Method for continuously and industrially producing monovalent ion selective anion exchange membrane and application of membrane

Abstract

The invention discloses a method for continuously and industrially producing a monovalent ion selective anion exchange membrane and application of the membrane. The method comprises the following steps: unwinding a dry anion exchange membrane roll, soaking the dry anion exchange membrane roll in a water tank, discharging the dry anion exchange membrane roll out of the water tank, sequentially feeding the dry anion exchange membrane roll into two electro-deposition tanks for electro-deposition, and sequentially and uniformly electro-depositing a sulfonic acid group-containing polymer and polyethyleneimine on one surface of the anion exchange membrane; spraying a glutaraldehyde aqueous solution on the surface of an electro-deposition layer of the cation exchange membrane in a spraying device, compounding with a polyester film, carrying out a cross-linking reaction in a drying device, and separating the polyester film from the anion exchange membrane after the polyester film is discharged from the drying device; wherein the anion exchange membrane is washed and rolled to obtain the monovalent ion selective anion exchange membrane with low membrane resistance and high monovalent anion selective permeability. The invention provides the application of the prepared monovalent ion selective anion exchange membrane in lithium extraction by salt lake old brine electrodialysis, and the energy consumption can be obviously reduced.

Description

Technical Field

[0001] The present invention belongs to the technical fields of functional polymer materials and electro-driven membrane separation technology, and particularly relates to a method for continuously and industrially producing a monovalent ion-selective anion exchange membrane and the application of the obtained membrane in the electrodialysis lithium extraction from old brine in salt lakes. Background Art

[0002] On the one hand, with the shrinking of fossil mineral resources reserves and the shortage of water resources, people are urged to explore the extraction of rich ions or fresh water resources from salt lake brines and seawaters, such as calcination, salting out, solvent extraction, precipitation, and adsorption to extract useful ions. However, this brings inevitable environmental pollution problems, thus limiting the application of these methods in the context of sustainable development. On the other hand, there are many harmful ions in drinking water, such as bromide ions, etc., which must be removed from the water. Membrane separation technology, especially ion exchange membranes, is an ion separation method with economy, environmental protection, and high selectivity, which can achieve the selective separation of corresponding ions from concentrated aqueous solutions containing chemically similar ions. In recent years, a large number of studies have focused on exploring many new methods and technologies for effective separation of mono- and divalent ions. Currently, the main mechanisms for the selective separation of monovalent anions are: 1) electrostatic repulsion effect; 2) pore size sieving effect; and 3) properties of ion-adsorbing membrane groups. However, at present, the monovalent ion-selective anion exchange membranes are produced by an intermittent production method. Meanwhile, the production process is complex, the production time is long, the production cost is high, and it is difficult to achieve continuous industrial production.

[0003] Chinese Patent Invention 201710119805.1 discloses a preparation method of a monovalent-selective anion exchange membrane. The preparation method is as follows: (1) First, a mixed solution of NSBC and NaCl is added to the feed liquid chamber, a NaCl solution is added to the concentrated chamber, and the Na2SO4 solution fills electrode chamber A and electrode chamber B. Then, the electro-pulse parameters are set, and an electro-pulse deposition is carried out by energization to deposit NSBC on the anion exchange membrane; (2) After depositing for a certain time, the solution in the feed liquid chamber is replaced with a mixed solution of HACC and NaCl, and the current directions on both sides are exchanged, and the electro-pulse deposition is continued while keeping the electro-pulse parameters unchanged to deposit HACC on the anion exchange membrane; (3) The operations of steps (1) and (2) are repeated, so that NSBC sugar and HACC are alternately deposited on the anion exchange membrane to obtain an anion exchange membrane with multiple layers of NSBC / HACC attached. The method for preparing the monovalent anion exchange membrane by using this invention cannot carry out continuous industrial production, and can only adopt an intermittent production method. Meanwhile, the production process is complex, the production time is long, and the production cost is high. Summary of the Invention

[0004] The object of the present invention is to provide a method for continuously and industrially producing a monovalent ion-selective anion exchange membrane and the application of the obtained membrane in the electrodialysis lithium extraction from old brine in salt lakes, so as to solve the technical problem that the current monovalent ion-selective anion exchange membrane cannot achieve industrial continuous production.

[0005] The above technical problem of the present invention is mainly solved by the following technical solutions:

[0006] In the first aspect, the present invention provides a method for continuously and industrially producing a monovalent ion-selective anion exchange membrane,

[0007] The method comprises the following steps:

[0008] After the anion exchange membrane dry film roll is unrolled by the first unrolling device, it enters a water tank filled with an aqueous sodium chloride solution for soaking, and after leaving the water tank, it enters the first electro-deposition tank for electro-deposition. The first electro-deposition solution in the first electro-deposition tank is a mixed solution composed of sodium chloride, water, and a polymer containing sulfonic acid groups. During the electro-deposition process, the total organic carbon content in the first electro-deposition solution is monitored in real time by the first total organic carbon on-line detection analyzer, and the monitoring result is fed back to the PLC control system (programmable logic controller control system). The addition of the first replenishing solution is controlled by the PLC control system. The first replenishing solution is a mixed solution composed of sodium chloride, water, and a polymer containing sulfonic acid groups. The sodium chloride concentration in the first replenishing solution is the same as that in the first electro-deposition solution, but the polymer concentration containing sulfonic acid groups is higher than that in the first electro-deposition solution. When the total organic carbon content in the first electro-deposition solution is reduced to 0.9 times the initial value, the first replenishing solution is added to the first electro-deposition tank to supplement the consumed polymer containing sulfonic acid groups. When the total organic carbon content in the first electro-deposition solution reaches 1.1 times the initial value, the first replenishing solution is no longer added, so as to maintain the basic constancy of the total organic carbon content in the first electro-deposition solution in the first electro-deposition tank (representing the basic constancy of the polymer content containing sulfonic acid groups), thereby realizing the uniform electro-deposition of the polymer containing sulfonic acid groups on one surface of the anion exchange membrane;

[0009] After the anion exchange membrane exits the first electroplating tank, it enters the second electroplating tank for electroplating. The second electroplating solution in the second electroplating tank is a mixed solution composed of sodium chloride, water, and polyethyleneimine (PEI). During the electroplating process, the total organic carbon content in the second electroplating solution is monitored in real time by a second total organic carbon on-line analyzer, and the monitoring results are fed back to the PLC control system (programmable logic controller control system). The addition of the second replenishing solution is controlled by the PLC control system. The second replenishing solution is a mixed solution composed of sodium chloride, water, and polyethyleneimine (PEI). The concentration of sodium chloride in the second replenishing solution is the same as that in the second electroplating solution, but the concentration of polyethyleneimine is higher than that in the second electroplating solution. When the total organic carbon content in the second electroplating solution is as low as 0.9 times the initial value, the second replenishing solution is added to the second electroplating tank to supplement the consumed polyethyleneimine. When the total organic carbon content in the second electroplating solution is as high as 1.1 times the initial value, the second replenishing solution is no longer added, so as to maintain the basic constancy of the total organic carbon content in the second electroplating solution in the second electroplating tank (representing the basic constancy of the polyethyleneimine (PEI) content), thereby realizing the uniform electroplating of polyethyleneimine onto the surface of the electroplated layer of the anion exchange membrane;

[0010] After the anion exchange membrane exits the second electroplating tank, it enters a spraying device to spray an aqueous glutaraldehyde solution onto the surface of the electroplated layer of the anion exchange membrane. Then, the electroplated surface after spraying the aqueous glutaraldehyde solution is compounded with a polyester film to protect the surface of the anion exchange membrane after spraying the aqueous glutaraldehyde solution. Then, it enters a drying device for cross-linking reaction. After exiting the drying device, the polyester film and the anion exchange membrane are separated. The anion exchange membrane is washed with water and then wound up to obtain a monovalent ion-selective anion exchange membrane.

[0011] In the present invention, the liquid in the water tank is an aqueous sodium chloride solution, and preferably the weight ratio of sodium chloride to water is the same as that in the first electroplating solution. This step can avoid the decrease in the sodium chloride concentration in the first electroplating tank due to foam formation.

[0012] In the present invention, a polymer containing sulfonic acid groups is first electrodeposited on one surface of the anion exchange membrane. This is because the anion exchange membrane is positively charged, and directly electrodepositing the positively charged PEI will cause mutual repulsion between the same charges. By first electrodepositing a negatively charged polymer containing sulfonic acid groups, the repulsion problem between the membrane and PEI can be effectively solved, which is beneficial to the bonding strength between the electrodeposited PEI and the membrane. In the electrodeposition step, since the polymer containing sulfonic acid groups in the first electrodeposition solution in the first electrodeposition tank is continuously consumed during the electrodeposition process, the concentration of the polymer containing sulfonic acid groups in the first electrodeposition solution continuously decreases, which will affect the thickness uniformity of the polymer deposition layer containing sulfonic acid groups, resulting in a decrease in the selectivity of mono- and polyvalent cations. Therefore, the present invention provides an on-line total organic carbon analyzer to continuously monitor the total organic carbon content in the first electrodeposition solution in the first electrodeposition tank, and feed back the real-time monitoring results to the PLC control system. Through the PLC control system, the addition of the first replenishing solution is controlled to timely supplement the consumed polymer containing sulfonic acid groups into the first electrodeposition tank and maintain the basic constancy of the total organic carbon content (representing the content of the polymer containing sulfonic acid groups) in the first electrodeposition solution in the first electrodeposition tank, so as to realize the uniform electrodeposition of the polymer containing sulfonic acid groups on the surface of the anion exchange membrane. Similarly, the on-line total organic carbon analyzer is also used to maintain the basic constancy of the total organic carbon content (representing the content of PEI) in the second electrodeposition solution in the second electrodeposition tank, so as to realize the uniform electrodeposition of PEI on the surface of the electrodeposition layer of the anion exchange membrane.

[0013] In the electrodeposition step of the first electrodeposition tank of the present invention, the thickness of the electrodeposited layer of the polymer containing sulfonic acid groups will affect the performance of the mono-valent ion selective anion exchange membrane. If the thickness of the electrodeposited layer of the polymer containing sulfonic acid groups is too thin, the selectivity of mono- and polyvalent anions will decrease; if the thickness of the electrodeposited layer of the polymer containing sulfonic acid groups is too thick, it will affect the flux of mono-valent ions. Further, the feeding mass ratio of sodium chloride: water: polymer containing sulfonic acid groups in the first electrodeposition solution is 18 - 30:1000:0.1 - 0.3; the current density of electrodeposition is 1 - 5 mA / cm 2 , the temperature of electrodeposition is 25 - 35 °C, and the electrodeposition time is 30 - 60 minutes, wherein the electrodeposition time is controlled by the unwinding speed of the dry film roll of the anion exchange membrane through the first unwinding device and the length of the first electrodeposition tank (7). Further still, in the first replenishing solution, the feeding weight ratio of sodium chloride, water, and polymer containing sulfonic acid groups is 18 - 30:1000:1 - 3.

[0014] Further, the polymer containing sulfonic acid groups is sulfonated polyether ether ketone (SPEEK) or sulfonated polyether sulfone (SPES); the exchange capacity of the polymer containing sulfonic acid groups is 1.3 - 1.6 mmol / g.

[0015] In the electrodeposition step of the second electrodeposition tank of the present invention, the thickness of the PEI electrodeposited layer affects the performance of the monovalent ion selective anion exchange membrane. If the thickness of the PEI electrodeposited layer is too thin, the selectivity of mono- and multivalent anions decreases; if the thickness of the PEI electrodeposited layer is too thick, it will affect the flux of monovalent ions. Further, the thickness of the PEI electrodeposited layer is controlled by controlling the electrodeposition conditions: the weight ratio of sodium chloride, water, and polyethyleneimine (PEI) in the second electrodeposition solution is 18-30:1000:0.1-0.5, and the current density of electrodeposition is 1-5 mA / cm 2 , the temperature of electrodeposition is 25-35 °C, and the electrodeposition time is 30-60 minutes, where the electrodeposition time is controlled by the unwinding speed of the anion exchange membrane and the length of the second electrodeposition tank. Further, in the second replenishing solution, the weight ratio of sodium chloride, water, and polyethyleneimine (PEI) is 18-30:1000:1-5. In the present invention, selecting high-molecular-weight PEI is beneficial to extending the service life of the monovalent ion selective anion exchange membrane compared to low-molecular-weight PEI. Preferably, the molecular weight of the polyethyleneimine (PEI) is 500,000-750,000.

[0016] In the present invention, the crosslinking agent glutaraldehyde is introduced by spraying. After spraying glutaraldehyde, a polyester film is covered on the spraying surface and then enters the drying device, which can avoid the volatilization of glutaraldehyde and ensure that PEI and glutaraldehyde can be fully crosslinked. Otherwise, the crosslinking is insufficient, which affects the selectivity of mono- and multivalent anions on the one hand, and on the other hand, it is easy to fall off during actual use, shortening the service life of the monovalent ion selective anion exchange membrane. Preferably, the mass concentration of the glutaraldehyde aqueous solution used for spraying is 0.1-0.5%, and the spraying amount is controlled by a third metering pump. The spraying amount is 10-20 g / m calculated by the mass of the glutaraldehyde aqueous solution sprayed on each square meter of the anion exchange membrane 2 . The crosslinking reaction is carried out in the drying device, and the crosslinking degree is controlled by controlling the crosslinking conditions: the temperature in the drying device is controlled at 35-45 °C, and the crosslinking reaction time is controlled at 30-60 min, where the crosslinking reaction time is controlled by the unwinding speed of the anion exchange membrane through the first unwinding device and the length of the drying device.

[0017] In the present invention, it is preferred that the unwinding speed of the dry film roll of the anion exchange membrane through the first unwinding device is 0.2-0.3 m / min.

[0018] In the present invention, the liquid in the water washing tank is water.

[0019] In the second aspect, the present invention provides an application of a monovalent ion selective anion exchange membrane prepared by the method according to the first aspect in the electrodialysis lithium extraction from old brine in salt lakes.

[0020] The above-mentioned lithium extraction from old brine in salt lakes by electrodialysis refers to the use of a two-compartment electrodialysis device assembled by arranging monovalent ion-selective cation exchange membranes and monovalent ion-selective anion exchange membranes in the order of cation / anion / cation / anion / cation for lithium extraction from old brine in salt lakes. The two compartments are a desalination compartment and a concentration compartment. The feed liquid in the desalination compartment is old brine in salt lakes, and the feed liquid in the concentration compartment is pure water.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] First, the continuous industrial production of monovalent ion-selective anion exchange membranes is realized, the labor intensity is reduced, the product quality is improved, and the production cost is also reduced.

[0023] Second, by performing single-sided electrodeposition of a PEI layer and single-sided chemical cross-linking on the anion exchange membrane, the membrane resistance can be reduced and the monovalent anion selective permeability of the membrane can be improved on the basis of ensuring that the flux of monovalent anions is not reduced.

[0024] Third, by performing single-sided electrodeposition of a polymer layer containing sulfonic acid groups on the anion exchange membrane, it is beneficial to improve the bonding fastness of the electrodeposited PEI layer.

[0025] Fourth, the monovalent ion-selective anion exchange membrane prepared by the present invention is used for lithium extraction from old brine in salt lakes by electrodialysis. Compared with the existing monovalent ion-selective anion exchange membrane, it can operate at a lower voltage and has lower energy consumption. Description of the Drawings

[0026] Figure 1 It is a process flow chart of the continuous production process of the monovalent ion-selective anion exchange membrane of the present invention.

[0027] 1 - First unwinding device, 2 - Water tank, 3 - First anode membrane tube, 4 - First replenishing tank, 5 - First metering pump, 6 - First cathode membrane tube, 7 - First electrodeposition tank, 8 - First pump, 9 - First overflow port, 10 - First circulation pipeline, 11 - Second cathode membrane tube, 12 - Second replenishing tank, 13 - Second metering pump, 14 - Second anode membrane tube, 15 - Second electrodeposition tank, 16 - Second pump, 17 - Second overflow port, 18 - Second circulation pipeline, 19 - Spraying device, 20 - Second unwinding device, 21 - Drying device, 22 - First winding device, 23 - Water washing tank, 24 - Second winding device, 25 - First heat exchange device, 26 - First heating device, 27 - Second heat exchange device, 28 - Second heating device, 29 - Manual tension device, 30 - Third replenishing tank, 31 - Third metering pump, 32 - First total organic carbon on-line analyzer, 33 - Second total organic carbon on-line analyzer. Detailed Embodiments

[0028] The present invention will be further described below in conjunction with specific embodiments.

[0029] In the embodiments of the present invention, those without specific conditions are carried out according to conventional conditions or conditions recommended by the manufacturer. For reagents or instruments without indicating the manufacturer, they are all conventional products that can be obtained by conventional technical means or purchased commercially.

[0030] The special devices used in the embodiments include a first total organic carbon on-line detection analyzer 32, a second total organic carbon on-line detection analyzer 33, and a first unwinding device 1, a water tank 2, a first electro-deposition tank 7, a second electro-deposition tank 15, a spraying device 19, a second unwinding device 20, a drying device 21, a first winding device 22, a water washing tank 23, and a second winding device 24 arranged in sequence; between the first unwinding device 1 and the water tank 2, inside the water tank 2, between the water tank 2 and the first electro-deposition tank 7, inside the first electro-deposition tank 7, between the first electro-deposition tank 7 and the second electro-deposition tank 15, inside the second electro-deposition tank 15, between the second electro-deposition tank 15 and the spraying device 19, between the spraying device 19 and the drying device 21, between the second unwinding device 20 and the drying device 21, between the drying device 21 and the first winding device 22, between the drying device 21 and the water washing tank 23, inside the water washing tank 23, and between the water washing tank 23 and the second winding device 24, there are all over rollers for transporting the anion exchange membrane dry film and / or the polyester film; above the first electro-deposition tank 7, a first replenishing tank 4 is installed, the bottom of the first replenishing tank 4 is communicated with the first electro-deposition tank 7 through a first connecting pipe, and a first metering pump 5 is arranged on the first connecting pipe; outside the first electro-deposition tank 7, a first circulation pipeline is provided to circulate the first electro-deposition liquid in the first electro-deposition tank 7, and the probe or sampling needle of the first total organic carbon on-line detection analyzer 32 is arranged in the first circulation pipeline to monitor the total organic carbon content in the first electro-deposition liquid of the first electro-deposition tank 7 in real time; above the second electro-deposition tank 15, a second replenishing tank 12 is installed, the bottom of the second replenishing tank 12 is communicated with the second electro-deposition tank 15 through a second connecting pipe, and a second metering pump 13 is arranged on the second connecting pipe; outside the second electro-deposition tank 15, a second circulation pipeline is provided to circulate the second electro-deposition liquid in the second electro-deposition tank 15, and the probe or sampling needle of the second total organic carbon on-line detection analyzer 33 is arranged in the second circulation pipeline to monitor the total organic carbon content in the second electro-deposition liquid of the second electro-deposition tank 15 in real time.

[0031] Further, the first electro-deposition tank 7 includes a first liquid storage tank, a first cathode membrane tube 6, a first anode membrane tube 3, a first heat exchange device 25, a first heating device 26, a first circulation pipeline 10 and a first pump 8. The first cathode membrane tube 6 and the first anode membrane tube 3 are respectively arranged at the upper and lower parts of the over-roller in the first liquid storage tank. The lower side of the first liquid storage tank is communicated with the inlet of the first liquid storage tank through the first circulation pipeline 10, and the first circulation pipeline 10 is provided with a first pump 8, a first heat exchange device 25 and a first heating device 26. The first cathode membrane tube 6 and the first anode membrane tube 3 are respectively connected to the negative electrode and the positive electrode, and the first cathode membrane tube 6 and the first anode membrane tube 3 are respectively provided with inlets and outlets for the electrode solution. Further, a first overflow port 9 is provided on the upper side of the first liquid storage tank.

[0032] Further, the second electro-deposition tank 15 includes a second liquid storage tank, a second cathode membrane tube 11, a second anode membrane tube 14, a second heat exchange device 27, a second heating device 28, a second circulation pipeline 18 and a second pump 16. The second anode membrane tube 14 and the second cathode membrane tube 11 are respectively arranged at the upper and lower parts of the over-roller in the second liquid storage tank. The lower side of the second liquid storage tank is communicated with the inlet of the second liquid storage tank through the second circulation pipeline 18, and the second circulation pipeline 18 is provided with a second pump 16, a second heat exchange device 27 and a second heating device 28. The second cathode membrane tube 11 and the second anode membrane tube 14 are respectively connected to the negative electrode and the positive electrode, and the second cathode membrane tube 11 and the second anode membrane tube 14 are respectively provided with inlets and outlets for the electrode solution. Further, a first overflow port 17 is provided on the upper side of the second liquid storage tank.

[0033] Further, the spraying device 19 includes a spray head, a third metering pump 31 and a third liquid replenishing tank 30. The spray head is arranged below the third metering pump 21 and the spraying direction of the spray head is aligned with the surface of the anion exchange membrane electro-deposition layer. The third metering pump controls the spraying amount.

[0034] Further, the drying device 21 includes an oven, a heating pack, an exhaust and a valve, an internal circulation and a valve, a fresh air and a valve, a lower air inlet and a valve, an upper air inlet and a valve, and a circulation fan.

[0035] Further, the special device further includes a manual tension regulating valve 29. The manual tension regulating valve 29 is arranged between the spraying device 19 and the drying device 21 to ensure uniform fitting of the anion exchange membrane and the polyester film.

[0036] Further, the membranes in the first cathode membrane tube 6, the second cathode membrane tube 11, the first anode membrane tube 3 and the second anode membrane tube 14 are all anion exchange membranes.

[0037] Further, the first winding device 22 is used for winding polyester film, the second winding device 24 is used for winding monovalent ion selective anion exchange membrane, and deviation rectifiers are respectively provided on the first winding device 22 and the second winding device 24.

[0038] The first and second total organic carbon on-line detection analyzers used in the embodiments of the present invention are both HACH BIOTECTOR B7000 on-line total organic carbon (TOC) analyzers. The polyester film is PET film. The exchange capacity of the sulfonated polyether ether ketone (SPEEK) is 1.3 mmol / g, and the exchange capacity of the sulfonated polyether sulfone (SPES) is 1.5 mmol / g.

[0039] Examples 1-9

[0040] A preparation method for continuously and industrially producing a monovalent ion selective anion exchange membrane, the steps of which are as follows:

[0041] After the anion exchange membrane dry film roll is unwound by the first unwinding device 1, it enters the water tank 2 for soaking, and after leaving the water tank 2, it enters the first electroplating tank 7 for electroplating. The first electroplating solution in the first electroplating tank 7 is a mixed solution composed of sodium chloride, water, and a polymer containing sulfonic acid groups. The first replenishing solution contained in the first replenishing tank 7 is also a mixed solution composed of sodium chloride, water, and a polymer containing sulfonic acid groups. The concentration of sodium chloride in the first replenishing solution is the same as that in the first electroplating solution, but the concentration of the polymer containing sulfonic acid groups is higher than that in the first electroplating solution. During the electroplating process, the first electroplating solution in the first electroplating tank is pumped out by the first pump 8 and then exchanges heat with the hot water heated by the first heating device 26 through the first heat exchange device 25 to control the temperature of the first electroplating solution in the first electroplating tank 7. At the same time, the probe of the first total organic carbon on-line detection analyzer 32 is placed in the first circulation pipeline 10, and the total organic carbon content in the first electroplating solution is monitored in real time by the first total organic carbon on-line detection analyzer 32, and the monitoring result is fed back to the PLC control system. The opening and closing of the first metering pump 5 are controlled by the PLC control system. That is, when the total organic carbon content in the first electroplating solution is reduced to 0.9 times the initial value, the first metering pump 5 is opened to supplement the consumed polyethyleneimine PEI into the first electroplating tank 7. When the total organic carbon content in the first electroplating solution is as high as 1.1 times the initial value, the first metering pump 5 is closed. If the liquid level height of the first electroplating solution in the first electroplating tank 7 reaches the first overflow port 9, the first electroplating solution will flow out through the first overflow port 9, so as to maintain the basic constancy of the total organic carbon content in the first electroplating solution in the first electroplating tank 7, thereby realizing the uniform electroplating of the polymer containing sulfonic acid groups onto one surface of the anion exchange membrane;

[0042] After the anion exchange membrane exits the first electroplating bath 7, it enters the second electroplating bath 15 for electroplating. The second electroplating solution in the second electroplating bath 15 is a mixed solution composed of sodium chloride, water, and polyethyleneimine. The second replenishing solution contained in the second replenishing tank 12 is also a mixed solution composed of sodium chloride, water, and polyethyleneimine. The sodium chloride concentration in the second replenishing solution is the same as that in the second electroplating solution, but the polyethyleneimine concentration is higher than that in the second electroplating solution. During the electroplating process, after the second electroplating solution in the second electroplating bath 15 is pumped out by the second pump 18, the second electroplating solution exchanges heat with the hot water heated by the second heating device 28 through the second heat exchange device 27 to control the temperature of the second electroplating solution in the second electroplating bath 15. At the same time, the probe of the second total organic carbon on-line analyzer 33 is placed in the second circulation pipeline 18, and the total organic carbon content in the second electroplating solution is monitored in real time by the second total organic carbon on-line analyzer 33 and the monitoring result is fed back to the PLC control system. The opening and closing of the second metering pump 13 are controlled through the PLC control system. That is, when the total organic carbon content in the second electroplating solution is as low as 0.9 times the initial value, the second metering pump 13 is opened to supplement the consumed polyethyleneimine into the second electroplating bath 15. When the total organic carbon content in the second electroplating solution is as high as 1.1 times the initial value, the second metering pump 13 is closed. If the liquid level height of the second electroplating solution in the second electroplating bath 15 reaches the second overflow port 17, the second electroplating solution will flow out through the second overflow port 17, so as to maintain the basic constancy of the total organic carbon content in the second electroplating solution in the second electroplating bath 15, thereby realizing the uniform electroplating of polyethyleneimine onto the electroplated layer surface of the anion exchange membrane;

[0043] After the anion exchange membrane exits the second electroplating bath 15, it enters the spraying device 9 to spray an aqueous glutaraldehyde solution onto the electroplated layer surface of the cation exchange membrane. The spray head is arranged below the third metering pump 21 and the spraying direction of the spray head is aligned with the electroplated layer surface of the anion exchange membrane. The third replenishing tank 30 contains an aqueous glutaraldehyde solution. The third metering pump 31 controls the spraying amount. After spraying, the sprayed surface of the anion exchange membrane is compounded with the polyester film unrolled by the second unwinding device 20, and then enters the drying device 21 for cross-linking reaction. After exiting the drying device 21, the polyester film and the anion exchange membrane are separated. The polyester film is wound by the first winding device 22, and the anion exchange membrane enters the water washing tank 23 for water washing. After exiting the water washing tank 23, it reaches the second winding device 24, and the wet film is wound up, that is, a monovalent ion-selective anion exchange membrane is obtained.

[0044] The specific process parameters and performance are shown in the following table. In Examples 1 to 7 and Comparative Example 1, the homogeneous anion exchange membrane of Zhejiang Baichen Low-Carbon Technology Co., Ltd. was used. The anion exchange membranes used in the first cathode membrane tube 6, the second cathode membrane tube 11, the first anode membrane tube 3, and the second anode membrane tube 14 were polyethylene heterogeneous anion exchange membranes produced by Shanghai Shanghua Water Treatment Materials Co., Ltd. Among them, Examples 1 to 7 were surface-modified according to the process in the following table, Comparative Example 1 was not surface-modified, and Comparative Example 2 used an imported single-valent anion selective exchange membrane (ACS).

[0045] Comparative Example 3

[0046] A preparation method for continuously industrially producing a single-valent ion selective anion exchange membrane, the steps of which are as follows:

[0047] After the dry film roll of the anion exchange membrane is unrolled by the first unrolling device 1, it enters the water tank 2 for soaking. After leaving the water tank 2, it enters the first electro-deposition tank 7 for electro-deposition. The first electro-deposition solution in the first electro-deposition tank 7 is a mixed solution composed of sodium chloride, water, and a polymer containing sulfonic acid groups. The first replenishing solution contained in the first replenishing tank 7 is also a mixed solution composed of sodium chloride, water, and a polymer containing sulfonic acid groups. Among them, the concentration of sodium chloride in the first replenishing solution is the same as that in the first electro-deposition solution, but the concentration of the polymer containing sulfonic acid groups is higher than that in the first electro-deposition solution. During the electro-deposition process, the first electro-deposition solution in the first electro-deposition tank is pumped out by the first pump 8 and then exchanges heat with the hot water heated by the first heating device 26 through the first heat exchange device 25 to control the temperature of the first electro-deposition solution in the first electro-deposition tank 7. At the same time, the probe of the first total organic carbon on-line detection analyzer 32 is placed in the first circulation pipeline 10, and the total organic carbon content in the first electro-deposition solution is monitored in real time by the first total organic carbon on-line detection analyzer 32, and the monitoring result is fed back to the PLC control system. The opening and closing of the first metering pump 5 are controlled by the PLC control system. That is, when the total organic carbon content in the first electro-deposition solution is reduced to 0.9 times the initial value, the first metering pump 5 is opened to supplement the consumed polyethyleneimine PEI into the first electro-deposition tank 7. When the total organic carbon content in the first electro-deposition solution is as high as 1.1 times the initial value, the first metering pump 5 is closed. If the liquid level height of the first electro-deposition solution in the first electro-deposition tank 7 reaches the first overflow port 9, the first electro-deposition solution will flow out through the first overflow port 9, so as to maintain the basic constancy of the total organic carbon content in the first electro-deposition solution in the first electro-deposition tank 7, thereby realizing the uniform electro-deposition of the polymer containing sulfonic acid groups onto one surface of the anion exchange membrane;

[0048] After the anion exchange membrane exits the first electro-deposition tank 7, it enters the second electro-deposition tank 15 for electro-deposition. The second electro-deposition solution in the second electro-deposition tank 15 is a mixed solution composed of sodium chloride, water, and polyethyleneimine. The second replenishing solution contained in the second replenishing tank 12 is also a mixed solution composed of sodium chloride, water, and polyethyleneimine. The concentration of sodium chloride in the second replenishing solution is the same as that in the second electro-deposition solution, but the concentration of polyethyleneimine is higher than that in the second electro-deposition solution. During the electro-deposition process, after the second electro-deposition solution in the second electro-deposition tank 15 is pumped out by the second pump 18, the second electro-deposition solution exchanges heat with the hot water heated by the second heating device 28 through the second heat exchange device 27 to control the temperature of the second electro-deposition solution in the second electro-deposition tank 15. At the same time, the probe of the second total organic carbon on-line detector 33 is placed in the second circulation pipeline 18, and the total organic carbon content in the second electro-deposition solution is monitored in real time by the second total organic carbon on-line detector 33, and the monitoring result is fed back to the PLC control system. The opening and closing of the second metering pump 13 are controlled by the PLC control system. That is, when the total organic carbon content in the second electro-deposition solution is as low as 0.9 times the initial value, the second metering pump 13 is opened to supplement the consumed polyethyleneimine into the second electro-deposition tank 15. When the total organic carbon content in the second electro-deposition solution is as high as 1.1 times the initial value, the second metering pump 13 is closed. If the liquid level height of the second electro-deposition solution in the second electro-deposition tank 15 reaches the second overflow port 17, the second electro-deposition solution will flow out through the second overflow port 17, so as to maintain the basic constancy of the total organic carbon content in the second electro-deposition solution in the second electro-deposition tank 15, thereby realizing the uniform electro-deposition of polyethyleneimine on the electro-deposition layer surface of the anion exchange membrane;

[0049] After the anion exchange membrane exits the second electro-deposition tank 15, it enters the spraying device 9 to spray an aqueous glutaraldehyde solution onto the electro-deposition layer surface of the cation exchange membrane. The nozzle is arranged below the third metering pump 21, and the spraying direction of the nozzle is aligned with the electro-deposition layer surface of the anion exchange membrane. The third replenishing tank 30 is filled with an aqueous glutaraldehyde solution. The third metering pump 31 controls the spraying amount. After spraying, the anion exchange membrane enters the drying device 21 for cross-linking reaction. After exiting the drying device 21, it enters the water washing tank 23 for water washing. After exiting the water washing tank 23, it reaches the second winding device 24, and the wet membrane is wound up, that is, a monovalent ion-selective anion exchange membrane is obtained.

[0050] The performance test method of the obtained monovalent anion-selective exchange membrane is as follows:

[0051] A small electro-dialysis device is used for testing. The electro-dialysis membrane stack specification is 110mm×270mm, 20 pairs of membranes, and the effective area of a single membrane is 0.0187m 2, the membranes are arranged in the pattern of anion / cation / anion / cation. The cation exchange membranes are the monovalent cation selective exchange membranes (model BCSCMT) produced by Zhejiang Baichen Low-carbon Technology Co., Ltd. The test conditions are as follows: a constant current mode with a current of 3.7 A is adopted. The solution in the desalination chamber is a mixed solution of 0.5 mol / L sodium chloride and 0.5 mol / L sodium sulfate. The water volume in the desalination chamber is 1.5 L, the concentration chamber is pure water with a volume of 0.4 L, the solution in the electrode chamber is 0.1 mol / L sodium nitrate solution, the flow rate of the feed liquid in each compartment is 1 L / min, and the electrodialysis operation temperature is controlled at 30 - 32 °C.

[0052] The definition of ion flux is: J = (C t - C0) / (S·N·t), where J is the ion flux, C0 is the ion concentration (mol / L) in the concentration chamber at the initial moment, C t is the ion concentration (mol / L) in the concentration chamber at time t, S is the effective area of the membrane, N is the number of membrane pairs in the membrane stack, t is the test time, and the test time in the specific implementation mode of the present invention is 2.5 h;

[0053] The definition of the selectivity separation coefficient is: where P is the selectivity separation coefficient, is the flux of monovalent anions calculated according to the above method, is the flux of divalent anions calculated according to the above method, is the concentration of monovalent anions (mol / L) in the desalination chamber at the initial time, is the concentration of divalent anions (mol / L) in the desalination chamber at the initial time. The anion concentration is detected by an inductively coupled plasma emission spectrometer, and the test standard is HJ776 - 2015.

[0054] Table 1

[0055]

[0056]

[0057]

[0058] Example 8: Application of Salt Lake Old Brine

[0059] A small - scale electrodialysis device is used for testing. The electrodialysis membrane stack specifications are 110 mm × 270 mm, with 20 pairs of membranes, and the effective area of a single membrane is 0.0187 m 2, adopting the arrangement of anion / cation / anion / cation, the cation exchange membrane uses the monovalent cation selective exchange membrane (model BCSCMT) produced by Zhejiang Baichen Low-carbon Technology Co., Ltd., and the anion exchange membrane uses the monovalent anion selective exchange membrane prepared in Example 5. The test conditions are as follows: adopting a constant current mode with a current of 3.7 A, the solution in the desalination chamber is old brine from salt lakes, the amount of water in the desalination chamber is 20 L of old brine from salt lakes, the concentration chamber is pure water with an amount of 1.5 L, the solution in the electrode chamber is 0.1 mol / L sodium sulfate solution, the flow rate of the feed liquid in each compartment is 1 L / min, and the electrodialysis operation temperature is controlled at 30 - 32 °C. The test time is 480 minutes. The ion concentration is detected by an inductively coupled plasma emission spectrometer, and the test standard is HJ776 - 2015.

[0060] Lithium recovery rate = (mass of lithium ions at the start in the fresh water chamber - mass of lithium ions at the end in the fresh water chamber) / mass of lithium ions at the start in the fresh water chamber × 100%;

[0061] Magnesium rejection rate = (mass of magnesium ions at the start in the fresh water chamber - mass of magnesium ions at the end in the fresh water chamber) / mass of magnesium ions at the start in the fresh water chamber × 100%;

[0062] Boron rejection rate % = (mass of boron at the start in the fresh water chamber - mass of boron at the end in the fresh water chamber) / mass of boron at the start in the fresh water chamber × 100%;

[0063] SO4 2- Sulfate rejection rate = (mass of sulfate ions at the start in the fresh water chamber - mass of sulfate ions at the end in the fresh water chamber) / mass of sulfate ions at the start in the fresh water chamber × 100%.

[0064] The data comparison of the application of Example 5 and Comparative Example 2 in old brine from salt lakes is shown in Table 2 below:

[0065] Table 2

[0066]

[0067]

Claims

1. A method for continuously and industrially producing a monovalent ion-selective anion exchange membrane, characterized in that: The method includes the following steps: After the dry film roll of the anion exchange membrane is unrolled by the first unrolling device, it enters a water tank filled with an aqueous sodium chloride solution for soaking, and then enters the first electro-deposition tank for electro-deposition after leaving the water tank. The first electro-deposition solution in the first electro-deposition tank is a mixed solution composed of sodium chloride, water, and a polymer containing sulfonic acid groups. During the electro-deposition process, the total organic carbon content in the first electro-deposition solution is monitored in real time by the first total organic carbon on-line detection analyzer, and the monitoring results are fed back to the PLC control system. The addition of the first replenishing solution is controlled by the PLC control system. The first replenishing solution is a mixed solution composed of sodium chloride, water, and a polymer containing sulfonic acid groups. The sodium chloride concentration in the first replenishing solution is the same as that in the first electro-deposition solution, but the concentration of the polymer containing sulfonic acid groups is higher than that in the first electro-deposition solution. When the total organic carbon content in the first electro-deposition solution is as low as 0.9 times the initial value, the first replenishing solution is added to the first electro-deposition tank to supplement the consumed polymer containing sulfonic acid groups. When the total organic carbon content in the first electro-deposition solution is as high as 1.1 times the initial value, the first replenishing solution is no longer added, so as to maintain the basic constancy of the total organic carbon content in the first electro-deposition solution in the first electro-deposition tank, thereby realizing the uniform electro-deposition of the polymer containing sulfonic acid groups onto one surface of the anion exchange membrane; After the anion exchange membrane leaves the first electro-deposition tank, it enters the second electro-deposition tank for electro-deposition. The second electro-deposition solution in the second electro-deposition tank is a mixed solution composed of sodium chloride, water, and polyethyleneimine. During the electro-deposition process, the total organic carbon content in the second electro-deposition solution is monitored in real time by the second total organic carbon on-line detection analyzer, and the monitoring results are fed back to the PLC control system. The addition of the second replenishing solution is controlled by the PLC control system. The second replenishing solution is a mixed solution composed of sodium chloride, water, and polyethyleneimine. The sodium chloride concentration in the second replenishing solution is the same as that in the second electro-deposition solution, but the concentration of polyethyleneimine is higher than that in the second electro-deposition solution. When the total organic carbon content in the second electro-deposition solution is as low as 0.9 times the initial value, the second replenishing solution is added to the second electro-deposition tank to supplement the consumed polyethyleneimine. When the total organic carbon content in the second electro-deposition solution is as high as 1.1 times the initial value, the second replenishing solution is no longer added, so as to maintain the basic constancy of the total organic carbon content in the second electro-deposition solution in the second electro-deposition tank, thereby realizing the uniform electro-deposition of polyethyleneimine onto the electro-deposited layer surface of the anion exchange membrane; After the anion exchange membrane leaves the second electro-deposition tank, it enters a spraying device to spray an aqueous glutaraldehyde solution onto the electro-deposited layer surface of the anion exchange membrane, and then the electro-deposited surface after spraying the aqueous glutaraldehyde solution is compounded with a polyester film to protect the surface of the anion exchange membrane after spraying the aqueous glutaraldehyde solution. Then it enters a drying device for cross-linking reaction. After leaving the drying device, the polyester film and the anion exchange membrane are separated. The anion exchange membrane is washed with water and then wound up to obtain a monovalent ion-selective anion exchange membrane.

2. The method according to claim 1, wherein: The feeding mass ratio of sodium chloride: water: sulfonic acid group-containing polymer in the first electroplating solution is 18-30: 1000: 0.1-0.3; the current density of electroplating is 1-5 mA / cm 2 , the temperature of electroplating is 25-35 °C, and the electroplating time is 30-60 minutes.

3. The method according to claim 2, wherein: In the first replenishing solution, the feeding weight ratio of sodium chloride, water, and the polymer containing sulfonic acid groups is 18 - 30:1000:1 - 3.

4. The method according to claim 1, characterized in that: The sulfonic acid group-containing polymer is sulfonated polyether ether ketone or sulfonated polyether sulfone; the ion exchange capacity of the sulfonic acid group-containing polymer is 1.3 to 1.6 mmol / g.

5. The method according to claim 1, wherein: The feeding weight ratio of sodium chloride, water, and polyethyleneimine in the second electroplating solution is 18-30:1000:0.1-0.5, the current density of electroplating is 1-5 mA / cm 2 , the temperature of electroplating is 25-35 °C, and the electroplating time is 30-60 minutes.

6. The method according to claim 5, wherein: In the second replenishing solution, the feeding weight ratio of sodium chloride, water, and polyethyleneimine is 18 to 30:1000:1 to 5.

7. The method according to claim 1, wherein: The molecular weight of the polyethyleneimine is 500,000 to 750,000.

8. The method according to claim 1, wherein: The mass concentration of the glutaraldehyde aqueous solution used for spraying is 0.1 to 0.5%, and the spraying amount is 10 to 20 g / m based on the mass of the glutaraldehyde aqueous solution sprayed on each square meter of the anion exchange membrane. 2 .

9. The method according to claim 1, wherein: The temperature in the drying device is controlled at 35 to 45 °C, and the cross-linking reaction time is controlled at 30 to 60 min.

10. Use of a univalent ion-selective anion exchange membrane prepared by the method according to any one of claims 1-9 in electrodialysis for lithium extraction from old brine in salt lakes.

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