Recyclable wood-based cellulose aerogel as well as preparation method and application thereof

Abstract

The invention discloses a recyclable wood-based cellulose aerogel and a preparation method and application thereof.The preparation method comprises the following steps that wood chips are soaked in a mixed solution of NaOH and Na2SO3, heating reaction is conducted for set time, then H2O2 is introduced into the mixed solution, and heating reaction continues for set time; after the reaction is finished, drying the wood chips, and then soaking the wood chips in an N, N-dimethylacetamide solution of hot LiCl for set time; the preparation method comprises the following steps: soaking wood chips in acetone for acetone regeneration after soaking is completed, soaking the wood chips in tert-butyl alcohol for replacement after regeneration is completed, and freeze-drying the wood chips after replacement is completed to obtain nanofiber wood aerogel; and carrying out sulfonation modification or carboxylation modification on the nanofiber wood aerogel. Cellulose nanofibers are extracted on the basis of a framework of a wood-based cellular structure, and wood-based CNF is further subjected to sulfonation modification or carboxylation modification, so that the content of surface groups and charges is increased, and micro-plastics are efficiently captured.

Description

Technical Field

[0001] The present invention belongs to the technical field of aerogel adsorption materials, and particularly relates to a recyclable wood-based cellulose aerogel and its preparation method and application. Background Art

[0002] The statements herein only provide background art related to the present invention and do not necessarily constitute prior art.

[0003] Nowadays, the extensive use of plastic products (such as packaging plastic bags, disposable plastic bottles, etc.) and the lack of effective recycling and removal methods have led to global pollutant problems. Microplastics that adsorb heavy metals, antibiotics, and other organic pollutants have been detected in human organs. To effectively and greenly remove and recycle microplastics, adsorption has received extensive attention from scientific researchers due to its advantages of low cost, wide adaptability, and easy implementation.

[0004] When designing adsorption materials for microplastic removal, surface functional groups and nanostructures are crucial factors. Firstly, the surface functional groups of the adsorption material provide molecular interaction sites between microplastics, such as electrostatic interaction, hydrogen bond, and π-π interaction. In addition, the porous nano-microstructure provides high permeability and abundant capture sites for microplastic adsorption. To effectively remove microplastics, researchers have conducted extensive research on adsorption materials, including the study of covalent / metal-organic frameworks, zeolites, sponges, aerogels, functionalization of biochars, and porous materials. For example, the literature reports that a layered double oxide material assembled with three-dimensional graphene-like carbon for microplastic removal has a microplastic removal rate ≥ 80% in a relatively wide pH range of 3 - 11 due to the adsorption mechanism of hydrogen bond, π-π binding, and p-π interaction. However, there are still many limitations such as low removal efficiency, high cost, complex operation process, and secondary pollution.

[0005] Wood consists of cellulose nanofibrils embedded in a hydrated hemicellulose and lignin matrix, which has attracted extensive attention in microplastic removal. To simulate the interconnected cell structure and directionally arranged channels of natural wood, traditional methods such as freeze-drying have been widely explored.

[0006] When directly using natural wood to prepare wood-based aerogels as adsorbents, to ensure the adsorption effect, it is not only required to completely retain its natural and ordered multi-level cell structure, but also necessary to fully expose reactive groups (such as -COOH, -NH2, -SO3H, etc.) through surface modification, while maintaining the mechanical stability required for practical applications. However, during the preparation process, it is inevitable to damage its multi-level cell structure, and it is difficult to perform surface modification, and the mechanical properties are difficult to guarantee. Summary of the Invention

[0007] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide a recyclable wood-based cellulose aerogel, its preparation method and application.

[0008] To achieve the above object, the present invention is realized through the following technical solutions:

[0009] In the first aspect, the present invention provides a preparation method of a recyclable wood-based cellulose aerogel, comprising the following steps:

[0010] Immerse the wood chips in a mixed solution of NaOH and Na2SO3, heat and react for a set time, then introduce H2O2 into it and continue to heat and react for a set time;

[0011] After the reaction is completed, dry the wood chips, and then immerse them in a hot LiCl solution in N,N-dimethylacetamide for a set time;

[0012] After the immersion is completed, immerse the wood chips in acetone for acetone regeneration. After the regeneration is completed, immerse the wood chips in tert-butanol for replacement, and freeze-dry the replaced wood chips to obtain nanofiber wood aerogel;

[0013] Perform sulfonation modification or carboxylation modification on the nanofiber wood aerogel, and that's it.

[0014] Immerse the wood chips in a mixed solution of NaOH and Na2SO3 and heat and react, aiming to remove lignin and hemicellulose in the wood chips.

[0015] The function of adding hydrogen peroxide is for oxidation reaction, to completely remove lignin and hemicellulose and remove the residual reaction reagents from the previous step.

[0016] Dissolve the delignified wood chips in LiCl / N,N-dimethylacetamide, aiming to dissolve cellulose and use it for regenerating cellulose nanofibers (CNF) in acetone in the next step.

[0017] Replace the cellulose nanofiber dispersion in tert-butanol to maintain the morphology of microscopic nanofibers and the loose and porous structure during freeze-drying.

[0018] The present invention extracts cellulose nanofibers on the basis of the framework of the wood-based cell structure by imitating the cell transport structure of trees, and further performs sulfonation modification or carboxylation modification on the wood-based CNF to increase the surface groups and charge content, so as to prepare functional fibrous wood-based aerogel.

[0019] The natural micron-sized pores in the aerogel are filled with a large amount of functionalized CNFs, which have a large specific surface area. While enhancing physical adsorption, they can maintain strong mechanical properties. At the same time, the pipes filled with CNFs have a certain capillary action, which can capture more microplastics. In addition, a large number of negatively charged groups and hydroxyl groups are connected in the aerogel, which can efficiently capture microplastic balls through physical adsorption, electrostatic adsorption, hydrogen bond adsorption and capillary action.

[0020] In some embodiments, in the mixed solution of NaOH and Na2SO3, the concentration of NaOH is 3-10 wt%, and the concentration of Na2SO3 is 1-5 wt%.

[0021] Preferably, in the mixed solution of NaOH and Na2SO3, the concentration of NaOH is 3-7 wt%, and the concentration of Na2SO3 is 1-3 wt%.

[0022] Preferably, the wood chips are impregnated in the mixed solution of NaOH and Na2SO3, and the temperature for the heating reaction is 90-100 °C, and the reaction time is 3-7 h. The reaction temperature can be 90 °C, 91 °C, 92 °C, 93 °C, 94 °C, 95 °C, 96 °C, 97 °C, 98 °C, 99 °C, 100 °C; the reaction time can be 3 h, 4 h, 5 h, 6 h, 7 h.

[0023] Preferably, H2O2 is introduced therein, and the temperature for the continued heating reaction is 90-100 °C, and the time is 5-10 h. The reaction temperature can be 90 °C, 91 °C, 92 °C, 93 °C, 94 °C, 95 °C, 96 °C, 97 °C, 98 °C, 99 °C, 100 °C; the reaction time can be 5 h, 6 h, 7 h, 8 h, 9 h, 10 h.

[0024] More preferably, in the reaction system, the concentration of H2O2 is 10%-30%, and % is the mass percentage.

[0025] In some embodiments, in the hot N,N-dimethylacetamide solution of LiCl, the concentration of LiCl is 5-10 wt%, the temperature is 90-100 °C, and the impregnation reaction is carried out for 20-30 h.

[0026] In some embodiments, the time for acetone regeneration is 30-40 h.

[0027] In some embodiments, during the replacement process of impregnating the wood chips in tert-butanol, the tert-butanol is replaced every 1-3 h.

[0028] In some embodiments, the method for sulfonation modification is: mixing nanofiber aerogel with an aqueous solution of NaIO4, reacting in the dark at 40-60 °C for 2-5 h, and after the reaction is completed, aldehyde-functionalized fibrous wood aerogel is obtained through washing treatment;

[0029] Add the aldehyde-functionalized fibrous wood aerogel to the NaHSO3 solution, carry out the sulfonation reaction for 2 - 5 h. After sulfonation, wash and vacuum freeze-dry to obtain the product.

[0030] Preferably, the concentration of NaIO4 in the aqueous NaIO4 solution is 5 - 15 mg / mL, preferably 7 - 12 mg / mL.

[0031] Preferably, the concentration of the NaHSO3 solution is 15 - 25 mg / mL, preferably 17 - 23 mg / mL.

[0032] In some embodiments, the method for carboxylation modification is as follows: Immerse the nanofiber aerogel in a mixed solution of TEMPO and NaBr, then add NaClO thereto and adjust the pH value of the system to weakly alkaline, react at room temperature for 4 - 8 h. After the reaction is completed, add ethanol to terminate the reaction;

[0033] Wash and dry the aerogel to obtain the carboxylated fibrous wood aerogel.

[0034] Preferably, in the mixed solution of TEMPO and NaBr, the concentration of TEMPO is 0.001 - 0.02 g / mL, and the concentration of NaBr is 0.02 - 0.5 g / mL.

[0035] Preferably, adjust the pH value of the system to 10.

[0036] Preferably, wash the aerogel with an ethanol / water solution (volume ratio 1:1) and deionized water.

[0037] In the second aspect, the present invention provides a recyclable wood-based cellulose aerogel prepared by the above preparation method.

[0038] In the third aspect, the present invention provides the application of the recyclable wood-based cellulose aerogel in microplastic adsorbents.

[0039] The beneficial effects obtained by one or more of the above embodiments of the present invention are as follows:

[0040] The present invention prepares nanofiber wood aerogel by delignification of balsa wood and in-situ generation of cellulose nanofibrils, and then carries out carboxylation / sulfonation modification. After sulfonation and carboxylation modification, the nanofiber wood aerogel has a three-dimensional multi-level porous scaffold structure and abundant surface groups, and the removal rates of microplastics reach 88.1% and 88.8% respectively, and the maximum removal amounts can reach 439.9 mg / g and 586.95 mg / g. Even after 10 cycles, the removal rate of microplastics by the nanofiber wood aerogel is still greater than 78%.

[0041] The current work provides eco-friendly and facile methods for preparing wood-derived hierarchically porous aerogels for efficient microplastic removal. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The accompanying drawings, which form a part of this specification, are used to provide a further understanding of the present invention. The schematic embodiments and descriptions thereof of the present invention are used to explain the present invention and shall not unduly limit the present invention.

[0043] Figure 1 It is a schematic diagram of the preparation of sulfonated cellulose aerogel and carboxylated cellulose aerogel and the adsorption of microplastic beads in the embodiments of the present invention;

[0044] Figure 2 In, A and E are SEM images of natural wood; B and F are SEM images of fibrillated wood aerogel; C and G are SEM images of carboxylated fibrillated wood aerogel; D and H are SEM images of sulfonated fibrillated wood aerogel;

[0045] Figure 3 It is a comparison chart of the relevant properties of natural wood, fibrillated wood aerogel, and modified fibrillated wood aerogel in the embodiments of the present invention. Among them, a is a comparison chart of FTIR infrared spectra, b is a comparison chart of XRD spectra, c is a Zeta potential comparison chart, and d is a mechanical property comparison chart;

[0046] Figure 4 In, A is the SEM image of MPS microplastic beads; B and C are the SEM images of functionalized fibrillated wood aerogel adsorbing MPS beads; D is the comparison chart of fluorescence spectra before and after functionalized fibrillated wood aerogel adsorbs MPS beads; E is the comparison chart of Raman spectra before and after functionalized fibrillated wood aerogel adsorbs MPS beads; F is the comparison chart of infrared spectra before and after functionalized fibrillated wood aerogel adsorbs MPS beads;

[0047] Figure 5 In, a is the comparison chart of the adsorption performance change of MPS-NH2 with the dosage change of natural wood and modified fibrillated aerogel; b is the comparison chart of the adsorption performance of natural wood and modified fibrillated aerogel on MPS-NH2 at different concentrations; c is the adsorption isotherm fitted by the Langmuir model; d is other adsorbents related to cellulose [1-8] Comparison of the efficiency of removing MPS-NH2 with this work. DETAILED DESCRIPTION OF THE INVENTION

[0048] It should be noted that the following detailed description is illustrative and is intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0049] The present invention will be further described below in conjunction with embodiments.

[0050] Example 1

[0051] A preparation method of recyclable wood-based cellulose aerogel includes the following steps:

[0052] 1) Preparation of fibrillated wood aerogel

[0053] Wood chips (about 5*5 cm 2 wood chips) were dissolved in NaOH / Na2SO3 solution (the concentration of NaOH is 5 wt%, and the concentration of Na2SO3 is 2.5 wt%) at a mass ratio of balsa wood:solution = 1:100, reacted at 100 °C for 5 h, and then boiled in 30% H2O2 at 100 °C for 7 h (5 wt% NaOH / 2.5 wt% Na2SO3). After the reaction, the wood chips were dried and then dissolved in 8 wt% LiCl / DMAc at 100 °C for 24 hours. The wood chips were immersed in acetone solution for 36 hours for regeneration, and then the regenerated wood chips were immersed in tert-butanol for replacement, with tert-butanol replaced every 2 hours for a total of 3 times. The replaced wood chips were freeze-dried to obtain nanofiber wood aerogel.

[0054] Balsa wood is a lightweight wood with a density only one-tenth of that of water. It is easy to remove lignin and hemicellulose and has a fluffy and porous wood cell structure, which helps to improve the microplastic adsorption efficiency subsequently.

[0055] 2) Preparation of sulfonated fibrillated wood aerogel

[0056] The nanofiber wood aerogel (1 g) and aqueous NaIO4 solution (100 mL, 10 mg / mL) were added to a round-bottom flask and magnetically stirred (500 r / min) at 50 °C in the dark for 4 h. After washing (repeatedly washing 3-5 times with deionized water to remove unreacted sodium periodate reagent), aldehyde-functionalized fibrillated wood aerogel was obtained.

[0057] The aldehyde-functionalized fibrillated wood aerogel was added to NaHSO3 solution (100 mL, 20 mg / mL) at a mass ratio of 1:2 and reacted at room temperature for 3 h for sulfonation modification.

[0058] Finally, the sulfonated nanofiber wood aerogel was thoroughly washed and vacuum freeze-dried for 24 h to obtain sulfonated fibrillated wood aerogel.

[0059] Example 2

[0060] A preparation method of recyclable wood-based cellulose aerogel includes the following steps:

[0061] 1) Preparation of fibrillated wood aerogel

[0062] Dissolve the wood chips in a NaOH / Na2SO3 solution (the concentration of NaOH is 5 wt%, and the concentration of Na2SO3 is 2.5 wt%) at a mass ratio of balsa wood:solution = 1:100, react at 100 °C for 5 h, then boil in 25% H2O2 at 100 °C for 7 h (5 wt% NaOH / 2.5 wt% Na2SO3). After the reaction, dry the wood chips, and then dissolve them in 8 wt% LiCl / DMAc at 100 °C for 24 h. Immerse the wood chips in an acetone solution for 36 h for acetone regeneration, and then immerse the regenerated wood chips in tert-butanol for displacement, replacing the tert-butanol every 2 h for a total of 3 times. Freeze-dry the wood chips after displacement to obtain nanofiber wood aerogel.

[0063] 2) Preparation of carboxylated fiber wood aerogel

[0064] Carboxylate the nanofiber wood aerogel according to the typical TEMPO oxidation protocol. Under magnetic stirring at 500 r / min, immerse the nanofiber aerogel (1 g) into a mixed solution (50 mL) of TEMPO (0.01 g) and NaBr (0.1 g). Then, gradually add 12 mmol NaClO (1.13 mL) dropwise to the mixture. Maintain the pH value at 10 by adding 0.1 M HCl or NaOH. After reacting at room temperature for 5 h, add ethanol to terminate the reaction. Thoroughly wash the obtained carboxylated fiber wood aerogel with ethanol / H2O (1:1) and deionized water to remove the residual reagents. Finally, obtain the carboxylated fiber wood aerogel by vacuum freeze-drying for 24 h.

[0065] Performance testing

[0066] Adsorption experiment of aerogel on MPS microspheres

[0067] Natural wood, the carboxylated fiber wood aerogel prepared in Example 1, and the sulfonated fiber wood aerogel prepared in Example 2 are used for the adsorption experiment of polystyrene (MPS) plastic microspheres.

[0068] MPS microspheres with different concentrations (0.005 mg / mL, 0.01 mg / mL, 0.015 mg / mL, 0.05 mg / mL, 0.1 mg / mL, 0.2 mg / mL, 0.5 mg / mL, 0.7 mg / mL, 0.9 mg / mL, 1 mg / mL, 3 mg / mL) were selected for the adsorption experiment. The adsorption process was carried out by mixing the aerogel (50 mg) with MPS microspheres (5 mL) in a mechanical oscillator at 300 rpm / min at 25 °C for 24 h. Then the suspension was collected and analyzed by a fluorescence spectrophotometer to determine the content of MPS microspheres. The removal efficiency and adsorption capacity were calculated by formulas (1) and (2):

[0069] Removal efficiency=(c0 - c t ) / c0 (1);

[0070] Adsorption capacity (q)=(c0 - c t ) / c0 (2);

[0071] where c0 and c t (mg / L) are the initial concentration of MPS microspheres and the concentration at t min, respectively, and Q (mg / g) is the adsorption amount of MPS microspheres in the aerogel per unit mass.

[0072] Characterization of fibrous wood-based aerogel

[0073] The porous structure of the fibrillated aerogel was observed by SEM ( Figure 2 ). Figure 2 A and 2E show the cross-sectional and longitudinal SEM images of natural wood, showing a honeycomb-like and interconnected cell microtubule structure. After selectively removing lignin and hemicellulose and regenerating to form cellulose nanofibrils, the 3D network structure of the fibrous wood aerogel can provide a loose and porous structure to facilitate the removal of microplastics ( Figure 2 B and 2F). After carboxylation and sulfonation surface modification ( Figure 2 C and 2G)( Figure 2 D and 2H), the aerogel still maintains the porous structure of the nanofibrillar wood aerogel.

[0074] Characterization of sulfonated cellulose aerogel and carboxylated cellulose aerogel

[0075] FT-IR spectra ( Figure 3 a) showed that after treatment with NaOH / Na2SO3, hemicellulose and lignin were successfully removed. To further study the structural evolution of natural wood and nanofibrillar wood aerogel, XRD tests were carried out ( Figure 3b), Natural wood, fibrous wood aerogel, and functionalized fibrous wood aerogel all exhibited typical cellulose I structures at 16.8° and 22.8°. After nanofiber treatment and surface modification, cellulose nanofibers were extracted into the wood cells and presented an amorphous structure, with peaks showing lower and broader intensities, indicating an amorphous transformation of cellulose nanofibers during the dissolution / regeneration process. Zeta potential analysis showed that the surface charge of MPS-NH2 microspheres was +79.2 mV, and that of nanofiber wood aerogel was -8.5 mV (as Figure 3 c). After surface modification, the surface charges of nanofiber wood aerogel decreased to -78.8 mV and -94.4 mV, respectively. Mechanical property tests showed that the presence of lignin and hemicellulose made natural wood hard, and after nanofibrillation treatment, lignin and hemicellulose in the cell structure were removed, resulting in a more flexible nanofibrous wood aerogel, as Figure 3 shown in d.

[0076] Adsorption performance of lignin nanofiber aerogel on MPS-NH2

[0077] SEM images ( Figure 4 B-4C) showed that MPS microspheres were successfully adsorbed into the pores of wood aerogel. The concentration of MPS microspheres before and after adsorption was analyzed by fluorescence absorption intensity at 572 nm, and the removal rate of MPS-NH2 was calculated to be 88.1% through an equation. The inset showed that the red MPS-NH2 microsphere dispersion became colorless after adsorption.

[0078] After the aerogel adsorbed MPS, characteristic Raman bands (4E) of MPS were observed at 1044 cm -1 and 1074 cm -1 . Compared with MPS, the Raman bands of MPS after being adsorbed by wood aerogel shifted to higher wavenumbers, indicating a decrease in the electron cloud density around the groups in nanofiber wood aerogel and the interaction between lone pair electrons and MPS. This showed that MPS was bound to -SO3H and -COOH in nanofiber wood aerogel through conjugation during the adsorption process.

[0079] FTIR spectroscopy was used to characterize the aerogel before and after adsorbing MPS. The results showed that after adsorption, the -CH stretching amounts of the aerogel increased at 2850 cm -1 and 2918 cm -1 , which was related to the surface adsorption of the aerogel and MPS. In addition, the small peak at 1735 cm -1 corresponded to the amide bond formed during the adsorption process of amino-modified microplastics and carboxylated and sulfonated aerogels, and corresponded to the characteristic peak of MPS.

[0080] To better study the adsorption performance, the effects of factors such as adsorbent dosage, initial concentration of MPS microspheres, and operation time on the adsorption performance of microplastics were investigated, and these factors were systematically studied.

[0081] By optimizing the experimental conditions, the optimal adsorption conditions of wood-based aerogel for MPS microspheres were obtained as follows: the adsorbent concentration was 10 mg / mL, and the initial concentration C0 of MPS microspheres was 0.5 mg / mL. At this time, the adsorption efficiencies of sulfonated fibrous wood aerogel and carboxylated wood-based aerogel for MPS microspheres reached 88.1% and 88.8% respectively, which were much higher than that of natural wood (65.2%). And the adsorption data well fitted the Langmuir model, indicating that the adsorption was a heterogeneous monolayer process. Figure 5 d Compared the removal efficiency of surface-modified nanofiber wood aerogel and previously reported adsorbents for microplastics, showing great potential for removing microplastics, with advantages such as convenient manufacturing process, high removal efficiency, cost-effectiveness, and recyclability.

[0082] Example 3

[0083] A preparation method of recyclable wood-based cellulose aerogel, comprising the following steps:

[0084] 1) Preparation of fibrous wood aerogel

[0085] Dissolve wood chips in NaOH / Na2SO3 solution at a mass ratio of balsa wood:solution = 1:100, react at 95 °C for 7 h, then boil in H2O2 at 100 °C for 5 h (5 wt% NaOH / 2.5 wt% Na2SO3). After the reaction, dry the wood chips, and then dissolve them in 5 wt% LiCl / DMAc at 100 °C for 30 hours. Immerse the wood chips in acetone solution for 36 hours for acetone regeneration, and then immerse the regenerated wood chips in tert-butanol for replacement, changing tert-butanol every 2 hours for a total of 3 times. Freeze-dry the wood chips after replacement to obtain nanofiber wood aerogel.

[0086] 2) Preparation of sulfonated fibrous wood aerogel

[0087] Add nanofiber wood aerogel (1 g) and aqueous NaIO4 solution (100 mL, 5 mg / mL) into a round-bottom flask, stir magnetically (500 r / min) at 45 °C in the dark for 5 h. Then obtain aldehyde-functionalized fibrous wood aerogel through impregnation treatment.

[0088] Add aldehyde-functionalized fibrous wood aerogel into NaHSO3 solution (100 mL, 25 mg / mL) at a mass ratio of 1:2, and react at room temperature for 4 h for sulfonation modification.

[0089] Finally, the sulfonated nanofiber wood aerogel was thoroughly washed and vacuum freeze-dried for 24 h to obtain the sulfonated fiber wood aerogel.

[0090] Example 4

[0091] A preparation method of a recyclable wood-based cellulose aerogel, comprising the following steps:

[0092] 1) Preparation of fibrillated wood aerogel

[0093] The wood chips were dissolved in a NaOH / Na2SO3 solution at a mass ratio of balsa wood:solution = 1:100, reacted at 100 °C for 3 h, and then boiled in H2O2 at 100 °C for 5 h (4 wt% NaOH / 2 wt% Na2SO3). After the reaction, the wood chips were dried, and then dissolved in 6 wt% LiCl / DMAc at 100 °C for 24 hours. The wood chips were immersed in an acetone solution for 36 hours for an acetone regeneration bath, and then the wood chips after the regeneration bath were immersed in tert-butanol for replacement, and the tert-butanol was changed every 2 hours for a total of 3 times. The replaced wood chips were freeze-dried to obtain nanofiber wood aerogel.

[0094] 2) Preparation of carboxylated fiber wood aerogel

[0095] The nanofiber wood aerogel was carboxylated and modified according to a typical TEMPO oxidation protocol. Under magnetic stirring at 500 r / min, the nanofiber aerogel (1 g) was immersed in a mixed solution (50 mL) of TEMPO (0.005 g) and NaBr (0.1 g). Then 12 mmol NaClO (1.13 mL) was added dropwise to the mixture. The pH value was maintained at 10 by adding 0.1 M HCl or NaOH. After reacting at room temperature for 6 hours, ethanol was added to terminate the reaction. The obtained carboxylated fiber wood aerogel was thoroughly washed with ethanol / H2O (1:1) and deionized water to remove the residual reagents. Finally, it was vacuum freeze-dried for 24 h to obtain the carboxylated fiber wood aerogel.

[0096] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A preparation method of recyclable wood-based cellulose aerogel, characterized in that: It includes the following steps: Immerse the wood chips in a mixed solution of NaOH and Na2SO3, heat and react for a set time, then add H2O2 thereto and continue to heat and react for a set time; After the reaction ends, dry the wood chips, and then immerse them in a hot N,N-dimethylacetamide solution of LiCl for a set time; After the immersion is completed, immerse the wood chips in acetone for acetone regeneration. After the regeneration is completed, immerse the wood chips in tert-butanol for displacement, and freeze-dry the displaced wood chips to obtain nanofiber wood aerogel; Sulfonate modification or carboxylation modification of the nanofiber wood aerogel can be carried out.

2. The preparation method of the recyclable wood-based cellulose aerogel according to claim 1, characterized in that: In the mixed solution of NaOH and Na2SO3, the concentration of NaOH is 3-10 wt%, and the concentration of Na2SO3 is 1-5 wt%; Preferably, in the mixed solution of NaOH and Na2SO3, the concentration of NaOH is 3-7 wt%, and the concentration of Na2SO3 is 1-3 wt%.

3. The preparation method of the recyclable wood-based cellulose aerogel according to claim 2, characterized in that: When the wood chips are immersed in the mixed solution of NaOH and Na2SO3, the heating reaction temperature is 90-100 °C, and the reaction time is 3-7 h; Preferably, when H2O2 is introduced thereto, the continued heating reaction temperature is 90-100 °C, and the time is 5-10 h; Preferably, in the reaction system, the concentration of H2O2 is 10%-30%, and % is the mass percentage.

4. The preparation method of the recyclable wood-based cellulose aerogel according to claim 1, characterized in that: In the hot N,N-dimethylacetamide solution of LiCl, the concentration of LiCl is 5-10 wt%, the temperature is 90-100 °C, and the immersion reaction is carried out for 20-30 h.

5. The preparation method of the recyclable wood-based cellulose aerogel according to claim 1, characterized in that: The time for acetone regeneration is 30-40 h; Preferably, during the process of immersing the wood chips in tert-butanol for displacement, tert-butanol is replaced every 1-3 h.

6. The preparation method of the recyclable wood-based cellulose aerogel according to claim 1, characterized in that: The method for sulfonate modification is: mix the nanofiber aerogel with an aqueous solution of NaIO4, react in the dark at 40-60 °C for 2-5 h. After the reaction is completed, an aldehyde-grouped fibrous wood aerogel is obtained through immersion treatment; Add the aldehyde-grouped fibrous wood aerogel to a NaHSO3 solution, carry out a sulfonation reaction for 2-5 h. After sulfonation, wash and vacuum freeze-dry to obtain the product.

7. The preparation method of the recyclable wood-based cellulose aerogel according to claim 6, characterized in that: The concentration of NaIO4 in the aqueous solution of NaIO4 is 5-15 mg / mL, preferably 7-12 mg / mL; Preferably, the concentration of the NaHSO3 solution is 15-25 mg / mL, preferably 17-23 mg / mL.

8. The preparation method of the recyclable wood-based cellulose aerogel according to claim 1, characterized in that: The method for carboxylation modification is: immerse the nanofiber aerogel in a mixed solution of TEMPO and NaBr, then add NaClO thereto and adjust the pH value of the system to be weakly alkaline, and react at room temperature for 4-8 h. After the reaction is completed, add ethanol to terminate the reaction; Wash and dry the aerogel to obtain a carboxylated fibrous wood aerogel; Preferably, in the mixed solution of TEMPO and NaBr, the concentration of TEMPO is 0.001-0.02 g / mL, and the concentration of NaBr is 0.02-0.5 g / mL; Preferably, adjust the pH value of the system to 10; Preferably, wash the aerogel with an ethanol / water solution and deionized water.

9. A recyclable wood-based cellulose aerogel, characterized in that: Prepared by the preparation method according to any one of claims 1-8.

10. Use of the recyclable wood-based cellulose aerogel according to claim 9 as a microplastic adsorbent.

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