A molecularly imprinted polymer membrane for adsorbing nicotine and a method for preparing the same

Abstract

This invention belongs to the field of functional molecularly imprinted material preparation, and relates to a molecularly imprinted polymer membrane for nicotine adsorption and its preparation method. The method includes the following steps: S1, preparing a PVDF ultrafiltration membrane: After preparing a PVDF casting solution, the PVDF casting solution is coated onto the surface of a flat plate, a membrane is scraped, and the membrane is immersed in a solution to separate the flat plate from the membrane, obtaining a PVDF ultrafiltration membrane; S2, using the PVDF ultrafiltration membrane as a carrier, preparing a nicotine molecularly imprinted polymer membrane: A mixed aqueous solution containing template nicotine molecules, a crosslinking agent, and functional monomers is prepared. The PVDF ultrafiltration membrane is then immersed in the mixed aqueous solution, and an initiator is added to carry out a polymerization reaction. After post-treatment, elution, and drying, a PVDF-based nicotine molecularly imprinted polymer membrane is obtained. The PVDF-based nicotine molecularly imprinted polymer membrane exhibits rapid and high nicotine adsorption performance, strong operability, good stability, and high reusability.

Description

Technical Field

[0001] This invention belongs to the field of preparation of functional molecularly imprinted materials, specifically relating to a molecularly imprinted polymer film for adsorbing nicotine and its preparation method. Background Technology

[0002] Nicotine is a pyridine alkaloid and the main alkaloid in tobacco. Currently, various brands of cigarettes are available on the market, and the nicotine content is an indicator of cigarette quality. To evaluate cigarette quality, nicotine content needs to be tested. Existing methods for nicotine content detection mainly include spectrophotometry, chromatography, and immunological methods. These methods suffer from drawbacks such as complex processes, expensive equipment, and long processing times.

[0003] In addition, nicotine is an important pharmaceutical and chemical raw material. It can be used as a highly effective and low-toxicity natural insecticide and is also an effective drug for treating Alzheimer's disease, Parkinson's disease, and depression. Nicotine is mainly found in tobacco leaves, accounting for more than 95% of the total alkaloid content in tobacco. Industrially, the production of natural nicotine uses waste tobacco by-products, which are extracted and concentrated using solvents, acids, or alkali solutions, followed by distillation. Current nicotine separation and purification methods have poor selectivity and still contain a significant amount of alkaloids with similar physicochemical properties to nicotine.

[0004] Molecular imprinting is a technique that combines materials chemistry, biochemistry, and polymer chemistry, possessing the ability to specifically recognize target analytes. The rapid development of molecular imprinting began with research on nicotine molecularly imprinted polymers, and has since garnered widespread attention. The synthesis of molecularly imprinted materials typically involves the following steps: First, in a solvent (also called a porogen), template molecules and functional monomers form host-guest complexes through covalent or non-covalent interactions between functional groups; then, a crosslinking agent is added, and monomer polymerization is initiated by an initiator, light, or heat, causing the host-guest complex and crosslinking agent to copolymerize via free radicals around the template molecules, forming a highly interconnected, rigid polymer; finally, the imprinted molecules are eluted or dissociated from the polymer. When the template molecule (imprinted molecule) comes into contact with the polymer monomer, multiple interaction sites are formed. This interaction is memorized during the polymerization process. When the template molecule is removed, the polymer, as the molecularly imprinted material, contains cavities with multiple interaction sites that match the spatial configuration of the template molecule. These cavities possess selective recognition properties for the template molecule and its analogues.

[0005] Existing nicotine molecularly imprinted materials have low nicotine adsorption capacity, poor stability, and low sensitivity, making them unsuitable for nicotine detection and purification. Summary of the Invention

[0006] To address the technical problems of existing nicotine molecularly imprinted materials, such as low nicotine adsorption capacity, poor stability, and low sensitivity, which prevent their use in nicotine detection and purification, this invention provides a method for preparing a molecularly imprinted polymer membrane for nicotine adsorption. This invention also provides a molecularly imprinted polymer membrane for nicotine adsorption prepared using this method.

[0007] The technical solution of the present invention:

[0008] A method for preparing a molecularly imprinted polymer film for nicotine adsorption includes the following steps:

[0009] S1. Preparation of PVDF ultrafiltration membrane: After preparing PVDF casting solution, the PVDF casting solution is coated onto the surface of a flat plate, the membrane is scraped, and then immersed in the solution to separate the flat plate from the membrane, thereby obtaining the PVDF ultrafiltration membrane.

[0010] S2. Using the PVDF ultrafiltration membrane as a carrier, prepare a nicotine molecularly imprinted polymer membrane: prepare a mixed aqueous solution containing template nicotine molecules, crosslinking agent and functional monomer, then immerse the PVDF ultrafiltration membrane in the mixed aqueous solution, add an initiator to carry out a polymerization reaction, and then perform post-treatment, elution and drying to obtain a PVDF-based nicotine molecularly imprinted polymer membrane.

[0011] Preferably, the step of preparing the PVDF casting solution in step S1 involves dissolving powdered PVDF and a pore-forming agent in a solvent, heating and stirring to prepare the PVDF casting solution, and allowing it to stand to remove air bubbles. The pore-forming agent is deionized water or polyvinylpyrrolidone, and the solvent is selected from one or more of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, and dimethyl sulfoxide. The ratio of PVDF powder, pore-forming agent, and solvent is 12g:0.5-1g:70-85g.

[0012] Preferably, in step S1, the heating temperature is 70-90℃, the heating time is 5-10 hours; the stirring speed is 700-950 rpm, and the settling time is 8-12 hours; the film thickness is controlled to be 150-250 micrometers during film coating; the plate is selected from any one of glass plate, plastic plate, and metal plate; the plate after coating and film coating is soaked in deionized water solution for 8-10 hours to separate the plate from the film.

[0013] The PVDF ultrafiltration membrane is stored in a 0.5-5 wt% NaHSO3 aqueous solution for later use, and soaked in clean water for 8-20 hours before use.

[0014] In step S2, the PVDF ultrafiltration membrane is immersed in a mixed aqueous solution containing the template molecule nicotine, a crosslinking agent, and a functional monomer for 2–5 hours. The functional monomer is a mixture of methacrylamide, acrylamide, and N,N-methylenebisacrylamide; the ratio of nicotine, methacrylamide, acrylamide, N,N-methylenebisacrylamide, deionized water, and PVDF ultrafiltration membrane is 0.05 mmol: 0.2–0.4 mmol: 0.2–0.4 mmol: 0.2–0.4 mmol: 85 mL: 2 g.

[0015] The crosslinking agent is chitosan and / or glutaraldehyde, and the amount of the crosslinking agent is 0.01 mmol to 10 mmol; the initiator is one or more of ammonium persulfate, azobisisobutyronitrile or 1-hydroxycyclohexyl phenyl ketone, and the amount of the initiator is 0.05 to 2 mmol, and the crosslinking time is 4 to 12 hours.

[0016] The post-processing step in step S2 involves soaking the product obtained from the polymerization reaction in deionized water for 4 to 8 hours, followed by repeated rinsing with deionized water to remove the unreacted functional monomers, crosslinking agents, and initiators from the surface of the PVDF ultrafiltration membrane.

[0017] The elution step in step S2 involves treating the post-processed product with formic acid, or a mixture of formic acid and ethanol, to remove the template molecule nicotine. The volume ratio of formic acid to ethanol is 1–20 mL: 1–20 mL.

[0018] The drying step involves placing the eluted product in a vacuum drying oven for vacuum drying. The temperature of the vacuum drying oven is set to 45–80°C, and the drying time is 8–12 hours.

[0019] A molecularly imprinted polymer membrane for adsorbing nicotine is prepared using the preparation method described above.

[0020] Beneficial technical effects of the present invention:

[0021] This invention discloses a method for preparing a molecularly imprinted polymer membrane for nicotine adsorption. Before synthesizing the molecularly imprinted material, nicotine and functional monomers capable of intermolecular interactions are mixed to form a molecular complex. This complex is then attached to the pores of a polyvinylidene fluoride (PVDF) ultrafiltration membrane. An initiator is then added to initiate a crosslinking reaction between nicotine and the functional monomers and crosslinking agent, constructing a highly crosslinked polymer material on the surface of the PVDF ultrafiltration membrane. Finally, nicotine molecules are removed from the highly crosslinked polymer material using chemical or physical methods, yielding a PVDF-based nicotine molecularly imprinted polymer membrane. This membrane contains numerous cavities with spatially matched and specifically arranged multiple interaction sites that are spatially matched to nicotine molecules, exhibiting high selectivity for nicotine molecules. The specific advantages of this PVDF-based nicotine molecularly imprinted polymer membrane are manifested in the following aspects:

[0022] (1) This method first controls the pore size and pore density of polyvinylidene fluoride (PVDF) in step S1, and then further controls the PVDF pore size in step S2. Specifically, a mixed aqueous solution containing template molecule nicotine, crosslinking agent, and functional monomer is first synthesized, and then the PVDF ultrafiltration membrane is immersed in the mixed aqueous solution for 2-5 hours. The molecular complex adheres to the pores on the surface and inside of the PVDF ultrafiltration membrane to reduce the pore size of the PVDF ultrafiltration membrane. By controlling the immersion time, the loading of crosslinking functional layer monomers is controlled, thereby controlling the pore size of the PVDF ultrafiltration membrane to obtain the maximum adsorption capacity. At the same time, since this method can form nicotine adsorption sites on both the surface and inside of the PVDF ultrafiltration membrane, the number of adsorption sites increases, and the membrane material contact area is large, resulting in increased adsorption efficiency and adsorption capacity. Therefore, this PVDF-based nicotine molecularly imprinted polymer membrane has the advantages of adjustable pore size and high adsorption capacity, as well as the characteristics of rapid adsorption and high selective recognition of surface molecular imprinting.

[0023] (2) This method uses a polyvinylidene fluoride (PVDF) ultrafiltration membrane as a functional carrier, and constructs a nicotine molecularly imprinted polymer on its surface to obtain a PVDF-based nicotine molecularly imprinted polymer membrane that specifically adsorbs nicotine. Because the nicotine molecularly imprinted polymer is formed on the membrane surface, it provides the support of the PVDF film and has an integral structure. For reuse, the membrane material can be directly extracted from the solution for separation, making it easier to recycle, highly operable, and easy to elute nicotine molecules.

[0024] (3) This method effectively utilizes organic small molecule monomers. The functional monomers are a mixture of methacrylamide, acrylamide and N,N-methylenebisacrylamide. Each of these three substances has a site / double bond that interacts with nicotine, thereby increasing the amount of adsorbable template molecule nicotine and thus increasing the number of holes. At the same time, by controlling the parameters of the crosslinking process, such as the ratio of monomer to PVDF ultrafiltration membrane, the type and amount of crosslinking agent, the amount of initiator and the crosslinking time, the surface functional layer can be tightly bound to the PVDF ultrafiltration membrane, thereby increasing the stability of the surface functional layer formed on the surface and inside of the ultrafiltration membrane and overcoming the shortcomings of common adsorbents such as poor stability and low sensitivity.

[0025] (4) Because the PVDF-based nicotine molecularly imprinted polymer film is easy to wash off and has good stability, the number of times it can be reused is greatly increased.

[0026] (5) By adjusting the parameters in the PVDF membrane preparation process, such as the optimal solution concentration, heating temperature and time, standing time, membrane thickness and plate material, a porous PVDF membrane material with a smooth surface, no defects and uniform pore size distribution can be obtained. Attached Figure Description

[0027] Figure 1 Infrared spectra of PVDF ultrafiltration membrane and PVDF-based nicotine molecularly imprinted polymer membrane;

[0028] Figure 2a SEM images of the surface of the PVDF-based nicotine molecularly imprinted polymer film, and Figure 2b SEM image of the cross section of a PVDF-based nicotine molecularly imprinted polymer film;

[0029] Figure 3a The adsorption isotherm of nicotine in aqueous solution by PVDF-based molecularly imprinted polymer membranes, and Figure 3b The adsorption kinetics curves of nicotine in aqueous solution by PVDF-based molecularly imprinted polymers are shown.

[0030] Figure 4 Comparison of the adsorption capacity of nicotine and its structurally similar substances by PVDF-based molecularly imprinted polymer films;

[0031] Figure 5 The results show the reproducibility of PVDF-based molecularly imprinted polymer films. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions will be clearly and completely described below through specific embodiments. Unless otherwise specified in the embodiments, conditions are performed according to conventional conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0033] Example 1

[0034] This embodiment provides a molecularly imprinted polymer membrane for adsorbing nicotine, which is prepared by the following method:

[0035] (1) Dissolve 12g of powdered PVDF and 1g of polyvinylpyrrolidone in 85g of N,N-dimethylformamide solution, stir at 75°C for 6 hours to form PVDF casting solution, stirring at 800rpm, and let stand for 12 hours to remove air bubbles from the solution.

[0036] (2) The obtained PVDF casting solution was coated onto the surface of a glass plate and a metal scraper was used to scrape the film to a thickness of 150 micrometers. The glass plate was immersed in a deionized water solution and soaked for 8 hours. The obtained PVDF ultrafiltration membrane was placed in a 4wt% NaHSO3 aqueous solution and soaked in clean water for 9 hours before use.

[0037] (3) Weigh a certain amount of deionized water, nicotine, crosslinking agent and functional monomer according to the proportion, add them to a beaker and stir for 30 minutes to prepare a mixed aqueous solution containing template nicotine, crosslinking agent and functional monomer. Then immerse the PVDF ultrafiltration membrane prepared in step (2) into the above mixed aqueous solution for 4 hours, add 0.05 mmol of initiator ammonium persulfate to carry out the polymerization reaction, and the reaction time is 4 hours to form a nicotine molecular imprinted polymer membrane on the PVDF surface.

[0038] The functional monomers are methacrylamide, acrylamide, and N,N-methylenebisacrylamide, and the crosslinking agent is chitosan (CS); the ratio of nicotine, methacrylamide, acrylamide, N,N-methylenebisacrylamide, deionized water, and PVDF ultrafiltration membrane is 0.05 mmol: 0.2 mmol: 0.2 mmol: 0.2 mmol: 85 mL: 2 g; the amount of chitosan is 2 mmol.

[0039] (4) After soaking the functionalized polymer membrane in step (3) in deionized water for 4 hours, rinse it repeatedly with deionized water 5 times to remove unreacted functional monomers, crosslinking agents and initiators.

[0040] (5) The product in step (4) was treated with a mixed solution of formic acid and ethanol in a volume ratio of 10 mL: 20 mL to remove nicotine from the nicotine molecularly imprinted membrane. The membrane was then vacuum dried at 50 °C for 10 hours to obtain a PVDF-based nicotine molecularly imprinted polymer membrane that selectively adsorbs nicotine, labeled as 1#.

[0041] Example 2

[0042] This embodiment provides a molecularly imprinted polymer membrane for adsorbing nicotine, which is prepared by the following method:

[0043] (1) Dissolve 12g of powdered PVDF and 0.5g of polyvinylpyrrolidone in 75g of N,N-dimethylformamide solution, stir at 75°C for 8 hours to form PVDF casting solution, stirring at 850rpm, and let stand for 8 hours to remove air bubbles from the solution.

[0044] (2) The obtained PVDF casting solution was coated onto the surface of a glass plate and a metal scraper was used to scrape the film to a thickness of 200 micrometers. The glass plate was immersed in a deionized water solution and soaked for 8 hours. The obtained PVDF ultrafiltration membrane was placed in a 0.5wt% NaHSO3 aqueous solution and soaked in clean water for 9 hours before use.

[0045] (3) Weigh a certain amount of deionized water, nicotine, crosslinking agent and functional monomer according to the proportion, add them to a beaker and stir for 30 minutes to obtain a mixed aqueous solution containing template nicotine, crosslinking agent and functional monomer. Immerse the PVDF ultrafiltration membrane prepared in step (2) into the mixed aqueous solution containing template nicotine, crosslinking agent and functional monomer for 5 hours. Add 0.3 mmol of initiator ammonium persulfate to carry out the polymerization reaction. The reaction time is 6 hours to form a nicotine molecular imprinted polymer membrane on the PVDF surface.

[0046] The functional monomers are methacrylamide, acrylamide, and N,N-methylenebisacrylamide, and the crosslinking agent is chitosan (CS); the ratio of nicotine, methacrylamide, acrylamide, N,N-methylenebisacrylamide, deionized water, and PVDF ultrafiltration membrane is 0.05 mmol: 0.3 mmol: 0.2 mmol: 0.3 mmol: 85 mL: 2 g; the amount of chitosan is 5 mmol.

[0047] (4) The functionalized polymer membrane in step (3) is soaked in deionized water for 6 hours and then rinsed repeatedly with deionized water 5 times to remove unreacted functional monomers, crosslinking agents and initiators.

[0048] (5) The product in step (4) was treated with a mixed solution of formic acid and ethanol in a volume ratio of 10 mL: 20 mL to remove nicotine from the nicotine molecularly imprinted membrane. The membrane was then vacuum dried at 60 °C for 8 hours to obtain a PVDF-based nicotine molecularly imprinted polymer membrane that selectively adsorbs nicotine, labeled as 2#.

[0049] Example 3

[0050] This embodiment provides a molecularly imprinted polymer membrane for adsorbing nicotine, which is prepared by the following method:

[0051] (1) Dissolve 12g of powdered PVDF and 1g of deionized water in 80g of N,N-dimethylformamide solution, stir at 75°C for 6 hours to form PVDF casting solution, stirring at 900rpm, and let stand for 10 hours to remove air bubbles from the solution.

[0052] (2) The obtained PVDF casting solution was coated onto the surface of a plastic plate and a metal scraper was used to scrape the film to a thickness of 150 micrometers. The plastic plate was immersed in a deionized water solution and soaked for 10 hours. The obtained PVDF ultrafiltration membrane was placed in a 2wt% NaHSO3 aqueous solution and soaked in clean water for 9 hours before use.

[0053] (3) Prepare a mixed aqueous solution containing template molecule nicotine, crosslinking agent and functional monomer. That is, add a certain amount of deionized water, nicotine, crosslinking agent and functional monomer weighed in proportion to a beaker and stir for 30 minutes to prepare a mixed aqueous solution containing template molecule nicotine, crosslinking agent and functional monomer. Immerse the prepared PVDF ultrafiltration membrane in the mixed aqueous solution containing template molecule nicotine, crosslinking agent and functional monomer for 2 hours. Add 0.8 mmol of initiator ammonium persulfate to carry out the polymerization reaction. The reaction time is 8 hours to form a nicotine molecular imprinted polymer membrane on the PVDF surface.

[0054] The functional monomers are methacrylamide, acrylamide, and N,N-methylenebisacrylamide, and the crosslinking agent is glutaraldehyde (GA); the ratio of nicotine, methacrylamide, acrylamide, N,N-methylenebisacrylamide, deionized water, and PVDF ultrafiltration membrane is 0.05 mmol: 0.2 mmol: 0.4 mmol: 0.4 mmol: 85 mL: 2 g; the amount of glutaraldehyde is 0.5 mmol.

[0055] (4) After soaking the functionalized polymer membrane in step (3) in deionized water for 6 hours, rinse it repeatedly with deionized water 5 times to remove unreacted functional monomers, crosslinking agents and initiators.

[0056] (5) The product in step (4) was treated with a mixed solution of formic acid and ethanol in a volume ratio of 20 mL: 2 mL to remove nicotine from the nicotine molecularly imprinted membrane. The membrane was then vacuum dried at 80 °C for 6 hours to obtain a PVDF-based nicotine molecularly imprinted polymer membrane that selectively adsorbs nicotine, labeled as 3#.

[0057] Example 4

[0058] This embodiment provides a molecularly imprinted polymer membrane for adsorbing nicotine, which is prepared by the following method:

[0059] (1) Dissolve 12g of powdered PVDF and 1g of polyvinylpyrrolidone in 85g of N,N-dimethylformamide solution, stir at 75°C for 5 hours to form PVDF casting solution, stirring at 800rpm, and let stand for 12 hours to remove air bubbles from the solution.

[0060] (2) The obtained PVDF casting solution was coated onto the surface of a metal plate and a metal scraper was used to scrape the film to a thickness of 250 micrometers. The metal plate was immersed in a deionized water solution and soaked for 8 hours. The obtained PVDF ultrafiltration membrane was placed in a 5wt% NaHSO3 aqueous solution and soaked in clean water for 9 hours before use.

[0061] (3) Prepare a mixed aqueous solution containing template molecule nicotine, crosslinking agent and functional monomer. Weigh a certain amount of deionized water, nicotine, crosslinking agent and functional monomer and add them to a beaker and stir for 30 minutes to prepare a mixed aqueous solution containing template molecule nicotine, crosslinking agent and functional monomer. Immerse the prepared PVDF ultrafiltration membrane in the mixed aqueous solution containing template molecule nicotine, crosslinking agent and functional monomer for 3 hours. Add 2 mmol of initiator ammonium persulfate to carry out the polymerization reaction. The reaction time is 12 hours to form a nicotine molecular imprinted polymer membrane on the PVDF surface.

[0062] The functional monomers are methacrylamide, acrylamide, and N,N-methylenebisacrylamide, and the crosslinking agent is glutaraldehyde (GA); the ratio of nicotine, methacrylamide, acrylamide, N,N-methylenebisacrylamide, deionized water, and PVDF ultrafiltration membrane is 0.05 mmol: 0.4 mmol: 0.4 mmol: 0.3 mmol: 85 mL: 2 g; the amount of glutaraldehyde is 2 mmol.

[0063] (4) After soaking the functionalized polymer membrane in step (3) in deionized water for 8 hours, rinse it repeatedly with deionized water 5 times to remove unreacted functional monomers, crosslinking agents and initiators.

[0064] (5) The product in step (4) was treated with a mixed solution of formic acid and ethanol in a volume ratio of 1 mL: 10 mL to remove nicotine from the nicotine molecularly imprinted membrane. The membrane was then vacuum dried at 75°C for 8 hours to obtain a PVDF-based nicotine molecularly imprinted polymer membrane that selectively adsorbs nicotine, labeled as 4#.

[0065] 1. Infrared testing

[0066] Taking Example 1 as an example, the prepared PVDF ultrafiltration membrane and the No. 1 PVDF nicotine molecularly imprinted polymer membrane were subjected to infrared spectroscopy, and the results are as follows: Figure 1 As shown in the infrared spectrum, the PVDF-based nicotine molecularly imprinted polymer film exhibits typical characteristic peaks of nicotine molecules.

[0067] 2. Scanning electron microscopy test

[0068] Taking Example 1 as an example, the prepared 1#PVDF nicotine molecularly imprinted polymer film was tested by electron microscopy. Figure 2a SEM images of the surface of the PVDF-based nicotine molecularly imprinted polymer film, and Figure 2b This is a cross-sectional SEM image of a PVDF-based nicotine molecularly imprinted polymer membrane. The SEM image shows that a nicotine-imprinted functional layer is attached to the surface and internal pores of the PVDF ultrafiltration membrane.

[0069] 3. Nicotine adsorption capacity test

[0070] 3.1 Adsorption performance test of PVDF-based nicotine molecularly imprinted polymer membrane at the same nicotine concentration: 20 mg of the PVDF-based nicotine molecularly imprinted polymer membrane prepared in Examples 1-4 was added to 10 mL of a 0.1 mmol nicotine solution. After static adsorption for 2 hours, the remaining nicotine concentration was determined by ICP-AES. The adsorption capacity of the PVDF-based nicotine molecularly imprinted polymer membrane prepared in Examples 1-4 can be obtained from the above experimental data. See Table 1 for details. The nicotine solution concentration was 0.01 mol / L. Figure 3a It is consistent with 1.6 g / L.

[0071] Table 1. Adsorption capacity of nicotine for PVDF-based nicotine molecularly imprinted polymer membranes in Examples 1-4

[0072] Example 1 Example 2 Example 3 Example 4 Product Number 1# 2# 3# 4# Dosage (mg) 20 20 20 20 Nicotine concentration (g / L) 1.6 1.6 1.6 1.6 Adsorption capacity Q (mg / g) 200 144 160 138

[0073] 3.2 Adsorption Performance Test of PVDF-based Nicotine Molecularly Imprinted Polymer Membrane at Different Nicotine Concentrations: 0.01 g of the PVDF-based nicotine molecularly imprinted polymer membrane prepared in Example 1 was weighed and added to 250 mL of nicotine solutions of different concentrations in conical flasks. The conical flasks were then sealed and placed in a constant-temperature shaker at 25°C for adsorption testing. After adsorption equilibrium, the remaining nicotine concentration was determined using ICP-AES. The adsorption capacity as a function of concentration (Q-CO) at 25°C was plotted using the above experimental data to obtain the adsorption performance of the PVDF-based nicotine molecularly imprinted membrane at different concentrations. Figure 3a As shown, the nicotine solution concentrations were 0.2 g / L, 0.5 g / L, 0.8 g / L, 1.0 g / L, 1.2 g / L, and 1.6 g / L, respectively.

[0074] 3.3 Effect of Adsorption Time on the Adsorption of Nicotine Molecularly Imprinted Polymer Membrane by PVDF-based Nicotine Molecularly Imprinted Polymer Membrane: 0.01 g of the PVDF-based Nicotine Molecularly Imprinted Polymer Membrane prepared in Example 1 was weighed and placed in a 250 mL Erlenmeyer flask containing 10 mL of a specific nicotine concentration. The flask was sealed and placed in a constant-temperature shaker for shaking. Within a specified time, the Erlenmeyer flasks containing the nicotine solution were sequentially removed, and the concentration of remaining nicotine in the solution was determined using ICP-AES. The adsorption capacity as a function of time (Q) was plotted using the above experimental data. t The curve of the change of -t) can be used to obtain the effect of adsorption time on the adsorption of nicotine by the molecularly imprinted membrane.

[0075] Table 1 shows that the PVDF-based nicotine molecularly imprinted polymer membranes prepared in Examples 1-4 have high adsorption capacities for nicotine. The adsorption isotherms and adsorption kinetics of nicotine in aqueous solution obtained by the PVDF-based nicotine molecularly imprinted polymer membranes are shown in Table 1. Figure 3a and Figure 3b As shown, the imprinted polymer matrix contains a large number of specific binding sites, which have a strong adsorption capacity for template molecules. Adsorption equilibrium is achieved within 130 minutes, and the adsorption capacity reaches 200 mg / g. It has the advantages of high nicotine adsorption capacity and fast adsorption rate.

[0076] 4. High-selectivity adsorption test

[0077] The high selective adsorption performance of PVDF-based nicotine molecularly imprinted polymer membranes for the template molecule nicotine can also be detected by the competitive adsorption of the template molecule nicotine with other substances. Here, the competitive adsorption of nicotine and its different analogues on PVDF-based molecularly imprinted polymer membranes was investigated. In 10 mL of a mixed solution of acetonitrile containing 0.1 mmol nicotine, 0.1 mmol indole, 0.1 mmol n-propanol, 0.1 mmol diphenylamine, 0.1 mmol trimethylolpropane, and 0.1 mmol pyridine, 20 mg of the PVDF-based nicotine molecularly imprinted polymer membrane prepared in Example 1 was added. After 5 hours of static adsorption, the adsorption amounts of each substance on the polymer were as follows: Figure 4 As shown. From Figure 4 It can be observed that the prepared PVDF-based nicotine molecularly imprinted polymer membrane exhibits high selective adsorption performance for nicotine.

[0078] 5. Reusability

[0079] The reusability of PVDF-based nicotine molecularly imprinted polymer membranes for template nicotine molecules can be tested by examining their adsorption performance after repeated use. The test method is as follows: 20 mg of the imprinted polymer is added to 10 mL of a solution containing 0.1 mmol nicotine. After static adsorption for 5 hours, the adsorption amount is calculated. The membrane is then removed, washed with a methanol-acetic acid (9:1, V / V) mixed solvent to remove the adsorbed nicotine, and dried. It is then placed back into 10 mL of a solution containing 0.1 mmol nicotine for another 5 hours of static adsorption, and the adsorption amount of nicotine is measured. This process is repeated 9 times.

[0080] Figure 5 The changes in the adsorption capacity of the molecularly imprinted composite material are shown across nine operations. Figure 5 It can be seen that the adsorption capacity did not change significantly after the material was reused multiple times, indicating high reusability.

[0081] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a molecularly imprinted polymer film for adsorbing nicotine, characterized in that, Includes the following steps: S1. Preparation of PVDF ultrafiltration membrane: After preparing PVDF casting solution, the PVDF casting solution is coated onto the surface of a flat plate, the membrane is scraped, and then immersed in the solution to separate the flat plate from the membrane, thereby obtaining the PVDF ultrafiltration membrane. The step of preparing the PVDF casting solution in step S1 is to dissolve powdered PVDF and a pore-forming agent in a solvent, heat and melt the mixture while stirring to prepare the PVDF casting solution, and then let it stand to remove air bubbles. The pore-forming agent is deionized water or polyvinylpyrrolidone, and the solvent is selected from one or more of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, and dimethyl sulfoxide; the ratio of PVDF powder, pore-forming agent, and solvent is 12g:0.5-1g:70-85g; the heating temperature is 70-90℃, the heating time is 5-10 hours; the stirring speed is 700-950rpm, and the standing time is 8-12 hours. S2. Using the PVDF ultrafiltration membrane as a carrier, prepare a nicotine molecularly imprinted polymer membrane: prepare a mixed aqueous solution containing template nicotine molecules, crosslinking agent and functional monomer, then immerse the PVDF ultrafiltration membrane in the mixed aqueous solution, add an initiator to carry out a polymerization reaction, and then perform post-treatment, elution and drying to obtain a PVDF-based nicotine molecularly imprinted polymer membrane. The PVDF ultrafiltration membrane is immersed in a mixed aqueous solution containing template molecule nicotine, crosslinking agent and functional monomer for 2 to 5 hours; The functional monomer is a mixture of methacrylamide, acrylamide, and N,N-methylenebisacrylamide; the ratio of nicotine, methacrylamide, acrylamide, N,N-methylenebisacrylamide, deionized water, and PVDF ultrafiltration membrane is 0.05 mmol: 0.2–0.4 mmol: 0.2–0.4 mmol: 0.2–0.4 mmol: 85 mL: 2 g.

2. The preparation method according to claim 1, characterized in that... In step S1, the thickness of the film is controlled to be 150-250 micrometers during the film scraping process.

3. The preparation method according to claim 1, characterized in that... The flat plate in step S1 is selected from any one of glass plate, plastic plate and metal plate.

4. The preparation method according to claim 1, characterized in that... In step S1, the plate after coating and scraping is immersed in deionized water for 8 to 10 hours to separate the plate from the membrane.

5. The preparation method according to any one of claims 1-4, characterized in that... The PVDF ultrafiltration membrane is stored in a 0.5-5 wt% NaHSO3 aqueous solution for later use, and soaked in clean water for 8-20 hours before use.

6. A molecularly imprinted polymer membrane for adsorbing nicotine, characterized in that... The sample was prepared using the preparation method described in any one of claims 1-5.

Images