Electrolysis: processes – compositions used therein – and methods – Electrolytic synthesis – Preparing inorganic compound
Reexamination Certificate
1997-03-17
2003-03-04
Phasge, Arun S. (Department: 1741)
Electrolysis: processes, compositions used therein, and methods
Electrolytic synthesis
Preparing inorganic compound
C205S701000, C205S742000, C205S746000
Reexamination Certificate
active
06527940
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method of simultaneously forming alkaline water of high purity and acid water of high purity using a two-chamber-type electrolytic cell. More specifically, the present invention relates to an electrolytic method of simultaneously forming (i) acid water which can be used for sterilization and disinfection and also for the treatment of skin diseases, and (ii) alkaline water having a low oxidation reduction potential which is good for drinking.
BACKGROUND OF THE INVENTION
The catholyte obtained by electrolyzing municipal water with a diaphragm cell or so-called alkali ion water is said to be effective as a medicine, and is also said to have improved taste. Thus, the catholyte has enjoyed widespread use. Recently, the reduced quality of municipal water has resulted in an unpleasant odor and bad taste. As a countermeasure therefor, an apparatus for producing alkali ion water (alkaline water) and which is capable of simultaneously removing impurities and deodorizing by incorporating active carbon or a microfilter in the above-described electrolytic cell has been widely used.
On the other hand, for the production and washing of electronic parts, specially prepared sulfuric acid, hydrofluoric acid, hydrogen peroxide, hydrochloric acid, etc., has hitherto been used. However, because impurities are introduced into this system and the purification technique for removing such impurities is troublesome, a method of producing acid water for washing by a water electrolysis technique has been proposed. The electrolysis is carried out by adding chloride ion to the anode chamber of the electrolytic cell to thereby obtain an acid electrolyte having a very high oxidation reduction potential. Because the solution has a strong sterilizing action and a strong disinfecting action initially as well as after use, sodium chloride or chloride ion alone remains to the same extent as in municipal water. When the used wash solution is discarded, problems such as secondary pollution, etc., do not occur. Thus, the above described solution has been widely used for various applications.
In the water electrolysis, when ammonium chloride (NH
4
Cl) or sodium chloride (NaCl) for example is used as an electrolyte in the anode chamber, the anodic reaction is a disproportionation reaction represented by:
Cl
−
+H
2
O→2H
+
+ClO
−
+2
e
−
The solution in the anode chamber becomes acidic with the hydrogen ion thus formed, and the resulting hypochlorous acid solution has a pH of 3 or less and an oxidation reduction potential (ORP) higher than 1.2 volts.
On the other hand, in the cathode chamber, hydroxide ion is formed and at the same time, part of the mineral components are transferred to the cathode side. The resulting drinking water which is formed as the catholyte and which can promote good health contains mineral components, has a slightly alkaline pH and has a very low ORP due to the generation of hydroxide ion and hydrogen. That is, it has been widely recognized that the decomposition of active chloride in municipal water by cathodic reduction, the reduction in oxidation reduction potential due to hydrogen generated by the electrolysis, the formation of alkali due to the hydroxy group simultaneously generated by the electrolysis, the transfer of calcium ion to the cathode side, etc., act to improve the water quality. All of this improves the taste when the catholyte is used as drinking water.
However, even if it is possible to simultaneously remove acid water from the anode chamber and alkaline water from the cathode chamber by such an electrolytic method, problems are encountered in that the separation provided by the diaphragm is not so effective, the electrolyte concentrations are increased and the acid and the alkali are mixed through the diaphragm. This results in reducing by one-half the effect of the electrolysis. Furthermore, the addition of sodium chloride to the anode chamber for obtaining stronger acid water is accompanied by the problem that the pH is slightly increased in the cathode chamber and the concentration of sodium chloride is also increased. As a result, water that is suitable for drinking is not always obtained. Also, the ORP increases in the anode chamber. However, when the electrolysis is carried out by paying attention to the increase in ORP alone, the pH of the anolyte is not sufficiently lowered and the washing effect of the water thus obtained is inadequate.
To avoid this problem, means of increasing the thickness of the diaphragm to thereby restrain the diffusion of each liquid, and also means of increasing the distance between electrodes to thereby prevent the reaction products from mixing with each other, have been proposed. However, because the electric conductivity of water is low, a large electric current cannot pass through the electrodes in such an electrolytic cell. A practical electrolytic current density is about 1 A/dm
2
, and even in a small-sized domestic apparatus, the electrode area must be increased by using from 3 to 5 electrodes each having an area of about 5×10 cm
2
. Such an electrolytic cell is disadvantageous in that the structure is complicated, the maintenance thereof takes too much time and labor, and furthermore, the electrolytic cell itself is too expensive.
To solve these problems, the present inventors previously proposed an electrolytic method capable of using a current density higher than several tens of A/dm
2
by closely contacting an electrode substance with an ion-exchange membrane, and by using the ion-exchange membrane thus prepared as a solid electrolyte. The electrolytic voltage in this method was about few volts, which made electrolysis possible at a voltage far lower than that found in conventional methods. In this method, the present inventors also proposed to produce an acid water having a high ORP in the anode chamber by adding a slight amount of an acid or a salt to the anode chamber, which acid water was to be used for washing an apparatus, etc. Also, the present inventors determined that in this case, by using a non-metallic salt, a low-ORP liquid containing a non-metallic alkali such as ammonia suitable for washing semiconductors, etc., was formed in the cathode chamber.
However, although the above described catholyte and anolyte are formed, the foregoing method is inadequate for simultaneously forming liquids for washing (sterilization) and for drinking. That is, when the salt of an inorganic acid such as hydrochloric acid, sulfuric acid, etc., is added to the anode chamber, an acid and a high-ORP electrolyte suitable for washing is obtained in the anode chamber. However, the alkaline property of the catholyte becomes too high and as a result, the catholyte is unsuitable for drinking.
Also, when a metal salt is added, the above objective is almost achieved and acid water having a low pH and alkali water having a weak alkaline property is obtained. However, there is a problem in that large electric currents are required. That is, in the case of using a neutral salt such as, for example, a chloride, the ORP is regulated by the concentration of hypochlorous acid thus formed. Hypochlorous acid in a concentration of from 1 to 5 ppm is sufficient, and chlorine gas is generated if the concentration thereof exceeds ppm. If the current efficiency of chlorine generation is assumed to be 10%, a pH of about 4 to 5 is achieved by the hydrochloric acid formed in the above described reaction. To achieve a desired pH of 3 or lower, excessive electrolysis which ignores the current efficiency of chlorine generation is needed. Chlorine gas is generated when the chloride ion concentration is high, and when the chloride ion concentration is low, ozone is generated in part and the electrolysis amounts to a simple water electrolysis. On the other hand, in the cathode chamber, alkaline water having an alkalinity that is unsuitable for drinking is obtained. This is due to the metal hydroxide formed from the metal salt and the hydroxide ion that is generated
Nakajima Yasuo
Nishiki Yoshinori
Shimamune Takayuki
Shimizu Hideto
Tanaka Masashi
Permelec Electrode Ltd.
Phasge Arun S,.
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