Characterization, Classification, Dry High Intensity Magnetic Separation (DHIMS) and Re-rinding Techniques to Improve the Mineral Performance of Sn-Ta-Nb Mineral Concentrate

Ta and Nb are considered critical raw materials; due to their properties and potential applications in wide 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 are obtained from mining wastes accumulated during old mining jobs in tailing ponds. The industrial processing flowsheet is based on successive gravimetric stages followed by low intensity magnetic separation to reduce ferromagnetic contaminants. 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, FRX and DRX was carried out to implement a size classification stage using a circular vibrating screen in the processing plant. The finest fractions, containing higher grades of well liberated Sn, Ta, Nb minerals, were the feeding for dry high intensity magnetic separation (DHIMS) multifactorial tests, while, coarse fractions were re-grinded to maximize performance. The good results obtained in these tests demonstrate that two products with commercial quality could 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, also increasing the overall recovery of the plant.