Anion exchange membrane with high hydroxide conductivity and method of preparation

Abstract

The application provides an anion exchange membrane with high hydroxyl ion conductivity and a preparation method. The anion exchange membrane base film after pre-treatment by soaking in deionized water is immersed in an aqueous phase solution, 3,3'-diamino benzidine is fully adsorbed, a rubber roller is used to remove the surface solution, and then the base film is immersed in an organic phase solution for interfacial polymerization reaction, so that the 3,3'-diamino benzidine adsorbed on the surface of the anion exchange membrane base film fully contacts with p-xylene dicarboxaldehyde in the organic phase solution and polymerization reaction occurs at the interface of the two phases to form a separation layer, then drying and solidification are carried out to improve the compactness and stability, and then the base film is treated by alkali doping to obtain the anion exchange membrane with high hydroxyl ion conductivity. The application significantly shortens the ion transmission path and improves the ion conductivity.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of ion exchange membrane materials, in particular to an anion exchange membrane with high hydroxyl ion conductivity and a preparation method. BACKGROUND

[0002] An anion exchange membrane is a special membrane material used for separating and transferring anions in a solution. Such a membrane is usually composed of a polymer with positively charged groups that can attract and conduct anions while preventing cations from passing through, and is widely used in fields such as water electrolysis, fuel cells, electrodialysis and water treatment.

[0003] As the most advanced water electrolysis technology, the development history of an anion exchange membrane water electrolysis system is relatively short, and the research on high-performance anion exchange membranes is still in the early exploration stage. Compared with mature proton exchange membranes, the ion conductivity and chemical stability of an anion exchange membrane are lower than those of a perfluorosulfonic acid membrane. In terms of conductivity, the ion conductivity of an anion exchange membrane for OH- is about half of that of a proton exchange membrane for H+, and the relatively low ion conductivity of an anion exchange membrane has been the main obstacle to the large-scale promotion of an anion exchange membrane water electrolysis system. Therefore, it is of great research significance to provide a simple method for preparing an anion exchange membrane with high hydroxyl ion conductivity. SUMMARY

[0004] The application aims to provide an anion exchange membrane with high hydroxyl ion conductivity and a preparation method, so as to solve the problem of relatively low ion conductivity of an anion exchange membrane.

[0005] In order to achieve the above application purposes, the application provides the following technical solutions.

[0006] The application provides a preparation method of an anion exchange membrane with high hydroxyl ion conductivity, which comprises the following steps: deionized water immersion pretreatment is performed on an anion exchange membrane base film to obtain an anion exchange membrane base film after deionized water immersion pretreatment; 3,3'-diamino benzidine is added to a mixture of deionized water and anhydrous ethanol to obtain an aqueous solution; p-xylylene glycol is added to a mixture of n-hexane and ethyl acetate to obtain an organic phase solution; the anion exchange membrane base film after deionized water immersion pretreatment is immersed in the aqueous solution, then the immersed base film is taken out, the surface solution is removed by a rubber roller, and then the base film is immersed in the organic phase solution to perform interfacial polymerization, so as to obtain a composite film with a polyazomethine separation layer; the composite film with the polyazomethine separation layer after interfacial polymerization is sequentially subjected to drying and solidification; the composite film with the polyazomethine separation layer after solidification is subjected to alkali doping treatment to obtain an anion exchange membrane.

[0007] The material of the anion exchange membrane base film is polyether sulfone, polyacrylonitrile, polyvinylidene fluoride, polyphenylene sulfide, and one or more combinations thereof.

[0008] According to one embodiment of the present application, the pre-treatment of soaking in deionized water comprises soaking the anion exchange membrane base film in deionized water at 20-30℃ for 48-72h, and replacing the deionized water every 24h.

[0009] According to one embodiment of the present application, the concentration of 3,3'-diaminobenzidine in the aqueous solution is 0.05wt%-2.00wt%, and the mass ratio of deionized water to anhydrous ethanol in the aqueous solution is 2:1.

[0010] According to one embodiment of the present application, the concentration of terephthaldehyde in the organic phase solution is 0.10wt%-3.00wt%, and the mass ratio of n-hexane to ethyl acetate in the organic phase solution is 2:1.

[0011] According to one embodiment of the present application, the time for immersing the anion exchange membrane base film after the pre-treatment of soaking in deionized water into the aqueous solution is 10-60min, and the time for the interfacial polymerization reaction is 3-10min.

[0012] According to one embodiment of the present application, the time for curing in the step of sequentially drying and curing the composite film of the polymethyleneimine separation layer after the interfacial polymerization reaction is 0.5-2.5min, and the curing temperature is 50-80℃.

[0013] According to one embodiment of the present application, the alkali doping treatment in the step of alkali doping treatment of the composite film of the polymethyleneimine separation layer after curing is soaking the composite film of the polymethyleneimine separation layer after curing in a 3mol / L KOH solution for 4-12h.

[0014] The present application provides an anion exchange membrane prepared by the above preparation method.

[0015] The application provides a kind of high hydroxyl ion conductivity anion exchange membrane and preparation method, respectively prepared after soaking pretreatment in deionized water anion exchange membrane base membrane, 3,3'-diamino benzidine containing aqueous solution, and containing p-xylylene glycol organic phase solution, again, after soaking pretreatment in deionized water anion exchange membrane base membrane is immersed in the aqueous solution, so that anion exchange membrane base membrane is fully adsorbed 3,3'-diamino benzidine, then take out the immersed base membrane and remove the surface solution with rubber roller to make subsequent interfacial polymerization reaction more uniform, again immersed in the organic phase solution and carried out interfacial polymerization reaction, make the 3,3'-diamino benzidine adsorbed on the surface of anion exchange membrane base membrane and p-xylylene glycol in organic phase solution fully contact and occur polymerization reaction at the interface of two phases, form separation layer on anion exchange membrane base membrane, then dry and solidify, to make the formed separation layer further crosslinking, improve its compactness and stability, then base membrane is treated with alkali, and high hydroxyl ion conductivity anion exchange membrane is obtained.The application utilizes nucleophilic substitution reaction between aldehyde group and diamino to generate aromatic polyazomethine with good chemical stability and high mechanical strength, and adopts room temperature interfacial polymerization to prepare composite membrane with ultra-thin polyazomethine separation layer.The ion transmission channel of compact polyazomethine separation layer can be regulated by changing the molecular configuration of aldehyde and amine monomers, and the thickness of compact polyazomethine separation layer can be adjusted by regulating the interfacial polymerization reaction conditions, so that the ion transmission path is significantly shortened and the ion conductivity is improved. BRIEF DESCRIPTION OF DRAWINGS

[0016] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creating laborious work.

[0017] Figure 1 As shown in the flow chart of the preparation method of a kind of high hydroxyl ion conductivity anion exchange membrane provided by an embodiment of the present disclosure. DETAILED DESCRIPTION

[0018] As Figure 1 shown, the application provides a preparation method of a kind of high hydroxyl ion conductivity anion exchange membrane, comprising the following steps:

[0019] S1, anion exchange membrane base membrane is soaked in deionized water for pretreatment, to obtain anion exchange membrane base membrane after soaking pretreatment in deionized water;

[0020] S2, 3,3'-diamino benzidine is added to the mixture of deionized water and anhydrous ethanol to obtain an aqueous solution;

[0021] S3, adding p-phthalaldehyde into a mixture of n-hexane and ethyl acetate to obtain an organic phase solution;

[0022] S4, immersing the pretreated anion exchange membrane base film in deionized water into the aqueous phase solution, then taking out the immersed base film, removing the surface solution with a rubber roller, and then immersing into the organic phase solution to perform interfacial polymerization reaction, to obtain a composite membrane of polyazomethine separation layer;

[0023] S5, sequentially drying and curing the composite membrane of polyazomethine separation layer after interfacial polymerization reaction;

[0024] S6, performing alkali doping treatment on the cured composite membrane of polyazomethine separation layer to obtain an anion exchange membrane.

[0025] In the embodiments of the present application, the raw materials used are all conventional commercially available products in the art, unless otherwise specified.

[0026] In the present application, the anion exchange membrane base film is immersed in deionized water for pretreatment to obtain an anion exchange membrane base film immersed in deionized water for pretreatment.

[0027] In the embodiments of the present application, the material of the anion exchange membrane base film can be one or more than two arbitrary combinations of polyether sulfone, polyacrylonitrile, polyvinylidene fluoride, and polyphenylene sulfide.

[0028] In the embodiments of the present application, the molecular weight cut-off of the anion exchange membrane base film can be 50 KDa-150 KDa, more preferably 100 KDa.

[0029] In the embodiments of the present application, the immersion pretreatment in deionized water preferably comprises: immersing the ion exchange membrane base film in deionized water at 20-30℃ for 48-72h, and replacing the deionized water every 24h.

[0030] In the present application, 3,3'-diaminobenzidine is added to a mixture of deionized water and anhydrous ethanol to obtain an aqueous phase solution, and the mass ratio of deionized water to anhydrous ethanol in the aqueous phase solution is 2:1.

[0031] In the embodiments of the present application, the concentration of 3,3'-diaminobenzidine in the aqueous phase solution can be 0.05 wt%-2.00 wt%, for example, 0.10 wt%-1.00 wt%. The present application controls the concentration of 3,3'-diaminobenzidine in the aqueous phase solution within the above range, so that the adsorption amount of 3,3'-diaminobenzidine on the anion exchange membrane base film is at the optimal reaction amount.

[0032] In the present application, p-phthalaldehyde is added to a mixture of n-hexane and ethyl acetate to obtain an organic phase solution, and the mass ratio of n-hexane to ethyl acetate in the organic phase solution is 2:1.

[0033] In the embodiment of the present application, the concentration of p-xylylene glycol in the organic phase solution can be 0.10 wt%-3.00 wt%, for example, 0.25 wt%-2.00 wt%. The present application controls the concentration of p-xylylene glycol in the organic phase solution in the above range to ensure that the interfacial polymerization reaction is at the optimal reaction degree.

[0034] In the embodiment of the present application, the preparation of the anion exchange membrane base film pretreated by soaking in deionized water, the aqueous phase solution, and the organic phase solution has no sequence.

[0035] After obtaining the anion exchange membrane base film pretreated by soaking in deionized water, the aqueous phase solution, and the organic phase solution, the present application immerses the anion exchange membrane base film pretreated by soaking in deionized water into the aqueous phase solution, then takes out the immersed base film, removes the surface solution with a rubber roller, and then immerses it into the organic phase solution for interfacial polymerization reaction to obtain a composite membrane with a polyazomethine separation layer.

[0036] In the embodiment of the present application, the time for immersing the anion exchange membrane base film pretreated by soaking in deionized water into the aqueous phase solution can be 10 min-60 min, for example, 15 min-45 min. The present application controls the time for immersing the anion exchange membrane base film pretreated by soaking in deionized water into the aqueous phase solution in the above range to make the 3,3'-diaminobenzidine in the aqueous phase solution fully adsorbed to the surface of the anion exchange membrane base film pretreated by soaking in deionized water.

[0037] In the embodiment of the present application, the time for interfacial polymerization reaction can be 3 min-10 min, for example, 4 min-8 min. The present application controls the time for interfacial polymerization reaction in the above range to make the 3,3'-diaminobenzidine adsorbed to the surface of the anion exchange membrane base film pretreated by soaking in deionized water and the p-xylylene glycol in the organic phase solution fully react.

[0038] After obtaining the composite membrane with a polyazomethine separation layer, the present application sequentially performs drying and curing on the composite membrane with a polyazomethine separation layer.

[0039] In the embodiment of the present application, the time for curing can be 0.5 min-2.5 min, for example, 1 min-2 min. In the embodiment of the present application, the temperature for curing can be 50 ℃-80 ℃. The present application controls the temperature and time for curing in the above range to make the anion exchange membrane separation layer in the optimal crosslinking state.

[0040] After obtaining the base film treated by thermal curing, the present application performs alkali doping treatment on the composite membrane with a polyazomethine separation layer treated by curing, that is, immerses it in a 3 mol / L KOH solution.

[0041] In the embodiment of the present application, the time of the alkali doping treatment can be 4 h-12 h, for example, 6 h-10 h. The present application controls the time of the alkali doping in the above range, so that the polyazomethine separation layer composite membrane sufficiently absorbs the alkali solution, constructs ion transmission channels, and facilitates ion conduction.

[0042] The preparation method of the anion exchange membrane with high hydroxide conductivity provided by the present application is simple in operation, mild in reaction conditions, and suitable for large-scale production.

[0043] The present application also provides an anion exchange membrane with high hydroxide conductivity prepared by the preparation method of the above technical solution.

[0044] The technical solutions in the present application will be clearly and completely described below in combination with the embodiments in the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the present application.

[0045] Embodiment 1

[0046] A preparation method of an anion exchange membrane with high hydroxide conductivity, (the steps without temperature marked below are all carried out at room temperature) the steps are as follows:

[0047] (1) A polyether sulfone (PES) anion exchange membrane base film (with a molecular weight cut-off of 100 KDa) with a size of 2 cm*2 cm is soaked in deionized water for deionized water soaking pretreatment, and the soaking time is 48 h, and the deionized water needs to be replaced every 24 h.

[0048] (2) 0.2 g of 3,3'-diaminobenzidine is mixed with 133.20 g of deionized water and 66.60 g of anhydrous ethanol to prepare a 3,3'-diaminobenzidine aqueous solution with a concentration of 0.1 wt%.

[0049] (3) 1 g of p-phthaldehyde is mixed with 132.67 g of n-hexane and 66.33 g of ethyl acetate to prepare an organic phase solution of p-phthaldehyde with a concentration of 0.5 wt%.

[0050] (4) The anion exchange membrane base film after deionized water soaking pretreatment obtained in step (1) is immersed in the aqueous solution obtained in step (2) for 45 min, then the immersed base film is taken out, the surface solution is removed by a rubber roller, and then the base film is immersed in the organic phase solution for interfacial polymerization reaction for 8 min, to obtain a polyazomethine separation layer composite membrane.

[0051] (5) The polyazomethine separation layer composite film obtained in step (4) is dried and then placed in a constant temperature drying oven for curing at 80°C for 1 min to obtain a cured polyazomethine separation layer composite film.

[0052] (6) The cured polyazomethine separation layer composite film obtained in step (5) is placed in a 3 mol / L KOH solution for 10 h to obtain a high hydroxide conductivity anion exchange membrane.

[0053] The high hydroxide conductivity anion exchange membrane prepared in Example 1 is stored in a sealed bag for subsequent measurement. A 1 mol / L KOH solution is selected as the electrolyte solution, and an electrochemical workstation is used to analyze the membrane by AC impedance spectroscopy, and then the hydroxide conductivity of the membrane is obtained by measuring the thickness of the membrane.

[0054] The test results show that the hydroxide conductivity of the high hydroxide conductivity anion exchange membrane prepared in Example 1 is 37.02 mS / cm.

[0055] Example 2

[0056] The high hydroxide conductivity anion exchange membrane is prepared according to the method of Example 1, except that in step (2), 0.5 g of 3,3'-diaminobenzidine is mixed with 133.00 g of deionized water and 66.50 g of anhydrous ethanol to prepare a 3,3'-diaminobenzidine aqueous solution with a concentration of 0.25 wt%.

[0057] The high hydroxide conductivity anion exchange membrane prepared in Example 2 is tested for performance according to the same method as Example 1. The test results show that the hydroxide conductivity of the high hydroxide conductivity anion exchange membrane prepared in Example 2 is 39.85 mS / cm.

[0058] Example 3

[0059] The high hydroxide conductivity anion exchange membrane is prepared according to the method of Example 1, except that in step (2), 1 g of 3,3'-diaminobenzidine is mixed with 132.67 g of deionized water and 66.33 g of anhydrous ethanol to prepare a 3,3'-diaminobenzidine aqueous solution with a concentration of 0.5 wt%.

[0060] The high hydroxide conductivity anion exchange membrane prepared in Example 3 is tested for performance according to the same method as Example 1. The test results show that the hydroxide conductivity of the high hydroxide conductivity anion exchange membrane prepared in Example 3 is 43.14 mS / cm.

[0061] Example 4

[0062] The high hydroxide conductivity anion exchange membrane was prepared according to the method of Example 1, except that in step (2), 1.5 g of 3,3'-diaminobenzidine was mixed with 132.33 g of deionized water and 66.17 g of anhydrous ethanol to prepare a 3,3'-diaminobenzidine aqueous solution with a concentration of 0.75 wt%.

[0063] The high hydroxide conductivity anion exchange membrane prepared in Example 4 was tested for performance according to the same method as Example 1. The test results showed that the hydroxide conductivity of the high hydroxide conductivity anion exchange membrane prepared in Example 4 was 41.78 mS / cm.

[0064] Example 5

[0065] The high hydroxide conductivity anion exchange membrane was prepared according to the method of Example 1, except that in step (2), 2 g of 3,3'-diaminobenzidine was mixed with 132.00 g of deionized water and 66.00 g of anhydrous ethanol to prepare a 3,3'-diaminobenzidine aqueous solution with a concentration of 1.00 wt%.

[0066] The high hydroxide conductivity anion exchange membrane prepared in Example 5 was tested for performance according to the same method as Example 1. The test results showed that the hydroxide conductivity of the high hydroxide conductivity anion exchange membrane prepared in Example 5 was 41.05 mS / cm.

[0067] Example 6

[0068] The high hydroxide conductivity anion exchange membrane was prepared according to the method of Example 1, except that in step (2), 1 g of 3,3'-diaminobenzidine was mixed with 132.67 g of deionized water and 66.33 g of anhydrous ethanol to prepare a 3,3'-diaminobenzidine aqueous solution with a concentration of 0.5 wt%. In step (3), 2 g of terephthaldehyde was mixed with 132.00 g of n-hexane and 66.00 g of ethyl acetate to prepare a terephthaldehyde organic phase solution with a concentration of 1.00 wt%.

[0069] The high hydroxide conductivity anion exchange membrane prepared in Example 6 was tested for performance according to the same method as Example 1. The test results showed that the hydroxide conductivity of the high hydroxide conductivity anion exchange membrane prepared in Example 6 was 47.69 mS / cm.

[0070] Comparative Example 1

[0071] An anion exchange membrane was prepared according to the method of Example 1, except that in step (3), 1 g of m-phthaldehyde was mixed with 132.67 g of n-hexane and 66.33 g of ethyl acetate to prepare an organic phase solution of m-phthaldehyde with a concentration of 0.5 wt%.

[0072] The anion exchange membrane with high hydroxide conductivity prepared in Comparative Example 1 was tested for performance according to the same method as in Example 1. The test results showed that the hydroxide conductivity of the anion exchange membrane with high hydroxide conductivity prepared in Comparative Example 1 was 12.56 mS / cm.

[0073] Comparative Example 2

[0074] An anion exchange membrane was prepared according to the method of Example 1, except that in step (3), 1 g of m-phthaldehyde was mixed with 132.67 g of n-hexane and 66.33 g of ethyl acetate to prepare an organic phase solution of m-phthaldehyde with a concentration of 0.5 wt%.

[0075] The anion exchange membrane with high hydroxide conductivity prepared in Comparative Example 2 was tested for performance according to the same method as in Example 1. The test results showed that the hydroxide conductivity of the anion exchange membrane with high hydroxide conductivity prepared in Comparative Example 2 was 28.45 mS / cm.

[0076] Comparative Example 3

[0077] An anion exchange membrane was prepared according to the method of Example 1, except that in step (4), the interfacial polymerization reaction time was 4 min.

[0078] The anion exchange membrane with high hydroxide conductivity prepared in Comparative Example 3 was tested for performance according to the same method as in Example 1. The test results showed that the hydroxide conductivity of the anion exchange membrane with high hydroxide conductivity prepared in Comparative Example 3 was 33.67 mS / cm.

[0079] Comparative Example 4

[0080] An anion exchange membrane was prepared according to the method of Example 1, except that in step (5), after the base membrane was dried, it was placed in a constant temperature drying oven for curing at 50°C for 1 min.

[0081] The anion exchange membrane with high hydroxide conductivity prepared in Comparative Example 4 was tested for performance according to the same method as in Example 1. The test results showed that the hydroxide conductivity of the anion exchange membrane with high hydroxide conductivity prepared in Comparative Example 4 was 35.67 mS / cm.

[0082] In conclusion, the hydroxyl conductivity of the anion exchange membrane prepared in Example 6 of the present application is 47.69 mS / cm, which is significantly higher than that of the comparative example.

[0083] The above only is the preferred embodiment of the present application, it should be pointed out that, for the ordinary skilled in the art, without departing from the principles of the present application, can also make a number of improvements and refinements, these improvements and refinements should also be considered as the protection scope of the present application.

[0084] In the description, the phrases "one embodiment", "an embodiment", etc. mean that the described embodiment can include a particular feature, structure, or characteristic, but every embodiment can not necessarily include the particular feature, structure, or characteristic. In addition, such phrases are not necessarily referring to the same embodiment. Furthermore, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted within the knowledge of one of ordinary skill in the art to effect such feature, structure, or characteristic in connection with an explicitly or implicitly described other embodiment.

[0085] It should be noted that, in this text, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that the process, method, article or equipment including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or includes elements inherent to such process, method, article or equipment. Without more limitations, the element defined by the statement "including a" does not exclude the presence of other identical elements in the process, method, article or equipment including the element.

[0086] The above only is the preferred embodiment of the present application, it should be pointed out that, for the ordinary skilled in the art, without departing from the principles of the present application, can also make a number of improvements and refinements, these improvements and refinements should also be considered as the protection scope of the present application.

Claims

1. A method for preparing an anion exchange membrane with high hydroxide conductivity, comprising the following steps: pretreating an anion exchange membrane base film by immersing it in deionized water to obtain an anion exchange membrane base film pretreated by immersing in deionized water; adding 3,3'-diaminobenzidine into a mixture of deionized water and anhydrous ethanol to obtain an aqueous phase solution; adding p-xylene dicarboxaldehyde into a mixture of n-hexane and ethyl acetate to obtain an organic phase solution; immersing the anion exchange membrane base film pretreated by immersing in deionized water into the aqueous phase solution, then taking out the immersed base film, removing the surface solution with a rubber roller, and then immersing the base film into the organic phase solution to perform interfacial polymerization, thereby obtaining a composite membrane with a polyazomethine separation layer; sequentially drying and curing the composite membrane with a polyazomethine separation layer after the interfacial polymerization; and performing alkali doping treatment on the cured composite membrane with a polyazomethine separation layer to obtain an anion exchange membrane; wherein the material of the anion exchange membrane base film is one of polyether sulfone, polyacrylonitrile, polyvinylidene fluoride, polyphenylene sulfide or a combination of two or more thereof. The pretreatment by immersing in deionized water comprises immersing the anion exchange membrane base film in deionized water at 20-30 ℃ for 48-72 h, and replacing the deionized water every 24 h. The concentration of 3,3'-diaminobenzidine in the aqueous phase solution is 0.05 wt%-2.00 wt%, and the mass ratio of deionized water to anhydrous ethanol in the aqueous phase solution is 2:

1. The concentration of p-xylene dicarboxaldehyde in the organic phase solution is 0.10 wt%-3.00 wt%, and the mass ratio of n-hexane to ethyl acetate in the organic phase solution is 2:

1. The time for immersing the anion exchange membrane base film pretreated by immersing in deionized water into the aqueous phase solution is 10-60 min, and the time for the interfacial polymerization is 3-10 min. The curing time in the step of sequentially drying and curing the composite membrane with a polyazomethine separation layer after the interfacial polymerization is 0.5-2.5 min, and the curing temperature is 50-80 ℃. The alkali doping treatment in the step of performing alkali doping treatment on the cured composite membrane with a polyazomethine separation layer comprises immersing the cured composite membrane with a polyazomethine separation layer in a 3 mol / L KOH solution for 4-12 h. 8.An anion exchange membrane prepared by the method of any one of claims 1-7.

2. The production method according to claim 1, characterized by, ​ 3. The production method according to claim 1, characterized by, ​ 4. The method of claim 1, wherein, ​ 5. The preparation method according to claim 1, characterized in that, ​ 6. The method of claim 1, wherein, ​ 7. The preparation method according to claim 1, characterized in that, ​ ​

Images