U.S. patent application number 10/281460 was filed with the patent office on 2003-04-17 for method and apparatus for purification treatment of water.
This patent application is currently assigned to NIPPON OIL CORPORATION. Invention is credited to Hirayama, Takayuki, Mizuta, Haruyoshi, Nakayama, Keisuke, Shimo, Yoshiyuki.
Application Number | 20030070940 10/281460 |
Document ID | / |
Family ID | 18637238 |
Filed Date | 2003-04-17 |
United States Patent
Application |
20030070940 |
Kind Code |
A1 |
Hirayama, Takayuki ; et
al. |
April 17, 2003 |
Method and apparatus for purification treatment of water
Abstract
A method for purifying water characterized in that a chamber is
separated by a diaphragm into an anode section and a cathode
section, a voltage is applied between the anode and the cathode
while an oxygen-containing gas is supplied to the cathode section
so as to generate a hypohaloric acid and hydrogen peroxide in the
anode and cathode sections, respectively, and the water to be
treated is first supplied to the anode section to be contacted with
the hypohaloric acid and is then introduced to the cathode section
to be contacted with the hydrogen peroxide.
Inventors: |
Hirayama, Takayuki;
(Yokohama-shi, JP) ; Nakayama, Keisuke;
(Yokohama-shi, JP) ; Shimo, Yoshiyuki;
(Yokohama-shi, JP) ; Mizuta, Haruyoshi;
(Yokohama-shi, JP) |
Correspondence
Address: |
AKIN GUMP STRAUSS HAUER & FELD L.L.P.
ONE COMMERCE SQUARE
2005 MARKET STREET, SUITE 2200
PHILADELPHIA
PA
19103-7013
US
|
Assignee: |
NIPPON OIL CORPORATION
|
Family ID: |
18637238 |
Appl. No.: |
10/281460 |
Filed: |
October 25, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10281460 |
Oct 25, 2002 |
|
|
|
PCT/JP01/03722 |
Apr 27, 2001 |
|
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Current U.S.
Class: |
205/746 ;
204/252; 204/275.1; 205/466 |
Current CPC
Class: |
C02F 1/4674 20130101;
C02F 2201/4613 20130101; C02F 2001/46133 20130101; C02F 2103/003
20130101; C02F 2303/185 20130101; C02F 2103/08 20130101; C02F
2201/4611 20130101; C02F 2201/46115 20130101; C02F 1/4672 20130101;
C02F 2001/46119 20130101; C02F 1/722 20130101 |
Class at
Publication: |
205/746 ;
205/466; 204/252; 204/275.1 |
International
Class: |
C25C 007/00; C25D
017/00; C25B 009/00; C25F 007/00 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 27, 2001 |
JP |
2000-127687 |
Claims
1. A method for purifying water wherein a chamber is partitioned
into an anode section and a cathode section by a diaphragm, a
voltage is applied between the anode and the cathode while an
oxygen-containing gas is supplied to said cathode section so as to
generate a hypohaloric acid and hydrogen peroxide in said anode
section and said cathode section, respectively, and the water to be
treated is first supplied to said anode section to be contacted
with the hypohaloric acid and is then introduced to said cathode
section to be contacted with hydrogen peroxide.
2. A method for purifying water wherein a chamber is partitioned
into an anode section and a cathode section by a diaphragm, a
voltage is applied between the anode and the cathode while an
oxygen-containing gas is supplied to said cathode section so as to
generate a hypohaloric acid and hydrogen peroxide in said anode
section and said cathode section, respectively, and the water to be
treated which has been supplied to said anode section so as to be
contacted with the hypohaloric acid is mixed with the water to be
treated which has been supplied to said cathode section to be
contacted with the hydrogen peroxide.
3. A method for purifying water wherein a chamber is partitioned
into an anode section and a cathode section by a diaphragm, a
voltage is applied between the anode and the cathode while an
oxygen-containing gas is supplied to said cathode section so as to
generate a hypohaloric acid and hydrogen peroxide in said anode
section and said cathode section, respectively, and the water to be
treated which has been supplied to said anode section so as to be
contacted with the hypohaloric acid is mixed with part of the water
to be treated which has been supplied to said cathode section to be
contacted with the hydrogen peroxide, followed by supplying the
mixture to said cathode section again.
4. The method according to claim 1, 2, or 3 wherein a carbon
electrode is used as a cathode, a metal electrode is used as an
anode, and a voltage of 1.5 V or higher and 20 V or lower is
supplied therebetween.
5. The method according to claim 1, 2, or 3 wherein the water to be
treated contains a halogen ion in an amount of 0.01 to 1 mol/l.
6. An apparatus for purifying water which comprises a chamber
separated by a partition at least part of which is formed by a
diaphragm, into an anode section provided therein with one or more
anodes generating a hypohaloric acid by the application of a
voltage and into a cathode section provided therein with one or
more cathodes generating hydrogen peroxide by the application of a
voltage wherein said anode section is provided with a supplying
tube for supplying the water to be treated thereto and an
introducing pipe for introducing the water treated in said anode
section to said cathode section and said cathode section is
provided with a supplying pipe for supplying thereto an
oxygen-containing gas and a discharging pipe for discharging the
water treated in said cathode section.
7. An apparatus for purifying water which comprises a chamber
separated by a partition at least part of which is formed by a
diaphragm, into an anode section provided therein with one or more
anodes generating a hypohaloric acid by the application of a
voltage and into a cathode section provided therein with one or
more cathodes generating hydrogen peroxide by the application of a
voltage wherein said anode section is provided with a supplying
pipe for supplying the water to be treated to the anode section and
a discharging pipe for discharging the water treated in the anode
section and said cathode section is provided with a supplying pipe
for supplying the water to be treated to the cathode section, a
supplying pipe for supplying an oxygen-containing gas to the
cathode section, and a discharging pipe for discharging the water
treated in the cathode section; and said discharging pipes of said
anode and cathode sections are connected with a mixing bath
provided with a discharging pipe for discharging the water purified
in said bath.
8. An apparatus for purifying water which comprises a chamber
separated by a partition at least part of which is formed by a
diaphragm, into an anode section provided therein with one or more
anodes generating a hypohaloric acid by the application of a
voltage and into a cathode section provided therein with one or
more cathodes generating hydrogen peroxide by the application of a
voltage wherein said anode section is provided with a supplying
pipe for supplying the water to be treated to the anode section and
a discharging pipe for discharging the water treated in the anode
section and said cathode section is provided with a supplying pipe
for supplying the water to be treated to the cathode section, a
supplying pipe for supplying an oxygen-containing gas to the
cathode section, and two discharging pipes for discharging the
water treated in the cathode section; and said discharging pipe of
said anode section is connected with one of said two discharging
pipes of said cathode section and further connected with said
supplying pipe for supplying the water to be treated into said
cathode section.
9. The apparatus for purifying water according to claim 6, 7, or 8
wherein a halogen ion adding bath is arranged at the prior stage of
said apparatus.
Description
TECHNICAL FIELD
[0001] The present invention relates to a novel method and
apparatus for purification treatment of water, and more
particularly to a method and apparatus which can provide
sterilization/cleaning, disinfection, and decoloration of water and
which are human-friendly and free from the pollution of the
environment.
BACKGROUND ART
[0002] Various plants such as petrochemical- and chemical-plants
and thermal/nuclear power stations need a large amount of
industrial water for cooling the heat exchangers, condensers, drain
systems and the like. However, many troubles caused by slimes due
to microbial pollution have occurred, resulting in various harmful
effects.
[0003] Other than industrial tap water, main sources of industrial
water are sea water, lake water, river water, and ground water.
Microbes in such industrial waters adsorb to walls and piping of
watering facilities and secrete a large quantity of adhesive
substances, resulting in the formation of slime layer where
microbes breed and form a skin. Such slime layers and microbe skin
bring disadvantages such as the decrease of the thermal exchange
rate upon cooling and the clogging of the strainer by peeled-off
slime.
[0004] Furthermore, in the case of using sea water, large ocean
living things such as barnacles, mussels, oysters or the like
absorb over microbe skin and possibly breed and grow there, causing
the clogging of the piping. However, currently there is nothing to
do but scraping off these living things using manpower
regularly.
[0005] In the case of using sea water or a mixed water of sea water
and fresh water in an aquarium, a sea water swimming pool, or a
cultivation farm, or for an aquaculture, it is desired that the
water is subjected to sterilization and cleaning treatment
beforehand. In order to preventing unwanted bacteria from breeding
in the storage tank, it is also desired that the tank is regularly
or constantly subjected to sterilization and cleaning
treatment.
[0006] Furthermore, washing water for medical tools is
indispensably sterilized and cleaned. Among such tools, medical
forceps and scissors, and dentures are required to be washed with a
detergent having a strong washing power because physical cleaning
can not wash sufficiently to the extent of narrow spaces between
the parts of the tools.
[0007] Various methods for sterilizing and cleaning such water have
been put into practice. A first measure may be exemplified by a
method in which a chemical agent containing hypochlorus acid or
hypobromous acid is added to the water to be treated. A method is
also known in which without using such a chemical agent, the water
to be treated is directly electrolyzed so as to form the oxide of a
hypochlorus acid or the like, as disclosed in Japanese Patent
Laid-Open Nos. 56-68454, 10-300367, and 4-330986.
[0008] However, in the case of forming the oxide of a hypochlorus
acid or the like by electrolysis, the hypochlorus acid may remain
in the water to be treated. If the concentration of the remaining
hypochlorus acid is high, it leads to a problem of secondary
pollution. Particularly, in the case of electrolyzing sea water,
trihalomethanes or aromatic organic chlorine compounds are
accidentally produced if some organic creatures in the sea water
are reacted with the hypochlorus acid.
[0009] Therefore, in the case of applying this method to water for
aquiculture, there is a risk of bringing the death of bred
creatures such as fish. If the treated water contacts with or is
taken into the human body, it adversely affects the human in terms
of safety by bringing thereto diseases such as cancer.
[0010] Since the medical tools subjected to sterilization/cleaning
using a hypochlorus acid can not be put in use as they are, it is a
common practice to rinse the tools using a large quantity of
sterile physiological saline. However, there are problems that such
process conducted after the sterilization/cleaning makes it
difficult to keep the tools in sterile conditions and the process
itself is bothersome.
[0011] As a second measure, there are methods using ultraviolet
radiation or heat treatment. However, these methods have also
problems that it is difficult to sterilize and clean the water to
be treated completely and the cost will be higher if the amount of
the water is increased, leading to the necessity of a large-scale
apparatus.
[0012] As a third measure, there have been proposed
sterilization/cleaning methods by ozone-treatment as disclosed in
Japanese Patent Laid-Open Publication Nos. 8-80493 and 7-210481.
However, needless to mention, these methods have not only
environmental problems that the remaining ozone adversely affects
the human body and the application of these methods to natural sea
water would cause the generation of hypobromous acid which is
extremely harmful to the human body, but also economical problems
that the cost for conducting the methods will be greatly
increased.
[0013] The present invention was made in view of the current
circumstances and the object of the present invention is to provide
a method and apparatus which can sterile and clean sea water, lake
water, river water, ground water and industrial water effectively
without causing the pollution of the environment.
DISCLOSURE OF THE INVENTION
[0014] It is known that when metal electrodes are immersed into
water containing a halogen ion, followed by the application of a
direct voltage, a hypohaloric acid is generated from the anode
resulting from the following reaction mechanism:
2H.sub.2O.fwdarw.O.sub.2+4H.sup.++4e.sup.- (1)
2X.sup.-.fwdarw.X.sub.2+2e.sup.- (2)
X.sub.2+H.sub.2OHOX+HX (3)
[0015] wherein X is a halogen atom.
[0016] Whereas, it is also known that when a direct voltage is
applied using a carbon electrode as a cathode, the following
reaction occurs at the surface of the cathode, resulting in the
generation of hydrogen peroxide ions:
O.sub.2+H.sub.2O+2e.sup.-.fwdarw.HO.sub.2.sup.-+OH.sup.- (4)
[0017] Therefore, when a metal electrode used as an anode and a
carbon electrode are immersed into water containing a halogen ion,
followed by the application of a direct voltage, a hypohaloric acid
can be generated from the anode in accordance with the above
reaction formulae (2) and (3) and simultaneously hydrogen peroxide
ions can be generated from the cathode in accordance with the
reaction formula (4).
[0018] Furthermore, it is also known that in the coexistence of a
hypohaloric acid and hydrogen peroxide ions, the following reaction
is instantly progressed whereby the hypohaloric acid and hydrogen
peroxide ions are converted to a halogen ion and water and oxygen,
respectively:
HOX+H.sub.2O.sub.2.fwdarw.X.sup.-+O.sub.2+H.sub.2O+H.sup.+ (5)
[0019] Next, when oxidation-reduction potentials are compared so as
to estimate the generation of the electric reaction formulae (1),
(2), and (4) including cathode reaction formula (6) below
corresponding, to formula (1), the formulae (1), (2), (4), and (6)
are directed to have a relationship represented by formulae (7),
(8), (9) and (10), respectively, by Nernst formula (refer to
"Electric-Chemical Handbook, edited by Electric-Chemical
Association), and when an electrolysis is carried out at a
potential at which the reaction represented by formulae (8) and
(9)(9') preferentially progress, the progress of the reaction of
formula (10) wherein a hydrogen gas is generated can be avoided
while inevitably the reaction of formula (7) progresses:
2H.sub.2O+2e.sup.-.fwdarw.H.sub.2+2OH.sup.- (6)
E(O.sub.2)=1.229-0.059pH (7)
E(Cl.sub.2)=1.396 (8)
E(H.sub.2O.sub.2)=0.695-0.059pH(pH<11.62) (9)
E(HO.sub.2.sup.-)=0.352-0.030pH(pH.gtoreq.11.62) (9')
E(H.sub.2)=-0.059pH (10).
[0020] Therefore, in such a case, since the reaction of formulae
(1) and (2) theoretically progress at the anode side, while only
the reaction of formula (4) progress at the cathode side,
stoichiometrically the production of hydrogen peroxide always
exceeds that of a hypohaloric acid.
[0021] It was found by the present inventors that water can be
purified by a method wherein an anode and a cathode is separated by
a diaphragm and two conduits are provided such that a hypohaloric
acid is generated from the anode and the remaining hypohaloric acid
after sterilization, cleaning, disinfection, and decoloration is
electrolyzed by hydrogen peroxide generated form the cathode.
[0022] That is, according to a first aspect of the present
invention, there is provided a method for purifying water wherein a
chamber is partitioned into an anode section and a cathode section
by a diaphragm, a voltage is applied between the anode and the
cathode while an oxygen-containing gas is supplied to the cathode
section so as to generate a hypohaloric acid and hydrogen peroxide
in the anode section and the cathode section, respectively, and the
water to be treated is first supplied to the anode section to be
contacted with the hypohaloric acid and is then introduced to the
cathode section to be contacted with hydrogen peroxide.
[0023] According to a second aspect of the present invention, there
is provided a method for purifying water wherein a chamber is
partitioned into an anode section and a cathode section by a
diaphragm, a voltage is applied between the anode and the cathode
while an oxygen-containing gas is supplied to the cathode section
so as to generate a hypohaloric acid and hydrogen peroxide in the
anode section and the cathode section, respectively, and the water
to be treated which has been supplied to the anode section so as to
be contacted with the hypohaloric acid is mixed with the water to
be treated which has been supplied to the cathode section to be
contacted with the hydrogen peroxide.
[0024] According to a third aspect of the present invention, there
is provided a method for purifying water wherein a chamber is
partitioned into an anode section and a cathode section by a
diaphragm, a voltage is applied to between the anode and the
cathode while an oxygen-containing gas is supplied to the cathode
section so as to generate a hypohaloric acid and hydrogen peroxide
in the anode section and the cathode section, respectively, and the
water to be treated which has been supplied to the anode section so
as to be contacted with the hypohaloric acid is mixed with part of
the water to be treated which has been supplied to the cathode
section to be contacted with the hydrogen peroxide, followed by
supplying the mixture to the cathode section again.
[0025] In the purification method according to the first, second,
and third aspect of the present invention, it is preferred that a
carbon electrode is used as the cathode, a metal electrode is used
as the anode, and a voltage of 1.5V or higher and 20V or lower is
applied therebetween.
[0026] In the purification method according to the first, second,
and third aspect of the present invention, the water to be treated
contains preferably a halogen ion in an amount of 0.1 to 1
mol/l.
[0027] According to a forth aspect of the present invention, there
is provided an apparatus for purifying water which comprises a
chamber separated by a partition at least part of which is formed
by a diaphragm, into an anode section provided therein with one or
more anodes generating a hypohaloric acid by the application of a
voltage and into a cathode section provided therein with one or
more cathodes generating a hydrogen peroxide by the application of
a voltage wherein the anode section is provided with a supplying
tube for supplying the water to be treated thereto and an
introducing pipe for introducing the water treated in the anode
section to the cathode section and the cathode section is provided
with a supplying pipe for supplying thereto an oxygen-containing
gas and a discharging pipe for discharging the water treated in the
cathode section.
[0028] According to a fifth aspect of the present invention, there
is provided an apparatus for purifying water which comprises a
chamber separated by a partition at least part of which is formed
by a diaphragm, into an anode section provided therein with one or
more anodes generating a hypohaloric acid by the application of a
voltage and into a cathode section provided therein with one or
more cathodes generating a hydrogen peroxide by the application of
a voltage wherein the anode section is provided with a supplying
pipe for supplying the water to be treated to the anode section and
a discharging pipe for discharging the water treated in the anode
section and the cathode section is provided with a supplying pipe
for supplying the water to be treated to the cathode section, a
supplying pipe for supplying an oxygen-containing gas to the
cathode section, and a discharging pipe for discharging the water
treated in the cathode section; and the discharging pipes of the
anode and cathode sections are connected with a mixing bath
provided with a discharging pipe for discharging the water purified
in the bath.
[0029] According to a sixth aspect of the present invention, there
is provided an apparatus for purifying water which comprises a
chamber separated by a partition at least part of which is formed
by a diaphragm, into an anode section provided therein with one or
more anodes generating a hypohaloric acid by the application of a
voltage and into a cathode section provided therein with one or
more cathodes generating a hydrogen peroxide by the application of
a voltage wherein the anode section is provided with a supplying
pipe for supplying the water to be treated to the anode section and
a discharging pipe for discharging the water treated in the anode
section and the cathode section is provided with a supplying pipe
for supplying the water to be treated to the cathode section, a
supplying pipe for supplying an oxygen-containing gas to the
cathode section, and two discharging pipes for discharging the
water treated in the cathode section; and the discharging pipe of
the anode section is connected with one of the two discharging
pipes of the cathode section and further connected with the
supplying pipe for supplying the water to be treated into the
cathode section.
[0030] In the apparatus according to the forth, fifth, and sixth
aspects of the present invention, a halogen ion adding bath is
preferably arranged in the prior stage of the apparatus.
[0031] As described above, in the first method of the present
invention, a chamber is separated by a diaphragm into an anode
section and a cathode section, a voltage is applied between the
anode and the cathode while an oxygen-containing gas is supplied so
as to generate a hypohaloric acid and hydrogen peroxide in the
anode section and cathode section, respectively, and the water to
be treated is first supplied into the anode section and sterilized
and cleaned by the hypohaloric acid. The water treated in the anode
section is next introduced into the cathode section where the
remaining hypohaloric acid is decomposed by the hydrogen peroxide.
Therefore, the water discharged from the cathodic section contains
no hypohaloric acid and thus will not pollute the environment.
[0032] In the second method of the present invention, the water to
be treated is supplied to the anode section and the cathode
section, individually such that the water in the anodic section is
sterilized and cleaned with the hypohaloric acid and the water in
the cathode section is sterilized and cleaned with hydrogen
peroxide. The water sterilized and cleaned in the anode section and
the water sterilized and cleaned in the cathode section are
introduced into the mixing bath, respectively wherein the remaining
hypohaloric acid after being subjected to the sterilization and
cleaning treatment is decomposed with the hydrogen peroxide.
Therefore, the water discharged from the mixing bath contains no
hypohaloric acid and thus will not pollute the environment.
[0033] Furthermore, in the third method of the present invention,
the water to be treated is supplied to the anode section and the
cathode section, individually such that the water in the anodic
section is sterilized and cleaned with the hypohaloric acid and the
water in the cathode section is sterilized and cleaned with
hydrogen peroxide. The water sterilized and cleaned in the anode
section is mixed with a part of the water sterilized and cleaned in
the cathode section. Although the remaining hypohaloric acid after
being subjected to sterilization and cleaning treatment in the
anode section is decomposed with hydrogen peroxide, the mixed water
is re-introduced into the cathode section thereby decomposing the
hypohaloric acid completely and further maintaining the cleaning
effect of the chamber walls by the introduction of the mixed water
for a long period of time.
[0034] No particular limitation is imposed on the concentration of
the halogen ion in the water to be treated. However, in order to
maintain a certain extent of sterilization effect, the
concentration is preferably 0.01 mol/L or higher and particularly
preferably 0.1 mol/L or higher. In order to lessen the load in the
apparatus and control the reaction easily, the concentration of 1
mol/L or lower is preferred.
[0035] A halogen ion adding bath is preferably arranged in the
prior stage the apparatus so as to adjust the concentration of a
halogen ion to be in the range. The halogen ion adding bath is
preferably connected with a supplying line for the water to be
treated.
[0036] The halogen ion is generally supplied as a halogenated
alkali such as halogenated sodium.
[0037] The operation mode of apparatuses according to the present
invention will be described with reference to the annexed
drawings.
[0038] FIG. 1 is a diagrammatic view of the chamber of an apparatus
for purifying water (also hereinafter referred to as a
water-treatment apparatus). FIG. 2 is a cross-sectional view of the
chamber. FIGS. 3 through 5 show the structural view showing the
operational modes of the water-treatment apparatuses.
[0039] In FIGS. 1 through 5, the numeral 1 indicates a
water-treatment apparatus for purifying the water to be treated by
annihilating the bacteria and virus existing in sea water, lake
water, river water, ground water, industrial water, and mixtures
thereof.
[0040] No particular limitation is imposed on the shape of the
chamber 2 of the water-treatment apparatus 1. Therefore, the
chamber 2 may be rectangular, polygonal or circular in the
cross-section. With the objective of being able to treat a large
amount of the water, the chamber 2 has preferably a pipe-like shape
whose cross section maybe circular, rectangular, or polygonal. No
particular limitation is imposed on the material of the chamber 2
as long as it has insulating properties and is free from erosion by
sea water or hydrogen peroxide. For example, the chamber 2 is
preferably formed from a synthetic resin such as polyolefin and
polyvinyl chloride, glass, a resinous lining material, titanium, or
stainless, nickel, or PTFE resin having excellent anti-erosion
properties. In the case of using a material such as metal which may
be decomposed by hydrogen peroxide, a film containing a
carbonaceous component or formed from other anti-erosive material
is formed on the material, i.e., on the inner walls of the chamber.
Alternatively, a metal material whose interior is treated to be
insulated may also be used in the present invention.
[0041] As shown in FIGS. 1 and 2, in the first embodiment, the
chamber 2 has a pipe-like shape whose lengthwise cross section is
rectangular. The chamber 2 is provided on one side with an anode 3
and on the opposing side with a cathode 4. No particular limitation
is imposed on the shape of the anode 3 and cathode 4. However,
those in the shape of a plate, mesh, or bar are preferably used.
For example, plate-like (rectangular) dimensionally-stable
electrodes are used, and these electrodes, i.e., the anode 3 and
the cathode 4 are arranged on the sides of the chamber 2 as shown
in FIG. 1. The anode 3 and the cathode 4 continuously extending in
the longitudinal direction may be arranged. Alternatively, as shown
in FIG. 1, a plurality of the plate-like anodes 3 and cathodes 4
each having a certain length may be arranged at certain intervals
such that the anodes 3 and the cathodes 4 face each other.
[0042] The anode 3 generates a hypohaloric acid in the water to be
treated by electrolysis and is also a counter electrode allowing
the cathode 4 to generate hydrogen peroxide. Although not
restricted, it is preferred to use metal which is free from elution
caused by an electric reaction and highly resistant to an oxidation
reaction because the elution of the anode material would pollute a
diaphragm 5.
[0043] No particular limitation is imposed on the material for the
anode as long as it can generate a hypohaloric acid. Eligible
materials are metals such as platinum, iridium, ruthenium, and
titanium and oxides thereof which are low in chlorine overvoltage,
are extremely low in wear, compared with other metals or oxides
thereof, and thus can be used for a long period of time without
changes. For example, there may be used titanium or a titanium
alloy substrate having the same characteristics as titanium, or
electrode materials such as niobium or tantalum whose surfaces are
coated with ruthenium oxide, palladium oxide, iridium oxide,
platinum, or a complex of two or more thereof. Furthermore, there
also may be used a metal web having a large surface area per unit
area.
[0044] The cathode 4 is an electrode generating hydrogen peroxide
by applying a voltage. No particular limitation is imposed on the
material of the cathode 4 as long as it enables dielectric
reduction. For example, the cathode material may be graphite, a
carbon-fiber material, or a porous shapeless carbon molded article.
Graphite may be those obtained by extruding and calcining,
embossing and calcining, or CIP forming and calcining coke. The
carbon-fiber material may be a knitted carbon-fiber material which
may be commercially available graphite felt or cloth. Of course,
carbon-fiber materials other than graphite felt or cloth may be
used.
[0045] The porous shapeless carbon material is a non-crystalline
and substantially non-oriented, i.e., non-anisotropic porous carbon
material. Such a material may be exemplified by porous shapeless
carbon-fibers and porous carbon molded articles.
[0046] The porous carbon fiber material may be obtained by the
following manner. A novolak-type phenol resin is melt-spun and then
heat-treated with formalin thereby obtaining a non-crystalline and
non-oriented phenol fiber wherein a three-dimensional cross-linking
is formed. This phenol fiber is anti-flammable, heat-resistant, and
chemical-resistant and thus if heated, is carbonized with
maintaining the shape thereby obtaining a carbon fiber with a
shapeless structure which is high in the carbon content. The phenol
fiber is free from melting or contraction. Therefore, the
carbonization of the fiber after being processed to be felt or
cloth can produce a shapeless carbon fiber felt or cloth. Although
this material does not have a crystalline structure which graphite
normally has, it is slightly cross-linked and flexible. Therefore,
this shapeless glassy carbon, i.e., glass-like carbon is the most
suitable for the electrode.
[0047] In order to maintain the shape of the porous carbon material
as the electrode, the material is preferably in felt-like or
cloth-like shape. The felt or cloth is preferably filled into a
frame for holding the electrode such that the desired area and
thickness can be obtained. The filling density significantly
influences the electrolysis efficiency. A low filling density would
reduce the electrolysis efficiency because the contact of the
electrode with oxygen and the water to be treated is not
sufficient. A too high filling density would reduce the
electrolysis efficiency because the flow of oxygen and the water to
be treated is hindered.
[0048] A voltage is applied to the anode 3 and the cathode 4 by
being connected to a constant voltage direct current source 6. When
applying a voltage, the reaction progress theoretically with the
application of a voltage of 1.5V. However, a higher voltage is
preferably applied such that the generation reactions of a
hypohaloric acid and hydrogen peroxide progress efficiently.
However, because a too high voltage brings about simultaneously the
hydrogen peroxide decomposition reaction and the hydrogen
generation reaction represented by formula (10) on the cathode,
other than the hydrogen peroxide generation reaction represented by
formula (9) and causes the decrease of the hydrogen peroxide
generation efficiency, the voltage varies depending on the
concentration or flow rate of an electrolyte but is selected from
the range of preferably not exceeding 20 V DC and more preferably
between 2 to 15 V. For the purpose of removing contaminants formed
on the surfaces of the electrodes during the operation, an electric
control circuit may be provided which circuit reverses
automatically the voltage between the anode 3 and the cathode 4
every certain period and for a certain period. The time periods are
preferably for 5 minutes every 24 hours.
[0049] The chamber 2 is sectioned by a partition wall 7 extending
parallel between the plate-like anodes 3 and cathodes 4 into an
anode section 8 and a cathode section 9. A part or the whole of the
partition wall 7 is formed by a diaphragm 5 such that an electric
current passes between the anode 3 and the cathode 4.
[0050] No particular limitation is imposed on the material of the
diaphragm 5 as long as an electric current flows between the anode
3 and the cathode 4. Preferred materials are electron insulation
porous films such as porous fluoroplastics, hydrocarbon resins, and
ion-exchange membranes.
[0051] Specific examples of porous fluoroplastics are
polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE).
Eligible hydrocarbon resins are those wherein polyethylene, POVAL
(PVA), polyacetylene, cellulose, or polyethylene chloride is used
as the base. These bases may be copolymerized in a suitable ratio.
Alternatively, the bases may be chemically modified with an
additive.
[0052] Examples of ion-exchange membranes are Nafion 117, Nafion
350, Nafion 902, and Nafion 961 having a sulfonic acid group or a
carboxylic acid, all of which are manufactured by Dupont.
Ion-exchange membranes can prevent each ion generated from the
anode or cathode from being consumed at the counter electrode side
and allow the electrolysis to progress promptly even in the case
where the electric conductivity of the electrolyte is low as is in
the present invention.
[0053] Further alternatively, inorganic materials such as glass
wool and asbestos may also be used as the diaphragm.
[0054] The diaphragm 5 (partition wall 7) is positioned in front of
the cathode 4, i.e., between the anode 3 and cathode 4. No
particular limitation is imposed on the space or distance between
the cathode 4 and the diaphragm 5. However, a narrower space or
distance is better thereby obtaining a higher current value. For
example, in the case of using a porous material such as graphite
felt, it may be contacted with the cathode. In the case of using a
graphite plate so as to allow water to pass through the space
between the diaphragm and the electrode, the distance between the
diaphragm and the cathode is preferably 50 cm or less and more
preferably 20 cm or less. No particular limitation is imposed on
the space or distance between the anode 3 and the diaphragm 5.
However, a narrower space or distance is better thereby obtaining a
higher current value. For example, in the case of using a mesh-like
diaphragm, they may be contacted to each other. In the case of
using a plate-like diaphragm shutting the flow of water completely,
the distance is preferably 0.5 to 50 cm and more preferably 1 to 20
cm.
[0055] No particular limitation is imposed on the fastening means
for the diaphragm 5 (partition wall 7). For example, as shown in
FIG. 2, the diaphragm may be fastened using bolts 10 and nuts 11.
Alternatively, the diaphragm may be fastened to the chamber 2 at
the anode section 8 side using fastening means such as screws,
bolts, and nuts.
[0056] An inlet 12 for introducing the water to be treated and an
outlet 13 for discharging the treated water are provided in one and
the other end of the anode section 8, respectively. An inlet 14 and
an outlet 15 are provided in one end and the other end of the
cathode section 9, respectively.
[0057] As shown in FIG. 3, in the first example of the
water-treatment apparatus, a supplying pipe 17 with a pump means 16
such a suction pump for supplying the water to be treated is
connected to the inlet 12 of the anode section 8, the outlet 13 of
the anode section is connected to the inlet 14 of the cathode
section 9 via a conduit 18, and the outlet 15 of the cathode
section 9 is connected to a discharging pipe 19 for discharging the
treated water.
[0058] In the embodiment shown in FIG. 3, although the flow
direction in the anode section 8 is the same as that in the cathode
section 9, the inlet and outlet of the anode section 8 or cathode
section 9 may be reversed such that the water flows in the reversed
direction.
[0059] It is preferred to supply oxygen in 0.1 to 1,000 times
(volume ratio) more of the water to be treated in the cathode
section 9 so as to effect the generation of hydrogen peroxide in
the cathode section efficiently. In order that, the cathode section
is preferably provided with an oxygen-containing gas supplying
means 20. As one example of such an oxygen-containing gas supplying
means 20, a supplying pipe for supplying an oxygen-containing gas
from an oxygen-containing gas source 22 via a flow meter 21 to the
cathode section may be connected to the conduit 18 or 28 located in
the upper stream of the inlet 14, as shown in FIG. 3 through 5.
Although not shown, as an another example, the oxygen-containing
gas supplying pipe may be directly connected to the cathode
section.
[0060] The mixing ratio of the water to be treated and the
oxygen-containing gas is arbitrary selected. For example, if the
oxygen-containing gas is not mixed and if the water to be treated
contains remaining dissolved oxygen, it is theoretically possible
to generate hydrogen peroxide. However, the amount of oxygen has a
great influence on the electrolysis efficiency. Therefore, a too
less amount of oxygen would fail to achieve sufficient contact with
the electrode and lead to poor electrolysis efficiency, resulting
in the shortage of oxygen, i.e., the raw material for generating
hydrogen peroxide. In such a case, the number of moles of the
generated hydrogen peroxide will be less than that of the generated
hypohaloric acid. A too much amount of the oxygen-containing gas
from the outer source would bother the flow of the electrolyte and
thus reduce the electrolysis efficiency. Therefore, the mixing
ratio of the oxygen-containing gas and the water to be treated is
selected such that the oxygen-containing gas/the water to be
treated (volume ratio) is 0.1 to 1,000 and preferably 1 to 500
thereby making it possible to disperse the water to be treated and
supply and discharge the water smoothly and thus to keep the
electrolysis efficiency high. From the viewpoint that an
electrolysis can be conducted in a high current efficiency also in
a high current density, it is preferred that the cathode is formed
into porous and the water to be treated is sprayed in an average
droplet size of 1 to 100 .mu.m.
[0061] Specific examples of the oxygen-containing gas are oxygen,
air, or PSA oxygen. The gas is preferably high in the oxygen
content so as to generate a large amount of hydrogen peroxide. From
an economic viewpoint, PSA oxygen is preferably used. PSA oxygen
can be obtained by absorbing nitrogen gas in the air by utilizing
the difference in activity with respect to the gas or the molecular
sieve effect with the use of zeolite, separating the nitrogen and
the oxygen, and then taking out only the oxygen gas. In this
operation, argon in the air remains in the oxygen and the purity
thereof is on the order of 95 percent.
[0062] The oxygen-containing gas which is substantially free of
carbon dioxide is preferred because the apparatus can be operated
at a high current efficiency for a long period of time. The
oxygen-containing gas substantially free of carbon dioxide can be
prepared by allowing the raw material gas to pass through an alkali
aqueous solution. However, with the objective of industrial
mass-production, the oxygen-containing gas substantially free of
carbon dioxide is preferably PSA oxygen obtained by absorbing and
removing the nitrogen gas from the air and then taking out the
oxygen fractions. Since carbon dioxide is absorbed and removed with
the nitrogen, PSA oxygen is substantially free of carbon dioxide.
With the objective of the sufficient supply of the
oxygen-containing gas to the water in the cathode section, the
pressure of the gas is preferably atmospheric pressure or
higher.
[0063] Next, the sterilization and cleaning of the water to be
treated which is sea water using the water-treatment apparatus 1
will be described but the present invention is not limited
thereto.
[0064] A direct voltage is applied to the anode 3 and the cathode 2
while driving the pump 16. Sea water is drawn by the pump 16 and
introduced through the supplying pipe 17 to the anode section 8.
The sea water is then introduced from the anode section 8 via the
conduit 18 to the cathode section 9.
[0065] By applying a voltage, a hypohaloric acid is generated from
the anode 3. The water is sterilized and cleaned by annihilating
the bacteria and virus in the sea water with this hypohaloric acid.
The sterilized and cleaned sea water (treated water) is introduced
into the cathode section 9 where the remaining hypohaloric acid is
reduced and decomposed by hydrogen peroxide generated from the
cathode 4. The sea water free of the hypohaloric acid is introduced
via the discharging pipe 19 to another system.
[0066] In this way, sea water is sterilized and cleaned in the
anode section 8 and the hypohaloric acid contributed to the
sterilization and cleaning treatment is decomposed by hydrogen
peroxide in the cathode section 9. Therefore, the treated sea water
contains no hypohaloric acid and thus will not pollute the
environment.
[0067] Therefore, the water-treatment apparatus 1 of the present
invention is free from any secondary pollution caused by the
treated water. Furthermore, the apparatus can sterilize and clean a
large quantity of the water to be treated and is highly
economical.
[0068] FIG. 4 shows the second example of the apparatus of the
present invention which is different from the apparatus 1 in that
the water to be treated introduced to the anode section 8 and the
cathode section 9, individually and then mixed in a mixing bath 23.
The same numerals are fixed to the same parts of the apparatus 1
and the description therefor is omitted.
[0069] As shown in FIG. 4, a supplying pipe 24 for the water to be
treated is connected to a first supplying pipe 26 having a pump
means 25 such as a suction pump and a second supplying pipe 28
having a pump means 27 such as a suction pump. The first supplying
pipe 26 and the second supplying pipe 28 are connected to the inlet
12 of the anode section 8 and the inlet 14 of the cathode section
9, respectively.
[0070] A first conduit 29 is connected at one end to the outlet 13
of the anode section 8 and at the other end to the mixing bath 23.
A second conduit 30 is connected at one end to the outlet 15 of the
cathode section 9 and at the other end to the mixing bath 23
whereby the treated water from the first and second conduits flows
thereinto and are mixed. Alternatively, the mixing bath 23 may be
provided with a stirring means (not shown) for stirring the mixed
water in the bath 23. A discharging pipe 31 is connected to the
mixing bath 23.
[0071] Although the anode and cathode sections 8, 9 are connected
via the conduits 29, 30 to the mixing bath 23, respectively, the
sections 8, 9 may be connected to the mixing bath 23 directly
without using the conduits. That is, the anode and cathode sections
8, 9 may be constructed integrally with the mixing bath 23.
[0072] In the apparatus constructed as shown in FIG. 4, the water
to be treated is introduced to the anode section 8 and the cathode
section 9, respectively by the action of the pumps 25, 27. The
water to be treated in the anode section 8 is sterilized and
cleaned by applying a voltage such that the bacteria and virus in
the water are annihilated by a hypohaloric acid generated from the
anode 3. The sterilized and cleaned water is then introduced via
the first conduit 29 to the mixing bath 23.
[0073] On the other hand, the water to be treated in the cathode
section 9 is sterilized and cleaned by applying a voltage such that
the bacteria and virus in the water are annihilated by hydrogen
peroxide generated from the cathode 4. The sterilized and cleaned
water is then introduced via the second conduit 30 to the mixing
bath 23.
[0074] In the mixing bath, the treated water introduced from the
anode and cathode sections 8, 9 is contacted and mixed with each
other. By mixing the water, the remaining hypohaloric acid
contained in the treated water from the anode section 8 is reduced
and decomposed with the hydrogen peroxide contained in the treated
water from the cathode section 9. Furthermore, although the treated
water from the cathode section 9 has been sterilized and cleaned by
hydrogen peroxide, the bacteria if remaining not sterilized and
cleaned by hydrogen peroxide are annihilated by the hypohaloric
acid contained in the treated water from the anode section 8
thereby effecting the sterilization and cleaning of the treated
water from the cathode section 9 more completely.
[0075] The water free of the hypohaloric acid is introduced via the
discharging pipe 31 to another system.
[0076] In this manner, the water to be treated is introduced to the
anode and cathode sections 8, 9 respectively and after being
sterilized and cleaned individually there is then introduced to the
mixing section 23 where the hypohaloric acid which has contributed
for the sterilization and cleaning in the anode section 9 is
decomposed by hydrogen peroxide. Since the treated water contains
no hypohaloric acid, it will not pollute the environment.
[0077] Therefore, the water-treatment apparatus 1 of the present
invention will not cause a secondary pollution and can sterilize
and clean a large quantity of the water to be treated and thus is
highly economical.
[0078] FIG. 5 shows a third example of the water-treatment
apparatus 1 of the present invention and is different from the
second example of the apparatus in that after the water to be
treated introduced to the anode and cathode sections 8, 9
respectively is mixed, the water is introduced to the cathode
section 9 again via a returning pipe 40. The same numerals are
applied to parts which are the same as those of the first example
and the descriptions are omitted.
[0079] As shown in FIG. 5, a supplying pipe 24 for the water to be
treated is connected to a first supplying pipe 26 provided with a
pump means 25 such as a suction pump and to a second supplying pipe
28 provided with a pump means 27 such as a suction pump. The first
supplying pipe 26 is connected to the inlet 12 of an anode section
8, while the second supplying pipe 28 is connected to the inlet 14
of the cathode section 9.
[0080] The outlet 13 of the anode section 8 is connected to a first
conduit 29, while the outlet 15 of the cathode section 9 is
connected to a second conduit 30. The first and second conduits are
connected directly to the returning pipe 40. The returning pipe 40
is connected via an inlet 41 for returning the water to the second
supplying pipe 28 such that the water is introduced again via the
inlet 14 to the cathode section 9. The water is discharged from an
outlet 42 via a discharging pipe 43.
[0081] In the water-treatment apparatus 1 structured as shown in
FIG. 5, the water to be treated is introduced to the anode and
cathode sections 8, 9, respectively by the action of the pumps 25,
27. The water to be treated in the anode section 8 is sterilized
and cleaned by applying a voltage such that the bacteria and virus
are annihilated by a hypohaloric acid generated from the anode 3.
The treated water is then introduced via the first conduit 29 to
the returning pipe 40.
[0082] On the other hand, the water to be treated in the cathode
section 9 is sterilized and cleaned by applying a voltage such that
the bacteria and virus are annihilated by hydrogen peroxide
generated from the cathode 4. The treated water is then discharged
from the system via the second conduit 30 and the discharging pipe
43 but the water passing through the second conduit 30 is
introduced to the returning pipe 40.
[0083] In the returning pipe 40, the hypohaloric acid is decomposed
by hydrogen peroxide and then the hypohaloric acid-free water is
introduced via the inlet 41 to the cathode section 9. By
introducing the water to the cathode section, the hypohaloric acid
can be decomposed completely.
[0084] The water free of hypohaloric acid is introduced via the
discharging pipe to another system.
[0085] In this manner, the water to be treated is introduced to the
anode and cathode sections 8, 9 respectively and after being
sterilized and cleaned individually there is then introduced to the
cathode section 9 where the hypohaloric acid which has contributed
for the sterilization and cleaning in the anode section 8 is
decomposed with hydrogen peroxide. Since the treated water contains
no hypohaloric acid, it will not pollute the environment.
[0086] Therefore, the water-treatment apparatus 1 of the present
invention will not cause a secondary pollution and can sterilize
and clean a large quantity of the water to be treated and thus is
highly economical.
[0087] The operation mode of the present invention has been
described with respect to the case where the water is treated with
a single apparatus. However, the water may be treated with a
plurality of the apparatuses 1 which may be arranged in series or
parallel. The apparatuses arranged in series can treat the water
more completely, while the apparatus arranged in parallel can
increase the treating amount per unit period.
[0088] FIG. 6 shows another example of the chamber 32 of the
apparatus of the present invention and is different from the
above-described chamber 2 in the outer shape and the arrangement of
an anode section 33 and a cathode section 34.
[0089] That is, the chamber 32 is in a cylindrical shape and
provided therein with an inner tube 35 having a smaller diameter
and arranged coaxially therewith. The chamber 32 is thus
dual-structured. The chamber has a pillar-shaped anode 36 arranged
coaxially therewith. The chamber 32, i.e., the outer tube is
provided on the inner surface with a plurality of (four in this
example) cathodes 37 arranged at certain intervals in the
circumference direction. The inner tube 35 has openings at each of
the portions aligned with the anode 36 and the cathode 37 facing
thereto. That is, four openings 38 are arranged in the inner tube
35 at intervals of 90 degrees in the circumferential direction
thereof while four cathodes 37 are arranged at intervals of 90
degrees on the inner peripheral surface of the chamber 32 which is
in the outer radial direction from the opening. The inner tube 35
is provided on its inner peripheral surface with a cylindrical
diaphragm 39 such that the inside and outside of the inner tube are
formed into an anode section 33 and a cathode section,
respectively. Therefore, after the water to be treated introduced
to the anode section 33 is discharged, it is again introduced to
the cathode section 34. The water to be treated passing through the
anode section 33 and the cathode section 34 is then mixed and
discharged.
[0090] By arranging the cathodes 37 and the anode 36 on the inner
peripheral surface and axial center of the chamber 32,
respectively, the surface area of the cathodes can be increased and
thus the amount of the treating substance generated therefrom can
be increased, thereby ensuring the treatment of the water. However,
if the water can be treated satisfactorily, the cathode 37 and the
anode 36 may be arranged on the axial center and inner peripheral
surface of the chamber 32, respectively.
[0091] Even though the chamber 32 of the water-treatment apparatus
is constructed as shown in FIG. 6, the apparatus can perform the
same effects as described above. When the apparatus of this example
is described with reference to the apparatus of the first example
shown in FIG. 3, by applying a direct voltage to the cathodes 37
and the anode 36 while driving a pump 16, part of the water to be
treated is suctioned by a pump 16 and introduced to the anode
section 33 and then to the cathode section 34.
[0092] The water to be treated in the anode section 33 is
sterilized and cleaned by applying a voltage such that the bacteria
and virus in the water are annihilated by a hypohaloric acid
generated from the anode 36. The sterilized and cleaned water is
then introduced to the cathode section 34 and the remaining
hypohaloric acid is reduced and decomposed by hydrogen peroxide
generated from the cathodes 37. Thereafter, the water free of
hypohaloric acid is introduced to another system or the like.
[0093] In this manner, since the water to be treated is sterilized
and cleaned in the anode section 33 and the hypohaloric acid which
has contributed for the sterilization and cleaning in the anode
section 33 is decomposed by hydrogen peroxide, the treated water
contains no hypohaloric acid and thus will not pollute the
environment.
[0094] Therefore, the water-treatment apparatus 1 of the present
invention is free from any secondary pollution caused by the
treated water. Furthermore the apparatus can sterilize and clean a
large quantity of the water to be treated and is highly
economical.
BEST MODE FOR CARRYING OUT THE INVENTION
[0095] The present invention is further described with reference to
the following examples and comparative example but is not limited
thereto.
EXAMPLE 1
[0096] In a polyvinyl chloride-made chamber 2 having a shape as
shown in FIGS. 1 with a length of 1 m, a width of 250 mm, and a
height of 100 mm, four graphite plates (EG-30X manufactured by
Nippon Carbon Co., Ltd.), with a size of 200 mm.times.80 mm and
four titanium-platinum plates with a size of 200 mm.times.80 mm are
mounted at intervals of 50 mm along the longitudinal direction of
the chamber 2, respectively. At the center of the chamber, "Nafion
117" manufactured by Dupont Co., Ltd. is arranged as a diaphragm.
The distance between the diaphragm and the graphite plates and
titanium-platinum plates was 100 mm.
[0097] Five sets of the water-treatment apparatus of the present
invention having such a chamber 2 are connected in series. As shown
in FIG. 3, the inlet 12 of the anode section 8 of the most upper
stream end chamber 2 is connected to the supplying pipe for the
water to be treated and the outlet 13 of the anode section 8 is
connected via the conduit 18 to the inlet 14 of the corresponding
cathode section 9.
[0098] The graphite plate electrode and titanium-platinum plate
electrode in each pair of electrodes were connected to a cathode
side and an anode side, respectively, and an electrolysis was
conducted such that the apparent current density and bath voltage
are to be 15 A/m.sup.2 and 1.6 to 2.2 V, respectively with a direct
current source. Sea water of a temperature of 15.degree. C.
containing microbes was allowed to pass the anode section at a rate
of 1 mm/sec by operating a sea water suction pump 16. As shown in
FIG. 3, before the water is introduced to the cathode section 9, it
was mixed with PSA oxygen supplied from an oxygen-supplying source
at a rate of 3 m/sec and introduced to the inlet 14. After part of
the water sterilized and cleaned in such a continuous manner was
sampled so as to measure the number of microbes and effective
haloric acid concentration, no microbes and effective haloric acid
was detected.
EXAMPLE 2
[0099] With the same electrolysis conditions of Example 1, the
inlet 12 of the anode section 8 and the inlet 14 of the cathode
section 9 in the most upper stream end chamber 2 are connected to a
supplying pipe for the water to be treated, respectively and a part
of the water after being mixed in a mixing bath 3 was sampled so as
to measure the number of microbes and effective haloric acid
concentration. However, no microbes and effective haloric acid was
detected.
Comparative Example 1
[0100] Under the same conditions of Example 1, the sterilization
and cleaning treatment was conducted only by the anode reaction.
The sea water after the treatment was sterilized and cleaned but
hypohaloric acid was detected.
APPLICABILITY IN THE INDUSTRY
[0101] The method and apparatus of the present invention can
achieve the effective sterilization and cleaning of the water to be
treated such as sea water, lake water, river water, ground water or
industrial water without polluting the environment.
BRIEF DESCRIPTION OF THE DRAWINGS
[0102] FIG. 1 is a schematic view of a first example of the chamber
of an apparatus according to the present invention.
[0103] FIG. 2 is a cross-sectional view of the apparatus shown in
FIG. 1.
[0104] FIG. 3 is a structural view showing a first example of
operational mode of the water-treatment apparatus of the present
invention.
[0105] FIG. 4 is a structural view showing a second example of
operational mode of the water-treatment apparatus of the present
invention.
[0106] FIG. 5 is a structural view showing a second example of
operational mode of the water-treatment apparatus of the present
invention.
[0107] FIG. 6 is a schematic view showing a second example of the
chamber of the water-treatment apparatus of the present
invention.
* * * * *