JP2008036496A - Electrodeionization equipment - Google Patents

Abstract

Disclosed is an electrodeionization apparatus that can operate stably, inexpensively, and efficiently for a long period of time without generating scale even if the water to be treated contains a hardness component.
In the electrodeionization apparatus, a plurality of anion exchange membranes 13 and cation exchange membranes 14 are alternately arranged between a cathode 12 and an anode 11 so that concentration chambers 15 and demineralization chambers 16 are alternately arranged. The bipolar chamber 20 is provided in the concentrating chamber 15, and the concentrating chamber 15 is partitioned into a cathode side compartment 15A and an anode side compartment 15B. Then, at least a part of the concentrated water in the cathode side compartment 15A is supplied to the desalting chamber 16 as treated water and also supplied to the anode side compartment 15B.
[Selection] Figure 1

Description

  The present invention relates to an electrodeionization apparatus in which a plurality of anion exchange membranes and cation exchange membranes are alternately arranged between a cathode and an anode to alternately form a concentration chamber and a desalting chamber. The present invention relates to an electrodeionization apparatus that prevents the generation of scale in a desalination chamber or a concentration chamber by improving the configuration of the concentration chamber.

  Conventionally, for production of deionized water used in various industries such as semiconductor manufacturing factory, liquid crystal manufacturing factory, pharmaceutical industry, food industry, electric power industry, etc. or consumer use or research facilities, etc., an electrode as shown in FIG. A plurality of anion exchange membranes (A membranes) 13 and cation exchange membranes (C membranes) 14 are alternately arranged between (anode 11 and cathode 12) to alternately form concentration chambers 15 and desalting chambers 16, An electrodeionization apparatus in which the anion exchanger and the cation exchanger made of ion exchange resin, ion exchange fiber, graft exchanger, or the like are mixed or filled in multiple layers in the desalting chamber 16 is widely used (see Patent Documents 1 to 3). ). In FIG. 4, 17 is an anode chamber, 18 is a cathode chamber, and 10 is a mixed resin of an anion exchange resin and a cation exchange resin.

The electrodeionization device efficiently generates desalination by generating H ⁺ ions and OH ⁻ ions by water dissociation and continuously regenerating the ion exchanger filled in the desalting chamber. is there. This electrodeionization apparatus does not require a regeneration treatment using chemicals like the ion exchange resin apparatus that has been widely used so far, and can be completely continuously sampled, and high-purity water can be obtained. Exhibits excellent effects.

However, when tap water that has been turbidized, dechlorinated, and softened from river water, groundwater, etc. at a water purification plant or the like is used directly as the water to be treated in an electrodeionization device or when the calcium concentration of the water to be treated is high (1 ) Since scale generation in the concentrating chamber and (2) deterioration of treated water conductivity due to increased CO ₂ load occur, tap water is not directly passed as treated water in the electrodeionization device. .

Among the problems (1) and (2) above, regarding the increase in the CO ₂ load in (2), a relatively inexpensive degassing device such as a degassing membrane or a decarboxylation tower is pretreated with an electrodeionization device. It can be solved by using it as a device.

  However, in order to prevent scale in the concentration chamber of (1), it is necessary to install a softening device or the like to completely remove the hardness component in the water, but when using a softening device, Regeneration is required, and the advantages of using a regeneration-free electrodeionization device are lost.

In order to solve such problems, as a pretreatment device for an electrodeionization device, a reverse osmosis membrane device (RO membrane device), decarboxylation is generally used to reduce hardness components and CO ₂ concentration. A method of installing a tower or the like is used.

  However, since the RO membrane device is operated at a high pressure of 0.5 to 2 MPa, expensive equipment is required and the operating cost increases. In addition, even when an RO membrane device is used as a pretreatment device for an electrodeionization device, calcium carbonate scale is generated in the concentration chamber of the electrodeionization device due to slight leakage of calcium from the RO membrane. There was also a problem that stable operation could not be performed.

  Thus, two stages of RO membrane devices are arranged in series to further remove calcium and the like, but this is not practical in terms of costs. For this reason, if treatment can be performed with a single-stage RO membrane device under normal water supply conditions, a pure water production system must be designed with a single-stage RO membrane device. In addition, there is a concern that scale cannot be generated in the concentration chamber because it cannot cope with the deterioration of water supply conditions such as an increase in the concentration of carbonic acid and the breakthrough of the RO membrane device.

In such an electrodeionization apparatus, a mechanism for generating scale will be described with reference to FIG.
Calcium carbonate is the most problematic factor for generating scale in electrodeionization equipment. In the electrodeionization apparatus, the water to be treated is generally branched and used as the supply water for the concentration chamber. In the concentration chamber 15, calcium ions (Ca ²⁺ ) are ion-exchanged and permeated from the desalting chamber 16 on the cation exchange membrane 14 side, and approach the surface of the anion exchange membrane 13 by electrical action. On the other hand, hydrogen carbonate ions (HCO ₃ ⁻ ) permeate from the desalting chamber 16 on the anion exchange membrane 13 side. In the concentration chamber 15, when the concentration of either calcium ion (Ca ²⁺ ) or hydrogen carbonate ion (HCO ₃ ⁻ ) is increased, calcium carbonate (CaCO ₃ ) is reacted by the following reactions (1) and (2). Is formed.
HCO ₃ ⁻ + OH ⁻ → CO ₃ ²⁻ + H ₂ O (1)
Ca ²⁺ + CO ₃ ²⁻ → CaCO ₃ (2)

  When scale occurs in the concentration chamber 15 in this manner, the electrical resistance increases and the voltage value cannot be kept constant, so that stable processing performance cannot be maintained. Moreover, since the above reaction is an irreversible reaction, if the reaction proceeds, there may be a situation where the module is finally replaced if the module is washed or further left standing.

In general, the saturation condition of calcium carbonate is represented by the following formula.
log [Ca ²⁺ ] + log [HCO ₃ ⁻ ] + pHs = log (Ks / K ₂ )
Ks: solubility product of calcium carbonate K ₂ : second dissociation constant of carbonic acid pHs: saturation pH of calcium carbonate

The difference between the pH in the actual aqueous solution and the saturated pH (pHs) of calcium carbonate is called the Langeria index (LSI),
LSI = pH-pHs> 0
Then, calcium carbonate is deposited.

Also in the concentration chamber 15 of the electrodeionization apparatus, OH ⁻ ions generated by water dissociation in the demineralization chamber 16 permeate from the anion exchange membrane 13 side, so that it is locally alkaline. For this reason, the LSI on the surface of the anion exchange membrane 13 becomes positive (> 0), so that calcium carbonate scale is deposited in the vicinity of the anion exchange membrane 13 in the concentration chamber 15. In addition, calcium hydroxide may be formed.

Therefore, the present applicant has previously proposed an electrodeionization apparatus having a bipolar membrane in the concentration chamber (see Patent Document 4) as a solution to the problem of scale generation in the concentration chamber.
Japanese Patent No. 1782943 Japanese Patent No. 2751090 Japanese Patent No. 2699256 JP 2001-198577 A

Although the scale of the concentrating chamber is suppressed by the electrodeionization apparatus described in Patent Document 4, when a lot of hardness components are contained in the water to be treated, the RO membrane apparatus is used as the pretreatment apparatus. even, calcium and magnesium hardness components leak from the RO membrane and the CO _2,, such as calcium or magnesium hydroxide is produced in the desalination chamber, calcium carbonate scale and the like are generated in the concentration chamber afraid There is a problem that stable operation cannot be performed for a long period of time depending on the quality of the water to be treated which is raw water, that is, the content of the hardness component.

  Moreover, since hydroxide ions are excessively generated in the anode-side concentration chamber partitioned by the bipolar membrane, there is a problem that scales such as calcium hydroxide and magnesium hydroxide are likely to be generated.

Therefore, it is conceivable to further reduce the hardness component and CO _{2 by} making the RO membrane device multi-stage and further treating the treated water with the RO membrane. It becomes a problem. This has been a problem to be solved in order for the electrodeionization apparatus to be widely used as a general industrial or consumer deionized water production apparatus.

  The present invention solves the above-mentioned conventional problems, and even if the water to be treated contains a large amount of hardness components, it is an electrodeionization that can be stably and inexpensively operated for a long period of time without generating scale. An object is to provide an apparatus.

  In order to solve the above problems, the present invention provides a plurality of anion exchange membranes and cation exchange membranes alternately arranged between a cathode and an anode to alternately form a concentration chamber and a desalting chamber, In the electrodeionization apparatus in which a bipolar membrane is provided in the concentrating chamber, and a cathode-side compartment and an anode-side compartment are formed in the concentrating chamber, at least a part of the effluent of the cathode-side compartment is transferred to the demineralization chamber and An electrodeionization apparatus having a flow path for supplying to the anode compartment is provided.

According to the above invention (invention 1), by arranging the bipolar membrane in the concentration chamber, the hydrogen carbonate ions that have permeated from the desalting chamber on the anion exchange membrane side into the concentration chamber and the permeation from the cation exchange membrane side have been transmitted. Since calcium ions are blocked by the bipolar membrane, calcium carbonate is not formed in the concentration chamber. Thereby, generation | occurrence | production of the calcium carbonate scale in a concentration chamber can be prevented. Furthermore, since hydroxide ions (OH ⁻ ) generated by water dissociation in the desalting chamber permeating from the anion exchange membrane side are also blocked by the bipolar membrane, calcium hydroxide is not formed in the concentration chamber. At this time, the cathode compartment is acidified by supplying hydrogen ions generated by water dissociation at the interface of the bipolar membrane, so the concentrated water in the cathode compartment is supplied to the desalting compartment. Thus, the pH of the water to be treated can be lowered, thereby preventing the generation of scales such as calcium hydroxide and magnesium hydroxide caused by excess hydroxide ions (OH ⁻ ). Moreover, by supplying the concentrated water in the cathode compartment to the anode compartment in the enrichment compartment, the pH of the feed water in the anode compartment can be lowered, and thereby excess hydroxide ions (OH ⁻ ) Generation of scales such as calcium hydroxide and magnesium hydroxide caused by the above can be prevented. Furthermore, since the absolute amount of ions in the anode compartment is increased by supplying the concentrated water in the cathode compartment to the anode compartment, there is also an effect of suppressing the increase in voltage due to the installation of the bipolar membrane.

  In the said invention (invention 1), it is preferable that the said bipolar membrane is provided so that the anion exchange layer surface may be located in the anode side, and a cation exchange layer surface may be located in the cathode side (invention 2).

According to the above invention (invention 2), the hydrogen carbonate ions permeating from the desalting chamber on the anion exchange membrane side into the concentration chamber and the calcium ions permeating from the cation exchange membrane side are blocked, and the anion exchange membrane Hydroxide ions (OH ⁻ ) generated by water dissociation in the desalting chamber permeating from the side can also be blocked by the bipolar membrane.

In the said invention (invention 1,2), it is preferable that the decarboxylation apparatus is provided in the middle of the flow path to the said demineralization chamber and / or the anode side compartment (invention 3). The concentrated water in the cathode side compartment contains not only hydrogen ions but also carbonate ions derived from CO _{2. When} this is supplied to the desalination compartment or anode compartment, the desalination compartment or anode Although there is a possibility that calcium carbonate may be generated by reacting with calcium ions in the side compartment, according to this invention (invention 3), CO ₂ can be removed by passing through a decarboxylation device in advance, Generation of calcium carbonate scale can be prevented. In addition, since the concentrated water in the cathode compartment is acidic, there is an effect that decarboxylation by a decarboxylation device such as a degassing membrane can be performed effectively.

  In the said invention (Invention 1-3), it is preferable to fill with an ion exchanger in the said concentration chamber (Invention 4). According to this invention (invention 4), since the ions easily flow by filling the ion exchanger in the concentration chamber, an increase in voltage due to the installation of the bipolar membrane can be suppressed.

  In the said invention (invention 1-4), it is preferable to fill the ion-exchange body in the said desalination chamber (invention 5). According to this invention (invention 5), the quality of deionized water obtained in the demineralization chamber can be further improved.

  Furthermore, in the said invention (invention 1-5), it is preferable to provide the flow path which supplies a part of effluent of the said desalination chamber to the inflow side of the said concentration chamber (invention 6). According to this invention (invention 6), even when treating water with a high calcium concentration such as tap water, by introducing a part of deionized water into the concentrating chamber, the circulating water in the concentrating chamber can be reduced. Dilution with deionized water can reduce the calcium concentration, thereby further preventing the generation of scale.

According to the electrodeionization apparatus of the present invention, since the bipolar membrane is disposed in the concentration chamber, hydrogen carbonate ions, hydroxide ions, and calcium ions do not associate in the concentration chamber. And the formation of calcium hydroxide can be suppressed, and even if a hardness component is contained in the water to be treated, the electrodeionization apparatus can be stably operated for a long time without generating scale in the concentration chamber. Further, by supplying the concentrated water in the cathode compartment to the desalting compartment and / or the anode compartment, the scale of calcium hydroxide, magnesium hydroxide or the like caused by excess hydroxide ions (OH ⁻ ) Occurrence can be prevented. Furthermore, the RO membrane device required as a pretreatment device can be minimized, and the equipment cost and the treatment cost can be reduced.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a schematic configuration diagram illustrating an electrodeionization apparatus according to an embodiment of the present invention, FIG. 2 is an enlarged cross-sectional view of a concentration chamber of the electrodeionization apparatus according to the embodiment, and FIG. It is a systematic diagram which shows the pure water manufacturing system provided with the electrodeionization apparatus which concerns on the same embodiment. 1 to 3, the same components as those of the conventional electrodeionization apparatus shown in FIGS. 4 and 5 are denoted by the same reference numerals.

  In the electrodeionization apparatus according to this embodiment, the bipolar membrane 20 is provided in the concentration chamber 15 to partition the concentration chamber 15, and the cathode-side partition chamber 15 </ b> A and the anode-side partition chamber 15 </ b> B are formed in the concentration chamber 15, Except that the concentration chamber 15 is filled with a mixed resin 21 of anion exchange resin and cation exchange resin, it has the same configuration as the conventional electrodeionization apparatus shown in FIG.

  The bipolar membrane 20 is installed in the concentration chamber 15 so that the anion exchange layer surface 20B of the bipolar membrane 20 is located on the anode 11 side and the cation exchange layer surface 20A of the bipolar membrane 20 is located on the cathode 12 side.

  The bipolar membrane 20 used in the present embodiment is not particularly limited as long as it has an anion exchange layer and a cation exchange layer and has high water electrolysis efficiency. In some cases, an anion exchange membrane and a cation exchange membrane may be used in an overlapping manner.

  In such an electrodeionization apparatus, the cathode side compartment 15A and the anode side compartment 15B are preferably filled with an ion exchanger, in particular, a mixed resin 21 of an anion exchange resin and a cation exchange resin.

  The volume ratio of the anion exchange resin to the cation exchange resin in the mixed resin 21 is not particularly limited, but the anion exchange resin / cation exchange resin is 10/90 to 90/10, particularly 30/70 to 70/30. Is preferred. Thereby, in the cathode side compartment 15A, the movement of hydrogen ions generated by water dissociation at the interface of the bipolar film 20 is promoted, while in the anode side compartment 15B, hydroxylation generated by water dissociation at the interface of the bipolar film 20 is promoted. The movement of object ions is promoted. As a result, current easily flows and voltage increase can be suppressed.

  The mixed resin 21 may change the volume ratio of the anion exchange resin / cation exchange resin between the cathode side compartment 15A and the anode side compartment 15B, or the cathode side compartment 15A and the anode side compartment 15B. You may change the volume ratio of anion exchange resin / cation exchange resin also in the upper and lower sides.

  At least a part of the concentrated water in the cathode-side compartment 15A of the electrodeionization apparatus as described above is supplied to the desalting chamber 16 as treated water and also supplied to the anode-side compartment 15B. Specifically, the present invention can be applied to a pure water production system as shown in FIG.

  That is, as shown in FIG. 3, the pure water production system includes a reverse osmosis membrane (RO membrane) device 31 to which the water to be treated W is supplied and a removal treatment for treating the RO treated water W1 that has passed through the RO membrane device 31. A deaeration device 32 that is a carbonic acid device and an electric deionization device 33 that processes the deaeration water W2 obtained by the deaeration device 32 in the demineralization chamber 16 to produce treated water (deionized water) W3 are provided.

  And the demineralization chamber 16 of this electrodeionization apparatus 33 is connected to the subsystem etc. via main flow path R1. Further, the desalting chamber 16 communicates with the anode chamber 17 and the cathode chamber 18 via flow paths R2 and R3 branched from the main flow path R1, and also on the cathode side via the flow paths R4 and R5. It communicates with the compartment 15A and the anode compartment 15B.

  The concentrated water flow path R6 discharged from the cathode side compartment 15A is open to the discharge side, and a part of the flow path R6 joins the main flow path R1 upstream of the deaeration device 32. Furthermore, the flow path R7 branched in the middle of the flow path R6 merges with the flow path R5 communicating with the anode side compartment 15B. In FIG. 3, B1 to B8 are flow rate adjusting mechanisms, and the flow rate in each flow path can be controlled to a desired value as necessary.

Next, the operation of the electrodeionization apparatus having such a configuration will be described.
As shown in FIG. 3, first, the water to be treated W is supplied to the RO membrane device 31 from the starting end of the main flow path R1, and the RO membrane device 31 performs the treatment, and calcium, silica, etc. contained in the water to be treated W Remove.

  And after supplying the RO process water W1 processed with this RO membrane apparatus 31 to the deaeration apparatus 32 and removing the carbonate ion etc. which are contained in the RO process water W1 as a carbon dioxide, the obtained deaeration water W2 is obtained. Is supplied to the demineralization chamber 16 of the electrodeionization device 33.

  In the electrodeionization device 33, the degassed water W2 is a main flow path R1 as treated water (deionized water) W3 from which ionic impurities such as calcium ions, magnesium ions, and bicarbonate ions have been removed in the desalting chamber 16. Supplied to the subsystem.

  In addition, a part of the treated water W3 is supplied to the anode chamber 17 and the cathode chamber 18 of the electrodeionization device 33 via the flow paths R2 and R3 branched from the main flow path R1, and the flow paths R4 and R3. It is supplied to the concentration chamber 15, that is, the cathode side compartment 15A and the anode side compartment 15B via R5.

  At this time, as shown in FIG. 2, since the bipolar membrane 20 is provided in the concentration chamber 15 of the electrodeionization device 33, the permeation into the concentration chamber 15 from the demineralization chamber 16 on the anion exchange membrane 13 side. The hydrogen carbonate ions and hydroxide ions thus transmitted cannot pass through the bipolar membrane 20, and the calcium ions and hydrogen ions transmitted from the cation exchange membrane 14 side also cannot pass through the bipolar membrane 20. For this reason, generation | occurrence | production of the calcium carbonate scale in the concentration chamber 15 is prevented. For convenience of explanation, the mixed resin 21 is omitted in FIGS. 2 and 3.

  At this time, in the bipolar film 20, water dissociation occurs by applying a voltage equal to or higher than the theoretical water electrolysis voltage (0.83V), so that a current flows. For this reason, the deionization performance of the electrodeionization apparatus 33 is not impaired by installing the bipolar membrane 20 in the concentration chamber 15.

  By such an action, the cathode compartment 15A is acidified by supplying hydrogen ions generated by water dissociation at the interface of the bipolar membrane 20. Therefore, a part of the concentrated water W4 in the cathode compartment 15A is joined to the main flow path R1 upstream of the deaeration device 32 via the flow path R6, and the flow path is branched in the middle of the flow path R6. Merge from R7 to flow path R5.

  Since the concentrated water W4 merged with the RO treated water W1 upstream of the deaeration device 32 contains carbonate ions and the like, decarbonation is first performed by the deaeration device 32. At this time, since the concentrated water W4 is acidic, decarboxylation by the degassing device 32 is performed more efficiently.

  Thereafter, the obtained deaerated water W2 is re-supplied to the desalting chamber 16, and the pH of the deaerated water W2 is lowered by mixing the acidic concentrated water W4. For this reason, generation | occurrence | production of the scale resulting from hydroxide ions, such as calcium hydroxide and magnesium hydroxide, can be suppressed in the desalting chamber 16.

  The supply amount of the concentrated water W4 to the RO treated water W1 may be an amount that provides a certain pH reduction effect in the desalting chamber 16, and may be about 1 to 15% with respect to the RO treated water W1. That's fine.

  The concentrated water W4 may be supplied to the demineralization chamber 16 without going through the deaeration device 32, or the concentrated water W4 is not supplied to the demineralization chamber 16 through the deaeration device 32. This may be determined in consideration of the amount of carbonate ions resupplied to the desalting chamber 16 and the hardness component in the water to be treated.

  The concentrated water W4 joins the treated water (deionized water) W3 flowing through the flow path R5 from the flow path R7 and is also supplied to the anode side compartment 15B, whereby the concentrated water W4 flows through the anode side compartment 15B. The pH of water (deionized water) W3 similarly decreases. Thereby, generation | occurrence | production of scales, such as calcium hydroxide and magnesium hydroxide, in the anode side compartment 15B can be suppressed. Furthermore, since the absolute amount of ions in the anode-side compartment 15B increases due to the inflow of the acidic concentrated water W4, the effect of suppressing the voltage increase due to the installation of the bipolar membrane 20 can also be obtained.

  The supply amount of the concentrated water W4 to the treated water (deionized water) W3 may be an amount that can provide a certain pH reduction effect in the anode-side compartment 15B, and is 1 to 10 with respect to the treated water W3. % Is sufficient.

  In the present embodiment, no deaeration device is installed in the flow path R5 and flow path R7 to the anode side compartment 15B, but there is a possibility that calcium carbonate is generated by carbonate ions in the concentrated water W4. If there is, a deaeration device may be installed in the flow path R5 or the flow path R7. By doing in this way, an electric current will flow easily and the stable treated water quality will be obtained.

  If the bipolar membrane 20 is simply disposed in the concentrating chamber 15, a scale may be generated when water having a high calcium concentration such as tap water is treated. Therefore, as shown in FIG. It is preferable to introduce a part of the deionized water (treated water) W3 in the salt chamber 16 into the concentration chamber 15 (the cathode side compartment 15A and the anode side compartment 15B). Thereby, concentration room circulating water can be diluted with deionized water W3, and the calcium concentration of concentration room circulating water can be reduced. Similarly, it is preferable to use deionized water as water in the electrode chambers (the anode chamber 17 and the cathode chamber 18).

  In the electrodeionization apparatus according to this embodiment, a cathode side compartment 15A and an anode side compartment 15B are formed in the concentration chamber 15, and a mixed resin 21 of an anion exchange resin and a cation exchange resin is formed in the concentration chamber 15. However, the deionization chamber 16 can be mixed or filled with an anion exchanger and a cation exchanger made of an ion exchange resin, an ion exchange fiber, a graft exchanger, or the like to obtain a deionized product. It is preferable in terms of improving water. Furthermore, the anode chamber 17 and the cathode chamber 18 may be filled with an ion exchanger.

Hereinafter, the present invention will be described more specifically with reference to comparative examples and examples.
In addition, the test apparatus used by the following comparative examples and Examples arrange | positions the following apparatus in series in order of the activated carbon apparatus and the electrodeionization apparatus.
Activated carbon device: "Kurikor KW10-30" manufactured by Kurita Kogyo Co., Ltd.
Electrodeionization equipment: “Kuritenon SH type” manufactured by Kurita Kogyo Co., Ltd.
Treated water volume: 100L / hr

Moreover, the following were prepared as to-be-processed water (city water) for a test.
Water to be treated: Concentration of feed water Ca 28ppm (CaCO ₃ conversion)
Water supply CO ₂ concentration 29ppm (CaCO ₃ conversion)

[Comparative Example 1]
The following ion exchange resin is used to fill the ion exchange membrane and demineralization chamber of the electrodeionization apparatus. The treated water has a current value of 6.5 A, a water recovery rate of 80%, an inlet conductivity of 170 μS / cm, and a concentration. Water was passed at a chamber initial flow rate of 25 L / hr, and the differential pressure in the concentrating chamber after 1 week, 1 month, 2 months and 3 months and the change over time of the applied voltage were measured. .
The results are shown in Table 1, and the applied voltage and outlet conductivity in the initial state are shown.
In addition, the to-be-processed water was used as the makeup water and the electrode chamber water.

Anion exchange membrane: "Aciplex A501SB" manufactured by Asahi Kasei Corporation
Cation exchange membrane: "Aciplex K501SB" manufactured by Asahi Kasei Corporation
Ion exchange resin: An anion exchange resin ("SA10A" manufactured by Mitsubishi Chemical Corporation) and a cation exchange resin ("SK1B" manufactured by Mitsubishi Chemical Corporation) mixed at a volume mixing ratio of 6: 4.

[Comparative Example 2]
A bipolar membrane was provided in the concentration chamber of the electrodeionization apparatus used in Comparative Example 1, and the electrodeionization apparatus shown in FIG. 1 was assembled by filling the concentration chamber with an ion exchange resin, and this electrodeionization apparatus was used. A water flow test was conducted in the same manner except for the above.
The results are shown in Table 1.
As the bipolar film, CMS (trade name) manufactured by Astom Co., Ltd. was used. The ion exchange resin and cation exchange resin are the same as those filled in the desalting chamber in Comparative Example 1.

[Example 1]
In the electrodeionization apparatus of Comparative Example 2, an electrodeionization apparatus was assembled by providing a flow path that merged from the concentrated water path of the cathode side compartment to the introduction flow path of the anode side compartment, and this electrodeionization apparatus was used. A water passage test was conducted in the same manner except that 5% of the concentrated water in the cathode compartment was supplied to the anode compartment together with deionized water from the desalting compartment.
The results are shown in Table 1.

[Example 2]
In the electrodeionization apparatus of Comparative Example 2, the electrodeionization apparatus was assembled by providing a flow path that merges from the concentrated water path of the cathode compartment to the introduction flow path to the demineralization chamber, and this electrodeionization apparatus was used. A water passage test was conducted in the same manner except that 10% of the concentrated water in the cathode compartment was supplied to the desalting chamber together with the water to be treated.
The results are shown in Table 1.

Example 3
In the electrodeionization apparatus of Comparative Example 2, a flow path that merges from the concentrated water flow path of the cathode side compartment to the introduction flow path of the anode side compartment is provided, and the concentrated water flow path of the cathode side compartment is connected to the demineralization chamber. An electric deionization apparatus is assembled by providing a flow path that merges with the introduction flow path. Using this electric deionization apparatus, 5% of the concentrated water in the cathode compartment is combined with the deionized water from the demineralization compartment to the anode compartment. A water flow test was conducted in the same manner except that 10% of the concentrated water in the cathode compartment was supplied to the desalting chamber along with the water to be treated.
The results are shown in Table 1.

  As is apparent from Table 1, the electrodeionization apparatus of Comparative Example 1 increased the differential pressure on the concentration chamber side in one week and became inoperable. In Comparative Example 2, the electrolysis voltage increased one week after the start of water flow. On the other hand, in the electrodeionization apparatuses of Examples 1 to 3, the increase in voltage was small and the operation was stable for 3 months, and the quality of the treated water obtained was also good. In particular, in the electrodeionization apparatus of Example 3 in which the concentrated water in the cathode compartment was supplied to both the concentration chamber and the desalting chamber, the problems of scale generation and conductivity were greatly improved, and the differential pressure and voltage were reduced. Little rise occurred.

It is a schematic block diagram which shows the electrodeionization apparatus which concerns on one Embodiment of this invention. It is sectional drawing which shows the flow of the ion in the concentration chamber of the electrodeionization apparatus which concerns on the same embodiment. It is a flowchart which shows the pure water manufacturing system using the electrodeionization apparatus which concerns on the same embodiment. It is a schematic block diagram which shows the conventional electrodeionization apparatus. It is sectional drawing which shows the flow of the ion in the concentration chamber of the conventional electrodeionization apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Anode 12 ... Cathode 13 ... Anion exchange membrane 14 ... Cation exchange membrane 15 ... Concentration chamber 15A ... Cathode side compartment 15B ... Anode side compartment 16 ... Desalination chamber 17 ... Anode chamber 18 ... Cathode chamber 20 ... Bipolar membrane 21 ... Mixed resin (cation exchange resin / cation exchange resin)
32 ... Deaerator (Decarbonizer)
33 ... Electrodeionization device W4 ... Concentrated water (concentrated water in cathode side compartment)
R6 ... channel R7 ... channel

Claims (6)

A plurality of anion exchange membranes and cation exchange membranes are alternately arranged between the cathode and the anode to alternately form a concentration chamber and a desalting chamber, and a bipolar membrane is provided in the concentration chamber, In the electrodeionization apparatus in which the cathode side compartment and the anode side compartment are formed,
An electrodeionization apparatus comprising a flow path for supplying at least a part of the effluent of the cathode side compartment to the desalting compartment and / or anode side compartment.   2. The electrodeionization apparatus according to claim 1, wherein the bipolar membrane is provided such that the anion exchange layer surface is located on the anode side and the cation exchange layer surface is located on the cathode side.   The electrodeionization apparatus according to claim 1 or 2, wherein a decarboxylation apparatus is provided in the middle of the flow path to the demineralization chamber and / or the anode-side compartment.   The electrodeionization apparatus according to any one of claims 1 to 3, wherein the concentration chamber is filled with an ion exchanger.   The electrodeionization apparatus according to any one of claims 1 to 4, wherein the demineralization chamber is filled with an ion exchanger. The electrodeionization apparatus according to any one of claims 1 to 5, further comprising a flow path for supplying a part of the effluent water of the demineralization chamber to the inflow side of the concentration chamber.

Images