Magnetic polyurethane foam, preparation method and application

Abstract

The invention provides magnetic polyurethane foam as well as a preparation method and application thereof. Magnetic Fe3O4 nanoparticles are modified in the polyurethane foam. The magnetic polyurethane foam has the advantages of precise aperture regulation and control, adsorption-magnetic separation synergy and surface activity enhancement, and integrates high adsorption capacity, environmental adaptability and recoverability. The magnetic polyurethane foam can effectively adsorb low-concentration nano plastic, and the removal rate of the low-concentration nano plastic reaches 97.88%-99.77%. Besides, the magnetic polyurethane foam has relatively high ion interference resistance, can still keep relatively high adsorption efficiency after repeated adsorption for five times, and is expected to play a key role in the field of nano plastic treatment.

Description

Technical Field

[0001] The present invention belongs to the technical field of magnetic adsorption materials, and relates to a magnetic polyurethane foam, a preparation method and an application thereof. Background Art

[0002] Microplastics and nanoplastics (Microplastics / Nanoplastics, abbreviated as MNPs) refer to plastic particles with diameters of 1 μm - 5 mm and diameters < 1 μm, and are a new type of environmental pollutant. MNPs pose a potential threat to the stability of the ecosystem and human health due to their microscopic size, wide distribution, difficult degradation characteristics, persistence in the environment, bioaccumulation and ecological toxicity, which has prompted the academic community to continuously explore technical means for the efficient removal of MNPs. Among them, the adsorption method has become a research hotspot for the removal of MNPs due to its advantages such as simple operation and low energy consumption.

[0003] Currently, common micro-nano plastic adsorption materials mainly include activated carbon, biochar, metal-organic framework materials MOFs, and carbon nanotubes, etc. Although the above materials all have high adsorption capacities for adsorbing microplastics, each has its disadvantages. For example, activated carbon and biochar have a low interception rate for nanoplastics due to the mismatch of pore sizes; although the pore size of MOFs can be adjusted, the structural collapse in the water environment easily causes a sharp drop in its actual adsorption capacity; carbon nanotubes have a high loss of effective specific surface area due to the aggregation effect, and the high separation energy consumption limits its engineering application. Therefore, there is a synergistic imbalance in the three dimensions of "pore size adaptability - surface interaction force - separation efficiency" for the above materials. In addition, the size of MNPs is small, and the Brownian motion and surface charge effects are significant, which makes it difficult for the above materials to capture MNPs through van der Waals forces, hydrogen bonds or electrostatic interactions, etc., and thus MNPs cannot be effectively removed.

[0004] Therefore, to increase the adsorption amount of materials for MNPs, the following problems must be overcome: (1) precisely regulating the pore size distribution of materials to improve the pore size adaptability between materials and nanoplastics, (2) stabilizing the material skeleton structure to improve the structural stability of materials, and (3) enhancing the diffusion rate of nanoplastics in materials to increase the surface active sites of materials. Summary of the Invention

[0005] The purpose of the present invention is to provide a magnetic polyurethane foam, a preparation method and an application thereof to solve the problem that existing MNPs are difficult to effectively remove.

[0006] To achieve the above purpose, the present invention adopts the following technical solutions: Polyurethane foams (PUFs) are high molecular polymers prepared from isocyanates as the main raw material under the action of various additives such as foaming agents, catalysts, and flame retardants. PUFs have a stable and adjustable three-dimensional network porous structure, high porosity, and great potential for chemical modification. Therefore, using them as adsorption materials for MNPs can, to a certain extent, solve the problems of unstable structure and low density of active adsorption sites in existing MNPs adsorption materials. However, the pore structure of traditional polyurethane foams is mainly macropores, and there are still problems with poor pore size adaptability between the adsorption material and MNPs when it is used as an MNPs adsorption material. Magnetic nanoparticles such as Fe3O4 and CoFe2O4 have a high specific surface area and abundant surface active sites. If they are introduced into polymer adsorption, not only can the pore structure of the adsorption material be optimized, the mass transfer process of the adsorbate be accelerated, and the adsorption equilibrium time be shortened, but also the adsorption material can be given the ability to be rapidly separated under an external magnetic field, improving the reuse rate of the adsorption material. Based on this, a magnetic polyurethane foam is provided in this application, and magnetic Fe3O4 nanoparticles are modified in the polyurethane foam.

[0007] In the magnetic polyurethane foam provided in this application, the -OH on the surface of the magnetic Fe3O4 nanoparticles reacts with the -NCO in the polyurethane foam to form Fe-O-C bonds, exerting the synergistic effect of the physical occupancy effect and interfacial stress of the magnetic Fe3O4 nanoparticles, realizing the precise regulation of the polyurethane foam from a single macroporous structure to a macroporous-mesoporous three-dimensional composite structure, increasing the specific surface area of the polyurethane foam, successfully matching the size distribution of 30 - 100 nm nanoplastics, and solving the problem of low nanoplastics interception rate caused by pore mismatch in existing adsorption materials.

[0008] The introduction of magnetic Fe3O4 nanoparticles significantly increases the adsorption active sites on the surface of the polyurethane foam, and its superparamagnetism endows the material with the ability of rapid magnetic response separation.

[0009] The introduction of magnetic Fe3O4 nanoparticles also makes the polyurethane foam have magnetic properties; at the same time, after adsorbing nanoplastics, the nanoplastics can be re-released by means of a weak reverse magnetic field. In addition, the magnetic polyurethane foam has excellent anti-ion properties and shows good elastic recovery ability after being compressed. Even after being used repeatedly for many times, it can still maintain an adsorption capacity of more than 90%, and the pore structure and adsorption sites can also remain stable.

[0010] In addition, in the magnetic polyurethane foam provided in this application, the diameter of the magnetic Fe3O4 nanoparticles is 5 - 200 nm, and the mass ratio of the magnetic Fe3O4 nanoparticles in the polyurethane foam is 1 - 5%.

[0011] This application also provides a preparation method of the magnetic polyurethane foam, and the method includes: S01: Disperse magnetic Fe3O4 nanoparticles in polyether polyol, add isocyanate, catalyst and foaming agent, and stir and foam to obtain foamed polyurethane foam.

[0012] Add magnetic Fe3O4 nanoparticles into polyether polyol, and disperse them for 30 s under mechanical stirring at 2000 rpm to make the magnetic Fe3O4 nanoparticles disperse into the polyether polyol. In this application, the average molecular weight of the polyether polyol is 2000 - 5000 g / mol, and the polyether polyol includes one or more of polyethylene glycol, polytetrahydrofuran, and polypropylene glycol.

[0013] Add isocyanate, catalyst and foaming agent to the mixture of magnetic Fe3O4 nanoparticles and polyether polyol, and stir and react for 10 - 30 s under the conditions of stirring rate of 100 - 300 r / min and stirring temperature of 20 - 40 °C until foaming occurs to obtain foamed polyurethane foam. Among them, the mass ratio of polyether polyol to isocyanate is 1.5:1 - 1:1.5, the addition amount of the catalyst is 0.06 - 0.4% of the total mass of polyether polyol and isocyanate, and the addition amount of the foaming agent is 0.6 - 1.8% of the total mass of polyether polyol and isocyanate.

[0014] In this application, the isocyanate includes one or more of toluene diisocyanate, isophorone diisocyanate, polymethylene polyphenyl isocyanate, and diphenylmethane diisocyanate. The catalyst includes one or more of triethylenediamine, stannous octoate, dibutyltin dilaurate, and tin isooctanoate, and the foaming agent includes water or ethanol.

[0015] S02: After the foamed polyurethane foam reacts at a temperature of 50 - 80 °C for 5 - 20 min, it is cured at room temperature, soaked and washed with distilled water, and freeze-dried to obtain magnetic polyurethane foam.

[0016] Place the foamed polyurethane foam in an oven at a temperature of 50 - 80 °C and react for 5 - 20 min, then cure it at room temperature for 2 - 8 h to obtain cured polyurethane foam. The cured polyurethane foam is placed in distilled water, soaked and washed repeatedly 3 times, and then placed in a freeze dryer at a temperature of -50 °C for freeze-drying for 8 h to obtain magnetic polyurethane foam.

[0017] In this application, the cured polyurethane foam is treated by freeze-drying to prevent the pore size and pore structure of the magnetic polyurethane foam from being affected by air drying at room temperature or drying by heating.

[0018] The above-mentioned magnetic polyurethane foam is used to adsorb micro-nano plastics in wastewater.

[0019] The present invention has the following beneficial effects: (1)Precise pore size regulation: -OH on the surface of magnetic Fe3O4 nanoparticles reacts with -NCO in polyurethane foam to form Fe-O-C bonds, exerting the synergistic effect of the physical occupancy effect and interfacial stress of magnetic Fe3O4 nanoparticles, realizing the precise regulation of polyurethane foam from a single macroporous structure to a macroporous-mesoporous three-dimensional composite structure, increasing the specific surface area of polyurethane foam, effectively matching the size distribution of 30-100nm nanoplastics, and significantly increasing the adsorption active sites on the surface of polyurethane foam.

[0020] (2)Adsorption-magnetic separation synergy: Magnetic Fe3O4 nanoparticles have superparamagnetism, which endows the material with rapid magnetic response separation ability, solving the energy consumption problem of traditional adsorbent centrifugation / filtration recovery.

[0021] (3)Surface activity enhancement: The active sites on the inner wall of the mesopores in the magnetic polyurethane foam have electrostatic interaction with the functional groups on the surface of nanoplastics, significantly increasing the adsorption amount of nanoplastics and shortening the equilibrium time.

[0022] (4)Low-concentration adsorption: The magnetic polyurethane foam can effectively adsorb low-concentration nanoplastics, and the removal rate of low-concentration nanoplastics reaches 97.88-99.77%.

[0023] (5)Anti-ion interference ability: The magnetic polyurethane foam has strong anti-ion interference ability and can still maintain a high adsorption efficiency after being adsorbed 5 times repeatedly. Description of the drawings

[0024] Figure 1 SEM images of the magnetic polyurethane foam prepared in Example 4 and the polyurethane foam prepared in Comparative Example 4; Figure 2 Mercury intrusion-extrusion curves and pore size distribution detection diagrams of the magnetic polyurethane foam prepared in Example 4 and the polyurethane foam prepared in Comparative Example 4; Figure 3 Detection diagram of the influence of NaCl solution on the adsorption of nanoplastics by the magnetic polyurethane foam prepared in Examples 1-4; Figure 4 Detection diagram of the influence of humic acid on the adsorption of nanoplastics by the magnetic polyurethane foam prepared in Examples 1-4; Figure 5 Detection diagram of the regeneration ability of the magnetic polyurethane foam prepared in Examples 1-4. Detailed implementation manners

[0025] The technical solutions of the present invention will be further explained and illustrated below through specific examples.

[0026] Example 1 An embodiment of the present application provides a magnetic polyurethane foam, and the preparation method of the magnetic polyurethane foam includes: S101: Add 0.16 g of magnetic Fe3O4 nanoparticles with a particle size of 5 nm to 10 g of polyethylene glycol with a molecular weight of 2000 g / mol, and disperse for 30 s under mechanical stirring at 2000 rpm to disperse the magnetic Fe3O4 nanoparticles into the polyethylene glycol. Add 6.67 g of toluene diisocyanate, 0.01 g of triethylenediamine, and 0.1 g of water to the mixture of magnetic Fe3O4 nanoparticles and polyethylene glycol, and stir and react for 10 s under the conditions of a stirring rate of 100 r / min and a stirring temperature of 20 °C until foaming occurs to obtain a foamed polyurethane foam.

[0027] S102: Place the foamed polyurethane foam in an oven at a temperature of 50 °C and react for 5 min, then cure at room temperature for 2 h to obtain a cured polyurethane foam. Place the cured polyurethane foam in distilled water, repeatedly soak and wash it 3 times, and then place it in a freeze dryer at a temperature of -50 °C for freeze-drying for 8 h to obtain a magnetic polyurethane foam.

[0028] Example 2 An embodiment of the present application provides a magnetic polyurethane foam, and the preparation method of the magnetic polyurethane foam includes: S201: Add 0.25 g of magnetic Fe3O4 nanoparticles with a particle size of 150 nm to 10 g of polytetrahydrofuran with a molecular weight of 5000 g / mol, and disperse for 30 s under mechanical stirring at 2000 rpm to disperse the magnetic Fe3O4 nanoparticles into the polytetrahydrofuran. Add 15 g of polymethylene polyphenyl isocyanate, 0.1 g of stannous octoate, and 0.45 g of ethanol to the mixture of magnetic Fe3O4 nanoparticles and polytetrahydrofuran, and stir and react for 30 s under the conditions of a stirring rate of 300 r / min and a stirring temperature of 40 °C until foaming occurs to obtain a foamed polyurethane foam.

[0029] S202: Place the foamed polyurethane foam in an oven at a temperature of 80 °C and react for 20 min, then cure at room temperature for 8 h to obtain a cured polyurethane foam. Place the cured polyurethane foam in distilled water, repeatedly soak and wash it 3 times, and then place it in a freeze dryer at a temperature of -50 °C for freeze-drying for 8 h to obtain a magnetic polyurethane foam.

[0030] Example 3 An embodiment of the present application provides a magnetic polyurethane foam, and the preparation method of the magnetic polyurethane foam includes: S301: Add 1 g of magnetic Fe3O4 nanoparticles with a particle size of 100 nm to 10 g of polyoxypropylene glycol with a molecular weight of 3000 g / mol, and disperse them for 30 s under mechanical stirring at 2000 rpm to disperse the magnetic Fe3O4 nanoparticles into the polyoxypropylene glycol. Add 10 g of isophorone diisocyanate, 0.04 g of stannous octoate, and 0.2 g of ethanol to the mixture of magnetic Fe3O4 nanoparticles and polyoxypropylene glycol, and stir and react for 20 s at a stirring rate of 200 r / min and a stirring temperature of 30 °C until foaming occurs to obtain a foamed polyurethane foam.

[0031] S302: Place the foamed polyurethane foam in an oven at 60 °C and react for 10 min, then cure at room temperature for 6 h to obtain a cured polyurethane foam. Place the cured polyurethane foam in distilled water, soak and wash it repeatedly 3 times, and then place it in a freeze dryer at -50 °C for freeze-drying for 8 h to obtain a magnetic polyurethane foam.

[0032] Example 4 The embodiment of the present application provides a magnetic polyurethane foam, and the preparation method of the magnetic polyurethane foam includes: S401: Add 0.6 g of magnetic Fe3O4 nanoparticles with a particle size of 20 nm to 10 g of polyoxypropylene glycol with a molecular weight of 3000 g / mol, and disperse them for 30 s under mechanical stirring at 2000 rpm to disperse the magnetic Fe3O4 nanoparticles into the polyoxypropylene glycol. Add 10 g of diphenylmethane diisocyanate, 0.04 g of dibutyltin dilaurate, and 0.2 g of water to the mixture of magnetic Fe3O4 nanoparticles and polyoxypropylene glycol, and stir and react for 20 s at a stirring rate of 200 r / min and a stirring temperature of 30 °C until foaming occurs to obtain a foamed polyurethane foam.

[0033] S402: Place the foamed polyurethane foam in an oven at 70 °C and react for 15 min, then cure at room temperature for 7 h to obtain a cured polyurethane foam. Place the cured polyurethane foam in distilled water, soak and wash it repeatedly 3 times, and then place it in a freeze dryer at -50 °C for freeze-drying for 8 h to obtain a magnetic polyurethane foam.

[0034] Comparative Example 1 This comparative example provides a polyurethane foam. The preparation method of the polyurethane foam is the same as that of Example 1, except that magnetic Fe3O4 nanoparticles are not added, but polyethylene glycol is directly added to toluene diisocyanate, triethylenediamine, and water.

[0035] Comparative Example 2 This comparative example provides a polyurethane foam. The preparation method of this polyurethane foam is the same as that of Example 2, except that magnetic Fe3O4 nanoparticles are not added, and instead, polytetrahydrofuran is directly added to polymethylene polyphenyl isocyanate, stannous octoate, and ethanol.

[0036] Comparative Example 3 This comparative example provides a polyurethane foam. The preparation method of this polyurethane foam is the same as that of Example 3, except that magnetic Fe3O4 nanoparticles are not added, and instead, polypropylene glycol is directly added to isophorone diisocyanate, stannous octoate, and ethanol.

[0037] Comparative Example 4 This comparative example provides a polyurethane foam. The preparation method of this polyurethane foam is the same as that of Example 4, except that magnetic Fe3O4 nanoparticles are not added, and instead, polypropylene glycol is directly added to diphenylmethane diisocyanate, dibutyltin dilaurate, and water.

[0038] In the examples of this application, SEM detection was respectively carried out on the magnetic polyurethane foam prepared in Example 4 and the polyurethane foam prepared in Comparative Example 4, and the following was obtained Figure 1 .

[0039] It can be seen from the following Figure 1 that the pore size structure of the polyurethane foam prepared in Comparative Example 4 is larger, while the pore size structure of the magnetic polyurethane foam prepared in Example 4 is significantly reduced. This indicates that magnetic Fe3O4 nanoparticles can increase the crosslinking density of the polyurethane foam through the interaction with the polyurethane foam matrix, thereby reducing the pore size structure of the polyurethane foam, which is beneficial to intercepting nanoplastics in wastewater during the adsorption process.

[0040] The specific surface area and mesoporous distribution of the MNPs adsorption material directly affect its adsorption capacity for adsorbates. Therefore, in this application, the mercury intrusion method was used to detect and analyze the specific surface area and pore size of the magnetic polyurethane foams prepared in Examples 1-4 and the polyurethane foams prepared in Comparative Examples 1-4, and Table 1 was obtained.

[0041] Table 1: Specific surface area and pore size data of the magnetic polyurethane foams in Examples 1-4 and the polyurethane foams in Comparative Examples 1-4 It can be seen from Table 1 that compared with the polyurethane foams in Comparative Examples 1-4, the specific surface area of the magnetic polyurethane foams prepared in Examples 1-4 is significantly increased and the average pore size is significantly reduced. This indicates that the magnetic polyurethane foams prepared in the examples of this application can solve the problem of pore size mismatch faced by current adsorption materials when adsorbing MNPs.

[0042] In addition, taking the magnetic polyurethane foam prepared in Example 4 and the polyurethane foam prepared in Comparative Example 4 as examples, mercury intrusion-extrusion curves and pore size distributions were detected, and the attached Figure 2 .

[0043] As can be seen from the attached Figure 2 , for the polyurethane foam prepared in Comparative Example 4, as the pore size increases, the cumulative intrusion volume first increases and then remains unchanged, and the differential intrusion volume is 0; while for the magnetic polyurethane foam prepared in Example 4, as the pore size increases, the cumulative intrusion volume first increases, then remains unchanged, and finally increases again, and the differential intrusion volume is initially 0, then increases, and finally decreases. This indicates that an obvious mesoporous structure appears in the magnetic polyurethane foam prepared in Example 4 of this application, and by changing the size of the magnetic polyurethane foam, the size of the MNPs plastic can be effectively matched, which is beneficial to the transport of the MNPs plastic within the magnetic polyurethane foam.

[0044] In addition, the present application examples respectively performed effective adsorption detection and low-concentration adsorption detection on the magnetic polyurethane foams prepared in Examples 1-4 and the polyurethane foams prepared in Comparative Examples 1-4. At the same time, interference ion detection and regeneration ability detection were also respectively performed on the magnetic polyurethane foams prepared in Examples 1-4, which are specifically described below.

[0045] 1. Effective adsorption detection To verify that the magnetic polyurethane foam prepared in the examples of the present application can effectively adsorb nanoplastics, the present application examples respectively performed adsorption detection on the magnetic polyurethane foams prepared in Examples 1-4 and the polyurethane foams prepared in Comparative Examples 1-4.

[0046] The specific process is as follows: 0.1 g of the magnetic polyurethane foams prepared in Examples 1-4 and the polyurethane foams prepared in Comparative Examples 1-4 were respectively placed in nanoplastic solutions with a volume of 40 mL and a concentration of 50 mg / L, and an oscillatory adsorption reaction was carried out at 25 °C for 2 h. After the oscillation ended, the concentration of the nanoplastic solution after adsorption was detected, and according to formula (1), the adsorption amount of the magnetic polyurethane foam and the polyurethane foam to the nanoplastics was calculated, and Table 2 was obtained.

[0047] Q0 = ((C0 - C t )·V) / m (1) Among them, C0 and C t respectively represent the concentrations of the nanoplastics before and after adsorption, mg / L; Q e (mg / g) represents the adsorption amount of the polyurethane foam to the nanoplastics, mg / g; V represents the dosage of the nanoplastics, mL; m represents the mass of different polyurethane foams, g.

[0048] Table 2: Adsorption amounts of the magnetic polyurethane foams in Examples 1-4 and the polyurethane foams in Comparative Examples 1-4 to nanoplastics As can be seen from Table 2, compared with the polyurethane foams prepared in Comparative Examples 1-4, the adsorption amount of the magnetic polyurethane foams prepared in Examples 1-4 for nanoplastics is significantly increased, indicating that the magnetic polyurethane foams prepared in the examples of the present application can effectively adsorb nanoplastics.

[0049] 2. Low-concentration adsorption detection To verify that the magnetic polyurethane foams prepared in the examples of the present application can effectively adsorb low-concentration nanoplastics, the examples of the present application respectively conduct low-concentration adsorption detection on the magnetic polyurethane foams prepared in Examples 1-4 and the polyurethane foams prepared in Comparative Examples 1-4.

[0050] The specific process is as follows: 0.1 g of the magnetic polyurethane foams prepared in Examples 1-4 and the polyurethane foams prepared in Comparative Examples 1-4 are respectively placed in nanoplastic solutions with a volume of 40 mL and a concentration of 10 mg / L, and an oscillating adsorption reaction is carried out at 25 °C for 2 h. After the oscillation ends, the concentration of the nanoplastic solution after adsorption is detected, and the removal rates of the magnetic polyurethane foams and the polyurethane foams for low-concentration nanoplastics are calculated according to formula (2) to obtain Table 3.

[0051] υ = V(C0 - C) / VC0 × 100% (2) Among them, υ - the removal rate of the polyurethane foam for nanoplastics, %; V - the volume of the polyurethane foam, mL; C0 - the concentration of the polyurethane foam before adsorption, mg / L; C - the concentration of the polyurethane foam after adsorption, mg / L.

[0052] Table 3: Removal rates of the magnetic polyurethane foams in Examples 1-4 and the polyurethane foams in Comparative Examples 1-4 for low-concentration nanoplastics As can be seen from Table 3, the removal rates of the polyurethane foams prepared in Comparative Examples 1-4 for low-concentration nanoplastics are 66.53 - 76.82%, while the removal rates of the magnetic polyurethane foams prepared in Examples 1-4 of the present application for low-concentration nanoplastics are 97.88 - 99.77%, far higher than those in Comparative Examples 1-4. This indicates that the magnetic polyurethane foams prepared in the examples of the present application can effectively remove low-concentration nanoplastics 3. Interference ion detection Na + and Cl - are common ions in water resources. In the examples of the present application, 3.5% NaCl is used as an interference factor to simulate the adsorption process in this environment and explore the influence of NaCl on the adsorption of nanoplastics by the magnetic polyurethane foam.

[0053] The specific process is as follows: 0.1 g of the magnetic polyurethane foams prepared in Examples 1-4 and the polyurethane foams prepared in Comparative Examples 1-4 were respectively placed in 3.5% NaCl solutions with a volume of 40 mL and a nanoplastics concentration of 500 mg / L, and subjected to an oscillating adsorption reaction at 25 °C for 2 h. After the oscillation ended, the concentration of the nanoplastics solution after adsorption was detected, and the adsorption amount of the magnetic polyurethane foam for the nanoplastics was calculated according to formula (1). At the same time, it was compared with the adsorption amount in a 500 mg / L aqueous solution under the same adsorption conditions.

[0054] It can be seen from Figure 3 that NaCl slightly interferes with the adsorption of nanoplastics by the magnetic polyurethane foam, but the influence is not significant, which indicates that the magnetic polyurethane foam prepared in the examples of this application has strong anti-ion interference ability.

[0055] In addition, in addition to NaCl, humic acid was used as a representative of organic matter in the examples of this application to study the influence of 20 mg / L humic acid on the adsorption of nanoplastics by the magnetic polyurethane foam.

[0056] The specific process is as follows: 0.1 g of the magnetic polyurethane foams prepared in Examples 1-4 and the polyurethane foams prepared in Comparative Examples 1-4 were respectively placed in 20 mg / L humic acid solutions with a volume of 40 mL and a nanoplastics concentration of 500 mg / L, and subjected to an oscillating adsorption reaction at 25 °C for 2 h. After the oscillation ended, the concentration of the nanoplastics solution after adsorption was detected, and the adsorption amount of the magnetic polyurethane foam for the nanoplastics was calculated according to formula (1). At the same time, it was compared with the adsorption amount in a 500 mg / L aqueous solution under the same adsorption conditions.

[0057] It can be seen from Figure 4 that humic acid is beneficial to the adsorption of nanoplastics by the magnetic polyurethane foam. This is mainly because the surface of humic acid contains abundant negative charges, which can aggregate nanoplastics into large-size aggregates in the water environment through electrostatic interaction, thereby promoting the adsorption of nanoplastics on the surface of the magnetic polyurethane foam.

[0058] 4. Detection of regeneration ability In order to prove that the magnetic polyurethane foam prepared in the examples of this application has regeneration ability after adsorbing nanoplastics, the examples of this application respectively carried out regeneration ability detection on the magnetic polyurethane foams prepared in Examples 1-4.

[0059] The specific process is as follows: The magnetic polyurethane foams prepared in Examples 1-4 were respectively placed in a 50 mg / L nanoplastics solution for adsorption for 2 h. After the adsorption ended, the initial adsorption capacity Q0 was calculated according to formula (1). Then, the magnetic polyurethane foams were taken out, ultrasonically treated in deionized water and absolute ethanol for 1 h respectively, taken out, and the adsorption experiment was carried out again, and the adsorption capacity was calculated again. The above operations were repeated 5 times and then the experiment was stopped. Then, the regeneration rate of the magnetic polyurethane foam was calculated according to formula (3) to obtain the attachment Figure 5 。

[0060] (3) where η is the regeneration efficiency of the polyurethane foam, %, Q0 (mg / g) is the first adsorption capacity of the magnetic polyurethane foam for nanoplastics, and Q n (mg / g) is the nth adsorption capacity of the magnetic polyurethane foam for nanoplastics.

[0061] It can be Figure 5 seen that the magnetic polyurethane foam prepared by the present invention not only has a high nanoplastics adsorption capacity but also has strong regenerability.

[0062] The above are only the preferred embodiments of the present application and are not used to limit the present application. For those skilled in the art, various changes and modifications can be made to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A magnetic polyurethane foam, characterized in that, The polyurethane foam is modified with magnetic Fe3O4 nanoparticles.

2. The magnetic polyurethane foam according to claim 1, wherein, The diameter of the magnetic Fe3O4 nanoparticles is 5 - 200 nm, and the mass ratio of the magnetic Fe3O4 nanoparticles in the polyurethane foam is 1 - 5%.

3. The preparation method of the magnetic polyurethane foam according to claim 1 or 2, characterized in that, Including: Disperse the magnetic Fe3O4 nanoparticles in polyether polyol, add isocyanate, catalyst and foaming agent, and stir and foam to obtain foamed polyurethane foam; After the foamed polyurethane foam reacts at a temperature of 50 - 80 °C for 5 - 20 min, it is cured at room temperature, soaked and washed with distilled water, and freeze-dried to obtain magnetic polyurethane foam.

4. The preparation method of the magnetic polyurethane foam according to claim 3, characterized in that The average molecular weight of the polyether polyol is 2000 - 5000 g / mol, and the polyether polyol includes one or more of polyethylene glycol, polytetrahydrofuran, and polypropylene glycol.

5. The preparation method of the magnetic polyurethane foam according to claim 3, characterized in that, The isocyanate includes one or more of toluene diisocyanate, isophorone diisocyanate, polymethylene polyphenyl isocyanate, and diphenylmethane diisocyanate.

6. The preparation method of the magnetic polyurethane foam according to claim 3, characterized in that, The catalyst includes one or more of triethylenediamine, stannous octoate, dibutyltin dilaurate, and tin isooctanoate, and the foaming agent includes water or ethanol.

7. The preparation method of the magnetic polyurethane foam according to claim 3, characterized in that, The mass ratio of the polyether polyol to the isocyanate is 1.5:1 - 1:1.5, the addition amount of the catalyst is 0.06 - 0.4% of the total mass of the polyether polyol and the isocyanate, and the addition amount of the foaming agent is 0.6 - 1.8% of the total mass of the polyether polyol and the isocyanate.

8. The preparation method of the magnetic polyurethane foam according to claim 3, characterized in that The stirring and foaming rate is 100 - 300 r / min, the stirring temperature is 20 - 40 °C, and the stirring time is 10 - 30 s.

9. The preparation method of the magnetic polyurethane foam according to claim 3, wherein The curing time is 2 - 8 h, the freeze-drying temperature is -50 °C, and the freeze-drying time is 8 h.

10. The magnetic polyurethane foam according to claim 1 or 2, or the magnetic polyurethane foam prepared by the preparation method according to any one of claims 3 - 9 is used for adsorbing nanoplastics in wastewater.

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