Polymer separation membrane prepared based on ultraviolet-water in-situ shearing technology, preparation method and application

Abstract

The invention provides a polymer separation membrane prepared based on an ultraviolet-water in-situ shearing technology, and a preparation method and application thereof, and belongs to the technical field of ion separation membranes. The preparation method comprises the following steps: firstly, introducing a water molecule permeable free volume cavity into a polymer film matrix in a fast heavy ion irradiation or solvent swelling manner, and then irradiating the polymer film soaked in water by ultraviolet light; water molecules in the membrane are subjected to photolysis under the action of ultraviolet light to generate hydroxyl free radicals with strong oxidizing property to attack polymer molecules around the hydroxyl free radicals, so that macromolecular chains are degraded to initiate in-situ shearing, and then a membrane channel which is in a sub-nanometer size and is highly ionized in a solution is formed in the membrane; the size of a membrane channel can be finely regulated and controlled on the sub-nanometer scale by controlling the ultraviolet-water in-situ shearing time; the obtained polymer separation membrane has good separation performance on monovalent / multivalent metal cations, and efficient separation of monovalent / divalent ions is achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of ion separation membranes, and specifically relates to a polymer separation membrane prepared based on "ultraviolet-water" in-situ shearing technology, a method for preparing the membrane, and an application of the membrane in ion separation. Background Art

[0002] Selective separation of monovalent and divalent ions plays an important role in energy storage and conversion, pollution monitoring and control, and clean industrial processes. Common separation processes include lithium extraction from salt lakes, recovery of industrial waste acid, hard water softening, and brine purification. Conventional separation methods are complex and energy-intensive, and precise separation at the nanometer and angstrom scales is difficult to achieve. Among the many new separation methods, membrane separation of monovalent and divalent ions has attracted widespread attention as an energy-efficient and environmentally friendly method. By constructing membrane materials with ion-selective permeability, researchers can achieve ion separation and concentration by allowing the desired ions in the solution to pass through the membrane while blocking the passage of other ions. Compared to inorganic membrane materials, organic polymer membranes offer significant advantages in flexibility, variety, cost, ease of processing, and application areas, and have now been successfully commercialized. However, because the mass transfer channels of polymer separation membranes are typically free-volume cavities formed by the random accumulation of polymer networks, the uneven channel size and tortuous mass transfer paths make the trade-off between membrane flux and selectivity difficult to strike. This severely restricts its development in areas requiring high-performance separation, such as lithium extraction from salt lakes.

[0003] Polymer separation membranes with uniformly sized channels can not only solve the problem that membrane flux and selectivity cannot be improved simultaneously, but also avoid the inherent brittleness problem of inorganic membranes. They have become a research hotspot in the field of separation membranes. Polymer separation membranes prepared by phase inversion and electrospinning technologies have shown broad application prospects in liquid separation, water treatment, biomedicine and other fields. However, during the preparation process, how to accurately control the pore size and ensure the uniformity of the pore size distribution remains a technical challenge. Slight changes in the microstructure may lead to inconsistent membrane performance, affecting its actual application effect. For fields such as ion separation, the selectivity and flux of the membrane need to be further optimized to meet the needs of more efficient separation. This involves multiple aspects such as material design, membrane structure optimization and process parameter adjustment.

[0004] Among the numerous preparation methods, track etching, a technique that combines high-energy particle irradiation and chemical etching, is widely used to prepare separation membranes with uniform pore sizes. When polymer membranes are irradiated with fast heavy ions, these ions leave localized damaged areas along their paths as they penetrate the membrane. These areas are known as ion tracks, but they cannot directly form subnanometer channels. The tracks typically require chemical etching to form interconnected channels. Therefore, the irradiated polymer membrane is subsequently immersed in a specific chemical etching solution (such as an alkaline or acidic solution). The chemical etching solution preferentially etches the track areas, forming nanochannels that penetrate the membrane. By controlling the etching time and conditions, the pore size and pore density can be precisely controlled. This technique offers high pore formation precision, strong controllability, a wide range of material options, and high flux, and has already played an important role in water treatment fields such as ultrafiltration and nanofiltration. However, due to the typically high track etching rate, it is difficult to prepare channels smaller than 5 nanometers in polymer membranes using this method. Furthermore, polymer separation membranes in certain applications require good mechanical strength and durability, which places higher demands on material selection and preparation processes.

[0005] Therefore, constructing uniform sub-nanometer channels on polymer membranes to achieve precise molecular separation remains a huge challenge. Summary of the Invention

[0006] The purpose of the present invention is to address the deficiencies in the prior art and provide a polymer separation membrane with sub-nanometer size and highly ionized membrane channels; another purpose of the present invention is to provide a "UV-water" pore-forming strategy that uses ultraviolet light to decompose water molecules to generate hydroxyl radicals to in situ shear the polymer membrane; another purpose of the present invention is to clarify the use of this polymer separation membrane and apply it to fields such as ion separation and lithium extraction from salt lakes.

[0007] The specific technical solution of the present invention is: a method for preparing a polymer separation membrane based on "UV-water" in-situ shearing technology, comprising the following steps:

[0008] 1) treating a polymer film substrate by means of rapid heavy ion irradiation or solvent swelling to obtain a polymer ion irradiated film or a polymer swollen film;

[0009] 2) soaking the polymer ion irradiated membrane or the polymer swollen membrane in deionized water to fully soak it;

[0010] 3) The polymer ion irradiation membrane or the polymer swelling membrane immersed in water is treated with vertical ultraviolet light to obtain a polymer separation membrane.

[0011] Furthermore, in step 1), the fast heavy ions are krypton ions with an energy of 2.15 GeV. 86 Kr 26+ The ion irradiation dose of the film is 5×10 10 ions / cm2 .

[0012] Furthermore, the polymer film substrate includes commercial polymer films such as polyetherimide (PEI) film, polyimide (PI) film, polyethylene terephthalate (PET) film or polyethersulfone (PES) film.

[0013] Furthermore, the solvent used for swelling the polymer membrane substrate is a mixed solvent of dimethyl sulfoxide and water, the volume ratio of dimethyl sulfoxide to water is 5:2, and the solvent swelling time is 1.5 to 2.5 hours.

[0014] Furthermore, in step 3), the irradiation intensity of the ultraviolet light is 35 mW / cm 2 The film irradiation treatment time is 2 to 40 hours.

[0015] Preferably, when using "UV-water" in situ shearing polymer ion irradiation membrane PEI-IIM to form a polymer separation membrane PEI-ICM, the optimal membrane irradiation treatment time is 20 hours; when using "UV-water" in situ shearing polymer ion irradiation membrane PI-IIM to form a polymer separation membrane PI-ICM, the optimal membrane irradiation treatment time is 10 hours; when using "UV-water" in situ shearing polymer ion irradiation membrane PET-IIM to form a polymer separation membrane PET-ICM, the optimal membrane irradiation treatment time is 2 hours; when using "UV-water" in situ shearing polymer swelling membrane PES-SM to form a polymer separation membrane PES-SCM, the optimal membrane irradiation treatment time is 2 hours.

[0016] Based on the above method, a polymer separation membrane can be prepared, which includes a polymer membrane matrix and ion-selective membrane channels introduced by fast heavy ion irradiation or solvent swelling method combined with "UV-water" in situ shearing treatment process. The polymer separation membrane is obtained by "UV-water" in situ shearing polymer ion irradiation membrane or polymer swelling membrane, the polymer ion irradiation membrane is obtained by fast heavy ion irradiation of the corresponding polymer membrane matrix, the polymer swelling membrane is obtained by immersing the polymer membrane matrix in the corresponding organic solvent for swelling, and fast heavy ion irradiation and solvent swelling play the role of introducing free volume cavities in the membrane that are permeable only to water molecules.

[0017] Furthermore, the size of the ion-selective membrane channels on the polymer separation membrane is at the sub-nanometer level. In aqueous solution, the membrane channels are highly ionized, causing the channel surface to carry a large amount of negative charge.

[0018] Furthermore, the channel size of the polymer separation membrane can be regulated at the sub-nanometer scale by controlling the UV irradiation time.

[0019] Furthermore, the thickness of the polymer separation membrane is on the order of micrometers.

[0020] The polymer separation membrane can be used in the process of monovalent / divalent ion separation and lithium extraction from salt lakes.

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] 1. This application is approved 86 Kr 26+ Ion irradiation of the membrane substrate results in an irradiated membrane or solvent-swollen membrane, which serves as a precursor. A series of tiny free-volume cavities permeable only to water molecules are introduced into the polymer membrane matrix, facilitating the diffusion of UV-visible water and the subsequent in-situ shearing process. When the membrane is immersed in water, the water molecules diffuse into the interior of the irradiated membrane, limiting the subsequent "UV-water" in-situ shearing process to the tiny areas of ion irradiation or solvent swelling without affecting other parts of the polymer membrane matrix. This forms transmembrane channels while essentially retaining the good mechanical flexibility and stability of the polymer.

[0023] 2. This application utilizes a "UV-water" in-situ shearing technique to treat irradiated or swollen membranes to prepare polymer separation membrane products. Upon ultraviolet irradiation, water molecules within the precursor membrane immersed in water photolyze to produce hydroxyl radicals (·OH). These radicals actively contact surrounding polymer chains, causing them to break and form new functional groups, ultimately forming subnanometer-scale transmembrane channels within the ion channel membrane.

[0024] 3. The channel size of the polymer separation membrane can be precisely controlled at the sub-nanometer scale by controlling the in-situ shearing time of "UV-water". The sub-nanometer-sized membrane channel ionizes in the aqueous solution to generate abundant surface negative charges, which enables the membrane to selectively pass monovalent metal ions (such as Li + , K + 、Na + ) and significantly hinder the multivalent metal ions (such as Mg 2+ , Ca 2+ 、La 3+ ) through, achieving efficient separation of ions;

[0025] 4. The membrane channels of the polymer separation membrane prepared in this application are selectively permeable to monovalent metal ions, and its ion separation performance far exceeds that of current commercial polymer membranes. Furthermore, due to the in-situ shearing restricted by water molecules, it can maintain good mechanical flexibility and stability even after long-term "UV-water" treatment.

[0026] 5. This application discloses a polymer separation membrane prepared using an ultraviolet-water (UV-W) in-situ shearing technique. The preparation process involves no chemical reagents, and the membrane with sub-nanometer pores is obtained through purely physical methods. This is a green and pollution-free method for preparing sub-nanometer pores. Compared with currently commercialized sub-nanometer pore membrane production methods, the preparation method used in this application has the advantages of a simple preparation process, relatively short membrane formation time, and economical material resources. It is expected to be widely promoted and applied in the future.

[0027] 6. The UV-W strategy proposed in this application successfully created sub-nanometer-sized channels in polymer membranes. This strategy is scalable and universal, and can not only meet the requirements of industrial applications for membrane ion selectivity and permeability, but also lay the foundation for converting various commercial polymers into polymer membranes with excellent separation performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The small figure (a) shows the change of ion selective permeability of PEI-ICM with the time of in-situ shearing treatment by ultraviolet-water (UV-W); the small figure (b) shows the change of ionic conductivity of PEI-ICM with the time of in-situ shearing treatment by UV-W;

[0029] Figure 2 The SEM and AFM images of the surface and cross-section of the PEI-ICM obtained when the UV-W in-situ shearing treatment time is 20 h and the PEI-IIM prepared in Example 1; wherein, (a) the inset is the SEM image of the top surface of the PEI-IIM, (b) the inset is the SEM image of the top surface of the PEI-ICM, (c) the inset is the SEM image of the cross-section of the PEI-IIM, (d) the inset is the SEM image of the cross-section of the PEI-ICM, (e) the inset is the AFM image of the PEI-IIM, and (f) the inset is the AFM image of the PEI-ICM; the surface roughness (Rq) of the PEI-IIM and PEI-ICM are 2.83 and 19.8, respectively;

[0030] Figure 3 Figure 2 shows the positron annihilation lifetime spectra and membrane ion conductance of PEI-ICM and PEI-IIM obtained after UV-W in situ shearing treatment for 20 h. (a) is the positron annihilation lifetime spectra, and (b) is the ionic conductance of PEI-ICM with different quaternary ammonium ions.

[0031] Figure 4 Figure 2 is the ion separation performance diagram of PEI-IIM under ideal conditions, where (a) shows the membrane flux of PEI-IIM for different metal ions, and (b) shows the selectivity of PEI-IIM for different ions;

[0032] Figure 5 is the ion separation performance diagram of PEI-ICM in binary salt solution;

[0033] Figure 6 These are photos of the PEI-IIM, PI-IIM, and PET-IIM prepared in Example 2;

[0034] Figure 7 The ion selectivity of PEI-IIM, PI-IIM and PET-IIM prepared in Example 2 under ideal conditions;

[0035] Figure 8 Figure 2 shows the ion transport properties of various PES-based membranes, where (a) is the IV curve of the original PESM, (b) is the IV curve of the PESM after directly exposing the PESM to UV light in water for 2 hours without swelling, (c) is the IV curve of the PESM swollen in a DMSO / water mixed solution (DMSO:H2O=5:2) for 2 hours, and (d) is the IV curve of the PES-SCM obtained in Example 3.

[0036] Figure 9 The ion transport characteristics of PEI-ICM and PEI-CEM; among them, (a) is the SEM photo of PEI-CEM prepared in Control Example 1, (b) is the membrane ion conductivity of PEI-CEM for different metal ions, and (c) shows the selectivity of PEI-CEM for different ions. DETAILED DESCRIPTION

[0037] The present invention provides a polymer separation membrane prepared based on "ultraviolet-water" in-situ shearing technology, a preparation method and application, and belongs to the field of ion separation membrane technology. First, a free volume cavity permeable to water molecules is introduced into the polymer membrane matrix by means of rapid heavy ion irradiation or solvent swelling. Then, the polymer membrane immersed in water is irradiated with ultraviolet light, so that the water molecules in the membrane are photolyzed under the action of ultraviolet light to generate strongly oxidizing hydroxyl radicals that attack the surrounding polymer molecules, causing the polymer chains to degrade and trigger in-situ shearing, thereby forming sub-nanometer-sized membrane channels in the membrane that are highly ionized in solution. By controlling the "ultraviolet-water" in-situ shearing time, the size of the membrane channels can be finely controlled at the sub-nanometer scale. The resulting polymer separation membrane has good separation performance for monovalent / multivalent metal cations. The membrane channels have strong size screening and electrostatic interaction with hydrated ions, which hinder the transmission of multivalent ions while promoting the transmission of monovalent ions, thereby achieving efficient separation of monovalent / divalent ions. Moreover, because the in-situ shearing process requires the participation of water molecules, the polymer membrane still has good mechanical flexibility and stability.

[0038] The technical solution of the present invention is further described below with reference to the accompanying drawings, but is not limited thereto. Any modification or equivalent replacement of the technical solution of the present invention that does not depart from the spirit and scope of the technical solution of the present invention should be included in the scope of protection of the present invention.

[0039] Example 1

[0040] (1) Using energy of 2.15GeV 86 Kr 26+ Ion irradiation of 10 μm thick PEI membrane with an irradiation dose of 5×10 10 ions / cm 2 ;

[0041] (2) completely immersing the PEI ion irradiated membrane (PEI-IIM) in deionized water;

[0042] (3) Use a peak wavelength of 365nm and an irradiation power of 35mW / cm 2 The PEI ion irradiation membrane immersed in water was irradiated with ultraviolet light for 10h, 20h, 30h and 40h respectively to obtain different polyetherimide ion channel membrane (PEI-ICM) products.

[0043] The ionic conductivity of the membranes obtained under different in situ shearing treatment times of “ultraviolet-water” (UV-W) was tested. The results are shown in Figure 1 , Figure 1 It shows that the ion selective permeability of PEI-ICM changes with the change of UV-W in situ shearing time; Figure 1 As shown in the small figure (a), after 10 hours of ultraviolet irradiation, the K + / Mg 2+ 、Na + / Mg 2+ He Li + / Mg 2+ The selectivities of PEI-ICM were 2209, 1603 and 1247, respectively. However, after 20 h of UV irradiation, the corresponding selectivities of PEI-ICM decreased to 1152, 1007 and 669, respectively. As the UV irradiation time increased to 20 h, the K + 、Na + He Li + The conductance more than doubled ( Figure 1 These results confirm that the UV-W treatment process precisely regulates the membrane channels at the subnanometer scale. As the UV exposure time is extended to 30 and 40 hours, the selectivity of PEI-ICM drops sharply to below 4 ( Figure 1(a) inset), demonstrating that the membrane channel increases with increasing UV-water treatment time; while the corresponding ionic conductivity increases only slightly ( Figure 1 (B), the change was not significant. Therefore, PEI-ICM treated with UV-water in situ shearing for 20 hours was selected as the test object for subsequent tests. It takes into account both selectivity and conductivity and has the best ion separation performance.

[0044] Figure 2 The following are SEM and AFM images of the surface and cross-section of PEI-IIM and PEI-ICM obtained after 20 hours of UV-W treatment. Observations show that the cross-section of PEI-ICM obtained by in situ shearing of PEI-IIM by UV-W treatment exhibits a vertical crack structure, resulting in surface roughness and the development of microstructures that penetrate the membrane. These phenomena indicate that UV-W treatment not only induces shearing on the surface, increasing roughness, but also induces shearing within the membrane, creating ion channels.

[0045] Figure 3 The middle panel (a) shows the positron annihilation lifetime spectrum, which shows the free volume of PEI-IIM and PEI-ICM. The rightward shift of the positron lifetime indicates that the membrane channel size increases during the "UV-water" treatment, proving that the "UV-water" in situ shearing generates membrane channels in the PEI membrane. Figure 3 In the middle panel (b), for these quaternary ammonium ions with the same charge, the ionic conductivity of PEI-ICM decreases sharply with the increase of ion diameter (especially from Increase to ), the PEI-ICM treated with "UV-water" showed size cutoff for quaternary ammonium cations of different diameters (i.e., ions with a diameter greater than 0.7 nm could not pass through), further proving that the in situ shearing of "UV-water" produced sub-nanometer-sized membrane channels in the membrane.

[0046] In addition to the ion conductivity test, PEI-ICM was further used as an electrodialysis membrane to study the ion selective separation ability of PEI-ICM; 1M different metal chloride solutions were used as raw materials for separation tests at a driving voltage of 5V. The results are shown in Figure 2. Figure 4 As shown, monovalent metal ions (K + 、Na + He Li + ) membrane flux far exceeds that of multivalent metal ions (Ba 2+ , Ca 2+ Mg 2+ and La 3 + ), by comparing the membrane flux of different ions, it was found that PEI-ICM had a + / Mg 2+ 、Na+ / Mg 2+ 、Li + / Mg 2+ The ideal selectivities were 1286, 1081, and 731, respectively, demonstrating that PEI-ICM has excellent ion selective permeability.

[0047] After the single ion transport behavior, the separation performance of the membrane in binary salt solution was evaluated. Under the condition of 1M mixed salt with a concentration ratio of 1:1 (0.5M XCl and 0.5M MCln on the feed side, X represents monovalent metals such as Li, Na, K, and M represents multivalent metals such as Mg, Ca, and La), the ion separation performance of PEI-ICM is shown in Figure 2. Figure 5 ,from Figure 5 It can be seen that the Li + / Mg 2 + The separation performance was superior to that of conventional polymer membranes and novel membrane materials such as MOFs, COFs, and layered membranes. Furthermore, the PEI-ICM demonstrated excellent monovalent / polyvalent ion separation performance over hundreds of days of continuous operation, demonstrating excellent chemical and structural stability. The ion selectivity of the PEI-ICM measured by electrodialysis permeation was generally consistent with the corresponding ion conductivity selectivity.

[0048] Example 2

[0049] (1) Using energy of 2.15GeV 86 Kr 26+ Ions were irradiated on 10 μm thick PEI, PI and PET films respectively, with an irradiation dose of 5×10 10 ions / cm 2 , the corresponding ion irradiated membranes were recorded as PEI-IIM, PI-IIM and PET-IIM;

[0050] (2) Completely immerse PEI-IIM, PI-IIM, and PET-IIM in deionized water;

[0051] (3) Use a peak wavelength of 365nm and an irradiation power of 35mW / cm 2 PEI-IIM, PI-IIM and PET-IIM immersed in water were irradiated with ultraviolet light for 20h, 10h and 2h respectively to obtain different ion separation membrane products, which were respectively recorded as PEI-ICM, PI-ICM and PET-ICM.

[0052] Figure 6The following are photos of three ion separation membrane products prepared using the "UV-water" in-situ shearing method. From the photos, we can see that these membranes have maintained complete morphology and good mechanical properties. The three membranes were tested for ion conductivity, and the results are shown in Figure 7 It can be found that all three membranes exhibit good ion selective separation performance, proving that the "UV-water" in situ shearing method has wide applicability.

[0053] Example 3

[0054] The difference from Example 1 is that, instead of the "UV-water" in-situ shearing method, this example uses solvent swelling to introduce continuous free volume on the polymer membrane matrix. The specific operation process is as follows:

[0055] A 25 μm-thick commercial polyethersulfone (PES) membrane was swollen for 2 h using a dimethyl sulfoxide / water mixed solution (DMSO and H2O in a volume ratio of 5:2). Subsequently, the swollen polyethersulfone membrane (PES-SM) was immersed in water for "UV-water" treatment to prepare a polyethersulfone swollen channel membrane (PES-SCM). By adjusting the corresponding UV irradiation time, the "UV-water" process within the membrane can be effectively controlled, thereby introducing highly charged sub-nanoscale channels into the membrane. It has been verified that the optimal time for PES-SM to form PES-SCM is 2 h. Figure 8 The ion transport properties of various PES-based membranes are shown. It can be seen from the figure that solvent swelling introduces a continuous free volume in the polyethersulfone membrane (PESM), allowing only water molecules to permeate. The subsequent UV-W treatment further introduces sub-nanometer-sized channels in these membranes, selectively transporting monovalent metal ions.

[0056] Comparative Example 1

[0057] (1) Using energy of 2.15GeV 86 Kr 26+ Ion irradiation of 10 μm thick PEI film with an irradiation dose of 1×10 10 ions / cm 2 , and obtain the irradiated membrane PEI-IIM;

[0058] (2) Prepare a 10% sodium hypochlorite (NaClO) solution;

[0059] (3) The resulting solution was heated to 50° C. in a beaker using a heatable ultrasonic cleaner and ultrasonicated;

[0060] (4) The PEI-IIM was completely immersed in a NaClO solution under ultrasonic conditions for chemical etching for 8 min;

[0061] (5) The etched polymer separation membrane PEI-CEM is completely immersed in deionized water to clean the membrane surface and residues in the membrane.

[0062] like Figure 9 As shown, the channel diameter of the prepared PEI-CEM membrane is about 20 nm ( Figure 9 (a) Inset), the ionic conductivity of the membrane was tested in 1M solutions of different metal chloride salts, and it was found that the changes in the ionic conductivity of the membrane in different solutions followed the changes in the ionic conductivity of the bulk solution ( Figure 9 (b) panel), the ion selectivity of the membrane is close to 1 ( Figure 9 (c) shows that the PEI-CEM prepared by track etching does not have ion separation performance, mainly because the membrane channel size prepared by this method is much larger than the sub-nanometer level.

Claims

1. A method for preparing a polymer separation membrane based on "UV-water" in-situ shearing technology, characterized in that: The steps include: 1) treating a polymer film substrate by means of rapid heavy ion irradiation or solvent swelling to obtain a polymer ion irradiated film or a polymer swollen film; 2) soaking the polymer ion irradiated membrane or the polymer swollen membrane in deionized water to fully soak it; 3) The polymer ion irradiation membrane or the polymer swelling membrane immersed in water is treated with vertical ultraviolet light to obtain a polymer separation membrane.

2. The method for preparing a polymer separation membrane based on the "UV-water" in-situ shearing technology according to claim 1, characterized in that: In step 1), the fast heavy ions are krypton ions with an energy of 1-5 GeV. 86 Kr 26+ The ion irradiation dose of the membrane is 1-15×10 10 ions / cm 2 .

3. The method for preparing a polymer separation membrane based on the "UV-water" in-situ shearing technology according to claim 1, characterized in that: The polymer film substrate includes commercial polymer films including polyetherimide film, polyimide film, polyethylene terephthalate film or polyethersulfone film.

4. The method for preparing a polymer separation membrane based on the "UV-water" in-situ shearing technology according to claim 1, characterized in that: The solvent for swelling the polymer membrane matrix is a mixed solvent of dimethyl sulfoxide and water, the volume ratio of dimethyl sulfoxide to water is 1-4:1, and the solvent swelling time is 0.5-5h.

5. The method for preparing a polymer separation membrane based on the "UV-water" in-situ shearing technology according to claim 1, characterized in that: In step 3), the UV irradiation process is carried out at room temperature, the UV irradiation intensity is 10-100 mW / cm 2 The film irradiation treatment time is 2 to 40 hours.

6. A polymer separation membrane, characterized in that It is prepared based on the method for preparing a polymer separation membrane described in any one of claims 1 to 5, wherein the polymer separation membrane includes a polymer membrane matrix and ion-selective membrane channels introduced by rapid heavy ion irradiation or solvent swelling method combined with "UV-water" in-situ shearing treatment process. The polymer separation membrane is obtained by "UV-water" in-situ shearing polymer ion irradiation membrane or polymer swelling membrane, the polymer ion irradiation membrane is obtained by rapid heavy ion irradiation of the corresponding polymer membrane matrix, the polymer swelling membrane is obtained by immersing the polymer membrane matrix in a corresponding organic solvent for swelling, and rapid heavy ion irradiation and solvent swelling play the role of introducing free volume cavities in the membrane that are permeable only to water molecules.

7. A polymer separation membrane according to claim 6, characterized in that: The size of the ion-selective membrane channels on the membrane is in the sub-nanometer range. In aqueous solution, the membrane channels are highly ionized, causing the channel surface to carry a large amount of negative charge.

8. The polymer separation membrane according to claim 6, wherein The membrane channel size can be regulated at the sub-nanometer scale by controlling the UV irradiation time.

9. The polymer separation membrane according to claim 6, wherein The thickness of the polymer separation membrane is on the order of microns.

10. Use of the polymer separation membrane according to claim 6 in monovalent ion / divalent ion separation and lithium extraction from salt lakes.

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