Preparation method of water-phase temperature-sensitive Cd (II) ion imprinted polymer

Abstract

The invention discloses a preparation method of a water-phase temperature-sensitive Cd (II) ion imprinted polymer, and belongs to the technical field of water pollution treatment. The preparation method comprises the following steps: (1) dissolving ZrCl4 and 2-aminoterephthalic acid in N, N-dimethylformamide, stirring to obtain a mixed solution, carrying out solvothermal reaction by using the mixed solution, and then sequentially carrying out centrifugal purification, washing, drying and grinding on a reaction product to obtain MOFs; and (2) dissolving Cd (NO3) 2.4 H2O and MOFs in a pore-forming solvent, adding a functional monomer and a temperature-sensitive functional monomer, stirring at room temperature to react, adding a cross-linking agent and an initiator, heating in a water bath to react, sequentially filtering and drying a reaction product, and finally removing template Cd (II) ions by using an eluent to obtain the Cd (II) ion imprinted polymer. The ion imprinted polymer prepared by the invention has more excellent adsorption performance, can be recycled and reused, and effectively alleviates the problems of environmental pollution and the like in the preparation process.

Description

Technical Field

[0001] The invention belongs to the technical field of water pollution treatment and relates to a method for preparing an aqueous temperature-sensitive Cd (II) ion-imprinted polymer. Background Art

[0002] Cadmium is one of the most toxic heavy metals. Because it easily accumulates and cannot be degraded in organisms, it poses a serious health risk to humans and animals and has been classified as a human carcinogen and teratogen. Unlike other heavy metals such as copper and zinc, cadmium is not an essential element for the human body and can be harmful even at extremely low concentrations. Therefore, the development of highly efficient, selective, and environmentally friendly cadmium ion removal materials to effectively remove cadmium ions while avoiding secondary pollution has become a research hotspot.

[0003] Adsorption is widely used in water pollutant treatment due to its simplicity, low cost, and high efficiency. Ion imprinting technology, a technique that specifically recognizes, adsorbs, and separates target ions, holds broad application prospects in water pollutant treatment due to its high selectivity, high sensitivity, and relatively low cost. Ion imprinting technology achieves specific recognition and efficient adsorption of specific ions by creating imprinted sites in polymers that match the shape, size, and function of the target ions.

[0004] Ion-imprinted polymers primarily remove specific pollutant ions from water through adsorption. Therefore, their adsorption capacity directly determines their ability to remove pollutant ions. Furthermore, the recycling of ion-imprinted polymers can help reduce costs and increase their utilization rate. Therefore, enhancing the adsorption capacity and enabling their recycling is of great significance. However, the current preparation process for ion-imprinted polymers typically requires the use of organic solvents, which can lead to environmental pollution, high production costs, and complex operations.

[0005] Therefore, it is necessary to provide a preparation method of aqueous temperature-sensitive Cd (II) ion-imprinted polymers to enhance the adsorption capacity of ion-imprinted polymers, effectively realize the recycling of ion-imprinted polymers, and reduce the environmental pollution risk generated during the preparation process, so that the ion-imprinted polymers have better performance in the field of water pollutant treatment. Summary of the Invention

[0006] To overcome the problems mentioned in the previous art, the present invention prepares a thermoresponsive Cd(II) ion-imprinted polymer using UiO-66-NH2 (MOFs) as a carrier. This improves the polymer's adsorption capacity for target ions and its temperature responsiveness, thereby enhancing its performance. Furthermore, the use of aqueous phase as a porogenic solvent during the preparation process mitigates the environmental pollution risks associated with the process.

[0007] In order to achieve the above object, the present invention is implemented through the following technical solutions: The preparation method comprises the following steps: (1) Preparation of MOFs: ZrCl4 and 2-aminoterephthalic acid are dissolved in N,N-dimethylformamide, stirred to obtain a mixed solution, and the mixed solution is used for solvent thermal reaction. After the reaction is completed, the reaction product is centrifuged, purified, washed, dried, and ground in sequence to obtain MOFs; (2) Preparation of Cd (II) ion imprinted polymer: Cd (NO3) 2·4H2O and the MOFs prepared in step (1) are dissolved in a porogenic solvent, and the functional monomer 3-mercaptopropionic acid and the thermosensitive functional monomer N-isopropylacrylamide are added. After stirring and reacting at room temperature for a certain period of time, the crosslinker N, N-methylenebisacrylamide and the initiator potassium persulfate are added, and the reaction is carried out under heating conditions in a water bath. After the reaction is completed, the reaction product is filtered and dried in sequence, and finally the template Cd (II) ions are removed with an eluent to obtain a Cd (II) ion imprinted polymer.

[0008] Preferably, in step (1), the volume ratio of the added amount of ZrCl4 and 2-aminoterephthalic acid to N,N-dimethylformamide is 1 mol:30 L.

[0009] Preferably, in step (1), the stirring time is 1 h.

[0010] Preferably, in step (1), the solvent thermal reaction temperature is 120° C. and the reaction time is 24 h.

[0011] Preferably, in step (1), the centrifugal purification speed is 3000 r / min and the purification time is 15 min.

[0012] The washing times were 6 times, wherein the 1st to 3rd washings were performed by filtration with ethanol, and the 4th to 6th washings were performed by filtration with distilled water.

[0013] Preferably, in step (2), the ratio of the amount of Cd(NO3)2·4H2O added to the pore-forming solvent is Cd(NO3)2·4H2O:pore-forming solvent = 5.00 mmol:1 L, the ratio of the amount of MOFs added to the pore-forming solvent is MOFs:pore-forming solvent = 0.50~3.00 g:1 L, and the ratio of the amount of 3-mercaptopropionic acid added to the pore-forming solvent is 3-mercaptopropionic acid:pore-forming solvent = 0.01~0.05 mol:1L, the ratio of the added amount of N-isopropylacrylamide to the porogenic solvent is N-isopropylacrylamide:porogenic solvent = 0.02mol:1L, the ratio of the added amount of N,N-methylenebisacrylamide to the porogenic solvent is N,N-methylenebisacrylamide:porogenic solvent = 0.10~0.40mol:1L; the ratio of the added amount of the initiator potassium persulfate to the porogenic solvent is potassium persulfate:porogenic solvent = 1.00g:1L.

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

[0015] Preferably, in step (2), the water bath heating temperature is 40-60° C., and the reaction time is 8-24 h.

[0016] Preferably, in step (2), the porogenic solvent is distilled water.

[0017] Preferably, in step (2), the eluent is a 0.50 mol / L HCl solution, and the elution time is 4 hours. 1. The amino-functionalized material UiO-66-NH2 described in the present invention has thermal and chemical stability, and its surface activity and electrophilic properties are relatively excellent, providing an excellent carrier basis for the construction of imprinting sites and the selective recognition of metal ions.

[0018] 2. The present invention introduces a temperature-sensitive functional monomer, N-isopropylacrylamide, to make the ion-imprinted polymer more sensitive to ambient temperature. This allows the ion-imprinted polymer to adsorb pollutant ions and then desorb them from the polymer by adjusting the temperature, thereby allowing the ion-imprinted polymer to be recycled.

[0019] 3. By using 3-mercaptopropionic acid as a functional monomer and taking advantage of its high water solubility at room temperature (around 20°C), the present invention uses an aqueous phase as the synthesis system, avoiding environmental pollution and post-processing problems caused by organic solvents, and making the process more environmentally friendly, efficient and safe.

[0020] 4. The present invention uses 3-mercaptopropionic acid as a functional monomer and UiO-66-NH2 as a substrate. The thiol and carboxyl groups in the functional monomer and the amino groups in UiO-66-NH2 can form multiple coordination with the target ion Cd (II) to form highly selective recognition sites, thereby reducing nonspecific adsorption.

[0021] 5. In the present invention, UiO-66-NH2 has high stability under strong acid / alkaline conditions, and the thiol group of 3-mercaptopropionic acid is not easily oxidized in an acidic environment. The combination of the two makes the material suitable for more complex wastewater environments.

[0022] 6. The preparation method of the present invention is simple and easy to implement, and can produce an ion-imprinted polymer with high selectivity, large adsorption capacity, and good removal effect of Cd(II) in water, which is suitable for industrial promotion and application. DETAILED DESCRIPTION

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

[0024] In the examples and comparative examples of the present invention, chemical reagents not otherwise specified were all commercially available analytically pure for use in the experiments.

[0025] Example 1: In this example, ion-imprinted polymers were prepared according to the following method: (1) Preparation of MOFs: 2.00 mmol ZrCl4 and 2.00 mmol 2-aminoterephthalic acid were dissolved in 60.00 mL N,N-dimethylformamide and magnetically stirred for 1 h to obtain a mixed solution. The mixed solution was transferred into a polytetrafluoroethylene-lined reactor and reacted at 120 °C for 24 h. After the reaction, the product was centrifuged for 15 min (speed 3000 r / min), and the purified product was filtered and washed with ethanol and deionized water three times each, dried, and ground to obtain white product MOFs.

[0026] (2) Preparation of Cd (II) ion-imprinted polymer: 0.10 mmol Cd (NO3)2·4H2O and 30.00 mg MOFs prepared in step (1) were dissolved in 20.00 mL distilled water, 0.40 mmol functional monomer 3-mercaptopropionic acid and thermosensitive monomer N-isopropylacrylamide were added, and the mixture was stirred on a magnetic stirrer at room temperature for 3 h; 4.00 mmol cross-linker N,N-methylenebisacrylamide and 20.00 mg initiator potassium persulfate were added, fully dissolved and shaken, and the mixture was heated in a water bath at 45°C for 8 h to form a polymer, which was filtered and dried. Finally, the template Cd (II) ions were removed by elution with 0.50 mol / L HCl solution for 4 h to obtain Cd (II) ion-imprinted polymer.

[0027] 20.00 mg of the Cd(II) ion-imprinted polymer prepared in Example 1 was used for adsorption in a solution with a Cd(II) concentration of 22.00 mg / mL at room temperature.

[0028] The results showed that the adsorption capacity of Cd(II) ion imprinted polymer was 3.73 mmol / g and the imprinting factor was 2.03.

[0029] The Cd(II) ion-imprinted polymer prepared in this example was placed at 35° C. for an adsorption experiment. The adsorbed ion-imprinted polymer was collected, and the experimental temperature of the ion-imprinted polymer was adjusted.

[0030] The results showed that at 35°C, the ion-imprinted polymer could maintain a high adsorption capacity for Cd(II). After adjusting the experimental temperature of the ion-imprinted polymer (either increasing or decreasing the temperature, the desorption rate could reach 92% when the temperature was lowered to 25°C), the adsorption capacity of the ion-imprinted polymer decreased and the pollutant ions were desorbed. This proves that after the introduction of temperature-sensitive functional monomers, the ion-imprinted polymer is more sensitive to temperature, which facilitates the desorption of pollutant ions and realizes the recycling of the ion-imprinted polymer.

[0031] Since temperature can regulate the pore state of the polymer, when the ion-imprinted polymer network is loose and the pores are in an expanded state, the pores are fully exposed to the polymer system, which is conducive to the entry and coordination of target ions, thereby achieving a high adsorption capacity. When the temperature of the polymer is regulated, the ion-imprinted polymer network shrinks, and the pores change from an expanded state to a contracted state. The pore volume decreases or even closes. At this time, the target ions have insufficient contact with the polymer imprinted cavity, the adsorption capacity decreases, and the desorption of the target ions can be achieved. Therefore, when the polymer is highly sensitive to temperature, the temperature change makes it easier to regulate the pore state of the polymer, facilitating the adsorption / desorption state transition of pollutant ions.

[0032] Example 2: In this example, the Cd(II) ion-imprinted polymer was prepared by the same method as in Example 1, except that the water bath heating temperature in this example was 40° C. and the reaction time was 24 h.

[0033] The Cd(II) ion-imprinted polymer prepared in this example was subjected to the same adsorption experiment as in Example 1.

[0034] The results showed that the adsorption capacity of Cd(II) ion imprinted polymer was 2.38 mmol / g and the imprinting factor was 1.51.

[0035] Example 3: In this example, the Cd(II) ion-imprinted polymer was prepared by the same method as in Example 1, except that the water bath heating temperature in this example was 50° C. and the reaction time was 15 h.

[0036] The Cd(II) ion-imprinted polymer prepared in this example was subjected to the same adsorption experiment as in Example 1.

[0037] The results showed that the adsorption capacity of Cd(II) ion imprinted polymer was 3.35 mmol / g and the imprinting factor was 1.87.

[0038] Example 4: This example adopts the same method as that of Example 1 to prepare Cd(II) ion-imprinted polymer, except that the water bath heating temperature in this example is 55°C.

[0039] The Cd(II) ion-imprinted polymer prepared in this example was subjected to the same adsorption experiment as in Example 1.

[0040] The results showed that the adsorption capacity of Cd(II) ion imprinted polymer was 3.18 mmol / g and the imprinting factor was 1.81.

[0041] Example 5: This example adopts the same method as that of Example 1 to prepare Cd(II) ion-imprinted polymer, except that the water bath heating temperature in this example is 60°C.

[0042] The Cd(II) ion-imprinted polymer prepared in this example was subjected to the same adsorption experiment as in Example 1.

[0043] The results showed that the adsorption capacity of Cd(II) ion imprinted polymer was 3.08 mmol / g and the imprinting factor was 1.86.

[0044] Example 6 In this example, ion-imprinted polymers were prepared according to the following method: (1) Preparation of MOFs: 2.00 mmol ZrCl4 and 2.00 mmol 2-aminoterephthalic acid were dissolved in 60.00 mL N,N-dimethylformamide and magnetically stirred for 1 h to obtain a mixed solution. The mixed solution was transferred into a polytetrafluoroethylene-lined reactor and reacted at 120 °C for 24 h. After the reaction, the product was centrifuged for 15 min (speed 3000 r / min), and the purified product was filtered and washed with ethanol and deionized water three times each, dried, and ground to obtain white product MOFs.

[0045] (2) Preparation of Cd (II) ion-imprinted polymer: 0.10 mmol Cd (NO3)2·4H2O and 60.00 mg MOFs prepared in step (1) were dissolved in 20.00 mL distilled water, 0.20 mmol functional monomer 3-mercaptopropionic acid and 0.40 mmol thermosensitive monomer N-isopropylacrylamide were added, and the mixture was stirred on a magnetic stirrer at room temperature for 3 h; 2.00 mmol cross-linker N,N-methylenebisacrylamide and 20.00 mg initiator potassium persulfate were added, fully dissolved and shaken, and the mixture was heated in a water bath at 45 °C for 8 h to form a polymer, which was filtered and dried. Finally, the template Cd (II) ions were removed by elution with 0.50 mol / L HCl solution for 4 h to obtain Cd (II) ion-imprinted polymer.

[0046] The Cd(II) ion imprinted polymer prepared in this example has similar properties to the Cd(II) ion imprinted polymer prepared in Example 1.

[0047] Example 7 In this example, ion-imprinted polymers were prepared according to the following method: (1) Preparation of MOFs: 2.00 mmol ZrCl4 and 2.00 mmol 2-aminoterephthalic acid were dissolved in 60.00 mL N,N-dimethylformamide and magnetically stirred for 1 h to obtain a mixed solution. The mixed solution was transferred into a polytetrafluoroethylene-lined reactor and reacted at 120 °C for 24 h. After the reaction, the product was centrifuged for 15 min (speed 3000 r / min), and the purified product was filtered and washed with ethanol and deionized water three times each, dried, and ground to obtain white product MOFs.

[0048] (2) Preparation of Cd (II) ion-imprinted polymer: 0.10 mmol Cd (NO3)2·4H2O and 10.00 mg MOFs prepared in step (1) were dissolved in 20.00 mL of distilled water, 1 mmol of functional monomer 3-mercaptopropionic acid and 0.40 mmol of thermosensitive monomer N-isopropylacrylamide were added, and the mixture was stirred on a magnetic stirrer at room temperature for 3 h; 8.00 mmol of cross-linking agent N,N-methylenebisacrylamide and 20.00 mg of initiator potassium persulfate were added, fully dissolved and shaken, and the mixture was reacted in a water bath at 45 °C for 8 h to form a polymer, which was filtered and dried. Finally, the template Cd (II) ions were removed by elution with 0.50 mol / L HCl solution for 4 h to obtain Cd (II) ion-imprinted polymer.

[0049] The Cd(II) ion imprinted polymer prepared in this example has similar properties to the Cd(II) ion imprinted polymer prepared in Example 1.

[0050] Comparative Example 1: The Cd(II) ion-imprinted polymer was prepared in this comparative example by the same preparation method as in the examples, except that no MOFs were added to the polymer in this comparative example.

[0051] The Cd(II) ion-imprinted polymer prepared in this comparative example was used for adsorption in a solution with a Cd(II) concentration of 20.00 mg / mL at room temperature.

[0052] The results showed that the adsorption capacity of the Cd(II) ion imprinted polymer was 2.51 mmol / g, and the imprinting factor was 1.54, which was about 32% lower than the adsorption capacity of Example 1 (3.73 mmol / g).

[0053] In summary, the Cd (II) ion-imprinted polymer prepared by the present invention has high selectivity and large adsorption capacity for Cd (II) ions in water. At the same time, the Cd (II) ion-imprinted polymer is temperature-sensitive, which facilitates the recycling and reuse of the ion polymer. The Cd (II) ion-imprinted polymer prepared by the present invention has excellent performance.

[0054] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made in form and details without departing from the scope defined by the claims of the present invention.

Claims

1. A method for preparing an aqueous temperature-sensitive Cd (II) ion-imprinted polymer, characterized in that: The preparation method comprises the following steps: (1) Preparation of MOFs: ZrCl4 and 2-aminoterephthalic acid are dissolved in N,N-dimethylformamide, stirred to obtain a mixed solution, and the mixed solution is used for solvent thermal reaction. After the reaction is completed, the reaction product is centrifuged, purified, washed, dried, and ground in sequence to obtain MOFs; (2) Preparation of Cd (II) ion imprinted polymer: Cd (NO3) 2·4H2O and the MOFs prepared in step (1) are dissolved in a porogenic solvent, and the functional monomer 3-mercaptopropionic acid and the thermosensitive functional monomer N-isopropylacrylamide are added. After stirring and reacting at room temperature for a certain period of time, the crosslinker N, N-methylenebisacrylamide and the initiator potassium persulfate are added, and the reaction is carried out under heating conditions in a water bath. After the reaction is completed, the reaction product is filtered and dried in sequence, and finally the template Cd (II) ions are removed with an eluent to obtain a Cd (II) ion imprinted polymer.

2. The preparation method according to claim 1, wherein: In the step (1), the volume ratio of the added amount of ZrCl4 and 2-aminoterephthalic acid to N,N-dimethylformamide is 1 mol:30 L.

3. The preparation method according to claim 1, wherein: In the step (1), the stirring time is 1 h.

4. The preparation method according to claim 1, wherein: In the step (1), the solvent thermal reaction temperature is 120° C. and the reaction time is 24 h.

5. The preparation method according to claim 1, wherein: In the step (1), the centrifugal purification speed is 3000 r / min and the purification time is 15 min; The washing times were 6 times, wherein the 1st to 3rd washings were performed by filtration with ethanol, and the 4th to 6th washings were performed by filtration with distilled water.

6. The preparation method according to claim 1, wherein: In the step (2), the ratio of the amount of Cd(NO3)2·4H2O added to the pore-forming solvent is Cd(NO3)2·4H2O:pore-forming solvent = 5.00 mmol:1 L, the ratio of the amount of MOFs added to the pore-forming solvent is MOFs:pore-forming solvent = 0.50~3.00 g:1 L, and the ratio of the amount of 3-mercaptopropionic acid added to the pore-forming solvent is 3-mercaptopropionic acid:pore-forming solvent = 0.01~0.05 mol :1L, the ratio of the addition amount of N-isopropylacrylamide to the porogenic solvent is N-isopropylacrylamide:porogenic solvent = 0.02 mol:1L, the ratio of the addition amount of N,N-methylenebisacrylamide to the porogenic solvent is N,N-methylenebisacrylamide:porogenic solvent = 0.10~0.40 mol:1L; the ratio of the addition amount of the initiator potassium persulfate to the porogenic solvent is potassium persulfate:porogenic solvent = 1.00 g:1L.

7. The preparation method according to claim 1, wherein: In the step (2), the reaction was stirred at room temperature for 3 h.

8. The preparation method according to claim 1, wherein: In the step (2), the water bath heating temperature is 40-60° C., and the reaction time is 8-24 h.

9. The preparation method according to claim 1, wherein: In the step (2), the porogenic solvent is distilled water.

10. The preparation method according to claim 1, characterized in that: In the step (2), the eluent is a 0.50 mol / L HCl solution, and the elution time is 4 h.