CN113248780A - Hydrophobic PVDF (polyvinylidene fluoride) membrane, preparation method and application thereof - Google Patents

Hydrophobic PVDF (polyvinylidene fluoride) membrane, preparation method and application thereof Download PDF

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CN113248780A
CN113248780A CN202110669195.9A CN202110669195A CN113248780A CN 113248780 A CN113248780 A CN 113248780A CN 202110669195 A CN202110669195 A CN 202110669195A CN 113248780 A CN113248780 A CN 113248780A
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membrane
pvdf membrane
sio
hydrophobic pvdf
alkali
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侯得印
王军
王凯
徐莉莉
张勇
李魁岭
曹爱新
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Research Center for Eco Environmental Sciences of CAS
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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
    • C08J9/36—After-treatment
    • C08J9/40—Impregnation
    • 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
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J7/00—Chemical treatment or coating of shaped articles made of macromolecular substances
    • C08J7/12—Chemical modification
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2327/00—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Derivatives of such polymers
    • C08J2327/02—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Derivatives of such polymers not modified by chemical after-treatment
    • C08J2327/12—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Derivatives of such polymers not modified by chemical after-treatment containing fluorine atoms
    • C08J2327/16—Homopolymers or copolymers of vinylidene fluoride

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Abstract

The disclosure provides a hydrophobic PVDF membrane, a preparation method and an application, wherein the preparation method of the hydrophobic PVDF membrane comprises the following steps: adding silicon dioxide into ethanol and stirring to disperse the silicon dioxide to obtain a mixed solution; then, ammonia water is used for adjusting the mixed solution to be alkaline; then adding vinyl trimethoxy silane into the mixed solution to prepare SiO2PVSQ alcosol; treating the polyvinylidene fluoride membrane by using alkali liquor to obtain an alkali-treated polyvinylidene fluoride membrane; impregnating the alkali-treated polyvinylidene fluoride film in the SiO2And preparing a hydrophobic PVDF membrane in PVSQ alcohol sol.

Description

Hydrophobic PVDF (polyvinylidene fluoride) membrane, preparation method and application thereof
Technical Field
The disclosure relates to the technical field of membrane distillation and water treatment, in particular to a hydrophobic PVDF membrane, a preparation method and an application.
Background
The Membrane Distillation (MD) technology is a new liquid separation technology that combines the traditional distillation process with the membrane separation technology, uses hydrophobic microporous membrane as medium, and uses the steam pressure difference caused by the temperature difference between two sides of hydrophobic membrane as driving force. Compared with the traditional distillation process, the membrane distillation operation temperature is lower, and low-grade waste heat such as solar energy can be utilized for operation. Meanwhile, compared with other pressure-driven membrane separation processes such as reverse osmosis and nanofiltration, the membrane distillation has lower operating pressure, so that expensive components such as a high-pressure pump or a high-pressure container are not needed, and the operating cost is reduced. In addition, the retention rate of non-volatile solutes such as ions and molecules in the original solution by membrane distillation can reach 100% theoretically. Therefore, membrane distillation treatment of domestic wastewater and industrial wastewater, and pharmaceutical and food processing are widely used.
In the membrane distillation process, a hydrophobic membrane serves as a mass transfer channel and a physical barrier at the cold side and the hot side, only allows steam to pass through, and is the core part of the membrane distillation. Therefore, the membrane pores of the hydrophobic membrane are kept dry and are not blocked, and the method plays a vital role in ensuring membrane distillation flux and salt rejection rate.
Currently, membranes used in membrane distillation processes are mainly commercial microfiltration membranes, made of hydrophobic polymers, such as polyvinylidene fluoride (PVDF), Polytetrafluoroethylene (PTFE) or polypropylene (PP). However, in the actual operation process, the membrane pores are easily wetted or blocked by pollutants, the efficiency of membrane distillation is reduced, and the wide application of membrane distillation is inhibited. The super-hydrophobic surface generally refers to a surface with a contact angle with water larger than 150 degrees and a rolling angle smaller than 10 degrees, has multiple unique surface properties of self-cleaning, water resistance, ice resistance, oxidation resistance, drag reduction and the like, and can effectively reduce membrane pollution and membrane wetting.
The preparation of the super-hydrophobic surface is mainly summarized into the following two ways: constructing a multi-layer micro/nano rough surface, or modifying a low surface energy substance on the surface with a certain roughness. In recent years, various methods of structuring a superhydrophobic surface have been reported, such as a sol-gel method, a template method, an electrospinning method, a plasma treatment method, a chemical vapor deposition method, and the like. However, the above-mentioned methods are difficult to be applied industrially on a large scale due to complicated steps, high technical costs or only a small sample.
Disclosure of Invention
Technical problem to be solved
In view of the above technical problems, the present disclosure provides a hydrophobic PVDF membrane, a method for preparing the same, and applications thereof, in order to at least partially solve one of the above technical problems.
(II) technical scheme
In order to solve the technical problem, the technical scheme of the disclosure is as follows:
as an aspect of the present disclosure, there is provided a method of preparing a hydrophobic PVDF membrane, including:
adding silicon dioxide into ethanol and stirring to disperse the silicon dioxide to obtain a mixed solution; then, ammonia water is used for adjusting the mixed solution to be alkaline; then adding vinyl trimethoxy silane into the mixed solution to prepare SiO2PVSQ alcosol;
treating the polyvinylidene fluoride membrane by using alkali liquor to obtain an alkali-treated polyvinylidene fluoride membrane;
impregnating the alkali-treated polyvinylidene fluoride film in the SiO2And preparing a hydrophobic PVDF membrane in PVSQ alcohol sol.
According to the embodiment of the disclosure, the silicon dioxide is added into the ethanol and stirred, wherein the stirring speed is 100-;
adding vinyl trimethoxy silane into the mixed solution and stirring to obtain SiO2The PVSQ alcohol sol comprises the stirring speed of 100-500r/min and the stirring time of 2-12 h.
According to the embodiment of the disclosure, the adding vinyl trimethoxy silane into the mixed solution and stirring comprises the following steps:
and carrying out ultrasonic dispersion before stirring, wherein the ultrasonic dispersion temperature is 20-80 ℃, and the dispersion time is 2-12 h.
According to the embodiment of the disclosure, the mass fraction of the silicon dioxide in the mixed solution is 0.5-5%.
According to the embodiment of the disclosure, the mass ratio of the added silicon dioxide to the vinyltrimethoxysilane is 1 to (5-20).
According to the embodiment of the disclosure, the treatment of the polyvinylidene fluoride membrane by using the alkali liquor comprises the following steps:
and soaking the polyvinylidene fluoride membrane in the alkali liquor for 2-12h at the temperature of 20-80 ℃ to obtain the alkali-treated polyvinylidene fluoride membrane.
According to an embodiment of the present disclosure, wherein the alkali solution is a sodium hydroxide solution;
the concentration of the sodium hydroxide solution is 2-6 mol.L-1。
According to an embodiment of the present disclosure, the alkali-treated polyvinylidene fluoride film is impregnated in the SiO2In the PVSQ alcohol sol, a hydrophobic PVDF membrane is prepared and comprises the following components:
the alkali-treated polyvinylidene fluoride film is on the SiO2The dipping temperature in the PVSQ alcohol sol is 20-80 ℃, and the dipping time is 20-120 min.
As another aspect of the present disclosure, there is provided a hydrophobic PVDF membrane prepared using the above preparation method.
As a third aspect of the present disclosure, there is provided a use of the above hydrophobic PVDF membrane in membrane distillation.
(III) advantageous effects
The preparation method of the hydrophobic PVDF membrane has the advantages of simple process, easily controlled process and convenient industrial application; in addition, the preparation method provided by the disclosure has the advantages of easily obtained raw materials, simple equipment, no need of expensive treatment equipment and low preparation cost; in addition, the preparation method provided by the disclosure has the advantages of high efficiency, rapidness, no fluorine solvent, environmental friendliness, wide application and the like.
The surface of the hydrophobic PVDF membrane prepared by the method presents a micro/nano coarse structure similar to the lotus leaf surface, and low surface energy hydrophobic groups such as vinyl and methoxy German are distributed on the surface of the hydrophobic PVDF membrane, so that the contact angle of the prepared hydrophobic PVDF membrane can reach 150-160 degrees, the rolling angle can be as low as 5-10 degrees, and simultaneously the performances such as porosity, aperture and the like of the hydrophobic PVDF membrane are not damaged, thereby greatly improving the anti-wetting property and anti-pollution property of the hydrophobic PVDF membrane, prolonging the service life of the hydrophobic PVDF membrane, and promoting the industrial application of the membrane distillation technology.
Drawings
FIG. 1 is a scanning electron micrograph and contact angle schematic of a hydrophobic PVDF film prepared in example 1 of the present disclosure;
FIG. 2 is a graph of the anti-fouling test of the hydrophobic PVDF membrane prepared in example 1 of the present disclosure versus a commercial PVDF membrane;
fig. 3 is a graph of the anti-wetting test of the hydrophobic PVDF membrane prepared in example 1 of the present disclosure versus a commercial PVDF membrane.
Detailed Description
For the purpose of promoting a better understanding of the objects, aspects and advantages of the present disclosure, reference is made to the following detailed description taken in conjunction with the accompanying drawings.
In the embodiments of the present disclosure, it is preferred,
PVDF is an abbreviation for polyvinylidene fluoride;
SiO2is silicon dioxide;
PVSQ is an abbreviation for vinyl silsesquioxane;
VTMOS is an abbreviation for vinyltrimethoxysilane.
According to an embodiment of the present disclosure, there is provided a method of preparing a hydrophobic PVDF film, including:
adding silicon dioxide into ethanol and stirring to disperse the silicon dioxide to obtain a mixed solution; then, ammonia water is used for adjusting the mixed solution to be alkaline; then, adding vinyl trimethoxy silane into the mixed solution to prepare SiO2PVSQ alcosol;
treating the polyvinylidene fluoride membrane by using alkali liquor to obtain an alkali-treated polyvinylidene fluoride membrane;
immersing the alkali-treated polyvinylidene fluoride film in SiO2And preparing a hydrophobic PVDF membrane in PVSQ alcohol sol.
The preparation method of the hydrophobic PVDF membrane has the advantages of simple process, easily controlled process and convenient industrial application; in addition, the preparation method provided by the disclosure has the advantages of easily obtained raw materials, simple equipment, no need of expensive treatment equipment and low preparation cost; in addition, the preparation method provided by the disclosure has the advantages of high efficiency, rapidness, no fluorine solvent, environmental friendliness, wide application and the like.
The surface of the hydrophobic PVDF membrane prepared by the method presents a micro/nano coarse structure similar to the lotus leaf surface, and low surface energy hydrophobic groups such as vinyl and methoxy German are distributed on the surface of the hydrophobic PVDF membrane, so that the contact angle of the prepared hydrophobic PVDF membrane can reach 150-160 degrees, the rolling angle can be as low as 5-10 degrees, and simultaneously the performances such as porosity, aperture and the like of the hydrophobic PVDF membrane are not damaged, thereby greatly improving the anti-wetting property and anti-pollution property of the hydrophobic PVDF membrane, prolonging the service life of the hydrophobic PVDF membrane, and promoting the industrial application of the membrane distillation technology.
Under the catalytic action of ammonia water, the hydrophobic modification of SiO by using vinyl trimethoxy silane2While preparing regular spherical vinyl silsesquioxane particles to prepare SiO2PVSQ hydrophobic alcosol.
According to the embodiment of the disclosure, ammonia is used for adjusting the pH value of the mixed solution to 8-13.
The pH value of the mixed solution is adjusted to 8-13 by ammonia water, so that the formation of a surface hydroxyl coating layer of silicon dioxide in ethanol can be promoted, and vinyl trimethoxy silane molecules can be grafted to the surface of the silicon dioxide.
According to the embodiment of the disclosure, the silicon dioxide is added into the ethanol and stirred, wherein the stirring speed is 100-500r/min, and the stirring time is 2-12 h.
According to embodiments of the present disclosure, for example, the stirring speed may be selected to be 100r/min, 200r/min, 300r/min, 400r/min, 500r/min, and so forth; the stirring time can be selected from 2h, 4h, 6h, 8h, 10h, 12h, and the like.
According toIn the embodiment of the disclosure, vinyl trimethoxy silane is added into the mixed solution and stirred to obtain SiO2The PVSQ alcohol sol comprises the stirring speed of 100-500r/min and the stirring time of 2-12 h.
According to embodiments of the present disclosure, for example, the stirring speed may be selected to be 100r/min, 200r/min, 300r/min, 400r/min, 500r/min, and so forth; the stirring time can be selected from 2h, 4h, 6h, 8h, 10h, 12h, and the like.
According to an embodiment of the present disclosure, vinyl trimethoxysilane is added to the mixed solution and stirred, including: ultrasonic dispersion is carried out before stirring, the temperature of ultrasonic dispersion is 20-80 ℃, and the dispersion time is 2-12 h.
According to embodiments of the present disclosure, for example, the temperature of ultrasonic dispersion may be selected to be 20 ℃, 30 ℃, 40 ℃, 50 ℃, 60 ℃, 80 ℃, and the like; the time of ultrasonic dispersion can be selected from 4h, 6h, 8h, 10h, 12h and the like.
According to the embodiment of the disclosure, the mass fraction of the silicon dioxide in the mixed solution is 0.5-5%.
According to an embodiment of the present disclosure, the mass fraction of the silica in the mixed liquid may be selected to be 0.5%, 1%, 2%, 3%, 4%, 5%, and the like.
According to the embodiment of the disclosure, the mass ratio of the added silicon dioxide to the vinyltrimethoxysilane is 1 to (5-20).
According to embodiments of the present disclosure, the mass ratio of silica to vinyltrimethoxysilane added can be selected from 1: 5, 1: 8, 1: 10, 1: 15, 1: 18, 1: 20, and the like.
According to an embodiment of the present disclosure, a polyvinylidene fluoride membrane is treated with an alkali solution, including:
soaking the polyvinylidene fluoride membrane in alkali liquor for 2-12h at the temperature of 20-80 ℃ to obtain the alkali-treated polyvinylidene fluoride membrane.
According to an embodiment of the present disclosure, wherein the lye is a sodium hydroxide solution.
According to an embodiment of the present disclosure, the concentration of the sodium hydroxide solution is 2-6 mol.L-1。
According to embodiments of the present disclosure, for example, the concentration of the sodium hydroxide solution may be selected to be 2mol · L-1、3mol·L-1、4mol·L-1、5mol·L-1、6mol·L-1And so on.
According to an embodiment of the present disclosure, an alkali-treated polyvinylidene fluoride film is impregnated in SiO2In the PVSQ alcohol sol, a hydrophobic PVDF membrane is prepared and comprises the following components: alkali treatment of polyvinylidene fluoride films on SiO2The dipping temperature in the PVSQ alcohol sol is 20-80 ℃, and the dipping time is 20-120 min.
According to embodiments of the present disclosure, for example, alkali treating a polyvinylidene fluoride film on SiO2The dipping temperature in the PVSQ alcohol sol can be selected from 20 deg.C, 30 deg.C, 40 deg.C, 50 deg.C, 60 deg.C, 80 deg.C, etc.
According to an embodiment of the present disclosure, there is provided a hydrophobic PVDF membrane prepared using the above preparation method.
According to an embodiment of the present disclosure, there is provided a use of the above hydrophobic PVDF membrane in membrane distillation.
The disclosure is further illustrated by the following specific examples:
example 1
A method of preparing a hydrophobic PVDF membrane, comprising:
(1)SiO2preparation of PVSQ alcohol sol:
mixing SiO2Adding into ethanol, magnetically stirring for 2 hr to obtain SiO2Fully dispersing to obtain a mixed solution, wherein SiO in the mixed solution2The mass fraction of (A) is 0.5%; then, adjusting the pH of the mixed solution to 8 by using ammonia water; then adding VTMOS into the mixed solution, and performing ultrasonic dispersion for 2h at 20 ℃; then stirring for 2 hours by adopting magnetic force to obtain SiO2PVSQ alcosol; wherein, SiO2The mass ratio of the crystal to the VTMOS is 1: 5.
(2) Preparation of alkali-treated PVDF film: immersing PVDF film in 2 mol. L-1And soaking the PVDF membrane in NaOH solution at 20 ℃ for 2 hours to introduce hydroxyl groups on the surface of the PVDF membrane, so as to obtain the alkali-treated PVDF membrane.
(3) Preparation of hydrophobic PVDF membrane: prepared by impregnating an alkali-treated PVDF at 20 ℃ in step (1)SiO of (2)2In a PVSQ alcohol sol, SiO2Grafting the membrane on the surface of an alkali-treated PVDF membrane; after soaking for 20min, the grafted PVDF film is prepared from SiO2And taking out the/PVSQ alcohol sol, and placing the sol at room temperature until the ethanol is completely volatilized to obtain the hydrophobic PVDF membrane.
The hydrophobic PVDF membrane (i.e., the modified superhydrophobic PVDF membrane) in example 1 was tested:
first, the contact angle and the rolling angle of the modified superhydrophobic PVDF film in example 1 were tested, and the results are shown in fig. 1.
Fig. 1 is a scanning electron micrograph and contact angle schematic of a modified superhydrophobic PVDF film prepared in example 1 of the disclosure.
As can be seen from the combination of FIG. 1, the modified super-hydrophobic PVDF film in example 1 has a water contact angle of 154.5 degrees and a rolling angle of 7.8 degrees, which indicates that SiO2The surface appearance of the modified super-hydrophobic PVDF membrane is changed by the PVSQ grafting layer, a multi-layer micro/nano rough surface is constructed, the surface can be regarded as a rough porous structure, the amount of air filled between a liquid drop and a membrane surface gap is increased, the contact area between the liquid drop and the membrane surface is reduced, and therefore the water contact angle of the surface of the modified membrane is increased.
② the modified super-hydrophobic PVDF membrane prepared in the example 1 is subjected to anti-fouling performance test:
the modified superhydrophobic PVDF membrane and the commercial PVDF membrane were subjected to a direct contact membrane distillation experiment (DCMD) for 150 hours using a mixed solution of 100g/L sodium chloride, 2.22g/L calcium chloride and 50mg/L humic acid as a feed solution, and the flux and conductivity of the DCMD were varied with time as shown in FIG. 2.
FIG. 2 is a graph of the anti-fouling test of a modified superhydrophobic PVDF membrane prepared in example 1 of the disclosure and a commercial PVDF membrane;
as can be seen from FIG. 2, the flux of the modified superhydrophobic PVDF membrane was lower than that of the commercial PVDF membrane in the initial stage due to the modified SiO grafted on the surface of the modified membrane2Blocking a small number of membrane pores, resulting in increased porosity and membrane thickness, increases the mass transfer resistance of the vapor through the membrane. However, the flux of the commercial PVDF membrane decreased significantly during the DCMD experimental run, while the modified superhydrophobic PVDF exhibited a relatively stable flux over timeAfter 60h of DCMD anti-pollution test, the modified super-hydrophobic PVDF membrane is larger than the commercial PVDF membrane, which shows that the commercial PVDF membrane is poorer in hydrophobicity and easier to be polluted. Thus, the modified superhydrophobic PVDF film prepared in the example 1 has good anti-fouling performance.
In terms of conductivity, the conductivity of the commercial PVDF membrane and the modified superhydrophobic PVDF membrane did not change significantly throughout the experiment. The conductivity of the modified super-hydrophobic PVDF membrane is always 5 mu S-cm-1The conductivity of the resulting mixture was closer to that of pure water (1.54. mu.S cm)-1) The salt rejection rate of the modified super-hydrophobic PVDF membrane is always over 99.99 percent. The conductivity of the commercial PVDF membrane is slightly increased compared with that of the modified super-hydrophobic PVDF membrane.
③ the modified super-hydrophobic PVDF membrane prepared in example 1 was subjected to anti-wetting property test:
the modified superhydrophobic PVDF membrane and the commercial PVDF membrane were subjected to a direct contact membrane distillation experiment (DCMD) for 2h using sodium chloride solutions containing sodium dodecyl sulfate at different concentrations as a feed solution, and the flux and conductivity of the DCMD as a function of time are shown in fig. 3.
The concentration of Sodium Dodecyl Sulfate (SDS) is 0.1mmol/L, 0.2mmol/L and 0.3mmol/L respectively; the concentration of sodium chloride was 35 g/L.
Fig. 3 is a graph of the anti-wetting test of the modified superhydrophobic PVDF membrane prepared in example 1 of the disclosure and a PVDF membrane that has not been treated by the method of the disclosure.
As can be seen from FIG. 3, the flux and conductivity curves of the modified super-hydrophobic PVDF membrane at SDS concentrations of 0.1mmol/L, 0.2mmol/L and 0.3mmol/L are relatively smooth; when the concentration of SDS of the commercial PVDF membrane is increased to 0.2mmol/L, the conductivity of the produced water on the seepage side in the membrane distillation process is obviously increased,
when the concentration of SDS continues to rise to 0.3mmol/L, the wetting phenomenon of the PVDF membrane is more serious, the conductivity of produced water rises rapidly, and the flux also has obvious attenuation, which indicates that membrane pores are fully wetted at this time, feed liquid can directly permeate the membrane pores to enter the exudation side, and the membrane distillation process can not be normally carried out. Therefore, it is demonstrated that the modified superhydrophobic PVDF film prepared in example 1 has good anti-wetting property.
Example 2
A method of preparing a hydrophobic PVDF membrane, comprising:
(1)SiO2preparation of PVSQ alcohol sol:
mixing SiO2Adding into ethanol, magnetically stirring for 4 hr to obtain SiO2Fully dispersing to obtain a mixed solution, wherein SiO in the mixed solution2The mass fraction of (A) is 1%; then, adjusting the pH of the mixed solution to 9 by using ammonia water; then adding VTMOS into the mixed solution, and performing ultrasonic dispersion for 4 hours at 30 ℃; then stirring for 4 hours by adopting magnetic force to obtain SiO2PVSQ alcosol; wherein, SiO2The mass ratio of the metal oxide semiconductor material to the VTMOS is 1: 8.
(2) Preparation of alkali-treated PVDF film: immersing PVDF film in 3 mol. L-1Is soaked for 4 hours at the temperature of 30 ℃ to introduce hydroxyl groups on the surface of the PVDF membrane, so as to obtain the alkali-treated PVDF membrane.
(3) Preparation of hydrophobic PVDF membrane: impregnating the alkali-treated PVDF in the SiO prepared in step (1) at 30 ℃2In a PVSQ alcohol sol, SiO2Grafting the membrane on the surface of an alkali-treated PVDF membrane; after soaking for 40min, the grafted PVDF film is prepared from SiO2And taking out the/PVSQ alcohol sol, and placing the sol at room temperature until the ethanol is completely volatilized to obtain the modified super-hydrophobic PVDF membrane.
The modified super-hydrophobic PVDF membrane prepared by the embodiment has a membrane water contact angle of 155.2 degrees and a rolling angle of 7.7 degrees. The modified super-hydrophobic PVDF membrane is subjected to a membrane distillation anti-pollution test for 150 hours by taking sodium chloride, humic acid and calcium chloride as feed liquids (containing 100g/L of sodium chloride, 2.22g/L of calcium chloride and 50mg/L of humic acid) and a membrane distillation anti-wetting test for 2 hours by taking sodium chloride and sodium dodecyl sulfate as feed liquids (the concentrations of the sodium dodecyl sulfate are respectively 0.1mmol/L, 0.2mmol/L and 0.3 mmol/L; and the concentration of the sodium chloride is 35g/L), so that the flux of the modified membrane is stable, and the phenomenon of membrane pollution or membrane wetting does not occur.
Example 3
A method of preparing a hydrophobic PVDF membrane, comprising:
(1)SiO2preparation of PVSQ alcohol sol:
mixing SiO2Adding into ethanol, magnetically stirring for 6h,make SiO2Fully dispersing to obtain a mixed solution, wherein SiO in the mixed solution2The mass fraction of (A) is 2%; then, adjusting the pH of the mixed solution to 10 by using ammonia water; then adding VTMOS into the mixed solution, and performing ultrasonic dispersion for 6 hours at 40 ℃; then stirring for 6 hours by adopting magnetic force to obtain SiO2PVSQ alcosol; wherein, SiO2The mass ratio of the crystal to the VTMOS is 1: 10.
(2) Preparation of alkali-treated PVDF film: immersing PVDF film in 4 mol. L-1Is soaked in NaOH solution at 40 ℃ for 6 hours to introduce hydroxyl groups on the surface of the PVDF membrane, so as to obtain the alkali-treated PVDF membrane.
(3) Preparation of hydrophobic PVDF membrane: impregnating the alkali-treated PVDF in the SiO prepared in step (1) at 40 ℃2In a PVSQ alcohol sol, SiO2Grafting the membrane on the surface of an alkali-treated PVDF membrane; after soaking for 40min, the grafted PVDF film is prepared from SiO2And taking out the/PVSQ alcohol sol, and placing the sol at room temperature until the ethanol is completely volatilized to obtain the modified super-hydrophobic PVDF membrane.
The membrane water contact angle of the modified super-hydrophobic PVDF membrane prepared by the embodiment is 155.7 degrees, and the rolling angle is 7.4 degrees. The modified super-hydrophobic PVDF membrane is subjected to a membrane distillation anti-pollution test for 150 hours by taking sodium chloride, humic acid and calcium chloride as feed liquids (containing 100g/L of sodium chloride, 2.22g/L of calcium chloride and 50mg/L of humic acid) and a membrane distillation anti-wetting test for 2 hours by taking sodium chloride and sodium dodecyl sulfate as feed liquids (the concentrations of the sodium dodecyl sulfate are respectively 0.1mmol/L, 0.2mmol/L and 0.3 mmol/L; and the concentration of the sodium chloride is 35g/L), so that the flux of the modified membrane is stable, and the phenomenon of membrane pollution or membrane wetting does not occur.
Example 4
A method of preparing a hydrophobic PVDF membrane, comprising:
(1)SiO2preparation of PVSQ alcohol sol:
mixing SiO2Adding into ethanol, magnetically stirring for 8 hr to obtain SiO2Fully dispersing to obtain a mixed solution, wherein SiO in the mixed solution2The mass fraction of (A) is 3%; then, adjusting the pH of the mixed solution to 11 by using ammonia water; then adding VTMOS into the mixed solution, and performing ultrasonic dispersion for 8 hours at 50 ℃; then stirring for 8 hours by adopting magnetic force to obtain SiO2PVSQ alcosol; wherein, SiO2The mass ratio of the metal oxide semiconductor material to the VTMOS is 1: 15.
(2) preparation of alkali-treated PVDF film: immersing PVDF film in 5 mol. L-1Is soaked in NaOH solution at 50 ℃ for 8 hours to introduce hydroxyl groups on the surface of the PVDF membrane, so as to obtain the alkali-treated PVDF membrane.
(3) Preparation of hydrophobic PVDF membrane: impregnating the alkali-treated PVDF in the SiO prepared in step (1) at 50 ℃2In a PVSQ alcohol sol, SiO2Grafting the membrane on the surface of an alkali-treated PVDF membrane; after soaking for 80min, the grafted PVDF film is prepared from SiO2And taking out the/PVSQ alcohol sol, and placing the sol at room temperature until the ethanol is completely volatilized to obtain the modified super-hydrophobic PVDF membrane.
The membrane water contact angle of the modified super-hydrophobic PVDF membrane prepared in the embodiment is 156.2 degrees, and the rolling angle is 7.4 degrees. The modified super-hydrophobic PVDF membrane is subjected to a membrane distillation anti-pollution test for 150 hours by taking sodium chloride, humic acid and calcium chloride as feed liquids (containing 100g/L of sodium chloride, 2.22g/L of calcium chloride and 50mg/L of humic acid) and a membrane distillation anti-wetting test for 2 hours by taking sodium chloride and sodium dodecyl sulfate as feed liquids (the concentrations of the sodium dodecyl sulfate are respectively 0.1mmol/L, 0.2mmol/L and 0.3 mmol/L; and the concentration of the sodium chloride is 35g/L), so that the flux of the modified membrane is stable, and the phenomenon of membrane pollution or membrane wetting does not occur.
Example 5
A method of preparing a hydrophobic PVDF membrane, comprising:
(1)SiO2preparation of PVSQ alcohol sol:
mixing SiO2Adding into ethanol, magnetically stirring for 10 hr to obtain SiO2Fully dispersing to obtain a mixed solution, wherein SiO in the mixed solution2The mass fraction of (A) is 4%; then, adjusting the pH of the mixed solution to 12 by using ammonia water; then adding VTMOS into the mixed solution, and performing ultrasonic dispersion for 10 hours at 60 ℃; then stirring for 10 hours by adopting magnetic force to obtain SiO2PVSQ alcosol; wherein, SiO2The mass ratio of the metal oxide semiconductor material to the VTMOS is 1: 18.
(2) Preparation of alkali-treated PVDF film: immersing PVDF membrane in 6 mol.L-1Soaking at 60 deg.C for 10h to introduce hydroxyl groups on the PVDF membrane surface to obtain alkaliAnd (3) treating the PVDF membrane.
(3) Preparation of hydrophobic PVDF membrane: impregnating the alkali-treated PVDF in the SiO prepared in step (1) at 60 ℃2In a PVSQ alcohol sol, SiO2Grafting the membrane on the surface of an alkali-treated PVDF membrane; after soaking for 100min, the grafted PVDF film is prepared from SiO2And taking out the/PVSQ alcohol sol, and placing the sol at room temperature until the ethanol is completely volatilized to obtain the modified super-hydrophobic PVDF membrane.
The membrane water contact angle of the modified super-hydrophobic PVDF membrane prepared in the example is 157.7 degrees, and the rolling angle is 6.9 degrees. The modified super-hydrophobic PVDF membrane is subjected to a membrane distillation anti-pollution test for 150 hours by taking sodium chloride, humic acid and calcium chloride as feed liquids (containing 100g/L of sodium chloride, 2.22g/L of calcium chloride and 50mg/L of humic acid) and a membrane distillation anti-wetting test for 2 hours by taking sodium chloride and sodium dodecyl sulfate as feed liquids (the concentrations of the sodium dodecyl sulfate are respectively 0.1mmol/L, 0.2mmol/L and 0.3 mmol/L; and the concentration of the sodium chloride is 35g/L), so that the flux of the modified membrane is stable, and the phenomenon of membrane pollution or membrane wetting does not occur.
Example 6
A method of preparing a hydrophobic PVDF membrane, comprising:
(1)SiO2preparation of PVSQ alcohol sol:
mixing SiO2Adding into ethanol, magnetically stirring for 12 hr to obtain SiO2Fully dispersing to obtain a mixed solution, wherein SiO in the mixed solution2The mass fraction of (A) is 5%; then, adjusting the pH of the mixed solution to 13 by using ammonia water; then adding VTMOS into the mixed solution, and performing ultrasonic dispersion for 12 hours at 80 ℃; then stirring for 12 hours by adopting magnetic force to obtain SiO2PVSQ alcosol; wherein, SiO2The mass ratio of the crystal to the VTMOS is 1: 20.
(2) Preparation of alkali-treated PVDF film: immersing PVDF membrane in 6 mol.L-1Is soaked in NaOH solution at the temperature of 80 ℃ for 12 hours to introduce hydroxyl groups on the surface of the PVDF membrane, so as to obtain the alkali-treated PVDF membrane.
(3) Preparation of hydrophobic PVDF membrane: impregnating the alkali-treated PVDF in the SiO prepared in step (1) at 80 ℃2In a PVSQ alcohol sol, SiO2Grafting the membrane on the surface of an alkali-treated PVDF membrane; after 120min of soaking, the grafted PVDF film from SiO2And taking out the/PVSQ alcohol sol, and placing the sol at room temperature until the ethanol is completely volatilized to obtain the modified super-hydrophobic PVDF membrane.
The membrane water contact angle of the modified super-hydrophobic PVDF membrane prepared in the example is 157.8 degrees, and the rolling angle is 6.6 degrees. The modified super-hydrophobic PVDF membrane is subjected to a membrane distillation anti-pollution test for 150 hours by taking sodium chloride, humic acid and calcium chloride as feed liquids (containing 100g/L of sodium chloride, 2.22g/L of calcium chloride and 50mg/L of humic acid) and a membrane distillation anti-wetting test for 2 hours by taking sodium chloride and sodium dodecyl sulfate as feed liquids (the concentrations of the sodium dodecyl sulfate are respectively 0.1mmol/L, 0.2mmol/L and 0.3 mmol/L; and the concentration of the sodium chloride is 35g/L), so that the flux of the modified membrane is stable, and the phenomenon of membrane pollution or membrane wetting does not occur.
The above embodiments are provided to further explain the purpose, technical solutions and advantages of the present disclosure in detail, and it should be understood that the above embodiments are only examples of the present disclosure and are not intended to limit the present disclosure, and any modifications, equivalents, improvements, etc. made within the spirit and principle of the present disclosure should be included in the scope of the present disclosure.

Claims (10)

1. A method of preparing a hydrophobic PVDF membrane, comprising:
adding silicon dioxide into ethanol and stirring to disperse the silicon dioxide to obtain a mixed solution; then, ammonia water is used for adjusting the mixed solution to be alkaline; then adding vinyl trimethoxy silane into the mixed solution to prepare SiO2PVSQ alcosol;
treating the polyvinylidene fluoride membrane by using alkali liquor to obtain an alkali-treated polyvinylidene fluoride membrane;
impregnating the alkali-treated polyvinylidene fluoride film in the SiO2And preparing a hydrophobic PVDF membrane in PVSQ alcohol sol.
2. The method for producing a hydrophobic PVDF membrane according to claim 1,
adding the silicon dioxide into ethanol and stirring, wherein the stirring speed is 100-500r/min, and the stirring time is 2-12 h;
adding vinyl trimethoxy silane into the mixed solution and stirring to obtain SiO2The PVSQ alcohol sol comprises the stirring speed of 100-500r/min and the stirring time of 2-12 h.
3. The method for producing a hydrophobic PVDF membrane according to claim 1,
adding vinyl trimethoxy silane into the mixed solution and stirring, wherein the method comprises the following steps:
and carrying out ultrasonic dispersion before stirring, wherein the ultrasonic dispersion temperature is 20-80 ℃, and the dispersion time is 2-12 h.
4. The method for producing a hydrophobic PVDF membrane according to claim 1,
wherein the mass fraction of the silicon dioxide in the mixed solution is 0.5-5%.
5. The method for producing a hydrophobic PVDF membrane according to claim 1,
the mass ratio of the added silicon dioxide to the added vinyl trimethoxy silane is 1: (5-20).
6. The method for producing a hydrophobic PVDF membrane according to claim 1,
the method for treating the polyvinylidene fluoride membrane by using the alkali liquor comprises the following steps:
and soaking the polyvinylidene fluoride membrane in the alkali liquor for 2-12h at the temperature of 20-80 ℃ to obtain the alkali-treated polyvinylidene fluoride membrane.
7. The method for producing a hydrophobic PVDF membrane according to claim 1,
wherein the alkali liquor is sodium hydroxide solution;
the concentration of the sodium hydroxide solution is 2-6 mol.L-1。
8. The method for preparing a hydrophobic PVDF membrane as defined in claim 1, wherein said alkali treatment is carried outA polyvinylidene fluoride film is impregnated in the SiO2In the PVSQ alcohol sol, a hydrophobic PVDF membrane is prepared and comprises the following components:
the alkali-treated polyvinylidene fluoride film is on the SiO2The dipping temperature in the PVSQ alcohol sol is 20-80 ℃, and the dipping time is 20-120 min.
9. A hydrophobic PVDF membrane prepared by the preparation method according to any one of claims 1 to 8.
10. Use of the hydrophobic PVDF membrane of claim 9 in membrane distillation.
CN202110669195.9A 2021-06-16 2021-06-16 Hydrophobic PVDF (polyvinylidene fluoride) membrane, preparation method and application thereof Pending CN113248780A (en)

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CN108499363A (en) * 2018-04-28 2018-09-07 广西民族大学 The method of the nano-silicon dioxide modified PVDF dewatering microporous films of fabricated in situ

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CN101279211A (en) * 2008-01-11 2008-10-08 北京工业大学 Preparation of polyvinylidene fluoride dewatering microporous film
CN104014259A (en) * 2014-05-27 2014-09-03 中国科学院过程工程研究所 Preparation method of hydrophobic separating membrane
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