Sine-wave polarographic determination of zirconium or niobium in aqueous media

The sine-wave polarographic determination of zirconium in aqueous media was investigated using solutions which were 0.55 – 5.5·10^-3M in zirconyl chloride and 1 M in potassium chloride and had been adjusted to pH 2.0 with hydrochloric acid. It was possible to determine zirconium in the concentration range of 0.05 to 0.4 mg per ml. The sine-wave polarographic behavior of zirconium in aqueous solutions in the pH range 2–3 is discussed. The sine-wave polarographic determination of niobium in aqueous media was investigated using concentrated sulfuric acid containing 5 to 0.1 mg of niobium per ml in a supporting electrolyte of citric acid; the determination of niobium was possible down to 0.1 mg of niobium per ml of concentrated sulfuric acid although the D.C. polarographic method was impractical for the determination of less than 0.5 mg of niobium per ml.     

Separation of95Zr and95Nb by means of sorption on silica gel from hydrochloric acid solutions

The adsorption behaviour of zirconium and niobium on silica gel from hydrochloric acid solutions was studied by batch equilibrations and passage through columns. On the basis of this, new methods are suggested for the separation and purification of⁹⁵Zr and⁹⁵Nb in hydrochloric acid and hydrochloric acid—methanol solutions. The methods are comparatively simple and rapid, and both zirconium and niobium can be obtained in a radiochemically pure state.     

Spectrophotometric determination of niobium in zirconium with 4-(2-pyridylazo)resorcinol

The direct spectrophotometric determination of niobium in zirconium alloys with 4-(2-pyridylazo)resorcinol is described. Samples are dissolved in hydrofluoricsulphuric acid mixture and the colour developed without the removal of fluoride. In the presence of EDTA only Co²⁺, Ta⁵⁺ and V⁵⁺ cause serious interference. The molar absorptivity is 3.67 .10⁴ in the presence of 1 /smg of zirconium, and Beer's law is obeyed up to 1.0μg Nb/ml. The method can be applied to zirconium alloys containing as little as 0.005% niobium.     

Separation of95Zr and95Nb from each other and from other fission products by adsorption and desorption on silica gel using hydrochloric acid solutions

The silica gel adsorption behaviour of zirconium, niobium, ruthenium and cerium in hydrochloric acid has been investigated by batch and column techniques. A satisfactory radiochemical separation of zirconium and niobium from each other and from other fission products has been achieved by a two column technique. The recommended procedure consists of sorption of all the nuclides on a primary silica gel column. Fifteen per cent of⁹⁵Nb, all of the zirconium and all of the other fission products are eluted first by washing with 5.5 M HCl. A second elution with concentrated hydrochloric acid then recovers the⁹⁵Nb (free from other products). The solution from the first elution after evaporation to 1 ml is then passed through another silica gel column and successively washed with 0.5M HCl, 5.5M HCl and concentrated HCl to obtain three fractions—other fission products—⁹⁵Zr free from other products—⁹⁵Nb free from other products, respectively.     

The determination of carbon in the refractory metals zirconium,niobium, tantalum and tungsten by instrumental deuteron activation analysis

Instrumental activation analysis is used for the determination of carbon in the refractory metals zirconium, niobium, tantalum and tungsten, based on the ¹²C(d, n)¹³N reaction induced by 5–7-MeV deuterons. ¹³N(t_{$\text{1}\text{2}$} = 10.0 min) is detected via its annihilation radiation. The contribution of ¹³N to the annihilation activity is separated from that of other β⁺-emitters by decay-curve analysis. The method is free of nuclear interferences. The possible spectrometric interferences are discussed. Concentrations of 65.1, 24.8, 1.04 and <0.015 μg C g^-1, with relative standard deviations of 4.0, 5.9 and 14.0%, were obtained for zirconium, niobium, tantalum and tungsten, respectively.     

Adsorption of fission products onto soils using a fission multitracer

The adsorption behavior of fission products to various soils was studied using a multitracer. The multitracer was prepared by neutron irradiation of ²³⁵U. Distribution coefficients of fission products were obtained for seventeen kinds of Japanese soils. It was found that zirconium, niobium, and rare earth elements show high distribution coefficients for all soil samples, however, elements like alkali metals show varied values.     

The determination of zirconium in its binary alloys with niobium and tantalum

A procedure is presented for the determination of zirconium in the presence of niobium or tantalum. The bulk of the niobium or tantalum is first removed by extracting with hexone from a 10M hyclrofluoric acid, 6M sulphuric acid solution of the sample. The zirconium is then. separated from any unextractcd earth, acid element by precipitation with ammonium hydroxide followed by the addition of hydrogen peroxide. Under these conditions, both the niobium and tantalum form soluble peroxy complexes whereas the zirconium is completely precipitated from solution. After the separation of the precipitate by filtration, it is re-dissolved in hydrochloric acid and the zirconium concentration is finally determined by titration with ethylenediaminetetraacetic acid.     

Measuring metal homogeneity in a matrix via the measurement of the ratio metal to matrix oxide using ICP-MS

A simple method has been developed that allows a fast determination of the homogeneity of an element M in an alloy, even for minor components. This is done by measuring a ratio of ion currents I, I ^M/I ^M’O, whereby M’ is the matrix element, by inductively coupled plasma mass spectrometry (ICP-MS). The method can be used to determine the homogeneity of one component in a binary alloy and allows to estimate the sample size necessary to minimise uncertainty contributions due to inhomogeneity in the analysis of such an alloy. In this work the homogeneity of a niobium/0.1% zirconium alloy was determined on 1 mg samples. Accurate weighings of these small samples are not required, as the method is based on the measurement of the niobium/zirconium amount ratio in the dissolved samples. As this ratio is fairly large, the Zr/NbO amount ratio was measured instead to decrease the magnitude of the measured ratio. This ratio was found to be sufficiently stable over time for homogeneity testing. In this particular case the Zr/NbO ratio in the samples was found to vary by 0.049 relative for a 1 mg samples size.     

Analysis of niobium alloys

An ion-exchange method was applied to the analysis of synthetic mixtures representing various niobium-base alloys. The alloying elements which were separated and determined include vanadium, zirconium, hafnium, titanium, molybdenum, tungsten and tantalum. Mixtures containing zirconium or hafnium, tungsten, tantalum and niobium were separated by means of a single short column. Coupled columns were employed for the resolution of mixtures containing vanadium, zirconium or titanium, molybdenum, tungsten and niobium. The separation procedures and the methods employed for the determination of the alloying elements in their separate fractions are described.     

Measuring metal homogeneity in a matrix via the measurement of the ratio metal to matrix oxide using ICP-MS

A simple method has been developed that allows a fast determination of the homogeneity of an element M in an alloy, even for minor components. This is done by measuring a ratio of ion currents I, I ^M/I ^M’O, whereby M’ is the matrix element, by inductively coupled plasma mass spectrometry (ICP-MS). The method can be used to determine the homogeneity of one component in a binary alloy and allows to estimate the sample size necessary to minimise uncertainty contributions due to inhomogeneity in the analysis of such an alloy. In this work the homogeneity of a niobium/0.1% zirconium alloy was determined on 1 mg samples. Accurate weighings of these small samples are not required, as the method is based on the measurement of the niobium/zirconium amount ratio in the dissolved samples. As this ratio is fairly large, the Zr/NbO amount ratio was measured instead to decrease the magnitude of the measured ratio. This ratio was found to be sufficiently stable over time for homogeneity testing. In this particular case the Zr/NbO ratio in the samples was found to vary by 0.049 relative for a 1 mg samples size. Received: 30 November 1998 / Revised: 22 March 1999 / Accepted: 27 March 1999     

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.

     

Separation of protactinium from uranium and other reaction products in the reaction of 60 MeV/nucleon 18O with natural uranium

Protactinium was produced by the reaction of 60 MeV/nucleon ¹⁸O with natural uranium. A simple, relatively fast radiochemical procedure was developed, which can be used for the extraction separation of protactinium from uranium and from the complex reaction products using 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone and tri-iso-octylamine as extractants. Measurements of the gamma-ray spectra for the separated protactinium fractions were performed with a HPGe detector. The measured g-ray spectrum of protactinium shows that the decontamination from the main impurity elements, especially zirconium and niobium, is quite satisfactory.     

Development of a method for the determination of 93Zr and 94Nb in radioactive waste using TEVA® resin

The behaviour of ⁹⁵Zr and ⁹⁵Nb isotopes on TEVA^® resin column was studied. The influence of hydrofluoric, hydrochloric, oxalic and sulphuric acids on the separation and chemical yield of zirconium and niobium was tested. The method is suitable for the separation of ⁹³Zr and ⁹⁴Nb isotopes from hydrofluoric, hydrochloric and sulphuric acid by using different concentrations of the acid for the load or elutes solutions. Samples from reactor and fuel assemblies such as the control-rod connection rod, shielding/absorber parts of fuel rods, neutron in-core measurement channels, pressure vessel basic construction material and internal cladding, core barrel and reactor protection tube unit were analysed.     

Separation of elements by means of fractional sublimation of their \-diketonates in the vapours of \-diketones

A possibility to use exchange reaction of metal \-diketonates and the vapours of \-diketones for the separation of volatile \-diketonate complexes by the method of fractional sublimation has been studied. When a mixture of thenoyltrifluoroacetonates of⁹⁵Zr–⁹⁵Nb and Th–²³³Pa is treated with a carrier gas containing hexafluoroacetylacetone vapours, zirconium and thorium, unlike niobium and protactinium, form volatile hexafluoroacetyl-acetonates which sublimate quite completely at 115°C. Niobium and protactinium remain in the initial sample in the form of nonvolatile compounds.     

Solvent extraction separations with bpha. applications to the microanalysis of niobium and zirconium in uranium

A detailed study of the benzoylphenylhydroxylamine (BPHA)-chloroform-hydrochloric acid solvent extraction system with 52 elements is described with emphasis placed on extraction of the easily hydrolyzed transition metals from strong hydrochloric acid. From this study, a separation procedure for hafnium, niobium, tantalum, titanium, vanadium, and zirconium from uranium was developed, and procedures are given for the microanalysis of niobium and zirconium in uranium. Niobium and zirconium are separated from uranium by extraction into BPHA-chloroform from 10-N HCl.The separated elements are then measured colorimetrically as the niobium-4-(2-pyridylazo)resorcinol and zirconium-arsenazo III complexes. The limit of detection is 1 μg/g U.     

The polarography of molybdenum,titanium and niobium in solutions of organic acids

Further work on the polarographic reduction of molybdenum(VI), niobium(V) and titanium(IV) in base electrolytes containing organic acids is reported. A base electrolyte of 0.5 M citric acid-0.025 M sulphuric acid-0.05 M thorium nitrate proved suitable for the determination of molybdenum and titanium in the presence of niobium, tantalum, tungsten and zirconium. A direct polarographic method using this base electrolyte is described for the determination of molybdenum in a niobium base alloy.     

Determination of niobium, titanium and zirconium by high-frequency plasma torch emission spectrometry and its application to steel

The basic conditions for the determination of niobium, titanium and zirconium with an argon plasma and a Hitachi UHF Plasma Spectrascan operated at 2450 MHz and 450 W maximum output, have been established. The niobium 405.89-nm, titanium 365.35-nm and zirconium 339.19-nm lines gave detection limits of 0.5, 0.1 and 2.0 p.p.m., respectively, when pure solutions were used. Effects of gas flow rates, high-frequency output and concentration of acids were examined. In applications to steel, titanium was determined without prior chemical separation from iron at the 499.95-nm line, whereas niobium and zirconium could not be determined in the presence of large amounts of iron. When a cupferron precipitation method followed by extraction of iron with methyl isobutyl ketone was applied, satisfactory results were obtained.     

Electrolytic production of niobium powder from chloride—fluoride melts containing compounds of niobium and zirconium

Electroreduction of niobium is studied in a chloride-fluoride electrolyte used for obtaining zirconium powder. Limiting densities of cathodic diffusion currents of the niobium discharge and diffusion coefficients for fluoride complexes of Nb(V) and Nb(IV) are determined as functions of temperature. Optimum electrolysis parameters are determined by studying how the cathodic current density, niobium concentration, and temperature affect the cathodic electrodeposition current efficiency. The morphology and granulometric composition of powdered niobium are investigated as functions of the electrolysis parameters. Effect of zirconium, as a melt component, on the electrolytic niobium production is discussed     

The differentiation of submicrogram amounts of inorganic and organomercury in water by flameless atomic absorption spectrometry

The basic conditions for the determination of niobium, titanium and zirconium with an argon plasma and a Hitachi UHF Plasma Spectrascan operated at 2450 MHz and 450 W maximum output, have been established. The niobium 405.89-nm, titanium 365.35-nm and zirconium 339.19-nm lines gave detection limits of 0.5, 0.1 and 2.0 p.p.m., respectively, when pure solutions were used. Effects of gas flow rates, high-frequency output and concentration of acids were examined. In applications to steel, titanium was determined without prior chemical separation from iron at the 499.95-nm line, whereas niobium and zirconium could not be determined in the presence of large amounts of iron. When a cupferron precipitation method followed by extraction of iron with methyl isobutyl ketone was applied, satisfactory results were obtained.     

Extraction-photometric determination of thorium with chlorophosphonazo-III

A simple and rapid spectrophotometric determination of thorium is described. The thorium-chlorophosphonazo-III complex is extracted into 3-methyl-1-butanol from 2.0–3.0 M hydrochloric acid solution. Maximum absorbance occurs at 620 and 670 nm and Beer's law is obeyed at the latter wavelength over the range of 0–15 μg per 10 ml of the organic phase. The molar absorptivity is 12.2·10⁴ l mole^-1 cm^-1 at 670 nm. Thorium can be determined in the presence of fluoride, oxalate, sulfate and EDTA. Many common cations do not interfere, but uranium, zirconium and niobium interfere seriously.