JP2003190821A - Electric demineralizing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric demineralizing apparatus from which high-purity demineralized water can be obtained stably for a long time while preventing the rise of operation voltage, and to provide an ion exchanger to be loaded in the electric demineralizing apparatus. <P>SOLUTION: In the demineralizing apparatus, a demineralizing chamber and a concentrating chamber are formed by arraying at least a part of a cation exchange membrane C and at least a part of an anion exchange membrane A alternately between an anode (+) and a cathode (-). The ion exchanger is arranged in the demineralizing chamber and/or the concentrating chamber, wherein the ion exchanger is obtained by introducing an ion exchanging group into a porous base material having communicated pores and is constituted so that the density of the pores is inclined. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric desalination apparatus and an ion exchanger, and more particularly, it has excellent workability in loading the ion exchanger, is easy to handle, and impedes the flow of a fluid to be treated. The present invention relates to a novel ion exchanger and an electric deionization device having a high ion exchange capacity capable of ensuring a sufficient flow path that does not need to be performed and sufficiently satisfying recent high requirements.

[0002]

2. Description of the Related Art An electric desalting apparatus is a cation exchange membrane and anion exchange membrane arranged between an anode and a cathode to alternately form a concentrating chamber and a desalting chamber, using a potential gradient as a driving source. ,
In the desalination chamber, the ions in the liquid to be treated are moved and separated through the ion exchange membrane to the concentration chamber to remove the ionic components in the liquid.

FIG. 1 shows the concept of a typical electric desalination apparatus. In the electric desalination apparatus shown in FIG. 1, an anion exchange membrane A and a cation exchange membrane C are alternately arranged between a cathode (−) and an anode (+) to form a desalination chamber and a concentration chamber. Has been done. By further repeating the alternating arrangement of the anion exchange membrane and the cation exchange membrane, a plurality of desalting chambers are formed in parallel. If necessary, the desalting chamber or the concentration chamber is filled with an ion exchanger to promote the movement of ions inside the chamber. Further, the compartments in contact with the anode and the cathode at both ends are generally called an anode chamber and a cathode chamber. Of these polar chambers, the most concentrated chamber on the electrode side may be used as the polar chamber, or an ion exchange membrane may be arranged further on the electrode side of the most concentrated chamber on the electrode side to form an independent polar chamber. In some cases. In the former case, the ion exchange membrane on the most cathode side is the cation exchange membrane, and the ion exchange membrane on the most anode side is the anion exchange membrane, and in the latter case, the ion exchange membrane on the most cathode side is the anion. The exchange membrane, the ion exchange membrane closest to the cathode, is a cation exchange membrane.

In the operation of such an electric desalination apparatus, a voltage is applied to the anode and the cathode, and water is supplied to the desalination chamber, the concentration chamber and the bipolar chamber. The water supplied to the concentrating chamber is called concentrated water, and the water supplied to the desalting chamber is called treated water. In this way, when the water to be treated and the concentrated water are introduced into the desalting chamber and the concentrating chamber, respectively, the cations and anions in the water are drawn to the cathode side and the anode side, respectively, but the ion exchange membrane selectively selects only ions of the same kind. Since it permeates, cations (Ca ²⁺ , Na ⁺ , Mg ²⁺ , H ^+, etc.) in the water to be treated are
Through the cation exchange membrane C to the concentration chamber on the cathode side, and also to the anions (Cl ⁻ , SO ₄ ²⁻ , HSiO ₃ ⁻ , CO ₃ ²⁻ , HCO ₃
^-, OH ^-, etc.) moves through the anion exchange membrane A on the anode side to the concentration compartment. On the other hand, the transfer of anions from the concentrating chamber to the desalting chamber and the transfer of cations from the concentrating chamber to the desalting chamber are
It is blocked due to the foreign ion blocking properties of the ion exchange membrane.
As a result, demineralized water having a reduced ion concentration is obtained in the demineralizing chamber, and concentrated water having an increased ion concentration is obtained in the concentrating chamber.

According to such an electric desalination apparatus, by using, for example, RO (reverse osmosis) -treated water containing a small amount of impurities as the water to be treated, pure water having a higher purity can be obtained as the desalinated water. be able to. However, in recent years, more advanced ultrapure water such as ultrapure water for semiconductor manufacturing has been required.

Therefore, various proposals have been made in order to obtain such higher-purity ultrapure water, for example, cation exchange resin beads and anion exchange resins as ion exchangers in a desalting chamber and / or a concentrating chamber. There has been proposed a method of promoting migration of ions in these chambers by mixing and filling beads. Further, as an ion exchanger, a cation exchange fiber material (nonwoven fabric, etc.) is provided on the cation exchange membrane side in a desalting chamber and / or a concentrating chamber.
A method of arranging the anion exchange fiber materials facing each other on the anion exchange membrane side or filling spacers or ion conductive spacers having ion conductivity between these ion exchange fiber materials has also been proposed. (See International Application PCT / JP99 / 01391 International Publication WO99 / 48820).

However, when the ion-exchange resin beads are used as the ion-exchanger, the complicated work of uniformly mixing the beads is required, and the treated water is prevented from short-circuiting and flowing in the desalting chamber. However, there is a problem in handleability when loading the ion exchanger, such as a complicated work of closely packing beads. Further, since the beads are tightly packed in the desalting chamber, it is necessary to maintain a high inflow pressure into the desalting chamber. When the anion exchange resin beads and the cation exchange resin beads are mixed and packed, desalting is performed. There is a problem in operating the equipment such that the mixing state may become non-uniform (unevenly distributed) due to fluctuations in the flow rate of the liquid to be treated when water is passed through the chamber, and beads may be damaged during use. It was difficult to stably obtain highly pure demineralized water for a long period of time.

Further, a non-woven fabric conventionally used as an ion exchanger (thickness: 0.1 to 1.0 mm, basis weight 10 to 100 g / m ² ,
When arranging only the ion-exchange fiber material with a fiber diameter of 10 to 70 μm), flow resistance of the water to be treated, etc. occurs, so it is necessary to keep the inflow pressure of the water to be treated high. There were problems such as being difficult to wash sufficiently so that the organic carbon component (TOC) did not elute from the exchanger, and it was difficult to obtain high-purity demineralized water stably over a long period of time. .

Therefore, in order to have a balance between the two, when using an ion exchange fiber material, it has been proposed to fill a spacer or an ion conductive spacer between the ion exchange fiber materials as described above. But,
When spacers are used as in these proposals,
Although not so much as in the case of beads, there was a problem that handling was poor in terms of loading because two members had to be arranged. Further, these spacers and the like are mainly for securing a flow passage of a fluid, and there is a limit to introducing many ion exchange groups, and the ion exchange ability, particularly the removal performance of anionic weak electrolytes, is poor, The problem is that the recently required high ion exchange capacity cannot be demonstrated, and it is necessary to apply electric energy from the outside to force ion movement, and the voltage applied from the electrode side must be increased. There was also.

[0010] In short, in the conventionally proposed technology,
There is still a problem that it is not possible to combine excellent processing performance that is excellent in loading operation and handleability and that can process at a high throughput per hour with excellent processing performance that a high-purity processing fluid can be obtained. It was

[0011]

SUMMARY OF THE INVENTION Therefore, the object of the present invention is to provide a novel ion exchanger capable of solving the above-mentioned problems and an electric desalination apparatus in which the ion exchanger is arranged. And

In particular, an object of the present invention is to ensure easy passages, easy preparation, excellent workability of loading an ion exchanger, easy handling, and a sufficient flow path that does not hinder the flow of the fluid to be treated. It can reduce the flow resistance of fluid such as water to be treated, reduce the power consumption during operation, and exhibit a high ion exchange capacity that can sufficiently meet the recent high demands, and it is stable for a long period of time. An object of the present invention is to provide an ion exchanger capable of obtaining a high-purity demineralized water in a sufficient amount, and an electric desalination apparatus in which the ion exchanger is arranged.

[0013]

The present invention has been made in order to solve the above-mentioned problems, and has communicating pores instead of conventional ion-exchange resin beads, ion-exchange nonwoven fabrics and other ion-exchangers, It is characterized in that a novel ion exchanger in which an ion exchange group is introduced into a porous substrate having a graded pore density of the communicating pores is used.

That is, according to the present invention, a desalting chamber and a concentrating chamber are formed by alternately arranging at least a part of the cation exchange membrane and the anion exchange membrane between the anode and the cathode. An ion exchanger having communicating pores is arranged in the chamber and / or the concentration chamber, and when the ion exchanger is arranged in the desalination chamber and / or the concentration chamber, the desalination chamber and / or the concentration chamber From the center of the chamber to the cation exchange membrane and /
Alternatively, an electric desalination apparatus characterized by being a vacancy density gradient ion exchanger obtained by introducing an ion exchange group into a porous substrate having a vacancy density inclined toward the anion exchange membrane, and a deionization device. A communication hole having a pore density that is inclined from the central portion of the desalting chamber and / or the concentration chamber toward the cation exchange membrane and / or the anion exchange membrane when placed in the salt chamber and / or the concentration chamber is provided. Provided is an ion exchanger having a vacancy density gradient, which is obtained by introducing an ion exchanger into a porous substrate having the same. In the electric deionization apparatus of the present invention, the vacancy density gradient ion exchanger is preferably loaded in at least the deionization chamber.

As the cation exchange membrane and the anion exchange membrane that can be used in the electric desalination apparatus of the present invention, known ion exchange membranes can be used without particular limitation. For example, as the cation exchange membrane, “NEOSEPTA CMB” and “NEOSEPTA CM1” manufactured by Tokuyama Corporation, and as the anion exchange membrane, for example, “NEOSEPTA A manufactured by Tokuyama Corporation”
Commercially available ion exchange membranes such as "HA" and "NEOSEPTA AM1" can be used without limitation.

In the present specification, the "communication holes" extend through the substrate from one side of the substrate to the other side of the opposite side, and the through holes communicate with each other vertically and horizontally. It means an inexhaustibly formed hole.

When the ion exchanger of the present invention is placed in the desalting chamber and / or the concentrating chamber, it faces the cation exchange membrane and / or the anion exchange membrane from the central portion of the desalting chamber and / or the concentrating chamber. And an ion exchange group is introduced into a porous base material having communicating pores having a sloping pore density.

The vacancy density gradient ion exchanger of the present invention is a cation exchanger prepared by introducing a cation exchange group into a porous substrate having communicating pores, and an anion exchanger prepared by introducing an anion exchange group, Alternatively, it is preferably an amphoteric ion exchanger obtained by introducing a cation exchange group and an anion exchange group. In the case of an amphoteric ion exchanger, it is preferable that the ratio of the anion exchange group and the cation exchange group is anion exchange capacity: anion exchange group: cation exchange group = 3: 1 to 4: 1. Makes it possible to satisfactorily desalinate weakly dissociative carbonic acid components, ions such as silica, HCO ₃ ⁻ , CO ₃ ²⁻ , and Si ²⁻ .

The gradient of the pore density of the ion exchanger according to the present invention is such that the pore density of the portion located in the central portion of the desalination chamber when loaded in the desalination chamber of the electric desalination apparatus is , The pore density of the portions located on both sides of the ion-exchange membrane constituting the desalination chamber is not enough to prevent passage of the water to be treated, and the water to be treated is sufficient to make sufficient contact with the ion-exchange groups. Any amount can be used as long as it can be introduced. Specifically, assuming that the pore density of the portion of the ion density gradient ion exchanger located on the ion exchange membrane side of the desalting chamber is 100%, the pore density of the portion located in the central portion of the desalting chamber is Is preferably 70% or less. For example, in the part located in the center of the desalination chamber, the number of pores having a relatively large pore size of about 1 mm or more is set to 5 to 25 pieces / 25.4 mm so that the passage of water to be treated is not hindered. Water can be satisfactorily passed, and at the part located on the ion exchange membrane side, about 1
By setting the number of pores having a pore diameter of less than mm to 25 / 25.4 mm or more, a sufficient amount of ion exchange groups can be introduced. That is, in the present specification, “high pore density”, that is, “hole density is 100%” means a case where a large number of pores having a relatively small pore diameter are contained per constant length, The "porosity density is low", that is, "the pore density is 70%" means that a small number of pores having a relatively large pore size are included in a certain length. Therefore, for example, at least two vacancy density gradient ion exchangers of the present invention can be used.
If the desalting chamber is filled with one sheet having a high pore density facing the ion-exchange membrane side and the other surface having a low pore density facing the central part of the desalting chamber, the pore density is The graded ion exchanger has a small diameter on the ion exchange membrane side, for example, a diameter of 1 mm.
Has a density of 25 holes / 25.4 mm or more, and has a large diameter on the other surface side facing the central part, for example, a diameter of 1 mm or more, preferably 1 mm to 5 mm. 25 pieces / 2
It is preferably inclined, such as 5.4 mm. Alternatively, when the desalting chamber is filled with only one of the gradient ion exchangers of pore density of the present invention, the density of pores having a small diameter, for example, less than 1 mm on both sides of the ion exchanger facing the ion exchange membrane. Is 25 pieces / 25.4 mm or more and has a large diameter in the central portion of the ion exchanger, for example, a diameter of 1 mm or more, preferably 1 mm to 5
It is preferable that the hole density is graded so that the hole density of mm is 5 / 25.4 mm to 25 / 25.4 mm.
By controlling the diameter and density of the holes in this way,
A sufficient amount of ion exchange groups can be introduced, and at the same time, the passage of the fluid to be treated is not obstructed. still,
In the present invention, the one side of the vacancy density gradient ion exchanger,
The other side or both sides is about 30 ~ from the surface of the ion exchanger.
It means a portion having a thickness of about 70%, for example, in the case of an ion exchanger having a total thickness of 3 mm, it means a portion 1 to 2 mm from the surface (hereinafter, the same in the present specification).

Further, it is preferable that the gradient of the pore density of the gradient ion-exchanger of the present invention gradually decreases from a high density surface to a low density surface at a reduction rate of about 30% or more. By setting the rate of decrease to about 30% or more, it is possible to secure a water passage for the water to be treated and at the same time to introduce sufficient ion-exchange groups to allow good ion exchange of the water to be treated.

The above-described vacancy density gradient ion exchanger of the present invention heat-bonds only one surface of the porous base material having communicating pores so that the vacancy density on one surface side is on the opposite surface side. It can be formed to be lower than the void density. Alternatively, both surfaces of the porous base material having the communicating pores may be heat-sealed to form the pore density of both surfaces lower than the pore density of the central portion. The material of the porous substrate having such open pores is an open-cell foam of a polyolefin-based polymer such as polyethylene (PE) or polypropylene (PP) or a polyester-based polymer such as polyethylene terephthalate (PET). And three-dimensional woven fabric can be preferably mentioned. As the open-cell foam, a polyolefin-based open-cell foam such as polyethylene-based porous material or polypropylene-based porous material can be preferably used, and as the three-dimensional woven fabric, polyethylene fibers, polypropylene fibers, etc. are three-dimensionally woven. A polyolefin-based three-dimensional woven fabric obtained by the above can be preferably used.

The vacancy density gradient ion exchanger of the present invention is obtained by introducing an ion exchange group into the porous substrate having the above-mentioned characteristics. The ion exchange group is preferably introduced so that the neutral salt decomposition capacity of the anion exchanger is 3 to 5 meq / g and the neutral salt decomposition capacity of the cation exchanger is 3 to 5 meq / g. When the neutral salt decomposing capacity is within this range, sufficient ion exchange ability is obtained to obtain desired ultrapure pure water.

As described above, the vacancy density gradient ion exchanger of the present invention is obtained by introducing a cation exchange group and an anion exchange group into a porous substrate having communicating pores. It is preferable that it is an anion exchanger or an amphoteric ion exchanger having a cation exchange group and an anion exchange group introduced therein. When it is a zwitterion exchanger,
The ratio of the anion exchange group and the cation exchange group is expressed by the ion exchange capacity, anion exchange group: cation exchange group = 3: 1 to
The ratio is preferably 4: 1. In this case, a weakly dissociative carbonic acid component, ions such as silica, HCO ₃ ⁻ , CO
₃ ²⁻ and Si ²⁻ can be desalted well.

In the vacancy density gradient ion exchanger of the present invention, the ion exchange group can be introduced into the porous substrate by preferably a graft polymerization method, particularly preferably a radiation graft polymerization method. Here, the radiation graft polymerization method is a technique of irradiating a polymer base material with radiation to form radicals, and reacting the radicals with the monomer to introduce the monomer into the base material. When the ion exchange group is introduced by the graft polymerization method or the radiation graft polymerization method, the porous substrate used in the present invention is a porous group having communicating pores of a polyolefin resin capable of growing a graft chain. It is preferably a material.

Examples of the radiation that can be used in the radiation graft polymerization method include α rays, β rays, γ rays, electron rays and ultraviolet rays. In the present invention, γ rays and electron rays are preferably used. The radiation graft polymerization method includes a pre-irradiation graft polymerization method in which a graft base material is previously irradiated with radiation and then brought into contact with a graft monomer to react, and a simultaneous irradiation graft polymerization method in which radiation is irradiated in the coexistence of the base material and the monomer. However, any method can be used in the present invention. Further, by the contact method of the monomer and the substrate, a liquid phase graft polymerization method of performing the polymerization while the substrate is immersed in the monomer solution, a gas phase graft polymerization method of performing the polymerization by contacting the substrate with the above monomer. An example is an impregnated gas phase graft polymerization method in which a substrate is immersed in a monomer solution and then taken out from the monomer solution to carry out the reaction in a gas phase. Any method can be used in the present invention.

The ion exchange group introduced into the open-cell substrate in the present invention is not particularly limited, and various cation exchange groups or anion exchange groups can be used. For example, as the cation exchange group, a strong acid cation exchange group such as a sulfone group, a medium acid cation exchange group such as a phosphate group, a weak acid cation exchange group such as a carboxyl group or a phenolic hydroxyl group, and an anion exchange group are 1
Weakly basic anion exchange groups such as primary to tertiary amino groups, strong basic anion exchange groups such as quaternary ammonium groups can be used, or ions having both the above cation exchange group and anion exchange group Exchangers can also be used.

These various ion exchange groups are subjected to graft polymerization, preferably radiation graft polymerization, using a monomer having these ion exchange groups, or a polymerizable monomer having a group convertible to these ion exchange groups. Can be introduced into an open-cell substrate by converting the group into an ion-exchange group after carrying out a graft polymerization using. Examples of the monomer having an ion exchange group that can be used for this purpose include acrylic acid (AAc), methacrylic acid, sodium styrenesulfonate (SSS),
Examples thereof include sodium methallyl sulfonate, sodium allyl sulfonate, sodium vinyl sulfonate, vinylbenzyl trimethyl ammonium chloride (VBTAC), diethylaminoethyl methacrylate and dimethylaminopropyl acrylamide. For example, by performing radiation graft polymerization using sodium styrene sulfonate as a monomer, it is possible to directly introduce a sulfonic acid group which is a strongly acidic cation exchange group into a substrate, and vinyl benzyl trimethyl ammonium chloride is used as a monomer. By carrying out radiation graft polymerization using the quaternary ammonium group, which is a strongly basic anion-exchange group, can be directly introduced into the substrate. Examples of the monomer having a group that can be converted into an ion exchange group include acrylonitrile, acrolein, vinylpyridine, styrene, chloromethylstyrene, glycidyl methacrylate (GMA) and the like. For example, glycidyl methacrylate is introduced into a substrate by radiation graft polymerization, and then a sulfonating group which is a strongly acidic cation exchange group is introduced into the substrate by reacting with a sulfonating agent such as sodium sulfite, or chloromethyl. After the styrene is graft-polymerized, the base material is immersed in a trimethylamine aqueous solution for quaternary ammonium conversion, whereby a quaternary ammonium group which is a strongly basic anion exchange group can be introduced into the base material.

The vacancy density gradient ion exchanger of the present invention has a surface having a low vacancy density and a surface having a high vacancy density, and further, the vacancy density is gradually inclined. It is possible to satisfy the balance requirements for both passage of fluid and introduction of ion exchange groups. In particular, the surface with a low pore density is located in the center of the desalting chamber and / or the concentrating chamber, and the surface with a high pore density is located on the ion exchange membrane side of both sides of the desalting chamber and / or the concentrating chamber. On the side of the central part, the passage of the fluid is not hindered, and on the side of the ion exchange membrane, sufficient ion exchange groups can be present. Further, compared to the case where different members are combined such as the conventional combination of the ion-exchange fiber material and the ion-conducting spacer, the complexity of loading is eliminated. Further, since the contact between the ion exchange group and the ions is increased, the applied voltage during operation can be reduced.

In the electric desalination apparatus of the present invention, the above-described vacancy density gradient ion exchanger of the present invention is arranged in a desalting chamber and / or a concentrating chamber, preferably at least a desalting chamber. Specifically, a cation exchanger is placed on the side of the cation exchange membrane, and an anion exchanger is placed on the side of the anion exchange membrane so that the surface with a low pore density faces the side of the ion exchange membrane,
Alternatively, the ion exchanger may be arranged so that both sides having a low pore density face the ion exchange membrane.

During operation of the electric desalination apparatus of the present invention, when the water to be treated is circulated through the desalination chamber and / or the concentrating chamber while applying a voltage between both electrodes, the water to be treated is along the flow direction. As a result, the ions in the water to be treated flow in the chamber while being in sufficient contact with the ion exchange groups existing along the flow direction of the water to be treated. Then, the cation exchanger is arranged on the cation exchange membrane side, and when the anion exchanger is arranged on the anion exchange membrane side, the cations in the water to be treated move to the cation exchanger and the cation exchange membrane side, Since the anion moves to the side of the anion exchanger and the anion exchange membrane, the separation and transfer of ions are promoted. On the other hand, when arranging the amphoteric ion exchanger, the ratio of the anion exchange group and the cation exchange group should be such that the ion exchange capacity is anion exchange group: cation exchange group = 3: 1 to 4: 1. Thus, a weakly dissociative carbonic acid component, silica, or the like can be favorably desalted.

When an anion exchanger and a cation exchanger are used as the vacancy density gradient type ion exchanger of the present invention, a desalting method using a plurality of cells using a plurality of cells having a desalting chamber and a concentrating chamber in combination is used. As an apparatus, an anion exchanger may be arranged in the desalting chamber of the first pass and a cation exchanger may be arranged in the desalting chamber of the second pass. In this case, it becomes extremely easy to fill the deionization chamber with the ion exchanger.

The electric desalination apparatus of the present invention comprises a desalination chamber and / or
Alternatively, since the concentration chamber is loaded with a vacancy density gradient ion exchanger, the flow of the fluid passing through a portion having a low vacancy density is not hindered, the pressure loss of the fluid can be reduced, and the communication pores Can be sufficiently contacted with the water to be treated and the ion-exchange groups, the separation and migration of ions is promoted, and further, in the part where the pore density is high, the ion-exchange groups and the water to be treated are introduced in large amounts. Since sufficient contact is made, a sufficient desalting treatment can be performed at a low applied voltage.

Further, by arranging the vacancy density gradient ion exchanger of the present invention in the concentration chamber, the movement of ions through the ion exchange membrane from the desalting chamber to the concentration chamber is promoted, and the applied voltage is further reduced. It is also possible to prevent precipitation of hardness components (Ca, Mg, etc.) on the surface of the ion exchange membrane on the concentration chamber side by preventing concentration polarization due to an increase in the contact area with concentrated water.

[0034]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in more detail below with reference to the accompanying drawings, but the present invention is not limited thereto.

FIG. 2 is a schematic diagram of an electric desalination apparatus in which the ion-exchange group-introduced ion-exchange group-introduced ion-exchange group of the present invention is arranged parallel to the flow direction of the water to be treated. The figure is shown. In the figure, for the purpose of explaining the features of the present invention, a desalting chamber and a concentrating chamber are shown as two chambers, but the number of the desalting chambers and the concentrating chambers can be appropriately increased as necessary. .

In FIG. 2, the electric desalination apparatus has an anion exchange membrane (A) and a cation exchange membrane (C) alternately arranged between an anode (+) and a cathode (-). , A desalination chamber and a concentration chamber are formed. In the figure, K represents a polar chamber. In the desalting chamber and the concentrating chamber, an anion exchanger obtained by introducing an anion exchange group into the communicating pore base material on the anion exchange membrane (A) side is used as a cation on the communicating pore base material on the cation exchange membrane (C) side. Each is filled with a cation exchanger formed by introducing an exchange group. Here, in the anion exchanger and the ion exchanger, the surface having a high pore density faces the side facing the central portion of the desalting chamber, and the hole density has a pore density on the side facing the anion exchange membrane and the cation exchange membrane. Each is arranged so that the lower side faces.

During operation of the electric desalination apparatus shown in FIG.
While applying a voltage to the anode (+) and the cathode (-), the water to be treated was introduced into the desalination chamber in the direction of the arrow from the bottom in the figure.
Water is passed through the concentration chambers. In the desalting chamber, the water to be treated flows through the cation exchanger and the anion exchanger toward the outlet of the desalting chamber (upward in the figure).
While the water to be treated passes through the desalting chamber, the anions pass through the communicating pores of the anion exchanger, move to the anion exchange membrane (A) side, pass through the adjacent concentrating chamber, and the cations: It moves to the cation exchange membrane (C) side through the communicating pores of the cation exchanger, passes through the adjacent concentration chamber, the ions are removed from the water to be treated, and the desalination chamber outlet is desalted. Water is obtained. Here, since the ion exchanger has a communicating pore structure, the movement of the water to be treated is not hindered and the loss of fluid pressure is very small. Further, the ion exchanger has a lower pore density near the center of the deionization chamber and a higher pore density closer to the ion exchange membrane, so that the flow of water to be treated is obstructed in the center. The flow of the water to be treated is delayed as it passes without passing through the ion exchange membrane, and the number of contacts between the ions in the water to be treated and the ion exchange groups increases. In the concentration chamber, the anions that have permeated the anion exchange membrane from the adjacent desalination chamber move to the anode side, but since the cation exchange membrane is placed on the anode side of the concentration chamber, it passes through this. It cannot be done and remains in the concentrating chamber. Similarly, the cations also remain in the concentrating chamber, so that concentrated water containing a large amount of ions can be obtained as a result.

[0038]

【Example】

[0039]

[Production Example 1] -Production of density-gradient anion exchanger A polyethylene-based porous body (manufactured by Sekisui Chemical Co., Ltd., average pore diameter 1.6 mm, pore diameter range 0.6 to 2.6 mm,
A porosity of 96%, a specific surface area of 30,000 m ² / m ³ , and a thickness of 3 mm) were used. Cut out this communicating hole base material to 10 cm × 30 cm and cut one side
1.8m thick with a hot plate (polytetrafluoroethylene surface treatment) heated to 220 ℃ for 1 minute.
A m-density gradient type communicating pore base material was used. At this time, at a thickness of 0 mm from the surface on the melted side, a diameter of about 0.1 mm to about 1.0
mm, average number of holes 0.7 mm, number of holes 54 / 25.4 mm, thickness 0.5
In mm, the density of pores having a diameter of about 0.5 to about 1.3 m and an average pore diameter of 1.0 mm is 32 / 25.4 mm, and the surface of the unmelted side has a diameter of about 1.6 to about 2.6 mm and a mean pore diameter of 2.1 mm. Is 15
The number was 25.4 mm. In this density gradient type communicating pore base material,
Irradiation with gamma rays (150 kGy) was performed under a nitrogen atmosphere. Chloromethylstyrene (m-form) was prepared by removing the polymerization inhibitor from the irradiated density gradient type continuous pore base material in advance with activated alumina.
70%: p-body 30%, manufactured by Seimi Chemical Co., Ltd., trade name CMS-AM)
It was immersed in the solution and reacted at 50 ° C. for 6 hours to obtain a density-gradient type chloromethylstyrene-grafted open pore base material (graft ratio: 215%). This density-gradient graft communication pore base material was quaternized with trimethylamine aqueous solution (10 wt%) and regenerated with sodium hydroxide solution to obtain a density-gradient anion exchanger (neutral salt decomposition capacity: 3.5 meq.
/ g (average value) was obtained. -Production of density-gradient cation exchanger As a communicating pore material, a polyethylene-based porous material (manufactured by Sekisui Chemical Co., Ltd., porosity 96%, pore size range 0.6 to 2.6 mm, average pore size 1.6 mm, specific surface area 30000 m ² / m ³ ) Was used. This open pore base material is cut out into 10 cm x 30 cm x 3 mm and one side is 220 ° C.
A hot plate (polytetrafluoroethylene surface treatment) heated to 1 minute was brought into close contact with the hot plate and melted to obtain a density gradient type continuous pore base material having a thickness of 1.8 mm. This density-gradient type communicating pore base material was irradiated with γ-rays (150 kGy) under a nitrogen atmosphere. This irradiated density-graded open-pore base material was immersed in a 10% methanol solution of glycidyl methacrylate, and it was placed at 45 ° C for 5 hours.
The reaction was allowed to proceed for a time to obtain a density-gradient type graft communication pore base material (graft ratio: 170%). This density-gradient type graft communication open-pore base material was immersed in a solution of sodium sulfite: isopropyl alcohol: water = 1: 1: 8 (weight ratio), and the temperature was changed to 80 ° C.
The reaction was conducted for 10 hours at room temperature to obtain a density gradient cation exchanger (neutral salt decomposition capacity: 3.3 meq / g (average value)).

[0040]

[Production Example 2] -Production of strongly basic anion exchange non-woven fabric A heat-bonded non-woven fabric having a basis weight of 55 g / m ² and a thickness of 0.35 mm made of a composite fiber of polyethylene (sheath) / polypropylene (core) having a fiber diameter of 17 μm and nitrogen. It was irradiated with an electron beam (150 kGy) in an atmosphere. Chloromethylstyrene (Seimi Chemical Co., trade name: CMS-AM) that had been degassed by nitrogen aeration after passing through an activated alumina packed bed to remove the polymerization inhibitor.
Immerse the irradiated non-woven fabric substrate in the solution, and
Reacted for hours. Then, the non-woven fabric was taken out of the solution, immersed in toluene for 3 hours to remove the homopolymer, and then dried to obtain a graft non-woven fabric (graft ratio: 161
%) Was obtained. This grafted non-woven fabric is quaternized with an aqueous trimethylamine solution (10 wt%) and regenerated with an aqueous sodium hydroxide solution to give a strongly basic anion exchange non-woven fabric (neutral salt decomposition capacity: 2.7-3.4 meq / g). Obtained. -Manufacture of strong acid cation exchange non-woven fabric A heat-bonded non-woven fabric with a basis weight of 55 g / m ² and a thickness of 0.35 mm consisting of a polyethylene (sheath) / polypropylene (core) composite fiber with a fiber diameter of 17 μm, under a nitrogen atmosphere, under an electron beam. (150 kGy) was irradiated. The irradiated non-woven fabric was immersed in a 10% methanol solution of glycidyl methacrylate, reacted at 45 ° C. for 4 hours and then dried to obtain a graft non-woven fabric (graft ratio: 131%). This graft non-woven fabric was treated with sodium sulfite: isopropyl alcohol: water = 1: 1: 8
Immerse in the (weight ratio) solution and react at 80 ° C for 10 hours,
Strongly acidic cation exchange nonwoven fabric (neutral salt decomposition capacity 2.72 meq / g
(Average value) was obtained. -Manufacture of anion-conducting spacers A diagonal net made of polyethylene with a thickness of 1.2 mm and a pitch of 3 mm was cooled with dry ice, and gamma rays (15
It was irradiated with 0 kGy). The irradiated cross network was immersed in chloromethylstyrene (m-body 70%: p-body 30%, Seimi Chemical Co., trade name: CMS-AM) from which the polymerization inhibitor was removed by activated alumina in advance, The reaction was carried out at 50 ° C. for 5 hours to obtain a chloromethylstyrene-grafted crosslink network (graft ratio: 90%). This graft cross network was quaternized with trimethylamine aqueous solution (10wt%) and regenerated with sodium hydroxide aqueous solution to obtain anion conductive spacer (neutral salt decomposition capacity: 1.6-1.9meq / g). It was -Manufacture of cation-conducting spacers 1.2 mm thickness and 3 mm pitch of polyethylene diagonal mesh is cooled with dry ice while gamma ray (15
It was irradiated with 0 kGy). The irradiated cross network is immersed in a mixed monomer solution of 25% sodium styrene sulfonate and 25% acrylic acid and reacted at 50 ° C for 3 hours to introduce sulfonic acid and acrylic acid-introduced cation conductive spacers (graft ratio: 153
%, Neutral salt decomposition capacity: 1.5-1.8 meq / g).

[0041]

[Embodiment 1] Electric desalination apparatus shown in FIG. 2 (2 desalination chambers:
Thickness 3mm; Concentration room 1 room: Thickness 1.5mm; Polar room: Thickness 3mm;
An electrode plate 5 cm × 25 cm; anion exchange membrane: Tokuyama “NEOSEPTA AHA”; cation exchange membrane: Tokuyama “NEOSEPTA CMB”) was constructed. That is, in the desalination chamber,
The density gradient cation exchanger produced in Production Example 1 was prepared on the cation exchange membrane side, and the density gradient anion exchanger produced in Production Example 1 was prepared on the anion exchange membrane side. The side surfaces containing a large number of holes are arranged one by one such that they face the ion exchange membrane side, and the concentrating chamber is provided with Production Example 2
The anion-conducting spacer and the cation-conducting spacer manufactured in 1 are arranged one by one such that the anion-conducting spacer is positioned on the anion-exchange membrane side and the cation-conducting spacer is positioned on the cation-exchange membrane side. The ion-conducting spacer produced in 2 was arranged on the cathode side with four anion-conducting spacers and on the anode side with four cation-conducting spacers.

A current (0.2 A) was applied between both electrodes, and the RO-treated water (conductivity: 0.5 ms / m) obtained by treating Fujisawa-shi water with a reverse osmosis membrane was removed at a flow rate of 10 L / h as water to be treated. It was allowed to flow into the salt chamber.
At the same time, concentrated water (flow rate 5 L / h) was made to flow into the concentration chamber.
The inflow pressure loss of the treated nest was 0.009 MPa. The specific resistance of the obtained treated water is 16 MΩ · cm, and the applied voltage is 30 V.
Met.

[0043]

[Comparative Example 1] The electric desalination apparatus shown in FIG. 3 (two desalination chambers:
Thickness 3mm; Concentration room 1 room: Thickness 1.5mm; Polar room: Thickness 3mm;
Electrode plate 5 cm x 25 cm; Anion exchange membrane: Tokuyama Corporation "NEOSEPTA AHA"; Cation exchange membrane: Tokuyama Corporation "NEOSEPTA CMB"), which is used as an ion exchanger in the desalting chamber and cations The cation-exchange nonwoven fabric produced in Production Example 2 was loaded on the exchange membrane side, and the anion-exchange nonwoven fabric produced in Production Example 2 was loaded on the anion-exchange membrane side one by one, and the cation-exchange nonwoven fabric and the anion-exchange nonwoven fabric were placed between them. An experiment was performed in the same manner as in Example 1 except that the anion-conducting spacers prepared in Preparation Example 2 were arranged on the anion-exchange nonwoven fabric side and the cation-conducting spacers were arranged on the cation-exchange nonwoven fabric side. Loss is 0.012MPa
The specific resistance of the obtained treated water was 9 MΩ · cm, and the applied voltage was 70V.

From these results, it can be seen that the desalination treatment capacity of the electric desalination apparatus is improved and the power consumption can be reduced by loading the vacancy density gradient ion exchanger of the present invention.

[0045]

EFFECT OF THE INVENTION Using the vacancy density gradient ion exchanger of the present invention and the electric desalination apparatus loaded with the ion exchanger,
It is easy to manufacture, has good workability for loading an ion exchanger, is easy to handle, and can secure a sufficient flow path that does not impede the flow of the fluid to be treated. It is possible to reduce the ion exchange capacity, particularly the flow resistance of the water to be treated, reduce the power consumption, and stably obtain a high-purity demineralized water in a sufficient amount for a long period of time.

In detail, since the ion exchanger of the present invention has a density gradient in the spatial density, it is possible to secure a sufficient flow channel mainly in a portion having a large spatial density, which makes it necessary to use a spacer. Since it is possible to dispose an ion exchanger having a sufficient ion exchange capacity over the entire desalting chamber and the like, it is possible to sufficiently remove even an anionic weak electrolyte. Further, since a large amount of ion exchange groups are introduced into the ion exchanger and the ion exchange groups and the ions in the water to be treated are in sufficient contact with each other, the ion exchange capacity is improved and at the same time the power consumption can be reduced. . Furthermore, since it is not necessary to use a large number of members, the loading operation is easy and the handleability is excellent.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing the concept of a typical electric desalination apparatus.

FIG. 2 is a schematic view showing an embodiment of an electric desalination apparatus of the present invention, and is also a schematic view of the electric desalination apparatus constructed in Example 1.

FIG. 3 is a schematic diagram of an electric desalination apparatus configured in Comparative Example 1.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) D06M 14/28 C02F 1/46 103 (72) Inventor Toru Akiyama 11-1 Haneda-Asahi-cho, Ota-ku, Tokyo EBARA CORPORATION (72) Inventor Kunio Fujiwara 4-2-1 Motofujisawa, Fujisawa-shi, Kanagawa Incorporated EBARA Research Institute (72) Inventor Yohei Takahashi 4-2-1 Motofujisawa, Fujisawa-shi, Kanagawa F-term in Ebara Research Institute Co., Ltd. (Reference) 4D006 GA17 HA47 JA02A JA04A JA04C JA30A JA41A JA42A JA43A JA44A KE02Q KE06Q KE18Q MA03 MA13 MA14 MB07 PA01 PB02 PB25 PB26 PC02 4A06 GA15 A03 GA12 A02 EB09 A39 A12 EB09 A39 EB09 A39 EB09 A39 A12 EB09 A39 EB12 EB09 A39 EB01 EB09 EB09 FB01 FA02 EB09 A09 EB09 EB09 FB01 FA39 EB09 EB09 EB01 FB01 FA02 EB09 EA09 EB09 EB01 FB01 FA02 BA08 BA46

Claims (6)

[Claims] 1. An ion exchange used in an electric desalination apparatus in which a cation exchange membrane and an anion exchange membrane are alternately arranged at least partially between an anode and a cathode to form a desalination chamber and a concentration chamber. Pore density inclined from the central part of the body toward the cation exchange membrane and / or the anion exchange membrane when placed in the desalting chamber and / or the concentrating chamber And an ion exchanger having a pore density gradient, wherein the ion exchanger is introduced into a porous substrate having communicating pores. 2. The ion exchanger according to claim 1, wherein the porous substrate is selected from an open-cell foam and a three-dimensional woven fabric, and the ion density gradient ion exchanger is the porous material. A cation exchanger or anion exchanger prepared by introducing a cation exchange group or an anion exchange group into the organic base material,
Alternatively, it is an amphoteric ion exchanger having a cation exchange group and an anion exchange group introduced therein, and a vacancy density gradient ion exchanger. 3. The vacancy density gradient ion exchanger according to claim 1 or 2, wherein the ion exchange group is introduced into the porous substrate by a radiation graft polymerization method. A vacancy density gradient ion exchanger characterized by being present. 4. The electric desalination apparatus according to claim 2, wherein the vacancy density gradient ion exchanger has a vacancy density on one surface side of 100%. In case,
A vacancy density gradient ion exchanger characterized in that the vacancy density is inclined so that the vacancy density on the opposite side is 70% or less. 5. The electric desalination apparatus according to claim 2 or 3, wherein the vacancy density gradient ion exchanger has a central portion when the vacancy density on both sides is 100%. A vacancy density gradient ion exchanger characterized in that the vacancy density is inclined so that the vacancy density is 70% or less. 6. A desalting chamber and a concentrating chamber are formed by alternately arranging at least a part of a cation exchange membrane and an anion exchange membrane between an anode and a cathode. An electric desalination apparatus, in which the ion exchanger having the communicating pores according to any one of claims 1 to 5 is arranged.