Composite material with core-shell structure as well as preparation method and application of composite material

Abstract

The invention belongs to the technical field of adsorbents, and discloses a core-shell structure composite material as well as a preparation method and application thereof. Ferroferric oxide is loaded on biochar by coprecipitation of ferric salt, ferrous salt and biochar, amination modification is performed by using polyethyleneimine, and a COF shell layer is prepared in situ by using a magnetic core. The shell layer is chemically connected with the magnetic core, and is coated by the COF shell, so that the structural stability is improved, the porous structure of the biochar is not easy to collapse, and the magnetic particles are not easy to fall off; the shell contains sulfonic acid groups, has electronegativity, and is combined with metal ions through electrostatic interaction, so that the adsorption sites of the adsorbent are increased. Meanwhile, the COF shell is of a porous structure, the specific surface area is large, the COF shell has the adsorption effect on metal ions, more adsorption sites are provided for the metal ions through the multiple adsorption effects of the COF shell and the magnetic core, and the removal rate is effectively increased.

Description

Technical Field

[0001] The present invention relates to the technical field of adsorbents, and in particular to a core-shell structure composite material and a preparation method and application thereof. Background Art

[0002] In the treatment of heavy metal wastewater pollution, adsorption methods are widely used due to their simplicity and low cost. Traditional adsorbents are mainly based on materials such as activated carbon and biochar. Although carbon materials have high specific surface area and abundant pores, their pore structures are unstable and prone to collapse. For example, during the dynamic adsorption process, traditional activated carbon's pores are easily eroded by fluids due to insufficient mechanical strength, resulting in collapse of the pores, which causes a 30-50% decrease in specific surface area and a significant reduction in adsorption capacity. For another example, when coffee ground biochar is cyclically adsorbing heavy metals, its adsorption efficiency decreases by approximately 60% relative to the initial value due to pore blockage. Furthermore, to facilitate the recovery of carbon material adsorbents, researchers have loaded magnetic particles onto the biochar surface. However, the magnetic particles and biochar are only physically adsorbed or weakly chemically bonded, and the magnetic particles easily fall off, causing adsorbent loss and even secondary water pollution.

[0003] To address these issues, various improvements have been proposed. For example, surface modification using silane coupling agents can enhance the bonding strength between magnetic particles and the carbon matrix, but this can potentially cover active sites and reduce adsorption efficiency. Another approach is to enhance the structural stability of the carbon matrix skeleton using crosslinkers, but these agents can clog pores, reducing adsorption performance and easily introducing toxic byproducts.

[0004] Therefore, how to provide a heavy metal adsorption material with stable structure, high adsorption performance, easy recovery and high cycle stability is an urgent problem to be solved. Summary of the Invention

[0005] The purpose of the present invention is to provide a core-shell structure composite material and a preparation method and application thereof, so as to solve the above-mentioned problems existing in existing adsorption materials.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] The present invention provides a method for preparing a core-shell structure composite material, comprising the following steps:

[0008] (1) Mixing ferric salt, ferrous salt, biochar, and water, adding sodium hydroxide solution to adjust the pH to 10-11, and reacting to obtain ferroferric oxide@biochar;

[0009] (2) mixing ferroferric oxide@biochar, polyethyleneimine, and methanol, and modifying the mixture to obtain modified biochar;

[0010] (3) Using the modified biochar as the core, mix the modified biochar, amino group-containing monomer, aldehyde group-containing monomer, and organic solvent, and react under closed conditions to obtain a core-shell structure composite material;

[0011] The amino group-containing monomer is 4,4'-diamino-[1,1'-biphenyl]-3,3'-disulfonic acid.

[0012] Preferably, the dosage ratio of the iron salt, ferrous salt, and biochar in step (1) is 0.02 - 0.1 mol: 0.01 - 0.05 mol: 1 - 10 g.

[0013] Preferably, the temperature of the reaction in step (1) is 25 - 35 °C; the time of the reaction is 1 - 4 h.

[0014] Preferably, the dosage ratio of the Fe₃O₄@biochar, polyethyleneimine, and methanol in step (2) is 3 - 15 g: 1 - 10 g: 100 mL.

[0015] Preferably, the temperature of the modification in step (2) is 50 - 90 °C; the time of the modification is 2 - 6 h.

[0016] Preferably, the dosage ratio of the modified biochar, amino group-containing monomer, aldehyde group-containing monomer, and organic solvent in step (3) is 1 g: 0.5 - 1 g: 1 - 2 g: 100 - 200 mL.

[0017] Preferably, the temperature of the reaction in step (3) is 110 - 130 °C; the time of the reaction is 60 - 80 h.

[0018] Preferably, the aldehyde group-containing monomer in step (3) is phloroglucinol trialdehyde; the organic solvent is a mixture of 1,4-dioxane and mesitylene.

[0019] The present invention also provides a core-shell structure composite material prepared by a preparation method of a core-shell structure composite material.

[0020] The present invention also provides an application of a core-shell structure composite material in adsorbing metal ions in water bodies.

[0021] It can be seen from the above technical solutions that, compared with the prior art, the present invention has the following beneficial effects:

[0022] (1) First, the present invention loads Fe₃O₄ on the biochar by coprecipitation of iron salt, ferrous salt and biochar, then modifies it with polyethyleneimine to form an amino group as the magnetic core; and then in-situ prepares a covalent organic framework (COF) shell layer on the surface of the magnetic core to obtain a core-shell structure composite adsorption material.

[0023] (2) In the present invention, the shell layer and the aminated modified magnetic core are chemically connected through Schiff base reaction, enhancing the connection strength between the core and the shell. After the coating of the COF shell in the present invention, on the one hand, the structural stability of the magnetic core is improved, the pore structure of the biochar is not easily collapsed, and the magnetic particles are not easily detached. On the other hand, the amino monomer used in the COF shell contains sulfonic acid groups and has a negative charge. It can combine with metal ions through electrostatic interaction, improving the binding strength of metal ions on the surface of the adsorbent and increasing the adsorption sites of the adsorbent. At the same time, the COF shell is a porous structure with a large specific surface area and also has an adsorption effect on metal ions. The multiple adsorption effects of the COF shell and the magnetic core provide more adsorption sites for metal ions, effectively improving the metal ion removal rate.

[0024] (3) The composite adsorbent of the present invention has magnetic particles of magnetite. After the adsorption is completed, the adsorbent can be magnetically separated and recovered, with simple recovery and high recovery efficiency, improving the problem that biochar powder is not easily recovered and there is a large loss. Moreover, after the coating of the COF shell, the detachment of magnetic particles during the adsorption-desorption cycle is reduced, prolonging the service life of the adsorbent. Specific embodiments

[0025] The present invention provides a preparation method of a core-shell structure composite material, including the following steps:

[0026] (1) Mix iron salt, ferrous salt, biochar, and water, add sodium hydroxide solution to adjust the pH to 10 - 11, and react to obtain magnetite@biochar;

[0027] (2) Mix magnetite@biochar, polyethyleneimine, and methanol, and carry out modification to obtain modified biochar;

[0028] (3) Using the modified biochar as the core, mix the modified biochar, amino-containing monomer, aldehyde group-containing monomer, and organic solvent, and react under closed conditions to obtain the core-shell structure composite material.

[0029] In the present invention, the preparation method of the biochar in step (1) is: after crushing the biomass raw material, pyrolyze it under a protective atmosphere to obtain biochar; the biomass raw material is preferably one or more of corn straw, coconut shell, and rice husk, further preferably corn straw or coconut shell, and more preferably corn straw; the particle size after crushing is preferably 0.1 mm - 2 cm, further preferably 0.5 mm - 1 cm, and more preferably 0.1 cm; the protective atmosphere is preferably a nitrogen atmosphere; the pyrolysis temperature is preferably 600 - 800 °C, further preferably 620 - 700 °C, and more preferably 650 °C; the pyrolysis time is preferably 1 - 2 h, further preferably 1.5 - 2 h, and more preferably 2 h.

[0030] In the present invention, the iron salt in step (1) is preferably ferric chloride and / or ferric nitrate, more preferably ferric chloride or ferric nitrate, and still more preferably ferric nitrate; the ferrous salt is preferably ferrous sulfate.

[0031] In the present invention, the dosage ratio of the iron salt, ferrous salt, and biochar in step (1) is preferably 0.02 - 0.1 mol: 0.01 - 0.05 mol: 1 - 10 g, more preferably 0.04 - 0.08 mol: 0.02 - 0.04 mol: 5 - 10 g, and still more preferably 0.06 mol: 0.03 mol: 10 g.

[0032] In the present invention, the dosage ratio of the biochar and water in step (1) is preferably 1 - 10 g: 50 - 100 mL, more preferably 5 - 10 g: 80 - 100 mL, and still more preferably 10 g: 100 mL.

[0033] In the present invention, the concentration of the sodium hydroxide solution in step (1) is preferably 1 - 8 mol / L, more preferably 2 - 6 mol / L, and still more preferably 5 mol / L.

[0034] In the present invention, the temperature of the reaction in step (1) is preferably 25 - 35 °C, more preferably 25 - 30 °C, and still more preferably 25 °C; the reaction time is preferably 1 - 4 h, more preferably 1 - 3 h, and still more preferably 2 h.

[0035] In the present invention, the dosage ratio of the Fe₃O₄@biochar, polyethyleneimine, and methanol in step (2) is preferably 3 - 15 g: 1 - 10 g: 100 mL, more preferably 5 - 13 g: 4 - 8 g: 100 mL, and still more preferably 12 g: 7 g: 100 mL.

[0036] In the present invention, the molecular weight of the polyethyleneimine in step (2) is preferably 300 - 2000, more preferably 600 - 2000, and still more preferably 1800.

[0037] In the present invention, the temperature of the modification in step (2) is preferably 50 - 90 °C, more preferably 60 - 85 °C, and still more preferably 80 °C; the modification time is preferably 2 - 6 h, more preferably 2.5 - 5 h, and still more preferably 3 h.

[0038] In the present invention, the dosage ratio of the modified biochar, amino - containing monomer, aldehyde - containing monomer, and organic solvent in step (3) is preferably 1 g: 0.5 - 1 g: 1 - 2 g: 100 - 200 mL, more preferably 1 g: 0.6 - 0.9 g: 1.1 - 1.5 g: 120 - 190 mL, and still more preferably 1 g: 0.8 g: 1.2 g: 180 mL.

[0039] In the present invention, the temperature of the reaction in step (3) is preferably 110 - 130 °C, more preferably 115 - 125 °C, and still more preferably 120 °C; the reaction time is preferably 60 - 80 h, more preferably 62 - 70 h, and still more preferably 64 h.

[0040] In the present invention, the amino-containing monomer in step (3) is preferably 4,4'-diamino-[1,1'-biphenyl]-3,3'-disulfonic acid.

[0041] In the present invention, the aldehyde group-containing monomer in step (3) is preferably phloroglucinol trialdehyde.

[0042] In the present invention, the organic solvent in step (3) is preferably a mixture of 1,4-dioxane and mesitylene; the volume ratio of 1,4-dioxane to mesitylene is preferably 1 - 3:1, more preferably 1.4 - 2.7:1, and still more preferably 2:1.

[0043] In the present invention, after the reaction in step (3), centrifugation, washing, and drying are also included; the washing is sequentially carried out with 1,4-dioxane, ethanol, and acetone.

[0044] The present invention also provides a core-shell structure composite material prepared by a method for preparing a core-shell structure composite material.

[0045] The present invention also provides an application of a core-shell structure composite material in adsorbing metal ions in water bodies.

[0046] In the present invention, the metal ions in the water body include one or more of Cd(II), Cr(VI), As(III), As(V), Pb(II), Cu(II), and Ni(II).

[0047] Next, the technical solutions in the embodiments of the present invention will be described clearly and completely. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0048] Example 1

[0049] This example provides a method for preparing a core-shell structure composite material, including the following steps:

[0050] (1) Crush corn straw to a particle size of 0.1 cm, and pyrolyze it at 650 °C for 2 h under a nitrogen atmosphere to obtain biochar;

[0051] (2) Stir and mix ferric nitrate, ferrous sulfate, biochar, and water evenly according to the dosage ratio of 0.06 mol: 0.03 mol: 10 g: 100 mL, add 5 mol / L sodium hydroxide solution to adjust the pH to 10.5, react at 25 °C for 2 h, then perform centrifugal separation, and wash 3 times with ethanol and water respectively, and vacuum dry at 80 °C for 6 h to obtain magnetite@biochar;

[0052] (3) Mix magnetite@biochar, polyethyleneimine (molecular weight of 1800), and methanol evenly according to the dosage ratio of 12 g: 7 g: 100 mL, modify at 80 °C for 3 h under stirring at 800 rpm. After the reaction is completed, cool to room temperature, filter, wash 3 times with water, and vacuum dry at 80 °C for 6 h to obtain modified biochar;

[0053] (4) Using the modified biochar as the core, and using 1,4-dioxane and mesitylene with a volume ratio of 2:1 as organic solvents, mix the modified biochar and the organic solvents, and successively add 4,4'-diamino-[1,1'-biphenyl]-3,3'-disulfonic acid and phloroglucinol trialdehyde, stir and mix evenly, so that the dosage ratio of the modified biochar, 4,4'-diamino-[1,1'-biphenyl]-3,3'-disulfonic acid, phloroglucinol trialdehyde, and organic solvent is 1 g: 0.8 g: 1.2 g: 180 mL. Then seal the reaction flask and react at 120 °C for 64 h under closed conditions. After the reaction is completed, cool to room temperature and centrifuge, and wash successively with 1,4-dioxane, ethanol, and acetone, repeat the washing 3 times until the supernatant is colorless, and vacuum dry at 80 °C for 12 h to obtain the core-shell structure composite material.

[0054] Example 2

[0055] This example provides a method for preparing a core-shell structure composite material, including the following steps:

[0056] (1) Crush the coconut shell to a particle size of 0.5 mm cm, and pyrolyze at 680 °C for 1.5 h under a nitrogen atmosphere to obtain biochar;

[0057] (2) Stir and mix ferric nitrate, ferrous sulfate, biochar, and water evenly according to the dosage ratio of 0.02 mol: 0.01 mol: 2 g: 100 mL, add 2 mol / L sodium hydroxide solution to adjust the pH to 10, react at 25 °C for 1 h, then perform centrifugal separation, and wash 3 times with ethanol and water respectively, and vacuum dry at 80 °C for 6 h to obtain magnetite@biochar;

[0058] (3) Mix 3 g of iron oxide @ biochar, 2 g of polyethyleneimine (molecular weight of 300), and 100 mL of methanol evenly, and modify at 60 °C for 2 h under stirring at 800 rpm. After the reaction, cool to room temperature, filter, wash 3 times with water, and dry in vacuum at 80 °C for 6 h to obtain modified biochar;

[0059] (4) Using the modified biochar as the core and 1,4-dioxane and mesitylene with a volume ratio of 1:1 as the organic solvents, mix the modified biochar and the organic solvents, and successively add 4,4'-diamino-[1,1'-biphenyl]-3,3'-disulfonic acid and phloroglucinol trialdehyde, and stir and mix evenly so that the dosage ratio of the modified biochar, 4,4'-diamino-[1,1'-biphenyl]-3,3'-disulfonic acid, phloroglucinol trialdehyde, and the organic solvent is 1 g: 0.5 g: 1 g: 100 mL. Then seal the reaction flask and react at 110 °C for 70 h under closed conditions. After the reaction, cool to room temperature and centrifuge, and wash successively with 1,4-dioxane, ethanol, and acetone, repeat washing 3 times until the supernatant is colorless, and dry in vacuum at 80 °C for 12 h to obtain the core-shell structure composite material.

[0060] Example 3

[0061] This example provides a preparation method of a core-shell structure composite material, including the following steps:

[0062] (1) Crush corn straw to a particle size of 1 cm, and pyrolyze at 700 °C for 1 h under a nitrogen atmosphere to obtain biochar;

[0063] (2) Stir and mix 0.04 mol of ferric nitrate, 0.02 mol of ferrous sulfate, 5 g of biochar, and 50 mL of water evenly, add 5 mol / L sodium hydroxide solution to adjust the pH to 10, react at 30 °C for 2 h, then centrifuge and wash 3 times with ethanol and water respectively, and dry in vacuum at 80 °C for 6 h to obtain iron oxide @ biomass carbon;

[0064] (3) Mix 8 g of iron oxide @ biochar, 1 g of polyethyleneimine (molecular weight of 1000), and 100 mL of methanol evenly, and modify at 70 °C for 4 h under stirring at 800 rpm. After the reaction, cool to room temperature, filter, wash 3 times with water, and dry in vacuum at 80 °C for 6 h to obtain modified biochar;

[0065] (4) Using the modified biochar as the core and 1,4-dioxane and mesitylene with a volume ratio of 1:1 as organic solvents, mix the modified biochar and the organic solvents, and successively add 4,4'-diamino-[1,1'-biphenyl]-3,3'-disulfonic acid and phloroglucinol trialdehyde, and stir and mix evenly. The dosage ratio of the modified biochar, 4,4'-diamino-[1,1'-biphenyl]-3,3'-disulfonic acid, phloroglucinol trialdehyde, and the organic solvent is 1 g:0.7 g:2 g:100 mL. Then seal the reaction flask and react at 130 °C for 72 h under airtight conditions. After the reaction is completed, cool to room temperature and then centrifuge, and wash successively with 1,4-dioxane, ethanol, and acetone, repeat the washing 3 times until the supernatant is colorless, and dry in vacuum at 80 °C for 12 h to obtain the core-shell structure composite material.

[0066] Example 4

[0067] This example provides a method for preparing a core-shell structure composite material, including the following steps:

[0068] (1) Crush corn straw to a particle size of 0.5 cm, and pyrolyze at 800 °C for 2 h under a nitrogen atmosphere to obtain biochar;

[0069] (2) Stir and mix evenly ferric nitrate, ferrous sulfate, biochar, and water according to the dosage ratio of 0.1 mol:0.05 mol:7 g:100 mL, add 5 mol / L sodium hydroxide solution to adjust the pH to 11, react at 35 °C for 2 h, then centrifuge and separate, and wash 3 times with ethanol and water respectively, and dry in vacuum at 80 °C for 6 h to obtain Fe₃O₄@biomass carbon;

[0070] (3) Mix Fe₃O₄@biochar, polyethyleneimine (molecular weight 1200), and methanol evenly according to the dosage ratio of 15 g:3 g:100 mL, modify at 90 °C with stirring at 800 rpm for 5 h. After the reaction is completed, cool to room temperature, filter, wash 3 times with water, and dry in vacuum at 80 °C for 6 h to obtain the modified biochar;

[0071] (4) Using modified biochar as the core and 1,4-dioxane and mesitylene with a volume ratio of 3:1 as organic solvents, mix the modified biochar and the organic solvents, and successively add 4,4'-diamino-[1,1'-biphenyl]-3,3'-disulfonic acid and phloroglucinol trialdehyde, and stir and mix evenly. The dosage ratio of the modified biochar, 4,4'-diamino-[1,1'-biphenyl]-3,3'-disulfonic acid, phloroglucinol trialdehyde, and the organic solvent is 1 g:1 g:2 g:200 mL. Then seal the reaction flask and react at 130 °C for 80 h under airtight conditions. After the reaction, cool to room temperature and centrifuge, and wash successively with 1,4-dioxane, ethanol, and acetone, and repeat the washing 3 times until the supernatant is colorless, and dry in vacuo at 80 °C for 12 h to obtain the core-shell structure composite material.

[0072] Comparative Example 1

[0073] This comparative example provides a Fe₃O₄@biochar composite material. The specific preparation method refers to steps (1) and (2) of Example 1.

[0074] Comparative Example 2

[0075] This comparative example provides a core-shell structure composite material. The specific preparation method refers to Example 1, and the difference is that step (3) is not carried out.

[0076] Test the adsorption performance of the composite materials of Examples 1 to 4 and Comparative Examples 1 to 2. Specifically: Prepare a simulated wastewater solution with a volume of 100 mL, a pH of 5, and an initial Cd(II) concentration of 1000 mg / L. The addition amount of the composite material is 1 g, and the adsorption time is 24 h. Measure the adsorption capacity of the composite material for Cd(II). The adsorption capacities of the composite materials of Examples 1 to 4 and Comparative Examples 1 to 2 for Cd(II) are 73.6 mg / g, 71.4 mg / g, 72.4 mg / g, 73.3 mg / g, 22.5 mg / g, and 68.8 mg / g, respectively.

[0077] Prepare a simulated wastewater solution with a volume of 100 mL, a pH of 5, and an initial Cr(VI) concentration of 1000 mg / L by the same method. The addition amount of the composite material is 1 g, and the adsorption time is 24 h. Measure the adsorption capacity of the composite material for Cr(VI). The adsorption capacities of the composite materials of Examples 1 to 4 and Comparative Examples 1 to 2 for Cr(VI) are 92.3 mg / g, 91.4 mg / g, 91.8 mg / g, 92.1 mg / g, 25.7 mg / g, and 86.5 mg / g, respectively.

[0078] The adsorption-desorption cycle performance of the composite materials of Examples 1-4 and Comparative Examples 1-2 was tested as follows: A simulated wastewater solution with a volume of 100 mL, a pH of 5, and an initial Cr(VI) concentration of 1000 mg / L was prepared. The addition amount of the composite material was 1 g, and the adsorption time was 24 h. After adsorption, the composite material adsorbed with Cr(VI) was desorbed in a 1 mol / L hydrochloric acid solution for 12 h. After desorption, it was washed with water until neutral, and adsorption and desorption were repeated. After the adsorption-desorption was repeated 10 times, the adsorption capacity of the composite material for Cr(VI) was tested. The ratio of the adsorption capacity after 10 adsorption-desorption repetitions to the initial adsorption capacity was used as the adsorption capacity retention rate to evaluate the adsorption-desorption cycle performance of the composite material. The adsorption capacity retention rates of the composite materials of Examples 1-4 and Comparative Examples 1-2 were 89.1%, 86.5%, 87.7%, 88.4%, 44.9%, and 68.4%, respectively. It can be seen that the core-shell structured composite material of the present invention has good cycle stability, while the adsorption capacity of the biochar material decreases significantly after multiple cycles, and the stability is poor. Moreover, the amination modification of Fe₃O₄@biochar enables Fe₃O₄@biochar to be connected to the COF shell through stable chemical bonds, and has higher stability after being compounded with the COF shell compared to unaminated Fe₃O₄@biochar.

[0079] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing a core-shell structure composite material, characterized in that, It includes the following steps: (1) Mix iron salt, ferrous salt, biochar and water, add sodium hydroxide solution to adjust the pH to 10 - 11, and carry out a reaction to obtain magnetite@biochar; (2) Mix magnetite@biochar, polyethyleneimine and methanol, and carry out modification to obtain modified biochar; (3) Using the modified biochar as the core, mix the modified biochar, amino - containing monomer, aldehyde - containing monomer and organic solvent, and carry out a reaction under closed conditions to obtain a core - shell structure composite material; The amino - containing monomer is 4,4’ - diamino - [1,1’ - biphenyl] - 3,3’ - disulfonic acid.

2. The preparation method of a core-shell structure composite material according to claim 1, characterized in that, In step (1), the dosage ratio of the iron salt, ferrous salt and biochar is 0.02 - 0.1 mol: 0.01 - 0.05 mol: 1 - 10 g.

3. The preparation method of a core-shell structure composite material according to claim 2, characterized in that, In step (1), the temperature of the reaction is 25 - 35 °C; the time of the reaction is 1 - 4 h.

4. The preparation method of a core-shell structure composite material according to claim 1 or 2, characterized in that, In step (2), the dosage ratio of magnetite@biochar, polyethyleneimine and methanol is 3 - 15 g: 1 - 10 g: 100 mL.

5. The preparation method of a core-shell structure composite material according to claim 4, wherein, In step (2), the temperature of the modification is 50 - 90 °C; the time of the modification is 2 - 6 h.

6. The preparation method of a core-shell structure composite material according to claim 5, characterized in that, In step (3), the dosage ratio of the modified biochar, amino - containing monomer, aldehyde - containing monomer and organic solvent is 1 g: 0.5 - 1 g: 1 - 2 g: 100 - 200 mL.

7. The preparation method of a core-shell structure composite material according to claim 6, characterized in that, In step (3), the temperature of the reaction is 110 - 130 °C; the time of the reaction is 60 - 80 h.

8. The preparation method of a core-shell structure composite material according to claim 7, characterized in that, In step (3), the aldehyde - containing monomer is phloroglucinol trialdehyde; the organic solvent is a mixture of 1,4 - dioxane and mesitylene.

9. A core - shell structure composite material prepared by the preparation method of a core - shell structure composite material according to any one of claims 1 - 8.

10. Application of the core - shell structure composite material according to claim 9 in adsorbing metal ions in water bodies.