Abstract
Ta and Nb are considered critical raw materials due to their properties and potential applications in a wide range of sectors. This study deals with Sn-Ta-Nb minerals from the Penouta mine (Orense, Spain), the only active mine in Europe producing tantalum minerals. These minerals are obtained from mining waste accumulated during old mining operations in tailing ponds. The industrial processing flowsheet is based on successive gravimetric stages followed by low intensity magnetic separation to reduce ferromagnetic contaminants. A Sn-Ta-Nb concentrate, with grades between 35–45% Sn and 4–7% Ta2O5 and Nb2O5, is obtained in this stage with plant recoveries around 60–70%, respectively. A chemical-mineralogical characterization by size fractions, XRF and XRD was carried out to implement a size classification stage in the processing plant. The finest fractions, containing higher grades of well-liberated Sn, Ta, and Nb minerals were utilized as the feed for dry high intensity magnetic separation (DHIMS) multifactorial tests, while coarse fractions were regrinded to maximize performance. The favorable results obtained in these tests demonstrate that two products with commercial quality can be obtained: a cassiterite concentrate with grades between 70–78% SnO2 and a tantalite-columbite concentrate with grades ranging between 12 and 14% Ta2O5 and Nb2O5, while also increasing the overall recovery of the plant.
Highlights
The modern and competitive economy relies heavily on a range of critical raw materials owing to the risk in their supply and their economic importance [1,2]
This study aims the chemical-mineralogical characterization by size fractions of the Sn, Ta and Nb primary concentrate to study the feasibility of continuing their mineral processing by carrying out operations such as classification by circular vibrating screen and dry high intensity magnetic separation (DHIMS, hereinafter) multifactorial tests
It can be noted that Sn, Ta, Nb contents increase with decreasing particle size, so that the highest concentration of these metals are found below 106 μm; on the contrary, MnO, Fe2O3, SiO2, MgO are commonly concentrated in coarser fractions, according to the findings of [10,11]
Summary
The modern and competitive economy relies heavily on a range of critical raw materials owing to the risk in their supply and their economic importance [1,2]. Among these critical raw materials are Ta and Nb, with significant applications in the technological and aeronautical fields [3]. These elements are mainly contained in minerals such as columbite and tantalite, which come mainly from the mines of Brazil and Central Africa respectively [2]. In order to reduce dependence on imports of Ta and Nb in Europe, it is necessary to increase the investigation of deposits that contain these elements and the processes for their concentration in Europe, within the framework of the Circular Economy [5].
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