Phosphonic acid-based functionalized ion single crystal material for recovering thorium from rare earth waste ore and nuclear wastewater and preparation method of phosphonic acid-based functionalized ion single crystal material

Abstract

The invention discloses a phosphonic acid group functionalized ionic single crystal material as well as a preparation method and application thereof. According to the invention, phosphonic acid groups are used as anion ligands, 1, 1-dialkyl-4, 4 '-dipyridyl dihalide is used as cation ligands, and the phosphonic acid group functionalized ion single crystal material is formed through self-assembly under the electrostatic attraction action of the phosphonic acid groups and pyridyl groups. The obtained phosphonic acid group functionalized ion single crystal has an anion skeleton, rich oxygen-containing groups and rich nitrogen coordination sites, and the adsorption performance of thorium recovered from rare earth waste ore and nuclear wastewater is remarkably improved. The ion single crystal material prepared by the invention is simple in preparation method, mild in condition, low in energy consumption in the preparation process, and green and environment-friendly. Pyridyl and phosphonic acid group in the phosphonic acid group functionalized ion single crystal play a synergistic adsorption role, so that the adsorption rate is increased, the problem of insufficient adsorption quantity caused by single acting site of a traditional adsorbent is solved, and the problems of low selectivity and difficulty in recovery of thorium from nuclear wastewater during recovery of thorium from rare earth waste ore are solved; and the method has good practical application value.

Description

Technical Field

[0001] The present invention belongs to the technical field of functional materials, and relates to a phosphonic acid-based functionalized ionic single crystal material and a preparation method thereof, which is mainly used as an adsorption separation material for the efficient and selective recovery of thorium from rare earth waste mines and nuclear wastewater. Background Art

[0002] In recent years, the use of thorium-based fuels in nuclear reactors has been a major research focus due to their outstanding characteristics, including proliferation resistance, low radioactive waste generation, and substantial cost-effectiveness compared to thorium-based fuels. Monazite ore, comprising 6%-12% of thorium phosphate, is the primary source of thorium. Generally, high-purity thorium is obtained through a sequential process of leaching, selective precipitation, separation, and purification. This traditional method often requires the consumption of large quantities of hazardous chemicals, placing a burden on the environment. Solvent extraction processes are widely used due to their rapidity, ease of operation, and cost-effectiveness. However, these processes require the use of large amounts of chelating agents and organic solvents, which not only increases costs but also poses environmental risks.

[0003] Organic ionic crystals are a class of crystalline materials composed of organic ions, typically exhibiting unique physical and chemical properties. The structure of these crystals is primarily composed of organic cations and inorganic anions or other organic anions bonded together by ionic bonds. The composition and structure of organic ionic crystals can be very diverse, depending on the type of organic molecules and anions used. This diversity allows them to exhibit different properties in different applications. Many organic ionic crystals have excellent optical properties, good electrical conductivity, and thermal stability. Based on the charge characteristics of the ionic bonds in the monomers and the designability of the organic groups, the functional groups, active adsorption sites, and physical and chemical properties of the material can be adjusted as needed, thereby designing and preparing organic ionic crystal materials with rich and diverse structures and properties.

[0004] Based on this, the present invention, based on extensive literature research and previous research work, fitted a variety of phosphonic acid-based ion crystals, explored the differences in the structures of different crystals and the effects of different functional groups on the materials, and examined their effects on the adsorption of radionuclides (233Th 4+ ) fields. Leveraging the inherent charge properties of ionic bonds and the designability of organic groups, we have designed and prepared phosphonate-based ionic crystal materials with diverse structures and properties. We utilize electrostatic interactions, pore effects, coordination between specific functional groups and nuclide ions, and π-π interactions to achieve material construction and selective separation of nuclide ions. We are advancing research in single crystal materials in chemistry, studying their adsorption mechanisms, and applying them to the efficient separation of nuclide ions in wastewater, resulting in some important results in the research of high-efficiency adsorbents. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a phosphonic acid-functionalized ionic single crystal material for recovering thorium from rare earth waste mines and nuclear wastewater, so as to solve the problem that the comprehensive performance (thorium extraction rate, adsorption capacity and adsorption selectivity, etc.) of existing thorium recovery materials from rare earth waste mines and nuclear wastewater is poor, resulting in their limited application in actual nuclear wastewater recovery of thorium.

[0006] The present invention discloses a phosphonate-functionalized ionic single crystal material, which can be used to recover thorium from waste rare earth mines and nuclear wastewater. The material uses phosphonate groups as anionic ligands and 1,1-dialkyl-4,4'-bipyridyl dihalide as cationic ligands. The material is self-assembled in a neutral solvent through electrostatic adsorption between phosphonate and pyridyl groups. The molar ratio of the phosphonate anionic ligand to the 1,1-dialkyl-4,4'-bipyridyl dihalide cationic ligand is 1:1. The specific preparation method includes the following steps: (1) The phosphonic acid anionic ligand is dissolved in dimethyl sulfoxide or ultrapure water to obtain an anionic ligand solution; the concentration of the anionic ligand solution is 0.01 mol / L~1 mol / L; (2) 1,1-dialkyl-4,4'-bipyridyl dihalide is dissolved in dimethyl sulfoxide (DMSO) or ultrapure water to obtain a cationic ligand solution; the concentration of the cationic ligand is 0.01 mol / L~1 mol / L; (3) Slowly add the cationic solution to the anionic solution and mix well: If the solvent is dimethyl sulfoxide, the mixed solution is placed in a sealed beaker containing ultrapure water, and allowed to stand at room temperature for one month or at 65-70°C for 3-7 days to precipitate crystals by an antisolvent diffusion method; the precipitated crystals are washed with ethanol or ultrapure water and dried to obtain a white phosphonic acid functionalized ionic single crystal material.

[0007] If the solvent is ultrapure water, the mixed solution is allowed to stand at room temperature for 7 days, and crystals are precipitated by evaporating an appropriate solvent; the precipitated crystals are washed with ethanol and dried to obtain a white phosphonic acid functionalized ionic single crystal material.

[0008] The phosphonic acid anionic ligand is a compound having one of the following structures: The structure of the 1,1-dialkyl-4,4'-bipyridyl dihalide is: Wherein, R is methyl, ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl, n-heptyl or n-octyl, and X is I or Br.

[0009] Testing has shown that the phosphonate-functionalized ion single crystal material prepared by the present invention exhibits significant adsorption of thorium ions in simulated rare earth mining wastewater at low concentrations. The phosphonate-functionalized ion single crystal material exhibits an adsorption capacity of up to 450 mg / g of thorium. These results demonstrate the significant advantages and enormous application potential of phosphonate-functionalized ion single crystal materials in extracting thorium from rare earth mining wastewater.

[0010] The present invention provides the application of the phosphonic acid functionalized ion single crystal material obtained by the preparation method in adsorbing and recovering thorium from rare earth waste mines or nuclear wastewater.

[0011] In summary, the present invention has the following advantages over the prior art: 1. Multiple adsorption sites: The multiple adsorption sites of the polyphosphonic acid functional groups in the anionic ligand and the pyridyl functional groups in the cationic ligand play a synergistic role, effectively improving the adsorption capacity of the adsorbent for thorium ions in rare earth wastewater; 2. Mild synthesis conditions: rapid synthesis at room temperature or below 70°C; 3. Excellent thorium enrichment capacity: A high enrichment adsorption capacity of 450 mg / g was achieved in an aqueous solution with a thorium concentration of 50 ppm; 4. High adsorption selectivity: In the presence of multiple rare earth element impurities, the phosphonic acid functionalized ion single crystal has extremely high selectivity for thorium ions. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is the unit cell diagram of the BPBP-Py phosphonate functionalized ion single crystal prepared in Example 1.

[0013] Figure 2 This is a scanning electron microscope image of the BPBP-Py phosphonic acid functionalized ion single crystal prepared in Example 1.

[0014] Figure 3 The adsorption kinetics of the BPBP-Py phosphonate functionalized ion single crystal prepared in Example 1 in a thorium-containing aqueous solution and the corresponding pseudo-first-order and pseudo-second-order kinetic model fitting results are shown.

[0015] Figure 4 The adsorption isotherm of the BPBP-Py phosphonate functionalized ion single crystal prepared in Example 1 in a thorium-containing aqueous solution and the corresponding Langmuir and Freundlich isotherm adsorption model fitting results.

[0016] Figure 5 Adsorption selectivity test results of BPBP-Py prepared in Example 1, PMBP-Py prepared in Example 2, and TP-Py phosphonic acid functionalized ion single crystals prepared in Example 3 in thorium-containing aqueous solution.

[0017] Figure 6 The long-term adsorption performance test results of the BPBP-Py phosphonic acid functionalized ion single crystal prepared in Example 1 in simulated rare earth wastewater.

[0018] Figure 7 This is the unit cell diagram of the PMBP-Py phosphonic acid functionalized ion single crystal prepared in Example 2.

[0019] Figure 8 This is a scanning electron microscope image of the PMBP-Py phosphonate functionalized ion single crystal prepared in Example 2.

[0020] Figure 9 This is the unit cell diagram of the TP-Py phosphonic acid functionalized ion single crystal prepared in Example 3.

[0021] Figure 10 This is a scanning electron microscope image of the TP-Py phosphonate functionalized ion single crystal prepared in Example 3. DETAILED DESCRIPTION

[0022] To further clarify the objectives, technical solutions, and advantages of the present invention, the following describes the preparation of the phosphonate-functionalized ionic single crystal material and its effectiveness in extracting thorium from nuclear wastewater, using specific examples. In the examples, where specific conditions are not specified, conventional conditions or those recommended by the manufacturer were followed. Reagents and instruments used, where the manufacturer is not specified, are commercially available conventional products.

[0023] Example 1: Preparation of BPBP-Py Phosphonate-functionalized Ionic Single Crystals (1) Preparation of BPBP-Py phosphonate functionalized ion single crystals: Disperse biphenyl-4,4-diphosphonic acid (BPBP, 0.04 mmol) in 2 mL of dimethyl sulfoxide and heat to completely dissolve it; dissolve 1,1'-dimethyl-4,4'-bipyridyl diiodide (Py, 0.04 mmol) in 2 mL of dimethyl sulfoxide, quickly mix the Py solution with the BPBP solution, then place the sample bottle containing the mixed solution in a beaker with a small amount of ultrapure water, heat it in an oven at 70 degrees Celsius for 3 days, precipitate the crystals by the antisolvent diffusion method, wash with ultrapure water, and dry to obtain light yellow block single crystals of BPBP-Py. Figure 1 As shown, the crystal structure of BPBP-Py belongs to the triclinic system and space group P-1. The crystal parameters are a = 10.277 Å, b = 13.623 Å, c = 18.550 Å, α = 72.101°, β = 75.291°, and γ = 80.899°.

[0024] (2) Morphology test: Figure 2 This is a scanning electron microscopy image of BPBP-Py. Figure 2It shows that the BPBP-Py phosphonate functionalized ionic single crystal material exhibits an ordered layered structure and regular block crystal form with a particle size of 1~2μm. Its special spatial structure is conducive to the adsorption of thorium ions.

[0025] (3) Thorium separation selectivity test in rare earth mixed sample test Thorium separation selectivity test for rare earth mixtures: 1 L of a simulated rare earth mixture was prepared with ultrapure water, maintaining a 20 mg / L concentration of each rare earth element. 20 mL of each diluted solution was transferred to a centrifuge tube, and 3 mg of BPBP-Py was added. Adsorption was then performed on a thermostatic oscillator. After adsorption, the adsorbent was filtered, and the thorium ion concentration in the filtrate was measured using inductively coupled plasma optical emission spectrometry (ICP-OES) or inductively coupled plasma mass spectrometry (ICP-MS). After adsorption for 2 hours at 25°C, the adsorption capacity reached 136 mg / g.

[0026] (4) Thorium extraction performance test from nuclear wastewater Simulated nuclear wastewater test: Prepare 1 L of simulated nuclear wastewater with ultrapure water, and calculate the feed mass according to the concentration in Table 1. Transfer 20 mL of each diluted solution to a centrifuge tube, then add 3 mg of BPBP-Py. Adsorption is performed on a constant-temperature oscillator. After adsorption, the adsorbent is filtered, and the thorium ion concentration in the filtrate is measured using inductively coupled plasma optical emission spectrometry (ICP-OES) or inductively coupled plasma mass spectrometry (ICP-MS). The adsorption capacity is calculated. After 2 hours of adsorption at 25°C, the adsorption capacity reaches 231 mg / g.

[0027] Figure 3 These are the fitting results of pseudo-first-order and pseudo-second-order kinetic models corresponding to the adsorption kinetics of BPBP-Py phosphonate functionalized ion single crystals in thorium-containing aqueous solution. Figure 4 It shows that the adsorption of thorium ions by BPBP-Py increases sharply within 20 minutes. The fitting results of pseudo-first-order and pseudo-second-order kinetics are very good, R 2 The values were 0.96674 and 0.97338, respectively. In addition, the Langmuir adsorption isotherm and Freundlich adsorption isotherm models were fitted ( Figure 4 ), the results show that the R of the Langmuir fitting equation 2 The higher the value, the more obvious the adsorption process is. 2 The value is only 0.86202, which is much lower than Langmuir's R 2The value is 0.94097, indicating that chemical adsorption in the form of ion exchange may exist during the adsorption process and is a single-layer adsorption on the surface of the material. In addition, Figure 5 The results show that the BPBP-Py phosphonate functionalized ion single crystal material has high selectivity for thorium ions, which is due to the synergistic effect of the phosphonate functional group and the pyridyl functional group to achieve precise adsorption. Figure 6 ), it can be observed that BPBP-Py material has a significant adsorption effect on thorium ions in the low concentration range (1-100 mg / L).

[0028] Example 2: Preparation of PMBP-Py Phosphonate-functionalized Ionic Single Crystals (1) Preparation of PMBP-Py phosphonate functionalized ion single crystals: Disperse (1,4-phenylenebis(methylene))diphosphonic acid (PMBP, 0.04 mmol) in 2 mL ultrapure water and heat to completely dissolve it; dissolve 1,1'-dimethyl-4,4'-bipyridyl diiodide (Py, 0.04 mmol) in 2 mL ultrapure water, quickly mix the Py solution with the PMBP solution, and let it stand at room temperature for 7 days. Crystals were precipitated by solvent evaporation, washed with ultrapure water, and dried to obtain white block single crystals of PMBP-Py. Figure 7 As shown in Figure 2, the crystal structure of PMBP-Py belongs to the triclinic system and the space group is P-1. The crystal parameters are a = 8.4543 Å, b = 9.8549 Å, c = 14.1661 Å, α = 83.6430°, β = 79.6850°, and γ = 82.3990°.

[0029] (2) Morphology test: Figure 8 This is a scanning electron microscopy image of PMBP-Py. Figure 8 It shows that the PMBP-Py phosphonate functionalized ionic single crystal material exhibits an ordered layered structure and regular block crystal form, with a particle size of about 1 μm. Its special spatial structure is conducive to the adsorption of thorium ions.

[0030] (3) Thorium separation selectivity test in rare earth mixed sample test Thorium separation selectivity test for rare earth mixtures: 1 L of a simulated rare earth mixture was prepared with ultrapure water, maintaining a 20 mg / L concentration of each rare earth element. 20 mL of each diluted solution was transferred to a centrifuge tube, and 3 mg of PMBP-Py was added. Adsorption was then performed on a thermostatic oscillator. After adsorption, the adsorbent was filtered, and the thorium ion concentration in the filtrate was measured using inductively coupled plasma optical emission spectrometry (ICP-OES) or inductively coupled plasma mass spectrometry (ICP-MS). After adsorption for 2 hours at 25°C, the adsorption capacity reached 51.05 mg / g.

[0031] Example 3: Preparation of TP-Py phosphonate functionalized ion single crystals (1) Preparation of TP-Py phosphonate functionalized ion single crystals: (1,4-phenylenebis(methylene))diphosphonic acid (TP, 0.04 mmol) was dispersed in 2 mL of dimethyl sulfoxide and heated to completely dissolve; 1,1'-dimethyl-4,4'-bipyridyl diiodide (Py, 0.04 mmol) was dissolved in dimethyl sulfoxide, the Py solution was quickly mixed with the TP solution, and then the sample bottle containing the mixed solution was placed in a beaker with a small amount of ultrapure water, and placed in a 70 degree Celsius oven for 7 days. The crystals were precipitated by the antisolvent diffusion method, washed with ultrapure water, and dried to obtain light yellow block single crystals of TP-Py. Figure 9 As shown in Figure 3, the crystal structure of TP-Py belongs to the triclinic system and the space group is P-1. The crystal parameters are a = 15.9330 Å, b = 16.0552 Å, c = 16.2563 Å, α = 102.349°, β = 90.584°, and γ = 90.704°.

[0032] (2) Morphology test: Figure 10 This is a scanning electron microscope image of TP-Py. Figure 10 It shows that the TP-Py phosphonic acid functionalized ionic single crystal material exhibits an ordered layered structure and regular block crystal form, with a particle size of about 1μm. Its special spatial structure is conducive to the adsorption of thorium ions.

[0033] (3) Thorium separation selectivity test in rare earth mixed sample test Thorium separation selectivity test for rare earth mixtures: 1 L of simulated rare earth mixture was prepared with ultrapure water, maintaining a concentration of 20 mg / L for each rare earth element. 20 mL of each diluted solution was placed in a centrifuge tube, and 3 mg of TP-Py was added. Adsorption was performed on a thermostatic oscillator. After adsorption, the adsorbent was filtered, and the thorium ion concentration in the filtrate was measured using inductively coupled plasma optical emission spectrometry (ICP-OES) or inductively coupled plasma mass spectrometry (ICP-MS). The adsorption capacity was calculated. After 2 hours of adsorption at 25°C, the adsorption capacity reached 7.93 mg / g.

Claims

1. A phosphonate-functionalized ionic single crystal material, characterized in that: It is formed by the self-assembly of phosphonic acid anionic ligands and 1,1-dialkyl-4,4'-bipyridyl dihalide cationic ligands through electrostatic adsorption; The phosphonic acid anionic ligand is one of the following structures: The structural formula of the 1,1-dialkyl-4,4'-bipyridyl dihalide cationic ligand is: Wherein, R is methyl, ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl, n-heptyl or n-octyl, and X is I or Br.

2. The phosphonic acid functionalized ionic single crystal material according to claim 1, characterized in that: The molar ratio of the phosphonic acid anion ligand to the 1,1-dialkyl-4,4'-bipyridyl dihalide cationic ligand is 1:

1.

3. A method for preparing the phosphonic acid functionalized ionic single crystal material according to claim 1 or 2, characterized in that: The following steps are involved: (1) Dissolving the phosphonic acid anionic ligand in dimethyl sulfoxide or ultrapure water to obtain an anionic ligand solution; (2) dissolving 1,1-dimethyl-4,4'-bipyridyl dihalide in dimethyl sulfoxide or ultrapure water to obtain a cationic ligand solution; (3) Slowly add the cationic solution to the anionic solution and mix well: If the solvent is dimethyl sulfoxide, place the mixed solution in a sealed beaker containing ultrapure water, and let it stand at room temperature for one month or at 65-70°C for 3-7 days to precipitate crystals by the antisolvent diffusion method; If the solvent is ultrapure water, the mixed solution is left to stand at room temperature for 7 days to evaporate the appropriate solvent to precipitate crystals; (4) The precipitated crystals are washed with ethanol or ultrapure water and dried to obtain phosphonic acid functionalized ionic single crystal materials.

4. The method for preparing a phosphonic acid functionalized ionic single crystal material according to claim 3, characterized in that: In step (1), the concentration of the anionic ligand solution is 0.01 mol / L~1 mol / L.

5. The method for preparing the phosphonic acid functionalized ionic single crystal material according to claim 3, characterized in that: In step (2), the concentration of the cationic ligand is 0.01 mol / L~1 mol / L.

6. Use of the phosphonic acid group functionalized ionic single crystal material according to any one of claims 1 to 2 or the phosphonic acid group functionalized ionic single crystal material obtained by the preparation method according to any one of claims 3 to 5 in the adsorption and recovery of thorium from waste rare earth mines or nuclear wastewater.

7. The use according to claim 6, characterized in that In rare earth ion impurities La 3+ 、Ce 3+ 、Pr 3+ 、Nd 3+ 、Sm 3+ 、Eu 3+ 、Gd 3+ 、Tb 3+ 、Dy 3+ 、Ho 3+ 、Er 3+ 、Tm 3+ 、Yb 3+ 、Lu 3+ 、Y 3+ In the presence of , the single crystal material has a highly selective adsorption of thorium ions.

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