JPH10137524A - Anti-bacterial activated carbon and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an anti-bacterial activated carbon excellent in duration of antibacterial activity by eluting silver into water in a stable low concentration over a long period. SOLUTION: This anti-bacterial activated carbon is constituted so as to carry 0.1-15 pts.wt. total of silver, silver oxide and silver sulfide expressed in terms of silver to 100 pts.wt. of activated carbon. The anti-bacterial activated carbon is obtained by dipping the activated carbon in an aq. solution of a water soluble silver salt, drying to carry silver and silver oxide on the activated carbon and next treating with a sulfidizing agent to sulfidize a part of silver and silver oxide carried on the activated carbon.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antibacterial activated carbon used for a water filter, a water purifier and the like as a filter medium for suppressing the growth of, for example, Escherichia coli and other bacteria contained in water, and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, for example, in order to remove harmful trihalomethanes contained in general tap water, there are various filters and water purifiers which treat tap water with activated carbon.
As is known, when bacteria such as Escherichia coli are mixed in these devices, they grow in the devices and contaminate the water treated by the devices. Therefore, in the case of a conventional filter, a water purifier, or the like, it is necessary to pass water through the device for a few minutes, so-called abandoned water, if 24 hours or more have passed after stopping water.

Therefore, in order to solve such a problem, activated carbon is conventionally supported with silver having a high antibacterial property, and this is often used as a filter medium of a filter or a water purification device.
However, when activated carbon carrying silver as described above is used as a filter medium, the amount of silver eluted into water is excessive in the initial stage, and for example, the standard value in the United States of 50
ppb, but then the amount of elution sharply decreases,
The bactericidal effect and the antibacterial property of suppressing the growth of bacteria become insufficient.
That is, the conventional silver-carrying activated carbon lacks the stability and sustainability of its antibacterial effect.

[0004]

DISCLOSURE OF THE INVENTION The present invention has been made to solve the above-mentioned problems in the silver-supported activated carbon conventionally used as a filter medium, and is intended to stabilize silver for a long period of time. Eluted in water at low concentration,
Thus, an object of the present invention is to provide an antibacterial activated carbon having excellent antibacterial activity and a method for producing the same.

[0005]

The antibacterial activated carbon according to the present invention comprises silver, silver oxide and silver sulfide in a total amount of 0.1 to 15 parts by weight in terms of silver based on 100 parts by weight of activated carbon. It is characterized by being carried by. Hereinafter, the total amount of silver, silver oxide, and silver sulfide carried on activated carbon in terms of silver is referred to as total silver carried amount.

According to the present invention, of the total silver carrying amount,
The proportion of silver sulfide is preferably from 5 to 80% by weight in terms of silver. Hereinafter, the ratio of silver sulfide in terms of silver in the total silver carried amount is simply referred to as silver sulfide carried ratio. In addition, the method for producing an antibacterial activated carbon according to the present invention comprises immersing activated carbon in an aqueous solution of a water-soluble silver salt, drying the activated carbon, supporting silver and silver oxide on the activated carbon, and then treating the activated carbon with a sulfurizing agent. In addition, a part of the silver and the silver oxide supported on the activated carbon is sulfurized.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The activated carbon used in the present invention is:
The type, shape and size are not particularly limited, but, for example, coconut palm, activated carbon granules, fibrous materials, honeycomb molded bodies, and the like can be preferably used.
The antibacterial activated carbon according to the present invention is obtained by immersing such activated carbon in an aqueous solution of a water-soluble silver salt, drying it, supporting silver and silver oxide, and then treating such activated carbon with a sulfurizing agent. The silver and part of the silver oxide are converted to silver sulfide.

As the water-soluble silver salt, for example, a carbonate or a nitrate is preferably used. The amount supported on these activated carbons is 0.1 to 100 parts by weight of activated carbon in terms of silver.
It is in the range of 15 parts by weight, preferably 0.5 to 10 parts by weight. After silver is thus supported on the activated carbon, the activated carbon may be fired at a relatively low temperature of about 100 to 300 ° C., if necessary. In particular, by firing at a temperature of 200 ° C. or higher, the loading ratio of silver oxide can be increased. Further, if necessary, sintering may be performed in a reducing atmosphere, whereby the loading ratio of silver can be increased.

In order to carry out the sulfurizing treatment of the activated carbon carrying silver and silver oxide in this manner, it is usually sufficient to immerse the activated carbon in an aqueous solution of a sulfurizing agent. Normally, sodium sulfide and ammonium sulfide are preferably used as the sulfurizing agent. However, in some cases, silver and silver oxide supported on the activated carbon can be sulfided by dispersing the activated carbon in water and blowing hydrogen sulfide into the water. After sulfided silver and silver oxide supported on activated carbon in water in this way, the resultant is filtered and dried to obtain activated carbon supporting silver and silver oxide.

[0010] If necessary, the activated carbon thus sulfurized may be calcined in a reducing atmosphere at a relatively low temperature of about 100 to 200 ° C. Can be done. In this way, by using silver, silver oxide and silver sulfide carried on activated carbon as sulfide, the amount of silver eluted into water can be kept low for a long period of time, and the antibacterial property can be maintained. Thus, silver can be suppressed from elution into water by the sulfurizing treatment of silver and silver oxide because the sulfurating treatment forms a silver sulfide coating with a very low elution amount on the surface of silver and silver oxide. To control the dissolution of silver, silver and silver oxide. However, the present invention is not limited by any theory.

According to the present invention, the total silver loading on the activated carbon is 0.1 to 15 parts by weight, preferably 0 to 15 parts by weight, based on 100 parts by weight of the activated carbon, mainly from the viewpoint of economy. The amount of silver sulfide carried is preferably in the range of 5 to 80% by weight, and more preferably in the range of 30 to 50% by weight. Preferably, there is. According to the present invention, silver, silver oxide and silver sulfide are supported on activated carbon at such a ratio, whereby silver can be stably eluted in water at a low level for a long period of time. That is, the antibacterial activated carbon according to the present invention is usually, after filtering treatment of several tens tons to 100 tons of water per 1000 mL, in the retained water,
Usually, in the range of 5-100 ppb, preferably 10-5
Silver can be eluted in water in the range of 0 ppb.

As described above, after obtaining activated carbon carrying silver and silver oxide, the activated carbon is reduced with a reducing agent, and then the activated carbon is treated with a sulphidating agent to carry the activated carbon on activated carbon. The antibacterial activated carbon according to the present invention can also be obtained by sulfurizing a part of the silver and silver oxide.
By reducing the activated carbon carrying silver and silver oxide with a reducing agent, the ratio of silver / silver oxide can be increased, and the ratio of silver / silver oxide is maintained high even after the sulfurating treatment. Here, since the elution rate of silver into water is lower than that of silver oxide, the thus obtained antibacterial activated carbon has a low initial silver elution rate in water and a low concentration. Can be continued for a longer period of time.

By incorporating the antibacterial activated carbon according to the present invention into a conventional water purification device as a filter medium, the water purification device can be provided with a hygienic function to be highly functional. Further, a filtration device using the antibacterial activated carbon according to the present invention as a filter medium may be used in combination with a conventional water purification device. Further, the antibacterial activated carbon according to the present invention may be used for treating water tanks in high-rise buildings. In this way, the use of the antibacterial activated carbon according to the present invention makes it possible to easily and inexpensively obtain safe living water such as drinking water and water for breeding animals and plants.

[0014]

As described above, the antibacterial activated carbon according to the present invention is obtained by carrying silver and silver oxide on activated carbon and subjecting a part of them to sulfuration treatment, so that they are stable for a long period of time. Thus, silver can be eluted into water at a low level, and thus can be suitably used as a filter medium for suppressing the growth of Escherichia coli and other bacteria in water.

[0015]

EXAMPLES The present invention will be described below with reference to examples.
The present invention is not limited by these examples.

Example 1 32 g of silver nitrate was dissolved in 10 L of distilled water, and 2 kg of coconut palm with a particle size of 0.1 to 0.3 mm was immersed in the obtained solution for 1 hour, followed by filtration and washing with water. And dried. Then, the activated carbon carrying silver and silver oxide was mixed with a 5% by weight aqueous solution of sodium sulfide nonahydrate 1 in this manner.
After being immersed in 0 L for 1 hour, the solution was filtered, sufficiently washed with water, and then dried at 110 ° C. for 24 hours to obtain an antibacterial activated carbon according to the present invention.

The total supported amount of silver, silver oxide and silver sulfide (total silver supported amount) in the thus obtained antibacterial activated carbon was determined by a fluorescent X-ray analyzer (3270 manufactured by Rigaku Corporation).
) Was determined from a quantitative analysis of silver by a calibration curve using As a result, the total silver carried amount was 100 parts by weight of activated carbon,
0.98 parts by weight. Similarly, the amount of sulfur in the antibacterial activated carbon was measured using a fluorescent X-ray analyzer (Rigaku Denki Co., Ltd. 3
The amount of silver sulfide carried was calculated in terms of silver based on the quantitative analysis using a calibration curve using Model 270), and it was 0.45 part by weight based on 100 parts by weight of activated carbon. As a result, the ratio of silver sulfide to the total amount of silver supported by the antibacterial activity was 45.9% by weight.

The silver / silver oxide (weight ratio in terms of silver) of the antibacterial activated carbon was measured using an X-ray photoelectron spectrometer (ESCA-850, manufactured by Shimadzu Corporation). there were. Next, antibacterial activated carbon 2
100 mL was packed in a vinyl chloride resin column, and 100 tons of tap water was passed through at a rate of 3 L / min. During that time, tap water was retained in the column at predetermined intervals for 8 hours to elute silver into the water. Was measured. The amount of silver eluted in water was quantitatively analyzed by a calibration curve by plasma emission spectrometry (ICP) using SPS-1200A manufactured by Seiko Denshi Co., Ltd. As shown in Table 1, the elution amount of silver was 20 to 50 p.
pb range.

Example 2 16 g of silver nitrate was dissolved in 10 L of distilled water, and 2 kg of coconut palm with a particle size of 0.1 to 0.3 mm was immersed in the obtained solution for 1 hour, followed by filtration and washing with water. . The activated carbon carrying silver and silver oxide in this way is again
L, and 1% by volume of hydrazine was added thereto. After the foaming was completed, the mixture was filtered, washed with water and dried after 30 minutes. Then, the activated carbon thus reduced in silver oxide was immersed in 10 L of a 5% by weight aqueous solution of sodium sulfide nonahydrate for 1 hour, filtered, washed thoroughly with water, and then dried at 110 ° C. for 2 hours.
After drying for 4 hours, an antibacterial activated carbon according to the present invention was obtained.

As a result of analyzing this antibacterial activated carbon in the same manner as in Example 1, the total amount of silver carried was 0.99 parts by weight in terms of silver with respect to 100 parts by weight of activated carbon. The amount of silver carried was 0.42 parts by weight in terms of silver based on 100 parts by weight of activated carbon. Therefore, the silver sulfide loading ratio was 42.4% by weight of the total silver loading having the antibacterial activity.

The ratio of silver / silver oxide (weight ratio in terms of silver) of the antibacterial activated carbon was 93/7. This antibacterial activated carbon was tested in the same manner as in Example 1, and the amount of silver eluted into water was measured. As shown in Table 1, the elution amount of silver was in the range of 10 to 40 ppb.

COMPARATIVE EXAMPLE 1 Using a commercial product having 1 part by weight of silver supported on 100 parts by weight of activated carbon from coconut palm, a test was conducted in the same manner as in Example 1, and the amount of silver eluted into water was measured. did. As shown in Table 1, the amount of silver eluted into water in the initial stage of water passage was extremely high, but the amount of elution rapidly decreased with time.

[0023]

[Table 1]

Comparative Example 2 The procedure of Example 1 was repeated, except that a 30% by weight aqueous solution of sodium sulfide nonahydrate was used to sulfide silver and silver oxide supported on activated carbon. , An antibacterial activated carbon was obtained. As a result of analyzing this antibacterial activated carbon in the same manner as in Example 1, the total amount of silver carried was 0.99 parts by weight with respect to 100 parts by weight of activated carbon, and the amount of silver sulfide carried was 100 parts by weight of activated carbon. On the other hand, it was 0.93 parts by weight in terms of silver. Therefore, the silver sulfide loading ratio was 94.9% by weight of the total silver loading having the antibacterial activity. After filling 200 mL of this antibacterial activated carbon into a vinyl chloride resin column and passing 5 tons of tap water at a rate of 3 L / min, the tap water was retained in the column for 8 hours to reduce the amount of silver eluted into the water. It was less than 5 ppb when measured in the same manner as in Example 1.

Example 3 and Comparative Examples 3 and 4 In the same manner as in Example 2, silver was supported in various amounts and hydrazine was reduced, and then the silver was sulfurized to obtain the antibacterial activated carbon according to the present invention. Obtained. Table 2 shows the total amount of silver carried in the antibacterial activated carbon, the conditions of the sulfurization and hydrazine reduction treatment, and the weight ratio of silver / silver oxide / silver sulfide in the antibacterial activated carbon in terms of silver. Further, in the same manner as in Example 1, 200 mL of each antibacterial activated carbon was packed in a vinyl chloride resin column, and tap water was supplied at a rate of 3 L / min for 5 tons and 50 tons.
After passing water through the column, tap water was retained in the column for 12 hours, and the amount of silver eluted into the water was measured in the same manner as in Example 1. The results are shown in Tables 2 and 3.

As shown in Tables 2 and 3, according to the antibacterial activated carbon of the present invention, the amount of silver eluted is in the range of 10 to 100 ppb, and preferably, in the range of 10 to 50 ppb. I have. On the other hand, the antibacterial activated carbon according to Comparative Example 3 has an excessive amount of total silver and an excessive amount of silver eluted into water regardless of the sulfidation treatment. On the other hand,
The antibacterial activated carbon according to Comparative Example 4 has a total silver loading within the range of the present invention, but has not been subjected to sulfidation, so that the initial silver elution is excessive and the silver elution is abrupt over time. And the persistence of silver elution is lacking.

In Tables 2 and 3, the sodium sulfide concentration is the sodium sulfide concentration (% by weight) of 10 L of the aqueous solution, and the hydrazine concentration is the volume% with respect to 10 L. The ratio of silver (metal), silver oxide and silver sulfide in the antibacterial activated carbon is a ratio (% by weight) in terms of silver.

[0028]

[Table 2]

[0029]

[Table 3]

Claims (7)

[Claims] 1. An antibacterial agent comprising silver, silver oxide and silver sulfide in a total amount of 0.1 to 15 parts by weight of silver based on 100 parts by weight of activated carbon. Activated carbon. 2. The antibacterial activated carbon according to claim 1, wherein the ratio of silver sulfide to silver, silver oxide and silver sulfide carried on the activated carbon is 5 to 80% by weight in terms of silver. 3. The activated carbon is immersed in an aqueous solution of a water-soluble silver salt, and then dried to deposit silver and silver oxide on the activated carbon. Then, the activated carbon is treated with a sulphidating agent to be activated on the activated carbon. A method for producing an antibacterial activated carbon, characterized in that a part of silver and silver oxide is sulfurized. 4. The method according to claim 3, wherein the sulfurizing agent is sodium sulfide or ammonium sulfide. 5. The activated carbon is immersed in an aqueous solution of a water-soluble silver salt and then dried to carry silver and silver oxide on the activated carbon. The activated carbon thus carrying silver and silver oxide is reduced with a reducing agent. Treatment, and then the activated carbon is treated with a sulfurizing agent,
A method for producing an antibacterial activated carbon, characterized in that a part of silver and silver oxide carried on the activated carbon is sulfurized. 6. The method according to claim 5, wherein the sulfurizing agent is sodium sulfide or ammonium sulfide. 7. The method according to claim 5, wherein the reducing agent is hydrazine.