Photocatalytic composite fiber air filter membrane and preparation method thereof

Abstract

The application relates to a protective filter membrane, in particular to a photocatalytic composite fiber air filter membrane and a preparation method thereof. The application develops an N-TiO2 supported chitosan fiber air filter membrane (N-TiO2@CS). The composite filter membrane not only effectively avoids the agglomeration problem of N-TiO2 powder, but also has the dual functions of efficient interception and in-situ degradation of pollen by visible light catalysis. Moreover, the N-TiO2@CS fiber air filter membrane disclosed by the application can inactivate 96% of pollen cells within 4 hours, and realizes self-cleaning and long-term use of the filter membrane.

Description

Technical Field

[0001] This invention relates to a protective filter membrane, specifically to an N-TiO2-supported chitosan fiber filter membrane for protecting against airborne allergens and its preparation method. Background Technology

[0002] Currently, while commercially available PP air filter membranes can physically trap airborne pollen, they cannot degrade it, leading to a risk of secondary release of allergens accumulated on the membrane. Although research has confirmed the potential of TiO2 nanoparticles to photocatalytically degrade pollen, they are only active under ultraviolet light, exhibiting extremely low catalytic efficiency in everyday environments. While nitrogen doping can broaden its visible light response range, N-TiO2 powder is prone to agglomeration in practical applications, resulting in decreased photocatalytic efficiency, and the powder's morphology makes it difficult to recycle. Furthermore, because pollen allergens in the air are dispersed, loose, free N-TiO2 powder cannot effectively contact pollen particles to achieve targeted catalytic degradation, lacking feasible practical applications and significantly limiting the practical application of this technology in air purification. Summary of the Invention

[0003] In view of this, the present invention discloses a photocatalytic composite fiber air filter membrane and its preparation method, which can effectively solve the following technical problems:

[0004] Currently available commercially available polypropylene (PP) air filter membranes can filter pollen, but they do not have the ability to degrade pollen and cannot fundamentally eliminate the risk of allergies. While titanium dioxide (TiO2) nanoparticles have the potential to photocatalytically degrade pollen, they are only effective under ultraviolet light and have poor activity under visible light. Furthermore, although nitrogen-doped titanium dioxide (N-TiO2) extends the visible light response range, its powder morphology is prone to agglomeration and difficult to recycle, making it unable to directly act on pollen particles dispersed in the air, thus limiting its practical application.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] The first objective of this invention is to provide a photocatalytic composite fiber air filter membrane, wherein the protective filter membrane is an N-TiO2 supported chitosan fiber air filter membrane N-TiO2@CS.

[0007] It should be noted that the N-TiO2-supported chitosan fiber air filter membrane (N-TiO2@CS) developed in this invention not only effectively avoids the agglomeration problem of N-TiO2 powder, but also possesses the dual functions of highly efficient retention and in-situ visible light photocatalytic degradation of pollen. Experiments show that this N-TiO2@CS fiber air filter membrane can inactivate 96% of pollen cells within 4 hours, achieving self-cleaning and long-term use of the filter membrane. Therefore, this invention significantly improves the actual photocatalytic efficiency of N-TiO2 in pollen degradation, providing a feasible new material solution for the control of airborne pollen pollution.

[0008] The second objective of this invention is to provide a method for preparing the photocatalytic composite fiber air filter membrane as described above, comprising the following steps:

[0009] ① Mix titanium source and anhydrous ethanol at a volume ratio of 1:4 at room temperature and stir to obtain solution A; mix concentrated nitric acid, anhydrous ethanol and ammonia at a volume ratio of 1:5:5 at room temperature and stir to obtain solution B;

[0010] ② Solution B is added dropwise to solution A and mixed at room temperature. After aging, a white sol is obtained. The sol is dried, and a nitrogen source is added and ground into a white powder. The molar ratio of the nitrogen source to the titanium source is (1:50) to (1:200). The nitrogen source is selected from one or more combinations of urea, triethylamine, and ammonia. The titanium source is selected from one or more combinations of tetrabutyl titanate, isopropyl titanate, and titanium tetrachloride.

[0011] ③ Place the white powder in a muffle furnace and calcine it at a heating rate of 2~5℃ to 400℃ for 3h to obtain light yellow N-TiO2 powder;

[0012] ④ Dissolve N-TiO2 powder in anhydrous ethanol at a material-to-liquid ratio of 0.005~0.04 g / mL, add 1~5% polyvinylpyrrolidone dispersant by mass, and then sonicate to obtain a uniform mixture. Immerse the mixture in a chitosan fiber membrane and sonicate. The dispersant is a high molecular weight surfactant, such as, but not limited to, one or more combinations of polyvinylpyrrolidone, polyethylene glycol, sodium dodecylbenzenesulfonate, and hexadecyltrimethylammonium bromide.

[0013] ⑤ Remove the chitosan fiber membrane, fix N-TiO2 with a crosslinking agent at a mass ratio of 0.5~2.0%, and dry to obtain N-TiO2@CS fiber membrane. The crosslinking agent is a non-toxic, natural biological crosslinking agent that can react with the amino groups on the chitosan molecular chain, such as genipin or tannic acid.

[0014] Compared with the prior art, the beneficial effects of the present invention are:

[0015] 1) The N-TiO2@CS fiber air filter membrane provided by this invention is mainly used as a novel air filtration material that is highly efficient and self-cleaning. This material can efficiently capture airborne allergens such as pollen through a dual mechanism of electrostatic adsorption and physical barrier. With its excellent photocatalytic properties, it can achieve in-situ degradation of adsorbed pollen under ambient visible light, effectively solving the problems of easy saturation, frequent replacement, and potential secondary pollution of traditional PP air filter membranes.

[0016] 2) Its applications are widely covered in the field of air purification, specifically including but not limited to: manufacturing various personal respiratory protective products; using it as the core filter element in indoor air purifiers, fresh air systems, and vehicle air purification devices; and applying it to ventilation and filtration systems in places with stringent requirements for air cleanliness, such as hospitals, laboratories, and precision manufacturing workshops.

[0017] 3) This invention significantly improves the actual photocatalytic efficiency of N-TiO2 in pollen degradation, providing an innovative technical solution for the treatment of airborne pollen pollution and fine particulate matter. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0019] Figure 1 Photos of commercial PP air filter membranes (left) and N-TiO2@CS fiber air filter membranes (right).

[0020] Figure 2 This is a scanning electron microscope image of a blank CS fiber membrane.

[0021] Figure 3 This is a scanning electron microscope image of the N-TiO2 nanoparticles prepared in Example 3 of the present invention.

[0022] Figure 4 This is a scanning electron microscope image of the N-TiO2@CS fiber air filter membrane prepared in Example 3 of the present invention.

[0023] Figure 5 This is the electron paramagnetic resonance spectrum of the N-TiO2@CS fiber air filter membrane prepared in Example 3 of the present invention.

[0024] Figure 6 This is a line graph showing the pollen survival rate of the N-TiO2@CS fiber air filter membrane and N-TiO2 nanoparticles under light irradiation in a photocatalytic experiment. Detailed Implementation

[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0026] The term "embodiment" used herein, as an example, is not necessarily to be construed as superior to or better than other embodiments. Performance testing in the embodiments of this application, unless otherwise specified, employs conventional testing methods in the art. It should be understood that the terminology used in this application is merely for describing particular implementations and is not intended to limit the scope of this disclosure.

[0027] Unless otherwise stated, the technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; other experimental methods and technical means not specifically mentioned herein refer to experimental methods and technical means commonly used by one of ordinary skill in the art.

[0028] In the description of this invention, it should be understood that the terms "middle", "upper", "lower", "rise", "fall", "vertical", "surface", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0029] To better illustrate the content of this application, numerous specific details are provided in the following detailed embodiments. Those skilled in the art should understand that this application can be implemented even without certain specific details. In the embodiments, some methods, means, instruments, and devices well-known to those skilled in the art are not described in detail in order to highlight the main points of this application.

[0030] Without conflict, the technical features disclosed in the embodiments of this application can be combined arbitrarily, and the resulting technical solution belongs to the content disclosed in the embodiments of this application.

[0031] This invention discloses a method for preparing a photocatalytic composite fiber air filter membrane, wherein the photocatalytic composite fiber air filter membrane is an N-TiO2 supported chitosan fiber air filter membrane (N-TiO2@CS).

[0032] To better understand the present invention, the following embodiments are provided for further detailed description of the present invention, but they should not be construed as limiting the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above-described invention are also considered to fall within the protection scope of the present invention.

[0033] Example 1

[0034] ① Mix tetrabutyl titanate and anhydrous ethanol at a volume ratio of 1:4 at room temperature and stir to obtain solution A; mix concentrated nitric acid, anhydrous ethanol and ammonia at a volume ratio of 1:5:5 at room temperature and stir to obtain solution B;

[0035] ② Solution B is added dropwise to solution A and mixed at room temperature. After aging, a white sol is obtained. The sol is dried, urea is added, and the mixture is ground into a white powder. The molar ratio of urea to tetrabutyl titanate is 1:50.

[0036] ③ The white powder was placed in a muffle furnace and calcined at 400°C at a heating rate of 3°C for 3 hours to obtain a light yellow N-TiO2 powder;

[0037] ④ Dissolve N-TiO2 powder in anhydrous ethanol at a material-to-liquid ratio of 0.005 g / mL, add 1% polyvinylpyrrolidone dispersant by mass, and then sonicate to obtain a uniform mixture. Immerse the mixture in a chitosan fiber membrane and sonicate.

[0038] ⑤ Remove the chitosan fiber membrane, fix N-TiO2 with 0.5% genipin crosslinking agent by mass, and dry to obtain N-TiO2@CS-#1 fiber membrane.

[0039] Example 2

[0040] ① Mix tetrabutyl titanate and anhydrous ethanol at a volume ratio of 1:4 at room temperature and stir to obtain solution A; mix concentrated nitric acid, anhydrous ethanol and ammonia at a volume ratio of 1:5:5 at room temperature and stir to obtain solution B;

[0041] ② Solution B is added dropwise to solution A and mixed at room temperature. After aging, a white sol is obtained. The sol is dried, urea is added, and the mixture is ground into a white powder. The molar ratio of urea to tetrabutyl titanate is 1:50.

[0042] ③ The white powder was placed in a muffle furnace and calcined at 400°C at a heating rate of 3°C for 3 hours to obtain a light yellow N-TiO2 powder;

[0043] ④ Dissolve N-TiO2 powder in anhydrous ethanol at a material-to-liquid ratio of 0.01 g / mL, add 1% polyvinylpyrrolidone dispersant by mass, and then sonicate to obtain a uniform mixture. Immerse the mixture in a chitosan fiber membrane and sonicate.

[0044] ⑤ Remove the chitosan fiber membrane, fix N-TiO2 with 0.5% genipin crosslinking agent by mass, and dry to obtain N-TiO2@CS-#2 fiber membrane.

[0045] Example 3

[0046] ① Mix tetrabutyl titanate and anhydrous ethanol at a volume ratio of 1:4 at room temperature and stir to obtain solution A; mix concentrated nitric acid, anhydrous ethanol and ammonia at a volume ratio of 1:5:5 at room temperature and stir to obtain solution B;

[0047] ② Solution B is added dropwise to solution A and mixed at room temperature. After aging, a white sol is obtained. The sol is dried, urea is added, and the mixture is ground into a white powder. The molar ratio of urea to tetrabutyl titanate is 1:50.

[0048] ③ The white powder was placed in a muffle furnace and calcined at 400°C at a heating rate of 3°C for 3 hours to obtain a light yellow N-TiO2 powder;

[0049] ④ Dissolve N-TiO2 powder in anhydrous ethanol at a material-to-liquid ratio of 0.02 g / mL, add 1% polyvinylpyrrolidone dispersant by mass, and then sonicate to obtain a uniform mixture. Immerse the mixture in a chitosan fiber membrane and sonicate.

[0050] ⑤ Remove the chitosan fiber membrane, fix N-TiO2 with 0.5% genipin crosslinking agent by mass, and dry to obtain N-TiO2@CS-#3 fiber membrane.

[0051] Example 4

[0052] ① Mix tetrabutyl titanate and anhydrous ethanol at a volume ratio of 1:4 at room temperature and stir to obtain solution A; mix concentrated nitric acid, anhydrous ethanol and ammonia at a volume ratio of 1:5:5 at room temperature and stir to obtain solution B;

[0053] ② Solution B is added dropwise to solution A and mixed at room temperature. After aging, a white sol is obtained. The sol is dried, urea is added, and the mixture is ground into a white powder. The molar ratio of urea to tetrabutyl titanate is 1:50.

[0054] ③ The white powder was placed in a muffle furnace and calcined at 400°C at a heating rate of 3°C for 3 hours to obtain a light yellow N-TiO2 powder;

[0055] ④ Dissolve N-TiO2 powder in anhydrous ethanol at a material-to-liquid ratio of 0.04 g / mL, add 1% polyvinylpyrrolidone dispersant by mass, and then sonicate to obtain a uniform mixture. Immerse the mixture in a chitosan fiber membrane and sonicate.

[0056] ⑤ Remove the chitosan fiber membrane, fix N-TiO2 with 0.5% genipin crosslinking agent by mass, and dry to obtain N-TiO2@CS-#4 fiber membrane.

[0057] To further demonstrate the beneficial effects of the present invention and to better understand it, the following experimental examples further illustrate the technical features disclosed in the present invention, but should not be construed as limiting the present invention. Other improvements made by those skilled in the art based on the above-described invention, without inventive effort, are also considered to fall within the protection scope of the present invention.

[0058] Test case

[0059] This experiment was conducted in a photochemical reaction chamber (product model: CEL-LB70, Beijing Zhongjiao Jinyuan Technology Co., Ltd.) under simulated sunlight using a xenon lamp light source system (product model: CEL-HXF300-S, Beijing Zhongjiao Jinyuan Technology Co., Ltd.). 0.05g of N-TiO2 particles and the aforementioned 6cm diameter N-TiO2@CS air filter membrane were used to perform photocatalysis on 0.3g of juniper pollen collected in Beijing for 0-4h. Samples were taken every 30min during the experiment, and the photocatalyzed pollen was stained with trypan blue. The pollen survival rate was observed under an optical microscope.

[0060] The results showed that the pollen survival rate remained at 90.15% after 4 hours of photocatalytic reaction with N-TiO2 particles. Analysis suggests that the nanoparticles easily aggregated in the reaction system, reducing the effective catalytic sites and resulting in uneven contact with pollen particles, severely limiting their photocatalytic efficiency. Under the same conditions, the pollen survival rate of the N-TiO2@CS air filter membrane decreased sharply to 3.53% after 4 hours of photocatalytic reaction, confirming the success of the strategy of loading N-TiO2 nanoparticles onto a porous chitosan fiber support. This support structure effectively prevents the aggregation of N-TiO2 nanoparticles, fully exposing the active sites; furthermore, the fiber membrane itself exhibits excellent electrostatic adsorption and physical retention of pollen and other particulate matter, significantly increasing the contact opportunity and reaction time between allergens and the catalytically active centers, thus achieving highly efficient synergistic purification.

[0061] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a photocatalytic composite fiber air filter membrane, characterized in that, The preparation steps are as follows: ① Mix titanium source and anhydrous ethanol at room temperature and stir to obtain solution A; mix concentrated nitric acid, anhydrous ethanol and ammonia water at room temperature and stir to obtain solution B; ② Solution B is added dropwise to solution A and mixed at room temperature. After aging, a white sol is obtained. The sol is dried, and a nitrogen source is added and the mixture is ground into a white powder. ③ The white powder was calcined in a muffle furnace to obtain a pale yellow N-TiO2 powder; ④ Dissolve N-TiO2 powder in anhydrous ethanol, add 1-5% dispersant by mass, and then sonicate to obtain a uniform mixture. Immerse the mixture in a chitosan fiber membrane and sonicate. ⑤ Remove the chitosan fiber membrane, fix N-TiO2 with a crosslinking agent at a mass ratio of 0.5~2.0%, and dry to obtain N-TiO2@CS fiber membrane; The volume ratio of titanium source to anhydrous ethanol is 1:4, and the volume ratio of concentrated nitric acid, anhydrous ethanol, and ammonia is 1:5:5; the molar ratio of nitrogen source to titanium source is 1:(50~200); the nitrogen source is selected from one or more combinations of urea, triethylamine, and ammonia; the titanium source is selected from one or more combinations of tetrabutyl titanate, isopropyl titanate, and titanium tetrachloride. In step ③, the calcination parameters are: calcining at 400℃ for 3 hours with a heating rate of 2~5℃. The ratio of N-TiO2 powder dissolved in anhydrous ethanol is 0.005~0.04 g / mL; the dispersant is a high molecular surfactant, specifically one or more combinations of polyvinylpyrrolidone, polyethylene glycol, sodium dodecylbenzenesulfonate, and hexadecyltrimethylammonium bromide.

2. The method for preparing the photocatalytic composite fiber air filter membrane according to claim 1, characterized in that, The crosslinking agent is a non-toxic, natural biological crosslinking agent that can react with the amino groups on the chitosan molecular chain, specifically genipin or tannic acid.

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