Porous graphene composite membrane material modified by molecular engineering technology as well as preparation and application of porous graphene composite membrane material

Abstract

The invention belongs to the technical field of graphene separation membranes, and discloses a molecular engineering technology modified porous graphene composite membrane material and preparation and application thereof, and a preparation method comprises the following steps: (1) preparing a nickel sheet substrate; (2) forming a membrane casting solution by using the segmented copolymer and sugar; (3) coating the surface of a nickel sheet substrate with the membrane casting solution, and pyrolyzing to obtain a porous graphene membrane PNG containing a carbon support layer; (4) performing Ni etching on the product, and transferring the product to a polymer film substrate to obtain a PNG / polymer composite film; and (5) adding a water-phase monomer solution to the PNG side of the PNG / polymer composite membrane, adding an oil-phase multi-acyl chloride monomer solution to the polymer membrane side, and carrying out interfacial polymerization reaction to obtain the molecular engineering modified graphene composite membrane material. A polyamide blocking structure is introduced, the pore size of the graphene film is effectively reduced, pore size distribution is tightened, meanwhile, positive charges are introduced, and the ion screening performance of the graphene composite film can be efficiently enhanced.

Description

Technical Field

[0001] The present invention belongs to the technical field of graphene separation membranes, and more specifically, relates to a porous graphene composite membrane material modified by molecular engineering technology and the preparation and application thereof. Background Art

[0002] Since most traditional ion separation technologies (extraction, precipitation, evaporation) are complex to operate, have high energy consumption, low efficiency, and cause great environmental pollution, membrane separation technology uses a membrane that has a selective effect on the separation object as a separation medium, and uses external driving forces (pressure difference, concentration difference, temperature difference, etc.) to achieve selective separation of elements, greatly improving separation efficiency, reducing environmental pollution, and reducing the complexity of the operation process. In the process of ion separation by membrane separation technology, the separation membrane selectively transmits the presence of different ions. The difference in transmission properties makes the two ions that need to be separated on the feed side and the permeate side respectively, thereby achieving ion separation.

[0003] Graphene membrane is a single-atom membrane material composed of hexagonal carbon atoms. It has high mechanical strength, stable chemical structure, atomic-level thickness and the ability to create adjustable nano-scale pores. The pore size distribution of graphene membranes is a key factor in determining their ion separation performance. Currently, the most commonly used methods are to control the membrane pore size distribution during the synthesis process, introduce a masking layer to control the membrane pore size distribution, and functionalize the membrane pores to achieve specific separation. Summary of the invention

[0004] In view of the above defects or improvement needs of the prior art, the purpose of the present invention is to provide a porous graphene composite membrane material modified by molecular engineering technology and its preparation and application, by improving the pore size, pore size distribution and charge near the pores of the graphene composite membrane, introducing a polyamide blocking structure, effectively reducing the pore size of the graphene membrane and tightening the pore size distribution, and introducing positive charges at the same time, which can effectively enhance the ion screening performance of the graphene composite membrane. In addition, the present invention has a simple structure and high separation efficiency, and can be widely used in the fields of lithium recovery from the leachate of waste lithium-ion battery positive electrode materials, heavy metal recovery, etc.

[0005] To achieve the above object, according to one aspect of the present invention, a method for preparing a molecularly engineered modified graphene composite film material is provided, characterized in that it comprises the following steps:

[0006] (1) polishing a nickel sheet having hexagonal Ni on the surface to obtain a nickel sheet substrate having a smooth surface;

[0007] (2) dissolving the block copolymer and the sugar in an organic solvent for a solvothermal reaction to obtain a casting solution; wherein the solvothermal reaction is carried out at a temperature of 150 to 200° C. for 2 to 4 hours;

[0008] (3) coating the casting solution on the surface of the nickel substrate, and then pyrolyzing it under a reducing atmosphere containing hydrogen, thereby obtaining a porous graphene membrane PNG containing a carbon support layer on the nickel substrate; wherein the pyrolysis is performed at a temperature of 400 to 600° C. for 1 to 3 hours;

[0009] (4) floating the product obtained in step (3) on the surface of the etching solution for Ni etching, and after the etching of the nickel sheet substrate is completed, transferring the product to the polymer film substrate to obtain a PNG / polymer composite film;

[0010] (5) adding an aqueous monomer solution to the PNG side of the PNG / polymer composite membrane so that the PNG side is in contact with the aqueous monomer solution, and at the same time, adding an oily polyacyl chloride monomer solution to the polymer membrane side of the PNG / polymer composite membrane so that the polymer membrane side is in contact with the oily polyacyl chloride monomer solution, wherein the aqueous monomer solution and the oily polyacyl chloride monomer solution are separated by the PNG / polymer composite membrane; and obtaining a molecularly engineered modified graphene composite membrane material through an interfacial polymerization reaction;

[0011] Among them, the size of the aqueous phase monomer used in the aqueous phase monomer solution in step (5) is smaller than the average pore size in the PNG / polymer composite membrane obtained in step (4); the pore size of the molecularly engineered modified graphene composite membrane material is determined by the size of the aqueous phase monomer; for the molecularly engineered modified graphene composite membrane material, when the size of a certain external component is greater than or equal to the pore size of the molecularly engineered modified graphene composite membrane material, the external component cannot pass through the molecularly engineered modified graphene composite membrane material; when the size of a certain external component is smaller than the pore size of the molecularly engineered modified graphene composite membrane material, the external component can pass through the molecularly engineered modified graphene composite membrane material.

[0012] As a further preferred embodiment of the present invention, in step (1), the nickel sheet having hexagonal Ni on the surface is obtained by heating the nickel sheet under a reducing atmosphere containing hydrogen for annealing and then cooling;

[0013] Preferably, the reducing atmosphere containing hydrogen is a mixture of hydrogen and argon, wherein the volume percentage concentration of hydrogen is 8-10%, and the volume percentage concentration of argon is 90-92%;

[0014] The annealing is performed at a temperature of 1100-1200°C.

[0015] As a further preferred embodiment of the present invention, in step (2), the block copolymer is any one of polystyrene-b-polymethyl methacrylate, polyisobutylene-g-polystyrene, ethylene-propylene rubber-g-polystyrene, and polystyrene-b-poly(4-vinylpyridine);

[0016] The sugar is any one of glucose, sucrose, turanose, maltose, lactose and trehalose;

[0017] The organic solvent is any one of dimethyl sulfoxide, sulfolane, diphenyl sulfone, N-methylpyrrolidone, N,N-dimethylformamide, and dimethylacetamide;

[0018] The ratio of the mass of the block copolymer, the mass of the sugar and the volume of the organic solvent meets the requirement of (0.1-1.0) g: (0.2-2.0) g: (2-20) ml.

[0019] As a further preference of the present invention, in step (3), the coating is performed by any one of spin coating and scraping coating.

[0020] As a further preferred embodiment of the present invention, in step (4), the etching solution is any one of nitric acid, hydrochloric acid, ferric chloride, ammonium persulfate, and sodium persulfate solution, and the concentration of the etching solution is 0.5 to 2 mol / L;

[0021] The polymer membrane substrate is any one of poly(p-phenylene terephthalate) (Kevlar), polyethersulfone membrane (PES), polyvinylidene fluoride membrane (PVDF), polytetrafluoroethylene membrane (PTFE) and polysulfone membrane (PSF).

[0022] As a further preferred embodiment of the present invention, in step (5), the aqueous monomer used in the aqueous monomer solution is any one of piperazine, 2-methylpiperazine, 2,5-dimethylpiperazine, 4-aminomethylpiperazine, 2,5-diethylpiperazine, p-phenylenediamine, m-phenylenediamine, mesitylenetriamine, diaminotoluene, ethylenediamine, propylenediamine, and polyethyleneimine; and the concentration of the aqueous monomer solution is 0.1 to 8 wt%;

[0023] The polyacyl chloride monomer used in the oil phase polyacyl chloride monomer solution is any one of trimesoyl chloride, terephthaloyl chloride, isophthaloyl chloride, biphenyl dichloride, benzene trisulfonyl chloride, propanoyl chloride, succinoyl chloride, glutaryl chloride, glutaryl chloride, adipoyl chloride, maleic chloride, cyclopropane trichloride, cyclobutane trichloride, cyclobutane tetrachloride, cyclopentane dichloride, cyclopentane trichloride, cyclopentane tetrachloride, cyclohexane dichloride, cyclohexane trichloride or cyclohexane tetrachloride; the concentration of the oil phase polyacyl chloride monomer solution is 0.05-4.0wt%;

[0024] Preferably, the oil phase solvent used in the oil phase polyacyl chloride monomer solution is any one of n-hexane, cyclohexane, heptane, octane, naphtha, Isopar-E, Isopar-G, Isopar-L or mineral oil.

[0025] According to another aspect of the present invention, the present invention provides a molecularly engineered modified graphene composite membrane material prepared by the above-mentioned preparation method.

[0026] According to another aspect of the present invention, the present invention provides the use of the above molecular engineering modified graphene composite membrane material as membrane separation.

[0027] As a further preferred embodiment of the present invention, the application is specifically the application of membrane separation in the process of ion separation; preferably, the application is specifically the application in the separation of monovalent and divalent ions.

[0028] As a further preferred embodiment of the present invention, the ion separation is specifically used for lithium recovery from the leachate of waste lithium-ion battery positive electrode materials.

[0029] The above technical scheme conceived by the present invention is compared with the prior art. The porous graphene composite membrane material modified by molecular engineering in the present invention is prepared by using graphene materials with high strength, stable properties and atomic-level thickness after interfacial polymerization modification. The present invention improves the pore size distribution and functionalization of the porous graphene membrane, artificially manufactures a blocking structure, and introduces positively charged functional groups at the same time, which can effectively enhance the ion screening efficiency; and the graphene membrane itself is only atomic-level thick, with low mass transfer resistance, and can achieve efficient ion transmission. The graphene membrane is a self-supporting graphene membrane formed by pyrolysis of a polymer, and then uses an aqueous phase amine-containing monomer and a polyacyl chloride monomer to adjust the pore size and modify the surface functional groups, so as to be prepared by such modification. On the one hand, the advantages of the graphene membrane such as high mechanical strength, stable chemical properties, corrosion resistance, and low mass transfer resistance are utilized; on the other hand, the modified graphene composite membrane material has high ion separation performance and is very suitable for practical applications. Taking piperazine as an example, the size of piperazine itself is about 0.7 nm. Based on the method of the present invention, using piperazine as the aqueous phase monomer can block the pores of the graphene film, reduce the pore size, and concentrate the pore size distribution. The corresponding molecular engineering modified graphene composite membrane material has a suitable pore size (pore size is concentrated at 0.7 nm) and charge distribution. As shown in Example 1 below, it can achieve accurate separation of different types of ions, and the selectivity can reach up to 10 2 Magnitude (the size of piperazine is about 0.7nm. During the interfacial polymerization reaction, the water-phase monomer and the oil-phase monomer are respectively applied to the two sides of the graphene film, so that piperazine, a water-phase monomer, can pass through the pores with a diameter greater than or equal to 0.7nm in the graphene film and undergo interfacial polymerization reaction with the oil-phase monomer on the opposite side, thereby blocking the larger pores in the graphene film, that is, it can block the pores with a diameter greater than or equal to 0.7nm, so that the pore size of the modified graphene film is smaller and the pore size distribution is more concentrated).

[0030] In the present invention, the water phase monomer is selected according to the pore size of the modified graphene membrane required for the separation target, and the pore size of the modified graphene membrane is determined by the size of the water phase monomer; when the size of a certain external component is greater than or equal to the pore size of the modified graphene membrane, the external component cannot be used to modify the graphene composite membrane material through molecular engineering; when the size of a certain external component is less than the pore size of the modified graphene membrane, the external component can be used to modify the graphene composite membrane material through molecular engineering. The graphene membrane produced by the traditional membrane making method has a wide pore size distribution and many defects, which greatly reduces its ion separation efficiency. Although the prior art also reports the interfacial polymerization method, that is, by using water phase monomers and oil phase monomers, the ultrafiltration membrane is modified by interfacial polymerization reaction, but these prior arts are mixed together during the modification process to form a complete separation layer. The present invention applies water-phase monomers and oil-phase monomers to both sides of the graphene film respectively, and selects water-phase monomers according to the separation membrane pore size required by the separation target. By using water-phase monomer materials whose water-phase monomer size is equal to the separation membrane pore size required by the separation target, the corresponding modified graphene film has a pore size after blocking that meets the critical size requirement, and the pore size distribution is more concentrated. In addition, the polyamide structure (PA) generated by interfacial polymerization is used to perform directional blocking near the graphene membrane pores and introduce positive charges, which can improve the ion separation efficiency.

[0031] The preparation method of the present invention is to use block copolymer and sugar as precursors, to form a porous graphene film with a carbon support layer by pyrolysis on an annealed nickel sheet, and then to use aqueous monomers (such as PIP) and polyacyl chloride monomers (such as TMC) molecules to block and modify the defects and macropores of the graphene film, so that the graphene composite membrane separation material prepared by modification has monovalent and polyvalent ion separation performance. The present invention utilizes block copolymer and sugar as precursors (specifically, the casting liquid formed by block copolymer and sugar), to form a porous graphene film with a support layer by pyrolysis (that is, a self-supporting porous graphene film is formed by pyrolysis of the casting liquid), and then utilizes aqueous phase amine-containing monomers and polyacyl chloride monomers to carry out molecular engineering modification to make it a separation membrane material with stable structure and high performance, so that the larger membrane pores are directional blocked and functionalized, and the porous graphene composite membrane material modified by molecular engineering obtained can effectively improve the ion separation efficiency as a whole, and can be particularly applied to accurate monovalent ion / divalent ion separation. By modifying the aqueous phase containing amine monomers and polyacyl chloride monomers, the membrane pore size is reduced, the pore size distribution is tightened, and the amino groups distributed near the membrane pores are positively charged, which is helpful for the separation of monovalent and divalent ions.

[0032] Specifically analyzed, the present invention can achieve the following beneficial effects:

[0033] (1) The present invention selects porous graphene membrane materials as the modification object, which has better mechanical strength and smaller mass transfer resistance than ordinary separation membrane materials. The porous graphene membrane has stable chemical properties, high mechanical strength and atomic-level thickness, which makes it have the potential to become an efficient separation membrane material.

[0034] (2) The graphene membrane separation material in the present invention is a graphene membrane modified by molecular engineering, which can effectively improve the ion separation efficiency and reduce the mass transfer resistance. The interfacial polymerization reaction of the aqueous phase containing amine monomers and polyacyl chloride monomers of the present invention can react near the macropores of the graphene membrane material and form a PA structure with blocking and positive charge, so that the material as a whole has a narrow pore size distribution. The synergistic effect of the smaller pore size and narrow pore size distribution of the material and the positive charge introduced near the membrane pores improves the ion separation ability.

[0035] The present invention can obtain a modified graphene membrane with different pore size distributions by changing the aqueous phase monomer used. For example, when piperazine with a molecular size of 0.7 nm is used to modify the graphene membrane, the size distribution of the modified graphene membrane obtained is concentrated at 0.7 nm; and when polyethyleneimine with a molecular size of 1.2 nm is used to modify the graphene membrane, the size distribution of the modified graphene membrane obtained is concentrated at 1.2 nm. The same is true for other aqueous phase monomers (such as 2-methylpiperazine, 2,5-dimethylpiperazine, 4-aminomethylpiperazine, 2,5-diethylpiperazine, p-phenylenediamine, m-phenylenediamine, mesitylenetriamine, diaminotoluene, ethylenediamine, propylenediamine).

[0036] The present invention introduces water-phase monomers and oil-phase monomers on both sides of a graphene membrane respectively, and forms a polyamide structure near the original larger-sized graphene membrane pores through an interfacial polymerization reaction to adjust the pore size distribution and charge distribution of the graphene membrane, rather than introducing water-phase and oil-phase monomers on the same side to form a complete polyamide layer on the surface of the graphene membrane. The specific pore size and charge regulation of the present invention enhances the separation efficiency of the membrane for ions.

[0037] (3) The graphene separation membrane material of the present invention can be particularly applied to the precise separation of monovalent and divalent ions. By using membrane separation technology, the present invention can recover valuable metal elements (such as Li element), and can be further used to construct a device for recovering valuable metal elements by step membrane separation, and recover high-value monovalent metal elements from wastewater containing a variety of metal ions. For example, separation membrane materials of different sizes can be prepared by changing the size of the composite membrane, and assembled into a separation membrane device to meet the needs of different application scenarios.

[0038] The present invention prepares a porous graphene membrane with a support membrane by a pyrolysis method, and reduces defects introduced in the graphene membrane transfer process by introducing a carbon support layer during the synthesis process; through molecular engineering modification, the pore size and pore size distribution of the membrane are adjusted at the microscopic (nanoscale) level, thereby increasing the ion separation efficiency; and at the same time, by introducing positive charges near the membrane pores, the separation efficiency of monovalent and divalent ions is further improved.

[0039] In summary, the present invention has a simple process and high ion separation efficiency, and can be widely used in the fields of valuable metal recovery. Based on the present invention, the graphene membrane can be modified by using different aqueous phase monomers to prepare modified graphene membranes with different separation effects. That is, different aqueous phase monomers can be selected according to actual separation needs to achieve a modified graphene membrane with a customized pore size distribution, thereby achieving a preset separation effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 It is a pore size distribution diagram (radius) of the single-layer porous graphene membrane (porous nanocrystalline graphene, PNG) obtained in Example 1 and the molecularly engineered single-layer porous graphene composite membrane (Molecular anchoring by PIP to porous nanocrystalline graphene membrane, MAP-PNG) obtained in Example 1.

[0041] Figure 2 It is a comparison diagram of the surface nano-infrared test of the separation membrane material of comparative example 1 and embodiment 1 of the present invention and an infrared spectrum diagram of a specific position; wherein, Figure 2 a in the figure is a comparison diagram of surface nano-infrared test, (1) and (2) small figures correspond to comparative example 1, and (3) and (4) small figures correspond to example 1; Figure 2 b corresponds to points ①, ②, and ③ from 1400cm -1 To 1700cm -1 Infrared spectrum of (the specific positions of points ①, ②, ③ are as follows Figure 2 (as shown in a in the figure).

[0042] Figure 3 It is a comparison chart of the surface potential measurement results of the membrane material PNG / Kevlar prepared in Comparative Example 1, the separation membrane material MAP-PNG / Kevlar obtained in Example 1, and the separation membrane material MAE-PNG / Kevlar obtained in Example 2.

[0043] Figure 4This is a comparison chart of the selectivity of the membrane material PNG / Kevlar prepared in Comparative Example 1, the separation membrane material MAP-PNG / Kevlar obtained in Example 1, and the separation membrane material MAE-PNG / Kevlar obtained in Example 2 during ion separation. DETAILED DESCRIPTION

[0044] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0045] The nickel sheet substrate used in the following examples is obtained by annealing and mechanical polishing a commercially available amorphous nickel sheet (the surface of the nickel sheet after annealing has a hexagonal crystal structure). The poly(p-phenylene terephthalate) (Kevlar) substrate used is obtained by synthesizing a Kevlar solution (i.e., a Kevlar hydrogel solution with a Kevlar concentration of 2 wt%), then scraping and phase-inverting in water, with a thickness of 200 microns. The Kevlar solution preparation process is specifically as follows: 2 g of KOH solid is added to a 200 ml reagent bottle, 2 ml of DI water, 2 g of Kevlar wire, 95 ml of DMSO are added, and magnetic stirring is performed at room temperature for more than 24 hours.

[0046] The polyethersulfone substrate (PES) used was commercially available and had a thickness of 120 μm.

[0047] Example 1

[0048] The method for preparing a single-layer porous graphene composite membrane material based on molecular engineering modification in this embodiment comprises the following steps:

[0049] (1) placing a nickel sheet in a tube furnace and annealing at 1100° C. in a hydrogen atmosphere of 9.1% by volume hydrogen and 90.9% by volume argon, and polishing to obtain a nickel sheet substrate with a smooth surface;

[0050] (2) 0.1 g of polystyrene-b-poly(4-vinylpyridine) (PS-b-P4VP) and 0.2 g of turanose were dissolved in 2 mL of N,N-dimethylformamide solution and reacted in a reactor at 200 °C for 4 h to obtain a casting solution;

[0051] (3) Spin coating the casting solution obtained in step (2) on the surface of a nickel sheet substrate at 1000 rpm for 30 s and 1500 rpm for 30 s, and pyrolyzing the solution in a tube furnace at 600° C. for 3 h to obtain a porous graphene membrane PNG (porous nanocrystalline graphene, PNG) containing a carbon support layer on the nickel sheet substrate; the pyrolysis is carried out under a H2 / Ar mixed gas, the same below.

[0052] (4) floating the product obtained in step (3) on the surface of a 1 mol / L FeCl3 solution for etching, and after the Ni substrate is completely etched, transferring it to a poly(p-phenylene terephthalate) diamine substrate (Kevlar) to obtain a PNG / Kevlar composite film;

[0053] (5) The PNG / Kevlar composite film obtained in step (4) is clamped in an H-type cell, and 0.2 wt % piperazine (PIP) solution (solvent is water) and 0.15 wt % trimesoyl chloride solution (solvent is n-hexane) are added to the PNG side and the Kevlar side, respectively, to obtain a molecularly engineered modified graphene composite film material.

[0054] In addition, the sample obtained in step (5) of this example is recorded as "MAP-PNG / Kevlar".

[0055] Separation membrane performance test:

[0056] Ion selectivity test of separation membrane. Ion selectivity is the ratio of the transmission rate of the membrane for different ions. Ion selectivity is tested in a laboratory-scale H-type device. The membrane is sandwiched between two reservoirs containing a single electrolyte solution. Silver and silver chloride are used as electrodes. The ion transmission behavior in the membrane is tested by linear sweep voltammetry (LSV). The ion concentration of all tested single electrolyte solutions is 0.1M (the corresponding cation chloride solution, such as KCl solution, is used during the test). The potential is 5mV s -1 The rate is scanned from -0.5V to +0.5V, the corresponding current value is recorded and the conductivity value is calculated. Finally, the ion selectivity is calculated according to the following formula:

[0057] Ion selectivity ratio = (Z j ·G i ) / (Z i ·G j )

[0058] Among them G i and G j is the conductivity value of two different ions (under different membranes, the conductivity value of the same ion may also be different). The conductivity value (G) is the ratio of the current to its corresponding voltage during the test.i and Z j is the charge state of the cation.

[0059] The surface potential of the samples modified by molecular engineering was measured, and the results were as follows Figure 3 As shown, it is not difficult to see that the surface potential of the graphene membrane modified by molecular engineering using piperazine increases from the negative potential before modification (corresponding to the PNG / Kevlar obtained in Comparative Example 1 below) to 660 mV, proving that positive charges are introduced while forming the PA structure, which is more conducive to the separation of cations of different valence states by the separation membrane.

[0060] The samples modified by molecular engineering were tested for ion selectivity. Figure 4 As shown, K + / Li + The selectivity can reach 20.8, Li + / Mg 2+ The selectivity can reach 15.9, K + / Mg 2+ The selectivity can reach 330.8.

[0061] Example 2

[0062] The method for preparing a single-layer porous graphene composite membrane material based on molecular engineering modification in this embodiment comprises the following steps:

[0063] (1) placing a nickel sheet in a tube furnace and annealing at 1100° C. in a hydrogen atmosphere of 10% by volume hydrogen and 90% by volume argon, and polishing to obtain a nickel sheet substrate with a smooth surface;

[0064] (2) 0.5 g of polystyrene-b-poly(4-vinylpyridine) (PS-b-P4VP) and 1.0 g of turanose were dissolved in 10 mL of N,N-dimethylformamide solution and reacted in a reactor at 180° C. for 3 h to obtain a casting solution;

[0065] (3) Spin coating the casting solution obtained in step (2) on the surface of a nickel substrate at 1000 rpm for 30 s and 1500 rpm for 30 s, and pyrolyzing the solution in a tube furnace at 500° C. for 2 h to obtain a porous graphene film PNG (porous nanocrystalline graphene, PNG) containing a carbon support layer on the nickel substrate;

[0066] (4) floating the product obtained in step (3) on the surface of a 1 mol / L FeCl3 solution for etching, and after the Ni substrate is completely etched, transferring it to a poly(p-phenylene terephthalate) diamine substrate (Kevlar) to obtain a PNG / Kevlar composite film;

[0067] (5) clamping the PNG / Kevlar composite film obtained in step (4) in an H-type cell, adding a 1 wt % polyethyleneimine (PEI) solution (the solvent is water) and a 0.15 wt % trimesoyl chloride (TMC) solution (the solvent is n-hexane) to the PNG side and the Kevlar side, respectively, to obtain a molecularly engineered modified graphene composite film material;

[0068] In addition, the sample obtained in step (5) of this example is recorded as "MAE-PNG / Kevlar".

[0069] The surface potential of the MAE-PNG / Kevlar film obtained in step (5) was measured. The results are as follows: Figure 3 As shown, it is not difficult to see that the surface potential of the graphene membrane modified by molecular engineering with polyethyleneimine increases from the negative potential before modification to 370mV, proving that positive charges are introduced while forming the PA structure, which is beneficial to the separation of cations of different valence states by the separation membrane. Of course, compared with the surface potential of the graphene membrane modified by molecular engineering with piperazine of 660mV in Example 1, the lower potential increase in Example 2 proves the introduction of less positive charges, indicating that fewer pores are blocked, which also verifies from the side that the size of the water phase molecules will block pores of different pore size ranges (the molecular size of piperazine is 0.7nm, while the molecular size of polyethyleneimine is 1.2nm), thereby affecting the pore size distribution and charge distribution of the separation membrane modified by molecular engineering.

[0070] The MAE-PNG / Kevlar membrane obtained in step (5) was tested for ion selectivity. Figure 4 As shown, K + / Li + The selectivity is 1.7, Li + / Mg 2+ The selectivity is 5.1, K + / Mg 2+ The selectivity is 8.6. It can be seen that the modification effect of Example 2 is not as good as that of Example 1. This is because the size of the aqueous phase monomer polyethyleneimine (PEI) is about 1.2nm. Although it can penetrate the pores on the graphene film with a pore size greater than 1.2nm, the pore size of the corresponding modified graphene film is Figure 1 Similar, the pore size is mainly distributed around 1.2nm, but due to K + The size of the ion is 0.66nm, Mg 2+ The size of the ion is 0.86nm, Li + The size of the ions is 0.76 nm. The membrane obtained in Example 2 has a larger pore size and cannot effectively separate these ions.

[0071] If the system to be separated is replaced, and in the replaced system to be separated, the size of one component is below 1.2 nm and the size of one component is above 1.2 nm, then the MAE-PNG / Kevlar membrane obtained in Example 2 will be able to achieve better separation effect and have greater application.

[0072] Example 3

[0073] The method for preparing a single-layer porous graphene composite membrane material based on molecular engineering modification in this embodiment comprises the following steps:

[0074] (1) placing a nickel sheet in a tube furnace and annealing at 1100° C. in a hydrogen atmosphere of 9.1% by volume hydrogen and 90.9% by volume argon, and polishing to obtain a nickel sheet substrate with a smooth surface;

[0075] (2) 0.1 g of polystyrene-b-poly(4-vinylpyridine) (PS-b-P4VP) and 0.2 g of turanose were dissolved in 2 mL of N,N-dimethylformamide solution and reacted in a reactor at 180° C. for 3 h to obtain a casting solution;

[0076] (3) Spin coating the casting solution obtained in step (2) on the surface of a nickel substrate at 1000 rpm for 30 s and 1500 rpm for 30 s, and pyrolyzing the solution in a tube furnace at 500° C. for 1 h to obtain a porous graphene membrane PNG (porous nanocrystalline graphene, PNG) containing a carbon support layer on the nickel substrate;

[0077] (4) floating the product obtained in step (3) on the surface of a 1 mol / L FeCl3 solution for etching, and after the Ni substrate is completely etched, transferring it to a poly(p-phenylene terephthalate) diamine substrate (Kevlar) to obtain a PNG / Kevlar composite film;

[0078] (5) The PNG / Kevlar composite film obtained in step (4) is clamped in an H-type cell, and 8 wt % piperazine (solvent is water) and 4 wt % trimesoyl chloride solution (solvent is n-hexane) are added to the PNG side and the Kevlar side, respectively, to obtain a molecularly engineered modified graphene composite film material.

[0079] The membrane obtained in step (5) was tested for ion selectivity, where K + / Li + The selectivity is 12.5, Li + / Mg 2+ The selectivity is 21.3, K + / Mg 2+ The selectivity is 266.3.

[0080] Example 4

[0081] The method for preparing a single-layer porous graphene composite membrane material based on molecular engineering modification in this embodiment comprises the following steps:

[0082] (1) placing a nickel sheet in a tube furnace and annealing at 1100° C. in a hydrogen atmosphere of 8% by volume hydrogen and 92% by volume argon, and polishing to obtain a nickel sheet substrate with a smooth surface;

[0083] (2) 0.1 g of polystyrene-b-poly(4-vinylpyridine) (PS-b-P4VP) and 0.2 g of turanose were dissolved in 2 mL of N,N-dimethylformamide solution and reacted in a reactor at 180° C. for 3 h to obtain a casting solution;

[0084] (3) Spin coating the casting solution obtained in step (2) on the surface of a nickel substrate at 1000 rpm for 30 s and 1500 rpm for 30 s, and pyrolyzing the solution in a tube furnace at 500° C. for 1 h to obtain a porous graphene membrane PNG (porous nanocrystalline graphene, PNG) containing a carbon support layer on the nickel substrate;

[0085] (4) floating the product obtained in step (3) on the surface of a 1 mol / L FeCl3 solution for etching, and after the Ni substrate is completely etched, transferring it to a poly(p-phenylene terephthalate) diamine substrate (Kevlar) to obtain a PNG / Kevlar composite film;

[0086] (5) The PNG / Kevlar composite film obtained in step (4) is clamped in an H-type cell, and 1.5 wt% m-phenylenediamine solution (solvent is water) and 1 wt% trimesoyl chloride solution (solvent is octane) are added to the PNG side and the Kevlar side, respectively, to obtain a molecularly engineered modified graphene composite film material.

[0087] The membrane obtained in step (5) was tested for ion selectivity, where K + / Li + The selectivity is 2.5, Li + / Mg 2+ The selectivity is 25.1, K + / Mg 2+ The selectivity is 62.8.

[0088] Example 5

[0089] The method for preparing a single-layer porous graphene composite membrane material based on molecular engineering modification in this embodiment comprises the following steps:

[0090] (1) placing a nickel sheet in a tube furnace and annealing at 1100° C. in a hydrogen atmosphere of 9.1% by volume hydrogen and 90.9% by volume argon, and polishing to obtain a nickel sheet substrate with a smooth surface;

[0091] (2) 0.1 g of polystyrene-b-poly(4-vinylpyridine) (PS-b-P4VP) and 0.2 g of turanose were dissolved in 2 mL of N,N-dimethylformamide solution and reacted in a reactor at 150 °C for 4 h to obtain a casting solution;

[0092] (3) Spin coating the casting solution obtained in step (2) on the surface of a nickel substrate at 1000 rpm for 30 s and 1500 rpm for 30 s, and pyrolyzing the solution in a tube furnace at 600° C. for 2 h to obtain a porous graphene membrane PNG (porous nanocrystalline graphene, PNG) containing a carbon support layer on the nickel substrate;

[0093] (4) floating the product obtained in step (3) on the surface of a 1 mol / L FeCl3 solution for etching, and after the Ni substrate is completely etched, transferring it to a poly(p-phenylene terephthalate) diamine substrate (Kevlar) to obtain a PNG / Kevlar composite film;

[0094] (5) The PNG / Kevlar composite film obtained in step (4) is clamped in an H-type cell, and 8 wt % m-phenylenediamine solution (solvent is water) and 4 wt % trimesoyl chloride solution (solvent is n-hexane) are added to the PNG side and the Kevlar side, respectively, to obtain a molecularly engineered modified graphene composite film material.

[0095] The membrane obtained in step (5) was tested for ion selectivity, where K + / Li + The selectivity is 1.7, Li + / Mg 2+ The selectivity is 20.5, K + / Mg 2+ The selectivity is 34.9.

[0096] Example 6

[0097] The method for preparing a single-layer porous graphene composite membrane material based on molecular engineering modification in this embodiment comprises the following steps:

[0098] (1) placing a nickel sheet in a tube furnace and annealing at 1100° C. in a hydrogen atmosphere of 10% by volume hydrogen and 90% by volume argon, and polishing to obtain a nickel sheet substrate with a smooth surface;

[0099] (2) 0.2 g of polystyrene-b-poly(4-vinylpyridine) (PS-b-P4VP) and 0.4 g of turanose were dissolved in 4 mL of N,N-dimethylformamide solution and reacted in a reactor at 150 °C for 4 h to obtain a casting solution;

[0100] (3) Spin coating the casting solution obtained in step (2) on the surface of a nickel substrate at 1000 rpm for 30 s and 1500 rpm for 30 s, and pyrolyzing the solution in a tube furnace at 600° C. for 1 h to obtain a porous graphene membrane PNG (porous nanocrystalline graphene, PNG) containing a carbon support layer on the nickel substrate;

[0101] (4) floating the product obtained in step (3) on the surface of a 1 mol / L FeCl3 solution for etching, and after the Ni substrate is completely etched, transferring it to a poly(p-phenylene terephthalate) diamine substrate (Kevlar) to obtain a PNG / Kevlar composite film;

[0102] (5) The PNG / Kevlar composite film obtained in step (4) is clamped in an H-type cell, and 8 wt % polyethyleneimine solution (solvent is water) and 4 wt % trimesoyl chloride solution (solvent is cyclohexane) are added to the PNG side and the Kevlar side, respectively, to obtain a molecularly engineered modified graphene composite film material.

[0103] The membrane obtained in step (5) was tested for ion selectivity, where K + / Li + The selectivity is 1.2, Li + / Mg 2+ The selectivity is 21.3, K + / Mg 2+ The selectivity is 25.6.

[0104] Example 7

[0105] The method for preparing a single-layer porous graphene composite membrane material based on molecular engineering modification in this embodiment comprises the following steps:

[0106] (1) placing a nickel sheet in a tube furnace and annealing at 1100° C. in a hydrogen atmosphere of 8% by volume hydrogen and 92% by volume argon, and polishing to obtain a nickel sheet substrate with a smooth surface;

[0107] (2) dissolving 0.2 g of polystyrene-b-polymethyl methacrylate (PS-b-PMMA) and 0.4 g of turanose in 4 mL of N,N-dimethylformamide solution and reacting them in a reactor at 180° C. for 4 h to obtain a casting solution;

[0108] (3) Spin coating the casting solution obtained in step (2) on the surface of a nickel substrate at 1000 rpm for 30 s and 1500 rpm for 30 s, and pyrolyzing the solution in a tube furnace at 600° C. for 3 h to obtain a porous graphene membrane PNG (porous nanocrystalline graphene, PNG) containing a carbon support layer on the nickel substrate;

[0109] (4) floating the product obtained in step (3) on the surface of a 1 mol / L FeCl3 solution for etching, and after the Ni substrate is completely etched, transferring it to a polyethersulfone substrate (PES) to obtain a PNG / PES composite membrane;

[0110] (5) The PNG / PES composite membrane obtained in step (4) is clamped in an H-type cell, and 0.1 wt % piperazine solution (solvent is water) and 0.05 wt % trimesoyl chloride solution (solvent is n-hexane) are added to the PNG side and the PES membrane side, respectively, to obtain a molecularly engineered modified graphene composite membrane material.

[0111] The membrane obtained in step (5) was tested for ion selectivity, where K + / Li + The selectivity is 8.4, Li + / Mg 2+ The selectivity is 6.5, K + / Mg 2+ The selectivity is 54.6.

[0112] Example 8

[0113] The method for preparing a single-layer porous graphene composite membrane material based on molecular engineering modification in this embodiment comprises the following steps:

[0114] (1) placing a nickel sheet in a tube furnace and annealing at 1200° C. in a hydrogen atmosphere of 9.1% by volume hydrogen and 90.9% by volume argon, and polishing to obtain a nickel sheet substrate with a smooth surface;

[0115] (2) dissolving 1 g of polystyrene-b-poly(4-vinylpyridine) (PS-b-P4VP) and 2 g of turanose in 20 mL of N,N-dimethylformamide solution and reacting them in a reactor at 200 °C for 4 h to obtain a casting solution;

[0116] (3) Spin coating the casting solution obtained in step (2) on the surface of a nickel substrate at 1000 rpm for 30 s and 1500 rpm for 30 s, and pyrolyzing the solution in a tube furnace at 600° C. for 2 h to obtain a porous graphene membrane PNG (porous nanocrystalline graphene, PNG) containing a carbon support layer on the nickel substrate;

[0117] (4) floating the product obtained in step (3) on the surface of a 1 mol / L ammonium persulfate solution for etching, and after the Ni substrate is completely etched, transferring it to a polyethersulfone substrate (PES) to obtain a PNG / PES composite membrane;

[0118] (5) The PNG / PES composite membrane obtained in step (4) is clamped in an H-type cell, and 0.2 wt % polyethyleneimine solution (solvent is water) and 0.4 wt % succinoyl chloride solution (solvent is heptane) are added to the PNG side and the PES membrane side, respectively, to obtain a molecularly engineered modified graphene composite membrane material.

[0119] The membrane obtained in step (5) was tested for ion selectivity, where K + / Li + The selectivity is 2.2, Li + / Mg 2+ The selectivity is 6.5, K + / Mg 2+ The selectivity is 14.3.

[0120] Example 9

[0121] The method for preparing a single-layer porous graphene composite membrane material based on molecular engineering modification in this embodiment comprises the following steps:

[0122] (1) placing a nickel sheet in a tube furnace and annealing at 1100° C. in a hydrogen atmosphere of 8% by volume hydrogen and 92% by volume argon, and polishing to obtain a nickel sheet substrate with a smooth surface;

[0123] (2) 0.2 g of polystyrene-b-poly(4-vinylpyridine) (PS-b-P4VP) and 0.4 g of turanose were dissolved in 4 mL of N,N-dimethylformamide solution and reacted in a reactor at 200 °C for 2 h to obtain a casting solution;

[0124] (3) Spin coating the casting solution obtained in step (2) on the surface of a nickel substrate at 1000 rpm for 30 s and 1500 rpm for 30 s, and pyrolyzing the solution in a tube furnace at 500° C. for 2 h to obtain a porous graphene membrane PNG (porous nanocrystalline graphene, PNG) containing a carbon support layer on the nickel substrate;

[0125] (4) floating the product obtained in step (3) on the surface of a 1 mol / L FeCl3 solution for etching, and after the Ni substrate is completely etched, transferring it to a poly(p-phenylene terephthalate) diamine substrate (Kevlar) to obtain a PNG / Kevlar composite film;

[0126] (5) The PNG / Kevlar composite film obtained in step (4) is clamped in an H-type cell, and 2 wt % piperazine solution (solvent is water) and 4 wt % trimesoyl chloride solution (solvent is n-hexane) are added to the PNG side and the Kevlar side, respectively, to obtain a molecularly engineered modified graphene composite film material.

[0127] The membrane obtained in step (5) was tested for ion selectivity, where K + / Li + The selectivity is 11.3, Li + / Mg 2+ The selectivity is 15.3, K + / Mg 2+ The selectivity is 172.9.

[0128] Comparative Example 1

[0129] This comparative example uses a single-layer porous graphene composite membrane (not modified by molecular engineering), which specifically includes the following steps:

[0130] (1) placing a nickel sheet in a tube furnace and annealing at 1100° C. in a hydrogen atmosphere of 9.1% by volume hydrogen and 90.9% by volume argon, and polishing to obtain a nickel sheet substrate with a smooth surface;

[0131] (2) 0.1 g of polystyrene-b-poly(4-vinylpyridine) (PS-b-P4VP) and 0.2 g of turanose were dissolved in 2 mL of N,N-dimethylformamide solution and reacted in a reactor at 200 °C for 3 h to obtain a casting solution;

[0132] (3) Spin coating the casting solution obtained in step (2) on the surface of a nickel substrate at 1000 rpm for 30 s and 1500 rpm for 30 s, and pyrolyzing the solution in a tube furnace at 500° C. for 1 h to obtain a porous graphene membrane PNG (porous nanocrystalline graphene, PNG) containing a carbon support layer on the nickel substrate;

[0133] (4) The product obtained in step (3) is floated on the surface of a 1 mol / L FeCl3 solution for etching. After the Ni substrate is completely etched, it is transferred to a poly(p-phenylene terephthalate) substrate (Kevlar) to obtain a PNG / Kevlar composite film.

[0134] In addition, the sample obtained in step (4) of this comparative example is recorded as "PNG / Kevlar".

[0135] The surface potential of the PNG / Kevlar film obtained in step (4) of Comparative Example 1 was measured. The results are as follows: Figure 3As shown, it is not difficult to see that the surface potential of the original PNG / Kevlar is -170mV, and the negative potential is not conducive to the separation of cations with different valence states.

[0136] The PNG / Kevlar membrane obtained in step (4) of comparative example 1 was tested for ion selectivity. The results are as follows: Figure 4 As shown, K + / Li + The selectivity is 1.5, Li + / Mg 2+ The selectivity is 1.2, K + / Mg 2+ The selectivity is 1.8.

[0137] The unmodified sample obtained in Comparative Example 1 and the sample modified by molecular engineering obtained in Example 1 were subjected to pore size simulation tests respectively. The results are as follows: Figure 1 As shown, it can be clearly seen that the pore size of the graphene membrane after molecular engineering modification is reduced (the size of piperazine is about 0.7nm, and the pore size of the modified graphene film is mainly distributed around 0.7nm), and the pore size distribution is narrower, which can improve the ion separation performance of the material. At the same time, nano-infrared tests were performed on the samples before modification and the samples after molecular engineering modification, and it can be clearly seen that the surface of the graphene membrane after molecular engineering modification is distributed with uneven polyamide structure, which can effectively reduce the pore size of the membrane and tighten the pore size distribution of the membrane. At the same time, positive charges are introduced near the membrane pores, which can further improve the ion separation performance of the material.

[0138] like Figure 1 As shown, the graphene membrane obtained in Comparative Example 1 has a larger pore size and a wider pore size distribution, while the molecularly engineered graphene composite membrane obtained after modification in Example 1 has a smaller pore size and a narrower pore size distribution.

[0139] Comparative Example 2

[0140] In this comparative example, the nickel sheet was not annealed, and was directly spin-coated and pyrolyzed, specifically comprising the following steps:

[0141] (1) polishing a commercially available amorphous nickel sheet to obtain a nickel sheet substrate with a smooth surface;

[0142] (2) 0.1 g of polystyrene-b-poly(4-vinylpyridine) (PS-b-P4VP) and 0.2 g of turanose were dissolved in 2 mL of N,N-dimethylformamide solution and reacted in a reactor at 180° C. for 2 h to obtain a casting solution;

[0143] (3) Spin coating the casting solution obtained in step (2) on the surface of a nickel substrate at 1000 rpm for 30 s and 1500 rpm for 30 s, and pyrolyzing the solution in a tube furnace at 600° C. for 1 h to obtain a porous graphene membrane PNG (porous nanocrystalline graphene, PNG) containing a carbon support layer on the nickel substrate;

[0144] (4) floating the product obtained in step (3) on the surface of a 1 mol / L FeCl3 solution for etching, and after the Ni substrate is completely etched, transferring it to a poly(p-phenylene terephthalate) diamine substrate (Kevlar) to obtain a PNG / Kevlar composite film;

[0145] (5) The PNG / Kevlar composite film obtained in step (4) is clamped in an H-type cell, and 2 wt % piperazine solution (solvent is water) and 4 wt % trimesoyl chloride solution (solvent is n-hexane) are added to the PNG side and the Kevlar side, respectively, to obtain a molecularly engineered modified graphene composite film material.

[0146] The membrane obtained in step (5) was tested for ion selectivity, where K + / Li + The selectivity is 1.1, Li + / Mg 2+ The selectivity is 1.2, K + / Mg 2+ The selectivity is 1.3.

[0147] Comparative Example 3

[0148] In this comparative example, only the nickel sheet is annealed without polishing to synthesize the graphene film, which specifically includes the following steps:

[0149] (1) placing a nickel sheet in a tube furnace and annealing at 1100° C. in a hydrogen atmosphere of 10% by volume hydrogen and 90% by volume argon to obtain a nickel sheet substrate;

[0150] (2) 0.1 g of polystyrene-b-poly(4-vinylpyridine) (PS-b-P4VP) and 0.2 g of turanose were dissolved in 2 mL of N,N-dimethylformamide solution and reacted in a reactor at 200 °C for 2 h to obtain a casting solution;

[0151] (3) Spin coating the casting solution obtained in step (2) on the surface of a nickel substrate at 1000 rpm for 30 s and 1500 rpm for 30 s, and pyrolyzing the solution in a tube furnace at 400° C. for 1 h to obtain a porous graphene membrane PNG (porous nanocrystalline graphene, PNG) containing a carbon support layer on the nickel substrate;

[0152] (4) floating the product obtained in step (3) on the surface of a 1 mol / L FeCl3 solution for etching, and after the Ni substrate is completely etched, transferring it to a polyethersulfone substrate (PES) to obtain a PNG / PES composite membrane;

[0153] (5) The PNG / PES composite membrane obtained in step (4) is clamped in an H-type cell, and 0.2 wt % piperazine solution (solvent is water) and 0.15 wt % trimesoyl chloride solution (solvent is n-hexane) are added to the PNG side and the PES side, respectively, to obtain a molecularly engineered modified graphene composite membrane material.

[0154] The membrane obtained in step (5) was tested for ion selectivity, where K + / Li + The selectivity is 1.2, Li + / Mg 2+ The selectivity is 1.3, K + / Mg 2+ The selectivity is 1.6.

[0155] Comparative Example 4

[0156] In this comparative example, the casting solution is not heat treated, and the graphene film is directly synthesized by spin coating, which specifically includes the following steps:

[0157] (1) placing a nickel sheet in a tube furnace and annealing at 1200° C. in a hydrogen atmosphere of 9.1% by volume hydrogen and 90.9% by volume argon, and polishing to obtain a nickel sheet substrate with a smooth surface;

[0158] (2) dissolving 0.5 g of polystyrene-b-poly(4-vinylpyridine) (PS-b-P4VP) and 1.0 g of turanose in 10 mL of N,N-dimethylformamide solution to obtain a casting solution;

[0159] (3) Spin coating the casting solution obtained in step (2) on the surface of a nickel substrate at 1000 rpm for 30 s and 1500 rpm for 30 s, and pyrolyzing the solution in a tube furnace at 400° C. for 1 h to obtain a porous graphene membrane PNG (porous nanocrystalline graphene, PNG) containing a carbon support layer on the nickel substrate;

[0160] (4) floating the product obtained in step (3) on the surface of a 1 mol / L ammonium persulfate solution for etching, and after the Ni substrate is completely etched, transferring it to a poly(p-phenylene terephthalate) diamine substrate (Kevlar) to obtain a PNG / Kevlar composite film;

[0161] (5) The PNG / Kevlar composite film obtained in step (4) is clamped in an H-type cell, and 0.2 wt % piperazine solution (solvent is water) and 0.15 wt % trimesoyl chloride solution (solvent is n-hexane) are added to the PNG side and the Kevlar side, respectively, to obtain a molecularly engineered modified graphene composite film material.

[0162] The membrane obtained in step (5) was tested for ion selectivity, where K + / Li + The selectivity is 1.0, Li + / Mg 2+ The selectivity is 1.1, K + / Mg 2+ The selectivity is 1.1.

[0163] Comparative Example 5

[0164] This comparative example does not perform pyrolysis after spin coating, and specifically includes the following steps:

[0165] (1) placing a nickel sheet in a tube furnace and annealing at 1200° C. in a hydrogen atmosphere of 9.1% by volume hydrogen and 90.9% by volume argon, and polishing to obtain a nickel sheet substrate with a smooth surface;

[0166] (2) 0.1 g of polystyrene-b-poly(4-vinylpyridine) (PS-b-P4VP) and 0.2 g of turanose were dissolved in 2 mL of N,N-dimethylformamide solution and reacted in a reactor at 200 °C for 3 h to obtain a casting solution;

[0167] (3) Spin coating the casting solution obtained in step (2) on the surface of the nickel substrate at 1000 rpm for 30 s and 1500 rpm for 30 s, and drying at room temperature for 1 h to obtain a film on the nickel substrate;

[0168] (4) floating the product obtained in step (3) on the surface of a 1 mol / L ammonium persulfate solution for etching, and after the Ni substrate is completely etched, transferring it to a poly(p-phenylene terephthalate) diamine substrate (Kevlar) to obtain a PNG / Kevlar composite film;

[0169] (5) The PNG / Kevlar composite film obtained in step (4) is clamped in an H-type cell, and 0.2 wt % piperazine solution (solvent is water) and 0.15 wt % trimesoyl chloride solution (solvent is n-hexane) are added to the PNG side and the Kevlar side, respectively, to obtain a molecularly engineered modified graphene composite film material.

[0170] The membrane obtained in step (5) was tested for ion selectivity, where K + / Li + The selectivity is 1.0, Li+ / Mg 2+ Selectivity is 1.0, K + / Mg 2+ The selectivity is 1.0.

[0171] Comparative Example 6

[0172] This comparative example is pyrolyzed at a relatively low temperature to synthesize a film after spin coating, specifically comprising the following steps:

[0173] (1) placing a nickel sheet in a tube furnace and annealing at 1100° C. in a hydrogen atmosphere of 9.1% by volume hydrogen and 90.9% by volume argon, and polishing to obtain a nickel sheet substrate with a smooth surface;

[0174] (2) 0.1 g of polystyrene-b-poly(4-vinylpyridine) (PS-b-P4VP) and 0.2 g of turanose were dissolved in 2 mL of N,N-dimethylformamide solution and reacted in a reactor at 200 °C for 3 h to obtain a casting solution;

[0175] (3) Spin coating the casting solution obtained in step (2) on the surface of a nickel substrate at 1000 rpm for 30 s and 1500 rpm for 30 s, and pyrolyzing the solution in a tube furnace at 300° C. for 2 h to obtain a porous graphene membrane PNG (porous nanocrystalline graphene, PNG) containing a carbon support layer on the nickel substrate;

[0176] (4) The product obtained in step (3) is floated on the surface of a 1 mol / L FeCl3 solution for etching. After the Ni substrate is completely etched, it is transferred to a poly(p-phenylene terephthalate) substrate (Kevlar) to obtain a PNG / Kevlar composite film.

[0177] (5) The PNG / Kevlar composite film obtained in step (4) is clamped in an H-type cell, and 0.2 wt % piperazine solution (solvent is water) and 0.15 wt % trimesoyl chloride solution (solvent is n-hexane) are added to the PNG side and the Kevlar side, respectively, to obtain a molecularly engineered modified graphene composite film material.

[0178] The membrane obtained in step (5) was tested for ion selectivity, where K + / Li + The selectivity is 1.1, Li + / Mg 2+ The selectivity is 1.1, K + / Mg 2+ The selectivity is 1.2.

[0179] Comparative Example 7

[0180] This comparative example treats the casting solution at a relatively low temperature, specifically comprising the following steps:

[0181] (1) placing a nickel sheet in a tube furnace and annealing at 1100° C. in a hydrogen atmosphere of 9.1% by volume hydrogen and 90.9% by volume argon, and polishing to obtain a nickel sheet substrate with a smooth surface;

[0182] (2) 0.1 g of polystyrene-b-poly(4-vinylpyridine) (PS-b-P4VP) and 0.2 g of turanose were dissolved in 2 mL of N,N-dimethylformamide solution and reacted in a reactor at 100 °C for 3 h to obtain a casting solution;

[0183] (3) Spin coating the casting solution obtained in step (2) on the surface of a nickel substrate at 1000 rpm for 30 s and 1500 rpm for 30 s, and pyrolyzing the solution in a tube furnace at 500° C. for 2 h to obtain a porous graphene membrane PNG (porous nanocrystalline graphene, PNG) containing a carbon support layer on the nickel substrate;

[0184] (4) floating the product obtained in step (3) on the surface of a 1 mol / L FeCl3 solution for etching, and after the Ni substrate is completely etched, transferring it to a poly(p-phenylene terephthalate) diamine substrate (Kevlar) to obtain a PNG / Kevlar composite film;

[0185] (5) The PNG / Kevlar composite film obtained in step (4) is clamped in an H-type cell, and 0.2 wt % piperazine solution (solvent is water) and 0.15 wt % trimesoyl chloride solution (solvent is n-hexane) are added to the PNG side and the Kevlar side, respectively, to obtain a molecularly engineered modified graphene composite film material.

[0186] The membrane obtained in step (5) was tested for ion selectivity, where K + / Li + The selectivity is 1.2, Li + / Mg 2+ The selectivity is 1.1, K + / Mg 2+ The selectivity is 1.3.

[0187] Comparative Example 8

[0188] This comparative example adopts the method of adding water phase monomer and oil phase monomer to the same side for modification, which specifically includes the following steps:

[0189] (1) placing a nickel sheet in a tube furnace and annealing at 1100° C. in a hydrogen atmosphere of 9.1% by volume hydrogen and 90.9% by volume argon, and polishing to obtain a nickel sheet substrate with a smooth surface;

[0190] (2) 0.1 g of polystyrene-b-poly(4-vinylpyridine) (PS-b-P4VP) and 0.2 g of turanose were dissolved in 2 mL of N,N-dimethylformamide solution and reacted in a reactor at 200 °C for 3 h to obtain a casting solution;

[0191] (3) Spin coating the casting solution obtained in step (2) on the surface of a nickel substrate at 1000 rpm for 30 s and 1500 rpm for 30 s, and pyrolyzing the solution in a tube furnace at 500° C. for 1 h to obtain a porous graphene membrane PNG (porous nanocrystalline graphene, PNG) containing a carbon support layer on the nickel substrate;

[0192] (4) floating the product obtained in step (3) on the surface of a 1 mol / L FeCl3 solution for etching, and after the Ni substrate is completely etched, transferring it to a poly(p-phenylene terephthalate) diamine substrate (Kevlar) to obtain a PNG / Kevlar composite film;

[0193] (5) The PNG / Kevlar composite film obtained in step (4) is clamped in an H-type cell, and 0.2wt% piperazine solution (solvent is water) and 0.15wt% trimesoyl chloride solution (solvent is n-hexane) are added to one side of the PNG in sequence, with the volume ratio of the two being 1:1, and no solution is added to the other side (i.e., the Kevlar side), thereby obtaining a molecularly engineered modified graphene composite film material.

[0194] The membrane obtained in step (5) was tested for ion selectivity, where K + / Li + The selectivity is 1.4, Li + / Mg 2+ The selectivity is 1.3, K + / Mg 2+ The selectivity is 1.8.

[0195] The above embodiments are only examples. For example, the aqueous phase monomer can be flexibly selected according to the pore size of the modified graphene membrane required for the separation target, and the aqueous phase monomer material whose molecular size is close to the pore size of the modified graphene membrane required by the target is selected (of course, the molecular size of the aqueous phase monomer is smaller than the average pore size in the PNG / polymer composite membrane before modification), such as piperazine, 2-methylpiperazine, 2,5-dimethylpiperazine, 4-aminomethylpiperazine, 2,5-diethylpiperazine, p-phenylenediamine, m-phenylenediamine, isophenyltriamine, diaminotoluene, ethylenediamine, propylenediamine, polyethyleneimine, etc.; for another example, spin coating can also be set by other rotation speeds and spin coating times (for example, it can be first spin coated at 1000-2000rpm for 30-60s, and then spin coated at 1000-3000rpm for 30-60s; of course, in addition to spin coating, other coating methods can also be used).

[0196] It will be easily understood by those skilled in the art that 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 and improvements 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 molecularly engineered modified graphene composite membrane material, characterized in that: The following steps are involved: (1) polishing a nickel sheet having hexagonal Ni on the surface to obtain a nickel sheet substrate having a smooth surface; (2) dissolving the block copolymer and the sugar in an organic solvent for a solvothermal reaction to obtain a casting solution; wherein the solvothermal reaction is carried out at a temperature of 150 to 200° C. for 2 to 4 hours; (3) coating the casting solution on the surface of the nickel substrate, and then pyrolyzing it under a reducing atmosphere containing hydrogen, thereby obtaining a porous graphene membrane PNG containing a carbon support layer on the nickel substrate; wherein the pyrolysis is performed at a temperature of 400 to 600° C. for 1 to 3 hours; (4) floating the product obtained in step (3) on the surface of the etching solution for Ni etching, and after the etching of the nickel sheet substrate is completed, transferring the product to the polymer film substrate to obtain a PNG / polymer composite film; (5) adding an aqueous monomer solution to the PNG side of the PNG / polymer composite membrane so that the PNG side is in contact with the aqueous monomer solution, and at the same time, adding an oily polyacyl chloride monomer solution to the polymer membrane side of the PNG / polymer composite membrane so that the polymer membrane side is in contact with the oily polyacyl chloride monomer solution, wherein the aqueous monomer solution and the oily polyacyl chloride monomer solution are separated by the PNG / polymer composite membrane; and obtaining a molecularly engineered modified graphene composite membrane material through an interfacial polymerization reaction; Among them, the size of the aqueous phase monomer used in the aqueous phase monomer solution in step (5) is smaller than the average pore size in the PNG / polymer composite membrane obtained in step (4); the pore size of the molecularly engineered modified graphene composite membrane material is determined by the size of the aqueous phase monomer; for the molecularly engineered modified graphene composite membrane material, when the size of a certain external component is greater than or equal to the pore size of the molecularly engineered modified graphene composite membrane material, the external component cannot pass through the molecularly engineered modified graphene composite membrane material; when the size of a certain external component is smaller than the pore size of the molecularly engineered modified graphene composite membrane material, the external component can pass through the molecularly engineered modified graphene composite membrane material.

2. The preparation method according to claim 1, characterized in that: In step (1), the nickel sheet having hexagonal Ni on the surface is obtained by heating the nickel sheet in a reducing atmosphere containing hydrogen for annealing and then cooling it; Preferably, the reducing atmosphere containing hydrogen is a mixture of hydrogen and argon, wherein the volume percentage concentration of hydrogen is 8-10%, and the volume percentage concentration of argon is 90-92%; The annealing is performed at a temperature of 1100-1200°C.

3. The preparation method according to claim 1, characterized in that: In step (2), the block copolymer is any one of polystyrene-b-polymethyl methacrylate, polyisobutylene-g-polystyrene, ethylene-propylene rubber-g-polystyrene, and polystyrene-b-poly(4-vinylpyridine); The sugar is any one of glucose, sucrose, turanose, maltose, lactose and trehalose; The organic solvent is any one of dimethyl sulfoxide, sulfolane, diphenyl sulfone, N-methylpyrrolidone, N,N-dimethylformamide, and dimethylacetamide; The ratio of the mass of the block copolymer, the mass of the sugar and the volume of the organic solvent meets the requirement of (0.1-1.0) g: (0.2-2.0) g: (2-20) ml.

4. The preparation method according to claim 1, characterized in that: In step (3), the coating is performed by any one of spin coating and scraping coating.

5. The preparation method according to claim 1, characterized in that: In step (4), the etching solution is any one of nitric acid, hydrochloric acid, ferric chloride, ammonium persulfate, and sodium persulfate solution, and the concentration of the etching solution is 0.5 to 2 mol / L; The polymer membrane substrate is any one of poly(p-phenylene terephthalate) (Kevlar), polyethersulfone membrane (PES), polyvinylidene fluoride membrane (PVDF), polytetrafluoroethylene membrane (PTFE) and polysulfone membrane (PSF).

6. The preparation method according to claim 1, characterized in that: In step (5), the aqueous monomer used in the aqueous monomer solution is any one of piperazine, 2-methylpiperazine, 2,5-dimethylpiperazine, 4-aminomethylpiperazine, 2,5-diethylpiperazine, p-phenylenediamine, m-phenylenediamine, mesitylenetriamine, diaminotoluene, ethylenediamine, propylenediamine, and polyethyleneimine; and the concentration of the aqueous monomer solution is 0.1 to 8 wt %; The polyacyl chloride monomer used in the oil phase polyacyl chloride monomer solution is any one of trimesoyl chloride, terephthaloyl chloride, isophthaloyl chloride, biphenyl dichloride, benzene trisulfonyl chloride, propanoyl chloride, succinoyl chloride, glutaryl chloride, glutaryl chloride, adipoyl chloride, maleic chloride, cyclopropane trichloride, cyclobutane trichloride, cyclobutane tetrachloride, cyclopentane dichloride, cyclopentane trichloride, cyclopentane tetrachloride, cyclohexane dichloride, cyclohexane trichloride or cyclohexane tetrachloride; the concentration of the oil phase polyacyl chloride monomer solution is 0.05-4.0wt%; Preferably, the oil phase solvent used in the oil phase polyacyl chloride monomer solution is any one of n-hexane, cyclohexane, heptane, octane, naphtha, Isopar-E, Isopar-G, Isopar-L or mineral oil.

7. A molecularly engineered modified graphene composite membrane material prepared by the preparation method according to any one of claims 1 to 6.

8. Application of the molecularly engineered modified graphene composite membrane material as claimed in claim 7 as membrane separation.

9. The use according to claim 8, characterized in that The application is specifically the application of membrane separation in the process of ion separation; preferably, the application is specifically the application in the separation of monovalent and divalent ions.

10. The use according to claim 8, characterized in that The ion separation is specifically used for lithium recovery from the leachate of waste lithium-ion battery positive electrode materials.

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