JP2001276831A - Electrolyzer for water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrolyzer improved in the physical properties of an electrolytic anode for enhancing the efficiency in the electrolyzer for water, and greatly improving the characteristics of produced water, especially sterilizing anode-water. SOLUTION: In the device by which an aqueous solution in an electrolytic room is electrolyzed by a membrane electrolytic method or a nonmembrane electrolytic method to obtain a production liquid having sterilizing property, a layer of noble metal such as Pt, Ir, Pd or Rh, etc., having catalytic property or its oxide, etc., is fitted to a surface of the anode of an electrolytic bath by electric plating or baking, and further the layer is sintered at a temp. of 200-1000 K in the atmosphere of nitrogen, argon or steam, etc., to activate it, to improve the catalystic performance. By using such electrode, polarization is prevented and the electrolytic efficiency is enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water electrolysis apparatus.

[0002]

2. Description of the Related Art Conventionally, a ferrite or titanium metal coated with platinum has been used as an electrode of a water electrolysis apparatus. The anodic sterilizing water generated by electrolyzing the dilute saline solution by the electrolysis device using this electrode tends to generate more chlorine gas than the amount of hypochlorous acid, chlorous acid, chloric acid, etc. is there. Also, it is difficult to prevent polarization by using this electrode, and the electrolysis efficiency is necessarily low.

[0003]

SUMMARY OF THE INVENTION Research on the problems in the mechanism of the bactericidal action of the anodic water obtained by electrolysis of dilute saline, etc., the problems in the sustainability of the bactericidal power, and the electrolytic efficiency. The key to the dissolution during the course of the process came to be attributed to the physical properties of the anode surface. Ultimately, it is due to the rate of reaction between the deposited material at the anode and the surrounding water molecules. That is, the substance deposited on the anode is Cl * (chlorine of the generator), which is converted to Cl ₂ (chlorine gas) in a very short time. The compound of formula Whether the bactericidal action of the anode water depends on the bactericidal activity of chlorine gas or hypochlorous acid, etc., causes a marked difference in the bactericidal mechanism (mechanism) and endurance, and at the same time greatly changes the electrolysis efficiency. I do. The best way to improve this is to impart catalytic performance to the anode surface.

[0004]

In order to obtain sterilizing water by electrolyzing an aqueous solution, a dilute solution (0.1 to 0.5%) of an alkali halide such as sodium chloride (NaCl) is usually used. According to the reaction shown below, Cage Cl ^- electric attraction forms a double layer of Helmholtz gathered anode by (Coulomb force) neutralized with momentarily anodic charge in contact with the anodic (oxidation) has been Cl * (chlorine generator) and , which reacts with water HCl (hydrochloric acid), HClO (hypochlorous acid), HClO ₂ (chlorite), or HClO ₃ * Cl did not make addition reaction (chlorate), etc. _Cl 2 ( Chlorine gas) (residual chlorine)
As it dissolves in water, a part of it dissipates into the air. At this time Cl
Since the transition time of * to Cl ₂ is very short, it is necessary to contact and react with water molecules very quickly in order to react with water. Cl ₂ is suppressed as much as possible the generation of Cl ₂ as quality but sterilizing water is easily soluble gas in water H
It is desirable that ClO, HClO ₂ and HClO ₃ be produced in large amounts. This is because of its problem of excellent sterilizing power and its persistence, and moreover, the presence of a large amount of Cl ₂ induces the production of halogenated methane (such as trihalomethane). In addition, the generation of Cl ₂ causes polarization at the anode, which requires a higher applied voltage for electrolysis, and disadvantageously lowers electrolysis efficiency.

There is a marked difference between the reaction rate of Cl * and Cl ₂ with water and its strength. Of course Cl * of more While it is intense, it is necessary therefore to cause the reaction of the early water than the moment that changes from Cl * to Cl _2. What promotes this reaction is the catalytic performance of the anode plate surface.
In the present invention, the surface of the anode plate is activated by heat treatment in an atmosphere. The atmosphere is preferably nitrogen, argon, water vapor or the like, and the temperature is preferably 200 ° K to 1000 ° K.

[0006]

When the anode plate subjected to the activation treatment is used, a higher effect can be obtained with a lower electrolysis voltage and electrolysis current than when an anode plate not subjected to the activation treatment is used.
This is because, due to the catalytic action of the activated anode, chlorine Cl * of the generator generated by anodic oxidation reacts quickly with nearby water to generate HClO or the like and dissolves in the water, resulting in non-conductive Cl _2. This is because the formation of a layer of (gaseous chlorine) is prevented, and so-called polarization is prevented.

On the other hand, when observing the characteristics of the generated sterilizing water, the pH of the water produced by the conventional apparatus rises fairly rapidly with time (the acidity decreases), and the ORP decreases (the sterility decreases). I do. This is thought to be due to evaporation of the acidic components and loss of the bactericidal substance, which is evidence that the bactericidal action is dependent on Cl ₂ . On the other hand, when the acid sterilizing water generated by the apparatus using the anode according to the present invention is allowed to stand, the pH decreases with the lapse of time and the acid value increases, or the ORP (sterilizing power) gradually decreases. This is because the amount of chloric acids such as HClO is larger than that of Cl _2, and HClO → HCl + O
* The progress of the reaction indicated by * indicates that HClO decreases and the amount of HCl increases, indicating that the main bactericidal activity is not due to chlorine but to chloric acid-based substances. ∵HClO is a weak acid. HCl is a strong acid. O
* Indicates that the germicidal power of the generator is strong. This phenomenon is evidence that the production amount of the target product is large and the conversion efficiency is excellent.

[0008]

EXAMPLE Two electrolytic cells having electrode plates of the same size of 6.5 cm in width and 15.5 cm in length were prepared, and one (A) was equipped with an anode plate not subjected to an activation treatment, and the other was used. On one side (B), an anode plate subjected to an activation treatment was mounted and compared. When a current of 12 V and 10 A was passed through (A) to electrolyze 0.2% saline at a flow rate of 1 liter per minute, sterilized water having pH = 2.6 ORP = 1155 mV was obtained as anode water. The applied voltage and current when water of the same pH and the same ORP was produced in (B) at the same flow rate was 10V9.5A. When the change with time was compared for the generated water, the following results appeared. (Both are kept in a closed container in a cool dark place.)

[0009]

First, as an effect of the present invention, a reduction in electric energy consumed for producing a target substance is recognized. At the same time, it is recognized that the physical properties of the product are improved, such as the storage stability of the product is improved.

Here, in order to explain the effect of the present invention, it is necessary to consider the electrolytic phenomenon a little further. Therefore, the mechanism of electrolysis will be considered focusing on the electrochemical phenomena near the anode, and the case of electrolyzing saline (NaCl.Aq) will be described as a typical example. Salt (NaCl) is a strong electrolyte which is dissociated as Na ⁺ ions and Cl ⁻ ions in an aqueous solution, and almost 10% in a dilute solution such as 0.2%.
It shows a dissociation rate close to 0%, 5 to 6 Na ⁺ ions,
The 1 ^- ion hydrates with 4 to 7 water molecules and exists as a hydrated ion. Therefore, Na ⁺ ion or Cl in the aqueous solution (because it attracts hydration water molecules)
^- behavior of ion is observed to be much dull motion than theoretically expected value. In addition, since a substance generated secondarily participates as the electrolysis proceeds, the appearance of the electrolysis becomes quite complicated at the end of the electrolysis (near the end of the electrolytic cell). However, the discussion here is for the purpose of explaining the effects of the invention, so avoiding strict discussion of all phenomena and complicating it,
The explanation is focused on relevant points for easy understanding. The salt is ionized in the aqueous solution as shown in the following formula, and the voltage between the electrodes (correctly, a voltage exceeding the sum of the monopolar potentials of chlorine and sodium [+1.360-(− 2.714) = exceeding 4.084 volts) to sequentially such following behavior when voltage is applied]. 1. ionization in saline in an aqueous solution NaCl⇔Na ^{+ +}
Cl ^- 2. Electrochemical Phenomenon at the Anode Since Cl ⁻ is a negatively charged particle, it is attracted to the plus electrode (anode) by the Coulomb force (electric force) and gathers. When Cl ⁻ comes into contact with the anode, the charge is instantaneously neutralized to Cl * (chlorine in atomic state / chlorine in the generator).
Cl * is, 2Cl * → to instantaneously as Cl ₂ becomes chlorine gas (molecular chlorine), Cl * violently Cl ₂ is slowly react with water to chemical changes such as the following. Most Cl ₂ dissolves in water as a gas. Here, in examining these chemical changes for the purpose of sterilization, substances that contribute to sterilization are Cl ₂ and O *. Cl ₂
Is too famous for sterilizing tap water. Very strong sterilizing power, only 0.1 ppm for drinking water
It has been recognized that the presence of a concentration is effective enough. A concentration of about 10 ppm is required to kill bacteria or a group of bacteria at a considerable concentration (about 1 million per cc of water), but it is easy to make sterile water of such a degree. That is, if a 0.2% saline solution is electrolyzed with a current of 10 A, about 1 liter of sterilized water can be generated per minute. Also, chlorine dissolves in 1 volume of water at room temperature under 1 atm of 2.3 volume. That is, 2.3 cc of chlorine gas can be dissolved in 1 cc of water. It is very convenient for usability. In contrast, O * (generator oxygen) is not so easy. The bactericidal power is as strong as Cl ₂ , but the chance of appearance is conditional. As can be seen from the above chemical formula, O *
Is produced by the decomposition of chloric acids (HClO hypochlorous acid, HClO ₂ chlorous acid, HClO ₃ chloric acid)
It becomes ordinary oxygen gas is quickly instantly cause a change of 2O * → O _2. (O ₂ has a disinfecting power not as strong as Cl _2. ) However, the aqueous solution of chloric acid in a closed container has a good preservation property and can be stored for several months by blocking direct sunlight and ultraviolet rays. In addition, this substance naturally decomposes very slowly and generates O * (slowly depletes), but when it comes into contact with an object (organic matter, etc.) such as bacteria, it instantaneously generates a large amount of O * and is powerful. It has an effective bactericidal action. In terms of storability, C
Cl ₂ not only is much more advantageous than l ₂ is the disadvantage that combines with that and organic substance is peculiar pungent odor is toxic to generate harmful substances such as trihalomethanes. ClO contained chlorine acids ^- such is harmless ones ionic, resulting in degradation Cl ^- ions are of importance as the major anion of body fluids for the organism, also decompose to produce O * is odorless After the end of the sterilization, it becomes O ₂ (oxygen gas) and has the function of reducing BOD and COD. From these points, in the electrolysis of saline for the purpose of obtaining sterilized water, the chemical formulas (1), (2), (3) and (6)
It is desirable to suppress the reaction which causes the generation of chlorine gas as much as possible. The anodic activation treatment according to the present invention exactly meets this need. That is, the strong catalytic performance of the anode catalyzes the reaction between Cl * deposited on the anode and water, and the reactions (1), (2) and (3) proceed preferentially. At the same time, the generation of chlorine gas is suppressed to prevent polarization, thereby enabling electrolysis at a low voltage and improving the electrolysis efficiency. * Note Electrolysis is a phenomenon caused by the movement of electric charges, and is therefore only related to the amount of electric charge transferred, that is, the product of current intensity and time.
It is independent of the applied voltage. The amount of the substance generated by the electrolysis is calculated by the following equation. Q = (M / nF) ×
A × T (gram) Q; amount of substance to be deposited (gram) M: atomic weight or formula weight of substance (sum of atomic weights of constituent atoms) n: valence or charge of formula weight F: Faraday number = 96500 Coulomb (the amount of electricity required to deposit one atom of a substance having a valence of 1 or one quantity of a substance having one charge per formula quantity) A; Amperage of electric current (1 ampere x the quantity of electricity moving per second) 1 coulomb) T; duration of action (seconds) This equation is independent of the applied voltage V (volts). On the other hand, the power watt is the product of the voltage V and the current A, so that the higher the applied voltage, the more power is consumed. If electrolysis can be performed with a smaller voltage, power consumption can be saved and efficiency can be improved.

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) C02F 1/76 C02F 1/76 A C25B 1/00 C25B 11/08 A 11/08 1/00 Z

Claims (1)

[Claims] An apparatus for electrolyzing an aqueous solution of an electrolyte by a diaphragm electrolysis method or a non-diaphragm electrolysis method to obtain a germicidal product solution, comprising platinum, iridium, palladium by plating or baking on the surface of the anode of an electrolytic cell. Or a layer of a noble metal having a catalytic property such as rhodium or an oxide thereof, and the layer is placed at 200 ° in an atmosphere furnace.
An electrolysis apparatus characterized by using an electrode whose catalytic performance is improved by firing activation at a temperature of K to 1000 ° K.