Preparation method of a magnetic nano adsorbent

Abstract

The preparation method of a magnetic nano adsorbent belongs to the technical field of magnetic nano material adsorption and separation. The present invention includes the following steps: preparing magnetic microspheres wrapped with silica, then grafting double bonds onto the microspheres, and then using EGDMA as both a functional monomer and a cross-linking agent, and using a plasticizer as a template to form a structure with specific recognition for the plasticizer on the surface of the microspheres. This solution does not require additional addition of functional monomers, reduces the use of raw materials, has a simpler preparation process, and has excellent recognition ability for plasticizers in ethanol aqueous solutions. The adsorption performance is better than that of the synthesis solution with additional addition of functional monomers, and the imprinting factor can reach up to 34.5 at most. This adsorbent can not only be used for the adsorption and removal of plasticizers in water, but also be applicable to the removal of plasticizers in alcohol-containing solutions, which is of great significance for environmental protection and food safety.

Description

Technical Field

[0001] The present invention relates to a preparation method of magnetic ethylene glycol dimethacrylate (EGDMA) nanomaterials, and belongs to the technical field of adsorption and separation of magnetic nanomaterials. Background Art

[0002] Phthalates acid-esters (PAEs) are one of the most widely used plasticizers. Adding them to plastic products can improve the molding and processing performance of plastics, endow the materials with better plasticity and tensile strength, and their presence has been detected in white wine, cosmetics, food packaging bags and water environment. PAEs are often regarded as an androgen or endocrine disruptor. Research shows that low concentrations of PAEs can cause harm to people's endocrine system, nervous system, reproductive system, etc. When reaching a certain concentration value in the body, it is even mutagenic, carcinogenic and teratogenic. Coupled with the frequent occurrence of plasticizer incidents at home and abroad recently, PAEs have become the focus of attention in the fields of environmental protection and food safety.

[0003] In the research on the removal of PAEs, the adsorption method is the commonly used method for removing PAEs at present, and it is also the most effective and reliable method for removing PAEs. However, in the actual system, the pollutants are not only complex in variety, but also uneven in content. The traditional adsorbents have weak anti-interference ability. When adsorbing and removing, the target molecules to be removed are easily affected by other pollutants, resulting in poor adsorption selectivity of the adsorbent. Since the molecularly imprinted polymer has three-dimensional imprinting sites matching the template molecule, it can resist the interference of some impurities in the environmental sample and selectively adsorb the template molecule. Therefore, it has broad application prospects in the detection of pollutants.

[0004] From current research, it is known that molecular imprinting technology has been applied to the removal and detection of various pollutants. However, at present, the preparation of molecularly imprinted polymers mainly uses traditional polymerization methods such as bulk polymerization, such as the research work of Zhang Xiaoming and Wen Fengqiu (Zhang Xiaoming. Preparation, Adsorption Properties and Application Research of Dibutyl Phthalate Imprinted Polymer [D]. Jiangsu University, 2016; Wen Fengqiu. Preparation and Application Research of Dibutyl Phthalate Molecularly Imprinted Polymer [D]. Xiangtan University, 2013). In terms of the selection of functional monomers, it is mainly based on the methacrylic acid (MAA) system, such as the research work of Yuan Xinhua and Yang Rui (Xinhua Yuan, Tiantian Liu, Lei Gao, et al., A convenient separation method for di(2-ethylhexyl)phthalate by novel superparamagnetic molecularly imprinted polymers [J]. ROYAL SOCIETY OF CHEMISTRY, 2018, 8(1): 36191-36199; Rui Yang, Yuxin Liu, Xiangyang Yan, et al., An Effective Method for the Synthesis of Yolk–Shell Magnetic Mesoporous Carbon–Surface Molecularly Imprinted Microspheres [J]. Journal of Materials Chemistry A, 2016, 00(1): 1-3). Although there are innovative improvements to the imprinting sites during the preparation process, the functional monomers forming the imprinted part are still single, which also makes the adsorption materials have disadvantages such as slow mass transfer rate, easy destruction of binding sites, difficulty in eluting template molecules, and long pretreatment period of the prepared materials.

[0005] Through comprehensive collation and comparison of reported literature, it is found that the preparation of such molecularly imprinted materials often requires the addition of monofunctional MAA, which first combines with the template molecule and then participates in the reaction to polymerize with EGDMA. The combination of MAA and the template molecule generally needs to be achieved by low-temperature static placement or long-time stirring. In view of the molecular characteristics of PAEs, its ester groups are not exposed, and it is not easy to combine with MAA. Therefore, MAA is not required in the system, and only EGDMA is needed. EGDMA has a double ester group structure. According to the principle of like dissolves like, it can have good affinity with PAEs. In addition, it has two double bonds in its structure, while MAA has only one double bond. Therefore, after removing MAA, the structure of the polymerized material will be denser. If the double bonds of EGDMA remain after polymerization, they can also undergo electron cloud interaction with the benzene ring of PAEs, further improving the adsorption affinity. The material preparation process omits the pretreatment stage, saves time, and reduces the economic cost of material preparation. Summary of the Invention

[0006] The object of the present invention is to prepare a new type of magnetic nano-molecularly imprinted material mainly composed of EGDMA. The obtained adsorbent material has excellent adsorption performance, strong environmental adaptability, good dispersibility and adsorption stability, and has great practical value in the field of adsorption and removal. In addition, the preparation process of the magnetic EGDMA nano-material is simple in operation and streamlined in steps. The reagent cost is lower than that of the previous MAA system, and the adsorption performance is more excellent, with the potential and value of industrial application.

[0007] The research work of the present invention improves the previous idea of mainly using MAA as the functional monomer and EGDMA as the cross-linking agent to prepare molecularly imprinted materials. According to the structural characteristics of the reagent molecules, EGDMA is used as both the functional monomer and the cross-linking agent. Without pretreatment operations such as pre-polymerization, low-temperature storage and overnight stirring, only one-step polymerization can achieve the two purposes of cavity imprinting of the functional monomer and the template molecule and cross-linking and coating of the material on the surface of the magnetic matrix. It changes the previous method of using MAA to provide hydrogen bonds to fix the template molecule, and uses the more powerful double bonds provided by the bifunctional group structure of EGDMA to replace the previous hydrogen bond fixation. Further strengthening the fixation between the new functional monomer EGDMA and the template molecule makes the formed imprinted cavity more stable. At the same time, EDGMA itself can undergo cross-linking polymerization. While fixing the template molecule, it is more convenient to cross-link the cavity into a dense network and coat it on the surface of the magnetic matrix material to complete the surface molecular imprinting of the material. While providing more and more stable cavity sites, it not only improves the overall adsorption capacity of the material, but also can achieve specific recognition and adsorption.

[0008] Preparation method of magnetic EGDMA nanomaterials: First, disperse 0.2 g of Fe3O4 nanoparticles in 200 mL of ethanol-water mixed solution (volume ratio of ethanol to water is 4:1) by ultrasonic wave, and add 3 mL of ammonia water (NH3·H2O, 28 wt%) into the solution. In the above-mentioned well-dispersed solution, slowly add 2 mL of tetraethyl orthosilicate (TEOS) drop by drop, and mechanically stir for 6 hours. Wash three times with ethanol and distilled water, and then vacuum dry at 50 °C for 6 hours to obtain Fe3O4@SiO2 microspheres. The transmission electron microscope characterization diagram is as Figure 1 shown.

[0009] Under ultrasonic conditions, disperse the obtained Fe3O4@SiO2 microspheres (0.2 g) evenly in toluene (80 mL). Add 6 mL of γ-methacryloxypropyltrimethoxysilane (KH570), purge with nitrogen for 15 min, and then place it in a 65 °C water bath and mechanically stir for 24 hours. After the reaction is completed, separate by an external magnet and wash repeatedly with ethanol and water. Place it in a vacuum dryer at 50 °C and dry for 6 hours to obtain Fe3O4@SiO2@KH570 microspheres.

[0010] Finally, ultrasonically disperse 0.1 mg of Fe3O4@SiO2@KH570 microspheres in 80 mL of acetonitrile solution. Add 1 mmol of phthalate esters (PAEs) as template molecules; 20 mmol of EGDMA acts as both a functional monomer to bind to the template molecules and a cross-linking agent to form fixed cavities; add 40 mg of azobisisobutyronitrile (AIBN) as a reaction initiator. After the entire reaction system is purged with nitrogen to remove oxygen for 30 min, place it in a 65 °C water bath and mechanically stir at 300 rpm for 24 hours to make EGDMA polymerize uniformly and densely on the surface of Fe3O4@SiO2@KH570 with PAEs. After the reaction is completed, separate by an external magnet, wash three times with ultrapure water and ethanol, and then use Soxhlet extraction method with methanol as the elution solution to wash off the template molecules participating in the polymerization and place it in a vacuum drying oven at 50 °C and vacuum dry for 6 hours. The basic structure of the material is as Figure 2 shown.

[0011] The preparation process of magnetic EGDMA materials is simpler and easier than the materials prepared by the previous MAA system, saves reagent costs, and shows good adsorption performance for the adsorption and removal of plasticizers in water and 30% alcohol-containing systems.

[0012] Exploration and control of some basic experimental conditions show that the magnetic EGDMA materials prepared under various conditions exhibit good adsorption performance for plasticizers in water and the 30% alcohol-containing system. For the materials polymerized with template molecules, under the adsorption condition with a maximum experimental adsorption capacity of 4 mg / g, the adsorption capacity in water can reach the theoretical maximum value, and it can also reach 2.907 mg / g in the 30% alcohol-containing system. Moreover, the imprinting factor (the ratio of the adsorption capacity of the imprinted material to that of the non-imprinted material) of the imprinted materials containing template molecules prepared under various conditions and the non-template imprinted polymerized materials is at least 1.3 times, and can reach up to 34.5 times at most. The preparation method of the magnetic EGDMA nanomaterials in this study has strong innovation and application prospects. Description of the Drawings

[0013] Figure 1 Transmission electron micrograph of Fe3O4@SiO2 microspheres

[0014] Figure 2 Schematic diagram of the structure of magnetic EGDMA nanomaterials Detailed Implementation Modes

[0015] The present invention will be specifically described below by way of examples. It should be noted that the examples are only used to further illustrate the present invention and should not be construed as limiting the protection scope of the present invention. Those skilled in the art can make some non-essential improvements and adjustments to the present invention based on the above content of the present invention.

[0016] Adsorption Test Conditions

[0017] The initial concentrations of the four PAEs pollutants (dimethyl phthalate DMP, diethyl phthalate DEP, diallyl phthalate DAP, and dibutyl phthalate DBP) contained in the configured adsorption solution are 10 mg / L respectively, the adsorption volume is 4 mL, the adsorbent is 10 mg, the time is 12 h, the temperature is 30 °C, and the rotation speed of the constant temperature water bath oscillator is 150 rpm.

[0018] For the mentioned adsorption materials, their preparation and adsorption experiments were carried out more than three times, and the adsorption data are the mean values.

[0019] Example 1 Basic Preparation of Materials in the EGDMA System

[0020] First, 0.2 g of Fe3O4 nanoparticles were dispersed in 200 mL of an ethanol-water mixed solution (ethanol: water volume ratio = 4:1) by ultrasonic treatment, and 3 mL of ammonia water (NH3·H2O, 28 wt%) was added to the solution. In the above-mentioned well-dispersed solution, 2 mL of tetraethyl orthosilicate (TEOS) was added dropwise, and mechanical stirring was carried out for 6 hours. It was washed three times with ethanol and distilled water, and then vacuum dried at 50 °C for 6 hours to obtain Fe3O4@SiO2 microspheres.

[0021] Under ultrasonic conditions, the obtained Fe3O4@SiO2 microspheres (0.2 g) were uniformly dispersed in toluene (80 mL). 6 mL of γ-methacryloxypropyltrimethoxysilane (KH570) was added. After purging with nitrogen for 15 min, it was placed in a 65 °C water bath and mechanically stirred for 24 hours. After the reaction was completed, it was separated by an external magnet and repeatedly washed with ethanol and water. It was dried in vacuo at 50 °C for 6 hours to obtain Fe3O4@SiO2@KH570 microspheres.

[0022] Finally, 0.1 mg of Fe3O4@SiO2@KH570 microspheres were ultrasonically dispersed in 80 mL of acetonitrile solution. There were three cases of adding 1 mmol of DBP (66.1 μL), DAP (58.5 μL) as template molecules and not adding PAEs; 20 mmol of EGDMA served as both a functional monomer to bind with the template molecule and a cross-linking agent to form fixed cavities; 40 mg of azobisisobutyronitrile (AIBN) was added as a reaction initiator. After the entire reaction system was purged with nitrogen to remove oxygen for 30 min, it was placed in a 65 °C water bath and mechanically stirred at 300 rpm for 24 hours to uniformly and densely polymerize EGDMA with PAEs on the surface of Fe3O4@SiO2@KH570. After the reaction was completed, it was separated by an external magnet, washed three times with ultrapure water and ethanol, and then extracted by Soxhlet extraction with methanol as the elution solution to wash away the template molecules participating in the polymerization and placed in a vacuum drying oven at 50 °C for vacuum drying for 6 hours.

[0023] The product was named FeSi@EGDMA-M (M is one kind of PAEs molecule). Without adding PAEs, it was a self-polymerized magnetic EGDMA material named FeSi@EGDMA-N. The adsorption data of the EGDMA system materials for four kinds of PAEs in water are shown in Table 1 below, and the adsorption data for PAEs in 30% ethanol content are shown in Table 2 below. The suffix N represents non-imprinted material, and M represents imprinted material.

[0024] Table 1 Adsorption performance of EGDMA system materials for four kinds of PAEs in water

[0025]

[0026] 1 The single component removed refers to the situation where there is only one type of PAEs pollutant (i.e., DBP) in the simulated solution. When the adsorbent adsorbs and removes it, only this one pollutant is adsorbed and removed (the same applies to the following tables).

[0027] 2 The four components removed refer to the situation where there are four types of PAEs pollutants (i.e., DMP, DEP, DAP, and DBP) in the simulated solution. When the adsorbent adsorbs and removes them, these four pollutants are simultaneously adsorbed and removed (the same applies to the following tables).

[0028] Table 2 Adsorption performance of EGDMA system materials for four PAEs in 30% ethanol aqueous solution

[0029]

[0030] From the adsorption data of the three groups of materials in the two adsorption systems, it is obvious that the preparation of the EGDMA system materials was successful. While ensuring a high adsorption capacity in both water and ethanol, the materials with template polymerization showed a much more obvious imprinting factor ((Qe (FeSi@EGDMA-M )) / Qe (FeSi@EGDMA-N )) (the factor range is 1.3 - 34.5).

[0031] Comparative example: Comparison with the prior art: Preparation of materials and adsorption data of the MAA system

[0032] In this scheme, EGDMA is directly used as the functional monomer and cross - linker, while the experimental methods reported in the literature are all of the MAA system, that is, MAA is additionally added as the functional monomer on the basis of this scheme. For comparison, we prepared the materials of the system with MAA according to the method exactly the same as that reported in the literature (Xinhua Yuan, Tiantian Liu, Lei Gao, et al., A convenient separation method for di(2 - ethylhexyl)phthalate by novel superparamagnetic molecularly imprinted polymers[J]. ROYAL SOCIETY OF CHEMISTRY, 2018, 8(1):36191 - 36199). The adsorption data of the materials with MAA for four PAEs in water are shown in Table 3 below, and the adsorption data of the materials with MAA for PAEs in 30% ethanol aqueous solution are shown in Table 4 below.

[0033] Table 3 Adsorption performance of MAA system materials for four PAEs in water

[0034]

[0035] Table 4 Adsorption Performance of MAA System Materials for Four Kinds of PAEs in 30% Ethanol Aqueous Solution

[0036]

[0037] Under the same adsorption conditions, by comparing with the adsorption data of the EGDMA system materials (in the part of "Experimental Example 1"), it can be clearly seen that the materials prepared by the EGDMA system are superior to the MAA system materials in both adsorption capacity and imprinting factor in the two systems.

[0038] The discovery of this system has significantly reduced the cost investment in the preparation process of this type of material, and improved the adsorption performance of the material in practical applications, expanding the scope of use of the material.

[0039] Example 2 Exploration of the Preparation Conditions of EGDMA System Materials - Reaction Time

[0040] First, disperse 0.2 g of Fe3O4 nanoparticles in 200 mL of ethanol-water mixed solution (ethanol: water volume ratio = 4:1) by ultrasonic wave, and add 3 mL of ammonia water (NH3·H2O, 28 wt%) to the solution. In the above-mentioned well-dispersed solution, add 2 mL of tetraethyl orthosilicate (TEOS) dropwise and stir mechanically for 6 hours. Wash three times with ethanol and distilled water, and then dry in vacuum at 50 °C for 6 hours to obtain Fe3O4@SiO2 microspheres.

[0041] Under ultrasonic conditions, disperse the obtained Fe3O4@SiO2 microspheres (0.2 g) evenly in toluene (80 mL). Add 6 mL of γ-methacryloxypropyltrimethoxysilane (KH570), after purging with nitrogen for 15 min, place it in a water bath at 65 °C and stir mechanically for 24 hours. After the reaction, separate by an external magnet and wash repeatedly with ethanol and water. Dry in vacuum at 50 °C for 6 hours to obtain Fe3O4@SiO2@KH570 microspheres.

[0042] Finally, ultrasonically disperse 0.1 mg of Fe3O4@SiO2@KH570 microspheres in 80 mL of acetonitrile solution. There are two cases: adding 1 mmol of DBP (66.1 μL) as the template molecule and not adding PAEs; 20 mmol of EGDMA acts as both the functional monomer to bind with the template molecule and the cross-linking agent to form fixed cavities; add 40 mg of azobisisobutyronitrile (AIBN) as the reaction initiator. After purging the oxygen in the whole reaction system with nitrogen for 30 min, place it in a water bath at 65 °C and stir mechanically at 300 rpm for reaction times of 8 - 32 hours respectively, so that EGDMA and PAEs are uniformly and densely polymerized on the surface of Fe3O4@SiO2@KH570.

[0043] After the reaction is completed, magnetic separation is carried out with an external magnet, and after washing three times with ultrapure water and ethanol, by means of Soxhlet extraction, using methanol as the elution solution, the template molecules participating in the polymerization are washed off and placed in a vacuum drying oven for vacuum drying at 50 °C for 6 hours. The material with the template molecule added is denoted as -M (the template is DBP), the material without the template molecule added is denoted as -N, and the preparation time unit in hours is written as H. The adsorption data of materials with different polymerization times for four PAEs in water are shown in Table 5 below, and the adsorption data of materials with different polymerization times for PAEs in 30% ethanol aqueous solution are shown in Table 6 below.

[0044] Table 5 Adsorption performance of materials with different polymerization times for four PAEs in water

[0045]

[0046] Table 6 Adsorption performance of materials with different polymerization times for four PAEs in 30% ethanol aqueous solution

[0047]

[0048] Based on the adsorption data of the materials prepared at four polymerization reaction times, it can be seen that 24 hours is the optimal polymerization time.

[0049] Example 3 Exploration of material preparation conditions in the EGDMA system - Template selection

[0050] First, 0.2 g of Fe3O4 nanoparticles are dispersed in 200 mL of ethanol-water mixed solution (ethanol: water volume ratio = 4:1) by ultrasonic wave, and 3 mL of ammonia water (NH3·H2O, 28 wt%) is added to the solution. In the above-mentioned well-dispersed solution, 2 mL of tetraethyl orthosilicate (TEOS) is added dropwise, and mechanical stirring is carried out for 6 hours. After washing three times with ethanol and distilled water, it is then vacuum dried at 50 °C for 6 hours to obtain Fe3O4@SiO2 microspheres.

[0051] Under ultrasonic conditions, the obtained Fe3O4@SiO2 microspheres (0.2 g) are uniformly dispersed in toluene (80 mL). 6 mL of γ-methacryloxypropyltrimethoxysilane (KH570) is added, after nitrogen is bubbled for 15 min, it is placed in a water bath at 65 °C and mechanically stirred for 24 hours. After the reaction is completed, separation is carried out by an external magnet, and it is repeatedly washed with ethanol and water. It is placed in a vacuum for drying at 50 °C for 6 hours to obtain Fe3O4@SiO2@KH570 microspheres.

[0052] Finally, 0.1 mg of Fe3O4@SiO2@KH570 microspheres were ultrasonically dispersed in 80 mL of acetonitrile solution. 1 mmol of DMP, bis(2-ethylhexyl) phthalate (DEHP), and diisononyl phthalate (DINP) were added respectively as template molecules; 20 mmol of EGDMA served both as a functional monomer to bind with the template molecules and as a crosslinking agent to form fixed cavities; 40 mg of azobisisobutyronitrile (AIBN) was added as a reaction initiator. After the entire reaction system was purged with nitrogen gas for 30 min to remove oxygen, it was placed in a 65 °C water bath and mechanically stirred at 300 rpm for 24 h to polymerize EGDMA and PAEs uniformly and densely on the surface of Fe3O4@SiO2@KH570.

[0053] After the reaction was completed, magnetic separation was carried out with an external magnet, and it was washed three times with ultrapure water and ethanol. Then, by means of Soxhlet extraction, methanol was used as the elution solution to wash away the template molecules participating in the polymerization, and it was placed in a vacuum drying oven and dried under vacuum at 50 °C for 6 h. The material added with template molecules is denoted as -M, and the material without added template molecules is denoted as -N. The adsorption data of materials with different template molecules for four PAEs in water are shown in Table 7 below, and the adsorption data of materials with different template molecules for PAEs in 30% ethanol aqueous solution are shown in Table 8 below.

[0054] Table 7 Adsorption performance of materials with different template molecules for four PAEs in water

[0055]

[0056] Table 8 Adsorption performance of materials with different template molecules for four PAEs in 30% ethanol aqueous solution

[0057]

[0058] Adding the two templates DBP and DAP used previously, and selecting three templates with different lengths to prepare materials. From the adsorption data, for the four PAEs existing in the adsorption system, when DBP was used as the template, the prepared materials still showed better performance.

[0059] Example 4 Exploration of the material preparation conditions of the EGDMA system - reaction temperature

[0060] First, 0.2 g of Fe3O4 nanoparticles were ultrasonically dispersed in 200 mL of ethanol-water mixed solution (ethanol: water volume ratio = 4:1), and 3 mL of ammonia water (NH3·H2O, 28 wt%) was added to the solution. In the above-mentioned well-dispersed solution, 2 mL of tetraethyl orthosilicate (TEOS) was added dropwise and mechanically stirred for 6 h. It was washed three times with ethanol and distilled water, and then vacuum dried at 50 °C for 6 h to obtain Fe3O4@SiO2 microspheres.

[0061] Under ultrasonic conditions, the obtained Fe3O4@SiO2 microspheres (0.2 g) were uniformly dispersed in toluene (80 mL). 6 mL of γ-methacryloxypropyltrimethoxysilane (KH570) was added. After purging with nitrogen for 15 min, the mixture was placed in a water bath at 60 - 70 °C and mechanically stirred for 24 hours. After the reaction, it was separated by an external magnet and washed repeatedly with ethanol and water. It was dried in vacuo at 50 °C for 6 hours to obtain Fe3O4@SiO2@KH570 microspheres.

[0062] Finally, 0.1 mg of Fe3O4@SiO2@KH570 microspheres were ultrasonically dispersed in 80 mL of acetonitrile solution. Two cases were considered: adding 1 mmol of DBP as a template molecule and not adding a template molecule; 20 mmol of EGDMA served as both a functional monomer to bind with the template molecule and a cross-linking agent to form fixed cavities; 40 mg of azobisisobutyronitrile (AIBN) was added as a reaction initiator. After the entire reaction system was purged with nitrogen to remove oxygen for 30 min, it was placed in a water bath at 60 °C, 65 °C, and 70 °C respectively and mechanically stirred at 300 rpm for 24 hours to polymerize EGDMA and PAEs uniformly and densely on the surface of Fe3O4@SiO2@KH570.

[0063] After the reaction, it was separated by an external magnet and washed three times with ultrapure water and ethanol. Then, by means of Soxhlet extraction, with methanol as the elution solution, the template molecules participating in the polymerization were washed away and dried in a vacuum drying oven at 50 °C in vacuo for 6 hours. The material with the added template molecule is denoted as -M (template is DBP), and the material without the added template molecule is denoted as -N. The adsorption data of the materials at different reaction temperatures for four PAEs in water are shown in Table 9 below, and the adsorption data for PAEs in 30% ethanol aqueous solution are shown in Table 10 below.

[0064] Table 9 Adsorption performance of materials at different reaction temperatures for four PAEs in water

[0065]

[0066] Table 10 Adsorption performance of materials at different reaction temperatures for four PAEs in 30% ethanol aqueous solution

[0067]

[0068] The reaction temperature was selected as 60 °C, 65 °C, and 70 °C based on the active range of the initiator. Considering the comprehensive energy consumption and adsorption performance, the reaction temperature was set at 65 °C as the best.

[0069] Example 5 Exploration of the material preparation conditions of the EGDMA system - stirring speed

[0070] First, 0.2 g of Fe3O4 nanoparticles were dispersed in 200 mL of an ethanol-water mixed solution (ethanol: water volume ratio = 4:1) by ultrasonic waves, and 3 mL of ammonia water (NH3·H2O, 28 wt%) was added to the solution. In the above-mentioned well-dispersed solution, 2 mL of tetraethyl orthosilicate (TEOS) was added dropwise, and mechanical stirring was carried out for 6 hours. It was washed three times with ethanol and distilled water, and then vacuum dried at 50 °C for 6 hours to obtain Fe3O4@SiO2 microspheres.

[0071] Under ultrasonic conditions, the obtained Fe3O4@SiO2 microspheres (0.2 g) were uniformly dispersed in toluene (80 mL). 6 mL of γ-methacryloxypropyltrimethoxysilane (KH570) was added. After purging with nitrogen for 15 min, it was placed in a water bath at 60 - 70 °C and mechanically stirred for 24 hours. After the reaction ended, it was separated by an external magnet and washed repeatedly with ethanol and water. It was dried in vacuo at 50 °C for 6 hours to obtain Fe3O4@SiO2@KH570 microspheres.

[0072] Finally, 0.1 mg of Fe3O4@SiO2@KH570 microspheres were ultrasonically dispersed in 80 mL of acetonitrile solution. Two cases were considered: adding 1 mmol of DBP as the template molecule and not adding the template molecule; 20 mmol of EGDMA served as both the functional monomer to bind with the template molecule and the cross-linking agent to form fixed cavities; 40 mg of azobisisobutyronitrile (AIBN) was added as the reaction initiator. After the entire reaction system was purged with nitrogen to remove oxygen for 30 min, it was placed in a water bath at 65 °C and mechanically stirred at 300 rpm and 500 rpm for 24 hours respectively, so that EGDMA and PAEs were uniformly and densely polymerized on the surface of Fe3O4@SiO2@KH570.

[0073] After the reaction ended, it was separated by an external magnet and washed three times with ultrapure water and ethanol. Then, in the way of Soxhlet extraction, with methanol as the elution solution, the template molecules participating in the polymerization were washed away and placed in a vacuum drying oven at 50 °C for vacuum drying for 6 hours. The material with the template molecule added is denoted as -M (the template is DBP), and the material without the template molecule added is denoted as -N. The adsorption data of materials with different reaction temperatures for four PAEs in water are shown in Table 11 below, and the adsorption data for PAEs in 30% ethanol aqueous solution are shown in Table 12 below.

[0074] Table 11 Adsorption performance of materials with different stirring speeds for four PAEs in water

[0075]

[0076] Table 12 Adsorption performance of materials with different stirring speeds for four PAEs in 30% ethanol aqueous solution

[0077]

[0078] The reaction stirring speed will, to a certain extent, accelerate the rate of the polymerization reaction. Considering the comprehensive motor energy consumption and adsorption performance, the stirring speed during the reaction is selected to be 300 rpm as the best.

Claims

1. A preparation method of a magnetic nano adsorbent, characterized in that, It includes the following steps: (1) Disperse 0.2 g of Fe3O4 nanoparticles in 200 mL of an ethanol-water mixed solution by ultrasonic wave, and add 3 mL of ammonia water with a concentration of 28 wt%; in the ethanol-water mixed solution, the volume ratio of ethanol to water is 4:1; in the above-mentioned well-dispersed solution, dropwise add 2 mL of tetraethyl orthosilicate, and mechanically stir for 6 hours; wash three times with ethanol and distilled water, and then vacuum dry at 50 °C for 6 hours to obtain Fe3O4@SiO2 microspheres; (2) Under ultrasonic conditions, uniformly disperse 0.2 g of Fe3O4@SiO2 microspheres in 80 mL of toluene; add 6 mL of γ-methacryloxypropyltrimethoxysilane, after nitrogen bubbling for 15 min, place it in a 65 °C water bath and mechanically stir for 24 hours; after the reaction is completed, separate by an external magnet, and wash repeatedly with ethanol and water; place it in a vacuum at 50 °C and dry for 6 hours to obtain Fe3O4@SiO2@KH570 microspheres; (3) Ultrasonically disperse 0.1 mg of Fe3O4@SiO2@KH570 microspheres in 80 mL of acetonitrile solution; add 1 mmol of phthalate ester as a template molecule; add ethylene glycol dimethacrylate EGDMA, which acts as both a functional monomer to bind to the template molecule and a cross-linking agent to form a fixed cavity, and the molar ratio of the template molecule to EGDMA is 1:18 - 1:21; add 40 mg of azobisisobutyronitrile as a reaction initiator; after the entire reaction system is filled with a nitrogen atmosphere and deoxygenated by bubbling for 30 min, place it in a 60 - 70 °C water bath and mechanically stir at 300 rpm for 8 - 32 h to polymerize EGDMA and PAEs on the surface of Fe3O4@SiO2@KH570.

2. The preparation method according to claim 1, wherein: The phthalate ester template molecule in the step (3) is one or more of dimethyl phthalate DMP, diethyl phthalate DEP, diallyl phthalate DAP, dibutyl phthalate DBP, bis(2-ethylhexyl) phthalate DEHP, or diisononyl phthalate DINP.

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