A bamboo fiber-based composite foam material and a preparation method and application thereof

Abstract

The application discloses a kind of bamboo fiber-based composite foam material and its preparation method and application, belong to biomass chemical technology and environmental remediation field.The bamboo fiber is mixed with micron fiber, polyvinyl alcohol, starch, after being stirred and foamed to form wet foam and frozen, solvent freeze-thaw replacement, placed in normal pressure drying to obtain bamboo fiber-based composite foam material.The composite foam material prepared by the application has ultra-high efficient capturing capacity for micro-nano plastic, the filtration efficiency reaches 100%, the filtration flux reaches 7200 L / m 2 / h, the adsorption capacity reaches 734 mg / g, the removal efficiency is high, and it can be reused, which greatly reduces the removal cost.

Description

Technical Field

[0001] This invention belongs to the field of biomass chemical technology and environmental remediation, specifically relating to a bamboo fiber-based composite foam material, its preparation method, and its application. Background Technology

[0002] Microplastics (referring to plastic particles <5 mm) pollution, as a significant threat to the Earth system boundary, has become a major concern in global environmental issues. Microplastics are present in almost all abiotic (including water, land, and atmosphere) and biotic (including plants, animals, and humans) ecosystems on Earth. Due to the continuously increasing annual production and waste emissions of plastic products, coupled with limited recycling and reuse rates and poor degradability, microplastic pollution has become a major global environmental challenge. Microplastics, through their own physicochemical properties and interactions with chemicals and microorganisms in the environmental media, can affect environmental quality and biological health. In particular, pollutants carried by these particles, such as chemicals and microorganisms, can spread between biotic and abiotic ecosystems, leading to complex pollution effects. Microplastics exhibit high physicochemical variability, including particle size, shape, polymer type, additives, aging time, and attached substances. To date, numerous studies have shown that microplastics are widely present in rivers, lakes, and urban wastewater.

[0003] Currently, physical methods such as conventional coagulation and flocculation, chemical methods such as photocatalysis, and microbial degradation have been successfully used to remove micro and nano-plastics. However, coagulation and flocculation require the addition of large amounts of chemical reagents, which not only easily causes secondary pollution but also has poor effectiveness (less than 10%) for plastics with small dimensions or special surface properties. Photocatalytic degradation requires a large energy input, while microbial degradation is slow and inefficient, limiting its large-scale application. Therefore, there is a need to develop a highly efficient, high-throughput, and multi-cycle removal material.

[0004] In recent years, there have been some studies on the removal of micro and nano-plastics. For example, patent (CN 118223330A) by Chen Lidong et al. uses vacuum filtration to load TEMPO-oxidized nanocellulose onto the surface of filter paper, and then cross-links it with glutaraldehyde to obtain a nanocellulose filter paper composite material. The filtration efficiency reaches 96%, but the filtration flux is only 784 L / m³. 2 / h. For example, Zhu Gaojian et al.'s patent (CN118440391A) prepared a polydopamine-cellulose nanocomposite aerogel material by freeze-drying polydopamine and quaternary ammonium salt modified nanocellulose, achieving a filtration flux of 1748 L / m³ for micro / nanoplastics. 2 / h. Therefore, the key is to further increase the filtration flux of the material while ensuring removal efficiency in order to meet the needs of large-scale applications. Summary of the Invention

[0005] The first technical problem to be solved by this invention is to provide a method for preparing bamboo fiber-based composite foam material, which has the advantages of simple preparation process and low cost. The second technical problem to be solved by this invention is to provide a bamboo fiber-based composite foam material prepared by the above method, which can efficiently filter and adsorb micro- and nano-plastics in water and has a broad spectrum effect in terms of size and type. The third technical problem to be solved by this invention is to provide the application of the above bamboo fiber-based composite foam material in micro- and nano-plastic filtration.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0007] A method for preparing a bamboo fiber-based composite foam material involves mixing bamboo fiber with micron-sized fiber, polyvinyl alcohol, and starch, stirring and foaming to form wet foam, freezing, solvent freeze-thaw displacement, and drying under normal pressure to obtain the bamboo fiber-based composite foam material.

[0008] Furthermore, the mass ratio of the microfiber to the bamboo fiber is 1~3:9~7, the polyvinyl alcohol accounts for 12~16 wt% of the total mass of the bamboo fiber and the microfiber, the starch accounts for 14~18 wt% of the total mass of the microfiber and the bamboo fiber, and the foam paste concentration is 2~4%.

[0009] Furthermore, the freezing temperature is -20 ℃ and the freezing time is 6 h.

[0010] Furthermore, the solvent freeze-thaw replacement method is as follows: solvent replacement is performed sequentially using 50% ethanol solution, 100% ethanol solution, 50% tert-butanol / ethanol solution and 100% tert-butanol solution, with each replacement time being 1 h.

[0011] Furthermore, the atmospheric pressure drying temperature is 25 °C, and the drying time is 24 h.

[0012] Furthermore, bamboo fiber-based composite foam materials are prepared by any of the methods described above.

[0013] Furthermore, the bamboo fiber-based composite foam material is used in filtering and adsorbing micro-nanoplastics.

[0014] Furthermore, the micro-nanoplastics used for filtration are selected from any one or a combination of at least two of polystyrene, carboxylated polystyrene, aminolated polystyrene, polypropylene, polyethylene, and polyethylene terephthalate, with a filtration concentration of 25 to 100 ppm and a micro-nanoplastics size of 500 to 10000 nm.

[0015] Furthermore, the composite foam material is recycled 1 to 12 times.

[0016] Furthermore, the micro / nanoplastics used for adsorption are selected from any one or a combination of at least two of polystyrene, carboxylated polystyrene, and aminolated polystyrene, with an adsorption temperature of 25 °C and a micro / nanoplastics size of 500~10000 nm.

[0017] Compared with the prior art, the present invention has the following advantages:

[0018] (1) The present invention uses bamboo fiber, micron fiber, starch and polyvinyl alcohol as base materials to prepare foam materials to replace petroleum-based foams, which can achieve the purpose of environmental friendliness.

[0019] (2) This invention uses bamboo fiber as the main component of foam and micron-fiber and starch as reinforcing agents to achieve control over the pore size of the foam material. It has a broad-spectrum effect on the type, size and concentration of ultra-efficient capture of micro- and nano-plastics, with a filtration efficiency of 100% and a filtration flux of 7200 L / m 2 / h, with an adsorption capacity of 734 mg / g.

[0020] (3) The bamboo fiber-based composite foam material of the present invention has excellent filtration efficiency and flux, is very little dependent on pressure drive and has excellent adsorption capacity, further ensuring low energy consumption. Attached Figure Description

[0021] Figure 1 Figure 1 shows the physical properties of the bamboo fiber-based composite foam materials prepared in Examples 2-10 through orthogonal experiments. Figure 2 shows the density of sample OE1-9 foam material, Figure 3 shows the volume change of sample OE1-9 wet foam before and after stirring, Figure 4 shows the stress-strain curve of sample OE1-9 foam material, and Figure 5 shows the Young's modulus of sample OE1-9 foam material.

[0022] Figure 2 Figure 8 shows the physical properties of bamboo fiber-based composite foam materials with different pulp concentrations prepared in Example 8 and Comparative Examples 1-2. Among them, Figure (a) is the stress-strain curve of composite foam materials with different pulp concentrations, Figure (b) is the Young's modulus of composite foam materials with different pulp concentrations, Figure (c) is the bubble microscope image of BF-4% wet foam, Figure (d) is the FE-SEM image of BF-2% composite foam, Figure (e) is the FE-SEM image of BF-3% composite foam, and Figure (f) is the FE-SEM image of BF-4% composite foam.

[0023] Figure 3These are the filtration performance graphs of bamboo fiber-based composite foam materials with different pulp concentrations prepared in Example 8 and Comparative Examples 1-2 for micro / nanoplastics. Specifically, Figure (a) shows the fluorescence curves of the composite foam materials with different pulp concentrations before and after filtering 50 ppm PS (Ф2μm); Figure (b) shows the filtration efficiency and flux of the composite foam materials with different pulp concentrations for 50 ppm PS (Ф2μm); Figure (c) shows the filtration efficiency and flux of BF-4% composite foam for PS (Ф2μm), PS-COOH (Ф2μm), and PS-NH2 (Ф2μm); Figure (d) shows the filtration efficiency and flux of BF-4% composite foam for PS of different sizes; Figure (e) shows the filtration efficiency and flux of BF-4% composite foam for PS of different concentrations; and Figure (f) shows the filtration performance of BF-4% composite foam for 50 ppm PS under different pH conditions. The filtration efficiency and flux of PS (Ф2μm) are shown in Figure (g), which is the FE-SEM image of 50 ppm PS (Ф2μm) filtered by BF-4% composite foam; Figure (h) is the FE-SEM image of 50 ppm PS-COOH (Ф2μm) filtered by BF-4% composite foam; and Figure (i) is the FE-SEM image of 50 ppm PS-NH2 (Ф2μm) filtered by BF-4% composite foam.

[0024] Figure 4 Figure 8 shows the cycling performance and general performance of the bamboo fiber-based composite foam material prepared in Example 8. Figure (a) shows the filtration efficiency of BF-4% composite foam after 12 cycles of filtration of 50 ppm PS (Ф2μm), Figure (b) shows the filtration flux of BF-4% composite foam after 12 cycles of filtration of 50 ppm PS (Ф2μm), and Figure (c) shows the filtration efficiency and filtration flux of BF-4% composite foam for PE, PET, and PP.

[0025] Figure 5 Figure 8 shows the adsorption performance of bamboo fiber-based composite foam material prepared in Example 8 on micro-nanoplastics. Figure (a) shows the adsorption capacity of BF-4% composite foam on micro-nanoplastics with different charges (50 ppm, Ф500 nm), and Figure (b) shows the adsorption capacity of BF-4% composite foam on PS of different sizes (50 ppm, Ф500 nm). Detailed Implementation

[0026] The present invention will be further illustrated below with reference to specific embodiments. These embodiments are implemented based on the technical solutions of the present invention, and it should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention.

[0027] In the following examples, MFC is microfiber, PVA is polyvinyl alcohol, CS is starch, MNPs is micro-nanoplastics, OE1~9 are samples 1~9 of the orthogonal experiment, BF2~4% are foam samples prepared with different fiber pulp concentrations under the OE-7 process, PS is polystyrene, PS-COOH is carboxylated polystyrene, PS-NH2 is aminated polystyrene, PE is polyethylene, PP is polypropylene, and PET is polyethylene terephthalate.

[0028] The bleached bamboo pulp fiber was purchased from Sichuan Yongfeng Paper Industry Co., Ltd.

[0029] Mechanically ground cellulose microfibers (20-40 μm in length) were purchased from Tianjin Wood Elf Biotechnology Co., Ltd.

[0030] Example 1

[0031] A method for preparing a bamboo fiber-based composite foam material specifically includes the following steps:

[0032] (1) First, prepare 300 g of 10% bamboo pulp fiber suspension. After the bamboo fiber is decomposed by the decomposition machine, it is ground to 10000 rpm by the PFI pulp mill. After the bamboo pulp suspension is equilibrated at room temperature for 3 days, the moisture content is measured by using a 4-hour oven at 105 ℃. Then, micronized fiber (the mass ratio of micronized fiber to bamboo fiber is 1:9, 2:8, 3:7) is mixed to prepare fiber suspensions of 2%, 3%, and 4% respectively.

[0033] (2) Add 1.6 g of CS particles to 38.4 g of deionized water at 75 °C and dissolve for 1 h to prepare CS solutions of 14, 16, and 18 wt%. Place the solutions in a refrigerator at 4 °C for 12 h to eliminate bubbles.

[0034] (3) Mix 14, 16, and 18 wt% CS solution with 2%, 3%, and 4% fiber suspension (where the mass ratio of micron fiber to bamboo fiber is 1:9, 2:8, and 3:7, respectively), add an appropriate amount of deionized water to make the system reach 10 g, stir evenly, add 12, 14, and 16 wt% PVA particles and stir at 10000 rpm for 1 min to obtain wet foam;

[0035] (4) Place the wet foam in a -20 ℃ freezer for 6 h, and place the frozen sample in 25 ℃ water to equilibrate to room temperature. Then, use 50% ethanol solvent, 100% ethanol solvent, 50% tert-butanol / ethanol solvent and 100% tert-butanol solvent to replace the solvent in sequence. Each replacement time is 1 h. After the replacement is completed, take out the sample and dry it under normal pressure at a temperature of 25 ℃ for 24 h to obtain bamboo fiber-based composite foam material.

[0036] Example 2

[0037] In preparing bamboo fiber-based composite foam material, 14 wt% CS solution was mixed with 2% fiber suspension (where the mass ratio of micron fiber to bamboo fiber was 1:9), and 12 wt% PVA particles were added and stirred. The remaining preparation methods and parameters were the same as in Example 1. OE-1 foam was prepared with a main pore size distribution of 12.3 μm.

[0038] Example 3

[0039] In preparing bamboo fiber-based composite foam material, 16 wt% CS solution was mixed with 2% fiber suspension (where the mass ratio of micron fiber to bamboo fiber was 2:8), and 14 wt% PVA particles were added and stirred. The remaining preparation methods and parameters were the same as in Example 1. OE-2 foam was prepared with a main pore size distribution of 11.1 μm.

[0040] Example 4

[0041] In preparing bamboo fiber-based composite foam material, 18 wt% CS solution was mixed with 2% fiber suspension (where the mass ratio of micron fiber to bamboo fiber was 3:7), and 16 wt% PVA particles were added and stirred. The remaining preparation methods and parameters were the same as in Example 1. OE-3 foam was prepared with a main pore size distribution of 9.1 μm.

[0042] Example 5

[0043] In preparing bamboo fiber-based composite foam material, 16 wt% CS solution was mixed with 3% fiber suspension (where the mass ratio of micron fiber to bamboo fiber was 3:7), and 12 wt% PVA particles were added and stirred. The remaining preparation methods and parameters were the same as in Example 1, and OE-4 foam with a main pore size distribution of 16.0 μm was obtained.

[0044] Example 6

[0045] In preparing bamboo fiber-based composite foam material, 18 wt% CS solution was mixed with 3% fiber suspension (where the mass ratio of micron fiber to bamboo fiber was 1:9), and 14 wt% PVA particles were added and stirred. The remaining preparation methods and parameters were the same as in Example 1. OE-5 foam was prepared with a main pore size distribution of 15.1 μm.

[0046] Example 7

[0047] In preparing bamboo fiber-based composite foam material, 14 wt% CS solution was mixed with 3% fiber suspension (where the mass ratio of micron fiber to bamboo fiber was 2:8), and 16 wt% PVA particles were added and stirred. The remaining preparation methods and parameters were the same as in Example 1. OE-6 foam with a main pore size distribution of 14.5 μm was obtained.

[0048] Example 8

[0049] In preparing bamboo fiber-based composite foam material, 18 wt% CS solution was mixed with 4% fiber suspension (where the mass ratio of micron fiber to bamboo fiber was 2:8), and 12 wt% PVA particles were added and stirred. The remaining preparation methods and parameters were the same as in Example 1, and OE-7 foam with a main pore size distribution of 15.4 μm was obtained.

[0050] Example 9

[0051] In preparing bamboo fiber-based composite foam material, 14 wt% CS solution was mixed with 4% fiber suspension (where the mass ratio of micron fiber to bamboo fiber was 3:7), and 14 wt% PVA particles were added and stirred. The remaining preparation methods and parameters were the same as in Example 1. OE-8 foam with a main pore size distribution of 14.9 μm was obtained.

[0052] Example 10

[0053] In preparing bamboo fiber-based composite foam material, 16 wt% CS solution was mixed with 4% fiber suspension (where the mass ratio of micron fiber to bamboo fiber was 1:9), and 16 wt% PVA particles were added and stirred. The remaining preparation methods and parameters were the same as in Example 1. OE-9 foam was prepared with a main pore size distribution of 14.1 μm.

[0054] The physical properties of the bamboo fiber-based composite foam materials prepared in Examples 2-10 were characterized, as shown in Table 1, which lists the effects of different factors on foam density, foam volume, elastic modulus, compressive strength, and average pore size. Figure 1 As shown, the following are, in order: (a) density image of sample OE1-9 foam material; (b) volume change diagram of sample OE1-9 wet foam; (c) stress-strain curve of sample OE1-9 foam material; (d) Young's modulus diagram of sample OE1-9 foam material.

[0055] Table 1. Range analysis results of orthogonal experiments on bamboo fiber-based composite foam materials

[0056]

[0057] Table 1 shows that the amount of slurry concentrate has the greatest impact on density, foam volume, elastic modulus, and compressive strength, while the amount of micron-sized fibers has the greatest impact on the average pore size of the foam. Figure 1 It is evident that when the pulp concentration and microfiber content are low, the composite foam material exhibits high density, large foam volume, and low compressive strength and elastic modulus. This is because the system contains fewer fibers, preventing larger wet foam particles from stably forming a composite foam material, resulting in a dense local structure, reduced and uneven pore size, and a high apparent density. As the pulp concentration, microfiber, and PVA content increase, the foam material's structure gradually transforms from a dense to a three-dimensional, loose structure, reducing density while increasing elastic modulus and compressive strength, and exhibiting more uniform pore size. Therefore, the optimal process conditions, determined through a combination of physical properties and range analysis, are: CS content of 14 wt%, PVA content of 16 wt%, pulp concentration of 4%, and a microfiber to bamboo fiber mass ratio of 2:8.

[0058] The orthogonal experimental range analysis results of Examples 2-10 show that the pulp content and the amount of micron fiber have the greatest impact on the physical properties and pore structure of the composite foam. Therefore, bamboo fiber-based composite foam with CS content of 14 wt%, PVA content of 12 wt%, and pulp content of 2-4% was selected for micro-nano plastic filtration experiments.

[0059] Comparative Example 1

[0060] In preparing bamboo fiber-based composite foam material, 18 wt% CS solution was mixed with 2% fiber suspension (where the mass ratio of micron fiber to bamboo fiber was 2:8), and 12 wt% PVA particles were added and stirred. The remaining preparation methods and parameters were the same as in Example 1, and BF-2% foam was prepared.

[0061] Comparative Example 2

[0062] In preparing bamboo fiber-based composite foam material, 18 wt% CS solution was mixed with 3% fiber suspension (where the mass ratio of micron fiber to bamboo fiber was 2:8), and 12 wt% PVA particles were added and stirred. The remaining preparation methods and parameters were the same as in Example 1, and BF-3% foam was prepared.

[0063] The physical properties of the composite foam materials prepared in Example 8 and Comparative Examples 1 and 2 were compared, such as... Figure 2 As shown, (a) stress-strain curves of composite foam materials with different slurry concentrations; (b) Young's modulus diagrams of composite foam materials with different slurry concentrations; (c) bubble micrographs of BF-4% wet foam; (d) FE-SEM images of BF-2% composite foam; (e) FE-SEM images of BF-3% composite foam; (f) FE-SEM images of BF-4% composite foam.

[0064] Depend on Figure 2 (a) and Figure 2 (b) shows that as the slurry concentration increases, the compressive strength increases from 9.5 kPa to 21.2 kPa, and the Young's modulus increases from 82.7 kPa to 383.5 kPa. This is attributed to the increase in fibers in the composite foam material stabilizing the three-dimensional structure of the foam, making the foam material structure stable and uniform, and enhancing its mechanical strength. Figure 2 (c) It can be found that under high-speed stirring, there are a large number of uniform and stable bubbles in the BF-4% wet foam, with pore size distribution ranging from 10 to 210 μm and an average size of 68.9 μm. Figure 2 (d) Figure 2 (e) and Figure 2 (f) SEM images of BF-2%, BF-3% and BF-4% respectively. It can be seen that as the fiber content increases, more micron-sized fibers intertwine to form a network structure, the pore size decreases and the three-dimensional morphology of the foam is stabilized, which is beneficial to improving mechanical properties.

[0065] Example 11

[0066] Experiment on microplastic filtration using bamboo fiber-based composite foam material: A composite foam sample with a height of 10 mm and a diameter of 15 mm was used as the filter matrix and filled into the bottom of the filter tube of the filtration device. The filter tube and filter pad were securely connected. 20 mL of ultrasonically dispersed micro-nanoplastics suspension was weighed and poured into the filter tube from above under a pressure of 0.1 bar, and the timing was started. After filtration, the timing was stopped and the filtrate was collected. The filtration efficiency and filtration flux were calculated based on the filtration area of ​​the filtration device, filtration time, volume of micro-nanoplastics suspension, initial concentration of micro-nanoplastics, and residual concentration after filtration.

[0067]

[0068]

[0069] Where μ is the filtration efficiency (%), and C0 and C f These represent the concentrations of micro-nanoplastics in the suspension before and after filtration (ppm), respectively, and J represents the filtration flux (L / m³). 2 / h), V f The effective filtration volume (L) of micro / nanoplastics, S a The effective filtration area (m²) of composite foam material 2 ), where t is the filtering time (h).

[0070] Example 12

[0071] The bamboo fiber-based composite foam materials prepared in Example 8 and Comparative Examples 1 and 2 were subjected to micro-nanoplastics filtration experiments. To investigate the effect of composite foam slurry concentration on the filtration performance of micro-nanoplastics, the filtration efficiency and flux of different slurry concentrations for 50 ppm PS (Ф2μm) were measured using the method described in Example 11. The results are as follows: Figure 3 (a) and Figure 3 As shown in (b).

[0072] Depend on Figure 3 (a) and Figure 3 (b) It can be seen that the filtration efficiencies of BF-2%, BF-3%, and BF-4% composite foam for PS are 91.7%, 97.4%, and 99.4%, respectively, with corresponding filtration fluxes of 17240, 12857, and 7257 L / m³. 2 / h. As the pulp concentration increased, the fluorescence intensity of the filtered water sample decreased, and the filtration efficiency gradually increased, indicating that the network structure formed by the fibers increased, providing more capture sites and enhancing the ability to retain PS. Therefore, BF-4% was selected for subsequent filtration tests.

[0073] Example 13

[0074] The bamboo fiber-based composite foam materials prepared in Example 8 and Comparative Examples 1 and 2 were subjected to micro-nanoplastics filtration experiments. Since CS is a cationic starch, the prepared composite foam materials are positively charged. To investigate the effect of electrostatics on the filtration performance of micro-nanoplastics, the filtration efficiency and filtration flux of PS, PS-COOH, and PS-NH2 (50 ppm, Ф2μm) were measured using the method described in Example 11. The results are as follows: Figure 3 As shown in (c).

[0075] Depend on Figure 3 (c) It can be seen that the filtration efficiency of BF-4% composite foam material for negatively charged PS and PS-COOH is 99.4% and 96.0%, respectively, with filtration efficiencies of 7257 and 8518 L / m³. 2 / h. The filtration efficiency of BF-4% composite foam material for positively charged PS-NH2 is 87.1%, and the filtration flux is 15340 L / m³. 2 / h. Figure 3 (g)-(i) are SEM images of PS, PS-COOH and PS-NH2 filtered by BF-4%, respectively. It can be clearly seen that there is a significant electrostatic attraction for negatively charged PS and PS-COOH. The microplastic microspheres are adsorbed onto the fibers in large quantities, which is due to the retention effect of the foam network structure on positively charged PS-NH2.

[0076] Example 14

[0077] The bamboo fiber-based composite foam materials prepared in Example 8 and Comparative Examples 1 and 2 were subjected to micro-nanoplastics filtration experiments. To investigate the effect of micro-nanoplastics size on filtration performance, the filtration efficiency and filtration flux for 50 ppmPS of different sizes (Ф500nm, Ф2μm, Ф5μm, Ф10μm) were measured using the method described in Example 11. The results are as follows: Figure 3 As shown in (d).

[0078] have Figure 3 (d) It can be seen that the filtration efficiencies of BF-4% for PS with sizes of 500 nm, 2 μm, 5 μm and 10 μm are 81.8%, 99.4%, 99.5% and 99.2%, respectively, and the filtration fluxes are 9409, 7257, 4038 and 2585 L / m, respectively. 2 / h, it can be clearly seen that as the PS size increases, the filtration efficiency increases, but the filtration flux decreases. This is because the increase in PS size will gradually block the pores of the upper layer of foam, forming a dense micro-nano plastic layer on the upper layer, which leads to a decrease in its filtration flux.

[0079] Example 15

[0080] The bamboo fiber-based composite foam materials prepared in Example 8 and Comparative Examples 1 and 2 were subjected to micro-nanoplastics filtration experiments. To investigate the effect of micro-nanoplastics concentration on filtration performance, the filtration efficiency and filtration flux for different concentrations of PS (Ф2μm 25 ppm, 50 ppm, 75 ppm, 100 ppm) were measured using the method described in Example 11. The results are as follows: Figure 3 As shown in (e).

[0081] have Figure 3 (e) shows that the filtration efficiencies of BF-4% for PS concentrations of 25 ppm, 50 ppm, 75 ppm, and 100 ppm are 98.8%, 99.4%, 98.5%, and 98.5%, respectively, with filtration fluxes of 18149, 7252, 5385, and 3264 L / m³, respectively. 2 / h.

[0082] Example 16

[0083] The bamboo fiber-based composite foam materials prepared in Example 8 and Comparative Examples 1 and 2 were subjected to micro-nanoplastics filtration experiments. To investigate the effect of water pH on the filtration performance of micro-nanoplastics, the filtration efficiency and flux of the composite foam for PS (Ф2μm) at different pH values ​​(3, 7, 11) were measured using the method described in Example 11. The results are as follows: Figure 3 As shown in (f).

[0084] have Figure 3(f) shows that when the pH is 3, 7, and 11, the filtration efficiencies of BF-4% for PS are 83.1%, 95.7%, and 71.9%, respectively, and the filtration fluxes are 10507, 12293, and 6144 L / m³, respectively. 2 The / h reading clearly shows that the filtration performance is optimal when the pH is neutral.

[0085] Example 17

[0086] The BF-4% composite foam prepared in Example 8 and Comparative Examples 1 and 2 were used to conduct a cyclic filtration test on 50 ppm PS (Ф2μm). The filtration efficiency and filtration flux at different cycles were determined using the method in Example 11.

[0087] The results are as follows Figure 4 (a) and Figure 4 As shown in (b), with the increase of the number of cycles, the filtration efficiency of BF-4% composite foam for PS remained above 99%, but the filtration flux gradually decreased and tended to stabilize, eventually remaining at 1000 L / m. 2 The result of / h indicates that the bamboo fiber-based composite foam material has stable recyclability.

[0088] Example 18

[0089] The BF-4% composite foam prepared in Example 8 was used to filter different types of micro / nanoplastics, and the filtration efficiency and filtration flux were determined using the method in Example 11.

[0090] The results are as follows Figure 4 As shown in (c), the filtration efficiencies of BF-4% composite foam for PE, PET, and PP are 99.3%, 98.4%, and 97.7%, respectively, with filtration fluxes of 6633, 10696, and 7517 L / m³. 2 / h, the above results indicate that bamboo fiber-based composite foam materials have a broad-spectrum filtering effect on micro-nanoplastics.

[0091] Example 19

[0092] Adsorption of micro- and nano-plastics by bamboo fiber-based composite foam material: Bamboo fiber-based composite foam material dried at normal pressure for 24 h was cut into cubes weighing 3 mg each, with dimensions of 6 mm (length, width, and height). 3 mL of ultrasonically dispersed micro- and nano-plastic suspension was weighed and placed in a centrifuge tube. The composite foam material was added to the centrifuge tube, and the tube was placed in a water bath at 100 rpm for 24 h for adsorption. After adsorption, the timer was stopped, and the suspension was collected. The adsorption capacity was calculated based on the concentrations of the micro- and nano-plastics before and after adsorption, the volume of the micro- and nano-plastic water, and the mass of the composite foam material.

[0093]

[0094] Where Q is the adsorption capacity (mg / g), and C0 and C are... f The values ​​represent the concentration of micro-nanoplastics in the suspension before and after adsorption (ppm), V is the volume of the micro-nanoplastics suspension (mL), and m is the weight of the composite foam (g).

[0095] Example 20

[0096] The bamboo fiber-based composite foam material prepared in Example 8 was subjected to an adsorption experiment on micro- and nano-plastics. To investigate the effect of electrostatic interaction on the adsorption performance of micro- and nano-plastics, the adsorption capacity of the composite foam for PS (50 ppm, Ф500 nm), PS-COOH (50 ppm, Ф500 nm), and PS-NH2 (50 ppm, Ф500 nm) was determined using the method described in Example 19. The results are as follows. Figure 5 As shown in (a).

[0097] Depend on Figure 5 (a) It can be seen that the adsorption capacity of BF-4% composite foam for negatively charged PS and PS-COOH is 743.1 mg / g and 933.9 mg / g, respectively, and the adsorption capacity for positively charged PS-NH2 is 251.9 mg / g, indicating that the composite foam has a better adsorption effect on negatively charged micro-nano plastics.

[0098] Example 21

[0099] The bamboo fiber-based composite foam material prepared in Example 8 was subjected to an adsorption experiment on micro- and nano-plastics. To investigate the effect of micro- and nano-plastic size on adsorption performance, the adsorption capacity of the composite foam for PS (Ф500nm), PS (Ф2000nm), PS (Ф5000nm), and PS (Ф10000nm) was determined using the method described in Example 19. The results are as follows: Figure 5 As shown in (b).

[0100] Depend on Figure 5 (b) It can be seen that the smaller the PS size, the better the adsorption effect and the larger the adsorption capacity of the composite foam. Specifically, when the PS size is 10000 nm, the adsorption capacity is 276.9 mg / g, and when the PS size is reduced to 500 nm, the corresponding adsorption capacity increases to 734.1 mg / g.

[0101] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a bamboo fiber-based composite foam material, characterized in that: Bamboo fiber is mixed with microfiber, polyvinyl alcohol, and starch. After stirring and foaming to form wet foam, the mixture is frozen, and the solvent is subjected to freeze-thaw displacement. The mixture is then dried under normal pressure to prepare bamboo fiber-based composite foam material. The mass ratio of microfiber to bamboo fiber is 1~3:9~7, polyvinyl alcohol accounts for 12~16wt% of the total mass of bamboo fiber and microfiber, starch accounts for 14~18wt% of the total mass of microfiber and bamboo fiber, and the foam paste concentration is 2~4%.

2. The method for preparing bamboo fiber-based composite foam material according to claim 1, characterized in that: The freezing temperature is -20℃ and the freezing time is 6 hours.

3. The method for preparing bamboo fiber-based composite foam material according to claim 1, characterized in that: The solvent freeze-thaw replacement method is as follows: solvent replacement is performed sequentially using 50% ethanol solution, 100% ethanol solution, 50% tert-butanol / ethanol solution and 100% tert-butanol solution, with each replacement time being 1 h.

4. The method for preparing bamboo fiber-based composite foam material according to claim 1, characterized in that: The atmospheric pressure drying temperature is 25℃, and the drying time is 24h.

5. The bamboo fiber-based composite foam material is prepared by the preparation method of bamboo fiber-based composite foam material according to any one of claims 1-4.

6. The application of the bamboo fiber-based composite foam material according to claim 5 in filtering micro / nanoplastics and adsorbing micro / nanoplastics.

7. The application of the bamboo fiber-based composite foam material according to claim 6, characterized in that: The micro-nanoplastics used for filtration are selected from any one or a combination of at least two of polystyrene, carboxylated polystyrene, aminolated polystyrene, polypropylene, polyethylene, and polyethylene terephthalate, with a filtration concentration of 25 to 100 ppm and a micro-nanoplastics size of 500 to 10000 nm.

8. The application of the bamboo fiber-based composite foam material according to claim 6, characterized in that: The composite foam material can be cycled 1 to 12 times.

9. The application of the bamboo fiber-based composite foam material according to claim 6, characterized in that: The micro / nanoplastics used for adsorption are selected from any one or a combination of at least two of polystyrene, carboxylated polystyrene, and aminolated polystyrene, with an adsorption temperature of 25°C and a micro / nanoplastics size of 500~10000 nm.

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