A hydrophobically modified cellulose air filter paper and its preparation method and application

Abstract

The application provides a hydrophobic modified cellulose air filter paper and a preparation method and application thereof, and the preparation method comprises the following steps: (1) beating bleached kraft softwood pulp board into bleached kraft softwood pulp; (2) performing mercerization treatment on the bleached kraft softwood pulp under the condition of continuous stirring by using a NaOH solution, then washing the pulp to neutral pH and dehydrating to obtain mercerized softwood pulp; (3) mixing the mercerized softwood pulp and the bleached kraft softwood pulp, then papermaking to form a raw paper; drying the raw paper to obtain a cellulose air filter paper base; (4) dissolving stearic acid in water to obtain a stearic acid emulsion; spraying the stearic acid emulsion to the surface of the cellulose air filter paper base, and drying to obtain the hydrophobic modified cellulose air filter paper. The obtained air filter paper has excellent hydrophobic performance and high mechanical strength, and can effectively remove suspended particulate matters and volatile organic compounds in air.

Description

Technical Field

[0001] This invention relates to the field of air filtration materials technology, specifically to a hydrophobically modified cellulose air filter paper, its preparation method, and its application. Background Technology

[0002] With rapid industrialization and urbanization, air pollution has become increasingly serious, with indoor air pollution (suspended particulate matter and volatile organic compounds) posing a particularly prominent threat to human health due to its insidious and long-term nature. Air filtration materials, as a core component of air purification, directly affect filtration efficiency and lifespan. Traditional cellulose-based air filter paper is widely used due to its advantages such as renewability, biodegradability, and low cost; however, its hydrophilicity leads to a significant decrease in filtration performance in humid environments. Furthermore, physical interception filtration methods cannot effectively remove volatile organic compounds from the air, limiting their application scope.

[0003] In recent years, hydrophobic modification technology has been introduced into the research and development of air filter materials to improve their applicability in complex environments. Stearic acid (SA), as a common hydrophobic modifier, has advantages such as low cost and significant modification effect, and has been widely used in material surface modification. However, existing hydrophobic modification methods are mostly concentrated in chemical vapor deposition or complex coating processes, which have problems such as complex processes, high costs, and difficulty in large-scale production. In addition, the mechanical properties and filtration efficiency of cellulose-based filter paper still need further improvement. Summary of the Invention

[0004] The purpose of this invention is to overcome the problems in the prior art, such as the complex hydrophobic modification process of cellulose-based air filter paper, the insufficient mechanical properties of filter paper prepared from pure silk photochemical fibers, and the inability to effectively remove volatile organic compounds at the same time. This invention provides a hydrophobic modified cellulose air filter paper, its preparation method, and its application. The resulting air filter paper has excellent hydrophobic properties, high mechanical strength, and can effectively remove suspended particulate matter and volatile organic compounds from the air.

[0005] This invention is achieved through the following technical solution: In a first aspect, the present invention provides a method for preparing hydrophobically modified cellulose air filter paper, comprising: (1) Pulping bleached sulfate softwood pulp board into bleached sulfate softwood pulp; (2) The bleached sulfate softwood pulp was treated with NaOH solution under continuous stirring, and then the pulp was washed with water until the pH was neutral and dehydrated to obtain mercerized softwood pulp. (3) After mixing mercerized softwood pulp and bleached sulfate softwood pulp, paper is formed to obtain base paper (CNF); the base paper is dried to obtain cellulose air filter paper substrate; (4) Dissolve stearic acid (SA) in water to obtain stearic acid emulsion; spray the stearic acid emulsion onto the surface of cellulose air filter paper substrate and dry to obtain hydrophobic modified cellulose air filter paper.

[0006] Preferably, in step (1), the bleached sulfate softwood pulp board is first soaked in water for 4-6 hours, and then transferred to a refiner, water is added for refining, the refining time is 2-4 hours, and the beating degree is preferably 35°SR.

[0007] Preferably, in step (2), the concentration of NaOH solution is 5 mol / L, and the ratio of bleached sulfate softwood pulp to NaOH solution is 1 g: 15 mL on an absolute dry basis.

[0008] Preferably, in step (2), the mercerizing treatment temperature is 20~70 ℃ and the time is 30~90 min.

[0009] Preferably, in step (3), 20% to 60% mercerized softwood pulp and 40% to 80% bleached sulfate softwood pulp are mixed and then used to form paper, based on the oven-dry weight and weight percentage.

[0010] Furthermore, in step (3), based on the oven-dry weight and weight percentage, 60% mercerized softwood pulp and 40% bleached sulfate softwood pulp are mixed and then used for papermaking.

[0011] Preferably, in step (4), ZnIn2S4 is dispersed in stearic acid emulsion, and then the stearic acid emulsion is sprayed onto the surface of the cellulose air filter paper substrate and dried to obtain hydrophobic modified cellulose air filter paper.

[0012] Furthermore, the preparation method of ZnIn2S4 is as follows: weigh out zinc source, indium source and sulfur source, dissolve them in water, and carry out hydrothermal reaction of the resulting mixed solution to obtain ZnIn2S4.

[0013] The zinc source, indium source, and sulfur source are ZnCl2, InCl3·4H2O, and thioacetamide, respectively, with a molar ratio of 1 mmol:1 mmol:2 mmol.

[0014] Furthermore, the ratio of ZnIn2S4, stearic acid, and cellulose air filter paper substrate is (0.39~3.13) mg: (0.78~2.34) mg: 1 cm⁻¹. 2 .

[0015] Secondly, the present invention provides a hydrophobically modified cellulose air filter paper obtained by the preparation method described above.

[0016] The hydrophobic angle of the hydrophobic modified cellulose air filter paper is above 130°.

[0017] Thirdly, the present invention provides an application of the hydrophobically modified cellulose air filter paper described above in filtering particulate matter in the air.

[0018] Hydrophobically modified cellulose air filter paper loaded with ZnIn2S4 can also be used for the catalytic degradation of volatile organic compounds in the air.

[0019] Compared with the prior art, the present invention has the following beneficial effects: This invention utilizes mercerization treatment to significantly enhance the crystallinity and surface activity of softwood pulp fibers, optimizing the fiber structure. Combined with stearic acid emulsion spraying modification, this yields cellulose-based air filter paper with excellent hydrophobic properties, achieving a hydrophobic angle exceeding 130°. Further control of the ratio of mercerized to unmercerized softwood pulp optimizes the filter paper's filtration efficiency and mechanical properties, significantly improving its filtration efficiency and durability. The resulting filter paper exhibits wear resistance, high air permeability, and high strength, making it suitable for air filtration in high-humidity environments. This invention, through the synergistic effect of mercerization pretreatment and hydrophobic modification, solves the problem of performance degradation in traditional cellulose filter paper under humid conditions, providing a highly efficient and durable new material for air filtration. Furthermore, the preparation method of this invention is simple, requires no complex equipment, and is low-cost.

[0020] Furthermore, the experimental results of this invention show that the filter paper prepared under different mixing ratios all have excellent filtration performance. Among them, when the ratio of bleached sulfate softwood pulp to mercerized softwood pulp is 6:4, the filter paper has the best mechanical strength and filtration efficiency. The filter paper achieves a PM2.5 filtration efficiency of 98.4%, a hydrophobic angle of 134°, a tensile strength of 23 kPa, an air permeability of 117.77 μm / pa·s, and a tear strength of 1077.42 mN.

[0021] Furthermore, this invention loads a highly active photocatalyst onto cellulose filter paper, achieving efficient and continuous indoor air purification through a dual-functional mechanism of "physical interception and enrichment - photocatalytic degradation." Specifically, a ZnIn2S4-stearic acid emulsion spraying method is used for catalyst immobilization and hydrophobic modification. The resulting air filter paper not only possesses hydrophobicity, enabling it to filter air in humid environments, but the loaded ZnIn2S4 can also catalytically degrade volatile organic compounds, making it suitable for air purification containing volatile organic compounds. Therefore, this invention not only significantly improves the hydrophobic properties of filter paper but also optimizes its air purification efficiency, demonstrating broad application prospects. Attached Figure Description

[0022] 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 some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 The filtration efficiency and pressure drop of the hydrophobic SA@CNF air filter paper in Examples 1-3 are shown.

[0024] Figure 2 The tensile strength of the hydrophobic SA@CNF air filter paper in Examples 1-3 and the ZnIn2S4@SA@CNF air filter paper in Example 4 is given.

[0025] Figure 3 The air permeability of the hydrophobic SA@CNF air filter paper in Examples 1-3 and the ZnIn2S4@SA@CNF air filter paper in Example 4 is given.

[0026] Figure 4 The tear strength is measured for the hydrophobic SA@CNF air filter paper in Examples 1-3 and the ZnIn2S4@SA@CNF air filter paper in Example 4.

[0027] Figure 5 The infrared spectra of the hydrophobic SA@CNF air filter paper in Example 2 and the ZnIn2S4@SA@CNF air filter paper in Example 4 are shown.

[0028] Figure 6 This is a SEM image of the ZnIn2S4@SA@CNF air filter paper in Example 4.

[0029] Figure 7 The filtration efficiency of hydrophobic SA@CNF air filter paper and ZnIn2S4@SA@CNF air filter paper for particulate matter in Example 2 is shown.

[0030] Figure 8 The effect of the loading of catalyst ZnIn2S4 on the photocatalytic degradation of formaldehyde in Examples 4-8.

[0031] Figure 9 The figures show the kinetic curves of the effect of the loading of catalyst ZnIn2S4 on the photocatalytic degradation of formaldehyde in Examples 4-8.

[0032] Figure 10 The degradation efficiency-time curves of five volatile organic compounds by photocatalytic degradation of ZnIn2S4@SA@CNF filter paper in Example 7 are shown.

[0033] Figure 11The kinetic curves for the photocatalytic degradation of five volatile organic compounds by ZnIn2S4@SA@CNF filter paper in Example 7 are shown. Detailed Implementation

[0034] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0035] It should be noted that the process equipment or apparatus not specifically mentioned in the following embodiments are all conventional equipment or apparatus in the art.

[0036] It should be noted that the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to these processes, methods, products, or apparatuses. Furthermore, unless otherwise stated, the numbering of each method step is merely a convenient tool for identifying each method step, and not intended to limit the order of the method steps or define the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention.

[0037] Example 1 (1) Weigh (360±5) g of bleached sulfate softwood pulp board, cut it into small pieces and soak it in 5 L of water for 4 h. Then transfer it to a grinder and add 22 L of water for pulping treatment for 4 h, controlling the pulping degree to 35°SR. Mix the obtained bleached sulfate softwood pulp (on an absolute dry basis) with 5 mol / L NaOH solution in a ratio of 1 g:15 mL, stir in a 50 ℃ constant temperature water bath for 60 min, wash until neutral and dehydrate to obtain mercerized softwood pulp.

[0038] (2) Bleached sulfate softwood pulp and mercerized softwood pulp were mixed in a mass ratio of 8:2 and then paper was formed to obtain the base paper. The paper was then dried in a 60 ℃ drying oven at normal pressure for 2 h to obtain the cellulose air filter paper substrate.

[0039] (3) Dissolve 0.1 g stearic acid (SA) in 50 mL of deionized water and stir at 800 rpm for 1 h at 75 ℃ to prepare a stearic acid emulsion; use a spray gun to uniformly spray the stearic acid emulsion onto the surface of the cellulose air filter paper substrate, controlling the spraying amount to 0.1 g SA corresponding to 32 × 2 cm. 2The surface area of ​​the filter paper was measured, and finally dried at 75 °C for 2 h to obtain hydrophobic SA@CNF air filter paper.

[0040] (4) The mechanical properties of the samples were evaluated by characterizing the tensile strength, air permeability, and tear resistance of the prepared filter paper: Tensile strength test: The tensile strength of the filter paper was tested using a universal testing machine in accordance with the standard GB / T 12914-2018. Air permeability test: The air permeability of the filter paper was tested using an air permeability tester in accordance with the GB / T 5453-1997 standard; Tear test: The tear strength of the filter paper was tested using a tear tester according to the GB / T 455 standard for paper. (5) Place the prepared air filter paper in an air filtration device, introduce air containing particulate matter, control the airflow speed to be 32 L / min, and the initial PM2.5 concentration to be 200 µg / m³. 3 The pressure difference and particulate matter concentration across the filter paper were measured every 10 minutes.

[0041] The results showed that at a relative humidity of 40%, the filter paper achieved a filtration efficiency of 98.0% for PM2.5 within 10 minutes, with a tensile strength of 21 kPa, an air permeability of 42.79 μm / pa·s, and a tear strength of 1260.48 mN.

[0042] Example 2 (1) Weigh (360±5) g of bleached sulfate softwood pulp board, cut it into small pieces and soak it in 5 L of water for 4 h. Then transfer it to a pulper and add 22 L of water for pulping treatment, controlling the pulping degree to 35 °SR. Mix the obtained bleached sulfate softwood pulp (on an absolute dry basis) with 5 mol / L NaOH solution in a mass ratio of 1 g: 15 mL, stir in a 50 ℃ constant temperature water bath for 60 min, wash until neutral and dehydrate to obtain mercerized softwood pulp.

[0043] (2) Bleached sulfate softwood pulp and mercerized softwood pulp were mixed in a ratio of 6:4. The pulp was then uniformly prepared by steps such as loosening, homogenizing and pressing. The pulp was then dried at normal pressure in a drying oven at 60 ℃ for 2 h to obtain cellulose air filter paper substrate.

[0044] (3) Dissolve 0.1 g stearic acid (SA) in 50 mL of deionized water and stir at 800 rpm for 1 h at 75 ℃ to prepare a stearic acid emulsion; use a spray gun to uniformly spray the stearic acid emulsion onto the surface of the cellulose air filter paper substrate, controlling the spraying amount to 0.1 g SA corresponding to 32 × 2 cm. 2 The surface area of ​​the filter paper was measured, and finally dried at 75 °C for 2 h to obtain hydrophobic SA@CNF air filter paper.

[0045] (4) The mechanical properties of the samples were evaluated by characterizing the tensile strength, air permeability, and tear resistance of the prepared filter paper: Tensile strength test: The tensile strength of the filter paper was tested using a universal testing machine in accordance with the standard GB / T 12914-2018. Air permeability test: The air permeability of the filter paper was tested using an air permeability tester in accordance with the GB / T 5453-1997 standard; Tear test: The tear strength of the filter paper was tested using a tear tester according to the GB / T 455 standard for paper. (5) Place the prepared air filter paper in an air filtration device, introduce air containing particulate matter, control the airflow speed to be 32 L / min, and the initial PM2.5 concentration to be 200 µg / m³. 3 The pressure difference and particulate matter concentration across the filter paper were measured every 10 minutes.

[0046] The results showed that at a relative humidity of 40%, the filter paper achieved a filtration efficiency of 98.4% for PM2.5 within 10 minutes, with a tensile strength of 23 kPa, an air permeability of 117.77 μm / pa·s, and a tear strength of 1077.42 mN.

[0047] Example 3 (1) Weigh (360±5) g of bleached sulfate softwood pulp board, cut it into small pieces and soak it in 5 L of water for 4 h. Then transfer it to a pulper and add 22 L of water for pulping treatment, controlling the pulping degree to 35 °SR. Mix the obtained bleached sulfate softwood pulp (on an absolute dry basis) with 5 mol / L NaOH solution at a mass ratio of 1 g: 15 mL, stir in a constant temperature water bath at 50 ℃ for 60 min, wash until neutral and dehydrate to obtain mercerized softwood pulp.

[0048] (2) Bleached sulfate softwood pulp and mercerized softwood pulp were mixed in a ratio of 4:6. The pulp was then uniformly prepared by steps such as loosening, homogenizing and pressing. The pulp was then dried at normal pressure in a drying oven at 60 ℃ for 2 h to obtain cellulose air filter paper substrate.

[0049] (3) Dissolve 0.1 g stearic acid (SA) in 50 mL of deionized water and stir at 800 rpm for 1 h at 75 ℃ to prepare a stearic acid emulsion; use a spray gun to uniformly spray the stearic acid emulsion onto the surface of the cellulose air filter paper substrate, controlling the spraying amount to 0.1 g SA corresponding to 32 × 2 cm. 2 The surface area of ​​the filter paper was measured, and finally dried at 75 °C for 2 h to obtain hydrophobic SA@CNF air filter paper.

[0050] (4) The mechanical properties of the samples were evaluated by characterizing the tensile strength, air permeability, and tear resistance of the prepared filter paper: Tensile strength test: The tensile strength of the filter paper was tested using a universal testing machine in accordance with the standard GB / T 12914-2018. Air permeability test: The air permeability of the filter paper was tested using an air permeability tester in accordance with the GB / T 5453-1997 standard; Tear test: The tear resistance of the filter paper was tested using a tear tester according to the GB / T 455 standard for paper. (5) Place the prepared air filter paper in an air filtration device, introduce air containing particulate matter, control the airflow speed to be 32 L / min, and the initial PM2.5 concentration to be 200 µg / m³. 3 The pressure difference and particulate matter concentration across the filter paper were measured every 10 minutes.

[0051] The results showed that at a relative humidity of 40%, the filter paper achieved a filtration efficiency of 90.2% for PM2.5 within 10 minutes, with a tensile strength of 12 kPa, an air permeability of 177.62 μm / pa·s, and a tear strength of 642.69 mN.

[0052] Example 4 A cellulose air filter paper substrate with a bleached sulfate softwood pulp and mercerized softwood pulp mass ratio of 6:4, as used in Example 2, was prepared by adding 0.025 g of ZnIn2S4 to 100 mL of stearic acid emulsion, dispersing it evenly, and then spraying it onto the surface of the cellulose air filter paper substrate. The spraying amount was controlled to be 0.1 g SA corresponding to a 32 × 2 cm area. 2 The surface area of ​​the filter paper was measured, and finally dried at 75 °C for 2 h to obtain ZnIn2S4@SA@CNF air filter paper with a hydrophobic angle of 137°.

[0053] Example 5 A cellulose air filter paper substrate with a bleached sulfate softwood pulp and mercerized softwood pulp mass ratio of 6:4, as described in Example 2, was used. 0.05 g of ZnIn2S4 was added to 100 mL of stearic acid emulsion, dispersed evenly, and then sprayed onto the surface of the cellulose air filter paper substrate. The spraying amount was controlled to be 0.1 g SA corresponding to a 32 × 2 cm area. 2 The surface area of ​​the filter paper was measured, and finally dried at 75 °C for 2 h to obtain ZnIn2S4@SA@CNF air filter paper with a hydrophobic angle of 130°.

[0054] Example 6 A cellulose air filter paper substrate with a bleached sulfate softwood pulp and mercerized softwood pulp mass ratio of 6:4, as described in Example 2, was used. 0.10 g of ZnIn2S4 was added to 100 mL of stearic acid emulsion, dispersed evenly, and then sprayed onto the surface of the cellulose air filter paper substrate. The spraying amount was controlled to be 0.1 g SA corresponding to a 32 × 2 cm area. 2 The surface area of ​​the filter paper was measured, and finally dried at 75 °C for 2 h to obtain ZnIn2S4@SA@CNF air filter paper with a hydrophobic angle of 134°.

[0055] Example 7 CNF filter paper substrate with a mass ratio of bleached sulfate softwood pulp and mercerized softwood pulp of 6:4, as used in Example 2, was sprayed onto the surface of the cellulose air filter paper substrate after adding 0.15 g of ZnIn2S4 to 100 mL of stearic acid emulsion and dispersing it evenly. The spraying amount was controlled to be 0.1 g SA corresponding to 32 × 2 cm. 2 The surface area of ​​the filter paper was measured, and finally dried at 75 °C for 2 h to obtain ZnIn2S4@SA@CNF air filter paper with a hydrophobic angle of 134°.

[0056] Example 8 A cellulose air filter paper substrate with a bleached sulfate softwood pulp and mercerized softwood pulp mass ratio of 6:4, as described in Example 2, was used. 0.20 g of ZnIn2S4 was added to 100 mL of stearic acid emulsion, dispersed evenly, and then sprayed onto the surface of the cellulose air filter paper substrate. The spraying amount was controlled to be 0.1 g SA corresponding to a 32 × 2 cm area. 2 The surface area of ​​the filter paper was measured, and finally dried at 75 °C for 2 h to obtain ZnIn2S4@SA@CNF air filter paper with a hydrophobic angle of 139°.

[0057] like Figure 1The figures show the filtration efficiency and pressure drop of the filter paper in Examples 1-3 for particulate matter. Filtration efficiency is an important indicator of air filter paper performance, directly affecting its ability to remove fine particulate matter. When the mass ratio of bleached sulfate softwood pulp to mercerized softwood pulp is 8:2, the PM2.5 filtration efficiency is 98.0%; when the mass ratio is 6:4, the PM2.5 filtration efficiency is 98.4%; and when the mass ratio is 4:6, the PM2.5 filtration efficiency is 90.2%. Overall, the filtration efficiency of the hydrophobic SA@CNF filter paper for particulate matter first increases and then decreases with the increase of the mercerized softwood pulp ratio, while the filtration pressure drop decreases with the increase of the mass ratio of bleached sulfate softwood pulp to mercerized softwood pulp. This indicates that mercerized softwood pulp can significantly reduce the filtration resistance of filter paper, decrease filtration energy consumption, and has the advantages of being green, environmentally friendly, and highly efficient. Overall, under the condition of a 6:4 mass ratio of bleached sulfate softwood pulp to mercerized softwood pulp, the optimized fiber distribution and pore structure improve the airflow path and enhance particle capture capacity.

[0058] like Figure 2 As shown, the hydrophobic SA@CNF filter paper in Example 2 exhibits higher tensile strength than that in Examples 1 and 3. Typically, mercerized softwood pulp fibers show decreased strength, and the tensile strength of the paper increases with the increase of the content of unmercerized bleached sulfate softwood pulp. The higher tensile strength of Example 2 is attributed to the good bonding between fibers and the uniform distribution of the material, thereby enhancing the tensile properties of the filter paper. This results in greater stability and durability of the filter paper under complex operating conditions.

[0059] like Figure 3 As shown, air permeability significantly improves with increasing mercerized softwood pulp proportion. Mercerization makes the fiber surface smoother and increases twist, leading to larger pores between fibers after papermaking. This factor is closely related to the air filtration process, representing lower air filtration resistance.

[0060] like Figure 4 As shown, the tear strength of filter paper is an important indicator for evaluating its resistance to tearing. In Example 2, the hydrophobic SA@CNF filter paper with a 6:4 mass ratio of bleached sulfate softwood pulp to mercerized softwood pulp exhibited a tear strength test value of 1077.525 mN, demonstrating excellent performance. Further increasing the proportion of mercerized softwood pulp (Example 3) resulted in a significant decrease in the tear strength value (642.69 mN) due to the reduced fiber strength caused by mercerization treatment. Compared to other ratios, the hydrophobic SA@CNF filter paper of Example 2 more effectively resisted tearing under external forces during processing, installation, and actual use, demonstrating superior durability.

[0061] Figures 2-4The tensile strength, air permeability, and tear strength of the ZnIn2S4@SA@CNF air filter paper were shown. The stress index of the filter paper loaded with ZnIn2S4 catalyst was higher than that of the hydrophobic SA@CNF filter paper in Examples 1-3. The air permeability was slightly reduced due to the partial network penetration of particulate matter being blocked, and the tear strength was also slightly reduced. Overall, this shows that the ZnIn2S4@SA@CNF air filter paper has good mechanical properties.

[0062] like Figure 5 The image shows the Fourier transform infrared (FTIR) spectrum of the ZnIn2S4@SA@CNF air filter paper. The image reveals characteristic peaks of the key components, indicating that the two components are fully bonded.

[0063] like Figure 6 The image shown is a scanning electron microscope (SEM) image of ZnIn2S4@SA@CNF air filter paper. As can be seen from the image, the cellulose air filter paper substrate material is composed of entangled and interwoven fibers, and spherical ZnIn2S4 particles are uniformly covered on the surface of the fibers, indicating that they are successfully loaded onto the cellulose air filter paper substrate.

[0064] like Figure 7 As shown, the ZnIn2S4@SA@CNF air filter paper exhibits higher efficiency in capturing PM 0.3~10 particles than the hydrophobic SA@CNF air filter paper in Example 2, with a particularly significant improvement in PM 0.3~0.5 particles, and a filtration efficiency of up to 100% for PM2.5. This indicates that the hierarchical pore structure after loading ZnIn2S4 nanoparticles effectively enhances the filtration performance for particulate matter.

[0065] like Figure 8 As shown, the photocatalytic performance of the ZnIn2S4@SA@CNF air filter paper in Examples 4-8 was evaluated using a xenon lamp system under simulated solar radiation conditions. Formaldehyde at an initial concentration of 200 ppm was used as the target pollutant for photocatalytic degradation. The dark reaction time was 40 min before the lamp was turned on, and samples were taken every 40 min. Figure 8 It can be seen that the removal rate of gaseous formaldehyde significantly increases with the increase of catalyst dosage, but the catalytic efficiency gradually stabilizes when the catalyst dosage reaches 150 mg (Example 7). However, excessive photocatalyst may block light and hinder many photocatalyst particles from participating in the reaction, leading to pollutant saturation. Increasing the catalyst loading can increase its contact area with the target pollutant due to the presence of more active sites. However, further increasing the catalyst dosage does not significantly improve its degradation efficiency because excessive formaldehyde will deposit on the photocatalyst surface, interfering with the catalytic activity of the active sites. Combined with the kinetic analysis of the reaction ( Figure 9The optimal loading of the photocatalyst ZnIn2S4 was determined to be 150 mg.

[0066] like Figure 10 As shown, the photocatalytic performance of the ZnIn2S4@SA@CNF air filter paper in Example 7 was evaluated using a xenon lamp system under simulated solar radiation conditions. Formaldehyde, benzene, toluene, p-xylene, and styrene (initial concentration 200 ppm) were used as target pollutants for photocatalytic degradation. The lamp was turned on after a 40-minute dark reaction period, and samples were taken every 40 minutes. Within 160 minutes, the degradation rates of the target pollutants by the ZnIn2S4@SA@CNF air filter paper reached 92.6%, 89.3%, 91.4%, 88.2%, and 91.6%, respectively. Figure 11 As shown, the corresponding degradation rates are 0.01193 min. -1 0.01078 min -1 0.01177min -1 0.01133min -1 0.0132min -1 It is evident that the prepared ZnIn2S4@SA@CNF air filter paper possesses high photocatalytic activity and adaptability to target pollutants.

[0067] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of this invention.

Claims

1. A method for preparing hydrophobically modified cellulose air filter paper, characterized in that, include: (1) Pulping bleached sulfate softwood pulp board into bleached sulfate softwood pulp; (2) The bleached sulfate softwood pulp was treated with NaOH solution under continuous stirring to obtain mercerized softwood pulp; (3) After mixing mercerized softwood pulp and bleached sulfate softwood pulp, paper is formed to obtain base paper; the base paper is dried to obtain cellulose air filter paper substrate; (4) Dissolve stearic acid in water to obtain stearic acid emulsion; spray the stearic acid emulsion onto the surface of cellulose air filter paper substrate and dry to obtain hydrophobic modified cellulose air filter paper.

2. The method for preparing hydrophobically modified cellulose air filter paper according to claim 1, characterized in that, In step (2), the mercerizing treatment temperature is 20~70 ℃ and the time is 30~90 min.

3. The method for preparing hydrophobically modified cellulose air filter paper according to claim 1, characterized in that, In step (3), based on the oven-dry weight and weight percentage, 20%~60% mercerized softwood pulp and 40%~80% bleached sulfate softwood pulp are mixed and then used for papermaking.

4. The method for preparing hydrophobically modified cellulose air filter paper according to claim 3, characterized in that, In step (3), based on the oven-dry weight and weight percentage, 60% mercerized softwood pulp and 40% bleached sulfate softwood pulp are mixed and then used for papermaking.

5. The method for preparing hydrophobically modified cellulose air filter paper according to claim 1, characterized in that, In step (4), ZnIn2S4 is dispersed in stearic acid emulsion, and then the stearic acid emulsion is sprayed onto the surface of cellulose air filter paper substrate and dried to obtain hydrophobic modified cellulose air filter paper.

6. The method for preparing hydrophobically modified cellulose air filter paper according to claim 5, characterized in that, The ratio of ZnIn2S4, stearic acid, and cellulose air filter paper substrate is (0.39~3.13) mg: (0.78~2.34) mg: 1 cm⁻¹ 2 .

7. Hydrophobic modified cellulose air filter paper obtained by the preparation method according to any one of claims 1 to 6.

8. The hydrophobically modified cellulose air filter paper according to claim 7, characterized in that, Its hydrophobic angle is above 130°.

9. The application of the hydrophobically modified cellulose air filter paper according to claim 7 in filtering particulate matter in the air.

10. The application of the hydrophobically modified cellulose air filter paper obtained by the preparation method according to any one of claims 5 to 6 in the catalytic degradation of volatile organic compounds in the air.

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