Magnetic driven self-diffusion zero-valent iron-based composite material, preparation method and application

Abstract

This invention discloses a magnetically driven self-diffusion zero-valent iron-based composite material, its preparation method, and its application, belonging to the technical field of environmental remediation functional materials. The composite material is composed of asymmetric bowl-shaped aminophenol-formaldehyde nanobowls and nano-zero-valent iron. It not only exhibits magnetically driven directional movement and autonomous diffusion capabilities distinct from traditional environmental remediation materials, but also demonstrates excellent removal efficiency for hexavalent chromium and other heavy metal pollution in water, relying on the chelating coordination effect of the aminophenol-formaldehyde nanobowl functional groups and the reduction and adsorption effects of zero-valent iron itself. Therefore, this invention effectively solves the problem in practical applications where traditional zero-valent iron-based remediation materials require external auxiliary means such as in-situ reaction zones and permeable reaction walls to achieve diffusion and migration. Simultaneously, by simply controlling the external magnetic field and conventional reaction conditions, efficient treatment of heavy metal pollution in water and soil systems and rapid material recovery can be achieved.

Description

Technical Field

[0001] This invention belongs to the field of environmental remediation functional materials technology, specifically relating to a magnetically driven self-diffusion zero-valent iron-based composite material, its preparation method, and its application. Background Technology

[0002] Zero-valent iron (ZVFe) possesses strong reducing power, good environmental compatibility, and is widely available and inexpensive, making it a functional material with great application potential in the field of heavy metal remediation in water and soil environments. ZVFe exists in various forms, including micron-sized iron, nano-sized ZVFe, and iron filings. It achieves efficient removal of heavy metal pollutants from water and soil environments primarily through multiple coupled processes such as chemical reduction, physical adsorption, and co-precipitation. Since the 1990s, ZVFe has been widely used for the reduction and fixation of heavy metal ions such as chromium, lead, mercury, and copper, as well as for pollution control.

[0003] Currently, nano-zero-valent iron still suffers from numerous drawbacks in practical applications, severely limiting its remediation efficiency and service life. Firstly, nano-zero-valent iron has a large specific surface area and high surface energy, and its inherent magnetic properties easily lead to aggregation, significantly reducing the specific surface area and active sites. This weakens its migration and diffusion capabilities in groundwater and soil pores, making it difficult to reach the core pollution area. Secondly, the material exhibits poor oxidation resistance and storage stability, easily undergoing spontaneous oxidation in air and oxygenated water environments, forming a dense passivation layer on the surface and causing deactivation of the active iron core. Thirdly, its low electron utilization efficiency makes it prone to ineffective side reactions with water and dissolved oxygen, significantly reducing the reduction and removal effect on target heavy metals. Various modification methods have been reported to optimize the performance of zero-valent iron. For example, Chinese patent CN114751502B uses aminocarboxylic acid compounds to chelate iron ions, preparing a core-shell modified zero-valent iron composite material in one step, which can effectively inhibit particle aggregation and oxidative deactivation. However, this process requires strict control of reaction conditions. Chinese patent CN119461622A prepares nitrided core-shell structured zero-valent iron through gas-phase synthesis, which effectively alleviates the surface passivation problem. However, this technology relies on dedicated high-temperature gas-phase equipment, which consumes a lot of energy. Summary of the Invention

[0004] Existing zero-valent iron (ZVFe) modification schemes and heavy metal pollution control technologies generally suffer from high preparation costs, complex processes, and stringent reaction conditions. More importantly, they lack the ability to controllably drive diffusion and achieve efficient recovery. Currently, there are no publicly reported patents on technologies that utilize the magnetic self-diffusion effect, combined with the synergistic effects of ZVFe reduction, adsorption, and complexation fixation, to achieve autonomous diffusion of ZVFe, controllable magnetic field recovery, and efficient removal of heavy metals. To address the shortcomings of these technologies, this invention provides a magnetically driven self-diffusion ZVFe-based composite material, its preparation method, and its applications.

[0005] This invention discloses a method for preparing a magnetically driven self-diffusion zero-valent iron-based composite material. First, aminophenol-formaldehyde nanospheres are prepared by self-condensation reaction under weakly alkaline conditions. Second, an organic solvent selective etching strategy is used to construct aminophenol-formaldehyde nanobowls with an asymmetric bowl-shaped structure. Finally, nano-zero-valent iron is loaded using an in-situ chemical reduction method to obtain a zero-valent iron-based aminophenol-formaldehyde nanobowl composite material with magnetically driven self-diffusion capability.

[0006] The preparation method of the magnetically driven self-diffusion zero-valent iron-based composite material specifically includes the following steps:

[0007] Step 1: At room temperature, 3-aminophenol and formaldehyde solution are dispersed in deionized water to obtain reaction solution I. Ammonia water is then added to adjust reaction solution I to be weakly alkaline. The reaction is continuously stirred magnetically for a certain period of time, and aminophenol formaldehyde nanospheres are prepared by self-condensation reaction.

[0008] Step 2: Add acetone solution to reaction solution I obtained in step 1, and stir magnetically for a certain period of time to induce selective etching reaction of organic solvent; after the reaction is completed, wash with deionized water multiple times, separate by centrifugation, and dry under constant temperature conditions to obtain asymmetric aminophenol formaldehyde nanobowls.

[0009] Step 3: Add a quantitative amount of aminophenol-formaldehyde nanobowls to a double-necked flask. Under the protection of nitrogen inert atmosphere, add an aqueous solution containing iron salt to obtain reaction solution II. Mix with magnetic stirring to allow iron ions to be fully adsorbed on the surface and inside the pores of the aminophenol-formaldehyde nanobowls.

[0010] Step 4: Dissolve the reducing agent in deionized water to obtain a reducing agent solution, and slowly add it dropwise to reaction solution II in the double-necked flask of step 3. After the addition is completed, continue to stir the reaction magnetically for a certain period of time. After the reaction is completed, the product is centrifuged, washed multiple times, and then vacuum dried to finally obtain the asymmetric aminophenol formaldehyde nanobowl-supported zero-valent iron composite material, namely the magnetically driven self-diffusion zero-valent iron-based composite material.

[0011] Preferably, in step 1, the molar ratio of 3-aminophenol to formaldehyde is 1:(1.1~1.8); the concentration of ammonia in mixed reaction solution I (NH3·H2O concentration) is 0.01~0.05 mol / L; and the polycondensation reaction time is 5~30 min.

[0012] Preferably, in step 2, the volume ratio of acetone to the reaction solution is (0.6~1.8):1; and the selective etching reaction time is 20~120 min.

[0013] Preferably, in step 3, the concentration of the iron salt in the reaction solution is 1~5 mg / mL; the concentration of the aminophenol-formaldehyde nanobowl in reaction solution II is 0.5~2 mg / mL; and the iron salt is one or more of ferrous ammonium sulfate hexahydrate, ferric chloride, and ferrous sulfate.

[0014] Preferably, in step 4, the in-situ reduction reaction time is 40-80 min; the concentration of the reducing agent solution is 3-10 mg / mL; the volume ratio of the reducing agent solution to reaction solution II is 1:1; and the reducing agent is one or more of sodium borohydride, hydrazine hydrate, and potassium borohydride.

[0015] The magnetically driven self-diffusion zero-valent iron-based composite material obtained by any of the above preparation methods can achieve directional movement, active diffusion and rapid recycling through an external magnetic field by utilizing the ferromagnetism of the zero-valent iron-based material, thus solving the problems of agglomeration, oxidation and difficulty in recycling of traditional zero-valent iron.

[0016] The magnetically driven self-diffusion zero-valent iron-based composite material obtained by any of the above preparation methods can be applied to the remediation of groundwater, surface water and soil contaminated by various heavy metal ions (such as chromium, lead, mercury, copper, etc.).

[0017] Beneficial effects:

[0018] (1) The magnetically driven self-diffusion zero-valent iron-based composite material disclosed in this invention has the directional movement, active diffusion and rapid recycling capabilities that traditional zero-valent iron-based environmental remediation materials do not have. Without the need for additional technical assistance such as in-situ reaction zones and permeable reaction walls, it can effectively overcome the obstacles of the heterogeneity of the aquifer and actively penetrate the low-permeability area, thereby solving the problem that traditional remediation materials cannot reach the polluted area, resulting in the spatial misalignment of the pollutants with the pollutants.

[0019] (2) The magnetically driven self-diffusion zero-valent iron-based composite material disclosed in this invention utilizes the porous confined structure of aminophenol formaldehyde nanobowls, which can effectively solve the technical problems of easy agglomeration, easy oxidation and difficult recycling of traditional zero-valent iron.

[0020] (3) The aminophenol-formaldehyde nanobowl molecular framework contains abundant phenolic hydroxyl and amino groups, which can play a chelating and coordination role; combined with the reduction, adsorption and complexation fixation effect of zero-valent iron itself, the composite material has excellent heavy metal ion removal performance. Taking the removal of hexavalent chromium in water as an example, the removal rate of hexavalent chromium can reach more than 90% within 60 min. Attached Figure Description

[0021] Figure 1 This is a flowchart illustrating the preparation process of the magnetically driven self-diffusion zero-valent iron-based composite material of the present invention.

[0022] Figure 2This is a time-lapse photograph taken by a digital camera of the magnetic drive motion of the magnetic drive self-diffusion zero-valent iron-based composite material prepared in Example 1 of the present invention.

[0023] Figure 3 The images show the magnetically driven directional motion and hexavalent chromium removal of the magnetically driven self-diffusion zero-valent iron-based composite material prepared in Example 1 of this invention.

[0024] Figure 4 The X-ray diffraction pattern of the magnetically driven self-diffusion zero-valent iron-based composite material prepared in Example 1 of this invention;

[0025] Figure 5 Transmission electron microscopy of the magnetically driven self-diffusion zero-valent iron-based composite material prepared in Example 1 of this invention;

[0026] Figure 6 The hysteresis loop of the magnetically driven self-diffusion zero-valent iron-based composite material prepared in Example 1 of this invention;

[0027] Figure 7 The curve showing the hexavalent chromium removal performance of the magnetically driven self-diffusion zero-valent iron-based composite material prepared in Example 1 of this invention.

[0028] Figure 8 This is a schematic diagram illustrating the magnetic drive motion and heavy metal pollution control application of the magnetically driven self-diffusion zero-valent iron-based composite material of the present invention. Detailed Implementation

[0029] The technical solution of the present invention will be described in detail below through embodiments, but the scope of protection of the present invention is not limited to the embodiments described.

[0030] Unless otherwise specified, all raw materials used in this invention are commercially available.

[0031] The materials obtained in the embodiments of the present invention were subjected to performance testing according to the following method:

[0032] Magnetic self-diffusion test: Weigh 10 mg of the composite material prepared in this invention and add it to 10 mL of deionized water to prepare a suspension of 1 g / L; transfer 500 μL of the above suspension and inject it into a specially shaped polyvinyl chloride plastic tube or an acrylic plate channel with 6 interconnected chambers. Apply an external magnetic field to regulate the material's movement behavior and use a digital camera to take time-lapse photos to record the migration and diffusion process of the composite material.

[0033] Heavy metal ion removal performance test: To verify the remediation effect of the composite material of the present invention on heavy metal pollution, hexavalent chromium ions were selected as simulated heavy metal pollutants. 4 mg of the composite material prepared in this invention was weighed and added to 20 mL of a 5 ppm hexavalent chromium aqueous solution, and the pH of the system was adjusted to 3. The material movement was controlled under the action of an external magnetic field, and the removal efficiency of hexavalent chromium was determined and calculated using the absorbance method.

[0034] Example 1

[0035] A method for preparing a magnetically driven self-diffusion zero-valent iron-based composite material includes the following steps:

[0036] Step 1: At room temperature, 0.1 g of 3-aminophenol and 0.05 mL of commercially available 27.5% concentrated ammonia solution were added to 30 mL of deionized water. After mixing thoroughly, 0.1 mL of commercially available 37% formaldehyde solution was added. The mixture was magnetically stirred at 600 rpm for 20 min, and aminophenol-formaldehyde nanospheres were prepared through a self-condensation reaction. The molar ratio of 3-aminophenol to formaldehyde was 1:1.5, and the concentration of ammonia solution in the mixed solution was 0.024 mol / L.

[0037] Step 2: Add 38 mL of acetone to the reaction system in Step 1, stir the mixture at 600 rpm for 60 min, wash the precipitate obtained by filtration with deionized water 3 times, centrifuge at 9000 rpm for 10 min, and vacuum dry at 40 ℃ for 24 h to obtain asymmetric aminophenol formaldehyde nanobowls.

[0038] Step 3: Under N2 atmosphere protection, dissolve 200 mg of ferrous ammonium sulfate hexahydrate in 10 mL of deionized water, transfer 1 mL of the solution into a double-necked flask and add 9 mL of deionized water, add 10 mg of the asymmetric aminophenol formaldehyde nanobowl obtained in step 1, and stir at 600 rpm for 60 min until fully adsorbed and mixed.

[0039] Step 4: Dissolve 40 mg of sodium borohydride in 10 mL of deionized water and inject it into a double-necked flask at a rate of 3 drops / s using a syringe. After the addition is complete, continue stirring at 600 rpm for 60 min. After the reaction is complete, wash the mixture three times with ethanol by centrifugation (centrifugation at 9000 rpm for 10 min each time) and dry it under vacuum at 60℃ for 24 h to obtain the asymmetric aminophenol formaldehyde nanobowl-supported zero-valent iron composite repair material, namely the magnetically driven self-diffusion zero-valent iron-based composite material.

[0040] Figure 8 This diagram illustrates the magnetic drive motion and heavy metal pollution control application of a magnetically driven self-diffusion zero-valent iron-based composite material. The heavy metal removal performance of the composite material prepared in Example 1 was tested using the following specific methods:

[0041] Four mg of magnetically driven self-diffusion zero-valent iron-based composite material was added to 20 mL of an aqueous solution with an initial concentration of 5 ppm hexavalent chromium. Under an external magnetic field, the composite material was directed to contact the contaminant, and the reaction was carried out at room temperature for 60 min. After the reaction, the supernatant was collected, and the concentration of hexavalent chromium was determined by ultraviolet spectrophotometry, and the removal rate was calculated. Simultaneously, the material was recovered using an external magnetic field, washed, dried, and collected for later use. The results showed that the hexavalent chromium removal rate was 92.3%, the magnetic field separation time was only 2 min, and the recovered material showed no obvious agglomeration.

[0042] Figure 2 This is a time-lapse photograph taken with a digital camera of the magnetically driven motion of the magnetically driven self-diffusion zero-valent iron-based composite material prepared in Example 1 of this invention. The time-lapse photograph shows that the composite material exhibits good magnetically driven directional motion and autonomous diffusion capabilities within straight, curved, and annular polyvinyl chloride plastic tube channels.

[0043] Figure 3 This image shows the magnetically driven directional movement and hexavalent chromium removal effect of the magnetically driven self-diffusion zero-valent iron-based composite material prepared in Example 1 of this invention. It can be observed that the composite material can move directionally between the chambers under the drive of an external magnetic field within an acrylic plate channel with six interconnected chambers, and exhibits excellent removal effect on hexavalent chromium contaminants within the chambers.

[0044] Figure 4 The X-ray diffraction pattern of the magnetically driven self-diffusion zero-valent iron-based composite material prepared in Example 1 of this invention is shown. The spectra reveal that the pure aminophenol-formaldehyde nanobowls do not exhibit any sharp diffraction peaks; the broad diffraction peaks appearing in the 25-45° range are typical diffraction characteristics of amorphous polymers. After loading zero-valent iron through confined chemical reduction, the characteristic diffraction peaks of zero-valent iron appear in the composite material's diffraction pattern, proving that zero-valent iron has been successfully loaded onto the surface and interior of the aminophenol-formaldehyde nanobowl carrier.

[0045] Figure 5 This is a transmission electron microscope image of the magnetically driven self-diffusion zero-valent iron-based composite material prepared in Example 1 of the present invention. As can be seen from the image, the prepared composite material exhibits a clear asymmetric bowl-shaped structure, and the dark shaded spots in the structure represent the loaded zero-valent iron-based material.

[0046] Figure 6 The image shows the hysteresis loop of the magnetically driven self-diffusion zero-valent iron-based composite material prepared in Example 1 of this invention. The curves show that the composite material possesses excellent ferromagnetic properties, meeting the application requirements for directional driving and rapid magnetic recovery under an applied magnetic field.

[0047] Figure 7The curve shows the hexavalent chromium removal performance of the magnetically driven self-diffusion zero-valent iron-based composite material prepared in Example 1 of this invention. The curves show that the aminophenol-formaldehyde nanobowls without zero-valent iron loading possess a certain adsorption and removal capacity for hexavalent chromium due to the abundant phenolic hydroxyl and amino groups on their molecular backbone. After loading with zero-valent iron, the hexavalent chromium removal performance of the magnetically driven self-diffusion zero-valent iron-based composite material is significantly improved, achieving near-complete removal of hexavalent chromium within 60 minutes.

[0048] Example 2

[0049] A method for preparing a magnetically driven self-diffusion zero-valent iron-based composite material includes the following steps:

[0050] Step 1: At room temperature, 0.1 g of 3-aminophenol and 0.05 mL of concentrated ammonia were added to 30 mL of deionized water. After mixing evenly, 0.1 mL of formaldehyde solution was added. The mixture was magnetically stirred at 600 rpm for 20 min. Aminophenol formaldehyde nanospheres were prepared by self-condensation reaction.

[0051] Step 2: Add 38 mL of acetone to the reaction system in Step 1, stir at 600 rpm for 60 min, wash three times with deionized water, centrifuge at 9000 rpm for 10 min, and vacuum dry at 40℃ for 24 h to obtain asymmetric aminophenol formaldehyde nanobowls.

[0052] Step 3: Under N2 atmosphere protection, dissolve 400 mg of ferrous ammonium sulfate hexahydrate in 10 mL of deionized water, transfer 1 mL of this solution into a double-necked flask and add 9 mL of deionized water, add 10 mg of the asymmetric aminophenol formaldehyde nanobowl obtained in Step 1, and stir at 600 rpm for 60 min until fully adsorbed and mixed.

[0053] Step 4: Dissolve 40 mg of sodium borohydride in 10 mL of deionized water and inject it into a double-necked flask at a rate of 3 drops / s using a syringe. After the addition is complete, continue stirring at 600 rpm for 60 min. After the reaction is complete, wash three times with ethanol by centrifugation (9000 rpm for 10 min each time), and dry under vacuum at 60℃ for 24 h to obtain the asymmetric aminophenol-formaldehyde nanobowl-supported zero-valent iron composite repair material, namely, the magnetically driven self-diffusion zero-valent iron-based composite material.

[0054] Example 3

[0055] A method for preparing a magnetically driven self-diffusion zero-valent iron-based composite material includes the following steps:

[0056] Step 1: At room temperature, 0.1 g of 3-aminophenol and 0.05 mL of concentrated ammonia were added to 30 mL of deionized water. After mixing evenly, 0.1 mL of formaldehyde solution was added. The mixture was magnetically stirred at 600 rpm for 20 min. Aminophenol formaldehyde nanospheres were prepared by self-condensation reaction.

[0057] Step 2: Add 38 mL of acetone to the reaction system in Step 1, stir at 600 rpm for 60 min, wash three times with deionized water, centrifuge at 9000 rpm for 10 min, and vacuum dry at 40℃ for 24 h to obtain asymmetric aminophenol formaldehyde nanobowls.

[0058] Step 3: Under N2 atmosphere protection, dissolve 200 mg of ferrous ammonium sulfate hexahydrate in 10 mL of deionized water, transfer 1 mL of the solution into a double-necked flask and add 9 mL of deionized water, add 10 mg of the asymmetric aminophenol formaldehyde nanobowl obtained in step 1, and stir at 600 rpm for 60 min until fully adsorbed and mixed.

[0059] Step 4: Dissolve 80 mg of sodium borohydride in 10 mL of deionized water and inject it into a double-necked flask at a rate of 3 drops / s using a syringe. After the addition is complete, continue stirring at 600 rpm for 60 min. After the reaction is complete, wash three times with ethanol by centrifugation (9000 rpm for 10 min each time), and dry under vacuum at 60℃ for 24 h to obtain the asymmetric aminophenol-formaldehyde nanobowl-supported zero-valent iron composite repair material, namely, the magnetically driven self-diffusion zero-valent iron-based composite material.

[0060] Comparative Example 1

[0061] Comparative Example 1 uses a single zero-valent iron material.

[0062] The preparation method of single zero-valent iron material is as follows:

[0063] Under N2 atmosphere protection, 200 mg of ferrous ammonium sulfate hexahydrate was dissolved in 10 mL of deionized water, 1 mL of this solution was transferred to a double-necked flask and 9 mL of deionized water was added; 40 mg of sodium borohydride was dissolved in 10 mL of deionized water and injected into the flask at a rate of 3 s / drop, and stirred at 600 rpm for 60 min; after the reaction, the mixture was washed three times by centrifugation with ethanol and dried under vacuum at 60 °C for 24 h to obtain a single zero-valent iron material.

[0064] Comparative Example 2

[0065] Comparative Example 2 selected a single asymmetric aminophenol formaldehyde nanobowl material (without nano zero-valent iron loading).

[0066] The preparation method of single asymmetric aminophenol-formaldehyde nanobowl material is as follows:

[0067] At room temperature, 0.1 g of 3-aminophenol and 0.05 mL of concentrated ammonia were added to 30 mL of deionized water and mixed thoroughly. Then, 0.1 mL of formaldehyde solution was added and the mixture was magnetically stirred at 600 rpm for 20 min. 38 mL of acetone was then added and the mixture was stirred at 600 rpm for 60 min. The mixture was washed three times with deionized water, centrifuged at 9000 rpm for 10 min, and vacuum dried at 40℃ for 24 h to obtain a single asymmetric aminophenol-formaldehyde nanobowl.

[0068] Comparative Example 3

[0069] Comparative Example 3 uses commercially available iron powder at retail price.

[0070] The material obtained in the above comparative examples was tested for its ability to remove hexavalent chromium from water. The comparison results with those of Examples 1-3 are shown in Table 1.

[0071] Table 1

[0072]

[0073] As shown in the table above, the magnetically driven self-diffusion zero-valent iron-based composite material disclosed in this invention, compared with single zero-valent iron, aminophenol formaldehyde nanobowls without nano-zero-valent iron, and conventional zero-valent iron powder, not only has a better hexavalent chromium removal efficiency, but can also achieve rapid separation and recovery under the action of an external magnetic field; at the same time, it effectively inhibits particle agglomeration, and has better stability and reusability, which is significantly better than the comparative samples.

[0074] In summary, this invention discloses a magnetically driven self-diffusion zero-valent iron-based composite material, its preparation method, and its applications. This magnetically driven self-diffusion zero-valent iron-based composite material is composed of aminophenol-formaldehyde nanobowls with an asymmetric bowl-like structure and confined in-situ chemically reduced nano-zero-valent iron. It not only exhibits magnetically driven directional movement, active diffusion, and rapid recovery capabilities distinct from traditional zero-valent iron-based environmental remediation materials, but also demonstrates excellent removal efficiency for heavy metal ions (such as hexavalent chromium) in water due to the porous confinement effect and chelating coordination effect of the abundant functional groups in the aminophenol-formaldehyde nanobowls, combined with the inherent reduction and adsorption properties of zero-valent iron. Therefore, the magnetically driven self-diffusion zero-valent iron-based composite material disclosed in this invention effectively solves the problems of diffusion migration, aggregation, oxidation, and difficult recovery that traditional zero-valent iron-based remediation materials require additional technical assistance (such as in-situ reaction zones, permeable reaction walls, etc.). Furthermore, through external magnetic field regulation and simple reaction condition control, controllable removal and material recovery of heavy metal pollution in water and soil can be achieved.

[0075] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for preparing a magnetically driven self-diffusion zero-valent iron-based composite material, characterized in that, First, aminophenol-formaldehyde nanospheres were prepared by self-condensation reaction under weakly alkaline conditions. Second, an aminophenol-formaldehyde nanobowl with an asymmetric bowl-shaped structure was constructed by selective etching with organic solvents. Finally, nano-zero valent iron was loaded by in-situ chemical reduction to obtain a magnetically driven self-diffusion zero valent iron-based composite material.

2. The preparation method according to claim 1, characterized in that, The preparation method includes the following steps: Step 1: At room temperature, 3-aminophenol and formaldehyde solution are dispersed in deionized water to obtain reaction solution I. Ammonia water is then added to adjust reaction solution I to be weakly alkaline. The reaction is continuously stirred magnetically for a certain period of time, and aminophenol formaldehyde nanospheres are prepared by self-condensation reaction. Step 2: Add acetone solution to reaction solution I obtained in step 1, and continuously stir magnetically for a certain period of time to induce organic solvent selective etching reaction; after the reaction is completed, wash with deionized water multiple times, separate by centrifugation, and dry under constant temperature conditions to obtain asymmetric aminophenol formaldehyde nanobowls. Step 3: Add a quantitative amount of aminophenol-formaldehyde nanobowls to a double-necked flask. Under the protection of nitrogen inert atmosphere, add an aqueous solution containing iron salt to obtain reaction solution II. Mix with magnetic stirring to allow iron ions to be fully adsorbed on the surface and inside the pores of the aminophenol-formaldehyde nanobowls. Step 4: Dissolve the reducing agent in deionized water to obtain a reducing agent solution, and slowly add it dropwise to reaction solution II in step 3. After the addition is complete, continue to stir the reaction with magnetic force for a certain period of time. After the reaction is completed, centrifuge the product, wash it multiple times, and then vacuum dry it to finally obtain the magnetically driven self-diffusion zero-valent iron-based composite material.

3. The preparation method according to claim 2, characterized in that, In step 1, the molar ratio of 3-aminophenol to formaldehyde is 1:(1.1~1.8); the concentration of ammonia in reaction solution I is 0.01~0.05 mol / L; and the polycondensation reaction time is 5~30 min.

4. The preparation method according to claim 2, characterized in that, In step 2, the volume ratio of acetone to reaction solution I is (0.6~1.8):1; the selective etching reaction time is 20~120 min.

5. The preparation method according to claim 2, characterized in that, In step 3, the concentration of iron salt in the reaction solution is 1~5 mg / mL; the concentration of aminophenol formaldehyde nanobowls in reaction solution II is 0.5~2 mg / mL; and the iron salt is one or more of ferrous ammonium sulfate hexahydrate, ferric chloride, and ferrous sulfate.

6. The preparation method according to claim 2, characterized in that, In step 4, the reaction time is 40-80 min; the concentration of the reducing agent solution is 3-10 mg / mL, and the volume ratio of the reducing agent solution to reaction solution II is 1:1; the reducing agent is one or more of sodium borohydride, hydrazine hydrate, and potassium borohydride.

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