JPH06158378A - Electrode for electrolyzing drinking water and manufacture of the same and ionized water forming device - Google Patents

Abstract

PURPOSE:To obtain an electrode for electrolyzing drinking water which has a long life and excels in durability and does not generate much chlorine compounds by providing a covering layer of platinum metal and tantalum oxide contg. Pi and Ta in the specified ratio on an electrically conductive substrate. CONSTITUTION:A covering layer of platinum metal and tantalum oxide and if necessary, iridium oxide contg. 30-99mol% Pi and 1-70mol% Ta and if necessary, <=40mol% Ir expressed in terms of metal is provided on an electrically conductive substrate. The covering layer is formed by applying solution contg. platinum compounds and tantalum compounds and if necessary, iridium compounds to the substrate before giving it heat treatment in an oxidizing atmosphere. Consequently, an electrode for electrolyzing drinking water of long life used in an ionized water forming device for getting alkaline ionized water is obtained. The electrode is used with anodic or cathodic inversion repeated and excels in durability and simultaneously does not generate much chlorine compounds.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode for electrolyzing drinking water, a method for producing the same, and an ion water producing apparatus using this electrode as an electrode for electrolysis.

[0002]

2. Description of the Related Art Conventionally, metallic titanium has been used as a conductive substrate.
A metal electrode provided with a coating layer of a white metal group metal or its oxide thereon is used in various fields of the electrolytic industry.

However, the above electrodes are rarely used for drinking water, especially for sterilizing tap water or for ionized water, except for some electrodes. Electrolysis of tap water has important purposes as follows. In other words, river lake water, which is the source of tap water, contains silicon, sodium, potassium, which are the main components of the crust,
Contains metal ions such as aluminium, magnesium and iron. These metal ions have a content of a few ppm to a few tens of ppm, and are sources of mineral water suitable for living organisms.

On the other hand, tap water, unlike the above-mentioned mineral water, is not sufficiently sterilized by filtration alone and must be safe even if the water pipe should be contaminated.
Sustainable chlorine is injected as a disinfectant. This amount is stipulated in the Enforcement Regulations of the Water Supply Act so that the residual chlorine amount at the end of the distribution pipe is 0.1 ppm or more for the free form and 0.4 ppm or more for the combined form. However, this chlorine having bactericidal activity not only impairs the taste of water but also produces chlorine compounds such as trihalomethane which may be a carcinogen, so it is desirable to remove chlorine as much as possible.

For this reason, as a conventional chlorine removing method, household water purifiers have been widely used for improving the quality of drinking water by removing free chlorine and decalcifying tap water before drinking. The water purifier has a structure in which an activated carbon filter bed or the like is attached to a tap water faucet, and is a method of keeping a wet state at all times.

As another removing method, drinking water is introduced into the electrolysis chamber, electrolyzed and taken out, and then ice-making is performed. Furthermore, as another method, an electrolytic cell (electrolysis chamber) is defined by a microporous diaphragm,
Conventionally, there has been proposed a device in which an anode made of platinum-plated titanium or ferrite and a cathode made of stainless steel are immersed in an electrolytic cell and a DC voltage is applied to these electrodes.
This device forms a DC electric field between the electrodes to collect metal ions such as sodium, potassium, and calcium on the cathode side, while collecting anions such as chlorine ions and bicarbonate ions on the anode side, and collects them in the electrolytic cell on the cathode side. Is an alkaline mineral (ionized water) containing a large amount of metal ions and a small number of anions, which is generated by electrolysis of water.

However, when mineral water is produced by using a conventional ferrite electrode as an anode, it is limited to a plate shape or a rod shape in terms of manufacturing and does not become thin. Also, because it is ceramic, it is susceptible to shock.

Further, an electrode obtained by plating or coating a titanium base material with a noble metal or a noble metal oxide is also used for this purpose. For example, an electrode coated with an oxide of ruthenium and titanium or an electrode coated with an oxide of ruthenium and tin is known as an anode for chlorine generation (Japanese Patent Publication Nos. 46-21884 and 4).
No. 8-3954, Japanese Patent Publication No. 50-11330).

However, ruthenium-based oxide electrodes cannot be used because ruthenium oxide is a harmful substance for food hygiene. Further, an electrode having a high efficiency of generating hypochlorous acid such as palladium oxide (Japanese Patent Publication No. 55-35473, Japanese Patent Publication No.
No. 5-8595), hypochlorous acid leaks into treated water such as alkaline water and has a chlorine odor, which is not suitable as drinking water. In addition, the platinum-plated titanium electrode or platinum-coated titanium electrode that has been conventionally used is safe in terms of food hygiene, the efficiency of hypochlorous acid generation at the anode is low, and there is no leakage of hypochlorous acid in alkaline water. Although it is less suitable, it is necessary to switch the anode and cathode because calcium ions or magnesium ions adhere to the surface of the cathode as hydroxides to hinder the performance of the device while electrolysis is continued in the device. In this case, since the anode and cathode are switched under a high voltage, these electrodes have a short electrode life.

Further, using these electrodes as an anode,
When used as an oxygen generating electrode, the electrode life is also shortened. This problem becomes more remarkable as the frequency of use increases.

Further, as electrodes for oxygen generation, iridium oxide-based and iridium oxide-tantalum oxide-based electrodes (JP-A-63-235493, JP-A-2-61083, JP-A-3-193889, JP-B-60). -2
No. 1232, Japanese Patent Publication No. 60-2207, Japanese Patent Application Laid-Open No. 57-116786, Japanese Patent Application Laid-Open No. 60-184690.
No.) is known, but sufficient corrosion resistance cannot be obtained during polarity reversal under high voltage. Further, there is a problem that the cost becomes commercially high.

[0012]

SUMMARY OF THE INVENTION A first object of the present invention is to provide an electrode for drinking water electrolysis, which has a long life and is excellent in durability even when the polarity reversal between electrodes is repeated when alkaline ionized water is obtained. To provide.

A second object of the present invention is to provide an electrode for electrolysis of drinking water which produces less chlorine components in addition to the above objects.

Another object of the present invention is to provide a manufacturing method capable of advantageously manufacturing the above electrode and an ionized water generator using the above electrode.

[0015]

DISCLOSURE OF THE INVENTION The present inventors have conducted various studies to develop an electrode which has excellent durability and can be used for electrolysis of drinking water over a long period of time. It has been found that by adding a specific proportion of tantalum oxide to platinum metal on a conductive substrate, the adhesion strength is strong without increasing the electric resistance, and further deterioration of the substrate due to titanium oxidation can be suppressed when it is used as an anode after polarity reversal. It was also found that the addition of iridium oxide in a specific ratio improves durability. The present invention has been completed based on these findings.

That is, the above objects are as follows (1) to (1
This is achieved by the configuration of 0). (1) An electrode for drinking water electrolysis, comprising a conductive substrate and a coating layer of platinum metal containing 30 to 99 mol% of platinum and 1 to 70 mol% of tantalum in terms of metal and tantalum oxide. (2) The coating layer further comprises iridium 40 in terms of metal.
The electrode for drinking water electrolysis according to (1) above, containing less than or equal to mol%. (3) The above (1) used as an anode for electrolyzing drinking water
Or the electrode for drinking water electrolysis of (2). (4) The above (1) or (2) used for the anode and / or the cathode when the polarities of the anode and the cathode are reversed and used.
Electrode for drinking water electrolysis. (5) A cathode and an anode are arranged in the electrolysis chamber via a diaphragm, and both electrodes are energized to obtain alkaline ionized water on the cathode side and acidic water on the anode side, which is used as the anode (1).
Or the electrode for drinking water electrolysis of (2). (6) When a cathode and an anode are arranged in the electrolysis chamber through a diaphragm and both electrodes are energized to obtain alkaline ionized water on the cathode side and acidic water on the anode side, the polarities of the cathode and the anode The electrode for drinking water electrolysis according to (1) or (2) above, which is used as a cathode and an anode when used by reversing. (7) After coating a solution containing a platinum compound and a tantalum compound on a conductive substrate, heat treatment is performed in an oxidizing atmosphere to obtain 30 to 99 mol% of platinum and 1 to 70 mol% of tantalum in terms of metal. A method for producing an electrode for drinking water electrolysis, which comprises forming a coating layer of contained platinum metal and tantalum oxide. (8) After coating a solution containing a platinum compound, a tantalum compound, and an iridium compound on a conductive substrate, heat treatment is performed in an oxidizing atmosphere to obtain platinum of 30 to 99 mol% and tantalum of 1 to 70 in terms of metal. A method for producing an electrode for drinking water electrolysis, which comprises forming a coating layer of platinum metal, tantalum oxide, and iridium oxide containing mol% and 40 mol% or less of iridium. (9) 2 inside the electrolysis chamber having the purified water inlet through the diaphragm
In one or more electrodes to define a compartment to define a compartment, each compartment is provided with an outlet, in the ionized water generation device for obtaining alkaline ionized water or acidic water from the outlet by energizing between the electrodes, An ionized water producing device using the electrode for electrolysis according to (1) or (2) above at least as an electrode used as an anode. (10) An ionized water generator which uses the electrolysis electrode of (1) or (2) for all of the electrodes, in which the polarities of the electrodes are reversed and electricity is applied between the electrodes.

[0017]

Specific Structure The specific structure of the present invention will be described in detail below.

Examples of the conductive substrate used in the electrode of the present invention include valve metals such as titanium, tantalum, zirconium and niobium, or alloys of two or more metals selected from these valve metals.

In the electrode of the present invention, a coating layer made of platinum metal and tantalum oxide is provided on these conductive substrates. The proportions of platinum and tantalum in this layer must be in the range of 99 mol% to 30 mol% platinum and 1 mol% to 70 mol% tantalum in terms of metal. Good results are obtained only within this range. If the tantalum exceeds 70 mol%, the overvoltage is increased and the life is shortened. Moreover, the electrode life is shortened when the polarity is reversed. On the other hand, if tantalum is less than 1 mol%, the adhesion strength is not obtained, and the effect of suppressing the oxidation of the substrate is not sufficiently exerted. In addition, the electrode life due to polarity reversal becomes insufficient.

[0020] To fully achieve the intended effect, 0.01 mg / cm ² platinum in terms of metal in the coating layer to 5 mg / cm ²
It is preferable to apply it in such a ratio. 0.01 mg / cm ²
If it is less than 5%, the effect of the present invention cannot be obtained, and if it exceeds 5 mg / cm ² , the adhesion strength is lowered.

Further, in the present invention, the coating layer is made of platinum metal, tantalum oxide and iridium oxide. The ratio of platinum, tantalum, and iridium in this layer is, in terms of metal, 99 mol% to 30 mol% of platinum, 1 mol% to 70 mol% of tantalum, and 40 mol% or less of iridium,
It is necessary that it is preferably in the range of 35 to 1 mol%. Thus, by adding iridium oxide in addition to the above composition, the life of the electrode is extended particularly when it is used as an anode, and the life of the electrode in polarity reversal is also sufficient. The reason why the iridium content is 40 mol% or less is that if the iridium content exceeds 40 mol%, the electrode life due to polarity reversal becomes short. Further, when used as an anode, chlorine is likely to be generated, so that it is not suitable for use when obtaining alkaline ionized water for beverages.

The proportion of platinum in the coating layer may be the same as in the above-mentioned coating layer of platinum metal and tantalum oxide.

Next, a method of manufacturing the above-mentioned electrode for water electrolysis will be described. In the case of a coating layer of platinum metal and tantalum oxide, after applying a solution containing a platinum compound and a tantalum compound on a conductive substrate, heat treatment is performed in an oxidizing atmosphere to obtain 99 mol% to 30 mol% of platinum and A coating layer made of platinum metal containing 1 mol% to 70 mol% of tantalum and tantalum oxide is provided.

At this time, the coating solution used is a compound that becomes platinum metal by thermal decomposition, such as chloroplatinic acid (H ₂ Pt).
Cl ₆ .6H ₂ O), a platinum compound such as platinum chloride, and a compound that becomes tantalum oxide by thermal decomposition, for example, a tantalum halide such as tantalum chloride or a tantalum compound such as tantalum alkoxide such as ethoxy tantalum are prescribed. It can be prepared by dissolving in a suitable solvent in a ratio. The heat treatment in an oxidizing atmosphere is carried out by applying the coating solution on the conductive substrate, drying, and then firing in the presence of oxygen, preferably at a temperature in the range of 400 to 650 ° C. This operation is repeated a plurality of times until the required loading amount is obtained, and the electrode of the present invention is obtained.

On the other hand, in the case of a coating layer of platinum metal, tantalum oxide and iridium oxide, a solution containing a platinum compound, a tantalum compound and an iridium compound is applied on a conductive substrate and then heat treated in an oxidizing atmosphere. Then, a coating layer composed of platinum metal containing 99 mol% to 30 mol% of platinum, 1 mol% to 70 mol% of tantalum, and 40 mol% or less of iridium, tantalum oxide, and iridium oxide is provided.

At this time, the coating solution used is a compound that becomes platinum metal by thermal decomposition, such as chloroplatinic acid (H ₂ PtC).
l ₆ · 6H ₂ O), and platinum compounds such as chloroplatinic, compounds comprising tantalum oxide by thermal decomposition, such as a compound comprising iridium oxide, tantalum chloride, the tantalum compound and the thermal decomposition of tantalum alkoxides such chloroiridic acid It can be prepared by dissolving the iridium compound and the iridium compound in a suitable solvent. After applying the coating solution prepared in this manner, a heat treatment is carried out in an oxidizing atmosphere to form a desired amount of the coating layer. The heat treatment in an oxidizing atmosphere is performed by applying the coating solution on a conductive substrate, drying it, and then firing it in the presence of oxygen, preferably at a temperature in the range of 400 to 650 ° C. This operation is repeated multiple times until the required loading amount is reached. In this way, a platinum-tantalum oxide-iridium oxide coating layer having a desired supporting amount is applied, and the electrode of the present invention is obtained.

The oxygen partial pressure in the oxidizing atmosphere is generally 0.05 atm or more.

By thus performing the heat treatment for forming the coating layer in an oxidizing atmosphere, the oxidation of tantalum oxide or iridium oxide is sufficient and the durability of the electrode is improved. On the other hand, when the heat treatment for forming the coating layer is not performed in an oxidizing atmosphere, the oxidation becomes insufficient and the metal exists in a free state, so that the durability of the electrode deteriorates.

The electrode for electrolysis of the present invention is provided as an anode in an electrolytic bath or an electrolytic chamber of drinking water. At this time, the oxygen overvoltage is low and the life is long. Also, less chlorine is generated. In particular, from the viewpoint of life, it is preferable to use a coating layer containing iridium oxide. At this time, this can also be used as a cathode.

The electrode for electrolysis according to the present invention is used as a cathode and an anode when electrolysis is performed by appropriately reversing the polarities of the electrodes in the case where alkaline ionized water is produced on the cathode side into drinking water. Is preferred. During the production of such alkaline ionized water, calcium or magnesium adheres to the cathode to lower the electrolysis efficiency. For this reason, the cathode and the anode are reversed to energize to remove these deposits to recover the electrolytic efficiency, that is, the water-forming efficiency. The electrode of the present invention has a long life even if polarity reversal is repeated, which is advantageous when such a usage method is adopted. Further, when the electrode of the present invention is used as an anode, chlorine (that is, hypochlorous acid) is hardly generated by electrolysis. Therefore, alkaline ionized water obtained by electrolysis on the cathode side has no chlorine leakage and is suitable for drinking water. It should be noted that, when used as an anode under conditions where the frequency of polarity reversal is low, a coating layer containing iridium oxide is preferable from the viewpoint of life.

FIG. 1 shows an example of the configuration of an ionized water generator (water generator) having an electrolytic cell for obtaining alkaline ionized water.

As shown in FIG. 1, the water generator 1 includes a calcium adding means 11 for adding calcium in accordance with the water quality of the raw water W ₀ introduced from the water source 2, and a purifying means for purifying water after adding calcium. 12, electrolysis means 13 which is an electrolyzer for electrolyzing purified water to obtain alkaline ionized water and acidic water
Have.

The calcium is added in the calcium adding means 11 when the well water or the like is used as the raw water, in order to replenish the ions as minerals and to make it alkaline easily. Usually, calcium addition is not so necessary in tap water containing hypochlorous acid. Calcium is added as calcium lactate or the like.

The purifying means 12 is provided with an antibacterial activated carbon and a hollow membrane, and removes chlorinated odor, red rust, various bacteria, etc.
It purifies water.

The electrolysis means 13 has a cathode 31 and an anode 32 arranged in a tank 131 via a diaphragm M, and has a structure in which purified water is introduced through an inlet 131a to energize both electrodes 31, 32. Has become. The electrode for electrolysis of the present invention is applied to the cathode 31 and the anode 32.

In FIG. 1, a hot water prevention valve 14 for preventing hot water from flowing into the calcium adding means 11 is installed upstream of the calcium adding means 11. Further, a water drain valve 16 for draining water of the calcium adding means 11 is installed. Further, a flow rate sensor 17 is installed downstream of the purification means 12 and upstream of the electrolysis means 13, and controls so that the amount of water flowing into the electrolysis means 13 is an appropriate amount.

A solenoid valve 19 is installed downstream of the outlet 131c of the electrolyzing means 13. Further, at the downstream of the other outlet 131b, a pH adjusting means 18 for setting the pH when alkaline ionized water is obtained via this flow path 18
Is provided. Further, the electrolysis means 13 is provided with a switching means 15 for reversing the polarities of the cathode 31 and the anode 32 in the electrolysis means 13.

In the structure of FIG. 1, the pH adjusting means 18
The water W ₁ obtained through is alkaline ionized water,
Water W ₂ obtained via the solenoid valve 19 is acidic water.

In the configuration of FIG. 1, the raw water W ₀ of the water source 2 is introduced into the calcium adding means 11 via the hot water prevention valve 14 (arrow f1 in the figure). However, when the water is hot water, the action of the hot water prevention valve 14 prevents the water from flowing into the calcium adding means 11 and flows in the direction of the arrow f2 in the figure. The water to which calcium has been added by the calcium adding means 11 is introduced into the purifying means 12. Here, the purified water obtained is introduced into the tank 131 of the electrolysis means 13 from the inlet 131a via the flow rate sensor 17. The purified water is electrolyzed here. By this electrolysis, alkaline ionized water W ₁ is obtained in the cathode chamber which is partitioned by the diaphragm M and in which the cathode 31 is arranged. In this case, the flow rate sensor 17 selects the optimum flow rate, and the pH adjusting means 18 sets the pH value of the alkaline ionized water W ₁ . The alkaline ionized water W ₁ thus obtained is taken out from the outlet 131b and used for drinking water or the like. On the other hand, acidic water W ₂ is obtained in the anode chamber in which the anode 32 is arranged. This is exit 13
It may be taken out from 1c through the solenoid valve 19 and used appropriately or may be discarded together with other unnecessary water in some cases. Since the generation of hypochlorous acid is suppressed in the acidic water W ₂ at this time, it is possible to prevent the chlorine content from flowing into the alkaline ionized water W ₁ and making it unsuitable for drinking water.

It should be noted that the diaphragm M is capable of migrating ions, circulating a liquid, etc., has no problem in food hygiene, and can be separated by forming a flow path of alkaline ionized water and acidic water. There is no particular limitation and it can be used.

Examples of such materials include polyethylene-based materials,
Examples include polypropylene-based and nylon-based resin membranes, ion exchange membranes, and ceramic porous membranes.

The electrolysis conditions described above are such that a voltage of about 5 to 50 V is applied and the current density is about 0.1 to 10 A / dm ² .

The electrodes 31, 32 used are plate-shaped in FIG. 1, but the distance between the electrodes at this time is about 1 to 20 mm, and the electrolytic cell capacity is about 0.1 to 5 liters. The flow rate of the purified water is about 0.5 to 20 liters / minute.

The alkaline ionized water thus obtained has a pH of about 7 to 10 and a chlorine content of about 0.01 to 1 ppm in terms of Cl ₂ . Further, the alkaline ionized water contains a mineral component such as Ca about 1.2 times or more that of the raw water.

On the other hand, the pH of the acidic water is about 3 to 6 and the chlorine content is about 0.1 to 10 ppm in terms of Cl ₂ .

Generally, alkaline ionized water is used as drinking water, and acidic water is used as lotion, cooking water, cleaning water and the like.

The raw water W ₀ in the above may be tap water, well water, or the like.

In the structure of FIG. 1, the purpose is to take out mainly the alkaline ionized water, but when the purpose is to take out the acidic water, the switching means 15 reverses the polarities of the electrodes 31, 32. , Outlet 13 of tank 131
The water taken out from 1b is made acidic. That is, electrolysis is performed using the electrode 31 as an anode and the electrode 32 as a cathode.

Further, in the electrode arrangement having the configuration of FIG. 1, when calcium or the like adheres to the cathode 31 to lower the electrolysis efficiency, the polarity of the electrode may be reversed to energize. That is, the electrode 31 serves as an anode and the electrode 32 serves as a cathode. This restores the electrolysis efficiency.

The electrode of the present invention has a long life even when used in such polarity reversal. Further, it has a long life even when used under high voltage.

In FIG. 1, a plate-shaped electrode is used.
The shape of the electrode of the present invention is not particularly limited and may be rod-shaped, columnar,
It may be cylindrical or the like. For example, in FIG.
As shown in (a) and (b), both are cylindrical cathodes 33.
It is also preferable that the anode 34 and the cathode 34 are arranged coaxially with the anode 34 inside and the cathode 33 outside, and the cylindrical diaphragm M1 is arranged between them.

The purified water is supplied from the inlet 131a to the tank 131.
The alkaline ionized water is taken out through the outlet 131b and the acidic water is taken out through the outlet 131c.

The electrode arrangement in the electrolysis means 13 may be that shown in FIGS. 3 (a) and 3 (b). Figure 3
2A and 2B, a cylindrical cathode 35 is additionally provided inside the anode 34 to separate the cathode 35 and the anode 34 from each other in FIGS. 2A and 2B. Diaphragm M2
Is arranged.

In FIG. 3, purified water is introduced from the inlet 131a, alkaline ionized water is taken out from the outlets 131d and 131e, and acidic water is taken out from the outlet 131f.

Although the electrode arrangement of the water cooler has been described above with reference to the illustrated example, it is not limited to this and may be various.

[0056]

EXAMPLES The present invention will be described in more detail below by showing specific examples of the present invention.

Example 1 A given chloroplatinic acid (H ₂ PtCl ₆ .6H ₂ O) and tantalum ethoxide (Ta (OC ₂ H ₅ ) ₅ ) were dissolved in butanol to change the platinum / tantalum composition ratio. A coating solution having a metal equivalent concentration of 80 g / l was prepared.

Separately, the above coating solution was applied onto a titanium substrate etched with hot oxalic acid with a brush, dried, and then placed in an electric furnace and baked at 550 ° C. while blowing air. The operations of coating, drying and baking were repeated an appropriate number of times until a predetermined loading amount was reached to prepare an electrode sample of a coating layer of platinum metal and tantalum oxide. Sample these
No. 1 to No. 6

Next, the prepared electrode (Sample No. 1)
~ No. 6), the oxygen overvoltage was measured. As a measuring method, a value at a current density of 2 A / dm ² was obtained in a 1 mol / l sulfuric acid aqueous solution at 30 ° C. by a potential scanning method. The results are shown in Table 1.

Further, about this electrode, 60 ° C., 1 mol / mol
A life test was performed in a sulfuric acid aqueous solution. Platinum was used as the cathode, the current density was 100 A / dm ² , and the sample Nos. 1 to N were used.
Electrolysis was performed using the electrode of o.6 as an anode. The results are also shown in Table 1.

Furthermore, this electrode was heated at 30 ° C. in standard water (sodium hydrogen carbonate (NaHCO ₃ ) 21 ppm).
, 28 ppm of calcium chloride (CaCl ₂ ), 30 ppm of magnesium sulfate (MgSO ₄ ) and 2.5 ppm of potassium hydrogen carbonate (KHCO ₃ )) were used to perform a life test with polarity reversal. Electrodes were electrolyzed at the current density of 5 A / dm ² by reversing the polarity every 15 minutes using the same type of electrode for both the anode and the cathode. The results are shown in Table 1.

The electrode life indicates the time during which electrolysis is possible, and the criteria in the table are as follows.

Polarity reversal in 1 mol / l sulfuric acid aqueous solution ○; 2000 hours or more ○; 1500 hours or more △; more than 1000 hours to less than 2000 hours △; more than 500 hours to less than 1500 hours ×; 1000 hours or less ×; 500 hours or less

The number of moles in the table is the metal equivalent.

[0065]

[Table 1]

As is clear from these results, the electrode of the present invention exhibits a lower oxygen overvoltage and a longer life even when the polarity is reversed, as compared with the comparative electrode.

Example 2 As in Example 1, the coating liquid for coating platinum metal, tantalum oxide and iridium oxide was treated with chloroplatinic acid and iridium chloride and tantalum so that the concentration was 80 g / l in terms of metal. It was prepared by dissolving ethoxide (Ta (OC ₂ H ₅ ) ₅ ) or tantalum butoxide (Ta (OC ₄ H ₃ ) ₅ ) in butanol. This coating solution was applied with a brush onto a titanium substrate that had been etched with hot oxalic acid, dried, and then placed in an electric furnace and baked at 550 ° C. while blowing air. The coating, drying and baking operations were repeated to prepare an electrode sample of a coating layer of platinum metal, tantalum oxide and iridium oxide. These are designated as sample No. 11 to No. 20.

Next, the oxygen overvoltage was measured and the life test was conducted on the prepared electrode in the same manner as in Example 1. The results are shown in Table 2.

The criteria of the electrode life in the table are as follows.

Polarity reversal in 1 mol / l sulfuric acid aqueous solution ◎; 3000 hours or more ○; 1500 hours or more ○; more than 2000 hours to less than 3000 hours △; more than 500 hours to less than 1500 hours △; more than 1000 hours to 2000 hours or less × ; 1000 hours or less

The number of moles in the table is the metal equivalent.

[0072]

[Table 2]

From Table 2, it can be seen that the electrode of the present invention is at a practical level in terms of oxygen overvoltage, and in particular, the life at polarity reversal is longer than that of the comparative one.

Example 3 Sample No. 2 of Example 1 was applied to the water vaporizer shown in FIG. 1 as a cathode and an anode. The structure of the electrolytic cell (electrolysis means) was as shown in FIG. The size of the cathode is 60mm,
Height 90mm, thickness 0.5mm, anode height is 40mm
mm, height 70 mm, and thickness 0.5 mm. The distance between the cathode and the anode was 3 mm, and a polypropylene diaphragm was provided in close contact with the anode to partition the cathode and the anode. The tank volume is 0.5 liter. The capacity of the anode chamber is 0.13 liter.

The above-mentioned water conditioner was subjected to electrolysis conditions of a flow rate of 3.5 liters / minute, a voltage of 30 V and a current density of 2 A / dm ² , and the total operation time per day for obtaining alkaline ionized water was 1
I used it for 6 months. In this case, it was assumed that the cathodes were used for 15 minutes each, and after 15 minutes of use, the polarities of the electrodes were reversed for 3 to 4 minutes to recover the performance of the cathode.
That is, a total of 1 per day by using the electrodes shown in FIG.
It was used for a total of 0.25 hours by reversing the time and the polarity of the electrodes.

During such 6 months of use, pH
Alkaline ionized water having a concentration of 9.9, a chlorine concentration (Cl ₂ conversion) of 0.1 ppm, and a calcium concentration (Ca conversion of 20 ppm) was stably obtained. There were almost no changes in pH, chlorine concentration and calcium concentration during this period.

In addition to the purpose of recovering the performance of the cathode during 6 months of use, the polarity of the electrode was appropriately reversed and used. In this case, acidic water having a pH of 5.7 was stably obtained.

In the above-mentioned water-making device, the same operation as above was carried out except that the cathode and the anode were sample No. 5 of Example 1, and electrolysis became impossible at the stage of use for 6 months. It was also confirmed that the electrode performance gradually deteriorates during this period of use.

Example 4 The same operation as in Example 3 was carried out except that the cathode and anode were changed to Sample No. 13 of Example 2 in the water generator of Example 3, and the operation was conducted for 6 months. It was possible to stably use the same as No. 3 of the present invention.

[0080]

INDUSTRIAL APPLICABILITY The electrode of the present invention exhibits sufficient durability even in drinking water electrolysis, that is, electrolysis by polarity reversal and under high voltage, especially in anodic reaction after polarity reversal, and can be used for a long period of time. Thus, the electrode of the present invention is suitable as an electrode for drinking water electrolysis.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an ionized water generator (water generator) of the present invention.

2A and 2B show an electrolytic cell to which the present invention is applied, in which FIG. 2A is a vertical sectional view and FIG. 2B is a sectional view taken along line AA of FIG.

3A and 3B show an electrolytic cell to which the present invention is applied, in which FIG. 3A is a vertical sectional view, and FIG. 3B is a sectional view taken along line BB of FIG.

[Explanation of symbols]

 1 water condenser 31-35 electrode M, M1-M2 diaphragm

[Procedure amendment]

[Submission date] November 26, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0067

[Correction method] Change

[Correction content]

Example 2 As in Example 1, the coating solution for coating platinum metal, tantalum oxide, and iridium oxide was treated with chloroplatinic acid and iridium acid chloride and tantalum so that the concentration was 80 g / l in terms of metal. It was prepared by dissolving ethoxide (Ta (OC ₂ H ₅ ) ₅ ) or tantalum butoxide (Ta (OC ₄ H ₉ ) ₅ ) in butanol. This coating solution was applied with a brush onto a titanium substrate that had been etched with hot oxalic acid, dried, and then placed in an electric furnace and baked at 550 ° C. while blowing air. The coating, drying and baking operations were repeated to prepare an electrode sample of a coating layer of platinum metal, tantalum oxide and iridium oxide. These are sample No. 11-No. 20.

Claims (10)

[Claims] 1. Platinum 30 to 30 in terms of metal on a conductive substrate.
An electrode for drinking water electrolysis provided with a coating layer of platinum metal containing 99 mol% and 1-70 mol% of tantalum and tantalum oxide. 2. The electrode for drinking water electrolysis according to claim 1, wherein the coating layer further contains 40 mol% or less of iridium in terms of metal. 3. The electrode for electrolyzing drinking water according to claim 1, which is used as an anode for electrolyzing drinking water. 4. The electrode for drinking water electrolysis according to claim 1, which is used as an anode and / or a cathode when the polarities of the anode and the cathode are reversed and used. 5. A cathode used as an anode when a cathode and an anode are arranged in the electrolysis chamber via a diaphragm and both electrodes are energized to obtain alkaline ionized water on the cathode side and acidic water on the anode side. 1 or 2 electrode for electrolysis of drinking water. 6. When a cathode and an anode are disposed in the electrolysis chamber via a diaphragm and both electrodes are energized to obtain alkaline ionized water on the cathode side and acidic water on the anode side, the cathode and the anode The electrode for drinking water electrolysis according to claim 1 or 2, which is used as a cathode and an anode when the polarity of is reversed. 7. A conductive substrate is coated with a solution containing a platinum compound and a tantalum compound and then heat-treated in an oxidizing atmosphere to obtain 30 to 99 mol% of platinum and 1 to 70 mol of tantalum in terms of metal. % Of a platinum metal containing tantalum oxide and a method for producing an electrode for drinking water electrolysis, which comprises forming a coating layer of tantalum oxide. 8. A conductive substrate is coated with a solution containing a platinum compound, a tantalum compound, and an iridium compound, and then heat-treated in an oxidizing atmosphere to obtain platinum 30 in terms of metal.
A method for producing an electrode for drinking water electrolysis, which comprises forming a coating layer of platinum metal, tantalum oxide, and iridium oxide containing ~ 99 mol%, 1-70 mol% tantalum, and 40 mol% or less of iridium. 9. An electrolysis chamber having a purified water inlet is provided with two or more electrodes via a diaphragm to define the compartments, each compartment is provided with an outlet, and electricity is applied between the electrodes. An ion water producing apparatus for obtaining alkaline ionized water or acidic water from the outlet, wherein the electrode for electrolysis according to claim 1 is used as at least an electrode used as an anode. 10. An ionized water producing apparatus using the electrolysis electrode according to claim 1 or 2 for reversing the polarities of the electrodes so that the electrodes are energized.