Supramolecular self-assembled uranium adsorbent, and preparation method and application thereof

Abstract

The application provides a kind of supramolecular self-assembly uranium adsorbent and its preparation method and application, the preparation raw material of the uranium adsorbent includes melamine, cyanuric acid and melamine phosphate, by selecting the three substances of melamine, cyanuric acid and melamine phosphate to carry out supramolecular self-assembly, the obtained uranium adsorbent can have high adsorption capacity, high adsorption rate and higher selectivity, and the preparation raw material is low in price and simple in preparation process, suitable for application in seawater uranium extraction.

Description

Technical Field

[0001] This invention belongs to the field of adsorbent technology, specifically relating to a supramolecular self-assembled uranium adsorbent and its preparation method. Background Technology

[0002] Nuclear energy, as a clean energy source with low carbon emissions, is an important energy option for humanity in addressing climate change. Uranium is the most critical element in nuclear energy production; however, conventional uranium reserves will be depleted globally in less than a century. Furthermore, mining uranium from terrestrial ores is costly and causes significant environmental damage. Therefore, considering current and future needs for uranium resources and environmental protection requirements, many methods have been developed in recent decades for capturing uranium from seawater and removing it from wastewater. However, selective uranium extraction remains extremely challenging due to the extremely low concentration of uranium and the coexistence of numerous competing ions.

[0003] Currently, various methods have been developed to recover uranium from seawater or remove uranium from nuclear wastewater. Among these methods, adsorption is widely used due to its simplicity of operation, ease of application, and cost-effectiveness, and has made significant progress in uranium separation and recovery. To date, various novel uranium adsorbent materials have been explored, including synthetic organic polymers, organic-inorganic frameworks, peptide hydrogels, and other materials. Based on the hard-soft acid-base theory, uranyl ions are considered Lewis hard acids and can typically form strong coordination bonds with phosphate groups. Phosphate groups are one of the main groups that endow biogenic materials with the ability to adsorb uranium. Currently, based on this property of phosphate groups, various phosphoric acid-functionalized adsorbents have been developed, exhibiting faster adsorption kinetics for uranyl ions. However, their demanding synthesis reaction conditions and high cost hinder the large-scale production of adsorbents and their application in uranium extraction.

[0004] Therefore, it is of great significance to develop a uranium adsorbent with high adsorption capacity, high selectivity, high adsorption rate, low cost, and simple preparation process. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a supramolecular self-assembled uranium adsorbent, its preparation method, and its application. The raw materials for preparing the uranium adsorbent include melamine, cyanuric acid, and melamine phosphate. The uranium adsorbent has the advantages of high adsorption capacity, rapid adsorption kinetics, and high selectivity, and the raw materials are inexpensive and the preparation process is simple.

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

[0007] In a first aspect, the present invention provides a supramolecular self-assembled uranium adsorbent, wherein the raw materials for preparing the uranium adsorbent include melamine, cyanuric acid and melamine phosphate.

[0008] The raw materials for preparing the supramolecular self-assembled uranium adsorbent provided by this invention include melamine, cyanuric acid, and melamine phosphate. Melamine and cyanuric acid can self-assemble into an organic supramolecular structure through in-plane hydrogen bonding and out-of-plane π-π interactions. However, the above-mentioned organic supramolecular structure lacks functional chelating sites for uranyl ions. Considering that melamine phosphate not only has a triazine ring that can form multiple hydrogen bonds, but also has functional phosphate groups, this invention selects melamine, cyanuric acid, and melamine phosphate for supramolecular self-assembly to form a phosphoric acid-functionalized supramolecular organic material for selective adsorption and separation of uranium, and has the advantages of high adsorption capacity, fast adsorption kinetics rate, and high selectivity.

[0009] Preferably, the molar ratio of melamine, cyanuric acid and melamine phosphate is 1:(0.5-2):(1-2).

[0010] The molar ratio of melamine to cyanuric acid is 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.6, or 1:1.8, etc.

[0011] The molar ratio of melamine to melamine phosphate is 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9, or 1:2.0, etc.

[0012] In a second aspect, the present invention provides a method for preparing the uranium adsorbent as described in the first aspect, the method comprising the following steps:

[0013] (1) Melamine and melamine phosphate are dissolved in an organic solvent to obtain a mixed solution; cyanuric acid is dissolved in an organic solvent to obtain a cyanuric acid solution;

[0014] (2) React the mixed solution obtained in step (1) with cyanuric acid solution to obtain the uranium adsorbent.

[0015] Preferably, the organic solvent in step (1) includes dimethyl sulfoxide.

[0016] Preferably, based on the volume of the mixed solution in step (1) being 1 mL, the molar amount of melamine is 0.1 to 0.3 mmol, for example, 0.12 mmol, 0.14 mmol, 0.16 mmol, 0.18 mmol, 0.2 mmol, 0.22 mmol, 0.24 mmol, 0.26 mmol, or 0.28 mmol.

[0017] Preferably, based on the volume of the mixed solution in step (1) being 1 mL, the molar amount of melamine phosphate is 0.1 to 0.3 mmol, for example, 0.12 mmol, 0.14 mmol, 0.16 mmol, 0.18 mmol, 0.2 mmol, 0.22 mmol, 0.24 mmol, 0.26 mmol, or 0.28 mmol.

[0018] Preferably, based on the volume of the cyanuric acid solution in step (1) being 1 mL, the molar amount of cyanuric acid is 0.2 to 0.4 mmol, for example, 0.22 mmol, 0.24 mmol, 0.26 mmol, 0.28 mmol, 0.3 mmol, 0.32 mmol, 0.34 mmol, 0.36 mmol, or 0.38 mmol.

[0019] Preferably, the reaction temperature in step (2) is 25 to 30°C, such as 25.5°C, 26°C, 26.5°C, 27°C, 27.5°C, 28°C, 28.5°C, 29°C or 29.5°C.

[0020] Preferably, the reaction time in step (2) is 10 to 30 minutes, such as 12 minutes, 14 minutes, 16 minutes, 18 minutes, 20 minutes, 22 minutes, 24 minutes, 26 minutes or 28 minutes.

[0021] Preferably, the reaction in step (2) is carried out under stirring conditions.

[0022] Preferably, the stirring speed is 400-550 r / min, such as 420 r / min, 440 r / min, 460 r / min, 480 r / min, 500 r / min, 520 r / min or 540 r / min.

[0023] Preferably, after the reaction in step (2) is completed, the steps of centrifugation, washing and drying are also included.

[0024] Preferably, the washing includes washing with anhydrous ethanol.

[0025] Preferably, the drying temperature is 65-100°C, such as 70°C, 75°C, 80°C, 85°C, 90°C, or 95°C.

[0026] As a preferred embodiment of the present invention, the preparation method includes the following steps:

[0027] (1) Melamine and melamine phosphate are dissolved in an organic solvent to obtain a mixed solution with a molar concentration of melamine of 0.1-0.3 mmol / mL and a molar concentration of melamine phosphate of 0.1-0.3 mmol / mL; cyanuric acid is dissolved in an organic solvent to obtain a cyanuric acid solution with a molar concentration of 0.2-0.4 mmol / mL.

[0028] (2) The mixed solution obtained in step (1) and the cyanuric acid solution are reacted at a temperature of 25-30°C and a stirring speed of 400-550 r / min for 10-30 min. After centrifugation, washing with anhydrous ethanol and drying at 65-100°C, the uranium adsorbent is obtained.

[0029] Thirdly, the present invention provides an application of the uranium adsorbent as described in the first aspect in uranium extraction from seawater.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] The raw materials for preparing the supramolecular self-assembled uranium adsorbent provided by this invention include melamine, cyanuric acid, and melamine phosphate. The uranium adsorbent has high adsorption capacity and fast adsorption kinetics, and exhibits high selectivity for uranyl ions in the presence of multiple competing ions, making it suitable for use in seawater uranium extraction. Attached Figure Description

[0032] Figure 1 Scanning electron microscope image of the uranium adsorbent provided in Example 1;

[0033] Figure 2 A bar chart showing the uranium adsorption capacity of the uranium adsorbent provided in Example 1 at different pH values;

[0034] Figure 3 This is a graph showing the change in uranium adsorption capacity of the uranium adsorbent provided in Example 1 at different times;

[0035] Figure 4 A graph showing the variation of uranium adsorption capacity of the uranium adsorbent provided in Example 1 at different equilibrium concentrations;

[0036] Figure 5 A bar chart showing the separation factor of the uranium adsorbent provided in Example 1 under different interfering ions;

[0037] Figure 6 Infrared spectra of the uranium adsorbent provided in Example 1 before and after adsorption of uranyl ions;

[0038] Figure 7 XPS full spectrum of the uranium adsorbent before and after adsorption of uranyl ions provided in Example 1;

[0039] Figure 8 The N1s spectra of the uranium adsorbent provided in Example 1 before and after adsorption of uranyl ions;

[0040] Figure 9 The O1s spectra of the uranium adsorbent provided in Example 1 before and after adsorption of uranyl ions. Detailed Implementation

[0041] 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 in any way.

[0042] Example 1

[0043] A supramolecular self-assembled uranium adsorbent, the preparation method of which includes the following steps:

[0044] (1) Dissolve 5 mmol of melamine in 30 mL of dimethyl sulfoxide by ultrasonication, and add 5 mmol of melamine phosphate to dissolve it to obtain a mixed solution;

[0045] 5 mmol of cyanuric acid was dissolved in 15 mL of dimethyl sulfoxide by ultrasonication to obtain a cyanuric acid solution.

[0046] (2) The mixed solution obtained in step (1) is mixed with cyanuric acid solution. A white precipitate is generated immediately after mixing. The mixture is reacted for 10 min under constant temperature of 25℃ and stirring speed of 400 r / min. After the reaction is completed, the product is transferred to a centrifuge tube for centrifugation. After washing three times with 30 mL of anhydrous ethanol, it is vacuum dried at 65℃ overnight and ground into fine powder to obtain the uranium adsorbent.

[0047] Example 2

[0048] A supramolecular self-assembled uranium adsorbent differs from Example 1 only in that the amount of cyanuric acid added is 2.5 mmol, while the other components, amounts, and preparation methods are the same as in Example 1.

[0049] Example 3

[0050] A supramolecular self-assembled uranium adsorbent differs from Example 1 only in that the amount of cyanuric acid added is 10 mmol, while the other components, amounts, and preparation methods are the same as in Example 1.

[0051] Example 4

[0052] A supramolecular self-assembled uranium adsorbent differs from Example 1 only in that the amount of melamine phosphate used is 3 mmol, while the other components, amounts, and preparation methods are the same as in Example 1.

[0053] Example 5

[0054] A supramolecular self-assembled uranium adsorbent differs from Example 1 only in that the amount of melamine phosphate used is 7 mmol, while the other components, amounts, and preparation methods are the same as in Example 1.

[0055] Example 6

[0056] A supramolecular self-assembled uranium adsorbent differs from Example 1 only in that the amount of melamine phosphate used is 9 mmol, while the other components, amounts, and preparation methods are the same as in Example 1.

[0057] Comparative Example 1

[0058] A supramolecular self-assembled uranium adsorbent differs from Example 1 only in that melamine phosphate is not added; all other components, dosages, and preparation methods are the same as in Example 1.

[0059] Comparative Example 2

[0060] A supramolecular self-assembly uranium adsorbent, without the addition of cyanuric acid, using only melamine and melamine phosphate, cannot undergo supramolecular self-assembly.

[0061] Performance testing:

[0062] 1. Appearance: The morphology of the supramolecular self-assembled uranium adsorbent provided in Example 1 was characterized using a scanning electron microscope (Zeiss Sigma 300, UK). The scanning electron microscope image of the uranium adsorbent provided in Example 1 is shown below. Figure 1 As shown;

[0063] from Figure 1 As can be seen, the supramolecular self-assembled uranium adsorbent obtained in Example 1 has an apparent morphology of nanoflower-shaped microspheres with a diameter of about 3 μm.

[0064] 2. Adsorption experiment:

[0065] (1) Determining the conditions:

[0066] ① Preparation of uranium stock solution: Accurately weigh 0.422 g UO2(NO3)2·6H2O into a 50 mL beaker, add deionized water, transfer to a 500 mL volumetric flask, and dilute to volume. Shake well. The solution concentration at this point is 400 mg·mL. -1 ;

[0067] ② Determination of optimal pH: Weigh 2.5 mg of the uranium adsorbent provided in Example 1 into a 125 mL plastic vial. Adjust the pH of the uranium stock solution to be between 3 and 9 using 0.1 mol / L HNO3 and 0.1 mol / L NaOH. Add 125 mL of 20 mg / mL uranium adsorbent. -1 A uranium solution with adjusted pH was placed in a constant-temperature shaking incubator (25℃, 220 rpm) and shaken for 20 minutes to reach adsorption equilibrium. The supernatant was collected using a syringe and filtered through a 0.22 μm aqueous filter. The uranium concentration in the solution before and after adsorption was determined using inductively coupled plasma optical emission spectrometry (ICP-OES), and the adsorption capacity was calculated. Where C0 (mg / L) is the initial uranium concentration in the solution, C e (mg / L) is the uranium concentration in the solution at adsorption equilibrium, V(L) is the solution volume, and m(g) is the mass of adsorbent added; the bar chart of uranium adsorption capacity of the uranium adsorbent provided in Example 1 at different pH values ​​is shown below. Figure 2 As shown;

[0068] from Figure 2 It can be determined that the optimal adsorption pH value of the uranium adsorbent provided in Example 1 is 6.0, and it was used in subsequent adsorption experiments.

[0069] ③ Determination of kinetic equilibrium time: Weigh 20 mg of the supramolecular self-assembled uranium adsorbent provided in Example 1 into a 1 L plastic bottle, and add 1 L of 20 mg·mL⁻¹. -1 A uranium solution with a pH of 6 was placed in a constant-temperature shaking shaker (25°C, 220 rpm) and samples were taken at different adsorption time points: 1 min, 2.5 min, 3.5 min, 5 min, 10 min, 12 min, 16 min, and 20 min. The supernatant was collected using a syringe and filtered through a 0.22 μm aqueous filter. The uranium concentration of the solution before and after adsorption was determined using ICP-OES, and the adsorption capacity was calculated. The resulting graph shows the change in uranium adsorption capacity of the uranium adsorbent provided in Example 1 at different times. Figure 3 As shown;

[0070] according to Figure 3 It can be seen that the kinetic data of the uranium adsorbent provided in Example 1 conforms to the pseudo-second-order kinetic model, belongs to chemical adsorption, and reaches adsorption equilibrium in 20 minutes.

[0071] ④ Determination of maximum adsorption capacity: Weigh 2.5 mg of the supramolecular self-assembled uranium adsorbent provided in Example 1 into a 125 mL plastic vial, and add 10 mg·mL⁻¹ of the adsorbent. -1 20 mg / mL -1 30 mg·mL -1 40 mg·mL-1 50 mg / mL -1 80 mg·mL -1 A uranium solution with a pH of 6 was placed in a constant-temperature shaking incubator (25°C, 220 rpm) and shaken for 20 minutes to reach adsorption equilibrium. The supernatant was collected using a syringe and filtered through a 0.22 μm aqueous filter. The uranium concentration of the solution before and after adsorption was determined using ICP-OES, and the adsorption capacity was calculated. The resulting graph shows the change in uranium adsorption capacity of the uranium adsorbent provided in Example 1 at different equilibrium concentrations. Figure 4 As shown;

[0072] from Figure 4 It can be seen that the isotherm data of the uranium adsorbent provided in Example 1 conforms to the Langmuir adsorption isotherm model, and the simulated maximum adsorption capacity is 945.58 mg / g.

[0073] The simulated maximum adsorption capacity of the uranium adsorbents provided in Examples 2-6 and Comparative Examples 1-2 were tested according to the above test methods. The test results are shown in Table 1.

[0074] Table 1

[0075] Maximum adsorption capacity (mg / g) Example 1 945.58 Example 2 620.14 Example 3 550.41 Example 4 160.24 Example 5 579.49 Example 6 420.23 Comparative Example 1 44.00 Comparative Example 2 /

[0076] As shown in Table 1, the supramolecular self-assembled uranium adsorbent provided by the present invention, formed by selecting raw materials with a specific molar ratio, has a high adsorption capacity for uranyl ions.

[0077] Specifically, the maximum adsorption capacity of the uranium adsorbents provided in Examples 1 to 6 is 160.24 to 945.58 mg / g; compared with Comparative Example 1, it can be seen that the maximum adsorption capacity of the uranium adsorbent obtained without the addition of melamine phosphate is lower, at only 44.00 mg / g.

[0078] (2) Effect of competing ions: Weigh 2.5 mg of the supramolecular self-assembled uranium adsorbent obtained in Example 1 into 125 mL plastic vials, and add 10 mg / mL of the adsorbent. -1 Uranium and other coexisting metal ions (Na) + K + Mg 2+ Ca 2+ 、Sr 2+ Co 2+ Ba 2+ Cu 2+ Ni 2+ Zn 2+ and Fe 2+The uranium adsorbent provided in Example 1 was placed in a binary mixed solution with a pH of 6 and placed in a constant-temperature shaking shaker (25°C, 220 rpm) for 20 min to reach adsorption equilibrium. The supernatant was collected with a syringe and filtered through a 0.22 μm aqueous filter. The uranium concentration and interfering ion concentration of the solution before and after adsorption were determined using ICP-OES. The separation factor histogram of the uranium adsorbent under different interfering ions is shown below. Figure 5 As shown;

[0079] from Figure 5 It can be seen that the uranium adsorbent provided in Example 1 has high selectivity for uranyl ions in the presence of different interfering ions.

[0080] (3) Infrared spectroscopy test: The adsorption of uranyl ions by the supramolecular self-assembled uranium adsorbent provided in Example 1 was tested using an infrared spectrometer (Bruker, Germany, Tensor 27). The infrared spectra of the uranium adsorbent provided in Example 1 before and after adsorption of uranyl ions are shown in the figure below. Figure 6 As shown, MCP-5 represents the state before adsorption, and MCP-5-U represents the state after adsorption.

[0081] from Figure 6 It can be seen that in the infrared spectrum of MCP-5, 3392 cm⁻¹ -1 1737cm -1 and 1664cm -1 The absorption peaks appearing at 1109 cm⁻¹ are the stretching vibration peaks of NH, C=O, and C=N, respectively. -1 and 952cm -1 The absorption peaks appearing at 769 cm⁻¹ are the stretching vibration peaks of P=O and POH, respectively. -1 The absorption peak appearing at 910 cm⁻¹ is the stretching vibration peak of the triazine ring; in the infrared spectrum of MCP-5-U(VI), the absorption peak at 910 cm⁻¹ is the stretching vibration peak of the triazine ring. -1 A new absorption peak appears at [O=U=O], which is attributed to [O=U=O]. 2+ The antisymmetric vibrations, in addition, the NH absorption peak red-shifted, and the P=O and PO absorption peaks blue-shifted, indicate that there is an interaction between nitrogen atoms, oxygen atoms and uranyl ions.

[0082] (4) Elemental Analysis: The supramolecular self-assembled uranium adsorbent provided in Example 1 was analyzed before and after adsorption of uranium amide ions using an X-ray photoelectron spectroscopy (Thermo Scientific, USA) instrument. The complete XPS spectra of the uranium adsorbent provided in Example 1 before and after adsorption of uranium amide ions are shown below. Figure 7 As shown, MCP-5 represents the state before adsorption, and MCP-5-U represents the state after adsorption.

[0083] exist Figure 7After adsorption of MCP-5-U, new binding energy peaks appear at 392.95 eV and 382.05 eV, which are characteristic peaks of uranyl ions, corresponding to U4f and U4f, respectively. 5 / 2 and U4f 7 / 2 ;

[0084] The adsorption of uranyl ions by the supramolecular self-assembled uranium adsorbent provided in Example 1 was tested using an X-ray photoelectron spectroscopy (Thermo, USA) instrument. The N1s spectra of the uranium adsorbent provided in Example 1 before and after adsorption of uranyl ions are shown below. Figure 8 As shown, MCP-5 represents the state before adsorption, and MCP-5-U represents the state after adsorption.

[0085] from Figure 8 It can be seen that the binding energy peaks at 399.91 eV and 398.74 eV of MCP-5 are attributed to -NH2 and =N-, respectively. After adsorption, these two peaks undergo a blue shift.

[0086] The adsorption of the supramolecular self-assembled uranium adsorbent provided in Example 1 was tested using an X-ray photoelectron spectroscopy (Thermo, USA) instrument. The O1s spectra of the uranium adsorbent provided in Example 1 before and after adsorption of uranyl ions are shown below. Figure 9 As shown, MCP-5 represents the state before adsorption, and MCP-5-U represents the state after adsorption.

[0087] from Figure 9 It can be seen that the binding energy peaks at 532.53 eV, 531.99 eV and 531.37 eV of MCP-5 are attributed to C=O / P=O, PO and OH, respectively. After adsorption, these three peaks red-shifted. These results are consistent with the results obtained from infrared spectroscopy, indicating that the complexation between -NH2, P=O and PO and uranyl ions is the main mechanism of uranium adsorbent adsorption.

[0088] In summary, the supramolecular self-assembled uranium adsorbent provided by this invention, formed by selecting organic adsorbents with specific molar ratios of reactants, achieves both rapid adsorption kinetics for uranyl ions and high adsorption capacity for uranyl ions, while also exhibiting excellent selectivity.

[0089] The applicant declares that this invention illustrates a supramolecular self-assembled uranium adsorbent, its preparation method, and its application through the above embodiments. However, this invention is not limited to the above process steps, meaning that this invention does not necessarily rely on the above process steps to be implemented. Those skilled in the art should understand that any improvements to this invention, equivalent substitutions of the raw materials used in this invention, additions of auxiliary components, and selection of specific methods all fall within the protection and disclosure scope of this invention.

Claims

1. A supramolecular self-assembled uranium adsorbent characterized in that, The raw material for preparing the uranium adsorbent comprises melamine, cyanuric acid and melamine phosphate in a molar ratio of 1:(0.5-2):(1-1.7); The preparation method of the supermolecular self-assembled uranium adsorbent comprises the following steps: (1) dissolving melamine and melamine phosphate in an organic solvent to obtain a mixed solution; dissolving cyanuric acid in an organic solvent to obtain a cyanuric acid solution; (2) reacting the mixed solution and the cyanuric acid solution obtained in step (1) to obtain the uranium adsorbent; The temperature of the reaction in step (2) is 25-30°C; The time of the reaction in step (2) is 10-30 min; The reaction in step (2) is carried out under stirring.

2. A method of preparing the uranium adsorbent of claim 1, characterized in that, The preparation method comprises the following steps: (1) dissolving melamine and melamine phosphate in an organic solvent to obtain a mixed solution; dissolving cyanuric acid in an organic solvent to obtain a cyanuric acid solution; (2) reacting the mixed solution and the cyanuric acid solution obtained in step (1) to obtain the uranium adsorbent; The temperature of the reaction in step (2) is 25-30°C; The time of the reaction in step (2) is 10-30 min; The reaction in step (2) is carried out under stirring.

3. The preparation method according to claim 2, characterized in that, The organic solvent in step (1) comprises dimethyl sulfoxide.

4. The production method according to claim 2, characterized by, The molar number of the melamine is 0.1-0.3 mmol based on 1 mL of the mixed solution in step (1).

5. The preparation method according to claim 2, characterized in that, The molar number of the melamine phosphate is 0.1-0.3 mmol based on 1 mL of the mixed solution in step (1).

6. The preparation method according to claim 2, characterized in that, The molar number of the cyanuric acid is 0.2-0.4 mmol based on 1 mL of the cyanuric acid solution in step (1).

7. The preparation method according to claim 2, characterized in that, The stirring speed is 400-550 r / min.

8. The preparation method according to claim 2, characterized in that, After the reaction in step (2) is completed, the method further comprises the steps of centrifugation, washing and drying.

9. The production method according to claim 8, characterized by, The washing comprises ethanol washing.

10. The method of claim 8, wherein, The drying temperature is 65-100°C.

11. Use of the uranium adsorbent according to claim 1 in seawater uranium extraction.

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