CA1297405C - Preservative for drinking water - Google Patents
Preservative for drinking waterInfo
- Publication number
- CA1297405C CA1297405C CA000487584A CA487584A CA1297405C CA 1297405 C CA1297405 C CA 1297405C CA 000487584 A CA000487584 A CA 000487584A CA 487584 A CA487584 A CA 487584A CA 1297405 C CA1297405 C CA 1297405C
- Authority
- CA
- Canada
- Prior art keywords
- silver
- water
- coral sand
- plated
- preservative
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
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- Water Treatment By Sorption (AREA)
Abstract
ABSTRACT
Preservative for drinking water is composed of silver-plated coral sand, which contains silver by weight of about 0.01 to 5 percent. The silver plating is preferably carried out by means of sputtering. The silver-plated coral sand preservative has a strong sterilizing power against bacteria in water and can maintain or even improve water quality over a long period and which can render the pH of water weakly alkaline and mineralize water.
Preservative for drinking water is composed of silver-plated coral sand, which contains silver by weight of about 0.01 to 5 percent. The silver plating is preferably carried out by means of sputtering. The silver-plated coral sand preservative has a strong sterilizing power against bacteria in water and can maintain or even improve water quality over a long period and which can render the pH of water weakly alkaline and mineralize water.
Description
PRESERVATIVF. FOR DRINKING WATER
Background of the Invention Field of the Invention The present invention relates to a preservative for drinking water, and in particular to a preservative for tap water which has a bacteriostatic effect as well as rendering tap water weakly alkaline when soaked in the tap water to produce an excellent quality of mineralized water ~rom the tap water.
Description of the Prlor Art In recent years, sources of water supplies have been contaminated by variety of chemicals, bacteria and other microorganisms and the like. For the purpose of preventing such contamination, large amounts of chlorine is used in the purification of the water.
However, chlorine has a strong smell and may chemically react with trace amounts of organic ; 20 compounds contained in the water to produce harmful products as well as spoil the taste of drinking water. Thus, activated charcoal is usually u-tilized as a filter to remove residual chlorine and harmful products from tap water to provide good-tasting drinking water. However, tap water which is dechlorinated by activated charcoal has no more sterilizing power and becomes foul where it is " ,,,~,.
.
.
7~
Background of the Invention Field of the Invention The present invention relates to a preservative for drinking water, and in particular to a preservative for tap water which has a bacteriostatic effect as well as rendering tap water weakly alkaline when soaked in the tap water to produce an excellent quality of mineralized water ~rom the tap water.
Description of the Prlor Art In recent years, sources of water supplies have been contaminated by variety of chemicals, bacteria and other microorganisms and the like. For the purpose of preventing such contamination, large amounts of chlorine is used in the purification of the water.
However, chlorine has a strong smell and may chemically react with trace amounts of organic ; 20 compounds contained in the water to produce harmful products as well as spoil the taste of drinking water. Thus, activated charcoal is usually u-tilized as a filter to remove residual chlorine and harmful products from tap water to provide good-tasting drinking water. However, tap water which is dechlorinated by activated charcoal has no more sterilizing power and becomes foul where it is " ,,,~,.
.
.
7~
retained in the filter, because bacteria in the water abruptly proliferate using as nutrition sources trace organic constituen-ts adsorbed in the activated charcoal.
Summary of the Invention The present invention is directed to a novel preservative for drinking water, which is composed of sandy coral stone or coral sand plated with about 0.01 to about 5 percent by weight of silver.
Pre~erably the sandy coral stone or coral sand is heated to be activated in an inert gas such as of argon or ni-trogen prior to the silver plating.
Furthermore, the silver plating is preferably carried out by means of sputterlng.
Description of the Preferred Embodiment The inventors of the present invention conducted various experiments and find that coral, namely, sandy coral stone or coral sand ~hereinafter referred to as coral sand) was an extremely effective water preservative which could be substituted for activated charcoal.
The present invention utilizes coral sand which is prepared by crushing corallite and contains about 96 percent by weight of calcium carbonate as a main ingredient, calcium phosphate as a secondary ingredient and heavy metals as trace constituents.
9~ 35 Further, the coral sand is heated in an inert atmosphere to activate it and is provided therein with a great number of pores having a very small diameter. The pores provide the coral sand with an extremely large surface area, as much as that of activated charcoal. Thereforel coral sand having such pores has a tendency to be plated with silver more than other materials. Miscroscopic observation showed that the pores extend from side to side in the coral sand much as if they were holes extending longitudinally in a lotus root, which results in the coral sand havi.ng a large surface area and high water-permeability.
The preservative oE the present invention comprises this coral sand which is the feature oE
the present invention.
.
By conducting various experiments, it was ; found that the amount of silver for plating the coral sand is preferably from about 0.01 wt% to about 5 wt% of the total weight of the silver-plated coral sand. More specifically, the silver-plated coral sand containing less than 0.01 wt% of silver has an inadequate sterilizing effect, while over 5 wt% of silver gives no further increase in the sterilizing effect and is also uneconomical.
.~
When the silver-plated coral sand having silver in the range of about 0.01 to about 5 wt~ is incorporated in water, some of the silver is released therefrom to in the water and the concentration of the silver ions in water becomes between about 20 to 50 ppb. However, experiments showed that this concentration does not exceed 50 , ~,, ppb. It has been confirmed also from experiments that such a trace amount of silver ions is harmless to humans.
The silver-plated coral sand containing calcium carbonate as a main ingredient chemically reacts with the residua] chlorine in tap water as shown by the following formula. As can be seen from the formula, the calcium carbonate in the silver-plated coral sand neutralizes acid radicals (H30+) released ln tap water during the sterilization using chlorine, so that hydrogencarbonate ions (HC03 ) and chlorlne ions (Cl ) are produced in the tap water.
C12 + H20 -~ 2CaC03 2Ca2 -~ 2HC03 + 2Cl + 0 Thus, tap water containing chlorine and which, therefore, is smelly and acidified is neutralized and deodorized to be rendered weakly alkaline and also is sterilized by nascent oxygen (Ca2 ) and other ions such as magnesium and kalium ions released from the silver-plated coral sand make tap water good-tasting mineralized water.
The silver-plated coral sand has a sterilizing effect, when it is incorporated in water, over a long period of time, e.g., for six - months or longer. Further, no nitric acid radical is detectable in water in which the silver-plated coral sand, in accordance with the present invention is soaked. The silver-plated coral sand of the present invention maintains its excellent sterilizing power but does not adversely affect , , .. ... , ~ ..
~;~g7~0~i water quality, even when water in which the silver-plated coral sand is soaked is stored for a long period of time. For example, water wherein the silver-plated coral sand was soaked was stored for one year and the water quality examined with reference to the water standard of the Japanese Water Law. Results are shown in the following Table I.
~2~74L~;
TABLE I
Test Item Standard Value Results Nitric acid and less than not nitrous acid- 10 mg/l detected induced nitrogen Chlorine ion less than 17.0 mg/l 200 mg/l Organic substances less than 4.3 mg/l (consumption of 10 mg/l potassium permanganate) General less than 0 bacteria 100/1 ml E. coli undetectable not detected Iron less than ditto 0.3 mg/l Calcium, less than 70.0 mg/l magnesium, etc. 300 mg/l (hardness) pH 5.8 - 8.6 7.2 :;;
.. . . .. ..
~7~
TABLE I - (cont'd.) Test Item Standard Value Results Odor not no smell offensive Taste ditto no taste Chromaticity less than 0 .
Turbid.ity less than 0 Residual - 0.1 chlorine , .. ~
.. .
~2~7~
A process for preparing a preservative, in accordance with the present invention will now be explained.
The process comprises the following steps.
Step 1:
Coral sand is crushed to 20 to 80 mesh, preferably 40 to 50 mesh and substantially dechlorinated by washing with water. The coral sand is then heated to between 200 and 400 C, preferably 10 about 350 C for about 2 to 4 hours, in an inert gas such as of argon or nitrogen under a reduced pressure of -20 to -50 mm Hg. This removes from the coral sand residual chlorine ions and activates the sand.
Step 2:
After completion of the above step, the activated coral sand is washed thoroughly under running water to rid it of nitric acid radicals.
This washing must be of a duration of 24 hours, since a brief washing such as one lasting only 3 hours, is insufficient to achieve the almost total removal of the nitric acid radicals. Further, a brief washing may result in detection of a considerably high concentration of nitric acid radical, which will not meet the legal water standard.
, '.`~
.
~2~
g Step 3:
After water washing, the activated coral sand is plated with silver as follows.
First, the coral sand is soaked in an aqueous solution of silver-ammonia obtained by mi~ing silver nitrate and ammonia water under a reduced pressure of -20 mm Hg to -50 mm Hg and maintaining the temperature of the solution at about 20C to 40C
for about one hour.
Next, to the solution is added a trace amount of a reducing agent, such as glucose, a Rochelle salt or formaldehyde.
After addition of the reducing agent, the coral sand thus soaked is left to stand at room temperature for about 10 to 20 hours, during which the surface of the coral sand turns black, which indicates the formation of metallic silver on the coral sand and completion of the silver plating.
Step 4:
After the silver plating, the coral sand is calcined at a temperature of between about 200C and 400C under a reduced pressure of about -20 to -50 mm Hg, in order to dry the silver-plated coral sand by evaporating the water therein.
L .~...
~7~
Step 5:
The silver-plated coral sand is thoroughly washed with water. It is preferable to wash the silver-plated coral sand with water for at least about 24 hours.
Step 6:
Finally, the washed silver-plated coral sand is disposed in a drying room wherein the temperature is maintained at about 50 to 80C for about 4 hours for drying.
The silver-plated coral sand obtained by the above-mentioned process contains 0.01 to 5 wt~ of silver.
:~ According to the above process, the coral sand can easily be plated with a desirable amount of silver. However, during the silver plating (Step 3), nitric acid ions (NO3 ) may also attach to the coral sand, which may result in the amount of (NO3 ) exceeding the legal water standard for drinking water, when the coral sand, which is silver-plated by the above process, is tested.
~ r .f~
., .
379~
To avoid this problem, the above process includes the removal treatment of the nitric acid radicals, after the silver plating. The addition of such treatment, however, may cause the silver plating (Step 3) to be more complex and take more time to carry out.
In order to simplify the silver plating process, sputtering can be utilized in place of the above-mentioned silver plating Step 3. In a silver plating step utilizing sputtering, the silver disposed on the cathode is sputtered onto the porous surface of the coral sand disposed on the anode.
The sputtering may be carried out in a conventional manner.
15For example, sputtering is carried out at a rate of adsorption of 4OA per minute in an argon gas of CO Torr for about one hour by means of a low-temperature plasma method.
This method does not include water washing and reducing treatments, which are essential to the - above-mentioned Step 3, and there are no nitric acid ions (N03 ) in water treated by the preservative, which is prepred by this method. Therefore, in accordance with the present invention, utilizing sputtering for the silver plating makes it possible to reduce the manufacturing cost, while producing an excellent preservative effect.
7~
The present invention will now be described in more detail with reference to an example below.
(Example~
One kilogram of coral sand grains crushed to 20 to 80 mesh was placed in a cylindrical sputtering chamber of a sputtering device. The chamber has an inner diameter of 20 cm and a height of 60 cm. The chamber was rotated at 60 rpm for about one hour and the air therein was exhausted by means of a vacuum pump to produce a vacuum therein. The chamber was then filled with argon gas of ]0 3 Torr. Using ~he low-temperature plasma method, the coral sand in the chamber was subjected to sputtering for about one hour so as to be plated with silver at a rate of adsorption of 400A/min.
.
The resultant silver-plated coral sand contained one percent by weight of silver. About 150 g of the silver-plated coral sand was placed in a cyclinder of 4.5 cm in inner diameter and 90 cm in length, ~hrough which tap water was passed at a rate of 2 lit./min. The ~uality of the passed-through water is shown in Table II.
~ , - 3L2~7~
TA~L~ II
Non-Treated Treated Item Water Water -Residual 0.5 0.0 Chlorine (ppm) pH 6.7 7.4 Bacteria O/ml O/ml Silver (ppb) not detected 45 The cylinder containing the silver-plated coral sand was then left to stand for two days without running tap water therethrough. Then tap water was again passed through the cylinder. The tap water passed through the cylinder and therefore ~ treated by the coral sand was tested and found to - contain no bacteria and to have a silver concentration of less than 50 ppb.
The preservative for the coral sand of the present invention has the following advantageous effects:
(1) Calcium carbonate as a main ingredient : of the silver-plated coral sand neutrali~es residual chlorine contained in tap water, thereby deodorizing the tap water.
., !
7g~5 (2) Further, calcium carbonate renders the pH of tap water weakly alka]ine, which is desirable for drinking water.
(3) Silver, which is soluble in tap water, has a bacteriostatic effect, preventing tap water from becoming foul, and therefore it becomes possible for tap water to be stored for a long period.
Summary of the Invention The present invention is directed to a novel preservative for drinking water, which is composed of sandy coral stone or coral sand plated with about 0.01 to about 5 percent by weight of silver.
Pre~erably the sandy coral stone or coral sand is heated to be activated in an inert gas such as of argon or ni-trogen prior to the silver plating.
Furthermore, the silver plating is preferably carried out by means of sputterlng.
Description of the Preferred Embodiment The inventors of the present invention conducted various experiments and find that coral, namely, sandy coral stone or coral sand ~hereinafter referred to as coral sand) was an extremely effective water preservative which could be substituted for activated charcoal.
The present invention utilizes coral sand which is prepared by crushing corallite and contains about 96 percent by weight of calcium carbonate as a main ingredient, calcium phosphate as a secondary ingredient and heavy metals as trace constituents.
9~ 35 Further, the coral sand is heated in an inert atmosphere to activate it and is provided therein with a great number of pores having a very small diameter. The pores provide the coral sand with an extremely large surface area, as much as that of activated charcoal. Thereforel coral sand having such pores has a tendency to be plated with silver more than other materials. Miscroscopic observation showed that the pores extend from side to side in the coral sand much as if they were holes extending longitudinally in a lotus root, which results in the coral sand havi.ng a large surface area and high water-permeability.
The preservative oE the present invention comprises this coral sand which is the feature oE
the present invention.
.
By conducting various experiments, it was ; found that the amount of silver for plating the coral sand is preferably from about 0.01 wt% to about 5 wt% of the total weight of the silver-plated coral sand. More specifically, the silver-plated coral sand containing less than 0.01 wt% of silver has an inadequate sterilizing effect, while over 5 wt% of silver gives no further increase in the sterilizing effect and is also uneconomical.
.~
When the silver-plated coral sand having silver in the range of about 0.01 to about 5 wt~ is incorporated in water, some of the silver is released therefrom to in the water and the concentration of the silver ions in water becomes between about 20 to 50 ppb. However, experiments showed that this concentration does not exceed 50 , ~,, ppb. It has been confirmed also from experiments that such a trace amount of silver ions is harmless to humans.
The silver-plated coral sand containing calcium carbonate as a main ingredient chemically reacts with the residua] chlorine in tap water as shown by the following formula. As can be seen from the formula, the calcium carbonate in the silver-plated coral sand neutralizes acid radicals (H30+) released ln tap water during the sterilization using chlorine, so that hydrogencarbonate ions (HC03 ) and chlorlne ions (Cl ) are produced in the tap water.
C12 + H20 -~ 2CaC03 2Ca2 -~ 2HC03 + 2Cl + 0 Thus, tap water containing chlorine and which, therefore, is smelly and acidified is neutralized and deodorized to be rendered weakly alkaline and also is sterilized by nascent oxygen (Ca2 ) and other ions such as magnesium and kalium ions released from the silver-plated coral sand make tap water good-tasting mineralized water.
The silver-plated coral sand has a sterilizing effect, when it is incorporated in water, over a long period of time, e.g., for six - months or longer. Further, no nitric acid radical is detectable in water in which the silver-plated coral sand, in accordance with the present invention is soaked. The silver-plated coral sand of the present invention maintains its excellent sterilizing power but does not adversely affect , , .. ... , ~ ..
~;~g7~0~i water quality, even when water in which the silver-plated coral sand is soaked is stored for a long period of time. For example, water wherein the silver-plated coral sand was soaked was stored for one year and the water quality examined with reference to the water standard of the Japanese Water Law. Results are shown in the following Table I.
~2~74L~;
TABLE I
Test Item Standard Value Results Nitric acid and less than not nitrous acid- 10 mg/l detected induced nitrogen Chlorine ion less than 17.0 mg/l 200 mg/l Organic substances less than 4.3 mg/l (consumption of 10 mg/l potassium permanganate) General less than 0 bacteria 100/1 ml E. coli undetectable not detected Iron less than ditto 0.3 mg/l Calcium, less than 70.0 mg/l magnesium, etc. 300 mg/l (hardness) pH 5.8 - 8.6 7.2 :;;
.. . . .. ..
~7~
TABLE I - (cont'd.) Test Item Standard Value Results Odor not no smell offensive Taste ditto no taste Chromaticity less than 0 .
Turbid.ity less than 0 Residual - 0.1 chlorine , .. ~
.. .
~2~7~
A process for preparing a preservative, in accordance with the present invention will now be explained.
The process comprises the following steps.
Step 1:
Coral sand is crushed to 20 to 80 mesh, preferably 40 to 50 mesh and substantially dechlorinated by washing with water. The coral sand is then heated to between 200 and 400 C, preferably 10 about 350 C for about 2 to 4 hours, in an inert gas such as of argon or nitrogen under a reduced pressure of -20 to -50 mm Hg. This removes from the coral sand residual chlorine ions and activates the sand.
Step 2:
After completion of the above step, the activated coral sand is washed thoroughly under running water to rid it of nitric acid radicals.
This washing must be of a duration of 24 hours, since a brief washing such as one lasting only 3 hours, is insufficient to achieve the almost total removal of the nitric acid radicals. Further, a brief washing may result in detection of a considerably high concentration of nitric acid radical, which will not meet the legal water standard.
, '.`~
.
~2~
g Step 3:
After water washing, the activated coral sand is plated with silver as follows.
First, the coral sand is soaked in an aqueous solution of silver-ammonia obtained by mi~ing silver nitrate and ammonia water under a reduced pressure of -20 mm Hg to -50 mm Hg and maintaining the temperature of the solution at about 20C to 40C
for about one hour.
Next, to the solution is added a trace amount of a reducing agent, such as glucose, a Rochelle salt or formaldehyde.
After addition of the reducing agent, the coral sand thus soaked is left to stand at room temperature for about 10 to 20 hours, during which the surface of the coral sand turns black, which indicates the formation of metallic silver on the coral sand and completion of the silver plating.
Step 4:
After the silver plating, the coral sand is calcined at a temperature of between about 200C and 400C under a reduced pressure of about -20 to -50 mm Hg, in order to dry the silver-plated coral sand by evaporating the water therein.
L .~...
~7~
Step 5:
The silver-plated coral sand is thoroughly washed with water. It is preferable to wash the silver-plated coral sand with water for at least about 24 hours.
Step 6:
Finally, the washed silver-plated coral sand is disposed in a drying room wherein the temperature is maintained at about 50 to 80C for about 4 hours for drying.
The silver-plated coral sand obtained by the above-mentioned process contains 0.01 to 5 wt~ of silver.
:~ According to the above process, the coral sand can easily be plated with a desirable amount of silver. However, during the silver plating (Step 3), nitric acid ions (NO3 ) may also attach to the coral sand, which may result in the amount of (NO3 ) exceeding the legal water standard for drinking water, when the coral sand, which is silver-plated by the above process, is tested.
~ r .f~
., .
379~
To avoid this problem, the above process includes the removal treatment of the nitric acid radicals, after the silver plating. The addition of such treatment, however, may cause the silver plating (Step 3) to be more complex and take more time to carry out.
In order to simplify the silver plating process, sputtering can be utilized in place of the above-mentioned silver plating Step 3. In a silver plating step utilizing sputtering, the silver disposed on the cathode is sputtered onto the porous surface of the coral sand disposed on the anode.
The sputtering may be carried out in a conventional manner.
15For example, sputtering is carried out at a rate of adsorption of 4OA per minute in an argon gas of CO Torr for about one hour by means of a low-temperature plasma method.
This method does not include water washing and reducing treatments, which are essential to the - above-mentioned Step 3, and there are no nitric acid ions (N03 ) in water treated by the preservative, which is prepred by this method. Therefore, in accordance with the present invention, utilizing sputtering for the silver plating makes it possible to reduce the manufacturing cost, while producing an excellent preservative effect.
7~
The present invention will now be described in more detail with reference to an example below.
(Example~
One kilogram of coral sand grains crushed to 20 to 80 mesh was placed in a cylindrical sputtering chamber of a sputtering device. The chamber has an inner diameter of 20 cm and a height of 60 cm. The chamber was rotated at 60 rpm for about one hour and the air therein was exhausted by means of a vacuum pump to produce a vacuum therein. The chamber was then filled with argon gas of ]0 3 Torr. Using ~he low-temperature plasma method, the coral sand in the chamber was subjected to sputtering for about one hour so as to be plated with silver at a rate of adsorption of 400A/min.
.
The resultant silver-plated coral sand contained one percent by weight of silver. About 150 g of the silver-plated coral sand was placed in a cyclinder of 4.5 cm in inner diameter and 90 cm in length, ~hrough which tap water was passed at a rate of 2 lit./min. The ~uality of the passed-through water is shown in Table II.
~ , - 3L2~7~
TA~L~ II
Non-Treated Treated Item Water Water -Residual 0.5 0.0 Chlorine (ppm) pH 6.7 7.4 Bacteria O/ml O/ml Silver (ppb) not detected 45 The cylinder containing the silver-plated coral sand was then left to stand for two days without running tap water therethrough. Then tap water was again passed through the cylinder. The tap water passed through the cylinder and therefore ~ treated by the coral sand was tested and found to - contain no bacteria and to have a silver concentration of less than 50 ppb.
The preservative for the coral sand of the present invention has the following advantageous effects:
(1) Calcium carbonate as a main ingredient : of the silver-plated coral sand neutrali~es residual chlorine contained in tap water, thereby deodorizing the tap water.
., !
7g~5 (2) Further, calcium carbonate renders the pH of tap water weakly alka]ine, which is desirable for drinking water.
(3) Silver, which is soluble in tap water, has a bacteriostatic effect, preventing tap water from becoming foul, and therefore it becomes possible for tap water to be stored for a long period.
(4) Calcium carbonate as a main ingredient and the other trace amount of constituents of the silver-pla-ted coral sand are soluble i.n and mineralize tap water, which becomes an e~ective source for supplying elements essential to the human body.
(5) The coral sand, which is used as a carrier for silver is a porous material having a large surface area to adsorb heavy metals, etc., whereby tap water is filtered or purified.
.
.
Claims (3)
1. Preservative for drinking water comprising coral sand which is plated with about 0.01 to about 5 percent by weight of silver.
2. Preservative of claim 1 wherein said silver plated coral sand has been heated in an inert gas to activate the sand.
3. Preservative of claim 1 or 2 wherein coral sand is plated with silver by sputtering.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000487584A CA1297405C (en) | 1985-07-26 | 1985-07-26 | Preservative for drinking water |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000487584A CA1297405C (en) | 1985-07-26 | 1985-07-26 | Preservative for drinking water |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1297405C true CA1297405C (en) | 1992-03-17 |
Family
ID=4131064
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000487584A Expired - Lifetime CA1297405C (en) | 1985-07-26 | 1985-07-26 | Preservative for drinking water |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1297405C (en) |
-
1985
- 1985-07-26 CA CA000487584A patent/CA1297405C/en not_active Expired - Lifetime
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |