A porous graphene composite film material modified by a molecular engineering technique and preparation and application thereof

Abstract

The application belongs to the technical field of graphene separation membrane, and discloses a porous graphene composite membrane material modified by molecular engineering technology and a preparation and application thereof, and the preparation method comprises the following steps: (1) preparing a nickel sheet substrate; (2) forming a casting solution by using block copolymer and sugar; (3) coating the casting solution on the surface of the nickel sheet substrate, and pyrolyzing to obtain a porous graphene membrane PNG containing a carbon support layer; (4) etching the product by Ni, and transferring to a polymer membrane substrate to obtain a PNG / polymer composite membrane; (5) adding an aqueous monomer solution on the PNG side of the PNG / polymer composite membrane, and adding an oil phase multi-acid chloride monomer solution on the polymer membrane side, and obtaining a molecular engineering modified graphene composite membrane material through an interfacial polymerization reaction. The application introduces a polyamide blocking structure, effectively reduces the pore size of the graphene membrane and tightens the pore size distribution, and simultaneously introduces positive charges, which can efficiently enhance the ion sieving performance of the graphene composite membrane.

Description

TECHNICAL FIELD

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

[0002] Since traditional ion separation technologies (extraction, precipitation, evaporation) are mostly complex in operation, high in energy consumption, low in efficiency, and large in environmental pollution, membrane technology separation is to use a membrane with selective action on the separation object as a separation medium, and to realize selective separation of elements by means of external driving force (pressure difference, concentration difference, temperature difference, etc.), thereby greatly improving the 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 has selective transmission for different ions, and the difference in transmission makes the two ions to be separated on the feed side and the permeate side respectively, thereby realizing the separation of ions.

[0003] The graphene membrane is a single-atom membrane material composed of hexagonal carbon atoms, which has high mechanical strength, stable chemical structure, atomic-level thickness, and the characteristics of creating adjustable nanoscale pores. The pore size distribution of the graphene membrane is a key factor determining its ion separation performance. At present, the commonly used methods are to adjust the pore size distribution of the membrane during synthesis, to introduce a masking layer to adjust the pore size distribution of the membrane, and to functionalize the membrane pores to realize specific separation. SUMMARY

[0004] In view of the above defects or improvement needs of the prior art, the purpose of the present application is to provide a porous graphene composite membrane material modified by molecular engineering technology and preparation and application thereof. By improving the pore size, pore size distribution and charge near the pore of the graphene composite membrane, introducing a polyamide blocking structure, effectively reducing the pore size and tightening the pore size distribution of the graphene membrane, and introducing positive charges, the ion sieving performance of the graphene composite membrane can be efficiently enhanced. Moreover, the present application has simple structure, high separation efficiency, and can be widely applied in the fields of waste lithium ion battery positive material leaching liquid lithium recovery, heavy metal recovery, etc.

[0005] To achieve the above-mentioned purpose, according to one aspect of the present application, a preparation method of a molecular engineering modified graphene composite membrane material is provided, characterized in that it comprises the following steps:

[0006] (1) polishing a nickel sheet with a hexagonal crystal Ni surface to obtain a nickel sheet substrate with a smooth surface;

[0007] (2) dissolving the block copolymer and the sugar in an organic solvent to perform a solvothermal reaction, to obtain a casting solution; wherein the solvothermal reaction is performed at a temperature of 150-200℃ for 2-4h;

[0008] (3) coating the casting solution on the surface of the nickel sheet substrate, and then pyrolyzing under a reducing atmosphere containing hydrogen, so as to obtain a porous graphene film PNG containing a carbon support layer on the nickel sheet substrate; wherein the pyrolyzing is pyrolyzing at a temperature of 400-600℃ for 1-3h;

[0009] (4) floating the product prepared in step (3) on the surface of an etching solution to etch the Ni, and after the etching of the nickel sheet substrate is completed, transferring the product to a 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 film, so as to make the PNG side contact with the aqueous monomer solution, and simultaneously adding an oil phase multi-acid chloride monomer solution to the polymer film side of the PNG / polymer composite film, so as to make the polymer film side contact with the oil phase multi-acid chloride monomer solution, the aqueous monomer solution and the oil phase multi-acid chloride monomer solution being separated by the PNG / polymer composite film; and obtaining a molecularly engineered graphene composite film material through interfacial polymerization;

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

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

[0013] Preferably, the reducing atmosphere containing hydrogen is a mixed gas 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℃.

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

[0016] The sugar is any one of glucose, sucrose, mesobiose, 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 shall satisfy (0.1-1.0)g:(0.2-2.0)g:(2-20)ml.

[0019] As a further preferred embodiment of the present invention, in step (3), the coating is performed by either spin coating or blade 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 (PES), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), and polysulfone (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; the concentration of the aqueous monomer solution is 0.1-8 wt%.

[0023] The polyacryl chloride monomer used in the oil phase polyacryl chloride monomer solution is any one of the following: pyromellitic trimethylolpropane chloride, terephthaloyl chloride, isophthaloyl chloride, biphenyl dimethylolpropane chloride, benzenetrisulfonyl chloride, triacrylyl propane chloride, triacrylyl succinate chloride, triacrylyl glutaryl chloride, triacrylyl glutaryl chloride, adipyl chloride, maleic diacrylyl chloride, cyclopropane triacrylyl chloride, cyclobutane triacrylyl chloride, cyclobutane tetraacrylyl chloride, cyclopentane diacrylyl chloride, cyclopentane triacrylyl chloride, cyclopentane tetraacrylyl chloride, cyclohexane diacrylyl chloride, cyclohexane triacrylyl chloride, or cyclohexane tetraacrylyl chloride; the concentration of the oil phase polyacryl chloride monomer solution is 0.05–4.0 wt%.

[0024] Preferably, the oil phase solvent used in the oil phase polyacrylamide 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 application, the present application provides a molecularly engineered modified graphene composite membrane material prepared by the above preparation method.

[0026] According to still another aspect of the present application, the present application provides an application of the above molecularly engineered modified graphene composite membrane material as membrane separation.

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

[0028] As a further preferred embodiment of the present application, the ion separation is particularly for lithium recovery from spent lithium-ion battery cathode material leaching solution.

[0029] Compared with the prior art, the above technical scheme conceived by the present application has the following advantages: the molecularly engineered modified porous graphene composite membrane material in the present application is prepared by modifying graphene material with high strength, stable properties and atomic level thickness through interfacial polymerization. The present application improves the pore size distribution and functionalization of the porous graphene membrane, artificially creates a blocking structure, and introduces a positive functional group, which can efficiently enhance the ion sieving efficiency. The graphene membrane itself has only an atomic level thickness, and has small mass transfer resistance, which can realize efficient ion transmission. The graphene membrane is a self-supporting graphene membrane formed by pyrolysis of a polymer, and then the pore size is adjusted and the surface functional group is modified using an aqueous amine-containing monomer and a multi-acid chloride monomer. On the one hand, the graphene membrane has high mechanical strength, stable chemical properties, corrosion resistance, and small mass transfer resistance; on the other hand, the modified graphene composite membrane material has high ion separation performance and is very suitable for practical applications. Taking aqueous piperazine as an example, the size of piperazine is about 0.7 nm. Based on the method of the present application, using piperazine as an aqueous monomer, the pores of the graphene film can be blocked, the pore size can be reduced, and the pore size distribution can be concentrated. The molecularly engineered modified graphene composite membrane material obtained accordingly has a suitable pore size (the pore size is concentrated in 0.7 nm) and charge distribution. As shown in Example 1 below, it can realize precise separation of different types of ions, and the selectivity can be as high as 10 2 orders of magnitude (the size of piperazine is about 0.7 nm. In the interfacial polymerization reaction, the aqueous monomer and the oil monomer are applied to the two sides of the graphene film, so that the aqueous monomer piperazine can react with the oil monomer on the opposite side through the pores with a diameter greater than or equal to 0.7 nm in the graphene film, thereby blocking the larger pores on the graphene film, i.e., the pores with a diameter greater than or equal to 0.7 nm can be blocked, so that the pore size of the modified graphene film is smaller and the pore size distribution is more concentrated).

[0030] In the present application, the water phase monomer is selected according to the pore size of the modified graphene film required by the separation target, and the pore size of the modified graphene film 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 film, 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 modified graphene film, the external component can pass through the molecularly engineered modified graphene composite membrane material. The graphene film prepared by the traditional membrane preparation method has a wide pore size distribution and many defects, which greatly reduces the ion separation efficiency. Although the existing technology also reports an interfacial polymerization method, that is, by using a water phase monomer and an oil phase monomer, an interfacial polymerization reaction is used to modify the ultrafiltration membrane, but these existing technologies mix the water phase monomer and the oil phase monomer together during the modification process to form a complete separation layer. In the present application, the water phase monomer and the oil phase monomer are applied to the two sides of the graphene film respectively, and the water phase monomer is selected according to the pore size of the separation film required by the separation target. By using a water phase monomer material with a size equal to the pore size of the separation film required by the separation target, the modified graphene film obtained has a pore size after plugging that meets the critical size requirement, and the pore size distribution is more concentrated. Moreover, the polyamide structure (PA) generated by interfacial polymerization can perform directional plugging near the graphene membrane pores and introduce positive charges, thereby improving the ion separation efficiency.

[0031] The preparation method of the present application uses block copolymer and sugar as precursors to form a porous graphene membrane with a carbon support layer by pyrolysis on an annealed nickel sheet, and then uses a water phase monomer (such as PIP) and a multi-acid chloride monomer (such as TMC) to plug and modify the defects and large pores of the graphene membrane. The graphene composite membrane separation material prepared by such modification has monovalent and multivalent ion separation performance. The present application uses block copolymer and sugar as precursors (specifically by forming a casting solution of block copolymer and sugar), forms a porous graphene membrane with a support layer by pyrolysis (i.e., forms a self-supporting porous graphene membrane by pyrolysis of the casting solution), and then uses a water phase amine-containing monomer and a multi-acid chloride monomer for molecular engineering modification to make it a stable structure and high-performance separation membrane material. The larger membrane pores are directionally plugged and functionalized, and the overall molecularly engineered modified porous graphene composite membrane material can effectively improve the ion separation efficiency, and can be particularly applied to precise monovalent / divalent ion separation. Through the modification of the water phase amine-containing monomer and the multi-acid chloride monomer, the membrane pore size is reduced, the pore size distribution is tightened, and the amino groups are distributed near the membrane pores, thereby having positive charges, which is helpful for monovalent and divalent ion separation.

[0032] In specific analysis, the present application can achieve the following beneficial effects:

[0033] (1) The porous graphene film material is selected as the modified object, and has better mechanical strength and smaller mass transfer resistance compared with ordinary separation membrane materials. The porous graphene film has stable chemical properties, high mechanical strength and atomic level thickness, which makes it have the potential to become a high-efficiency separation membrane material.

[0034] (2) The graphene film separation material in the application is modified by molecular engineering on the graphene film, which can effectively improve the ion separation efficiency and reduce the mass transfer resistance. The interfacial polymerization of the water phase amine monomer and the polyacyl chloride monomer can occur near the large pores of the graphene film material, and form a PA structure with plugging and positive charge, so that the material as a whole has a relatively narrow pore size distribution. The synergistic effect of the small pore size, the narrow pore size distribution and the introduction of positive charge near the membrane pores improves the ion separation capacity.

[0035] The application can obtain modified graphene films with different pore size distributions by changing the water phase monomers used. For example, when piperazine with a molecular size of 0.7 nm is used to modify the graphene film, the size distribution of the modified graphene film is concentrated at 0.7 nm; and when polyethyleneimine with a molecular size of 1.2 nm is used to modify the graphene film, the size distribution of the modified graphene film is concentrated at 1.2 nm. Other water phase monomers (such as 2-methylpiperazine, 2,5-dimethylpiperazine, 4-aminomethylpiperazine, 2,5-diethylpiperazine, p-phenylenediamine, m-phenylenediamine, m-phenylenediamine, m-phenylenediamine, ethylenediamine, propylenediamine) are the same.

[0036] The application adjusts the pore size distribution and charge distribution of the graphene film by introducing the water phase monomer and the oil phase monomer on both sides of the graphene film respectively, forming a polyamide structure near the original large size graphene film pores through interfacial polymerization, instead of introducing the water phase and the oil phase monomer on the same side to form a complete polyamide layer on the surface of the graphene film. The specific pore size and charge adjustment of the application enhances the ion separation efficiency of the membrane.

[0037] (3) The graphene separation film material in the application can be particularly applied to precise monovalent and divalent ion separation. By using membrane separation technology, the application can recover valuable metal elements (such as Li elements), and can be further used to construct a device for recovering valuable metal elements through a cascade membrane separation, to recover high-value monovalent metal elements from wastewater containing multiple metal ions. For example, different area sizes of separation membrane materials 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 porous graphene film with a supporting film is prepared by a pyrolysis method, defects introduced in a graphene film transfer process are reduced by introducing a carbon supporting layer in a synthesis process, the pore size and the pore size distribution of the film are adjusted in a micro (nanometer scale) by molecular engineering modification, the ion separation efficiency is increased, and the separation efficiency of monovalent and divalent ions is further improved by introducing positive charges near the film holes.

[0039] To sum up, the process is simple, the ion separation efficiency is high, and can be widely applied to the field of valuable metal recovery. Based on the application, the modified graphene film with different separation effects can be prepared by using different water phase monomers to modify the graphene film, that is, different water phase monomers can be selected to realize the modified graphene film with customized pore size distribution according to actual separation needs, so that the preset separation effect is realized. BRIEF DESCRIPTION OF DRAWINGS

[0040] Figure 1 The pore size distribution graph (radius) of the single-layer porous graphene film (porous nanocrystalline graphene, PNG) obtained from Comparative Example 1 and the molecular engineering modified single-layer porous graphene composite film (Molecular anchoring by PIP to porous nanocrystalline graphene membrane, MAP-PNG) obtained from Example 1.

[0041] Figure 2 The surface nanometer infrared test comparison graph and the infrared spectrum graph of specific positions of the separation film materials of Comparative Example 1 and Example 1 are shown in FIG. 1. Figure 2 In FIG. 1, a is the surface nanometer infrared test comparison graph, and (1) and (2) correspond to Comparative Example 1, and (3) and (4) correspond to Example 1. Figure 2 In FIG. 1, b corresponds to points ①, ② and ③, and the infrared spectrum graphs from 1400 cm -1 to 1700 cm -1 are shown in FIG. 2 (the specific positions of points ①, ② and ③ are shown in FIG. 1a). Figure 2

[0042] Figure 3 The surface potential measurement result comparison graph of the film material PNG / Kevlar prepared from Comparative Example 1, the separation film material MAP-PNG / Kevlar obtained from Example 1 and the separation film material MAE-PNG / Kevlar obtained from Example 2 is shown in FIG. 3.

[0043] Figure 4 ​A comparison chart of selectivity of the membrane material PNG / Kevlar prepared in Comparative Example 1, the separation membrane material MAP-PNG / Kevlar prepared in Example 1, and the separation membrane material MAE-PNG / Kevlar prepared in Example 2 in the ion separation process. DETAILED DESCRIPTION

[0044] In order to make the objects, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application and do not limit the present application. In addition, the technical features involved in each embodiment of the present application 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 of commercially available amorphous nickel sheets (the surface of the nickel sheet after annealing has a hexagonal crystal form). The poly-p-phenyleneterephthalamide (Kevlar) substrate used is obtained by synthesizing a Kevlar solution (i.e., a Kevlar hydrogel solution with a Kevlar concentration of 2 wt%), followed by blade coating and phase inversion in water, with a thickness of 200 microns. The Kevlar solution is prepared by adding 2 g of KOH solid to a 200 ml reagent bottle, then adding 2 ml of DI water, 2 g of Kevlar thread, pouring into 95 ml of DMSO, and stirring magnetically at room temperature for 24 h or more.

[0046] The polyethersulfone substrate (PES) used is commercially available, with a thickness of 120 microns.

[0047] Example 1

[0048] The preparation method of the single-layer porous graphene composite membrane material based on molecular engineering modification in this example includes the following steps:

[0049] (1) The nickel sheet is placed in a tube furnace and annealed at 1100°C under a hydrogen atmosphere of 9.1% hydrogen by volume and 90.9% argon by volume, and the polished nickel sheet substrate with a smooth surface is obtained after polishing;

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

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

[0052] (4) The product obtained in step (3) was etched by floating on the surface of a 1 mol / L FeCl3 solution, and after the Ni substrate was completely etched, it was transferred to a poly-p-phenylenediamine substrate (Kevlar) to obtain a PNG / Kevlar composite film;

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

[0054] In addition, the sample obtained in step (5) of the notebook embodiment is "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 different ions in the membrane, ion selectivity is tested by linear sweep voltammetry (LSV) in a laboratory-scale H-type device, with silver and silver chloride as electrodes, by clamping the membrane between two reservoirs containing single electrolyte solution, the ion concentration of all tested single electrolyte solutions is 0.1 M (during the test, the corresponding chloride salt solution of the cation is used, such as KCl solution). The potential is scanned from -0.5 V to +0.5 V at a rate of 5 mV s -1 , and the corresponding current value is recorded and the conductance 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] Where G i and G j are the conductance values of two different ions (under different membranes, the conductance value of the same ion may also differ), the conductance value (G) is the ratio of the current to its corresponding voltage during the test, and Zi and Z j is the charge valence of the cation.

[0059] The surface potential of the sample after molecular engineering modification was measured, and the results are shown in Figure 3 From the results, it can be seen that the surface potential of the graphene film modified by piperazine is increased from the negative potential before modification (PNG / Kevlar obtained in Comparative Example 1 hereinafter) to 660 mV, which proves that positive charges are introduced while forming PA structures, thereby being more conducive to the separation of the separation membrane for different valence cations.

[0060] And the ion selectivity test of the sample after molecular engineering modification is shown in Figure 4 The K + / Li + selectivity can reach 20.8, the Li + / Mg 2+ selectivity can reach 15.9, the K + / Mg 2+ selectivity can reach 330.8.

[0061] Example 2

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

[0063] (1) Place the nickel sheet in a tube furnace and anneal at 1100°C under a hydrogen atmosphere of 10% hydrogen volume and 90% argon volume. After polishing, a smooth nickel sheet substrate is obtained;

[0064] (2) Dissolve 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 and react in a reaction kettle at 180°C for 3 h to obtain a casting solution;

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

[0066] (4) Float the product obtained in step (3) on the surface of a 1 mol / L FeCl3solution for etching. After the Ni substrate is completely etched, transfer to a poly-para-phenylenediamine substrate (Kevlar) to obtain a PNG / Kevlar composite membrane;

[0067] (5) The PNG / Kevlar composite membrane obtained in step (4) is sandwiched in an H-shaped cell, and a 1 wt% polyethyleneimine (PEI) solution (solvent is water) and a 0.15 wt% trimesoyl chloride (TMC) solution (solvent is n-hexane) are added to the PNG side and the Kevlar side respectively to obtain a molecularly engineered modified graphene composite membrane material.

[0068] Additionally, the sample obtained in step (5) of this embodiment is referred to as "MAE-PNG / Kevlar".

[0069] The surface potential of the MAE-PNG / Kevlar film obtained in step (5) was measured, and the results are as follows: Figure 3 As shown, it is easy to see that the surface potential of the graphene film modified with polyethyleneimine increased from the negative potential before modification to 370mV, proving that a positive charge was introduced while forming the PA structure, which is beneficial for the separation membrane to separate cations of different valence states. Of course, compared with the surface potential of 660mV of the graphene film modified with piperazine in Example 1, the lower potential increase in Example 2 proves that less positive charge was introduced, indicating that fewer pores were blocked. This also indirectly verifies that the molecular size of the aqueous phase can affect the pore size distribution and charge distribution of the molecularly engineered separation membrane by blocking pores of different pore sizes (the molecular size of piperazine is 0.7nm, while the molecular size of polyethyleneimine is 1.2nm).

[0070] Furthermore, the ion selectivity of the MAE-PNG / Kevlar membrane obtained in step (5) was tested, and the results are as follows: Figure 4 As shown, where K + / Li + Selectivity is 1.7, Li + / Mg 2+ Selectivity is 5.1, K + / Mg 2+ The selectivity was 8.6. It is evident that the modification effect of Example 2 is not as good as that of Example 1. This is because the size of the aqueous monomer polyethyleneimine (PEI) is approximately 1.2 nm. Although it can pass through the pores in the graphene film with a pore size greater than 1.2 nm, the pore size of the corresponding modified graphene film is... Figure 1 Similarly, the pore size is mainly distributed around 1.2 nm, but due to K + The ion size is 0.66 nm, Mg 2+ The ion size is 0.86 nm, Li + The ions have a size of 0.76 nm. The membrane obtained in Example 2 has a large pore size and cannot effectively separate these ions accurately.

[0071] If the system to be separated is replaced, and in the replaced system to be separated, one component has a size of 1.2 nm or less, and one component has a size of 1.2 nm or more, then the MAE-PNG / Kevlar film obtained in Example 2 will be able to achieve better separation effect and have greater use.

[0072] Example 3

[0073] The preparation method of the single-layer porous graphene composite film material based on molecular engineering modification in the embodiment includes the following steps:

[0074] (1) Place the nickel sheet in a tube furnace and anneal at 1100°C under a hydrogen atmosphere of 9.1% hydrogen by volume and 90.9% argon by volume, and after polishing, obtain a nickel sheet substrate with a smooth surface;

[0075] (2) Dissolve 0.1 g of polystyrene-b-poly(4-vinylpyridine) (PS-b-P4VP) and 0.2 g of turanose in 2 mL of N,N-dimethylformamide solution and react in a reaction kettle at a temperature of 180°C for 3 h to obtain a casting solution;

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

[0077] (4) Float 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, transfer it to a poly-p-phenylenediamine substrate (Kevlar) to obtain a PNG / Kevlar composite film;

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

[0079] And the ion selectivity test of the film obtained in step (5) is carried out, in which K + / Li + selectivity is 12.5, Li + / Mg 2+ selectivity is 21.3, K + / Mg 2+ selectivity is 266.3.

[0080] Example 4

[0081] The preparation method of the single-layer porous graphene composite film material based on molecular engineering modification in this embodiment comprises the following steps:

[0082] (1) Put the nickel sheet in a tube furnace and anneal at 1100°C under a hydrogen atmosphere of 8% hydrogen by volume and 92% argon by volume, and after polishing, obtain a nickel sheet substrate with a smooth surface;

[0083] (2) Dissolve 0.1 g of polystyrene-b-poly(4-vinylpyridine) (PS-b-P4VP) and 0.2 g of turanose in 2 mL of N,N-dimethylformamide solution and react in a reaction kettle at a temperature of 180°C for 3 h to obtain a casting solution;

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

[0085] (4) Float 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, transfer it to a poly-p-phenylenediamine substrate (Kevlar) to obtain a PNG / Kevlar composite film;

[0086] (5) Clamp the PNG / Kevlar composite film obtained in step (4) in an H-cell, and add 1.5 wt% m-phenylenediamine solution (solvent: water) and 1 wt% trimesoyl chloride solution (solvent: octane) to the PNG side and the Kevlar side, respectively, to obtain a molecular engineering modified graphene composite film material.

[0087] And the film obtained in step (5) is subjected to ion selectivity test, wherein K + / Li + selectivity is 2.5, Li + / Mg 2+ selectivity is 25.1, K + / Mg 2+ selectivity is 62.8.

[0088] Example 5

[0089] The preparation method of the single-layer porous graphene composite film material based on molecular engineering modification in this embodiment comprises the following steps:

[0090] (1) The nickel sheet was placed in a tube furnace and annealed at 1100°C in a hydrogen atmosphere with 9.1% hydrogen volume and 90.9% argon volume. After polishing, a nickel sheet substrate with a smooth surface was obtained.

[0091] (2) Dissolve 0.1g polystyrene-b-poly(4-vinylpyridine) (PS-b-P4VP) and 0.2g turanose in 2mL N,N-dimethylformamide solution and react in a reactor at 150℃ for 4h to obtain casting solution;

[0092] (3) The casting solution obtained in step (2) was spin-coated on the surface of the nickel substrate at 1000 rpm for 30 s and 1500 rpm for 30 s, and then placed in a tube furnace for pyrolysis at 600 °C for 2 h to obtain a porous graphene film (PNG) containing a carbon support layer on the nickel substrate.

[0093] (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.

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

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

[0096] Example 6

[0097] The preparation method of the single-layer porous graphene composite membrane material based on molecular engineering modification in this embodiment includes the following steps:

[0098] (1) The nickel sheet is placed in a tube furnace and annealed at 1100°C in a hydrogen atmosphere with 10% hydrogen volume and 90% argon volume. After polishing, a nickel sheet substrate with a smooth surface is obtained.

[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 reaction kettle at a temperature of 150°C for 4 h to obtain a casting solution;

[0100] (3) The casting solution obtained in step (2) was spin-coated on the surface of a nickel sheet substrate at 1000 rpm for 30 s and 1500 rpm for 30 s, and was placed in a tube furnace for pyrolysis at 600°C for 1 h to obtain a porous nanocrystalline graphene (PNG) film containing a carbon support layer on the nickel sheet substrate;

[0101] (4) The product obtained in step (3) was floated on the surface of a 1 mol / L FeCl3 solution for etching, and after the Ni substrate was completely etched, it was transferred to a poly-p-phenylenediamine substrate (Kevlar) to obtain a PNG / Kevlar composite film;

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

[0103] And the film obtained in step (5) was subjected to ion selectivity test, in which K + / Li + selectivity was 1.2, Li + / Mg 2+ selectivity was 21.3, K + / Mg 2+ selectivity was 25.6.

[0104] Example 7

[0105] The preparation method of the single-layer porous graphene composite film material based on molecular engineering modification in this example comprises the following steps:

[0106] (1) A nickel sheet was placed in a tube furnace and annealed at a high temperature of 1100°C in a hydrogen atmosphere of 8% hydrogen by volume and 92% argon by volume, and after polishing, a nickel sheet substrate with a smooth surface was obtained;

[0107] (2) 0.2 g of polystyrene-b-poly(methyl methacrylate) (PS-b-PMMA) and 0.4 g of turanose were dissolved in 4 mL of N,N-dimethylformamide solution and reacted in a reaction kettle at a temperature of 180°C for 4 h to obtain a casting solution;

[0108] (3) The casting solution obtained in step (2) is spin-coated on the surface of a nickel sheet substrate at 1000 rpm for 30 s and 1500 rpm for 30 s, and is placed in a tube furnace for pyrolysis at 600°C for 3h to obtain a porous nanocrystalline graphene film (PNG) containing a carbon support layer on the nickel sheet substrate;

[0109] (4) The product obtained in step (3) is floated on the surface of a 1 mol / L FeCl3 solution for etching, and after the Ni substrate is completely etched, it is transferred to a polyether sulfone substrate (PES) to obtain a PNG / PES composite film;

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

[0111] And the film obtained in step (5) is subjected to ion selectivity test, in which the K + / Li + selectivity is 8.4, Li + / Mg 2+ selectivity is 6.5, K + / Mg 2+ selectivity is 54.6.

[0112] Example 8

[0113] The preparation method of the single-layer porous graphene composite film material based on molecular engineering modification in this embodiment comprises the following steps:

[0114] (1) A nickel sheet is placed in a tube furnace for high-temperature annealing at 1200°C under a hydrogen atmosphere of 9.1% hydrogen by volume and 90.9% argon by volume, and after polishing, a nickel sheet substrate with a smooth surface is obtained;

[0115] (2) 1g of polystyrene-b-poly(4-vinylpyridine) (PS-b-P4VP) and 2g of turanose are dissolved in 20mL of N,N-dimethylformamide solution and reacted in a reaction kettle at a temperature of 200°C for 4h to obtain a casting solution;

[0116] (3) The casting solution obtained in step (2) is spin-coated on the surface of a nickel sheet substrate at 1000 rpm for 30 s and 1500 rpm for 30 s, and is placed in a tube furnace for pyrolysis at 600°C for 2h to obtain a porous nanocrystalline graphene film (PNG) containing a carbon support layer on the nickel sheet substrate;

[0117] (4) The product obtained in step (3) is floated on the surface of a 1 mol / L ammonium persulfate solution for etching. After the Ni substrate is completely etched, it is transferred to a polyether sulfone substrate (PES) to obtain a PNG / PES composite film;

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

[0119] The film obtained in step (5) is subjected to ion selectivity testing, in which the K + / Li + selectivity is 2.2, Li + / Mg 2+ selectivity is 6.5, K + / Mg 2+ selectivity is 14.3.

[0120] Example 9

[0121] The preparation method of the single-layer porous graphene composite film material based on molecular engineering modification in this example comprises the following steps:

[0122] (1) A nickel sheet is placed in a tube furnace and annealed at 1100°C under a hydrogen atmosphere of 8% hydrogen by volume and 92% argon by volume. After polishing, a smooth nickel sheet substrate is obtained;

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

[0124] (3) The casting solution obtained in step (2) is spin-coated on the surface of the nickel sheet substrate at 1000 rpm for 30 s and 1500 rpm for 30 s, and then placed in a tube furnace and pyrolyzed at 500°C for 2 h to obtain a porous graphene film PNG containing a carbon support layer on the nickel sheet substrate;

[0125] (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-phenylenediamine terephthalate 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 2wt% piperazine solution (solvent is water) and 4wt% trimesoyl chloride solution (solvent is n-hexane) are added to the PNG side and the Kevlar side respectively, to obtain a molecularly engineered graphene composite film material.

[0127] And the ion selectivity test is performed on the film obtained in step (5), wherein 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 film (not molecularly engineered), which specifically includes the following steps:

[0130] (1) A nickel sheet is placed in a tube furnace for high-temperature annealing at 1100°C under a hydrogen atmosphere of 9.1% hydrogen volume and 90.9% argon volume, and after polishing, a nickel sheet substrate with a smooth surface is obtained;

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

[0132] (3) The casting solution obtained in step (2) is spin-coated on the surface of the nickel sheet substrate at 1000rpm for 30s and 1500rpm for 30s, and is placed in a tube furnace for pyrolysis at 500°C for 1h to obtain a porous graphene film PNG containing a carbon support layer on the nickel sheet substrate;

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

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

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

[0136] The ion selectivity test was also performed on the PNG / Kevlar film obtained in step (4) of Comparative Example 1, and the results are shown in Figure 4 As shown, the K + / Li + selectivity is 1.5, the Li + / Mg 2+ selectivity is 1.2, the K + / Mg 2+ selectivity is 1.8.

[0137] The unmodified sample obtained in Comparative Example 1 and the molecularly engineered modified sample obtained in Example 1 were subjected to pore size simulation test, and the results are shown in Figure 1 As shown, it can be clearly seen that the pore size of the molecularly engineered modified graphene film is reduced (the size of piperazine is about 0.7 nm, and the pore size of the modified graphene film is mainly distributed around 0.7 nm), the pore size distribution is narrower, and the ion separation performance of the material can be improved. Meanwhile, the unmodified sample and the molecularly engineered modified sample were subjected to nano-infrared test, and it can be clearly seen that the surface of the molecularly engineered modified graphene film is distributed with uneven polyamide structure, which can effectively reduce the pore size of the film and narrow the pore size distribution of the film, and the introduction of positive charge near the film pores can further improve the ion separation performance of the material.

[0138] As shown in Figure 1 Comparative Example 1, the graphene film has a larger pore size and a wider pore size distribution, while the molecularly engineered modified graphene composite film 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 but directly spin-coated and pyrolyzed, which specifically included the following steps:

[0141] (1) The commercially available amorphous nickel sheet was polished 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 reaction kettle at a temperature of 180°C for 2 h to obtain a casting solution;

[0143] (3) The casting solution obtained in step (2) was spin-coated on the surface of the nickel sheet substrate at 1000 rpm for 30 s and 1500 rpm for 30 s, and was placed in a tube furnace for pyrolysis at 600°C for 1 h to obtain a porous nanocrystalline graphene film (PNG) containing a carbon support layer on the nickel sheet substrate;

[0144] (4) The product obtained in step (3) was floated on the surface of a 1 mol / L FeCl3solution for etching, and after the Ni substrate was completely etched, it was transferred to a poly-p-phenylenediamine substrate (Kevlar) to obtain a PNG / Kevlar composite film;

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

[0146] And the film obtained in step (5) was subjected to ion selectivity test, in which K + / Li + selectivity was 1.1, Li + / Mg 2+ selectivity was 1.2, K + / Mg 2+ selectivity was 1.3.

[0147] Comparative Example 3

[0148] This comparative example only annealed the nickel sheet without polishing, and synthesized a graphene film, specifically including the following steps:

[0149] (1) The nickel sheet was placed in a tube furnace and annealed at 1100°C under a hydrogen atmosphere of 10% hydrogen by volume and 90% argon by volume 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 reaction kettle at a temperature of 200°C for 2 h to obtain a casting solution;

[0151] (3) The casting solution obtained in step (2) was spin-coated on the surface of the nickel sheet substrate at 1000 rpm for 30 s and 1500 rpm for 30 s, and was placed in a tube furnace for pyrolysis at 400°C for 1 h to obtain a porous nanocrystalline graphene film (PNG) containing a carbon support layer on the nickel sheet substrate;

[0152] (4) The product obtained in step (3) is floated on the surface of a 1 mol / L FeCl3solution for etching. After the Ni substrate is completely etched, it is transferred to a polyether sulfone substrate (PES) to obtain a PNG / PES composite film;

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

[0154] And the membrane obtained in step (5) is subjected to ion selectivity test, in which the K + / Li + selectivity is 1.2, Li + / Mg 2+ selectivity is 1.3, K + / Mg 2+ selectivity is 1.6.

[0155] Comparative Example 4

[0156] In this comparative example, the casting solution is not subjected to heat treatment, and the synthetic graphene film is directly spin-coated, which specifically includes the following steps:

[0157] (1) A nickel sheet is placed in a tube furnace and annealed at 1200°C under a hydrogen atmosphere of 9.1% hydrogen volume and 90.9% argon volume. After polishing, a smooth nickel sheet substrate is obtained;

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

[0159] (3) The casting solution obtained in step (2) is spin-coated on the surface of the nickel sheet substrate at 1000 rpm for 30 s and 1500 rpm for 30 s, and then placed in a tube furnace for pyrolysis at 400°C for 1 h to obtain a porous graphene film PNG containing a carbon support layer on the nickel sheet substrate;

[0160] (4) The product obtained in step (3) is floated on the surface of a 1 mol / L ammonium persulfate solution for etching. After the Ni substrate is completely etched, it is transferred to a poly-p-phenylenediamine terephthalate 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 0.2wt% piperazine solution (solvent is water) and 0.15wt% trimesoyl chloride solution (solvent is n-hexane) are added to the PNG side and the Kevlar side respectively to obtain a molecularly engineered graphene composite film material.

[0162] And the ion selectivity test is performed on the film obtained in step (5), wherein K + / Li + selectivity is 1.0, Li + / Mg 2+ selectivity is 1.1, K + / Mg 2+ 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) A nickel sheet is placed in a tube furnace for high-temperature annealing at 1200°C under a hydrogen atmosphere of 9.1% hydrogen volume and 90.9% argon volume, and after polishing, a nickel sheet substrate with a smooth surface is obtained;

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

[0167] (3) The casting solution obtained in step (2) is spin-coated on the surface of the nickel sheet substrate at 1000rpm for 30s and 1500rpm for 30s, and dried at room temperature for 1h to obtain a film on the nickel sheet substrate;

[0168] (4) The product obtained in step (3) is floated on the surface of a 1mol / L ammonium persulfate solution for etching, and after the Ni substrate is completely etched, it is transferred to a poly(p-phenylenediamine terephthalate) 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 0.2wt% piperazine solution (solvent is water) and 0.15wt% trimesoyl chloride solution (solvent is n-hexane) are added to the PNG side and the Kevlar side respectively to obtain a molecularly engineered graphene composite film material.

[0170] And the ion selectivity test is performed on the film obtained in step (5), wherein K + / Li + selectivity is 1.0, Li+ / Mg 2+ Selectivity of 1.0, K + / Mg 2+ Selectivity of 1.0.

[0171] Comparative Example 6

[0172] This comparative example synthesizes a film after spin coating at a lower temperature, and specifically includes the following steps:

[0173] (1) A nickel sheet is placed in a tube furnace for high-temperature annealing at 1100°C under a hydrogen atmosphere of 9.1% hydrogen by volume and 90.9% argon by volume, and after polishing, a nickel sheet substrate with a smooth surface is obtained;

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

[0175] (3) The casting solution obtained in step (2) is spin coated on the surface of the nickel sheet substrate at 1000 rpm for 30 s and 1500 rpm for 30 s, and is placed in a tube furnace for pyrolysis at 300°C for 2 h to obtain a porous nanocrystalline graphene film (PNG) containing a carbon support layer on the nickel sheet substrate;

[0176] (4) The product obtained in step (3) is floated on the surface of a 1 mol / L FeCl3 solution for etching, and after the Ni substrate is completely etched, it is transferred to a poly-p-phenylenediamine 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-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 graphene composite film material.

[0178] And the film obtained in step (5) is tested for ion selectivity, wherein K + / Li + Selectivity of 1.1, Li + / Mg 2+ Selectivity of 1.1, K + / Mg 2+ Selectivity of 1.2.

[0179] Comparative Example 7

[0180] The comparative example is to treat the casting solution at a lower temperature, which comprises the following steps:

[0181] (1) The nickel sheet was placed in a tube furnace for high temperature annealing at 1100°C under a hydrogen atmosphere of 9.1% hydrogen by volume and 90.9% argon by volume, and after polishing, a smooth nickel sheet substrate was obtained;

[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 reaction kettle at 100°C for 3 h to obtain a casting solution;

[0183] (3) The casting solution obtained in step (2) was spin-coated on the surface of the nickel sheet substrate at 1000 rpm for 30 s and 1500 rpm for 30 s, and was placed in a tube furnace for pyrolysis at 500°C for 2 h to obtain a porous nanocrystalline graphene film (PNG) containing a carbon support layer on the nickel sheet substrate;

[0184] (4) The product obtained in step (3) was floated on the surface of a 1 mol / L FeCl3 solution for etching, and after the Ni substrate was completely etched, it was transferred to a poly-p-phenylenediamine substrate (Kevlar) to obtain a PNG / Kevlar composite film;

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

[0186] And the film obtained in step (5) was tested for ion selectivity, in which K + / Li + selectivity is 1.2, Li + / Mg 2+ selectivity is 1.1, K + / Mg 2+ selectivity is 1.3.

[0187] Comparative Example 8

[0188] The comparative example is to modify by adding water phase monomers and oil phase monomers on the same side, which comprises the following steps:

[0189] (1) The nickel sheet was placed in a tube furnace for high temperature annealing at 1100°C under a hydrogen atmosphere of 9.1% hydrogen by volume and 90.9% argon by volume, and after polishing, a smooth nickel sheet substrate was obtained;

[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 reaction kettle at a temperature of 200°C for 3 h to obtain a casting solution;

[0191] (3) The casting solution obtained in step (2) was spin-coated on the surface of a nickel sheet substrate at 1000 rpm for 30 s and 1500 rpm for 30 s, and was placed in a tube furnace for pyrolysis at 500°C for 1 h to obtain a porous nanocrystalline graphene film (PNG) containing a carbon support layer on the nickel sheet substrate;

[0192] (4) The product obtained in step (3) was floated on the surface of a 1 mol / L FeCl3 solution for etching, and after the Ni substrate was completely etched, it was transferred to a poly-p-phenylenediamine substrate (Kevlar) to obtain a PNG / Kevlar composite film;

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

[0194] The film obtained in step (5) was subjected to ion selectivity testing, in which K + / Li + selectivity was 1.4, Li + / Mg 2+ selectivity was 1.3, K + / Mg 2+ selectivity was 1.8.

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

[0196] Those skilled in the art will readily understand that the above description is only the preferred embodiment of the present application, and is not intended to limit the present application, and any modifications, equivalent replacements and improvements made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a molecularly engineered graphene composite membrane material, characterized in that, The method comprises the following steps: (1) polishing a nickel sheet with a surface of hexagonal crystal Ni to obtain a nickel sheet substrate with a smooth surface; wherein the nickel sheet with a surface of hexagonal crystal Ni is obtained by annealing the nickel sheet under a reducing atmosphere containing hydrogen gas, and then cooling; (2) dissolving the block copolymer and the sugar in an organic solvent to perform a solvothermal reaction, thereby obtaining a casting solution; wherein the solvothermal reaction is performed at a temperature of 150-200 ℃ for 2-4 h; (3) coating the casting solution on the surface of the nickel sheet substrate, and then pyrolyzing under a reducing atmosphere containing hydrogen gas, thereby obtaining a porous graphene membrane PNG containing a carbon support layer on the nickel sheet substrate; wherein the pyrolysis is performed at a temperature of 400-600 ℃ for 1-3 h; (4) floating the product obtained in step (3) on the surface of an etching solution to etch the nickel, and then transferring the product to a polymer membrane substrate after the etching of the nickel sheet substrate is completed, thereby obtaining a PNG / polymer composite membrane; (5) adding an aqueous monomer solution to the PNG side of the PNG / polymer composite membrane to make the PNG side in contact with the aqueous monomer solution, and simultaneously adding an oil-phase multi-acid chloride monomer solution to the polymer membrane side of the PNG / polymer composite membrane to make the polymer membrane side in contact with the oil-phase multi-acid chloride monomer solution, wherein the aqueous monomer solution and the oil-phase multi-acid chloride monomer solution are separated by the PNG / polymer composite membrane; and performing an interfacial polymerization reaction to obtain a molecularly engineered graphene composite membrane material; In step (5), the aqueous monomer used in the aqueous monomer solution has a size smaller than the average pore size of the PNG / polymer composite membrane obtained in step (4); the pore size of the molecularly engineered graphene composite membrane material is determined by the size of the aqueous monomer; for the molecularly engineered graphene composite membrane material, when the size of an external component is greater than or equal to the pore size of the molecularly engineered graphene composite membrane material, the external component cannot pass through the molecularly engineered graphene composite membrane material; and when the size of an external component is smaller than the pore size of the molecularly engineered graphene composite membrane material, the external component can pass through the molecularly engineered graphene composite membrane material.

2. The preparation method according to claim 1, characterized in that, In step (1), the reducing atmosphere containing hydrogen gas is a mixture of hydrogen gas and argon gas, wherein the volume percentage concentration of hydrogen gas is 8-10%, and the volume percentage concentration of argon gas is 90-92%. The annealing is performed at a temperature of 1100-1200 ℃.

3. The preparation method according to claim 1, characterized in that, In step (2), the block copolymer is any one of polystyrene-b-poly(methyl methacrylate), polyisobutylene-g-polystyrene, ethylene-propylene rubber-g-polystyrene, and polystyrene-b-poly(4-vinylpyridine); The sugar is any one of glucose, sucrose, pinobetsose, 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 satisfies (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 any one of spin coating and blade coating.

5. The method of claim 1, wherein the step of forming the first and second layers is performed by a method selected from the group consisting of: sputtering, evaporation, and chemical vapor deposition. 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 0.5-2 mol / L. The polymer membrane substrate is any one of poly (p-phenylene terephthalamide) membrane, polyethersulfone membrane (PES), polyvinylidene fluoride membrane (PVDF), polytetrafluoroethylene membrane (PTFE), and polysulfone membrane (PSF).

6. The method of claim 1, wherein the step of forming the first and second layers is performed by a method selected from the group consisting of: sputtering, evaporation, and chemical vapor deposition. In step (5), the aqueous monomer solution uses any one of piperazine, 2-methylpiperazine, 2,5-dimethylpiperazine, p-phenylenediamine, m-phenylenediamine, m-phenylenediamine, m-phenylenediamine, ethylenediamine, propylenediamine, and polyethylenimine as the aqueous monomer, and the concentration of the aqueous monomer solution is 0.1-8 wt%. The oil phase solvent used in the oil phase multi-acid chloride monomer solution is any one of n-hexane, cyclohexane, heptane, octane, naphtha, Isopar-E, Isopar-G, Isopar-L, and mineral oil.

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

8. The application of the molecularly engineered modified graphene composite membrane material of claim 7 as a membrane separation. The application is specifically the application of the membrane separation in an ion separation process.

9. The use according to claim 8, wherein the compound is ###0002### The application is specifically the application in the separation of monovalent and divalent ions.

10. The use according to claim 9, wherein the compound is ###0002### The ion separation is specifically used for lithium recovery from a waste lithium ion battery cathode material leaching solution.

11. The use according to claim 9, wherein the compound is ###00010### or a pharmaceutically acceptable salt thereof. ​

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