Distribution Ratio Of Am Research Articles

Elucidation of the extraction of trivalent actinides using the DOHyA-HDEHP system: an experimental and theoretical approach.

A combined solvent system composed of an acidic and a neutral extractant is demonstrated as an effective system for the mutual separation of lanthanides and actinides from nitric acid solutions. The geometry and stability of various possible complexes formed under extraction and stripping conditions in a combined solvent system composed of N,N-dioctyl hydroxyacetamide (DOHyA) and bis(2-ethylhexyl)phosphoric acid (HDEHP) in the n-dodecane medium were studied both experimentally and theoretically. Experimental observations of the distribution ratios of Am(III) and Eu(III) in the combined solvent system revealed synergistic extraction of trivalent metal ions at all nitric acid concentrations. Density functional theory (DFT) calculations were employed to understand the geometric and electronic properties of the ligands and their corresponding complexes with Am(III) and Eu(III). The calculated results indicate that the feasibility and behaviour of complex formation in the combined solvent system using different methods are based on the energetic aspects of the formation reactions. The study also reveals the participation of the neutral and acid extractants in the combined solvent system facilitating the separation of Eu(III) and Am(III) from high-level liquid waste.

Comparative evaluation of radiolytic stability of aqueous soluble BTP and BTBP derivatives under static gamma irradiation

The radiolytic stability of aqueous solutions containing two different bis-1,2,4-triazines was studied under static gamma irradiation. Sulphophenyl derivatives of bis-1,2,4- triazinyl pyridine (SO3-Ph-BTP) and bis-1,2,4-triazinylbipyridine (SO3-Ph-BTBP) were dissolved in 0.1 M and 1 M HNO3 solutions and the impact of gamma irradiation was assessed by the measurement of distribution ratios of Am(III) and Eu(III) using irradiated samples. The results were compared for two different organic solvents containing N,N,N’,N’-tetraoctyldiglycolamide (TODGA) or N,N-didodecyl-N’,N’-dioctyldiglycolamide (D3DODGA). The separation efficiency of all the systems remained unchanged when the absorbed dose was 100 kGy, and gradually decreased at 200 kGy and 500 kGy. The radiolytic degradation was more apparent for SO3-Ph-BTBP in comparison to SO3-Ph-BTP at higher acidity. The degradation of sulphonate groups in the molecules was evidenced in ATR-FTIR spectral studies.

Endowing 2,6-bis-triazolyl-pyridine of poor extraction with superior efficiency for actinide/lanthanide separation at high acidity by anchoring to a macrocyclic scaffold

Exploring nitrogen-containing extractants for recovering hazardous minor actinides that are workable in solutions of high acidity has been a challenge in nuclear waste treatment. Herein, we report our findings that 2,6-bis-triazolyl-pyridine (PyTri), which is ineffective as a hydrophobic ligand for minor actinide separation, turns into an excellent extractant that exhibits unexpectedly high efficiency and selectivity (SFAm/Eu = 172, 1 M HNO3) when attaching to pillar[5]arene platform. Surprisingly, the distribution ratio of Am(III) (DAm) is 4300 times higher than that of the acyclic PyTri ligand. The solvent extraction performance of this pillar[5]arene-achored PyTri not only far exceeds the best known pillar[5]arene ligands reported to date, but also stays comparable to other reported outstanding extractants. Slope analysis indicates that each P[5]A-PyTri can bind two metal ions, which is further corroborated by spectroscopic characterizations. Thermodynamic studies imply that the extraction process is exothermic and spontaneous in nature. Complexation investigation via EXAFS technique and DFT calculations strongly suggest that each Eu(III) ion is coordinated to three PyTri arms through a nine-coordination mode. This work provides a N-donor extractant that can operate at high acidity for minor actinide partitioning and implicates a promising approach for transforming poor extractants into superior ones.

Investigations on the radiation stability of incinerable CHON based ionic liquid containing diglycolamide

The radiolytic degradation of tetra-2-ethylhexyl diglycolamide (T2EHDGA) and its solution with methyltrioctylammonium nitrate ([N1888][NO3]) was assessed by irradiating the individual liquids and the solution of T2EHDGA in [N1888][NO3] to different γ-absorbed dose levels, and determining the distribution ratio of Am(III) and Nd(III) in the irradiated organic phases. The data obtaining for the irradiated liquids were compared with those obtained for unirradiated liquid phase as well as with the conventional organic phase composed of T2EHDGA in n-dodecane (n-DD). While the distribution ratio of Am(III) in irradiated T2EHDGA/n-DD decreased with increase of absorbed dose, it was invariant in case of irradiated T2EHDGA/[N1888][NO3]. To understand this discrepancy, the distribution ratio of Am(III) as well as the loading behavior of Nd(III) in a solution of irradiated T2EHDGA present in unirradiated [N1888][NO3] as well as in the unirradiated T2EHDGA present in irradiated [N1888][NO3] was measured and compared. The results revealed that the irradiated systems containing either the irradiated T2EHDGA or irradiated [N1888][NO3] undergo degradation upon γ-irradiation, but when they were combined, they mutually facilitate the extraction of Am(III) and Nd(III) comparable to that observed in the unirradiated condition. This observation was also supported by the FTIR spectroscopic investigation of the irradiated organic phases.

Effects of Diluents on the Separation of Minor Actinides from Lanthanides with Tetradodecyl-1,10-phenanthroline-2,9-diamide from Nitric Acid Medium.

To investigate the effective separation of actinides (Ans) from lanthanides (Lns), single-stage batch extraction experiments were performed with a novel extractant, tetradodecyl-1,10-phenanthroline-2,9-diamide (TDdPTDA) with various diluents such as 3-nitrobenzotrifluoride (F-3), nitrobenzene, and n-dodecane for Am, Cm, and Lns. The extraction kinetics with TDdPTDA was rapid enough to perform continuous extraction experiments using mixer-settler extractors. The slopes of the distribution ratio versus the TDdPTDA concentration and the distribution ratio versus the nitric acid concentration were similar for F-3 and nitrobenzene systems, but different from the n-dodecane system. These differences were attributed to the characteristics of the diluents. This study revealed high distribution ratios of Am (DAm) and Cm (DCm) for TDdPTDA, with the high separation factors (SFs) of Am from Lns enough for their separation.

Separation of Am(III) from Eu(III) present in 3 M nitric acid medium using completely incinerable binary extractants

The extraction behavior of Am(III) and Eu(III) from nitric acid medium (0.001 M to 3 M) was studied in a binary solution of N,N-dioctylhydroxy acetamide (DOHyA) and bis(2-ethyhexyl)diglycolamic acid (HDEHDGA) in n-dodecane to evaluate the feasibility of separating Am(III) from Eu(III) present in 3–4 M nitric acid medium. The extraction of Am(III) and Eu(III) was studied as a function of various parameters. The results were compared with the individual extractants in n-dodecane. Synergic extraction of Am(III) and Eu(III) was observed at nitric acid concentrations above 0.5 M and antagonism at lower nitric acid region. The dependence of distribution ratio of Am(III) and Eu(III) on binary extractants was probed by the slope analysis of the extraction data, and the mechanism of Am(III) and Eu(III) extraction was determined at various acidities. The results revealed the possibility of single-cycle separation of Am(III) from Eu(III) with a separation factor ~13.

Complexation of a macrocyclic ligand, 2,6-di (N-methyl)formamide-calix[4]pyridine, with Eu(III) and extraction of Eu(III) and Am(III)

Abstract Complexation of a new macrocyclic compound, 2,6-dimethylformamide-calix[4]pyridine (L1 ), with Eu(III) was studied by spectrophotometry. Stability constants of the Eu(III)/L1 complex in different solvents were determined. The results reveal that L1 forms moderately strong complexes with Eu(III) and other lanthanides in aprotic solvents and shows little binding ability with transition metals. Moreover, the binding strength of L1 weakens significantly in protic solvents. Using 2-bromodecanoic acid as the synergistic reagent, L1 extracts Am(III) and Eu(III) successfully with a separation factor of SFAm/Eu=1.3, and the distribution ratios of Am(III) and Eu(III) increases as the aqueous acidity is decreased. DFT computational studies were conducted to corroborate the solvent extraction data, and compare the coordination properties of Am(III)/Eu(III) complexes with L1 and a related, 2,6-diformamide-calix[4]pyridine (L2 ). The computational results suggest that L2 could form stable complexes [ML]3+ and ML(NO3)3 [where M represent Am(III) or Eu(III)] in aqueous phase, in sharp contrast to the case of L1 where such complexes in aqueous phase are not stable.

Solvent extraction of americium(III) and europium(III) with 2,6-bis(5,6-diethyl-1,2,4-triazin-3-yl) pyridine in ionic liquids: Experimental study and molecular dynamics simulation

Abstract The extraction behaviors of Eu(III) and Am(III) from nitric acid medium by 2,6-bis(5,6-diethyl-1,2,4-triazin-3-yl) pyridine (C2-BTP) dissolved in four different room temperature ionic liquids (RTILs), viz. C2mim+ NTf 2 - , C4mim+ NTf 2 - , C6mim+ NTf 2 - , C8mim+ NTf 2 - , were investigated under different conditions. The distribution ratios of Am(III) and Eu(III) in C2-BTP/Cnmim+ NTf 2 - (n = 2, 4, 6, 8) were measured as a functions of the extraction time and the concentration of nitric acid. It is found that the systems exhibit slow kinetics in extraction, and the distribution ratios for Am(III) and Eu(III) decrease with higher nitric acid concentration. The extraction mechanism is found to be cation-exchange in RTILs, which is different compared to that in molecular diluents. Though higher temperature leads to faster kinetics in the experiment, the equilibrium time still remain over 24 h. However, the distribution ratios for Am(III) are significantly enhanced at higher temperature. From the computational practice, an encouraging conclusion is that the predominant conformer of C2-BTP is greatly changed in RTILs compared with those in gas phase and molecular diluents. It is this transformation that leads to the discrepancy of the extraction behaviors with C2-BTP in molecular diluents or RTILs, and the intermolecular interactions should be well tuned to design a delighting extracting system.

Effect of pKa on the extraction behavior of Am(III) in organo phosphorus acid and diglycolamide solvent system

Abstract A combination of neutral and acidic extractant has been proposed for the single-cycle separation of trivalent actinides from high-level liquid waste (HLLW). The nature of acidic extractant in the combined solvent formulation plays a profound role in deciding the extraction and stripping of trivalent actinides. Therefore, the extraction behavior of Am(III) in a solution of tetra-bis(2-ethylhexyl)-diglycolamide (TEHDGA) and acidic extractant (HA) was studied from nitric acid medium. The acidic extractants chosen were bis(2-ethylhexyl)phosphoric acid (HDEHP), bis(2-ethylhexyl)phosphonic acid (PC88A) and bis(2,4,4-trimethylpentyl)phosphinic acid (CYANEX-272) whose pKa values were 3.24, 4.51 and 6.37, respectively. The distribution ratio of Am(III) was measured as a function of various parameters such as concentration of nitric acid, TEHDGA, HA etc. The data were compared with those obtained in individual solvent systems namely 0.1 M TEHDGA/n-DD and HA/n-DD. Slope analysis of the extraction data indicated the synergic participation of both TEHDGA and HDEHP in the extraction of Am(III) at all acidities. However, antagonistic effect was observed at lower acidity when TEHDGA was mixed to PC88A or CYANEX-272 present in n-DD. Accordingly, a suitable mechanism has been proposed for the extraction of Am(III) at all acidities using these combined solvent formulation. Studies with fast reactor simulated high level liquid waste indicated that extraction of Am(III) was accompanied by co-extraction of lanthanides and unwanted metal ions such as Zr(IV), Mo(VI), Y(III) and Pd(II). However, addition of trans-1,2-diaminocyclohexane-N,N,N,N′-tetraaceticacid (CyDTA) reduced the extraction of unwanted metal ions. Batch extraction and stripping studies indicated the possibility of using 0.1 M TEHDGA+0.25 M HDEHP in n-dodecane for the single cycle separation of Am(III) from FR-SHLLW.

Extraction behavior of Am(III) and Eu(III) by tri-n-octylmethylammonium diglycolamate ionic liquid impregnated XAD-7

ABSTRACTAliquat-336-based strongly hydrophobic ionic liquid, tri-n-octylmethylammonium diglycolamate ([A336]+[DGA]−), was prepared and impregnated in Amberlite XAD-7 (abbreviated as [A336]+[DGA]−/XAD-7) for studying the extraction behavior of Am(III) and Eu(III) from nitric acid medium. The distribution ratio of Am(III) and Eu(III) in [A336]+[DGA]−/XAD-7 decreased with an increase in the concentration of nitric acid and the mechanism of trivalent metal ion extraction in the resin phase was elucidated. The uptake of Am(III) and Eu(III) in [A336]+[DGA]−/XAD-7 followed a second order and from the Langmuir adsorption model the apparent europium extraction capacity was determined. The conditions needed for efficient separation of Am(III) from Eu(III) was optimized.

Direct Selective Extraction of Trivalent Americium from PUREX Raffinate Using a Combination of CyMe4BTPhen and TEDGA—A Feasibility Study

ABSTRACTThe direct and selective extraction of Am(III) from simulated PUREX raffinate is demonstrated using a novel combination of the lipophilic extractant CyMe4BTPhen (2,9-bis(5,5,8,8-tetramethyl-5,6,7,8-tetrahydrobenzo[e]-[1,2,4]triazin-3-yl)-1,10-phenanthroline) and the hydrophilic complexant TEDGA (N,N,N’,N’-tetraethyl-diglycolamide) to enhance selectivity toward Am(III) extraction. Separation factors (SF) of up to SFAm/Cm = 4.9 were observed in tracer experiments using this combination of CyMe4BTPhen and TEDGA. Distribution ratios of stable isotopes of fission and activation products contained in a simulated PUREX raffinate solution are reported for the first time with CyMe4BTPhen, and some co-extracted metal ions are identified. The metal ions partly co-extracted from the simulated PUREX raffinate solution were Cu, Pd, Cd, Ag, Ni, and to a lesser extent Sn and Mo. The co-extraction of Pd and Ag was successfully suppressed using Bimet ((2S,2’S)-4,4’-(ethane-1,2-diylbis(sulfanediyl))bis(2-aminobutanoic acid)). The extraction was also studied as a function of the TEDGA concentration. The distribution ratios of Am and Cm can be adjusted by variation of the TEDGA concentration to yield DAm values >1 and DCm values <1. Separation factors for Am(III) over Cm(III) of up to SFAm/Cm = 2.4 were observed in these experiments. For Ln(III) + Y(III), distribution ratios below 1 were observed, thus enabling a direct extraction of Am(III) from simulated PUREX raffinate with a sufficient selectivity against trivalent lanthanides and Cm(III).

Synergic extraction of Am(III) and Eu(III) in N,N-dioctyl-2-hydroxyacetamide-bis(2-ethylhexyl)phosphoric acid solvent system

The present paper reports the extraction behavior of Am(III) and Eu(III) from nitric acid medium in a binary extractant system composed of a neutral extractant, namely N,N-dioctyl-2-hydroxyacetamide (DOHyA) and an acidic extractant, namely bis(2-ethylhexyl)phosphoric acid (HDEHP) present in n-dodecane (n-DD) diluent. The effect of nitric acid, extractant, and nitrate ion concentration on the distribution ratio of Am(III) and Eu(III) was studied in 0.2M DOHyA+0.25M HDEHP/n-DD and the results were compared with those obtained in the individual solvent system namely 0.2M DOHyA/n-DD and 0.25M HDEHP/n-DD. Synergic extraction of Am(III) and Eu(III) was observed in a binary solution and it was confirmed by slope analysis of extraction data and FT-IR spectroscopy. The present study also explored the feasibility of separating trivalent actinides from chemically similar lanthanides present in simulated high-level liquid waste (SHLLW) using the combined solvent system. A separation factor of Eu(III) over Am(III) of about 10 was achieved.

Radiolytic stability of N,N-di-alkyl-2-hydroxyacetamides

The radiation stability of N,N-di-alkyl-2-hydroxyacetamide derivatives having alkyl side chain varying from hexyl to decyl was studied as a function of absorbed dose of gamma irradiation up to 700 kGy. The samples were irradiated as neat, and as 0.2 M solutions in n-dodecane in the presence and absence of 4 M nitric acid. The radiolytic degradation of the compounds were assessed by the measurement of distribution ratio of Am(III) (DAm(III)) and also by the measurement of hydrodynamic properties such as density, viscosity and phase disengagement time.

Extraction behavior of Am(III) and Eu(III) in 1,3-diketonate based ionic liquid

Solvent extraction of americium(III) and europium(III) from nitric acid medium is carried by the solution of a functionalized ionic liquid (FIL), 1-butyl-3-methylimidazolium hexafluoro 1,3-diketonate ([C4mim][hfac]) present in 1–butyl–3–methylimidazolium bis(trifluoromethane-sulfonyl)imide, ([C4mim][NTf2]) diluent. The distribution ratio of Am(III) and Eu(III) was measured as a function of pH, concentration of FIL, nature of diluent and temperature. The D values increases with increase in pH. The slope analysis method revealed involvement of three FILs in the complexation. Complete removal of metal ion from extracted phase using the nitric acid. A separation factor of 25 was achieved for Am(III) over Eu(III) using polycarboxylic acid (DTPA) solution.

N,N-dialkyl-2-hydroxyacetamides for modifier-free separation of trivalent actinides from nitric acid medium

Abstract The alkyl derivatives of N,N,-dialkyl-2-hydroxyacetamide (DAHyA), namely, N,N,-dihexyl-2-hydroxyacetamide (DHHyA), N,N,-dioctyl-2-hydroxyacetamide (DOHyA), N,N,-didecyl-2-hydroxyacetamide (DDHyA), were synthesized and characterized by FT-IR, and NMR spectroscopy. The extraction behaviour of Am(III) in a solution of DAHyA in n-dodecane was studied as a function of various parameters to evaluate the feasibility of using DAHyA for partitioning of trivalent actinides from high-level liquid waste (HLLW). The distribution ratio of Am(III) (D Am(III)) in 0.1 M DAHyA/n-DD increased from 10−4 to &gt; 200 with increase in nitric acid concentration from 1 M to 6 M. A D Am(III) value 10–70 was obtained in a nitric acid concentration range from 3–4 M. The extraction of Am(III) in 0.1 M DAHyA/n-dodecane decreased in the order DHHyA &gt; DOHyA &gt; DDHyA. The third-phase formation behaviour of nitric acid and neodymium (III) in 0.2 M DAHyA/n-dodecane was studied. Near stoichiometric amount of neodymium (III) can be loaded in octyl and decyl derivatives without any third-phase formation from 3–4 M nitric acid medium. Unlike other extractants, the loaded trivalent metal ion in DAHyA can be recovered even with 1 M nitric acid. Therefore, the study revealed that N,N,-dialkyl-2-hydroxyacetamides are promising candidates for partitioning the trivalent actinides from HLLW.

Insights Into the Extraction of Am(III) by Aliquat-336 Based Ionic Liquids

The extraction behavior of Am(III) in a solution of tetra-(2-ethylhexyl)diglycolamide (TEHDGA) in n−dodecane (n−DD) or toluene was studied as a function of nitric acid concentration. The distribution ratio of Am(III) in 0.1 M TEHDGA/molecular diluent increased with increase in the concentration of nitric acid. Since the Aliquat-336 based ionic liquid namely, tri-n-octylmethylammonium di-(2-ethylhexyl)phosphate ([A336]+[DEHP]−) was miscible in molecular diluents such as n-DD and toluene, the extraction behavior of Am(III) in TEHDGA/molecular diluent was investigated in the presence of small concentrations of ionic liquid to understand the role of ionic liquid in extraction. The distribution ratio of Am(III) in 0.2 M [A336]+[DEHP]−/molecular diluent was negligible. Significant increase in distribution ratio of Am(III) was observed when [A336]+[DEHP]− was added to 0.1 M TEHDGA/molecular diluent. Since [A336]+[DEHP]− was converted into its components, namely tri-n-octylmethylammonium nitrate ([A336]+[NO3]−) and di-(2-ethylhexyl)phosphoric acid (HDEHP) when contacted with nitric acid, the extraction behavior of Am(III) in 0.1 M TEHDGA/molecular diluents was also studied in the presence of [A336]+[NO3]− and HDEHP to elucidate the mechanism of extraction. The study confirmed that the extraction of Am(III) in ionic liquid medium was controlled by constituents of ionic liquid and the distribution ratio of Am(III) obtained in organic phase was due to the resultant of contributions of ionic liquid constituents.

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.

Extraction Behavior of Am(III) and Eu(III) from Nitric Acid Medium in Tetraoctyldiglycolamide-Bis(2-Ethylhexyl)Phosphoric Acid Solution

The extraction behavior of Am(III) and Eu(III) in a solution of tetra-octyldiglycolamide (TODGA), bis(2-ethylhexyl)phosphoric acid (HDEHP), and n-dodecane (n-DD) was studied to understand the role of TODGA and HDEHP in the combined solvent system. The extraction behavior of these metal ions was compared with those observed in TODGA/n-DD and HDEHP/n-DD. The effect of various parameters such as concentrations of HNO3, TODGA, and HDEHP on the distribution ratio of Am(III) and Eu(III) was studied. Synergistic extraction of both the metal ions observed at lower acidities (<2.0 M) was attributed to the involvement of TODGA and HDEHP for extraction. However, the extraction of Am(III) and Eu(III) in the combined solvent was comparable with that observed in TODGA at higher acidities. The slope analysis of the extraction data confirmed the involvement of both the extractants at all acidities investigated in the present study.

The Actinide-Lanthanide Separation Concept

The Actinide-Lanthanide SEParation (ALSEP) concept is described. This concept is based on using an extractant phase consisting of either N,N,N’,N’-tetraoctyldiglycolamide (TODGA) or N,N,N’,N’-tetra(2-ethylhexyl)diglycolamide (T2EHDGA) combined with 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (HEH[EHP]) to separate Am and Cm from lanthanide and other fission and activation products in a single solvent extraction cycle. The neutral TODGA or T2EHDGA serves to co-extract the trivalent actinide and lanthanide ions from nitric acid media. The distribution ratios for Am and the lanthanides increase with increasing nitric acid concentration. TODGA extracts these elements more strongly than T2EHDGA from nitric acid, but the weaker extracting ability of T2EHDGA could allow separation of Am from the light lanthanides during the extraction step. Switching the aqueous phase chemistry to a citrate-buffered diethylenetriaminepentaacetic acid (DTPA) solution at pH 2.5 to 4 results in selective transfer of the actinides to the aqueous phase, thus resulting in separation of these two groups of elements. Separation factors on the order of 20 to 40 can easily be achieved in the ALSEP systems.

Extraction of trivalent americium and europium from nitric acid solution with a calixarene-based diglycolamide

A ligand derived from calix[4]arene functionalized at the lower rim with four diglycolamide (DGA) binding units containing n-butyl groups, which is denoted as calix[4]arene-BDGA, was synthesized and characterized by MS, 1H NMR and 13C NMR. The extraction behaviors of Am(III) and Eu(III) from nitric acid solution were investigated with calix[4]arene-BDGA in 95% kerosene/5% n-octanol (v/v). Effects of acidity, concentration of extractant and temperature on the distribution ratio of Am(III) and Eu(III) were evaluated. The results indicated the distribution ratio values of Am(III) and Eu(III) increase with the increase of nitric acid concentration in the examination of acidity range from 0.5 to 5.0mol/L. The ligand has a higher selectivity for Eu(III) than for Am(III) with the separation factor SFEu(III)/Am(III) values of 4.5–7.3. Slope analysis from nitric acid medium indicated that Am(III) and Eu(III) were extracted as di-solvated species by calix[4]arene-BDGA. The extraction mechanism was described and the thermodynamic parameters (ΔH, ΔS and ΔG) were also presented.