CN110975626B - Preparation method of photo-Fenton catalytic self-cleaning super-hydrophilic PVDF ultrafiltration membrane - Google Patents

Preparation method of photo-Fenton catalytic self-cleaning super-hydrophilic PVDF ultrafiltration membrane Download PDF

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CN110975626B
CN110975626B CN201911253671.8A CN201911253671A CN110975626B CN 110975626 B CN110975626 B CN 110975626B CN 201911253671 A CN201911253671 A CN 201911253671A CN 110975626 B CN110975626 B CN 110975626B
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CN110975626A (en
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孟晓荣
陈嘉智
王磊
王旭东
吕永涛
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Xian University of Architecture and Technology
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    • 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
    • B01D61/14—Ultrafiltration; Microfiltration
    • B01D61/145—Ultrafiltration
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D65/00—Accessories or auxiliary operations, in general, for separation processes or apparatus using semi-permeable membranes
    • B01D65/02—Membrane cleaning or sterilisation ; Membrane regeneration
    • 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
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/06—Organic material
    • B01D71/30—Polyalkenyl halides
    • B01D71/32—Polyalkenyl halides containing fluorine atoms
    • B01D71/34—Polyvinylidene fluoride
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2321/00—Details relating to membrane cleaning, regeneration, sterilization or to the prevention of fouling
    • B01D2321/16—Use of chemical agents
    • B01D2321/168—Use of other chemical agents

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Abstract

The invention discloses a preparation method of a light-Fenton catalytic self-cleaning super-hydrophilic PVDF ultrafiltration membrane. The method comprises the steps of preparing the PVDF super-hydrophilic ultrafiltration membrane by a one-step method; biomimetic mineralization of the membrane interface; the construction of a photo-Fenton catalytic oxidation system, the operation of self-cleaning anti-pollution application and other processes and methods. The preparation process of the self-cleaning anti-pollution ultrafiltration membrane provided by the invention is simple and convenient, the raw material source is easy to obtain, and the cost is low. The membrane surface has strong self-pollution resistance due to super-hydrophilicity and photo-Fenton catalytic oxidation characteristics, and can realize the quick self-cleaning function of the membrane after being polluted through the photo-Fenton catalytic oxidation process.

Description

Preparation method of photo-Fenton catalytic self-cleaning super-hydrophilic PVDF ultrafiltration membrane
Technical Field
The invention belongs to the field of membrane preparation, and particularly relates to a preparation method and application of a light-Fenton catalytic self-cleaning super-hydrophilic PVDF ultrafiltration membrane.
Background
The ultrafiltration technology has the advantages of high effluent quality, high separation efficiency, easy maintenance, compact structure and the like, and develops into a key technology for water treatment. However, due to practical application conditions and complexity of membrane separation systems, membrane fouling has always been a bottleneck problem for widespread application of membrane technology. In the ultrafiltration process, organic pollutants such as protein, polysaccharide, humic acid and the like in sewage are easy to adsorb on the surface of a hydrophobic membrane, a filter cake layer is formed and membrane pores are blocked, so that the membrane performance is deteriorated, and the operation energy consumption is increased.
The membrane is modified by hydrophilization, and simultaneously, advanced oxidation technologies such as photocatalysis and Fenton oxidation are combined, so that the method is an effective method for solving the problem of membrane pollution, and becomes one of hot spots for membrane material modification research. In recent years, the sol-gel method has been adopted by scholars at home and abroad,The ultrafiltration membrane with the photocatalytic self-cleaning performance is prepared by a blending method, a surface mineralization method, a phase inversion deposition method, a vacuum filtration method and the like. For example, CN107715699A adopts a blending method to blend polyetherimide with P25, spin-coating and spin-coating are carried out to prepare a membrane, then hydrogen titanium acid nano wires are grown on the surface of the membrane, and then hydrothermal reaction is carried out to prepare the polyetherimide photocatalytic ultrafiltration membrane with titanium dioxide nano wires loaded on the surface. The method is complex to operate, needs to react for a long time at a higher temperature, and is difficult to industrially apply. CN106902650A takes attapulgite-graphite-like phase carbon nitride composite material as photocatalytic material, and prepares the anti-pollution self-cleaning polyvinylidene fluoride flat ultrafiltration membrane by blending and phase inversion deposition methods. However, in the blending modification, the composite material is wrapped in the polymer material, so that the photocatalytic performance of the polymer material is obviously weakened, the composite material loaded by the phase inversion deposition method is not firmly combined with the membrane, the loss of the composite material can cause the photocatalytic performance of the membrane to be reduced, and secondary pollution is generated. CN108159888A reports that the prepared sol solution is blended with a casting solution, a non-woven fabric is used as a supporting layer, a base film is prepared by an immersion precipitation method, then the base film is dip-coated by a modified solution, the surface of the base film is subjected to a cross-linking reaction, and TiO is grafted2And the functional layer is used for preparing the ultrafiltration membrane with the ultraviolet light catalytic performance. However, the light energy of the ultraviolet light only accounts for less than 5 percent of the solar light energy, and the polymer film is seriously aged under the long-term irradiation of the ultraviolet light, so that the problems seriously limit the TiO2The practical application of the modified membrane. CN106943897A for doping nano Cu2And O is a catalyst to prepare the visible light catalytic flat ultrafiltration membrane by a blending method. The method widens the available wavelength range of photocatalysis to the visible light region, but the blending method results in a large amount of doped nano Cu2O is encapsulated in the polymer matrix, which severely affects the photocatalytic efficiency of the membrane. CN106582331A preparation of N-TiO2and/GO particles are loaded on the ultrafiltration membrane by a vacuum filtration method to prepare the photocatalytic ultrafiltration membrane with visible light activity. But due to N-TiO2the/GO particles lack interaction with the ultrafiltration membrane, and the particle loss problem exists in long-term use.
Disclosure of Invention
The invention aims to provide a preparation method of a light-Fenton super-hydrophilic PVDF ultrafiltration membrane and self-cleaning application thereof, aiming at the problems that the traditional photocatalytic self-cleaning ultrafiltration membrane is uneven in photocatalytic material distribution, low in photocatalytic efficiency, and needs to be self-cleaned under the condition of ultraviolet illumination. The membrane prepared by the method has the characteristics of super-hydrophilicity and photo-Fenton catalytic oxidation, has strong anti-pollution capability, and can realize the quick self-cleaning effect of the membrane after pollution through the visible light-Fenton process.
The invention is realized by the following technical scheme.
The preparation method of the light-Fenton catalytic self-cleaning super-hydrophilic PVDF ultrafiltration membrane comprises the following steps:
step 1, preparing a PVDF (polyvinylidene fluoride) ultra-hydrophilic ultrafiltration membrane by a one-pot method:
1) mixing 3-9% of monomer acrylic acid, 10-14% of alkalized polyvinylidene fluoride, 2-8% of macromolecular compatibilizer, 1-5% of anhydrous lithium chloride and 68-80% of organic solvent according to mass percent, stirring, dissolving, adding 1% of initiator, heating for polymerization, reacting, cooling, stopping polymerization, standing for defoaming, and preparing a grafting reaction mixed solution;
2) preparing the grafting reaction mixed solution into a macromolecular solution film with a certain thickness, pre-evaporating at room temperature, putting the film into a coagulating bath, carrying out phase splitting treatment, and repeatedly cleaning with deionized water to obtain the PVDF (polyvinylidene fluoride) ultra-hydrophilic ultrafiltration membrane prepared by the one-pot method;
step 2, biomimetic mineralization of a PVDF (polyvinylidene fluoride) ultra-hydrophilic ultrafiltration membrane interface:
immersing the PVDF super-hydrophilic ultrafiltration membrane prepared in the step 1 in a biomimetic mineralization liquid at 40-80 ℃ for 6-36 h, washing the membrane with water at room temperature after mineralization is finished, removing residual mineralization liquid and an unstable mineralization layer, and airing at room temperature to obtain the biomimetic mineralized super-hydrophilic PVDF ultrafiltration membrane;
step 3, performing photo-Fenton self-cleaning on the PVDF ultrafiltration membrane:
1) fixing the super-hydrophilic PVDF ultrafiltration membrane obtained in the step 2 on a cross-flow filtering device, filtering for 2 hours at room temperature under the transmembrane pressure difference of 0.1MPa by taking ultrafiltration stock solution as feed liquid, and taking out the polluted bionic mineralized super-hydrophilic PVDF ultrafiltration membrane after the filtration is finished;
2) fixing the polluted biomimetic mineralized super-hydrophilic PVDF ultrafiltration membrane in two hollow clamping pieces, immersing the clamping pieces in a container filled with a certain volume of light-Fenton system solution, placing the container in a photocatalytic reactor, and reacting for a certain time to complete the light-Fenton self-cleaning process of the ultrafiltration membrane.
With respect to the above technical solutions, the present invention has a further preferable solution:
preferably, the alkalized polyvinylidene fluoride is prepared by the following method:
stirring polyvinylidene fluoride with the average molecular weight of 50-100 ten thousand in 0.5mol/L KOH ethanol solution at 60 ℃ for 2h by adopting an alkalization defluorination treatment method, filtering after the reaction is finished, washing the filtrate with deionized water, and drying in vacuum at 60 ℃ to obtain the alkalized polyvinylidene fluoride.
Preferably, the macromolecular compatibilizer is one of polyvinylpyrrolidone with a molecular weight of 20000-50000, polyethylene glycol with a molecular weight of 10000-20000 and polyvinyl alcohol with a molecular weight of 80000-120000.
Preferably, the organic solvent is one or a mixture of two or more of N, N-dimethylformamide, N-dimethylacetamide, N-methyl-2-pyrrolidone and dimethyl sulfoxide.
Preferably, the biomimetic mineralization liquid is prepared by the following method:
dissolving a trivalent ferric salt into a hydrochloric acid solution or a sulfuric acid solution with the concentration of 0.001-0.01 mol/L, and keeping the concentration of the trivalent ferric salt in the solution at 10-20 g/L to obtain a mineralized liquid;
the ferric salt is ferric trichloride hexahydrate or ferric sulfate.
Preferably, in the step 1-1), stirring and dissolving at 60 ℃, adding an initiator, and heating to 60-90 ℃ for polymerization; after reacting for 1-6 h, cooling to 40 ℃, stopping polymerization, and standing for defoaming for 4 h;
the initiator is one of azodiisobutyronitrile or benzoyl peroxide.
Preferably, in the step 1-2), the grafting reaction mixed solution is scraped into a 150-250 μm thick polymer solution film directly by hand or through a flat film scraper, and after pre-evaporation for 15s at room temperature, the polymer solution film is placed into a sodium hydroxide solution coagulation bath with the temperature of 20-60 ℃ and the pH value of 12-13, and phase separation treatment is carried out for 2 min.
Preferably, in the step 3, the ultrafiltration stock solution is prepared by the following method:
dissolving 0.02g of representative pollutant in 1L of phosphate buffer solution with pH7.4 to obtain ultrafiltration stock solution; the representative contaminant is one of Bovine Serum Albumin (BSA), Humic Acid (HA) or Sodium Alginate (SA).
Preferably, in the step 3, the solution of the photo-Fenton system is an acidic solution with pH of 2-4 prepared by hydrochloric acid and containing 20-200 μ L/L of 30% hydrogen peroxide.
Preferably, in the step 3, the light source used in the photocatalytic reactor is a 300w xenon lamp provided with a 420nm filter; the distance between the film and the light source is 15-30cm, and the photocatalytic reaction time is 30-120 min.
Due to the adoption of the technical scheme, the invention has the following beneficial effects:
(1) the photo-Fenton super-hydrophilic PVDF ultrafiltration membrane prepared by the method disclosed by the invention is prepared by grafting hydrophilic monomer acrylic acid onto an alkalized PVDF chain by adopting a one-pot method for grafting modification, and further depositing a FeOOH photocatalytic layer with visible light-Fenton oxidation performance on the surface of a base membrane through biomimetic mineralization to obtain the photo-Fenton super-hydrophilic PVDF ultrafiltration membrane.
(2) According to the method for preparing the light-Fenton super-hydrophilic PVDF ultrafiltration membrane through the biomimetic mineralization process, the PAA-g-PVDF super-hydrophilic ultrafiltration membrane prepared by the one-pot method has rich carboxyl functional groups on the surface and inside, can provide carboxylate radicals which generate good chemical complexation and action with ferric ions, and can generate good acid-base buffering action on mineralized liquid. Therefore, the deposition amount of ferric ions in the biomimetic mineralization process is large, the speed is high, the uniformity is good and stable, the generation efficiency of the hydroxyl ferric oxide is high, the combination is firm, and the efficiency of the photo-Fenton process is stronger.
(3) The photo-Fenton self-cleaning biomimetic mineralized PVDF ultrafiltration membrane provided by the invention adopts a one-pot method technology combining the acrylic acid chemical grafting and phase inversion processes of a PVDF base membrane material, and the membrane preparation process is simple and convenient, is convenient to operate, is energy-saving and environment-friendly. The prepared acrylic acid grafted PVDF ultrafiltration membrane has super-hydrophilic characteristic, strong pollution resistance, photo-Fenton catalytic oxidation performance under the visible light catalysis condition, and dry storage and transportation performance. The water flux of the prepared ultrafiltration membrane is not less than 169.42L/m2·h，RBSANot less than 90.2%, the initial water contact angle is not more than 24.5%, and the flux recovery rate of the visible light-Fenton self-cleaning membrane is not less than 78.4%. The method is used for preparing the super-hydrophilic PVDF ultrafiltration membrane with good performance and self-cleaning performance through photo-Fenton catalysis.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principles of the invention:
FIG. 1 is an SEM photograph of a photo-Fenton type ultra-hydrophilic PVDF ultrafiltration membrane in example 1 of the present invention;
FIG. 2 is a FT-IR spectrum of a photo-Fenton type ultra-hydrophilic PVDF ultrafiltration membrane in example 1 of the present invention;
FIG. 3 is a photograph showing the water contact angle of the photo-Fenton type ultra-hydrophilic PVDF ultrafiltration membrane in example 1 of the present invention.
Detailed Description
The present invention will now be described in detail with reference to the drawings and specific embodiments, wherein the exemplary embodiments and descriptions of the present invention are provided to explain the present invention without limiting the invention thereto.
The invention provides a preparation method of a light-Fenton catalytic self-cleaning super-hydrophilic PVDF ultrafiltration membrane, which comprises the following steps:
step 1, preparing a PVDF (polyvinylidene fluoride) ultra-hydrophilic ultrafiltration membrane by a one-pot method:
according to the mass percentage, 3% -9% of monomer acrylic acid, 10% -14% of alkalized polyvinylidene fluoride, 2% -8% of macromolecular compatibilizer (polyvinylpyrrolidone with the molecular weight of 20000-50000, polyethylene glycol with the molecular weight of 10000-20000, polyvinyl alcohol with the molecular weight of 80000-120000), 1% -5% of anhydrous lithium chloride, 68% -80% of organic solvent (one or a mixture of more than two of N, N-dimethylformamide, N-dimethylacetamide, N-methyl-2-pyrrolidone and dimethyl sulfoxide), stirring and dissolving at 60 ℃, adding 1% of initiator (azodiisobutyronitrile or benzoyl peroxide), and heating to 60-90 ℃ for polymerization. And after reacting for 1-6 h, cooling to 40 ℃, stopping polymerization, and standing for defoaming for 6 h.
And (3) scraping the grafting reaction mixed solution into a 150-250 mu m thick polymer solution film directly by hand or through a flat film scraper, pre-evaporating for 15s at room temperature, placing the film into a sodium hydroxide solution coagulating bath with the temperature of 20-60 ℃ and the pH value of 12-13, carrying out phase separation treatment for 2min, and taking out. And repeatedly cleaning with deionized water, and removing residual solvent and impurities to obtain the PVDF super-hydrophilic ultrafiltration membrane prepared by the one-pot method.
Wherein the alkalized polyvinylidene fluoride is prepared by the following method:
stirring polyvinylidene fluoride with the average molecular weight of 50-100 ten thousand in 0.5mol/L KOH ethanol solution at 60 ℃ for 2h by adopting an alkalization defluorination treatment method, filtering after the reaction is finished, washing the filtrate with deionized water, and drying in vacuum at 60 ℃ to obtain the alkalized polyvinylidene fluoride.
Step 2, biomimetic mineralization of a PVDF (polyvinylidene fluoride) ultra-hydrophilic ultrafiltration membrane interface:
immersing the PVDF super-hydrophilic ultrafiltration membrane prepared in the step 1 in a biomimetic mineralization liquid at 40-80 ℃ for 6-36 h, washing the membrane with water at room temperature after mineralization is finished, removing residual mineralization liquid and an unstable mineralization layer, and airing at room temperature to obtain the biomimetic mineralized super-hydrophilic PVDF ultrafiltration membrane;
the biomimetic mineralization liquid is prepared by the following method:
dissolving ferric salt (ferric trichloride hexahydrate or ferric sulfate) in hydrochloric acid solution or sulfuric acid solution with the concentration of 0.001-0.01 mol/L, and keeping the concentration of the ferric salt in the solution at 10-20 g/L to obtain mineralized liquid;
step 3, performing photo-Fenton self-cleaning on the PVDF ultrafiltration membrane:
firstly, fixing the super-hydrophilic PVDF ultrafiltration membrane obtained in the step 2 on a cross-flow filtering device, filtering for 2 hours at room temperature under the transmembrane pressure difference of 0.1MPa by taking ultrafiltration stock solution as feed liquid, and taking out the polluted biomimetic mineralized super-hydrophilic PVDF ultrafiltration membrane after the filtration is finished;
the ultrafiltration stock solution is prepared by the following method:
dissolving 0.02g of representative pollutant in 1L of phosphate buffer solution with pH7.4 to obtain ultrafiltration stock solution; the representative contaminant is one of Bovine Serum Albumin (BSA), Humic Acid (HA) or Sodium Alginate (SA).
Fixing the polluted biomimetic mineralized super-hydrophilic PVDF ultrafiltration membrane in two hollow clamping pieces made of tetrafluoroethylene materials, immersing the clamping pieces in a container filled with a certain volume of light-Fenton system solution, placing the container in a photocatalytic reactor, and using a 300w xenon lamp filled with a 420nm optical filter as a light source; and (3) starting a photocatalytic reaction device when the distance between the membrane and the light source is 15-30cm, wherein the photocatalytic reaction time is 30-120 min, and finishing the photo-Fenton self-cleaning process of the ultrafiltration membrane.
The solution of the photo-Fenton system is an acidic solution with pH of 2-4, which contains 20-200 mu L/L of 30% hydrogen peroxide and is prepared by hydrochloric acid.
The invention is further illustrated by the following specific examples.
Example 1:
step 1, preparing a PVDF (polyvinylidene fluoride) ultra-hydrophilic ultrafiltration membrane by a one-pot method:
mixing 6% of monomer acrylic acid, 12% of alkalized polyvinylidene fluoride, 3% of polyvinylpyrrolidone with the molecular weight of 20000-50000, 3% of anhydrous lithium chloride and 75% of N, N-dimethylacetamide according to mass percentage, stirring and dissolving at 60 ℃, adding 1% of azobisisobutyronitrile, and heating to 80 ℃ for polymerization. After reacting for 2h, cooling to 40 ℃, stopping polymerization, standing and defoaming for 6 h.
And (3) scraping the grafting reaction mixed solution into a polymer solution film with the thickness of 200 mu m directly by hand or through a flat film scraper, pre-evaporating for 15s at room temperature, putting into a sodium hydroxide solution coagulating bath with the temperature of 60 ℃ and the pH value of 13, carrying out phase separation treatment for 2min, and taking out. And repeatedly cleaning with deionized water, and removing residual solvent and impurities to obtain the PVDF super-hydrophilic ultrafiltration membrane prepared by the one-pot method.
Wherein the alkalized polyvinylidene fluoride is prepared by the following method:
stirring polyvinylidene fluoride with the average molecular weight of 50-100 ten thousand in 0.5mol/L KOH ethanol solution at 60 ℃ for 2h by adopting an alkalization defluorination treatment method, filtering after the reaction is finished, washing the filtrate with deionized water, and drying in vacuum at 60 ℃ to obtain the alkalized polyvinylidene fluoride.
Step 2, biomimetic mineralization of a PVDF (polyvinylidene fluoride) ultra-hydrophilic ultrafiltration membrane interface:
immersing the PVDF super-hydrophilic ultrafiltration membrane prepared in the step 1 in a biomimetic mineralization liquid at 40 ℃ for 24h, after mineralization is finished, washing the membrane with water at room temperature, removing residual mineralization liquid and a weak mineralization layer, and airing at room temperature to obtain the biomimetic mineralized super-hydrophilic PVDF ultrafiltration membrane;
the biomimetic mineralization liquid is prepared by the following method:
dissolving ferric trichloride hexahydrate in hydrochloric acid solution with the concentration of 0.001mol/L, and keeping the concentration of ferric trichloride hexahydrate in the solution at 10g/L to obtain mineralized liquid;
step 3, performing photo-Fenton self-cleaning on the PVDF ultrafiltration membrane:
firstly, fixing the super-hydrophilic PVDF ultrafiltration membrane obtained in the step 2 on a cross-flow filtering device, filtering for 2 hours at room temperature under the transmembrane pressure difference of 0.1MPa by taking ultrafiltration stock solution as feed liquid, and taking out the polluted biomimetic mineralized super-hydrophilic PVDF ultrafiltration membrane after the filtration is finished;
the ultrafiltration stock solution is prepared by the following method:
dissolving 0.02g Bovine Serum Albumin (BSA) in 1L phosphate buffer solution with pH7.4 to obtain ultrafiltration stock solution; fixing the polluted biomimetic mineralized super-hydrophilic PVDF ultrafiltration membrane in two hollow clamping pieces made of tetrafluoroethylene materials, immersing the clamping pieces in a container filled with a certain volume of light-Fenton system solution, placing the container in a photocatalytic reactor, and using a 300w xenon lamp filled with a 420nm optical filter as a light source; and (3) starting a photocatalytic reaction device when the distance between the membrane and the light source is 30cm, wherein the photocatalytic reaction time is 30min, and finishing the photo-Fenton self-cleaning process of the ultrafiltration membrane.
The photo-Fenton system solution was an acidic solution of pH2 prepared from hydrochloric acid containing 20. mu.L/L of 30% hydrogen peroxide.
The water flux of the ultrafiltration membrane prepared in the embodiment is 228.96L/m2·h，RBSA90.8%, the initial water contact angle is 23.5%, and the flux recovery rate of the visible light-Fenton self-cleaning membrane is 78.4%.
The SEM photograph of the photo-Fenton type ultra-hydrophilic PVDF ultrafiltration membrane of the present example is shown in FIG. 1, the FT-IR spectrum is shown in FIG. 2, and the water contact angle photograph of the PVDF ultrafiltration membrane is shown in FIG. 3.
Example 2:
step 1, preparing a PVDF (polyvinylidene fluoride) ultra-hydrophilic ultrafiltration membrane by a one-pot method:
mixing 9% of monomer acrylic acid, 11% of alkalized polyvinylidene fluoride and 2% of mixture (1:1) of polyvinyl alcohol with the molecular weight of 80000-120000, 5% of anhydrous lithium chloride, 72% of N, N-dimethylformamide and dimethyl sulfoxide according to mass percentage, stirring and dissolving at 60 ℃, adding 1% of azobisisobutyronitrile, and heating to 70 ℃ for polymerization. After reacting for 3h, cooling to 40 ℃, stopping polymerization, standing and defoaming for 6 h.
And (3) scraping the grafting reaction mixed solution into a 150-micron-thick polymer solution film directly by hand or through a flat film scraper, pre-evaporating for 15s at room temperature, placing the film into a sodium hydroxide solution coagulation bath with the temperature of 30 ℃ and the pH value of 12, carrying out phase separation treatment for 2min, and taking out. And repeatedly cleaning with deionized water, and removing residual solvent and impurities to obtain the PVDF super-hydrophilic ultrafiltration membrane prepared by the one-pot method.
Wherein the alkalized polyvinylidene fluoride is prepared by the following method:
stirring polyvinylidene fluoride with the average molecular weight of 50-100 ten thousand in 0.5mol/L KOH ethanol solution at 60 ℃ for 2h by adopting an alkalization defluorination treatment method, filtering after the reaction is finished, washing the filtrate with deionized water, and drying in vacuum at 60 ℃ to obtain the alkalized polyvinylidene fluoride.
Step 2, biomimetic mineralization of a PVDF (polyvinylidene fluoride) ultra-hydrophilic ultrafiltration membrane interface:
immersing the PVDF super-hydrophilic ultrafiltration membrane prepared in the step 1 in a biomimetic mineralization liquid at 60 ℃ for 36h, after mineralization is finished, washing the membrane with water at room temperature, removing residual mineralization liquid and a weak mineralization layer, and airing at room temperature to obtain the biomimetic mineralized super-hydrophilic PVDF ultrafiltration membrane;
the biomimetic mineralization liquid is prepared by the following method:
dissolving ferric sulfate in a sulfuric acid solution with the concentration of 0.001mol/L, and keeping the concentration of the ferric sulfate in the solution at 15g/L to obtain mineralized liquid;
step 3, performing photo-Fenton self-cleaning on the PVDF ultrafiltration membrane:
firstly, fixing the super-hydrophilic PVDF ultrafiltration membrane obtained in the step 2 on a cross-flow filtering device, filtering for 2 hours at room temperature under the transmembrane pressure difference of 0.1MPa by taking ultrafiltration stock solution as feed liquid, and taking out the polluted biomimetic mineralized super-hydrophilic PVDF ultrafiltration membrane after the filtration is finished;
the ultrafiltration stock solution is prepared by the following method:
dissolving 0.02g Sodium Alginate (SA) in 1L phosphate buffer solution with pH of 7.4 to obtain ultrafiltration stock solution; fixing the polluted biomimetic mineralized super-hydrophilic PVDF ultrafiltration membrane in two hollow clamping pieces made of tetrafluoroethylene materials, immersing the clamping pieces in a container filled with a certain volume of light-Fenton system solution, placing the container in a photocatalytic reactor, and using a 300w xenon lamp filled with a 420nm optical filter as a light source; and (3) starting a photocatalytic reaction device when the distance between the membrane and the light source is 15cm, wherein the photocatalytic reaction time is 60min, and finishing the photo-Fenton self-cleaning process of the ultrafiltration membrane.
The photo-Fenton system solution was an acidic solution of pH2 prepared from hydrochloric acid containing 100. mu.L/L of 30% hydrogen peroxide.
The water flux of the ultrafiltration membrane prepared in the embodiment is 178.26L/m2·h，RBSA91.6%, the initial water contact angle is 18.6%, and the flux recovery rate of the visible light-Fenton self-cleaning membrane is 88.6%.
Example 3:
step 1, preparing a PVDF (polyvinylidene fluoride) ultra-hydrophilic ultrafiltration membrane by a one-pot method:
according to the mass percentage, 3 percent of monomer acrylic acid, 12 percent of alkalized polyvinylidene fluoride, 5 percent of polyethylene glycol with the molecular weight of 10000-20000, 1 percent of anhydrous lithium chloride and 78 percent of N, N-dimethylacetamide are mixed, stirred and dissolved at the temperature of 60 ℃, 1 percent of benzoyl peroxide is added, and the temperature is raised to 80 ℃ for polymerization. After 6h of reaction, the temperature is reduced to 40 ℃, the polymerization is stopped, and standing and defoaming are carried out for 6 h.
And (3) scraping the grafting reaction mixed solution into a polymer solution film with the thickness of 200 mu m directly by hand or through a flat film scraper, pre-evaporating for 15s at room temperature, putting into a sodium hydroxide solution coagulating bath with the temperature of 25 ℃ and the pH value of 12, carrying out phase separation treatment for 2min, and taking out. And repeatedly cleaning with deionized water, and removing residual solvent and impurities to obtain the PVDF super-hydrophilic ultrafiltration membrane prepared by the one-pot method.
Wherein the alkalized polyvinylidene fluoride is prepared by the following method:
stirring polyvinylidene fluoride with the average molecular weight of 50-100 ten thousand in 0.5mol/L KOH ethanol solution at 60 ℃ for 2h by adopting an alkalization defluorination treatment method, filtering after the reaction is finished, washing the filtrate with deionized water, and drying in vacuum at 60 ℃ to obtain the alkalized polyvinylidene fluoride.
Step 2, biomimetic mineralization of a PVDF (polyvinylidene fluoride) ultra-hydrophilic ultrafiltration membrane interface:
immersing the PVDF super-hydrophilic ultrafiltration membrane prepared in the step 1 in a biomimetic mineralization liquid at 50 ℃ for 18h, washing the membrane with water at room temperature after mineralization is finished, removing residual mineralization liquid and a weak mineralization layer, and airing at room temperature to obtain the biomimetic mineralized super-hydrophilic PVDF ultrafiltration membrane;
the biomimetic mineralization liquid is prepared by the following method:
dissolving ferric trichloride hexahydrate in hydrochloric acid solution with the concentration of 0.005mol/L, and keeping the concentration of ferric salt in the solution at 20g/L to obtain mineralized liquid;
step 3, performing photo-Fenton self-cleaning on the PVDF ultrafiltration membrane:
firstly, fixing the super-hydrophilic PVDF ultrafiltration membrane obtained in the step 2 on a cross-flow filtering device, filtering for 2 hours at room temperature under the transmembrane pressure difference of 0.1MPa by taking ultrafiltration stock solution as feed liquid, and taking out the polluted biomimetic mineralized super-hydrophilic PVDF ultrafiltration membrane after the filtration is finished;
the ultrafiltration stock solution is prepared by the following method:
dissolving 0.02g Humic Acid (HA) in 1L phosphate buffer solution with pH7.4 to obtain ultrafiltration stock solution; fixing the polluted biomimetic mineralized super-hydrophilic PVDF ultrafiltration membrane in two hollow clamping pieces made of tetrafluoroethylene materials, immersing the clamping pieces in a container filled with a certain volume of light-Fenton system solution, placing the container in a photocatalytic reactor, and using a 300w xenon lamp filled with a 420nm optical filter as a light source; and (3) starting a photocatalytic reaction device when the distance between the membrane and the light source is 20cm, wherein the photocatalytic reaction time is 100min, and finishing the photo-Fenton self-cleaning process of the ultrafiltration membrane.
The photo-Fenton system solution was an acidic solution of pH2 prepared from hydrochloric acid containing 50. mu.L/L of 30% hydrogen peroxide.
The water flux of the ultrafiltration membrane prepared in the embodiment is 243.74L/m2·h，RBSA90.2%, the initial water contact angle is 20.8%, and the flux recovery rate of the visible light-Fenton self-cleaning membrane is 82.4%.
Example 4:
step 1, preparing a PVDF (polyvinylidene fluoride) ultra-hydrophilic ultrafiltration membrane by a one-pot method:
mixing 8% of monomer acrylic acid, 10% of alkalized polyvinylidene fluoride, 8% of polyvinylpyrrolidone with the molecular weight of 20000-50000, 4% of anhydrous lithium chloride and 69% of N, N-dimethylformamide according to mass percentage, stirring and dissolving at 60 ℃, adding 1% of azobisisobutyronitrile, and heating to 75 ℃ for polymerization. After 5h of reaction, the temperature is reduced to 40 ℃, the polymerization is stopped, and standing and defoaming are carried out for 6 h.
And (3) scraping the grafting reaction mixed solution into a polymer solution film with the thickness of 250 microns directly by hand or through a flat film scraper, pre-evaporating for 15s at room temperature, putting into a sodium hydroxide solution coagulation bath with the temperature of 30 ℃ and the pH value of 13, carrying out phase separation treatment for 2min, and taking out. And repeatedly cleaning with deionized water, and removing residual solvent and impurities to obtain the PVDF super-hydrophilic ultrafiltration membrane prepared by the one-pot method.
Wherein the alkalized polyvinylidene fluoride is prepared by the following method:
stirring polyvinylidene fluoride with the average molecular weight of 50-100 ten thousand in 0.5mol/L KOH ethanol solution at 60 ℃ for 2h by adopting an alkalization defluorination treatment method, filtering after the reaction is finished, washing the filtrate with deionized water, and drying in vacuum at 60 ℃ to obtain the alkalized polyvinylidene fluoride.
Step 2, biomimetic mineralization of a PVDF (polyvinylidene fluoride) ultra-hydrophilic ultrafiltration membrane interface:
immersing the PVDF super-hydrophilic ultrafiltration membrane prepared in the step 1 in a biomimetic mineralization liquid at 80 ℃ for 6h, washing the membrane with water at room temperature after mineralization is finished, removing residual mineralization liquid and a weak mineralization layer, and airing at room temperature to obtain the biomimetic mineralized super-hydrophilic PVDF ultrafiltration membrane;
the biomimetic mineralization liquid is prepared by the following method:
dissolving ferric trichloride hexahydrate in hydrochloric acid solution with the concentration of 0.008mol/L, and keeping the concentration of ferric salt in the solution at 10g/L to obtain mineralized liquid;
step 3, performing photo-Fenton self-cleaning on the PVDF ultrafiltration membrane:
firstly, fixing the super-hydrophilic PVDF ultrafiltration membrane obtained in the step 2 on a cross-flow filtering device, filtering for 2 hours at room temperature under the transmembrane pressure difference of 0.1MPa by taking ultrafiltration stock solution as feed liquid, and taking out the polluted biomimetic mineralized super-hydrophilic PVDF ultrafiltration membrane after the filtration is finished;
the ultrafiltration stock solution is prepared by the following method:
dissolving 0.02g Bovine Serum Albumin (BSA) in 1L phosphate buffer solution with pH7.4 to obtain ultrafiltration stock solution; fixing the polluted biomimetic mineralized super-hydrophilic PVDF ultrafiltration membrane in two hollow clamping pieces made of tetrafluoroethylene materials, immersing the clamping pieces in a container filled with a certain volume of light-Fenton system solution, placing the container in a photocatalytic reactor, and using a 300w xenon lamp filled with a 420nm optical filter as a light source; and (3) starting a photocatalytic reaction device when the distance between the membrane and the light source is 30cm, wherein the photocatalytic reaction time is 120min, and finishing the photo-Fenton self-cleaning process of the ultrafiltration membrane.
The photo-Fenton system solution was an acidic solution of pH 3 prepared from hydrochloric acid containing 150. mu.L/L of 30% hydrogen peroxide.
The water flux of the ultrafiltration membrane prepared in the embodiment is 201.82L/m2·h，RBSA91.2%, the initial water contact angle is 24.5%, and the flux recovery rate of the visible light-Fenton self-cleaning membrane is 82.6%.
Example 5:
step 1, preparing a PVDF (polyvinylidene fluoride) ultra-hydrophilic ultrafiltration membrane by a one-pot method:
according to the mass percentage, 7% of monomer acrylic acid, 14% of alkalized polyvinylidene fluoride, 3% of polyvinylpyrrolidone with the molecular weight of 20000-50000, 5% of anhydrous lithium chloride and 70% of N-methyl-2-pyrrolidone are mixed, stirred and dissolved at the temperature of 60 ℃, 1% of azobisisobutyronitrile is added, and the mixture is heated to 90 ℃ for polymerization. After 4h of reaction, the temperature is reduced to 40 ℃, the polymerization is stopped, and standing and defoaming are carried out for 6 h.
And (3) scraping the grafting reaction mixed solution into a 150-micron-thick polymer solution film directly by hand or through a flat film scraper, pre-evaporating for 15s at room temperature, placing the film into a sodium hydroxide solution coagulating bath with the temperature of 40 ℃ and the pH value of 13, carrying out phase separation treatment for 2min, and taking out. And repeatedly cleaning with deionized water, and removing residual solvent and impurities to obtain the PVDF super-hydrophilic ultrafiltration membrane prepared by the one-pot method.
Wherein the alkalized polyvinylidene fluoride is prepared by the following method:
stirring polyvinylidene fluoride with the average molecular weight of 50-100 ten thousand in 0.5mol/L KOH ethanol solution at 60 ℃ for 2h by adopting an alkalization defluorination treatment method, filtering after the reaction is finished, washing the filtrate with deionized water, and drying in vacuum at 60 ℃ to obtain the alkalized polyvinylidene fluoride.
Step 2, biomimetic mineralization of a PVDF (polyvinylidene fluoride) ultra-hydrophilic ultrafiltration membrane interface:
immersing the PVDF super-hydrophilic ultrafiltration membrane prepared in the step 1 in a biomimetic mineralization liquid at 55 ℃ for 12h, after mineralization is finished, washing the membrane with water at room temperature to remove residual mineralization liquid and a weak mineralization layer, and airing at room temperature to obtain the biomimetic mineralized super-hydrophilic PVDF ultrafiltration membrane;
the biomimetic mineralization liquid is prepared by the following method:
dissolving ferric sulfate in a sulfuric acid solution with the concentration of 0.005mol/L, and keeping the concentration of the ferric sulfate in the solution at 15g/L to obtain mineralized liquid;
step 3, performing photo-Fenton self-cleaning on the PVDF ultrafiltration membrane:
firstly, fixing the super-hydrophilic PVDF ultrafiltration membrane obtained in the step 2 on a cross-flow filtering device, filtering for 2 hours at room temperature under the transmembrane pressure difference of 0.1MPa by taking ultrafiltration stock solution as feed liquid, and taking out the polluted biomimetic mineralized super-hydrophilic PVDF ultrafiltration membrane after the filtration is finished;
the ultrafiltration stock solution is prepared by the following method:
dissolving 0.02g Bovine Serum Albumin (BSA) in 1L phosphate buffer solution with pH7.4 to obtain ultrafiltration stock solution; fixing the polluted biomimetic mineralized super-hydrophilic PVDF ultrafiltration membrane in two hollow clamping pieces made of tetrafluoroethylene materials, immersing the clamping pieces in a container filled with a certain volume of light-Fenton system solution, placing the container in a photocatalytic reactor, and using a 300w xenon lamp filled with a 420nm optical filter as a light source; and (3) starting a photocatalytic reaction device when the distance between the membrane and the light source is 15cm, wherein the photocatalytic reaction time is 110min, and finishing the photo-Fenton self-cleaning process of the ultrafiltration membrane.
The photo-Fenton system solution was an acidic solution of pH 4 prepared from hydrochloric acid containing 200. mu.L/L of 30% hydrogen peroxide.
The water flux of the ultrafiltration membrane prepared in the embodiment is 169.40L/m2·h，RBSA92.8%, the initial water contact angle is 20.4%, and the flux recovery rate of the visible light-Fenton self-cleaning membrane is 92.8%.
Example 6:
step 1, preparing a PVDF (polyvinylidene fluoride) ultra-hydrophilic ultrafiltration membrane by a one-pot method:
according to the mass percentage, 3 percent of monomer acrylic acid, 13 percent of alkalized polyvinylidene fluoride, 2 percent of polyvinyl alcohol with the molecular weight of 80000-120000, 1 percent of anhydrous lithium chloride, 80 percent of N, N-dimethylacetamide and dimethyl sulfoxide are mixed, stirred and dissolved at the temperature of 60 ℃, 1 percent of azobisisobutyronitrile is added, and the mixture is heated to 85 ℃ for polymerization. After reacting for 1h, cooling to 40 ℃, stopping polymerization, standing and defoaming for 6 h.
And (3) scraping the grafting reaction mixed solution into a polymer solution film with the thickness of 200 mu m directly by hand or through a flat film scraper, pre-evaporating for 15s at room temperature, putting into a sodium hydroxide solution coagulating bath with the temperature of 55 ℃ and the pH value of 12, carrying out phase separation treatment for 2min, and taking out. And repeatedly cleaning with deionized water, and removing residual solvent and impurities to obtain the PVDF super-hydrophilic ultrafiltration membrane prepared by the one-pot method.
Wherein the alkalized polyvinylidene fluoride is prepared by the following method:
stirring polyvinylidene fluoride with the average molecular weight of 50-100 ten thousand in 0.5mol/L KOH ethanol solution at 60 ℃ for 2h by adopting an alkalization defluorination treatment method, filtering after the reaction is finished, washing the filtrate with deionized water, and drying in vacuum at 60 ℃ to obtain the alkalized polyvinylidene fluoride.
Step 2, biomimetic mineralization of a PVDF (polyvinylidene fluoride) ultra-hydrophilic ultrafiltration membrane interface:
immersing the PVDF super-hydrophilic ultrafiltration membrane prepared in the step 1 in a bionic mineralization liquid at 45 ℃ for 24 hours, washing the membrane with water at room temperature after mineralization is finished, removing residual mineralization liquid and a weak mineralization layer, and airing at room temperature to obtain the bionic mineralization super-hydrophilic PVDF ultrafiltration membrane;
the biomimetic mineralization liquid is prepared by the following method:
dissolving ferric sulfate in a sulfuric acid solution with the concentration of 0.007mol/L, and keeping the concentration of the ferric sulfate in the solution at 15g/L to obtain a mineralized liquid;
step 3, performing photo-Fenton self-cleaning on the PVDF ultrafiltration membrane:
firstly, fixing the super-hydrophilic PVDF ultrafiltration membrane obtained in the step 2 on a cross-flow filtering device, filtering for 2 hours at room temperature under the transmembrane pressure difference of 0.1MPa by taking ultrafiltration stock solution as feed liquid, and taking out the polluted biomimetic mineralized super-hydrophilic PVDF ultrafiltration membrane after the filtration is finished;
the ultrafiltration stock solution is prepared by the following method:
dissolving 0.02g Sodium Alginate (SA) in 1L phosphate buffer solution with pH of 7.4 to obtain ultrafiltration stock solution; fixing the polluted biomimetic mineralized super-hydrophilic PVDF ultrafiltration membrane in two hollow clamping pieces made of tetrafluoroethylene materials, immersing the clamping pieces in a container filled with a certain volume of light-Fenton system solution, placing the container in a photocatalytic reactor, and using a 300w xenon lamp filled with a 420nm optical filter as a light source; and (3) starting a photocatalytic reaction device when the distance between the membrane and the light source is 25cm, wherein the photocatalytic reaction time is 80min, and finishing the photo-Fenton self-cleaning process of the ultrafiltration membrane.
The photo-Fenton system solution was an acidic solution of pH2 prepared from hydrochloric acid containing 70. mu.L/L of 30% hydrogen peroxide.
The water flux of the ultrafiltration membrane prepared in the embodiment is 230.88L/m2·h，RBSA90.5%, the initial water contact angle is 21.6%, and the flux recovery rate of the visible light-Fenton self-cleaning membrane is 81.8%.
Example 7:
step 1, preparing a PVDF (polyvinylidene fluoride) ultra-hydrophilic ultrafiltration membrane by a one-pot method:
mixing 9% of monomer acrylic acid, 10% of alkalized polyvinylidene fluoride, 7% of polyethylene glycol with the molecular weight of 10000-20000, 5% of anhydrous lithium chloride and 68% of N, N-dimethylacetamide according to mass percentage, stirring and dissolving at 60 ℃, adding 1% of benzoyl peroxide, and heating to 60 ℃ for polymerization. After reacting for 2h, cooling to 40 ℃, stopping polymerization, standing and defoaming for 6 h.
And (3) scraping the grafting reaction mixed solution into a polymer solution film with the thickness of 200 mu m directly by hand or through a flat film scraper, pre-evaporating for 15s at room temperature, putting into a sodium hydroxide solution coagulating bath with the temperature of 45 ℃ and the pH value of 13, carrying out phase separation treatment for 2min, and taking out. And repeatedly cleaning with deionized water, and removing residual solvent and impurities to obtain the PVDF super-hydrophilic ultrafiltration membrane prepared by the one-pot method.
Wherein the alkalized polyvinylidene fluoride is prepared by the following method:
stirring polyvinylidene fluoride with the average molecular weight of 50-100 ten thousand in 0.5mol/L KOH ethanol solution at 60 ℃ for 2h by adopting an alkalization defluorination treatment method, filtering after the reaction is finished, washing the filtrate with deionized water, and drying in vacuum at 60 ℃ to obtain the alkalized polyvinylidene fluoride.
Step 2, biomimetic mineralization of a PVDF (polyvinylidene fluoride) ultra-hydrophilic ultrafiltration membrane interface:
immersing the PVDF super-hydrophilic ultrafiltration membrane prepared in the step 1 in a biomimetic mineralization liquid at 70 ℃ for 12h, after mineralization is finished, washing the membrane with water at room temperature to remove residual mineralization liquid and a weak mineralization layer, and airing at room temperature to obtain the biomimetic mineralized super-hydrophilic PVDF ultrafiltration membrane;
the biomimetic mineralization liquid is prepared by the following method:
dissolving ferric trichloride hexahydrate in hydrochloric acid solution with the concentration of 0.003mol/L, and keeping the concentration of ferric trichloride hexahydrate in the solution at 20g/L to obtain mineralized liquid;
step 3, performing photo-Fenton self-cleaning on the PVDF ultrafiltration membrane:
firstly, fixing the super-hydrophilic PVDF ultrafiltration membrane obtained in the step 2 on a cross-flow filtering device, filtering for 2 hours at room temperature under the transmembrane pressure difference of 0.1MPa by taking ultrafiltration stock solution as feed liquid, and taking out the polluted biomimetic mineralized super-hydrophilic PVDF ultrafiltration membrane after the filtration is finished;
the ultrafiltration stock solution is prepared by the following method:
dissolving 0.02g Humic Acid (HA) in 1L phosphate buffer solution with pH7.4 to obtain ultrafiltration stock solution; fixing the polluted biomimetic mineralized super-hydrophilic PVDF ultrafiltration membrane in two hollow clamping pieces made of tetrafluoroethylene materials, immersing the clamping pieces in a container filled with a certain volume of light-Fenton system solution, placing the container in a photocatalytic reactor, and using a 300w xenon lamp filled with a 420nm optical filter as a light source; and (3) starting a photocatalytic reaction device when the distance between the membrane and the light source is 20cm, wherein the photocatalytic reaction time is 40min, and finishing the photo-Fenton self-cleaning process of the ultrafiltration membrane.
The photo-Fenton system solution was an acidic solution of pH 3 prepared from hydrochloric acid containing 80. mu.L/L of 30% hydrogen peroxide.
The water flux of the ultrafiltration membrane prepared in the embodiment is 188.32L/m2·h，RBSA90.1%, the initial water contact angle is 19.8%, and the flux recovery rate of the visible light-Fenton self-cleaning membrane is 80.2%.
As can be seen from the above examples, the hydrophilicity of the membrane can be effectively improved by increasing the acrylic acid monomer content, controlling the grafting reaction temperature and time, and increasing the iron content; the increase of the iron content and the hydrogen peroxide addition amount in the mineralized liquid and the field application of the photo-Fenton self-cleaning time can obviously improve the flux recovery rate after membrane pollution.
The water flux of the prepared ultrafiltration membrane is not less than 169.42L/m2·h，RBSANot less than 90.2%, the initial water contact angle is not more than 24.5%, and the flux recovery rate of the visible light-Fenton self-cleaning membrane is not less than 78.4%. Therefore, the invention is a scientific and efficient production technology of the super-hydrophilic photo-Fenton catalytic ultrafiltration membrane.
The present invention is not limited to the above-mentioned embodiments, and based on the technical solutions disclosed in the present invention, those skilled in the art can make some substitutions and modifications to some technical features without creative efforts according to the disclosed technical contents, and these substitutions and modifications are all within the protection scope of the present invention.

Claims (5)

1. A preparation method of a photo-Fenton catalytic self-cleaning super-hydrophilic PVDF ultrafiltration membrane is characterized by comprising the following steps:
step 1, preparing a PVDF (polyvinylidene fluoride) ultra-hydrophilic ultrafiltration membrane by a one-pot method:
1) mixing 3-9% of monomer acrylic acid, 10-14% of alkalized polyvinylidene fluoride, 2-8% of macromolecular compatibilizer, 1-5% of anhydrous lithium chloride and 68-80% of organic solvent according to mass percent, stirring, dissolving, adding 1% of initiator, heating for polymerization, reacting, cooling, stopping polymerization, standing for defoaming, and preparing a grafting reaction mixed solution;
2) preparing the grafting reaction mixed solution into a macromolecular solution film with a certain thickness, pre-evaporating at room temperature, putting the film into a coagulating bath, carrying out phase splitting treatment, and repeatedly cleaning with deionized water to obtain the PVDF (polyvinylidene fluoride) ultra-hydrophilic ultrafiltration membrane prepared by the one-pot method;
step 2, biomimetic mineralization of a PVDF (polyvinylidene fluoride) ultra-hydrophilic ultrafiltration membrane interface:
immersing the PVDF super-hydrophilic ultrafiltration membrane prepared in the step 1 in a biomimetic mineralization liquid at 40-80 ℃ for 6-36 h, washing the membrane with water at room temperature after mineralization is finished, removing residual mineralization liquid and an unstable mineralization layer, and airing at room temperature to obtain the biomimetic mineralized super-hydrophilic PVDF ultrafiltration membrane;
the alkalized polyvinylidene fluoride is prepared by the following method:
stirring polyvinylidene fluoride with the average molecular weight of 50-100 ten thousand in 0.5mol/L KOH ethanol solution at 60 ℃ for 2h by adopting an alkalization defluorination treatment method, filtering after the reaction is finished, washing the filtrate with deionized water, and drying in vacuum at 60 ℃ to obtain alkalized polyvinylidene fluoride;
the macromolecular compatibilizer is one of polyvinylpyrrolidone with the molecular weight of 20000-50000, polyethylene glycol with the molecular weight of 10000-20000 and polyvinyl alcohol with the molecular weight of 80000-120000;
the water flux of the ultrafiltration membrane is not less than 169.42L/m2·h，RBSANot less than 90.2%, the initial water contact angle is not more than 24.5%, and the flux recovery rate of the membrane after light-Fenton self-cleaning is not less than 78.4%.
2. The method for preparing the photo-Fenton catalytic self-cleaning super-hydrophilic PVDF ultrafiltration membrane according to claim 1, wherein the organic solvent is one or a mixture of more than two of N, N-dimethylformamide, N-dimethylacetamide, N-methyl-2-pyrrolidone and dimethyl sulfoxide.
3. The preparation method of the photo-Fenton catalytic self-cleaning super-hydrophilic PVDF ultrafiltration membrane as claimed in claim 1, wherein the biomimetic mineralization liquid is prepared by adopting the following method:
dissolving a trivalent ferric salt into a hydrochloric acid solution or a sulfuric acid solution with the concentration of 0.001-0.01 mol/L, and keeping the concentration of the trivalent ferric salt in the solution at 10-20 g/L to obtain a mineralized liquid;
the ferric salt is ferric trichloride hexahydrate or ferric sulfate.
4. The preparation method of the photo-Fenton catalytic self-cleaning super-hydrophilic PVDF ultrafiltration membrane as claimed in claim 1, wherein in the step 1-1), the solution is stirred and dissolved at 60 ℃, an initiator is added, and the temperature is raised to 60-90 ℃ for polymerization; after reacting for 1-6 h, cooling to 40 ℃, stopping polymerization, and standing for defoaming for 4 h;
the initiator is one of azodiisobutyronitrile or benzoyl peroxide.
5. The preparation method of the photo-Fenton catalytic self-cleaning super-hydrophilic PVDF ultrafiltration membrane as claimed in claim 1, wherein in the step 1-2), the grafting reaction mixed solution is scraped into a 150-250 μm thick polymer solution film directly by hand or through a flat membrane scraper, and after pre-evaporation is carried out for 15s at room temperature, the polymer solution film is placed into a sodium hydroxide solution coagulation bath at 20-60 ℃ and pH 12-13 for phase separation treatment for 2 min.
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