KR102047212B1 - Active carbon catalyst decomposition method for elimination of hydrogen peroxide in waste sulfuric acid - Google Patents

Abstract

The present invention relates to a method for decomposing a remaining activated carbon catalyst for removing hydrogen peroxide in sulfuric acid waste, and more particularly, to a method for purifying sulfuric acid by decomposing hydrogen peroxide in sulfuric acid waste generated in a wafer cleaning process during a semiconductor manufacturing process through an activated carbon catalyst. A domestic semiconductor industry has been developed and increased to the highest level of the world. Herein, sulfuric acid waste containing hydrogen peroxide is inevitably generated but currently, a recycling technique is not sufficiently developed except for disposal through a calcium neutralization method or preparation of iron sulfate and a water treatment agent. According to the technique of the present invention, diluted sulfuric acid is produced to be used for an industrial resource in a method for removing and purifying impurities of the sulfuric acid waste, thereby having excellent pollution prevention and industrial economical cost reduction effects.

Description

Active carbon catalyst decomposition method for elimination of hydrogen peroxide in waste sulfuric acid}

The present invention relates to a method of catalytic decomposition of activated carbon for removing hydrogen peroxide in spent acid, and more particularly, to purify sulfuric acid by decomposing hydrogen peroxide contained in spent sulfuric acid generated in a wafer cleaning process during semiconductor manufacturing process through an activated carbon catalyst. It is about a method.

In the semiconductor manufacturing process, hydrogen peroxide (H ₂ O ₂ ) is a commonly used oxidant and is always used together with sulfuric acid (H ₂ SO ₄ ) to be used as a removal or etching solution of photoresist. Sulfate sulfate accounts for more than 30-40%.

Since waste acid has strong oxidative properties, hydrogen peroxide must be removed to lower oxidative properties in order to favor storage and recovery recycling. The general method of treating hydrogen peroxide is as follows.

(1) Heat decomposition: As shown in the following formula 1, when heated to a high temperature of 140 ℃ or more hydrogen peroxide is rapidly decomposed to release oxygen gas. The most problematic drawback of this method is the risk of high temperature exothermic reactions.

(2) Ultraviolet decomposition: Hydrogen peroxide molecules undergo a decomposition reaction when they absorb ultraviolet rays with a wavelength of 3200 to 3800Å. The drawback of this method is that the other constituents in the solution may absorb ultraviolet rays, so that the effect of hydrogen peroxide on ultraviolet rays is reduced. Therefore, the intensity of the ultraviolet light source should be strengthened, and other photochemical by-products may be generated, which is undesirable.

(3) Nitric Acid Decomposition: Nitric acid (HNO ₃ ) is added to sulfuric acid solution containing hydrogen peroxide to cause decomposition reaction to release oxygen gas. This process is accompanied by a high exothermic temperature in the decomposition reaction, so sulfuric acid gas can be released, and additional processes for removing nitric acid used as catalysts of the reaction are required.

(4) To react with hydrogen peroxide by adding other organic or inorganic materials as a reducing agent, this method can combine safety and reaction efficiency only when the reaction temperature is controlled to an appropriate temperature, and at the same time, the by-products of the reaction are used for subsequent waste solution. You must also consider whether to add processing.

Accordingly, the present inventors while studying a method for removing hydrogen peroxide in waste acid to overcome the above problems, simply decomposing hydrogen peroxide by adding existing activated carbon or nitric acid (Korean Patent Publication No. 10-2018-0051250 No., Korean Patent Registration No. 10-1641959) was completed by the step of adding a different content of activated carbon step by step to confirm that the exothermic temperature is lower, hydrogen peroxide decomposition time is shortened. In addition, by using activated carbon impregnated with iron oxide than conventional activated carbon, it was confirmed that the decomposition time of hydrogen peroxide was shortened, thereby completing the present invention.

Korean Registered Patent No. 10-1641959 (Invention name: Method for removing hydrogen peroxide from sulfuric acid-hydrogen peroxide solution and its treating agent, Applicant: Trussval Technology Company, Limited, Date of registration: 2016.07.18.) Korean Patent Publication No. 10-2018-0051250 (Invention name: hydrogen peroxide decomposition catalyst and its preparation method, hydrogen peroxide decomposition device and method using the catalyst, Applicant: Korea Institute of Science and Technology, published date: May 16, 2018) Korean Registered Patent No. 10-1237919 (Invention name: Recycling device for waste sulfuric acid contaminated with hydrogen peroxide, Applicant: So Kwang Min, Date of registration: 2013.02.21.)

SUMMARY OF THE INVENTION An object of the present invention is to provide an activated carbon catalytic decomposition method for removing hydrogen peroxide in waste acid, and more particularly, sulfuric acid by decomposition of hydrogen peroxide contained in waste acid generated in a wafer cleaning process during semiconductor manufacturing process through an activated carbon catalyst. It is to provide a method for purifying.

Another object of the present invention is to impregnate activated carbon with iron salts to promote hydrogen peroxide decomposition reactions, and by dividing activated carbon to shorten hydrogen peroxide decomposition time shorter, and to lower the reaction temperature to stably decompose hydrogen peroxide in waste acid sulfate to purify sulfuric acid. To provide a way to do it.

The present invention comprises the steps of collecting the spent sulfuric acid generated in the (first step) semiconductor industry;

(Second step) adding spent sulfuric acid to the retention type digestion tank;

(Third step) decomposing hydrogen peroxide in spent acid by adding activated carbon to the retention type digestion tank of the second step; And

(Fourth step) Transferring the sulfuric acid in which the hydrogen peroxide decomposition is completed in the third step to the sulfuric acid storage tank through a filtration device in the retention type decomposition tank; hydrogen peroxide removal method comprising a.

The retention type digestion tank of the second stage may be one or more installed to continuously remove hydrogen peroxide.

The activated carbon of the third step may be a granular form having a specific surface area of 500 to 3000 m 2 / g.

The activated carbon of the third step may be to use the activated carbon impregnated with iron salt solution and heat-treated impregnated iron oxide.

Decomposing hydrogen peroxide in the spent sulfuric acid of the third step may be to maintain an exothermic temperature of less than 30 ℃ during hydrogen peroxide decomposition.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

In the first step, spent sulfuric acid containing hydrogen peroxide is a solution containing hydrogen peroxide in sulfuric acid among by-products generated during the semiconductor production process. Generally, sulfuric acid 50-70 wt%, hydrogen peroxide 1-10 wt% and water 20-40 wt% It may be to include.

In the second stage, the retention type cracking tank includes an acid resistant tank including a filtering device capable of filtering activated carbon catalyst, an acid coated steel and a concrete tank, and a batch cracking tank and two or more cracking tanks using one cracking tank. The continuous digestion tank can be used to continuously supply and discharge spent sulfuric acid. Most preferably, it is preferable to use a continuous digester in which three digesters are connected. In this case, the content of activated carbon may be added differently to each decomposition tank connected in the continuous decomposition tank. Preferably, based on 100 parts by weight of spent sulfuric acid, activated carbon is added to each decomposition tank by 0.5 to 1 part by weight, 1 to 2 parts by weight, and 2 to 5 parts by weight to sequentially decompose hydrogen peroxide in spent acid. Waste acid is introduced from a decomposition tank in which less activated carbon is introduced, and hydrogen peroxide is sequentially decomposed and removed. In addition, in the case of removing hydrogen peroxide through a continuous decomposition tank, it is preferable that the spent acid of waste acid is 2 to 5 hours in each decomposition tank. If the residence time is less than 2 hours, hydrogen peroxide cannot be decomposed sufficiently, and if the residence time is more than 5 hours, the operation time of the equipment is long, and thus the production efficiency is not economical.

In addition, the residence-type decomposition method for removing hydrogen peroxide in waste acid is economically low due to the low installation and installation costs and operation costs of the digestion tank, and sulfuric acid from which hydrogen peroxide has been removed can be provided for recycling to various industries. It is an environmentally friendly way to recycle resources.

In the third step, it is preferable that the activated carbon has a specific surface area of 500 to 3,000 m 2 / g, more preferably 1,000 to 2,000 m 2 / g. If the specific surface area of the activated carbon is less than 500 m 2 / g, hydrogen peroxide decomposition reaction may not occur well or it may take a long time, and if the specific surface area is more than 3,000 m 2 / g, the hydrogen peroxide decomposition reaction may occur so actively that the reaction rate Difficult to control and expensive, economically undesirable.

The activated carbon may be activated carbon impregnated with iron oxide. More specifically, the activated carbon having a specific surface area of 500 to 3,000 m 2 / g may be put in an ethanol solution containing iron salt so that the ethanol solution containing iron salt may be impregnated in the activated carbon.

Activated carbon may be impregnated by mixing 150 to 300 parts by weight of an ethanol solution based on 100 parts by weight, and the ethanol solution may include any one or more of iron nitrate, iron chloride, iron hydroxide, and iron sulfate, and 100 weight of ethanol solution. It is preferable to include 0.01 to 2 parts by weight based on parts. Most preferably, 0.01 to 2 parts by weight of iron trinitrate is included. If the iron salt is less than 0.01 parts by weight may not be sufficient iron salt on the surface, if the iron salt is more than 2 parts by weight concentration of the iron salt is too high economically undesirable.

In addition, the ethanol solution containing the iron salt is preferably impregnated in the activated carbon is performed by a method of giving a vibration in the ultrasonic cleaner.

Activated carbon may be separated from the ethanol solution containing the iron salt and washed with water to remove the ethanol solution. The method for removing the ethanol solution is preferably washed 1 to 3 times with water. Iron salts that are not sufficiently washed with water and which are not impregnated are attached to activated carbon and are not impregnated during the hydrogen peroxide decomposition step in waste acid so that the remaining iron salts can contaminate sulfuric acid.

Thereafter, the activated carbon from which the ethanol solution is removed may be heat-treated at 300 to 500 ° C. to impregnate iron oxide on the surface of the activated carbon. If the heat treatment temperature is less than 300 ℃ iron oxidation may not be sufficient, if it exceeds 500 ℃ may be a waste of heating energy.

The type of iron oxide after the heat treatment may vary depending on the type of iron salt in the ethanol solution containing iron salt, but may be impregnated with iron oxide, which may be used for hydrogen peroxide decomposition, and trivalent iron oxide is preferably impregnated.

The impregnating material may be impregnated with pure iron oxide as well as other elements that may increase the efficiency of the hydrogen peroxide decomposition reaction.

Activated carbon impregnated with iron oxide according to the present invention may have an effect in decomposing and removing hydrogen peroxide in waste acid.

The present invention relates to a catalytic decomposition method of activated carbon for removing hydrogen peroxide in waste acid, and has a lower risk than a conventional method of removing waste acid by heating or simply adding nitric acid to remove hydrogen peroxide. It has a stable effect on the treatment of waste acid.

1 is a flow chart of purifying sulfuric acid in a method of removing hydrogen peroxide in spent sulfuric acid by a continuous continuous digestion tank removal method.
2 is a graph measuring the amount of oxygen gas generated after hydrogen peroxide decomposition when activated carbon is added to waste acid.

Hereinafter, a preferred embodiment of the present invention will be described in detail. However, the present invention is not limited to the embodiments described herein and may be embodied in other forms. Rather, it is provided to fully convey the spirit of the present invention to those skilled in the art so that the contents introduced herein are thoroughly and completely.

Example 1 Waste Sulfate Collection and Activated Carbon Preparation

Waste sulfuric acid of the present invention was used as a sulfuric acid containing hydrogen peroxide generated in the semiconductor industry, more specifically, 60% by weight sulfuric acid, 5% by weight hydrogen peroxide, 35% by weight of water was used. In addition, activated carbon was prepared to have a specific surface area of at least 950㎡ / g coal-based 8 × 30 mesh size.

Example 2 Preparation of Activated Carbon Impregnated with Iron Oxide

Activated carbon impregnated with activated carbon prepared in Example 1 was prepared. More specifically, the activated carbon prepared in Example 1 was first etched and oxidized in an acid solution. The acid solution was prepared with 95% (v / v) sulfuric acid and 70% (v / v) nitric acid in a ratio of 3: 1. Activated carbon was soaked at 25 ° C. for 24 hours. The acid solution treated activated carbon was washed repeatedly with distilled water to adjust the pH to neutral. Impregnation of the iron oxide on the neutralized activated carbon proceeded as follows.

Tri (III) iron nitrate (Fe (NO ₃ ) _{3 ·} 9H ₂ O) was added to ethanol to prepare a 3 wt% iron salt solution. Thereafter, the activated carbon was added to the iron salt solution, and the iron salt solution was placed in an ultrasonic cleaner to vibrate for 10 minutes so that the iron salt solution was impregnated with the activated carbon. Thereafter, the activated carbon impregnated with the iron salt solution was heat-treated at 100 ° C. for 1 hour to remove ethanol, and then heat-treated at 400 ° C. for 4 hours to oxidize the iron salt to prepare activated carbon impregnated with iron oxide.

Experimental Example 1. Confirmation of hydrogen peroxide decomposition time according to the amount of activated carbon

An experiment was conducted to determine the decomposition time of hydrogen peroxide according to the activated carbon or nitric acid input. For this experiment, a retention type digestion tank made of acid-resistant material was prepared, and 1 g, 2 g, 3 g, 4 g, and 5 g of activated carbon were prepared in the retention type digestion tank, respectively, and 100 g of spent sulfuric acid collected in Example 1 was retained. After pouring into the mold decomposition tank was measured the number of bubbles generated by the bubble collecting device, which is shown in Table 1 below. On the other hand, if bubbles no longer occur, it was determined that hydrogen peroxide decomposition was completed and the decomposition completion time was confirmed.

Activated Carbon Input Experimental Example 1-1 Experimental Example 1-2 Experimental Example 1-3 Experimental Example 1-4 Experimental Example 1-5 1 g of activated carbon Activated carbon 2g Activated carbon 3g Activated carbon 4g 5 g of activated carbon Elapsed time (hours) Number of bubble generation (pieces / minute) One 7 13 18 24 30 2 8 14 18 21 23 3 8 10 15 20 10 4 6 8 11 13 0 5 4 7 9 7 - 6 4 4 7 6 - 7 3 3 5 3 - 8 2 2 2 0 - 9 2 2 2 - - 10 2 One 2 - - Disassembly completion time (hours) 20 16 11 8 4

Referring to Table 1, it can be seen that the decomposition completion time of hydrogen peroxide is shortened as the amount of activated carbon is increased, and in Experimental Example 1-5, the decomposition completion time is 4 hours. When 1 g of activated carbon was added, the decomposition completion time was 20 hours, and 11 hours were maintained at 2 or less bubbles. Therefore, as the amount of activated carbon increased, it was confirmed that the decomposition time was faster.

Experimental Example 2. Confirmation of heat generation according to the amount of activated carbon

The experiment was carried out to check the exotherm generated in the hydrogen peroxide decomposition process according to the amount of activated carbon prepared in Example 1.

For this experiment, a retention type decomposition tank made of a acid-resistant tank was prepared, and 1 g, 2 g, 3 g, 4 g, and 5 g of activated carbon were prepared in the retention type decomposition tank, respectively, and 100 g of waste sulfate collected in Example 1 was prepared. The temperature change with time after pouring into each retention type digestion tank was measured, and is shown in Table 2 below.

division Activated carbon
input Temperature change When 1 hours 3 hours 5 hours 10 hours Experimental Example 2-1 1 g 24 ℃ 24 ℃ 25 ℃ 26 ℃ 26 ℃ Experimental Example 2-2 2 g 24 ℃ 25 ℃ 26 ℃ 27 ℃ 26 ℃ Experimental Example 2-3 3 g 24 ℃ 25 ℃ 28 ℃ 30 ℃ 30 ℃ Experimental Example 2-4 4 g 24 ℃ 30 ℃ 32 ℃ 34 ℃ - Experimental Example 2-5 5 g 24 ℃ 33 ℃ 35 ℃ - -

Referring to Table 2, Experimental Examples 2-1 to 2-3 represented 30 ° C. or less until the end of the reaction after the addition, and it was confirmed that heat generation was insufficient during the hydrogen peroxide decomposition process, whereas in Experimental Examples 2-4 and 2-5, It was confirmed that the exothermic temperature exceeded 30 ° C. In addition, when 3g or more of activated carbon based on 100g of sulfuric acid was added, sulfuric acid was contaminated due to activated carbon damage during decomposition, and sulfuric acid gas was generated, indicating that the stability was deteriorated.

Determination of the hydrogen peroxide decomposition time carried out in Experimental Example 1 and Experimental Example 2 shows that when the amount of activated carbon is increased, the decomposition time is shortened but the exothermic temperature is also increased. Therefore, simply increasing the amount of activated carbon is less stable in the decomposition of hydrogen peroxide, it can be confirmed that the addition of less activated carbon is not efficient because the hydrogen peroxide decomposition time is too long.

Experimental Example 3 Dividing Activated Carbon Stepwise to Decompose Hydrogen Peroxide

In this experimental example, an experiment was conducted to decompose hydrogen peroxide in waste acid by dividing activated carbon in stages. This experiment was carried out using a continuous digester connected with a retention digester. More specifically, the retention type digestion tank includes a filter device for filtering activated carbon and is made of an acid resistant tank, and is connected to three retention type digestion tanks to continuously supply and discharge spent sulfuric acid. A digestion tank was used. The three staying digestion tanks were digested (1), digested (2) and digested tanks (3), respectively, and the content of activated carbon was added to each digestion tank.

The amount of activated carbon in each cracking tank was 1g for the cracking tank 1, 2g for the cracking tank 2, and 4g for the cracking tank 3, respectively. Then, 100 g of spent sulfuric acid collected in Example 1 was poured into a decomposition tank (1), and after 4 hours of hydrogen peroxide decomposition reaction, the activated carbon was filtered and the spent sulfuric acid of the decomposition tank (1) was moved to the next decomposition tank (2), followed by hydrogen peroxide. The decomposition reaction was carried out. After 4 hours of further reaction in the decomposition tank (2), 4 g of activated carbon was transferred to the decomposition tank (3), where hydrogen peroxide decomposition reaction was performed. The decomposition of hydrogen peroxide in spent sulfuric acid was carried out step by step in the decomposition tank with the activated carbon input differently, and the decomposition time and the temperature change were measured in the same manner as in Experimental Examples 1 and 2, and the results are shown in Tables 3 and 4 below.

division Number of bubble generation (pieces / minute) 1 g of activated carbon
Disassembling tank (1) 2g of activated carbon
Disassembling tank (2) 4g activated carbon
Disassembling tank (3) Initial input 7 1 hours 8 2 hours 8 3 hours 8 4 hours Moved to disintegration tank (2) ⇒ 10 5 hours 9 6 hours 8 7 hours 4 8 hours Moved to digester (3) ⇒ 8 9 hours 2 10 hours 0

division Temperature change Initial input 1 hours 3 hours 6 hours 9 hours Decomposition tank with 1g of activated carbon (1) 24 ℃ 24 ℃ 25 ℃ - - Decomposing tank with 2g of activated carbon (2) - - - 27 ℃ - Decomposing tank with 4g of activated carbon (3) - - - - 30 ℃

Referring to Tables 3 and 4, it can be seen that decomposition was completed within 10 hours when the hydrogen peroxide decomposition in waste acid was divided into three stages. Compared with the decomposition time of hydrogen peroxide of Experimental Examples 1-1 to 1-3, it can be seen that the time is shortened, thereby increasing the amount of activated carbon input at the time when the content of the hydrogen peroxide in the sulfuric acid is lowered during the decomposition. It can be seen that the method can reduce the hydrogen peroxide decomposition time.

On the other hand, hydrogen peroxide decomposition time was not shorter than Experimental Examples 1-4 and 1-5, but sulfuric acid contamination and sulfuric acid gas by activated carbon generated in Experimental Examples 1-4 and 1-5 did not occur in Experimental Example 3, and In addition, the exothermic temperature is also shown below 30 ℃ to confirm that the decomposition of hydrogen peroxide in a stable state, it can be seen that the method of more effectively removing the hydrogen peroxide in waste acid sulfate.

Experimental Example 4 Hydrogen Peroxide Decomposed by Dividing Activated Carbon Impregnated with Iron Oxide Stepwise

In this experimental example, an experiment was conducted to decompose hydrogen peroxide in waste acid sulfate by dividing activated carbon impregnated with iron oxide in stages. The experiment was carried out in the same manner as in Experimental Example 3, but instead of activated carbon, activated carbon impregnated with iron oxide prepared in Example 2 was added, and beaker was changed at intervals of 3 hours after the addition of spent sulfuric acid. The decomposition time and temperature change accordingly are shown in Tables 5 and 6 below.

division Number of bubble generation (pieces / minute) Decomposition tank containing 1 g of activated carbon impregnated with iron oxide (1) Decomposing tank with 2g of activated carbon impregnated with iron oxide (2) Decomposition tank containing 4 g of activated carbon impregnated with iron oxide (3) Initial input 8 1 hours 9 2 hours 8 3 hours Moved to disintegration tank (2) ⇒ 12 4 hours 10 5 hours 9 6 hours Moved to digester (3) ⇒ 9 7 hours 3 8 hours 0 9 hours - 10 hours -

division Temperature change Initial input 1 hours 3 hours 5 hours 7 hours Decomposition tank containing 1 g of activated carbon impregnated with iron oxide (1) 24 ℃ 24 ℃ - - - Decomposing tank with 2g of activated carbon impregnated with iron oxide (2) - - 26 ℃ 26 ℃ - Decomposition tank containing 4 g of activated carbon impregnated with iron oxide (3) - - - - 29 ℃

Referring to Tables 5 and 6, it can be seen that decomposition was completed within 8 hours when the hydrogen peroxide decomposition in spent acid was divided into three stages. Comparing with Experimental Example 3 it can be confirmed that the hydrogen peroxide decomposition time is shorter and the exothermic temperature is also 30 ° C or less, which is more effective. There was no pollution due to the activated carbon damage, and no sulfuric acid gas was generated due to the low exothermic temperature.

Claims (5)

(First step) collecting spent sulfuric acid generated in the semiconductor industry;
(Second step) injecting sulfuric acid into the retention type digestion tank;
(Step 3) Decomposing hydrogen peroxide in the waste acid sulfuric acid by adding activated carbon in the granular form of the specific surface area 500 to 3000 m ² / g to the retention type decomposition tank of the ^second step; And
(4th step) the step of transferring the sulfuric acid in which the hydrogen peroxide decomposition is completed in the third step to the sulfuric acid storage tank through a filtration device in the retention type decomposition tank;
The retention type digestion tank is a continuous digestion tank connecting three digestion tanks, and the continuous digestion tank is a digestion tank containing 0.5 to 1 parts by weight of activated carbon based on 100 parts by weight of spent sulfuric acid, and 1 to 2 parts by weight based on 100 parts by weight of spent sulfuric acid. Method for removing hydrogen peroxide, characterized in that the decomposition tank is added and 2 to 5 parts by weight based on 100 parts by weight of spent sulfuric acid continuously connected. delete delete The method of claim 1,
The method of claim 3, wherein the activated carbon of step 3 is activated carbon impregnated with an iron salt solution and heat-treated to impregnate iron oxide. The method of claim 1,
Decomposing hydrogen peroxide in the spent sulfuric acid of the third step, the hydrogen peroxide removal method characterized in that the exothermic temperature is maintained at 30 ℃ or less when hydrogen peroxide decomposition.

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