Synergistic extraction of hexavalent actinides by HTTA and neutral donors-II

Synergistic extraction studies on Np(VI) and Pu(VI) have been carried out as a part of the programme on the synergistic extraction of hexavalent actinides. Extraction of Np(VI) and Pu(VI) were carried out by mixtures of HTTA and TBP in benzene from aqueous perchlorate and nitrate media. Equilibrium constant values for the various reaction equilibria involved were calculated from the data obtained by using slope-ratio as well as Job’s method. The extraction of Np(VI) by the synergistic mixture from 1M nitric acid indicated that the species NpO₂ (TTA) (NO₃). TBP was not involved in the extraction. The log values of K_A, K_AB and β_AB were −1.5, 2.92 and 4.43, respectively for Np(VI) and −1.63, 2.50 and 4.13 respectively for Pu(VI).     

Oxalate complexing of tetravalent actinides

The oxalate complexing of the tetravalent actinides Th(IV), Np(IV) and Pu(IV) in aqueous solutions was studied by the thenoyltrifluoroacetone extraction method, at unit ionic strength at 25°C and the stability constant values obtained are reported. The oxalate complexing of these ions follows the order Th(IV) < Np(IV) < Pu(IV).     

Studies on synergistic extraction of thorium by mixtures of HTTA and TBP

Synergistic extraction of Th(IV) from perchlorate medium by mixtures of HTTA and TBP was studied. These studies include the effect of the ionic strength, temperature and the diluents on the extraction. Ionic strength was found to influence the extraction of Th(TTA)₄ and Th(TTA)₄·TBP whereas the adduct formation in the organic phase was almost unaffected. Increase of temperature resulted in a decrease of the extraction of Th(IV). The stability of the adduct was found to decrease in the order, cyclohexane > benzene > chloroform.     

Synergistic extraction of tetravalent actinides by mixtures of a β-diketone and a sulfoxide

Synergistic extraction of tetravalent actinides, using mixtures of a β-diketone and several neutral organophosphorous extractants, was recently demonstrated. In this work the extraction of the ions Th(IV), Np(IV) and Pu(IV), from perchloric acid medium, by benzene solutions of a β-diketone, thenoyltrifluoroacetone (HTTA), in combination with a neutral organosulfoxide donor, di-n-octyl sulfoxide (DOSO), has been investigated. Two methods viz. the slope analysis method and JOB's method have been employed for the study. The species mainly responsible for the observed synergism, with the M(IV) ions studied, was found to be M(TTA)₄·DOSO. The extraction and adduct formation equilibrium constants are given.     

Solvent extraction studies on tetravalent selenium

A systematic study has been carried out on the extraction of SeI₄, by various water-immiscible organic solvents. Extraction has been investigated as a function of H₂SO₄ and Kl concentrations. It has been found that Se(IV) extraction is appreciably increased by addition of iodide ion to sulfuric acid solutions. On the other hand, the presence of water-miscible alcohols and acetone was found to enhance Se(IV) extraction from H₂SO₄–Kl solutions. In the light of the results, an extraction mechanism is suggested.     

Solvent extraction of tetravalent selenium

Summary A systematic study has been carried out on the extraction of SeI₄, by various water-immiscible organic solvents. Extraction has been investigated as a function of H₂SO₄ and KI concentrations. It has been found that the Se(IV) extraction is appreciably increased by addition of iodide ion to sulphuric acid solutions. In addition, the presence of water-miscible alcohols and acetone was found to enhance Se(IV) extraction from H₂SO₄-KI solutions. In the light of the obtained results an extraction mechanism is suggested.

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Untersuchungen zur Extraktion von vierwertigem Selen

Zusammenfassung Es wurde eine systematische Untersuchung zur Extraktion von SeI₄ mittels verschiedener mit Wasser nicht mischbarer organischer Lösungsmittel unternommen. Es wurde die Abhängigkeit der Extraktion von der Konzentration an H₂SO₄ und KI untersucht, wobei sich zeigte, daß die Se(IV)-Extraktion durch Zusatz von Iodid-Ionen zur schwefelsauren Lösung beträchtlich zu steigern ist. Weiters wurde gefunden, daß der Zusatz von wassermischbaren Alkoholen oder Aceton ebenfalls die Extraktion aus H₂SO₄-KI-Lösungen verbessert. Auf Basis dieser Resultate wird ein Extraktionsmechanismus vorgeschlagen.

     

New conceptual process for the extraction of actinides based on oxapentane-diamides

Several diamide derivates were synthesized in our laboratory. The extraction of actinides and some fission products by these compounds were studied. N,N,N’,N’-tetra-(2-ethylhexyl)-3-oxa pentanediamide [TEHOPDA) was proven to be a suitable extractant for the removal of actinides from nitric acid solution. The actinides can be stripped from the loaded solvent by the dilute nitric acid. TEHOPDA showed a high loading capacity to actinides and lanthanides with a mixture of n-octanol and kerosene as the diluent. Considering the effective-extraction and easy-stripping of actinides, 0.25 mol/l TEHOPDA — 30% n-octanol + 70% kerosene was selected as the solvent. A cascade extraction experiment was carried out with the simulated dissolver solution of spend fuel as feed. 99.99% U and 99.999% Am, Pu, and Np were extracted in a 4-stage test. Based on the experimental results, a conceptual reprocessing process was proposed.     

Polymeric structure of oxalato-bridged complexes of tetravalent actinides Th, U, Np and Pu

A series of isostructural oxalates of Th, U, Np, and Pu have been synthesized. The crystal structure of {C(NH(2))(3)}(4)[An(C(2)O(4))(4)]·2H(2)O comprises infinite [An(C(2)O(4))(4)](4n-) chains, guanidinium cations and water molecules. Each An atom is connected to five oxalate anions, two of which act as bridging tetradentate ligands, while the other three function as terminating bidentate ligands. Electron and IR spectra of the compounds as well as the results of thermal analysis correlate with their structure. An actinide contraction effect is demonstrated by a decrease in the An-O interatomic distances and the volumes of An atom coordination polyhedra and Voronoi-Dirichlet polyhedra. Ten-coordinate An oxalates are discussed in terms of continuous shape measures approach.     

Rapid column extraction method for actinides in soil

Summary The determination of actinides in environmental soil and sediment samples is very important for environmental monitoring as well as for emergency preparedness. A new, rapid actinide separation method has been developed and implemented that provides total dissolution of large soil samples, high chemical recoveries and effective removal of matrix interferences. This method uses stacked TEVA Resin^ò, TRU Resin^ò and DGA-Resin^ò cartridges from Eichrom Technologies (Darien, IL, USA) that allows the rapid separation of plutonium, neptunium, uranium, americium, and curium using a single multi-stage column combined with alpha-spectrometry. The method combines a rapid fusion step for total dissolution to dissolve refractory analytes and matrix removal using cerium fluoride precipitation to remove the difficult soil matrix. By using vacuum box cartridge technology with rapid flow rates, sample preparation time is minimized.     

Separation of trivalent actinides from lanthanides by solvent extraction

A method is presented for separating the trivalent actinides, mainly Am and Cm, from trivalent lanthanides by the use of only two solvent extractants. The first solvent removes the heavy lanthanides, leaving the Am, Cm and the lighterlanthanides; the second removes the Am and Cm. Because additional complexing agents are not required, waste-disposal and corrosion problems are reduced. Overall separation factors may be as high as several thousand for the separation of Am and Cm from lanthanides in the fission waste products from reactor fuel processing.     

Automated pressurized injection system for the separation of actinides by extraction chromatography

This article describes a novel separation scheme developed for an automated system to efficiently separate actinides in individual fractions. The automated pressurized injection (PI) system developed allows precise collection of high-purity actinide fractions (≥99 %) at elevated flow rates (15–30 mL min^?1) using two extraction chromatographic TEVA and DGA resins. This system is sufficiently robust to enable the use of highly viscous acid media, limit acid corrosion, and tolerate large amount of gases generated by redox reactions by some of the reagents. The PI system was successfully applied to the separation of actinides in individual fractions (recovery yield ≥97 % for Th, U, Np, Pu, and Am) and shows the absence of cross contamination even with highly concentrated actinide solutions. The methodology was also applied to the measurement of actinides in large spiked soil samples.     

Synergistic extraction of trivalent actinides and lanthanides using macrocyclic compounds

The combination of lipophilic macrocyclic oxygen donors with the extractant thenoyltrifluoroacetone /HTTA/ has been shown to have a significant synergistic effect on the extractions of trivalent actinides and lanthanides. The results show that the nitrogen containing cryptand /222BB/ is a more effective synergist than the crown ether compound /15-C-5/ with only oxygen donors.     

Studies on evaluation of modified TRUEX solvent for the partitioning of minor actinides

An attempt to modify the TRUEX solvent has been initiated by replacing TBP with long-chain alcohols such as isodecanol. Solvent extraction experiments have been carried out determining distribution ratios for Am(III) as a function of concentrations of nitric acid and isodecanol. Acid uptake constant for the combined organic phase has also been arrived at which strongly suggests the interaction of CMPO and isodecanol. The suitability of the organic phase was tested for simulated high-level waste solutions.     

Rapid sequential separation of actinides using Eichrom's extraction chromatographic material

The presence of ²²⁶ Ra in an estuary formerly affected by direct discharges of waste from a phosphate fertilizer complex has been investigated. Specific activities ranging from 3.6 to 45.2 mBq/l have been detected. In general, activity levels are lower than those detected when direct discharges were carried out. However, there is still a clear contamination due to the disposal of phosphogypsum in open air piles by the river. Moreover, it seems that ²²⁶ Ra is being redissolved from the contaminated bed sediments, which also contributes to an enhancement in the activity levels of the estuary waters.     

Liquid-liquid extraction of some actinides with polyethyleneglycol and its derivatives

Polyethyleneglycol (PEG) and its derivatives of high molecular weight were found to be employed as useful extractants for the solvent extraction of uranium. The extraction behaviors of uranium and neptunium were investigated, particularly concerning the dependence of the extractibility of uranium(VI) on the molecular weight of PEG. A dominating species of the extracted uranium(VI) thiocyanate complexes was assumed to be NH₄ UO₂(SCN)₃·(PEG). The extraction of protactinium was also preliminarily studied. The extraction of these actinides from an acidic thiocyanate solution increased in the order: uranium(VI)>protactinium(V)>neptunium(V).     

On the mechanism of extraction of trivalent actinides and lanthanides with alkylamine hydrochlorides

The method to study the mechanism of actinides (III) and lanthanides (III) liquid-liquid amine extraction from chloride media has been suggested. The technique is based on the determination of distribution coefficients for extraction of these elements from mixed salting-out agent solutions with common anion. Distribution coefficients were found to be independent of mean ion activity of lithium cation at constant water activity, when extraction of trace amounts of Eu (III) and Cm(III) by tri-n-octylammonium hydrochloride from mixed LiCl−CaCl₂ solutions occurred. It has been concluded that lithium cation does not enter into the complexed extracted.     

Improvement in flow-sheet of extraction chromatography for trivalent minor actinides recovery

Journal of Radioanalytical and Nuclear Chemistry - Extraction chromatography flow-sheet employing octyl(phenyl)-N,N-diisobutylcarbonoylmethylphosphine oxide and bis(2-ethylhexyl) hydrogen phosphate...     

A rapid sequential separation of actinides using Eichrom's extraction chromatographic material

For the past 10 years, Eichrom has provided a variety of innovative products for faster separation of radionuclides to radioanalytical laboratories. However, recently, environmental testing laboratories have been challenged to generate reliable data more quickly. To assist our customers with rapid separations, Eichrom has developed a new configuration for its existing extraction chromatographic material that operates with vacuum assisted flow. After pre-concentration of actinides from a given sample, the actinides are dissolved in a suitable solution. Appropriate Eichrom Resin Cartridges are placed on a vacuum box system. Sample solutions are then passed through the cartridges under optimal vacuum pressure. In this paper, a scheme for separation of actinides in different matrices are discussed using Eichrom Resin Cartridges. Time required for separations, test results and ease of use are the primary discussions of this paper.