Method for modifying activated carbon fiber cloth by composite hydrothermal method and application thereof

Abstract

This invention relates to the field of material modification technology, and discloses a method for modifying activated carbon fiber cloth using a composite hydrothermal method and its application. The method includes: immersing the activated carbon fiber cloth in a mixed solution of lactic acid and ammonium salt at a mass ratio of 1:(0.8-1.2), subjecting it to a water bath heating and shaking reaction at 70-90℃, and then removing the activated carbon fiber cloth for cleaning and drying. This method allows lactic acid and ammonium salt to simultaneously undergo acid oxidation modification, ammonium salt nitrogen modification, hydrothermal modification, and other composite modifications on the carbon structure of the ACF surface under a water bath shaking environment. Furthermore, the ammonium salt-lactic acid mixed solution can form a buffer solution system, ensuring the stability of the ACF water bath reaction environment. Through the above composite modification, a certain degree of etching can be produced on the ACF surface, increasing the specific surface area of ​​the carbon fibers and the number of active contact sites; acid oxidation modification can increase the number of oxygen-containing functional groups on the carbon fiber surface; and nitrogen modification by ammonium salt can increase the number of nitrogen-containing functional groups on the carbon fiber surface.

Description

Technical Field

[0001] This invention relates to the field of material modification technology, and in particular to a method for modifying activated carbon fiber cloth using a composite hydrothermal method and its application. Background Technology

[0002] Activated carbon fiber (ACF), as a novel adsorbent, possesses an excellent pore structure and a large specific surface area, exhibiting high adsorption capacity and stable chemical properties. Its fiber morphology is flexible and versatile, allowing it to be woven into various products to meet diverse needs. ACF is easy to recycle and does not cause secondary pollution, making it a leader in the environmental protection field. Whether for air purification, water treatment, or industrial waste gas treatment, ACF demonstrates strong adsorption capabilities, providing powerful support for environmental protection. Therefore, ACF is hailed as one of the most environmentally friendly materials of the 21st century and will undoubtedly play an even more important role in the future, contributing to the sustainable development of our planet. Certain modification techniques can further enhance the material's adsorption performance for pollutant gases.

[0003] Currently, the modification methods for activated carbon fiber (ACF) are becoming increasingly diversified, encompassing various techniques such as oxidation modification, plasma modification, microwave modification, supported modification, and photocatalytic modification. These methods not only effectively improve the performance of ACF but also provide broader possibilities for its application in different fields. Summary of the Invention

[0004] To obtain a desulfurization adsorption material that is efficient, inexpensive, and environmentally friendly, this invention provides a method for modifying activated carbon fiber cloth using a composite hydrothermal method and its application. This method allows lactic acid and ammonium salts to simultaneously undergo acid oxidation modification, ammonium salt nitrogen modification, hydrothermal modification, and other composite modifications on the carbon structure of the ACF surface under a water bath oscillation environment. Furthermore, the ammonium salt-lactic acid mixed solution can form a buffer solution system, ensuring the stability of the ACF water bath reaction environment. Through the above composite modification, a certain degree of etching can be produced on the ACF surface, increasing the specific surface area of ​​the carbon fibers and the number of active contact sites; acid oxidation modification can increase the number of oxygen-containing functional groups on the carbon fiber surface; and nitrogen modification by ammonium salts can increase the number of nitrogen-containing functional groups on the carbon fiber surface.

[0005] In this study, activated carbon fibers were placed in an iodine flask, and then mixed solutions of lactic acid and ammonium sulfate at different concentrations were poured in. The mixture was then placed in a water bath shaker for a one-step water bath shaking reaction. The research data showed that both lactic acid and ammonium sulfate water bath modifications significantly improved the adsorption performance of ACF-SO2. Furthermore, after mixing lactic acid and ammonium sulfate in a specific ratio and undergoing water bath composite modification, the adsorption performance of ACF was further enhanced, with m... 乳酸 :m 硫酸铵The optimal ratio of 1:1 was achieved, and the adsorption capacity of the modified ACF-SO2 reached 21.728 mg / g, which is 186.67% higher than that of the unmodified original tablet. This method uses a mixed water bath modification of lactic acid and ammonium sulfate, which results in milder reaction conditions and significant modification effects.

[0006] To achieve the above objectives, the present invention provides a method for modifying activated carbon fiber cloth using a composite hydrothermal method, the method comprising: The activated carbon fiber cloth was immersed in a mixed solution of lactic acid and ammonium salt in a mass ratio of 1:(0.8-1.2) and subjected to a water bath heating and shaking reaction at 70-90℃. After the reaction, the activated carbon fiber cloth was taken out and cleaned and dried.

[0007] Preferably, the lactic acid concentration in the mixed solution is 8 wt%.

[0008] Preferably, the process includes a pretreatment step: ultrasonically cleaning the activated carbon fiber cloth with water. More preferably, the water is changed every 10-20 minutes during the cleaning process, and the ultrasonic treatment lasts for 10-40 minutes.

[0009] Preferably, the ammonium salt is ammonium sulfate.

[0010] Preferably, after immersion, ultrasonic treatment is used to remove excess air bubbles.

[0011] Preferably, the oscillation speed is 100-200 r / min and the reaction time is 2-4 h.

[0012] Preferably, the drying temperature is 80-120℃ and the drying time is 1-6h.

[0013] A second aspect of the present invention provides a modified activated carbon fiber cloth, characterized in that it is prepared by the method described in the present invention.

[0014] A third aspect of the present invention provides the application of the activated carbon fiber cloth described herein in the preparation of desulfurization adsorption materials.

[0015] Compared with the prior art, the present invention has at least the following beneficial effects: 1. This composite modification method can significantly improve the adsorption capacity of ACF-SO2. The best modification effect is obtained when the mass ratio of lactic acid to ammonium sulfate is 1:1, which can make the adsorption capacity of ACF-SO2 reach 21.728 mg / g, which is 186.67% higher than that of the unmodified original tablet.

[0016] 2. This method uses food-grade lactic acid and mild ammonium sulfate as modifying reagents, which are more environmentally friendly than traditional strong acid and strong base modifying reagents. The entire modification process is also environmentally friendly. This method can provide a new approach for modifying activated carbon fibers. Attached Figure Description

[0017] Figure 1 shows the adsorption capacity of ACF-SO2 after hydrothermal modification with different concentrations of lactic acid; Figure 2 shows the adsorption capacity of ACF-SO2 modified by hydrothermal ammonium sulfate at different concentrations; Figure 3 shows the adsorption capacity of ACF-SO2 modified under different conditions; Figure 4 shows the FT-IR spectra of ACF materials hydrothermally modified with different concentrations of lactic acid; Figure 5 shows the FT-IR spectra of hydrothermally modified ACF materials with different concentrations of ammonium sulfate; Figure 6 shows the FT-IR spectra of hydrothermally modified ACF materials with different ammonium sulfate-lactic acid mass ratios; Figure 7 shows the SEM images of ACF materials under different optimal modification conditions. Detailed Implementation

[0018] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] Unless otherwise specified, the raw materials used in the following examples are all publicly available in the prior art, such as those that can be directly purchased or prepared according to publicly available preparation methods. The activated carbon fiber used in the examples was purchased from Beihai Carbon Materials Co., Ltd.

[0021] In the following examples, the method for calculating the SO2 absorption content of activated carbon fiber is as follows: In the formula: K: SO2 adsorption content of activated carbon fiber (mg / g); C0: Concentration of injected SO2 (mg / ml); V nd : Volume of SO2 injected (ml); C(1 / 2 I2): Concentration of iodine standard solution (mol / L); V1: The volume (ml) of iodine standard solution consumed by the remaining SO2 after adsorption by activated carbon fiber; 32.0: The mass (mg) of sulfur dioxide equivalent to 1 ml of 1 mol / L iodine standard solution; m ACF Mass of activated carbon fiber (g).

[0022] Ultrasonic pretreatment Cut activated carbon fiber cloth (hereinafter referred to as ACF) into 5*4cm square pieces, weighing approximately 0.4~0.5g. Place the cut ACF pieces into a clean beaker, pour in distilled water to completely submerge the ACF pieces. If the ACF pieces float, invert a clean funnel on top of the ACF pieces to ensure complete immersion. Place the beaker in an ultrasonic cleaner for ultrasonic treatment, changing the water every 15 minutes, and repeating the ultrasonic treatment twice to remove grease and other impurities from the surface of the ACF pieces. Then remove the ACF pieces and place them in an oven at 100℃ for 3 hours to remove surface moisture. Finally, clean and dry ACF pieces are obtained.

[0023] Example 1 Study on the modification of lactic acid by water bath treatment One ACF tablet, pretreated with ultrasound, was placed in each of five 250ml iodine flasks. Then, 100ml of lactic acid solution with mass fractions of 2%, 4%, 6%, 8%, and 10% were added respectively. The flasks were ultrasonically cleaned to remove excess air bubbles. They were then transferred to a water bath shaker at 80℃ and 150 rpm. Timing was started after the water bath temperature reached 80℃, and the reaction was continued for 3 hours. After cooling to room temperature, the ACF tablet was removed and placed in a 250ml beaker. It was then ultrasonically washed with water (water changed every 15 minutes, ultrasonication for 30 minutes). The tablets were then dried in an electric heating drying oven at 100℃ for 3 hours, and the SO2 adsorption capacity was tested. The optimal concentration for the lactic acid immersion water bath treatment was determined. The results are shown in Table 1.

[0024] Table 1. Adsorption capacity of ACF-SO2 after water bath composite modification treatment with different concentrations of lactic acid Table 1 shows the adsorption capacity of ACF-SO2 after modification with different concentrations of lactic acid. After lactic acid modification, the adsorption performance of ACF-SO2 was further improved. Within the lactic acid content range of 0%–4%, the adsorption performance of activated carbon fiber was significantly improved, while the effects of lactic acid modification at 4%–8% were very similar. The 8% lactic acid water bath modification showed the best effect, with an ACF-SO2 adsorption capacity reaching 16.610 mg / g, an increase of 119.14% compared to the unmodified original sheet. Therefore, we chose 8% lactic acid as the condition for the subsequent composite water bath modification investigation.

[0025] like Figure 1 As shown, initially, the ACF-SO2 concentration increases with increasing lactic acid concentration, with a significant improvement in the effect of 4% lactic acid modification compared to 2%. Subsequently, the adsorption performance of the carbon fiber material improves slowly with further increases in lactic acid concentration, until the optimal effect is achieved in an 8% lactic acid water bath, where the ACF-SO2 adsorption capacity reaches 16.610 mg / g, an increase of 119.14%. Afterward, increasing the lactic acid concentration to 10% results in a significant decrease in the material's adsorption performance. This is likely because excessively high lactic acid concentrations in a high-temperature water bath environment over-etch the ACF fiber bundles, causing structural damage to the fibers and ultimately leading to a decline in material performance. Therefore, we chose an 8% lactic acid concentration as the subsequent composite modification condition.

[0026] Example 2 Study on the modification of ammonium sulfate by water bath treatment One ACF (Acetic Acid Fluoride) tablet, pretreated with ultrasound, was placed in each of five 250ml iodine flasks. Then, 100ml of ammonium sulfate solutions with mass fractions of 2%, 4%, 6%, 8%, and 10% were added, respectively. The flasks were ultrasonically cleaned to remove excess air bubbles. Afterward, they were transferred to a water bath shaker at 80℃ and 150 rpm. Timing was started after the water bath temperature reached 80℃, and the reaction was continued for 3 hours. The iodine flasks were then removed. After cooling to room temperature, the ACF tablets were removed and placed in a 250ml beaker. The tablets were ultrasonically washed with water (water changed every 15 minutes, ultrasonication for 30 minutes). The tablets were then dried in an electric heating oven at 100℃ for 3 hours, and the SO2 adsorption capacity was tested. The optimal concentration of ammonium sulfate for water bath treatment was determined. The results are shown in Table 2.

[0027] Table 2. ACF-SO2 adsorption capacity under different concentrations of ammonium sulfate treatment Table 2 shows the adsorption capacity of ACF-SO2 modified with different concentrations of ammonium sulfate in a water bath. As the ammonium sulfate concentration increases, the adsorption performance of the ACF material gradually improves, reaching its maximum at 8% ammonium sulfate, where the ACF-SO2 adsorption capacity reaches 12.336 mg / g, representing a 62.75% increase in adsorption rate compared to the unmodified original tablet. However, with further increases in ammonium sulfate concentration, the ACF-SO2 adsorption performance slightly decreases.

[0028] like Figure 2 As shown, ammonium sulfate modification can further improve the adsorption performance of the material compared to the original tablet. Furthermore, the ACF-SO2 adsorption performance continuously increases with increasing ammonium sulfate concentration, reaching a maximum of 12.336 mg / g at 8% ammonium sulfate treatment, representing a 62.75% improvement compared to the original tablet. Therefore, we will next investigate whether mixing lactic acid and ammonium sulfate in different proportions can further improve the material performance.

[0029] Example 3 Investigation of the optimal composite modification conditions of lactic acid (A): ammonium sulfate (B) Because the adsorption capacity of ACF-SO2 increased the most under the above conditions under the 8% lactic acid water bath condition, we explored the optimal modification conditions by controlling the mass ratio of lactic acid to ammonium sulfate based on 8% lactic acid.

[0030] Place one ACF tablet (pretreated with ultrasound) into each of five 250ml iodine flasks, then pour in 100ml of water. A :m B Composite buffer solutions (8wt% lactic acid) were prepared at ratios of 1:0.4, 1:0.6, 1:0.8, 1:1, and 1:1.2. The solutions were ultrasonically cleaned in an ultrasonic cleaner to remove excess air bubbles from the ACF. The solutions were then transferred to a water bath shaker at 80℃ and 150 rpm. Timing was started after the water bath temperature reached 80℃, and the reaction was continued for 3 hours. The iodine flask was then removed. After cooling to room temperature, the ACF sheets were removed and placed in a 250 ml beaker. The sheets were ultrasonically cleaned with water (changing the water every 15 minutes for 30 minutes). The sheets were then dried in an electric heating oven at 100℃ for 3 hours, and the SO2 adsorption capacity was tested. The optimal conditions for the lactic acid (A):ammonium sulfate (B) composite modification treatment were obtained. The results are shown in Table 3.

[0031] Table 3. Adsorption capacity of modified ACF-SO2 with different mass ratios of lactic acid (A) and ammonium sulfate (B) Table 3 shows the adsorption capacity of ACF-SO2 modified with different mass ratios of lactic acid to ammonium sulfate. The data in the table show that the composite water bath modification effect is significantly better than that of single ammonium sulfate modification and single lactic acid modification, further enhancing the adsorption performance of the material. Furthermore, the composite modification effect increases with increasing ammonium sulfate concentration. At a lactic acid:ammonium sulfate ratio of 1:1, the ACF-SO2 adsorption capacity reaches 21.728 mg / g, representing a 186.67% improvement compared to the original tablet. However, with further increases in the ammonium sulfate mass ratio, the composite modification effect shows a significant decrease.

[0032] like Figure 3 As shown, m 乳酸 :m 硫酸铵 At a ratio of 1:1, the composite modification treatment achieved the best composite modification effect. The ACF-SO2 adsorption capacity reached 21.728 mg / g, and the adsorption rate increased by 186.67%.

[0033] Example 4 FT-IR characterization We used infrared spectroscopy to characterize the modified ACF in Examples 1-3 to explore the underlying mechanism of the modification.

[0034] like Figure 4 The image shows the FT-IR spectra of ACF materials modified with lactic acid in a water bath at different concentrations. After lactic acid modification, the materials exhibited spectra in the range of 1650–1740 cm⁻¹. -1 There is a distinct absorption peak, which is the absorption peak of C=O stretching vibration, in the range of 3200~3500 cm⁻¹. -1 and 1260~1400cm -1 The presence of distinct absorption peaks, representing the stretching and bending vibrations of -OH groups, suggests that lactic acid modification of carbon fibers resulted in the formation of numerous oxygen-containing functional groups such as -OH, -C=O, and -COOH on the surface. This indicates that lactic acid effectively oxidizes the carbon fibers, and these oxygen-containing functional groups significantly enhance the adsorption capacity of ACF-SO2. Furthermore, under lactic acid modification conditions (2%–8%), the absorption peaks of oxygen-containing functional groups in the ACF infrared spectrum were very pronounced. However, in the infrared spectrum data for 10% lactic acid water bath modification, the peaks of oxygen-containing functional groups began to decline, corresponding to a decrease in the ACF-SO2 adsorption capacity observed in the adsorption measurement experiment. This is likely because excessive oxidation and etching damages the carbon skeleton structure of the carbon fibers, disrupting the material's physical structure and ultimately affecting its adsorption performance.

[0035] like Figure 5 The image shows the FT-IR spectra of ACF modified with ammonium sulfate at different concentrations via water bath. After modification with ammonium sulfate, the material exhibits high spectral density in the range of 1020–1340 cm⁻¹. -1 An absorption peak appears, which is the CN stretching vibration peak, and it is also present in the range of 3300~3500 cm⁻¹. -1 and 1550~1650cm -1 The presence of distinct absorption peaks indicates the presence of -NH stretching and bending vibration peaks. Therefore, it can be inferred that after ammonium sulfate modification, the surface of the ACF material undergoes significant nitrogen modification, generating a large number of -NH basic functional groups, which effectively improves the AC-SO2 adsorption performance.

[0036] like Figure 6 The image shows the FT-IR spectra of ACF materials modified by water bath composite with different ammonium sulfate-lactic acid concentration ratios. The spectra show that ACF exhibits high activity in the 1020–1340 cm⁻¹ range. -1 CN stretching vibration peak appears, 3300~3500cm. -1 and 1550~1650cm -1 The material exhibits both -NH stretching and bending vibration peaks. Simultaneously, the material shows peak values ​​between 1650 and 1740 cm⁻¹. -1 An absorption peak for C=O stretching vibrations appears, particularly in the range of 3200–3500 cm⁻¹. -1 and 1260~1400cm -1Obvious absorption peaks for both -OH stretching vibration and bending vibration were observed. These results indicate that under ammonium sulfate-lactic acid composite water bath conditions, the ACF material undergoes simultaneous oxidation and nitrogen modification, resulting in a large number of oxygen- and nitrogen-containing functional groups on the material surface, further enhancing the ACF-SO2 adsorption capacity. However, when m... 乳酸 :m 硫酸铵 When the ratio is 1:1.2, the length is 1020~1340cm. -1 The CN stretching vibration peak, and the 3200~3500cm peak. -1 The significantly weakened absorption peak of the -OH stretching vibration indicates that excessively high mixed solution concentrations will over-etch the material, causing its performance to reach an inflection point and decline. Therefore, we will next observe the surface microstructure of the material under different modification conditions using SEM to further analyze the intrinsic mechanism of the modification.

[0037] Example 5 SEM characterization The ACF samples before and after modification in Examples 1-3 were characterized by SEM to investigate the changes in the microstructure of the carbon fibers.

[0038] like Figure 7 The following are SEM images of ACF materials under different optimal modification conditions: (a) original ACF sheet; (b) 3h 80℃ water bath treatment; (c) 8% lactic acid water bath treatment; (d) 8% ammonium sulfate water bath treatment; (e) m 乳酸 : m 硫酸铵 1:1 composite treatment. As shown in Figure (b), after treatment in an 80℃ water bath for 3 hours, the surface of the ACF-treated fiber did not change much compared to the original sheet, indicating that the 80℃ water bath environment did not affect the physical properties of ACF. However, as shown in Figure (c), treatment with 8% lactic acid in a water bath further increased the roughness and texture of the fiber surface, producing a significant etching effect. This increased the specific surface area and active sites of the material. Furthermore, with the increase in surface etching, a layer of lactic acid was loaded on the carbon fiber surface, and the increase in oxygen-containing functional groups enhanced the ACF-SO2 adsorption capacity. As shown in Figure (d), after modification with 8% ammonium sulfate in a water bath, the fiber surface showed a significant ammonium sulfate crystal loading, and the increase in amine groups effectively improved the material's adsorption performance. Figure (e) shows m... 乳酸 :m 硫酸铵SEM images of the ACF material surface after 1:1 composite treatment. The images show that the composite water bath treatment resulted in both significant etching and crystal loading on the material surface. The synergistic effect of oxidation etching and nitrogen modification loading is clearly visible on the carbon fiber surface. Simultaneously, the carbon fiber tubes thickened significantly after the composite water bath treatment, further enhancing the specific surface area and active sites of the carbon fibers, leading to optimal adsorption performance. However, the images also clearly show a high crystal loading on the material surface. Further increasing the concentration of the modifying reagent could result in excessive crystal loading, which would cover the carbon fiber surface and degrade the material's performance.

[0039] The embodiments of this application have been described above with reference to the accompanying drawings. Specific examples have been used to illustrate the principles and implementation methods of this application. The description of the above embodiments is only for the purpose of helping to understand the core ideas of this application. However, this application is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of this application without departing from the spirit and scope of the claims, and all of these forms are within the protection scope of this application.

Claims

1. A method for modifying activated carbon fiber cloth using a composite hydrothermal method, characterized in that, The method includes: The activated carbon fiber cloth was immersed in a mixed solution of lactic acid and ammonium salt in a mass ratio of 1:(0.8-1.2) and subjected to a water bath heating and shaking reaction at 70-90℃. After the reaction, the activated carbon fiber cloth was taken out and cleaned and dried.

2. The method according to claim 1, characterized in that, The concentration of lactic acid in the mixed solution is 8 wt%.

3. The method according to claim 1, characterized in that, The process includes a pretreatment step: ultrasonic water cleaning of the activated carbon fiber cloth.

4. The method according to claim 3, characterized in that, Change the water every 10-20 minutes during the cleaning process, and the ultrasonic treatment lasts for 10-40 minutes.

5. The method according to claim 1, characterized in that, The ammonium salt is ammonium sulfate.

6. The method according to claim 1, characterized in that, After immersion, ultrasonic treatment is used to remove excess air bubbles.

7. The method according to claim 1, characterized in that, The oscillation speed is 100-200 r / min, and the reaction time is 2-4 h.

8. The method according to claim 1, characterized in that, The drying temperature is 80-120℃, and the drying time is 1-6 hours.

9. A modified activated carbon fiber cloth, characterized in that, Prepared by the method described in any one of claims 1-8.

10. The application of the activated carbon fiber cloth according to claim 9 in the preparation of desulfurization adsorption materials.

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