Biomass carbon cellulose aerogel as well as preparation method and application thereof

Abstract

The invention relates to the technical field of micro-plastic pollution treatment, in particular to biomass carbon cellulose aerogel as well as a preparation method and application thereof. The method comprises the following steps: treating shiitake mushroom stick wastes to obtain biomass cellulose; the preparation method comprises the following steps: uniformly dispersing biomass cellulose in deionized water to form a suspension, and then freeze-drying the suspension to obtain cellulose aerogel; under the protection of nitrogen atmosphere, the cellulose aerogel is carbonized and then cooled to the room temperature, and BC aerogel is obtained; wherein the carbonization condition of the cellulose aerogel is as follows: the temperature is raised to 600-650 DEG C from room temperature at a heating rate of 3-5 DEG C / min, the temperature is kept for 10-15 minutes, the temperature is raised to 700-750 DEG C, the temperature is kept for 2-3 hours, and then the temperature is reduced. According to the method, the mushroom stick waste is applied to preparation of the biomass material, meanwhile, the harm of the waste to the ecological environment is greatly reduced, and the waste mushroom stick waste is turned into wealth.

Description

Technical Field

[0001] This invention belongs to the field of microplastic pollution treatment technology, and specifically relates to a biomass carbon fiber aerogel, its preparation method, and its application. Background Technology

[0002] Aerogels are porous materials that exhibit a unique spatial network structure, high specific surface area, and excellent electrical conductivity. They are commonly used to adsorb PM2.5 particles from the air.

[0003] Furthermore, with the widespread use of plastics, microplastic pollution is also prevalent. It has been found that microplastics accumulate in the aquatic food chain in both freshwater and saltwater environments, and this pollution throughout the natural environment inevitably leads to the accumulation of microplastics in the human body. Due to the widespread distribution of microplastics, the potential dangers associated with microplastics in the environment include physical damage to organisms, the potential release of toxic chemicals contained in the plastics, and the ability of microplastics to clog the digestive tract, inhibit feeding, and impair reproduction, thus creating a cascading effect on the entire ecosystem. Therefore, it is necessary to treat and adsorb microplastics in water bodies.

[0004] However, existing aerogels prepared from organic polymers and organic carbon nanomaterials using freeze-drying or supercritical drying techniques cannot adsorb microplastics, are non-biodegradable, difficult to recycle, and generate secondary pollution. Therefore, providing a renewable, biodegradable biomass carbon fiber aerogel material capable of adsorbing microplastics is of great significance. Summary of the Invention

[0005] To address the shortcomings of the prior art, the present invention aims to provide a biomass carbon fiber aerogel, its preparation method, and its application, thereby solving the problems existing in the background art and preparing a renewable, biodegradable biomass carbon fiber aerogel material that can be used to adsorb microplastics.

[0006] To address the aforementioned technical problems, this invention provides a method for preparing biomass carbon fiber aerogel, comprising the following steps: The waste from shiitake mushroom spawn is processed to obtain biomass cellulose; Biomass cellulose was uniformly dispersed in deionized water to obtain a suspension, and the suspension was freeze-dried to obtain cellulose aerogel. Cellulose aerogel was carbonized under a nitrogen atmosphere and then cooled to obtain BC aerogel. The carbonization conditions for cellulose aerogel are as follows: the temperature is increased from room temperature to 600℃~650℃ at a heating rate of 3℃ / min~5℃ / min, held for 10min~15min, then increased to 700℃~750℃, held for 2h~3h, and then cooled down.

[0007] Preferably, the freeze-drying temperature is -80℃ to -60℃, the freeze-drying time is 48h to 60h, and the freeze-drying pressure is 0.200mbar to 0.500mbar.

[0008] Preferably, the method for obtaining biomass cellulose from shiitake mushroom substrate waste includes the following steps: The surface of the shiitake mushroom spawn sticks was cleaned to obtain the treated shiitake mushroom spawn sticks. After processing, the shiitake mushroom logs are soaked in an alkaline solution, heated and stirred, filtered and washed to obtain shiitake mushroom logs with non-cellulose components removed. The shiitake mushroom logs, after removing non-cellulose components, were dispersed in a NaClO2 solution with a pH of 4-5. After stirring, heating, washing, and filtering, biomass cellulose was obtained.

[0009] Preferably, acetic acid is added to the NaClO2 solution to adjust the pH of the NaClO2 solution to 4-5.

[0010] NaClO2 is more stable under acidic conditions (pH 4-5) and can efficiently release active chlorine components (such as ClO2). - This effectively degrades non-cellulose impurities such as lignin.

[0011] Preferably, the mass ratio of the shiitake mushroom spawn sample to the alkaline solution is 0.04 g / mL to 0.08 g / mL, and the concentration of the alkaline solution is 1 mol / L to 1.2 mol / L.

[0012] Preferably, the mass ratio of biomass cellulose to deionized water is 1:1 to 1:1.5.

[0013] Preferably, the concentration of the NaClO2 solution is 0.40 mol / L to 0.50 mol / L, and the mass ratio of the NaClO2 solution to the shiitake mushroom log sample after removing non-cellulose components is 2:1 to 5:1.

[0014] At pH 4-5, 0.40 mol / L to 0.50 mol / L NaClO2... - The activation rate can reach over 95%, ensuring a moderate and controllable reaction rate. Excessive concentration will accelerate decomposition and reduce the utilization rate of available chlorine. A mass ratio of 2:1 to 5:1 ensures that the NaClO2 solution fully wets the mycelium sample, covering all lignin areas. A ratio that is too low (<2:1) may lead to insufficient localized oxidation, while a ratio that is too high (>5:1) wastes reagents and increases the difficulty of subsequent processing.

[0015] Preferably, the step of removing surface impurities from the waste mushroom substrate is as follows: dispersing the waste mushroom substrate, washing the dispersed waste mushroom substrate with deionized water, and then drying and constant temperature treatment to obtain waste mushroom substrate with surface impurities removed.

[0016] Preferably, the concentration of the alkali solution is 1 mol / L to 1.2 mol / L, and the mass-to-volume ratio of the treated shiitake mushroom logs to the alkali solution is 0.04 g / mL to 0.08 g / mL.

[0017] This invention provides a method for preparing biomass carbon fiber aerogel to obtain BC aerogel.

[0018] This invention provides the application of BC aerogel in eliminating the harm of microplastics to the ecological environment.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention utilizes waste mushroom substrate to produce a carbonized biomass cellulose aerogel that achieves efficient microplastic adsorption through a multi-scale synergistic mechanism. This is because the waste mushroom substrate contains a large amount of residual mushroom mycelium (fungal mycelial network), a natural high-molecular polymer that is biodegradable and does not produce secondary pollution. Furthermore, the waste residue from the mushroom substrate has a higher degree of fiber content. Therefore, the carbonized biomass cellulose aerogel prepared using waste mushroom substrate as raw material has a hierarchical porous structure (micropores / mesopores / macropores), capable of physically trapping microplastic particles from 1μm to 500μm. Simultaneously, the carbonized biomass cellulose aerogel is produced by placing the cellulose aerogel in a tube furnace... The temperature was increased from room temperature to 600℃~650℃ at a rate of 3℃ / min~5℃ / min, and carbonized for 10min~15min. Then, the temperature was increased to 700℃~750℃ and carbonized for 2h~3h. The resulting graphitized carbon layer and oxygen-containing functional groups (-COOH, -OH) enhanced chemical adsorption through π-π conjugation, hydrogen bonding, and electrostatic interactions. This reduced the hydrophobic functional groups on the surface of the carbonized biomass cellulose aerogel, further improving the affinity between the carbonized biomass cellulose aerogel and non-polar microplastics. This material can be applied to water bodies to adsorb microplastics, which can reduce water pollution to a certain extent. It is expected that this material can be applied to actual water bodies to solve the dual environmental problems of agricultural pollution and microplastic pollution.

[0020] In addition, waste mushroom substrate is a biodegradable organic biomass raw material. Therefore, the carbonized biomass cellulose aerogel prepared using waste mushroom substrate is also biodegradable and recyclable, and will not produce secondary pollution, breaking the traditional agricultural waste disposal method. Attached Figure Description

[0021] Figure 1FT-IR spectra of spent shiitake mushroom substrate, cellulose aerogel, and BC aerogel.

[0022] Figure 2 XRD patterns of spent shiitake mushroom substrate, cellulose aerogel, and BC aerogel.

[0023] Figure 3 Images show SEM images of spent shiitake mushroom substrate, cellulose aerogel, and BC aerogel. Image A shows a 10µm SEM image of spent shiitake mushroom substrate, image B shows a 100µm SEM image of spent shiitake mushroom substrate, image C shows a 0.5µm SEM image of spent shiitake mushroom substrate; image D shows a 10µm SEM image of cellulose aerogel, image E shows a 100µm SEM image of cellulose aerogel, image F shows a 0.5µm SEM image of cellulose aerogel, image G shows a 10µm SEM image of BC aerogel, image H shows a 100µm SEM image of BC aerogel, and image I shows a 0.5µm SEM image of BC aerogel.

[0024] Figure 4 Thermogravimetric analysis diagram of BC aerogel.

[0025] Figure 5 The images show the wettability of water droplets on the prepared BC aerogel, with the left, middle, and right images representing three parallel experiments.

[0026] Figure 6 For the determination of the compressibility of aerogel, (A) is the height at which the compressibility is to be determined, (B) is the height at the bottom when compressed, and (C) is the height after compression rebound.

[0027] Figure 7 This is a dynamic adsorption diagram of microplastics on BC aerogel.

[0028] Figure 8 The diagram shows the dynamic adsorption of PS and PMMA by the straw-based aerogel in Comparative Example 1.

[0029] Figure 9 The graphs show the dynamic adsorption amounts of PS and PMMA by biomass cellulose in Comparative Example 2.

[0030] Figure 10 The graphs show the dynamic adsorption amounts of PS and PMMA on the cellulose aerogel in Comparative Example 3.

[0031] Figure 11 The diagram shows the dynamic adsorption of PS and PMMA by the carbonized cellulose aerogel in Comparative Example 4. Detailed Implementation

[0032] The specific embodiments of the present invention are described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention. Unless otherwise specified, the experimental methods described in the embodiments of the present invention are conventional methods.

[0033] This invention addresses the challenge of resource utilization of discarded shiitake mushroom logs after edible fungi cultivation. Based on the characteristics of low lignin, high-activity functional groups (-NH2, -COOH), and oriented nanofibers (20nm~50nm) formed by fungal degradation, it innovatively designs carbonized biomass cellulose aerogel: carbonization at 300℃~750℃ retains oxygen-containing groups and generates a graphitized carbon layer, combined with freeze-drying to construct a hierarchical porous structure, achieving multi-mechanism synergistic adsorption (π-π conjugation).

[0034] In view of this, the present invention provides a biomass carbon fiber aerogel, its preparation method, and its application, which solves the problems existing in the prior art. By applying the waste of shiitake mushroom substrate to the preparation of biomass materials, the harm of waste to the ecological environment is greatly reduced, and the waste of shiitake mushroom substrate is turned into a treasure.

[0035] The technical solution of the present invention will be further described below through specific embodiments.

[0036] Example 1 A method for preparing biomass carbon fiber aerogel includes the following steps: (1) Extraction of biomass cellulose: Waste shiitake mushroom logs were crushed and dispersed into bulk, then washed five times with deionized water (until clean; if the quantity of waste shiitake mushroom logs is large, the number of washes may vary). The logs were then dried in a constant temperature oven at 80℃ for 24 hours until constant weight was achieved, yielding shiitake mushroom log samples with surface impurities removed. Subsequently, 20g of the surface-impurity-removed shiitake mushroom logs were immersed in 400mL of 1mol / L sodium hydroxide solution, and the mixture was magnetically stirred at 80℃ for 4 hours. The mixture was then filtered through multiple layers of gauze and washed repeatedly with deionized water to remove non-cellulose components, resulting in shiitake mushroom logs with non-cellulose components removed.

[0037] Acetic acid was added to 200 mL of a 0.44 mol / L NaClO2 solution to adjust the pH to 4. The weighed shiitake mushroom substrate sample (with non-cellulose components removed) was dispersed in the NaClO2 solution at a mass ratio of 2:1 (NaClO2 solution to non-cellulose-removed substrate). The mixture was then magnetically stirred at 80°C for 4 hours. Finally, after alternating washing with anhydrous ethanol and deionized water and filtering, biomass cellulose was obtained.

[0038] (2) Preparation of cellulose aerogel: Cellulose aerogels were successfully constructed from the biomass cellulose obtained in step (1) above using freeze-drying and carbonization techniques. The treated cellulose aerogels were uniformly dispersed in deionized water at a mass ratio of biomass cellulose to deionized water of 1:1 to form a uniform suspension. The suspension was then placed in a freezer and transferred to a freeze-drying oven. After freeze-drying at -60°C and 0.200 mbar for 48 hours, cellulose aerogels were obtained.

[0039] (3) Carbonization of cellulose aerogel (i.e., preparation of BC aerogel) The cellulose aerogel obtained in step (2) above was loaded into an OTF-1200X tube furnace and heated from room temperature to 650°C at a heating rate of 5°C / min in a nitrogen atmosphere. The temperature was held for 10 min, then increased to 700°C and held at 700°C for 2 h. The temperature was then lowered to room temperature to obtain carbon fiber aerogel (BC aerogel).

[0040] Example 2 A method for preparing biomass carbon fiber aerogel includes the following steps: (1) Extraction of biomass cellulose: Waste shiitake mushroom logs were crushed and dispersed into bulk, washed five times with deionized water, and then dried in a constant temperature oven at 80℃ for 24 hours until constant weight was achieved, obtaining shiitake mushroom log samples with surface impurities removed. Subsequently, 16g of the shiitake mushroom log sample with surface impurities removed was immersed in 400mL of 1.2mol / L sodium hydroxide solution, and the mixture was magnetically stirred at 80℃ for 4 hours. Then, it was filtered through multiple layers of gauze and washed multiple times with deionized water to remove non-cellulose components, obtaining shiitake mushroom log samples with non-cellulose components removed.

[0041] Acetic acid was added to 200 mL of a 0.40 mol / L NaClO2 solution to adjust the pH to 5. The weighed shiitake mushroom substrate sample (with non-cellulose components removed) was dispersed in the NaClO2 solution at a mass ratio of 5:1 (NaClO2 solution to non-cellulose-removed shiitake mushroom substrate). The mixture was then magnetically stirred at 80°C for 4 hours. Finally, after alternating washing with anhydrous ethanol and deionized water, and followed by filtration, biomass cellulose was obtained.

[0042] (2) Preparation of cellulose aerogel: Cellulose aerogels were successfully constructed from the biomass cellulose obtained in step (1) above using freeze-drying and carbonization techniques. The treated cellulose aerogels were uniformly dispersed in deionized water at a mass ratio of biomass cellulose to deionized water of 1:1.2 to form a uniform suspension. The suspension was then placed in a freezer and transferred to a freeze-drying oven. After freeze-drying at -80℃ and 0.500mbar for 60 hours, cellulose aerogels were obtained.

[0043] (3) Carbonization of cellulose aerogel (i.e., preparation of BC aerogel) The cellulose aerogel obtained in step (2) above was loaded into an OTF-1200X tube furnace and heated to 600°C at a heating rate of 3°C / min in a nitrogen atmosphere. After holding at this temperature for 15 min, the temperature was raised to 750°C and held at this temperature for 3 h before being cooled down to obtain carbon fiber aerogel (BC aerogel).

[0044] Example 3 A method for preparing biomass carbon fiber aerogel includes the following steps: (1) Extraction of biomass cellulose: Waste shiitake mushroom logs were crushed and dispersed into bulk, washed five times with deionized water, and then dried in a constant temperature oven at 80℃ for 24 hours until constant weight was achieved, obtaining shiitake mushroom log samples with surface impurities removed. Subsequently, 32g of the shiitake mushroom log sample with surface impurities removed was immersed in 400mL of 1.1mol / L sodium hydroxide solution, and the mixture was magnetically stirred at 80℃ for 4 hours. Then, it was filtered through multiple layers of gauze and washed multiple times with deionized water to remove non-cellulose components, obtaining shiitake mushroom log samples with non-cellulose components removed.

[0045] Acetic acid was added to 200 mL of 0.50 mol / L NaClO2 solution to adjust the pH to 4.5. The weighed shiitake mushroom substrate sample (with non-cellulose components removed) was dispersed in the NaClO2 solution at a mass ratio of 3:1 (NaClO2 solution to non-cellulose-removed shiitake mushroom substrate). The mixture was then magnetically stirred at 80 °C for 4 hours. Finally, after alternating washing with anhydrous ethanol and deionized water and filtering, biomass cellulose was obtained.

[0046] (2) Preparation of cellulose aerogel: Cellulose aerogels were successfully constructed from the biomass cellulose obtained in step (1) above using freeze-drying and carbonization techniques. The treated cellulose aerogels were uniformly dispersed in deionized water at a mass ratio of biomass cellulose to deionized water of 1:1.5 to form a uniform suspension. The suspension was then placed in a freezer and transferred to a freeze-drying oven. After freeze-drying at -70°C and 0.300 mbar for 50 hours, cellulose aerogels were obtained.

[0047] (3) Carbonization of cellulose aerogel (i.e., preparation of BC aerogel) The cellulose aerogel obtained in step (2) above was loaded into an OTF-1200X tube furnace and heated to 630°C at a heating rate of 4°C / min in a nitrogen atmosphere. The temperature was held at 630°C for 12 min, then increased to 730°C and held for 2.5 h before cooling to obtain carbon fiber aerogel (BC aerogel).

[0048] Comparative Example 1 The only difference between Comparative Example 1 and Example 1 is that the waste from shiitake mushroom substrate was replaced with straw, resulting in straw-based carbonized aerogel.

[0049] Comparative Example 2 The only difference between Comparative Example 2 and Example 1 is that the cellulose aerogel was not carbonized under nitrogen, and the product was cellulose aerogel.

[0050] Comparative Example 3 The only difference between Comparative Example 3 and Example 1 is that the carbonization temperature is 400°C and held for 1 hour.

[0051] Comparative Example 4 The only difference between Comparative Example 4 and Example 1 is that the carbonization temperature is 1000℃ and maintained for 5 hours.

[0052] Examples 1 to 3 above can all prepare carbon fiber aerogels and cellulose aerogels. The carbon fiber aerogel (BC aerogel), cellulose aerogel, and spent shiitake mushroom substrate prepared in Example 1 will be used for experimental material characterization. The carbon fiber aerogel (BC aerogel) prepared in Example 1 will be subjected to compressive strength, density and porosity, and molecular dynamics adsorption experiments.

[0053] (1) Fourier transform infrared spectroscopy (FTIR) test The chemical groups of three materials—BC aerogel, cellulose aerogel, and spent shiitake mushroom substrate—were characterized using infrared spectroscopy. Different materials exhibited different characteristic peaks in their infrared spectra. The three materials were separately mixed with potassium bromide, ground uniformly, poured into molds, pressed into tablets, and then the samples were fixed before being subjected to infrared spectroscopy at a wavenumber of 4000 cm⁻¹. -1 ~400cm -1 The resolution is 4cm. -1 The test was conducted to observe the changes in the peak diagram of each material.

[0054] like Figure 1 As shown, Figure 1 The spent mushroom logs of *Millettia dielsiana* are located at 839 cm. -1 The characteristic peak is because it exists in coordinated water (H2O) and is located at 1384 cm⁻¹.-1 The absorption peak observed at 1633 cm⁻¹ corresponds to the stretching vibration peak of CH. -1 and 1041cm -1 The peak at 2430 cm⁻¹ is an absorption peak generated by the CO stretching vibration. -1 The absorption peak corresponds to the NH stretching vibrations of primary and secondary amines, 3437 cm⁻¹. -1 The broad absorption bands in the vicinity indicate the presence of crystalline hydroxyl groups, which are infrared absorption peaks observed in spent shiitake mushroom substrate. After acid-base treatment, the infrared spectrum of cellulose aerogel exhibits characteristics similar to that of spent shiitake mushroom substrate, mainly attributed to the abundant carbohydrate content in the substrate. The infrared spectral characteristics of BC aerogel obtained after high-temperature carbonization change significantly, showing obvious differences compared to uncarbonized spent shiitake mushroom substrate and cellulose aerogel. BC aerogel at 870 cm⁻¹... -1 The position of the peak indicates the presence of epoxy groups in the BC aerogel, at 1384 cm⁻¹. -1 There is a methyl peak (CH3 bend) at 2430 cm⁻¹. -1 The peak at 3437 cm⁻¹ is related to the carbon-hydrogen bonds of alkanes, while the FT-IR spectrum at 3437 cm⁻¹... -1 A broad amino peak was observed. In the above results, the significant reduction of numerous hydrophilic oxygen-containing functional groups in the BC aerogel, derived from spent shiitake mushroom substrate, caused the BC aerogel to transform from hydrophilic to hydrophobic. The presence of surface functional groups is crucial for the adsorbent to remove microplastics from aqueous solutions.

[0055] (2) X-ray diffraction (XRD) test The crystal structures of BC aerogel, cellulose aerogel, and spent mushroom substrate were characterized by XRD (Panalytical Empyrean, Netherlands). Block samples of the three materials (1 cm to 2 cm in length and width, and no more than 15 mm in thickness) were placed on the sample stage of the diffractometer and tested under the conditions of scanning angle 10 to 80° and scanning speed 2° / min.

[0056] exist Figure 2In the XRD pattern of spent shiitake mushroom substrate, two strong diffraction peaks were observed at 22.25° and 24.43°. These two significant characteristic peaks indicate that the material conforms to the typical type I crystal structure of cellulose. After alkali washing and acid washing, the XRD pattern of cellulose aerogel from the spent shiitake mushroom substrate showed sharper and stronger characteristic peaks. Compared with the spent shiitake mushroom substrate, this indicates that the cellulose aerogel has higher crystallinity and purity. This result confirms the purification effect of the treatment process on the raw material and highlights the superiority of cellulose aerogel as a raw material. The XRD pattern of BC aerogel obtained after high-temperature carbonization of cellulose aerogel showed no new sharp and strong peaks. Instead, two broad and weak diffraction peaks appeared at 22.16° and 33.92°. These peaks are not characteristic peaks of cellulose but are consistent with typical amorphous carbon peaks. This indicates that the cellulose crystal structure in the cellulose aerogel was destroyed and transformed into amorphous carbon components during the high-temperature calcination process. This amorphous carbon structure typically has a low surface free energy, indicating that the more stable the molecules or atoms on the BC aerogel, the more hydrophobic the BC aerogel becomes, which has an important influence on the wettability of the subsequent microplastic solution.

[0057] (3) Scanning electron microscopy (SEM) test The morphology of three materials—BC aerogel, cellulose aerogel, and spent shiitake mushroom substrate—was observed using a scanning electron microscope (Sigma 300). Before operation, the samples of the three materials were ground in a mortar until they were free of particles and coated with a metal film to improve the conductivity of the samples and the observation effect. The control system was then started and the system self-test was completed. The samples were fixed on the sample stage and secured with sample clamps. The images of the three materials were observed at magnifications of 100µm, 10µm, and 0.5µm, respectively.

[0058] like Figure 3 As shown, spent shiitake mushroom substrate (A-C), cellulose aerogel (D-F), and BC aerogel (G-I) all exhibit a distinct porous microstructure. SEM images of cellulose aerogel (D-F) and BC aerogel (G-I) show that they retain the macroporous structure characteristics of cellulose aerogel. However, compared to spent shiitake mushroom substrate (A-C) and cellulose aerogel (D-F), BC aerogel (G-I) exhibits a different morphology under high-magnification SEM images. Cellulose aerogel is mainly composed of ribbon-like fibers hundreds of micrometers in length. Adjacent cellulose fibers are mechanically intertwined, forming a porous network framework structure. The cellulose surface is free of other impurities and is covered with rough, curved wrinkles. Figure 3(D~F). Because BC aerogel is prepared using a high-temperature carbonization method, it contains many bundles of parallel fibrils, with widths ranging from tens to hundreds of nanometers and lengths from several micrometers, exhibiting good adsorption properties in aqueous solutions. (In the image...) Figure 3 In G~I), numerous pores, dark spots, and cavities were observed in the BC aerogel, indicating the presence of microplastic adsorption sites on the BC aerogel surface. Figure 3 As shown in Figure E, the cellulose fibers are intertwined, and the BC aerogel retains the original structure of the cellulose aerogel. Compared with the structure of the cellulose aerogel before carbonization, the pore size and diameter of the fibers have slightly shrunk. Therefore, the skeletal structure of the BC aerogel after high-temperature calcination is more compact than that of the cellulose aerogel. Figure 3 G), the entangled fibers form abundant tortuous microchannels, which facilitates the aggregation of microplastics during aerogel permeation. Figure 3 In section I, the surface of the BC aerogel retains a rough structure, which is conducive to the joint construction of a rough porous spatial network framework, providing a good structural basis for intercepting microplastics.

[0059] (4) Thermogravimetric analysis (TGA) of BC aerogel. The powdered BC aerogel sample was evenly placed on a sample tray and subjected to thermogravimetric analysis at a heating rate of 10℃ / min and a termination temperature of 800℃. The relationship between sample mass and temperature was recorded in a specific atmosphere.

[0060] like Figure 4 As shown, the BC aerogel prepared in Example 1 underwent TGA in N2 and air. The initial weight loss up to 50°C was due to the removal of water or other volatile substances; the second weight loss occurred between 50°C and 600°C, due to the decomposition of the organic components in the corresponding samples; the weight loss above 600°C was due to the pyrolysis of the carbon skeleton. The BC aerogel showed a minimum weight loss of approximately 13% before 600°C, and a second minimum weight loss of approximately 20% was observed before 670°C in the high-temperature range. The BC aerogel exhibited good thermal stability in N2 up to 800°C.

[0061] (5) Water contact angle measurement (WCA) The water contact angle was measured at an ambient temperature of approximately 20°C and a humidity of 10%RH. 5 μl of deionized water with a pH of 2-12 was dropped onto the surface of the BC aerogel at a titration rate of 2 μl / s. To ensure the repeatability of the experiment, measurements were taken at three different locations on the sample, and the data were the average of the three measurements.

[0062] like Figure 5This indicates that the surface of the BC aerogel prepared in Example 1 was successfully tested using static WCA to demonstrate the wettability of the BC aerogel. The efficient selective adsorption plays a crucial role in the removal of microplastics from water. Figure 5 The wettability of BC aerogel in aqueous solution was demonstrated. The contact angle, obtained through three repeated measurements, was 120.28°, indicating that the surface of the BC aerogel based on spent shiitake mushroom substrate is hydrophobic, meaning that liquids do not easily wet the BC aerogel. When using BC aerogel to adsorb insoluble microplastics from different aqueous solutions, the hydrophobicity of the BC aerogel surface helps reduce water adhesion, thus minimizing interference with the adsorption process. This stability ensures that the BC aerogel maintains high adsorption performance even under prolonged or complex environmental conditions. Furthermore, after adsorbing microplastics, they can be separated from the water using simple physical separation methods (such as centrifugation and filtration), facilitating recycling and reuse. This reduces processing costs and improves the economic viability of BC aerogel in practical applications.

[0063] (6) Testing of compressive strength, density and porosity of carbon fiber aerogel (BC aerogel) The elastic material BC aerogel can be reused by subjecting it to multiple compression processes. The specific procedure is as follows: First, place a relatively regular rectangular block of BC aerogel flat on a horizontal surface and manually compress it with a glass slide. Compress it five times consecutively to completely expel the internal air. Then release the pressure to allow the aerogel to slowly recover. After it has fully recovered, measure the height of the BC aerogel. Repeat all the above procedures five times and calculate the relative height ratio using the following formula.

[0064] h c h0 is the initial height of the cellulose aerogel, and h0 is the recovered height after release. The density (ρ) and porosity (Φ) of BC aerogel are calculated as follows: Where m and v are the mass and volume of the BC aerogel, respectively; in It is the total bulk density of BC aerogel. c is the density of carbon.

[0065] like Figure 6The compression properties of BC aerogel are shown, indicating that BC fiber aerogel can recover from elastic deformation under external compression. When pressure is continuously applied to BC aerogel, the pores in the aerogel are continuously compacted. When the pressure is removed, the BC aerogel can return to its original state, exhibiting excellent elasticity. After 30 compression-release cycles, the relative height of BC aerogel still reaches 93.71%, and no significant collapse or breakage was observed during this process. This is likely due to the presence of the complex mechanical entanglement network and cross-linking structure formed between the cellulose fibers. These structures provide stable support and protection for the overall structure under compression and release forces, and also exhibit good resilience, which is beneficial for subsequent microplastic removal and repeated use. The density of BC aerogel is 0.204 g / cm³. 3 The lower density means more pores and a larger specific surface area, which helps increase the contact area and adsorption sites with microplastics. The low density of BC aerogel based on spent shiitake mushroom substrate is suitable for the adsorption of microplastics. The porosity of BC aerogel is 0.887. Porosity directly affects its adsorption capacity and rate for microplastics. High-porosity aerogels have more channels and cavities, which is conducive to the entry and adsorption of microplastic particles, and is more conducive to the adsorption of smaller particles.

[0066] (7) Molecular dynamics adsorption experiment Dynamic adsorption experiments were conducted to evaluate the reactions of BC aerogel, straw-based aerogel prepared in Comparative Example 1, cellulose aerogel prepared in Comparative Example 2, carbonized cellulose aerogel prepared in Comparative Example 3, and carbonized cellulose aerogel prepared in Comparative Example 4 with polymethyl methacrylate (PMMA) microplastics (5µm) and polystyrene nanoplastics (PS) (100nm) at room temperature (20℃). 50mg of BC aerogel was added to 40ml of microplastic solution (25mg / L), and the concentrations of the two microplastics remaining in the solution at different time points (0, 2, 4, 6, 8, 10, 12h) were obtained using a standard curve. The removal effect of BC aerogel on the two microplastics was measured before and after absorption. Each sample was tested in triplicate, and the average value was taken as the experimental result. The adsorption capacity was determined by the following formula:

[0067] q e =(C0-C e ) / m q t =(C0-C t V / m In the above adsorption capacity formula, C0 (mg / L) and C e (mg / L) represents the initial and equilibrium concentrations of PMMA and PS microplastics, respectively. t(mg / L) represents the concentration of PMMA and PS microplastics in the solution at a given time point, q e (mg / g) and q t (mg / g) represents the adsorption capacity of PMMA and PS microplastic solutions at equilibrium and at a given time point, respectively. The mass of BC aerogel is m (g), and the reaction volume is V (L).

[0068] like Figure 7 The dynamic adsorption capacity of BC aerogel for microplastics is shown, revealing that the adsorption capacity of both PS and PMMA microplastic solutions decreased with increasing adsorption time. At the initial concentration of 25 mg / L for 2 hours, there was no significant difference in the adsorption capacity of microplastics by BC aerogel between the two solutions, with PS only 0.4 mg / L higher than PMMA. Subsequently, the adsorption capacity continued to decrease, with the adsorption capacity of PS microplastic solution consistently higher than PMMA within the same time period. This may be due to specific π-π interactions or hydrogen bonds between the aromatic rings in the PS molecule and some functional groups on the BC aerogel surface, enhancing the adsorption capacity of BC aerogel for PS microplastics. PS microplastics essentially reached adsorption equilibrium at 10 hours. The decrease in removal efficiency may be due to the gradual saturation of adsorption sites on the BC aerogel during continuous adsorption, leading to the occupancy of these sites and a subsequent decrease in adsorption capacity until equilibrium is reached.

[0069] The kinetic adsorption experiment results showed that the adsorption rate of microplastics on BC aerogel was basically linear. PS microplastics could reach adsorption equilibrium in 10-12 hours, while PMMA microplastics had not yet reached equilibrium. The adsorption capacity of both types of microplastics gradually decreased over time. The decrease in removal efficiency may be due to the fact that the adsorption sites of BC aerogel gradually became saturated during the continuous adsorption process of microplastics. As the adsorption sites were gradually occupied, the subsequent adsorption capacity decreased until equilibrium was reached.

[0070] like Figure 8 To determine the dynamic adsorption capacity of PS and PMMA by the straw-based aerogel in Comparative Example 1, the following was performed: Figure 8 It can be seen that the dynamic adsorption capacity of straw-based aerogel for PS shows a slow upward trend followed by a downward trend, with the adsorption capacity reaching only 0.05 mg / g to 0.08 mg / g within 12 hours. The dynamic adsorption capacity of straw-based aerogel for PMMA also shows a slow upward trend followed by a downward trend, with the adsorption capacity reaching only 0.06 mg / g to 0.08 mg / g within 12 hours. Compared with the BC aerogel prepared in Example 1, it is found that the compatibility between straw-based aerogel and the target polymers (PS and PMMA) is poor, and there is a large mass transfer resistance.

[0071] like Figure 9To determine the dynamic adsorption capacity of cellulose aerogel for PS and PMMA in Comparative Example 2, the following parameters were measured: Figure 9 It can be seen that the dynamic adsorption capacity of cellulose aerogel for PS only reaches 0.05 mg / g to 0.065 mg / g within 12 hours, and the dynamic adsorption capacity of cellulose aerogel for PMMA shows an irregular trend, reaching 0.08 mg / g to 0.13 mg / g. Compared with the BC aerogel prepared in Example 1, it is found that the compatibility of cellulose aerogel with the target polymers (PS and PMMA) is poor and there is a large mass transfer resistance.

[0072] like Figure 10 To compare the dynamic adsorption capacities of carbonized cellulose aerogel for PS and PMMA in Example 3, the dynamic adsorption capacity of carbonized cellulose aerogel for PS only reached 0.06-0.10 mg / g within 12 hours. Figure 10 It can be seen that the dynamic adsorption capacity of carbonized cellulose aerogel for PMMA reaches 0.05-0.08 mg / g. Compared with the dynamic adsorption capacity of PS and PMMA of the carbonized cellulose aerogel prepared in Comparative Example 3, the dynamic adsorption capacity of carbonized cellulose aerogel for PMMA is relatively poor, and there is a large mass transfer resistance.

[0073] like Figure 11 To compare the dynamic adsorption capacity of carbonized cellulose aerogel for PS and PMMA in Example 4, the following was performed: Figure 11 It can be seen that the dynamic adsorption capacity of carbonized cellulose aerogel for PS only reaches 0.05 mg / g to 0.12 mg / g within 12 hours, and the dynamic adsorption capacity of carbonized cellulose aerogel for PMMA reaches 0.04 mg / g to 0.09 mg / g. Compared with the dynamic adsorption capacity of carbonized cellulose aerogel prepared in Comparative Example 4 for PS and PMMA, it can be seen that the compatibility of carbonized cellulose aerogel with the target polymers (PS and PMMA) is poor and there is a large mass transfer resistance.

[0074] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for preparing a biomass carbon cellulose aerogel, characterized by, The method comprises the following steps: The shiitake mushroom stick waste is treated to obtain biomass cellulose; The biomass cellulose is uniformly dispersed in deionized water to obtain a suspension, and the suspension is freeze-dried to obtain cellulose aerogel; The cellulose aerogel is carbonized under a nitrogen atmosphere, and BC aerogel is obtained after cooling. The carbonization conditions of the cellulose aerogel are as follows: the temperature is increased from room temperature to 600-650℃ at a rate of 3-5℃ / min, then the temperature is increased to 700-750℃ after 10-15min of holding, and then the temperature is decreased after 2-3h of holding.

2. The method for preparing biomass carbon fiber aerogel according to claim 1, characterized in that, The freeze-drying temperature is -80--60℃, the freeze-drying time is 48-60h, and the freeze-drying pressure is 0.200-0.500mbar.

3. The method for preparing biomass carbon fiber aerogel according to claim 1, characterized in that, The mass ratio of biomass cellulose to deionized water is 1:1-1:1.

5.

4. The method for preparing biomass carbon fiber aerogel according to claim 1, characterized in that, The method for obtaining biomass cellulose by treating shiitake mushroom stick waste comprises the following steps: The shiitake mushroom stick waste is subjected to surface impurity removal treatment to obtain treated shiitake mushroom stick; The treated shiitake mushroom stick is soaked in an alkali solution, heated and stirred, filtered, and washed to obtain shiitake mushroom stick with non-cellulose components removed; The shiitake mushroom stick with non-cellulose components removed is dispersed in a NaClO2 solution with a pH of 4-5, and then stirred and heated, washed, and filtered to obtain biomass cellulose.

5. The method for preparing biomass carbon fiber aerogel according to claim 4, characterized in that, Acetic acid is added to the NaClO2 solution to adjust the pH of the NaClO2 solution to 4-5.

6. The method for preparing biomass carbon fiber aerogel according to claim 4, characterized in that, The step of removing surface impurities from the shiitake mushroom stick waste is as follows: the shiitake mushroom stick waste is dispersed, the dispersed shiitake mushroom stick waste is washed with deionized water, and then dried and treated at a constant temperature to obtain shiitake mushroom stick waste with surface impurities removed.

7. The method for preparing biomass carbon fiber aerogel according to claim 3, characterized in that, The concentration of the alkali solution is 1-1.2mol / L, and the mass-to-volume ratio of the treated shiitake mushroom stick to the alkali solution is 0.04-0.08g / mL.

8. The method for preparing biomass carbon fiber aerogel according to claim 4, characterized in that, The concentration of the NaClO2 solution is 0.40-0.50mol / L, and the mass ratio of the NaClO2 solution to the shiitake mushroom stick with non-cellulose components removed is 2:1-5:

1.

9. The method for preparing biomass carbon cellulose aerogel according to any one of claims 1-8.

10. The application of the BC aerogel prepared by the method according to claim 9 in eliminating the harm of microplastics to the ecological environment.

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