An internal pressure type polyether sulfone hollow fiber ultrafiltration membrane, a preparation method and application thereof

Abstract

The application discloses an internal pressure type polyether sulfone hollow fiber ultrafiltration membrane and a preparation method and application thereof. The internal pressure type polyether sulfone hollow fiber ultrafiltration membrane has multistage pores; the inner surface of the internal pressure type polyether sulfone hollow fiber ultrafiltration membrane is modified by a natural phenolic compound, and the outer surface and pore wall are modified by soybean phosphatidylcholine. The internal pressure type polyether sulfone hollow fiber ultrafiltration membrane has both ultrahigh water flux and excellent anti-pollution performance, and is particularly suitable for high-risk pollution scenes such as advanced treatment of reclaimed water.

Description

Technical Field

[0001] This invention relates to the field of separation membrane technology, and more specifically, to an internal pressure polyethersulfone hollow fiber ultrafiltration membrane, its preparation method, and its application. Background Technology

[0002] In processes such as reclaimed water reuse and municipal wastewater treatment, dissolved microbial products (SMPs) are the primary cause of membrane fouling. SMPs are mainly composed of biopolymers such as proteins, polysaccharides, and nucleic acids released by microbial metabolism. They exhibit strong adhesion and a tendency to form gel layers. When using internal pressure polyethersulfone (PES) ultrafiltration membranes to treat such water bodies, SMPs rapidly adsorb and deposit on the inner surface and within the pores of the membrane, causing irreversible blockage of the membrane pores. This leads to a sharp decline in membrane flux, frequent cleaning, and a significant increase in operating energy consumption and costs.

[0003] Currently, methods to improve the antifouling ability of PES membranes mainly include blending hydrophilic polymers (such as polyvinylpyrrolidone, PVP) or inorganic nanoparticles (such as TiO2) in the casting solution. These methods have inherent drawbacks: First, the additives are prone to leaching during long-term operation, leading to unstable performance; second, this is a homogenization modification, which cannot provide differentiated protection for the different fouling mechanisms on the inner surface (facing the influent impact) and outer surface (on the effluent side) of the internal pressure membrane; third, the membrane pore structure prepared by the traditional phase inversion method is simple, making it difficult to achieve both high water flux and high rejection rate of small molecule components in SMP; finally, the finished membrane usually needs to be stored in a wet state, increasing storage and transportation costs.

[0004] Therefore, there is an urgent need for an internal pressure PES ultrafiltration membrane and its preparation method that can achieve long-term enhanced antifouling of the inner surface, synergistic internal and external functions, and have both ultra-high flux and high rejection rate through membrane structure design. Summary of the Invention

[0005] This invention is based on the inventor's discovery and understanding of the following facts and problems: Current internal pressure polyethersulfone ultrafiltration membranes have the following problems: additives are prone to leaching during long-term operation, resulting in unstable performance; differentiated protection is not provided for the different fouling mechanisms of the inner and outer surfaces of the internal pressure membrane; the membrane pore structure is simple, making it difficult to achieve both high water flux and high rejection rate of small molecule components in SMP; finished membranes usually need to be stored in a wet state, increasing storage and transportation costs.

[0006] This invention aims to at least partially address one of the technical problems in related technologies. To this end, embodiments of this invention propose an internally pressurized polyethersulfone hollow fiber ultrafiltration membrane, its preparation method, and its application, which combines ultra-high water flux and excellent antifouling performance, making it particularly suitable for high-risk pollution scenarios such as advanced reclaimed water treatment.

[0007] This invention provides an internal pressure polyethersulfone hollow fiber ultrafiltration membrane, which has multi-level pores; the inner surface of the internal pressure polyethersulfone hollow fiber ultrafiltration membrane is modified with natural phenolic compounds, and the outer surface and pore walls are modified with soybean phosphatidylcholine.

[0008] In some embodiments, the internally pressurized polyethersulfone hollow fiber ultrafiltration membrane includes nanoscale pores and microscale pores; And / or, the pure water contact angle on the inner surface of the internal pressure polyethersulfone hollow fiber ultrafiltration membrane is less than 50°; And / or, the internal pressure polyethersulfone hollow fiber ultrafiltration membrane has a pure water flux of not less than 300 L / (m³) at 0.1 MPa. 2 ·h·bar).

[0009] This invention provides a method for preparing an internally pressurized polyethersulfone hollow fiber ultrafiltration membrane, comprising the following steps: (1) The casting solution and the core solution are extruded through a hollow fiber spinneret to obtain nascent fibers; wherein the casting solution includes polyethersulfone, polymer porogen, thermoporogen and organic solvent; the core solution includes natural phenolic compounds and water; (2) The extruded nascent fibers enter an external coagulation bath for liquid-phase induced phase separation; the external coagulation bath includes soybean phosphatidylcholine, inorganic salts, glycerol and water; the inorganic salts include at least one of water-soluble carbonates or water-soluble bicarbonates; (3) Then heat treatment is performed to obtain an internal pressure polyethersulfone hollow fiber ultrafiltration membrane.

[0010] In some embodiments, in step (1), the mass percentage concentration of polyethersulfone in the casting solution is 15-22 wt%. And / or, in the casting solution, the mass percentage concentration of the polymeric pore-forming agent is 5-10 wt%; And / or, in the casting solution, the mass percentage concentration of the thermoporizing agent is 1-5 wt%.

[0011] In some embodiments, in step (1), the polymer porogen includes polyvinylpyrrolidone; And / or, the thermoporous agent includes at least one of ammonium carbonate or ammonium bicarbonate; And / or, the preparation of the casting solution includes: mixing polyethersulfone, polymeric porogen, thermoporogen and organic solvent, stirring to dissolve, and then performing degassing treatment to obtain the casting solution.

[0012] In some embodiments, in step (1), the natural phenolic compound includes at least one of tannic acid, gallic acid, or dopamine; And / or, the concentration of the natural phenolic compound in the core fluid is 0.5-3.0 g / L.

[0013] In some embodiments, in step (2), the water-soluble carbonate includes at least one of sodium carbonate and potassium carbonate; And / or, the water-soluble bicarbonate includes at least one of sodium bicarbonate and potassium bicarbonate; And / or, in the external coagulation bath, the concentration of soybean phosphatidylcholine is 0.5~5.0 g / L; And / or, in the external coagulation bath, the concentration of the inorganic salt is 1.0~10.0 g / L; And / or, in the external coagulation bath, the concentration of glycerol is 10~100g / L.

[0014] In some embodiments, in step (2), the temperature of the external coagulation bath is 20-30°C; And / or, the liquid-induced phase separation time is 24-48 h.

[0015] In some embodiments, in step (3), the temperature of the heat treatment is 50-80°C; And / or, the heat treatment time is 5-30 min; And / or, post-treatment is performed after heat treatment, the post-treatment including washing with water, soaking in glycerol solution and drying.

[0016] This invention provides an application of an internal pressure polyethersulfone hollow fiber ultrafiltration membrane for treating wastewater containing dissolved microbial products.

[0017] The internal pressure polyethersulfone hollow fiber ultrafiltration membrane provided by the present invention has an asymmetric hydrophilic gradient antifouling structure and a hierarchical pore structure. The membrane wall has an asymmetric gradient-modified antifouling structure, with the inner surface mainly modified by natural phenolic compounds and the outer surface and pore walls mainly modified by soybean phosphatidylcholine. The ultrafiltration membrane has micron-nano hierarchical pores, including micron-sized pores (e.g., finger-like pores / sponge pores) and nano-sized pores (bubble pores). Through its unique gradient modification and hierarchical pore design, the ultrafiltration membrane of the present invention exhibits extremely high resistance to soluble microbial product (SMP) contamination under internal pressure operation mode, while also possessing ultra-high water flux. The ultrafiltration membrane of the present invention also possesses ultra-high water flux (≥300 L / (m³)). 2 With its high efficiency (·h·bar) and excellent anti-pollution performance (flux recovery rate ≥96%), it is particularly suitable for high-risk pollution scenarios such as deep treatment of reclaimed water.

[0018] The preparation method of the internal pressure polyethersulfone hollow fiber ultrafiltration membrane provided by the present invention has a high degree of process integration. The composite coagulation bath and core liquid achieve internal and external gradient modification, and the combination of heat treatment achieves multi-level pore formation, which can simultaneously realize the internal and external gradient chemical modification of the membrane and the construction of multi-level physical channels. The external coagulation bath contains soybean phosphatidylcholine, water-soluble carbonate or bicarbonate and glycerol, and the core liquid contains natural phenolic compounds, so that the inner surface of the membrane is modified with natural phenolic compounds, and the outer surface and channels are modified with soybean phosphatidylcholine to form a gradient antifouling structure; at the same time, micron-level channels are formed through liquid-phase induced phase separation, and the thermal pore-inducing agent decomposes in the phase separation channels to generate nano-level bubble pores, thus constructing a micron-nano multi-level pore system.

[0019] The ultrafiltration membrane of this invention possesses a targeted antifouling mechanism: Targeting the application characteristics of internal pressure membranes, the inner surface is specifically reinforced using a core liquid modifier, a natural phenolic compound (e.g., tannic acid). This natural phenolic compound exhibits antifouling properties and contains hydrophilic phenolic hydroxyl groups, which reduce the adsorption of SMPs such as proteins and polysaccharides, thus constructing a tight first barrier against SMP adsorption. The outer surface and pores are provided with a durable zwitterionic hydration layer by soybean phosphatidylcholine (SPC), with hydrophilic groups facing the aqueous phase, further reducing the adsorption of SMPs such as proteins and polysaccharides and improving antifouling performance. Furthermore, SPC promotes the formation of larger finger-like pores, increasing membrane flux. This gradient design of internal and external chemical components and functions achieves a synergistic defense system against SMP contaminants, from "source interception" to "end-stage protection," maximizing the free fouling resistance (FRR).

[0020] The ultrafiltration membrane of this invention overcomes the performance trade-off: by organically combining "chemical phase separation pore formation" and "physical thermal foaming," a multi-level pore system with interconnected micron and nano-scale pores is created. The micron-scale pores ensure water flow rate under ultra-low resistance, while the nano-scale pores provide a huge specific surface area and fine sieving capability, thus synergistically achieving a balance between high throughput and high retention rate.

[0021] The ultrafiltration membrane of this invention has long-term stability: soybean phosphatidylcholine (SPC) is permanently bound to the PES network during phase separation through anchoring and natural phenolic compounds are bound through complexation / crosslinking, which fundamentally solves the problem of easy loss of traditional blending modifiers and ensures long-term stability of membrane performance.

[0022] The ultrafiltration membrane of this invention enables dry storage and immediate use: glycerol acts as a preservative, effectively supporting the complex three-dimensional hierarchical pore structure during the terminal drying process and preventing its collapse. This allows the membrane product to be stored and transported in a dry state, providing users with "ready-to-use" functionality and significantly reducing the overall cost of the industry chain.

[0023] The ultrafiltration membrane of this invention features a highly efficient and environmentally friendly process: the entire modification and asymmetric structure formation process is integrated into a standard internal pressure spinning process, eliminating the need for complex post-processing. The soybean phosphatidylcholine and natural phenolic compounds used are both bio-based materials, making them environmentally friendly and in line with green manufacturing trends. Attached Figure Description

[0024] Figure 1 These are scanning electron microscope (SEM) images of the inner surface of the internal pressure polyethersulfone hollow fiber ultrafiltration membranes after filtering the contaminated liquid simulating SMP in Examples 1, 2, 1, and 2. Detailed Implementation

[0025] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0026] An embodiment of the present invention provides an internal pressure polyethersulfone hollow fiber ultrafiltration membrane, wherein the internal pressure polyethersulfone hollow fiber ultrafiltration membrane has multi-level pores; the inner surface of the internal pressure polyethersulfone hollow fiber ultrafiltration membrane is modified with natural phenolic compounds, and the outer surface and pore walls are modified with soybean phosphatidylcholine.

[0027] The internal pressure polyethersulfone hollow fiber ultrafiltration membrane of this invention has an asymmetric hydrophilic gradient antifouling structure and a hierarchical pore structure. The membrane wall has an asymmetric gradient-modified antifouling structure, with the inner surface mainly modified by natural phenolic compounds and the outer surface and pore walls mainly modified by soybean phosphatidylcholine. Through its unique gradient modification and hierarchical pore design, the ultrafiltration membrane of this invention exhibits extremely high resistance to soluble microbial product (SMP) contamination under internal pressure operation mode, while also possessing ultra-high water flux. The ultrafiltration membrane of this invention also possesses ultra-high water flux (≥300 L / (m³)). 2 With its high efficiency (·h·bar) and excellent anti-pollution performance (flux recovery rate ≥96%), it is particularly suitable for high-risk pollution scenarios such as deep treatment of reclaimed water.

[0028] In some embodiments, the membrane wall of the internal pressure polyethersulfone hollow fiber ultrafiltration membrane has an asymmetric hydrophilic gradient structure. Specifically, the membrane wall of the internal pressure polyethersulfone hollow fiber ultrafiltration membrane has an asymmetric hydrophilic gradient antifouling structure; the inner surface is modified with natural phenolic compounds, and the outer surface and pore walls are modified with soybean phosphatidylcholine.

[0029] In some embodiments, the inner surface of the internal pressure polyethersulfone hollow fiber ultrafiltration membrane is modified with natural phenolic compounds, and the outer surface and pore walls are modified with soybean phosphatidylcholine. Optionally, natural phenolic compounds modify the inner surface through complexation and / or cross-linking; soybean phosphatidylcholine (SPC) modifies the outer surface and pore walls through anchoring.

[0030] In some embodiments, the internally pressurized polyethersulfone hollow fiber ultrafiltration membrane has a multi-level pore structure; optionally, it has a micron-nano level pore structure. Optionally, the internal pressure polyethersulfone hollow fiber ultrafiltration membrane (with pore structure) includes nanoscale pores and microscale pores; the pore size of the nanoscale pores is less than or equal to 100 nm; the pore size of the microscale pores is greater than or equal to 0.1 μm; optionally, the microscale pores and nanoscale pores are interconnected in a multi-level channel. Optionally, micron-sized pores are formed by liquid-induced phase separation; nano-sized pores are generated by the decomposition of a thermally induced pore agent; nano-sized pores are generated (have) within micron-sized channels; the micron-sized pores include finger-like pores and / or sponge pores, and the nano-sized pores include bubble pores.

[0031] In some embodiments, the inner diameter (diameter) of the internally pressurized polyethersulfone hollow fiber ultrafiltration membrane is 0.8-1.5 mm, specifically, for example, 0.8 mm, 1.0 mm, 1.2 mm, or 1.5 mm; the outer diameter (diameter) is 1.4-2 mm, specifically, for example, 1.4 mm, 1.5 mm, 1.8 mm, or 2.0 mm; and the thickness is 0.4-0.8 mm, specifically, for example, 0.4 mm, 0.6 mm, or 0.8 mm.

[0032] In some embodiments, the pure water contact angle of the inner surface of the internally pressurized polyethersulfone hollow fiber ultrafiltration membrane is less than 50°; and / or, the pure water flux of the internally pressurized polyethersulfone hollow fiber ultrafiltration membrane at an operating pressure of 0.1 MPa is not less than 300 L / (m²). 2 • h·bar); and / or, the flux recovery rate of the internally pressurized polyethersulfone hollow fiber ultrafiltration membrane is not less than 96%. In this embodiment of the invention, the ultrafiltration membrane also has ultra-high water flux (≥300 L / (m 2 With its high efficiency (·h·bar) and excellent anti-pollution performance (flux recovery rate ≥96%), it is particularly suitable for high-risk pollution scenarios such as deep treatment of reclaimed water.

[0033] A method for preparing an internally pressurized polyethersulfone hollow fiber ultrafiltration membrane according to an embodiment of the present invention includes the following steps: (1) The casting solution and the core solution are extruded through a hollow fiber spinneret to obtain nascent fibers; wherein the casting solution includes polyethersulfone, polymer porogen, thermoporogen and organic solvent; the core solution includes natural phenolic compounds and water; (2) The extruded nascent fibers enter an external coagulation bath for liquid-phase induced phase separation; the external coagulation bath includes soybean phosphatidylcholine, inorganic salts, glycerol and water; the inorganic salts include at least one of water-soluble carbonates or water-soluble bicarbonates; (3) Then heat treatment is performed to obtain an internal pressure polyethersulfone hollow fiber ultrafiltration membrane.

[0034] The method for preparing the internally pressurized polyethersulfone hollow fiber ultrafiltration membrane of this invention features high process integration. The composite coagulation bath and core liquid achieve gradient modification of the membrane's internal and external surfaces, and combined with heat treatment, achieve multi-level pore formation. This allows for simultaneous internal and external gradient chemical modification of the membrane and the construction of multi-level physical pores. The external coagulation bath contains soybean phosphatidylcholine, inorganic salts, and glycerol, while the core liquid contains natural phenolic compounds. This modifies the inner surface of the membrane with natural phenolic compounds, while the outer surface and pores are modified with soybean phosphatidylcholine, forming a gradient antifouling structure. Simultaneously, liquid-phase induced phase separation forms micron-sized pores, and the thermally induced pore-forming agent decomposes within the phase-separated pores to generate nano-sized gas bubbles, constructing a micron-nano multi-level pore system.

[0035] In some embodiments, in step (1), the casting solution includes polyethersulfone, a polymeric porogen, a thermal porogen, and an organic solvent; Optionally, the polymeric porogen includes polyvinylpyrrolidone; the thermal porogen includes at least one of ammonium carbonate or ammonium bicarbonate; the organic solvent includes N-methylpyrrolidone; the present invention does not impose any particular limitation on the molecular weight of polyethersulfone or the polymeric porogen; the present invention does not impose any particular limitation on the particle size of the raw material thermal porogen, for example, it can be 1-100 micrometers; Optionally, the polyethersulfone in the casting solution has a mass percentage concentration of 15-22 wt%, specifically, for example, 15 wt%, 17 wt%, 20 wt%, 21 wt%, or 22 wt%. The polymeric porogen has a mass percentage concentration of 5-10 wt%, specifically, for example, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, or 10 wt%. The mass percentage concentration of the thermoporous agent is 1-5 wt%, specifically, for example, 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%. The organic solvent has a mass percentage concentration of 70-80 wt%, specifically, for example, 70 wt%, 72 wt%, 75 wt%, 78 wt%, or 80 wt%. Optionally, the preparation of the casting solution includes: mixing polyethersulfone, polymeric porogen, thermoporogen and organic solvent, stirring to dissolve, and then performing degassing treatment to obtain the casting solution; optionally, stirring to dissolve at 60-85°C, specifically, for example, 60°C, 70°C, 80°C, 85°C; optionally, grinding the polyethersulfone and the raw material thermoporogen before mixing; Optionally, the temperature of the casting solution is 60-85°C, specifically, for example, 60°C, 70°C, 80°C, or 85°C.

[0036] In this embodiment of the invention, the internally pressurized polyethersulfone hollow fiber ultrafiltration membrane has a multi-level pore structure, including nanoscale pores and microscale pores. The pore structure of the ultrafiltration membrane includes microscale channels formed by liquid-induced phase separation and nanoscale bubble pores generated by the decomposition of thermally induced pore-forming agents. By optimizing the composition of the casting solution, it is beneficial to further improve the multi-level pore structure of the ultrafiltration membrane, and further improve the membrane flux and antifouling performance.

[0037] In some embodiments, in step (1), the core fluid comprises natural phenolic compounds and water; Optionally, the natural phenolic compound includes at least one of tannic acid, gallic acid, or dopamine; the water includes deionized water. Optionally, the concentration of the natural phenolic compound in the core fluid is 0.5-3.0 g / L, specifically, for example, 0.5 g / L, 1.0 g / L, 1.5 g / L, 2.0 g / L, 2.5 g / L, or 3.0 g / L; Optionally, the temperature of the core fluid is room temperature, for example, 20-30°C, specifically, for example, 20°C, 25°C, or 30°C.

[0038] In this embodiment of the invention, the inner surface is specifically reinforced using natural phenolic compounds, thus constructing a tight first barrier against SMP adsorption. By optimizing the types and concentrations of the natural phenolic compounds, the antifouling performance of the membrane can be further improved.

[0039] In some embodiments, in step (1), the casting solution and the core solution are extruded through a hollow fiber spinning head to obtain nascent fibers; the extrusion is co-extrusion. Optionally, the casting solution and core solution are subjected to internal pressure spinning; an internal pressure hollow fiber spinning device is used. Optionally, the internal pressure spinning of the casting solution and the core solution includes: extruding the casting solution through a hollow fiber spinning head, while injecting the core solution into the fiber cavity, and then entering an external coagulation bath for phase separation and molding; Optionally, the hollow fiber spinning head includes a central tube and an outer tube, with an annular gap formed between the central tube and the outer tube; optionally, the inner and outer diameters of the hollow fiber spinning head are 0.9 mm and 1.3 mm, respectively. Optionally, the internal pressure spinning of the casting solution and the core solution includes: extruding the casting solution through the annular gap of the hollow fiber spinning head, while simultaneously injecting the core solution into the fiber cavity through the central tube of the hollow fiber spinning head, and the extruded nascent fiber entering the external coagulation bath for liquid-phase induced phase separation.

[0040] In this embodiment of the invention, the forming of the membrane structure and the gradient chemical modification of the inner and outer surfaces are completed simultaneously during the extrusion and phase separation processes.

[0041] In some embodiments, in step (1), the flow rate ratio of the casting liquid to the core liquid is approximately 1-2:1, specifically, for example, 1:1, 1.2:1, 1.4:1, 1.5:1, 2:1.

[0042] In some embodiments, in step (1), the flow rate of the casting liquid is 1-3 m / s, specifically, for example, 1 m / s, 2 m / s, 3 m / s; the flow rate of the core liquid is 1-3 m / s, specifically, for example, 1 m / s, 2 m / s, 3 m / s.

[0043] In some embodiments, in step (2), the extruded nascent fibers enter an external coagulation bath for liquid-phase induced phase separation; the external coagulation bath includes soybean phosphatidylcholine, inorganic salts, glycerol and water; the inorganic salts include at least one of water-soluble carbonates or water-soluble bicarbonates; Optionally, the water-soluble carbonate includes at least one of sodium carbonate and potassium carbonate; the water-soluble bicarbonate includes at least one of sodium bicarbonate and potassium bicarbonate. Optionally, in the external coagulation bath, the concentration of soybean phosphatidylcholine is 0.5~5.0 g / L, specifically, for example, 0.5 g / L, 1.0 g / L, 2.0 g / L, 3.0 g / L, 4.0 g / L, 5.0 g / L; preferably, the concentration of soybean phosphatidylcholine is 1.0~3.0 g / L. Optionally, in the external coagulation bath, the concentration of the inorganic salt is 1.0~10.0 g / L, specifically, for example, 1.0 g / L, 2.0 g / L, 5.0 g / L, 8.0 g / L, 10.0 g / L, preferably, the concentration of the inorganic salt is 2.0~5.0 g / L; Optionally, in the external coagulation bath, the concentration of glycerol is 10~100g / L, specifically, for example, 10g / L, 20g / L, 30g / L, 50g / L, 60g / L, 80g / L, 100g / L, preferably, the concentration of glycerol is 30~60g / L; Optionally, the water includes deionized water; Optionally, the temperature of the external coagulation bath is 20-30°C, specifically, for example, 20°C, 25°C, or 30°C; the liquid-phase induced phase separation time is 24-48 h, specifically, for example, 24 h, 36 h, or 48 h. Optionally, the air gap is 0-15cm, specifically, for example, 0cm, 0.1cm, 1cm, 5cm, 10cm, 12cm, 15cm.

[0044] In this embodiment of the invention, a composite coagulation bath and core liquid are used to achieve internal and external gradient modification, and combined with heat treatment to achieve multi-level pore formation. The external coagulation bath contains soybean phosphatidylcholine, water-soluble carbonate or bicarbonate, and glycerol. Micron-sized channels are formed through liquid-phase induced phase separation, modifying the outer surface of the membrane and the channels with soybean phosphatidylcholine, forming an internal and external gradient antifouling structure. Specifically, during the liquid-phase induced phase separation process in the external coagulation bath, the polymeric pore-forming agent is displaced to form micron-sized channels. Soybean phosphatidylcholine and water-soluble carbonate / bicarbonate simultaneously enter the pores. Soybean phosphatidylcholine modifies the outer surface and channel walls, while water-soluble carbonate / bicarbonate adheres to the channel surface. Some salts decompose during the external coagulation process, further increasing membrane flux. The remaining salts decompose during heat treatment, further increasing membrane flux. This invention, by adjusting the content of soybean phosphatidylcholine, water-soluble carbonate, or water-soluble bicarbonate in the external coagulation bath, is beneficial for further improving membrane performance.

[0045] In some embodiments, the fibers are removed from the external coagulation bath and dried before heat treatment.

[0046] In some embodiments, in step (3), the temperature of the heat treatment is 50-80°C, specifically, for example, 50°C, 60°C, 70°C, 80°C; the time of the heat treatment is 5-30 min, specifically, for example, 5 min, 10 min, 20 min, 30 min; optionally, the heat treatment is performed using a circulating hot air oven.

[0047] In this embodiment of the invention, a composite coagulation bath and core liquid are used to achieve internal and external gradient modification, and heat treatment is combined to achieve multi-level pore formation. The nascent fibers are heat-treated to cause the thermal pore-inducing agent to decompose and generate gas, thereby generating nanoscale bubble channels in situ on the basis of the already formed phase-separated pore structure.

[0048] In some embodiments, in step (3), after heat treatment, post-treatment is performed, which includes water washing, glycerol solution soaking and drying, i.e., water washing, glycerol solution soaking and drying are performed sequentially; optionally, water washing includes washing the heat-treated fibers in a flowing clean water tank for 30 minutes; optionally, the glycerol solution is an aqueous glycerol solution with a concentration of 30-50 g / L, optionally 40 g / L, and the soaking time is 20-30 minutes, optionally 20 minutes; drying is carried out in a tunnel drying oven at a temperature of 40-60°C, optionally 50°C; and the finished dry film is obtained by winding.

[0049] In this embodiment of the invention, the heat-treated fibers are sequentially washed with water, soaked in glycerin protective solution, and dried, which helps to further improve the performance of the membrane.

[0050] An application of an internal pressure polyethersulfone hollow fiber ultrafiltration membrane according to an embodiment of the present invention is used to treat wastewater containing dissolved microbial products; and / or, for reclaimed water treatment.

[0051] In some embodiments, after the ultrafiltration membrane is used to filter a mixture of bovine serum albumin and sodium alginate to simulate SMP contamination solution, the flux recovery rate is not less than 96%.

[0052] The present invention will now be described with reference to specific embodiments. It should be noted that these embodiments are merely descriptive and do not limit the present invention in any way.

[0053] Example 1 A method for preparing an internally pressurized polyethersulfone hollow fiber ultrafiltration membrane includes the following steps: 1) Preparation of casting solution: Weigh polyethersulfone (PES, 19%), solvent N-methylpyrrolidone (NMP, 70%), polymer porogen polyvinylpyrrolidone (PVPK30, 8%), and thermoporogen ammonium carbonate (3%) by weight percentage, place them in a stirred tank, and mechanically stir at 80°C for 12 hours until completely dissolved and transparent. Then let it stand for 24 hours to remove bubbles to obtain the casting solution.

[0054] 2) Preparation of external coagulation bath: Add 2.0 g / L soybean phosphatidylcholine (dispersed and dissolved with ultrasonic assistance), 3.0 g / L sodium carbonate, and 50 g / L glycerol to deionized water, stir evenly, and control the temperature at (30±1)℃ to obtain the external coagulation bath.

[0055] 3) Core solution preparation: The core solution is a deionized aqueous solution containing 1.5 g / L tannic acid.

[0056] 4) Internal Pressure Spinning and Gradient Modification: An internal pressure hollow fiber spinning device is used. The deaerated casting solution is pumped to the annular extrusion of the spinneret (inner and outer diameter: 0.9mm / 1.3mm) via a metering pump; simultaneously, the core solution is injected through the central tube of the spinneret via a precision metering pump. The flow rate ratio of the casting solution to the core solution is controlled to be approximately 1.5:1, and the air gap is set to 5cm. The nascent fibers are placed in the aforementioned 25℃ external coagulation bath for 24 hours to complete phase separation and gradient modification.

[0057] 5) Heat treatment: Guide the formed nascent fibers through a 70℃ circulating hot air oven for 15 minutes.

[0058] 6) Post-treatment: The heat-treated fibers are first washed in a flowing clean water tank for 30 minutes, then immersed in a 40g / L glycerol aqueous solution for 20 minutes, and finally dried in a tunnel drying oven at 50℃. The finished dry membrane, i.e., internal pressure polyethersulfone hollow fiber ultrafiltration membrane, is obtained by winding.

[0059] Example 2 The preparation method is the same as that in Example 1, except that in step 2), the sodium carbonate (3.0 g / L) in the external coagulation bath is replaced with potassium bicarbonate (4.0 g / L).

[0060] Comparative Example 1 The preparation method is the same as that in Example 1, except that ammonium carbonate is not added to the casting solution in step 1); and step 5) is omitted, that is, no heat treatment step is performed after spinning.

[0061] Comparative Example 2 The preparation method is the same as in Example 1, except that in step 2), the external coagulation bath is pure water, that is, no soybean phosphatidylcholine, sodium carbonate and glycerol are added; in step 3), the core liquid is pure water, that is, no tannic acid is added.

[0062] Performance testing The performance of the internal pressure polyethersulfone hollow fiber ultrafiltration membranes prepared in the above embodiments and comparative examples was tested: (1) Pure water flux: Under a transmembrane pressure of 0.1 MPa, the pure water permeation flux of the membrane was tested [L / (m 2 ·h·bar)).

[0063] (2) Retention rate: Prepare a 500 mg / L Congo red aqueous solution as the feed liquid and test it at 0.1 MPa. Calculate the retention rate by measuring the absorbance of the feed liquid and the permeate liquid using an ultraviolet spectrophotometer.

[0064] (3) Resistance to SMP contamination: A filtration-washing cycle experiment was conducted using a simulated SMP contamination solution (1 g / L bovine serum albumin + 0.5 g / L sodium alginate dissolved in PBS buffer).

[0065] Flux recovery rate (FRR%) = (pure water flux after cleaning / initial pure water flux) × 100%.

[0066] Irreversible contamination rate (Rir%) = [(initial flux - recovered flux) / initial flux] × 100%.

[0067] Table 1

[0068] Figure 1 These are scanning electron microscope (SEM) images of the inner surface of the internal pressure polyethersulfone hollow fiber ultrafiltration membranes after filtering the contaminated liquid simulating SMP in Examples 1, 2, 1, and 2. A small number of white particles were observed, representing adsorbed contaminants. It can be seen that the surface of the internal pressure polyethersulfone hollow fiber ultrafiltration membrane of the present invention is smoother, with fewer adsorbed contaminants, and has better antifouling performance.

[0069] As shown in Table 1, the internal pressure polyethersulfone hollow fiber ultrafiltration membranes prepared in Examples 1 and 2 of this invention are far superior to Comparative Examples 1 and 2 in terms of pure water flux, rejection rate, and SMP fouling resistance. This fully demonstrates the effectiveness and synergy of the gradient modified structure and multi-level pore structure in the internal pressure polyethersulfone hollow fiber ultrafiltration membrane of this invention. It has extremely high resistance to SMP fouling under internal pressure operation mode and has a high flux, providing an excellent solution to the membrane fouling problem in reclaimed water treatment.

[0070] The performance of Example 1 and Example 2 is comparable, indicating that water-soluble carbonates or bicarbonates have similar effects as pH adjusters and structure optimizers in the internal pressure polyethersulfone hollow fiber ultrafiltration membrane system of the present invention, and both can have both ultra-high water flux and excellent antifouling performance.

[0071] Due to the lack of a thermoporizing agent and a thermoporizing step, Comparative Example 1 failed to form nanoscale pores. The flux, rejection rate, and SMP fouling resistance of the membrane in Comparative Example 1 were significantly lower than those in Example 1, demonstrating that the multi-level pore system of the present invention plays a key role in improving the overall performance of the membrane.

[0072] The membrane in Comparative Example 2, without gradient modification, exhibited significantly inferior performance across all indicators, particularly poor antifouling ability. The pure water flux and rejection rate of the membrane in Comparative Example 2 were also significantly reduced. This is because the natural phenolic compounds in Example 1 and soybean phosphatidylcholine form an asymmetric hydrophilic gradient, which can increase flux. Furthermore, soybean phosphatidylcholine and sodium carbonate are beneficial for further improving the hierarchical pore structure of the membrane, further increasing flux. Glycerol, as a protective agent, effectively supports the complex three-dimensional hierarchical pore structure during the terminal drying process, preventing its collapse.

[0073] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0074] Although the above embodiments have been shown and described, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Any changes, modifications, substitutions and variations made to the above embodiments by those skilled in the art are within the protection scope of the present invention.

Claims

1. An internally pressurized polyethersulfone hollow fiber ultrafiltration membrane, characterized in that, The internal pressure polyethersulfone hollow fiber ultrafiltration membrane has multi-level pores; the inner surface of the internal pressure polyethersulfone hollow fiber ultrafiltration membrane is modified with natural phenolic compounds, and the outer surface and pore walls are modified with soybean phosphatidylcholine. The method for preparing the internal pressure polyethersulfone hollow fiber ultrafiltration membrane includes the following steps: (1) The casting solution and the core solution are extruded through a hollow fiber spinneret to obtain nascent fibers; wherein the casting solution includes polyethersulfone, polymer porogen, thermoporogen and organic solvent; the core solution includes natural phenolic compounds and water; (2) The extruded nascent fibers enter an external coagulation bath for liquid-phase induced phase separation; the external coagulation bath includes soybean phosphatidylcholine, inorganic salts, glycerol and water; the inorganic salts include at least one of water-soluble carbonates or water-soluble bicarbonates; (3) Then heat treatment is performed to obtain an internal pressure polyethersulfone hollow fiber ultrafiltration membrane.

2. The internal pressure polyethersulfone hollow fiber ultrafiltration membrane according to claim 1, characterized in that, The internally pressurized polyethersulfone hollow fiber ultrafiltration membrane includes nanoscale pores and microscale pores. And / or, the pure water contact angle on the inner surface of the internal pressure polyethersulfone hollow fiber ultrafiltration membrane is less than 50°; And / or, the internal pressure polyethersulfone hollow fiber ultrafiltration membrane has a pure water flux of not less than 300 L / (m³) at 0.1 MPa. 2 ·h·bar).

3. A method for preparing an internally pressurized polyethersulfone hollow fiber ultrafiltration membrane as described in claim 1 or 2, characterized in that, Includes the following steps: (1) The casting solution and the core solution are extruded through a hollow fiber spinneret to obtain nascent fibers; wherein the casting solution includes polyethersulfone, polymer porogen, thermoporogen and organic solvent; the core solution includes natural phenolic compounds and water; (2) The extruded nascent fibers enter an external coagulation bath for liquid-phase induced phase separation; the external coagulation bath includes soybean phosphatidylcholine, inorganic salts, glycerol and water; the inorganic salts include at least one of water-soluble carbonates or water-soluble bicarbonates; (3) Then heat treatment is performed to obtain an internal pressure polyethersulfone hollow fiber ultrafiltration membrane.

4. The method for preparing the internal pressure polyethersulfone hollow fiber ultrafiltration membrane according to claim 3, characterized in that, In step (1), the polyethersulfone in the casting solution has a mass percentage concentration of 15-22 wt%. And / or, in the casting solution, the mass percentage concentration of the polymeric pore-forming agent is 5-10 wt%; And / or, in the casting solution, the mass percentage concentration of the thermoporizing agent is 1-5 wt%.

5. The method for preparing the internal pressure polyethersulfone hollow fiber ultrafiltration membrane according to claim 3, characterized in that, In step (1), the polymer porogen includes polyvinylpyrrolidone; And / or, the thermoporous agent includes at least one of ammonium carbonate or ammonium bicarbonate; And / or, the preparation of the casting solution includes: mixing polyethersulfone, polymeric porogen, thermoporogen and organic solvent, stirring to dissolve, and then performing degassing treatment to obtain the casting solution.

6. The method for preparing the internal pressure polyethersulfone hollow fiber ultrafiltration membrane according to claim 3, characterized in that, In step (1), the natural phenolic compound includes at least one of tannic acid, gallic acid, or dopamine; And / or, the concentration of the natural phenolic compound in the core fluid is 0.5-3.0 g / L.

7. The method for preparing the internal pressure polyethersulfone hollow fiber ultrafiltration membrane according to claim 3, characterized in that, In step (2), the water-soluble carbonate includes at least one of sodium carbonate and potassium carbonate; And / or, the water-soluble bicarbonate includes at least one of sodium bicarbonate and potassium bicarbonate; And / or, in the external coagulation bath, the concentration of soybean phosphatidylcholine is 0.5~5.0 g / L; And / or, in the external coagulation bath, the concentration of the inorganic salt is 1.0~10.0 g / L; And / or, in the external coagulation bath, the concentration of glycerol is 10~100g / L.

8. The method for preparing the internal pressure polyethersulfone hollow fiber ultrafiltration membrane according to claim 3, characterized in that, In step (2), the temperature of the external coagulation bath is 20-30℃; And / or, the liquid-induced phase separation time is 24-48 h.

9. The method for preparing the internal pressure polyethersulfone hollow fiber ultrafiltration membrane according to claim 3, characterized in that, In step (3), the temperature of the heat treatment is 50-80 ℃; And / or, the heat treatment time is 5-30 min; And / or, post-treatment is performed after heat treatment, the post-treatment including washing with water, soaking in glycerol solution and drying.

10. The application of the internal pressure polyethersulfone hollow fiber ultrafiltration membrane according to claim 1 or 2, or the internal pressure polyethersulfone hollow fiber ultrafiltration membrane prepared by any one of claims 3-9, characterized in that, Used to treat wastewater containing dissolved microbial products.

Images