Deep-eutectic solvent modified porous graphene oxide / polymer composite membrane as well as preparation and application thereof

Abstract

The invention relates to the technical field of pervaporation membrane separation, in particular to a deep-eutectic solvent modified porous graphene oxide / polymer composite membrane as well as preparation and application thereof. The composite membrane provided by the invention comprises a polymer membrane and deep-eutectic solvent modified porous graphene oxide powder dispersed in the polymer membrane, wherein the deep-eutectic solvent modified porous graphene oxide powder is porous graphene oxide powder of which a lamellar structure is connected with a deep-eutectic solvent; the eutectic solvent is a mixed solution of urea and choline chloride; amino groups of urea in the eutectic solvent react with carboxyl groups and epoxy groups on the surface of a porous graphene oxide sheet layer, hydroxyl groups in choline chloride react with carboxyl groups on the surface of the porous graphene oxide sheet layer, chemical bonding is carried out, and the butanol affinity of the porous graphene oxide is improved. The composite membrane is further applied to alcohol permselective pervaporation, and compared with the prior art, the composite membrane has the advantage that the permeation flux and alcohol / water separation factors of pervaporation separation can be remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of pervaporation membrane separation, in particular to a deep eutectic solvent modified porous graphene oxide / polymer composite membrane and its preparation and application. Background Art

[0002] As a reliable alternative fuel, butanol has advantages in fuel performance and economy. Bioethanol and biobutanol are mainly derived from fermentation broth, and the separation of butanol and water is of great significance for the industrialization of biofuels.

[0003] As an emerging membrane separation technology, pervaporation has the advantages of environmental friendliness and simple operation possessed by traditional membrane separation technologies on the one hand, and can also operate at a lower temperature, reducing operating energy consumption on the other hand. The pervaporation membrane separation technology has been applied to fields such as dehydration and recovery of organic substances, and separation of organic substances from organic substances. Among them, great achievements have been made in the dehydration of organic solvents and industrial applications have been obtained. However, there is still a large research space for the recovery of organic substances in wastewater. The core of pervaporation is the membrane material. To recover organic substances from water, the key lies in finding a hydrophobic and organicophilic polymer membrane. Commonly used polymer membranes include polydimethylsiloxane (PDMS), polyurethane (PU), polyvinylidene fluoride (PVDF), and polyether block copolyamide (PEBA), etc. However, the separation effect of these membrane materials on butanol still needs to be improved. Adding a suitable modification material to the polymer membrane is beneficial to improving the pervaporation performance of the membrane for butanol. Some of these modification materials have a porous structure, providing an additional channel for the diffusion of butanol molecules, and some contain hydrophobic groups and butanolophilic groups, reducing the adsorption of water by the membrane and enhancing the adsorption of butanol.

[0004] Graphene oxide has a large number of oxygen-containing functional groups introduced on the graphene sheets, and its chemical properties are active. Due to its unique two-dimensional sheet structure and certain layer spacing, it has attracted wide attention in the field of membrane separation. Currently, graphene oxide is mainly prepared by the improved Hummers method, which is environmentally friendly, efficient and has a high degree of oxidation. In order to apply graphene oxide to a specific membrane separation field, its surface active oxygen-containing functional groups are usually used to graft the desired groups to achieve changes in chemical properties and structure. Currently, hydrophilic modification and layer spacing adjustment are mainly carried out on it, and there are few studies on hydrophobic modification of graphene oxide to increase membrane hydrophobicity.

[0005] CN107226719A discloses a preparation method of a graphene oxide film and an application of the prepared graphene oxide film in dehydration of a high-concentration ethylene glycol solution. In this method, the surface of a porous ceramic tube substrate is pre-modified with α-Al2O3 of different particle sizes, and then a graphene oxide solution is coated on the carrier by dip coating to prepare a graphene oxide film; the pervaporation method is adopted to apply the prepared graphene oxide film to the dehydration process of a high-concentration ethylene glycol solution. CN107226719A aims to dehydrate from a high-concentration organic solvent, emphasizes multiple dip coatings of GO solution on the modified porous ceramic tube, uses a large amount of GO, has a complex film preparation method, and has poor stability of the GO layer.

[0006] Therefore, it is crucial to provide a technical solution that can solve the above technical problems. Summary of the Invention

[0007] To solve the above problems, the object of the present invention is to provide a deep eutectic solvent modified porous graphene oxide / polymer composite membrane and its preparation and application. The deep eutectic solvent modified porous graphene oxide / polymer composite membrane provided by the present invention can preferentially permeate organic molecules (alcohol molecules). This application emphasizes removing organic substances from low-concentration wastewater to achieve the purpose of butanol recovery.

[0008] In the present invention, the SP 3 hybrid C atoms in graphene oxide have strong reactivity and can be partially removed under the action of hydrogen peroxide and ammonia water to form pores; due to the presence of amino groups, the deep eutectic solvent can react with the carboxyl and epoxy groups on the surface of the porous graphene oxide sheets to carry out chemical bonding (generate amide groups), thereby enhancing the affinity of the porous graphene oxide for butanol. Adding it to the membrane can improve the pervaporation separation effect of butanol.

[0009] The object of the present invention can be achieved by the following technical solutions:

[0010] The first object of the present invention is to provide a deep eutectic solvent modified porous graphene oxide / polymer composite membrane, and the composite membrane includes a polymer membrane and deep eutectic solvent modified porous graphene oxide powder dispersed in the polymer membrane;

[0011] Among them, the deep eutectic solvent modified porous graphene oxide powder is porous graphene oxide powder with a deep eutectic solvent connected to the sheet structure;

[0012] The deep eutectic solvent is a mixed solution of urea and choline chloride;

[0013] The amino group of urea in the deep eutectic solvent reacts with the carboxyl and epoxy groups on the surface of the porous graphene oxide sheets, and the hydroxyl group in choline chloride reacts with the carboxyl group on the surface of the porous graphene oxide sheets to carry out chemical bonding, increasing the butanol affinity of the porous graphene oxide (which can improve the pervaporation separation effect of ethanol. Preferably, it is applied to the pervaporation separation of a butanol / water system with preferential alcohol permeation).

[0014] In one embodiment of the present invention, the polymer membrane is a pervaporation material thin film;

[0015] The pervaporation material is selected from one or more of polyether block copolyamide (PEBA), polydimethylsiloxane (PDMS), or polyurethane (PU);

[0016] The molar ratio of urea to choline chloride is 1-2:1 (preferably, the molar ratio of urea to choline chloride is 2:1).

[0017] The second object of the present invention is to provide a method for preparing a deep eutectic solvent-modified porous graphene oxide / polymer composite membrane, including the following steps:

[0018] (S1) Add hydrogen peroxide and ammonia water to the graphene oxide solution, mix well and heat for reaction, and perform post-treatment to obtain porous graphene oxide;

[0019] (S2) Dissolve the porous graphene oxide prepared in step (S1), add it to the deep eutectic solvent, mix well and heat for reaction, and perform post-treatment to obtain deep eutectic solvent-modified porous graphene oxide;

[0020] (S3) Mix the deep eutectic solvent-modified porous graphene oxide prepared in step (S2) with an alcohol solvent to obtain a deep eutectic solvent-modified porous graphene oxide suspension;

[0021] (S4) Mix the polymer membrane material with an organic solvent to obtain a membrane material solution;

[0022] (S5) Mix the deep eutectic solvent-modified porous graphene oxide suspension prepared in step (S3) with the membrane material solution prepared in step (S4) and perform heat treatment to obtain a casting solution;

[0023] (S6) Perform scraping and drying treatments on the casting solution prepared in step (S5) in sequence to obtain a deep eutectic solvent-modified porous graphene oxide / polymer composite membrane.

[0024] In one embodiment of the present invention, in step (S1), the graphene oxide solution is a mixed solution of graphene oxide powder and deionized water; the sheet diameter of the graphene oxide powder is 0.5-5 μm, and it has good dispersibility in alcohol solvents;

[0025] In the graphene oxide solution, the mass percentage of graphene oxide is 0.1-1%;

[0026] The volume ratio of the hydrogen peroxide to the ammonia water is 1:1-3 (preferably, the volume ratio of the hydrogen peroxide to the ammonia water is 1:1), and the hydrogen peroxide accounts for 1%-6% of the total volume of the graphene oxide dispersion (preferably, the hydrogen peroxide accounts for 5% of the total volume of the graphene oxide dispersion);

[0027] During the reaction, the temperature is 35-45 °C and the time is 0.5-2 h; preferably, the temperature is 40 °C and the time is 1.5 h;

[0028] The post-treatment is washing and drying; the washing process is specifically to wash successively with ethanol and distilled water; during the drying process, the temperature is 60-90 °C until the mass of the product remains unchanged.

[0029] In an embodiment of the present invention, in step (S2), the porous graphene oxide is dissolved in absolute ethanol,

[0030] The dosage ratio of the porous graphene oxide to the deep eutectic solvent is 0.1-0.5 g: 0.01-0.5 mol; (preferably, the dosage ratio of the porous graphene oxide to the deep eutectic solvent is 0.1 g: 0.01 mol)

[0031] During the reaction, the temperature is 80-120 °C and the time is 12-24 h; preferably, the temperature is 100 °C and the time is 12 h;

[0032] The post-treatment is washing and drying; the washing process is specifically to wash successively with ethanol and distilled water; during the drying process, the temperature is 60-90 °C until the mass of the product remains unchanged.

[0033] In an embodiment of the present invention, in step (S3), the alcohol solvent is selected from one of methanol or ethanol;

[0034] The dosage ratio of the deep eutectic solvent-modified porous graphene oxide to the alcohol solvent is 0.1 g: 20-100 mL.

[0035] In an embodiment of the present invention, in step (S4), the polymer membrane material is selected from one of polyether block copolyamide (PEBA), polydimethylsiloxane (PDMS), or polyurethane (PU);

[0036] The organic solvent is selected from one of n-butanol or N,N-dimethylformamide;

[0037] The mass ratio of the polymer membrane material to the organic solvent is 1-5:50.

[0038] In one embodiment of the present invention, in step (S5), the mass ratio of the deep eutectic solvent-modified porous graphene oxide to the polymer membrane material is 0.1-5:100; when the amount of the deep eutectic solvent-modified porous graphene oxide powder added is too small, the pervaporation separation performance of the prepared composite membrane does not change significantly; when the filling amount of the deep eutectic solvent-modified porous graphene oxide powder is too large, the dispersibility of the deep eutectic solvent-modified porous graphene oxide in the polymer membrane is poor, and agglomeration will occur, destroying the pervaporation performance of the composite membrane;

[0039] During the heat treatment process, the temperature is 60-80 °C and the time is 0.5-3 h.

[0040] In one embodiment of the present invention, in step (S6), after the casting solution is left standing for defoaming and cooled to 30-50 °C, a film scraping treatment and a drying treatment are carried out in sequence;

[0041] During the film scraping process, the amount of the casting solution used is 0.067-0.133 g / cm 2 ;

[0042] During the drying process, the temperature is 60-90 °C until the mass of the product remains unchanged;

[0043] Specifically, the casting solution is cooled to 30-50 °C, poured onto a horizontally placed glass plate, and the film is scraped with a glass scraper, and then left at room temperature for 1-6 h for drying. After the alcohol solvent has completely volatilized, the film is peeled off.

[0044] The third object of the present invention is to provide an application of a deep eutectic solvent-modified porous graphene oxide / polymer composite membrane in the pervaporation separation with preferential alcohol permeation;

[0045] Preferably, the pervaporation separation with preferential alcohol permeation is the pervaporation separation of a butanol / water system with preferential alcohol permeation.

[0046] Compared with the prior art, the present invention has the following beneficial effects:

[0047] The present invention applies a deep eutectic solvent-modified porous graphene oxide to a pervaporation membrane, giving full play to the advantages of the deep eutectic solvent-modified porous graphene oxide in pervaporation. The graphene oxide is porous to provide in-plane channels for small molecule permeation, and interlayer grafting expands the interlayer spacing to provide interlayer channels for small molecule permeation. The deep eutectic solvent and the porous graphene oxide are connected by chemical bonding, which not only improves the hydrophobic and organophilic properties of the graphene oxide, but also enables it to be uniformly dispersed in organic solvents. The polymer composite membrane added with the deep eutectic solvent-modified porous graphene oxide combines the advantages of both inorganic nanoparticles and polymers. On the premise of retaining the characteristics of the PEBA dense membrane, the hydrophobicity of the membrane is enhanced, and the membrane structure is optimized, thus breaking the "trade-off" effect of pervaporation and simultaneously improving the separation factor and permeation flux of the pervaporation membrane. Description of the Drawings

[0048] Figure 1 Figure 6 is a scanning electron micrograph of the DES-PGO powder prepared in Example 1 (DES: deep eutectic solvent);

[0049] Figure 2 Figure 10 is a scanning electron micrograph of the PGO powder prepared in Example 2 (PGO: porous graphene oxide);

[0050] Figure 3 Figure 14 is a BET pore size distribution diagram of the PGO powder prepared in Example 2;

[0051] Figure 4 Figure 18 is a scanning electron micrograph of the 1% DES-PGO / PEBA composite membrane prepared in Example 1;

[0052] Figure 5 Figure 22 is a scanning electron micrograph of the 1% PGO / PEBA composite membrane prepared in Example 2;

[0053] Figure 6 Figure 26 is a performance comparison diagram of the PEBA blank membrane prepared in Comparative Example 1, the deep eutectic solvent-modified porous graphene oxide / polymer composite membrane prepared in Example 1, and the porous graphene oxide / polymer composite membrane prepared in Example 2 for pervaporation separation of a 2.5% butanol aqueous solution at 40 °C;

[0054] Figure 7 Figure 30 is a performance comparison diagram of the composite membranes prepared in Examples 2 to 6. Detailed Embodiments

[0055] The present invention will be described in detail below with reference to the drawings and specific embodiments.

[0056] In the following embodiments, unless otherwise specified, the reagents used are commercially available reagents, and the detection means and methods used are conventional detection means and methods in the art.

[0057] Example 1

[0058] This example provides a method for preparing a deep eutectic solvent modified porous graphene oxide / polymer composite membrane, comprising the following steps:

[0059] (S1) Dissolve 0.1 g of graphene oxide powder (flake diameter 0.5 - 5 μm) in 45 mL of deionized water, stir, and then perform ultrasonic dispersion and mixing to obtain a graphene oxide solution;

[0060] (S2) Add 2.5 mL of hydrogen peroxide and 2.5 mL of ammonia water to the graphene oxide solution prepared in step (S1) (the volume ratio of hydrogen peroxide, ammonia water to the graphene oxide solution is 2.5:2.5:45), mix well, and heat for reaction (40 °C, magnetic stirring for 1.5 h). After centrifuging the reaction product, discarding the supernatant, wash the precipitate successively with ethanol and deionized water, and then perform drying treatment (80 °C, drying for 24 h) to obtain porous graphene oxide (labeled as "PGO");

[0061] (S3) Dissolve the porous graphene oxide prepared in step (S2) in 40 mL of absolute ethanol, mix well to obtain a porous graphene oxide solution;

[0062] (S4) Place urea and choline chloride in a molar ratio of 2:1, stir and mix well at 40 °C to obtain a deep eutectic solvent (labeled as "DES");

[0063] (S5) Mix the porous graphene oxide solution prepared in step (S3) with the deep eutectic solvent prepared in step (S4) (the mass ratio of porous graphene oxide to the deep eutectic solvent is 1:9), and heat for reaction (magnetic stirring and refluxing at 100 °C for 12 h). After centrifuging the reaction product, discarding the supernatant, wash the precipitate successively with ethanol and deionized water, and then place it in an oven for drying treatment (80 °C, 24 h) to obtain a deep eutectic solvent modified porous graphene oxide (labeled as "DES-PGO");

[0064] (S6) Mix the deep eutectic solvent modified porous graphene oxide prepared in step (S5) with 10 g of n-butanol solvent to obtain a deep eutectic solvent modified porous graphene oxide suspension;

[0065] (S7) Mix 1.5 g of PEBA with 15 g of n-butanol solvent to obtain a membrane material solution;

[0066] (S8) Mix the deep eutectic solvent modified porous graphene oxide suspension prepared in step (S6) with the membrane material solution prepared in step (S7) (the mass ratio of deep eutectic solvent modified porous graphene oxide to PEBA is 1:100), and perform heat treatment (70 °C, 2 h) to obtain a casting solution;

[0067] (S9) Scrape the casting solution prepared in step (S8) (0.083 g / cm 2 ), and dry it at 40 °C for 24 h to obtain a deep eutectic solvent modified porous graphene oxide / polymer composite membrane (labeled as "1% DES-PGO / PEBA (1.5 h) membrane").

[0068] Example 2

[0069] This example provides a method for preparing a porous graphene oxide / polymer composite membrane, including the following steps:

[0070] (S1) Dissolve 0.1 g of graphene oxide powder (sheet diameter 0.5 - 5 μm) in 45 mL of deionized water, stir, and then perform ultrasonic dispersion and mixing to obtain a graphene oxide solution;

[0071] (S2) Add 2.5 mL of hydrogen peroxide and 2.5 mL of ammonia water to the graphene oxide solution prepared in step (S1) (the volume ratio of hydrogen peroxide, ammonia water to the graphene oxide solution is 2.5:2.5:45), mix well, and heat for reaction (40 °C, magnetic stirring for 1.5 h). After centrifuging the reaction product and discarding the supernatant, wash the precipitate successively with ethanol and deionized water, and then perform drying treatment (80 °C, drying for 24 h) to obtain porous graphene oxide (labeled as "PGO");

[0072] (S3) Mix the porous graphene oxide prepared in step (S2) with 10 g of n-butanol solvent to obtain a porous graphene oxide solution;

[0073] (S4) Mix 1.5 g of PEBA with 15 g of n-butanol solvent to obtain a membrane material solution;

[0074] (S5) Mix the porous graphene oxide suspension prepared in step (S3) with the membrane material solution prepared in step (S4) (the mass ratio of porous graphene oxide to PEBA is 1:100), and perform heat treatment (70 °C, 2 h) to obtain a casting solution;

[0075] (S6) Scrape the casting solution prepared in step (S5) (0.083 g / cm 2 ), and dry it at 40 °C for 24 h to obtain a porous graphene oxide / polymer composite membrane (labeled as "1% PGO / PEBA (1.5 h) membrane").

[0076] Comparative Example 1

[0077] This comparative example provides a method for preparing a PEBA blank membrane, including the following steps:

[0078] (S1) Mix 1.5 g of PEBA with 15 g of n-butanol solvent to obtain a membrane material solution;

[0079] (S2) Perform a film scraping treatment on the membrane material solution prepared in step (S1) (0.083 g / cm 2 ), and dry it at 40 °C for 24 h to obtain a PEBA blank membrane.

[0080] Figure 1 and Figure 2 are the scanning electron microscope images of the DES-PGO powder prepared in Example 1 and the PGO powder prepared in Example 2, respectively. It can be seen that the eutectic solvent-modified graphene oxide powder still maintains its original flaky structure and has a reduced size, which is beneficial for dispersion in organic solvents.

[0081] Figure 3 is the BET pore size distribution diagram of PGO. It can be seen that after etching with hydrogen peroxide and ammonia water, defect pores appear on the surface of graphene oxide, and the average pore diameter is larger than the kinetic diameter of butanol and the kinetic diameter of water

[0082] Figure 4 and Figure 5 are the scanning electron microscope images of the 1% DES-PGO / PEBA (1.5 h) membrane prepared in Example 1 and the 1% PGO / PEBA (1.5 h) membrane prepared in Example 2, respectively. It can be seen that the composite membrane retains the characteristics of the original dense membrane of PEBA, and at the same time, the porous graphene oxide powder and the eutectic solvent-modified porous graphene oxide powder are relatively evenly dispersed in the composite membrane.

[0083] Perform pervaporation experiments on the eutectic solvent-modified porous graphene oxide / polymer composite membrane prepared in Example 1, the porous graphene oxide / polymer composite membrane prepared in Example 2, and the PEBA blank membrane prepared in Comparative Example 1; specifically, use a 2.5 wt% butanol / water solution as the feed liquid, and use the PEBA blank membrane, the 1% DES-PGO / PEBA (1.5 h) membrane, and the 1% PGO / PEBA (1.5 h) membrane as the pervaporation membranes to perform pervaporation experiments for alcohol / water separation. The pervaporation experiment data are as Figure 6 . Through Figure 6It can be found that after doping 1 wt% of porous graphene oxide (PGO) into PEBA, the total flux of the membrane increases by 73.6%. Among them, the butanol flux increases by 41.2%, and the separation factor decreases by 10.7%. Thus, it can be seen that PGO is beneficial to the permeation of both butanol and water. After doping 1 wt% of deep eutectic solvent-modified porous graphene oxide (DES-PGO) into PEBA, compared with the PGO / PEBA membrane doped with unmodified PGO without DES, the total flux is further increased by 65.1%. Among them, the butanol flux is increased by 142.6%, and the separation factor is increased by 32.2%. And both are significantly better than the PEBA blank membrane. It can be seen that the pervaporation performance of the mixed matrix membrane added with deep eutectic solvent-modified porous graphene oxide is better, and both the separation factor and the permeation flux are significantly improved.

[0084] Example 3

[0085] This example provides a method for preparing a porous graphene oxide / polymer composite membrane, which includes the following steps:

[0086] (S1) Dissolve 0.1 g of graphene oxide powder (sheet diameter is 0.5 - 5 μm) in 45 mL of deionized water and stir, then perform ultrasonic dispersion and mixing to obtain a graphene oxide solution;

[0087] (S2) Add 2.5 mL of hydrogen peroxide and 2.5 mL of ammonia water to the graphene oxide solution prepared in step (S1) (the volume ratio of hydrogen peroxide, ammonia water to the graphene oxide solution is 2.5:2.5:45), mix well, and heat for reaction (40 °C, magnetic stirring for 0.5 h). After centrifuging the reaction product and discarding the supernatant, wash the precipitate successively with ethanol and deionized water, and then perform drying treatment (80 °C, drying for 24 h) to obtain porous graphene oxide (marked as "PGO");

[0088] (S3) Mix the porous graphene oxide prepared in step (S2) in 10 g of n-butanol solvent to obtain a porous graphene oxide solution;

[0089] (S4) Mix 1.5 g of PEBA with 15 g of n-butanol solvent to obtain a membrane material solution;

[0090] (S5) Mix the porous graphene oxide suspension prepared in step (S3) with the membrane material solution prepared in step (S4) (the mass ratio of porous graphene oxide to PEBA is 1:100), and perform heat treatment (70 °C, 2 h) to obtain a casting solution;

[0091] (S6) Perform scraping treatment on the casting solution prepared in step (S5) (0.083 g / cm 2), dried at 40 °C for 24 h to obtain a porous graphene oxide / polymer composite membrane (labeled as "1% PGO / PEBA (0.5 h) membrane").

[0092] Example 4

[0093] This example provides a method for preparing a porous graphene oxide / polymer composite membrane, which includes the following steps:

[0094] (S1) Dissolve 0.1 g of graphene oxide powder (flake diameter 0.5 - 5 μm) in 45 mL of deionized water, stir, and then perform ultrasonic dispersion for 0.1 g to mix evenly to obtain a graphene oxide solution;

[0095] (S2) Add 2.5 mL of hydrogen peroxide and 2.5 mL of ammonia water to the graphene oxide solution prepared in step (S1) (the volume ratio of hydrogen peroxide, ammonia water to the graphene oxide solution is 2.5:2.5:45), mix evenly, and heat for reaction (40 °C, magnetic stirring for 1.0 h). After centrifuging the reaction product, discarding the supernatant, washing the precipitate successively with ethanol and deionized water, and then performing drying treatment (80 °C, drying for 24 h) to obtain porous graphene oxide (labeled as "PGO");

[0096] (S3) Mix the porous graphene oxide prepared in step (S2) evenly in 10 g of n-butanol solvent to obtain a porous graphene oxide solution;

[0097] (S4) Mix 1.5 g of PEBA with 15 g of n-butanol solvent to obtain a membrane material solution;

[0098] (S5) Mix the porous graphene oxide suspension prepared in step (S3) with the membrane material solution prepared in step (S4) (the mass ratio of porous graphene oxide to PEBA is 1:100), and perform heat treatment (70 °C, 2 h) to obtain a casting solution;

[0099] (S6) Perform scraping film treatment on the casting solution prepared in step (S5) (0.083 g / cm 2 ), dried at 40 °C for 24 h to obtain a porous graphene oxide / polymer composite membrane (labeled as "1% PGO / PEBA (1.0 h) membrane").

[0100] Example 5

[0101] This example provides a method for preparing a porous graphene oxide / polymer composite membrane, which includes the following steps:

[0102] (S1) Dissolve 0.1 g of graphene oxide powder (flake diameter 0.5 - 5 μm) in 45 mL of deionized water, stir, and then perform ultrasonic dispersion to mix 0.1 g evenly to obtain a graphene oxide solution;

[0103] (S2) Add 2.5 mL of hydrogen peroxide and 2.5 mL of ammonia water into the graphene oxide solution prepared in step (S1) (the volume ratio of hydrogen peroxide, ammonia water to the graphene oxide solution is 2.5:2.5:45), mix well, and heat for reaction (40 °C, magnetic stirring for 2.0 h). After centrifuging the reaction product and discarding the supernatant, wash the precipitate successively with ethanol and deionized water, and then perform drying treatment (80 °C, drying for 24 h) to obtain porous graphene oxide (marked as "PGO");

[0104] (S3) Mix the porous graphene oxide prepared in step (S2) in n-butanol solvent to obtain a porous graphene oxide solution;

[0105] (S4) Mix 1.5 g of PEBA with 15 g of n-butanol solvent to obtain a membrane material solution;

[0106] (S5) Mix the porous graphene oxide suspension prepared in step (S3) with the membrane material solution prepared in step (S4) (the mass ratio of porous graphene oxide to PEBA is 1:100), and perform heat treatment (70 °C, 2 h) to obtain a casting solution;

[0107] (S6) Perform a casting film treatment on the casting solution prepared in step (S5) (0.083 g / cm 2 ), dry at 40 °C for 24 h to obtain a porous graphene oxide / polymer composite membrane (marked as "1% PGO / PEBA(2.0 h) membrane").

[0108] Example 6

[0109] This example provides a method for preparing a porous graphene oxide / polymer composite membrane, including the following steps:

[0110] (S1) Dissolve 0.1 g of graphene oxide powder (flake diameter 0.5 - 5 μm) in 45 mL of deionized water, stir, and then perform ultrasonic dispersion and mixing to obtain a graphene oxide solution;

[0111] (S2) Add 2.5 mL of hydrogen peroxide and 2.5 mL of ammonia water into the graphene oxide solution prepared in step (S1) (the volume ratio of hydrogen peroxide, ammonia water to the graphene oxide solution is 2.5:2.5:45), mix well, then centrifuge, discard the supernatant, wash the precipitate successively with ethanol and deionized water, and perform drying treatment (80 °C, drying for 24 h) to obtain porous graphene oxide (marked as "PGO");

[0112] (S3) Mix the porous graphene oxide prepared in step (S2) in 10 g of n-butanol solvent to obtain a porous graphene oxide solution;

[0113] (S4) Mix 1.5 g of PEBA with 15 g of n-butanol solvent to obtain a membrane material solution;

[0114] (S5) Mix the porous graphene oxide suspension prepared in step (S3) with the membrane material solution prepared in step (S4) (the mass ratio of porous graphene oxide to PEBA is 1:100), and perform heat treatment (70 °C, 2 h) to obtain a casting solution;

[0115] (S6) Perform a film scraping treatment (0.083 g / cm 2 ) on the casting solution prepared in step (S5), and dry it at 40 °C for 24 h to obtain a porous graphene oxide / polymer composite membrane (labeled as "1% PGO / PEBA(0 h) membrane").

[0116] The performances of the composite membranes prepared in Examples 2 to 6 were compared, and the results are as Figure 7 shown (wherein, Example 2 is labeled as "1.5 h", Example 3 is labeled as "0.5 h", Example 4 is labeled as "1.0 h", Example 5 is labeled as "2.0 h", Example 6 is labeled as "0 h",), Figure 7 indicating that the membrane performance of 1% PGO / PEBA(1.5 h) obtained by etching porous graphene oxide for 1.5 h is better. Therefore, the etching time of graphene oxide in subsequent examples is taken as 1.5 h.

[0117] Example 7

[0118] This example is basically the same as Example 1, except that in this example, the molar ratio of urea to choline chloride is 1:1.

[0119] Example 8

[0120] This example is basically the same as Example 1, except that in this example, the molar ratio of urea to choline chloride is 3:2.

[0121] Example 9

[0122] This example is basically the same as Example 1, except that in this example, the mass ratio of PGO to DES is 2:8.

[0123] Example 10

[0124] This example is basically the same as Example 1, except that in this example, the mass ratio of PGO to DES is 3:7.

[0125] Example 11

[0126] This example is basically the same as Example 1, except that in this example, the mass ratio of PGO to DES is 4:6.

[0127] Example 12

[0128] This example is basically the same as Example 1, except that in this example, the mass ratio of PGO to DES is 5:5.

[0129] Example 13

[0130] This example is basically the same as Example 1, except that in this example, the mass ratio of the polymer PEBA to the deep eutectic solvent modified porous graphene oxide powder is 100:0.6.

[0131] Example 14

[0132] This example is basically the same as Example 1, except that in this example, the mass ratio of the polymer PEBA to the deep eutectic solvent modified porous graphene oxide powder is 100:0.8.

[0133] The properties of the deep eutectic solvent modified porous graphene oxide / polymer composite membranes prepared in Examples 7 to 14 are similar to those of the deep eutectic solvent modified porous graphene oxide / polymer composite membrane prepared in Example 1. Compared with the blank PEBA membrane, both the permeation flux and the butanol / water separation factor are significantly improved.

[0134] The above description of the embodiments is to enable those of ordinary skill in the art to understand and use the invention. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative efforts. Therefore, the present invention is not limited to the above embodiments, and all improvements and modifications made by those skilled in the art without departing from the scope of the present invention should be within the protection scope of the present invention.

Claims

1. A low eutectic solvent modified porous graphene oxide / polymer composite membrane, characterized in that: The composite membrane comprises a polymer membrane and a deep eutectic solvent-modified porous graphene oxide powder dispersed in the polymer membrane; Wherein, the low eutectic solvent modified porous graphene oxide powder is a porous graphene oxide powder with a low eutectic solvent connected to the sheet structure; The deep eutectic solvent is a mixed solution of urea and choline chloride; The amino groups of urea in the low eutectic solvent react with the carboxyl groups and epoxy groups on the surface of the porous graphene oxide sheet, and the hydroxyl groups in choline chloride react with the carboxyl groups on the surface of the porous graphene oxide sheet to form chemical bonds.

2. The deep eutectic solvent modified porous graphene oxide / polymer composite membrane according to claim 1, characterized in that: The polymer membrane is a pervaporation material film; The pervaporation material is selected from one or more of polyether block copolyamide, polydimethylsiloxane or polyurethane; The molar ratio of urea to choline chloride is 1-2:

1.

3. A method for preparing a deep eutectic solvent modified porous graphene oxide / polymer composite membrane according to any one of claims 1 to 2, characterized in that: The following steps are involved: (S1) adding hydrogen peroxide and ammonia water to the graphene oxide solution, mixing and heating to react, and post-treating to obtain porous graphene oxide; (S2) dissolving the porous graphene oxide prepared in step (S1), adding the mixture into a low eutectic solvent, mixing the mixture, and heating the mixture for reaction, followed by post-treatment to obtain a low eutectic solvent-modified porous graphene oxide; (S3) mixing the low eutectic solvent-modified porous graphene oxide prepared in step (S2) with an alcohol solvent to obtain a low eutectic solvent-modified porous graphene oxide suspension; (S4) mixing the polymer membrane material and the organic solvent to obtain a membrane material solution; (S5) mixing the low eutectic solvent modified porous graphene oxide suspension prepared in step (S3) and the membrane material solution prepared in step (S4) and heating them to obtain a membrane casting solution; (S6) The casting solution prepared in step (S5) is subjected to scraping treatment and drying treatment in sequence to obtain a low eutectic solvent-modified porous graphene oxide / polymer composite membrane.

4. The method for preparing a deep eutectic solvent modified porous graphene oxide / polymer composite membrane according to claim 3, characterized in that: In step (S1), the graphene oxide solution is a mixture of graphene oxide powder and deionized water; the flake diameter of the graphene oxide powder is 0.5 to 5 μm; In the graphene oxide solution, the mass percentage of graphene oxide is 0.1-1%; The volume ratio of the hydrogen peroxide to the ammonia solution is 1:1-3, and the hydrogen peroxide accounts for 1%-6% of the total volume of the graphene oxide dispersion; During the reaction, the temperature is 35-45°C and the reaction time is 0.5-2h; The post-treatment is washing and drying. The washing process is specifically washing with ethanol and distilled water in sequence. During the drying process, the temperature is 60-90° C. until the product quality remains unchanged.

5. The method for preparing a deep eutectic solvent modified porous graphene oxide / polymer composite membrane according to claim 3, characterized in that: In step (S2), porous graphene oxide is dissolved in anhydrous ethanol. The usage ratio of porous graphene oxide to low eutectic solvent is 0.1-0.5 g: 0.01-0.5 mol; During the reaction, the temperature is 80-120°C and the reaction time is 12-24h; The post-treatment is washing and drying. The washing process is specifically washing with ethanol and distilled water in sequence. During the drying process, the temperature is 60-90° C. until the product quality remains unchanged.

6. The method for preparing a deep eutectic solvent modified porous graphene oxide / polymer composite membrane according to claim 3, characterized in that: In step (S3), the alcohol solvent is selected from one of methanol and ethanol; The dosage ratio of the low eutectic solvent modified porous graphene oxide to the alcohol solvent is 0.1 g: 20-100 mL.

7. The method for preparing a deep eutectic solvent modified porous graphene oxide / polymer composite membrane according to claim 3, characterized in that: In step (S4), the polymer film material is selected from one of polyether block copolyamide, polydimethylsiloxane or polyurethane; The organic solvent is selected from one of n-butanol and N,N-dimethylformamide; The mass ratio of the polymer membrane material to the organic solvent is 1 to 5:

50.

8. The method for preparing a deep eutectic solvent modified porous graphene oxide / polymer composite membrane according to claim 3, characterized in that: In step (S5), the mass ratio of the low eutectic solvent-modified porous graphene oxide to the polymer membrane material is 0.1 to 1:100; During the heating treatment, the temperature is 60-80°C and the time is 0.5-3h.

9. The method for preparing a deep eutectic solvent modified porous graphene oxide / polymer composite membrane according to claim 3, characterized in that: In step (S6), the casting solution is allowed to stand for degassing and then cooled to 30-50° C., followed by film scraping and drying. During the scraping process, the amount of casting liquid is 0.067~0.133g / cm 2 ; During the drying process, the temperature is 60-90°C until the product quality remains unchanged.

10. Use of the deep eutectic solvent modified porous graphene oxide / polymer composite membrane as claimed in any one of claims 1 to 2 in pervaporation separation with preferential permeation of alcohol.

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