JPH06106161A - Activated carbon water purifier - Google Patents

Abstract

PURPOSE:To easily remove trihalomethane and free chlorine in tap water by carbonizing a carbonaceous raw material to activate the same and cooling the activated carbonized material to specific temp. or lower in predetermined gas to obtain granular activated carbon and using the obtained granular activated carbon and predetermined fibrous activated carbon as an adsorbent. CONSTITUTION:In a water purifier, granular activated carbon obtained by carbonizing a carbonaceous raw material and activating the carbonized material in an atmosphere with steam content of 15% or less until a BET specific surface area of 300-1500m<2>/g is obtained and subsequently cooling the activated one to 30 deg.C or lower in the same atmosphere or gas composed of a compsn. low in the contents of oxygen and steam as compared with said atmosphere and fibrous activated carbon with a specific surface area of 1400m<2>/g or more are used as an adsorbent. When activated carbon activated in gas having a specific compsn. and cooled in gas having a specific compsn. is used, high adsorption power is shown with respect to a low b.p. organochlorine compd. such as trihalomethane or chlorobromomethane present in water in low concn. and, when fibrous activated carbon is used in a mixed state, free chlorine is also adsorbed and removed other than an organochlorine compd.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a water purifier,
More specifically, granular activated carbon prepared in a specific range of specific surface area and specific conditions, which is excellent in adsorptivity of organic halogen compounds contained in water such as trihalomethane, and fibrous activated carbon which is excellent in adsorptivity of free chlorine. It is a water purifier used as an adsorbent.

[0002]

2. Description of the Related Art Activated carbon has been attracting attention as one of the methods for removing various harmful substances existing in tap water, especially organic chlorine compounds such as trichloromethane and chlorobromomethane, and free chlorine.

However, trichloromethane, chlorobromomethane, etc. in tap water have a small molecular weight and a relatively low boiling point, and their concentration is extremely dilute, so that conventional activated carbon can sufficiently remove these compounds. Does not have a high adsorptive property. It has only been known that activated carbon with a slightly lower activation rate and a relatively smaller specific surface area has a tendency to exhibit a relatively high adsorptivity for these compounds with a very low concentration.

Further, the granular activated carbon alone is not always sufficient in the removal property and sustainability of free chlorine in water, and the fibrous activated carbon is excellent in the removal property of free chlorine. It has been pointed out that it is difficult to sufficiently remove the organic chlorine compound due to the small amount.

[0005]

In recent years, with the deterioration of the quality of tap water, there is a strong demand for the removal of highly toxic trihalomethanes, organochlorine compounds, and the like. In view of this situation, we have developed an activated carbon with high adsorptivity that allows these compounds to be easily adsorbed and removed at room temperature to adsorb and remove these harmful substances contained in tap water as well as free chlorine. It is intended to provide a water purifier having excellent removability.

[0006]

[Means for Solving the Problems] Ordinary activated carbon is not sufficiently adsorptive enough to remove extremely dilute organic chlorine compounds such as trichloromethane and chlorobromomethane contained in tap water. However, the present inventors have noticed that activated carbon having a low activation rate and a relatively small specific surface area has a property of exhibiting a relatively high adsorptivity with respect to these compounds having a low concentration. The relationship between activation conditions in the range of activation degree and adsorptivity to these substances was examined. As a result, it was found that activated carbon having high adsorptivity to a dilute concentration of organic chlorine compound can be obtained by activating under specific conditions and further cooling to a constant temperature in the same atmosphere. Further, it has been found that an adsorbent excellent in not only removal of organic chlorine compounds such as trihalomethane but also removal of free chlorine can be obtained by mixing and using fibrous activated carbon, and based on this, the present invention was reached.

That is, the carbonaceous raw material is carbonized, and the BET specific surface area is 300 in an atmosphere having a water vapor content of about 15% (volume) or less.
Granular activated carbon obtained by activating until it reaches ~ 1500 m ² / g, and then cooling to about 300 ° C or less in the same atmosphere or in a gas with a composition with a lower oxygen and water vapor content, and a specific surface area of 1400 m ² / A water purifier characterized by using fibrous activated carbon of g or more as an adsorbent, and a BET specific surface area of 300
~ 1500 m ² / g of activated carbon in nitrogen gas and / or carbon dioxide gas substantially free of oxygen and / or steam
After processing at 500 ℃ or more, about 300 in the same atmosphere
Granular activated carbon obtained by cooling to below ℃, and specific surface area
A water purifier characterized by using fibrous activated carbon of 1400 m ² / g or more as an adsorbent.

Here, the BET specific surface area is Brunauer, Emme
It is the value measured by the surface area measurement method of the porous material proposed by tt and Teller. In this method, the adsorption amount of a monolayer is determined by an isotherm adsorption line, and the surface area is calculated by multiplying by the cross-sectional area of adsorbed molecules. In the case of activated carbon, it is usually measured using low-temperature nitrogen gas.

The term "substantially free of oxygen and / or water vapor" means a gas having a composition such that when the activated carbon is heat-treated, oxygen atoms bonded to the surface of the activated carbon do not exist, and specifically, oxygen is included. And a gas having a composition with a water vapor content of 1 to 2% or less. The present invention will be described in detail below.

As the carbonaceous raw material which can be used in the present invention, a wide variety of carbonaceous materials such as coconut shell or other wood carbide and coal can be used. Alternatively, these carbon materials may be molded by using a binder such as phenol resin, tar or pitch and then carbonized before use.

When activating the carbonaceous raw material, the atmosphere contains carbon dioxide gas in addition to water vapor, but the water vapor content is about
It must be below 15% (capacity). As shown in Example 8 and Comparative Examples 11 to 13, when activated under the condition that the water vapor content is high, the trihalomethane adsorptivity is clearly decreased. Although the effect of such a composition of an activating gas having a low water vapor content on the adsorptivity of activated carbon is not clear, the activated carbon obtained under such conditions may not retain oxygen atoms bound to the surface. It can be pointed out as one of the factors.

Further, the activation degree of activated carbon has a specific surface area of 300.
It is necessary to stop within the range of m ² / g or more and 1500 m ² / g or less. The activation degree is more preferably 700 m ² / g or more and 1200 m ² / g or less. When the specific surface area is 1500 m ² / g or more, the trihalomethane adsorption property decreases. Also, the average pore shape tends to be slightly larger.

When the activated carbon activated in the present invention is taken out of the system at a high temperature and brought into contact with a gas containing a large amount of water vapor, hydrogen gas or oxygen gas, the adsorption capacity is rapidly lowered. In the present invention, the activated carbon after activation needs to be taken out of the system after being cooled to a temperature of about 300 ° C. or lower in the atmosphere as it is or in a gas having a composition with a lower oxygen and water vapor content. The compositions of the utilization gas and the cooling gas do not necessarily have to be the same. As shown in Example 1 and Comparative Example 1, the adsorption capacity at a low boiling point and a low concentration is remarkably reduced when the air is taken out into the air at a temperature higher than 300 ° C.

In addition, the activated carbon obtained under the above conditions has a low activation rate, so that the activated yield is considerably higher than that of the activated carbon obtained under the ordinary conditions.

Ordinary activated carbon uses a carbonaceous raw material as a mixed gas such as steam and combustion gas and has a steam content of 40 to 50%.
In the atmosphere of, the specific surface area is activated up to 1400-2000m ² / g.
However, even if such activated carbon is used in the present invention, it does not show high adsorptivity to organic chlorine compounds such as trihalomethane.

The present invention is characterized by using activated carbon activated with a gas having a specific composition as described above and cooled in a gas having a specific composition. Such activated carbon exists in a dilute concentration in water. Highly adsorbable to low-boiling organic chlorine compounds such as chlorobenzene, trichloromethane, and chlorobromomethane.

Further included in this application is the invention of activated carbon for the removal of other organohalogen compounds in water. As the raw material of the present invention, there can be used waste activated carbon that is oxidized by contact with air or the like and has reduced adsorptivity, or activated carbon produced by a conventional method and having a specific surface area of 300 to 1500 m ² / g. Activated carbon obtained by treating these activated carbons in nitrogen gas and / or carbon dioxide gas substantially free of oxygen and / or water vapor at a temperature of about 500 ° C or higher, and cooling in the gas to a temperature of about 300 ° C or lower. Is.

Here, as the activated carbon, those obtained from a wide range of carbon materials such as coconut shell coal and coal can be used. The specific surface area of activated carbon must be 300-1500 m ² / g, but 400 m ²
It is more preferable if it is / g or more and 1200 m ² / g or less. When the specific surface area is 1500 m ² / g or more, the average pore shape tends to be slightly large. It is also recognized that the trihalomethane adsorption property is reduced.

Further, the heat treatment temperature must be about 500 ° C. or higher. At 500 ° C or lower, sufficient adsorptivity for organic chlorine compounds cannot be imparted. The treatment time is usually 20 to 180 minutes at a temperature of 500 ° C and a few minutes at 800 ° C.

Granular activated carbon must be used in the water purifier of the present invention. The activated carbon used in the present invention is prepared so as to enhance the adsorptivity to an organic chlorine compound such as trihalomethane, but when it is present in an extremely dilute state such as tap water, its saturated adsorption amount is low, and therefore purified water is used. In order to fill the small volume of the vessel with as much activated carbon as possible, it must be granular.

The particle size of the activated carbon is not particularly limited, but is 8 to 20.
0 mesh is preferable, and 50 to 100 mesh is more preferable. The smaller the particle size, the higher the adsorption rate and the amount used can be reduced to some extent. It should be noted that the term "granular" as used herein also includes activated carbon that has been molded into a certain shape such as granulated, crushed, and honeycomb shapes.

The fibrous activated carbon used in the present invention together with the granular activated carbon must have a specific surface area of 1400 m ² / g. In order to remove free chlorine in tap water, fibrous activated carbon, which has a large contact area with water, is preferable, and in order to completely remove free chlorine in tap water, one with a large specific surface area must be used. There is a need to. The specific surface area is preferably 1400 to 2700 m ² / g, and the preparation method is not particularly limited, but the one activated by the same atmosphere as the granular activated carbon used at the same time tends to be more preferable.

Fibers such as phenol resin, pitch, rayon, and acrylic fibers can be used as the raw material for the fibrous activated carbon.

The use ratio of the granular activated carbon and the fibrous activated carbon is not particularly limited, but preferably 10 to 90 parts by weight of the granular activated carbon and 90 to 10 parts by weight of the fibrous activated carbon, more preferably,
It is 40 to 20 parts by weight of fibrous activated carbon with respect to 60 to 80 parts by weight of granular activated carbon. When used in a water purifier, it is usually used by packing the column with granular activated carbon and fibrous activated carbon, but it is more uniform to pack both at a predetermined ratio than when packing separately, The pressure loss is also low, and it tends to increase both the removal ability of free chlorine and trihalomethane.

The water purifier of the present invention may use not only activated carbon but also a separation membrane in order to remove bacteria, mud and the like. By using the separation membrane together, the usable period of the water purifier can be further extended.

Further, although bacteria may be generated inside the water purifier, it is possible to impregnate silver on activated carbon and prevent bacterial growth by utilizing silver's ability to suppress bacterial growth. At this time, it is preferable to impregnate silver with granular activated carbon so that the chlorine removing ability and the trihalomethane removing ability of the water purifier are not impaired as much as possible.

The present invention will be described in more detail with reference to the following examples.

[0028]

【Example】

(Sample preparation method) 80 pieces of coal crushed to 10 to 32 mesh
After carbonization at 0 ℃, propane combustion gas (gas composition: nitrogen
80%, oxygen 0.2%, carbon dioxide 9.8%, steam 10%) at 900 ° C until a specific surface area of 500 m ² / g was reached, and then activated carbon was taken out in a nitrogen-substituted container and the nitrogen gas was removed. Samples No. 1 activated carbon was obtained by cooling to below 300 ° C.

Next, as in the case of Sample No. 1, the specific surface area was 500 m ^2.
Take the activated carbon activated to 500 g / g into nitrogen and
After cooling to ℃, it was taken out in the air and left to cool to obtain sample No. 2 activated carbon. Furthermore, the activated carbon of Sample No. 2 was treated for 10 minutes in an air stream of 700 ° C, N ₂ 50%, CO ₂ 50%, then taken out in nitrogen gas and cooled to room temperature.
O.3 activated carbon was obtained. Further, the activated carbon of sample No. 2 was treated in nitrogen at 900 ° C. for 5 minutes and then cooled to room temperature in nitrogen to obtain activated carbon of sample No. 4. These activated carbons were crushed by a roll mill to prepare 40 to 80 mesh.

As the fibrous activated carbon, phenol resin fiber (trade name Kynol) was used as propane combustion gas (gas composition:
80% nitrogen, 0.2% oxygen, 9.8% carbon dioxide, 10% steam)
After activating at 900 ℃ to a specific surface area of 1700 m ² / g, the sample was taken out in a container purged with nitrogen and cooled to 300 ℃ or less in the nitrogen gas to remove the fibrous activated carbon of Sample No. 21. Obtained. Next, take out the activated carbon fiber activated to a specific surface area of 1700 m ² / g as in Sample No. 21, and remove it at 500 ° C.
After cooling to room temperature, it was taken out in the air and left to cool to obtain sample No. 22 activated carbon fiber. Further, the activated carbon fiber of Sample No. 22 was heated in an air stream of 700 ° C, N ₂ 50%, CO ₂ 50% 10
After the treatment for a minute, the product was taken out in nitrogen and cooled to room temperature to obtain a sample No. 23 activated carbon fiber. Further, the activated carbon fiber of Sample No. 22 was treated in nitrogen at 900 ° C. for 5 minutes and then cooled to room temperature in nitrogen to obtain the activated carbon of Sample No. 24.

The preparation conditions of other samples are shown in Table 1 for granular activated carbon and Table 2 for fibrous activated carbon. Also, granular activated carbon
Nos. 5 and 6 and fibrous activated carbons Nos. 25 and 26 are activated carbons obtained by a usual method of activating with an activating gas having a water vapor content of 40 to 55% and then cooling in air.

[0032]

[Table 1]

[0033]

[Table 2]

(Examples 1 to 3, Comparative Examples 1 to 4) Sample No.
1 + No. 21 (Example 1), Sample No. 2 + No. 22 (Comparative Example 1), Sample No. 3 + No. 23 (Example 2), Sample No. 4 + No.
24 (Example 3), Sample No. 5 + No. 25 (Comparative Example 2), Sample
Table 1 shows No. 1 (Comparative Example 3) and Sample No. 21 (Comparative Example 4).
Fill the water purifier with an internal volume of 60 ml with
A solution containing 2 ppm of chloroform and 20 ppb of chloroform was passed through SV1000 hr ^-1 , and free chlorine and chloroform after passing through the column were quantified to calculate the removal rate.

The results are shown in Table 3.

[0036]

[Table 3]

(Examples 4 to 6, Comparative Examples 5 to 7) Sample No.
7 + No. 27 (Example 4), Sample No. 8 + No. 28 (Comparative Example 5), Sample No. 9 + No. 29 (Example 6), Sample No. 14 + No.
For 34 (Comparative Example 5), Sample No. 15 + No. 35 (Comparative Example 6) and Sample No. 16 + No. 36 (Comparative Example 7), the amount shown in Table 4 was filled in a water purifier having an internal volume of 60 ml, A solution containing 2 ppm of free chlorine and 20 ppb of chloroform was passed through SV1000 hr ^-1 , and the free chlorine and chloroform after passing through the column were quantified to calculate the removal rate.

The results are shown in Table 4.

[0039]

[Table 4]

(Example 7, Comparative Examples 8 to 10) Sample No. 10
+ No. 30 (Comparative Example 4), Sample No. 11 + No. 31 (Comparative Example 5),
Sample No.12 + No.32 (Comparative Example 6) and Sample No.13 + No.33
As for (Example 5), the amount shown in Table 5 was filled in a water purifier having an internal volume of 60 ml, and free chlorine was 2 ppm and chloroform was 10 ppb.
A liquid containing +10 ppb of dibromochloromethane was passed through at SV 1000 hr ^-1 , and free chlorine and trihalomethane after passing through the column were quantified and the removal rate was calculated.

The results are shown in Table 5.

[0042]

[Table 5]

(Example 8, Comparative Examples 11 to 13) Sample No. 17+
Table 6 shows No. 37 (Example 8), Sample No. 18 + No. 38 (Comparative Example 11), Sample No. 19 + No. 39 (Comparative Example 12) and Sample No. 20 + No. 40 (Example 13). Fill a water purifier with an internal volume of 60 ml, and pass a solution of 2 ppm of free chlorine and 10 ppb of chloroform + 10 ppb of dibromochloromethane at SV 1000hr ^-1 , and quantify free chlorine and trihalomethane after passing through the column. Then, the removal rate was calculated.

The results are shown in Table 6.

[0045]

[Table 6]

[0046]

INDUSTRIAL APPLICABILITY The granular activated carbon used in the water purifier of the present invention exhibits higher adsorptivity to organic halogen compounds such as trichloromethane and chlorobromomethane at room temperature than ordinary activated carbon. In addition, fibrous activated carbon has excellent adsorptivity with respect to free chlorine adsorptivity. By using both this granular activated carbon and fibrous activated carbon with excellent free chlorine adsorption, trihalomethane and free chlorine in tap water, such as trichloromethane and chlorobromomethane, which have recently become a problem as carcinogens, can be easily obtained. Can be removed.

Claims (2)

[Claims] 1. A carbonaceous material is carbonized to have a steam content of about 15
% (Volume) or less atmosphere, BET specific surface area 300-1500m ²
After activating until it reaches / g, the temperature is maintained at about 300 ° C in the same atmosphere or in a gas with a lower oxygen and water vapor content.
Granular activated carbon obtained by cooling to below and specific surface area 14
A water purifier characterized by using fibrous activated carbon of 00 m ² / g or more as an adsorbent. 2. Activated carbon having a BET specific surface area of 300 to 1500 m ² / g is treated at a temperature of about 500 ° C. or higher in nitrogen gas and / or carbon dioxide gas substantially free of oxygen and / or steam, and then, as it is. A water purifier characterized by using granular activated carbon obtained by cooling to about 300 ° C. or less in the atmosphere of, and fibrous activated carbon having a specific surface area of 1400 m ² / g or more as an adsorbent.