JPH08150326A - Production of deionized water by electrolytic deionization method - Google Patents

Abstract

PURPOSE: To increase the removal rate of the silica as an impurity in water to be treated by passing the water through a desalting chamber and concd. water through a concentration chamber in the opposite direction to each other and passing the water flowing into the desalting chamber initially through an anion exchanger bed. CONSTITUTION: When deionized water is produced, water to be treated is introduced into a desalting chamber 1, concd. water is introduced into a concentration chamber 2, and electrode water is allowed to flow into the anode compartment 14 and cathode compartment 15. An anion-exchange resin bed 22b and a cation-exchange resin bed 23b are arranged in the desalting chamber 1 in this order from the upper part as the ion-exchange resin bed. In this case, the water to be treated is allowed to flow down initially through an anion-exchange resin bed 22a to remove the anion in the water, and the water is then passed through a cation-exchange resin bed 23a to remove the cation. Deionization is repeated in the same way, and deionized water is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing deionized water by an electric deionization method, which is used in various industries such as semiconductor manufacturing industry, pharmaceutical industry, food industry, research facilities and the like, and more specifically silica. The present invention relates to a method for producing deionized water excellent in removing water.

[0002]

2. Description of the Related Art As a method for producing deionized water, a method has been conventionally known in which deionized water is passed through an ion-exchange resin to be treated. In this method, when the ion-exchange resin is saturated with ions, It is necessary to regenerate with an acid and alkaline aqueous solution, and in order to eliminate such a disadvantage in processing operation, in recent years, a deionized water production method by an electric deionization method, which does not require regeneration with a chemical, has been established and put to practical use. Has arrived.

In this electric deionization method, an ion exchanger such as an ion exchange resin or an ion exchange fiber is filled between the cation exchange membrane and the anion exchange membrane to form a desalting chamber, and both of the desalting chambers are formed. A concentration chamber is provided on the outside, and the deionization chamber and the concentration chamber are arranged between the positive electrode and the negative electrode, and the water to be treated flows into the deionization chamber while the voltage is applied, and the concentrated water flows into the concentration chamber. Impurity ions in the water to be treated are removed in the desalination chamber, and the impurity ions are electrically moved to the concentration chamber to produce deionized water. According to this method, the ion exchanger is saturated with ions. It has the advantage that it does not need to be regenerated by a drug because it is not used.

[0004]

However, in the method for producing deionized water by the electric deionization method, there is a problem that the removal rate of silica in the water to be treated is small, and in order to solve this problem, the present applicant has a problem. Previously, an electric deionized water producing apparatus was proposed in which the ion exchanger layer through which the water to be treated first passed was an anion exchanger layer (Japanese Patent Laid-Open No. 4-716).
No. 24).

Although this apparatus can improve the removal rate of silica, the inventors of the present invention have conducted extensive studies to establish a method for further increasing the removal rate of silica. As a result, the water flow direction of the untreated water supplied to the desalting chamber and the water flow direction of the concentrated water supplied to the concentrating chamber are opposite to each other, and the untreated water flowing into the demineralizing chamber is the first anion. The present inventors have obtained the knowledge that the removal rate of silica can be significantly improved by passing through the exchanger layer, and the present invention has been completed based on this finding.

An object of the present invention is to provide a method for producing deionized water by an electric deionization method, which can remove silica as an impurity in water to be treated with an extremely high removal rate.

[0007]

Means for Solving the Problems The present invention provides (1) a desalting chamber configured by filling an anion exchanger and a cation exchanger between a cation exchange membrane and an anion exchange membrane. Concentration chambers are provided on both sides of the deionization chamber via anion exchange membranes, and these deionization chamber and concentration chamber are arranged between an anode and a cathode, and water to be treated flows into the deionization chamber while applying voltage. In addition, in the method for producing deionized water by the electric deionization method, in which concentrated water flows into the concentrating chamber to remove impurity ions in the water to be treated and to produce deionized water, the water to be treated supplied to the desalting chamber is The water to be treated and the concentrated water flow into the desalting chamber and the concentrating chamber, respectively, so that the water flowing direction and the concentrated water supplied to the concentrating chamber are opposite to each other. Ensure that treated water first passes through the anion exchanger layer (2) Anion exchanger layer and cation exchanger layer are arranged in this order from the water inlet side of the water to be treated in the desalting chamber, and the deionized water is produced according to the order of the layer arrangement. A method for producing deionized water by the electric deionization method according to the above (1) in which treated water is allowed to pass through each ion exchanger layer, (3) an anion exchanger layer, and a cation exchanger layer are arranged in this order. Two or more sets of ion exchanger laminates are arranged so that the above layer arrangement is repeated, and the water to be treated passes through each ion exchanger layer according to the order of the layer arrangement constituted by the above (2). (4) A method for producing deionized water by the electric deionization method, (4) Anion exchanger layer, a cation exchanger layer, and a mixture of an anion exchanger and a cation exchanger in the desalination chamber in order from the inlet side of the water to be treated. Place the ion exchanger layer The method for producing deionized water by the electric deionization method according to (1) above, wherein the water to be treated passes through each ion-exchange layer according to the order of the layer arrangement, (5) anion-exchange layer, cation-exchange One set of ion-exchange laminates arranged in the order of body layers is arranged in two or more sets so that the above-mentioned layer arrangement is repeated, then mixed ion-exchanger layers are arranged, and according to the order of the layer arrangement constituted by this. A method for producing deionized water by the electric deionization method according to the above (4), wherein the water to be treated passes through each ion-exchange layer, and (6) anion exchange in the desalting chamber from the inlet side of the water to be treated. A body layer and a mixed ion exchanger layer of an anion exchanger and a cation exchanger are arranged, and the water to be treated is allowed to pass through each ion exchanger layer according to the order of the layer arrangement. Deionization by ion method The main point is the water production method.

In the method for producing deionized water by the electric deionization method, the water to be treated is supplied to the desalting chamber and the concentrated water is supplied to the concentrating chamber. The present invention relates to the supply of the water to be treated and the concentrated water. These water flow directions are opposite to each other. That is, in the present invention, when water to be treated is passed through the desalination chamber in a downward flow, concentrated water is passed through the concentration chamber in an upward flow, and water to be treated is passed in an upward flow into the desalination chamber. When water is passed, the concentrated water is passed downflow to the concentration chamber.

Further, according to the present invention, the water to be treated which has flowed into the desalting chamber is first passed through the anion exchanger layer. That is, the anion exchanger and the cation exchanger are filled in the desalting chamber,
Although there are various methods for arranging the ion exchanger layers, in the present invention, the layer arrangement is determined so that the ion exchanger layer through which the water to be treated first passes becomes the anion exchanger layer. .

Therefore, when the water to be treated is of downward flow, the anion exchanger layer is arranged above the desalting chamber and the other ion exchanger layer is arranged below it. When the same system is upward flowing water, the anion exchanger layer is arranged in the lower part of the desalting chamber and the other ion exchanger layer is arranged in the upper part thereof.

In the present invention, there may or may not be a partition wall between the anion-exchanger layer and another ion-exchanger layer adjacent to the anion-exchanger layer, and thus both layers may be in contact with each other. Alternatively, it may be in a non-contact state.

Hereinafter, the present invention will be described in detail by taking the case of producing deionized water using the apparatus shown in FIG. 1 as an example.

Explaining the structure of the apparatus shown in FIG. 1, 1 is a desalting chamber, 2 is a concentrating chamber, and a plurality of these desalting chambers 1 and concentrating chambers 2 are alternately provided. Usually, when constructing the desalting chamber 1, it is manufactured as one module product. That is, a cation exchange membrane 4 is formed on each side of a frame body 3 made of, for example, a synthetic resin and formed in a four-circle frame shape as shown in FIG.
The anion exchange membrane 5 is adhered, and the inner space thereof is filled with an ion exchanger, for example, an ion exchange resin (cation exchange resin and anion exchange resin) to produce a deionization module 6, and the ion exchange in the deionization module 6 is performed. The resin filling part is configured as the desalting chamber 1.

As described above, the space between the cation exchange membrane and the anion exchange membrane is filled with the cation exchange resin and the anion exchange resin. The method of filling these ion exchange resins, that is, the ion exchange resin layer As a way of arrangement,
When the water to be treated is of downward flowing water, the anion exchange resin layer is arranged above the desalting chamber 1 and the other ion exchange resin layer is arranged below it.

Therefore, as a mode of the layer arrangement of the ion exchange resin layer in the desalting chamber 1, an upper part of the desalting chamber 1 is an anion exchange resin layer, a lower part thereof is a cation exchange resin layer, and an upper part thereof is anion. An exchange resin layer, a lower portion thereof is a cation exchange resin layer, and two or more sets of the laminated portions are repeatedly provided in this order, an upper portion is an anion exchange resin layer, and a lower portion thereof is a cation exchange resin layer. A mode in which one set is provided or two or more sets are repeatedly provided, and further, a mixed ion exchange resin layer of a cation exchange resin and an anion exchange resin is provided below it, an upper part is an anion exchange resin layer, and a lower part thereof is a mixed ion exchange resin layer. There is a mode.

When the water to be treated is of upward flowing water, an anion exchange resin layer is arranged in the lower part of the desalting chamber 1 and another ion exchange resin layer is arranged in the upper part thereof. The specific layer arrangement aspect is the same as that of the above-mentioned downward flowing water, but only in the vertical direction, the same layer configuration is possible.

The frame 3 is used for filling the ion exchange resin.
The cation exchange membrane 4 (or the anion exchange membrane 5) is adhered to one side surface of the frame body 3, then the inner space of the frame body 3 is filled with an ion exchange resin, and the other side surface of the frame body 3 is filled with anion after the resin is filled. The exchange membrane 5 (or the cation exchange membrane 4) is adhered, and the ion exchange resin is sealed in the space formed by both the ion exchange membranes 4 and 5 and the frame 3. In this case, as shown in FIG. 2, a dividing bar 7 as a partition wall is provided in the frame body 3 so that each ion exchange resin can be independently filled depending on the type of the ion exchange resin to be filled. Is preferred. The number of dividing bars 7 is arbitrary. The figure shows an example in which three division bars are provided, whereby the demineralization chamber 1 has A, B,
It is divided into four rooms, C and D.

In the downward circulating water system, the room A is filled with an anion exchange resin, and the other rooms B, C and D are sequentially filled with, for example, a cation exchange resin, an anion exchange resin and a cation exchange resin. In the case of the upward flowing water system, the room D is filled with the anion exchange resin, and the other rooms C, B and A are sequentially filled with the cation exchange resin, the anion exchange resin and the cation exchange resin, for example.

By thus providing the dividing bars 7 in the frame 3, the work of filling each ion exchange resin is facilitated, and both ion exchange resin layers are mixed during transportation or operation of the apparatus. It is possible to maintain the divided state of each ion-exchange resin layer as it is when it is filled.

The split bar 7 is provided with a through hole 8 through which the ion exchange resin does not pass but only water passes. Reference numeral 9 is an inlet for treated water (however, it becomes a deionized water outlet in the case of upward flowing water), and 10 is a deionized water outlet (however, it becomes a treated water inlet in the case of upward flowing water).

A plurality of deionization modules 6 constructed as described above are arranged in parallel with each other. A spacer 11 made of a watertight member such as a rubber packing formed in a four-circle frame shape is interposed between the deionization modules 6 and 6, and the space portion thus formed constitutes the concentration chamber 2. In the internal space of the concentrating chamber 2, in order to prevent the adhesion of the ion exchange membranes 4 and 5 to each other and to secure a flow path of the concentrated water, a flow path forming material such as an ion exchange fiber or a synthetic resin net body is usually used. Is filled.

An anode 12 and a cathode 13 are arranged on both sides of the alternate arrangement of the desalting chamber 1 and the concentrating chamber 2 as described above. Partitioning films are provided in the vicinity of the anode 12 and the cathode 13, respectively, although not particularly shown. A space between the partition film and the anode 12 is defined as an anode chamber 14
And the space between the partition film and the cathode 13 is configured as the cathode chamber 15.

In the figure, 16 is a treated water inflow line, 17 is a deionized water outflow line, 18 is a concentrated water inflow line, and 19 is a concentrated water inflow line.
Is a concentrated water outflow line, 20 is an electrode water inflow line, and 21 is an electrode water outflow line.

In producing deionized water using the apparatus constructed as described above, the treated water inflow line 16 is used.
More water to be treated flows into the desalination chamber 1, concentrated water flows into the concentration chamber 2 through the concentrated water inflow line 18, and the anode chamber 1
4, the cathode chamber 15 electrode water inflow lines 20, 20 respectively
Through the electrode water. As the concentrated water, the same water as the water to be treated which is supplied to the desalting chamber 1 is usually supplied. On the other hand, a voltage is applied between the anode 12 and the cathode 13, and a direct current is passed in a direction perpendicular to the flow directions of the water to be treated and the concentrated water.

Hereinafter, as shown in FIG. 1, the water to be treated is supplied in the downward flowing water system, and the ion-exchange resin layer in the desalting chamber 1 is an anion-exchange resin layer 22a and a cation-exchange resin layer in order from the top. The present invention will be described in detail by exemplifying the case where the layers are arranged as 23a, the anion exchange resin layer 22b, and the cation exchange resin layer 23b.

The water to be treated supplied in a downward flow into the desalination chamber 1 first flows down in the anion exchange resin layer 22a. On the other hand, the concentrated water is supplied to the concentrating chamber 2 by an upward flowing water system in a direction opposite to the water flowing direction of the treated water.

First, the water to be treated is an anion exchange resin layer 22.
When passing through a, anions as impurity ions in the water to be treated are removed, and when passing through the next cation exchange resin layer 23a, cations as impurity ions are removed.
Thereafter, deionization is repeated in the same manner to obtain deionized water, and this deionized water flows out from the deionized water outflow line 17.

Impurity ions removed from the water to be treated in the desalination chamber 1 move to the concentration chamber 2 through the ion exchange membrane. That is, the anions are attracted to the anode 12 side and move to the adjacent concentrating chamber 2 through the anion exchange membrane 5, and the cations are attracted to the cathode 13 side and pass through the cation exchange membrane 4 to the adjacent concentrating chamber 2. Moving.

The concentrated water flowing through the concentrating chamber 2 receives the moving anions and cations and flows out from the concentrated water outflow line 19 as concentrated water in which impurity ions are concentrated. The electrode water flowing into the anode chamber 14 and the cathode chamber 15 from the electrode water inflow line 20 flows out from the electrode water outflow line 21.

When the water to be treated first passes through the anion exchange resin layer 22a in the desalting chamber, the removal rate of silica is improved, which is considered to be due to the following reason.

That is, when the water to be treated first comes into contact with the anion exchange resin, only the anion is mainly deionized among the impurity ions, and only the anion moves to the concentration chamber 2 and the deionization chamber 1 concerned. Cations remain in the anion exchange resin layer 22a, and an amount of alkali corresponding to the cations is temporarily generated, whereby the water to be treated becomes temporarily alkaline, so that the dissociation degree of silica is improved, and as a result, ,
It is considered that the dissociated ions of silica move to the concentrating chamber in a large amount and the removal rate of silica can be improved.

In the present invention, the removal rate of silica can be further increased by setting the water flow directions of the water to be treated and the water flow of the concentrated water to be opposite to each other. The reason is considered as follows.

That is, since the water to be treated which has flowed into the desalting chamber 1 flows down while being gradually deionized, the impurity ion concentration becomes smaller toward the lower part of the desalting chamber. Therefore, the ion concentration is the highest in the upper part of the desalting chamber (where the anion exchange resin layer 22a is arranged). On the other hand, the concentrated water that has flowed into the concentrating chamber 2 rises while receiving the ions moving from the desalting chamber, so that the ion concentration increases toward the upper part of the concentrating chamber. In this way, both the upper part of the desalting chamber and the upper part of the concentrating chamber have large ion concentrations,
In the desalting chamber and the concentrating chamber, the two portions having the highest ion concentration and high conductivity are adjacent to each other along the flow of the direct current.

As a result, the current density in the portion of the anion exchange resin layer 22a is increased, and the action of further promoting the movement of anions into the concentrating chamber occurs. By further promoting the movement of anions, the alkalinity of the water to be treated in the anion exchange resin layer 22a portion of the desalting chamber is further strengthened, so that the dissociation degree of silica is further increased. as a result,
The amount of dissociated ions of silica transferred to the concentrating chamber can be remarkably increased, and the removal rate of silica can be dramatically improved.

The dissociation equilibrium equation of silica is as follows.

[0036]

Embedded image

Here, pK ₁ and pK ₂ are dissociation constants, p
K ₁ = 9.8 and pK ₂ = 12.16.

According to the method of the present invention, the alkalinity of the water to be treated in the portion of the anion exchange resin layer 22a in the desalting chamber becomes stronger than that in the conventional method, and the silica is dissociated into the ionic state of HSiO ₃ ⁻ or SiO ₃ ^2−. To obtain the necessary and sufficient pH. Therefore, according to the invention, silica is
It is possible to remove either in the form of O ₃ ⁻ or in the form of SiO ₃ ²⁻ . However, the removal of divalent ions in the form of SiO ₃ ²⁻ requires twice as much current as the removal of monovalent ions in the form of HSiO ₃ ⁻ , resulting in increased power consumption and economic Since it is not a good idea, it is preferable to remove it in the form of HSiO ₃ ⁻ . To that end, the anion exchange resin layer 22a of the desalting chamber
It is preferable to perform deionization under the condition that the pH of the water to be treated in the portion is 9.5 to 11.0.

In addition, according to the present invention, it is effective for removing components which are generally considered to be relatively difficult to remove due to the weak electrolyte, and therefore, for example, carbonic acid (CO ₂ ) other than silica can be removed. It is also extremely effective in removing the above, and can improve its removal efficiency.

[0040]

【Example】

Examples, Comparative Examples Industrial water having the water quality shown in Table 1 was treated with a reverse osmosis membrane device to obtain permeated water having the water quality shown in the table. Using this permeated water as treated water and concentrated water, water is passed through a desalting chamber and a concentrating chamber in an electric deionized water production apparatus configured by arranging four deionization modules side by side (treated water Linear velocity is about 4
0 m / hr), a deionized water was produced by applying a current of about 1 A to produce deionized water.

In this case, the deionization treatment was carried out by variously changing the arrangement of the ion exchange resin layers in the deionization chamber and the conditions concerning the water flow direction of the water to be treated and the concentrated water as shown below. (Example 1): Anion exchange resin layer having a height of 300 mm, a cation exchange resin layer having a height of 100 mm, an anion exchange resin layer having a height of 100 mm, and a cation having a height of 100 mm, in this order from the treated water inlet side in the desalination chamber. Place the exchange resin layer,
The water to be treated was passed in a downward flow, and the concentrated water was passed in an upward flow. (Example 2): Anion exchange resin layer having a height of 300 mm and a height of 300 mm in order from the treated water inlet side in the desalination chamber
, A mixed ion exchange resin layer of anion exchange resin and cation exchange resin (mixing ratio is a volume ratio of anion exchange resin: cation exchange resin = 1: 2) is arranged, and the water to be treated is passed in a downward flow. The concentrated water was passed in an upward flow. (Comparative Example 1): The same as Example 1 except for the water flow system.
As the water flow system, both the water to be treated and the concentrated water were flowed in a downward flow. (Comparative Example 2): The same as Example 2 except for the water flow system.
As the water flow system, both the water to be treated and the concentrated water were flowed in a downward flow. (Comparative Example 3): A desalting chamber was filled with a mixed ion exchange resin (anion exchange resin: cation exchange resin = 2: 1 by volume ratio) of an anion exchange resin and a cation exchange resin, and the height was 600 mm. A mixed ion exchange resin layer was formed, water to be treated was passed in a downward flow, and concentrated water was passed in an upward flow. (Comparative Example 4): The same as Comparative Example 3 except for the water flow system.
As the water flow system, both the water to be treated and the concentrated water were flowed in a downward flow. The water quality of the resulting deionized water is shown in Table 2.

[0042]

[Table 1]

[0043]

[Table 2]

As is clear from the above results, according to the present invention, the removal rate of silica can be dramatically improved, and the quality of deionized water as a whole is as good as that of pure water.

As is clear from the results shown in Table 2, according to the present invention, the resistivity of deionized water is dramatically improved as compared with Comparative Examples 1 to 4. This shows that not only the silica removal rate but also the carbonic acid removal rate is improved by the method of the present invention.

[0046]

As described above, according to the present invention, the treated water to be supplied to the desalting chamber and the concentrated water to be supplied to the concentrating chamber are directed in opposite directions. Since the water to be treated and the concentrated water flow into the desalting chamber and the concentrating chamber, respectively, and the treated water that has flowed into the desalting chamber first passed through the anion exchanger layer, the anions that the treated water first passed through The current density in the exchange layer portion is increased, the transfer of anions to the concentrating chamber is promoted, the alkalinity of the water to be treated in the anion exchange layer portion is strengthened, and the dissociation of silica is thereby promoted. The removal rate can be dramatically improved as compared with the conventional method.

[Brief description of drawings]

FIG. 1 is a schematic vertical sectional view showing an example of an electric deionized water producing apparatus used for carrying out the method of the present invention.

FIG. 2 is an exploded perspective view showing a deionization module for forming a deionization chamber.

[Explanation of symbols]

 1 Desalination chamber 2 Concentration chamber 4 Cation exchange membrane 5 Anion exchange membrane 12 Anode 13 Cathode 22a Anion exchange resin layer

Claims (6)

[Claims] 1. A desalting chamber is formed by filling an anion exchanger and a cation exchanger between a cation exchange membrane and an anion exchange membrane, and both sides of the desalting chamber are formed through the cation exchange membrane and the anion exchange membrane. A concentrating chamber is provided in the demineralizing chamber, and the demineralizing chamber and the concentrating chamber are arranged between the anode and the cathode. While applying voltage, the water to be treated flows into the demineralizing chamber and the concentrated water flows into the concentrating chamber. In the method of producing deionized water by the electric deionization method, which removes impurity ions in the water to be treated and produces deionized water, the water flow direction of the treated water to be supplied to the desalting chamber and the concentrated water to be supplied to the concentration chamber. The untreated water and the concentrated water flow into the desalting chamber and the concentrating chamber, respectively, so that the water flows in the opposite directions, and the untreated water that flows into the desalting chamber first passes through the anion exchanger layer. By the electrodeionization method characterized by Method for producing deionized water. 2. An anion exchange layer and a cation exchange layer are arranged in this order from the treated water inlet side in the desalting chamber, and the treated water passes through each ion exchange layer in the order of the layer arrangement. The method for producing deionized water by the electric deionization method according to claim 1. 3. A set of ion exchanger laminates in which an anion exchanger layer and a cation exchanger layer are arranged in this order, and two or more sets are arranged so that the above layer arrangement is repeated. The method for producing deionized water by the electric deionization method according to claim 2, wherein the water to be treated is allowed to pass through each ion exchanger layer in order. 4. An anion exchanger layer, a cation exchanger layer, and a mixed ion exchanger layer of an anion exchanger and a cation exchanger are arranged in this order from the treated water inlet side in the desalting chamber, and the order of the layer arrangement is set. The method for producing deionized water by the electric deionization method according to claim 1, wherein the water to be treated is allowed to pass through the respective ion-exchange layers according to the method. 5. One set of ion exchanger laminates in which an anion exchanger layer and a cation exchanger layer are arranged in this order are arranged in two or more sets so that the above layer arrangement is repeated, and then a mixed ion exchanger layer is arranged. The method for producing deionized water by the electric deionization method according to claim 4, wherein the water to be treated passes through each of the ion-exchange layers according to the order of the layer arrangement constituted by the above. 6. An anion exchanger layer and a mixed ion exchanger layer of an anion exchanger and a cation exchanger are arranged in this order from the treated water inlet side in the demineralization chamber, and the treated water is treated according to the order of the layer arrangement. The method for producing deionized water by the electric deionization method according to claim 1, wherein the deionized water is passed through each ion exchanger layer.