A monovalent cation-selective separation membrane and a method for producing the same

Abstract

The application discloses a monovalent cation selective separation membrane and a preparation method thereof, and belongs to the technical field of ion exchange membranes. A bisamine monomer and an acyl chloride monomer are respectively dissolved in water and n-hexane to obtain an aqueous solution and an oil solution. A porous base film is fixed in the middle part of a central channel of a diffusion device, the aqueous solution and the oil solution are respectively poured into diffusion chambers on the upper and lower sides of the central channel, interfacial polymerization is carried out, then the membrane is taken out, washed with n-hexane, dried, and a monovalent cation selective separation membrane is obtained. The preparation method of the monovalent cation selective separation membrane has the advantages of low raw material cost, mild preparation conditions and simple operation, so that the membrane preparation cost can be greatly reduced, and the existence of chloromethyl on the membrane makes the polyamide structure more stable. Meanwhile, the electrodialysis Na + / Me4N + , K + / Me4N + Separation performance of the prepared monovalent cation selective separation membrane is superior to that of a commercial CIMS membrane, and has a wide application prospect in the fields of electronic-grade TMAH purification preparation and the like.

Description

Technical Field

[0001] This invention belongs to the field of ion exchange membrane technology, specifically relating to a monovalent cation selective separation membrane and its preparation method. Background Technology

[0002] Electronic-grade TMAH has wide applications in the field of electronic chemicals, but its preparation inevitably introduces difficult-to-remove Na+. + K + This significantly impacts the lifespan of electronic products, thus necessitating the purification of the prepared TMAH. TMAH purification essentially involves the removal of Me4N from the aqueous solution. + with Na + K + Electrodialysis, with its core technology of monovalent cation selective separation membrane, has the potential for large-scale application in the field of TMAH purification due to its advantages of being pollution-free and having high separation efficiency.

[0003] Currently, monovalent cation-selective separation membranes are mainly prepared through interfacial polymerization. Interfacial polymerization is a polymerization reaction that takes place at the interface of two immiscible solutions, offering several advantages. First, both the diamine monomer and the acyl chloride monomer are readily available, inexpensive, and easy to prepare; the reaction solution is simply prepared and then placed onto the membrane sequentially. Second, the resulting polyamide has a dense network structure and strong hydrophilicity, which endows the membrane with good ion selectivity and permeate flux. Traditional interfacial polymerization is carried out through impregnation, which leads to problems such as difficulty in controlling the reaction rate and uneven polyamide layer thickness. Therefore, diffusion interfacial polymerization for preparing monovalent cation-selective separation membranes has broad development prospects in the TMAH purification field.

[0004] CN202310856256.1 discloses a method for preparing nanofiltration membranes under the control of interfacial polymerization regulated by azide-type ionic additives. A porous substrate membrane is impregnated at room temperature in an aqueous solution of azide-type ionic organic amine molecules. The impregnated porous substrate membrane is then added to an oil phase of aromatic acyl chloride. Under ultraviolet light irradiation, an interfacial polymerization process is carried out to form a separation skin layer, simultaneously achieving the control of impregnation interfacial polymerization and the ionization modification of the polyamide network, thus constructing a high-performance composite nanofiltration membrane.

[0005] However, the existing interfacial polymerization modification methods, represented by the above methods, produce polyamide selective layers with uneven thickness and insufficient polyamide structure density when grown on porous substrates using the impregnation interfacial polymerization method, which makes it difficult to improve the ion separation performance of the membrane. Summary of the Invention

[0006] The purpose of this invention is to provide a monovalent cation selective separation membrane and its preparation method, using inexpensive raw materials, with mild preparation conditions, and producing polyamide with uniform and easily controllable thickness. Furthermore, the prepared monovalent cation selective separation membrane exhibits good electrodialysis performance for Na+. + / Me4N + K + / Me4N + The separation exhibits superior performance compared to commercial CIMS membranes, and has broad application prospects in fields such as electronic-grade TMAH purification and preparation.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A method for preparing a monovalent cation selective separation membrane includes the following steps: dissolving a diamine monomer in water to obtain an aqueous phase solution, dissolving an acyl chloride monomer in n-hexane to obtain an oil phase solution; and performing diffusion interfacial polymerization of the aqueous phase solution and the oil phase solution on the surface of a porous base membrane to obtain a monovalent cation selective separation membrane.

[0009] The diamine monomer is selected from piperazine, ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, o-phenylenediamine, m-phenylenediamine, and p-phenylenediamine;

[0010] The porous substrate contains a chloromethyl group that can react with the diamine monomer;

[0011] Furthermore, the porous substrate also contains sulfonic acid groups that can enhance ion flux;

[0012] Furthermore, the porous base membrane is a blend of chloromethylated polyethersulfone and sulfonated polyethersulfone;

[0013] The concentration of the diamine monomer in the aqueous solution is 0.2-1.0 wt / v%, and the concentration of the acyl chloride monomer in the oil solution is 0.01 wt / v%.

[0014] The diffusion interface polymerization is carried out using an H-type diffusion device, which consists of a central channel and diffusion chambers located above and below the central channel. A porous base film is fixed in the middle of the central channel of the diffusion device, and an oil phase solution is poured into the diffusion chamber located above the central channel, while an aqueous phase solution is poured into the diffusion chamber located below the central channel to carry out the diffusion interface polymerization reaction.

[0015] Furthermore, the diffusion interface polymerization reaction takes 20-120 minutes and is carried out at a temperature of 10-40°C.

[0016] A monovalent cation selective separation membrane prepared by the above-described preparation method.

[0017] The above-mentioned monovalent cation selective separation membrane is used in the selective separation of monovalent cations and the preparation of electronic-grade TMAH.

[0018] The beneficial effects of this invention are as follows:

[0019] (1) The diffusion interface polymerization method of the present invention can not only directionally grow polyamide selective layer on the membrane surface, but also has a simple preparation process and easy control of the reaction degree, which is conducive to the growth of uniform, dense and defect-free polyamide selective layer.

[0020] (2) Compared with existing monovalent cation selective separation membranes, the monovalent cation selective separation membrane prepared in this invention uses a porous membrane substrate with chloromethyl groups, which can undergo a substitution reaction with the diamine monomer, resulting in an interaction between the membrane substrate and the polyamide selective layer, and thus a more stable membrane structure. In addition, the membrane substrate also contains sulfonic acid groups, which can increase the ion flux of the membrane and further improve the monovalent cation separation performance of the membrane.

[0021] (3) The diffusion interface polymerization method used in this invention is universally applicable to different diamine monomers. Different diamine monomers can be used to prepare monovalent cation selective separation membranes with different properties according to the requirements. Attached Figure Description

[0022] Figure 1 The infrared spectra are of the upper surface (a) and lower surface (b) of the monovalent cation selective separation membranes prepared in Examples 1-5.

[0023] Figure 2 The images show the full-spectrum XPS spectra of the upper surface (a) and lower surface (b) of the monovalent cation selective separation membranes prepared in Examples 1-5.

[0024] Figure 3 The images show the SEM images of the upper surface, lower surface, and cross-section of the monovalent cation selective separation membranes prepared in Examples 1-5.

[0025] Figure 4 The water contact angles are the upper surface (a) and lower surface (b) of the monovalent cation selective separation membranes prepared in Examples 1-5.

[0026] Figure 5 The Na+ on the upper surface (a) and lower surface (b) of the monovalent cation selective separation membranes prepared in Examples 1-5 + / Me4N + K + / Me4N + Separation performance diagram. Detailed Implementation

[0027] To make the content of this invention easier to understand, the technical solution of this invention will be further described below with reference to specific embodiments, but this invention is not limited thereto.

[0028] All chemical reagents used in the embodiments of this invention are commercially available.

[0029] The chloromethylated polyethersulfone and sulfonated polyethersulfone blended base membrane (C / S-PES) used in this embodiment of the invention was prepared by a solvent-free phase inversion method. The specific steps were as follows: equal masses of chloromethylated polyethersulfone (CMPES) (the preparation of CMPES is disclosed in: Journal of Membrane Science, 2023, 673:121499.) and sulfonated polyethersulfone (SPES) (the preparation of SPES is disclosed in: Journal of Membrane Science, 2024, 706:122951. Specifically, HBS-PES-1.0 polymer) were weighed and dissolved in NMP. The solution was stirred at room temperature for 24 hours to ensure complete dissolution. The solution was then filtered through nonwoven fabric to remove impurities. The filtrate was then sonicated at room temperature for 10 minutes and allowed to stand overnight to remove air bubbles, resulting in a uniform and clear 25wt% casting solution. The casting solution was evenly poured onto a glass plate (in a long strip). Using a doctor blade, the casting solution was scraped onto the glass plate at a uniform and stable speed, controlling the thickness of the scraped casting solution to be 200 μm. The glass plate was then vertically immersed in a large container of ultrapure water and allowed to stand at room temperature until the membrane naturally detached from the glass plate. Finally, the membrane was removed and placed in ultrapure water, with the ultrapure water being changed several times to completely remove any NMP, yielding the C / S-PES base membrane.

[0030] In this embodiment of the invention, the diffusion device used for the diffusion interface polymerization reaction is H-shaped, consisting of a central channel and diffusion chambers located above and below the central channel. The inner diameter of the central channel is 4.4 cm and the outer diameter is 6.4 cm. The volume of the upper and lower diffusion chambers is 30 mL.

[0031] Example 1:

[0032] Piperazine (PIP) was dissolved in deionized water to obtain a PIP aqueous solution with a concentration of 0.2 wt / v%. Tristyrene chloride (TMC) was dissolved in n-hexane to obtain a TMC n-hexane solution with a concentration of 0.01 wt / v%. A C / S-PES membrane was cut to a size of 5 cm × 5 cm and fixed in the center of the central channel of the diffusion device. 30 mL of TMC n-hexane solution was poured into the diffusion chamber located above the central channel, and 30 mL of PIP aqueous solution was poured into the diffusion chamber located below the central channel. The diffusion interface polymerization reaction was carried out at room temperature for 60 min. After the reaction, the membrane was removed, and excess reaction solution was rinsed off the membrane surface with n-hexane. The membrane was then dried in a 60°C oven for 30 min to obtain a monovalent selective cation separation membrane (C / S-PES-0.2PIP). The water contact angle of the prepared monovalent selective cation separation membrane was measured to be 44.4° on the upper surface and 85.3° on the lower surface. The O / N value of XPS on the upper surface of the membrane was 1.83, the O / N value of XPS on the lower surface of the membrane was 15.33, and the thickness of the polyamide selective layer was 302 nm.

[0033] Electrodialysis experiments were conducted using the monovalent selective cation exchange membrane prepared in Example 1 at 25°C. 100 ml of deionized water and 100 ml of a 0.1 M NaCl (or KCl) / Me₄NHCO₃ mixed salt solution were added to the concentration chamber and desalination chamber, respectively, for circulation. The replenishment solution for the electrode chamber was 100 ml of 0.3 M Na₂SO₄, and the circulation flow rate was 40 ml / min. -1 The effective membrane area of ​​the device is 2 cm². 2 The operating current is constant at 0.004A (i.e., 2mA cm). -2 The Na content of the prepared monovalent selective cation separation membrane was measured. + The flux was 0.926 mol m -2 h -1 Na + / Me4N + Selectivity is 9.89, K + The flux was 0.961 mol m -2 h -1 K + / Me4N + The selectivity was 15.36, compared to commercial membranes (CIMS, Na₂O₃). + The flux is 0.556 mol m -2 h -1 Na + / Me4N + The selectivity is 18.42, K + The flux is 0.570 mol m -2 h -1 K+ / Me4N + Compared to Na, with a selectivity of 19.38%, + / Me4N + While the selectivity is similar, Na + The flux is higher.

[0034] Example 2:

[0035] A monovalent cation-selective separation membrane was prepared using a method similar to that in Example 1, except that the concentration of PIP in the PIP aqueous solution was changed to 0.4 wt / v%. The prepared monovalent selective cation separation membrane (C / S-PES-0.4PIP) was found to have a water contact angle of 42.8° on the upper surface and 80.9° on the lower surface. The O / N value of XPS on the upper surface was 1.34, and the O / N value of XPS on the lower surface was 14.46. The polyamide selective layer thickness was 418 nm. The membrane's electrodialysis Na... + The flux was 0.781 mol m -2 h -1 Na + / Me4N + The selectivity is 23.69, K + The flux was 0.774 mol m -2 h -1 K + / Me4N + The selectivity is 23.03.

[0036] Example 3:

[0037] A monovalent cation-selective separation membrane was prepared using a method similar to that in Example 1, except that the concentration of PIP in the PIP aqueous solution was changed to 0.6 wt / v%. The prepared monovalent selective cation separation membrane (C / S-PES-0.6PIP) was found to have a water contact angle of 42.2° on the upper surface and 81.1° on the lower surface. The O / N value of XPS on the upper surface was 1.09, and the O / N value of XPS on the lower surface was 13.21. The polyamide selective layer thickness was 524 nm. The membrane's electrodialysis Na... + The flux is 0.585 mol m -2 h -1 Na + / Me4N + The selectivity is 33.38, K + The flux was 0.602 mol m -2 h -1 K + / Me4N + The selectivity is 35.82.

[0038] Example 4:

[0039] A monovalent cation-selective separation membrane was prepared using a method similar to that in Example 1, except that the concentration of PIP in the PIP aqueous solution was changed to 0.8 wt / v%. The prepared monovalent selective cation separation membrane (C / S-PES-0.8PIP) was found to have a water contact angle of 36.4° on the upper surface and 85.0° on the lower surface. The O / N value of XPS on the upper surface was 1.35, and the O / N value of XPS on the lower surface was 4.92. The polyamide selective layer thickness was 699 nm. The membrane's electrodialysis Na... + The flux was 0.471 mol m -2 h -1 Na + / Me4N + The selectivity is 28.12, K + The flux was 0.516 mol m -2 h -1 K + / Me4N + The selectivity is 31.85.

[0040] Example 5:

[0041] A monovalent cation-selective separation membrane was prepared using a method similar to that in Example 1, except that the concentration of PIP in the PIP aqueous solution was changed to 1.0 wt / v%. The prepared monovalent selective cation separation membrane (C / S-PES-1.0PIP) was found to have a water contact angle of 34.8° on the upper surface and 84.5° on the lower surface. The O / N value of XPS on the upper surface was 1.19, and the O / N value of XPS on the lower surface was 15.15. The polyamide selective layer thickness was 841 nm. The membrane's electrodialysis Na... + The flux was 0.347 mol m -2 h -1 Na + / Me4N + The selectivity is 26.09, K + The flux was 0.370 mol m -2 h -1 K + / Me4N + The selectivity is 25.14.

[0042] Based on Examples 1-5, diffusion interfacial polymerization can directionally grow a polyamide selective layer on the surface of the membrane, and the preparation requirements are met at a PIP concentration of 0.6 wt / v%, with optimal performance. Further increasing the PIP concentration will affect the compactness and ion selectivity of the polyamide structure.

[0043] Figure 1The images show the infrared spectra of the upper and lower surfaces of the C / S-PES base membrane and the C / S-PES-XPIP series modified membrane (i.e., the monovalent selective cation separation membranes of Examples 1-5), with the peak at 1163 cm⁻¹. -1 and 1072cm -1 The peak at that location belongs to -SO3. - Characteristic peaks. Compared to C / S-PES base films, C / S-PES-XPIP series modified films exhibit a peak at 1368 cm⁻¹. -1 The new peak appearing at 1441 cm⁻¹ is the peak of the tertiary amine on the amide group. -1 The new peak at 1618 cm⁻¹ is attributed to the bending vibration peak of the methylene group on the PIP ring. -1 The new peaks appearing at 756 cm⁻¹ are stretching vibration peaks of the C=O group on the amide group. The appearance of these new peaks indicates that a polyamide selective layer can be grown on the surface of the C / S-PES film using diffusion interfacial polymerization. Meanwhile, at 756 cm⁻¹... -1 The peak appearing at this position is attributed to the chloromethyl group on CMPES. Compared to the C / S-PES base membrane, the peak intensity of the C / S-PES-XPIP series modified membrane at this position is weakened. This indicates that the chloromethyl group on CMPES reacted with PIP, thereby establishing an interaction force between the membrane substrate and the polyamide selective layer, making its structure more stable. In contrast, no characteristic peaks of amide groups and PIP rings were observed at the corresponding position on the lower surface of the membrane, indicating that diffusion interfacial polymerization does not grow a polyamide selective layer on the lower surface of C / S-PES. That is, diffusion interfacial polymerization can directionally grow a polyamide selective layer on the upper surface of the C / S-PES porous base membrane.

[0044] Figure 2The images show the full-spectrum XPS spectra of the upper and lower surfaces of the C / S-PES base membrane and the C / S-PES-XPIP series modified membranes (i.e., the monovalent selective cation separation membranes of Examples 1-5). The characteristic peaks at 284.80 eV and 531.88 eV belong to C1s and O1s, respectively. After diffusion interfacial polymerization, compared with the C / S-PES base membrane, the characteristic peak at 399.98 eV of the C / S-PES-XPIP series modified membrane is significantly enhanced, which belongs to N1s. This is consistent with its FT-IR results, further indicating that diffusion interfacial polymerization introduces a polyamide selective layer on the upper surface of the membrane. Furthermore, the characteristic peak at 199.8 eV is attributed to Cl2p. It is noteworthy that, compared to the C / S-PES base film, the C / S-PES-XPIP series modified films show almost no Cl2p peak. This is due to two reasons: first, the chloromethyl groups on the C / S-PES base film react with PIP, consuming some Cl; second, the polyamide selective layer grown on the film surface covers the chloromethyl groups, resulting in the undetectable Cl peak. This is consistent with the FT-IR results, proving that there is a chemical bond between the film substrate and the polyamide selective layer, suggesting a more stable structure. Additionally, the peak at 167.7 eV is attributed to S2p, originating from the -SO3- groups on the C / S-PES main chain and side chains. After diffusion interfacial polymerization, a polyamide selective layer grows on the C / S-PES surface; therefore, the S2p peak is not observed on the C / S-PES-XPIP series modified films, which is also consistent with expectations. In contrast, the elemental composition of the lower surface of the film did not change significantly, indicating that diffusion interfacial polymerization does not produce a polyamide selective layer on the lower surface of C / S-PES, which is consistent with the FTIR results.

[0045] Figure 3These are top, bottom, and cross-sectional views of the C / S-PES base membrane and the C / S-PES-XPIP series modified membranes (i.e., the monovalent selective cation separation membranes of Examples 1-5). On the top surface, the C / S-PES base membrane has a relatively smooth and flat morphology. The C / S-PES-XPIP series modified membranes both have numerous particulate materials on their top surfaces; these are polyamide particles. The presence of the polyamide layer makes the surface rougher. Furthermore, with increasing PIP concentration, the size of the polyamide particles slightly increases. The most uniform distribution of polyamide particles is observed when the PIP concentration is 0.6 wt / v%. As the PIP concentration further increases, the polyamide particles aggregate, resulting in uneven distribution, which is consistent with the XPS results. This indicates that both excessively low and high PIP concentrations affect the density of the grown polyamide. On the lower surface, the morphology of the C / S-PES base film and the C / S-PES-XPIP series modified films is very similar, both exhibiting numerous distinct porous structures. This is due to the formation of porous base films using non-solvent-induced phase inversion, and the presence of these porous structures facilitates efficient ion transport. However, no polyamide particles were observed on the lower surface of the C / S-PES-XPIP series modified films as on the upper surface, indicating that diffusion interfacial polymerization only directionally grows the polyamide selective layer on the upper surface of the C / S-PES film substrate. This is consistent with the FT-IR and XPS data results. Regarding the cross-section, the top of the C / S-PES base film cross-section is uniform and smooth, with no modified layer structure observed. In contrast, the top of the C / S-PES-XPIP series modified films cross-section shows a significantly additional modified structure, which is the polyamide selective layer grown on the upper surface of the film through diffusion interfacial polymerization. Furthermore, the thickness of the polyamide selective layer increases with increasing PIP concentration, a trend consistent with expectations. Meanwhile, in the cross-sectional view of the C / S-PES-XPIP series modified membrane, the membrane substrate and the polyamide selective layer are tightly bonded, and no detachment was found, which is the expected result. The presence of chloromethyl groups can react with PIP, thereby providing the interaction force between the membrane substrate and the polyamide selective layer.

[0046] Example 6:

[0047] A monovalent cation-selective separation membrane was prepared using a method similar to that in Example 3, except that the diffusion interface polymerization reaction time was changed to 20 min. The prepared monovalent selective cation separation membrane exhibited a water contact angle of 51.8° on its upper surface, an O / N value of 1.13 according to XPS, a polyamide selective layer thickness of 266 nm, and an electrodialysis Na... + The flux was 0.712 mol m -2 h -1 Na + / Me4N + The selectivity is 17.66, K + The flux was 0.782 mol m-2 h -1 K + / Me4N + The selectivity is 21.85.

[0048] Example 7:

[0049] A monovalent cation-selective separation membrane was prepared using a method similar to that in Example 3, except that the diffusion interface polymerization reaction time was changed to 40 min. The prepared monovalent selective cation separation membrane exhibited a water contact angle of 46.5° on its upper surface, an O / N value of 1.12 according to XPS, a polyamide selective layer thickness of 351 nm, and an electrodialysis Na... + The flux was 0.667 mol m -2 h -1 Na + / Me4N + The selectivity is 26.59, K + The flux is 0.650 mol m -2 h -1 K + / Me4N + The selectivity is 31.24.

[0050] Example 8:

[0051] A monovalent cation-selective separation membrane was prepared using a method similar to that in Example 3, except that the diffusion interface polymerization reaction time was changed to 80 min. The prepared monovalent selective cation separation membrane exhibited a water contact angle of 41.4° on its upper surface, an O / N value of 1.09 in XPS, a polyamide selective layer thickness of 601 nm, and an electrodialysis Na... + The flux was 0.521 mol m -2 h -1 Na + / Me4N + The selectivity is 41.47, K + The flux was 0.546 mol m -2 h -1 K + / Me4N + The selectivity is 44.11.

[0052] Example 9:

[0053] A monovalent cation-selective separation membrane was prepared using a method similar to that in Example 3, except that the diffusion interface polymerization reaction time was changed to 100 min. The prepared monovalent selective cation separation membrane exhibited a water contact angle of 37.4° on its upper surface, an O / N value of 1.18 in XPS, a polyamide selective layer thickness of 737 nm, and a Na+ electrodialysis performance of [missing information]. + The flux was 0.473 mol m-2 h -1 Na + / Me4N + The selectivity is 36.52, K + The flux was 0.480 mol m -2 h -1 K + / Me4N + The selectivity is 38.37.

[0054] Example 10:

[0055] A monovalent cation-selective separation membrane was prepared using a method similar to that in the previous example, except that the diffusion interface polymerization reaction time was changed to 20 min. The prepared monovalent selective cation separation membrane exhibited a water contact angle of 36.9° on its upper surface, an O / N value of 1.35 according to XPS, a polyamide selective layer thickness of 1.04 μm, and a Na+ electrodialysis performance of the membrane. + The flux was 0.415 mol m -2 h -1 Na + / Me4N + The selectivity is 34.12, K + The flux was 0.409 mol m -2 h -1 K + / Me4N + The selectivity is 35.14.

[0056] It is evident from Examples 6-10 that monovalent selective cation exchange membranes prepared with too short a diffusion interface polymerization time have a high O / N value, insufficiently dense polyamide structure, and relatively poor separation performance. Conversely, monovalent selective cation exchange membranes prepared with too long a polymerization time have an excessively thick polyamide selective layer, resulting in poor Na+ separation performance. + K + The flux is too low, therefore the optimal diffusion interface polymerization time is 80 min.

[0057] Example 11:

[0058] A monovalent cation-selective separation membrane was prepared using a method similar to that in Example 3, except that the diamine monomer PIP was replaced with ethylenediamine. The prepared monovalent selective cation separation membrane exhibited a water contact angle of 37.4° on its upper surface, an O / N value of 1.27 (XPS), a polyamide selective layer thickness of 564 nm, and an electrodialysis Na... + The flux was 0.612 mol m -2 h -1 Na + / Me4N + The selectivity is 36.41, K +The flux was 0.609 mol m -2 h -1 K + / Me4N + The selectivity rate is 39.61.

[0059] Example 12:

[0060] A monovalent cation-selective separation membrane was prepared using a method similar to that in Example 3, except that the diamine monomer PIP was replaced with diethylenetriamine. The prepared monovalent selective cation separation membrane was found to have a water contact angle of 44.9° on its upper surface, an O / N value of 1.33 for XPS, a polyamide selective layer thickness of 475 nm, and an electrodialysis Na... + The flux was 0.659 mol m -2 h -1 Na + / Me4N + The selectivity is 26.34, K + The flux was 0.669 mol m -2 h -1 K + / Me4N + The selectivity is 28.52.

[0061] Example 13:

[0062] A monovalent cation-selective separation membrane was prepared using a method similar to that in Example 3, except that the diamine monomer PIP was replaced with triethylenetetramine. The prepared monovalent selective cation separation membrane was found to have a water contact angle of 49.0° on its upper surface, an O / N value of 1.36 for XPS, a polyamide selective layer thickness of 341 nm, and an electrodialysis Na... + The flux was 0.662 mol m -2 h -1 Na + / Me4N + The selectivity is 19.26, K + The flux is 0.685 mol m -2 h -1 K + / Me4N + The selectivity is 25.64.

[0063] Example 14:

[0064] A monovalent cation-selective separation membrane was prepared using a method similar to that in Example 3, except that the diamine monomer PIP was replaced with tetraethylenepentamine. The prepared monovalent selective cation separation membrane was found to have a water contact angle of 66.0° on its upper surface, an O / N value of 1.47 (XPS), a polyamide selective layer thickness of 287 nm, and an electrodialysis Na... +The flux was 0.688 mol m -2 h -1 Na + / Me4N + The selectivity is 18.65, K + The flux was 0.694 mol m -2 h -1 K + / Me4N + The selectivity is 17.83.

[0065] Example 15:

[0066] A monovalent cation-selective separation membrane was prepared using a method similar to that in Example 3, except that the diamine monomer PIP was replaced with pentaethylenehexamine. The prepared monovalent selective cation separation membrane was found to have a water contact angle of 69.7° on its upper surface, an O / N value of 1.52 for XPS, a polyamide selective layer thickness of 159 nm, and an electrodialysis Na... + The flux was 0.724 mol m -2 h -1 Na + / Me4N + The selectivity is 11.90, K + The flux was 0.717 mol m -2 h -1 K + / Me4N + The selectivity is 14.23.

[0067] It is evident from Examples 11-15 that diffusion interfacial polymerization is effective for various aliphatic chain diamines. However, as the molecular chain length of the diamine monomer increases, the polyamide selective layer structure of the prepared monovalent selective cation separation membrane becomes less dense and too thin, resulting in lower Na+ content. + / Me4N + K + / Me4N + The fewer choices there are.

[0068] Example 16:

[0069] A monovalent cation-selective separation membrane was prepared using a method similar to that in Example 3, except that the diamine monomer PIP was replaced with o-phenylenediamine. The prepared monovalent selective cation separation membrane was found to have a water contact angle of 71.2° on its upper surface, an O / N value of 1.41 (XPS), a polyamide selective layer thickness of 861 nm, and a Na+ electrodialysis performance of [missing information]. + The flux was 0.547 mol m -2 h -1 Na + / Me4N + The selectivity is 11.07, K+ The flux was 0.534 mol m -2 h -1 K + / Me4N + The selectivity is 9.86.

[0070] Example 17:

[0071] A monovalent cation-selective separation membrane was prepared using a method similar to that in Example 3, except that the diamine monomer PIP was replaced with m-phenylenediamine. The prepared monovalent selective cation separation membrane was found to have a water contact angle of 75.5° on its upper surface, an O / N value of 1.34 (XPS), a polyamide selective layer thickness of 615 nm, and an electrodialysis Na... + The flux was 0.431 mol m -2 h -1 Na + / Me4N + The selectivity is 25.49, K + The flux was 0.437 mol m -2 h -1 K + / Me4N + The selectivity is 29.43.

[0072] Example 18:

[0073] A monovalent cation-selective separation membrane was prepared using a method similar to that in Example 3, except that the diamine monomer PIP was replaced with p-phenylenediamine. The prepared monovalent selective cation separation membrane was found to have a water contact angle of 78.3° on its upper surface, an O / N value of 1.35 (XPS), a polyamide selective layer thickness of 737 nm, and an electrodialysis Na... + The flux is 0.465 mol m -2 h -1 Na + / Me4N + The selectivity is 20.26, K + The flux was 0.441 mol m -2 h -1 K + / Me4N + The selectivity is 25.78.

[0074] It is evident from Examples 16-18 that diffusion interfacial polymerization is effective for various phenylenediamines, with m-phenylenediamine showing similar effects to p-phenylenediamine and exhibiting good Na+ properties. + / Me4N + K + / Me4N +Selectivity is poorest with o-phenylenediamine because its two primary amine groups are too close together, creating strong steric hindrance that hinders the interfacial polymerization reaction. + / Me4N + K + / Me4N + It also has the worst selectivity.

[0075] The results of the above examples show that the optimal concentration of the diamine monomer solution for preparing the monovalent cation selective separation membrane using the diffusion interfacial polymerization method of the present invention is 0.4 wt / v, the optimal diffusion interfacial polymerization reaction time is 60 min, and the optimal diamine monomer is piperazine. Compared with traditional impregnation interfacial polymerization, diffusion interfacial polymerization has the advantages of more controllable reaction process and more uniform and dense polyamide selective layer. At the same time, the C / S-PES substrate used can undergo substitution reaction with the diamine monomer due to the presence of chloromethyl groups, introducing interaction forces between the membrane substrate and the polyamide selective layer, making the prepared monovalent cation selective separation membrane more stable. Therefore, this method has broad development prospects.

[0076] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should be included in the scope of the present invention.

Claims

1. A method for preparing a monovalent cation selective separation membrane, characterized in that: A diamine monomer was dissolved in water to obtain an aqueous solution, and an acyl chloride monomer was dissolved in n-hexane to obtain an oil solution. The aqueous and oil solutions were then subjected to diffusion interfacial polymerization on the surface of a porous membrane to obtain a monovalent cation selective separation membrane. The porous base membrane contains chloromethyl groups that can react with diamine monomers; The porous base membrane contains sulfonic acid groups that can enhance ion flux. The concentration of the diamine monomer in the aqueous solution is 0.2-1.0 wt / v, and the concentration of the acyl chloride monomer in the oil solution is 0.01 wt / v. The diffusion interface polymerization is carried out using an H-type diffusion device, which consists of a central channel and diffusion chambers located above and below the central channel. A porous base film is fixed in the middle of the central channel of the diffusion device, and an oil phase solution is poured into the diffusion chamber located above the central channel, while an aqueous phase solution is poured into the diffusion chamber located below the central channel to carry out the diffusion interface polymerization reaction. The diffusion interface polymerization reaction takes 20-120 minutes and is carried out at a temperature of 10-40°C.

2. The preparation method according to claim 1, characterized in that: The diamine monomer is any one of piperazine, ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, o-phenylenediamine, m-phenylenediamine, and p-phenylenediamine.

3. The preparation method according to claim 1, characterized in that: The porous base membrane is a blend of chloromethylated polyethersulfone and sulfonated polyethersulfone.

4. A monovalent cation selective separation membrane prepared by the preparation method according to any one of claims 1-3.

5. The application of the monovalent cation selective separation membrane as described in claim 4 in the selective separation of monovalent cations and the preparation of electronic-grade TMAH.

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