JP2024097173A - Method for separating and regenerating anion exchange resin and cation exchange resin in ion exchange resin mixture - Google Patents

Abstract

To provide a method for separating and regenerating an anion exchange resin and a cation exchange resin in an ion exchange resin mixture, making it possible to reduce the usage of aqueous NaOH solutions when separating the anion exchange resin and the cation exchange resin in the ion exchange resin mixture using a seprex method.SOLUTION: By recovering and using a second aqueous NaOH solution that has been used in an anion exchange resin regeneration tower 4 as a first aqueous NaOH solution that separates a cation exchange resin mixed in an anion exchange resin in a seprex tower 3, the anion exchange resin is regenerated with high accuracy while the usage of the aqueous NaOH solutions is reduced.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for separating and regenerating mixed ion exchange resins of anion exchange resins and cation exchange resins used in non-regenerative ion exchange devices and mixed bed ion exchange devices used in pure water production systems, etc.

In pure water production systems, impurities in raw water are removed to improve the purity of the water. In order to remove ionic impurities, i.e., anionic and cationic impurities, a mixed-bed ion exchange system in which anion exchange resin and cation exchange resin are mixed and packed is commonly used. In this mixed-bed ion exchange system, when the ion exchange resin exchanges an amount of ions equivalent to the ion exchange capacity, it cannot remove any more ionic impurities and breaks through. Therefore, after a certain amount of water to be treated is treated before breakthrough, the ion exchange resin is recovered from the mixed-bed ion exchange system and regenerated with hydrochloric acid or caustic soda in a cation exchange resin regeneration tower and an anion exchange resin regeneration tower, respectively, for reuse. In this case, the anion exchange resin and the cation exchange resin are generally separated by passing the water in an upward flow and utilizing the difference in sedimentation speed due to the difference in specific gravity between the anion exchange resin and the cation exchange resin.

An example of this mixed ion exchange resin separation tower (backwash separation tower) is shown in FIG. 2. In FIG. 2, the mixed ion exchange resin separation tower 21 has a cylindrical separation tower body 21A with an inlet/outlet 22 at the bottom, a water supply pipe 23 with multiple discharge nozzles 23A as a water discharge section, and a drain port 24 at the top. A water collection plate 25 is arranged below the discharge nozzles 23A of the separation tower body 21A. An anion exchange resin discharge pipe 26 as an anion exchange resin discharge section is provided near the middle of the vertical direction in the separation tower 21, and a cation exchange resin discharge pipe 27 is provided below the anion exchange resin discharge pipe 26 and slightly above the water supply pipe 23. In addition, a peep hole 28 is formed on the side of the separation tower 21. 29 is an inlet for used mixed ion exchange resin provided on the upper side of the side of the separation tower 21.

In such a mixed ion exchange resin separation tower 21, used mixed ion exchange resin is put into the separation tower 21, followed by passing about 4% by weight of NaOH aqueous solution through it, and then leaving it for a predetermined time to adjust the shape of the ion exchange resin and increase the specific gravity difference. Then, pure water is injected from the inlet/outlet 22 and the NaOH aqueous solution in the separation tower is pushed out from the outlet 24 for cleaning. Then, the separation tower 21 is filled with a predetermined amount of separation water (pure water). At this time, the water level of the separation water is made to be higher than the top surface of the mixed ion exchange resin, specifically about 500 mm or less above.

Next, air is injected into the separation tower from the inlet/outlet 24, and the mixed ion exchange resin is bubbled to loosen the resin particles that have become entangled in a colloidal state. After that, the bubbling is stopped and the mixed ion exchange resin is allowed to settle on the water collection plate 25. At this time, the cation exchange resin, which has a high specific gravity, settles first, and the anion exchange resin, which has a low specific gravity, settles later. Next, in preparation for backwashing, pure water (water for separation) is introduced from the inlet/outlet 22 so that the separation tower 21 is filled with water.

In this full-water state, pure water is discharged from the discharge nozzle 23A and passed through in an upward flow, and adjustments are made while visually checking through the observation window 28 so that the separation interface is at the lower end of the suction port of the anion exchange resin extraction pipe 26. Then, the anion exchange resin is sucked through the anion exchange resin extraction pipe 26 and discharged as an anion exchange resin/water mixed phase flow, which is then removed. After draining, this anion exchange resin/water mixed phase flow is transferred to the anion exchange resin regeneration tower for anion exchange resin regeneration treatment.

After the anion exchange resin has been extracted in this manner, pure water is continuously discharged from the discharge nozzle 23A while being sucked through the cation exchange resin extraction pipe 27, and is discharged and extracted as a cation exchange resin/water mixed phase flow. This cation exchange resin/water mixed phase flow is drained and then transferred to a cation exchange resin regeneration separation tower for regeneration of the cation exchange resin. At this time, not all of the cation exchange resin is removed, but a certain amount is left to prevent contamination with the anion exchange resin.

However, the above-mentioned method for separating anion exchange resin and cation exchange resin has a problem in that the separation of the two is insufficient. In particular, the cation exchange resin can be separated well by leaving the interface portion in the separation tower 21, but there is a problem in that the cation exchange resin is likely to be mixed with the anion exchange resin that is extracted first.

Therefore, a method known as the Seplex method is used, in which a highly concentrated NaOH aqueous solution is used to separate the anion exchange resin from the cation exchange resin. The Seplex method uses the system and process shown in Figures 3 and 4.

In other words, the mixed ion exchange resin separation and regeneration system is composed of four towers, a backwash separation tower, a Seplex tower, an anion exchange resin regeneration tower, and a cation exchange resin regeneration tower, as shown in Figure 3. First, in the backwash separation tower, the anion exchange resin and the cation exchange resin are separated by the backwash separation process based on the difference in specific gravity, and the anion exchange resin is extracted. At this time, by passing an aqueous NaOH solution through the mixed ion exchange resin, the cation exchange resin is converted to the Na type and the anion exchange resin to the OH type, respectively, thereby increasing the difference in specific gravity between the anion exchange resin and the cation exchange resin, and reducing the contamination rate of the anion exchange resin and the cation exchange resin after backwash separation.

In this backwash separation process, the separated anion exchange resin contains a small amount of cation exchange resin, but the cation exchange resin is transferred to a Seplex separation tower, which acts as an anion exchange resin high-speed separation tower. Then, an aqueous NaOH solution with a specific gravity intermediate between the specific gravity of the anion exchange resin and the specific gravity of the cation exchange resin is injected into this Seplex separation tower, and the resin is loosened by bubbling and left to stand, causing the mixed cation exchange resin to settle to the bottom. This cation exchange resin is extracted and removed from the bottom of the Seplex separation tower. Pure water is then supplied into the tower to extrude and wash out the NaOH aqueous solution, and the remaining anion exchange resin is then extracted (Seplex separation process).

The extracted anion exchange resin is transferred to an anion exchange resin regeneration tower, where the anion exchange resin is regenerated and washed with an aqueous NaOH solution (anion exchange resin regeneration process). On the other hand, the cation exchange resin separated in the backwash separation process is transferred to a cation exchange resin regeneration tower, where the cation exchange resin is regenerated and washed by a standard method (cation exchange resin regeneration process).

The Seplex method described above allows anion exchange resin and thione exchange resin to be separated with minimal mixing of the other. However, the Seplex method supplies and recovers NaOH solution using the mechanism and procedure shown in Figure 4. That is, the NaOH solution supply and recovery mechanism 30 in the Seplex method supplies ultrapure water W from an ultrapure water supply source 34 via an ultrapure water supply pipe 35 to the backwash separation tower 31, the Seplex tower 32, and the anion exchange resin regeneration tower 33, and supplies unused concentrated NaOH aqueous solution N from a concentrated NaOH aqueous solution tank 36, so that each can supply a NaOH aqueous solution of a predetermined concentration. The used NaOH aqueous solution is stored in a waste liquid tank 38 from a waste NaOH aqueous solution discharge pipe 37, where the waste NaOH aqueous solution discharge branch pipes 37A, 37B, and 37C join, and is discarded. 39A, 39B, and 39C are specific gravity meters for adjusting the mixing ratio of ultrapure water W and concentrated NaOH aqueous solution SH to supply a NaOH aqueous solution of a predetermined concentration. Note that since FIG. 4 is an explanatory diagram of the supply and recovery of NaOH solution, the anion exchange resin regeneration tower is not shown.

In this way, in the past, unused NaOH solution was used in the backwash separation process, the Sephrex separation process, and the anion exchange resin regeneration process, and the NaOH solution after use was discarded. This resulted in the problem of using a large amount of NaOH aqueous solution.

The present invention has been made in consideration of the above problems, and aims to provide a method for separating and regenerating anion exchange resin and cation exchange resin in a mixed ion exchange resin, which can reduce the amount of NaOH solution used when separating the anion exchange resin and cation exchange resin of the mixed ion exchange resin using the Seplex method.

In view of the above object, the present invention provides a method for separating and regenerating anion exchange resin and cation exchange resin from a mixed ion exchange resin of anion exchange resin and cation exchange resin, comprising a backwash separation step in which the mixed ion exchange resin is introduced into a substantially cylindrical mixed ion exchange resin backwash separation tower having a mixed ion exchange resin introduction section, an anion exchange resin extraction section provided midway in the vertical direction, a cation exchange resin extraction section provided below the anion exchange resin extraction section, and an air and separation water injection section provided at the bottom, and separation water is passed through the air and separation water injection section in an upward flow into the separation tower to separate the mixed ion exchange resin by utilizing the difference in specific gravity; a transfer step in which the anion exchange resin above the separation interface between the anion exchange resin and the cation exchange resin is extracted from the anion exchange resin extraction section and transferred to an anion exchange resin advanced separation tower, and the remaining cation exchange resin is extracted from the cation exchange resin extraction section and transferred to a cation exchange resin regeneration tower; and a transfer step in which 5% by weight to 30% by weight of the anion exchange resin is introduced into the anion exchange resin advanced separation tower. The method for separating and regenerating anion exchange resin and cation exchange resin in a mixed ion exchange resin includes an anion exchange resin separation step in which the anion exchange resin is immersed in a first NaOH aqueous solution below to separate the cation exchange resin mixed in the anion exchange resin and discharge the cation exchange resin, an anion exchange resin regeneration step in which the anion exchange resin remaining in the anion exchange resin high-speed separation tower is regenerated with a second NaOH aqueous solution, and a cation exchange resin regeneration step in which the cation exchange resin in the cation exchange resin regeneration tower is regenerated. The method for separating and regenerating anion exchange resin and cation exchange resin in a mixed ion exchange resin includes an unused high-concentration NaOH aqueous solution as the second NaOH aqueous solution, and an NaOH aqueous solution recovered from the second NaOH aqueous solution used in the anion exchange resin regeneration step and the first NaOH aqueous solution used in the anion exchange resin separation step is used as the first NaOH aqueous solution (Invention 1).

According to this invention (Invention 1), unused high-concentration NaOH aqueous solution is used as the second NaOH aqueous solution to regenerate the anion exchange resin in the final stage, and the used second NaOH aqueous solution is recovered and reused as the first NaOH aqueous solution to separate the cation exchange resin in the anion exchange resin advanced separation tower, making it possible to regenerate the anion exchange resin with high accuracy while reducing the amount of NaOH aqueous solution used.

In the above invention (Invention 1), it is preferable to add unused high-concentration NaOH aqueous solution to the first NaOH aqueous solution (Invention 2).

According to this invention (Invention 2), the anion exchange resin advanced separation tower uses a higher concentration of NaOH aqueous solution than in the anion exchange resin regeneration process, so the concentration of the NaOH aqueous solution is insufficient if the used second NaOH aqueous solution is simply recovered and reused. Therefore, by adding unused high-concentration NaOH aqueous solution to achieve a NaOH aqueous solution concentration suitable for the anion exchange resin separation process, it is possible to recover and reuse the used second NaOH aqueous solution and to achieve a NaOH aqueous solution concentration suitable for the anion exchange resin separation process.

In the above invention (Invention 2), it is preferable to adjust the concentration of the second NaOH aqueous solution and/or the first NaOH aqueous solution with pure water (Invention 3).

According to this invention (Invention 3), the concentration of the NaOH aqueous solution can be adjusted with pure water, so that the anion exchange resin regeneration process and the anion exchange resin separation process can each be carried out appropriately.

In the above invention (Invention 1), in the backwash separation process in which the separation water is passed in an upward flow to separate the mixed ion exchange resin by utilizing the difference in specific gravity, it is preferable to pass a third NaOH aqueous solution through the mixed ion exchange resin to adjust the ion type, and to use, as the third NaOH aqueous solution, an NaOH aqueous solution recovered from the second NaOH aqueous solution used in the anion exchange resin regeneration process and the first NaOH aqueous solution used in the anion exchange resin separation process (Invention 4).

According to this invention (Invention 4), the third NaOH solution used for ion type adjustment in which a third NaOH aqueous solution is passed through the mixed ion exchange resin in the backwash separation process in which separation water is passed in an upward flow is the second NaOH aqueous solution used in the anion exchange resin regeneration process and the NaOH aqueous solution recovered from the first NaOH aqueous solution used in the anion exchange resin separation process. This makes it possible to reduce the amount of NaOH aqueous solution used while performing ion type adjustment, i.e., separation of the thione exchange resin in the anion exchange resin high-speed separation tower and regeneration of the anion exchange resin, with high accuracy.

In the above inventions (Inventions 1 to 4), it is preferable that the anion exchange resin and the cation exchange resin are porous ion exchange resins (Invention 5).

According to this invention (Invention 5), the specific gravity of the 5% by weight to 30% by weight NaOH aqueous solution can be set between the specific gravity of the porous anion exchange resin and the specific gravity of the porous ion exchange resin, so that the difference in specific gravity can be utilized in the anion exchange resin separation process to effectively separate the cation exchange resin mixed in the anion exchange resin.

According to the method for separating and regenerating anion exchange resin and cation exchange resin in a mixed ion exchange resin of the present invention, the second aqueous NaOH solution that has been used is recovered and used as the first aqueous NaOH solution for separating the cation exchange resin mixed in the anion exchange resin in the anion exchange resin high-speed separation tower, so that the anion exchange resin can be regenerated with high accuracy while reducing the amount of aqueous NaOH solution used.

FIG. 1 is a schematic diagram showing a method for supplying and recovering an aqueous NaOH solution in a method for separating and regenerating an anion exchange resin and a cation exchange resin in a mixed ion exchange resin according to an embodiment of the present invention. FIG. 2 is a schematic diagram showing an example of a separation column for anion exchange resin and cation exchange resin of a mixed ion exchange resin. FIG. 1 is a flow diagram showing a system for separating and regenerating anion exchange resin and cation exchange resin in a mixed ion exchange resin. FIG. 1 is a schematic diagram showing a method for supplying and recovering an aqueous NaOH solution in a conventional method for separating and regenerating an anion exchange resin and a cation exchange resin in a mixed ion exchange resin.

The method for separating and regenerating the anion exchange resin and the cation exchange resin in the mixed ion exchange resin of the present invention will be described in detail below with reference to the attached drawings.

[Mixed ion exchange resin separation and regeneration system]
The separation and regeneration system for the anion exchange resin and the cation exchange resin in the mixed ion exchange resin of this embodiment is the same as the separation and regeneration system shown in FIG. 3 described above, and therefore a detailed description thereof will be omitted.

(NaOH solution supply and recovery mechanism)
In this embodiment, the NaOH solution is supplied to and recovered from each component by a NaOH solution supply and recovery mechanism 1 in the Seplex method configured as shown in Fig. 1. That is, the NaOH solution supply and recovery mechanism 1 includes a backwash separation tower 2, a Seplex tower 3 as an anion exchange resin high-level separation tower, and an anion exchange resin regeneration tower 4, and is capable of supplying ultrapure water W from an ultrapure water supply source 5 via an ultrapure water supply pipe 6, and supplying unused concentrated NaOH aqueous solution N from a concentrated NaOH aqueous solution tank 7 via an NaOH aqueous solution supply pipe 10 to the regeneration tower 4 at a predetermined concentration. In addition, 8 is a recovery and supply tank for the NaOH aqueous solution, and the NaOH aqueous solution that has passed through the anion exchange resin regeneration tower 4 and the Seplex tower 3 is recovered via recovery pipes 11, 12, and 13, respectively, and then can be supplied to the backwash separation tower 2 and the Seplex tower 3 as a reused NaOH aqueous solution R via NaOH aqueous solution supply pipes 14, 14A, and 14B. Furthermore, 9 is a waste liquid tank, and the NaOH aqueous solution that has passed through the backwash separation tower 2 can be recovered via a waste pipe 15. Incidentally, 12A and 13A are spare waste pipes, and 16A, 16B, 16C, and 16D are specific gravity meters for adjusting the mixing ratio of ultrapure water W and concentrated NaOH aqueous solution SH to supply a NaOH aqueous solution of a predetermined concentration. Incidentally, since FIG. 1 is an explanatory diagram of the supply and recovery of the NaOH solution, the anion exchange resin regeneration tower is not shown.

[Method for separating and regenerating mixed ion exchange resins]
The method for separating and regenerating the anion exchange resin and the cation exchange resin in the mixed ion exchange resin of this embodiment is the same as the backwash separation step, the anion exchange resin separation step (hereinafter referred to as the Seplex separation step), the anion exchange resin regeneration step, and the cation exchange resin regeneration step in the separation and regeneration system shown in FIG. 3 described above, and therefore detailed description thereof will be omitted.

(Method of Supplying and Recovering NaOH Aqueous Solution)
Next, the method for supplying and recovering the NaOH solution according to the present embodiment using the NaOH solution supply and recovery mechanism 1 having the above-mentioned configuration will be described with reference to Fig. 1. The method for supplying and recovering the NaOH solution of the NaOH solution proceeds in the order of the backwash separation step, the anion exchange resin separation step, and the anion exchange resin regeneration step in chronological order, but in this embodiment, for convenience of explanation, the anion exchange resin regeneration step, the Seplex separation step, and the backwash separation step will be described in that order.

(Early stage)
In the initial state, it is preferable to carry out the backwash separation step, the anion exchange resin separation step, and the anion exchange resin regeneration step using aqueous NaOH solutions of suitable concentrations, and store used aqueous NaOH solution in the waste liquid tank 9. In addition, unused aqueous concentrated NaOH solution N is stored in the concentrated aqueous NaOH solution tank 7. The concentration of this aqueous concentrated NaOH solution N may be higher than the concentration of the aqueous NaOH solution in the Seplex separation step described below, and may be appropriately set, for example, within the range of 25 to 48% by weight depending on the concentration of the aqueous NaOH solution in the Seplex separation step.

(Anion exchange resin regeneration process)
In the regeneration process of the anion exchange resin, ultrapure water W is supplied from the ultrapure water supply pipe 6, and unused concentrated NaOH aqueous solution N is supplied from the concentrated NaOH aqueous solution tank 7 to the regeneration tower 4 of the anion exchange resin via the NaOH aqueous solution supply pipe 10. At this time, the concentration of NaOH is confirmed based on the specific gravity of the solution supplied to the regeneration tower 4 by the specific gravity meter 16C, and the flow rate of the ultrapure water W and/or the concentrated NaOH aqueous solution N is adjusted as necessary to prepare a NaOH aqueous solution of a desired concentration (for example, about 4% by weight). The anion exchange resin is regenerated as the final stage by using this clean NaOH aqueous solution. Then, the used NaOH aqueous solution used in the regeneration of this anion exchange resin is recovered in the recovery/supply tank 8 of the NaOH aqueous solution via the recovery pipe 12 and the recovery pipe 11. In addition, the NaOH aqueous solution (concentrated more than that in the regeneration process) used in the Sephrex separation process is also recovered and merged in the recovery/supply tank 8 of the NaOH aqueous solution, as described later. Therefore, the aqueous NaOH solution stored in the recovery and supply tank 8 for the aqueous NaOH solution is a more dilute aqueous NaOH solution than the aqueous NaOH solution used in the Sephrex separation step.

In this embodiment, pure water, particularly ultrapure water W, is used to dilute the concentrated NaOH aqueous solution N and adjust the concentration of the NaOH aqueous solution. Here, the ultrapure water W preferably has resistivity of 18.1 MΩ·cm or more, particles with a particle size of 50 nm or more and 1000 particles/L or less, live bacteria of 1 particle/L or less, TOC (Total Organic Carbon) of 1 μg/L or less, total silicon of 0.1 μg/L or less, metals of 1 ng/L or less, ions of 10 ng/L or less, hydrogen peroxide of 30 μg/L or less, and a water temperature of 25±2°C.

(Seplex separation process)
In the Seplex separation step, ultrapure water W is supplied from the ultrapure water supply pipe 6, and used aqueous NaOH solution SH is supplied from the NaOH aqueous solution recovery/supply tank 8 to the Seplex column 3 via the NaOH aqueous solution supply pipes 14, 14A. Here, the concentration of the aqueous NaOH solution used in the Seplex separation step is high, for example, about 9 to 25% by weight, so the concentration of the recovered aqueous NaOH solution R stored in the NaOH aqueous solution recovery/supply tank 8 is insufficient. Therefore, the shortage is roughly calculated from the concentration of the aqueous NaOH solution calculated by the specific gravity meter 16B, and the concentrated aqueous NaOH solution N is supplied to the Seplex column 3 via the NaOH aqueous solution supply pipe 10 from the concentrated aqueous NaOH solution tank 7. Separation is performed by the Seplex method using both the used aqueous NaOH solution R and the concentrated aqueous NaOH solution N (Seplex separation step). The aqueous NaOH solution used in the Seplex separation step is then recovered from the recovery pipe 13 to the NaOH aqueous solution recovery/supply tank 8 via the recovery pipe 11. It is preferable to provide a specific gravity meter 16D in the recovery and supply tank 8 for the aqueous NaOH solution as well, so as to confirm the concentration of NaOH stored in the recovery and supply tank 8.

(Backwash separation process)
In the backwash separation step, ultrapure water W is supplied from the ultrapure water supply pipe 6, and used NaOH aqueous solution R is supplied from the NaOH aqueous solution recovery/supply tank 8 to the backwash separation tower 2 via the NaOH aqueous solution supply pipes 14, 14B. At this time, the concentration of NaOH is confirmed based on the specific gravity of the solution supplied to the backwash separation tower 2 using the specific gravity meter 16A, and the flow rate of the ultrapure water W and/or the recovered NaOH aqueous solution R is adjusted as necessary to prepare a NaOH aqueous solution of a desired concentration (for example, about 4% by weight). The ion type is adjusted in the backwash separation step using this used NaOH aqueous solution R. The NaOH aqueous solution used for adjusting the ion type is then recovered from the waste pipe 15 to the waste liquid tank 9, where it is subjected to a predetermined treatment and then discarded.

If the aqueous NaOH solution after the Sephrex separation process and regeneration process cannot be reused due to its water quality, it can be collected from the spare waste pipes 12A and 13A into the waste liquid tank 9, where it can be subjected to the required treatment and then discarded.

The present invention has been described above based on the above embodiment, but the present invention is not limited to the above embodiment and can be modified in various ways. For example, the apparatus for implementing the Sephrex method can be configured in various ways, for example, in such a way that both the Sephrex separation process and the anion exchange resin regeneration process are performed within the Sephrex tower.

The present invention will be described in more detail with reference to the following specific examples.

[Example 1]
The anion exchange resin and cation exchange resin separation and regeneration device of the mixed ion exchange resin was composed of the mixed ion exchange resin backwash separation tower, the cation exchange resin regeneration tower, the Seplex separation tower, and the anion exchange resin regeneration tower, and the anion exchange resin was separated and purified and the anion exchange resin was regenerated by the process shown in Figure 3. At this time, the NaOH aqueous solution was supplied and recovered by the method shown in Figure 1.

The mixed resin to be separated was 600 L, with a cationic resin:anionic resin ratio of 1:1. The anionic exchange resin was a porous anionic exchange resin with a specific gravity of 1.05 g/mL (when wet), and the cationic exchange resin was a porous cation exchange resin with a specific gravity of 1.28 g/mL (when wet).

Unused concentrated NaOH aqueous solution N was diluted with pure water W and supplied from concentrated NaOH aqueous solution tank 7 to anion exchange resin regeneration tower 4. The NaOH aqueous solution used in the anion exchange resin regeneration process and the Seplex separation process described below was received in recovery/supply tank 8 and supplied to Seplex separation tower 3 as recycled NaOH aqueous solution R for reuse, and unused concentrated NaOH aqueous solution N and ultrapure water W were added as necessary to make up for any deficiencies in NaOH concentration. The recycled NaOH aqueous solution R from recovery/supply tank 8 was then reused for ion type adjustment in backwash separation tower 2.

In the ion type adjustment process of the backwash separation process, an aqueous NaOH solution adjusted to 4% by weight was used, and the regeneration level was set to 200 g-NaOH/LR for the anion resin. Here, the regeneration level [g--regenerant (NaOH/LR)] represents the amount of regenerant (100% conversion) used relative to the amount of resin. Here, since it is relative to the amount of anion resin, it represents the amount of regenerant used relative to 300 L of anion exchange resin, not 600 L of mixed resin.

In the Sephrex separation process, an aqueous NaOH solution adjusted to 16% by weight was used, and 1.5 times the amount (volume ratio) of the anion exchange resin was used.

A 4% by weight aqueous NaOH solution was used in the regeneration process, with the regeneration level being 50 g NaOH/LR for the anion resin.

The amounts of NaOH aqueous solution (100% equivalent) used in the backwash separation process, the Sephrex separation process and the regeneration process are shown in Table 1, and for reference, the specific gravity of a 16% NaOH aqueous solution, the specific gravity of the cation exchange resin (H type) before ion type adjustment, the anion exchange resin (OH type) before ion type adjustment and the cation exchange resin (Na type) after ion type adjustment are shown in Table 2.

As is clear from Table 1, 60 L of NaOH aqueous solution is required for backwash separation, but since the NaOH aqueous solution used in the Seplex separation process and regeneration process is reused, the amount of NaOH aqueous solution was essentially "0", and 87 L of NaOH aqueous solution was discarded.

[Comparative Example 1]
The anion exchange resin and cation exchange resin separation and regeneration device of the mixed ion exchange resin was composed of the mixed ion exchange resin backwash separation tower, the cation exchange resin regeneration tower, the Seplex separation tower, and the anion exchange resin regeneration tower, and the anion exchange resin was separated and purified by the process shown in Figure 3. At this time, the NaOH aqueous solution was supplied and recovered by the method shown in Figure 4.

The mixed resin to be separated was 600 L, with a cationic resin:anionic resin ratio of 1:1. The anionic exchange resin was a porous anionic exchange resin with a specific gravity of 1.05 g/mL (when wet), and the cationic exchange resin was a porous cation exchange resin with a specific gravity of 1.28 g/mL (when wet).

The NaOH aqueous solution used in the regeneration process of the anion exchange resin regeneration tower 4, the Separation process of the Separation tower 3, and the backwash separation process of the backwash separation tower 2 was discarded and not reused.

In the ion type adjustment process of the backwash separation process, an aqueous NaOH solution adjusted to 4% by weight was used, and the regeneration level was 200 g-NaOH/LR for the anion resin.

In the Sephrex separation process, an aqueous NaOH solution adjusted to 16% by weight was used, and 1.5 times the amount (volume ratio) of the anion exchange resin was used.

A 4% by weight aqueous NaOH solution was used in the regeneration process, with the regeneration level being 50 g NaOH/LR for the anion resin.

The amounts of NaOH aqueous solution (100% equivalent) used in the backwash separation process, the Sephrex separation process, and the regeneration process are shown in Table 3.

As is clear from Table 3, if the NaOH aqueous solution used in the backwash separation process, the Sephrex separation process, and the anion exchange resin regeneration process is unused and temporarily discarded, the total consumption is 147 L, which is an increase of 60 L (65% or more) of the amount of NaOH waste liquid compared to Example 1.

1 NaOH solution supply and recovery mechanism 2 Backwash separation tower 3 Seplex tower (anion exchange resin advanced separation tower)
Reference Signs List 4: Anion exchange resin regeneration tower 5: Ultrapure water supply source 6: Ultrapure water supply pipe 7: Concentrated NaOH aqueous solution tank 8: NaOH aqueous solution recovery/supply tank 9: Waste liquid tank 10: NaOH aqueous solution supply pipes 11, 12, 13: Recovery pipe 12A 13A: Spare waste pipes 14, 14A, 14B: NaOH aqueous solution supply pipe 15: Waste pipes 16A, 16B, 16C, 16D: Specific gravity meter W: Ultrapure water N: Concentrated NaOH aqueous solution R: Recycled NaOH aqueous solution

Claims (5)

A method for separating and regenerating anion exchange resin and cation exchange resin from a mixed ion exchange resin of anion exchange resin and cation exchange resin, comprising the steps of:
a backwash separation step in which the mixed ion exchange resin is introduced into a substantially cylindrical mixed ion exchange resin backwash separation tower having a mixed ion exchange resin introduction section, an anion exchange resin discharge section provided in the vertical direction, a cation exchange resin discharge section provided below the anion exchange resin discharge section, and an air and separation water injection section provided at the bottom, and separation water is passed through the air and separation water injection section in an upward flow into the separation tower to separate the mixed ion exchange resin by utilizing the difference in specific gravity;
a transfer step of extracting the anion exchange resin above the separation interface between the anion exchange resin and the cation exchange resin from the anion exchange resin extraction section and transferring it to an anion exchange resin high-speed separation tower, and extracting the remaining cation exchange resin from the cation exchange resin extraction section and transferring it to a cation exchange resin regeneration tower;
an anion exchange resin separation step of immersing the anion exchange resin high-speed separation tower in a first NaOH aqueous solution having a concentration of 5% by weight or more and 30% by weight or less to separate the cation exchange resin mixed in the anion exchange resin and discharging the cation exchange resin;
an anion exchange resin regeneration step of regenerating the anion exchange resin remaining in the anion exchange resin high-speed separation column with a second NaOH aqueous solution;
a cation exchange resin regeneration step of regenerating the cation exchange resin in the cation exchange resin regeneration tower;
A method for separating and regenerating anion exchange resin and cation exchange resin in a mixed ion exchange resin having
The method for separating and regenerating anion exchange resin and cation exchange resin in a mixed ion exchange resin comprises using an unused high-concentration NaOH aqueous solution as the second NaOH aqueous solution, and using, as the first NaOH aqueous solution, a second NaOH aqueous solution used in the anion exchange resin regeneration step, or a NaOH aqueous solution obtained by recovering the second NaOH aqueous solution used in the anion exchange resin regeneration step and the first NaOH aqueous solution used in the anion exchange resin separation step. The method for separating and regenerating anion exchange resin and cation exchange resin in a mixed ion exchange resin according to claim 1, wherein unused high-concentration NaOH aqueous solution is added to the first NaOH aqueous solution. The method for separating and regenerating anion exchange resin and cation exchange resin in a mixed ion exchange resin according to claim 2, wherein the concentration of the second NaOH aqueous solution and/or the first NaOH aqueous solution is adjusted with pure water. The method for separating and regenerating anion exchange resin and cation exchange resin in a mixed ion exchange resin according to claim 1, wherein in the backwash separation process in which the separation water is passed in an upward flow to separate the mixed ion exchange resin by utilizing the difference in specific gravity, a third NaOH aqueous solution is passed through the mixed ion exchange resin to adjust the ion type, and the third NaOH aqueous solution is a NaOH aqueous solution recovered from the second NaOH aqueous solution used in the anion exchange resin regeneration process and the first NaOH aqueous solution used in the anion exchange resin separation process. A method for separating and regenerating anion exchange resin and cation exchange resin in a mixed ion exchange resin according to any one of claims 1 to 4, wherein the anion exchange resin and the cation exchange resin are porous ion exchange resins.

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