JPH0661541B2 - Method and apparatus for removing hydrogen peroxide - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention relates to a method for removing hydrogen peroxide, which removes hydrogen peroxide from an aqueous solution containing a relatively large amount of hydrogen peroxide, and makes it possible to discharge the hydrogen peroxide. It relates to the device.

<Prior Art> In the electronic industry that manufactures semiconductors, so-called ultrapure water in which impurities such as fine particles, viable bacteria, and TOC are removed to the limit value, as well as various ions, is used for cleaning products. Such ultrapure water is filtered, ion exchange treated, reverse osmosis membrane treated,
Although it is manufactured by making full use of various techniques such as ultraviolet sterilization, in order to maintain the purity of the ultrapure water, the pipe for transferring the ultrapure water is regularly cleaned. The pipe cleaning is particularly performed for removing slime deposited in the stagnant part of the pipe and for sterilizing the entire wetted part, and the cleaning agent is usually 0.15% by weight to
An aqueous solution of 0.25 wt% hydrogen peroxide is used.

Therefore, in the electronic industry, the aqueous solution of hydrogen peroxide used for the cleaning is regularly discharged as a waste liquid.

Since such an aqueous solution containing hydrogen peroxide cannot be discharged as it is, conventionally, a reducing agent such as sodium sulfite is added to the waste liquid to neutralize the acidification of hydrogen peroxide and then discharged.

<Problems to be Solved by the Invention> However, the above-mentioned neutralizing method using a reducing agent has the following drawbacks.

First, the reaction time of hydrogen peroxide and sodium sulfite is 2-3
It takes a relatively long time, and therefore the reaction tank becomes large, and when the amount of the waste liquid is large, a large installation area is required for the reaction tank. In any case, even if soda remains, it becomes unsuitable for discharge, the acceptance range in discharge is extremely narrow compared to the acid or alkali neutralization reaction, and it is technically difficult to neutralize redox. Control becomes relatively complicated.

Therefore, the equipment cost of the processing apparatus equipped with such a reaction tank, automatic control mechanism, and stirring mechanism is relatively high, and a reducing agent such as sodium sulfite is constantly required, and the running cost is high.

The present invention eliminates such drawbacks in the conventional processing method,
An object of the present invention is to provide a method and apparatus for removing hydrogen peroxide, which does not require a large installation area, is easy to operate, and has relatively low initial cost and running cost.

<Means for Solving Problems> The first invention of the present invention relates to a method for removing hydrogen peroxide, which comprises adjusting the pH of an aqueous solution containing hydrogen peroxide to 10 or more and passing the solution through a granular activated carbon packed bed. The second invention of the present invention relates to an apparatus for carrying out the method of the present invention, in which a granular activated carbon packed bed is packed in upper and lower two layers in a tank and below each packed bed. A space part is formed, at least the space part formed below the upper granular activated carbon packed layer is connected to a gas vent pipe communicating to the outside, and an inflow pipe of an aqueous solution containing hydrogen peroxide is provided above the upper granular activated carbon packed layer. The present invention is characterized in that the processing liquid outflow pipes are connected to the spaces below the lower granular activated carbon packed bed.

<Operation> The present invention is to pass an aqueous solution containing hydrogen peroxide through a packed bed of granular activated carbon and decompose and remove hydrogen peroxide in the aqueous solution using the reducing power of the granular activated carbon. According to the experiments by the researchers, the treatment effect largely varies depending on the pH of the aqueous solution brought into contact with the granular activated carbon layer, and the satisfactory treatment effect cannot be obtained unless the pH is 10 or more, preferably 10.5 or more. I found out that.

That is, as shown in Examples described later, the packed bed height 60
As a result of passing an aqueous solution containing 0.2% by weight to 3.0% by weight of hydrogen peroxide through a 0 mm granular activated carbon layer at LV3 m / H to LV7 m / H, when the pH of the aqueous solution is 9 or less, it is considered that a short time is required. Hydrogen peroxide leaks into the processing solution at pH 10
A slight amount of hydrogen peroxide leaks into the processing solution when it is raised to 1, but it can be treated for a long time, and when the pH is raised to 10.5, hydrogen peroxide does not leak into the processing solution at all, and it is stable for a long time. I was able to handle it.

It is not clear at present why the treatment effect is enhanced by increasing the pH of the aqueous solution, but the following phenomenon occurs when observing the above-mentioned liquid passing state.

That is, when an aqueous solution containing hydrogen peroxide comes into contact with the granular activated carbon layer, a decomposition reaction immediately occurs and oxygen is generated. However, when the pH of the aqueous solution is 9 or less, oxygen is also generated inside the granular activated carbon packed layer, which causes bubbles. However, when the pH of the aqueous solution becomes 10 or more, the bubbles are not trapped in the packed bed.

It is considered that the leakage of hydrogen peroxide in the treatment liquid when the pH of the aqueous solution is 9 or less is due to the short path (channeling phenomenon) of the aqueous solution in the packed bed due to the bubbles.

Also, when the pH of the aqueous solution is raised to 10 or more, no bubbles are generated in the packed bed, so the decomposition rate of hydrogen peroxide obviously increases due to the increase of the contact pH, so that most of the hydrogen peroxide in the aqueous solution is granular. It is considered that it decomposes in the relatively upper part of the activated carbon packed bed.

In any case, adjusting the pH of the aqueous solution containing hydrogen peroxide to 10 or more is an essential requirement for achieving the intended purpose of the present invention.

When the aqueous solution containing hydrogen peroxide is brought into contact with the granular activated carbon to decompose and remove the hydrogen peroxide, a small amount of carbon monoxide is generated due to the reaction between the carbon component of the granular activated carbon and hydrogen peroxide. By making the pH alkaline, the carbon monoxide can be dissolved and fixed in the treatment liquid, and there is an effect that environmental pollution due to the generation of carbon monoxide, which is a harmful gas, can be prevented.

Next, an apparatus for carrying out the method of the present invention will be described below.

As described above, when the aqueous solution containing hydrogen peroxide is brought into contact with the granular activated carbon layer, hydrogen peroxide is decomposed and oxygen is generated, so that the channeling phenomenon due to the oxygen being confined in the packed layer of granular activated carbon does not occur. However, in the present invention, the contact pH is set as described above.
This is to avoid this by raising, and to have a structure in which the generated oxygen can be effectively discharged also in terms of the device.

FIG. 1 is an explanatory diagram showing a flow of an example of an embodiment of the device of the present invention, in which a screen 2A and 2B through which liquid passes but granular granular activated carbon does not pass, in a tank 1 whose upper side is open,
For example, a sheet of cloth covered with Saran cloth is installed in two upper and lower stages, and granular activated carbon is filled in the upper portions of the screens 2A and 2B to form an upper granular activated carbon layer 3 and a lower granular activated carbon layer 4. When forming the lower granular activated carbon layer 4, the granular activated carbon is filled from the side trunk manhole (not shown) of the tank 1 located below the screen 2A.
Spaces S ₁ and S ₂ are formed below the granular activated carbon layers 3 and 4, respectively.

A space formed by disposing a distributor 5 above the upper granular activated carbon layer 3 and connecting one end of an inflow pipe 6 of a stock solution, which is an aqueous solution containing hydrogen peroxide, to the distributor 5 and further below the lower granular activated carbon layer 4. The processing liquid outflow pipe 7 is connected to the portion S ₂ and the processing liquid outflow pipe 7 is connected.
The backwash water inflow pipe 8 is communicated with.

Further, a gas vent pipe 9 that is raised above the water surface formed above the upper granular activated carbon layer 3 is communicated with each space S ₁ and S ₂ , and the lower granular activated carbon layer 4 is connected to the gas vent pipe 9. The backwash drainage outflow pipe 10B for discharging the backwash drainage is communicated.

On the other hand, a backwash drainage outflow pipe 10A for discharging backwash drainage of the upper granular activated carbon layer 3 and one end of the caustic soda solution inflow pipe 11 are connected to the stock solution inflow pipe 6, and the caustic soda solution inflow pipe 11 is connected. The other end of the solution is communicated with the caustic soda solution tank 13 via the injection pump 12. In addition, a mixer 14 is attached downstream of the junction of the stock solution inflow pipe 6 and the caustic soda solution inflow pipe 11, and a pH electrode 15 is attached downstream of the mixer 14, and the pH electrode 15 and the injection pump are attached. 12 is instrumentally connected via a pH indicator controller 16. Reference numeral 17 is a blow pipe, and 18 to 24 are valves.

Next, the operation of this device will be described below.

At the beginning of the operation, the granular activated carbon is filled to form the layers 3 and 4, but when pulverized coal is mixed in the granular activated carbon, the valve 23, the valve 20 and the valve 19 are opened and the backwash water inflow pipe 8 is opened.
The backwash water is introduced from the above, the respective layers 3 and 4 are appropriately expanded, and the backwash drainage containing the pulverized coal is caused to flow out from the backwash drainage outflow pipes 10A and 10B. The backwashing step is appropriately performed even when the suspended substance is clogged in each of the layers 3 and 4 as the liquid passing step described below is continued and the pressure loss thereof increases. After such backwashing is completed, each valve is closed and the valve 24
To discharge the water in the tank 1 from the blow pipe 17.

Next, the valves 18, 21, and 22 are opened, the other valves are closed, and the stock solution is introduced from the stock solution inflow pipe 6 and the process solution is obtained from the process solution outflow pipe 7.

When the liquid is passed, the injection pump 12 is driven to mix the caustic soda solution with the stock solution to adjust the pH of the stock solution to 10 or more, preferably 10.5-11.0.

This adjustment is performed by instrumentally adjusting the caustic soda solution injection amount of the injection pump 12 by the pH indicator controller 16 so that the pH measured by the pH electrode 15 falls within a predetermined range determined in advance. .

The undiluted solution evenly distributed by the distributor 5 is dropped onto the upper surface of the upper granular activated carbon layer 3, and sequentially passed through the layer 3, the screen 2A, the lower granular activated carbon layer 4, and the screen 2B, and the liquid is collected in the space S ₂ and treated. The liquid flows out from the processing liquid outflow pipe 7. If the above-mentioned liquid flow is performed after the water in the tank 1 is discharged, the liquid flow continues, so that a relatively thin liquid is applied to the upper part of the upper granular activated carbon layer 3, the upper part of the lower granular activated carbon layer 4 and the bottom of the space S _2. A surface is formed.

The hydrogen peroxide present in the stock solution by such passage is decomposed by coming into contact with the granular activated carbon layer, but most of the oxygen generated by the decomposition is released from the upper surface of the upper granular activated carbon layer 3 to the atmosphere. . Further, a small amount of hydrogen peroxide remaining without being decomposed by the upper granular activated carbon layer 3 is immediately decomposed when coming into contact with the lower granular activated carbon layer 4, and the oxygen generated by the decomposition is degassed to communicate with the space S _1. Emitted from the pipe 9 to the atmosphere. Is released to the atmosphere in the same manner from the gas vent pipe 9 communicating with the space S ₂ even if oxygen is generated further in the space portion S _2.

As described above, in the apparatus of the present invention, the tank for filling the granular activated carbon is of the upper open type, and the granular activated carbon packed layers are filled in two stages, the space S between the upper granular activated carbon layer 3 and the lower granular activated carbon layer 4. _{Since 1} is provided and the gas vent pipe 9 communicating with the outside is connected to the space S ₁ , the generated oxygen can be easily released to the outside of the tank, and no bubbles are generated in the packed bed of granular activated carbon. It is possible to effectively prevent the leakage of hydrogen peroxide due to the channeling phenomenon.

Note that the tank 1 may be a closed type, and pressure type liquid flow may be used instead of gravity type liquid flow. In that case, a gas vent valve or the like is installed in the upper part of the tank 1 and the upper granular activated carbon layer 3 It is necessary to have a structure that releases oxygen generated from the atmosphere to the atmosphere.

The height of the packed bed of each of the granular activated carbon layers 3 and 4 in the apparatus of the present invention is suitably 400 mm to 600 mm, and it is not preferable that the packed bed is too thick because bubbles tend to occur in the packed bed. The flow rate should be lower as the content of hydrogen peroxide in the stock solution is higher. However, when the hydrogen peroxide content is 0.2% by weight, the flow rate should be around LV 7 m / H and the hydrogen peroxide content. Is 3% by weight, LV3m / H
The front and back are appropriate.

<Effect> As described above, since the method of the present invention can remove hydrogen peroxide by simply passing the stock solution through the granular activated carbon layer, a large reaction tank as in the conventional method is not required, and the installation area of the apparatus can be reduced. It can be operated easily and is easy to operate automatically, and the equipment cost of the device can be made lower than the conventional one. Furthermore, since a reducing agent such as sodium sulfite is not used, the running cost is also large. Can be reduced to Further, when the aqueous solution containing hydrogen peroxide is brought into contact with the granular activated carbon tank to decompose and remove the hydrogen peroxide with the reducing agent of the granular activated carbon, the pH of the stock solution is adjusted to 10 or more, so that the granular activated carbon layer It is possible to prevent air bubbles from being generated and effectively prevent leakage of hydrogen peroxide into the treatment liquid due to the channeling phenomenon of the raw liquid.

Further, the device of the present invention, while filling the upper and lower two layers of granular activated carbon packed bed in the tank, to form a space below each packed bed, at least in the space formed below the upper granular activated carbon layer, Since the structure is such that the gas vent pipe communicating with the outside is connected, hydrogen peroxide remaining in the treatment liquid of the upper granular activated carbon layer decomposes when it contacts the lower granular activated carbon, and even a small amount of hydrogen peroxide is generated. Even so, it is possible to easily release the oxygen from the gas vent pipe to the outside of the tank,
It is possible to more effectively prevent the leakage of hydrogen peroxide of the treatment liquid due to the channeling phenomenon without generating bubbles in the upper and lower granular activated carbon layers.

Examples will be described below to clarify the effects of the present invention.

〔Example〕

Granular activated carbon, DiaHope (registered trademark) 0 in the test column
08 is filled to a height of 600 mm and the hydrogen peroxide content is 0.2
For the stock solutions of wt%, 1.0 wt% and 3.0 wt%, the pH of the stock solutions was adjusted to 5.5, 7.0, 9.0, 10.0 and 10.5, respectively, and a liquid passing test was conducted. The flow rate is LV7m / h for the stock solution with a hydrogen peroxide content of 0.2% by weight, LV5m / H for the stock solution with a hydrogen peroxide content of 1.0% by weight, and LV3m for the stock solution with a hydrogen peroxide content of 3% by weight. / H
And

Figure 2 shows the results of passing hydrogen peroxide content of 0.2% by weight, Figure 3 shows the results of passing hydrogen peroxide content of 1.0% by weight, and Figure 3 shows the results of passing hydrogen peroxide content of 3.0% by weight. Each is shown in FIG.

As shown in FIGS. 2 to 4, when the pH of the stock solution was 9.0 or less, hydrogen peroxide leaked out in a short time. Further, when the state of liquid passage was observed, it was confirmed that air bubbles were generated in the packed bed in all cases where the pH was 9.0 or less.

When the pH of the stock solution is 10, the hydrogen peroxide slightly leaks to the treatment liquid, but it can be treated for a long time. When the pH is 10.5, hydrogen peroxide does not leak to the treatment liquid at all. It was possible to process stably for a long time.

[Brief description of drawings]

FIG. 1 is an explanatory view showing the flow of an example of an embodiment of the device of the present invention, and FIGS. 2, 3, and 4 are graphs showing the results of liquid passage in each example, with the treatment liquid on the vertical axis. Concentration of hydrogen peroxide (H ₂ O ₂ ) is shown, and the horizontal axis shows the treatment time. DESCRIPTION OF SYMBOLS 1 ... Tank, 2 ... Screen 3 ... Upper granular activated carbon layer 4 ... Lower granular activated carbon layer 5 ... Distributor 6 ... Stock solution inflow pipe, 7 ... Treatment liquid outflow pipe 8 ... Backwash water inflow pipe, 9 ... Gas vent pipe 10 ... Backwash drainage discharge pipe 11 ... Caustic soda solution inflow pipe 12 ... Injection pump, 13 ... Caustic soda solution tank 14 ... Mixer, 15 ... pH electrode 16 ... pH indicator controller, 17 ... Blow pipe 18-24 ... Valve , S ... Space section

Claims (2)

[Claims] 1. A method for removing hydrogen peroxide, which comprises removing the hydrogen peroxide from an aqueous solution containing hydrogen peroxide by adjusting the pH of the aqueous solution to 10 or more and passing it through a granular activated carbon packed bed. . 2. An apparatus for adjusting the pH of an aqueous solution containing hydrogen peroxide to 10 or more and passing it through a granular activated carbon packed bed,
The tank is filled with granular activated carbon filling tanks in upper and lower layers, and a space is formed below each packed bed, and a gas vent pipe communicating with the outside is connected to at least the space formed below the upper granular activated carbon packed bed. The upper part of the upper granular activated carbon packed bed is connected to an inflow pipe of an aqueous solution containing hydrogen peroxide, and the space part below the lower granular activated carbon packed bed is connected to an outflow pipe of the treatment liquid. Removal device.