Distribution Coefficients Of Am Research Articles

Studies on the uptake of Am(III) and Eu(III) on ionic liquid modified polystyrene-divinyl benzene

Abstract Imidazolium bis(2-ethylhexyl)phosphate ionic liquid was anchored on a polystyrene-divinylbenzene (PS-DVB) copolymer and the product (R-Im-DEHP) was studied for the extraction of Am(III) and Eu(III) from dilute nitric acid medium to examine the feasibility using the anchored adsorbent for their mutual separation. The effect of various parameters such as the duration of equilibration, concentration of nitric acid, europium ion, and diethylenetriaminepentaacetic acid (DTPA) in aqueous phase on the distribution coefficient (K d) of Am(III) and Eu(III) was studied. The distribution coefficient of Am(III) and Eu(III) decreased with increase in the concentration of nitric acid. Rapid extraction of metal ions in the initial stages of equilibration followed by the establishment of equilibrium occurred within 4 h. The data on the rate of uptake of Am(III) and Eu(III) were fitted into pseudo-first order and pseudo-second order rate equation. The extraction isotherm was fitted to Langmuir and Freundlich adsorption models and the apparent europium extraction capacity was determined. The mechanism of extraction was elucidated and the conditions needed for efficient separation of Am(III) from Eu(III) was optimized using DTPA. The study indicated the possibility of using R-Im-DEHP for the separation of Eu(III) from Am(III) with high separation factors.

Extraction-chromatographic properties and radiation resistance of a solid extractant based on di-2-ethylhexyl hydrogen phosphate

Extraction-chromatographic properties of LN-B200-S sorbent based on di-2-ethylhexyl hydrogen phosphate were studied. The equilibrium distribution coefficients of Am in the sorbent–HNO3 system, the total exchange capacity, and the capacity to breakthrough were determined. The influence of the absorbed dose on the above parameters was examined. The suggested extraction-chromatographic system was tested with a real solution of spent nuclear fuel from an RBMK-1000 reactor as applied to the recovery of the Am–Cm–Nd fraction.

Extraction behaviour of Am(III) and Eu(III) from nitric acid medium in TEHDGA-HDEHP impregnated resins

Abstract The extraction behaviour of Am(III) and Eu(III) from nitric acid medium was studied in the solvent impregnated resins containing extractants such as tetra-bis(2-ethylhexyl)diglycolamide (TEHDGA) or bis-(2-ethylhexyl)phosphoric acid (HDEHP) or mixture of TEHDGA+HDEHP. The rate of extraction of Am(III) and Eu(III) from 1 M nitric acid and the effect of various parameters, such as the concentration of nitric acid in aqueous phase and concentration of TEHDGA and HDEHP in resin phase, on the distribution coefficient of Am(III) and Eu(III) was studied. The distribution coefficient of Am(III) and Eu(III) in HDEHP-impregnated resin decreased and that in TEHDGA-impregnated resin increased, with increase in the concentration of nitric acid. However, in (TEHDGA+HDEHP) – impregnated resin, synergic extraction was observed at lower nitric acid concentration and antagonism at higher nitric acid concentration. The mechanism of Am(III) and Eu(III) extraction in the combined resin was investigated by slope analysis method. The extraction of various metal ions present in the fast reactor simulated high-level liquid waste was studied. The separation factor of Am(III) over Eu(III) was studied using citrate-buffered diethylenetriaminepentaacetic acid (DTPA) solution.

Extraction behaviour of Am(III) and Eu(III) from nitric acid medium in CMPO-HDEHP impregnated resins

Abstract Chromatographic resin containing extractants such as octyl(phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxide (CMPO) or bis-(2-ethylhexyl)phosphoric acid (HDEHP) or mixture of extractants (CMPO + HDEHP) in an acrylic polymer matrix was prepared and studied for the extraction of Am(III) and Eu(III) over a range of nitric acid concentration. The effect of various parameters such as concentration of nitric acid in aqueous phase and the concentration of CMPO and HDEHP in the resin phase was studied. The distribution coefficient of Am(III) and Eu(III) in the impregnated resin increased with increased in the concentration of nitric acid for CMPO-impregnated resin, whereas a reverse trend was observed in HDEHP impregnated resin. In case of resin containing both the extractants, synergism was observed at low nitric acid concentration and antagonism at high nitric acid concentration. The mechanism of extraction was probed by slope analysis method at 0.01 and 2 M nitric acid concentrations. Citrate-buffered DTPA was used for the selective separation of Am(III), and a separation factor of 3–4 was obtained at pH 3.

Extraction of Americium(III), Plutonium(IV, V) and Neptunium(V) with Calixarenes

The distribution coefficients of Am iii , Pu v , Pu iv and Np v on extraction from aqueous media with solutions of calix [4] arenes in 1,2-dichloro-ethane and their dependence on the structure of the macrocycles have been determined.

Interaction of 6,6′′-bis(5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-1,2,4-benzotriazin-3-yl)-2,2′:6′,2′′-terpyridine (CyMe4-BTTP) with some trivalent ions such as lanthanide(iii) ions and americium(iii)

The new ligand 6,6''-bis(5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-1,2,4-benzotriazin-3-yl)-2,2':6',2''-terpyridine (CyMe4-BTTP) has been synthesized in 4 steps from 2,2':6',2''-terpyridine. Detailed NMR and mass spectrometry studies indicate that the ligand forms 1:2 complexes with lanthanide(III) perchlorates where the aliphatic rings are conformationally constrained whereas 1:1 complexes are formed with lanthanide(III) nitrates where the rings are conformationally mobile. An optimized structure of the 1:2 solution complex with Yb(III) was obtained from the relative magnitude of the induced paramagnetic shifts. X-Ray crystallographic structures of the ligand and of its 1:1 complex with Y(III) were also obtained. The NMR and mass spectra of [Pd(CyMe4-BTTP)]n(2n+) are consistent with a dinuclear double helical structure (n = 2). In the absence of a phase-modifier, CyMe4-BTTP in n-octanol showed a maximum distribution coefficient of Am(III) of 0.039 (±20%) and a maximum separation factor of Am(III) over Eu(III) of 12.0 from nitric acid. The metal(III) cations are extracted as the 1:1 complex from nitric acid. The generally low distribution coefficients observed compared with the BTBPs arise because the 1:1 complex of CyMe4-BTTP is considerably less hydrophobic than the 1:2 complexes formed by the BTBPs. In M(BTTP)(3+) complexes, there is a competition between the nitrate ions and the ligand for the complexation of the metal.

Effect of oxide ions on separation factors of actinides from lanthanides in reductive extraction

Abstract The distribution coefficients of Am, Ce, and Eu between the salt and metal phases were measured at 1073 K in a reductive extraction system of equimolar NaCl-KCl melt and liquid Ga. By changing the solute concentrations, it was observed that the distribution coefficients were dependent on the oxide ion concentration in the system, possibly due to the formation of such compounds as AmO+. In addition, the mass balance of Am was possibly affected by the formation and precipitation of its oxychlorides and/or oxides in some runs. Taking these observations into consideration, the separation factor between Am and Ce was found to be around 30 in the present system.

Separation Factor of Americium from Cerium in Molten Chloride-Liquid Gallium Reductive Extraction System

The distribution coefficients of Am and Ce were measured in the eutectic LiCl-KCl/liquid Ga system at 773K. By using ZrCl4 as the oxide ion scavenger in order to avoid the formation of such oxychlorides as MO(n−2)+, the effect of oxide ion concentration was well controlled on the distribution coefficients of Am and Ce. The separation factor between Am and Ce was then obtained to be about 100. By comparing the present value with the other experimental and the predicted ones, it was confirmed that the Ga system was more selective than the Bi and Cd system.

Adsorption of Am(III) on red earth and natural hematite

The Am(III) adsorption isotherms on natural hematite, on a red earth and on three kinds of treated red earth samples were determined and compared. The treatment was performed to remove iron oxides, organic matter (OM) and both. The batch technique and aqueous Am(III) solutions with molarities less than 3 . 10-9 mol/l were used. A very high adsorbability of Am(III) on hematite was found, and in order to decrease the adsorption percentage, stable Eu3+ as a hold back carrier was added to the aqueous solution. All the isotherms were found to be linear. The strong effects of pH, ionic strength and fulvic acid (FA) on the Am(III) adsorption on natural hematite were demonstrated. A positive contribution of OM and an unexpectedly high negative influence of iron oxides on the Am(III) adsorption by the untreated red earth were found too. The average distribution coefficients of Am(III) adsorption on natural hematite, on red earth and on three kinds of treated red earth samples were determined, respectively, from these linear isotherms. The very high adsorbability of Am(III) on hematite and the very strong negative influence of iron oxides on the Am(III) adsorption on untreated red earth were distinctly demonstrated as well. It appears that the adsorbability of composed natural materials cannot be predicted from the adsorbabilities of each of the mineral components alone, due to possible interactions between the mineral components and the different characteristics of the composite.

Adsorption behavior of Am with gamma irradiated Thiacalix[4]arene impregnated silica adsorbent

Thiacalix[4]arene impregnated silica adsorbent which is called CAPS-SO 2-adsorbent in this paper shows the excellent separative performance of trivalent actinoids, such as Am from the high-level radioactive liquid waste (HLLW) in weak-acid solution. The chemical stability of the adsorbent was investigated under strong irradiation conditions. The amount of dissolved CAPS-SO 2 was only 1% by gamma-ray irradiation at a total dose of 1 MGy. The value of distribution coefficient of Am (Kd Am) at pH 4 by the adsorbent was constant even the high irradiation dose. Moreover, the separation factor of Am to lanthanoids is kept a high value. It was also found that the value of Kd Am by the irradiated CAPS-SO 2-adsorbent increases at pH 2.

Separation performance for trivalent actinides from lanthanides by thiacalix[4]arenes compounds impregnated silica ion-exchanger

Silica ion-exchangers impregnated new thiacalix[4]arenes compounds were prepared and investigated the adsorbed performance for Am and lanthanides. The maximum distribution coefficient of Am over the exchanger was 5000 cm 3/g in weak-acid solution. In contrast, the distribution coefficient of Nd or Eu was below 10 cm 3/g. It was shown that thiacalix[4]arenes compounds have the selective adsorption for Am. The influence of the gamma ray irradiation to the selective adsorption was also investigated.

Extraction of Actinides from HNO3 Solutions with Solutions of Dialkyl Methylphosphonates

Extraction of actinides with dialkyl methylphosphonates was studied with the aim to find a compromise between the use of highly effective but expensive chemicals, on the one hand, and weakly effective but cheap and readily available chemicals, on the other hand, and also to find possible ways of utilization of methylphosphonic dichloride, which is the starting substance in syntheses not only of dialkyl methylphosphonates, but also of chemical weapons. In systems with 3 M HNO3 as the aqueous phase and a solution of tributyl phosphate (TBP), diisoamyl methylphosphonate (DIAMP), or bidentate diphenyl(carbamoylmethyl)phosphine oxide (Ph2Bu2) in dichloroethane as organic phase, at equal concentrations of the organophosphorus compounds, the distribution coefficients of Am(III) increase in the order TBP 0.1 M and [HIAMP] < 1.5 M (HIAMP is isoamyl hydrogen methylphosphonate).

Valence Control and Solvent Extraction of Americium in the Presence of Ammonium Phosphotungstate

Fundamental investigations on valence control and solvent extraction of americium were carried out to develop a method for americium separation from reprocessing solution. In order to adjust americium valency from III to IV and VI, (NH4)10P2W 17O61 synthesized was used as complexant stabilizing Am(IV). Oxidation behavior of americium was investigated as a function of (NH4)10P2W 17O61 americium ratio. Using 0.1M (NH4)2S2O8 and 0.01M AgNO3 as oxidation reagent, Am(IV) was obtained quantitatively at the ratio of 15. On decreasing the ratio to 0.6, 92% of americium was adjusted to Am(VI). The concentration of (NH4)2S2O8 could be reduced to 1/15 compared to the previously reported method in which no complexant was used. Americium(IV) was also prepared by reacting O3 and AgNO3 but no Am(VI) was obtained even at low (NH4)10P2W 17O61 to americium ratio.Americium(VI) could be extracted by tri-n-butyl phosphate stably without influence of (NH4)10P2W 17O61. The distribution coefficient of Am(VI) was 4 between 100% tri-n-butyl phosphate and 1 M nitric acid, and separation factor from Nd(III) was 50.With regard to the americium separation method which implemented valence control followed by extraction, adding (NH4)10P2W 17O61 led to minimization of waste volume and improvement of extraction efficiency.

Valence Control and Solvent Extraction of Americium in the Presence of Ammonium Phosphotungstate.

Fundamental investigations on valence control and solvent extraction of americium were carried out to develop a method for americium separation from reprocessing solution. In order to adjust americium valency from III to IV and VI, (NH4)10P2W 17O61 synthesized was used as complexant stabilizing Am(IV). Oxidation behavior of americium was investigated as a function of (NH4)10P2W 17O61 americium ratio. Using 0.1M (NH4)2S2O8 and 0.01M AgNO3 as oxidation reagent, Am(IV) was obtained quantitatively at the ratio of 15. On decreasing the ratio to 0.6, 92% of americium was adjusted to Am(VI). The concentration of (NH4)2S2O8 could be reduced to 1/15 compared to the previously reported method in which no complexant was used. Americium(IV) was also prepared by reacting O3 and AgNO3 but no Am(VI) was obtained even at low (NH4)10P2W 17O61 to americium ratio.Americium(VI) could be extracted by tri-n-butyl phosphate stably without influence of (NH4)10P2W 17O61. The distribution coefficient of Am(VI) was 4 between 100% tri-n-butyl phosphate and 1 M nitric acid, and separation factor from Nd(III) was 50.With regard to the americium separation method which implemented valence control followed by extraction, adding (NH4)10P2W 17O61 led to minimization of waste volume and improvement of extraction efficiency.

Solvent Extraction of Americium(VI) by Tri-n-Butyl Phosphate

Solvent extraction of Am(VI) by tri-n-butyl phosphate (TBP) from nitric acid solutions was investigated to develop a novel method for partitioning americium from high level liquid waste generated through spent nuclear fuel reprocessing. Am(VI) was prepared using ammonium peroxodisulfate and silver nitrate. The distribution coefficients of Am(VI) were determined for extraction systems of various concentrations of nitric acid and TBP. Sufficiently stable Am(VI) could be extracted and the extraction reaction of Am(VI) was found to be the same as for other hexavalent actinides. The apparent equilibrium constant varied with the concentration of peroxodisulfate used for the valence control, which was ascribed to the competitive reaction of the extraction of Am(VI) and the complex formation of Am(VI) with sulfate ion produced by the decomposition of peroxodisulfate. A distribution coefficient of Am(VI) above 1 was obtained with undiluted TBP and the separation factor between Am(VI) and Nd(III) was 87±9. TBP extraction of Am(VI), after implementing valence control, was proved to be an effective method for the partitioning of americium from fission products such as rare earth elements.

Solvent Extraction of Americium(VI) by Tri-n-Butyl Phosphate.

Solvent extraction of Am(VI) by tri-n-butyl phosphate (TBP) from nitric acid solutions was investigated to develop a novel method for partitioning americium from high level liquid waste generated through spent nuclear fuel reprocessing. Am(VI) was prepared using ammonium peroxodisulfate and silver nitrate. The distribution coefficients of Am(VI) were determined for extraction systems of various concentrations of nitric acid and TBP. Sufficiently stable Am(VI) could be extracted and the extraction reaction of Am(VI) was found to be the same as for other hexavalent actinides. The apparent equilibrium constant varied with the concentration of peroxodisulfate used for the valence control, which was ascribed to the competitive reaction of the extraction of Am(VI) and the complex formation of Am(VI) with sulfate ion produced by the decomposition of peroxodisulfate. A distribution coefficient of Am(VI) above 1 was obtained with undiluted TBP and the separation factor between Am(VI) and Nd(III) was 87±9. TBP extraction of Am(VI), after implementing valence control, was proved to be an effective method for the partitioning of americium from fission products such as rare earth elements.

The liquid-liquid extraction of certain tripositive transplutonium ions from salted nitrate solutions with a tertiary and quaternary amine

The distribution coefficients of Am(III), Cm(III) and Cf(III) were measured from Li, Mg, Ca, Al and Fe(III) nitrate solutions using a high molecular weight tertiary and quaternary amine. The distribution coefficient of Am(III) was measured for the tertiary and quaternary amine systems as a function of the diluent, aqueous acid concentration, extractant concentration and aqueous nitrate concentration. Separation factors for Cm(III)/Am(III), Cf(III)/Am(III), Es(III)/Cf(III) and Eu(III)/Am(III) were determined for the two amine systems. The quaternary amine was shown to be a superior extractant for the transplutonium (III) ions compared to the tertiary amine.