Solvent extraction method for improving separation factor of trivalent americium and curium

Abstract

The invention relates to a solvent extraction method for improving a separation factor of trivalent americium and curium, which comprises the following steps: preparing an extraction organic phase solution containing an extraction agent and a synergistic extraction agent, the extraction agent being dithiophosphonic acid with long chain hydrocarbon substituents on two substituted benzene rings on phosphorus atoms; then co-extracting Am (III) / Cm (III) by using an extraction organic phase solution; carrying out selective reverse extraction on Cm (III) by adopting a water-phase solution containing a water-soluble complexing reverse extraction agent; and finally, carrying out primary reverse extraction on the residual Am (III) in the organic phase by using HNO3. According to the method provided by the invention, the separation factor of the trivalent americium and curium is increased from about 4 to more than 10, so that the separation factor of the americium and curium is greatly increased. Compared with the prior art, the extraction agent adopted in the method is higher in stability, the separation factor of americium and curium is high, and separation of trivalent actinide lanthanum and americium and curium can be achieved in one extraction and separation process in a synergistic extraction and complexing reverse extraction mode.

Description

Technical Field

[0001] This invention belongs to the field of nuclear chemical technology, specifically relating to a solvent extraction method for improving the separation factor of trivalent americium curium. Background Technology

[0002] In reactors, fissile materials such as uranium and plutonium undergo fission and neutron-trapping reactions to produce light lanthanides and minor actinides, respectively. Some of these fission products are highly neutron poisonous, and once they accumulate to a certain level, spent fuel must be removed. To improve the utilization rate of uranium resources and reduce the volume of radioactive waste, advanced fuel cycles not only require the separation and recycling of uranium and plutonium from spent fuel, but also the separation and utilization or separate disposal of the more radioactive minor actinides.

[0003] Currently, spent fuel unloaded from commercial nuclear power plants undergoes a PUREX (pure uranium-plutonium co-extraction) process for reprocessing to recover unfisified uranium and plutonium for reuse. Lanthanides, minor actinides, and other fission products are discharged into high-level radioactive waste. To further reduce the volume of high-level radioactive waste for final disposal, the waste requires further separation of actinides and lanthanides, as well as americium and curium. The ionic radii and charges of trivalent actinides and lanthanides are very similar, making separation difficult. Several separation processes for trivalent actinides and lanthanides have been validated through thermal experiments, but the subsequent separation of trivalent americium and curium is even more challenging due to their smaller difference in ionic potential. There are two main approaches to separating americium and curium: one is to oxidize trivalent americium to a higher valence state and separate it from trivalent curium, but the strong oxidants used place high demands on the equipment used in the separation process, making industrial application difficult; the other is to use solvent extraction or ion exchange to separate trivalent americium and curium, but this method has a lower separation factor and often requires very complex processes. Therefore, there is currently no very practical method for separating trivalent americium and curium for the treatment of industrial high-level radioactive waste. A breakthrough is still needed in the separation of trivalent actinides and lanthanides, to further improve the separation factor of americium and curium and achieve efficient separation of americium and curium, building upon the existing methods for separating trivalent lanthanum and actinides. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a solvent extraction method that improves the separation factor of trivalent actinium and curium, namely, a solvent extraction method for synergistic extraction of trivalent actinium systems. This method can significantly improve the stability of dithiophosphonic acid extractants and the distribution ratio of extracted An(III). Furthermore, it can further improve the separation factor of Am(III) / Cm(III) through stepwise complexation back-extraction, thereby achieving the separation of trivalent actinium and lanthanum and americium and curium in a single extraction process.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a solvent extraction method for improving the separation factor of trivalent americium-curium, the method comprising the following steps:

[0006] S1. Prepare an extractant organic phase solution containing an extractant and a co-extractant: Dissolve the extractant in an organic solvent to form an extractant solution; weigh a specified mass of the co-extractant and dissolve it in the extractant solution to prepare an extractant organic phase solution; wherein, the extractant is a dithiophosphonic acid with long-chain hydrocarbon substituents on two substituted benzene rings on the phosphorus atom;

[0007] S2. Co-extract Am(III) / Cm(III) using the extracted organic phase solution: Take the extracted organic phase solution into a centrifuge tube, add an equal volume of 5 mmol / L Nd(NO3)3 & Eu(NO3)3-1.0 mol / L NaNO3 solution to form a pre-equilibrium aqueous-organic phase system; take the aqueous phase dissolved in the pre-equilibrium aqueous-organic phase system... 241 Am(Ⅲ), 244 Cm(Ⅲ) tracer was added, and the completely dissolved aqueous phase was transferred back into the centrifuge tube. After extraction, the phases were separated by centrifugation to obtain the loaded sample. 241 Am(Ⅲ), 244 The organic phase of Cm(Ⅲ);

[0008] S3, Selective Back-Extraction Cm(III): Taking Load 241 Am(Ⅲ), 244 The organic phase of Cm(III) was transferred to a centrifuge tube, and an aqueous solution containing a water-soluble complexing stripping agent was added for selective stripping of Cm(III). After shaking, the phases were separated by centrifugation, and the organic and aqueous phase samples were taken separately to prepare the source and the α count was measured. The separation factor Am(III) / Cm(III) was calculated.

[0009] S4, the remaining Am(III) in the back-extracted organic phase.

[0010] Further, in step S1, the extractant is selected from one of bis(4-tert-butylphenyl)dithiophosphonic acid, bis(4-tert-pentylphenyl)dithiophosphonic acid, bis(4-ethylphenyl)dithiophosphonic acid, bis(4-propylphenyl)dithiophosphonic acid, bis(4-isopropylphenyl)dithiophosphonic acid, bis(4-n-butylphenyl)dithiophosphonic acid, bis(isobutylphenyl)dithiophosphonic acid, bis(2,4-diisopropylphenyl)dithiophosphonic acid, bis(2,5-diisopropylphenyl)dithiophosphonic acid, bis(4-neopentylphenyl)dithiophosphonic acid, and bis(4-ethylhexylphenyl)dithiophosphonic acid.

[0011] Further, in step S1, the preparation method of the extractant solution is as follows: First, weigh the ammonium salt of the extractant, add an organic solvent and an excess of 20-30% of 3 mol / L dilute hydrochloric acid, and stir thoroughly under inert gas protection to extract the extractant into the organic solvent; after the ammonium salt of the extractant is completely acidified and dissolved, separate the lower aqueous phase, wash the residual HCl in the organic phase with deionized water, and repeat the washing three times; finally, titrate the extractant concentration in the organic phase with NaOH standard solution, and adjust the extractant concentration with organic solvent.

[0012] Furthermore, in step S1, the organic solvent is selected from toluene, xylene, p-xylene, and kerosene.

[0013] Furthermore, in step S1, the co-extractant is an N-containing co-extractant or a neutral co-extractant;

[0014] The N-containing co-extractant is selected from one of bipyridine and its derivatives, o-phenanthroline and its derivatives, 2,2':6',2''-tripyridine, bis-1,2,4-triazinyl-2,6-pyridine and its derivatives; the neutral co-extractant is tributyl phosphate or trioctyl phosphate.

[0015] Furthermore, in the extracted organic phase solution, the concentration of the extractant is 0.2-0.5 mol / L, and the concentration of the co-extractant is 0.002-0.5 mol / L.

[0016] Furthermore, the specific methods for co-extraction of Am(III) / Cm(III) include:

[0017] S21. Take the extracted organic phase solution into a centrifuge tube, add an equal volume of 5 mmol / L Nd(NO3)3 & Eu(NO3)3-1.0 mol / L NaNO3 solution, and adjust the pH of the system to 2.5±0.5. Place the centrifuge tube in a constant temperature shaker and centrifuge to form a pre-equilibrium aqueous-organic phase system.

[0018] S22, take 0.1 mL of each. 241 Am(III), 0.1 mL 244 Cm(Ⅲ) tracer was placed in a small glass vial and slowly heated to remove the solvent and background acid. After the solution in the small glass vial was completely evaporated and cooled thoroughly, the aqueous phase from the pre-equilibrium aqueous-organic phase system was added to the small glass vial to dissolve. 241 Am(Ⅲ), 244 Cm(Ⅲ) tracer; after the aqueous phase in the glass bottle was completely dissolved, it was transferred back to the centrifuge tube, and the centrifuge tube was placed in a constant temperature shaker for extraction and centrifugation to separate the phases, thus obtaining the loaded phase. 241 Am(Ⅲ), 244 The organic phase of Cm(Ⅲ).

[0019] Furthermore, in step S21, NaOH or HNO3 is added to adjust the pH of the system to the range of 2.5 ± 0.5.

[0020] Furthermore, in step S21, the centrifuge tube is placed in a constant temperature shaker at 25°C and shaken for more than 10 minutes before centrifugation;

[0021] In step S22, the centrifuge tube is placed in a constant temperature shaker at 25°C and shaken for more than 30 minutes before centrifugation.

[0022] Further, in step S3, the water-soluble complexing stripping agent is selected from one of dialkylthiodiglycanic acid, dialkyldiglycanic acid, N,N,N',N'-tetraalkyl-diglycanamide, 2-carboxy-6-di(2-alkyl)aminopyridine, carboxylic acid, morpholine-substituted water-soluble diglycanic acid or diglycanamide, hydroxymethyl, hydroxyethyl-substituted diglycanamide, α-hydroxyacetic acid, and hydroxamic acid.

[0023] Furthermore, in step S3, Cm(III) is selectively back-extracted using aqueous solutions containing water-soluble complexing back-extractants of different concentrations, and the concentration of the water-soluble complexing back-extractant with the highest Am(III) / Cm(III) separation factor is selected.

[0024] Furthermore, in step S4, the remaining Am(III) in the organic phase is back-extracted once with 1 mol / L HNO3.

[0025] The beneficial effects of this invention are as follows: The solvent extraction method for improving the separation factor of trivalent americium-curium provided by this invention involves preparing an extraction organic phase solution containing an extractant and a co-extractant. The extractant is a dithiophosphonic acid with long-chain hydrocarbon substituents on two substituted benzene rings on a phosphorus atom. Then, Am(III) / Cm(III) are co-extracted with the extraction organic phase solution. Next, Cm(III) is selectively back-extracted with an aqueous phase solution containing a water-soluble complexing back-extractant. Finally, the remaining Am(III) in the organic phase is back-extracted once with HNO3. The method provided by this invention increases the separation factor of trivalent americium-curium from approximately 4 to over 10, significantly improving the separation factor. Compared with existing technologies, the extractant used in this invention has stronger stability and a higher americium-curium separation factor, allowing for the separation of trivalent actinium-lanthanum and americium-curium in a single extraction separation process with fewer stages. The main beneficial effects of this invention include:

[0026] 1. The extractant used is more stable than Cyanex 301, and has a higher Ln(III) / An(III) separation factor.

[0027] 2. When extractant and co-extractant are used together to extract An(III), the extraction pH value is lower and easier to control.

[0028] 3. Compared with using only the extractant, the co-extraction and complexation back-extraction methods can achieve the separation of Ln(III) / An(III) and americium-curium in one extraction cycle, and the separation factor of Am(III) / Cm(III) is higher. Attached Figure Description

[0029] Figure 1 This is a schematic diagram showing the separation factors of different concentrations of HDEOGA for americium in a 0.0025 mol / L bipyridine-0.2 mol / L bis(4-tert-butylphenyl)dithiophosphonic acid-xylene solution in Example 1 of the present invention;

[0030] Figure 2 This is a schematic diagram showing the separation factors of different concentrations of HMOROGA on americium-curium in a 0.005 mol / L phenanthroline-0.5 mol / L bis(4-isobutylphenyl)dithiophosphonic acid-xylene solution in Example 2 of the present invention. Detailed Implementation

[0031] The technical solutions in the embodiments of the present invention will be further clearly and completely described below with reference to the accompanying drawings and examples. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0032] It should be noted that in the description of the embodiments of the present invention, the terms "upper," "lower," "front," "rear," "front," "back," "left," "right," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention. In addition, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0033] In the separation process of trivalent lanthanum-actinium, the TALSPEAK and BTBP processes have relatively low separation factors for trivalent americium-curium, limiting their potential for further development. The separation factor of trivalent americium-curium using bis(2,4,4-trimethylpentyl)dithiophosphonic acid (Cyanex 301) developed by Tsinghua University can reach around 4, showing some development potential. However, the irradiation stability and chemical stability of this extractant are generally poor, affecting its industrial application. Furthermore, the aqueous pH for separating trivalent americium-curium using this extractant is 3-4, which is difficult to adjust in industrial processes. Therefore, when using Cyanex 301 to separate trivalent americium-curium, improvements are needed in two aspects: first, improving the irradiation stability and chemical stability of the extractant to make it suitable for systems with high radioactivity and strong acidity, such as high-level radioactive waste liquids; second, further enhancing the separation factor of the extractant to achieve complete separation of trivalent americium-curium through a simple process.

[0034] In view of the above, based on long-term research and practice, the inventors have developed a solvent extraction method to improve the separation factor of trivalent americium-curium. This method employs a solvent extraction method that co-extracts trivalent actinides to achieve the co-extraction of trivalent americium-curium, and uses a complexation back-extraction method to achieve the separation of trivalent americium-curium. Furthermore, the method provided in this embodiment can significantly improve the stability of dithiophosphonic acid extractants and the partition ratio of extracted An(III), and further improve the separation factor of Am(III) / Cm(III) through stepwise complexation back-extraction, achieving the separation of trivalent actinium-lanthanum and americium-curium in a single extraction process.

[0035] Specifically, in the method, the extractant is a dithiophosphonic acid with long-chain hydrocarbon substituents on the two substituted benzene rings on the phosphorus atom, such as bis(4-tert-butylphenyl)dithiophosphonic acid, bis(4-tert-pentylphenyl)dithiophosphonic acid, bis(4-ethylphenyl)dithiophosphonic acid, bis(4-propylphenyl)dithiophosphonic acid, bis(4-isopropylphenyl)dithiophosphonic acid, bis(4-n-butylphenyl)dithiophosphonic acid, bis(isobutylphenyl)dithiophosphonic acid, bis(2,4-diisopropylphenyl)dithiophosphonic acid, bis(2,5-diisopropylphenyl)dithiophosphonic acid, bis(4-neopentylphenyl)dithiophosphonic acid, and bis(4-ethylhexylphenyl)dithiophosphonic acid, etc. The structural formula of the extractant is shown below. This type of extractant has the advantages of high radiation stability, high antioxidant properties, and low half-extraction pH value.

[0036]

[0037] Among them, R1 and R2 are ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, tert-pentyl, neopentyl, diethylhexyl, etc.

[0038] In the method described, the co-extractant is an N-containing co-extractant or a neutral co-extractant. As shown below, N-containing co-extractants include, but are not limited to, 2,2'-bipyridyl (Bipy) and its derivatives, 1,10-phenanthroline (Bhen) and its derivatives, 2,2':6',2''-tripyridine (Terpy), bis-1,2,4-triazinyl-2,6-pyridine (BTP) and its derivatives; neutral co-extractants include tributyl phosphate (TBP), trioctyl phosphate (TEHP), etc.

[0039]

[0040]

[0041] TBP TEHP

[0042] In this embodiment, two extraction methods are used to selectively extract An(III) during the Ln(III) / An(III) extraction separation. The first method involves using an aryl-substituted dithiophosphonic acid extractant to extract An(III) within a pH range of 2-4, while Ln(III) remains in the aqueous phase. The second method involves using an extractant concentration of 0.2-0.5 mol / L and a co-extractant concentration of 0.002-0.5 mol / L in the organic phase, extracting An(III) within a pH range of 2-3, while Ln(III) remains in the aqueous phase. The diluents used in both methods include toluene, xylene, p-xylene, and kerosene. The aqueous and organic phases are mixed at a volume ratio of 1:1 (after stirring or shaking for a period of time), followed by centrifugation or static separation to separate An(III) and Ln(III).

[0043] Depending on the selected An(III) / Ln(III) separation method, the separation of Am(III) / Cm(III) can also be performed in two ways. If the first method is used, and no co-extractant is used during An(III) / Ln(III) separation, then 0.002-0.5 mol / L of co-extractant is added to the organic phase loaded with An(III) after An(III) / Ln(III) separation, and Cm(III) is selectively back-extracted from the organic phase using an aqueous phase containing a water-soluble complexing stripping agent within a pH range of 2-4. If the second method is used, since a co-extractant has already been used during An(III) / Ln(III) separation, then Cm(III) is directly selectively back-extracted from the organic phase using an aqueous phase containing a water-soluble complexing stripping agent within a pH range of 2-4. The complexing stripping agents used are as follows: dialkylthiodiglycanic acid (L1), dialkyldiglycanic acid (L2), N,N,N',N'-tetraalkyl-diglycanamide (L3), 2-carboxy-6-di(2-alkyl)aminopyridine (L4), carboxylic acid (L5), morpholine-substituted water-soluble diglycanic acid or diglycanamide (L6, L7), hydroxymethyl or hydroxyethyl-substituted diglycanamide (L8, L9), α-hydroxyacetic acid (L... 10 Hydroxime acid, etc. (L) 11 ).

[0044]

[0045] Wherein, R1 and R2 are methyl and ethyl.

[0046] The separation process of Am(III) / Cm(III) requires multi-stage countercurrent back-extraction with an aqueous phase containing a water-soluble complexing back-extraction agent to obtain an aqueous phase of Cm(III); finally, Am(III) is back-extracted with 1 mol / L HNO3 solution to achieve the separation of Am(III) / Cm(III).

[0047] This invention provides a solvent extraction method for improving the separation factor of trivalent americium-curium, comprising co-extracting Am(III) / Cm(III) with an extractant organic phase solution containing an extractant and a co-extractant, selectively back-extracting Cm(III) with an aqueous phase solution containing a water-soluble complexing back-extractant, and then back-extracting Am(III) with HNO3; the method includes the following steps:

[0048] S1. Prepare an extraction organic phase solution containing an extractant and a co-extractant: Dissolve the extractant in an organic solvent to form an extractant solution; then weigh a specified mass of the co-extractant and dissolve it in the extractant solution to prepare an extraction organic phase solution;

[0049] Optionally, in step S1, the extractant is a dithiophosphonic acid with long-chain hydrocarbon substituents on the two substituted benzene rings on the phosphorus atom, selected from one of bis(4-tert-butylphenyl)dithiophosphonic acid, bis(4-tert-pentylphenyl)dithiophosphonic acid, bis(4-ethylphenyl)dithiophosphonic acid, bis(4-propylphenyl)dithiophosphonic acid, bis(4-isopropylphenyl)dithiophosphonic acid, bis(4-n-butylphenyl)dithiophosphonic acid, bis(isobutylphenyl)dithiophosphonic acid, bis(2,4-diisopropylphenyl)dithiophosphonic acid, bis(2,5-diisopropylphenyl)dithiophosphonic acid, bis(4-neopentylphenyl)dithiophosphonic acid, and bis(4-ethylhexylphenyl)dithiophosphonic acid.

[0050] Specifically, in step S1, the preparation method of the extractant solution is as follows: First, weigh the ammonium salt of the extractant, add organic solvent and dilute hydrochloric acid, and stir thoroughly under the protection of an inert gas (such as Ar2) to extract the extractant into the organic solvent; after the ammonium salt of the extractant is completely acidified and dissolved, separate the lower aqueous phase, wash the residual HCl in the organic phase with deionized water, and repeat the washing three times; finally, titrate the concentration of the extractant in the organic phase with NaOH standard solution, and adjust the concentration of the extractant to 0.2-0.5 mol / L with organic solvent.

[0051] Optionally, in step S1, the dilute hydrochloric acid is 20% to 30% excess 3M dilute hydrochloric acid.

[0052] Optionally, in step S1, the co-extractant is an N-containing co-extractant or a neutral co-extractant. The N-containing co-extractant is selected from one of the following: 2,2'-bipyridyl (Bipy) and its derivatives, 1,10-phenanthroline (Bhen) and its derivatives, 2,2':6',2''-tripyridine (Terpy), bis-1,2,4-triazinyl-2,6-pyridine (BTP) and its derivatives; the neutral co-extractant is tributyl phosphate (TBP) or trioctyl phosphate (TEHP).

[0053] Optionally, the organic solvent is selected from toluene, xylene, p-xylene, and kerosene.

[0054] Specifically, in the extraction of the organic phase solution, the concentration of the extractant is 0.2-0.5 mol / L, and the concentration of the co-extractant is 0.002-0.5 mol / L.

[0055] S2, Co-extraction of Am(III) / Cm(III): Co-extraction of Am(III) / Cm(III) with an extractant and a co-extractant in an organic phase solution;

[0056] In step S2, the specific method for co-extracting Am(III) / Cm(III) includes:

[0057] S21. Take the extracted organic phase solution into a centrifuge tube, add an equal volume of 5 mmol / L Nd(NO3)3 & Eu(NO3)3-1.0 mol / L NaNO3 solution (as Ln(III) ions in the An(III) / Ln(III) separation), and adjust the pH of the system to the range of 2.5±0.5. Place the centrifuge tube in a constant temperature shaker and centrifuge to form a pre-equilibrium aqueous-organic phase system.

[0058] S22, take 0.1 mL of each. 241 Am(III), 0.1 mL 244 Cm(Ⅲ) tracer was placed in a small glass vial and slowly heated to remove the solvent and background acid. After the solution in the small glass vial was completely evaporated and cooled thoroughly, the aqueous phase from the pre-equilibrium aqueous-organic phase system was added to the small glass vial to dissolve. 241 Am(Ⅲ), 244 Cm(Ⅲ) tracer; after the aqueous phase in the glass bottle was completely dissolved, it was transferred back to the centrifuge tube, and the centrifuge tube was placed in a constant temperature shaker for extraction and centrifugation to separate the phases, thus obtaining the loaded phase. 241 Am(Ⅲ), 244 The organic phase of Cm(Ⅲ).

[0059] Optionally, in step S21, a small amount of NaOH or HNO3 is added to adjust the pH of the system to the range of 2.5 ± 0.5.

[0060] Specifically, in step S21, the centrifuge tube is placed in a constant temperature shaker at 25°C and shaken for more than 10 minutes before centrifugation; in step S22, the centrifuge tube is placed in a constant temperature shaker at 25°C and shaken for more than 30 minutes before centrifugation.

[0061] S3, Selective Back-Extraction Cm(III): Taking Load 241 Am(Ⅲ), 244 The organic phase of Cm(III) was transferred to a centrifuge tube, and an aqueous solution containing a water-soluble complexing stripping agent was added for selective stripping of Cm(III). After shaking, the phases were separated by centrifugation, and the organic and aqueous phase samples were taken separately to prepare the source and the α count was measured. The separation factor Am(III) / Cm(III) was calculated.

[0062] Optionally, in step S3, the water-soluble complexing stripping agent is selected from dialkylthiodiglycanic acid (L1), dialkyldiglycanic acid (L2), N,N,N',N'-tetraalkyl-diglycanamide (L3), 2-carboxy-6-di(2-alkyl)aminopyridine (L4), carboxylic acid (L5), morpholine-substituted water-soluble diglycanic acid or diglycanamide (L6, L7), hydroxymethyl or hydroxyethyl-substituted diglycanamide (L8, L9), α-hydroxyacetic acid (L... 10Hydroxime acid, etc. (L) 11 One of them.

[0063] Specifically, Cm(III) was selectively back-extracted using aqueous solutions containing water-soluble complexing stripping agents of different concentrations, and the concentration of the water-soluble complexing stripping agent with the highest Am(III) / Cm(III) separation factor was screened out.

[0064] S4, Back-extraction of Am(III): Back-extract the remaining Am(III) from the organic phase once with 1 mol / L HNO3.

[0065] Specifically, in step S4, the concentration of HNO3 is 1~3 mol / L.

[0066] The following examples further illustrate the solvent extraction method for improving the separation factor of trivalent americium curium.

[0067] Example 1

[0068] The extractant used in Example 1 is bis(4-tert-butylphenyl)dithiophosphonic acid, whose structural formula is shown below.

[0069]

[0070] The selected co-extractant was bipyridine (Bipy), whose structural formula is shown below. The diluent was xylene solution.

[0071]

[0072] The selected water-soluble complexing agent is HDEOGA, whose structural formula is shown below.

[0073]

[0074] (1) Preparation of an extraction organic phase solution containing extractant and co-extractant: 0.0025 mol / L bipyridine-0.2 mol / L bis(4-tert-butylphenyl)dithiophosphonic acid-xylene:

[0075] Preparation of 0.2 mol / L bis(4-tert-butylphenyl)dithiophosphonic acid-xylene: Weigh a certain mass of ammonium bis(4-tert-butylphenyl)dithiophosphonic acid solid into a blue-capped bottle, add a certain volume of xylene as a diluent and an excess of 20-30% 3M HCl to acidify the ammonium bis(4-tert-butylphenyl)dithiophosphonic acid. Stir thoroughly under Ar2 protection to extract the bis(4-tert-butylphenyl)dithiophosphonic acid into the xylene. After the ammonium bis(4-tert-butylphenyl)dithiophosphonic acid solid dissolves, separate the lower aqueous phase. Wash the organic phase with deionized water to remove residual HCl, repeating the washing three times. Finally, titrate the concentration of the extractant in the organic phase with NaOH standard solution, and adjust the concentration of the extractant bis(4-tert-butylphenyl)dithiophosphonic acid to 0.2 mol / L with an appropriate amount of xylene.

[0076] Preparation of 0.0025 mol / L bipyridine-0.2 mol / L bis(4-tert-butylphenyl)dithiophosphonic acid-xylene: Accurately weigh a certain mass of bipyridine and dissolve it in the above-mentioned 0.2 mol / L bis(4-tert-butylphenyl)dithiophosphonic acid-xylene solution to prepare a 0.0025 mol / L bipyridine-0.2 mol / L bis(4-tert-butylphenyl)dithiophosphonic acid-xylene solution, which will be used as the extraction organic phase solution.

[0077] (2) Am(III) / Cm(III) was co-extracted with an organic phase solution of 0.0025 mol / L bipyridine-0.2 mol / L bis(4-tert-butylphenyl)dithiophosphonic acid-xylene;

[0078] Take 15 mL of the extracted organic phase solution into a 50 mL centrifuge tube, add 15 mL of 5 mmol / L Nd(NO3)3 & Eu(NO3)3 - 1.0 mol / L NaNO3 solution, and add a very small amount of NaOH or HNO3 to adjust the pH of the system to the range of 2.5 ± 0.5. Place the centrifuge tube in a constant temperature shaker at 25℃ and shake for 10 minutes before centrifuging to form a pre-equilibrium aqueous phase-organic phase system.

[0079] Take 0.1 mL of each 241 Am(III), 0.1 mL 244 Cm(Ⅲ) tracer was placed in a small glass vial and slowly heated to remove the solvent and background acid. After the vial had cooled completely, 1 mL of the aqueous phase from the pre-equilibrated aqueous-organic phase system was added to the vial to dissolve. 241 Am(Ⅲ), 244 Cm(Ⅲ) tracer; the completely dissolved aqueous phase in the glass bottle was transferred back to a 50 mL centrifuge tube, and the centrifuge tube was placed in a constant temperature shaker for 30 minutes of extraction and then centrifuged to separate the phases to obtain the loaded phase. 241 Am(Ⅲ),244 The organic phase of Cm(Ⅲ);

[0080] (3) Selective back-extraction of Cm(III): 2 mL of loading solution was transferred into multiple centrifuge tubes. 241 Am(Ⅲ), 244 The organic phase of Cm(III) was selectively back-extracted by adding 2 mL of the water-soluble complexing agent HDEOGA at concentrations of 0.002 mol / L, 0.004 mol / L, 0.006 mol / L, 0.008 mol / L, 0.01 mol / L, and 0.012 mol / L, respectively. After shaking for 30 minutes, the phases were separated by centrifugation. 0.1 mL samples of both the organic and aqueous phases were taken for source preparation, and α counts were measured. The separation factor Am(III) / Cm(III) was calculated, and the results are as follows: Figure 1 As shown.

[0081] After back-extraction, the separation factor of Am(III) / Cm(III) reached over 10, with the 0.006 mol / L HDEOGA organic phase exhibiting the best separation factor. In the actual separation process, multi-stage countercurrent back-extraction of Am(III) / Cm(III) in the organic phase with 0.006 mol / L HDEOGA can achieve the separation of Am(III) / Cm(III).

[0082] (4) Back-extraction of Am(III): The remaining Am(III) in the organic phase is back-extracted once with 1 mol / L HNO3.

[0083] Example 2

[0084] The extractant used in Example 2 is bis(4-isobutylphenyl)dithiophosphonic acid, whose structural formula is shown below.

[0085]

[0086] The selected co-extractant was phenanthrene-9-phenanthroline (Bphen), whose structural formula is shown below. The diluent was xylene solution.

[0087]

[0088] The selected water-soluble complexing agent is morpholine-substituted diglycine acid (HMOROGA), whose structural formula is shown below.

[0089]

[0090] (1) Prepare an extraction organic phase solution containing extractant and co-extractant: 0.005 mol / L phenanthroline-0.5 mol / L bis(4-isobutylphenyl)dithiophosphonic acid-xylene:

[0091] To prepare a 0.5 mol / L bis(4-isobutylphenyl)dithiophosphonic acid-xylene solution: Weigh a certain mass of ammonium bis(4-isobutylphenyl)dithiophosphonic acid solid into a blue-capped bottle, add a certain volume of xylene as a diluent and an excess of 20-30% 3M HCl to acidify the ammonium bis(4-isobutylphenyl)dithiophosphonic acid. Stir thoroughly under Ar2 protection to extract the bis(4-isobutylphenyl)dithiophosphonic acid into the xylene. After the ammonium bis(4-isobutylphenyl)dithiophosphonic acid solid dissolves, separate the lower aqueous phase. Wash the organic phase with deionized water to remove residual HCl, repeating the washing three times. Finally, titrate the concentration of the extractant in the organic phase with NaOH standard solution, and adjust the concentration of the extractant bis(4-isobutylphenyl)dithiophosphonic acid to 0.5 mol / L with an appropriate amount of xylene.

[0092] Preparation of 0.005 mol / L phenanthroline-0.5 mol / L bis(4-isobutylphenyl)dithiophosphonic acid-xylene: Accurately weigh a certain mass of phenanthroline and dissolve it in the above-mentioned 0.5 mol / L bis(4-isobutylphenyl)dithiophosphonic acid-xylene solution to prepare a 0.005 mol / L phenanthroline-0.5 mol / L bis(4-isobutylphenyl)dithiophosphonic acid-xylene solution, which will be used as the extraction organic phase solution.

[0093] (2) Am(III) / Cm(III) was co-extracted with 0.005 mol / L phenanthroline-0.5 mol / L bis(4-isobutylphenyl)dithiophosphonic acid-xylene in the extractive organic phase solution;

[0094] Take 15 mL of the extracted organic phase solution into a 50 mL centrifuge tube, add 15 mL of 5 mmol / L Nd(NO3)3 & Eu(NO3)3 - 1.0 mol / L NaNO3 solution, and add a very small amount of NaOH or HNO3 to adjust the pH of the system to the range of 2.5 ± 0.5. Place the centrifuge tube in a constant temperature shaker at 25℃ and shake for 10 minutes before centrifuging to form a pre-equilibrium aqueous phase-organic phase system.

[0095] Take 0.1 mL of each 241 Am(III), 0.1 mL 244 Cm(Ⅲ) tracer was placed in a small glass vial and slowly heated to remove the solvent and background acid. After the vial had cooled completely, 1 mL of the aqueous phase from the pre-equilibrated aqueous-organic phase system was added to the vial to dissolve. 241 Am(Ⅲ), 244 Cm(Ⅲ) tracer; and the completely dissolved aqueous phase in the small glass bottle was transferred back to a 50 mL centrifuge tube, and the centrifuge tube was placed in a 25℃ constant temperature shaker for 30 minutes of shaking extraction, followed by centrifugation and phase separation to obtain the loaded phase.241 Am(Ⅲ), 244 The organic phase of Cm(Ⅲ);

[0096] (3) Selective back-extraction of Cm(III): 2 mL of loading solution was transferred into multiple centrifuge tubes. 241 Am(Ⅲ), 244 The organic phase of Cm(III) was selectively back-extracted by adding 2 mL of water-soluble complexing agent HMOROGA solutions at concentrations of 0.003 mol / L, 0.006 mol / L, 0.009 mol / L, 0.012 mol / L, 0.015 mol / L, and 0.018 mol / L, respectively. After shaking for 30 minutes, the phases were separated by centrifugation. 0.1 mL samples of both the organic and aqueous phases were taken for source preparation, and α counts were measured. The Am(III) / Cm(III) separation factor was calculated, and the results are as follows: Figure 2 As shown.

[0097] After back-extraction, the separation factor of Am(III) / Cm(III) reached over 10, with 0.009 mol / L HMOROGA exhibiting a better separation factor for Am(III) / Cm(III) in the organic phase. In the actual separation process, multi-stage countercurrent back-extraction of Am(III) / Cm(III) in the organic phase using 0.009 mol / L HMOROGA can achieve the separation of Am(III) / Cm(III).

[0098] (4) Back-extraction of Am(III): The remaining Am(III) in the organic phase is back-extracted once with 1 mol / L HNO3.

[0099] As can be seen from Examples 1 and 2, using dithiophosphonic acid with long-chain hydrocarbon substituents on the two substituted benzene rings of the phosphorus atom as the extractant, and with the addition of a co-extractant and a water-soluble complexing back-extractant, the separation factor of trivalent actinium curium increased from about 4 to over 10, significantly improving the separation factor of americium curium. The extraction and separation method provided by this invention uses an extractant with stronger stability and a high americium curium separation factor, achieving the separation of trivalent actinium lanthanum and americium curium in a single extraction and separation process with fewer stages.

[0100] Other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein. Thus, the invention also intends to include such variations and adaptations if they fall within the scope of the claims and their equivalents.

[0101] The above embodiments are merely illustrative examples of the present invention. The present invention may also be implemented in other specific ways or forms without departing from its spirit or essential characteristics. Therefore, the described embodiments should be considered illustrative rather than limiting in any respect. The scope of protection of the present invention should be defined by the claims, and any variations equivalent to the intent and scope of the claims should also be included within the scope of the present invention.

Claims

1. A solvent extraction method for improving the separation factor of trivalent americium-curium, characterized in that, The method includes the following steps: S1. Prepare an extractant organic phase solution containing an extractant and a co-extractant: Dissolve the extractant in an organic solvent to form an extractant solution; weigh a specified mass of the co-extractant and dissolve it in the extractant solution to prepare an extractant organic phase solution; wherein, the extractant is a dithiophosphonic acid with long-chain hydrocarbon substituents on two substituted benzene rings on the phosphorus atom; S2. Co-extract Am(III) / Cm(III) using the extracted organic phase solution: Take the extracted organic phase solution into a centrifuge tube, add an equal volume of 5 mmol / L Nd(NO3)3 & Eu(NO3)3-1.0 mol / L NaNO3 solution to form a pre-equilibrium aqueous-organic phase system; take the aqueous phase dissolved in the pre-equilibrium aqueous-organic phase system... 241 Am(Ⅲ), 244 Cm(Ⅲ) tracer was added, and the completely dissolved aqueous phase was transferred back into the centrifuge tube. After extraction, the phases were separated by centrifugation to obtain the loaded sample. 241 Am(Ⅲ), 244 The organic phase of Cm(Ⅲ); S3, Selective Back-Extraction Cm(III): Taking Load 241 Am(Ⅲ), 244 The organic phase of Cm(III) was transferred to a centrifuge tube, and an aqueous solution containing a water-soluble complexing stripping agent was added for selective stripping of Cm(III). After shaking, the phases were separated by centrifugation, and the organic and aqueous phase samples were taken separately to prepare the source and the α count was measured. The separation factor Am(III) / Cm(III) was calculated. S4, the remaining Am(III) in the back-extracted organic phase.

2. The solvent extraction method for improving the separation factor of trivalent americium-curium according to claim 1, characterized in that, In step S1, the extractant is selected from one of the following: di(4-tert-butylphenyl)dithiophosphonic acid, di(4-tert-pentylphenyl)dithiophosphonic acid, di(4-ethylphenyl)dithiophosphonic acid, di(4-propylphenyl)dithiophosphonic acid, di(4-isopropylphenyl)dithiophosphonic acid, di(4-n-butylphenyl)dithiophosphonic acid, di(4-isobutylphenyl)dithiophosphonic acid, di(2,4-diisopropylphenyl)dithiophosphonic acid, di(2,5-diisopropylphenyl)dithiophosphonic acid, di(4-neopentylphenyl)dithiophosphonic acid, and di(4-ethylhexylphenyl)dithiophosphonic acid.

3. The solvent extraction method for improving the separation factor of trivalent americium-curium according to claim 1, characterized in that, In step S1, the preparation method of the extractant solution is as follows: First, weigh the ammonium salt of the extractant, add organic solvent and excess 20-30% of 3 mol / L hydrochloric acid, and stir thoroughly under inert gas protection to extract the extractant into the organic solvent; after the ammonium salt of the extractant is completely acidified and dissolved, separate the lower aqueous phase, wash the residual HCl in the organic phase with deionized water, and repeat the washing three times; finally, titrate the extractant concentration in the organic phase with NaOH standard solution, and adjust the extractant concentration with organic solvent.

4. The solvent extraction method for improving the separation factor of trivalent americium-curium according to claim 1, characterized in that, In step S1, the organic solvent is selected from toluene, xylene, p-xylene, and kerosene.

5. The solvent extraction method for improving the separation factor of trivalent americium-curium according to claim 1, characterized in that, In step S1, the co-extractant is an N-containing co-extractant or a neutral co-extractant; The N-containing co-extractant is selected from one of bipyridine and its derivatives, o-phenanthroline and its derivatives, 2,2':6',2''-tripyridine, bis-1,2,4-triazinyl-2,6-pyridine and its derivatives; the neutral co-extractant is tributyl phosphate or trioctyl phosphate.

6. The solvent extraction method for improving the separation factor of trivalent americium-curium according to claim 1, characterized in that, In the extracted organic phase solution, the concentration of the extractant is 0.2-0.5 mol / L, and the concentration of the co-extractant is 0.002-0.5 mol / L.

7. The solvent extraction method for improving the separation factor of trivalent americium-curium according to claim 1, characterized in that, The specific methods for co-extraction of Am(III) / Cm(III) include: S21. Take the extracted organic phase solution into a centrifuge tube, add an equal volume of 5 mmol / L Nd(NO3)3 & Eu(NO3)3-1.0mol / L NaNO3 solution, and adjust the pH of the system to 2.5±0.

5. Place the centrifuge tube in a constant temperature shaker and centrifuge to form a pre-equilibrium aqueous-organic phase system. S22, take 0.1 mL of each. 241 Am(III), 0.1 mL 244 Cm(Ⅲ) tracer was placed in a small glass vial and slowly heated to remove the solvent and background acid. After the solution in the small glass vial was completely evaporated and cooled thoroughly, the aqueous phase from the pre-equilibrium aqueous-organic phase system was added to the small glass vial to dissolve. 241 Am(Ⅲ), 244 Cm(Ⅲ) tracer; after the aqueous phase in the glass bottle was completely dissolved, it was transferred back to the centrifuge tube, and the centrifuge tube was placed in a constant temperature shaker for extraction and centrifugation to separate the phases, obtaining the loaded phase. 241 Am(Ⅲ), 244 The organic phase of Cm(Ⅲ).

8. The solvent extraction method for improving the separation factor of trivalent americium-curium according to claim 7, characterized in that, In step S21, NaOH or HNO3 is added to adjust the pH of the system to the range of 2.5 ± 0.

5.

9. The solvent extraction method for improving the separation factor of trivalent americium-curium according to claim 7, characterized in that, In step S21, the centrifuge tube is placed in a constant temperature shaker at 25°C and shaken for more than 10 minutes before centrifugation; In step S22, the centrifuge tube is placed in a constant temperature shaker at 25°C and shaken for more than 30 minutes before centrifugation.

10. The solvent extraction method for improving the separation factor of trivalent americium-curium according to claim 1, characterized in that, In step S3, the water-soluble complexing stripping agent is selected from one of the following: dialkylthiodiglycanic acid, dialkyldiglycanic acid, N,N,N',N'-tetraalkyl-diglycanamide, 2-carboxy-6-di(2-alkyl)aminopyridine, carboxylic acid, morpholine-substituted water-soluble diglycanic acid or diglycanamide, hydroxymethyl, hydroxyethyl-substituted diglycanamide, α-hydroxyacetic acid, and hydroxamic acid.

11. The solvent extraction method for improving the separation factor of trivalent americium-curium according to claim 1, characterized in that, In step S3, Cm(III) is selectively back-extracted using aqueous solutions containing water-soluble complexing stripping agents of different concentrations, and the concentration of the water-soluble complexing stripping agent with the highest Am(III) / Cm(III) separation factor is selected.

12. The solvent extraction method for improving the separation factor of trivalent americium-curium according to claim 1, characterized in that, In step S4, the remaining Am(III) in the organic phase is back-extracted once with 1 mol / L HNO3.

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