Silver ion modified activated carbon fiber for purifying drinking water and its use

Abstract

This invention provides a silver ion-modified activated carbon fiber for drinking water purification and its application. The preparation of the silver ion-modified activated carbon fiber mainly includes: first, preparing pretreated viscose fiber; then, dispersing modified chitosan in a silver salt solution and stirring to mix, followed by adding the pretreated viscose fiber to obtain silver-loaded viscose fiber; finally, soaking, carbonizing, and activating the fiber in sodium dihydrogen phosphate solution to obtain silver ion-modified activated carbon fiber. The silver ion-modified activated carbon fiber for drinking water purification prepared by this invention exhibits high antibacterial rates against Escherichia coli and Staphylococcus aureus, effectively inhibiting pathogenic bacteria that may exist in drinking water; the silver ion release is relatively stable, with no significant attenuation after 30 days, and the silver ion release is lower than the national standard limit, meeting drinking water safety standards, and balancing long-term antibacterial effect and safety in use.

Description

Technical Field

[0001] This invention belongs to the field of drinking water purification materials technology, and particularly relates to a silver ion modified activated carbon fiber for drinking water purification and its application. Background Technology

[0002] Activated carbon fiber, due to its large specific surface area, possesses strong adsorption capacity, capable of adsorbing and removing organic matter from water, including trace amounts of carcinogenic or highly toxic aromatic substances. Therefore, it is gradually replacing activated carbon as an important material for advanced drinking water treatment. However, ordinary activated carbon fiber can only remove organic matter through physical adsorption, and its ability to kill pathogens in water is limited, easily leading to the proliferation of pathogens inside the filter cartridge and causing secondary pollution.

[0003] Therefore, existing technologies attempt to load silver-based antibacterial agents onto activated carbon fibers, utilizing the broad-spectrum antibacterial properties of silver ions to achieve the material's self-sterilization function. Currently, the preparation of silver-loaded materials mainly employs post-loading methods such as impregnation reduction, impregnation thermal decomposition, composite spinning, and electrochemical deposition, which involve loading silver onto pre-prepared activated carbon fibers using physicochemical methods.

[0004] However, these methods still have shortcomings: For example, the impregnation reduction method involves impregnating or spraying a solution containing silver ions to reduce silver ions to elemental silver, which then adheres to the activated carbon fiber. However, the silver tends to adhere to the fiber surface, making it easy to detach and resulting in poor antibacterial durability. The impregnation thermal decomposition method involves impregnating activated carbon fiber with a silver nitrate solution of a certain concentration, drying it, and then heating it at high temperature to decompose the silver salt into elemental silver, thus obtaining silver-loaded activated carbon fiber. However, the presence of silver can block some active sites on the activated carbon fiber, reducing the specific surface area and affecting the adsorption performance of the silver-loaded activated carbon fiber. In addition, this method requires harsh reaction conditions and high-end equipment, which is not conducive to large-scale production. Hollow activated carbon fiber prepared by composite spinning is simple, low-cost, and environmentally friendly, but the nano-silver is encapsulated inside the carrier, which is not conducive to contact with pathogens and limits the sterilization space.

[0005] Therefore, in view of the shortcomings of the post-silver loading method, which is that the activated carbon fiber and silver are not tightly bound and are easy to fall off, the present invention provides a silver ion modified activated carbon fiber prepared by the pre-silver loading method, which has excellent adsorption performance, broad-spectrum antibacterial performance and safe silver ion slow release characteristics, and can meet the actual needs of the drinking water purification industry. Summary of the Invention

[0006] The purpose of this invention is to provide a silver ion modified activated carbon fiber for drinking water purification, its preparation method and application, so as to solve the problems mentioned in the background art.

[0007] To achieve the above objectives, the present invention provides a silver ion-modified activated carbon fiber for drinking water purification, characterized in that the preparation of the silver ion-modified activated carbon fiber includes the following steps: (1) Add inorganic alkali and soaping agent to deionized water, stir to dissolve and form a treatment solution, then add viscose fiber to the treatment solution, stir at 80-100℃ for 20-30 minutes, and then rinse with clean water to obtain pretreated viscose fiber. (2) Disperse the modified chitosan in a silver salt solution and stir to mix. Then add the viscose fiber pretreated in step (1) and adjust the pH to 5.0-6.0 with organic acid. Stir at room temperature for 15-30 min and then add salting-out agent. Heat to 80-90℃ and continue the reaction for 20-40 min. After the reaction is completed, perform post-treatment to obtain silver-loaded viscose fiber. (3) The silver-loaded viscose fiber obtained in step (2) is made into silver-loaded viscose fiber felt using a needle punching device, then soaked in sodium dihydrogen phosphate solution for 6-10 hours, taken out and dried, and then carbonized and activated to obtain silver-loaded activated carbon fiber.

[0008] As a further improvement, the modified chitosan in step (2) is betaine-type zwitterionic modified chitosan; the betaine-type zwitterionic is dimethylpropyl sulfonate ethyl methacrylate.

[0009] In betaine-type zwitterionic modified chitosan, the anionic and cationic groups can form more stable coordination bonds with silver ions, achieving efficient loading and uniform dispersion of silver ions. If cationic modified chitosan is used, the silver ion loading will be lower due to the weaker complexation ability between the two, and the antibacterial effect will decrease accordingly.

[0010] As a further improvement, the preparation of the modified chitosan includes the following steps: (1) Add chitosan, glacial acetic acid and deionized water to a beaker and stir at room temperature to dissolve them to obtain a chitosan solution; (2) Add dimethylpropyl sulfonamide ethyl methacrylate and initiator to the chitosan solution in step (1), stir evenly to obtain a mixture, react the mixture at 50-60℃ under nitrogen atmosphere for 3-5 hours, after the reaction is completed, and then perform post-treatment to obtain modified chitosan.

[0011] As a further improvement, the soaping agent in step (1) is a nonionic soaping agent or anionic soaping agent.

[0012] As a further improvement, the soaping agent in step (1) is an anionic soaping agent; the anionic soaping agent is an acrylic polymer.

[0013] As a further improvement, in step (2), the silver salt is at least one of silver nitrate and silver sulfate; the concentration of the silver salt solution is 5-8 g / L.

[0014] As a further improvement, the salting-out agent in step (2) is at least one of sodium chloride, potassium chloride, and sodium sulfate.

[0015] As a further improvement, the carbonization temperature in step (3) is 300-500℃ and the activation temperature is 800-950℃.

[0016] As a further improvement, the activation in step (3) is carried out by water vapor activation for 10-30 minutes.

[0017] The present invention also provides the application of silver ion modified activated carbon fiber for drinking water purification in the preparation of drinking water purification materials; the drinking water purification materials are purification filter cartridges, filter membranes, or antibacterial filter layers.

[0018] Compared with the prior art, the beneficial effects of the present invention are: The silver ion modified activated carbon fiber for drinking water purification prepared by this invention has a high antibacterial rate against Escherichia coli and Staphylococcus aureus, reaching up to 99.9%, and can effectively inhibit pathogenic bacteria that may exist in drinking water. In the silver ion slow-release test, the silver ion release is relatively stable, with no significant decay after 30 days, and the silver ion release is lower than the national standard limit, which meets the drinking water safety standard, taking into account both long-term antibacterial effect and safety of use. This invention uses betaine-type zwitterionic modified chitosan as a silver ion complexing medium, which enables silver ions to form stable coordination bonds with modified chitosan. Combined with the surface activation effect of viscose fiber pretreatment, silver ions are efficiently loaded and uniformly dispersed in the fiber matrix, achieving good antibacterial effect and long-lasting silver loading effect. Sodium dihydrogen phosphate soaking, carbonization, and steam activation can give activated carbon fibers a high specific surface area and rich pore structure, giving them excellent adsorption performance. Combined with the loaded silver ions, it achieves the dual functions of adsorption and purification, antibacterial and bacteriostatic effects. The raw materials used in this invention are inexpensive and readily available, and the preparation process is simple, showing good industrialization prospects. Detailed Implementation

[0019] The present invention will be described below with reference to specific embodiments. It should be noted that the following embodiments are examples of the present invention and are used only to illustrate the invention, not to limit it. Other combinations and various modifications within the scope of the present invention can be made without departing from its spirit or scope.

[0020] In the following examples, except for modified chitosan A, carboxybetaine methacrylate-modified chitosan, and quaternary ammonium salt-modified chitosan, all other compounds, monomers, and related reagents used were commercially available. Specifically, viscose fiber was purchased from Shandong Oude Chemical Fiber Products Co., Ltd. (item number VS200); chitosan was purchased from Henan Bangrun Chemical Products Co., Ltd. (item number BR-024); acrylic polymer soap was purchased from Jiande Baisha Chemical Co., Ltd. (model number TH); and nonionic soap was purchased from Jiangmen Xinhui Qianyi Chemical Technology Co., Ltd. (model number QY-202). The preparation of modified chitosan A includes the following steps: (1) Add 5g chitosan, 10mL glacial acetic acid and 500mL deionized water to a beaker and stir at room temperature to dissolve to obtain chitosan solution; (2) Add 2.9g of dimethylpropyl sulfonamide ethyl methacrylate and 0.04g of potassium persulfate to the chitosan solution in step (1), stir until uniform to obtain a mixture, react the mixture at 60℃ under a nitrogen atmosphere for 4h, after the reaction is completed, cool to room temperature, drop the obtained mixture into 1L of 1mol / L sodium hydroxide solution at a rate of 3mL / min, let stand for 2h after the addition is completed, filter, rinse with deionized water, dry at 80℃ to obtain modified chitosan A.

[0021] The preparation of chitosan modified with carboxybetaine methacrylate includes the following steps: (1) Add 5g chitosan, 10mL glacial acetic acid and 500mL deionized water to a beaker and stir at room temperature to dissolve to obtain chitosan solution; (2) Add 2.7g of carboxybetaine methacrylate and 0.04g of potassium persulfate to the chitosan solution in step (1), stir until uniform to obtain a mixture, react the mixture at 50℃ under a nitrogen atmosphere for 4h, after the reaction is completed, cool to room temperature, drop the obtained mixture into 1L of 1mol / L sodium hydroxide solution at a rate of 3mL / min, let stand for 2h after the addition is completed, filter, rinse with deionized water, dry at 80℃ to obtain carboxybetaine methacrylate modified chitosan.

[0022] The preparation of quaternary ammonium salt modified chitosan includes the following steps: Add 5g of chitosan, 50mL of 40% sodium hydroxide solution, and 80mL of isopropanol to a flask in sequence. Stir at 50℃ for 4h. Then, slowly add 20g of 60% 2,3-epoxypropyltrimethylammonium chloride aqueous solution. After the addition is complete, raise the temperature to 70℃ and react for 7h. After the reaction is complete, cool to room temperature and adjust the pH to 7 with 10% dilute hydrochloric acid. Centrifuge and wash the product three times with an acetone-ethanol mixture (V / V = 4:1). Finally, place the product in a vacuum dryer at 50℃ for 24h to obtain quaternary ammonium salt modified chitosan.

[0023] Example 1 (1) Add 15g sodium hydroxide and 25g acrylic polymer soap to 2L of deionized water and stir until completely dissolved. Then add 150g viscose fiber and stir at 90℃ for 30min. Then wash twice with deionized water and squeeze out the water to obtain pretreated viscose fiber. (2) Disperse 80g of modified chitosan A in 500mL of silver nitrate solution with a concentration of 6g / L and stir to mix. Add 50g of pretreated viscose fiber, adjust the pH of the system to 5, stir at room temperature for 20min, add 30g of sodium chloride solution with a concentration of 60g / L, keep warm at 90℃ for 30min, neutralize the pH to 7 with sodium hydroxide solution with a concentration of 0.5g / L, wash twice with water, squeeze out the water, and dry at 60℃ to obtain silver-loaded viscose fiber; (3) The silver-loaded viscose fiber was made into silver-loaded viscose fiber felt using a needle punching device, and then soaked in 100g of 10wt% sodium dihydrogen phosphate solution for 10h. After taking it out, it was dried at 80℃. Under nitrogen atmosphere, it was heated to 300℃ at a rate of 5℃ / min for 30min for carbonization. Then, the temperature was further increased to 850℃ and water vapor was introduced for activation for 40min. Finally, it was cooled to room temperature to obtain silver ion modified activated carbon fiber.

[0024] Example 2 (1) Add 20g sodium hydroxide and 30g acrylic polymer soap to 2L deionized water and stir until completely dissolved. Then add 200g viscose fiber and stir at 90℃ for 30min. Then wash twice with deionized water and squeeze out the water to obtain pretreated viscose fiber. (2) 120g of modified chitosan A was dispersed in 600mL of silver nitrate solution with a concentration of 8g / L and stirred. 60g of pretreated viscose fiber was added, the pH of the system was adjusted to 5.5, and stirred at room temperature for 20min. Then 40g of sodium chloride solution with a concentration of 50g / L was added, and the mixture was kept at 90℃ for 40min. After neutralizing the pH to 7 with sodium hydroxide solution with a concentration of 0.6g / L, the mixture was washed twice with water, squeezed to remove water, and dried at 60℃ to obtain silver-loaded viscose fiber. (3) The silver-loaded viscose fiber was made into silver-loaded viscose fiber felt using a needle punching device, and then soaked in 100g of 10wt% sodium dihydrogen phosphate solution for 8h. After taking it out, it was dried at 80℃. Under nitrogen atmosphere, it was heated to 400℃ at a rate of 5℃ / min for 30min for carbonization. Then, the temperature was further increased to 900℃, and water vapor was introduced for activation for 30min. Finally, it was cooled to room temperature to obtain silver ion modified activated carbon fiber.

[0025] Example 3 The preparation is basically the same as in Example 1, except that the modified chitosan A in step (2) is replaced with carboxybetaine methacrylate modified chitosan.

[0026] Example 4 The preparation is basically the same as in Example 1, except that the modified chitosan A in step (2) is replaced with quaternary ammonium salt modified chitosan.

[0027] Example 5 The preparation is basically the same as in Example 1, except that the acrylic polymer soaping agent in step (1) is replaced with a nonionic soaping agent.

[0028] Comparative Example 1 The preparation is basically the same as in Example 1, except that the modified chitosan A in step (2) is replaced with chitosan (i.e. unmodified chitosan).

[0029] Comparative Example 2 The preparation is basically the same as in Example 1, except that the step (2) "disperse 80g of modified chitosan A in 500mL of silver nitrate solution with a concentration of 6g / L and stir to mix, and add 50g of pretreated viscose fiber" is replaced with "add 50g of pretreated viscose fiber to 500mL of silver nitrate solution with a concentration of 6g / L".

[0030] Comparative Example 3 The preparation is basically the same as in Example 1, except that the wording in step (3) "preparing silver-loaded viscose fiber felt, soaking it in 100g of 10wt% sodium dihydrogen phosphate solution for 10h, drying it at 80℃, and carbonizing it at 300℃ for 30min at a rate of 5℃ / min under nitrogen atmosphere" is replaced with "preparing silver-loaded viscose fiber felt, carbonizing it at 300℃ for 30min at a rate of 5℃ / min under nitrogen atmosphere".

[0031] The silver ion modified activated carbon fibers prepared in Examples 1-5 and Comparative Examples 1-3 were subjected to antibacterial and silver ion sustained-release tests, and the test methods are as follows: Antibacterial properties: Following the shaking method in GB / T 20944.3-2008, 0.75g of silver ion modified activated carbon fiber was placed in 70mL of 0.03mol / L phosphate buffer, and Escherichia coli / Staphylococcus aureus bacterial suspension (initial concentration 1×10⁻⁶) was added. 6 The bacterial concentrations were measured before and after contact (CFU / mL) at 24℃ and 150r / min for 24 hours. The inhibition rates of Escherichia coli and Staphylococcus aureus were calculated. The average value of three parallel tests was taken. Silver ion slow-release property: 50g of silver ion modified activated carbon fiber was loaded into the filter cartridge test device and a water filtration experiment was conducted. 3L of water was filtered every day (divided into two tests). The water flow rate was controlled at 15min / L. All filtered water was collected on 1d, 7d and 30d respectively. The silver content in the filtered water was tested using an inductively coupled plasma atomic emission spectrometer, which is the silver ion slow-release amount at the corresponding time. The measurement results are shown in Table 1: Table 1 As can be seen from the test results in Table 1, the silver ion modified activated carbon fiber prepared by this invention achieved an inhibition rate of over 95% in the antibacterial tests against Escherichia coli and Staphylococcus aureus. Among them, the inhibition rate of Examples 1 and 2 reached as high as 99.9%, demonstrating excellent broad-spectrum antibacterial performance. Furthermore, in the water filtration test, the silver ion release of the prepared silver ion modified activated carbon fiber was relatively stable at 1 day, 7 days, and 30 days, with no significant attenuation at 30 days, and the dissolution amount was far below the national standard limit, thus balancing long-term antibacterial effect and safety of use.

[0032] The test results of Comparative Examples 1-2 show that the release concentration of silver ions is low, and there is still no effective release after 7 days and 30 days. This indicates that the complexation between silver and the matrix is ​​poor when using only chitosan or without adding modified chitosan. Only some physically adsorbed silver ions exist, which are easily dissolved and depleted during carbonization and activation, and cannot achieve long-term sustained release. The test results of Comparative Example 3 without soaking in sodium dihydrogen phosphate show that the release concentration of silver ions is lower than that of the examples. This indicates that soaking in sodium dihydrogen phosphate can optimize the pore structure of activated carbon fibers, enhance the binding force and fixation of silver ions with the fiber matrix, and improve the antibacterial activity of Escherichia coli and Staphylococcus aureus to a certain extent.

[0033] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it. They should not be used to limit the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A silver ion-modified activated carbon fiber for drinking water purification, characterized in that, The preparation of the silver ion modified activated carbon fiber includes the following steps: (1) Add inorganic alkali and soaping agent to deionized water, stir to dissolve and form a treatment solution, then add viscose fiber to the treatment solution, stir at 80-100℃ for 20-30 minutes, and then rinse with clean water to obtain pretreated viscose fiber. (2) Disperse the modified chitosan in a silver salt solution and stir to mix. Then add the viscose fiber pretreated in step (1) and adjust the pH to 5.0-6.0 with organic acid. Stir at room temperature for 15-30 min and then add salting-out agent. Heat to 80-90℃ and continue the reaction for 20-40 min. After the reaction is completed, perform post-treatment to obtain silver-loaded viscose fiber. (3) The silver-loaded viscose fiber obtained in step (2) is made into silver-loaded viscose fiber felt using a needle punching device, then soaked in sodium dihydrogen phosphate solution for 6-10 hours, taken out and dried, and then carbonized and activated to obtain silver ion modified activated carbon fiber.

2. The silver ion modified activated carbon fiber for drinking water purification according to claim 1, characterized in that, In step (2), the modified chitosan is betaine-type zwitterionic modified chitosan; the betaine-type zwitterionic is dimethylpropyl sulfonate ethyl methacrylate.

3. The silver ion modified activated carbon fiber for drinking water purification according to claim 2, characterized in that, The preparation of the modified chitosan includes the following steps: (1) Add chitosan, glacial acetic acid and deionized water to a beaker and stir at room temperature to dissolve them to obtain a chitosan solution; (2) Add dimethylpropyl sulfonamide ethyl methacrylate and initiator to the chitosan solution in step (1), stir evenly to obtain a mixture, react the mixture at 50-60℃ under nitrogen atmosphere for 3-5 hours, after the reaction is completed, and then perform post-treatment to obtain modified chitosan.

4. The silver ion modified activated carbon fiber for drinking water purification according to claim 1, characterized in that, The soaping agent in step (1) is a nonionic soaping agent or anionic soaping agent.

5. The silver ion modified activated carbon fiber for drinking water purification according to claim 4, characterized in that, The soaping agent in step (1) is an anionic soaping agent; the anionic soaping agent is an acrylic polymer soaping agent.

6. The silver ion modified activated carbon fiber for drinking water purification according to claim 1, characterized in that, In step (2), the silver salt is at least one of silver nitrate and silver sulfate; the concentration of the silver salt solution is 5-8 g / L.

7. The silver ion modified activated carbon fiber for drinking water purification according to claim 1, characterized in that, In step (2), the salting-out agent is at least one of sodium chloride, potassium chloride, and sodium sulfate.

8. The silver ion modified activated carbon fiber for drinking water purification according to claim 1, characterized in that, In step (3), the carbonization temperature is 300-500℃ and the activation temperature is 800-950℃.

9. The silver ion modified activated carbon fiber for drinking water purification according to claim 1, characterized in that, In step (3), the activation is carried out by water vapor activation, and the activation time is 10-30 min.

10. The application of silver ion modified activated carbon fiber for drinking water purification according to any one of claims 1-9 in the preparation of drinking water purification materials; wherein the drinking water purification material is a purification filter element, a filter membrane, or an antibacterial filter layer.

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