CN107998897B - Surface hydrophilic modification method of polyvinylidene fluoride hollow fiber membrane - Google Patents
Surface hydrophilic modification method of polyvinylidene fluoride hollow fiber membrane Download PDFInfo
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Abstract
The invention discloses a surface hydrophilization modification method of a polyvinylidene fluoride hollow fiber membrane, belongs to the field of materials, and discloses a method for performing hydrophilization modification on the surface of the polyvinylidene fluoride hollow fiber membrane by using an efficient click chemistry method. The method has mild conditions, simple method and easily controlled process. Firstly, treating the membrane with strong alkali to carry out elimination reaction to remove C-F bonds to form C-C double bonds; and then, under the ultraviolet environment and the action of a photoinitiator, the hydrophilic group carried by the sulfhydryl compound is anchored on the surface of the membrane by utilizing the reaction of an S-H bond in the sulfhydryl compound and a C ═ C double bond. The polyvinylidene fluoride membrane has low surface energy and can not form hydrogen bonds with water molecules, and the hydrophilicity and the stain resistance of the membrane can be greatly enhanced after hydrophilic groups are introduced to the surface of the membrane.
Description
Technical Field
The invention belongs to the field of materials, and further relates to a preparation method of a hydrophilized modified polyvinylidene fluoride ultrafiltration hollow fiber membrane.
Background
Polyvinylidene fluoride (PVDF) is one of the most interesting film-making materials at present. PVDF is a semi-crystalline linear polymer with molecular chains exhibiting- (CH)2-CF2)nThe structure is an alternate structure, and the C-F bond has short length and high bond energy, so that the material has the characteristics of excellent mechanical property, heat resistance, chemical corrosion resistance, impact resistance, difficult degradation, easy film formation and the like. However, the surface energy of the polyvinylidene fluoride film is extremely low (25mN/m), and there are no hydrophilic groups such as hydroxyl group (-OH), carboxyl group (-COOH) or amino group (-NH) on the surface2) And the hydrophobic polymer can not generate hydrogen bond with water molecules, so that the hydrophobic polymer has strong hydrophobicity. In the water separation process, the strong hydrophobicity of the PVDF membrane can increase the driving pressure required by water to permeate the membrane pores, and the energy consumption required by the water treatment process is increased. Meanwhile, organic substances such as proteins, microorganisms, colloids and the like are easily adsorbed on the surface of the hydrophobic membrane, so that membrane pores are blocked, permeation flux is reduced, and the service life of the membrane is shortened. The above problems restrict the application of the PVDF membrane in a water phase separation system, and in order to improve the water flux of the membrane, reduce membrane pollution and prolong the service life of the membrane, the hydrophilic modification of the PVDF membrane becomes one of the hot spots of the research in the field of membrane science at present, and has very important practical significance.
The Chinese patent application CN 106215723A provides a preparation method of a super-hydrophilic composite PVDF ultrafiltration membrane, the hydrophilic composite PVDF ultrafiltration membrane is obtained by self-polymerization of dopamine on the surface of a PVDF membrane, grafting of aromatic polyacylchloride and grafting of silicon dioxide nanoparticles modified by ammonium salt end groups onto the PVDF membrane, and the contact angle is reduced to 46 degrees when the mass fraction of the nanoparticles is 0.08 wt%.
The Chinese patent application CN 103127841A proposes a preparation method of a polyvinylidene fluoride hydrophilic modified membrane, which prepares a hydrophilic PVDF membrane by directly blending a hydrophilic polymer methyl methacrylate into a PVDF membrane preparation system. When the hydrophilic polymer is added in an amount of 25 wt%, the membrane contact angle decreases to 64.2 °.
The Chinese patent application CN 102516584A provides a modification method of polyvinylidene fluoride membrane for resisting protein pollution. And forming a zwitterion copolymerization layer on the surface of the polyvinylidene fluoride membrane by a two-step polymerization grafting method. The contact angle dropped to 29.1 deg. at a grafting yield of zwitterionic 3- (methacrylamide) propyl-dimethyl (3-sulfopropyl) amine of 522. mu.g/cm 2.
The blending hydrophilic polymer as an additive has the problems of raw material loss and the like caused by poor compatibility of the additive and a membrane substrate, and the grafting modification has the disadvantages of complicated process, higher cost and the like. In order to solve some problems of the existing hydrophilic PVDF membrane modification method, the invention provides a modification method for introducing hydrophilic groups on the membrane surface and the surface of an internal pore channel by a click chemistry method, so as to realize the lasting hydrophilic modification of the PVDF hollow fiber ultrafiltration membrane.
Disclosure of Invention
Aiming at the properties of low surface energy, strong hydrophobicity and weak pollution resistance of the PVDF membrane, the invention provides a modification method for introducing hydrophilic groups on the surface of the membrane and the surface of an internal pore channel by a click chemistry method, so as to realize lasting hydrophilization and pollution resistance modification of the PVDF hollow fiber ultrafiltration membrane.
1. The steps are as follows:
(1) cleaning a PVDF hollow fiber ultrafiltration membrane: dipping a PVDF hollow fiber ultrafiltration membrane in absolute ethyl alcohol for 24 hours, and then repeatedly washing with deionized water;
(2) preparing alkali liquor: adding the potassium hydroxide solid into the mixed solution of ethanol and deionized water, and uniformly stirring to prepare an alkali solution.
(3) And (3) completely soaking the hollow fiber ultrafiltration membrane cleaned in the step (1) in the alkali liquor prepared in the step (2), and placing the hollow fiber ultrafiltration membrane in an environment at 60 ℃ for 5-120 min.
(4) And (4) taking out the hollow fiber ultrafiltration membrane subjected to the alkali treatment in the step (3), repeatedly washing the hollow fiber ultrafiltration membrane by using deionized water under ultrasonic oscillation until the hollow fiber ultrafiltration membrane is no longer alkaline, and soaking the washed hollow fiber ultrafiltration membrane subjected to the alkali treatment in ethanol for later use.
(5) Preparing a solution for modification: the solvent is ethanol. Adding a thiol-containing compound, a photoinitiator, and a reducing agent that resists disulfide bond formation to a solvent.
(6) And (3) transferring the PVDF hollow fiber ultrafiltration membrane soaked by the ethanol in the step (4) into the solution prepared in the step (5), and reacting under stirring and a nitrogen atmosphere in an ultraviolet lamp with the wavelength of 365nm for 1-5 h.
(7) And (4) taking out the modified hollow fiber ultrafiltration membrane in the step (6), and repeatedly washing the membrane with ethanol and deionized water to remove unreacted sulfhydryl-containing compounds and initiators.
2. In a preferred example of the first mode of the present invention, in the step (2), the mass fraction of ethanol in the alkaline solution solvent is 50 wt.%, and the mass fraction of the solute potassium hydroxide is 5 wt.% to 20 wt.%.
3. In a preferred example of the first mode of the present invention, the mass fraction of the thiol group-containing polymer in the modification solution in the step (5) is 10 wt.% to 50 wt.%, the mass fraction of the initiator is 0.2 wt.% to 1.0 wt.%, and the mass fraction of the reducing agent is 0.2 wt.% to 1.0 wt.%.
4. In a preferred example of the first mode of the present invention, the thiol-group-containing polymer in the modification solution in the step (5) may be one or more of 2-mercaptoethanol, mercaptoacetaldehyde, 2-mercaptoacetic acid, 3-mercaptopropionic acid, 4-mercaptobutyric acid, 2-mercaptopropionaldehyde, 3-mercapto-1-propylamine, 2-mercaptopropan-1-ol, 3-mercapto-1-propanol, 1-mercapto-2-propanone, and 2-mercapto-acetamide.
5. In a preferred example of the first mode of the present invention, the initiator in the modification solution in the step (5) is one or more of 2-hydroxy-2-methyl-1-phenyl-1-propanone, benzoin dimethyl ether, ethyl 2,4, 6-trimethylbenzoylphosphonate, 2-methyl-1- [ 4-methylthiophenyl ] -2-morpholino-1-propanone, 1-hydroxycyclohexyl phenyl ketone and 2-phenylbenzyl-2-dimethylamine-1- (4-morpholinobenzyl phenyl) butanone.
6. In a preferred embodiment of the first mode of the present invention, the reducing agent in the modification solution in the step (5) is one of triphenylphosphine, iodoacetamide, and dithiothreitol.
7. The invention has the beneficial effects that:
(1) the method for hydrophilization modification of the PVDF hollow fiber membrane surface is mild in condition, simple in method and easy to control in process.
(2) According to the invention, by means of high-efficiency click chemistry, hydrophilic groups are introduced to the surface of the membrane, so that the hydrophilicity and the pollution resistance of the surface of the membrane are effectively improved.
(3) The method provided by the invention can be used for surface hydrophilization treatment of the PVDF hollow fiber membrane, and the finished membrane can be applied to the sewage treatment industry and has a wide prospect.
Drawings
FIG. 1 is a surface static contact angle test chart of an unmodified PVDF hollow fiber ultrafiltration membrane.
Fig. 2 is a surface static contact angle test chart of the modified PVDF hollow fiber ultrafiltration membrane provided in embodiment 1 of the present invention.
Fig. 3 is a surface static contact angle test chart of the modified PVDF hollow fiber ultrafiltration membrane provided in embodiment 2 of the present invention.
Fig. 4 is a surface static contact angle test chart of the modified PVDF hollow fiber ultrafiltration membrane provided in embodiment 3 of the present invention.
Fig. 5 is a surface static contact angle test chart of the modified PVDF hollow fiber ultrafiltration membrane provided in embodiment 4 of the present invention.
Fig. 6 is a surface static contact angle test chart of the modified PVDF hollow fiber ultrafiltration membrane provided in comparative example 1 of the present invention.
Fig. 7 is a surface static contact angle test chart of the modified PVDF hollow fiber ultrafiltration membrane provided in comparative example 2 of the present invention.
FIG. 8 shows bovine serum albumin adsorption amounts of an unmodified hollow fiber ultrafiltration membrane, examples 1 to 4 of the present invention, and comparative examples 1 to 2.
FIG. 9 shows pure water fluxes of an unmodified hollow fiber ultrafiltration membrane, examples 1 to 4 of the present invention, and comparative examples 1 to 2.
The specific implementation mode is as follows:
example 1
(1) Cleaning a PVDF hollow fiber ultrafiltration membrane: dipping a PVDF hollow fiber ultrafiltration membrane in absolute ethyl alcohol for 24 hours, and then repeatedly washing with deionized water;
(2) preparing alkali liquor: adding the potassium hydroxide solid into a mixed solution of ethanol and deionized water in a mass ratio of 1:1, and uniformly stirring to prepare an alkali solution, wherein the mass fraction of potassium hydroxide in the solution is 5 wt.%.
(3) And (3) completely soaking the hollow fiber ultrafiltration membrane cleaned in the step (1) in the alkali liquor prepared in the step (2), and placing the hollow fiber ultrafiltration membrane in an environment at 60 ℃ for 5 min.
(4) And (4) taking out the hollow fiber ultrafiltration membrane subjected to the alkali treatment in the step (3), repeatedly washing the hollow fiber ultrafiltration membrane by using deionized water under ultrasonic oscillation until the hollow fiber ultrafiltration membrane is no longer alkaline, and soaking the washed hollow fiber ultrafiltration membrane subjected to the alkali treatment in ethanol for later use.
(5) Preparing a solution for modification: the solvent is ethanol. Mercaptoethanol, 2-hydroxy-2-methyl-1-phenyl-1-propanone and triphenylphosphine were added to the solvent. The mass fractions of mercaptoethanol, 2-hydroxy-2-methyl-1-phenyl-1-propanone and triphenylphosphine in the solution were 10 wt.%, 0.2 wt.%, respectively.
(6) And (3) transferring the PVDF hollow fiber ultrafiltration membrane soaked by the ethanol in the step (4) into the solution prepared in the step (5), and reacting under stirring and a nitrogen atmosphere in an ultraviolet lamp with the wavelength of 365nm for 1 h.
(7) And (4) taking out the modified hollow fiber ultrafiltration membrane in the step (6), and repeatedly washing the membrane with ethanol and deionized water to remove unreacted sulfhydryl-containing compounds and initiators.
As shown in fig. 1 and fig. 4, the tested static contact angle of the modified PVDF hollow fiber ultrafiltration membrane is 63.2 °, which is greatly reduced compared with the static contact angle of 88.1 ° of the unmodified PVDF hollow fiber ultrafiltration membrane. As shown in FIGS. 8 and 9, the amount of bovine serum albumin adsorbed was controlled to 22.3. mu.g/cm3Reduced to 12.5. mu.g/cm3The pure water flux change is not obvious, which shows that the structure is not obviously changed and the hydrophilicity is enhanced.
Example 2
(1) Cleaning a PVDF hollow fiber ultrafiltration membrane: dipping a PVDF hollow fiber ultrafiltration membrane in absolute ethyl alcohol for 24 hours, and then repeatedly washing with deionized water;
(2) preparing alkali liquor: adding the potassium hydroxide solid into a mixed solution of ethanol, deionized water, ethanol and deionized water in a mass ratio of 1:1, and uniformly stirring to prepare an alkali liquor, wherein the mass fraction of the potassium hydroxide is 10 wt.%.
(3) And (3) completely soaking the hollow fiber ultrafiltration membrane cleaned in the step (1) in the alkali liquor prepared in the step (2), and placing the hollow fiber ultrafiltration membrane in an environment at 60 ℃ for 10 min.
(4) And (4) taking out the hollow fiber ultrafiltration membrane subjected to the alkali treatment in the step (3), repeatedly washing the hollow fiber ultrafiltration membrane by using deionized water under ultrasonic oscillation until the hollow fiber ultrafiltration membrane is no longer alkaline, and soaking the washed hollow fiber ultrafiltration membrane subjected to the alkali treatment in ethanol for later use.
(5) Preparing a solution for modification: the solvent is ethanol. Mercaptoethanol, 2-hydroxy-2-methyl-1-phenyl-1-propanone and triphenylphosphine were added to the solvent. The mass fractions of mercaptoethanol, 2-hydroxy-2-methyl-1-phenyl-1-propanone and triphenylphosphine in the solution were 50 wt.%, 1 wt.%, respectively.
(6) And (3) transferring the PVDF hollow fiber ultrafiltration membrane soaked by the ethanol in the step (4) into the solution prepared in the step (5), and reacting under stirring and a nitrogen atmosphere in an ultraviolet lamp with the wavelength of 365nm for 4 hours.
(7) And (4) taking out the modified hollow fiber ultrafiltration membrane in the step (6), and repeatedly washing the membrane with ethanol and deionized water to remove unreacted sulfhydryl-containing compounds and initiators.
As shown in FIG. 1 and FIG. 5, P is modified by testThe static contact angle of the VDF hollow fiber ultrafiltration membrane is 29.6 degrees, and is greatly reduced compared with the static contact angle of 88.1 degrees of the unmodified PVDF hollow fiber ultrafiltration membrane. As shown in FIGS. 8 and 9, the amount of bovine serum albumin adsorbed was controlled to 22.3. mu.g/cm3Reduced to 5.6. mu.g/cm3The pure water flux change is not obvious, which shows that the structure is not obviously changed and the hydrophilicity is enhanced.
Example 3
(1) Cleaning a PVDF hollow fiber ultrafiltration membrane: dipping a PVDF hollow fiber ultrafiltration membrane in absolute ethyl alcohol for 24 hours, and then repeatedly washing with deionized water;
(2) preparing alkali liquor: adding the potassium hydroxide solid into a mixed solution of ethanol, deionized water, ethanol and deionized water in a mass ratio of 1:1, and uniformly stirring to prepare an alkali liquor, wherein the mass fraction of the potassium hydroxide is 20 wt.%.
(3) And (3) completely soaking the hollow fiber ultrafiltration membrane cleaned in the step (1) in the alkali liquor prepared in the step (2), and placing the hollow fiber ultrafiltration membrane in an environment at 60 ℃ for 120 min.
(4) And (4) taking out the hollow fiber ultrafiltration membrane subjected to the alkali treatment in the step (3), repeatedly washing the hollow fiber ultrafiltration membrane by using deionized water under ultrasonic oscillation until the hollow fiber ultrafiltration membrane is no longer alkaline, and soaking the washed hollow fiber ultrafiltration membrane subjected to the alkali treatment in ethanol for later use.
(5) Preparing a solution for modification: the solvent is ethanol. Mercaptoethanol, 2-hydroxy-2-methyl-1-phenyl-1-propanone and triphenylphosphine were added to the solvent. The mass fractions of mercaptoethanol, 2-hydroxy-2-methyl-1-phenyl-1-propanone and triphenylphosphine in the solution were 50 wt.%, 1 wt.%, respectively.
(6) And (3) transferring the PVDF hollow fiber ultrafiltration membrane soaked by the ethanol in the step (4) into the solution prepared in the step (5), and reacting under stirring and a nitrogen atmosphere in an ultraviolet lamp with the wavelength of 365nm for 5 hours.
(7) And (4) taking out the modified hollow fiber ultrafiltration membrane in the step (6), and repeatedly washing the membrane with ethanol and deionized water to remove unreacted sulfhydryl-containing compounds and initiators.
As shown in fig. 1 and fig. 6, the tested modified PVDF hollow fiber ultrafiltration membrane has a static contact angle of 51.4 degrees,compared with the static contact angle of 88.1 degrees of the hollow fiber ultrafiltration membrane of the unmodified PVDF, the ultrafiltration membrane has a greatly reduced static contact angle. As shown in FIGS. 8 and 9, the amount of bovine serum albumin adsorbed was controlled to 22.3. mu.g/cm3Reduced to 10.2. mu.g/cm3The pure water flux change is not obvious, which shows that the structure is not obviously changed and the hydrophilicity is enhanced.
Example 4
(1) Cleaning a PVDF hollow fiber ultrafiltration membrane: dipping a PVDF hollow fiber ultrafiltration membrane in absolute ethyl alcohol for 24 hours, and then repeatedly washing with deionized water;
(2) preparing alkali liquor: adding the potassium hydroxide solid into a mixed solution of ethanol, deionized water, ethanol and deionized water in a mass ratio of 1:1, and uniformly stirring to prepare an alkali liquor, wherein the mass fraction of the potassium hydroxide is 10 wt.%.
(3) And (3) completely soaking the hollow fiber ultrafiltration membrane cleaned in the step (1) in the alkali liquor prepared in the step (2), and placing the hollow fiber ultrafiltration membrane in an environment at 60 ℃ for 10 min.
(4) And (4) taking out the hollow fiber ultrafiltration membrane subjected to the alkali treatment in the step (3), repeatedly washing the hollow fiber ultrafiltration membrane by using deionized water under ultrasonic oscillation until the hollow fiber ultrafiltration membrane is no longer alkaline, and soaking the washed hollow fiber ultrafiltration membrane subjected to the alkali treatment in ethanol for later use.
(5) Preparing a solution for modification: the solvent is ethanol. Mercaptoethanol, 2-hydroxy-2-methyl-1-phenyl-1-propanone and triphenylphosphine were added to the solvent. The mass fractions of mercaptoethanol, 2-hydroxy-2-methyl-1-phenyl-1-propanone and triphenylphosphine in the solution were 20 wt.%, 0.4 wt.%, respectively.
(6) And (3) transferring the PVDF hollow fiber ultrafiltration membrane soaked by the ethanol in the step (4) into the solution prepared in the step (5), and reacting for 2 hours under stirring and a nitrogen atmosphere in an ultraviolet lamp with the wavelength of 365 nm.
(7) And (4) taking out the modified hollow fiber ultrafiltration membrane in the step (6), and repeatedly washing the membrane with ethanol and deionized water to remove unreacted sulfhydryl-containing compounds and initiators.
As shown in figure 1 and figure 7, the tested static contact angle of the modified PVDF hollow fiber ultrafiltration membrane is 31.7 degrees, and the static contact angle of the modified PVDF hollow fiber ultrafiltration membrane and the unmodified PVDF hollow fiber ultrafiltration membrane is static contactThe antenna angle is reduced by 88.1 degrees. As shown in FIGS. 8 and 9, the amount of bovine serum albumin adsorbed was controlled to 22.3. mu.g/cm3Reduced to 5.7. mu.g/cm3The pure water flux change is not obvious, which shows that the structure is not obviously changed and the hydrophilicity is enhanced.
Comparative example 1
(1) Cleaning a PVDF hollow fiber ultrafiltration membrane: dipping a PVDF hollow fiber ultrafiltration membrane in absolute ethyl alcohol for 24 hours, and then repeatedly washing with deionized water;
(2) preparing alkali liquor: adding the potassium hydroxide solid into a mixed solution of ethanol, deionized water, ethanol and deionized water in a mass ratio of 1:1, and uniformly stirring to prepare an alkali liquor, wherein the mass fraction of the potassium hydroxide is 10 wt.%.
(3) And (3) completely soaking the hollow fiber ultrafiltration membrane cleaned in the step (1) in the alkali liquor prepared in the step (2), and placing the hollow fiber ultrafiltration membrane in an environment at 60 ℃ for 2 min.
(4) And (4) taking out the hollow fiber ultrafiltration membrane subjected to the alkali treatment in the step (3), repeatedly washing the hollow fiber ultrafiltration membrane by using deionized water under ultrasonic oscillation until the hollow fiber ultrafiltration membrane is no longer alkaline, and soaking the washed hollow fiber ultrafiltration membrane subjected to the alkali treatment in ethanol for later use.
(5) Preparing a solution for modification: the solvent is ethanol. Mercaptoethanol, 2-hydroxy-2-methyl-1-phenyl-1-propanone and triphenylphosphine were added to the solvent. The mass fractions of mercaptoethanol, 2-hydroxy-2-methyl-1-phenyl-1-propanone and triphenylphosphine in the solution were 50 wt.%, 1 wt.%, respectively.
(6) And (3) transferring the PVDF hollow fiber ultrafiltration membrane soaked by the ethanol in the step (4) into the solution prepared in the step (5), and reacting under stirring and a nitrogen atmosphere in an ultraviolet lamp with the wavelength of 365nm for 4 hours.
(7) And (4) taking out the modified hollow fiber ultrafiltration membrane in the step (6), and repeatedly washing the membrane with ethanol and deionized water to remove unreacted sulfhydryl-containing compounds and initiators.
As shown in fig. 1 and fig. 2, the tested static contact angle of the modified PVDF hollow fiber ultrafiltration membrane is 81.9 degrees, and the static contact angle of the modified PVDF hollow fiber ultrafiltration membrane is reduced slightly compared with the static contact angle of 88.1 degrees of the unmodified PVDF hollow fiber ultrafiltration membrane. As shown in figures 8 and 9 of the drawings,the bovine serum protein adsorption quantity is 22.3 mu g/cm3Reduced to 21.9. mu.g/cm3The pure water flux change is not obvious, which shows that the structure is not obviously changed and the hydrophilicity is slightly enhanced.
Comparative example 2
(1) Cleaning a PVDF hollow fiber ultrafiltration membrane: dipping a PVDF hollow fiber ultrafiltration membrane in absolute ethyl alcohol for 24 hours, and then repeatedly washing with deionized water;
(2) preparing alkali liquor: adding the potassium hydroxide solid into a mixed solution of ethanol, deionized water, ethanol and deionized water in a mass ratio of 1:1, and uniformly stirring to prepare an alkali liquor, wherein the mass fraction of the potassium hydroxide is 10 wt.%.
(3) And (3) completely soaking the hollow fiber ultrafiltration membrane cleaned in the step (1) in the alkali liquor prepared in the step (2), and placing the hollow fiber ultrafiltration membrane in an environment at 60 ℃ for 10 min.
(4) And (4) taking out the hollow fiber ultrafiltration membrane subjected to the alkali treatment in the step (3), repeatedly washing the hollow fiber ultrafiltration membrane by using deionized water under ultrasonic oscillation until the hollow fiber ultrafiltration membrane is no longer alkaline, and soaking the washed hollow fiber ultrafiltration membrane subjected to the alkali treatment in ethanol for later use.
(5) Preparing a solution for modification: the solvent is ethanol. Mercaptoethanol, 2-hydroxy-2-methyl-1-phenyl-1-propanone and triphenylphosphine were added to the solvent. The mass fractions of mercaptoethanol, 2-hydroxy-2-methyl-1-phenyl-1-propanone and triphenylphosphine in the solution were 5 wt.%, 0.1 wt.%, respectively.
(6) And (3) transferring the PVDF hollow fiber ultrafiltration membrane soaked by the ethanol in the step (4) into the solution prepared in the step (5), and reacting under stirring and a nitrogen atmosphere in an ultraviolet lamp with the wavelength of 365nm for 4 hours.
(7) And (4) taking out the modified hollow fiber ultrafiltration membrane in the step (6), and repeatedly washing the membrane with ethanol and deionized water to remove unreacted sulfhydryl-containing compounds and initiators.
As shown in figures 1 and 2, the tested static contact angle of the modified PVDF hollow fiber ultrafiltration membrane is 84.9 degrees, and the static contact angle of the modified PVDF hollow fiber ultrafiltration membrane is reduced slightly compared with the static contact angle of 88.1 degrees of the unmodified PVDF hollow fiber ultrafiltration membrane. As shown in FIGS. 8 and 9, the amount of bovine serum albumin adsorbed was controlled to 22.3. mu.g/cm3Reduced to 21.6. mu.g/cm3The pure water flux change is not obvious, which shows that the structure is not obviously changed and the hydrophilicity is slightly enhanced.
Claims (6)
1. A surface hydrophilization modification method of a polyvinylidene fluoride hollow fiber membrane is characterized by comprising the following steps:
(1) cleaning a PVDF hollow fiber ultrafiltration membrane: dipping a PVDF hollow fiber ultrafiltration membrane in absolute ethyl alcohol for 24 hours, and then repeatedly washing with deionized water;
(2) preparing alkali liquor: adding the potassium hydroxide solid into a mixed solution of ethanol and deionized water, and uniformly stirring to prepare an alkali liquor;
(3) completely soaking the hollow fiber ultrafiltration membrane cleaned in the step (1) in the alkali liquor prepared in the step (2), and placing in an environment at 60 ℃ for 5-120 min;
(4) taking out the hollow fiber ultrafiltration membrane subjected to the alkali treatment in the step (3), repeatedly washing the hollow fiber ultrafiltration membrane by using deionized water under ultrasonic oscillation until the hollow fiber ultrafiltration membrane is no longer alkaline, and soaking the washed hollow fiber ultrafiltration membrane subjected to the alkali treatment in ethanol for later use;
(5) preparing a modified solution: the solvent is ethanol; adding a sulfhydryl-containing compound, a photoinitiator and a reducing agent for resisting disulfide bond formation into a solvent;
(6) transferring the PVDF hollow fiber ultrafiltration membrane soaked by the ethanol in the step (4) into the solution prepared in the step (5), and reacting under stirring and a nitrogen atmosphere in an ultraviolet lamp with the wavelength of 365nm for 1-5 h;
(7) and (4) taking out the modified hollow fiber ultrafiltration membrane in the step (6), and repeatedly washing the membrane with ethanol and deionized water to remove unreacted sulfhydryl-containing compounds and photoinitiators.
2. The surface hydrophilization modification method of the polyvinylidene fluoride hollow fiber membrane according to claim 1, wherein the mass fraction of ethanol in the alkali liquor in the step (2) is 50 wt.%, and the mass fraction of the solute potassium hydroxide is 5 wt.% to 20 wt.%.
3. The surface hydrophilization modification method of polyvinylidene fluoride hollow fiber membrane according to claim 1, wherein the mass fraction of the thiol-group-containing polymer in the modification solution in the step (5) is 10 wt.% to 50 wt.%, the mass fraction of the photoinitiator is 0.2 wt.% to 1.0 wt.%, and the mass fraction of the reducing agent is 0.2 wt.% to 1.0 wt.%.
4. The method for hydrophilizing the surface of a polyvinylidene fluoride hollow fiber membrane according to claim 1, wherein the thiol-containing polymer in the modification solution in the step (5) is one or more selected from the group consisting of 2-mercaptoethanol, mercaptoacetaldehyde, 2-mercaptoacetic acid, 3-mercaptopropionic acid, 4-mercaptobutyric acid, 2-mercaptopropionaldehyde, 3-mercapto-1-propylamine, 2-mercaptopropan-1-ol, 3-mercapto-1-propanol, 1-mercapto-2-acetone, and 2-mercapto-acetamide.
5. The method for hydrophilizing the surface of a polyvinylidene fluoride hollow fiber membrane according to claim 1, wherein the photoinitiator in the modification solution in the step (5) is one or more of 2-hydroxy-2-methyl-1-phenyl-1-propanone, benzoin dimethyl ether, ethyl 2,4, 6-trimethylbenzoylphosphonate, 2-methyl-1- [ 4-methylthiophenyl ] -2-morpholino-1-propanone, 1-hydroxycyclohexyl phenyl ketone and 2-phenylbenzyl-2-dimethylamine-1- (4-morpholinobenzyl phenyl) butanone.
6. The surface hydrophilization modification method of the polyvinylidene fluoride hollow fiber membrane according to claim 1, wherein the reducing agent in the modification solution in the step (5) is one of triphenylphosphine, iodoacetamide and dithiothreitol.
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