Chemistry: electrical and wave energy – Apparatus – Electrolytic
Patent
1997-02-21
1998-12-01
Valentine, Donald R.
Chemistry: electrical and wave energy
Apparatus
Electrolytic
204275, 204263, C25B 900, C25B 1500
Patent
active
058432914
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a water electrolyzer for electrochemically producing alkaline and/or acidic water. More particularly, the present invention is concerned with a water electrolyzer wherein scales, such as calcium carbonate, deposited on electrodes during electrolysis are effectively removed.
BACKGROUND ART
It is believed that hydroxyl ion (OH.sup.-) enriched alkaline water, which is often incorrectly referred-to as "alkaline ion water", is useful in health maintenance when served as potable water as well as in accentuating taste when used in cooking or for the preparation of beverages such as tea and coffee. Similarly, hydrogen ion (H.sup.+) enriched acidic water is known as being suitable for boiling noodles and washing faces. More importantly, highly acidic water which is obtained by electrolysis of an aqueous solution of sodium chloride and which therefore contains effective chlorine (hypochlorous acid or chlorine gas) has been noted as having a strong germicidal effect.
To produce alkaline and/or acidic water, an apparatus for electrolyzing water has been used hitherto which is often incorrectly referred-to in the art as "ion water generator". This apparatus, designed to subject water to electrolysis, includes an electrolytic cell having an anode and a cathode. As a direct electric potential is applied between the electrodes, the hydroxyl ions OH.sup.- being present in water due to electrolytic dissociation of water molecules will donate electrons to the anode at the anode-water interface and are thereby oxidized to form oxygen gas which is then removed away from the system. As a result, the H.sup.+ concentration is enhanced at the anode-water interface so that H.sup.+ enriched acidic water is resulted at the anode-water interface. At the cathode-water interface, on the other hand, H.sup.+ accepts electron from the cathode and is reduced to hydrogen to form hydrogen gas which is similarly eliminated from the system. As a result, the OH.sup.- concentration is increased whereby OH.sup.- enriched alkaline water is generated at the cathode side. When an aqueous solution of sodium chloride is subjected to electrolysis, chlorine gas is generated at the anode and is dissolved into water to form hypochlorous acid.
To preclude alkaline water and acidic water once generated by electrolysis from being mixed with each other and to take them out separately, the conventional electrolytic cells are typically provided with a water-impermeable but ion-permeable membrane 3 arranged between an anode plate 1 and a cathode plate 2 as schematically shown in FIG. 1, the electrolytic chamber being divided by the membrane into a flowpath 4 for alkaline water and a flowpath 5 for acidic water. The electrolytic cell of this type will be referred-to hereinafter as the "membrane-type" electrolytic cell.
As the electrolytic cell is operated, precipitation of scale 6 comprised of calcium carbonate, calcium hydroxide, magnesium hydroxide and the like takes place in the flowpath for alkaline water. Referring to FIG. 2 wherein the apparent solubility of calcium carbonate versus pH is shown, the mechanism of scale precipitation will be described with reference to calcium hydroxide by way of an example. It will be noted from the graph that under acid conditions, calcium carbonate is dissolved into water in the form of calcium ions. However, as the pH exceeds 8, the solubility is rapidly drops thereby giving rise to precipitation of calcium carbonate. In the electrolytic cell of the membrane type, the scale tends to precipitate predominantly on the membrane 3 rather than on the cathode 2, as shown in FIG. 1. Probably, this is because the porous nature of the membrane promotes precipitation of scale, in contrast to the cathode generally having a polished specular surface. Since the precipitates such as calcium carbonate are electrically insulating, the electrical resistance across the cell is increased thereby lowering the efficiency of electrolysis of the cell. In addition, formation of scale increases t
REFERENCES:
patent: 4810344 (1989-03-01), Okazaki
patent: 4867856 (1989-09-01), Okazaki
Eki Toshio
Enomoto Kazuyuki
Nishi Tomohiro
Otsuka Toshiharu
Toto Ltd.
Valentine Donald R.
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