A method for extracting neptunium without the catalytic action of coexisting ions

Abstract

The present application relates to a method for extracting neptunium without the catalysis of coexisting ions, which comprises the following steps: mixing a neptunium-containing aqueous solution, a phenolic compound and an organic phase containing an extractant to carry out a complexation-reduction-extraction reaction, and obtaining a neptunium-containing organic phase. The method provided by the present application can realize efficient extraction of neptunium without the catalysis of other coexisting metal ions, greatly widening the applicable scenarios of the method. In addition, the method provided by the present application does not need to use a separate reduction step, simplifying the operation process, and can significantly improve the extraction distribution ratio of neptunium compared with the existing salt-free reducing agent system.

Description

Technical Field

[0001] This invention relates to the field of nuclear fuel cycle and nuclide extraction technology, specifically to a method for extracting neptunium without relying on the catalytic action of coexisting ions. Background Technology

[0002] Neptunium (Np), a key component of spent fuel systems, has two main uses: firstly, it can be used in the production of plutonium, a heat source material for aerospace applications; secondly, its long half-life and extreme toxicity pose a persistent threat to the environment. Therefore, the recovery of Np from spent fuel is of significant strategic importance for the resource utilization of nuclear waste and the sustainable development of nuclear energy.

[0003] Np is typically found in spent fuel as pentavalent neptunyl (Np) V O2 + Neptunium exists in the form of monovalent neptunium, while pentavalent neptunium has a low overall charge value, making it difficult to recover directly using conventional extraction systems. Currently, the mainstream neptunium extraction method uses a non-metallic, salt-free reducing agent to convert it into the easily extractable tetravalent form before extraction. However, traditional salt-free reducing agents cannot directly reduce pure neptunium solutions; the process relies on the catalytic action of coexisting metal ions in spent fuel. Furthermore, the components and mechanisms that actually play a catalytic role in the spent fuel system are not yet fully understood. With the construction of various new reactors, the composition of spent fuel produced by different types of reactors and under multiple burnup conditions varies significantly. Therefore, this process relying on unknown catalytic components and conversion mechanisms carries potential operational risks and may not be able to handle the processing of spent fuels with different compositions in the future.

[0004] Therefore, it is imperative to develop a neptunium extraction method that does not depend on other catalytic components in the system (such as other metal ions coexisting in the spent fuel system). Summary of the Invention

[0005] To address the above problems, the present invention aims to provide a method for extracting neptunium without relying on the catalytic action of coexisting ions. Compared with existing technologies, the method provided by the present invention performs complexation-reduction-extraction steps simultaneously, eliminating the need for a separate reduction step. Furthermore, the method provided by the present invention does not require the catalytic action of other coexisting metal ions, greatly expanding the applicability of the method and significantly improving the neptunium extraction distribution ratio under conditions without other catalytic components.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] This invention provides a method for extracting neptunium without relying on coexisting ion catalysis, the method comprising the following steps:

[0008] A complexation-reduction-extraction reaction was carried out on a mixture of neptunium-containing aqueous solution, phenolic compounds, and an organic phase containing an extractant to obtain a neptunium-containing organic phase.

[0009] Because neptunium is usually in the form of pentavalent neptunyl (Np) V O2 + Np(V) exists in a form that is difficult to recover using conventional extraction systems. Therefore, current research uses non-metallic salt-free reducing agents to reduce pentavalent neptunium to tetravalent neptunium before extraction. Due to the large redox potential difference between Np(V) and Np(IV), and because the reduction process involves not only electron transfer but also the stripping of acyl oxygen atoms, conventional salt-free reducing agents are insufficient to independently achieve efficient Np(V)-Np(IV) conversion. Catalysis by coexisting metal ions in the system (e.g., spent fuel systems) is required to lower the activation energy of the reduction reaction. However, given the current lack of clarity regarding the catalytic components and mechanisms, relying solely on the catalytic effect of impurity ions will become a bottleneck limiting Np(V) reduction-extraction in various scenarios.

[0010] In this invention, based on the principle of altering the redox potential of metal ions through organic complexation, an aqueous solution containing neptunium, a phenolic compound, and an organic phase containing an extractant are mixed together to form a complexation-reduction-extraction coupled system. On one hand, by combining the inherent complexation effect of the extractant on neptunium within the solvent extraction system, the redox potential difference of neptunium can be reduced. On the other hand, by specifically selecting phenolic compounds with good hydrophobicity, which are more readily distributed in the organic phase compared to other salt-free reducing agents (especially hydrophilic salt-free reducing agents), the in-situ complexation-reduction-extraction of neptunium in the organic phase is achieved through the distribution effect of phenolic compounds in the organic phase and their reduction effect on neptunium. In summary, the method provided by this invention, through the synergistic effect of phenolic compounds and extractants, can fundamentally eliminate the dependence on coexisting metal ions in neptunium-containing solutions, greatly expanding the applicable scenarios of this method. Research has shown that in neptunium-containing solutions without other co-catalyzing ions, phenolic compounds can independently achieve highly efficient Np(V)-Np(IV) conversion, and compared to commonly used salt-free reducing agents, the neptunium extraction partition ratio can be increased by 1-2 orders of magnitude. Furthermore, the mixing process of the neptunium-containing aqueous solution, phenolic compounds, and the organic phase containing the extractant in this invention can be a direct one-step mixing, or a mixing of the phenolic compounds and the organic phase containing the extractant followed by mixing with the neptunium-containing solution, or a mixing of the neptunium-containing solution and the phenolic compounds followed by mixing with the organic phase containing the extractant. However, the complexation-reduction-extraction process is carried out in the first step under the condition that all three are present simultaneously. Therefore, compared to existing methods that require a reduction agent for a period of time, this invention eliminates the need for a separate reduction step, simplifying the operation process and improving work efficiency.

[0011] Preferably, the phenolic compound includes any one or a combination of at least two of catechol, resorcinol, hydroquinone, or phloroglucinol.

[0012] Preferably, the neptunium-containing aqueous solution comprises an acidic neptunium-containing aqueous solution.

[0013] Preferably, the acidic neptunium-containing aqueous solution contains any one or a combination of at least two of perchloric acid, nitric acid, sulfuric acid, phosphoric acid, or hydrochloric acid.

[0014] In this invention, the system after spent fuel treatment is generally a nitric acid system. The method provided by this invention is not only applicable to nitric acid systems, but also to neptunium-containing systems such as perchloric acid, sulfuric acid, phosphoric acid, or hydrochloric acid.

[0015] Preferably, the acidity of the neptunium-containing aqueous solution is 0.0001-5.0 mol / L, for example, it can be 0.0001 mol / L, 0.0005 mol / L, 0.001 mol / L, 0.005 mol / L, 0.01 mol / L, 0.05 mol / L, 0.1 mol / L, 0.5 mol / L, 1 mol / L, 2 mol / L, 3 mol / L, 4 mol / L or 5 mol / L, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0016] Preferably, the concentration of neptunium ions in the neptunium-containing aqueous solution is 10. -8 -10 -2 mol / L, for example, could be 10 -8 mol / L, 10 -7 mol / L, 10 -6 mol / L, 10 -5 mol / L, 10 -4 mol / L, 10 -3 mol / L or 10 -2 The values ​​are mol / L, but not limited to those listed; other unlisted values ​​within the range also apply.

[0017] Preferably, the phenolic compound is 10% of the neptunium ions contained in the neptunium-containing aqueous solution. 1 -10 6 Multiple equivalent, for example, could be 10 1 times, 10 2 times, 10 3 times, 10 4 times, 10 5 times or 10 6 The value can be multiples of, but is not limited to, the listed values; other unlisted values ​​within the range are also applicable.

[0018] In this invention, it is preferable to control the stoichiometric ratio of neptunium ions in the neptunium-containing aqueous solution of phenolic compounds within a specific range. On the one hand, if the stoichiometric ratio is too low, the content of reducing phenolic compounds will be insufficient, resulting in incomplete reduction of pentavalent neptunium and affecting its efficient extraction. On the other hand, if the stoichiometric ratio is too high, the content of phenolic compounds in the aqueous phase will increase, thereby enhancing their complexation with neptunium in the aqueous phase and affecting the extraction efficiency of neptunium.

[0019] Preferably, the extractant in the organic phase containing the extractant includes any one or a combination of at least two of amide extractants, phosphonic acid extractants, alkyl phosphonic acid extractants, or phosphate ester extractants.

[0020] It should be noted that the stronger the complexation between the extractant molecules and the metal ions, the greater the change in the redox potential difference of the metal ions, which is more conducive to the efficient conversion between different valence states. In this invention, the extractant is preferably any one or a combination of at least two of amide extractants, phosphonic acid extractants, alkylphosphine oxide extractants, or phosphate ester extractants. Through the strong complexation of the selected extractant on neptunium ions, the redox potential difference between different valence states of neptunium ions is reduced, and further combined with the reducing effect of phenolic compounds, efficient conversion between different valence states of neptunium ions is achieved.

[0021] Preferably, the concentration of the extractant in the organic phase containing the extractant is 0.01-3.0 mol / L, for example, it can be 0.01 mol / L, 0.05 mol / L, 0.1 mol / L, 0.5 mol / L, 0.8 mol / L, 1 mol / L, 1.2 mol / L, 1.5 mol / L, 2 mol / L, 2.2 mol / L, 2.5 mol / L, 2.8 mol / L or 3 mol / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0022] Preferably, the organic phase containing the extractant also contains a diluent.

[0023] Preferably, the diluent comprises an aliphatic compound and / or an aromatic compound.

[0024] Preferably, the volume ratio of the neptunium-containing aqueous solution to the extractant-containing organic phase is (1-10):(10-1), for example, it can be 1:10, 2:10, 3:10, 4:10, 5:10, 6:10, 7:10, 8:10, 9:10, 10:1, 9:1, 8:1, 7:1, 6:1, 5:1, 4:1, 3:1, 2:1 or 1:1, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0025] Preferably, stirring is performed during the complexation-reduction-extraction reaction.

[0026] Preferably, the time for the complexation-reduction-extraction reaction is 0.5-10 min, for example, it can be 0.5 min, 1 min, 2 min, 3 min, 4 min, 5 min, 6 min, 7 min, 8 min, 9 min or 10 min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0027] In this invention, the temperature of the complexation-reduction-extraction reaction is generally 10-40℃, for example, it can be 10℃, 15℃, 20℃, 25℃, 30℃, 35℃ or 40℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0028] As a preferred embodiment of the present invention, the method includes the following steps:

[0029] The mixed acidity ranges from 0.0001 to 5.0 mol / L, and the concentration of neptunium ions is 10. -8 -10 -2 A complexation-reduction-extraction reaction is carried out with a mol / L acidic aqueous solution containing neptunium, a phenolic compound, and an organic phase containing an extractant at a concentration of 0.01-3.0 mol / L, and the mixture is stirred for 0.5-10 min. The phenolic compound is a neptunium ion with a concentration of 10 mol / L. 1 -10 6 The volume ratio of the neptunium-containing aqueous solution to the extractant-containing organic phase is (1-10):(10-1), resulting in a neptunium-containing organic phase.

[0030] The phenolic compounds include any one or a combination of at least two of catechol, resorcinol, hydroquinone, or phloroglucinol; the acidic neptunium-containing aqueous solution contains any one or a combination of at least two of perchloric acid, nitric acid, sulfuric acid, phosphoric acid, or hydrochloric acid; the extractant in the organic phase containing the extractant includes any one or a combination of at least two of amide extractants, phosphonic acid extractants, alkylphosphonic oxyphosphate extractants, or phosphate ester extractants; the organic phase containing the extractant also contains a diluent, which includes aliphatic compounds and / or aromatic compounds.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] (1) The method provided by the present invention can achieve efficient complexation-reduction-extraction of neptunium without relying on other catalytic metal ions. Compared with the existing salt-free reduction system, it can improve the neptunium extraction distribution ratio by 1-2 orders of magnitude, greatly expanding the applicable scenarios of the method and avoiding the potential operational risks caused by the unclear catalytic components and catalytic mechanisms in the existing methods.

[0033] (2) The method provided by the present invention does not require a separate reduction step, and realizes complexation-reduction-extraction in situ at the same time, which simplifies the operation process and improves work efficiency.

[0034] (3) The method provided by the present invention is used to extract neptunium-containing aqueous solutions that do not contain other coexisting metal ions, and can achieve an extraction distribution ratio of neptunium of 3.23 or higher, and under preferred conditions, an extraction distribution ratio of 8.24 or higher. Attached Figure Description

[0035] Figure 1 This is a graph showing the neptunium extraction partition ratio results of Example 1 and Comparative Examples 1-8 of the present invention;

[0036] Figure 2 This is a graph showing the neptunium extraction partition ratio results of Example 2 and Comparative Examples 9-16 of the present invention;

[0037] Figure 3 This is a graph showing the neptunium extraction partition ratio results of Example 3 and Comparative Examples 17-24 of the present invention;

[0038] Figure 4 This is a graph showing the neptunium extraction partition ratio results of Example 4 and Comparative Examples 25-32 of the present invention. Detailed Implementation

[0039] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention.

[0040] Example 1

[0041] This embodiment provides a method for extracting neptunium without relying on the catalytic effect of coexisting ions, the method comprising the following steps:

[0042] The mixed acidity is 1 mol / L, and the Np(V) concentration is 10. -8 A complexation-reduction-extraction reaction was carried out in a nitric acid system containing neptunium aqueous solution (excluding metal ions other than Np), hydroquinone, and a 1 mol / L tributylphosphine oxide / n-dodecane organic phase, with stirring for 5 min. The hydroquinone was 10% of Np(V). 6 The neptunium-containing aqueous solution and the tributylphosphine / n-dodecane organic phase are in a volume ratio of 1:1 to obtain the neptunium-containing organic phase.

[0043] Example 2

[0044] This embodiment provides a method for extracting neptunium without relying on the catalytic effect of coexisting ions, the method comprising the following steps:

[0045] The mixed acidity is 0.0001 mol / L, and the Np(V) concentration is 10.-6 A complexation-reduction-extraction reaction was carried out in a sulfuric acid system containing neptunium aqueous solution (excluding metal ions other than Np), catechol, and a 0.5 mol / L di(2-ethylhexyl)phosphoric acid / toluene organic phase, with stirring for 0.5 min. The catechol was 10% of Np(V). 4 The neptunium-containing aqueous solution and the di(2-ethylhexyl)phosphoric acid / toluene organic phase are in a volume ratio of 10:1 to obtain the neptunium-containing organic phase.

[0046] Example 3

[0047] This embodiment provides a method for extracting neptunium without relying on the catalytic effect of coexisting ions, the method comprising the following steps:

[0048] The mixed acidity is 3 mol / L, and the Np(V) concentration is 10. -4 A complexation-reduction-extraction reaction was carried out in a perchloric acid system containing neptunium aqueous solution (excluding metal ions other than Np), resorcinol, and a 3 mol / L tributyl phosphate / n-dodecane organic phase, with stirring for 10 min. The resorcinol was 10% of Np(V). 2 The neptunium-containing aqueous solution and the tributyl phosphate / n-dodecane organic phase are in a volume ratio of 1:10 to obtain the neptunium-containing organic phase.

[0049] Example 4

[0050] This embodiment provides a method for extracting neptunium without relying on the catalytic effect of coexisting ions, the method comprising the following steps:

[0051] The mixed acidity is 5 mol / L, and the Np(V) concentration is 10. -2 A complexation-reduction-extraction reaction was carried out in a hydrochloric acid system containing neptunium aqueous solution (excluding metal ions other than Np), phloroglucinol, and an N,N,N′,N′-tetraoctyl-3-oxopramethylenediamide / n-dodecane organic phase at a concentration of 0.01 mol / L. The mixture was stirred for 5 min. The phloroglucinol was 10% of Np (V). 1 The neptunium-containing aqueous solution and the N,N,N′,N′-tetraoctyl-3-oxopramethylenediamide / n-dodecane organic phase are in a volume ratio of 1:1 to obtain the neptunium-containing organic phase.

[0052] Example 5

[0053] This embodiment provides a method for extracting neptunium without relying on coexisting ion catalysis. The only difference from Example 1 is that hydroquinone is 1 equivalent of Np(V).

[0054] Example 6

[0055] This embodiment provides a method for extracting neptunium without relying on coexisting ion catalysis. The only difference from Example 1 is that hydroquinone is Np(V) 10. 7 Equivalent times.

[0056] Comparative Examples 1-8

[0057] Comparative Examples 1-8 provide a method for extracting neptunium. The only difference between Comparative Example 1 and Example 1 is that hydroquinone is not added. The only difference between Comparative Examples 2-8 and Example 1 is that the hydroquinone is replaced with a salt-free reducing agent, which is ascorbic acid, urea, hydroxylamine hydrochloride, N,N-diethylhydroxylamine, acetaldehyde oxime, 50wt% hydroxylamine aqueous solution and 80wt% hydrazine hydrate, respectively. The equivalent multiple of the salt-free reducing agent to Np(V) is the same as that of hydroquinone.

[0058] Comparative Examples 9-16

[0059] Comparative Examples 9-16 provide a method for extracting neptunium. The only difference between Comparative Example 9 and Example 2 is that catechol is not added. The only difference between Comparative Examples 10-16 and Example 2 is that the catechol is replaced with a salt-free reducing agent, which is ascorbic acid, urea, hydroxylamine hydrochloride, N,N-diethylhydroxylamine, acetaldehyde oxime, 50wt% hydroxylamine aqueous solution and 80wt% hydrazine hydrate, respectively. The equivalent multiple of the salt-free reducing agent to Np(V) is the same as that of the catechol.

[0060] Comparative Examples 17-24

[0061] Comparative Examples 17-24 provide a method for extracting neptunium. The only difference between Comparative Examples 17 and Example 3 is that resorcinol is not added. The only difference between Comparative Examples 18-24 and Example 3 is that the resorcinol is replaced with a salt-free reducing agent, which is ascorbic acid, urea, hydroxylamine hydrochloride, N,N-diethylhydroxylamine, acetaldehyde oxime, 50 wt% hydroxylamine aqueous solution and 80 wt% hydrazine hydrate, respectively. The equivalent multiple of the salt-free reducing agent to Np(V) is the same as that of resorcinol.

[0062] Comparative Examples 25-32

[0063] Comparative Examples 25-32 provide a method for extracting neptunium. The only difference between Comparative Example 25 and Example 4 is that phloroglucinol is not added. The only difference between Comparative Examples 26-32 and Example 4 is that the phloroglucinol is replaced with a salt-free reducing agent, which is ascorbic acid, urea, hydroxylamine hydrochloride, N,N-diethylhydroxylamine, acetaldehyde oxime, 50wt% hydroxylamine aqueous solution and 80wt% hydrazine hydrate, respectively. The equivalent multiple of the salt-free reducing agent to Np(V) is the same as that of phloroglucinol.

[0064] The extraction partition ratio of neptunium in Examples 1-6 and Comparative Examples 1-32 was calculated, and D Np = Radioactivity of neptunium in the organic phase / Radioactivity of neptunium in the aqueous phase, wherein the radioactivity of neptunium in both the organic and aqueous phases was determined using a liquid scintillation detector. The results of Examples 1-6 are shown in Table 1, and the neptunium extraction partitions of Examples 1 and Comparative Examples 1-8 are shown in Table 2 and... Figure 1 As shown, the neptunium extraction partitions of Examples 2 and Comparative Examples 9-16 are shown in Table 3 and Figure 2 As shown, the neptunium extraction partitions of Examples 3 and Comparative Examples 17-24 are illustrated in Table 4 and... Figure 3 As shown, the neptunium extraction partition ratios for Example 4 and Comparative Examples 25-32 are presented in Table 5 and... Figure 4 As shown.

[0065] Table 1

[0066]

[0067]

[0068] Table 2

[0069] reducing agent <![CDATA[Distribution ratio D of neptunium extraction Np > Example 1 hydroquinone 8.24 Comparative Example 1 - 0.30 Comparative Example 2 ascorbic acid 0.40 Comparative Example 3 Urea 0.46 Comparative Example 4 Hydroxylamine hydrochloride 0.34 Comparative Example 5 N,N-Diethylhydroxylamine 0.30 Comparative Example 6 Acetaldehyde oxime 0.31 Comparative Example 7 50wt% hydroxylamine aqueous solution 0.28 Comparative Example 8 80% hydrazine hydrate 0.31

[0070] Table 3

[0071]

[0072]

[0073] Table 4

[0074] reducing agent <![CDATA[Distribution ratio D of neptunium extraction Np > Example 3 resorcinol 9.16 Comparative Example 17 - 0.30 Comparative Example 18 ascorbic acid 0.21 Comparative Example 19 Urea 0.23 Comparative Example 20 Hydroxylamine hydrochloride 0.14 Comparative Example 21 N,N-Diethylhydroxylamine 0.15 Comparative Example 22 Acetaldehyde oxime 0.17 Comparative Example 23 50wt% hydroxylamine aqueous solution 0.14 Comparative Example 24 80% hydrazine hydrate 0.19

[0075] Table 5

[0076]

[0077]

[0078] In the table, "-" indicates that no reducing agent is added.

[0079] (1) As can be seen from the data in Table 1, the method provided by the present invention can achieve an extraction distribution ratio of neptunium of 3.23 or higher without relying on other catalytic metal ions, and under better conditions it can achieve an extraction distribution ratio of 8.24 or higher.

[0080] (2) As can be seen from the data of Examples 1 and 5-6 in Table 1, the hydroquinone in Example 1 was 10 Np(V). 6 This is equivalent to 10 times the amount of hydroquinone Np(V) in Examples 5-6. 1 and 107 In terms of equivalent ratio, the neptunium extraction partition ratio in Example 1 reached 8.24, while in Examples 5 and 6 it only reached 3.23 and 4.35, respectively. It can be seen that the present invention preferably controls the equivalent ratio of phenolic compounds to Np(V) within a specific range, which can further coordinate the interaction between the extractant, Np(V) and phenolic compounds, thereby further improving the neptunium extraction partition ratio.

[0081] (3) As can be seen from the data of the examples and comparative examples in Tables 2-5, the present invention can achieve a higher extraction partition ratio by using phenolic compounds as reducing agents compared with not using a reducing agent or using other salt-free reducing agents. Taking the comparison between Example 1 and Comparative Examples 1-8 as an example, the extraction partition ratio in Example 1 can reach 8.24, while the maximum extraction partition ratio in Comparative Examples 1-8 can only reach 0.46. It can be seen that the method provided by the present invention can improve the extraction partition ratio of neptunium by 1-2 orders of magnitude without relying on other catalytic metal ions.

[0082] In summary, the method provided by this invention can achieve efficient complexation-reduction-extraction of neptunium without relying on other catalytic metal ions, greatly expanding the applicable scenarios of the method, simplifying the operation process, and improving work efficiency.

[0083] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for extracting neptunium without relying on coexisting ion catalysis, characterized in that, The method includes the following steps: A complexation-reduction-extraction reaction was carried out on a mixture of an aqueous solution containing neptunium, a phenolic compound, and an organic phase containing an extractant to obtain an organic phase containing neptunium. The phenolic compound is any one or a combination of at least two of catechol, resorcinol, hydroquinone, or phloroglucinol. The complexation-reduction-extraction reaction is carried out in one step, wherein the extractant complexes the neptunium ions, reduces the redox potential difference of neptunium, and the hydrophobic phenolic compound is distributed in the organic phase and reduces the neptunium, and the neptunium extraction-distribution ratio reaches 3.23 or higher.

2. The method according to claim 1, characterized in that, The neptunium-containing aqueous solution includes an acidic neptunium-containing aqueous solution.

3. The method according to claim 2, characterized in that, The acidic neptunium-containing aqueous solution contains any one or a combination of at least two of the following: perchloric acid, nitric acid, sulfuric acid, phosphoric acid, or hydrochloric acid.

4. The method according to claim 2, characterized in that, The acidity of the neptunium-containing aqueous solution is 0.0001-5.0 mol / L.

5. The method according to claim 1, characterized in that, The concentration of neptunium ions in the neptunium-containing aqueous solution is 10. -8 -10 -2 mol / L.

6. The method according to claim 1, characterized in that, The phenolic compound is 10% of the neptunium ions contained in the neptunium-containing aqueous solution. 1 -10 6 Equivalent times.

7. The method according to claim 1, characterized in that, The extractant in the organic phase containing the extractant includes any one or a combination of at least two of the following: amide extractants, phosphonic acid extractants, alkyl phosphonic acid extractants, or phosphate ester extractants.

8. The method according to claim 1, characterized in that, The concentration of the extractant in the organic phase containing the extractant is 0.01-3.0 mol / L.

9. The method according to claim 1, characterized in that, The organic phase containing the extractant also contains a diluent.

10. The method according to claim 9, characterized in that, The diluent includes aliphatic compounds and / or aromatic compounds.

11. The method according to claim 1, characterized in that, The volume ratio of the neptunium-containing aqueous solution to the extractant-containing organic phase is (1-10):(10-1).

12. The method according to claim 1, characterized in that, Stirring is performed during the complexation-reduction-extraction reaction.

13. The method according to claim 1, characterized in that, The complexation-reduction-extraction reaction takes 0.5-10 min.

14. The method according to claim 1, characterized in that, The method includes the following steps: The mixed acidity ranges from 0.0001 to 5.0 mol / L, and the concentration of neptunium ions is 10. -8 -10 -2 A complexation-reduction-extraction reaction is carried out with a mol / L acidic aqueous solution containing neptunium, a phenolic compound, and an organic phase containing an extractant at a concentration of 0.01-3.0 mol / L, and the mixture is stirred for 0.5-10 min. The phenolic compound is a neptunium ion with a concentration of 10 mol / L. 1 -10 6 The volume ratio of the neptunium-containing aqueous solution to the extractant-containing organic phase is (1-10):(10-1), resulting in a neptunium-containing organic phase. The acidic neptunium-containing aqueous solution contains any one or a combination of at least two of perchloric acid, nitric acid, sulfuric acid, phosphoric acid, or hydrochloric acid. The extractant in the organic phase containing the extractant includes any one or a combination of at least two of amide extractants, phosphonic acid extractants, alkylphosphonic oxyphosphate extractants, or phosphate ester extractants. The organic phase containing the extractant also contains a diluent, which includes aliphatic compounds and / or aromatic compounds.

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