Bis(2-ethylhexyl)sulfoxide as an extractant for americium(III) from aqueous nitrate media

Solven extraction separation of americium(III) from dilute aqueous nitrate media into n-dodecane by bis(2-ethylhexyl)sulfoxide (BESO) has been investigated over a wide range of experimentgal conditioins. Very poor extractablity of Am(III), necessitated the use of calcium nitrate as the salting-out agent. Effects of certain variables such as acidity, extractant concentration, salting-out agent concentration, organic diluents on the metal extraction by BESO have been examined in detail. By increasing the concentration of BESO in organic phase or calcium nitrate in aqueous phase, nearly quantitative extraction of americium even from moderate acidity is accomplished. Slope analyses applied to Am(III) distribution experiments from acidic nitrate solutions indicate predominant formation of the risolvated organic phase complex, Am(NO₃)₃)·3BESO for which equilibrium constant is found to be, log K_x=1.99. Extraction behavior of Am(III) has also been evlauated in the presence of several water-miscible polar organic solvents to stuy their possible synergistic effects on its extraction. Extractability of americium increased 5 to 10-fold withi increasing conentration of some of these additives, with maximum enhancement being observed in the presence of acetone or acetonitrile. Recovery of BESO from loaded americium is easily obtained using dilute nitric acid as the strippant.     

Separation of americium(III) from lanthanides(III) by nanofiltration-complexation in aqueous medium

The separation of Am(III) from a mixture of lanthanides(III) was performed in aqueous medium by nanofiltration combined with a complexation step using a DTPA derivative as selective complexing agent.     

Solvent extraction of Ga(III) and In(III) from aqueous halide media by adogen-364

Adogen-364 has been used for the extraction ofgallium(III) and indium(III) from halogen acid solutions, and the dependence of the extraction on chloride, bromide and iodide ion concentration studied. The separation of Ga(III), In(III) and Al(III) is reported and some conclusions have been drawn about the stoichiometry of the extracted species.     

A novel approach for extraction of plutonium and americium from aqueous complexing media

Journal of Radioanalytical and Nuclear Chemistry - A new approach for the extraction of plutonium and americium from aqueous media containing complexing ligands has been investigated using a new...     

Photoluminescence of americium(III) in aqueous and organic solutions

The influence of different solvents on Am³⁺·sold photoluminescen has been studied. A great increase of luminescence lifetime in deuterated DMSO compared with water was found. The sensitization of americium(III) photoluminescence by energy transfer from ligand (TTA or nalidixic acid) was realized for the first time. The photoluminescence of AmW₁₀ O₃₆ ^9– was discovered and some of its characteristics were measured. The use of photoluminescence for investigation of americium complex formation in solutions was demonstrated.     

Solvent extraction of Tm(III) by sulfoxides and mixtures of DPSO (di-N-pentyl sulfoxide) and HTTA (thenoyl-trifluoroacetone) from perchlorate and thiocyanate media

Extraction of Tm(III), from thiocyanate media, by different sulfoxides (R₂SO) has revealed that the extractable complex is Tm(SCN)₃·4 R₂SO. When mixtures of DPSO and HTTA are used for the extraction of Tm(III) from thiocyanate or perchlorate media, synergistic enhancement of the extraction of Tm(III) results. The complexes responsible for the enhanced extraction are Tm(TTA)₃·DPSO and Tm(TTA)₃·2 DPSO when perchlorate media were employed for the extraction and Tm(SCN)(TTA)₂·2 DPSO and Tm(SCN)₂(TTA)·3 DPSO, in addition to the above two when a thiocyanate medium was employed for the extraction. Values of equilibrium constants for some equilibria encountered in the extraction of Am(III) and Tm(III) by mixtures of DPSO and HTTA are given.     

The interpretation of X-ray diffraction by aqueous solutions of aluminum(III) nitrate and chromium(III) nitrate

Aqueous solutions of the nitrates of aluminum (0.5 M) and chromium (0.5 M) are investigated with X-ray diffraction at t = 25° C. The experimental intensity is interpreted in terms of an electron product-function which is a sum of various pair contributions. The contribution containing the information about cationic hydration has been evaluated by combining the results of separate experiments. The method is in several aspects quite different from what is usual. Still the results obtained are in general agreement with the data reported elsewhere. That is, sixfold coordination at 1.90 Å and 1.98 Å and a second shell containing about 12 water molecules appearing at 4.10–4.15 Å and 4.20–4.25 Å for Al³⁺ and Cr³⁺ respectively.     

Effect of gamma-radiation on the extraction of europium and americium by benzyldimethyldodecylammonium nitrate

Previously it was found that in the extraction separation on lanthanides and americium from acidic nitrate solutions of nuclear fission products, benzyldimethyldodecylammonium nitrate gives high values of separation coefficients. The change in the extraction capacity of this agent and its solutions in benzene in the extraction of Eu(III) and Am(III) was investigated as a function of the adsorbed dose of ionizing radiation. The slight reduction in the extraction of both metals is caused mainly by the radiolysis products of nitric acid in the organic phase that enter into secondary reactions with both the solvent and the extractant. Comparison of the radiation stability of benzyldimethyldodecylammonium nitrate systems with tertiary amines show that the changes in distribution coefficients in the range of investigated absorbed doses are significantly lower in the former case. The investigated system may be characterized as radiation stable up to about 100 kGy even in the presence of nitric acid.     

Ion flotation of lanthanum(III) and holmium(III) from nitrate and nitrate-chloride media

Ion flotation of lanthanum(III) and holmium(III) from nitrate and nitrate-chloride solutions with sodium dodecyl sulfate was studied. The distribution coefficients and their dependence on pH were determined.     

Cerium(III) extraction with oleic acid from nitrate solutions

Cerium(III) extraction with oleic acid in o-xylene from nitrate solutions was studied. The extraction mechanism and the dependence of the distribution ratio on pH and composition of the organic and aqueous phases were examined. The thermodynamic characteristics of extraction were calculated.     

Studies on the extraction behaviour of zirconium from mixed aqueous media with TBP

A systematic study is presented on the extraction of Zr(IV) by tri-n-butylphosphate from H₂SO₄, HNO₃, HCl and HBr solutions as well from binary mixtures of H₂SO₄ and halogen acids. It has been found that Zr(IV) extraction is appreciably increased by addition of halogen acid to sulphuric acid solutions. On the other hand, the presence of water-miscible alcohols and acetone was found to enhance Zr(IV) extraction from HCl and HNO₃ solutions. An investigation of extracted Zr complexes from pure acids and mixed aqueous media enabled an explanation of the observed enhancements. In the light of the obtained results, an extraction mechanism is suggested.     

Hydrolysis of americium(III)

A generalized scheme of americium(III) hydrolysis is proposed for a wide range of pH (1–10) and concentrations (10^–1–10^–10M). The data on Am(III) hydrolysis are presented in the form of three-dimensional isothermal diagram. This approach to the study of hydrolysis can be used for investigation of hydrolytic behaviour of most polyvalent ions.     

Complexation of americium(III) with humic acid by cation exchange and solvent extraction

Complexation of Am(III) with humic acid was studied at various pHs in 0.1M NaClO₄. The stability constants of the Am(III)—humate complexes were determined by a cation-exchange method. The values of log₁ and log₂ increased slightly with increases of pH from 4 to 6 and were found to be 6.9 and 11.6, respectively, at a pH of 5. Markedly larger values than these were obtained by a solvent extraction method. This discrepancy was also revealed by summarizing data from several literature sources. It is very likely that this can be ascribed to decreases in either humic acid and/or the extractant from the extraction system due to humate interactions at the aqueous-organic interface.This revised version was published online in November 2005 with corrections to the Cover Date.     

Radiation effects on the extraction of americium(III) with di(2-ethylhexyl) phosphoric acid

Radiation effects on the extraction of Am(III) with di (2-ethylhexyl) phosphoric acid (DEHPA) was studied by exposing DEHPA to gamma rays under various conditions. Gamma irradiation of undiluted DEHPA causes an enhancement of extraction of Am(III) due to the formation of mono (2-ethylhexyl) phosphoric acid (MEHPA) similarly to that of Nd(III). The presence of diluent during irradiation brought about a slight difference from the results in the absence of a diluent. The marked change occurred in Df when the organic solvent was exposed to γ-ray while being mixed with nitric acid solution. An initial slight increase of Df for Am(III) and Nd(III) was followed by a subsequent decrease beyond an absorbed dose of approximately 200 Wh·1⁻¹. This phenomenon was explained by the enhanced decomposition of DEHPA and the subsequent strong hydrolytic and radiolytic decomposition of MEHPA to H₃PO₄ in the aqueous phase, and the complex forming nature of H₃PO₄ with Am(III) and Nd(III).     

A study of radiation effects on the extraction of americium(III) with acidic organophosphates

Radiation effects on the extraction of americium(III) with several dialkylphosphoric and monoalkylphosphoric acids have been studied comparatively. The extractants were exposed to⁶⁰Co γ-rays in the absence and presence of diluent and HNO₃. The Df of Am(III) was measured and the yield of radiolytic products was determined after γ-irradiation as a function of the absorbed dose. Di(hexoxyethyl)phosphoric acid was the most susceptible to radiation among the extractants studied and its extractability was weakened by radiation regardless of the presence or absence of diluent or HNO₃. Diisodecylphosphoric acid itself showed an enhancement upon irradiation but incurred a depressant effect upon intimate contact with HNO₃·Mono(2-ethylhexyl)phosphoric acid showed a decrease of the Df of Am(III), similarly to DIDPA in the presence of HNO₃ during γ-irradiation. All the above extractants gave H₃PO₄ as the principal radiolytic product upon γ-irradiation upon intimate contact with HNO₃ causing decreasing solely the extraction of Am(III). Di(2-ethylhexyl)phosphoric acid proved to be the most stable extractant to radiation among those studied.     

Synergistic extraction of americium(III) with 2-thenoyltrifluoroacetone and crown ethers

Extracton, of Am³⁺ in benzene with 2-thenoyltrifluoroacetone (HTTA) and crown ethers (CEs) such as 15-crown-5, 18-crown-6, dicyclohexano-18-crown-6, dibenzo-18-crown-6, dicyclohexano-24-crown-8, and dibenzo-24-crown-8 was investigated. Synergistic effect by CE was observed regardless of the kind of CE examined. The extracted species was found to be Am(TTA)₃(CE), and adduct formation constants between Am(TTA)₃ and CE in the organic phase were determined. The sequence of constant could not be explained only by basicity of CE and the steric effect of CE should be taken into account to elucidate the adduct complex formation.     

Separation of AM(III) by extraction from nitrate solutions using some quaternary benzylammonium salts

Benzyldimethyldodecylammonium nitrate and benzyltrioctylammonium nitrate were used for the extraction of Am(III) from aqueous nitrate solutions. The dependence of the extraction performance for Am(III) on the concentration of nitric acid, the kind and concentration of salting-out agents in the aqueous phase, and the kind of solvent was investigated. Americium is extracted by the above quarternary salts as a R₄NAm(NO₃)₄ associate. The extraction of Am(III) is compared with the extraction of lanthanides. The high differences in the distribution coefficients for lanthanides and americium can be utilized for the separation of lanthanides and americium.     

Kinetics of americium and europium extraction by tert-butylthiacalix[4]arene from alkaline media

Kinetics of ¹⁵²Eu and ²⁴¹Am extraction by nitrogen-bearing alkyl amino phenol oligomer YaRB and tert-butylthiacalix[4]arene TCA from carbonate-alkaline media was studied. Both extractants efficiently extract americium and europium in pH interval 12–14. The maximum of americium extraction is located at the lower values of pH, compared with europium. YaRB extracts americium and europium faster than TCA, and at the same time, americium is extracted faster than europium by both extractants. In general, thiacalixarene TCA is regarded as more efficient extractant than alkyl amino phenol oligomer YaRB.