Separation Of Uranium Research Articles

Multiphysics Simulation of an Electrorefiner with Continuous Circulation of Molten Salt for Separation of Uranium and Neptunium

A 3-D continuous electrorefiner is designed and investigated using multiphysics simulation for the separation of uranium and neptunium from spent nuclear fuel in molten salt. The concentration distribution field, the electric field, the ionic flux density field, and the flow field are evaluated under galvanostatic and pulse electrorefining by numerical integration of the governing equations using finite element method. During the electrorefining without molten salt recirculation, the transport of the electroactive cations is controlled by diffusion and electromigration and high concentration gradient is built near electrodes. In a galvanostatic electrorefining with a current density of 50 A·m–2, the concentration of U3+ decreases to 26.7 mol·m–3 near cathode and increases to 62.5 mol·m–3 near anode within 40 s, and no co-deposition of uranium and neptunium occurs. In a galvanostatic electrorefining with a current density of 200 A·m–2, the concentration of U3+ decreases to 1.3 mol·m–3 near cathode and increases to 62.6 mol·m–3 near anode within 6.7 s, and the co-deposition of uranium and neptunium occurs after 0.28 mg of pure uranium is collected. With moderate molten salt recirculation, the transport of the electroactive cations is controlled by convection. The local concentrations of uranium ions approach steady near the electrodes within 32 s in a galvanostatic electrorefining of 50 A·m–2, and no co-deposition of uranium and neptunium occurs. Though the concentration of U3+ decreases to 21.1 mol·m–3 near cathode and increases to 62.6 mol·m–3 near anode within 6.7 s with a current density of 200 A·m–2, there is no co-deposition of uranium and neptunium occurred. In addition, it is proved that the pulse electrorefining does not improve the recovery of uranium compared with galvanostatic electrorefining with a corresponding average current.

Selective Crystallization Separation of Uranium(VI) Complexes from Lanthanides.

The limited availability of uranium (U) resources poses significant challenges to the advancement of nuclear energy. Recycling uranium from spent fuel is critical, but the coexistence of lanthanides (Ln) complicates the extraction process significantly. Here, we present an N/O ligand, (E)-N'-(pyridin-2-ylmethylene) picolinohydrazide (PYPH), designed for the selective recovery of U(VI) over Ln(III/IV) in acidic environments. 3,6-Bis(2-pyridinyl)-1,2,4,5-tetrazine (BPTZ) and N,N-dimethylformamide (DMF), when subjected to heat, gradually generate PYPH and formic acid in aqueous solution; this process can be employed for uranium recovery. This approach, known as the in situ reactive extraction technique, enhances capture capacity, selectivity, and acid resistance while effectively mitigating interference from Ce(IV). At pH 3 and 0.1 M HNO3, separation factors for the binary Ln(III/IV) and U(VI) systems exceeded 103 and 102, respectively, achieving purities exceeding 99%. Monocrystalline structure analysis revealed two-dimensional planar coordination complexes, demonstrating their exceptional selectivity. This study underscores the potential of PYPH in uranium recovery from spent fuel and proposes new avenues for developing innovative separation strategies for lanthanides and actinides (An) using structural and theoretical modeling.

Demonstration of Uranium(VI)/Plutonium(IV) Separation via Solvent Extraction by D2EHiBA in Annular Centrifugal Contactors

ABSTRACT The use of N,N-dialkylamides as alternatives for tri-n-butyl phosphate (TBP) as extractants in the reprocessing of spent nuclear fuel has been investigated since the 1960s. N,N-di-2-ethylhexyl isobutyramide (D2EHiBA) and N,N-di-2-ethylhexyl n-butyramide (D2EHBA) can selectively extract hexavalent and tetravalent actinides from nitric acid spent nuclear fuel solutions. Annular centrifugal contactors (ACCS) have been designed specifically for counter-current multi-stage solvent extraction in the nuclear sector. Their main advantages are a high stage efficiency, the ability to work at short residence times (seconds), and a small liquid hold-up. In the present study, a new D2EHiBA-based separation of hexavalent uranium from tetravalent plutonium was investigated using ACCs, where for safety and practical reasons the use of hydrazine or other reductant/complexant is avoided altogether. The extraction behavior of technetium-99 m, ruthenium-103, and americium-241 was also monitored under those process conditions. It was demonstrated that uranium(VI) can be quantitatively extracted and purified from plutonium(IV) using the D2EHiBA extractant. A U(VI)/Pu(IV) decontamination factor of more than 6000 was obtained. The excellent performance of the modified lab-scale BXP012 annular centrifugal contactors was demonstrated, and these contactors have proven to be a valuable tool in the upscaling of solvent extraction processes at the Belgian Nuclear Research Center (SCK CEN).

Artificial Photosynthetic Assemblies Constructed by NH2-UiO-66 Decorated with Spatially Separated Dual Cocatalysts for Enhanced Photocatalytic Uranium Reduction.

The phenomenon of rapid migration of photogenerated charges in natural photosynthetic systems has motivated the design of efficient photocatalysts capable of fast charge separation and efficient reaction kinetics for photocatalytically assisted enrichment and separation of uranium U(VI) in uranium wastewater. In this study, we developed a biomimetic photocatalytic system MnOx/NH2-UiO-66-rGO (M/UiO-rGO) with spatially separated dual cocatalysts. Among them, rGO functions to capture electrons and participates in reduction reactions, while MnOx captures holes and participates in oxidation reactions. The M/UiO-rGO catalyst exhibits excellent performance in photocatalytic reduction of uranium (reaching 91.8% in 1 h), and even under natural light conditions, it exhibits excellent uranium removal ability (80.4%). Using multispectral coupling technology, we further confirmed that enriched uranium undergoes a continuous and complex reaction process of "capture-reduction-free radical oxidation-nucleation-crystallization". This work presents a viable strategy for designing biomimetic photocatalysts with efficient charge separation and rapid reaction kinetics for environmental purification purposes.

Synthesis of (222)-oriented defect-rich MOF-808 membranes towards high-efficiency uranium rejection

Energy-efficient separation of uranium from seawater elicits huge interest for sustainable development of nuclear energy industry. Aiming at high-efficiency uranium separation from seawater, in this study, we pioneered room-temperature preparation of (222)-oriented defect-rich MOF-808 membrane using Zr6-oxo cluster as metal source through oriented growth. Benefitting from higher missing-linker number in the framework and minimized diffusion path length in the membrane, accurate and facilitated ion-transporting channels with size larger than kinetic diameters of hydrated ions of common metal ions (Mn+, n = 1, 2, 3) except uranyl ions (UO22+) were established. Compared with other metal ions, our membrane exhibited rejection rate of almost 100 % for UO22+ ions with ideal K+/UO22+, Na+/UO22+, Ca2+/UO22+, Mg2+/UO22+ and Fe3+/UO22+ selectivity achieving 9210, 8330, 4990, 3040 and 140 on the basis of size-sieving; moreover, obtained membrane enabled rapid and efficient separation of trace amounts of uranium (∼3.0 ppb) from natural seawater with considerable selectivity towards K+/UO22+ (315.0), Na+/UO22+ (314.5), Ca2+/UO22+ (295.0), Mg2+/UO22+ (285.5) and Fe3+/UO22+ (7.1) ion pairs, respectively. Compared with results reported in literature, our membrane displayed the highest screening precision among state-of-the-art nanofiltration membranes, holding great promise for practical uranium separation from seawater.

Efficient uranium(VI) separation based on a layered 2D Ti3C2Tx/hydroxyapatite hybrid membrane

Efficient uranium(VI) separation based on a layered 2D Ti3C2Tx/hydroxyapatite hybrid membrane

Engineering N-donor heterocycles on dioxin-linked covalent organic frameworks to in situ improvement uranium separation and extraction selectivity in wastewater and seawater

Engineering N-donor heterocycles on dioxin-linked covalent organic frameworks to in situ improvement uranium separation and extraction selectivity in wastewater and seawater

Coordination-Induced Magnetism Strategy for Highly Selective and Efficient Uranium Separation.

Highly efficient separation of dispersed uranium is important for the sustainable development of nuclear industry, and adsorption is the most recognized approach. However, there are many coexisting interfering metal ions that compete with uranyl ion for the chelating ligands in the adsorbents and lead to low separation selectivity and efficiency. Herein, a coordination-induced magnetism strategy is presented for the separation of uranium based on the conversion of diamagnetic cyanoferrocene (Fc-CN) nanocrystals to uranium-containing magnetic recoverable ferromagnetic aggregates. Different from previous adsorption strategies, this strategy combines the mechanisms of photocatalytic uranium enrichment and chemical uranium adsorption. Under light irradiation, electron of Fe(II) in Fc-CN is excited and transfers to uranyl ion via the cyano group to form tight coordination bond between N atom in cyano group and uranium. This phenomenon is unique for uranyl ion, and thus, a high uranium removal rate of 97.98% is achieved in simulated nuclear wastewater with the presence of tremendous interfering ions, proving its highly selective and efficient uranium separation performance. The ability to form highly stable magnetic aggregates via photoinduced interaction between Fc-CN and uranium enriches the understanding on the chemical properties of Fc-CN and uranium.

Enhancing uranium ion adsorption in wastewater: The role of PEI-PVA/CS xerogel

In the process of recovering uranium resources from uranium-containing wastewater (UCW) via adsorption methods, it is imperative to address challenges related to the stability and selectivity of adsorbents in the separation of uranium ions. Xerogel porous adsorbents have garnered significant research interest for their potential application in uranium ion adsorption, owing to their high porosity, robust plasticity, and abundant functional groups. Based on the efficient separation of uranium by acid-resistant polyvinyl alcohol/chitosan (PVA/CS) xerogel, polyethyleneimine (PEI) was selected to adjust its pores. By examining the characteristics of the modified xerogel both prior to and following U(VI) adsorption, optimizing the conditions for its U(VI) adsorption, and analyzing the separation mechanism of U(VI), the results demonstrate that PEI can effectively modify the pore environment of PVA/CS xerogel. Furthermore, PEI-PVA/CS xerogel maintains consistent U(VI) separation efficacy in UCW across a pH range of 2–7. After five cycles of uranium desorption and adsorption, the adsorption recovery capacity exceeds 97.7 %, with minimal interference from cations. The synergistic effect of -NH2 and -OH functional groups is responsible for the efficient separation of U(VI) by PEI-PVA/CS xerogel. This xerogel demonstrates the stability and selectivity required for U(VI) adsorbents, indicating its potential for engineering applications in UCW treatment.

Precipitation–Flotation Process for Molybdenum and Uranium Separation from Wastewater

The mining of molybdenum and uranium ores inevitably results in the generation of large volumes of wastewater containing low concentrations of metals, which poses significant threats to the environment. This study presents a novel precipitation–flotation process for the simultaneous separation of molybdenum and uranium from wastewater. A systematic investigation was conducted on the impacts of the type of precipitant, flotation reagent type, and flotation parameters on the experimental results. Ferric salt served better as a precipitant than aluminum salt and humic acid did, and sodium dodecyl sulfate (SDS) was more suitable than sodium dodecyl benzene sulfonate for acting as a surfactant and foaming agent. Under specific conditions, including a pH of 6.6, an Fe3+ dosage of 0.6 mmol·L−1, an SDS dosage of 40 mg·L−1, an air flow rate of 25 mL·min−1, and a flotation time of 10 min, the removal efficiencies of molybdenum and uranium reached 96.6% and 93.6%, respectively. After flotation, the molybdenum concentration, uranium concentration, chemical oxygen demand, and turbidity of the treated water all meet the emission standards. Furthermore, the metal removal mechanisms, including the particle size distribution, functional group structure, surface element composition, microstructure, and element distribution, were elucidated on the basis of characterization of the precipitation–flotation products.

Skeleton design engineering of covalent organic frameworks to enable in situ incorporation of coordination sites for improved extraction of uranyl ions

The development of advanced porous materials for effectively separating uranium from nuclear wastewater or seawater is a highly coveted yet formidable task. However, the importance of the covalent organic frameworks (COFs) skeletons and the specific arrangement of adjacent atoms is often disregarded when configuring coordination settings for chelating molecules. In this study, a novel material for oxygen-enriched COFs was developed. The optimized oxygen-rich COFs showed aligned neighboring bonds and triazine groups along the skeletons, resulting in an increase in uranyl binding sites and a threefold rise in the total number of binding sites. The synergistic interaction of ether bonds and triazine groups in the π-conjugated skeletons significantly reduced the energy band gap, leading to improved uranium affinity and recovery. The adsorption capacity reached an impressive 660 mg/g, surpassing that of most COF-based adsorbents using a chemical coordination mechanism in uranium-containing aqueous solutions. This study provides valuable insights into designing novel adsorbents for uranium separation.

Kinetic Study and Process Optimization of Plutonium Barrier Units for Enhanced Plutonium Stripping in the PUREX Process

In the PUREX (the plutonium uranium reduction extraction) process, a plutonium barrier unit (1BXX) is used to achieve deep plutonium stripping. According to the operating experience of the French reprocessing plant, after the separation of uranium and plutonium in the first cycle (1B + 1BXX), the plutonium barrier unit has excellent stripping effect, such that the removal of plutonium from uranium can already be achieved in the first cycle, and the second cycle only needs to focus on the removal of neptunium from uranium in order to obtain a qualified uranium product. In recent decades, China has also been actively conducting research on the plutonium barrier unit process to reduce the plutonium concentration in the primary uranium product in the first cycle to avoid the need to remove neptunium and plutonium at the same time in the second cycle, and to improve the efficiency and feasibility of reprocessing. Due to the lack of design basis for plutonium barriers to achieve deep plutonium stripping at present, this study conducts a basic study on the plutonium barrier unit, aiming to provide data for the optimization of plutonium barriers in the actual reprocessing process at a later date. In this work, a kinetic study on the reduction and stripping of trace plutonium from dibutyl phosphate-containing organic phases was carried out first, and the kinetic equations for the reduction and stripping of Pu(IV) by U(IV) under flow process conditions were obtained. The effects of U(IV) addition on the extraction loss of U(IV) and the concentration distribution of U(IV) at various stages were investigated by process simulation. Additionally, the oxidation of U(IV) under process conditions was investigated to clarify the process chemistry of U(IV) oxidation and to provide a reference for the oxidation consumption of U(IV). Finally, the process parameters of the plutonium barrier unit were preliminarily designed based on the above research.

Molecular and Supramolecular Study of Uranium/Plutonium Liquid-Liquid Extraction with N,N-Dialkylamides.

In the context of the separation of uranium and plutonium from spent fuel allowed by N,N-dialkylamides, three regioisomers of N,N-di(2-ethylhexyl) butyramide (DEHBA or ββ) and the diastereopure isomers of N-(2-ethylhexyl)-N-(oct-3-yl)butyramide (EHOBA or αβ) were synthesized to assess their extraction performance and to study the mechanisms at the origin of the differences observed between the stereo- and regioisomers. The N,N-dialkylamides showed differences in extraction, with a greater effect of regio- than stereoisomerism. A mechanistic study at both the molecular and supramolecular scales was initially applied to explain these effects. X-ray absorption and UV-vis spectroscopy showed that uranium is extracted by a UO2(NO3)2L2 complex, which is not very sensitive to steric hindrance, while plutonium is extracted by two complexes, Pu(NO3)4L2 and Pu(NO3)6(HL)2, which are differently affected by stereo- and regioisomerism. Investigations at the supramolecular scale also showed that Pu(NO3)4L2 complexes are disadvantaged by the bulkiness of the extractants, while Pu(NO3)6(HL)2 is favored by the preformation of larger supramolecular aggregates.

Separation and recovery of uranium and beryllium from acidic sulphate solutions by solvent extraction using mixture of organophosphonic extractants

Separation and recovery of uranium and beryllium from acidic sulphate solutions by solvent extraction using mixture of organophosphonic extractants

Technology for reprocessing mother liquor and washing solution from crystalization purification of HTGR SNF

The extractants diphenyl-N,N-dioctylcarbamoylmethylphosphine oxide and diphenyl-N,N-diisobutylcarbamoylmethylphosphine oxide for the processing of spent fuel were tested. The conditions for extraction and separation of uranium and TPE–REE were determined. A technological scheme was proposed for processing spent nuclear fuel from high-temperature gas-cooled reactors. During dynamic testing, at least 99.9% of uranium and plutonium and at least 99.5% of americium and rare earth elements were extracted. The TPE + REE and U+Pu fractions were isolated. The U+Pu fraction contained approximately 5% Am, while the TPE + REE fraction had less than 0.1% U and Pu.

Redox-active sp2-c connected metal covalent organic frameworks for selective detection and reductive separation of uranium

It is economically desirable to develop a material that can simultaneously detect and recover uranium. Herein, a CC-bridged two-dimensional metal-covalent organic framework (Cu-BTAN-AO MCOF) was constructed by condensation of metal single crystals with a rigid structure (Cu3(PyCA)3) and cyano monomers (BTAN) via Knoevenagel reaction for simultaneous detection and adsorption of uranium. The amidoxime group within the pore and the presence of unsaturated Cu(I) in the framework facilitate the adsorption of uranyl ions onto the amidoxime group, leading to fluorescence quenching via the photoinduced electron transfer (PET) mechanism, achieving a detection limit of as low as 167 nM uranyl ions. Furthermore, Cu-BTAN-AO demonstrates exceptional efficiency in capturing uranium from wastewater characterized by rapid kinetics and superior selectivity. It is noteworthy that Cu-BTAN-AO is the first example of simultaneous detection, adsorption and chemical reduction of uranium using metal centers and functional groups in MCOF, indicating that Cu-BTAN-AO has great potential for the detection and recovery of uranium-containing wastewater. This design strategy may also be applicable to advancing sensing and energy materials for other important metal ions.

Synthesis of homogeneous styrenic pyridine resin (LSL-030-bd) and its application to the separation of uranium and molybdenum

Synthesis of homogeneous styrenic pyridine resin (LSL-030-bd) and its application to the separation of uranium and molybdenum

A Remarkable Strategy to Hijack U(VI) from Mixed Metal Ion Solutions Using 1-Hydroxy-2-pyridone.

The present work envisages a chelation driven, facile, selective, and rapid method for uranium(VI) separation from a (U, Th) mixture using 1-hydroxy-2-pyridone (1,2-HOPO). Herein, U(VI) was selectively precipitated as the neutral [UO2(HOPO)2(H2O)]·nH2O (orange colored) complex while Th(IV) and other metal ions remained in the solution. The pH of the medium played a key role in facilitating the separation process.

Selective Leaching and Separation of Uranium from Ochre-Umm Greifat, Red Sea Coast, Central Eastern Desert, Egypt

The Ochre-Umm Greifat area is one of the Red Sea areas with high concentrations of iron and zinc, which is formed from hydrothermal solutions as a result of the structural activity that occurred in the Red Sea Zone during the Pleistocene period. These deposits are also accompanied by deposits of low- to high uranium grade. In addition to Zn, Pb, and Cu anomalies, particularly in fault zones and their branches affecting the study area, although there are numerous zinc minerals in the Ocher-Greifat area, uranium minerals are scarce, with only one mineral, compreignacite, being recorded and the majority of the uranium being present as an adsorbed element on iron and/or clay stones. In addition, uranothorite is extremely rare and occurs as fine grains embedded in rocks. A technological sample was taken from an iron-rich clay area in a fault zone and was found to assay 700-ppm uranium. The leachability of uranium from the used sample was investigated using an alkaline solution based on the chemical and mineralogical composition of the used sample. The selected ore is treated with Na2CO3 and NaHCO3 in the presence of H2O2 as oxidant. Many digestion factors are studied and optimized. Under the optimum leaching conditions, the uranium dissolution efficiency is around 84%. For the uranium separation, the pH of the leach liquor is adjusted at 10, then subjected to a solvent extraction step using 4% Aliquat®336/kerosene in the presence of isodecanol as third-phase prevention. The loaded organic solvent was then treated with NaOH/H2O2 solution as a stripping solution. Finally, the resultant solution is subjected to a precipitation step using ammonia solution.

Synthesis of Carboxyl-Functionalized COFs with Alternate Stable β-Ketoenamine and Benzimidazole Linkages: Unraveling Exceptional Solvent Effects for Efficient Uranium Separation.

The prevalent π-π interactions in 2D covalent organic frameworks (COFs) impart a certain flexibility to the structures, making the stacking of COF layers susceptible to external stimuli and introducing some structural disorder. Recent research indicates that the flexibility between COF layers and the associated disorder significantly influence their selective adsorption performance toward gas molecules. However, the adsorption process in a solution environment is more complex compared to gas-phase adsorption, involving interactions between adsorbents and adsorbates, as well as the solvation effects of flexible 2D COFs. Therefore, the inherent flexibility and disorder in 2D COFs under solution conditions and their impact on the adsorption performance of metal ions have not been observed yet. Herein, the synthesis of a novel carboxyl-functionalized COF featuring stable β-ketoenamine and benzimidazole linkages, named DMTP-COOH, is presented. DMTP-COOH exhibits excellent selective adsorption capability for uranium, with significantly different adsorption capacities observed after treatment with different solvents. This notable difference in adsorption capacity is observed under varying pH, concentration, time, and even in the presence of multiple competing ions. This work represents the first observation of the significant impact of solvent soaking treatment on the selective adsorption performance of COFs for uranium under liquid conditions.