Preparation method and application of multi-coordinated covalent organic framework material

Abstract

The present invention discloses a preparation method and application of a multi-coordinated covalent organic framework material, which belongs to the field of material preparation technology. The present invention utilizes 4,7-bis(4-aminophenyl)-α-methyl-1H-benzimidazole-2-methanol monomer and benzo[1,2-b:3,4-b':5,6-b']terthiophene-2,5,8-trialdehyde monomer or 2,4,6-tris(4-formaldehydephenyl)-1,3,5-triazine monomer to synthesize a novel multi-coordinated 2D COFs material with thorium adsorption and thorium-uranium ion separation selectivity by a solvent thermal method. The 2D COFs material prepared by the present invention has a large specific surface area, a regular one-dimensional open channel and abundant skeleton coordinated heteroatoms. Based on strong chemical coordination, the 2D COFs material has both ultrafast adsorption rate, high adsorption capacity and adsorption selectivity, and excellent recycling performance in the application of selective adsorption and separation of thorium.

Description

Technical Field

[0001] The present invention relates to the technical field of material preparation, and in particular to a preparation method and application of a multi-coordinated covalent organic framework material. Background Art

[0002] Nuclear energy, a clean, low-carbon energy source, is widely used in the nuclear power industry, with uranium-based fuel being the primary fuel for nuclear reactors. However, with the rapid growth of energy demand and the limited availability of uranium resources, the development and utilization of thorium-based nuclear fuel, which has abundant natural reserves, is becoming increasingly important.

[0003] Thorium is a fertile nuclear material. 232 Th can be converted into nuclear fuel for direct use after neutron bombardment in the reactor. 233 U. In addition, thorium has the advantages of large reserves, easy extraction, safety and greenness, and high fission energy, making it the most ideal substitute for uranium and plutonium. However, Th(IV) ions are chemically toxic and radioactive, and pose a great threat to the environment and human health. Therefore, the effective separation and enrichment of Th(IV) in nuclear wastewater is the key to solving environmental pollution problems and achieving efficient recycling of Th(IV) resources. Since thorium has similar chemical properties to rare earth elements and uranium, selective adsorption and separation of thorium from aqueous solutions is quite challenging. The adsorption method is considered to be an effective technical means of separating and recovering radioactive nuclides because of its low cost, low secondary waste and high recovery rate. However, the low stability, low adsorption capacity and low selectivity of the adsorption materials have always been bottlenecks restricting the development of this technology. Therefore, there is an urgent need to develop new solid adsorbents with high adsorption capacity and high adsorption selectivity for thorium.

[0004] Two-dimensional covalent organic frameworks (2D COFs) are a class of crystalline organic porous polymers with permanent porosity and highly ordered structures, possessing both hierarchical layered structures and one-dimensional open channels. Unlike other polymers, a notable feature of 2D COFs is that they can be pre-designed structurally. Topological design maps provide geometric guidance for tiling the expanded porous structure, while polycondensation reactions provide synthetic methods for constructing pre-designed primary and higher-order structures. Over the past decade, chemical advances in these two areas have laid the foundation for the field of covalent organic framework materials. It is precisely because of the structural characteristics and diversity of 2D COFs that they have become the most promising materials for the adsorption and separation of metal ions.

[0005] Currently, 2D COFs used in thorium adsorption primarily chemically coordinate with Th(IV) via the N sites on their C=N bonds, but these materials typically have limited adsorption capacity. Therefore, it is necessary to develop novel organic frameworks that incorporate more electron-rich groups into the 2D COFs framework and design efficient COFs adsorbents with multiple adsorption sites to address these challenges. Summary of the Invention

[0006] In view of the above-mentioned defects of the prior art, the present invention proposes a preparation method and application of a multi-coordinated covalent organic framework material to solve the problems raised by the above-mentioned background technology.

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

[0008] A multi-coordinate covalent organic framework material, wherein the structural formula of the multi-coordinate covalent organic framework material 2D COFs is shown as follows (I) or (II), (I) is TBN-TS COF, and (II) is TBN-TN COF:

[0009]

[0010]

[0011] Preferably, the preparation method of the multi-coordinate covalent organic framework material comprises the following steps: adding a nitrogen-rich amine monomer, an aldehyde monomer and an organic solvent into a 10 mL Pyrex tube, ultrasonically treating for 30 minutes, and mixing uniformly to obtain a mixture; then adding a catalyst to the mixture, freezing it in liquid nitrogen, evacuating and filling it with nitrogen multiple times, and then sealing the Pyrex tube with a flame gun while maintaining the vacuum state, cooling it to room temperature of 20-25°C, placing it in an oven for heating and crystallization, and then naturally cooling it to room temperature, filtering and collecting the solid, washing the solid with a solvent and stripping it overnight, heating and vacuum drying it to obtain the multi-coordinate covalent organic framework material.

[0012] Preferably, the nitrogen-rich amine monomer is 4,7-bis(4-aminophenyl)-α-methyl-1H-benzimidazole-2-methanol (TBN); the aldehyde monomer is one of benzo[1,2-b:3,4-b':5,6-b']terthiophene-2,5,8-trialdehyde (TS) or 2,4,6-tris(4-formaldehydephenyl)-1,3,5-triazine (TN).

[0013] Preferably, the organic solvent is one of a mixed solution of mesitylene and 1,4-dioxane in a volume ratio of 0.5 to 10:1, a mixed solution of o-dichlorobenzene and mesitylene in a volume ratio of 0.5 to 10:1, and a mixed solution of o-dichlorobenzene and n-butanol in a volume ratio of 1 to 10:1.

[0014] Preferably, the molar ratio of the nitrogen-rich amine monomer to the aldehyde monomer in the mixture is 1-3:1; the volume mass ratio of the organic solvent to the sum of the nitrogen-rich amine monomer and the aldehyde monomer is 0.4-5.0 mL:14.4-86.40 mg.

[0015] Preferably, the catalyst is a 3-9 mol / L acetic acid solution, and the ratio of the molar amount of the nitrogen-rich amine monomer to the volume of the catalyst is 0.03 mmol:0.01-1.0 mL.

[0016] Preferably, the reaction temperature of the heating crystallization is 70-150° C., and the reaction time is 1-7 days; the vacuum drying temperature is 80-150° C., and the drying time is 4-12 hours.

[0017] Preferably, the solvent in the solvent washing is at least one of tetrahydrofuran, acetone, methanol, N,N-dimethylformamide, and 1,4-dioxane.

[0018] Preferably, the multi-coordinate covalent organic framework material of the present invention is used in the efficient adsorption of thorium ions and the selective separation of thorium ions and uranium ions.

[0019] Preferably, the pH of the solution environment for adsorbing thorium ions is 4.0-5.0.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] (1) The present invention uses the amino monomer 4,7-bis(4-aminophenyl)-α-methyl-1H-benzimidazole-2-methanol containing nitrogen and oxygen coordinated heteroatoms and the sulfur-rich benzo[1,2-b:3,4-b':5,6-b']terthiophene-2,5,8-trialdehyde or nitrogen-rich 2,4,6-tris(4-formaldehydephenyl)-1,3,5-triazine monomer to prepare a multi-coordinated covalent organic framework material. This is the first synthetic report, and its structural formula has never been disclosed in the prior art.

[0022] (2) The multi-coordinated covalent organic framework material prepared by the present invention can achieve efficient adsorption and separation of thorium and thorium-uranium ions under acidic conditions (pH 4.0-5.0) due to the strong coordination interaction between the abundant N, O, and S heteroatoms in the skeleton structure and Th(IV). It not only has a high adsorption capacity and excellent reusability, but also exhibits an ultra-fast adsorption rate, reaching adsorption equilibrium within 30 minutes, thus solving the problems of low adsorption capacity and poor recycling performance of current thorium adsorption materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a synthetic route for the novel multi-coordinate covalent organic framework material according to the embodiment of the present invention;

[0024] Figure 2 PXRD patterns of two 2D COFs;

[0025] Figure 3 FT-IR spectra of two 2D COFs;

[0026] Figure 4 Nitrogen adsorption and desorption curves of two 2D COFs;

[0027] Figure 5 The adsorption amount and removal rate of the two 2D COFs at different pH values;

[0028] Figure 6 The adsorption kinetics of two 2D COFs;

[0029] Figure 7 are the adsorption isotherms of two 2D COFs;

[0030] Figure 8 The cyclic performance of two 2D COFs for thorium adsorption;

[0031] Figure 9 XPS spectra of TBN-TS COF before and after thorium adsorption. DETAILED DESCRIPTION

[0032] The technical solution of the present invention will be further described in detail below in conjunction with specific implementation methods.

[0033] Unless otherwise specified, the experimental methods used in the examples of the present invention are all conventional methods.

[0034] Unless otherwise specified, the materials, reagents, etc. used in the examples of the present invention can be obtained from commercial sources.

[0035] The nitrogen-rich amino monomer 4,7-bis(4-aminophenyl)-α-methyl-1H-benzimidazole-2-methanol (Cryst. Growth Des. 2019, 19, 3543-3550) used in the embodiment of the present invention can be synthesized by the method reported in the literature, benzo[1,2-b:3,4-b':5,6-b']trithiophene-2,5,8-trialdehyde can be purchased, and 2,4,6-tris(4-formaldehydephenyl)-1,3,5-triazine can be purchased.

[0036] Example 1

[0037] In a 10 mL Pyrex tube, 20.66 mg (0.060 mmol) of 4,7-bis(4-aminophenyl)-α-methyl-1H-benzimidazole-2-methanol monomer, 13.22 mg (0.040 mmol) of benzo[1,2-b:3,4-b':5,6-b']terthiophene-2,5,8-trialdehyde monomer, and 2 mL of a mixture of o-dichlorobenzene and n-butanol in a volume ratio of 1:1 were added to obtain a mixture, which was ultrasonically treated for 30 min. After in, 0.2 mL of a 6 mol / L acetic acid solution of the catalyst was added, followed by freezing in liquid nitrogen, evacuation and nitrogen filling three times, and then the Pyrex tube was sealed with a flame gun while maintaining the vacuum state. After room temperature, it was placed in a 120°C oven for heating and crystallization for 3 days. After cooling naturally to room temperature, the solid was collected by filtration, washed with tetrahydrofuran solvent and stripped overnight, and heated to 120°C and vacuum dried for 10 hours to obtain a new multi-coordinated covalent organic framework material as a yellow-brown powder, named TBN-TS COF. The synthesis route is detailed in the following. Figure 1 superior.

[0038] Example 2

[0039] In a 10 mL Pyrex tube, 10.33 mg (0.030 mmol) of 4,7-bis(4-aminophenyl)-α-methyl-1H-benzimidazole-2-methanol monomer, 13.22 mg (0.040 mmol) of 2,4,6-tris(4-formylphenyl)-1,3,5-triazine monomer, and 1 mL of a mixture of mesitylene and 1,4-dioxane (volume ratio: 3:1) were added. The mixture was sonicated for 20 min, and then 0.15 mL of a 6 mol / L acetic acid solution was added as a catalyst. The mixture was then frozen in liquid nitrogen, evacuated and filled with nitrogen three times, and the Pyrex tube was sealed with a flame gun while maintaining the vacuum. After room temperature, the mixture was heated in a 120°C oven for crystallization for 3 days. The solid was then collected by filtration after cooling to room temperature. The solid was washed with acetone solvent and stripped overnight, and then heated to 100°C and dried in vacuum for 12 h to obtain a new multi-coordinated covalent organic framework material as a bright yellow powder, named TBN-TN COF. Synthesis route details see Figure 1 Down.

[0040] Example 3

[0041] In a 10 mL Pyrex tube, 8.61 mg (0.025 mmol) of 4,7-bis(4-aminophenyl)-α-methyl-1H-benzimidazole-2-methanol monomer, 8.26 mg (0.025 mmol) of benzo[1,2-b:3,4-b':5,6-b']terthiophene-2,5,8-trialdehyde monomer, and 0.4 mL of a mixture of o-dichlorobenzene and mesitylene in a volume ratio of 1:1 were added to obtain a mixture, and the mixture was ultrasonically treated for 30 min. Then, 0.2 mL of a 3 mol / L acetic acid solution of the catalyst was added, and the mixture was subsequently frozen in liquid nitrogen. After evacuation and nitrogen filling three times, the Pyrex tube was sealed with a flame gun while maintaining the vacuum state. After room temperature, the mixture was placed in a 150°C oven for heating and crystallization for 1 day. After naturally cooling to room temperature, the solid was collected by filtration, washed with N,N-dimethylformamide solvent and stripped overnight, heated to 150°C and vacuum dried for 4 hours to obtain a new multi-coordinated covalent organic framework material as a yellow-brown powder, named TBN-TS COF.

[0042] Example 4

[0043] In a 10 mL Pyrex tube, 51.65 mg (0.150 mmol) of 4,7-bis(4-aminophenyl)-α-methyl-1H-benzimidazole-2-methanol monomer, 16.53 mg (0.050 mmol) of benzo[1,2-b:3,4-b':5,6-b']terthiophene-2,5,8-trialdehyde monomer, and 5.0 mL of a mixture of o-dichlorobenzene and mesitylene in a volume ratio of 1:1 were added to obtain a mixture, which was ultrasonically treated for 30 After 1 min, 1.0 mL of a 9 mol / L acetic acid solution of the catalyst was added, followed by freezing in liquid nitrogen, evacuation and nitrogen filling three times, and then the Pyrex tube was sealed with a flame gun while maintaining the vacuum state. After room temperature, it was placed in a 70°C oven for heating and crystallization for 7 days, and then naturally cooled to room temperature and filtered to collect the solid. The solid was washed with 1,4-dioxane solvent and stripped overnight, and heated to 80°C and vacuum dried for 12 hours to obtain a new multi-coordinated covalent organic framework material as a yellow-brown powder, named TBN-TS COF.

[0044] Comparative Example 1

[0045] The difference between this comparative example and Example 1 is that the nitrogen-rich amino monomer 4,7-bis(4-aminophenyl)-α-methyl-1H-benzimidazole-2-methanol (TBN) is replaced by another amino monomer: 4,4'-diaminoterphenyl (SEB), and the other operations are consistent with Example 1.

[0046] Comparative Example 2

[0047] The difference between this comparative example and Example 1 is that benzo[1,2-b:3,4-b':5,6-b']terthiophene-2,5,8-trialdehyde (TS) is replaced by another aldehyde monomer: 1,3,5-tris(p-formylphenyl)benzene (TFA), and the other operations are consistent with Example 1.

[0048] Comparative Example 3

[0049] The difference between this comparative example and Example 1 is that the nitrogen-rich amino monomer 4,7-bis(4-aminophenyl)-α-methyl-1H-benzimidazole-2-methanol (TBN) is replaced by another amino monomer: 1,3,5-tris(4-aminophenyl)benzene (THA), and the other operations are the same as in Example 1.

[0050] Experimental Example 1 Structure and property identification of multi-coordinated covalent organic framework materials

[0051] The powders of the novel multi-coordinated covalent organic framework materials obtained in Example 1 and Example 2 were subjected to X-ray diffraction and interference pattern measurement and Fourier transform to obtain X-ray diffraction patterns and Fourier infrared spectra (see Figure 2 、 Figure 3 ), the X-ray diffraction pattern can be used to determine that the method of the present invention has successfully synthesized a new type of multifunctional coordinated organic porous material. From the Fourier infrared spectrum, it can be seen that the new type of multi-coordinated framework material 2D COFs has a C=N bond stretching vibration peak, indicating that the Schiff base condensation reaction between the two monomers has successfully occurred to form an imine linker.

[0052] The nitrogen adsorption and desorption curves of the novel multi-coordinated covalent organic framework materials obtained in Example 1 and Example 2 are tested (see Figure 4 ), from the figure we can see that the S BET =901.05m 2 / g,d NLDFT =3.54nm, S of TBN-TN COF multi-coordination framework material BET =465.19m 2 / g,d NLDFT =3.58nm, both have large specific surface area and pore size.

[0053] Experimental Example 2: Adsorption performance of thorium under different experimental conditions

[0054] 2.1 The calculation is based on the following formula:

[0055] Adsorption amount calculation formula:

[0056] Removal rate calculation formula:

[0057] Where: q e is the adsorption capacity of thorium at adsorption equilibrium, mg / g;

[0058] C0 is the mass concentration of thorium in the initial solution, mg / L;

[0059] C e is the mass concentration of thorium in the solution at equilibrium, mg / L;

[0060] V is the volume of the solution, L;

[0061] m is the mass of the adsorbent, g;

[0062] η is the removal rate, 100%.

[0063] 2.2 The 2D COFs materials prepared in Example 1 and Example 2 were subjected to adsorption experiments at different pH values, with a pH range of 1.0 to 5.0, an initial concentration of 100 mg / L thorium solution, a solid-liquid ratio of 1:3, and an adsorption time of 24 h. The experimental results are shown in FIG. Figure 5 The materials of Example 1 and Example 2 reach a saturated adsorption capacity of 300 mg / g at a pH of 4.0, while these two materials do not adsorb or adsorb very little at a pH of 1 to 3.

[0064] 2.3 The adsorption kinetics experiment of the 2D COFs materials prepared in Example 1 and Example 2 was carried out. The initial concentration of the thorium solution was 100 mg / L, the solid-liquid ratio was 1:3, the pH was 4.0, and the adsorption time was 0 to 720 min. The experimental results are shown in FIG. Figure 6 As shown in the figure, the adsorption rate is very fast, and the adsorption equilibrium time is reached in 30 minutes. It also conforms to the pseudo-second-order kinetic model and belongs to the chemical adsorption process.

[0065] 2.4 The 2D COFs materials prepared in Example 1 and Example 2 were subjected to adsorption isotherm tests. The initial concentration of the thorium solution was 50-500 mg / L, the solid-liquid ratio was 1:6, the pH was 4.0, and the adsorption time was 24 h. The experimental results are shown in FIG. Figure 7 The maximum saturated adsorption capacity of the materials prepared in Example 1 and Example 2 is close to 1500 mg / g, and conforms to the Langmuir model, belonging to monolayer adsorption.

[0066] 2.5 A multi-component adsorption selectivity experiment was performed on the 2D COFs materials prepared in Example 1 and Example 2. Different competing ions (such as uranium, samarium, lanthanum, praseodymium, rubidium, gadolinium, and lutetium) coexisted with thorium in a mixed solution. The concentrations of the competing ions and thorium were both 100 mg / L, the solid-liquid ratio was 1:3, the pH was 4.0, and the adsorption time was 24 h. The adsorption amount of the multi-component elements was tested by ICP-OES (inductively coupled plasma optical emission spectrometry). The experimental results are shown in Table 1.

[0067] Table 1 Thorium and uranium separation selectivity SF of materials in Example 1 and Example 2 Th / U

[0068]

[0069] Thorium and uranium separation selectivity (SF Th / U ) is 12.73, and it hardly adsorbs samarium, lanthanum, praseodymium, rubidium, gadolinium and lutetium. Th / U ) is 13.52, and there is almost no adsorption of samarium, lanthanum, praseodymium, rubidium, gadolinium, and lutetium. Therefore, the multi-coordinated 2D COFs material prepared by this invention can achieve selective adsorption and separation of thorium, showing excellent adsorption selectivity and affinity for thorium.

[0070] 2.6 The 2D COFs materials prepared in Example 1 and Example 2 were subjected to a recycling performance test. The adsorbed multi-coordinated 2D COFs materials were eluted with 0.1M HNO3. The experimental results are shown in Figure 2. Figure 8 As shown, it can be seen that the adsorption capacity of the 2D COFs material remains almost unchanged after being recycled 5 times, indicating that the adsorbent material of the present invention has good cycle stability and high reuse rate.

[0071] 2.7 The 2D COFs material prepared in Example 1 was subjected to XPS performance testing to study the interaction between Th(IV) ions and the 2D COFs adsorbent. Figure 9 As shown in the figure, after the adsorption of Th(IV) ions, the electron binding energy of the O1s and N1s orbitals of the 2DCOFs material increased, and new peaks were observed, which were attributed to the Th-O coordination bond and Th-N coordination bond, respectively; similarly, after the adsorption of Th(IV) ions, the electron binding energy of the S2p orbital of the 2D COFs material also increased, indicating that the electron cloud of S moved toward the Th(IV) direction and combined with Th(IV), and the new peak that appeared can be attributed to the Th-S coordination bond.

[0072] Example 3 Comparison of Thorium Adsorption Performance

[0073] The 2D COFs materials prepared in Example 1, Example 2, and Comparative Examples 1 to 3 were tested for their adsorption performance for thorium. The initial concentration of the thorium solution was 100 mg / L, the solid-liquid ratio was 1:6, the pH was 4.0, and the adsorption time was 24 h. The test results are shown in Table 2:

[0074] Table 2 Comparison of adsorption performance of thorium

[0075]

[0076] As can be seen from Table 2, the thorium adsorption performance of the materials prepared in Example 1 and Example 2 is 1497.3 mg / g and 1462.8 mg / g, respectively; by comparing Example 1 and Example 2 with Comparative Example 2, it can be seen that replacing TS or TN with TFA will lead to a significant decrease in the adsorption capacity of thorium ions; by comparing Example 1 with Comparative Example 1, it can be seen that replacing TBN with SEB will lead to a significant decrease in the adsorption capacity of thorium ions; by comparing Example 2 with Comparative Example 3, it can be seen that replacing TBN with THA will lead to a significant decrease in the adsorption capacity of thorium ions; it can be seen that the 2D COFs material prepared by the combination of TBN-TS and TBN-TN has the best adsorption performance for thorium.

[0077] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A multi-coordinate covalent organic framework material, characterized in that: The structural formula of the multi-coordinated covalent organic framework material 2D COFs is shown below (I) or (II):

2. The method for preparing a multi-coordinated covalent organic framework material according to claim 1, wherein: The following steps are involved: A nitrogen-rich amine monomer, an aldehyde monomer and an organic solvent are added to a tube, and ultrasonic mixing is performed to obtain a mixture; a catalyst is then added to the mixture, and the mixture is frozen in liquid nitrogen. The tube is evacuated and filled with nitrogen, and the tube is sealed with a flame. After cooling to 20-25° C., the tube is heated for crystallization, and a solid is collected. The solid is washed with a solvent and vacuum dried to obtain a multi-coordinated covalent organic framework material.

3. The method for preparing a multi-coordinated covalent organic framework material according to claim 2, wherein: The nitrogen-rich amino monomer is 4,7-bis(4-aminophenyl)-α-methyl-1H-benzimidazole-2-methanol; the aldehyde monomer is benzo [1,2-b:3,4-b':5,6-b']trithiophene-2,5,8-trialdehyde or 2,4,6-tris(4-formylphenyl)-1,3,5-triazine.

4. The method for preparing a multi-coordinated covalent organic framework material according to claim 2, wherein: The organic solvent is one of a mixed solution of mesitylene and 1,4-dioxane in a volume ratio of 0.5 to 10:1, a mixed solution of o-dichlorobenzene and mesitylene in a volume ratio of 0.5 to 10:1, and a mixed solution of o-dichlorobenzene and n-butanol in a volume ratio of 1 to 10:

1.

5. The method for preparing a multi-coordinated covalent organic framework material according to claim 2, wherein: The molar ratio of the nitrogen-rich amine monomer to the aldehyde monomer in the mixture is 1-3:1; the volume mass ratio of the organic solvent to the sum of the nitrogen-rich amine monomer and the aldehyde monomer is 0.4-5.0 mL:14.4-86.40 mg.

6. The method for preparing a multi-coordinated covalent organic framework material according to claim 2, wherein: The catalyst is a 3-9 mol / L acetic acid solution, and the ratio of the molar amount of the nitrogen-rich amine monomer to the volume of the catalyst is 0.03 mmol:0.01-1.0 mL.

7. The method for preparing a multi-coordinated covalent organic framework material according to claim 2, wherein: The reaction temperature of the heating crystallization is 70-150° C., and the reaction time is 1-7 days; the vacuum drying temperature is 80-150° C., and the drying time is 4-12 hours.

8. The method for preparing a multi-coordinated covalent organic framework material according to claim 2, wherein: The solvent in the solvent washing is at least one of tetrahydrofuran, acetone, methanol, N,N-dimethylformamide, and 1,4-dioxane.

9. Use of the multi-coordinate covalent organic framework material according to claim 1 or the multi-coordinate covalent organic framework material prepared by the preparation method according to any one of claims 2 to 8 in the efficient adsorption of thorium ions and the separation and selection of thorium ions and uranium ions.

10. The use according to claim 9, characterized in that The pH value of the solution environment for adsorbing thorium ions is 4.0-5.0.

Images