CN109012232B - Preparation method of anti-shrinkage polytetrafluoroethylene composite nanofiltration membrane - Google Patents
Preparation method of anti-shrinkage polytetrafluoroethylene composite nanofiltration membrane Download PDFInfo
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- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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- B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
- B01D71/06—Organic material
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- B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
- B01D61/02—Reverse osmosis; Hyperfiltration ; Nanofiltration
- B01D61/027—Nanofiltration
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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- B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
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- B01D2325/36—Hydrophilic membranes
Abstract
The invention relates to the technical field of environment-friendly materials, and discloses a preparation method of an anti-shrinkage polytetrafluoroethylene composite nanofiltration membrane. The preparation method comprises the steps of firstly preparing a mixed solution containing modified rod-shaped silicon dioxide and an oil phase solution, then respectively immersing the hydrophilic polytetrafluoroethylene microporous base membrane into the mixed solution and the oil phase solution to carry out interfacial polymerization reaction, and polymerizing a polyamide separation layer on the surface of the hydrophilic polytetrafluoroethylene microporous base membrane. The polytetrafluoroethylene composite nanofiltration membrane has better anti-shrinkage performance, can keep and prevent the polyamide separation layer of the composite nanofiltration membrane from being damaged and replaced by thermal shrinkage, thereby keeping the separation performance of the nanofiltration membrane.
Description
Technical Field
The invention relates to the technical field of environment-friendly materials, in particular to a preparation method of an anti-shrinkage polytetrafluoroethylene composite nanofiltration membrane.
Background
The membrane separation technology is a modern novel high-efficiency separation technology, is particularly suitable for the requirements of modern industry on energy conservation, production efficiency improvement, low-grade raw material utilization and environmental pollution elimination, and becomes an important component part for realizing economic sustainable development strategy. According to the size of the separation material, the difference of physical and chemical properties, the structure and aperture size of the membrane and the properties of different membrane materials, the corresponding various membranes are widely applied at present: ultrafiltration, nanofiltration, reverse osmosis, electrodialysis, membrane electrolysis, dialysis, gas separation, pervaporation, membrane distillation, and the like. In recent ten years, nanofiltration is a novel pressure-driven membrane separation process which is newly developed, is one of the hot spots of the research in the field of national and foreign membrane separation at present, and can be applied to the fields of sewage treatment, water softening and seawater desalination. For separating organic matters from an aqueous solution, the molecule of the nanofiltration membrane is nano-scale, the separation characteristic of nanofiltration is positioned between reverse osmosis and the ultrafiltration membrane, generally, the nanofiltration membrane can intercept saccharide low-molecular organic matters and multivalent salts, the interception rate of the nanofiltration membrane on single salt is only 10-80%, the nanofiltration membrane has great permeability, the interception rate on bivalent and high-valent salts is more than 90%, and the ion selectivity characteristic of the nanofiltration membrane enlarges the application field of the nanofiltration membrane. The nanofiltration membrane comprises a membrane substrate and a separation layer covering the surface of the membrane substrate, wherein the membrane substrate plays a supporting role, and the separation layer plays a role in separating water from pollutants (the water can permeate the separation layer, and the pollutants cannot permeate the separation layer). At present, most of membrane substrates are polysulfone, polyethersulfone, polyvinylidene fluoride and the like, but the membrane substrates have the problems of poor strength and acid and alkali resistance, and the application field is limited. The polytetrafluoroethylene membrane substrate is resistant to high temperature, strong acid and strong base, and has wide application prospect.
Chinese patent publication No. CN104324622 discloses a preparation method of a polytetrafluoroethylene composite nanofiltration membrane, which comprises the steps of activating a hydrophobic polytetrafluoroethylene microporous membrane, then carrying out water phase impregnation and oil phase impregnation, and finally carrying out heating treatment to obtain the polytetrafluoroethylene composite nanofiltration membrane. The invention utilizes the characteristics that the polytetrafluoroethylene microporous base membrane has high strength and does not need an additional supporting layer, the membrane preparation process is simple, and in addition, the unique node-fibril microporous structure of the polytetrafluoroethylene microporous membrane is utilized, so that the bonding strength between the base membrane and the nanofiltration modified layer is greatly improved, and the performance of the composite nanofiltration membrane is improved. The polytetrafluoroethylene microfiltration membrane is easy to shrink under the heating material, and a separation layer formed on the polytetrafluoroethylene base membrane through interfacial polymerization can be broken in the shrinking process, so that the separation performance of the composite nanofiltration membrane is reduced.
Disclosure of Invention
The invention provides a preparation method of an anti-shrinkage polytetrafluoroethylene composite nanofiltration membrane, aiming at overcoming the problem that the separation layer is broken and replaced due to thermal shrinkage of a polytetrafluoroethylene microporous base membrane in the prior art, so that the separation performance of the composite nanofiltration membrane is reduced.
In order to achieve the purpose, the invention adopts the following technical scheme: a preparation method of an anti-shrinkage polytetrafluoroethylene composite nanofiltration membrane comprises the following steps:
1) preparing a mixed solution: adding triethylenetetramine into deionized water to prepare 0.5-3 wt% triethylenetetramine aqueous solution, then adding modified rodlike silicon dioxide, wherein the mass ratio of the modified rodlike silicon dioxide to the triethylenetetramine is 1: 3-5, and stirring to obtain mixed solution a;
2) preparing an oil phase solution: adding trimesoyl chloride into a normal hexane solvent to prepare a trimesoyl chloride solution b with the concentration of 0.1-0.8 wt%;
3) interfacial polymerization: immersing the hydrophilic polytetrafluoroethylene microporous base membrane into the mixed solution a for ultrasonic oscillation for 1-5 min, taking out the hydrophilic polytetrafluoroethylene microporous base membrane, removing the redundant mixed solution a on the surface, and then immersing the hydrophilic polytetrafluoroethylene microporous base membrane into a trimesoyl chloride solution b for standing reaction for 30-60 s to obtain a nascent state composite nanofiltration membrane;
4) and (3) crosslinking and curing: and (3) carrying out heat treatment on the nascent state composite nanofiltration membrane at the temperature of 45-52 ℃ for 10-20 min to obtain the anti-shrinkage polytetrafluoroethylene composite nanofiltration membrane.
In the interfacial polymerization reaction, triethylenetetramine and trimesoyl chloride react on the surface of the hydrophilic polytetrafluoroethylene microporous base membrane, so that a polyamide separation layer with a separation effect on pollutants and ions is covered on the surface of the hydrophilic polytetrafluoroethylene microporous base membrane. According to the preparation method, modified rodlike silicon dioxide is added into triethylenetetramine, rodlike silicon dioxide is embedded into the polyamide separation layer in the interfacial polymerization process, the rodlike silicon dioxide plays a role of a framework, and the strength of the polyamide separation layer is greatly increased, so that the polyamide separation layer is tightly combined and is not easy to break and exchange under the action of thermal contraction external force, and the excellent separation performance of the composite nanofiltration membrane is maintained; the polyamide separation layer with higher strength can block the shrinkage of the polytetrafluoroethylene-based membrane in the heat treatment process, and the shrinkage of the polytetrafluoroethylene-based membrane reduces the aperture of the microporous base membrane, so that the water flux is reduced; in addition, the silicon dioxide has an antibacterial effect, so that bacteria are prevented from breeding in the composite nanofiltration membrane, and the composite nanofiltration membrane is prevented from being polluted and damaged.
Preferably, the preparation method of the hydrophilic polytetrafluoroethylene microporous base membrane in the step 3) comprises the following steps: carrying out plasma treatment on a polytetrafluoroethylene microporous base membrane in a nitrogen atmosphere, then soaking the polytetrafluoroethylene microporous base membrane subjected to plasma treatment into an ethanol water solution of a modified polygonatum odoratum polysaccharide extract, adding an initiator azodiisobutyronitrile, reacting at 60-65 ℃ for 3-5 hours, taking out the polytetrafluoroethylene microporous base membrane, washing with deionized water to remove unreacted monomers, and drying to obtain the hydrophilic polytetrafluoroethylene microporous base membrane.
Preferably, the preparation method of the modified polygonatum odoratum polysaccharide extract comprises the following steps: adding the polygonatum odoratum polysaccharide extract into 65-80 wt% of ethanol water solution, wherein the mass concentration of the polygonatum odoratum polysaccharide extract is 10-15 wt%, and then adding a catalyst SbCl5The method comprises the steps of adding a catalyst in an amount which is 2-3.5% of the weight of an anhydrous ethanol aqueous solution, uniformly stirring and mixing, slowly dropwise adding allyl glycidyl ether, wherein the addition amount of the allyl glycidyl ether is 20-40 wt% of the weight of the polygonatum odoratum polysaccharide extract, reacting at 65-70 ℃ for 2-4 hours in a heat preservation manner, and sequentially performing rotary evaporation concentration and vacuum drying after the reaction is finished to obtain the modified polygonatum odoratum polysaccharide extract.
The modified Polygonatum odoratum polysaccharide extract is obtained by modifying Polygonatum odoratum polysaccharide extract, and grafting alkylene on the molecule of Polygonatum odoratum polysaccharide extract.
The polygonatum odoratum polysaccharide extract has more hydrophilic functional groups such as-OH, -COOH and the like, and the modified polygonatum odoratum polysaccharide extract is used as a hydrophilic modification substance of the hydrophobic polytetrafluoroethylene microfiltration base membrane, so that the hydrophobic polytetrafluoroethylene microfiltration base membrane has a better hydrophilic modification effect.
Epoxy groups on allyl glycidyl ether in the catalyst SbCl5Under the condition, the ring opening is carried out, and the reaction is carried out with-OH on the polygonatum polysaccharide extract, so that allyl glycidyl ether is connected to the polygonatum polysaccharide extract molecules, the polygonatum polysaccharide extract molecules are provided with alkylene, and the ring opening reaction process of the allyl glycidyl ether and the polygonatum polysaccharide extract is as follows:
wherein A represents Polygonatum odoratum polysaccharide extract.
C-F bonds on a polytetrafluoroethylene molecular chain are broken to generate free radicals, the modified polygonatum odoratum polysaccharide extract is provided with olefin groups, and free radical polymerization is carried out under the action of an initiator azobisisobutyronitrile, so that the modified polygonatum odoratum polysaccharide extract is connected to the polytetrafluoroethylene microporous base membrane, and the polytetrafluoroethylene microporous base membrane has better hydrophilic performance.
Preferably, the mass concentration of the modified polygonatum odoratum polysaccharide extract is 2-10%.
Preferably, the mass fraction of the ethanol aqueous solution is 60-70%.
Preferably, the initiator azobisisobutyronitrile accounts for 0.2-0.5% of the ethanol aqueous solution by mass concentration.
Preferably, the preparation method of the modified rod-shaped silica in the step 1) comprises the following steps:
adding rod-shaped silicon dioxide into water, then adding titanium sulfate and urea, controlling the pH value of the aqueous solution to be 1.5-2.2, stirring and hydrolyzing at 70-80 ℃ for 7-10 h, controlling the stirring speed to be 50-60 r/min, filtering after the hydrolysis is finished, drying the filtrate, then sintering at 400-500 ℃ for 3-5 h, then cooling to 200-250 ℃, preserving heat for 1-2 h, and cooling to obtain the modified rod-shaped silicon dioxide.
Titanium sulfate is hydrolyzed under the action of urea to generate nano titanium dioxide, the nano titanium dioxide is deposited on the modified rod-shaped silicon dioxide, so that nano protrusions are formed on the surface, the roughness of the surface of the rod-shaped silicon dioxide is increased, polyamide macromolecules of the separating layer are entangled on the rod-shaped silicon dioxide, the combination stability of the polyamide macromolecules and the rod-shaped silicon dioxide is greatly increased due to the increase of the roughness of the rod-shaped silicon dioxide, and the strength of the polyamide separating layer is further increased; in addition, since the nano titanium dioxide is deposited on the modified rod-shaped silicon dioxide, Ti4+The carboxyl on the polygonatum odoratum polysaccharide extract connected with the polytetrafluoroethylene microfiltration base membrane forms coordination, so that the stability of the connection of the polyamide separation layer and the polytetrafluoroethylene microfiltration base membrane is improved, the polyamide separation layer is not easy to fall off from the polytetrafluoroethylene microfiltration base membrane under the action of high water pressure, and the excellent separation performance of the composite nanofiltration membrane is kept for a long time.
Preferably, the amount of the rod-like silica added is 10 to 15wt% of water.
Preferably, the mass ratio of the rod-shaped silica to the titanium sulfate is 1: 0.4-0.8.
Preferably, the mass ratio of the titanium sulfate to the urea is 1: 4-5.5.
Therefore, the invention has the following beneficial effects: (1) the polytetrafluoroethylene composite nanofiltration membrane has better anti-shrinkage performance, can be kept, and can prevent the polyamide separation layer of the composite nanofiltration membrane from being damaged and replaced by thermal shrinkage, so that the separation performance of the nanofiltration membrane is kept; (2) the modified polygonatum odoratum polysaccharide extract has good hydrophilicity, and can greatly improve the hydrophilicity of the hydrophobic polytetrafluoroethylene microporous base membrane.
Detailed Description
The technical solution of the present invention is further illustrated by the following specific examples.
In the present invention, unless otherwise specified, all the raw materials and equipment used are commercially available or commonly used in the art, and the methods in the examples are conventional in the art unless otherwise specified.
Example 1
The preparation method of the hydrophilic polytetrafluoroethylene microporous base membrane comprises the following steps:
carrying out plasma treatment on a polytetrafluoroethylene microporous base membrane in a nitrogen atmosphere, then soaking the polytetrafluoroethylene microporous base membrane subjected to the plasma treatment into an ethanol water solution of a modified polygonatum polysaccharide extract, wherein the mass concentration of the modified polygonatum polysaccharide extract is 5%, the mass fraction of the ethanol water solution is 65%, adding an initiator azobisisobutyronitrile, the mass concentration percentage of the initiator azobisisobutyronitrile to the ethanol water solution is 0.3%, reacting for 4h at 63 ℃, taking out the polytetrafluoroethylene microporous base membrane, washing with deionized water to remove unreacted monomers, and drying to obtain the hydrophilic polytetrafluoroethylene microporous base membrane.
The preparation method of the modified polygonatum odoratum polysaccharide extract comprises the following steps:
adding Polygonatum odoratum polysaccharide extract into 75% ethanol water solution with mass concentration of 12 wt%, and adding catalyst SbCl5The adding amount of the catalyst is 2.5 percent of the mass of the anhydrous ethanol water solution, the mixture is stirred and mixed evenly, and then the allyl glycidyl is slowly drippedAdding oil ether and allyl glycidyl ether 30 wt% of rhizoma Polygonati Odorati polysaccharide extract, reacting at 68 deg.C for 3 hr, and performing rotary evaporation, concentration and vacuum drying to obtain modified rhizoma Polygonati Odorati polysaccharide extract.
The preparation method of the modified rod-shaped silicon dioxide comprises the following steps:
adding rod-shaped silicon dioxide into water, wherein the addition amount of the rod-shaped silicon dioxide is 12 wt% of the water, then adding titanium sulfate and urea, the mass ratio of the titanium sulfate to the urea is 1:5, the mass ratio of the rod-shaped silicon dioxide to the titanium sulfate is 1:0.6, controlling the pH value of an aqueous solution to be 2, stirring and hydrolyzing at 75 ℃ for 8h, controlling the stirring speed to be 55r/min, filtering after the hydrolysis is finished, drying a filter, sintering at 460 ℃ for 4h, cooling to 220 ℃, preserving the temperature for 1.5h, and cooling to obtain the modified rod-shaped silicon dioxide.
The preparation method of the anti-shrinkage polytetrafluoroethylene composite nanofiltration membrane comprises the following steps:
1) preparing a mixed solution: adding triethylenetetramine into deionized water to prepare a triethylenetetramine aqueous solution with the concentration of 2 wt%, then adding modified rodlike silicon dioxide, wherein the mass ratio of the modified rodlike silicon dioxide to the triethylenetetramine is 1:4, and stirring to obtain a mixed solution a;
2) preparing an oil phase solution: adding trimesoyl chloride into a normal hexane solvent to prepare a 0.6 wt% trimesoyl chloride solution b;
3) interfacial polymerization: immersing the hydrophilic polytetrafluoroethylene microporous base membrane into the mixed solution a for ultrasonic oscillation for 3min, taking out the hydrophilic polytetrafluoroethylene microporous base membrane, removing the redundant mixed solution a on the surface, and then immersing the hydrophilic polytetrafluoroethylene microporous base membrane into a trimesoyl chloride solution b for standing reaction for 45s to obtain a nascent state composite nanofiltration membrane;
4) and (3) crosslinking and curing: and (3) carrying out heat treatment on the nascent state composite nanofiltration membrane at 48 ℃ for 15min to obtain the anti-shrinkage polytetrafluoroethylene composite nanofiltration membrane.
Example 2
The preparation method of the hydrophilic polytetrafluoroethylene microporous base membrane comprises the following steps:
carrying out plasma treatment on a polytetrafluoroethylene microporous base membrane in a nitrogen atmosphere, then soaking the polytetrafluoroethylene microporous base membrane subjected to the plasma treatment into an ethanol water solution of a modified polygonatum polysaccharide extract, wherein the mass concentration of the modified polygonatum polysaccharide extract is 3%, the mass fraction of the ethanol water solution is 65%, adding an initiator azobisisobutyronitrile, the mass concentration percentage of the initiator azobisisobutyronitrile to the ethanol water solution is 0.3%, reacting for 4h at 62 ℃, taking out the polytetrafluoroethylene microporous base membrane, washing with deionized water to remove unreacted monomers, and drying to obtain the hydrophilic polytetrafluoroethylene microporous base membrane.
The preparation method of the modified polygonatum odoratum polysaccharide extract comprises the following steps:
adding Polygonatum odoratum polysaccharide extract into 68 wt% ethanol water solution, adding catalyst SbCl5Adding catalyst in an amount of 2.5% of the weight of the anhydrous ethanol aqueous solution, stirring and mixing uniformly, slowly dropwise adding allyl glycidyl ether in an amount of 25 wt% of the polygonatum odoratum polysaccharide extract, reacting at 66 ℃ for 2.5h under heat preservation, and after the reaction is finished, sequentially performing rotary evaporation concentration and vacuum drying to obtain the modified polygonatum odoratum polysaccharide extract.
The preparation method of the modified rod-shaped silicon dioxide comprises the following steps:
adding rod-shaped silicon dioxide into water, wherein the addition amount of the rod-shaped silicon dioxide is 12 wt% of the water, then adding titanium sulfate and urea, the mass ratio of the titanium sulfate to the urea is 1:4.5, the mass ratio of the rod-shaped silicon dioxide to the titanium sulfate is 1:0.5, controlling the pH value of the aqueous solution at 1.8, stirring and hydrolyzing at 72 ℃ for 8h, controlling the stirring speed at 55r/min, filtering after the hydrolysis is finished, drying the filtrate, then sintering at 420 ℃ for 3.5h, then cooling to 210 ℃, preserving heat for 1.2h, and cooling to obtain the modified rod-shaped silicon dioxide.
The preparation method of the anti-shrinkage polytetrafluoroethylene composite nanofiltration membrane comprises the following steps:
1) preparing a mixed solution: adding triethylenetetramine into deionized water to prepare 0.8wt% triethylenetetramine aqueous solution, adding modified rodlike silicon dioxide, wherein the mass ratio of the modified rodlike silicon dioxide to the triethylenetetramine is 1:3.5, and stirring to obtain mixed solution a;
2) preparing an oil phase solution: adding trimesoyl chloride into a normal hexane solvent to prepare a 0.2 wt% trimesoyl chloride solution b;
3) interfacial polymerization: immersing the hydrophilic polytetrafluoroethylene microporous base membrane into the mixed solution a for ultrasonic oscillation for 2min, taking out the hydrophilic polytetrafluoroethylene microporous base membrane, removing the redundant mixed solution a on the surface, and then immersing the hydrophilic polytetrafluoroethylene microporous base membrane into a trimesoyl chloride solution b for standing reaction for 35s to obtain a nascent state composite nanofiltration membrane;
4) and (3) crosslinking and curing: and (3) carrying out heat treatment on the nascent state composite nanofiltration membrane at 46 ℃ for 12min to obtain the anti-shrinkage polytetrafluoroethylene composite nanofiltration membrane.
Example 3
The preparation method of the hydrophilic polytetrafluoroethylene microporous base membrane comprises the following steps:
carrying out plasma treatment on a polytetrafluoroethylene microporous base membrane in a nitrogen atmosphere, then soaking the polytetrafluoroethylene microporous base membrane subjected to the plasma treatment into an ethanol water solution of a modified polygonatum polysaccharide extract, wherein the mass concentration of the modified polygonatum polysaccharide extract is 8%, the mass fraction of the ethanol water solution is 65%, adding an initiator azobisisobutyronitrile, the mass concentration percentage of the initiator azobisisobutyronitrile to the ethanol water solution is 0.4%, reacting for 4h at 64 ℃, taking out the polytetrafluoroethylene microporous base membrane, washing with deionized water to remove unreacted monomers, and drying to obtain the hydrophilic polytetrafluoroethylene microporous base membrane.
The preparation method of the modified polygonatum odoratum polysaccharide extract comprises the following steps:
adding Polygonatum odoratum polysaccharide extract into 75% ethanol water solution with mass concentration of 13 wt%, and adding catalyst SbCl5The catalyst is added in an amount which is 3% of the mass of the anhydrous ethanol water solution, the mixture is stirred and mixed uniformly, then the allyl glycidyl ether is slowly added dropwise, the addition amount of the allyl glycidyl ether is 35 wt% of the polygonatum odoratum polysaccharide extract, the heat preservation reaction is carried out for 3.5h at 68 ℃, and after the reaction is finished, the rotary evaporation concentration and the vacuum drying are sequentially carried out to obtain the modified polygonatum odoratum polysaccharide extract.
The preparation method of the modified rod-shaped silicon dioxide comprises the following steps:
adding rod-shaped silicon dioxide into water, wherein the addition amount of the rod-shaped silicon dioxide is 14 wt% of the water, then adding titanium sulfate and urea, the mass ratio of the titanium sulfate to the urea is 1:5, the mass ratio of the rod-shaped silicon dioxide to the titanium sulfate is 1:0.7, controlling the pH value of an aqueous solution to be 2, stirring and hydrolyzing at 78 ℃ for 9h, controlling the stirring speed to be 55r/min, filtering after the hydrolysis is finished, drying a filter, sintering at 480 ℃ for 4.5h, cooling to 240 ℃, preserving heat for 1.8h, and cooling to obtain the modified rod-shaped silicon dioxide.
The preparation method of the anti-shrinkage polytetrafluoroethylene composite nanofiltration membrane comprises the following steps:
1) preparing a mixed solution: adding triethylenetetramine into deionized water to prepare a triethylenetetramine aqueous solution with the concentration of 2.5 wt%, then adding modified rodlike silicon dioxide, wherein the mass ratio of the modified rodlike silicon dioxide to the triethylenetetramine is 1:4.5, and stirring to obtain a mixed solution a;
2) preparing an oil phase solution: adding trimesoyl chloride into a normal hexane solvent to prepare a 0.6 wt% trimesoyl chloride solution b;
3) interfacial polymerization: immersing the hydrophilic polytetrafluoroethylene microporous base membrane into the mixed solution a for ultrasonic oscillation for 4min, taking out the hydrophilic polytetrafluoroethylene microporous base membrane, removing the redundant mixed solution a on the surface, and then immersing the hydrophilic polytetrafluoroethylene microporous base membrane into a trimesoyl chloride solution b for standing reaction for 30-60 s to obtain a nascent state composite nanofiltration membrane;
4) and (3) crosslinking and curing: and (3) carrying out heat treatment on the nascent state composite nanofiltration membrane at 50 ℃ for 18min to obtain the anti-shrinkage polytetrafluoroethylene composite nanofiltration membrane.
Example 4
The preparation method of the hydrophilic polytetrafluoroethylene microporous base membrane comprises the following steps:
carrying out plasma treatment on a polytetrafluoroethylene microporous base membrane in a nitrogen atmosphere, then soaking the polytetrafluoroethylene microporous base membrane subjected to the plasma treatment into an ethanol water solution of a modified polygonatum polysaccharide extract, wherein the mass concentration of the modified polygonatum polysaccharide extract is 5%, the mass fraction of the ethanol water solution is 62%, adding an initiator azobisisobutyronitrile, the mass concentration percentage of the initiator azobisisobutyronitrile in the ethanol water solution is 0.4%, reacting for 3.5h at 64 ℃, taking out the polytetrafluoroethylene microporous base membrane, washing with deionized water to remove unreacted monomers, and drying to obtain the hydrophilic polytetrafluoroethylene microporous base membrane.
The preparation method of the modified polygonatum odoratum polysaccharide extract comprises the following steps:
adding Polygonatum odoratum polysaccharide extract into 70 wt% ethanol water solution, adding catalyst SbCl5Adding catalyst in an amount of 2.5% of the weight of the anhydrous ethanol aqueous solution, stirring and mixing uniformly, slowly dropwise adding allyl glycidyl ether in an amount of 35 wt% of the polygonatum odoratum polysaccharide extract, reacting at 66 ℃ for 2.5h under heat preservation, and after the reaction is finished, sequentially performing rotary evaporation concentration and vacuum drying to obtain the modified polygonatum odoratum polysaccharide extract.
The preparation method of the modified rod-shaped silicon dioxide comprises the following steps:
adding rod-shaped silicon dioxide into water, wherein the addition amount of the rod-shaped silicon dioxide is 14 wt% of the water, then adding titanium sulfate and urea, the mass ratio of the titanium sulfate to the urea is 1:5, the mass ratio of the rod-shaped silicon dioxide to the titanium sulfate is 1:0.5, controlling the pH value of an aqueous solution to be 2, stirring and hydrolyzing at 78 ℃ for 8h, controlling the stirring speed to be 55r/min, filtering after the hydrolysis is finished, drying a filter, sintering at the high temperature of 450 ℃ for 3.5h, cooling to 240 ℃, preserving the temperature for 1.5h, and cooling to obtain the modified rod-shaped silicon dioxide.
The preparation method of the anti-shrinkage polytetrafluoroethylene composite nanofiltration membrane comprises the following steps:
1) preparing a mixed solution: adding triethylenetetramine into deionized water to prepare a triethylenetetramine aqueous solution with the concentration of 2.5 wt%, then adding modified rodlike silicon dioxide, wherein the mass ratio of the modified rodlike silicon dioxide to the triethylenetetramine is 1:3.5, and stirring to obtain a mixed solution a;
2) preparing an oil phase solution: adding trimesoyl chloride into a normal hexane solvent to prepare a 0.2 wt% trimesoyl chloride solution b;
3) interfacial polymerization: immersing the hydrophilic polytetrafluoroethylene microporous base membrane into the mixed solution a for ultrasonic oscillation for 4min, taking out the hydrophilic polytetrafluoroethylene microporous base membrane, removing the redundant mixed solution a on the surface, and then immersing the hydrophilic polytetrafluoroethylene microporous base membrane into a trimesoyl chloride solution b for standing reaction for 50s to obtain a nascent state composite nanofiltration membrane;
4) and (3) crosslinking and curing: and (3) carrying out heat treatment on the nascent state composite nanofiltration membrane at 50 ℃ for 15min to obtain the anti-shrinkage polytetrafluoroethylene composite nanofiltration membrane.
Example 5
The preparation method of the hydrophilic polytetrafluoroethylene microporous base membrane comprises the following steps:
carrying out plasma treatment on a polytetrafluoroethylene microporous base membrane in a nitrogen atmosphere, then soaking the polytetrafluoroethylene microporous base membrane subjected to the plasma treatment into an ethanol water solution of a modified polygonatum polysaccharide extract, wherein the mass concentration of the modified polygonatum polysaccharide extract is 10%, the mass fraction of the ethanol water solution is 70%, adding an initiator azobisisobutyronitrile, the mass concentration percentage of the initiator azobisisobutyronitrile to the ethanol water solution is 0.5%, reacting for 5 hours at 65 ℃, taking out the polytetrafluoroethylene microporous base membrane, washing with deionized water to remove unreacted monomers, and drying to obtain the hydrophilic polytetrafluoroethylene microporous base membrane.
The preparation method of the modified polygonatum odoratum polysaccharide extract comprises the following steps:
adding Polygonatum odoratum polysaccharide extract into 80 wt% ethanol water solution, adding catalyst SbCl5And the addition amount of the catalyst is 3.5 percent of the mass of the anhydrous ethanol aqueous solution, stirring and mixing uniformly, slowly dropwise adding allyl glycidyl ether, the addition amount of the allyl glycidyl ether is 40 percent by weight of the polygonatum odoratum polysaccharide extract, carrying out heat preservation reaction at 70 ℃ for 4 hours, and carrying out rotary evaporation concentration and vacuum drying in sequence after the reaction is finished to obtain the modified polygonatum odoratum polysaccharide extract.
The preparation method of the modified rod-shaped silicon dioxide comprises the following steps:
adding rod-shaped silicon dioxide into water, wherein the addition amount of the rod-shaped silicon dioxide is 15wt% of the water, then adding titanium sulfate and urea, the mass ratio of the titanium sulfate to the urea is 1:5.5, the mass ratio of the rod-shaped silicon dioxide to the titanium sulfate is 1:0.8, controlling the pH value of the aqueous solution to be 2.2, stirring and hydrolyzing at 80 ℃ for 10h, controlling the stirring speed to be 60r/min, filtering after the hydrolysis is finished, drying a filtrate, then sintering at high temperature of 500 ℃ for 5h, then cooling to 250 ℃, preserving heat for 2h, and cooling to obtain the modified rod-shaped silicon dioxide.
The preparation method of the anti-shrinkage polytetrafluoroethylene composite nanofiltration membrane comprises the following steps:
1) preparing a mixed solution: adding triethylenetetramine into deionized water to prepare a triethylenetetramine aqueous solution with the concentration of 3wt%, then adding modified rodlike silicon dioxide, wherein the mass ratio of the modified rodlike silicon dioxide to the triethylenetetramine is 1:5, and stirring to obtain a mixed solution a;
2) preparing an oil phase solution: adding trimesoyl chloride into a normal hexane solvent to prepare a 0.8wt% trimesoyl chloride solution b;
3) interfacial polymerization: immersing the hydrophilic polytetrafluoroethylene microporous base membrane into the mixed solution a for ultrasonic oscillation for 5min, taking out the hydrophilic polytetrafluoroethylene microporous base membrane, removing the redundant mixed solution a on the surface, and then immersing the hydrophilic polytetrafluoroethylene microporous base membrane into a trimesoyl chloride solution b for standing reaction for 60s to obtain a nascent state composite nanofiltration membrane;
4) and (3) crosslinking and curing: and (3) carrying out heat treatment on the nascent state composite nanofiltration membrane at 52 ℃ for 20min to obtain the anti-shrinkage polytetrafluoroethylene composite nanofiltration membrane.
Example 6
The preparation method of the hydrophilic polytetrafluoroethylene microporous base membrane comprises the following steps:
carrying out plasma treatment on a polytetrafluoroethylene microporous base membrane in a nitrogen atmosphere, then soaking the polytetrafluoroethylene microporous base membrane subjected to the plasma treatment into an ethanol water solution of a modified polygonatum polysaccharide extract, wherein the mass concentration of the modified polygonatum polysaccharide extract is 2%, the mass fraction of the ethanol water solution is 60%, adding an initiator azobisisobutyronitrile, the mass concentration percentage of the initiator azobisisobutyronitrile in the ethanol water solution is 0.2%, reacting for 3h at 60 ℃, taking out the polytetrafluoroethylene microporous base membrane, washing with deionized water to remove unreacted monomers, and drying to obtain the hydrophilic polytetrafluoroethylene microporous base membrane.
The preparation method of the modified polygonatum odoratum polysaccharide extract comprises the following steps:
adding Polygonatum odoratum polysaccharide extract into 65% ethanol water solution with mass concentration of 10 wt%, and adding catalyst SbCl5Adding a catalyst in an amount of 2% by mass of the anhydrous ethanol aqueous solution, stirring and mixing uniformly, slowly dropwise adding allyl glycidyl ether in an amount of 20 wt% of the polygonatum odoratum polysaccharide extract, carrying out heat preservation reaction at 65 ℃ for 2h, and carrying out rotary evaporation concentration and vacuum drying in sequence after the reaction is finished to obtain the modified polygonatum odoratum polysaccharide extract.
The preparation method of the modified rod-shaped silicon dioxide comprises the following steps:
adding rod-shaped silicon dioxide into water, wherein the addition amount of the rod-shaped silicon dioxide is 10 wt% of the water, then adding titanium sulfate and urea, the mass ratio of the titanium sulfate to the urea is 1:4, the mass ratio of the rod-shaped silicon dioxide to the titanium sulfate is 1:0.4, controlling the pH value of an aqueous solution at 1.5, stirring and hydrolyzing at 70 ℃ for 7h, controlling the stirring speed at 50r/min, filtering after the hydrolysis is finished, drying a filter, sintering at high temperature of 400 ℃ for 3h, cooling to 200 ℃, preserving heat for 1h, and cooling to obtain the modified rod-shaped silicon dioxide.
The preparation method of the anti-shrinkage polytetrafluoroethylene composite nanofiltration membrane comprises the following steps:
1) preparing a mixed solution: adding triethylenetetramine into deionized water to prepare 0.5 wt% triethylenetetramine aqueous solution, adding modified rodlike silicon dioxide, wherein the mass ratio of the modified rodlike silicon dioxide to the triethylenetetramine is 1:3, and stirring to obtain mixed solution a;
2) preparing an oil phase solution: adding trimesoyl chloride into a normal hexane solvent to prepare a 0.1 wt% trimesoyl chloride solution b;
3) interfacial polymerization: immersing the hydrophilic polytetrafluoroethylene microporous base membrane into the mixed solution a for ultrasonic oscillation for 1min, taking out the hydrophilic polytetrafluoroethylene microporous base membrane, removing the redundant mixed solution a on the surface, and then immersing the hydrophilic polytetrafluoroethylene microporous base membrane into a trimesoyl chloride solution b for standing reaction for 30s to obtain a nascent state composite nanofiltration membrane;
4) and (3) crosslinking and curing: and (3) carrying out heat treatment on the nascent state composite nanofiltration membrane at 45 ℃ for 10min to obtain the anti-shrinkage polytetrafluoroethylene composite nanofiltration membrane.
Comparative example 1
The difference between the comparative example 1 and the example 1 is that the modified rod-shaped silicon dioxide is not added in the step 1) in the preparation method of the anti-shrinkage polytetrafluoroethylene composite nanofiltration membrane.
Comparative example 2
The difference between the comparative example 2 and the example 1 is that the hydrophilic polytetrafluoroethylene microporous base membrane in the step 3) in the preparation method of the anti-shrinkage polytetrafluoroethylene composite nanofiltration membrane is a commercially available hydrophilic polytetrafluoroethylene microporous base membrane.
And (3) testing the performance of the composite nanofiltration membrane:
the separation performance and flux of the polytetrafluoroethylene composite nanofiltration membrane are tested, a magnesium sulfate aqueous solution with the concentration of 1g/L and a PEG400 solution with the concentration of 100mg/L are respectively prepared, the polytetrafluoroethylene composite nanofiltration membrane is operated for 1h under the conditions of 25 ℃ and the operating pressure of 0.2MPa, then the separation performance and the flux of water of the polytetrafluoroethylene composite nanofiltration membrane are tested, and the test results are as follows:
by comparing the examples 1, 3 and 5 with the comparative example 1, the composite nanofiltration membrane of the invention can be obtained to Mg2+The rejection rate and the PEG400 rejection rate have higher rejection rate, because the rod-shaped silicon dioxide is embedded into the polyamide separation layer in the interfacial polymerization process, and the rod-shaped silicon dioxide plays a role of a framework, so that the strength of the polyamide separation layer is greatly increased, the polyamide separation layer is tightly combined and is not easy to break and exchange under the action of thermal contraction external force, and the excellent separation performance of the composite nanofiltration membrane is maintained; compared with the comparative example 2, the composite nanofiltration membrane of the invention has higher water flux, which is obtained by comparing the examples 1, 3 and 5 with the comparative example 2, because the modified polygonatum odoratum polysaccharide extract has more hydrophilic groups, so that the hydrophilic performance of the composite nanofiltration membrane is improved, and the composite nanofiltration membrane has higher water flux;in addition, the water flux of the composite nanofiltration membrane in the comparative example 1 is higher than that of the composite nanofiltration membrane in the example, and the composite nanofiltration membrane in the comparative example 1 breaks the separation layer under the action of the external force of thermal contraction, so that the compactness of the separation layer is reduced, and the water flux is increased.
Although the present invention has been described with reference to a preferred embodiment, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (8)
1. The preparation method of the anti-shrinkage polytetrafluoroethylene composite nanofiltration membrane is characterized by comprising the following steps of:
1) preparing a mixed solution: adding triethylenetetramine into deionized water to prepare 0.5-3 wt% triethylenetetramine aqueous solution, then adding modified rodlike silicon dioxide, wherein the mass ratio of the modified rodlike silicon dioxide to the triethylenetetramine is 1: 3-5, and stirring to obtain mixed solution a; the preparation method of the modified rodlike silicon dioxide comprises the following steps: adding rod-shaped silicon dioxide into water, then adding titanium sulfate and urea, controlling the pH value of the aqueous solution to be 1.5-2.2, stirring and hydrolyzing at 70-80 ℃ for 7-10 h, controlling the stirring speed to be 50-60 r/min, filtering after the hydrolysis is finished, drying the filtrate, then sintering at the high temperature of 400-500 ℃ for 3-5 h, then cooling to 200-250 ℃, preserving heat for 1-2 h, and cooling to obtain modified rod-shaped silicon dioxide;
2) preparing an oil phase solution: adding trimesoyl chloride into a normal hexane solvent to prepare a trimesoyl chloride solution b with the concentration of 0.1-0.8 wt%;
3) interfacial polymerization: immersing the hydrophilic polytetrafluoroethylene microporous base membrane into the mixed solution a for ultrasonic oscillation for 1-5 min, taking out the hydrophilic polytetrafluoroethylene microporous base membrane, removing the redundant mixed solution a on the surface, and then immersing the hydrophilic polytetrafluoroethylene microporous base membrane into a trimesoyl chloride solution b for standing reaction for 30-60 s to obtain a nascent state composite nanofiltration membrane; the preparation method of the hydrophilic polytetrafluoroethylene microporous base membrane comprises the following steps: carrying out plasma treatment on a polytetrafluoroethylene microporous base membrane in a nitrogen atmosphere, then soaking the polytetrafluoroethylene microporous base membrane subjected to the plasma treatment into an ethanol water solution of a modified polygonatum odoratum polysaccharide extract, adding an initiator azobisisobutyronitrile, reacting at 60-65 ℃ for 3-5 hours, taking out the polytetrafluoroethylene microporous base membrane, washing with deionized water to remove unreacted monomers, and drying to obtain a hydrophilic polytetrafluoroethylene microporous base membrane;
4) and (3) crosslinking and curing: and (3) carrying out heat treatment on the nascent state composite nanofiltration membrane at the temperature of 45-52 ℃ for 10-20 min to obtain the anti-shrinkage polytetrafluoroethylene composite nanofiltration membrane.
2. The preparation method of the anti-shrinkage polytetrafluoroethylene composite nanofiltration membrane according to claim 1, wherein the addition amount of the rod-shaped silica is 10-15 wt% of water.
3. The preparation method of the anti-shrinkage polytetrafluoroethylene composite nanofiltration membrane according to claim 1, wherein the mass ratio of the rod-shaped silica to the titanium sulfate is 1: 0.4-0.8.
4. The preparation method of the anti-shrinkage polytetrafluoroethylene composite nanofiltration membrane according to claim 1, wherein the mass ratio of the titanium sulfate to the urea is 1: 4-5.5.
5. The preparation method of the anti-shrinkage polytetrafluoroethylene composite nanofiltration membrane according to claim 1, wherein the mass concentration of the modified polygonatum odoratum polysaccharide extract is 2-10%.
6. The preparation method of the anti-shrinkage polytetrafluoroethylene composite nanofiltration membrane according to claim 1, wherein the mass fraction of the ethanol aqueous solution is 60-70%.
7. The preparation method of the anti-shrinkage polytetrafluoroethylene composite nanofiltration membrane according to claim 1, wherein the mass concentration of the initiator azobisisobutyronitrile in the ethanol aqueous solution is 0.2-0.5%.
8. The preparation method of the anti-shrinkage polytetrafluoroethylene composite nanofiltration membrane according to claim 1, wherein the preparation method of the modified polygonatum odoratum polysaccharide extract comprises the following steps: adding the polygonatum odoratum polysaccharide extract into 65-80 wt% of ethanol water solution, wherein the mass concentration of the polygonatum odoratum polysaccharide extract is 10-15 wt%, and then adding a catalyst SbCl5The method comprises the steps of adding a catalyst in an amount which is 2-3.5% of the weight of an anhydrous ethanol aqueous solution, uniformly stirring and mixing, slowly dropwise adding allyl glycidyl ether, wherein the addition amount of the allyl glycidyl ether is 20-40 wt% of the weight of the polygonatum odoratum polysaccharide extract, reacting at 65-70 ℃ for 2-4 hours in a heat preservation manner, and sequentially performing rotary evaporation concentration and vacuum drying after the reaction is finished to obtain the modified polygonatum odoratum polysaccharide extract.
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