Preparation method and application of PTFE composite filter material with denitrification function

Abstract

This invention discloses a method for preparing and applying PTFE composite filter media with denitrification function, belonging to the field of filtration material technology. Using high-temperature resistant PTFE polymer needle-punched filter media as the substrate, polydopamine and MXene are used to functionalize the surface of the filter media fibers to improve the dispersion and synergistic effect of the catalyst on the fiber surface. A manganese-cerium denitrification catalyst precursor is uniformly loaded onto the surface of the filter media fibers using an equal-volume impregnation method, followed by calcination to obtain the active components of the denitrification catalyst. Finally, hydrogen peroxide is impregnated to further activate the composite filter media and enhance its low-temperature denitrification activity. The PTFE composite filter media prepared by this invention exhibits excellent denitrification capability at low temperatures while retaining its original dust filtration effect during preparation. It can meet the requirements of integrated low-temperature denitrification and dust removal in industrial exhaust gas, effectively overcoming the shortcomings of existing tail-end flue gas purification systems, such as complexity and high treatment costs.

Description

Technical Field

[0001] This invention belongs to the field of filtration material technology, specifically relating to a method for preparing and applying a PTFE composite filter material with denitrification function. Background Technology

[0002] Nitrogen oxides (NO) x NOx and particulate matter are the main air pollutants emitted by coal-fired power plants, coking facilities, and cement production units. They play a key role in the formation of photochemical smog, ozone layer depletion, and the acceleration of global warming. Ammonia-based selective catalytic reduction (NH3-SCR) is currently the most advanced NOx emission reduction technology. x One of the emission reduction technologies. In existing NH3-SCR technology systems, Mn-based catalysts have advantages such as abundant variable valence states, high electron mobility, high redox performance at low temperatures, low cost, low toxicity, and environmental friendliness. Furthermore, cerium doping can effectively improve the sulfur resistance of manganese-based catalysts. Therefore, research on manganese-cerium oxides as active components of low-temperature SCR catalysts has received widespread attention from scholars both domestically and internationally. However, the selection of relevant supports mainly focuses on solid materials such as TiO2, Al2O3, and activated carbon. In addition, in traditional industrial flue gas treatment processes, denitrification and dust removal need to be carried out in separate steps, resulting in large equipment footprints and high resource consumption.

[0003] In recent years, the demand for industrial flue gas treatment has increased significantly. As the core material for flue gas purification, the technological iteration and functional integration of dust collector filter media have become a key focus in the industry. Traditional filter media mainly focus on single dust removal functions, while composite filter media with denitrification functions (that is, denitrification catalysts are directly loaded onto dust collector filter media) have become a research hotspot because they can simplify purification systems and reduce costs.

[0004] Currently, the domestic technology for preparing denitrification functional composite filter media mostly involves first preparing a catalyst, and then loading it onto the filter media using a binder or some physical methods, such as patents: CN115337712A, CN115193160A, CN115155305A, CN116870586A, CN119215552A, etc. This method results in uneven catalyst dispersion, large loading, and easy clogging of the internal pores of the filter media, thus affecting air permeability. Furthermore, the physical adhesion effect leads to insufficient bonding between the catalyst and the filter media, which can easily cause the active components to detach. In addition, there are some patents such as CN106731226A, CN106334372A, CN118649704A, and CN111359673A, which prepare denitrification functional composite filter media by in-situ growth of denitrification catalysts on filter media fibers. These methods also have problems such as unstable catalyst loading, low low-temperature catalytic activity, and poor catalyst sulfur resistance. Summary of the Invention

[0005] To address the shortcomings of the existing technologies mentioned in the background section, this invention provides a method for preparing and applying a PTFE composite filter material with denitrification function. This preparation method not only prevents the loaded catalyst from clogging the fiber channels, thus preserving the original dust filtration effect of the filter material, but also ensures a very good bonding strength between the catalyst and the filter material, preventing the catalyst from falling off during use due to dust removal operations. The resulting composite filter material has excellent nitrogen oxide removal capabilities at low temperatures, meeting the requirements for integrated low-temperature denitrification and dust removal in industrial exhaust gases, and effectively overcoming the shortcomings of existing tail gas purification systems, such as complexity and high treatment costs.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] A method for preparing a PTFE composite filter material with denitrification function involves using high-temperature resistant polytetrafluoroethylene (PTFE) polymer needle-punched filter material as a carrier. First, the surface of the PTFE is functionalized with polydopamine. Then, the PTFE is immersed in MXene ink, and electrostatic attraction is used to uniformly adsorb MXene sheets onto the surface of the polydopamine to fully activate the originally inert PTFE fiber surface. Next, a mixed solution of manganese salt and cerium salt is immersed into the composite filter material using an equal-volume impregnation method. Finally, the composite filter material is dried, calcined, and activated to obtain the PTFE composite filter material with denitrification function.

[0008] Specifically, it includes the following steps:

[0009] (1) Take a clean PTFE filter material, soak it in ethanol once, then immerse it in an alkaline aqueous solution of dopamine, stir it at a certain temperature for a period of time, then take it out and dry it so that the surface of the filter material fiber is uniformly coated with a polydopamine functional layer.

[0010] (2) MXene ink was prepared by chemically etching ternary layered carbide Ti3AlC2 with a fluorine-containing solution. Then, the polydopamine-modified filter material obtained in step (1) was immersed in the above ink. After standing for a period of time, the filter material was taken out and dried.

[0011] (3) Based on the amount of solution that the PTFE filter material can adsorb at one time, the filter material obtained in step (2) is impregnated in a certain amount of manganese salt and cerium salt mixed solution by the method of equal volume impregnation, left to stand for a period of time, and placed in an oven to dry, so that the metal salts are dispersed and deposited on the surface of the modified fiber filter material.

[0012] (4) Place the dried PTFE filter material obtained in step (3) into a muffle furnace and calcine it for a period of time at a temperature lower than the maximum operating temperature of the PTFE filter material to fully decompose the metal salts on it.

[0013] (5) Finally, the filter material in step (4) is taken out and placed in a hydrogen peroxide solution of a certain concentration for activation treatment. Finally, it is washed and dried to obtain PTFE composite filter material with denitrification function.

[0014] In the above preparation method: the air permeability of the PTFE filter material in step (1) is 20-200 L / dm³. 2 The thickness is between 0.5 and 3 mm, and the basis weight is between 100 and 1000 g / m². 2 It has properties that are resistant to strong acids, strong alkalis and high temperatures of at least 260°C.

[0015] In the above preparation method: the dopamine concentration in step (1) is 0.1-10 g / L; the alkaline aqueous solution is prepared from one or more compounds selected from sodium hydroxide, potassium hydroxide, ammonia or tris(hydroxymethyl)aminomethane, and the pH is between 8 and 10.

[0016] In the above preparation method: the concentration of MXene ink in step (2) is 0-10 g / L, the pH value of the solution is 6-8, the standing soaking time is 0.5-48 h, the drying temperature is between 30-120℃, and the drying time is 0.5-48 h.

[0017] In the above preparation method: the manganese salt in step (3) is selected from one or more of manganese nitrate, manganese chloride, manganese sulfate and manganese acetate, and the cerium salt is selected from one or more of cerium nitrate, cerium chloride, cerium sulfate and cerium acetate. The mixed solution is prepared by deionized water and ethanol in any proportion; the molar ratio of manganese salt and cerium salt is between 1:0 and 1:3, and the mass ratio of the total amount of manganese salt and cerium salt to the mass of filter material is controlled between 0.01:1 and 3:1; the volume impregnation time is 0.5-48h, the drying temperature is between 30-120℃, and the drying time is 0.5-48h.

[0018] In the above preparation method: the calcination temperature in step (4) is between 200-260℃ and the calcination time is 0.5-12h.

[0019] In the above preparation method: the activation process in step (5) is to place the composite filter material in hydrogen peroxide with a mass concentration of 0.1%-30% for oxidation treatment for 0.5-48h; the drying temperature is between 60-120℃ and the drying time is 0.5-48h.

[0020] Another objective of this invention is to provide an integrated low-temperature denitrification and dust removal application of the PTFE composite filter material prepared by the above method in industrial exhaust gas.

[0021] The beneficial effects of this invention are:

[0022] 1. The PTFE composite filter material prepared by this invention combines the dual functions of dust removal and low-temperature denitrification, simplifying the originally complex industrial exhaust gas after-treatment method, greatly saving the space and cost of industrial exhaust gas treatment, and has strong economic practicality; at the same time, the use of the equal volume impregnation method can effectively control the catalyst loading; the activation treatment of hydrogen peroxide can further improve the low-temperature activity of the catalyst, making the preparation method simple and easy to implement, and enabling large-scale industrial production.

[0023] 2. The surface of the filter fiber is functionalized by using polydopamine and MXene ink, which provides active sites for the anchoring and dispersion of the catalyst, making it uniformly dispersed and firmly bonded on the filter fiber. At the same time, the doping of MXene improves the dispersion, loading and synergistic effect of the catalyst on the fiber surface. Its unique physicochemical properties and structure enable it to establish a strong correlation with the active components of the denitrification catalyst, thus exhibiting better low-temperature denitrification activity and sulfur resistance. Attached Figure Description

[0024] The invention will now be further described with reference to the accompanying drawings.

[0025] Figure 1 This is a diagram of a self-made tubular SCR reactor used in the activity testing of composite filter media.

[0026] Figure 2 This is a scanning electron microscope image of the composite filter material according to Embodiment 1 of the present invention.

[0027] Figure 3 The image shows the sulfur resistance effect of the composite filter material of Embodiment 1 of the present invention under the conditions of 180°C and 100ppm SO2 atmosphere.

[0028] In the diagram: 1. Gas source; 2. Pressure reducing valve; 3. Flow meter; 4. Mixer; 5. Air preheater; 6. Heating and catalytic reactor; 7. Test sample; 8. Flue gas analyzer. Detailed Implementation

[0029] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. 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.

[0030] like Figure 1The diagram shows a self-made tubular SCR reactor device, which includes a gas source 1, a pressure reducing valve 2, and a flow meter 3 connected in sequence. The flow meter 3 is connected to the heating and catalytic reactor 6 through a mixer 4 and an air preheater 5. The heating and catalytic reactor 6 is directly connected to a flue gas analyzer 8, and the test sample 7 is placed inside the heating and catalytic reactor 6.

[0031] In the following examples, MXene inks were prepared by the following steps: 2g of lithium fluoride was weighed and added to a polytetrafluoroethylene reactor containing a mixture of 31mL concentrated hydrochloric acid and 9mL deionized water. After stirring for 15min, 2g of Ti3AlC2 was slowly added, and the reaction was continued at 40℃ for 24h. The obtained product was then washed multiple times by centrifugation with 1mol / L hydrochloric acid solution until pH>6, thus obtaining MXene ink. Its concentration can be adjusted according to the degree of dilution.

[0032] The activity evaluation of the composite filter media was performed on a self-made tubular SCR reactor, the schematic diagram of which is shown below. Figure 1 As shown, the composite filter media (test sample 7) is placed in the middle of the heating and catalytic reactor 6. An experimental tubular resistance furnace is used to control the test temperature of the sample, and a flow meter 3 controls the flow rate of each gas. The gas composition simulates that of flue gas, i.e., NO 500 ppm, NH3 500 ppm, O2 5%, and the remainder N2, with a total gas flow rate of 300 mL / min. Before entering the tubular resistance furnace, the gas is first mixed uniformly by a mixer 4, and then preheated to a certain temperature by an air preheater 5. The experimental test temperature range is 100-180℃. A flue gas analyzer 8 is used to determine the composition and content of the inlet and outlet gases in the tubular resistance furnace. Each test point must be tested after the temperature has stabilized for at least 10 minutes. The denitrification activity of the composite filter media is calculated from the concentration of nitrogen oxides (NOx) at the inlet and outlet, as shown in the following formula:

[0033]

[0034] Example 1

[0035] After immersing 1.1782g of cleaned circular PTFE filter media in an ethanol solution, immediately add 2g / L of dopamine alkaline solution, adjust the pH to approximately 8.5 using tris(hydroxymethyl)aminomethane, and stir at room temperature for 12 hours. Then remove the filter media, rinse it with deionized water and ethanol, and vacuum dry it at 60℃ for 12 hours. The dried filter media is then immersed again in approximately 1g / L of freshly prepared MXene ink with a pH of approximately 6.5, allowed to stand for 12 hours, then removed, cleaned, and vacuum dried at 60℃ for 12 hours. Take 2 mL of a homogeneous mixed solution containing 0.38 mL of manganese nitrate aqueous solution and 0.1502 g of cerium nitrate (molar ratio of manganese salt to cerium salt is 1:0.2, and the mass ratio of total manganese salt to cerium salt to filter media is 0.38:1) to completely impregnate the modified PTFE filter media, and let it stand at room temperature for 12 h. Then, place it in an oven and dry it at 110 °C for 2 h. Finally, place the dried filter media in a muffle furnace and calcine it at 250 °C for 2 h. After cooling, remove the composite filter media and activate it in a 10% hydrogen peroxide aqueous solution for 1 h. Then, wash it and dry it at 110 °C for 12 h to obtain the PTFE composite filter media loaded with manganese-cerium denitration catalyst. Using a German M60x flue gas analyzer, the denitration rate was 82.6% at a reaction temperature of 160 °C and 91.5% at a reaction temperature of 180 °C. Figure 2 The image shown is a scanning electron microscope image of the composite filter material in this embodiment.

[0036] Example 2

[0037] After immersing 1.1718g of cleaned circular PTFE filter media in an ethanol solution, immediately add 2g / L of dopamine alkaline solution, adjust the pH to approximately 9 using tris(hydroxymethyl)aminomethane, and stir at room temperature for 18 hours. Then remove the filter media, rinse it with deionized water and ethanol, and vacuum dry it at 80℃ for 16 hours. The dried filter media is then immersed again in approximately 1g / L of freshly prepared MXene ink with a pH of approximately 6.5, allowed to stand for 12 hours, then removed, cleaned, and vacuum dried at 80℃ for 12 hours. Take 2 mL of a homogeneous mixed solution containing 0.25 mL of manganese nitrate aqueous solution and 0.3030 g of cerium nitrate (molar ratio of manganese salt to cerium salt is 1:0.54, and the mass ratio of total manganese salt to cerium salt to filter media is 0.42:1) and completely impregnate the modified PTFE filter media. Let it stand at room temperature for 12 h, then place it in an oven and dry at 110 °C for 4 h. Finally, place the dried filter media in a muffle furnace and calcine at 250 °C for 2 h. After cooling, remove the composite filter media and activate it in a 1% hydrogen peroxide solution for 1 h, then wash and dry at 110 °C for 12 h to obtain the PTFE composite filter media loaded with the manganese-cerium denitration catalyst. Using a German M60x flue gas analyzer, the denitration rate was 72.8% at a reaction temperature of 160 °C and 76.6% at a reaction temperature of 180 °C.

[0038] Example 3

[0039] A 1.2189g sample of cleaned circular PTFE filter media was immersed in an ethanol solution, and immediately then added to a 2g / L dopamine alkaline solution. The pH was adjusted to approximately 9 using ammonia, and the mixture was stirred at room temperature for 18 hours. Afterward, the filter media was removed, rinsed with deionized water and ethanol, and then vacuum-dried at 80℃ for 16 hours. The dried filter media was then immersed again in approximately 2g / L of freshly prepared MXene ink with a pH of approximately 6.5, allowed to stand for 12 hours, rinsed, and vacuum-dried at 80℃ for 12 hours. 2mL of an aqueous solution containing 0.5mL of manganese nitrate (manganese salt to filter media mass ratio of 0.32:1) was used to completely impregnate the modified PTFE filter media, and the mixture was allowed to stand at room temperature for 12 hours. It was then placed in an oven and dried at 110℃ for 4 hours. Finally, the dried filter media was calcined in a muffle furnace at 250℃ for 2 hours. After cooling, the composite filter media was removed and activated in a 10% hydrogen peroxide solution for 1 hour. It was then washed and dried at 110℃ for 12 hours to obtain the PTFE composite filter media loaded with a pure manganese oxide denitrification catalyst. Using a German M60x flue gas analyzer, the denitrification rate was measured to be 75.1% at a reaction temperature of 160℃ and 80.8% at a reaction temperature of 180℃.

[0040] Example 4

[0041] After immersing 1.0893g of cleaned circular PTFE filter media in an ethanol solution, it was immediately added to a 4g / L dopamine alkaline solution. The pH was adjusted to approximately 8.5 using tris(hydroxymethyl)aminomethane and stirred at room temperature for 18 hours. The filter media was then removed, rinsed with deionized water and ethanol, and vacuum dried at 60°C for 10 hours. The dried filter media was then immersed again in approximately 1g / L of freshly prepared MXene ink with a pH of approximately 6.5, allowed to stand for 12 hours, and then removed, cleaned, and vacuum dried at 80°C for 12 hours. Take 2 mL of a homogeneous mixed solution containing 0.46 mL of manganese nitrate aqueous solution and 0.1836 g of cerium nitrate (molar ratio of manganese salt to cerium salt is 1:0.2, and the mass ratio of total manganese salt to cerium salt to filter media is 0.46:1) and completely impregnate the modified PTFE filter media. Let it stand at room temperature for 12 h, then place it in an oven and dry at 80℃ for 6 h. Finally, place the dried filter media in a muffle furnace and calcine at 230℃ for 4 h. After cooling, remove the composite filter media and activate it in a 5% hydrogen peroxide solution for 2 h, then wash and dry at 110℃ for 12 h to obtain the PTFE composite filter media loaded with the manganese-cerium denitration catalyst. Using a German M60x flue gas analyzer, the denitration rate was 82.5% at a reaction temperature of 160℃ and 85% at a reaction temperature of 180℃.

[0042] Example 5

[0043] A 1.1267g sample of cleaned circular PTFE filter media was immersed in an ethanol solution, and immediately then added to a 4g / L dopamine alkaline solution. The pH was adjusted to approximately 8.5 using ammonia, and the mixture was stirred at room temperature for 16 hours. Afterward, the filter media was removed, rinsed with deionized water and ethanol, and then vacuum-dried at 60℃ for 6 hours. The dried filter media was then immersed again in approximately 2g / L of freshly prepared MXene ink with a pH of approximately 7, allowed to stand for 12 hours, rinsed, and then vacuum-dried at 80℃ for 12 hours. 2mL of a homogeneous mixture containing 0.23mL of manganese nitrate aqueous solution and 0.7232g of cerium nitrate (molar ratio of manganese salt to cerium salt is 1:1) was prepared.

[0044] 1.6 The total amount of manganese and cerium salts to the filter media was 0.8:1. The modified PTFE filter media was completely impregnated and allowed to stand at room temperature for 6 hours. Then, it was dried in an oven at 80°C for 12 hours. Finally, the dried filter media was calcined in a muffle furnace at 220°C for 4 hours. After cooling, the composite filter media was removed and activated in a 20% hydrogen peroxide solution for 2 hours. It was then washed and dried at 110°C for 12 hours to obtain the PTFE composite filter media loaded with manganese and cerium denitrification catalyst. The denitrification rate was 64.5% at a reaction temperature of 160°C and 69.6% at a reaction temperature of 180°C, as measured by a German M60x flue gas analyzer.

[0045] Example 6

[0046] After immersing 1.0343g of cleaned circular PTFE filter media in an ethanol solution, immediately add 1g / L of dopamine alkaline solution, adjust the pH to approximately 8.5 using tris(hydroxymethyl)aminomethane, and stir at room temperature for 18 hours. Then remove the filter media, rinse it with deionized water and ethanol, and vacuum dry it at 60℃ for 10 hours. The dried filter media is then immersed again in approximately 0.5g / L of freshly prepared MXene ink with a pH of approximately 7, allowed to stand for 12 hours, then removed, cleaned, and vacuum dried at 80℃ for 12 hours. A homogeneous mixed solution containing 0.92 mL of manganese nitrate aqueous solution and 0.3634 g of cerium acetate (molar ratio of manganese salt to cerium salt is 1:0.27, and the mass ratio of total manganese salt to cerium salt to filter media is 1.03:1) was used to completely impregnate the modified PTFE filter media. The solution was allowed to stand at room temperature for 12 hours, then dried in an oven at 80°C for 6 hours. Finally, the dried filter media was calcined in a muffle furnace at 230°C for 4 hours. After cooling, the composite filter media was removed and activated in a 10% hydrogen peroxide solution for 2 hours, then washed and dried at 110°C for 12 hours to obtain the PTFE composite filter media loaded with the manganese-cerium denitration catalyst. Using a German M60x flue gas analyzer, the denitration rate was 84.6% at a reaction temperature of 160°C and 88.2% at a reaction temperature of 180°C.

[0047] Comparative Example 1

[0048] After immersing 1.1467g of cleaned circular PTFE filter media in an ethanol solution, immediately add 2g / L of dopamine alkaline solution, adjust the pH to approximately 8.5 using tris(hydroxymethyl)aminomethane, and stir at room temperature for 12 hours. Then remove the filter media, rinse it with deionized water and ethanol, and vacuum dry it at 60℃ for 12 hours. The dried filter media is then immersed again in approximately 1g / L of freshly prepared MXene ink with a pH of approximately 6.5, allowed to stand for 12 hours, then removed, cleaned, and vacuum dried at 60℃ for 12 hours. Take 2 mL of a homogeneous mixed solution containing 0.38 mL of manganese nitrate aqueous solution and 0.14982 g of cerium nitrate (molar ratio of manganese salt to cerium salt is 1:0.2, and the mass ratio of total manganese salt to cerium salt to filter media is 0.38:1) and completely impregnate the modified PTFE filter media. Let it stand at room temperature for 12 h, then place it in an oven and dry it at 110 °C for 2 h. Finally, place the dried filter media in a muffle furnace and calcine it at 250 °C for 2 h.

[0049] PTFE composite filter media loaded with manganese-cerium denitrification catalyst was obtained. Using a German M60x flue gas analyzer, the denitrification rate was 76.6% at a reaction temperature of 160℃ and 85.8% at a reaction temperature of 180℃.

[0050] Comparative Example 2

[0051] A 1.3889g sample of cleaned circular PTFE filter media was immersed in an ethanol solution, and immediately then added to a 2g / L dopamine alkaline solution. The pH was adjusted to approximately 9 using ammonia water, and the mixture was stirred at room temperature for 18 hours. Afterward, the media was removed, rinsed with deionized water and ethanol, and then vacuum-dried at 80℃ for 16 hours. 2mL of a solution containing 0.5mL of manganese nitrate (manganese salt to filter media mass ratio 0.28:1) was used to completely impregnate the modified PTFE filter media, which was then allowed to stand at room temperature for 12 hours. Next, it was placed in an oven and dried at 110℃ for 4 hours. Finally, the dried filter media was calcined in a muffle furnace at 250℃ for 2 hours. After cooling, the composite filter media was removed and activated in a 10% hydrogen peroxide solution for 1 hour, then washed and dried at 110℃ for 12 hours to obtain the PTFE composite filter media loaded with a pure manganese oxide denitrification catalyst. The denitrification rate was 71.1% when the reaction temperature was 160℃, and 71.5% when the reaction temperature was 180℃, as measured by the German M60x flue gas analyzer.

[0052] During the implementation of the examples, it was found that the main factors affecting the low-temperature denitrification performance of the PTFE composite filter material of the present invention include the molar ratio of metal ions in the manganese-cerium mixed solution, the mass ratio of metal salt to filter material, and whether it is impregnated with MXene ink and activated with hydrogen peroxide. The Mn / Ce molar ratio of manganese salt and cerium salt in the mixed solution has a significant impact on the number and morphology of surface active sites of the catalyst, thus affecting its low-temperature denitrification activity. Comparative Example 1 shows that the low-temperature denitrification activity of the composite filter material without hydrogen peroxide activation is about 6% lower than that of Example 1. Comparative Example 2, without MXene impregnation, also shows a worse denitrification effect compared to Example 3. This is mainly because MXene adsorbs on the surface of the polydopamine-modified fiber, increasing the dispersion, loading, and synergistic effect of the catalyst on the fiber surface, thereby enhancing the low-temperature denitrification effect of the composite filter material.

[0053] In addition, we also conducted sulfur resistance tests on Example 1, which showed the best results, and the results are as follows: Figure 3 As shown, the composite filter material exhibits better sulfur resistance and recovery ability than most denitrification and dust removal filter materials under conditions of 180℃ and 100ppm SO2 atmosphere.

[0054] The above detailed embodiments provide a specific description of the analytical methods involved in this invention. It should be noted that the above description is only intended to help those skilled in the art better understand the methods and ideas of this invention, and is not intended to limit the scope of the invention. Without departing from the principles of this invention, those skilled in the art can make appropriate adjustments or modifications to this invention, and such adjustments and modifications should also fall within the protection scope of this invention.

Claims

1. A method for preparing a PTFE composite filter material with denitrification function, characterized in that, Using PTFE polymer needle-punched filter media as a carrier, the surface of the media is first functionalized with polydopamine. Then, the media is immersed in MXene ink, and electrostatic attraction is used to uniformly adsorb MXene sheets onto the polydopamine surface to fully activate the originally inert PTFE fiber surface. Next, a mixed solution of manganese salt and cerium salt is immersed into the above composite filter media using an equal-volume impregnation method. Finally, after drying, calcining, and activation, the composite filter media is obtained as a PTFE composite filter media with denitrification function. Includes the following steps: (1) Take a clean PTFE filter material, soak it in ethanol once, then immerse it in an alkaline aqueous solution of dopamine, stir it at a certain temperature for a period of time, then take it out and dry it so that the surface of the filter material fiber is uniformly coated with a polydopamine functional layer. (2) MXene ink was prepared by chemical etching of ternary layered carbide Ti3AlC2 with fluorine-containing solution. Then, the polydopamine modified filter material obtained in step (1) was immersed in the above ink. After standing for a period of time, the filter material was taken out and dried. (3) Based on the amount of solution that the PTFE filter material can adsorb at one time, the filter material obtained in step (2) is impregnated in a certain amount of manganese salt and cerium salt mixed solution by the method of equal volume impregnation, left to stand for a period of time, and placed in an oven to dry, so that the metal salts are dispersed and deposited on the surface of the modified fiber filter material. (4) Place the dried PTFE filter material obtained in step (3) in a muffle furnace and calcine it for a period of time at a temperature lower than the maximum operating temperature of the PTFE filter material to fully decompose the metal salts on it. (5) Finally, the filter material in step (4) is taken out and placed in a hydrogen peroxide solution of a certain concentration for activation treatment. Finally, it is washed and dried to obtain PTFE composite filter material with denitrification function.

2. The method for preparing a PTFE composite filter material with denitrification function according to claim 1, characterized in that, The air permeability of the PTFE filter media in step (1) is 20-200 L / dm. 2 The thickness is between 0.5 and 3 mm, and the basis weight is between 100 and 1000 g / m². 2 It can withstand temperatures up to 260℃.

3. The method for preparing a PTFE composite filter material with denitrification function according to claim 1, characterized in that, The dopamine concentration in step (1) is 0.1-10 g / L; the alkaline aqueous solution is prepared from one or more compounds of sodium hydroxide, potassium hydroxide, ammonia or tris(hydroxymethyl)aminomethane, with a pH between 8 and 10.

4. The method for preparing a PTFE composite filter material with denitrification function according to claim 1, characterized in that, In step (2), the concentration of MXene ink is 0-10 g / L, the pH value of the solution is 6-8, the standing soaking time is 0.5-48 h, the drying temperature is between 30-120℃, and the drying time is 0.5-48 h.

5. The method for preparing a PTFE composite filter material with denitrification function according to claim 1, characterized in that, In step (3), the manganese salt is selected from one or more of manganese nitrate, manganese chloride, manganese sulfate and manganese acetate, and the cerium salt is selected from one or more of cerium nitrate, cerium chloride, cerium sulfate and cerium acetate; the molar ratio of manganese salt to cerium salt is between 1:0 and 1:3, and the mass ratio of the total amount of manganese salt and cerium salt to the filter material is controlled between 0.01:1 and 3:1; the volume impregnation time is 0.5-48 h, the drying temperature is between 30-120℃, and the drying time is 0.5-48 h.

6. The method for preparing a PTFE composite filter material with denitrification function according to claim 1, characterized in that, The calcination temperature in step (4) is between 200-260℃ and the calcination time is 0.5-12 h.

7. The method for preparing a PTFE composite filter material with denitrification function according to claim 1, characterized in that, The activation process in step (5) involves oxidizing the composite filter material in hydrogen peroxide with a mass concentration of 0.1%-30% for 0.5-48 hours; the drying temperature is between 60-120℃ and the drying time is 0.5-48 hours.

8. The application of PTFE composite filter material prepared by the preparation method according to any one of claims 1-7 in low-temperature denitrification and dust removal in industrial exhaust gas.

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