Modified glass fiber filter material for oil-solid two-phase particle air filtration and preparation method thereof

Abstract

The application belongs to the technical field of oil-solid two-phase particle filtration, and particularly relates to a modified glass fiber filter material for oil-solid two-phase particle air filtration and a preparation method thereof. The modified glass fiber filter material is obtained by depositing a modified nano-silica solution on the surface of the glass fiber filter material through an impregnation method; wherein the modified nano-silica is obtained by modifying nano-silica with a silane coupling agent. The modified nano-silica is obtained by grafting a functional group with lipophilic properties on the surface of the nano-silica through the silane. The modified nano-silica is added to the surface of the filter material to change the roughness of the filter material surface, which changes the wettability of the filter material from two aspects, realizes the separation of oil and solid particles deposited on the filter material, quickly transports the oil liquid accumulated on the filter material surface to the inside of the filter material, enhances the flow capacity of the oil liquid on the filter fiber, inhibits the formation of an oil film, and reduces the growth rate of the pressure drop in the filtration process.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of oil-solid two-phase particle filtration, and particularly relates to a modified glass fiber filter material for oil-solid two-phase particle air filtration and a preparation method thereof. BACKGROUND

[0002] In the industry of mechanical processing and metal rolling, a large amount of fine oil-solid two-phase particles are often generated due to the evaporation and condensation of metal processing liquid and the splashing of workpiece debris, as shown in the following formula (1). Figure 1 The migration and movement of oil mist and solid particles in the workshop are accompanied by complex particle collision and mixing processes, and part of the oil mist will also condense on the solid as a condensation nucleus. Finally, an oil-solid two-phase particle distribution system is formed in the workshop, with oil phase as the main component and solid particles as the accompanying component. These particles have the characteristics of small particle size, high concentration and complex chemical composition, and after being inhaled into the human body, they can deposit in the deep part of the respiratory tract and cause respiratory tract infection, pneumonia and even cancer and other diseases, which seriously endanger the health of human body and the quality of the environment.

[0003] The most important means for high-efficiency purification of oil mist particles in existing research is filtration purification equipment, which uses the inertial interception of fiber materials and the diffusion of particles to capture pollutants in the gas flow, thereby achieving the purpose of purifying waste gas. According to the type and porosity of the fiber material, the filtration equipment can be divided into five types: primary efficiency, medium efficiency, medium-high efficiency, sub-high efficiency and high efficiency filters. For the industry of mechanical processing, etc., due to the small particle size (generally less than 2.5 microns), high-efficiency filters are often used for purification. However, the low porosity of high-efficiency filters leads to high purification resistance and high energy consumption. Moreover, when removing oil-solid two-phase particles, the adhesion of the two-phase particles increases due to their mixing, which easily causes adhesion on the windward surface, thereby significantly increasing the filtration resistance, and more seriously, even damaging the filter material, resulting in energy and economic losses.

[0004] Therefore, in order to effectively improve the efficiency of high-efficiency purifiers for oil-solid two-phase fine particles, the surface modification method is considered to improve the wettability of the filter material, increase the oil transport capacity of the filter material, and inhibit the accumulation of oil on the windward surface, so as to achieve the purpose of reducing the running resistance and prolonging the service life. It provides a new research path for the strategic goal of national energy saving and emission reduction and green production. SUMMARY

[0005] The present application aims to provide a modified glass fiber filter material for oil-solid two-phase particle air filtration, which overcomes the above technical problems in the prior art.

[0006] The present application aims to provide a preparation method of a modified glass fiber filter material for oil-solid two-phase particle air filtration.

[0007] To this end, the technical solutions provided by the present application are as follows:

[0008] A modified glass fiber filter material for oil-solid two-phase particulate air filtration is obtained by depositing a modified nano-silica solution onto the surface of the glass fiber filter material using an impregnation method.

[0009] Among them, modified nano-silica is obtained by modifying nano-silica with a silane coupling agent.

[0010] The silane coupling agent is methyltrimethoxysilane, n-octyltriethoxysilane, dodecyltriethoxysilane, isobutyltriethoxysilane, or KH560.

[0011] The modified nano-silica solution is obtained by dissolving the modified nano-silica in anhydrous ethanol.

[0012] The mass concentration of the modified nano-silica solution is 0.01-0.1%.

[0013] A method for preparing a modified glass fiber filter material for oil-solid two-phase particulate air filtration includes the following steps:

[0014] Step 1) Prepare modified nano-silica powder;

[0015] Step 2) Prepare a modified nano-silica solution;

[0016] Step 3) Prepare modified glass fiber filter material.

[0017] Step 1) The specific method for preparing modified nano-silica powder is as follows: using nano-silica with a particle size of 15-30nm as the solute, and anhydrous ethanol and deionized water in a ratio of 3-4:1 as the solvent, a 1-3wt% nano-silica suspension is prepared. The suspension is stirred with a constant temperature magnetic stirrer and heated to 65-75℃. The pH is adjusted to 3-4 with anhydrous oxalic acid, and 3-4vol% silane coupling agent is added dropwise. The suspension is reacted at a constant temperature of 65-75℃ for 5.5-6.5h to obtain the modified nano-silica suspension.

[0018] After the modified nano-silica suspension is naturally dried, it is filtered under reduced pressure in several stages and dried in a constant temperature drying oven at 100-120℃ for 1.5-2 hours to obtain solid modified nano-silica. After coarsely grinding the solid modified nano-silica with a mortar and pestle, it is added to a nano-pulverizer and pulverized to 15-30nm to obtain modified nano-silica.

[0019] Step 2) The specific process for preparing the modified nano silica solution is as follows: Dissolve the modified nano silica in anhydrous ethanol and stir at a constant temperature of 65-75℃ for 0.3-0.5h to obtain the solution.

[0020] Step 3) The specific process for preparing modified glass fiber filter material is as follows: First, immerse the glass fiber filter material in a 50 vol% ethanol solution at 70-80℃ for 15-20 minutes to wash away the adhesive and dust on the surface of the filter material. Then, dry the washed glass fiber filter material at a constant temperature of 100-120℃ for 1.5-2 hours. Finally, immerse it in a modified nano-silica solution for 20-30 minutes and air dry it naturally for 24 hours to obtain the modified glass fiber filter material.

[0021] The beneficial effects of this invention are:

[0022] The modified glass fiber filter material for oil-solid two-phase particulate air filtration provided by this invention is obtained by grafting lipophilic functional groups onto the surface of nano-silica with silane to obtain modified nano-silica. Modified nano-silica is then added to the surface of the filter material to change the surface roughness of the filter material. This changes the wettability of the filter material from two aspects, enhances the flowability of oil on the filter fibers, inhibits the formation of oil film, and achieves the purpose of reducing the operating resistance of the filter material.

[0023] The modified glass fiber filter media of this invention has excellent oil diffusion performance, which can separate oil deposited on the filter media from solid particles, quickly transport the oil accumulated on the surface of the filter media to the interior of the filter media, inhibit the formation of liquid film, and reduce the rate of pressure drop increase during filtration. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of particle generation during the cutting process;

[0025] Figure 2 This is a schematic diagram of the oil-solid two-phase particle deposition on the surface of existing glass fiber filter media and the modified glass fiber filter media of this invention.

[0026] Figure 3 This is a schematic diagram illustrating the principle of nano-silica modification.

[0027] Figure 4 This is a schematic diagram illustrating the principle of glass fiber filter material modification in this invention;

[0028] Figure 5 The curves show the pressure drop of modified glass fiber filter media prepared with modified silica solutions of different concentrations as a function of time.

[0029] Figure 6 The curves show the filtration efficiency of modified glass fiber filter media prepared with modified silica solutions of different concentrations for particles of different sizes.

[0030] Figure 7 These are pressure drop curves over time for modified glass fiber filter media prepared with different silanes;

[0031] Figure 8These are the efficiency variation curves of modified glass fiber filter media prepared with different silanes;

[0032] Figure 9 These are the dust holding capacity variation curves of modified glass fiber filter media prepared with different silanes;

[0033] Figure 10 These are infrared spectra of nano-silica modified with different silane coupling agents;

[0034] Figure 11 These are the thermogravimetric curves of nano-silica modified with different silane coupling agents. Detailed Implementation

[0035] The following specific embodiments 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.

[0036] Exemplary embodiments of the present invention will now be described with reference to the accompanying drawings. However, the present invention may be embodied in many different forms and is not limited to the embodiments described herein. These embodiments are provided to fully and completely disclose the invention and to fully convey its scope to those skilled in the art. The terminology used in the exemplary embodiments illustrated in the drawings is not intended to limit the invention.

[0037] Unless otherwise stated, the terms used herein (including technical terms) have their common meaning as understood by one of ordinary skill in the art. Furthermore, it is understood that terms defined in commonly used dictionaries should be understood to have a meaning consistent with the context of their relevant field, and not to be interpreted as having an idealized or overly formal meaning.

[0038] Example 1

[0039] This invention provides a modified glass fiber filter material for oil-solid two-phase particulate air filtration, which is obtained by depositing a modified nano-silica solution onto the surface of the glass fiber filter material through an impregnation method;

[0040] Among them, modified nano-silica is obtained by modifying nano-silica with a silane coupling agent.

[0041] The surface wettability of filter media depends on the surface energy of the solid and the surface tension of the liquid. The greater the surface energy of the solid, the easier it is to be wetted by the liquid. The surface energy of glass fiber filter media is determined by both the surface chemical composition and microstructure. Therefore, the main methods to change the wettability of filter media are: 1. chemical surface modification, 2. constructing a rough surface. To achieve the change of filter media wettability through the above two methods, the modified glass fiber filter media for oil-solid two-phase particulate air filtration provided by this invention is obtained by grafting lipophilic functional groups onto the surface of nano-silica with silane to obtain modified nano-silica. Modified nano-silica is then added to the surface of the filter media to change the surface roughness. The resulting modified glass fiber filter media is a superlipophilic material with excellent oil diffusion properties, such as... Figure 2 As shown, it can separate oil deposited on the filter media from solid particles, quickly transport the oil accumulated on the surface of the filter media to the interior of the filter media, inhibit the formation of liquid film, and reduce the rate of pressure drop increase during filtration.

[0042] Example 2

[0043] Based on Example 1, this example provides a modified glass fiber filter material for oil-solid two-phase particulate air filtration, wherein the silane coupling agent is methyltrimethoxysilane, n-octyltriethoxysilane, dodecyltriethoxysilane, isobutyltriethoxysilane, or KH560.

[0044] The principle of nano-silica modification in this invention:

[0045] like Figure 3 As shown, ① under acidic conditions, silane hydrolyzes three Si-OC2H5 groups into Si-OH bonds, and the Si-OH groups undergo dehydration condensation to form siloxane oligomers containing Si-OH groups. ② The hydroxyl groups (Si-OH) in the siloxane oligomers form hydrogen bonds with the hydroxyl groups (-OH) on the surface of nano-silica. During the heating and curing process, a dehydration reaction occurs, forming covalent bonds with the nano-silica. ③ One silanol group in the silane molecule covalently bonds with the surface of nano-silica, while the other two silanol groups condense with or become free from the silanol groups in other silanes.

[0046] Example 3

[0047] Based on Example 1, this example provides a modified glass fiber filter material for oil-solid two-phase particulate air filtration, wherein the modified nano-silica solution is obtained by dissolving the modified nano-silica in anhydrous ethanol.

[0048] Schematic diagram of filter media modification principle. Modified nano-silica is dissolved in anhydrous ethanol to obtain a modified solution. The modified nano-silica is then deposited onto the filter media surface using an impregnation method, thus simultaneously altering the surface roughness and performing surface chemical modification. For example... Figure 4 As shown.

[0049] Example 4

[0050] This embodiment provides a method for preparing modified glass fiber filter media for oil-solid two-phase particulate air filtration, including the following steps:

[0051] Step 1) Prepare modified nano-silica powder;

[0052] Step 2) Prepare a modified nano-silica solution;

[0053] Step 3) Prepare modified glass fiber filter material.

[0054] Step 1) The specific method for preparing modified nano-silica powder is as follows: using nano-silica with a particle size of 15-30nm as the solute, and anhydrous ethanol and deionized water in a ratio of 3-4:1 as the solvent, a 1-3wt% nano-silica suspension is prepared. The suspension is stirred with a constant temperature magnetic stirrer and heated to 65-75℃. The pH is adjusted to 3-4 with anhydrous oxalic acid, and 3-4vol% silane coupling agent is added dropwise. The suspension is reacted at a constant temperature of 65-75℃ for 5.5-6.5h to obtain the modified nano-silica suspension.

[0055] After the modified nano-silica suspension is naturally dried, it is filtered under reduced pressure in several stages and dried in a constant temperature drying oven at 100-120℃ for 1.5-2 hours to obtain solid modified nano-silica. After coarsely grinding the solid modified nano-silica with a mortar and pestle, it is added to a nano-pulverizer and pulverized to 15-30nm to obtain modified nano-silica.

[0056] Step 2) The specific process for preparing the modified nano silica solution is as follows: Dissolve the modified nano silica in anhydrous ethanol and stir at a constant temperature of 65-75℃ for 0.3-0.5h to obtain the solution.

[0057] Step 3) The specific process for preparing modified glass fiber filter material is as follows: First, immerse the glass fiber filter material in a 50 vol% ethanol solution at 70-80℃ for 15-20 minutes to wash away the adhesive and dust on the surface of the filter material. Then, dry the washed glass fiber filter material at a constant temperature of 100-120℃ for 1.5-2 hours. Finally, immerse it in a modified nano-silica solution for 20-30 minutes and air dry it naturally for 24 hours to obtain the modified glass fiber filter material.

[0058] Example 5

[0059] Based on Example 4, this example provides a modified glass fiber filter material for oil-solid two-phase particulate air filtration. First, modified nano-silica powder is prepared. Using 15nm nano-silica as the solute and anhydrous ethanol and deionized water in a 3:1 ratio as the solvent, a 2wt% nano-silica suspension is prepared. The suspension is stirred using a constant-temperature magnetic stirrer and heated to 70°C. The pH is adjusted to 3-4 with anhydrous oxalic acid, and 3vol% silane coupling agent is slowly added dropwise. The reaction is carried out at 70°C for 5.5 hours to obtain the modified nano-silica suspension. After naturally drying the modified nano-silica suspension, it is filtered under reduced pressure in stages and dried in a 120°C constant-temperature drying oven for 2 hours to obtain solid modified nano-silica. The solid modified nano-silica is coarsely ground using a mortar and pestle and then added to a nano-pulverizer to pulverize it to 15nm, obtaining the modified nano-silica.

[0060] Then, a modified solution was prepared. 0.03 wt% modified nano-silica was dissolved in anhydrous ethanol and stirred at a constant temperature of 70 °C for 0.5 h to obtain a superoleophilic modified nano-silica solution.

[0061] Finally, superoleophilic modified glass fiber filter media was prepared. The original filter media used in this embodiment was glass fiber filter paper produced by Chongqing Zaisheng Technology Co., Ltd., and the relevant parameters are shown in Table 1.

[0062] Table 1 Performance parameters of filter materials

[0063]

[0064] The original glass fiber filter material was immersed in a 50 vol% ethanol solution at 70°C for 15 minutes to wash off the adhesive and dust on the surface of the filter material. The washed glass fiber filter material was then dried at a constant temperature of 120°C for 2 hours. After that, it was immersed in a modified nano silica solution for 20 minutes and then air-dried naturally for 24 hours to obtain a super oleophilic glass fiber filter material.

[0065] Example 6

[0066] The concentration of the modified nano-silica solution directly affects the surface roughness of the filter material. The chain length of the silane coupling agent and the functional groups on the non-coupling side affect the roughness and surface modification of the filter material, respectively. Therefore, this embodiment conducts the following experiments to investigate the effects of the concentration of the modified nano-silica solution and different silane coupling agents.

[0067] The experimental setup and specific testing procedures are detailed in patent CN202222856399.6. Oil-solid two-phase particles were used as the pollution source in the experiment, with a concentration of 300 mg / m³. 3 The oil phase accounts for 80%, and the filtration velocity is 0.12 m / s.

[0068] This invention is based on the National Natural Science Foundation of China project, project number 52478104, titled "Morphological Evolution Mechanism and Efficiency Enhancement and Drag Reduction Method of Oil-Solid Particles in Self-Circulating Ventilation and Purification Process".

[0069] I. Modified nano-silica solutions at different concentrations

[0070] Following the preparation process in Example 5, modified nano-silica solutions with mass concentrations of 0.01%, 0.03%, 0.05%, and 0.1% were prepared, resulting in four types of superoleophilic modified glass fiber filter materials prepared from the modified nano-silica solutions of different concentrations. The silane coupling agent used in all cases was n-octyltriethoxysilane.

[0071] The resistance change curves of the four filter media were measured respectively, and the results are as follows: Figure 5 As shown, it can be observed that when the concentration of the modified solution is 0.03%, the filter media exhibits the slowest rate of resistance increase and the longest service life.

[0072] Efficiency Study of Superoleophilic Filter Materials Prepared from Modified Nano-Silica Solutions of Different Concentrations Figure 6 As shown in the figure (from left to right: TPM, 0.3-1μm, 1-5μm, >5μm), for particles >1μm, the filter media modified with a 0.03wt% solution exhibits the highest initial efficiency. Specifically, the initial efficiency of TPM (all particle sizes >0.3μm) is 0.9–7.1% higher than other filter media. The final filtration efficiency is relatively similar. For particles <1μm, the filtration efficiency is higher when the modified solution concentration is >0.05wt%, mainly because the increased concentration of the modified solution reduces the pore size within the filter media, making it easier for smaller particles to be captured.

[0073] II. Types of Silane Coupling Agents. Five different silane coupling agents were selected for the modification of nano-silica; their names and characteristics are shown in Table 2. Superoleophilic glass fiber filter materials were prepared by modifying nano-silica with the following five silane coupling agents. Infrared spectra of nano-silica modified with different silane coupling agents are shown below. Figure 10 As shown.

[0074] 1100, 800, 465cm -1 The peaks at these locations correspond to the Si-O-Si and Si-O bond characteristics of the silicon dioxide structure, and the peak shape variation reflects the degree of surface modification. (2800–3000 cm⁻¹) -1 The region is the characteristic region of the CH stretching vibration peak. The different peak shapes are due to the differences in CH vibration caused by the introduction of alkyl chains of different lengths and structures by different silanes (especially evident in samples 2 and 3). 3200–3600 cm⁻¹ -1The region represents the stretching vibration peak of hydroxyl (-OH), which is more pronounced in unmodified silica. This is because the silane modification process consumes surface hydroxyl groups by forming silicon-oxygen bonds (Si-O-Si).

[0075] Thermogravimetric curves are as follows Figure 11 As shown, two weight loss steps are displayed. In the range of 50–150 °C, the weight of unmodified nano-silica decreases sharply, mainly due to the adsorption of water on the surface of silica. Since the surface of modified nano-silica is hydrophobic, the weight loss in this temperature range is less than that of unmodified nano-silica. Figure 11 In the middle, looking from the far right, from top to bottom, are the original filter material, silane 1, silane 4, silane 2, silane 5, and silane 3.

[0076] The weight loss is more pronounced in the 200–600℃ range, and the thermogravimetric curves of nano-silica modified with different silanes show significant differences. This is mainly due to the loss of the organosilane layer, and the longer the silane chain, the greater the weight loss. Therefore, comprehensive analysis of infrared spectroscopy and thermogravimetric curves confirms the successful grafting modification of nano-silica.

[0077] The experiment used oil-solid two-phase particles as the pollution source, with a concentration of 300 mg / m³. 3 With an oil phase content of 80% and a filtration velocity of 0.12 m / s, the resistance and efficiency changes of five filter media (all obtained by impregnation in a 0.03 wt% modified nano-silica solution for 20 min) were tested. The results are as follows: Figure 7 .

[0078] Table 2 Selection of Silane Coupling Agents

[0079]

[0080] Experimental results show that the modified glass fiber exhibits varying degrees of reduced resistance compared to the original filter media. The lifespan of the filter media modified with non-polar functional groups is longer than that modified with polar functional groups. At 0.03 wt%, shorter chains generally have a longer lifespan than longer chains, with the optimal chain length being n-octyltriethoxysilane, which increases the lifespan by 71% compared to the original filter media. Two non-polar methyl functional groups do not offer an advantage over a single methyl functional group.

[0081] Efficiency Study of Superoleophilic Modified Glass Fiber Filter Media Prepared with Different Silanes, as shown in the following figure Figure 8As shown. For particles >1μm, the filtration efficiency of the modified filter media did not change significantly compared to the unmodified media (-1.9% to 6.2%). Specifically, the initial and final filtration efficiencies of the silane 2-modified filter media increased by 3.4% and 1.6%, respectively. For particles <1μm, the initial filtration efficiency of the modified filter media was improved to varying degrees compared to the unmodified media. Specifically, the initial filtration efficiency of the silane 1-modified filter media increased by 15.6% compared to the unmodified media, and the final filtration efficiency of the silane 2-modified filter media increased by approximately 1.6% compared to the unmodified media.

[0082] like Figure 9 As shown, the dust holding capacity of the modified filter media is improved to varying degrees compared with the original filter media. Among them, the dust holding capacity of silane 2 and 4 is increased by 30.2% and 32.6%, respectively.

[0083] In summary, the modified glass fiber filter media obtained by this invention can separate oil deposited on the filter media from solid particles, rapidly transport oil accumulated on the surface of the filter media into the interior of the filter media, enhance the flow capacity of oil on the filter fibers, inhibit the formation of oil film, and reduce the rate of pressure drop increase during filtration.

[0084] The above examples are merely illustrative of the present invention and do not constitute a limitation on the scope of protection of the present invention. All designs that are the same as or similar to the present invention are within the scope of protection of the present invention.

Claims

1. A modified glass fiber filter material for oil-solid two-phase particulate air filtration, characterized in that: The modified nano-silica solution was deposited onto the surface of glass fiber filter material by an impregnation method; the mass concentration of the modified nano-silica solution was 0.01-0.1%. The modified nano-silica is obtained by modifying nano-silica with a silane coupling agent, and the particle size of the modified nano-silica is 15-30 nm. The silane coupling agent is methyltrimethoxysilane, n-octyltriethoxysilane, dodecyltriethoxysilane, or isobutyltriethoxysilane.

2. The modified glass fiber filter material for oil-solid two-phase particulate air filtration according to claim 1, characterized in that: The modified nano-silica solution is obtained by dissolving the modified nano-silica in anhydrous ethanol.

3. The method for preparing a modified glass fiber filter material for oil-solid two-phase particulate air filtration according to claim 1 or 2, characterized in that: Includes the following steps: Step 1) Prepare modified nano-silica powder; Step 2) Prepare a modified nano-silica solution; Step 3) Prepare modified glass fiber filter material.

4. The method for preparing a modified glass fiber filter material for oil-solid two-phase particulate air filtration according to claim 3, characterized in that: Step 1) The specific method for preparing modified nano-silica powder is as follows: using nano-silica with a particle size of 15-30nm as the solute, and anhydrous ethanol and deionized water in a ratio of 3-4:1 as the solvent, a 1-3wt% nano-silica suspension is prepared. The suspension is stirred with a constant temperature magnetic stirrer and heated to 65-75℃. The pH is adjusted to 3-4 with anhydrous oxalic acid, and 3-4 vol% silane coupling agent is added dropwise. The suspension is reacted at a constant temperature of 65-75℃ for 5.5-6.5h to obtain the modified nano-silica suspension. After the modified nano-silica suspension is naturally dried, it is filtered under reduced pressure in several stages and dried in a constant temperature drying oven at 100-120℃ for 1.5-2 hours to obtain solid modified nano-silica. After coarsely grinding the solid modified nano-silica with a mortar and pestle, it is added to a nano-pulverizer and pulverized to 15-30nm to obtain modified nano-silica.

5. The method for preparing a modified glass fiber filter material for oil-solid two-phase particulate air filtration according to claim 3, characterized in that: Step 2) The specific process for preparing the modified nano silica solution is as follows: Dissolve the modified nano silica in anhydrous ethanol and stir at a constant temperature of 65-75℃ for 0.3-0.5h to obtain the solution.

6. The method for preparing a modified glass fiber filter material for oil-solid two-phase particulate air filtration according to claim 3, characterized in that: Step 3) The specific process for preparing modified glass fiber filter material is as follows: First, immerse the glass fiber filter material in a 50 vol% ethanol solution at 70-80℃ for 15-20 minutes to wash away the adhesive and dust on the surface of the filter material. Then, dry the washed glass fiber filter material at a constant temperature of 100-120℃ for 1.5-2 hours. Finally, immerse it in a modified nano-silica solution for 20-30 minutes and air dry it naturally for 24 hours to obtain the modified glass fiber filter material.

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