CN112774457B - Polymer microfiltration membrane and preparation method and application thereof - Google Patents
Polymer microfiltration membrane and preparation method and application thereof Download PDFInfo
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Abstract
The invention discloses a polymer microfiltration membrane and a preparation method and application thereof. The surface and the interior of the microfiltration membrane are of three-dimensional network pore structures which are communicated with each other, polymer fibers of the microfiltration membrane are interwoven to form a three-dimensional fiber network structure similar to a loofah sponge structure, and the cross section of the microfiltration membrane is of a structure in which a polymer fiber framework and holes of the same type are distributed along the thickness direction of the membrane. The polymer microfiltration membrane has the characteristics of high penetration, high specific surface area, special wettability and ultralow oil adhesion. The membrane is prepared by taking a high molecular polymer as a material through a method of combining atomization pretreatment and a non-solvent induced phase separation method, and can be used for aspects of gas filtration, liquid filtration, adsorption materials, catalysis, drug slow-release materials, anti-adhesion coatings, oil product delivery, oil spill interception and the like.
Description
Technical Field
The invention relates to the technical field of membrane preparation, in particular to a polymer microfiltration membrane with a loofah sponge-like structure, and a preparation method and application thereof.
Background
Natural nanofibers such as spider silk and silk have received much attention for their excellent properties, but their industrial development is limited due to lack of natural resources. In order to realize the artificial preparation of the nano-fiber, researchers have explored for many years, wherein the electrostatic spinning technology has become one of the main approaches for effectively preparing the nano-fiber material due to the advantages of simple manufacturing device, low spinning cost, various spinnable substances, controllable process and the like.
Electrostatic spinning is that under strong electric field, the liquid drop at the needle head changes from spherical to conical, and the fiber filament is spread from the tip of the cone to be jet-spun and solidified at the receiving device. In this way polymer filaments of a diameter of a few nanometers to a few micrometers can be produced. The electrostatic spinning fiber is widely applied to the fields of environmental protection, health, energy and the like in recent years due to high specific surface area, high porosity and special physical and chemical properties. Such as high efficiency filtration and separation membrane materials in environmental management, membrane materials for energy storage and conversion in energy devices, tissue culture and wound dressing materials in the medical field, and the like. Researchers mainly endow the nano-fibers with different morphologies and functions by means of material modification (CN109713203A), multiple material compounding (J.Power Sources,2014,261,1-6) and morphology control (adv.Funct.Mater.2018,28,1705051).
However, the production of nanofiber membranes using electrospinning techniques also faces some problems that need to be addressed. Although various industrial scale electrospinning apparatuses have been designed with different types of spinning/collecting attachments, the throughput is generally too low. The spinning efficiency of the state of the art is at the highest a few grams per hour per needle, and the output of one equipment is limited to a few tens of kilograms per day, resulting in the application of the final product mostly only in experimental stages. High voltage electricity poses operational risks to workers and the solvent typically constitutes 70-90 wt% of the solution during solution electrospinning. Evaporation of the solvent into the environment would result in environmental burdens and safety issues, as well as wasted chemicals. When flammable organic solvents are used, a large amount of flammable gas is generated, resulting in a fire hazard. So that the design of a high-yield spinning nanofiber separation membrane by adopting an environment-friendly technology is very important. In addition, as shown in the electron micrograph of fig. 9 (from j. mater. chem.b 2014,2,181-.
Disclosure of Invention
In order to solve the problems in the prior art, the invention provides a polymer microfiltration membrane as well as a preparation method and application thereof. The polymer is dissolved in a solvent to prepare a membrane casting solution, and the polymer microfiltration membrane with the structure similar to that of the electrostatic spinning nanofiber membrane can be efficiently prepared by a method of combining atomization pretreatment and non-solvent induced phase separation.
One of the objectives of the present invention is to provide a polymeric microfiltration membrane, wherein the surface and the interior of the microfiltration membrane are three-dimensional network pore structures which are mutually communicated, and the polymeric fibers of the microfiltration membrane are interwoven to form a three-dimensional fiber network structure similar to a loofah sponge structure.
Furthermore, the cross section of the microfiltration membrane is of a polymer fiber framework and hole structure with basically consistent appearance along the membrane thickness direction, namely the cross section of the microfiltration membrane is of a structure in which the polymer fiber framework and holes of the same type are distributed along the membrane thickness direction, and the holes of the same type mean that the holes distributed on the cross section of the microfiltration membrane are of the same type when viewed from the whole cross section of the microfiltration membrane, and the phenomenon that the membrane surface layer and the membrane bottom layer have holes of different types does not exist. For example, microfiltration or ultrafiltration membranes obtained by conventional non-solvent phase inversion often have different types of pore structures simultaneously present on the membrane cross section, with sponge-like pore structures near the membrane surface and large finger-like pore structures near the middle and bottom of the membrane.
The loofah sponge structure can be seen in the microscopic picture of loofah sponge shown in fig. 10. The polymeric fibers of the polymeric microfiltration membrane are connected with each other instead of being simply lapped, so that a three-dimensional network structure similar to the loofah sponge structure shown in fig. 10, namely a loofah sponge-like structure, which is firmly connected with each other, is formed, for example, as shown in fig. 1-6; wherein the fiber and the holes among the fibers form the through hole structure of the polymer micro-filtration membrane. Wherein the cross-sectional diameter of the single polymer fiber constituting the three-dimensional fiber network structure is irregularly changed and is less than 2 mu m.
The linear portions of the individual polymer fibers forming the three-dimensional fiber network structure are less than 10 μm in length, as can be seen in particular in the linear portion notation of fig. 5. The length of single polymer fiber in the nanofiber membrane prepared by the electrostatic spinning method is at least in the centimeter level, so that the polymer fiber skeleton structure in the invention is obviously different from the fiber structure obtained by the electrostatic spinning method.
The average pore diameter of the microfiltration membrane is 0.01-5 μm, preferably 0.1-3 μm.
The surface of the polymer microfiltration membrane and the through pores of the open pore structure in the internal structure form gaps between mutually overlapped fibers in the structure similar to the nanofiber membrane prepared by electrostatic spinning, and can play similar effects of separation, filtration, adsorption and the like. The polymer microfiltration membrane is different from a nanofiber membrane obtained by electrostatic spinning, the polymer of the polymer microfiltration membrane has a fibrous three-dimensional network structure, and polymer fibers are directly connected with each other and are not overlapped; the polymer micro-filtration membrane has firm connection among polymer fibers, thereby improving the structural stability and the mechanical strength of the membrane.
The polymer microfiltration membrane is prepared by an atomization pretreatment and non-solvent induced phase separation method.
The main membrane material of the polymer microfiltration membrane is a polymer which can be formed into a membrane by adopting a non-solvent phase inversion method. The polymeric microfiltration membrane includes a hydrophilic microfiltration membrane and a hydrophobic microfiltration membrane, if classified by wettability of the prepared microfiltration membrane. The hydrophilic polymer film can be prepared by taking the hydrophilic polymer material as a matrix, and the hydrophobic polymer film can be prepared by taking the hydrophobic polymer material as a matrix.
The polymer includes but is not limited to general high molecular polymer or modified polymer thereof for preparing membrane. Preferably, the polymer is at least one of general film-forming polymers such as polyvinylidene fluoride, polysulfone, polyethersulfone, sulfonated polyethersulfone, polyacrylonitrile, polyacrylic acid, polylactic acid, polyamide, chitosan, polyimide, cellulose acetate, polystyrene, polyolefin, polyester, polychlorotrifluoroethylene, polyvinyl chloride, silicone resin and the like, or modified polymers thereof.
Wherein the hydrophilic polymer is selected from at least one of sulfonated polyether sulfone, polyacrylonitrile, polyacrylic acid, polylactic acid, polyamide, chitosan, polyimide, polyester, chitin, cellulose acetate and the like;
the hydrophobic polymer is at least one selected from polyvinylidene fluoride, polysulfone, polyethersulfone, polyolefin, polychlorotrifluoroethylene, polyvinyl chloride, polystyrene, silicone resin and the like.
The polymer microfiltration membrane also can comprise a common inorganic salt pore-forming agent for preparing the membrane and/or various inorganic nano particles such as nano-scale inorganic filler and the like. Common inorganic salt pore-forming agents include LiCl and ZnCl 2 、MgCl 2 LiBr, etc., inorganic filler has MnO 2 、SiO 2 ZnO, etc.
The porous surface of the microfiltration membrane preferably has a micron/submicron-sized concave structure, and a reticular pore structure is distributed on the concave structure. The size of the concave structure is 0.5-10 mu m. The depression structures having micron/submicron dimensions can be prepared by a hydrophilic polymer under relatively low humidity environmental conditions of less than 40%.
The microstructure of the microfiltration membrane is densely covered with the reticular through hole structure, so that the surface roughness of the porous membrane is obviously higher, and Ra can reach 1-10 mu m. The increase in surface roughness may increase the wettability of the membrane surface, making the hydrophilic surface more hydrophilic and the hydrophobic surface more hydrophobic, while the increase in wettability is beneficial for enhancing the selective separation function of the membrane. Based on the synergistic effect of the pore structure and the surface/interface wettability, the obtained hydrophilic film shows strong hydrophilicity and underwater lipophobicity, and the hydrophilic film has the function of forming a high-stability hydrated protective layer on the surface of the film after the surface of the film is in contact with water, so that the effect of inhibiting the adhesion of oil drops underwater is achieved. Based on the synergistic effect of the pore structure and the surface/interface wettability, the obtained hydrophobic film shows strong hydrophobicity and lipophilicity. The special wettability endows the film with the application in the aspects of separation, adsorption and the like.
The invention also aims to provide a preparation method of the polymer microfiltration membrane, which comprises the step of carrying out atomization pretreatment on a polymer solution and combining a non-solvent induced phase separation method to prepare the polymer microfiltration membrane.
The atomization pretreatment process of the present invention is very different from the conventional steam induced phase separation (VIPS), which means that phase separation occurs under certain high humidity (or saturation humidity) conditions, and does not involve an atomized droplet bath.
The formation of polymer membranes is a complex non-equilibrium process, and the time and extent of phase separation depends on the kinetics of the phase separation process, and mass transfer exchange between the non-solvent and the solvent is one of the key factors that change the final membrane structure and properties. The non-solvent for the vapor-induced phase separation is introduced into the polymer solution from the gas phase. In this case, the precipitation is very slow, there is no concentration gradient of the dope solution in the film thickness direction due to the slow introduction amount of the non-solvent, and the dope solution precipitates almost simultaneously in the entire film thickness direction. However, the VIPS method is very slow in film formation, requires several hours for film formation, is inefficient, and is difficult to realize industrial continuous production. The atomization pretreatment method adopted by the invention can control the non-solvent atomization small drops to enter the casting solution to ensure that the casting solution is uniformly and partially separated from the surface layer to the bottom layer, thereby achieving the effect similar to that of the traditional VIPS method without obvious concentration gradient of the casting solution in the thickness direction of the film in a short time, and then realizing further complete phase separation and complete solidification of the film structure by the traditional non-solvent induced phase transformation method. Because the composition change of the non-solvent in the casting solution is gradual, the filtering membrane structure prepared by the atomization pretreatment process is basically uniform in the thickness direction, namely the skin layer structure is basically the same as the bottom layer structure. Therefore, the film section of the obtained polymer microfiltration membrane is a polymer fiber framework and hole structure with basically consistent appearance along the film thickness direction, namely the polymer fiber framework and the holes of the same type are distributed.
The key technology of the microfiltration membrane prepared by the invention is the combination of atomization pretreatment and a non-solvent induced phase separation method (NIPS), and the preparation method of the polymer microfiltration membrane is preferably carried out according to the following steps:
1) dissolving a high molecular polymer in a solvent to prepare a polymer solution;
2) scraping the polymer solution, and then carrying out atomization pretreatment, wherein the atomization pretreatment is to stay in an atomized droplet bath;
3) and immersing into a coagulating bath to obtain the polymer microfiltration membrane.
In the step 1), the concentration of the polymer solution is 5-25 wt%, preferably 6-20 wt%. The prepared polymer solution is used as casting solution.
In the step 1), the solvent isGood solvents capable of dissolving the high molecular polymer include, but are not limited to, N-dimethylformamide, N-methylpyrrolidone, N-dimethylacetamide, dimethylsulfoxide, tetrahydrofuran, dioxane, acetonitrile (CH) 3 CN), acetone, chloroform, toluene, hexane and octane.
In step 1), the polymer solution is preferably prepared and then defoamed.
In step 1), the polymer solution may further include a common inorganic salt pore-forming agent for preparing a membrane and/or various inorganic nanoparticles such as nanoscale inorganic fillers, and the amount of the inorganic salt pore-forming agent and/or various inorganic nanoparticles is conventional or adjusted according to the requirements of actual conditions. Common inorganic salt pore-forming agents include LiCl and ZnCl 2 、MgCl 2 LiBr, etc., inorganic filler has MnO 2 、SiO 2 ZnO, etc.
In the step 2), the polymer solution is uniformly coated on a support layer or a substrate material for scraping.
The supporting layer or the substrate material can be used as a supporting layer material or a substrate material for coating a polymer solution in the prior art, and may include but is not limited to: porous support materials such as non-woven fabrics and woven fabrics, and smooth base materials such as glass plates.
In the step 2), the wet film is scraped by the polymer solution, and the thickness is not particularly limited, and the thickness of the scraped film is preferably 50 to 500 μm, and more preferably 75 to 300 μm.
In the step 2), the atomization pretreatment is that the polymer solution is kept in contact with the atomized liquid drop bath for a certain time after being coated. The method in which the atomized liquid droplet bath is obtained is not particularly limited, and conventional various methods of liquid atomization, such as pressure atomization, rotary disc atomization, high-pressure gas stream atomization, sonic atomization, and the like, can be employed.
The size of the liquid drops in the liquid drop bath is preferably 1-50 mu m, and more preferably 5-18 mu m; the atomization pretreatment time is preferably 1 s-20 min, and more preferably 5-60 s.
The liquid drops in the atomization pretreatment are poor solvents of the high molecular polymer, can be single-component solvents such as water, ethanol, glycol and the like, can also be composed of water and polar aprotic solvents or other solvents, and can also be solutions of salts, acids and bases.
Further, it is desirable to control ambient humidity conditions throughout the experimental run, including relatively low humidity conditions of less than 40% and relatively high humidity conditions of greater than or equal to 40%. Some hydrophilic polymer microfiltration membrane surfaces can form recessed structures with micron/submicron dimensions under ambient conditions of room temperature, less than 40% of relatively low humidity; under the environment condition of relative high humidity of more than or equal to 40 percent, a uniform filament-like network structure is formed on the surface of the membrane. As environmental conditions affect the rate of exchange between solvent and non-solvent, and thus the membrane microstructure.
The coagulating bath of the separation membrane for NIPS phase inversion in step 3) is a poor solvent for the polymer, and can be single component such as water, ethanol, ethylene glycol, etc., or mixture of water and polar aprotic solvent or other solvent, such as sodium hydroxide aqueous solution.
The third purpose of the invention is to provide the application of the polymer microfiltration membrane in the fields of gas filtration, liquid filtration, adsorption materials, catalysis, drug slow-release materials, anti-adhesion coatings, oil product transportation, oil spill interception and the like.
The polymer microfiltration membrane provided by the invention has the characteristics similar to those of an electrostatic spinning nanofiber membrane in structure, has the characteristics of special wettability, ultralow oil adhesion, high specific surface area and the like in performance, is environment-friendly and good in stability, and has the performance of resisting pollution of oil, organic matters, biomass, bacteria, microorganisms and the like. Can replace part of the existing application markets of the electrostatic spinning nanofiber membrane, such as the applications of liquid, gas filtration, catalysis, adsorption and the like in the environmental field; wound dressings in the field of bioengineering; battery separator materials in the energy field, and the like.
Compared with the electrostatic spinning film-making technology, the invention is characterized in that: the polymer microfiltration membrane can be prepared by adding an atomization pretreatment process before the non-solvent induced phase separation process commonly applied in the existing industry, the production efficiency can reach several meters per minute, and the polymer microfiltration membrane is easy to industrially apply. In addition, the cross-sectional structure of the polymer microfiltration membrane of the invention not only presents a structure similar to a nanofiber membrane, namely, the through pores of the open pore structure in the polymer microfiltration membrane structure of the invention form gaps between fibers which are similar to the lapped fibers in the nanofiber membrane structure prepared by electrostatic spinning; meanwhile, the film forming process of the non-solvent phase inversion method enables a polymer rich phase to be formed when a high molecular polymer is separated out from a non-solvent and connected with each other to form a whole, so that the polymer fibers are connected with each other to form a stable three-dimensional network structure, and therefore, the nanofiber structure-imitated microfiltration membrane has better structural stability, and is more suitable for liquid filtration occasions needing to bear certain impact stress than the common nanofiber membrane. The preparation process of the invention does not need high-pressure operation, and is environment-friendly, safe and energy-saving.
Drawings
FIG. 1 is a surface topography map of a polymer film of example 1.
FIG. 2 is a topographical view of the polymer film of example 1.
FIG. 3 is a surface topography of the polymer film of example 5.
FIG. 4 is a topographical view of the polymer film of example 5.
FIG. 5 is a surface topography map of a polymer film of example 6.
FIG. 6 is a topographical profile view of a polymer film of example 6.
FIG. 7 is a surface topography of the comparative example 1 polymer film.
FIG. 8 is a topographical view of a polymer film of comparative example 1.
Fig. 9 is a cross-sectional view of a prior art nanofiber membrane.
Fig. 10 is a photograph of the shape of the loofah sponge.
Detailed Description
Exemplary embodiments that embody the features and advantages of the present application are described in detail below. It is understood that the present application is capable of many variations in different embodiments without departing from the scope of the application, and that the data and figures of the embodiments are to be interpreted as illustrative and not in a limiting sense.
In the following examples, the present application provides a high molecular polymer microfiltration membrane that is formed by phase separation of a high molecular polymer solution by an atomization pretreatment process in combination with a non-solvent. The separation membrane shows different wettability by the synergistic effect of the polymers with different surface energies and the rough surface microstructure. The present invention will be further described with reference to the following examples.
In the examples of the present invention, the chemical agents used were all commercially available products, and were not subjected to any special purification treatment unless otherwise mentioned.
Spraying equipment: the high-pressure nozzle is SK508 from Huarise technology Limited, Dongguan, and the ultrasonic humidifier is Haoqi HQ-JS 130H.
Example 1
Weighing Polyacrylonitrile (PAN) and dissolving in N-methylpyrrolidone (NMP), heating to 60 ℃, stirring to prepare a raw material solution with the concentration of 8 wt%, and vacuumizing and defoaming; uniformly scraping the prepared solution on non-woven fabric by using a scraper, controlling the coating thickness to be 200 mu m, and then staying in an atomized liquid drop bath generated by ultrasonic atomization for 30 s; then immersing the film into deionized water coagulating bath for complete phase separation; and washing with water to obtain the separation membrane, wherein the surface of the separation membrane presents an obvious concave structure, the size of the concave structure is 0.5-4 mu m, and the average pore diameter of pores is 269 nm. The membrane preparation is completed under 20% -35% low humidity environment condition. The oil-water separation experiment was carried out using the same, and the results are shown in Table 1.
Example 1 surface topography of polymer film see fig. 1, cross-sectional topography see fig. 2; the polyacrylonitrile microfiltration membrane in the embodiment 1 is of a loofah-like structure, the surface and the interior of the microfiltration membrane are of three-dimensional network pore structures which are communicated with each other, polymer fibers of the microfiltration membrane are interwoven to form a three-dimensional fiber network, and the cross section of the microfiltration membrane is of a structure in which the polymer fibers and holes are distributed.
Example 2
Weighing Polyacrylonitrile (PAN) and nano-silica, dissolving the Polyacrylonitrile (PAN) and the nano-silica in N, N-Dimethylformamide (DMF) according to the mass concentration of 6% and 2%, heating and stirring the mixture uniformly at the temperature of 60 ℃, and then vacuumizing and defoaming the mixture; uniformly scraping the prepared solution on non-woven fabric by a scraper, controlling the coating thickness to be 100 mu m, and then staying in an atomized liquid drop bath generated by ultrasonic atomization for 15 s; then immersing the film into deionized water coagulating bath for complete phase separation; and washing with water to obtain the separation membrane, wherein the surface of the separation membrane presents an obvious concave structure, the size of the concave structure is 0.5-5 mu m, and the average pore diameter of pores is 314 nm. The film preparation is completed under 30% -38% low humidity environment condition.
The oil-water separation experiment was carried out using the same, and the results are shown in Table 1.
Example 3
Weighing Cellulose Acetate (CA), dissolving the CA in acetone, stirring to prepare a raw material solution with the concentration of 8 wt%, and vacuumizing and defoaming; uniformly scraping the prepared solution on a clean glass plate by using a scraper, controlling the coating thickness to be 200 mu m, and then staying in an atomized liquid drop bath generated by ultrasonic atomization for 30 s; then immersing the film into deionized water coagulating bath for complete phase separation; the surface of the separation membrane presents an obvious concave structure, the size of the concave structure is 1-4 mu m, and the average pore diameter of pores is 106 nm. The film preparation is completed under the condition of 15% -30% of low-humidity environment.
The oil-water separation experiment was carried out using the same, and the results are shown in Table 1.
Example 4
Weighing Polyacrylonitrile (PAN), dissolving in DMF, heating to 60 ℃, stirring to prepare a raw material solution with the concentration of 8 wt%, and vacuumizing and defoaming; uniformly scraping the prepared solution on non-woven fabric by using a scraper, controlling the coating thickness to be 200 mu m, and then staying in an atomized liquid drop bath generated by ultrasonic atomization for 35 s; immersing the film into a 1mol/L sodium hydroxide aqueous solution coagulating bath for complete phase separation; and washing with water to obtain the separation membrane, wherein the surface of the separation membrane presents an obvious concave structure, the size of the concave structure is 1-5 mu m, and the average pore diameter of pores is 435 nm. The membrane preparation is completed under 20% -35% low humidity environment condition.
The oil-water separation experiment was carried out using the same, and the results are shown in Table 1.
Example 5
Weighing Polyacrylonitrile (PAN) and dissolving in N-methylpyrrolidone (NMP), heating to 60 ℃, stirring to prepare a raw material solution with the concentration of 8 wt%, and vacuumizing and defoaming; uniformly scraping the prepared solution on non-woven fabric by a scraper, controlling the coating thickness to be 150 μm, and then staying in an atomized liquid drop bath generated by ultrasonic atomization for 40 s; then immersing the film into deionized water coagulating bath for complete phase separation; and washing with water to obtain the separation membrane, wherein the average pore diameter of pores is 437 nm. The membrane preparation is completed under the relative high humidity environment condition of 50-80%, and the surface of the separation membrane has no obvious concave structure. The oil-water separation experiment was carried out using the same, and the results are shown in Table 1.
The surface topography of the polymer film of example 5 is shown in FIG. 3, and the cross-sectional topography is shown in FIG. 4; it can be seen that the polyacrylonitrile microfiltration membrane of example 5 has a loofah-like structure, the surface and the interior of the microfiltration membrane have three-dimensional network pore structures which are communicated with each other, polymer fibers of the microfiltration membrane are interwoven to form a three-dimensional fiber network, and the cross section of the microfiltration membrane has a structure in which the polymer fibers and pores are distributed.
Example 6
Weighing polyvinylidene fluoride (PVDF), dissolving the PVDF in N-methylpyrrolidone (NMP), heating to 70 ℃, stirring to prepare a raw material solution with the concentration of 8 wt%, and vacuumizing and defoaming; uniformly scraping the prepared solution on non-woven fabric by a scraper, controlling the coating thickness to be 150 μm, and then staying in an atomized liquid drop bath generated by ultrasonic atomization for 40 s; then immersing the film into deionized water coagulating bath for complete phase separation; and washing with water to obtain the separation membrane, wherein the average pore diameter of pores is 487 nm. The membrane preparation is completed under the relative high humidity environment condition of 50-80%, and the surface of the separation membrane has no obvious concave structure. The oil-water separation experiment was carried out using the same, and the results are shown in Table 1.
Surface topography of the polymer film of example 6 referring to FIG. 5, the cross-sectional topography referring to FIG. 6; it can be seen that the polyvinylidene fluoride microfiltration membrane of example 6 has a loofah-like structure, the surface and the interior of the microfiltration membrane are of a three-dimensional network pore structure which is communicated with each other, polymer fibers of the microfiltration membrane are interwoven to form a three-dimensional fiber network, and the cross section of the microfiltration membrane is of a structure in which the polymer fibers and holes are distributed.
Example 7
Weighing Polystyrene (PS) and lithium chloride, respectively dissolving the PS and the lithium chloride in N, N-Dimethylformamide (DMF) according to the mass concentration of 6% and 0.5%, heating to 50 ℃, uniformly stirring, and vacuumizing and defoaming; uniformly scraping the prepared solution on non-woven fabric by a scraper, controlling the coating thickness to be 150 μm, and then staying in an atomized liquid drop bath generated by ultrasonic atomization for 30 s; then immersing the film into deionized water coagulating bath for complete phase separation; washing with water to obtain the separation membrane, wherein the average pore diameter of pores is 1217 nm. The membrane preparation is completed under the relative high humidity environment condition of 60-80%, and the surface of the separation membrane has no obvious concave structure.
The oil-water separation experiment was carried out using the same, and the results are shown in Table 1.
Comparative example 1
Weighing Polyacrylonitrile (PAN), dissolving in NMP, heating to 60 ℃, stirring to prepare a raw material solution with the concentration of 8 wt%, and vacuumizing and defoaming; uniformly scraping the prepared solution on non-woven fabric by using a scraper, controlling the coating thickness to be 150 mu m, and then soaking the non-woven fabric into deionized water coagulation bath for complete phase conversion; and washing with water to obtain the separation membrane, wherein the average pore diameter of pores of the separation membrane is 35 nm. The oil-water separation experiment was carried out using the same, and the results are shown in Table 1.
Comparative example 1 surface morphology of separation membrane referring to fig. 7, it can be seen that the surface of the separation membrane is a typical surface morphology of a common flat ultrafiltration membrane, i.e. the surface is substantially covered by a flat polymer layer, on which a small number of small holes are distributed; the section (see fig. 8) is that the surface layer close to the membrane is in a sponge hole structure, and the lower part is in combination with a finger hole structure, so the whole structure does not have a loofah sponge-like structure.
Comparative example 2
Weighing Polyacrylonitrile (PAN), dissolving in DMF, heating to 60 ℃, stirring to prepare a raw material solution with the concentration of 8 wt%, and vacuumizing and defoaming; uniformly scraping the prepared solution on non-woven fabric by a scraper, controlling the thickness of the coating to be 200 mu m, then staying in a constant temperature and humidity box at room temperature and humidity of 100% for 40s, and then immersing the film in a deionized water solution coagulation bath for complete phase separation; and washing with water to obtain the separation membrane, wherein the average pore diameter of the separation membrane is 40 nm. The oil-water separation experiment was carried out using the same, and the results are shown in Table 1.
Comparative example 3
Weighing cellulose acetate, dissolving the cellulose acetate in NMP, heating the mixture to 60 ℃, stirring the mixture to prepare a raw material solution with the concentration of 8 wt%, and vacuumizing and defoaming the solution; uniformly scraping the prepared solution on non-woven fabric by a scraper, controlling the coating thickness to be 150 mu m, and then immersing the non-woven fabric in a deionized water coagulation bath for complete phase conversion; and washing with water to obtain the separation membrane, wherein the average pore diameter of the pores of the separation membrane is 24 nm. The oil-water separation experiment was carried out using the same, and the results are shown in Table 1.
Comparative example 4
Weighing polyvinylidene fluoride (PVDF), dissolving the PVDF in N-methylpyrrolidone (NMP), heating to 70 ℃, stirring to prepare a raw material solution with the concentration of 8 wt%, and vacuumizing and defoaming; uniformly scraping the prepared solution on non-woven fabric by a scraper, wherein the coating thickness is controlled to be 150 mu m; then immersing the film into deionized water coagulating bath for complete phase separation; and washing to obtain the separation membrane, wherein the average pore diameter of pores is 48 nm.
Oil-water separation experiments were performed on the membranes and the results are shown in table 1. The particle size of the small oil drop or the small water drop in the prepared oil-water emulsion (O/W) or (W/O) is 0.3-3 mu m, and the vast majority of the oil drops are in submicron scale. The hydrophilic membrane is used for filtering O/W emulsion, and the hydrophobic membrane is used for filtering W/O emulsion. The separation characteristics and the anti-pollution capability of the filter membrane are comprehensively evaluated through the data. The testing pressure is adjusted between 1kPa and 0.2MPa according to different diaphragms. And after one round of test is finished, taking out the test membrane, washing the test membrane clean, testing the recovered oil-water flux, and evaluating the anti-pollution capacity and long-term usability of the test membrane.
TABLE 1 comparison of film Properties of examples 1-7 and comparative examples 1-4
(test pressure of 10kPa for example and 0.1MPa for comparative example)
Claims (15)
1. A polymer microfiltration membrane, the surface and inside of the microfiltration membrane are three-dimensional network pore structures which are communicated with each other, and polymer fibers of the microfiltration membrane are interwoven to form a three-dimensional fiber network structure similar to a loofah sponge structure; the section of the micro-filtration membrane is a structure distributed with a polymer fiber framework and holes of the same type along the thickness direction of the membrane; the average pore diameter of the microfiltration membrane is 0.1-5 mu m; the surface of the polymer microfiltration membrane is provided with a recess structure with micron/submicron size; the size of the concave structure is 0.5-10 mu m; the polymer is polyacrylonitrile;
the polymeric microfiltration membrane is prepared by the following steps:
1) dissolving a polymer in a solvent to prepare a polymer solution;
2) scraping the polymer solution, and then carrying out atomization pretreatment, wherein the atomization pretreatment is to stay in an atomized droplet bath;
3) immersing into a coagulating bath to obtain the polymer microfiltration membrane;
the humidity of the droplet bath is a relatively low humidity condition of less than 40%.
2. The polymeric microfiltration membrane according to claim 1, wherein:
the diameter of the cross section of the single polymer fiber forming the three-dimensional fiber network structure is less than or equal to 2 mu m.
3. The polymeric microfiltration membrane according to claim 1, wherein:
the linear portions of the individual polymer fibers comprising the three-dimensional fiber network structure are less than 10 μm in length.
4. The polymeric microfiltration membrane according to claim 1, wherein:
the average pore diameter of the microfiltration membrane is 0.1-3 mu m.
5. A method for preparing a polymeric microfiltration membrane according to any one of claims 1 to 4, characterized by comprising the steps of:
1) dissolving a polymer in a solvent to prepare a polymer solution;
2) scraping the polymer solution, and then carrying out atomization pretreatment, wherein the atomization pretreatment is that the polymer solution stays in an atomized liquid drop bath;
3) immersing into a coagulating bath to obtain the polymer microfiltration membrane;
the humidity of the droplet bath is a relatively low humidity condition of less than 40%.
6. The method for preparing a polymeric microfiltration membrane according to claim 5 wherein:
in the step 1), the concentration of the polymer solution is 5-25 wt%;
in step 1), the solvent is selected from good solvents for the polymer.
7. The method for preparing a polymeric microfiltration membrane according to claim 6 wherein:
the concentration of the polymer solution is 6-20 wt%.
8. The method for preparing a polymeric microfiltration membrane according to claim 5 wherein:
in the step 2), uniformly coating the polymer solution on a support layer or a substrate material for film scraping; and/or the presence of a gas in the gas,
in the step 2), the thickness of the scraped film is 50-500 μm.
9. The method for preparing a polymeric microfiltration membrane according to claim 8 wherein:
the thickness of the scratch film is 75 to 300 μm.
10. The method for preparing a polymeric microfiltration membrane according to claim 5 wherein:
in the step 2), the size of the liquid drops in the liquid drop bath is 1-50 mu m;
in the step 2), the atomization pretreatment time is 1 s-20 mins;
in step 2), the droplets are poor solvents for the polymer.
11. The method for preparing a polymeric microfiltration membrane according to claim 10 wherein:
the size of the liquid drops in the liquid drop bath is 5-18 mu m;
the atomization pretreatment time is 5-60 s.
12. The method for preparing a polymeric microfiltration membrane according to claim 5 wherein:
in step 3), the coagulation bath is a poor solvent for the polymer.
13. The method for preparing a polymeric microfiltration membrane according to claim 6 wherein:
the good solvent of the polymer is at least one selected from N, N-dimethylformamide, N-methylpyrrolidone, N-dimethylacetamide, dimethyl sulfoxide, tetrahydrofuran, dioxane, acetonitrile, acetone, chloroform, toluene, benzene, hexane and octane.
14. The method for preparing a polymeric microfiltration membrane according to claim 10 or 12, wherein:
the poor solvent of the polymer is selected from at least one of water, ethanol and glycol.
15. The polymeric microfiltration membrane according to any one of claims 1 to 4 or the polymeric microfiltration membrane obtained by the preparation method according to any one of claims 5 to 14, for use in the fields of gas filtration, liquid filtration, adsorption materials, catalysis, drug release materials, anti-adhesion coatings, oil transportation and oil spill interception.
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| EP20883104.0A EP4052782A4 (en) | 2019-11-01 | 2020-10-27 | Polymer-based film, preparation method therefor, and use thereof |
| CA3159649A CA3159649A1 (en) | 2019-11-01 | 2020-10-27 | Polymer-based film, preparation method therefor, and use thereof |
| BR112022008103A BR112022008103A2 (en) | 2019-11-01 | 2020-10-27 | POLYMER-BASED MEMBRANE, METHOD FOR PREPARING A POLYMER-BASED MEMBRANE, USE OF A POLYMER-BASED MEMBRANE AND FUNCTIONAL MATERIAL |
| KR1020227018601A KR20220092591A (en) | 2019-11-01 | 2020-10-27 | Polymer-based membrane, manufacturing method and use thereof |
| JP2022525350A JP2023500114A (en) | 2019-11-01 | 2020-10-27 | Polymer-based membranes, methods of making and uses thereof |
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| CN113304626A (en) * | 2021-06-25 | 2021-08-27 | 北创清源(北京)科技有限公司 | High-molecular separation membrane and composite phase separation preparation method and device thereof |
| CN114100199A (en) * | 2021-11-25 | 2022-03-01 | 北京化工大学 | Liquid-liquid extraction separation method applied to water quality alkyl mercury detection and special oil-water separation membrane thereof |
| CN115283013A (en) * | 2022-08-31 | 2022-11-04 | 哈尔滨工业大学水资源国家工程研究中心有限公司 | Preparation method of nano manganese dioxide organic catalytic membrane |
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