CN115626877B - Selenium-tungsten polyacid, preparation method thereof and application thereof in ultrafiltration separation of actinide ions - Google Patents

Abstract

The invention discloses a seleno-tungstic acid, a preparation method and application thereof in ultrafiltration separation of actinium ions, wherein the seleno-tungstic acid { Se } ₆ W ₄₅ [ CH ] ₃ ) ₂ NH ₂ ] ₁₅ Na _0.8 (H ₃ O) _8.2 [Se ₆ W ₄₅ O ₁₅₉ (H ₂ O) ₉ ]·27H ₂ O belongs to monoclinic system, and the space group is P2 ₁ The unit cell parameters are: a= 15.6207 (6), b= 33.5801 (11), c= 20.8294 (7), α=90°, β= 98.130 (2) °, γ=90°,

by mixing precursor Na ₂₄ [H ₆ Se ₆ W ₃₉ O ₁₄₄ ]·74H ₂ O is dissolved in water, organic amine and inorganic acid are added in sequence for treatment, and the seleno-tungstic acid { Se) is obtained ₆ W ₄₅ }. Seleno-tungstic acid { Se } ₆ W ₄₅ A cavity was provided with a planar donor site that precisely coordinated to the pentagonal cone coordination geometry of the hexavalent actinide ion. The selenium tungsten polyacid { Se } ₆ W ₄₅ The nano-scale clusters can be formed by selectively coordinating hexavalent actinium ions, so that the efficient complexing and separation of actinium ions are realized, the interception coefficient of actinium ions is up to 96%, the recovery rate of ultrafiltration separation americium is up to more than 92%, and the problem that hexavalent americium is difficult to stabilize and separate is effectively solved.

Description

A kind of selenide tungstic acid and its preparation method and its application in ultrafiltration separation of actinide ions

technical field

The invention relates to the technical field of adsorption and separation, in particular to selenium tungsten polyacid {Se ₆ W ₄₅ }, its preparation method and its application in the ultrafiltration separation of actinide ions.

Background technique

Americium (Am), a by-product of nuclear power generation, is a major contributor to the long-term radiotoxicity of high-level waste (HLW) in the nuclear fuel cycle. The effective recovery of Am and its transformation into short-lived or stable nuclides will greatly reduce the impact of nuclear energy on the environment. In HLW, the coexistence of lanthanides (Lns) with high neutron cross-sections severely affects their transmutation efficiency, thus requiring an effective separation between Am and Lns, which is one of the most challenging chemical separations in modern industry. This difficulty mainly stems from their similar chemical behavior, since both Am and Lns exist in solution as thermodynamically stable trivalent cations, especially with nearly identical ionic radii and coordination chemistries.

Conventional separation methods exploit the subtle bonding differences between trivalent Am ions and Lns ions, where nitrogen- or sulfur-containing extractants cause Am to be preferentially assigned over Lns through a solvent extraction process. However, this separation strategy is still hampered by the limited ability to distinguish between Am(III) and Ln(III) and the generation of large amounts of secondary radioactive organic waste. At present, although researchers from various countries have explored various techniques, including solvent extraction, precipitation and ion exchange methods, the reduction potentials of AmO ₂ ²⁺ /AmO ₂ ⁺ and AmO ₂ ²⁺ /Am ³⁺ are 1.60V and 1.68V (vs. SCE at pH 0). Thus, when Am(VI) ions contact organic extractants/solvents or pass through the column, Am(III) species can be generated within seconds, making these separations much less efficient. Therefore, there is an urgent need for a method for efficiently separating actinide ions (including americium) and lanthanide ions.

Contents of the invention

The technical problem to be solved by the present invention is to provide a kind of selenide tungsten polyacid {Se ₆ W ₄₅ } and its preparation method and its application in the ultrafiltration separation of actinide ions. Selenide tungstic polyacid {Se ₆ W ₄₅ } for holes, this site can precisely coordinate with the pentagonal bipyramidal coordination geometry of actinide ions (AnO ₂ ²⁺ ), but is not suitable for binding the globular coordination of lanthanide ions By coordinating selenide tungsten polyacid {Se ₆ W ₄₅ } with hexavalent actinide ions to form nanoscale clusters, the efficient separation of actinide ions and lanthanide ions is achieved.

In order to solve the above technical problems, the present invention provides the following technical solutions:

The first aspect of the present invention provides a selenium tungstic acid {Se ₆ W ₄₅ }, whose chemical formula is [(CH ₃ ) ₂ NH ₂ ] ₁₅ Na _0.8 (H ₃ O) _8.2 [Se ₆ W ₄₅ O ₁₅₉ (H ₂ O) ₉ ]·27H ₂ O; the polyacid {Se ₆ W ₄₅ } belongs to the monoclinic crystal system, the space group is P2 ₁ /m, and the unit cell parameters are: a=15.6207(6), b=33.5801( 11), c=20.8294(7), α=90°, β=98.130(2)°, γ=90°,

The second aspect of the present invention provides a method for preparing the selenium tungstic acid {Se ₆ W ₄₅ } described in the first aspect, adding an organic amine salt and an inorganic acid to the aqueous solution of the precursor polyacid {Se ₆ W ₃₉ }, After the acidification treatment, the polyselenotungstic acid {Se ₆ W ₄₅ } is obtained by standing still; the precursor polyacid {Se ₆ W ₃₉ } is Na ₂₄ [H ₆ Se ₆ W ₃₉ O ₁₄₄ ]·74H ₂ O.

Further, add an organic amine salt to the aqueous solution of the precursor polyacid {Se ₆ W ₃₉ }, stir and dissolve, then add an inorganic acid for acidification treatment, and obtain the selenium tungsten polyacid {Se ₆ W 39 } after standing for 12-36 hours ₄₅ } Crystal.

Further, the organic amine salt is dimethylammonium chloride and/or dimethylammonium nitrate.

Further, the inorganic acid is nitric acid and/or hydrochloric acid.

Further, the molar ratio of the precursor polyacid {Se ₆ W ₃₉ }, organic amine salt and inorganic acid is 1:100-150:100-150, for example 1:145:126.

Further, after standing still, the crystals of selenotungstic acid {Se ₆ W ₄₅ } were washed with cold water, and dried at room temperature for later use.

The third aspect of the present invention provides an application of the selenide tungstic acid {Se ₆ W ₄₅ } described in the first aspect in the ultrafiltration separation of actinide ions.

Further, add an oxidizing agent to the aqueous solution containing actinide ions, and after the actinide ions are converted into AnO ₂ ²⁺ , then add selenium tungstic acid {Se ₆ W ₄₅ } and AnO ₂ ²⁺ to form nano-scale clusters for super Separation by filtration; Wherein, An is U, Np, Pu or Am;

Further, in step (1), the oxidizing agent is high copper periodate.

Further, in step (1), the nanoscale clusters are formed under the condition of pH≤1.

The fourth aspect of the present invention provides an application of the selenide tungstic polyacid {Se ₆ W ₄₅ } described in the first aspect in separating americium ions and lanthanide ions.

Further, add an oxidizing agent to the solution containing americium ions and lanthanide ions to convert the americium ions into AmO ₂ ²⁺ , then add selenium tungstic acid {Se ₆ W ₄₅ } and AmO ₂ ²⁺ to form nanoscale clusters, Nanoscale clusters are obtained by ultrafiltration separation, and the nanoscale clusters retained after separation are collected.

Further, the nano-scale clusters formed by selenide tungstic acid {Se ₆ W ₄₅ } and AmO ₂ ²⁺ were reduced to obtain trivalent americium ions, and the released selenide tungstic acid {Se ₆ W ₄₅ } was recovered by ultrafiltration.

Beneficial effects of the present invention:

1. The present invention has designed and synthesized a water-soluble cavernous selenium tungsten polyacid {Se ₆ W ₄₅ }, which is equipped with a hole with a planar donor site, which can be combined with the pentagonal doublet of AnO ₂ ²⁺ The cone coordination geometry is precisely matched, and it is completely unsuitable for binding spherical coordination of lanthanide ions. Therefore, the synthesized selenium tungstic acid {Se ₆ W ₄₅ } can be precisely coordinated with AnO ₂ ²⁺ to form nanoscale clusters , so that hexavalent actinide ions, especially hexavalent americium ions, can be stabilized to a level sufficient for separation applications, effectively solving the problem of instability of hexavalent americium ions in the oxidation method, and realizing efficient separation of americium ions and lanthanide ions.

2. The present invention forms nano-scale clusters based on selenium tungsten polyacid {Se ₆ W ₄₅ } recognition coordination AnO ₂ ²⁺ , improves the stability of hexavalent actinide ions, and utilizes the size difference between nano-scale clusters and lanthanide ions , the fast and efficient separation of actinide ions and lanthanide ions is realized by the method of ultrafiltration separation. This technical method is simple to operate, low in energy consumption, and has no secondary organic waste liquid, which is environmentally friendly. The efficient separation of actinium ions provides a new idea.

Description of drawings

Figure 1 is a schematic diagram of the assembly of selenium tungstic acid {Se ₆ W ₄₅ } synthesized from the precursor polyacid {Se ₆ W ₃₉ } in Example 1;

Fig. 2 is the UV-vis-NIR spectrogram in the spectral titration process of embodiment 2, UO ₂ ²⁺ (a), PuO ₂ ²⁺ (b), NpO ₂ ²⁺ (c) and AmO ₂ ²⁺ (d) ;

Fig. 3 is the UV-vis-NIR spectrum of the 0.25mM Am 0.1M HNO aqueous solution oxidized by periodate high copper (III) in the presence of 2.0eq selenium tungstic acid {Se ₆ W ₄₅ } for 24h _;

Figure 4 shows the self-reduction of Am(VI) in the presence of polyacid {Se ₆ W ₄₅ } or in the presence of dodecane;

Figure 5 is the chemical equation for the assembly reaction of selenide tungstic acid {Se ₆ W ₄₅ } and hexavalent actinide ions;

Fig. 6 is the structure chart of An(VI)-POM, An(VI) and the average bond length table of An=O;

Figure 7 is a single crystal picture of U(VI)-POM, Np(VI)-POM, Pu(VI)-POM and Am(VI)-POM and its UV-vis-NIR spectrum;

Fig. 8 is U(VI), Np(VI), Pu(VI), Am(VI) ultrafiltration separation coefficient of rejection;

Fig. 9 is the comparison of separation factor and recovery rate in the nanometer polyacid ultrafiltration described in embodiment 4 and other americium oxidation separation technologies;

Fig. 10 is a schematic diagram of separating americium ions and lanthanide ions by using selenium tungstic acid {Se ₆ W ₄₅ } ultrafiltration separation method.

Detailed ways

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field of the invention. The terms used herein in the description of the present invention are for the purpose of describing specific embodiments only, and are not intended to limit the present invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, so that those skilled in the art can better understand the present invention and implement it, but the examples given are not intended to limit the present invention.

The synthesis of embodiment 1 selenide tungstic acid {Se ₆ W ₄₅ }

This example involves the synthesis of a selenium tungstic polyacid {Se ₆ W ₄₅ }, the synthesis schematic diagram is shown in Figure 1, and the specific preparation process is as follows:

Add 30 mg of Na ₂₄ [H ₆ Se ₆ W ₃₉ O ₁₄₄ ]·74H ₂ O({Se ₆ W ₃₉ }) (0.0024 mmol) into a vial, dissolve it with 800 μL of aqueous solution, and add 30 mg of (CH ₃ ) ₂ NH ₂ Cl (0.368mmol), stirred and dissolved, then added 20 μL 6M HNO ₃ solution to acidify. After standing for one day, colorless blocky crystals were obtained at the bottom of the solution. The resulting crystalline product was washed with cold water and dried at room temperature.

变为/>

且多酸{Se₆W₄₅}带有的空穴具有四个平面氧配体的位点。经单晶X射线衍射(SCXRD)分析，制备得到的多酸[(CH₃)₂NH₂]₁₅Na_0.8(H₃O)_8.2[Se₆W₄₅O₁₅₉(H₂O)₉]·27H₂O(简写为{Se₆W₄₅})。元素分析理论值:C,2.81；H 1.70；N,1.64；Na,0.14；Se,3.69；W,64.60.实验值((％)):C,3.18；H,1.34；N,1.68；Na,0.14；Se,3.73；W,63.29。{Se₆W₄₅}属于单斜晶系，空间群为P2₁/m，晶胞参数为：a＝15.6207(6),b＝33.5801(11),c＝20.8294(7)，α＝90°,β＝98.130(2)°,γ＝90°,/>

As shown in Figure 1, the precursor polyacid {Se ₆ W ₃₉ } and organic amine form the target selenide tungstic acid {Se ₆ W ₄₅ } under acidic conditions, and the hole diameter is given by

becomes />

And the hole contained by the polyacid {Se ₆ W ₄₅ } has four planar oxygen ligand sites. According to single crystal X-ray diffraction (SCXRD) analysis, the prepared polyacid [(CH ₃ ) ₂ NH ₂ ] ₁₅ Na _0.8 (H ₃ O) _8.2 [Se ₆ W ₄₅ O ₁₅₉ (H ₂ O) ₉ ]·27H ₂ O (abbreviated as {Se ₆ W ₄₅ }). Theoretical value of elemental analysis: C, 2.81; H 1.70; N, 1.64; Na, 0.14; Se, 3.69; W, 64.60. Experimental value ((%)): C, 3.18; 0.14; Se, 3.73; W, 63.29. {Se ₆ W ₄₅ } belongs to the monoclinic crystal system, the space group is P2 ₁ /m, and the unit cell parameters are: a＝15.6207(6), b＝33.5801(11), c＝20.8294(7), α＝90° ,β=98.130(2)°,γ=90°,/>

Example 2 Complexation of selenium tungstic acid {Se ₆ W ₄₅ } and hexavalent actinide ions

This embodiment takes actinide elements (An) ²³⁸ U, ²³⁷ Np, ²⁴² Pu and ²⁴³ Am as examples to study the complexing ability of selenium tungsten polyacid {Se ₆ W ₄₅ } to hexavalent actinide ions. The specific operations are as follows:

(1) Preparation of hexavalent actinide ions AnO ₂ ²⁺ : Take 400 μL of actinide ions (0.575 mM) in 0.1M HNO ₃ aqueous solution, add 1.7 mg of high copper periodate, shake for 10 minutes, and measure the concentration by ultraviolet-visible - A near-infrared (UV-vis-NIR) spectrometer monitors the generation of AnO ₂ ²⁺ ions.

(2) Complexation of selenide tungstic acid {Se ₆ W ₄₅ } and hexavalent actinide ions: Dissolve the selenide tungstic acid {Se ₆ W ₄₅ } prepared by the method described in Example 1 in 0.1M HNO ₃ aqueous solution Prepare 2.0mM selenide tungstic acid {Se ₆ W ₄₅ } solution, add the selenide tungstic acid {Se ₆ W ₄₅ } solution dropwise to the solution containing hexavalent actinide ions AnO ₂ ²⁺ in step (1) (10 μL each time), after shaking, observe the change of the characteristic absorption peak of An(VI) by a spectrometer.

Spectral titration results are shown in Figures 2a-2d, among which, Figures 2b-2d are the results of adding selenium tungstic acid {Se ₆ W ₄₅ } to NpO ₂ ²⁺ , PuO ₂ ²⁺ , and AmO ₂ ²⁺ solutions respectively. Spectral change diagram, it can be seen from the figure that the corresponding characteristic absorption peaks changed significantly after adding selenium tungsten polyacid {Se ₆ W ₄₅ }; in Figure 2b, the wavelength 831nm corresponds to the characteristic peak of PuO ₂ ²⁺ , and the wavelength 841nm corresponds to It is the characteristic peak of PuO ₂ ²⁺ -polyacid {Se ₆ W ₄₅ } complex (referred to as Pu(VI)-POM), with the increase of selenium tungstic acid {Se ₆ W ₄₅ } titration, the characteristic peak corresponding to 831nm The absorption of the peak decreases, and the corresponding absorption of the characteristic peak of Pu(VI)-POM corresponding to 841nm increases; in Figure 2c, the wavelength 1224nm corresponds to the characteristic peak of NpO ₂ ²⁺ , and the wavelength 1251nm corresponds to NpO ₂ ²⁺ -polyacid The characteristic peak of {Se ₆ W ₄₅ } complex (Np(VI)-POM for short); in Figure 2d, the wavelength 666nm corresponds to the characteristic peak of AmO ₂ ²⁺ , and the wavelength 677nm corresponds to AmO ₂ ²⁺ -polyacid{ The characteristic peak of Se ₆ W ₄₅ } complex (referred to as Am(VI)-POM). According to the calculation of the titration data, a 1:1 complex is formed between the above-mentioned AnO ₂ ^{2 +} and selenide tungstic acid {Se ₆ W ₄₅ }.

Further research on the stability of complexes formed by selenide tungstic acid {Se ₆ W ₄₅ } and hexavalent actinide ions AnO ₂ ²⁺ , taking the extremely unstable Am(VI) as an example, at 2.0eq selenium tungstic acid In the presence of {Se ₆ W ₄₅ }, the change of UV-vis-NIR spectrum of 0.25 mMAm 0.1 M HNO ₃ aqueous solution oxidized with copper(III) periodate within 24 hours is shown in Fig. 3, and the complexed product is only Reduced by 0.67%; In addition, the self-reduction rate of Am(VI) in the presence of selenide tungstic acid {Se ₆ W ₄₅ } or dodecane was studied, the results are shown in Figure 4, Am(VI) in polyacid The reduction kinetic rate in the system is only -5.71×10 ^-4 mM/h, which is at least two orders of magnitude slower than the self-reduction or dodecane-induced reduction kinetic rate of free AmO ₂ ²⁺ ions. From the above solution chemical test results, it can be seen that with the help of the strong complexation of inorganic selenide tungstic acid {Se ₆ W ₄₅ }, Am(VI) can be continuously stabilized to the level of separation application that could not be achieved before.

The crystal structure of embodiment 3 hexavalent actinide polyacids (An(VI)-POM)

In order to further explore the interaction between AnO ₂ ²⁺ ions and selenide tungstic acid {Se ₆ W ₄₅ }, this example uses AnO ₂ ²⁺ ions (An= ²³⁸ U, ²³⁷ Np, ²⁴² Pu and ²⁴³ Am) A series of An(VI)-POM crystals were prepared by reacting with selenide tungstic acid {Se ₆ W ₄₅ } in solution. The preparation conditions and results are shown in Fig. 5. Among them, UO ₂ ²⁺ , NpO ₂ ²⁺ , PuO ₂ ²⁺ were reacted with selenium tungstic acid {Se ₆ W ₄₅ } at room temperature and pH 1 for 1 day to obtain the corresponding An(VI)-POM crystals, AmO ₂ ²⁺ and selenium tungstic acid {Se ₆ W ₄₅ } was reacted at 4°C and pH 1 for 6h to obtain Am(VI)-POM single crystal.

为了证明硒钨多酸{Se₆W₄₅}中AnO₂ ²⁺离子的氧化态，利用这些单晶样品测试了固态UV-vis-NIR吸收光谱，如图7所示，展示了典型电子跃迁，包括349nm(UO₂ ²⁺)的电荷转移跃迁和841nm(PuO₂ ²⁺)、1242nm(NpO₂ ²⁺)以及674nm(AmO₂ ²⁺)的5f→5f跃迁，与实施例2中光谱滴定结果相吻合。Single crystal X-ray diffraction (SCXRD) analysis shows that the above-mentioned An(VI)-POM single crystals have isomorphic structures, and all belong to the monoclinic space group P2 ₁ /m; as shown in Figure 6, AnO ₂ ²⁺ ions are completely encapsulated in Inside the predesigned holes, the equatorial oxygen atoms of AnO ₂ ²⁺ ions are provided by four different WO ₆ ^6- groups and a coordination water, forming a pentagonal bipyramidal coordination geometry. In An(VI)-POM, the average An=O axial bond lengths of U(VI), Np(VI), Pu(VI) and Am(VI) are 1.734(2), 1.727(3), 1.714, respectively (4) and

In order to prove the oxidation state of AnO ₂ ²⁺ ions in selenide tungstic acid {Se ₆ W ₄₅ }, solid-state UV-vis-NIR absorption spectra were tested using these single crystal samples, as shown in Figure 7, showing typical electronic transitions, Including 349nm (UO ₂ ²⁺ ) charge transfer transition and 841nm (PuO ₂ ²⁺ ), 1242nm (NpO ₂ ²⁺ ) and 674nm (AmO ₂ ²⁺ ) 5f → 5f transition, and the spectral titration results in Example 2 match.

According to the above crystallographic results and spectral data results, it can be seen that the holes in selenide tungstic acid {Se ₆ W ₄₅ } can precisely match the coordination geometry of AnO ₂ ²⁺ ions.

Example 4 Selenium tungstic acid {Se ₆ W ₄₅ } ultrafiltration separation of actinide ions

In this example, selenium tungsten polyacid {Se ₆ W ₄₅ } is used to separate hexavalent americium ions by ultrafiltration, which mainly includes oxidation, nano-scale cluster assembly, ultrafiltration separation and reduction recovery process. The specific operation steps are as follows:

(1) Oxidation: Take 400 μL of Am(III) (0.25 mM) in 0.1M HNO ₃ aqueous solution, add 1.7 mg of high copper periodate, shake for 10 minutes, and determine about 99% Am(VI) by spectroscopy;

(2) Nanoscale cluster assembly: Take 80 μL of the oxidized Am solution, add it to 1.0 mL of 0.1M HNO ₃ aqueous solution containing selenium tungstic acid {Se ₆ W ₄₅ } (polyacid concentration 0.5 mg/mL), place Shake the shaker for 5 minutes;

(3) Ultrafiltration separation: take 450 μL and use a 0.5mL ultrafiltration tube (Pall, 3kDa MWCO) to centrifuge for 10-20 minutes under the centrifugal force of 5000×g in a centrifuge to obtain nano-scale cluster Am(VI)-POM;

(4) Reduction recovery: Am(III) is obtained by adding hydrogen peroxide to the purified Am(VI)-POM, which is recovered by ultrafiltration to release selenium tungstic acid {Se ₆ W ₄₅ } for the next separation cycle.

Take 100 μL each of the starting americium polyacid mixed solution, the permeate separated by ultrafiltration in step (3) and the permeate separated by ultrafiltration in step (4), add 2 mL of liquid flash liquid and mix well, then use liquid flash The radioactivity was measured by the instrument. In order to quantify the separation effect, the rejection coefficient (R) was calculated by the following formula:

R=(1-C _p /C _f )×100% (I)

Wherein, C _f and C _p are α radioactive counts (CPM) in the initial americium polyacid mixed solution and the permeate after ultrafiltration in step (3), respectively.

In addition, this embodiment adopts the above-mentioned multi-acid complex ultrafiltration method to process U(VI), Np(VI), Pu(VI) and Eu(III) respectively, and the results are shown in Figure 8, where U(VI), The rejection coefficients of Np(VI), Pu(VI) and Am(VI) are all over 90%, and Eu is still a trivalent ion after the above-mentioned oxidation treatment, and its rejection coefficient is only 1.7±0.6%, as shown in Figure 9, The separation factor of americium and lanthanide ions separated by the ultrafiltration separation method of the present invention is greater than 750, which is much higher than other separation techniques. The rate of recovery is obtained by calculating the ratio of the permeate after the ultrafiltration separation of step (4) and the alpha radioactive count in the initial americium polyacid mixed solution, and the rate of recovery after calculating Am through the above-mentioned method is higher than 92%, which is significantly higher than The corresponding data of other americium oxidation-related separation technologies disclosed so far are summarized in Table 1 below.

Table 1 Americium recovery rate in americium oxidation separation technology

Ref.1: B.J.Mincher, L.R.Martin, N.C.Schmitt, Solv.Extract.Ion Exch.30,445-456(2012).

Ref. 2: M. Kamoshida, T. Fukasawa, J. Nucl. Sci. Technol. 33, 403-408 (1996).

Ref. 3: M. Kamoshida, T. Fukasawa, F. Kawamura, J. Nucl. Sci. Technol. 35, 185-189 (1998).

Ref.4:B.J.Mincher et al.,Solv.Extract.Ion Exch.32,153-166(2014).

Ref.5: J.D.Burns, B.A.Moyer, Inorg.Chem.55, 8913-8919(2016).

Ref. 6: Y. Koma, A. Aoshima, M. Kamoshida, A. Sasahira, J. Nucl. Sci. Technol. 3, 317-32 (2002).

The above U(VI), Np(VI), Pu(VI), Am(VI) respectively refer to UO ₂ ²⁺ , NpO ₂ ²⁺ , PuO ₂ ²⁺ , AmO ₂ ²⁺ ; Am(III), Eu( III) respectively refer to the trivalent ions of the corresponding elements.

The above-mentioned embodiments are only preferred embodiments for fully illustrating the present invention, and the protection scope of the present invention is not limited thereto. Equivalent substitutions or transformations made by those skilled in the art on the basis of the present invention are all within the protection scope of the present invention. The protection scope of the present invention shall be determined by the claims.

Claims (8)

1. A polyacid {Se ₆ W ₄₅ }, characterized in that its chemical formula is [(CH ₃ ) ₂ NH ₂ ] ₁₅ Na _0.8 (H ₃ O) _8.2 [Se ₆ W ₄₅ O ₁₅₉ (H ₂ O) ₉ ]·27H ₂ O; the polyacid {Se ₆ W ₄₅ } belongs to the monoclinic crystal system, the space group is P2 ₁ /m , and the unit cell parameters are: a=15.6207(6), b=33.5801(11), c=20.8294(7), α=90°, β=98.130(2)°, γ=90°, V=10816.1(7)Å ³ . 2. a preparation method of multi-acid {Se ₆ W ₄₅ } as claimed in claim 1, is characterized in that, in precursor multi-acid {Se ₆ W ₃₉ } aqueous solution, add organic amine salt, inorganic acid, after acidification treatment Stand still to obtain the polyacid {Se ₆ W ₄₅ }; the precursor polyacid {Se ₆ W ₃₉ } is Na ₂₄ [H ₆ Se ₆ W ₃₉ O ₁₄₄ ]·74H ₂ O; The organic amine salt is dimethylammonium chloride and/or dimethylammonium nitrate; the inorganic acid is nitric acid and/or hydrochloric acid. 3. The preparation method according to claim 2, characterized in that, add organic amine salt to the aqueous solution of precursor polyacid {Se ₆ W ₃₉ }, add inorganic acid after stirring and dissolving to carry out acidification treatment, and leave standstill for 12 ~ After 36 h, the polyacid {Se ₆ W ₄₅ } crystals were obtained. 4. The preparation method according to claim 2, wherein the molar ratio of the precursor polyacid {Se ₆ W ₃₉ }, organic amine salt and inorganic acid is 1:100~150:100~150. 5. An application of the polyacid {Se ₆ W ₄₅ } as claimed in claim 1 in ultrafiltration separation of actinide ions. 6. The application according to claim 5, characterized in that an oxidizing agent is added to the aqueous solution containing actinide ions, and after the actinide ions are converted into AnO ₂ ²⁺ , polyacid {Se ₆ W ₄₅ } and AnO ₂ ²⁺ forms nano-scale clusters and is separated by ultrafiltration; where An is U, Np, Pu or Am. 7 . The application according to claim 6 , wherein the oxidizing agent is copper periodate; and the nanoscale clusters are formed under the condition of pH≤1. 8. The application of the polyacid {Se ₆ W ₄₅ } claimed in claim 1 in the separation of americium ions and lanthanide ions, is characterized in that, in the solution containing americium ions and lanthanide ions, an oxidizing agent is added, and the americium After the ions are converted into AmO ₂ ²⁺ , polyacid {Se ₆ W ₄₅ } and AmO ₂ ²⁺ are added to form nano-scale clusters, which are separated by ultrafiltration to obtain nano-scale clusters, and the intercepted nano-scale clusters are collected for reduction treatment. Trivalent americium ions were obtained, and the released polyacid {Se ₆ W ₄₅ } was recovered by ultrafiltration.

Images