Composite film and preparation method and application thereof

Abstract

The application belongs to the technical field of membrane materials, and particularly relates to a composite membrane and a preparation method and application thereof. The composite membrane comprises a gas-permeable photocatalytic hydrophobic layer, a support layer and a gas-permeable layer which are sequentially attached; the gas-permeable photocatalytic hydrophobic layer comprises an organic silicon base material and a light-responsive catalyst; the support layer comprises a support base material and a reinforcing phase; the support layer has holes; and the gas-permeable layer comprises a gas-permeable polymer material. The composite membrane can balance the oxygen permeability and mechanical strength, has excellent biological affinity, and has a self-cleaning function.

Description

Technical Field

[0001] This invention belongs to the field of membrane material technology, specifically relating to a composite membrane, its preparation method, and its application. Background Technology

[0002] In the field of water treatment, membrane aerated biofilm reactor (MABR) technology has the advantages of high-efficiency nitrogen removal and low energy consumption. Among existing technologies, the oxygen mass transfer rate of silica gel membranes is >15 gO2 / m 2 ·d), but its mechanical strength is extremely low (3-5 MPa), making it prone to breakage and failure; while polyvinylidene fluoride (PVDF) membranes have higher strength (8-10 MPa), but their oxygen mass transfer rate is insufficient (<8 gO2 / m). 2 (d) It is difficult to meet the treatment requirements of high ammonia nitrogen wastewater. MABR membranes have long faced the technical bottleneck of balancing oxygen permeability and mechanical strength. At the same time, the insufficient biocompatibility of MABR membrane materials leads to poor and uneven biofilm formation, affecting the usable area of ​​the MABR membrane. In addition, after long-term use, the biofilm thickness on the membrane surface of MABR membranes can become too thick. An excessively thick biofilm increases the thickness of the outer anoxic zone, increasing the resistance to the transfer of ammonia nitrogen and other substrates to the inner aerobic zone. At the same time, an excessively thick biofilm also leads to the mass transfer resistance of oxygen diffusion from the inner side to the outer side, affecting oxygen mass transfer characteristics.

[0003] In the operation of traditional MABR membranes, in order to control the appropriate biofilm thickness on the membrane surface and cause thicker biofilms to detach, frequent chemical cleaning (1-2 times per week) or large-volume aeration is required to scrub the membrane surface, resulting in short membrane life (usually <1 year) and high operation and maintenance energy costs. Summary of the Invention

[0004] Therefore, one of the technical problems to be solved by the present invention is to overcome the defects of existing composite membranes that cannot simultaneously achieve oxygen permeability and mechanical strength, thereby providing a composite membrane, its preparation method and application.

[0005] The second technical problem to be solved by this invention is that existing composite membranes have problems such as excessively thick biofilms and difficulty in detachment, thereby providing a composite membrane, its preparation method and application.

[0006] Therefore, the present invention provides the following technical solution:

[0007] The first aspect of the present invention protects a composite membrane, wherein the composite membrane comprises a breathable photocatalytic hydrophobic layer, a support layer and a breathable layer sequentially laminated together;

[0008] The breathable photocatalytic hydrophobic layer comprises an organosilicon matrix material and a photoresponsive catalyst;

[0009] The support layer includes a support matrix material and a reinforcing phase;

[0010] The support layer has holes;

[0011] The breathable layer comprises a breathable polymer material.

[0012] In this invention, the photoresponsive catalyst can generate hydroxyl radicals (·OH) and (·O) under sunlight, especially ultraviolet light irradiation. 2- ).

[0013] In one optional embodiment, the thickness of the breathable photocatalytic hydrophobic layer is 50-100 μm, the thickness of the support layer is 100-200 μm, and the thickness of the breathable layer is 10-20 μm.

[0014] In one optional embodiment, the thickness of the breathable photocatalytic hydrophobic layer is 60-80 μm, the thickness of the support layer is 120-160 μm, and the thickness of the breathable layer is 12-15 μm.

[0015] In one alternative embodiment, the organosilicon matrix material is linked to a photoresponsive catalyst via a silane coupling agent.

[0016] In this invention, the silane coupling agent has a bifunctional group. One end can chemically react with the active groups on the surface of the organosilicon matrix to form a strong chemical bond, and the other end can combine with the photoresponsive catalyst to improve the compatibility between the organosilicon matrix material and the photoresponsive catalyst. The silane coupling agent is a conventional silane coupling agent in the art, typically and non-limitingly including at least one of KH-550, KH-560, and KH-570.

[0017] In one optional embodiment, the organosilicon matrix material includes at least one of polydimethylsiloxane (PDMS), polymethylethylenesiloxane (PMVS), methylphenyl silicone rubber (MPQ), and fluorosilicone rubber (FVMQ).

[0018] In one optional embodiment, the photoresponsive catalyst includes at least one of TiO2, SrTiO3, ZnO, and SnO2; TiO2 is optional.

[0019] In one alternative embodiment, the average particle size of the photoresponsive catalyst is 20-50 nm.

[0020] In one optional embodiment, the mass ratio of the organosilicon matrix material to the photoresponsive catalyst is 100:(5-10).

[0021] In one optional embodiment, the supporting matrix material includes at least one of polyvinylidene fluoride (PVDF), polyethersulfone (PES), and polysulfone (PSU), and may be selected as polyvinylidene fluoride.

[0022] In one optional embodiment, the reinforcing phase includes at least one of graphene, carbon nanotubes, and silicon dioxide, and may be sheet-like graphene with an average lateral size of 1-5 μm and 5-8 longitudinal layers, which can be uniformly dispersed in the support layer and can provide better modulus and strength.

[0023] In one alternative embodiment, the mass ratio of the supporting matrix material to the reinforcing phase is (15-20):(0.5-1).

[0024] In one alternative embodiment, the porosity of the support layer is 70%-80%, and the average pore size is 0.1μm-0.5μm.

[0025] In one alternative embodiment, the breathable polymer material is a conventional breathable material in the art, typically and non-limitingly including at least one of hexamethyldisiloxane (HMDSO), polytetrafluoroethylene (PTFE), polyethylene (PE), and polypropylene (PP).

[0026] In this invention, the oxygen mass transfer rate of the composite membrane is ≥11 g O2 / m 2 / d; the surface contact angle of the breathable photocatalytic hydrophobic layer is >120°; the interlayer bonding strength between the breathable photocatalytic hydrophobic layer and the support layer is ≥1MPa; the tensile strength of the support layer is ≥11MPa.

[0027] A second aspect of this invention protects a method for preparing the aforementioned composite membrane, wherein the preparation method includes the following steps:

[0028] S1, the prepolymer of the organosilicon matrix material, the photoresponsive catalyst and the first solvent are mixed, coated on the substrate surface and cured, and then peeled off to obtain a breathable photocatalytic hydrophobic layer;

[0029] S2, the supporting matrix material, the reinforcing phase, the pore-forming agent and the second solvent are mixed and coated on the surface of the breathable photocatalytic hydrophobic layer to undergo a phase transition and obtain an intermediate product;

[0030] S3, deposit breathable polymer material monomers on the surface of the intermediate product away from the breathable photocatalytic hydrophobic layer, and carry out polymerization reaction to obtain a composite membrane.

[0031] In this invention, the prepolymer of the silicone matrix material is a conventional prepolymer in the art, which is commercially available. Typically, without limitation, the prepolymer of the silicone matrix material is Dow Corning Sylgard® 184 PDMS prepolymer, with A (prepolymer):B (curing agent) = 10:1.

[0032] In this invention, in step S1, since the mass of the PDMS prepolymer is almost entirely converted into the mass of the final polymer, the mass ratio of the organosilicon matrix material prepolymer to the photoresponsive catalyst is the same as the mass ratio of the organosilicon matrix material to the photoresponsive catalyst specified in the first aspect of this invention. The first solvent is a conventional solvent in the art, typically, but not limited to, including at least one of n-hexane and tetrahydrofuran; during mixing, sonication for 30-60 minutes can be used to make the mixing more uniform, and the solid content of the solution after mixing is 20-25 wt%; the substrate is a conventional substrate in the art, typically, but not limited to, a polyethylene terephthalate release film (PET).

[0033] In this invention, in step S2, the porogen is a conventional porogen in the art, typically, but not limited to, a water-soluble porogen. Water-soluble porogens are easy to remove and may include at least one of polyvinylpyrrolidone (PVP) and sodium chloride; the mass ratio of the supporting matrix material to the porogen is (15-20):(2-5). The second solvent is a conventional solvent in the art, typically, but not limited to, the second solvent includes at least one of N,N-dimethylacetamide (DMAC) and N,N-dimethylformamide (DMF); the solid content of the mixed solution is 20-25 wt%.

[0034] In an optional embodiment, in step S1, a silane coupling agent is also used to modify the photoresponsive catalyst; the modification method is a conventional method in the art, typically non-limiting, with a temperature of 20-25°C, a time of 2-12 h, and a stirring speed of 30-50 rpm.

[0035] In one optional embodiment, the permeable photocatalytic hydrophobic layer further includes a plasma activation step before step S2; optionally, the gas atmosphere for plasma activation is argon and / or helium, the power is 50-80W, and the time is 30-60s.

[0036] In one optional embodiment, the curing conditions include a temperature of 80-100°C and a time of 1-2 hours.

[0037] In one alternative implementation, the conditions for the phase transition include a temperature of 20-25°C and a time of 18-24 hours.

[0038] In one optional embodiment, the polymerization reaction conditions include: a vacuum environment (pressure 0.05-0.1 Pa), a temperature of 80-85°C, and a time of 2-4 hours.

[0039] In this invention, the type of monomer of the breathable polymer material is determined by the breathable polymer material defined in the first aspect of this invention, as long as it can react to generate the corresponding polymer. Typically, without limitation, hexamethyldisiloxane (HMDSO) monomer is introduced to obtain polydimethylsiloxane.

[0040] The third aspect of this invention protects the application of the aforementioned composite membrane or the composite membrane prepared by the aforementioned method in a membrane aeration biofilm reactor.

[0041] This invention uses conventional methods to prepare the composite membrane into a hollow fiber membrane for application. Typically, without limitation, the preparation method includes the following steps: winding the composite membrane onto a mandrel (tension 0.5-1N), heat-treating it at 100-120℃ for 1-2 hours, cooling it, and then cutting it to obtain a hollow fiber membrane with an outer diameter of 1-3 mm, an inner diameter of 0.5-1 mm, and a length of 1-2 m.

[0042] The technical solution of this invention has the following advantages:

[0043] 1. This invention provides a composite membrane, wherein the composite membrane comprises a breathable photocatalytic hydrophobic layer, a support layer, and a breathable layer sequentially bonded together; the breathable photocatalytic hydrophobic layer comprises an organosilicon matrix material and a photoresponsive catalyst; the support layer comprises a support matrix material and a reinforcing phase; the support layer is porous; the breathable layer comprises a breathable polymer material; the composite membrane of this invention can balance oxygen permeability and mechanical strength, has excellent biocompatibility, and has a self-cleaning function;

[0044] Nitrification requires the participation of microorganisms, and the aggregation of microorganisms requires oxygen. The permeable layer of this invention can selectively allow oxygen to pass through while preventing impurities in the wastewater from passing through, thus avoiding impurities from clogging the pores of the support layer. Because of the pores in the support layer, oxygen can pass through smoothly and reach the permeable photocatalytic hydrophobic layer, allowing microorganisms to aggregate on the surface of the composite membrane and form a biofilm. At the same time, the photoresponsive catalyst dispersed in the organosilicon matrix material also increases the static friction of the permeable photocatalytic hydrophobic layer to a certain extent, which is conducive to the attachment of microorganisms. Microorganisms achieve uniform biofilm formation, and the composite membrane exhibits excellent biocompatibility, ensuring the smooth progress of the nitrification reaction.

[0045] The reinforcing phase in the support layer has high modulus and high strength, and is uniformly dispersed in the support matrix material. It can effectively transfer and share external pressure, avoid stress concentration, and improve mechanical properties.

[0046] The breathable photocatalytic hydrophobic layer, comprising an organosilicon matrix material, is difficult to wet with water molecules, reducing pollution at its source. The photoresponsive catalyst generates hydroxyl radicals (·OH) and superoxide radicals (·O) upon excitation by light (such as ultraviolet / visible light). 2-The main pathways by which free radicals degrade organic matter on the membrane surface include bond breaking (attacking C-C and CH bonds in the organic molecular chain, causing it to break down into smaller molecules), mineralization (ultimately oxidizing the organic matter into CO2 and H2O), and biofilm inhibition (destroying the microbial cell membrane structure and inactivating bacteria). These highly oxidizing free radicals can non-selectively degrade organic matter (such as proteins, oils, polysaccharides, humic acids, etc.) attached to the membrane surface, achieving "self-cleaning." This allows thicker biofilms to detach quickly, alleviating membrane fouling and improving the anisotropic mass transfer and diffusion of oxygen and pollutants. Compared with aeration flushing and chemical rinsing, this reduces maintenance costs and significantly extends the membrane's service life.

[0047] 2. The composite membrane of the present invention further limits the thickness of each layer, which can further improve the balance between oxygen permeability, mechanical strength, biocompatibility and self-cleaning ability.

[0048] 3. This invention provides a method for preparing a composite membrane, wherein the preparation method includes the following steps: S1, mixing a prepolymer of an organosilicon matrix material, a photoresponsive catalyst, and a first solvent, coating the mixture onto a substrate surface, curing it, and then peeling it off to obtain a breathable photocatalytic hydrophobic layer; S2, mixing a supporting matrix material, a reinforcing phase, a pore-forming agent, and a second solvent, coating the mixture onto the surface of the breathable photocatalytic hydrophobic layer, and performing a phase transition to obtain an intermediate product; S3, depositing a breathable polymer material monomer on the surface of the intermediate product away from the breathable photocatalytic hydrophobic layer, and performing a polymerization reaction to obtain a composite membrane; the preparation method of this invention uses a layered original material... The method of on-site preparation improves the compatibility and bonding force between membrane layers, making the membrane layers adhere more tightly, thereby improving mechanical properties and oxygen permeability. The hydrophobic layer containing a photoresponsive catalyst can effectively achieve the shedding of thicker biofilms and reduce membrane fouling by virtue of its superhydrophobic and photocatalytic properties, achieving "self-cleaning". In the support layer, the high-modulus and high-strength reinforcing phase is uniformly dispersed in the support matrix material, which can efficiently transfer and disperse external stress, avoid stress concentration, and significantly improve the overall mechanical properties. In addition, the gas-permeable photocatalytic hydrophobic layer, the support layer with through holes, and the gas-permeable layer form a continuous mass transfer channel, ensuring excellent oxygen permeability.

[0049] 4. In the preparation method of the present invention, the air-permeable photocatalytic hydrophobic layer is further activated by plasma before step S2. Through plasma activation, chemical bonds are formed between the hydrophobic layer and the support layer, thereby improving the bonding force between the film layers.

[0050] 5. The application of the composite membrane of the present invention in a membrane aerated biofilm reactor (MABR) provides a sustainable self-cleaning solution for MABR technology; furthermore, in application, it includes shutting down reactor aeration and stirring, solid-liquid sedimentation and stratification within the reactor, irradiating the composite membrane with a light source, and the photoresponsive catalyst generating hydroxyl radicals (·OH) and superoxide radicals (·O) under light excitation (such as ultraviolet / visible light).2- This method can remove pollutants and thick microbial layers attached to the surface of membrane materials. Compared with existing methods that use chemical agents or excessive aeration to treat the biological layer on the membrane surface, the process is simpler and reduces costs. Attached Figure Description

[0051] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0052] Figure 1 This is a schematic diagram of the composite membrane in Example 1;

[0053] Figure 2 These are images of the composite membrane application in Example 1, showing the membrane hanging on the substrate.

[0054] Figure 3 This is an image of the composite membrane application in Comparative Example 1;

[0055] Figure 4 These are electron microscope images of the composite membrane from Example 1 after it has been coated with film and irradiated with ultraviolet light for 10 minutes.

[0056] Figure 5 These are electron microscope images of the composite membrane from Example 1 after it has been coated with film and irradiated with ultraviolet light for 20 minutes.

[0057] Figure 6 These are electron microscope images of the composite membrane from Example 1 after it has been coated with UV light for 30 minutes.

[0058] Figure Labels

[0059] 1- Breathable photocatalytic hydrophobic layer; 2- Support layer; 3- Breathable layer; 4- Inner cavity. Detailed Implementation

[0060] The following embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.

[0061] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0062] Prepolymer of polydimethylsiloxane: Dow Corning Sylgard® 184 PDMS prepolymer, A (prepolymer): B (curing agent) = 10:1;

[0063] The plasma equipment is Diener Electronic Pico (low-pressure radio frequency plasma system).

[0064] Example 1

[0065] This embodiment provides a composite membrane, including the following steps:

[0066] S1. KH-550 silane coupling agent was used to modify anatase TiO2 with an average particle size of 30 nm. The mass ratio of KH-550 silane coupling agent to anatase TiO2 was 3:100. The modification temperature was 25℃, the time was 6 h, and the stirring speed was 40 rpm to obtain the modified product. The prepolymer of polydimethylsiloxane, the modified product, and n-hexane were mixed to obtain a mixed solution with a solid content of 20 wt%. The mass ratio of polydimethylsiloxane prepolymer to modified product was 100:8. The mixed solution was coated on the surface of polyethylene terephthalate and cured at 90℃ for 1.5 h. After peeling, a breathable photocatalytic hydrophobic layer was obtained.

[0067] The gas-permeable photocatalytic hydrophobic layer was placed in a plasma device for treatment. The gas atmosphere was controlled as argon, the power was 60W, and the time was 40s to obtain the activated gas-permeable photocatalytic hydrophobic layer.

[0068] S2, a mixed solution was prepared by mixing polyvinylidene fluoride, sheet graphene, polyvinylpyrrolidone and N,N-dimethylacetamide, wherein the mass ratio of polyvinylidene fluoride, sheet graphene and polyvinylpyrrolidone was 18:0.7:3, the average transverse size of sheet graphene was 2μm, the number of longitudinal layers was 5, and the solid content of the mixed solution was 22wt%. The mixed solution was coated on the surface of the activated gas-permeable photocatalytic hydrophobic layer to carry out phase transition at 25℃ for 24h to obtain an intermediate product.

[0069] S3. Under vacuum, hexamethyldisiloxane monomer is coated on the surface of the intermediate product far from the activated permeable photocatalytic hydrophobic layer, and polymerization reaction is carried out at 80°C for 2 hours to obtain a composite film.

[0070] Example 2

[0071] This embodiment provides a composite membrane, including the following steps:

[0072] S1. ZnO with an average particle size of 30 nm was modified using KH-550 silane coupling agent, wherein the mass ratio of KH-550 silane coupling agent to ZnO was 5:100, the modification temperature was 20℃, the time was 12 h, and the stirring speed was 30 rpm to obtain a modified product. The prepolymer of polydimethylsiloxane, the modified product and n-hexane were mixed to obtain a mixed solution with a solid content of 25 wt%, wherein the mass ratio of polydimethylsiloxane prepolymer to modified product was 100:8. The mixed solution was coated on the surface of polyethylene terephthalate and cured at a temperature of 80℃ for 1.0 h. After peeling, a breathable photocatalytic hydrophobic layer was obtained.

[0073] The gas-permeable photocatalytic hydrophobic layer was placed in a plasma device for treatment. The gas atmosphere was controlled as argon, the power was 60W, and the time was 40s to obtain the activated gas-permeable photocatalytic hydrophobic layer.

[0074] S2, a mixed solution was prepared by mixing polyvinylidene fluoride, sheet graphene, polyvinylpyrrolidone and N,N-dimethylacetamide, wherein the mass ratio of polyvinylidene fluoride, sheet graphene and polyvinylpyrrolidone was 18:1.0:3, the average transverse size of sheet graphene was 2μm and the number of longitudinal layers was 3, and the solid content of the mixed solution was 25wt%. The mixed solution was coated on the surface of the activated gas-permeable photocatalytic hydrophobic layer to carry out phase transition at 20℃ for 24h to obtain an intermediate product.

[0075] S3. Under vacuum, hexamethyldisiloxane monomer is coated on the surface of the intermediate product far from the activated permeable photocatalytic hydrophobic layer, and a polymerization reaction is carried out at a temperature of 83°C for 3 hours to obtain a composite film.

[0076] Example 3

[0077] This embodiment provides a composite membrane, including the following steps:

[0078] S1. SnO2 with an average particle size of 50 nm was modified using KH-550 silane coupling agent. The mass ratio of KH-550 silane coupling agent to SnO2 was 4:100. The modification temperature was 22℃, the time was 8 h, and the stirring speed was 50 rpm to obtain the modified product. The prepolymer of polydimethylsiloxane, the modified product, and n-hexane were mixed to obtain a mixed solution with a solid content of 21 wt%. The mass ratio of the prepolymer of polydimethylsiloxane to the modified product was 100:7. The mixed solution was coated on the surface of polyethylene terephthalate and cured at 85℃ for 1.4 h. After peeling, a breathable photocatalytic hydrophobic layer was obtained.

[0079] The gas-permeable photocatalytic hydrophobic layer was placed in a plasma device for treatment. The gas atmosphere was controlled as argon, the power was 60W, and the time was 45s to obtain the activated gas-permeable photocatalytic hydrophobic layer.

[0080] S2, a mixed solution was prepared by mixing polyvinylidene fluoride, sheet graphene, polyvinylpyrrolidone and N,N-dimethylacetamide, wherein the mass ratio of polyvinylidene fluoride, sheet graphene and polyvinylpyrrolidone was 18:1.0:3, the average transverse size of sheet graphene was 3 μm and the number of longitudinal layers was 4, and the solid content of the mixed solution was 25 wt%. The mixed solution was coated on the surface of the activated gas-permeable photocatalytic hydrophobic layer to carry out phase transition at 20 °C for 24 h to obtain an intermediate product.

[0081] S3, Under vacuum, hexamethyldisiloxane monomer is coated on the surface of the intermediate product far from the activated permeable photocatalytic hydrophobic layer, and polymerization reaction is carried out at 80℃ for 3.5h to obtain a composite film.

[0082] Example 4

[0083] This embodiment provides a composite membrane, including the following steps:

[0084] The method is the same as in Example 1, except that plasma treatment is not performed in step S1, and step S2 is performed directly after obtaining the breathable photocatalytic hydrophobic layer.

[0085] Example 5

[0086] This embodiment provides a composite membrane, including the following steps:

[0087] The method is the same as in Example 1, except that in step S1, TiO2 is replaced with an equal mass of SrTiO3.

[0088] Example 6

[0089] This embodiment provides a composite membrane, including the following steps:

[0090] S1, following the method of Example 1, except that the curing temperature is 85°C and the time is 1.0h, and a breathable photocatalytic hydrophobic layer is obtained after peeling;

[0091] S2, following the method of Example 1, except that the mixed solution is coated on the surface of the activated breathable photocatalytic hydrophobic layer to carry out a phase transition at a temperature of 21°C for 20 hours to obtain an intermediate product.

[0092] S3, following the method of Example 1, except that the polymerization reaction is carried out at a temperature of 83°C for 3 hours;

[0093] The thickness of the breathable photocatalytic hydrophobic layer is 55 μm, the thickness of the support layer is 200 μm, and the thickness of the breathable layer is 10 μm.

[0094] Example 7

[0095] This embodiment provides a composite membrane, including the following steps:

[0096] S1, a mixture of polydimethylsiloxane prepolymer, anatase TiO2 with an average particle size of 30 nm, and n-hexane was prepared to obtain a mixed solution with a solid content of 20 wt%. The mass ratio of polydimethylsiloxane prepolymer to anatase TiO2 with an average particle size of 30 nm was 100:8. The mixed solution was coated onto the surface of polyethylene terephthalate and cured at 90 °C for 1.5 h. After peeling, a breathable photocatalytic hydrophobic layer was obtained. The breathable photocatalytic hydrophobic layer was then treated in a plasma device with an argon atmosphere, a power of 60 W, and a treatment time of 40 s to obtain an activated breathable photocatalytic hydrophobic layer.

[0097] S2, according to the method of Example 1;

[0098] S3, in accordance with the method of Example 1.

[0099] Comparative Example 1

[0100] This comparative example provides a composite membrane, comprising the following steps:

[0101] S1, a mixed solution was prepared by mixing polyvinylidene fluoride, sheet graphene, polyvinylpyrrolidone and N,N-dimethylacetamide, wherein the mass ratio of polyvinylidene fluoride, sheet graphene and polyvinylpyrrolidone was 18:0.7:3, the average transverse size of sheet graphene was 2μm and the number of longitudinal layers was 5, and the solid content of the mixed solution was 22wt%. The mixed solution was coated on the surface of the activated gas-permeable photocatalytic hydrophobic layer to carry out phase transition at a temperature of 25℃ for 24h to obtain an intermediate product.

[0102] S2, Under vacuum, hexamethyldisiloxane monomer is coated on the surface of the intermediate product far from the activated permeable photocatalytic hydrophobic layer, and a polymerization reaction is carried out at 80°C for 2 hours to obtain a composite film.

[0103] Comparative Example 2

[0104] This comparative example provides a composite membrane, comprising the following steps:

[0105] S1. KH-550 silane coupling agent was used to modify anatase TiO2 with an average particle size of 30 nm. The mass ratio of KH-550 silane coupling agent to anatase TiO2 was 3:100. The modification temperature was 25℃, the time was 6 h, and the stirring speed was 40 rpm to obtain the modified product. The prepolymer of polydimethylsiloxane, the modified product, and n-hexane were mixed to obtain a mixed solution with a solid content of 20 wt%. The mass ratio of polydimethylsiloxane prepolymer to modified product was 100:8. The mixed solution was coated on the surface of polyethylene terephthalate and cured at 90℃ for 1.5 h. After peeling, a breathable photocatalytic hydrophobic layer was obtained.

[0106] The gas-permeable photocatalytic hydrophobic layer was placed in a plasma device for treatment. The gas atmosphere was controlled as argon, the power was 60W, and the time was 40s to obtain the activated gas-permeable photocatalytic hydrophobic layer.

[0107] S2, Under vacuum conditions, hexamethyldisiloxane monomer is coated onto the surface of the activated permeable photocatalytic hydrophobic layer and polymerized at 80°C for 2 hours to obtain a composite membrane.

[0108] Comparative Example 3

[0109] This comparative example provides a composite membrane, comprising the following steps:

[0110] S1. KH-550 silane coupling agent was used to modify anatase TiO2 with an average particle size of 30 nm. The mass ratio of KH-550 silane coupling agent to anatase TiO2 was 3:100. The modification temperature was 25℃, the time was 6 h, and the stirring speed was 40 rpm to obtain the modified product. The prepolymer of polydimethylsiloxane, the modified product, and n-hexane were mixed to obtain a mixed solution with a solid content of 20 wt%. The mass ratio of polydimethylsiloxane prepolymer to modified product was 100:8. The mixed solution was coated on the surface of polyethylene terephthalate and cured at 90℃ for 1.5 h. After peeling, a breathable photocatalytic hydrophobic layer was obtained.

[0111] The gas-permeable photocatalytic hydrophobic layer was placed in a plasma device for treatment. The gas atmosphere was controlled as argon, the power was 60W, and the time was 40s to obtain the activated gas-permeable photocatalytic hydrophobic layer.

[0112] S2, a mixed solution was prepared by mixing polyvinylidene fluoride, sheet graphene, polyvinylpyrrolidone, and N,N-dimethylacetamide, wherein the mass ratio of polyvinylidene fluoride, sheet graphene, and polyvinylpyrrolidone was 18:0.7:3, the average transverse size of the sheet graphene was 2 μm, the number of longitudinal layers was 5, and the solid content of the mixed solution was 22 wt%. The mixed solution was coated on the surface of the activated permeable photocatalytic hydrophobic layer to undergo a phase transition at a temperature of 25 °C for 24 h, thereby obtaining a composite film.

[0113] Comparative Example 4

[0114] This comparative example provides a composite membrane, comprising the following steps:

[0115] S1, the prepolymer of polydimethylsiloxane and n-hexane are mixed to obtain a mixed solution with a solid content of 20wt%. The mixed solution is coated on the surface of polyethylene terephthalate and cured at a temperature of 90℃ for 1.5h. After peeling, a breathable photocatalytic hydrophobic layer is obtained.

[0116] S2, according to the method of Example 1;

[0117] S3, in accordance with the method of Example 1.

[0118] Comparative Example 5

[0119] This comparative example provides a composite membrane, comprising the following steps:

[0120] S1, according to the method of Example 1;

[0121] S2, polyvinylidene fluoride, sheet graphene, and N,N-dimethylacetamide were mixed to obtain a mixed solution, wherein the mass ratio of polyvinylidene fluoride to sheet graphene was 18:0.7, the average transverse size of the sheet graphene was 2 μm, the number of longitudinal layers was 5, and the solid content of the mixed solution was 22 wt%. The mixed solution was coated on the surface of the activated gas-permeable photocatalytic hydrophobic layer to carry out a phase transition at a temperature of 25 °C for 24 h to obtain an intermediate product.

[0122] S3, in accordance with the method of Example 1.

[0123] Comparative Example 6

[0124] This comparative example provides a composite membrane, comprising the following steps:

[0125] S1, following the method of Example 1, except that the prepolymer of polydimethylsiloxane is replaced with an equal mass of waterborne polyurethane (PU) prepolymer with the same solid content (purchased from Dongguan Guangtai Plastic Raw Materials Co., Ltd., brand name is casting type liquid PU, item number is GT1095).

[0126] S2, according to the method of Example 1;

[0127] S3, in accordance with the method of Example 1.

[0128] Comparative Example 7

[0129] This comparative example provides a composite membrane, comprising the following steps:

[0130] S1, according to the method of Example 1;

[0131] S2, following the method of Example 1, except that sheet graphene was not added, that is, polyvinylidene fluoride, polyvinylpyrrolidone and N,N-dimethylacetamide were mixed to obtain a mixed solution, wherein the mass ratio of polyvinylidene fluoride to sheet polyvinylpyrrolidone was 18:3, the solid content of the mixed solution was 22wt%, the mixed solution was coated on the surface of the activated gas-permeable photocatalytic hydrophobic layer to carry out phase transition at a temperature of 25°C for 24 hours, and an intermediate product was obtained;

[0132] S3, in accordance with the method of Example 1.

[0133] Comparative Example 8

[0134] This comparative example provides a composite membrane, comprising the following steps:

[0135] S1, according to the method of Example 1;

[0136] S2, according to the method of Example 1;

[0137] S3, following the method of Example 1, except that in step S3, the hexamethyldisiloxane monomer is replaced with an equal mass of a mixture of bisphenol A type epoxy resin (E-51) and curing agent (polyamide 650) (mass ratio E-51:polyamide 650=100:35), and a polymerization reaction is carried out at a temperature of 80°C for 2 hours to obtain a composite film.

[0138] Test case

[0139] (1) The thicknesses of the breathable photocatalytic hydrophobic layer, the support layer, and the breathable layer were measured using the scanning electron microscope (SEM) cross-sectional method, and the integers were retained.

[0140] The porosity of the support layer was tested using the BET method.

[0141] The average size of the pores in the support layer was tested using the mercury indentation method.

[0142] The test results are shown in Table 1.

[0143] Table 1. Thickness of the breathable photocatalytic hydrophobic layer, support layer, and breathable layer; porosity and average pore size of the support layer.

[0144]

[0145] In the comparison, " / " indicates that it does not exist.

[0146] (2) The surface contact angle of the breathable photocatalytic hydrophobic layer was tested using a German Dataphysics OCA25 optical contact angle measuring instrument;

[0147] (3) The interlayer bonding strength between the breathable photocatalytic hydrophobic layer and the support layer was determined by the "Determination of Coating Adhesion - Pull-off Method" (GB / T 5210-2006);

[0148] (4) The tensile strength shall be tested in accordance with ISO 527-3:2018 (Tension properties of plastics - Part 3: Tensile strength of films and sheets);

[0149] The test results are shown in Table 2.

[0150] Table 2 Physical property tests of composite membranes

[0151]

[0152] (5) Test method for oxygen mass transfer rate: Calculate according to the following formula:

[0153] ;

[0154] ;

[0155] ;

[0156] In the formula, OTE represents oxygen utilization efficiency, which is the proportion of oxygen transferred to the biofilm from the air / oxygen supplied to the MABR membrane module, expressed as % .

[0157] O 2,in The percentage of oxygen in the air entering the MABR membrane cavity is constant at 20.9%.

[0158] O 2,out The percentage of oxygen in the exhaust gas of a MABR membrane module, %

[0159] F V This is the volume loss coefficient;

[0160] OTR is the oxygen mass transfer rate, g O2 / m 2 / d;

[0161] Q air Airflow rate, L / d;

[0162] The relative molecular mass of oxygen is 32;

[0163] The standard molar volume constant for the gas is 22.4;

[0164] S bf The area of ​​the MABR biofilm is m. 2 .

[0165] (6) The composite membrane is used for wastewater treatment, wherein the wastewater is municipal wastewater containing ammonia nitrogen (concentration 10~75mg / L). The initial rate is defined as the rate after the oxygen mass transfer stabilizes (the oxygen content in the tail gas of the MABR membrane module is 18% as the baseline value for oxygen mass transfer stabilization). The time when the oxygen mass transfer rate drops to 75% of the initial rate is recorded as the self-cleaning frequency.

[0166] (7) Ultraviolet light (wavelength 365nm, light intensity 8mW / cm) 2 After 2 hours of illumination, the illumination was turned off, gas supply was restarted, and the recovery of oxygen mass transfer performance was observed. The rate at which oxygen mass transfer stabilized was defined as the recovery rate, and the cycle stability of the membrane was tested. Cycle stability = (recovery rate / initial rate) × 100%;

[0167] (8) The composite membranes of the examples and comparative examples were applied by winding them onto a mandrel (tension 0.75N) and heat-treating them at 110°C for 1.5 hours. After cooling, they were cut into 1.5m lengths to obtain hollow fiber membranes with an inner diameter of 0.75mm. A schematic diagram of the hollow fiber membrane is shown below. Figure 1 As shown in the figure, we can see the breathable photocatalytic hydrophobic layer 1, the support layer 2, the breathable layer 3, and the inner cavity 4.

[0168] Methods for testing the nitration reaction rate:

[0169] ;

[0170] NH x,inf —Ammonia nitrogen concentration entering the MABR reaction unit, mg / L;

[0171] NH x,eff —Ammonia nitrogen concentration effluent from the MABR reactor unit, mg / L;

[0172] A – MABR membrane area;

[0173] Q inf —Flow rate through the MABR reactor unit, m 3 / d;

[0174] NR—MABR nitration rate, g N / m 2 / d;

[0175] The test results are shown in Table 3.

[0176] Table 3. Oxygen transfer rate, self-cleaning frequency, cycle stability, and nitration rate of the MABR reactor unit of the composite membrane.

[0177]

[0178] Because the oxygen mass transfer rate and nitrification reaction rate of Comparative Example 8 were below the detection limit and were not detected, they have no practical value. Therefore, no further testing was conducted, and " / " indicates that no test was performed.

[0179] A photograph of the composite film after use in Example 1 is shown below. Figure 2 As shown in the image, a photograph of the composite membrane in Comparative Example 1 after use is shown. Figure 3 As shown in the figure, it can be seen that the biolayer of Example 1 is coated on the surface of the hollow fiber membrane, forming a uniform biofilm, while the biolayer of Comparative Example 1 is not uniformly coated. The composite membrane of Example 1 has good biocompatibility. Combined with the nitrification reaction rate data in the table, it can be seen that due to the uniform coating, the nitrification reaction can be fully carried out, and the nitrification reaction rate is high.

[0180] The MABR reactor is intermittently stopped from stirring and aeration. After the suspended sludge in the MABR unit settles, the surface of the MABR membrane is irradiated with sunlight to activate the photocatalytic reaction using ultraviolet rays. After irradiation for 10 minutes, as... Figure 4 As shown in the figure, a small portion of the thick biofilm covering the surface of the breathable photocatalytic hydrophobic layer has detached, indicating that the photocatalytic reaction has been activated; after irradiation for 20 minutes, as... Figure 5 As shown in the figure, it can be seen that the relatively thick biofilm covering the surface of the breathable photocatalytic hydrophobic layer has virtually no effective adhesion to the membrane material; after irradiation for 30 minutes, as... Figure 6 As shown in the figure, the organic matter on the membrane surface has been largely removed, effectively controlling the biofilm thickness, alleviating membrane fouling, and thus improving the anisotropic mass transfer efficiency of oxygen and pollutants, thereby enhancing the removal effect of pollutants.

[0181] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A composite film, characterized by, The composite film is composed of a gas-permeable photocatalytic hydrophobic layer, a support layer and a gas-permeable layer which are sequentially attached; The gas-permeable photocatalytic hydrophobic layer comprises an organic silicon base material and a light-responsive catalyst; The support layer comprises a support base material and a reinforcing phase; The support layer has pores; The gas-permeable layer comprises a gas-permeable polymer material; The thickness of the gas-permeable photocatalytic hydrophobic layer is 60-80 μm, the thickness of the support layer is 120-160 μm, and the thickness of the gas-permeable layer is 12-15 μm; The preparation method of the composite film comprises the following steps: S1, mixing a prepolymer of an organic silicon base material, a light-responsive catalyst and a first solvent, coating on the surface of a substrate, curing, peeling off to obtain a gas-permeable photocatalytic hydrophobic layer; S2, mixing a support base material, a reinforcing phase, a pore-forming agent and a second solvent, coating on the surface of the gas-permeable photocatalytic hydrophobic layer, phase inversion to obtain an intermediate product; S3, depositing a gas-permeable polymer material monomer on the surface of the intermediate product away from the gas-permeable photocatalytic hydrophobic layer, and performing polymerization reaction to obtain a composite film; In step S1, the light-responsive catalyst is also modified by using a silane coupling agent; the organic silicon base material is connected with the light-responsive catalyst through the silane coupling agent; The gas-permeable photocatalytic hydrophobic layer further comprises a step of plasma activation before step S2.

2. The composite film according to claim 1, characterized by, The organic silicon base material comprises at least one of polydimethylsiloxane, polymethylvinylsiloxane, methylphenyl silicone rubber and fluorosilicone rubber; And / or, the light-responsive catalyst comprises at least one of TiO2, SrTiO3, ZnO and SnO2; And / or, the average particle size of the light-responsive catalyst is 20-50 nm; And / or, the mass ratio of the organic silicon base material and the light-responsive catalyst is 100:(5-10).

3. The composite film of claim 1, wherein The support base material comprises at least one of polyvinylidene fluoride, polyether sulfone and polysulfone; And / or, the reinforcing phase comprises at least one of graphene, carbon nanotube and silicon dioxide; And / or, the mass ratio of the support base material and the reinforcing phase is (15-20):(0.5-1); And / or, the porosity of the support layer is 70%-80%, and the average size of the pores is 0.1 μm-0.5 μm.

4. The production method according to claim 1, characterized by, The curing conditions include a temperature of 80-100℃ and a time of 1-2h; And / or, the phase inversion conditions include a temperature of 20-25℃ and a time of 18-24h; And / or, the polymerization reaction conditions include a pressure of 0.05-0.1 Pa, a temperature of 80-85℃ and a time of 2-4h.

5. Application of the composite film of any one of claims 1-4 in a membrane aerated biofilm reactor.

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