JP2020157252A - Electric deionized water manufacturing apparatus, and manufacturing method of deionized water - Google Patents

Abstract

To provide a novel EDI apparatus capable of preventing a weak acid component from passing a cation exchange membrane and moving from a concentration chamber to a desalination chamber and capable of removing the weak acid component from water to be processed while disposing an anion exchanger in a concentration chamber for suppressing scaling.SOLUTION: In an electric deionized water manufacturing apparatus, at least one desalination processing portion is provided between a cathode and an anode facing each other, the desalination processing portion including a desalination chamber filled with an ion exchanger and a pair of concentration chambers provided at both adjacent sides of the desalination chamber. Each of the pair of concentration chambers is filled with the ion exchanger. The desalination chamber is adjacent to, in the pair of concentration chambers, the concentration chamber at the cathode side via a cation exchange membrane, and the concentration chamber at the anode side via an anion exchange membrane. Water to be processed is made to pass the desalination chamber, to obtain deionized water from the desalination chamber. The ion exchanger filled in the concentration chamber at the cathode side includes: an ion exchange resin containing an anion exchange resin; and a nonwoven fabric or a woven fabric containing a cation exchange fabric.SELECTED DRAWING: Figure 1

Description

The present invention relates to an electric deionized water production apparatus.

The electric deionized water production device (hereinafter, may be referred to as "EDI device") is a device that combines electrophoresis and electrodialysis. The basic configuration of a general EDI device is as follows. That is, the EDI device includes a desalination chamber, a pair of concentration chambers arranged on both sides of the desalination chamber, an anode (positive electrode) chamber arranged outside one concentration chamber, and the outside of the other concentration chamber. It has a cathode (minus pole) chamber arranged in. The desalting chamber has an anion exchange membrane and a cation exchange membrane arranged opposite to each other, and an ion exchanger (anion exchanger and / and a cation exchanger) filled between the exchange membranes. The water to be treated is supplied to the desalination chamber, and the anion component and the cation component existing in the water to be treated move from the desalting chamber to the concentration chamber through the anion exchange membrane and the cation exchange membrane, respectively, and are treated from the desalting chamber. Water or deionized water is obtained, and concentrated water is obtained from the concentration chamber.

In the EDI apparatus, a phenomenon may occur in which a weak acid component contained in concentrated water passes through a cation exchange membrane that separates a concentration chamber and a desalination chamber and diffuses into the treated water, reducing the purity of the treated water. This is because weak acid components such as carbonic acid, silica (silicic acid), and boron (boric acid) take the form of molecules (neutral molecules) that are not partially ionized in response to changes in pH and the like. This is due to the fact that it is not easily affected by the selective permeability of the exchange membrane. For example, carbonic acid has an equilibrium relationship shown by the following equation. In the case of carbonic acid, the forms of the non-ionized molecule (neutral molecule) are CO ₂ and H ₂ CO ₃ , which can easily pass through the cation exchange membrane.
_{CO 2 + H 2 O ⇔ H} 2 CO 3 ⇔ HCO 3 - + H + ⇔ CO 3 2- + 2H +
For boron, there is an equilibrium relationship represented by the following equation.
_{B (OH) 3 + H 2} O ⇔ B (OH) 4 - + H +
In the case of boron, the form of the non-ionized molecule (neutral molecule) is B (OH) ₃ .

In addition, scales such as magnesium hydroxide may be generated in the EDI device. Patent Document 1 describes a method of filling an anion exchanger in a concentration chamber as a method of suppressing the formation of scale. This document discloses that an EDI apparatus in which an anion exchanger is filled in a concentration chamber significantly reduces the purity of treated water due to a weak acid component, and an EDI apparatus capable of suppressing this decrease in purity has been proposed. ..

In the EDI apparatus disclosed in Patent Document 2, the ion exchanger existing in a certain desalting chamber or concentrating chamber is either an ion exchange resin bead or at least one non-woven fabric or woven fabric made of ion exchange fibers. Consists of. This document merely discloses a configuration in which only ion exchange resin beads are arranged in the desalting chamber and only the non-woven fabric (and spacer) is arranged in the concentrating chamber.

International Publication No. 2011/152226 Special Table 2007-516506

In EDI equipment, it is very important to remove the weak acid component from the water to be treated.

An object of the present invention is to prevent the weak acid component from moving from the concentration chamber to the desalting chamber through the cation exchange membrane while arranging an anion exchanger in the concentration chamber to suppress scale formation. Is to provide a new EDI apparatus capable of removing the water from the water to be treated. Another object of the present invention is to provide a new method for producing deionized water using such an EDI device.

According to one aspect of the invention
At least one desalting treatment section is provided between the facing cathode and the anode.
The desalting treatment unit has a desalting chamber filled with an ion exchanger and a pair of concentrating chambers provided on both sides of the desalting chamber, and each of the pair of concentrating chambers is filled with the ion exchanger. Being done
The desalting chamber is adjacent to the cathode side concentration chamber of the pair of concentration chambers via a cation exchange membrane, and an anion exchange membrane is provided in the anode side concentration chamber of the pair of concentration chambers. Adjacent through
An electric deionized water production apparatus for obtaining deionized water from the desalting chamber by passing water to be treated through the desalting chamber.
The ion exchanger filled in the cathode side concentration chamber of the pair of concentration chambers is an electric deionized water containing an ion exchange resin containing an anion exchange resin and a non-woven fabric or woven fabric containing cation exchange fibers. Manufacturing equipment is provided.

According to another aspect of the invention
A method for producing deionized water, in which deionized water is produced by passing water to be treated through the desalting chamber of an electric deionized water production device.
The water to be treated contains at least one selected from the group consisting of boron, carbonic acid and silica.
Provided is a method for producing deionized water, wherein the electric deionized water producing apparatus is the electric deionized water producing apparatus.

According to one aspect of the present invention, while arranging an anion exchanger in the concentration chamber to suppress scale formation, it suppresses the movement of the weak acid component from the concentration chamber to the desalting chamber through the cation exchange membrane. , A new EDI device capable of removing a weak acid component from the water to be treated is provided. Further, according to another aspect of the present invention, a new method for producing deionized water using such an EDI device is provided.

It is a schematic cross-sectional view which shows the schematic structure of one form of the EDI apparatus of this invention. It is a schematic cross-sectional view which shows the schematic structure of another form of the EDI apparatus of this invention. It is a schematic cross-sectional view which shows the schematic structure of still another form of the EDI apparatus of this invention. It is a schematic cross-sectional view which shows the schematic structure of still another form of the EDI apparatus of this invention. It is a schematic cross-sectional view which shows the schematic structure of the EDI apparatus used in an Example.

Examples of the ion exchanger include an ion exchange resin and an ion exchange fiber. Examples of the anion exchanger include an anion exchange resin (AER), and examples of the cation exchanger include a cation exchange resin (CER). An ion exchange resin is a synthetic resin in which a functional group (ion exchange group) is introduced into a polymer base having a three-dimensional network structure, and a commonly used resin has a particle size of, for example, 0.1. It is a spherical particle of about 1.0 mm. Examples of the polymer base of the ion exchange resin include a styrene-divinylbenzene copolymer (styrene-based) and an acrylic acid-divinylbenzene copolymer (acrylic-based).

Ion exchange resins are roughly classified into cation exchange resins whose functional groups are acidic and anion exchange resins whose functional groups are basic. Further, depending on the type of ion exchange group to be introduced, a strongly acidic cation exchange resin and a weakly acidic cation are used. There are exchange resins, strong basic anion exchange resins, weak basic anion exchange resins, and the like. Some strongly basic anion exchange resins have, for example, a quaternary ammonium group as a functional group (ion exchange group), and as a weakly basic anion exchange resin, for example, primary to tertiary amines are functional. Some have as a base. Some strongly acidic cation exchange resins have, for example, a sulfonic acid group as a functional group, and some weakly acidic cation exchange resins have, for example, a carboxyl group as a functional group.

In the present invention, a non-woven fabric or a woven fabric containing an ion exchange fiber, particularly a cation exchange fiber is used. The cation exchange fiber has a structure in which a functional group (ion exchange group) is introduced into the fiber as a base material. Some cation exchange fibers have, for example, a sulfonic acid group as a functional group. Further, the cation exchange fiber has a property of adsorbing a cation (the same applies to a cation exchange resin). The non-woven fabric or woven fabric may contain non-ion exchange fibers (fibers into which no functional group has been introduced) in addition to the cation exchange fibers. The base material of the cation exchange fiber and the material of the non-ion exchange fiber are preferably polyester, polyethylene, polypropylene, polyolefin, or polyacrylonitrile-based resin from the viewpoint of physical strength. The non-ion exchange fibers have a function of increasing the overall strength (adhesion between fibers) of the non-woven fabric or the woven fabric.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings, but the present invention is not limited thereto.

FIG. 1 shows a basic aspect of the EDI apparatus based on the present invention. The EDI device is provided with at least one desalting treatment section between the opposing cathode 12 and the anode 11. This desalination treatment unit has a desalination chamber 23 and a pair of concentration chambers 22 and 24 provided on both sides of the desalination chamber 23, and also has an anion exchange membrane (AEM) 32 and a cation exchange membrane (CEM) 33. Also has. Water to be treated is passed through the desalting chamber 23 to obtain deionized water from the desalting chamber 23.

The desalting chamber 23 is adjacent to the cathode side concentration chamber 24 of the pair of concentration chambers 22 and 24 via the cation exchange membrane 33, and the anode side concentration chamber 22 of the pair of concentration chambers 22 and 24. Adjacent to the anion exchange membrane 32. The desalting chamber 23 is partitioned by an anion exchange membrane 32 located on the side facing the anode 11 and a cation exchange membrane 33 located on the side facing the cathode 12.

In the EDI apparatus shown in FIG. 1, between the anode chamber 21 provided with the anode 11 and the cathode chamber 25 provided with the cathode 12, the concentration chamber 22, the desalting chamber 23, and the concentration chamber 24 are arranged in this order from the anode chamber 21 side. Is provided. The anode chamber 21 and the concentration chamber 22 are adjacent to each other via the cation exchange membrane 31, and the concentration chamber 24 and the cathode chamber 25 are adjacent to each other via the anion exchange membrane 34.

The desalting chamber 23 is filled with an ion exchanger (anion exchanger and / or cation exchanger) in order to capture the ions contained in the water to be treated. In particular, it is preferable that the desalting chamber 23 is filled with at least an anion exchanger in order to capture the anion of the weak acid component contained in the water to be treated and remove it from the water to be treated. In the example shown in FIG. 1, the desalting chamber 23 is filled with an anion exchanger and a cation exchanger as a mixed bed (MB). However, only the anion exchanger may be filled in the desalting chamber 23. Alternatively, one or more anion exchanger beds (beds made of anion exchangers) and one or more cation exchanger beds (beds made of cation exchangers) may be provided in the desalting chamber 23. .. In this case, in order to reduce the concentration of the weak acid component in the treated water that is finally discharged from the desalination chamber, the ion exchanger that the water to be treated finally passes through becomes the anion exchanger in this order. And the cation exchanger bed is preferably filled in the desalting chamber. As the anion exchanger, for example, an anion exchange resin (AER) is used, and as the cation exchanger, for example, a cation exchange resin (CER) is used.

The pair of concentrating chambers 22 and 24 are each filled with an ion exchanger. The ion exchanger in the concentration chamber 24 contains an ion exchange resin. The ion exchanger in the concentration chamber 24 also includes a non-woven fabric containing cation exchange fibers or a woven fabric containing cation exchange fibers. The ion exchanger in the concentrating chamber 24 may also include the non-woven fabric and the woven fabric. The ion exchanger in the concentration chamber 24 can consist of at least one of the non-woven fabric and the woven fabric, and an ion exchange resin.

The ion exchanger in the concentration chamber 22 can contain an ion exchange resin, and may be made of an ion exchange resin in some cases. The ion exchanger in the concentration chamber 22 does not have to include a non-woven fabric containing cation exchange fibers or a woven fabric containing cation exchange fibers, but may include. In the latter case, as the ion exchanger in the concentration chamber 22, one having the same configuration as the ion exchanger in the concentration chamber 24 can be used.

The ion exchange resin in the concentration chamber 24 contains an anion exchange resin (AER) in order to suppress scale formation. Similarly, the ion exchange resin in the concentration chamber 22 can also contain an anion exchange resin (AER). The ion exchange resin in the concentrating chamber 22 and the concentrating chamber 24 may each be made of an anion exchange resin, or may be made of an anion exchange resin and a cation exchange resin (CER), respectively. Of the ion exchange resins in the concentration chamber 24, the ratio of the anion exchange resin is preferably 50% or more, more preferably 100% (all anion exchange resins). The same applies to the ratio of the anion exchange resin to the ion exchange resin in the concentration chamber 22.

In the example shown in FIG. 1, the ion exchanger filled in the concentration chamber 24 is composed of an anion exchange resin (AER) and a non-woven fabric 40 containing cation exchange fibers. The ion exchanger filled in the concentration chamber 22 is composed of an anion exchange resin (AER) and does not contain either a non-woven fabric or a woven fabric.

Nonwovens and woven fabrics containing cation exchange fibers are water permeable. Therefore, when the weak acid component is liberated inside the non-woven fabric or the woven fabric, the liberated weak acid component can be discharged into the concentrated water discharged from the concentrating chamber provided with the non-woven fabric or the woven fabric. That is, the weak acid component liberated inside the non-woven fabric 40 is discharged from the concentration chamber 24 by the water flowing in the non-woven fabric 40. In short, the non-woven fabric and the woven fabric containing the cation exchange fiber block the movement of the weak acid component from the anion exchange resin (AER) in the concentration chamber 24 to the cation exchange membrane 33, and discharge the weak acid component from the concentration chamber 24. Function. Further, since the non-woven fabric and the woven fabric containing the cation exchange fiber have conductivity, it is possible to suppress an increase in the operating voltage of the EDI device.

It is preferable that the non-woven fabric or woven fabric containing the cation exchange fiber is installed parallel to the water flow direction in the concentration chamber in which the non-woven fabric or woven fabric is present. In FIG. 1, the non-woven fabric 40 is installed in parallel in the water flow direction in the concentration chamber 24. This is effective to prevent the weak acid component (having a negative charge) from migrating and reaching the cation exchange membrane 33 separating the desalting chamber 23 and the concentration chamber 24, and is therefore treated with the weak acid component. It is effective for suppressing the decrease in water purity.

Further, the non-woven fabric or woven fabric is in contact with the cathode side surface of the cation exchange membrane (the cation exchange membrane that separates the concentration chamber in which the non-woven fabric or woven fabric is present and the desalting chamber adjacent to the concentration chamber). , It is preferable that it is installed. In particular, ion exchange contained in the concentration chamber on the cathode side surface of the cation exchange membrane (the cation exchange membrane that separates the concentration chamber in which the non-woven fabric or woven fabric is present and the desalting chamber adjacent to the concentration chamber). It is preferable that the resin does not come into contact with the resin. Therefore, a non-woven fabric or a woven fabric can be provided between the surface of the cation exchange membrane on the cathode side and the ion exchange resin. In FIG. 1, the non-woven fabric 40 is in contact with the surface of the cation exchange membrane 33 (which separates the concentration chamber 24 and the desalination chamber 23) on the cathode side. A non-woven fabric 40 is provided between them so that the surface of the cation exchange membrane 33 on the cathode side does not come into contact with the anion exchange resin (AER) in the concentration chamber 24. This is effective to prevent the weak acid component (having a negative charge) from migrating and reaching the cation exchange membrane 33 separating the desalting chamber 23 and the concentration chamber 24, and is therefore treated with the weak acid component. It is effective for suppressing the decrease in water purity.

Preferably, the non-woven fabric 40 (or woven fabric) is provided in contact with the entire surface of the cathode side surface of the cation exchange membrane 33. However, this is not the case, and the nonwoven fabric 40 (or woven fabric) may be provided so as to be in contact with a part of the cathode side surface of the cation exchange membrane 33. In this case, it is preferable to dispose of the cation exchange membrane 33 adjacent to the outlet of the desalting chamber 23 on the cathode side (for example, only about the lower half of the concentration chamber 24 in FIG. 1). This is because it is easy to prevent the weak acid component that has moved through the cation exchange membrane 33 near the outlet of the desalting chamber 23 from leaking into the treated water.

The texture of the non-woven fabric or woven fabric is preferably more than 50 g / m ² , more preferably 100 g / m ² or more. This is because it is easy to prevent the ion exchange resin from penetrating the non-woven fabric or the woven fabric and coming into contact with the cation exchange membrane, and to suppress the movement of the weak acid component from the ion exchange resin to the cation exchange membrane. From the viewpoint of water permeability, the basis weight is preferably 2000 g / m ² or less.

The thickness of the non-woven fabric or woven fabric is preferably 0.1 mm or more, more preferably 0.3 mm or more. This is because it is easy to discharge the liberated weak acid component through a non-woven fabric or a woven fabric. The thickness is preferably 9.0 mm or less, more preferably 0.6 mm or less. This is because even if it is thicker than this, an increase in the effect of discharging weak acid components cannot be expected so much.

From the viewpoint of the conductivity of the nonwoven fabric or woven fabric, the mass ratio of the cation exchange fibers to the nonwoven fabric or woven fabric (hereinafter, may be referred to as "mixture ratio") is preferably 25% by mass or more, and 60% by mass or more. More preferred. From the viewpoint of physical strength, the mixing ratio is preferably 80% by mass or less.

In this EDI device, the cation exchanger is filled in the anode chamber 21, and the anion exchanger is filled in the cathode chamber 25. However, the anode chamber 21 and the cathode chamber 25 do not necessarily have to be filled with an ion exchanger.

Deionized water can be produced by passing water to be treated containing at least one selected from the group consisting of boron, carbonic acid and silica through the EDI apparatus of the present invention. The concentration of these components in the water to be treated does not matter.

The production of deionized water (treated water) by the EDI apparatus shown in FIG. 1 will be described below. Supply water is passed through the anode chamber 21, the concentration chambers 22 and 24, and the cathode chamber 25, and the water to be treated is passed through the desalination chamber 23 with a DC voltage applied between the anode 11 and the cathode 12. .. Then, the ionic component in the water to be treated is adsorbed by the ion exchanger in the desalting chamber 23, deionization (demineralization) treatment is performed, and the deionized water flows out from the desalting chamber 23 as treated water. At this time, in the desalting chamber 23, a water dissociation reaction occurs mainly at the interface between different types of ion exchangers (which may be ion exchange membranes) depending on the applied voltage, and hydrogen ions and hydroxide ions are generated. Then, the hydrogen ions and hydroxide ions exchange ions with the ion components previously adsorbed on the ion exchanger in the desalting chamber 23 and release them from the ion exchanger. Of the liberated ionic components, the anion moves to the concentrating chamber 22 on the anode side via the anion exchange membrane 32 and is discharged as concentrated water from the concentrating chamber 22, and the cation is concentrated on the cathode side via the cation exchange membrane 33. It moves to the chamber 24 and is discharged as concentrated water from the concentration chamber 24. Eventually, the ionic components in the water to be treated supplied to the desalination chamber 23 move to the concentration chambers 22 and 24 and are discharged, and at the same time, the ion exchanger in the desalination chamber 23 is regenerated. The electrode water is discharged from the anode chamber 21 and the cathode chamber 25.

As the cation exchange membrane 31, the anion exchange membrane 32, the cation exchange membrane 33 and the anion exchange membrane 34, those known in the fields of EDI equipment and electrodialysis equipment (ED) can be used, respectively.

As the anode 11 and the cathode 12, those known in the field of EDI equipment can be used. For example, stainless steel is used for the cathode, and a noble metal such as platinum or a noble metal-plated electrode is used for the anode.

Further, for example, the anode 11 and the cathode 12, the anode chamber 21, the concentration chambers 22 and 24, the desalting chamber 23, the cathode chamber 25, the cation exchange membranes 31 and 33, and the anion exchange membranes 32 and 34 are formed into appropriate frames (for example). Can be accommodated in (not shown).

As the water to be supplied and the water to be treated, those known in the field of EDI equipment can be used. Generally, permeated water of a reverse osmosis (RO) membrane is used, and it is more preferable that the RO membrane is treated in two or more stages. In addition, carbonic acid may be removed using a decarbonation tower or a decarbonation membrane. Further, in recent years, water treated by EDI may be used as supply water or water to be treated. The supplied water and the water to be treated may be the same water or different waters.

The phenomenon that the weak acid component passes through the cation exchange membrane 33 is greatly affected by the coexisting ions in the concentration chamber 24 (for example, the passage of boron through the cation exchange membrane is affected by carbonic acid, silica, etc.) and coexists in the concentration chamber 24. The lower the ion concentration, the more prominent it appears. When water is continuously passed through two or more stages of the EDI device, the coexisting ion concentration in the concentration chamber 24 of the subsequent EDI device is low, so that the phenomenon is more likely to be more pronounced in the subsequent EDI device than in the previous EDI device. .. In such a case, it is particularly effective to apply the present invention to the subsequent EDI apparatus in which the EDI-treated water is supplied to the concentration chamber 24. Further, the present invention can be suitably applied to an EDI device in which reverse osmosis membrane permeated water is supplied to the concentration chamber 24. For example, when the boron concentration in the reverse osmosis membrane permeated water or EDI-treated water supplied to the concentration chamber 24 is 1 μg / L or more, the effect of the present invention becomes remarkable, and when it is 250 μg / L or more, it becomes more remarkable.

In the apparatus shown in FIG. 1, supply water is introduced into the anode chamber 21, the concentration chambers 22 and 24, and the cathode chamber 25 from above, water (electrode water or concentrated water) is discharged from below, and desalting is performed. Water to be treated is supplied to the chamber 23 from above, and the treated water is discharged downward. However, this is not the case, and the flow direction of water can be appropriately determined. Further, instead of supplying water to the anode chamber 21 from the outside, the outlet water (electrode water) of the cathode chamber 25 may be supplied to the anode chamber 21 and vice versa.

The present invention also includes a configuration in which the concentration chamber also serves as an electrode chamber. For example, the cathode chamber 25 may be omitted by providing a cathode in the concentration chamber 24 shown in FIG. Even in this case, the desalting treatment unit composed of the desalting chamber and the pair of concentrating chambers is arranged between the cathode and the anode.

Although the basic configuration of the EDI device based on the present invention has been described above, the present invention can be widely applied to EDI devices having various configurations. Hereinafter, a configuration example of an EDI device to which the present invention can be applied will be described.

FIG. 2 shows another form of an EDI device based on the present invention. The EDI device can have a plurality of desalting treatment units. For that purpose, a plurality of basic configurations (that is, cell sets) consisting of [concentration chamber | anion exchange membrane (AEM) | desalting chamber | cation exchange membrane (CEM) | concentration chamber] are juxtaposed between the anode and the cathode. Can be done. At this time, adjacent concentration chambers can be shared between adjacent cell sets. The EDI apparatus shown in FIG. 2 is based on the apparatus shown in FIG. 1 in which one cell set is composed of an anion exchange membrane 32, a desalting chamber 23, a cathode exchange membrane 33, and a concentration chamber 24. Is arranged between the concentration chamber 22 closest to the anode chamber 21 and the cathode chamber 25 (N is an integer of 1 or more).

The anode chamber 21 is filled with a cation exchange resin (CER), and the concentration chambers 22 and 24 and the cathode chamber 25 are filled with an anion exchange resin (AER). The desalting chamber 23 is filled with an anion exchange resin and a cation exchange resin in a mixed bed (MB). In each cell set, the non-woven fabric 40 containing the cation exchange fiber is arranged in the concentration chamber 24 on the cathode side of the pair of concentration chambers 22 and 24. Therefore, the non-woven fabric 40 containing the cation exchange fiber is arranged in all the concentration chambers except the concentration chamber 22 closest to the anode chamber 21. In other words, the non-woven fabric 40 is arranged in all the concentration chambers existing on the cathode 12 side of the desalting chamber closest to the anode 11. Of course, the non-woven fabric may be used instead of the non-woven fabric 40.

Further, instead of supplying water to the anode chamber 21 from the outside, the outlet water of the cathode chamber 25 is supplied to the anode chamber 21. Further, unlike the one shown in FIG. 1, in the anode chamber 21, the concentration chambers 22 and 24, and the cathode chamber 25, the flow of water goes from the bottom to the top. Therefore, the flow direction of water in the desalting chamber 23 is opposite to the flow direction of water in the concentration chambers 22 and 24 on both sides thereof.

The diffusion of the weak acid component from the concentration chamber 24 to the desalting chamber 23 through the cation exchange membrane 33 is also affected by the concentration of the weak acid component in the concentration chamber 24, and the higher the concentration, the greater the amount of diffusion. In the concentration chamber 24, the concentration ratio increases and the concentration of the weak acid component also increases from the inlet to the outlet. As shown in FIG. 2, by arranging the inlet side of the concentrating chamber 24 so as to be adjacent to the outlet side of the desalting chamber 23, diffusion from the concentrating chamber 24 can be diffused at a position close to the treated water outlet of the desalting chamber 23. It is possible to suppress the occurrence of more. Therefore, the flow direction of water in the concentration chamber 24 is the flow of water in the adjacent desalting chamber 23 (the desalting chamber 23 in the form shown in FIG. 2, and the second small desalting chamber 27 in the form shown in FIGS. 3 and 4). It is preferable to have a direction and a countercurrent.

In the EDI apparatus based on the present invention, an intermediate ion exchange membrane (IIEM) is provided between the anion exchange membrane on the anode side and the cation exchange membrane on the cathode side in each desalting chamber, and the desalting chamber is provided by the intermediate ion exchange membrane. It can be divided into a first small desalination chamber and a second small desalination chamber. Then, the water to be treated is supplied to one of the first small desalination chamber and the second small desalination chamber, and the water flowing out from the small desalination chamber is sent to the other small desalination chamber. The first and second small desalination chambers can be arranged in communication so as to flow in. As the intermediate ion exchange membrane, either an anion exchange membrane or a cation exchange membrane can be used. At this time, the small desalting chamber on the anode side is referred to as the first small desalting chamber, and the small desalting chamber on the cathode side is referred to as the second small desalting chamber. For example, the first small desalination chamber is filled with at least an anion exchanger and the second small desalination chamber is filled with at least a cation exchanger.

FIG. 3 shows an example of an EDI device in which the desalination chamber is divided into two small desalination chambers by an intermediate ion exchange membrane. In this EDI device, each desalting chamber 23 in the EDI apparatus shown in FIG. 2 is divided into a first small desalting chamber 26 on the anode 11 side and a second small desalting chamber 27 on the cathode 12 side by an intermediate ion exchange membrane 36. It has a partitioned configuration. The first small desalting chamber 26 is located between the anion exchange membrane 32 and the intermediate ion exchange membrane 36, and the second small desalting chamber 27 is located between the cation exchange membrane 33 and the intermediate ion exchange membrane 36. To do. In this example, an anion exchange membrane is used as the intermediate ion exchange membrane 36.

The first small desalting chamber 26 on the anode 11 side is filled with an anion exchange resin, and the second small desalting chamber 27 on the cathode 12 side is filled with a cation exchange resin.

The water to be treated is first supplied to the second small desalination chamber 27, and the outlet water from the second small desalination chamber 27 is parallel to the water flow in the second small desalination chamber 27. It is supplied to 1 small desalination chamber 26, and deionized water is obtained as treated water from the 1st small desalination chamber 26. Water flow in the anode chamber 21, concentration chambers 22, 24 and cathode chamber 25 (from bottom to top) as opposed to water flow in the first and second small desalting chambers 26 and 27 (from top to bottom). Toward) is a countercurrent.

FIG. 4 shows another example of an EDI device in which the desalination chamber is divided into two small desalination chambers by an intermediate ion exchange membrane. In this EDI apparatus, each desalting chamber 23 in the EDI apparatus shown in FIG. 2 is subjected to the first small desalination on the anode 11 side by the intermediate ion exchange membrane 36 located between the anion exchange membrane 32 and the cation exchange membrane 33. It has a structure divided into a salt chamber 26 and a second small desalting chamber 27 on the cathode 12 side. The first small desalting chamber 26 is located between the anion exchange membrane 32 and the intermediate ion exchange membrane 36, and the second small desalting chamber 27 is located between the cation exchange membrane 33 and the intermediate ion exchange membrane 36. To do. Also in this example, an anion exchange membrane is used as the intermediate ion exchange membrane 36.

The first small desalting chamber 26 is filled with an anion exchange resin. A cation exchange resin is placed in the inlet side region of the second small desalination chamber 27, and an anion exchange resin is placed in the outlet side region. That is, the cation exchanger bed and the anion exchanger bed are provided in this order in the second small desalting chamber 27 along the water flow direction of the water to be treated.

The first small desalination chamber 26 and the second small desalination chamber 26 and the second so that the water to be treated is supplied to the first small desalination chamber 26 and the water flowing out from the first small desalination chamber 26 flows into the second small desalination chamber 27. The small desalination chamber 27 is connected. Deionized water is obtained as treated water from the second small desalting chamber 27. Therefore, the desalination chamber 23 is filled with the anion exchanger bed and the cation exchanger bed in the order in which the ion exchanger through which the water to be treated last passes becomes the anion exchanger.

In this device, the flow of water in the first small desalination chamber 26 and the flow of water in the second small desalination chamber 27 are countercurrents.

From the viewpoint of increasing the purity of the treated water that is finally discharged from the desalination chamber, in the desalination chamber, the ion exchanger that the water to be treated last passes through becomes the anion exchanger, and the cation exchanger bed and the anion. It is preferable to use the exchange bed alternately. This applies not only to the form shown in FIG. 4 but also to the form shown in FIG. For example, in the form shown in FIG. 4, it is preferable that the final stage of the laminate of the ion exchanger beds provided in the second small desalination chamber 27 is the anion exchanger bed.

According to the present invention, by installing both the anion exchange resin and the non-woven fabric or woven fabric containing the cation exchange fiber in the concentration chamber 24, the mixture moves from the concentration chamber to the desalination chamber while suppressing scale formation. The amount of the weak acid component to be added can be reduced, and the weak acid can be easily removed.

[Example 1]
Using an EDI apparatus having the configuration shown in FIG. 5, boron was used as a weak acid component, and the amount of boron permeated through the cation exchange membrane 33 was evaluated. This device had the same configuration as the device shown in FIG. 1, except for the following points.
The concentrating chamber located on the anode side of the desalting chamber 23 was a concentrating chamber 51 having an anode 11 and also serving as an anode chamber. The concentration chamber 51 was filled with a cation exchange resin.
A cation exchange membrane 52 was used as a membrane separating the concentration chamber 51 and the desalination chamber 23.
-The desalting chamber 23 was filled with a cation exchange resin. By filling the desalting chamber 23 with a cation exchange resin that does not capture boron, it becomes easier to discharge boron from the desalting chamber 23.
-The outlet water of the cathode chamber 25 was supplied to the concentration chamber 51.
-Boron-containing water was supplied to the concentration chamber 24, and boron-free water was supplied to the desalting chamber 23 and the cathode chamber 25.

The boron concentration in the outlet water of the desalting chamber 23 was measured. The amount of boron permeated is a value obtained by dividing the mass flow rate of boron contained in the outlet water of the desalting chamber 23 (boron concentration × flow rate of the outlet water of the desalting chamber) by the effective film area of the cation exchange membrane 33.

The specifications and test conditions of the EDI device used are shown below. The cation exchange resin (CER) filled in the concentrating chamber 51 and the desalting chamber 23 is common, and the anion exchange resin (AER) filled in the concentrating chamber 24 and the cathode chamber 25 is common.
-Concentration chamber 51: Dimensions length 50 x width 40 x thickness 10 mm, CER filling / desalination chamber 23: Dimensions length 50 x width 40 x thickness 10 mm, CER filling / concentration chamber 24: dimensions length 50 x width 40 x thickness 10 mm, AER-filled / cathode chamber 25: Dimensions 50 x 40 x 10 mm thick, AER-filled / CER: Strongly acidic cation exchange resin (particle size: 0.5 mm, base: styrene / divinylbenzene copolymer)
-AER: Strongly basic anion exchange resin (particle size: 0.5 mm, base: styrene / divinylbenzene copolymer)
Nonwoven fabric 40: Nonwoven fabric containing cation exchange fibers having the thickness, mixing ratio, and texture shown in Table 1 (base material is polypropylene).
-Boron-free water: Ultrapure water (specific resistance 18.2 MΩ · cm, boron concentration less than 20 ng / L)
-Boron-containing water: Boron-free water with boron added at 250 μg / L-Flow rate of water discharged from each chamber: 6 L / h
-Applied current density: 1.0 A / dm ² .

[Examples 2 to 5]
The boron permeation amount was determined in the same manner as in Example 1 except that the non-woven fabric 40 containing the cation exchange fibers having the properties shown in Table 1 was used.

[Comparative Example 1]
The boron permeation amount was determined in the same manner as in Example 1 except that the non-woven fabric 40 was not provided in the EDI device.

Table 1 shows the amount of boron permeation obtained in each example and the voltage between the anode and the cathode when measuring the amount of boron permeation. Compared with Comparative Example 1, in Examples 1 to 5, the amount of boron permeating from the concentration chamber to the desalting chamber could be reduced.

11 Anode 12 Cathode 21 Anode chamber 22, 24 Concentration chamber 23 Desalting chamber 25 Cathode chamber 26 First small desalting chamber 27 Second small desalting chamber 31, 33, 52 Proton exchange membrane (CEM)
32, 34 Anion exchange membrane (AEM)
36 Intermediate Ion Exchange Membrane (IIEM)
51 Concentration chamber that doubles as an anode chamber

Claims (7)

At least one desalting treatment section is provided between the facing cathode and the anode.
The desalting treatment unit has a desalting chamber filled with an ion exchanger and a pair of concentrating chambers provided on both sides of the desalting chamber, and each of the pair of concentrating chambers is filled with the ion exchanger. Being done
The desalting chamber is adjacent to the cathode side concentration chamber of the pair of concentration chambers via a cation exchange membrane, and an anion exchange membrane is provided in the anode side concentration chamber of the pair of concentration chambers. Adjacent through
An electric deionized water production apparatus for obtaining deionized water from the desalting chamber by passing water to be treated through the desalting chamber.
The ion exchange body filled in the cathode side concentration chamber of the pair of concentration chambers includes an ion exchange resin containing an anion exchange resin and a non-woven fabric or woven fabric containing cation exchange fibers.
Electric deionized water production equipment. The electric deionized water producing apparatus according to claim 1, wherein the nonwoven fabric or woven fabric is installed in parallel with the water flow direction in the concentration chamber in which the nonwoven fabric or woven fabric is present. The non-woven fabric or woven fabric is installed in a state of being in contact with the surface on the cathode side of the cation exchange membrane that separates the concentrating chamber in which the non-woven fabric or woven fabric is present and the desalting chamber adjacent to the concentrating chamber. The electric deionized water production apparatus according to claim 1 or 2. The electric deionized water production apparatus according to any one of claims 1 to 3, wherein the non-woven fabric or woven fabric has a texture of more than 50 g / m ² . The electric deionized water production apparatus according to any one of claims 1 to 4, wherein the thickness of the nonwoven fabric or woven fabric is 0.1 mm or more. The electric deionized water production apparatus according to any one of claims 1 to 5, wherein the ratio of the cation exchange fiber to the non-woven fabric or the woven fabric is 25% by mass or more. A method for producing deionized water, in which deionized water is produced by passing water to be treated through the desalting chamber of an electric deionized water production device.
The water to be treated contains at least one selected from the group consisting of boron, carbonic acid and silica.
The method for producing deionized water, which comprises the electric deionized water producing apparatus according to any one of claims 1 to 6.

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