Aminooxime fluorinated cyclotriphosphazene covalent organic polymers, their preparation methods and applications

Abstract

This invention provides an aminooxime-fluorinated cyclotriphosphazene covalent organic polymer, its preparation method, and its applications. The preparation method involves first preparing a high-purity phosphorus-fluoride exchange monomer under ice bath conditions, then using this monomer to conduct room-temperature nucleophilic substitution polymerization with hexafluorocyclotriphosphazene to construct a cyano-functionalized fluorinated cyclotriphosphazene porous framework. Finally, under mild conditions, the cyano group is converted into an aminooxime chelating group through hydroxylamine modification. This ensures that the entire preparation process is mild, controllable, and has few side reactions, thereby guaranteeing that each intermediate has a regular structure and high purity. At the same time, it preserves the chemical stability and porous structure of the polymer framework, and introduces a large number of aminooxime active sites with specific coordination ability for uranium ions into the material surface and pores. Finally, an aminooxime-fluorinated cyclotriphosphazene covalent organic polymer with high adsorption capacity, strong selectivity, and excellent anti-interference performance is obtained.

Description

Technical Field

[0001] This invention relates to the field of elemental separation technology, specifically to an aminooxime fluorinated cyclotriphosphazene covalent organic polymer, its preparation method, and its application. Background Technology

[0002] Currently, methods for uranium separation and enrichment mainly include chemical precipitation, ion exchange, membrane separation, and adsorption. Among these, adsorption is widely recognized as the most promising technology for seawater uranium extraction and uranium-containing wastewater treatment due to its simplicity, low cost, and wide applicability. Traditional adsorbent materials such as activated carbon and zeolite, while possessing the advantage of low cost, generally suffer from bottlenecks such as low adsorption capacity (typically below 100 mg / g), poor selectivity, and insufficient mechanical strength. Precisely because of these performance limitations of traditional adsorbent materials, developing functional materials with excellent selectivity and high adsorption capacity for application in wastewater and seawater uranium removal has become an important and urgent issue to be addressed. Summary of the Invention

[0004] In view of the technical problems existing in the background art, this application provides an aminooxime fluorinated cyclotriphosphazene covalent organic polymer, its preparation method and application, aiming to solve the technical problems of existing uranium removal adsorbents having low adsorption capacity, poor uranium selectivity, weak resistance to interference from coexisting ions in seawater, and insufficient mechanical strength, making it difficult to achieve efficient enrichment of low-concentration uranium and deep purification of uranium-containing wastewater.

[0005] In a first aspect, embodiments of this application provide a method for preparing an aminooxime fluorinated cyclotriphosphazene covalent organic polymer, the method comprising: S10, PCN, imidazole and tert-butyltrimethylchlorosilane are dispersed in a first organic solvent and stirred in an ice bath until the reaction is complete; then, the first organic solvent is removed and the organic phase is extracted, and the organic phase is dried and purified to obtain the phosphorus-fluoride exchange monomer. S20, phosphorus-fluorine exchange monomer, hexafluorocyclotriphosphazene and organic strong base reagent are dispersed in a second organic solvent and stirred at room temperature until the nucleophilic substitution polymerization reaction is complete; then, the first solid phase product is obtained by solid-liquid separation, and the first solid phase product is washed and dried to obtain cyano-functionalized fluorinated cyclotriphosphazene covalent organic polymer. S30: A cyano-functionalized fluorinated cyclotriphosphazene covalent organic polymer is mixed with a hydroxylamine salt modifier and ultrasonically dispersed. After adjusting the pH of the system to neutral, the mixture is stirred at 40–80°C under an inert atmosphere until the reaction is complete. Then, the second solid phase product is collected by solid-liquid separation. The second solid phase product is washed and dried to obtain the aminooxime fluorinated cyclotriphosphazene covalent organic polymer.

[0006] Specifically, step S10 employs a mild ice bath stirring system, which allows for precise temperature control and suppression of side reactions, ensuring the regular structure and excellent purity of the phosphorus-fluoride exchange monomer. The reaction conditions are mild, the operation is simple, and the cost is low. Step S20 relies on room-temperature nucleophilic substitution polymerization, requiring no extreme conditions. This green and energy-efficient process efficiently constructs a three-dimensional porous framework for a cyano-functionalized fluorinated triphosphazene covalent organic polymer with excellent chemical stability, acid and alkali resistance, and mechanical strength. The introduced cyano groups also reserve sufficient active sites for subsequent modification. Step S30 utilizes ultrasonic dispersion to improve raw material mixing efficiency. Combined with neutral pH, mild heating, and inert atmosphere protection, this avoids damage to the polymer framework and efficiently converts cyano groups into aminooxime functional groups with strong chelating ability for uranium ions. The resulting target polymer possesses a regular porous structure, high stability, and dedicated uranium coordination sites, perfectly addressing the shortcomings of traditional adsorbents such as low adsorption capacity, poor selectivity, and weak anti-interference ability. It is suitable for complex conditions such as low-concentration uranium enrichment in seawater and deep purification of uranium-containing wastewater, demonstrating extremely high practical value.

[0007] Preferably, in step S10, the molar ratio of PCN, imidazole and tert-butyltrimethylchlorosilane is 1:(4-8):(4-8); the temperature of the ice bath stirring is 0-5°C, and the stirring time is 20-32h.

[0008] Specifically, the above molar ratio parameters can achieve a balanced proportion of the three raw materials, which can ensure that the core reaction proceeds fully and significantly improve the synthesis conversion rate of phosphorus-fluorine exchange monomers, while effectively avoiding side reactions and residual impurities caused by excessive amounts of a single raw material. This ensures that the intermediate structure is regular and the purity meets the standards from the source, and eliminates the interference of impurities on subsequent polymerization and modification processes. The above ice bath stirring temperature can precisely suppress the occurrence of side reactions, control the reaction rate steadily, and prevent the decomposition of raw materials or damage to the product structure caused by excessive temperature, thus maintaining the stability of the entire reaction system. The above stirring time can ensure that the raw materials are fully contacted and mixed, and that the reaction is complete, avoiding incomplete reaction that reduces monomer yield, while also preventing process redundancy and increased energy consumption due to excessive time.

[0009] Preferably, in step S10, water and ethyl acetate are used as a combined extractant for extraction and separation; after the organic phase is dried with anhydrous sodium sulfate, column chromatography is performed using a mixture of ethyl acetate and petroleum ether at a volume ratio of 1:10 as the eluent to obtain the phosphorus-fluoride exchange monomer.

[0010] Specifically, the aforementioned compound extractant utilizes the complementary polarity of the two phases to achieve rapid and efficient separation of the target product from unreacted raw materials and water-soluble byproducts in the reaction system, accurately collecting the organic phase without product residue loss. Anhydrous sodium sulfate is used to dry the organic phase, resulting in a gentle and thorough drying process that efficiently removes residual moisture, preventing interference with subsequent polymerization reactions, and avoids side reactions with the target monomer or damage to the monomer structure, thus preserving the monomer integrity to the greatest extent. A 1:10 volume ratio mixture of ethyl acetate and petroleum ether is used as the column chromatography eluent, whose elution polarity is highly compatible with phosphorus and fluoride exchange monomers, enabling precise separation of the target monomer from trace impurities and effectively improving monomer purity and yield.

[0011] Preferably, in step S20, the molar ratio of phosphorus-fluorine exchange monomer to hexafluorocyclotriphosphazene is 1:(5-8); the stirring time at room temperature is 20-30 h; the first solid product is washed sequentially with a second organic solvent, ethanol, and water, and then vacuum dried to obtain a cyano-functionalized fluorinated cyclotriphosphazene covalent organic polymer.

[0012] Specifically, the above molar ratio parameters ensure that the nucleophilic substitution polymerization reaction proceeds fully, efficiently constructing a stable porous framework, while avoiding side reactions and waste caused by excessive raw materials; the above stirring time ensures that the monomers are fully polymerized, balancing reaction efficiency and process economy; the first solid product is washed sequentially with a second organic solvent, ethanol, and water to thoroughly remove impurities and improve purity, and subsequent vacuum drying avoids high temperature damage to the porous structure and cyano active sites, retaining excellent stability and providing a high-quality intermediate for subsequent aminooxime modification, ensuring the adsorption performance of the final product.

[0013] Preferably, in step S10, the amount of the first organic solvent is 10-30 mL based on 1 mmol PCN; in step S20, the amount of the second organic solvent is 0.8-1.5 mL based on 1 mmol phosphorus-fluorine exchange monomer, and the amount of the organic strong base reagent is 0.15-0.3 mL.

[0014] Specifically, S10 uses 1 mmol PCN as a baseline to limit the amount of the first organic solvent, which can control the concentration of the reaction system to a moderate level. This ensures that the raw materials are fully dispersed and dissolved, and that the reaction proceeds smoothly and efficiently, while avoiding excessive solvent waste or insufficient solvent leading to uneven reaction. S20 uses 1 mmol of phosphorus-fluorine exchange monomer as a baseline to regulate the amount of the second organic solvent and strong organic base, which can precisely match the requirements of nucleophilic substitution polymerization, maintain the optimal reaction system, improve polymerization efficiency and product structural regularity, and at the same time strictly control reagent dosage, reduce loss and impurity residue.

[0015] Preferably, the first organic solvent and the second organic solvent both include any one of tetrahydrofuran, diethyl ether, and methyl tert-butyl ether, and the strong organic base reagent includes any one of DBU (1,8-diazabicyclo(5,4,0)-7-undecene), DBN (1,5-diazabicyclo[4,3,0]nonene), and triethylenediamine.

[0016] Specifically, the aforementioned preferred organic solvents and strong organic base reagents are all inert aprotic polar solvents and non-nucleophilic acid-binding agents. Their solubility and catalytic acid-binding ability match the reaction requirements, ensuring that each step of the reaction proceeds efficiently and stably. At the same time, the reagents are diverse and versatile, facilitating process implementation and raw material selection, which is beneficial to improving the reproducibility of polymer preparation and product quality.

[0017] Preferably, in step S30, the mass ratio of the cyano-functionalized fluorinated cyclotriphosphazene covalent organic polymer to the hydroxylamine salt modifying agent is 1:(0.8-1.2); the pH of the system is adjusted to neutral using a saturated sodium bicarbonate solution, and the stirring time is 20-28 h; the second solid product is washed sequentially with ethanol and water and then vacuum dried to obtain the aminooxime fluorinated cyclotriphosphazene covalent organic polymer.

[0018] Specifically, a suitable material mass ratio ensures full functional group transformation without reagent residue, a saturated sodium bicarbonate solution gently adjusts the pH to avoid damage to the polymer skeleton, an appropriate stirring time ensures complete reaction, and stepwise washing and vacuum drying effectively remove impurities, ultimately obtaining a target polymer with complete structure, high purity, and excellent uranium adsorption performance.

[0019] Secondly, the present invention also provides an aminooxime fluorinated cyclotriphosphazene covalent organic polymer, which is prepared by the above-described method for preparing the aminooxime fluorinated cyclotriphosphazene covalent organic polymer.

[0020] Specifically, the aminooxime fluorinated cyclotriphosphazene covalent organic polymer prepared by this invention has a regular porous framework structure, excellent chemical stability and mechanical strength, and is rich in aminooxime functional groups with specific chelating ability for uranium ions. It has high adsorption capacity, strong selectivity and good anti-interference ability, and can effectively achieve efficient enrichment of low-concentration uranium in seawater and deep purification of uranium-containing wastewater. It solves the technical defects of traditional adsorption materials such as low adsorption capacity, poor selectivity and insufficient stability, and has outstanding application value in the fields of seawater uranium extraction and uranium-containing wastewater treatment.

[0021] Thirdly, the present invention also provides an application of the above-mentioned aminooxime fluorinated cyclotriphosphazene covalent organic polymer as an adsorbent for uranium removal in wastewater and seawater.

[0022] Specifically, when this aminooxime fluorinated cyclotriphosphazene covalent organic polymer is used as an adsorbent for uranium removal from wastewater and seawater, it can effectively resist the interference of coexisting ions such as calcium, magnesium, and vanadium in seawater due to its high capacity and high selectivity of uranium chelation performance. This enables the efficient enrichment of low-concentration uranium and the deep purification of uranium-containing wastewater. At the same time, the material has good chemical stability and can be reused, thus possessing the dual value of resource recovery and environmental governance, and has broad application prospects.

[0023] Preferably, the pseudo-second-order kinetic rate constant k2 of the aminooxime fluorinated cyclotriphosphazene covalent organic polymer for uranium solution is 0.000393 g mg. -1 min -1 The maximum adsorption capacity Q for uranium max 292.0 mg g -1 .

[0024] Specifically, this aminooxime fluorinated cyclotriphosphazene covalent organic polymer exhibits an extremely fast adsorption rate and ultra-high adsorption capacity for uranium, along with excellent pseudo-second-order kinetic rate constant and maximum adsorption capacity, enabling it to rapidly and efficiently capture uranium ions. It is particularly suitable for the enrichment of low-concentration uranium in seawater and the deep treatment of uranium-containing wastewater, significantly improving uranium removal efficiency and treatment effect.

[0025] Beneficial Effects: This invention provides an aminooxime-fluorinated cyclotriphosphazene covalent organic polymer, its preparation method, and its application. The preparation method involves first preparing a high-purity phosphorus-fluoride exchange monomer under ice bath conditions, then using this monomer to conduct room-temperature nucleophilic substitution polymerization with hexafluorocyclotriphosphazene to construct a cyano-functionalized fluorinated cyclotriphosphazene porous framework. Finally, under mild conditions, the cyano group is converted into an aminooxime chelating group through hydroxylamine modification. This ensures that the entire preparation process is mild, controllable, and has few side reactions, thereby guaranteeing that each intermediate has a regular structure and high purity. At the same time, it preserves the chemical stability and porous structure of the polymer framework, and introduces a large number of aminooxime active sites with specific coordination ability for uranium ions into the material surface and pores. Finally, an aminooxime-fluorinated cyclotriphosphazene covalent organic polymer with high adsorption capacity, strong selectivity, and excellent anti-interference performance is obtained, effectively solving the technical problems of low adsorption capacity, poor selectivity, and difficulty in adapting to complex seawater and wastewater systems of traditional adsorbents. Attached Figure Description

[0026] To more clearly illustrate the technical solutions of this application, the accompanying drawings used in this application will be briefly described below. Obviously, the drawings described below are merely some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without any creative effort.

[0027] Figure 1 This is a flowchart of the synthetic route for the aminooxime fluorinated cyclotriphosphazene covalent organic polymer provided in Example 1. Figure 2 The adsorption kinetics fitting curve of HFP-PNH on uranium solution provided in Example 1; Figure 3 The isotherm fitting curve of HFP-PNH adsorption on uranium solution provided in Example 1; Figure 4 The cyclic adsorption-extraction capacity curve of uranium by HFP-PNH provided in Example 1; Figure 5 The curve of uranium adsorption in a simulated seawater system provided in Example 1. Detailed Implementation

[0028] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0029] To address the shortcomings of existing uranium adsorbents, such as low adsorption capacity, poor selectivity for uranium ions, weak resistance to interference from coexisting ions in seawater and wastewater, and insufficient chemical stability and mechanical strength, which make it difficult to meet the practical application requirements of efficient enrichment of extremely low concentrations of uranium in seawater and deep purification of uranium-containing radioactive wastewater to meet discharge standards, and the technical defects of existing preparation processes such as stringent conditions, poor controllability of product structure, and low functional group loading efficiency, this invention provides an aminooxime fluorinated cyclotriphosphazene covalent organic polymer, its preparation method, and its application. Through a stepwise and controllable mild synthesis process, a novel covalent organic polymer adsorbent with both a stable porous framework and highly active aminooxime chelating sites is precisely constructed. This optimizes the product structure and performance from the source, effectively breaking through the performance bottlenecks of traditional adsorbents, while simplifying the preparation process and improving process economy. Ultimately, it achieves high-capacity, high-selectivity, rapid, and stable adsorption of uranium ions, meeting the dual core needs of marine uranium resource recovery and utilization and nuclear industry uranium-containing wastewater pollution treatment, filling the technological gap in high-performance uranium adsorbent materials in related fields.

[0030] The technical solution of the present invention will now be described in conjunction with specific embodiments.

[0031] Example 1 (Preparation of aminooxime fluorinated cyclotriphosphazene covalent organic polymer (HFP-PNH):) Example 1 provides an aminooxime fluorinated cyclotriphosphazene covalent organic polymer and its preparation method, such as... Figure 1 The preparation steps shown are as follows: Step (1) Preparation of phosphorus-fluoride exchange monomer (PCN-OTBS): Weigh 0.211 g (0.001 mol) of 4,4'-dihydroxy-[1,1'-biphenyl]-3-carboxynitrile (PCN), 0.408 g (0.006 mol) of imidazole, 0.904 g (0.006 mol) of tert-butyltrimethylchlorosilane, and 20 mL of tetrahydrofuran. Stir for 24 h in an ice bath. After the reaction is complete, evaporate the tetrahydrofuran by rotary evaporation, add water and ethyl acetate for extraction, take the organic phase, dry with anhydrous sodium sulfate, and pass through a column with ethyl acetate and petroleum ether (v / v=1:10) to obtain phosphorus-fluoride exchange monomer (PCN-OTBS).

[0032] Step (2) Preparation of cyanofluorinated cyclotriphosphazene covalent organic polymer (HFP-PCN): Weigh out the phosphorus-fluorine exchange monomer PCN-OTBS (0.439 mg, 0.001 mol), hexafluorocyclotriphosphazene (1.493 g, 0.006 mol), tetrahydrofuran (1 mL), and DBU (0.2 mL), and stir at room temperature for 24 h. After the reaction is complete, filter, wash successively with tetrahydrofuran, ethanol, and water, and dry under vacuum to obtain cyanofluorinated cyclotriphosphazene covalent organic polymer (HFP-PCN).

[0033] Step (3) Preparation of aminooxime fluorinated cyclotriphosphazene covalent organic polymer (HFP-PNH): Weigh 0.5 g of cyanofluorinated cyclotriphosphazene covalent organic polymer (HFP-PCN) and 0.5 g of hydroxylamine hydrochloride, disperse by ultrasonication, adjust the pH to neutral with saturated sodium bicarbonate solution, and then stir at 60 °C for 24 h under nitrogen protection. After the reaction is complete, filter, wash with ethanol and water, and vacuum dry to obtain aminooxime fluorinated cyclotriphosphazene covalent organic polymer (HFP-PNH).

[0034] Example 2 (Adsorption Kinetics Experiment): Example 2 conducted adsorption kinetic experiments on the HFP-PNH material of Example 1, systematically evaluated the experimental data, and used pseudo-first-order kinetic models and pseudo-second-order kinetic models to fit and analyze the experimental data of HFP-PNH material in order to clarify the adsorption kinetic characteristics and adsorption mechanism.

[0035] Figure 2 This is the HFP-PNH adsorption kinetics fitting curve for uranium solution in Example 1, including actual experimental data points for HFP-PNH, the fitting curve of the pseudo-first-order kinetic model, and the fitting curve of the pseudo-second-order kinetic model; from Figure 2It can be seen that, compared with the pseudo-first-order kinetic model, the pseudo-second-order kinetic model has a better fit to the experimental data, with a correlation coefficient R0. 2 =0.9160, and the theoretical adsorption capacity calculated by this model is in better agreement with the actual experimental results. Detailed fitting data are shown in Table 1. Table 1

[0036] From the experimental data in Table 1 and Figure 2 The model fitting results show that the adsorption behavior of the aminooxime fluorinated cyclotriphosphazene covalent organic polymer (HFP-PNH) on uranium solution conforms to a pseudo-second-order kinetic model, and the adsorption process is classified as chemisorption. The calculated pseudo-second-order kinetic rate constant k2 for HFP-PNH on uranium solution is 0.000393 g mg. -1 min -1 .

[0037] Example 3 (Adsorption Isotherm Experiment): Example 3 further investigates the adsorption isotherm of HFP-PNH for uranium solution in Example 1, determines the maximum adsorption capacity of the material for uranium, and uses the Langmuir adsorption isotherm model (a classic monolayer adsorption theory model, the core assumption of which is that the adsorbent surface sites are uniform and homogeneous, the adsorbate molecules undergo monolayer saturation adsorption only on the adsorbent surface, there is no multilayer adsorption and intermolecular interaction, suitable for fitting the chemisorption behavior of homogeneous surfaces) and the Freundlich adsorption isotherm model (an empirical multilayer adsorption model, suitable for adsorption systems on non-uniform surfaces, assuming that the energy distribution of adsorbent surface sites is non-uniform, the adsorption amount is exponentially related to the equilibrium concentration of the adsorbate, there is no fixed saturation adsorption amount, and it is mostly used for characterizing non-ideal adsorption behavior) to fit the experimental data and analyze the adsorption behavior characteristics of the material.

[0038] Figure 3 This is the adsorption isotherm fitting curve of HFP-PNH for uranium solution in Example 1. The curve includes actual experimental data points of HFP-PNH, the fitting curve of the Langmuir isotherm model, and the fitting curve of the Freundlich isotherm model. Figure 3 It can be seen that the correlation coefficient R of the Langmuir model is... 2 The correlation coefficient R0 of the Freundlich model is 0.9775. 2The correlation coefficient of the Langmuir model is 0.9561, which is closer to 1, indicating that the adsorption behavior of uranium by HFP-PNH is more consistent with the Langmuir adsorption isotherm model. This suggests that the adsorption process is monolayer adsorption, and the adsorption sites on the material surface are uniformly distributed. Furthermore, the maximum adsorption capacity Q of uranium by HFP-PNH was calculated using the Langmuir model. max 292.0 mg g -1 The specific adsorption isotherm fitting data are shown in Table 2: Table 2

[0039] Example 4 (Cyclic Adsorption Extraction Experiment): To further evaluate the actual uranium extraction capability of HFP-PNH in Example 1, a cyclic adsorption experiment was conducted in Example 4: 50 mg of HFP-PNH adsorbent was weighed and placed in a self-made circulating device, using a concentration of 40 mg / L. -1 Uranium solution, at 20 ml min -1 The flow rate was used to conduct a circulating adsorption experiment using a circulating pump. After 5 days of continuous contact, the concentration of the remaining uranium solution was tested and analyzed using inductively coupled plasma optical emission spectroscopy (ICP-OES) to calculate the uranium extraction capacity per unit mass of adsorbent.

[0040] Figure 4 This is the cyclic adsorption-extraction capacity curve of uranium for HFP-PNH in Example 1 of this invention; (The curve is derived from...) Figure 4 It can be seen that the maximum extraction capacity of HFP-PNH in this cyclic adsorption system can reach 141.7 mg g. -1 This indicates that the material has excellent practical performance in the uranium extraction process.

[0041] Example 5 (Adsorption experiment in simulated seawater environment): Example 5 simulates a real seawater environment to test the uranium adsorption performance of HFP-PNH in a complex seawater system as described in Example 1. The specific operation is as follows: First, 0.15 kg of sea salt is dissolved in 5 L of deionized water, and then 0.165 mL of a 100 mg / L solution is added. -1 A standard uranium solution was prepared to obtain a uranium concentration of approximately 0.0033 mg / L. - ¹ A simulated seawater solution was prepared, with the temperature controlled at approximately 25℃ and the pH value at approximately 8.3. 50 mg of HFP-PNH adsorbent was weighed and placed into a self-made circulation device, and the simulated seawater in the storage bottle was circulated at a rate of 20 ml / min. -1The flow rate was used to conduct a circulating adsorption experiment using a circulating pump. After 5 days of continuous reaction, the concentration of the remaining uranium solution was tested and analyzed using inductively coupled plasma optical emission spectroscopy (ICP-OES) to calculate the amount of uranium adsorbed per unit mass of adsorbent.

[0042] Figure 5 This is the uranium adsorption curve of HFP-PNH in a simulated seawater system in Example 1; from Figure 5 It can be seen that even under complex environments closely resembling real seawater, characterized by low uranium concentration, high salinity, and weak alkalinity, this adsorbent can still effectively adsorb uranium ions. After a 5-day simulated seawater circulation adsorption experiment, the adsorption capacity of uranium per unit mass of HFP-PNH reached 2.356 mg g. -1 This fully demonstrates its excellent anti-interference ability and actual adsorption performance, and shows great practical application potential in the fields of uranium extraction from natural seawater and marine uranium resource recovery.

[0043] Based on the experimental results of Examples 2 to 5 above, compared with conventional uranium adsorbent materials, the aminooxime fluorinated cyclotriphosphazene covalent organic polymer (HFP-PNH) prepared in this invention has significant technical advantages, as follows: First, the material exhibits excellent adsorption kinetics. The adsorption of uranium by the material conforms to a pseudo-second-order kinetic model, indicating specific chemisorption. The adsorption process is highly targeted, and the pseudo-second-order kinetic rate constant k2 is 0.000393 g mg. -1 min -1 It can quickly capture uranium ions, which is far superior to traditional materials that mainly rely on physical adsorption, and can significantly shorten the adsorption treatment cycle. Secondly, its adsorption capacity is significantly superior, and its adsorption behavior conforms to the Langmuir monolayer adsorption model. The adsorption sites on the material surface are evenly distributed, and the maximum adsorption capacity Q for uranium is [missing information]. max Up to 292.0 mg g -1 It far exceeds the adsorption limit of conventional adsorption materials, and the uranium loading efficiency per unit mass of material is extremely high, resulting in more outstanding processing efficiency. Third, it exhibits stable performance in cyclic applications, maintaining 141.7 mg g even after prolonged continuous adsorption in a dynamic cyclic adsorption system. - ¹ It has the largest extraction capacity, stable long-term adsorption performance, and can be reused, which solves the defects of traditional adsorption materials such as easy deactivation, high cost per use, and difficulty in adapting to industrial continuous processing. Fourth, it exhibits exceptional adaptability to complex environments, achieving a concentration of 2.356 mg g even in simulated seawater environments with high salinity, weak alkalinity, and extremely low uranium concentration. -1 It has an effective adsorption capacity and excellent resistance to interference from coexisting ions, breaking through the bottleneck of the rapid performance drop of conventional adsorption materials in actual seawater and complex uranium-containing wastewater. It has dual application value in both seawater uranium extraction and deep purification of uranium-containing wastewater. Fifth, the preparation process is mild and controllable, using mild reaction conditions throughout, without the need for harsh equipment such as high temperature and high pressure. The product has a regular structure, high functional group loading efficiency, and good process repeatability, making it more suitable for large-scale mass production. This fills the technological gap of existing high-performance uranium adsorbent materials, which are complex to prepare, costly, and difficult to industrialize.

[0044] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A method for preparing an aminooxime fluorinated cyclotriphosphazene covalent organic polymer, characterized in that, The method includes: S10, PCN, imidazole and tert-butyltrimethylchlorosilane are dispersed in a first organic solvent and stirred in an ice bath until the reaction is complete; then, the first organic solvent is removed and the organic phase is extracted, and the organic phase is dried and purified to obtain a phosphorus-fluoride exchange monomer. S20, the phosphorus-fluorine exchange monomer, hexafluorocyclotriphosphazene and organic strong base reagent are dispersed in a second organic solvent and stirred at room temperature until the nucleophilic substitution polymerization reaction is complete; then, the first solid phase product is obtained by solid-liquid separation, and the first solid phase product is washed and dried to obtain cyano-functionalized fluorinated cyclotriphosphazene covalent organic polymer. S30, the cyano-functionalized fluorinated cyclotriphosphazene covalent organic polymer is mixed with hydroxylamine salt modifying agent and ultrasonically dispersed. After adjusting the pH of the system to neutral, the mixture is stirred at 40-80°C under an inert atmosphere until the reaction is complete. Then, the second solid product is collected by solid-liquid separation. The second solid product is washed and dried to obtain the aminooxime fluorinated cyclotriphosphazene covalent organic polymer.

2. The method for preparing the aminooxime fluorinated cyclotriphosphazene covalent organic polymer according to claim 1, characterized in that, In step S10, the molar ratio of PCN, imidazole and tert-butyltrimethylchlorosilane is 1:(4-8):(4-8); the temperature of the ice bath stirring is 0-5℃ and the stirring time is 20-32h.

3. The method for preparing the aminooxime fluorinated cyclotriphosphazene covalent organic polymer according to claim 2, characterized in that, In step S10, water and ethyl acetate are used as a combined extractant for extraction and separation. After the organic phase is dried with anhydrous sodium sulfate, it is purified by column chromatography using a mixture of ethyl acetate and petroleum ether at a volume ratio of 1:10 as the eluent to obtain the phosphorus-fluoride exchange monomer.

4. The method for preparing the aminooxime fluorinated cyclotriphosphazene covalent organic polymer according to claim 1, characterized in that, In step S20, the molar ratio of the phosphorus-fluorine exchange monomer to hexafluorocyclotriphosphazene is 1:(5-8); the stirring time at room temperature is 20-30 h; the first solid product is washed sequentially with the second organic solvent, ethanol, and water, and then vacuum dried to obtain the cyano-functionalized fluorinated cyclotriphosphazene covalent organic polymer.

5. The method for preparing the aminooxime fluorinated cyclotriphosphazene covalent organic polymer according to claim 1, characterized in that, In step S10, based on 1 mmol PCN, the amount of the first organic solvent used is 10-30 mL; in step S20, based on 1 mmol of the phosphorus-fluorine exchange monomer, the amount of the second organic solvent used is 0.8-1.5 mL, and the amount of the organic strong base reagent used is 0.15-0.3 mL.

6. The method for preparing the aminooxime fluorinated cyclotriphosphazene covalent organic polymer according to claim 5, characterized in that, Both the first organic solvent and the second organic solvent include any one of tetrahydrofuran, diethyl ether, and methyl tert-butyl ether, and the strong organic base reagent includes any one of DBU, DBN, and triethylenediamine.

7. The method for preparing the aminooxime fluorinated cyclotriphosphazene covalent organic polymer according to claim 1, characterized in that, In step S30, the mass ratio of the cyano-functionalized fluorinated triphosphazene covalent organic polymer to the hydroxylamine salt modifying agent is 1:(0.8-1.2). The pH of the system was adjusted to neutral using a saturated sodium bicarbonate solution, and the stirring time was 20–28 h. The second solid product was washed sequentially with ethanol and water and then vacuum dried to obtain the aminooxime fluorinated cyclotriphosphazene covalent organic polymer.

8. An aminooxime fluorinated cyclotriphosphazene covalent organic polymer, characterized in that, It is prepared by the method for preparing aminooxime fluorinated cyclotriphosphazene covalent organic polymer as described in any one of claims 1 to 7.

9. The application of the aminooxime fluorinated cyclotriphosphazene covalent organic polymer as described in claim 8 as an adsorbent for uranium removal in wastewater and seawater.

10. The application according to claim 9, characterized in that, The pseudo-second-order kinetic rate constant k2 of the aminooxime fluorinated cyclotriphosphazene covalent organic polymer for uranium solution is 0.000393 g mg. -1 min -1 The maximum adsorption capacity Q for uranium max 292.0 mg g -1 .

Images