Modified base membrane, graphene oxide nanofiltration membrane as well as preparation method and application of modified base membrane and graphene oxide nanofiltration membrane

Abstract

The invention provides a modified base membrane, a graphene oxide nanofiltration membrane and a preparation method and application thereof. The preparation method of the graphene oxide nanofiltration membrane comprises the following steps: soaking a to-be-treated base membrane in a modification liquid, and taking out the to-be-treated base membrane to obtain a modified base membrane, wherein the preparation raw materials of the modification liquid comprise m-phenylenediamine and persulfate; and loading the graphene oxide nanosheet on the modified base membrane to obtain the graphene oxide nanofiltration membrane. According to the present invention, the simple and easy membrane preparation method is adopted, on the premise of ensuring the stability of the graphene oxide nanofiltration membrane, the good flux and the good rejection rate on the dye molecules are achieved, the application prospect of the graphene oxide nanofiltration membrane in the water treatment direction is expanded, and the technical defect that the current graphene oxide nanofiltration membrane is easy to swell is solved.

Description

Technical Field

[0001] The present invention relates to the field of membrane separation in the direction of water treatment, and in particular to a modified base membrane, a graphene oxide nanofiltration membrane, and a preparation method and application thereof. Background Art

[0002] Water shortages and water pollution remain two of the most serious challenges facing the world. Printing and dyeing wastewater is considered one of the most difficult industrial wastewaters to treat due to its large volume, high content of organic pollutants, and small molecular weight. Traditional water treatment technologies, including physical, chemical, and biological methods, struggle to meet water quality requirements. The emergence of membrane separation technology has overcome the limitations of traditional water treatment methods. As one of the most advanced membrane separation technologies, nanofiltration membranes offer enhanced retention capabilities for small molecule pollutants.

[0003] The most typical nanofiltration membrane is graphene oxide. Graphene oxide contains abundant hydrophilic oxygen-containing functional groups, which give it a negative charge. Its unique two-dimensional layered nanochannels allow water molecules to pass through while retaining other molecules. Furthermore, the non-oxidized regions of graphene oxide provide a low-friction flow channel, enabling rapid diffusion of water molecules and improving water flux. However, the abundance of oxygen-containing functional groups on graphene oxide also makes it highly susceptible to water absorption and swelling in humid or aqueous environments, reducing the stability of graphene oxide nanofiltration membranes and resulting in low dye retention.

[0004] In view of this, it is necessary to provide a modified base membrane, a graphene oxide nanofiltration membrane, a preparation method and an application thereof, so as to solve or at least alleviate the technical problem of how to ensure the stability of the graphene oxide nanofiltration membrane and improve the dye retention rate. Summary of the Invention

[0005] The main purpose of the present invention is to provide a modified base membrane, a graphene oxide nanofiltration membrane, a preparation method and an application thereof, aiming to solve the above-mentioned technical problems of ensuring the stability of the graphene oxide nanofiltration membrane and improving the dye retention rate.

[0006] To achieve the above object, the present invention provides a method for preparing a modified base film, comprising: soaking the base film to be treated in a modifying liquid, and obtaining the modified base film after taking it out; the raw materials for preparing the modifying liquid include m-phenylenediamine and persulfate.

[0007] Furthermore, the concentration of m-phenylenediamine in the modifying liquid is 0.1-1.3 wt %; the molar ratio of m-phenylenediamine to the persulfate is 0.8-1.2:0.8-1.2; when the base film to be treated is immersed in the modifying liquid, the preparation time of the modifying liquid does not exceed 10 minutes; the persulfate includes ammonium persulfate.

[0008] Furthermore, the method for obtaining the modified liquid includes: mixing a m-phenylenediamine solution and a persulfate solution to obtain the modified liquid; the volume ratio of the m-phenylenediamine solution to the persulfate solution is 1:1-3; the solvent of the m-phenylenediamine solution includes a hydrochloric acid solution, and the solvent of the persulfate solution includes water; the mixing time is 1-10 minutes, and the mixing is carried out at a temperature of 20-50°C.

[0009] Furthermore, the soaking time is not less than 5 hours; the soaking is carried out at a temperature of 10-40° C.; the base membrane to be treated is hydrophilic; and the base membrane to be treated includes a hydrophilic polyethersulfone membrane.

[0010] The present invention also provides a modified base film, which is prepared by any of the above-mentioned methods for preparing the modified base film.

[0011] The present invention also provides a method for preparing a graphene oxide nanofiltration membrane, comprising: obtaining a modified base membrane using any of the above-mentioned methods for preparing a modified base membrane; then, loading graphene oxide nanosheets on the modified base membrane to obtain a graphene oxide nanofiltration membrane.

[0012] Furthermore, the graphene oxide nanosheets have carboxyl groups; the ratio of the graphene oxide nanosheets to the modified base film is 0.01-0.05 mg:44 cm 2 ;

[0013] The graphene oxide nanosheets are loaded in the form of a graphene oxide nanosheet dispersion;

[0014] The loading process includes: naturally depositing the graphene oxide nanosheet dispersion on the modified base film, and then performing vacuum filtration; the natural deposition time is 2-10 minutes.

[0015] The present invention also provides a graphene oxide nanofiltration membrane, which is prepared using any of the above-mentioned methods for preparing the graphene oxide nanofiltration membrane.

[0016] The present invention also provides a use of any of the graphene oxide nanofiltration membranes described above in filtering dyes.

[0017] Furthermore, the dye exists in water; the dye includes one or more of Evans blue, methyl blue, Congo red, chrome black T and methyl orange.

[0018] Compared with the prior art, the present invention has at least the following advantages:

[0019] The present invention adopts a simple and easy membrane preparation method, which ensures the stability of the graphene oxide nanofiltration membrane while achieving good flux and dye retention rate for dye molecules, expanding the application prospects of graphene oxide membranes in water treatment and solving the technical defects of current graphene oxide nanofiltration membranes caused by easy swelling.

[0020] In the present invention, m-phenylenediamine is reacted with a persulfate initiator to generate poly-m-phenylenediamine, which simultaneously grows in situ along the fiber structure of the base membrane. Subsequently, graphene oxide nanosheets are deposited on the surface of the modified base membrane. The nitrogen functional groups on the surface of the poly-m-phenylenediamine react with the -COOH groups on the graphene oxide to form amide bonds, thereby partially reducing the graphene oxide, achieving interlayer fixation, and preventing expansion.

[0021] The present invention conducts dye filtration experiments on graphene oxide nanofiltration membranes, intercepts dyes through size screening and electrostatic repulsion, and has good separation performance for dyes in water while ensuring high stability of the graphene oxide membrane. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0023] Figure 1 The SEM images of the base membrane before and after modification in Example 1 of the present invention are shown; in the figure, (a) is a hydrophilic polyethersulfone membrane; (b) is a modified base membrane B;

[0024] Figure 2 FTIR images of the base membrane before and after modification in Example 1 of the present invention; in the figure, PES is a hydrophilic polyethersulfone membrane, and PES-PmPD is a modified base membrane B;

[0025] Figure 3 This is a graph showing the relationship between the poly-m-phenylenediamine loading at different m-phenylenediamine concentrations in Example 1 of the present invention;

[0026] Figure 4 This is the SEM image of PES-PmPD-GO membrane material B in Example 2 of the present invention;

[0027] Figure 5Surface XPS graphs of PES-PmPD-GO membrane material B in Example 2 and PES-GO membrane material in Example 8 of the present invention; in the figure, PES-PmPD-GO refers to PES-PmPD-GO membrane material B in Example 2, and PES-GO refers to PES-GO membrane material in Example 8;

[0028] Figure 6 Graphene oxide deposition amounts and graphene oxide layer thicknesses in Example 2 of the present invention are shown in FIG.

[0029] Figure 7 This is a comparative analysis of the membrane flux and retention rate of PES-PmPD-GO membrane material B and PES-GO membrane in Example 8 of the present invention; in the figure, PES-PmPD-GO refers to PES-PmPD-GO membrane material B, and PES-GO refers to PES-GO membrane material.

[0030] The realization of the objectives, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0031] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0032] Moreover, the technical solutions between the various embodiments of the present invention may be combined with each other, but this must be based on the fact that ordinary technicians in this field can implement them. When the combination of technical solutions is mutually contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0033] When numerical ranges are given in the examples, it should be understood that, unless otherwise specified in the present invention, both endpoints of each numerical range and any value between the two endpoints can be selected. Unless otherwise defined, all technical and scientific terms used in the present invention are consistent with the prior art knowledge and description of the present invention by those skilled in the art. The present invention can also be implemented using any prior art methods, equipment and materials that are similar or equivalent to the methods, equipment and materials described in the examples of the present invention. In the present invention, the calculation method of membrane flux (J) is Where, V is the permeate volume (L), P is the nanofiltration pressure (bar), and A is the membrane area (m 2 ), △t is the nanofiltration time (h); the retention rate (R) is calculated as follows: Where Cp is the concentration of the permeate and Cf is the concentration of the initial solution.

[0034] The invention provides a method for preparing a modified base film, comprising: soaking a base film to be treated in a modifying liquid, and obtaining the modified base film after taking it out; the raw materials for preparing the modifying liquid include m-phenylenediamine and persulfate; and the persulfate includes ammonium persulfate.

[0035] In the present invention, when the treated base membrane is immersed in the modifying solution, the modifying solution is prepared within 10 minutes; that is, during the immersion process, the m-phenylenediamine and persulfate are mixed for less than 10 minutes, specifically 1-10 minutes, or even 3-7 minutes. It should be noted that the modifying solution needs to be freshly prepared in the present invention primarily because in situ growth is required on the membrane surface. Therefore, the m-phenylenediamine and persulfate are pre-mixed in the modifying solution before the immersion process is immediately performed.

[0036] In the present invention, the base membrane to be treated is hydrophilic and comprises a hydrophilic polyethersulfone membrane; that is, the hydrophilic polyethersulfone membrane can be used as the base membrane to be treated. The pore size of the base membrane to be treated is 0.1-0.3 μm, further 0.2-0.25 μm, and the base membrane to be treated can also be an ultrafiltration base membrane.

[0037] In the present invention, the prepared concentration of the m-phenylenediamine in the modified liquid is 0.1-1.3wt%, further 0.1-0.7wt%, and further 0.3-0.5wt%; the molar ratio of the m-phenylenediamine to the persulfate is 0.8-1.2:0.8-1.2; in the present invention, the prepared concentration is the concentration of the m-phenylenediamine at the final volume of the modified liquid.

[0038] In the present invention, the modified liquid is obtained by: mixing a m-phenylenediamine solution and a persulfate solution to obtain the modified liquid; before the mixing, dropwise adding the persulfate solution to the m-phenylenediamine solution at a rate of 5-15 mL / min, and stirring during the dropwise addition process.

[0039] The volume ratio of the m-phenylenediamine solution to the persulfate solution is 1:1-3; the solvent of the m-phenylenediamine solution includes a hydrochloric acid solution with a concentration of 1-3 mol / L, and the solvent of the persulfate solution includes water; the m-phenylenediamine solution is prepared from the m-phenylenediamine and the hydrochloric acid solution, and the persulfate solution is prepared from the persulfate and water. In the present invention, the mixing time does not exceed 10 minutes, further 1-10 minutes, and further 3-7 minutes; the mixing is carried out at a temperature of 20-50°C, and further at a temperature of 35-45°C.

[0040] Specifically, the m-phenylenediamine is dissolved in the hydrochloric acid solution and stirred for 5-15 minutes to obtain the m-phenylenediamine solution; the persulfate is dissolved in deionized water and stirred for 25-35 minutes to obtain the persulfate solution.

[0041] In the present invention, the soaking time is not less than 5 hours or not less than 8 hours, further 8-15 hours, further 8-10 hours; the soaking is carried out at a temperature of 10-40°C, specifically at room temperature.

[0042] The preparation method of the modified base film further comprises: drying the modified base film after being taken out; the drying method includes vacuum drying, forced air drying, etc.

[0043] The present invention also provides a modified base film, which is prepared by any of the above-mentioned methods for preparing the modified base film.

[0044] The present invention also provides a method for preparing a graphene oxide nanofiltration membrane, comprising: obtaining a modified base membrane by adopting any of the above-mentioned methods for preparing a modified base membrane; then, loading graphene oxide nanosheets on the modified base membrane to obtain a highly stable graphene oxide nanofiltration membrane (PES-PmPD-GO membrane material).

[0045] In the present invention, the graphene oxide nanosheets have carboxyl groups; specifically, the manufacturer of the graphene oxide nanosheets is Changzhou Sixth Element Materials Technology Co., Ltd., model SE3122, and its oxygen-containing functional groups include -OH, -COOH, and COC; the ratio of the graphene oxide nanosheets to the modified base film is 0.01-0.05 mg:44 cm 2 , further 0.018-0.05mg: 44cm 2 , further 0.02-0.05mg: 44cm 2 , further 0.02-0.03mg: 44cm 2 , can also be 0.018-0.022mg: 44cm 2 .

[0046] The graphene oxide nanosheets are loaded in the form of a graphene oxide nanosheet dispersion; the graphene oxide nanosheet dispersion comprises the graphene oxide nanosheets and water; the ratio of the graphene oxide nanosheets to water can be 0.01-0.05 mg / 50 mL, further 0.02-0.05 mg / 50 mL, and further 0.018-0.022 mg / 50 mL; in a specific operation, the graphene oxide nanosheets are ultrasonically dispersed in water to obtain the graphene oxide nanosheet dispersion; the power of the ultrasonic dispersion can be 300-500 W.

[0047] In the present invention, the loading process includes: naturally depositing the graphene oxide nanosheet dispersion on the modified base film, followed by vacuum filtration; the natural deposition time is 2-10 minutes. In specific operation, the graphene oxide dispersion is slowly poured onto the base film and naturally deposited for 2-10 minutes (preferably 3-7 minutes), followed by vacuum filtration; during the vacuum filtration, the vacuum pump parameter can be -0.1 MPa.

[0048] In the present invention, the method for preparing the graphene oxide nanofiltration membrane further comprises: after completing the loading, drying the loaded modified base membrane; the drying method may be vacuum drying.

[0049] As a supplementary explanation to the present invention, the present invention modifies the basement membrane to be treated by immersing it in a mixed solution of m-phenylenediamine and persulfate at a certain concentration. After immersion at room temperature for a certain period of time, the basement membrane is removed and dried to obtain a modified basement membrane. Graphene oxide nanosheets are deposited on the modified basement membrane by vacuum filtration to obtain a PES-PmPD-GO membrane material. The PES-PmPD-GO membrane is then used to study its dye separation performance. The graphene oxide nanofiltration membrane of the present invention can be prepared using a simple method. Molecular diffusion of poly(m-phenylenediamine) crosslinks the graphene oxide layers, maintaining the stability of the graphene oxide layers while exhibiting good membrane flux and extremely high dye retention.

[0050] In the present invention, the base membrane to be modified is immersed in a solution of m-phenylenediamine and persulfate. The m-phenylenediamine generates poly-m-phenylenediamine under the initiation of persulfate, and the poly-m-phenylenediamine can grow on the fiber structure of the base membrane. Subsequently, graphene oxide is deposited on the modified base membrane. The poly-m-phenylenediamine reacts with the carboxyl groups of the graphene oxide to form amide bonds, which fix the layers and prevent expansion, thereby forming a graphene oxide nanofiltration membrane with high stability.

[0051] The present invention also provides a highly stable graphene oxide nanofiltration membrane, which is prepared using any of the above-mentioned methods for preparing the graphene oxide nanofiltration membrane.

[0052] The present invention also provides a use of any of the graphene oxide nanofiltration membranes described above in filtering dyes.

[0053] In the present invention, the dye is an organic dye; the dye includes one or more of Evans blue, methyl blue, Congo red, chrome black T and methyl orange; further includes Evans blue, methyl blue, Congo red, chrome black T, preferably Congo red.

[0054] In the present invention, the dye is present in water, the concentration of the dye in the water is 15-25 mg / L, the filtration is nanofiltration, and the pressure of the nanofiltration process is 0.08-0.12 MPa.

[0055] As a supplementary explanation of the application in the present invention, the PES-PmPD-GO membrane of the present invention intercepts dye molecules through size screening and electrostatic exclusion, and the presence of interlayer amide bonds can alleviate the swelling phenomenon of graphene oxide.

[0056] The following are specific examples of the present invention:

[0057] Example 1

[0058] 1. Dissolve 0.15g, 0.625g, 1.07g, 1.55g and 2g of m-phenylenediamine in 50mL of 2mol / L hydrochloric acid solution respectively and stir for 10min to obtain m-phenylenediamine solution A, m-phenylenediamine solution B, m-phenylenediamine solution C, m-phenylenediamine solution D and m-phenylenediamine solution E respectively.

[0059] 0.32 g, 1.32 g, 2.26 g, 3.27 g and 4.23 g of ammonium persulfate were respectively dissolved in 100 mL of deionized water and stirred for 30 min to obtain ammonium persulfate solution A, ammonium persulfate solution B, ammonium persulfate solution C, ammonium persulfate solution D and ammonium persulfate solution E, respectively.

[0060] 2. Add m-phenylenediamine solution A to ammonium persulfate solution A at a rate of 10 mL / min and stir at 40°C for 5 min to obtain modified solution A.

[0061] Add m-phenylenediamine solution B to ammonium persulfate solution B at a rate of 10 mL / min, and stir at 40°C for 5 min to obtain modified solution B.

[0062] Add m-phenylenediamine solution C to ammonium persulfate solution C at a rate of 10 mL / min, and stir at 40°C for 5 min to obtain modified solution C.

[0063] Add m-phenylenediamine solution D to ammonium persulfate solution D at a rate of 10 mL / min, and stir at 40°C for 5 min to obtain modified solution D.

[0064] Add m-phenylenediamine solution E to ammonium persulfate solution E at a rate of 10 mL / min and stir at 40°C for 5 min to obtain modified solution E.

[0065] 3. Take a hydrophilic polyethersulfone membrane (manufacturer: Nantong Longjin Membrane Technology Co., Ltd., model: DPE090-022L-N0, pore size: 0.22 μm, diameter: 90 mm, round), and soak it in modifying liquid A, modifying liquid B, modifying liquid C, modifying liquid D, and modifying liquid E at room temperature for 9 hours, respectively. After taking it out, air dry it for 24 hours to obtain modified base membrane A, modified base membrane B, modified base membrane C, modified base membrane D, and modified base membrane E, respectively.

[0066] In this embodiment, the m-phenylenediamine concentration corresponding to the modified base film A is 0.1wt%, the m-phenylenediamine concentration corresponding to the modified base film B is 0.4wt%, the m-phenylenediamine concentration corresponding to the modified base film C is 0.7wt%, the m-phenylenediamine concentration corresponding to the modified base film D is 1wt%, and the m-phenylenediamine concentration corresponding to the modified base film E is 1.3wt%.

[0067] In this embodiment, see Figure 1 As shown, the modified base membrane fiber structure is obviously wrapped with a layer of polymer; see Figure 2 As shown, FTIR confirmed that this layer of polymer is poly(m-phenylenediamine); see Figure 3 As shown, the m-phenylenediamine concentration gradient is linearly related to the poly-m-phenylenediamine loading on the base membrane.

[0068] Example 2

[0069] After ultrasonically dispersing 0.01 mg, 0.02 mg, 0.03 mg, 0.04 mg and 0.05 mg of graphene oxide nanosheets in 50 mL of deionized water (ultrasonic power of 400 W), the obtained graphene oxide nanosheet dispersions were deposited (loaded) on the modified base membrane B in Example 1, and vacuum dried for 24 hours to obtain PES-PmPD-GO membrane material A, PES-PmPD-GO membrane material B, PES-PmPD-GO membrane material C, PES-PmPD-GO membrane material D, and PES-PmPD-GO membrane material E, respectively.

[0070] In this and subsequent examples, although the membrane diameter is 90 mm, after being installed in the filtration device, the diameter that can participate in the load is 75 mm, and the area of the load area on the membrane for deposition corresponds to 44 cm 2 .

[0071] In this embodiment, the manufacturer of the graphene oxide nanosheets is Changzhou Sixth Element Materials Technology Co., Ltd., the model number is SE3122, and the graphene oxide nanosheets have oxygen-containing functional groups such as -OH, -COOH, and COC.

[0072] In this embodiment, the deposition (loading) process is as follows: slowly pouring the graphene oxide nanosheet dispersion onto the modified base film B and allowing it to naturally deposit for 5 minutes, followed by vacuum filtration, with the vacuum pump parameter being -0.1 MPa.

[0073] In this embodiment, see Figure 4 As shown, graphene oxide is tightly connected to the base film; see Figure 5 As shown, the nitrogen functional groups on the surface of poly(m-phenylenediamine) react with the -COOH groups on graphene oxide to form amide bonds; see Figure 6 As shown, the deposition amount of graphene oxide is linearly related to the thickness.

[0074] Example 3

[0075] Take the PES-PmPD-GO membrane material B in Example 2 (cut in the loading area before use), and use the PES-PmPD-GO membrane material B to filter the Evans blue dye (Evans blue aqueous solution).

[0076] In this example, the dye concentration is 20 mg / L, the pressure of the nanofiltration process is 0.1 MPa, and the membrane area is 8 cm 2 , the nanofiltration time is 90min.

[0077] Example 4

[0078] Take the PES-PmPD-GO membrane material B in Example 2 (cut in the loading area before use), and use the PES-PmPD-GO membrane material B to filter the methyl blue dye (methyl blue aqueous solution).

[0079] In this example, the dye concentration is 20 mg / L, the pressure of the nanofiltration process is 0.1 MPa, and the membrane area is 8 cm 2 , the nanofiltration time is 90min.

[0080] Example 5

[0081] Take the PES-PmPD-GO membrane material B in Example 2 (cut in the loading area before use), and use the PES-PmPD-GO membrane material B to filter the Congo red dye (aqueous solution of Congo red).

[0082] In this example, the dye concentration is 20 mg / L, the pressure of the nanofiltration process is 0.1 MPa, and the membrane area is 8 cm 2 , the nanofiltration time is 90min.

[0083] Example 6

[0084] Take the PES-PmPD-GO membrane material B in Example 2 (cut in the loading area before use), and use the PES-PmPD-GO membrane material B to filter the chrome black T dye (aqueous solution of chrome black T).

[0085] In this example, the dye concentration is 20 mg / L, the pressure of the nanofiltration process is 0.1 MPa, and the membrane area is 8 cm 2 , the nanofiltration time is 90min.

[0086] Example 7

[0087] Take the PES-PmPD-GO membrane material B in Example 2 (cut in the loading area before use), and use the PES-PmPD-GO membrane material B to filter the methyl orange dye (aqueous solution of methyl orange).

[0088] In this example, the dye concentration is 20 mg / L, the pressure of the nanofiltration process is 0.1 MPa, and the membrane area is 8 cm 2 , the nanofiltration time is 90min.

[0089] Analysis example 1

[0090] The membrane flux and rejection rate in Examples 3-7 were analyzed. The rejection rate of PES-PmPD-GO membrane material B for Evans blue, methyl blue, Congo red and chrome black T exceeded 95%, and the membrane flux exceeded 30LMH / bar, or was around 30LMH / bar.

[0091] Specifically, in Examples 3-7, the retention rates of Evans blue, methyl blue, Congo red, chrome black T, and methyl orange were 99%, 98%, 99%, 95%, and 85%, respectively; the membrane fluxes of Evans blue, methyl blue, Congo red, chrome black T, and methyl orange were 28LMH / bar, 36LMH / bar, 47LMH / bar, 31LMH / bar, and 33LMH / bar, respectively.

[0092] Example 8

[0093] 1. Compared with the preparation process of PES-PmPD-GO membrane material B in Example 2, only the modified base membrane B was adjusted to a hydrophilic polyethersulfone membrane (unmodified, consistent with the material used in Example 1), and other conditions remained unchanged to obtain a PES-GO membrane material.

[0094] 2. Take the PES-GO membrane material and the PES-PmPD-GO membrane material B in Example 2, cut them in the load area, and filter Congo red dye (Congo red aqueous solution) respectively; the dye concentration is 20 mg / L, the pressure of the nanofiltration (filtration) process is 0.1 MPa, and the membrane area is 8 cm 2 , the nanofiltration time is 90min.

[0095] In this example, the rejection rate of PES-GO membrane for Congo red dye is only 65% because graphene oxide swells in water, while the rejection rate of PES-PmPD-GO membrane material B for Congo red dye remains at 99%, showing good stability. For XPS comparison analysis of PES-PmPD-GO membrane material B and PES-GO membrane, see Figure 5 As shown; the membrane flux and rejection rate comparison of PES-PmPD-GO membrane material B and PES-GO membrane can be seen in Figure 7 shown.

[0096] Specifically, the membrane fluxes corresponding to PES-PmPD-GO membrane material B and PES-GO membrane material are 47LMH / bar and 77LMH / bar, respectively; the retention rates corresponding to PES-PmPD-GO membrane material B and PES-GO membrane material are 99% and 65%, respectively.

[0097] Example 9

[0098] Compared with the preparation process of PES-PmPD-GO membrane material B in Example 2, only the modified base membrane B was adjusted to modified base membrane A, modified base membrane C, modified base membrane D, and modified base membrane E in Example 1, and other conditions remained unchanged, obtaining PES-PmPD-GO membrane material a, PES-PmPD-GO membrane material c, PES-PmPD-GO membrane material d, and PES-PmPD-GO membrane material e, respectively.

[0099] PES-PmPD-GO membrane materials a, c, d, and e were cut in the loading area and then filtered with Congo red dye (aqueous solution of Congo red). The dye concentration was 20 mg / L, the pressure during the nanofiltration (filtration) process was 0.1 MPa, and the membrane area was 8 cm. 2 , the nanofiltration time is 90min.

[0100] In this embodiment, the membrane fluxes of PES-PmPD-GO membrane material a, PES-PmPD-GO membrane material c, PES-PmPD-GO membrane material d, and PES-PmPD-GO membrane material e were 42LMH / bar, 37LMH / bar, 25LMH / bar, and 17LMH / bar, respectively, and the rejection rates were 97%, 98%, 97%, and 97%, respectively.

[0101] Example 10

[0102] Take the PES-PmPD-GO membrane material A, PES-PmPD-GO membrane material C, PES-PmPD-GO membrane material D, and PES-PmPD-GO membrane material E in Example 2; after cutting in the load area, filter Congo red dye (Congo red aqueous solution) respectively; the dye concentration is 20 mg / L, the pressure of the nanofiltration (filtration) process is 0.1 MPa, and the membrane area is 8 cm 2 , the nanofiltration time is 90min.

[0103] In this embodiment, the membrane fluxes of PES-PmPD-GO membrane material A, PES-PmPD-GO membrane material C, PES-PmPD-GO membrane material D, and PES-PmPD-GO membrane material E are 52LMH / bar, 27LMH / bar, 13LMH / bar, and 8LMH / bar, respectively, and the retention rates are 78.65%, 99%, 99%, and 99%, respectively.

[0104] The above technical solutions of the present invention are only preferred embodiments of the present invention and do not limit the patent scope of the present invention. All equivalent structural transformations made by using the contents of the present invention's description and drawings under the technical concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A method for preparing a modified base film, characterized in that: include: Soaking the base film to be treated in the modification liquid, and taking it out to obtain the modified base film; The modified liquid is prepared from raw materials including m-phenylenediamine and persulfate.

2. The method for preparing a modified base film according to claim 1, wherein: The concentration of m-phenylenediamine in the modifying liquid is 0.1-1.3 wt %; the molar ratio of m-phenylenediamine to the persulfate is 0.8-1.2:0.8-1.2; when the base film to be treated is immersed in the modifying liquid, the preparation time of the modifying liquid does not exceed 10 minutes; the persulfate includes ammonium persulfate.

3. The method for preparing a modified base film according to claim 1, wherein: The method for obtaining the modified liquid includes: mixing a m-phenylenediamine solution and a persulfate solution to obtain the modified liquid; the volume ratio of the m-phenylenediamine solution to the persulfate solution is 1:1-3; the solvent of the m-phenylenediamine solution includes a hydrochloric acid solution, and the solvent of the persulfate solution includes water; the mixing time is 1-10 minutes, and the mixing is performed at a temperature of 20-50°C.

4. The method for preparing a modified base film according to claim 1, wherein: The soaking time is not less than 5 hours; the soaking is carried out at a temperature of 10-40° C.; the base membrane to be treated is hydrophilic; and the base membrane to be treated includes a hydrophilic polyethersulfone membrane.

5. A modified base film, characterized in that: The modified base film is prepared by the preparation method of any one of claims 1 to 4.

6. A method for preparing a graphene oxide nanofiltration membrane, characterized in that: include: Obtaining a modified base film by adopting the preparation method of the modified base film according to any one of claims 1 to 4; Then, the graphene oxide nanosheets are loaded on the modified base membrane to obtain a graphene oxide nanofiltration membrane.

7. The method for preparing a graphene oxide nanofiltration membrane according to claim 6, wherein The graphene oxide nanosheets have carboxyl groups; the ratio of the graphene oxide nanosheets to the modified base film is 0.01-0.05 mg:44 cm 2 ; The graphene oxide nanosheets are loaded in the form of a graphene oxide nanosheet dispersion; The loading process includes: naturally depositing the graphene oxide nanosheet dispersion on the modified base film, and then performing vacuum filtration; The duration of the natural sedimentation is 2-10 minutes.

8. A graphene oxide nanofiltration membrane, characterized in that The graphene oxide nanofiltration membrane is prepared by the preparation method of the graphene oxide nanofiltration membrane according to claim 6 or 7.

9. Use of the graphene oxide nanofiltration membrane according to claim 8 in filtering dyes.

10. The use according to claim 9, characterized in that The dye exists in water; the dye includes one or more of Evans blue, methyl blue, Congo red, chrome black T and methyl orange.

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