JPH05302216A - Modification of carbonaceous fiber - Google Patents

Abstract

PURPOSE:To provide a process for producing a modified pitch-based carbonaceous fiber capable of effectively adsorbing and removing trihalomethane precursor substances. CONSTITUTION:The modified carbonaceous fiber can be produced by hydrophilizing a carbonaceous fiber having a specific surface area of 0.1-1,200m<2>/g with an oxidizing agent, supporting an alkaline earth metal on the hydrophilized surface and activating the product.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for modifying carbonaceous fibers.

In this specification, "%" means
It shall mean "% by weight".

[0003]

2. Description of the Related Art In recent years, trace amounts of organic substances have been contained in tap water as a result of pollution of rivers, lakes and marshes by industrial water, urban sewage and the like. These organic substances cause a musty odor of tap water, and some of them react with chlorine to produce harmful substances (eg, trihalomethane) that are said to have carcinogenicity. In order to do so, it is necessary to perform more advanced processing in the future.

An activated carbon treatment method is known as a typical example of a sophisticated water treatment method. Recently, it has been attempted to carry out water treatment by using pitch-type fibrous activated carbon (hereinafter referred to as ACF unless otherwise required), which is inexpensive and has high adsorption ability, in place of the granular activated carbon which has been used so far. .. In particular, Japanese Examined Patent Publication No. 63-67566 discloses a carbonaceous fiber having a surface area of 30 to 1200 m ² / g and a pore volume of 30 to 300 angstrom and a pore volume of 0.1 cc / g or less. A method for producing activated carbon fibers carrying at least one of iron, cobalt, nickel and manganese compounds, heat-treated at 650 to 1050 ° C. in oxidizing gas or combustion waste gas to carry out activation treatment. Have been shown to increase the pore volume after treatment with pore diameters of 30 to 300 angstroms. However, since many precursors of trihalomethane (hereinafter referred to as THM) have a relatively large molecular weight, ACF generally has a large proportion of fine pores (micropores) having a radius of 10 angstroms or less.
Then, sufficient adsorption removal of the THM precursor cannot be performed. In addition, it is difficult to increase the number of pores having a diameter of 20 to 300 angstroms by the method disclosed in the above document. Especially for pitch-based ACF, it has been found that it is impossible to increase the pore size of 20 to 300 angstrom by the method described in the above-mentioned document.

[0005]

Therefore, the present invention is
The main object of the present invention is to provide a method for producing ACF that can effectively remove the HM precursor by adsorption.

[0006]

Means for Solving the Problems As a result of various studies in view of the current state of the art as described above, the present inventor has performed a hydrophilization treatment on a carbonaceous fiber with an oxidant to give a specific substance as a catalyst. After activation, when activating with steam,
It has been found that the pores (mesopores) having a radius of about 15 to 150 angstroms are increased to obtain a modified ACF capable of sufficiently adsorbing and removing the THM precursor.

That is, the present invention provides the following method for modifying carbonaceous fibers: "Specific surface area 0.1 to 1"
A method for modifying carbonaceous fibers, which comprises subjecting 200 m ² / g of carbonaceous fibers to hydrophilic treatment with an oxidizing agent, carrying an alkaline earth metal thereon, and then carrying out activation treatment. "
The carbonaceous fiber used as a raw material in the present invention is a carbonaceous fiber having a specific surface area of 0.1 to 1200 m ² / g according to the BET method.

In the present invention, first, a carbon fiber is subjected to a hydrophilizing treatment (oxidizing treatment of the surface of the carbon fiber) with an oxidizing agent, and then an alkaline earth metal is carried thereon to carry out an activating treatment. Examples of the oxidizing agent include sodium hypochlorite, potassium hypochlorite, hydrogen peroxide, chlorine gas (wet), and the like, and alkaline earth metal sources include calcium acetate, calcium formate, calcium oxalate. , Barium acetate, barium acetate, calcium citrate and the like. The treatment with these oxidizing agents and the method for applying the alkaline earth metal are not particularly limited, but include a method of immersing the carbonaceous fiber in an aqueous solution containing them under normal pressure or reduced pressure, including a carbonaceous fiber There are a method of immersing in an aqueous solution under normal pressure or a reduced pressure and boiling, a method of spraying an aqueous solution containing these on carbonaceous fibers, and the like. Hydrophilizing treatment with an oxidizing agent such as sodium hypochlorite (hereinafter simply referred to as sodium hypochlorite unless otherwise required) and alkaline earth metal such as calcium acetate (hereinafter simply referred to as calcium acetate unless otherwise required) More preferably, the carbon fiber is immersed in an aqueous solution of sodium hypochlorite under atmospheric pressure, boiled, and then immersed in an aqueous solution of calcium acetate.

The amount of the oxidizing agent applied to the carbonaceous fiber and the amount of the alkaline earth metal supported may vary depending on the degree of modification of the carbonaceous fiber.
Sodium hypochlorite (effective chlorine 5% or more) 1-25%
The range is about 0.1 to 2% of calcium acetate (as Ca). When the amount of sodium hypochlorite is too small, the carbon surface is not sufficiently hydrophilized, so that the amount of Ca supported as a catalyst decreases, and the reaction rate of the activation treatment becomes slow. At this time, if the activation temperature is increased to increase the reaction rate, the yield of modified ACF decreases. On the other hand, if the amount of sodium hypochlorite is too large, the strength of the modified ACF may decrease. On the other hand, if the amount of calcium acetate is too small,
Mesopores cannot be fully opened, and only micropores increase. When the amount of calcium acetate is too large, the carbon surface is corroded other than the opening of the pores, which causes a problem that the yield is lowered and the strength of the modified ACF is lowered.

Next, the carbonaceous fiber carrying the alkaline earth metal, which has been treated with the oxidizing agent as described above, is subjected to activation treatment with steam. The steam activation treatment for this reforming may be performed according to a conventional method and is not particularly limited. For example, the carbonaceous fiber treated with an oxidizing agent and carrying an alkaline earth metal is housed in a container. Then, after replacing the air in the container with an inert gas (He, Ar, N _2, etc.), the temperature is raised to about 400 to 900 ° C., then steam is introduced, and the temperature is increased to about 550 to 900 ° C. for 5 to 60 ° C. Hold for about a minute.

The carbonaceous fiber after the modification is, if necessary,
The desired product is obtained by deashing and washing by acid washing or the like.

According to the method of the present invention, the conditions of the oxidizing agent treatment,
By appropriately adjusting the amount of alkaline earth metal supported, the activation conditions, and the like, carbonaceous fibers having various pore characteristics can be produced. For example, when the THM precursor is adsorbed and removed, the pore volume due to mesopores having a pore diameter of about 15 to 150 angstroms is 0.25 to 0.6 c.
It suffices to produce a modified carbonaceous fiber of about c / g. In addition, other applications (catalyst carrier, adsorption and removal of harmful gas in gas phase, adsorption and removal of harmful component in liquid phase, etc.)
It is also possible to obtain modified carbonaceous fibers having different pore characteristics.

[0013]

INDUSTRIAL APPLICABILITY According to the present invention which adopts a novel means of treating raw carbonaceous fiber with an oxidizing agent, TH
A modified carbonaceous fiber having pore characteristics suitable for adsorptive removal of M precursor is obtained. Such modified carbonaceous fibers are particularly suitable for advanced treatment of tap water.

Further, according to the present invention, the pore characteristics of the carbonaceous fiber can be arbitrarily adjusted by appropriately adjusting the conditions of the oxidizing agent treatment, the amount of the alkaline earth metal supported, the activation conditions and the like. Modified carbonaceous fibers suitable for applications other than tap water treatment can also be produced.

Furthermore, the method of the present invention comprises 0.1 m ² /
It is useful because carbonaceous fibers having a very small surface area of about g can be modified.

[0016]

EXAMPLES Examples and experimental examples will be shown below to further clarify the features of the present invention.

Example 1 ACF (trademark "A-10", manufactured by Adol Co., BET
Specific surface area of 1080 m ² / g and pore volume of pores with a radius of 10 angstroms or less, the total pore volume = 0.
57 g / 95% of 57 ml / g) was immersed in 400 ml of a 1.8% aqueous solution of sodium hypochlorite (effective chlorine 5% or more), boiled at 100 ° C. for 20 minutes, and then added to a 4.8% calcium acetate aqueous solution to give 10 Immerse for a minute and place under reduced pressure to adsorb the calcium component to the pores inside the ACF, then
The CF was subjected to centrifugal dehydration. As a result, 3.0% of calcium acetate was supported on the ACF.

Then, the ACF treated as described above
Was placed in a tubular furnace, and after the inside of the furnace was replaced with He, temperature rising was started, and when the temperature in the tube reached 600 ° C, steam was introduced, and steam partial pressure was 50% and the temperature was 700 ° C under conditions of 95%. Activated modification treatment for minutes, then immersed in dilute hydrochloric acid solution and left for 12 hours, then boiled in ion-exchanged water,
Decalcification was performed to obtain 1.9 g of the modified ACF of the present invention.

The modified ACF thus obtained has a specific surface area of 1100 m ² / g, and the pore volume due to mesopores having a radius of 15 to 150 angstroms is the total pore volume (1.
0 ml / g) was 50% or more.

Experimental Example 1 0.2 g of the modified ACF obtained in Example 1 was added to 120 ml of molasses-phosphate buffer solution, shaken at 60 ° C. for 60 minutes to adsorb molasses, and then the filtrate was subjected to membrane filtration. UV of the filtrate
When the chromaticity was measured with (E ₄₂₀ ) and the decolorization rate was calculated,
It was 90% or more. The decolorization rate similarly obtained for the ACF before modification was 2.3%.

Molasses molecules are known to be adsorbed by pores having a radius of 14 angstroms or more. Therefore, from the above results, the method of the present invention significantly improves the pore characteristics of ACF. it is obvious.

Experimental Example 2 Aluminum sulfate as a coagulant was added to Edogawa river water at a ratio of 40 ppm as aluminum, and the mixture was subjected to coagulation-precipitation treatment and then filtered.

Next, 300 ml of the above treated water was placed in an Erlenmeyer flask, and the modified ACF30 obtained in Example 1 was added thereto.
After adding mg, the Erlenmeyer flask was tightly capped and the mixture was kept at 20 ° C. for 3 minutes.
The mixture was stirred by a magnetic stirrer for an hour to adsorb the THM precursor contained in the treated water.

Then, the modified A is prepared by the headspace method.
When the adsorption performance of the THM precursor by CF was measured, it was 340 μg / g. T by ACF before reforming
Since the adsorption performance of the HM precursor (formability) was 60 μg / g, it is clear that the THM precursor adsorption performance was significantly improved.

The THM precursor concentration in the raw water used in the experiment was 43 μg / l.

Example 2 Pitch-based carbonaceous fibers having a specific surface area of 0.2 m ² / g according to the BET method were placed in a cylindrical furnace, and the air inside the furnace was replaced with He.
The temperature was raised and heat treatment was performed at 700 ° C. for 10 minutes. The pitch-based carbonaceous fiber after the heat treatment is dipped in a 5% sodium hypochlorite aqueous solution, boiled at 100 ° C. for 20 minutes, and then dipped in a 9.6% calcium acetate aqueous solution for 15 minutes to obtain a calcium component under reduced pressure. Was carried.

Next, the pitch-based carbonaceous fiber treated as described above is put into a tubular furnace, the inside of the furnace is replaced with He, and then the temperature rise is started, and when the temperature inside the tube reaches 600 ° C., Steam was introduced and the furnace temperature was kept at 820 ° C. for 120 minutes to carry out activation reforming treatment to obtain a modified carbonaceous fiber of the present invention.

Experimental Example 3 0.2 g of the modified carbonaceous fiber obtained in Example 2 was added to 120 ml of molasses-phosphate buffer to adsorb molasses at 60 ° C. for 60 minutes, and then the filtrate was subjected to membrane filtration. , The filtrate is UV (E
_The chromaticity was measured at ₄₂₀ ) and the decolorization rate was calculated to be 7
It was 6.8% or more.

From the above results, it is clear that the pore characteristics of the carbonaceous fiber are remarkably modified by the method of the present invention.

Example 3 (a) The carbonaceous fiber (A) having a specific surface area of 1050 m ² / g by the BET method was kept in hydrogen gas at 800 ° C. for 80 minutes and cooled to obtain 0.6 of calcium acetate (as Ca). %
After immersing in the solution for 10 minutes to support Ca, steam reforming was performed under the conditions shown in Table 1 to obtain ACF (B).

(B) Specific surface area of 1050 by BET method
m ² / g of carbonaceous fiber (A) was immersed in a 0.6% solution of calcium acetate (as Ca) for 10 minutes to support Ca, and then steam reformed under the conditions shown in Table 1 to obtain ACF.
(C) was obtained.

(C) Specific surface area of 1050 by BET method
Immerse m ² / g of carbonaceous fiber (A) in 0.1% hydrogen peroxide solution at 100 ° C. for 20 minutes (hydrophilization treatment), and then in a 0.6% solution of calcium acetate (as Ca) for 10 minutes. After immersing and supporting Ca, steam reforming was performed under the conditions shown in Table 1 to obtain ACF (D).

(D) Specific surface area of 1050 by BET method
Immerse m ² / g carbonaceous fiber (A) in a 20% aqueous solution of sodium hypochlorite for 20 minutes at 100 ° C. (hydrophilization treatment)
Then, it was immersed in a 0.6% solution of calcium acetate (as Ca) for 10 minutes to support Ca, and steam reformed under the conditions shown in Table 1 to obtain ACF (E).

The four kinds of ACF thus obtained were subjected to the same test as in Example 3 to measure the molasses decolorization rate.
The results of yield and decolorization rate are also shown in Table 1.

Table 1 Activation temperature x time yield Molasses decolorization rate (° C) (min) (%) (%) ACF (A) -2.3 ACF (B) 840 x 150 65.0 10.7 ACF (C) 830 × 150 66.2 27.2 ACF (D) 815 × 150 66.8 39.1 ACF (E) 740 × 87 61.8 99.0 From the results shown in Table 1, ACF was provided with Ca. After that, by activating (see ACF (B) to (E)), AC
It is clear that the molasses decolorization rate of F is improved.

In the case where a hydrophilic treatment is performed in advance using an oxidizing agent prior to the addition of Ca (ACF (D))
And (E)), the molasses decolorization rate is high and activation can be performed at low temperature and in a short time as compared with the case where no hydrophilic treatment is performed (see ACF (B) and (C)). it is obvious.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical display location C02F 1/28 D D01F 11/12 D06M 11/07 11/44 7199-3B D06M 7/00 A ( 72) Inventor Tadahiro Mori 23 Uji Kozakura, Uji City, Kyoto Prefecture Central Research Institute, Unitika Ltd. (72) Inventor Keizo Kajioka 4-1-2, Hiranocho, Chuo-ku, Osaka City, Osaka Prefecture Osaka Gas Co., Ltd.

Claims (1)

[Claims] 1. A carbon which is characterized in that a carbonaceous fiber having a specific surface area of 0.1 to 1200 m ² / g is subjected to a hydrophilic treatment with an oxidizing agent, and then an alkaline earth metal is supported on the carbonaceous fiber to carry out an activation treatment. Method for quality fiber.