Method for efficiently separating uranyl ions based on titanium-based metal organic framework material

Abstract

The invention discloses a method for efficiently separating uranyl ions based on a titanium-based metal organic framework material, the titanium-based metal organic framework material is MOF-902, and the adsorption separation of the uranyl ions can be realized by adding the titanium-based metal organic framework material into a liquid containing the uranyl ions. The invention develops a novel adsorbent for uranyl ion separation, which can realize rapid selective separation of uranyl ions.

Description

Technical Field

[0001] The invention belongs to the field of uranium extraction from seawater, and in particular relates to a method for efficiently separating uranyl ions based on titanium-based metal organic framework materials. Background Art

[0002] In the context of global warming, compared with traditional fossil fuels such as coal, oil, and natural gas, nuclear energy has attracted much attention as a clean energy with high energy density and long sustainable operation time. Uranium (U) is the main fuel for nuclear reactors. 238 U. 235 U. 234 U exists in three forms. Currently, nuclear power plants use 235 U is mainly purified and separated from uranium ore. It is estimated that the world's proven uranium mines on land will be exhausted in more than a century and cannot meet the long-term demand for nuclear power generation. In addition to conventional uranium resources on land, the ocean also has huge uranium reserves, which are nearly 1,000 times the reserves on land. Therefore, extracting uranium from unconventional uranium-containing resources such as seawater is of great significance to maintaining the development of nuclear energy. The seawater uranium extraction technology is even called "one of the seven chemical separation technologies that changed the world." The existing seawater uranium extraction technologies can be divided into adsorption, chemical deposition, solvent extraction, etc. Among them, the adsorption method has the advantages of simple operation and low energy consumption, and has become the most widely studied method for seawater uranium extraction. The key to the adsorption method lies in the adsorbent. Many adsorbents such as fiber, gel, clay and zeolite have been used for seawater uranium extraction. However, due to the extremely low uranium concentration in seawater (~3.3 ppb), the presence of a large number of coexisting competing ions and the complexity of the marine environment, it is still difficult to construct an adsorbent that meets the practical application requirements such as fast kinetics, good selectivity, and high adsorption capacity.

[0003] Metal-organic frameworks (MOFs) are a type of porous material composed of metal centers and organic ligands. They have the advantages of large specific surface area, adjustable pore size and shape, and easy modification. They are widely used in gas adsorption, storage and separation. In recent years, they have also been used to separate dyes, antibiotics and heavy metal ions in water. Compared with gas adsorption, the application of MOFs in the adsorption of solution ions has to consider stability issues. Summary of the invention

[0004] The present invention aims to provide a method for efficiently separating uranyl ions based on titanium-based metal organic framework materials.

[0005] To achieve the above object, the present invention adopts the following technical solution: A method for efficiently separating uranyl ions based on titanium-based metal organic framework materials. The titanium-based metal organic framework material is MOF-902, the metal center of which is titanium, and the organic ligands are p-aminobenzoic acid and 4,4'-biphenyldicarboxaldehyde.

[0006] Furthermore, the titanium-based metal organic framework material is specifically added into a liquid containing uranyl ions to achieve selective adsorption of uranyl ions.

[0007] Furthermore, the titanium-based metal organic framework material is added in an amount of 0.5 g / L in the liquid containing uranyl ions.

[0008] Furthermore, the liquid includes seawater.

[0009] MOFs centered on high-valent metal ions have a high coordination number, and can reduce the attack on metal clusters through steric hindrance, thereby improving stability. At the same time, the porous structure of MOFs is conducive to improving mass transfer kinetics, and changing the organic ligands of MOFs can provide different coordination sites to improve adsorption selectivity and adsorption capacity. The metal organic framework material MOF-902 selected in the present invention has a large pore size and contains a large number of Lewis base coordination sites. It can achieve rapid selective adsorption and separation of uranyl ions through the different coordination abilities of these coordination sites in the pores for different ions.

[0010] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a method for efficiently separating uranyl ions based on titanium-based metal organic framework materials. The large pore size of the titanium-based metal organic framework MOF-902 is conducive to the transmission of uranyl ions, can accelerate the adsorption equilibrium, and achieve faster mass transfer kinetics, so that it can adsorb more than 90% of the uranyl ions in the liquid within 20 minutes. In addition, the pores of MOF-902 contain a large number of N sites that can coordinate with uranyl ions, which can improve the adsorption selectivity of the material for uranyl ions. In addition, the high-valent metal ion Ti 4+ The metal organic framework MOF-902 with uranyl ions as the core has good stability in solution. Therefore, MOF-902 can achieve rapid adsorption of uranyl ions with certain selectivity, which can provide a reference for expanding the application of metal organic frameworks in the field of uranium extraction from seawater. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 Schematic diagram of the synthesis of titanium-based metal organic framework MOF-902 prepared in Example 1.

[0012] Figure 2 This is the X-ray diffraction pattern of the titanium-based metal organic framework MOF-902 prepared in Example 1.

[0013] Figure 3 This is a curve diagram of the removal rate of uranyl ions by the titanium-based metal organic framework MOF-902 at different adsorption times in Example 2.

[0014] Figure 4This is a comparison chart of the removal rate of uranyl ions by the titanium-based metal organic framework MOF-902 in Example 3 under the conditions of different competing ions. DETAILED DESCRIPTION

[0015] In order to make the contents of the present invention easier to understand, the technical solution of the present invention is further described below in conjunction with specific implementation methods, but the present invention is not limited thereto.

[0016] Example 1 Synthesis of titanium-based metal organic framework MOF-902 like Figure 1 As shown, MOF-902 was synthesized by a one-pot solvothermal method. Specifically, 147.2 mg of 4,4'-biphenyldicarboxaldehyde was added to 6 mL of methanol, and ultrasonic mixing was performed to obtain solution A. 192 mg of 4-aminobenzoic acid and 119 μL of tetrabutyl titanate were dissolved in 6 mL of methanol and ultrasonically dissolved to obtain solution B. Solution A was dropped into solution B, and after ultrasonic mixing, it was transferred to a 25 mL reactor and heated at 140 °C for 3 days. After cooling to room temperature, it was transferred to a centrifuge tube and centrifuged at 8000 rpm for 5 min to separate the product. The product was washed three times with N,N-dimethylacetamide and methanol, respectively, and then soaked in dichloromethane for 3 days (the solvent was changed once a day), centrifuged to remove the solvent, and then activated at 130 °C for 24 h to obtain the final product.

[0017] Figure 2 The X-ray diffraction diagram of the synthesized MOF-902 is shown in Figure 1. As can be seen from the figure, the XRD characteristic peaks of the synthesized MOF-902 correspond to the characteristic peaks of the MOF-902 material simulated by the software, proving that MOF-902 was successfully synthesized.

[0018] Example 2 Adsorption experiment of titanium-based metal organic framework MOF-902 on uranyl ions Prepare 10 mL of 20 mg / L uranyl ion solution (pH=6.0), add 5 mg of the titanium-based metal organic framework material MOF-902 prepared in Example 1, and stir and adsorb with a magnetic stirrer at a speed of 300 r / min. Draw 0.2 mL of sample solution with a disposable syringe at 0, 20, 40, 60, 80, 100, and 120 min, filter with a 0.22 μm filter membrane, and dilute to a certain concentration range. Test the uranyl ion content in the solution by ICP-MS. The results are shown in Figure 3 .

[0019] Depend on Figure 3It can be seen that the titanium-based metal organic framework material MOF-902 can remove more than 90% of uranyl ions in the solution within 20 minutes, and can reach adsorption equilibrium within 40 minutes. The removal rate of uranyl ions in the solution is about 99%, which proves that the material has a fast adsorption rate for uranyl ions.

[0020] Example 3 Competitive adsorption experiment of titanium-based metal organic framework MOF-902 on uranyl ions Prepare 10 mL of Na + Mg 2+ , Ca 2+ 、Zn 2+ , Sr 2+ The uranyl ion solution (pH=6.0) was prepared, and the ion concentration was 20 mg / L. Then 5 mg of the titanium-based metal organic framework material MOF-902 prepared in Example 1 was added to the solution, and the adsorption was stirred at 300 r / min with a magnetic stirrer. The sample solution was drawn with a disposable syringe before and 120 minutes after adsorption, filtered with a 0.22 μm filter membrane, and diluted to a certain concentration range. The uranyl ion content in the solution was measured by ICP-MS. The results are shown in Figure 4 .

[0021] Depend on Figure 4 It can be seen that the titanium-based metal organic framework material MOF-902 has a high removal rate for uranyl ions, which can reach more than 99%, while the removal rate for competitive ions is relatively low, which proves that the material has a certain selectivity in the adsorption of uranyl ions.

[0022] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made according to the scope of the patent application of the present invention should fall within the scope of the present invention.

Claims

1. A method for efficiently separating uranyl ions based on titanium-based metal organic framework materials, characterized in that: The titanium-based metal organic framework material is MOF-902, the metal center of which is titanium, and the organic ligands are p-aminobenzoic acid and 4,4'-biphenyldicarboxaldehyde.

2. A method for efficiently separating uranyl ions based on titanium-based metal organic framework materials according to claim 1, characterized in that: Specifically, the titanium-based metal organic framework material is added into a liquid containing uranyl ions to achieve selective adsorption of uranyl ions.

3. The method for efficiently separating uranyl ions based on titanium-based metal organic framework materials according to claim 2, characterized in that: The amount of the titanium-based metal organic framework material added to the liquid containing uranyl ions is 0.5 g / L.

4. A method for efficiently separating uranyl ions based on titanium-based metal organic framework materials according to claim 2 or 3, characterized in that: The liquid includes seawater.

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