Method for purifying non-aqueous liquid and purification apparatus, and method for manufacturing ion exchange resin and pretreatment apparatus

Abstract

A method for purifying a non-aqueous liquid using an ion exchange resin is provided, which reduces the amount of water contained in the liquid in a simple and economical manner without requiring a large amount of non-aqueous liquid. The method for purifying a non-aqueous liquid using an ion exchange resin comprises a pretreatment process in which the ion exchange resin is contacted with a non-aqueous liquid for pretreatment having a dielectric constant of 20 or more at 25°C, and a purification process in which the ion exchange resin after the pretreatment process is contacted with a non-aqueous liquid to be purified, wherein the dielectric constant of the non-aqueous liquid for pretreatment at 25°C is greater than the dielectric constant of the non-aqueous liquid to be purified at 25°C, and the concentration of the metal to be reduced in the non-aqueous liquid for pretreatment is 5 μg / L or less.

Description

Technology Field

[0001] The present invention relates to a method for purifying a non-aqueous liquid using an ion exchange resin with reduced water content, a purification apparatus, a method for manufacturing an ion exchange resin, and a pretreatment apparatus. Background Technology

[0002] Recently, highly purified non-aqueous solutions with impurities removed have been utilized as chemical solutions in semiconductor manufacturing processes and as electrolytes for lithium-ion batteries. Distillation is a known method for purifying non-aqueous solutions by distilling to remove impurities. However, distillation presents technical challenges, such as high equipment costs, the requirement of enormous energy for the distillation process, and the difficulty of achieving high levels of purification. Therefore, a method for purifying non-aqueous solutions using ion exchange resins or ion exchange filters has been proposed. According to the ion exchange method, high levels of impurity removal can be achieved with low equipment costs and energy savings.

[0003] Ion exchange resins consist of approximately 50% water by weight, and water leached from the ion exchange resin during non-aqueous liquid purification becomes an impurity in the non-aqueous liquid. Therefore, before using the ion exchange resin for non-aqueous liquid purification, it is necessary to reduce the water content contained in the ion exchange resin. Methods for reducing the water content of the ion exchange resin include vacuum drying of the ion exchange resin (Patent Documents 1 to 3) or passing a non-aqueous liquid through the ion exchange resin in addition to vacuum drying (Patent Document 4). Additionally, a method for reducing water content by circulating a liquid through a zeolite and an ion exchange resin is also known (Patent Document 5). Prior art literature

[0004] (Patent Document 0001) JP 2004-181351 A (Patent Document 0002) JP 2004-181352 A (Patent Document 0003) JP 2004-249238 A (Patent Document 0004) JP 2000-505042 A (Patent Document 0005) JP 2020-121261 A The problem to be solved

[0005] However, in a method using vacuum drying alone, the moisture content of the ion exchange resin cannot be sufficiently reduced. Furthermore, it has been found that when a method of passing a non-aqueous liquid through the ion exchange resin in addition to vacuum drying is used, a large amount of non-aqueous liquid, amounting to tens to hundreds of times the volume of the ion exchange resin, is required. In addition, when vacuum drying is used, there is a problem in that strong basic anion exchange resins with low heat resistance decompose due to the heat during drying, and their functional groups become inferior. Moreover, in a method using zeolite, there is a concern that metal ions may leach out from the zeolite itself, thereby contaminating the purification solution.

[0006] Accordingly, the present invention aims to provide a method for manufacturing an ion exchange resin and a pretreatment apparatus that can obtain an ion exchange resin with reduced water content simply and economically without requiring a large amount of non-aqueous liquid, and a method and apparatus for purifying non-aqueous liquid using said ion exchange resin. means of solving the problem

[0007] Taking the above problem into account, the inventors carefully examined the matter and found that by using a pretreatment non-aqueous liquid having high affinity for water and a dielectric constant of 20 or higher, such as methanol, to replace the water in the resin, and then bringing the resin into contact with the non-aqueous liquid to be purified, the amount of non-aqueous liquid used can be significantly reduced compared to the case where the pretreatment non-aqueous liquid is not used, and thus the present invention was completed.

[0008] That is, the present invention is a method for purifying a non-aqueous liquid using an ion exchange resin, comprising a pretreatment process in which the ion exchange resin is brought into contact with a non-aqueous liquid for pretreatment having a dielectric constant of 20 or more at 25°C, and a purification process in which the ion exchange resin after the pretreatment process is brought into contact with a non-aqueous liquid to be purified, wherein the dielectric constant of the non-aqueous liquid for pretreatment at 25°C is greater than the dielectric constant of the non-aqueous liquid to be purified at 25°C, and the concentration of the metal to be reduced in the non-aqueous liquid for pretreatment is 5 μg / L or less.

[0009] In addition, the present invention is a purification device for a non-aqueous liquid using an ion exchange resin, comprising a pretreatment device having a pretreatment means for contacting the ion exchange resin with a non-aqueous liquid for pretreatment having a relative permittivity of 20 or more at 25°C, and a purification device having a purification means for contacting the ion exchange resin contacted with the non-aqueous liquid for pretreatment with a non-aqueous liquid to be purified, wherein the relative permittivity of the non-aqueous liquid for pretreatment at 25°C is greater than the relative permittivity of the non-aqueous liquid to be purified at 25°C, and the concentration of the metal to be reduced in the non-aqueous liquid for pretreatment is 5 μg / L or less.

[0010] In addition, the present invention is a pretreatment device for an ion exchange resin used for purifying a non-aqueous liquid, comprising a pretreatment means for contacting the ion exchange resin with a non-aqueous liquid for pretreatment having a dielectric constant of 20 or more at 25°C, wherein the pretreatment means is characterized by passing the non-aqueous liquid for pretreatment through the ion exchange resin at a rate of 1 BV or more.

[0011] In addition, the present invention is a method for manufacturing an ion exchange resin used for purifying a non-aqueous liquid, comprising a pretreatment process in which the ion exchange resin is brought into contact with a non-aqueous liquid for pretreatment having a dielectric constant of 20 or more at 25°C, wherein the dielectric constant of the non-aqueous liquid for pretreatment at 25°C is greater than the dielectric constant of the non-aqueous liquid to be purified at 25°C, and the concentration of the metal to be reduced in the non-aqueous liquid for pretreatment is 5 μg / L or less. Effects of the invention

[0012] According to the present invention, a method for manufacturing an ion exchange resin and a pretreatment apparatus can be provided to obtain an ion exchange resin with reduced water content in a simple and economical manner without requiring a large amount of non-aqueous liquid, and a method for purifying a non-aqueous liquid and a purification apparatus using said ion exchange resin can be provided. Brief explanation of the drawing

[0013] FIG. 1 is a schematic diagram showing the configuration of a purification device according to one embodiment of the present invention. FIG. 2 is a schematic diagram showing the configuration of a purification device according to one embodiment of the present invention. Figure 3 is a graph showing the results of Reference Example 1. Figure 4 is a graph showing the results of Reference Example 2. Figure 5 is a graph showing the results of Comparative Example 1 and Example 1. Figure 6 is a graph showing the results of Comparative Example 2 and Example 2. Specific details for implementing the invention

[0014] Method for purifying non-aqueous solutions, method for manufacturing ion exchange resins

[0015] The method for purifying a non-aqueous liquid according to the present invention is a method for purifying a non-aqueous liquid using an ion exchange resin, comprising a pretreatment process in which the ion exchange resin is brought into contact with a non-aqueous liquid for pretreatment having a relative permittivity of 20 or more at 25°C, and a purification process in which the ion exchange resin after the pretreatment process is brought into contact with a non-aqueous liquid to be purified. In addition, the relative permittivity of the non-aqueous liquid for pretreatment at 25°C is greater than the relative permittivity of the non-aqueous liquid to be purified at 25°C, and the concentration of the metal to be reduced in the non-aqueous liquid for pretreatment is 5 μg / L or less.

[0016] In addition, the method for manufacturing an ion exchange resin according to the present invention is a method for manufacturing an ion exchange resin used for purifying non-aqueous liquids, and includes the above-mentioned pretreatment process.

[0017] The present invention will be described in detail below.

[0018] [Pretreatment Process]

[0019] The pretreatment process is a process of contacting an ion exchange resin with a pretreatment non-aqueous solution having a relative permittivity of 20 or higher at 25°C. By performing this pretreatment process, the moisture contained in the ion exchange resin can be efficiently reduced. As a result, when the ion exchange resin is used to purify a non-aqueous solution to be purified, the leaching of water from the resin can be suppressed. Furthermore, by using a pretreatment non-aqueous solution that is more compatible with water than the non-aqueous solution to be purified, the moisture in the resin can be replaced with the pretreatment non-aqueous solution in advance, thereby reducing the total amount of non-aqueous solution used. Additionally, the ion exchange resin may be dried by vacuum drying or the like before use in the pretreatment process.

[0020] (Ion exchange resin)

[0021] The ion exchange resin used in the present invention may be either a cation exchange resin or an anion exchange resin, or it may be a chelate resin. The ion exchange resin is obtained, for example, by introducing functional groups into a copolymer having a three-dimensional network structure obtained by copolymerizing styrene and divinylbenzene (DVB) in the presence of a catalyst and a dispersant. The ion exchange resin may be a transparent gel type with small pore diameters, a macroreticular type (MR type) or macroporous type (also called porous type or hypoporous type) having macropores with large pore diameters.

[0022] Examples of cation exchange resins used in the present invention include a strongly acidic cation exchange resin having a sulfonic acid group and a weakly acidic cation exchange resin having a carboxylic acid group. The ionic type of the cation exchange resin is not limited, but a hydrogen ion type (H-type) is preferred from the perspective of removing impurities such as metals. When the ion exchange resin includes a cation exchange resin, even if the pretreatment non-aqueous solution contains some metal impurities, they can be removed by the cation exchange resin. Therefore, it is preferable that the ion exchange resin includes at least a cation exchange resin. Examples of cation exchange resins include, for instance, Amberlite (registered trademark) IRN99H (gel-type strong acid cation exchange resin, trade name, manufactured by Du Pont), Amberjet (registered trademark) 1060H (gel-type strong acid cation exchange resin, trade name, manufactured by Du Pont), ORLITE (registered trademark) DS-1 (gel-type strong acid cation exchange resin, trade name, manufactured by Organo Corporation), ORLITE (registered trademark) DS-4 (macroporous-type strong acid cation exchange resin, trade name, manufactured by Organo Corporation), Amberlite (registered trademark) IRC76 (macroporous-type weak acid cation exchange resin, manufactured by Du Pont), and Amberlite (registered trademark) FPC3500 (macroporous-type weak acid cation exchange resin, manufactured by Du Pont), but are not limited to these.

[0023] Examples of anion exchange resins used in the present invention include strong basic anion exchange resins having quaternary ammonium bases and weak basic anion exchange resins having primary to tertiary amino groups. The ionic type of the anion exchange resin is not limited, but from the perspective of removing impurities such as metals, hydroxide ion type (OH type), carbonate type, or bicarbonate type are generally used. Examples of anion exchange resins include ORLITE (registered trademark) DS-2 (gel-type strong basic anion exchange resin, trade name, product of Organo Corporation), DS-6 (MR-type weak basic anion exchange resin, trade name, product of Organo Corporation), Amberlite (registered trademark) IRA743 (macroporous-type boron selective resin, product of Du Pont), but are not limited to these.

[0024] The chelating resin used in the present invention is not particularly limited, but examples include ORLITE (registered trademark) DS-21 and DS-22 (macroporous type chelating resin, trade name, product of Organo Corporation).

[0025] In addition, a monolithic organic porous ion exchanger may be used instead of an ion exchange resin. As for the monolithic organic porous ion exchanger, there are no particular restrictions as long as an ion exchange group is introduced into a monolithic organic porous body.

[0026] Examples of monolithic organic porous ion exchangers include, for instance, a monolithic organic porous ion exchanger composed of a continuous framework phase and a continuous pore phase, wherein the thickness of the continuous framework is 1 to 100 μm, the average diameter of the continuous pores is 1 to 1000 μm, the total pore volume is 0.5 to 50 mL / g, cation exchangers, anion exchangers, or chelate groups are introduced, the ion exchange capacity per mass in a dry state is 1 to 6 mg equivalent / g, and the ion exchangers are uniformly distributed within the organic porous ion exchanger (hereinafter also referred to as the "first type of monolithic organic porous ion exchanger").

[0027] In addition, as a first type of monolithic organic porous ion exchanger, there is a monolithic organic porous ion exchanger in which bubble-shaped macropores overlap each other and the overlapping portion becomes an opening with an average diameter of 30 to 300 μm, the total pore volume is 0.5 to 10 mL / g, a cation exchanger or anion exchanger is introduced, the ion exchange capacity per mass in a dry state is 1 to 6 mg equivalent / g, the ion exchangers are uniformly distributed within the organic porous ion exchanger, and in the SEM image of the cross-section of the continuous macropore structure (dry body), the area of ​​the skeletal portion appearing in the cross-section is 25 to 50% of the image area.

[0028] In addition, as a monolithic organic porous ion exchanger of the first type, there is a co-bounded structure comprising a three-dimensionally continuous framework having an average thickness of 1 to 60 μm made of an aromatic vinyl polymer containing 0.1 to 5.0 mol% of cross-linked structural units among the total constituent units into which ion exchangers are introduced, and three-dimensionally continuous pores having an average diameter of 10 to 200 μm between the frameworks, having a total pore volume of 0.5 to 10 mL / g, having a cation exchanger or anion exchanger introduced, having an ion exchange capacity per mass in a dry state of 1 to 6 mg equivalent / g, and having ion exchangers uniformly distributed within the organic porous ion exchanger.

[0029] Here, it is generally known that the performance of removing impurities in various ion exchange resins is higher in strongly acidic resins than in weakly acidic resins, and higher in strongly basic resins than in weakly basic resins. During their investigation, the inventors confirmed that when performing solvent exchange of water contained in various resins, strongly acidic cation exchange resins require a larger amount of solvent for solvent exchange than weakly acidic cation exchange resins or chelate resins, and strongly basic anion exchange resins require a larger amount of solvent for solvent exchange than weakly basic anion exchange resins; that is, water in the resin is difficult to exchange with the solvent. However, according to the pretreatment process of the present invention, it became clear that even when using strongly acidic cation exchange resins or strongly basic anion exchange resins that are difficult to exchange with the solvent, the effect of significantly reducing the required amount of solvent can be obtained. As such, the purification method according to the present invention is effective for weakly acidic cation exchange resins, chelate resins, and weakly basic anion exchange resins, but the above effects can be further enhanced, particularly when strong acidic cation exchange resins or strong basic anion exchange resins are used. That is, the effects of the present invention are further enhanced when the ion exchange resin includes at least one of a strong acidic cation exchange resin and a strong basic anion exchange resin. Of course, other resins such as weakly acidic cation exchange resins, weakly basic anion exchange resins, and chelate resins may be combined with strong acidic cation exchange resins or strong basic anion exchange resins. Furthermore, as mentioned above, it is known that strong basic anion exchange resins have low heat resistance, but according to the present invention, since there is no need to dry the resin, the problem of the lowering of functional groups when using strong basic anion exchange resins can also be solved.

[0030] In addition, in order to solvent-exchange the moisture contained within the resin, it is necessary for the water to exit the resin while the solvent fills the resin. For this reason, resins with larger pores are advantageous for solvent exchange. Since the pore diameter is larger in MR-type, porous, or hypoporous types than in gel-type types, MR-type, porous, and hypoporous resins are more advantageous for solvent exchange compared to gel-type resins. On the other hand, since resins with a high degree of crosslinking have smaller pores, it can be said that highly crosslinked gel-type resins are the most difficult to solvent-exchange. However, according to the pretreatment process of the present invention, it has become clear that the amount of solvent required can be significantly reduced even when using a highly crosslinked gel-type strong acid cation exchange resin that is difficult to solvent-exchange. That is, the purification method according to the present invention can further exhibit the above effect when using a highly crosslinked gel-type strong acid cation exchange resin, particularly among strong acid cation exchange resins. Of course, other resins such as weak acid cation exchange resins, weak basic anion exchange resins, and chelate resins may be combined with the highly cross-linked gel-type strong acid cation exchange resin. In addition, the highly cross-linked gel-type strong acid cation exchange resin is, specifically, a gel-type strong acid cation exchange resin having a degree of cross-linking of 16% to 24%.

[0031] Furthermore, regarding the ion exchange resin used in the present invention, it is preferable to use an ion exchange resin in which the amount of metal impurities contained therein has been reduced prior to the pretreatment process, from the perspective of preventing contamination of the non-aqueous liquid to be purified by metal impurities. As a method for reducing the amount of metal impurities contained in the ion exchange resin, known methods may be used; for example, a method of converting the ionic form of the cation exchange resin to the H form using an acid such as hydrochloric acid or sulfuric acid may be cited. According to this method, it is possible to reduce the amount of metal impurities in the resin simultaneously with the conversion of the ion exchanger. In addition, when using a commercially available ion exchange resin as exemplified above (e.g., ORLITE (registered trademark) DS series, product of Organo Corporation) in which the amount of metal impurities contained therein has been reduced prior to the present invention, the pretreatment process can be carried out on the said ion exchange resin as is.

[0032] (Non-aqueous solution for pretreatment)

[0033] As a pretreatment non-aqueous solution, a non-aqueous solution having a dielectric constant of 20 or higher at 25°C is used. It is preferable that the dielectric constant of the pretreatment non-aqueous solution at 25°C be 25 or higher. Additionally, as a pretreatment non-aqueous solution, a non-aqueous solution having a dielectric constant at 25°C greater than that of the non-aqueous solution to be purified is used. Specifically, examples of pretreatment non-aqueous solutions include alcohols such as methanol and ethanol, glycols such as ethylene glycol and propylene glycol, and acetonitrile.

[0034] It is preferable that the moisture concentration in the pretreatment non-aqueous solution be 100 ppm or less, and more preferable that it be 60 ppm or less. If the moisture concentration in the pretreatment non-aqueous solution is 100 ppm or less, contamination of the resin by moisture caused by the pretreatment non-aqueous solution during the pretreatment process can be prevented. Examples of pretreatment non-aqueous solutions with a moisture concentration of 100 ppm or less include electronic industry (EL) grade pretreatment non-aqueous solutions. Furthermore, the moisture concentration (ppm) is a value measured by the Karl Fischer method using, for example, a Karl Fischer volumetric moisture meter (product name: Aquacounter AQ-2200, manufactured by Hiranuma Co., Ltd.). ppm represents the mass ratio of water to the target non-aqueous solution. From the perspective of availability of grades suitable for the electronics industry, as a pretreatment non-aqueous solution, alcohol with a water concentration of 100 ppm or less is preferred, and methanol with a water concentration of 100 ppm or less is particularly preferred.

[0035] In addition, the concentration of the metal to be reduced in the pretreatment non-aqueous solution is 5 μg / L or less. That is, in the present invention, the metal impurities to be reduced in the pretreatment non-aqueous solution do not affect the non-aqueous solution to be purified. For example, if the concentration of the metal to be reduced in the pretreatment non-aqueous solution is high at 10 μg / L, the H-type exchanger of the ion exchange resin is consumed to remove the metal in the pretreatment non-aqueous solution during the pretreatment process stage. Furthermore, since the non-aqueous solution has low diffusivity into the ion exchange resin, it is necessary to lower the flow rate compared to the case in water in order to achieve the metal removal performance of the ion exchange resin. Consequently, metal impurities originating from the pretreatment non-aqueous solution are prone to remaining in the resin or piping, and there is a possibility that they may affect the subsequent purification of the non-aqueous solution. Therefore, in order to avoid reducing the amount of functional groups of the ion exchange resin effective for purification of the non-aqueous solution to be purified, and to suppress metal contamination or effects on purification caused by the non-aqueous solution for pretreatment, the concentration of the metal to be reduced in the non-aqueous solution for pretreatment must be 5 μg / L or less.

[0036] Examples of major metals included in the pretreatment non-aqueous solution and the non-aqueous solution to be purified include Ag, Al, Ba, Ca, Cd, Co, Cr, Cu, Fe, K, Li, Mg, Mn, Na, Ni, Pb, Sr, Zn, etc. Among these, Na, K, Ca, Fe, and Al may be cited as metals to be reduced. In this specification, the concentration of metals to be reduced refers to the concentration of the sum of the concentrations of each of these metals to be reduced. Metal impurities in the pretreatment non-aqueous solution can also be removed by contact with an ion exchange resin that performs solvent exchange if the concentration is around several μg / L, but it is preferable for the amount of metal contained to be low. The concentration of metals to be reduced in the pretreatment non-aqueous solution may be, for example, 0.005 to 5 μg / L, and preferably 2 μg / L or less. In addition, the concentration of the metal to be reduced in the non-aqueous solution to be purified before purification may be, for example, 0.01 to 100 μg / L. Here, the metal concentration in the non-aqueous solution can be measured using, for example, an Agilent 8900 triple quadrupole ICP-MS (product name: Agilent Technologies Inc.).

[0037] As a non-aqueous solution for pretreatment, commercially available reagents as exemplified above may be used. Additionally, before use as a non-aqueous solution for pretreatment, if necessary, a treatment may be performed to reduce the concentration of the metal to be reduced to 5 μg / L or less using an ion exchange resin or an ion adsorption membrane with reduced moisture content.

[0038] The method of contacting the ion exchange resin with the pretreatment non-aqueous solution is not particularly limited, but includes batch processing and continuous flow processing using a column. Among these, the continuous flow processing method is preferred from the perspective of operability and efficiency.

[0039] In a continuous liquid treatment method, the ion exchange resin is packed into a purification tower, such as a column. The height of the resin packing layer in the purification tower is not particularly limited and can be, for example, 300 mm or more, preferably 600 to 1500 mm. Furthermore, in the embodiments described below, since purification is performed simply on a small scale, the height of the resin packing layer in the purification tower is not limited to this. Subsequently, the non-aqueous liquid for pretreatment, for example, SV (space velocity, h -1 ) A liquid is passed through at a rate of 0.5 to 50, for example, 1 BV or more, preferably 1 to 20 BV, and more preferably 2 to 15 BV. Here, BV (Bed volume) refers to the flow rate multiple of the non-aqueous liquid passed through relative to the amount of resin. The direction of the flow may be either downward or upward. By passing the liquid in this way, the moisture contained in the ion exchange resin is sequentially replaced by the pretreatment non-aqueous liquid and removed.

[0040] Next, the batch processing method is described. First, an ion exchange resin is filled into a reaction vessel equipped with a stirrer. Next, a pretreatment non-aqueous liquid is filled into the reaction vessel. The volume ratio is not particularly limited, but it is preferable to have 2 to 200 parts non-aqueous liquid to 1 part resin. Afterward, it is preferable to let it stand for, for example, about 0.1 to 16 hours, in order to ensure good fusion of the resin and the non-aqueous liquid. After standing, the stirrer is operated to uniformly mix the resin and the non-aqueous liquid. The stirring speed and stirring time can be appropriately determined based on the size of the reaction vessel, the throughput, etc. After stirring is finished, the resin and the pretreatment non-aqueous liquid are separated by filtration, thereby obtaining a resin from which moisture has been removed.

[0041] In addition, the ion exchange resin that has undergone the pretreatment process may be stored while immersed in the pretreatment solution used during the pretreatment process until it is used for the purification of the non-aqueous solution to be purified. In that case, when using it for actual purification, the resin and the pretreatment solution can be separated and used for the purification of the non-aqueous solution to be purified.

[0042] [Refining Process]

[0043] The purification process is a process of contacting the ion exchange resin, with reduced moisture content after the above pretreatment process, with a non-aqueous liquid to be purified.

[0044] (Purification target non-aqueous)

[0045] The non-aqueous liquid to be purified is, for example, a chemical solution and solvent used in the electronics industry. In addition, the non-aqueous liquid to be purified has a dielectric constant (25°C) that is smaller than that of the non-aqueous liquid for pretreatment. Specifically, examples of non-aqueous liquids to be purified include propylene glycol 1-monomethyl ether 2-acetate (PGMEA), propylene glycol monomethyl ether (PGME), and isopropyl alcohol (IPA). These may be used individually or in combination of two or more types. Various additives or other chemical solutions dissolved and mixed in these chemical solutions or solvents may also be used. Among these, the purification method according to the present invention is preferably used for the purification of PGME, PGMEA, a mixture of PGME and PGMEA, and IPA, particularly PGMEA and IPA.

[0046] As a method for contacting the ion exchange resin after the pretreatment process with the non-aqueous liquid to be purified, a method similar to the aforementioned method for contacting the ion exchange resin with the non-aqueous liquid for pretreatment can be cited. The resin packing height of the purification tower and the amount of non-aqueous liquid relative to the amount of resin (flow rate ratio) are as described above, but can be adjusted appropriately.

[0047] In addition, when performing actual purification by contacting the non-aqueous solution to be purified with an ion exchange resin, if necessary, a treatment may be performed to replace the non-aqueous solution for pretreatment with the non-aqueous solution to be purified. In that case, the non-aqueous solution to be purified can be replaced with the non-aqueous solution for pretreatment by passing it through at a rate of typically 1 to 20 BV. Since the non-aqueous solution for pretreatment and the non-aqueous solution to be purified mix easily, it is considered that most of the non-aqueous solution for pretreatment is pushed out and removed by solvent exchange with the non-aqueous solution to be purified by performing this treatment. However, if a small amount of the non-aqueous solution for pretreatment remains and becomes an impurity in the non-aqueous solution to be purified, it is desirable to appropriately analyze the concentration of the non-aqueous solution for pretreatment in the non-aqueous solution to be purified and to pass the non-aqueous solution to be purified until the concentration of the non-aqueous solution for pretreatment is reduced to or below the target concentration.

[0048] In the present invention, when a highly crosslinked strong acidic cation exchange resin is used as the ion exchange resin, the resin has small pores as described above and is the most difficult resin to solvent exchange. However, when the pretreatment according to the present invention is performed and moisture is removed from the inside of the resin, subsequent intrusion of the non-aqueous liquid to be purified or water from the surface of the resin into the interior becomes difficult. Here, it is known that PGMEA, which is preferably used as the non-aqueous liquid to be purified in the present invention, reacts with water and undergoes hydrolysis during purification to produce acetic acid. However, it has become clear that by performing the pretreatment process according to the present invention to sufficiently reduce the moisture concentration in the resin, a secondary effect is obtained in which the production of acetic acid can be suppressed even during the flow of liquid when purifying PGMEA using a highly crosslinked strong acidic cation exchange resin.

[0049] Pretreatment device for ion exchange resins

[0050] The pretreatment apparatus for an ion exchange resin according to the present invention is a pretreatment apparatus for an ion exchange resin used for purifying a non-aqueous liquid, and comprises a pretreatment means for contacting the ion exchange resin with a non-aqueous liquid for pretreatment having a relative permittivity of 20 or more at 25°C. The details of the pretreatment means are the same as those described in the pretreatment process above, and as the non-aqueous liquid for pretreatment, it is preferable to use methanol with a water concentration of preferably 100 ppm or less, more preferably 60 ppm or less. In addition, in the pretreatment means, the non-aqueous liquid for pretreatment is passed through the ion exchange resin at a rate of 1 BV or more, preferably 1 to 20 BV, more preferably 2 to 15 BV. The pretreatment apparatus for an ion exchange resin according to the present invention may be used in combination with a purification apparatus having a purification means for contacting the ion exchange resin contacted with the non-aqueous liquid for pretreatment with a non-aqueous liquid to be purified, as described below. When using a combination of both, a common one or a different one may be used as the purification tower packed with ion exchange resin.

[0051] Non-liquid purification device

[0052] The purification apparatus for non-aqueous liquids according to the present invention is a purification apparatus for non-aqueous liquids using an ion exchange resin, comprising a pretreatment apparatus having a pretreatment means for contacting the ion exchange resin with a non-aqueous liquid for pretreatment having a relative permittivity of 20 or more at 25°C, and a purification apparatus having a purification means for contacting the ion exchange resin contacted with the non-aqueous liquid for pretreatment with a non-aqueous liquid to be purified. In addition, the relative permittivity of the non-aqueous liquid for pretreatment at 25°C is greater than the relative permittivity of the non-aqueous liquid to be purified at 25°C, and the concentration of the metal to be reduced in the non-aqueous liquid for pretreatment is 5 μg / L or less. The details of the pretreatment means and the purification means are the same as those described above according to the pretreatment process and the purification process.

[0053] FIG. 1 is a schematic diagram showing the configuration of a purification device for non-aqueous liquid according to an embodiment of the present invention. FIG. 1 shows an example of a purification device comprising the same ion exchange resin tower, as a pretreatment device having a pretreatment means and a purification device having a purification means. First, a non-aqueous liquid for pretreatment is passed downward from a storage tank (2) using a pump (P) into an ion exchange resin filled in an ion exchange resin tower (1). The waste liquid of the non-aqueous liquid for pretreatment containing water contained in the ion exchange resin is stored in a storage tank (3). Then, the non-aqueous liquid to be purified in the storage tank (4) is passed downward from the top of the ion exchange resin tower (1) using a pump (P), and purification is performed. The waste liquid of the mixed liquid containing the non-aqueous liquid to be purified and the non-aqueous liquid for pretreatment at the beginning of the flow is stored in the storage tank (3). Then, the non-aqueous liquid to be purified after purification is recovered from the storage tank (5). Additionally, the mixed liquid stored in the reservoir (3) may be recovered, distilled, and then reused or discarded. A batten and a mesh (6) are provided at the bottom of the ion exchange resin tower (1). Before performing pretreatment, the ion exchange resin may be washed with an acid-alkali aqueous solution (not shown) or pure water or ultrapure water (ultrapure water line (7)). Also, after washing with the acid-alkali aqueous solution, etc., a pure water wash is performed. During the pure water wash, the conductivity or resistivity value is checked by a conductivity meter or resistivity meter (8) installed at the outlet of the ion exchange resin tower (1), and the acid-alkali aqueous solution, etc., is managed so that it does not mix with the pretreatment non-aqueous liquid. In addition, the delivery of the non-aqueous liquid may be performed for each non-aqueous liquid using a pump (P) as shown in FIG. 1, or it may be performed using a single pump by switching with a valve.

[0054] FIG. 2 shows an example of a purification device for non-aqueous liquids in which (a) a pretreatment device equipped with a pretreatment means and (b) a purification device equipped with a purification means are installed separately. First, in the pretreatment device shown in FIG. 2(a), a non-aqueous liquid for pretreatment is passed downward from a storage tank (12) using a pump (P) through an ion exchange resin filled in an ion exchange resin tower (11). The waste liquid of the non-aqueous liquid for pretreatment containing moisture contained in the ion exchange resin is stored in a storage tank (13). A lint and a mesh (14) are provided at the bottom of the ion exchange resin tower (11). Before performing pretreatment, the ion exchange resin may be washed with an acid-alkali aqueous solution (not shown) or pure water or ultrapure water (ultrapure water line (15)). Additionally, after washing with an acidic alkaline aqueous solution, etc., a pure water washing is performed. During the pure water washing, the conductivity or resistivity value is checked by a conductivity meter or resistivity meter (16) installed at the outlet of the ion exchange resin tower (11), and the acidic alkaline aqueous solution, etc. is managed so that it does not mix with the pretreatment non-aqueous solution. Next, the ion exchange resin that has undergone pretreatment is filled into the ion exchange resin tower (17) equipped in the purification device shown in FIG. 2(b). Subsequently, the non-aqueous solution to be purified is passed through the ion exchange resin tower (17) from the storage tank (18) using a pump (P) to perform purification. The waste liquid of the mixed solution containing the non-aqueous solution to be purified and the pretreatment non-aqueous solution at the beginning of the passage is stored in the storage tank (19). Then, the purified non-aqueous solution to be purified that is eluted from the outlet of the ion exchange resin tower (17) is recovered into the storage tank (20). A conductivity meter or a resistivity meter (23) is installed at the outlet of the ion exchange resin tower (17). In addition, the pretreatment of the ion exchange resin and the purification of the non-aqueous liquid to be purified do not necessarily need to be performed continuously. If the pretreatment and the purification of the non-aqueous liquid to be purified are not performed continuously, the ion exchange resin after pretreatment should be stored so as not to come into contact with moisture or metal impurities.

[0055] When an ion exchange resin used for the purification of non-aqueous liquid is converted into a regenerated form by a regenerating agent such as an acid or alkaline aqueous solution and regenerated for use, the non-aqueous liquid is first washed away, and then regeneration is performed using an acid or alkaline aqueous solution. At that time, for the sake of exchange efficiency, it is preferable to wash away the non-aqueous liquid, for example, by washing with methanol, and then wash away the methanol by washing with pure water. The ion exchange resin regenerated by the regenerating agent is reused for the purification of non-aqueous liquid by removing the regenerating agent with pure water and then performing pretreatment with methanol, etc.

[0056] The present invention will be specifically described below by way of examples, but the present invention is not limited to these examples.

[0057] Examples

[0058] The methods for measuring moisture concentration, metal concentration, and acetic acid concentration are as follows.

[0059] (Moisture concentration)

[0060] The water concentration (mass ppm) in the non-aqueous solution was measured by the Karl Fischer method using a Karl Fischer volumetric water meter (product name: Aquacounter AQ-2200, manufactured by Hiranuma Co., Ltd.). ppm represents the mass ratio of water to the target non-aqueous solution. In the following examples, the water concentration may differ even with the same solvent, but this is due to differences in lot.

[0061] (Metal concentration)

[0062] Metal concentration was measured using an Agilent 8900 triple quadrupole ICP-MS (product name, Agilent).

[0063] (Acetic acid concentration)

[0064] The acetic acid concentration (mass ppm) in PGMEA was measured using a capillary electrophoresis system (product name: Agilent 7100, manufactured by Otsuka Electronics Co., Ltd).

[0065] Ion exchange resin

[0066] The details of each ion exchange resin used in the following examples are as follows.

[0067] · AMBERLITE (Registered Trademark) IRN99H (Trade Name, DuPont Product): Gel-type strongly acidic cation exchange resin, Degree of crosslinking: 16%, Resin material: Styrene-divinylbenzene copolymer, Type of ion exchange group: Sulfonic acid group

[0068] · AMBERJET (registered trademark) 1060H (trade name, DuPont product): Gel-type strongly acidic cation exchange resin, degree of crosslinking: 16%

[0069] · ORLITE (Registered Trademark) DS-1 (Trade Name, Organo Corporation Product): Gel-type strongly acidic cation exchange resin, Resin material: Styrene-divinylbenzene copolymer, Type of ion exchanger: Sulfonic acid group

[0070] · ORLITE (Registered Trademark) DS-2 (Trade Name, Organo Corporation Product): Gel-type strong basic anion exchange resin, Resin material: Styrene-divinylbenzene copolymer, Type of ion exchanger: Quaternary ammonium group

[0071] · ORLITE (Registered Trademark) DS-21 (Trade Name, Organo Corporation Product): Macroporous weakly acidic chelate resin, Resin material: Styrene-divinylbenzene copolymer, Type of ion exchanger: Aminophosphate group

[0072] [Reference Example 1: Comparison of Solvent Substitution Amounts by Type of Ion Exchange Resin]

[0073] 50 ml each of water-wet ion exchange resins DS-2, DS-1, and DS-21 were packed into a PFA column (inner diameter: 16 mm, height: 300 mm), and IPA with a moisture concentration of 30 ppm (product name: TOCUSHO IPA (registered trademark) SE grade, manufactured by Tokuyama Corporation) was added at SV=5 h -1 The supply was continued until the BV reached 30. The moisture concentration in the IPA at the column outlet at each BV was analyzed, and the effect of solvent exchange was confirmed. The results are shown in Table 1 and Figure 3. In addition, the ion exchange resin in a wet state is obtained by contacting the ion exchange resin with an atmosphere of 100% relative humidity at 25°C for at least 30 minutes.

[0074] As shown in Table 1 and Figure 3, DS-2, a strong basic anion exchange resin, showed a water concentration of about 60 ppm at 30 BV, and DS-1, a strong acidic cation exchange resin, showed a water concentration of 250 ppm at 30 BV, and neither showed a reduction in water concentration to a level equivalent to the original solution. On the other hand, DS-21, a chelate resin having a weak acidic cation group, showed a reduction in water concentration to a level equivalent to the original solution at 15 BV. From these results, it is believed that in the strong acidic cation exchange resin and the strong basic anion exchange resin, water molecules are hydrated with the strong acidic cation exchange group or the strong basic anion exchange group, so they are in a state where solvent substitution is difficult.

[0075]

[0076] [Reference Example 2: Comparison of solvent substitution amounts by strongly acidic cation exchange resins with different degrees of crosslinking]

[0077] 50 ml each of water-wet AMBERJET 1060H (degree of crosslinking: 16%) and DS-1 (having a normal degree of crosslinking) were packed into a PFA column (inner diameter: 16 mm, height: 300 mm), and IPA with a moisture concentration of 30 ppm (product name: TOCUSHO IPA (registered trademark) SE grade, manufactured by Tokuyama Corporation) was added at SV=5 h -1 Supply was applied, and the supply was continued until the BV reached 30. The moisture concentration in the IPA at the column outlet at each BV was analyzed, and the effect of solvent exchange was confirmed. The results are shown in Table 2 and Figure 4.

[0078]

[0079] As shown in Table 2, AMBERJET 1060H, a highly crosslinked gel-type strong acid cation exchange resin, had a moisture concentration of 563 ppm at 30 BV, which is higher than that of DS-1, which has a general degree of crosslinking and is not highly crosslinked. It is believed that highly crosslinked gel-type strong acid cation exchange resins are more difficult to solvent exchange than strong acid cation exchange resins with a general degree of crosslinking because the pores are small and, in addition to the influence of hydration, the exchange of water and solvent is difficult to occur.

[0080] [Reference Example 3: Concentration of metal to be reduced in pretreatment methanol]

[0081] The concentrations of five types of elements targeted for reduction were measured in methanol (EL grade, FUJIFILM Wako Pure Chemical Corporation product) used as a non-aqueous pretreatment solution. As shown in Table 3, the concentration of the metals targeted for reduction was 1 μg / L or less.

[0082]

[0083] [Comparative Example 1: Substitution of PGMEA in a highly crosslinked strong acidic cation exchange resin]

[0084] 50 ml of water-wet IRN99H was packed into a PFA column (inner diameter: 16 mm, height: 300 mm), and PGMEA (product name: PM Thinner, manufactured by Tokyo Ohka Kogyo Co., Ltd.), a hydrolyzable solvent with a moisture concentration of 45 ppm and a target metal concentration of 1 μg / L or less, was added at SV=5 h -1 It was supplied. Supply was continued until the BV reached 30, and the moisture concentration in the PGMEA at the column outlet at each BV was analyzed to confirm the effect of solvent exchange. The results are shown in Table 4 and Figure 5. As shown in Table 4, when solvent exchange was performed using only PGMEA without performing a pretreatment process, the moisture concentration at 20 BV was approximately 450 ppm.

[0085]

[0086] [Example 1: Methanol-PGMEA Substitution of Highly Crosslinked Strong Acidic Cation Exchange Resin]

[0087] 50 ml of water-wet IRN99H was packed into a PFA column (inner diameter: 16 mm, height: 300 mm). Subsequently, as a non-aqueous pretreatment solution, methanol (EL grade, product of FUJIFILM Wako Pure Chemical Corporation) with a moisture concentration of 33 ppm and a metal concentration to be reduced of 1 μg / L or less, as described in Reference Example 3, was applied at SV=5 h -1 It was supplied. The supply of methanol was continued until the BV reached 12, and the water concentration in the methanol at the column outlet at each BV was analyzed. Subsequently, PGMEA (product name: PM Thinner, manufactured by Tokyo Ohka Kogyo Co., Ltd.) with a water concentration of 45 ppm and a metal concentration of 1 μg / L or less was supplied from a total non-aqueous volume (total amount of methanol and PGMEA) of 12 BV to 16 BV (the range enclosed by the dotted line in the graph shown in Fig. 5), and the water concentration in the PGMEA at the column outlet at each BV was analyzed. The results are shown in Table 5 and Fig. 5.

[0088]

[0089] As shown in Table 5 and Figure 5, in Example 1, when methanol was passed through at 12 BV as a pretreatment non-aqueous liquid, the water concentration was reduced to a level equivalent to that of the PGMEA to be purified. Subsequently, PGMEA was passed through to replace the methanol inside the resin with the PGMEA to be purified. Although the amount of PGMEA passed was 4 BV, it is believed that the methanol was almost removed at the point of passing through at 3 BV, so the total amount of non-aqueous liquid required is estimated to be 15 BV. Thus, in Example 1, the water inside the resin could be replaced with the non-aqueous liquid with a clearly smaller amount of non-aqueous liquid compared to Comparative Example 1.

[0090] In addition, in this embodiment, methanol and PGMEA were substituted by passing PGMEA through 3 BV as described above. Since PGMEA and methanol mix easily, most of the methanol is believed to be pushed out and removed by solvent substitution by PGMEA. However, if the remaining methanol poses a problem as an impurity, it is desirable to analyze the methanol concentration in PGMEA appropriately and pass PGMEA through until the methanol concentration is reduced to below the target concentration.

[0091] [Comparative Example 2: Substitution of IPA in Strongly Basic Anion Exchange Resin]

[0092] 50 ml of water-wet DS-2 was packed into a PFA column (inner diameter: 16 mm, height: 300 mm). Subsequently, IPA (product name: TOCUSHO IPA (registered trademark) SE grade, manufactured by Tokuyama Corporation) with a moisture concentration of 18 ppm and a target metal concentration of 1 μg / L or less was added at SV=5 h -1It was supplied. Supply was continued until the BV reached 30, and the moisture concentration in the IPA at the column outlet at each BV was analyzed. The results are shown in Table 6 and Figure 6. As shown in Table 6, the moisture concentration in the IPA at the column outlet after passing through 30 BV was approximately 60 ppm.

[0093]

[0094] [Example 2: Methanol-IPA Substitution of Strongly Basic Anion Exchange Resin]

[0095] 50 ml of water-wet DS-2 was packed into a PFA column (inner diameter: 16 mm, height: 300 mm). Subsequently, as a non-aqueous solution for pretreatment, methanol (EL grade, product of FUJIFILM Wako Pure Chemical Corporation) with a moisture concentration of 31 ppm and a metal concentration to be reduced of 1 μg / L or less, as described in Reference Example 3, was applied at SV=5 h -1 It was supplied. The supply of methanol was continued until the BV reached 5, and the water concentration in the methanol at the column outlet was analyzed. Subsequently, until the total non-aqueous volume (total amount of methanol and IPA) reached 20 BV, IPA (product name: TOCUSHO IPA (registered trademark) SE grade, Tokuyama Corporation product) with a water concentration of 21 ppm and a metal concentration of 1 μg / L or less was supplied (the range enclosed by the dotted line in the graph shown in Fig. 6), and the water concentration in the IPA at the column outlet at each BV was analyzed. The results are shown in Table 7 and Fig. 6.

[0096]

[0097] As shown in Table 7, in Example 2, at the point where the total non-aqueous liquid volume was about 15 BV, the moisture concentration at the column outlet could be reduced to a level equivalent to that of the IPA used. Thus, by passing methanol through as a pretreatment process, the moisture inside the resin could be replaced with non-aqueous liquid with a clearly smaller amount of non-aqueous liquid than in Comparative Example 2.

[0098] [Comparative Example 3: Acetic Acid Production]

[0099] PGMEA was passed through a PFA column (inner diameter: 16 mm, height: 300 mm) packed with 36 mL of AMBERJET 1060H, a highly cross-linked gel-type strong acid cation exchange resin, at 20 BV in the same order as in Comparative Example 1. The moisture concentration in the PGMEA at the column outlet at the time of passing through at 20 BV was measured to be 1005 ppm. The treated solution after this passage was stored overnight, and the acetic acid concentration of the supernatant was analyzed. As shown in Table 8, it was higher than the acetic acid concentration of the stock solution, confirming the production of acetic acid by hydrolysis.

[0100] [Example 3: Formation of Acetic Acid]

[0101] Methanol (target metal concentration 1 μg / L or less) and PGMEA (target metal concentration 1 μg / L or less) were passed through a PFA column (inner diameter: 16 mm, height: 300 mm) packed with 36 mL of AMBERJET 1060H, a highly cross-linked gel-type strong acidic cation exchange resin, in the same order as in Example 1 (except that PGMEA was passed through 4 BV further) at a total non-aqueous volume of 20 BV (total non-aqueous volume). At the point when the total non-aqueous volume of 20 BV was passed, the moisture concentration in the PGMEA at the column outlet was 58 ppm, which was equivalent to the level of the PGMEA used. The treated solution after this passage was stored overnight, and the acetic acid concentration of the supernatant was analyzed. As shown in Table 8, it showed a value equivalent to that of the stock solution, confirming that almost no acetic acid was generated after solvent exchange.

[0102]

[0103] Highly crosslinked gel-type strong acidic cation exchange resins are considered to have smaller pores and less inflow and outflow of PGMEA from the resin surface to the interior compared to MR-type resins, even if they are highly crosslinked. Therefore, compared to gel-type resins that are not highly crosslinked, or MR-type, porous, and hypoporous resins, it is considered that acetic acid is less likely to be produced by the hydrolysis of PGMEA.

[0104] As described above, the highly crosslinked gel-type strong acidic cation exchange resin was a resin that was difficult to solvent exchange, but by performing pretreatment using a non-aqueous liquid for pretreatment according to the present invention, water could be exchanged with a small amount of non-aqueous liquid, and purification could be performed while suppressing the hydrolysis of PGMEA. Explanation of the symbols

[0105] 1: Ion exchange resin tower 2: Retention tank (non-aqueous liquid for pretreatment) 3: Retention tank (waste liquid) 4: Retention tank (non-aqueous liquid to be purified before purification) 5: Retention tank (non-aqueous liquid to be purified after purification) 6: Duck neck and mesh 7: Ultrapure water line 8: Conductivity meter or resistivity meter P: Pump 11: Ion exchange resin tower 12: Retention tank (non-aqueous liquid for pretreatment) 13: Retention tank (waste liquid) 14: Duckneck and Meshi 15: Ultrapure water line 16: Conductivity meter or resistivity meter 17: Ion exchange resin tower 18: Retention tank (non-aqueous liquid to be purified before purification) 19: Retention tank (waste liquid) 20: Retention tank (non-aqueous liquid to be purified after purification) 21: Duck neck and mesh 22: Ultrapure water line 23: Conductivity meter or resistivity meter

Claims

Claim 1 A method for purifying a non-aqueous liquid using an ion exchange resin, comprising: a pretreatment process in which the ion exchange resin is brought into contact with a non-aqueous liquid for pretreatment having a dielectric constant of 20 or more at 25°C; and a purification process in which the ion exchange resin after the pretreatment process is brought into contact with a non-aqueous liquid to be purified, wherein the dielectric constant of the non-aqueous liquid for pretreatment at 25°C is greater than the dielectric constant of the non-aqueous liquid to be purified at 25°C, the concentration of the metal to be reduced in the non-aqueous liquid for pretreatment is 5 μg / L or less, and the non-aqueous liquid for pretreatment is methanol having a water concentration of 100 ppm or less. Claim 2 delete Claim 3 A method for purifying a non-aqueous solution according to claim 1, wherein the ion exchange resin comprises at least a cation exchange resin. Claim 4 A method for purifying a non-aqueous solution according to claim 3, wherein the cation exchange resin is a gel-type strongly acidic cation exchange resin having a degree of crosslinking of 16% to 24%. Claim 5 A method for purifying a non-aqueous liquid according to any one of claims 1, 3, or 4, wherein the non-aqueous liquid to be purified is selected from PGME, PGMEA, a mixture of PGME and PGMEA, and IPA. Claim 6 A purification apparatus for non-aqueous liquids using an ion exchange resin, comprising: a pretreatment apparatus having a pretreatment means for contacting the ion exchange resin with a non-aqueous liquid for pretreatment having a relative permittivity of 20 or more at 25°C; and a purification apparatus having a purification means for contacting the ion exchange resin contacted with the non-aqueous liquid for pretreatment with a non-aqueous liquid to be purified, wherein the relative permittivity of the non-aqueous liquid for pretreatment at 25°C is greater than the relative permittivity of the non-aqueous liquid to be purified at 25°C, the concentration of the metal to be reduced in the non-aqueous liquid for pretreatment is 5 μg / L or less, and the non-aqueous liquid for pretreatment is methanol having a water concentration of 100 ppm or less. Claim 7 delete Claim 8 In claim 6, a non-aqueous liquid purification apparatus wherein the ion exchange resin comprises at least a cation exchange resin. Claim 9 A pretreatment device for an ion exchange resin used for purifying a non-aqueous liquid to be purified, comprising a pretreatment means for contacting the ion exchange resin with a non-aqueous liquid for pretreatment having a relative permittivity of 20 or more at 25°C, wherein the pretreatment means is a means for passing methanol, in which the moisture concentration of the non-aqueous liquid for pretreatment is 100 ppm or less, through the ion exchange resin at a rate of 1 BV or more, and wherein the relative permittivity of the non-aqueous liquid for pretreatment at 25°C is greater than the relative permittivity of the non-aqueous liquid to be purified at 25°C. Claim 10 A method for manufacturing an ion exchange resin used for purifying a non-aqueous liquid to be purified, comprising a pretreatment process in which the ion exchange resin is contacted with a non-aqueous liquid for pretreatment having a relative permittivity of 20 or more at 25°C, wherein the relative permittivity of the non-aqueous liquid for pretreatment at 25°C is greater than the relative permittivity of the non-aqueous liquid to be purified at 25°C, the concentration of the metal to be reduced in the non-aqueous liquid for pretreatment is 5 μg / L or less, and the non-aqueous liquid for pretreatment is methanol having a water concentration of 100 ppm or less.

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