Cation exchange resin, preparation method thereof, ion exchange membrane for separating alkali metal species, and electrodialysis device for lithium extraction

Abstract

A cation exchange resin according to the present disclosure comprises a first repeating unit represented by the following Chemical Formula 1; and a second repeating unit represented by the following Chemical Formula 2: [Chemical Formula 1] (in Chemical Formula 1, X and X'are each independently hydrogen or an alkali metal species (E), and A1 is represented by the following Chemical Formula 3 or Chemical Formula 4) [Chemical Formula 2] (in Chemical Formula 2, A2 is represented by the following Chemical Formula 3 or Chemical Formula 4), [Chemical Formula 3] (In Chemical Formula 3, Z1 is-S-,-O-,-C (O)-, or-C (R1R2)-, and R1 and R2 are each independently hydrogen, a C1 to C2 alkyl group, a halogen, or a halogen-substituted C1 to C2 alkyl group), [Chemical Formula 4].

Description

Cross-references to related applications

[0001] This application claims priority to Korean Patent Application No. 10-2023-0127404, filed with the Korean Intellectual Property Office on September 22, 2023, and Korean Patent Application No. 10-2023-0188239, filed with the Korean Intellectual Property Office on December 21, 2023, the entire contents of which are incorporated herein by reference. Technical Field

[0002] This disclosure relates to cation exchange resins and their preparation methods, ion exchange membranes containing the cation exchange resins for separating alkali metal species, and electrodialysis apparatuses for lithium extraction. Background Technology

[0003] Electrodialysis is a device that uses cation exchange membranes and anion exchange membranes, driven by direct current, to separate and concentrate ionic substances in a solution. Traditionally, electrodialysis has been used for seawater desalination, desalination processes, heavy metal removal from soil, and the treatment of various industrial wastes. However, in recent years, electrodialysis has attracted much attention as an environmentally friendly lithium extraction process, as lithium is a key mineral material in secondary batteries.

[0004] Among ion exchange membranes, cation exchange membranes (which are the main materials used for lithium extraction via electrodialysis) are the core materials that selectively allow only lithium ions to pass through and concentrate them into the form of lithium hydroxide. Commercially available cation exchange membranes in recent years are in the form of pure perfluorosulfonic acid (PFSA) ion exchange resin, pure cross-linked polystyrene resin containing sulfonated functional groups, or impregnated with polymer supports.

[0005] However, while fluorinated ion exchange resins have high ionic conductivity and excellent chemical stability, they are very expensive, have reduced high-temperature stability, and are subject to stricter regulations due to environmental pollution issues.

[0006] Furthermore, sulfonated polystyrene resin is prone to cracking during membrane drying. Therefore, sulfonated polystyrene resin should be used in the form of composite membranes. However, its processing is more difficult, and its mechanical and chemical stability is far inferior to that of fluorinated cation exchange resins.

[0007] Therefore, there is a need to develop a cation exchange resin for lithium extraction that not only improves mechanical and chemical stability but also exhibits better economic benefits than fluorinated cation exchange resins. Summary of the Invention

[0008] [Technical Issues]

[0009] To address this problem, this disclosure aims to provide a cation exchange resin with higher ionic conductivity, superior chemical stability, and lower preparation cost than conventional fluorinated cation exchange resins, as well as a method for preparing the cation exchange resin.

[0010] Furthermore, this disclosure aims to provide an ion exchange membrane for separating alkali metal species, which is prepared using cation exchange, and an electrodialysis apparatus for lithium extraction.

[0011] [Technical Solution]

[0012] According to another aspect, this disclosure provides a cation exchange resin comprising a first repeating unit represented by the following chemical formula 1 and a second repeating unit represented by the following chemical formula 2.

[0013] [Chemical Formula 1]

[0014]

[0015] (In chemical formula 1,

[0016] X and X′ are each independently a hydrogen or alkali metal species (E), A 1 (Represented by the following chemical formula 3 or chemical formula 4)

[0017] [Chemical Formula 2]

[0018]

[0019] (In chemical formula 2,

[0020] A 2 (represented by the following chemical formula 3 or chemical formula 4).

[0021] [Chemical Formula 3]

[0022]

[0023] (In chemical formula 3,

[0024] Z 1 -S-, -O-, -C(O)-, or -C(R) 1 R 2 )-,and

[0025] R 1 and R 2 Each of the following is independently hydrogen, a C1 to C2 alkyl group, a halogen, or a C1 to C2 alkyl group substituted with a halogen.

[0026] [Chemical Formula 4]

[0027]

[0028] According to another aspect, this disclosure provides a cation exchange resin composition comprising a cation exchange resin and an ion exchange membrane for separating alkali metal species (M), which is obtained by forming a membrane of the resin composition.

[0029] According to yet another aspect, this disclosure provides an ion exchange membrane comprising a cation exchange resin for separating alkali metal species (M).

[0030] According to another aspect, this disclosure provides an electrodialysis apparatus for lithium extraction, comprising an ion exchange membrane for separating alkali metal species (M).

[0031] According to another aspect, this disclosure provides a method for preparing a cation exchange resin, comprising subjecting a reaction mixture to a polymerization reaction, the reaction mixture comprising a first monomer represented by chemical formula 7; a second monomer represented by chemical formula 8; a third monomer represented by chemical formula 9 or chemical formula 10; and a polymerization solvent.

[0032] [Chemical Formula 7]

[0033]

[0034] (In chemical formula 7,

[0035] L 1 and L 2 Each is a leaving group removed during the polymerization reaction, and each is an independent halogen element.

[0036] [Chemical Formula 8]

[0037]

[0038] (In chemical formula 8,

[0039] X and X′ are each independently hydrogen or alkali metal species (E), without including alkali metal species (M).

[0040] L 3 and L 4 Each is a leaving group that is removed during the polymerization reaction, and each is an independent halogen element.

[0041] [Chemical Formula 9]

[0042]

[0043] (In chemical formula 9,

[0044] Z 1 -S-, -O-, -C(O)-, or -C(R) 1 R 2 )-,and

[0045] R 1 and R 2 Each of the following is independently hydrogen, a C1 to C2 alkyl group, a halogen, or a halogen-substituted C1 to C2 alkyl group, and

[0046] L 5 and L 6 Each is a leaving group that is removed during the polymerization reaction, and each is independently a cation of an alkali metal species (E) or a hydrogen atom.

[0047] [Chemical Formula 10]

[0048]

[0049] (In chemical formula 10,

[0050] L 7 and L 8 Each is a leaving group that is removed during the polymerization reaction, and each is independently a cation of an alkali metal species (E) or a hydrogen atom.

[0051] [Beneficial Effects]

[0052] The cation exchange resin according to this disclosure comprises repeating units having a structure in which phenyl groups and / or sulfonated phenyl groups are bonded to phenyl sulfone structures substituted with sulfonic acid groups via thioether bonds, thereby exhibiting excellent ion exchange performance. In the cation exchange resin according to this disclosure, the bond strength when phenyl groups are bonded to each other via thioether groups is higher than the bond strength when phenyl groups are bonded to each other via ether groups. Therefore, higher chemical stability can be achieved compared to conventional commercial sulfonated polystyrene.

[0053] Furthermore, the cation exchange resin according to this disclosure can be synthesized using low-cost monomers and allows for a simple polymerization process. Therefore, the preparation cost of this cation exchange resin is lower than that of conventional commercially available fluorine-based ion exchange resins.

[0054] Furthermore, the ion exchange membrane for separating alkali metal species (M) prepared using the cation exchange resin according to this disclosure exhibits excellent swelling characteristics and excellent alkali resistance when immersed in water. Therefore, this ion exchange membrane can operate stably over a wide pH range.

[0055] Furthermore, when preparing ion exchange membranes for separating alkali metal species (M) using the cation exchange resin according to this disclosure, porous polyolefins or inorganic fibers with excellent dimensional stability and low cost can be used as supports. Therefore, inexpensive ion exchange membranes with excellent mechanical durability can be prepared. Attached Figure Description

[0056] Figure 1 This is a flowchart illustrating a method for preparing a cation exchange resin according to the present disclosure; and

[0057] Figure 2 This is a schematic diagram of an electrodialysis apparatus for lithium extraction according to the present disclosure. Detailed Implementation

[0058] This disclosure will now be described in detail.

[0059] Cation exchange resin

[0060] The cation exchange resin according to this disclosure will now be described first.

[0061] The cation exchange resin according to this disclosure comprises a first repeating unit represented by the following chemical formula 1 and a second repeating unit represented by the following chemical formula 2.

[0062] [Chemical Formula 1]

[0063]

[0064] In chemical formula 1,

[0065] X and X′ can each be independently hydrogen or an alkali metal species (E). In this case, the alkali metal species (E) can be, for example, Li, Na or K, preferably Na or K.

[0066] [Chemical Formula 2]

[0067]

[0068] In chemical formula 2, A 2 It can be represented by the following chemical formula 3 or chemical formula 4.

[0069] [Chemical Formula 3]

[0070]

[0071] In chemical formula 3, Z 1 -S-, -O-, -C(O)-, or -C(R) 1 R 2 )-, and R 1 and R 2 Each of the following is independently hydrogen, a C1 to C2 alkyl group, a halogen, or a halogen-substituted C1 to C2 alkyl group. Preferably, Z 1 It can be -S- or -O-.

[0072] [Chemical Formula 4]

[0073]

[0074] At the same time, A in chemical formula 1 1 And A in chemical formula 2 2 They may be the same or different from each other. However, from the perspective of ease of synthesis and manufacturing cost, A is preferred. 1 and A 2 They are the same.

[0075] Specifically, A in chemical formula 1 1 And A in chemical formula 2 2 It can be represented by the following chemical formula 3, or by chemical formula 4.

[0076] The first repeating unit contains a sulfonic acid group substituted on a phenyl group, which acts as a cation exchanger, thereby achieving high ion exchange performance. Furthermore, due to the structure of the first and second repeating units, where benzene is bonded through thioether groups (with higher bonding strength than ether groups), excellent chemical stability, such as pH stability, is exhibited. Therefore, the cation exchange resin according to this disclosure, comprising the first and second repeating units, exhibits high ion exchange performance and excellent chemical stability.

[0077] Specifically, the first repeating unit can be represented by the following chemical formula 1A.

[0078] [Chemical Formula 1A]

[0079]

[0080] In chemical formula 1A, X, X′, and A 1 All are identical to those described in Formula 1. When the sulfonic acid group is substituted at the position shown in Formula 1A, the synthesis is easier and further exhibits excellent ion exchange performance.

[0081] Furthermore, the cation exchange resin according to this disclosure may comprise a first repeating unit and a second repeating unit in a molar ratio of 30:70 to 70:30, preferably 30:70 to 60:40, and more preferably 30:70 to 50:50. When the first repeating unit and the second repeating unit satisfy the above molar ratio, they exhibit excellent ion exchange performance, excellent chemical stability, and excellent swelling characteristics. When the molar ratio of the first repeating unit is less than the above range, the content of sulfonic acid groups used as the cation exchanger decreases, which may lead to a decrease in ion exchange capacity. When the molar ratio exceeds the above range, water absorption increases, which may lead to a deterioration in swelling characteristics.

[0082] More specifically, the cation exchange resin according to this disclosure may contain repeating units represented by the following chemical formula 5 or repeating units represented by chemical formula 6.

[0083] [Chemical Formula 5]

[0084]

[0085] In chemical formula 5, X and X′ are defined the same as in chemical formula 1, and Z... 1 R 1 and R 2 All are the same as the definitions in chemical formula 3.

[0086] Meanwhile, m1 is a positive number greater than 0 and less than or equal to 1, preferably a positive number in the range of 0.3 to 0.7, 0.3 to 0.6, or 0.3 to 0.5. When m1 meets the above ranges, it exhibits excellent ion exchange performance, excellent chemical stability, and excellent swelling characteristics. When m1 is too small, the content of sulfonic acid groups used as the cation exchanger may decrease, which may lead to a decrease in ion exchange capacity. When m1 is too large, the water absorption rate may increase, thereby reducing the swelling characteristics.

[0087] n1 can be an integer in the range of 30 to 1000, preferably an integer in the range of 30 to 800. When n meets the above range, the weight-average molecular weight of the cation exchange resin can be appropriately controlled. When n1 is too small, the ion exchange capacity and mechanical properties may decrease. When n1 is too large, the viscosity of the resin composition may increase, thereby making the preparation of the ion exchange membrane difficult.

[0088] [Chemical Formula 6]

[0089]

[0090] In chemical formula 6, X and X′ are defined the same as in chemical formula 1, and Z... 1 R 1 and R 2 All are the same as the definitions in chemical formula 3.

[0091] Simultaneously, m2 is a positive number greater than 0 and less than or equal to 1, and preferably a positive number in the range of 0.3 to 0.7, 0.3 to 0.6, or 0.3 to 0.5. When m2 meets the above ranges, it exhibits excellent ion exchange performance, excellent chemical stability, and excellent swelling characteristics. When m2 is too small, the content of sulfonic acid groups used as the cation exchanger may decrease, resulting in a decrease in ion exchange capacity. When m2 is too large, the water absorption rate may increase, thereby reducing the swelling characteristics.

[0092] n2 can be an integer ranging from 50 to 1000, preferably from 30 to 800. When n2 meets the above range, the weight-average molecular weight of the cation exchange resin can be appropriately controlled. When n2 is too small, the ion exchange capacity and mechanical properties may decrease. When n2 is too large, the viscosity of the resin composition may increase, making it difficult to prepare the ion exchange membrane.

[0093] Furthermore, the weight-average molecular weight of the cation exchange resin according to this disclosure can range from 50,000 g / mol to 500,000 g / mol, preferably from 50,000 g / mol to 400,000 g / mol, and more preferably from 100,000 g / mol to 400,000 g / mol. When the weight-average molecular weight of the cation exchange resin meets the above range, the preparation of the ion exchange membrane is easy, and the ion exchange membrane can exhibit excellent mechanical strength.

[0094] Methods for preparing cation exchange resins

[0095] The method for preparing the cation exchange resin according to this disclosure will now be described.

[0096] The cation exchange resin according to this disclosure can be prepared by the following steps: polymerizing a reaction mixture comprising a first monomer represented by the following chemical formula 7, a second monomer represented by the following chemical formula 8, a third monomer represented by the following chemical formula 9 or chemical formula 10, and a polymerization solvent.

[0097] Figure 1 A method for preparing a cation exchange resin according to the present disclosure is shown.

[0098] like Figure 1 As shown, the method for preparing the cation exchange resin according to the present disclosure includes the following steps: adding a polymerization solvent to a mixture of a first monomer, a second monomer and a third monomer to form a reaction mixture (S1), and polymerizing the reaction mixture to synthesize the cation exchange resin (S2).

[0099] Furthermore, the method for preparing the cation exchange resin according to the present disclosure may further include (if necessary) the following steps: separating the synthesized cation exchange resin and washing and drying the result to prepare a solid-phase cation exchange resin (S3), and redissolving the solid-phase cation exchange resin to form a liquid-phase cation exchange resin composition (S4).

[0100] The method for preparing the cation exchange resin according to this disclosure will now be described in more detail.

[0101] First, a polymerization solvent is added to a mixture of the first monomer, the second monomer, and the third monomer to form a reaction mixture (step S1).

[0102] In this case, the first monomer is a compound represented by the following chemical formula 7, which constitutes the second repeating unit in the cation exchange resin according to the present disclosure, so as to provide mechanical and chemical stability to the cation exchange resin.

[0103] [Chemical Formula 7]

[0104]

[0105] In chemical formula 7, L 1 and L 2 Each of these is a leaving group that is removed during the polymerization reaction and can be an independent halogen element such as F, Cl, Br or I, or a hydrogen atom, preferably a halogen element.

[0106] Specifically, the first monomer may be diphenyl sulfone, 4,4′-dihalodiphenyl sulfone, or a combination thereof. Among them, 4,4′-dichlorodiphenyl sulfone (DCDPS) is particularly preferred.

[0107] Preferably, a compound with a purity of at least 99% can be used as the first monomer. When a compound with a purity of less than 99% is used as the first monomer, side reactions may occur due to impurities.

[0108] Meanwhile, based on the total weight of 100 parts by weight of the combination of the first to third monomers, the content of the first monomer can range from 10 parts by weight to 40 parts by weight, preferably from 20 parts by weight to 35 parts by weight, and more preferably from 22 parts by weight to 35 parts by weight.

[0109] When the content of the first monomer in the total monomers meets the above range, the proportion of the second repeating unit in the cation exchange resin can be appropriately formed, thereby ensuring excellent mechanical properties and excellent chemical stability.

[0110] Secondly, the second monomer is a compound constituting the first repeating unit in the cation exchange resin according to the present disclosure, intended to impart cation exchange properties to the cation exchange resin, and is represented by the following chemical formula 8.

[0111] [Chemical Formula 8]

[0112]

[0113] In chemical formula 8, X and X′ are each independently hydrogen or an alkali metal species (E). In this case, the alkali metal species (E) can be Li, Na, or K, preferably Na or K.

[0114] L 3 and L 4 Each is a leaving group that is removed during the polymerization reaction, and each can be an independent halogen element such as F, Cl, Br or I, preferably F or Cl.

[0115] For example, the second monomer can be prepared by sulfonating the first monomer as described in reaction formula 1 below, preferably using a compound with a purity of at least 97%. When a compound with a purity of less than 97% is used as the second monomer, side reactions may occur due to impurities.

[0116] [Reaction Formula 1]

[0117]

[0118] Specific examples of the second monomer include disodium 3,3′-disulfonated-4,4′-dichlorodiphenyl sulfone (SDCDPS), disodium 3,3′-disulfonated-4,4′-difluorodiphenyl sulfone (SDFDPS), or combinations thereof. Among them, disodium 3,3′-disulfonated-4,4′-dichlorodiphenyl sulfone (SDCDPS) is particularly preferred.

[0119] Based on the total weight of 100 parts by weight of the first to third monomer combination, the content of the second monomer can range from 20 parts by weight to 55 parts by weight, preferably from 25 parts by weight to 40 parts by weight, and more preferably from 30 parts by weight to 40 parts by weight. When the content of the second monomer in the total monomers meets the above range, the content of sulfonic acid groups in the cation exchange resin is appropriately formed, thereby achieving excellent ion exchange capacity.

[0120] Next, the third monomer is a compound represented by the following chemical formula 9 or chemical formula 10, which improves the chemical stability and mechanical properties of the cation exchange resin by reacting with the first and second monomers to form a thioether bond between the first and second repeating units.

[0121] [Chemical Formula 9]

[0122]

[0123] In chemical formula 9, Z 1 -S-, -O-, -C(O)-, or -C(R) 1 R 2 -, preferably -S- or -O-. R 1 and R 2 Each can independently be a hydrogen atom, a C1 to C2 alkyl group, a halogen, or a C1 to C2 alkyl group substituted with a halogen.

[0124] L 5 and L 6 Each of these is a leaving group that is removed during the polymerization reaction, and each can be independently a cation of an alkali metal species (E) or a hydrogen atom, preferably hydrogen.

[0125] [Chemical Formula 10]

[0126]

[0127] In chemical formula 10, L 7 and L 8 Each of these is a leaving group that is removed during the polymerization reaction, and each can be independently a cation of an alkali metal species (E) or a hydrogen atom, preferably hydrogen.

[0128] For example, the third monomer includes 4,4′-thiobis(benzyl)thiophenol (TBBT), biphenyl-4,4′-dithiophenol, 4,4′-oxobis(benzyl)thiophenol, bis(4-mercaptophenyl) sulfone, and benzene-1,4-dithiophenol. Among these, 4,4′-thiobis(benzyl)thiophenol (TBBT) is particularly preferred.

[0129] It is preferable to use a compound with a purity of at least 98% as the third monomer. When a compound with a purity of less than 98% is used as the third monomer, side reactions may occur due to impurities.

[0130] Based on the total weight of 100 parts by weight of the first to third monomers, the content of the third monomer can range from 30 to 60 parts by weight, preferably from 30 to 50 parts by weight, and more preferably from 35 to 50 parts by weight. When the content of the third monomer in the total monomers meets the above range, the first and second monomers can be bonded by thioether groups with high bonding strength, thereby preparing a cation exchange resin with excellent mechanical properties and excellent chemical stability.

[0131] Simultaneously, the reaction mixture may contain a first monomer and a second monomer in a molar ratio ranging from 30:70 to 70:30, preferably 40:60 to 70:30, and more preferably 50:50 to 70:30. When the reaction mixture contains the first monomer and the second monomer in the above molar ratio, the molar ratio of the first repeating unit and the second repeating unit in the cation exchange resin is appropriately formed, thereby exhibiting excellent ion exchange performance, excellent chemical stability, and excellent swelling characteristics.

[0132] Next, the polymerization solvent used to dissolve the first to third monomers to allow the polymerization reaction is not limited in type, as long as the polymerization solvent dissolves the monomers. For example, the polymerization solvent may include individual N-methyl-2-pyrrolidone (NMP), toluene, dimethylacetamide (DMAc), N,N-dimethylformamide, dimethyl sulfoxide, or 1,3-dimethyl-2-imidazolium ketone, or combinations thereof. Preferably, the polymerization solvent may be N-methyl-2-pyrrolidone, toluene, dimethylacetamide, or combinations thereof.

[0133] Meanwhile, the polymerization solvent preferably has high purity and low moisture content. When the purity of the polymerization solvent is low, impurities may adversely affect the polymerization reaction; when the moisture content is high, the degree of polymerization of the resin may decrease. Specifically, a polymerization solvent with a purity of at least 99% and a moisture content of less than 500 ppm can be used.

[0134] The content of the polymerization solvent allows for a solid content concentration and viscosity sufficient to enable the polymerization reaction to proceed smoothly.

[0135] For example, the content of the polymerization solvent may allow the solid content concentration in the reaction mixture to be in the range of 10 wt% to 50 wt%, preferably 15 wt% to 40 wt%, more preferably 15 wt% to 35 wt%.

[0136] Additionally, the reaction mixture may contain a catalyst, if necessary. This catalyst is used to activate the polymerization reaction and may include, for example, K₂CO₃, CaCO₃, or CeCO₃ alone, or combinations thereof. It is preferred to use a catalyst with a purity of at least 99%, as side reactions may occur due to impurities when using low-purity catalysts.

[0137] Meanwhile, based on the total weight obtained from 100 parts by weight of the combination of the first to third monomers, the catalyst content can range from 15 parts by weight to 35 parts by weight, preferably 20 parts by weight to 35 parts by weight, and more preferably 20 parts by weight to 30 parts by weight. When the catalyst content meets the above range, it exhibits excellent polymerization reaction acceleration effect.

[0138] Next, the reaction mixture is polymerized to synthesize a cation exchange resin (step S2).

[0139] The polymerization reaction can be carried out with or without a catalyst, and the polymerization temperature range is 150°C to 200°C, preferably 160°C to 195°C, and more preferably 170°C to 195°C. When the polymerization reaction is carried out within the above temperature range, the polymerization proceeds smoothly while minimizing the occurrence of side reactions.

[0140] Meanwhile, when cation exchange resin is synthesized by polymerization reaction, if necessary, a solid-phase cation exchange resin can be obtained by separating, washing and drying the synthesized resin (step S3).

[0141] Specifically, the synthesized resin is precipitated in deionized water or isopropanol solvent, the precipitated resin is separated from the solution, and the separated resin is washed and dried to obtain a solid-phase cation exchange resin.

[0142] Subsequently, the solid-phase cation exchange resin is dissolved in a solvent to form a liquid-phase cation exchange resin composition (step S4).

[0143] As a solvent for redissolution, N-methyl-2-pyrrolidone (NMP), dimethylacetamide (DMAc), N,N-dimethylformamide, dimethyl sulfoxide, or 1,3-dimethyl-2-imidazolium ketone may be used, with N-methyl-2-pyrrolidone (NMP), dimethylacetamide (DMAc), or mixtures thereof preferred.

[0144] Meanwhile, the solid content concentration of the liquid phase cation exchange resin composition can range from 10wt% to 30wt%, preferably from 20wt% to 30wt%.

[0145] Furthermore, the viscosity range of the liquid phase cation exchange resin composition can be from 1,500 cP to 50,000 cP, preferably from 2,000 cP to 30,000 cP, wherein the viscosity is measured using a Brookfield viscometer at 25°C.

[0146] When the solid content concentration and viscosity of the liquid phase cation exchange resin composition meet the above ranges, the plasticity and / or coating performance are excellent during the preparation of the ion exchange membrane.

[0147] When the above process is performed in addition, the KCl salt, moisture and / or gases generated during the polymerization reaction are removed, thereby further improving the ion exchange performance, chemical stability and mechanical properties of the cation exchange resin, and the viscosity of the cation exchange resin is controlled by the redissolution process, thereby improving the plasticity of the ion exchange membrane.

[0148] In the method for preparing the cation exchange resin according to this disclosure, the required preparation cost is low due to the use of low-cost monomers. Therefore, it exhibits superior economic benefits compared to conventional commercially available fluorinated ion exchange resins.

[0149] Ion exchange membrane

[0150] The ion exchange membrane according to this disclosure will now be described.

[0151] The ion exchange membrane according to this disclosure can be an ion exchange membrane for separating alkali metal species (M), such that the alkali metal species (M) are separated, and comprises a cation exchange resin and / or a cation exchange resin composition according to this disclosure. In this case, the alkali metal species (M) can be Li, Na, or K, particularly Li.

[0152] For example, the ion exchange membrane may be a molded membrane of a cation exchange resin composition according to the present disclosure, and the molded membrane may be prepared using film-forming methods well known in the art, such as impregnation, casting or coating.

[0153] Specifically, the ion exchange membrane according to this disclosure may include a cation exchange resin according to this disclosure, the cation exchange resin comprising a first repeating unit represented by [Chemical Formula 1] and a second repeating unit represented by [Chemical Formula 2], and may also include a support if necessary.

[0154] For example, the support may include inorganic fibers, such as glass wool, glass felt, or ceramic wool, but this disclosure is not limited thereto.

[0155] Alternatively, the support may be a porous support formed of a polymer material. For example, the porous support may be a woven or nonwoven fabric comprising at least one selected from polyethylene, polypropylene, polybenzimidazole, polyvinylidene fluoride, polytetrafluoroethylene, polyphenylene sulfide, polyetheretherketone, polyethersulfone, polyarylethersulfone, polyetherketone, polyamide imide, and polyetherimide.

[0156] In this case, the ion exchange membrane may be a structure in which the cation exchange resin according to the present disclosure is coated on a porous support.

[0157] The thickness of the cation exchange resin layer coated on the porous support can range from 20 μm to 300 μm, preferably from 20 μm to 200 μm, and more preferably from 30 μm to 150 μm. When the thickness meets the above range, both the durability of the membrane can be maintained and excessive increase in membrane resistance can be prevented.

[0158] The ion exchange membrane for separating alkali metal species (M) according to this disclosure can be manufactured at low cost and exhibits performance comparable to conventional commercial fluorine-based ion exchange membranes, thus offering excellent economic benefits.

[0159] Specifically, the ion exchange capacity (IEC) of the ion exchange membrane according to this disclosure can range from 1.0 mEq / g to 2.0 mEq / g, preferably from 1.1 mEq / g to 1.8 mEq / g, and more preferably from 1.1 mEq / g to 1.7 mEq / g.

[0160] Furthermore, the hydrogen ion conductivity of the ion exchange membrane according to this disclosure at 25°C can range from 0.02 S / cm to 0.12 S / cm, preferably from 0.02 S / cm to 0.10 S / cm, and more preferably from 0.02 S / cm to 0.09 S / cm. When the ion exchange capacity and hydrogen ion conductivity of the ion exchange membrane meet the above ranges, alkali metal ions (M) can be effectively separated, and the membrane resistance can be minimized.

[0161] Furthermore, the ion exchange membrane for separating alkali metal species (M) according to this disclosure exhibits excellent chemical stability, particularly excellent alkali resistance, which reduces membrane damage and loss even with pH fluctuations and allows the membrane to maintain its stable form.

[0162] Furthermore, the ion exchange membrane for separating alkali metal species (M) according to this disclosure exhibits excellent durability even in humid environments due to its low swelling. Specifically, when the ion exchange membrane is immersed in water, its degree of swelling (i.e., the rate of change in membrane thickness before and after immersion) can be at most 40%, preferably in the range of 5% to 40%, more preferably in the range of 5% to 35%, and still more preferably in the range of 5% to 30%. When the swelling meets the above range, the performance degradation due to membrane deformation can be minimized.

[0163] As described above, the ion exchange membrane according to this disclosure can be effectively applied to electrodialysis apparatuses used for lithium extraction.

[0164] Electrodialysis apparatus for lithium extraction.

[0165] An electrodialysis apparatus for lithium extraction according to this disclosure will now be described.

[0166] The electrodialysis apparatus for lithium extraction according to this disclosure may include an ion exchange membrane for separating alkali metal species (M) as a cation exchange membrane. When the ion exchange membrane according to this disclosure is applied to an electrodialysis apparatus for lithium extraction, excellent durability can be ensured through a low-cost preparation process compared to the application of fluorine-based ion exchange membranes. Furthermore, compared to expensive fluorine-based ion exchange membranes, the ion exchange membrane according to this disclosure offers greater economic benefits in the separation and concentration of lithium hydroxide (LiOH).

[0167] An electrodialysis device for lithium extraction is a device that selectively allows ions to pass through an ion exchange membrane within an electric field, thereby separating lithium ions from the solution. Figure 2 An example of an electrodialysis apparatus for lithium extraction according to this disclosure is shown. Reference will be made below. Figure 2 This disclosure describes an electrodialysis apparatus for lithium extraction.

[0168] Reference Figure 2 The electrodialysis apparatus 100 for lithium extraction according to this disclosure includes: an oxidation electrode 10 and a reduction electrode 20 disposed opposite to each other; a cation exchange membrane 30 and an anion exchange membrane 40 alternately disposed between the oxidation electrode 10 and the reduction electrode 20; and a spacer 50 disposed between the cation exchange membrane 30 and the anion exchange membrane 40. In this case, the cation exchange membrane 30 is an ion exchange membrane for separating alkali metal species (M) according to this disclosure. Meanwhile, bipolar membranes 60 and 70 may be further disposed between the electrode and the ion exchange membrane.

[0169] An oxidation electrode 10 and a reduction electrode 20 are provided to provide an electromotive force to the electrodialysis apparatus, wherein the oxidation electrode 10, which serves as the cathode, provides power to attract anions from the treated water undergoing electrodialysis through anion exchange membrane 40, and the reduction electrode 20, which serves as the anode, provides power to attract cations from the treated water through cation exchange membrane 30.

[0170] A cation exchange membrane 30 and an anion exchange membrane 40 are provided to selectively pass through and separate cations and anions, respectively. A plurality of cation exchange membranes 30 and a plurality of anion exchange membranes 40 are alternately disposed between the oxidation electrode 10 and the reduction electrode 20. In this case, the cation exchange membrane 30 is an ion exchange membrane comprising a cation exchange resin according to the present disclosure.

[0171] The spacer 50 is placed between the cation exchange membrane 30 and the anion exchange membrane 40 to separate the cation exchange membrane 30 and the anion exchange membrane 40 and ensure that the treated water can pass through, and contains a non-insulating material that allows the movement of ions and electrolytes.

[0172] Meanwhile, bipolar membranes 60 and 70 are membranes in the form of a combination of cation exchange layers and anion exchange layers, and are arranged in a reverse bias state in which the cation exchange layer of the bipolar membrane faces the anode and the anion exchange layer faces the cathode. The bipolar membrane can decompose water molecules into hydrogen ions and hydroxide ions. When a bipolar membrane is provided, the anions and cations separated from the ion exchange membrane can react with the H+ ions separated from the bipolar membrane. + Ions and OH - Ionic reactions convert anions and cations into compound forms that are easily recovered and / or utilized.

[0173] Next, a method for extracting lithium using the electrodialysis apparatus 100 described above will be described.

[0174] First, lithium-containing treated water (F) is introduced between the cation exchange membrane 30 and the anion exchange membrane 40, and water is introduced between the bipolar membrane 60 and the electrodes 10 and 20. In this case, the lithium-containing treated water (F) may include, for example, lithium sulfate (LiSO4) from waste lithium secondary batteries or waste liquid generated during the manufacturing process of lithium secondary batteries, but this disclosure is not limited thereto.

[0175] After the treatment water (F) and water are introduced, or simultaneously with the introduction, a voltage is applied to the oxidation electrode 10 and the reduction electrode 20. When a voltage is applied to the electrodes, water decomposes in the bipolar film to generate H₂. + Ions and OH - Lithium ions, used to treat water containing lithium ions (Li + As it passes through the cation exchange membrane 30, it moves toward the reduction electrode 20, treating anions (e.g., SO42-) contained in the water. 2-It moves toward the oxidation electrode 10 while passing through the anion exchange membrane 40.

[0176] Lithium ions (Li) moving toward the oxide electrode 10 + The anions (SO₄²⁻) combine with OH⁻ ions generated in the bipolar membrane to form LiOH(P), and lithium can be extracted from the treated water by recovering LiOH. Simultaneously, anions (SO₄²⁻) migrate towards the reduction electrode 20. 2- ) can be with H + Ion bonding, through the interaction of anions and H+ + The products formed by ion bonding and the residual treated water can be discharged separately from LiOH to the outside of the electrodialysis unit.

[0177] [Invention Model]

[0178] The embodiments of this disclosure will be described in detail below so that those skilled in the art to which this disclosure pertains can easily reproduce this disclosure. However, this disclosure may be implemented in various forms and is not limited to the embodiments described herein.

[0179] Examples and Comparative Examples

[0180] Example 1

[0181] <Preparation of Cation Exchange Resins>

[0182] Install a gas inlet, Dean-Stark water separator, condenser, thermometer, and stirrer in a 500 mL round-bottom flask, and place the flask under a nitrogen atmosphere for 30 minutes.

[0183] 18.56 g DCDPS, 13.61 g SDCDPS and 23.10 g TBBT (used as monomers), 14.46 g K2CO3 (used as catalyst), and 207 g NMP (used as solvent) were added to a round-bottom flask and the mixture was stirred to completely dissolve the components, thereby preparing the reaction mixture.

[0184] Subsequently, the reaction mixture was heated to 150°C and held for more than 1 hour, then heated to 175°C and held for more than 2 hours, while maintaining the polymerization reaction at this temperature until the desired viscosity was reached.

[0185] Subsequently, salt byproducts were removed by filtration, and cation exchange resin was obtained by water precipitation. The obtained resin was washed sequentially with water and isopropanol (IPA) to remove residual impurities, and then dried in a vacuum drying oven at 80°C for 24 hours to obtain a solid-phase cation exchange resin (sulfonated polysulfide sulfone, SPTES). This solid-phase cation exchange resin was then dissolved in NMP solvent to achieve a solid content concentration of 20 wt%, thereby obtaining a transparent liquid-phase cation exchange resin composition.

[0186] <Preparation of Ion Exchange Membranes>

[0187] A liquid cation exchange resin composition was coated onto a glass plate with a doctor blade and then dried in an oven at 80°C for 12 hours to prepare an ion exchange membrane.

[0188] Example 2

[0189] Except for introducing 15.91 g DCDPS and 18.15 g SDCDPS during the preparation of the cation exchange resin, the cation exchange resin composition and the ion exchange membrane containing the cation exchange resin composition were prepared in the same manner as in Example 1.

[0190] Example 3

[0191] Except for introducing 13.26 g DCDPS and 22.68 g SDCDPS during the preparation of the cation exchange resin, the cation exchange resin composition and the ion exchange membrane containing the cation exchange resin composition were prepared in the same manner as in Example 1.

[0192] Comparative Example 1

[0193] Except for introducing 18.56g DCDPS, 13.61g SDCDPS and 17.21g BP (biphenol) as monomers to prepare sulfonated polyether sulfone (SPES) resin during the preparation of cation exchange resin, the cation exchange resin composition and the ion exchange membrane containing the cation exchange resin composition were prepared by the same method as in Example 1.

[0194] Comparative Example 2

[0195] Except for introducing 15.91g DCDPS, 18.15g SDCDPS and 17.21g BP (biphenol) as monomers to prepare sulfonated polyether sulfone (SPES) during the preparation of cation exchange resin, the cation exchange resin composition and the ion exchange membrane containing the cation exchange resin composition were prepared in the same manner as in Example 1.

[0196] Comparative Example 3

[0197] Commercially available sulfonated PPO ion exchange resin (InnoChemTech's InnoSol-C) was used. 100 Preparation of ion exchange membranes.

[0198] The compositions of the reaction solutions used to prepare cation exchange resins in Examples 1 to 3 and Comparative Examples 1 to 2 are shown in Table 1 below.

[0199] Table 1

[0200]

[0201] In Table 1, mol% refers to the molar percentage of each monomer relative to the total number of moles of all monomers in the reaction solution. DCDPS is dichlorodiphenyl sulfone (4,4′-dichlorodiphenyl sulfone, CAS No. 80-07-9, molecular weight: 287.15 g / mol), SDCDPS is disodium dichlorodiphenyl sulfone disulfonate (3,3′-disulfonated-4,4′-dichlorodiphenyl sulfone disodium, CAS No. 51698-33-0, molecular weight: 491.25 g / mol), TBBT is thiobis(thiophenol) (4,4′-thiobis(thiophenol), CAS No. 19362-77-7, molecular weight: 250.39 g / mol), and BP is biphenol (molecular weight: 186.21 g / mol). NMP is N-methylpyrrolidone.

[0202] Experimental Example 1: Evaluation of Ion Exchange Capacity

[0203] Ion exchange membranes prepared according to Examples 1 to 3 and Comparative Examples 1 to 3 were immersed in 1.5M sulfuric acid aqueous solution at room temperature for 24 hours, washed with deionized water, and then dried in a vacuum oven at 80°C. The dried membranes were cut into samples with a width of 1 cm and a length of 3 cm, the weight of the samples was weighed, and then the samples were immersed in 100 mL of 0.01M NaCl aqueous solution for 24 hours. After that, the samples were titrated with 0.01M NaOH aqueous solution using an automatic acid-base titrator (Metrohm, 888 Titrando) until the pH value reached 7. The ion exchange capacity (IEC) was measured by substituting the sample weight and the volume of NaOH aqueous solution used for titration into the following equation (1). The measurement results are shown in Table 2 below.

[0204] Equation (1):

[0205]

[0206] (v: volume of NaOH aqueous solution used in titration (mL), c: molar concentration of NaOH aqueous solution (M), w: sample weight (g))

[0207] Experimental Example 2: Evaluation of Hydrogen Ion Conductivity

[0208] The ion exchange membranes prepared in Examples 1 to 3 and Comparative Examples 1 to 3 were immersed in a 1.5M sulfuric acid aqueous solution at room temperature for 24 hours, washed with deionized water, and then stored while still immersed in deionized water. The thickness of the immersed ion exchange membrane was then measured. The membrane was then installed in a conductivity measurement cell, placed in a 25°C oven, and connected to an AC impedance measuring device (Neoscience; VSP-300) to evaluate the ionic conductivity of hydrogen ions. The measurement results are shown in Table 2 below.

[0209] Table 2

[0210]

[0211] Referring to [Table 2], it can be determined that the ion exchange capacity and hydrogen ion conductivity of Examples 1 to 3 are comparable to those of Comparative Examples 1 to 3. Furthermore, it can be determined that for Examples 1 to 3, the ion exchange capacity and hydrogen ion conductivity increase with increasing molar percentage of SDCDPS in the reaction solution.

[0212] Experimental Example 3: Evaluation of pH Stability

[0213] After preparing solutions with pH ranges from 1 to 14 using aqueous solutions of HCl and KOH, the ion exchange membranes prepared according to Examples 1 to 3 and Comparative Examples 1 to 3 were immersed in these pH solutions, respectively. After 30 days, the pH stability of each ion exchange membrane was evaluated by checking whether the membrane shape remained unchanged and the amount of residual compounds. The results are shown in Table 3 below.

[0214] Table 3

[0215]

[0216] In Table 3, “O” indicates that the ion exchange membrane retains its shape without breaking at each pH and that the compound residue is at least 80%. “X” indicates that the ion exchange membrane fails to retain its shape and breaks at each pH, ​​or that the compound residue is at most 60%. Referring to Table 3, it can be determined that the pH stability of the ion exchange membranes according to Examples 1 to 3 is superior to that of Comparative Examples 1 to 3.

[0217] Experimental Example 4: Evaluation of Swelling

[0218] The ion exchange membranes prepared according to Examples 1 to 3 and Comparative Examples 1 to 3 were immersed in water at 25°C for 48 hours. The volume change rate of the ion exchange membranes before and after immersion was measured and the swelling degree (%) was evaluated. The swelling degree is defined by the following equation (2).

[0219] Equation (2): Swelling degree (%) = {(Volume of ion exchange membrane after immersion − Volume of ion exchange membrane before immersion) / Volume of ion exchange membrane before immersion} × 100

[0220] The measurement results are shown in Table 4 below.

[0221] Table 4

[0222]

[0223] Referring to [Table 4], it can be determined that the ion exchange membranes prepared according to Examples 1 to 3 exhibit superior swelling characteristics compared to the ion exchange membranes prepared according to Comparative Examples 1 to 2. Furthermore, for the ion exchange membrane of Comparative Example 1, although the contents of DCDPS and SDCDPS are equal, its swelling characteristics are reduced compared to the ion exchange membrane of Example 1 prepared using a thiophenol monomer cation exchange resin.

Claims

1. A cation exchange resin, comprising: The first repeating unit represented by the following chemical formula 1; and The second repeating unit represented by the following chemical formula 2 [Chemical Formula 1] ; (In chemical formula 1, X and X′ are each independently a hydrogen or alkali metal species (E), and A) 1 (Represented by the following chemical formula 3 or chemical formula 4) [Chemical Formula 2] ; (In chemical formula 2, A) 2 (Represented by the following chemical formula 3 or chemical formula 4) [Chemical Formula 3] ; (In chemical formula 3, Z) 1 -S-, -O-, -C(O)-, or -C(R) 1 R 2 )-, R 1 and R 2 Each of the following is independently hydrogen, a C1 to C2 alkyl group, a halogen, or a C1 to C2 alkyl group substituted with a halogen. [Chemical Formula 4] 。 2. The cation exchange resin of claim 1, wherein the first repeating unit is represented by the following chemical formula 1A. [Chemical Formula 1A] ; (In chemical formula 1A, X and X′ are each independently a hydrogen or alkali metal species (E), and A) 1 (Represented by the following chemical formula 3 or chemical formula 4) [Chemical Formula 3] ; (In chemical formula 3, Z) 1 -S-, -O-, -C(O)-, or -C(R) 1 R 2 )-, and R 1 and R 2 Each of the following is independently a hydrogen atom, a C1 to C2 alkyl group, a halogen, or a C1 to C2 alkyl group substituted with a halogen. [Chemical Formula 4] 。 3. The cation exchange resin according to claim 1, wherein Z 1 It can be either -S- or -O-.

4. The cation exchange resin according to claim 1, wherein A in chemical formula 1 1 And A in chemical formula 2 2 It is represented by chemical formula 3.

5. The cation exchange resin according to claim 1, wherein A in chemical formula 1 1 And A in chemical formula 2 2 All are represented by chemical formula 4.

6. The cation exchange resin of claim 1, wherein the cation exchange resin comprises a first repeating unit and a second repeating unit in a molar ratio of 30:70 to 70:

30.

7. The cation exchange resin of claim 1, wherein the cation exchange resin comprises repeating units represented by the following chemical formula 5. [Chemical Formula 5] ; (In chemical formula 5, X and X′ are each independently hydrogen or alkali metal species (E).) Z 1 -S-, -O-, -C(O)-, or -C(R) 1 R 2 )-, R 1 and R 2 Each of the following is independently a hydrogen atom, a C1 to C2 alkyl group, a halogen, or a C1 to C2 alkyl group substituted with a halogen. m1 is a positive number greater than 0 and less than or equal to 1, and n1 is an integer in the range of 50 to 1,000.

8. The cation exchange resin of claim 7, wherein m1 is a positive number in the range of 0.3 to 0.

7.

9. The cation exchange resin of claim 1, wherein the cation exchange resin comprises units represented by the following chemical formula 6. [Chemical Formula 6] ; (In chemical formula 6, X and X′ are each independently hydrogen or alkali metal species (E). m2 is a positive number greater than 0 and less than or equal to 1. n2 is an integer in the range of 50 to 1,000.

10. The cation exchange resin of claim 9, wherein m2 is a positive number in the range of 0.3 to 0.

7.

11. The cation exchange resin of claim 1, wherein the alkali metal species (E) is sodium (Na) or potassium (K).

12. The cation exchange resin of claim 1, wherein the weight-average molecular weight of the cation exchange resin is in the range of 50,000 g / mol to 500,000 g / mol.

13. A cation exchange resin composition comprising: The cation exchange resin according to any one of claims 1 to 12.

14. An ion exchange membrane for separating alkali metal species (M), said ion exchange membrane being obtained as a membrane formed from the cation exchange resin composition of claim 13.

15. An ion exchange membrane for separating alkali metal species (M), said ion exchange membrane comprising: The cation exchange resin according to any one of claims 1 to 12.

16. The ion exchange membrane of claim 15, wherein the ion exchange membrane for separating alkali metal species (M) further comprises a support.

17. The ion exchange membrane of claim 16, wherein the support comprises inorganic fibers, and The cation exchange resin is immersed in the support.

18. The ion exchange membrane of claim 16, wherein the inorganic fibers comprise at least one selected from the group consisting of glass felt, glass wool, and ceramic wool.

19. The ion exchange membrane of claim 16, wherein the support is a porous polymer membrane, and The cation exchange resin is coated on the porous support.

20. The ion exchange membrane of claim 19, wherein the thickness of the cation exchange resin coated on the porous support ranges from 20 μm to 300 μm.

21. The ion exchange membrane of claim 15, wherein the ion exchange capacity (IEC) of the ion exchange membrane ranges from 1.0 mEq / g to 2.0 mEq / g.

22. The ion exchange membrane of claim 15, wherein the ion exchange membrane has a hydrogen ion conductivity in the range of 0.02 S / cm to 0.12 S / cm at 25°C.

23. The ion exchange membrane of claim 15, wherein the degree of swelling, expressed by the following equation (2) and measured by immersing the ion exchange membrane in water at 25°C for 48 hours, is at most 40%. Equation (2): Swelling degree (%) = {(volume of ion exchange membrane after immersion − volume of ion exchange membrane before immersion) / volume of ion exchange membrane before immersion} × 100.

24. The ion exchange membrane of claim 15, wherein the alkali metal species (M) is lithium (Li).

25. An electrodialysis apparatus for lithium extraction, the electrodialysis apparatus comprising: The ion exchange membrane for separating alkali metal species (M) according to claim 15.

26. A method for preparing a cation exchange resin, comprising: The reaction mixture is subjected to a polymerization reaction, the reaction mixture comprising a first monomer represented by chemical formula 7; a second monomer represented by chemical formula 8; a third monomer represented by chemical formula 9 or chemical formula 10; and a polymerization solvent. [Chemical Formula 7] ; (In chemical formula 7, L) 1 and L 2 Each is a leaving group removed during the polymerization reaction and each is an independent halogen element. [Chemical Formula 8] ; (In chemical formula 8, X and X′ are each independently a hydrogen or alkali metal species (E), L 3 and L 4 Each is a leaving group removed during the polymerization reaction and each is an independent halogen element. [Chemical Formula 9] ; (In chemical formula 9, Z 1 -S-, -O-, -C(O)-, or -C(R) 1 R 2 )-, R 1 and R 2 Each of the following is independently hydrogen, a C1 to C2 alkyl group, a halogen, or a halogen-substituted C1 to C2 alkyl group, and L 5 and L 6 Each is a leaving group removed during the polymerization reaction and is independently a cation of an alkali metal species (E) or a hydrogen atom. [Chemical Formula 10] ; (In chemical formula 10, L 7 and L 8 Each is a leaving group that is removed during the polymerization reaction and is independently a cation of an alkali metal species (E) or a hydrogen atom.

27. The method for preparing a cation exchange resin as described in claim 26, wherein L 5 L 6 L 7 and L 8 All are hydrogen atoms.

28. The method for preparing a cation exchange resin as described in claim 26, wherein the reaction mixture comprises a first monomer and a second monomer in a molar ratio ranging from 30:70 to 70:

30.

29. The method for preparing a cation exchange resin as described in claim 26, wherein polymerization is carried out at a temperature of at least 150°C and at most 200°C.

30. The method for preparing a cation exchange resin as described in claim 26, wherein the polymerization reaction is carried out in the presence of a catalyst.

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