JPS63143277A - Method and device for generating sodium hypochlorite - Google Patents

Abstract

PURPOSE:To produce a soln. of sodium hypochlorite in the concn. conforming to the Food Sanitation Law by using an anode coated with a mixture consisting of Pt, PdO, RuO2, and TiO2 in a specified ratio, and electrolyzing an aq. NaCl soln. under specified conditions. CONSTITUTION:The device is formed with a cooling unit 6 consisting of the cooling coil 4 provided around a vessel 1 and a cooling condenser 5, a cathode 3 connected to the timer 7 and rectifier 8 fixed to the vessel 1, and an anode 2. The anode 2 is formed by coating a ternary mixture consisting of 3-42wt% Pt, 3-34wt% PdO, and 42-92wt% RuO2 and a mixture contg. 20-40wt% TiO2, based on the ternary mixture, on Ti or a Ti alloy. In such a structure, >=10wt% aq. NaCl soln. is kept at 10-22 deg.C, and electrolysis is carried out at 10-500A/dm<2> cathode current density and 10-20A/dm<2> anode current density and in 1/1.4-1/40 ratio of the cathode current density to the anode current density. By this method, a soln. contg. >=4% sodium hypochlorite is produced.

Description

Detailed Description of the Invention (Industrial Field of Application) This invention relates to a method and apparatus for generating sodium hypochlorite. A method for easily producing sodium hypochlorite with a high concentration of 1% or more, and a small-sized sodium hypochlorite generator for the same.

(Prior art) Chlorine treatment has been widely used in grocery stores, cafeterias, fish and meat stores, food departments of retail stores, etc. for cleaning sterilization, oxidation treatment of waste liquids, and disinfection of water and sewage systems. Sodium hypochlorite has been used as a Commercially available sodium hypochlorite with a concentration of 12% is usually used for these treatments, but the concentration decreases during storage, requires a large storage space, and has problems such as 1) handling, economical efficiency, etc. There were two problems.

In order to solve these problems 1: The present applicant is small,
In addition, he proposed a sodium hypochlorite generator that had a compact structure and was inexpensive (W Application 6O-161255). This device has 3
% of dilute salt water is electrolyzed to obtain an effective chlorine concentration of 13.
This is a device that can generate a sodium hypochlorite solution containing O'OOppm (1.3%) with high current efficiency, but even if the current efficiency is ignored and electrolysis is performed, the maximum yield is 20,000p.
Only a sodium hypochlorite solution of about pm (2%) can be obtained, and it is almost impossible to obtain a sodium hypochlorite solution of 4% or more, which is approved as a food additive under the Food Sanitation Act.

(Problems to be Solved by the Invention) An object of the present invention is to improve the above-mentioned apparatus and provide a small-sized apparatus capable of obtaining a sodium hypochlorite solution having a concentration that complies with the Food Sanitation Law. .

A further object of the present invention is to provide a method for generating a sodium hypochlorite solution with a high concentration of 4% or more.

(Means for Solving the Problems) The present inventors have conducted various studies to solve the above problems, and have found a method for generating sodium hypochlorite that can achieve the above objects, and a generation method used therein. The device has now been completed.

That is, the device of the present invention comprises a container, a cooling unit provided around or inside the container and comprising a cooling coil and a cooling condenser, and a cathode and an anode fixed to the container and connected to a timer and a rectifier. and the effective area ratio of the cathode and anode is 1:1.4.
~1;40, and the anode is made of titanium or titanium alloy, 3 to 42% by weight of platinum, and 3 to 34% by weight of palladium oxide.
% by weight, a ternary mixture of platinum group metals of platinum-palladium oxide-ruthenium dioxide having a composition of 42-94% by weight of ruthenium dioxide;
This is a sodium hypochlorite generator coated with a mixture consisting of 40% titanium. Furthermore, the present invention uses an anode having the above-mentioned special coating, maintains an aqueous solution with a sodium chloride concentration of 10% by weight or more at 10 to 22°C, and maintains a cathode current density and an anode current density of 10 to 5%, respectively.
00A/dIo" and 10-20 A/c1m",
And the ratio of anode current density to cathode current density is 1:1.4 ~
This is a method of electrolysis at a ratio of 1:40.

The present invention will be explained with reference to the following drawings. FIG. 1 is a schematic diagram showing a specific example of the apparatus of the present invention. A power supply box 9 is provided at an appropriate position near the container 1 filled with saline solution 10, and houses a rectifier 3 for converting alternating current into direct current and a timer 7 for setting the electrolysis time. A cathode 3 and an anode 2 connected by a rectifier 8 are suspended and fixed to the upper part of the container 1 so as to face each other. The purpose of the present invention can be achieved by attaching the electrodes by inserting them from the side or bottom of the container 1 so that they are removed one inch apart, rather than by hanging and fixing them as shown in the drawings. A cooling coil 4 is wound around the container 1, and the saline solution 10 is cooled by a refrigerant sent from a cooling condenser 5. In this case, if the cooling coil 4 is made of a material that is resistant to sodium hypochlorite, it can be placed directly into the saline solution 10 for cooling. These containers 1, a cooling unit 6 consisting of a cooling coil 4 and a cooling condenser 5, and a power supply box 9 are housed in an outer box 13 to constitute a sodium hypochlorite generator. Note that 11 is a sodium hypochlorite outlet υ, which is connected to the bottom of the container 1. This device 1 is equipped with a power supply hood 12 connected to a timer 7.

As an electrode, the anode 2 is made of platinum having a composition of 3 to 42% by weight of platinum, 3 to 34% by weight of palladium oxide, and 42 to 94% by weight of ruthenium dioxide on titanium or a titanium alloy. - a platinum group metal ternary mixture of palladium oxide and ruthenium dioxide;
An electrode coated with a mixture consisting of 0 to 40% by weight of titanium dioxide (Japanese Patent Publication No. 35473/1983) is used, and the cathode 3 is mainly made of titanium, Hastelloy or stainless steel plates, or expanded plates. A round bar is used.

The coating of the anode 2 used in the present invention is adjusted as follows. After the titanium surface has been degreased, it is treated with hexachloric acid or oxalic acid, and a coating liquid is applied thereon by coating or dipping. For the coating solution, platinum tetrachloride, palladium dioxide, and ruthenium trichloride were selected so that the platinum-palladium oxide-ruthenium dioxide ratio was within the range of the present invention, and a small amount of hydrochloric acid was added, followed by n-butyl alcohol to completely dissolve them. let A predetermined amount of Petyl Titanium 1 is added to this for adjustment. After drying, heat in air at a heating temperature of 450 to 600°C for 10 to 30 minutes. Coating and heating are repeated several times t&9 to obtain a coating of desired thickness.

The distance between the anode 2 and the cathode 3 is 1 to 7I, and a protective tube is attached around the electrode to protect the electrode, if necessary. The effective area ratio of the cathode 3 and anode 2 used in the device of the present invention is set to 1:1.4 to 1:40, and the current density of the cathode is set to be 1.4 to 40 times that of the anode. If the area of the cathode is made larger than this effective area ratio (that is, if the cathode current density is made smaller than 1.4 times that of the anode), ineffective decomposition of sodium hypochlorite produced in one electrolysis occurs, resulting in a high concentration of sodium hypochlorite. Unable to obtain sodium hypochlorite solution 5 Also, if the area of the cathode is made smaller than this area ratio, that is, if the cathode current density is made larger than 40 times that of the anode, the current value per cross-sectional area becomes too high. Therefore, it is difficult to apply electricity, and the heat generated when electricity is applied increases, making it impossible to obtain a highly concentrated sodium hypochlorite solution.In addition, in the present invention, the effective area of the electrode is defined as the Refers to the total area of the electrode that is immersed and subjected to electrolysis.

Further, in the present invention, when the ratio of the anode current density to the cathode current density is 1 m1.4 to 1:40, the current density flowing through the cathode and the anode is 10 to 500 A/dm'' and 10-20 A, respectively. /dm”. If the current density of the cathode is lower than the above range, the sodium hypochlorite produced by electrolysis will be ineffectively decomposed, making it impossible to obtain a highly concentrated sodium hypochlorite solution. Moreover, if the current density of the cathode is higher than the above range, the electrolytic voltage will be 10 V or more, leading to destruction of the electrode, which is dangerous. If the current density of the anode is lower than the above range, the ability to generate sodium hypochlorite by electrolysis is lacking, and a highly concentrated sodium hypochlorite solution cannot be obtained. Furthermore, if the current density of the anode is higher than the above range, the heat generated from the anode will increase and the liquid temperature will rise, causing the generated sodium hypochlorite to decompose and making it impossible to obtain high-concentration sodium hypochlorite. Not only that, but the life of the anode is shortened, which is disadvantageous.

A rectifier 8 consisting of a transformer and a rectifying element and a timer 7 are built into the power supply box 9, which is mainly made of plastic.
A cathode 3 and an anode 2t are connected to the rectifier terminal. Further, the seven Y knobs of the timer 7 can be mounted on the surface of the power supply box 9 along with a power switch and a lamp to serve as an operation panel. The capacity of container 1 is determined by the required amount of sodium hypochlorite, but it is usually 1 to 1 for places where small quantities are used.
20N is selected, the material of the container 1 is mainly a commercially available plastic container from an economical point of view, and the timer 7 is normally 1
Items that can be set within days will be selected. Once the container capacity and the electrolysis time determined by the timer are determined, the electrolysis current that should reach a maximum of 6% is automatically determined, and a rectifier with a capacity that matches this electrolysis current is set. The outer box 13 of the sodium hypochlorite generator is sized mainly to match the cooling condenser 5, and if the power supply box 9 is also incorporated, the outer box 13 is sized further to match its capacity. Device manufactured in this way $::
If the electrolysis is started by adding di-salt water without being thoroughly cleaned, the concentration of sodium hypochlorite increases almost linearly with the electrolysis time, reaching a maximum of 6% after 12 hours. For the concentration, use a timer to freely select and measure one salt according to the electrolysis time (refined salt, common salt, ordinary salt, etc. can be used for 1 hour).
All you have to do is dissolve it in a predetermined amount of water and put it into the container 1. If the salt concentration is made low, even if 24 hour ri11 electrolysis is performed, 4
Since it is not possible to obtain hypochlorous acid sorghum with a concentration of 10% or more, in the present invention, a saline solution whose salt concentration is adjusted to 10% or more by weight is used.

As a power source for the device of the present invention, a general household 100V power source is used, which is converted to a voltage of 3 to IOV, 10 to 25 A, and a constant current through a rectifier. When a saline solution of 10% or more is electrolyzed with the above voltage and current, the temperature of the solution rises and ineffective decomposition of sodium hypochlorite begins, so in the device of the present invention, the cooling condenser is activated to reduce the temperature of the solution to 0.
Electrolysis is carried out while maintaining the temperature at ~22°C, preferably 13-17°C.

If the liquid temperature is lower than this, a sodium hypochlorite solution of 4% or more can be obtained, but the life of the anode will be shortened. If the liquid temperature is made too high, the decomposition of sodium hypochlorite will be accelerated, making it impossible to obtain a highly concentrated sodium hypochlorite solution.

(Example) Next, the unreleased month will be explained in more detail using an example.

Example 1 Outer diameter is medium 160m+++, depth 160mm, height 2
The electrode was inserted and fixed vertically into approximately the center of the upper opening of a 20 mm hard PVC container.

A cooling coil is wrapped around this container, and a cooling condenser (power supply 100 mm, output 40 W, refrigerant: Freon R-
12) was connected. The anode is a single anode plate coated on both sides with a mixture of 25% by weight of platinum, 20% by weight of palladium oxide, and 55% by weight of ruthenium dioxide, to which 3% by weight of titanium dioxide is added. (vertical i 40
+nm, ! , 50 +nl*.

Two uncoated titanium plates (length: 140 mm, 1 mm) are used to sandwich this anode.
1jsmm, thickness 2mm) with a pole vI distance of 115n+m, and the cathode was attached. Note that the effective area ratio between the cathode and the anode was about 1-3.5. A rectifier and a timer capable of passing approximately 15 A of direct current were housed in a hard PVC power supply box, the rectifier was connected to the anode and cathode, and a 100 V AC power cord was drawn out from the timer via a fuse. These containers, cooling condenser, power supply box, etc. were all housed in an outer box to form a sodium hypochlorite generator.

A separately prepared and dissolved 20% saline solution (3.51 g) was placed in a container, the power hood was connected to an AC 100 V power source, the timer was set for 12 hours, and the power switch was turned on. While cooling the area around the container to a temperature of 3 to 17° C., a direct current of 15 A was applied.

When experiments were conducted several times under the same conditions, a sodium hypochlorite solution with an effective chlorine concentration of 4.08 to 4.5% and a liquid temperature of 13 to 17°C was obtained in one case after 12 hours. At this time, the current density of the anode is 10.3 A/di2, and the current density of the cathode is 38.3
At A/d+n'-, the current concentration was 4.3 A/1. The pH of the solution was 8.1 at the start and 9.3 at the end.

Example 2 The operation was carried out in the same manner as in Example 1 except that the saline solution concentration in one container was 10%. At 13:00 f'Jl f&, the effective chlorine concentration was 4.0% and the liquid temperature was 13 to 17°C. Sodium hypochlorite fi(p) 49.4) was obtained.

Example 3 Salt solution put in a container: Operation was carried out in the same manner as in Example 1, except that the agricultural degree was 30%, and after 10 hours, 4
．． 1%, approximately 5.0% after 20 hours, liquid temperature 13-17℃
Sodium hypochlorite solution (p)19. ;2) was obtained.

Example 4 A titanium rod (length 140+nm, diameter 2In+I) was used as a cathode.
l) on both sides of the anode, with two poles l1 illll distance 3 + o
After 11 hours, the concentration was 4.01% and the liquid temperature was 15.5.
A sodium hypochlorite solution (pH 9.2>) was obtained at ℃.The effective area ratio of the cathode and anode was 1:4.1, and the current density of the cathode and anode was 42 and 9 A/dm, respectively. ``It was approximately 10,3 A/c1m2.

Examples 5 to 13 and Comparative Examples 1 to 2 Same as Example 1 except that a direct current of 17.8 A was applied and the area ratio of the cathode and anode was changed. The concentration of sodium chlorate was measured.The results are shown in Table 1.For comparison, the current density of the anode was operated outside the range of the present invention. It was not possible to obtain a concentrated sodium hypochlorite solution.

Comparative Example 3 An apparatus having the same structure, dimensions, materials, and electrode materials as in Example 1 was used except for the cooling unit. 20% saline solution mixed and dissolved separately in a container 3.51! It was placed,
Connect the power hood to an AC 10θV power source and set the timer to 1.
After waiting for 2 hours, the power switch was turned on to supply 15 A of direct current. The liquid temperature was 16℃ at the start, but after 12 hours it rose to 39℃, and the effective chlorine concentration was 2.5℃.
% of sodium hypochlorite was obtained.

Comparative Example 4 In the apparatus of Example 1, the dimensions of the two titanium plates used as cathodes were 140cm long and 20nn+ wide.

It was operated with a thickness of 2fflIn. The liquid temperature of the sodium hypochlorite obtained after 12 hours was 15°C, and the effective chlorine concentration was 2.9%. Note that the effective area ratio of the cathode and anode was 1:1.2.

Comparative Example 5 Two titanium rods (length 15n++n, diameter 3I) were used as cathodes.
An attempt was made to operate in the same manner as in Example 1 except that the distance between the electrodes was 3111 m, using a titanium electrode. Electrolysis was interrupted because there was a risk of damage. The effective area ratio of the anode to the cathode is 1:51. It was S.

Comparative Example 6 In the apparatus of Example 1, the anode used was an anode (length: 140 mm) in which titanium was coated with 40% by weight of ruthenium dioxide and 60% by weight of titanium dioxide.
The operation was carried out in the same manner as in Example 1 except that the thickness was 5iN50mm and the thickness was 2n+m'). The temperature of the sodium hypochlorite solution obtained after 12 hours was 19°C, -9, and the effective chlorine concentration was 2.5.
%Met.

(Effect of the invention) The sodium hypochlorite generation method and generation device of the present invention are as follows:
Once you have mixed and prepared saline solution with a concentration of 0% or more, all you have to do is set the timer to SeraF and turn on the power switch to generate a highly concentrated sodium hypochlorite solution of 4% or more. Since the concentration of sodium hypochlorite obtained from this device is 4% or more, it complies with the Food Sanitation Act and can be used as a food warming product. The produced sodium hypochlorite exhibits an effect equal to or greater than that of commercially available sodium hypochlorite, and its stability is also good. The device of the present invention has an extremely simple structure and is simple! i. The parts are simple and assembled. In other words, there are no moving parts, no need for complicated control parts (such as automatic foot control), and no sudden failures. Furthermore, the structure of the device is simple, and everything including the power supply box can be integrated into one, making it extremely compact, easy to carry, and can be placed anywhere.

The device of the present invention has simple components as mentioned above, and uses commercially available ready-made products, and since there are no connecting pipes, it is easy to manufacture and can be manufactured very easily.

Conventionally, it was considered extremely difficult to achieve ultra-miniaturization that satisfies both economic efficiency and performance, but this device is a batch type and has a single-wood structure;
As a result, a high-concentration sodium hypochlorite solution can be obtained with high current efficiency and low running costs even when miniaturized.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a specific example of the apparatus of the present invention. 1. Container 2. Anode 3. Cathode 4. Cooling coil 5. Cooling condenser 6. Cooling 22)
7. Timer 8. Rectifier 9. Power supply box

Claims (2)

[Claims] (1) A platinum group metal ternary mixture of platinum-palladium oxide-ruthenium dioxide having a composition of 3-42% by weight of platinum, 3-34% by weight of palladium oxide, and 42-94% by weight of ruthenium dioxide on titanium or a titanium alloy. An aqueous solution with a sodium chloride concentration of 10% by weight or more is maintained at 10 to 22°C using an anode coated with a mixture of titanium dioxide and 20 to 40% by weight of the mixture, and the cathode current density is and anode current density from 10 to 50, respectively.
0A/dm^2 and 10-20A/dm^2, and the ratio of anode current density to cathode current density is 1:1.4-1:
A method for generating sodium hypochlorite, characterized by electrolyzing the sodium hypochlorite at a concentration of 40%. (2) a container 1, a cooling unit 6 consisting of a cooling coil 4 and a cooling condenser 5 provided around or inside the container 1, and a timer 7 fixed to the container 1;
and a cathode 3 and an anode 2 connected by a rectifier 8, and the effective area ratio of the cathode 3 and anode 2 is 1:1.4 to
1:40, and the anode 2 is made of platinum-palladium oxide-ruthenium dioxide having a composition of 3 to 42% by weight of platinum, 3 to 34% by weight of palladium oxide, and 42 to 94% by weight of ruthenium dioxide on titanium or a titanium alloy. a ternary mixture of platinum group metals, and 20 to 40% by weight of said mixture.
A sodium hypochlorite generator characterized by being coated with a mixture of titanium dioxide and titanium dioxide.