JPS6034789A - Filter medium for water purifier - Google Patents

Abstract

PURPOSE:To obtain a filter medium for water purifier inhibiting proliferation of bacteria even if the water stagnates during purification, from a mixture consisting of 20-30wt% active carbon supporting silver, 10-15wt% active carbon supporting copper, and 55-70wt% pure active carbon. CONSTITUTION:20-30wt% active carbon supporting 0.35-1.0wt% silver on the surface, 10-15wt% active carbon supporting 0.5-3.0wt% copper on the surface, and 55-70wt% pure active carbon are mixed to obtain a filter medium for a water purifier. By regulating the amt. of silver supported by the active carbon to 0.35-1.0wt%, the concn. of silver ion in the stagnating water is regulated to 10-50ppb. When the above described filter medium is used, elution of silver is retarded by the presence of copper ion. Proliferation of bacteria is prevented even if stagnation of water for a long time is caused since proliferation of bacteria is inhibited by the sterilizing effect of coexisting copper ion.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a filter medium for a water purifier that purifies and sterilizes domestic water such as drinking water.

In recent years, as the quality of raw water for drinking water has deteriorated, the amount of chlorine added to water for disinfection at water treatment plants after sedimentation and filtration has increased, resulting in unpleasant taste and odor caused by residual chlorine in tap water. It becomes. This problem is particularly acute in the summer, and recently unpleasant tastes and odors have been caused not only by chlorine but also by the microorganisms that cause red geo. In order to remove residual chlorine from tap water, water purifiers using activated carbon as a filter material have been proposed, and some of them are in practical use for household use, but this type of water purifier cannot remove residual chlorine. As a result, when the water is stopped, bacteria proliferate in the water that remains in the water purifier, and the water that comes out of the water purifier at the beginning of water flow becomes unsuitable for drinking. Therefore, as filter media for water purifiers, filter media that not only removes residual chlorine but also suppresses the growth of bacteria are available, for example,
It has been proposed in Japanese Patent Publication No. 3608, Japanese Patent Publication No. 52-38666, Japanese Patent Application Laid-Open No. 51-90996, and has been put into practical use. These filter media are a mixture of activated carbon with silver supported on its surface (hereinafter referred to as silver-supported activated carbon) and high activity.While the activated carbon adsorbs and removes chlorine from water, it also removes residual chlorine. The decrease in bactericidal action is compensated for by the bactericidal action of silver ions eluted from silver-supported activated carbon.
It is designed to suppress the growth of bacteria. When this type of filter media is used, it is recognized that it is effective in inhibiting the growth of bacteria in standing water, but its bactericidal effect depends on the concentration of silver ions in the water, so if the amount of silver supported is small or the water temperature is In cold winter months, there was a drawback that it was not possible to prevent the growth of bacteria in standing water. The problem of the amount of silver supported can be easily solved by increasing the amount of silver supported in the summer to the extent that the silver ion concentration does not exceed the upper limit of 50 ppb-L of the U.S. drinking water quality standard, but the bactericidal effect at low water temperatures may be reduced. It was not possible to prevent the decline.

The present invention provides a filter medium for water purifiers that can remove residual chlorine from tap water regardless of the seasonal RO such as winter or summer, and at the same time does not cause bacterial growth even if water remains in the water purifier. It is characterized by consisting of 10 to 30% by weight of activated carbon with silver supported on its surface, 10 to 15% by weight of activated carbon with copper supported on its surface, and the remainder pure activated carbon. Found in filter media for water purifiers.

In a preferred embodiment of the present invention, activated carbon having 0.35 to 1.0% by weight of silver supported on its surface is used as the silver-supported activated carbon. Further, as the copper-supported activated carbon, activated carbon having 0.5 to 3.0% by weight of copper supported on its surface is used.

The reason why the proportion and amount of silver supported in the silver-supported activated carbon material were determined as described above is as follows. That is, if the proportion of silver-supported activated carbon is less than 10% by weight, the spacing between the silver-supported active particles is too large and the water passing between the large number of pure activated carbon particles in between cannot be completely sterilized. This is because if the amount exceeds 30% by weight, the concentration of silver ions in the retained water may exceed 50 PPb in summer due to the amount of silver supported. In addition, the amount of silver supported is 0.35 compared to activated carbon that supports silver.
The reason for setting the silver ion concentration to 1.0% by weight was to keep the silver ion concentration in the retained water within the range of 10 PPb to 50 ppb regardless of whether it is winter or summer, and also from the viewpoint of cost.

In addition, copper-supported activated carbon can inhibit the growth of bacteria in water, especially by interacting with silver ions eluted from silver-supported activated carbon.
It is used in combination with the purpose of suppressing the growth in winter when the water temperature is low, and if the content is less than 10% by weight, it will not be possible to inhibit the growth of Achromobacter, Flavobacterium, Pseudomonas, etc., which grow at low temperatures. This is because if the content exceeds % by weight, the concentration of copper ions in the retained water becomes too high. The amount of copper supported on activated carbon is 0.
The content is set at 5 to 3% by weight in order to ensure that the amount of copper eluted in winter and summer falls within the range of 50 PPb to IPPm.

Generally, in order to obtain the desired bactericidal effect at room temperature, a silver ion concentration of approximately 20 ppb or more is required, but when the material of the present invention is used, the amount of silver eluted is reduced due to the presence of copper ions. suppressed, and the silver ion concentration was 10 ppbJ)J
, even if the water temperature drops to 10°C and the silver ion concentration drops below 10 ppb, the bactericidal action of the coexisting copper ions suppresses the growth of bacteria, so the water remains in the water for a long time. However, bacteria will not grow.

The silver-supported activated carbon used in the present invention is preferably one in which silver is precipitated on the surface of the activated carbon by a silver mirror reaction. This is because activated carbon with silver precipitated on one surface by silver mirror reaction does not lose its adsorption capacity and adsorption capacity of the activation method itself, and it is easy to obtain any amount of silver supported. .

Further, the copper-supported activated carbon used in the present invention is preferably one in which copper is deposited on the surface of the activated carbon by electroless plating. This is because, in this case as well, the deposited copper does not impair the adsorption ability and adsorption capacity of the activation method itself, as in the case of silver-supported activated carbon.

Examples of the present invention will be described below.

Example 1 After washing and drying 200 g of activated carbon (steam-activated coconut shell activated carbon with a particle size of 8 to 32 mesh, the same applies hereinafter in this example), an aqueous solution 2 containing 10 PPm of stannous chloride was prepared.
00 mJ was added, and after the generation of bubbles had stopped, the liquid was drained, and then hydroxylated with 500 mJ of an aqueous solution containing 8 g of silver nitrate and 100 * t of 28% ammonia water. At the same time as adding the first liquid IE, 0.5 ml of 65% nitric acid was added to the aqueous solution 100++7 containing 10 g of sucrose for color strength. The two liquids were added and stirred well for 5 minutes at 20°C to precipitate silver on the surface of the activated carbon particles.Next, the activated carbon on which silver had been precipitated was washed with water several times and dried with hot air at 110°C for 2 hours to remove the activated carbon. 1
Silver-supported activated carbon carrying 8.9 M9 of silver per g was obtained.

Separately, 20Of activated carbon was washed with 0.1% palladium chloride solution, washed with 200ml of an aqueous solution containing 10 PPm of stannous chloride, drained, and then washed with 170 y/l of Rochelle salt and water. Sodium oxide 50g/β
and copper sulfate 35 f/l aqueous solution 30011/
, and immediately add 150ml of 40% formaldehyde solution.
After adding t, copper was precipitated on the surface of the activated particles by heating to 50°C, followed by washing with water and drying to obtain copper-supported activated carbon in which 15.61119 copper was supported per 1f of activated carbon.

37.59 g of silver-supported activated carbon thus obtained, 37.5 g of copper-supported activated carbon, and 225 g of pure activated carbon were mixed to make a filter material for a water purifier, and the number of viable bacteria and the elution amount of copper and silver in the retained water were measured. did. The results are shown in Table 1 together with the results for Comparative Examples A and C.

Comparative Example A is a filter medium made of a mixture of silver-supported activated carbon and pure activation, and the amount of silver per gram of filter medium was 1.34~. Comparative Example B is a filter medium containing silver-supported activated carbon and pure activated carbon, and the amount of silver per gram of filter medium was 0.71. Comparative example C is a filter medium containing silver-supported activated carbon and pure activated carbon, and filter medium 1
The amount of silver per g was 1 mg.

In addition, to measure the number of viable bacteria, attach the water purifier to the tap water faucet,
After 304 hours of water was discharged, the water was allowed to stand for the specified time shown in the table, and after the time had elapsed, 50 ml of the initial runoff water was collected, 1πt of it was placed in a Petri dish, and the presence of common viable bacteria was measured using a standard agar culture method. Regarding the amount of silver and copper eluted, 250 s+t of the initial effluent water was collected after the water had been retained for a specified period of time, and 1 ml of concentrated nitric acid was added and boiled to reduce the amount by 10 times, and the amount was determined by atomic absorption spectrometry.

The number of viable bacteria was measured in June, and the water temperature at the time of measurement was 20°C.

Table 1 As is clear from the results in Table 1, the water purifier using the filter medium according to the present invention has a viable count of O even after 72 hours of water retention, and an eluted amount of silver of 18 ppb, which is lower than that of the United States. It fully satisfies the drinking water quality standard of 50 PPb or less, and also has copper content of 108 to 135 ppb, which is well below the standard value I PPm or less, and is better than the conventional ones shown in Comparative Examples A to C°. shows excellent performance.

Example 2 In the same manner as in Example 1, 17.31 per active 77117
Silver-supported activated carbon carrying ffg of silver was produced, and 15 parts by weight of this silver-supported activated carbon, 10 parts by weight of the copper-supported activated carbon prepared in Example 1, and 75 parts by weight of pure activated carbon were mixed, and this mixture was used as a filter material in a cartridge. Fill it up, set it in the water purifier, attach it to the water faucet, and do the same as in Example 1.
Initial runoff water after staying for a specified time in winter (water temperature 10°)
The number of general viable bacteria and the amount of silver and copper eluted in C) were measured.

The results are shown in Table 2.

As is clear from the results in Table 2, the lumber of the present invention exhibits an excellent bacterial growth prevention effect even at low temperatures.

In the above examples, silver and copper are supported on activated carbon separately, but copper is further precipitated on the surface of silver-supported activated carbon, or silver is further precipitated on the surface of copper-supported activated carbon. It is also possible to use In either case, silver and copper can be deposited by the methods described in the Examples. However, if silver and copper are supported on the surface of the same activated carbon particles, the amount of the previously supported metal will be significantly reduced, and there will also be a problem in terms of cost, so they are supported separately as in the example. is preferable.

As explained above, according to the present invention, by using silver-supported activated carbon and copper-supported activated carbon in combination with pure activated carbon, the growth of bacteria in standing water can be prevented regardless of the season, and furthermore,
The unpleasant taste and odor caused by residual chlorine in tap water can be completely removed.

Patent applicant: Zojirushi Mahobin Co., Ltd. Representative patent attorney: Aohaku Ao and 2 others

Claims (3)

[Claims] (1) Silver-supported activated carbon 20-30% by weight, copper-supported activated carbon 1
A filter medium for a water purifier, characterized in that it is a mixture of 0 to 15% by weight of pure activated carbon and 55 to 70% by weight of pure activated carbon. (2) The filter medium according to claim 1, wherein the silver-supported activated carbon supports 0.35 to 1.0% by weight of silver. (3) The material according to claim 1 or 2, wherein the copper-supported activated carbon supports 0.5 to 3% copper.