A magnetic chitosan polyelectrolyte brush and its preparation method and application

Abstract

The present invention provides a magnetic chitosan polyelectrolyte brush, a preparation method and application thereof. The preparation method of the magnetic chitosan polyelectrolyte brush comprises the following steps: preparation of magnetic chitosan particles, preparation of magnetic chitosan particles, initiation reaction and graft polymerization reaction. The preparation method of the present invention adopts microfluidic technology combined with a one-step method to prepare magnetic chitosan particles. The prepared magnetic chitosan particles have better magnetic responsiveness and more uniform particle size. In addition, the magnetic chitosan particles are modified with methacrylic anhydride (MA) and then grafted with a photoinitiator HMEM, which can provide more grafting sites for subsequent grafted polymer chains, thereby improving the grafting efficiency and grafting density of the subsequent grafted polymer chains.

Description

Technical Field

[0001] The invention belongs to the technical field of functional polymer materials, and particularly relates to a magnetic chitosan polyelectrolyte brush and a preparation method and application thereof. Background Art

[0002] Nanopolyelectrolytes are widely used in protein adsorption, heavy metal adsorption, water treatment and other fields due to their surface charge, but their recovery is difficult and costly; nanomagnetic adsorbents have a large specific surface area, their magnetic core can be quickly separated by a magnetic field, and their outer layer can adsorb heavy metal ions and dyes through electrostatic effects, but they have stability issues, high preparation costs, limited regeneration efficiency and selectivity for specific pollutants.

[0003] Magnetic chitosan polyelectrolyte brushes are a special polymer structure formed by combining charged polymer chains (polyelectrolyte brushes) with magnetic chitosan. This material usually has a core-shell structure, in which the core part is composed of magnetic materials (such as ferrite, etc.) and the shell part is composed of chitosan and its modified polyelectrolyte brushes. Chitosan chains carry a large number of active groups (such as amino, hydroxyl, etc.), which can further combine with polyelectrolyte chains to form a brush-like structure; because the material contains magnetic components, the magnetic chitosan polyelectrolyte brush has magnetic responsiveness and can be manipulated and separated by an external magnetic field; the polyelectrolyte brush part is responsive to specific external environmental conditions (such as pH value, ionic strength, temperature, etc.) and can change its conformation and surface properties; chitosan is a natural polymer with good biocompatibility and biodegradability, so the magnetic chitosan polyelectrolyte brush has potential application value in the biomedical field; because the chitosan chain carries a large number of active groups and the polyelectrolyte brush structure can increase the specific surface area and adsorption sites of the material, the magnetic chitosan polyelectrolyte brush exhibits excellent performance in the fields of adsorption and separation.

[0004] Existing methods for preparing magnetic chitosan polyelectrolyte brushes mainly involve chemically modifying the surface of a magnetic core to form a chitosan layer, and then using physical adsorption or chemical modification to graft charged polymer chains onto the surface of the chitosan layer to form a polyelectrolyte brush structure. The magnetic chitosan polyelectrolyte brush material prepared by this method has uneven particle size and poor magnetic responsiveness. In addition, the grafting reaction efficiency during the preparation process is low, and only a single polyelectrolyte chain can be grafted, resulting in a small number of target functional groups. Summary of the Invention

[0005] In view of the shortcomings of the current preparation methods of magnetic chitosan polyelectrolyte brushes, the purpose of the present invention is to provide a magnetic chitosan polyelectrolyte brush and its preparation method and application, so as to solve the problems of low preparation efficiency, single polyelectrolyte chain that can be grafted, few target functional groups, and uneven particle size of the prepared magnetic chitosan polyelectrolyte brush material and poor magnetic responsiveness of the existing preparation methods.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] The first aspect of the present invention is to provide a method for preparing a magnetic chitosan polyelectrolyte brush, comprising the following steps:

[0008] S1. Preparation of magnetic chitosan particles: According to the molar ratio of Fe 2+ :Fe 3+ =1:1-2 Take divalent and trivalent iron salts and fully dissolve them in deionized water to obtain a first solution; add the first solution dropwise to the alkaline chitosan solution to obtain magnetic chitosan particles in one step;

[0009] S2 modification of magnetic chitosan particles: using methacrylic anhydride to modify the surface of the magnetic chitosan particles to obtain methacrylated magnetic chitosan particles;

[0010] S3 initiation reaction: Under a nitrogen atmosphere, a photoinitiator HMEM was grafted onto the surface of the methacrylated magnetic chitosan particles to obtain magnetic chitosan particles with a photoinitiator HMEM on the surface;

[0011] S4. Graft polymerization reaction: The magnetic chitosan particles with the photoinitiator HMEM on the surface are mixed with functional monomers. Under oxygen-free and ultraviolet light irradiation conditions, the functional monomers are grafted on the surface of the magnetic chitosan particles to form an elongated molecular chain structure, thereby preparing a magnetic chitosan polyelectrolyte brush.

[0012] Furthermore, in step S1, the molar ratio of the divalent iron salt to the trivalent iron salt is Fe 2+ :Fe 3+ =1:1.5.

[0013] When the molar ratio of ferrous salt to ferric salt is Fe 2+ :Fe 3+ =1:1.5, the prepared magnetic chitosan particles have the best particle size uniformity and the best magnetic responsiveness.

[0014] Furthermore, the preparation of the magnetic chitosan particles in step S1 specifically includes the following steps:

[0015] S11. Weigh ferric chloride and ferrous chloride according to a molar ratio of FeCl2: FeCl3 = 1:1 to 2 and fully dissolve them in deionized water to obtain a first solution;

[0016] S12. Weigh a certain amount of chitosan and add it to deionized water, stir and disperse it thoroughly, and adjust the pH of the chitosan solution to 10-13 using sodium hydroxide to obtain an alkaline chitosan solution;

[0017] S13. The first solution is placed in a syringe pump, propelled by the syringe pump, thoroughly mixed by a vortex mixer, and then added dropwise to the alkaline chitosan solution. The alkaline chitosan solution is stirred during addition. After the addition is completed, the reaction is continued with stirring for 1 to 2 hours; wherein the stirring speed is: 800 to 1200 r / min;

[0018] S14. After the reaction is completed, the magnetic chitosan particles are obtained by multiple water washing and external magnetic field purification.

[0019] Furthermore, in step S2, the preparation of the methacrylated magnetic chitosan particles specifically includes the following steps:

[0020] S21. The magnetic chitosan particles and the carbonate-sodium bicarbonate buffer solution are mixed and stirred to dissolve, and the pH is adjusted to 8 to 10 to obtain a second solution;

[0021] S22. Add a certain amount of methacrylic anhydride to the second solution and react at 50-55°C in the dark for 1.5-2.5h;

[0022] S23. After the reaction is completed in the dark, the product obtained in step S22 is washed with water multiple times and then collected by an external magnetic field to obtain the methacrylated magnetic chitosan particles.

[0023] Furthermore, the structural formula of the methacrylic anhydride is:

[0024]

[0025] Furthermore, in step S3, the preparation of the magnetic chitosan particles with a photoinitiator HMEM on the surface specifically includes the following steps:

[0026] S31. Take the methacrylated magnetic chitosan particles, add a small amount of potassium persulfate, and dissolve in deionized water to obtain a third solution;

[0027] S32. Under a nitrogen atmosphere, 70-90°C, the photoinitiator HMEM was slowly added to the third solution at a rate of 2 to 3 drops per second through a syringe, and the reaction was protected from light for 1.5 to 2.5 hours;

[0028] S33. After the light-proof reaction is completed, the product obtained in step S32 is washed with water several times and then collected by an external magnetic field to obtain the magnetic chitosan particles with the photoinitiator HMEM on the surface.

[0029] Furthermore, the photoinitiator HMEM is 2-[p-(2-hydroxy-2-methylpropiophenone)]-ethylene glycol-methacrylate (HMEM); the structural formula of the photoinitiator HMEM is:

[0030]

[0031] Furthermore, the photoinitiator HMEM is synthesized from 2-hydroxy-4'-[(2-hydroxyethoxy)-2-methylpropiophenone (HMP)] as a raw material, by introducing a terminal double bond through the Schotten-Baumann reaction of its hydroxyl group and methacryloyl chloride (MC).

[0032] Furthermore, in step S4, the preparation of the magnetic chitosan polyelectrolyte brush specifically includes the following steps:

[0033] S41. Magnetic chitosan particles with a photoinitiator HMEM on their surfaces were mixed with functional monomers and then subjected to a graft polymerization reaction under ultraviolet light using nitrogen as a protective gas. The functional monomers were grafted onto the surface of the magnetic chitosan particles to form elongated molecular chains. The reaction was allowed to proceed for 1.5 to 2.5 hours to prepare a magnetic chitosan polyelectrolyte brush.

[0034] S42. The product obtained in step S41 is washed with water multiple times and then collected by applying an external magnetic field to obtain a purified magnetic chitosan polyelectrolyte brush.

[0035] Furthermore, in step S41, the mass ratio of the functional monomer to the magnetic chitosan particles with a photoinitiator HMEM on the surface is (1-10):1.

[0036] Furthermore, in step S41, the mass ratio of the functional monomer to the magnetic chitosan particles with a photoinitiator HMEM on the surface is 3:1.

[0037] When the mass ratio of functional monomers to magnetic chitosan particles with photoinitiator HMEM on the surface is 3:1, the particle size uniformity of the prepared magnetic chitosan polyelectrolyte brushes is the best.

[0038] Furthermore, the functional monomer is methacryloyloxyethyltrimethylammonium chloride (DMC), acrylic acid (AA), 2-acrylamide-2-methylpropanesulfonic acid (AMPS), sodium p-styrenesulfonate (SS), 2-aminoethyl ester hydrochloride (AMA) or [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfonic acid propyl) ammonium hydroxide (SBMA).

[0039] The second aspect of the present invention is to provide a magnetic chitosan polyelectrolyte brush prepared according to the above preparation method.

[0040] The third aspect of the present invention is to provide an application of a magnetic chitosan polyelectrolyte brush in the field of wastewater treatment. The magnetic chitosan polyelectrolyte brush is the above-mentioned magnetic chitosan polyelectrolyte brush or is prepared by the above-mentioned preparation method.

[0041] Compared with the prior art, the present invention has at least the following beneficial effects:

[0042] The present invention's method for preparing magnetic chitosan polyelectrolyte brushes utilizes microfluidics (using a syringe pump for propulsion, followed by dropwise addition to a magnetic chitosan solution after thorough mixing in a vortex mixer, enabling full control of the ratio and rate of addition of the mixed solution) combined with a one-step process to produce magnetic chitosan particles. The resulting magnetic chitosan particles exhibit enhanced magnetic responsiveness and a more uniform particle size. Furthermore, the magnetic chitosan particles, modified with methacrylic anhydride (MA) and then grafted with a photoinitiator, HMEM, provide more grafting sites for subsequent grafted polymer chains, thereby improving the grafting efficiency and density of the subsequent grafted polymer chains.

[0043] 2. Compared with the traditional method of grafting polymer chains, the preparation method of the magnetic chitosan polyelectrolyte brush of the present invention adopts the photoinitiated polymerization method to prepare the magnetic chitosan polyelectrolyte brush. While grafting more charged functional groups, it greatly improves the reaction efficiency and has good repeatability, and has a broader application prospect in the field of water treatment.

[0044] 3. The present invention adopts a photopolymerization method to prepare a magnetic chitosan polyelectrolyte brush by surface grafting. The surface grafting density is high, and the grafting density can be regulated by the amount of photoinitiator added. The brush layer thickness of the magnetic chitosan polyelectrolyte brush can be adjusted by changing the monomer amount, reaction time, ionic strength and pH value.

[0045] 4. The present invention prepares magnetic chitosan polyelectrolyte brushes through photoinitiated polymerization. By controlling the feed mass ratio (grafted monomer: magnetic chitosan nanoparticles) and polymerization reaction time, the polyelectrolyte chain length of the obtained magnetic chitosan polyelectrolyte brushes can be effectively controlled. In addition, no toxic substances that are difficult to remove are introduced during the preparation process. The brushes have good biocompatibility, which gives them broad application prospects in biomedical applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 This is a flow chart for preparing the magnetic chitosan polyelectrolyte brush according to Example 2 of the present invention.

[0047] Figure 2IR spectra of magnetic chitosan particles (CS-MNP) and cationic magnetic chitosan polyelectrolyte brushes (MSPB-DMC) prepared in Example 1 of the present invention.

[0048] Figure 3 This is a dynamic hysteresis loop diagram of the cationic magnetic chitosan polyelectrolyte brush (MSPB-DMC) prepared in Example 1 of the present invention.

[0049] Figure 4 The electron microscope and physical pictures of the magnetic chitosan particles (CS-MNP) and cationic magnetic chitosan polyelectrolyte brushes (MSPB-DMC) prepared in Example 1 of the present invention are shown. DETAILED DESCRIPTION

[0050] The present invention will be further described below with reference to specific embodiments in conjunction with the accompanying drawings. It should be understood that these embodiments are only intended to illustrate the present invention and are not intended to limit the scope of the present invention.

[0051] The preparation method of the magnetic chitosan polyelectrolyte brush of the present invention comprises the following steps: dissolving divalent and trivalent iron salts in deionized water, and then adding the salts dropwise to an alkaline chitosan solution using microfluidic technology to prepare magnetic chitosan particles in one step; modifying the surface of the magnetic chitosan particles with methacrylic anhydride (MA), and then grafting a laboratory-made photoinitiator 2-[p-(2-hydroxy-2-methylpropiophenone)]-ethylene glycol-methacrylate (HMEM); and finally grafting different functional monomers such as methacryloyloxyethyltrimethylammonium chloride (DMC), acrylic acid (AA), 2-acrylamide-2-methylpropanesulfonic acid (AMPS), sodium p-styrenesulfonate (SS), 2-aminoethyl ester hydrochloride (AMA), and [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfonic acid propyl)ammonium hydroxide (SBMA) under ultraviolet light through a photoinitiated polymerization reaction to prepare the magnetic chitosan polyelectrolyte brush.

[0052] The light removal initiator 2-[p-(2-hydroxy-2-methylpropiophenone)]-ethylene glycol-methacrylate (HMEM) used in the present invention is a drug that can be purchased on the market.

[0053] The structural formula of methacrylic anhydride is:

[0054]

[0055] The preparation method of the photoinitiator (HMEM) is as follows: using 2-hydroxy-4'-[(2-hydroxyethoxy)-2-methylpropiophenone) (HMP) as a raw material, utilizing its hydroxyl group and methacryloyl chloride (MC) to introduce a terminal double bond through the Schotten-Baumann reaction to synthesize the photoinitiator 2-[p-(2-hydroxy-2-methylpropiophenone)]-ethylene glycol-methacrylate (HMEM).

[0056] The structural formula of the photoinitiator (HMEM) is:

[0057]

[0058] The chain length of the magnetic chitosan polyelectrolyte brush of the present invention = (D 磁性壳聚糖聚电解质刷 -D 磁性壳聚糖粒子 ) / 2

[0059] Example 1

[0060] The preparation of the cationic magnetic chitosan polyelectrolyte brush (MSPB-DMC) of this embodiment comprises the following steps:

[0061] 1. Preparation of magnetic chitosan particles:

[0062] S11. Weigh 0.2 mol of ferric chloride and 0.3 mol of ferrous chloride and dissolve them in 50 ml of deionized water to obtain a first solution;

[0063] S12. Take 2g chitosan and 300ml deionized water in a three-necked flask, disperse with high-speed stirring, and adjust the pH of the chitosan solution to 12 using sodium hydroxide to obtain an alkaline chitosan solution;

[0064] S13. The first solution was placed in a syringe pump, propelled by a syringe pump, thoroughly mixed by a vortex mixer, and then added dropwise to the alkaline chitosan solution. The alkaline chitosan solution was stirred during addition. After the addition was completed, the reaction was continued with stirring for 1 h; wherein the stirring speed was 800 r / min;

[0065] S14. After the reaction is completed, the magnetic chitosan particles are obtained by multiple water washing and external magnetic field purification.

[0066] 2. Modification of magnetic chitosan particles:

[0067] S21. 1 g of the magnetic chitosan particles obtained in step S14 was dissolved in 100 ml of 1 M carbonate-sodium bicarbonate buffer, mixed and stirred to dissolve, and the pH was adjusted to 9 to obtain a second solution;

[0068] S22. 1.17 ml of methacrylic anhydride was added to the second solution and reacted at 50-55 ° C in the dark for 2 h;

[0069] S23. After the reaction is completed in the dark, the product obtained in step S22 is washed with water several times and then collected by an external magnetic field to obtain methacrylated magnetic chitosan particles.

[0070] 3. Triggering reaction:

[0071] S31. Take 0.5g of methacrylated magnetic chitosan particles obtained in step S23, 10mg of potassium persulfate and 100ml of deionized water and fully dissolve to obtain a third solution;

[0072] S32. The third solution was placed in a three-necked flask, evacuated with nitrogen five times, and placed in a 75°C oil bath with stirring. 0.5 g of the photoinitiator HMEM was slowly added to the third solution using a syringe (at a rate of 2 to 3 drops / s). The reaction was incubated in the dark for 1.5 h.

[0073] S33. After the light-proof reaction is completed, the product obtained in step S32 is washed with water several times and then collected by an external magnetic field to obtain the magnetic chitosan particles with the photoinitiator HMEM on the surface.

[0074] 4. Graft polymerization reaction:

[0075] S41. Weigh 0.5 g of the magnetic chitosan particles with the photoinitiator HMEM obtained in step S33 and 1.5 g of methacryloyloxyethyltrimethylammonium chloride (DMC) and add them to a photoreactor. Use nitrogen as a protective gas and carry out a graft polymerization reaction under ultraviolet light. The functional monomer is grafted on the surface of the magnetic chitosan particles to form an elongated molecular chain structure. The reaction is carried out for 2 h to prepare a cationic magnetic chitosan polyelectrolyte brush (MSPB-DMC).

[0076] S42. The product obtained in step S41 is washed with water multiple times and then collected by an external magnetic field to obtain a purified cationic magnetic chitosan polyelectrolyte brush (MSPB-DMC). The chain length of the obtained magnetic chitosan polyelectrolyte brush is 213 nm.

[0077] The magnetic chitosan particles obtained in step S14 and the cationic magnetic chitosan polyelectrolyte brush (MSPB-DMC) obtained in step S42 were characterized by infrared spectroscopy. Figure 2 As shown, from Figure 2 It can be seen that the prepared magnetic chitosan nanoparticles and cationic magnetic chitosan polyelectrolyte brushes (MSPB-DMC) both detected the characteristic peak of chitosan at 1637 cm -1 , 3308cm -1 , 601cm -1 The characteristic peak of magnetic nanoparticles, 893 cm -1It is the characteristic peak of functional monomer DMC, proving the successful grafting of DMC.

[0078] The cationic magnetic chitosan polyelectrolyte brush (MSPB-DMC) obtained in step S42 was subjected to VSM characterization, and the dynamic hysteresis loop diagram is shown as follows: Figure 3 As shown, from Figure 3 It can be seen that the saturation magnetic response intensity of the magnetic chitosan polyelectrolyte brush is 18.12emu / g, the magnetic responsiveness is strong, and it can be quickly adsorbed by external magnetism.

[0079] The magnetic chitosan particles (CS-MNP) obtained in step S14 and the cationic magnetic chitosan polyelectrolyte brushes (MSPB-DMC) obtained in step S42 were characterized by SEM and TEM. Figure 4 As shown, Figure 4 The left picture in the middle is an electron microscope image and a physical picture of the magnetic chitosan particles (CS-MNP) obtained in step S14; the right picture is an electron microscope image and a physical picture of the cationic magnetic chitosan polyelectrolyte brush (MSPB-DMC) obtained in step S42; Figure 4 It can be seen that the prepared magnetic chitosan particles (CS-MNP) and magnetic chitosan polyelectrolyte brushes (MSPB-DMC) are granular and have relatively uniform particle size.

[0080] Example 2

[0081] Preparation of cationic magnetic chitosan polyelectrolyte brushes (MSPB-AMPS) in this example (see Figure 1 ), compared with Example 1, the difference of this embodiment is that the functional monomers used in the graft polymerization reaction are different, specifically:

[0082] S41. Weigh 0.5 g of the magnetic chitosan particles with the photoinitiator HMEM on the surface obtained in step S33 and 1.5 g of 2-acrylamide-2-methylpropanesulfonic acid (AMPS) and add them to a photoreactor. Use nitrogen as a protective gas and carry out graft polymerization under ultraviolet light. The functional monomer is grafted on the surface of the magnetic chitosan particles to form an elongated molecular chain structure. The reaction is carried out for 2 h to prepare a cationic magnetic chitosan polyelectrolyte brush MSPB-AMPS.

[0083] S42. The product obtained in step S41 is washed with water multiple times and then collected by an external magnetic field to obtain a purified cationic magnetic chitosan polyelectrolyte brush MSPB-AMPS. The chain length of the obtained magnetic chitosan polyelectrolyte brush is 197 nm.

[0084] Example 3

[0085] The preparation of the cationic magnetic chitosan polyelectrolyte brush (MSPB-AA) in this embodiment is different from that in Example 1 in that the functional monomers used in the graft polymerization reaction are different, specifically:

[0086] S41. Weigh 0.5 g of the magnetic chitosan particles with the photoinitiator HMEM obtained in step S33 and 1.5 g of acrylic acid (AA) and add them to a photoreactor. Use nitrogen as a protective gas and carry out graft polymerization under ultraviolet light. The functional monomers are grafted on the surface of the magnetic chitosan particles to form an elongated molecular chain structure. The reaction is carried out for 2 h to prepare a cationic magnetic chitosan polyelectrolyte brush MSPB-AA.

[0087] S42. The product obtained in step S41 is washed with water multiple times and then collected by an external magnetic field to obtain a purified cationic magnetic chitosan polyelectrolyte brush MSPB-AA. The chain length of the obtained magnetic chitosan polyelectrolyte brush is 155 nm.

[0088] Example 4

[0089] The preparation of the cationic magnetic chitosan polyelectrolyte brush (MSPB-SS) in this embodiment is different from that in Example 1 in that the functional monomers used in the graft polymerization reaction are different, specifically:

[0090] S41. Weigh 0.5 g of the magnetic chitosan particles with the photoinitiator HMEM obtained in step S33 and 1.5 g of sodium p-styrene sulfonate (SS) and add them to a photoreactor. Use nitrogen as a protective gas and carry out graft polymerization under ultraviolet light. The functional monomers are grafted on the surface of the magnetic chitosan particles to form an elongated molecular chain structure. The reaction is carried out for 2 h to prepare a cationic magnetic chitosan polyelectrolyte brush MSPB-SS.

[0091] S42. The product obtained in step S41 is washed with water multiple times and then collected by an external magnetic field to obtain a purified cationic magnetic chitosan polyelectrolyte brush MSPB-SS. The chain length of the obtained magnetic chitosan polyelectrolyte brush is 98 nm.

[0092] Example 5

[0093] The preparation of the cationic magnetic chitosan polyelectrolyte brush (MSPB-AMA) in this embodiment is different from that in Example 1 in that the functional monomers used in the graft polymerization reaction are different, specifically:

[0094] S41. Weigh 0.5 g of the magnetic chitosan particles with the photoinitiator HMEM obtained in step S33 and 1.5 g of 2-aminoethyl ester hydrochloride (AMA) and add them to a photoreactor. Use nitrogen as a protective gas and carry out graft polymerization under ultraviolet light. The functional monomer is grafted on the surface of the magnetic chitosan particles to form an elongated molecular chain structure. The reaction is carried out for 2 h to prepare a cationic magnetic chitosan polyelectrolyte brush MSPB-AMA.

[0095] S42. The product obtained in step S41 is washed with water multiple times and then collected by an external magnetic field to obtain a purified cationic magnetic chitosan polyelectrolyte brush MSPB-AMA. The chain length of the obtained magnetic chitosan polyelectrolyte brush is 66 nm.

[0096] Example 6

[0097] The preparation of the cationic magnetic chitosan polyelectrolyte brush (MSPB-SBMA) in this embodiment is different from that in Example 1 in that the functional monomers used in the graft polymerization reaction are different, specifically:

[0098] S41. Weigh 0.5 g of the magnetic chitosan particles with the photoinitiator HMEM obtained in step S33 and 0.5 g of [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfonic acid propyl)ammonium hydroxide (SBMA), mix them, and add them to a photoreactor. Use nitrogen as a protective gas and carry out a graft polymerization reaction under ultraviolet light. The functional monomer is grafted on the surface of the magnetic chitosan particles to form an elongated molecular chain structure. The reaction is carried out for 2 h to prepare a cationic magnetic chitosan polyelectrolyte brush MSPB-SBMA.

[0099] S42. The product obtained in step S41 is washed with water multiple times and then collected by an external magnetic field to obtain a purified cationic magnetic chitosan polyelectrolyte brush MSPB-SBMA. The chain length of the obtained magnetic chitosan polyelectrolyte brush is 134 nm.

[0100] Example 7

[0101] The preparation of the cationic magnetic chitosan polyelectrolyte brush (MSPB-DMC) in this embodiment is different from that in Example 1 in that the mass ratio of the functional monomer used in the graft polymerization reaction to the magnetic chitosan nanoparticles is different to 1:1. Specifically,

[0102] S41. Weigh 0.5 g of the magnetic chitosan particles with the photoinitiator HMEM obtained in step S33 and 0.5 g of methacryloyloxyethyltrimethylammonium chloride (DMC) and add them to a photoreactor. Use nitrogen as a protective gas and carry out a graft polymerization reaction under ultraviolet light. The functional monomer is grafted on the surface of the magnetic chitosan particles to form an elongated molecular chain structure. The reaction is carried out for 2 h to prepare a cationic magnetic chitosan polyelectrolyte brush MSPB-DMC.

[0103] S42. The product obtained in step S41 is washed with water multiple times and then collected by an external magnetic field to obtain a purified cationic magnetic chitosan polyelectrolyte brush MSPB-DMC. The chain length of the obtained magnetic chitosan polyelectrolyte brush is 15 nm.

[0104] Example 8

[0105] The preparation of the cationic magnetic chitosan polyelectrolyte brush (MSPB-DMC) in this embodiment is different from that in Example 1 in that the mass ratio of the functional monomer used in the graft polymerization reaction to the magnetic chitosan nanoparticles is different to 2:1. Specifically,

[0106] S41. Weigh 0.5 g of the magnetic chitosan particles with the photoinitiator HMEM obtained in step S33 and 1 g of methacryloyloxyethyltrimethylammonium chloride (DMC) and add them to a photoreactor. Use nitrogen as a protective gas and carry out a graft polymerization reaction under ultraviolet light. The functional monomer is grafted on the surface of the magnetic chitosan particles to form an elongated molecular chain structure. The reaction is carried out for 2 h to prepare a cationic magnetic chitosan polyelectrolyte brush MSPB-DMC.

[0107] S42. The product obtained in step S41 is washed with water multiple times and then collected by an external magnetic field to obtain a purified cationic magnetic chitosan polyelectrolyte brush MSPB-DMC. The chain length of the obtained magnetic chitosan polyelectrolyte brush is 146 nm.

[0108] Example 9

[0109] The preparation of the cationic magnetic chitosan polyelectrolyte brush (MSPB-DMC) in this embodiment is different from that in Example 1 in that the mass ratio of the functional monomer used in the graft polymerization reaction to the magnetic chitosan nanoparticles is different to 4:1. Specifically,

[0110] S41. Weigh 0.5 g of the magnetic chitosan particles with the photoinitiator HMEM obtained in step S33 and 2 g of methacryloyloxyethyltrimethylammonium chloride (DMC) and add them to a photoreactor. Use nitrogen as a protective gas and carry out a graft polymerization reaction under ultraviolet light. The functional monomer is grafted on the surface of the magnetic chitosan particles to form an elongated molecular chain structure. The reaction is carried out for 2 h to prepare a cationic magnetic chitosan polyelectrolyte brush MSPB-DMC.

[0111] S42. The product obtained in step S41 is washed with water multiple times and then collected by an external magnetic field to obtain a purified cationic magnetic chitosan polyelectrolyte brush MSPB-DMC. The chain length of the obtained magnetic chitosan polyelectrolyte brush is 322 nm.

[0112] Example 10

[0113] The preparation of the cationic magnetic chitosan polyelectrolyte brush (MSPB-DMC) in this embodiment is different from that in Example 1 in that the mass ratio of the functional monomer used in the graft polymerization reaction to the magnetic chitosan nanoparticles is different to 7:1. Specifically,

[0114] S41. Weigh 0.5 g of the magnetic chitosan particles with the photoinitiator HMEM obtained in step S33 and 3.5 g of methacryloyloxyethyltrimethylammonium chloride (DMC) and add them to a photoreactor. Use nitrogen as a protective gas and carry out a graft polymerization reaction under ultraviolet light. The functional monomer is grafted on the surface of the magnetic chitosan particles to form an elongated molecular chain structure. The reaction is carried out for 2 h to prepare a cationic magnetic chitosan polyelectrolyte brush MSPB-DMC.

[0115] S42. The product obtained in step S41 is washed with water multiple times and then collected by an external magnetic field to obtain a purified cationic magnetic chitosan polyelectrolyte brush MSPB-DMC. The chain length of the obtained magnetic chitosan polyelectrolyte brush is 550 nm.

[0116] Example 11

[0117] The preparation of the cationic magnetic chitosan polyelectrolyte brush (MSPB-DMC) in this embodiment is different from that in Example 1 in that the mass ratio of the functional monomer used in the graft polymerization reaction to the magnetic chitosan nanoparticles is different to 10:1. Specifically,

[0118] S41. Weigh 0.5 g of the magnetic chitosan particles with the photoinitiator HMEM obtained in step S33 and 5 g of methacryloyloxyethyltrimethylammonium chloride (DMC), mix them, and add them to a photoreactor. Use nitrogen as a protective gas and carry out a graft polymerization reaction under ultraviolet light. The functional monomer is grafted on the surface of the magnetic chitosan particles to form an elongated molecular chain structure. The reaction is carried out for 2 h to prepare a cationic magnetic chitosan polyelectrolyte brush MSPB-DMC.

[0119] S42. The product obtained in step S41 is washed with water multiple times and then collected by an external magnetic field to obtain a purified cationic magnetic chitosan polyelectrolyte brush MSPB-DMC. The chain length of the obtained magnetic chitosan polyelectrolyte brush is 631 nm.

[0120] Example 12

[0121] The preparation of the cationic magnetic chitosan polyelectrolyte brush (MSPB-DMC) in this embodiment is different from that in Example 1 in that the graft polymerization reaction time is different, specifically:

[0122] S41. Weigh 0.5 g of the magnetic chitosan particles with a photoinitiator HMEM on the surface obtained in step S33 and 1.5 g of methacryloyloxyethyltrimethylammonium chloride (DMC), mix them, and add them to a photoreactor. Use nitrogen as a protective gas and carry out a graft polymerization reaction under ultraviolet light. The functional monomer is grafted on the surface of the magnetic chitosan particles to form an elongated molecular chain structure. The reaction is carried out for 0.5 h to prepare a cationic magnetic chitosan polyelectrolyte brush MSPB-DMC.

[0123] S42. The product obtained in step S41 is washed with water multiple times and then collected by an external magnetic field to obtain a purified cationic magnetic chitosan polyelectrolyte brush MSPB-DMC. The chain length of the obtained magnetic chitosan polyelectrolyte brush is 64.8 nm.

[0124] Example 13

[0125] The preparation of the cationic magnetic chitosan polyelectrolyte brush (MSPB-DMC) in this embodiment is different from that in Example 1 in that the graft polymerization reaction time is different, specifically:

[0126] S41. Weigh 0.5 g of the magnetic chitosan particles with the photoinitiator HMEM obtained in step S33 and 1.5 g of methacryloyloxyethyltrimethylammonium chloride (DMC) and add them to a photoreactor. Use nitrogen as a protective gas and carry out a graft polymerization reaction under ultraviolet light. The functional monomer is grafted on the surface of the magnetic chitosan particles to form an elongated molecular chain structure. The reaction is carried out for 1 h to prepare a cationic magnetic chitosan polyelectrolyte brush MSPB-DMC.

[0127] S42. The product obtained in step S41 is washed with water multiple times and then collected by an external magnetic field to obtain a purified cationic magnetic chitosan polyelectrolyte brush MSPB-DMC. The chain length of the obtained magnetic chitosan polyelectrolyte brush is 165.1 nm.

[0128] The above embodiments are intended only to illustrate the technical concepts and features of the present invention. Their purpose is to enable those skilled in the art to understand the contents of the present invention and implement them accordingly. They are not intended to limit the scope of protection of the present invention. Any equivalent changes or modifications made in accordance with the spirit of the present invention are intended to be covered by the scope of protection of the present invention.

Claims

1. A method for preparing a magnetic chitosan polyelectrolyte brush, characterized in that: The following steps are involved: S1. Preparation of magnetic chitosan particles: According to the molar ratio of Fe 2+ :Fe 3+ =1:1~2 Take divalent and trivalent iron salts and fully dissolve them in deionized water to obtain a first solution; add the first solution dropwise to the alkaline chitosan solution to obtain magnetic chitosan particles in one step; S2 modification of magnetic chitosan particles: using methacrylic anhydride to modify the surface of the magnetic chitosan particles to obtain methacrylated magnetic chitosan particles; S3 initiation reaction: Under a nitrogen atmosphere, a photoinitiator HMEM was grafted onto the surface of the methacrylated magnetic chitosan particles to obtain magnetic chitosan particles with a photoinitiator HMEM on the surface; S4. Graft polymerization reaction: The magnetic chitosan particles with the photoinitiator HMEM on the surface are mixed with functional monomers. Under oxygen-free and ultraviolet light irradiation conditions, the functional monomers are grafted on the surface of the magnetic chitosan particles to form an elongated molecular chain structure, thereby preparing a magnetic chitosan polyelectrolyte brush, wherein the photoinitiator HMEM is 2-[p-(2-hydroxy-2-methylpropiophenone)]-ethylene glycol methacrylate (HMEM).

2. The method for preparing a magnetic chitosan polyelectrolyte brush according to claim 1, wherein In step S1, the molar ratio of the divalent iron salt to the trivalent iron salt is Fe 2+ :Fe 3+ =1:1.

5.

3. The method for preparing the magnetic chitosan polyelectrolyte brush according to claim 1, wherein The preparation of the magnetic chitosan particles in step S1 specifically includes the following steps: S11 according to the molar ratio of FeCl2: FeCl3 = 1:1 ~ 2 weighed ferric chloride and ferrous chloride, fully dissolved in deionized water to obtain a first solution; S12. Chitosan was added to deionized water, stirred and dispersed, and the pH of the chitosan solution was adjusted to 10~13 using sodium hydroxide to obtain an alkaline chitosan solution; S13. The first solution was placed in a syringe pump, propelled by the syringe pump, thoroughly mixed by a vortex mixer, and then added dropwise to the alkaline chitosan solution. The alkaline chitosan solution was stirred during addition. After the addition was completed, the reaction was continued with stirring for 1 to 2 hours; wherein the stirring speed was: 800 to 1200 r / min; S14. After the reaction is completed, the magnetic chitosan particles are obtained by multiple water washing and external magnetic field purification.

4. The method for preparing a magnetic chitosan polyelectrolyte brush according to claim 1, wherein In step S2, the preparation of the methacrylated magnetic chitosan particles specifically includes the following steps: S21. The magnetic chitosan particles and carbonate - sodium bicarbonate buffer were mixed and stirred to dissolve, and the pH was adjusted to 8 to 10 to obtain a second solution; S22. Add a certain amount of methacrylic anhydride to the second solution and react at 50-55°C in the dark for 1.5-2.5h; S23. After the reaction is completed in the dark, the product obtained in step S22 is washed with water multiple times and then collected by an external magnetic field to obtain the methacrylated magnetic chitosan particles.

5. The method for preparing the magnetic chitosan polyelectrolyte brush according to claim 1, wherein In step S3, the preparation of the magnetic chitosan particles with a photoinitiator HMEM on the surface specifically includes the following steps: S31. Take the methacrylated magnetic chitosan particles, add a small amount of potassium persulfate, and dissolve in deionized water to obtain a third solution; S32. Under a nitrogen atmosphere, at 70-90°C, the photoinitiator HMEM was slowly added to the third solution at a rate of 2-3 drops per second via syringe injection, and the reaction was carried out in the dark for 1.5-2.5 h; S33. After the light-proof reaction is completed, the product obtained in step S32 is washed with water several times and then collected by an external magnetic field to obtain the magnetic chitosan particles with the photoinitiator HMEM on the surface.

6. The method for preparing the magnetic chitosan polyelectrolyte brush according to claim 1, characterized in that: In step S4, the preparation of the magnetic chitosan polyelectrolyte brush specifically comprises the following steps: S41. Magnetic chitosan particles coated with a photoinitiator, HMEM, were mixed with functional monomers and then subjected to a graft polymerization reaction under ultraviolet light using nitrogen as a protective gas. The functional monomers were grafted onto the surface of the magnetic chitosan particles to form elongated molecular chains. The reaction lasted for 1.5–2.5 h, yielding magnetic chitosan polyelectrolyte brushes. S42. The product obtained in step S41 is washed with water multiple times and then collected by applying an external magnetic field to obtain a purified magnetic chitosan polyelectrolyte brush.

7. The method for preparing the magnetic chitosan polyelectrolyte brush according to claim 6, characterized in that: In step S41, the mass ratio of the functional monomer to the magnetic chitosan particles with a photoinitiator HMEM on the surface is (1-10):

1.

8. The method for preparing the magnetic chitosan polyelectrolyte brush according to claim 1, characterized in that: The functional monomer is methacryloyloxyethyltrimethylammonium chloride (DMC), acrylic acid (AA), 2-acrylamide-2-methylpropanesulfonic acid (AMPS), sodium p-styrenesulfonate (SS), 2-aminoethyl ester hydrochloride (AMA) or [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfonic acid propyl)ammonium hydroxide (SBMA).

9. A magnetic chitosan polyelectrolyte brush, characterized in that: Prepared according to the preparation method according to any one of claims 1 to 8.

10. Application of a magnetic chitosan polyelectrolyte brush in the field of wastewater treatment, characterized in that: The magnetic chitosan polyelectrolyte brush is the magnetic chitosan polyelectrolyte brush according to claim 9 or is prepared by the preparation method according to any one of claims 1 to 8.

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