Used non-regeneration type mixed bed ion exchange resin separation method and recycling method, and single bed ion exchange resin production method

Abstract

To provide a used non-regeneration type mixed bed ion exchange resin separation method which can obtain an ion exchange resin that can suppress mixing of a counter ion exchange resin, and occurrence of cracks on a resin surface, and is recyclable in wide applications.SOLUTION: A used non-regeneration type mixed bed ion exchange resin separation method has a separation step of separating a strong acid cation exchange resin and a strong basic anion exchange resin contained in a used non-regeneration type mixed bed ion exchange resin, wherein the separation step has a first separation step of bringing first solution capable of converting an ion type of at least one resin into a salt type into contact with a non-regeneration type mixed bed ion exchange resin, and a second separation step of bringing second solution having an intermediate specific gravity between a true specific gravity of the strong acid cation exchange resin and a true specific gravity of the strong basic anion exchange resin into contact with the non-regeneration type mixed bed ion exchange resin, and the first solution is diluted solution having concentration lower than that of the second solution.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for separating and reusing used non-regenerated mixed-bed ion exchange resins and a method for producing single-bed ion exchange resins. [Background technology]

[0002] As methods for separating the cation exchange resin and anion exchange resin contained in used mixed-bed ion exchange resin, the following methods have been considered: 1. Separation by converting the ionic form of the resin, 2. Separation by surface treatment, and 3. Separation by specific gravity using saturated salt water (Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 51-117179 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the above-mentioned methods 1 and 2, the counter ion exchange resin (hereinafter also referred to as "foreign resin") is mixed into the separated ion exchange resin. In addition, in the above-mentioned method 3, cracks occur on the resin surface due to the simultaneous influence of shrinkage due to conversion of the ionic form of the resin and shrinkage due to osmotic pressure, which limits the uses of the ion exchange resins (cation exchange resin and anion exchange resin) separated from the mixed bed ion exchange resin.

[0005] The present invention aims to provide a method for separating used non-regenerated mixed-bed ion exchange resins, which can suppress the incorporation of counter ion exchange resins and the occurrence of cracks on the resin surface, and can produce ion exchange resins that can be reused in a wide range of applications. The present invention also aims to provide a method for recycling ion exchange resins derived from used non-regenerated mixed-bed ion exchange resins separated by the separation method. A further object of the present invention is to provide a method for producing single-bed ion exchange resins using the separation method. [Means for solving the problem]

[0006] The present invention provides a method for separating used non-regenerated mixed bed ion exchange resins, comprising a separation step of separating a strongly acidic cation exchange resin and a strongly basic anion exchange resin contained in the used non-regenerated mixed bed ion exchange resins, the method comprising: The separation step a first separation step in which a first solution capable of converting the ionic form of at least one of the strongly acidic cation exchange resin and the strongly basic anion exchange resin contained in the non-regenerated mixed bed ion exchange resin into a salt form is brought into contact with the non-regenerated mixed bed ion exchange resin; a second separation step in which a second solution having an intermediate specific gravity between the true specific gravity of the strongly acidic cation exchange resin and the true specific gravity of the strongly basic anion exchange resin is contacted with the non-regenerated mixed bed ion exchange resin that has been subjected to the first separation step; and The method for separating spent non-regenerated mixed bed ion exchange resins, wherein the first solution is a dilute solution having a lower concentration than the second solution.

[0007] The present invention also relates to a method for recycling used non-regenerated mixed-bed ion exchange resins, in which the strongly acidic cation exchange resin or strongly basic anion exchange resin separated by the above-mentioned method is reused as a non-regenerated mixed-bed ion exchange resin or a single-bed ion exchange resin.

[0008] Furthermore, the present invention is a method for producing a single-bed ion exchange resin, which comprises a step of separating used non-regenerated mixed-bed ion exchange resin using the above method. [Effects of the Invention]

[0009] According to the present invention, it is possible to suppress the incorporation of counter ion exchange resins and the occurrence of cracks on the resin surface during separation of used non-regenerated mixed-bed ion exchange resins, and it is possible to obtain reusable ion exchange resins for a wide range of applications from used non-regenerated mixed-bed ion exchange resins. The obtained recycled ion exchange resins can be reused as non-regenerated mixed-bed ion exchange resins or single-bed ion exchange resins. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic diagram illustrating a part of the technical concept according to the present invention. [Figure 2] 3 is a photograph showing the separation state of a mixed-bed ion exchange resin after (i) the first separation step and (ii) the second separation step in Example 1. [Figure 3] 1 is a photograph showing the separation state of a mixed-bed ion-exchange resin after the second separation step in Comparative Example 2. DETAILED DESCRIPTION OF THE INVENTION

[0011] In the electronics industry, where high-purity pure water and ultrapure water are required, such as in the liquid crystal and semiconductor industries, non-regenerative ion exchange resin units are often installed at the end of primary water purification systems or in subsystem water purification systems to remove trace amounts of ions. While single-bed and dual-bed ion exchange resin units are sometimes used, mixed-bed ion exchange resin units are the most commonly used. In this specification, the ion exchange resins used in mixed-bed non-regenerative ion exchange resin units, i.e., the ion exchange resins used in mixed-bed non-regenerative ion exchange resin units, are referred to as "non-regenerative mixed-bed ion exchange resins." To reuse used non-regenerative mixed-bed ion exchange resins after use in a mixed-bed non-regenerative ion exchange resin unit, it is first necessary to separate the cation exchange resin and anion exchange resin contained in the used non-regenerative mixed-bed ion exchange resin. In this process of separating the cation exchange resin and the anion exchange resin, two patterns occur: (a) the cation exchange resin and the anion exchange resin cannot be completely separated, resulting in partial contamination of one resin with the other (a pattern of mismatched resin contamination), and (b) the cation exchange resin and the anion exchange resin can be almost completely separated (a pattern of complete separation). The present inventors have conducted extensive research into methods for reusing used, non-regenerated ion exchange resins that have been separated and regenerated in this manner. As a result, they have found that various methods are possible, such as reusing used non-regenerated ion exchange resins assuming the presence of mismatched resins (a) above), or reusing used non-regenerated ion exchange resins assuming minimal resin contamination (less than 0.1% mismatched resin contamination rate) and almost complete separation (a pattern of complete separation). Based on these findings, they have completed a series of inventions, including the present invention.

[0012] Among these inventions, the present invention relates to a method for recycling used non-regenerated mixed-bed ion exchange resins, with the premise that the cation exchange resin and the anion exchange resin are almost completely separated. Specifically, this specification describes an invention relating to the recycling of used non-regenerated mixed-bed ion exchange resins, characterized by a method for separating the cation exchange resin and the anion exchange resin contained in the used non-regenerated mixed-bed ion exchange resin. The present invention will be described in detail below.

[0013] <Method for separating used non-regenerated mixed-bed ion exchange resin> The method for separating used non-regenerated mixed bed ion exchange resin according to the present invention includes at least a separation step of separating the strongly acidic cation exchange resin and the strongly basic anion exchange resin contained in the used non-regenerated mixed bed ion exchange resin.

[0014] [Non-regenerative mixed-bed ion exchange resin] As described above, a non-regenerated mixed-bed ion exchange resin is a non-regenerated ion exchange resin used in a mixed-bed non-regenerated ion exchange resin device. Known mixed-bed ion exchange resins can be used as such non-regenerated mixed-bed ion exchange resins. Mixed-bed ion exchange resins are generally composed of a strongly acidic H-type cation exchange resin and a strongly basic OH-type anion exchange resin. The mixed-bed ion exchange resin is not particularly limited, but examples of commercially available products that can be used include ESP-2 (trade name, manufactured by Organo Corporation), AmberTec UP6040 H / OH (trade name, manufactured by DuPont de Nemours), DIAION SMT200L (trade name, manufactured by Mitsubishi Chemical Corporation), UltraClean UCW9966 (trade name, manufactured by Purolite), and LEWATIT UltraPure 1294MD (trade name, manufactured by Lanxess). The mixing ratio (volume ratio) of the strongly acidic cation exchange resin and the strongly basic anion exchange resin in the mixed-bed ion exchange resin is not limited, and the resins can be combined in any mixing ratio. The base material of the mixed-bed ion exchange resin may be either a transparent gel type with small pores, a macrolitercular type (MR type) with large macropores, or a macroporous type (also called a porous type or a hyperporous type).

[0015] [Separation process] The separation step is a step of separating the strongly acidic cation exchange resin and the strongly basic anion exchange resin contained in the used non-regenerated mixed bed ion exchange resin after it has been used in the purification treatment of the water to be treated. In the present invention, the separation step includes at least two steps: a first separation step and a second separation step. The first separation step is a step of contacting the used non-regenerated mixed bed ion exchange resin with a first solution capable of converting the ionic form of at least one of the strongly acidic cation exchange resin and the strongly basic anion exchange resin contained in the non-regenerated mixed bed ion exchange resin to a salt form. The second separation step is a step of contacting the non-regenerated mixed bed ion exchange resin that has been subjected to the first separation step with a second solution having a specific gravity intermediate between the true specific gravity of the strongly acidic cation exchange resin and the true specific gravity of the strongly basic anion exchange resin. The first solution is a solution having a lower concentration than the second solution (also referred to as a "dilute solution").

[0016] In the method disclosed in Patent Document 1, the cation exchange resin and the anion exchange resin are separated in one step using a separation liquid having an intermediate specific gravity between the resins. However, this conventional method of separating the resins in one step has the problem that in addition to shrinkage due to conversion of the ionic form of the resin, the high concentration of the separation liquid increases the effect of shrinkage due to osmotic pressure, causing cracks (cracking and fractures) on the surface of the resin. According to the present invention, by providing a first step as a preliminary step in which separation is performed using a dilute solution having a lower concentration than the separation liquid, it is possible to suppress the occurrence of cracks due to the concentration of the separation liquid.

[0017] (First Separation Step) In the first separation step, a first solution, which is a dilute solution capable of converting the ionic form of at least one of the strongly acidic cation exchange resin and the strongly basic anion exchange resin contained in the used non-regenerated mixed bed ion exchange resin into a salt form, is brought into contact with the non-regenerated mixed bed ion exchange resin.

[0018] <First Solution> The first solution is a dilute solution having a lower concentration than the second solution described below. The state of the resin after contacting the first solution with a used non-regenerated mixed-bed ion exchange resin is affected by the flow direction of the first solution. That is, when the first solution is passed through the resin in a downward flow, the two resins do not separate at this stage (see FIG. 2(i)). On the other hand, when the first solution is passed through the resin in an upward flow, the strongly acidic cation exchange resin and the strongly basic anion exchange resin are separated to some extent. The first solution is not particularly limited as long as it is a solution (ionic solution) that can convert the ionic form of at least one of the strongly acidic cation exchange resin and the strongly basic anion exchange resin to a salt form. Examples of such first solutions include aqueous solutions such as saline, hydrochloric acid, sulfuric acid, aqueous sodium hydroxide, aqueous potassium hydroxide, aqueous ammonium chloride, aqueous calcium chloride, aqueous sodium carbonate, aqueous sodium sulfate, aqueous sodium acetate, and aqueous formic acid. However, as mentioned above, the first solution may be any ionic solution, and is not limited thereto. When the first solution is an acid, the ionic form of the strongly basic anion exchange resin is converted to the salt form, when the first solution is a base, the ionic form of the strongly acidic cation exchange resin is converted to the salt form, and when the first solution is a salt, the ionic forms of both the strongly acidic cation exchange resin and the strongly basic anion exchange resin are converted to the salt form.

[0019] The first solution may be a different type of solution from the second solution described below, or may be the same type of solution as the second solution but with a different concentration. However, from the viewpoint of operational efficiency in carrying out the separation step, it is preferable that the first solution and the second solution be the same type of solution. In this case, the first solution is preferably an aqueous solution selected from the group consisting of saline, hydrochloric acid, and sodium hydroxide aqueous solution.

[0020] The concentration of the first solution is not limited as long as it is lower than the concentration of the second solution. However, from the viewpoint of suppressing the occurrence of cracks on the resin surface, the concentration of the first solution is preferably, for example, less than 3N (less than 3 mol / L in the case of sodium hydroxide solution), and more preferably 2N or less (2 mol / L or less in the case of sodium hydroxide solution). Furthermore, the concentration of the first solution is preferably 0.1N or more (0.1 mol / L or more in the case of sodium hydroxide solution). The concentration of the first solution or the second solution refers to the gram equivalent of the salt, acid, or base contained in each solution.

[0021] (Second Separation Step) In the second separation step, a second solution having a specific gravity intermediate between the true specific gravity of the strongly acidic cation exchange resin and the strongly basic anion exchange resin constituting the non-regenerative mixed-bed ion exchange resin and having a higher concentration than the first solution is contacted with the non-regenerative mixed-bed ion exchange resin that has undergone the first separation step. As shown in Figure 2(ii), by further contacting the non-regenerative mixed-bed ion exchange resin that has undergone the first separation step with the second solution, the strongly acidic cation exchange resin and the strongly basic anion exchange resin are almost completely separated through the second solution. Since the cation exchange resin usually has a higher specific gravity than the anion exchange resin, after the second separation step, the anion exchange resin (A), the second solution (B), and the cation exchange resin (C) are separated from the top. Note that, as described below, the first solution that was passed in the previous step may be removed before the second solution is passed. When this operation is performed, the second solution (B) shown in Figure 2(ii) contains only the second solution, whereas when this operation is not performed, the second solution (B) shown in Figure 2(ii) contains not only the second solution but also the first solution that was previously administered.

[0022] <Second Solution> The second solution is not limited as long as it has a higher concentration than the first solution and a specific gravity intermediate between the true gravity of a strongly acidic cation exchange resin and that of a strongly basic anion exchange resin. Here, the "true specific gravity of a strongly acidic cation exchange resin" in the "intermediate specific gravity between the true specific gravity of a strongly acidic cation exchange resin and that of a strongly basic anion exchange resin" refers to the true specific gravity of the H-form or salt-form strongly acidic cation exchange resin after the second solution has been passed through, and the "true specific gravity of a strongly basic anion exchange resin" refers to the true specific gravity of the OH-form or salt-form strongly basic anion exchange resin after the second solution has been passed through. In other words, the intermediate specific gravity refers to a specific gravity that is greater than the true specific gravity of the strongly basic anion exchange resin having the corresponding ionic form after the second solution has been passed through, but smaller than the true specific gravity of the strongly acidic cation exchange resin having the corresponding ionic form after the second solution has been passed through. Furthermore, the true specific gravity of the second solution (the intermediate specific gravity) is the true specific gravity of the second solution if the first solution is removed before the second solution is passed through. If the removal is not performed, the true specific gravity is, strictly speaking, the true specific gravity of the mixed solution obtained by mixing the first and second solutions. However, even in the latter case, it is possible to make the specific gravity of the mixed solution closer to the true specific gravity of the second solution itself by adjusting the amount of the second solution passed through. Therefore, even in the latter case, the true specific gravity of the second solution (the specific gravity of the mixed solution) can be considered to be approximately the same as the true specific gravity of the second solution itself by appropriately adjusting the amount of the second solution passed through.

[0023] Examples of the second solution include aqueous solutions such as saline, hydrochloric acid, and sodium hydroxide. As described above, the second solution may be a different type of solution from the first solution. However, from the viewpoint of operational efficiency in carrying out the separation step, it is preferable that the first solution and the second solution be the same type of solution. Furthermore, from the viewpoint of ease of handling the solvent, the second solution is preferably saline, and may be, for example, saturated saline.

[0024] The concentration of the second solution is not limited as long as it allows the intermediate specific gravity to be achieved. However, from the viewpoint of completely separating the strongly acidic cation exchange resin and the strongly basic anion exchange resin, the concentration of the second solution is preferably such that the true specific gravity is at least 0.02 g / mL higher than that of the anion exchange resin having the corresponding ionic form and at least 0.02 g / mL lower than that of the cation exchange resin having the corresponding ionic form. That is, the difference between the true specific gravity of the anion exchange resin having the corresponding ionic form and that of the second solution is preferably at least 0.02 g / mL, and the difference between the true specific gravity of the cation exchange resin having the corresponding ionic form and that of the second solution is preferably at least 0.02 g / mL. Furthermore, the difference between the true specific gravity of the anion exchange resin having the corresponding ionic form and that of the second solution is preferably at most 0.5 g / mL, more preferably at most 0.2 g / mL. Similarly, the difference between the true specific gravity of the cation exchange resin having the corresponding ionic form and the true specific gravity of the second solution is preferably 0.5 g / mL or less, more preferably 0.2 g / mL or less.

[0025] A method for contacting the first and second solutions with a non-regenerative mixed-bed ion exchange resin includes, for example, sequentially passing the first and second solutions through a non-regenerative mixed-bed ion exchange resin packed in an appropriate container such as an ion exchange resin tower. The method for passing each solution can be appropriately determined. The flow direction of each solution may be either upflow or downflow. However, when passing the second solution, in particular, upflow is preferred from the viewpoint of efficiently separating the cation exchange resin and the anion exchange resin. The amount of the first solution passed can be, for example, an amount equal to or greater than the amount required to satisfy the exchange capacity of the strongly acidic cation exchange resin and the strongly basic anion exchange resin. After passing the first solution, the second solution may be passed subsequently. Alternatively, after passing the first solution, the first solution may be pressure-fed with a gas (such as nitrogen or air) and extracted, and then the second solution may be passed. The amount of the second solution passed through the second ion exchange resin may be, for example, an amount sufficient to sufficiently separate the strongly acidic cation exchange resin from the strongly basic anion exchange resin. The second solution may be circulated as long as the concentration is maintained at a level sufficient to maintain the desired intermediate specific gravity. If the second solution is passed through the second ion exchange resin while the first solution remains, the true specific gravity of the second solution will change significantly. However, by increasing the amount of the second solution, the second solution (including the first solution) can be adjusted to the desired intermediate specific gravity. Therefore, the amount of the second solution passed through the second ion exchange resin may be appropriately adjusted to achieve the desired intermediate specific gravity.

[0026] After the second separation step, the cation exchange resin and the anion exchange resin separated using the second solution (optionally containing the first solution) can be recovered as follows. First, the anion exchange resin is discharged from the upper discharge pipe by backwashing (upward flow) using the second solution. Then, the cation exchange resin is discharged from the lower discharge pipe by downward flow using the second solution. In this way, the separated resins can be recovered, but the method for recovering the resins is not limited to the above method as long as both resins can be separated and recovered.

[0027] The foreign resin contamination rate of the ion exchange resins (cation exchange resin and anion exchange resin) obtained by the separation method of the present invention is preferably less than 0.1%. The foreign resin contamination rate refers to the proportion (by volume) of foreign resin (anion exchange resin) contained in the cation exchange resin obtained after separation, or the proportion (by volume) of foreign resin (cation exchange resin) contained in the anion exchange resin obtained after separation. The foreign resin contamination rate can be calculated using the following formula (I): Contamination rate of foreign resin (%) = (volume of foreign resin mixed in / total volume of ion exchange resin) × 100 (I)

[0028] In the separation method according to the present invention, the occurrence of cracks on the resin surface is suppressed, and therefore the ion exchange resin obtained by separation has a high PBC (perfect sphericity). In the present invention, the decrease rate (XY (%)) of the PBC (Y (%)) of each ion exchange resin separated through the second separation step from the PBC (X (%)) of each ion exchange resin before separation is preferably less than 5%. Furthermore, the decrease rate of the PBC is more preferably less than 4%. The PBC of an ion exchange resin can be calculated using the following formula (II): PBC (%) = (1 - number of resin particles that are not spherical or have scratches / total number of resin particles observed) × 100 (II) In measuring PBC, it is preferable to observe 100 or more resin particles in total before evaluation.

[0029] As described above, the separation method of the present invention performs a two-stage separation process on used non-regenerated mixed-bed ion exchange resin, thereby preventing the incorporation of other resins and the occurrence of cracks on the resin surface. As a result, the ion exchange resin can be reused over a long period of time. Furthermore, because the generation of fine particles and TOC elution caused by cracks in the resin are suppressed, when the ion exchange resin is reused, the deterioration of the quality of the ultrapure water to be purified is suppressed, and stable operation is possible by preventing an increase in differential pressure.

[0030] <Method for reusing used non-regenerated mixed bed ion exchange resin> The separated strongly acidic cation exchange resin and strongly basic anion exchange resin obtained by the separation method of the present invention can be reused as non-regenerated mixed-bed ion exchange resins or single-bed ion exchange resins after undergoing a regeneration step. That is, the method for reusing used non-regenerated mixed-bed ion exchange resins of the present invention is a method for reusing the recycled strongly acidic cation exchange resin and / or strongly basic anion exchange resin obtained by the separation method of used non-regenerated mixed-bed ion exchange resin of the present invention as non-regenerated mixed-bed ion exchange resins or single-bed ion exchange resins, respectively. The regeneration step can be carried out by a known method.

[0031] <Method of manufacturing single-bed ion exchange resin> As described above, the separation method according to the present invention can produce an ion exchange resin that can be reused as a single-bed ion exchange resin. That is, the present invention can also be said to be a method for producing a single-bed ion exchange resin, which includes a step of separating a used non-regenerated mixed-bed ion exchange resin using the separation method according to the present invention. Note that the respective descriptions of the separation method according to the present invention can also be applied to the method for producing a single-bed ion exchange resin according to the present invention. [Example]

[0032] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples.

[0033] The following tests were carried out using ESP-2 (trade name, manufactured by Organo Corporation) as a used non-regenerated mixed-bed ion exchange resin.

[0034] [Example 1] 3 L of 1N (1 mol / L) saline solution as the first solution was passed downward through an acrylic column packed with 1000 mL of the mixed-bed ion exchange resin (first separation step). During this process, the strongly acidic cation exchange resin in the mixed-bed ion exchange resin was converted to the Na form, and the strongly basic anion exchange resin was converted to the Cl form. At this stage, as shown in Figure 2(i), the two resins were not separated, and the state was the same as before the first solution was passed through (before separation). Subsequently, the first solution was removed by pressure pumping with air, and then 20 L of saturated saline solution (true specific gravity: 1.19) as the second solution was passed upward through the mixed-bed ion exchange resin (second separation step). As a result, the cation exchange resin and the anion exchange resin were separated through the second solution, as shown in Figure 2(ii).

[0035] Next, the anion exchange resin was extracted from the upper extraction pipe by backwashing (upward flow) using the second solution, and then the cation exchange resin was extracted from the lower extraction pipe by downward flow using the second solution. The foreign resin contamination rate and PBC (perfect sphericity) of the obtained cation exchange resin and anion exchange resin were measured using the methods described below. The PBC was also measured for the cation exchange resin and anion exchange resin before separation. The results are shown in Table 1.

[0036] (Contamination rate of different resins) First, 20 mL of the recovered cation exchange resin or anion exchange resin was placed in a container containing 100 mL of saturated saline, and the number of anion exchange resins that had risen to the surface of the cation exchange resin layer or that had settled in the anion exchange resin layer was visually confirmed and recovered. The volume of each recovered (contaminated) resin was then measured. The foreign resin contamination rate was calculated from the obtained resin volume using the following formula. Contamination rate of foreign resin (cation) = (volume of contaminated anion exchange resin / 20 mL) x 100 (%) Contamination rate of foreign resin (anion) = (volume of contaminated cation exchange resin / 20 mL) x 100 (%) The foreign resin contamination rate (cation) indicates the contamination rate of anion exchange resin mixed into cation exchange resin, and the foreign resin contamination rate (anion) indicates the contamination rate of cation exchange resin mixed into anion exchange resin.

[0037] (PBC) The cation exchange resin and anion exchange resin before separation, as well as the cation exchange resin and anion exchange resin obtained after separation, were each observed using an optical microscope. Specifically, the resins were arranged so that approximately 100 resin particles could be observed in the field of view, and the number of spherical resin particles, cracked resin particles, crushed resin particles, and irregularly shaped non-spherical resin particles were counted, and the PBC was calculated using the above formula (II). Note that in the above formula (II), "non-spherical resin particles or resin particles with scratches" includes cracked resin particles, crushed resin particles, and irregularly shaped non-spherical resin particles.

[0038] [Comparative Example 1] The strongly acidic cation exchange resin and strongly basic anion exchange resin in the mixed-bed ion exchange resin were separated in one stage by passing 20 L of saturated saline solution upward through an acrylic column packed with 1000 mL of the mixed-bed ion exchange resin used in Example 1. The cation exchange resin and anion exchange resin recovered by the same method as in Example 1 were measured for the foreign resin contamination rate and PBC in the same manner as in Example 1. The results are shown in Table 1.

[0039] [Example 2] The strongly acidic cation exchange resin and the strongly basic anion exchange resin in the mixed-bed ion exchange resin were separated in two stages by the same procedure as in Example 1, except that a 1N (1 mol / L) aqueous sodium hydroxide solution was used as the first solution and a 3.55N (12.5% ​​by mass) aqueous sodium hydroxide solution (true specific gravity: 1.13) was used as the second solution. The cation exchange resin and anion exchange resin recovered by the same method as in Example 1 were measured for the foreign resin contamination rate and PBC in the same manner as in Example 1. The results are shown in Table 2.

[0040] Comparative Example 2 The strongly acidic cation exchange resin and the strongly basic anion exchange resin in the mixed-bed ion exchange resin were separated in two stages using the same procedure as in Example 2, except that the first solution and the second solution were used interchangeably. Figure 3 shows the state of separation of the cation exchange resin and the anion exchange resin. The cation exchange resin and the anion exchange resin recovered by the same method as in Example 1 were measured for the foreign resin contamination rate and PBC in the same manner as in Example 1. The results are shown in Table 2.

[0041] [Table 1]

[0042] [Table 2]

[0043] As shown in Table 1, the method of Example 1, in which the first separation step is performed using a dilute solution with a lower concentration than the solution used in the second separation step, and then the second separation step is performed using saturated saline solution, was found to be able to suppress the occurrence of cracks on the resin surface while maintaining a low rate of foreign resin contamination compared to the method of Comparative Example 1, in which separation is performed in one step.

[0044] Furthermore, as shown in Table 2, in Comparative Example 2, in which a solution with a higher concentration than the second solution was used as the first solution, it was found that the foreign resin contamination rate (cation) increased and the PBC also decreased. Note that this example shows an example in which saline or sodium hydroxide solution was used as the first and second solutions. However, a person skilled in the art would expect that similar results to those of Examples 1 and 2 would be obtained even when other ionic solutions were used.

[0045] The present invention includes the following configurations. [Configuration 1] A method for separating used non-regenerated mixed bed ion exchange resins, comprising a separation step of separating a strongly acidic cation exchange resin and a strongly basic anion exchange resin contained in the used non-regenerated mixed bed ion exchange resins, The separation step a first separation step in which a first solution capable of converting the ionic form of at least one of the strongly acidic cation exchange resin and the strongly basic anion exchange resin contained in the non-regenerated mixed bed ion exchange resin into a salt form is brought into contact with the non-regenerated mixed bed ion exchange resin; a second separation step in which a second solution having an intermediate specific gravity between the true specific gravity of the strongly acidic cation exchange resin and the true specific gravity of the strongly basic anion exchange resin is contacted with the non-regenerated mixed bed ion exchange resin that has been subjected to the first separation step; and 1. A method for separating used non-regenerated mixed bed ion exchange resin, wherein the first solution is a dilute solution having a lower concentration than the second solution. [Configuration 2] 2. The method for separating used non-regenerated mixed-bed ion exchange resin according to claim 1, wherein the first solution is an aqueous solution selected from the group consisting of saline, hydrochloric acid, sulfuric acid, aqueous sodium hydroxide, aqueous potassium hydroxide, aqueous ammonium chloride, aqueous calcium chloride, aqueous sodium carbonate, aqueous sodium sulfate, aqueous sodium acetate, and aqueous formic acid. [Configuration 3] 3. The method for separating a used non-regenerated mixed bed ion exchange resin according to claim 1 or 2, wherein the second solution is an aqueous solution selected from the group consisting of saline, hydrochloric acid, and aqueous sodium hydroxide. [Configuration 4] 4. The method for separating a used non-regenerated mixed-bed ion exchange resin according to any one of configurations 1 to 3, wherein the first solution is the same type of solution as the second solution. [Configuration 5] 5. The method for separating used non-regenerated mixed-bed ion exchange resins according to any one of claims 1 to 4, wherein the PBC (percent sphericity, %) of each ion exchange resin separated through the second separation step is reduced by less than 5% from the PBC (%) of each ion exchange resin before separation. [Configuration 6] A method for reusing a used non-regenerated mixed-bed ion exchange resin, comprising reusing a strongly acidic cation exchange resin or a strongly basic anion exchange resin separated by the method according to any one of aspects 1 to 5 as a non-regenerated mixed-bed ion exchange resin or a single-bed ion exchange resin. [Configuration 7] A method for producing a single-bed ion exchange resin, comprising a step of separating a used non-regenerated mixed-bed ion exchange resin using the method according to any one of aspects 1 to 5. [Explanation of symbols]

[0046] A: Anion exchange resin B: Second solution C: Cation exchange resin

Claims

1. A method for separating used non-regenerated mixed bed ion exchange resins, comprising a separation step of separating a strongly acidic cation exchange resin and a strongly basic anion exchange resin contained in the used non-regenerated mixed bed ion exchange resins, The separation step a first separation step in which a first solution capable of converting the ionic form of at least one of the strongly acidic cation exchange resin and the strongly basic anion exchange resin contained in the non-regenerated mixed bed ion exchange resin into a salt form is contacted with the non-regenerated mixed bed ion exchange resin; a second separation step in which a second solution having an intermediate specific gravity between the true specific gravity of the strongly acidic cation exchange resin and the true specific gravity of the strongly basic anion exchange resin is contacted with the non-regenerated mixed bed ion exchange resin that has been subjected to the first separation step; and 1. A method for separating spent non-regenerated mixed bed ion exchange resin, wherein the first solution is a dilute solution having a lower concentration than the second solution.

2. 2. The method for separating used non-regenerated mixed bed ion exchange resin according to claim 1, wherein the first solution is an aqueous solution selected from the group consisting of saline, hydrochloric acid, sulfuric acid, aqueous sodium hydroxide, aqueous potassium hydroxide, aqueous ammonium chloride, aqueous calcium chloride, aqueous sodium carbonate, aqueous sodium sulfate, aqueous sodium acetate, and aqueous formic acid.

3. 2. The method for separating spent non-regenerated mixed bed ion exchange resin according to claim 1, wherein the second solution is an aqueous solution selected from the group consisting of saline, hydrochloric acid, and aqueous sodium hydroxide.

4. 2. The method for separating spent non-regenerated mixed bed ion exchange resin according to claim 1, wherein the first solution is the same type of solution as the second solution.

5. 2. The method for separating used non-regenerated mixed bed ion exchange resins according to claim 1, wherein the PBC (percentage of sphericity, %) of each ion exchange resin separated through the second separation step is reduced by less than 5% from the PBC (%) of each ion exchange resin before separation.

6. A method for reusing used non-regenerated mixed bed ion exchange resins, comprising reusing the strongly acidic cation exchange resin or strongly basic anion exchange resin separated by the method according to any one of claims 1 to 5 as a non-regenerated mixed bed ion exchange resin or a single bed ion exchange resin.

7. A method for producing a single-bed ion exchange resin, comprising the step of separating used non-regenerated mixed-bed ion exchange resin using the method according to any one of claims 1 to 5.

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