An improved Re/W separation protocol for preparation of carrier-free186Re

An Al₂(WO₄)₃ target bombarded with a proton beam (28.5 MeV, 20 A) for 1 hour was completely dissolved in about 5 ml of hot 2N NaOH and the clear solution was neutralized with 2N HCl. The resulted white precipitate of Al₂(WO₄)₃ can be separated from the solution by centrifugation and decantation. The supematant containing radioactive Re as ReO ₄ ^– was loaded onto a column (1 cm×10 cm) of activated alumina (100–200 mesh). Eluted with 10 ml of saline, the carrier-free ReO ₄ ^– was collected, while the small amount of Al₂(WO₄)₃ in the supematant was adsorbed on the column. The total yield of ReO ₄ ^– was 94.7% and the breakthrough of WO ₄ ^2– , only 1.0·10^–6 M. The whole separation process can be accomplished within 30 minutes. This rapid and efficient Re/W separation protocol is applicable to the preparation of carrier-free¹⁸⁶Re, when an enrichel Al₂(¹⁸⁶WO₄)₃ target is used.     

Extraction of plutonium from acidic media using various phosphine oxides

Extraction, loading and stripping studies of Pu(IV) have been carried out using three phosphine oxides namely Cyanex^Ò-923 (cyn-923), Cyanex^Ò-925 (cyn-925) and TOPO in dodecane from nitric acid medium. All the three phosphine oxides have shown very high extraction of Pu. The order of extraction for Pu by these compounds is cyn-923 > TOPO - cyn-925. Loading of Pu (30.0 mg/l) in 3.0M HNO₃ was carried out using 5% solution of each of the phosphine oxides in dodecane. It was found that even at an organic to aqueous phase ratio of 1:10, the loading of Pu is >96%. From the loaded organic phase, Pu could be almost quantitatively stripped using 0.1 or 0.5M oxalic acid. The extraction of Pu(IV) with cyn-925 has also been carried out from HCl, HNO₃ or HClO₄ (0.5 to 9.1M). The species extracted into the cyn-925/dodecane phase from 3.0M HNO₃ or HCl media was found to be Pu(L)₄ ^.2 cyn-925 where L = NO₃ ^– or Cl^–. Similar species were observed to be formed when dodecane was replaced by xylene, chlorobenzene or o-dichlorobenzene.     

Determination of plutonium in environmental samples by controlled valence in aniion exchange

The title method was successfully used for collecting^239,249Pu from 200 litres of seawater by coprecipitation with 16 g FeSO₄·7H₂O under redcing conditions witout filtering. The plutonium is leached by concentrate HNO₃+HCl from the coprecipitate and the solid particles. The precipitate is heated at 400°C and digested in aqua regia. Na₂SO₃ and NaNO₂ have been applied to obtain the Pu⁴⁺ valence state in 0.5–1N HNO₃ for different samples. Plutonium and thorium are coadsorbed on anionic resin from 8N HNO₃. The column is eluted with 8N HNO₃ containing fresh NaNO₂ to keep the Pu⁴⁺ state for uranium decontaination. The system of the column is changed from 8N HNO₃ to concentrated HCl with 50 ml concentrated HCl containing a few milligrams of NaNO₂. Furtheer decontaimination of torium was achieved by elution with concentrated HCl instead of 9N HCl. The plutonium is successfully stripped by H₂O, NaOH, 2N HNO₃ and 0.5N HNO₃ containign 0.01M NaNO₃. The chemica yield of plutonium for a 2001 seawate sample is 60–80%. The resolution of the electroplated thin source is very good.     

Anion exchange equilibrium of uranium and several other elements in mineral acid solutions containing tetrafluoroboric acid

Volume distribution coefficients /Dv/ were determined for the adsorption of U and several other elements on anion-exchange resin from mixed solutions of tetrafluoroboric acid and nitric acid or hydrochloric acid, and the effect of tetrafluoroboric acid on the adsorption of each element was studied. The addition of tetrafluoroboric acid, in general, slightly decreased the Dv values while Zr was weakly adsorbed in the HBF₄–HCl and HBF₄–HNO₃ solutions and Nb in the HBF₄–HNO₃ solutions.     

210Pb and210Po in tobacco-with a special focus on estimating the doses of210Po to man

Studies have been carried out on the solubility of Pu(III) oxalate by precipitation of Pu(III) oxalate from varying concentrations of HNO₃/HCl (0.5–2.0M) solutions and also by equilibrating freshly prepared Pu(III) oxalate with solutions containing varying concentrations of HNO₃/HCl, oxalic acid and ascorbic acid. Pu(III) solutions in HNO₃ and HCl media were prepared by reduction of Pu(IV) with ascorbic acid. 0.01–0.10M ascorbic acid concentration in the aqueous solution was maintained as holding reductant. The solubility of Pu(III) oxalate was found to be a minimum in 0.5M–1M HNO₃/HCl solutions containing 0.05M ascorbic acid and 0.2M excess oxalic acid in the supernatant.     

Synthesis,protonation and substitution behaviour of K3[ReO2(CN)4]

Summary The preparation and characterization of salts of the [ReO₂(CN)₄]^3–, [ReO(OH)(CN)₄]^2–, [ReO(H₂O)(CN)₄]^–, [Re₂O₃(CN)₈]^4– and [ReO(NCS)(CN)₄]^2– species are described. The nature of the protonation reactions of [ReO₂(CN)₄]^3– was established by the successful isolation of these salts.     

Selective separation and reversed phase extraction of zirconium and hafnium from a multitracer solution

The solvent extraction of Zr and Hf was studied using 444-trifluoro-1-(2-thienyl)-1,3-butanedione (TTA) from a multitracer solution containing carrier-free radioisotopes of Zr, Hf, and other elements. The multitracer was prepared from Au foil irradiated with high-energy heavy-ion beams. Effects of HCl and HNO₃ concentrations and organic solvent on the extraction and coextraction of other radionuclides have been studied. It was found that decalin (decahydronaphthalene) was the best solvent among 14 solvents studied and the optimum aqueous phase was 2 mol·dm^–3 HCl or HNO₃. About 2–10% of Sr, Rb, Sc and Nb were coextracted with Zr and Hf. The reversed phase extraction of Zr and Hf was also developed by using ethylenediaminetetraacetic acid (EDTA) solution at pH range of 8.5–10.     

Paper chromatography of noble metals in mixed chloride-nitrate media with use of solutions of liquid anion exchangers as mobile phases

Summary The chromatographic behaviour of nine noble metals on paper strips impregnated with mixtures of HCl and HNO₃ and developed with solutions of secondary and tertiary amine salts or quatermary alkylammonium salts in organic diluents was investigated. It was found that very sharp separation of the pair Pt–Pd is obtainable at development of chromatograms with 0.1 Aliquat 336 in xylene or with 0.1 mol dm^–3 TOA in kerosene at high concentrations of the acids in the stationary phase. The increase of concentration of HNO₃ in acids mixture decreases the R_F or R_M values for the platinum metals more distinctly than increase of concentration of HCl.     

Reversed-phase partition chromatographic separation of minor actinides with bis(2-ethylhexyl) sulfoxide from acidic nitrate PUREX waste solutions

The uptake behavior of U(VI), Pu(IV), Am(III) and a few long-lived fission products from nitric acid media by bis(2-ethylhexyl) sulfoxide (BESO) adsorbed on Chromosorb has been studied U(VI), Pu(IV) and Zr(IV) are taken up appreciably as compared to trivalent actinides/lanthanides including some coexisting fission product contaminants which are weakly sorbed on the column. Chromosorb could be loaded with (1.12±0.03) g of BESO per g of the support. Maximum sorption is observed around 4–5 mol·dm^–3 HNO₃ for both U(VI) and Pu(IV), which are sorbed as their disolvates. The elution of (U(VI) and Pu(IV) from the metal loaded sorbent has also been optimized. Desorption of U(VI) is easily accomplished with dilute nitric acid (ca. 0.01 mol·dm^–3)while Pu(IV) is reductively stripped with 0.1 mol·dm^–3 NH₂OH·HCl. Effective sequential separation of U(VI), Pu(IV) and Am(III) from their several admixtures could be readily achieved from real medium and low level active acidic process raffinates.     

Variations in the gross alpha and beta activity in surface waters at the Atomic Weapons Establishment Aldermaston (UK)

N,N,N′,N′-tetra-2-ethylhexyldiglycolamide (T2EHDGA) has been used for the preferential extraction of ⁹⁰Y from its mixture with ⁹⁰Sr from HNO₃ as well as HCl medium. The separation efficiencies have been found out under varying experimental conditions. The extracted species were determined from T2EHDGA concentration variation experiments carried out at 3 M nitric acid as well as HCl and were found out to be Y(X₃)₃·3(TEHDGA)_(o) for both the extraction systems, where X = NO₃ ⁻ and Cl⁻, respectively. Comparison of the T2EHDGA and TODGA based separation methods is also made. In order to avoid third phase formation, iso-decanol has been used as the modifier in all the studies. The modifier content was optimized to 30% for 4 M HCl and 20% for 6 M HNO₃ as the feed aqueous phases. Separation schemes were developed for the separation of carrier free ⁹⁰Y and the purity was checked by the half-life measurement method.     

Kinetics of the oxidation of nitrous acid by tetrachloroaurate(III) inHCl

Summary The kinetics of the reaction between nitrous acid and gold(III) in an HCl medium was studied. The reaction was first order with respect to [Au^III] and [HNO₂]·H⁺ and Cl^- ions inhibit the rate and alkali metal ions have specific effects on the rate. The reaction appears to involve different gold(III) species, viz. AuCl _inf4 ^sup– , AuCl₃(OH₂) and AuCl₃(OH)^–, which undergo a two-equivalent reduction to gold(I) leading to the formation of NO _inf2 ^sup+ which under-goes rapid hydrolysis to give nitric acid.     

Solvent Extraction of Rhenium(VII) for Preparation of No-Carrier-Added 186Re Saline Solution with High Specific Volume Activity

By using ¹⁸⁸Re as a radiotracer, the extraction behavior of Re(VII) by a tertiary amine extractant N-235 from HCl and the back-extraction behavior of Re(VII) by HNO₃ and ammonia were studied. A chemical separation procedure, which combined the acid alumina column and solvent extraction was established. The procedure was rapid and efficient for the separation of ¹⁸⁶Re from ¹⁸⁶W irradiated by 16 MeV deuterons. No-carrier-added ¹⁸⁶ReO₄ ^– saline solution with high specific volume activity was obtained. The overall recovery yield of ¹⁸⁶Re was about 85%.     

Monooctyl-α-(4-carboxyanilino)benzylphosphonic acid as a new reagent for extraction and separation of lead(II) and bismuth(III)

Monooctyl--(4-carboxyanilino)benzylphosphonic acid (H₂L) was investigated as a novel reagent for the extraction and separation of lead(II) and bismuth(III) from nitrate solutions. Stoichiometric ionization constants of H₂L in ethanol — water mixtures determined by potentiometric NaOH titration had values pK_a1 2.25 and pK_a2 4.33. Ethanol and chloroform solutions of H₂L followed Beer's law at 300 nm and 296 nm, molar absorptivities being 2.94·10⁴ mol^–1·l·cm^–1 and 2.85·10⁴ mol^–1·l·cm^–1, respectively. HNO₃ and HCl were also extracted into chloroform solutions containing H₂L. Bismuth(III) was quantitatively transferred into the chloroform H₂L solution at pH 1, and lead(II) at 3.5. The value of the separation factor D_Bi/D_Pb is 160 at pH 1.     

Liquid-liquid extraction of uranium(VI) from aqueous acidic solutions using Alamine, TBP and CYANEX systems

Liquid-liquid extraction of uranium(VI) (UO₂ ²⁺) from aqueous acidic (HCl and HNO₃) solutions into a co-existing organic phase containing Alamine 308 (triisooctyl amine), TBP (tri-n-butyl phosphate) or CYANEX 302 (bis(2,4,4-trimethylpentyl) monothiophosphinic acid) and diluent (toluene) was studied at isothermal conditions (298.2 K) at aqueous phase acidity varying in the range 0.5-6 mol/dm³. All solvent systems exhibit a maximum distribution ratio restricted in the acidity range 3-4 mol/dm³. An obvious difference in extraction behavior through amine system has been observed for two acids, HCl and HNO₃, distinguishing the divergent interactions attributed to the different mechanism of complexation depending on the acidic medium. The high degree of separation of UO₂ ²⁺ from HNO₃ solution is feasible through a complex formation with extractants ranging in the order CYANEX 302 > TBP > Alamine 308. The results were correlated using various versions of the mass action law, i.e., a chemodel approach and a modified version of the Langmuir equilibrium model comprising the formation of one or at least two U(VI)-extractant aggregated structures.     

Extraction of actinium with di (2-ethylhexyl) phosphoric acid from hydrochloric and nitric acid solutions

The extraction of actinium with HDEHP from Cl^– and NO ₃ ^– systems has been investigated. It was found that extraction of actinium from HCl solutions is much better than from HNO₃ solutions. Stability constants of the actinium complexes Ac(X^–)²⁺, X^–=Cl^– or NO ₃ ^– , were determined. Our results show that actinium formed less stable complexes with Cl^– than with NO ₃ ^– ligands.     

New effective and selective extractants for separation and determination of silver

Summary Isopropyl-N-alkylthiocarbamates have been studied as extractants for preconcentration of silver trace amounts and for separation of silver macroquantities. It has been shown that the 0.05M reagents in chloroform extract trace amounts of silver with high distribution coefficients from HNO₃, H₂SO₄, HClO₄ and HCl solutions in wide range of their concentrations. The highest selectivity is obtained when HNO₃, H₂SO₄ or HClO₄ solutions are used. Besides silver only mercury and palladium are extracted. When HC1 solutions are used, gold is also transferred into organic phase. Isopropyl-N-alkylthiocarbamates are effective for extraction of silver from its concentrated (up to 1M) solutions, particularly from HNO₃ solutions: more than 99.9% of silver is extracted even at 2-fold reagent excess. Some characteristics of reagents themselfes have been investigated, such as dissociation, protonation, distribution between organic and aqueous phases and association in organic solvents. The thion forms are found to be predominant. Silver is extracted as coordination solvated compounds Ag(HL) _n X, where X=Cl, Br, J, NO₃. Sulfur serves as a donor atom for their formation.The procedures for silver determination in geological samples by flame atomic absorption (3×10^–7%) and atomic emission (1×10^–7%) have been developed. The procedures for atomic emission determination of 23 trace elements (5×10^–8–1×10^–5%) and for electrothermal atomic absorption determination of 17 trace elements (4×10^–9–8×10^–6%) in high purity silver have also been developed.

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Neue wirksame und selektive Extraktionsmittel für die Trennung und Bestimmung von Silber

Zusammenfassung Isopropyl-N-alkylthiocarbamate wurden als Extraktionsmittel für die Anreicherung von Silberspuren und für die Abtrennung von Makromengen Silber geprüft. Es ergab sich, daß solche 0,05M, in Chloroform gelöste Reagenzien Silberspuren mit hohen Verteilungskoeffizienten aus HNO₃, H₂SO₄, HClO₄ und HCl extrahieren. Die beste Selektivität wurde mit HNO₃, H₂SO₄ oder HClO₄erzielt. Neben Silber werden nur Quecksilber und Palladium extrahiert. Verwendet man HCl, so geht auch Gold in die organische Phase. Isopropyl-N-alkylthiocarbamate eignen sich für die Extraktion von Silber aus konzentrierten (bis zu 1M) Lösungen, besonders aus HNO₃: mehr als 99,9% Silber werden mit zweifachem Reagensüberschuß extrahiert. Einige charakteristische Eigenschaften der in Rede stehenden Reagenzien wurden untersucht: z. B. die Dissoziation, die Protonation, die Verteilung zwischen organischer und wäßriger Phase und die Assoziation in organischen Lösungsmitteln. Hauptsächlich liegen diese Reagenzien in Thionform vor. Silber wird als Ag(HL) _n X extrahiert, worin X für Cl, Br, J oder NO₃ steht. Schwefel fungiert als Donatoratom für deren Bildung.Verfahren zur Silberbestimmung in geologischen Proben mit Hilfe der Flammen-Atomabsorption (3×10^–7%) bzw. der atomaren Emission (l×10^–7) wurden ausgearbeitet. Außerdem wurden auch Verfahren zur Bestimmung von 23 Spurenelementen mittels atomarer Emission (5×10^–8 bis 1×10^–5%) und von 17 Spurenelementen mittels elektrothermaler Atomabsorption (4×10^–9 bis 8×10^–6%) in hochgereinigtem Silber entwickelt.

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The paper has been presented at the Fifth European Conference on Analytical Chemistry (Euroanalysis V), Cracow, August 26–31, 1984.     

Influence of chloride and sediment matrix on the extractability of HgS (cinnabar and metacinnabar) by nitric acid

The extractability of metacinnabar and cinnabar, alone or in the presence of some sediment components, with various concentrations of HNO₃ (1, 4, 6, and 14 M) was studied. Both forms of HgS (0.2–0.3 mg HgS in 10–20 mL of acid) were insoluble in all HNO₃ concentrations as pure compounds. The presence of FeCl₃ enhanced solubility of both cinnabar and metacinnabar, especially when concentrated HNO₃ was used for the extraction. As the same effect was not obtained in the presence of FeOOH, we concluded that chloride and not Fe³⁺ was responsible for HgS dissolution. In fact, addition of very low chloride concentration to concentrated HNO₃ provoked partial (Cl>10^–4 M) or even total dissolution (Cl>10^–2 M) of HgS. In dilute HNO₃ (4–6 M) cinnabar was much less affected by chloride addition than metacinnabar. Extraction of HgS by concentrated HNO₃ in the presence of sediment of various salinities demonstrated that the amount of dissolved HgS increased with the increase of the sediment salinity (from freshwater to estuarine and marine sediment), confirming that chloride enhances dissolution of HgS. Removal of chloride by washing the sediment with Milli-Q water significantly reduced dissolution of added HgS during extraction by concentrated HNO₃. These results demonstrate that conclusions based on the extraction schemes using concentrated HNO₃ as single extractant or as the first extractant in the sequential extraction procedures can be biased. A verification of artifactual oxidation of HgS, when using more concentrated HNO₃ as extractant, would help to verify reliability of the applied extraction procedure.     

Extraction of99Mo-molybdophosphate and99mTc-pertechnetate from various acid solutions by bis/2-ethylhexyl/ phosphoric acid

The extractability of⁹⁹Mo-molybdophosphoric acid H₃/PMo₁₂O₄₀/ and^99mTc-pertechnetic acid /PTcO₄/ in 20% (v/v) bis /2-ethylhexyl/ phosphoric acid /HDEHP/ in benzene has been investigated at different concentrations of HCl, HBr and HNO₃ acids. The effect of extractant concentration and diluent on the extractability of molybdophosphoric and pertechnetic acids with 20% (v/v) HDEHP in benzene from different concentrations of HCl acid has also been studied.⁹⁹Mo-molybdo-phosphoric acid was found to be selectively extracted and separated from^99mTc-pertechnetic acid with 20% HDEHP in benzene at an acidity of about 0.49M HCl, HBr and HNO₃. The extractability of H₃/PMo₁₂O₄₀/ from these acids generally follows the decreasing order HBr>HCl>HNO₃. The separation factors /K_d molybdophosphoric/K_d pertechnetic/ were found to be 12.9×10⁵ and 7.6×10⁵ for HBr and HCl, respectively. The extractability of pertechnetic acid follows the order HCl>HBrHNO₃. Benzene is the diluent due to its radiation stability. A new procedure for the separation of^99mTc from⁹⁹Mo was suggested.     

Kinetic and equilibrium study of substitution reactions oftrans-tetracyanodioxorhenate(V) ions with monodentate nucleophiles

Summary The kinetics of the substitution reactions of the protonated froms oftrans-tetracyanodioxorthenate(V) with thiourea (TU),N-methylthiourea (NMTU),N, N-dimethylthiourea (NNDMTU) and hydrazoic acid (HN₃) were studied. The results were compared with those obtained for similar reactions of [WO₂(CN)₄]^4–. This study showed that the diprotonated form [ReO(H₂O)(CN)₄]^– is the only species reactive towards substitution reactions (and not the [ReO(OH)(CN)₄]^2– ion) and that only the aqua ligand in [ReO(H₂O)(CN)₄]^– is substituted by the incoming group. A dissociative mechanism is proposed for the substitution reactions between [ReO(H₂O)(CN)₄]^– and the monodentate nucleophiles. The i.r. data for these Re^v complexes are reported and discussed in terms of the relativetrans influence of the various monodentate ligands.     

Nitrogen isotope exchange between nitric oxide and nitric acid

The rate of nitrogen isotope exchange between NO and HNO₃ has been measured as a function of nitric acid concentration of 1.5–4M·1^–1. The exchange rate law is shown to beR=k[HNO₃]²[N₂O₃] and the measured activation energy isE=67.78kJ ·M^–1 (16.2 kcal·M^–1). It is concluded that N₂O₃ participates in¹⁵N/¹⁴N exchange between NO and HNO₃ at nitric acid concentrations higher than 1.5M·1^–1.