Electrode composite structure and tap water purifier capable of removing free residual chlorine from 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 used for reducing and removing free residual chlorine in tap water and capable of separating and recovering generated hydrogen and oxygen, and a water purifier for tap water using the same.

Background Art

[0002] According to the Waterworks Act, in water purification plants where tap water is produced, chlorine is added so that no miscellaneous bacteria grow, and it is obligatory to maintain a residual chlorine concentration of a certain level or higher in the tap water. Residual chlorine includes free residual chlorine (Cl 2 , HOCl, OCl ― ) and combined residual chlorine (a compound in which hydrogen in NH 3 is replaced by chlorine, such as monochloroamine), but it is required that free residual chlorine with strong bactericidal power remains at 0.1 mg / L or more in tap water at the faucet. However, when the residual chlorine concentration in tap water increases, it has a bleachy smell and may also react with vitamin C (ascorbic acid) in food, so the target value for the residual chlorine concentration is less than 1 mg / L. Also, for "delicious water", it is desirably 0.4 mg / L or less. Water purification plants that produce tap water have long widely used "slow filtration" that can reduce miscellaneous bacteria with the help of biological purification using algae and the like. However, after World War II, after adding chemicals (such as polyaluminum chloride) to the turbid water taken from the river to cause the turbidity to coagulate and settle, physical "rapid filtration" has been widely carried out. As a result, rather than relying on biological purification to remove miscellaneous bacteria, it often relies on adding a large amount of chlorine to remove miscellaneous bacteria, and the free residual chlorine concentration at the faucet is likely to increase. In addition, the problem of trihalomethanes generated by the reaction between the added chlorine and humins in the raw tap water has also been raised. Also, frequent clogging of the separation membrane in the filter occurs due to "rapid filtration" of raw water with a large amount of turbidity, and there is a need to often backwash the separation membrane to eliminate clogging. Among people, there is a growing tendency to refrain from drinking raw tap water with a bleachy smell, and it is considered that the above circumstances are the reasons why many people buy bottled water and use it for drinking.

[0003] Devices commercially available under the name "water purifier" are devices that remove "harmful substances" in tap water. Among the "harmful substances", in particular, in order to remove free residual chlorine and other organic chlorine compounds (such as trihalomethanes), many pass tap water through an activated carbon layer. However, in such devices, mold grows in the activated carbon layer over time, and it has been pointed out that this growth is unsanitary. Also, inside a commercially available "alkaline electrolyzed water (alkaline ion water) generator" (Non-Patent Document 1) or a device simply called a "water conditioner", tap water from the faucet is subjected to an electrolysis reaction to generate hydrogen on the cathode side. However, the free residual chlorine in the tap water is not reduced and removed by the generated hydrogen, and is removed by passing the tap water through an activated carbon layer (Patent Documents 1 and 2).

[0004] As an electrode for electrolyzing tap water, it is highly desirable to use a platinum plate or a platinum plate with platinum black, which is difficult to be oxidized and has a catalytic action. However, platinum is expensive, which is a drawback. In this specification, in the following descriptions, the part described as "platinum plate" shall mean "platinum plate or platinum plate with platinum black". In the electrolysis reaction of water, 2H 2 O → 2H 2 + O 2 As represented by the reaction formula, hydrogen gas (hereinafter also simply referred to as "hydrogen") and oxygen gas (hereinafter also simply referred to as "oxygen") are generated at the cathode and anode, respectively, in a molar ratio of 2:1. In the electrolysis of water, at the anode, mainly 2H 2 O → O 2 + 4H + + 4e - An oxidation reaction represented by the reaction formula occurs, and oxygen gas is generated. At that time, when a metal electrode such as relatively inexpensive stainless steel is used as the anode metal, in addition to the reaction of generating oxygen, iron, nickel, chromium, etc. in the stainless steel are oxidized, and they become cations and elute into the electrolytic solution, which is an undesirable side reaction, or a side reaction also occurs in which oxides or hydroxides of these metals adhere to the electrode surface as an anodic oxide film (Non-Patent Document 2).

[0005] In order to minimize the overvoltage and reduce the loss of electrical energy in the electrolysis of water, and also to suppress the amount of platinum used, instead of using the platinum plate itself, electrodes in which platinum powder is adhered to the surface of a conductor substrate such as a carbon plate, or electrode plates in which powders of alloys of other transition metal elements such as palladium and iridium in addition to platinum are fixed to the surface of a conductor substrate have been developed. However, such electrode plates are difficult to fabricate, expensive, and have the drawback that the electrode surface is liable to deteriorate when a current is continuously passed for a long time. As an electrode, using a platinum plate makes the surface less likely to deteriorate and has durability even when a current is continuously passed for a long time. However, since platinum is expensive, it is required to use as little platinum as possible.

Prior Art Documents

Patent Documents

[0006] [Patent Document 1] Japanese Unexamined Patent Application Publication No. 2013-138996 [Patent Document 2] Japanese Unexamined Patent Application Publication No. 2009-207962 [Patent Document 3] WO2014077211A1 (The inventors are the same as those of the present invention) [Non-Patent Document]

[0007] [Non-Patent Document 1] "Applied Engineering of Water", edited by the Leading Research and Development Committee on "Advanced Engineering of Water" of the Japan Society for the Promotion of Science, Nikkan Kogyo Shimbun, Ltd., 2011, pp. 127-131 [Non-Patent Document 2] "Electrochemistry for Surface Technologists", by Shiro Haruyama, Maruzen, 2015, pp. 217-226 [Non-Patent Document 3] "Water Treatment Technology", by Yoroku Wada, Tokyo Denki University Press, pp. 54-57, 2011 [Non-Patent Document 4] "Technology for Purifying and Improving Water Environment" (supervised by Masataka Sugawara), CMC Publishing, 2010, pp. 189-190 [Summary of the Invention] [Problems to be Solved by the Invention]

[0008] In a water purification plant for supplying tap water, chlorine is added to sterilize various bacteria, and the free residual chlorine (Cl 2 , HOCl, OCl ― ) remaining in the faucet water is required to remain at 0.1 mg / L or more as described in

[0002] . However, when the concentration of residual chlorine in tap water increases, it has a bleachy smell and may also react with vitamin C (ascorbic acid) in food. Therefore, the target value for the concentration of residual chlorine is set to be less than 1 mg / L. Also, for "tasty water", it is desirable to be 0.4 mg / L or less. In commercially available "water purifiers", tap water from the faucet is passed through an activated carbon layer to remove free residual chlorine and organic chlorine compounds, etc. However, it has been pointed out that mold grows in the activated carbon layer over time, and this growth poses a problem of being unhygienic. In the electrolysis of water, at the cathode, 2H 2 O + 2e - → H 2 + 2OH - A reduction reaction as represented by the reaction formula occurs. The hydrogen just generated at the cathode is also called "hydrogen in the generation period", which has strong reactivity and a strong property of reducing other substances. If free residual chlorine can be removed by hydrogen with strong reactivity and large reducing power in the electrolysis of water, there is no need to use an activated carbon layer where mold is likely to grow for tap water. Therefore, for free residual chlorine, instead of passing tap water through an activated carbon layer that is said to be prone to mold growth, in the electrolysis reaction of water, an electrolysis device has been demanded that is devised to effectively utilize the reducing power of hydrogen generated at the cathode by using a platinum electrode composite structure that also has a catalytic effect as an electrode to reduce and remove free residual chlorine in tap water. In currently commercially available devices called "alkaline electrolyzed water (alkaline ion water) generation devices" and "water conditioners", tap water is electrolyzed to generate hydrogen. However, as described in

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

[0009] Platinum is difficult to oxidize and also functions as a catalyst, so it is a desirable metal for use as an electrode material in the electrolysis of water. However, since it is expensive, in terms of cost, it is desirable to use a thin platinum plate with a small aspect ratio and thin platinum wires to minimize its usage as much as possible. However, simply connecting a thin platinum plate and thin platinum wires together is inevitably weak in strength. For example, even if one attempts to join a thin platinum wire and a lead wire (such as a copper wire) that communicates with an external power source directly inside or outside the electrolytic cell by soldering or the like, the thin platinum wire is easily broken and prone to disconnection. Also, it is difficult to pass a thin platinum wire through the sealing means of the electrolytic cell. Even if it can pass through, as it is, air can enter from the outside through the small gap between the platinum wire and the sealing means, or conversely, the gas inside the electrolytic cell can flow out to the outside. As a result, it is difficult to maintain the airtightness of the electrolytic cell. There has been a demand to overcome the problem of developing an electrode that has mechanical strength while using such a thin platinum plate and thin platinum wires as the electrode metal and can still maintain the airtightness of the electrolytic cell.

[0010] Although platinum is desirable as the anode metal in the electrolytic cell, platinum is expensive, and even if a thin platinum plate and thin platinum wires are used, the device will be expensive. When using a cheaper metal that is more easily oxidized than platinum, when that metal comes into contact with the electrolytic solution, in addition to the reaction of generating oxygen mainly on the anode side, side reactions often occur where the metal is oxidized to become cations and does not dissolve into the electrolytic solution, or forms an anodic oxide film and adheres to the electrode surface. (Non-Patent Document 2) By using, instead of expensive platinum, other relatively inexpensive noble metals or metals such as cheaper nickel that form an oxide film on the surface and are less likely to be oxidized to the interior as the anode, the device can be made cheaper, and if it is possible to remove free residual chlorine in tap water to obtain potable tap water, that would be desirable in a practical sense. However, in that case, even if there is a possibility that the anode metal dissolves in the electrolytic solution, the amount is extremely small and does not affect health at all even if the tap water after passing through the device is drunk. There has been a demand to overcome the problem of developing an electrode for electrolyzing water. If a large number of such electrolytic devices that can be manufactured at low cost are used in parallel, the amount of tap water from which free residual chlorine has been removed can be increased. Furthermore, it can be expected that the generation rate of hydrogen gas and oxygen gas can be increased. When electrolyzing with an electrolyte solution used in a general electrolysis reaction, the recovered hydrogen gas and oxygen gas often contain droplets in which the electrolyte has dissolved. For hydrogen, for example, there is a risk of corroding the metal part of the container storing hydrogen in a fuel cell, leading to an explosion accident. Also, for oxygen, if it is used, for example, to assist human breathing, it may cause health damage. On the other hand, by electrolyzing safe tap water, the separated and accumulated hydrogen gas and oxygen gas do not contain such droplets, so they are safe and have high utility value. There has been a demand to overcome the problem of developing such a water electrolysis device.

Means for Solving the Problems

[0011] As a result of intensive research to solve all such problems, the inventor has made the invention described below. The embodiments described here are merely embodiments of the invention, and the technical scope of the invention is not limited thereto.

[0012] Near the upper end of a thin and small-sized platinum plate (for example, about 3.0 cm in length and width × about 1.4 cm, thickness 0.05 mm), a thin platinum wire (for example, outer diameter 0.3 mm, length 13 cm) is joined by electric welding (a method of flowing a large current through the joint part of the platinum wire and the platinum plate and melting and joining the platinum by the heat generated from the electrical resistance of that part), and it is preferable to coat it with a resinous adhesive or the like to reinforce the strength of the joint part of the platinum plate and the platinum wire and increase the strength. When soldering one end of the platinum wire on the side opposite to the end connected to the platinum plate electrode and one end of a lead wire (such as a copper wire) connected to an external power source, and trying to make the platinum wire penetrate the sealing means of the electrolytic cell, the platinum wire is likely to break. Also, even if the platinum wire can penetrate the sealing means, gas in the electrolytic cell flows out from a slight gap between the platinum wire and the penetration part of the sealing means, and air enters from the outside. To prevent such a situation from occurring, the inventor has taken the following measures. Extend the upper end of the platinum wire on the side opposite to the end connected to the platinum plate upward, and insert it into the opening at the lower end of a metal tube with a certain strength, such as a stainless steel tube, whose inner diameter is slightly larger than the outer diameter of the platinum wire (when using a platinum wire with a diameter of 0.3 mm as 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), and either let the metal tube penetrate it (Figure 1a) or insert the upper end of the platinum wire until it reaches at least 3 cm or more inside the inner part of the metal tube (Figure 1b). And the part where the thin platinum wire is inserted into the opening at the lower end of the metal tube is sealed with an adhesive, such as a resinous adhesive or the like, to prevent the electrolytic solution and the gas in the electrolytic cell from entering the metal tube. Further, the upper end part of the metal tube containing the platinum wire is also sealed with an adhesive, such as a resinous adhesive or the like, to prevent gas from leaking out of the inside of the cylindrical container or to prevent gas from entering the electrolytic cell from the outside. At this time, since the platinum wire is thin, it is not adhered to the inner surface of the metal tube. However, inside the metal tube, it is naturally and gently bent, and it is always in partial contact with the inner side wall of the metal tube having 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. However, by increasing the length of the portion of the platinum wire inserted inside the metal tube, an electric current can flow with almost no electrical resistance. When the length of the portion where the platinum wire is 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. Therefore, it is desirable that the length of the metal tube be within 10 cm. Furthermore, when using a metal tube with an inner diameter 0.7 mm or more larger than the outer diameter of the platinum wire, by inserting a thin metal wire into the gap between the platinum wire and the inner surface of the metal tube, the electrical resistance can be reduced and an electric current can flow. Note that the above-mentioned metal tube may be a circular tube or an arbitrary angular metal square tube. In this specification, in the following description, in order to prevent the description from becoming complicated, the portion described as "metal tube" shall mean "metal tube or metal square tube". Furthermore, since the platinum wire is in contact with the inner side surface of the metal tube such as a stainless steel tube, frictional force acts and it does not fall out downward. On the other hand, since the platinum wire is not in overall close contact with the inner surface of the metal tube, if the adhesive, such as a resinous adhesive, at the portion where the platinum wire is inserted from the lower end opening of the metal tube and at the upper end opening of the metal tube is peeled off, the platinum wire can be easily pulled out of the metal tube by hand. That is, even if the metal tube is fixed in close contact with the sealing means of the electrolytic cell, the platinum wire can be easily pulled out and replaced from the metal tube, and the platinum electrode composite structure can also be used in another electrolytic cell. Also, if a metal that is more easily oxidized than platinum, such as stainless steel, comes into contact with the electrolytic solution as an electrode inside the electrolytic cell, mainly on the anode side, the metal in the electrode is oxidized to become cations and dissolve into the electrolytic solution, or forms an anodic oxide film and adheres to the electrode surface. Therefore, on the surface of the metal tube, at parts where there is a possibility of contact with the electrolytic solution, it should be coated with an organic material insoluble in water, such as a heat-shrinkable tube or synthetic resin paint. However, on the surface of the metal tube at the part where the metal tube is in close contact with and penetrates the sealing means of the electrolytic cell, and on a part of the surface near the upper end of the metal tube protruding outside the electrolytic cell, in order to be able to solder or connect with a clamp to the lead wire connected to the external power supply so that current can flow, do not coat it with an insoluble organic material such as a heat-shrinkable tube or synthetic resin paint. As described above, when making the platinum electrode composite structure by reinforcing the platinum wire with the metal tube, while maintaining the strength as an electrode, the airtightness of the electrolytic cell can still be maintained, and it becomes possible to completely prevent the electrode metal from coming into contact with the electrolytic solution and being oxidized. It has been confirmed that such a platinum plate, the platinum wire, and the platinum electrode composite structure mechanically reinforced with the metal tube have durability even when current is passed for a long time and can stably promote the electrolysis reaction of water. Among commercially available water electrolysis devices or devices called "water conditioners", there are some that use an electrode with platinum plating on a titanium plate as an electrode. However, it is difficult to weld the titanium plate to other metals, and it is difficult to completely prevent lead wires such as stainless steel wires and copper wires connected to the titanium plate from coming into contact with the electrolytic solution (tap water). Therefore, the platinum electrode composite structure of the present invention is superior to the electrode with platinum plating on a titanium plate in that it can mainly prevent the oxidation of the metal on the anode side.

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

[0011] as the cathode and anode, while bringing them close to each other but not in contact with each other, a cation exchange membrane (Nafion, NRE-211 manufactured by DuPont, etc.) is arranged as a diaphragm between the cathode and the anode. Even in tap water with a very low electrical conductivity, when a safe DC voltage of 9V or less is applied between the anode and the cathode to perform an electrolysis reaction, the electrical resistance of the cation exchange membrane in tap water is relatively small, and the membrane thickness is also thin, so a current of 150 - 200 mA can flow. Compared with commercially available water electrolysis devices, hydrogen gas and oxygen gas are generated at the cathode and anode, respectively, at a comparable rate. The generated hydrogen gas and oxygen gas can be separated and dissipated into the atmosphere, or a gas accumulation tube can be provided at the upper part of the electrolytic cell to separate and recover them for effective utilization. The ratio of the amount of substance of hydrogen gas and oxygen gas generated at the cathode and anode, respectively, is almost close to 2:1. When attempting to electrolyze tap water in such a manner, it was confirmed that by simply passing an electric current for 4 - 5 minutes for electrolysis, most of the free residual chlorine can be reduced and removed by the highly reactive hydrogen that has just been generated at the cathode, without passing the tap water through an activated carbon layer. According to the experimental results of the present inventor, when the free residual chlorine in tap water at the water supply faucet was 0.25 - 0.35 mg / L, by applying a voltage of 6 - 9V and passing a current of 150 - 200 mA for 4 - 5 minutes, as measured by the DPD colorimetric method, not only the tap water on the cathode side but also the tap water on the anode side had the free residual chlorine reduced to less than 0.05 mg / L. This is presumably because the hydrogen that has just been generated at the cathode reduces and removes the free residual chlorine in tap water. The free residual chlorine in the tap water on the anode side is also reduced and removed. One reason is that a small amount of the just-generated hydrogen permeates through the cation exchange membrane (PEM, Nafion (NRE-211 manufactured by DuPont), etc.) (a phenomenon called "cross over", which may occur because hydrogen molecules are small) and moves to the anode side, and the free residual chlorine is reduced and removed by that hydrogen. The structure of free residual chlorine changes depending on the pH of the surrounding water. When the pH is 3 or less (acidic), it is mainly Cl 2At pH values of 4 to 7 (near neutral), it mainly exists as HOCl, and at pH values of 8 or higher (alkaline), it mainly exists as OCl ― and is considered to be the case. Its oxidizing power is Cl 2 , > HOCl > OCl ― . In an aqueous solution, OCl ― is considered to have significantly lower oxidizing and bactericidal powers compared to HOCl (Non-Patent Document 3). On the cathode side in electrolysis, 2H 2 O + 2e - → H 2 + 2OH - reacts as such to generate hydrogen, and tap water becomes alkaline due to the generation of OH - . On the anode side, 2H 2 O → O 2 + 4H + + 4e - reacts as such to generate oxygen, and tap water becomes acidic due to the generation of H + . Since 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, as a function of hydrogen, more free residual chlorine can be reduced in the acidic solution on the anode side than in the alkaline solution on the cathode side. Therefore, it can be inferred that even a small amount of hydrogen that permeates through the cation exchange membrane from the cathode side to the anode side can reduce free residual chlorine by that amount. In commercially available "alkaline electrolyzed water (alkaline ion water) generating devices" (Non-Patent Document 1) or devices simply referred to as "water conditioners," it is advertised that "alkaline ion water" is generated by electrolysis within the device. However, if the "alkaline ion water" is weakly alkaline, as described above, in tap water, free residual chlorine exists in the form of OCl ― , and its oxidizing and bactericidal powers are lower compared to tap water from a faucet. It is speculated that it becomes difficult to be reduced by the hydrogen generated at the cathode. In the water purifier of the present invention, even if a small amount of hydrogen moves (crosses over) to the anode side, most of the hydrogen and oxygen generated on the cathode side and the anode side of the electrolytic cell are separated and accumulated or released to the outside within the electrolytic cell, which should be noted. If the hydrogen and oxygen generated at the cathode and anode respectively remain mixed in the same space, there is a risk of explosion triggered by an electrical short circuit or the like. It should be noted that when the current is continuously passed through the water purifier of the present invention for 4 to 5 minutes or longer, the tap water on the cathode side gradually becomes weakly basic (pH 8 to pH 10), and the tap water on the anode side becomes weakly acidic (pH 5 to pH 7). After passing the current for several minutes, if the aqueous solution on the cathode side and the tap water on the anode side are mixed and discharged from the electrolytic cell, it has been discovered that an aqueous solution (tap water) that is almost neutral and in which most of the free residual chlorine has been reductively removed can be continuously obtained. Furthermore, after passing the current, by adjusting 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, the pH of the tap water discharged from the electrolytic cells on the cathode side and the anode side and mixed in the water storage tank can be adjusted to be close to the target value. When the water purifier of this embodiment electrolyzes safe tap water, the airtightness of the electrolytic cell is maintained, the strength of the electrodes is maintained, and on the anode side, the problem of preventing side reactions such as metals that are more easily oxidized than platinum, such as iron, chromium, and copper, coming into contact with the electrolyte and being oxidized to become cations and eluting into the electrolyte or fixing an anodic oxide film on the surface of the metal pipe can also be overcome. Therefore, it has been confirmed that the tap water after electrolysis can be used directly for drinking. However, since miscellaneous bacteria will mix in and grow in the tap water from which free residual chlorine has been removed over time, it is not preferable to drink it as drinking water if it is left as it is for a long time. Also, in the device called the "water conditioner", although the electrolysis reaction of water is taking place, almost none of the hydrogen and oxygen generated at the cathode and anode are effectively utilized. In contrast, in the water purifier of the present invention, the hydrogen (cathode) gas and oxygen (anode) gas generated by electrolyzing safe tap water do not contain droplets composed of electrolyte-dissolved water droplets. Therefore, for hydrogen, for example, it corrodes the metal part of the container storing hydrogen in a fuel cell, leading to an explosion accident, or for oxygen, even if it is used, for example, to assist human breathing, no health damage will occur. It has been confirmed that it is extremely effective for applications that emphasize safety. By the way, if an inexpensive dialysis cellophane membrane can be used instead of the cation exchange membrane, the device can also be made inexpensive. However, the electrical resistance of the dialysis cellophane membrane (such as visking tubing) in water is more than 10 times greater than that of the cation exchange membrane. For example, at a low voltage of 12V or less, only a small current flows, and it has been found that it is not suitable for use in an electrolysis device using tap water as an electrolyte.

[0014] In the activated carbon layer provided in the commercially available water purifier, organic chlorine compounds other than free residual chlorine can also be adsorbed and removed, but the activated carbon layer also has the problem that mold is likely to occur. Regarding trihalomethane as an organic chlorine compound (which is generated by the reaction of chlorine added for sterilization in the process of purifying water with organic compounds such as humin in water, and is a general term for four substances: chloroform, bromodichloromethane, dibromochloromethane, and bromoform), strict standards have been set for its content in tap water in Japan. For example, regarding chloroform, which is said to be the most abundant among trihalomethanes, the Japanese standard for tap water is 0.06 mg / L or less (0.3 mg / L or less of the WHO standard). In Japan, in the process of purifying and supplying tap water, measures are taken to aerate the tap water as necessary to reduce the concentration of trihalomethanes. If necessary, after passing the tap water through the electrolysis device of the present invention, a simple device similar to the mechanism of a "jet layer type VOC (Volatile Organic Compounds) removal device" (Non-Patent Document 4) is provided, in which air is blown into the tap water to transfer chloroform into the air and discharge it outside. In this way, the concentration of trihalomethanes (including chloroform) in tap water can be reduced. Since trihalomethanes are volatile, heating or boiling tap water can remove most of the trihalomethanes (including chloroform) in the tap water. Of course, there is also a method of attaching an activated carbon layer separately. In that case, considering that mold grows on the activated carbon layer, it is necessary to frequently replace the activated carbon layer with a new one. In addition, in the tap water in Japan, even in the water from the faucet, since the free residual chlorine is managed to be 0.1 mg / L or more, there are not many miscellaneous bacteria (such as Escherichia coli) in the tap water, and it is considered that there is almost no need to pass it through a ceramic filter, a hollow fiber membrane, etc. intentionally. Also, among the commercially available water purifiers, some pass tap water through a ceramic filter, a hollow fiber membrane, etc., but problems such as clogging with bacteria and turbidity during use have been pointed out, and they cannot be used continuously for a long time. Therefore, in the present invention, among the "harmful substances" that are desirable to be removed, particular attention is paid to "free residual chlorine". In the device with the structure shown in

[0011] and

[0012] , a platinum electrode composite structure with sufficient structural strength can be formed by the thin platinum plate, the thin platinum wire joined thereto, and the metal tube. Without passing the tap water through an activated carbon layer where mold may occur, a water electrolysis device can be fabricated that can reduce and remove free residual chlorine and the like from tap water by electrolyzing the tap water using a cation exchange membrane (such as Nafion, NRE-211 made by DuPont) as a diaphragm. That is, it has been found that with the water purifier of the present invention, most of the "free residual chlorine" can be removed without passing through the activated carbon layer, and since the structure is simple, clogging does not occur.

[0015] Platinum is desirable as the metal used as the electrode among the electrolytic devices described in

[0011] to

[0013] . However, platinum is expensive, and even if a thin platinum plate and thin platinum wire are used, the device will be expensive. Therefore, instead of the platinum plate and platinum wire as the electrode, by using other relatively inexpensive noble metals or cheaper metals such as nickel, which form an oxide film on the surface and are difficult to be oxidized to the inside, it is valuable to explore a method that can remove the free residual chlorine in tap water while making the device cheaper. When nickel is used as the anode, even though nickel may be oxidized and a trace amount of nickel metal ions may dissolve in tap water, if the amount is extremely small, drinking the tap water after passing through the device will hardly affect health. By adjusting the flow rate of the tap water passing through the device and ensuring that the residence time of the tap water in the device is not too long, it is also possible to drink the tap water. Also, the above nickel ions are not included in the water quality standard items in tap water in the Waterworks Law and are considered to be relatively less harmful. When using a nickel wire, if a nickel wire with an outer diameter of about 0.3 to 0.5 mm is coated with a heat shrinkable tube and the heat shrinkable tube and the sealing means are adhered with an adhesive at the part passing through the sealing means of the electrolytic cell, it is not necessarily necessary to pass the nickel wire through a stainless steel tube with a certain degree of strength (Patent Document 3). If a large number of such inexpensive electrolytic devices are used in parallel, the amount of tap water that can remove free residual chlorine can be increased, and the generation rate of hydrogen and oxygen obtained by separation can also be increased. Based on these comprehensive findings, the inventor has developed a highly functional platinum electrode composite structure that can minimize the use of expensive platinum, has a relatively low manufacturing cost, is easy to handle and durable, as well as a water purifier using this platinum electrode composite structure. In order to make the device less expensive, while using a metal electrode composite structure such as other precious metals or nickel whose surface forms an oxide film and is not easily oxidized to the inside, it is possible to remove free residual chlorine in tap water, and also to separate, recover and effectively utilize hydrogen and oxygen generated from the electrodes, and thus invented a water purifier.

Advantages of the Invention

[0016] Although the electrode in the electrolysis device according to the present invention uses expensive platinum, a thin platinum plate (for example, about 3.0 cm × about 1.4 cm, thickness 0.05 mm) is used as the electrode, and a thin platinum wire (for example, diameter 0.3 mm, length 13 cm) is also used for the lead wire, so the amount of platinum used is quite small and it does not become so expensive (for example, if a platinum wire with a diameter of 1.0 mm is used, the price will be more than 10 times higher). If the upper end of the thin platinum wire is inserted into at least 3 cm inside a strong metal tube such as stainless steel that airtightly penetrates the sealing means (when a platinum wire with a diameter of 0.3 mm is used as the platinum wire, 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 is always in partial contact with the inner side surface of the metal tube, so there is almost no electrical resistance between the platinum plate and the external power supply terminal through the metal tube, and current can flow. Also, the part where the platinum wire is inserted from the opening at the lower end of the metal tube and the opening at the upper end of the metal tube are sealed with an adhesive, such as a resinous adhesive, etc., so it is possible to completely prevent air from entering from the outside of the metal tube where the platinum wire is located, and the gas accumulated in the electrolytic cell from flowing out to the outside. Also, on the outer surface of the metal tube that may come into contact with the electrolytic solution (tap water), it is coated with an organic material insoluble in water, such as a heat shrinkable tube 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 tap water with low electrical conductivity is used as the electrolytic solution, a cation exchange membrane with a relatively low electrical resistance is used as the diaphragm, and the cathode and anode of the present invention are brought close to each other for electrolysis. Even at a low voltage of 6 to 7 V (preferably 12 V or less for safety), by flowing a current of 150 to 200 mA for only 4 to 5 minutes, most of the free residual chlorine in the tap water can be reduced and removed by the hydrogen generated on the cathode side. Although hydrogen is not generated on the anode side, a small amount of the hydrogen just generated on the cathode side permeates through the cation exchange membrane (such as Nafion, NRE-211 made by DuPont, etc.) and moves (cross over) to the anode side. Therefore, most of the free residual chlorine in the tap water on the anode side can also be reduced and removed. If the current is continuously passed for a long time, the tap water on the cathode side gradually becomes weakly basic (pH 8 to pH 10), and the tap water on the anode side gradually becomes weakly acidic (pH 5 to pH 7). However, if the tap water discharged from the electrolytic cell on the anode side and the tap water on the cathode side are put into the same water storage tank and mixed, it becomes almost neutral tap water with most of the free residual chlorine removed. Furthermore, by adjusting the mixing ratio of the tap water on the anode side and the aqueous solution on the cathode side, potable tap water with the target pH can be obtained.

[0018] The electrode of the present invention shown in

[0015] uses a thin platinum plate (for example, about 3.0 cm × about 1.4 cm, thickness 0.05 mm) as the electrode and also uses a thin platinum wire (for example, diameter 0.3 mm, length 13 cm) for the lead wire, and although the amount of platinum used is small, platinum is expensive, so the device is still expensive. Therefore, even if tap water is electrolyzed using a metal such as nickel, which is cheaper than platinum and has an oxide film formed on the surface and is difficult to be oxidized to the inside, as the electrode, it is possible to remove the free residual chlorine in the tap water. When nickel is used as the electrode, although there is a possibility that it may be oxidized and dissolved into the tap water as nickel ions, the amount is very small. By adjusting the flow rate of the tap water passing through the device and by not making the residence time of the tap water in the device too long, the tap water after electrolysis can be used for drinking. Also, nickel ions are not included in the water quality standard items in tap water in the Waterworks Act, so their harmfulness is considered to be small. When connecting a nickel wire with an outer diameter of about 0.3 to 0.5 mm to a nickel plate as an electrode, it is not always necessary to pass the nickel wire through a stainless steel tube with a certain strength. Instead, the nickel wire can be coated with a heat-shrinkable tube, and at the part passing through the sealing means of the electrolytic cell, the heat-shrinkable tube and the sealing means can be adhered with an adhesive to maintain the airtightness of the electrolytic cell (Patent Document 3). If a large number of such inexpensive electrolytic devices are used in parallel, the flow rate of tap water that can remove free residual chlorine can be increased, and furthermore, the generation rate of hydrogen gas and oxygen gas obtained by separation can also be increased. When electrolyzing with an electrolyte solution used in a general electrolysis reaction, the hydrogen gas and oxygen gas accumulated often contain water droplets and droplets in which the electrolyte is dissolved. Such hydrogen gas may corrode the metal part of the metal container used for storage, for example, for use in a fuel cell, leading to an explosion accident. Also, if such oxygen gas is used, for example, for assisting human breathing, it may have an adverse effect on human health. In contrast, in the device of the present invention, since the hydrogen gas and oxygen gas separated and accumulated by electrolyzing safe tap water do not contain water droplets and droplets in which the electrolyte is dissolved, there is no such concern as described above, and it is safe and highly valuable for use.

Best Mode for Carrying Out the Invention

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

Examples

[0020] Hereinafter, embodiments of the present invention will be described with reference to the drawings. As exemplarily illustrated in FIG. 1, the platinum electrode composite structure of the present invention has, near the upper end of a thin platinum plate (for example, 3.0 cm × 1.4 cm, thickness 0.05 mm) 1, one end of a thin platinum wire 2 having an outer diameter of 0.3 mm and a length of 13 cm or more connected by electric welding (it is desirable to add an adhesive to the connected portion to reinforce it in terms of strength). The end on the opposite side of the platinum wire 2 is inserted into the opening at the lower end of a metal tube 3 having a certain strength, such as a stainless steel tube with an inner diameter 0.1 to 0.7 mm larger than the outer diameter of the platinum wire and a length of 5 to 20 cm (when using a platinum wire with a diameter of 0.3 mm as the platinum wire, 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 2 is inserted into the metal tube 3 so that it penetrates the metal tube 3 and protrudes 1 to 2 cm from the metal tube (FIG. 1a), or the upper end of the platinum wire 2 is inserted until it reaches at least 3 cm or more inside the metal tube 3 (FIG. 1b). Then, the portion where the thin platinum wire 2 is inserted into the metal tube 3 is sealed with an adhesive 4, such as a resinous adhesive, so that the electrolytic solution (tap water) in the electrolytic cell and the gas in the electrolytic cell do not enter the metal tube 3. Further, the upper end portion of the metal tube 3 containing the platinum wire 2 is also sealed with an adhesive 4, such as a resinous adhesive. With this configuration, gas does not leak from the inside of the electrolytic cell and the metal tube 3, or gas does not enter the electrolytic cell and the metal tube 3 from the outside. The platinum wire 2 is not adhered to the inner surface of the metal tube, but is naturally gently curved inside the metal tube 3. Since the metal tube 3 has a thin 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. Between the platinum plate 1, the platinum wire 2, and the metal tube 3, an electric current can flow with almost no electrical resistance. When, for example, a stainless steel pipe is used as the metal pipe that is a component of the platinum electrode composite structure serving as the anode inside the electrolytic cell, if it comes into contact with tap water (the electrolytic solution), metals such as iron, nickel, and chromium inside the stainless steel that are more easily oxidized than platinum may be oxidized to become cations and dissolve into the electrolytic solution, or form an anodic oxide film and adhere to the electrode surface. Therefore, the surface portion of the metal pipe 3 that may come into contact with tap water (the electrolytic solution) is coated with a non-conductive and water-insoluble organic material such as a heat-shrinkable tube or a synthetic resin paint. However, for the portion where the metal pipe penetrates the sealing means of the electrolytic cell and a part of the surface near the upper end of the metal pipe protruding outside the electrolytic cell, such coating is not applied so that it can be soldered or connected with a banana clip to the lead wire connected to the external power source to allow current to flow. One platinum electrode composite structure is formed by the thin platinum plate 1, the thin platinum wire 2, and the metal pipe 3 with a certain degree of strength as described above, and two of these platinum electrode composite structures are used as the cathode and anode in the electrolysis of tap water. Furthermore, since the difference between the inner diameter of the metal pipe 3 and the outer diameter of the inserted platinum wire 2 is as small as 0.1 to 0.7 mm, as a result of the platinum wire coming into contact with the inner side wall of the metal pipe such as a stainless steel pipe, a frictional force acts in the longitudinal direction and it 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 pipe, if the adhesive 4, such as a resinous adhesive, at the portion where the platinum wire 2 is inserted from the lower end of the metal pipe and at the upper end of the metal pipe is peeled off, the platinum wire 2 can be easily pulled out of the metal pipe 3 by hand. That is, even if the metal pipe is tightly fixed to the sealing means of the electrolytic cell, the platinum plate 1 and the platinum wire 2 can be easily pulled out of the metal pipe 3 and replaced. Therefore, 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, 3) as a component of the electrolytic cell has, for example, an outer diameter of 5 to 7 cm and an inner diameter of 4 to 6 cm if it is cylindrical, and a cross-sectional size of about 4 cm × 4 cm if it is a square cylinder. The cylindrical body 5 has a length of 13 to 18 cm, and one end thereof is adhered near the center of a non-conductive flat plate 6 (for example, an acrylic resin flat plate of 17 cm × 17 cm and a thickness of about 5 mm) obtained by non-conductive treatment of the surface of a resin flat plate or metal with a size of 16 to 20 cm in length and width, and is completely blocked. The other end of the cylindrical body 5 has the same size as the non-conductive flat plate 6, but as shown in Figs. 2a and 2b, it is adhered to a non-conductive flat plate 7 having an opening (the opening has a diameter of 3 to 6 cm if it is circular and a size of about 4 cm × 4 cm if it is square) near the center, so that the opening of the cylindrical body 5 can completely cover the opening of the non-conductive flat plate 7. Let two such containers be electrolytic cell A (Fig. 2a) and electrolytic cell B (Fig. 2b). In electrolytic cell A and electrolytic cell B, at the upper part of the side surface of the cylindrical body 5 at a position very close to the opening of the non-conductive flat plate 7, in electrolytic cell A, hydrogen generated by the electrolysis of water is accumulated, and in electrolytic cell B, oxygen generated by the electrolysis of water is accumulated. There are provided gas accumulation pipes 11 (electrolytic cell A) and 12 (electrolytic cell B) which are about 2 cm in outer diameter with graduations, about 20 to 30 cm in length, extend upward, and have an opening and closing valve 13 that can be opened and closed at the upper end. Further, on the side surface of the cylindrical body 5 at a position close in the direction away from the opening of the non-conductive flat plate 7, there are nozzles 14, 16 (Fig. 2a, Fig. 2b) with an inner diameter of about 6 mm for introducing tap water, and on the side surface of each cylindrical body 5 at a position close to the non-conductive flat plate 6 on the opposite side of the opening, there are provided nozzles 15, 17 (Fig. 2a, Fig. 2b, Fig. 3) with an inner diameter of about 6 mm for draining tap water from the electrolytic cell. Also, on the side surface of the cylindrical body 5 between nozzles 14 and 15 and between nozzles 16 and 18, preliminary nozzles 19, 20 with an inner diameter of about 6 mm are respectively provided. The preliminary nozzles 19, 20 are used to partially extract the electrolytic solution to measure the pH etc. of the electrolytic solution in electrolytic cell A and electrolytic cell B, or to join a silicone rubber tube extending upward and a liquid reservoir to the nozzles, and by moving the liquid reservoir up and down, the volume of the hydrogen and oxygen accumulated inside the gas accumulation pipes 11 from electrolytic cell A and 12 from electrolytic cell B with graduations under atmospheric pressure can be determined. The non-conductive flat plates 7 of the two electrolytic cells A and B shall be non-conductive flat plates with an outer edge that is 4 to 6 cm away from the side surface of the cylindrical body to which they are adhered. This is to enable the non-conductive flat plates 7 of each of the electrolytic cells A and B to be clamped by a fitting 21 such as a clamp outside the cylindrical body 5 (Figs. 3 and 4). When manufacturing the electrolytic cells A and B in such a form, when the non-conductive flat plates 7 of the two containers face each other, adjust the shape, shape of the opening, size, and position of the non-conductive flat plate 7 so that the respective openings fit exactly, and at the outer part of the cylindrical body 5, make it a structure that is clamped from the outside using about 4 to 6 fixing fittings 21 such as clamps on both sides of the two non-conductive flat plates 7 (Fig. 3). Between the non-conductive flat plates 7 of the electrolytic cells A and B facing each other, place two silicone rubber sheets with openings of the same size and position as the non-conductive flat plates 7 and a thickness of about 1 mm as packing 22, and place the two platinum electrode composite structures (cathode 8 and anode 9) described in

[0018] therebetween. Further, insert a positive ion exchange membrane (PEM, positive ion exchange membrane, Nafion, DuPont NRE-211, etc.) 10 so that its upper, lower, left, and right widths cover about 1 to 2 cm wider than the openings of the non-conductive flat plate 6 (Fig. 3), and it has a structure that is clamped by fittings 21 such as about 4 to 6 clamps from the outside of the two non-conductive flat plates.However, regarding 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 (for example, 3.0 cm × 1.4 cm, thickness 0.05 mm) of the platinum electrode composite structure in

[0018] is positioned in the opening of the non-conductive flat plate 7 as shown in FIG. 4. The two platinum wires 2 and the metal tubes 3 are arranged close enough to be in close contact with both sides of the cation exchange membrane 10. The platinum wires 2 (for example, outer diameter 0.3 mm, length 13 cm) and the metal tubes 3 (for example, 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 away from each other in an alternating direction. Further, the two metal tubes 3 of the platinum electrode composite structure protrude 6 to 7 cm above from the outer edge of the non-conductive flat plate 7 and are 2 to 4 cm apart from each other (FIGS. 3 and 4). Also, the respective platinum wires 2 and metal tubes 3 forming the cathode and the anode are separated by the cation exchange membrane 10 so that no current flows between them (FIGS. 4, 5, and 6). Between the two non-conductive flat plates 7, at the position shown in FIG. 4, the cation exchange membrane 10 is used as a diaphragm to sandwich the platinum electrode composite structure (cathode and anode), and silicone rubber sheets with a thickness of about 1 mm on both sides thereof are sandwiched as packings 22 and strongly clamped from the outside of the non-conductive flat plates 7 with fittings 21 such as clamps. Thus, the electrolytic solution (tap water) is prevented from leaking to the outside. However, in order to further prevent the electrolytic solution (tap water) from leaking to the outside, an adhesive is sufficiently applied to the outer edge portions of the two non-conductive flat plates 7. However, even if the electrolytic solution (tap water) leaks out, it is safe water and there is no danger at all. The two electrolytic cells (electrolytic cell A and electrolytic cell B) sandwich the two platinum electrode composite structures (cathode 8 and anode 9) and the cation exchange membrane 10, and are combined to be the main part of the device for removing free residual chlorine by electrolyzing tap water and accumulating and recovering hydrogen and oxygen (electrolytic cell 23, FIG. 3). To show the positional relationship between 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, the cross-sectional view seen from the side is shown in FIG. 5, and the cross-sectional view seen from above is shown in FIG. 6. As shown in Fig. 7, tap water discharged from the water tap 24 is directly branched, or after being once stored in the water storage tank 25, and then branched. For the electrolytic cell A (cathode side), tap water is introduced from the nozzle 14 of the cylindrical body 5 of the electrolytic cell A while adjusting the flow rate with the flow rate regulator 26. For the electrolytic cell B (anode side), tap water is introduced from the nozzle 16 of the cylindrical body 5 while adjusting the flow rate with the flow rate regulator 27. In the electrolytic cell 23, on both sides of the cation exchange membrane 10, platinum electrode composite structures (cathode 8 and anode 9) immersed in tap water are brought close to each other. A lead wire from a DC power source is connected to the uncoated part of the metal tube 3 of the platinum electrode composite structure protruding above the non-conductive flat plate 7 to apply a voltage and pass an electric current to electrolyze tap water. At the cathode 8 and the anode 9, hydrogen and oxygen are generated respectively, but are separated by the cation exchange membrane 10. In the electrolytic cell A, hydrogen accumulates in the gas accumulation tube 11, and in the electrolytic cell B, oxygen accumulates in the gas accumulation tube 12. The hydrogen and oxygen accumulated in the gas accumulation tubes 11 and 12 can be discharged to the outside by opening the on-off valve 13 at the upper end of the accumulation tube and sucking from the outside, or can be discharged to the outside by being extruded by the water pressure of tap water. In the electrolytic cell 23, even when a DC voltage of about 6 - 7V, a relatively low voltage, is applied to the two platinum electrode composite structures (cathode and anode), and even when the electrolyte in which the electrodes are immersed is tap water with a low electrical conductivity such as tap water, a current of about 150 - 200 mA flows. In the electrolytic cell A (cathode side), tap water with most of the free residual chlorine removed is discharged from the nozzle 15, and in the electrolytic cell B (anode side), tap water with most of the free residual chlorine removed is discharged from the nozzle 17. For tap water with a free residual chlorine of 0.2 - 0.4 mg / L at the water tap, by simply passing an electric current for 4 - 5 minutes, the experimental result shows that according to the measurement result by the DPD colorimetric method, the free residual chlorine in the tap water on both the cathode side and the anode side is less than 0.05 mg / L. This is because the hydrogen generated on the cathode side reduces the free residual chlorine in the tap water on the cathode side. However, since a part of the hydrogen generated on the cathode side permeates through the cation exchange membrane 9 and moves to the anode side (cross over), it is considered that the free residual chlorine in the tap water on the anode side is also reduced. In the electrolytic cell A, tap water is introduced from the nozzle 14 and drained from the nozzle 15. In the electrolytic cell B, tap water is introduced from the nozzle 16 and drained from the nozzle 17. However, since the tap water does not pass through an activated carbon layer, a ceramic filter, etc. in either electrolytic cell, the pressure loss of the tap water is almost zero. The tap water discharged from the drain nozzle 15 of the electrolytic cell A on the cathode side tends to become weakly alkaline, and the tap water discharged from the drain nozzle 17 of the electrolytic cell B on the anode side tends to become weakly acidic. However, most of the free residual chlorine has been removed from both tap waters, and when they are mixed in the water storage tank 28 from the nozzles 30 and 31 of the water storage tank 28, the tap water becomes almost neutral. By adjusting the flow rates of the tap water introduced respectively with the flow regulators 26 and 27, as shown in Fig. 8, the pH of the tap water entering and being mixed in the water storage tank 28 can also be adjusted. An air vent nozzle 32 is also provided at the upper part of the water storage tank 28. By opening the on-off valve 29 located near the bottom of the side surface of the water storage tank and discharging the tap water therefrom, the tap water can be used for drinking. However, since the free residual chlorine concentration of the tap water stored in the water storage tank 28 is low, care must be taken because there is a possibility that miscellaneous bacteria may invade and proliferate from the air if it is stored for a long time. Furthermore, when an aqueous solution of a general electrolyte is electrolyzed, the hydrogen gas generated and the oxygen gas generated on the anode side (electrolytic cell B) often contain droplets in which the electrolyte is dissolved. However, such droplets are not contained in the hydrogen gas and oxygen gas generated by electrolyzing safe tap water. Therefore, for hydrogen, for example, the metal part of the container storing the hydrogen stored in a fuel cell will not be corroded and hydrogen will not leak out to cause an explosion accident. Also, for oxygen, for example, even if it is used as human breathing gas, it will not harm health. Both are safe and highly useful.

[0022] Although platinum is desirable as the anode metal for the platinum electrode composite structure shown in 〔0018〕, platinum is expensive, and even if a thin platinum plate and a thin platinum wire are used, the device will be costly. Therefore, among the platinum electrode composite structures described in 〔0018〕, instead of platinum, other noble metals such as gold, or less expensive metals such as nickel, which form an oxide film on the surface and are less likely to be oxidized internally, are used to make the device less expensive while removing free residual chlorine in tap water. At this time, on the anode side, even if a relatively inexpensive noble metal or nickel is oxidized and its metal ions may dissolve slightly in tap water, when the amount is extremely small, by adjusting the amount of tap water introduced and not making the residence time of tap water in the device too long, it is possible to ensure that drinking the tap water after passing through the device will have no impact on health. If a large number of such inexpensive electrolytic devices are used in parallel, the amount of tap water from which free residual chlorine can be removed can be increased, and the generation rates of hydrogen and oxygen obtained by separation can also be increased. At this time, when hydrogen is used, for example, in a fuel cell and oxygen is used, for example, in human breathing gas, in addition to removing free residual chlorine, a highly effective effect in another aspect can also be expected.

Brief Description of the Drawings

[0023]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

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-blackened 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 tap water and gas from entering or leaving, and the surface portion of the metal tube that may come into contact with tap water is coated with an organic material that 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.

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