Modified separation membrane and preparation method and application thereof

Abstract

The application relates to a modified separation membrane in the technical field of membrane materials, a preparation method and application thereof. The modified separation membrane comprises a base film and a nanostructure layer on the upper surface of the base film and the membrane hole surface close to one side of the upper surface of the base film; wherein the pore size of the base film is 120-400 mu m; the nanostructure layer is composed of microparticles with a size of 100-1000 nm; the preparation method comprises 3D printing of the separation membrane; and the upper surface of the separation membrane and the membrane hole surface close to one side of the upper surface of the separation membrane are subjected to plasma treatment. The modified separation membrane preparation method combines the 3D printing technology and the membrane separation technology, improves the traditional membrane preparation process, finds a more optimal membrane replacement process, and the modification method is free of chemical agents, has the advantages of being more convenient and fast to operate, high in separation efficiency, low in processing cost, green and pollution-free, and the like, and has important significance in the aspects of membrane separation technology improvement and application of oily wastewater treatment.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of film materials, in particular to a modified separation film and a preparation method and application thereof. BACKGROUND

[0002] Due to frequent oil leakage accidents and increasing oil-containing wastewater caused by industrial production, the global ecological environment is seriously damaged, and the treatment of oil-containing wastewater is crucial. The membrane technology is considered to be one of the most effective technologies for oil-water separation at present, which has the advantages of low cost, simple operation, high efficiency and ecological friendliness. However, in the actual oil-water separation process, the separation efficiency is easily restricted by the trade-off effect between flux and separation efficiency, and the membrane pollution phenomenon is prone to occur, which leads to the blockage of the membrane holes and affects the separation efficiency and service life of the membrane. SUMMARY

[0003] The application aims to provide a modified separation film and a preparation method and application thereof. The modified separation film provided by the application has a very high flux, has superhydrophilicity and oil-repellency under water, and can realize efficient oil-water separation through gravity.

[0004] According to a first aspect of the application, a modified separation film is provided, comprising a base film and a nanostructure layer on the upper surface of the base film and the membrane hole surface close to the upper surface of the base film; wherein the pore size of the base film is 120-400 mu m; the nanostructure layer is composed of microparticles with a size of 100-1000 nm.

[0005] By using the modified separation film in the technical solution, the pore size of the membrane hole of the base film is set to 120-400 mu m, preferably 140-200 mu m, the mutual restriction of the selection performance and the permeation performance is overcome, and the nanostructure layer is formed on the upper surface of the base film and the membrane hole surface close to the upper surface of the base film through the plasma treatment technology, so that the surface of the separation film is rough and contains hydroxyl groups, thereby improving the hydrophilicity, ensuring a high flux under the premise of ensuring a high separation efficiency, having superhydrophilicity and oil-repellency under water, and realizing efficient oil-water separation through gravity.

[0006] In addition, the modified separation film according to the application can be further improved in terms of material and structure, as listed below.

[0007] In some embodiments of the application, the base film and the nanostructure layer are both made of acrylonitrile-butadiene-styrene copolymer.

[0008] In some embodiments of the application, the molar proportion of each monomer of the acrylonitrile-butadiene-styrene copolymer is that acrylonitrile accounts for 15% to 35%, butadiene accounts for 5% to 30%, and styrene accounts for 40% to 60%.

[0009] In some embodiments of the present application, the modified separation membrane is formed by plasma treatment of the upper surface of the separation membrane and the membrane hole surface close to the upper surface of the separation membrane.

[0010] In some embodiments of the present application, the thickness of the base membrane is 254-610 μm.

[0011] In some embodiments of the present application, the modified separation membrane has an oil-water separation retention rate of not less than 99% under the action of gravity, and a membrane flux of not less than 100000 L·m -2 ·h -1 ;

[0012] Preferably, the oil-water mixture has an oil to water ratio of 0.4-9:1.

[0013] The definition of "retention rate" in the present application is: R = (1-C1 / C0)*100%, wherein R is the retention rate, C1 is the oil concentration of the permeate, and C0 is the oil concentration of the feed liquid.

[0014] The definition of "flux" in the present application is: the amount of water passing through per square meter of membrane area per hour.

[0015] According to a second aspect of the present application, a method for preparing the modified separation membrane described above is provided, comprising: 3D printing a separation membrane; and plasma treating the upper surface of the separation membrane and the membrane hole surface close to the upper surface of the separation membrane.

[0016] In addition, the preparation method according to the present application can also have the following additional technical features:

[0017] In some embodiments of the present application, in the plasma treatment step, air is used as the reaction gas for plasma treatment, and a nanostructure layer is formed on the surface; wherein the radio frequency frequency is 12-15 MHz, and the radio frequency power is 6.8-18 W.

[0018] In some embodiments of the present application, the plasma treatment time is 2.5-3.5 minutes.

[0019] Preferably, the plasma treatment time is 3 minutes.

[0020] According to a third aspect of the present application, the modified separation membrane described above is provided for use in oil-water separation.

[0021] Compared with the prior art, the technical scheme of the present application has the following beneficial effects:

[0022] 1. The application is prepared by using plasma to treat the 3D printed base film to obtain a plasma modified ABS separation membrane, which has super hydrophilicity and underwater oleophobicity modified separation membrane and excellent anti-fouling performance and cycle flux, and the rejection rate of diesel oil-containing wastewater under the action of gravity can reach more than 99%, and the membrane flux can reach 100000L·m -2 ·h -1 Therefore, it has good economic benefits.

[0023] 2. The application uses a 3D printer to directly print an ABS base film, which only needs to input the design model into the printer, without manual operation for film preparation, so that a membrane with regular shape and neat membrane hole arrangement can be obtained. The method for preparing the membrane is simple and fast, the operation method is simple, the cost is low, and the method has obvious promotion advantages.

[0024] 3. The application modifies the membrane by a simple plasma method; the operation method is simple and fast, the modification method is solvent-free, non-toxic and green, and is suitable for large-scale industrial application.

[0025] 4. The modified separation membrane prepared by the application has very high water flux and rejection rate, and can complete efficient oil-water separation under the action of gravity driving, and has good anti-pollution property and recyclability, so that the service life of the membrane is increased, and the method has obvious promotion advantages. BRIEF DESCRIPTION OF DRAWINGS

[0026] Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The accompanying drawings are included to provide a description of the preferred embodiments and are not meant to limit the scope of the present application. Moreover, the same reference numerals in the attached drawings indicate the same or similar components. In the drawings:

[0027] Figure 1 is a preparation flowchart of the super-hydrophilic plasma ABS modified separation membrane of the application;

[0028] Figure 2 is a SEM diagram of the ABS base film and the plasma treated separation membrane, Figure 2 a is the ABS base film, Figure 2 b-f are modified separation membranes treated by plasma for different times;

[0029] Figure 3 is a flux and oil-water separation efficiency diagram of the ABS original membrane and the ABS modified separation membrane with different pore sizes under the action of gravity, Figure 3 a is a flux diagram, Figure 3 b is an oil-water separation efficiency diagram. DETAILED DESCRIPTION

[0030] It should be noted that the embodiments described are merely some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of protection of the present application.

[0031] The following description refers to the accompanying drawings. In the following description, same numbers in different drawings represent the same or similar elements unless otherwise represented. The implementations described in the following exemplary embodiments are not meant to represent all implementations consistent with the present application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of the present application as detailed in the appended claims.

[0032] In the description of the present application, it should be understood that the terms "first", "second", etc. are used only for the purpose of description, and cannot be understood as indicating or implying relative importance. For those of ordinary skill in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances. In addition, in the description of the present application, "multiple" means two or more, unless otherwise stated. The association between the associated objects is described as "and / or", which means that there can be three relationships, for example, A and / or B can represent the following three cases: A exists alone, A and B exist together, and B exists alone. The character " / " generally represents an "or" relationship between the associated objects before and after it.

[0033] Although membrane technology has the advantages of low cost, simple operation, high efficiency and ecological friendliness, it is considered to be one of the most effective technologies for existing oil-water separation. However, in the actual separation process, it is easy to be restricted by the "trade-off" effect between flux and separation efficiency, and membrane pollution phenomenon is easy to occur, which leads to membrane hole blockage, affecting the separation efficiency and service life of the membrane.

[0034] Therefore, the problem of membrane pollution has become one of the problems to be solved in membrane separation technology. In addition to further breakthroughs on the basis of existing advantages, it is necessary to develop a membrane separation technology with higher separation efficiency and more friendly to the ecological environment. However, it is difficult for current membrane materials to make a major breakthrough in this regard, and finding new membrane processes is the main breakthrough point at present.

[0035] The exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. As shown, the preparation method of the plasma-modified 3D-printed separation membrane includes the steps of base film 3D printing, base film cleaning and drying, and base film plasma treatment. Figure 1

[0036] Embodiment 1

[0037] The present embodiment provides a plasma-modified 3D-printed ABS separation membrane, and the preparation method thereof is as follows:

[0038] ​Base film 3D printing; an industrial 3D printer (F170, Stratasys, USA) prints the ABS base film with uniform and regular membrane holes according to the designed coordinates by the fused deposition technology, the thickness of the base film is 254 microns, and the acrylonitrile-butadiene-styrene (ABS) copolymer used has a CAS number of 9003-56-9, a molecular formula of C 15 H 17 N, a molecular weight of 211.30218, and a molar ratio of each monomer in the acrylonitrile-butadiene-styrene copolymer of acrylonitrile: butadiene: styrene = 1:1:2, and the precision of the 3D printer is set to 0.005 inches.

[0039] Since the printing model needs to be fused and deposited on the soluble support material, when separated, it is soaked in a sodium hydroxide solution with a temperature of 70 DEG C and a pH of 12 for 10 minutes until the model can be easily peeled off.

[0040] The ABS base film with a pore size of 300*400 microns is obtained, and the corresponding plasma modified 3D printed ABS separation film is prepared according to the following steps.

[0041] Base film cleaning and drying; the prepared ABS base film is thoroughly cleaned with pure water, then air-dried to remove water, or can also be placed in an oven at 60 DEG C for drying to obtain a pretreated ABS base film.

[0042] Base film plasma treatment; using a plasma surface treatment device, specifically a Harrick plasma cleaning machine PDC-32G-2, the base film is treated by plasma in a vacuum state with air as the reaction gas to form a nano structure layer on the surface of the base film; wherein the radio frequency frequency is 13.56 MHz and the radio frequency power is 18 W.

[0043] Examples 2-18 use the same preparation process as Example 1, the only difference is the pore size of the ABS base film and the plasma treatment time.

[0044] The specific membrane hole size and process parameters in Examples 1-18 in the application are shown in Table 1 below.

[0045] Table 1 Related parameters of plasma modified 3D printed ABS separation film

[0046]

[0047]

[0048] Since the influence of different plasma treatment time on the ABS separation membrane is only the surface microstructure, the optical images of the ABS modified separation membranes of Examples 2, 5, 8, 11, 14 and 17 are selected, and the optical images of each ABS modified separation membrane include three different magnifications, and the optical image scales are 10 μm, 2 μm and 400 nm, respectively, so as to be more intuitive to observe.

[0049] The optical images of the ABS original membrane and the ABS modified separation membranes after plasma treatment are shown in Figure 2 Figure 2 a is the image of the ABS original membrane, i.e. the optical image of Example 5 without plasma treatment, Figure 2 b-f are the images of the plasma treatment for 1-5 minutes, i.e. the optical images of Examples 8, 11, 2, 14 and 17, respectively.

[0050] According to the SEM images, we can see that the surface of the ABS original membrane is relatively smooth. After using plasma treatment for 1 minute, the surface of the membrane has no obvious change; with the increase of the plasma treatment time, the surface structure of the membrane is gradually destroyed, forming a nanostructure similar to foam; using plasma treatment makes the surface of the membrane rough, which is beneficial to the increase of the hydrophilicity of the membrane. Figure 2

[0051] Through the wettability test of the membrane, under the condition of the radio frequency of 13.56 MHz and the radio frequency power of 18 W, when the plasma treatment time is 3 minutes, the hydrophilicity of the membrane is the best, i.e. the optimal treatment time. With the increase of the treatment time, the performance of the membrane does not obviously improve, i.e. the optimal value is reached at 3 minutes, and there is no practical significance to increase the treatment time, and there are problems such as waste of energy consumption. Therefore, the plasma instrument treatment time is about 2.5-3.5 min, which is the best; according to the difference of the base film material, such as the base film material is styrene-acrylonitrile-acrylate rubber body copolymer or polyurethane and other thermoplastic polymer materials, and the difference of the radio frequency and the radio frequency power, the treatment time can also be adjusted accordingly, so as to make the nanostructure layer reach the optimal performance.

[0052] Experimental Example

[0053] The ABS modified separation membranes of Examples 1-3 and the ABS original membranes of Examples 4-6 are selected, diesel oil and water are mixed in a ratio of 1:1, and the separation test of the oil-water mixture is carried out only under the action of gravity. The test results are shown in Figure 3 Figure 3 ​​​Fig. 1 is a diagram showing the membrane flux and retention rate of ABS original film and ABS modified separation film with 300 mμm*400 mμm, 140 mμm*200 mμm and 120 mμm*120 mμm aperture, wherein Bare is ABS original film, and modified is ABS modified separation film, Figure 3 a is a diagram showing the membrane flux, Figure 3 b is a diagram showing the retention rate of oil in oil-water separation.

[0054] As shown in Figure 3 a, as a whole, the membrane flux of ABS modified separation film of Comparative Examples 1-3, or ABS original film of Examples 4-6, decreases with the decrease of aperture; and for the same aperture of the film, the flux of ABS modified separation film after plasma treatment is significantly improved than that of ABS original film without treatment, for Comparative Examples 1 and 4, Examples 2 and 5, and Examples 3 and 6.

[0055] As shown in Figure 3 b, the subsequent oil-water separation experiment shows that the separation efficiency of ABS original film of Comparative Examples 4, 5 and 6 is 0% regardless of the aperture size, which indicates that ABS original film cannot be used for oil-water separation. The separation efficiency of oil-water mixture of ABS modified separation film of Example 1 and ABS original film of Example 4 is also 0%, which indicates that although the hydrophilicity and oil-repellency under water of ABS modified separation film of Example 1 are greatly improved, the too large aperture still cannot make the oil be retained on the film surface. Reducing the aperture of the film to make the liquid surface tension larger can make the oil be completely retained on the film surface, for example, the retention rate of diesel oil of ABS modified separation film of Examples 2 and 3 reaches more than 99.70%, and the smaller the aperture, the higher the retention rate. And the ABS modified separation film of Example 2 has extremely high retention rate and flux, the retention rate is 99.75%, and the flux is 117304 L·m -2 ·h -1 .

[0056] The above merely describes the preferred embodiments of the present application, but the protection scope of the present application is not limited thereto, and any changes or replacements within the technical scope disclosed by the present application can be easily thought by those skilled in the art, which should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A modified separation membrane, characterized in that, The modified separation membrane comprises a base membrane made of acrylonitrile-butadiene-styrene copolymer and a nanostructure layer of acrylonitrile-butadiene-styrene copolymer on the upper surface of the base membrane and on the pore surface near the upper surface of the base membrane; the modified separation membrane is formed by plasma treatment of the upper surface of the separation membrane made of acrylonitrile-butadiene-styrene copolymer and the pore surface near the upper surface of the separation membrane. The pore size of the base film is 120-400 μm; The nanostructure layer is composed of particles with a size of 100-1000 nm.

2. The modified separation membrane according to claim 1, characterized in that, The molar percentages of the monomers in the acrylonitrile-butadiene-styrene copolymer are as follows: acrylonitrile accounts for 15% to 35%, butadiene accounts for 5% to 30%, and styrene accounts for 40% to 60%.

3. The modified separation membrane according to claim 1, characterized in that, The thickness of the base film is 254-610 μm.

4. The modified separation membrane according to claim 1, characterized in that, The modified separation membrane has an oil-water rejection rate of not less than 99% under gravity and a membrane flux of not less than 100,000 L·m⁻¹. -2 ·h -1 .

5. A method for preparing the modified separation membrane according to any one of claims 1-4, characterized in that, include: 3D printing separation membrane; Plasma treatment is performed on the upper surface of the separation membrane and the membrane pore surface on the side close to the upper surface of the separation membrane.

6. The preparation method according to claim 5, characterized in that, In the plasma treatment step, air is used as the reactive gas for plasma treatment to form a nanostructure layer on the surface; wherein the radio frequency is 12-15MHz and the radio frequency power is 6.8-18W.

7. The preparation method according to claim 6, characterized in that, The plasma treatment time is 2.5-3.5 minutes.

8. The preparation method according to claim 7, characterized in that, The plasma treatment time is 3 minutes.

9. The application of a modified separation membrane prepared by the method of any one of claims 1-4 or any one of claims 5-8 in oil-water separation.

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