CN110496541B - Modified composite fiber membrane for oil-water separation and preparation method thereof - Google Patents

Modified composite fiber membrane for oil-water separation and preparation method thereof Download PDF

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CN110496541B
CN110496541B CN201910835083.9A CN201910835083A CN110496541B CN 110496541 B CN110496541 B CN 110496541B CN 201910835083 A CN201910835083 A CN 201910835083A CN 110496541 B CN110496541 B CN 110496541B
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CN110496541A (en
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陈仰
蒋兰英
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Central South University
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D17/00—Separation of liquids, not provided for elsewhere, e.g. by thermal diffusion
    • B01D17/02—Separation of non-miscible liquids
    • B01D17/0202—Separation of non-miscible liquids by ab- or adsorption
    • 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
    • B01D67/0009—Organic membrane manufacture by phase separation, sol-gel transition, evaporation or solvent quenching
    • B01D67/0011—Casting solutions therefor
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
    • B01D67/0081—After-treatment of organic or inorganic membranes
    • B01D67/0088—Physical treatment with compounds, e.g. swelling, coating or impregnation
    • 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
    • B01D71/40—Polymers of unsaturated acids or derivatives thereof, e.g. salts, amides, imides, nitriles, anhydrides, esters
    • B01D71/42—Polymers of nitriles, e.g. polyacrylonitrile
    • 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
    • D01F1/00—General methods for the manufacture of artificial filaments or the like
    • D01F1/02—Addition of substances to the spinning solution or to the melt
    • D01F1/10—Other agents for modifying properties
    • 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
    • D01F6/44—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from mixtures of polymers obtained by reactions only involving carbon-to-carbon unsaturated bonds as major constituent with other polymers or low-molecular-weight compounds
    • D01F6/54—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from mixtures of polymers obtained by reactions only involving carbon-to-carbon unsaturated bonds as major constituent with other polymers or low-molecular-weight compounds of polymers of unsaturated nitriles
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2325/00—Details relating to properties of membranes
    • B01D2325/38—Hydrophobic membranes

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Abstract

The invention discloses a modified composite fiber membrane for oil-water separation and a preparation method thereof, wherein a solution containing PAN and a solution containing MOFs are mixed to obtain a membrane casting solution, and the membrane casting solution is subjected to electrostatic spinning to prepare a base membrane; drying the base membrane, and coating with fluorosilane steam to obtain a nanofiber membrane; the casting solution comprises 5-12 wt% of PAN, 0.2-1 wt% of MOFs and 87-94.8 wt% of polar solvent; the MOFs is NH2UIO-66 (Zr). The preparation method disclosed by the invention is simple to operate and good in film forming property, the MOFs material is uniformly distributed in the fiber, the water contact angle of the surface of the film is 150.4 degrees, the super-hydrophobic condition is achieved, the adsorption capacity of the composite fiber film on the silicone oil reaches 33.7g/g, and the oil flux for separating dichloromethane under the action of gravity is 2286 L.m‑2h‑1The separation efficiency is over 99.8 percent, and the oil flux after ten times of circulation is still kept at 1792 L.m‑2h‑1The device is used for efficiently separating oil from water.

Description

Modified composite fiber membrane for oil-water separation and preparation method thereof
Technical Field
The invention relates to a modified composite fiber membrane for oil-water separation and a preparation method thereof, belonging to the technical field of preparation of hydrophobic oleophilic oil-water separation membranes.
Background
With the development of industry and the continuous improvement of living standard of people, a large amount of oily wastewater is discharged into natural water, the density of oil is less than the property of water, so that the oily wastewater floats on the surface of the water, the oxygen exchange between the water and the atmospheric environment is isolated, aquatic animals and plants die and rot due to oxygen deficiency, a large amount of anaerobic bacteria are bred, oxygen in the water is further consumed, and a vicious circle is formed. And some micron oil drops are uniformly dispersed in water in the presence of a surfactant to form an emulsion, which causes serious harm to the environmental quality. Therefore, the development of new materials to reduce the influence of oily wastewater on the environment and human beings is the focus of research in this field.
The current methods for oil-water separation mainly comprise: adsorption, air-float, membrane separation, chemical reagent, and the like. Compared with other methods, the membrane separation method is simpler to operate, is economical and practical, has less chemical residues in the treated water body, and is more concerned. The oil-water separation membrane mainly comprises: the hydrophobic oleophilic separation membrane has higher affinity performance to oil, can be used for separating oil-water mixture and can also be used as an oil adsorbent. However, the type, viscosity and surface tension of oil have a great influence on the oil-water separation performance, and oil having a large viscosity and surface tension hardly permeates the membrane surface, which is a factor of lowering the membrane separation efficiency, and therefore, a membrane material having a high affinity for oil droplets has been developed, which has a great practical value.
Besides materials, the rough membrane surface has a positive effect on overcoming the surface tension of oil drops, the nanofiber membrane prepared by electrostatic spinning is formed by stacking fibers, and the rough net structure of the nanofiber membrane enables the nanofiber membrane to have the advantage of oil-water separation. Commonly used materials include polyvinylidene fluoride (PVDF), Polystyrene (PS), Polytetrafluoroethylene (PTFE), Polyacrylonitrile (PAN), and the like. When the membrane materials are used as adsorbents for oil-water separation, the adsorption capacity is not high, and when the membrane materials are used as filtering membranes for separation, the flux is not high, so that the requirement of practical application of oil-water separation cannot be met.
Disclosure of Invention
In order to solve the technical problems of poor selectivity, low removal rate, low membrane flux and the like of the conventional oil-water separation membrane, the invention provides a nanofiber membrane for oil-water separation and a preparation method thereof, aiming at improving the hydrophobicity, lipophilicity and oil-water separation efficiency of the obtained material.
The invention relates to a preparation method of a nanofiber membrane for oil-water separation, which comprises the following steps: mixing the solution containing PAN and the solution containing MOFs to obtain a membrane casting solution, and preparing a base membrane from the membrane casting solution through electrostatic spinning; drying the base membrane, and coating with fluorosilane steam to obtain a nanofiber membrane;
the casting solution comprises 5-12 wt% of PAN, 0.2-1 wt% of MOFs and 87-94.8 wt% of polar solvent;
the MOFs is NH2-UIO-66(Zr)。
The invention firstly selects the MOFs as NH2UIO-66(Zr), which is blended with PAN to obtain a nanofiber membrane with hydrophobic surface and pores, NH in an electrostatic spinning mode2UIO-66(Zr) is one of the MOFs that is hydrophilic and stable in the environment, the inventors have found NH2UIO-66(Zr) not only enables the stable synthesis of said nanofibrous membrane and prolongs its service life, but also NH2UIO-66(Zr) has hexahedron with a cavity structure, and after blended spinning with PAN, the surface roughness of the nanofiber membrane can be increased, and the siphon effect generated when the nanofiber membrane is contacted with liquid is beneficial to increasing the flux of the material; and the fluorosilane steam generated by steam coating freely passes through the film holes, so that the internal structure of the material can be effectively modified, and the effect of draining water in the holes is achieved.
Meanwhile, the inventor discovers through a great deal of research that the composite nanofiber membrane with good appearance, super-hydrophobicity, super-oleophylicity and good oil-water separation characteristic can be prepared unexpectedly by matching the membrane casting solution with the membrane forming mode.
According to the method, the base membrane is prepared by the electrostatic spinning method through the matching of materials with the mass in the membrane casting solution, and the method of steam coating is combined, so that the nanofiber membrane with excellent super-hydrophobic, super-oleophilic and oil-water separation performances is obtained.
Regulating the PAN content in the membrane casting solution within a proper range can be helpful for preparing a nanofiber membrane with small fiber diameter, large pore volume and high membrane flux; however, when the PAN content is too high (e.g., above the upper limit), the viscosity of the dope solution increases, which affects the electrospinning process and affects the properties of the fiber membrane.
Preferably, the content of PAN in the membrane casting solution is 9-11 wt%; further preferably 10 wt%.
Researches show that the PAN membrane casting solution is matched with the MOFs components, so that the lipophilicity and the hydrophobicity of the membrane are improved; however, when the MOFs content is too high (for example, higher than the above-mentioned upper limit value), the performance of the fiber film is not significantly improved, and the fiber film is liable to be agglomerated, which affects the spinning process.
Preferably, the content of MOFs in the casting solution is 0.6-1 wt%; further preferably 1 wt%.
Preferably, in the casting solution, the polar solvent is N, N-dimethylformamide.
Preferably, in the PAN-containing solution, the mass fraction of PAN is 10 to 24 wt%.
Preferably, the PAN-containing solution is prepared in the following manner: adding PAN into N, N-dimethylformamide, and mixing at 40-60 deg.C.
Preferably, the molecular weight of the PAN is 13 to 15 ten thousand.
A great deal of research shows that by adopting the PAN with the molecular weight, the fiber membrane with high flux, uniform diameter and no broken filament chain beads can be prepared under the electrostatic spinning condition.
Preferably, in the solution containing the MOFs, the mass fraction of the MOFs is 0.4-2 wt%;
preferably, the preparation method of the solution containing the MOFs is as follows: adding MOFs into N, N-dimethylformamide, and uniformly mixing at normal temperature to obtain the finished product.
As a further preferred method, the preparation method of the MOFs comprises: zirconium tetrachloride (ZrCl)4) Adding the mixed solution and 2-amino terephthalic acid into a mixed solvent to obtain a mixed solution, stirring the mixed solution at 100 +/-1 ℃ for reacting for 24-25h, and carrying out solid-liquid separation to obtain MOFs; in the mixed solution, ZrCl4The concentration of the 2-amino terephthalic acid is 0.0172-0.0344mol/L, and the concentration of the 2-amino terephthalic acid is 0.0172-0.0344 mol/L; the mixed solvent is obtained by mixing acetic acid and N, N-dimethylformamide according to the volume ratio of 3-6: 100.
In the actual operation process, after solid-liquid separation, N-dimethylformamide is adopted for cleaning three times to obtain the needed MOFs.
Preferably, the particle size of the MOFs is 50nm to 90 nm.
The particle size of the MOFs needs to be effectively controlled, and too small particle size is not beneficial to uniform dispersion, and too large particle size can influence the electrostatic spinning process, such as the electrostatic spinning needle can be blocked. Under the condition of the preparation method, the particle size of the MOFs can be controlled within the range of 50nm-90 nm.
In the invention, the prepared solution containing MOFs and the solution containing PAN are mixed according to the volume ratio of 1:1 at normal temperature to obtain the required casting solution.
Preferably, in the electrostatic spinning process, the spinning voltage is controlled to be 12-14KV, the distance between the spinneret and the receiving plate is 14-16cm, and the flow rate of the casting solution is 1-2 ml/h.
In the practical operation process, the casting solution is filled into an injector, a needle head with the number of 22 is connected, the distance between the needle head and the roller is adjusted to be 15cm, 14kv high-voltage static electricity is connected to the needle head, the flow rate of the casting solution is controlled to be 1-2mL/h, the winding speed of the roller is controlled to be 300-450rn/min, and the base film is obtained for 1-3 h.
The drying process may be carried out by conventional methods.
Preferably, the fluorosilane is 1H,1H,2H, 2H-perfluorooctyltriethoxysilane.
The inventor finds that the optimal hydrophobic effect can be obtained by selecting 1H,1H,2H, 2H-perfluorooctyltriethoxysilane for steam coating through a large number of experiments, and in addition, the 1H,1H,2H, 2H-perfluorooctyltriethoxysilane also has the characteristics of high boiling point and small volatilization amount at high temperature, so that the coating is safer for environment and experimenters.
Preferably, the specific process of the steam coating is as follows: the base film is treated for 6-12H under the steam of 1H,1H,2H, 2H-perfluorooctyltriethoxysilane at 120-140 ℃.
In the actual operation process, the basement membrane and an open glass bottle containing 1H,1H,2H, 2H-perfluorooctyltriethoxysilane are placed in a sealed Teflon bottle, and are treated at 120 ℃ for 6 hours to obtain the nanofiber membrane.
In the invention, the steam coating modification treatment is carried out on the base membrane obtained by the preparation method of the nanofiber membrane, so that the performance of the obtained composite nanofiber membrane can be obviously improved, for example, the hydrophobic performance of the composite nanofiber membrane is improved, and the oleophylic performance of the composite nanofiber membrane is improved.
In the invention, after the hexahedral MOFs with the cavity structure is compounded with the PAN, the obtained membrane structure is beneficial to fluorine silane steam to freely pass through the membrane holes, and the internal structure of the material can be effectively modified.
Using NH in the invention2UIO-66(Zr) complexed with PAN and steam-coated, complementary, synergistic if not using NH2UIO-66(Zr) or conventional soaking modification cannot simultaneously modify the inside and the outside of the membrane, so that the surface and the pores are hydrophobic.
The invention also provides the nanofiber membrane for oil-water separation prepared by the preparation method.
Advantageous effects
The invention provides a preparation method of a nanofiber membrane for oil-water separation, which takes Polyacrylonitrile (PAN) as a high polymer material, wherein the PAN is a cheap and easily-obtained high polymer material and has excellent physicochemical properties and electrostatic tensile property, and the PAN is an excellent material for preparing an electrostatic spinning fiber membrane.
Simultaneously, the MOFs is initially selected to be NH2UIO-66(Zr), which is blended with PAN and then electrospun to obtain a nanofiber membrane of a material with hydrophobic surface and pores, NH2UIO-66(Zr) is one of the MOFs that is hydrophilic and stable in the environment, the inventors have found NH2UIO-66(Zr) not only enables the stable synthesis of said nanofibrous membrane and prolongs its service life, but also NH2UIO-66(Zr) has hexahedron with a cavity structure, and after blended spinning with PAN, the surface roughness of the nanofiber membrane can be increased, and the siphon effect generated when the nanofiber membrane is contacted with liquid is beneficial to increasing the flux of the material; the fluorosilane steam generated by steam coating can freely pass through the film holes, and can effectivelyThe internal structure of the material is modified to achieve the effect of dewatering in the holes.
The preparation method disclosed by the invention is simple to operate and good in film forming property, the MOFs material is uniformly distributed in the fiber, the water contact angle of the surface of the film is 150.4 degrees, the super-hydrophobic condition is achieved, the adsorption capacity of the composite fiber film on the silicone oil reaches 33.7g/g, and the oil flux for separating dichloromethane under the action of gravity is 2286 L.m-2h-1The separation efficiency is over 99.8 percent, and the oil flux after ten times of circulation is still kept at 1792 L.m-2h-1The method is used for efficiently separating oil from water, and has industrial application prospect.
Drawings
FIG. 1 is an SEM image of a composite nanofiber membrane prepared in example 1 and a water and oil contact angle image; wherein a is a film structure SEM image, b is a water contact angle image, and c is an oil contact angle image;
FIG. 2 is an SEM image of a composite nanofiber membrane prepared in example 2 and water and oil contact angle images; wherein a is a film structure SEM image, b is a water contact angle image, and c is an oil contact angle image;
FIG. 3 is an SEM image of the composite nanofiber membrane prepared in example 3 and a water and oil contact angle image; wherein a is a film structure SEM image, b is a water contact angle image, and c is an oil contact angle image;
FIG. 4 is a diagram of the oil-water mixture separated by the composite nanofiber membrane prepared in example 3; wherein the upper layer is pure water, the lower layer is dichloromethane, a is before separation, and b is after separation.
Detailed Description
PAN: the molecular weight is 13-15 ten thousand.
Example 1
Preparation of MOFs
MOFs prepared by mixing 0.0172mol/L zirconium tetrachloride (ZrCl)4) 0.0172 mol/L2-amino terephthalic acid is dissolved in a mixed solvent of acetic acid and N, N-dimethylformamide according to the mixture ratio of 3/100(V/V), stirred and reacted for 24 hours at 100 ℃, and obtained particles are centrifugally separated and washed by N, N-dimethylformamide for three times to obtain the MOFs.
Preparation of PAN solution
The PAN solution is prepared by uniformly mixing 15 ten thousand molecular weight polyacrylonitrile and solvent N, N-dimethylformamide according to the weight percentage of 20wt% and 80wt% at 60 ℃.
Preparation of MOFs solution
The MOFs solution is prepared by uniformly mixing 0.4 wt% of MOFs obtained in the step I and 99.6 wt% of N, N-dimethylformamide serving as a solvent at normal temperature.
Preparation of casting solution
The casting solution is prepared by uniformly mixing the solutions obtained in the second step and the third step at normal temperature according to the volume ratio of 1/1 (V/V).
Preparation of base film
And (4) filling the casting solution obtained in the step (iv) into a 10mL syringe, connecting a No. 22 needle by using a Teflon catheter, adjusting the distance between the needle and the roller to be 15cm, introducing 14kv high-voltage static electricity at the needle, wherein the flow rate of the casting solution is 1mL/h, the winding speed of the roller is 300rn/min, and the base film is obtained after 2 h.
Modification of composite nano fiber film
And (4) placing the base membrane obtained in the fifth step and an open glass bottle containing 1H,1H,2H, 2H-perfluorooctyltriethoxysilane into a sealed Teflon bottle, and treating at 120 ℃ for 6 hours to obtain the modified composite nanofiber membrane.
The hydrophobic property of the modified composite fiber membrane is improved, the water contact angle reaches 137.7 degrees, the oleophylic property is improved, the oil contact angle (kerosene) is 112 degrees, the oil adsorption capacity (kerosene) is 16.7g/g, and the oil flux under the action of gravity is 37 L.m-2h-1。
Example 2
Preparation of MOFs
MOFs prepared by mixing 0.0172mol/L zirconium tetrachloride (ZrCl)4) 0.0172 mol/L2-amino terephthalic acid is dissolved in a mixed solvent of acetic acid and N, N-dimethylformamide according to the mixture ratio of 3/100(V/V), stirred and reacted for 24 hours at 100 ℃, and obtained particles are centrifugally separated and washed by N, N-dimethylformamide for three times to obtain the MOFs.
Preparation of PAN solution
The PAN solution is prepared by uniformly mixing 15 ten thousand molecular weight polyacrylonitrile and solvent N, N-dimethylformamide according to the weight percentage of 20wt% and 80wt% at 60 ℃.
Preparation of MOFs solution
The MOFs solution is prepared by uniformly mixing 1 wt% of MOFs obtained in the step I and 99 wt% of N, N-dimethylformamide serving as a solvent at normal temperature.
Preparation of casting solution
The casting solution is prepared by uniformly mixing the solutions obtained in the second step and the third step at normal temperature according to the volume ratio of 1/1 (V/V).
Preparation of base film
And (4) filling the casting solution obtained in the step (iv) into a 10mL syringe, connecting a No. 22 needle by using a Teflon catheter, adjusting the distance between the needle and the roller to be 15cm, introducing 14kv high-voltage static electricity at the needle, wherein the flow rate of the casting solution is 1mL/h, the winding speed of the roller is 300rn/min, and the base film is obtained after 2 h.
Modification of composite nano fiber film
And (4) placing the base membrane obtained in the fifth step and an open glass bottle containing 1H,1H,2H, 2H-perfluorooctyltriethoxysilane into a sealed Teflon bottle, and treating at 120 ℃ for 6 hours to obtain the modified composite nanofiber membrane.
The hydrophobic property of the modified composite fiber membrane is obviously improved, the water contact angle reaches 143 degrees, the oleophylic property is obviously improved, the oil contact angle (kerosene) is 75 degrees, the oil adsorption capacity is increased, and the oil adsorption capacity (kerosene) is 21.6 g/g.
Example 3
Preparation of MOFs
MOFs prepared by mixing 0.0172mol/L zirconium tetrachloride (ZrCl)4) 0.0172 mol/L2-amino terephthalic acid is dissolved in a mixed solvent of acetic acid and N, N-dimethylformamide according to the mixture ratio of 3/100(V/V), stirred and reacted for 24 hours at 100 ℃, and obtained particles are centrifugally separated and washed by N, N-dimethylformamide for three times to obtain the MOFs.
Preparation of PAN solution
The PAN solution is prepared by uniformly mixing 15 ten thousand molecular weight polyacrylonitrile and solvent N, N-dimethylformamide according to the weight percentage of 20wt% and 80wt% at 60 ℃.
Preparation of MOFs solution
The MOFs solution is prepared by uniformly mixing 2wt% of MOFs obtained in the step I and 98wt% of N, N-dimethylformamide serving as a solvent at normal temperature.
Preparation of casting solution
The casting solution is prepared by uniformly mixing the solutions obtained in the second step and the third step at normal temperature according to the volume ratio of 1/1 (V/V).
Preparation of base film
And (4) filling the casting solution obtained in the step (iv) into a 10mL syringe, connecting a No. 22 needle by using a Teflon catheter, adjusting the distance between the needle and the roller to be 15cm, introducing 14kv high-voltage static electricity at the needle, wherein the flow rate of the casting solution is 1mL/h, the winding speed of the roller is 300rn/min, and the base film is obtained after 2 h.
Modification of composite nano fiber film
And (4) placing the base membrane obtained in the fifth step and an open glass bottle containing 1H,1H,2H, 2H-perfluorooctyltriethoxysilane into a sealed Teflon bottle, and treating at 120 ℃ for 6 hours to obtain the modified composite nanofiber membrane.
The hydrophobic property of the modified composite fiber membrane is obviously improved, the water contact angle reaches 150.4 degrees, the oleophylic property is obviously improved, the oil contact angle (kerosene) is 0 degree, and the oil flux under the action of gravity is 2286 L.m-2h-1The oil flux after ten cycles is still 1792 L.m-2h-1The separation efficiency is over 99.8%.
Example 4
Preparation of MOFs
MOFs prepared by mixing 0.0172mol/L zirconium tetrachloride (ZrCl)4) 0.0172 mol/L2-amino terephthalic acid is dissolved in a mixed solvent of acetic acid and N, N-dimethylformamide according to the mixture ratio of 3/100(V/V), stirred and reacted for 24 hours at 100 ℃, and obtained particles are centrifugally separated and washed by N, N-dimethylformamide for three times to obtain the MOFs.
Preparation of PAN solution
The PAN solution is prepared by uniformly mixing 15 ten thousand molecular weight polyacrylonitrile and solvent N, N-dimethylformamide according to the weight percentage of 20wt% and 80wt% at 60 ℃.
Preparation of MOFs solution
The MOFs solution is prepared by uniformly mixing 2wt% of MOFs obtained in the step I and 98wt% of N, N-dimethylformamide serving as a solvent at normal temperature.
Preparation of casting solution
The casting solution is prepared by uniformly mixing the solutions obtained in the second step and the third step at normal temperature according to the volume ratio of 1/1 (V/V).
Preparation of base film
And (4) filling the casting solution obtained in the step (iv) into a 10mL syringe, connecting a No. 22 needle by using a Teflon catheter, adjusting the distance between the needle and the roller to be 15cm, introducing 14kv high-voltage static electricity at the needle, wherein the flow rate of the casting solution is 1mL/h, the winding speed of the roller is 300rn/min, and the base film is obtained after 3 h.
Modification of composite nano fiber film
And (4) placing the base membrane obtained in the fifth step and an open glass bottle containing 1H,1H,2H, 2H-perfluorooctyltriethoxysilane into a sealed Teflon bottle, and treating at 120 ℃ for 6 hours to obtain the modified composite nanofiber membrane.
The hydrophobic and oleophylic properties of the modified composite fiber membrane are obviously improved, and the oil adsorption capacity (kerosene) is 22.9 g/g.
Comparative example 1
The difference from example 3 is only that the type of MOFs (ZIF-8) is changed as follows:
preparation of casting solution
The casting solution is prepared by uniformly mixing 10 wt%, 1 wt% and 89 wt% of polyacrylonitrile with a molecular weight of 15 ten thousand, ZIF-8 and a solvent N, N-dimethylformamide at 60 ℃.
Preparation of base film
Filling the membrane casting solution obtained in the step I into a 10mL syringe, connecting a No. 22 needle by using a Teflon catheter, adjusting the distance between the needle and a roller to be 15cm, introducing 14kv high-voltage static electricity at the needle, wherein the flow rate of the membrane casting solution is 1mL/h, the winding speed of the roller is 300rn/min, and the base membrane is obtained after 2 h.
③ modification of composite nanofiber membrane
And (4) placing the base membrane obtained in the fifth step and an open glass bottle containing 1H,1H,2H, 2H-perfluorooctyltriethoxysilane into a sealed Teflon bottle, and treating at 120 ℃ for 6 hours to obtain the modified composite nanofiber membrane.
The hydrophobic property of the modified composite fiber membrane is improved, the water contact angle reaches 140.7 degrees, the oleophylic property is obviously improved, the oil contact angle (kerosene) is 63 degrees, and the oil flux is 862 L.m under the action of gravity-2h-1。
Comparative example 2
The only difference from example 3 is that the modification method (immersion method) was changed as follows:
preparation of MOFs
MOFs prepared by mixing 0.0172mol/L zirconium tetrachloride (ZrCl)4) 0.0172 mol/L2-amino terephthalic acid is dissolved in a mixed solvent of acetic acid and N, N-dimethylformamide according to the mixture ratio of 3/100(V/V), stirred and reacted for 24 hours at 100 ℃, and obtained particles are centrifugally separated and washed by N, N-dimethylformamide for three times to obtain the MOFs.
Preparation of PAN solution
The PAN solution is prepared by uniformly mixing 15 ten thousand molecular weight polyacrylonitrile and solvent N, N-dimethylformamide according to the weight percentage of 20wt% and 80wt% at 60 ℃.
Preparation of MOFs solution
The MOFs solution is prepared by uniformly mixing 2wt% of MOFs obtained in the step I and 98wt% of N, N-dimethylformamide serving as a solvent at normal temperature.
Preparation of casting solution
The casting solution is prepared by uniformly mixing the solutions obtained in the second step and the third step at normal temperature according to the volume ratio of 1/1 (V/V).
Preparation of base film
And (4) filling the casting solution obtained in the step (iv) into a 10mL syringe, connecting a No. 22 needle by using a Teflon catheter, adjusting the distance between the needle and the roller to be 15cm, introducing 14kv high-voltage static electricity at the needle, wherein the flow rate of the casting solution is 1mL/h, the winding speed of the roller is 300rn/min, and the base film is obtained after 2 h.
Modification of composite nano fiber film
Soaking the basement membrane obtained in the fifth step in a 1H,1H,2H, 2H-perfluorooctyltriethoxysilane solution for 30min to obtain the modified composite nanofiber membrane.
The hydrophobic property of the modified composite fiber membrane is improved, the water contact angle reaches 141 degrees, the oleophylic property is obviously improved, the oil contact angle (kerosene) is 0 degree, and the oil flux under the action of gravity is 1617 L.m-2h-1The separation efficiency was 90%.

Claims (2)

1. A preparation method of a nanofiber membrane for oil-water separation is characterized by comprising the following steps: the method comprises the following steps:
preparation of MOFs
Dissolving 0.0172mol/L zirconium tetrachloride and 0.0172 mol/L2-amino terephthalic acid in a mixed solvent of acetic acid and N, N-dimethylformamide, wherein the volume ratio of the acetic acid to the N, N-dimethylformamide in the mixed solvent is 3: 100; stirring and reacting for 24 hours at 100 ℃, centrifugally separating out the obtained particles, and washing with N, N-dimethylformamide for three times to obtain the MOFs;
preparation of PAN solution
Is prepared by uniformly mixing 15 ten thousand of polyacrylonitrile with molecular weight and solvent N, N-dimethylformamide according to the weight percentage of 20wt percent and 80wt percent at 60 ℃;
preparation of MOFs solution
The MOFs solution is prepared by uniformly mixing 2wt% of MOFs obtained in the step I and 98wt% of N, N-dimethylformamide serving as a solvent at normal temperature;
preparation of casting solution
And (3) preparing the casting solution from the solutions obtained in the second step and the third step according to the volume ratio of 1:1, mixing uniformly at normal temperature;
preparation of base film
Filling the casting solution obtained in the step (iv) into a 10mL syringe, connecting a No. 22 needle with a Teflon catheter, adjusting the distance between the needle and the roller to be 15cm, introducing 14kv high-voltage static electricity at the needle, wherein the flow rate of the casting solution is 1mL/h, the winding speed of the roller is 300rn/min, and the base film is obtained after 2 h;
modification of nanofiber membranes
And (4) placing the base membrane obtained in the fifth step and an open glass bottle containing 1H,1H,2H, 2H-perfluorooctyltriethoxysilane into a sealed Teflon bottle, and treating at 120 ℃ for 6 hours to obtain the modified composite nanofiber membrane, namely the nanofiber membrane for oil-water separation.
2. A nanofiber membrane for oil-water separation prepared by the preparation method as claimed in claim 1.
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