A Review of Niobium-Tantalum Separation in Hydrometallurgy
Niobium and tantalum are chemically similar and are associated with each other in nature which makes it very difficult to separate. For many years, the separation of tantalum from niobium involved the fractional crystallization of potassium heptafluorotantalate away from potassium oxypentafluoroniobate monohydrate, this method has been supplanted by solvent extraction from fluoride-containing solutions by the use of solvent extractants such as Octanol, bis(2-ethylhexyl)phosphoric acid (DEHPA), Alamine 336, methyl isobutyl ketone (MIBK), tri-nbutyl phosphate (TBP) or cyclohexanone. A detailed review of the various processes involved in the breakdown treatment of niobium and tantalum primary sources, extraction and separation and newer processes of extraction as well as the various technique involved were discussed. Keyword: Niobium, Tantalum, Columbite, Tantalite, Solvent extractant and Solvent extraction.
Salting Out Effect of Electrolyte Solutions in The Extraction of Tantalum and Niobium Using Aqueous Biphase System
The salting-out effect of various solutions of electrolyte in the extraction of tantalum and niobium using aqueous biphasic system (ABS) was investigated. This was achieved by leaching ball-milled Tantalite ore with mineral acids (H2SO4 and HF) in the ratio of 3:1. The leached liquor was then divided into five parts and each part mixed with ABS formed (e.g. PEG-3350/20wt/wt Na2CO3) for the extraction of tantalum and niobium and then with Na2SO4, K2CO3, K2SO4, KBr, and KI salts in turn. The amount of tantalum pent oxide extracted was determined using X-ray fluorescence method. The results show that the percentage tantalum extracted was in the range of 28.17% to 54.93% i.e. increased in the order KI< KBr < K2CO3< Na2SO4, < K2SO4 with 28.17%, 30.28%, 34.51%, 43.31% and 54.93% respectively; while that of niobium pent oxide increased in the order KI< KBr < K2CO3< Na2SO4, < K2SO4 with 27.3%, 29.35%, 33.78%, 34.64% and 41.98% respectively. In conclusion electrolyte with high ionic charge and hydration radius salts-out Ta2O5 better in the ABS/electrolyte system than those with low values.
Solvent Extraction Separation of Nb and Ta at Mho : Potentialities if Cyanex® 923 Versus Mibk.
ABSTRACT Since 1963, MHO is running an industrial solvent extraction unit in its Hoboken plant for the extraction and separation of Niobium and Tantalum from concentrated HF - H 2 SO 4 solutions with MIBK. The flowsheet of this production unit is shown. An alternative process with Cyanex® 923 i.o. MIBK as extractant has been developed through a lab scale test program. The development work as well as the resulting flowsheet are discussed. Eventually both processes are compared.