Preparation method of sulfonic acid-based porous organic polymer and application thereof in adsorption of uranyl ions and trace metal ions

Abstract

The application discloses a preparation method of a sulfonic acid-based porous organic polymer and application of the sulfonic acid-based porous organic polymer in adsorption of uranyl ions and trace metal ions. The preparation method comprises the following steps: firstly, benzylization modification is conducted on a cyclodextrin to obtain a benzylated cyclodextrin monomer; then, the benzylated cyclodextrin monomer is subjected to a Friedel-Crafts alkylation polymerization reaction with a linker under catalysis of a catalyst to construct a porous organic polymer with high crosslinking degree; and finally, chlorosulfonic acid is used for sulfonation modification to introduce high-density sulfonic acid group active sites. The obtained polymer combines the host-guest recognition ability of the cyclodextrin and the rapid mass transfer effect of the porous skeleton, and exhibits extremely fast adsorption kinetic response and excellent adsorption capacity. The material has simple preparation process and high stability, and is especially suitable for superfast extraction of ultra-low-concentration uranyl ions in seawater.

Description

Technical Field

[0001] This invention belongs to the field of environmental protection technology, specifically relating to the preparation of a sulfonic acid-based porous organic polymer and its application in uranyl ion adsorption. Background Technology

[0002] Uranium is the core fuel for nuclear power generation. With the increasing global demand for nuclear power, extracting uranium resources from seawater, which has reserves approximately 1,000 times that of land, has become crucial for ensuring energy security. However, the concentration of uranium in seawater is extremely low (approximately 3.3 ppb), and it exists primarily in the form of stable carbonate complexes, making extraction extremely difficult.

[0003] Among existing uranium extraction technologies, adsorption is considered the most promising method due to its low energy consumption and ease of operation. However, existing adsorption materials often face technical bottlenecks such as slow adsorption rates and long times to reach adsorption equilibrium (usually several hours or even days). In open seawater flow systems, the slow adsorption kinetics greatly limit the actual uranium capture efficiency of the materials.

[0004] In recent years, porous organic polymers (POPs) have become a research hotspot due to their advantages such as tunable structure and large specific surface area. However, how to further enhance the instantaneous affinity of materials for uranyl ions and the diffusion rate within the pores through molecular design while ensuring high chemical stability remains a major challenge in the field of uranium extraction from seawater. Therefore, developing a novel functionalized porous material with both ultra-high adsorption rate and high adsorption capacity is of significant engineering importance for the efficient development of marine uranium resources. Summary of the Invention

[0005] Therefore, the present invention aims to provide a method for preparing a sulfonic acid-based porous organic polymer and its applications. This polymer combines the molecular recognition properties of cyclodextrin with the high porosity of porous organic polymers (POPs) and introduces a high density of sulfonic acid groups, thus constructing a uranium extraction material with ultrafast kinetic response and high adsorption capacity. The material prepared by this invention exhibits excellent uranium capture efficiency in complex water bodies and seawater.

[0006] To achieve the above objectives, the present invention specifically adopts the following technical solution: The method for preparing the sulfonic acid-functionalized porous organic polymer adsorbent provided by the present invention includes the following steps: 1) Cyclodextrin, benzyl bromide, and sodium hydride were added to N,N-dimethylformamide in a specific order. The solution was cooled to 0°C, and then the temperature was raised to room temperature under a nitrogen atmosphere. After reacting for 6-8 hours, methanol was added to quench the reaction. The reaction solution was mixed with water and extracted with dichloromethane. The organic layer was dried with a drying agent and concentrated by rotary evaporation to obtain a pale yellow oily product. The crude product was purified by silica gel chromatography (petroleum ether and ethyl acetate in a volume ratio of 8:1).

[0007] 2) The pale yellow oily substance obtained in step 1) and the crosslinking agent were dissolved in 1,2-dichloroethane. The mixture was heated to 45°C and reacted for 5 hours under the action of a catalyst. The temperature was then increased to 80°C and the reaction was continued for 19 hours. After cooling the reaction to room temperature, the brown product was collected. The filter cake was washed successively with 1,2-dichloroethane, methanol, and water. After Soxhlet extraction for 24 hours, the solid product was vacuum dried at 80°C for 24 hours to obtain a porous organic polymer material.

[0008] 3) Dissolve the solid obtained in step 2) in an organic solvent, add a sulfonating agent, react at room temperature for 72 hours, and then filter, wash with water and dry the product to obtain a sulfonic acid-based porous organic polymer.

[0009] The specific reaction process of the technical solution provided by this invention is as follows:

[0010] Furthermore, the desiccant mentioned in step 1) is an anhydrous salt desiccant, which may be anhydrous sodium sulfate.

[0011] Further, the cyclodextrin mentioned in step 1) is at least one of α-cyclodextrin, β-cyclodextrin, and γ-cyclodextrin.

[0012] Further, the catalyst mentioned in step 2) is a Lewis acid, and is at least one of zinc dichloride, ferric chloride, zirconium tetrachloride, antimony pentachloride, aluminum trichloride, tin tetrachloride, boron trifluoride, and copper chloride.

[0013] Further, the crosslinking agent mentioned in step 2) is at least one of 1,2-dichloroethane, dimethoxymethane, 1,4-p-dichlorobenzyl, p-tetrachlorobenzyl, 1,4-dichlorobutane, 4-(chloromethyl)benzoyl chloride, terephthaloyl chloride, 2,4-dichlorobenzyl chloride, m-dichlorobenzyl, o-dichlorobenzyl, 1,3,5-tribromobenzene, 1,3,5-tris(4-bromophenyl)benzene, 1,3,5-tris(3-bromophenyl)benzene, 4,4'-biphenyl diacetyl chloride, 4,4-dichlorobiphenyl, p-chlorobenzylidene dichloro, 1,2,4,5-tetrabromomethylbenzene, tetra(4-bromophenyl)ethylene, biphenyl dichlorobenzyl, 1,3,5-tris(bromomethyl)benzene, 2,3-dichlorobenzyl bromide, 2,5-dichlorobenzyl chloride, and 4-bromophenylethyl bromide.

[0014] Further, the organic solvent mentioned in step 3) is selected from at least one of the following: 1,2-dichloroethane, 1,2-dibromoethane, 1,1,2,2-tetrachloroethane, 1,1,2-trichloroethane, 1,1,2,2-tetrabromoethane, dibromomethane, dichloromethane, tribromomethane, and trichloromethane.

[0015] Furthermore, the sulfonating agent mentioned in step 3) is chlorosulfonic acid.

[0016] The second objective of this invention is to protect the sulfonic acid-based porous organic polymer prepared by the above method.

[0017] A third objective of this invention is to protect the application of the sulfonic acid-based porous organic polymer in the adsorption of uranyl ions in aqueous solutions containing uranyl ions. It is particularly suitable for the ultra-rapid extraction of ultra-low concentrations of uranyl ions from seawater, and for its application in the adsorption of trace metal ions. These trace metal ions include Na, Mg, Al, K, Ca, Cr, Mn, Fe, Ni, Cu, Sn, Ti, V, Co, Zn, Ga, Sb, Ba, Pb, Bi, and other metal ions.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The polymer prepared in this invention exhibits ultrafast adsorption kinetics, reaching adsorption equilibrium within 15 seconds. This is attributed to the highly branched porous framework providing extremely short mass transfer paths, and the synergistic effect of the cyclodextrin cavity on the "pre-capture" of uranyl ions, which is significantly better than similar materials reported in the literature.

[0019] (2) This invention is the first to utilize the intraluminal host-guest inclusion effect of cyclodextrin and the strong chemical complexation effect of the peripheral sulfonic acid groups. This "dual capture" mode not only greatly improves the equilibrium adsorption capacity, but also ensures efficient capture capability in ultra-low concentration (ppb level) environments.

[0020] (3) The introduction of sulfonic acid groups significantly improves the wettability of porous organic polymers in aqueous phase. This favorable physicochemical environment facilitates the rapid diffusion of uranyl ions to the active sites deep within the material, thereby improving the utilization rate of functional groups.

[0021] (4) The material skeleton is composed of strong covalent bonds (CC / C-Ar), which has excellent chemical stability and can withstand the salinity of seawater and weak alkaline environment. Moreover, the preparation process does not require complicated post-processing and has good industrial application potential. Attached Figure Description

[0022] Figure 1 The images show the precursor BnCD NMR (left) and infrared spectrum (right). Figure 2These are the infrared spectra of the polymer before sulfonation (left) and after sulfonation (right); Figure 3 It represents the sulfonate grafting amount of the four adsorbents; Figure 4 It is a sulfonic acid-based porous organic polymer for UO2 2+ Adsorption isotherm plot; Figure 5 It is a sulfonic acid-based porous organic polymer for UO2 2+ Adsorption kinetics diagram. Detailed Implementation

[0023] The present invention will now be described in detail with reference to the accompanying drawings and embodiments, but the applicable embodiments of the present invention are not limited thereto. Example 1

[0024] In this embodiment, a method for preparing a sulfonic acid-based porous organic polymer includes the following steps: Cyclodextrin β-CD (500 mg) was dissolved in anhydrous N,N-dimethylformamide (10 mL). The solution was cooled to 0°C, and sodium hydride (740 mg) was added in portions under a nitrogen atmosphere. After stirring for 15 minutes, benzyl bromide (2.20 mL) was slowly added, and the reaction mixture was heated to room temperature. After stirring for 24 hours, the reaction mixture was quenched by adding methanol (5 mL), the resulting residue was diluted with water (100 mL), and extracted with dichloromethane (3 × 50 mL). The organic layers were combined, washed with brine, dried over anhydrous sodium sulfate, filtered, and concentrated using a rotary evaporator. The crude product was purified by silica gel chromatography (petroleum ether:ethyl acetate = 8:1) to give the precursor BnCD.

[0025] The structure is confirmed as follows: Figure 1 The NMR analysis results showed that the peaks in the 7.0-7.5 ppm range corresponded to the trisubstituted phenyl signals at the C2, C3, and C6 positions; Figure 1 1450-1600 cm⁻¹ in the infrared spectrum -1 The stretching vibration peaks within the range are attributed to benzene ring skeletal vibrations. The above spectral characteristics indicate that the precursor has been initially synthesized. Example 2

[0026] In this embodiment, a method for preparing a sulfonic acid-based porous organic polymer includes the following steps: β-BnCD (0.46 g) and dimethoxymethane FDA (0.48 g), or 1,4-dichlorobenzyl(DCX) (1.1 g), or biphenyl dichlorobenzyl(BCMBP) (1.58 g), or 1,3,5-tris(bromomethyl)benzyl(TBB) (2.25 g) were dissolved in 1,2-dichloroethane (10 mL), and then FeCl3 (1.03 g) was slowly added under a nitrogen atmosphere at room temperature. The reaction system was fitted with a condenser, and the reaction was carried out at 45 °C for 5 hours, followed by refluxing at 80 °C for 19 hours. After cooling to room temperature, the brown precipitate was collected by filtration and washed with methanol and water until the filtrate became colorless. Further purification was then carried out by Soxhlet extraction with methanol for 24 hours. The polymer was then vacuum dried at 80 °C for 24 hours to obtain a brown powder. Example 3

[0027] In this embodiment, a method for preparing a sulfonic acid-based porous organic polymer includes the following steps: A brown powder (1 g) was dissolved in 1,2-dichloroethane (30 mL) with stirring at 0°C. After complete dissolution, a solution of chlorosulfonic acid (10 mL) in 1,2-dichloroethane (20 mL) was added. The solution was heated to room temperature and reacted for 72 hours after 30 minutes. After cooling, the resulting brown / black solid was poured into excess deionized water (1000 mL), then filtered and washed. The product was separated from the solution by filtration, and the pH of the filtrate was measured with indicator paper. This process was repeated until the pH of the filtrate was 7. The polymer was then dried at room temperature for several hours, followed by drying in a vacuum oven at 80°C for 24 hours to obtain the sulfonic acid-based porous organic polymer.

[0028] The structure is confirmed as follows: Figure 2 The infrared spectrum of the polymer before sulfonation shows that the synthesized polymer still contains 1450-1600 cm⁻¹. -1 The vibrational peak of the aromatic ring skeleton indicates that the crosslinking reaction of Friedel-Crafts alkylation was successful; in the infrared spectrum of the sulfonated polymer, the peak at 1172 cm⁻¹ indicates crosslinking success. -1 With 1086cm -1 The nearby peaks correspond to the asymmetric and symmetric stretching vibrations of the O=S=O bond, respectively, while the 623cm peak... -1 The nearby peaks are attributed to the stretching vibrations of the CS single bond, and these features confirm that the polymer sulfonic acid groups have been successfully grafted.

[0029] Table 1 shows the nitrogen adsorption-desorption data of the polymers before and after sulfonation. The materials exhibit a type IV nitrogen adsorption isotherm, indicating the existence of a hierarchical pore structure with a certain proportion of micropores, mesopores, and macropores. With increasing crosslinking agent chain length, the BET specific surface area of ​​the initial polymer tends to increase. After chlorosulfonic acid sulfonation, the specific surface area of ​​the materials tends to decrease due to the blockage of some pores by the sulfonic acid groups, further confirming the successful introduction of sulfonic acid groups. Even with a decrease in BET, the sulfonated polymer still maintains a satisfactory BET value and degree of sulfonation, which is beneficial for achieving rapid and efficient uranium adsorption.

[0030] Table 1. Pore structure data of polymers before and after sulfonation obtained by polymerization with different linker lengths and lengths.

[0031] Preliminary performance tests revealed that the sulfonated polymer with β-CD as the core exhibited performance at 10000 μg. L -1 The lowest remaining uranyl ion concentration in the solution was 0.61 μg. L -1 And the highest adsorption capacity is 362.88 mg g. -1 This indicates that its adsorption performance is good. Therefore, in order to further evaluate the adsorption behavior of sulfonated polymer materials for uranyl ions, the adsorption of uranyl ions by polymers synthesized with β-CD as the core and linkers of different lengths was studied.

[0032] Application Examples:

[0033] Adsorption performance of the four adsorbents prepared in Examples 3, 2, and 1 1. Adsorption properties of sulfonic acid-based porous organic polymers The main experimental procedure for adsorbing uranyl ions and other metal ions using sulfonic acid-based porous organic polymers is as follows: Weigh a certain amount of adsorbent, and at an initial concentration of 10–400 mg… L -1 The metal ions were adsorbed by shaking in the solution. After shaking, the supernatant was taken and the concentration of the remaining ions in the solution after adsorption was measured by ICP-OES and ICP-MS.

[0034] The adsorption capacity of sulfonic acid-based porous organic polymers can be calculated using the following formula: Q = (C0 - C e )V / m, where Q is the adsorption capacity (mg) of the sulfonic acid-based porous organic polymer. g -1 C0 is the initial concentration of the adsorbent (mg). L -1 );C e The remaining concentration (mg) of the supernatant after adsorption. L -1 V is the volume of the adsorbent (L); m is the mass of the polymer (g).

[0035] 2. Results 2.1 Comparison of Adsorption Effects of Four Adsorbents Figure 4 and Figure 5 The effects of initial uranium concentration and adsorption time on the adsorption of UO2 by sulfonic acid-based porous organic polymers were investigated. 2+ The effect. 5 mg of sulfonic acid-based porous organic polymer was added to 10 mL of solutions containing different concentrations of UO2. 2+ In an aqueous solution, the mixture was shaken in a constant-temperature shaker for 24 h. After adsorption, the solution was filtered through a 0.22 μm microporous membrane, and the remaining UO2 in the filtrate was determined by inductively coupled plasma mass spectrometry. 2+ Concentration. The adsorption capacity is calculated based on the concentration difference before and after adsorption, and the results are as follows: Figure 4 As shown, the polymer with BCMBP as the crosslinking agent had the highest adsorption capacity of 362.88 mg. g -1 This is mainly attributed to the fact that while maintaining a high specific surface area, the material forms a hierarchical porous structure that is more conducive to the diffusion of uranyl ions, and achieves efficient grafting of sulfonic acid groups, providing abundant active sites for uranyl ions.

[0036] Add 10 mg of sulfonic acid-based porous organic polymer to 25 mL of a solution containing 200 mg of [polymer / material]. L -1 UO2 2+ Samples were taken at different time points in an aqueous solution under stirring conditions. After filtration through a 0.22 μm microporous membrane, the residual UO2 in the filtrate was determined by inductively coupled plasma mass spectrometry. 2+ Concentration, adsorption capacity calculated and adsorption kinetic curve plotted, results as follows: Figure 5 As shown, all four adsorbents exhibited extremely rapid adsorption responses, reaching adsorption equilibrium within 15 seconds. This rapid adsorption phase can be attributed to the significantly enhanced hydrophilicity of the polymer surface after sulfonic acid modification, which greatly reduces the liquid film mass transfer resistance; the unique cylindrical cavity structure of cyclodextrin also contributes to the adsorption of UO2. 2+ With physical confinement and host-guest pre-recognition capabilities, coupled with a high density of strong -SO3H complexing sites on its framework, the β-BnCD-BCMBP-S adsorbent material achieves extremely rapid capture of uranyl ions. Calculations show that the β-BnCD-BCMBP-S adsorbent material effectively captures UO2. 2+ Allocation coefficient K d The value reached 3.1 × 10 7 mL g -1 Far exceeding the generally accepted threshold for high-performance adsorption materials (>10) 6mL g -1 This further confirms the adsorption effect of the adsorbent material on UO2. 2+ The high affinity of uranyl ions is demonstrated by experimental results. The sulfonic acid-based porous organic polymer prepared in this invention exhibits excellent adsorption efficiency for uranyl ions, showing promising application prospects.

[0037] 2.2 Desorption effect of adsorbent material in other solvents The sulfonic acid-based porous organic polymer synthesized in this invention is not only suitable for the adsorption of uranyl ions in water, but also for the removal of trace metal ions from solvents such as N-methylpyrrolidone, isopropanol, and acetonitrile. For example, after adsorption in an N-methylpyrrolidone solution, the residual metal ion content is less than 1 μg·L⁻¹. -1 The purity reaches over 99.9% (Table 2). Therefore, the material prepared by this invention has broad application prospects.

[0038] Table 2. Metal ion concentrations before and after adsorption of N-methylpyrrolidone solution

[0039] The above description is only a preferred embodiment of the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered to be included within the protection scope of the present invention.

Claims

1. A method for preparing a sulfonic acid-based porous organic polymer, characterized in that: Benzylated cyclodextrin and linkers were polymerized under the action of a catalyst to obtain a porous organic polymer precursor; then, the precursor was sulfonated with a sulfonating agent to introduce sulfonic acid groups to obtain the sulfonic acid-based porous organic polymer.

2. The preparation method according to claim 1, characterized in that: Includes the following steps: 1) Dissolve cyclodextrin in N,N-dimethylformamide, then add sodium hydride and benzyl bromide in portions, and react under N2 atmosphere to obtain benzylated cyclodextrin monomer; 2) Dissolve the benzylated cyclodextrin monomer and linker obtained in step 1) in 1,2-dichloroethane, add a catalyst, and carry out a polymerization reaction to obtain a porous organic polymer; 3) Dissolve the porous organic polymer obtained in step 2) in an organic solvent, add a sulfonating agent to carry out a sulfonation reaction, and after the reaction is completed, filter, wash and dry to obtain a sulfonic acid-based porous organic polymer.

3. The preparation method according to claim 2, characterized in that: The cyclodextrin is at least one of α-cyclodextrin, β-cyclodextrin, and γ-cyclodextrin.

4. The preparation method according to claim 2, characterized in that: The linker is at least one of 1,2-dichloroethane, dimethoxymethane, 1,4-p-dichlorobenzyl, p-tetrachlorobenzyl, 1,4-dichlorobutane, 4-(chloromethyl)benzoyl chloride, terephthaloyl chloride, 2,4-dichlorobenzyl chloride, m-dichlorobenzyl, o-dichlorobenzyl, 1,3,5-tribromobenzene, 1,3,5-tris(4-bromophenyl)benzene, 1,3,5-tris(3-bromophenyl)benzene, 4,4'-biphenyldiacetyl chloride, 4,4-dichlorobiphenyl, p-chlorobenzylidene dichloro, 1,2,4,5-tetrabromomethylbenzene, tetra(4-bromophenyl)ethylene, biphenyl dichlorobenzyl, 1,3,5-tris(bromomethyl)benzene, 2,3-dichlorobenzyl bromide, 2,5-dichlorobenzyl chloride, and 4-bromophenylethyl bromide.

5. The preparation method according to claim 2, characterized in that: The catalyst is at least one of zinc dichloride, ferric chloride, zirconium tetrachloride, antimony pentachloride, aluminum trichloride, tin tetrachloride, boron trifluoride, and copper chloride; the sulfonating agent is chlorosulfonic acid.

6. The preparation method according to claim 2, characterized in that: The organic solvent is at least one of 1,2-dichloroethane, 1,2-dibromoethane, 1,1,2,2-tetrachloroethane, 1,1,2-trichloroethane, 1,1,2,2-tetrabromoethane, dibromomethane, dichloromethane, tribromomethane, and chloroform.

7. The preparation method according to claim 2, characterized in that: The polymerization reaction was carried out under a nitrogen atmosphere at a temperature of 80°C for 24 hours.

8. The preparation method according to claim 2, characterized in that: The sulfonation reaction was first stirred under ice bath conditions, and then reacted at room temperature for 72 hours.

9. A sulfonic acid-based porous organic polymer prepared by the method according to any one of claims 1-8.

10. The application of the sulfonic acid-based porous organic polymer according to claim 9 in the adsorption of uranyl ions and trace metal ions.

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