JPH0884994A - Treatment of liquid containing oxidizing agent - Google Patents

Abstract

PURPOSE: To provide a method for treating liquid containing an oxidizing agent in which a plenty of oxidizing agents are rapidly decomposed at a low treatment cost by a simple operation. CONSTITUTION: An oxidizing agent is decomposed by bringing liquid containing the oxidizing agent into contact with a catalyst having the alloy coating of platinum-tungsten, platinum-molybdenum, palladium-tungsten and palladium- molybdenum on a corrosion resistant metallic substrate such as stainless steel and titanium. Alloy coating is preferably eutected coating obtained by electroplating.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating an oxidizing agent-containing liquid, and more particularly to a method for treating a waste liquid containing an oxidizing agent such as peracetic acid or hydrogen peroxide.

[0002]

2. Description of the Related Art At present, a large amount of waste liquid containing peracetic acid and hydrogen peroxide is discharged from a drainage system of a semiconductor manufacturing plant, and waste liquid containing various oxidizing agents is also discharged from other chemical plants. The treatment is regarded as an important issue. Heretofore, the decomposition of these oxidizers has been carried out by decomposition with an activated carbon tower and by contact with other organic substances in the decomposition waste liquid by addition of a reducing agent of sodium sulfite.

However, even if the above method is adopted, a large number of microorganisms grow in the activated carbon layer due to decomposition by the activated carbon tower, deteriorating the water quality of the recovered water, and reducing the reducing agent in the treatment by adding a reducing agent such as sodium sulfite. However, there were many problems such as an increase in processing cost due to the above-mentioned cost, delicate control of the amount of reducing agent added, and an increase in salt generated by the reaction with the reducing agent. In addition, the reaction with organic substances does not cause problems such as increase of treatment cost and increase of generated salt, but the reaction rate is slow, and if a large amount of treatment is attempted, decomposition cannot be done in time and oxidizer remains as waste water. There was a problem that it was released.

[0004]

DISCLOSURE OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems that have hitherto been made, and the treatment cost is easy, and a large amount of oxidizing agent can be decomposed rapidly by a simple operation. A method for treating an oxidant-containing liquid is provided.

[0005]

The above object is to bring a catalyst having an alloy coating of platinum-tungsten, platinum-molybdenum, palladium-tungsten, or palladium-molybdenum on a corrosion-resistant metal substrate into contact with an oxidizing agent-containing liquid to form an oxidizing agent. Is achieved by decomposing. The contact between the catalyst and the oxidant-containing liquid is efficiently achieved by circulatingly supplying the oxidant-containing liquid to the catalyst container. The alloy coating is preferably an alloy coating obtained by electroplating. Furthermore, as the above-mentioned corrosion resistant metal substrate, stainless steel, titanium and the like are preferable.

[0006]

The present inventors have previously used platinum-tungsten, platinum-
Molybdenum, palladium-tungsten, palladium-
It has been found that a plating deposition coating such as molybdenum has catalytic activity and is particularly effective for decomposing a reducing agent such as hydrazine. (JP-A-6-379, JP-A-6-3
After that, however, it became clear that the alloy catalyst obtained by the above plating also had a reducing catalyst capacity for decomposing the oxidizing agent, and it became possible to treat the oxidizing agent such as peracetic acid. According to this method, the oxidant is decomposed into harmless compounds (for example, peracetic acid is water and acetic acid), there is no need to add other chemicals, there is no fear of by-products from the reaction, and the reaction rate is high. Since it is fast, large-scale processing is possible.

The catalyst can be brought into contact with the oxidant-containing liquid simply by introducing the catalyst into the liquid, but by providing a catalyst storage container and circulatingly supplying the oxidant-containing liquid, the oxidant can be efficiently supplied. Can be disassembled. The corrosion-resistant metal substrate used as the catalyst substrate is not particularly limited, but readily available stainless steel, titanium, or the like is used.

[0008]

[Example 1] A 35-mesh net (50 mm x 50 mm) made of stainless steel wire having a diameter of 0.3 mm was placed in a 5% aqueous solution of an electrolytic degreasing agent (manufactured by Nippon Electroplating Engineers: Eatrex # 12). At 60 ℃, voltage 5V
Electrolyte degreasing is performed for 60 seconds, followed by washing with water, dipping in 6N hydrochloric acid solution for 30 seconds, further washing with water, and then using a gold strike plating bath (Nippon Electroplating Engineers: Aurobond TCL) at 50 ° C, voltage 2V 60
Gold plated for seconds. Then, after washing with water, immersing in a 5% sulfuric acid aqueous solution for 30 seconds, and washing with water, plating is performed in the following palladium-molybdenum alloy plating bath under the following conditions, and the desired palladium-molybdenum eutectoid coating 3
A catalyst with g was obtained. (Plating bath) Palladium chloride 1.5 g Sodium molybdate 60 g Phosphate buffer solution Ammonium phosphate salt

After the above was dissolved in 800 ml of water, the pH was adjusted with 0.5N sodium hydroxide aqueous solution and finally with water.
Diluted to 1000 ml. (Plating conditions) Temperature 60 ° C. Current density 0.3 A / dm ² Plating time 6.5 minutes The obtained plating coating was 13.1% by weight of molybdenum and 86.9% by weight of palladium.

Decomposition of peracetic acid was carried out using the obtained catalyst coated with a palladium-molybdenum alloy. A waste liquid containing 4,000 ppm of peracetic acid was prepared in a 10-liter reaction container and circulated and supplied to the container containing the above catalyst. After circulating for 1 hour (at room temperature and atmospheric pressure), the waste liquid was collected and the concentration of peracetic acid was measured and found to be about 6 ppm. The circulation was further continued, and after 2 hours, the waste liquid was collected again and the concentration of peracetic acid was measured, and it was found to be almost 0 ppm.

[0011]

Conventional Example 1 10 l of the same waste liquid as that used in Example 1 was prepared, and sodium sulfite was added thereto to try to decompose it. Sodium sulfite (10 g) was added and stirred for 2 hours.
It only drops to 1,000ppm, and 10% of sodium sulfite is added.
When g was added and the mixture was stirred for 6 hours, the decomposition of peracetic acid was completed, but COD was 1 due to the excessive addition of sodium sulfite.
It became 2,000 ppm, and it became impossible to discharge it to wastewater.

[0012]

As described above, according to the method for treating an oxidant-containing liquid of the present invention, a large amount of oxidant can be decomposed rapidly with a low treatment cost and a simple operation, and the wastewater treatment cost can be reduced. It is very useful.

Claims (5)

[Claims] 1. A catalyst having a platinum-tungsten, platinum-molybdenum, palladium-tungsten, or palladium-molybdenum alloy coating on a corrosion-resistant metal substrate is placed in a catalyst storage container, and an oxidant-containing liquid is circulated and supplied to the catalyst storage container. A method for treating an oxidant-containing liquid, which comprises decomposing the oxidant with. 2. The method for treating an oxidizing agent-containing liquid according to claim 1, wherein the alloy coating is an alloy coating obtained by electroplating. 3. The catalyst has a gold-plated intermediate layer between a corrosion resistant metal substrate and platinum-tungsten, platinum-molybdenum, palladium-tungsten or palladium-molybdenum. The method for treating an oxidizing agent-containing liquid according to claim 2. 4. The method for treating an oxidizing agent-containing liquid according to claim 1, 2 or 3, wherein the corrosion-resistant metal substrate is stainless steel. 5. The method for treating an oxidant-containing solution according to claim 1, 2 or 3, wherein the corrosion-resistant metal substrate is titanium.