Flotação de minerais portadores de terras raras de depósitos de Goiás

Abstract

Rare earth elements (REEs) are key players in the energy transition and the development of a more sustainable matrix. However, over the years, China has come to dominate this market alone. Many countries have started to include REEs as strategic elements and to invest efforts in their production. Brazil has the third-largest reserve in the world but contributed only 0.2% to global production in 2021. Studies suggest that Brazilian reserves could be much larger, possibly even surpassing those of China, but there is still a need to develop routes capable of enabling this production. In this study, flotation tests were conducted on three ores from different locations in the state of Goiás, where potential deposits for REE production are found. Different collectors, depressants, and pH ranges were tested in a single flotation stage (rougher) aiming for metallurgical recoveries and grade elevations. Collectors tested included SHA (salicylhydroxamic acid), EPM MIN 233/20, macaúba pulp oil, Flotinor® 1682, Flotigam® 7500, and Lioflot®. As depressants, corn starch Stargill™ and sodium silicate (mod. 1 and 2.16) were used. The samples named CMOC, MOSAIC, and Iporá come from the Catalão II, Catalão I deposits, and the Iporá/GO region, respectively. The tests were conducted in a Denver benchtype flotation cell, with operational parameters defined in preliminary trials according to the CMOC company standard, which was part of the MoCa Project, a partnership between Brazilian and German institutions aimed at utilizing REEs discarded in the niobium beneficiation process at their unit in Catalão/GO. For the CMOC sample, the best results were obtained using SHA (500 g/t) and sodium silicate (mod. 2.16) (250 g/t), with metallurgical recoveries of 42.9%, a grade of 1.7%, and an enrichment of 2.93 times at pH 9. The MOSAIC sample was tested only with SHA (500 g/t) and sodium silicate (mod. 2.16), with a metallurgical recovery of 24.6%, a grade of 0.67%, and an enrichment of 1.18 times at a dosage of 750 g/t of sodium silicate. For the Iporá sample, the best results were achieved with macaúba pulp oil (500 g/t) and corn starch (800 g/t) for metallurgical recoveries of rare earth oxides of 63%, a grade of 4.5%, and an enrichment of 1.8 times at pH 8. The synergistic mixture of macaúba pulp oil (500 g/t) and SHA (100 g/t) with corn starch (800 g/t) also yielded similar results at pH 8. Although some tests have shown promise, it is essential to test synergistic mixtures of reagents that enable the production of REEs from deposits located in the state of Goiás.