JPH0824636A - Production of adsorbent and water purifying apparatus using the same - Google Patents

Abstract

PURPOSE:To produce an adsorbent capable of efficiently removing, a low b.p. halogen type org. matter present in water in a low concn. over a long period of time and to provide a water purifying apparatus utilizing the adsorbent. CONSTITUTION:Activated carbon obtained by carbonizing and activating org. matter and proper in mode pore diameter is selected and ash on the surface of activated carbon is removed by boiling. Next, activated carbon is subjected to heat treatment under a high vacuum to remove the hoydrophilic functional group on the surface of activated carbon to make activated carbon hydrophobic. By this method, an excellent adsorbent enhanced in the compatibility with a low b.p. halogen type org. matter is obtained. By forming a packed bed composed of this adsorbent, a water purifying apparatus is completed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an adsorbent for adsorbing and removing low-boiling-point halogenated organic substances from tap water, ground water, waste water, etc., and a water purification apparatus using the adsorbent.

[0002]

2. Description of the Related Art There are cases where low-boiling halogenated organic substances (such as chloroform and trichloroethylene) are dissolved in tap water, ground water and the like. In particular, with respect to tap water and groundwater, carcinogenicity of low boiling point halogenated organic substances has recently been pointed out.

Therefore, when tap water or ground water is used for food and drink, it is desirable to remove the low boiling point halogenated organic matter from tap water.

Regarding the drainage, for example, drainage containing trichlorethylene such as the drainage of a cleaning shop is considered, and it is desirable to remove it because it causes groundwater pollution.

Conventionally, activated carbon has been used to remove the above-mentioned low-boiling halogenated organic substances. This activated carbon is made from natural organic matter such as coconut shells, coal and sawdust, and synthetic organic matter such as phenol resin, acrylic resin, petroleum pitch and coal pitch, which are carbonized and produced by activation treatment. .

However, the amount of activated carbon adsorbed on the low boiling point halogenated organic material is smaller than that of other substances to be adsorbed.

When removing low-boiling halogen-based organic substances, even if the granular activated carbon is made of coconut shell, which is said to be suitable among activated carbons, the equilibrium concentration of chloroform is 0.02 mg obtained from the adsorption isotherm at 25 ° C. The adsorption amount per weight of activated carbon at / L is about 0.2 to 0.6 mg / g (for example, 0.39 mg / g in the case of granular activated carbon “GW” manufactured by Kuraray Chemical Co., Ltd.).

This means that, assuming a water purifier filled with 200 g of the above-mentioned "GW", the adsorption amount of chloroform is 0.39 (mg / g) even if all activated carbons are ideally adsorbed to an equilibrium state. × 200 (g) = 78 (mg)
When the chloroform concentration of the inflow water is 0.1 mg / L, 78 (mg) /0.1 (mg / L) = 780
Only the treatment of the inflow water of (L) can be expected, which requires frequent replacement of activated carbon, which is inconvenient and uneconomical.

Further, since the adsorption capacity is low, the reliability of the removal treatment of the low boiling point halogenated organic matter is low.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to efficiently and efficiently remove low boiling point halogenated organic substances present in water at low concentrations.
And to provide a method for producing an adsorbent that can be removed over a long period of time.

In another aspect, the object of the present invention is to provide a low boiling point halogenated organic substance which is present in tap water at a low concentration.
It is an object of the present invention to provide a small-sized and compact water purifying apparatus which can be effectively removed over a long period of time with a small amount of an adsorbent and has excellent maintainability.

[0012]

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention 1) decreases the affinity between a solvent (water) and an adsorbent, and the affinity between a solute (a low boiling point halogenated organic substance) and the adsorbent. It is found that the adsorption energy between the solute and the adsorbent increases when the amount of water is increased. There is a hydrophilic functional group that exists, and this part is hydrophilized, 3) The knowledge that ash remains as a hydrophilic impurity on the surface of activated carbon, 4) High vacuum or hydrogen 5) The technical idea that the hydrophilic functional group can be removed by heating in an atmosphere containing a trace amount of a reducing gas such as, a low activity gas such as nitrogen, or an inert gas such as argon. Heat treatment First, the technical idea that the hydrophobicity of the activated carbon surface can be improved by removing the ash existing on the activated carbon surface, and 6) because the adsorption phenomenon of activated carbon is caused by intermolecular force,
It is based on the technical idea that there is a suitable activated carbon pore diameter according to the molecular size of the substance to be adsorbed.

Therefore, the method for producing an adsorbent of the present invention is
It is characterized in that the conventional activated carbon is heated under a high vacuum to remove the hydrophilic functional group, thereby increasing the adsorptivity of the low boiling point halogenated organic substance on the surface of the activated carbon.

The maximum temperature during the heat treatment is from 500 ° C. to 20
It is possible in the range of 00 ° C.

The mode pore diameter of the activated carbon used at this time is preferably in the range of 1.0 to 3.0 nm in order to improve the adsorption efficiency. The mode pore diameter described here is defined as the pore diameter having the largest proportion of the pore volume when the distribution of the pore volume with respect to the pore diameter is measured by the water vapor adsorption method.

Further, in order to remove the ash content on the surface of the activated carbon, it is preferable to carry out a chemical treatment such as a boiling treatment or a nitric acid treatment before the heat treatment.

[0017]

The adsorbent prepared according to the present invention has improved affinity to the adsorbent of low boiling point halogenated organic compounds such as chloroform, which has been weakly adsorbed to conventional activated carbon, and therefore has a high affinity for the organic compounds. It has excellent adsorption performance.

[0018]

【Example】

Experimental example 1 (fibrous activated carbon) Kuraray Chemical Co., Ltd. phenol resin raw material fibrous activated carbon "FR-15" (mode pore diameter 2.4 nm), "F
R-20 "(mode pore diameter 3.2 nm) and" FR
-25 "(mode pore diameter 4.4 nm), Osaka Gas Co., Ltd. coal pitch raw material fibrous activated carbon" A-10 ", Toho Rayon Co., Ltd. acrylic resin raw material fibrous activated carbon" F "
E-300 "and" FE-400 "are manufactured by Nippon Vacuum Technology Co., Ltd.
Using a vacuum heat treatment furnace, the heat treatment shown in FIGS. 1 to 3 was carried out in a hydrogen gas atmosphere of 0.5 Torr.
An adsorbent of the present invention was obtained.

An equilibrium adsorption test was carried out in accordance with the following procedure in order to investigate the adsorption performance of this adsorbent with respect to low boiling point halogenated organic substances. (1) In order to shorten the time required to reach equilibrium, the adsorbent crushed to a particle size of 100 μm or less in a mortar was dried at 110 ° C. for 3 hours or more. (2) Add 0 and 1 of this sample to a 100 mL vial.
Chloroform solution with a concentration of 100 μg / L was collected in 100 m
L was added, the container was sealed, and the mixture was shaken at 25 ° C. for 1 hour. (3) Then, the equilibrium concentration of each vial was determined according to the method for measuring trihalomethanes of the water supply test method (Japan Water Works Association). (4) Equilibrium concentration and adsorption amount per unit weight of adsorbent were calculated and regressed by the Freundlich equation to obtain equilibrium concentration of 20 μg.
The amount of adsorption per unit weight of the adsorbent at the time of / L was determined.

The results are shown in FIG. From this, it was confirmed that the chloroform adsorption performance was improved by the heat treatment regardless of the raw material of the fibrous activated carbon, and that the heat treatment had an effect of removing hydrophilic functional groups such as phenolic hydroxyl groups and carboxyl groups. It was The reaction for removing the hydrophilic functional group proceeds efficiently at 500 ° C. or higher, while 2000 ° C. or lower is preferable because of the facility economy of the heat treatment temperature. Therefore, the maximum temperature during heat treatment is preferably 500 ° C. or higher and 2000 ° C. or lower .

Experimental Example 2 (Washing Treatment of Fibrous Activated Carbon) The above "FR-15" was subjected to the following two pretreatments prior to the heat treatment for the purpose of removing ash which is a hydrophilic impurity. That is, it was boiled in pure water for 2 hours, washed with pure water and dried at 110 ° C (boiling treatment), and immersed in 60% nitric acid for 1 hour, washed with pure water and dried at 110 ° C. These were subjected to the heat treatment shown in FIG. 3 in a hydrogen gas atmosphere of 0.5 Torr using the vacuum heat treatment furnace.

According to the method of the equilibrium adsorption test described in Experimental Example 1, the adsorbent amount per unit weight of the adsorbent at an equilibrium concentration of 20 μg / L was determined. Table 1 shows the results.

[0023]

[Table 1]

From this, the adsorption performance of chloroform was in the order of boiling treatment> nitric acid treatment> non-treatment.

The purpose of the pretreatment is to remove the ash on the surface of the activated carbon, and therefore the boiling treatment and nitric acid treatment in this experiment are not the only problem, and other methods may be used.

Experimental Example 3 (Granular Activated Carbon) Kuraray Chemical Co., Ltd. coconut shell raw material granular activated carbon "GW"
(Mode pore diameter of 2.1 nm), "GA" (mode pore diameter of 1.6 nm) and "GLC" (mode pore diameter of 2.8 nm) using the vacuum heat treatment furnace described above at 0.5 To
The heat treatments shown in FIGS. 1 to 3 were each performed in a hydrogen gas atmosphere of rr.

According to the method of the equilibrium adsorption test described in Experimental Example 1 above, the adsorbed amount per unit weight of the adsorbent at an equilibrium concentration of 20 μg / L was determined. The result is shown in FIG. As a result, the adsorption performance of chloroform was improved or not (“GA”), and the maximum temperature of 1200 ° C. was good for the improved adsorption performance.

Regarding the activated carbon used in Experimental Examples 1 and 3, the mode pore diameter measured by the steam adsorption method and the adsorption per unit weight of activated carbon at the equilibrium concentration of 20 μg / L during unheated treatment The relationship between the amounts is shown in FIG. From this, it is understood that it is desirable to perform heat treatment using activated carbon having a mode pore diameter of 1.0 nm to 3.0 nm. However, from the result of “GA”, regarding the maximum temperature of the heat treatment, there is an optimum temperature related to the starting material and the mode pore size of the activated carbon.

Experimental Example 4 (Powdered Activated Carbon) Coconut shell manufactured by Kuraray Chemical Co., Coal, and plant-derived powdered activated carbons "P-60" and "PK-D" were used at 0.5 Torr in the vacuum heat treatment furnace. The heat treatments shown in FIGS. 1 to 3 were carried out in a hydrogen gas atmosphere.

The adsorbent thus obtained was subjected to an equilibrium concentration of 20 μg / L in accordance with the equilibrium adsorption test method described in Experimental Example 1 above.
At that time, the amount of adsorption per unit weight of the adsorbent was determined. The result is shown in FIG. 7. From this, the adsorption performance of chloroform was improved, and the maximum temperature of 1200 ° C was the best.

From the experimental examples described above, 1) that the heat treatment under high vacuum of the present invention is effective for improving the adsorption performance, regardless of the starting material and shape of the activated carbon. Removal of organic ash is also effective in improving the adsorption performance, 3) It is preferable that the mode pore diameter of the activated carbon as a raw material by the steam adsorption method is in the range of 1.0 to 3.0 nm, 4) Heat treatment The optimum temperature is about 800 ℃ to 1200 ℃
It is understood that the range of is preferable.

Next, an example of a water purifier filled with an adsorbent manufactured according to the present invention will be described.

The equilibrium concentration of the granular activated carbon "GW" heat-treated at the maximum temperature of 1200 ° C in Experimental Example 3 was 20 μg / L.
The adsorption amount per unit weight of the adsorbent at that time was 1.8 mg / g as shown in FIG. The water purifier of this embodiment contains a packed bed of 200 g of this adsorbent. At this time, assuming that all the adsorbents were ideally adsorbed to the equilibrium state, the adsorbed amount of chloroform was 1.8 (mg / g) × 20.
0 (g) = 360 (mg), and assuming the chloroform concentration of the inflow water to be 0.1 mg / L, 360 (mg) /
The influent water of 0.1 (mg / L) = 3600 (L) can be treated. As described above, this assumes an ideal situation, so the actual life is shorter than this, but it can be seen that the life is greatly extended compared to conventional activated carbon.

Since the water purification apparatus of the present invention has a simple structure for filling the adsorbent prepared according to the above-mentioned manufacturing method, when it is also intended to remove suspended fine particle components,
It is also possible to have a configuration in which a filtration stage is provided before or after the adsorbent-packed layer, and also as a water purification device with a so-called alkaline ionized water producing function provided with an electrolytic cell for electrolyzing water. It is also possible.

[0035]

As described above, according to the present invention,
By heating under high vacuum to remove hydrophilic functional groups,
It is possible to obtain an adsorbent having excellent adsorption performance by increasing the affinity of the activated carbon surface for low boiling point halogenated organic substances.

Further, prior to the heat treatment, the activated carbon is boiled or a chemical treatment such as nitric acid is used to remove the ash on the surface of the activated carbon, the mode pore diameter of the activated carbon as a raw material is selected within an optimum range, and the heat treatment is performed. The maximum temperature is 500
By carrying out in the range of ℃ to 2000 ℃, it is possible to obtain an adsorbent having more excellent adsorption performance.

The water purification apparatus containing this adsorbent is small and compact, but it is possible to effectively remove the low boiling point halogenated organic substances present in tap water at a low concentration for a long period of time with a small amount of adsorbent. It is possible, the running cost of the water purifier can be reduced, and the removal reliability can be increased.

[Brief description of drawings]

FIG. 1 is a heat treatment diagram at a maximum temperature of 800 ° C. in Experimental Example 1, Experimental Example 3, and Experimental Example 4.

FIG. 2 is a heat treatment diagram at a maximum temperature of 1000 ° C. in Experimental Example 1, Experimental Example 3, and Experimental Example 4.

FIG. 3 is a heat treatment diagram of the maximum temperature of 1200 ° C. in Experimental Examples 1 to 4.

FIG. 4 is a graph showing the results of Experimental Example 1, showing the effect of heat treatment of fibrous activated carbon.

FIG. 5 is a graph showing the results of Experimental Example 3, showing the effect of heat treatment of granular activated carbon.

FIG. 6 is a graph showing the relationship between the mode pore diameter and the adsorption performance of the unheated activated carbon used in Experimental Example 1 and Experimental Example 3.

FIG. 7 is a graph showing the results of Experimental Example 4, showing the effect of heat treatment of powdered activated carbon.

Claims (7)

[Claims] 1. A method for producing an adsorbent, which is obtained by heating activated carbon obtained by carbonizing and activating an organic substance under high vacuum. 2. A method for producing an adsorbent, which is obtained by subjecting activated carbon obtained by carbonizing and activating an organic matter to a washing treatment and then a heating treatment under a high vacuum. 3. The method for producing an adsorbent according to claim 2, wherein the cleaning treatment is a boiling treatment and a chemical treatment including nitric acid. 4. The high vacuum means an atmosphere containing nothing other than residual air, or a reducing gas such as hydrogen, carbon monoxide or ammonia, a low active gas such as nitrogen, or argon. The method for producing an adsorbent according to any one of claims 1 to 3, wherein the atmospheric pressure is 0.5 Torr or less in an atmosphere containing a trace amount of an inert gas. 5. The method for producing an adsorbent according to any one of claims 1 to 4, wherein the mode pore diameter of the activated carbon by the steam adsorption method is in the range of 1.0 nm to 3.0 nm. 6. The maximum temperature of the heat treatment is from 500 ° C. to 2 °
The method for producing an adsorbent according to any one of claims 1 to 5, which is in the range of 000 ° C. 7. A water purification apparatus using an adsorbent produced by the production method according to any one of claims 1 to 6.