A method for regulating the microstructure and pore size of a hollow fiber ceramic membrane and the resulting product

Abstract

The present invention discloses a method for regulating the microstructure and pore size of a hollow fiber ceramic membrane and the resulting product. Based on the phase inversion process of dry / wet spinning, the method optimizes and rationally designs the types of ceramic raw materials and the coarse and fine particle grading in the spinning slurry, introduces a suitable surfactant as an additive, and designs a combination of an internal coagulant (core liquid) and an external coagulation bath (external coagulant). Nanoparticles migrate to the outer surface of the wet membrane during the extrusion molding and phase inversion process to form a small particle cortex, thereby obtaining an asymmetric hollow fiber ceramic ultrafiltration membrane with a small pore size (pore size ≤ 25 nm, average pore size ≤ 20 nm) and a narrow pore size distribution range. The present invention overcomes the problem that the existing technology cannot produce ceramic ultrafiltration membranes with small pore size and high separation accuracy using the phase inversion method. While greatly simplifying the membrane preparation process and reducing the preparation cost, the prepared ceramic membrane can better meet the requirements of refined separation applications.

Description

Technical Field

[0001] The present invention relates to the technical field of ceramic materials, and in particular to a method for regulating the microstructure and pore size of a hollow fiber ceramic membrane and a product obtained therefrom. Background Art

[0002] Compared with organic membranes, ceramic membranes have advantages such as good chemical stability, high mechanical strength, long service life, and easy cleaning and regeneration. They are suitable for particularly harsh working environments and are therefore increasingly valued. They have been widely used in important industrial fields such as wastewater treatment, seawater desalination, chemical and energy, biopharmaceuticals, and food processing, making important contributions to environmental protection, energy conservation and emission reduction, and the upgrading and reconstruction of traditional industries. For traditional multi-channel tubular and flat ceramic membranes, in order to reduce membrane permeation resistance and improve membrane separation accuracy, the membrane is generally designed into a multi-layer asymmetric structure, including a large particle support layer that provides mechanical strength, a separation layer formed by the accumulation of small particles, and an intermediate layer to prevent the particles in the separation layer from leaking into the support layer (the intermediate layer can be single or multi-layer, and at least 2 to 3 intermediate layers are required for ultrafiltration / nanofiltration membranes). However, using this type of ceramic membrane prepared by the particle stacking method, it is generally difficult to obtain a separation layer with a narrow pore size distribution range after firing due to the uneven size of the ceramic powder particles. At the same time, it is necessary to undergo multiple impregnation coating and multiple high-temperature firing processes to obtain an asymmetric structure membrane, which greatly increases the preparation cost of the ceramic membrane. The cumbersome preparation process is also prone to increase membrane defects, affecting the quality stability and separation accuracy of the ceramic membrane.

[0003] In order to effectively address the key issues that have hindered the development of ceramic membrane technology, improve membrane separation performance, and reduce the cost of membrane preparation and application, asymmetric hollow fiber ceramic membranes prepared by the phase inversion method have received significant attention in recent years. Compared with the traditional multi-channel tubular and flat ceramic membranes prepared by particle stacking, the phase inversion method can produce asymmetric microtubular membranes through a one-step dry / wet spinning process and a single high-temperature sintering process. The membrane tube walls are thin, which greatly simplifies the preparation process and reduces preparation and raw material costs. In addition, hollow fiber ceramic membranes have the advantages of high membrane packing density and large effective separation area per unit volume, making it easy to miniaturize membrane separation equipment. When using the phase inversion method to prepare ceramic membranes in the prior art, a single type of ceramic powder is generally mixed with a polymer binder and a solvent to prepare a spinning slurry. After forming and high-temperature sintering, only a microfiltration membrane with a separation layer pore size mainly distributed between 0.1 and 1.0 μm (average pore size greater than 0.1 μm) can be obtained. The pore size distribution of the membrane is wide, resulting in low membrane separation precision and still unable to meet the requirements of fine filtration separation. With the current existing technology, it is still impossible to prepare ceramic ultrafiltration membranes with small pore size and high separation accuracy through phase inversion method. Summary of the Invention

[0004] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a method for regulating the microstructure and pore size of a hollow fiber ceramic membrane. Based on the phase inversion process of dry / wet spinning, by optimizing and rationally designing the type of ceramic raw materials and the coarse and fine particle grading in the spinning slurry, introducing a suitable surfactant as an additive, and designing a combination of an internal coagulant (core liquid) and an external coagulation bath (external coagulant), the nanoparticles migrate to the outer surface of the wet membrane during the extrusion molding and phase inversion process to form a small particle cortex, thereby obtaining an asymmetric structure hollow fiber ceramic ultrafiltration membrane with a small pore size (pore size ≤ 25 nm, average pore size ≤ 20 nm) and a narrow pore size distribution range. This method overcomes the problem that the prior art cannot prepare a ceramic ultrafiltration membrane with a small pore size and high separation accuracy using the phase inversion method. While greatly simplifying the membrane preparation process and reducing the preparation cost, the prepared ceramic membrane can better meet the requirements of fine separation applications. Another object of the present invention is to provide a product obtained by using the above-mentioned method for regulating the microstructure and pore size of a hollow fiber ceramic membrane.

[0005] The purpose of the present invention is achieved through the following technical solutions:

[0006] The present invention provides a method for regulating the microstructure and pore size of a hollow fiber ceramic membrane, comprising the following steps:

[0007] (1) Preparation of ceramic base powder

[0008] The ceramic base material is composed of 80-90 wt% of 3 mol% yttria-stabilized zirconia micropowder and 10-20 wt% of nano-oxide powder; wherein the nano-oxide powder is aluminum oxide, silicon oxide, or titanium oxide powder, and the average particle size of the 3 mol% yttria-stabilized zirconia micropowder is more than 20 times the average particle size of the nano-oxide powder; the ceramic base materials are dry-mixed in a mixer according to the composition ratio to obtain ceramic base material powder;

[0009] (2) Preparation of spinning slurry

[0010] Polyethersulfone (PES) particles are added to N-methyl-2-pyrrolidone (NMP) solvent and dissolved to obtain a polymer solution; a nonionic surfactant is added to the polymer solution and dissolved, and then the ceramic base material powder is added and stirred to obtain a spinning slurry; the contents of the polyethersulfone, N-methyl-2-pyrrolidone, nonionic surfactant, and ceramic base material powder in the spinning slurry are 7-10 wt%, 36-40 wt%, 1-2.5 wt%, and 48-55 wt%, respectively;

[0011] (3) Dry / wet spinning

[0012] The spinning slurry is loaded into a spinning forming device, and after vacuum degassing, it is extruded through a spinneret with an internal insert under a nitrogen pressure of 0.2 to 1 bar, and immersed in an external coagulation bath for solidification and forming. After forming, it is taken out and naturally dried at room temperature to obtain a ceramic membrane body;

[0013] (4) High temperature firing

[0014] The ceramic membrane blank is first heated to 800-850°C at a rate of 1-2°C / min in a nitrogen atmosphere and kept warm for 1-2 hours, then heated to 1100-1300°C at a rate of 2-4°C / min in an air atmosphere and kept warm for 2-5 hours; then cooled to 300-500°C at a rate of 5°C / min, and finally cooled naturally to obtain a small-pore hollow fiber composite ceramic ultrafiltration membrane with an average pore diameter of the separation membrane layer ≤20nm.

[0015] Furthermore, in step (1) of the present invention, the average particle size of the 3 mol% yttria-stabilized zirconia micropowder is 0.5-1.5 μm, and the average particle sizes of the aluminum oxide, silicon oxide, and titanium oxide powders are 30-100 nm, 20-50 nm, and 5-20 nm, respectively; preferably, the silicon oxide powder is 1.5 mol% magnesium oxide-doped silicon oxide powder.

[0016] In the above scheme, in step (1) of the present invention, dry mixing is carried out in a mixer for 3 to 4 hours. In step (2), the molecular weight of the polyethersulfone is 10,000 to 50,000; and the nonionic surfactant is a combination of polyoxyethylene sorbitan monolaurate (Tween 20) or polyoxyethylene sorbitan monopalmitate (Tween 40) and polyethylene glycol (PEG600 or PEG800).

[0017] In the above scheme, the internal coagulant (core liquid) in the inner tube of step (3) of the present invention is water, and its outflow rate is 30 to 80 mL / min; the extrusion speed of the spinning slurry is 1.7 to 2.2 cm / s, and after extrusion, it enters the external coagulation bath (external coagulant) through an air distance of 2 to 3 cm; the external coagulation bath is an alcohol-water solution with an ethanol content of 70 to 80 vol%, and the immersion time is 12 to 24 hours.

[0018] The product obtained by using the above-mentioned method for regulating the microstructure and pore size of hollow fiber ceramic membranes is an asymmetric hollow fiber composite ceramic ultrafiltration membrane. The inner side of the membrane is a large-pore porous inner cortex formed by the accumulation of small particles. The middle is a support layer formed by the accumulation of large particles and having finger-like pores. The outer side of the membrane is a small-pore porous outer cortex formed by the accumulation of nanoparticles, which serves as the separation membrane layer. The outer separation membrane layer of the hollow fiber composite ceramic ultrafiltration membrane has an average pore size of 5 to 20 nm, a maximum pore size no more than 1.5 times the average pore size, a thickness of 0.5 to 2 μm, a membrane porosity of 45 to 52.5%, a flexural strength of 90 to 116 MPa, and a pure water flux of 151 to 447 LMH / bar.

[0019] The present invention has the following beneficial effects:

[0020] (1) The present invention creatively uses ceramic powder particles with large differences in particle size and density. During the dry / wet spinning and phase inversion process, under the synergistic effect of the shear force generated by nitrogen pressure extrusion molding and the mass transfer exchange between the external coagulant and the solvent and its surfactant in the slurry, the highly hydrophilic lightweight nanoparticles in the slurry can quickly migrate to the surface of the extruded wet membrane, gradually enriching on the outer surface of the hollow fiber ceramic membrane precursor to form a separation layer composed of small particles. By using a hydrophilic surfactant composite additive with a specific molecular weight and HLB value range, while reducing the viscosity and lubricity of the slurry, the nanoparticles are driven to migrate rapidly to the surface of the membrane precursor under the combined action of the extrusion shear force and the external coagulant / solute mass transfer exchange. In this process, an alcohol-water solution with weakened gelling ability is used as an external coagulation bath to delay the solidification of the wet membrane surface layer, ensuring that enough nanoparticles migrate to the surface layer to enrich and form a nanoparticle membrane layer. In addition, by combining the heat treatment process of first heat treatment in a protective atmosphere and then high-temperature sintering in air, the growth of grains of the membrane separation layer components can be inhibited and the porosity of the separation layer can be increased, thereby obtaining a highly permeable small-pore hollow fiber ceramic ultrafiltration membrane.

[0021] (2) The method of the present invention can be used to prepare a hollow fiber ceramic ultrafiltration membrane separation layer with a small pore size and high porosity. The pore size is easily controlled and has a narrow distribution range (the maximum pore size of the separation membrane layer does not exceed 1.5 times the average pore size), thereby meeting the requirements for efficient and high-precision separation of different substances. The method of the present invention can also be used to prepare a hollow fiber ceramic microfiltration membrane with a narrow pore size distribution range and high separation precision.

[0022] (3) The ceramic ultrafiltration membrane is prepared by the method of the present invention. Since some small particles exist between the joints of large particles, the large particles can be promoted to form stronger neck connections during the high-temperature sintering process, which is beneficial to improving the mechanical strength of the ceramic membrane. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The present invention will be described in further detail below with reference to the embodiments and accompanying drawings:

[0024] Figure 1 Schematic diagram of the microstructure of the hollow fiber composite ceramic ultrafiltration membrane of the present invention;

[0025] Figure 2 This is a SEM image of the hollow fiber composite ceramic ultrafiltration membrane prepared in the present invention (a: cross section; b: outer surface). DETAILED DESCRIPTION

[0026] Example 1:

[0027] This embodiment provides a method for controlling the microstructure and pore size of a hollow fiber ceramic membrane, and the steps are as follows:

[0028] (1) Preparation of ceramic base powder

[0029] The ceramic base material is composed of 85 wt% of 3 mol% yttria-stabilized zirconia powder with an average particle size of 1 μm and 15 wt% of aluminum oxide (Al2O3) powder with an average particle size of 80 nm. The ceramic base material powder is obtained by dry mixing in a mixer for 3 hours according to the composition ratio.

[0030] (2) Preparation of spinning slurry

[0031] Polyethersulfone (PES E2010) particles with a molecular weight of 10,000 to 50,000 are added to an N-methyl-2-pyrrolidone (NMP) solvent and stirred thoroughly to dissolve to obtain a uniform polymer solution; nonionic surfactants polyoxyethylene sorbitan monolaurate (Tween 20) and polyethylene glycol (PEG800) are added to the polymer solution and stirred thoroughly to dissolve, and then the ceramic base material powder is slowly added and stirred thoroughly to obtain a spinning slurry; the contents of the polyethersulfone, N-methyl-2-pyrrolidone, polyoxyethylene sorbitan monolaurate, polyethylene glycol, and ceramic base material powder in the spinning slurry are 8 wt%, 40 wt%, 1 wt%, 1 wt%, and 50 wt%, respectively;

[0032] (3) Dry / wet spinning

[0033] The above spinning slurry was loaded into a stainless steel slurry tank in a spinning forming device, and after vacuum degassing, it was extruded at a speed of 2 cm / s through a spinneret with an inner tube (outer diameter and inner diameter were 2.3 mm and 1.0 mm, respectively) under a nitrogen pressure of 0.5 bar. During the extrusion process, the flow rate of the internal coagulant (core liquid) water flowing out of the inner tube was controlled by a flow meter to be 40 mL / min. After extrusion, it passed through an air distance of 2 cm and then entered an external coagulation bath (an alcohol-water solution with an ethanol content of 80 vol%) and was immersed for 24 h for curing and molding. After molding, it was taken out and naturally dried at room temperature to obtain a ceramic membrane blank;

[0034] (4) High temperature firing

[0035] The above-mentioned ceramic membrane body was first heated to 800°C at a rate of 1.5°C / min in a nitrogen atmosphere and kept warm for 1 hour, and then heated to 1250°C at a rate of 3°C / min in an air atmosphere and kept warm for 4 hours; then cooled to 500°C at a rate of 5°C / min, and finally cooled naturally to obtain a 3YSZ / Al2O3 hollow fiber composite ceramic ultrafiltration membrane with an average pore size of 19 nm in the outer separation membrane layer.

[0036] Example 2:

[0037] This embodiment provides a method for controlling the microstructure and pore size of a hollow fiber ceramic membrane, and the steps are as follows:

[0038] (1) Preparation of ceramic base powder

[0039] The ceramic base material is composed of 90 wt% of 3 mol% yttria-stabilized zirconia powder with an average particle size of 0.8 μm and 10 wt% of 1.5 mol% magnesium oxide-doped silicon oxide (SiO2) powder with an average particle size of 30 nm. The ceramic base material powder is obtained by dry mixing in a mixer for 4 hours according to the composition ratio.

[0040] (2) Preparation of spinning slurry

[0041] Polyethersulfone (PES E2010) particles with a molecular weight of 10,000 to 50,000 are added to an N-methyl-2-pyrrolidone (NMP) solvent and stirred thoroughly to dissolve to obtain a uniform polymer solution; nonionic surfactants polyoxyethylene sorbitan monopalmitate (Tween 40) and polyethylene glycol (PEG600) are added to the polymer solution and stirred thoroughly to dissolve, and then the ceramic base material powder is slowly added and stirred thoroughly to obtain a spinning slurry; the contents of the polyethersulfone, N-methyl-2-pyrrolidone, polyoxyethylene sorbitan monopalmitate, polyethylene glycol, and ceramic base material powder in the spinning slurry are 7.5 wt%, 40 wt%, 1 wt%, 1.5 wt%, and 50 wt%, respectively;

[0042] (3) Dry / wet spinning

[0043] The above spinning slurry was loaded into a stainless steel slurry tank in a spinning forming device, and after vacuum degassing, it was extruded at a speed of 2 cm / s through a spinneret with an inner tube (outer diameter and inner diameter were 2.3 mm and 1.0 mm, respectively) under a nitrogen pressure of 0.6 bar. During the extrusion process, the flow rate of the internal coagulant (core liquid) water flowing out of the inner tube was controlled by a flow meter to be 50 mL / min. After extrusion, it passed through an air distance of 2 cm and then entered an external coagulation bath (an alcohol-water solution with an ethanol content of 80 vol%) and was immersed for 24 h for curing and molding. After molding, it was taken out and naturally dried at room temperature to obtain a ceramic membrane blank;

[0044] (4) High temperature firing

[0045] The above-mentioned ceramic membrane blank was first heated to 800°C at a rate of 1.5°C / min in a nitrogen atmosphere and kept warm for 1 hour, and then heated to 1150°C at a rate of 3°C / min in an air atmosphere and kept warm for 3 hours; then cooled to 300°C at a rate of 5°C / min, and finally cooled naturally to obtain a 3YSZ / SiO2 hollow fiber composite ceramic ultrafiltration membrane with an average pore size of 9 nm in the outer separation membrane layer.

[0046] Example 3:

[0047] This embodiment provides a method for controlling the microstructure and pore size of a hollow fiber ceramic membrane, and the steps are as follows:

[0048] (1) Preparation of ceramic base powder

[0049] The ceramic base material is composed of 83 wt% of 3 mol% yttria-stabilized zirconia powder with an average particle size of 0.6 μm and 17 wt% of titanium oxide (TiO2) powder with an average particle size of 18 nm. The ceramic base material powder is obtained by dry mixing in a mixer for 4 hours according to the composition ratio.

[0050] (2) Preparation of spinning slurry

[0051] Polyethersulfone (PES E2010) particles with a molecular weight of 10,000 to 50,000 are added to an N-methyl-2-pyrrolidone (NMP) solvent and stirred thoroughly to dissolve to obtain a uniform polymer solution; nonionic surfactants polyoxyethylene sorbitan monopalmitate (Tween 40) and polyethylene glycol (PEG600) are added to the polymer solution and stirred thoroughly to dissolve, and then the ceramic base material powder is slowly added and stirred thoroughly to obtain a spinning slurry; the contents of the polyethersulfone, N-methyl-2-pyrrolidone, polyoxyethylene sorbitan monopalmitate, polyethylene glycol, and ceramic base material powder in the spinning slurry are 7 wt%, 38 wt%, 1 wt%, 1.5 wt%, and 52.5 wt%, respectively;

[0052] (3) Dry / wet spinning

[0053] The above spinning slurry was loaded into a stainless steel slurry tank in a spinning forming device, and after vacuum degassing, it was extruded at a speed of 2 cm / s through a spinneret with an inner tube (outer diameter and inner diameter were 2.3 mm and 1.0 mm, respectively) under a nitrogen pressure of 0.7 bar. During the extrusion process, the flow rate of the internal coagulant (core liquid) water flowing out of the inner tube was controlled by a flow meter to be 50 mL / min. After extrusion, it passed through an air distance of 2 cm and then entered an external coagulation bath (an alcohol-water solution with an ethanol content of 75 vol%) and was immersed for 24 hours for curing and molding. After molding, it was taken out and naturally dried at room temperature to obtain a ceramic membrane blank;

[0054] (4) High temperature firing

[0055] The above-mentioned ceramic membrane body was first heated to 800°C at 1.5°C / min in a nitrogen atmosphere and kept warm for 1 hour, and then heated to 1100°C at 3°C / min in an air atmosphere and kept warm for 5 hours; then cooled to 500°C at 5°C / min, and finally cooled naturally to obtain a 3YSZ / TiO2 hollow fiber composite ceramic ultrafiltration membrane with an average pore size of 5nm in the outer separation membrane layer.

[0056] like Figure 1 and Figure 2 As shown, the hollow fiber composite ceramic ultrafiltration membrane prepared by the present invention presents an asymmetric structure, and its cross-section is mainly composed of inner and outer skin layers and a support layer with long finger-like holes in the middle, that is, the inner side of the membrane is a large-pore porous inner skin layer formed by the accumulation of small particles, the middle is a support layer formed by the accumulation of large particles and having finger-like holes, and the outer side of the membrane is a small-pore porous outer skin layer formed by the accumulation of nanoparticles and serving as a separation membrane layer; the surface of the outer separation membrane layer presents a uniform porous structure.

[0057] The structural parameters and physical properties of the small-pore hollow fiber composite ceramic ultrafiltration membranes prepared in Examples of the present invention are shown in Table 1. Ultrafiltration membranes of varying pore sizes all exhibit advantages such as a narrow pore size distribution, high porosity, and high pure water permeation flux. Due to the high open porosity of the separation layer of the ultrafiltration membrane prepared by the present invention, its pure water permeation flux is more than twice that of a multilayer ceramic ultrafiltration membrane with a similar pore size prepared by conventional methods.

[0058] Table 1 Structural parameters and physical properties of the hollow fiber composite ceramic ultrafiltration membrane prepared in the embodiment of the present invention

[0059]

Claims

1. A method for regulating the microstructure and pore size of a hollow fiber ceramic membrane, characterized in that The following steps are involved: (1) Preparation of ceramic base powder The ceramic base material is composed of 80-90 wt% of 3 mol% yttria-stabilized zirconia micropowder and 10-20 wt% of nano-oxide powder; wherein the nano-oxide powder is aluminum oxide, silicon oxide, or titanium oxide powder, and the average particle size of the 3 mol% yttria-stabilized zirconia micropowder is more than 20 times the average particle size of the nano-oxide powder; the ceramic base materials are dry-mixed in a mixer according to the composition ratio to obtain ceramic base material powder; (2) Preparation of spinning slurry Adding polyethersulfone particles to an N-methyl-2-pyrrolidone solvent and dissolving them to obtain a polymer solution; adding a nonionic surfactant to the polymer solution and dissolving it, and then adding the ceramic base material powder and stirring and mixing uniformly to obtain a spinning slurry; the contents of the polyethersulfone, N-methyl-2-pyrrolidone, nonionic surfactant, and ceramic base material powder in the spinning slurry are 7-10 wt%, 36-40 wt%, 1-2.5 wt%, and 48-55 wt%, respectively; (3) Dry / wet spinning The spinning slurry is loaded into a spinning forming device, and after vacuum degassing, it is extruded through a spinneret with an internal insert under a nitrogen pressure of 0.2 to 1 bar, and immersed in an external coagulation bath for solidification and forming. After forming, it is taken out and naturally dried at room temperature to obtain a ceramic membrane body; (4) High temperature firing The ceramic membrane blank is first heated to 800-850°C at a rate of 1-2°C / min in a nitrogen atmosphere and kept warm for 1-2 hours, then heated to 1100-1300°C at a rate of 2-4°C / min in an air atmosphere and kept warm for 2-5 hours; then cooled to 300-500°C at a rate of 5°C / min, and finally cooled naturally to obtain a small-pore hollow fiber composite ceramic ultrafiltration membrane with an average pore diameter of the separation membrane layer ≤20nm.

2. The method for controlling the microstructure and pore size of a hollow fiber ceramic membrane according to claim 1, wherein: In the step (1), the average particle size of the 3 mol% yttria-stabilized zirconia powder is 0.5-1.5 μm, and the average particle sizes of the aluminum oxide, silicon oxide, and titanium oxide powders are 30-100 nm, 20-50 nm, and 5-20 nm, respectively.

3. The method for controlling the microstructure and pore size of a hollow fiber ceramic membrane according to claim 1 or 2, characterized in that: The silicon oxide powder is 1.5 mol % magnesium oxide doped silicon oxide powder.

4. The method for controlling the microstructure and pore size of a hollow fiber ceramic membrane according to claim 1, wherein: In the step (1), the dry mixing is performed by a mixer for 3 to 4 hours.

5. The method for controlling the microstructure and pore size of a hollow fiber ceramic membrane according to claim 1, wherein: The molecular weight of the polyethersulfone in step (2) is 10,000 to 50,000; the nonionic surfactant is a combination of polyoxyethylene sorbitan monolaurate or polyoxyethylene sorbitan monopalmitate and polyethylene glycol.

6. The method for controlling the microstructure and pore size of a hollow fiber ceramic membrane according to claim 1, wherein: The internal coagulant in the inner tube of step (3) is water, and its outflow rate is 30 to 80 mL / min; the extrusion speed of the spinning slurry is 1.7 to 2.2 cm / s, and after extrusion, it enters the external coagulation bath through an air distance of 2 to 3 cm; the external coagulation bath is an alcohol-water solution with an ethanol content of 70 to 80 vol%, and the immersion time is 12 to 24 hours.

7. A product obtained by using the method for controlling the microstructure and pore size of a hollow fiber ceramic membrane according to any one of claims 1 to 6, characterized in that: It is a hollow fiber composite ceramic ultrafiltration membrane with an asymmetric structure. The inner side of the membrane is a large-pore porous inner layer formed by the accumulation of small particles, the middle is a support layer formed by the accumulation of large particles and has finger-like pores, and the outer side of the membrane is a small-pore porous outer layer formed by the accumulation of nanoparticles, which serves as the separation membrane layer.

8. The product according to claim 7, characterized in that: The average pore size of the surface separation membrane layer of the hollow fiber composite ceramic ultrafiltration membrane is 5 to 20 nm, the maximum pore size does not exceed 1.5 times the average pore size, the thickness is 0.5 to 2 μm, the membrane porosity is 45 to 52.5%, the bending strength of the ceramic ultrafiltration membrane is 90 to 116 MPa, and the pure water flux is 151 to 447 LMH / bar.

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