A carbon particle / fiber composite filter material, its preparation method and application

Abstract

The present invention discloses a carbon particle / fiber composite filtration material, its preparation method and application, belonging to the technical field of material preparation. It includes fibers and nano-carbon particles, and the mass ratio of nano-carbon particles to fibers is 1:100 to 1:500; wherein the diameter of the fibers is 10 to 100 μm; a carbon thin layer composed of nano-carbon particles is in-situ polycondensed on the fiber surface, the average particle size of the nano-carbon particles is 100 to 700 nm, the thickness of the carbon thin layer is 100 to 700 nm, its coating rate on the fiber surface is more than 95%, and no carbon thin layer crosslinking is formed in the gaps / channels between multiple fibers. The nano-carbon particles uniformly cover the fiber surface, and the uniformly distributed nano-carbon particles increase the dielectric constant of the fiber; the carbon particles have a large specific surface area and strong capture ability for sub-micron fine particles, and are suitable for high-efficiency filtration in a polarized electric field, so that the composite material simultaneously has the characteristics of high efficiency, low resistance and high dielectric performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of material preparation, and more specifically, relates to a carbon particle / fiber composite filter material, its preparation method and application, which can be used in fields such as air purification. Background Art

[0002] Currently, the main method for purifying indoor air PM2.5 is filtration. Fiber materials are common filtration media, but high-efficiency fiber filter materials will cause an increase in filtration resistance and excessive energy consumption. Utilizing the electrostatic effect to strengthen the adsorption force between particles and fibers is an effective means to achieve low-resistance and high-efficiency removal of PM2.5. Now, electret fiber filtration technology, particle pre-charging filtration technology, fiber continuous charging filtration technology, and dual-electric-field particle-fiber double-charging filtration technology have been developed. Among them, dual-electric-field double-charging enhances the Coulomb force between particles and fibers and improves the adsorption ability of fibers to sub-micron and particulate matter, which is the most effective electrostatic-enhanced particle filtration technology currently. The core of the dual-electric-field double-charging filtration technology lies in the dielectric properties of the fiber. The filtration material with high dielectric properties is polarized in the electric field, and induced charges are generated on the fiber surface, forming a polarization electric field. The upstream particles are charged in the form of corona discharge, and the charged particles enter the electric field and are captured by the fibers under the action of the Coulomb force, thereby improving the filtration efficiency of PM2.5. The induced charges are mainly concentrated on the fiber surface, so a dielectric coating can be constructed on the surface of conventional fibers to prepare a composite filter material that meets the requirements.

[0003] In addition, graphene is also sprayed or enriched on the fiber to achieve purposes such as adsorption. For example, in the application publication patent CN107974841A, a preparation method of a polyurethane fiber air conditioner filter screen is mentioned. Graphene is added to heptane to obtain a graphene suspension; 0.5 - □1L of organosilicon resin, 0.05 - □0.1L of polyurethane prepolymer, and 5 - □10g of curing agent are sequentially added under stirring conditions to make a mixed solution; the polyurethane fiber fabric is leached in trifluorooctyltriethoxysilane and then naturally dried; the mixed solution is evenly sprayed on the polyurethane fiber fabric and naturally dried to obtain the polyurethane fiber air conditioner filter screen. However, graphene has a high price, which is not conducive to large-scale use and promotion. At the same time, graphene will block the filtration gaps / pores and increase the filtration resistance.

[0004] The application of nano-biomass colloidal carbon in the field of modified fibers generally adopts the method of melt spinning: for example, in the application publication patent CN114921868A, a preparation method of nano-biochar modified melt direct spinning superfine denier polyester fiber is mentioned. After the polyester esterification reaction is completed, the modified nano-biomass carbon material is added, and then polycondensation reaction is carried out, and the polyester melt after the polycondensation reaction is spun to obtain the nano-biochar modified melt direct spinning superfine denier polyester fiber.

[0005] Although the mixing degree of nano-biomass colloidal carbon is high in this preparation method, due to the dispersion of biochar powder, the biomass carbon cannot be evenly loaded on the fiber surface, and the dielectric properties of the fiber are not high. Summary of the Invention

[0006] 1. Problems to be Solved

[0007] In view of the above technical problems and to solve the problem of uneven dispersion of existing biochar on the fiber surface, the object of the present invention is to provide a carbon particle / fiber composite filter material and its preparation method, which can make the biochar evenly dispersed on the fiber surface and obtain a filter material with high dielectric properties on the premise of ensuring that the filtration resistance does not increase.

[0008] Another object of the present invention is to provide a filter element having the above carbon particle / fiber composite filter material, and a filter device having the above, which are used in the field of air purification.

[0009] 2. Technical Solutions

[0010] To solve the above problems, the technical solutions adopted by the present invention are as follows:

[0011] The carbon particle / fiber composite filter material prepared from biomass of the present invention includes fibers and nano-carbon particles, and the mass ratio of the nano-carbon particles to the fibers is 1:100 to 1:500; wherein the diameter of the fibers is 10 to 100 μm;

[0012] A carbon thin layer composed of nano-carbon particles is in-situ polycondensed on the fiber surface. The average particle size of the nano-carbon particles is 100 to 700 nm, the thickness of the carbon thin layer is 100 to 700 nm, its coating rate on the fiber surface is more than 95%, and no carbon thin layer crosslinking is formed in the gaps / channels between multiple fibers.

[0013] The above carbon thin layer crosslinking can be understood as the carbon particle thin layers on adjacent or nearby fibers growing around, thereby covering the fiber surface over a large area and filling the gaps / pores between multiple fibers (the fibers have gaps / channels for gas passage).

[0014] In a possible implementation manner of the present invention, the nano-carbon particles are spherical.

[0015] In a possible implementation manner of the present invention, a carbon thin layer composed of nano-carbon particles is uniformly formed in-situ polymerization on the fiber surface. The detection method for the uniform distribution of the carbon particles on the fiber surface is as follows: randomly take n samples at different parts of the carbon particle / fiber composite filter material, where n is a positive integer greater than or equal to 10, analyze the content of the carbon particles on the fiber surface, and the coefficient of variation of the content of the carbon particles in the n samples ≤ 8%.

[0016] In a possible implementation manner of the present invention, the fiber is selected from any one or more of lactide polymer fiber, glycolide polymer fiber, polyester fiber (abbreviation: polyester (PET)), polyamide fiber (abbreviation: nylon, polyamide, nylon (PA)), polypropylene fiber (abbreviation: polypropylene (PP)), polyethylene fiber (PE), polyvinyl chloride fiber (abbreviation: chloroprene (PVC)), polyacrylonitrile fiber (abbreviation: acrylic fiber, artificial wool), viscose fiber, polyurethane fiber (PU).

[0017] The present invention also provides a method for preparing the above-mentioned carbon particle / fiber composite filter material. The preparation method is an in-situ growth method, and the in-situ growth method includes the following steps:

[0018] Step S1, drying: removing impurities from the biomass raw material and performing drying treatment to obtain biomass material A;

[0019] Step S2, concentrated acid hydrolysis: taking a certain amount of biomass material A obtained in step S1 and concentrated sulfuric acid, promoting the strong acid to fully hydrolyze cellulose and hemicellulose into reducing sugars, and mixing them in a ratio of 5 - 30 g / ml; fully stirring under the condition of 40 - 50 °C, and the hydrolysis time is 15 - 20 min to obtain a mixed solution B; on the premise of this solid-liquid ratio, the cellulose of biomass material A can accelerate hydrolysis and improve the hydrolysis rate.

[0020] Step S3, dilution and separation: adding distilled water to the mixed solution B obtained in step S2, diluting the sulfuric acid concentration to a mass fraction of 32% - 42%, and performing solid-liquid separation to obtain a sugar-acid solution C;

[0021] Step S4, preparing composite fiber: selecting a suitable fiber and immersing it in the sugar-acid solution prepared in step S3, placing it in a drying oven at 85 - 95 °C under normal pressure, and performing the carbonization reaction of reducing sugar for 5 - 7 h to form a dense and uniform biomass nano-carbon thin layer on the fiber surface, thereby obtaining the carbon particle / fiber composite filter material;

[0022] At this time, the acid acts as a catalyst and dehydrating agent to promote the dehydration and polycondensation of sugar molecules and perform the carbonization reaction of reducing sugar, forming a dense and uniform biomass nano-spherical carbon thin layer on the fiber surface to achieve the purpose of modifying the fiber to have high dielectric properties.

[0023] In a possible implementation manner of the present invention, in step S2, the biomass includes but is not limited to rice husks, straws, poplar fluffs, and coconut shells.

[0024] In a possible implementation manner of the present invention, in step S2, the mass fraction of the concentrated sulfuric acid is 62% - 82%. If the above-mentioned concentrated sulfuric acid ratio is too low, the hydrolysis efficiency will be low; if the concentrated sulfuric acid ratio is too high, the carbonization of cellulose and hemicellulose will be obvious, affecting the yield of reducing sugar.

[0025] In a possible implementation manner of the present invention, in step S4, the fiber is selected from any one or more of polylactide polymer fiber, polyglycolide polymer fiber, polyester fiber (abbreviation: polyester (PET)), polyamide fiber (abbreviation: nylon, polyamide, nylon (PA)), polypropylene fiber (abbreviation: polypropylene (PP)), polyethylene fiber (PE), polyvinyl chloride fiber (abbreviation: chloroprene (PVC)), polyacrylonitrile fiber (abbreviation: acrylic fiber, artificial wool), viscose fiber, polyurethane fiber (PU).

[0026] In a possible implementation manner of the present invention, in step S4, the detection method for the uniform distribution of the carbon particles on the fiber surface is as follows: randomly take n samples at different positions of the carbon particle / fiber composite filter material, where n is a positive integer greater than or equal to 10, analyze the content of the carbon particles on the fiber surface, and the coefficient of variation of the content of the carbon particles in the n samples ≤ 8%.

[0027] The present invention also provides a filter element, including parallel metal meshes respectively connected to the positive electrode and the ground electrode, and the above-mentioned carbon particle / fiber composite filter material is interposed between the metal meshes, and induced charges are generated through the polarization effect to capture the charged fine particles.

[0028] 3. Beneficial effects

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0030] (1) For the carbon particle / fiber composite filter material of the present invention, the nano-carbon particles uniformly cover the fiber surface, and the uniformly distributed nano-carbon particles increase the relative dielectric constant ε of the fiber r from 1.26 to 4.74; the carbon particles have a large specific surface area and strong capture ability for sub-micron fine particles, and are suitable for efficient filtration of PM2.5 in a polarized electric field. At the same time, since the particle size of the carbon particles is at the nano level, it is a dense and uniform thin layer structure on the fiber surface, and no carbon thin layer cross-linking is formed in the gaps / pores between multiple fibers, so it will not block the fiber pores and cause an increase in additional filtration resistance, making the composite material have the characteristics of high efficiency, low resistance, and high dielectric performance at the same time;

[0031] (2) For the preparation method of the carbon particle / fiber composite filter material of the present invention, in-situ polycondensation and carbonization are formed on the fiber surface to generate flocculent carbon particles with an average particle size of 100-700 nm. In-situ polycondensation carbonization can obtain nano-carbon materials with uniform particle size, and the morphology and structure can be precisely controlled according to the carbonization time;

[0032] (3) The present invention combines the preparation of nano-biomass colloidal carbon with the filter material to realize a preparation process of high-efficiency, low-cost, and simple-operation nano-biomass colloidal carbon-fiber composite material;

[0033] (4) The carbon particle / fiber composite filter material of the present invention is applied to the filtration of indoor air particulate matter in a double - electric - field and double - charging mode; the biomass nano - carbon with high dielectric properties is polarized in the electric field to generate induced charges, forming an external electric field to capture charged particles. At the same time, the ozone - decomposition ability of the biomass carbon can adsorb and decompose the ozone generated by corona discharge. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The technical solutions of the present invention will be further described in detail below in conjunction with the drawings and embodiments. However, it should be understood that these drawings are only designed for the purpose of explanation and therefore do not limit the scope of the present invention. In addition, unless otherwise specified, these drawings are only intended to conceptually illustrate the structural configurations described herein and are not necessarily drawn to scale.

[0035] Figure 1 It is a schematic diagram of the in - situ growth process based on the present invention;

[0036] Figure 2 It is a schematic diagram of the dense and uniform biomass nano - carbon @ filter fiber prepared according to the present invention;

[0037] Figure 3 It is an SEM image of the acid - hydrolyzed in - situ dehydration - condensation carbonized nano - carbon spheres of the present invention;

[0038] Figure 4 It is a schematic diagram of the double - electric - field and double - charging air - filtration device of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0039] The exemplary embodiments of the present invention are described in detail below. Although these exemplary embodiments are described in sufficient detail to enable those skilled in the art to implement the present invention, it should be understood that other embodiments can be achieved and various changes can be made to the present invention without departing from the spirit and scope of the present invention. The following more detailed description of the embodiments of the present invention does not limit the scope of the claimed present invention, but is only for illustrative purposes and does not limit the description of the features and characteristics of the present invention, in order to present the best mode of implementing the present invention and to enable those skilled in the art to implement the present invention. Therefore, the scope of the present invention is only defined by the appended claims.

[0040] The nano - carbon particle / fiber composite filter material prepared by the present invention applies the double - electric - field and double - charging air - filtration technology to effectively remove PM2.5, O3, etc. in indoor air. Its raw materials are widely sourced and environmentally friendly, and it also has broad application prospects in the fields of catalysts and adsorbents.

[0041] As is well known, in the case of polycrystalline graphite, the relative dielectric constant increases linearly with the reciprocal of the grain size. Graphite with nanoscale dimensions has high dielectric constant characteristics, which can enhance the range and intensity of the local induced electric field inside the filter fiber. Although the use of graphene can increase the dielectric constant, graphene not only has a high price but also is difficult to control the growth situation, resulting in the porosity of the filter material not meeting the requirements and restricting the use of the filter fiber.

[0042] The preparation method of the carbon particle / fiber composite filter material of the present invention, and the above preparation method is an in-situ growth method, and the specific in-situ growth method includes the following steps:

[0043] Step S1, drying: removing impurities from the biomass raw material and drying to obtain biomass material A; the biomass includes but is not limited to rice husks, straws, poplar fluffs, coconut shells, and preferably rice husks, and rice husks contain more cellulose and hemicellulose;

[0044] Step S2, concentrated acid hydrolysis: taking a certain amount of biomass material A obtained in step S1 and concentrated sulfuric acid, the mass fraction of the above concentrated sulfuric acid is 62% - 82%. If the proportion of the above concentrated sulfuric acid is too low, the hydrolysis efficiency will be low, and if the proportion of the concentrated sulfuric acid is too high, the carbonization of cellulose and hemicellulose will be obvious, affecting the yield of reducing sugar; promoting the strong acid to fully hydrolyze cellulose and hemicellulose into reducing sugar, and mixing them in a ratio of 5 - 30 g / ml; fully stirring under the condition of 40 - 50 °C, and the hydrolysis time is 15 - 20 min to obtain a mixed solution B; under the premise of this solid-liquid ratio, the cellulose of the biomass material A can accelerate hydrolysis and improve the hydrolysis rate;

[0045] Step S3, dilution and separation: adding distilled water to the mixed solution B obtained in step S2, diluting the sulfuric acid concentration to a mass fraction of 32% - 42%, and performing solid-liquid separation to obtain a sugar-acid solution C;

[0046] Step S4, preparing composite fibers: selecting appropriate fibers and immersing them in the sugar-acid solution prepared in step S3, and placing them in a drying oven at 85 - 95 °C under normal pressure for 5 - 7 h for the carbonization reaction of reducing sugar, forming a dense and uniform biomass nano-carbon thin layer on the fiber surface to obtain a carbon particle / fiber composite filter material. At this time, the acid in the solution acts as a catalyst and dehydrating agent to promote the dehydration and condensation of sugar molecules and carry out the carbonization reaction of reducing sugar, forming a dense and uniform biomass nano-carbon thin layer on the fiber surface to achieve the purpose of modifying the fiber to have high dielectric properties.

[0047] It should be noted that according to the understanding of the prior art, the polymer fiber substrate needs to be grafted or adhered (using hydrogen bond force) to the hydroxy-containing substance under strong alkaline conditions. However, the hydrolysis of cellulose in the biomass of the present invention needs to be carried out under acidic conditions. Moreover, in an acidic environment, acid-resistant polymer fibers are selected, and there is no need to add an alkali solution to the sugar-acid solution to adjust the pH. At the same time, an in-situ growth method is adopted to form a carbon thin layer on the fiber surface, and no carbon thin layer cross-linking is formed in the gaps / pores between multiple fibers, and the fiber pores are unobstructed, with a small filtration resistance, so that the composite filter material has the characteristics of high efficiency, low resistance, and high dielectric performance at the same time.

[0048] The possible reason for the analysis is as follows: In the sugar-acid solution, when the temperature is set at 85-95 °C, the fiber substrate is relatively easy to be expanded and stretched, so that the hydroxy functional groups of the fiber substrate are exposed. There are a large number of hydrogen ions in the solution, and the hydroxy functional groups are surrounded by hydrogen ions, resulting in a decrease in the hydrogen bond force between the reducing sugar with hydroxy and the fiber substrate. A large number of reducing sugars are free in the solution, and some of the reducing sugars adhered to the surface of the fiber substrate are quickly dehydrated and polycondensed under the action of acid to undergo a carbonization reaction, which in turn provides sites for the continuous carbonization of the reducing sugar. The free reducing sugars grow around the site carbon particles to form a two-dimensional structure of the carbon thin layer.

[0049] The above-mentioned method for detecting the compactness: The morphology and surface element distribution of the fiber can be observed and analyzed by using a field emission SEM and its equipped EDS to determine whether it is compact. After testing, the carbon particle / fiber composite filter material prepared by the present invention has good compactness of the carbon thin layer on it.

[0050] The detection method for the uniform distribution of the above-mentioned carbon particles on the fiber surface is as follows: Randomly take n samples at different parts of the above-mentioned carbon particle / fiber composite filter material, where n is a positive integer greater than or equal to 10, and analyze the content of carbon particles on the fiber surface. The coefficient of variation of the content of carbon particles in the above n samples ≤ 8%. The coefficient of variation is also called the "standard deviation rate", which is the ratio of the standard deviation to the average multiplied by 100%. The coefficient of variation is an absolute value reflecting the degree of data dispersion. The smaller the coefficient of variation value, the smaller the degree of data dispersion, indicating that the content of carbon particles at different parts of the fiber surface varies less, and the distribution of carbon particles on the fiber surface is more uniform.

[0051] For example, randomly take 10 samples at different parts of the carbon particle / fiber composite filter material. It can be obtained that the average content of carbon particles on the fiber in the 10 samples is 25 wt%, the sample standard deviation is 0.1 wt%, and the coefficient of variation is 0.4%. It can be considered that the carbon particles are uniformly distributed on the fiber surface.

[0052] The nano-biomass colloidal carbon of the present invention not only has a large specific surface area, strong adsorption, corrosion resistance, high temperature resistance, and stable chemical properties, but also has excellent dielectric properties. The mass ratio of nano-spherical carbon particles to fibers is 1:100 to 1:500; the diameter of the fibers is 10 to 100 μm; a carbon thin layer composed of nano-carbon particles is formed in-situ on the fiber surface. The average particle size of the nano-carbon particles is 100 to 700 nm, the thickness of the carbon thin layer is 100 to 500 nm, and its coating rate on the fiber surface is more than 95%. Combining Figure 2 it can be seen that no carbon thin layer cross-linking is formed in the gaps / channels between multiple fibers.

[0053] The above-mentioned carbon thin layer cross-linking can be understood as the carbon particle thin layers on adjacent or nearby fibers growing around, thus covering the fiber surface in a large area and filling the gaps / channels between multiple fibers (the fibers have gaps / channels for gas passage).

[0054] After being detected by a specific surface area and pore size analysis instrument, the carbon particle / fiber composite filter material of the present invention has a dielectric constant of 4.74 on the premise of maintaining a porosity of 85.4%, which is 3.48 higher than the dielectric constant of the prior art (the relative dielectric constant ε of the fiber is increased by the uniformly distributed nano-carbon particles r from 1.26 to 4.74).

[0055] In addition, the biomass nano-carbon prepared by in-situ polycondensation carbonization of the present invention has a porous structure and a large specific surface area, which can increase the dust holding capacity of the fiber and extend the service life of the filter; the strong adsorption ability of the biomass carbon leads to the enrichment of O3 at local positions, catalytically reducing O3 to O2, and removing ozone generated by corona discharge of particulate charge while removing particulate matter.

[0056] The above-mentioned fibers have certain acid resistance and are selected from any one or more of lactide polymer fibers, glycolide polymer fibers, polyester fibers (abbreviation: polyester (PET)), polyamide fibers (abbreviation: nylon, polyamide, nylon (PA)), polypropylene fibers (abbreviation: polypropylene (PP)), polyethylene fibers (PE), polyvinyl chloride fibers (abbreviation: chloron (PVC)), polyacrylonitrile fibers (abbreviation: acrylic, artificial wool), viscose fibers, polyurethane fibers (PU). Preferably, they are polyester fibers (abbreviation: polyester (PET)), polyamide fibers (abbreviation: nylon, polyamide, nylon (PA)) and polyurethane fibers (PU), where:

[0057] The above-mentioned polyester fiber refers to a polyester formed by polycondensation of monomers having both hydroxyl and carboxyl groups, or a polyester formed by polycondensation of aliphatic dicarboxylic acids and aliphatic diols, or a polyester or copolyester formed by ring-opening polymerization of aliphatic lactones. The molecular weight of the aliphatic polyester is 50,000 - 250,000. The polyester formed by polycondensation of monomers having both hydroxyl and carboxyl groups is polylactic acid directly polycondensed from lactic acid; the polyester formed by polycondensation of aliphatic dicarboxylic acids and aliphatic diols is polybutylene succinate, polyhexamethylene sebacate, polyethylene succinate or polyhexylene succinate; the polyester formed by ring-opening polymerization of aliphatic lactones is polylactic acid formed by ring-opening polymerization of lactide, and polycaprolactone formed by ring-opening polymerization of caprolactone; the copolyester is poly (lactic-co-glycolic acid).

[0058] The above-mentioned polyamide fiber refers to polyhexamethylene adipamide obtained by polycondensation of diamine and diacid, and the chemical structural formula of its long-chain molecule is: H-[HN(CH2)XNHCO(CH2)YCO] n -OH; or obtained by polycondensation or ring-opening polymerization of caprolactam, and the chemical structural formula of its long-chain molecule is: H-[NH(CH2)XCO] n -OH.

[0059] The above-mentioned polyurethane fiber is a block copolymer of a polyester or polyether containing hydroxyl groups at the ends and an aromatic diisocyanate. It is composed of alternating flexible long-chain segments (soft segments) and rigid short-chain segments (rigid segments). The soft segments are low-molecular-weight polyester or polyether segments without crystallinity, which are easily deformed under stress, so that the obtained fiber can be stretched and deformed; the rigid segments are aromatic diisocyanate segments with crystallinity and capable of producing transverse cross-linking, which do not deform under stress, can prevent transverse slippage, and make the obtained fiber have sufficient resilience. The content of soft segments in the polyurethane fiber chain segment structure is generally not less than 80% - 85%. According to the components of the soft segments, it can be divided into two types: polyester type and polyether type. DuPont Company in the United States produces polyether type, and American Synthetic Rubber Company produces polyester type.

[0060] Example 1

[0061] For the preparation method of the carbon particle / fiber composite filter material in this example, 10 g of dry rice husk is weighed and mixed with 100 ml of sulfuric acid with a mass fraction of 72%. Stir for 10 min under the condition of a 50°C water bath. After solid-liquid separation, the filtrate is a sugar-acid solution containing sugars and acids; dilute the sugar-acid solution with water, adjust the mass fraction of sulfuric acid to 42%, and completely immerse the PU fiber. Under normal pressure, in a 95°C drying oven, dehydration, polycondensation, and carbonization reactions occur for 5 h, and nano-scale flocculent carbon sphere particles with an average particle size of 300 nm are formed on the surface of the PU fiber. The nano-scale flocculent carbon sphere particles are continuously arranged to form a carbon thin layer of 700 nm.

[0062] The carbon particle / PU fiber composite filter material prepared in this example filters submicron particulate matter in indoor air. Using outdoor particles as the pollution source, the wind speed is controlled at v = 1.1 m / s, and the experimental conditions are: T = 34 - 36 °C, relative humidity 23% - 29%, discharge voltage U1 = +9 kV, polarization voltage U2 = +21 kV. The filtration efficiency of the above carbon particle / PU fiber composite filter material for 0.3 μm particulate matter is shown in the following table.

[0063]

[0064] Example 2

[0065] The preparation method of the carbon particle / PU fiber composite filter material in this example: Weigh 10 g of dry rice husk and mix it with 100 ml of sulfuric acid with a mass fraction of 82%. Stir for 10 min under the condition of a 45 °C water bath. After solid-liquid separation, the filtrate is a sugar-acid solution containing sugars and acids; Dilute the sugar-acid solution with water, adjust the mass fraction of sulfuric acid to 36%, and completely immerse the PU fiber. Under normal pressure conditions, in a 95 °C drying oven, dehydration, polycondensation, and carbonization reactions occur for 6 h, and nano-scale flocculent carbon sphere particles with an average particle size of 400 nm are formed on the surface of the PU fiber. The nano-scale flocculent carbon sphere particles are continuously arranged to form a 600 nm carbon thin layer.

[0066] The carbon particle / PU fiber composite filter material prepared in this example filters submicron particulate matter in indoor air. Using outdoor particles as the pollution source, the wind speed is controlled at v = 1.1 m / s, and the experimental conditions are: T = 34 - 36 °C, relative humidity 23% - 29%, discharge voltage U1 = +9 kV, polarization voltage U2 = +21 kV. The filtration efficiency of the above carbon particle / PU fiber composite filter material for 0.3 μm particulate matter is shown in the following table.

[0067]

[0068] Example 3

[0069] The preparation method of the carbon particle / PU fiber composite filter material in this example: Weigh 10 g of dry coconut shell and mix it with 100 ml of sulfuric acid with a mass fraction of 76%. Stir for 20 min under the condition of a 40 °C water bath. After solid-liquid separation, the filtrate is a sugar-acid solution containing sugars and acids; Dilute the sugar-acid solution with water, adjust the mass fraction of sulfuric acid to 32%, and completely immerse the filter fiber. Under normal pressure conditions, in a 95 °C drying oven, dehydration, polycondensation, and carbonization reactions occur for 6 h, and nano-scale flocculent carbon sphere particles with an average particle size of 200 nm are formed on the surface of the PU fiber. The nano-scale flocculent carbon sphere particles are continuously arranged to form a 500 nm carbon thin layer.

[0070] The carbon particle / PU fiber composite filter material prepared in this example filters sub-micron particulate matter in indoor air. Using outdoor particles as the pollution source, the wind speed is controlled at v = 1.1 m / s, and the experimental conditions are: T = 34 - 36 °C, relative humidity 23% - 29%, discharge voltage U1 = +9 kV, polarization voltage U2 = +21 kV. The filtration efficiency of the above carbon particle / PU fiber composite filter material for 0.3-μm particulate matter is shown in the following table.

[0071]

[0072] Example 4

[0073] The preparation method of the carbon particle / PET fiber composite filter material in this example: Weigh 10 g of dry straw and mix it with 100 ml of sulfuric acid with a mass fraction of 62%. Stir for 10 min under the condition of a 50 °C water bath. After solid-liquid separation, the filtrate is a sugar-acid solution containing sugars and acids. Dilute the sugar-acid solution with water to adjust the mass fraction of sulfuric acid to 42%, and completely immerse the PET fibers. Under normal pressure conditions, in a 90 °C drying oven, dehydration, polycondensation, and carbonization reactions occur for 6 h, forming nano-scale flocculent carbon sphere particles with an average particle size of 500 nm on the surface of the PET coarse filter fibers. The nano-scale flocculent carbon sphere particles are continuously arranged to form a carbon thin layer of 700 nm.

[0074] The carbon particle / PET fiber composite filter material prepared in this example filters sub-micron particulate matter in indoor air. Using outdoor particles as the pollution source, the wind speed is controlled at v = 1.1 m / s, and the experimental conditions are: T = 34 - 36 °C, relative humidity 23% - 29%, discharge voltage U1 = +9 kV, polarization voltage U2 = +21 kV. The filtration efficiency of the above carbon particle / PET fiber composite filter material for 0.3-μm particulate matter is shown in the following table.

[0075]

[0076] The above schematically describes the present invention and its embodiments. This description is not restrictive. What is shown in the drawings is only one of the embodiments of the present invention, and the actual structure is not limited thereto. Therefore, if those of ordinary skill in the art are inspired by it and, without departing from the gist of the present invention, design similar structural forms and embodiments to this technical solution without creative efforts, they shall fall within the protection scope of the present invention.

Claims

1. A carbon particle / fiber composite filter material, comprising fibers and nano-carbon particles, characterized in that: The mass ratio of the nano-carbon particles to the fibers is 1:100 to 1:500; wherein the diameter of the fibers is 10 to 100 μm; A carbon thin layer composed of nano-carbon particles is formed in-situ on the fiber surface. The average particle size of the nano-carbon particles is 100 to 700 nm; the thickness of the carbon thin layer is 100 to 700 nm, and no cross-linking of the carbon thin layer is formed in the gaps / pores between multiple fibers; The fibers are selected from any one or more of lactide polymer fibers, glycolide polymer fibers, polyester fibers, polyamide fibers, polypropylene fibers, polyethylene fibers, polyvinyl chloride fibers, polyacrylonitrile fibers, viscose fibers, and polyurethane fibers.

2. The carbon particle / fiber composite filter material according to claim 1, characterized in that: The nano-carbon particles are spherical.

3. The carbon particle / fiber composite filter material according to claim 1, wherein: A carbon thin layer composed of nano-carbon particles is uniformly formed in-situ on the fiber surface. The detection method for the uniform distribution of the carbon particles on the fiber surface is as follows: Randomly take n samples at different positions of the carbon particle / fiber composite filter material, where n is a positive integer greater than or equal to 10, analyze the content of the carbon particles on the fiber surface, and the coefficient of variation of the content of the carbon particles in the n samples ≤ 8%.

4. A method for preparing the carbon particle / fiber composite filter material according to any one of claims 1 to 3, characterized in that: The preparation method is the in-situ growth method, and the in-situ growth method includes the following steps: Step S1, drying: Remove impurities from the biomass raw material and obtain biomass material A through drying treatment; Step S2, concentrated acid hydrolysis: Take a certain amount of biomass material A obtained in Step S1 and concentrated sulfuric acid, and mix them in a ratio of 5 to 30 g / ml; Stir well at 40 to 50 °C, and the hydrolysis time is 15 to 20 min to obtain a mixed solution B; Step S3, dilution and separation: Add distilled water to the mixed solution B obtained in Step S2 to dilute the sulfuric acid concentration to a mass fraction of 32% to 42%, and perform solid-liquid separation to obtain a sugar-acid solution C; Step S4, preparation of composite fibers: Select fibers and immerse them in the sugar-acid solution prepared in Step S3. Under normal pressure, place them in a drying oven at 85 to 95 °C for a carbonization reaction of reducing sugar for 5 to 7 h to form a dense and uniform biomass nano-carbon thin layer on the fiber surface, and obtain a carbon particle / fiber composite filter material.

5. The preparation method of the carbon particle / fiber composite filter material according to claim 4, characterized in that: In Step S2, the biomass is rice husk, straw, poplar catkin or coconut shell.

6. The preparation method of the carbon particle / fiber composite filter material according to claim 4, characterized in that: In Step S2, the mass fraction of the concentrated sulfuric acid is 62% to 82%.

7. The preparation method of the carbon particle / fiber composite filter material according to claim 4, characterized in that: In Step S4, the detection method for the uniform distribution of the carbon particles on the fiber surface is as follows: Randomly take n samples at different positions of the carbon particle / fiber composite filter material, where n is a positive integer greater than or equal to 10, analyze the content of the carbon particles on the fiber surface, and the coefficient of variation of the content of the carbon particles in the n samples ≤ 8%.

8. A filter element, comprising parallel metal meshes respectively connected to a positive electrode and a ground electrode, characterized in that: The metal mesh is interposed with the carbon particle / fiber composite filter material according to any one of claims 1 to 3, and induced charges are generated through the polarization effect to capture charged fine particles.

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