Preparation method and application of two-dimensional MXene-conductive polymer layered separation membrane with adjustable pore size

Abstract

The application belongs to the field of membrane separation technology, and provides a preparation method and application method of a two-dimensional MXene-conductive polymer layered separation membrane with adjustable pore size. The two-dimensional MXene-conductive polymer layered separation membrane is a two-dimensional MXene membrane prepared by vacuum-assisted filtration, and a conductive polymer monomer is embedded between the membrane layers, and then prepared by in-situ electrochemical polymerization. The advantages are that the preparation is simple and easy to operate, and no expensive equipment is needed. The conductive polymer in the membrane layer greatly improves the mechanical stability and oxidation resistance of the membrane structure, and the conductive performance and electrochemical capacitance characteristics are excellent. The membrane can be used as a desalination membrane and a conductive electrode at the same time, an electric potential can be applied to the membrane surface, the membrane pore size can be controlled by electrochemical regulation, and the selective separation of monovalent salt, divalent salt and dye molecules can be realized.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of membrane separation technology, and particularly relates to a preparation method and application of a two-dimensional MXene-conductive polymer layered separation membrane with adjustable pore size. BACKGROUND

[0002] The information disclosed in this Background section is for the purpose of increasing the understanding of the background of the application without admitting that any of the information constitutes prior art.

[0003] With the rapid growth of population and industrial economy, water resource shortage and water pollution have become one of the most serious challenges in the development of human society. Membrane separation technology is one of the most promising water treatment technologies in the 21st century, which has high separation efficiency, low energy consumption, easy operation, easy integration and scaling, and easy combination with other technologies, and has been highly valued by countries around the world, with great development potential.

[0004] In recent years, the development of new nanofunctional materials has provided an opportunity for the preparation of high-performance membranes. Among them, two-dimensional nanomaterials have attracted great attention in the field of membrane separation technology due to their unique physicochemical properties, microstructure and pore size screening characteristics. By controlling the stacking mode and spacing between the layers of two-dimensional nanomaterials, the construction and precise control of nanochannels between the layers can make the membrane exhibit significantly higher water permeability than traditional separation membranes, and also have the ability to separate molecules and ions with nanometer or angstrom precision and speed. Transition metal carbide / nitride (MXene) material is a new type of two-dimensional nanosheet material composed of 5 atomic layers (Ti and C atomic layers stacked alternately), which has excellent mechanical rigidity and toughness, hydrophilicity, electrical conductivity, electrochemical capacitance characteristics, material compatibility and functional adjustability, and can be assembled into two-dimensional separation membranes with uniform nanometer or angstrom channels, which has great potential in water treatment and desalination. However, due to the excellent water affinity of MXene, it is easy to swell in water environment, which leads to the increase of the spacing between the membrane layers, thus reducing the space limitation ability of the membrane layer and reducing its retention capacity. By cross-linking, heat treatment and other methods to stabilize the MXene membrane layer, it is still very difficult to precisely control and construct the membrane pore in nanometer or angstrom scale, and the spacing between the stabilized membrane layers is also difficult to further adjust as needed to meet different separation requirements. This limits its application in controllable and selective separation of molecules and ions (such as selective separation of specific ions and dye desalination). SUMMARY

[0005] In order to solve the above problems, the application provides a preparation method of a two-dimensional MXene-conductive polymer layered separation membrane with adjustable pore size, and an application method of electrochemically regulating the pore size of the membrane for selectively separating molecules and ions. The two-dimensional MXene-conductive polymer layered separation membrane is prepared by vacuum-assisted filtration of MXene and in-situ electrochemical polymerization of a conductive polymer. The application method of electrochemically regulating the pore size of the membrane for selectively separating molecules and ions uses the two-dimensional MXene-conductive polymer layered separation membrane as a working electrode, applies an external voltage, and uses the electrochemical properties of MXene and the conductive polymer and the electrical responsiveness of the nanostructure of the conductive polymer to achieve selective separation of monovalent salt, divalent salt and dye molecules.

[0006] In order to achieve the above-mentioned purpose, the application adopts the following technical solutions:

[0007] In a first aspect, the application provides a preparation method of a two-dimensional MXene-conductive polymer layered separation membrane with adjustable pore size, comprising:

[0008] The dispersion liquid of two-dimensional MXene nanosheets and the conductive polymer monomer solution are mixed uniformly at a volume ratio of 1:1-1.2, vacuum-assisted filtration is used to load them on a support membrane substrate, and drying is performed to obtain a two-dimensional MXene-conductive polymer monomer composite membrane.

[0009] The conductive polymer monomer solution is used as an electrolyte, the two-dimensional MXene-conductive polymer monomer composite membrane is used as a working electrode, in-situ electrochemical polymerization is performed in a three-electrode system, and the two-dimensional MXene-conductive polymer layered separation membrane with adjustable pore size is obtained.

[0010] The conductive polymer monomer solution contains an acid dopant.

[0011] The composite membrane is prepared by the method of vacuum-assisted filtration+in-situ electrochemical polymerization, the conductive polymer is compounded between the two-dimensional MXene membrane layers, the pore size of the membrane is regulated by using the good electrochemical properties of MXene and the conductive polymer and the electrical responsiveness of the nanostructure of the conductive polymer, and the controllable regulation of water flux and the selective separation of monovalent salt, divalent salt and dye molecules are realized.

[0012] In some embodiments, the concentration of the dispersion liquid of two-dimensional MXene nanosheets is 0.05-0.5 mg / mL. -1 .

[0013] In some embodiments, the conductive polymer monomer is selected from one of polyaniline, polypyrrole, polythiophene and respective derivatives thereof;

[0014] In some embodiments, the concentration of the conductive polymer monomer solution is 0.2-2.0 M.

[0015] In some embodiments, the acid dopant is selected from at least one of hydrochloric acid, sulfuric acid, perchloric acid, salicylic acid, citric acid, p-toluenesulfonic acid, dodecylbenzenesulfonic acid, polystyrene sulfonic acid, polyacrylic acid, polyvinyl sulfonic acid, and polymethacrylic acid.

[0016] In some embodiments, the concentration of the acid dopant in the conductive polymer monomer solution is 0.5-2.0 M.

[0017] In some embodiments, in the three-electrode system, the counter electrode is an electrode made of platinum, gold, titanium, stainless steel, glassy carbon, or graphite, and the reference electrode is a saturated calomel electrode or a silver / silver chloride electrode.

[0018] In some embodiments, the specific conditions of the in-situ electrochemical polymerization are that the potential range of the cyclic voltammetry scan is -0.2-1.2 V, the scan rate is 0.005-0.05 V s -1 , and the scan cycle number is 10-100.

[0019] More specifically, the method comprises:

[0020] (1) etching Ti3AlC2 with a hydrochloric acid solution containing LiF and removing the un-exfoliated Ti3AlC2 precipitate by centrifugal separation to obtain a dispersion of two-dimensional MXene nanosheets, then preparing a conductive polymer monomer solution and adding it to the MXene dispersion, mixing thoroughly, and then loading it on a support membrane substrate by vacuum-assisted filtration, and naturally drying at room temperature for 6-8 h to form a two-dimensional MXene-conductive polymer monomer composite membrane.

[0021] (2) using a cyclic voltammetry in-situ electrochemical polymerization method to polymerize the conductive polymer monomer molecules on the two-dimensional MXene-conductive polymer monomer composite membrane obtained in step (1), using the conductive polymer monomer solution as the electrolyte, using the two-dimensional MXene-conductive polymer monomer composite membrane as the working electrode, and performing electrochemical cyclic voltammetry scanning in a three-electrode system (working electrode, counter electrode, and reference electrode), controlling the voltage range of the cyclic voltammetry scan, the scan rate, and the scan cycle number, and polymerizing the conductive polymer monomer in the interlayer pores of the MXene by electrochemical in-situ polymerization, and after the polymerization reaction is completed, washing the prepared membrane with high-purity water and then treating it at 30-60℃ for 1-2 h to obtain a two-dimensional MXene-conductive polymer layered separation membrane.

[0022] In a second aspect, the application provides a two-dimensional MXene-conductive polymer layered separation membrane with adjustable pore size prepared by the above method.

[0023] In some embodiments, the thickness of the two-dimensional MXene-conductive polymer layered separation membrane layer is 50-1000 nm.

[0024] In a third aspect of the present application, a method for electrochemically regulating the pore size of a membrane for selectively separating molecules and ions is provided, comprising:

[0025] The two-dimensional MXene-conductive polymer layered separation membrane described above is sealed into a membrane module, wherein the two-dimensional MXene-conductive polymer layered separation membrane simultaneously serves as a separation membrane and a conductive electrode, is connected to a direct current power supply through a wire, and a counter electrode is placed on the water inlet side or the permeate water outlet side. By applying a voltage between the membrane electrode and the counter electrode, an electric potential is generated on the membrane surface, driving the counter ions (ions with opposite charges to the membrane layer) to regulate the membrane pore size in the form of ion intercalation or ion deintercalation in the conductive polymer between the membrane layers, thereby achieving controllable regulation of water flux and selective separation of monovalent salt, divalent salt and dye molecules.

[0026] In some embodiments, the counter electrode is one of a platinum mesh, a gold mesh, a titanium mesh, a stainless steel mesh, and a carbon fiber cloth.

[0027] In some embodiments, the voltage between the two-dimensional MXene-conductive polymer layered separation membrane electrode and the counter electrode ranges from 0 to 3.0 V, and the membrane surface potential ranges from 0 to -1.5 V vs. Ag / AgCl.

[0028] The present application relates to a preparation method and application method of a two-dimensional MXene-conductive polymer layered separation membrane with adjustable pore size, which has the following characteristics: the preparation method of the two-dimensional MXene-conductive polymer layered separation membrane is to embed conductive polymer monomers between the layers of a two-dimensional MXene membrane prepared by vacuum-assisted filtration, and then prepare by in-situ electrochemical polymerization. In the prepared two-dimensional MXene-conductive polymer layered separation membrane, the conductive polymer is located between the MXene membrane layers and forms a MXene-conductive polymer composite structure through cross-linking polymerization, which has good conductivity. In addition, the conductive polymer structure also has electrochemical responsiveness, and ion intercalation and deintercalation occurs under electrochemistry, which can cause changes in the volume of the conductive polymer, thereby causing changes in the membrane layer spacing (for example, when a negative potential is applied to the membrane, as the negative potential increases, ion intercalation increases, causing the volume of the conductive polymer to increase, resulting in an increase in the membrane layer spacing). Therefore, the two-dimensional MXene-conductive polymer layered separation membrane can regulate the pore size of the membrane through electrochemistry, thereby achieving controllable regulation of water flux and selective separation of molecules and ions.

[0029] Advantages of the present application

[0030] (1) The preparation of the two-dimensional MXene-conductive polymer layered separation membrane with adjustable pore size in the application is simple, easy to operate, and does not require expensive equipment; the presence of the conductive polymer in the two-dimensional MXene-conductive polymer layered separation membrane layer greatly improves the mechanical stability and oxidation resistance of the membrane structure, and the conductive performance and electrochemical characteristics are excellent; the membrane can be used as a separation membrane and a conductive electrode at the same time, an electric potential is applied on the membrane layer, the pore size is adjusted through electrochemical regulation, and the selective separation of monovalent salt, divalent salt and dye molecules can be realized.

[0031] (2) The preparation method of the application is simple, practical and easy to popularize. BRIEF DESCRIPTION OF DRAWINGS

[0032] The drawings accompanying the specification of the application serve to provide a further understanding of the application, and the exemplary embodiments of the application and the description thereof serve to explain the application and do not constitute an improper limitation of the application.

[0033] Figure 1 is the cyclic voltammetry scanning curve picture of the two-dimensional MXene-polyaniline layered separation membrane prepared by the preparation method involved in the application (Example 1).

[0034] Figure 2 is the scanning electron microscope picture of the surface of the two-dimensional MXene-polyaniline layered separation membrane prepared by the preparation method involved in the application (Example 2).

[0035] Figure 3 is the scanning electron microscope picture of the cross section of the two-dimensional MXene-polyaniline layered separation membrane prepared by the preparation method involved in the application (Example 2). Wherein, 1 is the two-dimensional MXene-polyaniline layered separation membrane layer, and 2 is the polyether sulfone support film base. DETAILED DESCRIPTION

[0036] It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the application. Unless otherwise specified, all technical and scientific terms used in the application have the same meaning as generally understood by those skilled in the art to which the application belongs.

[0037] The application will be further described in detail below in conjunction with specific examples, which should be noted that the specific examples are an explanation of the application rather than a limitation.

[0038] Example 1:

[0039] A preparation method of a two-dimensional MXene-conductive polymer layered separation membrane with adjustable pore size, which is implemented according to the following steps:

[0040] (1) 1.6g LiF is added to 20mL 9mol / L-1 Ti3AlC2 was etched in 10 M HCl solution at 45℃ for 36 h, and then the two-dimensional MXene nanosheets were obtained by ultrasonic exfoliation and centrifugation to remove the unexfoliated Ti3AlC2 precipitate. The dispersion of the two-dimensional MXene nanosheets was diluted to 0.05 mg mL -1 ; then a 0.2 M aniline monomer solution was prepared, which contained 1.0 M p-toluenesulfonic acid, and then 10 mL of the MXene dispersion was uniformly mixed with 10 mL of the aniline monomer solution, and then the mixture was loaded on a polyvinylidene fluoride hollow fiber membrane substrate by vacuum-assisted filtration, and then the two-dimensional MXene-aniline composite membrane was formed by natural drying at room temperature for 8 h.

[0041] (2) The aniline monomer molecules were polymerized on the two-dimensional MXene-aniline composite membrane obtained in step (1) by using a cyclic voltammetry in-situ electrochemical polymerization method, the two-dimensional MXene-aniline composite membrane was used as the working electrode, and the electrochemical cyclic voltammetry scanning was performed in a three-electrode system (membrane electrode, platinum sheet counter electrode and silver / silver chloride reference electrode), the voltage range of the cyclic voltammetry scanning was controlled to be 0-1.2 V, the scanning speed was 0.01 V s -1 , and the scanning cycle number was 10, so as to polymerize the aniline monomer in the interlayer pores of the MXene by electrochemical in-situ polymerization, and then the prepared membrane was washed with high-purity water, and then the two-dimensional MXene-polyaniline layered separation membrane was obtained by treating at 30℃ for 2 h.

[0042] An application method of electrochemically regulating the pore size of a membrane for selectively separating molecules and ions, and the specific implementation steps are as follows:

[0043] The two-dimensional MXene-polyaniline layered separation membrane was sealed into a membrane module, the two-dimensional MXene-polyaniline layered separation membrane was used as a separation membrane and a conductive electrode at the same time, a platinum wire was connected to a direct current power supply, a platinum mesh was placed as a counter electrode on the water inlet side, and the two-dimensional MXene-polyaniline layered separation membrane was used as a cathode and a voltage was applied; a 2 g L -1 of NaCl solution was used as raw water, and the water permeability and salt retention rate of the membrane were tested. When the applied voltage was 0 V, 0.5 V, 1.0 V, 1.5 V, 2.0 V and 2.5 V (corresponding to the membrane surface potential of 0 V vs. Ag / AgCl, -0.14 V vs. Ag / AgCl, -0.38 V vs. Ag / AgCl, -0.63 V vs. Ag / AgCl, -0.91 V vs. Ag / AgCl and -1.19 V vs. Ag / AgCl), the permeability was 16.2 L m -1 h -1 bar -1 , 17.2 L m -1 h-1 bar -1 、19.4L m -1 h -1 bar -1 、22.7L m -1 h -1 bar -1 、25.3L m -1 h -1 bar -1 、26.5L m -1 h - 1 bar -1 , and the salt retention rates were 27.0%, 17.6%, 2.5%, 0.9%, 0.3% and 0.2% respectively.

[0044] Example 2:

[0045] A method for preparing a two-dimensional MXene-conductive polymer layered separation membrane with adjustable pore size is specifically implemented according to the following steps:

[0046] (1) 1.6 g LiF was added to 20 mL 9 mol L -1 Ti3AlC2 was etched in HCl solution at 40 °C for 48 h, and then ultrasonically stripped. The unstripped Ti3AlC2 precipitate was removed by centrifugation to obtain a dispersion of two-dimensional MXene nanosheets, which was diluted to 0.2 mg mL -1 ; Then, a 1.0 M pyrrole monomer solution was prepared, and hydrochloric acid was added to make its concentration 1.0 M. Subsequently, 10 mL of MXene dispersion was evenly mixed with 10 mL of pyrrole monomer solution, and then loaded onto a polyethersulfone flat membrane substrate by vacuum-assisted filtration. It was naturally dried at room temperature for 6 hours to form a two-dimensional MXene-pyrrole composite membrane.

[0047] (2) Pyrrole monomer molecules were polymerized on the two-dimensional MXene-pyrrole composite film obtained in step (1) using a cyclic voltammetry in-situ electrochemical polymerization method. The pyrrole monomer solution was used as the electrolyte, and the two-dimensional MXene-pyrrole composite film was used as the working electrode. Electrochemical cyclic voltammetry scanning was performed under a three-electrode system (membrane electrode, titanium counter electrode, and saturated calomel reference electrode). The voltage range of the cyclic voltammetry scanning was controlled to be -0.1 to 1.0 V, and the scanning rate was 0.05 V s -1 The scanning cycle number was 50 times, and the pyrrole monomer was polymerized in situ in the pores between the MXene layers by electrochemical in situ. After the polymerization reaction, the prepared membrane was rinsed with high-purity water and then treated at 40°C for 1h to obtain a two-dimensional MXene-polypyrrole layered separation membrane.

[0048] An application method for electrochemically regulating membrane pore size for selective separation of molecules and ions, the specific implementation steps are:

[0049] The above-mentioned two-dimensional MXene-polypyrrole layered separation membrane was sealed into a membrane assembly, wherein the two-dimensional MXene-polypyrrole layered separation membrane served as both a separation membrane and a conductive electrode, and was connected to a DC power supply via a titanium wire. A titanium mesh was placed on the water inlet side as a counter electrode, and a voltage was applied to the two-dimensional MXene-polypyrrole layered separation membrane as a cathode. 2 g L -1 The water permeability and salt rejection of the membrane were tested using Na2SO4 solution as the raw water. When the applied voltage was 0V, 0.5V, 1.0V, 1.5V, 2.0V, and 2.5V (the corresponding membrane surface potentials were 0V vs.Ag / AgCl, -0.14V vs.Ag / AgCl, -0.38V vs.Ag / AgCl, -0.63V vs.Ag / AgCl, -0.91V vs.Ag / AgCl, and -1.19V vs.Ag / AgCl), the permeability was 1.33L m -1 h -1 bar -1 、13.8L m -1 h -1 bar -1 、14.9L m -1 h -1 bar -1 、17.1L m -1 h -1 bar -1 、19.0L m -1 h -1 bar -1 、21.5L m -1 h - 1 bar -1 , the salt retention rates were 90.2%, 87.4%, 86.2%, 84.8%, 38.3% and 0.5% respectively.

[0050] Example 3:

[0051] A method for preparing a two-dimensional MXene-conductive polymer layered separation membrane with adjustable pore size is specifically implemented according to the following steps:

[0052] (1) 1.6 g LiF was added to 20 mL 9 mol L -1 Ti3AlC2 was etched in HCl solution at 50 °C for 24 h, and then ultrasonically stripped. The unstripped Ti3AlC2 precipitate was removed by centrifugation to obtain a dispersion of two-dimensional MXene nanosheets, which was diluted to 0.5 mg mL-1 ; then a 1.0 M 3,4-ethylenedioxythiophene monomer solution was prepared, which contained polystyrene sulfonic acid with a concentration of 1.0 M, and then 5 mL of the MXene dispersion liquid was uniformly mixed with 5 mL of the pyrrole monomer solution, and then it was loaded on a polysulfone flat membrane substrate by vacuum-assisted filtration, and naturally dried at room temperature for 8 h to form a two-dimensional MXene-3,4-ethylenedioxythiophene composite membrane.

[0053] (2) A 3,4-ethylenedioxythiophene monomer molecule was polymerized on the two-dimensional MXene-3,4-ethylenedioxythiophene composite membrane obtained in step (1) by using a cyclic voltammetry in-situ electrochemical polymerization method, with a 3,4-ethylenedioxythiophene monomer solution as an electrolyte, a two-dimensional MXene-3,4-ethylenedioxythiophene composite membrane as a working electrode, and an electrochemical cyclic voltammetry scan was performed in a three-electrode system (membrane electrode, graphite sheet counter electrode, and saturated calomel reference electrode), and the voltage range of the cyclic voltammetry scan was controlled to be -0.2-1.0 V, the scan speed was 0.5 V s -1 , and the scan cycle number was 100 times, so as to polymerize the 3,4-ethylenedioxythiophene monomer in the interlayer pores of the MXene by electrochemical in-situ, and after the polymerization reaction was completed, the prepared membrane was washed with high-purity water, and then treated at 60°C for 1 h to obtain a two-dimensional MXene-poly-3,4-ethylenedioxythiophene layered separation membrane.

[0054] An application method of electrochemically regulating the pore size of a membrane for selectively separating molecules and ions, and the specific implementation steps are as follows:

[0055] The two-dimensional MXene-poly-3,4-ethylenedioxythiophene layered separation membrane described above was sealed into a membrane module, wherein the two-dimensional MXene-poly-3,4-ethylenedioxythiophene layered separation membrane simultaneously served as a separation membrane and a conductive electrode, a stainless steel wire was connected to a direct current power supply, a carbon fiber cloth was placed on the water permeation side as a counter electrode, and the two-dimensional MXene-poly-3,4-ethylenedioxythiophene layered separation membrane was used as a cathode and a voltage was applied; 2 g L -1 of NaCl and 0.1 g L -1The mixed solution of Congo red dye is raw water. When the applied voltage is 0V, 0.5V, 1.0V, 1.5V, 2.0V, and 2.5V (the corresponding membrane surface potential is 0V vs.Ag / AgCl, -0.14V vs.Ag / AgCl, -0.38V vs.Ag / AgCl, -0.63V vs.Ag / AgCl, -0.91V vs.Ag / AgCl, and -1.19V vs.Ag / AgCl), the dye retention rates are 98.9%, 99.0%, 99.1%, 99.5%, 99.6%, and 99.8%, respectively, and the NaCl salt retention rates are 28.0%, 19.9%, 4.7%, 1.0%, 0.5%, and 0.2%, respectively.

[0056] Comparative Example 1

[0057] The difference from Example 1 is that only MXene is used for vacuum-assisted filtration to prepare a two-dimensional MXene layered separation membrane, which is used as a working electrode for separation application. Specific steps are as follows:

[0058] 1.6 g LiF was added to 20 mL 9 mol L -1 Ti3AlC2 was etched in HCl solution at 45 °C for 36 h, and then ultrasonically stripped. The unstripped Ti3AlC2 precipitate was removed by centrifugation to obtain a dispersion of two-dimensional MXene nanosheets, which was diluted to 0.05 mg mL -1 Then, 10 mL of MXene dispersion was loaded on the polyvinylidene fluoride hollow fiber membrane substrate by vacuum-assisted filtration and dried naturally at room temperature for 8 h to form a two-dimensional MXene layered separation membrane.

[0059] The above-mentioned two-dimensional MXene layered separation membrane was sealed into a membrane assembly, wherein the two-dimensional MXene layered separation membrane served as both a separation membrane and a conductive electrode, and was connected to a DC power supply via a platinum wire. A platinum mesh was placed on the water inlet side as a counter electrode, and a voltage was applied to the two-dimensional MXene layered separation membrane as a cathode. 2 g L -1 The NaCl solution was used as the raw water to test the water permeability and salt retention rate of the membrane. When the applied voltage was 0V, 0.5V, 1.0V, 1.5V, 2.0V, and 2.5V (the corresponding membrane surface potential was 0V vs.Ag / AgCl, -0.14V vs.Ag / AgCl, -0.38V vs.Ag / AgCl, -0.63V vs.Ag / AgCl, -0.91V vs.Ag / AgCl, and -1.19V vs.Ag / AgCl), the permeability was 3.5L m -1 h -1 bar -1 、3.4L m-1 h -1 bar -1 、3.6Lm -1 h -1 bar -1 、3.6L m -1 h -1 bar -1 、3.7L m -1 h -1 bar -1 、3.8L m -1 h -1 bar -1 The salt retention rates were 15.2%, 15.4%, 15.1%, 14.7%, 14.8% and 14.5% respectively.

[0060] Comparative Example 2

[0061] The difference from Example 1 is that no electrochemical polymerization was performed, and the two-dimensional MXene-aniline composite membrane prepared in step (1) was directly used as the working electrode for separation application. Specific steps were implemented as follows:

[0062] 1.6 g LiF was added to 20 mL 9 mol L -1 Ti3AlC2 was etched in HCl solution at 45 °C for 36 h, and then ultrasonically stripped. The unstripped Ti3AlC2 precipitate was removed by centrifugation to obtain a dispersion of two-dimensional MXene nanosheets, which was diluted to 0.05 mg mL -1 ; Then, a 0.2M aniline monomer solution was prepared, which contained 1.0M p-toluenesulfonic acid. Subsequently, 10mL of MXene dispersion was evenly mixed with 10mL of aniline monomer solution. It was then loaded onto a polyvinylidene fluoride hollow fiber membrane substrate by vacuum-assisted filtration and naturally dried at room temperature for 8h to form a two-dimensional MXene-aniline composite membrane.

[0063] The above-mentioned two-dimensional MXene-aniline composite membrane was sealed into a membrane assembly, wherein the two-dimensional MXene-aniline composite membrane served as both a separation membrane and a conductive electrode, and was connected to a DC power supply via a platinum wire. A platinum mesh was placed on the water inlet side as a counter electrode, and a voltage was applied to the two-dimensional MXene-aniline composite membrane as a cathode. 2 g L -1The NaCl solution was used as the raw water to test the water permeability and salt retention rate of the membrane. When the applied voltage was 0V, 0.5V, 1.0V, 1.5V, 2.0V, and 2.5V (the corresponding membrane surface potential was 0V vs.Ag / AgCl, -0.14V vs.Ag / AgCl, -0.38V vs.Ag / AgCl, -0.63V vs.Ag / AgCl, -0.91V vs.Ag / AgCl, and -1.19V vs.Ag / AgCl), the permeability was 11.8L m -1 h -1 bar -1 、11.9L m -1 h -1 bar -1 、11.9L m -1 h -1 bar -1 、12.0L m -1 h -1 bar -1 、12.1L m -1 h -1 bar -1 、12.1L m -1 h -1 bar -1 The salt retention rates were 23.1%, 22.5%, 22.6%, 22.3%, 22.4% and 22.2% respectively.

[0064] Comparative Example 3

[0065] The composite film was prepared using the method of Example 1 in patent CN 115268119 A. Test results showed that the prepared composite film could not achieve the regulation of the pore size between MXene layers, nor did it have the ability to selectively separate molecules and ions.

[0066] From the comparison between Example 1 and Comparative Examples 1 and 2, it can be seen that compared with the two-dimensional MXene layered separation membrane or the two-dimensional MXene-aniline composite membrane "without electrochemical polymerization", the two-dimensional MXene-conductive polymer layered separation membrane of the present invention can achieve the regulation of the pore size between the MXene layers and has a better ability to selectively separate molecules and ions.

[0067] From the comparison of Example 1 and Comparative Example 3, it can be seen that in the present application, the conductive polymer monomer is mixed with the MXene solution and vacuum filtration is performed, so that the conductive polymer monomer enters the interlayer of the MXene nanosheet, and then in-situ electrochemical polymerization is performed; while in the patent CN 115268119 A, a conductive polymer solution is directly used for electrodeposition, and is loaded on the surface of the MXene film. In this method, the conductive polymer is directly used and the electrochemical polymerization process is not involved, so the pore size of the MXene interlayer cannot be regulated, and the ability to selectively separate molecules and ions is also not possessed.

[0068] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. 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 two-dimensional MXene-conductive polymer layered separation membrane with adjustable pore size, characterized in that, Comprising: mixing a dispersion liquid of two-dimensional MXene nanosheets with a conductive polymer monomer solution uniformly at a volume ratio of 1:1-1.2, loading it on a support membrane substrate by vacuum-assisted filtration, drying to obtain a two-dimensional MXene-conductive polymer monomer composite membrane; carrying out in-situ electrochemical polymerization under a three-electrode system with the conductive polymer monomer solution as an electrolyte and the two-dimensional MXene-conductive polymer monomer composite membrane as a working electrode, to obtain the two-dimensional MXene-conductive polymer composite membrane; wherein the conductive polymer monomer solution contains an acid dopant; the conductive polymer monomer is selected from one of polyaniline, polypyrrole, polythiophene and respective derivatives thereof.

2. The method for preparing an adjustable-aperture two-dimensional MXene-conductive polymer layered separation membrane according to claim 1, characterized in that, The concentration of the dispersion liquid of the two-dimensional MXene nanosheet is 0.05-0.5 mg mL -1 .

3. The method for preparing an adjustable-aperture two-dimensional MXene-conductive polymer layered separation membrane according to claim 1, characterized in that, The concentration of the conductive polymer monomer solution is 0.2-2.0 M.

4. The method for preparing an adjustable-aperture two-dimensional MXene-conductive polymer layered separation membrane according to claim 1, wherein, The acid dopant is selected from at least one of hydrochloric acid, sulfuric acid, perchloric acid, salicylic acid, citric acid, p-toluenesulfonic acid, dodecylbenzenesulfonic acid, polystyrene sulfonic acid, polyacrylic acid, polyvinyl sulfonic acid, and polymethacrylic acid. Alternatively, the concentration of the acid dopant in the conductive polymer monomer solution is 0.5-2.0 M.

5. The method for preparing an adjustable-aperture two-dimensional MXene-conductive polymer layered separation membrane according to claim 1, wherein, In the three-electrode system, the counter electrode is an electrode made of platinum, gold, titanium, stainless steel, glassy carbon or graphite, and the reference electrode is a saturated calomel electrode or a silver / silver chloride electrode.

6. The method for preparing an adjustable-aperture two-dimensional MXene-conductive polymer layered separation membrane according to claim 1, wherein, The specific conditions of the in situ electrochemical polymerization are: the potential range of the cyclic voltammetry scan is -0.2~1.2 V, and the scan rate is 0.005~0.05 V s -1 , the number of scanning cycles is 10~100 times.

7. The method of any one of claims 1-6, wherein the tunable pore size two-dimensional MXene-conductive polymer layered separation membrane is characterized by, The thickness of the two-dimensional MXene-conductive polymer layered separation membrane layer is 50-1000 nm.

8. A method of electrochemically tuning the pore size of a membrane for the selective separation of molecules, ions, characterized in that, Comprising: sealing the two-dimensional MXene-conductive polymer layered separation membrane of claim 7 into a membrane module, wherein the two-dimensional MXene-conductive polymer layered separation membrane simultaneously serves as a separation membrane and a conductive electrode, is connected to a direct current power source through a wire, and a counter electrode is placed on the water inlet side or the permeate water outlet side, a voltage is applied between the membrane electrode and the counter electrode to generate an electric potential on the membrane surface, drive the counter ions in the conductive polymer between the membrane layers in the form of ion intercalation or ion deintercalation to regulate the membrane pore size, and realize controllable regulation of water flux and selective separation of monovalent salt, divalent salt and dye molecules.

9. The method of claim 8, wherein the electrochemically modulated membrane pore size is used for selective separation of molecules, ions, wherein The counter electrode is one of a platinum mesh, a gold mesh, a titanium mesh, a stainless steel mesh and a carbon fiber cloth.

10. The method for selectively separating molecules and ions by electrochemically regulating membrane pore size according to claim 8, characterized in that: The voltage between the two-dimensional MXene-conductive polymer layered separation membrane electrode and the counter electrode ranges from 0 to 3.0 V, and the membrane surface potential ranges from 0 to -1.5 V vs. Ag / AgCl; wherein vs. Ag / AgCl refers to the membrane surface potential when the silver / silver chloride electrode is the reference electrode.

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