Haematein as a reagent for thorium, zirconium and uranium

Summary Haematein gives violet colored complexes with thorium and uranium and an orange colored complex with zirconium of the stoichiometric ratios 16, 13, and 11 respectively of the metal and the reagent (Job's method). The reagent and the complexes of thorium, uranium and zirconium show absorption maxima at 520–540 m, 520–540 m 500–520 m respectively. In observations at 540 m in 60 percent aqueous acetone 0.05 mg of thoria (a 12 fold excess of cerite earths has no influence), 0.029 mg U₃O₈ and 0.025 mg of zirconia may be determined. The spectral characteristics of the complexes indicate a similarity in character in spite of differences in stoichiometric composition.     

Determination of uranium and thorium in complex samples using chromatographic separation, ICP-MS and spectrophotometric detection

The paper describes a research of possible application of UTEVA and TRU resins and anion exchanger AMBERLITE CG-400 in nitrate form for the isolation of uranium and thorium from natural samples. The results of determination of distribution coefficient have shown that uranium and thorium bind on TRU and UTEVA resins from the solutions of nitric and hydrochloric acids, and binding strength increases proportionally to increase the concentration of acids. Uranium and thorium bind rather strongly to TRU resin from the nitric acid in concentration ranging from 0.5 to 5 mol L⁻¹, while large quantities of other ions present in the sample do not influence on the binding strength. Due to the difference in binding strength in HCl and HNO₃ respectively, uranium and thorium can be easily separated from each other on the columns filled with TRU resin. Furthermore, thorium binds to anion exchanger in nitrate form from alcohol solutions of nitric acid very strongly, while uranium does not, so they can be easily separated. Based on these results, we have created the procedures of preconcentration and separation of uranium and thorium from the soil, drinking water and seawater samples by using TRU and UTEVA resins and strong base anion exchangers in nitrate form. In one of the procedures, uranium and thorium bind directly from the samples of drinking water and seawater on the column filled with TRU resin from 0.5 mol L⁻¹ HNO₃ in a water sample. After binding, thorium is separated from uranium with 0.5 mol L⁻¹ HCl, and uranium is eluted with deionised water. By applying the described procedure, it is possible to achieve the concentration factor of over 1000 for the column filled with 1 g of resin and splashed with 2 L of the sample. Spectrophotometric determination with Arsenazo III, with this concentration factor results in detection limits below 1 μg L⁻¹ for uranium and thorium. In the second procedure, uranium and thorium are isolated from the soil samples with TRU resin, while they are separated from each other on the column filled with anion exchanger in alcohol solutions. Anion exchanger combined with alcohol solutions enables isolation of thorium from soil samples and its separation from a wide range of elements, as well as spectrophotometric determination, ICP-MS determination, and other determination techniques.     

Thermodynamics of extraction of tetravalent plutonium,uranium, thorium and zirconium

Thermodynamic treatment of the experimental data on the extraction of quadrivalent Pu, U, Th and Zr with tri-n-butyl phosphate (TBP) from nitric acid solutions is presented. It is shown that the extraction of all the quadrivalent metals studied is going according to the same mechanism: M(OH)^4?i+(4?i)NO ₃ ^? +2TBP?M(OH)_i(NO₃)_4?i·2 TBP. For Zr, i=0, 1, and 2; for the remaining M(IV), i=0 and 1. The thermodynamic constants of extraction of M(IV) with the kerosene solutions of TBP according to the above mentioned equation are as follows: Zr: K ₀ ⁰ =0.6; K ₁ ⁰ =14; K ₂ ⁰ =5. Pu: K ₀ ⁰ =380; K ₁ ⁰ =4.8·10⁴. U: K ₀ ⁰ =300; K ₁ ⁰ =1.8·10⁴. Th: K ₀ ⁰ ～150. It has been established that Zr and Pu(IV) are extracted into 2-thenoyltrifluoracetone (HA) from perchloric acid solutions under the formation of MA₄ and M(ClO₄)A₃ species. For the extraction from nitric acid solutions, the species formed are ZrA₄ and Zr(NO₃)A₃ in the case of Zr, PuA₄ and Pu(OH)A₃ in the case of Pu. The differences in the qualitative and quantitative characteristics of the extraction of M(IV) with TBP and HA from nitric and perchloric acids are explained by the effect of the character of the acid and of ionic potential upon the structure of the hydration shell of M _aq ⁴⁺ .     

Anion exchange separation of uranium, thorium and bismuth

Summary A method for the anion exchange separation of uranium, thorium and bismuth is described, using the strongly basic anion exchanger Dowex 1 X8. These three elements are simultaneously adsorbed on the resin (nitrate form) from a solution consisting of 96% n propanol and 4% 5 n nitric acid. The separation of thorium and bismuth from uranium is effected by washing the column with a mixture consisting of 80% methanol and 20% 5n nitric acid (elution of uranium). To separate thorium from bismuth the resin is then treated with a solution consisting of 80% methanol and 20% 6n hydrochloric acid whereby the thorium is eluted. Finally the bismuth is removed by washing the column with 1 n nitric acid. The experimental conditions for this separation scheme have been selected after the determination of the distribution coefficients of uranium, thorium, and bismuth in different mixtures of aliphatic alcohols with nitric and hydrochloric acid.

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Zusammenfassung Zur Trennung von Uran, Thorium und Wismut wird der stark basische Anionenaustauscher Dowex 1X8 verwendet. Aus einem Lösungsmittelgemisch von 96% n-Propanol und 4% 5n Salpetersäure werden die drei Elemente zusammen an dem Austauscher (Nitratform) adsorbiert. Mit einer Mischung von 80% Methanol und 20% 5n Salpetersäure wird sodann das Uran eluiert. Thorium wird mit einem Gemisch von 80% Methanol und 20% 6n Salzsäure ausgewaschen und schließlich wird mit 1 n Salpetersäure das Wismut von der Säule entfernt. Die Verteilungskoeffizienten der drei Metalle wurden in verschiedenen Gemischen von aliphatischen Alkoholen und Salz- sowie Salpetersäure bestimmt.

     

Recovery of uranium and thorium from zirconium oxychloride by solvent extraction

A solvent extraction process is proposed to recover uranium and thorium from the crystal waste solutions of zirconium oxychloride. The extraction of iron from hydrochloride medium with P350, the extraction of uranium from hydrochloride with N235, and the extraction of thorium from the mixture solutions of nitric acid and the hydrochloric acid with P350 was investigated. The optimum extraction conditions were evaluated with synthetic solutions by studying the parameters of extractant concentration and acidity. The optimum separation conditions for Fe (III) are recognized as 30% P350 and 4.5 to 6.0 M HCl. The optimum extraction conditions for U (VI) are recognized as 25% N235 and 4.5 to 6.0 M HCl. And the optimum extraction conditions for Th (VI) are recognized as 30% P350 and 2.5 to 3.5 M HNO₃ in the mixture solutions. The recovery of uranium and thorium from the crystal waste solutions of zirconium oxychloride was investigated also. The results indicate that the recoveries of uranium and thorium are 92 and 86%, respectively.     

Chromatographic separation of rare earths and uranium from thorium

Ohne Zusammenfassung     

Anion-exchange separation of thorium and protactinium from uranium matrix

Summary The distribution behaviour of Th⁴⁺, Pa⁵⁺, and UO₂ ²⁺ ions between the anion-exchanger Amberlite IRA-400 and acetic acid-hydrochloric acid mixtures, has been investigated. It was found that the general behaviour of Th⁴⁺ ions is similar to that of UO₂ ²⁺ ions though the latter are much more highly adsorbed by the resin than Th⁴⁺. Protactinium exhibited a different behaviour from both Th⁴⁺ and UO₂ ²⁺ ions. The separation factors were calculated, and a Chromatographic procedure for sequential isolation of each element was developed.

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Zusammenfassung Das Verteilungsverhalten von Th⁴⁺, Pa⁵⁺ und UO₂ ²⁺ zwischen dem Anionenaustauscher Amberlit IRA-400 und Gemischen aus Essigsäure und Salzsäure wurde untersucht. Das allgemeine Verhalten von Th⁴⁺ ist ähnlich dem von Uranylionen, wenngleich letztere von dem Harz viel stärker adsorbiert werden als Th⁴⁺. Protactinium zeigt ein abweichendes Verhalten im Vergleich zu Th⁴⁺ und UO₂ ²⁺. Die Trennfaktoren wurden berechnet und ein chromatographisches Verfahren zur Isolierung der angeführten Ionen entwickelt.

     

Sequential separation and determination of uranium and thorium isotopes in soil samples with Microthene-TOPO chromatographic column and alpha-spectrometry

In the method, soil was fused together with Na₂CO₃ and Na₂O₂ at 600 °C, uranium and thorium were leached out with HCl, HNO₃ and HF, and HClO₄ was used to eliminate the residual HF through evaporation. The leaching solution (2 M HNO₃) was passed through a Microthene-TOPO column to adsorb uranium and thorium. Thorium was first eluted with 2 M HCl and electrodeposited in 0.025 M H₂C₂O₄ + 0.15 M HNO₃ on a stainless steel disc. Uranium was eluted with a 0.025 M ammonium oxalate solution and also electrodeposited. Both thorium and uranium isotopes on the discs were measured separately by α-spectrometry.     

Anion-exchange separation of uranium (VI) from thorium,zirconium, titanium,lanthanides and other elements in malonic and ascorbic acid media

Summary The anion-exchange behaviour of uranium (VI) has been studied extensively in various mineral acid media [1], but similar studies with organic acid solutions are lacking. Although the negatively charged complex of uranium in acetic acid was studied [2, 3], very small amounts of uranium could be separated and phosphate interfered. Such studies were further extended to non-aqueous media [4]. The anionic ascorbate complex of uranium and thorium were separated by selective elution with 1 mol dm^–3 hydrochloric acid and 3 mol dm^–3 sulphuric acid [5–7] respectively. Some attempts were also made to study complexes of uranium in formic and propionic acid [1] and it was separated from copper and thorium in oxalate media [4]. However systematic studies in malonate and to some extent in ascorbate media are lacking. This paper presents such studies.     

Ion-exchange separation of uranium,thorium and plutonium isotopes from environmental samples

Radioisotopes of uranium, thorium and plutonium in water, soil and fertilizer samples, have been chemically separated and determined by alpha-spectrometry method. Radiochemical procedure involving ion-exchange, enabled to determine these isotopes in very low concentrations (under 50 Bq/g).²³²U,²²⁹Th and²³⁸Pu were used as a tracers for radiochemical yield recoveries (up to 90%). Thin layer sources have been obtained by electrodeposition.     

Comparison of the ion-exchange behaviour of zirconium, thorium, vanadium, uranium, stannic and titanium tungstates

Zirconium, thorium, uranium, vanadium, stannic and titanium tungstates have been prepared and their properties such as ion-exchange capacity, K(d) values of metal ions, chemical composition and stability have been compared. Titanium tungstate was found to be the most stable, and to have negligible capacity for tervalent cations.     

Fast and simple radiochemical method for the separation of uranium,thorium and lanthanum

The concept of using paper chromatography on papers impregnated with liquid anion or cation exchangers is extended to the separation of trace elements through filtration on filter papers loaded with suitable extractant. The uptake of uranium, thorium and lanthanum from HCl and HNO₃ media of different molarities by a filter paper treated with tri-octyl amine (TOA) is investigated. The effect of the different parameters on the uptake of the studied elements is experimented. A simple and fast radiochemical procedure is developed for the separation of La, Th and U from each other.     

Potentiometric determination of stepwise stability constants of zirconium, thorium and uranium chelates of asparagine and glutamine

The metal chelates of Zr(IV), Th(IV) and U(VI) with asparagine and glutamine have been studied potentiometrically. Stepwise stability constants in 0.1 M sodium perchlorate at 25 degrees are as follows. Asparaginate chelates-log K(1) 8.80, log K(2) 6.25 for Zr, log K(1) 6.79, log K(2) 6.16 for U, log K(1) 8.28, log K(2) 7.77 and log K(3) 7.72 for Th. Glutaminate chelates-log K(1) 8.75, log K(2) 6.10 for Zr, log K(1) 6.63, log K(2) 6.22 for U, log K(1) 8.30, log K(2) 7.61 and log K(3) 7.55 for Th.     

Separation of thorium,uranium and neptunium on chromatographic columns loaded with ammonium 12-molybdophosphate

The separation of thorium, uranium and neptunium with chromatographic columns loaded with ammonium 12-molybdophosphate (AMP) was carried out in different media with variable amounts of the elements. Columns of different sizes were used. Good separation yields were obtained, and the recovery of the elements was always greater than 95%. The use of AMP columns appears to be a useful method in the analytical chemistry of these actinide elements and it is particularly valuable in the purification and recovery of actinides in the +4 oxidation state.     

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.     

Concentration, separation and determination of scandium, zirconium, hafnium and thorium with a silica-based sulphonic acid cation-exchanger

A study has been made of the dependence of the sorption of scandium, zirconium, hafnium and thorium from aqueous solutions with a silica-based sulphonic cation-exchanger (SCE-SiO(2)) on the concentration and nature of the acid medium, time of contact, concentration of the element, and the ionic strength. The selectivity decreases in the order Zr approximately Hf > Th > Sc > Fe(III). The sorption characteristics of silica gel and SCE-SiO(2) have been compared, and the sorption mechanism is discussed. The SCE-SiO(2) exchanger has been used for 100-fold concentration of scandium, zirconium, hafnium and thorium from their 10(-8)-10(-7) M solutions, and a spectrophotometric method has been developed for their determination with a detection limit of 0.5 ng/ml for Zr and Sc and 0.1 ng/ml for Hf and Th. Zirconium and hafnium have been determined in the solvent phase by X-ray fluorescence and atomic-emission methods.     

Spectrophotometric determination of zirconium, uranium, thorium and rare earths with arsenazo III after extractions with thenoyltrifluoroacetone and tri-n-octylamine

A method is described for the spectrophotometric determination of microgram amounts of zirconium, uranium(VI), thorium and rare earths with Arsenazo III after systematic separation by extraction. First zirconium is extracted into a xylene solution of thenoyltrifluoroacetone (TTA) from about 4M hydrochloric acid. Uranium(VI) is then extracted into a xylene solution of tri-n-octy lamine from about 4M hydrochloric acid. Thorium is next extracted into TTA solution at pH about 1.5, and finally rare earths are extracted into TTA solution at pH about 4.7. Each metal is back-extracted from the organic phase before determination.