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An Overview of the Recent Status of Critical and Strategic Metal Production and Development in India
Published in Abhilash, Ata Akcil, Critical and Rare Earth Elements, 2019
B.D. Pandey, Abhilash, Pratima Meshram
Unlike titanium, physical and chemical separation of niobium and tantalum is needed for the extraction of these metals by halide metallurgy. Tantalum and niobium occur in nature as mixed oxide – columbite–tantalite mineral having the general formula of (Fe, Mn)(Ta, Nb)2O6. This mineral has been the major resource in India and is obtained as a by-product from mica mining. The process of separation of the two homologous metals includes hydrofluoric acid dissolution to bring Ta and Nb values into the solution, and separation by SX system using TBP (Mirji et al., 1999). The separation of Nb–Ta includes the following steps: Material preparation through crushing/grinding.Direct dissolution in HF/sodium hydroxide fusion.Solvent extraction using TBP as a solvent.Precipitation of niobium hydroxide/tantalum hydroxide.Calcination of hydroxide to fluoride salt.
Altered pyrochlore from the Szklary rare-element pegmatite, Lower Silesia, Poland
Published in Adam Piestrzyński, Mineral Deposits at the Beginning of the 21st Century, 2001
Minerals of the columbite group are the most common Nb-Ta phases as well as the principal source of these elements. Their chemical composition may be expressed as AB2O6, in which A is mainly Fe2+ or Mn2+ (more rarely Mg), whereas B is Nb and Ta. The pyrochlore group species are less common than columbites, but they constitute quite a large and chemically much more diversified mineral family. According to Hogarth (1977), with later modifications by Ercit et al. (1994) and Lumpkin & Ewing (1995), the general formula of pyrochlore minerals is: A2-mB2X6-wY1-n·pH2O, where A is Ca, Na, K, Sb3+, U, Pb, Sr, Th, REEs, Bi3+, Ba, Mn2+, Fe2+; B is mostly Nb, Ta, Ti, and minor W, Zr, Sn, Fe3+, Si, Al; X is O, OH; while Y is OH, O and F. Hogarth (1977) defined three main subgroups of the pyrochlore group on the basis of major B-site cations: pyrochlore subgroup with Nb+Ta > 2Ti and Nb > Ta, micro lite subgroup with Nb+Ta > 2Ti and Ta ≥ Nb), and betafite subgroup with 2Ti ≥ Nb+Ta. Ercit et al. (1993) distinguished pyrochlores with the so-called normal structure, with cations at the A site and anions at the Y site, and the so-called inverse pyrochlores, with large cations (Cs, Rb, and minor K) at the Y site, and vacancies at the A site. Vacancies at the A, X and Y sites result in pyro chlore s with defected structures (m = 0-1.7, w = 0-0.7, n = 0-1), stabilized by the incorporation of p = 0-2 H2O molecules (Lumpkin & Ewing 1995). Ercit et al. (1994) elucidated the mechanism of water introduction at the A site and determined the maximum content of H2O per formula unit as 1+3/8m, corresponding to 10-15 wt.% H2O. However, there have been found such pyrochlore species in which analytical totals are below 85 wt.%. In such cases a certain deficit of B cations may occur and the standard normalization of the atomic contents to 2 B atoms per formula unit (apfu) sometimes fails. Possibility of the B-cations mobilization was suggested by Lumpkin & Ewing (1995), basing on the results of Gieré (1990). Very high water contents estimated from analytical totals may indicate that H2O molecules might occur not only at the A and Y sites, but also at other structural positions, e.g. O vacancies.
Process Applications and Challenges in Mineral Beneficiation and Recovery of Niobium from Ore Deposits – A Review
Published in Mineral Processing and Extractive Metallurgy Review, 2022
Nnaemeka Stanislaus Nzeh, Samson Adeosun, Abimbola Patricia Popoola, Abraham Adeleke, Daniel Okanigbe
Columbite, tantalite or coltan and pyrochlore ores are regarded as the most important primary mineral sources of Nb and Ta and also their major sources of industrial or commercial production (Berhe et al. 2017; Parker and Fleischer 1968; Sanchez-Segado et al. 2015; Shikika et al. 2020). Columbite otherwise called niobite or columbate/niobate is a hard, heavy complex oxide ore of the crystalline black mineral group. It is primarily a mineral ore for Nb and often times for Ta and niobate of Fe and Mn. These elements however are the considerable constituents of the ore, possessing a general chemical formula of (Fe,Mn)(Nb,Ta)2O6 (Ayanda and Adekola 2011; Baba et al. 2018; Ige et al. 2005). The mineral columbite has a submetallic luster and an orthorhombic or body centered cubic (BCC) crystal structure. Columbite mineral is generally described as a low-grade complex oxide ore of majorly metal oxide compounds like niobium penta-oxide (Nb2O5) of ~55–78% content and ~5–30% tantalum penta-oxide (Ta2O5) as its main constituents in the ore composition with significant associated oxide gangue minerals/elemental impurities (Agulyansky 2004; Ayeni, Ibitoye and Adeleke 2012; Baba et al. 2018; Bamalli, Moumouni and Chaanda 2011; Berhe et al. 2017; Ryan 2018).
Kinetics and mechanism of low-temperature aluminothermic reduction of manganese tantalate
Published in Canadian Metallurgical Quarterly, 2022
Alexander Klyushnikov, Roza Gulyaeva, Sofia Petrova, Lyudmila Udoeva
Tantalum is a rare refractory metal with high strength and plastic characteristics that have led to its widespread use in many areas of industry [1]. The majority of tantalum produced is used in electric vacuum and chemical engineering, in the production of electrolytic capacitors, hard and heat-resistant alloys [1, 2]. Common natural sources of tantalum include ores containing minerals of the tantalo-niobates group, which are isomorphic series of complex oxides with the general formula (Fe,Mn)(Nb,Ta)2O6. Depending on the predominance of niobium or tantalum, the mineral is called columbite or tantalite. Tantalum production from such ores is possible according to a scheme that includes [1–5] gravity concentration, acid leaching of concentrates with the transfer of niobium and tantalum to a solution, extraction separation of niobium and tantalum, aluminothermic reduction of Ta2O5 with alloying additives of manganese or iron (in the form of metals or oxides), vacuum heating and electron-beam remelting of Ta–Al–Mn or Ta–Al–Fe alloys to obtain pure tantalum. At the Ta2O5 reduction stage, the addition of alloying additives and excess aluminium to the batch mixture reduces the melting points of the alloy and slag and contributes to their effective separation in the liquid phase [3]. At the same time, manganese and iron are initially present in tantalite (columbite), so it is advisable to exclude hydrometallurgical operations from the process flowsheet and obtain alloys of the Ta–Nb–Al–Mn–Fe system by direct aluminothermic reduction of tantalum-containing concentrates.