Preparation method and adsorption method of ethyl carbamate magnetic molecular imprinting adsorbent

Abstract

The invention relates to the technical field of material preparation, separation and purification, in particular to a preparation method and an adsorption method of an ethyl carbamate magnetic molecular imprinting adsorbent. The magnetic surface molecular imprinting adsorbent for removing ethyl carbamate has the characteristics of high adsorption efficiency, low cost, reusability and environment friendliness. The method comprises the following steps: modifying magnetic ferroferric oxide and wrapping a molecular imprinting layer, adding nano ferroferric oxide into absolute ethyl alcohol, carrying out ultrasonic dispersion, dropwise adding tetraethoxysilane and ammonia water, stirring, collecting a solid by using a magnet, washing and drying the obtained solid, re-dispersing the solid into ethyl alcohol, and drying, so as to obtain the magnetic molecularly imprinted polymer. Heating is performed, gamma-(methacryloyloxy) propyl trimethoxy silane (KH-570) is added, and an obtained product is washed and dried; and dispersing the obtained product and ethyl carbamate in a 4-ethylbenzoic acid imprinting system for polymerization, and washing the template to obtain the magnetic surface molecular imprinting adsorbent.

Description

Technical Field

[0001] This invention relates to the field of material preparation and separation and purification technology, specifically to a method for preparing and adsorbing a urethane magnetic molecularly imprinted adsorbent. Background Technology

[0002] Ethyl carbamate, also known as urethane, is a fermentation byproduct naturally found in alcoholic beverages (such as wine, spirits, sake, rice wine, and beer), soy sauce, bread, pickles, and other fermented foods. This is because during fermentation or storage, precursor substances (such as urea, cyanate esters, and ethanol) undergo a chemical reaction to form ethyl carbamate. However, ethyl carbamate has toxic side effects and is classified as a Group 2A carcinogen by the International Agency for Research on Cancer, thus posing health risks to certain types of people who frequently ingest it. Governments worldwide are highly concerned about the residual pollution hazards of ethyl carbamate and have established maximum permissible residue thresholds for ethyl carbamate in various environmental and food-related matrices.

[0003] Commonly used methods for the adsorption, removal, and control of urethane include: (1) Activated carbon adsorption method: Utilizing the porous structure of activated carbon, ethyl carbamate is captured through van der Waals forces and hydrophobic interactions to achieve separation and removal.

[0004] (2) Molecular sieve method: The regular microporous structure of molecular sieve after activation and the polar adsorption of surface hydroxyl and cations are used to remove ethyl carbamate.

[0005] (3) Resin adsorption method: Utilize the ion / hydrophobic interaction of ion exchange resin / macroporous adsorption resin to adsorb and remove ethyl carbamate.

[0006] (4) Enzyme source control method: By modifying and screening low urea-producing yeast, the generation of ethyl carbamate can be controlled at the source.

[0007] (5) Enzymatic degradation method: By adding acidic urease during fermentation, the urea content during fermentation is reduced, thereby reducing the amount of ethyl carbamate produced, or ethyl carbamate degrading enzymes are modified and screened to directly decompose ethyl carbamate.

[0008] However, none of the above methods can completely solve the industry's problems. Conventional adsorbents such as molecular sieves have strong adsorption capacity, but their specificity is extremely poor. They lack the ability to target ethyl carbamate and easily adsorb flavor substances such as esters and acids simultaneously, greatly affecting the taste. Enzymes, on the other hand, have problems such as instability, enzyme inactivation under high concentrations of ethanol, and high costs, which limit their large-scale promotion.

[0009] Application number 2022114960913, entitled "A Method for Preparing and Applying a Magnetic Molecularly Imprinted Polymer," discloses a one-step preparation method of silanized Fe3O4 nanoparticles using a combination of coprecipitation and sol-gel copolymerization. The resulting Fe3O4@SiO2 nanoparticles have a fine texture and good dispersibility. These nanoparticles are used as the magnetic core carrier for the molecularly imprinted polymer. The Fe3O4@SiO2 is vinyl-modified with 3-(methacryloyloxy)propyltrimethoxysilane to enable copolymerization with a crosslinking agent. The magnetic molecularly imprinted polymer is prepared using ethyl carbamate as the template molecule, methacrylic acid as the functional monomer, and N,N-dimethylformamide and deionized water as porogens. However, the invention has the following problems: while the adsorption capacity is large at high EC concentrations, the adsorption capacity at low EC concentrations is unknown. Static adsorption begins at an EC concentration of 20 mg / L, far exceeding the possible residual value of EC in actual wine samples. While the adsorption capacity is good at high concentrations, the adsorption effect may not be guaranteed at low concentrations.

[0010] Application No. 202411510452.4 discloses a molecularly imprinted magnetic covalent organic framework nanomaterial, its preparation method, and its application. The method involves adding Fe3O4 nanoparticles, ethyl carbamate, substituted triazine aromatic amines, 2,4,6-trihydroxypyromellitic aldehyde, and 1,3,5-triazine-2,4,6-tricarboxaldehyde to dimethyl sulfoxide and mixing. Anhydrous acetic acid is then added, and the mixture is stirred at room temperature. After the reaction, Fe3O4@COFs are obtained by magnetic separation. The Fe3O4@COFs are then washed with ethanol solution, water, and dried to obtain the molecularly imprinted magnetic covalent organic framework nanomaterial MIPs-Fe3O4@COFs, which still achieves a ethyl carbamate removal efficiency of over 97%. However, the problems include the unknown toxicity of the materials used and their relatively high cost, which limits production and promotion. Summary of the Invention

[0011] In view of this, in order to solve the problem that the prior art cannot achieve targeted adsorption of ethyl carbamate, the present invention provides a method for preparing and adsorbing a magnetic molecularly imprinted adsorbent of ethyl carbamate, which achieves high-capacity adsorption of ethyl carbamate in acetonitrile and has great potential for application to wine systems.

[0012] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a method for preparing a urethane magnetic molecularly imprinted adsorbent, firstly, by using magnetic Fe3O4, the adsorbent is endowed with recyclable properties, then by introducing polymerizable active groups through vinyl groups, and then adding 4-VBA and urethane to prepolymerize and form a complex, adding a crosslinking agent and an initiator to initiate the polymerization reaction, and after the reaction, the template is eluted to obtain the magnetic urethane molecularly imprinted adsorbent.

[0013] Specifically, the following steps are included: 1) Add 10-30 mg of nano-Fe3O4 to 0.5-1.5 mL of anhydrous ethanol, and disperse evenly by ultrasonication to obtain a mixed solution; 2) Take the mixed solution obtained in step 1), add tetraethoxysilane dropwise, add 1 mL of 28% ammonia water and stir, then separate the solid with a magnet. After washing the separated solid with water and ethanol in sequence, place it in a vacuum drying oven at 60℃ to dry it, and obtain silicon dioxide-coated iron(III) oxide. 3) The 40-45 mg of silica-coated iron oxide obtained in step 2) is redispersed in 2-5 mL of ethanol. KH-570 is added dropwise. Vinyl groups are branched on the surface of the silica-coated iron oxide obtained in step 2). After heating and stirring with an electric heating mantle, the black solid is collected by a magnet. After washing with water and ethanol, it is dried under vacuum at 60°C to obtain vinyl-branched iron oxide. 4) The vinyl branched iron oxide obtained in step 3) was added to an acetonitrile solution of ethyl carbamate for imprinting. Then, 1-1.5 mg of monomer 4-vinylbenzoic acid, 3-4 µL of crosslinking agent and 0.15-0.25 mg of initiator were added. The product was collected, the solid was washed with a Soxhlet extractor and dried to obtain a magnetic ethyl carbamate molecularly imprinted adsorbent.

[0014] Furthermore, in step 1), the ultrasonic treatment power is 200W~450W, and the particle size distribution of nano-ferric oxide is 50~300nm.

[0015] Furthermore, the volume ratio (mL) of the mixed solution to tetraethoxysilane in step 2) is 1:0.02.

[0016] Furthermore, in step 3), the branching process requires heating at 65°C under nitrogen protection for 4 hours.

[0017] Furthermore, in step 4), the crosslinking agent is ethylene glycol dimethacrylate; the initiator is azobisisobutyronitrile. The dosage of vinyl tert-Fe3O4 is 1.5-2.5 mg, the dosage of ethyl carbamate is 1.5-2.0 mg, and the dosage of acetonitrile is 1 mL. The elution solvent in the extractor is methanol and acetic acid in a volume ratio of 9:1; The reaction was stirred at 500 rpm for 24 hours, and the support was ferric oxide with vinyl branches.

[0018] Application of the magnetic molecularly imprinted adsorbent in the adsorption of ethyl carbamate.

[0019] A magnetic molecular imprint adsorption method for adsorbing ethyl carbamate includes the following steps: A standard solution of urethane was prepared using acetonitrile and ethanol as solvents. The solution was then mixed with HAc-NaAc buffer and a molecularly imprinted adsorbent. The content of urethane before and after adsorption was detected by gas chromatography-mass spectrometry. Furthermore, the HAc-NaAc buffer is an acetate-sodium acetate buffer.

[0020] Furthermore, the amount of magnetic molecularly imprinted adsorbent used is 4-20 mg, and the volume of acetonitrile and ethanol solution of ethyl carbamate is 15-25 mL.

[0021] Compared with the prior art, the present invention has the following advantages: (1) The 4-VBA monomer of this invention introduces hydrophobic interaction and hydrogen bond, which enhances the adsorption capacity of the adsorbent through dual pathways. This endows the adsorbent with excellent low-concentration EC adsorption capacity. Through large-scale molecular imprinted monomer experiments, it has been verified that this monomer has EC adsorption capacity that cannot be replaced by other common monomers.

[0022] (2) The raw materials of the present invention are low in toxicity and readily available, avoiding the use of highly toxic aldehydes and other raw materials as preparation materials. The preparation process is simple and reliable and has the potential for large-scale preparation.

[0023] (3) The method of the present invention is simple to operate, highly specific, low in cost, and has a high adsorption capacity, which can effectively remove ethyl carbamate.

[0024] (4) High adsorption capacity at low ethyl carbamate (EC) concentration. In this invention, the adsorption concentration of EC was set at 200 µg / L, which is consistent with the normal residual state of ethyl carbamate in wine samples. Subsequent adsorption and detection were carried out using this spiked solution. The results showed that the adsorption capacity was excellent, achieving high adsorption capacity adsorption of EC at a low concentration, with performance comparable to other adsorbents. Attached Figure Description

[0025] Figure 1 This is a flowchart illustrating the preparation process of the present invention.

[0026] Figure 2 The image shown is a scanning electron microscope (SEM) image of Fe3O4@SiO2@MIP prepared in Example 1.

[0027] Figure 3 The image shown is a scanning electron microscope (SEM) image of Fe3O4@SiO2@NIP prepared in Example 1.

[0028] Figure 4 The EC standard curve obtained by gas chromatography-mass spectrometry (GC-MS) in Example 1 is based on national standards.

[0029] Figure 5 The preparation conditions and carrier dosage screening diagram for Example 1 are shown.

[0030] Figure 6The chart shows the adsorption conditions and adsorbent dosage screening method obtained in Example 1.

[0031] Figure 7 The optimal pH screening diagram for adsorption conditions obtained in Example 1 is shown.

[0032] Figure 8 The adsorption kinetic curves were obtained for Example 1. Detailed Implementation

[0033] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. It should be understood that the following embodiments are only used to explain the present invention and are not intended to limit the present invention.

[0034] The working principle of this invention is as follows: First, the adsorbent is recyclable by using magnetic Fe3O4. Then, a vinyl group is introduced as a branch, followed by the addition of 4-VBA and urethane for prepolymerization to form a complex. A crosslinking agent and initiator are then added to initiate the polymerization reaction. After the reaction, the template is eluted, and the molecularly imprinted polymer is successfully prepared. This molecularly imprinted polymer, in turn, can selectively adsorb EC because 4-VBA contains a benzene ring and formic acid groups, while also introducing hydrophobic interactions and hydrogen bonds, thus endowing the adsorbent with high adsorption capacity.

[0035] Example 1: A method for preparing a urethane magnetic molecularly imprinted adsorbent (Fe3O4@SiO2@MIP) includes the following steps: 1) Add 20 mg of 150 nm nano-iron oxide to 1 mL of anhydrous ethanol and disperse it evenly by ultrasonication (the power of ultrasonic treatment is 350 W) to obtain a mixed solution; 2) Take 1 mL of the mixed solution obtained in step 1), add 0.02 mL of tetraethoxysilane, add 1 mL of 28% ammonia water and stir, then separate the solid with a magnet. After washing the separated solid with water and ethanol in sequence, place it in a vacuum drying oven at 60℃ to dry, and obtain silicon dioxide-coated iron(III) oxide. 3) The 43 mg of silica-coated iron oxide obtained in step 2) was redispersed in 3 mL of ethanol, and γ-(methacryloyloxy)propyltrimethoxysilane (KH-570) was added dropwise. Vinyl groups were added to the surface of the silica-coated iron oxide obtained in step 2). The decanting process required heating at 65 °C under nitrogen protection to avoid oxidation, and the reaction was carried out for 4 h. After heating and stirring with an electric heating mantle, the black solid was collected by a magnet. After washing with water and ethanol, it was dried under vacuum at 60 °C to obtain vinyl-deformed iron oxide. 4) Take 2.0 mg of the vinyl branched iron(III) oxide obtained in step 3) and add it to an acetonitrile solution of ethyl carbamate for imprinting (the amount of ethyl carbamate is 1.5-2.0 mg, and the amount of acetonitrile is 1 mL). Then add 1.32 mg of monomer 4-vinylbenzoic acid (4-VBA), 3.77 µL of crosslinking agent ethylene glycol dimethacrylate (EGDMA), and 0.20 mg of initiator azobisisobutyronitrile (AIBN). The reaction is stirred at 500 rpm and carried out for 24 h. Collect the product, wash the solid with a Soxhlet extractor (the eluent in the extractor is methanol and acetic acid in a volume ratio of 9:1), and dry to obtain the magnetic ethyl carbamate molecularly imprinted adsorbent.

[0036] A magnetic molecular imprint adsorption method for adsorbing ethyl carbamate includes the following steps: A standard solution of urethane was prepared using acetonitrile and ethanol solvents. The solution was then mixed with an acetate-sodium acetate buffer solution and a molecularly imprinted adsorbent. The content of urethane before and after adsorption was detected by gas chromatography-mass spectrometry (GC-MS). The amount of magnetic molecularly imprinted adsorbent used was 10 mg, and the volume of the acetonitrile and ethanol solution of urethane was 20 mL.

[0037] Example 2: A method for preparing a urethane magnetic molecularly imprinted adsorbent (Fe3O4@SiO2@MIP) includes the following steps: 1) Add 30 mg of 300 nm nano-iron oxide to 1.5 mL of anhydrous ethanol and disperse it evenly by ultrasonication (ultrasonication power is 450 W) to obtain a mixed solution; 2) Take 1 mL of the mixed solution obtained in step 1), add 0.02 mL of tetraethoxysilane, add 1 mL of 28% ammonia water and stir, then separate the solid with a magnet. After washing the separated solid with water and ethanol in sequence, place it in a vacuum drying oven at 60℃ to dry it, and obtain silicon dioxide-coated iron(III) oxide. 3) The 45 mg of silica-coated iron oxide obtained in step 2) was redispersed in 5 mL of ethanol, and KH-570 was added dropwise. Vinyl groups were dendriticed on the surface of the silica-coated iron oxide obtained in step 2). The dendriticing process required heating at 65 °C under nitrogen protection to avoid oxidation. The reaction was carried out for 4 h. After heating and stirring with an electric heating mantle, the black solid was collected with a magnet. After washing with water and ethanol, it was dried under vacuum at 60 °C to obtain vinyl-dendriticized iron oxide. 4) Add 2.5 mg of vinyl dendritic iron oxide obtained in step 3) to an acetonitrile solution of ethyl carbamate for imprinting (the amount of ethyl carbamate is 1.5-2.0 mg, and the amount of acetonitrile is 1 mL). Then add 1.5 mg of monomer 4-vinylbenzoic acid (4-VBA), 4 µL of crosslinking agent ethylene glycol dimethacrylate (EGDMA), and 0.25 mg of initiator azobisisobutyronitrile (AIBN). The reaction is stirred at 500 rpm and carried out for 24 h. Collect the product, wash the solid with a Soxhlet extractor (the eluent in the extractor is methanol and acetic acid in a volume ratio of 9:1), and dry to obtain magnetic ethyl carbamate molecularly imprinted adsorbent.

[0038] A magnetic molecular imprint adsorption method for adsorbing ethyl carbamate includes the following steps: A standard solution of ethyl carbamate was prepared using acetonitrile and ethanol solvents. The solution was then mixed with an acetate-sodium acetate buffer solution and a molecularly imprinted adsorbent. The content of ethyl carbamate before and after adsorption was detected by gas chromatography-mass spectrometry (GC-MS). The amount of magnetic molecularly imprinted adsorbent used was 20 mg, and the volume of the ethyl carbamate acetonitrile and ethanol solution was 25 mL.

[0039] Example 3: A method for preparing a urethane magnetic molecularly imprinted adsorbent (Fe3O4@SiO2@MIP) includes the following steps: 1) Add 10 mg of 50 nm nano-iron oxide to 0.5 mL of anhydrous ethanol and disperse it evenly by ultrasonication (ultrasonication power is 200 W) to obtain a mixed solution; 2) Take 1 mL of the mixed solution obtained in step 1), add 0.02 mL of tetraethoxysilane, add 1 mL of 28% ammonia water and stir, then separate the solid with a magnet. After washing the separated solid with water and ethanol in sequence, place it in a vacuum drying oven at 60℃ to dry it, and obtain silicon dioxide-coated iron(III) oxide. 3) The 40 mg of silica-coated iron oxide obtained in step 2) was redispersed in 2 mL of ethanol, and KH-570 was added dropwise. Vinyl groups were dendriticed on the surface of the silica-coated iron oxide obtained in step 2). The dendriticing process required heating at 65 °C under nitrogen protection to avoid oxidation. The reaction was carried out for 4 h. After heating and stirring with an electric heating mantle, the black solid was collected with a magnet. After washing with water and ethanol, it was dried under vacuum at 60 °C to obtain vinyl-dendriticized iron oxide. 4) Add 1.5 mg of vinyl dendritic iron oxide obtained in step 3) to an acetonitrile solution of ethyl carbamate for imprinting (the amount of ethyl carbamate is 1.5-2.0 mg, and the amount of acetonitrile is 1 mL). Then add 1 mg of monomer 4-vinylbenzoic acid (4-VBA), 3 µL of crosslinking agent ethylene glycol dimethacrylate (EGDMA), and 0.15 mg of initiator azobisisobutyronitrile (AIBN). The reaction is stirred at 500 rpm and carried out for 24 h. The product is collected, and the solid is washed with a Soxhlet extractor (the eluent in the extractor is methanol and acetic acid in a volume ratio of 9:1). After drying, the magnetic ethyl carbamate molecularly imprinted adsorbent is obtained.

[0040] A magnetic molecular imprint adsorption method for adsorbing ethyl carbamate includes the following steps: A standard solution of urethane was prepared using acetonitrile and ethanol solvents. The solution was then mixed with an acetate-sodium acetate buffer solution and a molecularly imprinted adsorbent. The content of urethane before and after adsorption was detected by gas chromatography-mass spectrometry (GC-MS). The amount of magnetic molecularly imprinted adsorbent used was 4 mg, and the volume of the acetonitrile and ethanol solution of urethane was 15 mL.

[0041] Example 4: A method for preparing a urethane magnetic molecularly imprinted adsorbent (Fe3O4@SiO2@MIP) includes the following steps: 1) Add 15 mg of ferric oxide nanoparticles with a particle size distribution of 280 nm to 1.3 mL of anhydrous ethanol and disperse evenly by ultrasonication (ultrasonication power of 300 W) to obtain a mixed solution; 2) Take 1 mL of the mixed solution obtained in step 1), add 0.02 mL of tetraethoxysilane, add 1 mL of 28% ammonia water and stir, then separate the solid with a magnet. After washing the separated solid with water and ethanol in sequence, place it in a vacuum drying oven at 60℃ to dry it, and obtain silicon dioxide-coated iron(III) oxide. 3) The 43 mg of silica-coated iron(III) oxide obtained in step 2) was redispersed in 3 mL of ethanol, and KH-570 was added dropwise. Vinyl groups were dendriticed on the surface of the silica-coated iron(III) oxide obtained in step 2). The dendriticing process required heating at 65 °C under nitrogen protection to avoid oxidation. The reaction was carried out for 4 h. After heating and stirring with an electric heating mantle, the black solid was collected with a magnet. After washing with water and ethanol, it was dried under vacuum at 60 °C to obtain vinyl-dendriticized iron(III) oxide. 4) Add 2.0 mg of vinyl dendritic iron oxide obtained in step 3) to an acetonitrile solution of ethyl carbamate for imprinting (the amount of ethyl carbamate is 1.5-2.0 mg, and the amount of acetonitrile is 1 mL). Then add 1.3 mg of monomer 4-vinylbenzoic acid (4-VBA), 3.5 µL of crosslinking agent ethylene glycol dimethacrylate (EGDMA), and 0.2 mg of initiator azobisisobutyronitrile (AIBN). The reaction is stirred at 500 rpm and carried out for 24 h. Collect the product, wash the solid with a Soxhlet extractor (the eluent in the extractor is methanol and acetic acid in a volume ratio of 9:1), and dry to obtain the magnetic ethyl carbamate molecularly imprinted adsorbent.

[0042] A magnetic molecular imprint adsorption method for adsorbing ethyl carbamate includes the following steps: A standard solution of ethyl carbamate was prepared using acetonitrile and ethanol solvents. The solution was then mixed with an acetate-sodium acetate buffer solution and a molecularly imprinted adsorbent. The content of ethyl carbamate before and after adsorption was detected by gas chromatography-mass spectrometry (GC-MS). The amount of magnetic molecularly imprinted adsorbent used was 4-20 mg, and the volume of the ethyl carbamate acetonitrile and ethanol solution was 15-25 mL.

[0043] Example 1 is the preferred embodiment of the present invention, as shown in the scanning electron microscope. Figure 2 and Figure 3 Fe3O4@SiO2@MIP particles exhibit coarse, spherical morphology with agglomeration. Fe3O4@SiO2@NIP particles also exhibit spherical morphology, consistent with scanning electron microscopy. Figure 2 No obvious differences were observed, but the particle size was significantly larger than that of magnetic iron oxide, indicating that the molecularly imprinted polymer was successfully prepared.

[0044] It should be noted that the volume ratio of the elution solvent for preparing Fe3O4@SiO2@MIP is methanol:acetic acid = 9:1. The time can be adjusted flexibly according to the actual effect. Generally, the end of the process is when there is no EC mass spectrometry peak in the eluent.

[0045] The optimized experiment is as follows: The carrier dosage was screened, and the EC concentration was quantified by gas chromatography-mass spectrometry (GC-MS). The results are shown in [Figure number missing]. Figure 5 .

[0046] Q = (C0 - C) t ) / M adsorbent (1) C0—Initial EC concentration, µg / L; C t —EC concentration at culture time t, µg / L; M adsorbent —Adsorbent dosage, mg; Depend on Figure 5It can be seen that the amount of carrier used is 20mg, and the adsorption capacity Q of the adsorbent is the largest at this time. The adsorption capacity is calculated according to formula (1) and is 10.82mg / g.

[0047] Example 1: Adsorption method of magnetic molecularly imprinted polymers. 1. Establishment of the gas chromatography-mass spectrometry method First, a standard curve was established according to the national standard (GB5009.223-2014). Ethyl carbamate (EC) solutions containing 200 ng / mL of D5-ethyl carbamate were prepared according to a certain gradient. The standard curve was plotted with EC concentration on the x-axis and the ratio of EC peak area to D5-ethyl carbamate peak area on the y-axis. See details below. Figure 4 The two have a good linear relationship.

[0048] 2. Screening of adsorbent dosage Different masses of adsorbent were added to 20 mL of EC acetonitrile / ethanol solution with a concentration of 200 µg / L. The solution was placed on a shaker and shaken at 160 rpm / min for 40 min at a constant temperature of 25 °C. The EC concentration of the liquid was then measured. The results are shown below. Figure 6 .

[0049] Depend on Figure 6 It can be seen that as the amount of adsorbent added increases, the adsorption capacity first increases and then decreases. The results show that Q is the largest at 8 mg, so the subsequent experiments used an addition amount of 8 mg.

[0050] 3. Optimal pH screening Add 2 mL of HAc-NaAc buffer solution with different pH values ​​to 20 mL of EC acetonitrile solution with a concentration of 200 µg / L, add 8 mg of adsorbent, place the system on a shaker, keep the temperature at 25 °C and shake at 160 rpm / min for 40 min, remove the solution, remove the magnetic adsorbent, and perform gas chromatography-mass spectrometry (GC-MS) detection.

[0051] See results Figure 7 The results showed that pH=4 was the optimal pH for adsorption.

[0052] 4. EC Adsorption Kinetics Determination The adsorption kinetics of EC were determined by taking seven 50 mL centrifuge tubes using the parallel sample tube method. 20 mL of EC acetonitrile / ethanol solution with a concentration of 200 µg / L was added to each tube, followed by 2 mL of HAc-NaAc (pH=4) buffer solution. Then, 8 mg of magnetically imprinted adsorbent was added. The system was placed on a shaker and shaken at 160 rpm / min for 0–2 h at a constant temperature of 25 °C. The solutions in the tubes were collected at fixed intervals for gas chromatography-mass spectrometry (GC-MS) analysis.

[0053] See results Figure 8The figure shows that adsorption reaches equilibrium at 40 min, with the maximum adsorption capacity Q. max The adsorption capacity can reach 22.40 mg / g, and MIP consistently outperforms NIP in terms of adsorption effect.

[0054] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for preparing a urethane magnetic molecularly imprinted adsorbent, characterized in that, First, by using magnetic Fe3O4, the adsorbent is endowed with recyclable characteristics. Then, through the introduction of a polymerization active group by grafting vinyl, 4-VBA and urethane are added to form a complex by pre-polymerization. A crosslinking agent and an initiator are added to initiate the polymerization reaction. After the reaction, the template is eluted to obtain a magnetic urethane molecularly imprinted adsorbent.

2. The method for preparing a urethane magnetic molecularly imprinted adsorbent according to claim 1, characterized in that, Specifically, the method comprises the following steps: 1) 10-30 mg of nano-Fe3O4 is added to 0.5-1.5 mL of anhydrous ethanol, and ultrasonic dispersion is performed to obtain a mixed solution; 2) The mixed solution obtained in step 1) is taken, tetraethoxysilane is added dropwise, 1 mL of ammonia water with a concentration of 28% is added and stirred, then the solid is separated by a magnet, the separated solid is sequentially washed with water and ethanol, and then dried in a vacuum drying box at 60°C to obtain Fe3O4 coated with SiO2; 3) 40-45 mg of Fe3O4 coated with SiO2 obtained in step 2) is dispersed in 2-5 mL of ethanol again, KH-570 is added dropwise, and the vinyl group is grafted on the surface of the product Fe3O4 coated with SiO2 obtained in step 2). After heating and stirring with an electric heating jacket, the black solid is collected by a magnet, washed with water and ethanol, and dried in a vacuum drying box at 60°C to obtain Fe3O4 grafted with a vinyl group; 4) The Fe3O4 grafted with a vinyl group obtained in step 3) is added to an acetonitrile solution of urethane for imprinting, then 1-1.5 mg of monomer 4-vinylbenzoic acid, 3-4 μL of a crosslinking agent and 0.15-0.25 mg of an initiator are added, the product is collected, the solid is washed with a Soxhlet extractor, dried, and a magnetic urethane molecularly imprinted adsorbent is obtained.

3. The production method according to claim 2, characterized by, The power of ultrasonic treatment in step 1) is 200 W-450 W, and the particle size distribution of nano-Fe3O4 is 50-300 nm.

4. The production method according to claim 2 or 3, characterized by, In step 2), the volume ratio (mL) of the mixed solution to tetraethoxysilane is 1:0.

02.

5. The preparation method according to claim 4, characterized in that, In step 3), the grafting process needs to be heated at 65°C under nitrogen protection, and the reaction is performed for 4 h.

6. The production method according to claim 5, wherein In step 4), the crosslinking agent is ethylene glycol dimethacrylate, and the initiator is azobisisobutyronitrile. The dosage of Fe3O4 grafted with a vinyl group is 1.5-2.5 mg, the dosage of urethane is 1.5-2.0 mg, and the dosage of acetonitrile is 1 mL. The elution solvent in the extractor is methanol and acetic acid, and the volume ratio is 9:

1. The stirring speed of the reaction is 500 rpm, the reaction is performed for 24 h, and the carrier is Fe3O4 grafted with a vinyl group.

7. The use of the magnetic molecularly imprinted adsorbent according to any one of claims 1-5 in adsorbing urethane.

8. A magnetic molecularly imprinted adsorption method for adsorbing ethyl carbamate, characterized by, The method comprises the following steps: A urethane standard solution is prepared by using acetonitrile and ethanol solvents, the solution is mixed with an HAc-NaAc buffer and a molecularly imprinted adsorbent, and the content of urethane before and after adsorption is detected by gas chromatography-mass spectrometry.

9. The magnetic molecularly imprinted adsorption method for adsorbing ethyl carbamate according to claim 8, characterized by, The HAc-NaAc buffer is an acetic acid-sodium acetate buffer.

10. The magnetic molecularly imprinted adsorption method for adsorbing ethyl carbamate according to claim 8, characterized by, The dosage of the magnetic molecularly imprinted adsorbent is 4-20 mg, and the volume of the urethane acetonitrile and ethanol solution is 15-25 mL.

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