JP2003266081A - Activated carbon for decomposing hydrogen peroxide and treatment method for hydrogen peroxide-containing wastewater - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain activated carbon for decomposing hydrogen peroxide capable of decomposing hydrogen peroxide in hydrogen peroxide-containing wastewater with high efficiency over a long period of time, and to provide a treatment method for hydrogen peroxide-containing wastewater. <P>SOLUTION: A compound of at least one metal selected from Ag, Pt, Pd, Cu and Fe and an activated carbon precursor are kneaded and dispersed to obtain a mixture. This mixture is subjected to infusible treatment and/or carbonation treatment and the treated mixture is subsequently activated to obtain hydrogen peroxide decomposing activated carbon with a metal content of 0.01 mass % or more being a decomposition material for hydrogen peroxide. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has a high decomposition activity in removing hydrogen peroxide contained in hydrogen peroxide-containing wastewater, for example, sterilization cleaning wastewater generated in sterilization cleaning of semiconductor manufacturing plants or ultrapure water production lines. The present invention relates to a method for treating activated carbon for decomposing hydrogen peroxide, which comprises:

[0002]

2. Description of the Related Art Hydrogen peroxide is used in various fields as a cleaning agent, a germicide or a bleaching agent. for that reason,
Wastewater containing hydrogen peroxide is discharged from semiconductor manufacturing factories, textile factories, plating factories, and the like. In particular, in semiconductor device manufacturing applications, hydrogen peroxide is often used for wafer cleaning, cleaning and sterilization of ultrapure water feed pipes, etc., and a large amount of wastewater containing hydrogen peroxide with high concentration is discharged, which has an impact on the environment. There is concern.

However, in the conventional treatment method using a reducing agent such as sodium sulfite, which is a method for decomposing hydrogen peroxide, there is concern about the influence on the treatment cost due to the use of a large amount of chemicals and the secondary pollution due to excessive chemical outflow. was there. In addition, a treatment method using an enzyme such as catalase requires a wide space such as a temporary storage tank in order to reduce the decomposition efficiency due to an inhibitor, ensure optimum pH adjustment and secure a sufficient reaction time. In semiconductor applications that discharge hydrogen-containing wastewater, the treatment cost is high, which is a problem.

In order to solve these problems when treating wastewater containing hydrogen peroxide, many methods utilizing the reduction catalytic action of activated carbon, methods utilizing metallic catalysts, etc. have been proposed. Examples of the method using activated carbon include the methods described in JP-A-05-00811, JP-A-08-039079, JP-A-07-171561 and the like, but the fact that the life of the catalytic action of activated carbon is short and There are problems such as leakage to the post-treatment process and clogging of piping due to pulverization of the activated carbon. Further, activated carbon itself has a drawback that the reaction apparatus reacts with hydrogen peroxide at a slow rate, resulting in an increase in size of the apparatus, and is not suitable for removing wastewater containing high-concentration hydrogen peroxide.

As a method for treating wastewater containing high-concentration hydrogen peroxide, Japanese Patent No. 2960057 and Japanese Patent Laid-Open No.
Japanese Patent Laid-Open No. 5-261369 and Japanese Patent Laid-Open No. 10-314760 propose methods of using a treatment material in which a metal catalyst is supported on a porous material. However, even in these cases, since the metal catalyst is simply attached to the porous body, there is a problem that the attached metal leaks into the treated water, the amount of the attached metal decreases, the performance deteriorates, and the durability problem. Still not resolved.

Further, a conventional granular hydrogen peroxide decomposition catalyst,
In particular, in the case of the treatment with the filling method of the catalytic granular activated carbon, the decomposition efficiency is lowered due to poor contact such as channeling (the wastewater passes through only a part of the activated carbon layer) due to the generation of decomposition gas and floating of the packing material itself. However, the device becomes complicated, for example, a means for venting gas is required. Further, in the method described in Japanese Patent Application Laid-Open No. 07-171561, a method of removing bubbles in the granular activated carbon layer by backwashing the granular activated carbon layer at the time point when the degradation activity is confirmed to decrease is also taken. The device becomes complicated. Furthermore, the second patent
According to the method described in Japanese Patent No. 655299, wastewater is brought into contact with an upward flow in a fluidized bed of granular activated carbon. In this method, although the activity of activated carbon declines slowly, there is a problem in that some of the activated carbon particles are crushed and pulverized due to mutual contact of activated carbon particles and contact with the wall of the treatment tower, and flow out to the subsequent treatment process. To do.

On the other hand, the inventors of the present invention have also used various metals as activated carbon fibers in order to solve the problems of low activity of decomposing hydrogen peroxide due to small specific surface area of granular activated carbon or powdered activated carbon and leakage to treated water due to pulverization. Japanese Patent Application Laid-Open No. 7-144189 proposes a method for treating wastewater containing hydrogen peroxide using a cartridge containing a decomposed material as a main component. However, this method was also unsuitable for long-term application to the treatment of wastewater containing high-concentration hydrogen peroxide because of the performance degradation due to leakage of adhered metals into the treated water.

[0008]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems and contains a hydrogen peroxide decomposing material and a hydrogen peroxide-containing material which have stable decomposition activity for a long period of time even against wastewater containing a high concentration of hydrogen peroxide. The technical problem is to provide a method for treating wastewater.

[0009]

The present inventors have arrived at the present invention as a result of extensive studies to solve the above problems. That is, the present invention has the following structures. (1) Kneading a compound of at least one metal selected from Ag, Pt, Pd, Cu and Fe and an activated carbon precursor,
A decomposing material for hydrogen peroxide obtained by inactivating and / or carbonizing a mixture obtained by dispersion and then activating the mixture, which is characterized by containing 0.01% by mass or more of a metal component. Activated carbon for hydrogen peroxide decomposition. (2) The activated carbon for decomposing hydrogen peroxide described in (1) above, or a filter or a molded body containing the activated carbon for decomposing hydrogen peroxide as a main component is packed in a treatment tower, and waste water containing hydrogen peroxide is charged in the treatment tower. A method for treating wastewater containing hydrogen peroxide, which comprises passing liquid.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below. The activated carbon for decomposing hydrogen peroxide of the present invention is Ag, P
Metals such as t, Pd, Cu and Fe are retained at the stage of the activated carbon precursor. For example, a mixture containing a silver compound and an activated carbon precursor is infusibilized and / or carbonized, and then the treated body is treated. Is obtained by activating.

The activated carbon precursor is not particularly limited as long as it becomes activated carbon by a method such as carbonization or infusibilization and can be mixed with the metal or metal compound. As such an activated carbon precursor, for example, an organic substance generally used for producing activated carbon can be used. Specifically, any of polyacrylonitrile, polyvinyl alcohol, phenol resin (novolac), pitch, etc. may be used. Among these, it is preferable to use the pitch because the theoretical carbonization yield during carbonization is large. The type of pitch is not particularly limited, and the same pitch as that used in the known production of activated carbon can be used.

Ag, P, which is a raw material of the activated carbon of the present invention,
A mixture of a metal or a metal compound selected from t, Pd, Cu and Fe and an activated carbon precursor can be prepared by mixing both components with a solvent. Here, as the above-mentioned metal compound, those soluble in a solvent are preferably used. The metal compound may be an inorganic compound or an organic compound.

Examples of the inorganic compound include silver nitrate, silver sulfate, silver acetate, silver diammine, platinum chloride, potassium chloroplatinate, palladium chloride, palladium nitrate, tetraammine palladium, copper chloride, tetraammine palladium,
Examples thereof include iron chloride, iron nitrate and iron acetate.

Examples of the organic compound include bisacetylacetonatoplatinum, bisacetylacetonatocopper, and trisacetylacetonatoiron.

The solvent used here is capable of dissolving both the activated carbon precursor and the above metal compound. Such a solvent is not particularly limited, but methanol, quinoline, acetic acid or the like can be appropriately selected depending on the type of the activated carbon precursor or metal compound used.

When the activated carbon precursor and the metal compound are mixed using a solvent, the activated carbon precursor may be added to and mixed in a solvent in which the metal compound is dissolved, or in a solvent in which the activated carbon precursor is dissolved. The metal compound may be added to and mixed with.

The amount of metal or metal compound contained in the activated carbon precursor is such that, in the activated carbon after the activation treatment, the metal component, that is, the content as a simple metal is 0.01% by mass or more, preferably 0.1% by mass. The amount of the metal or metal compound to be mixed with the activated carbon precursor is set so as to be 1.0% by mass. If the content of the metal component in the activated carbon after the activation treatment is less than 0.01% by mass, the decomposition activity with respect to hydrogen peroxide decreases, which is not preferable.

It is usually preferable to remove the solvent from the mixture of the metal or metal compound prepared as described above and the activated carbon precursor. As a method for removing the solvent, a conventional means such as vacuum distillation can be adopted.

The activated carbon for decomposing hydrogen peroxide of the present invention can be obtained by preparing activated carbon using a mixture of the above-mentioned activated carbon precursor and a metal or a metal compound. When preparing activated carbon, as a first method, after infusibilizing a mixture of an activated carbon precursor and a metal or a metal compound,
Apply activation treatment. As a second method, the mixture is infusibilized, then carbonized, and then activated. Further, as a third method, the mixture is carbonized and then activated. In these methods, infusible treatment, carbonization treatment and activation treatment are
It can be carried out according to a conventional method and is not particularly limited.

That is, the carbonization treatment is carried out at 5 to 10 ° C. in an inert gas atmosphere such as nitrogen gas or argon gas.
Heating to 800-1200 ° C at a heating rate of about 1 / min,
It can be carried out by holding the maximum temperature for about 1 to 60 minutes. In addition, the infusibilizing treatment is performed, for example, in an atmosphere of an inert gas or an oxygen-containing gas at 0.1 to 5 ° C /
It can be carried out by heating the mixture to a temperature about 400 ° C. lower than the melting point of the activated carbon precursor at a heating rate of about a minute.

Further, the activation treatment may be carried out according to a known activation treatment method, for example, in an atmosphere of steam, carbon dioxide, oxygen or a mixed gas thereof, or a gas obtained by diluting these gases with an inert gas such as nitrogen. In the atmosphere, it is usually heated to about 800 to 1200 ° C, and the maximum temperature is 5
It can be carried out by holding for about 120 minutes.

The activated carbon for decomposing hydrogen peroxide thus obtained may be in the form of powder, granular or fibrous activated carbon as long as it contains 0.01% by mass or more of the metal component as a simple metal. However, in consideration of water resistance, handleability such as filling or processing of the treatment tower, fibrous activated carbon is preferable. Also, the larger the specific surface area of the activated carbon, the more finely and uniformly the particles of the metal or metal compound can be dispersed, resulting in high performance, but practically, if it is 500 m ² / g or more, Hydrogen peroxide can be decomposed efficiently.

The form of activated carbon for decomposing hydrogen peroxide is as follows:
The activated carbon for decomposing hydrogen peroxide may be filled in the container as it is, but it is processed into an appropriate shape by a conventional method such as a wet molding method such as a vacuum suction method or a papermaking method or a dry molding method, and treated as a filter or a molded body. You may fill a tower.
When the activated carbon for decomposing hydrogen peroxide of the present invention is contacted with wastewater containing hydrogen peroxide, hydrogen peroxide can be decomposed with high efficiency. This is because the metal component contained in the activated carbon is a metal. It is recognized that it acts as a catalyst to decompose hydrogen peroxide.

When the activated carbon for decomposing hydrogen peroxide is formed into a sheet, or molded into a filter or a molded body, a low melting point synthetic fiber in an amount 1/20 to 3 times (mass ratio) that of the activated carbon for decomposing hydrogen peroxide is used. By mixing the organic binder or inorganic binder described in 1 above with activated carbon, it is possible to obtain a sheet-like material, a filter, or a molded product that is lightweight and has excellent handleability. In this case, if the amount of binder exceeds three times the amount of activated carbon, the decomposition performance of hydrogen peroxide will decrease. Also, if the amount of binder is small and less than 1/20 of that of activated carbon, the mechanical strength will decrease, making it slightly difficult to apply to actual wastewater treatment.

As the low-melting synthetic fiber which is an organic binder used when a sheet-like material, a filter or a molded product is mixed with activated carbon, polyester fiber, polyolefin fiber, polyamide fiber, polyacrylonitrile fiber or the like should be used. You can As the inorganic binder, there are lithium silicate, sulfuric acid band, silica sol, alumina sol, water glass and the like, and one or more of them can be used.

When the activated carbon for decomposing hydrogen peroxide was made into a sheet and used as a filter or a molded body, activated carbon for decomposing hydrogen peroxide and synthetic fibers as an organic binder were supplied and mixed to form a web. Then, a method of forming a sheet by needle punching or heat treatment, or a method of forming a web only from the activated carbon and then sandwiching it with a synthetic fiber non-woven fabric, and subjecting it to needle punching or heat treatment to obtain an activated carbon sheet for decomposing hydrogen peroxide There is. As a method of molding the activated carbon and the inorganic binder, the activated carbon and the inorganic binder are dispersed in water in a predetermined amount, sucked into a mold having a predetermined shape, and further dehydrated and heat-treated to cure the inorganic binder. There is a way to do it.

As the shape of the filter or the molded body, the activated carbon sheet for decomposing hydrogen peroxide produced as described above is spirally wound and heat-treated into a cylindrical or cylindrical cartridge type, or a small circular shape. Pellets such as oval and multi-lobed may be packed in the treatment tower. In addition, suspended solids (SS) in the wastewater to be treated
In order to prevent clogging of the filter and to prevent channeling and floating of the packing material itself due to generation of decomposition gas, a planar hydrogen peroxide decomposition carbon sheet and corrugated hydrogen peroxide are used. It is preferable to use a filter having an opening in which a decomposition activated carbon sheet is alternately laminated or spirally wound to form a honeycomb structure.

[0028]

EXAMPLES Next, specific examples of the present invention will be described with reference to examples. The evaluation of the hydrogen peroxide decomposition activity in the examples was carried out by measuring the hydrogen peroxide concentration in 10 mL of the treated water by the iodometric titration method and comparing the hydrogen peroxide concentration of the treated water with the simulated semiconductor cleaning wastewater for treatment. The ratio was obtained and evaluated. Example 1, Comparative Examples 1 to 3 Pitch fibers obtained by melt spinning and infusibilizing a mixture of coal pitch as a raw material and kneading and mixing silver acetate at 30 ° C. at 30 ° C.
Fibrous activated carbon (BET specific surface area 1800 m ² / g, Ag content 1.0% by mass: Example 1) obtained by activating steam for minutes was melt-spun and infusibilized without metal kneading. Obtained Comparative Examples 1-2 (Comparative Example 1 is A- manufactured by Unitika Ltd.)
15: BET specific surface area 1710 m ² / g, Comparative Example 2 is a sample of Unitika A-10: BET specific surface area 1200 m ² / g) and a comparative example in which silver acetate was impregnated and Ag was impregnated at 1.0% by mass. 3 (Unitika A-15: BET specific surface area 17
00m ² / g) in a glass column filled with 20mL of each sample, pH 6-7, about 25 ° C, hydrogen peroxide concentration 5000
Simulated semiconductor cleaning waste water of mg / L was passed by upflow at SV = 50 h ⁻¹ . Then, the hydrogen peroxide concentration of the treated water was measured to evaluate the hydrogen peroxide decomposition activity, and the results are shown in FIG.

As is apparent from FIG. 1, when the activated carbon fiber of Example 1 was used, even if the liquid flow rate was about 15,000 bed volumes (BV), the inlet side concentration C ₀ relative to the outlet side concentration C ₁ The ratio was almost 0, but in Comparative Examples 1 and 2, the ratio increased from the beginning, and in Comparative Example 3, this ratio increased with an increase in the flow rate, and hydrogen peroxide remained in the treated water.

Example 2 and Comparative Example 4 A web of fibrous activated carbon (weight per unit area: 160 g / m ² ) kneaded with about 1.0% by mass of Ag was used as a nonwoven fabric of polyester / polypropylene composite fiber having a core-sheath structure (manufactured by Unitika Ltd.). A sheet having a unit weight of 200 g / m ² was produced by a needle punching method by sandwiching it up and down with a trade name of Unicel unit weight 40 g / m ² ), and the sheet was rolled into a column to produce a cartridge having an outer diameter of 100 mm and a length of 250 mm. The obtained cartridge was packed in an acrylic column, pH 6-7, about 25 ° C, hydrogen peroxide concentration
5000 mg / L of semiconductor cleaning simulated waste water was passed by upward flow at SV = 10 ^-1 . Further, as Comparative Example 4, Ag is 1.0
A column filled with a cartridge prepared by the same method as in Example 1 using fibrous activated carbon impregnated with mass% was also passed by upward flow, and the hydrogen peroxide concentration of the treated water was measured to decompose hydrogen peroxide. The activity was evaluated and the results are shown in FIG.

As is clear from FIG. 2, in the second embodiment,
Even when the liquid passage weight of about 10000 bets volume (BV), the ratio of the entrance side concentration C outlet side concentration C ₁ relative to _0, was almost 0, Comparative Example 4, with increasing liquid passing amount this The ratio increased and hydrogen peroxide began to remain in the treated water.

Example 3, Comparative Example 5 Fibrous activated carbon (BET) obtained by steam-activating the pitch fibers melt-spun and infusibilized for 30 minutes at about 850 ° C. using coal pitch as a raw material, kneading and mixing silver acetate. Specific surface area 1800
m ² / g, Ag content 1.0% by mass) and silver acetate impregnated, and Comparative Example 5 carrying 1.0% by mass Ag (Unitika A-15: BET specific surface area: 1700 m ² / g) ), Each of which is filled with 20 mL of the sample, into a glass column at pH 6 to
7. A semiconductor cleaning simulated waste water having a hydrogen peroxide concentration of 5000 mg / L at about 25 ° C. was passed by an upward flow at SV = 50 h ⁻¹ , and the Ag concentration in the treated water was measured by ICP emission spectrometry.
Table 1 shows the obtained evaluation results.

[0033]

[Table 1]

As shown in Table 1, it was confirmed that when the activated carbon for decomposing hydrogen peroxide of Example 3 was used, the amount of supported Ag eluted was small and the hydrogen peroxide decomposing activity was maintained for a long period of time.

Example 4, Comparative Example 6 Using coal pitch as a raw material, potassium chloroplatinate was kneaded and melt-spun and infusible pitch fiber was prepared at about 850 ° C.
Fibrous activated carbon obtained by steam activation for 30 minutes (BET specific surface area 1068 m ² / g, Pt content 1.8% by mass)
And potassium chloroplatinate are added, and Pt is 1.0% by mass.
A glass column filled with 20 mL of each sample of Comparative Example 6 (A-15 manufactured by Unitika Ltd .: BET specific surface area: 1700 m ² / g) was filled with a semiconductor having a pH of 6 to 7 at about 25 ° C. and a hydrogen peroxide concentration of 5000 mg / L. Cleaning simulated drainage is SV = 50h
^-1 was passed by upward flow. The hydrogen peroxide concentration of the treated water was measured to evaluate the hydrogen peroxide decomposition activity, and the results are shown in Fig. 3.
Shown in.

As is apparent from FIG. 3, when the activated carbon fiber of Example 4 was used, even if the liquid flow rate was about 10,000 bed volumes (BV), the inlet side concentration C ₀ relative to the outlet side concentration C ₁ The ratio was about 0, but in Comparative Example 6, this ratio increased with an increase in the flow rate, and hydrogen peroxide came to remain in the treated water.

[0037]

The activated carbon for decomposing hydrogen peroxide of the present invention is
It has extremely high hydrogen peroxide decomposition activity, excellent durability and processing characteristics, and metal elution during processing can be minimized. Therefore, this activated carbon or a filter or molded body containing this activated carbon as a main component is used. If it is used, wastewater containing high concentration of hydrogen peroxide can be treated stably for a long period of time.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the flow rate (BV) passed through a column filled with the samples of Example 1 and Comparative Examples 1 to 3 and the hydrogen peroxide concentration ratio of the treatment liquid.

FIG. 2 is a graph showing the relationship between the flow rate (BV) through the column packed with the samples of Example 2 and Comparative Example 4 and the hydrogen peroxide concentration ratio of the treatment liquid.

FIG. 3 is a graph showing the relationship between the flow rate (BV) through the column packed with the samples of Example 4 and Comparative Example 6 and the hydrogen peroxide concentration ratio of the treatment liquid.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Shiraishi             23 Uji Kozakura, Uji City, Kyoto Prefecture Unitika Ltd.             Shikisha Central Research Institute F-term (reference) 4D019 AA03 AA04 BA03 BB02 BB08                       BB12 BB13 BB14 BC07 CA03                       CB02 CB03                 4D038 AA08 AB26 BB15 BB20                 4D050 AA13 AB33 BA04 BC06                 4G069 AA03 AA08 BB02A BB02B                       BC08A BC08B BC31A BC32A                       BC32B BC66A BC72A BC75A                       BC75B CA05 CA10 CA11                       EA10 EA14 FA01 FA02 FB07                       FB34 FC08

Claims (2)

[Claims] 1. A mixture obtained by kneading and dispersing at least one metal selected from Ag, Pt, Pd, Cu and Fe and a compound of the metal and an activated carbon precursor, and infusibilizing and / or carbonizing the mixture. After that, a decomposing material of hydrogen peroxide obtained by activating treatment, containing 0.01% of metal component
Activated carbon for decomposing hydrogen peroxide, characterized by containing at least mass%. 2. A treatment tower is filled with the activated carbon for decomposing hydrogen peroxide according to claim 1, or a filter or a molded body containing the activated carbon for decomposing hydrogen peroxide as a main component, and the treatment tower is supplied with hydrogen peroxide-containing wastewater. A method for treating wastewater containing hydrogen peroxide, characterized in that the wastewater contains hydrogen peroxide.