JP2006026488A - Electric desalter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric desalter which can inhibit scale generation and enables long-term stable operation. <P>SOLUTION: In the electric desalter, desalting chambers and concentration chambers are formed by disposing a plurality of ion-exchange membranes between a cathode and an anode, and an anode chamber and a cathode chamber are formed by the anode and the cathode, and the ion-exchange membranes adjacent to them respectively. A part of desalted water discharged from the desalting chambers is supplied as the inlet water of the anode chamber, and a part of or all of the outlet water of the anode chamber is supplied as the inlet water of the concentration chamber. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an improvement related to a so-called electric desalination apparatus, and provides an electric desalination apparatus having performance far exceeding that of a conventional electric desalination apparatus.

  The electric desalination equipment forms a concentrating chamber and a desalting chamber by arranging a cation exchange membrane and an anion exchange membrane between the cathode and anode electrodes, and uses a potential gradient as a driving source to treat the desalting chamber. Ion components are removed by moving and separating ions in the water through the ion exchange membrane to the concentration chamber.

  In FIG. 1, the conceptual diagram of the conventional typical electric desalination apparatus is shown. 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. Yes. By further repeating the alternating arrangement of the anion exchange membrane and the cation exchange membrane, a plurality of desalting chambers and concentration chambers are alternately formed. If necessary, the desalting chamber and the concentration chamber are filled with an ion exchanger, which promotes the movement of ions in each chamber. Further, the sections in contact with the anode and the cathode at both ends are generally called an anode chamber and a cathode chamber, and serve to exchange electrons of current applied by a direct current. In FIG. 1, there are three desalting chambers and four concentrating chambers, and further outside the outermost concentrating chamber, an anode chamber with an anode and a cation exchange membrane, and a cathode chamber with a cathode and an anion exchange membrane. The formed form is shown. In this embodiment, the anode chamber and the cathode chamber function to dilute / desalinate ions, that is, function as a desalting chamber.

In the operation of such an electric desalination apparatus, a voltage is applied to the anode and the cathode, and water is passed through the desalination chamber, the concentration chamber, and the electrode chamber. Water to be treated for ions is supplied to the desalting chamber, and water of appropriate water quality is passed through the concentration chamber and the polar chamber, respectively. FIG. 1 shows an example in which RO treated water is supplied to all of the desalting chamber, the concentration chamber, and the polar chamber. In this way, when water is passed through the desalting chamber, the concentration chamber, and the polar chamber while being energized, in the desalting chamber, cations and anions in the water to be treated are drawn to the cathode side and the anode side, respectively, and the anion exchange membrane and the cation Since each of the exchange membranes selectively permeates only anions or cations, cations (Ca ²⁺ , Na ⁺ , Mg ²⁺ , H ^+, etc.) in the water to be treated pass through the cation exchange membrane C to the cathode side concentrating chamber and the anions. (Cl ⁻ , SO ₄ ²⁻ , HSiO ₃ ⁻ , HCO ₃ ⁻ , OH ^{− and the} like) move through the anion exchange membrane A to the concentration chamber on the anode side. On the other hand, the movement of the anion from the cathode side concentration chamber to the desalting chamber and the movement of the cation from the anode side concentration chamber to the desalting chamber are blocked by the different sign ion blocking property of the ion exchange membrane. As a result, desalted water having a reduced ion concentration is obtained from the desalting chamber, and concentrated water having an increased ion concentration is obtained from the concentrating chamber. The water discharged from the anode chamber and the cathode chamber (outlet water) is generally called anode water and cathode water, respectively.

  According to such an electrical desalting apparatus, pure water with higher purity can be obtained as desalted water by using water with less impurities equivalent to, for example, RO (reverse osmosis membrane) treated water as the treated water. Recently, more advanced ultrapure water, such as ultrapure water for semiconductor manufacturing, has been required. Therefore, in a recent electric desalination apparatus, a desalination chamber and / or a concentration chamber and / or a polar chamber are mixed with cation exchange resin beads and anion exchange resin beads as an ion exchanger, and these are filled. A method of promoting the movement of ions in the room is known. Furthermore, as an ion exchanger, a cation exchange fiber material (nonwoven fabric, etc.) is placed on the cation exchange membrane side and an anion exchange fiber material on the anion exchange membrane side in the desalting chamber. There has also been proposed a method of filling a spacer or an ion conductive spacer with ion conductivity between them (for example, Patent Documents 1 and 2).

  In the electric desalination apparatus of the above-described type, when water to be treated is passed through a desalting chamber filled with an ion exchanger, the salt to be removed in the water to be treated and the ion exchange group of the ion exchanger are ionized. An exchange reaction takes place to remove the salt. For example, when NaCl is used as the salt to be removed, a sulfonic acid group is used as the cation exchange group, and a quaternary ammonium salt is used as the anion exchange group, it can be explained as follows.

When the water to be treated in which the salt to be removed (NaCl) is dissolved comes into contact with the cation exchanger, cations (Na ⁺ ) in the water to be treated are ion-exchanged by the cation exchange groups and adsorbed on the solid phase (cation exchanger) to be removed. (Equation 1).

Formula 1

  The water to be treated from which a certain amount of cations has been removed by contacting with the cation exchanger is then contacted with the anion exchanger. At this time, the acid (HCl) produced by the ion exchange reaction (formula 1) by the cation exchange group is completely neutralized as shown in formula 2.

Formula 2

On the other hand, the salt to be removed in the water to be treated that has not reacted with the cation exchanger comes into contact with the anion exchanger, and as shown in Formula 3, the anion (Cl ⁻ ) is ion-exchanged by the anion exchange group, and the solid phase (anion It is adsorbed and removed by the exchanger.

Formula 3

  Next, the water to be treated comes into contact with the cation exchanger, and the alkali (NaOH) generated by the ion exchange reaction (Formula 3) by the anion exchange group is neutralized as shown in Formula 4.

Formula 4

In the electric desalination apparatus of the above-mentioned system, it is possible to obtain high purity pure water by such a mechanism.
Further, in the electric desalination apparatus in which the ion exchanger is filled into the chamber as described above, the portion where the cation exchange group and the anion exchange group come into contact in the desalination chamber and / or the concentration chamber filled with the ion exchanger. Exists. In particular, at the site where the cation exchange group and the anion exchange group in the desalting chamber come into contact, dissociation of water under a rapid potential gradient (Equation 5):

Formula 5

The ion exchanger in the desalting chamber is continuously and efficiently regenerated by the H ⁺ ions and OH ⁻ ions generated by this dissociation (hydrolysis), thereby making it possible to obtain high-purity pure water. Yes.

  Like the electric desalination apparatus described above, the cation exchange fiber material is placed in contact with the cation exchange membrane in the desalination chamber, the anion exchange fiber material is placed in contact with the anion exchange membrane, and the anion exchange with the cation exchange fiber material. When an ion conductive spacer is arranged between the fiber material and the ion exchange membrane and the ion exchanger (ion exchange fiber material and ion conductive spacer), a continuous cation exchanger packed bed and an anion exchanger packed bed Is formed. For this reason, since the ion to be removed once ion-exchanged and moved to the solid phase can be easily moved from the desalting chamber to the concentrating chamber without desorbing again to the aqueous phase, further efficient desalting treatment is possible. .

In such a structure, if the energization operation is continued, the functional group counter ions are locally deficient at the contact site between the cation exchanger and the anion exchanger, and water in the vicinity of the functional group is required to compensate for the deficient counter ions. Dissociates, and H ⁺ ions and OH ⁻ ions can be continuously supplied to the cation exchange group and the anion exchange group.

In such a desalting process, when the water to be treated contains a high concentration of hardness components such as calcium ions and magnesium ions, the desalted hardness components are concentrated from the desalting chamber through the cation exchange membrane. At the same time, OH ⁻ ions generated by the dissociation of water in the desalting chamber also move to the concentration chamber through the anion exchange membrane. Then, in the conventional electric desalting apparatus, the concentration is increased by interaction such as local increase in pH in the concentration chamber caused by the moved OH ⁻ ions and concentration polarization accompanying movement of the high concentration hardness component to the concentration chamber. Calcium salt or magnesium salt scale is generated on the surface of the ion exchange membrane in the room or on the surface of the electrode in the polar chamber. This has been recognized for many years as a major problem in the operation of electric desalination equipment, and countermeasures have been studied. The occurrence of the scale may cause an increase in applied voltage, an increase in supply water pressure, and the like, and may cause an event that greatly impedes stable operation of the electric desalination apparatus. Conventionally, as a means to solve this problem, regular chemical cleaning is performed for the purpose of dissolving the deposited scale components, or ion transfer per unit area of the ion exchange membrane is reduced to perform ion exchange. In order to loosen the concentration polarization on the film surface, a large film area is taken, an electron conductor such as a carbon material is used as a filler in contact with the cathode electrode plate to prevent local pH change, or Measures have been taken, such as circulating a chemical solution adjusted to an acidic pH to the concentration chamber or electrode chamber. Furthermore, it has been studied to pass the water to be treated through the anode chamber and use the acidified anode chamber outlet water as the concentration chamber supply water.

In addition, wastewater from semiconductor factories and the like contains metal ions such as copper ions and highly corrosive ions such as hydrofluoric acid at a high concentration. Therefore, when desalting the semiconductor factory wastewater with an electric desalination apparatus, metal ions such as copper ions are deposited as metal on the cathode plate, while hydrofluoric acid or the like corrodes the electrode plate. In order to solve this problem, an ion exchange membrane is further inserted between the electrode chamber and the desalting chamber in contact with the electrode chamber, so that the electrode chamber has a desalting function from a chamber having a conventional concentration function. It has been studied to change to an existing chamber and to supply demineralization chamber outlet water (demineralized water) as electrode chamber inlet water (Patent Document 3). However, if this factory wastewater (treated water) contains a hardness component such as calcium ions, the concentration chamber adjacent to the cathode chamber contains more OH ⁻ ions generated by the cathode reaction than the other concentration chambers. Since it moves, scales are likely to precipitate, which may impede operation.

Japanese Patent Laid-Open No. 5-64726 International publication W099 / 48820 pamphlet Japanese Patent Laid-Open No. 11-308435

  An object of the present invention is to solve the problem of scale deposition in the electrode chamber and the concentration chamber described above, and to provide an electric desalination apparatus that can be stably operated for a long period of time.

As a means for solving the above-mentioned problems, the present inventors have intensively studied, and as a result, have reached the knowledge of the present invention described below. That is, a part of the desalination chamber outlet water (demineralized water) of the electric desalination apparatus from which hardness components such as calcium ions and magnesium ions, which are the main causes of scale generation, are removed and become pure water is treated as an anode. When supplied as the inlet water of the chamber, an anion (for example, Cl ⁻ , SO ₄ ²⁻ , HCO ₃ ⁻⁾ is used as the outlet water of the anode chamber due to H ⁺ generated by the electrode reaction of the anode and an anion component moving to the anode chamber. Etc.) acidic water with a large content. By supplying the acidified anode chamber outlet water as the inlet water of the cathode chamber or the concentration chamber where the scale is likely to be generated, it is possible to suppress the generation of scale in the cathode chamber and / or the concentration chamber. This eliminates the need for periodic washing with chemicals for dissolving scale components, expansion of the ion exchange membrane area, and the use of special materials such as carbon fillers. As a device, stable long-term operation becomes possible. In addition, when the electrode chamber performs the function of dilution / desalting, the water to be treated is supplied as the inlet water of the anode chamber, and the outlet water of the anode chamber is supplied as the inlet water to the concentration chamber adjacent to the cathode chamber. Then, due to the effect of the outlet water of the anode chamber whose pH has changed to acidic due to the electrode reaction at the anode, the pH increase in the concentration chamber adjacent to the cathode chamber where the scale is most likely to occur is prevented, and stable long-term operation is possible. become. That is, this invention is comprised by the following various aspects.

  1. By disposing a plurality of ion exchange membranes between the cathode and the anode, a desalting chamber and a concentration chamber are formed, and further, an anode chamber and a cathode chamber are respectively formed by the anode, the cathode and the ion exchange membrane adjacent thereto. An electric desalination apparatus that supplies a part of the desalted water discharged from the desalting chamber as the inlet water of the anode chamber and a part or all of the outlet water of the anode chamber as the inlet water of the concentrating chamber It is comprised so that the electric-type desalination apparatus characterized by the above-mentioned.

  2. By disposing a plurality of ion exchange membranes between the cathode and the anode, a desalting chamber and a concentration chamber are formed, and further, an anode chamber and a cathode chamber are respectively formed by the anode, the cathode and the ion exchange membrane adjacent thereto. An electric desalination apparatus that supplies a part of the desalted water discharged from the desalting chamber as the inlet water of the anode chamber and a part or all of the outlet water of the anode chamber as the inlet water of the cathode chamber. It is comprised so that the electric-type desalination apparatus characterized by the above-mentioned.

  3. By disposing a plurality of ion exchange membranes between the cathode and the anode, a desalting chamber and a concentration chamber are formed, and further, an anode chamber and a cathode chamber are respectively formed by the anode, the cathode and the ion exchange membrane adjacent thereto. An electric desalination apparatus for supplying a part of the desalted water discharged from the desalting chamber as the inlet water of the anode chamber, and a part or all of the outlet water of the anode chamber in the concentrating chamber adjacent to the cathode chamber An electrical desalination apparatus configured to be supplied as inlet water.

Hereinafter, the structural example of the electrical desalination apparatus which concerns on the various aspects of this invention is demonstrated concretely.
FIG. 2 is a conceptual diagram illustrating a configuration example of an electrical desalination apparatus according to one embodiment of the present invention. An anion exchange membrane (A) and a cation exchange membrane (C) are disposed between the cathode (-vertically) and the anode (+) to define a concentration chamber and a desalting chamber. In FIG. 2, as in FIG. 1, three desalting chambers and four concentrating chambers are arranged, and further on the outer side of the outermost concentrating chamber, the anode chamber is composed of an anode and a cation exchange membrane, and the cathode and anion are exchanged. A form in which a cathode chamber is formed with a film is shown. In this embodiment, the anode chamber and the cathode chamber function to dilute / desalinate ions, that is, function as a desalting chamber.

  In operation, a voltage is applied to the anode and the cathode, and water is passed through the desalting chamber and the concentration chamber. In FIG. 2, RO treated water is supplied to the desalting chamber and the concentration chamber (except for the concentration chamber adjacent to the cathode chamber). A part of the treated water (desalted water) discharged from the desalting chamber is supplied to the anode chamber as inlet water of the anode chamber. Part or all of the outlet water from the anode chamber is then supplied to the cathode chamber as inlet water for the cathode chamber and also to the concentration chamber adjacent to the cathode chamber. Further, the outlet water from the anode chamber can be supplied to another concentration chamber. Alternatively, RO treatment water can be supplied to all the concentration chambers, and the anode chamber outlet water can be supplied only to the cathode chamber.

Thus, when a part of the desalted water after the desalting treatment is supplied as the inlet water of the anode chamber, the desalted water is pure water from which hardness components such as calcium ions and magnesium ions are almost removed. Then, H ⁺ produced by the electrode reaction of the anode causes the outlet water from the anode chamber to have an acidic pH. By supplying this to the cathode chamber where the scale is likely to be generated, the concentrating chamber adjacent to the cathode chamber, and further to the other concentrating chamber as the inlet water, the generation of scale in these chambers can be suppressed.

In addition, in the electric desalination apparatus in which the concentration chamber is formed adjacent to the anode chamber as shown in FIG. 2, the outlet water of the concentration chamber adjacent to the anode chamber is used as the cathode chamber and / or the concentration chamber, In particular, it can be supplied as the inlet water of the concentrating chamber adjacent to the cathode chamber. FIG. 3 shows a mode in which the outlet water of the anode chamber is supplied to the cathode chamber, and the outlet water of the concentration chamber adjacent to the anode chamber is supplied to the concentration chamber adjacent to the cathode chamber. In the electric desalination apparatus in which the concentration chamber is formed adjacent to the anode chamber as shown in FIGS. 2 and 3, the H ⁺ generated by the electrode reaction of the anode in the concentration chamber adjacent to the anode chamber. Moves through the cation exchange membrane and mixes in the water, and the anion component moving through the anion exchange membrane from the adjacent desalting chamber is mixed in the water, so that the outlet water from the concentration chamber is an anion (for example, (Cl ⁻ , SO ₄ ²⁻ , HCO ₃ ^{− and the} like). By supplying the outlet water of the concentrating chamber adjacent to the anode chamber having a high content of the anion that has become acidic to the cathode chamber or the concentrating chamber (especially the concentrating chamber adjacent to the cathode chamber) where scale is easily generated. The generation of scale in these rooms can be suppressed. In this case, it is not always necessary to supply the outlet water of the anode chamber to the cathode chamber, and the cathode chamber is supplied with the outlet water of the concentrating chamber adjacent to the cathode chamber or supplied with RO treated water. May be.

  FIGS. 2 and 3 show an embodiment in which the present invention is applied to an electric desalination apparatus in which the electrode chamber has a function of dilution / desalting. However, as shown in FIG. The present invention can also be applied to an electric desalination apparatus having a function of concentration. In the electric desalination apparatus shown in FIG. 4, an anion exchange membrane (A) and a cation exchange membrane (C) are arranged between a cathode (−) and an anode (+) to define a concentration chamber and a desalting chamber. Has been. In FIG. 4, four desalting chambers and three concentrating chambers are arranged, and further outside the outermost desalting chamber, the anode chamber is composed of an anode and an anion exchange membrane, and the cathode chamber is composed of a cathode and a cation exchange membrane. The form in which is formed is shown. In this embodiment, the anode chamber and the cathode chamber serve to concentrate ions, that is, function as a concentration chamber.

  In the electric desalination apparatus having such a configuration, in the same manner as described above, RO treatment water is supplied to the desalination chamber and the concentration chamber, and a part of the treated water (desalted water) discharged from the desalination chamber is supplied to the anode chamber. To the anode chamber as inlet water. Part or all of the outlet water from the anode chamber is then supplied to the cathode chamber as inlet water for the cathode chamber. Further, the outlet water from the anode chamber can be supplied to at least a part of the concentration chamber.

As described above, when a part of the desalted water after the desalting treatment is supplied as the inlet water of the anode chamber, in the anode chamber, H ⁺ generated by the electrode reaction of the anode passes through the anion exchange membrane from the adjacent desalting chamber. Since the moving anion component is mixed in the water, the outlet water from the anode chamber becomes acidic water with a high content of anions (for example, Cl ⁻ , SO ₄ ²⁻ , HCO ₃ ^−, etc.). By supplying the outlet water of the anode chamber having a large content of the anion that has become acidic to the cathode chamber or the concentrating chamber where scale is likely to be generated, the generation of scale in these chambers can be suppressed.

  Examples of the ion exchange membrane used to constitute the electric desalination apparatus according to the present invention include NEOSEPTA CMX (Tokuyama) as the cation exchange membrane, and NEOSEPTA AMX (Tokuyama) as the anion exchange membrane. Etc. can be used.

  In the electric desalination apparatus according to the present invention, it is preferable that the desalting chamber, the concentration chamber, and the electrode chamber are each filled with an ion exchanger. By filling the desalting chamber, the concentration chamber, and the electrode chamber with an ion exchanger, the movement of ions in these chambers can be promoted.

  In the electric desalination apparatus according to the present invention, as described above, for example, ion exchange resin beads are used as the ion exchanger that can be filled in at least one of the desalination chamber, the concentration chamber, and the polar chamber. Can do. As an ion exchange resin bead that can be used for such a purpose, those produced by using beads obtained by crosslinking polystyrene with divinylbenzene as a base resin, which are known in the art, can be used. For example, when producing a strongly acidic cation exchange resin having a sulfonic acid group, the above-mentioned base resin is treated with a sulfonating agent such as sulfuric acid or chlorosulfonic acid to perform sulfonation, and the base material is sulfonated. By introducing a group, a strongly acidic cation exchange resin is obtained. For example, when producing a strongly basic anion exchange resin having a quaternary ammonium group, the base resin is subjected to a chloromethylation treatment and then reacted with a tertiary amine such as trimethylamine to form a quaternary ammonium. By performing the conversion, a strongly basic anion exchange resin is obtained. Such a production method is well known in the art, and ion exchange resin beads produced by such a method are, for example, Dowex MONOSPHERE 650C (Dow Chemical), Amberlite IR-120B (Rohm & Haas), Dowex MONOSPHERE. 550A (Dow Chemical) and Amberlite IRA-400 (Rohm & Haas) are commercially available.

  In the electric desalination apparatus according to the present invention, a cation exchange fiber material and an anion exchange fiber material can be used as an ion exchanger filled in at least one of the desalination chamber and the polar chamber. As the ion exchange fiber material used for this purpose, a material obtained by introducing an ion exchange group into a polymer fiber substrate by a graft polymerization method is preferably used. The grafted substrate made of polymer fibers may be a polyolefin-based polymer, for example, a kind of single fiber such as polyethylene or polypropylene, or a composite fiber composed of a polymer having a different core and sheath. It may be. Examples of the composite fibers that can be used include core-sheath composite fibers having a polyolefin-based polymer, for example, polyethylene as a sheath component, and polymers other than those used as the sheath component, for example, polypropylene as a core component. . A material obtained by introducing an ion exchange group into such a composite fiber material using a radiation graft polymerization method is preferable as the ion exchange fiber material used in the present invention because it has excellent ion exchange capability and can be produced with a uniform thickness. Examples of the form of the ion exchange fiber material include woven fabric and nonwoven fabric.

  In addition, a combination of an ion exchange fiber material and a spacer or an ion conductive spacer provided with an ion exchange function may be used to fill at least one of the desalting chamber and the polar chamber.

  As an ion conductive spacer that can be used for this purpose in the electrical desalting apparatus according to the present invention, polyolefin polymer resin, for example, a polyethylene oblique network (net) conventionally used in electrodialysis tanks. ) Is used as a base material, and an ion exchange function is imparted thereto using a radiation graft polymerization method, since it is excellent in ion conductivity and dispersibility of water to be treated.

  The ion exchange fiber material and ion conductive spacer used in the electrical desalting apparatus according to the present invention are preferably manufactured using a radiation graft polymerization method. The radiation graft polymerization method is a technique in which a monomer is introduced into a substrate by irradiating a polymer substrate with radiation to form radicals and reacting the monomer with this.

  Examples of radiation that can be used in the radiation graft polymerization method include α rays, β rays, gamma rays, electron beams, ultraviolet rays, and the like. In the present invention, gamma rays and electron beams are preferably used. The radiation graft polymerization method includes pre-irradiation graft polymerization method in which a graft substrate is irradiated with radiation in advance and then brought into contact with the graft monomer and reacted, and simultaneous irradiation graft polymerization method in which radiation is irradiated in the presence of the substrate and the monomer. However, in the present invention, any method can be used. In addition, by the contact method of the monomer and the base material, a liquid phase graft polymerization method for performing polymerization while the base material is immersed in the monomer solution, a vapor phase graft polymerization method for performing the polymerization by bringing the base material into contact with the vapor of the monomer, Examples of the method include an impregnation gas phase graft polymerization method in which the base material is immersed in the monomer solution and then taken out from the monomer solution and reacted in the gas phase, and any method can be used in the present invention.

  As an ion exchange group introduce | transduced into fiber base materials, such as a nonwoven fabric, and a spacer base material, various cation exchange groups or anion exchange groups can be used without being specifically limited. For example, as the cation exchange group, a strong acid cation exchange group such as a sulfonic acid group, a neutral acid cation exchange group such as a phosphate group, a weak acid cation exchange group such as a carboxyl group, and the anion exchange group include primary to Weakly basic anion exchange groups such as tertiary amino groups, strong basic anion exchange groups such as quaternary ammonium groups can be used, or ion exchange having both of the above cation exchange groups and anion exchange groups The body can also be used.

  These various ion exchange groups are graft-polymerized using monomers having these ion-exchange groups, preferably radiation graft polymerization, or using polymerizable monomers having groups convertible to these ion-exchange groups. By converting the group into an ion exchange group after graft polymerization, it can be introduced into the fiber substrate or spacer substrate. Examples of monomers having ion exchange groups that can be used for this purpose include acrylic acid (AAc), methacrylic acid, sodium styrenesulfonate (SSS), sodium methallylsulfonate, sodium allylsulfonate, sodium vinylsulfonate, vinyl Examples thereof include benzyltrimethylammonium chloride (VBTAC), diethylaminoethyl methacrylate, dimethylaminopropylacrylamide and the like. For example, by performing radiation graft polymerization using sodium styrenesulfonate as a monomer, a sulfonic acid group that is a strongly acidic cation exchange group can be directly introduced into the substrate, and vinylbenzyltrimethylammonium chloride is used as a monomer. The quaternary ammonium group, which is a strongly basic anion exchange group, can be directly introduced into the base material by carrying out radiation graft polymerization. Examples of the monomer having a group that can be converted into an ion exchange group include acrylonitrile, acrolein, vinylpyridine, styrene, chloromethylstyrene, and glycidyl methacrylate (GMA). For example, glycidyl methacrylate is introduced into a substrate by radiation graft polymerization, and then a sulfonic acid 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 chloro After graft polymerization of methylstyrene, a quaternary ammonium group which is a strongly basic anion exchange group can be introduced into the substrate by immersing the substrate in an aqueous trimethylamine solution to perform quaternary ammonium formation.

  Furthermore, in the electric desalination apparatus according to the present invention, as proposed in the international application PCT / JP2003 / 017033 filed by the applicant, an anion exchange fiber material is provided in at least one of the desalting chamber and the electrode chamber. In addition, at least one of the layers of the cation exchange fiber material may be stacked and filled so as to cross the water direction. Examples described later show a form in which ion-exchange fiber materials are filled in a demineralization chamber by crossing them in the direction of water flow. Thus, since at least one of the layer of the anion exchange fiber material and the cation exchange fiber material is laminated so as to intersect the flow direction of the water to be treated, all of the water to be treated penetrates through the fiber material, Flows from one surface to the other. Therefore, since the water to be treated can be sufficiently supplied to the entire ion exchange fiber material having many usable ion exchange groups, these ion exchange groups can be effectively utilized. This greatly increases the number of ion exchange groups available per length of desalting chamber (the direction in which the water to be treated flows), so that the length of the desalting chamber is shortened compared to the conventional one. be able to. The ion exchange fiber material has the above-described problem of pressure loss. Thus, in the electric desalination apparatus according to the present invention, the length along the flow direction of the water to be treated in the desalination chamber is set to the conventional value. Since it can be made much shorter than that, the increase in the pressure loss of the water to be treated is not a problem in practice.

  Further, by adopting the configuration as described above, the contact portion between the anion exchanger and the cation exchanger in the desalting chamber, that is, the site of occurrence of hydrolysis is formed over the entire cross section of the water stream to be treated. In addition, it is possible to supply a large amount of water to be treated to the hydrolysis generation site to promote regeneration of the ion exchanger by hydrolysis and decomposition of weak electrolytes such as TOC and silica. In order to achieve such an object, it is preferable that the anion exchange fiber material and the cation exchange fiber material filled in the desalting chamber are in contact with each other.

  Hereinafter, the present invention will be described in more detail using specific examples. The following description shows specific examples of the present invention, and the present invention is not limited to these descriptions.

Production Example 1: Production of Cation Exchange Nonwoven Fabric A heat-sealed nonwoven 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 was used as a base material. . The nonwoven fabric substrate was irradiated with an electron beam (150 kGy) in a nitrogen atmosphere. The irradiated nonwoven substrate was immersed in a 10% methanol solution of glycidyl methacrylate and reacted at 45 ° C. for 4 hours. The non-woven fabric substrate after the reaction is immersed in a dimethylformamide solution at 60 ° C. for 5 hours to remove the polymer (homopolymer) not bonded to the base material, thereby obtaining a non-woven fabric material graft-polymerized with glycidyl methacrylate. It was. This grafted nonwoven fabric was immersed in a solution of sodium sulfite: isopropyl alcohol: water = 1: 1: 8 (weight ratio) and reacted at 80 ° C. for 10 hours to introduce sulfonic acid groups, and then hydrochloric acid (5 wt% ) To obtain a strongly acidic cation exchange nonwoven fabric (neutral salt decomposition capacity 471 meq / m ² ). This was designated as “cation exchange nonwoven fabric”.

Production Example 2: Production of anion exchange nonwoven fabric The same nonwoven fabric substrate as in Production Example 1 was irradiated with an electron beam (150 kGy) in a nitrogen atmosphere. Chloromethylstyrene (product name: CMS-AM, manufactured by Seimi Chemical Co., Ltd.) was passed through the activated alumina packed bed to remove the polymerization inhibitor, and nitrogen aeration was performed. The nonwoven fabric substrate that had been irradiated with the electron beam was immersed in the chloromethylstyrene solution after the deoxygenation treatment and reacted at 50 ° C. for 6 hours. Thereafter, the nonwoven fabric was taken out from the chloromethylstyrene solution, immersed in toluene for 3 hours to remove the homopolymer, and a nonwoven fabric material grafted with chloromethylstyrene was obtained. The graft nonwoven is quaternized in a trimethylamine solution (10% by weight) and then regenerated with an aqueous sodium hydroxide solution (5% by weight) to give a strongly basic anion having a quaternary ammonium group. An exchange nonwoven fabric (neutral salt decomposition capacity 350 meq / m ² ) was obtained. This was designated as “anion exchange nonwoven fabric”.

Production Example 3: Production of Cation Conductive Spacer As a base material for the ion conducting spacer, a polyethylene oblique network having a thickness of 1.2 mm and a pitch of 3 mm was used. Sodium styrenesulfonate as a graft monomer and acrylic acid as an auxiliary monomer were used. .
While cooling with dry ice, γ-rays (150 kGy) were irradiated to a polyethylene oblique mesh in a nitrogen atmosphere. This irradiated oblique network is immersed in a mixed monomer solution of sodium sulfonate and acrylic acid and reacted at 75 ° C. for 3 hours to obtain a graft oblique network material (cation conductive spacer) having a sulfonic acid group and a carboxyl group. Obtained. The neutral salt decomposition capacity was 189 meq / m ² and the total exchange capacity was 834 meq / m ² . This was designated as “cation conductive spacer”.

Production Example 4: Production of Anion Conductive Spacer While cooling with dry ice, the same polyethylene oblique mesh as in Production Example 3 was irradiated with γ rays (150 kGy) in a nitrogen atmosphere. This irradiated oblique network was immersed in a mixed monomer of VBTAC (vinylbenzyltrimethylammonium) and DMAA (dimethylacrylamide) and reacted at 50 ° C. for 3 hours to obtain a grafted oblique network of VBTAC and DMAA. The neutral salt decomposition capacity of the obtained grafted oblique network was calculated to be 198 meq / m ² . This was designated as “anion conducting spacer”.

Example 1
An electric desalination apparatus having the configuration shown in FIG. 5 was assembled. Between the cathode and the anode, a cation exchange membrane C (Tokuyama: NEOSEPTA CMB) and an anion exchange membrane A (Tokuyama: NEOSEPTA AHA) are alternately arranged, and the cation exchange membrane on the anode side and the anion exchange on the cathode side are arranged. There are six concentration chambers defined by the membrane, and five desalination chambers defined by the anion exchange membrane on the anode side and the cation exchange membrane on the cathode side, and are defined by the anode and cation exchange membrane on the outermost side. In addition, an electric desalination apparatus in which an anode chamber and a cathode chamber defined by a cathode and an anion exchange membrane were formed was constructed (in the drawing, description of an intermediate chamber arrangement was omitted). The thickness of the desalting chamber was 20 mm, the size of the electrode was 50 mm long × 50 mm wide, and the thickness of the concentration chamber and the electrode chamber was 3 mm. In the desalination chamber, the cation exchange nonwoven fabric (22 mm × 52 mm) produced in Production Example 1 and regenerated with hydrochloric acid, and the anion exchange nonwoven fabric (22 mm × 52 mm) produced in Production Example 2 and regenerated with alkali are shown in FIG. As shown, 25 sheets were alternately stacked and filled in a direction intersecting with the flow direction of the water to be treated (that is, horizontally). In both concentrating chambers, two anion conducting spacers produced in Production Example 4 are arranged on the anion exchange membrane in parallel with the anion exchange membrane, and 2 cation conducting spacers produced in Production Example 3 are placed on the cation exchange membrane surface. The plates were placed in parallel with the cation exchange membrane. Further, four cation conductive spacers manufactured in Production Example 3 are arranged in the anode chamber in parallel to the cation exchange membrane, and four anion conductive spacers manufactured in Production Example 4 are arranged in the cathode chamber in parallel to the anion exchange membrane. Placed.

Applying 0.4A direct current between both electrodes, 0.2MΩcm RO treated water (reverse osmosis membrane treated water: silica concentration 0.1-0.3ppm, water temperature 14 ° C-26 ° C, TOC concentration 120ppb) I passed water. Water flow is 50 Lh ⁻¹ (SV = 200 h ⁻¹ ) out of the RO treated water with a total flow rate of 62.5 Lh ⁻¹ , and is passed through the desalting chamber to 12 concentration chambers other than the concentration chamber adjacent to the cathode chamber. .5 Lh ^-1 was passed through. Each 5LH ^-1 of the desalination chamber outlet water (demineralized) 50Lh ^-1 was passed through the anode compartment as an anode chamber inlet water, the anode chamber outlet water into the concentrating compartment adjacent to the cathode compartment and a cathode compartment 2. Water was passed through 5 Lh ⁻¹ each. Outlet water (total 17.5 Lh ⁻¹ ) from each concentration chamber and cathode chamber was discharged as concentrated water. After 1 minute of operation, 18.2 MΩcm water was obtained as the desalination chamber outlet water (treated water), and a water quality of 18.0 MΩcm or more was stably obtained even after 5000 hours of operation. Further, the TOC concentration of the treated water was 7.2 ppb after 25 hours, and reached the equilibrium value at 5.3 ppb. The pressure loss in the desalination chamber and the concentration chamber was 0.05 MPa both after 24 hours and after 1000 hours of operation.

The operating voltage was 205 V after 24 hours of operation, 221 V after 1000 hours, and 252 V after 5000 hours.
When the electric desalting apparatus was disassembled after 5000 hours of operation and the inside was observed, no scale deposition was observed in any of the concentration chamber, anode chamber, or cathode chamber.

Comparative Example 1
Using an electric desalination apparatus having the same configuration as in Example 1, a 0.4 A direct current was applied between both electrodes, and 0.2 MΩcm RO treated water (reverse osmosis membrane treated water: silica concentration 0.1). -0.3 ppm, water temperature 14 ° C.-26 ° C., TOC concentration 120 ppb). As shown in FIG. 6, 50 Lh ⁻¹ (SV = 200 h ⁻¹ ) of RO treated water having a total flow rate of 70 Lh ⁻¹ is passed through the desalting chamber, and the anode chamber, the cathode chamber, and the concentration chamber. 20 Lh ^-1 was passed through.

  After 1 minute of operation, 18.2 MΩcm water was obtained as the desalination chamber outlet water (treated water), and a water quality of 18.0 MΩcm or more was stably obtained even after 5000 hours of operation. Further, the TOC concentration of the treated water became 7.5 ppb after 25 hours and reached the equilibrium value at 5.6 ppb. The pressure loss in the desalting chamber and the concentrating chamber was 0.05 MPa after 24 hours and 1000 hours, and 0.10 MPa after 5000 hours.

The operating voltage was 197 V after 24 hours of operation, 258 V after 1000 hours, and 531 V after 5000 hours.
After the operation for 5000 hours, the electric desalting apparatus was disassembled and the inside was observed. As a result, precipitation of white scale was confirmed in each concentration chamber and cathode chamber, and the components were analyzed. The main components were calcium salt and magnesium salt. It was.

  From the results of the above Examples and Comparative Examples, it can be seen that according to the present invention, it was possible to suppress the generation of scale in the concentration chamber and the polar chamber, particularly in the cathode chamber.

  According to the present invention, in the electric desalination apparatus, a part of the desalted water is supplied as the anode chamber inlet water, and the acidic water obtained as the anode chamber outlet water is used for the cathode chamber and the concentration chamber, in which scale easily occurs, particularly By supplying it to the concentrating chamber adjacent to the cathode chamber, it is possible to reduce the deposition of scale as compared with the conventional electric desalination apparatus. It is possible to provide an electric desalination apparatus capable of stably obtaining high-purity pure water throughout operation.

It is a conceptual diagram which shows the structure of the conventional electric desalination apparatus. It is a conceptual diagram which shows the structure of the electrical desalination apparatus which concerns on 1 aspect of this invention. It is a conceptual diagram which shows the structure of the electrical desalination apparatus which concerns on the other aspect of this invention. It is a conceptual diagram which shows the structure of the electrical desalination apparatus which concerns on the other aspect of this invention. It is a conceptual diagram which shows the structure of the electric desalination apparatus which concerns on 1 aspect of this invention used in Example 1. FIG. It is a conceptual diagram which shows the structure of the conventional electric desalination apparatus used in the comparative example 1.

Claims (6)

  By disposing a plurality of ion exchange membranes between the cathode and the anode, a desalting chamber and a concentration chamber are formed, and further, an anode chamber and a cathode chamber are respectively formed by the anode, the cathode and the ion exchange membrane adjacent thereto. An electric desalination apparatus that supplies a part of the desalted water discharged from the desalting chamber as the inlet water of the anode chamber and a part or all of the outlet water of the anode chamber as the inlet water of the concentrating chamber It is comprised so that the electric-type desalination apparatus characterized by the above-mentioned.   By disposing a plurality of ion exchange membranes between the cathode and the anode, a desalting chamber and a concentration chamber are formed, and further, an anode chamber and a cathode chamber are respectively formed by the anode, the cathode and the ion exchange membrane adjacent thereto. An electric desalination apparatus that supplies a part of the desalted water discharged from the desalting chamber as the inlet water of the anode chamber and a part or all of the outlet water of the anode chamber as the inlet water of the cathode chamber. It is comprised so that the electric-type desalination apparatus characterized by the above-mentioned.   By disposing a plurality of ion exchange membranes between the cathode and the anode, a desalting chamber and a concentration chamber are formed, and further, an anode chamber and a cathode chamber are respectively formed by the anode, the cathode and the ion exchange membrane adjacent thereto. An electric desalination apparatus for supplying a part of the desalted water discharged from the desalting chamber as the inlet water of the anode chamber, and a part or all of the outlet water of the anode chamber in the concentrating chamber adjacent to the cathode chamber An electrical desalination apparatus configured to be supplied as inlet water.   By disposing a plurality of ion exchange membranes between the cathode and the anode, a desalting chamber defined by the anion exchange membrane on the anode side and the cation exchange membrane on the cathode side, a cation exchange membrane on the anode side and the cathode side A concentration chamber defined by the anion exchange membrane is formed, and further, adjacent to the concentration chamber on the most electrode side, an anode chamber defined by the anode and the cation exchange membrane, and a cathode and an anion exchange membrane. A part of the outlet water discharged from the concentrating chamber adjacent to the anode chamber and supplying a part of the desalted water as the inlet water of the anode chamber. Or it is comprised so that all may be supplied as inlet water of a concentration chamber, The electric desalination apparatus characterized by the above-mentioned.   By disposing a plurality of ion exchange membranes between the cathode and the anode, a desalting chamber defined by the anion exchange membrane on the anode side and the cation exchange membrane on the cathode side, a cation exchange membrane on the anode side and the cathode side A concentration chamber defined by the anion exchange membrane is formed, and further, adjacent to the concentration chamber on the most electrode side, an anode chamber defined by the anode and the cation exchange membrane, and a cathode and an anion exchange membrane. A part of the outlet water discharged from the concentrating chamber adjacent to the anode chamber and supplying a part of the desalted water as the inlet water of the anode chamber. Alternatively, the electric desalination apparatus is configured to supply the whole as the inlet water of the cathode chamber.   By disposing a plurality of ion exchange membranes between the cathode and the anode, a desalting chamber defined by the anion exchange membrane on the anode side and the cation exchange membrane on the cathode side, a cation exchange membrane on the anode side and the cathode side A concentration chamber defined by the anion exchange membrane is formed, and further, adjacent to the concentration chamber on the most electrode side, an anode chamber defined by the anode and the cation exchange membrane, and a cathode and an anion exchange membrane. A part of the outlet water discharged from the concentrating chamber adjacent to the anode chamber and supplying a part of the desalted water as the inlet water of the anode chamber. Alternatively, an electrical desalting apparatus is configured to supply the whole as inlet water of a concentrating chamber adjacent to the cathode chamber.

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