Preparation method of ion-thermal sensitive composite gel for efficient extraction of nicotine

Abstract

The application discloses a preparation method of an ion-thermal sensitive composite gel for efficiently extracting nicotine. The method comprises the following steps: physically mixing boron nitride (BN) and anhydrous citric acid, ball milling, washing, centrifuging and drying to obtain boron nitride nanosheets. Then, the boron nitride nanosheets and ionic liquid are reacted under a nitrogen atmosphere for 24 h to obtain ionic liquid-boron nitride nanosheets (IL-BNNs). The IL-BNNs are dispersed into a monomer solution, a crosslinking agent is added after the formation of the gel, and then tetramethylethylenediamine and ammonium persulfate are added and stirred in an ice bath. The mixed system is transferred into a mold to react for 12-24 h to obtain the ion-thermal sensitive composite gel. The application forms dense nicotine binding sites in the interior of the composite material by using ionic liquid, so that the adsorption-desorption performance of the material to nicotine is enhanced. Meanwhile, the desorption performance of the material is strengthened by using the thermal conductivity of boron nitride and the phase change characteristics of the gel, so that the nicotine extraction process is simplified, and the amount of eluent in the nicotine recovery process is reduced.

Description

Technical Field

[0001] This invention belongs to the field of tobacco alkaloid extraction and separation, specifically relating to a method for preparing an ion-thermosensitive composite gel for nicotine extraction. Background Technology

[0002] Nicotine possesses biological activity and unique pharmacological effects, and is widely used in medicine, agriculture, and the tobacco industry. Tobacco is the primary source of nicotine, making its extraction from tobacco of great significance. However, traditional solvent extraction methods utilize large amounts of organic solvents, posing a significant threat to human health and the environment. Achieving green, efficient, and recyclable extraction of nicotine from tobacco extracts is one of the urgent problems to be solved.

[0003] Ionic liquids are compound salts composed of organic cations and organic or inorganic anions, which are liquid at or near room temperature. In extraction and separation applications, compared to traditional organic solvents, ionic liquids offer advantages such as non-volatility, low toxicity, and high selectivity. Through van der Waals forces, hydrogen bonds, and electrostatic forces between cations and anions, they show broad application prospects in the extraction and separation of aromatic hydrocarbons, halogenated hydrocarbons, and metal ions. However, ionic liquids generally have high viscosity, which is detrimental to the mass transfer process during extraction and makes it difficult to separate the target analyte from the ionic liquid. As extractants, ionic liquids are difficult to store for long periods, and there are also issues with loss during recovery.

[0004] Hydrogels are a class of novel, low-toxicity, and biodegradable polymer materials. They possess the properties of solid materials, maintaining a certain shape and size, while also exhibiting the fluidity of liquids, allowing free penetration of small-molecule solvents or solutes both inside and outside. Thermosensitive hydrogels, in particular, exhibit phase transition properties, undergoing a hydrophobic-to-hydrophilic transformation at specific temperatures, thereby altering the adsorption-desorption properties of the gel material for different small molecules. Thermosensitive hydrogel composites have made significant contributions to fields such as extraction and separation, and drug delivery. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a simple method for preparing an ion-thermal composite gel with strong nicotine adsorption-desorption capabilities. By utilizing ionic liquids to form dense nicotine binding sites within the composite material, the adsorption-desorption performance of the material for nicotine is enhanced. Simultaneously, the desorption performance is strengthened by utilizing the thermal conductivity of boron nitride and the phase transition properties of the gel, thereby simplifying the nicotine extraction process and reducing the amount of eluent used in nicotine recovery.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] A method for preparing an ion-thermosensitive composite gel for efficient nicotine extraction includes the following steps:

[0008] Preparation of boron nitride nanosheets: Hexagonal boron nitride was mixed with anhydrous citric acid and then ball-milled. After ball milling, the powder was poured into a container of water and stirred, filtered, and washed until the pH of the washing solution was close to neutral. The obtained powder was then dispersed in water, centrifuged, and the supernatant was taken and centrifuged and dried multiple times to obtain boron nitride nanosheets (carboxyl-functionalized boron nitride nanosheets BNNs).

[0009] Preparation of ionic liquid-boron nitride nanosheets: The boron nitride nanosheets obtained in (1) were dispersed in a certain amount of ionic liquid, stirred and reacted under nitrogen atmosphere, repeatedly washed and filtered, and then dried to obtain ionic liquid-boron nitride nanosheets.

[0010] Preparation of ionic liquid thermosensitive gel: The ionic liquid-boron nitride nanosheets obtained in (2) were dispersed in an aqueous solution containing a certain amount of isopropylacrylamide monomer (NIPAM). After stirring to form a colloid, the crosslinking agent N,N-methylenebisacrylamide was added. Stirring was continued until fully dissolved, and then tetramethylethylenediamine was added and stirred under ice bath. Finally, the initiator ammonium persulfate was added and stirred evenly. The mixture was transferred into a mold and polymerized at room temperature for 10-12 h to obtain a white composite material, which is the ionic thermosensitive composite gel for efficient nicotine extraction.

[0011] As a further preferred embodiment of this technical solution, the mass ratio of hexagonal boron nitride to anhydrous citric acid in step (1) is 1:1~5.

[0012] As a further preferred embodiment of this technical solution, in step (1), the grinding beads are made of zirconium oxide and have a diameter of 0.5 cm. The grinding speed is 220-250 r / min, and the grinding time is 10-12 h. In step (1), the centrifugation is performed by first centrifuging at 3000 r / min, then taking the upper suspension, and then centrifuging at 8000 r / min for 5 min.

[0013] As a further preferred embodiment of this technical solution, the molar ratio of boron nitride nanosheets to ionic liquid in step (2) is 1:3.

[0014] As a further preferred embodiment of this technical solution, the ionic liquid in step (2) is any one of 1-ethyl-3-methylimidazolium tetrafluoroborate ([EMIm][BF4]), 1-propyl-3-methylimidazolium tetrafluoroborate ([PMIm][BF4]), and 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIm][BF4]).

[0015] As a further preferred embodiment of this technical solution, in step (2), boron nitride nanosheets are dispersed in an ionic liquid and stirred under a nitrogen atmosphere for 24-48 hours.

[0016] As a further preferred embodiment of this technical solution, the mass ratio of ionic liquid-boron nitride nanosheets to isopropylacrylamide monomer in step (3) is 0.5~2:1.

[0017] As a further preferred embodiment of this technical solution, in step (3), the mass ratio of isopropylacrylamide monomer, crosslinking agent N,N-methylenebisacrylamide, and initiator ammonium persulfate is 100:1:10, and the mass-to-volume ratio of isopropylacrylamide monomer to tetramethylethylenediamine is 1g:35~40µL.

[0018] As a further preferred embodiment of this technical solution, the reaction is carried out in step (3) with stirring under an ice bath for 2-3 hours.

[0019] The application of the ion-thermosensitive composite gel prepared by the method of the present invention in the extraction of nicotine.

[0020] The ion-thermosensitive composite gel of the present invention is applied to the adsorption and separation of tobacco alkaloids, and exhibits a strong adsorption-desorption function for nicotine.

[0021] The principle of this invention: Addressing the hazards of organic solvents in traditional solvent extraction methods, this invention proposes an ionic liquid immobilization strategy. Ionic liquids are loaded onto the surface of boron nitride nanosheets and uniformly dispersed within the cross-linked network of a thermosensitive gel, forming dense adsorption sites and a uniform thermally conductive network. The binding sites of the ionic liquid enhance the adsorption performance for nicotine. Simultaneously, the excellent thermal conductivity of boron nitride and the phase transition properties of the thermosensitive gel accelerate the desorption rate of nicotine, reduce the use of eluents, and simplify the nicotine recovery process.

[0022] The ion-thermosensitive composite gel material prepared in this invention shows, through SEM analysis, that boron nitride nanosheets loaded with ionic liquid are uniformly grown within the cross-linked network of the gel, forming dense nicotine adsorption sites and a thermally conductive network. Nicotine adsorption tests indicate that the composite material exhibits excellent nicotine adsorption performance, with an adsorption capacity of approximately 81.5 mg / g. Since the phase transition temperature of the ionic liquid composite gel is approximately 40°C, the structure of the composite gel changes from hydrophilic to hydrophobic at this temperature, causing the gel structure to shrink and releasing hydrophilic nicotine into the eluent. The desorption performance of the nicotine-adsorbed composite material was tested by placing it in anhydrous ethanol adsorbent at 40°C. The results show that the composite material can achieve nicotine desorption within 12-15 minutes, with a desorption capacity of 79.4 mg / g and a desorption rate as high as 97.2%.

[0023] Compared with the prior art, the advantages of this invention are:

[0024] 1. This invention utilizes mechanical ball milling to exfoliate boron nitride sheets, which not only effectively prepares boron nitride nanosheets but also successfully modifies the surface of boron nitride with oxygen-containing groups, which is beneficial for the loading of ionic liquids.

[0025] 2. The ion gel composite material prepared by this invention is used to extract nicotine from tobacco pure oil. The material has a stable structure and stable physicochemical properties, which not only avoids the use of volatile organic solvents, but also facilitates the recovery and recycling of the extractant.

[0026] 3. The ion-thermosensitive composite gel material for nicotine adsorption prepared in this invention enables the successful loading of boron nitride nanosheets with good thermal conductivity into the cross-linked network of the gel, which not only has excellent adsorption performance for nicotine, but also enhances the desorption process of nicotine.

[0027] 4. This invention utilizes the adsorption sites of nicotine in ionic liquids to construct a composite material that exhibits excellent nicotine adsorption performance. The ionic liquid can be replaced to extract different active substances from tobacco.

[0028] 5. The ion-thermosensitive composite gel prepared by this invention has excellent selectivity for nicotine and can selectively extract nicotine from tobacco essential oil with complex composition.

[0029] 6. The ion-thermosensitive composite gel prepared by this invention has a mature process, which ingeniously combines the adsorption performance of ionic liquid for nicotine, the thermal conductivity of boron nitride, and the phase change characteristics of thermosensitive gel, and has certain innovations. Attached Figure Description

[0030] Figure 1 The images show SEM images of the PNIPAM thermosensitive gel of Comparative Example 1 and the ion thermosensitive composite gel material (IL-BNNs@P) of the present invention.

[0031] Figure 2 The adsorption curves of nicotine on composite materials supported by different types of ionic liquids are shown.

[0032] Figure 3 The adsorption curves of nicotine for composite materials with different IL-BNNs powder loadings are shown.

[0033] Figure 4 The graph shows the adsorption performance of the ion-thermosensitive composite gel for nicotine and three main impurities.

[0034] Figure 5 This is a comparison chart showing the test results of nicotine desorption performance of ion-sensitive thermosensitive composite gel and the commonly used nicotine adsorbent AB-8 macroporous resin. Implementation

[0035] The following examples further illustrate the present invention in detail. It should be understood that the following examples are only for further explanation 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 description of the present invention are within the scope of protection of the present invention. The specific process parameters, etc., in the following examples are merely examples within a suitable range; that is, those skilled in the art can make appropriate selections within the appropriate range based on the description herein, and are not intended to be limited to the specific values ​​in the examples below. Example

[0036] A method for preparing an ion-thermosensitive composite gel for nicotine extraction includes the following steps:

[0037] (1) Preparation of boron nitride nanosheets: Hexagonal boron nitride and anhydrous citric acid were physically mixed at a mass ratio of 1:5, and then poured into a ball mill jar (using zirconia grinding beads with a diameter of 0.5 cm) and ball-milled at 220 r / min for 12 h. After ball milling, the powder was poured into a beaker containing deionized water and stirred, filtered, and washed until the pH of the washing solution was close to neutral. Then the obtained powder was dispersed in water, centrifuged at 3000 r / min, and the upper suspension was taken and centrifuged at 8000 r / min for 5 min. After multiple centrifugations and drying, boron nitride nanosheets were obtained.

[0038] (2) Preparation of ionic liquid-boron nitride nanosheets: The boron nitride nanosheets obtained in (1) were dispersed in the ionic liquid [EMIm][BF4] according to a molar ratio of boron nitride nanosheets to ionic liquid of 1:3. The mixture was stirred for 24 h under a nitrogen atmosphere, repeatedly washed and filtered with deionized water, and then dried at 80 °C to obtain ionic liquid-boron nitride nanosheets.

[0039] (3) Preparation of ionic liquid thermosensitive gel: 1.2 g of ionic liquid [EMIm][BF4]-boron nitride nanosheets were dispersed in 6 mL of aqueous solution containing 0.8 g of isopropylacrylamide. After stirring to form a colloid, 0.008 g of N,N-methylenebisacrylamide was added as a crosslinking agent. Stirring was continued until fully dissolved, followed by the addition of 30 µL of tetramethylethylenediamine and stirring in an ice bath for 2 h. Finally, 0.08 g of initiator ammonium persulfate was added and stirring was continued until homogeneous. The mixture was then transferred to a mold and polymerized at room temperature for 12 h to obtain a white composite material, which is the highly efficient ionic thermosensitive composite gel for nicotine extraction. The composite material was soaked in deionized water for 24 h before use. Example

[0040] A method for preparing an ion-thermosensitive composite gel for nicotine extraction includes the following steps:

[0041] (1) Preparation of boron nitride nanosheets: Hexagonal boron nitride and anhydrous citric acid were physically mixed at a mass ratio of 1:5, and then poured into a ball mill jar (using zirconia ball milling beads with a diameter of 0.5 cm) and ball milled at 220 r / min for 12 h. After ball milling, the powder was poured into a beaker containing deionized water and stirred, filtered, and washed until the pH of the washing solution was close to neutral. Then the obtained powder was dispersed in water, centrifuged at 3000 r / min, and the upper suspension was taken and centrifuged at 8000 r / min for 5 min. After multiple centrifugations and drying, boron nitride nanosheets were obtained.

[0042] (2) Preparation of ionic liquid-boron nitride nanosheets: The boron nitride nanosheets obtained in (1) were dispersed in the ionic liquid [PMIm][BF4]. The mixture was stirred for 24 h under a nitrogen atmosphere, repeatedly washed and filtered with deionized water, and then dried at 80 °C to obtain ionic liquid-boron nitride nanosheets.

[0043] (3) Preparation of ionic liquid thermosensitive gel: 1.2 g of the ionic liquid [PMIm][BF4]-boron nitride nanosheets obtained in (2) was dispersed in 6 mL of an aqueous solution containing 0.8 g of isopropylacrylamide. After stirring to form a colloid, 0.008 g of N,N-methylenebisacrylamide was added as a crosslinking agent. Stirring was continued until fully dissolved, and then 30 µL of tetramethylethylenediamine was added and stirred in an ice bath for 2 h. Finally, 0.08 g of ammonium persulfate initiator was added and stirred until homogeneous. The mixture was then transferred to a mold and polymerized at room temperature for 12 h to obtain a white composite material, which is the ionic thermosensitive composite gel for efficient nicotine extraction. Example

[0044] A method for preparing an ion-thermosensitive composite gel for nicotine extraction includes the following steps:

[0045] (1) Preparation of boron nitride nanosheets: Hexagonal boron nitride and anhydrous citric acid were physically mixed at a mass ratio of 1:5, and then poured into a ball mill jar (using zirconia grinding beads with a diameter of 0.5 cm) and ball-milled at 220 r / min for 12 h. After ball milling, the powder was poured into a beaker containing deionized water and stirred, filtered, and washed until the pH of the washing solution was close to neutral. Then the obtained powder was dispersed in water, centrifuged at 3000 r / min, and the upper suspension was taken and centrifuged at 8000 r / min for 5 min. After multiple centrifugations and drying, boron nitride nanosheets were obtained.

[0046] (2) Preparation of ionic liquid-boron nitride nanosheets: The boron nitride nanosheets obtained in (1) were dispersed in the ionic liquid [BMIm][BF4]. The mixture was stirred for 24 h under a nitrogen atmosphere, washed repeatedly with deionized water and filtered, and then dried at 80 °C to obtain ionic liquid-boron nitride nanosheets.

[0047] (3) Preparation of ionic liquid thermosensitive gel: 1.2 g of the ionic liquid [BMIm][BF4]-boron nitride nanosheets obtained in (2) was dispersed in 6 mL of an aqueous solution containing 0.8 g of isopropylacrylamide. After stirring to form a colloid, 0.008 g of N,N-methylenebisacrylamide was added as a crosslinking agent. Stirring was continued until fully dissolved, and then 30 µL of tetramethylethylenediamine was added and stirred in an ice bath for 2 h. Finally, 0.08 g of ammonium persulfate initiator was added and stirred until homogeneous. The mixture was then transferred to a mold and polymerized at room temperature for 12 h to obtain a white composite material, which is the ionic thermosensitive composite gel for efficient nicotine extraction. Example

[0048] A method for preparing an ion-thermosensitive composite gel for nicotine extraction includes the following steps:

[0049] (1) Preparation of boron nitride nanosheets: Hexagonal boron nitride and anhydrous citric acid were physically mixed at a mass ratio of 1:5, and then poured into a ball mill jar (using zirconia grinding beads with a diameter of 0.5 cm) and ball-milled at 220 r / min for 12 h. After ball milling, the powder was poured into a beaker containing deionized water and stirred, filtered, and washed until the pH of the washing solution was close to neutral. Then the obtained powder was dispersed in water, centrifuged at 3000 r / min, and the upper suspension was taken and centrifuged at 8000 r / min for 5 min. After multiple centrifugations and drying, boron nitride nanosheets were obtained.

[0050] (2) Preparation of ionic liquid-boron nitride nanosheets: The boron nitride nanosheets obtained in (1) were dispersed in the ionic liquid [EMIm][BF4]. The mixture was stirred for 24 h under a nitrogen atmosphere, repeatedly washed and filtered with deionized water, and then dried at 80 °C to obtain ionic liquid-boron nitride nanosheets.

[0051] (3) Preparation of ionic liquid thermosensitive gel: 0.4 g of the ionic liquid [EMIm][BF4]-boron nitride nanosheets obtained in (2) was dispersed in 6.8 mL of an aqueous solution containing 0.8 g of isopropylacrylamide. After stirring to form a colloid, 0.008 g of N,N-methylenebisacrylamide was added as a crosslinking agent. Stirring was continued until fully dissolved, and then 30 µL of tetramethylethylenediamine was added and stirred in an ice bath for 2 h. Finally, 0.08 g of ammonium persulfate initiator was added and stirred until homogeneous. The mixture was then transferred to a mold and polymerized at room temperature for 12 h to obtain a white composite material, which is the ionic thermosensitive composite gel for efficient nicotine extraction. Example

[0052] A method for preparing an ion-thermosensitive composite gel for nicotine extraction includes the following steps:

[0053] (1) Preparation of boron nitride nanosheets: Hexagonal boron nitride and anhydrous citric acid were physically mixed at a mass ratio of 1:5, and then poured into a ball mill jar (using zirconia grinding beads with a diameter of 0.5 cm) and ball-milled at 220 r / min for 12 h. After ball milling, the powder was poured into a beaker containing deionized water and stirred, filtered, and washed until the pH of the washing solution was close to neutral. Then the obtained powder was dispersed in water, centrifuged at 3000 r / min, and the upper suspension was taken and centrifuged at 8000 r / min for 5 min. After multiple centrifugations and drying, boron nitride nanosheets were obtained.

[0054] (2) Preparation of ionic liquid-boron nitride nanosheets: The boron nitride nanosheets obtained in (1) were dispersed in the ionic liquid [EMIm][BF4]. The mixture was stirred for 24 h under a nitrogen atmosphere, repeatedly washed and filtered with deionized water, and then dried at 80 °C to obtain ionic liquid-boron nitride nanosheets.

[0055] (3) Preparation of ionic liquid thermosensitive gel: 0.8 g of the ionic liquid [EMIm][BF4]-boron nitride nanosheets obtained in (2) was dispersed in 6.4 mL of an aqueous solution containing 0.8 g of isopropylacrylamide. After stirring to form a colloid, 0.008 g of N,N-methylenebisacrylamide was added as a crosslinking agent. Stirring was continued until fully dissolved, and then 30 µL of tetramethylethylenediamine was added and stirred in an ice bath for 2 h. Finally, 0.08 g of ammonium persulfate initiator was added and stirred until homogeneous. The mixture was then transferred to a mold and polymerized at room temperature for 12 h to obtain a white composite material, which is the ionic thermosensitive composite gel for efficient nicotine extraction. Example

[0056] A method for preparing an ion-thermosensitive composite gel for nicotine extraction includes the following steps:

[0057] (1) Preparation of boron nitride nanosheets: Hexagonal boron nitride and anhydrous citric acid were physically mixed at a mass ratio of 1:5, and then poured into a ball mill jar (using zirconia grinding beads with a diameter of 0.5 cm) and ball-milled at 220 r / min for 12 h. After ball milling, the powder was poured into a beaker containing deionized water and stirred, filtered, and washed until the pH of the washing solution was close to neutral. Then the obtained powder was dispersed in water, centrifuged at 3000 r / min, and the upper suspension was taken and centrifuged at 8000 r / min for 5 min. After multiple centrifugations and drying, boron nitride nanosheets were obtained.

[0058] (2) Preparation of ionic liquid-boron nitride nanosheets: The boron nitride nanosheets obtained in (1) were dispersed in the ionic liquid [EMIm][BF4]. The mixture was stirred for 24 h under a nitrogen atmosphere, repeatedly washed and filtered with deionized water, and then dried at 80 °C to obtain ionic liquid-boron nitride nanosheets.

[0059] (3) Preparation of ionic liquid thermosensitive gel: 1.6 g of the ionic liquid [EMIm][BF4]-boron nitride nanosheets obtained in (2) was dispersed in 5.6 mL of an aqueous solution containing 0.8 g of isopropylacrylamide. After stirring to form a colloid, 0.008 g of N,N-methylenebisacrylamide was added as a crosslinking agent. Stirring was continued until fully dissolved, and then 30 µL of tetramethylethylenediamine was added and stirred in an ice bath for 2 h. Finally, 0.08 g of ammonium persulfate initiator was added and stirred until homogeneous. The mixture was then transferred to a mold and polymerized at room temperature for 12 h to obtain a white composite material, which is the ionic thermosensitive composite gel for efficient nicotine extraction.

[0060] Preparation of pure thermosensitive gel PNIPAM: 0.008 g of N,N-methylenebisacrylamide was added as a crosslinking agent to 5.6 mL of an aqueous solution containing 0.8 g of isopropylacrylamide and stirred until fully dissolved. Then, 30 µL of tetramethylethylenediamine was added and stirred in an ice bath for 2 h. Finally, 0.08 g of ammonium persulfate initiator was added and stirring continued until homogeneous. The mixture was then transferred to a mold and polymerized at room temperature for 12 h to obtain pure thermosensitive gel PNIPAM.

[0061] The surface morphology of pure thermosensitive gel PNIPAM and the ion-thermosensitive composite gel material prepared in Example 1 of this invention was characterized using a Hitachi S-3400N low-magnification scanning electron microscope (Japan). Figure 1 As shown. Among them Figure 1 The material on the left is pure thermosensitive gel. Figure 1The image on the right shows the ionic liquid thermosensitive composite gel material prepared in Example 1. It can be seen that IL-BNNs are grown inside the cross-linked network of the composite material of this invention. The layered IL-BNNs material accumulates on the cross-linked network of the gel, resulting in a change in the morphology of the gel pores.

[0062] The nicotine adsorption performance of the composite materials prepared in Implementation Cases 1-3 was analyzed.

[0063] The composite materials prepared in Examples 1-3 were immersed in deionized water for 24 hours. After 24 hours, the materials were removed and the water adhering to the surface was gently wiped off with filter paper. 0.5 g of the ionic liquid thermosensitive gel composite material was cut with a knife and placed in ethyl acetate solutions with nicotine concentrations of 50, 100, 150, 250, 400, 600, 800, 1000, and 1200 mg / L, respectively, and shaken on a mechanical shaker for 12 hours. The materials were then removed, and the remaining nicotine content in the solution was detected using gas chromatography. The adsorption capacity of the material for nicotine was calculated, and the results are as follows: Figure 2 As shown.

[0064] Depend on Figure 2 It can be seen that the composite material modified by [EMIm][BF4] has the best adsorption performance for nicotine. This is because among the three ionic liquids, the side chain alkyl group of [EMIm][BF4] is the shortest, resulting in the least steric hindrance for its binding with nicotine. Therefore, this ionic liquid has the best adsorption performance for nicotine.

[0065] The nicotine adsorption performance of the composite materials prepared in Case Studies 1, 4, 5, and 6 was analyzed.

[0066] The composite materials prepared in Examples 1, 4, 5, and 6 (ionic liquid-boron nitride nanosheets (IL-BNNs) with a mass of 0.4 g to 1.6 g, i.e., the mass fraction of IL-BNNs added was 5% to 20% of the total mass of the composite material) were immersed in deionized water. After 24 h, they were removed and the water adhering to the surface of the material was gently wiped off with filter paper. Four 0.5 g samples of the ionic liquid thermosensitive gel composite materials were cut with a knife and placed in ethyl acetate solutions with nicotine concentrations of 30, 40, 50, 80, 100, 150, 200, 250, 350, 500, 650, 800, 1000, and 1200 mg / L, respectively, and shaken on a mechanical shaker for 12 h. The materials were removed and the remaining nicotine content in the solution was detected by gas chromatography. The adsorption capacity of nicotine for composite materials with different IL-BNNs doping amounts was calculated, and the results are as follows: Figure 3 As shown.

[0067] Depend on Figure 3It can be seen that when the mass fraction of IL-BNNs is 5%~15%, with the increase of IL-BNNs loading, the adsorption sites of nicotine in the cross-linked network of the gel material also increase and gradually become denser, resulting in an increase in the adsorption capacity of the composite material for nicotine. However, when the IL-BNNs loading is 20%, the doping of a large number of IL-BNNs causes the excess IL-BNNs to fail to be fixed in the gel network and spontaneously aggregate, obscuring the original nicotine adsorption sites, hindering the interaction between the ionic liquid and nicotine, and thus reducing the adsorption capacity of nicotine.

[0068] The selective adsorption of nicotine was tested on the composite material prepared in Example 1 in a raw material solution with a nicotine concentration of 200 mg / L. The prepared composite material was immersed in deionized water for 24 h, then removed and the surface water was gently wiped off with filter paper. 0.5 g of the ionic liquid thermosensitive gel composite material was cut with a knife and placed in an ethyl acetate solution with a nicotine concentration of 200 mg / L, and mechanically shaken for 12 h. The material was then removed, and the remaining nicotine and three impurities (neoptiadiene, ethyl hexadecanoate, and linolenic acid) in the solution were detected by gas chromatography. The extraction rates of nicotine and impurities were calculated, and the results are shown below. Figure 4 As shown.

[0069] Figure 4 The results showed that the ionic liquid thermosensitive composite gel achieved an extraction rate of 93.5% for nicotine. The partition coefficient of nicotine in this extractant was as high as 258.6, significantly higher than the partition coefficients of the three impurities (neoptiadiene, ethyl hexadecanoate, and linolenic acid were 7.6, 14.3, and 15.4, respectively). This indicates that the composite extractant exhibits good selectivity for nicotine.

[0070] The nicotine desorption performance of the composite material prepared in Case 1 and the commonly used nicotine adsorbent AB-8 macroporous resin were compared.

[0071] 0.5 g of the material prepared in Experimental Case 1 and 0.5 g of AB-8 macroporous resin were placed in an ethyl acetate solution with a nicotine concentration of 200 mg / L. After adsorption by shaking for 12 h, the material and macroporous resin were removed. The nicotine-adsorbed composite material and AB-8 macroporous resin were placed in an exchange column, washed with anhydrous ethanol, and the column temperature was maintained at 40 °C to dynamically elute the nicotine from the material and AB-8 macroporous resin. The nicotine content in the eluent was detected by gas chromatography, and the nicotine desorption rate was calculated.

[0072] Depend on Figure 5As can be seen, thanks to the phase change properties of the thermosensitive gel, this material reaches desorption equilibrium in an ethanol solution at 40 °C in just 12-15 min, with a desorption amount of 79.4 mg / g and a desorption rate as high as 97.2%. In contrast, AB-8 macroporous resin requires at least 150 min to reach desorption equilibrium. Compared to AB-8 macroporous resin, the thermosensitive composite material can achieve rapid desorption of nicotine at 40 °C. During dynamic elution, the shorter desorption time means less elution solvent is used. This indicates that the ionic liquid thermosensitive composite material of the present invention not only simplifies the nicotine extraction process but also reduces the cost of nicotine recovery.

[0073] The examples provided in this invention are not intended to limit the implementation of the invention. Those skilled in the art will recognize that various variations and modifications can be made based on the above description. It is neither necessary nor possible to exhaustively describe all possible implementations. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of the claims.

Claims

1. A method for preparing an ion-thermal composite gel for efficient nicotine extraction, characterized in that, The method includes the following steps: (1) Preparation of boron nitride nanosheets: Hexagonal boron nitride was mixed with anhydrous citric acid and then ball-milled. After ball milling, the powder was poured into a container of water and stirred, filtered and washed until the pH of the washed solution was close to neutral. The obtained powder was then dispersed in water, centrifuged, and the upper suspension was taken and centrifuged and dried multiple times to obtain boron nitride nanosheets. (2) Preparation of ionic liquid-boron nitride nanosheets: The boron nitride nanosheets obtained in (1) are dispersed in a certain amount of ionic liquid, stirred and reacted under nitrogen atmosphere, repeatedly washed and filtered, and then dried to obtain ionic liquid-boron nitride nanosheets. (3) Preparation of ionic liquid thermosensitive gel: The ionic liquid-boron nitride nanosheets obtained in (2) are dispersed in an aqueous solution containing a certain amount of isopropylacrylamide monomer. After stirring to form a colloid, crosslinking agent N,N-methylenebisacrylamide is added. Stirring is continued until fully dissolved, then tetramethylethylenediamine is added and stirred under ice bath. Finally, ammonium persulfate initiator is added and stirred evenly. The mixture is transferred into a mold and polymerized at room temperature for 10-12 h to obtain a white composite material, which is the ionic thermosensitive composite gel for efficient nicotine extraction.

2. The method for preparing the highly efficient nicotine extraction ion-thermosensitive composite gel according to claim 1, characterized in that: In step (1), the mass ratio of hexagonal boron nitride to anhydrous citric acid is 1:1-5.

3. The method for preparing the highly efficient ion-thermosensitive composite gel for nicotine extraction according to claim 1, characterized in that: In step (1), the grinding balls are made of zirconium oxide and have a diameter of 0.5 cm. The grinding speed is 220-250 r / min and the grinding time is 10-12 h.

4. The method for preparing the highly efficient nicotine extraction ion-thermosensitive composite gel according to claim 1, characterized in that: In step (2), the molar ratio of boron nitride nanosheets to ionic liquid is 1:

3.

5. The method for preparing the highly efficient ion-thermal composite gel for nicotine extraction according to claim 1, characterized in that: The ionic liquid in step (2) is any one of 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-propyl-3-methylimidazolium tetrafluoroborate, and 1-butyl-3-methylimidazolium tetrafluoroborate.

6. The method for preparing the highly efficient ion-thermosensitive composite gel for nicotine extraction according to claim 1, characterized in that: In step (2), boron nitride nanosheets are dispersed in an ionic liquid and stirred under a nitrogen atmosphere for 24-48 hours.

7. The method for preparing the highly efficient nicotine extraction ion-thermosensitive composite gel according to claim 1, characterized in that: In step (3), the mass ratio of ionic liquid-boron nitride nanosheets to isopropylacrylamide monomer is 0.5~2:

1.

8. The method for preparing the highly efficient ion-thermosensitive composite gel for nicotine extraction according to claim 1, characterized in that: In step (3), the mass ratio of isopropylacrylamide monomer, crosslinking agent N,N-methylenebisacrylamide, and initiator ammonium persulfate is 100:1:10; the mass-to-volume ratio of isopropylacrylamide monomer to tetramethylethylenediamine is 1g:35~40µL.

9. The method for preparing the highly efficient nicotine extraction ion thermosensitive composite gel according to claim 1, wherein in step (3), the reaction is stirred in an ice bath for 2-3 h.

10. The application of the ion-sensitive thermosensitive composite gel prepared by the method according to any one of claims 1 to 9, characterized in that: Application of ion-thermosensitive composite gel in nicotine extraction.

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