CN114345146A - Modified polypropylene oil-water separation membrane and preparation method thereof - Google Patents
Modified polypropylene oil-water separation membrane and preparation method thereof Download PDFInfo
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Abstract
The invention discloses a modified polypropylene oil-water separation membrane and a preparation method thereof, wherein the method comprises the following steps: providing a polypropylene porous film base material; carrying out corona activation treatment on a polypropylene porous film base material under the conditions that the corona treatment temperature is not higher than 30 ℃, the corona power is 0.1-5000W and the corona time is 0.01-10 min to obtain an activated polypropylene film; placing the activated polypropylene film in a grafting reaction solution to carry out chemical grafting reaction, wherein the grafting reaction solution comprises a grafting monomer aqueous solution, and the grafting monomer contains an ethylenic functional group of carboxyl, amido, cyano, hydroxyl or amido; the two sides of the activated polypropylene film are modified to obtain the modified polypropylene oil-water separation film, and the film material has excellent structure and performance stability, higher water flux, excellent wettability and oil-water separation efficiency.
Description
Technical Field
The invention belongs to the technical field of material preparation, and particularly relates to a modified polypropylene oil-water separation membrane and a preparation method thereof.
Background
Water is an indispensable precious resource in life, and waste water recycling and resource recovery become new subjects and trends of waste water treatment and are one of the core problems in environmental engineering. The large volume of oily wastewater discharged directly into the environment without treatment causes human and natural life threatening water pollution problems. Therefore, in order to protect ecology and human health, oily wastewater must be treated and then discharged into the environment. According to the source of the oily wastewater and the existing form of oil in water, the oily wastewater can be divided into four types of floating oil, dispersed oil, emulsified oil and dissolved oil: floating oil: the oil film of continuous phase floats on the water surface to form an oil film or an oil layer. The oil globule particles are large, typically greater than 100 μm. Dispersing oil: the micro oil drops are suspended and dispersed in a water phase, are unstable and can be gathered into larger oil drops to be converted into floating oil, and the particle size of the oil drops is generally 10-100 mu m. Emulsion oil: because of the existence of the surface active agent, the oil is emulsion in water, and the system is stable. The particle size of the oil drops is very small, generally less than 10 μm, and most of the oil drops are 0.1-2 um.
Dissolving oil: the molecular state is dispersed in water to form an oil-water homogeneous system which is very stable and is generally lower than 5-15 mg/L. The oil droplets have a very small particle size, sometimes as small as a few nanometers.
The traditional methods of centrifugation, oil absorption, air flotation, gravity sedimentation, biological oxidation and the like have high separation cost, complex operation process and low oil-water separation efficiency, and are not suitable for treating emulsion oily wastewater with oil drops of less than 20 mu m. Although the traditional oil-water separation materials, such as particle powder materials, sponge or sponge-like materials, foam materials, etc., have separation performance, the traditional oil-water separation materials have the disadvantages of low separation efficiency, poor reusability, secondary pollution to the environment, etc., so that the development of advanced and efficient oil-water separation materials and the attempt of new oil-water separation technologies are urgently needed.
In recent years, the membrane separation technology is one of the technologies widely applied in environmental engineering, and has the advantages of convenient operation, high separation efficiency and the like compared with other traditional technologies. The membrane separation technology has a very wide application in the field of water treatment, and the most critical part of the technology is the separation membrane material. Based on the selective permeability of the separation membrane, the membrane separation technology utilizes the difference of the particle sizes of substances in a mixed solution to complete the separation, purification and concentration of a mixture under the condition of taking external conditions or chemical potential difference as driving force. The membrane separation technology has the characteristics of normal-temperature operation, no phase change, chemical change, good selectivity, strong adaptability, low energy consumption and the like. Currently, the membrane technologies commonly used in water treatment include: microfiltration, ultrafiltration, nanofiltration, reverse osmosis, electrodialysis, etc. Among them, the membrane separation techniques that only use pressure as a driving force are microfiltration, ultrafiltration, nanofiltration and reverse osmosis. The corresponding four types of separation membrane materials have obvious differences in pore size, structure and operation pressure difference.
Although the super-wettability nanofiber separation membrane has great potential in treating oily wastewater and industrial oily wastewater, the existing related research and application are still in a primary exploration stage, and the aspects of theoretical research, preparation method, practical application and the like still face a series of challenges, and a fine microstructure constructed on the separation membrane is easily damaged mechanically and chemically polluted; the durability and acid and alkali resistance of the separation membrane need to be further improved; most of the innovative synthetic methods cannot be produced on a large scale; separation speed and membrane pore size are somewhat contradictory, and how to solve the problem of efficient and high-throughput separation of various small-sized substances is a problem to be solved.
Disclosure of Invention
In view of the above, the present invention provides a modified polypropylene oil-water separation membrane and a preparation method thereof, so as to at least partially solve the above technical problems.
In order to achieve the above technical objects, according to one aspect of the present invention, there is provided a method for preparing a modified polypropylene oil-water separation membrane, comprising:
providing a polypropylene porous film base material;
carrying out corona activation treatment on the polypropylene porous film base material under the conditions that the corona treatment temperature is not higher than 30 ℃, the corona power is 0.1-5000W and the corona time is 0.01-10 min to obtain an activated polypropylene film;
placing the activated polypropylene film in a grafting reaction solution to perform chemical grafting reaction, wherein the grafting reaction solution comprises a grafting monomer aqueous solution, and the grafting monomer contains an ethylenic functional group of carboxyl, amido, cyano, hydroxyl or amido;
and modifying two surfaces of the activated polypropylene film to obtain the modified polypropylene oil-water separation film.
According to the embodiment of the invention, the polypropylene porous film base material is a polypropylene microporous film or a nanofiber film; the pore diameter of the polypropylene microporous membrane or the nanofiber membrane comprises: 10-300 nm; the porosity of the polypropylene microporous membrane or the nanofiber membrane is not lower than 35%; the longitudinal tensile strength of the polypropylene microporous membrane or the nanofiber membrane is not lower than 80 MPa; the transverse tensile strength of the polypropylene microporous membrane or the nanofiber membrane is not lower than 25 MPa.
According to an embodiment of the present invention, the polypropylene porous film base material having a symmetrical structure comprises: and carrying out corona activation and grafting on two surfaces of the polypropylene porous film base material to obtain the modified polypropylene oil-water separation membrane.
According to the embodiment of the invention, the chemical grafting reaction is carried out on the activated polypropylene film to obtain the modified polypropylene oil-water separation membrane, which comprises the following steps:
and (2) placing the activated polypropylene film in a grafting reaction solution, carrying out deoxidization treatment, carrying out chemical grafting reaction at a first preset temperature for a first preset time, and cleaning and drying to obtain the modified polypropylene oil-water separation membrane.
According to the embodiment of the invention, before the grafting reaction, nitrogen or argon is used for oxygen removal; the deoxidizing time is 1-100 min.
According to an embodiment of the present invention, the grafting monomer includes any one of: acrylic acid, acrylamide, acrylonitrile, hydroxyethyl acrylate, dopamine;
the mass concentration of the grafting monomer in the grafting monomer aqueous solution comprises the following components: 1 to 30 wt%.
According to an embodiment of the present invention, the first preset temperature includes: 30-90 ℃; the first preset duration includes: 1-100 min, wherein the grafting rate to the modified polypropylene oil-water separation membrane comprises: 1 to 200 wt%.
According to an embodiment of the present invention, the solution used for the cleaning includes: deionized water and ethanol solution; the drying temperature includes: 40-70 ℃, wherein the drying time comprises: 6-36 h.
As another aspect of the present invention, the present invention also provides a modified polypropylene oil-water separation membrane having a graft structure containing a carboxyl group, an amide group, a cyano group, a hydroxyl group and an amine group.
According to an embodiment of the present invention, a modified polypropylene oil-water separation membrane obtained by any one of the above-described methods.
According to an embodiment of the present invention, the above-mentioned modified polypropylene oil-water separation membrane includes: the thickness of the modified polypropylene oil-water separation membrane is 5-150 mu m, the surface water contact angle of the modified polypropylene oil-water separation membrane is less than 20 degrees, the underwater surface oil contact angle of the modified polypropylene oil-water separation membrane is more than 150 degrees, and the water flux is 200L m-2h-1Above, the oil-water separation efficiency is not lower than 98%.
According to the embodiment of the invention, the polypropylene porous film base material is subjected to corona activation treatment, unstable active groups including free radicals or peroxy groups are generated on the surface of the polypropylene porous film base material through corona activation, and then an activated polypropylene film is obtained; the method comprises the following steps of carrying out chemical grafting reaction on an activated polypropylene film, and enabling unstable active groups generated on the surface of the activated polypropylene film to react with ethylenic bond functional groups of carboxyl, amido, cyano, hydroxyl or amido contained in a grafting monomer to generate nano particles to obtain the modified polypropylene oil-water separation film, wherein the grafting converts the hydrophobicity of fibers on the surface of the polypropylene film into hydrophilicity, changes the contact angle of water, and increases the water flux and the oil-water separation efficiency of the modified polypropylene oil-water separation film. However, other activation methods, such as electron beam, gamma ray, plasma, etc., cannot achieve the object of the present invention by simple chemical grafting. The preparation method of the modified polypropylene oil-water separation membrane provided by the invention is simple in process and controllable in process, and can be used for industrial production.
Drawings
FIG. 1 is a scanning electron micrograph schematically showing a modified polypropylene oil-water separation membrane prepared according to example one of the present invention;
fig. 2 schematically shows a scanning electron micrograph of the modified polypropylene oil-water separation membrane prepared in example two of the present invention.
Detailed Description
In order that the objects, technical solutions and advantages of the present invention will become more apparent, the present invention will be further described in detail with reference to the accompanying drawings in conjunction with the following specific embodiments.
In the related art, the widely used membrane separation method can only effectively separate the floating oil and the dispersed oil, the emulsified oil and the dissolved oil can not be effectively separated, and the membrane material for oil-water separation has the serious problem of membrane pollution.
The preparation of the anti-pollution separation membrane aiming at all types of oily wastewater has important research significance and application value.
In recent years, with the rise of surface and interface science, materials with special wettability, namely materials with hydrophilic, oleophilic, hydrophobic and oleophobic characteristics, are rapidly developed. Researches show that a material with special wettability can be obtained by regulating and controlling the microstructure or chemical composition of the surface of the material, and efficient oil-water separation can be realized by means of the special wettability of the material. Many attempts are made and certain progress and breakthrough are made in the aspect of separating the oil-water mixture by using the special wetting material, but the problems of limited types of the separated oil-water mixture, rigorous separation conditions, low efficiency, difficulty in continuous operation and the like still exist, and the design and construction of the material which has high-efficiency oil-water-oil-water separation efficiency and is easy for large-scale production become the key point of the research and development of the current oil-water separation material.
Therefore, the invention provides a preparation method of a modified polypropylene oil-water separation membrane, which comprises the following steps:
providing a polypropylene porous film base material; carrying out corona activation treatment on the polypropylene porous film base material under the conditions that the corona treatment temperature is not higher than 30 ℃, the corona power is 0.1-5000W and the corona time is 0.01-10 min to obtain an activated polypropylene film; placing the activated polypropylene film in a grafting reaction solution to perform chemical grafting reaction, wherein the grafting reaction solution comprises a grafting monomer aqueous solution, and the grafting monomer contains an ethylenic functional group of carboxyl, amido, cyano, hydroxyl or amido; and modifying two surfaces of the activated polypropylene film to obtain the modified polypropylene oil-water separation film.
In the embodiment of the invention, the polypropylene porous film base material is subjected to corona activation treatment, and unstable active groups are generated on the surface of the polypropylene porous film base material through corona activation to obtain an activated polypropylene film; the preparation method comprises the following steps of carrying out chemical grafting reaction on an activated polypropylene film, and enabling unstable active groups generated on the surface of the activated polypropylene film to react with ethylenic bond functional groups of carboxyl, amido, cyano, hydroxyl or amido contained in a grafting monomer to generate nanoparticles to obtain a modified polypropylene oil-water separation membrane.
According to the embodiment of the invention, the polypropylene porous film base material is a polypropylene microporous film or a nanofiber film; the pore diameter of the polypropylene microporous membrane or the nanofiber membrane comprises: 10-300 nm, and the porosity of the polypropylene microporous membrane or the nanofiber membrane is not less than 35%; the longitudinal tensile strength of the polypropylene microporous membrane or the nanofiber membrane is not lower than 80 MPa; the transverse tensile strength of the polypropylene microporous membrane or the nanofiber membrane is not lower than 25 MPa.
In the embodiment of the invention, the porous membrane can enable the base material to have higher specific surface area only by meeting the pore diameter and porosity, thereby providing a foundation for the subsequent functional modification of the porous membrane and the improvement of water flux; the mechanical property of the porous membrane is limited, so that the separation membrane has a good use effect, and the damage in the use process is prevented.
In the embodiment of the invention, the pore diameter of the polypropylene microporous membrane or the nanofiber membrane is 10-300 nm, such as 10nm, 50nm, 100nm, 150nm, 250nm and 300 nm; the porosity of the polypropylene microporous membrane or nanofiber membrane is not less than 35%, e.g., 40%, 50%, 80%; the polypropylene microporous membrane or nanofiber membrane has a longitudinal tensile strength of not less than 80MPa, for example, 90MPa, 100MPa, 150 MPa; the polypropylene microporous membrane or nanofiber membrane has a transverse tensile strength of not less than 25MPa, for example, 30MPa, 35MPa, 40 MPa.
According to an embodiment of the present invention, the above polypropylene porous film base material is subjected to corona activation treatment to obtain an activated polypropylene film comprising:
subjecting the polypropylene porous film base material to corona treatment at a temperature of not higher than 30 deg.C, e.g., 10 deg.C, 20 deg.C, 30 deg.C; the corona power is 0.1-5000W, such as 0.1W, 100W, 500W, 1000W, 2500W and 5000W; and performing corona activation treatment for 0.01-10 min (for example, 0.01min, 1min, 5min, 8min and 10 min) to obtain the activated polypropylene film.
In the embodiment of the invention, unstable active groups are generated on the surface of the polypropylene porous film base material through corona activation and are used for grafting reaction. These reactive groups include radicals, peroxy compounds, etc., and numerous experiments have shown that the composition of these reactive groups is particularly complex and that the object of the invention can only be achieved by corona treatment and by satisfying the above conditions. However, other activation methods, such as electron beam, gamma ray, plasma, etc., cannot achieve the object of the present invention by simple chemical grafting.
According to an embodiment of the present invention, the polypropylene porous film base material having a symmetrical structure comprises: and (3) carrying out corona activation and grafting on two surfaces of the polypropylene porous film base material to obtain the modified polypropylene oil-water separation membrane.
In the embodiment of the invention, the polypropylene porous film base material is a symmetrical film material, the surface of the polypropylene porous film base material is a smooth fiber net structure, and the modified polypropylene oil-water separation film symmetrical in the thickness direction is obtained by modifying two surfaces of the polypropylene porous film base material.
The invention modifies two sides of the polypropylene porous film simultaneously to obtain the modified polypropylene porous film, which has excellent structure and performance stability, higher water flux, excellent wettability and oil-water separation efficiency.
According to the embodiment of the invention, the chemical grafting reaction is carried out on the activated polypropylene film to obtain the modified polypropylene oil-water separation membrane, which comprises the following steps:
and (2) placing the activated polypropylene film in a grafting reaction solution, carrying out chemical grafting reaction at a first preset temperature for a first preset time, and cleaning and drying to obtain the modified polypropylene oil-water separation membrane.
In the embodiment of the invention, unstable active groups generated on the surface of the activated polypropylene film react with ethylenic functional groups of carboxyl, amido, cyano, hydroxyl or amido contained in the grafting monomer to generate nanoparticles, so as to obtain the modified polypropylene oil-water separation film, wherein the grafting converts the hydrophobicity of fibers on the surface of the polypropylene film into hydrophilicity, changes the oil-water contact angle, and increases the water flux and the oil-water separation efficiency of the modified polypropylene oil-water separation film.
In the embodiment of the invention, nitrogen or argon is used for deoxidizing before the grafting reaction begins; the time for the oxygen removal is 1-100 min, for example, 1min, 10min, 50min, 100 min.
In the embodiment of the invention, in order to prevent the free radicals or active groups generated by corona activation from quenching and improve the efficiency and uniformity of subsequent reactions, oxygen removal operation is carried out before the chemical grafting reaction is started.
According to an embodiment of the present invention, wherein the grafting monomer comprises any one of the following: acrylic acid, acrylamide, acrylonitrile, hydroxyethyl acrylate, dopamine;
the mass concentration of the grafting monomer in the grafting monomer aqueous solution comprises the following components: 1 to 30 wt%, for example, 1 wt%, 15 wt%, 25 wt%, 30 wt%.
In the examples of the present invention, the graft monomer contains an ethylenic functional group having hydrophilicity such as a carboxyl group, an amide group, a cyano group, a hydroxyl group, and an amine group.
According to an embodiment of the present invention, the first preset temperature includes: 30 to 90 ℃, e.g., 30 ℃, 50 ℃, 80 ℃, 90 ℃; the first preset duration includes: 1-100 min, for example, 1min, 20min, 50min, 80min, 100min, the grafting ratio to the modified polypropylene oil-water separation membrane comprises: 1 to 200 wt%, 1 wt%, 50 wt%, 100 wt%, 150 wt%, 200 wt%.
According to an embodiment of the present invention, the solution used for the cleaning includes: deionized water and ethanol solution; the drying temperature includes: 40-70 deg.C, e.g., 40 deg.C, 50 deg.C, 60 deg.C, 70 deg.C, the drying time comprising: 0.5 to 10 hours, for example, 0.5 hour, 1 hour, 5 hours, 10 hours.
In the embodiment of the present invention, for example, deionized water and ethanol solution are used as the cleaning solution to remove the solution in the post-treatment solution.
The invention also provides a modified polypropylene oil-water separation membrane with a grafting structure containing carboxyl, amido, cyano, hydroxyl and amido and with a pore diameter of 10-300 nm.
In the embodiment of the invention, the modified polypropylene oil-water separation membrane is obtained by reacting an unstable active group generated on the surface of an activated polypropylene membrane with an ethylenic bond functional group of carboxyl, amido, cyano, hydroxyl or amido contained in a grafting monomer to generate nanoparticles, wherein the grafting converts the hydrophobicity of fibers on the surface of the polypropylene membrane into hydrophilicity, changes the contact angle of water, and increases the water flux and the oil-water separation efficiency of the modified polypropylene oil-water separation membrane.
According to an embodiment of the present invention, the above-mentioned modified polypropylene oil-water separation membrane includes: the thickness of the modified polypropylene oil-water separation membrane is 5-150 mu m, the surface water contact angle of the modified polypropylene oil-water separation membrane is less than 20 degrees, the underwater surface oil contact angle of the modified polypropylene oil-water separation membrane is more than 150 degrees, and the water flux is 200L m-2h-1Above, the oil-water separation efficiency is not lower than 98%.
In the embodiment of the invention, the modified polypropylene oil-water separation membrane has excellent hydrophile lipophilicity, high water flux, super wettability and excellent oil-water separation efficiency.
The present invention will be explained in further detail with reference to specific examples.
The modified polypropylene oil-water separation membranes in the following examples were prepared according to the following general method, which comprises the following steps.
A preparation method of a modified polypropylene oil-water separation membrane can be applied to high-efficiency oil-water separation, and comprises the following steps:
the method comprises the following steps: carrying out corona activation treatment on a polypropylene porous film base material with the aperture of 10-300 nm, the porosity of not less than 35%, the longitudinal tensile strength of not less than 80MPa and the transverse tensile strength of not less than 25 MPa; the polypropylene porous film matrix material is a polypropylene microporous film or a nanofiber film and is prepared by a dry-process biaxial tension technology; the temperature of the corona activation treatment is not higher than 30 ℃, the corona power is 0.1-5000W, and the corona time is 0.01-10 min.
Step two: carrying out grafting reaction on the polypropylene porous film material subjected to corona activation treatment to obtain a modified polypropylene oil-water separation film which can be applied to high-efficiency oil-water separation; the grafting reaction is carried out by placing the activated polypropylene porous film into a grafting reaction solution for reaction for a period of time, taking out and cleaning to obtain a modified polypropylene oil-water separation film; the grafting reaction solution is a grafting monomer aqueous solution; used in grafting reaction solutionThe grafting monomer is acrylic acid, acrylamide, acrylonitrile, hydroxyethyl acrylate, dopamine and the like; the mass concentration range of the grafting monomer in the grafting reaction solution is 1-30 wt%; the solvent of the grafting reaction solution is deionized water; before the grafting reaction begins, oxygen removal operation is required; the oxygen removal operation is to remove oxygen in the reaction device and the reaction liquid by using nitrogen or argon; the oxygen removal time is 1-100 min; the grafting reaction temperature is 30-90 ℃; the grafting reaction time is 1-100 min; after the grafting reaction is finished, cleaning the modified polypropylene oil-water separation membrane by using deionized water and an ethanol solution to obtain a modified polypropylene oil-water separation membrane; the grafting rate of the modified polypropylene oil-water separation membrane is 1-200 wt%; the modified polypropylene oil-water separation membrane is dried after being cleaned; the drying equipment is a blast oven; the drying temperature is 40-70 ℃; the drying time is 0.5-10 h. The thickness of the prepared modified polypropylene oil-water separation membrane is 5-150 mu m, and the surface water contact angle of the modified polypropylene oil-water separation membrane is<20 degrees, modified polypropylene oil-water separation membrane underwater surface oil contact angle>150 DEG water flux of modified polypropylene oil-water separation membrane>200L m-2h-1Oil-water separation efficiency of oil-water separation membrane of modified polypropylene>98％。
Example 1
A preparation method of a modified polypropylene oil-water separation membrane is applied to high-efficiency oil-water separation.
The method comprises the following steps: preparing a polypropylene nanofiber membrane by a dry-method biaxial stretching method; carrying out corona activation treatment on the obtained polypropylene nanofiber membrane for 100s under the condition of 200W;
step two: placing the corona film in a grafting reaction solution, deoxidizing for 40min by using nitrogen, and carrying out grafting reaction for 60min in a 20 wt% acrylic acid solution at 80 ℃ under the water bath heating condition to prepare the functionalized grafted modified polypropylene oil-water separation film; and (3) washing the functionalized grafted modified polypropylene oil-water separation membrane with water to prepare the modified polypropylene oil-water separation membrane.
And (3) carrying out hydrophilicity test and Scanning Electron Microscope (SEM) characterization on the finally obtained modified polypropylene oil-water separation membrane.
Fig. 1 schematically shows a scanning electron micrograph of the modified polypropylene oil-water separation membrane prepared in example 1 of the present invention.
As shown in figure 1, the membrane surface of the three-dimensional connected network structure of the obtained modified polypropylene oil-water separation membrane constructs a nanoparticle structure. As is clear from fig. 1, the modified propylene oil-water separation membrane prepared in example 1 had a nanoparticle structure formed on the membrane surface of the three-dimensional interconnected network structure of the modified polypropylene oil-water separation membrane. The original hydrophobicity of the fibers on the nanofiber membrane is changed into hydrophilicity, and the hydrophilicity of the modified polypropylene oil-water separation membrane is endowed.
The results of the water contact angle measurement are shown in Table 1.
TABLE 1 measurement results of separation Membrane Performance
| Performance of | Example 1 | Example 2 | Example 3 | Comparative example 1 | Comparative example 2 | Comparative example 3 |
| Water contact Angle (°) | 10 | 18 | 0 | 0 | / | 95 |
| Underwater oil contact Angle (°) | 156 | 152 | 158 | 153 | / | / |
| Water flux (L m)-2h-1) | 1100 | 980 | 1300 | 690 | 30-60 | 150 |
| Oil-water separation efficiency (%) | 99.4 | 99.2 | 99.5 | 99 | 99 | / |
As can be seen from Table 1, the modified polypropylene oil-water separation membrane prepared in example 1 had a water contact angle of 10 degrees, an underwater oil contact angle of 156 degrees, and a water flux of 1100L m-2h-1And the oil-water separation efficiency is 99.4%, so that the hydrophilicity test shows that the modified polypropylene oil-water separation membrane prepared in example 1 has super-wettability, higher water flux and high oil-water separation efficiency.
Example 2
A preparation method of a modified polypropylene oil-water separation membrane can be applied to high-efficiency oil-water separation. The preparation method comprises the following steps:
the method comprises the following steps: preparing a polypropylene nanofiber membrane by a dry-method biaxial stretching method; carrying out corona activation treatment on the obtained polypropylene nanofiber membrane for 10s under the condition of 500W;
step two: placing the polypropylene nanofiber membrane subjected to corona in a grafting reaction solution, deoxidizing for 40min by using nitrogen, and carrying out grafting reaction for 30min in 20 wt% acrylamide solution at 80 ℃ under the water bath heating condition to prepare a modified polypropylene oil-water separation membrane; and washing the polypropylene separation membrane with water to obtain the modified polypropylene oil-water separation membrane.
And (3) carrying out hydrophilicity test and Scanning Electron Microscope (SEM) characterization on the finally obtained modified polypropylene oil-water separation membrane.
Fig. 2 schematically shows a scanning electron micrograph of the modified polypropylene oil-water separation membrane prepared in example 2 of the present invention.
As can be seen from FIG. 2, the nano-particle structure is constructed on the membrane surface of the three-dimensional connected network structure of the obtained modified polypropylene oil-water separation membrane. As is clear from fig. 2, the modified propylene oil-water separation membrane prepared in example 2 was provided with hydrophilicity by changing the original hydrophobicity of the fibers on the nanofiber membrane to hydrophilicity.
The results of the water contact angle measurement are shown in Table 1.
As can be seen from Table 1, the modified polypropylene oil-water separation membrane prepared in example 2 had a water contact angle of 18 degrees, an underwater oil contact angle of 152 degrees, and a water flux of 980L m-2h-1And the oil-water separation efficiency is 99.2%, so that the hydrophilicity test shows that the modified polypropylene oil-water separation membrane prepared in example 2 has super-wettability, higher water flux and high oil-water separation efficiency.
Example 3
A preparation method of a modified polypropylene oil-water separation membrane can be applied to high-efficiency oil-water separation. The preparation method comprises the following steps:
the method comprises the following steps: preparing a polypropylene nanofiber membrane by a dry-method biaxial stretching method; carrying out corona activation treatment on the obtained polypropylene nanofiber membrane for 40s under the condition of 500W;
step two: placing the polypropylene nanofiber membrane subjected to corona in a grafting reaction solution, deoxidizing for 40min by using nitrogen, and carrying out grafting reaction for 60min in 20 wt% acrylamide solution at 80 ℃ under the water bath heating condition to prepare a modified polypropylene oil-water separation membrane; and (3) washing the polypropylene separation membrane with water to obtain the modified polypropylene oil-water separation membrane with super wettability.
The results of the water contact angle measurement are shown in Table 1.
As is apparent from Table 1, the modified polypropylene oil-water separation membrane prepared in example 3 had a water contact angle of 0 degrees, an underwater oil contact angle of 158 degrees, and a water flux of 1300 degrees 1300L m-2h-1And the oil-water separation efficiency is 99.5%, so that the hydrophilicity test shows that the modified polypropylene oil-water separation membrane prepared in example 3 has super-wettability, higher water flux and high oil-water separation efficiency.
Comparative example 1
Comparative example 1 is a scientific research article published by Chinese scholars in Journal of Membrane Science, entitled Poly (vinyl alcohol) Modification of Poly (vinylidenefluoride) Microfiltration Membranes for Oil/Water Emulsion Separation of a non-environmental radial Method (Journal of Membrane Science 2021,619,118792), and a modified polyvinylidene Fluoride Separation Membrane was prepared according to the Method provided herein.
The results of the water contact angle measurement are shown in Table 1. As can be seen from Table 1, the modified polyvinylidene fluoride separation membrane prepared in comparative example 1 had a water contact angle of 0 °, an underwater oil contact angle of 153 °, and a water flux of 690Lm-2h-1The oil-water separation efficiency is 99%.
Comparative example 2
A commercial SUF submerged ultrafiltration membrane module from bi water resources was used.
The results of the water contact angle measurement are shown in Table 1.
As can be seen from Table 1, the water flux of comparative example 2 is 30 to 60L m-2h-1The oil-water separation efficiency is 99%.
Comparative example 3 a method for preparing a modified polypropylene oil-water separation membrane. The preparation method comprises the following steps:
the method comprises the following steps: preparing a polypropylene nanofiber membrane by a dry-method biaxial stretching method; performing electron beam irradiation activation treatment on the obtained polypropylene nanofiber membrane, wherein the irradiation dose is 15 kGy;
step two: placing the activated polypropylene nanofiber membrane in a grafting reaction solution to remove oxygen for 40min by using nitrogen, and carrying out grafting reaction for 60min in a 20 wt% acrylamide solution at 80 ℃ under the water bath heating condition to prepare a modified polypropylene oil-water separation membrane; and washing the polypropylene separation membrane with water to obtain the modified polypropylene oil-water separation membrane.
The results of the water contact angle measurement are shown in Table 1.
As can be seen from Table 1, the modified polypropylene oil-water separation membrane prepared in comparative example 3 had a water contact angle of 95 deg., and since the modified polypropylene oil-water separation membrane was still hydrophobic, the underwater oil contact angle test and the oil-water separation efficiency test were not conducted, and the water flux was only 150L m-2h-1. Therefore, the result shows that only the modified polypropylene oil-water separation membrane prepared by the method has wettability, higher water flux and higher oil-water separation efficiency.
Therefore, the modified polypropylene oil-water separation membranes prepared in examples 1 to 3 of the present invention were compared with those of comparative example 1 in terms of hydrophilicity and underwater oleophobicity.
The test result shows that the modified polypropylene oil-water separation membrane has super-wettability and excellent oil-water separation efficiency, and has higher water flux than comparative example 2 of comparative example 1.
Compared with the commercial membrane of the comparative example 2, the modified polypropylene oil-water separation membrane prepared by the method provided by the invention has the characteristics of hydrophilicity and lipophobicity, obviously increased water flux, high flux and high oil-water separation efficiency, and the polypropylene oil-water separation membrane is changed from hydrophobicity to super-hydrophilicity; the modified polypropylene oil-water separation membrane has good industrial application prospect in the fields of water treatment, ion adsorption and material separation.
The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are only exemplary embodiments of the present invention and are not intended to limit the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. A preparation method of a modified polypropylene oil-water separation membrane comprises the following steps:
providing a polypropylene porous film base material;
carrying out corona activation treatment on the polypropylene porous film base material under the conditions that the corona treatment temperature is not higher than 30 ℃, the corona power is 0.1-5000W and the corona time is 0.01-10 min to obtain an activated polypropylene film;
placing the activated polypropylene film in a grafting reaction solution to perform chemical grafting reaction, wherein the grafting reaction solution comprises a grafting monomer aqueous solution, and the grafting monomer contains an ethylenic functional group of carboxyl, amido, cyano, hydroxyl or amido;
and modifying two surfaces of the activated polypropylene film to obtain the modified polypropylene oil-water separation film.
2. The method of claim 1, wherein the polypropylene porous film matrix material is a polypropylene microporous membrane or a nanofiber membrane;
the pore diameter of the polypropylene microporous membrane or the nanofiber membrane comprises: 10-300 nm; the porosity of the polypropylene microporous membrane or the nanofiber membrane is not lower than 35%; the longitudinal tensile strength of the polypropylene microporous membrane or the nanofiber membrane is not lower than 80 MPa; the transverse tensile strength of the polypropylene microporous membrane or the nanofiber membrane is not lower than 25 MPa.
3. The method of claim 1, wherein the polypropylene apertured film base material having a symmetrical structure comprises: and carrying out corona activation and grafting on two surfaces of the polypropylene porous film base material to obtain the modified polypropylene oil-water separation membrane.
4. The method of claim 1, wherein the subjecting the activated polypropylene film to a chemical grafting reaction to obtain a modified polypropylene oil-water separation membrane comprises:
and placing the activated polypropylene film in a grafting reaction solution, carrying out deoxidization treatment, carrying out chemical grafting reaction at a first preset temperature for a first preset time, and cleaning and drying to obtain the modified polypropylene oil-water separation membrane.
5. The method of claim 1, wherein the grafting monomer comprises any one of: acrylic acid, acrylamide, acrylonitrile, hydroxyethyl acrylate, dopamine;
the mass concentration of the grafting monomer in the grafting monomer aqueous solution comprises the following components: 1 to 30 wt%.
6. The method of claim 4, wherein the first preset temperature comprises: 30-90 ℃; the first preset duration includes: 1-100 min, wherein the grafting ratio of the modified polypropylene oil-water separation membrane comprises: 1 to 200 wt%.
7. The method of claim 4, wherein the washing employs a solution comprising: deionized water and ethanol solution; the drying temperature comprises: and at 40-70 ℃, wherein the drying time comprises: 6-36 h.
8. A modified polypropylene oil-water separation membrane is a modified polypropylene oil-water separation membrane with a graft structure containing carboxyl, amido, cyano, hydroxyl and amido.
9. The modified polypropylene oil-water separation membrane according to claim 8, which is obtained by the method according to any one of claims 1 to 7.
10. The modified polypropylene oil-water separation membrane of claim 8, comprising: the thickness of the modified polypropylene oil-water separation membrane is 5-150 mu m, the surface water contact angle of the modified polypropylene oil-water separation membrane is less than 20 degrees, the underwater surface oil contact angle of the modified polypropylene oil-water separation membrane is more than 150 degrees, and the water flux is 200L m-2h-1Above, the oil-water separation efficiency is not lower than 98%.
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