CN107185417B

CN107185417B - Sulfonated polyether sulfone membrane and preparation method thereof, sulfonated polysulfone membrane and preparation method and application thereof

Info

Publication number: CN107185417B
Application number: CN201710481372.4A
Authority: CN
Inventors: 吴翠明; 汪国胜; 张旭; 吴永会; 徐传芹
Original assignee: Hefei University of Technology
Current assignee: Hefei University of Technology
Priority date: 2017-06-22
Filing date: 2017-06-22
Publication date: 2021-01-01
Anticipated expiration: 2037-06-22
Also published as: CN107185417A

Abstract

The invention provides a sulfonated polyether sulfone membrane and a preparation method thereof, and a sulfonated polysulfone membrane and a preparation method thereof. The sulfonated polyether sulfone membrane provided by the application is prepared by a sulfonated polyether sulfone phase inversion method, and the sulfonated polysulfone membrane is prepared by sulfonated polysulfone phase inversion method. The application also provides a bipolar membrane electrodialysis device, wherein the cation exchange membrane of the bipolar membrane electrodialysis device is the sulfonated polyether sulfone membrane or the sulfonated polysulfone membrane. The application also provides a method for separating amino acid mixed liquor by using the bipolar membrane electrodialysis device. The sulfonated polyether sulfone membrane and the sulfonated polysulfone membrane prepared by the invention have excellent mechanical property, electrical property and stability, have porous structures, are used for separating amino acid mixed liquor in the bipolar membrane electrodialysis process, and amino acid molecules with positive charges can more easily migrate through the membranes, so that higher recovery rate and current efficiency are obtained.

Description

Sulfonated polyether sulfone membrane and preparation method thereof, sulfonated polysulfone membrane and preparation method and application thereof

Technical Field

The invention relates to the technical field of cation exchange membranes, in particular to a sulfonated polyether sulfone membrane and a preparation method thereof, a sulfonated polysulfone membrane and a preparation method thereof, a bipolar membrane electrodialysis device and a method for separating amino acid mixed liquor.

Background

Amino acids are used as raw materials for many foods and chemicals and have important food and commercial values. Amino acids can be produced by fermentation, enzymatic catalysis or chemical synthesis, and the obtained amino acid mother liquor has complicated components and many byproducts, so further separation and purification are needed. Traditional membrane separation technologies such as ultrafiltration and nanofiltration mainly use the difference of membrane pore size and molecular size to separate different components, so that it is difficult to separate mixed amino acids with very close molecular weights.

Electrodialysis, a new membrane separation technique, can separate different mixed amino acid solutions, but some problems are encountered during the separation. For example, the pH of the solution may change due to the migration of amino acid molecules during the separation process, and the amino acid molecules have different chargeability under different pH conditions, thereby greatly reducing the degree of amino acid separation. In addition, most of the previous studies have focused on the separation of mixed amino acid solutions by dense commercial membranes, but the separation efficiency is low because of the large resistance of dense commercial membranes to the transfer of macromolecules.

Bipolar membrane electrodialysis as a new membrane separation technique, H can be generated by electrolysis of water molecules⁺And OH^-Ions, generation of H⁺And OH^-The ions will bind to the amino acid molecules and thereby maintain a stable pH in the recovery compartment, and thus the degree of separation can be greatly increased. Fig. 1 is a schematic structural diagram of a Bipolar Membrane Electrodialysis (BMED) device, which is composed of a membrane stack device (1), a feed liquid tank (2), a recovery tank (3), an electrode liquid tank (4), a first peristaltic pump (5), a second peristaltic pump (6), a third peristaltic pump (7), a direct-current power supply (8), an anode plate (9) and a cathode plate (10); FIG. 2 is a schematic diagram of a BMED membrane stack device (1), wherein the membrane stack device (1) is formed by arranging a bipolar membrane (BP-1), a cation exchange membrane (C), a bipolar membrane (BP-2), an organic glass clapboard and a silica gel gasket at intervals from an anode to a cathode in sequence, and is finally fixed by an anode plate and a cathode plate; the electrode plates (9 and 10) are formed by respectively embedding titanium ruthenium-coated electrodes on a BMED front clamping plate and a BMED rear clamping plate. An anode chamber is formed between the anode plate (9) and the bipolar membrane (BP-1), a feed liquid chamber is formed between the bipolar membrane (BP-1) and the cation exchange membrane (C), and the cation exchange membrane (C)) And the bipolar membrane (BP-2) form a lysine recovery chamber, and a cathode chamber is formed between the bipolar membrane (BP-2) and the cathode plate (10); the anode plate (9) and the cathode plate (10) are respectively connected with the anode and the cathode of the direct current power supply through leads; the cathode chamber and the anode chamber are connected in series, so that the cathode/anode chamber, the feed chamber and the lysine recovery chamber form three circulation loops. Thus, it has become possible to achieve the separation of two amino acids of similar molecular weights by means of bipolar membrane electrodialysis.

Disclosure of Invention

The sulfonated polyethersulfone membrane and the sulfonated polysulfone membrane provided by the invention are used as cation exchange membranes of a bipolar membrane electrodialysis device, can realize separation of two amino acids with approximate molecular weights, and have higher amino acid recovery rate and current efficiency.

The application provides a sulfonated polyether sulfone membrane which is prepared from sulfonated polyether sulfone through a phase inversion method.

Preferably, the ion exchange capacity of the sulfonated polyether sulfone is 0.15-0.4 mmol/g.

The application also provides a preparation method of the sulfonated polyether sulfone membrane, which comprises the following steps:

and (3) carrying out phase conversion on the sulfonated polyether sulfone in water to obtain the sulfonated polyether sulfone membrane.

Preferably, the phase inversion process specifically comprises:

mixing sulfonated polyether sulfone with an organic solvent to obtain a coating liquid;

coating the coating liquid on a substrate, and soaking in water to obtain a sulfonated polyether sulfone membrane; the organic solvent is N-methyl pyrrolidone or a mixed solution of N-methyl pyrrolidone and dichloromethane; the temperature of the water is 0-35 ℃.

The application also provides a sulfonated polysulfone membrane prepared by the phase inversion method of sulfonated polysulfone.

Preferably, the ion exchange capacity of the sulfonated polysulfone is 0.08-0.4 mmol/g.

The application also provides a preparation method of the sulfonated polysulfone membrane, which comprises the following steps:

and (3) carrying out phase conversion on the sulfonated polysulfone in water to obtain the sulfonated polysulfone membrane.

Preferably, the phase inversion process specifically comprises:

mixing sulfonated polysulfone with an organic solvent to obtain a coating liquid;

coating the coating liquid on a substrate, and soaking in water to obtain a sulfonated polysulfone membrane; the organic solvent is N-methyl pyrrolidone or a mixed solution of N-methyl pyrrolidone and dichloromethane; the temperature of the water is 0-35 ℃.

The application also provides a bipolar membrane electrodialysis device, wherein a cation exchange membrane of the bipolar membrane electrodialysis device is the sulfonated polyether sulfone membrane prepared by the preparation method in the scheme or the sulfonated polysulfone membrane prepared by the preparation method in the scheme or the scheme.

The application also provides a method for separating amino acid mixed liquor by using the bipolar membrane electrodialysis device, which comprises the following steps:

adding a mixed solution of a first amino acid and a second amino acid into a feed liquid tank, adding a strong electrolyte into an electrode liquid tank, and adding a second amino acid solution into a recovery tank; the first amino acid is negatively charged amino acid in the mixed solution, and the second amino acid is positively charged amino acid in the mixed solution;

and starting the first peristaltic pump, the second peristaltic pump and the third peristaltic pump, starting the direct-current power supply, and transferring the second amino acid in the feed liquid tank to the recovery tank after operation to obtain the separated first amino acid and the second amino acid.

Preferably, the first amino acid is glutamic acid, and the second amino acid is lysine; the concentration of glutamic acid in the feed liquid tank is 0.02-0.1 mol/L, the concentration of lysine in the feed liquid tank is 0.02-0.1 mol/L, and the concentration ratio of glutamic acid to lysine is (1-5): (1-5); the concentration of lysine in the recovery tank is 0.005-0.03 mol/L.

The sulfonated polyether sulfone membrane and the sulfonated polysulfone membrane have excellent mechanical property, electrical property and stability, and simultaneously can carry a plurality of water molecules because the sulfonated polyether sulfone membrane and the sulfonated polysulfone membrane both have finger-shaped holes, so that amino acid molecules with positive charges can easily migrate through the membrane when migrating through the membrane, the amino acid molecules have larger sizes, and the resistance is smaller when passing through the larger finger-shaped holes, therefore, when the sulfonated polyether sulfone membrane or the sulfonated polysulfone membrane is used as a cation exchange membrane of a bipolar membrane electrodialysis device, two amino acids with different charges and similar molecular weights can be effectively separated, and has higher amino acid recovery rate and current efficiency. Furthermore, the sulfonated polysulfone membrane can contain elliptical holes in the skin layer of the membrane and finger holes in the inner layer, so that the separation efficiency and the current efficiency are further improved.

Drawings

FIG. 1 is a schematic diagram of the structure of a Bipolar Membrane Electrodialysis (BMED) apparatus according to the present invention;

FIG. 2 is a schematic diagram of the structure of a membrane stack device (1) in a BMED device according to the present invention;

FIG. 3 is an infrared spectrum of sulfonated polyethersulfone membranes and sulfonated polysulfone membranes in examples 1-6 of the present invention;

FIG. 4 is a field emission scanning electron microscope image of the dense sulfonated polyethersulfone membrane prepared in example 1 of the present invention;

FIG. 5 is a field emission scanning electron micrograph of a SPES-4 film prepared in example 1 of the present invention;

FIG. 6 is a field emission scanning electron micrograph of a SPES-25 film prepared according to example 3 of the present invention;

FIG. 7 is a field emission scanning electron micrograph of a SPES-D-4 film prepared in example 4 of the present invention;

FIG. 8 is a SEM image of SPSf-4 film prepared in example 5 of the present invention;

FIG. 9 is a SEM image of SPSf-25 film prepared in example 6 of the present invention.

Detailed Description

For a further understanding of the invention, reference will now be made to the preferred embodiments of the invention by way of example, and it is to be understood that the description is intended to further illustrate features and advantages of the invention, and not to limit the scope of the claims.

The embodiment of the invention discloses a sulfonated polyether sulfone membrane, which is prepared from sulfonated polyether sulfone by a phase inversion method.

In the case of sulfonated polyethersulfone membranes, the sulfonated polyethersulfone membranes are prepared by a phase inversion method. The sulfonated polyether sulfone is well known in the prior art, can be purchased from the market, and can also be prepared according to the existing method; the sulfonation process of the polyether sulfone comprises the following specific steps:

and (2) mixing the polyethersulfone with dichloromethane to obtain a solution with the mass concentration of 5-20%, and adding a mixed solution of a sulfonating agent and dichloromethane to obtain the sulfonated polyethersulfone.

In the above process, the sulfonating agent is well known to those skilled in the art, and there is no particular limitation to this application; illustratively, the sulfonating agent is chlorosulfonic acid and concentrated sulfuric acid, and in particular embodiments, the sulfonating agent is chlorosulfonic acid. The volume ratio of the sulfonating agent to the dichloromethane is 1: (1-10), in a specific embodiment, the volume ratio of the sulfonating agent to the dichloromethane is 1: (3-8).

More specifically, the sulfonation process of the polyether sulfone is as follows:

adding 1.5-2.5 kg of polyether sulfone and 5-8L of dichloromethane into a reaction kettle, stirring, and adding 5-8L of dichloromethane while stirring to completely dissolve the polyether sulfone; after the polyether sulfone is completely dissolved, adding a mixed solution of 1-2L of dichloromethane and 0.2-0.8L of chlorosulfonic acid into a reaction kettle in two batches; after reacting for 15-25 h at 40 ℃, discharging the mixed solution from the bottom of the reaction kettle, and putting the mixed solution into a large amount of water at 20-50 ℃ to obtain solid sulfonated polyether sulfone; crushing the solid sulfonated polyether sulfone by using a crusher to obtain sulfonated polyether sulfone powder, washing the sulfonated polyether sulfone powder by using water until the cleaning solution is neutral, filtering the solution, and drying the solution for 24 hours at the temperature of between 60 and 100 ℃ to obtain a finished sulfonated polyether sulfone product.

In the process, the sulfonating agent is added into the solution dissolved with the polyethersulfone for grafting sulfonic acid groups on a polyethersulfone molecular chain to obtain sulfonated polyethersulfone, so that a sulfonated polyethersulfone membrane prepared subsequently is negatively charged and has ion selectivity.

The ion exchange capacity of the sulfonated polyether sulfone prepared by the method is 0.15-0.4 mmol/g, and in a specific embodiment, the ion exchange capacity of the sulfonated polyether sulfone is 0.2-0.35 mmol/g.

Specifically, the application also provides a preparation method of the sulfonated polyether sulfone membrane, which comprises the following steps:

In the process of preparing the sulfonated polyethersulfone membrane, the preparation of the sulfonated polyethersulfone is described in detail in the above-mentioned content, and the details are not repeated herein. The phase transformation process is carried out in water, and the preparation of the sulfonated polyether sulfone membrane specifically comprises the following steps:

In the process of preparing the sulfonated polyether sulfone membrane, firstly preparing a membrane coating liquid, namely dissolving sulfonated polyether sulfone in an organic solvent; in the dissolving process of sulfonated polyether sulfone, when the sulfonated polyether sulfone is dissolved in N-methyl pyrrolidone, the mass concentration of the obtained coating liquid is preferably 15-35%, in the embodiment, the mass concentration of the coating liquid is more preferably 23-25%; when the sulfonated polyether sulfone is dissolved in the mixed solution of N-methyl pyrrolidone and dichloromethane, the mass concentration of the obtained coating solution is preferably 15-35%, the mass concentration of dichloromethane in the coating solution is preferably 6-18%, in the embodiment, the mass concentration of the coating solution is more preferably 23-25%, and the mass concentration of dichloromethane in the coating solution is more preferably 11-13%.

According to the invention, the coating liquid is coated on a substrate and then the film is prepared by a phase inversion method. The substrate is preferably a glass plate and a teflon plate well known to those skilled in the art, and the present application is not particularly limited, and a teflon plate is more preferable in the examples.

And (3) preparing the film on the coated substrate by a phase inversion method, wherein the phase inversion method is to immerse the coated substrate in water at a certain temperature to form the film. The temperature of the water is preferably 0-35 ℃, and in the embodiment, the temperature is more preferably 2-6 ℃ or 23-27 ℃. The depth of the water is preferably 300 to 500 times, and in an embodiment, more preferably 380 to 420 times the thickness of the thin coating film.

The coated substrate is immersed in water at different temperatures, so that porous structures with different shapes and pore diameters can be obtained, and the application range of the prepared sulfonated polyether sulfone membrane is expanded.

The invention also provides a sulfonated polysulfone membrane prepared by the phase inversion method of sulfonated polysulfone.

The sulfonated polysulfone membrane is prepared by a method of phase inversion of sulfonated polysulfone. The sulfonated polysulfone is well known in the prior art, can be obtained from the market, and can also be prepared according to the existing method; the sulfonation process of the polysulfone is as follows:

mixing polysulfone with dichloroethane to obtain a solution with the mass concentration of 1-15%, and adding a mixed solution of a sulfonating agent and dichloroethane to obtain sulfonated polysulfone.

In the above process, the sulfonating agent is well known to those skilled in the art, and there is no particular limitation to this application; the sulfonating agent is chlorosulfonic acid and concentrated sulfuric acid, and specifically, the sulfonating agent is chlorosulfonic acid. The volume ratio of the sulfonating agent to the dichloroethane is 1: (10-60), more specifically, the volume ratio of the sulfonating agent to the dichloroethane is 1: (30-50).

More specifically, the sulfonation process of the polysulfone is as follows:

adding 5-10 g of polysulfone and 50-150 ml of dichloroethane into a 250ml two-necked flask with a condenser pipe and connected with a nitrogen protection device, introducing nitrogen for 1h, and dropwise adding a mixed solution of 1-4 ml of chlorosulfonic acid and 10-30 ml of dichloroethane into the two-necked flask, wherein the time is 20-40 minutes. The resulting mixture was then stirred at 30 ℃ for 12 hours. After the sulfonation reaction is finished, putting the sulfonated polysulfone into a large amount of water at the temperature of 20-50 ℃ to obtain solid sulfonated polysulfone; and crushing the solid sulfonated polysulfone by using a crusher to obtain sulfonated polysulfone powder, washing the sulfonated polysulfone powder by using water until the cleaning solution is neutral, filtering the solution, and drying the solution in vacuum at 40-80 ℃ for 24 hours to obtain a sulfonated polysulfone finished product.

In the process, the sulfonating agent is added into the solution dissolved with polysulfone for grafting sulfonic groups on the polysulfone molecular chain to obtain sulfonated polysulfone, so that the sulfonated polysulfone membrane prepared subsequently is negatively charged and has ion selectivity.

The ion exchange capacity of the sulfonated polysulfone prepared by the method is 0.08-0.4 mmol/g, and in a specific embodiment, the ion exchange capacity of the sulfonated polysulfone is 0.1-0.3 mmol/g. The phase inversion process of the sulfonated polysulfone is well known to those skilled in the art, and there is no particular limitation in this application.

Specifically, the application also provides a preparation method of the sulfonated polysulfone membrane, which comprises the following steps:

In the process of preparing the sulfonated polysulfone membrane, the preparation of the sulfonated polysulfone is described in detail in the above, and will not be described herein. The phase inversion process is carried out in water, and specifically, the sulfonated polysulfone membrane is prepared by:

In the process of preparing the sulfonated polysulfone, firstly, a membrane coating liquid is prepared, namely, the sulfonated polysulfone is dissolved in an organic solvent; in the process of dissolving the sulfonated polysulfone, when the sulfonated polysulfone is dissolved in N-methyl pyrrolidone, the mass concentration of the obtained coating liquid is preferably 15% to 35%, in the embodiment, the mass concentration of the coating liquid is more preferably 23% to 25%; when the sulfonated polysulfone is dissolved in the mixed solution of N-methylpyrrolidone and dichloromethane, the mass concentration of the obtained coating solution is preferably 15% to 35%, the mass concentration of dichloromethane in the coating solution is preferably 6% to 18%, in the embodiment, the mass concentration of the coating solution is more preferably 23% to 25%, and the mass concentration of dichloromethane in the coating solution is more preferably 11% to 13%.

And (3) preparing a film on the coated substrate by a phase inversion method, wherein the coated substrate is immersed in water at a certain temperature to form the film. The temperature of the water is preferably 0-35 ℃, and in the embodiment, the temperature is more preferably 2-6 ℃ or 23-27 ℃. The depth of the water is preferably 300 to 500 times, and in an embodiment, more preferably 380 to 420 times the thickness of the thin coating film.

The coated substrate is immersed in water at different temperatures, so that porous structures with different shapes and pore diameters can be obtained, and the application range of the prepared sulfonated polysulfone membrane is expanded.

The preparation method of the sulfonated polyether sulfone membrane and the sulfonated polysulfone membrane adopts a phase inversion method, and comprises the steps of dissolving sulfonated polyether sulfone or sulfonated polysulfone in an organic solvent to obtain a membrane coating liquid, coating the membrane coating liquid on a substrate, and then soaking the coated substrate in gel bath water to perform a phase splitting process and a phase inversion process; the phase separation process is that the organic solvent and water are mutually diffused through a liquid film/water interface after the coating liquid is immersed in water, the exchange between the organic solvent and the water reaches a certain degree, and the coating liquid becomes a thermodynamically unstable system, so that the coating liquid is subjected to phase separation to determine a film hole structure; the phase inversion process refers to that after the phase of the coating liquid system is separated, the organic solvent and water are further exchanged, and the condensation and interphase flow of membrane pores and the polymer rich phase membrane forming are carried out.

In the present application, in order to produce porous membranes with different forms, a phase inversion process is performed by changing the type of the membrane material, the phase inversion temperature and adding dichloromethane, so as to control the size of the pores by controlling the rate of the phase separation process, as detailed in the following examples.

In the process of preparing the sulfonated polyether sulfone membrane or the sulfonated polysulfone membrane, membrane layers with different pore structures are preferably prepared in water at 0-35 ℃, specifically, the sections of the sulfonated polyether sulfone series membrane (SPES) and the sulfonated polysulfone series membrane (SPSf) prepared at 0-35 ℃ both contain finger-shaped pores, but membrane skins are different, for example, the SPES series membrane (including the SPES-4 membrane, the SPES-25 membrane and the SPES-D-4 membrane) skins are spongy pores, and the SPSf series membrane (including the SPSf-4 membrane and the SPSf-25 membrane) skins contain elliptic pores; the spongy pores are denser than the elliptical pores, and therefore can carry relatively fewer water molecules inside the membrane, and thus the resistance to the migration of lysine molecules through the membrane is greater, whereas the elliptical pores can carry more water molecules inside the membrane, and thus the resistance to the migration of lysine molecules through the membrane is less. Therefore, the SPSf series membrane has higher separation efficiency and current efficiency and lower energy consumption than the SPES series membrane.

The water content, the surface resistance and the tensile strength of the sulfonated polyether sulfone membrane or the sulfonated polysulfone membrane also influence the separation of the amino acid mixed solution, and specifically, the higher the water content is, the smaller the surface resistance is, the higher the separation efficiency and the current efficiency obtained when the sulfonated polyether sulfone membrane or the sulfonated polysulfone membrane is applied to the bipolar membrane electrodialysis device for separating the amino acid mixed solution are, and the lower the energy consumption is; this is because the higher the water content, the more water molecules carried inside the membrane, the easier it is for the amino acid molecules to migrate through the membrane as hydrated ions; the smaller the sheet resistance, the higher the current density at the same voltage when the amino acid molecules migrate through the membrane. The higher the tensile strength is, the better the mechanical strength is, when the bipolar membrane electrodialysis device is applied to separating amino acid mixed liquor, the membrane is required to have higher mechanical strength, so that the membrane is not easy to damage and deform, and is beneficial to recycling for many times.

Therefore, the application also provides a bipolar membrane electrodialysis device, and the cation exchange membrane of the bipolar membrane electrodialysis device is the sulfonated polyether sulfone membrane or the sulfonated polysulfone membrane in the scheme.

The Bipolar Membrane Electrodialysis (BMED) device described herein is a device well known to those skilled in the art, and is not particularly limited in this application, and a specific structural schematic diagram of the BMED device is shown in fig. 1: the device comprises a membrane stack device (1), a feed liquid tank (2), a recovery tank (3), an electrode liquid tank (4), a first peristaltic pump (5), a second peristaltic pump (6), a third peristaltic pump (7), a direct-current power supply (8), an anode plate (9) and a cathode plate (10); FIG. 2 is a schematic diagram of a BMED membrane stack device (1), wherein the membrane stack device (1) is formed by arranging a bipolar membrane (BP-1), a cation exchange membrane (C), a bipolar membrane (BP-2), an organic glass clapboard and a silica gel gasket at intervals from an anode to a cathode in sequence, and is finally fixed by an anode plate and a cathode plate; the electrode plates (9 and 10) are formed by respectively embedding titanium ruthenium-coated electrodes on a BMED front clamping plate and a BMED rear clamping plate. An anode chamber is formed between the anode plate (9) and the bipolar membrane (BP-1), a feed liquid chamber is formed between the bipolar membrane (BP-1) and the cation exchange membrane (C), a recovery chamber is formed between the cation exchange membrane (C) and the bipolar membrane (BP-2), and a cathode chamber is formed between the bipolar membrane (BP-2) and the cathode plate; the anode plate (9) and the cathode plate (10) are respectively connected with the anode and the cathode of the direct current power supply through leads; the cathode chamber and the anode chamber are connected in series, and therefore, the cathode/anode chamber, the feed chamber and the recovery chamber respectively constitute a circulation circuit.

The cation exchange membrane in the BMED membrane stack device is a porous sulfonated polyether sulfone membrane or sulfonated polysulfone membrane prepared by the preparation method in the scheme, and other parts of the bipolar membrane electrodialysis device are not particularly limited in the application and are all parts commonly adopted in the field. Preferably, the bipolar membrane (BP) is an FBM membrane provided by fumtech, germany.

In the BMED device, a cathode chamber and an anode chamber are connected in series, so that the cathode/anode chamber, a feed liquid chamber and a recovery chamber respectively and independently form a circulation loop; in the circulation loop, an inlet and an outlet of a feed liquid chamber are communicated with a feed liquid tank (2) through a guide pipe, an inlet and an outlet of a recovery chamber are communicated with a recovery tank (3) through a guide pipe, a cathode chamber is communicated with an anode chamber through a guide pipe to form an electrode chamber of the BMED, an inlet and an outlet of the BMED are respectively communicated with an electrode liquid tank (4) through guide pipes, power for the feed liquid tank (2), the recovery tank (3) and the electrode liquid tank (4) to enter the membrane stack device (1) is respectively provided by a first peristaltic pump (5), a second peristaltic pump (6) and a third peristaltic pump (7), and the volume flow of each compartment can be controlled through the peristaltic pumps, so that the circulation loop of the feed liquid chamber, the circulation loop of the lysine recovery chamber and the circulation loop of the electrode liquid chamber.

In view of the above, the present application also provides a method for separating an amino acid mixed solution by using the above bipolar membrane electrodialysis device, comprising the steps of:

and starting the first peristaltic pump, the second peristaltic pump and the third peristaltic pump, starting the direct-current power supply, and transferring the second amino acid in the feed liquid tank to the recovery tank after operation to obtain the separated first amino acid solution and the second amino acid solution.

In order to realize the separation of the amino acid mixed liquor, the amino acid mixed liquor is two kinds of amino acids with different charges in the solution, specifically, a first amino acid with negative charges in the mixed liquor and a second amino acid with positive charges in the mixed liquor; the bipolar membrane electrodialysis device provided by the application has a good separation effect especially on two amino acids with approximate molecular weights. In specific examples, the present application exemplifies the separation of two amino acids, glutamic acid and lysine. The method specifically comprises the following steps:

adding a glutamic acid and lysine mixed solution into a feed liquid tank, adding a low-concentration lysine solution into a recovery tank, and adding a strong electrolyte solution into an electrode liquid tank;

the first peristaltic pump, the second peristaltic pump and the third peristaltic pump are started, the direct-current power supply is started, the lysine molecules are transferred to the recovery chamber from the material liquid chamber after operation, the concentration of the lysine in the recovery tank is increased along with the operation of the device, and therefore the effective separation of the glutamic acid and the lysine is realized.

In the process, the concentration of glutamic acid and lysine in the feed liquid tank is 0.02-0.1 mol/L, and the concentration ratio of the glutamic acid to the lysine is (1-5): (1-5); in a specific embodiment, the concentration of the glutamic acid and the lysine is 0.05 mol/L. The strong electrolyte in the electrode liquid tank is well known to those skilled in the art, and is exemplified by sodium sulfate, sodium nitrate, potassium sulfate, sodium hydroxide or potassium hydroxide, and in a specific embodiment, the strong electrolyte is sodium sulfate with a concentration of 0.05-0.3 mol/L. The concentration of the glutamic acid in the recovery tank is 0.005-0.03 mol/L; in a specific embodiment, the concentration of the glutamic acid is 0.01 mol/L.

In the above treatment process, the operation of the bipolar membrane electrodialysis device can be performed in a manner well known to those skilled in the art, and the application is not particularly limited.

In the process of separating the mixed liquid of glutamic acid and lysine, the peristaltic pump is started before the power is switched on, so that the solutions in the feed liquid tank, the recovery tank and the electrode liquid tank respectively circulate in each compartment in the membrane stack device to exhaust air bubbles in the compartments. The apparatus was started after switching on the power supply, and the experiment was ended after 6 hours of constant current operation. The constant current is preferably 0.05-0.3A.

The application provides a preparation method of a porous sulfonated polyether sulfone membrane and a sulfonated polysulfone membrane, and the porous sulfonated polyether sulfone membrane and the sulfonated polysulfone membrane are used as a cation exchange membrane for a bipolar membrane electrodialysis process to separate two amino acids with similar molecular weights and different charges, so that the problems of low recovery rate and low current efficiency of mixed amino acid separation when a compact membrane is applied to electrodialysis are solved.

For further understanding of the present invention, the sulfonated polysulfone membranes, the sulfonated polyethersulfone membranes, and applications thereof provided by the present invention are described in detail below with reference to examples, and the scope of the present invention is not limited by the following examples.

Example 1 preparation of porous sulfonated polyethersulfone Membrane SPES-4 by Low temperature phase inversion

(1) Preparation of sulfonated polyether sulfone: 2kg of polyether sulfone and 6.7L of dichloromethane are mixed and then added into a reaction kettle, and 6.8L of dichloromethane solution is added while stirring to completely dissolve the polyether sulfone; then mixing 1.5L of dichloromethane and 0.5L of chlorosulfonic acid, adding the mixture into a reaction kettle in two batches, stirring the mixture while adding, and reacting the mixture for 20 hours at 40 ℃; and then discharging the mixed solution from the bottom of the reaction kettle, putting the mixed solution into water at 45 ℃ for precipitation, crushing the obtained solid by using a crusher to obtain sulfonated polyether sulfone powder, washing the sulfonated polyether sulfone powder by using water until the cleaning solution is neutral, filtering the solution, and drying the solution at 90 ℃ for 24 hours to obtain a finished sulfonated polyether sulfone product. The ion exchange capacity of the sulfonated polyether sulfone is tested to be 0.2mmol/g, and the test method is reported on page 350 of volume 340-;

(2) preparing a porous sulfonated polyether sulfone membrane by low-temperature phase transformation: adding 40g of sulfonated polyether sulfone solid powder into 123.2mL of N-methylpyrrolidone, stirring for 72h to obtain 24 wt% of coating liquid, and vacuumizing to remove bubbles in the coating liquid; and (3) coating 2-3 mL of the coating liquid on a polytetrafluoroethylene plate, then flatly placing the coated substrate in water at 4 ℃ for soaking for 30-60 minutes, wherein the depth of the water is 300-500 times of the thickness of a thin coating layer, and forming to obtain a porous membrane named as an SPES-4 membrane.

For comparison, a sulfonated polyether sulfone dense membrane is also prepared, and the specific process is as follows:

coating the film coating liquid obtained by dissolving the sulfonated polyether sulfone on a glass plate, horizontally placing the glass plate into an oven, carrying out heat treatment according to the heat treatment method of 40-4 h, 60-4 h and 80-4 h, then slowly uncovering the formed film from the glass plate, immersing the film into a sodium chloride solution for later use, marking as a sulfonated polyether sulfone compact film, and naming the film as dense SPES membrane by English.

(3) Characterization of the membrane: the SPES-4 film is characterized and observed by water content, tensile strength, surface resistance, infrared spectrum and a field emission scanning electron microscope, and the result is as follows: water content of SPES-4 membranes214.0%, tensile strength of 3.30MPa, and sheet resistance of 4.51. omega. cm²。

The IR spectrum of the SPES-4 film is shown in FIG. 3, where curve a in FIG. 3 is the IR spectrum curve of the SPES-4 film, as can be seen from FIG. 3, at 3000-3300cm^-1A characteristic absorption peak of-OH in sulfonic acid group appears; at-1025 cm^-1And 1180cm^-1Respectively are the symmetric and asymmetric telescopic vibration absorption peaks of the sulfonic group; at 1240cm^-1And 714-725cm^-1The absorption peaks of (a) are respectively caused by the vibration of C-O-C and C ═ C; the results show that the sulfonation of the polyethersulfone achieves the expected effect, and the sulfonated polyethersulfone membrane is obtained.

The field emission scanning electron micrograph of the SPES-4 membrane is shown in FIG. 5, the section (a-1) is a full-scale view (magnified 300 times), the section (a-2) is a partial magnified view (magnified 5000 times), and the section (a-3) is a partial magnified view (magnified 50000 times), showing that the section of the membrane contains a large number of finger-shaped pores, indicating that a porous sulfonated polyethersulfone membrane was successfully prepared.

The water content of the sulfonated polyether sulfone dense membrane used as a comparison is 4.1 percent, the tensile strength is 46.48MPa, and the surface resistance is more than 80 omega cm². Fig. 4 is a field emission scanning electron microscope image of a sulfonated polyethersulfone dense membrane, wherein in fig. 4, the image (a-1) is a full-view cross section image (magnified 300 times), the image (a-2) is a partial magnified image (magnified 5000 times) of the membrane cross section, and the image (a-3) is a partial magnified image (magnified 50000 times) of the membrane cross section, and as can be seen from fig. 4, no significant pores are observed in the interior of the membrane, indicating that a dense membrane is produced by heat treatment.

Example 2 porous sulfonated polyethersulfone membranes SPES-4 separation of amino acids by Bipolar Membrane Electrodialysis (BMED)

A BMED experiment is carried out on the SPES-4 membrane obtained in example 1, the BMED device is schematically shown in figure 1, and the BMED device consists of a membrane stack device (1), a feed liquid tank (2), a recovery tank (3), an electrode liquid tank (4), a first peristaltic pump (5), a second peristaltic pump (6), a third peristaltic pump (7), a direct current power supply (8), an anode plate (9) and a cathode plate (10); the bipolar membranes (BP-1) and (BP-2) used in the membrane stack device (1) are both FBM membranes provided by Fumatech company in Germany, and the cation exchange membrane (C) is the SPES-4 membrane prepared in example 1;the different membranes are arranged in sequence as shown in figure 2, and are formed by arranging a bipolar membrane (BP-1), a cation exchange membrane (C), a bipolar membrane (BP-2), an organic glass clapboard and a silica gel gasket at intervals from an anode to a cathode, and are finally fixed by an anode plate and a cathode plate. The effective areas of the single films in the film stack device (1) are all 20cm². Wherein the inlet and the outlet of the feed liquid chamber are communicated with a feed liquid tank (2) through a guide pipe, the inlet and the outlet of the lysine recovery chamber are communicated with a recovery tank (3) through a guide pipe, the cathode chamber is communicated with the anode chamber through a guide pipe to form an electrode chamber of the BMED, the inlet and the outlet of the BMED are respectively communicated with an electrode liquid tank (4) through a guide pipe, the power of the feed liquid tank (2), the recovery tank (3) and the electrode liquid tank (4) entering the membrane stack device (1) is respectively provided by a first peristaltic pump (5), a second peristaltic pump (6) and a third peristaltic pump (7), and the volume flow of each compartment can be controlled to be 300mL/min through the peristaltic pumps, so that a feed liquid chamber circulation loop, a recovery chamber circulation loop and an electrode liquid chamber circulation loop are formed, and the. An anode plate (9) and a cathode plate (10) of the membrane stack device (1) are respectively connected with the positive electrode and the negative electrode of a direct current power supply (8) through leads.

The BMED device is used for treating the mixed solution of glutamic acid and lysine to separate the glutamic acid from the lysine. Adding 250mL of a mixed solution of 0.05mol/L glutamic acid and 0.05mol/L lysine into the feed liquid tank (2); adding 250mL of 0.01mol/L lysine solution into a recovery tank (3); 250mL of 0.1mol/L Na was added to the electrode liquid tank (4)₂SO₄A solution; the flow rate of peristaltic pumps (5), (6) and (7) was adjusted to 300mL/min, bubbles in each circulation compartment were removed after 10min, then the BMED device was operated under constant current of 0.07A by turning on the DC power supply (8), and the concentration of lysine molecules in the recovery chamber was increased from 0.01mol/L to 0.043mol/L after 6h, at which time the experiment was stopped.

The results show that: under the condition of constant current of 0.07A, the recovery rate of lysine molecules is 76.7 percent, the energy consumption is 6.43 kW.h/kg, and the current efficiency is 62.0 percent. During the experimental operation, the pH of the recovery chamber has small change and is stabilized in the range of 9.88-9.96. After the experiment, the purity of the lysine was checked, and the result was about 100%.

As a comparisonCMX membranes and dense sulfonated polyethersulfone membranes available from Asahi Glass Company, Japan, were also used in the BMED process, which was performed in the same manner as the BMED process of the SPES-4 membranes. According to the report of volume 373 in 2015, page 38-46 of the journal Desalination, the CMX film has a water content of 25-30% and an area resistance of 2.0-3.5 omega cm²The ion exchange capacity is 1.5 to 1.8 mmol/g.

The results of BMED experiments using CMX reference membranes were: the recovery rate of lysine is 48.1%, the purity is about 100%, the energy consumption is 8.16 kW.h/kg, and the current efficiency is 40.1%. During the experimental operation, the pH variation of the recovery room is small and is stabilized in the range of 9.85-9.98.

When BMED experiments were carried out using dense membranes of sulfonated polyethersulfone, it was found that the voltage required was too high to be in the range of the power source (60V), and BMED experiments could not be carried out under the same conditions. This is because the sulfonated polyethersulfone dense membranes have no significant porosity, resulting in low water content and high sheet resistance.

From the above analysis results, it can be seen that the SPES-4 membrane prepared in example 1 has significantly improved lysine recovery rate and current efficiency compared to the reference membrane CMX, because the SPES-4 membrane has a finger-shaped pore structure capable of greatly reducing the migration resistance of lysine molecules; and a high purity lysine product can also be obtained using a SPES-4 membrane. By contrast, the dense sulfonated polyethersulfone membrane cannot be applied to the BMED process in the experiment, and the advantages of the porous structure of the membrane are further verified.

Example 3 preparation of porous sulfonated polyethersulfone membrane SPES-25 by normal temperature phase inversion

This example was prepared as the SPES-4 membrane of example 1, except that: in the process of phase inversion of the coated substrate in water, the water temperature is adjusted to 25 ℃, and the obtained membrane is named as SPES-25 membrane.

SPES-25 membranes were characterized in the same manner as SPES-4 membranes of example 1. Experimental results show that the SPES-25 film has a water content of 237.80%, a tensile strength of 3.69MPa, and an area resistance of 18.62. omega. cm²。

The IR spectrum of the SPES-25 film is shown in FIG. 3(b), and the characteristic absorption peaks are the same as those of the SPES-4 film of example 1.

A field emission scanning electron micrograph of a SPES-25 film is shown in FIG. 6, a (a-1) is a full view (magnified 300 times) of a cross section of the film, a (a-2) is a partial magnified view (magnified 5000 times) of a cross section of the film, and a (a-3) is a partial magnified view (magnified 50000 times) of a cross section of the film, and it can be seen from FIG. 6 that a cross section of the film contains finger-shaped pores, indicating that a SPES-25 film prepared by phase inversion in water at 25 ℃ also has a porous structure; and the SPES-25 film is thicker than the SPES-4 film, indicating that the SPES-25 film is more relaxed at 25 deg.C.

The BMED apparatus and procedure were as in example 2 and the results show that: under the condition of constant current of 0.07A, the recovery rate of lysine molecules is 52.0 percent, the purity is about 100 percent, the current efficiency is 44.1 percent, and the energy consumption is 8.74 kW.h/kg. During the experimental operation, the pH variation of the recovery chamber is small and is stabilized within the range of 9.95-10.03.

From the above analysis results, it is known that the porous membrane having the finger-shaped pores can be obtained by the phase inversion method of sulfonated polyethersulfone in water at normal temperature. The SPES-25 membrane has improved lysine recovery and current efficiency compared to the reference membrane CMX, and the lysine purity of both is close to 100%, which is related to the porous structure of the SPES-25 membrane which can reduce the migration resistance of lysine molecules.

Example 4 preparation of porous sulfonated polyethersulfone membranes SPES-D-4 by low temperature methylene chloride containing phase inversion procedure

Preparation of the film: adding 40g of sulfonated polyether sulfone powder into a mixed solution of 103.76mL of N-methylpyrrolidone and 15.08mL of dichloromethane, stirring for 72h to obtain a 24 wt% coating solution, wherein the mass concentration of dichloromethane in the coating solution is 12%, and vacuumizing to remove bubbles in the coating solution; coating 2-3 mL of coating liquid on a polytetrafluoroethylene plate, horizontally placing the coated substrate in water at 4 ℃ for soaking for 30-60 minutes, wherein the depth of the water is 300-500 times of the thickness of a thin coating layer, and forming to obtain a porous membrane named as SPES-D-4 membrane.

The test result shows that: the SPES-D-4 film had a water content of 197.9%, a tensile strength of 4.45MPa, and an area resistance of 7.90. omega. cm²(ii) a The film has an IR spectrum shown in FIG. 3(c) and characteristic absorption peaksSame SPES-4 membrane as in example 1.

FIG. 7 is a field emission scanning electron micrograph of a SPES-D-4 film, in which FIG. 7 shows a full sectional view (magnified 300 times) of the film in FIG. 7, FIG. 2 shows a partial magnified view (magnified 5000 times) of the sectional view of the film in FIG. 7, and FIG. 3 shows a partial magnified view (magnified 50000 times) of the sectional view of the film in FIG. 7.

The BMED apparatus and procedure were as in example 2 and the results show that: under the condition of constant current of 0.07A, the recovery rate of lysine molecules is 63.0 percent, the purity is about 100 percent, the current efficiency is 51.0 percent, and the energy consumption is 9.53 kW.h/kg. During the experimental operation, the pH of the recovery chamber has small change and is stabilized in the range of 9.78-9.91.

From the above analysis results, it is found that the SPES-D-4 membrane obtained in this example also has a finger-shaped pore structure, and thus the SPES-D-4 membrane still has a great improvement in the recovery rate of lysine and the current efficiency as compared with the reference membrane CMX.

Example 5 preparation of porous sulfonated polysulfone Membrane SPSf-4 by Low temperature phase inversion

This example was prepared as the SPES-4 membrane of example 1, except that: and (3) replacing sulfonated polyethersulfone powder with sulfonated polysulfone powder, wherein the ion exchange capacity of the sulfonated polyethersulfone is 0.1mmol/g, and the obtained membrane is named as SPSf-4 membrane.

For comparison, a sulfonated polysulfone dense membrane was also prepared, which was prepared in the same manner as the sulfonated polyethersulfone dense membrane of example 1, except that: and (3) replacing sulfonated polyethersulfone powder with sulfonated polysulfone powder, and naming the obtained membrane as the sulfonated polysulfone dense membrane.

The test shows that the water content of the SPSf-4 film is 289.1%; tensile strength of 2.61MPa and surface resistance of 0.35 omega cm²。

The infrared spectrum of the SPSf-4 film is shown in FIG. 3(d), at 2800-^-1A characteristic absorption peak of-CH appears; at-1030 cm^-1And 1170-1190cm^-1Respectively are the symmetric and asymmetric telescopic vibration absorption peaks of the sulfonic group; at 1240cm^-1And 714-^-1The peak values of (a) are due to the vibration of C-O-C and C ═ C, respectively; the above results indicate that the sulfonated polysulfone material contains-SO 3-groups.

FIG. 8 shows a SEM image of the SPSf-4 film, in which FIG. 8 shows a full-scale cross-sectional view (magnified 300 times) of the film in FIG. 8, FIG. 2 shows a partially magnified view (magnified 5000 times) of the cross-sectional surface of the film in FIG. 8, and FIG. 3 shows a partially magnified view (magnified 50000 times) of the cross-sectional surface of the film in FIG. 8.

The BMED apparatus and procedure were as in example 2 and the results show that: under the condition of constant current of 0.07A, the recovery rate of lysine molecules is 74.4%, the purity is 86.1%, the current efficiency is 63.1%, and the energy consumption is 4.82 kW.h/kg. During the experimental operation, the pH variation of the recovery chamber is small and is stabilized in the range of 9.30-9.83.

The water content of the comparative sulfonated polysulfone dense membrane was 5.8%; the tensile strength is 49.97MPa, and the surface resistance is more than 80 omega cm². When BMED experiments were carried out using dense membranes of sulfonated polyethersulfone, it was found that the voltage required was too high to be in the range of the power source (60V), and BMED experiments could not be carried out under the same conditions.

From the analysis results, the SPSf-4 membrane obtained in the embodiment also contains a finger-shaped pore structure, so that the SPSf-4 membrane has great advantages over the commercial CMX membrane in the aspects of the recovery rate, the current efficiency and the energy consumption of lysine; moreover, the water content of the SPSf-4 membrane is larger than that of the SPES-4 membrane, and the upper skin layer of the SPSf-4 membrane contains large oval pores, so that lysine molecules can more easily migrate through the membrane, and the SPSf-4 membrane is more advantageous than the SPES-4 membrane in terms of the recovery rate, current efficiency and energy consumption of lysine; however, the elliptical macroporous structure of the upper cortex also causes leakage of a certain amount of glutamic acid molecules, so that the purity of the lysine product is reduced.

Example 6 preparation of porous sulfonated polysulfone Membrane (SPSf-25) by Normal temperature phase inversion

The preparation method of this example is the same as that of the SPSf-4 film in example 5, except that: and in the process of carrying out phase inversion on the coated substrate in water, the water temperature is 25 ℃, and the obtained film is named as SPSf-25.

The test shows that the water content of the SPSf-25 membrane is 370.1 percent; tensile strength of 1.77MPa and surface resistance of 0.81 omega cm². The IR spectrum of the film is shown in FIG. 3(e), and the characteristic absorption peak is the same as that of the SPSf-4 film in example 5.

The SPSf-25 membrane field emission scanning electron microscope is shown in FIG. 9, the diagram (a-1) is a cross-sectional overall view (magnified 300 times), the diagram (a-2) is a partial magnified view (magnified 5000 times) of the membrane cross-section, and the diagram (a-3) is a partial magnified view (magnified 50000 times) of the membrane cross-section, and it can be seen from FIG. 9 that the membrane cross-section also contains finger-shaped pores, but the upper skin layer of the membrane contains elliptical pores smaller than those of the SPSf-4 membrane, indicating that the pore size of the upper skin layer of the sulfonated polysulfone membrane is related to the water temperature in the phase inversion process.

The BMED apparatus and procedure were the same as in example 2, and SPSf-25 membrane was applied to the BMED procedure, and the results showed that: under the condition of constant current of 0.07A, the recovery rate of lysine molecules is 71.6 percent, the purity is 84.7 percent, the current efficiency is 54.3 percent, and the energy consumption is 6.52 kW.h/kg. During the experimental operation, the pH of the recovery chamber has small change and is stabilized in the range of 9.51-9.82.

From the above analysis results, it can be seen that the SPSf-25 membrane obtained in this example also has a finger-shaped pore structure, and thus has great advantages over the commercial CMX membrane in terms of lysine recovery, current efficiency and energy consumption. In addition, the elliptical pores of the epithelial layer of the SPSf-25 membrane are smaller than those of the SPSf-4 membrane, so that the membrane is slightly inferior to the SPSf-4 membrane in terms of the recovery rate of lysine, current efficiency and energy consumption.

The results of the BMED experiments on the homemade SPES-4, SPES-25, SPES-D-4, SPSf-4 and SPSf-25 membranes and the commercial CMX membranes of the above examples are summarized as shown in Table 1:

TABLE 1 BMED results data Table for porous sulfonated polyethersulfone membranes, sulfonated polysulfone membranes, and commercial membrane CMX prepared in accordance with the inventive examples

Table 1 shows that after running for 6h under the same conditions, the homemade porous sulfonated polyethersulfone membrane yielded much higher recovery and current efficiency of lysine than the commercial CMX membrane, with a lysine purity of about 100%. Therefore, the sulfonated polyethersulfone membrane prepared by the invention is easier to migrate lysine molecules to the recovery chamber when separating the mixed solution of glutamic acid and lysine, and the porous structure of the sulfonated polyethersulfone membrane can reduce the resistance of the lysine molecules to migrate through the membrane. Compared with a commercial membrane CMX, the home-made porous sulfonated polysulfone membrane has higher lysine recovery rate and current efficiency and lower energy consumption in BMED application; the sulfonated polysulfone membrane prepared by the invention has great advantages in separating the mixed solution of glutamic acid and lysine compared with the commercial membrane CMX.

By combining the experimental results, the porous sulfonated polyether sulfone membrane and the sulfonated polysulfone membrane prepared by the invention have obvious advantages compared with commercial CMX membranes in the aspect of separating mixed liquor of glutamic acid and lysine by being used as cation exchange membranes of the bipolar membrane electrodialysis device.

The above description of the embodiments is only intended to facilitate the understanding of the method of the invention and its core idea. It should be noted that, for those skilled in the art, it is possible to make various improvements and modifications to the present invention without departing from the principle of the present invention, and those improvements and modifications also fall within the scope of the claims of the present invention.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for separating amino acid mixed liquor by using a bipolar membrane electrodialysis device is characterized by comprising the following steps:

starting the first peristaltic pump, the second peristaltic pump and the third peristaltic pump, starting the direct-current power supply, and transferring the second amino acid in the feed liquid tank to the recovery tank after operation to obtain the separated first amino acid and the second amino acid;

the cation exchange membrane of the bipolar membrane electrodialysis device is a sulfonated polyether sulfone membrane;

the preparation method of the sulfonated polyether sulfone membrane comprises the following steps:

performing phase conversion on sulfonated polyether sulfone in water to obtain a sulfonated polyether sulfone membrane; the temperature of the water is 0-35 ℃.

2. The method according to claim 1, wherein the sulfonated polyethersulfone has an ion exchange capacity of 0.15 to 0.4 mmol/g.

3. The method according to claim 1, wherein during the preparation of the sulfonated polyethersulfone membrane, the phase inversion process comprises:

coating the coating liquid on a substrate, and soaking in water to obtain a sulfonated polyether sulfone membrane; the organic solvent is N-methyl pyrrolidone or a mixed solution of N-methyl pyrrolidone and dichloromethane.

4. A method for separating amino acid mixed liquor by using a bipolar membrane electrodialysis device is characterized by comprising the following steps:

the cation exchange membrane of the bipolar membrane electrodialysis device is a sulfonated polysulfone membrane;

the preparation method of the sulfonated polysulfone membrane comprises the following steps:

performing phase conversion on sulfonated polysulfone in water to obtain a sulfonated polysulfone membrane; the temperature of the water is 0-35 ℃.

5. The method according to claim 4, wherein the sulfonated polysulfone has an ion exchange capacity of 0.08 to 0.4 mmol/g.

6. The method according to claim 4, wherein during the preparation of the sulfonated polysulfone membrane, the phase inversion process is specifically:

coating the coating liquid on a substrate, and soaking in water to obtain a sulfonated polysulfone membrane; the organic solvent is N-methyl pyrrolidone or a mixed solution of N-methyl pyrrolidone and dichloromethane.

7. The method of claim 1 or 4, wherein the first amino acid is glutamic acid and the second amino acid is lysine; the concentration of glutamic acid in the feed liquid tank is 0.02-0.1 mol/L, the concentration of lysine in the feed liquid tank is 0.02-0.1 mol/L, and the concentration ratio of glutamic acid to lysine is (1-5): (1-5); the concentration of lysine in the recovery tank is 0.005-0.03 mol/L.