An extraction separation system and method for separating trivalent transplutonium elements

Abstract

This invention relates to the fields of nuclear fuel reprocessing and radiochemical separation technology, providing an extraction separation system and method for separating trivalent plutonium elements. Specifically, it provides a highly efficient separation method for adjacent plutonium elements: americium (Am), curium (Cm), and californium (Cf). This method is based on a "two-phase competitive extraction" strategy, constructing an extraction separation system composed of an organic phase extractant and an aqueous phase selective hydrophilic ligand. This system achieves highly selective separation of the three elements while directionally transferring the target element californium (Cf) to the organic phase. This invention provides an innovative, efficient, and industrially promising separation and purification solution for addressing the industrial challenge of separating trivalent plutonium elements.

Description

Technical Field

[0001] This invention relates to the field of nuclear fuel reprocessing and radiochemical separation technology, and more specifically, to an extraction separation system and method for separating trivalent plutonium. Background Technology

[0002] In the field of superplutonium separation, americium (Am), curium (Cm), and californium (Cf), as important trivalent superplutonium elements, play a crucial role in nuclear energy utilization, radioactive isotope preparation, and superheavy element synthesis. However, Am(III), Cm(III), and Cf(III) have extremely similar chemical properties in strongly acidic solutions and very small differences in ionic radii, making their efficient separation extremely difficult.

[0003] Currently, traditional separation methods mainly rely on processes such as ion exchange chromatography, which suffer from problems such as lengthy processes, harsh operating conditions, and limited separation efficiency. Although solvent extraction technology has advantages such as simple operation and ease of continuous implementation, existing extraction systems often struggle to achieve high selective separation between Am, Cm, and Cf, especially in effectively distributing target elements to opposite phases, thus limiting its practical application in process flows. Summary of the Invention

[0004] This invention provides an extraction separation system and method for separating trivalent superplutonium elements, specifically involving an efficient separation method for adjacent superplutonium elements americium (Am), curium (Cm), and californium (Cf), as well as a separation system based on a "two-phase competitive extraction" strategy.

[0005] To achieve the objectives of this invention, in a first aspect, this invention provides an extraction separation system for separating trivalent plutonium, the extraction separation system comprising: a) an organic phase containing a lipophilic extractant capable of complexing trivalent plutonium; and b) an aqueous phase being a solution containing nitric acid and containing a water-soluble selective ligand. The water-soluble selective ligand has a stronger complexing ability for americium (III) and / or curium (III) than for californium (III).

[0006] Furthermore, the lipid-soluble extractant is 2,2'-oxydi(N,N-dioctylacetamide), i.e., TODGA.

[0007] Furthermore, the concentration of TODGA in the organic phase is 0.05-0.2 M, and it is prepared by a diluent consisting of n-dodecane and n-octanol in a volume ratio of 8:1 to 20:1.

[0008] Preferably, the concentration of TODGA in the organic phase is 0.1 M, and it is prepared by a diluent consisting of n-dodecane and n-octanol in a volume ratio of 9:1.

[0009] Furthermore, the water-soluble selective ligand is the compound Phen-2DIC2OH and / or Phen-2DIC2OMe, with the following structural formula: For compounds Phen-2DIC2OH and Phen-2DIC2OMe, please refer to the literature Bin Li, Yu Kang, Ziyi Zhang, Ludi Wang, Haoyu Li, Yuxiao Guo, Guo Wang, Li Wang. Xiaoyan Tang, and Chao Xu . On the design of effective water-soluble actinide-masking ligandsthrough ligand structure modulation. Adv. Sci. , 2025, e12292.

[0010] Furthermore, the concentration of the water-soluble selective ligand in the aqueous phase is from 5 mM to 30 mM, preferably 20 mM.

[0011] Furthermore, the concentration of nitric acid in the aqueous phase is from 0.5 M to 3.0 M, preferably 1.0 M.

[0012] Furthermore, the organic phase and the aqueous phase are mixed in equal volumes.

[0013] Secondly, the present invention provides the application of the extraction and separation system in the separation of trivalent plutonium elements americium (Am), curium (Cm) and californium (Cf).

[0014] Thirdly, the present invention provides a method for separating trivalent superplutonium from a mixture containing americium (III), curium (III) and californium (III), wherein the extraction separation system is used to separate trivalent superplutonium from a mixture containing americium (III), curium (III) and californium (III); The method includes: adding a mixture (mixture liquid) containing americium (III), curium (III) and californium (III) to be separated into an aqueous phase, then contacting the organic phase with the aqueous phase, and under competitive extraction conditions, allowing californium (III) to be preferentially extracted into the organic phase, while americium (III) and curium (III) are retained in the aqueous phase, thereby achieving the separation of californium (III) from americium (III) and curium (III).

[0015] Furthermore, the competitive extraction conditions are as follows: extraction at 1000 rpm for 30-120 minutes (preferably 120 minutes) under constant temperature of 25°C, followed by centrifugation after extraction.

[0016] Furthermore, the centrifugation conditions are: centrifugation at 3000 rpm for 1-5 min.

[0017] By employing the above technical solution, the present invention has at least the following advantages and beneficial effects: (i) This invention provides a highly efficient separation method for adjacent ultraplutonium elements americium (Am), curium (Cm), and californium (Cf). Based on a "two-phase competitive extraction" strategy, this method constructs an extraction and separation system composed of an organic phase extractant and an aqueous phase selective hydrophilic ligand (i.e., a water-soluble selective ligand). This system enables highly selective separation of the three elements while directionally transferring the target element californium (Cf) to the organic phase, thus forming a simple and efficient separation technology.

[0018] (ii) The separation efficiency and selectivity are extremely high. The liquid-liquid extraction part obtains an ultra-high single-stage separation factor through the ligand competition mechanism.

[0019] (iii) The process flow is significantly simplified and flexible. Liquid-liquid extraction reduces the number of stages and simplifies the process flow.

[0020] (iv) It has strong anti-interference ability and high separation efficiency in a wide range of acidity windows, making it suitable for processing complex systems.

[0021] (v) This invention provides a complete set of innovative, efficient and industrially promising separation and purification solutions to solve the industrial problem of separating trivalent superplutonium. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the water-soluble selective ligand structure of the present invention.

[0023] Figure 2 The extraction and separation effect of Phen-2DIC2OH on Am / Cm / Cf under different acidity conditions is shown in the preferred embodiment of the present invention.

[0024] Figure 3 The extraction and separation effect of the system on Am / Cm / Cf at different concentrations of Phen-2DIC2OH in the preferred embodiment of the present invention is shown.

[0025] Figure 4 The extraction and separation effect of Phen-2DIC2OH on Am / Cm / Cf at different ionic strengths in a preferred embodiment of the present invention.

[0026] Figure 5The extraction and separation effect of Phen-2DIC2OH on Am / Cm / Cf at different equilibrium times in a preferred embodiment of the present invention.

[0027] Figure 6 The extraction and separation effect of Phen-2DIC2OMe on Am / Cm / Cf under different acidity conditions in a preferred embodiment of the present invention.

[0028] Figure 7 The extraction and separation effect of Am / Cm / Cf on the system at different concentrations of Phen-2DIC2OMe in the preferred embodiment of the present invention is shown.

[0029] Figure 8 The extraction and separation effect of Phen-2DIC2OMe on Am / Cm / Cf at different ionic strengths in a preferred embodiment of the present invention.

[0030] Figure 9 The extraction and separation effect of Phen-2DIC2OMe on Am / Cm / Cf at different equilibration times in a preferred embodiment of the present invention. Detailed Implementation

[0031] To address the industrial challenge of separating trivalent superplutonium elements, this invention provides a separation system based on a "two-phase competitive extraction" strategy and an efficient separation method for adjacent superplutonium elements americium (Am), curium (Cm), and californium (Cf).

[0032] The separation system provided by this invention introduces a hydrophilic ligand with selective recognition capability (i.e., a water-soluble selective ligand) into the aqueous phase, creating thermodynamic competition with the broad-spectrum extractant in the oil phase. This enables efficient and highly selective separation of Am(III), Cm(III), and Cf(III) under strongly acidic conditions. The hydrophilic ligand used in this invention, through precise control of its terminal groups, can significantly influence the partitioning behavior of Cf without altering the core coordination structure, achieving selective transfer from the aqueous phase to the oil phase. This system possesses advantages such as high separation factor, fast equilibrium speed, wide operating window, and resistance to complex matrix interference, providing a novel and practical technical approach for the efficient separation and purification of plutonium.

[0033] This invention proposes a "two-phase ligand competitive extraction separation" strategy. The core of this strategy lies in constructing a two-phase extraction system comprising an aqueous phase and an organic phase, and introducing functional ligands with different size selectivity into this system. Specifically, a water-soluble ligand (such as Phen-2DIC2OH or Phen-2DIC2OMe) with a strong affinity for trivalent plutonium with a large ionic radius is used in the aqueous phase, while a lipophilic extractant (such as TODGA) with a strong complexing ability for various trivalent plutonium metal ions with similar radii is used in the organic phase. When a mixed solution containing Am(III) / Cm(III) / Cf(III) comes into contact with this system, the two ligands competitively coordinate with the target ion, thereby transforming the small differences in the ionic radii of the three plutonium metal ions into significant differences in their partitioning behavior between the two phases. By precisely controlling the concentration of water-soluble ligands and extraction conditions (such as acidity), this system can achieve efficient and highly selective separation of Am(III), Cm(III), and Cf(III) in a single or minimal extraction step. This method not only fundamentally overcomes the dependence on multi-stage extraction in traditional methods, significantly simplifying the process and reducing energy and material consumption, but also greatly improves separation selectivity due to the enhanced recognition ability of target ions resulting from the introduction of aqueous ligands. Furthermore, the reagents used in this system can be designed to be more environmentally compatible, thereby reducing secondary pollution and conforming to the principles of green chemistry and sustainable development. This invention provides a novel technical approach for the separation of key adjacent trivalent plutonium elements such as californium (Cf), and has broad prospects for industrial application.

[0034] The present invention adopts the following technical solution: In a first aspect, the present invention provides a method for separating trivalent transplutonium from a mixture containing americium (III), curium (III), and californium (III), comprising the following steps: S1. A two-phase extraction system is provided, the system comprising: A) an organic phase containing a lipophilic extractant capable of complexing trivalent plutonium; and B) an aqueous phase containing americium(III), curium(III) and californium(III) ions to be separated, and a water-soluble selective ligand, wherein the water-soluble selective ligand has a stronger complexing ability for americium(III) and / or curium(III) than for californium(III); S2. The organic phase is brought into contact with the aqueous phase under competitive extraction conditions, so that californium (III) is preferentially extracted into the organic phase, while americium (III) and curium (III) are retained in the aqueous phase, thereby achieving the separation of californium (III) from americium (III) and curium (III).

[0035] Furthermore, the lipid-soluble extractant is 2,2'-oxydi(N,N-dioctylacetamide), i.e., TODGA.

[0036] Furthermore, the water-soluble selective ligand is the compound Phen-2DIC2OH and / or Phen-2DIC2Ome.

[0037] Furthermore, the aqueous phase is a nitric acid solution.

[0038] Preferably, the concentration of the nitric acid solution is 1.0 M to 2.0 M, more preferably 1.0 M.

[0039] Furthermore, the concentration of the water-soluble selective ligand in the aqueous phase is from 5 mM to 30 mM, preferably 20 mM.

[0040] Furthermore, the organic phase comprises a diluent consisting of n-dodecane and n-octanol, wherein the concentration of TODGA is 0.1 M.

[0041] Preferably, the diluent is a mixture of n-dodecane and n-octanol in a volume ratio of 9:1.

[0042] Furthermore, the competitive extraction conditions are as follows: extraction at 1000 rpm for 120 minutes at a constant temperature of 25°C, followed by centrifugation (e.g., 3000 rpm) after extraction.

[0043] Secondly, the present invention provides an extraction separation system for separating trivalent superplutonium, the system comprising: a) an organic phase containing the lipid-soluble extractant 2,2'-oxydi(N,N-dioctylacetamide), i.e., TODGA; and b) an aqueous phase, which is a solution containing nitric acid and contains a water-soluble selective ligand. The water-soluble selective ligand and the lipid-soluble extractant form competitive complexes with the americium(III), curium(III) and californium(III) ions added to the aqueous phase, resulting in a higher selective distribution ratio of californium(III) than that of americium(III) and curium(III), thus preferentially extracting them into the organic phase.

[0044] Furthermore, the concentration of nitric acid in the aqueous phase is 1.0 M to 2.0 M, preferably 1.0 M.

[0045] Furthermore, the concentration of the water-soluble selective ligand is from 5 mM to 30 mM, preferably 20 mM.

[0046] Furthermore, the concentration of TODGA in the organic phase is 0.1 M, and it is prepared using a diluent composed of n-dodecane and n-octanol; Preferably, the diluent is a mixture of n-dodecane and n-octanol in a volume ratio of 9:1.

[0047] Furthermore, the organic phase and the aqueous phase are mixed in equal volumes.

[0048] The following examples are used to illustrate the present invention, but are not intended to limit the scope of the invention. Unless otherwise specified, the technical means used in the examples are conventional means well known to those skilled in the art, and the raw materials used are all commercially available products.

[0049] In this invention, a mature commercial organic phase extractant, 2,2'-oxydi(N,N-dioctylacetamide) (TODGA, CAS No.: 342794-43-8), is used as a co-extractant in the organic phase. It is preferably prepared by dissolving TODGA in a mixed solvent consisting of 90 v / v % n-dodecane and 10 v / v % n-octanol, wherein the concentration of TODGA is 0.1 M. The aqueous phase contains the tracer amount of trivalent plutonium ions to be separated, different concentrations of nitric acid, and specific hydrophilic ligands (structures shown in the figure). Figure 1 The solution shown.

[0050] The liquid scintillation spectrometer used in the following examples was purchased from PerkinElmer, USA, model Quantulas 1220; the alpha spectrometer was purchased from CANBERRA, USA, model 7200-12.

[0051] Example 1: An extraction separation system (Phen-2DIC2OH system) and separation method for separating trivalent plutonium. The extraction and separation method in this embodiment specifically includes the following steps: For the Phen-2DIC2OH system, firstly, an aqueous phase solution containing different acidities (1.0 - 3.0 M) is prepared, wherein the concentration of Phen-2DIC2OH is 10 mM. The prepared aqueous phase solution is mixed with an equal volume of 100 mM TODGA organic phase solution, and a tracer stock solution of Am(III) / Cm(III) / Cf(III) (the counts of the three ultraplutonium elements are all 10000 cpm / 10 μL) is added. The mixture is then fully extracted at 1000 rpm for 120 minutes at a constant temperature of 25°C. After extraction, the mixture is separated by centrifugation at 3000 rpm for 2 minutes. Samples are taken from both phases, and the radioactivity is measured using a liquid scintillation spectrometer and an alpha spectrometer. The partition ratio and separation factor are calculated. The partition ratio and separation factor are defined as two important separation evaluation indicators as follows: When the two-phase system reaches extraction equilibrium, the distribution ratio of metal ions (M) between the aqueous and organic phases is ( D M ) is defined as the concentration of the metal ion in the organic phase. C Org.) and the concentration of the metal ion in the aqueous phase ( C aq. The ratio of ) to: Separation factor ( SF An / An The separation efficiency of the extraction system for two metal ions is used to evaluate the separation effect of the two metal ions, and is defined as the distribution ratio of the two metal ions ( ). D M The ratio of ) to: Experimental results are as follows Figure 2 As shown, the extraction experiment results indicate that with increasing acidity, the partition ratios of Am(III), Cm(III), and Cf(III) all significantly increase. D Am Increased from 0.03 to 105, D Cm It increased from 0.15 to 622. D Cf The separation factor increased from 4.48 to 4638. The optimal value was achieved at 1.0 M HNO3. SF Am / Cm It is 6.61. SF Am / Cf It is 309. SF Cm / Cf The value was 46.8. This phenomenon stems from the dual influence of acidity on the degree of ligand protonation and the extraction capacity of TODGA. In a moderately acidic solution environment, the protonated and deprotonated forms of the ligands reach an optimal balance, allowing the geometry of the coordination cavity and the electron cloud density to best distinguish the radius differences of metal ions, thus achieving selective complexation. When the solution environment is under high acidity conditions, excessive protonation disrupts this balance, leading to a decrease in selectivity. This indicates that the optimal operating window for this separation system is between 1.0 M and 2.0 M HNO3. In actual processes, the acidity of the aqueous solution needs to be reasonably controlled to achieve the best separation effect.

[0052] The effect of different concentrations of Phen-2DIC2OH (5, 10, 20, 30, 40, 50 mM) in the aqueous phase on the extraction and separation performance was further investigated. The acidity of the aqueous phase was kept constant at 1.0 M HNO3, and the organic phase was 100 mM TODGA. All extraction experiments were conducted under strictly controlled isothermal conditions, maintaining a consistent phase volume ratio and mixing intensity to accurately assess the influence of ligand concentration on separation performance. The experimental results are as follows: Figure 3 As shown: Extraction experiments showed that the partition ratio decreased significantly with increasing concentration of water-soluble ligands. DAm Decreased from 0.73 to 0.02. D Cm Decrease from 3.15 to 0.30, D Cf The separation factor decreased from 81.5 to 7.55. The optimal separation factor was achieved at a water-soluble ligand concentration of 20 mM. SF Am / Cm It is 13.3. SF Am / Cf It is 505. SF Cm / Cf The value was 38.0. This phenomenon reveals the influence of ligand concentration on the extraction and separation effect. Therefore, in actual processes, it is necessary to reasonably control the concentration of Phen-2DIC2OH in the aqueous solution to achieve the best separation effect.

[0053] In addition, the effect of different NaNO3 concentrations (0, 0.5, 1.0, 1.5, 2.0, 2.5 M) in the aqueous phase on the extraction performance was investigated. The aqueous phase was fixed at 1.0 M HNO3 and 20 mM Phen-2DIC2OH, and the organic phase was 100 mM TODGA. Special attention was paid to controlling the accuracy of ionic strength during the experiment; precise weighing and thorough dissolution of NaNO3 were used to ensure accurate NaNO3 concentration. All operations were performed under standardized radioactive experimental conditions to ensure the reliability of the experimental data, and all operations were performed under isothermal conditions to eliminate the influence of temperature fluctuations on the experimental results. The experimental results are as follows: Figure 4 As shown: Extraction experiments showed that the partition ratio continuously increased with increasing ionic strength. D Am Increased from 0.08 to 3.10, D Cm It increased from 1.06 to 21.8. D Cf The separation factor increased from 40.1 to 438.3. All factors showed a decreasing trend. SF Am / Cm It dropped from 13.3 to 7.03. SF Am / Cf From 505 to 142, SF Cm / Cf The concentration decreased from 38.0 to 20.1. This is mainly attributed to the combined effects of salting out and competition: the high ionic strength environment not only enhances the extraction ability of TODGA, but may also affect the stability of metal-ligand complexes in the aqueous phase, adversely affecting the separation effect. Therefore, in process applications, it is necessary to more strictly control the interference of ionic strength on the separation of Am(III) / Cm(III) / Cf(III).

[0054] In the extraction time-kinetics test, eight time points were set: 1, 3, 5, 10, 20, 30, 60, and 120 min. The aqueous phase was fixed at 1.0 M HNO3 and 20 mM Phen-2DIC2OH, and the organic phase was 100 mM TODGA. The extraction reaction was terminated immediately at each preset time point, and centrifugation and sample collection were performed rapidly to accurately track the kinetic characteristics of the partition ratio changing over time during extraction. The experimental results are as follows: Figure 5 As shown: The extraction results showed that the partition ratios of the three metal ions, Am(III), Cm(III), and Cf(III), generally increased with increasing extraction time. D Am From a minimum of 0.05 to 0.08, D Cm It increased from a low of 0.51 to 1.06. D Cf The concentration increased from a minimum of 14.4 to 40.1. The extraction process essentially reached equilibrium within 10 min, with Cf(III) exhibiting slightly slower kinetics. This led to... SF Am / Cf From a low of 325 to 505, SF Cm / Cf It increased from a low of 28.1 to 38.0, while SF Am / Cm The system is relatively stable. Kinetic studies show that it has a relatively fast extraction rate, which is beneficial for practical process operation.

[0055] Example 2: An extraction separation system (Phen-2DIC2OMe system) and separation method for separating trivalent plutonium. For the Phen-2DIC2OMe system, firstly, aqueous solutions with different acidities (1.0-3.0 M) were prepared, with a Phen-2DIC2OMe concentration of 10 mM. The prepared aqueous solutions were mixed with an equal volume of 100 mM TODGA organic solution, and a tracer stock solution of Am(III) / Cm(III) / Cf(III) (same as in Example 1) was added. Extraction was carried out at 1000 rpm for 120 minutes at a constant temperature of 25°C. After extraction, the mixture was separated by centrifugation at 3000 rpm for 2 minutes. Samples were taken from both phases, and the radioactivity was measured using a liquid scintillation spectrometer and an alpha spectrometer. The partition ratio and separation factor were then calculated.

[0056] Experimental results are as follows Figure 6As shown, the extraction experiment results indicate that with increasing acidity, the partition ratios of Am(III), Cm(III), and Cf(III) all significantly increase. D Am Increased from 0.02 to 99.0, D Cm Increased from 0.05 to 565, D Cf The separation factor increased from 0.31 to 4720. At 1.0 M HNO3, SF Am / Cm It is 4.69. SF Am / Cf It is 101. SF Cm / Cf The value was 21.5. This phenomenon is similar to that of Phen-2DIC2OH, stemming from the dual influence of acidity on the degree of ligand protonation and TODGA extraction capacity. Test results indicate that the optimal operating window for this separation system is also between 1.0 M and 2.0 M HNO3. In practical processes, the acidity of the aqueous solution needs to be reasonably controlled to achieve the best separation effect.

[0057] The effects of different concentrations of Phen-2DIC2OMe (5, 10, 20, 30, 40, 50 mM) in the aqueous phase on the extraction and separation performance were further investigated. The acidity of the aqueous phase was kept constant at 1.0 M HNO3, and the organic phase was 100 mM TODGA. All extraction experiments were conducted under strictly controlled isothermal conditions, maintaining a consistent phase volume ratio and mixing intensity to accurately assess the influence of ligand concentration on separation performance. The experimental results are as follows: Figure 7 As shown: Extraction experiments showed that the partition ratio decreased significantly with increasing concentration of water-soluble ligands. D Am Decreased from 0.53 to 0.04, D Cm It decreased from 2.19 to 0.24. D Cf The separation factor decreased from 41.5 to 5.26. The optimal separation factor was achieved at a water-soluble ligand concentration of 20 mM. SF Am / Cm It is 8.6. SF Am / Cf It is 203. SF Cm / Cf The value was 23.6. This phenomenon also reveals the influence of ligand concentration on the extraction and separation effect. Therefore, in actual processes, it is necessary to reasonably control the concentration of Phen-2DIC2OH in the aqueous solution to achieve the best separation effect.

[0058] In addition, the effect of different NaNO3 concentrations (0, 0.5, 1.0, 1.5, 2.0, 2.5 M) in the aqueous phase on the extraction performance was investigated. The aqueous phase was fixed at 1.0 M HNO3 and 20 mM Phen-2DIC2OMe, and the organic phase was 100 mM TODGA. During the experiment, special attention was paid to controlling the accuracy of ionic strength; precise weighing and thorough dissolution were used to ensure accurate NaNO3 concentration. All operations were performed under standardized radioactive experimental conditions to ensure the reliability of the experimental data, and all operations were performed under isothermal conditions to eliminate the influence of temperature fluctuations on the experimental results. The experimental results are as follows: Figure 8 As shown: Extraction experiments showed that the partition ratio continuously increased with increasing ionic strength. D Am It increased from 0.06 to 2.48. D Cm It increased from 0.51 to 9.89. D Cf The separation factor increased from 12.0 to 92.5. All separation factors showed a decreasing trend. SF Am / Cm It dropped from 8.60 to 3.98. SF Am / Cf It dropped from 203 to 37.2. SF Cm / Cf The concentration decreased from 23.6 to 9.34. This is also mainly attributed to the combined effects of salting out and competition: the high ionic strength environment not only enhances the extraction ability of TODGA, but may also affect the stability of metal-ligand complexes in the aqueous phase, adversely affecting the separation effect. Therefore, in process applications, it is necessary to more strictly control the interference of ionic strength on the separation of Am(III) / Cm(III) / Cf(III).

[0059] In the extraction time-kinetics test, eight time points were set: 1, 3, 5, 10, 20, 30, 60, and 120 min. The aqueous phase was fixed at 1.0 M HNO3 and 20 mM Phen-2DIC2OMe, and the organic phase was 100 mM TODGA. The extraction reaction was terminated immediately at each preset time point, and centrifugation and sample collection were performed rapidly to accurately track the kinetic characteristics of the partition ratio changing over time during extraction. The experimental results are as follows: Figure 9 As shown: The extraction results showed that the partition ratios of the three metal ions, Am(III), Cm(III), and Cf(III), generally increased with increasing extraction time. D Am From a minimum of 0.05 to 0.06, DCm From a minimum of 0.30 to 0.55, D Cf The concentration increased from a low of 6.49 to 12.5. The extraction process essentially reached equilibrium within 10 min, with Cf(III) exhibiting slightly slower kinetics. This led to... SF Am / Cf It increased from a low of 158 to 213. SF Cm / Cf It increased from a low of 19.3 to 22.7, while SF Am / Cm The system is relatively stable. Kinetic studies show that it has a relatively fast extraction rate, which is beneficial for practical process operation.

[0060] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. An extraction separation system for separating trivalent plutonium, characterized in that, The extraction and separation system comprises: a) an organic phase containing a fat-soluble extractant capable of complexing trivalent plutonium; and b) an aqueous phase, which is a solution containing nitric acid and contains a water-soluble selective ligand. The water-soluble selective ligand has a stronger complexing ability for americium (III) and / or curium (III) than for californium (III).

2. The extraction and separation system according to claim 1, characterized in that, The lipid-soluble extractant is 2,2'-oxydi(N,N-dioctylacetamide), i.e., TODGA.

3. The extraction and separation system according to claim 2, characterized in that, The concentration of TODGA in the organic phase is 0.05-0.2 M, and it is prepared by a diluent consisting of n-dodecane and n-octanol in a volume ratio of 8:1 to 20:

1.

4. The extraction and separation system according to claim 3, characterized in that, The concentration of TODGA in the organic phase is 0.1M, and it is prepared by a diluent consisting of n-dodecane and n-octanol in a volume ratio of 9:

1.

5. The extraction and separation system according to claim 1, characterized in that, The water-soluble selective ligands are compounds Phen-2DIC2OH and / or Phen-2DIC2OMe, with the following structural formulas: 。 6. The extraction and separation system according to claim 5, characterized in that, The concentration of the water-soluble selective ligand in the aqueous phase is from 5 mM to 30 mM, preferably 20 mM.

7. The extraction and separation system according to claim 1, characterized in that, The nitric acid concentration in the aqueous phase is from 0.5 M to 3.0 M, preferably 1.0 M; and / or, The organic phase and the aqueous phase are mixed in equal volumes.

8. The application of the extraction and separation system according to any one of claims 1-7 in the separation of trivalent ultraplutonium elements americium (Am), curium (Cm) and californium (Cf).

9. A method for separating trivalent plutonium from a mixture containing americium(III), curium(III), and californium(III), characterized in that, The trivalent superplutonium element is separated from a mixture containing americium(III), curium(III) and californium(III) using the extraction separation system according to any one of claims 1-7; The method includes: adding a mixture containing americium (III), curium (III) and californium (III) to be separated into an aqueous phase, then contacting the organic phase with the aqueous phase, and under competitive extraction conditions, allowing californium (III) to be preferentially extracted into the organic phase, while americium (III) and curium (III) are retained in the aqueous phase, thereby achieving the separation of californium (III) from americium (III) and curium (III).

10. The method according to claim 9, characterized in that, The competitive extraction conditions are: extraction at 1000 rpm for 30-120 minutes at a constant temperature of 25℃, followed by centrifugation after extraction. Preferably, the centrifugation conditions are: centrifugation at 3000 rpm for 1-5 min.

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