CN113144903B - High-flux super-hydrophilic/underwater super-oleophobic Janus membrane modification method - Google Patents
High-flux super-hydrophilic/underwater super-oleophobic Janus membrane modification method Download PDFInfo
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- 239000012528 membrane Substances 0.000 title claims abstract description 109
- 238000002715 modification method Methods 0.000 title claims abstract description 8
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 48
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims abstract description 40
- 239000002041 carbon nanotube Substances 0.000 claims abstract description 34
- 229910021393 carbon nanotube Inorganic materials 0.000 claims abstract description 34
- VYFYYTLLBUKUHU-UHFFFAOYSA-N dopamine Chemical compound NCCC1=CC=C(O)C(O)=C1 VYFYYTLLBUKUHU-UHFFFAOYSA-N 0.000 claims abstract description 34
- 238000000034 method Methods 0.000 claims abstract description 27
- 230000002209 hydrophobic effect Effects 0.000 claims abstract description 18
- 229960003638 dopamine Drugs 0.000 claims abstract description 17
- 239000011248 coating agent Substances 0.000 claims abstract description 14
- 238000000576 coating method Methods 0.000 claims abstract description 14
- 229920002873 Polyethylenimine Polymers 0.000 claims abstract description 12
- 239000000243 solution Substances 0.000 claims description 42
- 239000002033 PVDF binder Substances 0.000 claims description 29
- 229920002981 polyvinylidene fluoride Polymers 0.000 claims description 29
- 238000001035 drying Methods 0.000 claims description 25
- 239000000463 material Substances 0.000 claims description 18
- 239000000725 suspension Substances 0.000 claims description 16
- 229910052799 carbon Inorganic materials 0.000 claims description 14
- 230000008021 deposition Effects 0.000 claims description 13
- 230000008569 process Effects 0.000 claims description 13
- 238000011068 loading method Methods 0.000 claims description 11
- 230000004048 modification Effects 0.000 claims description 10
- 238000012986 modification Methods 0.000 claims description 10
- 239000007983 Tris buffer Substances 0.000 claims description 8
- 239000011664 nicotinic acid Substances 0.000 claims description 8
- 239000002243 precursor Substances 0.000 claims description 6
- 238000002360 preparation method Methods 0.000 claims description 6
- 238000003756 stirring Methods 0.000 claims description 6
- 238000001291 vacuum drying Methods 0.000 claims description 6
- 241000237536 Mytilus edulis Species 0.000 claims description 5
- 235000020638 mussel Nutrition 0.000 claims description 5
- 239000007788 liquid Substances 0.000 claims description 4
- 238000003760 magnetic stirring Methods 0.000 claims description 2
- 239000003364 biologic glue Substances 0.000 claims 1
- 230000004907 flux Effects 0.000 abstract description 10
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 abstract description 7
- 239000011148 porous material Substances 0.000 abstract description 5
- 238000005516 engineering process Methods 0.000 abstract description 4
- 238000001308 synthesis method Methods 0.000 abstract 1
- 239000002086 nanomaterial Substances 0.000 description 9
- 238000001000 micrograph Methods 0.000 description 7
- 238000004821 distillation Methods 0.000 description 5
- 230000000694 effects Effects 0.000 description 5
- 239000000047 product Substances 0.000 description 4
- 238000000926 separation method Methods 0.000 description 4
- 238000006243 chemical reaction Methods 0.000 description 3
- 239000003292 glue Substances 0.000 description 3
- -1 polytetrafluoroethylene Polymers 0.000 description 3
- 239000002994 raw material Substances 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- 238000009210 therapy by ultrasound Methods 0.000 description 3
- 239000002351 wastewater Substances 0.000 description 3
- 238000009826 distribution Methods 0.000 description 2
- 229920001343 polytetrafluoroethylene Polymers 0.000 description 2
- 239000004810 polytetrafluoroethylene Substances 0.000 description 2
- 230000035484 reaction time Effects 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- 241001465754 Metazoa Species 0.000 description 1
- 239000004743 Polypropylene Substances 0.000 description 1
- 230000001070 adhesive effect Effects 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000004140 cleaning Methods 0.000 description 1
- 239000000356 contaminant Substances 0.000 description 1
- 238000005137 deposition process Methods 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 239000003344 environmental pollutant Substances 0.000 description 1
- 239000012527 feed solution Substances 0.000 description 1
- 125000000524 functional group Chemical group 0.000 description 1
- 230000003993 interaction Effects 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 239000012466 permeate Substances 0.000 description 1
- 231100000719 pollutant Toxicity 0.000 description 1
- 229920001690 polydopamine Polymers 0.000 description 1
- 238000006116 polymerization reaction Methods 0.000 description 1
- 229920001155 polypropylene Polymers 0.000 description 1
- 230000002035 prolonged effect Effects 0.000 description 1
- 238000001338 self-assembly Methods 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 230000003075 superhydrophobic effect Effects 0.000 description 1
- 238000003786 synthesis reaction Methods 0.000 description 1
Classifications
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- 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
- B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
- B01D61/36—Pervaporation; Membrane distillation; Liquid permeation
- B01D61/364—Membrane distillation
-
- 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
- B01D67/0093—Chemical modification
-
- 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
- B01D67/0095—Drying
-
- 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
- B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
- B01D69/06—Flat membranes
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- 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
- B01D71/26—Polyalkenes
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- 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
- B01D71/36—Polytetrafluoroethene
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2325/00—Details relating to properties of membranes
- B01D2325/36—Hydrophilic membranes
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- Chemical Kinetics & Catalysis (AREA)
- Engineering & Computer Science (AREA)
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Abstract
A modification method of a Janus membrane with high flux and super-hydrophilicity/underwater super-oleophobicity adopts a dopamine and polyethyleneimine codeposition technology to coat hydrophilic carbon nanotubes on the surface of one side of a hydrophobic membrane, so as to synthesize a stable hydrophilic carbon nanotube coating, so that one side of the membrane maintains the original characteristic while the other side has excellent super-hydrophilicity/underwater super-oleophobicity, the membrane flux is increased, and the oil pollution resistance of the membrane is improved; the synthesis method comprises the steps of coating the carbon nano tube ethanol solution on the surface of the membrane in a negative pressure vacuum mode, and then adopting a dopamine and polyethyleneimine codeposition mode to stably fix the coated carbon nano tube, wherein the pore diameter of the obtained modified Janus membrane is 0.2-0.25 mu m, the water contact angle is 9 degrees, the oil contact angle is 180 degrees, and the modified Janus membrane has extremely high hydrophilicity and super oleophobic property. The method is simple and efficient, and the prepared super-hydrophilic/underwater super-oleophobic janus membrane has high flux and oil pollution resistance.
Description
Technical Field
The invention belongs to the technical field of chemical industry, and particularly relates to a high-flux, super-hydrophilic/underwater super-oleophobic Janus membrane modification technology suitable for a hydrophobic polyvinylidene fluoride (PVDF) membrane.
Background
In the water treatment process, the membrane distillation is a novel efficient and energy-saving heat-driven separation process, and the feed solution can be heated by utilizing various low-quality heat sources such as solar energy, geothermal energy and the like in the membrane separation process. In a typical membrane separation process, a hydrophobic porous membrane acts as a medium for separating hot and cold materials, while not allowing entry of hot liquid, but allowing entry of water vapor through the membrane pores. PVDF polyvinylidene fluoride, which drives water vapor from the feed side to the permeate side of the membrane due to the difference in vapor pressure on both sides of the membrane caused by the temperature difference, is the most commonly used membrane raw material for membrane distillation, and has excellent thermal stability, chemical stability, and excellent mechanical strength, etc. However, the hydrophobicity of the conventional commercial membrane has a great problem in treating oil-type wastewater, and the strong hydrophobic-hydrophobic interaction between oil drops and the surface of the membrane makes the membrane easily wetted by nonpolar contaminants such as oil. According to the inspire that the surfaces of animals such as fishes in nature show excellent oil pollution resistance and self-cleaning performance, the surfaces of the films are required to be subjected to hydrophilic modification, so that the oil pollution resistance of the films is improved.
The traditional hydrophilic modification method for the hydrophobic membrane comprises the following steps: template method, layer-by-layer self-assembly, etc., but all have the disadvantages of complex modification process, poor hydrophilic stability, more flux reduction, easy damage to membrane structure, etc. Therefore, there is an objective need in the art to develop a method that will not compromise the overall performance of the membrane, but will also improve the hydrophilicity of the membrane, increasing flux and oil stain resistance.
Disclosure of Invention
The invention aims to provide a high-flux super-hydrophilic/underwater super-oleophobic Janus membrane modification method. The method solves the problem that the surface of the membrane is easy to be wetted by nonpolar pollutants such as oil when the hydrophobic property of the membrane material in the current membrane distillation process section is used for treating the oil wastewater, and the Janus membrane can be applied to the process conditions of treating the oil wastewater by constructing a hydrophilic oleophobic porous network on the surface of one side of the membrane, so that the service life of a membrane component is prolonged.
In order to achieve the above purpose, the present invention provides the following technical solutions:
the high-flux super-hydrophilic/underwater super-oleophobic Janus membrane modification method comprises the synthesis steps of carbon nanotube precursor preparation, hydrophobic membrane pretreatment, carbon nanotube loading and mussel bionic codeposition hydrophilic modification.
Wherein, the preparation of the carbon nanotube precursor solution comprises the following steps: dissolving hydrophilic carbon nanotube in 5-50ml absolute ethanol solution, uniformly dispersing the material in the ethanol solution by adopting ultrasonic waves, and processing for 60min to prepare carbon nanotube-ethanol suspension with certain concentration;
wherein the hydrophobic membrane pretreatment step comprises: immersing a PVDF flat membrane in an ethanol solution, treating the PVDF flat membrane for 10min in an ultrasonic mode, and drying the loaded membrane in a constant temperature drying oven at 80 ℃ for 24h;
wherein the carbon nanotube loading step comprises: loading the carbon nanotube-ethanol suspension obtained in the carbon nanotube precursor solution preparation step on a dried film product obtained in the hydrophobic film pretreatment step by adopting a vacuum negative pressure pump;
further, the load vacuum degree provided by the negative pressure vacuum pump is 0.05-0.10Mpa;
further, the load deposition temperature is 10-40 ℃;
further, the load deposition time is 60-240 min;
further, the rotating speed of the solution stirring rotor in the negative pressure process is 100-400r/min;
further, the membrane product after vacuum loading is placed in a constant temperature drying oven at 60 ℃ for 6 hours;
wherein, the step of hydrophilic modification of the mussel bionic method codeposition comprises the following steps: preparing a tris solution with a proper concentration of dopamine and polyethylenimine, immersing a membrane product loaded and dried by the carbon nano tube in the tris solution, and stirring to enable a membrane side loaded with a carbon nano tube coating and the tris solution to generate a codeposition effect, so as to form a super-hydrophilic oleophobic porous network structure, wherein the hydrophilic coating has the roughness of a micro-nano structure, and has remarkable flux increasing and oil pollution resisting effects and excellent performance;
further, the concentration of the dopamine and polyethyleneimine solution is 2mg/L and 6mg/L respectively;
further, the reaction temperature in the step is 25 ℃ at normal temperature;
further, the rotation speed of the solution stirring rotor in the co-deposition process is 400r/min;
further, the codeposition reaction time is 6-24 hours;
further, the membrane product after the reaction is dried in a vacuum drying oven at 60 ℃.
The hydrophobic membrane is a polyvinylidene fluoride membrane, and the invention is also applicable to modification of hydrophobic membranes such as polytetrafluoroethylene, polypropylene and the like.
Compared with the prior art, the invention has the following beneficial effects:
(1) The hydrophilic coating raw material is selected as a carbon nano tube material, the material has extremely strong hydrophilicity and chemical activity, has more surface oxygen-containing active functional groups and smaller particle size, and can form an ultra-hydrophilic thin layer coating on the surface of a hydrophobic membrane without causing flux reduction of the membrane material.
(2) Because the membrane component has different use conditions, the thickness of the carbon nano tube co-deposited hydrophilic coating can be adjusted according to the specific conditions of water quality and water quantity, and the thickness of the hydrophilic coating can be easily controlled by changing the loading amount of the carbon nano tube dispersion liquid.
(3) The carbon nano tube is used as a codeposition precursor, the formed hydrophilic coating has the roughness of a micro-nano structure, the flux increase and oil pollution resistance effects are remarkable, the performance is excellent, and the toughness of the PVDF film can be effectively improved by a proper amount of hydrophilic coating.
(4) The polydopamine and PVDF film matrix have strong adhesive action, and the affinity and the surface energy of the hydrophilic coating synthesized on the film surface by the codeposition technology of dopamine self-polymerization assembly behavior are improved.
(5) When the Janus membrane is used for carrying out the membrane distillation technology process, the energy consumption of the membrane process involving the two-phase interface can be effectively reduced.
(6) The film preparation method is simple, easy to operate and control, only needs to control the conditions of raw material consumption, stirring rate, reaction time, drying temperature and the like, does not need other special equipment, has short reaction flow and low cost, and is easy for mass production and industrialization.
Drawings
FIG. 1 is a scanning electron microscope image of an untreated PVDF film.
Fig. 2 is a scanning electron microscope image of PVDF film after processing according to example 1 of the invention.
Fig. 3 is a scanning electron microscope image of PVDF film after processing according to example 2 of the invention.
FIG. 4 is a scanning electron microscope image of a PVDF film after treatment according to example 3 of the present invention.
Fig. 5 is a graph of the surface hydrophilic contact angle and underwater oil contact angle of Janus films after treatment of examples 1, 2, and 3.
FIG. 6 is a graph of pore size distribution of the original PVDF membrane.
Fig. 7 is a graph of the pore size distribution of Janus membranes after the treatment of example 2.
Detailed Description
The invention will be further described with reference to the accompanying drawings and examples
Aiming at the problems of the existing hydrophobic membrane in the field of membrane distillation, the invention provides a modification method for preparing a super-hydrophilic/underwater super-oleophobic Janus membrane by adopting a mussel bionic method, which comprises the following steps of:
s1, a preparation process of a carbon nano tube precursor liquid comprises the steps of dissolving hydrophilic carbon nano tubes in 5-50ml of absolute ethanol solution, uniformly dispersing materials in the ethanol solution by adopting ultrasonic waves, and preparing a carbon nano tube-ethanol suspension with a certain concentration for 60min, wherein the thickness of a coating is controlled by the dosage of the suspension;
s2, a hydrophobic membrane pretreatment process comprises immersing a PVDF flat membrane in an ethanol solution, treating for 10min by adopting an ultrasonic mode, and drying the loaded membrane in a constant temperature drying oven at 80 ℃ for 24h;
s3, a carbon nano tube loading process: a certain amount of carbon nano tube-ethanol suspension prepared in the step S1 is loaded on a PVDF flat membrane of the step S2 under the negative pressure environment with the vacuum degree of 0.05-0.10MPa by adopting a vacuum pump, the deposition temperature is 10-40 ℃, the deposition time is 60-240 min, the rotor rotation speed is 100-400r/min, and then the carbon nano tube-ethanol suspension is dried in a constant temperature drying oven at 60 ℃ for 6h;
s4, a mussel bionic method codeposition hydrophilic modification process: 2mg/L dopamine solution and 6mg/L polyethyleneimine solution are selected and added into tris 8.5 solution, the membrane material of S3 is immersed into the solution for stirring under the constant temperature of 25 ℃, the magnetic stirring speed is 400r/min, the codeposition time is 6-24h, a porous hydrophilic network is formed on the surface of the membrane, and then the membrane material is dried in a vacuum drying oven at 60 ℃.
The invention is further illustrated by the following examples.
Example 1
S1, dissolving hydrophilic carbon nanotubes in 5ml of absolute ethanol solution, and carrying out ultrasonic treatment for 60min to uniformly disperse the materials to prepare a carbon nanotube-ethanol suspension with a certain concentration;
s2, immersing the PVDF flat membrane in an ethanol solution, treating the PVDF flat membrane for 10min in an ultrasonic mode, and drying the loaded membrane in a constant temperature drying oven at 80 ℃ for 24h;
s3, loading 5mL of carbon nano tube-ethanol suspension prepared by S1 on a PVDF flat membrane of S2 under a negative pressure environment with the vacuum degree of 0.05-0.10MPa, wherein the deposition temperature is 25 ℃, the deposition time is 60min, the rotor rotation speed is 400r/min, and then drying for 6h in a constant temperature drying oven with the temperature of 60 ℃;
s4, immersing the membrane material of the S3 in a tris 8.5 solution of 2mg/L dopamine solution and 6mg/L polyethylenimine solution at the constant temperature of 25 ℃ for 6h at 400r/min, and drying in a vacuum drying oven at 60 ℃. Referring to fig. 2, a scanning electron microscope image of the super-hydrophilic/underwater super-oleophobic Janus membrane synthesized by the method in embodiment 1 of the present invention shows that after dopamine is deposited, a layer of bionic glue is deposited on the surface of the carbon nanotube, and meanwhile, the super-hydrophilic/underwater super-oleophobic Janus membrane has a certain micro-nano structure, and the excellent micro-nano structure further improves the hydrophilicity.
Example 2
S1, dissolving hydrophilic carbon nanotubes in 5ml of absolute ethanol solution, and carrying out ultrasonic treatment for 60min to uniformly disperse the materials to prepare a carbon nanotube-ethanol suspension with a certain concentration;
s2, immersing the PVDF flat membrane in an ethanol solution, treating the PVDF flat membrane for 10min in an ultrasonic mode, and drying the loaded membrane in a constant temperature drying oven at 80 ℃ for 24h;
s3, loading 5mL of carbon nano tube-ethanol suspension prepared by S1 on a PVDF flat membrane of S2 under a negative pressure environment with the vacuum degree of 0.05-0.10MPa, wherein the deposition temperature is 25 ℃, the deposition time is 60min, the rotor rotation speed is 400r/min, and then drying for 6h in a constant temperature drying oven with the temperature of 60 ℃;
s4, immersing the membrane material of the S3 into a tris 8.5 solution of 2mg/L dopamine solution and 6mg/L polyethylenimine solution at the constant temperature of 25 ℃ for 12h at 400r/min, and drying in a vacuum drying oven at 60 ℃.
Referring to fig. 3, a scanning electron microscope image of the super-hydrophilic/underwater super-oleophobic Janus membrane synthesized by the method in embodiment 2 of the present invention shows that after dopamine is deposited, a layer of bionic glue is deposited on the surface of the carbon nanotube, and meanwhile, the super-hydrophilic/underwater super-oleophobic Janus membrane has a certain micro-nano structure, and the excellent micro-nano structure further improves the hydrophilicity.
Example 3
S1, dissolving hydrophilic carbon nanotubes in 5ml of absolute ethanol solution, and carrying out ultrasonic treatment for 60min to uniformly disperse the materials to prepare a carbon nanotube-ethanol suspension with a certain concentration;
s2, immersing the PVDF flat membrane in an ethanol solution, treating the PVDF flat membrane for 10min in an ultrasonic mode, and drying the loaded membrane in a constant temperature drying oven at 80 ℃ for 24h;
s3, loading 5mL of carbon nano tube-ethanol suspension prepared by S1 on a PVDF flat membrane of S2 under a negative pressure environment with the vacuum degree of 0.05-0.10MPa, wherein the deposition temperature is 25 ℃, the deposition time is 60min, the rotor rotation speed is 400r/min, and then drying for 6h in a constant temperature drying oven with the temperature of 60 ℃;
s4, immersing the membrane material of the S3 into a tris 8.5 solution of 2mg/L dopamine solution and 6mg/L polyethylenimine solution at the constant temperature of 25 ℃ for 24 hours, and performing co-deposition at 400r/min and drying in a vacuum drying oven at 60 ℃. Referring to fig. 4, a scanning electron microscope image of the super-hydrophilic/underwater super-oleophobic Janus membrane synthesized by the method in embodiment 3 of the present invention shows that after dopamine is deposited, a layer of bionic glue is deposited on the surface of the carbon nanotube, and meanwhile, the nano-structure is provided, and the polytetrafluoroethylene membrane surface after being treated by the method is changed from hydrophobic to super-hydrophobic, so that the nano-structure has an excellent anti-pollution effect.
As can be seen from the combination of the three examples, the dopamine deposition time has a certain influence on the micro-nano structure of the carbon nanotube surface, and compared with the film synthesized in example 2, the Janus film surface structure synthesized in example 3 has no significant increase in load capacity and reduced performance, which indicates that the loading time verified in example 2 is more suitable for 12 hours, and a large amount of hydrophilic carbon nanotube porous network is loaded to form, so that the hydrophilicity and oleophobicity of one side of the Janus film are effectively improved;
referring to fig. 5, in the embodiment 2 of the present invention, the water contact angle of the Janus membrane is 9 °, which indicates that the modified Janus membrane has good hydrophilicity, the dynamic contact angle of underwater oil is 180 °, and the modified membrane shows ultra-low adhesion force with oil drops and excellent super-oleophobic property in the dynamic process that the oil drops gradually contact and leave from the membrane surface;
referring to fig. 6 and 7, the Janus membrane synthesized by the invention can reduce the pore diameter on the hydrophobic membrane from 0.35-0.5 μm to 0.2-0.25 μm, thereby effectively improving the separation efficiency of the Janus membrane and improving the flux.
In summary, the invention relates to a carbon nanotube-based method for codeposition modification of dopamine and polyethyleneimine, which comprises the steps of coating the carbon nanotubes on the surface of a membrane, and then codeposition of dopamine and polyethyleneimine, wherein the modified Janus membrane has excellent flux and hydrophilicity and strong oil pollution resistance.
The above description of the embodiments is provided to facilitate a person skilled in the art to make and use the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art who is skilled in the art to which the present invention pertains should make equivalent substitutions or modifications according to the technical solution of the present invention and its inventive concept within the scope of the present invention.
Claims (1)
1. A modification method of a high-flux super-hydrophilic/underwater super-oleophobic Janus membrane is characterized in that carbon nanotubes are coated on the surface of a hydrophobic polyvinylidene fluoride PVDF membrane in a negative pressure vacuum mode, and then hydrophilic carbon nanotubes are fixed on the surface of the membrane by using biological glue formed by codeposition of dopamine and polyethyleneimine, so that a porous and high-flux super-hydrophilic/underwater super-oleophobic modified Janus network membrane is constructed;
the method for modifying the high-flux super-hydrophilic/underwater super-oleophobic Janus membrane of the hydrophobic membrane comprises the following steps:
s1, a preparation process of a carbon nano tube precursor liquid comprises the steps of dissolving hydrophilic carbon nano tubes in 5-50ml of absolute ethanol solution, uniformly dispersing materials in the ethanol solution by adopting ultrasonic waves, and preparing a carbon nano tube-ethanol suspension with a certain concentration for 60min, wherein the thickness of a coating is controlled by the dosage of the suspension;
s2, a hydrophobic membrane pretreatment process comprises immersing a PVDF flat membrane in an ethanol solution, treating for 10min by adopting an ultrasonic mode, and then drying for 24h in a constant temperature drying oven at 80 ℃;
s3, a carbon nano tube loading process: a certain amount of carbon nano tube-ethanol suspension prepared in the step S1 is loaded on a PVDF flat membrane of the step S2 under the negative pressure environment with the vacuum degree of 0.05-0.10MPa by adopting a vacuum pump, the deposition temperature is 10-40 ℃, the deposition time is 60-240 min, the rotor rotation speed is 100-400r/min, and then the carbon nano tube-ethanol suspension is dried in a constant temperature drying oven at 60 ℃ for 6h;
s4, a mussel bionic method codeposition hydrophilic modification process: 2mg/L dopamine solution and 6mg/L polyethyleneimine solution are selected and added into tris 8.5 solution, the membrane material of S3 is immersed into the solution for stirring under the constant temperature of 25 ℃, the magnetic stirring speed is 400r/min, the codeposition time is 6-24h, a porous hydrophilic network is formed on the surface of the membrane, and then the membrane material is dried in a vacuum drying oven at 60 ℃.
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| CN114288872B (en) * | 2022-01-12 | 2022-09-20 | 广东省科学院生态环境与土壤研究所 | High-stability and high-flux polydopamine nanoparticle modified membrane and preparation method and application thereof |
| CN114478024B (en) * | 2022-03-02 | 2022-12-02 | 哈尔滨工业大学（威海） | Preparation method of negative-charge pollution-resistant ceramic membrane |
| CN114588844B (en) * | 2022-03-18 | 2023-07-21 | 杭州师范大学 | Application of double-sided hollow fiber membrane reactor in Suzuki-Miyaura reaction and membrane reactor thereof |
| CN115138221B (en) * | 2022-07-26 | 2023-07-18 | 南京工业大学 | Application and preparation method of Janus ceramic membrane in dispersion strengthening gas distribution process |
| CN117358076B (en) * | 2023-12-07 | 2024-04-12 | 新乡学院 | Hydrophilic high-performance polyvinylidene fluoride/MOFs composite membrane and preparation method thereof |
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| CN111573780A (en) * | 2020-04-09 | 2020-08-25 | 中国科学院宁波材料技术与工程研究所 | Photothermal membrane distiller, preparation method and application thereof, and water treatment equipment |
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| CN107158980A (en) * | 2017-06-07 | 2017-09-15 | 浙江大学 | Utilized thin film composite membranes reacted based on air liquid interface and its preparation method and application |
| CN111573780A (en) * | 2020-04-09 | 2020-08-25 | 中国科学院宁波材料技术与工程研究所 | Photothermal membrane distiller, preparation method and application thereof, and water treatment equipment |
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