Electrode composite structure and water purifier of tap water which can remove free residual chlorine in tap water

Abstract

To provide a water purifier without chlorine odor and capable of generating tasty water and solving the problem in which it gets mold in an active carbon with time and the mold grows to cause insanitary like a commercially-available water purifier, and an electrode composite structure used as the water purifier.SOLUTION: Provided are: a platinum electrode composite structure where a thin white platinum plate is used as an electrode, one end of a platinum line is joined to the platinum plate or a platinum plate with a platinum black, an inner diameter of one end on the opposite side of the platinum line is slightly greater than an outer diameter of the platinum line, the platinum line is penetrated through a conductive metal tube with intensity of some degree such as a stainless tube or inserted into the inside by 3 cm or more from an opening in a lower end of the metal tube; and a water purifier using the same.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to an electrode composite structure that is used to reduce and remove free residual chlorine in tap water and can separate and recover generated hydrogen and oxygen, and a tap water purifier using the same. [Background technology]

[0002] According to the Water Supply Act, water purification plants that produce tap water are required to add chlorine to prevent the growth of bacteria, and to maintain a certain level of residual chlorine in tap water. Residual chlorine includes free residual chlorine (Cl2, HOCl, OCl). ― ) and combined residual chlorine (compounds in which the hydrogen in NH3 is replaced with chlorine, such as monochloramine), but tap water at the water tap is required to have at least 0.1 mg / L of free residual chlorine, which has strong bactericidal properties. However, if the residual chlorine concentration in tap water becomes too high, it can cause a chlorine smell and can also react with vitamin C (ascorbic acid) in food, so the target residual chlorine concentration is set at less than 1 mg / L. For water to be "delicious," it is considered desirable for it to be 0.4 mg / L or less. Water purification plants that produce tap water have long used "slow sand filtration," which uses algae and other biological purification agents to reduce bacteria. However, after World War II, it became common to administer chemicals (such as polyaluminum chloride) to turbid water taken from rivers to cause the turbid matter to coagulate and settle, and then perform physical "rapid sand filtration." As a result, instead of biological purification, people tend to rely on adding a lot of chlorine to remove bacteria, and the free residual chlorine concentration at the taps tends to be high. In addition, the problem of trihalomethanes, which are produced by the reaction of the added chlorine with humic substances in the raw tap water, has also been raised, and the separation membranes in the filters often become clogged when the raw water contains a lot of turbid matter through "rapid sand filtration," and the separation membranes must be frequently backwashed to remove the clogging. In addition, people tend to refrain from drinking tap water that smells of chlorine raw, and more and more people are buying bottled water to drink, which is thought to be due to the above-mentioned reasons.

[0003] Commercially available devices called "water purifiers" are devices that remove "harmful substances" from tap water, and many of them pass tap water through a layer of activated carbon to remove "harmful substances," particularly free residual chlorine and other organic chlorine compounds (such as trihalomethanes). However, with such devices, problems have been pointed out in which mold grows in the activated carbon layer over time, causing it to multiply and become unsanitary. Furthermore, in commercially available devices known as "alkaline electrolyzed water (alkaline ionized water) generators" (Non-Patent Document 1) or simply "water purifiers," tap water from a water tap is electrolyzed to generate hydrogen at the cathode. However, the free residual chlorine in the tap water is not reduced and removed by the hydrogen generated; instead, it is removed by passing the tap water through an activated carbon layer (Patent Documents 1 and 2).

[0004] For the electrodes used in the electrolysis of tap water, it is highly desirable to use platinum plates or platinum-plated platinum plates, which are resistant to oxidation and have catalytic properties. However, platinum has the drawback of being expensive. In the following description of this specification, the term "platinum plate" means "platinum plate or platinum-plated platinum plate." In the electrolysis of water, hydrogen gas (hereinafter simply referred to as "hydrogen") and oxygen gas (hereinafter simply referred to as "oxygen") are generated at the cathode and anode, respectively, in a ratio of 2:1, as shown by the reaction formula 2H2O → 2H2 + O2. In the electrolysis of water, at the anode, mainly 2H2O → O2 + 4H + +4e - An oxidation reaction represented by the following reaction formula occurs, generating oxygen gas. If, for example, a relatively inexpensive metal electrode such as stainless steel is used as the anode metal, in addition to the reaction that generates oxygen, undesirable side reactions occur in which iron, nickel, chromium, etc. in the stainless steel are oxidized and become cations that dissolve in the electrolyte, or the oxides or hydroxides of these metals are fixed to the electrode surface as an anodic oxide film (Non-Patent Document 2).

[0005] In order to minimize the overvoltage in water electrolysis and reduce the loss of electrical energy, and to limit the amount of platinum used, electrodes have been developed in which platinum powder is attached to the surface of a conductive substrate such as a carbon plate, rather than using a platinum plate itself, and electrode plates in which alloy powder of platinum and other transition metal elements such as palladium and iridium is fixed to the surface of a conductive substrate. However, such electrode plates are difficult to manufacture, expensive, and have the drawback that the electrode surface is easily deteriorated when a current is passed through them for a long period of time. For electrodes, platinum plates are more durable because the surface is less likely to deteriorate even if current is passed through them for a long time. However, platinum is expensive, so it is desirable to use as little platinum as possible. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent Publication No. 2013-138996 [Patent Document 2] Patent Publication No. 2009-207962 [Patent Document 3] WO2014077211A1 (the inventor is the same as the inventor of the present invention) [Non-patent literature]

[0007] [Non-Patent Document 1] "Water Application Engineering", Japan Society for the Promotion of Science, Leading Research and Development Committee on "Advanced Water Engineering", Nikkan Kogyo Shimbun, 2011, pp. 127-131 [Non-Patent Document 2] "Electrochemistry for Surface Engineers" by Shiro Haruyama, Maruzen, 2015, p217-226 [Non-Patent Document 3] "Water Treatment Technology" by Yoroku Wada, Tokyo Denki University Press, pp. 54-57, 2011 [Non-Patent Document 4] Water Environment Purification and Improvement Technology (Supervised by Masataka Sugawara) CMC Publishing, 2010, p189-190 Summary of the Invention [Problem to be solved by the invention]

[0008] In water purification plants that supply tap water, chlorine is added to kill bacteria, and the free residual chlorine (Cl2, HOCl, OCl) that remains in the tap water is called ― ) is required to remain at a concentration of 0.1 mg / L or more, as described in

[0002] . However, if the concentration of residual chlorine in tap water becomes too high, it can cause a chlorine smell and can also react with vitamin C (ascorbic acid) in food, so the target concentration of residual chlorine is less than 1 mg / L. Also, for "delicious water," it is considered desirable to have a concentration of 0.4 mg / L or less. Commercially available "water purifiers" pass tap water from the water tap through a layer of activated carbon to remove free residual chlorine and organic chlorine compounds. However, it has been pointed out that mold grows in the activated carbon layer over time and becomes unsanitary. In the electrolysis of water, the cathode reacts with 2H2O + 2e - → H2+2OH - A reduction reaction occurs as shown in the reaction formula. Hydrogen just generated at the cathode is also called "nascent hydrogen" and is highly reactive and has a strong tendency to reduce other substances. If free residual chlorine could be removed by electrolysis of water using hydrogen, which is highly reactive and has a large reducing power, there would be no need to use an activated carbon layer, which is prone to mold growth, in tap water. Therefore, regarding free residual chlorine, instead of passing tap water through an activated carbon layer, which is said to be prone to mold growth, an electrolysis device has been sought that uses a platinum electrode composite structure, which also has a catalytic effect, as an electrode in the electrolysis reaction of water, and effectively utilizes the reducing power of hydrogen generated at the cathode to reduce and remove free residual chlorine in tap water. Currently, commercially available devices known as "alkaline electrolyzed water (alkaline ionized water) generators" and "water purifiers" electrolyze tap water to generate hydrogen, but as described in

[0003] , this hydrogen cannot effectively reduce and remove free residual chlorine, so the tap water is passed through an activated carbon layer to adsorb and remove the free residual chlorine and organic chlorine compounds in the tap water (Patent Documents 1 and 2). Furthermore, in these devices, the hydrogen and oxygen generated at the cathode and anode, respectively, during the electrolysis of tap water are not separated and collected, and the separated hydrogen and oxygen are not effectively utilized.

[0009] Platinum is difficult to oxidize and acts as a catalyst, making it a desirable metal for use as an electrode material in the electrolysis of water. However, it is expensive, so from a cost perspective, in order to minimize the amount of platinum used, it is desirable to use a thin platinum plate that is not large in length and width, and to use thin platinum wire for the lead wires. However, simply connecting a thin platinum plate and a thin platinum wire is inevitably weak in terms of strength. For example, even if one tries to directly solder a thin platinum wire to a lead wire (such as a copper wire) that leads to an external power source inside or outside the electrolytic cell, the thin platinum wire easily bends and breaks. It is also difficult to make the thin platinum wire penetrate the sealing means of the electrolytic cell, and even if it does penetrate, air will enter from the outside through the small gap between the platinum wire and the sealing means, or conversely, gas inside the electrolytic cell will leak out to the outside, making it difficult to maintain the airtightness of the electrolytic cell. There was a need to overcome the problem of developing electrodes that use such thin platinum plates and thin platinum wires as the electrode metal, while still having sufficient mechanical strength and being able to maintain the airtightness of the electrolytic cell.

[0010] Platinum is desirable as the anode metal in the electrolytic cell, but platinum is expensive, and even if a thin platinum plate and a thin platinum wire are used, the device will be expensive. When using a cheaper metal that is less expensive than platinum but more easily oxidized than platinum, when the metal comes into contact with the electrolyte, mainly on the anode side, in addition to a reaction that generates oxygen, a side reaction often occurs in which the metal is oxidized to become a cation and does not dissolve in the electrolyte, or forms an anodic oxide film and adheres to the electrode surface (Non-Patent Document 2). It would be practically desirable to use a relatively inexpensive precious metal, or even cheaper nickel, as the anode, which has an oxide film formed on its surface and is not easily oxidized, instead of expensive platinum, to make the device more inexpensive and obtain drinkable tap water by removing the free residual chlorine from the tap water. However, in this case, even if the anode metal may dissolve in the electrolyte, the amount is extremely small, and there is no effect on health even if the tap water is drunk after passing through the device. If many such electrolysis devices that can be produced at low cost are used in parallel, the amount of tap water from which the free residual chlorine has been removed can be increased. Furthermore, it is expected that the generation rate of hydrogen gas and oxygen gas can be increased. When electrolysis is performed using an electrolyte solution used in general electrolysis reactions, the hydrogen gas and oxygen gas recovered tend to contain droplets of dissolved electrolyte, which in the case of hydrogen can corrode the metal parts of the container that stores hydrogen in a fuel cell, for example, and can lead to explosions. In the case of oxygen, if it is used to assist human breathing, it can cause health problems. By electrolyzing safe tap water, the hydrogen gas and oxygen gas that are separated and collected do not contain such droplets, making them safe and highly useful. There has been a need to overcome the challenge of developing such a water electrolysis device. [Means for solving the problem]

[0011] The present inventors have conducted extensive research to solve all of the above problems, and have made the invention described below. The embodiments described herein are merely examples of the invention, and the technical scope of the invention is not limited thereto.

[0012] A thin platinum wire (e.g., outer diameter 0.3 mm, length 13 cm) is joined to the upper end of a thin, small-sized platinum plate (e.g., approximately 3.0 cm in length and width × approximately 1.4 cm, thickness 0.05 mm) by electric welding (a method in which a large current is passed through the joint between the platinum wire and the platinum plate, and the platinum is melted and joined by the heat generated by the electrical resistance in that area), and it is preferable to increase the strength of the joint between the platinum plate and the platinum wire by covering it with a resinous adhesive or the like to reinforce the strength. When one end of the platinum wire opposite to the end connected to the platinum plate electrode is soldered to one end of a lead wire (such as a copper wire) connected to an external power source and the platinum wire is attempted to pass through the sealing means of the electrolytic cell, the platinum wire is likely to break. Even if the platinum wire can pass through the sealing means, gas in the electrolytic cell will escape from the small gap between the platinum wire and the penetration part of the sealing means, and air will enter from the outside. In order to prevent such a thing from happening, the inventor has taken the following measures. The upper end of the platinum wire, which is opposite to the end connected to the platinum plate, is extended upward, and inserted into a metal tube having a certain degree of strength, such as a stainless steel tube with an inner diameter slightly larger than the outer diameter of the platinum wire (for example, a stainless steel metal tube with an outer diameter of 0.6 mm, an inner diameter of 0.4 mm, and a length of 10 cm, when a platinum wire with a diameter of 0.3 mm is used as the platinum wire), from the opening at the lower end, so that the metal tube is penetrated (FIG. 1a), or the upper end of the platinum wire is inserted at least 3 cm deep into the metal tube (FIG. 1b). The portion where the thin platinum wire is inserted into the opening at the lower end of the metal tube is sealed with an adhesive, for example, a resinous adhesive, so that the electrolyte and gas in the electrolytic cell do not enter the metal tube. Furthermore, the upper end portion of the metal tube containing the platinum wire is also sealed with an adhesive, for example, a resinous adhesive, so that gas does not leak from the inside of the cylindrical container, or gas does not enter the electrolytic cell from the outside. At this time, since the platinum wire is thin, the platinum wire is not bonded to the inner surface of the metal tube, but is naturally and gently bent within the metal tube, and is always in partial contact with the inner side wall of the metal tube, which has an inner diameter 0.1 to 0.7 mm larger than the outer diameter of the platinum wire. When the difference between the outer diameter of the platinum wire and the inner diameter of the metal tube becomes large, the electrical resistance between the platinum wire and the metal tube tends to increase, but by increasing the length of the portion of the platinum wire inserted into the metal tube, it is possible to pass a current with almost no electrical resistance. Note that, if the length of the portion of the platinum wire inserted into the metal tube becomes long, the frictional force between the inner surface of the metal tube and the platinum wire increases, making it difficult to insert the platinum wire into the metal tube, so the length of the metal tube is preferably within 10 cm. Furthermore, when the inner diameter of the metal tube is 0.7 mm or more larger than the outer diameter of the platinum wire, a thin metal wire can be inserted into the gap between the platinum wire and the inner surface of the metal tube, thereby reducing the electrical resistance and allowing current to flow. In addition, the above-mentioned metal tube may be a circular tube or a metal square tube of any rectangular shape, and in the following description of this specification, in order to avoid complicating the description, the part written as "metal tube" means "metal tube or metal square tube." Furthermore, since the platinum wire is in contact with the inner side of the metal tube, such as a stainless steel tube, frictional force is applied and the platinum wire does not fall out downward. On the other hand, since the platinum wire is not in full contact with the inner surface of the metal tube, if the adhesive, such as a resin adhesive, is peeled off from the part where the platinum wire is inserted from the opening at the lower end of the metal tube and from the opening at the upper end of the metal tube, the platinum wire can be easily pulled out of the metal tube by hand. In other words, even if the metal tube is fixed in close contact with the sealing means of the electrolytic cell, the platinum wire is easily pulled out of the metal tube and replaced, and the platinum electrode composite structure can be used in another electrolytic cell. Furthermore, when a metal that is more easily oxidized than platinum, such as stainless steel, is used as an electrode in an electrolytic cell in contact with the electrolyte, the metal in the electrode, mainly on the anode side, is oxidized to become a positive ion and dissolves in the electrolyte, or forms an anodic oxide film and adheres to the electrode surface. Therefore, the surface of the metal tube in those areas that may come into contact with the electrolyte should be covered with a water-insoluble organic material, such as a heat shrink tube or synthetic resin paint. However, the surface of the metal tube at the portion where it penetrates in close contact with the sealing means of the electrolytic cell, and the portion of the surface near the upper end of the metal tube protruding outside the electrolytic cell are not covered with insoluble organic materials such as heat shrink tubing or synthetic resin paint, so that they can be soldered to a lead wire connected to an external power source or connected with an alligator clip to allow current to flow. As described above, by forming a platinum electrode composite structure in which the platinum wire is reinforced with the metal tube, it is possible to maintain the strength of the electrode while still maintaining the airtightness of the electrolytic cell, and to completely prevent the electrode metal from coming into contact with the electrolyte and being oxidized. It has been confirmed that such a platinum electrode composite structure mechanically reinforced with the platinum plate, platinum wire, and metal tube is durable even when a current is passed through it for a long time, and can stably proceed with the electrolysis reaction of water. Incidentally, some commercially available water electrolysis devices, or devices known as "water purifiers," use platinum-plated titanium plates as electrodes; however, titanium plates are difficult to weld to other metals, and it is difficult to completely prevent lead wires such as stainless steel wires and copper wires connected to the titanium plates from coming into contact with the electrolyte (tap water). Therefore, the platinum electrode composite structure of the present invention is superior to platinum-plated titanium plates in that it is able to prevent the metal from being oxidized, mainly on the anode side.

[0013] In tap water, two platinum electrode composite structures shown in

[0011] are used as the cathode and anode, and a cation exchange membrane (Nafion, DuPont NRE-211, etc.) is placed between the cathode and anode as a diaphragm so that they are close to each other but do not come into contact with each other. Even in tap water with very low electrical conductivity, when a safe direct current voltage of 9V or less is applied between the anode and cathode to perform an electrolysis reaction, the electrical resistance of the cation exchange membrane in tap water is relatively small and the membrane is thin, so a current of 150 to 200mA can be passed. Hydrogen gas and oxygen gas are generated at the cathode and anode, respectively, at a speed comparable to that of commercially available water electrolysis devices. The generated hydrogen gas and oxygen gas can be separated and released into the atmosphere, or a gas collection tube can be installed at the top of the electrolysis cell to separate and collect them for effective use. The ratio of the amounts of hydrogen gas and oxygen gas generated at the cathode and anode, respectively, is approximately 2:1. When tap water was electrolyzed using this method, it was confirmed that by simply passing a current through the tap water for 4 to 5 minutes, the majority of the free residual chlorine could be reduced and removed by the highly reactive hydrogen just generated at the cathode, without the tap water passing through an activated carbon layer. In the results of the experiments conducted by the inventors, when the free residual chlorine in the tap water at the water faucet was 0.25 to 0.35 mg / L, the free residual chlorine in the tap water at the anode side as well as the cathode side was reduced to less than 0.05 mg / L by simply passing a current of 150 to 200 mA at a voltage of 6 to 9 V for 4 to 5 minutes, as measured by the DPD colorimetric method. It is believed that this occurs because the hydrogen just generated at the cathode reduces and removes the free residual chlorine in the tap water.One reason why the free residual chlorine in the tap water on the anode side is also reduced and removed is that a small amount of the just generated hydrogen passes through the cation exchange membrane (PEM, Nafion (DuPont NRE-211), etc.) (a phenomenon called cross over, which may occur because the hydrogen molecules are small) and moves to the anode side, where the free residual chlorine is reduced and removed by this hydrogen. The structure of free residual chlorine changes depending on the pH of the surrounding water. When the pH is below 3 (acidic), it is mainly Cl2, when the pH is between 4 and 7 (near neutral), it is mainly HOCl, and when the pH is above 8 (alkaline), it is mainly OCl. ― It is believed that the oxidation power is Cl2>HOCl> OCl. ― In aqueous solution, OCl ― is considered to have significantly lower oxidizing and bactericidal power than HOCl (Non-Patent Document 3). In electrolysis, at the cathode, 2H2O + 2e - → H2+2OH - This reaction produces hydrogen, and tap water is OH. - The anode becomes alkaline due to the generation of 2H2O → O2 + 4H + +4e - This reaction produces oxygen, and tap water is H + The solution becomes acidic due to the generation of hydrogen. The oxidizing power of free residual chlorine is greater in the acidic solution on the anode side than in the alkaline solution on the cathode side, so hydrogen can reduce more free residual chlorine in the acidic solution on the anode side than in the alkaline solution on the cathode side. Therefore, even if the amount of hydrogen that crosses over from the cathode side through the cation exchange membrane is small, it can be assumed that it can reduce free residual chlorine. Commercially available "alkaline electrolytic water (alkaline ionized water) generators" (Non-Patent Document 1) or simply "water purifiers" are advertised as producing "alkaline ionized water" through electrolysis within the device. However, if the "alkaline ionized water" is weakly alkaline, as mentioned above, the free residual chlorine in tap water is OCl. ― It exists in this structure, and since its oxidizing and bactericidal power is weaker than that of tap water from a water faucet, it is presumed that it is less susceptible to reduction by the hydrogen generated at the cathode. It should be noted that in the water purifier of the present invention, although a small amount of hydrogen may cross over to the anode side, most of the hydrogen and oxygen generated on the cathode and anode sides of the electrolytic cell are separated in the electrolytic cell and either accumulated or released to the outside. If the hydrogen and oxygen generated on the cathode and anode are mixed and retained in the same space, there is a risk of an explosion due to an electrical short circuit or the like. It should be noted that if an electric current is continuously applied for 4 to 5 minutes or more in the water purifier of the present invention, the tap water on the cathode side gradually becomes weakly alkaline (pH 8 to pH 10), and the tap water on the anode side gradually becomes weakly acidic (pH 5 to pH 7). It was discovered that if an electric current is applied for several minutes, and then the aqueous solution on the cathode side and the tap water on the anode side are mixed and discharged from the electrolytic cell, an aqueous solution (tap water) that is nearly neutral and in which most of the free residual chlorine has been reduced and removed can be continuously obtained. Furthermore, if the amount of tap water introduced into the electrolytic cell on the cathode side and the amount of tap water introduced into the electrolytic cell on the anode side are adjusted after the electric current is applied, the pH of the tap water discharged from the electrolytic cells on the cathode side and the anode side and mixed in the water tank can be adjusted to a value close to the target. When safe tap water is electrolyzed using the water purifier of this embodiment, the airtightness of the electrolytic cell is maintained, and the strength of the electrodes is maintained. Furthermore, it is possible to overcome the problem of preventing side reactions in which metals that are more easily oxidized than platinum, such as iron, chromium, and copper, come into contact with the electrolyte and are oxidized to become cations on the anode side, which dissolve in the electrolyte, or which cause an anodic oxide film to adhere to the surface of the metal tube. Therefore, it was confirmed that tap water after electrolysis can be used as it is for drinking. However, tap water from which free residual chlorine has been removed can become contaminated with bacteria from the air and begin to grow over time, so if it is left for a long period of time, it is not suitable for drinking. In the device referred to as the "water purifier," an electrolysis reaction of water is carried out, but most of the hydrogen and oxygen generated at the cathode and anode are not effectively utilized. In contrast, in the water purifier of the present invention, the hydrogen (cathode) gas and oxygen (anode) gas produced by electrolyzing safe tap water do not contain droplets of dissolved electrolyte. Therefore, hydrogen will not corrode the metal parts of the container that stores hydrogen in a fuel cell, for example, which could lead to an explosion, and oxygen will not pose a health hazard even if it is used to assist human breathing, for example. Therefore, it has been confirmed that this invention is extremely effective in applications where safety is a priority. By the way, if inexpensive cellophane membranes for dialysis could be used instead of cation exchange membranes, the equipment could also be made cheaper. However, it has been found that the electrical resistance of cellophane membranes for dialysis (such as visking tubing) in water is more than 10 times greater than that of cation exchange membranes, and only a small amount of current flows at low voltages, for example below 12 V, making it unsuitable for use in electrolysis equipment that uses tap water as the electrolyte.

[0014] The activated carbon layer installed in commercially available water purifiers can adsorb and remove organic chlorine compounds other than free residual chlorine, but the activated carbon layer has the problem of being prone to mold growth. There are strict standards set for the content of trihalomethanes, an organic chlorine compound, in tap water in Japan (a general term for four substances: chloroform, bromodichloromethane, dibromochloromethane, and bromoform, which are produced when chlorine added for sterilization during the water purification process reacts with organic compounds such as humin in the water). For example, the Japanese standard for chloroform, which is said to be the most abundant trihalomethane, in tap water is 0.06 mg / L or less (the WHO standard is 0.3 mg / L or less). In Japan, in the process of purifying and supplying tap water, aeration of tap water is also done as necessary to reduce the concentration of trihalomethanes. If necessary, the concentration of trihalomethanes (including chloroform) in tap water can be reduced by installing a simple device similar to the mechanism of the "spouted bed type VOC (Volatile Organic Compounds) removal device" (Non-Patent Document 4), which blows air into the tap water after passing it through the electrolysis device of the present invention, moving chloroform into the air and discharging it to the outside, and since trihalomethanes are volatile, most of the trihalomethanes (including chloroform) in tap water can be removed by heating or boiling the tap water. Of course, there may be a method of attaching a separate activated carbon layer for this purpose, but in that case, it is necessary to frequently replace the activated carbon layer with a new one, considering that mold will grow on the activated carbon layer. In Japan, tap water is managed so that the free residual chlorine is at least 0.1 mg / L, so there are not many germs (such as E. coli) in the tap water and it is thought that there is almost no need to pass it through ceramic filters, hollow fiber membranes, etc. Also, some commercially available water purifiers pass tap water through ceramic filters, hollow fiber membranes, etc., but problems have been pointed out with these becoming clogged with bacteria and turbidity during use, and they cannot be used continuously for long periods of time. Therefore, in the present invention, among the "harmful substances" that are desirable to remove, we have focused on "free residual chlorine" in particular, and have found that in an apparatus having a structure as shown in

[0011] and

[0012] , a structurally strong platinum electrode composite structure can be formed by the thin platinum plate, the thin platinum wire joined thereto, and the metal tube, and that it is possible to produce a water electrolysis apparatus that can reduce and remove free residual chlorine and the like from tap water by electrolyzing tap water using a cation exchange membrane (Nafion, DuPont NRE-211, etc.) as a diaphragm, without passing the tap water through an activated carbon layer where mold may grow. In other words, it was discovered that the water purifier of the present invention can remove most of the "free residual chlorine" without passing the water through an activated carbon layer, and because of its simple structure, it does not clog.

[0015] Platinum is a desirable metal for use as an electrode in the electrolytic device described in

[0011] to

[0013] . However, platinum is expensive, and even if a thin platinum plate and a thin platinum wire are used, the device will be expensive. Therefore, it is worthwhile to explore a method for removing free residual chlorine in tap water while making the device more inexpensive by using a metal that is resistant to oxidation through the formation of an oxide film on the surface, such as other relatively inexpensive precious metals or even cheaper nickel, instead of platinum plates and platinum wires as electrodes. When nickel is used as the anode, nickel may be oxidized and a small amount of nickel metal ions may dissolve in the tap water, but if the amount is extremely small, drinking the tap water after passing through the device will have almost no effect on health. By adjusting the flow rate of tap water passing through the device and by not allowing the tap water to remain in the device for too long, the tap water can be made drinkable. In addition, the above-mentioned nickel ions are not included in the water quality standards for tap water in the Water Supply Act, and are considered to be relatively less harmful. When using nickel wire, if a nickel wire having an outer diameter of about 0.3 to 0.5 mm is covered with a heat shrink tube and the heat shrink tube and the sealing means of the electrolytic cell are bonded with an adhesive to seal the portion where the nickel wire passes through the sealing means, it is not necessarily necessary to pass the nickel wire through a stainless steel tube having a certain degree of strength (Patent Document 3). By connecting a large number of such inexpensive electrolysis devices in parallel, it is possible to increase the amount of tap water from which free residual chlorine can be removed, and also to increase the rate at which hydrogen and oxygen are produced by separation. Based on this comprehensive knowledge, the present inventor has invented a platinum electrode composite structure that is highly functional, uses as little expensive platinum as possible, is relatively inexpensive to manufacture, and is easy to handle and durable; and a water purifier that uses this platinum electrode composite structure. In order to make the device even more inexpensive, the inventor has also invented a water purifier that can remove free residual chlorine in tap water and can separate, recover, and effectively use hydrogen and oxygen generated from the electrodes by using metal electrode composite structures of other precious metals, such as nickel, which is resistant to oxidation because an oxide film is formed on the surface, instead of platinum. Effect of the Invention

[0016] Although the electrodes in the electrolysis apparatus of the present invention use expensive platinum, the electrodes are made of thin platinum plates (e.g., about 3.0 cm × about 1.4 cm, 0.05 mm thick) and the lead wires are made of thin platinum wires (e.g., 0.3 mm diameter, 13 cm length), and the amount of platinum used is significantly reduced, so the cost is not that high (for example, if a platinum wire with a diameter of 1.0 mm were used, the price would be more than 10 times higher). If the upper end of the thin platinum wire is inserted at least 3 cm into a strong metal tube such as stainless steel that hermetically penetrates the sealing means (when a platinum wire with a diameter of 0.3 mm is used, for example, a metal tube with an outer diameter of 0.6 mm, an inner diameter of 0.4 mm, and a length of 10 cm), the platinum wire will always be in partial contact with the inner side of the metal tube, so that current can flow from the platinum plate through the metal tube to the external power terminal with almost no electrical resistance. In addition, the part where the platinum wire is inserted from the opening at the bottom end of the metal tube and the opening at the top end of the metal tube are sealed with an adhesive, for example a resinous adhesive, completely preventing air from entering from the outside of the metal tube containing the platinum wire and completely preventing gas accumulated in the electrolytic cell from leaking out. In addition, the outer surface of the metal tube, which may come into contact with the electrolyte (tap water), is covered with a water-insoluble organic material such as heat shrink tubing or synthetic resin paint, so the metal on the surface of the metal tube is not oxidized.

[0017] In the device of the present invention, when electrolysis is performed by placing the cathode and anode of the present invention close to each other using tap water with low electrical conductivity as the electrolyte and a cation exchange membrane with relatively low electrical resistance as the diaphragm, most of the free residual chlorine in the tap water can be reduced and removed by hydrogen generated on the cathode side by simply passing a current of 150-200 mA for 4-5 minutes, even at a low voltage of 6-7 V (preferably 12 V or less for safety reasons). Although no hydrogen is generated on the anode side, a small amount of the hydrogen just generated on the cathode side crosses over through the cation exchange membrane (Nafion, DuPont NRE-211, etc.) to the anode side, so that most of the free residual chlorine in the tap water on the anode side can also be reduced and removed. If an electric current is continued for a long period of time, the tap water on the cathode side will gradually become slightly alkaline (pH 8-10), and the tap water on the anode side will gradually become slightly acidic (pH 5-7). However, if the tap water discharged from the electrolytic cell on the anode side and the tap water on the cathode side are placed in the same water tank and mixed, the tap water will have most of the free residual chlorine removed and will become nearly neutral. Furthermore, by adjusting the mixing ratio of the tap water on the anode side and the aqueous solution on the cathode side, it is possible to obtain drinkable tap water with the desired pH.

[0018] The electrode of the present invention shown in

[0015] uses a thin platinum plate (e.g., about 3.0 cm x about 1.4 cm, thickness 0.05 mm) as the electrode and a thin platinum wire (e.g., diameter 0.3 mm, length 13 cm) as the lead wire, thereby reducing the amount of platinum used; however, platinum is expensive, so the device is still expensive. Therefore, it is possible to remove free residual chlorine from tap water by electrolyzing tap water using electrodes made of less expensive metals such as nickel, which have an oxide film formed on the surface and are less likely to be oxidized to the inside, instead of platinum. When nickel is used as the electrode, it may be oxidized and dissolved into the tap water as nickel ions, but the amount is very small, and the tap water after electrolysis can be made drinkable by adjusting the flow rate of the tap water passing through the device and by not letting the tap water remain in the device for too long. In addition, nickel ions are not included in the water quality standards for tap water under the Water Supply Act, so their harmfulness is considered to be low. When connecting a nickel wire having an outer diameter of about 0.3 to 0.5 mm to a nickel plate as an electrode, it is not necessary to pass the nickel wire through a stainless steel tube having a certain degree of strength. The airtightness of the electrolytic cell can be maintained by covering the nickel wire with a heat shrink tube and bonding the heat shrink tube to the sealing means with an adhesive at the portion where the wire passes through the sealing means of the electrolytic cell (Patent Document 3). By connecting a large number of such inexpensive electrolysis devices in parallel, it is possible to increase the flow rate of tap water from which free residual chlorine can be removed, and also to increase the rate at which hydrogen gas and oxygen gas are generated by separation. When electrolysis is performed using an electrolyte solution used in general electrolysis reactions, the accumulated hydrogen gas and oxygen gas often contain droplets and splashes of dissolved electrolyte. Such hydrogen gas may corrode the metal parts of a metal container in which hydrogen gas is stored for use in a fuel cell, leading to an explosion, and such oxygen gas may have a negative effect on human health if used to assist breathing. In contrast, the hydrogen gas and oxygen gas separated and accumulated by electrolysis of safe tap water in the device of the present invention do not contain droplets and splashes of dissolved electrolyte, eliminating the above concerns and making the device safe and highly useful. BEST MODE FOR CARRYING OUT THEINVENTION

[0019] The best mode of the present invention will be described with reference to the following examples. EXAMPLES

[0020] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. As shown in FIG. 1, the platinum electrode composite structure of the present invention is formed by connecting one end of a thin platinum wire 2 having an outer diameter of 0.3 mm and a length of 13 cm or more to the upper end of a thin platinum plate 1 (e.g., 3.0 cm×1.4 cm, thickness 0.05 mm) by electric welding (it is desirable to add an adhesive to the connected portion to reinforce the strength), and inserting the other end of the platinum wire 2 into the inside of a metal tube 3 having a certain degree of strength, such as a stainless steel tube having a length of 5 to 20 cm and an inner diameter 0.1 to 0.7 mm larger than the outer diameter of the platinum wire (when a platinum wire having a diameter of 0.3 mm is used as the platinum wire, for example, the metal tube has an outer diameter of 0.6 mm, an inner diameter of 0.4 mm, and a length of 10 cm) from the opening at the lower end, so that the platinum wire 2 penetrates the metal tube 3 and protrudes from the metal tube by 1 to 2 cm (FIG. 1a), or the upper end of the platinum wire 2 is inserted at least 3 cm deep into the metal tube 3 (FIG. 1b). The portion where the thin platinum wire 2 is inserted into the metal tube 3 is sealed with adhesive 4, for example a resinous adhesive, to prevent the electrolyte (tap water) in the electrolytic cell and the gas in the electrolytic cell from entering the metal tube 3. Furthermore, the upper end portion of the metal tube 3 containing the platinum wire 2 is also sealed with adhesive 4, for example a resinous adhesive. This configuration prevents gas from leaking out from the inside of the electrolytic cell and the metal tube 3, and prevents gas from entering the electrolytic cell and the metal tube 3 from the outside. Although the platinum wire 2 is not bonded to the inner surface of the metal tube, it naturally bends gently within the metal tube 3, and since the metal tube 3 is a thin tube with an inner diameter that is only 0.1 to 0.7 mm larger than the outer diameter of the platinum wire, the platinum wire 2 is always in partial contact with the inner side wall of the metal tube 3, and current can flow between the platinum plate 1, the platinum wire 2, and the metal tube 3 with almost no electrical resistance. For example, when a stainless steel pipe is used as a metal pipe constituting a platinum electrode composite structure serving as an anode inside an electrolytic cell, if it comes into contact with tap water (electrolyte), metals inside the stainless steel that are more easily oxidized than platinum, such as iron, nickel, and chromium, may be oxidized to become cations and dissolve in the electrolyte, or may form an anodic oxide film and adhere to the electrode surface, so the surface portion of the metal pipe 3 that may come into contact with tap water (electrolyte) is covered with a non-conductive, water-insoluble organic material, such as a heat shrink tube or synthetic resin paint. However, such covering is not provided for the portion where the metal pipe penetrates the sealing means of the electrolytic cell and the part of the surface near the upper end of the metal pipe protruding outside the electrolytic cell, so that a current can be passed through the metal pipe by soldering or connecting with an alligator clip to a lead wire connected to an external power source. As shown above, a platinum electrode composite structure is formed by using a thin platinum plate 1, a thin platinum wire 2, and a metal tube 3 having a certain degree of strength, and the two platinum electrode composite structures are used as the cathode and anode for electrolysis of tap water. Furthermore, the difference between the inner diameter of the metal tube 3 and the outer diameter of the platinum wire 2 to be inserted is as small as 0.1 to 0.7 mm, so that the platinum wire comes into contact with the inner side wall of the metal tube, such as a stainless steel tube, and as a result, frictional force acts in the longitudinal direction and does not fall out downward. On the other hand, since the platinum wire 2 is not in full contact with the inner surface of the metal tube, if the adhesive 4, for example, a resin-like adhesive, is peeled off from the part where the platinum wire 2 is inserted from the lower end of the metal tube 3 and from the upper end of the metal tube, the platinum wire 2 can be easily pulled out of the metal tube 3 by hand. In other words, even if the metal tube is fixed in close contact with the sealing means of the electrolytic cell, the platinum plate 1 and platinum wire 2 are easily pulled out of the metal tube 3 and replaced, so that the platinum electrode composite structure of the present invention can also be used in another electrolytic cell.

[0021] The cylindrical body 5 (Figs. 2a, 2b, and 3) as a component of the electrolytic cell is, for example, 5 to 7 cm in outer diameter and 4 to 6 cm in inner diameter if cylindrical, or 4 cm x 4 cm in cross section if rectangular. The cylindrical body 5 is 13 to 18 cm long, and one end of the cylindrical body 5 is completely sealed by being bonded to the center of a non-conductive flat plate 6 (e.g., an acrylic resin plate, 17 cm x 17 cm, and 5 mm thick) that is 16 to 20 cm in length and width and has a non-conductive surface made of a resin or metal. The other end of the cylindrical body 5 is bonded to a non-conductive flat plate 7 that is the same size as the non-conductive flat plate 6 but has an opening near the center (the opening is 3 to 6 cm in diameter if circular, or 4 cm x 4 cm if rectangular), as shown in Figs. 2a and 2b, so that the opening of the cylindrical body 5 can completely cover the opening of the non-conductive flat plate 7. Two of these containers are designated electrolytic cell A (FIG. 2a) and electrolytic cell B (FIG. 2b). In electrolytic cell A and electrolytic cell B, a gas collection tube 11 (electrolytic cell A) and a gas collection tube 12 (electrolytic cell B) are provided on the upper part of the side surface of cylindrical body 5 at a position very close to the opening of non-conductive plate 7, respectively. The gas collection tube 11 (electrolytic cell A) and the gas collection tube 12 (electrolytic cell B) are provided, which are graduated, have an outer diameter of about 2 cm, a length of about 20 to 30 cm, extend upward, and have an open / close valve 13 at their upper ends that can be opened and closed, for collecting hydrogen generated by electrolysis of water in electrolytic cell A and oxygen generated by electrolysis of water in electrolytic cell B. Furthermore, nozzles 14, 16 (Figs. 2a, 2b) with an inner diameter of about 6 mm for introducing tap water are provided on the side of the cylindrical body 5 at positions close to and away from the opening of the non-conductive flat plate 7, and nozzles 15, 17 (Figs. 2a, 2b, 3) with an inner diameter of about 6 mm for draining tap water from the electrolytic cell are provided on the side of each cylindrical body 5 at positions close to the non-conductive flat plate 6 on the opposite side of the opening. In addition, spare nozzles 19, 20 with an inner diameter of about 6 mm are provided on the side of the cylindrical body 5 between the nozzles 14, 15 and between the nozzles 16, 18. The spare nozzles 19, 20 are used to extract a portion of the electrolyte in electrolytic cells A and B in order to measure the pH and other properties of the electrolyte, or to connect an upwardly extending silicone rubber tube and a liquid reservoir to the nozzle, so that by raising and lowering the reservoir, it is possible to determine the gas volume under atmospheric pressure of the hydrogen and oxygen accumulated inside the graduated gas collection tube 11 from electrolytic cell A and the gas collection tube 12 from electrolytic cell B. The non-conductive plates 7 of the two electrolytic cells A and B are non-conductive plates of a size such that their outer edges are 4 to 6 cm away from the side of the cylindrical body to which they are attached. This is so that the non-conductive plates 7 of the electrolytic cells A and B can be fastened with metal fittings 21 such as clamps on the outside of the cylindrical body 5 (Figs. 3 and 4). The electrolytic cells A and B are produced in this shape, and the shape, size and position of the openings of the non-conductive plates 7 are adjusted so that the openings of the non-conductive plates 7 of the two containers fit together when they are faced to each other, and the structure is designed so that the two non-conductive plates 7 can be fastened from the outside using about 4 to 6 fixing metal fittings 21 such as clamps on both sides of the outer part of the cylindrical body 5 (Fig. 3). Between the non-conductive flat plates 7 of electrolytic cell A and electrolytic cell B facing each other, two silicone rubber sheets with a thickness of about 1 mm and an opening of the same size and position as the non-conductive flat plates 7 are placed as gaskets 22, and two platinum electrode composite structures (referred to as cathode 8 and anode 9) described in

[0018] are placed between them, and a cation exchange membrane (PEM, positive ion exchange membrane, Nafion, DuPont NRE-211, etc.) 10 is inserted between them so that its top, bottom, left and right widths cover the opening of the non-conductive flat plate 6 by about 1 to 2 cm (Figure 3), and the two non-conductive flat plates are fastened from the outside with about 4 to 6 metal fittings 21 such as clamps.However, with regard to the platinum electrode composite structure (cathode 8 and anode 9) between the non-conductive flat plates 7, when the electrolytic cell A and the electrolytic cell B are combined, the platinum plate (e.g., 3.0 cm x 1.4 cm, thickness 0.05 mm) of the platinum electrode composite structure of

[0018] is positioned at the opening of the non-conductive flat plate 7 as shown in FIG. 4, and the two platinum wires 2 and the metal tube 3 are arranged close enough to be in close contact with both sides of the cation exchange membrane 10, and the platinum wires 2 (e.g., outer diameter 0.3 mm, length 13 cm) and the metal tube 3 (e.g., stainless steel metal tube with outer diameter 0.6 mm, inner diameter 0.4 mm, length 10 cm) connected thereto are extended obliquely upward and in alternate directions, and further, the two metal tubes 3 of the platinum electrode composite structure protrude 6 to 7 cm above the outer edge of the non-conductive flat plate 7 and are spaced 2 to 4 cm apart from each other. The platinum wire 2 and metal tube 3 constituting the cathode and anode are separated by a cation exchange membrane 10 to prevent current from flowing between them (Figures 4, 5, and 6). 4, a platinum electrode composite structure (cathode and anode) is sandwiched between the two non-conductive flat plates 7 with a cation exchange membrane 10 as a diaphragm, and a silicone rubber sheet with a thickness of, for example, about 1 mm is sandwiched on both sides of the structure as packing 22, and the non-conductive flat plates 7 are tightly fastened from the outside with metal fittings 21 such as clamps, so that the electrolyte (tap water) does not leak out, but to further prevent the electrolyte (tap water) from leaking out, a sufficient amount of adhesive is applied to the outer edges of the two non-conductive flat plates 7. However, even if the electrolyte (tap water) does leak out, it is safe water and there is no danger. Two electrolytic cells (electrolytic cell A and electrolytic cell B) are combined with two platinum electrode composite structures (cathode 8 and anode 9) and a cation exchange membrane 10 sandwiched between them to form the main part of the device (electrolytic cell 23, FIG. 3) that removes free residual chlorine caused by electrolysis of tap water and collects and recovers hydrogen and oxygen. In order to show the relative positions of the two electrolytic cells (electrolytic cell A and electrolytic cell B), the platinum electrode composite structures (cathode 8 and anode 9), and the cation exchange membrane 10, a cross-sectional view seen from the side is shown in FIG. 5, and a cross-sectional view seen from above is shown in FIG. 6. As shown in Figure 7, tap water from a water supply tap 24 is introduced directly, or is first stored in a water supply tank 25 and then branched so that tap water is introduced into electrolytic cell A (cathode side) from nozzle 14 of cylindrical body 5 of electrolytic cell A while the flow rate is adjusted by flow regulator 26, and tap water is introduced into electrolytic cell B (anode side) from nozzle 16 of cylindrical body 5 while the flow rate is adjusted by flow regulator 27. In the electrolytic cell 23, the platinum electrode composite structure (cathode 8 and anode 9) immersed in tap water is placed close to both sides of the cation exchange membrane 10, and a lead wire from a DC power source is connected to the part of the metal tube 3 of the platinum electrode composite structure protruding above the non-conductive flat plate 7 that is not covered with an organic material, to apply a voltage and pass a current, thereby electrolyzing the tap water. Hydrogen and oxygen are generated at the cathode 8 and the anode 9, respectively, but are separated by the cation exchange membrane 10, with hydrogen being accumulated in the gas accumulation tube 11 in the electrolytic cell A and oxygen being accumulated in the gas accumulation tube 12 in the electrolytic cell B. The hydrogen and oxygen accumulated in the gas accumulation tubes 11 and 12, respectively, can be discharged to the outside by suction by opening the opening / closing valve 13 at the top end of the accumulation tube, or can be pushed out by the water pressure of the tap water and discharged to the outside. In electrolytic cell 23, even if a low DC voltage of about 6 to 7 V is applied to two platinum electrode composite structures (cathode and anode), and even if the electrolyte in which the electrodes are immersed is tap water with low electrical conductivity such as tap water, a current of about 150 to 200 mA flows, and tap water from which most of the free residual chlorine has been removed is discharged from nozzle 15 in electrolytic cell A (cathode side) and from nozzle 17 in electrolytic cell B (anode side). Experimental results showed that the free residual chlorine in tap water at the water supply faucet was 0.2 to 0.4 mg / L, but by simply passing a current for 4 to 5 minutes, the free residual chlorine in both the cathode side and the anode side tap water was less than 0.05 mg / L, according to the measurement results using the DPD colorimetric method. This occurs because the hydrogen generated on the cathode side reduces the free residual chlorine in the tap water on the cathode side. However, some of the hydrogen generated on the cathode side permeates the cation exchange membrane 9 and moves to the anode side (crosses over), so it is thought that the free residual chlorine is also reduced in the tap water on the anode side. In electrolytic cell A, tap water is introduced through nozzle 14 and discharged through nozzle 15, and in electrolytic cell B, tap water is introduced through nozzle 16 and discharged through nozzle 17. However, since the tap water does not pass through an activated carbon layer, ceramic filter, etc. in either electrolytic cell, there is almost no pressure loss of the tap water. The tap water discharged from the drain nozzle 15 of the electrolytic cell A on the cathode side tends to be weakly alkaline, and the tap water discharged from the drain nozzle 17 of the electrolytic cell B on the anode side tends to be weakly acidic, but most of the free residual chlorine has been removed from both tap waters, and when they are mixed in the water tank 28 from the nozzles 30 and 31 of the water tank 28, they become almost neutral tap water. By adjusting the flow rate of the tap water introduced into each tank with the flow rate regulators 26 and 27, as shown in FIG. 8, the pH of the tap water entering the water tank 28 and being mixed can also be adjusted. An air vent nozzle 32 is also provided on the top of the water tank 28. By opening the on-off valve 29 located near the bottom of the side of the water tank, the tap water discharged from there can be used for drinking. However, since the tap water stored in the water tank 28 has a low concentration of free residual chlorine, care must be taken because bacteria may enter from the air and grow if it is stored for a long period of time. Furthermore, when a typical electrolyte solution is electrolyzed, the hydrogen gas that is generated and the oxygen gas that is generated on the anode side (electrolytic cell B) often contain droplets of dissolved electrolyte, but the hydrogen gas and oxygen gas that are generated by electrolyzing safe tap water do not contain such droplets. Therefore, with regard to hydrogen, for example, the metal parts of the container that stores the hydrogen stored in the fuel cell will not corrode, causing hydrogen to leak and resulting in an explosion, and with regard to oxygen, for example, it will not be harmful to human health even if it is used as a breathing gas, so both are safe and highly useful.

[0022] In the platinum electrode composite structure shown in

[0018] , platinum is desirable as the anode metal, but platinum is expensive, and even if a thin platinum plate and a thin platinum wire are used, the device will be expensive. Therefore, there is a method of using other precious metals such as gold or less expensive nickel, which have an oxide film formed on the surface and are not easily oxidized to the inside, instead of platinum in the platinum electrode composite structure described in

[0018] , to remove free residual chlorine in tap water while making the device more inexpensive. In this case, although there is a possibility that a relatively inexpensive precious metal or nickel is oxidized on the anode side and a small amount of the metal ion is dissolved in the tap water, when the amount is extremely small, by adjusting the amount of tap water introduced and not allowing the tap water to remain in the device for too long, it is possible to drink the tap water after passing through the device without any adverse effect on health. By connecting many such inexpensive electrolysis devices in parallel, it is possible to increase the amount of tap water from which free residual chlorine can be removed, and also to increase the rate at which hydrogen and oxygen are generated by separation. In this case, when the hydrogen is used, for example, in a fuel cell and the oxygen is used, for example, as human respiratory gas, it is expected that the electrolysis devices will be highly effective in other respects in addition to removing free residual chlorine. [Brief description of the drawings]

[0023] [Figure 1] A platinum (or other metal) electrode composite structure. A thin platinum wire is electrically welded to the upper end of a thin platinum plate or platinum-blackened platinum plate, and inserted into the opening at the lower end of a metal tube with a certain degree of strength, such as a stainless steel tube with an inner diameter slightly larger than the outer diameter of the platinum wire. The part 4 where the platinum wire is inserted from the lower end of the metal tube, and the upper end of the metal tube are sealed with an adhesive, such as a resinous adhesive. In addition, parts of the metal tube surface that may come into contact with the electrolyte (tap water) are covered with a non-conductive, water-insoluble organic material, such as a heat shrink tube or synthetic resin paint. [Diagram 2]Electrolytic cell A and electrolytic cell B, in which platinum composite electrode structures are immersed in tap water. The electrolytic cells are filled with tap water and in which the composite electrode structures acting as cathodes or anodes are immersed, and are equipped with collection tubes for gas generated from the electrodes and nozzles for supplying and draining tap water. The two electrolytic cells (electrolytic cell A and electrolytic cell B) in which the composite electrode structures acting as cathodes or anodes are immersed have a structure in which their shapes and openings fit together perfectly when the non-conductive flat plates with openings in their cylindrical parts are placed facing each other. (Figures 2a and 2b) [Diagram 3] This is a perspective view of the entire main part of an apparatus for removing free residual chlorine and separating and accumulating hydrogen and oxygen. The apparatus is constructed by inserting a positive ion exchange membrane (PEM, Nafion, DuPont NRE-211, etc.) between two electrolytic cells, electrolytic cell A and electrolytic cell B, which are filled with tap water for removing free residual chlorine as shown in Figure 2, and arranging platinum electrode composite structures (cathode and anode) adjacent to both sides of the PEM and combining them. [Figure 4] This shows the relative positions of the platinum electrode plate 2, platinum wire 3, and metal tube 4 of the platinum electrode composite structure (cathode, anode) in each electrolytic cell, at the opening where the non-conductive flat plates 7 of electrolytic cell A and electrolytic cell B come together. [Diagram 5] A cross-sectional side view of the main part of the electrolysis device to show the relative positions of two electrolysis cells (electrolysis cell A and electrolysis cell B), platinum electrode composite structure (cathode 8 and anode 9), cation exchange membrane 10, and packing. [Figure 6] A cross-sectional view of the main part of the electrolysis device from above, showing the relative positions of two electrolysis cells (electrolysis cell A and electrolysis cell B), platinum electrode composite structure (cathode 8 and anode 9), cation exchange membrane 10, and packing. [Figure 7] A diagram of a water tank for temporarily storing tap water from a water faucet, and a device for introducing tap water through a flow regulator into electrolytic cell A and electrolytic cell B. [Figure 8] A diagram of the water tanks that store the tap water discharged from electrolytic cells A and B, and the device that extracts the tap water as drinkable tap water.

Claims

1. A platinum electrode composite structure, characterized in that one end of a thin platinum wire is joined to a platinum plate or a platinum-plated platinum plate, the opposite end of the platinum wire is inserted into the interior of a conductive metal tube whose inner diameter is slightly larger than the outer diameter of the platinum wire, the platinum wire is in partial longitudinal contact with the inner side of the conductive metal tube, both ends of the metal tube containing the platinum wire are sealed with an adhesive to prevent electrolyte and gas from entering or leaving, and the surface portion of the metal tube which may come into contact with tap water is coated with an organic material which is non-conductive and insoluble in water.

2. 2. The platinum electrode composite structure according to claim 1, wherein the length of said thin platinum wire is 4 to 20 cm, and the length of said conductive metal tube is 4 to 20 cm.

3. A metal electrode composite structure comprising an electrode plate made of a metal such as gold or nickel whose surface is protected by an oxide film and which is resistant to oxidation to the inside, instead of a platinum plate, in the platinum electrode composite structure according to claims 1 and 2, a lead wire connected to the electrode plate, and the metal tube.

4. One end of the cylindrical electrolytic cell is completely sealed with a non-conductive flat plate, while the other end has a non-conductive flat plate with an opening bonded thereto. The two electrolytic layers are arranged so that their openings face each other. In each of the electrolytic cells, a gas collection tube for collecting hydrogen or oxygen generated by electrolysis of water is provided on a side surface of the cylindrical body located very close to the opening of the non-conductive flat plate, In two electrolytic cells, each of which is provided with a nozzle for introducing tap water in a direction away from the opening of the cylindrical body and with a nozzle for discharging tap water from the electrolytic cell on a side surface near the opposite end of the cylindrical body, a cation exchange membrane is inserted between the non-conductive flat plate having two openings, and the electrode plates, which are components of the electrode composite structure according to any one of claims 1 to 3, are positioned at the openings of the non-conductive flat plate adjacent to both sides of the cation exchange membrane, The metal wire and the metal tube connected thereto are also separated by the cation exchange membrane so as not to come into contact with each other, and are extended in different directions in a staggered manner, and a lead wire from an external DC power source is connected to the outer portion of the non-conductive flat plate of the metal tube, A packing is also sandwiched on the outside of each of the electrode composite structures, and the non-conductive flat plates are tightly fastened from the outside with fixing metal fittings. Tap water from a water supply faucet is introduced directly or once introduced into a water supply tank and then branched into the two electrolytic cells separated by the cation exchange membrane as a diaphragm, while adjusting the flow rate. In the tap water of each of the electrolytic cells, two electrode composite structures according to any one of claims 1 to 3 are immersed as a cathode and an anode adjacent to both sides of the cation exchange membrane; A direct current is passed through the water to electrolyze it, and hydrogen and oxygen are generated on the cathode and anode sides, respectively, and are separated and accumulated by the cation exchange membrane. The water purifier is characterized in that tap water discharged from the electrolytic cells on the cathode side and the anode side is placed in one water storage tank and mixed.

5. The water purifier according to claim 4, wherein the opening has a diameter of 3 to 6 cm.

6. 5. The water purifier according to claim 4, wherein said non-conductive plate is an acrylic resin plate.

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