Preparation method of styrene-based macroporous negative resin

Abstract

The application discloses a preparation method of a styrene macroporous anion resin, and comprises the following steps: 1) preparation of macroporous white balls; 2) chloromethylation; 3) composite amination; 4) transformation and post-treatment. The application introduces rigid norbornene monomer copolymerization, significantly improves the thermal stability and mechanical strength of the resin; an "organic pore-forming agent + inorganic pore-forming agent" composite pore-forming system is adopted, a hierarchical porous structure coexisting micropores, mesopores and macropores is successfully constructed, and thus the adsorption capacity and mass transfer rate of the resin are effectively improved; a composite amination reaction is adopted, the N-alkyl imidazole adopted can generate imidazolium salt functional groups, the resin has good selectivity for hydrophobic anions such as perchlorate, and the urotropine adopted provides additional crosslinking and chelating sites, thereby enhancing the mechanical strength and heavy metal ion removal capacity of the resin; the prepared anion resin has good selectivity, good thermal stability, high mechanical strength and good pore-forming effect.

Description

Technical Field

[0001] This invention relates to a method for preparing a styrene-based macroporous anion exchange resin, belonging to the field of macroporous resin technology. Background Technology

[0002] Ion exchange resins are a class of functional polymer materials with a three-dimensional network structure, widely used in water treatment, drug separation, catalysis, and analytical detection. Styrene-based anion exchange resins are among the most widely used ion exchange resins due to their high mechanical strength, good chemical stability, and readily available raw materials.

[0003] Traditional styrene-based anion resins are typically prepared by suspension polymerization to create styrene-based white spheres, followed by chloromethylation and amination. However, existing styrene-based anion resins still have shortcomings, such as: 1) insufficient selectivity for specific anions (e.g., perchlorate, nitrate); 2) the thermal stability and mechanical strength of the resin need further improvement; and 3) the pore-forming agent system is mostly a single organic pore-forming agent (e.g., good solvents like toluene and xylene, poor solvents like fatty alcohols, n-butanol, isopropanol, hexane, kerosene, etc., and high molecular weight polymers like polystyrene and polyacrylates), resulting in limited pore-forming effects. Summary of the Invention

[0004] In view of the above-mentioned problems existing in the prior art, the purpose of this invention is to provide a method for preparing styrene-based macroporous anion exchange resin.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing a styrene-based macroporous anion exchange resin includes the following steps: 1) Preparation of macroporous white spheres: Styrene monomer, norbornene monomer, divinylbenzene, composite porogen and initiator are mixed to form an oil phase. The oil phase is subjected to suspension polymerization in an aqueous phase containing a dispersant. After polymerization, the composite porogen is removed by sequential treatment with acid solution and organic solvent to obtain macroporous white spheres. 2) Chloromethylation: The macroporous white spheres obtained in step 1) are subjected to a chloromethylation reaction to obtain chloromethylated macroporous white spheres, i.e., chlorospheres; 3) Complex amination: The chlorine spheres obtained in step 2) are swollen in a solvent, and the first amination reagent and the second amination reagent are added sequentially to carry out a complex amination reaction; 4) Transformation and post-treatment: The product of step 3) is transformed with alkaline solution and washed until neutral to obtain styrene-based macroporous anion exchange resin. The norbornene monomer is 5-norbornene-2-methanol or 5-norbornene-2-carboxylic acid; The composite porogen comprises an organic porogen and an inorganic porogen. The organic porogen is selected from at least one of n-heptane, cyclohexane, ethylbenzene, cumene, and tert-butylbenzene. The inorganic porogen is obtained by modifying nano-calcium carbonate with hydrogen-containing silicone oil. The first amination reagent is N-alkylimidazole, and the second amination reagent is hexamethylenetetramine.

[0006] In one embodiment, in step 1), the amount of norbornene monomer used is 2-8% of the mass of styrene monomer; the amount of divinylbenzene used is 5-20% of the mass of styrene monomer.

[0007] In one embodiment, in step 1), the initiator is benzoyl peroxide or azobisisobutyronitrile, and its amount is 0.5-2% of the total mass of styrene monomer, norbornene monomer, and divinylbenzene. In this invention, styrene monomer, norbornene monomer, and divinylbenzene are polymerizable components participating in the polymerization reaction, and the total mass of styrene monomer, norbornene monomer, and divinylbenzene is equivalent to the total mass of monomers in the polymerization reaction.

[0008] In one embodiment, in step 1), the dispersant is polyvinyl alcohol, and its dosage is 0.5-1.5% of the mass of the aqueous phase; the mass ratio of the oil phase to the aqueous phase is 1:2.5-1:5.

[0009] In a preferred embodiment, the aqueous phase further includes sodium chloride, wherein the amount of sodium chloride is 0.5-2.0% of the mass of the aqueous phase.

[0010] In one embodiment, in step 1), the mass ratio of organic porogen to inorganic porogen in the composite porogen is 1:1 to 3:1, and the amount of composite porogen used is 50-90% of the total mass of styrene monomer, norbornene monomer and divinylbenzene.

[0011] In a preferred embodiment, the preparation of the inorganic porogen includes the following steps: Nano-calcium carbonate and hydrogen-containing silicone oil are mixed at a mass ratio of 100:5-100:15 and heated and stirred at 100-120℃ for 30-60 minutes. After the reaction is completed, the mixture is cooled to room temperature and the resulting product is vacuum dried to obtain an inorganic pore-forming agent.

[0012] In one embodiment, in step 1), the acid solution is a 1-3 mol / L hydrochloric acid solution used to dissolve the inorganic porogen; the organic solvent is ethanol or acetone used to extract the organic porogen.

[0013] In a preferred embodiment, step 1) is performed as follows: 1.1) Aqueous phase preparation: Add the dispersant and NaCl to deionized water, heat to 55-65℃ to dissolve, and obtain the aqueous phase for later use; 1.2) Oil phase preparation: Styrene monomer, norbornene monomer, divinylbenzene, composite porogen and initiator are mixed evenly to obtain the oil phase; 1.3) Suspension polymerization: Add the oil phase to the aqueous phase, emulsify for 20-40 minutes under nitrogen protection, then heat to 75-80℃ for 3-5 hours, then heat to 85-95℃ for 1-3 hours to mature. After the reaction is complete, filter and wash with hot water to obtain white balls. 1.4) Removal of pore-forming agents: Pickling: Add the white balls to the acid solution (solid-liquid ratio 1:3-1:5), stir at 45-55℃ for 1-3 hours, filter, and wash with water until neutral (to remove inorganic pore-forming agents). Solvent extraction: The acid-washed white spheres are loaded into a Soxhlet extractor and extracted with an organic solvent (ethanol or acetone) for 6-10 hours (to remove organic porogens). The spheres are then vacuum dried at 55-65°C to obtain macroporous white spheres.

[0014] In one embodiment, step 1) further comprises modified magnetic nanoparticles in the oil phase. These modified magnetic nanoparticles are obtained by modifying nano-ferric oxide with a silane coupling agent KH-570, and their amount is 1-10% of the total mass of styrene monomer, norbornene monomer, and divinylbenzene. The addition of modified magnetic nanoparticles not only imparts superparamagnetism to the resin, facilitating rapid magnetic separation and recovery, but also enhances the mechanical strength of the resin skeleton.

[0015] In a preferred embodiment, the preparation of the modified magnetic nanoparticles includes the following steps: Nano-iron oxide was dispersed in an ethanol / water mixed solvent (volume ratio 9:1), silane coupling agent KH-570 was added, the pH was adjusted to 4-5 with acetic acid, and the mixture was stirred and pre-hydrolyzed at room temperature for 20-40 minutes. Then, the mixture was stirred and reacted at 70-80℃ for 3-6 hours. After the reaction was completed, the mixture was magnetically separated, washed, and dried to obtain modified magnetic nanoparticles.

[0016] In a preferred embodiment, the amount of silane coupling agent KH-570 in the modified magnetic nanoparticles is 10-20% of the mass of the nano-ferric oxide. KH-570 modifies the nano-ferric oxide, improving not only its compatibility with the oil phase but, more importantly, allowing its terminal methacrylyl groups to participate in monomer copolymerization. This covalently anchors the nano-ferric oxide within the resin framework, ensuring that the magnetic particles are not lost during subsequent acid washing to remove the inorganic pore-forming agent, thus guaranteeing the long-term stability of the resin's magnetic response performance.

[0017] In one embodiment, in step 2), the macroporous white spheres are first swollen with a chloromethylating agent, and then subjected to a chloromethylation reaction under the action of a catalyst (specifically, the reaction time is 6-12 hours and the reaction temperature is 45-60℃) to obtain chloromethylated macroporous white spheres, i.e., chlorospheres.

[0018] In a preferred embodiment, the chloromethylating agent is chloromethyl ether (CMME) or 1,4-dichloromethoxybutane (BCMB), and the amount of the chloromethylating agent is 3-7 times (preferably 5-7 times) the mass of the macroporous white spheres; the catalyst is anhydrous zinc chloride, and the amount of the catalyst is 30-60% of the mass of the macroporous white spheres.

[0019] In a preferred embodiment, step 2) is performed as follows: Macroporous white spheres were added to a chloromethylating agent and allowed to swell at room temperature for 1-3 hours. Then, a catalyst was added, and the temperature was raised to 45-60°C. The reaction was carried out for 6-12 hours for chloromethylation. After the reaction, the mixture was cooled to room temperature, filtered, and the resulting product was washed with alcohol (preferably methanol) and water until neutral to obtain chloromethylated macroporous white spheres, i.e., chlorospheres. The mild reaction conditions ensured that the chlorine content in the prepared chlorospheres was stable and controllable.

[0020] In one embodiment, in step 3), the first amination reagent N-alkylimidazole is N-butylimidazole or N-hexylimidazole, and the molar ratio of the first amination reagent to the chloromethyl group on the chlorobenzene is 1.2:1-2:1; the molar ratio of the second amination reagent hexamethylenetetramine to the chloromethyl group on the chlorobenzene is 0.3:1-1:1.

[0021] In one embodiment, step 3) specifically involves: first, reacting the chlorine ball with the first amination reagent at 60-90°C for 8-24 hours, filtering and washing the product, and then reacting the obtained product with the second amination reagent at 60-80°C for 4-12 hours.

[0022] In one embodiment, in step 3), when the chlorine bulbs are swollen, the ratio of the mass of the chlorine bulbs to the volume of the solvent is (1:8-1:12) g / mL.

[0023] In a preferred embodiment, step 3) is performed as follows: The chlorine bulbs are added to the first solvent and swollen for 1-3 hours. Then, the first amination reagent is added, and the amination reaction is carried out at 60-90℃ for 8-24 hours. After the reaction is completed, the mixture is filtered, and the product is washed with alcohol (preferably ethanol) and water to obtain an intermediate. The intermediate is then added to the second solvent and swollen for 1-3 hours. Then, the second amination reagent is added, and the amination reaction is carried out at 60-80℃ for 4-12 hours. After the reaction is completed, the mixture is filtered, and the product is washed with alcohol (preferably ethanol) and water.

[0024] In a preferred embodiment, the first solvent is N,N-dimethylformamide (DMF); the second solvent is a mixed solvent consisting of a C1-C4 alcohol (e.g., methanol, ethanol, isopropanol, tert-butanol, preferably ethanol) and water (preferably a 40-60 wt% aqueous alcohol solution, with a 50 wt% aqueous ethanol solution being more desirable), and the ratio of the mass of the intermediate to the volume of the second solvent is (1:7-1:12) g / mL.

[0025] In one embodiment, in step S4), the alkaline solution is a 0.5-2 mol / L sodium hydroxide solution or potassium hydroxide solution; the transformation conditions are soaking at room temperature for 1-4 hours, repeated 1-3 times. The transformed resin is repeatedly washed with deionized water until the pH of the effluent is <8 and no white precipitate (Cl) is detected by AgNO3 solution. - Once the washing is complete, it can be considered that the washing is finished.

[0026] Compared with the prior art, the present invention has the following significant advantages: This invention introduces rigid norbornene monomer copolymerization, which significantly improves the thermal stability and mechanical strength of the resin. It employs a composite pore-forming system of "organic pore-forming agent + inorganic pore-forming agent," successfully constructing a hierarchical porous structure with micropores, mesopores, and macropores, thereby effectively improving the resin's adsorption capacity and mass transfer rate. A composite amination reaction is used, in which N-alkylimidazolium generates imidazolium salt functional groups, resulting in good selectivity for hydrophobic anions such as perchlorate. Urotropine provides additional crosslinking and chelation sites, thereby enhancing the resin's mechanical strength and heavy metal ion removal capacity. The prepared anion resin exhibits good selectivity, good thermal stability, high mechanical strength, and excellent pore-forming effect. Furthermore, the entire preparation method uses mild reaction conditions and is easily scalable for large-scale production, possessing significant industrial application value. Detailed Implementation

[0027] The technical solution of the present invention will be further described in detail and completely below with reference to the embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. Experimental methods in the following embodiments that do not specify specific conditions are generally performed under conventional conditions or as recommended by the manufacturer. Example 1

[0028] I. Preparation of Inorganic Pore-forming Agent (Hydrogen-containing Silicone Oil Modified Nano-calcium Carbonate) 100g of nano-calcium carbonate (CaCO3, particle size 30-80nm, Zhejiang Zhoushan Mingri Nanomaterials Co., Ltd.) was added to a reactor, along with 10g of hydrogen-containing silicone oil (PMHS, hydrogen equivalent 0.18%, viscosity 25-35cs, Shandong Dayi Chemical Co., Ltd.). The temperature was raised to 110℃, and the reaction was carried out under mechanical stirring for 45 minutes. After the reaction was completed, the mixture was cooled to room temperature. The resulting product was then placed in a vacuum drying oven and vacuum dried at 70℃ and -0.09MPa for 4 hours to obtain a powdered inorganic pore-forming agent (hydrogen-containing silicone oil modified nano-calcium carbonate), which was sealed and stored for later use.

[0029] II. Preparation of Styrene-based Macroporous Anion Resins 1) Preparation of macroporous white spheres: Aqueous phase preparation: Dissolve 1.0 g of dispersant polyvinyl alcohol (PVA-1788, Shanghai Aladdin Biochemical Technology Co., Ltd.) and 1.0 g of sodium chloride in 100 mL of deionized water, heat to 60 °C to dissolve, and obtain the aqueous phase for later use; Oil phase preparation: 20g styrene (St, Shanghai Aladdin Biochemical Technology Co., Ltd.), 1.2g 5-norbornene-2-methanol (NB-OH, Sigma-Aldrich (Shanghai) Trading Co., Ltd.), 4g divinylbenzene (DVB, Shandong Dongda Chemical Industry Co., Ltd.), composite porogen (8g hydrogen-containing silicone oil modified nano calcium carbonate, 6g n-heptane, 6g cumene), and 0.4g initiator benzoyl peroxide (BPO, Shanghai Maclean Biochemical Technology Co., Ltd.) were mixed and ultrasonically dispersed for 15 minutes to ensure uniform mixing of all components, thus obtaining the oil phase. Suspension polymerization: The oil phase was added to the aqueous phase (oil phase:water phase mass ratio of 1:3.3), and under nitrogen protection, the mixture was stirred and emulsified at 300 rpm for 30 minutes. Then, the temperature was raised to 78℃ for polymerization for 4 hours, and then the temperature was raised to 90℃ for curing for 2 hours. After the reaction was completed, the mixture was filtered and washed with hot water to obtain white balls. Pore-forming agent removal: Acid washing: Add the white spheres to a 2 mol / L hydrochloric acid solution (solid-liquid ratio 1:5), stir at 50℃ for 2 hours, filter, and wash with water until neutral (the hydrogen-containing silicone oil modified layer in the inorganic porogen will hydrolyze during acid washing, thus being removed along with the nano-calcium carbonate, and will not remain in the resin to affect the pore structure. In this way, the inorganic porogen can be removed by acid washing and water washing without causing hydrogen-containing silicone oil residue); Solvent extraction: Load the acid-washed white spheres into a Soxhlet extractor, extract with anhydrous ethanol for 8 hours (to remove the organic porogen), and vacuum dry at 60℃ to obtain macroporous white spheres; 2) Chloromethylation: 10g of the macroporous white spheres obtained in step 1) were added to 50mL of chloromethyl ether (CMME, Qidu Welfare Chemical Plant, Linzi District, Zibo City; chloromethyl ether density is approximately 1.06 g / mL; actual amount used is approximately 53g, about 5.3 times the mass of the macroporous white spheres). The mixture swelled at room temperature for 2 hours. Then, 5g of anhydrous zinc chloride (ZnCl2, Sinopharm Chemical Reagent Co., Ltd.; zinc chloride amount is 50% of the mass of the macroporous white spheres) was added. The mixture was heated to 50℃ under mechanical stirring and maintained at this temperature for 10 hours. After the reaction was complete, the mixture was cooled to room temperature and filtered. The resulting product was washed three times with methanol and then washed with deionized water until neutral to obtain chloromethylated macroporous white spheres, i.e., chlorospheres. The chlorine content in the chlorospheres was determined using the Volhard method: 0.5g of chlorospheres was accurately weighed and added to 10mL of... A 0.5 mol / L sodium hydroxide ethanol solution was refluxed for 2 hours. After cooling, 20 mL of dilute nitric acid was added for acidification. The solution was then titrated with a 0.1 mol / L silver nitrate standard solution, using ferric ammonium sulfate as an indicator, to calculate the chlorine content. The chlorine content in the chlorine bulb was found to be 18.2%. 3) Complex amination: 5g of the chlorobean obtained in step 2) was added to 50mL of N,N-dimethylformamide (DMF) (chlorobean:DMF=1:10, g / mL), and swollen at room temperature for 2 hours. Then, 4.1g of N-butylimidazole (BuIm, Shanghai Aladdin Biochemical Technology Co., Ltd., with a molar ratio of 1.3:1 to the chloromethyl group on the chlorobean, and the molar amount of chloromethyl group on the chlorobean was calculated as 0.0256 mol based on a chlorine content of 18.2%) was added. The mixture was stirred at 80℃ for 12 hours. After the reaction was completed, the mixture was filtered, and the resulting product was washed twice with 50mL of anhydrous ethanol and twice with 50mL of deionized water to obtain the intermediate. The obtained intermediate was added to 50 mL of 50% ethanol aqueous solution (intermediate:solvent = 1:10, g / mL), and swollen at room temperature for 1 hour. Then, 1.8 g of hexamethylenetetramine (HMTA, Sinopharm Chemical Reagent Co., Ltd., with a molar ratio of 0.5:1 to the initial chloromethyl group on the chlorosphere) was added, and the mixture was stirred at 70 °C for 8 hours. After the reaction was completed, the mixture was filtered, and the obtained product was washed twice with 50 mL of anhydrous ethanol and twice with 50 mL of deionized water. 4) Transformation and post-treatment: Add the product from step 3) to a 1 mol / L sodium hydroxide solution (solid-liquid ratio 1:10), soak at room temperature for 2 hours, filter, wash the obtained product repeatedly with deionized water until the pH of the effluent is <8, and dry under vacuum at 60℃ to obtain styrene-based macroporous anion resin. Example 2

[0030] The difference between this embodiment and Embodiment 1 is that: Step 1) In the preparation of macroporous white spheres, the norbornene monomer was replaced with 5-norbornene-2-carboxylic acid (NB-COOH, Shanghai Aladdin Biochemical Technology Co., Ltd.), with an amount of 1.2g; the composite pore-forming agent used was 8g of hydrogen-containing silicone oil modified nano-calcium carbonate, 6g of n-heptane, and 6g of ethylbenzene. Step 2) During chloromethylation, the chloromethylation reagent was changed to 1,4-dichloromethoxybutane (BCMB, Shandong Xingfu New Materials Co., Ltd.), with a dosage of 60 mL (BCMB, density approximately 1.07 g / mL, dosage approximately 64.2 g, approximately 6.4 times the mass of the macroporous white spheres). The reaction temperature was 55℃, and the reaction time was 12 hours. The chlorine content of the chlorospheres was determined to be 16.5% by the Volhard method. In step 3), during the compound amination, the first amination reagent is replaced with N-hexylimidazole (HeIm, Shanghai Aladdin Biochemical Technology Co., Ltd.), and its molar ratio with chloromethyl is 1.3:1. The rest is the same as in Example 1. Example 3

[0031] The difference between this embodiment and Embodiment 1 is that: Step 1) During the preparation of macroporous white spheres, 2g of modified magnetic nanoparticles (KH-570 modified nano-ferric oxide, accounting for approximately 7% of the total monomer mass) were added to the oil phase. The nanoparticles were ultrasonically dispersed for 15 minutes to ensure uniform dispersion in the oil phase. The specific preparation of the modified magnetic nanoparticles was as follows: 10g of nano-Fe3O4 (particle size 10-30nm, Beijing Deco Island Gold Technology Co., Ltd.) was dispersed in a mixed solvent of 80mL anhydrous ethanol and 9mL deionized water (ethanol:water = 9:1, volume ratio). The dispersion was ultrasonically dispersed for 20 minutes. 1.5g of silane coupling agent KH-570 (Nanjing Shuguang Chemical Group Co., Ltd.) was added. The pH was adjusted to 4.5 with glacial acetic acid. The mixture was stirred and pre-hydrolyzed at room temperature for 30 minutes. The temperature was raised to 75℃ and stirred under nitrogen protection for 5 hours. After the reaction was completed, the mixture was separated by a magnet, the supernatant was discarded, and the product was washed three times with 50mL anhydrous ethanol and twice with 50mL deionized water. The washed product was dried in a vacuum drying oven at 50℃ for 10 hours and then ground through a 200-mesh sieve to obtain modified magnetic nanoparticles, which were then sealed and stored for later use. The rest is the same as in Example 1.

[0032] Comparative Example 1 The difference between this comparative example and Example 1 is as follows: Step 1) When preparing macroporous white spheres, 5-norbornene-2-methanol (NB-OH) is not added to the oil phase, and the amount of styrene is adjusted to 21.2g to keep the total amount of monomer constant; The rest is the same as in Example 1.

[0033] Comparative Example 2 The difference between this comparative example and Example 1 is as follows: Step 1) In the preparation of macroporous white spheres, the porogen in the oil phase is changed to the traditional single organic porogen toluene (dosage 20g), and no inorganic porogen (hydrogen-containing silicone oil modified nano calcium carbonate) is added. The rest is the same as in Example 1.

[0034] Comparative Example 3 The difference between this comparative example and Example 1 is as follows: Step 3) When the chlorospheres undergo the amination reaction, the first amination reagent N-butylimidazole (BuIm) is not added. Instead, hexamethylenetetramine (HMTA, with a molar ratio of 1.3:1 to chloromethyl) is used for one-step amination. The reaction conditions are 80°C for 20 hours. The rest is the same as in Example 1.

[0035] Comparative Example 4 The difference between this comparative example and Example 1 is as follows: Step 3) When the chlorospheres undergo amination reaction, the second amination reagent hexamethylenetetramine (HMTA) is not added. Instead, N-butylimidazole (BuIm, with a molar ratio of 1.8:1 to chloromethyl) is used for one-step amination. The reaction conditions are 80°C for 20 hours. The rest is the same as in Example 1.

[0036] Comparative Example 5 The difference between this comparative example and Example 1 is as follows: Step 3) When the chlorospheres undergo amination reaction, the amination reagent is changed to a 30% trimethylamine aqueous solution (molar ratio of 1.5:1 with chloromethyl), and the reaction is carried out at 40°C for 12 hours to perform a one-step amination, without performing a second-step amination; The rest is the same as in Example 1.

[0037] The performance of the styrene-based macroporous anion exchange resins prepared in Examples 1-3 and Comparative Examples 1-5 was tested, specifically as follows: 1. Ion Exchange Capacity (IEC): Determined by back titration. Accurately weigh 0.5 g of dry resin, add 25 mL of 0.1 mol / L HCl standard solution, soak for 24 hours, take 10 mL of the supernatant, and titrate with 0.1 mol / L NaOH standard solution. Use phenolphthalein as an indicator and calculate the IEC using the following formula: IEC (mmol / g) = (C_HCl × V_HCl - C_NaOH × V_NaOH) / m_dry; m_dry is the mass of dry resin; 2. Moisture content and swelling rate: Determined according to GB / T 5759-2000 method. The resin was soaked in deionized water for 24 hours, and the wet weight (W_wet) and wet volume (V_wet) were measured. Then, it was dried at 105℃ to constant weight, and the dry weight (W_dry) and dry volume (V_dry) were measured. The moisture content and swelling rate were calculated using the following formula: Moisture content (%) = (W_wet - W_dry) / W_wet × 100%; Swelling rate (%) = (V_wet - V_dry) / V_dry × 100%; 3. Mechanical strength: The crushing strength of the resin was measured using a single-particle strength tester. The average value of 50 resin particles was taken, and the unit is N / particle. 4. Selective adsorption (ClO4) - ): Preparation of ClO4 - and NO3 - The mixed solution (NO3) - / ClO4 - Molar ratio 100:1, ClO4 - Weigh 0.1 g of resin (OH form) with an initial concentration of 20 mg / L, add 100 mL of the above mixed solution (solid-liquid ratio 1 g / L), and shake at 180 rpm for 4 hours at 25 °C. After adsorption, filter and determine the residual ClO4 in the filtrate using ion chromatography (Dionex ICS-600). - Concentration, the distribution coefficient Kd is calculated using the following formula: Kd(mL / g)=(C0-C e ) / C e ×V / m; where: C0 is the initial ClO4 - Concentration (mg / L), C e ClO4 after adsorption equilibrium - Concentration (mg / L), V is the solution volume (mL), m is the resin mass (g), and the larger the Kd value, the stronger the resin's effect on ClO4. - The better the selection; 5. Metal ions (Cu) 2+ Removal rate: Accurately weigh 0.1964 g of copper sulfate pentahydrate (CuSO4·5H2O), dissolve it in deionized water and bring the volume to 1000 mL to prepare Cu... 2+ For a 50 mg / L solution, accurately weigh 0.1 g of resin (OH form) and add it to 100 mL of the above Cu solution. 2+The solution (solid-liquid ratio 1 g / L) was adjusted to pH 5.5 ± 0.5 with dilute NaOH solution. The conical flask was placed in a constant-temperature shaker and shaken for adsorption at 25℃ and 180 rpm for 4 hours. After adsorption, the solution was filtered, and the residual Cu in the filtrate was determined by atomic absorption spectrophotometry. 2+ Concentration, Cu is calculated using the following formula. 2+ Removal rate: Cu 2+ Removal rate (%) = (50 - C_e) / 50 × 100%; where C_e is the Cu in the solution after adsorption. 2+ Concentration (mg / L); 6. Specific surface area and pore size: The BET specific surface area analyzer was used to determine the specific surface area. N2 was used as the adsorbate. The adsorption-desorption isotherm was measured at 77K. The specific surface area was calculated by the BET method and the pore size distribution was calculated by the BJH method. 7. Thermal stability: 1) Thermogravimetric analysis (TGA): Thermogravimetric analysis (TA Instruments, Q500) was used to determine the initial thermal decomposition temperature (T_d, measured at 5% weight loss) under a nitrogen atmosphere. The heating rate was 10℃ / min and the temperature range was 30-800℃. 2) Heat resistance performance (exchange capacity reduction rate) test: According to DL / T 953-2005 "Determination of Heat Resistance of Strong Basic Anion Exchange Resins for Water Treatment", two equal amounts of hydroxide-type anion exchange resin were taken. One sample was tested according to GB / T 5760-2000 to determine the strong base exchange capacity on a wet basis before heating (Q_before); the other sample was immersed in 200 mL of deionized water and placed in a constant temperature water bath at 95±1℃ for 100 hours (maintaining the liquid level and changing the position every 24 hours). After cooling, the strong base exchange capacity on a wet basis after heating was measured (Q_after). The exchange capacity reduction rate (R) was calculated according to the following formula. R =(Q_before -Q_after) / Q_before×100%; The test results are shown in Table 1.

[0038] Table 1 Performance test data of styrene-based macroporous anion exchange resins prepared in Examples 1-3 and Comparative Examples 1-5

[0039] As shown in Table 1, the styrene-based macroporous anion exchange resins prepared in Examples 1-3 of this invention have the following characteristics: ion exchange capacity (IEC) of 2.08-2.25 mmol / g, water content of 48-52%, swelling ratio of 13.2-15.0%, crushing strength of 3.8-4.2 N / particle, and ClO4 content of 100%. -Selectivity Kd value is 12500-14100 mL / g, Cu 2+ The removal rate is 38-42%, and the BET specific surface area is 362-385 m². 2 The styrene-based macroporous anion exchange resin prepared in this embodiment exhibits excellent comprehensive performance in terms of ion exchange capacity, mechanical strength, selective adsorption, and thermal stability. The average pore size is 18.5-20.2 nm, the initial thermal decomposition temperature is 278-285℃, and the exchange capacity decrease rate is 7.8-8.5%. Furthermore, comparing Example 1 and Example 2, it can be seen that Example 2 has a better effect on ClO4. - The selectivity is superior to that of Example 1, indicating that the N-hexylimidazole used in Example 2 provides stronger hydrophobic interactions compared to the N-butylimidazole used in Example 1, thereby enhancing the resin's resistance to ClO4. - With further improved selectivity, the crushing strength of Example 2 is better than that of Example 1, indicating that the 5-norbornene-2-carboxylic acid used in Example 2, compared with the 5-norbornene-2-methanol used in Example 1, has a carboxyl group that can provide additional hydrogen bond crosslinking sites, thereby improving the crushing strength of the resin. Comparing Example 1 and Example 3, it can be seen that the crushing strength of Example 3 is better than that of Example 1, indicating that the KH-570 modified nano-Fe3O4 used in Example 3 not only imparts superparamagnetism to the resin, but also enhances the mechanical strength of the resin. Furthermore, as can be seen from the table, the overall performance of the styrene-based macroporous anion resins prepared in Examples 1-3 is significantly better than that of the styrene-based macroporous anion resins prepared in Comparative Examples 1-5. This may be because: 1) Compared with Comparative Example 1: No norbornene monomer (NB-OH) was added during the preparation of Comparative Example 1. Compared with Example 1, the crushing strength and initial thermal decomposition temperature of Comparative Example 1 were significantly reduced. This indicates that after the rigid bicyclic structure of norbornene monomer is embedded in the polymer backbone, it can effectively suppress the thermal motion of molecular chains at high temperature and enhance the resistance of the polymer network to external forces, thereby significantly improving the mechanical strength and thermal stability of the resin. 2) Comparison of Example 1 and Comparative Example 2: Comparative Example 2 used the traditional single organic porogen toluene, without adding an inorganic porogen (hydrogen-silicone oil-modified nano-calcium carbonate). Compared with Example 1, the BET specific surface area and average pore size of Comparative Example 2 were significantly reduced, and ClO4... -The selectivity Kd value decreased significantly because a single organic porogen cannot form a stable macroporous structure during polymerization, and the pore size distribution is uneven. However, the "organic porogen + hydrogen-containing silicone oil modified inorganic nanoparticles" composite porogen system used in the embodiments of this invention utilizes the lipophilicity of hydrogen-containing silicone oil modified nano-calcium carbonate to stably disperse it in the oil phase. After polymerization, it is removed by acid washing, leaving macropores and macropores inside the resin. Together with the micropores and mesopores formed by the organic porogen, they form a hierarchical porous structure, thereby improving the specific surface area and mass transfer channels, and enhancing the adsorption capacity and selectivity. 3) Comparison of Examples 1 and Comparative Example 3: Comparative Example 3 only used hexamethylenetetramine for amination without the addition of N-butylimidazole. Compared with Example 1, the IEC and ClO4 of Comparative Example 3 were significantly different. - Selectivity Kd value, Cu 2+ The removal rates all decreased because, although hexamethylenetetramine can provide a cross-linking structure, the number of quaternary ammonium salts generated by its reaction with chloromethyl is limited, failing to provide a high density of anion exchange sites; while the imidazolium salt functional groups generated by the N-alkylimidazolium in the examples have a high density of positive charge centers, and the conjugated structure of the imidazolium ring is highly sensitive to hydrophobic anions (ClO4). - The embodiment has specific recognition capabilities, thereby making the exchange capacity and selectivity of the embodiment significantly better than those of Comparative Example 3; 4) Comparison of Examples with Comparative Example 4: Comparative Example 4 only used N-butylimidazole for amination without adding hexamethylenetetramine. Compared with Examples, Comparative Example 4 showed a significantly increased swelling ratio and decreased crushing strength, and also showed a greater effect on Cu. 2+ It has virtually no removal ability because hexamethylenetetramine reacts with chloromethyl groups in the second amination step to form an additional cross-linking network, effectively limiting excessive swelling of the resin and improving dimensional stability and mechanical strength. Simultaneously, the polar groups such as amine groups (-NH2, -NH-) generated from hexamethylenetetramine hydrolysis can serve as chelating sites for heavy metal ions, endowing the resin with Cu... 2+ Removal ability; 5) Comparison of Example 1 and Comparative Example 5: Comparative Example 5 used conventional trimethylamine for amination. Compared with Example 1, the ClO4 in Comparative Example 5... - The selectivity Kd value decreased significantly, while the rate of decrease in exchange capacity increased significantly. This is because the quaternary ammonium groups generated by trimethylamine affect ClO4. - The selectivity of the traditional quaternary ammonium group is poor, and the thermal stability of the traditional quaternary ammonium group is lower than that of the imidazolium salt. However, the imidazolium salt generated by the N-alkyl imidazolium used in the examples has a more stable conjugated structure and is more resistant to degradation in high-temperature aqueous solutions, thus making the thermal stability of the examples significantly better than that of Comparative Example 5.

[0040] Finally, it should be noted that the above are only some preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above content of the present invention shall fall within the scope of protection of the present invention.

Claims

1. A method for producing a styrene-based macroporous anion resin, characterized by, Includes the following steps: 1) Preparation of macroporous white spheres: Styrene monomer, norbornene monomer, divinylbenzene, composite porogen and initiator are mixed to form an oil phase. The oil phase is subjected to suspension polymerization in an aqueous phase containing a dispersant. After polymerization, the composite porogen is removed by sequential treatment with acid solution and organic solvent to obtain macroporous white spheres. 2) Chloromethylation: The macroporous white spheres obtained in step 1) are subjected to a chloromethylation reaction to obtain chloromethylated macroporous white spheres, i.e., chlorospheres; 3) Complex amination: The chlorine spheres obtained in step 2) are swollen in a solvent, and the first amination reagent and the second amination reagent are added sequentially to carry out a complex amination reaction; 4) Transformation and post-treatment: The product of step 3) is transformed with alkaline solution and washed until neutral to obtain styrene-based macroporous anion exchange resin. The norbornene monomer is 5-norbornene-2-methanol or 5-norbornene-2-carboxylic acid; The composite porogen comprises an organic porogen and an inorganic porogen. The organic porogen is selected from at least one of n-heptane, cyclohexane, ethylbenzene, cumene, and tert-butylbenzene. The inorganic porogen is obtained by modifying nano-calcium carbonate with hydrogen-containing silicone oil. The first amination reagent is N-alkylimidazole, and the second amination reagent is hexamethylenetetramine.

2. The method for preparing a styrenic macroporous anion resin according to claim 1, characterized by, In step 1), the amount of norbornene monomer used is 2-8% of the mass of styrene monomer; the amount of divinylbenzene used is 5-20% of the mass of styrene monomer.

3. The method for preparing styrene-based macroporous anion exchange resin according to claim 1, characterized in that, In step 1), the initiator is benzoyl peroxide or azobisisobutyronitrile, and its amount is 0.5-2% of the total mass of styrene monomer, norbornene monomer and divinylbenzene.

4. The method for preparing styrene-based macroporous anion exchange resin according to claim 1, characterized in that, In step 1), the dispersant is polyvinyl alcohol, and its dosage is 0.5-1.5% of the mass of the aqueous phase; the mass ratio of the oil phase to the aqueous phase is 1:2.5-1:

5.

5. The method for preparing styrene-based macroporous anion exchange resin according to claim 1, characterized in that, In step 1), the mass ratio of organic porogen to inorganic porogen in the composite porogen is 1:1-3:1, and the amount of composite porogen used is 50-90% of the total mass of styrene monomer, norbornene monomer and divinylbenzene.

6. The method for preparing styrene-based macroporous anion exchange resin according to claim 1, characterized in that, The preparation of the inorganic porogen includes the following steps: Nano-calcium carbonate and hydrogen-containing silicone oil are mixed at a mass ratio of 100:5-100:15 and heated and stirred at 100-120℃ for 30-60 minutes. After the reaction is completed, the mixture is cooled to room temperature and the resulting product is vacuum dried to obtain an inorganic pore-forming agent.

7. The method for preparing styrene-based macroporous anion exchange resin according to claim 1, characterized in that, In step 1), the oil phase also contains modified magnetic nanoparticles, which are obtained by modifying nano-iron oxide with silane coupling agent KH-570, and the amount of the modified magnetic nanoparticles is 1-10% of the total mass of styrene monomer, norbornene monomer and divinylbenzene.

8. The method for preparing styrene-based macroporous anion exchange resin according to claim 1, characterized in that, In step 2), the macroporous white spheres are first swollen with a chloromethylating agent, and then subjected to a chloromethylation reaction under the action of a catalyst to obtain chloromethylated macroporous white spheres, i.e., chlorospheres; the chloromethylating agent is chloromethyl ether or 1,4-dichloromethoxybutane, and the amount of the chloromethylating agent is 3-7 times the mass of the macroporous white spheres; the catalyst is anhydrous zinc chloride, and the amount of the catalyst is 30-60% of the mass of the macroporous white spheres.

9. The method for preparing styrene-based macroporous anion exchange resin according to claim 1, characterized in that, In step 3), the first amination reagent N-alkylimidazole is N-butylimidazole or N-hexylimidazole, and the molar ratio of the first amination reagent to the chloromethyl group on the chlorosphere is 1.2:1-2:1; the molar ratio of the second amination reagent hexamethylenetetramine to the chloromethyl group on the chlorosphere is 0.3:1-1:

1.

10. The method for preparing styrene-based macroporous anion exchange resin according to claim 1, characterized in that, In step 3), the composite amination reaction is specifically as follows: first, the chlorine ball is amination reaction with the first amination reagent at 60-90℃ for 8-24 hours, and after filtration and washing, the obtained product is amination reaction with the second amination reagent at 60-80℃ for 4-12 hours.

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