Multifunctional and multipurpose separation membrane, defect-free dense layer polyamide layer separation membrane and preparation method thereof

Abstract

The application discloses a multifunctional separation membrane and a preparation method thereof, and relates to the field of membrane separation materials and preparation technology. The method comprises the following steps: firstly, placing an amine monomer solution in a container, bending one side of a hydrophobic membrane and slowly floating the bottom surface of the hydrophobic membrane on the surface of the amine monomer solution, and providing an open environment system for the hydrophobic membrane; then, starting from the edge of the top surface of the hydrophobic membrane, adding an acyl chloride monomer solution by using a rubber head dropper; finally, under normal temperature conditions, the acyl chloride monomer and the amine monomer on the bottom surface of the hydrophobic membrane are subjected to a reverse polymerization reaction, and after being taken out and washed with water, the hydrophobic membrane is dried in an oven, and the multifunctional membrane is obtained. The multifunctional membrane can be simultaneously applied to the fields of reverse osmosis, nanofiltration, permeation gasification and membrane distillation, and the anti-wetting performance of the multifunctional membrane is improved by about 1-2 orders of magnitude, the multifunctional membrane can greatly expand the treatment of low-surface-energy high-salt wastewater, the vapor flux and efficiency of membrane distillation can be improved and improved, and the service life of the membrane distillation is greatly prolonged.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of membrane materials and their preparation technology, in particular to a multifunctional and multipurpose separation membrane and a preparation method thereof. BACKGROUND

[0002] Human society cannot do without the separation of materials, among which the separation of chemical products accounts for 30% of the world's total energy consumption, and 70% of which is consumed by separation. In addition, with the rapid development of industrialization and the frequent occurrence of extreme weather, water shortage has become a pressing problem. In recent years, membrane separation technology has developed rapidly, and different types of membranes have been developed for different separation systems, such as reverse osmosis membranes, membrane distillation membranes, nanofiltration membranes, gas separation membranes, and permeation gasification membranes.

[0003] For example, the prior art CN 108654407 A discloses a method and device for preparing a composite nanofiltration membrane, comprising the following steps:

[0004] Step one, selecting a hydrophobic support as the base film of the nanofiltration membrane; step two, using a reverse interfacial polymerization reaction method, immersing the selected base film in an oil phase monomer; step three, immersing the completely immersed base film in a water phase monomer for reaction; step four, heat-treating the reacted base film to obtain a composite nanofiltration membrane. The prior art uses a reverse interfacial polymerization reaction method or an additive-assisted interfacial polymerization reaction method to generate a polyamide active separation layer less than 50 nm on a hydrophobic PTFE / PVA nanofiber base film, and finally prepares a PTFE / PVA composite nanofiltration membrane.

[0005] CN114797504B discloses a preparation method of a sulfonated polyamide / hydrophobic polymer full-heat exchange composite membrane, which comprises: covering a hydrophobic polymer membrane on the surface of a multi-amine aqueous solution with a certain concentration, and injecting a multi-acyl chloride organic solution with a certain concentration above the polymer membrane. The multi-acyl chloride organic solution fully infiltrates the polymer membrane and diffuses to the other side of the polymer membrane, contacts the multi-amine aqueous solution and forms an immiscible interfacial layer, and the multi-amine and the multi-acyl chloride perform interfacial polycondensation to generate a dense thin layer of aromatic cross-linked polyamide at the interfacial layer, thereby obtaining a polyamide-hydrophobic polymer composite membrane. The composite membrane is applied to the field of heat exchange technology.

[0006] The membranes prepared in the prior art are all applied to specific fields, and are difficult to be applied to different fields, because the process technology in the prior art is difficult to prepare a multifunctional layer membrane, such as the preparation method of a sulfonated polyamide / hydrophobic polymer full heat exchange composite membrane disclosed in CN114797504B, in which a lower reaction container, an upper reaction container and a fixing clamp are used to fix the polyethylene porous membrane, so that although the reverse polymerization method is used, bubbles are generated during the addition of acyl chloride, and the bubbles are difficult to be discharged under the action of the reaction container, which inevitably causes the formation of a large amount of bubbles at the interface, which causes a large number of defects during film formation, resulting in a low water pressure through the membrane; in addition, the functional layer formed after most of the hydrophilic modification is very dense, which seriously affects the water transmission flux, resulting in a decrease in separation performance. Therefore, the process for preparing the membrane is particularly crucial for regulating the microtopography of the multifunctional layer membrane and then regulating the separation performance. If the process for preparing the membrane is improved, the prepared membrane can be applied to different fields, which can solve the single technical problem existing in the application of the membrane in the field.

[0007] Therefore, the prior art needs to be further improved. SUMMARY

[0008] One of the purposes of the present application is to provide a preparation method of a multifunctional membrane, which can be simultaneously applied to the fields of reverse osmosis, nanofiltration, permeation gasification and membrane distillation, especially in the field of membrane distillation, the anti-wetting performance is increased by about 1-2 orders of magnitude, which can greatly expand the treatment of low surface energy high salt and high organic solvent wastewater, and the dense layer has little effect on the permeation flux of the membrane, which can greatly improve and improve the vapor flux and efficiency of membrane distillation.

[0009] In order to achieve the above purpose, the following technical scheme is adopted in the present application:

[0010] A preparation method of a multifunctional membrane, wherein the multifunctional membrane refers to a membrane that can be simultaneously applied to the fields of reverse osmosis, nanofiltration, permeation gasification or membrane distillation;

[0011] The preparation method comprises:

[0012] Step one, respectively configuring an amine monomer solution with a mass fraction of 0.1% to 5% and an acyl chloride monomer solution with a mass fraction of 0.01% to 0.5%;

[0013] Step two, placing the prepared amine monomer solution in a container, bending one side of the hydrophobic membrane and slowly floating the bottom surface of the hydrophobic membrane on the surface of the amine monomer solution, and the floating environment provides an open environment system for the hydrophobic membrane; the acyl chloride monomer solution is placed in a rubber dropper;

[0014] Step three, starting from the edge of the top surface of the hydrophobic membrane, the acyl chloride monomer solution is added by using a rubber dropper;

[0015] The dropwise adding process is: dropwise adding along the edge of the top surface of the hydrophobic membrane, when a drop wets the hydrophobic membrane, then dropwise adding again along the wet area, and sequentially dropwise adding from outside to inside until the surface of the hydrophobic membrane is completely wetted and covers a certain volume of acyl chloride monomer; in the dropwise adding process, the hydrophobic membrane can remove the generated by-product gas under an open environment system;

[0016] Step four, under normal temperature conditions, the acyl chloride monomer and the amine monomer on the bottom surface of the hydrophobic membrane undergo a reverse polymerization reaction for 18-180 min, and after taking out and washing with water, the hydrophobic membrane is placed in an oven for drying, and a multifunctional membrane is obtained.

[0017] The preparation method of the multifunctional membrane, the acyl chloride monomer solution is a benzene tricarboxylic acid chloride or 2, 6-naphthalene dicarboxylic acid chloride solution in n-hexane.

[0018] The preparation method of the multifunctional membrane, the amine monomer solution is m-phenylenediamine, polyethyleneimine, piperazine or dopamine.

[0019] The preparation method of the multifunctional membrane, the amine monomer solution is m-phenylenediamine.

[0020] The preparation method of the multifunctional membrane, the hydrophobic membrane is a PVDF flat membrane, a hollow fiber membrane, a PTFE flat membrane, a hydrophobic PE membrane or a hydrophobic PP membrane.

[0021] The preparation method of the multifunctional membrane, the hydrophobic membrane is a PTFE flat membrane.

[0022] The preparation method of the multifunctional membrane, the average molecular weight of the polyethyleneimine is 400-200,000.

[0023] An additive is added to the amine monomer solution, and the additive is a mixed solution of triethylamine and camphor sulfonic acid.

[0024] The purpose of the present application is to provide a multifunctional membrane prepared by the above preparation method.

[0025] A multifunctional membrane is prepared by the above preparation method, the multifunctional membrane has acid and alkali resistance, high temperature resistance and organic solvent resistance; the multifunctional membrane has a Janus composite structure with hydrophilic-hydrophobic.

[0026] Compared with the prior art, the present application has the following beneficial technical effects:

[0027] The application provides a preparation method of a multifunctional membrane, which directly floats the hydrophobic membrane on an amine monomer solution by using the performance of the hydrophobic membrane, and then combines a subsequent drop method to prepare the multifunctional membrane suitable for reverse osmosis, nanofiltration, permeation gasification or membrane distillation.

[0028] The multifunctional membrane prepared by the application is formed on one side and has a Janus composite structure of hydrophilicity and hydrophobicity.

[0029] In the preparation method, the reaction time is 18-170 min, which is much longer than the reaction time of 15 min in the prior art, and with the extension of the reaction time, the reaction in the multifunctional membrane can be carried out to form the dense sponge-like sealing agent semi-closed finger-shaped hole, which leads to the multifunctional use.

[0030] In the application, the hydrophobic membrane is directly floated on the amine monomer solution, which is different from the closed environment system formed by the reaction container and the fixed clamp in the prior art, and the hydrophobic membrane is exposed to the environment, which is equivalent to forming an open environment system. The main purpose of this setting is that the wetting performance of the hydrophobic membrane itself can form a solid-liquid interface on the water surface, and when the acyl chloride monomer solution is added dropwise on the hydrophobic membrane, the liquid droplets quickly spread around due to the low surface energy in the organic phase. In addition, because the hydrophobic membrane hole itself has a large amount of air, if the drop is added randomly, the air in the membrane cannot be discharged, which leads to the formation of a large number of bubbles at the interface, which leads to a large number of defects in the film formation. Therefore, in the open environment system, the hydrophobic membrane is slowly added drop by drop along the edge of the hydrophobic membrane, and then added again along the wetting area until the surface of the hydrophobic membrane is completely wetted and covered with a certain volume of acyl chloride monomer. In addition, the most important thing is that in the open environment system, when a large amount of hydrogen chloride by-product is produced, it can be well discharged and consumed to promote the reaction to continue, thereby obtaining the multifunctional layer of the application.

[0031] The application can well control the morphology change of the multifunctional separation membrane by adjusting the reaction time and the monomer concentration, and can form the morphology from the porous loose layer to the dense layer, and the thickness of the in-situ grown dense layer is controllable. It is found through relevant experiments that the multifunctional membrane of the application can be applied to the fields of reverse osmosis, nanofiltration, permeation gasification and membrane distillation, especially in the field of membrane distillation, the anti-wetting performance is improved by about 1-2 orders of magnitude, which can greatly expand the treatment of low surface energy, high salt and high organic solvent wastewater, and the dense layer has little effect on the permeation flux of the membrane, which can greatly improve the vapor flux and efficiency of the membrane distillation. BRIEF DESCRIPTION OF DRAWINGS

[0032] The application will be further described below in combination with the drawings:

[0033] Figure 1 Figure 1 is a SEM image of a raw membrane (hydrophobic membrane) of the present application;

[0034] Figure 2 Figure 3 is a SEM image of a raw membrane and a multifunctional membrane reacted for 15 min in Example 9;

[0035] Figure 3 Figure 5 is a SEM image of a raw membrane and a multifunctional membrane reacted for 30 min in Example 10;

[0036] Figure 4 Figure 7 is a SEM image of a raw membrane and a multifunctional membrane reacted for 90 min in Example 11;

[0037] Figure 5 Figure 9 is a SEM image of a polyamide layer separation membrane with a defect-free dense layer prepared in Example 12. DETAILED DESCRIPTION

[0038] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application.

[0039] The technical solutions of the present application will be further described in detail below with reference to the drawings.

[0040] The raw materials mentioned in the present application can be purchased through commercial channels.

[0041] The hydrophobic membrane mentioned in the present application can be a PVDF flat membrane, a hollow fiber membrane, a PTFE flat membrane, a hydrophobic PE membrane or a hydrophobic PP membrane, and the present application mainly studies the PVDF flat membrane, the PTFE flat membrane and the hollow fiber membrane.

[0042] Example 1:

[0043] The hydrophobic membrane in the present embodiment is a PTFE flat membrane.

[0044] A preparation method of a multifunctional membrane, specifically comprising the following steps:

[0045] Step one, respectively configure 2.5% by mass fraction of m-phenylenediamine, 3% by mass fraction of additive triethylamine, 4% by mass fraction of camphor sulfonic acid solution and 0.15% by mass fraction of trimesoyl chloride in n-hexane solution;

[0046] Step two, place the prepared m-phenylenediamine solution, triethylamine and camphor sulfonic acid solution in a container, bend one side of the hydrophobic membrane and slowly float the bottom surface of the hydrophobic membrane on the surface of the amine monomer solution, and the floating environment provides an open environment system for the hydrophobic membrane; place the trimesoyl chloride in n-hexane solution in a rubber bulb dropper;

[0047] Step three, from the edge of the top surface of the hydrophobic membrane, using a rubber head dropper to drop the solution of trimesoyl chloride in n-hexane;

[0048] The drop process is: along the edge of the top surface of the hydrophobic membrane, drop by drop, when a drop wets the hydrophobic membrane, drop again along the wet area, in turn from outside to inside until the surface of the hydrophobic membrane is completely wetted and covered with a certain volume of trimesoyl chloride in n-hexane solution; during the drop process, the hydrophobic membrane can exclude the byproduct gas generated in the open environment system;

[0049] Step four, under normal temperature conditions, the solution of trimesoyl chloride in n-hexane on the bottom surface of the hydrophobic membrane and m-phenylenediamine undergo a reverse polymerization reaction for 165 min, after taking out and washing with water, it is placed in a 60 degree oven for drying, and a multifunctional membrane is obtained, which has a 150-400 nm dense polymer layer on the surface, as shown in Figure 1 .

[0050] The multifunctional membrane prepared in this example was tested, and the test results are shown in Table 1.

[0051] Table 1. Test results of multifunctional membrane

[0052]

[0053]

[0054] Example 2:

[0055] The difference from Example 1 is:

[0056] In step one, 0.1% m-phenylenediamine solution and 0.01% trimesoyl chloride in n-hexane solution were prepared respectively. The experimental results are shown in Table 2.

[0057] Table 2. Test results of multifunctional membrane

[0058] Item Test Medium Example 2 Acid Resistance Test Hydrochloric Acid Resistant to pH less than 2 Base Resistance Test Sodium Hydroxide Resistant to pH greater than 10 Nanofiltration Test 2000 ppm Sodium Sulfate Rejection greater than 45% RO Test 2000 ppm Sodium Chloride Rejection greater than 35% Pervaporation Ethanol:Water (8:2) Separation Factor greater than 35 Membrane Distillation Tested on 3.5% Sodium Chloride Rejection greater than 99.2%

[0059] Example 3:

[0060] The difference from Example 1 is:

[0061] In step one, 5% m-phenylenediamine solution and 0.5% trimesoyl chloride in n-hexane solution were prepared respectively. The experimental results are shown in Table 3.

[0062] Table 3. Test results of multifunctional membrane

[0063] Item Test Medium Example 3 Acid Resistance Test Hydrochloric Acid Resistant to pH less than 3 Base Resistance Test Sodium Hydroxide Resistant to pH greater than 10 Nanofiltration Test 2000 ppm Sodium Sulfate Rejection greater than 80% RO Test 2000 ppm Sodium Chloride Rejection greater than 75% Pervaporation Ethanol:Water (8:2) Separation Factor greater than 25 Membrane Distillation Tested on 3.5% Sodium Chloride Rejection greater than 99.6%

[0064] Example 4:

[0065] The hydrophobic membrane in this embodiment is a PTFE flat membrane.

[0066] A method for preparing a multifunctional membrane, specifically comprising the following steps:

[0067] Step one, respectively configure the n-hexane solution of 3% polyethyleneimine and 0.25% trimesoyl chloride;

[0068] Step two, place the prepared polyethyleneimine in a container, bend one side of the hydrophobic membrane and slowly float the bottom surface in the amine monomer solution, the floating environment provides an open environment system for the hydrophobic membrane; place the n-hexane solution of trimesoyl chloride in a rubber dropper;

[0069] Step three, start from the edge of the top surface of the hydrophobic membrane, and drop the n-hexane solution of trimesoyl chloride with a rubber dropper;

[0070] The dropping process is: drop one drop at a time along the edge of the top surface of the hydrophobic membrane, when a drop wets the hydrophobic membrane, drop again along the wet area, and drop in turn from outside to inside until the surface of the hydrophobic membrane is completely wetted and covered with a certain volume of n-hexane solution of 2,6-naphthalene dicarboxylic acid chloride; during the dropping process, the hydrophobic membrane can remove the generated by-product gas under the open environment system;

[0071] Step four, under normal temperature conditions, the n-hexane solution of trimesoyl chloride on the bottom surface of the hydrophobic membrane reacts with polyethyleneimine for 165 minutes, take out, wash with water, and then dry in an oven to obtain a multifunctional membrane. The experimental results are shown in Table 4.

[0072] Table 4. Test results of multifunctional membrane

[0073] Item Test Medium Example 4 Acid Resistance Test Hydrochloric Acid Resistant to pH less than 2 Base Resistance Test Sodium Hydroxide Resistant to pH greater than 10 Nanofiltration Test 2000 ppm Sodium Sulfate Rejection greater than 55% RO Test 2000 ppm Sodium Chloride Rejection greater than 25% Pervaporation Ethanol:Water (8:2) Separation Factor greater than 35 Membrane Distillation Tested on 3.5% Sodium Chloride Rejection greater than 99%

[0074] Example 5:

[0075] The hydrophobic membrane in this embodiment is a PTFE flat membrane.

[0076] A method for preparing a multifunctional membrane, specifically comprising the following steps:

[0077] Step one, respectively configure the n-hexane solution of 3% polyethyleneimine and 0.25% trimesoyl chloride;

[0078] Step two, place the prepared polyethyleneimine in a container, bend one side of the hydrophobic membrane and slowly float the bottom surface in the amine monomer solution, the floating environment provides an open environment system for the hydrophobic membrane; place the n-hexane solution of trimesoyl chloride in a rubber dropper;

[0079] Step three, from the edge of the top surface of the hydrophobic membrane, the solution of trimesoyl chloride in n-hexane is added dropwise using a rubber bulb dropper;

[0080] The dropwise addition process is that one drop is added along the edge of the top surface of the hydrophobic membrane, when a drop wets the hydrophobic membrane, the next drop is added along the wetted area, and the drops are added in turn from the outside to the inside until the surface of the hydrophobic membrane is completely wetted and covered with a certain volume of the solution of 2,6-naphthalene dicarboxylic acid chloride in n-hexane; during the dropwise addition process, the hydrophobic membrane can remove the generated by-product gas under the open environment system;

[0081] Step four, under normal temperature conditions, the solution of trimesoyl chloride in n-hexane on the bottom surface of the hydrophobic membrane reacts with piperazine for 165 min, and then the obtained product is taken out, washed with water, and dried in an oven to obtain a multifunctional membrane. The experimental results are shown in Table 5.

[0082] Table 5. Test results of the multifunctional membrane

[0083] Item Test Medium Example 5 Acid Resistance Test Hydrochloric Acid Resistant to pH less than 4 Base Resistance Test Sodium Hydroxide Resistant to pH greater than 10 Nanofiltration Test 2000 ppm Sodium Sulfate Rejection greater than 45% RO Test 2000 ppm Sodium Chloride Rejection greater than 30% Pervaporation Ethanol:Water (8:2) Separation Factor greater than 20 Membrane Distillation Tested on 3.5% Sodium Chloride Rejection greater than 99%

[0084] Example 6:

[0085] The hydrophobic membrane in this example is a PTFE flat membrane.

[0086] A method for preparing a multifunctional membrane, specifically comprising the following steps:

[0087] Step one, prepare a solution of dopamine with a mass fraction of 3% and a solution of trimesoyl chloride in n-hexane with a mass fraction of 0.25%, respectively;

[0088] Step two, place the prepared dopamine in a container, bend one side of the hydrophobic membrane and make the bottom surface slowly float on the surface of the amine monomer solution, and the floating environment provides an open environment system for the hydrophobic membrane; place the solution of trimesoyl chloride in n-hexane in a rubber bulb dropper;

[0089] Step three, from the edge of the top surface of the hydrophobic membrane, the solution of trimesoyl chloride in n-hexane is added dropwise using a rubber bulb dropper;

[0090] The dropwise addition process is that one drop is added along the edge of the top surface of the hydrophobic membrane, when a drop wets the hydrophobic membrane, the next drop is added along the wetted area, and the drops are added in turn from the outside to the inside until the surface of the hydrophobic membrane is completely wetted and covered with a certain volume of the solution of 2,6-naphthalene dicarboxylic acid chloride in n-hexane; during the dropwise addition process, the hydrophobic membrane can remove the generated by-product gas under the open environment system;

[0091] Step four, under normal temperature conditions, the solution of trimesoyl chloride in n-hexane on the bottom surface of the hydrophobic membrane reacts with piperazine for 165 min, and then the obtained product is taken out, washed with water, and dried in an oven to obtain a multifunctional membrane. The experimental results are shown in Table 5.

[0092] Table 6. Multifunctional membrane test results

[0093] Item Test Medium Example 6 Acid Resistance Test Hydrochloric Acid Resistant to pH less than 2 Base Resistance Test Sodium Hydroxide Resistant to pH greater than 10 Nanofiltration Test 2000 ppm Sodium Sulfate Rejection greater than 75% RO Test 2000 ppm Sodium Chloride Rejection greater than 55% Pervaporation Ethanol:Water (8:2) Separation Factor greater than 30 Membrane Distillation Tested on 3.5% Sodium Chloride Rejection greater than 99.5%

[0094] Example 7:

[0095] The difference between this example and Example 1 is that the hydrophobic membrane in this example is a PVDF flat membrane. The experimental results are shown in Table 7.

[0096] Table 7. Multifunctional membrane test results

[0097] Item Test Medium Example 7 Acid Resistance Test Hydrochloric Acid Resistant to pH less than 2 Base Resistance Test Sodium Hydroxide Resistant to pH greater than 10 Nanofiltration Test 2000 ppm Sodium Sulfate Rejection greater than 70% RO Test 2000 ppm Sodium Chloride Rejection greater than 60% Pervaporation Ethanol:Water (8:2) Separation Factor greater than 28 Membrane Distillation Tested on 3.5% Sodium Chloride Rejection greater than 99.3%

[0098] Example 8:

[0099] The difference between this example and Example 1 is that the hydrophobic membrane in this example is a hollow fiber membrane. The experimental results are shown in Table 8.

[0100] Table 8. Multifunctional membrane test results

[0101] Item Test Medium Example 8 Acid Resistance Test Hydrochloric Acid Resistant to pH less than 2 Base Resistance Test Sodium Hydroxide Resistant to pH greater than 10 Nanofiltration Test 2000 ppm Sodium Sulfate Rejection greater than 68% RO Test 2000 ppm Sodium Chloride Rejection greater than 57% Pervaporation Ethanol:Water (8:2) Separation Factor greater than 25 Membrane Distillation Tested on 3.5% Sodium Chloride Rejection greater than 99.5%

[0102] Example 9:

[0103] The difference between this example and Example 1 is that:

[0104] In Step Four, the reverse polymerization reaction between the n-hexane solution of trimesoyl chloride and m-phenylenediamine on the bottom surface of the hydrophobic membrane was carried out for 15 min at room temperature. The SEM image of the multifunctional membrane after 15 min of reaction is shown in Figure 2 .

[0105] Example 10:

[0106] The difference between this example and Example 1 is that:

[0107] In Step Four, the reverse polymerization reaction between the n-hexane solution of trimesoyl chloride and m-phenylenediamine on the bottom surface of the hydrophobic membrane was carried out for 30 min at room temperature. The SEM image of the multifunctional membrane after 30 min of reaction is shown in Figure 3 .

[0108] Example 11:

[0109] The difference between this example and Example 1 is that:

[0110] In Step Four, the reverse polymerization reaction between the n-hexane solution of trimesoyl chloride and m-phenylenediamine on the bottom surface of the hydrophobic membrane was carried out for 90 min at room temperature. The SEM image of the multifunctional membrane after 90 min of reaction is shown in Figure 4 .

[0111] Example 12:

[0112] The hydrophobic membrane in this embodiment is a PTFE flat membrane.

[0113] A method for preparing a polyamide layer separation membrane with a defect-free dense layer, specifically comprising the following steps:

[0114] Step one, respectively configure 3% of m-phenylenediamine solution containing 0.2-8% of anion and cation resin, 2% of additive triethylamine, 4% of camphor sulfonic acid solution and 0.15% of trimesoyl chloride in n-hexane solution;

[0115] Step two, place the prepared m-phenylenediamine solution, triethylamine and camphor sulfonic acid solution in a container, bend one side of the hydrophobic membrane and slowly float the bottom surface on the surface of the amine monomer solution, and provide an open environment system for the hydrophobic membrane; place the trimesoyl chloride in n-hexane solution in a rubber dropper;

[0116] Step three, start from the edge of the top surface of the hydrophobic membrane, and drop the trimesoyl chloride in n-hexane solution with a rubber dropper;

[0117] The dropping process is: drop one drop at a time along the edge of the top surface of the hydrophobic membrane, when one drop wets the hydrophobic membrane, drop again along the wet area, and drop from outside to inside in turn until the surface of the hydrophobic membrane is completely wetted and covered with a certain volume of trimesoyl chloride in n-hexane solution; during the dropping process, the hydrophobic membrane can remove the generated by-product gas under the open environment system;

[0118] Step four, under normal temperature conditions, the trimesoyl chloride in n-hexane solution on the bottom surface of the hydrophobic membrane reacts with m-phenylenediamine for 30 minutes, then take out, wash with water and dry in a 60-degree oven.

[0119] Step five, under normal temperature conditions, perform secondary interfacial polymerization, clamp the dried membrane on the membrane frame, pour the m-phenylenediamine solution containing resin into the membrane pool for a period of time, then pour out the amine solution in the membrane so that there is no visible water, then pour in the trimesoyl chloride in n-hexane solution to make it react, take out, wash with water and dry in a 60-degree oven.

[0120] A polyamide layer separation membrane with a defect-free dense layer is obtained, which has a layer of wrinkled polymer dense layer on the surface, as shown in Figure 5 .

[0121] The polyamide layer separation membrane with a defect-free dense layer prepared in this embodiment was tested, and the test results are shown in Table 9.

[0122] Table 9. Test results of multifunctional membrane

[0123] Item Test Medium Example 1 Acid Resistance Test Hydrochloric Acid Resistant to pH less than 2 Base Resistance Test Sodium Hydroxide Resistant to pH greater than 10 Nanofiltration Test 2000 ppm Sodium Sulfate Rejection greater than 90% RO Test 2000 ppm Sodium Chloride Rejection greater than 80% Pervaporation Ethanol:Water (8:2) Separation factor greater than 30 Membrane distillation Test 3.5% sodium chloride Retention greater than 99.5%

[0124] Comparative Example 1:

[0125] The hydrophobic membrane in the present comparative example is a PTFE flat membrane.

[0126] A method for preparing a multifunctional membrane, specifically comprising the following steps:

[0127] Step one, respectively configure 3% mass fraction of m-phenylenediamine solution, 0.25% mass fraction of benzene tricarboxylic acid chloride in n-hexane solution;

[0128] Step two, place the prepared m-phenylenediamine solution in a container, bend one side of the hydrophobic membrane and make its bottom surface slowly float on the surface of the amine monomer solution, and the floating environment provides an open environment system for the hydrophobic membrane;

[0129] Step three, place the benzene tricarboxylic acid chloride in n-hexane solution in a beaker, pour the benzene tricarboxylic acid chloride in n-hexane solution onto the hydrophobic membrane, so that the hydrophobic membrane is completely wetted;

[0130] Step four, under normal temperature conditions, the benzene tricarboxylic acid chloride in n-hexane solution on the bottom surface of the hydrophobic membrane reacts with m-phenylenediamine for 15 min, take out, wash with water, and then place in an oven for drying, to obtain a multifunctional membrane. The experimental results are shown in Table 10.

[0131] Table 10

[0132]

[0133] Comparative Example 2:

[0134] The hydrophobic membrane in the present comparative example is a PTFE flat membrane.

[0135] A method for preparing a multifunctional membrane, specifically comprising the following steps:

[0136] Step one, respectively configure 3% mass fraction of m-phenylenediamine solution, 0.25% mass fraction of benzene tricarboxylic acid chloride in n-hexane solution;

[0137] Step two, place the prepared m-phenylenediamine solution in a container, use a reactor to fix the hydrophobic membrane, and make the bottom surface of the hydrophobic membrane just contact the m-phenylenediamine solution; place the benzene tricarboxylic acid chloride in n-hexane solution in a rubber bulb dropper;

[0138] Step three, start from the edge of the top surface of the hydrophobic membrane, and add the benzene tricarboxylic acid chloride in n-hexane solution by using a rubber bulb dropper;

[0139] The dropwise adding process is: dropwise adding along the edge of the top surface of the hydrophobic membrane, when a drop wets the hydrophobic membrane, again dropwise adding along the wet area, and sequentially dropwise adding from outside to inside until the surface of the hydrophobic membrane is completely wetted and covers a certain volume of the uniform benzene tricarboxylic acid chloride n-hexane solution; in the dropwise adding process, the hydrophobic membrane can remove the generated by-product gas under an open environment system;

[0140] Step four, under normal temperature conditions, the benzene tricarboxylic acid chloride n-hexane solution on the bottom surface of the hydrophobic membrane and m-phenylenediamine occur anti-polymerization reaction for 15 min, after taking out and washing with water, drying in an oven, a multifunctional membrane is obtained. The experimental results are shown in Table 11.

[0141] Table 11

[0142]

[0143] Under the guidance of the above examples, those skilled in the art can also use other hydrophobic membranes such as hydrophobic PE membrane or hydrophobic PP membrane to prepare a multifunctional membrane.

[0144] Those skilled in the art should recognize that the above embodiments are only used to illustrate the present application, and are not used as a limitation on the present application, and as long as the above examples are appropriately changed and changed within the scope of the spirit of the present application, they fall within the scope of the present application.

Claims

1. A method for preparing a multifunctional membrane, characterized in that, The aforementioned multifunctional membrane refers to a membrane that can be applied in the fields of reverse osmosis, nanofiltration, pervaporation, or membrane distillation. The preparation method includes: Step 1: Prepare solutions of amine monomers with a mass fraction of 0.1% to 5% and solutions of acyl chloride monomers with a mass fraction of 0.01% to 0.5% respectively; Step 2: Place the prepared amine monomer solution in a container, bend one side of the hydrophobic membrane and let its bottom surface float slowly on the surface of the amine monomer solution, providing an open environment for the hydrophobic membrane; place the acyl chloride monomer solution in a dropper. Step 3: Starting from the edge of the top surface of the hydrophobic membrane, add the acyl chloride monomer solution dropwise using a dropper; The dripping process is as follows: dripping one drop at a time along the edge of the top surface of the hydrophobic membrane. After the first drop wets the hydrophobic membrane, dripping is repeated along the wetted area. This process is continued from the outside in until the surface of the hydrophobic membrane is completely wetted and covered with a certain volume of acyl chloride monomer. During the dripping process, the hydrophobic membrane can eliminate the generated byproduct gases in an open environment. Step 4: Under normal temperature conditions, the acyl chloride monomer and amine monomer undergo an anti-polymerization reaction on the bottom surface of the hydrophobic membrane for 18-180 minutes. After removal, washing with water, and drying in an oven, a multifunctional membrane is obtained. The hydrophobic membrane is a PVDF flat sheet membrane, a PTFE flat sheet membrane, a hydrophobic hollow fiber membrane, a hydrophobic PE membrane, or a hydrophobic PP membrane; The multifunctional membrane has the properties of acid and alkali resistance, high temperature resistance and organic solvent resistance; the multifunctional membrane has a hydrophilic-hydrophobic Janus composite structure.

2. The method for preparing a multifunctional membrane according to claim 1, characterized in that: The acyl chloride monomer solution is a hexane solution of pyromellitic methyl methacrylate chloride or 2,6-naphthalenedicarboxylic acid chloride.

3. The method for preparing a multifunctional membrane according to claim 1, characterized in that: The amine monomer solution is m-phenylenediamine, polyethyleneimine, piperazine, or dopamine.

4. The method for preparing a multifunctional membrane according to claim 3, characterized in that: The amine monomer solution is m-phenylenediamine.

5. The method for preparing a multifunctional membrane according to claim 3, characterized in that: The hydrophobic membrane is a PTFE flat sheet membrane; the average molecular weight of the polyethyleneimine is 400 to 200,000.

6. The method for preparing a multifunctional membrane according to claim 1, characterized in that: In step one, an additive is added to the amine monomer solution, wherein the additive is a mixed solution of triethylamine and camphor sulfonic acid.

7. A method for preparing a defect-free, dense polyamide layer separation membrane, characterized in that, The aforementioned defect-free, dense polyamide layer separation membrane refers to a membrane that can be applied in the fields of reverse osmosis, nanofiltration, pervaporation, or membrane distillation. The preparation method includes: Step 1: Prepare solutions of amine monomers with a mass fraction of 0.1% to 5% and solutions of acyl chloride monomers with a mass fraction of 0.01% to 0.5% respectively; Step 2: Place the prepared amine monomer solution in a container, bend one side of the hydrophobic membrane and let its bottom surface float slowly on the surface of the amine monomer solution, providing an open environment for the hydrophobic membrane; place the acyl chloride monomer solution in a dropper. Step 3: Starting from the edge of the top surface of the hydrophobic membrane, add the acyl chloride monomer solution dropwise using a dropper; The dripping process is as follows: dripping one drop at a time along the edge of the top surface of the hydrophobic membrane. After the first drop wets the hydrophobic membrane, dripping is repeated along the wetted area. This process is continued from the outside in until the surface of the hydrophobic membrane is completely wetted and covered with a certain volume of acyl chloride monomer. During the dripping process, the hydrophobic membrane can eliminate the generated byproduct gases in an open environment. Step 4: Under normal temperature conditions, the acyl chloride monomer and amine monomer undergo an anti-polymerization reaction on the bottom surface of the hydrophobic film for 18-180 minutes. After removing and washing with water, place it in an oven to dry, thus completing one interfacial polymerization. Step 5: Prepare a solution of amine monomers containing anionic and cationic resins or quaternized and sulfonated polymers and an acyl chloride monomer solution of a certain concentration; fix the membrane dried in Step 4, then pour the solution of amine monomers containing anionic and cationic resins or quaternized and sulfonated polymers onto the dried membrane, react for a period of time, and then blow dry; then pour the acyl chloride monomer solution onto the dried membrane, react for a period of time; finally, dry in an oven to complete the secondary interfacial polymerization and obtain a defect-free, dense polyamide layer separation membrane; The aforementioned anionic and cationic resins refer to acrylic resins functionalized with sulfonic acid groups or quaternary ammonium groups; quaternized and sulfonated polymers refer to perfluorosulfonic acid membranes, quaternized polystyrene, sulfonated polystyrene, sulfonated polyether ether ketone, sulfonated polyarylether sulfone, and quaternized chitosan membranes.

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