Silicon carbide-based membrane, synthesis method and purification device for domestic sewage

Abstract

The invention relates to a silicon carbide-based membrane, a synthesis method and a purification device for domestic sewage, and relates to the technical field of sewage treatment.The silicon carbide-based membrane is prepared from silicon carbide (SiC), borosilicate glass frit, a pore-forming agent and an adhesive, the particle size of the silicon carbide is 0.5-35 microns, the weight fraction of the borosilicate glass frit is 10-25 wt% of the weight of the SiC, and the weight fraction of the pore-forming agent is 10-25 wt% of the weight of the adhesive. The pore-forming agent is at least one of graphite powder, polymethyl methacrylate and polyvinyl chloride and accounts for 1-10wt% of the weight of SiC, the adhesive is at least one of polyvinyl alcohol and polyethylene glycol and accounts for 5-10wt% of the weight of SiC, the mass fraction of Al2O3 in the borosilicate glass material is 1-7%, and the mass fraction of Al2O3 in the borosilicate glass material is 1-7%. The bending strength and the acid-base tolerance of the silicon carbide-based membrane in the purification device can be improved, and meanwhile, the silicon carbide-based membrane also has relatively high purification performance on oily sewage.

Description

Technical Field

[0001] The present invention relates to the technical field of sewage treatment, and in particular to a silicon carbide-based membrane, a synthesis method and a purification device for domestic sewage. Background Art

[0002] Domestic wastewater or grey water from showers, basins, kitchen sinks, washing machines may differ from industrial wastewater as they may contain high organic loads, soaps and detergents, with major contaminants being proteins, carbohydrates, oils, other compounds dissolved and suspended, and harmful pathogens.

[0003] A Chinese invention patent application with publication number CN115155328A and publication date October 11, 2022 proposes a method for preparing a polyether functionalized polymer membrane for oil production wastewater treatment, which discloses a method for preparing a polyether functionalized polymer membrane for oil production wastewater treatment, comprising the following steps: Step 1, mixing polyvinylidene fluoride, graphene dispersion, pore-forming agent and N-methylpyrrolidone, stirring, standing, and removing bubbles to obtain a casting liquid; Step 2, cooling the casting liquid, placing it on a glass plate, and scraping out a uniform flat membrane; soaking the flat membrane in deionized water to obtain a base membrane; Step 3, soaking the obtained base membrane in a modifying liquid, then washing it with deionized water, and drying it.

[0004] The method introduces the treated graphene oxide into the ultrafiltration membrane to improve the compatibility of the modified graphene oxide in the ultrafiltration membrane, thereby improving the hydrophilicity of the ultrafiltration membrane. The better the hydrophilicity of the ultrafiltration membrane, the better the anti-organic pollution performance of the ultrafiltration membrane.

[0005] With regard to the above technical solutions, the low water-oil separation efficiency and chemical stability, high tendency to be polluted and limited service life of this type of material limit its application areas. Summary of the invention

[0006] In order to improve the water-oil separation efficiency and chemical stability in wastewater treatment, the present invention provides a silicon carbide-based membrane, a synthesis method and a purification device for domestic sewage.

[0007] In a first aspect, the present invention provides a silicon carbide-based membrane for domestic sewage, comprising the following components: Silicon carbide (SiC), borosilicate glass frit, a pore former and an adhesive, wherein the silicon carbide particle size is 0.5-35 μm, the weight fraction of the borosilicate glass frit is 10-25wt% of the weight of SiC, the pore former is at least one of graphite powder, polymethyl methacrylate and polyvinyl chloride, the weight fraction of which is 1-10wt% of the weight of SiC, the adhesive is at least one of polyvinyl alcohol and polyethylene glycol, the weight fraction of which is 5-10wt% of the weight of SiC, and the mass fraction of Al2O3 in the borosilicate glass frit is 1-7%.

[0008] By adopting the above technical solution, during the heat treatment process, the glass material is transformed into a viscous glass phase during the sintering process, and SiC is oxidized during the sintering process in the air to form SiO2. The SiO2 produced by oxidation is partially dissolved into the viscous glass phase. The glass phase forms bonds between SiC particles, acts as a bonding material between SiC particles, and acts as a protective layer for SiO2. All membrane supports are composed of SiC and trace amounts of SiO2. The viscous flow of the glass bonding phase enhances the compactness of the silicon carbide-based film and forms a uniform microstructure. When the glass content is sufficient, the SiC particles are bonded more completely, the distance between pores is reduced, the support strength is increased, the critical defect size is reduced, the bending strength is increased, and its durability is increased. After adding the pore-forming agent, the average porosity increases, which is beneficial to the flow of sewage and filtration. Silicon carbide-based membranes have a narrow pore size distribution and are suitable for wastewater treatment. They exhibit excellent water permeability and outstanding separation performance for oil / water emulsions. They have excellent permeability and are effective in treating oily wastewater. The permeability decreases after wastewater particles are intercepted, and the membrane can be fully restored by simple backwashing physical cleaning.

[0009] Optionally, the silicon carbide-based membrane for domestic sewage further includes: yttrium oxide (Y2O3), and the weight fraction of the yttrium oxide is 1-5wt% of the weight of SiC.

[0010] By adopting the above technical solution, Y2SiO5 will be generated when the SiC, alumina, SiO2, and yttrium oxide powders are mixed in the glass material. When the temperature is further increased, Y2SiO5 reacts with SiO2 to form Y2Si2O7. Due to the low viscosity of Y2SiO5, the alumina particles will dissolve quickly. When SiO2 is saturated with alumina, mullite will nucleate in a very short time. Subsequently, as the alumina particles continue to dissolve in the glass, mullite will grow, reducing the growth temperature of mullite. On the other hand, due to the consumption of the siliceous phase, the concentration of Y2SiO5 increases with the growth of mullite grains. When Y2SiO5 reaches the composition of Y2Si2O7, precipitation will occur, thereby forming crystalline Y2Si2O7, further improving the bending strength of the silicon carbide-based film.

[0011] Optionally, the silicon carbide-based membrane for domestic sewage further comprises: kaolin, and the weight fraction of the kaolin is 3-10wt% of the weight of SiC.

[0012] By adopting the above technical scheme, due to the bonding of clay, the bonding between SiC particles is increased, and this larger bonding area can make the SiC sample have higher strength. SiC is oxidized to amorphous SiO2 at high temperature; kaolin will be converted into metakaolin at high temperature, and at higher temperature, it will be converted into mullite and amorphous SiO2. The crystallization of amorphous silicon dioxide can enhance the bonding between SiC particles and improve the strength of porous SiC ceramics. The amorphous SiO2 produced by SiC oxidation and kaolin decomposition is converted into cristobalite, and increases with the increase of sintering temperature. At the same time, mullite also crystallizes out. In the presence of clay, the formation temperature of mullite is reduced. Finally, there are two polymorphic SiC, cristobalite and mullite phases in the ceramic, which increases the bonding strength between SiC particles and clay, and further improves the bending strength of silicon carbide-based membranes.

[0013] Optionally, the silicon carbide particle size is 0.5-25 μm.

[0014] By adopting the above technical solution, when smaller particles are used for a given amount of glass frit, the bonding area is large, and the support strength increases as the distance between pores decreases; when smaller particles are used, the critical defect size decreases.

[0015] In a second aspect, the present invention provides a method for synthesizing a silicon carbide-based membrane for domestic sewage, comprising the following steps: Ball milling: The SiC, glass frit and pore former described in the first aspect are mixed by ball milling in distilled water using SiC grinding balls and a plastic jar for 24 hours, and dried to remove the solvent to obtain a mixed powder; Pressing: mixing the mixed powder with the binder aqueous solution described in the first aspect, fully blending and pressing, and drying the pressed sample in an air oven at 100° C. for 24 hours to obtain a sample; Sintering: The sample was heated to 850-1500°C in air at a heating rate of 1-3°C / min, and then kept at the temperature for 2-4 hours to obtain a silicon carbide-based film.

[0016] By adopting the above technical solution, the raw materials are evenly mixed by ball milling, pressed into a suitable shape and sintered to obtain a silicon carbide-based film.

[0017] Optionally, the ball milling step is: Ball milling: The SiC, glass material, pore former and auxiliary materials, wherein the auxiliary material is at least one of the kaolin and Y2O3 described in the first aspect, are mixed by ball milling in distilled water using SiC grinding balls and a plastic jar for 24 hours, and dried to remove the solvent to obtain a mixed powder.

[0018] By adopting the above technical solution, by adding kaolin, Y2O3 or kaolin and Y2O3, it helps to improve the mechanical strength of the silicon carbide based film and increase its durability.

[0019] Optionally, there is a coating step after the sintering step: Lamination: The concentration is 10 -4 M of aluminum nitrate nonahydrate is dissolved in 1L of deionized water, 200-230g of SiC powder is added to the mixture and mixed for 5-15 minutes, the pH value of the suspension is adjusted to 10, and spherical alumina grinding beads are used for grinding for 48 hours to ensure homogeneity, and a binder of 1wt% of the mass of the SiC powder is added, wherein the binder is at least one of polyvinyl alcohol and polyethylene glycol, and then continuously stirred at room temperature, coated on the silicon carbide-based film by dip coating, and then dried completely, and the film is sintered in the range of 1400-1800°C for 4 hours in an argon atmosphere, and finally a surface oxidation step is performed at a temperature of 600-800°C to obtain a coated silicon carbide-based film.

[0020] By adopting the above technical solution, a uniform, defect-free and smooth coating layer was successfully formed on the silicon carbide substrate. The sintering temperature was reduced after using aluminum nitrate nonahydrate. The reduction of sintering temperature effectively reduced the production cost of the coating layer. Finally, the surface oxidation step was carried out at a temperature below 800°C to remove residual carbon that may remain in the pores. The prepared coated silicon carbide-based membrane exhibits good chemical resistance in both alkaline and acidic environments, and no change in membrane strength is found. It has good mechanical resistance and can effectively avoid the decrease in mechanical strength of the glass-bonded SiC membrane carrier in acidic or alkaline solutions. It can be used for domestic wastewater treatment and can also be used for treatment of dirt layers that require chemical cleaning.

[0021] In the third aspect, a purification device for domestic sewage comprises a housing and a silicon carbide-based membrane, wherein a plurality of internal pipelines are arranged inside the silicon carbide-based membrane, a connecting shell is arranged at the end of the silicon carbide-based membrane, the interior of the connecting shell is communicated with the internal pipelines of the silicon carbide-based membrane, the silicon carbide-based membrane is arranged in the housing, and the silicon carbide-based membrane is connected to the housing through the connecting shell, a water storage cavity is opened on the side wall of the housing, the connecting shell is communicated with the water storage cavity, a drain pipe is arranged on the housing, and the drain pipe is communicated with the water storage cavity; a plurality of silicon carbide-based membranes are provided, and the silicon carbide-based membranes are not communicated with each other.

[0022] In summary, the present invention includes at least one of the following beneficial technical effects: The viscous flow of the glass bonding phase of the present invention enhances the compactness of the silicon carbide-based film and forms a uniform microstructure. When the glass material content is sufficient, the SiC particles are bonded more completely, the distance between pores is reduced, the support strength is increased, the critical defect size is reduced, the bending strength is increased, and its durability is increased. The invention reduces the growth temperature of mullite, and the growth of mullite can enhance the bonding between SiC particles, improve the strength of porous SiC ceramics, and further improve the bending strength of the silicon carbide-based membrane.

[0023] The coated silicon carbide-based membrane of the present invention exhibits good chemical resistance in both alkaline and acidic environments, and no change in membrane strength is found. It has good mechanical resistance and effectively avoids the reduction in mechanical strength of the glass-bonded SiC membrane carrier in acidic or alkaline solutions. It can be used for domestic wastewater treatment and can also be used for treatment of dirt layers that require chemical cleaning. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic structural diagram of a domestic sewage purification device of the present invention; Figure 2 It is a schematic cross-sectional view of the structure of the domestic sewage purification device of the present invention; Figure 3 This is a structural diagram of the silicon carbide-based film of the present invention; Figure 4 A schematic diagram of the exploded structure of the silicon carbide-based membrane and the connecting shell of the present invention from one viewing angle; Figure 5 It is a schematic diagram of the explosion structure of the silicon carbide-based membrane and the connecting shell from another perspective of the present invention.

[0025] Explanation of the reference numerals: 1. Box body; 2. Connecting shell; 3. Silicon carbide-based membrane; 4. Drain pipe; 5. Internal pipeline. DETAILED DESCRIPTION

[0026] The present invention is further described in detail below with reference to the embodiments.

[0027] Example 1: This example discloses a silicon carbide-based membrane for domestic sewage, comprising the following components: silicon carbide (SiC), borosilicate glass frit, a pore former and an adhesive. The silicon carbide particle size is 15 μm, the weight fraction of the borosilicate glass frit is 10 wt % of the weight of SiC, the pore former is polymethyl methacrylate, and the weight fraction is 7 wt % of the weight of SiC, the adhesive is polyvinyl alcohol, and the weight fraction is 10 wt % of the weight of SiC, and the mass fraction of Al2O3 in the borosilicate glass frit is 7%.

[0028] A method for synthesizing a silicon carbide-based film comprises the following steps: Ball milling: The SiC, glass frit and pore former were mixed by ball milling in distilled water using SiC grinding balls and a plastic jar for 24 hours, and dried to remove the solvent to obtain a mixed powder; Pressing: Mix the mixed powder with the binder aqueous solution, fully blend and press, and dry the pressed sample in an air oven at 100° C. for 24 hours to obtain a sample; Sintering: The sample was heated to 850°C in air at a heating rate of 3°C / min and sintered for 2 hours to obtain a silicon carbide-based film.

[0029] A purification device for domestic sewage, It includes a housing 1 and a silicon carbide base film 3, The silicon carbide based membrane 3 is provided with a plurality of internal pipes 5, and a connecting shell 2 is provided at the end of the silicon carbide based membrane 3, and the interior of the connecting shell 2 is connected with the internal pipes 5 of the silicon carbide based membrane 3, the silicon carbide based membrane 3 is arranged in the box body 1, and the silicon carbide based membrane 3 is connected with the box body 1 through the connecting shell 2, a water storage cavity is opened on the side wall of the box body 1, and the connecting shell 2 is connected with the water storage cavity, and a drain pipe 4 is provided on the box body 1, and the drain pipe 4 is connected with the water storage cavity; there are a plurality of silicon carbide based membranes 3, and the silicon carbide based membranes 3 are not connected with each other.

[0030] A plurality of inner pipes 5 are provided inside the silicon carbide based membrane 3, and connecting shells 2 are provided at both ends of the silicon carbide based membrane 3. The sewage is purified by the silicon carbide based membrane 3 to obtain purified water which flows into the inner pipes 5. The connecting shell 2 is provided to lock the purified water in the inner pipes 5 and drain it into the connecting shell 2. The connecting shell 2 is connected to the box body 1, and the purified water is discharged through the drain pipe 4 of the box body 1.

[0031] Example 2: This example discloses a silicon carbide-based membrane for domestic sewage, comprising the following components: silicon carbide (SiC), borosilicate glass frit, a pore former, an adhesive and auxiliary materials, wherein the auxiliary material is kaolin, the silicon carbide particle size is 15 μm, the weight fraction of the borosilicate glass frit is 10 wt % of the weight of SiC, the pore former is polymethyl methacrylate, and the weight fraction is 7 wt % of the weight of SiC, the adhesive is polyvinyl alcohol, and the weight fraction is 10 wt % of the weight of SiC, the weight fraction of kaolin is 7 wt % of the weight of SiC, and the mass fraction of Al2O3 in the borosilicate glass frit is 7%.

[0032] A method for synthesizing a silicon carbide-based film comprises the following steps: Ball milling: The SiC, glass frit, pore former and auxiliary materials are mixed by ball milling in distilled water using SiC grinding balls and a plastic jar for 24 hours, and dried to remove the solvent to obtain a mixed powder; Sintering: The sample was heated to 1400°C in air at a heating rate of 2°C / min and sintered for 1 hour, and then sintered at 850°C for 2 hours to obtain a silicon carbide-based film.

[0033] The rest is exactly the same as in Example 1.

[0034] Example 3: This example discloses a silicon carbide-based membrane for domestic sewage, comprising the following components: silicon carbide (SiC), borosilicate glass frit, a pore former, an adhesive and auxiliary materials, wherein the auxiliary material is Y2O3, the silicon carbide particle size is 15 μm, the weight fraction of the borosilicate glass frit is 10wt% of the weight of SiC, the pore former is polymethyl methacrylate, and the weight fraction is 7wt% of the weight of SiC, the adhesive is polyvinyl alcohol, and the weight fraction is 10wt% of the weight of SiC, the weight fraction of yttrium oxide is 4wt% of the weight of SiC, and the mass fraction of Al2O3 in the borosilicate glass frit is 7%.

[0035] The rest is exactly the same as in Example 2.

[0036] Example 4: This example discloses a silicon carbide-based membrane for domestic sewage, comprising the following components: silicon carbide (SiC), borosilicate glass frit, a pore former, an adhesive and auxiliary materials, wherein the auxiliary materials are kaolin and Y2O3, the silicon carbide particle size is 15 μm, the weight fraction of the borosilicate glass frit is 10 wt% of the weight of SiC, the pore former is polymethyl methacrylate, and the weight fraction is 7 wt% of the weight of SiC, the adhesive is polyvinyl alcohol, and the weight fraction is 10 wt% of the weight of SiC, the weight fraction of yttrium oxide is 2 wt% of the weight of SiC, and the weight fraction of kaolin is 4.5 wt% of the weight of SiC.

[0037] The rest is exactly the same as in Example 2.

[0038] Example 5: This example discloses a silicon carbide-based membrane for domestic sewage, comprising the following components: silicon carbide (SiC), borosilicate glass frit, a pore former, an adhesive and auxiliary materials, wherein the auxiliary materials are kaolin and Y2O3, the silicon carbide particle size is 15 μm, the weight fraction of the borosilicate glass frit is 10 wt% of the weight of SiC, the pore former is polymethyl methacrylate, and the weight fraction is 7 wt% of the weight of SiC, the adhesive is polyvinyl alcohol, and the weight fraction is 10 wt% of the weight of SiC, the weight fraction of yttrium oxide is 2 wt% of the weight of SiC, the weight fraction of kaolin is 4.5 wt% of the weight of SiC, and the mass fraction of Al2O3 in the borosilicate glass frit is 7%.

[0039] The washed silicon carbide-based membrane of Example 4 was used to treat domestic wastewater.

[0040] The rest is exactly the same as Example 4.

[0041] Comparative example: This comparative example discloses a silicon carbide-based membrane for domestic sewage, comprising the following components: silicon carbide (SiC), a pore former and a binder, wherein the silicon carbide particle size is 15 μm, the pore former is polymethyl methacrylate, and the weight fraction is 7 wt % of the weight of SiC; the binder is polyvinyl alcohol, and the weight fraction is 10 wt % of the weight of SiC.

[0042] A method for synthesizing a silicon carbide-based film comprises the following steps: Ball milling: The SiC and pore former are mixed by ball milling in distilled water using SiC grinding balls and a plastic jar for 24 hours, and dried to remove the solvent to obtain a mixed powder; Pressing: Mix the mixed powder with the binder aqueous solution, fully blend and press, and dry the pressed sample in an air oven at 100° C. for 24 hours to obtain a sample; Sintering: The sample was heated to 1900°C in air at a heating rate of 3°C / min and sintered for 2 hours to obtain a silicon carbide-based film.

[0043] A purification device for domestic sewage, which is exactly the same as Example 1.

[0044] The silicon carbide-based films prepared in Example 1, Example 2, Example 3, Example 4, Example 5 and the comparative example were tested and tested, and the data are shown in Table 1.

[0045] Table 1: Data comparison of Example 1, Example 2, Example 3, Example 4, Example 5 and Comparative Example.

[0046] Oil removal rate (%) Total suspended solids removal rate (%) Chemical oxygen demand removal rate (%) Flexural strength (MPa) Example 1 95.7 85.2 89.2 38.5 Example 2 96.8 87.5 90.7 45.8 Example 3 96.3 87.6 90.3 46.1 Example 4 98.8 90.3 92.3 53.6 Example 5 98.8 90.3 92.3 53.6 Comparative Example 85.2 76.3 83.3 16.2 It can be seen from the comparison of Example 1 and the comparative example in Table 1 that the viscous flow of the glass bonding phase enhances the compactness of the silicon carbide-based film and forms a uniform microstructure. When the glass material content is sufficient, the SiC particles are more completely bonded, the distance between pores is reduced, the supporting strength is increased, the critical defect size is reduced, and the bending strength is increased. Due to the addition of glass material, the microstructure is better, the pores are regular and the connectivity is good, and the oil removal rate is also improved.

[0047] By comparing Example 1 with Example 2, Example 3 and Example 4, it can be seen that by adding kaolin and / or Y2O3 to reduce the growth temperature of mullite, the growth of mullite can enhance the bonding between SiC particles, improve the strength of porous SiC ceramics, and further improve the flexural strength and oil removal rate of silicon carbide-based membranes. Kaolin and Y2O3 alone are also effective in improving the flexural strength and oil removal rate of silicon carbide-based membranes, but the synergistic effect of the two on the performance improvement of silicon carbide-based membranes is stronger.

[0048] By comparing Example 4 and Example 5, it can be seen that the rinsed silicon carbide-based membrane has almost no difference in purification efficiency and bending strength for domestic sewage, can be reused, and has high durability.

[0049] Example 6: This example discloses a silicon carbide-based membrane for domestic sewage, comprising the following components: silicon carbide (SiC), borosilicate glass frit, a pore former, an adhesive and auxiliary materials, wherein the auxiliary materials are kaolin and Y2O3, the silicon carbide particle size is 15 μm, the weight fraction of the borosilicate glass frit is 10 wt% of the weight of SiC, the pore former is polymethyl methacrylate, and the weight fraction is 7 wt% of the weight of SiC, the adhesive is polyvinyl alcohol, and the weight fraction is 10 wt% of the weight of SiC, the weight fraction of yttrium oxide is 2 wt% of the weight of SiC, the weight fraction of kaolin is 4.5 wt% of the weight of SiC, and the mass fraction of Al2O3 in the borosilicate glass frit is 7%.

[0050] A method for synthesizing a silicon carbide-based film comprises the following steps: Lamination: The concentration is 10 -4 M of aluminum nitrate nonahydrate was dissolved in 1 L of deionized water, 200 g of SiC powder was added to the mixture and mixed for 10 minutes, 1 M NH3 aqueous solution was added dropwise to adjust the pH value of the suspension to 10, and spherical alumina grinding beads were used to grind for 48 hours to ensure homogeneity, 1 wt% of the SiC powder mass of the binder was added, and the binder was at least one of polyvinyl alcohol and polyethylene glycol, and then continuously stirred at room temperature, coated on the silicon carbide-based film by dip coating, and then completely dried at 40°C, and the film was sintered at 1600°C for 4 hours under an argon atmosphere, and finally a surface oxidation step was performed at a temperature of 600°C to obtain a coated silicon carbide-based film.

[0051] The rest is exactly the same as in Example 1.

[0052] Example 7: The silicon carbide-based film obtained in Example 4 was immersed in a solution with a pH of 3 for 30 days.

[0053] Example 8: The silicon carbide-based film obtained in Example 4 was immersed in a solution with a pH of 11 for 30 days.

[0054] Example 9: The coated silicon carbide-based film obtained in Example 6 was placed in a solution with a pH of 3 and immersed for 30 days.

[0055] Example 10: The coated silicon carbide-based film obtained in Example 6 was placed in a solution with a pH of 11 and immersed for 30 days.

[0056] The silicon carbide-based films prepared in Example 6, Example 7, Example 8, Example 9, and Example 10 were tested and tested, and the data are shown in Table 2.

[0057] Table 2: Data comparison of Example 6, Example 7, Example 8, Example 9, and Example 10.

[0058] Initial flexural strength (MPa) Flexural strength after immersion in pH=3 for 30 days (MPa) Flexural strength after immersion in pH=11 for 30 days (MPa) Example 6 54.3 - - Example 7 53.6 38.2 - Example 8 53.6 - 32.2 Example 9 54.3 54.3 - Example 10 54.3 - 54.3 By comparing Example 6, Example 7, Example 8, Example 9 with Example 10 in Table 2, it can be seen that the silicon carbide-based membrane exposed to acidic or alkaline solutions will suffer from partial loss of glass modifiers (Na, K, Ca, Ba), which usually leads to a decrease in the mechanical properties of the glass, while the coated silicon carbide-based membrane exhibits good chemical resistance in both alkaline and acidic environments, and no change in membrane strength is found. It has good mechanical resistance and effectively avoids the decrease in the mechanical strength of the glass-bonded SiC membrane carrier caused by acidic or alkaline solutions. It can be used for domestic wastewater treatment and can also be used for treatment of dirt layers that require chemical cleaning.

[0059] The above are all preferred embodiments of the present invention, and are not intended to limit the protection scope of the present invention. Therefore, any equivalent changes made based on the structure, shape, and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A silicon carbide-based film comprising the following components: Silicon carbide, borosilicate glass frit, a pore former and an adhesive, wherein the silicon carbide particle size is 0.5-35 μm, the weight fraction of the borosilicate glass frit is 10-25wt% of the weight of the silicon carbide, the pore former is at least one of graphite powder, polymethyl methacrylate and polyvinyl chloride, and the weight fraction is 1-10wt% of the weight of the silicon carbide, the adhesive is at least one of polyvinyl alcohol and polyethylene glycol, and the weight fraction is 5-10wt% of the weight of the silicon carbide, and the mass fraction of Al2O3 in the borosilicate glass frit is 1-7%.

2. A silicon carbide-based film according to claim 1, characterized in that: The silicon carbide-based film composition also includes yttrium oxide, and the weight fraction of the yttrium oxide is 1-5wt% of the weight of the silicon carbide.

3. The silicon carbide-based film according to claim 1, characterized in that: The silicon carbide-based film composition also includes kaolin, and the weight fraction of the kaolin is 3-10wt% of the weight of the silicon carbide.

4. The silicon carbide-based film according to claim 1, characterized in that: The silicon carbide particle size is 0.5-25 μm.

5. A method for synthesizing a silicon carbide-based film, for synthesizing the silicon carbide-based film according to any one of claims 1 to 4, comprising the following steps: Ball milling: mixing the silicon carbide, glass frit and pore former according to claim 1 in distilled water using silicon carbide grinding balls and a plastic jar by ball milling for 24 hours, and drying to remove the solvent to obtain a mixed powder; Pressing: mixing the mixed powder with the binder aqueous solution according to any one of claims 1 to 4, fully blending and pressing, and drying the pressed sample in an air oven at 100° C. for 24 hours to obtain a sample; Sintering: The sample was heated to 850-1500°C in air at a heating rate of 1-3°C / min, and then kept at the temperature for 2-4 hours to obtain a silicon carbide-based film.

6. The method for synthesizing a silicon carbide-based film according to claim 5, characterized in that: The ball milling step is: Ball milling: Silicon carbide, glass frit, pore former and auxiliary materials, wherein the auxiliary material is at least one of kaolin and yttrium oxide, are mixed by ball milling in distilled water using silicon carbide grinding balls and a plastic jar for 24 hours, and dried to remove the solvent to obtain a mixed powder.

7. The method for synthesizing a silicon carbide-based film according to claim 5, characterized in that: The sintering step is followed by a coating step: Lamination: The concentration is 10 -4 M of aluminum nitrate nonahydrate is dissolved in 1L of deionized water, 200-230g of silicon carbide powder is added to the mixture and mixed for 5-15 minutes, the pH value of the suspension is adjusted to 10, and spherical alumina grinding beads are used for grinding for 48 hours to ensure homogeneity, and a binder of 1wt% of the mass of the silicon carbide powder is added, wherein the binder is at least one of polyvinyl alcohol and polyethylene glycol, and then continuously stirred at room temperature, coated on the silicon carbide-based film by dip coating, and then dried completely, and the film is sintered in the range of 1400-1800°C for 4 hours in an argon atmosphere, and finally a surface oxidation step is performed at a temperature of 600-800°C to obtain a coated silicon carbide-based film.

8. A purification device for domestic sewage, characterized in that: It comprises a housing (1), and also comprises a silicon carbide-based membrane (3) as claimed in any one of claims 1 to 4 or a silicon carbide-based membrane (3) obtained by the synthesis method of the silicon carbide-based membrane (3) as claimed in any one of claims 5 to 7, wherein a plurality of internal pipelines (5) are arranged inside the silicon carbide-based membrane (3), a connecting shell (2) is arranged at the end of the silicon carbide-based membrane (3), the interior of the connecting shell (2) is communicated with the internal pipelines (5) of the silicon carbide-based membrane (3), the silicon carbide-based membrane (3) is arranged in the housing (1), and the silicon carbide-based membrane (3) is connected to the housing (1) through the connecting shell (2), a water storage cavity is opened on the side wall of the housing (1), the connecting shell (2) is communicated with the water storage cavity, and a drainage pipe (4) is arranged on the housing (1), and the drainage pipe (4) is communicated with the water storage cavity; A plurality of silicon carbide base films (3) are provided, and the silicon carbide base films (3) are not connected to each other.

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