Multi-dimensional structure glass fiber oil-water separation filter membrane with controllable pore diameter

Abstract

The invention provides an aperture-controllable multidimensional structure glass fiber oil-water separation filter membrane, and relates to the technical field of filter membrane preparation, the filter membrane has asymmetric aperture gradient distribution in the thickness direction, and is composed of a coarse pore support layer, a gradient transition layer and a micro-nano separation layer, and the preparation method comprises the steps of differential pulping and multi-runner step-by-step drifting forming. An inorganic nano rough structure body grows on the surface of fine fibers of the micro-nano separation layer through an in-situ sol-gel mineralization technology, a micron-nano two-stage composite rough structure is constructed, hydrophilic finishing is combined, the underwater super-oleophobic characteristic is achieved, the filter membrane is endowed with excellent self-cleaning capacity and oil stain resistance, meanwhile, a wet strength agent and a cross-linking agent are introduced into the filter membrane, and the filter membrane has the good self-cleaning capacity and oil stain resistance. The pore diameter gradient structure is locked through gradient thermocuring, the wet tensile strength and the pressure-resistant stability of the filter membrane are greatly improved, the problems that the flux and the precision of a traditional filter membrane are difficult to consider, the structural stability is poor, and the filter membrane is prone to being blocked by oil stains are effectively solved, and dual optimization of the filter efficiency and the economic benefits is achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of filter membrane preparation, in particular to a glass fiber oil-water separation filter membrane with controllable pore size and multi-dimensional structure. BACKGROUND

[0002] If the oil-containing wastewater generated in industrial production and daily life is directly discharged without treatment, it will cause serious pollution to the environment. According to the particle size and dispersion state of oil droplets, oil-containing wastewater is usually divided into three categories: floating oil, dispersed oil and emulsified oil. Among them, emulsified oil is the most difficult to treat due to its high thermodynamic stability. At present, the methods for removing emulsified oil in water mainly include traditional physical methods (such as gravity sedimentation and air flotation), chemical methods (such as flocculant demulsification and adsorption method) and membrane separation technology. Membrane separation technology has become a research hotspot in the field of oil-water separation due to its high separation efficiency, small occupation area and simple operation.

[0003] Glass fiber filter membrane, as an important membrane separation material, is widely used in water treatment, air purification and solid-liquid separation due to its advantages such as acid and alkali resistance, high temperature resistance, high mechanical strength and relatively low cost. The existing glass fiber filter membrane is usually prepared by wet papermaking process, which forms a porous structure by random interweaving of fibers. In the prior art, the industrialized preparation of glass fiber filter membrane usually adopts mature wet forming process, i.e. wet papermaking technology. This process includes highly dispersing glass fibers in water, adjusting fiber morphology by beating, and then forming by screen, dewatering, drying and finally solidification. This preparation method can realize mass production and continuous production, and the prepared filter membrane has a three-dimensional random interwoven porous network structure, which is widely used in air filtration, liquid precision filtration and battery separator, etc.

[0004] The above patent documents and prior art have the following technical problems in use:

[0005] Problem one, the pore size distribution of the traditional wet-prepared glass fiber filter membrane is relatively uniform, and the porosity is fixed. In order to effectively intercept micron or sub-micron emulsified oil droplets, the average pore size of the filter membrane must be designed very small, which directly leads to a sharp increase in filtration resistance and a very low effective flux, seriously limiting the industrial application efficiency and economic benefit.

[0006] Problem two, the fiber filter membrane prepared by traditional wet method mainly relies on the physical entanglement between fibers, and the structure is loose. Under high pressure operation conditions for oil-water separation, the fiber network is easy to deform, the pore size increases or the interlayer peels off, resulting in unstable separation precision, even "filtering" phenomenon, which cannot meet the requirements of long-term stable operation in industry.

[0007] Question 3: Ordinary glass fiber lacks functional modification on its surface. While it has a certain degree of hydrophilicity, it is not "superhydrophilic." When processing high-concentration or high-viscosity oil-water emulsions, oil droplets easily adhere to and adsorb onto the fiber surface and pore walls, forming a dense oil layer. This leads to rapid clogging of the filter membrane pores, a rapid decline in separation performance (especially flux), difficulty in regeneration, and a short service life. Summary of the Invention

[0008] Technical problems to be solved

[0009] To address the shortcomings of existing technologies, this invention provides a multi-dimensional glass fiber oil-water separation filter membrane with controllable pore size, thus solving the technical problems existing in the prior art.

[0010] Technical solution

[0011] To achieve the above objectives, the present invention provides the following technical solution: a multi-dimensional glass fiber oil-water separation filter membrane with controllable pore size. The filter membrane has an asymmetric pore size gradient distribution in the thickness direction and includes, from bottom to top, a coarse-pore support layer, a gradient transition layer, and a micro-nano separation layer. The coarse-pore support layer is composed of unpulped coarse glass fibers with an aspect ratio greater than 500 interwoven to form micron-sized macropore channels. The micro-nano separation layer is composed of fine glass fibers that have undergone high-intensity pulping to produce microfibrils. Inorganic nano-rough structures are grown in situ on the surface of the fine glass fibers. The gradient transition layer is located between the coarse-pore support layer and the micro-nano separation layer and is formed by mixing and interweaving coarse and fine glass fibers in a gradually varying concentration manner.

[0012] Preferably, the inorganic nano-rough structure is a silica nanoprotrusion or a titanium dioxide nanocluster, which is anchored to the glass fiber surface by chemical bonds formed by a silane coupling agent, forming a micron-fiber-nanoparticle secondary composite rough structure. The average pore size of the filter membrane ranges from 0.2 micrometers to 50 micrometers and decreases continuously along the thickness direction.

[0013] Preferably, the fine glass fibers in the micro-nano separation layer are in a filament-broom state due to the pulping process, and the fiber surface has peeled nanofibers, which form a three-dimensional network interception structure with the main fiber skeleton.

[0014] Preferably, the filter membrane also incorporates a wet strength agent and a crosslinking agent. The wet strength agent is a polyamide epichlorohydrin resin, and the crosslinking agent forms a resin bridge at the fiber contact point, locking the pore size gradient distribution structure.

[0015] Preferably, the preparation method includes the following steps:

[0016] Sp1: Raw material pretreatment: Two glass fiber raw materials with different average diameters are selected and immersed in an acidic solution for activation treatment to remove surface impurities and introduce hydrophilic hydroxyl groups. Then, they are washed with water until neutral to obtain pretreated coarse fibers and pretreated fine fibers.

[0017] Sp2: Differential de-dissociation pulping: The pretreated coarse fibers are decomposed at low speed in the dispersion medium to maintain the integrity of the fiber morphology and prepare coarse fiber pulp. The pretreated fine fibers are subjected to high-concentration refining in the dispersion medium and the beating degree is controlled to 45SR-85SR to make the fibers split and micronized, and prepare fine fiber pulp with high beating degree.

[0018] Sp3: In-situ modification within the slurry: a surfactant and nano-precursor solution are added to the high freeness fine fiber slurry obtained from Sp2, the pH value is adjusted to an acidic or alkaline catalytic environment, and the precursor is induced to hydrolyze under stirring conditions to grow nanoparticles in situ on the surface of fine fibers and microfibers to obtain functionalized micro-nano slurry.

[0019] Sp4: Gradient slurry preparation: Prepare multiple portions of mixed slurry and prepare pure coarse fiber slurry, mixed transition slurry and pure functionalized micro-nano slurry according to the volume ratio of coarse fiber slurry to functionalized micro-nano slurry. The ratio of the two in the mixed transition slurry changes in a gradient.

[0020] Sp5: Step-by-step flow forming: On an inclined or long mesh forming machine, a multi-channel headbox is used to sequentially flow pure coarse fiber slurry, mixed transition slurry and pure functionalized micro-nano slurry to the forming mesh section according to the difference in slurry density. Gravity dehydration is used to allow the fibers of each layer to settle naturally in a wet state and interpenetrate with each other to form a wet film preform with a pore size gradient.

[0021] Sp6: Wet pressing and setting: The wet membrane preform is dehydrated by multi-stage roller pressing. The fiber layers are tightly bonded by controlling the linear pressure, and the thickness and porosity of the filter membrane are initially controlled.

[0022] Sp7: Step-by-step thermosetting: The wet-pressed filter membrane is sent to the drying section. First, free water is removed in the low-temperature zone, and then cross-linking and curing are carried out in the high-temperature zone. This allows the nanoparticles generated in situ to form a strong chemical bond with the fiber surface, while the wet strength agent is cured and locked to lock the three-dimensional pore structure.

[0023] Sp8: Surface activation finishing: The cured filter membrane is further reduced by plasma treatment or spraying with a hydrophilic finishing agent, and then cut to obtain the finished product.

[0024] Preferably, in Sp2, the high-consistency pulping treatment uses a disc mill or a PFI mill, and the increase rate of the specific surface area of ​​the fine fibers is controlled to be above 200% by adjusting the spacing and rotation speed of the mill discs.

[0025] Preferably, in the Sp3, the nano-precursor solution is a tetraethyl orthosilicate ethanol solution, and the in-situ growth of nanoparticles is carried out at 40-60 degrees Celsius for 1-3 hours.

[0026] Preferably, in Sp5, the multi-channel headbox precisely controls the thickness of the gradient transition layer by adjusting the flow rate ratio and concentration ratio of the coarse fiber component slurry and the functionalized micro / nano fiber slurry. The pore size gradient change is manifested as the average pore size continuously decreasing from 50 micrometers to 100 micrometers on the side of the coarse pore support layer to 0.5 micrometers to 5 micrometers on the side of the micro / nano separation layer along the thickness direction of the filter membrane.

[0027] Preferably, in Sp5, the purely functionalized micro-nano slurry is located on the top layer, and the ratio of the flow rate to the grid speed is controlled between 0.9 and 1.1 to avoid slurry disturbance from damaging the gradient structure.

[0028] Preferably, the low-temperature pre-drying temperature of the Sp7 fed into the drying section is 80 to 105 degrees Celsius, and the high-temperature calcination temperature is 150 to 200 degrees Celsius.

[0029] Beneficial effects

[0030] This invention provides a multi-dimensional glass fiber oil-water separation filter membrane with controllable pore size. It has the following beneficial effects:

[0031] 1. This invention employs differentiated pulping and step-by-step flow molding techniques to construct a continuous gradient structure from a coarse-pore support layer to a micro-nano separation layer. The coarse-pore support layer provides a low-resistance main channel and mechanical support, ensuring high throughput. The micro-nano separation layer is responsible for the final fine separation and demulsification, ensuring high precision. This structure, with a dense upper layer and a sparse lower layer, decouples filtration resistance and separation precision. While maintaining a high removal rate for tiny emulsified oil droplets, it improves the instantaneous water flux of the filter membrane and the dirt-holding capacity during use, achieving a dual optimization of filtration efficiency and economic benefits.

[0032] 2. This invention constructs a multidimensional structure with high mechanical stability through differentiated pulping, interfacial entanglement, and stepwise thermosetting. The microfibers generated by pulping increase the physical entanglement force between fibers. At the same time, the thermosetting step enables the introduced wet strength agent and crosslinking agent to form a strong chemical "bridge" or "fusion point" at the fiber contact point, achieving dual reinforcement of physical entanglement and chemical locking. While maintaining high porosity, the filter membrane's wet tensile strength and pressure resistance are greatly improved, effectively resisting the shear force and pressure changes generated during the separation process, ensuring the long-term stability and reliability of filtration performance.

[0033] 3. This invention introduces inorganic nano-rough structures on the fiber surface through in-situ sol-gel mineralization technology and performs hydrophilic finishing, constructing a secondary rough structure of micron-fiber skeleton and nanoparticles on the fiber surface. Combined with the hydroxyl groups of the glass fiber itself, it achieves superoleophobic surface wetting properties underwater. When oil droplets come into contact with the filter membrane surface, they are separated by a stable water film, making it difficult for them to adhere to and penetrate the pores. This gives the filter membrane excellent self-cleaning ability and anti-oil ability, effectively extending the service life and regeneration cycle of the filter membrane and significantly reducing operation and maintenance costs. Attached Figure Description

[0034] Fig. 1 This is a flow chart of the filter membrane preparation process of the present invention;

[0035] Fig. 2 This is a schematic diagram of the overall structure of the filter membrane of the present invention;

[0036] Fig. 3 This is a cross-sectional view of the filter membrane of the present invention.

[0037] Among them: 1. Filter membrane; 101. Coarse pore support layer; 102. Gradient transition layer; 103. Micro-nano separation layer. Detailed Implementation

[0038] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Specific Implementation Example 1:

[0040] like Figs. 1-3As shown, a multi-dimensional glass fiber oil-water separation filter membrane with controllable pore size is presented. The filter membrane 1 has an asymmetric pore size gradient distribution in the thickness direction and includes, from bottom to top, a coarse-pore support layer 101, a gradient transition layer 102, and a micro / nano separation layer 103. The coarse-pore support layer 101 is composed of unslurred coarse glass fibers with an aspect ratio greater than 500 interwoven to form micron-sized macropore channels. The micro / nano separation layer 103 is composed of fine glass fibers that have undergone high-intensity slurry treatment to produce microfibrils. Inorganic nano-rough structures are grown in situ on the surface of the fine glass fibers. The gradient transition layer 102 is located between the coarse-pore support layer 101 and the micro / nano separation layer 103 and is composed of coarse and fine glass fibers mixed and interwoven in a gradually varying concentration manner. The inorganic nano-rough structure consists of silica nano-protrusions or titanium dioxide nanoclusters, which are anchored to the glass fiber surface by chemical bonds formed by silane coupling agents, forming a two-dimensional composite rough structure of micron-fibers and nanoparticles. The average pore size of the filter membrane 1 ranges from 0.2 microns to 50 microns and decreases continuously along the thickness direction. The fine glass fibers in the micro-nano separation layer 103 are in a filament-broom state due to pulping treatment, and the fiber surface has peeled nanofibers. A three-dimensional network interception structure is formed between the nanofibers and the main fiber skeleton. A wet strength agent and a crosslinking agent are also introduced into the filter membrane 1. The wet strength agent is polyamide epichlorohydrin resin, and the crosslinking agent forms resin bridges at the fiber contact points, locking the pore size gradient distribution structure.

[0041] Filter membrane 1 is an asymmetric composite fiber porous material with a multi-level pore size gradient. It is constructed on an alkali-free or low-alkali glass fiber matrix and is a composite porous medium with precise geometric and chemical asymmetry in the thickness direction. The total thickness of filter membrane 1 is designed to be around 350 mm. Up to 550 Within this range, the overall porosity is maintained between 75% and 85% to ensure high strength and sufficient fluid capacity. The filter membrane 1 is not a homogeneous single layer, but rather consists of three interpenetrating regions at the interface, defined from bottom to top as: a coarse-pore support layer 101, a gradient transition layer 102, and a micro / nano separation layer 103. The average pore size distribution of the filter membrane 1 exhibits an exponentially decreasing trend, with an average pore size of 30 mm at the bottom. -50 Average aperture at the top: 0.2 -2 This asymmetric structure design, with its "dense on top and sparse on the bottom," is designed to resolve the conflict between flux and precision. The upper micropores are responsible for intercepting tiny emulsified oil droplets (demulsification), while the lower macropores are responsible for allowing water to flow through quickly and accommodating the intercepted oil droplet aggregates, thereby minimizing the transmembrane pressure difference (TMP) and increasing the dirt-holding capacity.

[0042] The coarse-pore support layer 101 serves as the base of the filter membrane 1, accounting for 45% to 60% of the total thickness of the filter membrane. This layer is made of alkali-free glass fiber (E-glass) or acid-resistant glass fiber (C-glass), with its single filament diameter precisely controlled at 12 mm. up to 18 Between 8mm and 10mm in length and with an aspect ratio controlled at >500, these fibers undergo low dispersion energy treatment during wet forming without any pulping. This layer of fibers retains its original cylindrical straight rod morphology, with a smooth surface and no filament splitting or buffing, thus creating a maximum average pore size of 40mm. Up to 60 The highly interconnected large-pore channels and the large-diameter coarse fibers have extremely high bending stiffness (high Young's modulus), which can form a rigid skeleton. Under high hydraulic shock, this layer will not undergo compression deformation, thus ensuring the overall volume stability of the filter membrane 1 and preventing channel collapse. The fact that the fiber is not pulped means that the fiber specific surface area is small, and the pores formed by the accumulation are large and interconnected. This provides a "highway" for the permeating water phase, ensuring that the filter membrane as a whole has high flux. The significance of this layer is to provide resistance to high shear force of the fluid and to act as a hydraulic buffer area to evenly distribute external pressure to the upper functional layer.

[0043] The thickness of the micro-nano separation layer 103 is controlled between 20% and 30%. It is the core area for achieving high-precision separation and anti-fouling functions in the filter membrane 1, responsible for demulsification and fine separation. This layer is made of ultra-fine glass fiber cotton with an original diameter of 0.5 mm. Up to 1.5 During the fiber preparation process, high-energy beating must be performed to strictly control the degree of freeness. to Due to the high-intensity mechanical shearing action, a large number of nanofibers, ranging in diameter from 50 nm to 200 nm, are stripped from the ends and surfaces of individual fine glass fibers. These nanofibers no longer adhere tightly to the main framework but extend outwards, building a dense "spider web structure" between the main fiber framework. The filtration function of the micro-nano separation layer 103 is achieved by the three-dimensional mesh interception structure formed by the interweaving of these densely fibrous and broom-like structures. This structure significantly increases the specific surface area of ​​the filter membrane, effectively intercepting and coalescing emulsified oil droplets. The basic principle involves in-situ growth of inorganic nano-rough structures on the fiber surface, specifically silica nanoprotrusions or titanium dioxide nanoclusters. These inorganic nano-rough structures must grow on the fiber surface through an in-situ sol-gel reaction during the fine glass fiber slurry stage, rather than through post-coating. If silica nanoprotrusions are used, the precursor is tetraethyl orthosilicate (TEOS); if titanium dioxide nanoclusters are used, the precursor is tetrabutyl titanate (TBOT). The particle size of the nanoparticles must be controlled within a uniform range of 30 nm to 60 nm. A silane coupling agent such as... -Aminopropyltriethoxysilane KH550, acting as a molecular bridge, undergoes hydrolysis of its siloxane ends in an acidic environment, resulting in a dehydration condensation reaction with the silanol groups on the glass fiber surface to form stable siloxane covalent bonds. This firmly anchors the nanoparticles to the fiber surface, achieving chemical anchoring and preventing particle detachment. This secondary composite rough structure of microfibers and nanoparticles enables the achievement of an underwater oil contact angle greater than [value missing]. The physical basis of the superoleophobic properties is that the nanofibers generated by the fracturing of fibers greatly reduce the pore size, which can physically intercept emulsified oil droplets of the micron or even submicron size. According to the Cassie-Baxter model, the superposition of micron fibers (primary structure) and nanoparticles (secondary structure) creates an extremely high surface roughness. Combined with the glass fiber itself and the hydrophilic hydroxyl groups introduced on its surface, when the filter membrane is immersed in water, the rough structure will firmly lock a layer of water film. When oil droplets come into contact with the filter membrane, they are actually in contact with this water film (the water-oil contact area is extremely small), thus exhibiting underwater superoleophobic properties and preventing oil droplets from adhering and clogging.

[0044] The gradient transition layer 102 is a key area for ensuring the overall stability and durability of the filter membrane. This layer accounts for 20% to 30% of the total thickness and is composed of coarse glass fibers and fine glass fibers that have undergone high pulping treatment. During the molding process, these fibers are mixed and interwoven with each other in a gradually changing concentration manner. The details of the concentration gradient are as follows: on the side near the coarse pore support layer 101, the mass proportion of coarse fibers is approximately 70%-80%, while on the side near the micro / nano separation layer 103, the mass proportion of fine fibers increases to 80%-90%. If the micro / nano separation layer 103 is directly applied to the coarse pore support layer... On the support layer 101, the bonding force between the two layers is weak, and they are prone to delamination under backwashing or high pressure. The presence of the gradient transition layer 102 realizes the smooth transition of "fiber entanglement", physically locking the two layers together. This continuous gradient eliminates stress concentration between layers with different porosities and prevents interlayer delamination under high pressure backwashing or high pressure differential operation. The presence of this layer effectively smooths the sudden change in local pressure drop when the fluid transitions between coarse pores and micro pores, prevents the fluid from directly impacting the fragile micro-nano separation layer 103, plays a buffering and flow equalization role, and protects the integrity of the micro-nano structure.

[0045] The wet strength agent is polyamide epichlorohydrin resin (PAE), which is uniformly distributed on the negatively charged glass fiber surface through electrostatic adsorption during the molding process. The PAE resin forms a protective film between the fibers, preventing water molecules from penetrating and disrupting the hydrogen bonds between the fibers, thus significantly improving the wet tensile strength of the filter membrane. The crosslinking agent is preferably a blocked isocyanate or polycarboxylic acid, concentrated at the physical contact points between the fibers. In the subsequent high-temperature stepped thermosetting steps... to At the specified temperature, the crosslinking agent undergoes esterification or condensation reaction with the hydroxyl groups or PAE on the fiber surface. This reaction forms an insoluble and infusible three-dimensional network resin bridge at the physical contact points of the fibers, "welding" the overlapping fiber points together. This effectively locks the three-dimensional pore size gradient distribution structure of the entire filter membrane, greatly improving the compressive modulus and dimensional stability of the filter membrane under wet conditions and high pressure differential, ensuring the long-term reliability of separation performance. Specific Implementation Example 2:

[0047] like Figs. 1-3 As shown, based on the content of the above specific embodiments, the following content is further disclosed:

[0048] The preparation process of the filter membrane includes the following steps:

[0049] Sp1: Raw material pretreatment: Two glass fiber raw materials with different average diameters are selected and immersed in an acidic solution for activation treatment to remove surface impurities and introduce hydrophilic hydroxyl groups. Then, they are washed with water until neutral to obtain pretreated coarse fibers and pretreated fine fibers.

[0050] Operating procedure: For samples with an average diameter greater than 10... Coarse glass fibers with an average diameter of less than 3 Fine glass fibers are placed into different activation tanks. First, they are soaked in 0.1N to 1N hydrochloric acid or dilute sulfuric acid solution at a temperature of 50°C to 70°C for 1 to 3 hours. After activation, the fibers are transferred to a washing tank and rinsed with deionized water in a multi-stage countercurrent rinsing process until the pH of the washing solution reaches a neutral range of 6.5 to 7.5.

[0051] Operational requirements and objectives: Acid activation aims to remove alkali metal ions, impurities, and residual organic binders from the surface of glass fibers, and to expose and increase the number of silanol (Si-OH) hydroxyl groups on the fiber surface. This is a key step to enhance the effects of subsequent chemical modification (Sp3) and wet strength agent adsorption (Sp7). The determination scheme is to achieve a neutral pH value to ensure a stable chemical reaction environment for subsequent steps.

[0052] Sp2: Differential de-dissociation pulping: Pretreated coarse fibers are decomposed at low speed in a dispersion medium to maintain the integrity of the fiber morphology and prepare coarse fiber pulp. Pretreated fine fibers are subjected to high-consistency refining in a dispersion medium, and the beating degree is controlled to 45SR-85SR to cause fiber splitting and micronization, and prepare high-beating fine fiber pulp. The high-consistency refining treatment uses a disc mill or PFI mill. By adjusting the disc spacing and rotation speed, the specific surface area increase rate of fine fibers is controlled to be above 200%.

[0053] Process operation procedure:

[0054] Coarse fiber treatment: The pretreated coarse fibers are dispersed in a dispersion medium (usually deionized water) with a concentration of 0.5% to 1.5% using a low-speed propeller or low-shear disperser. The dispersing time is controlled within 5 minutes. The purpose is to perform only preliminary deagglomeration and ensure that the fibers are not damaged or flocculent. The freeness (SR) value of the dispersed coarse fiber slurry must be kept below 10°SR. Fine fiber high-consistency refining: The pretreated fine fibers are prepared into a high-consistency slurry of 3% to 5%. The slurry is continuously or intermittently refined using a disc mill or PFI refiner. During operation, the freeness (SR) value and specific surface area of ​​the output slurry are monitored in real time by inputting the combination parameters of the mill disc spacing and rotation speed. The refining must be precisely controlled within the preset range of 45°SR to 85°SR.

[0055] The control logic is based on real-time feedback from the online pulping degree meter. When the SR value reaches the target value, the pulp delivery pump is automatically started to draw the fine fiber pulp out of the pulping system. The determination scheme is that the specific surface area increase rate of the fine fiber pulp must reach more than 200% of the original specific surface area. This is the quantitative standard for judging whether the fiber has undergone sufficient fibrillation.

[0056] Sp3: In-situ modification within the slurry: A surfactant and a nano-precursor solution are added to the high freeness fine fiber slurry obtained from Sp2. The pH value is adjusted to an acidic or alkaline catalytic environment. Under stirring conditions, the precursor is induced to hydrolyze, and nanoparticles are grown in situ on the surface of the fine fibers and microfibers to obtain a functionalized micro-nano slurry. The nano-precursor solution is an ethanol solution of tetraethyl orthosilicate. The in-situ growth of nanoparticles is carried out at 40-60 degrees Celsius for 1-3 hours.

[0057] Process operation procedure: The high-beating fine fiber slurry prepared by Sp2 is transferred to the reactor. Under continuous stirring, a surfactant (such as nonionic or anionic) is added first to improve the stability of the slurry. Then, the nano precursor solution, namely the ethanol solution of tetraethyl orthosilicate (TEOS), is slowly added dropwise. The temperature of the reactor must be strictly controlled within the range of 40℃ to 60℃. The pH value is precisely adjusted to the acidic 3.0 to 5.0 or alkaline 8.5 to 10.5 catalytic environment required for the hydrolysis reaction by adding ammonia or acetic acid.

[0058] Operational details and implementation mechanism: The reaction time is controlled between 1 and 3 hours to ensure that TEOS is fully hydrolyzed and condensed. Silica nanoparticles are grown in situ on the silanol sites on the surface of fine fibers and microfibrils. The in situ growth depends on the -OH sites generated by activation in Sp1. The output is a functionalized micro-nano slurry with chemically bonded nanoparticles.

[0059] Sp4: Gradient slurry preparation: Prepare multiple portions of mixed slurry and prepare pure coarse fiber slurry, mixed transition slurry and pure functionalized micro-nano slurry according to the volume ratio of coarse fiber slurry to functionalized micro-nano slurry. The ratio of the two in the mixed transition slurry changes in a gradient.

[0060] This step is the input data preparation stage for constructing the pore size gradient of filter membrane 1. Pure coarse fiber slurry: a coarse fiber slurry containing only Sp2, which is used to form the coarse-porous support layer 101.

[0061] Pure functionalized micro / nano slurry: a functionalized micro / nano slurry containing only Sp3, which is used to form micro / nano separation layer 103;

[0062] Mixed transition slurry: Prepare multiple slurries, and by accurately calculating the volume ratio and dry weight ratio, make the ratio of coarse fiber slurry to functionalized micro-nano slurry change in a gradient in N consecutive slurries. That is, N=3 transition slurries can be prepared with ratios of 80%:20%, 50%:50% and 20%:80% (coarse fiber: micro-nano fiber).

[0063] Objective: To provide the Sp5 multi-channel headbox with slurry inputs with different settling velocities and final porosities, achieving a continuous variation in pore size from 50µm to 0.5µm.

[0064] Sp5: Step-by-step flow forming: On an inclined or long screen forming machine, a multi-channel headbox is used to sequentially flow pure coarse fiber slurry, mixed transition slurry, and pure functionalized micro-nano slurry to the forming screen section according to the density difference of the slurry. Gravity dehydration is used to allow the fibers of each layer to settle naturally in a wet state and interpenetrate with each other to form a wet film preform with a pore size gradient. The multi-channel headbox precisely controls the thickness of the gradient transition layer 102 by adjusting the flow rate ratio and concentration ratio of the coarse fiber component slurry and the functionalized micro-nano fiber slurry. The pore size gradient change is manifested as the average pore size continuously decreasing from 50 micrometers to 100 micrometers on the side of the coarse pore support layer 101 to 0.5 micrometers to 5 micrometers on the side of the micro-nano separation layer 103 along the thickness direction of the filter membrane. The pure functionalized micro-nano slurry is controlled to be on the top layer, and the ratio of the flow rate to the screen speed is controlled between 0.9 and 1.1 to avoid slurry disturbance from damaging the gradient structure.

[0065] Process operation procedure: On the inclined or long screen forming machine, use a multi-channel headbox or sequential flow system for operation:

[0066] Bottom layer laying: First, pure coarse fiber slurry is fed to the forming mesh section and quickly dehydrated by vacuum suction to form a wet coarse-porous support layer 101.

[0067] Gradient transition: Next, according to the predetermined flow interval, the mixed transition slurry prepared by Sp4 is sequentially flowed and covered on the coarse-pore support layer 101;

[0068] Top layer laying: Finally, the pure functional micro-nano slurry is flowed as the top layer;

[0069] The key control logic lies in maintaining the ratio R of the flow rate to the net speed. For the top layer of pure functionalized micro-nano slurry, this ratio R must be strictly controlled within a narrow range of 0.9 to 1.1 to ensure that the slurry forms a uniform coverage on the net and avoids eddies and water flow instability caused by slurry disturbance, which would destroy the deposited gradient structure. At the same time, by adjusting the flow rate ratio and concentration ratio of each slurry, the final thickness of the gradient transition layer 102 is precisely controlled, which usually accounts for 20% to 30% of the total thickness. The judgment scheme is that the thickness tolerance of the wet film blank must be controlled within ±5%.

[0070] Sp6: Wet pressing and setting: The wet membrane preform is dehydrated by multi-stage roller pressing. The fiber layers are tightly bonded by controlling the linear pressure, and the thickness and porosity of the filter membrane are initially controlled.

[0071] Process operation flow: The wet film preform undergoes multi-stage dewatering on a continuous blanket and roller pressing system, typically using N... The three-stage press rolls have their linear pressure (PL) precisely calculated and input for each stage to ensure a gradual increase in dehydration rate.

[0072] Operational details and objectives: By controlling the linear pressure PL, not only is the moisture content of the wet membrane reduced to below 50%, but more importantly, physical compression is used to promote tight bonding between fiber layers, especially at the interface of the three layers, to enhance the physical entanglement between fibers, initially lock the pore structure, and achieve preliminary control of the final thickness and porosity of the filter membrane.

[0073] Sp7: Step-by-step thermosetting: The wet-pressed filter membrane 1 is sent to the drying section. First, free water is removed in the low-temperature zone, and then cross-linking and curing are carried out in the high-temperature zone. This allows the in-situ generated nanoparticles to form a strong chemical bond with the fiber surface, while the wet strength agent is cured and locked to lock the three-dimensional pore structure. The low-temperature pre-drying temperature is 80 degrees Celsius to 105 degrees Celsius, and the high-temperature calcination temperature is 150 degrees Celsius to 200 degrees Celsius.

[0074] Process operation flow: The wet-pressed filter membrane is fed into a multi-stage drying tunnel:

[0075] Low-temperature pre-drying (removal of free water): The filter membrane enters the low-temperature zone, with the temperature controlled between 80°C and 105°C. The main purpose of this stage is to evaporate free water and avoid structural damage caused by rapid evaporation at high temperatures. High-temperature calcination and curing (chemical locking): The filter membrane enters the high-temperature zone, with the temperature controlled between 150°C and 200°C.

[0076] High-temperature calcination is the key to permanently locking the filter membrane structure. At this temperature, the wet strength agent PAE undergoes a cross-linking reaction. At the same time, the in-situ grown nanoparticles undergo final chemical bonding and solidification with the silicon coupling agent on the fiber surface. This chemical bonding permanently locks the pore size gradient structure formed by Sp5, ensuring that the filter membrane does not undergo pore size migration or structural creep in water and under high pressure.

[0077] Sp8: Surface activation finishing: The cured filter membrane 1 is further reduced by plasma treatment or spraying with a hydrophilic finishing agent, and then cut to obtain the finished product.

[0078] Process operation flow: After curing, the filter membrane 1 undergoes final surface treatment. This can be done by using plasma treatment (such as oxygen or air plasma) to bombard the surface of the filter membrane 1 with low intensity for a few seconds to tens of seconds, or by using spraying / immersion to apply a hydrophilic finishing agent (such as polyvinyl alcohol or special polymers).

[0079] The aim is to further improve the surface free energy of the 103-layer filter membrane, maximizing its hydrophilicity and hydration capacity, thereby ensuring the reliability of its underwater superoleophobic properties. The determination method involves taking a sample of the finished filter membrane and testing its underwater oil contact angle, which must meet the performance requirement of an underwater oil contact angle greater than 150°. Finally, the finished filter membrane is cut and wound according to application specifications. Specific Implementation Example 3:

[0081] like Figs. 1-3 As shown, based on the content of the above specific embodiments, the following content is further disclosed:

[0082] The following details the production line using a 1.5-meter-wide continuous long-net wet forming process to prepare products with a diameter of 0.5... Practical operation steps of glass fiber filter membrane 1 with minimum pore size and gradient structure:

[0083] Sp1: Raw material activation and preparation: At the beginning of the preparation, the coarse glass fiber (average D) that serves as the framework is first activated. The fiber surface was pretreated with 12 mm of ultrafine glass fiber (average D≈1.5 μm) as a functional layer. This process was achieved by soaking the fiber in a dilute acid solution at 60 °C for 2 hours. The purpose was to thoroughly remove impurities from the fiber surface and expose and increase the hydrophilic silanol groups. Subsequently, the fiber was rinsed with deionized water in a countercurrent manner until the pH of the rinsing solution reached 7.0 ± 0.2, ensuring that the fiber surface was in the most suitable activation state for subsequent chemical reactions.

[0084] Sp2: Differentiated pulping and fiber morphology shaping: After the raw materials are activated, they enter the differential de-dissociation stage. The coarse fibers are gently decomposed in a low-speed disperser to maintain their rigid columnar structure and the pulping degree is maintained at SR<10°. The fine fibers are then pulped in a high-shear PFI refiner with high concentration. By precisely controlling the pulping parameters, the fibers are forced to undergo fibrillation, so that the pulping degree accurately reaches 70°SR. This SR value determines the number of nanofibers peeled off from the fine fibers, thereby locking the minimum pore size of the micro-nano separation layer from the source.

[0085] Sp3: In-situ Nanomodification and Functionalization within the Slurry: A key step in imparting superoleophobic properties to filter membrane 1 is introducing a high-freezing-degree fine fiber slurry into a reactor equipped with a precise temperature control system. A TEOS ethanol solution is slowly added dropwise to the slurry as a nano-precursor, while the temperature is precisely controlled at 55°C and the pH is adjusted to the acidic catalytic range. Under continuous stirring, TEOS undergoes hydrolysis and condensation, resulting in the in-situ growth of 30nm to 60nm nanofibers on the surface of the fine fibers and microfibers. Nanoparticles are ultimately anchored through chemical bonding, and this step completes the construction of the micro-nano secondary roughness of the functional layer.

[0086] Sp4: Gradient slurry preparation and chemical reinforcing agent addition: Before molding, the slurry is precisely prepared according to the requirements of the three-layer structure of the filter membrane. First, pure coarse fiber slurry and pure functionalized micro-nano slurry are prepared. Then, multiple mixed transition slurries are prepared in a gradient ratio of 70%:30% to 30%:70%. At the same time, 1.5%wt of PAE wet strength agent and 0.3%wt of crosslinking agent are added to all slurries to ensure that the chemical reinforcing agent is uniformly dispersed and adsorbed on the fiber surface, in preparation for subsequent thermosetting and locking structure.

[0087] Sp5: Step-by-step flow forming and gradient structure construction: This is the decisive step in achieving the pore size gradient distribution. The slurry is sequentially and rapidly flowed to the long web forming zone through a multi-channel headbox, and the flow sequence strictly follows the pure coarse fiber (bottom layer). Mixed transition slurry The principle of pure functionalized micro-nano slurry (top layer) is to allow fiber layers with different settling characteristics to permeate each other in a wet state by precisely controlling the vacuum dewatering rate below the long wire, forming a stable fiber entanglement interface between the layers. At the same time, the flow rate of the top micro-nano slurry is strictly controlled to be R=0.95 with the wire speed ratio to avoid any disturbance that could damage the established gradient structure.

[0088] Sp6: Wet pressing and initial structural solidification: The formed wet film preform is then dehydrated by multi-stage pressing with three-stage press rollers. By increasing the linear pressure (from 20kN / m to 60kN / m), free water is forcibly discharged, and the moisture content of the filter membrane is reduced to below 30%. This physical setting process not only completes the initial dehydration, but more importantly, by applying compaction stress, it maximizes the contact area between fibers, initially locks the pore structure, and creates favorable conditions for the final chemical crosslinking.

[0089] Sp7: Step-by-step thermosetting and permanent structural locking: After wet pressing, the filter membrane enters a multi-segment drying tunnel for step-by-step thermosetting. First, residual free water is gently removed in a low-temperature zone of 95°C. Then, it enters a high-temperature calcination zone of 180°C and stays for 20 minutes. Under high temperature, PAE and crosslinking agent undergo thermosetting reaction, forming strong resin bridges or chemical junctions at fiber contact points. This step achieves permanent chemical locking of the pore size gradient structure constructed by Sp5, ensuring that the filter membrane can maintain the stability of size and pore size when subjected to high pressure impact.

[0090] Sp8: Surface Activation Finishing and Finished Product Output: As the final performance assurance step, the cured filter membrane enters... The plasma treatment chamber further activates the surface of the micro-nano separation layer 103 through 20 seconds of low-power bombardment, removing any trace amounts of residual hydrophobic impurities and maximizing the hydrophilicity and hydration capacity of the filter membrane. After the finished filter membrane is tested and confirmed to have an underwater oil contact angle greater than 155°, it can be wound up, cut, and packaged for storage. Specific Implementation Example 4:

[0092] like Figs. 1-3 As shown, based on the content of the above specific embodiments, the following content is further disclosed:

[0093] To further verify the feasibility of the technical solution in this application, the following case study is provided:

[0094] Case Study 1: Fabrication Process of High-Precision Hydraulic Oil Purification Filter Membrane: The goal of this case study is to achieve ultra-high precision filtration (0.5... (Level) and ultra-high structural durability to withstand high-voltage pulses:

[0095] The activation steps remain unchanged to ensure complete exposure of the silanol groups on the surface of both coarse and fine fibers; the beating degree of the fine fibers is significantly increased to 80°SR to maximize the degree of fiber microfibrilization, aiming to form the densest and smallest pore micro-nano network during Sp5 molding, thereby effectively intercepting 4% of the hydraulic oil. The following particulate pollutants; nanoparticle selection Because titanium dioxide has better thermal stability and chemical inertness, it is more suitable for oil immersion and high-temperature working environments. Meanwhile, the amount of silane coupling agent used is increased by 50%, ensuring… Nanoparticles can be firmly chemically anchored to the fiber surface in the high-shear environment of hydraulic oil. The dosage of wet-strength agent PAE is increased to 3.0%wt to increase the adsorption sites on the fiber surface and the density of subsequent cross-linking reactions, laying a chemical foundation for the filter membrane to resist high-pressure impact. The thickness ratio of the micro-nano separation layer 103 is increased to 35%, emphasizing the precision filtration function. At the same time, the flow rate ratio R is precisely controlled at 1.05 during flow to ensure close fiber packing. Compared with the standard process, the upper limit of the linear pressure of wet pressing is slightly increased to further compact the fibers, reduce the initial porosity, and enhance the physical contact between fibers. The high-temperature calcination temperature is increased to 190°C and extended to 30 minutes. This strengthening curing step aims to ensure that PAE and cross-linking agent form the most complete three-dimensional chemical cross-linking network, giving the filter membrane unparalleled wet compressive stability and anti-structural creep ability under long-term high-pressure pulses. Standard plasma treatment is used to ensure that the surface layer is extremely hydrophilic, which is beneficial to the filter membrane's coalescence and separation effect on trace amounts of emulsion water in hydraulic oil.

[0096] Case Study 2: Preparation Process of High-Fluidity Industrial Emulsified Wastewater Treatment Membrane: The core objective of this case study is to maximize water flux while ensuring long-term antifouling properties to adapt to large-scale wastewater treatment.

[0097] The activation step uses an acid solution, but the pH of the neutralization liquid after washing is more strictly controlled to meet the requirements of subsequent zwitterionic surfactants. The beating degree of the fine fibers is reduced to 55°SR, a key flux optimization operation. This involves appropriately sacrificing extremely low precision (targeting ~5µm oil droplet rejection) in exchange for a relatively loose fiber packing structure, thereby significantly reducing water flow resistance and achieving the high flux target. The SiO2 nanoparticles remain unchanged, but the surfactant is replaced with a zwitterionic surfactant and its dosage is increased. This adjustment ensures that the stability of the nanoparticles and fiber surfaces is not compromised in complex industrial wastewater environments with high ionic strength and pH fluctuations. The thickness of the coarse-porous support layer 101 is increased to 60%, providing better support for the aqueous phase. The widest low-resistance main channel optimizes the overall water flux; a flow rate ratio of R=1.1 (slight stretching) is used for the top layer laying, slightly stretching the fibers to form slightly oriented pores, further reducing the transmembrane resistance of the aqueous phase; a lower upper limit of linear pressure is used for wet pressing to avoid over-compacting the fibers, thus retaining more pore space to support high flux; the curing process maintains standard temperature and time to ensure basic structural locking; instead of energy-consuming plasma treatment, a PVA (polyvinyl alcohol) hydrophilic finishing agent is used. PVA forms a stable hydrophilic hydrogel layer on the surface of the micro / nano separation layer 103. This chemical coating can better resist long-term penetration and adhesion of oil in water treatment, ensuring the FRR performance of the filter membrane during long-term operation.

[0098] Case Study 3: Preparation Process of High-Temperature Fuel / Oil-Water Separation Coalescing Filter Membrane: The goal of this case study is to achieve deep dehydration of fuels (such as kerosene), requiring the filter membrane to possess excellent chemical inertness and thermal stability under high-temperature oil immersion conditions.

[0099] The fiber raw material has been upgraded to high-heat-resistant borosilicate glass fiber. The pH of the activated washing solution must be strictly controlled at neutral to avoid any acid or alkali residue affecting subsequent high-temperature stability. The beating degree has been significantly reduced, increasing the minimum pore size of the 103-layer micro / nano separation layer to 10-20 μm. This adjustment represents a fundamental functional change: the filter membrane is no longer a fine separator but a highly efficient coalescer, requiring appropriately large pores to promote the aggregation and growth of tiny water droplets. The nano-precursor selection... This material possesses higher thermal decomposition temperature and chemical stability to ensure that the nanostructure does not degrade long-term in hot oil at 80°C; the wet strength agent PAE is maintained at the standard dosage, but a small amount of polymeric dispersant is added to ensure that coarse and fine fibers can still be uniformly dispersed even at high slurry concentrations, which is beneficial for achieving the coalescence function; the thickness of the bottom support layer 101 is appropriately increased to ensure that the coalesced water droplets have enough space to settle due to gravity; the wet pressing pressure is kept at a moderate level to ensure fiber bonding while avoiding excessive compaction that would affect the coalescence porosity; the high-temperature calcination temperature is set at the maximum of 200°C, and the curing time is extended to ensure The chemical bonding strength between nanoparticles and fibers is the highest, which is the key to ensuring the long-term stable operation of the filter membrane under high-temperature hot oil immersion environment; standard plasma treatment is used to ensure hydrophilicity in the initial stage, so as to facilitate the capture of tiny moisture in the fuel.

[0100] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising a reference structure" does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes the element.

[0101] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A multi-dimensional glass fiber oil-water separation filter membrane with controllable pore size, characterized in that: The filter membrane (1) has an asymmetric pore size gradient distribution in the thickness direction, and from bottom to top includes a coarse pore support layer (101), a gradient transition layer (102), and a micro-nano separation layer (103). The coarse pore support layer (101) is composed of unpulped coarse glass fibers with an aspect ratio greater than 500 interwoven to form micron-sized macropore channels. The micro-nano separation layer (103) is composed of fine glass fibers that have undergone high-intensity pulping to produce microfibrils. Inorganic nano-rough structures are grown in situ on the surface of the fine glass fibers. The gradient transition layer (102) is located between the coarse pore support layer (101) and the micro-nano separation layer (103), and is formed by mixing and interweaving coarse glass fibers and fine glass fibers in a gradually changing concentration manner.

2. The multi-dimensional glass fiber oil-water separation filter membrane with controllable pore size according to claim 1, characterized in that: The inorganic nano-rough structure is a silicon dioxide nanoprotrusion or a titanium dioxide nanocluster, which is anchored to the glass fiber surface by chemical bonds formed by a silane coupling agent, forming a micron fiber-nanoparticle secondary composite rough structure. The average pore size of the filter membrane (1) ranges from 0.2 microns to 50 microns and decreases continuously along the thickness direction.

3. The multi-dimensional glass fiber oil-water separation filter membrane with controllable pore size according to claim 1, characterized in that: The fine glass fibers in the micro-nano separation layer (103) are in a filament-broom state due to pulping treatment, and the fiber surface has peeled nanofibers. The nanofibers and the main fiber skeleton form a three-dimensional network interception structure.

4. The multi-dimensional glass fiber oil-water separation filter membrane with controllable pore size according to claim 1, characterized in that: The filter membrane (1) also incorporates a wet strength agent and a crosslinking agent. The wet strength agent is polyamide epichlorohydrin resin, and the crosslinking agent forms a resin bridge at the fiber contact point, locking the pore size gradient distribution structure.

5. A method for preparing a multi-dimensional glass fiber oil-water separation filter membrane with controllable pore size according to any one of claims 1-4, characterized in that: The preparation method includes the following steps: Sp1: Raw material pretreatment: Two glass fiber raw materials with different average diameters are selected and immersed in an acidic solution for activation treatment to remove surface impurities and introduce hydrophilic hydroxyl groups. Then, they are washed with water until neutral to obtain pretreated coarse fibers and pretreated fine fibers. Sp2: Differential de-dissociation pulping: The pretreated coarse fibers are decomposed at low speed in the dispersion medium to maintain the integrity of the fiber morphology and prepare coarse fiber pulp. The pretreated fine fibers are subjected to high-concentration refining in the dispersion medium and the beating degree is controlled to 45SR-85SR to make the fibers split and micronized, and prepare fine fiber pulp with high beating degree. Sp3: In-situ modification within the slurry: a surfactant and nano-precursor solution are added to the high freeness fine fiber slurry obtained from Sp2, the pH value is adjusted to an acidic or alkaline catalytic environment, and the precursor is induced to hydrolyze under stirring conditions to grow nanoparticles in situ on the surface of fine fibers and microfibers to obtain functionalized micro-nano slurry. Sp4: Gradient slurry preparation: Prepare multiple portions of mixed slurry and prepare pure coarse fiber slurry, mixed transition slurry and pure functionalized micro-nano slurry according to the volume ratio of coarse fiber slurry to functionalized micro-nano slurry. The ratio of the two in the mixed transition slurry changes in a gradient. Sp5: Step-by-step flow forming: On an inclined or long mesh forming machine, a multi-channel headbox is used to sequentially flow pure coarse fiber slurry, mixed transition slurry and pure functionalized micro-nano slurry to the forming mesh section according to the difference in slurry density. Gravity dehydration is used to allow the fibers of each layer to settle naturally in a wet state and interpenetrate with each other to form a wet film preform with a pore size gradient. Sp6: Wet pressing and setting: The wet membrane preform is dehydrated by multi-stage roller pressing. The fiber layers are tightly bonded by controlling the linear pressure, and the thickness and porosity of the filter membrane are initially controlled. Sp7: Step-by-step thermosetting: The wet-pressed filter membrane (1) is sent to the drying section. First, free water is removed in the low-temperature zone, and then cross-linking and curing are carried out in the high-temperature zone. This allows the nanoparticles generated in situ to form a strong chemical bond with the fiber surface, while the wet strength agent is cured and locked to lock the three-dimensional pore structure. Sp8: Surface activation finishing: The cured filter membrane (1) is further reduced by plasma treatment or spraying with a hydrophilic finishing agent, and then cut to obtain the finished product.

6. The method for preparing a multi-dimensional glass fiber oil-water separation filter membrane with controllable pore size according to claim 5, characterized in that: In Sp2, the high-consistency pulping process uses a disc mill or a PFI mill, and the increase rate of the specific surface area of ​​the fine fibers is controlled to be above 200% by adjusting the spacing and rotation speed of the mill discs.

7. The method for preparing a multi-dimensional glass fiber oil-water separation filter membrane with controllable pore size according to claim 5, characterized in that: In the Sp3, the nano-precursor solution is a tetraethyl orthosilicate ethanol solution, and the in-situ growth of nanoparticles is carried out at 40-60 degrees Celsius for 1-3 hours.

8. The method for preparing a multi-dimensional glass fiber oil-water separation filter membrane with controllable pore size according to claim 5, characterized in that: In the Sp5, the multi-channel headbox precisely controls the thickness of the gradient transition layer (102) by adjusting the flow rate ratio and concentration ratio of the coarse fiber component slurry and the functionalized micro / nano fiber slurry. The pore size gradient change is manifested as the average pore size continuously decreasing from 50 micrometers to 100 micrometers on the side of the coarse pore support layer (101) to 0.5 micrometers to 5 micrometers on the side of the micro / nano separation layer (103) along the thickness direction of the filter membrane.

9. The method for preparing a multi-dimensional glass fiber oil-water separation filter membrane with controllable pore size according to claim 5, characterized in that: In Sp5, the purely functionalized micro-nano slurry is positioned on the top layer, and the ratio of the flow rate to the grid speed is controlled between 0.9 and 1.1 to avoid slurry disturbance that could damage the gradient structure.

10. The method for preparing a multi-dimensional glass fiber oil-water separation filter membrane with controllable pore size according to claim 5, characterized in that: The low-temperature pre-drying temperature of the Sp7 feeder into the drying section is 80 to 105 degrees Celsius, and the high-temperature calcination temperature is 150 to 200 degrees Celsius.

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