A method for preparing high adsorptive activated carbon fiber

Abstract

This application relates to the field of activated carbon fiber technology, specifically disclosing a method for preparing highly adsorbent activated carbon fibers. This application uses oxidized modified viscose fiber as a precursor, which is then activated by plasma and subsequently seeded with nanocrystals to form a carbon-silicon composite intermediate. After carbonization, the silica is removed by hydrofluoric acid etching, resulting in a relatively continuous hierarchical porous structure. Plasma post-treatment is then used to adjust the surface properties of the activated carbon fiber surface and the pores. Compared to activated carbon fibers prepared using conventional phosphoric acid activation methods currently available on the market, the activated carbon fibers obtained in this application improve the mass transfer efficiency of macromolecular pollutants through their hierarchical porous structure. Furthermore, the pores, after plasma post-treatment, can fully utilize their adsorption and binding capacity for polycyclic aromatic hydrocarbons (PAHs). Therefore, the activated carbon fibers obtained in this application have a higher adsorption capacity for PAHs.

Description

Technical Field

[0001] This application relates to the field of adsorption materials technology, and more specifically, it relates to a method for preparing highly adsorbent activated carbon fibers. Background Technology

[0002] With the increasing demands for industrial development and environmental governance, the efficient treatment of persistent organic pollutants (PAHs) such as polycyclic aromatic hydrocarbons (PAHs) has become a crucial issue in the environmental protection field. PAHs are characterized by high toxicity, difficulty in degradation, and easy accumulation, posing a potential threat to the ecological environment and human health. Adsorption separation technology, due to its simplicity, high efficiency, and wide applicability, is currently the mainstream technical route for PAH treatment, and the core of this technical route is highly adsorbent materials.

[0003] Activated carbon fiber, as a new generation of high-performance adsorbent materials, is widely used in various scenarios such as waste gas treatment, advanced wastewater treatment, and volatile organic compound (VOC) recovery due to its advantages such as large specific surface area, rich pore structure, and fast adsorption / desorption rates. Phosphoric acid impregnation is currently a commonly used process for preparing porous carbon materials. This method involves impregnating the fiber raw material in a phosphoric acid solution. Utilizing the activation and catalytic effects of phosphoric acid, pore construction and functional group regulation are achieved during heat treatment, thereby preparing an adsorbent material with a specific pore structure. By adjusting parameters such as phosphoric acid concentration, impregnation time, and activation temperature, the specific surface area and pore structure of the material can be controlled to a certain extent, enabling its application in the adsorption and purification of common small-molecule pollutants.

[0004] Regarding the aforementioned technologies, the inventors believe that although activated carbon fibers prepared by the conventional phosphoric acid activation method have excellent adsorption effects on volatile organic small molecule pollutants, their adsorption effect on polycyclic aromatic hydrocarbons is still relatively limited, thus restricting the application of activated carbon fibers in the treatment of polycyclic aromatic hydrocarbons. Summary of the Invention

[0005] In related technologies, activated carbon fibers have limited adsorption effects on polycyclic aromatic hydrocarbons. To improve this deficiency, this application provides a method for preparing highly adsorbent activated carbon fibers.

[0006] This application provides a method for preparing highly adsorbent activated carbon fiber, using the following technical solution: A method for preparing highly adsorbent activated carbon fiber includes the following steps: (1) Clean the precursor and air dry it for later use; in this step, the precursor is oxidized modified viscose fiber, and the carboxyl content of the oxidized modified viscose fiber is 0.80-1.25 mmol / g. (2) The precursor after natural drying in step (1) is subjected to plasma surface activation to obtain activated fibers. The activated fibers are immersed in a nano-crystal seed dispersion, and after ultrasonic-assisted impregnation and drying, seed-modified fibers are obtained. The nano-crystal seed dispersion includes the following components: 1.6-4.8 wt% silicon source, 3.8-6.2 wt% carbon source, 0.1-0.2% dispersant, and the balance is made up to 100 wt% by deionized water. The silicon source includes nano-silica and tetraethyl orthosilicate, and the carbon source includes glucose. (3) The seed modified fiber is vacuum impregnated with a composite impregnation solution containing phosphoric acid and silica. Then the seed modified fiber is placed in a carbonization furnace for gradient heating carbonization. After carbonization, the seed is removed by soaking in hydrofluoric acid. After cleaning and drying, it is then subjected to plasma post-treatment to obtain highly adsorbent activated carbon fiber.

[0007] By adopting the above technical solution, this application first selects oxidized modified viscose fiber with a surface carboxyl content of 0.80-1.25 mmol / g as a precursor, and then cleans and naturally dries it. The oxidized modified viscose fiber surface has an appropriate amount of carboxyl groups, which can improve the polarity and reactivity of the precursor surface, providing a good foundation for subsequent plasma surface activation and the loading of the nanocrystal seed dispersion. At the same time, controlling the carboxyl content within the above range can improve the seed bonding ability while avoiding the impact on the fiber skeleton integrity due to excessive oxidation.

[0008] Subsequently, this application subjectes the naturally dried precursor to plasma surface activation treatment to obtain activated fibers. Plasma surface activation can further improve the wettability, roughness, and number of active sites on the fiber surface, making it easier for the nanocrystalline seed dispersion to disperse and adhere to the fiber surface and permeable areas. Therefore, when the precursor is immersed in the nanocrystalline seed dispersion and subjected to ultrasonic-assisted impregnation, the nano-silica, tetraethyl orthosilicate, and glucose in the nanocrystalline seed dispersion can be uniformly loaded onto the surface of the activated fiber, forming a relatively stable seed-modified layer during subsequent drying, thus obtaining seed-modified fibers. Nano-silica and tetraethyl orthosilicate together serve as silicon sources, which is beneficial for providing removable silicon-based templates during subsequent carbonization and etching; glucose, as a carbon source, is beneficial for forming carbonaceous coating or carbon-based filling structures around the silicon source, improving the bonding stability between the seed-modified layer and the fiber matrix; the dispersing agent helps reduce the agglomeration of silicon source particles, maintaining good dispersion stability of the seed dispersion.

[0009] Subsequently, this application uses a composite impregnation solution containing phosphoric acid and silica to vacuum impregnate the seed-modified fibers. Vacuum impregnation can remove some air from the fiber pores and the seed-modified layer, allowing phosphoric acid and silica to penetrate more fully into the fiber surface and internal permeable areas. Phosphoric acid can play a role in dehydration, cross-linking, and activation during the subsequent carbonization process, promoting the formation of a stable carbon skeleton in viscose fibers and external carbon sources, and facilitating the generation of microporous structures; silica can form a silicon-based dispersed phase together with the aforementioned silicon source, assisting in regulating the development of the pore structure inside the carbon skeleton during the carbonization process.

[0010] Subsequently, the seed-modified fibers, after composite impregnation treatment, were placed in a carbonization furnace for gradient heating carbonization. During the gradient heating process, the fiber precursor, glucose, and activated components in the composite impregnation solution gradually undergo dehydration, condensation, carbonization, and structural rearrangement, transforming the fiber matrix into an activated carbon fiber skeleton. Simultaneously, the silicon-based components formed from nano-silica, tetraethyl orthosilicate, and silicic acid components can serve as inorganic template phases dispersed in the carbon skeleton, participating in the regulation of pore structure. Through the above process, an intermediate structure composed of a carbon skeleton and a silicon-based dispersed phase is formed in the carbonization product, providing conditions for subsequent etching and pore formation.

[0011] After carbonization, this application uses hydrofluoric acid immersion to remove the seed crystals. Hydrofluoric acid can selectively remove silicon-based components such as silicon dioxide from the carbonization products, transforming the sites previously occupied by the silicon-based dispersed phase into pores. This results in a hierarchical porous structure in the activated carbon fibers, where micropores, mesopores, and partially interconnected channels coexist. This porous structure provides ample adsorption space and facilitates the diffusion of polycyclic aromatic hydrocarbon molecules within the fibers, reducing mass transfer resistance during the entry of large molecular pollutants into adsorption sites. Cleaning and drying after hydrofluoric acid etching remove residual acid and soluble byproducts, ensuring the stability of subsequent plasma post-processing and the safety of the material.

[0012] Finally, this application applies plasma post-treatment to the cleaned and dried activated carbon fibers. Plasma post-treatment can regulate the surface properties of the activated carbon fiber surface and the accessible pore regions, increase surface active sites, and improve their interaction with polycyclic aromatic hydrocarbon molecules. Thus, based on the aforementioned improvement of mass transfer process through hierarchical pore structure, this application further enhances the adsorption affinity of the pore surface for polycyclic aromatic hydrocarbons through surface property regulation, achieving a synergistic effect between pore structure regulation and surface property optimization.

[0013] In summary, the method of this application, through the continuous combination of oxidative modification of viscose fiber precursors, plasma surface activation, nanocrystalline seed dispersion and loading, composite impregnation, gradient temperature carbonization, hydrofluoric acid etching, and plasma post-treatment, can prepare highly adsorbent activated carbon fibers suitable for the adsorption of polycyclic aromatic hydrocarbons (PAHs). The resulting activated carbon fibers possess both a hierarchical porous structure that facilitates the diffusion of PAH molecules and their entry into adsorption sites, and surface interaction characteristics regulated by plasma treatment, thereby improving their equilibrium adsorption capacity for PAHs such as naphthalene, phenanthrene, and pyrene. Simultaneously, the carbon skeleton formed by composite impregnation and gradient carbonization helps maintain the structural integrity of the material, reducing the breakage rate during use, thus giving the material both good adsorption performance and structural stability.

[0014] Preferably, the silicon source further includes mesoporous silica, wherein the weight of the mesoporous silica accounts for 0.5-1.0% of the total weight of the nanocrystal seed dispersion.

[0015] By employing the above technical solution, mesoporous silica, as part of the silicon source, can be loaded onto the surface and permeable regions of activated fibers along with the nanocrystal seed dispersion, and participate in pore structure regulation during subsequent carbonization and hydrofluoric acid etching. Controlling its dosage within the range of 0.5-1.0% is beneficial in improving the openness of the pore structure while reducing pore blockage or structural defects caused by excessive enrichment of inorganic silicon sources, thereby enhancing the adsorption performance and structural stability of activated carbon fibers for polycyclic aromatic hydrocarbons.

[0016] Preferably, the silicon source further includes γ-aminopropyltriethoxysilane.

[0017] By adopting the above technical solution, γ-aminopropyltriethoxysilane can improve the interfacial compatibility between inorganic silicon source and fiber matrix, enhance the adhesion stability of silicon source on fiber surface, and reduce the tendency of nanocrystal seeds to agglomerate or fall off during impregnation, drying and carbonization processes. This is conducive to the subsequent formation of a more uniform pore structure and improves the adsorption performance of activated carbon fiber for polycyclic aromatic hydrocarbons.

[0018] Preferably, the silicon source further includes halloysite nanotubes, the weight of which accounts for 0.3-0.5% of the total weight of the nanocrystal seed dispersion.

[0019] By employing the above technical solution, halloysite nanotubes exhibit a tubular morphology and can participate in subsequent pore structure regulation as an inorganic dispersion component in the silicon source system. Controlling their dosage within the range of 0.3-0.5% is beneficial for improving the connectivity and dispersion uniformity of the pore structure, while reducing the risk of particle agglomeration or pore blockage due to excessive dosage. This improves the adsorption performance of activated carbon fibers for polycyclic aromatic hydrocarbons and reduces the tendency for material breakage.

[0020] Preferably, the carbon source further includes phenolic resin nanospheres, the weight of which accounts for 1-2% of the total weight of the nanocrystalline seed dispersion.

[0021] By employing the above technical solution, phenolic resin nanospheres exhibit high char residue and good thermal stability. During carbonization, they can transform into carbonaceous microdomains and combine with the main carbon skeleton formed by the carbonization of viscose fibers. Because phenolic resin molecules contain aromatic ring structures, the carbon phase formed after carbonization enhances the π-π and hydrophobic interactions of polycyclic aromatic hydrocarbon molecules on the pore surface, thereby strengthening the adsorption affinity of activated carbon fibers for polycyclic aromatic hydrocarbons such as naphthalene, phenanthrene, and pyrene. Simultaneously, phenolic resin nanospheres, as an external carbon source dispersed in the seed-modified layer, can supplement the carbon skeleton structure during carbonization, alleviating the problem of weak or collapsed pore walls caused by local shrinkage and improving the structural stability of the material. Controlling its dosage within the range of 1-2% helps to increase the aromatic carbon phase and stabilize the carbon skeleton while avoiding excessive carbon phase deposition that would reduce the openness of the pores.

[0022] Preferably, the dispersing agent includes one of polyvinyl alcohol and polyethylene glycol.

[0023] By employing the above-mentioned technical solutions, both polyvinyl alcohol and polyethylene glycol possess good water solubility and dispersing aid properties. They can improve the dispersion stability of components such as nano-silica, mesoporous silica, halloysite nanotubes, and phenolic resin nanospheres in aqueous systems through adsorption, hydrogen bonding, or steric hindrance effects. Furthermore, their steric hindrance effects can reduce the aggregation of nanocrystal seeds. Compared to relying solely on the dispersion of inorganic particles themselves, the addition of these polymeric dispersants reduces the tendency for particle aggregation and sedimentation in the nanocrystal seed dispersion, allowing the seed components to adhere more uniformly to the surface of the activated fiber and its permeable regions. With uniform seed distribution, the pore structure formed by subsequent carbonization and etching becomes more homogeneous, which helps reduce local pore blockage or structural defects, thereby improving the adsorption capacity and structural stability of activated carbon fibers for polycyclic aromatic hydrocarbons.

[0024] Preferably, the composite impregnation solution also contains 3-5 wt% sucrose.

[0025] By employing the above technical solution, sucrose, as a small-molecule carbohydrate, can enter the surface and permeable regions of the seed-modified fiber along with phosphoric acid and silica during the composite impregnation process. It then undergoes dehydration, condensation, and carbonization reactions during subsequent carbonization, forming a supplementary carbon phase. This supplementary carbon phase helps improve the carbonization yield and, together with the fiber's main carbon skeleton, forms a more stable carbon structure. Simultaneously, the dehydration, cross-linking, and carbonization of sucrose under the action of phosphoric acid helps regulate the pore structure development during carbonization, making the distribution of micropores and mesopores more suitable for the diffusion and adsorption of polycyclic aromatic hydrocarbon molecules. Controlling the sucrose content within the range of 3-5 wt% is beneficial for balancing carbon skeleton stability and pore openness; if the sucrose content is too low, the supplementary carbon source and structural regulation effects will be insufficient; if the content is too high, excessive carbon phase deposition may occur during carbonization, reducing the openness of some pores.

[0026] Preferably, the oxidized modified viscose fiber is prepared according to the following method: (1) Add viscose fiber to water to obtain fiber dispersion. Mix TEMPO, sodium bromide and sodium hypochlorite and add them to the fiber dispersion. Adjust the pH to 10-10.5 with sodium hydroxide to obtain reaction solution. (2) Continue to stir the reaction solution and add sodium hydroxide solution as needed to keep the pH of the reaction solution in the range of 10-10.5. After the reaction is 70-90 min, add ethanol to quench the reaction. (3) The reaction product is filtered, and the obtained fiber is washed and dried to obtain oxidized modified viscose fiber.

[0027] By employing the above-mentioned technical solution, the TEMPO / sodium bromide / sodium hypochlorite oxidation system can selectively oxidize the primary hydroxyl groups at the C6 position of the cellulose molecular chain in viscose fibers, introducing carboxyl groups onto the fiber surface, thereby improving the polarity, hydrophilicity, and reactivity of the viscose fiber surface. Controlling the reaction pH within the range of 10-10.5 is beneficial for maintaining the reactivity of the TEMPO oxidation system; controlling the reaction time within the range of 70-90 min is beneficial for obtaining a moderately oxidized fiber surface, avoiding insufficient oxidation leading to low carboxyl content, and avoiding excessive oxidation causing a decrease in fiber strength or damage to the skeletal integrity. The resulting oxidized and modified viscose fiber surface has an appropriate amount of carboxyl groups, providing a good foundation for subsequent plasma surface activation, nanocrystal seed dispersion impregnation loading, and composite impregnation treatment, thus improving the uniformity of seed loading and the stability of subsequent pore structure construction.

[0028] Preferably, in step (3) of preparing the oxidized modified viscose fiber, the specific method for washing the obtained fiber is as follows: first soak it in sodium hydroxide solution and oxalic acid in sequence, and then wash it with deionized water.

[0029] By employing the above-mentioned technical solution, sequentially treating the fiber surface with sodium hydroxide solution, oxalic acid, and deionized water, inorganic salts, oxidant residues, and other soluble impurities remaining after the oxidation reaction can be more thoroughly removed, and the fiber surface structure can be moderately adjusted. Specifically, sodium hydroxide solution treatment helps remove some acidic residues and causes moderate swelling of the fiber surface, improving accessibility during subsequent washing and impregnation processes; oxalic acid treatment removes residual metal ions and other impurities through acid washing and chelation, reducing the adverse effects of residual impurities on subsequent carbonization and activation processes; deionized water washing removes soluble salts and small molecules remaining after the aforementioned treatments, resulting in a cleaner precursor surface. This step-by-step washing process improves the consistency of the surface state of the oxidized viscose fiber, providing a more stable precursor base for subsequent plasma activation, seed loading, and carbonization pore formation.

[0030] Preferably, in step (3) of preparing the oxidized modified viscose fiber, the drying method used is freeze drying.

[0031] By employing the above-mentioned technical solution, freeze-drying removes moisture from the fibers through ice crystal sublimation. Compared to conventional heating drying, this reduces fiber shrinkage and pore closure caused by capillary action during liquid evaporation, thus better preserving the fluffy state and permeable structure of the oxidized modified viscose fibers. The resulting precursor is more conducive to the dispersion entering the permeable regions inside the fiber bundle or on the fiber surface during subsequent plasma surface activation and nanocrystalline seed dispersion impregnation, improving the uniformity of seed loading. With uniform seed loading, the pore structure formed by subsequent composite impregnation, carbonization, and hydrofluoric acid etching is also more likely to remain uniform and stable, thereby improving the adsorption performance of activated carbon fibers for polycyclic aromatic hydrocarbons and reducing the tendency for material breakage.

[0032] In summary, this application has the following beneficial effects: 1. This application uses oxidized viscose fiber as a precursor, which is then activated by plasma and subsequently seeded with nanocrystals to form a carbon-silicon composite intermediate. After carbonization, the silica is removed by hydrofluoric acid etching, resulting in a relatively continuous hierarchical porous structure. Plasma post-treatment is then used to adjust the surface properties of the activated carbon fiber surface and the pores. Compared to commercially available activated carbon fibers, the activated carbon fiber prepared in this application improves the mass transfer efficiency of macromolecular pollutants through its hierarchical porous structure. Furthermore, the pores, after plasma post-treatment, can fully utilize their adsorption and binding capacity for polycyclic aromatic hydrocarbons (PAHs). Therefore, the activated carbon fiber prepared in this application has a higher adsorption capacity for PAHs.

[0033] 2. In this application, the seed crystal system is preferably controlled by a combination of components such as mesoporous silica, halloysite nanotubes, and phenolic resin nanospheres. Mesoporous silica and halloysite nanotubes, as silicon source components, participate in the pore structure control during subsequent carbonization and etching processes, which is beneficial to improving the openness and connectivity of the activated carbon fiber pore structure. Phenolic resin nanospheres, as an external carbon source, participate in the formation of the carbon skeleton, which is beneficial to improving the stability of the carbon skeleton and reducing the tendency of pore structure collapse or material breakage. The synergistic effect of these components enables the resulting activated carbon fiber to achieve both high polycyclic aromatic hydrocarbon adsorption capacity and good structural stability.

[0034] 3. The method of this application preferably involves pretreatment of the oxidized modified viscose fiber through step-by-step washing and freeze-drying. Step-by-step washing helps remove residual impurities after the oxidation reaction, making the precursor surface more stable; freeze-drying helps reduce the tendency of fiber shrinkage and pore closure during conventional drying, maintaining the precursor in a better permeable state. This pretreatment process improves the uniformity of the loading of the nanocrystalline seed dispersion on the fiber surface and permeable regions, providing a more stable precursor basis for the subsequent pore structure construction in composite impregnation, carbonization, and etching processes, thereby further improving the adsorption performance and structural stability of activated carbon fibers for polycyclic aromatic hydrocarbons. Detailed Implementation

[0035] The present application will be further described in detail below with reference to the embodiments, preparation examples and comparative examples. Unless otherwise specified, the raw materials used in the embodiments of the present application can be obtained commercially. The viscose fiber is a short-cut viscose fiber with an average length of 5 mm and a linear density of 1.8 dtex; the nano-silica has an average particle size of 75 nm and a specific surface area of ​​220 m² / g; the tetraethyl orthosilicate has a purity of not less than 98%; the mesoporous silica is SBA-15 type mesoporous silica with an average pore size of 6-8 nm and a specific surface area of ​​600-800 m² / g; the γ-aminopropyltriethoxysilane has a purity of not less than 98%; the halloysite nanotubes have an outer diameter of 40-80 nm, an inner diameter of 10-30 nm and a length of 0.5-1.5 μm; the phenolic resin nanospheres have an average particle size of 75 nm and a specific surface area of ​​220 m² / g ... The particle size is 100-300 nm, and the amount of phenolic resin nanospheres is based on solid mass; the glucose is anhydrous glucose; the sodium citrate is analytical grade; the degree of alcoholysis of polyvinyl alcohol is 87-89%, and the average degree of polymerization is 1700-1800; the number average molecular weight of polyethylene glycol is 800; commercially available silica sol is used, and the mass concentration of silica sol as SiO2 is 20-30 wt%; the phosphoric acid is commercially available phosphoric acid with a mass concentration of 85 wt%, which is diluted according to the total concentration of the composite impregnation solution before use; the hydrofluoric acid is a 5 wt% hydrofluoric acid solution obtained by diluting commercially available hydrofluoric acid; and the sucrose is analytical grade sucrose.

[0036] Preparation example of oxidative modified viscose fiber The following explanation uses Preparation Example 1 as an example.

[0037] Preparation Example 1 In this preparation example, the oxidized modified viscose fiber was prepared according to the following method: (1) Viscose fiber was added to water at a weight ratio of 1:100 to obtain a fiber dispersion. TEMPO, sodium bromide and sodium hypochlorite were mixed at a weight ratio of 0.13:4.7:7.5. The mixture of TEMPO, sodium bromide and sodium hypochlorite was added to the fiber dispersion at a ratio of 0.13 mmol of TEMPO per gram of fiber. The pH was adjusted to 10 using sodium hydroxide to obtain a reaction solution. (2) Continue to stir the reaction solution and add sodium hydroxide solution as needed to keep the pH of the reaction solution in the range of 10-10.5. After 70 min of reaction, add ethanol to quench the reaction. (3) The reaction product was filtered, and the fiber obtained by filtration was immersed in deionized water for 90 min and then dried at 105℃ to obtain oxidized modified viscose fiber with a carboxyl content of 0.8 mmol / g.

[0038] Preparation Example 2 The difference between this preparation example and preparation example 1 is that the timing of adding ethanol to quench the reaction in step (2) is 80 minutes after the start of the reaction, and the final product is an oxidized modified viscose fiber with a carboxyl content of 1.08 mmol / g.

[0039] Preparation Example 3 The difference between this preparation example and preparation example 1 is that the timing of adding ethanol to quench the reaction in step (2) is 90 min after the start of the reaction, and the final product is an oxidized modified viscose fiber with a carboxyl content of 1.21 mmol / g.

[0040] Preparation Example 4 The difference between this preparation example and preparation example 3 is that the washing operation in step (3) is replaced by: soaking in 8wt% sodium hydroxide solution at 50°C for 45 min, then soaking in 0.2mol / L oxalic acid solution at 40°C for 30 min, then washing with deionized water until the pH of the washing solution is 7.0, filtering and drying, and finally obtaining oxidized modified viscose fiber with a carboxyl content of 1.24mmol / g.

[0041] Preparation Example 5 The difference between this preparation example and preparation example 4 is that the drying operation in step (3) is replaced by freeze drying at -60℃ and -0.08MPa for 4 hours to finally obtain oxidized modified viscose fiber with a carboxyl content of 1.25mmol / g.

[0042] Example Examples 1-5 The following description uses Example 1 as an example.

[0043] Example 1

[0044] In this embodiment, the precursor is the oxidized modified viscose fiber of Preparation Example 1; the nanocrystal seed dispersion includes the following components: 1.6 wt% silicon source, 3.8 wt% carbon source, 0.1% dispersant, and the balance is made up to 100 wt% by deionized water; the silicon source is nano-silica (average particle size 75 nm) and tetraethyl orthosilicate, with nano-silica:tetraethyl orthosilicate = 10:1 (weight ratio), the carbon source is glucose, and the dispersant is sodium citrate.

[0045] The nanocrystal seed dispersion in this embodiment was prepared according to the following method: First, the dispersing agent was added to deionized water and stirred to dissolve. Then, the silicon source was added and ultrasonically dispersed for 25 minutes. Subsequently, the carbon source was added and stirred for another 45 minutes to obtain a nanocrystalline seed dispersion.

[0046] This embodiment provides a method for preparing highly adsorbent activated carbon fiber, including the following steps: (1) Weigh 200g of the precursor, wash it and let it air dry for later use; (2) The dried precursor was subjected to plasma surface activation. The activation parameters were: power 120W, time 15min, and atmosphere argon. After activation, activated fibers were obtained. The activated fibers were immersed in a nanocrystal seed dispersion for ultrasonic-assisted impregnation. The ultrasonic-assisted impregnation parameters were: power 300W, temperature 40℃, and time 60min. After ultrasonic-assisted impregnation and drying, seed modified fibers were obtained. (3) The seed-modified fibers were vacuum impregnated with a composite impregnation solution containing phosphoric acid and silicic acid (the weight ratio of silicic acid to phosphoric acid was 3:1, the total concentration was 5.5wt%, and the total concentration was calculated as the total mass of the effective components of silicic acid and phosphoric acid in the silicic acid sol, based on SiO2). The vacuum impregnation parameters were: vacuum degree -0.09MPa, temperature 50℃, and time 90min. After vacuum impregnation, the seed-modified fibers were placed in a carbonization furnace for gradient heating carbonization. The heating program was: 100-200℃ (low temperature curing section, heating rate 1-2℃ / min, holding time 1-2h, air / N2 atmosphere), 200-400℃ (pre-carbonization section, heating rate 2-3℃ / min, holding time 2-3h, argon atmosphere), 500-700℃ (carbonization section). The process involves heating at a rate of 3-5℃ / min for 2-3 hours under an argon atmosphere, followed by an activation phase at 700-900℃ (heating rate 5-8℃ / min, holding for 1-2 hours under a steam / CO2 atmosphere). A buffer phase is set at 800-850℃ (holding for 30-60 minutes under an argon atmosphere). After carbonization, the carbon is allowed to cool naturally. Seed crystals are removed by immersion in hydrofluoric acid at a concentration of 5 wt%, a temperature of 25℃, and a time of 120 minutes. After hydrofluoric acid etching, the carbon is repeatedly washed with deionized water until the pH of the washing solution reaches 6.5-7.5. After drying at 105℃ for 4 hours, plasma post-treatment is performed according to the following parameters: power 150W, time 20 minutes, and an air atmosphere. Highly adsorbent activated carbon fibers are obtained after this treatment.

[0047] As shown in Table 1, the main difference between Examples 1-5 is that the raw material ratios of the nanocrystal seed dispersions are different.

[0048] Table 1 Raw material ratio of nanocrystalline seed dispersion

[0049] Examples 6-8 Example 6

[0050] The difference between this embodiment and embodiment 5 is that the silicon source also includes mesoporous silica (SBA-15), the proportion of mesoporous silica in the nanocrystal seed dispersion is 0.5wt%, and the proportion of silicon source in the nanocrystal seed dispersion is 2.3wt%.

[0051] As shown in Table 2, the difference between Examples 6-8 is that the proportions of mesoporous silica and silicon source as a whole in the nanocrystal seed dispersion are different.

[0052] Table 2. Proportion of mesoporous silica and silicon source

[0053] Example 9

[0054] The difference between this embodiment and Embodiment 8 is that the silicon source also includes γ-aminopropyltriethoxysilane, the proportion of γ-aminopropyltriethoxysilane in the nanocrystal seed dispersion is 1.5wt%, the proportion of silicon source in the nanocrystal seed dispersion is 4.3wt%, and γ-aminopropyltriethoxysilane and tetraethyl orthosilicate are added together to the dispersion system.

[0055] Example 10

[0056] The difference between this embodiment and embodiment 9 is that the silicon source also includes halloysite nanotubes, the proportion of halloysite nanotubes in the nanocrystal seed dispersion is 0.3wt%, and the proportion of silicon source in the nanocrystal seed dispersion is 4.6wt%.

[0057] As shown in Table 3, the difference between Examples 10-12 is that the proportions of halloysite nanotubes and silicon source as a whole in the nanocrystal seed dispersion are different.

[0058] Table 3. Proportion of Halloysite nanotubes and silicon sources

[0059] In Examples 13-24, unless otherwise specified, the silicon source composition and the proportion of silicon source in the nanocrystal seed dispersion are the same as in the previous example cited therein.

[0060] Example 13

[0061] The difference between this embodiment and Embodiment 12 is that the carbon source also includes phenolic resin nanospheres, the proportion of phenolic resin nanospheres in the nanocrystal seed dispersion is 1 wt%, and the total proportion of carbon source in the nanocrystal seed dispersion is 5.2 wt%.

[0062] As shown in Table 4, the difference between Examples 13-15 is that the proportions of phenolic resin nanospheres and carbon source as a whole in the nanocrystal seed dispersion are different.

[0063] Table 4. Proportion of phenolic resin nanospheres and carbon source

[0064] Example 16

[0065] The difference between this embodiment and embodiment 14 is that polyvinyl alcohol is used as the dispersing agent, and the content of the dispersing agent is still 0.18 wt%.

[0066] Example 17

[0067] The difference between this embodiment and Example 16 is that polyethylene glycol is used as the dispersing agent, and the content of the dispersing agent is still 0.18 wt%.

[0068] Example 18

[0069] The difference between this embodiment and Embodiment 17 is that the composite impregnation solution also contains 3 wt% sucrose. When preparing the composite impregnation solution, the sucrose is first dissolved in deionized water, and then phosphoric acid and silicic acid are added in sequence and stirred until the system is uniform.

[0070] As shown in Table 5, the difference between Examples 18-20 is that the sucrose concentration in the composite impregnation solution is different.

[0071] Table 5 Sucrose concentration in the composite impregnation solution

[0072] Based on Example 20, Examples 21-24 respectively replaced the preparation examples of oxidized modified viscose fibers, as shown in Table 6.

[0073] Table 6 Examples of preparation of oxidized modified viscose fibers

[0074] Comparative Examples To further illustrate that the preferred range of each dependent technical feature in this application is not arbitrarily selected, the following comparative examples are also provided. These comparative examples all still fall under the preparation method of highly adsorbent activated carbon fiber as defined in claim 1, but the amounts of some components do not fall within the preferred range defined by the corresponding dependent claims, and are therefore used for comparison with the preferred solutions in the examples.

[0075] Comparative Example 1 The difference between this comparative example and Example 5 is that the silicon source also includes mesoporous silica, the proportion of mesoporous silica in the nanocrystal seed dispersion is 0.3 wt%, and the proportion of silicon source in the nanocrystal seed dispersion is 2.1 wt%.

[0076] Comparative Example 2 The difference between this comparative example and Example 5 is that the silicon source also includes mesoporous silica, the proportion of mesoporous silica in the nanocrystal seed dispersion is 1.3 wt%, and the proportion of silicon source in the nanocrystal seed dispersion is 3.1 wt%.

[0077] Comparative Example 3 The difference between this comparative example and Example 9 is that the silicon source also includes halloysite nanotubes, the proportion of halloysite nanotubes in the nanocrystal seed dispersion is 0.2wt%, and the proportion of silicon source in the nanocrystal seed dispersion is 4.5wt%.

[0078] Comparative Example 4 The difference between this comparative example and Example 9 is that the silicon source also includes halloysite nanotubes, the proportion of halloysite nanotubes in the nanocrystal seed dispersion is 0.7wt%, the proportion of γ-aminopropyltriethoxysilane in the nanocrystal seed dispersion is adjusted to 1.3wt%, and the total proportion of silicon source in the nanocrystal seed dispersion is 4.8wt%.

[0079] Comparative Example 5 The difference between this comparative example and Example 12 is that the carbon source also includes phenolic resin nanospheres, the proportion of phenolic resin nanospheres in the nanocrystal seed dispersion is 0.5wt%, and the total proportion of carbon source in the nanocrystal seed dispersion is 4.7wt%.

[0080] Comparative Example 6 The difference between this comparative example and Example 12 is that the carbon source also includes phenolic resin nanospheres, the proportion of phenolic resin nanospheres in the nanocrystal seed dispersion is 2.3 wt%, the proportion of glucose in the nanocrystal seed dispersion is adjusted to 3.8 wt%, and the total proportion of carbon source in the nanocrystal seed dispersion is 6.1 wt%.

[0081] Comparative Example 7 The difference between this comparative example and Example 17 is that the composite impregnation solution also contains 1.5 wt% sucrose.

[0082] Comparative Example 8 The difference between this comparative example and Example 17 is that the composite impregnation solution also contains 6.5 wt% sucrose.

[0083] Comparative Example Comparative Example 1 A method for preparing ordinary activated carbon fiber includes the following steps: (1) Weigh 200g of unmodified viscose fiber, wash it in deionized water for 30min, take it out and dry it at 105℃ for 4h for later use; (2) Vacuum impregnation of viscose fibers treated in step (1) is performed directly using phosphoric acid impregnation solution. The concentration of the phosphoric acid impregnation solution is 20wt%, and the vacuum impregnation parameters are: vacuum degree -0.09MPa, temperature 50℃, and time 90min. (3) After vacuum impregnation, the viscose fiber is placed in a carbonization furnace for gradient heating carbonization. The heating program is as follows: 100-200℃, heating rate 1-2℃ / min, holding for 1-2h, atmosphere is air / N2 atmosphere; 200-400℃, heating rate 2-3℃ / min, holding for 2-3h, atmosphere is argon; 500-700℃, heating rate 3-5℃ / min, holding for 2-3h, atmosphere is argon; 700-900℃, heating rate 5-8℃ / min, holding for 1-2h, atmosphere is water vapor / CO2 atmosphere; among which, a buffer section is set at 800-850℃, holding for 30-60min, atmosphere is argon. (4) After carbonization, the carbon is cooled naturally and washed with deionized water until the pH of the washing solution is 6.5-7.5. Then it is dried at 105℃ for 4 hours to obtain ordinary activated carbon fiber.

[0084] Comparative Example 2 The difference between this comparative example and Example 3 is that it does not include the plasma surface activation step and the plasma post-treatment step; the remaining steps and parameters are the same as in Example 3.

[0085] In this comparative example, the precursor used was the oxidized modified viscose fiber from Preparation Example 1; the nanocrystalline seed dispersion included the following components: 1.7 wt% silicon source, 4.1 wt% carbon source, 0.15% dispersant, and the balance was made up to 100 wt% by deionized water; the silicon source was nano-silica and tetraethyl orthosilicate, with a nano-silica:tetraethyl orthosilicate ratio of 8:1, the carbon source was glucose, and the dispersant was sodium citrate.

[0086] This comparative example provides a method for preparing activated carbon fiber, comprising the following steps: (1) Weigh 200g of precursor, wash and air dry for later use; (2) The precursor dried in step (1) is directly immersed in the nanocrystal seed dispersion for ultrasonic-assisted impregnation. The ultrasonic-assisted impregnation parameters are: power 300W, temperature 40℃, time 60min. After ultrasonic-assisted impregnation and drying, seed modified fibers are obtained. (3) The seed modified fiber was vacuum impregnated with a composite impregnation solution containing phosphoric acid and silicic acid. The weight ratio of silicic acid to phosphoric acid in the composite impregnation solution was 3:1 and the total concentration was 5.5wt%. The vacuum impregnation parameters were: vacuum degree -0.09MPa, temperature 50℃, and time 90min. (4) After vacuum impregnation, the seed modified fiber is placed in a carbonization furnace for gradient heating carbonization. The heating procedure is the same as in Example 3. (5) After carbonization, the carbon is cooled naturally. The seed crystals are removed by soaking in 5wt% hydrofluoric acid at 25°C for 120 minutes. The carbon is then washed with deionized water until the pH of the washing solution is 6.5-7.5. Finally, the carbon is dried at 105°C for 4 hours to obtain activated carbon fiber.

[0087] This comparative example did not undergo plasma surface activation or plasma post-treatment.

[0088] Performance testing methods The activated carbon fibers prepared in all the above embodiments and comparative examples were subjected to performance testing. The testing indicators and methods are as follows: I. Polycyclic Aromatic Hydrocarbon (PAH) Adsorption Capacity: Naphthalene, phenanthrene, and pyrene were selected as target pollutants. The equilibrium adsorption capacity of activated carbon fiber for PAHs was tested using the static adsorption method. In each test, the activated carbon fiber sample amount was 0.05 g, and the PAH simulation liquid volume was 200 mL. The naphthalene, phenanthrene, and pyrene simulation solutions were obtained by diluting stock solutions prepared with methanol. The volume fraction of organic solvent in the test system did not exceed 0.5%. The initial concentrations of naphthalene, phenanthrene, and pyrene were 500 mg / L, 50 mg / L, and 10 mg / L, respectively. The test temperature was 25℃ for all tests. The quantitative activated carbon fiber samples were placed in the above-mentioned polycyclic aromatic hydrocarbon (PAH) simulation solution and oscillated at a constant temperature for 24 hours. After the adsorption reached equilibrium, the supernatant was filtered through a 0.22 μm organic filter membrane. The residual concentration of the corresponding PAHs in the equilibrium solution was determined by high performance liquid chromatography (HPLC). The detection wavelength was set according to the target analyte. The mobile phase was an acetonitrile-water system. The equilibrium adsorption capacity of the sample for naphthalene, phenanthrene, and pyrene was calculated based on the material conservation formula.

[0089] II. Structural stability test: Weigh 5.0g of sample and place it in a conical flask containing 100mL of deionized water. Shake at 150r / min for 10h in a reciprocating shaking device. After shaking, filter the sample through a 100-mesh sieve, collect the debris that passes through the sieve, dry and weigh it. Calculate the breakage rate according to the percentage of the debris mass to the sample mass before the test, which is used to characterize the stability of the carbon skeleton and pore structure.

[0090] Table 7. Test results of adsorption performance and structural stability of activated carbon fiber ;

[0091] Combining Examples 1-5 and Comparative Example 1 with Table 7, it can be seen that the equilibrium adsorption capacities of naphthalene, phenanthrene, and pyrene measured in Examples 1-5 are significantly higher than those in Comparative Example 1, while the breakage rates are significantly lower. This is because Examples 1-5 use oxidized modified viscose fiber as a precursor and, through the synergistic effects of nanocrystalline seed dispersion loading, composite impregnation, gradient temperature carbonization, hydrofluoric acid etching, and plasma post-treatment, construct a relatively continuous hierarchical porous structure inside the activated carbon fiber. At the same time, the adsorption effect is adjusted on the pore surface, thereby improving the adsorption capacity of activated carbon fiber for polycyclic aromatic hydrocarbons. In contrast, Comparative Example 1 uses a common phosphoric acid impregnation carbonization process, which lacks the technical features of oxidized modified precursor, nanocrystalline seed template, hydrofluoric acid etching, and plasma post-treatment. It cannot fully construct a relatively continuous hierarchical porous system, nor can it form sufficient active adsorption sites inside and outside the pores. Therefore, the measured equilibrium adsorption capacity of polycyclic aromatic hydrocarbons is lower, and the breakage rate is higher. In Examples 1-5, as the ratio of nano-silica to tetraethyl orthosilicate and the ratio of silicon source, carbon source and dispersant were adjusted, the overall equilibrium adsorption capacity of naphthalene, phenanthrene and pyrene increased and the overall breakage rate decreased. This indicates that under the above ratio conditions, the matching between nano-silicon source, organic carbon source and dispersant is good, which is beneficial to seed dispersion and loading and subsequent pore structure formation, and is beneficial to the formation of a more stable and continuous pore structure after carbonization and etching.

[0092] Combining Example 3 and Comparative Example 2 with Table 7, it can be seen that the equilibrium adsorption capacities of naphthalene, phenanthrene, and pyrene measured in Comparative Example 2 are all lower than those in Example 3, while the breakage rate is higher. This is because Comparative Example 2 did not undergo plasma surface activation and plasma post-treatment, thus it was impossible to improve the binding ability of the precursor surface to the nanocrystalline seed dispersion through pre-treatment, nor could it adjust the surface properties of the activated carbon fiber surface and pores through post-treatment. Therefore, the uniformity of seed loading and the adsorption activity of the pore surface in Comparative Example 2 are inferior to those in Example 3, resulting in a lower adsorption capacity for polycyclic aromatic hydrocarbons and relatively poor stability of the carbon skeleton and pore structure.

[0093] Combining Examples 5-8 and Comparative Examples 1-2 with Table 7, it can be seen that after adding mesoporous silica to the silicon source, the equilibrium adsorption capacities of naphthalene, phenanthrene, and pyrene measured in Examples 6-8 are all higher than those in Example 5, while the breakage rates are all lower than those in Example 5. This indicates that mesoporous silica, as a hard template, participates in the construction of the pore structure and can help form more mesoporous channels during carbonization and subsequent hydrofluoric acid etching, thereby improving pore connectivity and reducing the mass transfer resistance of polycyclic aromatic hydrocarbon molecules during diffusion inside the activated carbon fiber. Comparative Example 1 shows a lower amount of mesoporous silica compared to Examples 6-8, resulting in a lower polycyclic aromatic hydrocarbon (PAH) adsorption capacity. This is because a lower amount of mesoporous silica makes it difficult to fully utilize the mesoporous template function, limiting the number of mesoporous channels formed. Comparative Example 2 shows a higher amount of mesoporous silica compared to Examples 6-8, resulting in a lower adsorption capacity and a higher breakage rate. This is because an excessively high amount of mesoporous silica can easily lead to localized enrichment of the inorganic silicon source, affecting the uniformity of the pore structure and causing localized thinning of the pore walls or pore structure defects after etching. Therefore, a mesoporous silica content in the range of 0.5-1.0 wt% is more beneficial for balancing PAH adsorption capacity and structural stability.

[0094] Combining Examples 8 and 9 with Table 7, it can be seen that the equilibrium adsorption capacities of naphthalene, phenanthrene, and pyrene measured in Example 9 are all higher than those in Example 8, while the breakage rate is lower. This is because γ-aminopropyltriethoxysilane was further added to the silicon source in Example 9. γ-aminopropyltriethoxysilane, as a silane coupling agent, can form an interfacial bridge between the inorganic silicon source particles and the organic fiber matrix, improving the bonding stability of the silicon source on the fiber surface and reducing the agglomeration or detachment of nanocrystals during impregnation, drying, and carbonization, thereby resulting in a more uniform and stable pore structure. Therefore, Example 9 is superior to Example 8 in terms of polycyclic aromatic hydrocarbon adsorption capacity and anti-breakage performance.

[0095] Combining Examples 9-12 and Comparative Examples 3-4 with Table 7, it can be seen that after adding halloysite nanotubes to the silicon source, the equilibrium adsorption capacities of naphthalene, phenanthrene, and pyrene measured in Examples 10-12 are all higher than those in Example 9, while the breakage rates are all lower than those in Example 9. This indicates that the one-dimensional hollow tubular structure of halloysite nanotubes can assist in constructing interconnected mass transfer channels inside the carbon skeleton, reducing the diffusion resistance of polycyclic aromatic hydrocarbon molecules in the channels. At the same time, halloysite nanotubes can also act as an inorganic reinforcing phase dispersed in the carbon skeleton, providing support for the carbon skeleton. In Comparative Example 3, the amount of halloysite nanotubes added was lower than that in Examples 10-12, and its adsorption capacity was also lower. This is because when the amount of halloysite nanotubes added is low, the mass transfer channel construction and framework support are insufficient. In Comparative Example 4, the amount of halloysite nanotubes added was higher, and the composition of the composite silicon source was adjusted accordingly. Its adsorption capacity was still lower than that in Examples 10-12, indicating that when the content of halloysite nanotubes is too high and the proportion of inorganic tubular components in the silicon source system is too large, it is easy to cause local agglomeration or pore blockage, which weakens the diffusion efficiency of polycyclic aromatic hydrocarbon molecules. Therefore, halloysite nanotubes in the range of 0.3-0.5 wt% are more conducive to exerting the synergistic effect of mass transfer channel construction and framework support.

[0096] Combining Examples 12-15 and Comparative Examples 5-6 with Table 7, it can be seen that after adding phenolic resin nanospheres to the carbon source, the equilibrium adsorption capacities of naphthalene, phenanthrene, and pyrene measured in Examples 13-15 were all higher than those in Example 12, while the breakage rates were all lower than those in Example 12. This indicates that the phenolic resin nanospheres have a high carbonization yield, and after carbonization, they can form a carbon phase rich in aromatic structures, providing favorable π-π interaction sites for polycyclic aromatic hydrocarbon molecules such as naphthalene, phenanthrene, and pyrene, thereby enhancing the adsorption affinity of the pore surface for polycyclic aromatic hydrocarbons. At the same time, the phenolic resin nanospheres can also serve as a carbon skeleton reinforcing phase, improving the structural stability of the material. In Comparative Example 5, the amount of phenolic resin nanospheres added was lower than that in Examples 13-15, and its adsorption capacity was lower than that in Examples 13-15. This is because the amount of aromatic carbon phase formed was insufficient, which could not fully enhance the adsorption affinity of the pore surface for polycyclic aromatic hydrocarbons. In Comparative Example 6, the proportion of phenolic resin nanospheres was higher than in Examples 13-15, and the proportion of phenolic resin nanospheres relative to glucose in the carbon source composition was further increased. However, its adsorption capacity was lower than in Example 15, while its breakage rate was higher. This indicates that when the proportion of phenolic resin nanospheres is too high, the aromatic carbon phase formed after carbonization may accumulate in local pores, affecting the degree of pore openness and thus weakening the diffusion and adsorption of polycyclic aromatic hydrocarbon molecules. Therefore, a phenolic resin nanosphere content of 1-2 wt% is more conducive to balancing the construction of aromatic adsorption sites and the degree of pore openness.

[0097] Combining Examples 14 and 16-17 with Table 7, it can be seen that the equilibrium adsorption capacities of naphthalene, phenanthrene, and pyrene measured in Examples 16-17 are all higher than those in Example 14, while the breakage rates are lower. This is because the dispersing agent in Examples 16-17 was replaced with polyvinyl alcohol or polyethylene glycol instead of sodium citrate. Polyvinyl alcohol and polyethylene glycol, as polymeric dispersing agents, can more effectively reduce the aggregation tendency among nano-silicon source particles, mesoporous silica, halloysite nanotubes, and phenolic resin nanospheres, improve the stability of the nanocrystalline seed dispersion, and make the components more uniformly loaded on the surface and inside the precursor. Compared with Example 16, the equilibrium adsorption capacities and breakage rates of naphthalene, phenanthrene, and pyrene in Example 17 are relatively similar, indicating that polyvinyl alcohol and polyethylene glycol have good applicability in this system.

[0098] Combining Examples 17-20 and Comparative Examples 7-8 with Table 7, it can be seen that after adding sucrose to the composite impregnation solution, the equilibrium adsorption capacities of naphthalene, phenanthrene, and pyrene measured in Examples 18-20 were all higher than those in Example 17, while the breakage rates were all lower than those in Example 17. This indicates that sucrose can participate in the carbonization process as an auxiliary carbon source, improving the carbonization yield, and can promote carbon skeleton crosslinking together with phosphoric acid and silica, which helps to regulate the pore structure development during the carbonization process, enabling the obtained material to maintain good adsorption performance and structural stability. In Comparative Example 7, the sucrose content was lower than that in Examples 18-20, and its adsorption capacity was lower than that in Examples 18-20. This is because when the sucrose content is low, the auxiliary carbon source and crosslinking regulation effects are insufficient. In Comparative Example 8, the sucrose content was higher than that in Examples 18-20, and its adsorption capacity was lower than that in Examples 18-20, and the breakage rate was higher than that in Examples 18-20. This is because when the sucrose content is too high, excessive carbon phase deposition is easily formed during the carbonization process, leading to a decrease in the openness of some pores and weakening the mass transfer efficiency of polycyclic aromatic hydrocarbon molecules. Therefore, a sucrose content of 3-5 wt% is more conducive to improving the degree of cross-linking of the carbon skeleton and maintaining the openness of the pores.

[0099] Combining Examples 20 and 21-24 with Table 7, it can be seen that the overall equilibrium adsorption capacities of naphthalene, phenanthrene, and pyrene measured in Examples 21-24 are higher than those in Example 20, while the overall breakage rate is lower than that in Example 20. This is because Examples 21-24 changed the preparation method of the oxidized modified viscose fiber. The oxidized modified viscose fiber used in Examples 21 and 22 has a higher surface carboxyl group content, which can provide more binding sites for nanocrystal seed loading, and is conducive to uniform seed loading and subsequent pore structure construction. Example 23 uses a step-by-step washing method, which can remove residual impurities and moderately adjust the fiber surface structure, improving the accessibility of subsequent reactions. Example 24 further uses freeze-drying, which can reduce the capillary shrinkage effect in the conventional drying process, reduce fiber shrinkage and pore closure tendency, and keep the precursor in a better permeable state, thus being more conducive to the infiltration and diffusion of the nanocrystal seed dispersion. Therefore, the equilibrium adsorption capacity of naphthalene, phenanthrene and pyrene measured in Example 24 was the highest and the breakage rate was the lowest, indicating that the oxidized modified viscose fiber obtained in Preparation Example 5 was most beneficial for subsequent seed loading, hierarchical pore structure construction and structural stability maintenance.

[0100] The above embodiments are merely explanations of this application and are not intended to limit it. After reading this specification, those skilled in the art can make modifications to the embodiments of this application without contributing any inventive step, but such modifications are protected by patent law as long as they are within the scope of the claims of this application.

Claims

1. A method for producing high adsorptive activated carbon fiber, characterized by comprising the steps of: Includes the following steps: ​ (1) Clean the precursor and air dry it for later use; in this step, the precursor is oxidized modified viscose fiber, and the carboxyl content of the oxidized modified viscose fiber is 0.80-1.25 mmol / g. (2) The precursor after natural drying in step (1) is subjected to plasma surface activation to obtain activated fibers. The activated fibers are immersed in a nano-crystal seed dispersion, and after ultrasonic-assisted impregnation and drying, seed-modified fibers are obtained. The nano-crystal seed dispersion includes the following components: 1.6-4.8 wt% silicon source, 3.8-6.2 wt% carbon source, 0.1-0.2% dispersant, and the balance is made up to 100 wt% by deionized water. The silicon source includes nano-silica and tetraethyl orthosilicate, and the carbon source includes glucose. (3) The seed modified fiber is vacuum impregnated with a composite impregnation solution containing phosphoric acid and silica. Then the seed modified fiber is placed in a carbonization furnace for gradient heating carbonization. After carbonization, the seed is removed by soaking in hydrofluoric acid. After cleaning and drying, it is then subjected to plasma post-treatment to obtain highly adsorbent activated carbon fiber.

2. The method for preparing highly adsorbent activated carbon fiber according to claim 1, characterized in that, The silicon source also includes mesoporous silica, the weight of which accounts for 0.5-1.0% of the total weight of the nanocrystal seed dispersion.

3. The method for preparing highly adsorbent activated carbon fiber according to claim 2, characterized in that, The silicon source also includes γ-aminopropyltriethoxysilane.

4. The method for preparing highly adsorbent activated carbon fiber according to claim 3, characterized in that, The silicon source also includes halloysite nanotubes, the weight of which accounts for 0.3-0.5% of the total weight of the nanocrystal seed dispersion.

5. The method for preparing highly adsorbent activated carbon fiber according to claim 1, characterized in that, The carbon source also includes phenolic resin nanospheres, the weight of which accounts for 1-2% of the total weight of the nanocrystalline seed dispersion.

6. The method for preparing highly adsorbent activated carbon fiber according to claim 5, characterized in that, The dispersing agent includes one of polyvinyl alcohol and polyethylene glycol.

7. The method for preparing highly adsorbent activated carbon fiber according to claim 6, characterized in that, The composite impregnation solution also contains 3-5 wt% sucrose.

8. The method for preparing highly adsorbent activated carbon fiber according to claim 1, characterized in that, The oxidized modified viscose fiber is prepared according to the following method: (1) Add viscose fiber to water to obtain fiber dispersion. Mix TEMPO, sodium bromide and sodium hypochlorite and add them to the fiber dispersion. Adjust the pH to 10-10.5 with sodium hydroxide to obtain reaction solution. (2) Continue to stir the reaction solution and add sodium hydroxide solution as needed to keep the pH of the reaction solution in the range of 10-10.

5. After the reaction is 70-90 min, add ethanol to quench the reaction. (3) The reaction product is filtered, and the obtained fiber is washed and dried to obtain oxidized modified viscose fiber.

9. The method for preparing highly adsorbent activated carbon fiber according to claim 8, characterized in that, In step (3) of preparing the oxidized modified viscose fiber, the specific method for washing the obtained fiber is as follows: first soak it in sodium hydroxide solution and oxalic acid in sequence, and then wash it with deionized water.

10. The method for preparing highly adsorbent activated carbon fiber according to claim 9, characterized in that, In step (3) of preparing the oxidized modified viscose fiber, the drying method used is freeze drying.

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