CN115105968B - Formaldehyde-removing porous separation membrane with micro-nano structure, and preparation method and application thereof - Google Patents
Formaldehyde-removing porous separation membrane with micro-nano structure, and preparation method and application thereof Download PDFInfo
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Abstract
The invention discloses a formaldehyde-removing porous separation membrane with a micro-nano structure, and a preparation method and application thereof. The separation membrane is provided with a highly-penetrating network pore structure, nanoscale protrusions are distributed on a polymer framework forming the network pore structure, and a catalyst is dispersed in the separation membrane, wherein the catalyst comprises nano manganese dioxide and optional cerium oxide and/or copper oxide, and the polymer is a polymer mixture at least comprising two polymers. The preparation method comprises the steps of preparing a solution containing a mixture of a catalyst and a polymer, and then preparing the porous separation membrane through atomization pretreatment and a non-solvent induced phase separation method. The preparation method is simple, raw materials are easy to obtain, the production cost is low, and the obtained formaldehyde-removing porous separation membrane with the micro-nano structure shows good formaldehyde removing performance, can be applied to removing formaldehyde in air or water, and has great industrial application prospect.
Description
Technical Field
The invention relates to the technical field of formaldehyde removal, in particular to a formaldehyde removal porous separation membrane with a micro-nano structure, and a preparation method and application thereof.
Background
Formaldehyde is a colorless gas with strong pungent odor that is volatile and also readily soluble in organic solvents such as water, alcohols, ethers, and the like. Formaldehyde has a relatively high toxicity and has been classified as a carcinogenic, teratogenic substance by the world health organization. At present, common formaldehyde removal methods include adsorption methods, plant degradation methods, ozone oxidation methods, catalytic oxidation methods, and the like. The adsorption method has limited absorption capacity and needs regeneration after the adsorption carrier is saturated; the plant degradation method has low efficiency and limited formaldehyde absorption capacity; the ozone oxidation method is easy to cause secondary pollution; the catalytic oxidation method is the most effective, convenient and rapid method for removing formaldehyde at present. The most commonly used catalysts for the catalytic oxidation to remove formaldehyde can be divided into noble metal catalysts and transition metal oxide catalysts.
CN110743570a discloses a method for preparing a catalyst containing a porous structure substrate and a method for decomposing formaldehyde by using the catalyst. Firstly, preparing an aqueous solution containing noble metals, regulating the pH value of the solution to 7.5-10 by using sodium hydroxide, soaking a substrate with a porous structure in the solution for 2-4 hours, taking out the substrate, thoroughly drying the substrate in a forced air drying box, calcining the substrate at 200 ℃ for 1-8 hours, and naturally cooling the substrate to room temperature.
CN107115858A discloses a method for degrading formaldehyde in room, which involves containing MoO 3 、CeO 2 Al and Al 2 O 3 The ternary composite catalyst is used for degrading organic pollutants, especially indoor formaldehyde. The catalyst is MoO 3 /CeO 2 /Al 2 O 3 Ternary composite nanofibers incorporating MoO 3 /CeO 2 /Al 2 O 3 The formaldehyde-containing aqueous solution slowly passes through the membrane reactor and is introduced with oxygen, and after several cycles, the degradation rate of formaldehyde can reach 60% -90%.
CN106582148A discloses an electrospinning composite micro-nano fiber air filtering membrane and a preparation method thereof. The air filtering membrane is prepared by an electrostatic spinning method, and the composite micro-nano fiber of the air filtering membrane consists of nano silver particles, enteromorpha activated carbon/titanium dioxide composite particles and water-insoluble high molecular polymers, wherein the enteromorpha activated carbon/titanium dioxide composite particles are prepared by an electrostatic spinning TiO (titanium dioxide) 2 High-molecular polymer/enteromorpha nano-particle composite nanofiber membrane is subjected to high-temperature heat treatment,Acid washing and pulverizing.
In summary, in the existing catalytic oxidation formaldehyde removal technology, noble metal catalysts such as palladium and platinum are used, or a nanofiber membrane material is prepared from transition metal oxide and polymer through electrostatic spinning. The former has higher use cost and difficult product popularization. The latter has limited application value because of low production efficiency, complex process control factors and high equipment cost of the current electrostatic spinning technology.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides the formaldehyde-removing porous separation membrane with the micro-nano structure, which has good formaldehyde removing effect, low preparation cost and simple process and is suitable for large-scale production, and the preparation method and the application thereof.
One of the purposes of the invention is to provide a formaldehyde-removing porous separation membrane with a micro-nano structure, wherein the porous separation membrane has a through network pore structure, nano-scale protrusions are distributed on a polymer framework forming the network pore structure, a catalyst is dispersed in the separation membrane, the catalyst comprises nano manganese dioxide and optional cerium oxide and/or copper oxide, and the polymer is a polymer mixture comprising at least two polymers.
The porous separation membrane has a highly-communicated network pore structure, and nano-scale protrusions are distributed on the skeleton structure of the network pores. Wherein the average pore diameter of the porous separation membrane is 0.1-10 mu m, and the size of the protrusions distributed on the framework is 20-400 nm. The existence of the micro-nano structure increases the contact area of the network pore skeleton with air or water.
The network pore structure is a three-dimensional netlike porous structure, and the network pore structure is mutually communicated. The porous separation membrane has a volume porosity of 50 to 95%, preferably 70 to 90%.
The catalyst may be nano manganese dioxide or a manganese dioxide nano composite catalyst, wherein the manganese dioxide nano composite catalyst comprises manganese dioxide and at least one of a second component cerium oxide or a third component copper oxide.
Wherein the average particle size of manganese dioxide, cerium oxide and copper oxide is 20-80 nm.
The mass ratio of manganese dioxide, cerium oxide and copper oxide is preferably 1 (0-0.5): 0-0.25, preferably 1 (0.1-0.3): 0.05-0.2.
The polymer mixture comprises a polymer 1 and a polymer 2, wherein,
the polymer 1 is at least one selected from polyvinyl chloride, polysulfone, polyethersulfone, sulfonated polyethersulfone, polyacrylonitrile, cellulose acetate, polyvinylidene fluoride, polyimide, acrylonitrile-styrene copolymer and modified polymer thereof;
the polymer 2 is at least one selected from chitosan, polyvinylpyrrolidone, polyethylene glycol, polyvinyl alcohol and polyoxyethylene polyoxypropylene ether block copolymer.
The weight ratio of the polymer 1 to the polymer 2 is preferably 1 (0.01 to 5), more preferably 1: (0.1-3).
The mass ratio of the catalyst to the polymer mixture is (0.01-0.5): 1, preferably (0.05-0.25): 1.
The porous separation membrane is prepared by an atomization pretreatment and non-solvent induced phase separation method.
The micro-nano structure of the invention refers to a micro-scale interpenetrating network polymer framework and a nano-scale raised small particle structure on the framework. The surface and the inside of the porous separation membrane are of a three-dimensional polymer skeleton structure formed by interweaving polymer fibers, and thus a three-dimensional network pore structure which is mutually communicated is formed.
The second object of the present invention is to provide a method for preparing the formaldehyde-removing porous separation membrane, which comprises the steps of preparing a solution containing a mixture of a catalyst and a polymer, and then preparing the formaldehyde-removing porous separation membrane by combining atomization pretreatment with a non-solvent induced phase separation method.
The present invention provides a great distinction from Vapor Induced Phase Separation (VIPS), which refers to the phase separation that occurs under certain high humidity (or saturation humidity) conditions, without involving an atomized droplet bath. The VIPS film making process is very slow, the film making time usually needs several hours, the efficiency is low, and the industrial continuous production is difficult to realize. The atomization pretreatment method can lead the casting solution to be evenly and partially separated from the surface layer to the bottom layer by controlling the non-solvent atomized small liquid drops to enter the casting solution, thereby achieving the effect of no obvious casting solution concentration gradient in the film thickness direction similar to that obtained by the traditional VIPS method in a short time, and then achieving further complete phase separation and complete solidification of the film structure by the traditional non-solvent induced phase inversion method. The preparation method of the formaldehyde-removing porous separation membrane with the micro-nano structure is basically not influenced by environmental humidity.
The key technology of the separation membrane prepared in the invention is to integrate atomization pretreatment with a non-solvent induced phase separation method (NIPS), and the preparation method of the formaldehyde-removing porous separation membrane is preferably carried out according to the following steps:
(1) Dispersing the catalyst in a solvent by ultrasonic to prepare a dispersion liquid of the catalyst;
(2) Dissolving a polymer mixture comprising a polymer 1 and a polymer 2 in a solvent to prepare a polymer solution;
(3) Mixing the dispersion liquid with a polymer solution to obtain a casting solution, scraping a film of the casting solution, and then performing atomization pretreatment, wherein the atomization pretreatment is to stay in an atomized liquid drop bath;
(4) Immersing in a coagulating bath to obtain the porous separation membrane.
Further, in step (1), the catalyst may be nano manganese dioxide or a manganese dioxide nano composite catalyst, wherein the manganese dioxide nano composite catalyst includes manganese dioxide and at least one of cerium oxide or copper oxide.
Wherein the mass ratio of manganese dioxide to cerium oxide to copper oxide is 1 (0-0.5) (0-0.25), preferably 1 (0.1-0.3) (0.05-0.2).
In step (1), the solvent is a good solvent for Polymer 1 and Polymer 2, which is a solvent commonly used in the art to dissolve Polymer 1 and Polymer 2, including but not limited to N, N-dimethylformamide, N-methylpyrrolidone, N-dimethylacetamide, dimethylsulfoxide,tetrahydrofuran, dioxane, acetonitrile (CH) 3 CN), acetone, chloroform.
In the step (2), the polymer 1 is at least one selected from polyvinyl chloride, polysulfone, polyethersulfone, sulfonated polyethersulfone, polyacrylonitrile, cellulose acetate, polyvinylidene fluoride, polyimide, acrylonitrile-styrene copolymer, and modified polymers thereof.
The polymer 2 is at least one selected from chitosan, polyvinylpyrrolidone, polyethylene glycol, polyvinyl alcohol and polyoxyethylene polyoxypropylene ether block copolymer.
The weight ratio of the polymer 1 to the polymer 2 is preferably 1 (0.01 to 5), more preferably 1: (0.1-3).
In step (2), the solvent is a good solvent for Polymer 1 and Polymer 2, which is a solvent commonly used in the art to dissolve Polymer 1 and Polymer 2, including but not limited to N, N-dimethylformamide, N-methylpyrrolidone, N-dimethylacetamide, dimethylsulfoxide, tetrahydrofuran, dioxane, acetonitrile (CH) 3 CN), acetone, chloroform.
In the step (2), the polymer solution is preferably defoamed after being prepared.
In the step (3), the total content of the polymer in the casting solution is 5 to 25wt%, preferably 6 to 20wt%.
In the casting solution, the ratio of the mass of the catalyst to the total mass of the polymer is (0.01 to 0.5): 1, preferably (0.05 to 0.25): 1.
In the step (3), the casting solution is uniformly coated on the supporting layer or the substrate material for film scraping.
The support layer or substrate material required for coating the casting solution may be any support layer material or substrate material used as a polymer solution in the prior art, and may include, but is not limited to: porous support materials such as nonwoven fabrics and woven fabrics, and smooth base materials such as glass plates.
In the step (3), a wet film is scraped with the casting solution, and the scraped film thickness is 50 to 500. Mu.m, preferably 75 to 300. Mu.m.
In the step (3), the atomization pretreatment is to apply the casting film liquid and then stay in contact with the casting film liquid in an atomized liquid drop bath for a certain time. The method of obtaining the atomized droplet bath is not particularly limited, and various conventional methods of liquid atomization, such as pressure atomization, rotary disk atomization, high-pressure air stream atomization, ultrasonic atomization, and the like, may be employed.
The size of the droplets in the droplet bath is preferably 1 to 50 μm, more preferably 5 to 18 μm;
the atomization pretreatment time is preferably 1s to 20min, more preferably 5s to 3min.
The droplets in the atomization pretreatment are poor solvents of the polymer 1, and can be single components such as water, ethanol, glycol and the like, or can be mixed by water and polar aprotic solvents or other solvents, or can be solutions of salts, acids and alkalis, such as sodium hydroxide aqueous solution.
The coagulation bath in the step (4) is a poor solvent of the polymer 1, and may be a single component of water, ethanol, ethylene glycol, or may be a mixture of water and a polar aprotic solvent or other solvents, such as sodium hydroxide aqueous solution.
In the present invention, because of the solubility and wettability differences between the two polymers 1 and 2, there is a difference in phase separation speed in the process of non-solvent induced phase separation, i.e., a skeleton and a nano-protrusion structure are formed.
The invention also provides the formaldehyde removing porous separation membrane or the porous separation membrane obtained by the preparation method, which is used for removing formaldehyde in air or water.
The formaldehyde-removing porous separation membrane can be applied to an air filtering material or a formaldehyde material removing material in water.
The formaldehyde-removing porous separation membrane with the micro-nano structure provided by the invention is prepared from nano manganese dioxide or a manganese dioxide nano composite catalyst and a polymer. Wherein, the nano manganese dioxide or the manganese dioxide nano composite catalyst plays a role in removing formaldehyde through catalytic oxidation. The separation membrane has a highly-communicated network pore structure, and nano-scale protrusions are distributed on the framework structure of the network pore. The highly penetrating network pore structure provides the separation membrane with a large porosity, while the presence of the micro-nano structure increases the surface area of the network pore skeleton in contact with air or water. The increase of the porosity and the surface area improves the adsorption capacity of the separation membrane, so that the formaldehyde-removing porous separation membrane with the micro-nano structure shows good formaldehyde removing effect.
The formaldehyde-removing porous separation membrane with the micro-nano structure and the preparation method thereof have the following advantages:
(1) The formaldehyde-removing porous separation membrane with the micro-nano structure provided by the invention has good formaldehyde removing performance, the preparation method is simple, the raw materials are cheap and easy to obtain, and the production cost is low.
(2) Compared with the conventional non-solvent induced phase separation preparation process, the preparation process of the formaldehyde-removing porous separation membrane with the micro-nano structure provided by the invention is only added with one atomization pretreatment process, and can be used for large-scale continuous preparation, so that the formaldehyde-removing porous separation membrane with the micro-nano structure has a great industrial application prospect.
Drawings
FIG. 1 is a surface topography (1 KX) of a porous separation membrane of example 1.
FIG. 2 is a surface topography (2 ten thousand times) of the porous separation membrane of example 1.
Detailed Description
Exemplary embodiments that exhibit the features and advantages of the present application are described in detail in the following description. It should be understood that various changes can be made in the embodiments of the present application without departing from the scope of the application, the data and drawings of the embodiments are for illustrative purposes and are not intended to be limiting.
In the following examples, manganese dioxide was purchased from Shanghai Nameko Nano technologies Co., ltd, the average particle size was 50nm, cerium oxide was purchased from Shanghai ink high new materials technologies Co., ltd, the average particle size was 30nm, copper oxide was purchased from Shanghai Michelin Biochemical technologies Co., ltd, the average particle size was 40nm, polyacrylonitrile, sulfonated polyethersulfone, polyethylene glycol, cellulose acetate was purchased from Beijing Enoka technologies Co., ltd, and other chemical reagents were all purchased from state drug group chemical reagents Co., ltd.
Spraying equipment: the high-pressure nozzle is SK508 of the Fangguan-GmbH technology, the ultrasonic humidifier is HQ-JS130H, and the liquid drop bath is deionized water.
The surface morphology of the porous separation membrane was observed by Hitachi S-4800 type high resolution Field Emission Scanning Electron Microscope (FESEM).
The performance test and evaluation method of the formaldehyde-removing porous separation membrane with the micro-nano structure provided by the invention comprises the following steps:
formaldehyde removal rate: under a certain time, the concentration of the formaldehyde in the stock solution C 0 Concentration C of formaldehyde after membrane treatment 1 Dividing the difference by the concentration of formaldehyde in the stock solution. Namely: r= (C 0 -C 1 )/C 0 ×100％。
In the examples provided herein, acetylacetone spectrophotometry was used to test the concentration of formaldehyde in a solution.
Volume porosity: the volume porosity epsilon of the film was calculated by weighing the dry film and wet film. The calculation formula is as follows:
wherein m is wet For wet film mass, m dry For dry film mass ρ w Is the density of water ρ p Is the density of the polymer.
Example 1
Weighing 8g of Polyacrylonitrile (PAN) and 8g of polyvinylpyrrolidone (PVP) and adding into 54g of N, N-Dimethylformamide (DMF), heating to 60 ℃ and stirring for 12 hours for later use; 1g of manganese dioxide, 0.2g of cerium oxide and 0.1g of copper oxide are weighed and added into 28.7g of DMF, ultrasonic oscillation is carried out for 30min, then the mixture is mixed with DMF solution of PAN and PVP, and casting solution is obtained after uniform stirring; uniformly scraping the casting film liquid on the non-woven fabric by using a scraper, controlling the coating thickness to be 150 mu m, and then staying for 30s in an atomized liquid drop bath generated by ultrasonic atomization; immersing the film into deionized water coagulation bath to completely phase separate; the formaldehyde-removing porous separation membrane M1 with a micro-nano structure is obtained after water washing, the volume porosity is 88%, the average pore diameter of the porous separation membrane is 352nm, and the size of protrusions distributed on a framework is 100-200 nm.
The surface morphology of M1 is shown in fig. 1 and 2 (SEM).
M1 was immersed in an aqueous formaldehyde solution for 24 hours, and the formaldehyde concentration in the solution before and after the immersion was measured, and the formaldehyde removal rate was calculated as shown in Table 1.
Example 2
Weighing 10g of sulfonated polyethersulfone and 5g of polyethylene glycol, adding the sulfonated polyethersulfone and the 5g of polyethylene glycol into 55g N-methylpyrrolidone (NMP), heating to 60 ℃ and stirring for 12 hours for standby; weighing 0.8g of manganese dioxide and 0.2g of cerium oxide, adding into 29g of DMF, carrying out ultrasonic oscillation for 30min, then mixing with NMP solution of sulfonated polyethersulfone and polyethylene glycol, and uniformly stirring to obtain casting solution; uniformly scraping the casting film liquid on the non-woven fabric by using a scraper, controlling the coating thickness to be 100 mu m, and then staying for 10s in an atomized liquid drop bath generated by ultrasonic atomization; immersing the film into deionized water coagulation bath to completely phase separate; the formaldehyde-removing porous separation membrane M2 with a micro-nano structure is obtained after water washing, the volume porosity is 82%, the average pore diameter of the porous separation membrane is 417nm, and the size of protrusions distributed on a framework is 50-150 nm.
M2 was immersed in an aqueous formaldehyde solution for 24 hours, and the formaldehyde concentration in the solution before and after the immersion was measured, and the formaldehyde removal rate was calculated as shown in Table 1.
Example 3
Weighing 12g of sulfonated polyether sulfone and 1g of polyvinyl alcohol, adding into 57g of dimethyl sulfoxide (DMSO), heating to 80 ℃ and stirring for 12 hours for later use; weighing 0.2g of nano manganese dioxide, adding into 29.8g of DMSO, carrying out ultrasonic oscillation for 30min, then mixing with a DMSO solution of sulfonated polyether sulfone and polyvinyl alcohol, and uniformly stirring to obtain a casting solution; uniformly scraping the casting film liquid on the 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 2min; immersing the film into deionized water coagulation bath to completely phase separate; the formaldehyde-removing porous separation membrane M3 with a micro-nano structure is obtained after water washing, the volume porosity of the formaldehyde-removing porous separation membrane M3 is 79%, the average pore diameter of the porous separation membrane is 482nm, and the size of protrusions distributed on a framework is 200-300 nm.
M3 was immersed in an aqueous formaldehyde solution for 24 hours, and the formaldehyde concentration in the solution before and after the immersion was measured, and the formaldehyde removal rate was calculated as shown in Table 1.
Example 4
6g of polyethersulfone and 9g of Pluronic F-127 are weighed into 55g of NMP, heated to 70 ℃ and stirred for 12 hours for standby; 2g of manganese dioxide, 0.6g of cerium oxide and 0.4g of copper oxide are weighed and added into 27g of NMP, ultrasonic oscillation is carried out for 30min, then the mixture is mixed with NMP solution of polyethersulfone and Pluronic F-127, and casting solution is obtained after uniform stirring; uniformly scraping the casting film liquid on the non-woven fabric by using a scraper, controlling the coating thickness to be 150 mu m, and then staying in an atomized liquid drop bath generated by ultrasonic atomization for 1min; immersing the film into deionized water coagulation bath to completely phase separate; the formaldehyde-removing porous separation membrane M4 with a micro-nano structure is obtained after water washing, the volume porosity is 75%, the average pore diameter of the porous separation membrane is 528nm, and the size of protrusions distributed on a framework is 200-300 nm.
M4 is soaked in formaldehyde aqueous solution for 24 hours, the formaldehyde concentration in the solution before and after soaking is tested, and the formaldehyde removal rate is calculated, and the result is shown in Table 1.
Example 5
6g of polyethersulfone and 18g of PVP are weighed and added into 56g of NMP, and the mixture is heated to 70 ℃ and stirred for 12 hours for standby; 1.2g of nano manganese dioxide is weighed and added into 18.8NMP, ultrasonic oscillation is carried out for 30min, then the mixture is mixed with NMP solution of polyethersulfone and PVP, and casting solution is obtained after uniform stirring; uniformly scraping the casting film liquid on the non-woven fabric by using a scraper, controlling the coating thickness to be 100 mu m, and then staying for 30s in an atomized liquid drop bath generated by ultrasonic atomization; immersing the film into deionized water coagulation bath to completely phase separate; the formaldehyde-removing porous separation membrane M5 with a micro-nano structure is obtained after water washing, the volume porosity is 81%, the average pore diameter of the porous separation membrane is 446nm, and the size of protrusions distributed on a framework is 100-200 nm.
M5 was immersed in an aqueous formaldehyde solution for 24 hours, and the formaldehyde concentration in the solution before and after the immersion was measured, and the formaldehyde removal rate was calculated as shown in Table 1.
Example 6
12g of cellulose acetate and 8g of polyethylene glycol are weighed and dissolved in 60g of acetone, heated to 40 ℃ and stirred for 12 hours for standby; weighing 0.4g of manganese dioxide and 0.2g of cerium oxide, adding into 19.4g of acetone, carrying out ultrasonic oscillation for 30min, then mixing with an acetone solution of cellulose acetate and polyethylene glycol, and uniformly stirring to obtain a casting solution; uniformly scraping the casting film liquid on the non-woven fabric by using a scraper, controlling the coating thickness to be 250 mu m, and then staying for 10s in an atomized liquid drop bath generated by ultrasonic atomization; immersing the film into deionized water coagulation bath to completely phase separate; the formaldehyde-removing porous separation membrane M6 with a micro-nano structure is obtained after water washing, the volume porosity of the formaldehyde-removing porous separation membrane M6 is 78%, the average pore diameter of the porous separation membrane is 385nm, and the size of protrusions distributed on a framework is 50-150 nm.
M6 is soaked in formaldehyde aqueous solution for 24 hours, the formaldehyde concentration in the solution before and after soaking is tested, and the formaldehyde removal rate is calculated, and the result is shown in Table 1.
Comparative example 1
8g of PAN and 8g of PVP are weighed and added into 54g of DMF, and the mixture is heated to 60 ℃ and stirred for 12 hours for standby; 1g of manganese dioxide, 0.2g of cerium oxide and 0.1g of copper oxide are weighed and added into 28.7g of DMF, ultrasonic oscillation is carried out for 30min, then the mixture is mixed with DMF solution of PAN and PVP, and casting solution is obtained after uniform stirring; uniformly scraping the casting film liquid on non-woven fabrics by using a scraper, controlling the coating thickness to be 150 mu m, and immersing the non-woven fabrics in deionized water coagulation bath for complete phase inversion; after washing with water, a separation membrane C1 was obtained, which had a volume porosity of 48% and an average pore diameter of 56nm.
C1 is soaked in formaldehyde aqueous solution for 24 hours, formaldehyde concentration in the solution before and after soaking is tested, and formaldehyde removal rate results are shown in Table 1.
Comparative example 2
8g of PAN and 8g of PVP are weighed and added into 84g of DMF, and the mixture is heated to 60 ℃ and stirred for 12 hours to obtain casting solution; uniformly scraping the casting film liquid on the non-woven fabric by using a scraper, controlling the coating thickness to be 150 mu m, and then staying for 30s in an atomized liquid drop bath generated by ultrasonic atomization; immersing the film into deionized water coagulation bath to completely phase separate; the separation membrane C2 is obtained after water washing, the volume porosity of the separation membrane C2 is 85%, the average pore diameter of the porous separation membrane is 378nm, and the size of the protrusions distributed on the framework is 100-200 nm.
C2 is soaked in formaldehyde aqueous solution for 24 hours, the formaldehyde concentration in the solution before and after soaking is tested, and the formaldehyde removal rate is calculated, and the result is shown in Table 1.
Comparative example 3
0.5g of nano manganese dioxide is weighed and added into formaldehyde aqueous solution to be soaked for 24 hours, formaldehyde concentration in the solution before and after soaking is tested, and formaldehyde removal rate results are shown in table 1.
TABLE 1
As can be seen from the comparative examples and comparative examples, the formaldehyde-removing porous separation membrane with micro-nano structure prepared by the method has higher formaldehyde removal rate than the separation membrane prepared by the traditional non-solvent phase inversion method (NIPS). The formaldehyde removal rate of the separation membrane C1 prepared by the NIPS method is 41.6%, the formaldehyde removal rate of the porous separation membrane C2 without nano manganese dioxide prepared by the method is 1.2%, the formaldehyde removal rate of the pure nano manganese dioxide is 65.2%, and the formaldehyde removal rate of the formaldehyde removal porous separation membranes M1-M6 with micro-nano structures prepared by the method is more than 86%. This is because the separation membrane has a highly penetrating network pore structure, and nano-scale protrusions are distributed on the skeleton structure of the network pore. The highly penetrating network pore structure provides the separation membrane with a large porosity, while the presence of the micro-nano structure increases the surface area of the network pore skeleton in contact with air or water. The increase of the porosity and the surface area improves the adsorption capacity of the separation membrane, so that the formaldehyde-removing porous separation membrane with the micro-nano structure shows good formaldehyde removing effect.
The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, a number of simple variants of the technical solution of the invention are possible, including combinations of the individual technical features in any other suitable way, which simple variants and combinations should likewise be regarded as being disclosed by the invention, all falling within the scope of protection of the invention.
Claims (15)
1. A formaldehyde-removing porous separation membrane with a micro-nano structure, wherein the porous separation membrane has a through network pore structure, nanoscale protrusions are distributed on a polymer framework forming the network pore structure, a catalyst is dispersed in the separation membrane, the catalyst comprises nano manganese dioxide and cerium oxide and/or copper oxide, the mass ratio of cerium oxide to manganese dioxide is greater than 0 to 0.5, and the mass ratio of copper oxide to manganese dioxide is greater than 0 to 0.25; the polymer is a polymer mixture comprising at least two polymers, the polymer mixture comprises a polymer 1 and a polymer 2, the polymer 1 is at least one selected from polyvinyl chloride, polysulfone, polyethersulfone, sulfonated polyethersulfone, polyacrylonitrile, cellulose acetate, polyvinylidene fluoride, polyimide, acrylonitrile-styrene copolymer and modified polymers thereof, and the polymer 2 is at least one selected from chitosan, polyvinylpyrrolidone, polyethylene glycol, polyvinyl alcohol and polyoxyethylene polyoxypropylene ether block copolymer;
the formaldehyde-removing porous separation membrane is prepared by the following steps:
(1) Dispersing the catalyst in a solvent by ultrasonic to prepare a dispersion liquid of the catalyst;
(2) Dissolving a polymer mixture comprising a polymer 1 and a polymer 2 in a solvent to prepare a polymer solution;
(3) Mixing the dispersion liquid with a polymer solution to obtain a casting solution, scraping a film of the casting solution, and then performing atomization pretreatment, wherein the atomization pretreatment is to stay in an atomized liquid drop bath;
(4) Immersing in a coagulating bath to obtain the porous separation membrane.
2. The porous separation membrane of claim 1, wherein:
the average pore diameter of the porous separation membrane is 0.1-10 mu m, and the size of the protrusions distributed on the framework is 20-400 nm; and/or the number of the groups of groups,
the volume porosity of the porous separation membrane is 50-95%.
3. The porous separation membrane of claim 2, wherein:
the volume porosity of the porous separation membrane is 70-90%.
4. The porous separation membrane of claim 1, wherein:
the average particle size of manganese dioxide, cerium oxide and copper oxide is 20-80 nm.
5. The porous separation membrane of claim 1, wherein:
the mass ratio of manganese dioxide, cerium oxide and copper oxide is 1 (0.1-0.3) to 0.05-0.2.
6. A method for producing the porous separation membrane according to any one of claims 1 to 5, comprising the steps of:
(1) Dispersing the catalyst in a solvent by ultrasonic to prepare a dispersion liquid of the catalyst;
(2) Dissolving a polymer mixture comprising a polymer 1 and a polymer 2 in a solvent to prepare a polymer solution;
(3) Mixing the dispersion liquid with a polymer solution to obtain a casting solution, scraping a film of the casting solution, and then performing atomization pretreatment, wherein the atomization pretreatment is to stay in an atomized liquid drop bath;
(4) Immersing in a coagulating bath to obtain the porous separation membrane.
7. The method for producing a porous separation membrane according to claim 6, wherein:
in the step (3), the total content of the polymer in the casting solution is 5-25 wt%; and/or the number of the groups of groups,
the weight ratio of the polymer 1 to the polymer 2 is 1 (0.01-5); and/or the number of the groups of groups,
in the casting solution, the ratio of the mass of the catalyst to the total mass of the polymer is (0.01-0.5): 1.
8. The method for producing a porous separation membrane according to claim 7, wherein:
the total content of the polymer in the casting solution is 6 to 20 weight percent; and/or the number of the groups of groups,
the weight ratio of the polymer 1 to the polymer 2 is 1: (0.1-3); and/or the number of the groups of groups,
in the film casting solution, the ratio of the mass of the catalyst to the total mass of the polymer is (0.05-0.25): 1.
9. the method for producing a porous separation membrane according to claim 6, wherein:
in the step (3), the casting solution is uniformly coated on a supporting layer or a substrate material for film scraping; and/or the number of the groups of groups,
in the step (3), the thickness of the scratch film is 50-500 μm.
10. The method for producing a porous separation membrane according to claim 9, wherein:
the thickness of the scraping film is 75-300 mu m.
11. The method for producing a porous separation membrane according to claim 6, wherein:
in the step (3), the size of the liquid drops in the liquid drop bath is 1-50 mu m; and/or the number of the groups of groups,
in the step (3), the atomization pretreatment time is 1 s-20 min.
12. The method for producing a porous separation membrane according to claim 11, wherein:
the size of the liquid drops in the liquid drop bath is 5-18 mu m; and/or the number of the groups of groups,
the atomization pretreatment time is 5 s-3 min.
13. The method for producing a porous separation membrane according to claim 6, wherein:
in the steps (1) and (2), the solvent is a good solvent for the polymer 1 and the polymer 2;
in the step (3), the liquid drop is a poor solvent of the polymer 1; and/or the number of the groups of groups,
in the step (4), the coagulation bath is a poor solvent for the polymer 1.
14. The method for producing a porous separation membrane according to claim 13, characterized in that:
the good solvent is at least one selected from N, N-dimethylformamide, N-dimethylacetamide, acetone, N-methylpyrrolidone, dimethyl sulfoxide, tetrahydrofuran, dioxane, acetonitrile, chloroform and tetramethyl sulfoxide; and/or the number of the groups of groups,
the poor solvent is at least one selected from water, ethanol and ethylene glycol.
15. A porous separation membrane according to any one of claims 1 to 5 or a porous separation membrane obtained by the production method according to any one of claims 6 to 14 for removing formaldehyde from air or water.
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