Filter element material and preparation method thereof

Abstract

The invention discloses a filter element material and a preparation method thereof. The filter element material comprises the following components in percentage by mass: 15-60% of a honeycomb support matrix; 30%-40% of a filter base material; 0-50% of a coating base material; the invention relates to the technical field of water purification filter elements. According to the filter element material and the preparation method thereof, a stable supporting structure is kept in the preparation process of the gamma-Al2O3 / BN composite ceramic layer through the polypropylene and the cellulose nanofibers, a filtering base material is obtained in a gradient low-temperature sintering mode, small particles and pollutants in water are effectively removed, and the filter element material has excellent filtering performance and is suitable for being used in water treatment. The activated carbon fiber and the polyether sulfone are coated on the filtering base material in an electrostatic spinning manner, so that the wear resistance and the compressive strength of the filter element are improved while good filtering performance and water permeability are ensured, a honeycomb supporting matrix can be removed through a high-temperature combustion manner, the water permeability is further improved, and in the combustion process, the combustion efficiency is improved. The activated carbon fibers are physically activated, so that the adsorption capacity is further improved.

Description

Technical Field

[0001] The present invention relates to the technical field of water purification filter elements, and specifically to a filter element material and a preparation method thereof. Background Art

[0002] A filter element is the main component that plays a filtering role in a filter. The filter element removes a small amount of solid particles in the liquid, which can protect the normal operation of the equipment or the cleanliness of the air. When the fluid enters the filter element with a filter screen of a certain specification, its impurities are blocked, and the clean fluid flows out through the filter element.

[0003] At present, the filter element materials on the market have deficiencies in terms of water permeability and filtration efficiency, and it is difficult to meet the requirements of specific application scenarios. For example, activated carbon and ceramic filter elements have good water permeability but low filtration efficiency; another example is reverse osmosis membrane and nanofiltration membrane filter elements, which have high filtration efficiency but poor water permeability, are prone to blockage, and with use, the filter element needs to be replaced regularly, and the reuse rate of the replaced filter element is low. Therefore, a filter element material and a preparation method thereof are specifically proposed to achieve high filtration efficiency and high water permeability while also having the advantage of convenient reuse. Summary of the Invention

[0004] In view of the deficiencies of the prior art, the present invention provides a filter element material and a preparation method thereof, which solve the problems that the existing filter elements cannot maintain high filtration efficiency and high water permeability at the same time, and have a low reuse rate.

[0005] To achieve the above objectives, the present invention is realized through the following technical solutions: A filter element material, the components of which by mass percentage include: Honeycomb support matrix: 15% - 60%; Filtering base material: 30% - 40%; Coating base material: 0 - 50%.

[0006] The present invention is further configured as: The honeycomb support matrix is made by 3D printing of polypropylene and cellulose nanofibers, and the polypropylene and cellulose nanofibers by weight ratio include: 16 - 19:0.5 - 1.2.

[0007] The cellulose nanofibers are unmodified cellulose nanofibers with a lignin residue of less than 1%. Polypropylene and cellulose nanofibers generate water and carbon dioxide after combustion. Among them, the cellulose molecular chain (C6H 10 O5)n is completely oxidized under oxygen-rich conditions at 500°C: C6H 10 O5 + 6O2 → 6CO2 + 5H2O The present invention is further configured as: The filtering base material includes nano-aluminum oxide and boron nitride nanosheets, and the nano-aluminum oxide and boron nitride nanosheets by weight ratio include: 7 - 12:0.7 - 1.1.

[0008] The present invention is further configured such that: the coated substrate includes activated carbon fibers and polyethersulfone, and the activated carbon fibers and polyethersulfone include, by weight ratio: 0.8 - 1.3:8 - 12.

[0009] The present invention also discloses a preparation method of a filter element material, which specifically includes the following steps: Step 1: Mix polypropylene and cellulose nanofibers evenly according to a weight ratio of 16 - 19:0.5 - 1.2, and then 3D print them into a honeycomb structure to obtain a honeycomb support matrix. Step 2: Immerse the honeycomb support matrix into an alumina sol containing boron nitride nanosheets, vertically lift it at a speed of 0.3 - 0.6 m / min, repeat 3 times to form a uniform coating, and then perform gradient low-temperature sintering to obtain a γ-Al2O3 / BN composite ceramic layer as the filter substrate. Step 3: Mix activated carbon fibers and polyethersulfone evenly according to a weight ratio of 0.8 - 1.3:8 - 12, load them into a spinning machine, and form a fiber membrane with a thickness of 45 - 55 μm on the surface of the γ-Al2O3 / BN composite ceramic layer under the environment of a voltage of 20 kV and a receiving distance of 15 cm to obtain a composite filter element.

[0010] The present invention is further configured such that: the pore diameter of the honeycomb structure in Step 1 is 1 - 3 mm, and the wall thickness is 0.3 - 0.5 mm.

[0011] The present invention is further configured such that: the gradient low-temperature sintering method in Step 2 includes: Heat the sintering furnace to a temperature of 80 - 120 °C and keep it warm for 45 - 60 min to dry and cure the alumina sol coating containing boron nitride nanosheets. Heat the sintering furnace to a temperature of 150 - 180 °C and keep it warm for 60 - 90 min to preliminarily sinter the dried and cured alumina sol coating containing boron nitride nanosheets into a ceramic layer. Heat the sintering furnace to a temperature of 200 - 220 °C and keep it warm for 120 - 180 min to densify the ceramic layer.

[0012] The present invention is further configured such that: it further includes placing the composite filter element in a muffle furnace, heating it to 380 - 400 °C at a rate of 10 °C / min, keeping it warm for 25 - 45 min, then taking it out and cooling it to room temperature, and rinsing it with compressed air at 0.3 - 0.5 MPa to obtain a regenerated permeable filter element.

[0013] The present invention provides a filter element material and a preparation method thereof. It has the following beneficial effects: (1) The present invention prepares a honeycomb support matrix from polypropylene and cellulose nanofibers. During the preparation of the γ-Al2O3 / BN composite ceramic layer, a stable support structure is maintained. Then, a filter substrate is obtained by gradient low-temperature sintering, which can effectively remove fine particles and pollutants in water and has excellent filtration performance. Subsequently, activated carbon fibers and polyethersulfone are coated on the filter substrate by electrospinning, which can ensure good filtration performance and water permeability while improving the wear resistance and compressive strength of the filter element. Moreover, by means of high-temperature combustion, the honeycomb support matrix can be removed to further improve water permeability. During the combustion process, the activated carbon fibers are physically activated to further improve the adsorption capacity.

[0014] (2) By means of high-temperature combustion, the present invention can also clean impurities from the regenerated permeable filter element to achieve secondary utilization. It has the advantages of high reuse rate and convenient cleaning. Specific Embodiments

[0015] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0016] Embodiment 1 A preparation method of a filter element material specifically includes the following steps: Step 1: Mix polypropylene and cellulose nanofibers evenly according to a weight ratio of 16:1.2, and then 3D print them into a honeycomb structure with a pore diameter of 2 mm and a wall thickness of 0.4 mm to obtain a honeycomb support matrix. The mass ratio of the honeycomb support matrix in the filter element material is 20%, which is used to provide structural strength and support to ensure that the filter element does not deform under high pressure or complex working conditions; Step 2: Mix nano-aluminum oxide and boron nitride nanosheets evenly according to a weight ratio of 7:1.1 to obtain an alumina sol containing boron nitride nanosheets. Immerse the honeycomb support matrix in the alumina sol containing boron nitride nanosheets, and vertically lift it at a speed of 0.3 m / min. Repeat 3 times to form a uniform coating, and then put it into a sintering furnace. Heat the sintering furnace to 95°C and keep it warm for 55 min to dry and cure the alumina sol coating containing boron nitride nanosheets; Heat the sintering furnace to 160°C and keep it warm for 80 min to preliminarily sinter the dried and cured alumina sol coating containing boron nitride nanosheets into a ceramic layer; Heat the sintering furnace to 210 °C and keep it at this temperature for 150 min to densify the ceramic layer, obtaining a γ-Al2O3 / BN composite ceramic layer as the filter substrate. The mass ratio of the filter substrate in the filter element material is 30%, which is the core part of the filter element material, responsible for intercepting pollutants, ensuring sufficient filtration area and filtration accuracy, and at the same time balancing the air permeability and filtration efficiency of the material. Among them, the thickness of the γ-Al2O3 / BN composite ceramic layer is 53 μm; Step 3: Mix activated carbon fibers and polyethersulfone evenly according to a weight ratio of 0.8:12, then load them into a spinning machine. Under the conditions of a voltage of 20 kV and a receiving distance of 15 cm, form a fiber membrane with a thickness of 45 μm on the surface of the γ-Al2O3 / BN composite ceramic layer as the coating substrate. The mass ratio of the coating substrate in the filter element material is 50%, which is used to protect the filter substrate, prevent material shedding or damage, and further improve the adsorption capacity, obtaining a composite filter element.

[0017] The filter element obtained in this embodiment is composed of a honeycomb support matrix, a filter substrate, and a coating substrate.

[0018] Example 2 A preparation method of a filter element material specifically includes the following steps: Step 1: Mix polypropylene and cellulose nanofibers evenly according to a weight ratio of 18:0.9, and then 3D print them into a honeycomb structure with a pore diameter of 3 mm and a wall thickness of 0.3 mm to obtain a honeycomb support matrix. The mass ratio of the honeycomb support matrix in the filter element material is 15%; Step 2: Mix nano-aluminum oxide and boron nitride nanosheets evenly according to a weight ratio of 9:1 to obtain an alumina sol containing boron nitride nanosheets. Immerse the honeycomb support matrix in the alumina sol containing boron nitride nanosheets, vertically lift it at a speed of 0.5 m / min, repeat 3 times to form a uniform coating, and then put it into a sintering furnace. Heat the sintering furnace to 95 °C and keep it at this temperature for 55 min to dry and cure the alumina sol coating containing boron nitride nanosheets; Heat the sintering furnace to 160 °C and keep it at this temperature for 80 min to preliminarily sinter the dried and cured alumina sol coating containing boron nitride nanosheets into a ceramic layer; Heat the sintering furnace to 210 °C and keep it at this temperature for 150 min to densify the ceramic layer, obtaining a γ-Al2O3 / BN composite ceramic layer as the filter substrate. The mass ratio of the filter substrate in the filter element material is 35%. Among them, the thickness of the γ-Al2O3 / BN composite ceramic layer is 55 μm; Step 3: Mix activated carbon fibers and polyethersulfone evenly at a weight ratio of 1.2:9, then load them into a spinning machine. Under the conditions of a voltage of 20 kV and a receiving distance of 15 cm, form a fiber membrane with a thickness of 55 μm on the surface of the γ-Al2O3 / BN composite ceramic layer as the coating substrate. The mass percentage of the coating substrate in the filter element material is 50% to obtain a composite filter element. Step 4: Place the composite filter element in a muffle furnace, heat it to 385 °C at a rate of 10 °C / min, keep it warm for 45 min, then take it out and cool it to room temperature, and rinse it with compressed air at 0.5 MPa to obtain a regenerated permeable filter element.

[0019] The filter element obtained in this embodiment is composed of a filtering substrate and a coating substrate.

[0020] Example 3 A preparation method of a filter element material specifically includes the following steps: Step 1: Mix polypropylene and cellulose nanofibers evenly at a weight ratio of 19:0.5, and then 3D print them into a honeycomb structure with a pore diameter of 1 mm and a wall thickness of 0.3 mm to obtain a honeycomb support matrix. The mass percentage of the honeycomb support matrix in the filter element material is 60%. Step 2: Mix nano-alumina and boron nitride nanosheets evenly at a weight ratio of 12:0.7 to obtain an alumina sol containing boron nitride nanosheets. Immerse the honeycomb support matrix in the alumina sol containing boron nitride nanosheets, vertically lift it at a speed of 0.6 m / min, repeat 3 times to form a uniform coating, and then put it into a sintering furnace. Heat the sintering furnace to 95 °C and keep it warm for 55 min to dry and cure the alumina sol coating containing boron nitride nanosheets. Heat the sintering furnace to 160 °C and keep it warm for 80 min to preliminarily sinter the dried and cured alumina sol coating containing boron nitride nanosheets into a ceramic layer. Heat the sintering furnace to 210 °C and keep it warm for 150 min to densify the ceramic layer and obtain a γ-Al2O3 / BN composite ceramic layer as the filtering substrate. The mass percentage of the filtering substrate in the filter element material is 40%. Among them, the thickness of the γ-Al2O3 / BN composite ceramic layer is 64 μm.

[0021] The filter element obtained in this embodiment is composed of a honeycomb support matrix and a filtering substrate.

[0022] Example 4 Based on Example 3, this embodiment further includes the following steps: Step 3: Place the honeycomb support matrix with the filtering substrate coated on it in a muffle furnace, heat it to 396 °C at a rate of 10 °C / min, keep it warm for 25 min, then take it out and cool it to room temperature, and rinse it with compressed air at 0.3 MPa to obtain a regenerated permeable filter element.

[0023] The filter element obtained in this embodiment is composed of a filtering substrate.

[0024] For the above-mentioned Embodiment 1, Embodiment 2, Embodiment 3 and Embodiment 4, the regeneration conditions for obtaining the filter element are as follows: monitor the decline rate of the water permeability rate of the filter element. When the decline rate of the water permeability rate is greater than or equal to 15%, regeneration treatment is required. The specific regeneration treatment methods include: Place the filter element in a muffle furnace, heat it to 500°C at a rate of 10°C / min, keep it warm for 35 minutes, then take it out and cool it to room temperature, and rinse it with compressed air at 0.5 MPa to obtain a regenerated water-permeable filter element.

[0025] As a detailed description, physical activation occurs when activated carbon fibers burn at 400°C, and the specific surface area increases from 800 m² / g to 1200 m² / g, enhancing the subsequent adsorption performance.

[0026] After repeated tests, it is found that the filter elements prepared in Embodiment 1, Embodiment 2, Embodiment 3 and Embodiment 4 can be regenerated at least 5 times. The judgment method for qualified filter elements is as follows: The water permeability rate is greater than or equal to 90%. Analyze the integrity of the pore structure by X-ray tomography. A qualified filter element has a pore deformation rate less than or equal to 5%.

[0027] Comparative experiment According to the preparation methods provided in the above-mentioned Embodiment 1, Embodiment 2, Embodiment 3 and Embodiment 4, obtain Filter Element 1, Filter Element 2, Filter Element 3 and Filter Element 4 respectively, and conduct water permeability rate tests with reverse osmosis membrane filter elements and nanofiltration membrane filter elements. The test results are shown in Table 1: Water permeation rate L / (m2·h·bar) Compressive strength (MPa) Filter element 1 185 75 Filter element 2 478 68 Filter element 3 250 55 Filter element 4 520 35 Reverse osmosis membrane filter element 35 63 Nanofiltration membrane filter element 52 40 Table 1 As can be seen from Table 1, the water permeability rates of the filter elements provided by the present invention are all superior to those of reverse osmosis membrane filter elements and nanofiltration membrane filter elements. Moreover, both Filter Element 1 and Filter Element 2 are superior to reverse osmosis membrane filter elements and nanofiltration membrane filter elements in terms of both water permeability rate and compressive strength. Among them, Filter Element 2 is the optimal embodiment.

[0028] Furthermore, for the filter elements prepared according to the above-mentioned embodiments, the void connectivity rate is greater than or equal to 90%, and the water penetration pressure difference is less than or equal to 20 MPa. Among them, the inner layer pore diameter of Filter Element 2 is 3 μm, and the outer layer pore diameter is 76 μm.

[0029] When the water permeability decline rates of filter element 1, filter element 2, filter element 3, and filter element 4 are greater than or equal to 15%, after the filter elements are regenerated, the regenerated filter element 1, regenerated filter element 2, regenerated filter element 3, and regenerated filter element 4 are obtained respectively. Then, the water permeability rate is detected according to the ISO 10545-3 standard, and the compressive strength is detected according to the GB / T 1964-2020 standard. The test results are shown in Table 2: Water permeation rate L / (m2·h·bar) Compressive strength (MPa) Regenerated filter element 1 476 68 Regenerated filter element 2 473 67 Regenerated filter element 3 518 35 Regenerated filter element 4 513 35 Table 2 As can be seen from Table 2, after the regeneration treatment, the water permeability and compressive strength of the filter elements prepared according to the preparation methods provided in Example 1 and Example 2 are similar, and the water permeability and compressive strength of the filter elements prepared according to the preparation methods provided in Example 3 and Example 4 are similar. That is, after the regeneration treatment, while the honeycomb support matrix is eliminated and the compressive strength decreases, the water permeability increases. Based on this characteristic, filter element 1, filter element 2, filter element 3, and filter element 4 can be used in different use environments, and after the regeneration treatment, they can all be reused by switching the use environment.

[0030] In summary, the filter element material provided by the present invention has the advantages of high filtration efficiency, high water permeability, and being renewable, with low maintenance costs, and can be effectively applied to sterile filtration systems and the treatment of wastewater containing strongly corrosive particles.

[0031] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A filter element material, characterized in that: Its components by mass percentage include: Honeycomb support matrix: 15% - 60%; Filter substrate: 30% - 40%; Coating substrate: 0 - 50%.

2. The filter element material according to claim 1, characterized in that: The honeycomb support matrix is made by 3D printing of polypropylene and cellulose nanofibers, and the polypropylene and cellulose nanofibers by weight ratio include: 16 - 19:0.5 - 1.

2.

3. A filter element material according to claim 1 or 2, characterized in that: The filter substrate includes nano-aluminum oxide and boron nitride nanosheets, and the nano-aluminum oxide and boron nitride nanosheets by weight ratio include: 7 - 12:0.7 - 1.

1.

4. A filter element material according to claim 1 or 2, characterized in that: The coating substrate includes activated carbon fibers and polyethersulfone, and the activated carbon fibers and polyethersulfone by weight ratio include: 0.8 - 1.3:8 - 12.

5. A method for preparing the filter element material according to any one of claims 1-4, characterized in that: Specifically, it includes the following steps: Step 1: Mix polypropylene and cellulose nanofibers evenly according to the weight ratio of 16 - 19: 0.5 - 1.2, and then 3D print them into a honeycomb structure to obtain the honeycomb support matrix; Step 2: Immerse the honeycomb support matrix into the alumina sol containing boron nitride nanosheets, vertically lift it at a speed of 0.3 - 0.6 m / min, repeat 3 times to form a uniform coating, and then perform gradient low-temperature sintering to obtain the γ-Al2O3 / BN composite ceramic layer as the filter substrate; Step 3: Mix activated carbon fibers and polyethersulfone evenly according to the weight ratio of 0.8 - 1.3:8 - 12, load them into a spinning machine, and under the environment of a voltage of 20 kV and a receiving distance of 15 cm, form a fiber membrane with a thickness of 45 - 55 μm on the surface of the γ-Al2O3 / BN composite ceramic layer to obtain a composite filter element.

6. The preparation method of a filter element material according to claim 5, characterized in that: The pore diameter of the honeycomb structure in Step 1 is 1 - 3 mm, and the wall thickness is 0.3 - 0.5 mm.

7. The preparation method of a filter element material according to claim 5 or 6, characterized in that: The gradient low-temperature sintering method in Step 2 includes: Heat the sintering furnace to a temperature of 80 - 120 °C and keep it warm for 45 - 60 min to dry and cure the alumina sol coating containing boron nitride nanosheets; Heat the sintering furnace to a temperature of 150 - 180 °C and keep it warm for 60 - 90 min to preliminarily sinter the dried and cured alumina sol coating containing boron nitride nanosheets into a ceramic layer; Heat the sintering furnace to a temperature of 200 - 220 °C and keep it warm for 120 - 180 min to densify the ceramic layer.

8. A method for preparing a filter element material according to claim 5 or 6, characterized in that: It also includes placing the composite filter element in a muffle furnace, heating it to 380 - 400 °C at a rate of 10 °C / min, keeping it warm for 25 - 45 min, then taking it out and cooling it to room temperature, and flushing it with compressed air at 0.3 - 0.5 MPa to obtain a regenerated permeable filter element.