CN116036887A - Preparation method of anti-pollution and anti-wetting composite membrane distillation membrane - Google Patents

Preparation method of anti-pollution and anti-wetting composite membrane distillation membrane Download PDF

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CN116036887A
CN116036887A CN202211662811.9A CN202211662811A CN116036887A CN 116036887 A CN116036887 A CN 116036887A CN 202211662811 A CN202211662811 A CN 202211662811A CN 116036887 A CN116036887 A CN 116036887A
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membrane
coating
solution
membrane distillation
wetting
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王志宁
张娜
张娇娇
杨欣
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Shandong University
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/06—Organic material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
    • B01D61/36—Pervaporation; Membrane distillation; Liquid permeation
    • B01D61/364—Membrane distillation
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
    • B01D61/36—Pervaporation; Membrane distillation; Liquid permeation
    • B01D61/366—Apparatus therefor
    • 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
    • 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
    • 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
    • B01D69/12—Composite membranes; Ultra-thin membranes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2323/00—Details relating to membrane preparation
    • B01D2323/26—Spraying processes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2325/00—Details relating to properties of membranes
    • B01D2325/36—Hydrophilic membranes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A20/00—Water conservation; Efficient water supply; Efficient water use
    • Y02A20/124—Water desalination
    • Y02A20/131—Reverse-osmosis

Abstract

The invention relates to a preparation method of an anti-pollution and anti-wetting composite membrane distillation membrane, which comprises the steps of firstly carrying out surface hydrophilic modification on a hydrophobic microporous membrane, then adding tannic acid into a polyvinyl alcohol solution, coating the hydrophilic modified hydrophobic microporous membrane by using the solution to obtain the composite membrane distillation membrane with oil pollution resistance and surfactant wetting resistance, comprehensively improving the membrane distillation performance, ensuring high permeation flux and salt rejection rate, obtaining excellent anti-pollution and anti-wetting performance, having excellent treatment effect on a high-salt solution of an oil emulsion containing a surfactant, having good structural stability and durability, being beneficial to the application of the membrane distillation membrane in actual high-salt wastewater treatment, having wide raw material sources, environment-friendly process, low preparation cost and being beneficial to the mass production and market popularization and application in the membrane distillation field.

Description

Preparation method of anti-pollution and anti-wetting composite membrane distillation membrane
Technical Field
The invention belongs to the technical field of membrane distillation, and particularly relates to a preparation method of an anti-pollution and anti-wetting composite membrane distillation membrane.
Background
A Membrane Distillation (MD) is a desalting technology based on a membrane method and a thermal method, wherein a hydrophobic microporous membrane is used as a separation barrier, a vapor pressure difference generated by a temperature difference of feed liquid at two sides of the membrane is used as a mass transfer driving force to push water vapor to permeate the membrane, and ultrapure water is obtained by condensation at a permeation side, so that separation of non-volatile solutes and water in feed liquid is realized. Compared with advanced water treatment technologies such as Reverse Osmosis (RO), low-temperature multi-effect distillation (MED) and multi-stage flash evaporation (MSF), the membrane distillation has low working temperature, can utilize low-grade heat sources such as industrial waste heat, solar energy, geothermal energy and the like, and has low energy consumption; is insensitive to the salt concentration of the feed solution, and can break through the upper limit of the salt concentration of the RO treatment solution (70000 mg L) -1 ) The method comprises the steps of carrying out a first treatment on the surface of the Separation is realized through phase change, and the theoretical desalination rate is up to 100%; the equipment is simple and modularized, and the investment cost is low. However, as the core of membrane distillation technology, hydrophobic microporous membranes are mainly faced with membrane pollution and membrane wetting challenges when treating complex high-salt wastewater, greatly limiting the further applications of membrane distillation technology.
Membrane fouling is mainly caused by organic contaminants in the feed solution, such as proteins, oil droplets, etc., which can adhere to the surface of the hydrophobic microporous membrane and the inside of the pore canal through hydrophobic-hydrophobic interactions, blocking the membrane pores, resulting in a substantial decrease in membrane permeation flux. The membrane wetting is mainly initiated by low surface energy substances or amphiphilic substances in the feed liquid, particularly surfactants, which are widely existing in various waste water, can reduce the surface tension of the feed liquid, reduce the liquid inlet pressure (LEP) of the membrane, and enable the feed liquid to directly penetrate through membrane holes, thereby greatly reducing salt interception and process failure. Thus, membrane fouling and membrane wetting are bottleneck problems that need to be addressed during use of membrane distillation membranes.
In order to solve the problems, a hydrophilic layer is constructed on the surface of the hydrophobic microporous membrane, and the contact between pollutants and the hydrophobic membrane is blocked. However, the current method mainly has the following problems: (1) The hydrophilic layer is introduced to increase additional mass transfer resistance and reduce the permeation flux of the membrane; (2) The hydrophilic coating has complex preparation process, relates to high temperature, chemical crosslinking and other steps, and is not environment-friendly; (3) The binding force between the hydrophilic functional layer and the hydrophobic microporous membrane is poor, and the membrane stability is poor. Therefore, development of a green and efficient anti-pollution coating construction method is needed to obtain a high-performance membrane distillation membrane, and long-term stability in the high-salt wastewater treatment process is ensured.
Disclosure of Invention
The invention provides a preparation method of an anti-pollution and anti-wetting composite membrane distillation membrane, which aims at the defects of the prior art.
According to the invention, the surface of the hydrophobic microporous membrane is subjected to hydrophilic modification, and tannic acid is added into a polyvinyl alcohol solution, so that the hydrophilic modified hydrophobic microporous membrane is coated by the solution, thus the composite membrane distillation membrane with the oil pollution resistance and surfactant wetting resistance effects is obtained, the high permeation flux and salt rejection rate can be maintained, and the long-term operation stability is improved.
The technical scheme of the invention is as follows:
a preparation method of an anti-pollution and anti-wetting composite membrane distillation membrane comprises the following steps:
1) Dissolving a bionic adhesive and a crosslinking agent into Tris-HCl buffer solution with pH value of 8.0-9.0 to obtain a modified solution, contacting the upper surface of a hydrophobic microporous membrane with the modified solution, standing, carrying out surface hydrophilic modification on the hydrophobic microporous membrane, fully cleaning the membrane and drying to obtain a hydrophobic microporous membrane with one surface subjected to hydrophilic modification;
2) Adding polyvinyl alcohol (PVA) and Tannic Acid (TA) into water, and uniformly stirring at 90-98 ℃ to obtain coating liquid;
3) And (3) coating the coating liquid obtained in the step (2) on the surface of the hydrophilic modified hydrophobic film on one side obtained in the step (1), and drying to obtain the PVA/TA layer modified composite film.
According to the invention, in the step 1), the bionic adhesive is dopamine or plant polyphenol substances, and the cross-linking agent is an amino-rich polymer and/or transition metal ions.
Further preferably, the biomimetic adhesive is dopamine. Plant polyphenols are carried out according to the prior art.
Further preferably, the amino-rich polymer is a polyethyleneimine or a polyamidoamine dendrimer, and the transition metal ion is Cu 2+ Or Fe (Fe) 3+ 。
According to the invention, in the step 1), the concentration of the bionic adhesive in the modified liquid is 0.5-5mg/mL, and when the cross-linking agent is an amino-rich polymer, the mass ratio of the amino-rich polymer to the bionic adhesive is (0.1-5): 1; when the cross-linking agent is a transition metal ion, the molar ratio of the metal ion to the bionic adhesive is (0.1-5): 1.
According to a preferred embodiment of the invention, in step 1), the hydrophobic membrane is an intrinsically hydrophobic polymeric microporous membrane.
According to a preferred embodiment of the invention, in step 1), the hydrophobic membrane is a polyvinylidene fluoride, polytetrafluoroethylene or polypropylene microfiltration membrane.
According to a preferred embodiment of the invention, in step 1), the standing time is 2 to 24 hours.
According to the invention, in the step 2), the mass percentage of the polyvinyl alcohol in the coating liquid is 6-10%, and the mass ratio of the tannic acid to the polyvinyl alcohol is (1-4) (30-50).
According to a preferred embodiment of the invention, in step 2), the stirring time is from 5 to 10 hours.
According to the invention, in step 2), the coating is performed by doctor blade, drop coating, spray coating, spin coating or natural casting.
According to the invention, in the step 2), the drying mode is natural airing or drying, the temperature is 25-60 ℃ and the time is 0.5-12 h.
An anti-pollution and anti-wetting composite membrane distillation membrane is prepared by the method.
The application of the anti-pollution and anti-wetting composite membrane distillation membrane is used for membrane distillation, and when the membrane distillation membrane is applied, one side coated with polyvinyl alcohol and tannic acid is contacted with feed liquid.
According to the present invention, the feed liquid is preferably a mixed solution of water and salt to which a surfactant and/or oil is added.
After the PVA/TA coating liquid is coated on the surface of the hydrophobic microporous membrane with one surface modified by hydrophilic, the PVA/TA coating liquid is dried, the polymer network is contracted and intertwined, and a stable PVA/TA coating layer is formed on the surface of the membrane, so that the composite membrane distillation membrane is obtained. Because of the high hydrophilicity of PVA and TA, the PVA/TA coating has the characteristics of high hydrophilicity in air and super oleophobic property under water, and can play a role in resisting oil pollution under water. In addition, TA is used as a hydrogen bond reinforcing agent, so that the combination between PVA polymer chain segments can be further enhanced, and the polymer network structure can be regulated and controlled. When the TA addition amount is small, the regulation and control on the PVA network structure are limited, and a good anti-wetting effect cannot be achieved; and when excessive amount is added, the strong interaction between TA and PVA makes the solution nonuniform, and massive aggregates are generated to influence the quality of subsequent film formation. The PVA polymer network can be densified by adding a proper amount of the surfactant, so that the surfactant can be well blocked, and the wetting is prevented. The high hydration of the PVA/TA coating can reduce the energy required by the evaporation of the water in the feed liquid, thereby ensuring the high permeation flux in the membrane distillation process. PVA/TA coated microporous membranes are effective in treating high salt solutions containing surfactants and oil droplets.
The beneficial effects of the invention are as follows:
1. firstly, carrying out surface hydrophilic modification on a hydrophobic microporous membrane, then adding tannic acid into a polyvinyl alcohol solution, and coating the hydrophilic modified hydrophobic microporous membrane by using the solution to obtain a composite membrane distillation membrane with oil pollution resistance and surfactant wetting resistance; the high hydrophilic characteristic and the underwater super oleophobic characteristic (oil contact angle is more than 150 degrees) of the polyvinyl alcohol/tannic acid coating enable a firm hydration layer to be formed on the surface of the membrane in the membrane distillation process, contact between oil substances and the hydrophobic membrane is blocked, and therefore the effect of resisting pollution of the oil substances is achieved.
2. The tannic acid is adopted as the hydrogen bond reinforcing agent, so that the compactness of the polyvinyl alcohol network structure can be further regulated and controlled, and the composite membrane distillation membrane can effectively resist wetting of surfactant substances.
3. Firstly, carrying out surface hydrophilic modification on a hydrophobic microporous membrane, then adding tannic acid into a polyvinyl alcohol solution, and coating the hydrophilic modified hydrophobic microporous membrane by using the solution to obtain a composite membrane distillation membrane with oil pollution resistance and surfactant wetting resistance; the strong hydrogen bond interaction between the hydrophilic polyvinyl alcohol/tannic acid coating and water molecules can reduce the evaporation enthalpy of the water, and part of the water molecules leave the evaporation interface in a cluster form, so that the high permeation flux in the membrane distillation process is ensured.
4. The method provided by the invention realizes comprehensive improvement of membrane distillation performance, ensures high permeation flux and salt interception rate, obtains excellent anti-pollution and anti-wetting performance, has excellent treatment effect on high-salt solution of oil emulsion containing stable surfactant, has good structural stability and durability, and is beneficial to application in actual high-salt wastewater treatment.
5. Compared with other methods, the method does not need subsequent chemical crosslinking and high-temperature treatment processes, is more environment-friendly, can be amplified, has low raw material cost and is suitable for industrial production.
Drawings
FIG. 1 is a scanning electron microscope image of the surface of a polytetrafluoroethylene microporous membrane according to example 1 of the invention.
FIG. 2 is a scanning electron microscope image of the surface of the composite membrane distillation membrane according to example 1 of the present invention.
FIG. 3 is a sectional Scanning Electron Microscope (SEM) image of a composite membrane distillation membrane according to embodiment 1 of the present invention.
FIG. 4 is a graph of water flux and conductivity scattergrams of a composite membrane distillation membrane of example 1 of the present invention.
FIG. 5 is a graph showing the underwater oil contact angle of polyvinylidene fluoride films before and after modification in example 2 of the present invention.
FIG. 6 is a graph showing water flux and conductivity of a composite membrane distillation membrane according to example 2 of the present invention.
FIG. 7 is a graph showing the conductivity scatter of the composite polytetrafluoroethylene film obtained by different tannic acid addition amounts in the polyvinyl alcohol coating of the invention.
FIG. 8 shows wetting of composite polytetrafluoroethylene films obtained by different tannic acid addition amounts in the polyvinyl alcohol coating of the invention.
Detailed Description
In order to fully understand the technical scheme and the beneficial effects of the present invention for those of ordinary skill in the art, the following description is further made with reference to the accompanying drawings and specific embodiments.
Example 1
A preparation method of an anti-pollution and anti-wetting composite membrane distillation membrane comprises the following steps:
1) Dissolving 0.2g of dopamine and 0.2g of polyethyleneimine into 100mL of Tris-HCl buffer solution (50 mM, pH=8.5) to obtain a modified solution, contacting the upper surface of a polytetrafluoroethylene membrane with the modified solution, standing for 12h, cleaning the membrane, and drying to obtain a polytetrafluoroethylene membrane with one surface subjected to hydrophilic modification;
2) Preparing a polyvinyl alcohol/tannic acid coating solution: the mass fraction of the polyvinyl alcohol is 8%, the mass ratio of the tannic acid to the polyvinyl alcohol is 2:40, specifically, 4g of the polyvinyl alcohol and 0.2g of the tannic acid are added into 45.8g of water, and the mixture is heated and stirred for 5 hours at 95 ℃ to obtain a coating liquid, and the coating liquid is cooled for standby;
3) Fixing the film obtained in the step 1) on a glass plate, scraping and coating the coating liquid on the surface of the hydrophilic modified hydrophobic film modified film by using a scraper with a gap of 100 mu m, airing at room temperature for 3 hours to obtain a composite film distillation film, namely a polyvinyl alcohol/tannic acid modified polytetrafluoroethylene composite film, and soaking in deionized water for standby.
The polytetrafluoroethylene film used in this example without any modification and the resulting composite membrane distillation film were characterized by scanning electron microscopy.
Fig. 1 is a surface scanning electron microscope image of a polytetrafluoroethylene microporous membrane without any modification, fig. 2 is a surface scanning electron microscope image of a composite membrane distillation membrane, and fig. 3 is a section scanning electron microscope image of the composite membrane distillation membrane.
As can be seen from FIGS. 1 to 3, the polytetrafluoroethylene microporous membrane has a porous structure formed by combining fibers and nodules, while the surface of the composite membrane distillation membrane coating is compact and flat, the section shows that the thickness of the hydrophilic layer of polyvinyl alcohol/tannic acid is about 3.7 mu m, and the porous structure has good structural integrity with the polytetrafluoroethylene membrane.
The performance of the composite membrane distillation membrane obtained in example 1 was tested using a solution containing 3.5% sodium chloride, 1000ppm mineral oil and 0.1mM sodium dodecyl sulfate as a feed liquid, with a coating layer facing the feed liquid, a feed side temperature set at 65 ℃, and a condensation side temperature set at 20 ℃, using a direct contact membrane distillation apparatus, and the conductivity and flux changes of the cold test were monitored in real time.
As can be seen from FIG. 4, the obtained composite membrane always maintains a stable permeation flux, 21.11kgm, during the treatment of the salt solution containing mineral oil and surfactant -2 h -1 The conductivity remained low after 24h, 1.96. Mu.Scm -1 The salt interception rate is up to 99.99%, which indicates that the composite membrane distillation membrane has excellent anti-pollution and anti-wetting properties. In addition, when the solution containing only 3.5% of sodium chloride was treated, the permeation flux of the composite membrane was almost unchanged from that of the original membrane, and was 20.34kgm, respectively -2 h -1 And 20.06kgm -2 h -1 The salt interception rates are 100%, which shows that the introduction of the polyvinyl alcohol/tannic acid coating with the micron-sized thickness does not cause extra mass transfer resistance, and the permeation flux and the salt interception of the modified composite membrane are maintained at higher levels.
Example 2
A preparation method of an anti-pollution and anti-wetting composite membrane distillation membrane comprises the following steps:
1) Dissolving 0.2g of tannic acid and 0.038g of ferric chloride into 100mL of Tris-HCl buffer solution (50 mM, pH=8.8) to obtain a modified solution, contacting the upper surface of a polyvinylidene fluoride membrane with the modified solution, standing for 6h, cleaning the membrane, and drying to obtain a polyvinylidene fluoride membrane with one surface subjected to hydrophilic modification;
2) Preparing a polyvinyl alcohol/tannic acid solution: 7% of polyvinyl alcohol by mass and 1:35 of tannic acid and polyvinyl alcohol by mass. Specifically, 3.5g of polyvinyl alcohol and 0.1g of tannic acid are added into 46.4g of water, heated and stirred for 8 hours at 90 ℃ to obtain coating liquid, and cooled for standby.
3) Fixing the film obtained in the step 1) on a glass plate, scraping and coating the coating liquid on the surface of the film by using a scraper with a gap of 100 mu m, drying for 1h at 30 ℃ to obtain a polyvinyl alcohol/tannic acid modified polyvinylidene fluoride composite film, and soaking in deionized water for standby.
The polyvinylidene fluoride film before and after modification was tested for underwater oil contact angle by a contact angle meter, and as shown in fig. 5, the original polyvinylidene fluoride film without any modification exhibited characteristics of oleophilic under water, the underwater oil contact angle was 39.2 °, and the composite film distillation film exhibited characteristics of superoleophobic, and the underwater oil contact angle was 155.1 °.
The anti-fouling performance of the composite membrane distillation membrane was evaluated in the manner of the membrane performance test in example 1 using a solution containing 3.5% sodium chloride and 2000ppm mineral oil as feed solution, see fig. 6.
FIG. 6 shows that the obtained composite membrane distillation membrane always maintains stable permeation flux, 22.42kgm, during the treatment of mineral oil-containing salt solution -2 h -1 The conductivity was still low after 24h, 1.60. Mu.Scm -1 The salt interception rate is up to 100%, which indicates that the composite membrane has excellent oil pollution resistance.
Example 3
A preparation method of an anti-pollution and anti-wetting composite membrane distillation membrane comprises the following steps:
the preparation method as described in example 1 is different in that:
and 3) spraying the solution obtained in the step 2) on the surface of the polytetrafluoroethylene film with the hydrophilically modified surface obtained in the step 1) in a spraying mode, wherein the pressure of a spray gun is 0.5MPa, the spray gun is 10cm vertical to the surface of the film, and the spraying thickness is 10 mu m. Drying at 60 ℃ for 0.5h to obtain the composite membrane distillation membrane, and soaking in deionized water for standby.
The anti-wetting performance of the composite membrane distillation membrane was evaluated in the membrane performance test manner in example 1 using a solution containing 3.5% sodium chloride and 0.4mM sodium dodecyl sulfate as a feed solution.
The obtained composite membrane always maintains stable permeation flux of 19.70kgm in the treatment process of salt solution containing sodium dodecyl sulfate -2 h -1 The conductivity remained low after 24h, 2.14. Mu.Scm -1 The salt interception rate is up to 99.99%, which indicates that the composite film has excellent surfactant wetting resistance.
Comparative example 1
The feed solution of example 2 was treated as in example 2 using an untreated polytetrafluoroethylene membrane. The results show that the initial permeate flux of the membrane is as low as 10kgm -2 h -1 And reduced to zero after 35min, the surface polytetrafluoroethylene hydrophobic membrane suffered from severe oil contamination due to the hydrophobic membraneThe oleophilic nature of water (left panel of fig. 5) is thus unsuitable for the treatment of oily high-salinity wastewater.
Comparative example 2
The procedure is as in example 1, except that:
in step 2), 4g of polyvinyl alcohol and 0.5g of tannic acid were added to 45.5g of water, and the mixture was heated and stirred at 95℃for 5 hours.
As a result, it was found that the tannic acid content in the prepared solution was high, the resulting coating liquid was not uniform, and a large amount of bulky substances were generated inside, because of the strong interaction of tannic acid and polyvinyl alcohol, so that the polyvinyl alcohol molecular chains were excessively entangled and aggregated, and a composite film having a uniform and defect-free coating could not be subsequently produced using the coating.
The wettability resistance of the composite polytetrafluoroethylene film was evaluated in the manner of the film property test in example 1, using a solution containing 3.5% sodium chloride and 0.4mM sodium dodecyl sulfate as a feed solution, at a tannic acid to polyvinyl alcohol mass ratio of 5:40.
The results showed that the conductivity of the film after 24 hours was 1.22. Mu. Scm, compared with the film obtained in example 1 -1 Rise to 20.61. Mu.Scm -1 Showing the drop in truncated salt, membrane wetting occurred, fig. 7. The film backside photograph (fig. 8) also demonstrates the localized wetting phenomenon after the film distillation operation is completed, while the composite film obtained in example 1 does not wet. This comparative example demonstrates that excessive addition of tannic acid reduces the anti-wetting properties of the composite film.
Comparative example 3
The procedure is as in example 1, except that:
the solution prepared in step 2) was free of tannic acid, and 4g of polyvinyl alcohol was dissolved in 46g of water.
The wettability resistance of the polyvinyl alcohol composite polytetrafluoroethylene film was evaluated in the manner of the film property test in example 1 using a solution containing 3.5% sodium chloride and 0.4mM sodium dodecyl sulfate as a feed solution.
The results showed that the conductivity of the membrane was 1.29. Mu.Scm after 24 hours -1 Up to 39.38. Mu.Scm -1 Indicating that the salt interception is reduced and film wetting occursFig. 7. The film backside photograph (fig. 8) also demonstrates the localized wetting phenomenon after the film distillation operation is completed. This comparative example demonstrates the necessity of improved anti-wetting properties with the addition of tannic acid.
The above embodiments are preferred embodiments of the present invention, and are not intended to limit the present invention, but any modifications, equivalent substitutions or improvements made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims (10)

1. A preparation method of an anti-pollution and anti-wetting composite membrane distillation membrane comprises the following steps:
1) Dissolving a bionic adhesive and a crosslinking agent into Tris-HCl buffer solution with pH value of 8.0-9.0 to obtain a modified solution, contacting the upper surface of a hydrophobic microporous membrane with the modified solution, standing, carrying out surface hydrophilic modification on the hydrophobic microporous membrane, fully cleaning the membrane and drying to obtain a hydrophobic microporous membrane with one surface subjected to hydrophilic modification;
2) Adding polyvinyl alcohol (PVA) and Tannic Acid (TA) into water, and uniformly stirring at 90-98 ℃ to obtain coating liquid;
3) And (3) coating the coating liquid obtained in the step (2) on the surface of the hydrophilic modified hydrophobic film on one side obtained in the step (1), and drying to obtain the PVA/TA layer modified composite film.
2. The method according to claim 1, wherein in step 1), the biomimetic adhesive is dopamine or plant polyphenols, and the cross-linking agent is an amino-rich polymer and/or a transition metal ion.
3. The preparation method according to claim 2, wherein the bionic adhesive is dopamine, the amino-rich polymer is polyethyleneimine or polyamide-amine dendrimer, and the transition metal ion is Cu 2+ Or Fe (Fe) 3+ 。
4. The preparation method according to claim 2, wherein in the step 1), the concentration of the bionic adhesive in the modified liquid is 0.5-5mg/mL, and when the cross-linking agent is an amino-rich polymer, the mass ratio of the amino-rich polymer to the bionic adhesive is (0.1-5): 1; when the cross-linking agent is a transition metal ion, the molar ratio of the metal ion to the bionic adhesive is (0.1-5): 1.
5. The method according to claim 1, wherein in step 1), the hydrophobic membrane is an intrinsically hydrophobic polymer microporous membrane, preferably a polyvinylidene fluoride, polytetrafluoroethylene or polypropylene microporous membrane, and the standing time is 2 to 24 hours.
6. The preparation method according to claim 1, wherein in the step 2), the mass percentage of the polyvinyl alcohol in the coating liquid is 6-10%, and the mass ratio of the tannic acid to the polyvinyl alcohol is (1-4): 30-50.
7. The method according to claim 1, wherein in the step 2), the stirring time is 5-10 hours, the coating mode is blade coating, drop coating, spray coating, spin coating or natural casting, the drying mode is natural airing or drying, the temperature is 25-60 ℃, and the time is 0.5-12 hours.
8. An anti-pollution and anti-wetting composite membrane distillation membrane prepared by the method of claim 1.
9. The use of the anti-fouling, moisture-resistant composite membrane distillation membrane of claim 8 for membrane distillation, wherein the side coated with polyvinyl alcohol and tannic acid is contacted with a feed liquid.
10. Use according to claim 9, wherein the feed solution is a mixed solution of water and salt with the addition of surfactants and/or oils.
CN202211662811.9A 2022-12-23 2022-12-23 Preparation method of anti-pollution and anti-wetting composite membrane distillation membrane Pending CN116036887A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117258546A (en) * 2023-10-26 2023-12-22 山东大学 Preparation method of MXene-based hydrogel composite photo-thermal membrane distillation membrane

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117258546A (en) * 2023-10-26 2023-12-22 山东大学 Preparation method of MXene-based hydrogel composite photo-thermal membrane distillation membrane

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