Super-hydrophilic oil-water separation membrane, and preparation method and application thereof

Abstract

The application belongs to the technical field of membrane separation materials, and discloses an ultrahydrophilic oil-water separation membrane, a preparation method and application thereof, and comprises the following steps: 2-(2-bromoisobutyryloxy)ethyl methacrylate monomers are prepared from 2-hydroxyethyl methacrylate and 2-bromoisobutyryl bromide, and a polymer with an atom transfer radical polymerization initiator is prepared through a free radical polymerization reaction; the polymer with the atom transfer radical polymerization initiator and polyacrylonitrile are dissolved into a solvent, and a PAN / P(AN-g-BIEM) blended membrane is prepared through a non-solvent induced phase separation method; and a hydrophilic polymer brush is grafted to the surface of the PAN / P(AN-g-BIEM) blended membrane to obtain the ultrahydrophilic oil-water separation membrane; the ultrahydrophilic oil-water separation membrane prepared by the application has a high separation flux, excellent oil-water separation efficiency and separation performance for different oil-in-water emulsions.

Description

Technical Field

[0001] This invention belongs to the field of membrane separation materials technology, and specifically relates to a superhydrophilic oil-water separation membrane, its preparation method, and its application. Background Technology

[0002] With the rapid development of industry, the petrochemical, food, textile, metal, and machinery industries discharge large amounts of oily wastewater. This oily wastewater is difficult to separate effectively using traditional separation methods, causing serious pollution problems. Membrane separation technology has advantages such as high demulsification separation efficiency, low energy consumption, simple operation process, no secondary pollution, and strong versatility, showing broad application prospects in the field of emulsified oily wastewater treatment. However, traditional membrane materials, especially polymer membranes, are easily contaminated by oil droplets during actual use, leading to a decrease in separation flux and thus a significant decrease in separation efficiency. Summary of the Invention

[0003] To address the technical problems existing in the prior art, this invention provides a superhydrophilic oil-water separation membrane, its preparation method, and its application, in order to solve the technical problem that traditional membrane materials are easily contaminated by oil droplets in the treatment of emulsified oily wastewater, leading to a decrease in separation flux and thus a significant decrease in separation efficiency.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0005] This invention provides a method for preparing a superhydrophilic oil-water separation membrane, comprising:

[0006] 2-(2-bromoisobutyryloxy)ethyl methacrylate monomer was prepared by using 2-hydroxyethyl methacrylate and 2-bromoisobutyryl bromide;

[0007] A polymer with an atom transfer radical polymerization initiator was prepared by using the 2-(2-bromoisobutyryloxy)ethyl methacrylate monomer via free radical polymerization.

[0008] The polymer with the atom transfer radical polymerization initiator was dissolved in a solvent with polyacrylonitrile, and a PAN / P(AN-g-BIEM) blend membrane was prepared by a non-solvent-induced phase separation method.

[0009] The superhydrophilic oil-water separation membrane is obtained by brush grafting a hydrophilic polymer onto the surface of the PAN / P(AN-g-BIEM) blend membrane using atom transfer radical polymerization.

[0010] Furthermore, the process for preparing 2-(2-bromoisobutyryloxy)ethyl methacrylate monomer using 2-hydroxyethyl methacrylate and 2-bromoisobutyryl bromide is as follows:

[0011] Dichloromethane, triethylamine, and hydroxyethyl methacrylate were mixed and reacted under cold water bath conditions. Then, 2-bromoisobutyryl bromide was added and reacted under nitrogen protection and ice-water bath conditions to obtain the reaction product.

[0012] The reaction product is filtered and washed to obtain a filtrate;

[0013] The filtrate is washed to obtain an organic phase;

[0014] The organic phase was dried, filtered, and distilled under reduced pressure to obtain a yellow liquid, which is the monomer of 2-(2-bromoisobutyryloxy) methacrylate.

[0015] Furthermore, the process of preparing a polymer with an atom transfer radical polymerization initiator by using the 2-(2-bromoisobutyryloxy)ethyl methacrylate monomer via free radical polymerization is as follows:

[0016] The 2-(2-bromoisobutyryloxy)ethyl methacrylate monomer, ACN, AIBN and N,N-dimethylformamide were mixed and subjected to free radical polymerization to obtain the free radical polymerization product.

[0017] The free radical polymerization product is subjected to precipitation, dissolution, and reprecipitation to obtain a polymer with an atom transfer radical polymerization initiator.

[0018] Furthermore, the process of preparing a PAN / P (AN-g-BIEM) blend membrane by dissolving the polymer with the atom transfer radical polymerization initiator in a solvent containing polyacrylonitrile and employing a solvent-inducing phase separation method is as follows:

[0019] The polymer containing the atom transfer radical polymerization initiator, polyacrylonitrile, additives and solvent are mixed and stirred until completely dissolved. The mixture is then placed in a vacuum oven and allowed to stand to remove air bubbles, thus obtaining the casting solution.

[0020] The casting solution was subjected to phase inversion to obtain a PAN / P(AN-g-BIEM) blend membrane.

[0021] Furthermore, the additive is polyvinylpyrrolidone, and the solvent is N,N-dimethylformamide.

[0022] Furthermore, the mass ratio of the polymer with the atom transfer radical polymerization initiator to the polyacrylonitrile is (1-4):(6-9).

[0023] Furthermore, the hydrophilic polymer brush is a hydrophilic zwitterionic polymer brush pSBMA.

[0024] Furthermore, the process of grafting a hydrophilic polymer onto the surface of the PAN / P (AN-g-BIEM) blend membrane using atom transfer radical polymerization to obtain the superhydrophilic oil-water separation membrane is as follows:

[0025] The PAN / P(AN-g-BIEM) blend membrane, methanol and water were mixed in a mixed solvent, and 2,2'-bipyridine and methacryloylethyl sulfobetaine were mixed and stirred to degas, so as to obtain a reaction mixture solution.

[0026] Cuprous bromide was added to the reaction mixture, and atom transfer radical polymerization was carried out under a nitrogen atmosphere to obtain an ATRP polymerized modified film.

[0027] The ATRP polymer-modified membrane was washed and dried to obtain the superhydrophilic oil-water separation membrane.

[0028] The present invention also provides a superhydrophilic oil-water separation membrane, which is prepared by the aforementioned method for preparing superhydrophilic oil-water separation membranes.

[0029] The present invention also provides an application of a superhydrophilic oil-water separation membrane, which is used to separate oil and water in emulsified oily wastewater.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0031] This invention provides a superhydrophilic oil-water separation membrane and its preparation method. It utilizes 2-hydroxyethyl methacrylate and 2-bromoisobutyryl bromide to prepare 2-(2-bromoisobutyryloxy)ethyl methacrylate monomer. The 2-(2-bromoisobutyryloxy)ethyl methacrylate monomer undergoes free radical polymerization to prepare a polymer with an atom transfer radical polymerization initiator. This polymer with the atom transfer radical polymerization initiator is used as a halogenated macromolecular initiator and added to the casting solution. The density of ATRP-initiated active sites is controlled by adjusting the feed ratio. A PAN / P (AN-g-BIEM) blend membrane is then prepared using a solvent-inducible phase separation method. A superhydrophilic oil-water separation membrane was prepared by grafting hydrophilic zwitterionic polymer brushes (pSBMA) onto the surface of a blend membrane using ATRP polymerization. The superhydrophilic oil-water separation membrane prepared in this invention exhibits high separation flux, excellent oil-water separation efficiency, and separation performance for different oil-in-water emulsions. The substrate of the superhydrophilic oil-water separation membrane contains a large amount of P(AN-g-BIEM) copolymer, providing ample reaction sites and enhancing the hydrophilicity of the membrane. Simultaneously, the superhydrophilic oil-water separation membrane is grafted with zwitterionic polymer brushes possessing excellent hydrophilicity via atom transfer radical polymerization, forming a hydration layer on the membrane surface, which significantly reduces pollutant adsorption and deposition.

[0032] Furthermore, the mass ratio of the polymer with the atom transfer radical polymerization initiator to the polyacrylonitrile is controlled at (1-4):(6-9). Using PAN / P (AN-g-BIEM) as the substrate of the separation membrane, a superhydrophilic oil-water separation membrane is prepared by ATRP polymerization. The obtained superhydrophilic oil-water separation membrane can separate different oil-in-water emulsions, providing a new idea and method for the preparation of oil-water separation and the antifouling performance of the membrane. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 The monomer of 2-(2-bromoisobutyryloxy)ethyl methacrylate (BIEM) in Example 1 1 H-NMR spectrum;

[0035] Figure 2 The P(AN-g-BIEM) copolymer in Example 1 1 H-NMR spectrum;

[0036] Figure 3 SEM images of the PAN / P(AN-g-BIEM) blend membrane and the PAN-PSBMA membrane in Example 1;

[0037] Figure 4 The infrared spectra of the PAN film, PAN / P(AN-g-BIEM) blend film, and PAN-PSBMA film in Example 1 are shown below; curve a is the infrared spectrum of the PAN film; curve b is the infrared spectrum of the PAN / P(AN-g-BIEM) blend film; and curve c is the infrared spectrum of the PAN-PSBMA film.

[0038] Figure 5 This is a schematic diagram showing the change of water contact angle over time for the PAN membrane, PAN / P(AN-g-BIEM) blend membrane, and PAN-PSBMA membrane in Example 1.

[0039] Figure 6 The separation efficiency and throughput of the superhydrophilic oil-water separation membranes prepared by polymers with atom transfer radical polymerization initiators and polyacrylonitrile in Examples 1-4 at mass ratios of 1:9, 2:8, 3:7, and 4:6 for petroleum ether / oil-in-water emulsions are shown.

[0040] Figure 7 This is a bar chart showing the separation flux of the superhydrophilic oil-water separation membrane for different oil-in-water emulsions in Example 2. Detailed Implementation

[0041] To make the technical problems, technical solutions, and beneficial effects solved by this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0042] This invention provides a method for preparing a superhydrophilic oil-water separation membrane, comprising the following steps:

[0043] Step 1: Prepare 2-(2-bromoisobutyryloxy)ethyl methacrylate (BIEM) monomer using 2-hydroxyethyl methacrylate (HEMA) and 2-bromoisobutyryl bromide (BiBB).

[0044] The process for preparing BIEM monomers is as follows:

[0045] Dichloromethane, triethylamine, and hydroxyethyl methacrylate were mixed and reacted in an ice-water bath for a predetermined time. Then, BiBB was added using a constant-pressure dropping funnel, and the reaction was carried out in an ice-water bath under nitrogen protection to obtain the reaction product. The reaction product was filtered to remove the precipitated solid, which was washed with dichloromethane. The filtrate was then washed successively with deionized water, NaHCO3 aqueous solution, and saturated NaCl aqueous solution to obtain the organic phase. The organic phase was dried with anhydrous sodium sulfate, filtered, and distilled under reduced pressure to remove dichloromethane from the filtrate. The resulting yellow liquid was the BIEM monomer.

[0046] Step 2: Using the BIEM monomer, a polymer (P(AN-g-BIEM)) with an atom transfer radical polymerization (ATRP) initiator is prepared by free radical polymerization reaction; wherein, P(AN-g-BIEM) is a macromolecular initiator containing a halide.

[0047] Specifically, the preparation process of (P(AN-g-BIEM)) includes the following steps:

[0048] BIEM monomer, ACN and AIBN were dissolved in N,N-dimethylformamide (DMF) to obtain a reaction solution. The solution was stirred under a nitrogen atmosphere to carry out a free radical polymerization reaction to obtain a free radical polymerization product. The polymerization product was purified by precipitation, dissolution and reprecipitation to obtain P(AN-g-BIEM).

[0049] Step 3: Dissolve P(AN-g-BIEM) and polyacrylonitrile (PAN) in a preset solvent and prepare a PAN / P(AN-g-BIEM) blend membrane by a non-solvent-induced phase separation method; wherein the preset solvent is N,N-dimethylformamide (DMF).

[0050] Specifically, the preparation process of the PAN / P(AN-g-BIEM) blend membrane includes the following steps:

[0051] Polyvinylpyrrolidone (PVP) was added to DMF as an additive and stirred until completely dispersed to obtain a PVP dispersion. P(AN-g-BIEM) and PAN were added to the PVP dispersion at a mass ratio of (1-4):(6-9), and stirring was continued until completely dissolved. The mixture was then placed in a vacuum oven to stand and remove air bubbles to obtain a casting solution. The casting solution was subjected to phase inversion to obtain a PAN / P(AN-g-BIEM) blend membrane.

[0052] Step 4: Using atom transfer radical (ATRP) polymerization, a hydrophilic polymer brush is grafted onto the surface of the PAN / P (AN-g-BIEM) blend membrane to prepare the superhydrophilic oil-water separation membrane; wherein, the hydrophilic polymer brush is a hydrophilic zwitterionic polymer brush pSBMA.

[0053] Specifically, the process of grafting a hydrophilic polymer onto the surface of the PAN / P (AN-g-BIEM) blend film using atom transfer radical polymerization (ATRP) is as follows:

[0054] The PAN / P(AN-g-BIEM) blend membrane was placed in a reactor, and a mixed solvent of methanol and deionized water, 2,2'-bipyridine, and methacryloylethyl sulfobetaine were added. The mixture was stirred and degassed to obtain a reaction mixture. Cuprous bromide was added to the reaction mixture, and ATRP polymerization was carried out under a nitrogen atmosphere to obtain an ATRP polymerized modified membrane. The ATRP polymerized modified membrane was washed and dried to obtain the superhydrophilic oil-water separation membrane.

[0055] Preparation principle:

[0056] The method for preparing the superhydrophilic oil-water separation membrane of the present invention firstly synthesizes BIEM monomer through the reaction between HEMA and BiBB; then, a macromolecular initiator containing halides, namely P(AN-g-BIEM), is prepared by free radical polymerization of the BIEM monomer; the prepared P(AN-g-BIEM) is added to the casting solution, and the density of ATRP initiation active sites is controlled by adjusting the feed ratio of PAN and P(AN-g-BIEM); then, a PAN / P(AN-g-BIEM) blend membrane is prepared by solvent-inducible phase separation; finally, using P(AN-g-BIEM) as a site, zwitterionic pSBMA is grafted onto the surface of the PAN / P(AN-g-BIEM) blend membrane by ATRP polymerization, which further improves the wettability of the membrane, and the pSBMA establishes a stable hydration layer on the membrane surface, preventing oil from penetrating into the membrane interior, thus increasing the surface hydrophilicity and water flux.

[0057] Example 1

[0058] This embodiment 1 provides a method for preparing a superhydrophilic oil-water separation membrane, including the following steps:

[0059] Step 1: Add 97.8 g of dichloromethane, 15.6 g of triethylamine, and 10.0 g of HEMA to a 250 mL three-necked round-bottom flask. Place the flask containing dichloromethane, triethylamine, and HEMA in an ice-water bath, purge with nitrogen, and react at 0 °C for 45 min. Then, add 21.2 g of BiBB over 30 min using a constant-pressure dropping funnel. Next, react in an ice-water bath under nitrogen protection for 6 h to obtain the reaction product. Filter the reaction product to remove the precipitated solid. Wash the solid with dichloromethane. Wash the filtrate twice, successively with 200 mL of deionized water, 200 mL of 0.5 mol / L NaHCO3 aqueous solution, and 200 mL of saturated NaCl aqueous solution, to obtain the organic phase. Dry the organic phase with anhydrous sodium sulfate and filter. Then, perform vacuum distillation to remove dichloromethane from the filtrate to obtain a yellow solution, which is the BIEM monomer.

[0060] Step 2: Dissolve BIEM monomer, ACN, and AIBN in N,N-dimethylformamide (DMF) to obtain a reaction solution; wherein the molar ratio of BIEM monomer to ACN in the reaction solution is 105:1; purge the reaction solution with nitrogen gas for at least 20 min, then stir at 80 °C under a nitrogen atmosphere to carry out a free radical polymerization reaction for 12 h to obtain a free radical polymerization product; precipitate the reaction product in methanol and collect the solid product by filtration; redissolve the solid product in 10 mL of DMF, precipitate it again in a mixture of acetone and methanol, filter, and place the collected solid product in a vacuum drying oven at 20 °C for more than 2 days to obtain P(AN-g-BIEM) polymer; wherein the volume ratio of acetone to methanol in the mixture of acetone and methanol is 1:1.

[0061] Step 3: Dissolve 0.15g of polyvinylpyrrolidone (PVP) in 4.325mL of DMF and stir at 65℃ and 600rpm for 0.5h until PVP is completely dispersed to obtain a PVP dispersion. Then, add P(AN-g-BIEM) and PAN in a mass ratio of 1:9 to the PVP dispersion. After that, continue stirring and dissolving at 65℃ for 10h to obtain the initial casting solution. Place the initial casting solution in a vacuum oven for vacuum degassing for 30min and let it stand at room temperature for 6h to completely remove the air bubbles and form a uniform casting solution. Place the uniform casting solution on a glass substrate and use a 250μm thick doctor blade to evenly coat it onto the glass substrate to obtain a membrane substrate. Then, transfer it to a pure water coagulation bath for phase inversion. After standing for 24h, transfer the membrane to deionized water and soak it for 48h to remove residual solvent and store it for later use to obtain a PAN / P(AN-g-BIEM) blend membrane.

[0062] Step 4: The PAN / P (AN-g-BIEM) blend membrane was placed in a mixed solvent of 100 mL methanol and 100 mL deionized water. 133.6 mg of 2,2'-bipyridine and 1.2 g of SBMA were added, and the mixture was stirred and degassed twice to obtain a reaction mixture. Then, 40 mg of CuBr was added to the reaction mixture, and the polymerization reaction was carried out at 60 °C under a nitrogen atmosphere for 12 h. After the reaction was completed, the membrane was washed three times with deionized water and ethanol, and then dried to obtain the superhydrophilic oil-water separation membrane.

[0063] Example 2

[0064] The preparation method of the superhydrophilic oil-water separation membrane provided in this embodiment 2 is basically the same as the preparation method of the superhydrophilic oil-water separation membrane described in embodiment 1 above in terms of process and principle; the difference is that in step 3 of embodiment 2, P(AN-g-BIEM) and PAN are added to the PVP dispersion in a mass ratio of 2:8; the remaining steps are the same and will not be described again here.

[0065] Example 3

[0066] The preparation method of the superhydrophilic oil-water separation membrane provided in this embodiment 3 is basically the same as the preparation method of the superhydrophilic oil-water separation membrane described in embodiment 1 above in terms of process and principle; the difference is that in step 3 of embodiment 3, P(AN-g-BIEM) and PAN are added to the PVP dispersion in a mass ratio of 3:7; the remaining steps are the same and will not be described again here.

[0067] Example 4

[0068] The preparation method of the superhydrophilic oil-water separation membrane provided in Example 4 is basically the same in process and principle as the preparation method of the superhydrophilic oil-water separation membrane described in Example 1 above; the difference is that in step 3 of Example 4, P(AN-g-BIEM) and PAN are added to the PVP dispersion in a mass ratio of 4:6; the remaining steps are the same and will not be repeated here.

[0069] Performance test results analysis and explanation:

[0070] As attached Figure 1 As shown, attached Figure 1 The example 1 provides the monomer of 2-(2-bromoisobutyryloxy)ethyl methacrylate (BIEM). 1 H-NMR spectrum; from the attached Figure 1 As can be seen, δ = 6.16 ppm (1H), 5.62 ppm (1H, CH2=C), 4.45 ppm (4H, -CH2-CH2-), 1.97 ppm (9H, CH3, C(Br)(CH3)2). The peak positions of the above peaks are completely consistent with the peak positions of the monomer. At the same time, the ratio of the peak area size is consistent with the ratio of the number of hydrogen atoms in the monomer at the above peak positions, indicating that the target product BIEM monomer was successfully synthesized.

[0071] As attached Figure 2 As shown, attached Figure 2 The P(AN-g-BIEM) copolymer in Example 1 is given in the example. 1 The H-NMR spectrum; from the attached Figure 2As can be seen, CH protons along the skeleton (a) appear at around 3-3.3 ppm, CH2 protons along the skeleton appear at around 1.9-2.3 ppm, and CH2 protons in BIEM (b) appear at around 4.3-4.5 ppm. All hydrogens in the P(AN-g-BIEM) copolymer have been assigned, proving that the P(AN-g-BIEM) copolymer was successfully synthesized.

[0072] As attached Figure 3 As shown, attached Figure 3 The attached document provides SEM images of the PAN / P(AN-g-BIEM) blend membrane and the PAN-PSBMA membrane from Example 1; Figure 3 As can be seen from the scanning electron microscope (SEM) observation of the surface and cross-sectional morphology of the membrane, the SEM results show that the prepared membrane has an asymmetric structure composed of a dense top layer and a porous sublayer, which originates from the instantaneous phase separation phenomenon of the PAN casting solution during the preparation process; among which, as shown in the attached figure... Figure 3 (a) Figure 3 (b) Figure 3 As shown in (c), at the same magnification, all membranes exhibit well-distributed nanoporous surfaces. Based on SEM images, the average surface pore size is estimated to be approximately 0.01 μm, typical of ultrafiltration (UF) membranes, displaying a distinct porous structure; see attached image. Figure 3 (d) Figure 3 (e) Figure 3 As shown in (f), a cross-sectional scanning electron microscope image of the prepared membrane is displayed. A very similar asymmetric membrane structure with large and wide finger-shaped voids can be clearly observed in most cross-sectional areas of all the membranes. The above results indicate that the surface modification process of the pSBMA chain does not affect the internal structure of the PAN membrane.

[0073] As attached Figure 4 As shown, attached Figure 4 The infrared spectra of the PAN film, PAN / P(AN-g-BIEM) blend film, and PAN-PSBMA film in Example 1 are given in Appendix 1; Figure 4 As can be seen from the graph, curve a is the infrared spectrum curve of the PAN film, located at 2937 cm⁻¹. -1 2242cm -1 and 1452cm -1 The characteristic peaks at 1731 cm⁻¹ are attributed to the stretching vibration peaks of CH, C≡N, and CC, respectively. -1 The peak at 1271 cm⁻¹ is attributed to the C=O absorption peak, possibly because the polyacrylonitrile used is an industrial product and may contain other copolymers with C=O functional groups; curve b is the infrared spectrum of the PAN / P(AN-g-BIEM) blend film, at 1271 cm⁻¹. -1 It is the stretching vibration peak of CO in BIEM, 643 cm⁻¹-1 The absorption peak at 1041 cm⁻¹ is the stretching vibration peak of C-Br in BIEM, indicating the successful preparation of the PAN / P(AN-g-BIEM) blend membrane; curve c is the infrared spectrum of the PAN-PSBMA membrane, with the peak at 1041 cm⁻¹. -1 1193cm -1 An infrared absorption peak, which can be attributed to O=S=O, appeared at 1625 cm⁻¹. -1 The location that can be attributed to -CN appeared. + The infrared absorption peak is at 627 cm⁻¹. -1 The presence of an infrared absorption peak that can be attributed to a CS bond indicates that pSBMA was successfully grafted onto the surface of the blend film.

[0074] As attached Figure 5 As shown, attached Figure 5 The diagram below shows the water contact angle of the PAN membrane, PAN / P(AN-g-BIEM) blend membrane, and PAN-PSBMA membrane over time in Example 1. To evaluate the hydrophilicity of the prepared membranes, the change in the water contact angle in the air was measured over a predetermined time period. Figure 5 The results show that the initial WCA of the PAN membrane was 78.2°, which decreased to approximately 53.2° after about 360 seconds. Compared to the original PAN membrane, the hydrophilicity of the PAN / P(AN-g-BIEM) membrane slightly increased, with an initial WCA of 67.4°, which decreased to approximately 48.8° after 360 seconds, indicating better water adsorption. The initial WCA of the PAN-PSBMA membrane was 57.8°, which was lower than that of the PAN / P(AN-g-BIEM) membrane, and it reached 0° within about 300 seconds. The difference in WCA between the PAN / P(AN-g-BIEM) and PAN-PSBMA membranes is mainly due to the hydrophilicity of the zwitterionic polymer on the surface of the PAN-PSBMA membrane. These results indicate that the zwitterionic polymer brushes modified on the membrane surface greatly improve the surface energy of the membrane, thus giving the PAN-PSBMA membrane its excellent hydrophilicity.

[0075] As attached Figure 6 As shown, attached Figure 6 The figure shows the separation efficiency and flux of superhydrophilic oil-water separation membranes prepared in Examples 1-4 with the mass ratio of the polymer with the atom transfer radical polymerization initiator to the polyacrylonitrile being 1:9, 2:8, 3:7, and 4:6, respectively, for petroleum ether / oil-in-water emulsions; from the figure... Figure 6 As can be seen from the data, the separation flux of the superhydrophilic oil-water separation membranes prepared in Examples 1-4 is 431.026 Lm, respectively. -2 h -1 bar -1 263.881Lm -2 h-1 bar -1 258.657Lm -2 h -1 bar -1 and 240.657Lm -2 h -1 bar -1 The separation efficiencies were 90.13%, 91.09%, 91.06%, and 91.06%, respectively, with an additional pressure of 2 bar introduced during the flux tests. The experimental results showed that the flux of the four membranes differed significantly, mainly due to the amount of P(AN-g-BIEM) copolymer added. Among them, the membrane with the highest separation efficiency was obtained when the mass ratio of the polymer with the atom transfer radical polymerization initiator to the polyacrylonitrile was 8:2.

[0076] As attached Figure 7 As shown, attached Figure 7 Example 2 presents the permeation flux of a superhydrophilic oil-in-water separation membrane prepared at a mass ratio of 2:8 of the polymer with an atom transfer radical polymerization initiator to the polyacrylonitrile for four different oil-in-water emulsions: toluene / water, petroleum ether / water, n-hexane / water, and 1,2-dichloroethane / water. The fluxes are 154.9 Lm. -2 h -1 bar -1 263.8Lm -2 h -1 bar -1 134.518Lm -2 h -1 bar -1 and 121.092Lm -2 h -1 bar -1 An additional pressure of 2 bar was introduced during the above flux test. As can be seen from the results, the flux of the four oil-in-water emulsions differs greatly, which is mainly related to the properties of the oil itself.

[0077] The superhydrophilic oil-water separation membrane and its preparation method described in this invention synthesize BIEM monomer through the reaction between HEMA and BiBB; prepare a macromolecular initiator, P(AN-g-BIEM), using free radical polymerization; add the prepared P(AN-g-BIEM) macromolecular initiator to the casting solution, and control the density of ATRP initiation active sites by controlling the feed ratio; prepare a PAN / P(AN-g-BIEM) blend membrane using a solvent-inducible phase separation method; and graft a hydrophilic zwitterionic polymer brush (pSBMA) onto the membrane using ATRP polymerization. A superhydrophilic oil-water separation membrane was prepared on the surface of a mixed membrane. The substrate of the prepared superhydrophilic oil-water separation membrane contains a large amount of P(AN-g-BIEM) copolymer, providing ample reaction sites and improving the hydrophilicity of the separation membrane. Simultaneously, the superhydrophilic oil-water separation membrane is grafted with a zwitterionic polymer brush exhibiting excellent hydrophilicity via atom transfer radical polymerization, forming a hydration layer on the membrane surface, significantly reducing pollutant adsorption and deposition. Furthermore, the oil-water separation composite membrane possesses high separation flux, excellent oil-water separation efficiency, and excellent separation performance for different oil-in-water emulsions.

[0078] In this invention, the density of ATRP-initiated active sites is controlled by adjusting the feed ratio of the polymer with the atom transfer radical polymerization initiator to the polyacrylonitrile; the adsorption and deposition of pollutants are greatly reduced by forming a hydrated layer on the membrane surface; and it has high separation flux, excellent oil-water separation efficiency, and separation performance for different oil-in-water emulsions.

[0079] The above embodiments are merely one of the implementation methods for achieving the technical solution of the present invention. The scope of protection claimed by the present invention is not limited to this embodiment, but also includes any variations, substitutions and other implementation methods that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention.

Claims

1. A method for preparing a super-hydrophilic oil-water separation membrane, characterized in that, The application relates to a super-hydrophilic oil-water separation membrane and a preparation method thereof. 2-(2-bromoisobutyryloxy)ethyl methacrylate monomer BIEM is prepared by using hydroxyethyl methacrylate and 2-bromoisobutyryl bromide; A polymer P(AN-g-BIEM) with an atom transfer radical polymerization initiator is prepared by using the 2-(2-bromoisobutyryloxy)ethyl methacrylate monomer BIEM and through a free radical polymerization reaction; The specific process is as follows: The 2-(2-bromoisobutyryloxy)ethyl methacrylate monomer BIEM, acrylonitrile AN, AIBN and N,N-dimethylformamide are mixed to perform a free radical polymerization reaction, so as to obtain a free radical polymerization reaction product; The free radical polymerization reaction product is subjected to precipitation, dissolution and re-precipitation treatment, so as to obtain the polymer P(AN-g-BIEM) with the atom transfer radical polymerization initiator; The polymer P(AN-g-BIEM) with the atom transfer radical polymerization initiator and polyacrylonitrile are dissolved into a solvent, and a PAN / P(AN-g-BIEM) blending membrane is prepared by using a non-solvent induced phase separation method; the mass ratio of the polymer with the atom transfer radical polymerization initiator to the polyacrylonitrile is (1-4):(6-9); A hydrophilic polymer brush is grafted onto the surface of the PAN / P(AN-g-BIEM) blending membrane by using atom transfer radical polymerization, so as to obtain the super-hydrophilic oil-water separation membrane; The hydrophilic polymer brush is a hydrophilic zwitterionic polymer brush pSBMA; The specific process is as follows: The PAN / P(AN-g-BIEM) blending membrane, a mixed solvent of methanol and water, 2,2'-dipyridyl and methacryloyl ethyl sulfobetaine are mixed and stirred to be degassed, so as to obtain a reaction mixed solution; Cuprous bromide is added into the reaction mixed solution, and atom transfer radical polymerization is performed under a nitrogen atmosphere, so as to obtain an ATRP polymerization modified membrane; The ATRP polymerization modified membrane is washed and dried, so as to obtain the super-hydrophilic oil-water separation membrane.

2. The method of claim 1, wherein the superhydrophilic oil-water separation membrane is prepared by the steps of: The process for preparing the 2-(2-bromoisobutyryloxy)ethyl methacrylate monomer by using hydroxyethyl methacrylate and 2-bromoisobutyryl bromide is as follows: Dichloromethane, triethylamine and hydroxyethyl methacrylate are mixed, and after reaction under a cold water bath condition, 2-bromoisobutyryl bromide is added; the reaction is performed under nitrogen protection and under an ice water bath condition, so as to obtain a reaction product; The reaction product is filtered and washed, so as to obtain a filtrate; The filtrate is washed, so as to obtain an organic phase; The organic phase is dried, filtered and distilled under reduced pressure, so as to obtain a yellow liquid, i.e. the 2-(2-bromoisobutyryloxy)ethyl methacrylate monomer.

3. The method for preparing a superhydrophilic oil-water separation membrane according to claim 1, characterized in that, The process for dissolving the polymer with the atom transfer radical polymerization initiator and the polyacrylonitrile into a solvent and preparing the PAN / P(AN-g-BIEM) blending membrane by using a non-solvent induced phase separation method is as follows: The polymer with the atom transfer radical polymerization initiator, the polyacrylonitrile, an additive and a solvent are mixed, and after stirring to be completely dissolved, the mixture is placed in a vacuum oven to remove bubbles, so as to obtain a casting solution. The casting solution is phase inverted to obtain a PAN / P(AN-g-BIEM) blend membrane.

4. The method of claim 3, wherein the superhydrophilic oil-water separation membrane is prepared by the steps of: The additive is polyvinylpyrrolidone, and the solvent is N,N-dimethylformamide.

5. A super-hydrophilic oil-water separation membrane, characterized in that, The super-hydrophilic oil-water separation membrane is prepared by the method of any one of claims 1-4.

6. Use of a superhydrophilic oil-water separation membrane according to claim 5, characterized in that, The super-hydrophilic oil-water separation membrane is used for oil-water separation of emulsified oily wastewater.

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