Behavior of zirconium and hafnium ions in ultramicroconcentrations investigated by horizontal zone electrophoresis in free electrolyte*

The electrophoresis of zirconium and hafnium ions in aqueous solutions was investigated. No-carrier-added ⁸⁸Zr and ¹⁷⁵Hf have been used in microconcentrations (10^-11M). The complexation of zirconium and hafnium with DTPA has been investigated in a large pH interval. The stability constants of the Zr-DTPA and Hf-DTPA complexes were determined for the first time by the method of horizontal zone electrophoresis in free electrolyte. The electrophoretic behavior of Zr(IV) and Hf(IV) ions in nitric acid solutions has also been studied.     

Reversed phase chromatographic separation of zirconium,niobium and hafnium tracers with HDEHP

Effective separation of the congeneric pair of elements, zirconium and hafnium and also niobium which was in admixtures with zirconium as daughter in its isotopic form were achieved through reversed phase column and paper extraction chromatographic procedures using di-(2-ethylhexyl)phosphoric acid (HDEHP) as the liquid exchanger. In reversed phase column chromatographic separation, the tracers,⁹⁵Zr,⁹⁵Nb and^175,181Hf, were extracted by HDEHP impregnated on kieselguhr and were sequentially eluted with 6N H₂SO₄+xN oxalic acid+H₂O₂(where x=0.1, 0.5 and 2). Similarly, in reversed phase paper chromatographic study in which a coating of HDEHP on Whatman No. 1 chromatographic paper was used as stationary phase, the mobile phase, 18N H₂SO₄+0.1N oxalic acid + H₂O₂, helped in separating the elements with favorable separation factors. Under the optimal conditions, the separation and decontamination of the elements in both methods were found to be quantitative, as verified by -spectrometric studies.     

A chelating resin containing 1-(2-thiazolylazo)-2-naphthol as the functional group; synthesis and sorption behavior for trace metal ions

A new polystyrene-divinylbenzene resin containing 1-(2-thiazolylazo)-2-naphthol (TAN) functional group was synthesized and its sorption behavior for 19 metal ions including Zr(IV), Hf(IV) and U(VI) was investigated by batch and column experiments. The chelating resin showed a high sorption affinity for Zr(IV) and Hf(IV) at pH 2. Some parameters affecting the sorption of the metal ions are detailed. The breakthrough and overall capacities were measured under optimized conditions. The overall capacities of Zr(IV) and Hf(IV) that were higher than those of the other metal ions were 0.92 and 0.87 mmol/g, respectively. The elution order of metal ions at pH 4 was evaluated as: Zr(IV)>Hf(IV)>Th(IV)>V(V)>Nb(V)>Cu(II)>U(VI)>Ta(V)>Mo(VI)>Cr(III)>Sn(IV)>W(VI). Quantitative recovery of most metal ions except Zr(IV) was achieved using 2 M HNO₃. Desorption and recovery of Zr(IV) was successfully performed with 2 M HClO₄ and 2 M HCl.     

Mandelazo I As A Reagent For Zr(IV) Determination

Abstract

A spectromeric study of the reaction of the Zr(IV) ions with Mandelazo I was carried out. Absorption spectra revealed that the maximum absorption of the zirconium compound appears at a wavelength (316 nm) different from the maxima of the reagent (253 and 390 nm). Beer-Lambert law is followed for zirconium concentrations of the order of 8.8x 10^?5 M (i.e. 8 μg Zr (IV)/mL). Possible interferences of ions such as Be(II), Cu(II), Zn(II), Al(III), Th(IV), U(VI), Mn(II), Fe(III), Co(II) and Ni(II) were investigated in connection with some masking agents such as SO₄ ^2- and C₂O₄ ^2-. Also, the solid state Zr(IV)-Mandelazo I compound was prepared and characterized by nitrogen and thermogravimetric analyses.     

The ion chromatographic separation of high valence metal cations using a neutral polystyrene resin dynamically modified with dipicolinic acid

A neutral polystyrene resin column, dynamically loaded with dipicolinic acid at a concentration of 0.1 mM in 1 M potassium nitrate eluent, was investigated for the separation characteristics of a number of high valence metal cations over the pH range 0-3. The metal species studied were Th(IV), U(VI), Zr(IV), Hf(IV), Ti(IV), Sn(IV), V(IV) and V(V), Fe(III) and Bi(III), of which Ti(IV), Sn(IV), V(IV) and Fe(III) did not show any retention. For the remaining metal ions, significant retention was obtained with good peak shapes, except for Th(IV), which moved only slightly from the solvent front with some tailing. The retention order at pH 0.3 was Th(IV) < V(V) < Bi(III) < U(VI) < Hf(IV) < Zr(IV). A notable feature of this separation system was the high selectivity shown for uranium, zirconium and hafnium, the last two being nearly resolved in 15 min on the relatively short 10 cm column.     

Simultaneous determination of zirconium and hafnium as ternary complexes with 5-Br-PADAP and fluoride using solid-phase extraction and reversed-phase liquid chromatography

Solid-phase extraction (SPE) along with reversed-phase liquid chromatography (RP-LC) was used for the simultaneous determination of Zr(IV) and Hf(IV) by means of their ternary chelates with fluoride and 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP). The conditions of SPE sorption were examined in detail: type of SPE column, volume of the sample, volume of the eluent, concentrations of metal ions, fluoride salt, chromogenic reagent, organic phase, and pH. It was established that the sorption of Zr(IV) and Hf(IV), as their ternary chelates, on SPE Zorbax SPE C18 (EC) cartridge was the most efficient, when the sample containing metal ion (Zr(IV), Hf(IV), both, up to 2 μg), 5-Br-PADAP 1.5×10⁻⁴, NaF 7.5×10⁻⁵ mol l⁻¹, methanol 40%, pH 4.5±1 was applied for the SPE sorption. The chelates were discarded from SPE cartridge using acetonitrile/water (99.75+0.25, v/v) eluent containing 3.8×10⁻⁴ mol l⁻¹ sodium fluoride and subsequently separated by RP-LC method. The RP-LC separation of both chelates was optimized and Zorbax SB-C18 analytical LC column along with acetonitrile/water (65+35, v/v) eluent containing the 1.5×10⁻⁴ mol l⁻¹ sodium fluoride was used. The established SPE/LC conditions allow Zr(IV) 0.08-2.0 μg and Hf(IV) 0.04-2.0 μg determination in a sample volume up to 150 ml. The detection limits, 0.03 μg Hf(IV) and 0.05 μg Zr(IV), were obtained. Recoveries, (94±2)% for Hf(IV) chelate and (106±2)% for Zr(IV) chelate were obtained, when 1 μg of Zr(IV) and Hf(IV) ions were determined by the present SPE/LC method from the sample volume of 100 ml. The established, pre-concentration SPE conditions, along with the LC separation and determination allow the assay of Zr(IV) and Hf(IV) in complicated matrix materials. The present SPE/LC method was applied to the determination of Zr(IV) and Hf(IV) in tap water and reference geological material (rock, NCS DC 73303; certified content: Zr, 27.7×10⁻³% (w/w) and Hf, 6.5×10⁻⁴% (w/w)).     

A density‐functional theory approach to the separation of K2ZrF6 and K2HfF6 via fractional crystallization

Because of the low absorption cross‐section for thermal neutrons of zirconium (Zr) as opposed to hafnium (Hf), Zr‐metal must essentially be Hf‐free (<100 ppm Hf) to be suitable for use in nuclear reactors. However, Zr and Hf always occur together in nature, and due to very similar chemical and physical properties, their separation is particularly difficult. Separation can be achieved by traditional liquid–liquid extraction or extractive distillation processes, using Zr(Hf)Cl₄ as feedstock. However, the production of K₂Zr(Hf)F₆ via the plasma dissociation route, developed by the South African Nuclear Energy Corporation Limited (Necsa), could facilitate the development of an alternative separation process. In this theoretical study, the results of density‐functional theory (DFT) simulations of K₂Zr_(1‐z)Hf_zF₆ solid solutions [using Cambridge Serial Total Energy Package (CASTEP)] are presented, for which the supercell approach was applied in an attempt to determine whether solid solution formation during crystallization from aqueous solutions (fractional crystallization) is thermodynamically possible, which would hinder the separation efficiency of this method. Consequently, the calculated thermodynamic properties of mixing were used to evaluate the separation efficiency of Zr and Hf by fractional crystallization using a thermodynamic model to calculate the relative distribution coefficients. The small mixing enthalpies that were calculated from the DFT results, indicates that lattice substitution of Zr(IV) by Hf(IV) in K₂ZrF₆ could occur with relative ease. This is not surprising, considering the close similarities between Zr and Hf, and it was therefore concluded that K₂Zr_(1‐z)Hf_zF₆ solid solution formation might well restrict the separation efficiency of Zr and Hf by fractional crystallization of K₂Zr(Hf)F₆. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

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.     

Adsorption properties of charcoal impregnated with stannic chloride

Adsorption behaviour of the individual tracer ions:¹³⁴Cs(I),^85,89Sr(II),^131,133Ba (II),⁹⁰Y(III),¹⁴¹Ce(III),^152,154Eu(III),⁹⁵Zr(IV),^175,181Hf(IV),⁹⁵Nb(V),⁶⁰Co(II),¹¹⁵Cd(II),^99mTc(VII), and¹³¹I(-I) on charcoal impregnated with stannic chloride from Hcl solutions, was investigated. Batch equilibrium distribution coefficients of the respective ions indicated strong anion exchange properties towards impregnated charcoal. The column breakthrough sorption capacity was of the order of 0.62–0.66 meq·g^–1 of dry adsorbent. Small chromatographic columns of impregnated charcoal could achieve rapid and quantitative separation procedures in HCl medium. Strongly adsorbed anions such as TcO ₄ ^– and I^– ions could be eluted with NH₄SCN and NH₄NO₂ eluents, respectively.     

Voltammetric determination of zirconium using azo compounds

The Optimum oconditions for zirconium complexation with azo compounds are found. The applicability of Eriochrome Red B, Calcon, and Calcion to the voltammetric determination of zirconium, total Zr(IV) and Hf(IV), and Zr(IV) in the presence of Zn(II), Cu(II), Cd(II), Ni(II), or Ti(IV) is demonstrated. The developed procedures are used to determine zirconium in a terbium alloy and in an alloy for airplane wheel drums.     

Anwendung von Silicagel in der anorganischen Analyse. Abtrennung des Thoriums von Zirkonium

Zusammenfassung Die Sorption des Thoriums und Zirkoniums an Silicagel aus ÄDTA und Weinsäure wurde verfolgt. Bei ph 7 in Gegenwart von Weinsäure durchläuft das Zirkonium die Silicagelkolonne, während Th(IV) quantitativ sorbiert wird. Diese Tatsache wurde zur Trennung des Thoriums von Zirkonium im Konzentrationsverhältnis 1200 angewandt. Da Zr(IV) aus 0,5-n HCl quantitativ sorbiert wird, woraus die Th(IV)-sorption praktisch gleich Null ist, kann auf diese Weise Zr(IV) von einem beträchtlichen Überschuß an Th(IV) getrennt werden. Die Trennung ist noch im Verhältnis 11000 quantitativ.

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Summary The sorption of thorium and zirconium on silica gel from EDTA and tartaric acid was followed. At ph 7 and in the presence of tartaric acid, the zirconium passes through the silica gel column, whereas Th(IV) is sorbed quantitatively. This finding was employed for the separation of thorium from zirconium in a concentration ratio of 1200. Because Zr(IV) is quantitatively sorbed from 0.5N HCl, while the sorption of Th(IV) is practically zero from this medium, Zr(IV) can be separated from a considerable excess of Th(IV) in this way. The separation is still quantitative at a ratio of 11000.

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Résumé On a suivi l'adsorption du thorium et du zirconium sur silicagel à partir d'EDTA et d'acide tartrique. A pn 7, en présence d'acide tartrique, le zirconium traverse la colonne de silicagel, alors que le thorium-IV est adsorbé quantitativement. On a mis à profit cet état de fait pour séparer le thorium du zirconium pour des concentrations dans le rapport 1200. Comme le zirconium-IV est adsorbé quantitativement à partir d'HCl 0,5N, tandis que l'adsorption du thorium-IV est alors pratiquement nulle, on peut séparer de cette manière le zirconium-IV d'un excès important de thorium-IV. La séparation est encore quantitative pour le rapport 11000.

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Herrn Prof. Dr. Ing.M. Jureek zum 60. Geburtstag gewidmet.     

Electrophoretic method for the determination of diffusion coefficients of ions in aqueous solutions*

The electrophoretic method was recently developed for the determination of diffusion coefficients of ions in aqueous solution. By solving the Fick's second law in the presence of unlimited media and constant quantity of diffusing species we obtain a relationship between the diffusion coefficient and the standard deviation of the distribution profile. The diffusion coefficients of Cd(II), In(III), Zr(IV), Hf(IV), Pu(VI) and [InDTPA]^2– in nitric acid solution were determined as well as the effective charge of In-DTPA complex at pH 4.50.     

Consecutive thin-layer chromatographic separation of Zr(IV), Hf(IV) and many other ions on silica gel in nitric acid-hydrogen peroxide media

The thin-layer chromatographic (TLC) behaviour of 64 ions including Zr(IV) and Hf(IV) has been surveyed on systems composed of silica gel and of nitric acid and nitric acid-hydrogen peroxide media. In the 0.5 mol 1(-1) HNO(3)-3% (w/v) H(2)O(2) solution, only Hf(IV) adsorbed very strongly, whereas Zr(IV) and many other ions showed no or weak adsorption. Stepwise development with diluted nitric acid and subsequently with nitric acid-hydrogen peroxide solution allowed the consecutive separation of three-component mixtures consisting of Zr(IV), Hf(IV) and one of many other accompanying elements, such as Mo(VI), Nb(V), Th(IV), Ti(IV), U(VI) and rare earths(III), to be conducted simply and effectively.     

Synthesis and Efficiency of an Epoxy-Urea Chelating Resin for Preconcentrating and Separating Trace Bi,In, Sn,Zr, V And Ti From Solution Samples

Abstract

A new epoxy-urea chelating resin was synthesized from epoxy resin and used for the preconcentration and separation of trace Bi(III), In(III), Sn(IV), Zr(IV), V(V) and Ti(IV) ions from solution samples. The analyzed ions can be enriched at pH 5 at a flow rate of 1–4 ml/min, and can be also desorbed with 10 mL of 2 M HCl +0.1g NH₄F solution from the resin column, with recoveries over 97%. The chelating resin reused 6 times can still adsorb quantitatively the Bi, In, Sn, Zr, V and Ti ions, and eighty to thousand-fold excesses of Ca(II), Mg(II), Cu(II), Zn(II), Al(III), Sb(III), Ni(II), Mn(II) and Fe(III) cause little interference with the enrichment and determination of these ions. The RSDs of the proposed method for the determination of 500–50 ng/ml Bi, In and Sn, 50–5.0 ng/ml Zr, V and Ti were in the range of 0.4 ～ 4.0%, the enrichment factor of the resin for the ions is in the range of 10–100. The recoveries of added standard in waste water are between 96% and 100%, and the concentration of each ion in alloy steel sample determined by the method is in good agreement with the reference value analyzed by a steel plant with average error <2.8%.     

Extraction and separation of zirconium from hafnium by using nano-structured supramolecular solvent microextraction method

In the present study, a simple versatile extraction method based on supramolecular solvent microextraction followed by inductively coupled plasma atomic emission spectrometry was developed for the extraction, separation and determination of zirconium (Zr) from hafnium (Hf). Zr and Hf were complexed with bis(2,4,4-trimethylpentyl) phosphinic acid, to obtain hydrophobic complex, and extracted into supramolecular solvent phase. The effective parameters on the supramolecular solvent microextraction efficiency were studied and optimized by using two different optimization methods: one variable at a time and central composite design. Under the optimum conditions, the linear range of 0.3–200.0 and 2.0–200.0 µg L^?1, detection limits (S/N = 3) of 0.1 and 0.6 µg L^?1, and precisions (n = 5) of 3.2–4.9% and 3.0–5.1% were obtained for Zr and Hf, respectively. Finally, the proposed method has been successfully applied for the extraction and separation of these cations in zirconium ore sample.     

Extraction and separation of Zr,Nb and Hf by Aliquat 336 and its mixtures with TOPO from acidic thiocyanate media

Presence of thiocyanate ions results in appreciable extraction of Zr(IV) by Aliquat 336 from low aqueous HCl acidities, i.e., 0.1 to 4.5M. The variation of concentrations of HCl, thiocyanate and Aliquat 336 greatly influences the extent of extraction. Mixtures of Aliquat 336 and TOPO result in synergistic extraction of Zr and Hf from acidic thiocyanate media, the extracted species being the disolvate with TOPO. By controlled adjustment of HCl, SCN^– and Aliquat 336 concentrations, separation of Zr, Nb and Hf is possible. A maximum separation factor (D_Nb/D_Zr) of 3675 has been achieved under certain conditions.     

Efficiency and application of poly(acryldinitrophenylamidrazone-dinitroacrylphenylhydrazine) chelating fiber for pre-concentrating and separating trace Au(III), Ru(III), In(III), Bi(III), Zr(IV), V(V), Ga(III) and Ti(IV) from solution samples

Poly(acryldinitrophenylamidrazone-dinitroacrylphenylhydrazine) chelating fiber was synthesized from polyacrylonitrile fiber and used for enrichment and separation for traces of Au(III), Ru(III), In(III), Bi(III), Zr(IV), V(V), Ga(III) and Ti(IV) ions from solution samples. The acidity, rate, re-use, capacity and interference on the adsorption of ions on the chelating fiber as well as the conditions of desorption of these ions from the chelating fiber were investigated by means of inductively coupled plasma optical emission spectrometry. The results show that 10-100 ngml(-1) of Au(III), Ru(III), In(III), Bi(III), Zr(IV), V(V), Ga(III) and Ti(IV) ions can be quantitatively enriched by the chelating fiber at a 2 mlmin(-1) of flow rate in the range pH 4-5, and desorbed quantitatively with 20 ml of 5 M HCl for In(III), Bi(III), Zr(IV), V(V), Ga(III), Ti(IV) and 20 ml of 4 M HCl+2% CS(NH(2))(2) solution for Au(III), Ru(III) (with recovery>95%). 50- to 500- fold excesses of Fe(III), Al(III), Mg(II), Mn(II), Ca(II), Cu(II), Ni(II) ions cause little interference in the concentration and determination of analyzed ions. When the fiber was reused for 8 times, the recoveries of the above ions enriched by the fiber were still over 87%. The relative standard deviations (RSDs) for the enrichment and determination of 10 ngml(-1) Au, Ru, In, Bi, Ga and 1 ngml(-1) Zr, V, Ti were lower than 3.0%. The results obtained for these ions in real solution samples by this method were basically in agreement with the given values with average errors of less than 6.3%. FT-IR spectra show that existence of NNCNHNH, OCNHNH and NO(2) functional groups are verified in chelating fiber, and Au(III) or Ru(III) is mainly combined with nitrogen (or oxygen) of the groups to form a chelate complex.     

Precise simultaneous determination of zirconium and hafnium in silicate rocks,meteorites and lunar samples

A precise, sensitive and rapid analytical technique has been developed for the simultaneous determination of Zr and Hf in natural silicate matrices. The technique is based on radiochemical neutron activation analysis and employs a rapid fusion dissolution of the sample and simultaneous precipitation of the Zr−Hf pair with p-hydroxybenzene arsonic acid in an acidic medium. The indicator radionuclides,⁹⁵Zr and¹⁸¹Hf, are counted with a pair of high resolution Ge(Li) detectors and the⁹⁵Zr activity is corrected for the contribution from U fission. The chemical yields of the radiochemical separation are based on Hf carrier, which quantitatively carries both Zr and Hf. The yield is determined by reactivation of the processed samples and standards with a²⁵²Cf isotopic neutron source and by counting the 18.6 sec half-life^179mHf. The sensitivity, precision and accuracy of the procedure are demonstrated by replicate analyses of several standard rocks, meteorites and lunar samples which exhibit a wide range of Zr and Hf abundances.     

TLC separation of some inorganic ions on diethylenetriamine impregnated layers

Summary A suitable TLC method for the separation of Co, Zn, Ni, As, Pb, Cd, Hg, Ag, Th, Se, Sn(IV), Fe(II), U, V, Cu, Ti, Zr and Sb on silica gel impregnated with diethylenetriamine and using ethanol-acetone-acetic acid (70∶50∶20) or (40∶50∶20) as solvent systems and employing 1% K₄Fe(CN)₆ or 0.5% dithizone as visualisation reagents has been developed.     

Synthesis,structural characterization,and thermal properties of zirconium(IV) <Emphasis Type="Italic">β</Emphasis>-ketodiester complexes

Mono- and bi-nuclear Zr(IV) β-ketodiester complexes of general formulas [Zr(dtbacdc)₄] (1), [Zr(dmacdc)₃(OⁱPr)]₂ (2), and [Zr(dtbacdc)₃(OⁱPr)]₂ (3), (dtbacdc = di-tert-butyl-1,3-acetonedicarboxylato and dmacdc = dimethyl-1,3-acetonedicarboxylato ligands) were successfully isolated, when zirconium(IV) isopropoxide reacted with the four- ((1)) or twofold ((2), (3)) excess of di-alkyl 1,3-acetonedicarboxylates (CO(CH₂COOR′)₂, R′ = Me, ^tBu). Analysis of single-crystal X-ray diffraction data showed that (1) crystallizes in the monoclinic system (C 2/c (no. 15)). The structure of this compound consists of monomers, which are composed of Zr(IV) ions surrounded by eight oxygen atoms derived from four chelating β-ketodiester ligands. The stoichiometry and the bi-nuclear structure of (2) and (3) using spectroscopic methods (IR and NMR), and mass spectrometry have been determined. Thermal analysis and variable temperature IR (VT-IR) spectroscopy have been used to study the thermal stability and thermal decomposition pathway of synthesized Zr(IV) compounds.