Hollow fiber ultrafiltration membrane and its preparation method and application

Abstract

The present invention relates to hollow fiber ultrafiltration membrane and its preparation method and application, wherein, the preparation method of hollow fiber ultrafiltration membrane comprises the following steps: high molecular polymer, porogen and diluent are configured to homogeneous casting solution, porogen includes aldehyde compound and metal chloride, and metal chloride is selected from at least one of calcium chloride, magnesium chloride, ferric chloride, and cupric chloride; melamine, hydroxide and water are configured to core liquid, and the pH value of core liquid is 10-13; Casting solution and core liquid are extruded to form hollow fiber membrane embryo, and then the hollow fiber membrane embryo is passed through air section, enters cooling bath and phase separation occurs and solidifies and forms, removes diluent, obtains hollow fiber ultrafiltration membrane, the temperature of cooling bath is 10 DEG C to 20 DEG C, and cooling bath includes sodium hydroxide, urea, cellulose and water. The hollow fiber ultrafiltration membrane prepared by this preparation method has high pressure resistance and water flux, and simultaneously has excellent anti-pollution performance, can be better applied to water treatment.

Description

Technical Field

[0001] The present invention relates to the technical field of water treatment membranes, in particular to a hollow fiber ultrafiltration membrane and a preparation method and application thereof. Background Art

[0002] Existing polysulfone or polyethersulfone hollow fiber membranes are mostly produced using a non-solvent-induced phase separation method. However, this method typically involves adding a large proportion of solvent to the casting solution, resulting in large finger-like pores within the hollow fiber membranes. This poorly withstands pressure and results in a thick, dense cortex, which in turn reduces water flux. Furthermore, existing hollow fiber membranes also suffer from poor anti-fouling properties. Summary of the Invention

[0003] Based on this, it is necessary to provide a hollow fiber ultrafiltration membrane and its preparation method and application to address the above problems. The hollow fiber ultrafiltration membrane prepared by this preparation method has high pressure resistance and water flux, and at the same time has excellent anti-pollution performance, and can be better used in water treatment.

[0004] A method for preparing a hollow fiber ultrafiltration membrane comprises the following steps:

[0005] A high molecular weight polymer, a porogen, and a diluent are prepared into a homogeneous casting solution, wherein the porogen comprises an aldehyde compound and a metal chloride, and the metal chloride is selected from at least one of calcium chloride, magnesium chloride, ferric chloride, and copper chloride;

[0006] preparing a core liquid with melamine, hydroxide and water, wherein the pH value of the core liquid is 10-13;

[0007] The casting liquid and the core liquid are extruded to form a hollow fiber membrane embryo, and then the hollow fiber membrane embryo passes through an air section and enters a cooling bath to undergo phase separation and solidification, and the diluent is removed to obtain a hollow fiber ultrafiltration membrane, wherein the temperature of the cooling bath is -10°C to -20°C, and the cooling bath includes sodium hydroxide, urea, cellulose and water.

[0008] In one embodiment, the mass fraction of the high molecular weight polymer in the casting solution is 15%-20%;

[0009] And / or, the mass fraction of the porogen in the casting solution is 1.5%-7%;

[0010] And / or, the mass fraction of the aldehyde compound in the casting solution is 1%-3%;

[0011] And / or, the mass fraction of the metal chloride in the casting solution is 0.5%-1%.

[0012] In one embodiment, the mass fraction of melamine in the core liquid is 1%-5%;

[0013] And / or, the mass fraction of the hydroxide in the core liquid is 0.5%-1.5%.

[0014] In one embodiment, the mass fraction of the sodium hydroxide in the cooling bath is 7%-10%;

[0015] And / or, the mass fraction of urea in the cooling bath is 12%-15%;

[0016] And / or, the mass fraction of the cellulose in the cooling bath is 0.5%-2.5%.

[0017] In one embodiment, the high molecular weight polymer is selected from at least one of polysulfone, polyethersulfone, polyetherketone, and polyacrylonitrile;

[0018] And / or, the diluent is at least one selected from N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, and dimethyl sulfoxide;

[0019] And / or, the porogen further comprises an auxiliary agent, wherein the auxiliary agent is selected from at least one of polyvinyl pyrrolidone, alcohols, lithium chloride, and potassium chloride;

[0020] And / or, the aldehyde compound is at least one selected from formaldehyde, acetaldehyde, glyoxal, and glutaraldehyde.

[0021] In one embodiment, the hydroxide is selected from sodium hydroxide and / or potassium hydroxide;

[0022] And / or, the core liquid further includes an additive, and the additive is selected from at least one of N,N-dimethylformamide, N,N-dimethylacetamide, glycerol, N-methylpyrrolidone, ethanol, and dimethyl sulfoxide.

[0023] In one embodiment, the mass fraction of the additive in the core liquid is 1.5%-6.5%.

[0024] In one embodiment, the method for preparing the casting solution comprises the following steps: mixing the polymer, the porogen, and the diluent, stirring and dissolving them at 120° C.-160° C. for 20 h-50 h, and then vacuum degassing at 120° C.-160° C. for 8 h-10 h to obtain the casting solution;

[0025] And / or, the length of the air segment is 15 cm-20 cm.

[0026] A hollow fiber ultrafiltration membrane is prepared by the hollow fiber ultrafiltration membrane preparation method as described above.

[0027] An application of the hollow fiber ultrafiltration membrane as described above in water treatment equipment.

[0028] In the preparation method of the hollow fiber ultrafiltration membrane of the present invention, in the process of extruding the casting liquid and the core liquid to form a hollow fiber membrane embryo, the casting liquid and the core liquid are in contact, and the aldehyde compounds in the casting liquid and the melamine in the core liquid undergo a condensation reaction under alkaline conditions to form a porous network structure polymer. The porous network structure polymer will be interspersed in the hollow fiber membrane embryo, which can effectively regulate the pore size distribution of the hollow fiber ultrafiltration membrane, thereby effectively improving the pressure resistance of the hollow fiber ultrafiltration membrane and helping to improve the water flux of the hollow fiber ultrafiltration membrane; at the same time, the metal chloride in the casting liquid will also react with the hydroxide in the core liquid to generate nanoparticles And dispersed in the hollow fiber membrane embryo, the presence of the nanoparticles can effectively increase the water production channel of the hollow fiber ultrafiltration membrane, further improving the water flux of the hollow fiber ultrafiltration membrane; at the same time, in the cooling bath, the porogen and diluent in the casting solution will diffuse into the cooling bath, causing the high molecular polymer to precipitate and solidify into a shape, so that the hollow fiber membrane embryo forms a hollow fiber ultrafiltration membrane, and in this process, since the cooling bath is a cellulose solution, the surface of the hollow fiber ultrafiltration membrane can be coated with a cellulose layer, achieving hydrophilic modification of the hollow fiber ultrafiltration membrane, thereby improving the hydrophilic properties of the hollow fiber ultrafiltration membrane, thereby improving the anti-pollution performance of the hollow fiber ultrafiltration membrane. Therefore, the hollow fiber ultrafiltration membrane prepared by the present invention has high pressure resistance and water flux, and at the same time has excellent anti-pollution performance, and can be better applied to water treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0030] Figure 1 This is an electron microscope image of the hollow fiber ultrafiltration membrane prepared in Example 1 of the present invention;

[0031] Figure 2 for Figure 1 A partial enlarged view of the hollow fiber ultrafiltration membrane;

[0032] Figure 3 This is an electron microscope image of the hollow fiber ultrafiltration membrane prepared in Comparative Example 1 of the present invention;

[0033] Figure 4 This is an electron microscope image of the hollow fiber ultrafiltration membrane prepared in Comparative Example 3 of the present invention;

[0034] Figure 5 This is an electron microscope image of the hollow fiber ultrafiltration membrane prepared in Comparative Example 4 of the present invention;

[0035] Figure 6 This is an electron microscope image of the hollow fiber ultrafiltration membrane prepared in Comparative Example 5 of the present invention;

[0036] Figure 7 This is an electron microscope image of the hollow fiber ultrafiltration membrane prepared in Comparative Example 10 of the present invention. DETAILED DESCRIPTION

[0037] To facilitate understanding of the present invention, the present invention will be described in more detail below. However, it should be understood that the present invention can be implemented in many different forms and is not limited to the embodiments or examples described herein. On the contrary, the purpose of providing these embodiments or examples is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0038] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art of the technical field of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments or embodiments and are not intended to limit the present invention. The optional scope of the term "and / or" used herein includes any one of two or more related listed items, and also includes any and all combinations of related listed items, including any two related listed items, any more related listed items, or the combination of all related listed items.

[0039] The method for preparing a hollow fiber ultrafiltration membrane provided by the present invention comprises the following steps:

[0040] A high molecular weight polymer, a porogen, and a diluent are prepared into a homogeneous casting solution, wherein the porogen comprises an aldehyde compound and a metal chloride, and the metal chloride is selected from at least one of calcium chloride, magnesium chloride, ferric chloride, and copper chloride;

[0041] preparing a core liquid with melamine, hydroxide and water, wherein the pH value of the core liquid is 10-13;

[0042] The casting liquid and the core liquid are extruded to form a hollow fiber membrane embryo, and then the hollow fiber membrane embryo passes through an air section and enters a cooling bath to undergo phase separation and solidification, and the diluent is removed to obtain a hollow fiber ultrafiltration membrane, wherein the temperature of the cooling bath is -10°C to -20°C, and the cooling bath includes sodium hydroxide, urea, cellulose and water.

[0043] In the present invention, a thermally induced phase separation method is adopted to prepare a hollow fiber ultrafiltration membrane. Specifically, in the process of extruding the casting liquid and the core liquid to form a hollow fiber membrane embryo, the casting liquid and the core liquid are in contact. Since the pH value of the core liquid is 10-13, the aldehyde compounds in the casting liquid can undergo a condensation reaction with the melamine in the core liquid to form a porous network structure polymer. The porous network structure polymer will be interspersed in the hollow fiber membrane embryo, which can effectively regulate the pore size distribution of the hollow fiber ultrafiltration membrane and increase its porosity, thereby effectively improving the pressure resistance of the hollow fiber ultrafiltration membrane and helping to improve the water flux of the hollow fiber ultrafiltration membrane; at the same time, the metal chloride in the casting liquid will also react with the hydroxide in the core liquid to generate nanoparticles and disperse in the hollow fiber membrane embryo. The presence of the nanoparticles can effectively increase the water production channel of the hollow fiber ultrafiltration membrane and further improve the water flux of the hollow fiber ultrafiltration membrane.

[0044] When the hollow fiber membrane embryo passes through the air section and enters the cooling bath for phase separation and solidification, in the cooling bath, the porogen and diluent in the casting liquid will diffuse into the cooling bath, causing the high molecular polymer to precipitate and solidify into shape, so that the hollow fiber membrane embryo forms a hollow fiber ultrafiltration membrane with higher porosity. At the same time, in this process, since the cooling bath is a cellulose solution, cellulose will adhere to the surface of the hollow fiber ultrafiltration membrane to form a cellulose layer due to the hydrophilic and insoluble characteristics of cellulose in water, thereby realizing the hydrophilic modification of the hollow fiber ultrafiltration membrane, thereby improving the hydrophilic properties of the hollow fiber ultrafiltration membrane, thereby improving the anti-pollution performance of the hollow fiber ultrafiltration membrane.

[0045] Therefore, the hollow fiber ultrafiltration membrane prepared by the present invention has high pressure resistance and water flux, and also has excellent anti-pollution performance, and can be better applied in water treatment.

[0046] Optionally, the mass fraction of the high molecular weight polymer in the casting solution is 15%-20%. With this configuration, the membrane structure and performance of the hollow fiber ultrafiltration membrane can be adjusted by regulating the amount of the high molecular weight polymer.

[0047] Furthermore, the high molecular polymer is selected from at least one of polysulfone, polyethersulfone, polyetherketone and polyacrylonitrile, preferably polysulfone and / or polyethersulfone; such an arrangement is conducive to improving the mechanical properties and chemical resistance of the hollow fiber ultrafiltration membrane.

[0048] Optionally, the mass fraction of the porogen in the casting solution is 1.5%-7%; by such a setting, the porosity of the hollow fiber ultrafiltration membrane can be regulated by adjusting the dosage of the porogen, thereby improving the continuity of the hollow fiber ultrafiltration membrane pores and further improving the water flux of the hollow fiber ultrafiltration membrane.

[0049] Optionally, the mass fraction of the aldehyde compound in the casting liquid is 1%-3%; the mass fraction of the melamine in the core liquid is 1%-5%; such an arrangement, by controlling the amount of the aldehyde compound in the casting liquid and the melamine in the core liquid, is conducive to allowing the aldehyde compound and melamine to undergo sufficient condensation polymerization to generate a polymer with a porous network structure, which can better adjust the membrane structure of the hollow fiber ultrafiltration membrane, thereby improving the mechanical properties and water flux of the hollow fiber ultrafiltration membrane.

[0050] Furthermore, the aldehyde compound is selected from at least one of formaldehyde, acetaldehyde, glyoxal, and glutaraldehyde.

[0051] In the present invention, the porogen further includes an auxiliary agent, and the auxiliary agent is selected from at least one of polyvinyl pyrrolidone, alcohols, lithium chloride, and potassium chloride.

[0052] In one embodiment, the mass fraction of the auxiliary agent in the casting solution is 1%-3%.

[0053] Optionally, the diluent is selected from at least one of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, and dimethyl sulfoxide.

[0054] Optionally, the mass fraction of the metal chloride in the casting liquid is 0.5%-1%; the mass fraction of the hydroxide in the core liquid is 0.5%-1.5%; with such an arrangement, by controlling the amount of metal chloride in the casting liquid and the amount of hydroxide in the core liquid, the amount of nanoparticles formed can be controlled, which is conducive to better dispersion of the nanoparticles in the hollow fiber ultrafiltration membrane, further improving the water flux of the hollow fiber ultrafiltration membrane; at the same time, by controlling the amount of hydroxide in the core liquid, the pH value of the core liquid can also be better regulated, further ensuring the condensation reaction between melamine in the core liquid and the aldehyde compounds in the casting liquid.

[0055] Furthermore, the hydroxide is selected from sodium hydroxide and / or potassium hydroxide.

[0056] In the present invention, the core liquid further comprises an additive, and the additive is selected from at least one of N,N-dimethylformamide, N,N-dimethylacetamide, glycerol, N-methylpyrrolidone, ethanol, and dimethyl sulfoxide.

[0057] Furthermore, the mass fraction of the additive in the core liquid is 1.5%-6.5%.

[0058] Optionally, the mass fraction of the cellulose in the cooling bath is 0.5%-2.5%; such a setting is conducive to forming a uniform hydrophilic cellulose layer on the surface of the hollow fiber ultrafiltration membrane, further improving the hydrophilicity of the hollow fiber ultrafiltration membrane, and then better improving the anti-pollution performance of the hollow fiber ultrafiltration membrane.

[0059] Optionally, the mass fraction of the sodium hydroxide in the cooling bath is 7%-10%; the mass fraction of the urea in the cooling bath is 12%-15%. Such an arrangement can better achieve rapid dissolution of cellulose to form a stable cellulose solution.

[0060] In the present invention, the preparation method of the casting solution comprises the following steps: mixing the high molecular weight polymer, the porogen and the diluent, stirring and dissolving them at 120°C-160°C for 20h-50h, and then vacuum degassing at 120°C-160°C for 8h-10h to obtain the casting solution.

[0061] In one embodiment, the stirring speed is 80 rpm-120 rpm.

[0062] In one embodiment, the high molecular weight polymer is in a dry state. This configuration can avoid the influence of the water contained in the high molecular weight polymer on the composition of the casting solution.

[0063] Optionally, the length of the air segment is 15cm-20cm.

[0064] In one embodiment, the diluent is removed using an extractant. Specifically, the solidified hollow fiber ultrafiltration membrane is immersed in the extractant to extract the diluent. The extractant is preferably water. It is understood that unreacted porogen can also be removed during this process, resulting in a clean hollow fiber ultrafiltration membrane.

[0065] In one embodiment, the casting solution and the core solution are injected into a cannulated spinneret using a dry-wet spinning device, and are extruded from the spinneret together to form a hollow fiber membrane embryo, wherein the spinning speed is 16 m / min-18 m / min.

[0066] In one embodiment, before the casting solution and the core solution are extruded to form the hollow fiber membrane embryo, the casting solution is filtered using a filter screen with 250-350 meshes.

[0067] The present invention also provides a hollow fiber ultrafiltration membrane prepared using the above-described method for preparing a hollow fiber ultrafiltration membrane. The hollow fiber ultrafiltration membrane has high pressure resistance and water flux, as well as excellent anti-pollution properties, and can be better applied in water treatment.

[0068] In addition, the present invention also provides a use of the hollow fiber ultrafiltration membrane as described above in water treatment equipment.

[0069] In one embodiment, the water treatment device may be a water purification device.

[0070] The hollow fiber ultrafiltration membrane, its preparation method, and its application are further described below by the following specific examples. However, those skilled in the art will understand that the following examples are merely illustrative of the present invention and should not be construed as limiting the scope of the present invention. Where specific conditions are not specified in the examples, the experiments were carried out under conventional conditions or conditions recommended by the manufacturer. Reagents or instruments used, for which the manufacturer is not specified, are all commercially available conventional products.

[0071] Example 1

[0072] Polysulfone (dry state), formaldehyde, magnesium chloride and N,N-dimethylformamide are placed in a stirring tank, and then stirred at 130°C and a rotation speed of 100 rpm for 20 hours, and then vacuum degassed at 120°C for 10 hours to obtain a homogeneous casting liquid, wherein the mass fraction of the polysulfone in the casting liquid is 18%, the mass fraction of the formaldehyde is 2%, and the mass fraction of the magnesium chloride is 0.7%; melamine, sodium hydroxide and water are prepared into a core liquid, wherein the mass fraction of the melamine in the core liquid is 3%, the mass fraction of the sodium hydroxide is 1%, and the pH value of the core liquid is about 12.5; sodium hydroxide, urea, cellulose and water are prepared into a cooling bath, wherein the mass fraction of the sodium hydroxide in the cooling bath is 8%, the mass fraction of the urea is 13%, the mass fraction of the cellulose is 1.2%, and the temperature of the cooling bath is controlled to be -15°C.

[0073] The casting solution and core solution obtained above were injected into a cannulated spinneret by dry-wet spinning equipment, and extruded from the spinneret together to form a hollow fiber membrane embryo, wherein the spinning speed was 18m / min; the hollow fiber membrane embryo passed through a 15cm air section, entered a -15℃ cooling bath to undergo phase separation and solidification, and finally immersed in 40℃ pure water for extraction treatment for 36h to obtain the following Figure 1-Figure 2 The hollow fiber ultrafiltration membrane shown.

[0074] Example 2

[0075] Polyethersulfone (dry state), glyoxal, calcium chloride and N,N-dimethylacetamide are placed in a stirring tank, and then stirred at 120°C and a rotation speed of 100 rpm for 30 hours, and then vacuum degassed at 140°C for 9 hours to obtain a homogeneous casting solution, wherein, in the casting solution, the mass fraction of the polyethersulfone is 15%, the mass fraction of the glyoxal is 1%, and the mass fraction of the calcium chloride is 0.5%; melamine, potassium hydroxide and water are prepared into a core liquid, wherein, in the core liquid, the mass fraction of the melamine is 1%, the mass fraction of the potassium hydroxide is 0.5%, and the pH value of the core liquid is about 10; sodium hydroxide, urea, cellulose and water are prepared into a cooling bath, wherein, in the cooling bath, the mass fraction of the sodium hydroxide is 7%, the mass fraction of the urea is 12%, the mass fraction of the cellulose is 0.5%, and the temperature of the cooling bath is controlled to be -10°C.

[0076] The casting liquid and core liquid obtained above were injected into a tube-type spinneret by means of a dry-wet spinning device, and extruded from the spinneret together to form a hollow fiber membrane embryo, wherein the spinning speed was 18 m / min; the hollow fiber membrane embryo passed through an 18 cm air section, entered a -10°C cooling bath to undergo phase separation and solidification, and finally immersed in 40°C pure water for extraction treatment for 36 hours to obtain a hollow fiber ultrafiltration membrane.

[0077] Example 3

[0078] Polyether ketone (dry state), glutaraldehyde, ferric chloride and dimethyl sulfoxide are placed in a stirring tank, and then stirred at 160°C at a rotation speed of 100 rpm for 25 hours, and then vacuum degassed at 160°C for 8 hours to obtain a homogeneous casting liquid, wherein, in the casting liquid, the mass fraction of the polyether ketone is 20%, the mass fraction of the glutaraldehyde is 3%, and the mass fraction of the ferric chloride is 1%; melamine, sodium hydroxide and water are prepared into a core liquid, wherein, in the core liquid, the mass fraction of the melamine is 5%, the mass fraction of the sodium hydroxide is 1.5%, and the pH value of the core liquid is about 13; sodium hydroxide, urea, cellulose and water are prepared into a cooling bath, wherein, in the cooling bath, the mass fraction of the sodium hydroxide is 10%, the mass fraction of the urea is 15%, the mass fraction of the cellulose is 2.5%, and the temperature of the cooling bath is controlled to be -20°C.

[0079] The casting liquid and core liquid obtained above were injected into a tube-type spinneret by means of a dry-wet spinning device, and extruded from the spinneret together to form a hollow fiber membrane embryo, wherein the spinning speed was 18 m / min; the hollow fiber membrane embryo passed through a 20 cm air section, entered a -20°C cooling bath to undergo phase separation and solidification, and finally immersed in 40°C pure water for extraction treatment for 36 hours to obtain a hollow fiber ultrafiltration membrane.

[0080] Example 4

[0081] Compared with Example 1, Example 4 differs only in that the mass fraction of polysulfone in the casting solution is 12%, and other conditions are the same to obtain a hollow fiber ultrafiltration membrane.

[0082] Example 5

[0083] Compared with Example 1, Example 5 differs only in that the mass fraction of polysulfone in the casting solution is 25%, and other conditions are the same to obtain a hollow fiber ultrafiltration membrane.

[0084] Example 6

[0085] Compared with Example 1, Example 6 differs only in that the mass fraction of formaldehyde in the casting solution is 0.05%, and the other conditions are the same to obtain a hollow fiber ultrafiltration membrane.

[0086] Example 7

[0087] Compared with Example 1, Example 7 differs only in that the mass fraction of formaldehyde in the casting solution is 5%, and the other conditions are the same, thereby obtaining a hollow fiber ultrafiltration membrane.

[0088] Example 8

[0089] Compared with Example 1, Example 8 differs only in that the mass fraction of magnesium chloride in the casting solution is 0.1%, and other conditions are the same to obtain a hollow fiber ultrafiltration membrane.

[0090] Example 9

[0091] Compared with Example 1, Example 9 differs only in that the mass fraction of the magnesium chloride in the casting solution is 2%, and the other conditions are the same, thereby obtaining a hollow fiber ultrafiltration membrane.

[0092] Example 10

[0093] Compared with Example 1, Example 10 differs only in that the mass fraction of melamine in the core liquid is 0.1%, and other conditions are the same to obtain a hollow fiber ultrafiltration membrane.

[0094] Example 11

[0095] Compared with Example 1, Example 11 differs only in that the mass fraction of melamine in the core liquid is 6%, and other conditions are the same to obtain a hollow fiber ultrafiltration membrane.

[0096] Example 12

[0097] Compared with Example 1, Example 12 differs only in that the mass fraction of the sodium hydroxide in the core liquid is 0.1%, and the other conditions are the same to obtain a hollow fiber ultrafiltration membrane.

[0098] Example 13

[0099] Compared with Example 1, Example 13 differs only in that the mass fraction of the sodium hydroxide in the core liquid is 2%, and the other conditions are the same to obtain a hollow fiber ultrafiltration membrane.

[0100] Example 14

[0101] Example 14 is different from Example 1 only in that the mass fraction of the sodium hydroxide in the cooling bath is 6%, and the other conditions are the same to obtain a hollow fiber ultrafiltration membrane.

[0102] Example 15

[0103] Compared with Example 1, Example 15 differs only in that the mass fraction of urea in the cooling bath is 10%, and other conditions are the same to obtain a hollow fiber ultrafiltration membrane.

[0104] Example 16

[0105] Compared with Example 1, Example 16 differs only in that the mass fraction of the cellulose in the cooling bath is 0.1%, and other conditions are the same to obtain a hollow fiber ultrafiltration membrane.

[0106] Example 17

[0107] Compared with Example 1, Example 17 differs only in that the mass fraction of the cellulose in the cooling bath is 3%, and the other conditions are the same, thereby obtaining a hollow fiber ultrafiltration membrane.

[0108] Example 18

[0109] Compared with Example 1, Example 18 differs only in that, in the step of preparing the casting solution, the casting solution also contains lithium chloride, and the mass fraction of the lithium chloride in the casting solution is 1%. Other conditions are the same, and a hollow fiber ultrafiltration membrane is obtained.

[0110] Example 19

[0111] Compared with Example 1, Example 19 differs only in that, in the step of preparing the core liquid, the core liquid also contains N,N-dimethylformamide, and the mass fraction of N,N-dimethylformamide in the core liquid is 1.5%. The other conditions are the same, and a hollow fiber ultrafiltration membrane is obtained.

[0112] Example 20

[0113] Compared with Example 1, Example 20 differs only in that, in the step of preparing the core liquid, the core liquid also contains glycerol, and the mass fraction of the glycerol in the core liquid is 6.5%. The other conditions are the same, and a hollow fiber ultrafiltration membrane is obtained.

[0114] Comparative Example 1

[0115] Comparative Example 1 is different from Example 1 only in that, in the step of preparing the casting solution, the casting solution does not contain formaldehyde, and the other conditions are the same, and the following is obtained: Figure 3 The hollow fiber ultrafiltration membrane shown.

[0116] Comparative Example 2

[0117] Comparative Example 2 is different from Example 1 only in that potassium chloride is used instead of magnesium chloride in the step of preparing the casting solution, and the other conditions are the same to obtain a hollow fiber ultrafiltration membrane.

[0118] Comparative Example 3

[0119] Comparative Example 3 is different from Example 1 only in that, in the step of preparing the casting solution, the casting solution does not contain magnesium chloride, and the other conditions are the same, and the following is obtained: Figure 4 The hollow fiber ultrafiltration membrane shown.

[0120] Comparative Example 4

[0121] Comparative Example 4 is different from Example 1 only in that, in the step of preparing the core liquid, the core liquid does not contain melamine, and the other conditions are the same, and the following is obtained: Figure 5 The hollow fiber ultrafiltration membrane shown.

[0122] Comparative Example 5

[0123] Comparative Example 5 is different from Example 1 only in that, in the step of preparing the core liquid, the core liquid does not contain sodium hydroxide, and the pH value of the core liquid is about 6.3. The other conditions are the same, and the following is obtained: Figure 6 The hollow fiber ultrafiltration membrane shown.

[0124] Comparative Example 6

[0125] Comparative Example 6 is different from Example 1 only in that, in the step of preparing the core liquid, the mass fraction of sodium hydroxide in the core liquid is 0.05%, and the pH value of the core liquid is about 8. Other conditions are the same, and a hollow fiber ultrafiltration membrane is obtained.

[0126] Comparative Example 7

[0127] Comparative Example 7 is different from Example 1 only in that, in the step of preparing the core liquid, the mass fraction of sodium hydroxide in the core liquid is 2%, and the pH value of the core liquid is about 13.8. Other conditions are the same, and a hollow fiber ultrafiltration membrane is obtained.

[0128] Comparative Example 8

[0129] Comparative Example 8 is different from Example 1 only in that, in the step of preparing the cooling bath, the cooling bath does not contain sodium hydroxide, urea, or cellulose. Other conditions are the same, and a hollow fiber ultrafiltration membrane is obtained.

[0130] Comparative Example 9

[0131] Comparative Example 9 is different from Example 1 only in that, in the step of preparing the cooling bath, the cooling bath does not contain sodium hydroxide, and the other conditions are the same to obtain a hollow fiber ultrafiltration membrane.

[0132] Comparative Example 10

[0133] Comparative Example 10 is different from Example 1 only in that, in the step of preparing the cooling bath, the cooling bath does not contain urea, and the other conditions are the same, and the following is obtained: Figure 7 The hollow fiber ultrafiltration membrane shown.

[0134] Comparative Example 11

[0135] Comparative Example 11 is different from Example 1 only in that, in the step of preparing the cooling bath, the cooling bath does not contain cellulose. Other conditions are the same, and a hollow fiber ultrafiltration membrane is obtained.

[0136] Comparative Example 12

[0137] Comparative Example 12 is different from Example 1 only in that the temperature of the cooling bath is -5°C, and the other conditions are the same to obtain a hollow fiber ultrafiltration membrane.

[0138] The inner diameter, outer diameter, porosity, dense cortex thickness, water flux, rejection rate, pressure resistance, and anti-pollution performance of the hollow fiber ultrafiltration membranes prepared in Examples 1-20 and Comparative Examples 1-12 were tested, respectively. The test results are shown in Table 1-2. The specific test methods are as follows:

[0139] Inner diameter and outer diameter testing: tested using a scanning electron microscope.

[0140] Porosity test: The test is carried out using a scanning electron microscope and multifunctional image analysis software.

[0141] Dense cortex thickness test: tested using a scanning electron microscope.

[0142] Water flux test: The test was conducted using a membrane performance tester, where the test pressure was 0.1 MPa and the inlet water was pure water.

[0143] Pressure resistance performance test: A membrane performance tester is used to perform the bubble point method test. Specifically, one end of the hollow fiber ultrafiltration membrane is sealed with glue, and gas is passed into the other end. The entire hollow fiber ultrafiltration membrane is placed in water, and the pressure is increased. When bubbles appear around the hollow fiber ultrafiltration membrane, the pressure is recorded and determined as the maximum pressure that the hollow fiber ultrafiltration membrane can withstand, that is, the corresponding pressure resistance is obtained.

[0144] Table 1

[0145]

[0146]

[0147] Table 2

[0148]

[0149] At the same time, the anti-pollution performance of the hollow fiber ultrafiltration membranes prepared in Examples 1-20 and Comparative Examples 1-12 was tested respectively. The test conditions were as follows: the hollow fiber ultrafiltration membrane was placed in a 1000 ppm bovine serum albumin solution and placed at 40°C for 30 days. The hollow fiber ultrafiltration membrane was then cleaned and then subjected to a performance test using pure water as the inlet water condition. The test results are shown in Tables 3-4.

[0150] Table 3

[0151]

[0152]

[0153] Table 4

[0154]

[0155] It should be noted that in Tables 1-4, the membrane water flux (F) is calculated by the volume of water passing through the hollow fiber ultrafiltration membrane in a certain period of time, and the formula is: F = V / (A×T), wherein V is the volume of water passing through the hollow fiber ultrafiltration membrane per unit time, A is the effective membrane area, and T is time.

[0156] The calculation formula of the water flux recovery rate is: (pure water flux of the hollow fiber ultrafiltration membrane after pollution / pure water flux of the initial hollow fiber ultrafiltration membrane)×100%.

[0157] from Figure 1-Figure 2 It can be seen from the figure that the pore size distribution of the hollow fiber ultrafiltration membrane prepared in Example 1 of the present invention is relatively uniform and the porosity is relatively high; Figure 3 It can be seen from the figure that the hollow fiber ultrafiltration membrane prepared in Comparative Example 1 does not contain formaldehyde in the casting solution, so it is impossible to form a polymer with a porous network structure, resulting in a low porosity and a small pore size of the hollow fiber ultrafiltration membrane. Figure 4It can be seen that the hollow fiber ultrafiltration membrane prepared in Comparative Example 3 does not contain magnesium chloride in the casting solution, so nanoparticles cannot be formed, resulting in a lower porosity and a denser hollow fiber ultrafiltration membrane, indicating that the formation of nanoparticles has a greater impact on the pores; Figure 5 It can be seen that the hollow fiber ultrafiltration membrane prepared in Comparative Example 4 does not contain melamine in the core liquid, and therefore, a polymer with a porous network structure cannot be formed, resulting in a low porosity and a dense hollow fiber ultrafiltration membrane. Figure 6 It can be seen that the hollow fiber ultrafiltration membrane prepared in Comparative Example 5 does not contain sodium hydroxide in the core liquid, and the core liquid is close to weak acidity, which causes formaldehyde and melamine to be unable to react, resulting in a low porosity of the hollow fiber ultrafiltration membrane; Figure 7 It can be seen that the hollow fiber ultrafiltration membrane prepared in Comparative Example 10 does not contain urea, which causes the cellulose to be insoluble and deposited on the tube wall. In addition, the porosity and pore size of the hollow fiber ultrafiltration membrane are slightly increased.

[0158] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0159] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A method for preparing a hollow fiber ultrafiltration membrane, characterized in that: The steps include: A high molecular weight polymer, a porogen, and a diluent are prepared into a homogeneous casting solution, wherein the porogen comprises an aldehyde compound and a metal chloride, and the metal chloride is selected from at least one of calcium chloride, magnesium chloride, ferric chloride, and copper chloride; preparing a core liquid with melamine, hydroxide and water, wherein the pH value of the core liquid is 10-13; The casting liquid and the core liquid are extruded to form a hollow fiber membrane embryo, and then the hollow fiber membrane embryo passes through an air section and enters a cooling bath to undergo phase separation and solidification, and the diluent is removed to obtain a hollow fiber ultrafiltration membrane, wherein the temperature of the cooling bath is -10°C to -20°C, and the cooling bath includes sodium hydroxide, urea, cellulose and water.

2. The method for preparing a hollow fiber ultrafiltration membrane according to claim 1, wherein: The mass fraction of the high molecular weight polymer in the casting solution is 15%-20%; And / or, the mass fraction of the porogen in the casting solution is 1.5%-7%; And / or, the mass fraction of the aldehyde compound in the casting solution is 1%-3%; And / or, the mass fraction of the metal chloride in the casting solution is 0.5%-1%.

3. The method for preparing a hollow fiber ultrafiltration membrane according to claim 1, wherein: The mass fraction of the melamine in the core liquid is 1%-5%; And / or, the mass fraction of the hydroxide in the core liquid is 0.5%-1.5%.

4. The method for preparing a hollow fiber ultrafiltration membrane according to claim 1, wherein: The mass fraction of the sodium hydroxide in the cooling bath is 7%-10%; And / or, the mass fraction of urea in the cooling bath is 12%-15%; And / or, the mass fraction of the cellulose in the cooling bath is 0.5%-2.5%.

5. The method for preparing a hollow fiber ultrafiltration membrane according to any one of claims 1 to 4, characterized in that: The high molecular polymer is selected from at least one of polysulfone, polyethersulfone, polyetherketone and polyacrylonitrile; And / or, the diluent is at least one selected from N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, and dimethyl sulfoxide; And / or, the porogen further comprises an auxiliary agent, wherein the auxiliary agent is selected from at least one of polyvinyl pyrrolidone, alcohols, lithium chloride, and potassium chloride; And / or, the aldehyde compound is at least one selected from formaldehyde, acetaldehyde, glyoxal, and glutaraldehyde.

6. The method for preparing a hollow fiber ultrafiltration membrane according to any one of claims 1 to 4, characterized in that: The hydroxide is selected from sodium hydroxide and / or potassium hydroxide; And / or, the core liquid further includes an additive, and the additive is selected from at least one of N,N-dimethylformamide, N,N-dimethylacetamide, glycerol, N-methylpyrrolidone, ethanol, and dimethyl sulfoxide.

7. The method for preparing a hollow fiber ultrafiltration membrane according to claim 6, wherein: The mass fraction of the additive in the core liquid is 1.5%-6.5%.

8. The method for preparing a hollow fiber ultrafiltration membrane according to any one of claims 1 to 4, characterized in that: The preparation method of the casting solution comprises the following steps: mixing the high molecular weight polymer, the porogen and the diluent, stirring and dissolving at 120° C.-160° C. for 20 h-50 h, and then vacuum degassing at 120° C.-160° C. for 8 h-10 h to obtain the casting solution; And / or, the length of the air segment is 15 cm-20 cm.

9. A hollow fiber ultrafiltration membrane prepared by the method for preparing a hollow fiber ultrafiltration membrane according to any one of claims 1 to 8.

10. Use of the hollow fiber ultrafiltration membrane according to claim 9 in water treatment equipment.

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