Preparation method of selective composite ion exchange membrane for separation and concentration

Abstract

The invention discloses a preparation method of a selective composite ion exchange membrane for separation and concentration, according to the method, two sides of a woven fabric are coated with a base membrane, the woven fabric can provide a supporting effect, and the woven fabric has excellent tensile strength, so that the obtained ion exchange membrane has relatively high mechanical strength; a compact base membrane is prepared from a charged high-molecular polymer with a high functionalization degree, so that the surface of the base membrane has more active sites to complete ion exchange, the ion flux is improved to realize high-power concentration of ions, and due to the existence of a polyamide layer, the prepared composite ion exchange membrane has a monovalent ion and divalent ion separation effect; in conclusion, the selective composite ion exchange membrane prepared by the invention can simultaneously realize separation of monovalent ions and divalent ions and high-power concentration of monovalent ions; the method has the advantages of being simple and easy to implement, the operation process is smooth, continuous production can be effectively achieved, the production efficiency is improved, and large-scale application in the industrial process is facilitated.

Description

Technical Field

[0001] The invention relates to a method for preparing a selective composite ion exchange membrane for separation and concentration, belonging to the technical field of ion exchange membranes. Background Art

[0002] At present, the commonly used seawater desalination technologies include evaporation, membrane separation and process integration. Membrane separation methods include reverse osmosis, nanofiltration and electrodialysis. Among them, reverse osmosis and nanofiltration are widely used in the seawater desalination industry. However, seawater is a mixed salt solution containing a large amount of monovalent and divalent salts. Although reverse osmosis can obtain fresh water, it faces the problem of concentrated water discharge. If the concentrated water is discharged into the sea area with weak exchange capacity, it may cause harm to the marine ecological environment and aquaculture. In addition, the concentrated water obtained from seawater desalination is rich in resources such as sodium chloride and magnesium salts. It is a waste of resources to discharge it directly without using it. Although nanofiltration can separate monovalent and divalent salts in seawater, the concentration effect of nanofiltration can only reach 15% at most. Electrodialysis technology can achieve high concentration while separating salts, which is a very promising seawater desalination technology.

[0003] The key to achieving salt separation and concentration by electrodialysis lies in its core component - the selective ion exchange membrane. Due to its own selectivity, the selective ion exchange membrane allows monovalent ions to pass through and intercepts divalent ions, thereby achieving the effect of salt separation. However, at present, only companies such as FUMATECH and ASTOM have developed selective ion exchange membranes, and there are no mature selective ion exchange membranes in China. This is mainly because there is no method for continuous production of high-performance selective ion exchange membranes, which is also an important reason why electrodialysis technology has not been widely used in seawater desalination. Therefore, the development of a selective composite ion exchange membrane preparation scheme for separation and concentration is of great significance to seawater desalination. Summary of the invention

[0004] In view of the deficiencies in the prior art, the present invention provides a method for preparing a selective composite ion exchange membrane for separation and concentration, thereby realizing continuous production of the selective composite ion exchange membrane and solving the problem that traditional selective ion exchange membranes cannot meet the needs of commercial production.

[0005] The technical solution of the present invention to solve the above technical problems is as follows: A method for preparing a selective composite ion exchange membrane for separation and concentration, comprising the following steps:

[0006] S1, dissolving a highly charged polymer in a first organic solvent by heating and stirring to form a 10-25wt% casting solution, and after the highly charged polymer is completely dissolved, allowing the formed casting solution to stand for degassing;

[0007] S2, dissolving a polyamine in pure water to prepare a 1-5 wt% amine-containing aqueous solution; dissolving a polyacid chloride in a second organic solvent to prepare a 0.1-0.5 wt% acyl chloride organic solution;

[0008] S3, applying the degassed casting solution to both sides of the woven fabric fixed on the equipment by using a coating head, slowly passing through an oven to dry at a first set speed to form an ion exchange base membrane, and collecting the solution at the terminal of the ion exchange base membrane production line;

[0009] S4, immersing the collected ion exchange base membrane into and passing through a water tank containing the amine-containing aqueous solution at a second set speed, so that the amine-containing aqueous solution is fully in contact with the ion exchange base membrane, and then removing excess aqueous solution on the surface of the ion exchange base membrane through a silica gel roller;

[0010] S5. After removing the excess aqueous solution from the surface, the ion exchange base membrane is transferred to the membrane head for coating the acyl chloride organic solution in the functional layer coating production line, and the acyl chloride organic solution is coated on one side of the ion exchange base membrane by the membrane head. The height of the membrane head from the ion exchange base membrane is adjusted so that the membrane head can coat the organic solution evenly and flatly, and the interfacial polymerization reaction is completed to form a polyamide layer. The membrane is then dried in the next oven at a third set speed, and finally collected by rollers at the terminal of the functional layer coating production line to obtain a selective composite ion exchange membrane.

[0011] As a preferred embodiment of the method for preparing a selective composite ion exchange membrane for separation and concentration, in step S1, the highly charged polymer is at least one of sulfonated polyethersulfone, sulfonated polysulfone, sulfonated polystyrene, sulfonated polyphenylene oxide, sulfonated polyvinylidene fluoride, sulfonated polyetheretherketone, brominated polyphenylene oxide, quaternized polyphenylene oxide, quaternized polysulfone, and chloromethylated polyarylethersulfone;

[0012] The functionalization degree of the highly charged macromolecular polymer is 25-50%.

[0013] As a preferred embodiment of the method for preparing a selective composite ion exchange membrane for separation and concentration, in step S1, the first organic solvent for dissolving the highly charged polymer is at least one of N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, acetone, tetrahydrofuran, and ethylene glycol monomethyl ether.

[0014] As a preferred embodiment of the method for preparing a selective composite ion exchange membrane for separation and concentration, in step S1, the highly charged polymer is heated and stirred at a temperature of 60-90° C. and the stirring time is 4-12 h.

[0015] As a preferred embodiment of the method for preparing a selective composite ion exchange membrane for separation and concentration, in step S2, the polyamine is at least one of ethylenediamine, hexamethylenediamine, m-phenylenediamine, piperazine, and polyethyleneimine;

[0016] The polyacid chloride is at least one of trimesoyl chloride and terephthaloyl chloride.

[0017] As a preferred embodiment of the method for preparing a selective composite ion exchange membrane for separation and concentration, in step S2, the second organic solvent for dissolving the polyacid chloride is at least one of n-hexane, n-heptane, n-decane, cyclohexane, ISOPAR G, and ISOPAR E.

[0018] As a preferred embodiment of the method for preparing a selective composite ion exchange membrane for separation and concentration, in step S3, the coating width of the coating head is 200-400 μm.

[0019] As a preferred embodiment of the method for preparing a selective composite ion exchange membrane for separation and concentration, in step S3, the first set speed of the fabric coated with the casting liquid and fixed on the casting machine is 0.1-1 m / min after being dried in an oven; the oven drying temperature is 30-130°C.

[0020] As a preferred embodiment of the method for preparing a selective composite ion exchange membrane for separation and concentration, in step S4, the second set speed at which the ion exchange base membrane is immersed in and passes through the water tank filled with the amine-containing aqueous solution is 0.1-0.5 m / min.

[0021] As a preferred embodiment of the method for preparing a selective composite ion exchange membrane for separation and concentration, in step S5, the third set speed for drying the polyamide layer formed by the interfacial polymerization reaction in the next oven is 0.2-1 m / min, and the temperature in the oven is 60-120°C.

[0022] The beneficial effects of the present invention are as follows: by coating the base film on both sides of the woven fabric, the woven fabric can provide support, and the woven fabric has excellent tensile strength, so that the obtained ion exchange membrane has strong mechanical strength; a denser base film is prepared by using a charged polymer with a high degree of functionalization (25-50%), so that there are more active sites on the surface of the base film to complete ion exchange, thereby improving the ion flux and realizing high-fold ion concentration, and due to the presence of the polyamide layer, the composite ion exchange membrane prepared by the present invention has a monovalent and divalent ion separation effect; in summary, the selective composite ion exchange membrane prepared by the present invention can simultaneously realize the separation of monovalent and divalent ions and high-fold concentration of monovalent ions; in addition, the production method of the present invention is simple and easy to operate, the operation process is smooth, and continuous production can be effectively realized, which not only improves production efficiency, but also facilitates large-scale application in industrial processes. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the implementation methods of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for the implementation methods or the description of the prior art. Obviously, the drawings in the following description are only exemplary, and for ordinary technicians in this field, other implementation drawings can be derived from the provided drawings without creative work.

[0024] The structures, proportions, sizes, etc. illustrated in this specification are only used to match the contents disclosed in the specification so as to facilitate understanding and reading by persons familiar with the technology. They are not used to limit the conditions under which the present invention can be implemented, and therefore have no substantial technical significance. Any structural modification, change in proportion or adjustment of size shall still fall within the scope of the technical contents disclosed in the present invention without affecting the effects and purposes that can be achieved by the present invention.

[0025] Figure 1 A schematic diagram of an ion exchange base membrane production line in a method for preparing a selective composite ion exchange membrane for separation and concentration provided in an embodiment of the present invention;

[0026] Figure 2 A schematic diagram of a functional layer coating production line in a method for preparing a selective composite ion exchange membrane for separation and concentration provided in an embodiment of the present invention;

[0027] Figure 3 A schematic diagram of an electrodialysis process for applying a selective composite cation exchange membrane provided by an embodiment of the present invention to an experiment for separating and concentrating monovalent and divalent cations;

[0028] Figure 4 A schematic diagram of the final NaCl concentration in the concentration chamber of a selective composite cation exchange membrane provided by an embodiment of the present invention when used in a monovalent and divalent cation separation and concentration experiment;

[0029] Figure 5 A schematic diagram of the separation ratio of the selective composite cation exchange membrane provided in an embodiment of the present invention to monovalent and divalent cations in an experiment of separation and concentration of monovalent and divalent cations;

[0030] Figure 6 A schematic diagram of an electrodialysis process for applying a selective composite anion exchange membrane provided by an embodiment of the present invention to an experiment for separating and concentrating monovalent and divalent anions;

[0031] Figure 7 A schematic diagram of the final NaCl concentration in the concentration chamber of a selective composite anion exchange membrane provided by an embodiment of the present invention when applied to a monovalent and divalent anion separation and concentration experiment;

[0032] Figure 8A schematic diagram of the separation ratio of the selective composite anion exchange membrane provided in an embodiment of the present invention for monovalent and divalent anions in an experiment for separating and concentrating monovalent and divalent anions. DETAILED DESCRIPTION

[0033] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present invention, so the present invention is not limited by the specific embodiments disclosed below.

[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0035] Example 1

[0036] Embodiment 1 of the present invention provides a method for preparing a selective composite ion exchange membrane for separation and concentration, comprising the following steps:

[0037] S1, dissolving a highly charged polymer in a first organic solvent by heating and stirring to form a 10-25wt% casting solution, and after the highly charged polymer is completely dissolved, allowing the formed casting solution to stand for degassing;

[0038] The highly charged polymer is at least one of sulfonated polyethersulfone, sulfonated polysulfone, sulfonated polystyrene, sulfonated polyphenylene oxide, sulfonated polyvinylidene fluoride, sulfonated polyetheretherketone, brominated polyphenylene oxide, quaternized polyphenylene oxide, quaternized polysulfone, and chloromethylated polyarylethersulfone; the functionalization degree of the highly charged polymer is 25-50%;

[0039] Among them, the organic matter in the first organic solvent for dissolving the highly charged polymer is at least one of N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, acetone, tetrahydrofuran, and ethylene glycol monomethyl ether; the temperature for heating and stirring the highly charged polymer is 60-90°C, and the stirring time is 4-12h.

[0040] S2, dissolving a polyamine in pure water to prepare a 1-5 wt% amine-containing aqueous solution; dissolving a polyacid chloride in a second organic solvent to prepare a 0.1-0.5 wt% acyl chloride organic solution;

[0041] The polyamine is at least one of ethylenediamine, hexamethylenediamine, m-phenylenediamine, piperazine, and polyethyleneimine; the polyacyl chloride is at least one of trimesoyl chloride and terephthaloyl chloride. The second organic solvent for dissolving the polyacyl chloride is at least one of n-hexane, n-heptane, n-decane, cyclohexane, ISOPAR G, and ISOPAR E.

[0042] S3, applying the degassed casting solution to both sides of the woven fabric fixed on the equipment by using a coating head, slowly passing through an oven to dry at a first set speed to form an ion exchange base membrane, and collecting the solution at the terminal of the ion exchange base membrane production line;

[0043] S4, immersing the collected ion exchange base membrane into and passing through a water tank containing the amine-containing aqueous solution at a second set speed, so that the amine-containing aqueous solution is fully in contact with the ion exchange base membrane, and then removing excess aqueous solution on the surface of the ion exchange base membrane through a silica gel roller;

[0044] S5. After removing the excess aqueous solution from the surface, the ion exchange base membrane is transferred to the membrane head for coating the acyl chloride organic solution in the functional layer coating production line, and the acyl chloride organic solution is coated on one side of the ion exchange base membrane by the membrane head. The height of the membrane head from the ion exchange base membrane is adjusted so that the membrane head can coat the organic solution evenly and flatly, and the interfacial polymerization reaction is completed to form a polyamide layer. The membrane is then dried in the next oven at a third set speed, and finally collected by rollers at the terminal of the functional layer coating production line to obtain a selective composite ion exchange membrane.

[0045] See also Figure 1 In the ion exchange base membrane production line, the degassed casting liquid is poured into the feeding hopper. After the production line is started, the casting liquid in the feeding hopper is put into the coating head. The coating width of the coating head is 200-400μm. The coating head adopts a slit coating method to coat the casting liquid on both sides of the fabric, and then slowly passes through the oven for drying at a first set speed of 0.1-1m / min. The oven drying temperature is 30-130℃ to form an ion exchange base membrane, which is collected at the terminal of the ion exchange base membrane production line.

[0046] See also Figure 2, immerse the collected ion exchange base membrane at a second set speed of 0.1-0.5m / min and pass through a water tank containing an amine aqueous solution, so that the amine aqueous solution is fully in contact with the ion exchange base membrane, and then pass through several silica gel rollers to remove excess aqueous solution on the surface of the base membrane; then the base membrane is further conveyed through the equipment to a membrane head where an acyl chloride organic solution can be applied, and the acyl chloride organic solution is applied to one side of the membrane by the membrane head, and the organic solution is evenly and flatly applied by the membrane head by adjusting the distance between the membrane head and the base membrane, and an interfacial polymerization reaction is completed on one side of the base membrane to form a polyamide layer, and then it is dried in the next oven at a third set speed of 0.2-1m / min, and the temperature in the oven is 60-120°C, and finally collected by rollers at the terminal to obtain a selective composite ion exchange membrane.

[0047] Example 2

[0048] Embodiment 2 of the present invention provides a method for preparing a selective composite ion exchange membrane for separation and concentration, wherein a sulfonated polysulfone with a sulfonation degree of 50% is added to acetone (the ratio of sulfonated polysulfone to acetone is 1:9), and stirred at 60°C for 12 hours to obtain a 10wt% casting solution. After the casting solution is allowed to stand for degassing, the casting solution is poured into a coating head, and the casting solution is distributed on both sides of the woven fabric. The coating head width is adjusted to 200 μm, and the casting solution is evenly coated on both sides of the woven fabric by conveying the woven fabric forward. The woven fabric coated with the casting solution is slowly conveyed to an oven at a speed of 1 m / min for drying to obtain a dense ion exchange base membrane, and the temperatures of the front, middle and rear three sections of the oven are 30°C, 50°C and 30°C, respectively.

[0049] Prepare a 1wt% m-phenylenediamine aqueous solution and pour it into the water tank until the liquid level covers all rollers in the water tank. Dissolve trimesoyl chloride in n-hexane to prepare a 0.1wt% TMC organic solution, and pour the TMC organic solution into the membrane head.

[0050] The dried ion exchange base membrane is immersed in a water tank and slowly passed through the water tank at a speed of 0.1m / min to ensure that the base membrane is fully in contact with the m-phenylenediamine aqueous solution. After the ion exchange base membrane passes through the water tank, the silicone roller outside the water tank squeezes out excess water droplets on the surface of the base membrane, and then passes through the membrane head, and the TMC organic solution in the membrane head is applied to one side of the membrane, and the distance between the membrane heads is adjusted to use the membrane head to apply the organic solution evenly and flatly. The wet membrane coated with TMC organic solution is dried in an oven at a speed of 0.2m / min to obtain a selective composite cation exchange membrane. The temperatures of the front, middle and rear three sections of the oven are 75℃, 90℃ and 75℃ respectively. Finally, the selective composite cation exchange membrane is transported to the terminal and collected on the terminal roller.

[0051] Example 3

[0052] Embodiment 3 of the present invention provides a method for preparing a selective composite ion exchange membrane for separation and concentration, wherein a sulfonated polyethersulfone with a sulfonation degree of 25% is added to DMF (the addition ratio of sulfonated polyethersulfone and DMF is 1:3), and stirred at 85°C for 5h to obtain a 25wt% casting solution. After the casting solution is allowed to stand for degassing, the casting solution is poured into a coating head, and the casting solution is distributed on both sides of the woven fabric. The coating head width is adjusted to 400μm, and the casting solution is evenly coated on both sides of the woven fabric by conveying the woven fabric forward. The woven fabric coated with the casting solution is slowly conveyed to an oven at a speed of 0.2m / min for drying to obtain a dense ion exchange base membrane, and the temperatures of the front, middle and rear three sections of the oven are 80°C, 120°C and 80°C, respectively.

[0053] Prepare a piperazine aqueous solution with a mass fraction of 2wt% and pour it into the water tank until the liquid level covers all rollers in the water tank. Dissolve trimesoyl chloride in n-hexane to prepare a TMC organic solution with a concentration of 0.1wt%, and put the TMC organic solution into the organic solution hopper.

[0054] The dried ion exchange base membrane is immersed in a water tank and slowly passed through the water tank at a speed of 0.2m / min to ensure that the base membrane is fully in contact with the piperazine aqueous solution. After the base membrane passes through the water tank, the silicone roller outside the water tank squeezes out excess water droplets on the surface of the base membrane, and then passes through the membrane head, and the TMC organic solution in the membrane head is applied to one side of the membrane, and the distance between the membrane heads is adjusted to use the membrane head to apply the organic solution evenly and flatly. The wet membrane coated with TMC organic solution is dried in an oven at a speed of 0.2m / min to obtain a selective composite cation exchange membrane. The temperatures of the front, middle and rear three sections of the oven are 120℃, 90℃ and 120℃ respectively. Finally, the selective composite cation exchange membrane is transported to the terminal and collected on the terminal roller.

[0055] Example 4

[0056] Embodiment 4 of the present invention provides a method for preparing a selective composite ion exchange membrane for separation and concentration, wherein a sulfonated polyetheretherketone with a sulfonation degree of 25% is added to NMP (the ratio of sulfonated polyetheretherketone and NMP is 1:4), and stirred at 90°C for 4 hours to obtain a 20wt% casting solution. After the casting solution is allowed to stand for degassing, the casting solution is poured into a coating head, and the casting solution is distributed on both sides of the woven fabric. The coating head width is adjusted to 400 μm, and the casting solution is evenly coated on both sides of the woven fabric by conveying the woven fabric forward. The woven fabric coated with the casting solution is slowly conveyed to an oven at a speed of 0.1 m / min for drying to obtain a dense ion exchange base membrane, and the temperatures of the front, middle and rear three sections of the oven are 90°C, 130°C and 90°C, respectively.

[0057] Prepare a 5wt% piperazine aqueous solution and pour it into the water tank until the liquid level covers all rollers in the water tank. Dissolve trimesoyl chloride in ISOPAR G to prepare a 0.25wt% TMC organic solution, and pour the TMC organic solution into the organic solution hopper.

[0058] The dried ion exchange base membrane is immersed in a water tank and slowly passed through the water tank at a speed of 0.5m / min to ensure that the base membrane is fully in contact with the piperazine aqueous solution. After the base membrane passes through the water tank, the silicone roller outside the water tank squeezes out excess water droplets on the surface of the base membrane, and then passes through the membrane head, and the TMC organic solution in the membrane head is applied to one side of the membrane, and the distance between the membrane heads is adjusted to use the membrane head to apply the organic solution evenly and flatly. The wet membrane coated with TMC organic solution is dried in an oven at a speed of 0.5m / min to obtain a selective composite cation exchange membrane. The temperatures of the front, middle and rear three sections of the oven are 60℃, 80℃ and 60℃ respectively. Finally, the selective composite cation exchange membrane is transported to the terminal and collected on the terminal roller.

[0059] Example 5

[0060] Embodiment 5 of the present invention provides a method for preparing a selective composite ion exchange membrane for separation and concentration, wherein a quaternary ammonium polyphenylene ether with a functionalization degree of 30% is added to DMF (the ratio of quaternary ammonium polyphenylene ether and DMF is 1:4), and stirred at 85°C for 5 hours to obtain a 20wt% casting solution. After the casting solution is allowed to stand for degassing, the casting solution is poured into the coating head, and the casting solution is distributed on both sides of the woven fabric. The coating head width is adjusted to 300 μm, and the casting solution is evenly coated on both sides of the woven fabric by conveying the woven fabric forward. The woven fabric coated with the casting solution is slowly conveyed to an oven at a speed of 0.2 m / min for drying to obtain a dense ion exchange base membrane, and the temperatures of the front, middle and rear three sections of the oven are 60°C, 90°C and 60°C, respectively.

[0061] Prepare a 2wt% m-phenylenediamine aqueous solution and pour it into the water tank until the liquid level covers all rollers in the water tank. Dissolve trimesoyl chloride in ISOPAR G to prepare a 0.25wt% TMC organic solution, and pour the TMC organic solution into the organic solution hopper.

[0062] The dried ion exchange base membrane is immersed in a water tank and slowly passed through the water tank at a speed of 0.2m / min to ensure that the base membrane is fully in contact with the m-phenylenediamine aqueous solution. After the base membrane passes through the water tank, the silicone roller outside the water tank squeezes out excess water droplets on the surface of the base membrane, and then passes through the membrane head, and the TMC organic solution in the membrane head is applied to one side of the membrane, and the distance between the membrane heads is adjusted to use the membrane head to apply the organic solution evenly and flatly. The wet membrane coated with TMC organic solution is dried in an oven at a speed of 0.5m / min to obtain a selective composite anion exchange membrane. The temperatures of the front, middle and rear three sections of the oven are 60℃, 80℃ and 60℃ respectively. Finally, the selective composite anion exchange membrane is transported to the terminal and collected on the terminal roller.

[0063] Example 6

[0064] Embodiment 6 of the present invention provides a method for preparing a selective composite ion exchange membrane for separation and concentration, wherein a chloromethylated polyarylethersulfone having a functionalization degree of 25% is added to DMAC (the ratio of chloromethylated polyarylethersulfone and DMAC addition is 1:5), and stirred at 80°C for 5h to obtain a 15wt% casting solution. After the casting solution is allowed to stand for degassing, the casting solution is poured into the coating head, and the casting solution is distributed on both sides of the woven fabric. The coating head width is adjusted to 400μm, and the casting solution is evenly coated on both sides of the woven fabric by conveying the woven fabric forward. The woven fabric coated with the casting solution is slowly conveyed to an oven at a speed of 0.2m / min for drying to obtain a dense ion exchange base membrane, and the temperatures of the front, middle and rear three sections of the oven are 60°C, 80°C and 60°C, respectively.

[0065] Prepare a 2wt% piperazine aqueous solution and pour it into the water tank until the liquid level covers all rollers in the water tank. Dissolve trimesoyl chloride in ISOPAR G to prepare a 0.5wt% TMC organic solution, and pour the TMC organic solution into the organic solution hopper.

[0066] The dried ion exchange base membrane is immersed in a water tank and slowly passed through the water tank at a speed of 0.2m / min to ensure that the base membrane is fully in contact with the piperazine aqueous solution. After the base membrane passes through the water tank, the silicone roller outside the water tank squeezes out excess water droplets on the surface of the base membrane, and then passes through the membrane head, and the TMC organic solution in the membrane head is applied to one side of the membrane, and the distance between the membrane heads is adjusted to use the membrane head to apply the organic solution evenly and flatly. The wet membrane coated with TMC organic solution is dried in an oven at a speed of 1m / min to obtain a selective composite anion exchange membrane. The temperatures of the front, middle and rear three sections of the oven are 60℃, 80℃ and 60℃ respectively. Finally, the selective composite anion exchange membrane is transported to the terminal and collected on the terminal roller.

[0067] Example 7

[0068] The selective composite cation exchange membrane obtained in the embodiment of the present invention (the selective composite cation exchange membranes obtained in Examples 2, 3, and 4 are named C1, C2, and C3, respectively) was applied to an electrodialysis system to carry out selectivity and concentration tests. The schematic diagram of the electrodialysis principle is shown in FIG. Figure 3 As shown. In the figure, from left to right are the anode plate, anode chamber, anion exchange membrane, desalination chamber, selective composite cation exchange membrane, concentration chamber, anion exchange membrane, cathode chamber, cathode plate, where the polyamide layer of the selective composite cation exchange membrane faces the desalination chamber. At the beginning of the experiment, 0.3M Na2SO4 solution, 1.0M NaCl+0.1M MgCl2 mixed solution, and 0.01M NaCl solution were introduced into the anode chamber / cathode chamber, desalination chamber, and concentration chamber, respectively. During operation, the anode chamber and the cathode chamber were connected in series. After the experiment started, 200A / m was applied to both sides of the membrane stack. 2 The selective composite cation exchange membrane was replaced by a commercial cation exchange membrane, and its separation and concentration performance were tested under the same parameters. Figure 4 , 5 As shown in the figure, respectively, the NaCl concentration in the concentration chamber at the end of the experiment and the membrane's Na+ and Mg 2+ The separation ratio is Figure 4 , 5 It can be seen that when C1, C2, and C3 membranes are used, the final NaCl concentration in the concentration chamber is significantly higher than that of commercial membranes, and the C1, C2, and C3 membranes have a significant effect on Na+ and Mg 2+ The separation ratio is also better than that of commercial membranes. Therefore, the selective composite cation exchange membrane obtained by the present invention has excellent concentration performance and separation performance.

[0069] Example 8

[0070] The selective composite anion exchange membrane obtained in the examples of the present invention (the selective composite anion exchange membranes obtained in Examples 5 and 6 are named A1 and A2, respectively) were applied to an electrodialysis system to carry out selectivity and concentration tests. The schematic diagram of the electrodialysis principle is shown in FIG. Figure 6 As shown. In the figure, from left to right are the cathode plate, cathode chamber, cation exchange membrane, desalination chamber, selective composite anion exchange membrane, concentration chamber, cation exchange membrane, anode chamber, and anode plate, wherein the polyamide layer of the selective composite anion exchange membrane faces the desalination chamber. At the beginning of the experiment, 0.3M Na2SO4 solution, 0.1M NaCl+0.1M Na2SO4 mixed solution, and 0.01M NaCl solution were introduced into the anode chamber / cathode chamber, desalination chamber, and concentration chamber, respectively. During operation, the anode chamber and the cathode chamber were connected in series. After the start of the experiment, 100A / m 2The selective composite anion exchange membrane was replaced by a commercial anion exchange membrane, and its separation performance and concentration performance were tested under the same parameters. Figure 7 , 8 The following are the NaCl concentration in the concentration chamber and the membrane's Cl - 、SO4 2- The separation ratio is Figure 7 , 8 It can be seen that when using A1 and A2 membranes, the final NaCl concentration in the concentration chamber is significantly higher than that of the commercial membrane, and the A1 and A2 membranes have a significant effect on the Cl - 、SO4 2- The separation ratio is also better than that of commercial membranes. Therefore, the selective composite cation exchange membrane obtained by the present invention has excellent concentration performance and separation performance.

[0071] In summary, the present invention provides a method for preparing a selective composite ion exchange membrane for separation and concentration, wherein a highly charged polymer is dissolved in a first organic solvent by heating and stirring to form a 10-25wt% casting solution, and after the highly charged polymer is completely dissolved, the casting solution is allowed to stand for degassing; a polyamine is dissolved in pure water to prepare a 1-5wt% amine-containing aqueous solution; a polyacyl chloride is dissolved in a second organic solvent to prepare a 0.1-0.5wt% acyl chloride organic solution; the degassed casting solution is applied to both sides of a woven fabric fixed to the device by a coating head, and slowly dried in an oven at a first set speed to form an ion exchange base membrane, and the ion exchange base membrane is collected at the terminal of the ion exchange base membrane production line; the collected ion exchange base membrane is The ion exchange base membrane is immersed in and passes through the water tank containing the amine-containing aqueous solution at a second set speed, so that the amine-containing aqueous solution is fully in contact with the ion exchange base membrane, and then the excess aqueous solution on the surface of the ion exchange base membrane is removed by a silicone roller; the ion exchange base membrane after the excess aqueous solution on the surface is removed is transferred to the membrane head for coating the acyl chloride organic solution in the functional layer coating production line, and the acyl chloride organic solution is coated on one side of the ion exchange base membrane by the membrane head, and the height of the membrane head from the ion exchange base membrane is adjusted so that the membrane head coats the organic solution evenly and flatly, completing the interfacial polymerization reaction to form a polyamide layer, and then passing through the next oven at a third set speed for drying, and finally collected by a roller at the terminal of the functional layer coating production line to obtain a selective composite ion exchange membrane. The present invention coats the base film on both sides of the woven fabric, and the woven fabric can provide support, and the woven fabric has excellent tensile strength, so that the obtained ion exchange membrane has strong mechanical strength; a charged high molecular polymer with a high degree of functionalization (25-50%) is used to prepare a denser base film, so that the surface of the base film has more active sites to complete ion exchange, thereby improving the ion flux and realizing high-fold ion concentration, and due to the presence of the polyamide layer, the composite ion exchange membrane prepared by the present invention has a monovalent and divalent ion separation effect; in summary, the selective composite ion exchange membrane prepared by the present invention can simultaneously realize the separation of monovalent and divalent ions and high-fold concentration of monovalent ions; in addition, the production method of the present invention is simple and easy to implement, the operation process is smooth, and continuous production can be effectively realized, which not only improves production efficiency, but also facilitates large-scale application in industrial processes.

[0072] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0073] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for preparing a selective composite ion exchange membrane for separation and concentration, characterized in that: The following steps are involved: S1, dissolving a highly charged polymer in a first organic solvent by heating and stirring to form a 10-25wt% casting solution, and after the highly charged polymer is completely dissolved, allowing the formed casting solution to stand for degassing; S2, dissolving a polyamine in pure water to prepare a 1-5 wt% amine-containing aqueous solution; dissolving a polyacid chloride in a second organic solvent to prepare a 0.1-0.5 wt% acyl chloride organic solution; S3, applying the degassed casting solution to both sides of the woven fabric fixed on the equipment by using a coating head, slowly passing through an oven to dry at a first set speed to form an ion exchange base membrane, and collecting the solution at the terminal of the ion exchange base membrane production line; S4, immersing the collected ion exchange base membrane into and passing through a water tank containing the amine-containing aqueous solution at a second set speed, so that the amine-containing aqueous solution is fully in contact with the ion exchange base membrane, and then removing excess aqueous solution on the surface of the ion exchange base membrane through a silica gel roller; S5. After removing the excess aqueous solution from the surface, the ion exchange base membrane is transferred to the membrane head for coating the acyl chloride organic solution in the functional layer coating production line, and the acyl chloride organic solution is coated on one side of the ion exchange base membrane by the membrane head. The height of the membrane head from the ion exchange base membrane is adjusted so that the membrane head can coat the organic solution evenly and flatly, and the interfacial polymerization reaction is completed to form a polyamide layer. The membrane is then dried in the next oven at a third set speed, and finally collected by rollers at the terminal of the functional layer coating production line to obtain a selective composite ion exchange membrane.

2. The method for preparing a selective composite ion exchange membrane for separation and concentration according to claim 1, characterized in that: In step S1, the highly charged high molecular polymer is at least one of sulfonated polyethersulfone, sulfonated polysulfone, sulfonated polystyrene, sulfonated polyphenylene oxide, sulfonated polyvinylidene fluoride, sulfonated polyetheretherketone, brominated polyphenylene oxide, quaternized polyphenylene oxide, quaternized polysulfone, and chloromethylated polyarylethersulfone; The functionalization degree of the highly charged macromolecular polymer is 25-50%.

3. The method for preparing a selective composite ion exchange membrane for separation and concentration according to claim 1, characterized in that: In step S1, the first organic solvent for dissolving the highly charged polymer is at least one of N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, acetone, tetrahydrofuran, and ethylene glycol monomethyl ether.

4. The method for preparing a selective composite ion exchange membrane for separation and concentration according to claim 1, characterized in that: In step S1, the highly charged polymer is heated and stirred at a temperature of 60-90°C and a stirring time of 4-12 hours.

5. The method for preparing a selective composite ion exchange membrane for separation and concentration according to claim 1, characterized in that: In step S2, the polyamine is at least one of ethylenediamine, hexamethylenediamine, m-phenylenediamine, piperazine, and polyethyleneimine; The polyacid chloride is at least one of trimesoyl chloride and terephthaloyl chloride.

6. The method for preparing a selective composite ion exchange membrane for separation and concentration according to claim 1, characterized in that: In step S2, the second organic solvent for dissolving the polyacid chloride is at least one of n-hexane, n-heptane, n-decane, cyclohexane, ISOPAR G, and ISOPAR E.

7. The method for preparing a selective composite ion exchange membrane for separation and concentration according to claim 1, characterized in that: In step S3, the coating width of the coating head is 200-400 μm.

8. The method for preparing a selective composite ion exchange membrane for separation and concentration according to claim 1, characterized in that: In step S3, the first set speed of the woven fabric coated with the casting solution and fixed on the casting machine through oven drying is 0.1-1 m / min; the oven drying temperature is 30-130°C.

9. The method for preparing a selective composite ion exchange membrane for separation and concentration according to claim 1, characterized in that: In step S4, the second set speed at which the ion exchange base membrane is immersed in and passes through the water tank filled with the amine-containing aqueous solution is 0.1-0.5 m / min.

10. The method for preparing a selective composite ion exchange membrane for separation and concentration according to claim 1, characterized in that: In step S5, the third set speed for drying the polyamide layer formed after the interfacial polymerization reaction in the next oven is 0.2-1 m / min, and the temperature in the oven is 60-120°C.

Images