JP2002263654A - Electrochemical water treating unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrochemical water treating unit which can suppress the adhesion of a hard component and can perform a stable operation by reducing the concentration ratio of the ions in the concentration chamber. SOLUTION: This electrochemical water treating unit is provided with an electrodialysis tank 1 obtained by bringing a plurality of units together so that electrode plates A, B2 and 3 are common, wherein each unit has a configuration in which a cation exchange membrane 4 and an anion exchange membrane 5 are alternately arranged, at least one deionization chamber and a concentration chamber are formed and the electrode plates A, B2 and 3 are disposed at both ends. In this configuration, a predetermined electric current can be supplied without applying high voltage and efficient deionization can be attained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrochemical device for removing cations such as sodium ions and calcium ions and anions such as chloride ions and sulfate ions mainly contained in service water such as tap water. It relates to a water treatment device.

[0002]

2. Description of the Related Art Generally, for desalination of seawater and production of salt from seawater, an electrodialysis method comprising an ion exchange membrane and an electric field applying means is used. In addition, an electrodialysis method that does not require a regeneration operation is widely used for the production of ion-exchanged water and ultrapure water used for semiconductor production and the like.

In the above-mentioned electrodialysis method, a cation exchange membrane and an anion exchange membrane are alternately arranged, and a voltage is applied while flowing water to be treated into a desalination chamber of an electrodialysis tank having a desalination chamber and a concentration chamber. Is applied to perform electrodialysis to produce deionized water. In the deionization chamber, the ion exchange membrane is self-regenerated using an acid and an alkali by water dissociation. In these devices, many efforts have been made in materials and configurations to improve desalination efficiency and reliability.

FIG. 7 is a schematic cross-sectional view of a conventional electrodialysis apparatus proposed in Japanese Patent Application Laid-Open No. 3-224688, which will be described below.

The anode plate 101 and the cathode plate 102 are housed in an anode chamber 103 and a cathode chamber 104, respectively. An anion exchange membrane 1 is provided between the anode chamber 103 and the cathode chamber 104.
05, desalination room 107, cation exchange membrane 106, concentration room 1
08 are alternately stacked to form a dialysis tank. Desalination room 10
A mixture of a regenerative weakly acidic cation exchanger and a regenerative weakly basic anion exchanger is accommodated in 7. The anode chamber 103 and the cathode chamber 104 are filled with an electrolyte solution for imparting conductivity. This can be achieved by circulating a part of the concentrated water.

[0006] The water to be treated is passed through the desalting chamber 107 and the concentrating chamber 108 of the electrodialyzer constructed as described above.
01 and the cathode plate 102 by applying a DC voltage to the
Predetermined deionized water can be obtained from the desalting chamber 107. The concentrated water in which the ion content is concentrated is supplied to the concentration chamber 10
8 will be discharged.

[0007] The ion exchanger contained in the desalting chamber is made of granular ion-exchange resin beads or ion-exchange fibers, or as described in JP-A-8-155272.
A sheet-shaped ion exchanger having a thickness of 0.1 mm to 1.1 mm has been proposed.

[0008]

However, many of the electrodialyzers that have been proposed in the past are mainly intended to obtain ultrapure water, and the water to be treated has an electric conductivity that has passed through a reverse osmosis membrane. 5 μS / cm (2.35 mg in NaCl concentration)
/ L), and the electrical resistance is as high as 200 KΩcm.
For this reason, as in the above-described conventional example, a device has been devised to fill the desalting chamber with an ion exchanger and reduce the applied voltage by reducing the electric resistance. However, when the water to be treated is water obtained by treating river water, groundwater, or the like, since the electric conductivity is as high as 100 to 300 μS / cm, the electric resistance is low, and the ion exchanger is installed in the desalination chamber. Electrodialysis is possible without filling. Therefore, it is possible to reduce the thickness of the desalting chamber (the distance between the cation exchange membrane and the anion exchange membrane) and further reduce the electric resistance. However, in order to treat a large amount of water, it is necessary to form a multilayered structure. As a result, since the distance between the electrodes is long, the electric resistance is increased, and there is a problem that it cannot be dealt with only by filling the deionization chamber with the ion exchanger.

Therefore, in order to solve these problems, the present invention provides an electrochemical water treatment apparatus capable of flowing a predetermined current without applying a high voltage and achieving efficient deionization. With the goal.

Another object of the present invention is to provide an electrochemical water treatment apparatus capable of reducing the concentration of ionic components in a concentration chamber to suppress the adhesion of a hardness component and capable of operating stably.

Another object of the present invention is to provide an efficient electrochemical water treatment apparatus capable of applying an optimum voltage according to the deionization rate of each electrolytic unit.

Another object of the present invention is to provide an electrochemical water treatment apparatus capable of simultaneously extracting alkaline ionized water suitable for drinking and acidic water having an astringent effect.

[0013]

In order to achieve the above object, the present invention provides a cation exchange membrane and an anion exchange membrane which are alternately arranged, and at least one or more deionization chambers and concentration chambers are formed. An electrochemical water treatment apparatus having a configuration in which a plurality of units each having an electrode pair disposed at both ends are stacked so as to have a common electrode.

The present invention also provides a water passage to the deionization chamber as a water passage that flows in parallel within the electrolysis unit and serially flows between the electrolysis units. An electrochemical water treatment apparatus is constituted by a water passage that flows in parallel between the electrolysis units and between the electrolysis units.

As a result, since the electric circuit can be driven at a low voltage, the electric circuit can be simplified and reduced in weight, and the adhesion of a hardness component can be prevented.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION According to the first aspect of the present invention, a cation exchange membrane and an anion exchange membrane are alternately arranged, and at least one or more deionization chambers and concentration chambers are formed.
This is an electrochemical water treatment system equipped with an electrodialysis tank in which units with electrode pairs arranged at both ends are stacked so that the electrodes are common, reducing the operating voltage and making the electric circuit simpler and lighter. it can.

According to a second aspect of the present invention, in the electrochemical water treatment apparatus according to the first aspect, means for passing water to the deionization chamber is provided in parallel within the unit and in series between the units. And a means for passing water to the concentration chamber is constituted by a water passage flowing in parallel between the units and between the units.Since the ion concentration in the concentration chamber does not become extremely high, the hardness component Adhesion can be prevented.

According to a third aspect of the present invention, in the electrochemical water treatment apparatus according to the first aspect, a potential is independently applied to the anodes of the electrode pairs. In addition, since an optimal voltage according to the electric conductivity of each electrolytic unit can be applied, efficient operation can be performed.

According to a fourth aspect of the present invention, in the electrochemical water treatment apparatus according to the first aspect, water passed between the anode of the electrode pair and the opposed ion exchange membrane is used. It separates and takes water, and separates and takes in water that has passed between the cathode and the opposing ion exchange membrane, so that alkali ion water and acidic water can be taken out at the same time.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1) FIG. 1 is a sectional view showing a configuration of an electrochemical water treatment apparatus according to Embodiment 1 of the present invention, and FIG. FIG. 3 is a plan view, FIG. 3 is a plan view of a concentrating unit in the electrochemical water treatment device, and FIG. 4 is a perspective view showing a positional relationship between a deionizing unit and a concentrating unit in the electrochemical water treatment device.

As shown in FIG. 1, the electrodialysis tank 1 in the electrochemical water treatment apparatus has the following configuration. That is, the cation exchange membrane 4 (for example, Asahi Kasei K501) and the spacer 6 (for example, Nippon Valqua thermoplastic polyurethane elastomer, trade name: Taffletan) between the two electrode chamber cells 17 in which the electrode plates A2 and B3 are arranged. , An anion exchange membrane 5 (for example, Asahi Kasei A
501), the order of the spacers 6 is set as one set, and multiple layers are stacked. Further, the next electrode plate A2 is shared with the electrode plate B3.
Are stacked in layers in the order of the anion exchange membrane 5, the spacer 6, the cation exchange membrane 4, and the spacer 6 as a set between the electrode chamber cells 17 in which. Subsequently, a large number of cation exchange membranes 4, spacers 6, anion exchange membranes 5, and spacers 6 are grouped in order between the electrode chamber cells 17 in which the next electrode plate B3 is arranged with the electrode plate A2 in common. Laminate.

The electrodialysis layer 1 is completed by tightening and fixing the thus repeatedly laminated ones from the outside. The thinner the spacer 6 is, the more efficient the electrodialysis can be. However, if the thickness is too thin, the pressure increases and a large amount of flow cannot be flowed.

In the figure, reference numeral 7 denotes a water inlet for the desalination chamber, 8 denotes a water inlet for the concentration chamber, 9 denotes a water inlet for the pole room, 10 denotes a water outlet for the desalination chamber, 11 denotes a water outlet for the concentrated water, and 12 denotes a water outlet for the polar water ( Cathodes) and 13 are polar water outlets (anodes).

Next, the water passage will be described with reference to FIGS. 2, 3 and 4. Spacer 6 is spacer center part 1
In order to avoid contact between the deionized portion 5 and the hollow or the ion exchange membranes, the deionized portion 5 has a shape in which a projection is partially formed from the outer frame portion toward the hollow portion. Water entering the central deionization section 18 is connected to the right-angled communication hole 14 penetrating the distal end of the spacer opening 16 opened toward the outer frame so as to be orthogonal to the membrane. The right-angled communication hole 14 penetrating perpendicular to the membrane is arranged in the outer frame portion, is arranged so as to penetrate the laminated body of the anion exchange membrane 5, the spacer 6, and the cation exchange membrane 4, and has the electrode plate A2 (+ ) Side, the spacer 6 in which the anion exchange membrane 5, the spacer 6, and the cation exchange membrane 4 are laminated in this order is opened toward the spacer hollow portion 15, and from the adjacent electrode plate A2 (+) side, the positive The spacers 6 laminated in the order of the ion exchange membrane 4, the spacer 6, and the anion exchange membrane 5 are closed toward the spacer hollow portion 15.

With such a structure in which the opening and the closed portion are alternately repeated, a water passage through which water can pass through all the deionized portions 18 is formed by the right-angled communication holes 14. The water discharge channel is disposed at a position substantially opposed to the water inlet and the central deionization unit, and is connected to the right-angled communication hole 14 orthogonal to the membrane similarly to the water inlet.

On the other hand, the water entering the concentrating section is supplied to the electrode plate A2 (+)
From the side, the cation exchange membrane 4, the spacer 6, and the anion exchange membrane 5 are stacked in this order. The spacer 6 has a spacer opening 16 opened from the spacer hollow portion 15 to the outer frame portion, and a deionization portion 18. Has a right-angled communication hole 14 at a position different from the water inlet channel. The spacer portion in which the anion exchange membrane 5, the spacer 6, and the cation exchange membrane 4 are laminated in this order from the electrode plate A2 (+) side is not connected to the rectangular communication hole 14 and the hollow portion. The water discharged from the concentrating unit is disposed at a position substantially opposite to the water input unit with the hollow part interposed therebetween, and is connected to the right-angled communication hole 14 via the spacer opening 16. On the other hand, electrode water
Independently of the other water passages, water enters the hollow space between the electrode plates A, B2, 3, the spacer 6, the anion / cation exchange membranes 4, 5 and discharges water from the other end. Anode water and cathodic water are obtained depending on the polarity of the electrodes.

The specific path of the water to be treated will be described. The water to be treated passed through the deionization section 18 between a pair of electrodes is desorbed by applying a DC voltage to the electrode plates A, B2 and 3. It is ionized and collected, and the next electrode plates A, B2,
Water is passed through the deionization section 18 between the three. By repeating this, water with a gradually higher deionization rate is generated. The feature of this method is that water with a high deionization rate can be obtained at a low applied voltage.

FIG. 5 shows the relationship between the voltage and the deionization rate.
The deionization rate is linear in a low voltage region, but deviates from the straight line as the voltage increases. This is thought to be due to the fact that the current flowing as the voltage is increased is used for electrolysis of water other than ion separation in water, so that the efficiency decreases. Therefore, an optimal ion separation method is to increase efficiency by performing low-voltage and multi-stage processing.

On the other hand, it is not necessary to concentrate the concentrated water by performing a multi-stage treatment. On the contrary, if the concentration is too high, a phenomenon occurs in which ions diffuse to the deionization chamber side against the potential gradient due to the concentration diffusion, which is not convenient. For this reason, the concentrated water flows from the same direction at the same time over all of the plurality of concentration chambers in a plurality of stages, so that a single-stage treatment is performed.

Further, the electrode water does not need to be subjected to multi-stage treatment. When the electrode water is treated in multiple stages,
Becomes too high, and calcium precipitation easily occurs. In the case of drinking as alkaline ionized water, a pH of about 9 is appropriate, so that one-stage treatment is sufficient, and the amount of treated water is increased by parallel treatment.

Hereinafter, specific examples of the deionization treatment will be described. As the conditions, as raw water, distilled water prepared by adjusting calcium chloride to a hardness of 100 mg / L was used. Electrodialysis layer, electrode area 100mm x 180mm
The distance between the anion exchange membrane and the cation exchange membrane, that is, the thickness of the spacer was set to 0.75 mm. The number of layers was six in the deionization chamber and seven in the concentration chamber. The flow rate was 2 L / min in the deionization chamber, 0.5 L / min in the concentration chamber, and 0.5 L / min for the anode and cathode in the pole chamber. The treatment was performed at an applied voltage of 60 V using a DC power supply.

FIG. 6 shows the relationship between the number of stages, the deionization rate and the current. The number of stages was 1, 2, 3, and 4, and the deionization rate was measured. The deionization rate per stage was around 50%, but the total deionization ratio exceeded 90% at the third stage, and was at a practical level.

According to a second aspect of the present invention, in the electrochemical water treatment apparatus according to the first aspect, means for passing water to the deionization chamber is provided in parallel within the unit and in series between the units. And a means for passing water to the concentration chamber is constituted by a water passage flowing in parallel between the units and between the units.Since the ion concentration in the concentration chamber does not become extremely high, the hardness component Adhesion can be prevented.

[0035]

As is clear from the above description, the electrochemical water treatment apparatus of the present invention employs a multistage treatment and uses a part of the electrodes in common.
In addition, it can be performed in one electrodialysis tank, which has the effect of improving deionization efficiency and realizing a low-cost electrodialysis tank.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a configuration of an electrochemical water treatment apparatus according to a first embodiment of the present invention.

FIG. 2 is a plan view of a deionization part in the electrochemical water treatment apparatus.

FIG. 3 is a plan view of a concentration unit in the electrochemical water treatment apparatus.

FIG. 4 is a perspective view showing a positional relationship between a deionization part and a concentration part in the electrochemical water treatment apparatus.

FIG. 5 is a diagram showing voltage versus deionization rate in the electrochemical water treatment apparatus.

FIG. 6 is a diagram showing the number of dialysis stages versus the deionization rate in the electrochemical water treatment apparatus.

FIG. 7 is a schematic sectional view of a conventional electrodialysis apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electrodialysis tank 2 Electrode plate A 3 Electrode plate B 4 Cation exchange membrane 5 Anion exchange membrane 6 Spacer 7 Deionization room water inlet 8 Concentration room water inlet 9 Electrode room water inlet 10 Deionization room water outlet 11 Concentrated water spout Water outlet 12 Polar water spout (cathode) 13 Polar water spout (anode) 14 Right-angled communication hole 15 Spacer hollow 16 Spacer opening 17 Electrode chamber cell 18 Deionizer

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4D006 GA17 HA47 JA04A JA04B JA41A JA42A JA43A JA44A KB11 KE02Q KE03Q KE17Q MA03 MB07 PB06 PB25 PB26 PC02 4D025 AA02 AB07 AB14 AB18 BA08 BA13 BB15 DA05 DA06 4D061EB EB DB EB19

Claims (4)

[Claims] 1. A unit in which cation exchange membranes and anion exchange membranes are alternately arranged, at least one or more deionization chambers and concentration chambers are formed, and a unit in which electrode pairs are arranged at both ends is a common electrode. An electrochemical water treatment apparatus, comprising a plurality of stacked electrodialysis tanks. 2. The means for passing water to the deionization chamber is constituted by a water passage which flows in parallel within the unit and the means for flowing in series between the units. The means for passing water to the concentrating chamber is provided in parallel between the units and between the units. 2. The electrochemical water treatment apparatus according to claim 1, wherein the apparatus is constituted by a flowing water passage. 3. The electrochemical water treatment apparatus according to claim 1, wherein an electric potential is independently applied to the anodes of the electrode pairs. 4. An electrode pair, in which water passed between an anode and an opposing ion exchange membrane is separated and taken, and water passed between a cathode and an opposing ion exchange membrane is separated. The electrochemical water treatment apparatus according to claim 1, wherein the water is taken out.