Extraction Of Actinides Research Articles

Insights into the Third Phase Formation Behaviour of N,N‐Didodecyl‐N’,N’‐Dioctyl Diglycolamide in n‐Dodecane Investigated by Dynamic Light Scattering and FTIR Spectroscopy

AbstractN,N‐didodecyl‐N’,N’‐dioctyl diglycolamide (D3DODGA) was regarded as a promising ligand for the extraction of trivalent lanthanides and actinides from nuclear waste, owing to the absence of undesirable third phase formation during liquid‐liquid extraction. However, the reason for the absence of third phase formation in D3DODGA as compared to other diglycolamides was not known. To unravel the absence of third phase formation, the extraction behaviour of nitric acid and Nd(III) in 0.2 M D3DODGA in n‐dodecane (n‐DD) was studied and the reverse micellar aggregation behaviour of the organic phase was probed by dynamic light scattering (DLS) and FTIR spectroscopy. The results were compared with those obtained in popular ligands abbreviated as TODGA, TEHDGA and TDdDGA in n‐dodecane under similar conditions. The limiting reverse micellar aggregate size for third phase formation was determined to be 11.6 nm at the limiting nitric acid concentration of 0.54 M in organic phase. The investigations revealed that the absence of third phase in D3DODGA and TDdDGA was due to the presence of long chain dodecyl group attached to the molecule, as compared to the octyl moiety present in TODGA and TEHDGA. As a result, it was possible to load higher concentration of nitric acid or Nd(III) in D3DODGA without the problem of third phase formation. In view of this, the D3DODGA in n‐DD can be employed efficiently for the separation of trivalent actinides and lanthanides from nuclear waste.

Solvent Optimization Studies for a New EURO-GANEX Process with 2,2’-Oxybis(N,N-di-n-decylpropanamide) (mTDDGA) and Its Radiolysis Products

ABSTRACT The diglycolamide 2,2’-oxybis(N,N-di-n-decylpropanamide) (mTDDGA) is being studied as an extractant for actinides and lanthanides in the European Grouped Actinide Extraction (EURO-GANEX) process. The aim is the development of a more simplified process using a single extractant instead of a mixture of extractants used in the current EURO-GANEX process. This work presents solvent optimization studies of mTDDGA, with regards to the extraction characteristics of the different diastereomers of mTDGA and of mixed diastereomer solutions. Also radiolysis behavior has been studied by irradiation of solvent extraction systems in a gamma irradiation facility using 60Co. The availability of irradiated organic solutions made it possible to gain valuable insights into the plutonium loading capacity after gamma-irradiation of the solvent up to 445 kGy and to quantify degradation compounds. Solvent extraction characteristic of the major degradation compounds themselves were determined. Like other methylated diglycolamides, we found a remarkable difference in extraction of up to two orders of magnitude between the two diastereomers. High plutonium loading (36 g L−1) is feasible using this single extractant, even after absorbing a dose of 445 kGy. This remarkable observation is possibly promoted by the presence of the main degradation compound which extracts plutonium verywell.

A comparison on the use of DEHBA or TBP as extracting agent for tetra- and hexavalent actinides in the CHALMEX Process

The Chalmers Grouped ActiNide EXtraction process is a solvent extraction process for the homogeneous recycling of spent nuclear fuel. The use of TBP for the extraction of tetra- and hexavalent actinides can be problematic for several reasons, including troublesome degradation products causing crud formation, decreased extraction yield and the possibility of explosive red oil reactions. Here, the substitution of TBP by a N,N-dialkyl monoamide, DEHBA, is investigated. The findings suggest that DEHBA can be a suitable extracting agent for use in the CHALMEX solvent, although identified drawbacks need to be further investigated.

Extraction of Actinides and Lanthanides from Nitric Acid Solutions with Polyphosphinylbenzenes

Extraction of Actinides and Lanthanides from Nitric Acid Solutions with Polyphosphinylbenzenes

Supercritical Fluid Extraction of Uranium, Plutonium and Thorium

In recent decades, extraction of actinides (U,Pu,Th) employing supercritical CO2has drawn attention owing to its inherent potential to minimize liquid waste generation. Supercritical Fluid Extraction (SFE) offers faster extraction with fine control over extraction process by means of varying pressure , temperature conditions. Supercritical Fluids have hybridproperties of liquid and gas. Liquid like solvation and gas like diffusivity enable topenetrate deep inside solid matrix, extracting component of interest, thus capable of extraction from liquid as well as solid matrix. Metal ion is complexed withsuitable organic compound, which gets soluble in SC CO2 . SC CO2 acts as a solvent and after extractionescapes as gas leaving behind extractant. Various types of ligands such organophosphorus compounds, -diketones, macrocyclic compounds, amides, dithiocarbamates are employed.SFE offers attractive alternative to reprocessing of spent nuclear fuel and radioactive waste.In this paper, research work carried out on the SFE of actinides (U,Pu,Th) has been reviewed.

Supercritical Fluid Extraction of Uranium, Plutonium and Thorium: A Review

In recent decades, extraction of actinides (U,Pu,Th) employing supercritical CO2has drawn attention owing to its inherent potential to minimize liquid waste generation. Supercritical Fluid Extraction (SFE) offers faster extraction with fine control over extraction process by means of varying pressure , temperature conditions. Supercritical Fluids have hybridproperties of liquid and gas. Liquid like solvation and gas like diffusivity enable topenetrate deep inside solid matrix, extracting component of interest, thus capable of extraction from liquid as well as solid matrix. Metal ion is complexed withsuitable organic compound, which gets soluble in SC CO2 . SC CO2 acts as a solvent and after extractionescapes as gas leaving behind extractant. Various types of ligands such organophosphorus compounds, -diketones, macrocyclic compounds, amides, dithiocarbamates are employed.SFE offers attractive alternative to reprocessing of spent nuclear fuel and radioactive waste.In this paper, research work carried out on the SFE of actinides (U,Pu,Th) has been reviewed.

Force Field Parameterization of Actinyl Molecular Cations Using the 12-6-4 Model.

In this work, a set of 12-6-4 force fields (FFs) parameters were developed for the actinyl molecular cations, AnO2n+ (n = 1, 2), from uranium to plutonium for classical molecular dynamics (MD) for four water models: TIP3P, SPC/E, OPC3, and TIP4Pew. Such a non-bonded potential model taking into account the induced dipole between the metallic center and the surrounding molecules has shown better performances for various cations than the classic 12-6 non-bonded potentials. The parametrization method proposed elsewhere for metallic cations has been extended to these molecular cations. In contrast to the actinyl 12-6 FFs from the literature, the new models reproduce correctly both solvation and thermodynamic properties, thanks to the inclusion of the induced dipole term (C4). The transferability of such force fields was assessed by performing MD simulations of carbonato actinyl species, which are highly implicated in actinide migration or actinide extraction from seawater. A highly satisfying agreement was found when comparing the EXAFS signals computed from our MD simulation to the experimental ones. The set of FFs developed here opens new possibilities for the study of actinide chemistry.

Advanced solid-phase extraction of tetravalent actinides using a novel hierarchically porous functionalized silica monolith

Separation of actinides is of great concern from the perspective of nuclear energy development and environmental issues, and the development of a highly efficient solid-phase extraction (SPE) process holds significant promise for actinide separation. However, the slow mass transfer kinetics in the currently available SPE separation media limited the throughput and efficiency, rendering the separation process more challenging. Hierarchically porous structures with well-organized and highly interconnected pore systems have been shown to provide efficient mass transfer and enhanced performance in nature. Herein, this paper reports the synthesis of a crack-free diglycolamic acid-functionalized silica monolith with hierarchical macro and meso porous structure for SPE. The hierarchically porous structures were retained upon mild modifications, which favored the convective mass transport and provided more binding sites, resulting in fast kinetics and high throughput. The separation ability was evaluated based on the separation and recovery of Th(IV) from a complex matrix. A superior Th(IV) separation performance (Kd > 2.6 × 104 mL/g) was achieved in the presence of alkaline earth metals, rare earth elements, and uranium within 1 min by batch sorption, and the maximum separation coefficients of Th(IV)/Ln(III) and Th(IV)/U(VI) exceed 1000 and 140, respectively. Particularly, the synthesized material allowed the separation of Th from monazite leachates with highly efficient recovery (> 96%) at a high flow rate (5 mL/min) by column study. Investigation of the binding mechanism revealed the formation of a stable coordination complex (Th(NO3)L3) via Th−O bonds. The material was also employed for the extraction of Pu(IV), and satisfactory sorption was achieved. Thus, this new functionalized material has potential application prospects for an improved actinide separation process.

Theoretical Insights into the Selective Separation of Am(III)/Eu(III) Using Hydrophilic Triazolyl-Based Ligands

Designing ligands with efficient actinide (An(III))/lanthanide (Ln(III)) separation performance is still one of the key issues for the disposal of accumulated radioactive waste and the recovery of minor actinides. Recently, the hydrophilic ligands as promising extractants in the innovative Selective ActiNide Extraction (i-SANEX) process show excellent selectivity for Am(III) over Eu(III), such as hydroxylated-based ligands. In this work, we investigated the selective back-extraction toward Am(III) over Eu(III) with three hydrophilic hydroxylated triazolyl-based ligands (the skeleton of pyridine La, bipyridine Lb, and phenanthroline Lc) using scalar-relativistic density functional theory. The properties of three hydrophilic hydroxylated ligands and the coordination structures, bonding nature, and thermodynamic properties of the Am(III) and Eu(III) complexes with three ligands have been evaluated using multiple theoretical methods. The results of molecular orbitals (MOs), quantum theory of atoms in molecules (QTAIMs), and natural bond orbital (NBO) reveal that Am-N bonds possess more covalent character compared to Eu-N bonds. The thermodynamic results indicate that the complexing ability of Lb and Lc with metal ions is almost the same, which is stronger than that of La. However, La has the best Am(III)/Eu(III) selectivity among three ligands, which is attributed to the largest difference in covalency between Am-Ntrzl and Eu-Ntrzl bonds in MLa(NO3)3. This work provides an in-depth understanding of the preferential selectivity of the hydrophilic hydroxylated ligands with An(III) over Ln(III) and also provides theoretical support for designing potential hydrophilic ligands with excellent separation performance of Am(III)/Eu(III).

Theoretically exploring the bonding properties of trivalent transuranic elements with 2‐(2‐amino‐2‐oxyethoxy) acetic acid

AbstractIn recent years, the extraction of actinides from high‐level liquid waste is a key step in nuclear waste disposal. However, it is difficult to separate and extract adjacent trivalent actinides An (III) due to similar electron configuration in outer layers. Therefore, studying the law of the bonding between ligands and actinides is essential for designing robust ligands. Here, we demonstrate the in‐group transuranic actinides separation ability of 2‐(2‐amino‐2‐oxoethoxy) acetic acid (HL) through quasi‐relativistic density functional theory (DFT). In the acidic environment of HCl, the extraction of An (III) is governed by cation‐exchange mechanism, forming the complexes [ML2 (H2O)2]+(M = Np, Pu, Am, Cm, Bk) with the deprotonated L− anion during the extraction process. Through calculating the molecular structure and thermodynamic properties of the complexes [ML2 (H2O)2]+, it shows that there exists weak covalent interaction between trivalent transuranic metal ions and ligands L−. Both electrostatic potential and molecular orbital analyses of the ligand L− indicate that the n‐dodecane is an excellent organic solvent for extraction of actinide ions than cyclohexanone. Bonding nature analysis validates that the interaction between An (III) and ligand L− gradually weakens from Np to Cm, and then strengthens from Cm to Bk. The peculiar extraction property of Cm3+ may be connected with its unique electronic structure. Our study may provide reference for understanding the bonding between actinides and ligands, and explore the extraction properties of ligands in different organic solvents, aiming at designing more efficient ligands for the separation of actinides.

Studies on the separation treatment of high-level liquid waste by bisamide podand(I): Extraction and separation of An(III) from Ln(III)

A process for actinide(III) and lanthanum(III) extraction separation from high-level liquid waste (HLLW) was proposed, with N,N,N',N' -tetraoctyl diglycolamide (TODGA) as the extractant, tri- n ‑butyl phosphate (TBP) as the phase modifier and 2,6-bis[1-(propan-1-ol)-1,2,3-triazol-4-yl]pyridine (PyTri-Diol or PTD) as hydrophilic stripping agent. This ‘hot test’ was successfully carried out, achieving 99.92% removal of americium-241 ( 241 Am) with a separation factor SF (Eu/Am) of 3.8 × 10 3 in the actinide(III) product solution. The results show that bisamide podand extractants can effectively realize the extraction and separation of actinide(III) and lanthanum(III) from Chinese commercial HLLW and thus have a bright practical application potential for the treatment of commercial HLLW. A process for extraction and separation of An(III) and Ln(III) from HLLW in a hot test was proposed in which N,N,N',N' -tetraoctyl diglycolamide and tri- n ‑butyl phosphate (TODGA + TBP) was used as the extractant and 2,6-bis[1-( propan -1- ol )-1,2,3- triazol -4- yl ]pyridine (PyTri-Diol or PTD) was used as the aqueous stripping agent.

Developing Accelerator Mass Spectrometry Capabilities for Anthropogenic Radionuclide Analysis to Extend the Set of Oceanographic Tracers

Recent major advances in Accelerator Mass Spectrometry (AMS) at the Vienna Environmental Research Accelerator (VERA) regarding detection efficiency and isobar suppression have opened possibilities for the analysis of additional long-lived radionuclides at ultra-low environmental concentrations. These radionuclides, including 233U, 135Cs, 99Tc, and 90Sr, will become important for oceanographic tracer application due to their generally conservative behavior in ocean water. In particular, the isotope ratios 233U/236U and 137Cs/135Cs have proven to be powerful fingerprints for emission source identification as they are not affected by elemental fractionation. Improved detection efficiencies allowed us to analyze all major long-lived actinides, i.e., 236U, 237Np, 239,240Pu, 241Am as well as the very rare 233U, in the same 10 L water samples of a depth profile from the northwest Pacific Ocean. For this purpose, a simplified and very flexible chemical purification procedure based on extraction chromatography (a single UTEVA® column) was implemented which can be extended by a DGA® column for Am purification. The procedure was validated with the reference materials IAEA-381/385. With the additional increase in ionization efficiency expected for the extraction of actinides as fluoride molecules from the AMS ion source, a further reduction of chemical processing may become possible. This method was successfully applied to an exemplary set of air filter samples. In order to determine the quantitative 237Np concentration reliably, a 236Np spike material is being developed in collaboration with the University of Tsukuba, Japan. Ion-Laser Interaction Mass Spectrometry (ILIAMS), a novel technique for the efficient suppression of stable isobaric background, has been developed at VERA and provides unprecedented detection sensitivity for the fission fragments 135Cs, 99Tc, and 90Sr. The corresponding setup is fully operational now and the isobar suppression factors of >105 achieved, in principle, allow for the detection of the mentioned radionuclides in the environment. Especially for 90Sr analysis, this new approach has already been validated for selected reference materials (e.g., IAEA-A-12) and is ready for application in oceanographic studies. We estimate that a sample volume of only (1–3) L ocean water is sufficient for 90Sr as well as for 135Cs analysis, respectively.

Characterization of the ALSEP Process: Investigating Equilibrium and Intermediate Complexes of the Scrub Stage

ABSTRACT A unique combination of real-time and conventional optical spectroscopy, off-line chemical analyses, and equilibrium solvent extraction measurements were employed to monitor progressive changes in the speciation of the organic-phase complexes of neodymium or americium in the biphasic scrub stage of the Actinide-Lanthanide Separation (ALSEP) solvent extraction process proposed for trivalent actinide/lanthanide separations. Consistent with the findings of other researchers, four unique organic-phase species are identified by three separate methods of multivariate analysis. The organic phase initially contains M(TEHDGA)2(HEH[EHP])2(NO3)3 complexes. As the ALSEP organic phase is scrubbed with an aqueous malonate buffer, the complex loses HNO3 to form M(TEHDGA)2(H(EH[EHP])2)(NO3)2 as the first organic-phase intermediate species. Further contact with the scrub aqueous phase forms a second intermediate species, M(TEHDGA)(H(EH[EHP])2)2(NO3), and eventually a complex containing only HEH[EHP], M{H(EH[EHP])2}3 (where TEHDGA = N,N,N’,N’-tetra(2-ethylhexyl)diglycolamide and HEH[EHP] = 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester). Similar intermediate species were also observed in equilibrium ALSEP organic phases when lower aqueous concentrations of nitric acid (e.g., 0.5 M HNO3) were used to extract actinides or lanthanides.

Extraction of Ln(III) and An(III) by N,N-di(2-ethylhexyl)- thio-diglycolamic Acid

ABSTRACT The extraction of Nd(III), Eu(III), Am(III), and Cm(III), trivalent lanthanides and actinides in high level nuclear waste, by the extractant N,N-di(2-ethylhexyl)-thio-diglycolamic acid (HDEHSDGA, HA) is investigated via thermochemical and spectroscopic methods. In this study, HDEHSDGA behaves as a conventional mono-basic cation-exchanging ligand extracting Ln(III) and An(III) from nitrate solutions of pH region. The information obtained from the extraction experiments and the spectroscopic analyses indicate that the primary extracted complex species may be MA3 · 2H2O for these four cations and likely for the other trivalent f-elements. In the extracted complexes, the anionic monomer extractant A− coordinates to the metal ions presumably forming bidentate coordination via the carbonyl oxygen atom and one of the oxygen atoms of the carboxylate; it appears that the thio-ether does not directly participate in the complexation reaction. The results ultimately demonstrate that HDEHSDGA does not exhibit significant selectivity for An(III) over Ln(III), in contrast to results reported in a previous study conducted with unpurified extractant.

Theoretical Study Progress on Application of Ionic Liquids in Extraction and Separation of Lanthanides and Actinides

Theoretical Study Progress on Application of Ionic Liquids in Extraction and Separation of Lanthanides and Actinides

Progress on Extraction and Separation of Lanthanides and Actinides With Task-Specific Ionic Liquids

Progress on Extraction and Separation of Lanthanides and Actinides With Task-Specific Ionic Liquids

Pyridine diglycolamide: A novel ligand for plutonium extraction from nitric acid medium

A novel ligand N, N, N’, N’ tetra-isobutyl pyridine diglycolamide (PDGA) was synthesized and tested for extraction of actinides and fission products present in high level liquid waste (HLLW). The ligand was studied in presence of two different diluents- nitrobenzene (NB), a molecular diluent and 3-methyl-1-octyl immidazolium bis[(trifluoromethyl)sulfonyl] imide, an Ionic Liquid (IL). Unusual selectivity towards tetravalent plutonium over minor actinides and alkali & alkaline metal ions present in nuclear waste was showed by PDGA in presence of NB as diluent. The trend in kinetics of extraction as well as dependency of DPu(IV) values with nitric acid concentration was found to be different for two diluents studied. Mechanism of extraction was also varied for the two diluents studied. It followed solvation mechanism for NB whereas for IL it was a combination of solvation and ion-exchange mechanism. The calculated Gibbs free energy of extraction, ΔGext for Pu(IV) using density functional theory was found to be higher than that of other competitive metal ions corroborating the results from solvent extraction experiment. Further, ΔGext was found to be highly negative for metal and ionic liquid cations thus complimenting the experimental findings of ion exchange mechanism for a metal cation with cation of the ionic liquid.

Solid-phase extraction of 225Ac using ion-imprinted resin and 243Am as a radioactive tracer for internal dosimetry and incorporation measurements

Actinium-225 is a highly radiotoxic alpha-emitting radionuclide, which is currently in the spotlight owing to its promising radiotherapeutic applications in nuclear medicine. Personnel involved in the production and handling of actinium-225 is exposed to a risk of accidental incorporation of this radionuclide. Radiological protection regulations require regular monitoring of incorporation and internal dosimetry assessment for workers manipulating open radioactive sources. Urine is often used as a biological sample for measuring the incorporation of actinides, however it requires a radiochemical separation with a certified metrological tracer to enable quantitative determination. There is no stable, nor sufficiently long-lived radioactive isotopes of actinium to provide a metrological yield tracer. In this article, we propose an application of an ion-imprinted polymer resin to extract actinium-225 from urine employing americium-243 as a radioactive tracer. The radiochemical separation was followed by a quantitative determination with alpha-spectrometry. Solid-phase extraction of both actinides from urine using ion-imprinted polymer resin resulted in good radiochemical yields: 57.7 ± 16.5% (n = 17) for actinium-225 and 62.8 ± 18.0% (n = 17) for americium-243. Equivalent recoveries showed that americium-243 is a suitable yield tracer for the determination of actinium-225 with an ion-imprinted polymer resin. Combined with a different measurement technique, this method can be applied for the separation of other isotopes of actinium, such as actinium-227.

New route to amide-functionalized N-donor ligands enables improved selective solvent extraction of trivalent actinides.

A new general synthetic route to selective actinide extracting ligands for spent nuclear fuel reprocessing has been established. The amide-functionalized ligands separate Am(III) and Cm(III) from the lanthanides with high selectivities and show rapid rates of metal extraction. The ligands retain the advantages of the analogous unfunctionalized ligands derived from camphorquinone, whilst also negating their main drawback; precipitate formation when in contact with nitric acid. These studies could enable the design of improved solvent extraction processes for closing the nuclear fuel cycle.

Solubility studies on 2-hydroxyisobutyric acid in supercritical carbon dioxide: Solubility evaluation and application to actinide extraction

• First report on solubility of 2-hydroxyisobutyric acid in SCCO 2. • Solubility correlated with semi-empirical/empirical and equation of state models. • Development of supercritical method for recovery of actinide ions. • Demonstration of recovery of U and Th from aqueous/solid/cellulose matrix. The solubility of 2-hydroxyisobutyric acid in supercritical carbon dioxide is experimentally determined using a flow saturation technique. The experimental solubility data was generated at 308, 313, 318 and 323 K with pressures ranging from 10 to 20 MPa. The solubility data was found to range from 0.4 × 10 −3 mol·mol −1 to 5.7 × 10 −3 mol·mol −1 . The solubility data was correlated with two semi-empirical equations, Mendez-Santiago and Chrastil equation. The self-consistency of the data is verified with Mendez-Santiago model. Peng-Robinson equation of state combined with van der Walls mixing rules was also employed to correlate the solubility data. All three models have successfully correlated the solubility data with an average deviation of < 7%. Based on the solubility data, supercritical fluid extraction based method was developed for the recovery of uranium and thorium from solid/liquid matrices (cellulose matrix, uranyl and thorium nitrates, aqueous medium) using 2-hydroxyisobutyric acid as a ligand.