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.

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A Review of Niobium-Tantalum Separation in Hydrometallurgy

The Halides of Niobium and Tantalum

A review of solvent extraction separation studies of niobium and tantalum, either individually or together from other associated elements, using various solvents, is presented.

Solvent extraction separation of niobium and tantalum

Methyl isobutyl ketone (MIBK) is an industrially important solvent and chemical intermediate, which after methyl methacrylate and bisphenol A is the third largest tonnage product obtained from acetone MIBK is produced by four different routes: a three-step process via diacetone alcohol and mesityl oxide intermediates; a one-step process from acetone and hydrogen; a one-step process from isopropyl alcohol; and a single or multistep mixed feed process MIBK is generally considered to exhibit low mammalian toxicity However, MIBK must be handled with adequate ventilation Its vapor is heavier than air and can travel a considerable distance to a source of ignition The major use of MIBK is as a solvent for surface coatings It is also used in a variety of nonsurface-coating applications As a raw material it is used in the manufacture of rubber antiozonants


Keywords:

methyl isobuty ketone;
acetone;
solvents;
antiozonants;
mesityl oxide

Methyl Isobutyl Ketone

The acute and sub-acute toxicity of potassium niobate and niobium pentachloride has been investigated. Single intravenous doses of 20 mg Nb/kg or less to rats, rabbits, and dogs were not fatal. The LD50 (seven-day) value for mice and rats given a single intraperitoneal injection of potassium niobate was 13 and 92 mg Nb/kg, respectively. The oral LDso (seven-day) value for the rat was 725 mg Nb/kg. Renal injury was observed in all species following parenteral injection at doses ranging from 20 to 50 mg Nb/kg. Repeated intraperitoneal injections of nobium pentachloride or potassium niobate of 30 mg Nb/kg resulted in renal injury and death. Dietary levels as high as 1% of either compound were ingested by rats, for a seven-week period, without effect. The nephrotoxic action of niobium was not observed when the niobium salt was complexed with ascorbic acid prior to injection.

The Toxicity of Niobium Salts

A liquid-liquid extraction process for making tantalum and niobium boosts production rates 200% over the original process, and increases purity of the refractory metals from 99.7% to more than 99.9%. Key to the method is a series of mixer-settler boxes which operate on the principle of countercurrent extraction. Tantalum and niobium fluorides are fed into the boxes, and are separated from each other on the basis of solubility in methyl isobutyl ketone and aqueous solution at various acid concentrations. (auth)

Donald J. Soisson

Papers

STAFF-INDUSTRY COLLABORATIVE REPORT Tantalum and Niobium