Basalt-based nanofiber membrane coated filter material and preparation method thereof
By constructing a gradient pore structure and a surface nano-catalytic layer in basalt fiber filter media, the problems of insufficient catalytic degradation of dioxins and filtration capacity of basalt fiber filter media at high temperatures are solved, achieving high-efficiency filtration and self-cleaning effects.
Patent Information
- Application Number
- CN202511782384.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-29
- Publication Date
- 2026-02-10
AI Technical Summary
Existing basalt fiber filter media are difficult to catalytically degrade dioxins at high temperatures, and the filtration mechanism is mainly deep filtration, resulting in poor filtration capacity for ultrafine particles and difficulty in dust removal.
The basalt-based nanofiber membrane filter material adopts an inside-out gradient pore size structure and has a nanocatalytic layer on its surface, which contains metal oxide nanoparticles and nano-silica clusters for catalytic degradation of dioxins. The gradient structure achieves high-precision, low-resistance filtration.
It achieves efficient catalytic degradation of dioxins, improves filtration accuracy and self-cleaning ability, extends filter media life, and reduces flow resistance and cleaning difficulty.
Smart Images
Figure CN121490474A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of filter material technology, specifically relating to a basalt-based nanofiber membrane coated filter material and its preparation method. Background Technology
[0002] With the acceleration of industrialization, flue gas emissions from industries such as thermal power generation, steel, cement, and waste incineration have become major sources of air pollution. my country's "Emission Standard of Air Pollutants for Thermal Power Plants" (GB13223-2003) requires that the concentration of particulate matter emissions from newly built coal-fired boilers be ≤50mg / m³, and in some key areas, ≤20mg / m³. Traditional technologies such as electrostatic precipitators and wet dust collectors are no longer sufficient to meet the ultra-low emission requirements. In particular, existing dust removal filter materials cannot meet the requirements for high temperature resistance, long service life, and self-cleaning.
[0003] Basalt fiber's high-temperature resistance makes it an ideal alternative material. However, basalt fiber still has significant shortcomings as a filter media: First, its smooth surface and high chemical inertness make it difficult to catalytically degrade gaseous pollutants such as dioxins; second, its filtration mechanism is mainly based on deep filtration, which has poor filtration capacity for ultrafine particles and cannot automatically clean itself. Summary of the Invention
[0004] To address the shortcomings of existing technologies, one aspect of this invention provides a basalt-based nanofiber membrane-coated filter media. This filter media possesses an inner-to-outer gradient pore size structure, enabling high-precision, low-resistance surface filtration. Simultaneously, its surface is constructed with a nano-catalytic functional layer capable of catalytically degrading pollutant particles such as dioxins. Furthermore, this invention also provides a method for preparing the basalt-based nanofiber membrane-coated filter media, which is suitable for industrial production.
[0005] As a first aspect of the present invention, a basalt-coated filter material is provided, comprising a basalt fiber substrate and a nanocatalytic layer distributed on the surface of the basalt fiber substrate, wherein the fiber diameter of the basalt fiber substrate decreases from the bottom layer to the top layer.
[0006] The nanocatalytic layer is distributed in clusters on the surface of the fiber voids of the basalt fiber substrate, and the composition of the nanocatalytic layer includes metal oxide nanoparticles and nano-silica.
[0007] In the aforementioned basalt-coated filter media, the bottom layer fiber diameter of the basalt fiber substrate is 5-12 μm, and the surface layer fiber diameter is 1-4 μm.
[0008] In the above-mentioned basalt-coated filter material, the surface layer of the basalt fiber substrate is also mixed with aluminum silicate ceramic fibers with a diameter of less than 1 μm.
[0009] In the above-mentioned basalt-coated filter material, the metal oxide nanoparticles are cerium and manganese composite oxides.
[0010] In another aspect, a method for preparing basalt-based nanofiber membrane coated filter material is also provided, comprising the following steps:
[0011] S1. Prepare basalt fibers with fiber diameters of 5-12 μm and 1-4 μm;
[0012] S2. Using the fibers prepared in S1 as raw materials, prepare basalt fiber substrates with fiber diameter decreasing from the bottom layer to the surface layer.
[0013] S3. The surface of the basalt fiber substrate obtained in S2 is treated to obtain a nano-catalytic layer that is distributed in clusters on the surface of the basalt fiber substrate.
[0014] In the above-mentioned method for preparing basalt-coated filter media, step S1, the step of preparing basalt fibers with a fiber diameter of 5-12 μm and a fiber diameter of 1-4 μm, includes:
[0015] Acid-washed basalt ore raw materials are mixed and melted with a flux, and then the bottom layer fibers with an average diameter of 5-12 μm and the top layer fibers with an average diameter of 1-4 μm are prepared by controlling the process parameters through centrifugal spinning.
[0016] In the above-mentioned method for preparing basalt-coated filter media, step S2, which uses the fibers prepared in S1 as raw materials to prepare a basalt fiber substrate with fiber diameter decreasing from the bottom layer to the top layer, includes:
[0017] S201. Disperse bottom layer fibers with an average diameter of 5-12 μm and top layer fibers with an average diameter of 1-4 μm in water to form uniformly distributed bottom layer slurry and top layer slurry.
[0018] S202. Using a multi-layer inclined mesh forming device, the bottom layer slurry is first transported to the forming mesh to form a loose bottom layer; before the bottom layer is completely dehydrated, the top layer slurry is covered on the bottom layer; using the power of water flow, the fine fibers of the top layer are enriched in the upper part to form a wet preform with a gradient distribution of fiber diameter.
[0019] S203. After drying the wet blank, sintering and strengthening it at 800-900℃ is carried out to obtain a basalt fiber substrate with fiber diameter decreasing from the bottom layer to the surface layer.
[0020] In the above-mentioned method for preparing basalt-coated filter media, in step S201, aluminum silicate ceramic fibers and biomass soluble fibers are added to the surface slurry, wherein the biomass soluble fibers serve as a temporary binder.
[0021] In the above-mentioned method for preparing basalt-coated filter media, step S3 involves treating the surface of the basalt fiber substrate obtained in S2 to obtain a nano-catalytic layer distributed in clusters on the surface of the basalt fiber substrate. Specific steps include:
[0022] S301. Prepare tetraethyl orthosilicate sol containing catalytic metal salt;
[0023] S302. The tetraethyl orthosilicate sol is impregnated into the bottom layer and / or top layer of the basalt fiber substrate by means of impregnation.
[0024] S303. The basalt fiber substrate impregnated with tetraethyl orthosilicate sol obtained in S202 is heat-treated at 300-500°C to convert the sol into silicon dioxide carrying metal oxide nanoparticles.
[0025] In the above-mentioned method for preparing basalt-coated filter media, the filter media obtained after step S303 is immersed in a complex solution of tannic acid and metal ions, and after being taken out, it is dried and heat-treated at 200-350℃ to form a catalytic active layer on the structure of the filter media.
[0026] The beneficial effects of this invention are as follows: the fiber diameter of the basalt fiber substrate decreases from the bottom layer to the top layer, resulting in a filter material with a stepped fiber diameter distribution. Coarse particles are intercepted at the bottom layer, while fine particles are captured in the dense top layer, ensuring both filtration accuracy and easy dust removal. The metal oxide nanoparticles in the nanocatalytic layer are Ce-Mn composite oxides, which can effectively catalyze the degradation of dioxins at 180-400℃, completing filtration and catalysis simultaneously, thus achieving the self-cleaning effect of the filter material. Furthermore, the basalt fiber is resistant to high temperatures, which can greatly extend the service life of the filter material. Attached Figure Description
[0027] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings used in the description of the specific embodiments or the prior art will be briefly introduced below.
[0028] Figure 1 This is an electron microscope image of a nanocatalytic layer on the surface of a basalt fiber substrate in one embodiment of the present invention. Detailed Implementation
[0029] The embodiments of the technical solution of the present invention will be described in detail below. These embodiments are only used to illustrate the technical solution of the present invention more clearly, and are therefore merely examples and should not be used to limit the scope of protection of the present invention.
[0030] It should be noted that, unless otherwise stated, the technical or scientific terms used in this application should have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.
[0031] As a first aspect of the present invention, a basalt-based nanofiber membrane coating filter material is provided, comprising a substrate composed of basalt fibers and a nanocatalytic layer disposed on the surface of the surface fibers of the basalt fiber substrate; the basalt fiber substrate has a gradient structure, wherein the fiber diameter of the gradient structure substrate decreases from the bottom layer to the surface layer, and the nanocatalytic layer comprises a clustered structure composed of metal oxide nanoparticles and nano-silica.
[0032] In some embodiments, the bottom layer of the gradient structure substrate is composed of basalt fibers with a diameter of 5-12 μm, and the top layer is composed of basalt fibers with a diameter of 1-4 μm. To improve the filtration accuracy of the surface, aluminosilicate ceramic fibers with an average diameter of less than 1 μm are mixed into the top layer.
[0033] In some embodiments, the metal oxide nanoparticles are a composite of cerium oxide (CeO2) and manganese oxide (MnO2). This composite exhibits superior low-temperature catalytic reduction performance and can effectively disrupt the molecular structure of dioxins.
[0034] As a second aspect of the present invention, a method for preparing a basalt-based nanofiber membrane-coated filter material is provided, comprising the following steps:
[0035] Step S1: Preparation of basalt fibers of different diameters. After acid washing and drying of crushed basalt rock particles with a 10%–20% hydrochloric acid solution, 100 parts by weight are mixed with 5 parts by weight of soda ash as a flux; the mixture is then melted in a high-temperature furnace at 1480–1500℃ for at least 2 hours to obtain a homogeneous melt.
[0036] Preparation of the base fiber: The melt was introduced into the first centrifugal spinning machine, the rotation speed was controlled at 2800 rpm, the drawing roller gap was 1.2 mm, and basalt fibers with an average diameter of about 8 μm were prepared.
[0037] Preparation of surface layer fibers: The melt was introduced into a second centrifugal spinning machine, the rotation speed was controlled at 4500 rpm, and the drawing roller gap was 0.8 mm, to prepare basalt fibers with an average diameter of about 2.5 μm.
[0038] Step S2: Prepare gradient structure basalt composite filter material substrate.
[0039] S201. The fibers of different diameters obtained in step S1 are dispersed in water to prepare a bottom layer slurry and a top layer slurry. Preferably, 3-8 wt% of aluminosilicate ceramic fibers are mixed into the top layer slurry. At the same time, 1-3 wt% of lyocell fibers are added to the slurry as a temporary binder.
[0040] S202. The bottom layer slurry is conveyed to the multi-layer inclined mesh forming machine to form a loose bottom layer. Before the bottom layer is dehydrated, the top layer slurry is covered on the bottom layer, and the wet blank is naturally formed by the water flow dynamics, with the fiber diameter from the bottom layer to the top layer being coarse to fine and the density from sparse to dense.
[0041] S203. After drying the wet blank, it is transferred to a high-temperature sintering furnace and sintered at a temperature of 800-900℃. During this process, the lyocell fibers are burned off, while the basalt fibers and ceramic fibers undergo solid-phase sintering at the contact points, forming strong weld points. The resulting basalt fiber substrate has a high-strength, high-porosity network structure.
[0042] Step S3: Surface nano-modification to form a catalytic layer.
[0043] S301. Preparation of catalytic sol. Using tetraethyl orthosilicate as a precursor and ethanol and water as solvents, SiO2 sol is prepared under ammonia catalysis. Cerium nitrate and manganese nitrate, which act as catalysts, are added to the prepared SiO2 sol, and the mixture is stirred to dissolve the catalytic metal salts cerium nitrate and manganese nitrate in the SiO2 sol.
[0044] S302, Surface Coating. Using the dip-coating method, the surface layer of the basalt fiber substrate with a gradient structure obtained in step S2 is brought into contact with and loaded with the SiO2 sol obtained in S301.
[0045] S303, Gel and Curing: The substrate with SiO2 sol loaded after step S302 is aged at room temperature, allowing the SiO2 sol to form a gel on the fiber surface through hydrolysis-condensation reaction. Subsequently, heat treatment at 300-500℃ transforms the gel into a robust inorganic nano-SiO2 coating. This process simultaneously converts the metal salts into highly active CeO2 and MnO2 nanoparticles. This SiO2 coating grows in situ on the fiber surface, forming a firmly anchored cluster structure, such as... Figure 1 As shown.
[0046] S304. To further improve the dispersibility and loading strength of the catalytic components, the filter material forming the catalytic layer is immersed in a complex solution of tannic acid and metal ions Ce³⁺ and Mn²⁺. Utilizing the self-polymerization properties of tannic acid under weakly alkaline conditions, a highly adhesive polytannic acid film is then coated onto the already formed cluster structure to further anchor the catalytic active sites. Finally, after heat treatment at 200-350℃, the final basalt-coated filter material is obtained.
[0047] Example 1
[0048] Preparation of melt: After acid washing and drying of crushed basalt rock particles with a 10%–20% hydrochloric acid solution, take 100 parts by weight; mix them evenly with 5 parts by weight of soda ash as a flux; melt them in a high-temperature furnace at 1480–1500℃ for at least 2 hours to obtain a homogeneous melt.
[0049] Preparation of the base fiber: The melt was introduced into the first centrifugal spinning machine, the rotation speed was controlled at 2800 rpm, the drawing roller gap was 1.2 mm, and basalt fibers with an average diameter of about 8 μm were prepared.
[0050] Preparation of surface layer fibers: The melt was introduced into a second centrifugal spinning machine, the rotation speed was controlled at 4500 rpm, and the drawing roller gap was 0.8 mm, to prepare basalt fibers with an average diameter of about 2.5 μm.
[0051] Pulping steps: The bottom layer fibers and top layer fibers are dispersed with water at a mass concentration of 0.1%, and 2 wt% Lyocell fiber relative to the fiber mass is added as a temporary binder. An additional 5 wt% of aluminosilicate ceramic fibers with an average diameter of 0.8 μm are added to the top layer slurry.
[0052] Gradient forming: Using an inclined wire mesh forming machine, the bottom layer slurry is first applied to the wire mesh to form a wet layer of about 1.5 mm thickness; before dewatering, the top layer slurry is applied to cover it, forming a top layer of about 0.5 mm thickness. By adjusting the water pressure and vacuum, the fine fibers are enriched in the upper part to form a gradient structure wet preform.
[0053] Sintering reinforcement: The wet blank is dried at 105℃ and then sent into a mesh belt sintering furnace. The temperature is raised to 850℃ at a rate of 5℃ / min and held for 30 minutes. Then it is naturally cooled to room temperature to obtain a gradient structure basalt composite filter material substrate.
[0054] The obtained substrate with a gradient structure was then nano-sized on its surface. 20 ml of tetraethyl orthosilicate was added to 80 ml of anhydrous ethanol and stirred to form a tetraethyl orthosilicate solution. 2.17 g of cerium nitrate nonahydrate and 1.79 g of 50% manganese nitrate solution were dissolved in a mixture of 20 ml of deionized water and 20 ml of ethanol, and 1 ml of concentrated ammonia was added to prepare the catalyst solution. Under vigorous stirring, the catalyst solution was slowly added dropwise to the tetraethyl orthosilicate solution, and stirring continued for 2 hours, forming a pale yellow transparent catalytic sol.
[0055] The surface layer of the sintered and reinforced gradient-structured basalt composite filter material substrate was immersed in a sol for 10 seconds and then pulled out at a uniform speed of 100 mm / min. The substrate was then aged at room temperature for 24 hours to allow the sol to fully gel.
[0056] The gelled filter material was placed in a muffle furnace and heated to 450°C at a rate of 2°C / min. After holding at this temperature for 1 hour, it was allowed to cool naturally. At this point, a silica cluster structure carrying CeO2-MnO2 nanoparticles was formed on the fiber surface.
[0057] Testing showed that the basalt-coated filter media prepared in this embodiment had a unit area mass of 550 g / m² and a thickness of 2.0 mm. At 250℃, its degradation efficiency for gaseous dioxins reached over 85%. After 10,000 cycles of 0.6 MPa pulse cleaning experiments, the filtration efficiency showed a slight decrease, and the catalyst layer slightly detached.
[0058] Example 2:
[0059] Preparation of melt: After washing and drying the crushed basalt rock particles with 10%–20% hydrochloric acid solution, take 100 parts by weight; mix them evenly with 5 parts by weight of soda ash, and melt them at 1480–1500℃ for at least 2 hours to obtain a homogeneous melt.
[0060] Fiber preparation: The melt was fed into two centrifugal spinning machines. The first machine was operated at a speed of 2800 rpm and a drawing roller gap of 1.2 mm to produce bottom layer fibers with an average diameter of about 8 μm; the second machine was operated at a speed of 4500 rpm and a drawing roller gap of 0.8 mm to produce top layer fibers with an average diameter of about 2.5 μm.
[0061] Pulping and Molding: The bottom layer fibers and top layer fibers were dispersed in water at a mass concentration of 0.1%, and 2 wt% lyocell fibers were added as a temporary binder. An additional 5 wt% aluminosilicate ceramic fibers with an average diameter of 0.8 μm were added to the top layer slurry. Using an inclined mesh forming device, the bottom layer slurry was first applied to form a wet layer of approximately 1.5 mm thickness, and then, before dehydration, the top layer slurry was applied to form a top layer of approximately 0.5 mm thickness. The water pressure and vacuum were adjusted to enrich the fine fibers on top, obtaining a gradient structure wet preform.
[0062] Sintering reinforcement: After drying the wet blank at 105℃, it is heated to 850℃ at 5℃ / min in a mesh belt sintering furnace and held for 30 minutes. After natural cooling, a gradient structure basalt composite filter material substrate is obtained.
[0063] Catalyst layer construction: A tetraethyl orthosilicate solution was prepared by mixing 20 ml of tetraethyl orthosilicate with 80 ml of anhydrous ethanol. 2.17 g of cerium nitrate nonahydrate and 1.79 g of 50% manganese nitrate solution were dissolved in a mixture of 20 ml of deionized water and 20 ml of ethanol, and 1 ml of concentrated ammonia was added as the catalyst solution. The catalyst solution was slowly added dropwise to the tetraethyl orthosilicate solution under vigorous stirring, and stirring was continued for 2 hours to obtain a pale yellow catalytic sol. The substrate surface was immersed in the sol for 10 seconds using the dip-coating method, and then pulled at a speed of 100 mm / min. The sol was aged at room temperature for 24 hours to allow gelation. Subsequently, the temperature was increased to 450℃ at 2℃ / min and held for 1 hour in a muffle furnace. After natural cooling, a silica cluster structure supporting CeO2-MnO2 nanoparticles was formed on the fiber surface.
[0064] Surface nano-modification: Prepare 500 mL of a pH 8.5 Tris-HCl buffer solution, add 2.17 g of cerium nitrate nonahydrate (Ce(NO3)3·9H2O, 5.0 mmol) and 1.79 g of 50% manganese nitrate (Mn(NO3)2) solution (providing 5.0 mmol of Mn²⁺), and 0.5 g of tannic acid, and stir until completely dissolved to form a biomimetic anchoring working solution. Immerse the filter media, which has undergone the sol-gel step and preliminary heat treatment at 450℃, into this 500 mL buffer solution, ensuring that the solution completely covers the surface layer of the basalt filter media, and slowly shake at 40℃ for 2 hours.
[0065] Remove the filter media, gently rinse with deionized water, dry it, and then heat-treat it at 300°C for 1 hour under nitrogen protection. This process partially carbonizes the polytannic acid into nitrogen-doped carbon and completely converts the metal ions into nano-oxides, thereby obtaining a functional filter media with higher catalytic activity and stronger loading.
[0066] Tests showed that the filter material obtained in this embodiment achieved a dioxin degradation efficiency of up to 90% at 200℃, demonstrating excellent low-temperature catalytic activity. After ultrasonic oscillation treatment at 300W for 30 minutes, no signs of detachment were observed under an electron microscope, and the catalytic activity did not decrease, indicating that the catalyst layer has extremely strong adhesion.
[0067] Comparative example:
[0068] Using the same basalt fiber raw material as in Example 1, but without gradient molding and surface nano-modification, coarse and fine fibers were mixed and then prepared into needle-punched felt filter material with a thickness of 2.0 mm through conventional needle-punching process.
[0069] Test results show that the comparative filter media has a filtration efficiency of 95% for 0.3μm particles and an initial pressure drop of 110Pa. However, in the dust holding capacity test, its pressure drop rises much faster than that of the filter media in Examples 1 and 2, and the residual pressure drop after cleaning is high. Furthermore, this filter media cannot degrade dioxins.
[0070] The following statistical analysis compares the performance indicators of the comparative example with those of Example 1 and Example 2.
[0071] Table 1. Comparison of performance indicators between the comparative example and Examples 1 and 2
[0072] Performance indicators Example 1 Example 2 Comparative Example Filtration efficiency (0.3μm particles) 98.9% 99% 95% Initial pressure drop (Pa) 95 98 110 Dust holding capacity The pressure drop increases slowly, and the residual pressure decreases after dust removal. The pressure drop increases slowly, and the residual pressure decreases after dust removal. The pressure drop increases rapidly, and the residual pressure is high after dust removal. Dust removal performance After 10,000 cleaning cycles, the filtration efficiency decreased slightly. After 10,000 cleaning cycles, the filtration efficiency shows no decline. Filtration efficiency is prone to fluctuation and decline after dust removal. Dioxin degradation Decomposition efficiency >85% at 250℃ 90% can be achieved at 200℃ Non-degradable Catalyst layer firmness After 10,000 pulse cleaning cycles, the catalyst layer only peeled off slightly. After 30 minutes of ultrasonic vibration, there was no sign of detachment. No catalyst layer
[0073] Analysis of the table above shows that the initial filtration efficiency of the comparative example and Examples 1 and 2 is relatively high, but Examples 1 and 2 have better precision due to the rich fine fibers in their surface layers. The gradient structure of Examples 1 and 2 facilitates gas passage, reduces flow resistance, and lowers initial energy consumption. The gradient structure of Examples 1 and 2 traps most particulate matter in the surface layer, making it easy to remove; the comparative example has deep dust accumulation, making it difficult to clean. Examples 1 and 2 have catalytic components loaded on their surfaces through nano-sizing, enabling them to purify high-temperature exhaust gases. Compared to Example 1, Example 2 shows better adhesion between the catalytic layer and the substrate, and better dioxin degradation ability at lower temperatures.
[0074] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention.
Claims
1. A basalt-based nanofiber membrane coated filter material, characterized in that, It includes a basalt fiber substrate and a nanocatalytic layer distributed on the surface of the basalt fiber substrate, wherein the fiber diameter of the basalt fiber substrate decreases from the bottom layer to the top layer; The nanocatalytic layer is distributed in clusters on the surface of the fiber voids of the basalt fiber substrate, and the composition of the nanocatalytic layer includes metal oxide nanoparticles and nano-silica.
2. The basalt-coated filter material according to claim 1, characterized in that, The bottom layer fiber of the basalt fiber substrate has a diameter of 5-12 μm, and the surface layer fiber has a diameter of 1-4 μm.
3. The basalt-coated filter material according to claim 2, characterized in that, The surface layer of the basalt fiber substrate also contains aluminum silicate ceramic fibers with a diameter of less than 1 μm.
4. The basalt-coated filter material according to claim 1, characterized in that, The metal oxide nanoparticles are cerium and manganese composite oxides.
5. A method for preparing basalt-based nanofiber membrane coated filter media as described in any one of claims 1-4, characterized in that, Includes the following steps: S1. Prepare basalt fibers with fiber diameters of 5-12 μm and 1-4 μm; S2. Using the fibers prepared in S1 as raw materials, prepare basalt fiber substrates with fiber diameter decreasing from the bottom layer to the surface layer. S3. The surface of the basalt fiber substrate obtained in S2 is treated to obtain a nano-catalytic layer that is distributed in clusters on the surface of the basalt fiber substrate.
6. The preparation method according to claim 5, characterized in that, Step S1, the steps for preparing basalt fibers with a diameter of 5-12 μm and a diameter of 1-4 μm, include: Acid-washed basalt ore raw materials are mixed and melted with a flux, and then the bottom layer fibers with an average diameter of 5-12 μm and the top layer fibers with an average diameter of 1-4 μm are prepared by controlling the process parameters through centrifugal spinning.
7. The preparation method according to claim 6, characterized in that, Step S2, using the fibers prepared in S1 as raw materials, involves preparing a basalt fiber substrate with fiber diameters decreasing from the bottom layer to the top layer, including: S201. Disperse bottom layer fibers with an average diameter of 5-12 μm and top layer fibers with an average diameter of 1-4 μm in water to form uniformly distributed bottom layer slurry and top layer slurry. S202. Using a multi-layer inclined mesh forming device, the bottom layer slurry is first transported to the forming mesh to form a loose bottom layer; before the bottom layer is completely dehydrated, the top layer slurry is covered on the bottom layer; using the power of water flow, the fine fibers of the top layer are enriched in the upper part to form a wet preform with a gradient distribution of fiber diameter. S203. After drying the wet blank, sintering and strengthening it at 800-900℃ is carried out to obtain a basalt fiber substrate with fiber diameter decreasing from the bottom layer to the surface layer.
8. The preparation method according to claim 7, characterized in that, In step S201, aluminum silicate ceramic fibers and biomass soluble fibers are added to the surface slurry, wherein the biomass soluble fibers serve as a temporary binder.
9. The preparation method according to claim 8, characterized in that, Step S3 involves treating the surface of the basalt fiber substrate obtained in S2 to obtain a nano-catalytic layer distributed in clusters on the surface of the basalt fiber substrate. Specific steps include: S301. Prepare tetraethyl orthosilicate sol containing catalytic metal salt; S302. The tetraethyl orthosilicate sol is impregnated into the bottom layer and / or top layer of the basalt fiber substrate by means of impregnation. S303. The basalt fiber substrate impregnated with tetraethyl orthosilicate sol obtained in S202 is heat-treated at 300-500°C to convert the sol into silicon dioxide carrying metal oxide nanoparticles.
10. The preparation method according to claim 9, characterized in that, The filter material obtained after step S303 is immersed in a complex solution of tannic acid and metal ions, then dried and heat-treated at 200-350℃ to form a catalytic active layer on the structure of the filter material.