Graphene oxide composite filter membrane as well as preparation method and application thereof

Abstract

The invention provides a graphene oxide composite filter membrane as well as a preparation method and application thereof. The preparation method of the graphene oxide composite filter membrane comprises the following steps: firstly, preparing a silicon dioxide nanoparticle dispersion liquid, carrying out surface modification on the silicon dioxide nanoparticle dispersion liquid by using polyvinylpyrrolidone, and then combining metal ions with an organic ligand on the surface to form a metal organic framework material with a core-shell structure, so as to obtain the graphene oxide composite filter membrane. And finally, compounding the graphene oxide with the core-shell structure metal organic framework through pi-pi conjugation, metal complexing and hydrogen-bond interaction to form a filter membrane to complete adsorption removal of tetracycline molecules. The adsorption value of the pure metal organic framework material is only 446 mg / g, and the adsorption value of the composite filter membrane formed by compounding the core-shell structure metal organic framework and the graphene oxide under the dark conditions of 1 bar and 273 K can reach 800 mg / g or above.

Description

Technical Field

[0001] The present invention relates to the technical field of nanofiltration composite membrane materials, and in particular to a graphene oxide composite filter membrane and a preparation method and application thereof. Background Art

[0002] With the development of agricultural breeding, people's use of antibiotics has greatly increased, and agricultural wastewater containing a large amount of unmetabolized antibiotics is inevitably produced. The antibiotics in the wastewater will lead to the challenge of antibiotic resistance and the emergence of super bacteria. Tetracycline is an antibiotic widely used in animal husbandry and human treatment. At present, the more mature method for tetracycline adsorption is the adsorbent adsorption method, which uses granular adsorbents to adsorb tetracycline. However, this method also has its obvious shortcomings, such as low adsorption efficiency, difficulty in recovery and easy formation of secondary pollution. Therefore, a green and environmentally friendly membrane adsorbent has been developed, which is of great help in treating wastewater.

[0003] Metal-organic framework materials were first proposed by scientists Cromy RJ Kirby and Wolfgang MAOstwal in Nature in 1995. They are a type of crystalline porous material formed by metal ions or metal clusters and organic ligands connected by coordination bonds. They have excellent adsorption properties for tetracycline molecules through π-π conjugation, metal complexation and hydrogen bonding. Graphene oxide is a two-dimensional carbon material with a large number of oxygen-containing functional groups. Its six-membered ring structure and -OH provide adsorption sites for tetracycline, greatly improving the adsorption performance of tetracycline.

[0004] However, there is currently no technical solution to combine metal organic framework materials with graphene oxide to prepare filter membranes and use them to adsorb tetracycline. Summary of the invention

[0005] In view of the above problems, the present invention provides a graphene oxide composite filter membrane and a preparation method and application thereof, so as to solve or at least partially solve the defects existing in the prior art.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions: In a first aspect, the present invention provides a method for preparing a graphene oxide composite filter membrane, comprising the following steps: preparing a silica nanoparticle dispersion; The silica nanoparticle dispersion is dispersed in methanol, and then polyvinyl pyrrolidone is added, ultrasonicated, and then a methanol solution containing a Co salt is added, and finally a 2-methylimidazole methanol solution is added, stirred, centrifuged, and dried to obtain a core-shell structure metal organic framework material; dispersing graphene oxide in water to obtain a graphene oxide dispersion; Dispersing the core-shell structure metal organic framework material in ethanol to obtain a metal organic framework material dispersion; After the metal organic framework material dispersion liquid and the graphene oxide dispersion liquid are mixed, vacuum filtration is performed to form a membrane to obtain a graphene oxide composite filter membrane.

[0007] Preferably, the method for preparing the silica nanoparticle dispersion comprises the following steps: Mixing tetraethyl silicate and ethanol to obtain a first solution; Mixing aqueous ammonia, water and ethanol to obtain a second solution; adding the first solution to the second solution, stirring, centrifuging, and washing to obtain silica nanoparticles; The silicon dioxide nanoparticles are dispersed in ethanol to obtain a silicon dioxide nanoparticle dispersion.

[0008] Preferably, in the step of mixing tetraethyl silicate and ethanol to obtain the first solution, the volume ratio of tetraethyl silicate to ethanol is (2-3):(22-23); In the step of mixing aqueous ammonia, water and ethanol to obtain a second solution, the volume ratio of aqueous ammonia, water and ethanol is (1.6-1.7):(2-5):(18-21); In the steps of adding the first solution to the second solution, stirring, centrifuging, washing, obtaining silica nanoparticles, and dispersing the silica nanoparticles in ethanol, the volume ratio of the first solution, the second solution, and the ethanol is (24-26):(21.6-27.7):(50-60); The mass concentration of the ammonia water is 25-30%.

[0009] Preferably, the polyvinyl pyrrolidone is added in the form of polyvinyl pyrrolidone methanol solution; and the Co salt is Co(NO3)2·6H2O.

[0010] Preferably, the silica nanoparticle dispersion is dispersed in methanol, then a polyvinyl pyrrolidone methanol solution is added, ultrasonicated, then a methanol solution containing Co(NO3)2·6H2O is added, and finally a 2-methylimidazole methanol solution is added; Wherein, in the step of dispersing the silica nanoparticle dispersion into methanol, the volume ratio of the silica nanoparticle dispersion to methanol is (3-4):(80-100); In the polyvinyl pyrrolidone methanol solution, the mass volume ratio of polyvinyl pyrrolidone to methanol is (0.1-0.3) g: (15-20) mL; The mass volume ratio of Co(NO3)2·6H2O to methanol in the methanol solution containing Co(NO3)2·6H2O is (120-130) mg:(10-15) mL; The mass volume ratio of 2-methylimidazole to methanol in the 2-methylimidazole methanol solution is (1.5-2) g: (60-70) mL; The volume ratios of the silica nanoparticle dispersion, the methanol in the polyvinyl pyrrolidone methanol solution, the methanol in the methanol solution containing Co(NO3)2·6H2O, and the methanol in the 2-methylimidazole methanol solution are (3~4):(15~20):(10~15):(60~70).

[0011] Preferably, in the step of dispersing graphene oxide in water to obtain a graphene oxide dispersion, the mass volume ratio of graphene oxide to water is (12-13) mg:(50-60) mL.

[0012] Preferably, in the step of dispersing the core-shell structure metal organic framework material in ethanol to obtain a metal organic framework material dispersion, the mass volume ratio of the core-shell structure metal organic framework material to ethanol is (5~6) mg:(5~10) mL.

[0013] Preferably, the metal organic framework material dispersion and the graphene oxide dispersion are stirred and mixed for 2 to 3 hours, and then vacuum filtered under a pressure difference of 0.8 to 1 bar to form a membrane to obtain a graphene oxide composite filter membrane.

[0014] Preferably, the first solution is added to the second solution, stirred for 10 to 15 hours, centrifuged, and washed to obtain silica nanoparticles; The silica nanoparticle dispersion is added to methanol and ultrasonically dispersed for 15 to 20 minutes. Then polyvinyl pyrrolidone is added and ultrasonic dispersion is continued for 15 to 20 minutes. Then a methanol solution containing Co salt is added and ultrasonic dispersion is continued for 15 to 20 minutes. Finally, 2-methylimidazole methanol solution is added and stirred for 3 to 5 hours. The mixture is centrifuged and dried to obtain a core-shell structured metal organic framework material.

[0015] In a second aspect, the present invention further provides a graphene oxide composite filter membrane, which is prepared using the preparation method.

[0016] In a third aspect, the present invention also provides a graphene oxide composite filter membrane prepared by the preparation method or the use of the graphene oxide composite filter membrane in the adsorption and removal of tetracycline.

[0017] The graphene oxide composite filter membrane and its preparation method and application of the present invention have the following beneficial effects compared with the prior art: 1. The preparation method of the graphene oxide composite filter membrane of the present invention comprises the following steps: firstly preparing a silicon dioxide nanoparticle dispersion, modifying its surface by using polyvinyl pyrrolidone, then combining metal ions with organic ligands on the surface to form a metal organic framework material with a core-shell structure, and finally compounding the graphene oxide with the metal organic framework with a core-shell structure through π-π conjugation, metal complexation and hydrogen bonding to form a filter membrane to complete the adsorption and removal of tetracycline molecules; 2. The preparation method of the graphene oxide composite filter membrane of the present invention combines metal organic framework materials with graphene oxide, greatly improving the adsorption performance of tetracycline molecules, and is energy-efficient, environmentally friendly and easy to recycle. Graphene oxide and metal organic framework materials already have the ability to be mass-produced, so the preparation of the composite membrane meets the conditions for mass production and is suitable for large-scale applications; the adsorption value of a simple metal organic framework material is only 446 mg / g, and under the dark conditions of 1 bar and 273K, the adsorption value of the composite filter membrane formed by the composite of the core-shell structure metal organic framework and graphene oxide can reach more than 800 mg / g. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] 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 prior art descriptions. Obviously, the drawings described below are only some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0019] Figure 1 This is a SEM image of the metal organic framework material prepared in Comparative Example 1; Figure 2 This is a SEM image of the core-shell metal organic framework material prepared in Example 1; Figure 3 The XRD pattern of the core-shell metal organic framework material prepared in Example 1; Figure 4 is a SEM image of a cross section of the graphene oxide composite filter membrane prepared in Example 1; Figure 5 This is a bar chart comparing the adsorption performance of the graphene oxide composite filter membrane prepared in Examples 1-2 and the pure metal organic framework material of Comparative Example 1. DETAILED DESCRIPTION

[0020] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. 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 creative work are within the scope of protection of the present invention.

[0021] It should be noted that the order of description of the following embodiments is not intended to limit the preferred order of the embodiments. In addition, in the description of the present application, the term "including" means "including but not limited to". Various embodiments of the present invention may be in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity and should not be understood as a rigid limitation on the scope of the present invention; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within the range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the numbered ranges, such as 1, 2, 3, 4, 5 and 6, which apply regardless of the range. In addition, whenever a numerical range is indicated in this article, it is meant to include any cited numbers (fractions or integers) within the indicated range.

[0022] The present invention provides a method for preparing a graphene oxide composite filter membrane, comprising the following steps: S1, preparing a silica nanoparticle dispersion; S2, dispersing the silica nanoparticle dispersion in methanol, then adding polyvinyl pyrrolidone, ultrasonicating, then adding a methanol solution containing a Co salt, and finally adding a 2-methylimidazole methanol solution, stirring, centrifuging, and drying to obtain a core-shell structure metal organic framework material; S3, dispersing graphene oxide in water to obtain a graphene oxide dispersion; S4, dispersing the core-shell structure metal organic framework material in ethanol to obtain a metal organic framework material dispersion; S5. After mixing the metal organic framework material dispersion liquid and the graphene oxide dispersion liquid, vacuum filtration is performed to form a membrane to obtain a graphene oxide composite filter membrane.

[0023] The metal organic framework mainly presents a porous structure, has a high specific surface area, and has good tetracycline adsorption performance. Graphene oxide has a certain adsorption effect on tetracycline, wherein the six-membered ring structure forms a π-π conjugation with the tetracycline molecule, and -OH and the like provide adsorption sites for tetracycline, thereby increasing the adsorption amount. The present invention combines the metal organic framework with graphene oxide, greatly improving the tetracycline adsorption activity, and is applied to the efficient adsorption of tetracycline in agricultural wastewater.

[0024] The preparation method of the graphene oxide composite filter membrane of the present invention is designed to first prepare a silicon dioxide nanoparticle dispersion, use polyvinyl pyrrolidone to modify the surface of the dispersion, then combine metal ions with organic ligands on the surface to form a metal-organic framework material with a core-shell structure, and finally composite the graphene oxide with the core-shell structure metal-organic framework through π-π conjugation, metal complexation and hydrogen bonding to form a filter membrane to complete the adsorption and removal of tetracycline molecules.

[0025] The advantages of the present invention are that the metal organic framework material is compounded with graphene oxide, which greatly improves the adsorption performance of tetracycline molecules, and is highly efficient, energy-saving, environmentally friendly and easy to recycle. Graphene oxide and metal organic framework materials have the ability to be mass-produced, so the preparation of the composite membrane meets the conditions for mass production and is suitable for large-scale application.

[0026] In some embodiments, a method for preparing a silica nanoparticle dispersion comprises the following steps: S11, mixing tetraethyl silicate and ethanol to obtain a first solution; S12, mixing aqueous ammonia, water and ethanol to obtain a second solution; S13, adding the first solution to the second solution, stirring, centrifuging, and washing to obtain silica nanoparticles; S14, dispersing the silicon dioxide nanoparticles in ethanol to obtain a silicon dioxide nanoparticle dispersion.

[0027] In some embodiments, in the step of mixing tetraethyl silicate and ethanol to obtain a first solution, the volume ratio of tetraethyl silicate to ethanol is (2-3):(22-23); In the step of mixing aqueous ammonia, water and ethanol to obtain a second solution, the volume ratio of aqueous ammonia, water and ethanol is (1.6-1.7):(2-5):(18-21); In the steps of adding the first solution to the second solution, stirring, centrifuging, washing, obtaining silica nanoparticles, and dispersing the silica nanoparticles in ethanol, the volume ratio of the first solution, the second solution, and the ethanol is (24-26):(21.6-27.7):(50-60); The mass concentration of ammonia water is 25~30%.

[0028] In some embodiments, polyvinyl pyrrolidone is added in the form of polyvinyl pyrrolidone methanol solution; and the Co salt is Co(NO3)2·6H2O.

[0029] In some embodiments, the silica nanoparticle dispersion is dispersed in methanol, then a polyvinyl pyrrolidone methanol solution is added, ultrasonicated, then a methanol solution containing Co(NO3)2·6H2O is added, and finally a 2-methylimidazole methanol solution is added; Wherein, in the step of dispersing the silica nanoparticle dispersion into methanol, the volume ratio of the silica nanoparticle dispersion to methanol is (3-4):(80-100); In the polyvinyl pyrrolidone methanol solution, the mass volume ratio of polyvinyl pyrrolidone to methanol is (0.1~0.3) g: (15~20) mL; The mass volume ratio of Co(NO3)2·6H2O to methanol in the methanol solution containing Co(NO3)2·6H2O is (120~130)mg:(10~15)mL; The mass volume ratio of 2-methylimidazole to methanol in 2-methylimidazole methanol solution is (1.5~2) g: (60~70) mL; The volume ratios of the silica nanoparticle dispersion, the methanol in the polyvinyl pyrrolidone methanol solution, the methanol in the methanol solution containing Co(NO3)2·6H2O, and the methanol in the 2-methylimidazole methanol solution are (3~4):(15~20):(10~15):(60~70).

[0030] In some embodiments, in the step of dispersing graphene oxide in water to obtain a graphene oxide dispersion, the mass volume ratio of graphene oxide to water is (12-13) mg:(50-60) mL.

[0031] In some embodiments, in the step of dispersing the core-shell structure metal organic framework material in ethanol to obtain a metal organic framework material dispersion, the mass volume ratio of the core-shell structure metal organic framework material to ethanol is (5~6) mg:(5~10) mL.

[0032] In some embodiments, after the metal organic framework material dispersion and the graphene oxide dispersion are mixed, the core-shell structure metal organic framework material and the graphene oxide are filtered on a cellulose acetate filter membrane carrier by vacuum filtration assisted method, so that the two are composited to form a composite filter membrane with a layered stacking structure to obtain a graphene oxide composite filter membrane.

[0033] In some embodiments, the metal organic framework material dispersion and the graphene oxide dispersion are stirred and mixed for 2 to 3 hours, and then vacuum filtered under a pressure difference of 0.8 to 1 bar to form a membrane to obtain a graphene oxide composite filter membrane.

[0034] In some embodiments, the first solution is added to the second solution, stirred for 10 to 15 hours, centrifuged, and washed to obtain silica nanoparticles; The silica nanoparticle dispersion is added to methanol and ultrasonically dispersed for 15 to 20 minutes. Then polyvinyl pyrrolidone is added and ultrasonic dispersion is continued for 15 to 20 minutes. Then a methanol solution containing Co salt is added and ultrasonic dispersion is continued for 15 to 20 minutes. Finally, 2-methylimidazole methanol solution is added and stirred for 3 to 5 hours. The mixture is centrifuged and dried to obtain a core-shell structured metal organic framework material.

[0035] Based on the same inventive concept, the present invention also provides a graphene oxide composite filter membrane, which is prepared by the above-mentioned preparation method.

[0036] Based on the same inventive concept, the present invention also provides a graphene oxide composite filter membrane prepared by the above preparation method or the use of the above graphene oxide composite filter membrane in adsorbing and removing tetracycline.

[0037] The adsorption value of a simple metal-organic framework material can reach 446 mg / g. Under dark conditions of 1 bar and 273 K, the adsorption value of a composite filter membrane formed by combining a core-shell structure metal-organic framework with graphene oxide can reach more than 800 mg / g.

[0038] The following further describes the graphene oxide composite filter membrane of the present application and its preparation method and application with specific examples. This section further describes the content of the present invention in conjunction with specific examples, but should not be construed as limiting the present invention. Unless otherwise specified, the technical means used in the examples are conventional means well known to those skilled in the art. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art.

[0039] In the following examples, the cellulose acetate filter membrane has a pore size of 0.22 μm, brand YOYOBIO, and item number J-SYA0674.

[0040] Example 1

[0041] The present invention provides a method for preparing a graphene oxide composite filter membrane, comprising the following steps: S1, preparing a silica nanoparticle dispersion, specifically comprising the following steps: S11, adding 2.23 mL of tetraethyl silicate and 22.77 mL of ethanol into a beaker to form a first solution; S12, adding 1.67 mL of 28% ammonia water, 2.5 mL of deionized water, and 20.83 mL of ethanol into a beaker to form a second solution; S13, under stirring, adding the first solution dropwise to the second solution, continuing stirring for 10 hours, centrifuging, and washing three times with ethanol to obtain silica nanoparticles; S14, dispersing the silicon dioxide nanoparticles into 50 mL of ethanol to obtain a silicon dioxide nanoparticle dispersion; S2. Preparation of core-shell metal organic framework materials, specifically comprising the following steps: S21, adding 3.5 mL of the silica nanoparticle dispersion into 90 mL of methanol and ultrasonically dispersing for 15 min to obtain a third solution; S22, dissolving 0.2 g of polyvinyl pyrrolidone in 18 mL of methanol to obtain a polyvinyl pyrrolidone methanol solution; adding the polyvinyl pyrrolidone methanol solution to the third solution, and continuing ultrasonication for 15 min to obtain a fourth solution; S23, dissolving 125 mg of Co(NO3)2·6H2O in 12 mL of methanol to obtain a methanol solution containing Co(NO3)2·6H2O; adding the methanol solution containing Co(NO3)2·6H2O to the fourth solution, and continuing ultrasonication for 15 min to obtain a fifth solution; S24, dissolving 1.5 g of 2-methylimidazole in 60 mL of methanol to obtain a 2-methylimidazole methanol solution; adding the 2-methylimidazole methanol solution to the fifth solution, continuing to stir for 3 h, washing three times with methanol, centrifuging, and drying in a vacuum oven at 80° C. for 12 h to obtain 70 mg of a purple core-shell metal organic framework material; S3, adding 12.5 mg of graphene oxide to 50 mL of deionized water, stirring to obtain a brown, uniformly dispersed graphene oxide dispersion; S4, ultrasonically dispersing 5 mg of the core-shell structure metal organic framework in 5 mL of ethanol to obtain a metal organic framework material dispersion; S5. After stirring and mixing the metal organic framework material dispersion in S4 and the graphene oxide dispersion in S3 for 2 hours, the core-shell structure metal organic framework material and graphene oxide are filtered on a cellulose acetate filter membrane carrier under a pressure difference of 1 bar by vacuum filtration assisted method, so that the two are combined to form a composite filter membrane with a layered stacking structure to obtain a graphene oxide composite filter membrane.

[0042] This embodiment also provides a tetracycline adsorption performance test experiment: 5 mg of tetracycline is weighed and added to a 50 mL titration bottle, deionized water is added to the titration bottle scale line, and a tetracycline aqueous solution with a concentration c0 of 100 mg / L is formed by stirring and dissolving. Then, the tetracycline aqueous solution is added to a vacuum filtration auxiliary device equipped with the graphene oxide composite filter membrane prepared in Example 1, and the solution is filtered under dark conditions at a temperature of 273K and a filtration pressure of 1 bar. Finally, the tetracycline concentration c1 of the filtered solution is measured to be 17.1 mg / L. The removal rate is calculated to be 82.9% by the formula (c0-c1) / c0×100%, and the adsorption value is 829 mg / g (such as Figure 5 as shown).

[0043] Example 2

[0044] The present invention provides a method for preparing a graphene oxide composite filter membrane, comprising the following steps: S1, preparing a silica nanoparticle dispersion, specifically comprising the following steps: S11, adding 2.23 mL of tetraethyl silicate and 22.77 mL of ethanol into a beaker to form a first solution; S12, adding 1.67 mL of 28% ammonia water, 5 mL of deionized water, and 18.33 mL of ethanol into a beaker to form a second solution; S13, under stirring, adding the first solution dropwise to the second solution, continuing stirring for 10 hours, centrifuging, and washing three times with ethanol to obtain silica nanoparticles; S14, dispersing the silicon dioxide nanoparticles into 50 mL of ethanol to obtain a silicon dioxide nanoparticle dispersion; S2. Preparation of core-shell metal organic framework materials, specifically comprising the following steps: S21, adding 3.5 mL of the silica nanoparticle dispersion into 90 mL of methanol and ultrasonically dispersing for 15 min to obtain a third solution; S22, dissolving 0.2 g of polyvinyl pyrrolidone in 18 mL of methanol to obtain a polyvinyl pyrrolidone methanol solution; adding the polyvinyl pyrrolidone methanol solution to the third solution, and continuing ultrasonication for 15 min to obtain a fourth solution; S23, dissolving 125 mg of Co(NO3)2·6H2O in 12 mL of methanol to obtain a methanol solution containing Co(NO3)2·6H2O; adding the methanol solution containing Co(NO3)2·6H2O to the fourth solution, and continuing ultrasonication for 15 min to obtain a fifth solution; S24, dissolving 1.5 g of 2-methylimidazole in 60 mL of methanol to obtain a 2-methylimidazole methanol solution; adding the 2-methylimidazole methanol solution to the fifth solution, continuing to stir for 3 h, washing three times with methanol, centrifuging, and drying in a vacuum oven at 80° C. for 12 h to obtain 70 mg of a purple core-shell metal organic framework material; S3, adding 12.5 mg of graphene oxide to 50 mL of deionized water, stirring to obtain a brown, uniformly dispersed graphene oxide dispersion; S4, ultrasonically dispersing 5 mg of the core-shell structure metal organic framework in 5 mL of ethanol to obtain a metal organic framework material dispersion; S5. After stirring and mixing the metal organic framework material dispersion in S4 and the graphene oxide dispersion in S3 for 2 hours, the core-shell structure metal organic framework material and graphene oxide are filtered on the cellulose acetate filter membrane carrier under the action of a pressure difference of 0.8 bar by vacuum filtration assisted method, so that the two are combined to form a composite filter membrane with a layered stacking structure to obtain a graphene oxide composite filter membrane.

[0045] This embodiment also provides a tetracycline adsorption performance test experiment: 5 mg of tetracycline is weighed and added to a 50 mL titration bottle, deionized water is added to the titration bottle scale line, and a tetracycline aqueous solution with a concentration c0 of 100 mg / L is formed by stirring and dissolving. Then, the tetracycline aqueous solution is added to a vacuum filtration auxiliary device equipped with the graphene oxide composite filter membrane prepared in Example 2, and the solution is filtered under dark conditions at a temperature of 273K and a filtration pressure of 1 bar. Finally, the tetracycline concentration c1 of the filtered solution is measured to be 17.65 mg / L. The removal rate is calculated to be 82.35% by the formula (c0-c1) / c0×100%, and the adsorption value is 823.5 mg / g (such as Figure 5 as shown).

[0046] Comparative Example 1 This comparative example provides a method for preparing a metal organic framework material, comprising the following steps: Weigh 1g Co(NO3)2•6H2O and 0.5g polyvinylpyrrolidone and add them to 60mL methanol to obtain solution A. Weigh 0.5g 2-methylimidazole and 3 microliters of triethylamine and add them to 60ml methanol to obtain solution B. Then add solution B to solution A under stirring, stir for 10 minutes, and let it stand for 24 hours. Finally, centrifuge and wash three times with methanol to obtain a metal organic framework material with a particle size of 400nm.

[0047] This comparative example also provides a tetracycline adsorption performance test experiment: 5 mg of tetracycline is weighed and added to a 50 mL titration bottle, deionized water is added to the titration bottle scale line, and a tetracycline aqueous solution with a concentration c0 of 100 mg / L is formed by stirring and dissolving, 10 mg of the metal organic framework material prepared in comparative example 1 is weighed and added to the solution, and stirred for 24 hours under dark conditions at a temperature of 273 K. Finally, the tetracycline concentration c1 of the supernatant after adsorption treatment is measured by centrifugation, which is 10.8 mg / L. The removal rate is calculated by the formula (c0-c1) / c0×100%, and the adsorption value is 446 mg / g (such as Figure 5 as shown).

[0048] Performance Characterization Figure 1 This is the SEM image of the metal organic framework material prepared in Comparative Example 1.

[0049] from Figure 1 It can be seen that the particle size of the metal organic framework material prepared in Comparative Example 1 is 400 nm, and it is a metal organic framework material with a typical polyhedral structure.

[0050] Figure 2 This is the SEM image of the core-shell structure metal organic framework material prepared in Example 1.

[0051] from Figure 2 It can be seen that the surface of the silica particles is coated with a layer of metal-organic framework material.

[0052] Figure 3 This is the XRD spectrum of the core-shell metal organic framework material (i.e., SiO2@ZIF-67) prepared in Example 1.

[0053] Figure 4 This is a SEM image of the cross section of the graphene oxide composite filter membrane prepared in Example 1.

[0054] from Figure 4 It can be seen that the core-shell structured metal organic framework nanoparticles are evenly distributed between the two-dimensional graphene oxide layers.

[0055] Figure 5 The graph is a comparative columnar graph of the adsorption performance of the graphene oxide composite filter membrane prepared in Examples 1 and 2 and the pure metal organic framework material of Comparative Example 1. Among them, the composite filter membrane 1 corresponds to Example 1, and the composite filter membrane 2 corresponds to Example 2.

[0056] from Figure 5 It can be seen that the adsorption value of tetracycline by the simple metal organic framework material is only 446 mg / g, while the adsorption value of tetracycline by the graphene oxide composite filter membrane of the present invention can reach more than 800 mg / g.

[0057] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a graphene oxide composite filter membrane, characterized in that: The following steps are involved: preparing a silica nanoparticle dispersion; The silica nanoparticle dispersion is dispersed in methanol, and then polyvinyl pyrrolidone is added, ultrasonicated, and then a methanol solution containing a Co salt is added, and finally a 2-methylimidazole methanol solution is added, stirred, centrifuged, and dried to obtain a core-shell structure metal organic framework material; dispersing graphene oxide in water to obtain a graphene oxide dispersion; Dispersing the core-shell structure metal organic framework material in ethanol to obtain a metal organic framework material dispersion; After the metal organic framework material dispersion liquid and the graphene oxide dispersion liquid are mixed, vacuum filtration is performed to form a membrane to obtain a graphene oxide composite filter membrane; The polyvinyl pyrrolidone is added in the form of polyvinyl pyrrolidone methanol solution; the Co salt is Co(NO3)2·6H2O; The silica nanoparticle dispersion was dispersed in methanol, and then polyvinyl pyrrolidone methanol solution was added, ultrasonicated, and then a methanol solution containing Co(NO3)2·6H2O was added, and finally a 2-methylimidazole methanol solution was added; Wherein, in the step of dispersing the silica nanoparticle dispersion into methanol, the volume ratio of the silica nanoparticle dispersion to methanol is (3-4):(80-100); In the polyvinyl pyrrolidone methanol solution, the mass volume ratio of polyvinyl pyrrolidone to methanol is (0.1-0.3) g: (15-20) mL; The mass volume ratio of Co(NO3)2·6H2O to methanol in the methanol solution containing Co(NO3)2·6H2O is (120-130) mg:(10-15) mL; The mass volume ratio of 2-methylimidazole to methanol in the 2-methylimidazole methanol solution is (1.5-2) g: (60-70) mL; The volume ratios of the silica nanoparticle dispersion, the methanol in the polyvinyl pyrrolidone methanol solution, the methanol in the methanol solution containing Co(NO3)2·6H2O, and the methanol in the 2-methylimidazole methanol solution are (3~4):(15~20):(10~15):(60~70).

2. The method for preparing the graphene oxide composite filter membrane according to claim 1, wherein: The preparation method of the silicon dioxide nanoparticle dispersion comprises the following steps: Mixing tetraethyl silicate and ethanol to obtain a first solution; Mixing aqueous ammonia, water and ethanol to obtain a second solution; adding the first solution to the second solution, stirring, centrifuging, and washing to obtain silica nanoparticles; The silicon dioxide nanoparticles are dispersed in ethanol to obtain a silicon dioxide nanoparticle dispersion.

3. The method for preparing the graphene oxide composite filter membrane according to claim 2, wherein: In the step of mixing tetraethyl silicate and ethanol to obtain a first solution, the volume ratio of tetraethyl silicate to ethanol is (2-3):(22-23); In the step of mixing aqueous ammonia, water and ethanol to obtain a second solution, the volume ratio of aqueous ammonia, water and ethanol is (1.6-1.7):(2-5):(18-21); In the steps of adding the first solution to the second solution, stirring, centrifuging, washing, obtaining silica nanoparticles, and dispersing the silica nanoparticles in ethanol, the volume ratio of the first solution, the second solution, and the ethanol is (24-26):(21.6-27.7):(50-60); The mass concentration of the ammonia water is 25-30%.

4. The method for preparing the graphene oxide composite filter membrane according to claim 1, wherein: In the step of dispersing graphene oxide in water to obtain a graphene oxide dispersion, the mass volume ratio of graphene oxide to water is (12-13) mg:(50-60) mL.

5. The method for preparing the graphene oxide composite filter membrane according to claim 1, characterized in that: In the step of dispersing the core-shell structure metal organic framework material in ethanol to obtain a metal organic framework material dispersion, the mass volume ratio of the core-shell structure metal organic framework material to ethanol is (5-6) mg: (5-10) mL; The metal organic framework material dispersion liquid and the graphene oxide dispersion liquid are stirred and mixed for 2 to 3 hours, and then vacuum filtered under a pressure difference of 0.8 to 1 bar to form a membrane, thereby obtaining a graphene oxide composite filter membrane.

6. The method for preparing the graphene oxide composite filter membrane according to claim 3, characterized in that: The first solution is added to the second solution, stirred for 10-15 hours, centrifuged, and washed to obtain silica nanoparticles; The silica nanoparticle dispersion is added to methanol and ultrasonically dispersed for 15 to 20 minutes. Then polyvinyl pyrrolidone is added and ultrasonic dispersion is continued for 15 to 20 minutes. Then a methanol solution containing Co salt is added and ultrasonic dispersion is continued for 15 to 20 minutes. Finally, 2-methylimidazole methanol solution is added and stirred for 3 to 5 hours. The mixture is centrifuged and dried to obtain a core-shell structured metal organic framework material.

7. A graphene oxide composite filter membrane, characterized in that: The method is prepared by the preparation method according to any one of claims 1 to 6.

8. Use of a graphene oxide composite filter membrane prepared by the preparation method according to any one of claims 1 to 6 or a graphene oxide composite filter membrane according to claim 7 in the adsorption and removal of tetracycline.

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