A method for preparing an aqueous thermosensitive Cr(III) ion-imprinted polymer

Abstract

This invention discloses a method for preparing an aqueous thermosensitive Cr(III) ion-imprinted polymer, belonging to the field of water pollution treatment technology. The method includes the following steps: (1) dissolving aminated multi-walled carbon nanotubes and potassium carbonate in N,N-dimethylformamide, and adding bromopropylene to obtain vinylated multi-walled carbon nanotubes; (2) dissolving CrCl3·6H2O, a functional monomer, and a thermosensitive monomer in a porous solvent composed of ethanol and water, adding vinylated multi-walled carbon nanotubes, ethylene glycol dimethacrylate, and azobisisobutyronitrile to obtain the Cr(III) ion-imprinted polymer. This invention introduces the thermosensitive functional monomer N-isopropylacrylamide, enabling the ion-imprinted polymer to respond to changes in ambient temperature and accurately identify and adsorb target ions in complex environments. The introduction of the thermosensitive functional monomer allows the polymer to form a hydrophilic layer, reducing non-specific adsorption caused by impurities such as humic acid, and improving the adsorption capacity and selectivity for target ions.

Description

Technical Field

[0001] This invention relates to the field of water pollution treatment technology, specifically to a method for preparing an aqueous temperature-sensitive Cr(III) ion-imprinted polymer. Background Technology

[0002] Cr(III) is an essential trace element for the human body, but it is also a common contact allergen. Upon contact with the human body, it penetrates the skin's surface and binds to proteins in the skin to form a complete antigen, thus triggering a type IV allergic reaction. Simultaneously, inhaling dust or fumes containing trivalent chromium can irritate the respiratory tract, potentially leading to rhinitis, pharyngitis, or even asthma. Furthermore, high concentrations of trivalent chromium released into water bodies can be toxic to aquatic organisms such as fish and algae, impacting ecosystem health. Therefore, developing highly efficient, energy-saving, selective Cr(III) ion removal materials that avoid secondary pollution has become a current research hotspot.

[0003] Adsorption methods are widely used in water pollutant treatment due to their simplicity, economy, and efficiency. Among them, ion imprinting technology can specifically identify, adsorb, and separate target ions, offering advantages of high selectivity and high sensitivity, while remaining relatively inexpensive and showing broad application prospects. The core of this technology lies in forming "imprinted cavities" within a polymer matrix that are complementary to the target ion in size, configuration, and chemical functional groups, thereby achieving efficient and specific capture of the ion.

[0004] As adsorbents for water pollution treatment, the ability of ion-imprinted polymers to treat wastewater depends on their adsorption and binding capacity for target ions. Traditional imprinted polymers, once synthesized, have fixed properties and parameters, and cannot intelligently respond to changes in the external environment. They also cannot accurately identify and adsorb target ions in complex real-world environments. Therefore, designing and synthesizing polymers that can respond to environmental changes is of great significance. Furthermore, real-world wastewater often contains large amounts of humic acid or natural organic matter. These contaminants can cause non-specific adsorption on the surface of traditional adsorbents, leading to blockage of adsorption sites, decreased polymer adsorption performance, and even difficulties in recycling and regeneration.

[0005] In summary, it is necessary to provide a method for preparing a thermosensitive Cr(III) ion-imprinted polymer to enhance its adsorption capacity, enabling it to respond to environmental changes and effectively achieve precise adsorption of target ions in actual water samples. This would also reduce the impact of non-specific adsorption on its performance and lifespan, thereby expanding the application prospects of ion-imprinted polymers in the field of wastewater treatment. Summary of the Invention

[0006] To address or partially address the problems existing in related technologies, this invention provides a method for preparing an aqueous temperature-sensitive Cr(III) ion-imprinted polymer. This method endows the imprinted polymer with temperature responsiveness, thereby enhancing its adsorption capacity for target ions in complex real-world environments. Simultaneously, it imbues the polymer with a certain degree of "anti-fouling" capability, mitigating the blockage of adsorption sites caused by non-specific adsorption during the adsorption process.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows: a method for preparing an aqueous thermosensitive Cr(III) ion-imprinted polymer, the innovation of which lies in the following steps: (1) Preparation of vinylized multi-walled carbon nanotubes: Aminated multi-walled carbon nanotubes and potassium carbonate were dissolved in N,N-dimethylformamide and ultrasonically stirred to obtain a mixed solution. Bromopropylene was added and a solvothermal reaction was carried out. After the reaction was completed, the reaction product was filtered, washed, dried, ground and sieved in sequence to obtain vinylized multi-walled carbon nanotubes. (2) Preparation of Cr(III) ion-imprinted polymer: CrCl3·6H2O, functional monomer 4-vinylpyridine and thermosensitive monomer N-isopropylacrylamide were dissolved in a pore-forming solvent composed of ethanol and water to form polymerization system A. After prepolymerization reaction under stirring at room temperature, the vinylized multi-walled carbon nanotubes obtained in step (1) were added to system A. After ultrasonic dispersion, crosslinking agent ethylene glycol dimethacrylate and initiator azobisisobutyronitrile were added to form polymerization system B. Polymerization was carried out under water bath conditions. After the reaction was completed, the reaction products were filtered and dried in sequence. Finally, the template Cr(III) ions were removed with the eluent to obtain Cr(III) ion-imprinted polymer Cr(III)-IIP@V-MWCNTs.

[0008] Preferably, in step (1), the concentration of aminated multi-walled carbon nanotubes in the mixed solution is 40 mg / mL, the concentration of potassium carbonate is 66.4 mg / mL, and the volume ratio of bromopropylene to N,N-dimethylformamide is 0.85:25.

[0009] Preferably, in step (1), the ultrasonic dispersion time is 43-47 min.

[0010] Preferably, in step (1), the conditions for the solvothermal reaction are: a reaction temperature of 64-66℃ and a reaction time of 23-25h.

[0011] Preferably, in step (1), the washing is performed 6 times, wherein the first and second washings are performed by filtration with N,N-dimethylformamide, the third and fourth washings are performed by filtration with deionized water, and the fifth and sixth washings are performed by filtration with anhydrous ethanol.

[0012] Preferably, in step (2), in polymerization system B, the concentration of CrCl3·6H2O is 5.00 mmol / L, the concentration of vinylized multi-walled carbon nanotubes is 0.50~3.00 g / L, the concentration of 4-vinylpyridine is 0.01~0.05 mol / L, the concentration of N-isopropylacrylamide is 0.01~0.05 mol / L, the concentration of ethylene glycol dimethacrylate is 0.06~0.30 mol / L, and the concentration of the initiator azobisisobutyronitrile is 1.25 g / L.

[0013] Preferably, the molar ratio of 4-vinylpyridine to N-isopropylacrylamide is 1:1.

[0014] Preferably, in step (2), the reaction is stirred at room temperature for 2-3 hours.

[0015] Preferably, in step (2), the water bath heating temperature is 64-66℃ and the reaction time is 20-24h.

[0016] Preferably, in the pore-forming solvent of step (2), the volume ratio of ethanol to water is 1:1.

[0017] Preferably, in step (2), the removal of template Cr(III) ions by elution includes three elutions: the first elution is a 0.10 mol / L HNO3 solution, and the elution time is 5 h; the second and third elutions are 0.05 mol / L EDTA solutions, and the elution time is 8 h for each; the pH of the EDTA solution is 5.

[0018] This invention provides a method for preparing an aqueous thermosensitive Cr(III) ion-imprinted polymer, which has the following beneficial effects: (1) This invention introduces the thermosensitive functional monomer N-isopropylacrylamide, enabling the ion-imprinted polymer to respond to changes in ambient temperature, thereby accurately identifying and adsorbing target ions in complex environments. At the same time, the introduction of the thermosensitive functional monomer enables the polymer to form a hydrophilic layer, that is, a "hydration layer" is formed on the polymer surface through hydration, which directly shields the physical adhesion of macromolecules such as humic acid, reduces non-specific adsorption caused by them, and improves the adsorption capacity and adsorption selectivity for target ions.

[0019] (2) The preparation method of the present invention is simple and easy to implement, and the ion-imprinted polymer prepared has advantages such as high selectivity, large adsorption capacity, and good removal effect of Cr(III) in water, and is suitable for industrial promotion and application.

[0020] (3) By using 4-vinylpyridine as a functional monomer, the present invention works synergistically with vinylized multi-walled carbon nanotubes to enable the prepared ion-imprinted polymer to form highly selective recognition sites with the target ion Cr(III), thereby further improving the adsorption performance.

[0021] (4) The multi-walled carbon nanotubes of the present invention are one-dimensional carbon nanomaterials composed of multiple layers of columnar graphene, which have advantages such as good thermal stability, high chemical stability, high mechanical strength, and large specific surface area. Vinylated multi-walled carbon nanotubes modified based on this material can provide an excellent carrier for the construction of polymer imprinting sites and the selective recognition of target ions, thereby effectively improving the adsorption performance of ion-imprinted polymers.

[0022] (5) Vinylated multi-walled carbon nanotubes still have high stability under strong acid / base conditions, and 4-vinylpyridine, as a functional monomer, is not easily oxidized in acidic environments. The combination of the two can make the material suitable for more complex wastewater environments. Detailed Implementation

[0023] The present invention will be further described in detail below with reference to specific embodiments, but the scope of protection of the present invention is not limited to the content described.

[0024] Example 1 This embodiment describes a method for preparing an aqueous thermosensitive Cr(III) ion-imprinted polymer, the steps of which are as follows: (1) Preparation of vinylated multi-walled carbon nanotubes: 1.00 g of aminated multi-walled carbon nanotubes and 12.00 mmol (about 1.66 g) of anhydrous potassium carbonate were dissolved in 25 mL of N,N-dimethylformamide and ultrasonically vibrated for 45 min to obtain a mixed solution. After purging the mixed solution with nitrogen for 5 min, 0.85 mL of bromopropylene was slowly added dropwise. The mixture was sealed and reacted in a water bath at 65 °C under light protection for 24 h. After the reaction was completed, the reaction product was filtered and washed twice each with N,N-dimethylformamide, deionized water and anhydrous ethanol. Then it was dried, ground and sieved to obtain black powdered vinylated multi-walled carbon nanotubes.

[0025] (2) Preparation of Cr(III) ion-imprinted polymer: 0.10 mmol CrCl3·6H2O, 0.30 mmol functional monomer 4-vinylpyridine and 0.30 mmol thermosensitive monomer N-isopropylacrylamide (molar ratio of 4-vinylpyridine to N-isopropylacrylamide is 1:1) were dissolved in 20.00 mL of a mixture of ethanol and water (volume ratio = 1:1) to form a pore-forming solvent. The mixture was placed in a constant temperature shaker and shaken for 3 h at room temperature. Then, 30.00 mg of vinylized multi-walled carbon nanotubes prepared in step (1) were added. After ultrasonic shaking for 45 min, 4.00 mmol crosslinking agent ethylene glycol dimethacrylate and 25.00 mg initiator azobisisobutyronitrile were added. After dissolving and shaking, nitrogen gas was purged for 3 min to remove oxygen. The mixture was then reacted in a water bath at 65 °C for 24 h to form a polymer. After the reaction was completed, the polymer was filtered and dried, and then eluted for the first time with 0.10 mol / L HNO3 solution for 5 h; then eluted for the second and third times with 0.05 mol / L EDTA solution (pH=5) for 8 h each time, in order to remove the template ion Cr(III) and obtain the Cr(III) ion imprinted polymer.

[0026] Verification Experiment 1 The 20.00 mg Cr(III) ion-imprinted polymer prepared in the example was used for adsorption in a solution with a Cr(III) concentration of 15.31 mg / mL at adsorption temperatures of 25 °C, 35 °C, and 45 °C.

[0027] When the adsorption temperature is 25℃, the adsorption of Cr(Ⅲ) ion-imprinted polymer reaches adsorption equilibrium after 5 h, with an adsorption capacity of 3.73 mmol / g and an imprinting factor of 2.08.

[0028] When the adsorption temperature is 35℃, the adsorption of Cr(Ⅲ) ion-imprinted polymer reaches adsorption equilibrium after 5 hours, with an adsorption capacity of 4.24 mmol / g, which is about 14% higher than that at 25℃.

[0029] When the adsorption temperature is 45℃, the adsorption of Cr(Ⅲ) ion-imprinted polymer reaches adsorption equilibrium after 5 hours, with an adsorption capacity of 1.71 mmol / g, which is about 54% lower than that at 25℃.

[0030] The experimental results show that after introducing the temperature-sensitive functional monomer, increasing the adsorption temperature to 35℃ causes the polymer network to shrink moderately. This adjusts the cavity of the recognition site without burying it, thus enhancing its recognition and binding ability with the target ion. However, excessively increasing the temperature (45℃) will cause the polymer network to collapse and close severely, physically burying the recognition site and resulting in a decrease in adsorption.

[0031] Verification Experiment 2 The Cr(III) ion-imprinted polymer prepared in Example 1 was used in a mixed ion solution of Cr(III), Co(II), Ni(II), Pb(II), Cd(II), and Cu(II) (each ion concentration 100 mg·L⁻¹). -1 Adsorption was carried out at 25℃.

[0032] partition coefficients of each ion K d25 and selectivity coefficient k 25 As shown in Table 1: Table 1 The Cr(III) ion-imprinted polymer prepared in this embodiment was used in a mixed ion solution of Cr(III), Co(II), Ni(II), Pb(II), Cd(II), and Cu(II) (each ion concentration 100 mg·L⁻¹). -1 The adsorption occurs at a temperature of 35℃.

[0033] The partition coefficients and selectivity coefficients of each ion are shown in Table 2: Table 2 Comparing Tables 1 and 2, it can be seen that the selectivity coefficients of each ion are significantly improved at an adsorption temperature of 35℃.

[0034] The results show that the temperature sensitivity of the ion-imprinted polymer is improved after the introduction of the temperature-sensitive functional monomer. When the imprinted polymer is applied to the treatment of complex water samples, the specific selective adsorption performance for target ions can be enhanced by changing the adsorption temperature.

[0035] In summary, the Cr(III) ion-imprinted polymer prepared by this invention exhibits high selectivity and a large adsorption capacity for Cr(III) ions in water. Furthermore, this polymer is temperature-sensitive, and its specific adsorption performance for target ions can be improved by controlling the adsorption temperature, thus imparting it with certain anti-fouling properties. Therefore, the Cr(III) ion-imprinted polymer prepared by this invention possesses excellent performance characteristics.

[0036] Verification Experiment 3 Under otherwise unchanged conditions, this embodiment also investigated the effect of the amount of vinylized multi-walled carbon nanotubes added on the adsorption amount and imprinting factor. The adsorption temperature for this verification was 25°C.

[0037] When the amount of vinylized multi-walled carbon nanotubes was 10 mg, the adsorption of Cr(III) ion-imprinted polymer reached adsorption equilibrium in 5 h, with an adsorption capacity of 3.06 mmol / g and an imprinting factor of 1.18.

[0038] When the amount of vinylized multi-walled carbon nanotubes was 20 mg, the adsorption of Cr(III) ion-imprinted polymer reached adsorption equilibrium in 5 h, with an adsorption capacity of 2.61 mmol / g and an imprinting factor of 1.30.

[0039] When the amount of vinylized multi-walled carbon nanotubes was 30 mg, the adsorption of Cr(III) ion-imprinted polymer reached adsorption equilibrium in 5 h, with an adsorption capacity of 3.73 mmol / g and an imprinting factor of 2.08.

[0040] When the amount of vinylized multi-walled carbon nanotubes was 40 mg, the adsorption of Cr(III) ion-imprinted polymer reached adsorption equilibrium in 5 h, with an adsorption capacity of 2.80 mmol / g and an imprinting factor of 1.05.

[0041] When the amount of vinylized multi-walled carbon nanotubes was 50 mg, the adsorption of Cr(III) ion-imprinted polymer reached adsorption equilibrium in 5 h, with an adsorption capacity of 2.90 mmol / g and an imprinting factor of 1.19.

[0042] When the amount of vinylized multi-walled carbon nanotubes was 60 mg, the adsorption of Cr(III) ion-imprinted polymer reached adsorption equilibrium in 5 h, with an adsorption capacity of 3.24 mmol / g and an imprinting factor of 1.29.

[0043] The experimental results above show that the amount of vinylized multi-walled carbon nanotubes directly affects the performance of Cr(III) ion-imprinted polymers.

[0044] Example 2 This embodiment describes a method for preparing an aqueous thermosensitive Cr(III) ion-imprinted polymer, the steps of which are as follows: (1) Preparation of vinylated multi-walled carbon nanotubes: 1.00 g of aminated multi-walled carbon nanotubes and 12.00 mmol (about 1.66 g) of anhydrous potassium carbonate were dissolved in 25 mL of N,N-dimethylformamide and ultrasonically vibrated for 43 min to obtain a mixed solution. After purging the mixed solution with nitrogen for 5 min, 0.85 mL of bromopropylene was slowly added dropwise. The mixture was sealed and reacted in a water bath at 64 °C under light protection for 25 h. After the reaction was completed, the reaction product was filtered and washed twice each with N,N-dimethylformamide, deionized water and anhydrous ethanol. Then it was dried, ground and sieved to obtain black powdered vinylated multi-walled carbon nanotubes.

[0045] (2) Preparation of Cr(III) ion-imprinted polymer: 0.10 mmol CrCl3·6H2O, 0.30 mmol functional monomer 4-vinylpyridine and 0.30 mmol thermosensitive monomer N-isopropylacrylamide (molar ratio of 4-vinylpyridine to N-isopropylacrylamide is 1:1) were dissolved in 20.00 mL of a mixture of ethanol and water (volume ratio = 1:1) to form a pore-forming solvent. The mixture was placed in a constant temperature shaker and shaken for 2 h at room temperature. Then, 30.00 mg of vinylized multi-walled carbon nanotubes prepared in step (1) were added. After ultrasonic shaking for 45 min, 1.2 mmol of crosslinking agent ethylene glycol dimethacrylate and 25.00 mg of initiator azobisisobutyronitrile were added. After dissolving and shaking, nitrogen gas was purged for 3 min to remove oxygen. The mixture was then reacted in a water bath at 64 °C for 22 h to form a polymer. After the reaction was completed, the polymer was filtered and dried, and then eluted for the first time with 0.10 mol / L HNO3 solution for 5 h; then eluted for the second and third times with 0.05 mol / L EDTA solution (pH=5) for 8 h each time, in order to remove the template ion Cr(III) and obtain the Cr(III) ion imprinted polymer.

[0046] The 20.00 mg Cr(III) ion-imprinted polymer prepared in the example was used for adsorption in a solution with a Cr(III) concentration of 15.31 mg / mL at 25 °C.

[0047] The results showed that the adsorption of the Cr(III) ion-imprinted polymer reached adsorption equilibrium at 5 h, with an adsorption capacity of 3.50 mmol / g and an imprinting factor of 1.96.

[0048] Example 3 This embodiment describes a method for preparing an aqueous thermosensitive Cr(III) ion-imprinted polymer, the steps of which are as follows: (1) Preparation of vinylated multi-walled carbon nanotubes: 1.00 g of aminated multi-walled carbon nanotubes and 12.00 mmol (about 1.66 g) of anhydrous potassium carbonate were dissolved in 25 mL of N,N-dimethylformamide and ultrasonically vibrated for 47 min to obtain a mixed solution. After purging the mixed solution with nitrogen for 5 min, 0.85 mL of bromopropylene was slowly added dropwise. The mixture was sealed and reacted in a water bath at 66 °C under light protection for 23 h. After the reaction was completed, the reaction product was filtered and washed twice each with N,N-dimethylformamide, deionized water and anhydrous ethanol. Then it was dried, ground and sieved to obtain black powdered vinylated multi-walled carbon nanotubes.

[0049] (2) Preparation of Cr(III) ion-imprinted polymer: 0.10 mmol CrCl3·6H2O, 0.30 mmol functional monomer 4-vinylpyridine and 0.30 mmol thermosensitive monomer N-isopropylacrylamide (molar ratio of 4-vinylpyridine to N-isopropylacrylamide is 1:1) were dissolved in 20.00 mL of a mixture of ethanol and water (volume ratio = 1:1) to form a pore-forming solvent. The mixture was placed in a constant temperature shaker and shaken for 2 h at room temperature. Then, 30.00 mg of vinylized multi-walled carbon nanotubes prepared in step (1) were added. After ultrasonic shaking for 45 min, 6 mmol of crosslinking agent ethylene glycol dimethacrylate and 25.00 mg of initiator azobisisobutyronitrile were added. After dissolving and shaking, nitrogen gas was purged for 3 min to remove oxygen. The mixture was then reacted in a water bath at 66 °C for 20 h to form a polymer. After the reaction was completed, the polymer was filtered and dried, and then eluted for the first time with 0.10 mol / L HNO3 solution for 5 h; then eluted for the second and third times with 0.05 mol / L EDTA solution (pH=5) for 8 h each time, in order to remove the template ion Cr(III) and obtain the Cr(III) ion imprinted polymer.

[0050] The 20.00 mg Cr(III) ion-imprinted polymer prepared in the example was used for adsorption in a solution with a Cr(III) concentration of 15.31 mg / mL at 25 °C.

[0051] The results showed that the adsorption of the Cr(III) ion-imprinted polymer reached adsorption equilibrium at 5 h, with an adsorption capacity of 3.67 mmol / g and an imprinting factor of 1.88.

[0052] Comparative Example 1 In this embodiment, the same method as in Example 1 was used to prepare Cr(Ⅲ) ion-imprinted polymer, except that: the amount of 4-vinylpyridine, a functional monomer added to the pore-forming solvent in step (2), was 0.10 mmol, and the amount of N-isopropylacrylamide, a thermosensitive monomer added, was 0.10 mmol.

[0053] The 20.00 mg Cr(III) ion-imprinted polymer prepared in Comparative Example 1 was used for adsorption in a solution with a Cr(III) concentration of 15.31 mg / mL at 25 °C.

[0054] The results showed that the adsorption of the Cr(III) ion-imprinted polymer reached adsorption equilibrium at 5 h, with an adsorption capacity of 2.59 mmol / g and an imprinting factor of 1.38.

[0055] Compared with the Cr(III) ion-imprinted polymer of Example 1, the Cr(III) ion-imprinted polymer prepared in Comparative Example 3 has poor performance. This is because the amount of functional monomer and thermosensitive monomer N-isopropylacrylamide is reduced, resulting in a decrease in the number of recognition sites of the prepared polymer in Cr(III)-containing solutions.

[0056] Comparative Example 2 This comparative example uses the same method as Example 1 to prepare Cr(Ⅲ) ion-imprinted polymer, except that: the amount of 4-vinylpyridine, a functional monomer added to the pore-forming solvent in step (2), is 0.5 mmol, and the amount of N-isopropylacrylamide, a thermosensitive monomer added, is 0.5 mmol.

[0057] The 20.00 mg Cr(III) ion-imprinted polymer prepared in Comparative Example 2 was used for adsorption in a solution with a Cr(III) concentration of 15.31 mg / mL at 25 °C.

[0058] The results showed that the adsorption of the Cr(III) ion-imprinted polymer reached adsorption equilibrium at 5 h, with an adsorption capacity of 2.49 mmol / g and an imprinting factor of 1.77.

[0059] Compared with the Cr(III) ion-imprinted polymer of Example 1, the Cr(III) ion-imprinted polymer prepared in Comparative Example 4 has poor performance. This is because the excessive amount of functional monomers and thermosensitive monomer N-isopropylacrylamide leads to excessive cross-linking of the polymer, which increases steric hindrance and disrupts the hydrophilic-hydrophobic balance.

[0060] Comparative Example 3 The comparative example uses the same preparation method as Example 1 to prepare Cr(Ⅲ) ion-imprinted polymers, the difference being that the thermosensitive monomer N-isopropylacrylamide was not added in this comparative example.

[0061] The 20.00 mg Cr(III) ion-imprinted polymer prepared in this comparative example was used for adsorption in a solution with a Cr(III) concentration of 15.31 mg / mL at 25 °C.

[0062] The results showed that the adsorption of the Cr(III) ion-imprinted polymer reached adsorption equilibrium at 5 h, with an adsorption capacity of 2.55 mmol / g and an imprinting factor of 1.29. Compared with the adsorption capacity of Example 1 (3.73 mmol / g), the adsorption capacity decreased by about 29%. This is because the absence of functional monomers caused the polymer to lose its temperature-responsive "elasticity," resulting in relative collapse or increased rigidity of its structural network, which increased mass transfer resistance. At the same time, the loss of the "hydration layer" weakened its passive defense against impurities such as humic acid, thus interfering with specific recognition and binding.

[0063] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing an aqueous thermosensitive Cr(III) ion-imprinted polymer, characterized in that: Includes the following steps: (1) Preparation of vinylized multi-walled carbon nanotubes: Aminated multi-walled carbon nanotubes and potassium carbonate were dissolved in N,N-dimethylformamide and ultrasonically stirred to obtain a mixed solution. Bromopropylene was added and a solvothermal reaction was carried out. After the reaction was completed, the reaction product was filtered, washed, dried, ground and sieved in sequence to obtain vinylized multi-walled carbon nanotubes. (2) Preparation of Cr(III) ion-imprinted polymer: CrCl3·6H2O, functional monomer 4-vinylpyridine and thermosensitive monomer N-isopropylacrylamide were dissolved in a pore-forming solvent composed of ethanol and water to form polymerization system A. After prepolymerization reaction under stirring at room temperature, the vinylized multi-walled carbon nanotubes obtained in step (1) were added to system A. After ultrasonic dispersion, crosslinking agent ethylene glycol dimethacrylate and initiator azobisisobutyronitrile were added to form polymerization system B. Polymerization was carried out under water bath conditions. After the reaction was completed, the reaction products were filtered and dried in sequence. Finally, the template Cr(III) ions were removed with the eluent to obtain Cr(III) ion-imprinted polymer.

2. The method for preparing the aqueous thermosensitive Cr(III) ion-imprinted polymer according to claim 1, characterized in that: In step (1), the concentration of aminated multi-walled carbon nanotubes in the mixed solution is 40 mg / mL, the concentration of potassium carbonate is 66.4 mg / mL, and the volume ratio of bromopropylene to N,N-dimethylformamide is 0.85:

25.

3. The method for preparing the aqueous thermosensitive Cr(III) ion-imprinted polymer according to claim 1, characterized in that: In step (1), the ultrasonic dispersion time is 43-47 min.

4. The method for preparing the aqueous thermosensitive Cr(III) ion-imprinted polymer according to claim 1, characterized in that: In step (1), the conditions for the solvothermal reaction are: reaction temperature of 64-66℃ and reaction time of 23-25h.

5. The method for preparing the aqueous thermosensitive Cr(III) ion-imprinted polymer according to claim 1, characterized in that: In step (1), the washing is performed 6 times, with the first and second washings using N,N-dimethylformamide, the third and fourth washings using deionized water, and the fifth and sixth washings using anhydrous ethanol.

6. The method for preparing the aqueous thermosensitive Cr(III) ion-imprinted polymer according to claim 1, characterized in that: In step (2), in polymerization system B, the concentration of CrCl3·6H2O is 5.00 mmol / L, the concentration of vinylized multi-walled carbon nanotubes is 0.50~3.00 g / L, the concentration of 4-vinylpyridine is 0.01~0.05 mol / L, the concentration of N-isopropylacrylamide is 0.01~0.05 mol / L, the concentration of ethylene glycol dimethacrylate is 0.06~0.30 mol / L, and the concentration of the initiator azobisisobutyronitrile is 1.25 g / L.

7. The method for preparing the aqueous thermosensitive Cr(III) ion-imprinted polymer according to claim 1, characterized in that: In step (2), the reaction is stirred at room temperature for 2-3 hours.

8. The method for preparing the aqueous thermosensitive Cr(III) ion-imprinted polymer according to claim 1, characterized in that: In step (2), the water bath heating temperature is 64-66℃ and the reaction time is 20-24h.

9. The method for preparing the aqueous thermosensitive Cr(III) ion-imprinted polymer according to claim 1, characterized in that: In step (2), the volume ratio of ethanol to water in the pore-forming solvent is 1:

1.

10. The method for preparing the aqueous thermosensitive Cr(III) ion-imprinted polymer according to claim 1, characterized in that: In step (2), the removal of template Cr(III) ions by elution includes three elutions: the first elution is a 0.10 mol / L HNO3 solution, and the elution time is 5 h; the second and third elutions are 0.05 mol / L EDTA solutions, and the elution time is 8 h for each; the pH of the EDTA solution is 5.

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