JP3975362B2 - Catalytic activated carbon - Google Patents

Description

The present invention relates to activated carbon having a catalytic action for decomposing hydrogen peroxide used for sterilizing detergents, bleaching detergents, etc. into water and oxygen, and the residual waste in industrial waste liquids used in such applications. The present invention relates to activated carbon having a catalytic action for decomposing hydrogen oxide.

Hydrogen peroxide is widely used for sterilization bleaching washing of foods, fibers, etc., washing electronic materials such as printed circuit boards, and in recent years for hair decolorization of hair pretreatment. Discharging the waste liquid in which hydrogen peroxide remains after use to the river as it is adversely affects the organisms in the water, causing the destruction of the ecosystem. When transporting waste liquid in which hydrogen peroxide remains in a tank lorry or the like, hydrogen peroxide is decomposed by friction generated by the shaking of the vehicle, and the generated oxygen increases the internal pressure of the tank, causing an explosion risk.
In addition, when it is introduced into the waste liquid treatment layer, it slowly decomposes, and sludge in which oxygen bubbles generated at that time are precipitated is diffused again into the water, thereby reducing the efficiency of waste liquid treatment. Therefore, it becomes necessary to decompose hydrogen peroxide remaining in the waste liquid.

Conventionally, it is decomposed with activated carbon such as coconut shell, manganese dioxide, or an enzyme such as catalase. However, when activated carbon is used, there is a disadvantage that the decomposition ability is low and a long time is required. When manganese dioxide is used, manganese elutes in the liquid and adversely affects the environment. In addition, with enzymes such as catalase, pH capable of decomposing hydrogen peroxide is mainly limited to the neutral range, making it difficult to use in a wide range.

According to claim 9 of JP-A-5-811, an activated carbon material capable of decomposing hydrogen peroxide is obtained by heating polyacrylonitrile fibrous activated carbon to 400 to 1100 ° C. in a reducing gas atmosphere.

In JP-A-7-232072, 100 to 300 iridium is applied to a porous granular carrier such as alumina.
A catalyst for decomposing hydrogen peroxide is obtained after forming a thin film with a thickness of μm, firing and reducing treatment.

In JP-A-7-024315, catalytic activated carbon is obtained by carbonization activation of an acrylonitrile compound or an acrylonitrile mixture. In this example, an acrylic fiber having an acrylonitrile content of 85% or 95% as an acrylonitrile compound or a mixture is cut into 0.5 mm, mixed and granulated with a binder such as pitch, and then activated by carbonization to activate hydrogen peroxide decomposition catalytic activated carbon. Have gained.

In JP 2003-266081, a mixture obtained by kneading and dispersing at least one metal compound of silver, platinum, palladium, copper and iron and an activated carbon precursor is infusible and / or
Alternatively, after carbonization, activation treatment is performed to obtain activated carbon for hydrogen peroxide decomposition containing 0.01% by weight or more of a metal component.

JP-A-5-811 Japanese Unexamined Patent Publication No. 7-232072 JP 7-024315 A Japanese Patent Laid-Open No. 2003-266081

However, in Japanese Patent Laid-Open No. 5-811, acrylonitrile carbon fiber is heated in a reducing gas, and a large amount of inert gas and associated expenses are required to form the atmosphere.

In JP-A-7-232072, iridium formed as a thin film on a porous granular carrier such as alumina is the main component of hydrogen peroxide decomposition and is not a carbide. Further, when decomposing a high-concentration hydrogen peroxide-containing waste liquid, the iridium thin film is peeled off from the surface of the carrier due to vigorously generated oxygen bubbles, leading to a decrease in decomposition performance, and iridium may be mixed into the treatment liquid.

In JP-A-7-024315, acrylonitrile compounds and mixtures are activated by carbonization, but they are not combusted in an oxidizing atmosphere.
Although the carbonization is activated after granulation after cutting, it requires a cutting step, which causes high cost. Also, the molding strength is very low.

In Japanese Patent Laid-Open No. 2003-266081, metals such as silver and platinum are the main components of hydrogen peroxide decomposition, and carbide precursors are only their carriers. Similarly to Japanese Patent Laid-Open No. 7-232072, there is a high possibility that metals will fall off during the treatment of high concentration hydrogen peroxide-containing wastewater, resulting in degradation of degradation performance and elution of metals into waste liquid.

The present invention solves the above dissatisfaction points without using an inert gas,
An object of the present invention is to provide a hydrogen peroxide-decomposing catalytic activated carbon in which the main component of hydrogen peroxide decomposition is activated carbon derived from an acrylonitrile copolymer rather than metals.

The hydrogen peroxide decomposition catalytic activated carbon of the present invention burns an acrylonitrile copolymer in an oxidizing atmosphere having an oxygen concentration of 3% or more (most simply burns in the air), and converts the glassy acrylonitrile copolymer melt. Obtain it, or after making it into powder form, mix it with pitch or tar, which is a well-known binder, in any proportion, add water to the molding machine and mold it into granules, 700-1200 It is obtained by performing a steam activation treatment at a temperature of ° C., and can be decomposed even when the pH of the hydrogen peroxide-containing liquid is strongly acidic. Acrylonitrile copolymer contains 50% by weight of acrylonitrile.
If the polymer contains more than acrylic fiber, modacrylic fiber, ABS resin,
Etc. can be used alone or in combination.

When these acrylonitrile copolymers are put into a suitable container and burned in air, a vitreous hard amorphous melt is obtained. Of course, air may be introduced into a known carbonization furnace and burned. This melt is put into a known carbonization furnace, preferably a rotary kiln, heated to 700 to 1200 ° C., and a gas such as water vapor is introduced to obtain activated carbon having a specific surface area of 600 m ² / g or more. As the activation gas, water vapor, carbon dioxide, oxygen and the like can be used. The specific surface area, which is one of the indicators of the degree of activation, is 600
m 2 ^{/ g} or more, preferably better to set 750~1000m 2 ^{/ g,} the decomposition performance of smaller even or too large hydrogen peroxide decreases.

In addition, after pulverizing the acrylonitrile copolymer melt obtained by burning in air or introducing air into a known carbonization furnace and combusting it, any known binder, such as tar, pitch, etc. After adding the water and adding to water into a molding machine and granulating the granulated product into a carbonization furnace and rotary kiln, the temperature is raised to 700-1200 ° C,
Gas activation can be performed with steam or the like to obtain granular hydrogen peroxide decomposition catalytic activated carbon.

The mixing ratio of the acrylonitrile copolymer melt and the binder may be arbitrary, but the decomposition rate is low when the melt is small, and the strength of the granulated product cannot be obtained when the binder is small. It is better to set the melt to 50-80% by weight.

A thermosetting resin such as tar, pitch, molasses, lignin, and phenol resin can be used as the binder to be formed into granules. The granular hydrogen peroxide decomposition catalytic activated carbon can be dry or wet pulverized to produce a powdered decomposition catalytic activated carbon.
The decomposition rate is faster in powder form than granular form.

In recent years, a large amount of hydrogen peroxide-containing liquid mixed with sulfuric acid or the like has been used for cleaning printed circuit boards of electronic components. In addition, bleaching disinfectants are often used in place of sodium hypochlorite containing chlorine, and hydrogen peroxide-containing industrial waste liquid is increasing, and the necessity for its decomposition treatment is increasing.
The hydrogen peroxide decomposing catalytic activated carbon according to the present invention provides a decomposing catalytic activated carbon that can be decomposed regardless of pH, has a low risk of elution of metals, and can be produced by an inexpensive method. .

(Function)
In the present invention, a glassy amorphous melt obtained by burning an acrylonitrile copolymer in an oxidizing atmosphere serves as the main component of the hydrogen peroxide decomposition catalytic activated carbon, and it is used alone or mixed with a binder. Then, the activated carbon having a specific surface area of 600 m ² / g or more obtained by gas activation after being molded serves as a decomposition catalytic activated carbon of hydrogen peroxide.

A few millimeters of chip-like acrylonitrile copolymer was put in a small amount into a cylindrical container opened on one side and ignited and burned to obtain a massive glassy melt (the combustion gas was introduced into the exhaust gas combustion device and treated) To do). The bulk melt was poured into a rotary kiln, after heated to 950 ° C., subjected to steam activation, specific surface area was obtained hydrogen peroxide decomposition catalyst activated carbon 700m 2 ^{/ g.}

This decomposition catalyst activated carbon is pulverized to 0.75mm or less and 1ppm of 3000ppm hydrogen peroxide water
The hydrogen peroxide decomposition rate measured after 15 minutes was 55%. The decomposition rate was determined by titrating potassium permanganate.
(Comparative Example 1)
The hydrogen peroxide decomposition rate of coconut shell activated carbon (specific surface area 1010 m ² / g) was measured in the same manner as in Example 1 to be 4%.

The acrylic fiber was burned in the same manner as in Example 1 to obtain a scale-like melt. It
The mixture was pulverized to 0.75 mm or less, mixed with a pitch pulverized to the same particle size at 6: 4, kneaded with water, and formed into a cylindrical shape having a diameter of 5 mm and a length of 10 mm. This was put into a rotary kiln, heated to 900 ° C., and steam was added to obtain granular hydrogen peroxide decomposition catalytic activated carbon having a specific surface area of 800 m ² / g. After 20 g of this was put into 1 L of 3000 ppm hydrogen peroxide solution, the hydrogen peroxide decomposition rate measured after 90 minutes was 100%.
Similarly, 20 g is taken and filled into a glass U-tube with a capacity of 40 ml, pH 1.8, water temperature 20 ° C.
Printed circuit board microetching waste liquid in which 2,200ppm of hydrogen peroxide remains is passed at a volume rate (SV) of 5 hr-1, and the hydrogen peroxide decomposition rate of the waste liquid flowing out in contact with the decomposition catalyst activated carbon is 100% initially. It was 95% after 100 hours, 86% after 200 hours, and 40% after 800 hours.

The granular hydrogen peroxide decomposition catalytic activated carbon obtained in Example 2 was dry-pulverized to obtain a fine hydrogen peroxide decomposition catalytic activated carbon having an average particle size of 5 μm. Take 1g of it,
Throw in 1 liter of aqueous solution with 100,000 ppm hydrogen peroxide at pH 6.5 and water temperature of 25 ° C.
The decomposition rate after 120 minutes was measured and found to be 99%.

Claims (2)

Hydrogen peroxide with a specific surface area of 600 m ² / g or more, characterized by activating the melt of acrylonitrile copolymer obtained by igniting and burning acrylonitrile copolymer in an oxidizing atmosphere with an oxygen concentration of 3% or more A method for producing cracked catalytic activated carbon. The melt of acrylonitrile copolymer obtained by igniting and burning acrylonitrile copolymer in an oxidizing atmosphere with an oxygen concentration of 3% or more is powdered, mixed with a binder, formed into granules, and then activated. A method for producing a hydrogen peroxide-decomposing catalytic activated carbon having a specific surface area of 600 m ² / g or more.