A two-dimensional polymer composite membrane and its preparation method and application

Abstract

The present invention relates to the field of membrane separation technology, and in particular to a two-dimensional polymer composite membrane, its preparation method, and application. The preparation method comprises the following steps: adding trialdehyde phloroglucinol to an organic solvent to form an organic phase, adding a cyano group-containing diamine monomer to an acidic aqueous solution to form an aqueous phase, separating the organic phase from the aqueous phase using a support membrane, and allowing the trialdehyde phloroglucinol in the organic phase and the cyano group-containing diamine monomer to undergo a Schiff base reaction on the surface of the support membrane to form a two-dimensional polymer layer. The two-dimensional polymer composite membrane prepared by the present invention has high separation performance in the monovalent / monovalent metal ion separation process.

Description

Technical Field

[0001] The present invention relates to the field of membrane separation technology, and in particular to a two-dimensional polymer composite membrane and a preparation method and application thereof. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance understanding of the overall background of the invention and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to those skilled in the art.

[0003] Lithium resources, a key raw material for electronic devices and electric vehicles, are known as "white gold." Salt lake brine resources contain large amounts of lithium resources, making lithium extraction from salt lakes of great social and economic significance. Currently, research on lithium extraction from salt lakes primarily focuses on separating magnesium ions and lithium ions in salt lake brine. Salt lake lithium extraction technologies vary depending on the magnesium / lithium ratio in the salt lake brine. Low magnesium / lithium ratio salt lake lithium extraction technologies primarily utilize precipitation, while high magnesium / lithium ratio salt lake lithium extraction technologies primarily utilize adsorption, electrodialysis, membrane separation, and extraction. Compared to other separation technologies, membrane separation technology offers advantages such as high separation efficiency, simple operation, environmental friendliness, and low energy consumption, and has been widely used and researched in the process of lithium extraction from salt lakes.

[0004] At present, magnesium ions and lithium ions can be separated efficiently by membrane separation technology. + , K + 、Li + With the same valence and similar hydration radius (Na + : K + : Li + : ), using membrane separation technology to separate monovalent / monovalent metal ions in salt lakes (Na + / Li + or K + / Li + Separation) is a current research difficulty in lithium extraction from salt lakes. Therefore, the development of membrane materials for separation (especially high-efficiency separation) is the key to solving the problem. Summary of the Invention

[0005] In order to address the deficiencies of the prior art, the purpose of the present invention is to provide a two-dimensional polymer composite membrane, a preparation method and application thereof. The two-dimensional polymer composite membrane prepared by the present invention has high separation performance in the monovalent / monovalent metal ion separation process, especially the modified two-dimensional polymer composite membrane has excellent separation performance.

[0006] In order to achieve the above object, the technical solution of the present invention is:

[0007] In a first aspect, a method for preparing a two-dimensional polymer composite membrane comprises the following steps:

[0008] Trialdehyde phloroglucinol is added to an organic solvent to prepare an organic phase, a cyano group-containing diamine monomer is added to an acidic aqueous solution to prepare an aqueous phase, the organic phase and the aqueous phase are separated by a support membrane, and the trialdehyde phloroglucinol in the organic phase and the cyano group-containing diamine monomer undergo a Schiff base reaction on the surface of the support membrane to form a two-dimensional polymer layer, thereby obtaining;

[0009] The cyano-containing diamine monomer is an organic compound containing at least one cyano group and two primary amino groups.

[0010] The present invention uses trialdehyde phloroglucinol and a diamine monomer containing a cyano group to form a covalent organic framework through a Schiff base reaction. The framework has a large number of pore structures and active groups such as ketone groups and cyano groups. The organic phase and the aqueous phase are separated by a support membrane, and the Schiff base reaction is carried out on the surface of the support membrane located at the oil-water interface, so that a two-dimensional polymer layer is grown in situ at the liquid-solid interface. During the process of in-situ growth of the two-dimensional polymer layer, the pore structure of the two-dimensional polymer layer can be adjusted by adjusting the number of cyano groups in the diamine monomer. Experiments have found that the separation of monovalent / monovalent metal ions can be achieved by coordinating the pore structure of the adjusted two-dimensional polymer layer with active groups such as ketone groups and cyano groups.

[0011] In order to further improve the separation effect of monovalent / monovalent metal ions, the present invention can use hydroxylamine to modify the formed two-dimensional polymer layer. In this method, hydroxylamine can react with the cyano group in the two-dimensional polymer layer to produce acyloxime groups. This makes the two-dimensional polymer layer contain oxime groups. Experimental studies have shown that the two-dimensional polymer composite membrane containing oxime groups has a better separation effect of monovalent / monovalent metal ions.

[0012] In another aspect, a two-dimensional polymer composite membrane is obtained by the preparation method described in the first aspect of the present invention.

[0013] Thirdly, a method for separating potassium ions and lithium ions is provided, in which water and a solution containing potassium ions and lithium ions are placed on both sides of the above-mentioned two-dimensional polymer composite membrane, respectively, and allowed to separate statically; in this separation process, osmotic pressure is used as the driving force for separation, which is more energy-saving and environmentally friendly than electric drive and pressure drive.

[0014] In a fourth aspect, a two-dimensional polymer composite membrane or a method for separating potassium ions and lithium ions is used in extracting lithium from salt lakes.

[0015] The beneficial effects of the present invention are:

[0016] 1. The present invention selects trialdehyde phloroglucinol and a diamine monomer containing a cyano group to undergo a Schiff base reaction on the surface of a support membrane to form a two-dimensional polymer layer. This not only adjusts the pore structure of the two-dimensional polymer layer, but also introduces active groups such as ketone groups and cyano groups. Through the coordination of the physical structure and the active groups, the separation of monovalent / monovalent metal ions is achieved, and the separation of monovalent metal ions in the process of lithium extraction from salt lakes can be achieved. In addition, the present invention uses hydroxylamine modification to convert some cyano groups into oxime groups, which can further improve the separation effect of monovalent / monovalent metal ions. + / Li + During the separation process, K + Permeation rate and true K + / Li + The selectivity can reach 306mmol / m 2 h and 5.6, which can achieve efficient separation of monovalent metal ions during lithium extraction from salt lakes.

[0017] 2. The two-dimensional polymer composite membrane of the present invention has a simple and safe preparation process, does not involve high temperature, high pressure or high energy consumption such as electricity, has a low preparation cost, and is suitable for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0019] Figure 1 Schematic diagram of the preparation of a cyano-containing two-dimensional polymer composite membrane according to Example 1 of the present invention;

[0020] Figure 2 FTIR spectrum of the cyano-containing two-dimensional polymer composite membrane TpPa-CN6 according to Example 1 of the present invention;

[0021] Figure 3 is the XRD spectrum of the cyano group-containing two-dimensional polymer composite membrane TpPa-CN6 according to Example 1 of the present invention;

[0022] Figure 4 1 is an SEM image of the cyano group-containing two-dimensional polymer composite membrane TpPa-CN6 according to Example 1 of the present invention, wherein a is a surface image of the membrane and b is a cross-sectional image of the membrane;

[0023] Figure 5 FTIR spectrum of the acyloxime-containing two-dimensional polymer composite membrane TpPa-AO6 according to Example 2 of the present invention;

[0024] Figure 6 is the XRD spectrum of the acyloxime group-containing two-dimensional polymer composite film TpPa-AO6 of Example 2 of the present invention;

[0025] Figure 7 1 is the SEM spectrum of the acyloxime-containing two-dimensional polymer composite membrane TpPa-AO6 of Example 2 of the present invention, a is a surface view, and b is a cross-sectional view;

[0026] Figure 8 FTIR spectrum of the cyano-containing two-dimensional polymer composite membrane TpPa-CN3 according to Example 3 of the present invention;

[0027] Figure 9 is an XRD spectrum of the cyano group-containing two-dimensional polymer composite membrane TpPa-CN3 according to Example 3 of the present invention;

[0028] Figure 10 3 is an SEM image of the cyano group-containing two-dimensional polymer composite membrane TpPa-CN3 of Example 3 of the present invention, a is a surface view, and b is a cross-sectional view;

[0029] Figure 11 is the FTIR spectrum of the acyloxime group-containing two-dimensional polymer composite membrane TpPa-AO3 of Example 6 of the present invention;

[0030] Figure 12 is the XRD spectrum of the acyloxime group-containing two-dimensional polymer composite film TpPa-AO3 of Example 6 of the present invention;

[0031] Figure 13 1 is a SEM spectrum of the acyloxime-containing two-dimensional polymer composite membrane TpPa-AO3 of Example 6 of the present invention, a is a surface view, and b is a cross-sectional view;

[0032] Figure 14 FTIR spectrum of the two-dimensional polymer composite membrane TpPa-CN0 of Comparative Example 1 of the present invention;

[0033] Figure 15 is the XRD spectrum of the two-dimensional polymer composite membrane TpPa-CN0 of Comparative Example 1 of the present invention;

[0034] Figure 16 1 is an SEM image of the two-dimensional polymer composite membrane TpPa-CN0 of Comparative Example 1 of the present invention, a is a surface view, and b is a cross-sectional view;

[0035] Figure 17 K of the two-dimensional polymer composite membrane prepared in Examples 1, 2, 3, 6 and Comparative Example 1 in a single KCl solution and a LiCl solution + / Li + Separation performance;

[0036] Figure 18 K of the two-dimensional polymer composite membrane prepared in Examples 1, 2, 3, 6 and Comparative Example 1 in a KCl / LiCl mixed solution + / Li +Separation performance;

[0037] Figure 19 This is a performance comparison chart of the acyloxime-based two-dimensional polymer composite membrane prepared in Example 2 and other membranes reported in the literature in K+ / Li+ separation applications. DETAILED DESCRIPTION

[0038] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention belongs.

[0039] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0040] Considering that the difficulty of extracting lithium from salt lakes lies in the separation of monovalent / monovalent metal ions by membrane materials, the present invention proposes a two-dimensional polymer composite membrane and its preparation method and application.

[0041] A typical embodiment of the present invention provides a method for preparing a two-dimensional polymer composite membrane, comprising the following steps:

[0042] Trialdehyde phloroglucinol is added to an organic solvent to prepare an organic phase, a cyano group-containing diamine monomer is added to an acidic aqueous solution to prepare an aqueous phase, the organic phase and the aqueous phase are separated by a support membrane, and the trialdehyde phloroglucinol in the organic phase and the cyano group-containing diamine monomer undergo a Schiff base reaction on the surface of the support membrane to form a two-dimensional polymer layer, thereby obtaining;

[0043] The cyano-containing diamine monomer is an organic compound containing at least one cyano group and two primary amino groups.

[0044] In some embodiments, the organic solvent is one or more of mesitylene, 1,4-dioxane, ethyl acetate, tetrahydrofuran, methanol, o-dichlorobenzene, or n-butanol, preferably a mesitylene / ethyl acetate mixed solvent. Specifically, the volume ratio of mesitylene to ethyl acetate is 2.5 to 6.5:1.

[0045] In some embodiments, the diamine monomer containing a cyano group is 2,5-diaminoterephthalonitrile and / or 2,5-diaminobenzonitrile.

[0046] In some embodiments, the acidic aqueous solution is one or more of hydrochloric acid aqueous solution, acetic acid aqueous solution, trifluoromethanesulfonic acid aqueous solution or p-toluenesulfonic acid aqueous solution, preferably acetic acid aqueous solution. Specifically, the concentration of the acetic acid aqueous solution is 3.5 to 6.5 mol / L.

[0047] The present invention found that the solvent has a great influence on the density and crystallinity of the final prepared two-dimensional polymer film. When the organic solvent is selected as a mixed solvent of mesitylene / ethyl acetate and the aqueous hydrochloric acid solution is selected as an aqueous acetic acid solution, the two-dimensional polymer has better film-forming properties and crystallinity, and thus has better monovalent / monovalent metal ion separation performance.

[0048] In some embodiments, the addition ratio of trialdehyde phloroglucinol to the organic solvent is 0.1-1:30-50, mmol:mL.

[0049] In some embodiments, the addition ratio of the cyano group-containing diamine monomer to the acidic aqueous solution is 0.15-1.5:30-50, mmol:mL.

[0050] In some embodiments, the support membrane is a polyacrylonitrile membrane, a polysulfone membrane, a polyethersulfone membrane, an aluminum oxide membrane or a polyimide membrane, preferably a polyacrylonitrile membrane. The present invention does not impose any particular restrictions on the source of the support membrane, and the support membrane can be purchased from commercial sources.

[0051] In some embodiments, the temperature for forming the two-dimensional polymer layer is 30-70°C, more preferably 30-35°C.

[0052] In some embodiments, the time for forming the two-dimensional polymer layer is 2 to 7 days, more preferably 3.5 to 5.5 days.

[0053] In some embodiments, a post-modification process is further included, wherein the post-modification process is: modifying the two-dimensional polymer layer with hydroxylamine to convert the cyano group into an oxime group.

[0054] Specifically, the post-modification process comprises the following steps: placing the support membrane with the two-dimensional polymer layer grown on the surface in a hydroxylamine solution for reaction.

[0055] More specifically, the hydroxylamine in the hydroxylamine solution is a hydroxylamine aqueous solution or hydroxylamine hydrochloride. The hydroxylamine aqueous solution generally has a mass concentration of 45-55%. The solvent in the hydroxylamine solution is an alcohol solvent, which may be one or more of methanol, ethanol, isopropanol, or n-butanol, with ethanol being more preferred.

[0056] More specifically, the temperature of the post-modification process is 30-80°C, preferably 30-35°C.

[0057] More specifically, the post-modification process lasts for 12 to 72 hours, preferably at 48 to 72°C.

[0058] Another embodiment of the present invention provides a two-dimensional polymer composite membrane obtained by the preparation method described in the first aspect of the present invention.

[0059] A third embodiment of the present invention provides a method for separating potassium ions and lithium ions, wherein water and a solution containing potassium ions and lithium ions are placed on both sides of the above-mentioned two-dimensional polymer composite membrane, respectively, and allowed to stand for separation.

[0060] A fourth embodiment of the present invention provides an application of the above-mentioned two-dimensional polymer composite membrane or the method for separating potassium ions and lithium ions in extracting lithium from salt lakes.

[0061] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments and comparative examples.

[0062] Example 1

[0063] A method for preparing a cyano-containing two-dimensional polymer composite film comprises the following steps:

[0064] (1) Weigh 21.0 mg (0.1 mmol) of trialdehyde phloroglucinol (Tp), dissolve it in 50 mL of mesitylene / ethyl acetate mixed solution, and ultrasonicate it in an ultrasonic machine for 10 minutes to ensure that the solid is fully dissolved; weigh 23.7 mg (0.15 mmol) of 2,5-diaminoterephthalonitrile (Pa-CN2), dissolve it in 50 mL of acetic acid aqueous solution, and ultrasonicate it in an ultrasonic machine for 10 minutes to ensure that the solid is fully dissolved.

[0065] (2) First, a polyacrylonitrile membrane was used as a support membrane and vertically sandwiched in the middle of a homemade H-shaped trough. Then, the solutions of the aldehyde monomer and the amine monomer in step (1) were added to both sides of the H-shaped trough respectively.

[0066] (3) The H-shaped tank to which the solution was added in step (2) was placed in an oven at 30° C. and reacted for 4 days. After the reaction was completed, a two-dimensional polymer composite membrane containing cyano groups was obtained, which was recorded as TpPa-CN6 membrane.

[0067] In Example 1 Figure 1 Schematic diagram of the preparation of cyano-containing two-dimensional polymer composite membrane.

[0068] The TpPa-CN6 membrane prepared in Example 1 was subjected to FTIR spectrum test, and the results were as follows: Figure 2 As shown, it can be seen that the TpPa-CN6 membrane containing cyano groups was successfully prepared.

[0069] The TpPa-CN6 film prepared in Example 1 was subjected to XRD test, and the results were as follows: Figure 3As shown, it can be seen that the synthesized two-dimensional polymer film is highly crystalline.

[0070] The TpPa-CN6 membrane prepared in Example 1 was subjected to SEM testing, and the results were as follows: Figure 4 As shown, its dense structure and film thickness can be seen.

[0071] Example 2

[0072] A method for preparing a two-dimensional polymer composite film containing an acyl oxime group comprises the following steps:

[0073] (1) Weigh 200 μL of 50% hydroxylamine aqueous solution, add it to 100 mL of ethanol, and ultrasonicate it in an ultrasonic machine for 10 minutes to ensure that the hydroxylamine is fully dissolved in the ethanol.

[0074] (2) The cyano-containing two-dimensional polymer composite membrane prepared in Example 1 is placed in the hydroxylamine solution prepared in step (1) to convert the cyano groups in the two-dimensional polymer composite membrane into oxime groups.

[0075] (3) The hydroxylamine solution containing the two-dimensional polymer composite membrane was placed in an oven at 30° C. and reacted for 72 hours.

[0076] (4) After the reaction is completed, the two-dimensional polymer composite membrane is continuously washed with deionized water and ethanol solution to obtain a two-dimensional polymer composite membrane containing acyloximine groups, which is recorded as TpPa-AO6 membrane.

[0077] The TpPa-AO6 film prepared in Example 2 was tested by FTIR spectrum. The results are as follows: Figure 5 As shown, it can be seen that the cyano groups in the two-dimensional polymer composite film were successfully converted into oxime groups.

[0078] The TpPa-AO6 film prepared in Example 2 was subjected to XRD test, and the results were as follows: Figure 6 As shown, it can be seen that after acylation, the two-dimensional polymer composite film still maintains good crystallinity.

[0079] The TpPa-AO6 membrane prepared in Example 2 was subjected to SEM testing, and the results were as follows: Figure 7 As shown, its dense structure and film thickness can be seen.

[0080] Example 3

[0081] This embodiment is the same as embodiment 1, except that 2,5-diaminoterephthalonitrile is replaced by an equal molar amount of 2,5-diaminobenzonitrile to obtain a two-dimensional polymer composite membrane containing cyano groups, which is recorded as TpPa-CN3 membrane.

[0082] The TpPa-CN3 film prepared in Example 3 was tested by FTIR spectrum. The results are as follows: Figure 8As shown, it can be seen that the TpPa-CN3 membrane containing cyano groups was successfully prepared.

[0083] The TpPa-CN3 film prepared in Example 3 was subjected to XRD test, and the results were as follows: Figure 9 As shown, it can be seen that the synthesized two-dimensional polymer film is highly crystalline.

[0084] The TpPa-CN3 membrane prepared in Example 3 was subjected to SEM testing, and the results were as follows: Figure 10 As shown, its dense structure and film thickness can be seen.

[0085] Example 4

[0086] This embodiment is the same as embodiment 1, except that the polyacrylonitrile membrane is replaced by a polysulfone membrane.

[0087] Example 5

[0088] This embodiment is the same as embodiment 1, except that the polyacrylonitrile film is replaced by a polyimide film.

[0089] Example 6

[0090] This embodiment is the same as Example 2, except that the cyanide-containing two-dimensional polymer composite membrane prepared in Example 1 is replaced by the cyanide-containing two-dimensional polymer composite membrane prepared in Example 3 to obtain a two-dimensional polymer composite membrane containing acyl oxime groups, which is recorded as TpPa-AO3 membrane.

[0091] The TpPa-AO6 film prepared in Example 6 was subjected to FTIR spectrum test, and the results were as follows: Figure 11 As shown, it can be seen that the cyano groups in the two-dimensional polymer composite film were successfully converted into oxime groups.

[0092] The TpPa-AO6 film prepared in Example 6 was subjected to XRD test, and the results were as follows: Figure 12 As shown, it can be seen that after acylation, the two-dimensional polymer composite film still maintains good crystallinity.

[0093] The TpPa-AO6 membrane prepared in Example 6 was subjected to SEM testing, and the results were as follows: Figure 13 As shown, its dense structure and film thickness can be seen.

[0094] Example 7

[0095] This embodiment is the same as embodiment 2, except that the cyanide-containing two-dimensional polymer composite membrane prepared in embodiment 1 is replaced by the cyanide-containing two-dimensional polymer composite membrane prepared in embodiment 4.

[0096] Example 8

[0097] This embodiment is the same as embodiment 2, except that the cyanide-containing two-dimensional polymer composite membrane prepared in embodiment 1 is replaced by the cyanide-containing two-dimensional polymer composite membrane prepared in embodiment 5.

[0098] Comparative Example 1

[0099] This comparative example is the same as Example 1, except that 2,5-diaminoterephthalonitrile is replaced by an equal molar amount of p-phenylenediamine to prepare a two-dimensional polymer composite membrane, which is recorded as TpPa-CN0.

[0100] The TpPa-CNO film prepared in Comparative Example 1 was subjected to FTIR spectrum test, and the results were as follows: Figure 14 As shown, it can be seen that the TpPa-CN0 membrane containing cyano groups was successfully prepared.

[0101] The TpPa-CNO film prepared in Comparative Example 1 was subjected to XRD test, and the results were as follows: Figure 15 As shown, it can be seen that the synthesized two-dimensional polymer film is highly crystalline.

[0102] The TpPa-CNO membrane prepared in Comparative Example 1 was subjected to SEM testing, and the results were as follows: Figure 16 As shown, its dense structure and film thickness can be seen.

[0103] Application Example 1

[0104] The two-dimensional polymer composite membranes of Examples 1, 2, 3, 6 and Comparative Example 1 were subjected to a monovalent / monovalent metal ion separation test. The specific test process is as follows:

[0105] Prepare 100 mL of KCl solution (0.1 mol / L) and 100 mL of LiCl solution (0.1 mol / L) as the feed solution;

[0106] Place the cyano or acyl oxime-containing two-dimensional polymer composite membrane vertically in the middle of an H-type membrane pool. Add 100 mL of KCl solution or LiCl solution (0.1 mol / L) prepared in step (1) to the side facing the two-dimensional polymer layer, and add ultrapure water to the other side of the H-type membrane pool. Stir both sides of the H-type membrane pool at the same time. After 3 hours, take the solution on the ultrapure water side and then use inductively coupled plasma mass spectrometry to check the K content of the solution. + or Li + concentration, and an ideal monovalent / monovalent metal ion separation test was performed under this system.

[0107] Figure 17 The K of the two-dimensional polymer composite membrane containing cyano and acyl oxime prepared in Example 1 and Example 2 under single KCl solution and LiCl solution + / Li +Separation performance. From the separation performance diagram, it can be seen that the acyloximate two-dimensional polymer composite membrane exhibits a better K + / Li + Separation performance, K + Permeation flux and ideal K + / Li + The selectivity reached 340.2mmol / m 2 ·h and 6.4.

[0108] Application Example 2

[0109] The two-dimensional polymer composite membranes of Examples 1, 2, 3, 6 and Comparative Example 1 were subjected to a monovalent / monovalent metal ion separation test. The specific test process is as follows:

[0110] (1) Prepare 100 mL of KCl / LiCl mixed solution (0.1 mol / L) as the feed solution;

[0111] (2) Place the two-dimensional polymer composite membrane containing cyano or acyl oxime groups vertically in the middle of an H-type membrane pool. Add 100 mL of the KCl / LiCl mixed solution (0.1 mol / L) prepared in step (1) to the side facing the two-dimensional polymer layer, and add ultrapure water to the other side of the H-type membrane pool. Stirring is applied to both sides of the H-type membrane pool. After 3 hours, the solution on the ultrapure water side is taken and then the K content in the solution is checked using an inductively coupled plasma mass spectrometer. + or Li + concentration, and actual monovalent / monovalent metal ion separation tests were carried out under this system.

[0112] Figure 18 K is the K of the two-dimensional polymer composite membrane containing cyano and acyloxime groups prepared in Examples 1, 2, 3, 6 and Comparative Example 1 in a KCl / LiCl mixed solution. + / Li + Separation performance. From the separation performance diagram, it can be seen that the acyloximate two-dimensional polymer composite membrane exhibits a better K + / Li + Separation performance, K + Permeation flux and actual K + / Li + The selectivity reached 306mmol / m 2 ·h and 5.6.

[0113] Figure 19 The acyloxime-based two-dimensional polymer composite membrane prepared in Example 2 is comparable to other membranes reported in the literature in terms of K + / Li + Performance comparison chart in separation applications, the results show that the acyloxime-based two-dimensional polymer composite membrane exhibits excellent comprehensive K + / Li +The separation performance exceeds that reported in current literature, indicating that the membrane has more practical industrial application value.

[0114] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for preparing a two-dimensional polymer composite membrane, comprising: The process is as follows: Trialdehyde phloroglucinol is added to an organic solvent to prepare an organic phase, a cyano group-containing diamine monomer is added to an acidic aqueous solution to prepare an aqueous phase, the organic phase and the aqueous phase are separated by a support membrane, and the trialdehyde phloroglucinol in the organic phase and the cyano group-containing diamine monomer undergo a Schiff base reaction on the surface of the support membrane to form a two-dimensional polymer layer, thereby obtaining; Wherein, the diamine monomer containing a cyano group is an organic compound containing at least one cyano group and two primary amino groups; the diamine monomer containing a cyano group is 2,5-diaminoterephthalonitrile and / or 2,5-diaminobenzonitrile; The organic solvent is a mesitylene / ethyl acetate mixed solvent; The method further comprises a post-modification process, wherein the post-modification process comprises: modifying the two-dimensional polymer layer with hydroxylamine to convert the cyano group into an acyloxime group.

2. The method for preparing a two-dimensional polymer composite membrane according to claim 1, wherein: The volume ratio of mesitylene to ethyl acetate is 2.5~6.5:

1.

3. The method for preparing a two-dimensional polymer composite membrane according to claim 1, wherein: The acidic aqueous solution is one or more of a hydrochloric acid aqueous solution, an acetic acid aqueous solution, a trifluoromethanesulfonic acid aqueous solution or a p-toluenesulfonic acid aqueous solution.

4. The method for preparing a two-dimensional polymer composite membrane according to claim 3, wherein: The acidic aqueous solution is an acetic acid aqueous solution.

5. The method for preparing a two-dimensional polymer composite membrane according to claim 4, wherein: The concentration of the acetic acid aqueous solution is 3.5~6.5 mol / L.

6. The method for preparing a two-dimensional polymer composite membrane according to claim 1, wherein: The supporting membrane is a polyacrylonitrile membrane, a polysulfone membrane, a polyethersulfone membrane, an aluminum oxide membrane or a polyimide membrane.

7. The method for preparing a two-dimensional polymer composite membrane according to claim 1, wherein: The addition ratio of trialdehyde phloroglucinol and organic solvent is 0.1~1:30~50, mmol:mL.

8. The method for preparing a two-dimensional polymer composite membrane according to claim 1, wherein: The addition ratio of the cyano group-containing diamine monomer and the acidic aqueous solution is 0.15-1.5:30-50, mmol:mL.

9. The method for preparing a two-dimensional polymer composite membrane according to claim 1, wherein: The temperature for forming the two-dimensional polymer layer is 30~70℃.

10. The method for preparing a two-dimensional polymer composite membrane according to claim 9, wherein: The temperature for forming the two-dimensional polymer layer is 30~35℃.

11. The method for preparing a two-dimensional polymer composite membrane according to claim 1, wherein: The time required to form the two-dimensional polymer layer is 2 to 7 days.

12. The method for preparing a two-dimensional polymer composite membrane according to claim 11, wherein: The time required to form the two-dimensional polymer layer is 3.5 to 5.5 days.

13. The method for preparing a two-dimensional polymer composite membrane according to claim 1, wherein: The post-modification process comprises the following steps: placing a support membrane with a two-dimensional polymer layer grown on the surface thereof in a hydroxylamine solution for reaction.

14. The method for preparing a two-dimensional polymer composite membrane according to claim 13, wherein: The hydroxylamine in the hydroxylamine solution is a hydroxylamine aqueous solution or hydroxylamine hydrochloride.

15. The method for preparing a two-dimensional polymer composite membrane according to claim 13, wherein: The solvent in the hydroxylamine solution is an alcohol solvent.

16. The method for preparing a two-dimensional polymer composite membrane according to claim 15, wherein: The alcohol solvent is one or more of methanol, ethanol, isopropanol or n-butanol.

17. The method for preparing a two-dimensional polymer composite membrane according to claim 16, wherein: The alcohol solvent is ethanol.

18. The method for preparing a two-dimensional polymer composite membrane according to claim 13, wherein: The temperature of the post-modification process is 30~80℃.

19. The method for preparing a two-dimensional polymer composite membrane according to claim 18, wherein: The temperature of the post-modification process is 30~35℃.

20. The method for preparing a two-dimensional polymer composite membrane according to claim 13, wherein: The post-modification process takes 12 to 72 hours.

21. The method for preparing a two-dimensional polymer composite membrane according to claim 20, wherein: The post-modification process takes place at 48-72°C.

22. A two-dimensional polymer composite film, characterized in that: Obtained by the preparation method according to any one of claims 1 to 21.

23. A method for separating potassium ions and lithium ions, characterized in that: Water and a solution containing potassium ions and lithium ions are placed on both sides of the two-dimensional polymer composite membrane according to claim 22, respectively, and allowed to stand for separation.

24. Use of the two-dimensional polymer composite membrane or the method for separating potassium ions and lithium ions according to claim 22 in extracting lithium from salt lakes.

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