JPH0839078A - How to decompose hydrogen peroxide - Google Patents

Abstract

PURPOSE:To effectively restore the decomposition capacity of hydrogen peroxide contained in activated carbon in decomposing hydrogen peroxide by bringing water containing hydrogen peroxide into contact with an alkali agent before bringing the same into contact with activated carbon to decompose hydrogen peroxide. CONSTITUTION:When hydrogen peroxide contained in semiconductor washing waste water if decomposed and removed, water containing hydrogen peroxide is passed through an activated carbon(AC) column 1 from piping 11 to obtain treated water from piping 12. An alkali aq. soln. such as sodium hydroxide is passed through the AC column 1 to regenerate activated carbon. At the time of regeneration, at first, the supply of raw water is stopped and a pump P1 is operated to pass the alkali aq. soln. in an alkali water tank 2 through the AC column 1 and regeneration waste water is discharged from piping 15. After the washing of the AC column 1 is completed, the pump P1 is stopped while a pump P2 is operated and backwashing water in a backwashing water tank 3 is,,, passed through the AC column 1 to wash away alkali.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for decomposing hydrogen peroxide, and more particularly, it makes hydrogen peroxide (H ₂ O ₂ ) contained in semiconductor cleaning waste water discharged from a semiconductor manufacturing process more efficient by activated carbon. It relates to a method of decomposing and removing.

[0002]

2. Description of the Related Art Semiconductor cleaning waste water discharged from a semiconductor manufacturing process contains H ₂ O ₂ used as an etching agent. In treating this semiconductor cleaning wastewater and recovering it as ultrapure water, H ₂ O ₂ contained in the semiconductor cleaning wastewater causes the flocculation of sludge to float, and
Since it becomes a COD source, it must be removed.

Conventionally, semiconductor cleaning wastewater discharged from the semiconductor manufacturing process is an activated carbon (AC) tower, a weakly basic anion exchange resin (WA) tower, a strongly acidic cation exchange resin (SC) tower, and a strongly basic anion exchange resin. After water is sequentially passed through the (SA) tower, it is passed through a pure water producing apparatus and reused as ultrapure water (Japanese Patent Publication No. 61-1192).
In this method, H ₂ O ₂ in the semiconductor cleaning wastewater is AC
It is decomposed and removed in the tower.

[0004]

In the above conventional method, when treating semiconductor washing wastewater containing 50 to 500 ppm of H ₂ O _{2 and} having a pH of ₂ to 4, H ₂ O ₂ leaks from the AC tower. There has been a problem that the device in the subsequent stage is adversely affected by deteriorating the resin in the ion exchange resin tower in the subsequent stage and the separation membrane in the reverse osmosis membrane separation device in the pure water producing device.

This is because the pH of the waste water is on the acidic side of 2 to 4, so that the decomposition of H ₂ O ₂ by AC becomes difficult. By continuing water flow, AC deteriorates and H ₂ O
₂ Decomposition ability is decreasing. This is because.

Conventionally, the H ₂ O ₂ leaked from the AC tower is
It is decomposed using a reducing agent such as sodium sulfite. However, since the leak amount of H ₂ O ₂ is not constant, it is difficult to control the optimum injection amount of the reducing agent. Therefore, there is a method of preventing the leak of H ₂ O ₂ without using the reducing agent. Is desired.

The present invention solves the above-mentioned conventional problems, and AC
An object of the present invention is to provide a method for obtaining a treated water in which H ₂ O ₂ decomposition efficiency in a column is maintained high and H ₂ O ₂ is removed to an extremely low concentration.

[0008]

The method for decomposing hydrogen peroxide according to the present invention is a method for decomposing hydrogen peroxide by bringing water containing hydrogen peroxide into contact with activated carbon, after contacting activated carbon with an alkaline agent. The activated carbon is contacted with water containing hydrogen peroxide.

In the method of the present invention, the alkaline agent is an aqueous solution of an alkali salt such as sodium hydroxide (NaOH) or potassium hydroxide (KOH), or is obtained when the anion exchange resin is regenerated with the alkaline agent. It is possible to use reclaimed waste water, etc., and its pH is preferably 11 or more.

Further, it is preferable that the activated carbon is thoroughly washed with water after such treatment with an alkaline agent. In this case, no particular restriction on the quality of the wash water, the raw water H ₂ O ₂
Contained water may be used.

In general, when treating the activated carbon packed in the AC tower, it is desirable to wash with water after passing the alkaline agent under the following passing conditions.

Alkaline agent water-flowing method: not particularly limited, either upward flow or downward flow is possible. Alkaline-agent water flow rate: There is no particular limitation, but usually,
SV = ^{1 to} about 20 hr ⁻¹ Alkaline agent water passage time: 1 to 30 minutes, preferably 5 to 10
Water separation washing method: SV = 2 hr ⁻¹ or more and 5 minutes or more Hereinafter, the method for decomposing hydrogen peroxide of the present invention will be described in detail with reference to the drawings.

1 and 2 are system diagrams showing an embodiment of the method for decomposing hydrogen peroxide of the present invention.

In FIG. 1, raw water (H ₂ O ₂ -containing water) is piped 1
In the system in which the treated water is obtained from the pipe 12 by downwardly circulating water from the AC tower 1 to the AC tower 1, sodium hydroxide (NaO
H) or the like is passed through to regenerate the activated carbon.

That is, in the regeneration, first, the supply of raw water is stopped, the pump P ₁ is operated, and the alkaline aqueous solution in the alkaline water tank 2 is passed upward through the pipes 13 and 14 to the AC tower. 1 and the recycled waste water is discharged from the pipe 15. After sufficiently washing with the alkaline aqueous solution, the pump P ₁ is stopped and the pump P ₂ is operated so that the backwash water in the backwash water tank 3 flows upward to the AC tower 1 through the pipes 16 and 14. Pass water through and wash out the alkali thoroughly. This cleaning drainage is discharged from the pipe 15.

After the regeneration with the alkaline aqueous solution and the washing with water in this manner, the pump P ₂ is stopped and the raw water passage treatment is restarted.

FIG. 2 shows a system in which raw water is circulated downward from the pipe 21 to the AC tower 1, and outflow water of the AC tower is circulated downward from the pipe 22 to the WA tower 4 to obtain treated water from the pipe 23. ,
The activated carbon of the AC tower 1 is regenerated by using the recycled waste water of the WA tower 4.

That is, when regenerating, the WA from the pipe 24 is used.
The regenerated liquid of WA is passed through the tower 4 in a downward flow, the regenerated waste water of the WA tower discharged from the pipe 25 is passed in an upward flow of the AC tower 1, and the regenerated waste water of the AC tower 1 is piped. It is discharged from 26.

The water washing of the AC tower 1 after the regeneration may be carried out by passing the waste water obtained in the water washing of the WA tower through the pipe 25, or by passing the washing water from a separately provided washing water tank. You may go by doing.

As described above, if the method uses the regenerated waste water of the WA tower as the alkaline agent, in particular, in the method of sequentially passing the semiconductor cleaning waste water to the AC tower, the WA tower, the SC tower, and the SA tower, AC There is an advantage that the recycled wastewater of the WA tower provided in the latter stage of the tower can be effectively used.

The method of decomposing hydrogen peroxide of the present invention as described above contains 50 to 1000 ppm of H ₂ O ₂ and has a pH of ₂ to _2.
It is extremely effective in treating the acidic wastewater of No. 5, especially semiconductor cleaning wastewater.

Further, the method of the present invention is not only activated carbon Part H ₂ O ₂ decomposition performance has deteriorated using the decomposition process of removing H ₂ O _2, also effectively applicable to new activated carbon Thus, it is possible to recover the H ₂ O ₂ decomposition performance of the activated carbon after use and improve the H ₂ O ₂ decomposition performance of the new activated carbon.

[0023]

By treating the activated carbon with an alkaline agent, the ability of the activated carbon to decompose H ₂ O ₂ can be remarkably enhanced.

It is presumed that the effect of improving the H ₂ O ₂ decomposing ability of the activated carbon by this alkaline agent is based on the following factors.

(I) The pores of activated carbon are on the alkaline side, and H ₂ O ₂ is easily decomposed. (ii) The surface of the activated carbon is washed with an alkaline agent to enhance the surface activity, thereby improving the H ₂ O ₂ decomposing ability.

[0026]

EXAMPLES The present invention will be described in more detail with reference to specific examples.

Example 1 SV = 10 hr of semiconductor cleaning wastewater having a pH of 3 to 4 and an H ₂ O ₂ concentration of 350 ppm was applied to the AC towers of the following sample Nos. 1 to 4.
H ₂ O of treated water (AC tower outflow water) obtained by passing water at ^-1
_{The two} concentrations are shown in Table 1. The values for Sample Nos. 3 and 4 are the values one month after the passage (resumption) of water.

Sample No. 1: Packed with new activated carbon Sample No. 2: Sample No. 1 AC tower with the above semiconductor cleaning wastewater passed for 3 months Sample No. 3: Sample No. 2 AC 4% by weight N in the tower
An aqueous solution of aOH was passed at SV = 15 hr ⁻¹ for 30 minutes, and then pure water was passed at SV = 30 hr ⁻¹ for 30 minutes to obtain NaOH.
Washed out sample No. 4: Sample No. 2 AC tower with WA tower N
The recycled wastewater obtained when regenerated with an aOH aqueous solution is SV =
Pass water for 15 minutes at 15 hr ^-1 , and then add pure water to SV = 30
Washed by passing water for 30 minutes at hr ^-1

[0029]

[Table 1]

From Table 1, it is possible to convert the H ₂ O ₂ decomposing capacity to a new activated carbon by passing an alkali such as NaOH or NaOH regeneration waste liquid through the activated carbon whose H ₂ O ₂ decomposing capacity has been reduced by long-term use. It turns out that they can be recovered equally.

[0031]

As described in detail above, according to the method for decomposing hydrogen peroxide of the present invention, the H ₂ O ₂ decomposing ability of activated carbon can be effectively recovered or improved by a simple operation.
It is possible to efficiently decompose and remove H ₂ O ₂ .

[Brief description of drawings]

FIG. 1 is a system diagram showing an example method of a method for decomposing hydrogen peroxide of the present invention.

FIG. 2 is a system diagram showing another example method of the method for decomposing hydrogen peroxide of the present invention.

[Explanation of symbols]

 1 AC tower 2 Alkaline water tank 3 Backwash water tank 4 WA tower

Claims (1)

[Claims] 1. A method of decomposing hydrogen peroxide by bringing water containing hydrogen peroxide into contact with activated carbon, the method comprising contacting activated carbon with an alkaline agent, and then contacting water containing hydrogen peroxide with the activated carbon. A characteristic method for decomposing hydrogen peroxide.