CN113914013A - Electrostatic spinning forming method of cationic nanofiber membrane - Google Patents

Electrostatic spinning forming method of cationic nanofiber membrane Download PDF

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CN113914013A
CN113914013A CN202111392038.4A CN202111392038A CN113914013A CN 113914013 A CN113914013 A CN 113914013A CN 202111392038 A CN202111392038 A CN 202111392038A CN 113914013 A CN113914013 A CN 113914013A
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cationic
nanofiber membrane
woven fabric
mass
polyvinylidene fluoride
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CN113914013B (en
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徐至
万弘毅
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East China University of Science and Technology
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    • D—TEXTILES; PAPER
    • D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
    • D04H—MAKING TEXTILE FABRICS, e.g. FROM FIBRES OR FILAMENTARY MATERIAL; FABRICS MADE BY SUCH PROCESSES OR APPARATUS, e.g. FELTS, NON-WOVEN FABRICS; COTTON-WOOL; WADDING ; NON-WOVEN FABRICS FROM STAPLE FIBRES, FILAMENTS OR YARNS, BONDED WITH AT LEAST ONE WEB-LIKE MATERIAL DURING THEIR CONSOLIDATION
    • D04H1/00—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres
    • D04H1/40—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties
    • D04H1/42—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties characterised by the use of certain kinds of fibres insofar as this use has no preponderant influence on the consolidation of the fleece
    • D04H1/4374—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties characterised by the use of certain kinds of fibres insofar as this use has no preponderant influence on the consolidation of the fleece using different kinds of webs, e.g. by layering webs
    • 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
    • B01D61/02—Reverse osmosis; Hyperfiltration ; Nanofiltration
    • B01D61/025—Reverse osmosis; Hyperfiltration
    • 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
    • B01D61/02—Reverse osmosis; Hyperfiltration ; Nanofiltration
    • B01D61/027—Nanofiltration
    • 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
    • B01D67/0006—Organic membrane manufacture by chemical reactions
    • 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
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/06—Organic material
    • B01D71/76—Macromolecular material not specifically provided for in a single one of groups B01D71/08 - B01D71/74
    • B01D71/78—Graft polymers
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F259/00—Macromolecular compounds obtained by polymerising monomers on to polymers of halogen containing monomers as defined in group C08F14/00
    • C08F259/08—Macromolecular compounds obtained by polymerising monomers on to polymers of halogen containing monomers as defined in group C08F14/00 on to polymers containing fluorine
    • D—TEXTILES; PAPER
    • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
    • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
    • D01F6/00—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof
    • D01F6/02—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from homopolymers obtained by reactions only involving carbon-to-carbon unsaturated bonds
    • D01F6/08—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from homopolymers obtained by reactions only involving carbon-to-carbon unsaturated bonds from polymers of halogenated hydrocarbons
    • D01F6/12—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from homopolymers obtained by reactions only involving carbon-to-carbon unsaturated bonds from polymers of halogenated hydrocarbons from polymers of fluorinated hydrocarbons
    • D—TEXTILES; PAPER
    • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
    • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
    • D01F6/00—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof
    • D01F6/28—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from copolymers obtained by reactions only involving carbon-to-carbon unsaturated bonds
    • D01F6/32—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from copolymers obtained by reactions only involving carbon-to-carbon unsaturated bonds comprising halogenated hydrocarbons as the major constituent
    • D—TEXTILES; PAPER
    • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
    • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
    • D01F6/00—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof
    • D01F6/96—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from other synthetic polymers
    • D—TEXTILES; PAPER
    • D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
    • D04H—MAKING TEXTILE FABRICS, e.g. FROM FIBRES OR FILAMENTARY MATERIAL; FABRICS MADE BY SUCH PROCESSES OR APPARATUS, e.g. FELTS, NON-WOVEN FABRICS; COTTON-WOOL; WADDING ; NON-WOVEN FABRICS FROM STAPLE FIBRES, FILAMENTS OR YARNS, BONDED WITH AT LEAST ONE WEB-LIKE MATERIAL DURING THEIR CONSOLIDATION
    • D04H1/00—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres
    • D04H1/40—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties
    • D04H1/42—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties characterised by the use of certain kinds of fibres insofar as this use has no preponderant influence on the consolidation of the fleece
    • D04H1/4282—Addition polymers
    • D04H1/4318—Fluorine series
    • D—TEXTILES; PAPER
    • D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
    • D04H—MAKING TEXTILE FABRICS, e.g. FROM FIBRES OR FILAMENTARY MATERIAL; FABRICS MADE BY SUCH PROCESSES OR APPARATUS, e.g. FELTS, NON-WOVEN FABRICS; COTTON-WOOL; WADDING ; NON-WOVEN FABRICS FROM STAPLE FIBRES, FILAMENTS OR YARNS, BONDED WITH AT LEAST ONE WEB-LIKE MATERIAL DURING THEIR CONSOLIDATION
    • D04H1/00—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres
    • D04H1/40—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties
    • D04H1/42—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties characterised by the use of certain kinds of fibres insofar as this use has no preponderant influence on the consolidation of the fleece
    • D04H1/4326—Condensation or reaction polymers
    • D04H1/435—Polyesters
    • D—TEXTILES; PAPER
    • D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
    • D04H—MAKING TEXTILE FABRICS, e.g. FROM FIBRES OR FILAMENTARY MATERIAL; FABRICS MADE BY SUCH PROCESSES OR APPARATUS, e.g. FELTS, NON-WOVEN FABRICS; COTTON-WOOL; WADDING ; NON-WOVEN FABRICS FROM STAPLE FIBRES, FILAMENTS OR YARNS, BONDED WITH AT LEAST ONE WEB-LIKE MATERIAL DURING THEIR CONSOLIDATION
    • D04H1/00—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres
    • D04H1/70—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres characterised by the method of forming fleeces or layers, e.g. reorientation of fibres
    • D04H1/72—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres characterised by the method of forming fleeces or layers, e.g. reorientation of fibres the fibres being randomly arranged
    • D04H1/728—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres characterised by the method of forming fleeces or layers, e.g. reorientation of fibres the fibres being randomly arranged by electro-spinning

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  • Polymers & Plastics (AREA)
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  • Separation Using Semi-Permeable Membranes (AREA)
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Abstract

The invention relates to an electrostatic spinning forming method of a cation nanofiber membrane, which comprises the following steps: s1: introducing cationic groups into partially defluorinated polyvinylidene fluoride by using a chemical grafting method by taking a polyester non-woven fabric as a substrate of a film to form a spinning solution; s2: and (3) preparing the nanofiber membrane from the spinning solution through an electrostatic spinning process. Compared with the prior art, the preparation method of the cationic nanofiber membrane does not involve the use of toxic volatile organic compounds, and does not have the strict requirement on the preparation environment; the cation nanofiber membrane prepared by the method can effectively remove polyfluorinated compounds in water under the driving of gravity, has the characteristic of low energy consumption, and is suitable for industrial popularization.

Description

Electrostatic spinning forming method of cationic nanofiber membrane
Technical Field
The invention relates to the field of water pollution treatment, in particular to an electrostatic spinning forming method of a cationic nanofiber membrane.
Background
Polyfluoro compounds are used as common industrial additives and coatings, and are widely used in the industries of textile, daily chemical industry and the like due to the oil stain resistance and physical and chemical stability. Due to bioaccumulation and recalcitrance, polyfluoro compounds can migrate through (1) in aqueous environments and the atmosphere; and (2) the food chain accumulates both pathways into the human body, causing reproductive toxicity. In the international society, in 2009, "stockholm convention on persistent organic pollutants" the regulation of polyfluoro compounds represented by perfluorooctanesulfonic acid was carried out, and the related regulations were issued successively in many countries to limit the discharge of polyfluoro compounds in wastewater. Therefore, the treatment of polyfluorinated compounds in water environment has important ecological significance.
The common treatment approaches at present comprise two major types of treatment, namely adsorption treatment, nanofiltration treatment and reverse osmosis membrane treatment. Due to the characteristics of high toxicity and low concentration of the polyfluorinated compound, the common adsorption method mainly comprising activated carbon and ion exchange resin has the defects of low selectivity, low adsorption rate and the like; the nanofiltration and reverse osmosis membrane method can effectively screen polyfluorinated compounds, but requires working pressure of at least 5 to 7 atmospheres and has relatively high energy consumption requirement. Therefore, the development of the polyfluorinated compound treatment method with low energy consumption and high efficiency has important social and economic benefits.
Disclosure of Invention
The invention aims to overcome the defects in the prior art and provide the electrostatic spinning forming method of the cationic nanofiber membrane, the cationic nanofiber membrane prepared by the method can effectively remove polyfluorinated compounds in water under the driving of gravity, has the characteristic of low energy consumption, and is suitable for industrial popularization.
In the conception process of the technical scheme, the applicant considers that the nanofiber membrane technology can give consideration to physical filtration and electrostatic adsorption effects due to the characteristics of large specific surface area, easiness in chemical modification, easiness in preparation and the like, and certain progress is made in oil-water separation, salt screening and heavy metal adsorption at present. The pore diameter of the nanofiber membrane can be regulated and controlled by controlling the parameters of the electrostatic spinning method, so that the required working pressure is reduced, and the aim of reducing energy consumption is fulfilled. However, considering the electronegativity of the polyfluoro compound, the common nanofiber membrane mainly composed of cellulose and polyvinylidene fluoride cannot effectively remove the polyfluoro compound due to the weak electric property of the surface. Therefore, the technical scheme develops the electrostatic spinning forming method of the cationic nanofiber membrane, and is beneficial to realizing low energy consumption and high-efficiency treatment of the polyfluorinated compound.
The purpose of the invention can be realized by the following technical scheme:
the technical scheme aims to protect an electrostatic spinning forming method of a cation nanofiber membrane, and the method comprises the following steps:
s1: introducing cationic groups into partially defluorinated polyvinylidene fluoride by using a chemical grafting method by taking a polyester non-woven fabric as a substrate of a film to form a spinning solution;
s2: and (3) preparing the nanofiber membrane from the spinning solution through an electrostatic spinning process.
Further, in S1, cationic groups are introduced through chemical grafting to change the zeta potential of the product surface and increase the conductivity and viscosity of the spinning solution, so as to form the stretched and integrated nano-fiber with the diameter of 50-140 nm.
Further, in S1, the method includes the following steps:
s1-1: taking a polyester non-woven fabric, cleaning the surface of the polyester non-woven fabric, drying the polyester non-woven fabric, and using the polyester non-woven fabric as a supporting layer of the cationic nanofiber membrane;
s1-2: dissolving polyvinylidene fluoride in N, N-dimethylformamide solution, adding polyethylene polyamine to perform partial defluorination to form a grafting reaction precursor;
s1-3: and carrying out rotary evaporation dehydration on methacryloyloxyethyl trimethyl ammonium chloride containing cationic groups, and then carrying out grafting reaction on the methacryloyloxyethyl trimethyl ammonium chloride, an initiator and a grafting reaction precursor to form a spinning solution.
Further, in S1-2, polyvinylidene fluoride was dissolved in N, N-dimethylformamide so that the mass of polyvinylidene fluoride was 8% of the mass of N, N-dimethylformamide, and after mixing uniformly, polyethylene polyamine was added so that the mass of polyethylene polyamine was 1% of the mass of N, N-dimethylformamide, and partial defluorination was carried out for 6 hours to obtain a grafting reaction precursor solution.
Further, in S1-3, methacryloyloxyethyl trimethylammonium chloride dehydrated by rotary evaporation and an initiator potassium persulfate were added to the grafting reaction precursor solution, the grafting reaction was continued for 2 hours, and the spinning solution was obtained by cooling.
Further, the operating conditions of the rotary evaporation process were 35 ℃ and 94000 Pa.
Further, in S1-3, dehydrated methacryloyloxyethyltrimethyl ammonium chloride was present in an amount of 4% by mass of the grafting precursor solution, and potassium persulfate was present in an amount of 0.04% by mass of the grafting precursor solution.
Further, in S1-2, the weight average molecular weight of the polyvinylidene fluoride was 180000.
Further, in S1-2, the temperature of the partial defluorination reaction is 70 ℃;
in S1-3, the temperature of the grafting reaction was 75 ℃.
Further, in S1-3, the methacryloyloxyethyl trimethyl ammonium chloride accounts for 50% of the mass of the polyvinylidene fluoride.
Further, in S2, transferring the spinning solution to an injector of an electrostatic spinning apparatus, wrapping the polyester non-woven fabric on a cylindrical collector, controlling the injection speed to be 0.2mL/h, adjusting the distance between the nozzle of the injector and the collector, and providing an external voltage, and finally forming a cationic nanofiber membrane on the surface of the polyester non-woven fabric substrate;
further, the cooled spinning solution is transferred to an injector of an electrostatic spinning instrument, and external voltage is provided between an injector nozzle and a collector to perform spray forming on the polymer solution, so that fibers with the diameter of 50-140 nanometers are formed on a cylindrical collector wrapped by the polyester non-woven fabric, and finally the cationic nanofiber membrane is obtained.
Further, the injection speed of the electrostatic spinning process is 0.2mL/h, the working voltage is 21kV, the working distance between the nozzle and the cylindrical collector is 0.1 meter, and the relative humidity is 65%.
Compared with the prior art, the invention has the following technical advantages:
(1) according to the preparation method, a cationic group is introduced through a grafting reaction, so that the adsorption capacity of the negative polyfluoro compound is enhanced.
(2) According to the preparation method disclosed by the invention, the conductivity and viscosity of the spinning solution are increased while the cationic groups are introduced, so that the generation of thinner fibers in the electrostatic spinning process is facilitated, the relative surface area is increased, and more adsorption sites are provided for removing polyfluorinated compounds.
(3) By the preparation method, 96.2 percent of perfluorooctane sulfonate and 94.3 percent of perfluorooctanoic acid can be removed simultaneously under the driving of gravity; compared with common nanofiltration and reverse osmosis membrane technologies, the process does not need additional pressure driving (at least 5-7 atmospheres), and is beneficial to reducing energy consumption.
Drawings
FIG. 1 is a flow chart of a method for preparing a cationic nanofiber membrane in accordance with the present invention;
FIG. 2 is a microstructure diagram of a cationic nanofiber membrane (best effort example 4) prepared in accordance with the present invention;
FIG. 3 is a graph of the zeta potential of the surface of a cationic nanofiber membrane (best effort, example 4) prepared in accordance with the present invention;
FIG. 4 is a graph comparing the clearance of polyfluoro compounds from examples 1-5 of the present invention.
Detailed Description
The invention is described in detail below with reference to the figures and specific embodiments. In the technical scheme, characteristics such as preparation means, materials, structures or composition ratios and the like which are not explicitly described are all regarded as common technical characteristics disclosed in the prior art.
For further illustration of the objects, aspects and products of the present invention, the present invention will be described in detail below by combining the drawings with the examples. It should be noted that the following embodiments are only used for illustrating the present invention and are not to be construed as limiting the present invention.
Fig. 1 is a flow chart of the preparation of the cationic nanofiber membrane according to the present invention, wherein the specific preparation method refers to the most preferred example 4 (examples 1, 2, 3, 5 can be regarded as comparative examples).
To better demonstrate the beneficial effects of the cationic nanofiber membranes prepared by the preparation method of the present invention, two representative polyfluoro compounds (perfluorooctanesulfonic acid and perfluorooctanoic acid) were subjected to gravity-driven scavenging experiments in combination with the following specific examples:
example 1
(1) And taking the polyester non-woven fabric, cleaning the surface of the polyester non-woven fabric, and drying the polyester non-woven fabric for later use.
Example 2
(1) And taking the polyester non-woven fabric, cleaning the surface of the polyester non-woven fabric, and drying the polyester non-woven fabric for later use.
(2) Dissolving polyvinylidene fluoride with the weight-average molecular weight of about 180000 in N, N-dimethylformamide, wherein the mass ratio is 8%; and uniformly mixing, adding polyethylene polyamine with the mass ratio of 1%, and carrying out partial defluorination reaction for 6 hours at 70 ℃ to obtain the spinning solution.
(3) Cooling the spinning solution, transferring the spinning solution into an injector of an electrostatic spinning instrument, and wrapping the polyester non-woven fabric on a cylindrical collector; controlling the injection speed to be 0.2mL/h, adjusting the distance between the nozzle of the injector and the collector to be 0.1 m, providing an external voltage of 21kV, and finally forming a nanofiber membrane on the surface of the polyester non-woven fabric substrate.
Example 3
(1) And taking the polyester non-woven fabric, cleaning the surface of the polyester non-woven fabric, and drying the polyester non-woven fabric for later use.
(2) Dissolving polyvinylidene fluoride with the weight-average molecular weight of about 180000 in N, N-dimethylformamide, wherein the mass ratio is 8%; after being mixed evenly, polyethylene polyamine is added, the mass percentage of which is 1 percent, and partial defluorination reaction is carried out for 6 hours at the temperature of 70 ℃, thus obtaining the grafting reaction precursor solution.
(3) Adding methacryloyloxyethyl trimethyl ammonium chloride (QA) dehydrated by rotary evaporation and an initiator potassium persulfate (mass ratio of 0.04%) into a grafting reaction precursor solution; controlling the reaction temperature to be 75 ℃, keeping the reaction temperature for 2 hours, and cooling to obtain a spinning solution; in this example QA represents 25% by mass of the polyvinylidene fluoride.
(4) Transferring the spinning solution into an injector of an electrostatic spinning instrument, and wrapping the polyester non-woven fabric on a cylindrical collector; controlling the injection speed to be 0.2mL/h, adjusting the distance between the injector nozzle and the collector to be 0.1 m, and providing an external voltage of 21kV, and finally forming a cationic nanofiber membrane on the surface of the polyester non-woven fabric substrate (the mass ratio of QA to polyvinylidene fluoride is 0.25: 1).
Example 4
(1) And taking the polyester non-woven fabric, cleaning the surface of the polyester non-woven fabric, and drying the polyester non-woven fabric for later use.
(2) Dissolving polyvinylidene fluoride with the weight-average molecular weight of about 180000 in N, N-dimethylformamide, wherein the mass ratio is 8%; after being mixed evenly, polyethylene polyamine is added, the mass percentage of which is 1 percent, and partial defluorination reaction is carried out for 6 hours at the temperature of 70 ℃, thus obtaining the grafting reaction precursor solution.
(3) Adding methacryloyloxyethyl trimethyl ammonium chloride (QA) dehydrated by rotary evaporation and an initiator potassium persulfate (mass ratio of 0.04%) into a grafting reaction precursor solution; controlling the reaction temperature to be 75 ℃, keeping the reaction temperature for 2 hours, and cooling to obtain a spinning solution; QA in this example represents 50% by mass of the polyvinylidene fluoride.
(4) Transferring the spinning solution into an injector of an electrostatic spinning instrument, and wrapping the polyester non-woven fabric on a cylindrical collector; controlling the injection speed to be 0.2mL/h, adjusting the distance between the injector nozzle and the collector to be 0.1 m, and providing an external voltage of 21kV, and finally forming a cationic nanofiber membrane on the surface of the polyester non-woven fabric substrate (the mass ratio of QA to polyvinylidene fluoride is 0.5: 1).
Example 5
(1) And taking the polyester non-woven fabric, cleaning the surface of the polyester non-woven fabric, and drying the polyester non-woven fabric for later use.
(2) Dissolving polyvinylidene fluoride with the weight-average molecular weight of about 180000 in N, N-dimethylformamide, wherein the mass ratio is 8%; after being mixed evenly, polyethylene polyamine is added, the mass percentage of which is 1 percent, and partial defluorination reaction is carried out for 6 hours at the temperature of 70 ℃, thus obtaining the grafting reaction precursor solution.
(3) Adding methacryloyloxyethyl trimethyl ammonium chloride (QA) dehydrated by rotary evaporation and an initiator potassium persulfate (mass ratio of 0.04%) into a grafting reaction precursor solution; controlling the reaction temperature to be 75 ℃, keeping the reaction temperature for 2 hours, and cooling to obtain a spinning solution; in this example QA represents 75% by mass of the polyvinylidene fluoride.
(4) Transferring the spinning solution into an injector of an electrostatic spinning instrument, and wrapping the polyester non-woven fabric on a cylindrical collector; controlling the injection speed to be 0.2mL/h, adjusting the distance between the injector nozzle and the collector to be 0.1 m, and providing an external voltage of 21kV, and finally forming a cationic nanofiber membrane on the surface of the polyester non-woven fabric substrate (the mass ratio of QA to polyvinylidene fluoride is 0.75: 1).
FIG. 2 is a micro-topography of a cationic nanofiber membrane of a preferred embodiment of the present invention (example 4); analysis by scanning electron microscopy gave: the diameter of the fiber is 50-140 nanometers, the fiber is well formed, and no obvious fracture occurs. FIG. 3 is a surface zeta potential plot of the cationic nanofiber membrane described in example 4: by the cationic group grafting, the zeta potential of the surface of the cationic nanofiber membrane described in example 4 is maintained above +40mV between pH6-8, and the zeta potential is significantly improved compared with that of example 2 without the grafted cationic group. The grafting of the cationic group is beneficial to improving the adsorption affinity of the nanofiber membrane and the electronegative polyfluoro compound, thereby improving the removal effect.
In the polyfluoro compound removal experiment, perfluorooctane sulfonate and perfluorooctanoic acid are used as representatives of the polyfluoro compound, and quantitative test is carried out by a liquid chromatography-mass spectrometer; and a polyester nonwoven fabric substrate (example 1) and example 2 grafted with no cationic group were used as a control for performance testing. The specific experiment is as follows: preparing a mixed solution of perfluorooctane sulfonate and perfluorooctanoic acid with initial concentration of 0.5mg/L in distilled water, and simulating an actual water environment (pH 7.5, solution conductivity 700 mu S/cm) by adding sodium dihydrogen phosphate (pH buffer solution) and sodium chloride (ionic strength regulator); the films described in the above examples 1 to 5 were sequentially placed in a vacuum filtration bottle and clamped, and 50ml of the mixed solution of perfluorooctane sulfonate and perfluorooctanoic acid was added to each of the films to perform a cleaning test; and after no liquid drops leak out, measuring the concentration of the residual perfluorooctane sulfonate and perfluorooctanoic acid in the solution. Wherein examples 3, 4, 5 achieve effective scavenging of perfluorooctanesulfonic acid and perfluorooctanoic acid by grafting of cationic groups (as depicted in FIG. 4); preferred embodiment 4 has significant advantages in terms of clearance compared with a polyester nonwoven fabric substrate (embodiment 1) and a polyvinylidene fluoride nanofiber membrane (embodiment 2) without grafted cationic groups by adjusting suitable grafting ratios to achieve 96.2% and 94.3% clearance for perfluorooctane sulfonate and perfluorooctanoic acid, respectively, and embodies the benefits of the preparation method of the present invention.
The experiment shows that the cation nanofiber method provided by the invention can obviously improve the removal efficiency of the nanofiber membrane on the polyfluorinated compound.
The embodiments described above are described to facilitate an understanding and use of the invention by those skilled in the art. It will be readily apparent to those skilled in the art that various modifications to these embodiments may be made, and the generic principles described herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present invention is not limited to the above embodiments, and those skilled in the art should make improvements and modifications within the scope of the present invention based on the disclosure of the present invention.

Claims (10)

1. The electrostatic spinning forming method of the cationic nanofiber membrane is characterized by comprising the following steps of:
s1: introducing cationic groups into partially defluorinated polyvinylidene fluoride by using a chemical grafting method by taking a polyester non-woven fabric as a substrate of a film to form a spinning solution;
s2: and (3) preparing the nanofiber membrane from the spinning solution through an electrostatic spinning process.
2. The electrostatic spinning forming method of a cationic nanofiber membrane as claimed in claim 1, wherein in S1, cationic groups are introduced through chemical grafting to change zeta potential on the surface of the product and increase conductivity and viscosity of the spinning solution, so as to form a stretched and integrated nanofiber with a diameter of 50-140 nm.
3. The method of claim 1, wherein the step of S1 comprises:
s1-1: taking a polyester non-woven fabric, cleaning the surface of the polyester non-woven fabric, drying the polyester non-woven fabric, and using the polyester non-woven fabric as a supporting layer of the cationic nanofiber membrane;
s1-2: dissolving polyvinylidene fluoride in N, N-dimethylformamide solution, adding polyethylene polyamine to perform partial defluorination to form a grafting reaction precursor;
s1-3: and carrying out rotary evaporation dehydration on methacryloyloxyethyl trimethyl ammonium chloride containing cationic groups, and then carrying out grafting reaction on the methacryloyloxyethyl trimethyl ammonium chloride, an initiator and a grafting reaction precursor to form a spinning solution.
4. The electrospinning molding method of a cationic nanofiber membrane according to claim 2, wherein in S1-2, polyvinylidene fluoride is dissolved in N, N-dimethylformamide so that the mass of polyvinylidene fluoride is 8% of the mass of N, N-dimethylformamide, polyethylene polyamine is added after uniform mixing so that the mass of polyethylene polyamine is 1% of the mass of N, N-dimethylformamide, and partial defluorination reaction is performed for 6 hours to obtain a grafting reaction precursor solution.
5. The method of claim 2, wherein in S1-3, methacryloyloxyethyl trimethyl ammonium chloride dehydrated by spin-steaming and potassium persulfate as an initiator are added to a precursor solution for the grafting reaction, the grafting reaction is continued for 2 hours, and the spinning solution is obtained by cooling.
6. The method of claim 2, wherein in S1-3, the dehydrated methacryloyloxyethyl trimethyl ammonium chloride accounts for 4% by mass of the grafting precursor solution, and the potassium persulfate accounts for 0.04% by mass of the grafting precursor solution.
7. The method of claim 2, wherein in S1-2, the weight average molecular weight of the polyvinylidene fluoride is 180000.
8. The electrostatic spinning forming method of the cationic nanofiber membrane as claimed in claim 2, wherein in S1-2, the temperature of the partial defluorination reaction is 70 ℃;
in S1-3, the temperature of the grafting reaction was 75 ℃.
9. The method according to claim 5, wherein in S1-3, the methacryloyloxyethyltrimethyl ammonium chloride accounts for 50% of the mass of the polyvinylidene fluoride.
10. The electrospinning forming method of a cationic nanofiber membrane according to claim 2, wherein in S2, the spinning solution is transferred to an injector of an electrospinning apparatus, the polyester nonwoven fabric is wrapped on a cylindrical collector, the injection speed is controlled to be 0.2mL/h, the distance between the nozzle of the injector and the collector is adjusted, an external voltage is provided, and finally the cationic nanofiber membrane is formed on the surface of the polyester nonwoven fabric substrate;
the external voltage of the electrospinning apparatus was set to 21kV, and the distance between the injector nozzle and the collector was 0.1 m.
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