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1 Physicochemical Problems of Mineral Processing

1 2024

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Production of pure tantalum and niobium oxides by hydrometallurgical processing of coltan smelter cake from Tanganyika Province/RD Congo using NH4HF2-KOH flux system

Kitungwa Bertin K., Yuma Phalaris M., Kalenga Mubiayi. Pierre, Shengo Michel L., Ngubeni Grace, Moloto Nosipho, Mbayo Marsi K., Kyona Crépin W.

Physicochemical Problems of Mineral Processing

2024

Vol. 60, iss. 4

art. no. 192436

Pure tantalum and niobium oxides were produced from the molten cake after mixing oreNH4HF2-KOH in a respective mass ratio of 1/4/3. This resulted in solubilization yields of over 95% for Nb and around 92% for Ta in sulfuric acid solution 3 molar. Extraction of tantalum and niobium using octan-2-ol yielded over 95% niobium and 98% tantalum when pH is set at 0.5-1.0 and 1.5-2 respectively. The compounds K3NbOF6, K3NbO4 and K2TaF7 were identified after melting. While in aqueous solution ionic species such as NbF6 (OH) 23-, NbF6- and TaF72- are likely to be identified. Precipitation of tantalum and niobium in NH4OH solution (pH=7.50-8.0) as hydrated oxides after stripping with distilled water and crystallization identified hydrated oxides such as Ta2O5.nH2O, Nb2O5.nH2O. These two oxides were associated with a small amount of SiO2.nH2O as an impurity resulting from the extraction and precipitation of tantalum and niobium. SEM-EDS, XRD, TGA-DTG and FTIR analyses identified and characterized these compounds.