JPH05131120A - Electric regeneration type desalting apparatus - Google Patents

Abstract

PURPOSE:To keep stable water quality over a long time, to enable desalting treatment from small capacity to large capacity and to facilitate maintenance and control. CONSTITUTION:In an electric regeneration type desalting apparatus wherein the desalting chamber of an electrodyalizer is packed with an ion exchanger to remove an ion from a liquid, an amphoteric ion exchanger having both of a cation exchange group and an anion exchange group is used as the ion exchanger. The ion exchanger is produced by utilizing radiation graft polymerization. By this constitution, the scaling-up of the desalting apparatus, the simplification of a production process and the stabilization of treated water quality are achieved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for removing ions from a liquid, and more specifically, to pure water production in the electric power, nuclear power, electronic industry, pharmaceutical manufacturing industry, food manufacturing industry and chemical product manufacturing. The present invention relates to an apparatus for desalting high-concentration liquid in a process in industry.

[0002]

2. Description of the Related Art Methods for removing ions from a liquid are roughly classified into three types: reverse osmosis, electrodialysis and ion exchange. It is said that reverse osmosis is advantageous for desalting high salt solutions such as seawater, electrodialysis for solutions having a lower salt concentration, and ion exchange for solutions having a lower salt concentration.

In conventional electrodialysis, ions are moved by using a potential difference as a driving force. Therefore, when the ion concentration becomes low, the current efficiency becomes poor and the concentration of demineralized water is limited to several hundred ppm. Kollsman
U.S. Pat. No. 2,815,320 discloses a method of filling a desalting chamber with an ion exchanger to increase current efficiency. This patent was over 30 years old, but there are many problems such as scale adhesion to membranes and ion exchange resins,
It was not put to practical use.

However, against the background of improvement in membrane performance, advancement of pretreatment methods, demand from the industrial world for desalination equipment that does not require complicated regeneration equipment, and social trends demanding resource and energy saving. , Electric regenerative desalination equipment has been reviewed. A modification of the earlier electric regenerative desalination apparatus is disclosed in Millipore Corporation U.S. Pat. No. 4,632,745 and is commercially available.

By the way, the current electric regenerative desalination system is
A cation exchange resin and an anion exchange resin are mixed and filled in the desalting chamber. This ion exchange resin has a diameter of 0.
It is a sphere of 4 to 0.6 mm. This is uniformly filled in a space partitioned by two sheets of ion-exchange resin to form a cell, and many layers of such a cell are stacked in a filter press shape to assemble the device. Thus, this method requires great care in the manufacturing process and is extremely complicated. For example, if the ion exchange resin or its crushed debris leaks from the end of the frame, the purity of demineralized water decreases. Further, since the differential pressure increases largely, the flow rate cannot be large. Although some devices are devised so that the ion exchange resin layer that has been contaminated or densified can be backwashed, it is difficult to uniformly disperse the cation and anion exchange resins.

The biggest reason for filling the ion exchange resin is to facilitate the movement of ions. Therefore, if the two ion-exchange resins are separated or unevenly distributed, the number of passages for ion movement is reduced, and there is a possibility that a predetermined purity cannot be obtained. On the other hand, in terms of maintenance, when replacing a defective cell, it is difficult to remove only that portion.

Due to the above-mentioned problems, the electric regeneration type desalination apparatus is suitable for a specific application such as a laboratory for which the capacity is small and the required water quality is not strict.

[0008]

In view of the above problems,
INDUSTRIAL APPLICABILITY The present invention solves various problems caused by filling with an ion exchange resin, can maintain stable water quality for a long period of time, can process small to large volumes, and is easy to maintain and manage. It is an object to provide a regenerative desalination apparatus.

[0009]

[Means for Solving the Problems] In order to solve the above problems,
The electric regenerative desalting apparatus according to the present invention is characterized in that an amphoteric ion exchanger sharing both a cation exchange group and an anion exchange group is used as an ion exchanger in a desalting chamber of an electrodialysis apparatus.

Although it is not impossible to produce an amphoteric ion exchanger even by the conventional technique, considering the fact that an ion exchanger in the shape of a fibrous or porous material is obtained, and practical problems, etc. It is optimal to use the graft polymerization according to the invention.

Generally, the radial graft polymerization method is suitable for the present invention in the following points.

(First point) Graft polymerization, as called graft polymerization, has a graft side chain formed from a main chain of a base material by a covalent bond from a microscopic point of view. A new function can be imparted while maintaining the physical and chemical properties of the base material that is the main chain. Conventional ion-exchange resins use a cross-linking agent such as divinylbenzene to form a three-dimensional network structure in order to maintain the bead shape and maintain the physical strength. Therefore, the ion exchange group introduced into such a structure has low mobility. In the radiation-induced graft polymerization, the graft chain having an ion-exchange group does not have a crosslinked structure, so that the mobility is large, which facilitates the movement of counterions and is preferable in the present invention.

(Second point) Radiation graft polymerization is
Since the shape of the base material can be selected relatively freely, it is possible to select a base material having a shape suitable for this application such as a membrane / fiber or a void material. For example, when a fiber is selected as the base material, the following characteristics are provided.

Woven and non-woven fabrics, which are single fibers or aggregates of single fibers, and products obtained by introducing ion exchange groups into these processed products by utilizing radiation graft polymerization can be handled in the form of a membrane or cloth, and therefore ion exchange can be performed. The desalting chamber sandwiched between the membranes can be easily loaded by optionally performing a molding process. This facilitates upsizing of the device.

If the fiber length is extremely short, the characteristics of the fiber will be lost, and the fiber will be cumbersome to handle like powder, so that the fiber length is preferably longer than the intermembrane distance of the ion exchange membrane. Further, although the cross section of the fiber is usually circular, a fiber or an assembly of fibers such as a star cross section, a cross cross section, and a hollow fiber having a larger surface area, for example, in consideration of the water quality of raw water and an increase in pressure loss. Can be selected.

(Third point) By applying fibers as a base material to radiation-induced graft polymerization, there are the following additional advantages.

(1) In the case of an ion exchange resin, in order for the ions in the resin to move and reach the membrane, it is difficult for the ions of the same type to move unless the resin of the same type is in close contact. If a mixture of ion exchange resins is used, they may separate during manufacturing or backwashing, and even if they are in an ideal mixed state,
Since the resins contact each other only at points, the ions must pass through several very narrow passages in order to move.

In the case of ion-exchange fibers produced by radiation-induced graft polymerization, since the passage of ions is secured as a continuum from one ion-exchange membrane to the other ion-exchange membrane, good treated water quality is stable. can get.

(2) The type, fiber diameter and packing density of the base material can be selected in consideration of the flow rate, pressure loss, current efficiency, etc., and the base material can be further processed and used.

(3) A woven fabric, a non-woven fabric, or the like, which is an aggregate of fibers, can also serve as a spacer by being loaded between the membranes, so that device assembly and maintenance / inspection work during manufacturing can be easily performed.

(Fourth point) It is also possible to use a net-like net-like material or a processed product thereof, a film-like material or a processed product thereof in addition to the fiber, and it has the same advantages as those of the fiber described above. is doing. In addition to the above, porous materials such as sponge-like materials and foams and processed products thereof are also suitable materials for the present invention.

Further points to be solved As described above, the radiation graft polymerization method is an advantageous method for the present invention. However, if the cation exchanger and the anion exchanger were produced separately, both of them would be eliminated. Further processing is necessary because the ion exchange groups must be evenly dispersed when loaded into the salt chamber. For example, even when a single fiber of an ion exchange fiber or a nonwoven fabric is produced, it is necessary to cut and mix or weave in some cases in order to disperse both ion exchange groups.

Solution Method However, the radiation graft polymerization method is a method in which various functional groups can be simultaneously introduced by a method of contacting the irradiated substrate with the polymerizable monomer. An amphoteric ion exchanger can be easily produced by introducing a monomer having a cation exchange group or convertible to a cation exchange group and a monomer having an anion exchange group or a monomer convertible to an anion exchange group into a substrate. You can If this is utilized, the ion-exchange groups will be dispersed and further processing will not be necessary.

(Specific Means) The ionizing radiation used in the radiation graft polymerization may be α, β, γ rays, electron rays or ultraviolet rays, and any of them can be used. However, γ rays, electron rays or the like can be used. It is particularly suitable for the present invention.

As a method for graft-polymerizing the substrate and the monomer, a simultaneous irradiation method in which the substrate and the monomer coexist in the presence of radiation, and a method in which only the substrate is previously irradiated with radiation,
There is a pre-irradiation method in which the polymerizable monomer and the substrate are brought into contact with each other, and any of them is possible in the present invention, but the pre-irradiation method has a feature that side reactions other than the graft polymerization are less likely to be generated.

The co-graft and the two-stage graft are suitable for producing an amphoteric ion exchanger having both cation and anion exchange groups by using the pre-irradiation method using γ rays or electron beams.

(Explanation of Co-Graft) In co-grafting, after irradiating the base polymer with radiation, a monomer having a cation exchange group or a monomer capable of converting into a cation exchange group and a monomer having an anion exchange group is used. Alternatively, the amphoteric ion exchanger can be produced by bringing the monomer capable of converting into an anion exchange group into contact with the substrate in a mixed state and performing a secondary treatment if necessary.

(Explanation of Two-Step Graft) In the two-step graft, after irradiation of the base polymer with radiation, a monomer having a cation exchange group or a monomer convertible into a cation exchange group is graft-polymerized on the base. Then, a monomer having an anion exchange group or a monomer convertible to an anion exchange group may be graft-polymerized on the base material. Two
Graft polymerization is possible even if the order in which the monomers are reacted is reversed, and can be appropriately determined in consideration of operability and the like. Radiation may be irradiated again before reacting the second stage monomer, but if the amount of radicals present is sufficient, the next reaction may be performed as it is. (Vapor / Liquid Phase Graft) Depending on how the base material is brought into contact with the monomer, it is classified into vapor phase graft polymerization in which the monomer is vapor and liquid phase graft polymerization in which the monomer is liquid. In the present invention, it can be appropriately determined in consideration of the vapor pressure of the monomer and the use.

The amphoteric ion exchanger manufactured in this manner does not require secondary processing such as mixing or weaving both the cation exchanger and the anion exchanger. It can be used as it is.

(Type of Substrate) As the organic polymer of the substrate used in the radiation graft polymerization of the present invention, any one can be used, but polyolefins typified by polyethylene, polypropylene, PTFE, vinyl chloride, etc. Particularly suitable are halogenated polyolefins typified by and olefin-halogenated olefin copolymers typified by ethylene-tetrafluoroethylene copolymer.

(Type of ion exchange group) As the ion exchange group to be introduced into the substrate, a cation exchange group is a sulfone group,
Strongly basic quaternary ammonium groups and lower amines such as carboxyl groups, phosphate groups, and anion exchange groups, that is, 3
General acidic / basic ion exchange groups such as weakly basic groups containing secondary amines, secondary amines or primary amines are practical, and are appropriately selected in consideration of the type of target liquid and required water quality. You can choose.

(Type of Monomer) The monomer having an ion exchange group used in the present invention includes acrylic acid, methacrylic acid, crotonic acid, itaconic acid, sodium vinyl sulfonate and sodium aryl sulfonate as a monomer having a cation exchange group. , Sodium styrene sulfonate, 2-acrylamido-2-methylpropane sulfonic acid, phosphorous acrylate, and the like, but are not limited to this range.

Examples of the monomer having an anion exchange group used in the present invention include arylamine, quaternary chloromethylstyrene, aminoalkyl acrylates, and the like, but are not limited to this range. ..

Examples of the monomer capable of introducing an ion exchange group include styrene, chloromethylstyrene, vinylpyridine, glycidyl acrylate, glycidyl methacrylate, acrylonitrile, and acrolein, but the monomer is not limited to this range.

Styrene or the like can be converted into a cation exchange group or an anion exchange group by a secondary reaction. In this case, it is sufficient to graft one kind of monomer, but it is necessary to control the secondary reaction and determine the amount of both ion-exchange groups introduced. It is one of the features of the present invention that both ion-exchange groups can be introduced by using only one kind of monomer.

Combined Use with Various Ion Exchangers In the present invention, the amphoteric ion exchanger produced by radiation graft polymerization may be used alone, or may be used in combination with an ordinary beaded ion exchange resin. Further, it may be used in combination with a non-amphoteric cation exchanger or anion exchanger produced by radiation graft polymerization. Furthermore, an amphoteric ion exchanger that does not depend on radiation graft polymerization and a non-amphoteric cation exchanger or anion exchanger that is produced by radiation graft polymerization may be used in combination, and it is appropriately selected in consideration of economical efficiency and required water quality. be able to.

The present invention will be described in more detail with reference to the following examples.

[0038]

【Example】

Example 1 A non-woven fabric having a basis weight of 50 g / m ² made of polypropylene fibers having a fiber diameter of 30 μm was irradiated with 100 KGy of accelerated electron beams in a nitrogen atmosphere using an electron beam accelerator (accelerating voltage 2 MeV, electron beam current 1 mA). After that, this was immersed in a mixed solution of acrylic acid and chloromethylstyrene, and co-graft-polymerized at a temperature of 50 ° C. for 8 hours to obtain a graft polymer having a graft ratio of 150%. Next, this non-woven fabric was immersed in a 2% aqueous solution of sodium hydroxide to convert the carboxyl group into a sodium type, then immersed in a 10% aqueous solution of dimethylamine, and reacted at a temperature of 50 ° C. for 2 hours. The ion exchange capacity per gram of this nonwoven fabric was 3.2 meq / g for cation exchange capacity and 2.1 meq for anion exchange capacity.
/ G. This amphoteric ion-exchange non-woven fabric was loaded into the desalting chamber of the experimental dialysis machine and treated with synthetic raw water (electric conductivity 187 μs / cm) in which salt was dissolved, resulting in an electric conductivity of treated water of 5.6 μs / cm. Fell. The treatment result of the raw water before loading the amphoteric ion exchanger was 27 under the same conditions.
The electric regenerative desalting charge of the present invention loaded with an amphoteric ion exchanger was effective for desalting treatment.

Example 2 A substrate similar to that in Example 1 was irradiated with an accelerated electron beam under the same conditions, and acrylic acid was heated at a temperature of 45 ° C.
At room temperature for 3 hours. Then, this was immersed in a solution of glycidyl methacrylate and reacted in the liquid phase at a temperature of 50 ° C. for 7 hours to carry out two-step graft polymerization. This non-woven fabric is immersed in a 10% aqueous solution of diethanolamine and the temperature is adjusted to 70
The reaction was carried out at ℃ for 3 hours. When the ion exchange capacity was measured, the calaion exchange capacity was 4.1 meq per 1 g of the nonwoven fabric.
/ G, and the anion exchange capacity was 2.4 meq / g.
When this non-woven fabric was loaded into the desalting chamber of the experimental electrodialyzer of Example 1 and treated with synthetic raw water under the same conditions, the electric conductivity of the treated water was lowered to 8.3 μs / cm, and zwitterion was detected. The electric regenerative desalination apparatus of the present invention loaded with an exchanger was effective for desalination treatment.

[0040]

The radiation graft polymerization has various advantages. However, if the cation exchanger and the anion exchanger were manufactured separately, both ion exchangers were woven before loading into the desalting chamber. Molding processing such as was necessary.
However, according to the present invention, it suffices to select the base material in consideration of the target water quality, the required water quality, the treatment flow rate, the pressure loss, etc., and the ion exchanger is not molded. Therefore, it has become possible to increase the size of the desalination apparatus, simplify the manufacturing process, and stabilize the quality of treated water.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hideo Kawazu 11-1 Haneda Asahi-cho, Ota-ku, Tokyo Inside the EBARA CORPORATION (72) Inventor Hideaki Sekiguchi 11-1 Haneda-Asahi-cho, Ota-ku, Tokyo In the EBARA CORPORATION (72) Inventor Takayuki Saito 11-1 Haneda-Asahi-cho, Ota-ku, Tokyo Inside the EBARA CORPORATION

Claims (5)

[Claims] 1. A device for removing ions from a liquid by filling a desalting chamber of an electrodialysis device with an ion exchanger, and the amphoteric ion exchange sharing both a cation exchange group and an anion exchange group as the ion exchanger. An electric regeneration type desalination device characterized by using a body. 2. The apparatus according to claim 1, wherein at least one of the ion exchangers is an amphoteric ion exchanger sharing both a cation exchange group and an anion exchange group. 3. The device according to claim 1, wherein at least one kind of the ion exchanger is manufactured by utilizing radiation graft polymerization. 4. A woven or non-woven fabric in which the base material used for the graft polymerization is an aggregate of short fibers, processed products thereof, reticulated materials and processed products thereof, film materials and processed products thereof, and void materials. A device according to any one of claims 1 to 3, which is selected from the group consisting of: and a processed product thereof. 5. The ion exchange group of the ion exchanger produced by utilizing the radiation graft polymerization, wherein the cation exchange group is a sulfone group, a phosphate group and a carboxyl group, and the anion exchange group is a quaternary ammonium salt, a tertiary amine, The device according to any one of claims 1 to 4, which is selected from a secondary amine and a primary amine.