USP researchers study rare earths in the Barreira Complex, in Roraima, focusing on nanotechnology for separation

In the Barreira Complex, clays with high cation exchange capacity (CTC) were identified, which allows them to attract and retain positively charged elements. Clay particles are negatively charged, while rare earth elements are positively charged. This difference causes the elements to remain attached to the clays.

The afternoon program began around 2pm by Professor Nilson Francisquini, PhD in Geology, from the University of Brasília (UnB), with the lecture “Challenges in prospecting and exploring rare earth deposits of the ionic absorption type: Brazilian examples”.

During the lecture, among other topics, he explained the characteristics of clays where rare earth elements can be found, such as ionic clays, capable of "trapping" the elements.

The area studied in Caracaraí has ​​more than 120 thousand hectares, rocks and clays with a shiny appearance, and is located between two mountains.

For Henrique, the size of the complex is comparable to the territorial area of ​​the city of São Paulo and requires extensive mapping work.

During the question and answer session, he highlighted that academic research is important to understand the region's mineral potential and develop forms of exploration that consider sustainability and environmental protection criteria.

Asked whether the Caracaraí region can technically be considered a rare earth reserve, researcher Henrique Eisi Toma stated that it is still too early to make a classification.

According to him, the project has been underway [at USP] for six months and, during this period, the team has already mapped the central region of the complex and carried out more than 100 exploratory analyses. Now, the samples undergo more detailed analysis to identify which rare earths are present and in what quantities.

“Now it’s scientific, so we have to have all the results of these analyzes to know how much rare earths there actually are,” he explained.

“We will use water with the clay, we will use sulfates […] this study is essential to define what the procedure is, what process we will choose to continue the program”, explained Kalil Toledo.

The researcher explained that the separation of rare earths is a difficult process and can require a large amount of resources, solvents and energy, which is not always economically viable. Therefore, the study seeks to work with clays, present in the area in Roraima and considered simpler to process.

The University of São Paulo (USP) began studying the rare earths of Roraima, in the Barreira Complex, in January 2026 and seeks to identify which elements are present in the region, measure their concentration and develop ways to separate them with nanotechnology, which is presented by Toma this Friday (18).

When talking about rare earths, Eisi highlighted the importance of the elements for the industry. In the case studied in Roraima, the proposal is to use nanotechnology to manipulate and separate elements, which have very similar chemical properties and, therefore, are difficult to process and separate.