Extractive Recovery of Tantalum(V) and Niobium(V) with Octanol from Hydrofluoric Acid Solutions Containing Large Amounts of Titanium(IV)

Extractive recovery with n-octanol of tantalum(V) and niobium(V) from hydrofluoric acid solutions containing large amounts of titanium (up to 2-3 M) was studied. The conditions were found for separation of tantalum(V) and niobium(V) from titanium(IV), allowing recovery of 95.7 and 84.1% of tantalum and niobium fluoride complexes, respectively, in one extraction cycle, with 2.6% recovery of titanium.     

Isolation of niobium,tantalum, and titanium complex fluoride salts with alkali metal cations

Fluoride and oxofluoride salts of niobium, tantalum, and titanium were isolated. They precipitated from aqueous solutions and upon washing of organic extracts with aqueous solutions of ammonium, potassium, and sodium salts. The compositions of the isolated compounds were studied. Different compositions were established for the niobium salts that precipitated upon the dissolution of unwashed niobium hydroxide in hydrofluoric acid under the atmospheric pressure, in an autoclave, and upon addition of sodium, potassium, and ammonium salts to purely fluoride solutions of niobium, as well as for the tantalum ammonium and sodium salts isolated from aqueous and organic solutions. The data obtained can be used for the synthesis of niobium, tantalum, and titanium complex fluoride salts with various compositions.     

The quantitative separation and determination of tantalum and niobium using anion exchange chromatographY

A method is described for separating .and determining niobium and tantalum in mixtures of the two. A solution of the two elements in 3M hydrochloric.0.1M hydrofluoric acid is put on a column of Deacidite FF, the niobium is rapidly eluted with 3M hydrochloric.0.1M hydrofluoric acid and the tantalum is recovered by elution with 4M ammonium chloride-M ammonium fluoride. A complete separation is obtained and the two elements are recovered as their oxides after precipitation. The effecth of some other elements have been examined.     

Effect of Phase Composition on Sulfuric Acid Leaching of Tantalum-containing Alloys

Phase composition of iron-based tantalum-niobium alloys (Ta 2-5, Nb 3-6, Si up to 12, C 1.4-2.4%) was studied. The kinetics of leaching of ferroalloys with H₂SO₄ aqueous solutions and with mixtures of sulfuric and hydrofluoric acids was considered. The conditions of hydrochemical treatment of the alloys, which make it possible to concentrate niobium and tantalum in the solid residue through dissolution of up to 94% of Fe, 90% of Mn, and 70% of Si, were found.     

Extraction Recovery of Tantalum(V) and Niobium(V) from Hydrofluoric and Hydrofluoric-Sulfuric Acid Aqueous Solutions with Octanol

Comparative study of extraction of tantalum(V) and niobium(V) with octanol and tributyl phosphate was made. The data on distribution of tantalum(V) and niobium(V) between octanol and hydrofluoric and hydrofluoric-sulfuric acid aqueous solutions were obtained. The flowsheet for preparation of pure tantalum and niobium oxides was developed.     

Processing of Precipitates of Hydrated Tantalum(V), Niobium(V), and Titanium(IV) Oxides in Loparite Technology

Conditions were studied for the dissolution in HF of hydrated tantalum(V), niobium(V), and titanium(IV) oxides, which are formed by acid decomposition of loparite, and also for the selective extraction of Ta(V) with octanol from the resulting fluotitanic solutions.     

Radiochemical separations by adsorption on some oxides of groups IVB and VB

The interactions between titanium dioxide, niobium pentoxide and tantalum pentoxide and 55 elements have been studied by batch experiments in nitric acid. The variation of the distribution ccefficients with nitric acid concentration is presented and discussed. The adsorption mechanism for some ions has also been investigated. Column experiments have been carried out to check the practical use of the investigated oxides in radiochemical separations. A^99mTc generator based on the use of TiO₂ is also presented.     

Interaction of loparite concentrate with ammonium hydrodifluoride

Results obtained in a study of the interaction between the loparite concentrate and ammonium hydrodifluoride are reported. It was found that the reactions of the main components of the concentrate with NH₄HF₂ yield complex ammonium fluorometallates. It was shown that water leaching of the fluorinated product makes it possible to transfer niobium and tantalum into solution together with fluoroammonium salts of titanium and silicon and to concentrate rare-earth elements in the insoluble residue in the form of complex salts of general formula NaLnF₄.     

Separation of trace concentrations of tantalum from niobium and some other heavy metal ions by extraction with N-oxide of trioctylamine

The distribution of tantalum(V) between 0.1M trioctylamine oxide dissolved in xylene and sulphuric acid solutions has been studied. On the basis of results on the distribution, it is concluded that at sulphuric acid concentration 0.5M, tantalum is probably extracted by a solvate mechanism as the complex Ta(OH) (SO₄)₂·3TOAO. It has also been shown that tantalum can be quantitatively separated from niobium, uranium, thorium and rare earth elements by extraction with N-oxide of trioctylamine from 0.5M sulphuric acid solution.     

Solvent extraction and separation of zirconium,niobium and tantalum by 2-carbethoxy-5-hydroxy-1-(4-tolyl)-4-pyridone

Summary Extraction of zirconium, niobium and tantalum from oxalic and hydrofluoric acid solutions, by 2-carbethoxy-5-hydroxy-1-(4-tolyl)-4-pyridone (HA) dissolved in chloroform was studied. Extraction mechanism for the extraction of zirconium from oxalate solutions and of niobium from fluoride solutions is proposed. Separation of zirconium and niobium from oxalate solution as well as from fluoride solution and tantalum and niobium from fluoride solution is described. Back-extraction of these metals is possible by hydrofluoric and oxalic acid. Results obtained show that the efficiency of extraction by HA decreases in the sequence tantalum > niobium > zirconium.

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Zusammenfassung Die Extraktion von Zirkonium, Niob und Tantal aus oxalsauren und fluorwasserstoffsauren Lösungen mit Hilfe einer chloroformischen Lösung von 2-Carbäthoxy-5-hydroxy-(4-tolyl)-4-pyridon wurde untersucht. Ein Extraktionsmechanismus für Zirkonium aus Oxalatlösungen und für Niob aus Fluoridlösungen wurde vorgeschlagen. Die Trennung von Zirkonium und Niob aus einer Oxalatlösung oder aus einer Fluoridlösung sowie von Tantal und Niob aus einer Fluoridlösung wurde beschrieben. Die Rückextraktion dieser Metalle mit Flußsäure und Oxalsäure ist möglich. Die Ergebnisse zeigen, daß die Effizienz der Extraktion in der Reihenfolge Tantal > Niob > Zirkonium abfällt.

     

Colorimetric determination of niobium in titanium alloys

There is need for a method for the determination of niobium in titanium alloys, since niobium-titanium alloys are becoming increasingly important. The determination of niobium in this type of alloy is an extremely difficult matter. Many approaches were tried before the problem was solved. In the method proposed in this paper the sample is dissolved in a mixture of hydrofluoric and nitric acids, the solution evaporated to a small volume, and boric acid added. Two tannic acid separations are then made to separate the niobium from the bulk of the titanium. The niobium, is determined colorimetrically by the thiocyanate method using a water-acetone medium. A study was made of the possible interference of elements that might be present in titanium alloys. It was found that the presence of tantalum causes two opposing tendencies. Tantalum can cause high results for niobium because it forms a complex with thiocyanate which is visually colorless but shows some absorption. Tantalum can cause low results for niobium by hindering the development of the niobium color. The resultant effect of the tantalum depends upon the amount of tantalum present, the amount of niobium present and the ratio of tantalum to niobium. The presence of more than one per cent. tungsten can lead to high results for niobium. Other elements that might be present in titanium alloys do not interfere with the method. The procedure is designed for titanium alloys containing 0.05 to 10 per cent. niobium. The method is reasonably rapid. Six determinations can be finished in two days. The method should be applicable to many other materials besides titanium alloys.     

Separation of niobium and tantalum with cupferron

An attempt to separate niobium and tantalum by cupfcrron was only moderately successful at pH 4.5 to 5.5 in the presence of a magnesia mixture as a coagulating agent. A more satisfactory separation of niobium and tantalum from each other, tried out up to ratios of 30:1 and 1.30, is effected with Sn⁺² or Sn⁺⁴ as a co-precipitating agent under the conditions described niobium can be separated, in the presence of complexone III, from almost all the ions except U, Be, Ti and PO₄^-3. Iron and other tervalent elements, when present in 100 fold excess with respect to niobium, require double precipitation The method gives highly satisfactory results when applied to the analysis of niobium in niobium-molybdenum stainless steel.The use of titanium as a co-precipitant is less successful than that of tin     

Destructive and non-destructive determination of titanium in yttrium,niobium and tantalum oxides by photon activation

Destructive and non-destructive procedures have been developed for the determination of titanium by photon activation analysis. The non-destructive analyses with an internal standard method are performed on niobium and tantalum oxides while destructive determinations, including non-isotope addition and radiochemical separation, are applied to yttrium oxide samples.     

Annealing of thin B/Nb<Subscript>2</Subscript>N bilayers,B/Nb bilayers and Nb/B/Nb trilayers via rapid thermal processing (RTP)

B/Nb and B/Nb₂N bilayers and Nb/B/Nb trilayers of about 550 nm total thickness have been deposited on Si(100) wafers with 100 nm thermally grown oxide. Nb and B layers were deposited by magnetron sputtering. Nb₂N layers were prepared by nitridation of Nb films via rapid thermal processing (RTP). The samples were annealed subsequently at temperatures between 600 and 1,200 °C in an RTP system under Ar or NH₃ gas flow to study interdiffusion and reactivity of niobium, boron and nitrogen. Formation of phases was investigated by X-ray diffraction (XRD); surface morphology and roughness were studied via scanning electron microscopy (SEM) and atomic force microscopy (AFM), respectively. Elemental depth profiles of selected samples were recorded by secondary ion mass spectrometry (SIMS). Annealing of the B/Nb bilayers and Nb/B/Nb trilayers under Ar leads to the formation of Nb₃B₂ at 1,200 °C at the B/Nb interface. At lower temperatures the high oxygen content in the boron layer is supposed to hinder the formation of borides due to formation of glass-like boron oxides. In NH₃ several niobium nitrides are formed but no boride phases. Here again the reactivity of boron with niobium is suppressed by the high oxygen content and boron oxide formation. During annealing of the B/Nb₂N bilayers no borides were formed indicating that well-formed Nb₂N is an effective diffusion barrier for B.     

Separation and gravimetric determination of niobium,tantalum and titanium by precipitation with n-benzoyl-n-phenylhydroxylamine

A method is described for the separation and gravimetric determination of niobium, tantalum and titanium by precipitation with N-benzoyl-N-phenylhydroxylamine. Titanium is kept in solution with EDTA and hydrogen peroxide, and the earth acids are precipitated in 1N sulphuric acid Niobium and tantalum are separated and determined by a modification of the method of MAJUMDAR AND MUKHERJEE. All three metals are finally precipitated with N-benzoyl-N-phenyl-hydroxylamine. In the analysis of complex materials niobium, tantalum and titanium are separated from other constituents by a double precipitation with N-benzoyl-N-phenylhydroxylamine in the presence of EDTA and tartaric acid     

Separation of niobium and tantalum with phenylarsonic acid

Phenylarsonic acid permits satisfactory separation of niobium and tantalum and estimation of tantalum from an oxalate solution containing sulphuric acid up to pH 5.8. For complete precipitation of niobium the pH should exceed 4.8. In mixtures, tantalum is precipitated below pH 3.0 and niobium is then precipitated above pH 5.0. When the oxalate concentration is high, recovery of niobium with cupferron is recommended. When the ratio of Nb₂O₅, to Ta₂O₅ exceeds 2:1, reprecipitation of tantalum is necessary. The effect of interfering ions is studied.     

Analysis of alloys of titanium,niobium and tantalum by ion exchange

A procedure for the analysis of alloys of titanium, niobium and tantalum is described. After dissolution the metals are separated by ion exchange in hydrochloric-hydrofluoric acid media. Finally the metals are determined spectrophotometrically,     

Determination of niobium, tantalum, zirconium, and hafnium by atomic emission spectrometry using directed thermochemical reactions

A method is proposed for determining niobium, tantalum, zirconium, and hafnium in mineral stocks. It is based on the preliminary synthesis of analyte complexes in hydrofluoric acid containing cadmium oxide. It was shown by spectrographic measurements that the decomposition products of complexes in a small chamber electrode of an ac carbon arc are volatile individual analyte fluorides.     

Substitution features in the isomorphous replacement series for metal-organic compounds (NbxTa1−x)4O2(OMe)14(ReO4)2, x=0.7, 0.5, 0.3—Single-source precursors of complex oxides with organized porosity

Trimetallic oxoalkoxide complexes (Nb_0.7Ta_0.3)₄O₂(OMe)₁₄(ReO₄)₂ (I), (Nb_0.3Ta_0.7)₄O₂(OMe)₁₄(ReO₄)₂ (II) and (Nb_0.5Ta_0.5)₄O₂(OMe)₁₄(ReO₄)₂ (III) were obtained by the interaction of rhenium heptoxide (VII) Re₂O₇ with niobium and tantalum alkoxides M₂(OMe)₁₀ (M=Nb, Ta) in toluene. The centrosymmetric molecules (I)-(III) can be considered as a product of condensation of two M₂(OMe)₉(OReO₃) molecules with the formation of two oxo-bridges. The specific feature of the structure is the uneven distribution of metal atoms in the crystallographic positions, where one symmetry-independent position, connected via μ-O with a perrhenate ReO₄⁻ group, is predominantly occupied by niobium atoms, while the other one connected via alkoxide groups has a higher tantalum content. The distribution of Nb and Ta in the structure is truly even only for compound III. The niobium and tantalum content is varied to a different extent for I (less) and for II (more), which is apparently due to small differences in the sizes of these two cations, resulting in preferences for packing of different molecules in the structures. Thermal decomposition of (Nb_1−xTa_x)₄O₂(OMe)₁₄(ReO₄)₂ (x=0.3, 0.5, 0.7) in air leads to the formation of crystalline species of solid solutions based on tantalum and niobium oxides displaying semi-ordered pores with the size of 100−250 nm. In the dry nitrogen atmosphere, the decomposition leads to the amorphous complex oxides containing rhenium, niobium and tantalum.