CN105199135A - Preparation method of magnetic composite microspheres - Google Patents

Abstract

The invention discloses a method for preparing magnetic composite microspheres. The method comprises the following steps: modifying highly cross-linked porous polymer microspheres with a modifier; impregnating the modified microspheres in a metal cation solution; impregnating the impregnated Under the protection of inert gas, the microspheres undergo a precipitation reaction in an alkaline solution to obtain magnetic composite microspheres with a core-shell structure. The magnetic composite microsphere prepared by the method of the present invention has the advantages of porosity, magnetism, solvent resistance, etc., so it can be directly used for adsorption and separation of organic impurities, and is also convenient for magnetic separation and recovery, and has application prospects in the fields of water treatment, chromatographic separation, and the like.

Description

A kind of preparation method of magnetic composite microsphere

technical field

The invention belongs to the technical field of polymer materials, in particular to a preparation method of magnetic composite microspheres.

Background technique

Due to the stable physical and chemical structure, magnetic composite microspheres have a wide range of uses in the fields of chromatographic separation, biomedicine, biological detection, coatings, environmental engineering and catalytic engineering. In the application of magnetic composite microspheres, on the one hand, it is required to have a high magnetic content, that is, a high specific saturation magnetization; on the other hand, it is also required that the magnetic particles be evenly distributed, and the preparation process is simple and controllable.

From the point of view of the preparation route, most of the magnetic composite microspheres are prepared by first preparing magnetic metal oxide particles, and then subjecting them to a certain surface treatment, and then compounding the magnetic particles with polymers to form magnetic composite microspheres. The composite methods of magnetic particles and polymers mainly include: embedding method, emulsion method, layer-by-layer self-assembly and seed swelling method. The embedding method is to uniformly disperse the magnetic particles in the polymer solution, and then volatilize the solvent by atomization, evaporation and other methods to prepare magnetic composite microspheres. This method is simple to operate, but the properties such as particle size and morphology of the prepared product are not easy to control. Although the emulsion method can overcome the problems of the embedding method in terms of particle size and shape control, it often needs to use surfactants in the preparation process of this method, which is easy to contaminate the product and affect its performance to a certain extent. The layer-by-layer assembly method uses polymer microspheres as templates to adsorb polyelectrolytes on their surfaces, and then utilizes the attraction effect between polyelectrolytes and the surface charges of magnetic particles to coat and assemble the surface of the microspheres layer by layer to prepare magnetic composite microspheres. The principle of this method is simple, but in order to obtain magnetic composite microspheres with high magnetic content, it is necessary to repeatedly coat and assemble the surface of the microspheres, and the operation is cumbersome. The seed swelling method is to use the swelling effect of the solvent on the polymer microspheres, so that the microspheres adsorb magnetic metal oxide particles during the volume expansion process to prepare magnetic composite microspheres. The seed swelling system is mainly composed of seed microspheres (or seed droplets), monomer (or monomer droplets), dispersed phase, initiator, stabilizer, etc., and sometimes it is necessary to add swelling aids. The magnetic composite microspheres prepared by the seed swelling method have high magnetic content and uniform distribution of magnetic particles, but the preparation process of this method is more complicated and the cost is higher.

In addition to the above methods, US Patent No. US4774265 also discloses a method for preparing magnetic composite microspheres, which is similar to the seed swelling method. The method is to first prepare macroporous or non-porous polymer microspheres containing specific groups, and then place the polymer microspheres in an organic solvent. The solvent contains specific metal cations that are continuously absorbed into the interior of the polymer microspheres as the microspheres swell. The swollen microspheres are finally placed in a certain solution, and magnetic metal oxide particles are generated inside or on the surface of the microspheres through a precipitation reaction. Although the method does not need to synthesize magnetic particles separately, the polymer microspheres used have low cross-linking degree and poor solvent resistance, which affect the application of the magnetic composite microspheres.

Therefore, it is necessary to provide a method for preparing magnetic composite microspheres, which is easy to operate and can prepare magnetic composite microspheres without separately synthesizing magnetic particles.

Contents of the invention

The first technical problem to be solved by the present invention is to provide a method for preparing magnetic composite microspheres, which is easy to operate and can prepare magnetic composite microspheres without separately synthesizing magnetic particles.

The second technical problem to be solved by the present invention is to provide a magnetic composite microsphere.

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

A preparation method of magnetic composite microspheres, comprising the steps of:

The highly cross-linked porous polymer microspheres are modified by modifiers; the modified microspheres are impregnated in a metal cation solution; the impregnated microspheres are subjected to a precipitation reaction in an alkaline solution under the protection of an inert gas to obtain Magnetic composite microspheres with core-shell structure.

The crosslinked porous polymer microspheres include polydivinylbenzene microspheres or polydivinylbenzene and styrene copolymerized microspheres, preferably, the crosslinked porous polymer microspheres have an insoluble content of 80 -98%, the BET specific surface area is 200-1000m ² /g, the pore size is between 2-10nm, more preferably, the insoluble content of the cross-linked porous polymer microspheres is 90-98%, the BET specific surface area It is 400-800m ² /g, and the pore size is 2-6nm.

The modifying agent is a strong oxidant solution, preferably concentrated sulfuric acid or concentrated nitric acid. Preferably, the mass ratio of modifier dosage to porous polymer microspheres is 2-40:1, more preferably, the mass ratio of modifier dosage to porous polymer microspheres is 10-20:1; modifier The modification temperature is 40-60° C., and the modification time of the modifier is 10-60 minutes.

The metal cation solution is an aqueous solution containing Fe ²⁺ and Fe ³⁺ ions; the concentration of the metal cation solution containing Fe ²⁺ and Fe ³⁺ ions is 0.5-5mol/L; the metal cation solution containing Fe ²⁺ and Fe ³⁺ The molar ratio of Fe ²⁺ and Fe ³⁺ in the metal cation aqueous solution of ⁺ ions is 1:1-4; the temperature at which the highly cross-linked porous polymer microspheres are immersed in the metal cation-containing aqueous solution is 40-70°C; The immersion time of the highly cross-linked porous polymer microspheres in the aqueous solution containing metal cations is 2-24 hours.

The alkaline substance in the alkaline solution is NaOH, ammonia water, KOH or LiOH; the reaction temperature in the precipitation reaction is 40-90°C, preferably, the reaction temperature in the precipitation reaction is 60-90°C; The pH value of the precipitation reaction is 8-14; the reaction time of the precipitation reaction is 10-600min, preferably, the reaction time of the precipitation reaction is 30-120min.

The protective gas is an inert gas, one or more selected from nitrogen, argon and neon, preferably nitrogen.

The preparation method further includes separating the magnetic composite microspheres, preferably using an external magnetic field to separate the magnetic composite microspheres.

The preparation method further comprises washing the modified microspheres, preferably by centrifuging the modified microspheres, washing them with deionized water until neutral, and collecting the washed microspheres by centrifugation; The linked porous polymer microspheres are added into an aqueous solution containing metal cations to carry out an impregnation reaction, preferably, the impregnation reaction is carried out under sealed conditions.

A magnetic composite microsphere has the advantages of porosity, magnetism, solvent resistance and the like.

The beneficial effects of the present invention are as follows:

The preparation method of the invention has the advantages of oriented deposition of magnetic nanoparticles on the surface of microspheres, and easy adjustment and control of the composition, thickness and performance of the magnetic particle film. Moreover, the preparation method is easy to operate, and the magnetic composite microsphere can be prepared without separately synthesizing magnetic particles.

The magnetic composite microsphere prepared by the invention has the advantages of porosity, magnetism, solvent resistance, etc., so it can be directly used for adsorption and separation of organic impurities, and is also convenient for magnetic separation and recovery, and has application prospects in the fields of water treatment, chromatographic separation, and the like.

Description of drawings

The specific implementation manners of the present invention will be further described in detail below in conjunction with the accompanying drawings.

FIG. 1 shows a scanning electron micrograph of the magnetic composite microsphere of Example 1.

FIG. 2 shows an enlarged scanning electron micrograph of the magnetic composite microsphere of Example 1. FIG.

FIG. 3 shows the response of the magnetic composite microspheres of Example 1 under an external magnetic field.

FIG. 4 shows the magnetic performance test curve of the magnetic composite microsphere of Example 1.

FIG. 5 shows a scanning electron micrograph of the magnetic composite microsphere of Example 2.

FIG. 6 shows a scanning electron micrograph of the magnetic composite microsphere of Example 3.

FIG. 7 shows a scanning electron micrograph of the magnetic composite microsphere of Example 4.

FIG. 8 shows a scanning electron micrograph of the magnetic composite microsphere of Example 5.

FIG. 9 shows a scanning electron micrograph of the magnetic composite microsphere of Example 6.

Detailed ways

In order to illustrate the present invention more clearly, the present invention will be further described below in conjunction with preferred embodiments and accompanying drawings. Similar parts in the figures are denoted by the same reference numerals. Those skilled in the art should understand that the content specifically described below is illustrative rather than restrictive, and should not limit the protection scope of the present invention.

The polydivinylbenzene microspheres or polystyrene and polydivinylbenzene copolymer microspheres used in the examples have an insoluble content of 80%-98%, a BET specific surface area of 200-1000m ² /g, and a pore size of 2 -10nm.

Example 1

The highly cross-linked porous polydivinylbenzene microsphere is used as the base material, the insoluble content is 95%, the BET specific surface area is 325m ² /g, and the pore diameter is 4nm. Add 0.5 g of the microspheres into a round bottom flask, stir, and raise the temperature to 40°C. Add 10 g of concentrated nitric acid drop by drop, and after 30 minutes of treatment, slowly dilute the solution, centrifuge, and wash with deionized water until neutral. Add the treated microspheres into an aqueous solution containing Fe ²⁺ and Fe ³⁺ at a concentration of 2mol/L, the ratio of Fe ²⁺ to Fe ³⁺ is 1:2, mix, seal, and place in an oven. Set the oven temperature to 70 °C. After 6 hours, take it out and centrifuge. The microspheres obtained by centrifugation were added to a round-bottomed flask filled with deionized water, a nitrogen protective atmosphere was introduced, the temperature was raised to 70° C., and NaOH solution was added dropwise until pH=12. After reacting for 30 minutes, magnetic composite microspheres can be obtained by applying an external magnetic field for separation. The magnetic content of the magnetic composite microsphere is 35.7%, the saturation magnetic content is 23.888 emu/g, and the BET specific surface area is 207 m ² /g. The scanning electron microscope of the magnetic composite microsphere is shown in Figure 1. The cross-section of the coating layer of the magnetic composite microsphere is shown in Fig. 2 . The response performance of the magnetic composite microspheres to an external magnetic field is shown in Figure 3. The magnetic performance curves of the magnetic composite microspheres are shown in Fig. 4 .

Example 2

The highly cross-linked porous polydivinylbenzene and styrene copolymerized microspheres are used as the substrate, the insoluble content is 98%, the BET specific surface area is 730m ² /g, and the pore diameter is 2.8nm. Add 0.5 g of the microspheres into a round bottom flask, stir, and raise the temperature to 60°C. Add 10 g of concentrated sulfuric acid drop by drop, and after 10 min of treatment, slowly dilute the solution, centrifuge, and wash with deionized water until neutral. Add the treated microspheres into an aqueous solution containing Fe ²⁺ and Fe ³⁺ at a concentration of 0.5mol/L, the ratio of Fe ²⁺ to Fe ³⁺ is 1:1, mix, seal, and place in an oven. Set the oven temperature to 40 °C. After 12 hours, the centrifugation was taken out, and the microspheres obtained by centrifugation were added to a round-bottomed flask, and a nitrogen protective atmosphere was introduced, the temperature was raised to 90° C., and KOH solution was added drop by drop until pH=14. After 2 hours of reaction, the magnetic composite microspheres can be obtained by applying an external magnetic field to separate. The magnetic content of the magnetic composite microsphere is 55.3%, the saturation magnetic content is 35.187 emu/g, and the BET specific surface area is 458 m ² /g. The scanning electron microscope of the magnetic composite microsphere is shown in FIG. 5 .

Example 3

The highly cross-linked porous polydivinylbenzene and styrene copolymerized microspheres are used as the substrate, the insoluble content is 90%, the BET specific surface area is 242m ² /g, and the pore diameter is 10nm. Add 0.5 g of the microspheres into a round bottom flask, stir, and raise the temperature to 50°C. Add 20 g of concentrated sulfuric acid drop by drop, and after 60 min of treatment, slowly dilute the solution, centrifuge, and wash with deionized water until neutral. Add the treated microspheres into an aqueous solution containing Fe ²⁺ and Fe ³⁺ at a concentration of 5mol/L, the ratio of Fe ²⁺ to Fe ³⁺ is 1:4, mix, seal, and place in an oven. Set the oven temperature to 50 °C. After 24 hours, take out the centrifuge, put the microspheres obtained by centrifugation into a round bottom flask, pass through a nitrogen protective atmosphere, raise the temperature to 40° C., and add ammonia solution drop by drop until pH=8. After reacting for 10 hours, magnetic composite microspheres can be obtained by applying an external magnetic field for separation. The magnetic content of the magnetic composite microsphere is 13.6%, the saturation magnetic content is 12.443 emu/g, and the BET specific surface area is 178 m ² /g. The scanning electron microscope of the magnetic composite microsphere is shown in Figure 6.

Example 4

The highly cross-linked porous polydivinylbenzene and styrene copolymerized microspheres are used as the substrate, the insoluble content is 80%, the BET specific surface area is 452m ² /g, and the pore diameter is 6.1nm. Add 0.5 g of the microspheres into a round bottom flask, stir, and raise the temperature to 40°C. Add 10 g of concentrated nitric acid drop by drop, and after 30 minutes of treatment, slowly dilute the solution, centrifuge, and wash with deionized water until neutral. Add the treated microspheres into an aqueous solution containing Fe ²⁺ and Fe ³⁺ at a concentration of 3mol/L, the ratio of Fe ²⁺ to Fe ³⁺ is 1:3, mix, seal, and place in an oven. Set the oven temperature to 60 °C. After 8 hours, the centrifuge was taken out, the centrifuged microspheres were added into a round bottom flask, a nitrogen protective atmosphere was introduced, the temperature was raised to 60° C., and LiOH solution was added drop by drop until pH=10. After reacting for 4 hours, the magnetic composite microspheres can be obtained by applying an external magnetic field for separation. The magnetic content of the magnetic composite microsphere is 40.5%, the saturation magnetic content is 27.585 emu/g, and the BET specific surface area is 345 m ² /g. The scanning electron microscope of the magnetic composite microsphere is shown in Figure 7.

Example 5

The highly cross-linked porous polydivinylbenzene microsphere is used as the substrate, the insoluble content is 85%, the BET specific surface area is 200m ^{2 /} g, and the pore diameter is 8.4nm. Add 0.5 g of the microspheres into a round bottom flask, stir, and raise the temperature to 40°C. Add 15 g of concentrated nitric acid drop by drop, and after 30 minutes of treatment, slowly dilute the solution, centrifuge, and wash with deionized water until neutral. Add the treated microspheres into an aqueous solution containing Fe ²⁺ and Fe ³⁺ at a concentration of 1mol/L, the ratio of Fe ²⁺ to Fe ³⁺ is 1:1, mix, seal, and place in an oven. Set the oven temperature to 40 °C. After 16 hours, take out the centrifuge, add the microspheres obtained by centrifugation into a round bottom flask, pass through a nitrogen protective atmosphere, raise the temperature to 80° C., and add NaOH solution drop by drop until pH=14. After reacting for 6 hours, the magnetic composite microspheres can be obtained by applying an external magnetic field for separation. The magnetic content of the magnetic composite microsphere is 22.3%, the saturation magnetic content is 21.058 emu/g, and the BET specific surface area is 148 m ² /g. The scanning electron microscope of the magnetic composite microsphere is shown in Figure 8.

Example 6

The highly cross-linked porous polydivinylbenzene microsphere is used as the substrate, the insoluble content is 97%, the BET specific surface area is 1000m ² /g, and the pore diameter is 2nm. Add 0.5 g of the microspheres into a round bottom flask, stir, and raise the temperature to 50°C. Add 5 g of concentrated nitric acid drop by drop, and after 60 min of treatment, slowly dilute the solution, centrifuge, and wash with deionized water until neutral. Add the treated microspheres into an aqueous solution containing Fe ²⁺ and Fe ³⁺ at a concentration of 5mol/L, the ratio of Fe ²⁺ to Fe ³⁺ is 1:3, mix, seal, and place in an oven. Set the oven temperature to 70 °C. After 16 hours, take out the centrifuge, add the microspheres obtained by centrifugation into a round bottom flask, pass through a nitrogen protective atmosphere, raise the temperature to 80° C., and add NaOH solution drop by drop until pH=13. After 2 hours of reaction, the magnetic composite microspheres can be obtained by applying an external magnetic field for separation. The magnetic content of the magnetic composite microsphere is 50.5%, the saturation magnetic content is 42.144emu/g, and the BET specific surface area is 513m ² /g. The scanning electron microscope of the magnetic composite microsphere is shown in Fig. 9 .

Example 7

The highly cross-linked porous polydivinylbenzene microsphere is used as the substrate, the insoluble content is 92%, the BET specific surface area is 557m ² /g, and the pore diameter is 3.4nm. Add 0.5 g of the microspheres into a round bottom flask, stir, and raise the temperature to 40°C. Add 1 g of concentrated sulfuric acid drop by drop, and after 30 minutes of treatment, slowly dilute the solution, centrifuge, and wash with deionized water until neutral. Add the treated microspheres into an aqueous solution containing Fe ²⁺ and Fe ³⁺ at a concentration of 1mol/L, the ratio of Fe ²⁺ to Fe ³⁺ is 1:1, mix, seal, and place in an oven. Set the oven temperature to 70 °C. After 2 hours, the centrifugation was taken out, the centrifuged microspheres were added into a round bottom flask, a nitrogen protective atmosphere was introduced, the temperature was raised to 80° C., and NaOH solution was added dropwise until pH = 14. After reacting for 6 hours, the magnetic composite microspheres can be obtained by applying an external magnetic field for separation. The magnetic content of the magnetic composite microsphere is 34.3%, the saturation magnetic content is 27.058 emu/g, and the BET specific surface area is 321 m ² /g.

Example 8

The highly cross-linked porous polydivinylbenzene and styrene copolymerized microspheres are used as the substrate, the insoluble content is 88%, the BET specific surface area is 342m ² /g, and the pore diameter is 5.6nm. Add 0.5 g of the microspheres into a round bottom flask, stir, and raise the temperature to 50°C. Add 5 g of concentrated sulfuric acid drop by drop, and after 60 min of treatment, slowly dilute the solution, centrifuge, and wash with deionized water until neutral. Add the treated microspheres into an aqueous solution containing Fe ²⁺ and Fe ³⁺ at a concentration of 5mol/L, the ratio of Fe ²⁺ to Fe ³⁺ is 1:2, mix, seal, and place in an oven. Set the oven temperature to 60 °C. After 24 hours, take out the centrifuge, put the microspheres obtained by centrifugation into a round bottom flask, pass through a nitrogen protective atmosphere, raise the temperature to 50° C., and add ammonia solution drop by drop until pH=10. After 2 hours of reaction, the magnetic composite microspheres can be obtained by applying an external magnetic field for separation. The magnetic content of the magnetic composite microsphere is 36.5%, the saturation magnetic content is 36.745 emu/g, and the BET specific surface area is 255 m ² /g.

Example 9

The highly cross-linked porous polydivinylbenzene and styrene copolymerized microspheres are used as the substrate, the insoluble content is 98%, the BET specific surface area is 953m ² /g, and the pore diameter is 2.1nm. Add 0.5 g of the microspheres into a round bottom flask, stir, and raise the temperature to 60°C. Add 20 g of concentrated sulfuric acid drop by drop, and after 60 min of treatment, slowly dilute the solution, centrifuge, and wash with deionized water until neutral. Add the treated microspheres into an aqueous solution containing Fe ²⁺ and Fe ³⁺ at a concentration of 3mol/L, the ratio of Fe ²⁺ to Fe ³⁺ is 1:2.5, mix, seal, and place in an oven. Set the oven temperature to 50 °C. After 24 hours, take out the centrifuge, put the microspheres obtained by centrifugation into a round bottom flask, pass through a nitrogen protective atmosphere, raise the temperature to 70° C., and add KOH solution drop by drop until pH=14. After reacting for 6 hours, the magnetic composite microspheres can be obtained by applying an external magnetic field for separation. The magnetic content of the magnetic composite microsphere is 43.5%, the saturation magnetic content is 36.285 emu/g, and the BET specific surface area is 545 m ² /g.

Example 10

The highly cross-linked porous polydivinylbenzene microsphere is used as the substrate, the insoluble content is 91%, the BET specific surface area is 625m ² /g, and the pore diameter is 3.6nm. Add 0.5 g of the microspheres into a round bottom flask, stir, and raise the temperature to 40°C. Add 10 g of concentrated nitric acid drop by drop, and after 20 min of treatment, slowly dilute the solution, centrifuge, and wash with deionized water until neutral. Add the treated microspheres into an aqueous solution containing Fe ²⁺ and Fe ³⁺ at a concentration of 5mol/L, the ratio of Fe ²⁺ to Fe ³⁺ is 1:3, mix, seal, and place in an oven. Set the oven temperature to 70 °C. After 6 hours, take it out and centrifuge. The microspheres obtained by centrifugation were added to a round-bottomed flask filled with deionized water, a nitrogen protective atmosphere was introduced, the temperature was raised to 70°C, and NaOH solution was added dropwise until pH = 13. After reacting for 8 hours, magnetic composite microspheres can be obtained by applying an external magnetic field for separation. The magnetic content of the magnetic composite microsphere is 28.7%, the saturation magnetic content is 27.556 emu/g, and the BET specific surface area is 358 m ² /g.

Example 11

The highly cross-linked porous polydivinylbenzene and styrene copolymerized microspheres are used as the substrate, the insoluble content is 87%, the BET specific surface area is 342m ² /g, and the pore diameter is 4.8nm. Add 0.5 g of the microspheres into a round bottom flask, stir, and raise the temperature to 40°C. Add 4 g of concentrated nitric acid drop by drop, and after 10 min of treatment, slowly dilute the solution, centrifuge, and wash with deionized water until neutral. Add the treated microspheres into an aqueous solution containing Fe ²⁺ and Fe ³⁺ at a concentration of 5mol/L, the ratio of Fe ²⁺ to Fe ³⁺ is 1:4, mix, seal, and place in an oven. Set the oven temperature to 40 °C. After 18 hours, take out the centrifuge, add the microspheres obtained by centrifugation into a round bottom flask, pass through a nitrogen protective atmosphere, raise the temperature to 90° C., and add NaOH solution drop by drop until pH=12. After 2 hours of reaction, the magnetic composite microspheres can be obtained by applying an external magnetic field for separation. The magnetic content of the magnetic composite microsphere is 19.5%, the saturation magnetic content is 18.344emu/g, and the BET specific surface area is 266m ² /g.

Apparently, the above-mentioned embodiments of the present invention are only examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those of ordinary skill in the art can also make It is impossible to exhaustively list all the implementation modes here, and any obvious changes or changes derived from the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims (10)

1. a preparation method of magnetic composite microspheres, is characterized in that, comprises the steps: The highly cross-linked porous polymer microspheres are modified by modifiers; the modified microspheres are impregnated in a metal cation solution; the impregnated microspheres are subjected to a precipitation reaction in an alkaline solution under the protection of an inert gas to obtain Magnetic composite microspheres with core-shell structure. 2. The preparation method according to claim 1, characterized in that, the preparation method further comprises washing the modified microspheres. 3. The preparation method according to claim 1, characterized in that, the preparation method further comprises separating the magnetic composite microspheres, preferably, using an external magnetic field to separate the magnetic composite microspheres. 4. The preparation method according to claim 1, wherein the crosslinked porous polymer microspheres comprise polydivinylbenzene microspheres or polydivinylbenzene and styrene copolymer microspheres. 5. The preparation method according to claim 4, characterized in that, the cross-linked porous polymer microspheres have an insoluble content of 80-98%, a BET specific surface area of 200-1000m ² /g, and a pore diameter of 2 between -10nm; preferably, the cross-linked porous polymer microspheres have an insoluble content of 90-98%, a BET specific surface area of 400-800m ² /g, and a pore diameter of 2-6nm. 6. preparation method according to claim 1 is characterized in that, described modifying agent is strong oxidizing agent type solution and is vitriol oil or concentrated nitric acid; Preferably, the mass ratio of modifying agent consumption and porous polymer microsphere is 2-40:1; more preferably, the mass ratio of modifier dosage to porous polymer microspheres is 10-20:1. 7. The preparation method according to claim 6, characterized in that, the modification temperature of the modifier is 40-60° C., and the modification time of the modifier is 10-60 min. 8. preparation method according to claim 1, is characterized in that, described metal cation solution is the aqueous solution that comprises Fe ²⁺ and Fe ³⁺ ions; Preferably, described metal that comprises Fe ²⁺ and Fe ³⁺ ions The concentration of the cation solution is 0.5-5mol/L, and the molar ratio of Fe ²⁺ and Fe ³⁺ in the metal cation aqueous solution containing Fe ²⁺ and Fe ³⁺ ions is 1:1-4; the highly cross-linked porous The immersion temperature of the polymer microspheres in the aqueous solution containing metal cations is 40-70°C; the immersion time of the highly cross-linked porous polymer microspheres in the aqueous solution containing metal cations is 2-24 hours. 9. The preparation method according to claim 1, characterized in that, the alkaline substance in the alkaline solution is NaOH, ammonia, KOH or LiOH. 10. The preparation method according to claim 1, characterized in that, the reaction temperature in the precipitation reaction is 40-90°C, preferably, the reaction temperature of the precipitation reaction is 60-90°C; the precipitation reaction The pH value of the reaction is 8-14; the reaction time of the precipitation reaction is 10-600min, preferably, the reaction time of the precipitation reaction is 30-120min.