes Câmara, who researched light-scattering materials for random lasers at Poli. “Neodymium is mixed with glass made with tellurium and zinc oxides, a simple material to make and with great solubility, which makes it possible to increase the amount of rare earths in the mixture, making the laser more efficient.” The research findings, article published in the Journal of Luminescence , last May. Câmara intends to continue studies applying the technology in microelectronic devices.

The light-emitting properties of rare earths are also being researched for application in solar cells, or photovoltaic devices, which convert sunlight into electrical energy, in a study carried out at Ipen, which works in the graduate program in partnership with USP. “The objective is to develop and modify materials with persistent luminescence, that is, where emission occurs from minutes to hours after the excitation of the light source ceases, with visible emission, specifically in the green region, analogous to the maximum emission of the solar spectrum, using also the ultraviolet (UV) band for energy conversion”, reports Leonardo Francisco, the researcher responsible for the work. “The material used is a strontium aluminate matrix combined with europium and dysprosium, two rare earths. Europium emits light in the green region and increases UV light absorption, while dysprosium acts as a ‘trap’ for the storage of energy in the material, which causes persistent luminescence.” According to the researcher, the material is already being manufactured on a large scale, but it is necessary to produce it in the form of nanoparticles, better suited to the dimensions of solar cells. The research, described in dissertation master directed by Maria Claudia France Felinto da Cunha, from the Chemistry Center and Environment (CQMA) of IPEN, defended on March 1, is reported in article of the Journal of Alloys and Compounds , published on June 3. The study had the collaboration of the IQ, the National Synchrotron Light Laboratory (LNLS) and UFPE, in addition to financial support from Capes, CNPq, FAPESP and the National Nuclear Energy Commission (CNEN).

Also at Ipen, the use of rare earths was tested in surface treatments of metals, commonly used in industry to protect against wear, corrosion and oxidation. “Yttrium, lanthanum, neodymium, samarium and gadolinium, in the form of oxides and nitrates, were tried in the boreation of steel, a process that hardens the metal surface with the addition of boron, carried out in ovens at temperatures between 900 and 1000 degrees Celsius (°C)”, says researcher Cesar Roberto Kiral Santaella, author of the work, described in the thesis PhD defended at Ipen on June 16, 2020, supervised by Marina Fuser Pillis, from the Material Science and Technology Center (CCTM) at Ipen. “Mixed to the process reagents, rare earths accelerated the diffusion of boron, resulting in an increase in the thickness of the formed surface layers, which opens up the possibility of reducing the metal treatment time and, consequently, energy consumption. ” The research had the collaboration of the CQMA, the Federal Universities of Grande ABC (UFABC) and Rio Grande do Sul (UFRGS), and the Leibniz Institut, in Bremen (Germany).

Another application of rare earths is in automotive catalysts, which filter the carbon and particulate material (soot) produced by vehicles, reducing the emission of pollutants. At FFLCRP, a study by the Rare Earth Laboratory tested the use of a filter made of ceramic material (cordierite), already used in exhaust pipes, impregnated with a rare earth compound, cerium oxide (ceria). “The exhausts of vehicles powered by diesel and biodiesel eliminate a large amount of soot, which generates several problems for human health and has been the target of restrictive measures by the National Environmental Council (Conama) for the year 2022”, says Viviane de Carvalho Gomes, who carried out the research, under the guidance of Professor Osvaldo Antonio Serra. “Rare earths promote the complete combustion of the particulate material at a lower temperature than the combustion of soot. When alone, elemental carbon decomposes at 600°C, and with the presence of these catalysts this temperature dropped to 370°C.” The work, which had the collaboration of IFSC, UFPE, Federal University of Rio de Janeiro (UFRJ) and Warwick University (United Kingdom), was presented at the 1stCongress Frontiers of Nanoscience and Nanotechnology: Advances, held by young Brazilian scientists at the end of October. Currently, the FFCLRP group is writing an article for future publication. Viviane comments that for the technique to reach the market, it is necessary to complete the tests on stationary engines for diesel and biodiesel systems, in addition to the partnership with the private sector to develop tests on mobile diesel systems, that is, vehicles that circulate with fuels.”

Comments are closed.