CN115105968A - 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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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
- B01D69/02—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor characterised by their properties
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/22—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by diffusion
- B01D53/228—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by diffusion characterised by specific membranes
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
- B01D67/0002—Organic membrane manufacture
- B01D67/0009—Organic membrane manufacture by phase separation, sol-gel transition, evaporation or solvent quenching
- B01D67/0013—Casting processes
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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- B01D2257/00—Components to be removed
- B01D2257/70—Organic compounds not provided for in groups B01D2257/00 - B01D2257/602
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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- B01D2325/00—Details relating to properties of membranes
- B01D2325/10—Catalysts being present on the surface of the membrane or in the pores
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
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- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A50/00—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE in human health protection, e.g. against extreme weather
- Y02A50/20—Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters
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 has a highly-through network pore structure, nano-scale protrusions are distributed on a polymer skeleton 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 at least comprising two polymers. The preparation method comprises the steps of preparing a solution containing a catalyst and polymer mixture, and then preparing the porous separation membrane by combining 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, the obtained formaldehyde-removing porous separation membrane with the micro-nano structure shows good formaldehyde removal performance, can be applied to removing formaldehyde in air or water, and has great industrial application prospects.
Description
Technical Field
The invention relates to the technical field of formaldehyde removal, in particular to a formaldehyde-removing porous separation membrane with a micro-nano structure, and a preparation method and application thereof.
Background
Formaldehyde is a colorless gas which is volatile and easily soluble in organic solvents such as water, alcohol, ether and the like and has strong pungent odor. Formaldehyde has high toxicity and is listed as a carcinogenic and teratogenic substance by the world health organization. At present, the common formaldehyde removal methods include an adsorption method, a plant degradation method, an ozone oxidation method, a catalytic oxidation method, 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 removing formaldehyde by catalytic oxidation can be classified into noble metal catalysts and transition metal oxide catalysts.
CN110743570A discloses a preparation method of 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, adjusting 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 h, taking out the substrate, completely drying the substrate in a blast drying oven, calcining the substrate for 1-8 h at 200 ℃, and naturally cooling the substrate to room temperature.
CN107115858A discloses a method for degrading indoor formaldehyde, relating to a material containing MoO 3 、CeO 2 And Al 2 O 3 The three-way composite catalyst is used for degrading organic pollutants, particularly indoor formaldehyde. The catalyst is MoO 3 /CeO 2 /Al 2 O 3 Ternary composite nanofibers of MoO 3 /CeO 2 /Al 2 O 3 The water solution containing formaldehyde is slowly passed through the membrane reactor, and oxygen is introduced, after several circulations, the degradation rate of formaldehyde can reach 60% -90%.
CN106582148A discloses an electrospinning composite micro-nanofiber air filtering membrane and a preparation method thereof. The air filtering membrane is prepared by an electrostatic spinning method, and the composite micro-nanofiber of the air filtering membrane is composed of nano-silver particles, enteromorpha activated carbon/titanium dioxide composite particles and a water-insoluble high polymer, wherein the enteromorpha activated carbon/titanium dioxide composite particles are formed by electrospinning TiO 2 The/high molecular polymer/enteromorpha nano particle composite nanofiber membrane is prepared by high-temperature heat treatment, acid pickling and crushing.
In summary, in the existing technology for removing formaldehyde by catalytic oxidation, noble metal catalysts such as palladium, platinum and the like are used, or a transition metal oxide and a polymer are prepared into a nanofiber membrane material by electrostatic spinning. The former has higher use cost and difficult product popularization. The latter has limited application value due to low production efficiency, complex process control factors and high equipment cost of the prior electrostatic spinning technology.
Disclosure of Invention
The invention aims to solve the technical problem of the prior art and provides a formaldehyde-removing porous separation membrane with a micro-nano structure, which has the advantages of good formaldehyde-removing effect, low preparation cost, simple process and suitability for large-scale production, and a preparation method and application thereof.
The invention aims to provide a formaldehyde-removing porous separation membrane with a micro-nano structure, wherein the porous separation membrane is provided with a through network pore structure, nano-scale protrusions are distributed on a polymer skeleton 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 at least comprising two polymers.
The porous separation membrane has a highly-through network pore structure, and nanometer-scale protrusions are distributed on a skeleton structure of the network pore. Wherein the average pore diameter of the porous separation membrane is 0.1-10 μm, and the size of the protrusions distributed on the skeleton is 20-400 nm. Due to the micro-nano structure, the contact area of the network pore framework and air or water is increased.
The network pore structure is a three-dimensional reticular porous structure which is communicated with each other. The volume porosity of the porous separation membrane is 50-95%, and preferably 70-90%.
The catalyst can be nano manganese dioxide or a manganese dioxide nanocomposite catalyst, wherein the manganese dioxide nanocomposite catalyst includes manganese dioxide and at least one of a second component cerium oxide or a third component copper oxide.
Wherein the average particle size of the manganese dioxide, the cerium oxide and the copper oxide is 20-80 nm.
The mass ratio of manganese dioxide, cerium oxide and copper oxide is preferably 1 (0-0.5) to 0-0.25, and preferably 1 (0.1-0.3) to 0.05-0.2.
The polymer mixture comprises polymer 1 and polymer 2, wherein,
the polymer 1 is selected from at least one of 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 (0.01-5), more preferably 1: (0.1 to 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 refers to a micron-sized interpenetrating network polymer framework and a structure of nano-sized small raised particles on the framework. The surface and the inside of the porous separation membrane are in a three-dimensional polymer skeleton structure formed by interweaving polymer fibers, and thus, an interpenetrating three-dimensional network pore structure is formed.
The second purpose of the invention is to provide a preparation method of 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 and a non-solvent induced phase separation method.
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 VIPS method has very slow film making process, needs hours of film making time, has low efficiency 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. The preparation method of the formaldehyde-removing porous separation membrane with the micro-nano structure is basically not influenced by the environmental humidity.
The key technology of the separation membrane prepared in the invention is the combination of atomization pretreatment and 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) ultrasonically dispersing a catalyst in a solvent to prepare a dispersion liquid of the catalyst;
(2) dissolving a polymer mixture containing 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 membrane casting solution, scraping the membrane casting solution, and then carrying out atomization pretreatment, wherein the atomization pretreatment is that the membrane casting solution stays in an atomized liquid drop bath;
(4) and immersing into a coagulating bath to obtain the porous separation membrane.
Further, in step (1), the catalyst may be nano manganese dioxide or manganese dioxide nanocomposite catalyst, wherein the manganese dioxide nanocomposite catalyst includes manganese dioxide and at least one of cerium oxide or copper oxide.
Wherein the mass ratio of manganese dioxide, cerium oxide and copper oxide is 1 (0-0.5) to 0-0.25, preferably 1 (0.1-0.3) to 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 for dissolving polymer 1 and polymer 2, and includes but is not limited to N, N-dimethylformamide, N-methylpyrrolidone, N-dimethylacetamide, dimethylsulfoxide, tetrahydrofuran, dioxane, acetonitrile (CH) 3 CN), acetone and 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 (0.01-5), 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 for dissolving polymer 1 and polymer 2, and includes, but is not limited to, N-dimethylformamide, N-methylpyrrolidone, N-dimethylacetamide, dimethylsulfoxide, tetrahydrofuran, dioxane, acetonitrile (CH) 3 CN), acetone and chloroform.
In the step (2), the polymer solution is preferably prepared and then defoamed.
In the step (3), the total content of the polymer in the casting solution is 5-25 wt%, preferably 6-20 wt%.
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, and preferably (0.05-0.25): 1.
And (3) uniformly coating the casting solution on a support layer or a substrate material for film scraping.
The supporting layer or substrate material required for coating the casting solution can be used as the supporting layer material or substrate material for coating the polymer solution in the prior art, and can 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 (3), a wet film is scraped by using the casting film liquid, and the thickness of the scraped film is 50-500 micrometers, preferably 75-300 micrometers.
In the step (3), the atomization pretreatment is to stay and contact the casting solution in an atomized liquid drop bath for a certain time after the casting solution is 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, ultrasonic 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 1s to 20min, more preferably 5s to 3 min.
The liquid drops in the atomization pretreatment are poor solvents of the polymer 1, can be single-component solvents such as water, ethanol, glycol and the like, can be mixed by water and polar aprotic solvents or other solvents, and can also be solutions of salts, acids and bases, such as sodium hydroxide aqueous solution.
In the step (4), the coagulating bath is a poor solvent of the polymer 1, and can be a single component such as water, ethanol, ethylene glycol and the like, or can be a mixture of water and a polar aprotic solvent or other solvents, such as a sodium hydroxide aqueous solution.
In the present invention, because of the solubility and wettability differences of the two polymers 1 and 2, there is a difference in phase separation speed in the process of phase separation by a non-solvent, i.e., a skeleton and a nano-projection structure are formed.
The invention also aims to provide 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 filter material or a material for removing formaldehyde in water.
The formaldehyde-removing porous separation membrane with the micro-nano structure is prepared from nano manganese dioxide or manganese dioxide nano composite catalyst and polymer. Wherein, the nano manganese dioxide or manganese dioxide nano composite catalyst plays a role in catalyzing, oxidizing and removing formaldehyde. The separation membrane has a highly-through network pore structure, and nanometer-scale protrusions are distributed on the skeleton structure of the network pore. The highly-through network pore structure enables the separation membrane to have large porosity, and meanwhile, the existence of the micro-nano structure increases the contact surface area of the network pore framework and 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 a good formaldehyde-removing effect.
The formaldehyde-removing porous separation membrane with the micro-nano structure and the preparation method thereof provided by the invention 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, and is simple in preparation method, cheap and easily available in raw materials and low in production cost.
(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 only adds one atomization pretreatment process, and can be used for large-scale continuous preparation, so that the preparation process has great industrial application prospects.
Drawings
Fig. 1 is a surface topography (1 kx) of the 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 embody features and advantages of the present application are described in detail below. It should be understood that the present application is capable of many variations in various embodiments, which may be made without departing from the scope of the present 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, manganese dioxide was purchased from Shanghai Naoho nano technologies, Inc., with an average particle size of 50nm, cerium oxide was purchased from Shanghai Megaku technologies, Inc., with an average particle size of 30nm, copper oxide was purchased from Shanghai Michelin Biochemical technologies, Inc., with an average particle size of 40nm, polyacrylonitrile, sulfonated polyether sulfone, polyethylene glycol, cellulose acetate were purchased from Beijing YinoKa technologies, Inc., and other chemicals were purchased from national chemical group, Inc.
Spraying equipment: the high-pressure nozzle adopts SK508 from Huarise technology Limited, Dongguan city, the ultrasonic humidifier adopts Haoqi HQ-JS130H, and the liquid drop bath is deionized water.
The surface morphology of the porous separation membrane is observed by a high-resolution Field Emission Scanning Electron Microscope (FESEM) of Hitachi S-4800 model.
The invention provides a method for testing and evaluating the performance of a formaldehyde-removing porous separation membrane with a micro-nano structure, which comprises the following steps:
the formaldehyde removal rate is as follows: at a certain time, the concentration of formaldehyde in the stock solution is C 0 And the concentration C of formaldehyde after membrane treatment 1 The difference is divided by the concentration of formaldehyde in the stock solution. Namely: r ═ C 0 -C 1 )/C 0 ×100％。
In the embodiment provided by the invention, the concentration of formaldehyde in the solution is tested by adopting an acetylacetone spectrophotometry method.
Volume porosity: the volume porosity epsilon of the film was calculated by weighing the dry and wet films. The calculation formula is as follows:
wherein m is wet M is the wet film mass dry Is dry film quality, ρ w Is the density of water, p p Is the density of the polymer.
Example 1
Weighing 8g of Polyacrylonitrile (PAN) and 8g of polyvinylpyrrolidone (PVP), adding into 54g N, N-Dimethylformamide (DMF), heating to 60 ℃, and stirring for 12 hours for later use; weighing 1g of manganese dioxide, 0.2g of cerium oxide and 0.1g of copper oxide, adding into 28.7g of DMF, carrying out ultrasonic oscillation for 30min, then mixing with DMF solution of PAN and PVP, and stirring uniformly to obtain a casting solution; uniformly scraping and coating the membrane casting solution on non-woven fabric by 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 30 s; then immersing the film into deionized water coagulating bath for complete phase separation; and washing with water to obtain the formaldehyde-removing porous separation membrane M1 with a micro-nano structure, wherein the volume porosity of the membrane is 88%, the average pore diameter of the porous separation membrane is 352nm, and the sizes of the protrusions distributed on the framework are 100-200 nm.
Surface topography of M1 see fig. 1 and 2 (SEM).
Soaking M1 in formaldehyde aqueous solution for 24h, testing the formaldehyde concentration in the solution before and after soaking, and calculating the formaldehyde removal rate, and the results are shown in Table 1.
Example 2
Weighing 10g of sulfonated polyether sulfone and 5g of polyethylene glycol, adding into 55g N-methyl pyrrolidone (NMP), heating to 60 ℃, and stirring for 12 hours for later use; weighing 0.8g of manganese dioxide and 0.2g of cerium oxide, adding the manganese dioxide and the cerium oxide into 29g of DMF, carrying out ultrasonic oscillation for 30min, then mixing the mixture with a sulfonated polyether sulfone and a polyethylene glycol (NMP) solution, and uniformly stirring to obtain a membrane casting solution; uniformly scraping the casting solution on a 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; then immersing the film into deionized water coagulating bath for complete phase separation; and washing with water to obtain the noraldehyde porous separation membrane M2 with a micro-nano structure, wherein the volume porosity of the noraldehyde porous separation membrane M2 is 82%, the average pore diameter of the porous separation membrane is 417nm, and the sizes of the protrusions distributed on the framework are 50-150 nm.
M2 was soaked in formalin for 24 hours, the concentration of formaldehyde in the solution before and after soaking was measured, and the results of calculating the formaldehyde removal rate are 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 the nano manganese dioxide into 29.8g of DMSO, carrying out ultrasonic oscillation for 30min, then mixing the nano manganese dioxide with the DMSO solution of sulfonated polyether sulfone and polyvinyl alcohol, and uniformly stirring to obtain a casting solution; uniformly scraping the casting solution on a non-woven fabric by a scraper, controlling the coating thickness to be 200 mu m, and then staying for 2min in an atomized liquid drop bath generated by ultrasonic atomization; then immersing the film into deionized water coagulating bath for complete phase separation; washing to obtain the formaldehyde-removing porous separation membrane M3 with a micro-nano structure, wherein the volume porosity is 79%, the average pore diameter of the porous separation membrane is 482nm, and the sizes of protrusions distributed on a framework are 200-300 nm.
Soaking M3 in formaldehyde aqueous solution for 24h, testing the formaldehyde concentration in the solution before and after soaking, and calculating the formaldehyde removal rate, and the results are shown in Table 1.
Example 4
Weighing 6g of polyether sulfone and 9g of Pluronic F-127, adding into 55g of NMP, heating to 70 ℃, and stirring for 12h for later use; weighing 2g of manganese dioxide, 0.6g of cerium oxide and 0.4g of copper oxide, adding the materials into 27g of NMP, carrying out ultrasonic oscillation for 30min, then mixing the materials with a polyether sulfone and a Pluronic F-127 NMP solution, and uniformly stirring to obtain a casting solution; uniformly scraping the casting solution on a non-woven fabric by a scraper, controlling the coating thickness to be 150 mu m, and then staying for 1min in an atomized liquid drop bath generated by ultrasonic atomization; then immersing the film into deionized water coagulating bath for complete phase separation; and washing with water to obtain the formaldehyde-removing porous separation membrane M4 with a micro-nano structure, wherein the volume porosity of the membrane is 75%, the average pore diameter of the porous separation membrane is 528nm, and the sizes of the protrusions distributed on the framework are 200-300 nm.
Soaking M4 in formaldehyde aqueous solution for 24h, testing the formaldehyde concentration in the solution before and after soaking, and calculating the formaldehyde removal rate, and the results are shown in Table 1.
Example 5
Weighing 6g of polyether sulfone and 18g of PVP, adding into 56g of NMP, heating to 70 ℃, and stirring for 12 hours for later use; weighing 1.2g of nano manganese dioxide, adding the nano manganese dioxide into 18.8NMP, carrying out ultrasonic oscillation for 30min, then mixing with a solution of polyether sulfone and PVP NMP, and stirring uniformly to obtain a membrane casting solution; uniformly scraping and coating the membrane casting 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 30 s; then immersing the film into deionized water coagulating bath for complete phase separation; and washing to obtain the formaldehyde-removing porous separation membrane M5 with a micro-nano structure, wherein the volume porosity of the membrane is 81%, the average pore diameter of the porous separation membrane is 446nm, and the sizes of the protrusions distributed on the framework are 100-200 nm.
M5 was soaked in formalin for 24 hours, the concentration of formaldehyde in the solution before and after soaking was measured, and the results of calculating the formaldehyde removal rate are shown in Table 1.
Example 6
Weighing 12g of cellulose acetate and 8g of polyethylene glycol, dissolving in 60g of acetone, heating to 40 ℃, and stirring for 12 hours for later use; weighing 0.4g of manganese dioxide and 0.2g of cerium oxide, adding the manganese dioxide and the cerium oxide into 19.4g of acetone, carrying out ultrasonic oscillation for 30min, then mixing the obtained mixture with an acetone solution of cellulose acetate and polyethylene glycol, and uniformly stirring to obtain a casting solution; uniformly scraping and coating the membrane casting solution on non-woven fabric by a scraper, controlling the coating thickness to be 250 mu m, and then staying in an atomized liquid drop bath generated by ultrasonic atomization for 10 s; then immersing the film into deionized water coagulating bath for complete phase separation; and washing with water to obtain the formaldehyde-removing porous separation membrane M6 with a micro-nano structure, wherein the volume porosity of the membrane is 78%, the average pore diameter of the porous separation membrane is 385nm, and the sizes of the protrusions distributed on the framework are 50-150 nm.
Soaking M6 in formaldehyde aqueous solution for 24h, testing the formaldehyde concentration in the solution before and after soaking, and calculating the formaldehyde removal rate, and the results are shown in Table 1.
Comparative example 1
Weighing 8g of PAN and 8g of PVP, adding into 54g of DMF, heating to 60 ℃, and stirring for 12 hours for later use; weighing 1g of manganese dioxide, 0.2g of cerium oxide and 0.1g of copper oxide, adding into 28.7g of DMF, carrying out ultrasonic oscillation for 30min, then mixing with DMF solution of PAN and PVP, and stirring uniformly to obtain a casting solution; uniformly scraping the casting solution on non-woven fabric by a scraper, controlling the coating thickness to be 150 mu m, and then soaking the non-woven fabric in a deionized water coagulating bath for complete phase conversion; and washing with water to obtain the separation membrane C1, wherein the volume porosity of the separation membrane C1 is 48%, and the average pore diameter of the separation membrane C is 56 nm.
C1 was soaked in formalin for 24 hours, the concentration of formaldehyde in the solution before and after soaking was measured, and the results of calculating the formaldehyde removal rate are shown in Table 1.
Comparative example 2
Weighing 8g of PAN and 8g of PVP, adding into 84g of DMF, heating to 60 ℃, and stirring for 12 hours to obtain a membrane casting solution; uniformly scraping the casting solution on a 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; then immersing the film into deionized water coagulating bath for complete phase separation; and washing to obtain the separation membrane C2, wherein the volume porosity is 85%, the average pore diameter of the porous separation membrane is 378nm, and the sizes of the protrusions distributed on the skeleton are 100-200 nm.
C2 was soaked in formalin for 24 hours, the concentration of formaldehyde in the solution before and after soaking was measured, and the results of calculating the formaldehyde removal rate are shown in Table 1.
Comparative example 3
0.5g of nano manganese dioxide is weighed and added into the formaldehyde water solution to be soaked for 24 hours, the formaldehyde concentration in the solution before and after soaking is tested, and the result of calculating the formaldehyde removal rate is shown in table 1.
TABLE 1
Compared with the separation membrane prepared by the traditional non-solvent phase inversion method (NIPS), the formaldehyde-removing porous separation membrane with the micro-nano structure prepared by the method has higher formaldehyde removal rate. 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 which is prepared by the method and does not contain nano-manganese dioxide is 1.2%, the formaldehyde removal rate of pure nano-manganese dioxide is 65.2%, and the formaldehyde removal rates of the formaldehyde-removing porous separation membranes M1-M6 which are prepared by the method and have the micro-nano structures are more than 86%. This is because the separation membrane has a highly through-network pore structure, and the nano-sized protrusions are distributed on the skeletal structure of the network pores. The highly-through network pore structure enables the separation membrane to have high porosity, and meanwhile, the existence of the micro-nano structure increases the contact surface area of the network pore framework and 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 a good formaldehyde-removing effect.
The preferred embodiments of the present invention have been described above in detail, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, many simple modifications can be made to the technical solution of the invention, including various technical features being combined in any other suitable way, and these simple modifications and combinations should also be regarded as the disclosure of the invention, and all fall within the scope of the invention.
Claims (14)
1. A formaldehyde-removing porous separation membrane with a micro-nano structure is provided with a through network pore structure, nano-scale protrusions are distributed on a polymer skeleton forming the network pore structure, a catalyst is dispersed in the separation membrane and comprises nano-manganese dioxide and optional cerium oxide and/or copper oxide, and the polymer is a polymer mixture at least comprising two polymers.
2. The porous separation membrane according to 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 skeleton is 20-400 nm; and/or the presence of a gas in the gas,
the volume porosity of the porous separation membrane is 50-95%, and preferably 70-90%.
3. The porous separation membrane according to claim 1, wherein: 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 polymers thereof; and/or the presence of a gas in the gas,
the polymer 2 is at least one selected from chitosan, polyvinylpyrrolidone, polyethylene glycol, polyvinyl alcohol and polyoxyethylene polyoxypropylene ether block copolymer.
4. The porous separation membrane according to claim 1, wherein:
the average particle size of the manganese dioxide, cerium oxide and copper oxide is 20-80 nm.
5. The porous separation membrane according to claim 1, wherein:
the mass ratio of manganese dioxide, cerium oxide and copper oxide is 1 (0-0.5) to 0-0.25, preferably 1 (0.1-0.3) to 0.05-0.2.
6. A porous separation membrane according to any one of claims 1 to 5, wherein:
the porous separation membrane is prepared by an atomization pretreatment and non-solvent induced phase separation method.
7. A method for preparing a porous separation membrane according to any one of claims 1 to 6, wherein a solution comprising a mixture of the catalyst and a polymer is prepared, and then the porous separation membrane is prepared by an atomization pretreatment combined with a non-solvent induced phase separation method.
8. The method for producing a porous separation membrane according to claim 7, characterized by comprising the steps of:
(1) ultrasonically dispersing a catalyst in a solvent to prepare a dispersion liquid of the catalyst;
(2) dissolving a polymer mixture containing 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 membrane casting solution, scraping the membrane casting solution, and then carrying out atomization pretreatment, wherein the atomization pretreatment is that the membrane casting solution stays in an atomized liquid drop bath;
(4) and immersing into a coagulating bath to obtain the porous separation membrane.
9. The method for producing a porous separation membrane according to claim 8, characterized in that:
in the step (3), the total content of the polymer in the casting solution is 5-25 wt%, preferably 6-20 wt%; and/or the presence of a gas in the gas,
the weight ratio of the polymer 1 to the polymer 2 is 1 (0.01-5), preferably 1: (0.1 to 3); and/or the presence of a gas in the gas,
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, and preferably (0.05-0.25): 1.
10. the method for producing a porous separation membrane according to claim 8, characterized in that:
in the step (3), uniformly coating the casting 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 (3), the thickness of the scraped film is 50 to 500 μm, preferably 75 to 300 μm.
11. The method for producing a porous separation membrane according to claim 8, characterized in that:
in the step (3), the size of the liquid drops in the liquid drop bath is 1-50 μm, preferably 5-18 μm; and/or the presence of a gas in the gas,
in the step (3), the atomization pretreatment time is 1 s-20 min, preferably 5 s-3 min.
12. The method for producing a porous separation membrane according to claim 8, characterized in that:
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 drops are poor solvents of the polymer 1; and/or the presence of a gas in the gas,
in the step (4), the coagulation bath is a poor solvent for the polymer 1.
13. The method for producing a porous separation membrane according to claim 12, 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 presence of a gas in the gas,
the poor solvent is at least one selected from water, ethanol and glycol.
14. Use of the porous separation membrane according to any one of claims 1 to 6 or the porous separation membrane obtained by the production method according to any one of claims 7 to 13 for removing formaldehyde from air or water.
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