A MXene-based sandwich structure composite membrane separation material and a preparation method thereof

Abstract

The application discloses a kind of based on MXene interlayer structure composite membrane separation material and preparation method thereof.Material includes porous substrate as bottom film and the mass ratio of porous Mxene monolayer nanosheet, two-dimensional material nanosheet, porous MXene monolayer nanosheet and two-dimensional material nanosheet on porous substrate is 1:(1-10);Preparation method is that two-dimensional material nanosheet solution is extracted and filtered and deposited in porous substrate to form bottom film, MXene nanosheet solution is extracted and filtered and deposited to form middle layer, two-dimensional material nanosheet solution is extracted and filtered and covered on surface to obtain interlayer structure MXene composite separation film.The preparation method of the application is simple, raw material cost is low and green, realizes the effective separation of deuterium water and other hydrogen compounds, enhances the anti-swelling performance of membrane, provides a large number of adsorption sites, and enhances selectivity.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of material preparation, in particular to a sandwich structure composite membrane separation material based on MXene and a preparation method thereof. BACKGROUND

[0002] The over-reliance of power production on fossil fuels leads to the continuous emission of large amounts of greenhouse gases such as carbon dioxide, which causes great harm to the ecological environment. In order to reduce the dependence on fossil fuels, it is urgent to develop cleaner and sustainable energy. Nuclear energy, as a new green energy, not only provides a large amount of carbon-free electricity, but also is friendly to the ecological environment. Hydrogen isotope is one of the main raw materials of nuclear energy, and ensuring its safe and sustainable supply is the key to maintaining the sustainable development of the nuclear industry.

[0003] Currently, the separation of hydrogen isotopes in industry is mainly based on thermodynamic and kinetic differences, such as chemical exchange method and multi-stage low-temperature distillation method. However, these technologies have problems such as environmental pollution, high energy consumption, and poor selectivity. Therefore, it is of great significance to develop a simple, efficient, and environmentally friendly method for the separation of hydrogen isotopes.

[0004] Based on the proposal of "quantum sieving effect", a series of advanced nano-adsorbent materials have been synthesized, including carbon, zeolite, MOFs, COFs and POFs, etc., which realize the effective separation of hydrogen isotopes. However, factors such as harsh conditions, high cost, and unsatisfactory separation effect hinder the practical application of adsorbents in industry. Membrane separation, as a new separation technology, is favored by researchers due to its many advantages such as structural stability, strong applicability, and simple operation.

[0005] Chinese patent CN 113262650 A discloses a two-dimensional MOF membrane for hydrogen isotope purification, which is composed of M 2+ As a metal center, benzimidazole is used as an organic ligand to form a membrane with the general formula M2(Bim)4; wherein M is one or more of Zn, Co and Ni. The application also discloses a preparation method of the two-dimensional MOF membrane. The two-dimensional MOF membrane for hydrogen isotope purification and the preparation method thereof have excellent membrane separation performance, high permeation rate and high selectivity in the application of purifying mixed gas of hydrogen isotope and impurity gas.

[0006] CN 106552480 A discloses a zeolite molecular sieve membrane for separating hydrogen isotopes and inert gases, and a preparation method and application thereof, and belongs to the field of membrane materials. Under the condition of 60-140 DEG C, a portion of precursor solution is reacted for 4-48 h to obtain zeolite crystal seeds, the zeolite crystal seeds are mixed with deionized water to prepare a zeolite crystal seed suspension, the support after polishing and cleaning is immersed in the zeolite crystal seed suspension for 10-30 s to precoat the seeds, and then dried; then under the condition of 60-140 DEG C, the support pre-coated with the seeds is placed in a portion of precursor solution and reacted for 4-48 h, and then the reacted support is washed and dried to obtain the zeolite molecular sieve membrane; wherein each portion of the precursor solution is formed by mixing an aluminum source, a silicon source, sodium hydroxide and deionized water. The preparation method is simple in operation and low in cost, and the prepared zeolite molecular sieve membrane has good performance. The application of the zeolite molecular sieve membrane in separating hydrogen isotopes and inert gas mixture has low separation temperature and simple separation conditions.

[0007] CN 115779701 A discloses a preparation method of a two-dimensional material composite proton exchange membrane for hydrogen isotope separation, comprising the following steps: (1) configuration of a PFSA type polymer solution; (2) preparation of a nanosheet dispersion liquid; (3) preparation of a composite proton exchange membrane: the nanosheet dispersion liquid is added to the PFSA type polymer solution, mixed uniformly, then poured into a mold under heating conditions to stand and form a film, and finally cooled to room temperature, and the formed film is taken out as the two-dimensional material composite proton exchange membrane for hydrogen isotope separation. The two-dimensional material composite proton exchange membrane prepared by the method has good mechanical properties and hydrogen isotope screening ability, and can significantly reduce the energy consumption of electrolytic separation of protium and tritium and improve the separation coefficient of protium and tritium when applied to a proton exchange membrane (PEM) electrolytic cell.

[0008] CN 108176225 A discloses a method for hydrogen and oxygen isotope separation. The modified iPP-PLA hollow fiber membrane is arranged in a 15-50 cm high disc membrane as packing in a rectifying column, and tap water is heated and rectified to separate hydrogen and oxygen isotopes. The present application replaces the metal wire mesh packing in the traditional rectifying column with the hollow fiber membrane prepared by the present application as packing, and further modifies the surface of the hollow fiber membrane to further improve the separation ability of hydrogen and oxygen isotopes, which has great significance for the field of isotope separation.

[0009] The reported membrane separation materials have realized effective separation of hydrogen isotope mixed gas. However, there are still the following limitations: 1) single application field, only effective separation of hydrogen and other mixed gas can be realized, and liquid phase compounds such as deuterium water cannot be directly treated; 2) selectivity problem: separation is realized by the difference between hydrogen isotopes in thermodynamics and kinetics, but it is difficult to realize accurate separation due to the extremely similar physicochemical properties; 3) separation by distillation and other methods requires high separation equipment, needs to invest a lot of site construction and equipment maintenance cost, and the operation is complicated; 4) the raw materials such as rare metals are expensive, and the complex membrane preparation process makes it difficult to put into practical use. SUMMARY

[0010] The application provides a sandwich structure composite membrane separation material based on MXene and a preparation method.

[0011] The application inserts hydrophilic macromolecules into the layered structure of the porous MXene membrane based on strong hydrogen bond interaction, so that the hydrophilic macromolecules become a bridge connecting adjacent nanosheets, adjust the interlayer spacing of the MXene, improve the mechanical strength of the membrane, and the hydrophilic macromolecules have a large number of surface groups, can provide more adsorption sites, and increase the screening effect of hydrogen isotopes; in addition, a sandwich structure is designed, and the thickness of the two-dimensional nanosheet layer can be adjusted to effectively adjust the water flow rate.

[0012] The technical scheme adopted by the application is:

[0013] A sandwich structure composite membrane separation material based on MXene and a preparation method, the material comprises a porous substrate as a bottom membrane and a porous Mxene monolayer nanosheet and a two-dimensional material nanosheet on the porous substrate, and the mass ratio of the porous Mxene monolayer nanosheet and the two-dimensional material nanosheet is 1:(1-10).

[0014] The two-dimensional material nanosheet is at least one of graphene material, transition metal sulfide, transition metal selenide, nano metal oxide, black phosphorus or boron nitride, the graphene material includes GO, rGO and Mxene, the transition metal sulfide includes MoS2 and WS2, the transition metal selenide includes MoSe2 and WSe2, the nano metal oxide includes Al2O3 and TiO2, the diameter of the two-dimensional material nanosheet ranges from 0.2 to 4 microns, and the thickness ranges from 1 to 10 nanometers.

[0015] The porous substrate is at least one of polyether sulfone PES film, polypropylene PP film, polyvinylidene fluoride PVDF film, nylon filter film, water-based hybrid fiber microporous filter MCE film, cellulose acetate CA film and polytetrafluoroethylene film PTFE film.

[0016] The composite membrane separation material is a two-dimensional material nanosheet solution deposited on a porous substrate to form a bottom film, a porous MXene monolayer nanosheet solution is filtered to form an intermediate layer, and a two-dimensional material nanosheet solution is filtered to cover the surface of a sandwich structure.

[0017] The method comprises the following steps:

[0018] 1) Under the conditions of 10-60 DEG C and pH=5-10, the porous MXene monolayer nanosheet is added to the deionized water solution, the hydrophilic macromolecule is added to the ionic water solution, and the ultrasonic treatment is carried out to obtain solution I;

[0019] 2) Under the conditions of 10-60 DEG C and pH=5-10, the two-dimensional material is added to the deionized water solution, and the ultrasonic treatment is carried out to obtain solution II;

[0020] 3) Under the conditions of 10-60 DEG C and pH=5-10, first, the solution II is vacuum filtered on the surface of the porous substrate to form a two-dimensional material bottom film, then the solution I is vacuum filtered to form an intermediate layer, and finally, the solution II is vacuum filtered to cover the surface to form a "sandwich" sandwich structure, and the sandwich structure MXene composite separation membrane is obtained after vacuum drying.

[0021] The specific preparation of the monolayer MXene nanosheet in step 1) is as follows:

[0022] 1.1) Under the conditions of 10-18 DEG C and pH=4-10, the MXene nanosheet is added to the solvent and ultrasonic treatment is carried out for 1h to obtain the MXene monolayer nanosheet solution, and the acid solution is slowly added to the MXene monolayer nanosheet solution to obtain the MXene / strong acid mixed solution;

[0023] 1.2) After magnetic stirring of the MXene / strong acid mixed solution, it is placed in a vacuum oven for baking, the temperature is 40-80℃, vacuum drying for 24-48h to remove the solvent, and the MXene / strong acid mixed colloid is obtained, the MXene / strong acid mixed colloid is added to the deionized water solution as a cleaning agent, and under the condition of 3500r / min-4000r / min, the residual reagents and impurities in the deionized water solution containing MXene / strong acid mixed colloid are removed by centrifugal treatment, and the porous MXene monolayer nanosheet is obtained.

[0024] The hydrophilic macromolecule in the step 1) is cucurbituril CB5, theanine TH, tannic acid TA, dopamine DA or tea polyphenol GTP;

[0025] The mass ratio of the porous MXene monolayer nanosheet and the hydrophilic macromolecule is 10:(0.1-10);

[0026] The loading capacity of the sandwich structure MXene composite separation membrane prepared in the step 3) is 0.25-5g / m 2 The film thickness ranges from 0.01 to 2um.

[0027] The diameter of the MXene nanosheet involved in the step 1.1) ranges from 0.2 to 4um, and the thickness ranges from 1 to 10nm.

[0028] The acid solution in the step 1.1) is sulfuric acid, nitric acid, hydrochloric acid or hydrofluoric acid, and the acid solution mass ranges from 10 to 80wt%.

[0029] The solvent in the step 1.1) is water, dimethyl sulfoxide DMSO, N,N-dimethylformamide DMF, tetrahydrofuran THF, acetone or propylene carbonate PC.

[0030] The application field of the MXene sandwich structure composite membrane separation material includes hydrogen isotope separation, deuterium water enrichment, radioactive nuclear wastewater treatment, low deuterium water preparation, seawater desalination, industrial wastewater treatment, etc.

[0031] The beneficial effects of the present application are:

[0032] The preparation method of the film material is simple, the raw material cost is low and green, the effective separation of deuterium water and other hydrogen compounds is realized, the solution transmission path is a longitudinal-lateral three-dimensional transmission path, the transmission distance is shortened, the flux of the film is improved, the interlayer structure of the film is adjusted by introducing a hydrophilic macromolecule, the anti-swelling performance of the film is enhanced, a large number of adsorption sites are provided, and the selectivity is enhanced. The sandwich type sandwich structure film material is designed, which can realize liquid phase separation of deuterium water and other substances and efficient recovery under the conditions of normal temperature and pressure by pressure driven filtration, and has extremely high water flux, excellent practical application value and economic effect. The composite material prepared by the method has great application prospect in the fields of hydrogen isotope separation, deuterium water enrichment, radioactive nuclear wastewater treatment, low deuterium water preparation, seawater desalination, industrial wastewater treatment and the like. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 Figure is a diagram of the separation performance of deuterium water by different MXene sizes.

[0034] Figure 2 Figure is a diagram of the separation performance of deuterium water by different hydrophilic macromolecules.

[0035] Figure 3 Figure is a diagram of the separation performance of deuterium water by the mass ratio of MXene to hydrophilic macromolecule.

[0036] Figure 4 Figure is a diagram of the separation performance of deuterium water by different film thicknesses. DETAILED DESCRIPTION

[0037] The application will be further described in detail below in combination with the drawings and specific embodiments.

[0038] The embodiments of the application are as follows:

[0039] Embodiment 1

[0040] 1) Under the conditions of 10-60℃ and pH=5-10, 0.64 mg of porous MXene monolayer nanosheet is added to 50 ml of deionized water solution, and after stirring uniformly, 0.128 mg of cucurbituril CB5 is added to the ion water solution and ultrasonic treatment is performed, to obtain a mixed solution I with a mass ratio of MXene: CB5 of 10:2

[0041] 2) Under the conditions of 10-60℃ and pH=5-10, 1 mg of GO nanosheet is added to 50 ml of deionized water solution and ultrasonic treatment is performed to obtain a solution II of 0.02 g / L;

[0042] 3) First, 25 ml of solution II is vacuum filtered on a polyether sulfone PES membrane with a diameter of 50 mm to form a two-dimensional material bottom film, then 50 mL of solution I is vacuum filtered and deposited to form an intermediate layer, and finally 25 ml of solution II is vacuum filtered to cover the surface. After vacuum drying, a sandwich structure MXene composite separation membrane is obtained.

[0043] After drying, the MXene composite membrane is placed in a separation device to separate a 10% content of deuterium water / light water mixed solution. The content of deuterium water in the filtrate is measured by nuclear magnetic resonance spectrometer. Test analysis shows that the separation factor of MXene composite membrane for deuterium water is 2.59.

[0044] The specific preparation of single-layer MXene nanosheet in step 1) is as follows:

[0045] 1.1) Under the condition of 10-18℃ and pH=4-10, MXene nanosheet is added to the solvent and ultrasonic treated for 1h to obtain MXene single-layer nanosheet solution. Slowly add acidic solution to the MXene single-layer nanosheet solution and stir at room temperature for 0.1-3h until evenly dispersed to obtain MXene / strong acid mixed solution;

[0046] 1.2) Under the condition of 40-80℃, the MXene / strong acid mixed solution is magnetically stirred and then placed in a vacuum oven for 24-48h to remove the solvent to obtain MXene / strong acid mixed colloid. The MXene / strong acid mixed colloid is added to the deionized water solution as a cleaning agent and centrifuged at 3500r / min-4000r / min to remove residual reagents and impurities in the deionized water solution containing MXene / strong acid mixed colloid to obtain porous MXene single-layer nanosheet.

[0047] Examples 2-6

[0048] MXene nanosheets with lateral sizes of 0.5, 1, 2, 3 and 4μm were respectively selected as raw materials, and the rest of the conditions were the same as in Example 1. The results are shown in Figure 1 , and the MXene-based composite membrane with a size of 4μm has a better separation performance.

[0049]

[0050]

[0051] Examples 7-11

[0052] Tannic acid, cucurbituril, theanine, dopamine, and tea polyphenol were respectively selected as raw materials of hydrophilic macromolecules, and the rest of the conditions were the same as in Example 1. The results are shown in Figure 2 , and the separation performance of MXene / cucurbituril composite membrane is the best.

[0053] test Macromolecular types Separation factor Example 7 Tannic acid 1.86 Example 8 Cucurbita 2.23 Example 9 Theanine 2.13 Example 10 dopamine 1.90 Example 11 Tea polyphenols 1.98

[0054] Examples 12-18

[0055] The mass ratios of MXene to cucurbituril were 10:0.1, 10:0.5, 10:1, 10:2, 10:3, 10:4, and 10:5, with other conditions the same as in Example 1. The results are as follows: Figure 3 As shown, the separation performance is optimal when the mass ratio of MXene to cucurbituril is 10:3.

[0056] test mass ratio Separation factor Example 12 10:0.1 1.75 Example 13 10:0.5 1.84 Example 14 10:1 1.93 Example 15 10:2 2.04 Example 16 10:3 2.24 Example 17 10:4 2.16 Example 18 10:5 1.98

[0057] Examples 19-23

[0058] MXene-based composite films of different thicknesses were prepared by adjusting the mass of the MXene / cucurbitaurea mixed solution, with other conditions the same as in Example 1. The results are as follows: Figure 4 As shown, the separation factor of the adsorbent material for hydrogen isotopes is above 2.25 when the membrane thickness is in the range of 400 to 1200.

[0059]

[0060]

[0061] The above specific embodiments are used to explain and illustrate the present invention, but not to limit the present invention. Any modifications and changes made to the present invention within the spirit and scope of the claims shall fall within the protection scope of the present invention.

[0062] The above description is only a preferred embodiment of the present invention. Therefore, all equivalent changes or modifications made to the structure, features and principles described in the claims of this patent application are included in the scope of this patent application.

Claims

1. A method for preparing a composite membrane separation material based on MXene, characterized in that, Includes the following steps: 1) Porous MXene monolayer nanosheets were added to a deionized aqueous solution, hydrophilic macromolecules were added to the deionized aqueous solution and ultrasonic treatment was performed to obtain solution I; 2) Two-dimensional nanosheets were added to a deionized aqueous solution and subjected to ultrasonic treatment to obtain solution II; 3) First, solution II is vacuum filtered onto the surface of a porous substrate to form a two-dimensional material bottom film. Then, solution I is added and vacuum filtered to form an intermediate layer. Finally, solution II is added and vacuum filtered to cover the surface. After vacuum drying, a sandwich structure MXene composite separation membrane is obtained. The sandwich structure MXene composite separation membrane includes a porous substrate as the bottom membrane and porous MXene monolayer nanosheets and two-dimensional material nanosheets located on the porous substrate, wherein the mass ratio of the porous MXene monolayer nanosheets to the two-dimensional material nanosheets is 1:(1~10).

2. The method for preparing a composite membrane separation material based on MXene according to claim 1, characterized in that, The specific preparation of the porous MXene monolayer nanosheets in step 1) is as follows: 1.1) Add MXene nanosheets to a solvent and sonicate to obtain an MXene monolayer nanosheet solution. Add an acidic solution to the MXene monolayer nanosheet solution to obtain an MXene / strong acid mixed solution. 1.2) After magnetically stirring the MXene / strong acid mixed solution, it was placed in a vacuum oven for baking to obtain MXene / strong acid mixed colloid. The MXene / strong acid mixed colloid was added to a deionized water solution and centrifuged at 12000 r / min for 15 min to remove residual reagents and impurities in the deionized water solution containing the MXene / strong acid mixed colloid, thus obtaining porous MXene monolayer nanosheets.

3. The method for preparing a composite membrane separation material based on MXene according to claim 1, characterized in that: The hydrophilic macromolecules in step 1) are cucurbituril CB5, theanine TH, tannic acid TA, dopamine DA, or tea polyphenol GTP, and the mass ratio of the porous MXene monolayer nanosheets to the hydrophilic macromolecules is 10:(0.1-10); the loading of the sandwich structure MXene composite separation membrane prepared in step 3) is 0.25-5 g / m³. 2 The film thickness ranges from 0.01 to 2 μm.

4. The method for preparing a composite membrane separation material based on MXene according to claim 2, characterized in that, The MXene nanosheets involved in step 1.1) have a diameter range of 0.2~4μm and a thickness range of 1~10 nm.

5. The method for preparing a composite membrane separation material based on MXene according to claim 2, characterized in that: The acidic solution in step 1.1) is sulfuric acid, nitric acid, hydrochloric acid or hydrofluoric acid, and the mass range of the acidic solution is 10~80wt%.

6. The method for preparing a composite membrane separation material based on MXene according to claim 2, characterized in that: The solvent in step 1.1) is water, dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), tetrahydrofuran (THF), acetone, or propylene carbonate (PC).

7. The method for preparing a composite membrane separation material based on MXene according to claim 1, characterized in that: The two-dimensional material nanosheets are at least one of graphene, transition metal sulfides, transition metal selenides, nano-metal oxides, black phosphorus, or boron nitride. The graphene materials include GO, rGO, and Mxene. The transition metal sulfides include MoS2 and WS2. The transition metal selenides include MoSe2 and WSe2. The nano-metal oxides include Al2O3 and TiO2. The diameter of the two-dimensional material nanosheets ranges from 0.2 to 4 μm, and the thickness ranges from 1 to 10 nm.

8. The method for preparing a composite membrane separation material based on MXene according to claim 1, characterized in that: The porous substrate is at least one of the following: polyethersulfone (PES) membrane, polypropylene (PP) membrane, polyvinylidene fluoride (PVDF) membrane, nylon filter membrane, aqueous mixed fiber microporous filter (MCE) membrane, cellulose acetate (CA) membrane, and polytetrafluoroethylene (PTFE) membrane.

9. The method for preparing a composite membrane separation material based on MXene according to claim 1, characterized in that: The composite membrane separation material is a sandwich structure consisting of a two-dimensional material nanosheet solution deposited on a porous substrate to form a bottom membrane, a porous MXene monolayer nanosheet solution deposited to form an intermediate layer, and a two-dimensional material nanosheet solution deposited on the surface.

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