JP2001149762A - Ion exchange membrane and electric deionized water production device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ion exchange membrane having an entirely new structure for suppressing lowering of silica removing efficiency, and also preventing lowering of ion removing efficiency, even though an electric current value is increased, and an electric deionized water production device using it. SOLUTION: In the ion exchange membrane having a multi-layered structure with at least three layers arranged with a water permeable layer at the intermediate part in the membrane thickness direction, and water nonpermeable ion exchange body layers at the both sides, and the electric deionized water production device alternately and plurally provided with desalting rooms partitioned with the ion exchange membrane and concentration rooms between electrodes applied with direct current voltage, at least a portion of the ion exchange membranes consists of an ion exchange membrane having a multi-layered structure with at least three layers arranged with the water permeable layer at the intermediate part in the membrane thickness direction and water nonpermeable ion exchange body layers at the both sides, and also water to be treated made to flow in the desalting room, while water is passed through the water permeable layer, is desalted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ion-exchange membrane having a novel structure capable of preventing performance degradation and an electric deionized water producing apparatus using the same.

[0002]

2. Description of the Related Art As a method for producing deionized water, a method for producing deionized water by an electric deionization method which does not require regeneration with a chemical has been put to practical use. That is, a desalting chamber and a concentrating chamber separated by a plurality of ion exchange membranes are provided alternately between the cathode and the anode, and the desalting chamber contains, for example, a mixed bed of ion exchange resin, and is covered by the desalting chamber. This is a continuous deionization method using an electrodialysis deionization device in which ions in the water to be treated are moved through the treated water to the concentration chamber side.

In a conventional electric deionized water producing apparatus, a hard water softening apparatus or a reverse osmosis membrane separator is provided at a preceding stage in order to prevent the hardness components of magnesium and calcium existing in the water to be treated from being deposited on the ion exchange membrane. The device is usually installed. Raw water is treated by a water softener or reverse osmosis membrane separator, and the treated water is treated by an electric deionized water producing device to produce advanced deionized water. However, in Japan, since the hardness components of river water and other components are less than those in Europe and the United States, raw water is treated with a reverse osmosis membrane separator without installing a water softening device, and the treated water is used as an electric deionized water production device. There are many examples to supply to.

[0004]

However, the conventional electric deionized water producing apparatus has the following problems. First, as described above, when raw water is treated by a reverse osmosis membrane separator without installing a water softener as described above, and the treated water is supplied to an electro-deionized water production device, the reverse osmosis membrane separation is required. Hardness of supply water (concentration of Ca, Mg) by device
Is mostly removed, but there is a trace amount of the hard component remaining without being removed.

In an electric deionized water producing apparatus, when treated water is passed through a desalting chamber of the apparatus, impurity ions in the treated water are adsorbed by an ion exchange resin in the desalting chamber and are highly desalted. Pure water is produced. On the other hand, impurity ions are adsorbed on the ion exchange resin in the desalting chamber, and the impurity ions are moved to the enrichment chamber of the device by applying a direct current, and the impurity ions are condensed in the concentrated water flowing through the enrichment chamber. It is concentrated. Most of the concentrated impurity ions are N
a, Cl ions, etc., but a small amount of hardness component (Ca, M
g) is also included.

[0006] Such a hardness component is a cation having a positive ion, and the cation moves to the cathode side when a direct current is applied to the electric deionized water producing apparatus. Here, since the cathode side in the concentration chamber is partitioned by the anion exchange membrane, cations cannot pass through the anion exchange membrane, and as a result, the hardness component is concentrated on the surface of the anion exchange membrane in the concentration chamber. .

Further, in the electric deionized water producing apparatus, when a direct current is applied, water is dissociated by an electrolysis reaction inside the deionization chamber, and H ⁺ ions and OH ^- ions are generated. This anion (OH ⁻ ) moves to the anode side by applying a direct current to the electric deionized water producing apparatus. Here, since the anode side in the desalting chamber is partitioned by the anion exchange membrane, the anions pass through this anion exchange membrane and move to the concentration chamber.

[0008] As described above, on the surface of the concentration chamber side of the anion exchange membrane, the hardness component that cannot be passed through the anion exchange membrane and the O component that has passed through the anion exchange membrane from the desalination chamber side.
H ^- ions are present, and the condition is such that the hardness component easily precipitates as a scale.

[0009] The amount of OH ^- ions generated here is proportional to the current density of the applied DC current.
Since the amount of H ^- ions increases, the pH increases, and the hardness component tends to precipitate as a scale. When calcium ions are alkaline, calcium carbonate CaCO _3.
2H ₂ O scale is easily generated, and magnesium ion easily generates magnesium hydroxide Mg (OH) ₂ when alkaline, particularly when the pH is 10 or more. In the electric deionized water production apparatus, it is said that the pH of the surface of the anion exchange membrane rises from 10 to 12, and the surface of the anion exchange membrane on the side of the enrichment chamber is in a condition where the scale is extremely likely to precipitate as described above. I can say.

[0010] The inventors of the present invention have found that when scale is deposited on the surface of the anion exchange membrane of the electric deionized water producing apparatus on the side of the enrichment chamber under such conditions, the following phenomenon occurs and the performance is reduced. I found that. That is, when the scale of the hardness component precipitates on the surface of the anion exchange membrane on the side of the concentration chamber, the amount of silica permeating the anion exchange membrane and moving to the concentration chamber decreases. Although the cause has not been completely elucidated,
It is estimated as follows. When a dense layer of the scale of the hardness component is formed on the surface of the anion exchange membrane on the side of the concentration chamber, silica becomes difficult to permeate through the dense layer. In many cases, silica is formed by combining a large number of silica molecules to form a polymer, and is presumed to be hardly permeated due to a large ionic radius as compared with ions other than silica. When the scale of the hardness component precipitates on the surface of the anion exchange membrane on the side of the concentration chamber as described above, the silica is difficult to permeate, and thus a problem occurs in that the silica removal rate in the electric deionized water production apparatus is reduced.

As a second problem, in the electric deionized water producing apparatus, in principle, the amount of ions to be removed can be increased by increasing the current value to be supplied, and as a result, the ion removal rate is increased. Can be higher. Therefore, even if the ion concentration in the water to be treated is high, the ion removal rate can be increased by increasing the current value, and it is thought that it is possible to obtain a high treated water quality, that is, a treated water quality with a high ion removal rate. ing.

However, the present inventors have found that when the current value is increased, the quality of the treated water may be deteriorated, that is, the ion concentration of the treated water may be increased.

To estimate the cause, in the electric deionized water producing apparatus, the removed ions are concentrated in the concentrated water. Therefore, when the ion concentration in the water to be treated is high, the ion concentration in the concentrated water also becomes relatively high. Here, the concentration chamber is separated by two types of ion exchange membranes, that is, a cation exchange membrane and an anion exchange membrane, and each ion exchange membrane has a property of transmitting its counter ion and not transmitting non-counter ion. The selectivity between the counter ion and the non-counter ion is referred to as the transport number. In an ideal state, only the counter ion is permeated and the non-counter ion is not transmitted at all. The transport number for the counter ion in this state is 1.

[0014] When the external solution concentration of the ion exchange membrane is low, the transport number of the ion exchange membrane is as close to 1 as possible, but as the external solution concentration increases, the transport number decreases. Usually, the transport number of the ion exchange membrane used is 0.9999 (99.99%) or more, and the amount of non-counter ions leaking to the treated water side is 1 / 10,000 or less. For example, the electric conductivity of the concentrated water is 1000 μS /
In the case of cm, when it is considered that an amount of ions equivalent to 1/10000 of the ion leaks to the treated water side, the increase in electric conductivity due to this is 1000 μS / cm ÷ 10000 = 0.1 μS
/ Cm, and the electric conductivity of the treated water is 0.1 μS / cm.
It will rise to the extent.

In an electrodialyzer or the like, the required treatment water quality is about 50 to 300 μS / cm, and the amount of non-counter ions that leak through the ion exchange membrane to the treatment water side is substantially negligible. is there. However, in the electric deionized water production apparatus, the required treated water quality is 0.1 to 0.0
Very high purity of 55 μS / cm. Therefore, even a small amount of ion leakage has an unexpectedly large effect on treated water quality. Increasing the current value promotes the movement of counter ions that permeate through the ion exchange membrane and move toward the concentration chamber, increasing the amount of ion removal. The amount of ions also increases, and the effect on the quality of treated water deteriorates.

As described above, when the ion concentration in the water to be treated is high, the ion concentration in the concentrated water becomes relatively high, and even a slight decrease in the transport number greatly affects the quality of the treated water.
Further, in this case, when the current value is increased, leakage of non-counter ions to the treated water side also increases. The present inventors presume that increasing the current value for such a reason will deteriorate the quality of the treated water.

Therefore, an object of the present invention is to focus mainly on the first and second problems described above, and particularly to suppress a decrease in the silica removal rate, and to suppress a decrease in the ion removal rate even when the current value is increased. An object of the present invention is to provide an ion exchange membrane having a completely new structure which can be prevented, and an electric deionized water producing apparatus using the same.

[0018]

In order to achieve the above object, an ion exchange membrane of the present invention comprises at least a water-permeable layer at an intermediate portion in the thickness direction and a non-water-permeable ion-exchange layer on both sides thereof. It is characterized by having a multilayer structure of layers.

In this ion exchange membrane, the non-water-permeable ion exchanger layers disposed on both sides of the water-permeable layer are made of the same type of membrane. That is, both the water-impermeable ion exchangers are both formed of an anion exchange membrane or a cation exchange membrane.

The water-permeable layer can be formed by, for example, a porous channel material. Further, the water-permeable layer may be formed by an ion exchanger, for example, a structure filled with an ion exchange resin or ion exchange fibers, or a molded structure.
Further, the water-permeable layer can be formed by a spacer, for example, a spacer having an ion exchange group. further,
The water-permeable layer can be formed in a simple space.

The water passage of the water permeable layer may be formed, for example, such that the water permeable layer communicates with the outside of one non-water permeable ion exchanger layer and the other water permeable ion exchange layer is placed at another position. It may be a structure communicating with the outside of the body layer. Alternatively, it is also possible to adopt a structure in which the water-permeable layer is formed as an independent flow path outside the both non-water-permeable ion exchanger layers.

The electric deionized water producing apparatus according to the present invention is constituted by using such an ion exchange membrane. That is, the electric deionized water producing apparatus according to the present invention is an electric deionized water comprising a plurality of alternately provided deionization chambers and concentration chambers defined by an ion exchange membrane between electrodes to which a DC voltage is applied. In the water producing apparatus, at least a part of the ion exchange membrane is formed from an ion exchange membrane having a multilayer structure of at least three layers in which a water-permeable layer is provided at an intermediate portion in a film thickness direction and a non-water-permeable ion exchanger layer is provided on both sides thereof. And desalinating the water to be treated that has flowed into the desalination chamber while passing water through the water-permeable layer.

In this electric deionized water producing apparatus, when the ion exchange membrane is used at a position corresponding to the anion exchange membrane in the conventional structure, for example, a non-water-permeable anion exchanger layer is provided on both end faces. Using an anion exchanger layer having water permeability in the middle part, when the ion exchange membrane is used as a cation exchange membrane, having a non-water permeable cation exchanger layer on both end faces, in the middle part A cation exchanger layer having water permeability can be used. In particular, in the electric deionized water producing apparatus according to the present invention, it is preferable that the ion exchange membrane having the multilayer structure is disposed at least at the position of the anion exchange membrane in the conventional structure. Preferably, the ion exchanger layer comprises an anion exchange membrane. However, in the present electric deionized water producing apparatus, the above-mentioned multilayered ion exchange membrane may be used only for the anion exchange membrane, or the above-mentioned multilayered ion exchange membrane may be used only for the cation exchange membrane. Further, a multilayer ion exchange membrane may be used for both the anion exchange membrane and the cation exchange membrane. Further, the water permeable layer in the middle may be a layer formed from an ion exchanger having an ion exchange group, or may be a layer formed from a water permeable material having no ion exchange group.

The water-permeable layer of the ion exchange membrane may have a structure for forming a water passage for collecting water from the desalting chamber and discharging the water to the concentrating chamber, or a water passage independent of the desalting chamber and the concentrating chamber. A structure that forms a water channel can also be used.

The ion-exchange membrane according to the present invention as described above has a special unconventional structure having a multilayer structure of a water-permeable layer in the middle and a non-water-permeable ion-exchange layer on both sides thereof. In particular, by having a water-permeable layer in between, it is possible to exert the function of preventing the above-mentioned reduction in the silica removal rate and deterioration in the quality of treated water. Therefore, in the electric deionized water producing apparatus according to the present invention using the ion exchange membrane, the following excellent effects can be obtained.

As described in the first problem, when the scale of the hardness component is deposited on the surface of the anion exchange membrane of the electric deionized water producing apparatus on the side of the enrichment chamber, silica becomes difficult to permeate. The silica removal rate in the ionized water production device decreases. However, in the electro-deionized water production apparatus according to the present invention, the above-mentioned multilayered ion exchange membrane is used as the anion exchange membrane, and the water permeable formed between both non-water permeable ion exchanger layers comprising the anion exchange membrane. The water to be treated introduced into the desalination chamber is desalted while passing through the bed.
Among the non-water-permeable ion exchanger layers arranged on both sides of the ion exchange membrane having a multilayer structure, the one closer to the enrichment chamber is referred to as the enrichment chamber side ionic layer (or the enrichment chamber side anion layer or the enrichment chamber side cation layer), The one near the desalination chamber is the ion layer on the desalination chamber side (or the anion layer on the desalination chamber side or the cation layer on the desalination chamber side)
In this case, the scale of the hardness component is deposited on the surface of the anion layer on the side of the concentration chamber on the side of the concentration chamber, on which silica hardly permeates. However, since no scale is formed in the anion layer on the desalination room side, the permeation of silica does not become difficult.
The silica in the water to be treated flowing through the desalting chamber permeates through the anion layer on the desalting chamber side and moves to the central permeable layer. At this time, the silica moves inside the permeable layer due to the water flowing through the permeable layer. Then, it is discharged outside the anion exchange membrane. Therefore, even if scale is formed on the surface of the anion layer on the side of the concentration chamber facing the concentration chamber, the silica removal rate of the electrodeionized water producing apparatus does not substantially deteriorate.

As described in the second problem, when the concentration of ions in the water to be treated is high, the concentration of ions in the concentrated water becomes relatively high, and even if the transport number is slightly reduced, the concentration of the treated water is reduced. The impact on water quality will be significant. In this case, when the current value is increased, the amount of permeated ions increases, and when the current value is increased, the quality of the treated water may be deteriorated.
However, the ion exchange membrane used in the present invention has a non-water permeable ion exchanger layer on both sides, a water permeable layer in the middle, and is treated while passing water through the water permeable layer of the ion exchange membrane. Since the water is subjected to the desalination treatment, the movement of the non-counter ion from the concentration chamber to the desalination chamber is prevented by at least the two non-water-permeable ion exchanger layers on both sides. Therefore, the total transport number of the two impermeable ion-exchange layers is a value obtained by multiplying the transport numbers of both the impermeable ion-exchange layers, and is extremely higher than that of a single ion-exchange membrane. It will be. As a result, the amount of non-counter ions leaking to the treated water side is suppressed to an extremely small amount, thereby preventing the treated water quality from deteriorating.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. FIG.
FIG. 2 shows an example of the structure of an ion-exchange membrane according to an embodiment of the present invention and a desalination chamber and a concentration chamber of an electric deionized water producing apparatus using the same. FIG. 2 shows the electric deionized water producing apparatus. 1 shows a schematic overall configuration of FIG.

In FIG. 1, reference numeral 1 denotes an ion-exchange membrane having a multilayer structure according to one embodiment of the present invention, which is configured as an anion-exchange membrane in this embodiment. As the cation exchange membrane 2, a single ion exchange membrane is used as in the conventional case. Of course, the multilayered ion exchange membrane according to the present invention may be used for the cation exchange membrane, and the multilayered ion exchange membrane may be used for both the anion exchange membrane and the cation exchange membrane.

The ion exchange membrane 1 (anion exchange membrane) in the multilayer structure shown in FIG. 1 has a three-layer structure in which a water-permeable layer 3 is disposed in the middle in the thickness direction and non-water-permeable ion-exchange layers 4 and 5 are disposed on both sides of the water-permeable layer. Consists of a structure. It is also possible to configure a multilayer structure having more than three layers, having a plurality of water-permeable layers and a further large number of non-water-permeable ion exchanger layers.

In the present embodiment, the water permeable layer 3 is formed from a porous channel material. However, the water permeable layer 3 is formed by filling or molding an ion exchanger such as ion exchange resin or ion exchange fiber. It is also possible. It is also possible to form with a spacer having water permeability, in which case,
It is also possible to form with a spacer having an ion exchange group. If the water-permeable layer forming material is given ion-exchange properties, the electric resistance of the whole ion-exchange membrane having a multilayer structure can be reduced, and the applied DC voltage required during the desalination treatment can be reduced.

The water-impermeable ion exchanger layers 4 and 5 are each formed of an anion exchange membrane in this embodiment. At least one of these water-impermeable ion exchanger layers 4, 5;
It is also possible to integrally mold the water permeable layer forming material (the porous channel material in the present embodiment).

A plurality of ion exchange membranes 1 and a cation exchange membrane 2
Are alternately arranged, and a desalting chamber 6 and a concentration chamber 7 are defined and alternately arranged. In the present embodiment, the desalting chamber 6 is filled with an ion exchange resin 8 as an ion exchanger. The to-be-treated water 9 flows into the desalting chamber 6, and the desalted treated water 10 flows out of the desalting chamber 6. A concentrated water 11 is passed through the concentration chamber 7.

In the present embodiment, a part of the water 9 to be treated is used as the water passing through the water-permeable layer 3. A water intake port 12 is opened at a portion of the anion layer 4 on the upstream side of the desalting chamber 6, and a drain port 13 is opened at a portion of the anion layer 5 on the downstream side of the concentration chamber 7. The water to be treated taken from the water intake 12 is passed through the permeable layer 3 and then drained.
3 is discharged to the concentration chamber 7. That is, since water is passed from the highest-pressure portion to the lowest-pressure portion in the system shown in FIG. 1, the water flow to the permeable layer 3 is naturally performed.

The water passing through the water permeable layer 3 may be any water as long as the water has a low hardness component concentration, but the water to be treated passing through the electric deionized water producing apparatus as described above is used. It is convenient to use. Since the concentrated water used in the electric deionized water producing apparatus has a relatively high hardness component concentration, when the concentrated water is passed through the permeable layer 3, the concentration of the anion exchanger layers 4 and 5 facing the permeable layer 3 is reduced. It is not preferable because scale is deposited on the surface.

It should be noted that the water permeable layer 3 is formed of a porous channel material,
As described above, it may be formed by an ion exchanger, a spacer, and a spacer having an ion exchange group, or may be formed in a space without using a special forming material. Further, in the above embodiment, the water-permeable layer 3 communicates with the outside of one of the anion exchanger layers 4 (on the desalting chamber 6 side) to collect water therefrom, and the outside of the other anion exchanger layer 5 (the concentration chamber). 7 side) and drained to it, but it is configured as an independent channel outside the both impermeable ion exchanger layers, and suitable water having a low hardness component concentration is formed. You may make it flow.

When the ion exchange membrane 1 having a multilayer structure is an anion exchange membrane as described above, both sides use an ion exchange membrane of a water-impermeable anion exchanger layer, and when the ion exchange membrane 1 is a cation exchange membrane, both sides use a water impermeable membrane. An ion exchange membrane of a cation exchanger layer is used.

The ion exchange membrane having a multilayer structure according to the present invention comprises:
It can be manufactured by applying a conventional ion exchange membrane manufacturing technique, but is not limited to a conventionally known technique. Hereinafter, some specific examples will be described.

(1) A cation exchange group such as a sulfonic acid group, a carboxylic acid group or a phosphate group having a negative charge in an aqueous solution, or a precursor of a cation exchange group such as a sulfonyl halide group is bound. A water-insoluble, linear, branched polymer, water-insoluble solution in an appropriate organic solvent is applied or adhered to both surfaces of a water-permeable porous body such as a woven fabric, nonwoven fabric, or sintered polymer membrane. The solvent can be scattered to produce a porous material having a water-permeable porous body at the center and a cation exchange membrane layer on both sides. In this case, when a polymer having a precursor of a cation exchange group is used, it is necessary to carry out an exchange reaction to an appropriate cation exchange group after film formation.

Similarly, in an aqueous solution of an anion exchange group, for example, an onium base such as a quaternary ammonium base, a quaternary phosphonium base, or a tertiary sulfonium base, a primary, secondary, or tertiary amine, etc. A linear, branched, high-performance, water-insoluble, solution in a suitable organic solvent, which has a charge of, or a functional group capable of easily introducing an anion exchange group such as a haloalkyl group, is dissolved as described above. It is applied to both sides of a permeable porous body such as woven fabric, nonwoven fabric, sintered polymer membrane, and the solvent is scattered, assuming that there is a permeable porous body in the center and an anion exchange membrane layer on both sides Can be manufactured. In this case, when a polymer having a functional group such as a haloalkyl group is used, it reacts with an appropriate amine, for example, trimethylamine, N, N, N ', N',-tetramethylethylenediamine, etc. After forming the ion exchange group,
Need to be introduced.

(2) A cation exchange membrane or an anion exchange membrane in the form of a thin film is produced by a casting method or the like, or a commercially available cation exchange membrane or anion exchange membrane is bonded to a suitable adhesive, for example, a rubber-based adhesive. Point bonding or line bonding with an agent, a double-sided adhesive tape, or the like, and the remaining void portion can be made into a water-permeable portion.

(3) A thin film of a polymer having a cation exchange group or an anion exchange group and having thermoplasticity, and having a thermoplastic property having a function of easily converting into a cation exchange group or an anion exchange group. A polymer thin film and the like, a porous body made of a material having a higher softening temperature than the polymer film, for example, a porous body of polytetrafluoroethylene, alumina, laminated on top of a sintered porous body of an inorganic substance such as silica, and the like, The body is integrated by heating and pressing, and a water-permeable porous body is provided at the center, and a cation exchange base layer or an anion exchange base layer can be formed on both surfaces.

Although some examples have been described above, the present invention is not limited to the above examples, and a water-permeable porous body can be produced by a method that can be conceived by those skilled in the art. Yes, it may be configured as an ion exchange membrane having a thin film of an anion exchanger layer or a cation exchanger layer on both surfaces.

The above-exemplified ion exchange membrane having a water-permeable porous body in the intermediate portion and an anion exchanger layer or a cation exchanger layer on both surfaces may have a multilayer structure of three or more layers depending on the purpose. That is, an ion exchange membrane having n water-permeable porous layers and comprising (n + 1) anion exchanger layers and cation exchanger layers can be produced by a similar method.

The apparatus for producing electric deionized water according to the present invention is constituted by using the ion exchange membrane constituted as described above. FIG. 1 shows a main part thereof, and FIG. 2 shows a schematic overall configuration. In FIG. 2, reference numeral 21 indicates the entire electric deionized water producing apparatus. Electrodes 22, 2 to which a DC voltage is applied
3, the desalting chamber 6 and the concentrating chamber 7 are alternately formed and arranged using the frame 41, and the end plate 42
It is fixed at. Electrodes 22 and 23 are arranged at the outermost part of the alternate arrangement of the desalting chamber 6 and the concentration chamber 7, and the insides thereof are formed in the electrode chambers 24 and 25. The to-be-treated water 9 flows into each of the desalination chambers 6 through the to-be-treated water inflow pipe 26, and the desalted treated water 10 is discharged from each of the desalination chambers 6 through the treated water discharge pipe 27. The concentrated water 11 flows into each of the concentration chambers 7 via the concentrated water inflow pipe 28, and is discharged from each of the concentration chambers 7 via the concentrated water discharge pipe 29. The electrode water 30 flows into each of the electrode chambers 24 and 25 via an electrode water inflow pipe 31, and is discharged from each of the electrode chambers 24 and 25 via an electrode water discharge pipe 32. The supply and discharge route of the concentrated water and the supply and discharge route of the electrode water can be shared. In the embodiment shown in FIG. 2, the water to be treated, the concentrated water, and the electrode water flow in the same direction as a parallel flow, but may be countercurrent in the reverse flow direction.

In the ion exchange membrane 1 configured as described above and the electric deionized water producing apparatus 21 using the same, the water 9 to be treated flowing into the desalting chamber 6 is desalinated. On the side of the concentration chamber 7, the scale of the hardness component is deposited on the surface of the concentration chamber 7 side of the concentration chamber-side anion layer 5,
Although silica hardly permeates on this surface, no scale is formed on this surface because the surface of the anion layer 4 on the desalting chamber side faces the water-permeable layer 3, and silica permeates from the desalting chamber 6 side. There is no difficulty. Therefore, the silica in the water to be treated flowing in the desalting chamber 6 easily passes through the anion layer 4 on the side of the desalting chamber 6 and moves to the intermediate water-permeable layer 3. The moved silica moves inside the water permeable layer 3 by the water flowing through the water permeable layer 3, and is discharged to the outside of the anion exchange membrane 5, that is, into the concentration chamber 7 through the drain port 13. Therefore,
Even if scale is formed on the surface of the concentration room side anion layer 5 facing the concentration room 7, the silica removal rate of the electric deionized water producing apparatus 21 does not deteriorate.

In the anion layer 5 on the concentration chamber side of the ion exchange membrane 1, most of the non-counter ions are blocked, but a part of the non-counter ions are permeated. However, the non-counter ion is first permeable layer 3
And the water flowing through the water-permeable layer 3 is again discharged to the outside of the ion exchange membrane 1, that is, into the concentration chamber 7 through the drain 13. Since the desalting chamber side anion layer 4 is provided next to the water permeable layer 3, non-counter ions flowing into the water permeable layer 3 are also blocked by the desalting chamber side anion layer 4. Since the non-counter ion is blocked by the two ion layers of the concentration room side anion layer 5 and the desalting room side anion layer 4,
The amount of non-counter ions leaking to the desalting chamber 6 is extremely small.

For example, if the transport number of one ionic layer is assumed to be 0.9999 (99.99%), the total transport number of both ionic layers is 1- (1-0.9999) × (1- 0.9999) =
0.9999999, and the amount of non-counter ions leaking to the treated water is extremely small.

Therefore, even when the ion concentration in the water to be treated is high and the ion concentration in the concentrated water is relatively high, the total transport number in the ion exchange membrane 1 can be maintained at an extremely high level. The amount of non-counter ions leaking to the water is suppressed to a very small amount, thereby preventing the quality of treated water from deteriorating. At this time, even if the current value is increased, since the total transport number is extremely high as described above, the influence of the increased current can be suppressed to a negligible level, and the deterioration of the treated water quality is substantially reduced. Will be prevented.

[0050]

EXAMPLE The test was carried out as follows using an electric deionized water producing apparatus having the configuration shown in FIG. Example 1 In the multilayer ion-exchange membrane 1 illustrated in FIG. 1, a water-permeable portion (width 120 mm, length) is provided as a water intake at a portion of the anion layer 4 on the side of the desalination chamber close to the entrance of the desalination chamber (the inlet of the water to be treated). 5m
m). Similarly, a drain port 1 is located in a portion of the anion layer 5 on the side of the enrichment chamber close to the outlet of the enrichment chamber (the outlet of the concentrated water).
As No. 3, a water permeable portion (width 120 mm, length 5 mm) was provided. Further, the outer peripheral portion of the ion exchange membrane 1 was bonded with an adhesive so that water did not flow out of the water permeable layer 3. As a result, part of the water to be treated that has flowed into the desalting chamber 6 flows from the water intake port 12 into the permeable layer 3 of the ion exchange membrane 1, passes through the permeable layer 3, and then from the drain port 13 to the concentration chamber 7. I let it flow. For this reason, there is no need to separately provide a water supply channel for the water permeable layer 3, and the apparatus is simplified.

The electric deionized water producing apparatus 21 used in the experiment was 600 mm long, 250 mm wide and 200 m deep.
and the desalination chamber 6 inside is 400 mm long and 15 mm wide.
0 mm and 8 mm in thickness. There are 12 desalination chambers 6, and a concentrating chamber 7 having a thickness of 1 mm is provided between the desalination chambers 6. Electrode chambers 24 and 25 are arranged on the outermost side.
Inside the desalting chamber 6, an anion exchange resin IRA-402 and a cation exchange resin IR-1 manufactured by Rohm and Haas Co.
480 ml of an equivalent mixture of 20B and 20B is filled. The desalting chamber 6 is sandwiched between the ion exchange membrane 1 as a multilayered anion exchange membrane and the cation exchange membrane 2 from both sides.

The multilayered anion exchange membrane 1 used here was manufactured as follows. Commercially available polysulfone (Ude
lP-1700, manufactured by Amoco Co.) was dissolved in 50 parts of ethylene dichloride, 500 parts of ethylene dichloride, 1 part of anhydrous zinc chloride was dissolved therein, and 50 parts of chloromethylethyl ether was added thereto. The reaction was carried out at 30 ° C for 30 hours. This was put into a large excess of methyl alcohol to precipitate chloromethylated polysulfone. The polymer was taken out, dried, dissolved again in ethylene dichloride, and placed in a large excess of methyl alcohol to take out the polymer. After this purification step was repeated twice, the polymer (chloromethylated polysulfone) was dried under reduced pressure. As a result of elemental analysis,
The amount of Cl in the polymer was 6.95%.

This chloromethylated polysulfone was dissolved in chloroform to a concentration of 30% to obtain a viscous solution. A 1-mm-thick nonwoven fabric (manufactured by Japan Vilene Co., Ltd.) was immersed in this viscous solution, allowed to adhere to both surfaces, and dried. The weight increase of the nonwoven fabric was 35%. There are layers of polychloromethylstyrene on both sides of the nonwoven. Subsequently, the polymer film was immersed in a methanol solution of 20% N, N, N ', N',-tetramethylethylenediamine at room temperature for 24 hours to form a crosslinked structure simultaneously with amination of the chloromethyl group. . The anion exchange capacity of the ion-exchange membrane 1 having the water-permeable layer 3 at the center thereof and the water-impermeable anion-exchange membrane layers 4 and 5 on both sides was measured by a usual method. g dry film.

Comparative Example 1 In Comparative Example 1, an experimental apparatus (electric deionized water producing apparatus) was assembled in the same manner as in Example 1, and the anion exchange membrane used was the same multi-layer anion exchange membrane as in Example. The water inlet 12 and the drain 13 are not provided, and water is prevented from flowing into the central permeable layer 3. That is, the performance was not so different from that of a single anion exchange membrane.

In this experiment, desalinated water desalinated by the reverse osmosis membrane device was used as feed water for the electric deionized water producing device, and about 30 times under the same experimental conditions (see Table 1) in both Example 1 and Comparative Example 1.
It was operated for a day and the treated water quality was compared. Table 2 shows the experimental results.

[0056]

[Table 1]

[0057]

[Table 2]

As can be seen from the experimental results in Table 2, the silica removal rate in Comparative Example 1 was low and the electrical conductivity of the treated water was high, whereas in Example 1, the silica removal rate was high and the electrical conductivity of the treated water was high. , The quality of the treated water is improved, and the effect of the present invention is clearly shown.

[0059]

As described above, according to the ion exchange membrane and the electric deionized water producing apparatus using the same according to the present invention, the water permeable layer and the non-water permeable ion exchanger provided on both sides thereof are provided. By using a multi-layered ion exchange membrane composed of layers, it is possible to maintain a high silica removal rate in desalination treatment for a long period of time, and to prevent non-counter ions from leaking to the treated water side to prevent deterioration of treated water quality. Can be.

[Brief description of the drawings]

FIG. 1 is a partial sectional view of an electric deionized water producing apparatus using an ion exchange membrane according to one embodiment of the present invention.

FIG. 2 is an overall schematic configuration diagram of the electric deionized water production apparatus of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ion exchange membrane 2 Cation exchange membrane 3 Water permeable layer 4, 5 Non-water permeable ion exchanger layer 6 Demineralization room 7 Concentration room 8 Ion exchange resin 9 Water to be treated 10 Treated water 11 Concentrated water 12 Water intake 13 Drain 21 Electric deionized water production apparatus 22, 23 Electrodes 24, 25 Electrode chamber 26 Inflow pipe for treated water 27 Treated water discharge pipe 28 Concentrated water inflow pipe 29 Concentrated water discharge pipe 30 Electrode water 31 Electrode water inflow pipe 32 Electrode water discharge pipe 41 Frame 42 End plate

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (reference) // C08J 5/22 C02F 1/46 103 F term (reference) 4D006 GA17 HA42 JA04C KA31 KB11 KE02P KE12P KE13P KE16P KE17P KE18P KE19P MA03 MA06 MA13 MA14 MA40 MB06 MC03 MC30 MC62X MC73 MC74 MC75 MC77 MC78 NA01 NA05 NA41 NA46 PA01 PB02 PB23 4D061 DA03 DB13 EA02 EB01 EB04 EB13 EB17 EB19 EB22 4F071 AA01 AA03A55A03 AA03 AA03 AA03 AA03 AA03 AA01 AL06C AR00A AR00C BA03 BA06 BA10A BA10C DG15B DJ00B GB90 JD05A JD05B JD05C

Claims (12)

[Claims] 1. An ion-exchange membrane having a multilayer structure of at least three layers in which a water-permeable layer is provided at an intermediate portion in a thickness direction and a non-water-permeable ion exchanger layer is provided on both sides of the water-permeable layer. 2. The ion exchange membrane according to claim 1, wherein the non-water permeable ion exchanger layers disposed on both sides of the water permeable layer are made of the same type of membrane. 3. The ion exchange membrane according to claim 1, wherein the water permeable layer is formed of a porous channel material. 4. The ion exchange membrane according to claim 1, wherein the water permeable layer is formed of an ion exchanger. 5. The ion exchange membrane according to claim 1, wherein the water permeable layer is formed by a spacer having an ion exchange group. 6. The water-permeable layer is formed in a space,
The ion exchange membrane according to claim 1. 7. The water-permeable layer communicates with the outside of one non-water-permeable ion exchanger layer and communicates with the outside of the other non-water-permeable ion exchanger layer at another position. ,
The ion exchange membrane according to claim 1. 8. The ion-exchange membrane according to claim 1, wherein the water-permeable layer is formed as an independent flow path outside the both non-water-permeable ion exchanger layers. 9. An electric deionized water producing apparatus comprising a plurality of alternately provided deionization chambers and concentration chambers defined by ion exchange membranes between electrodes to which a DC voltage is applied. At least a part thereof is formed of an ion-exchange membrane having a multilayer structure of at least three layers in which a water-permeable layer is provided at an intermediate portion in the thickness direction and a non-water-permeable ion-exchanger layer is provided on both sides of the water-permeable layer. An electric deionized water production apparatus, which performs a desalination treatment of the water to be treated that has flowed into a desalination chamber while being watered. 10. The water-impermeable ion-exchange layers of the ion-exchange membrane having the multilayer structure are each composed of an anion-exchange membrane.
An electric deionized water producing apparatus according to claim 9. 11. The electric deionized water producing apparatus according to claim 9, wherein the water permeable layer forms a water passage for collecting water from the desalting chamber and discharging the water to the concentration chamber. 12. The electric deionized water producing apparatus according to claim 9, wherein the water permeable layer forms a water passage independent of the desalting chamber and the concentration chamber.