JPH1090212A - Method to detect end point of hydrogen peroxide decomposition reaction and method to collect sulfuric acid from waste liquid employing this detective method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method to detect an end point of hydrogen peroxide decomposition reaction and a method to collect sulfuric acid from waste liquid employing such detective method. SOLUTION: This is a method to detect the reaction end point, when hydrogen peroxide is decomposed and sulfuric acid is formed by introducing sulfurous acid into a solution containing sulfuric acid and hydrogen peroxide and making the hydrogen peroxide react on the sulfurous acid, from a sudden variation of an oxidation-reduction potential measurement occurred at the time reaction termination caused by an oxidation-reduction potential electrode dipped in the solution. By utilizing this method, hydrogen peroxide is decomposed and sulfuric acid is formed by introducing sulfurous acid into a solution containing sulfuric acid and hydrogen peroxide and making the hydrogen peroxide and the sulfurous acid react on each other.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an ORP measurement value obtained by detecting the amount of sulfurous acid added by a redox potential electrode (hereinafter also referred to as an ORP electrode) when recovering sulfuric acid from a waste liquid containing sulfuric acid and hydrogen peroxide. It relates to a method of controlling a sudden change.

[0002]

2. Description of the Related Art Solutions containing sulfuric acid and hydrogen peroxide are frequently used as an etching agent, a surface treatment agent, etc. in the production of semiconductors, the production of printed wiring boards, the resist stripping step, the surface processing of various metals, and the like. Since the solution containing sulfuric acid and hydrogen peroxide (hereinafter sometimes referred to as “sulfuric acid-hydrogen peroxide solution”) contains sulfuric acid and hydrogen peroxide, it is subjected to an acid neutralization treatment with an alkaline agent, It cannot be disposed of without hydrogen removal treatment. Also, in the case where the sulfuric acid contained therein is used variously effectively, the hydrogen peroxide contained in the sulfuric acid-hydrogen peroxide solution is harmful, and it is necessary to remove the hydrogen peroxide.

As a method for removing hydrogen peroxide, a method of decomposing hydrogen peroxide while supplying hydrogen to a hydrogen peroxide decomposition catalyst (Japanese Patent Laid-Open No. 61-186208), an electroless copper plating catalyst (JP-A-3-86298) and a method of decomposing hydrogen peroxide through a waste liquid having a raised temperature to a carbonaceous material (JP-A-5-345188). I have. However, in the method of decomposing hydrogen peroxide while supplying hydrogen to the hydrogen peroxide decomposition catalyst, it is necessary to use extremely flammable hydrogen gas, and there is a problem that the activity of the catalyst is reduced. The method using a catalyst solution for an electroless copper plating catalyst requires a catalyst solution for an electroless copper plating catalyst, and has a problem that it cannot be used when this solution is not available. In the method of decomposing hydrogen peroxide through a waste liquid at an elevated temperature to a carbonaceous substance, there is a risk associated with heating a strongly acidic solution containing hydrogen peroxide, and furthermore, energy for heating is also required. There is a problem.

In order to carry out these methods, it is necessary to measure the concentration of hydrogen peroxide. Conventionally, a capacitance analysis method, a colorimetric analysis method, and an analysis method using an ORP electrode (Japanese Unexamined Patent Application Publication No.
-216544) was known. The analysis method using an ORP electrode has been particularly used in the oxidation-reduction reaction between an aqueous solution containing hydrogen peroxide and a reduced product because the measurement method is simpler than the capacitance analysis method and the colorimetric analysis method. However, for example, JP-A-3-2165 using an ORP electrode utilizing an oxidation-reduction reaction between potassium permanganate and hydrogen peroxide.
In the method described in Japanese Patent No. 44-44, there are many errors due to measurement, and the end point of the reaction cannot be detected accurately.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a measuring method which overcomes the drawbacks of the conventional hydrogen peroxide concentration measuring method, and to use the measuring method to remove sulfuric acid and hydrogen peroxide from a waste liquid. It is to provide a method for recovering sulfuric acid.

[0006]

Means for Solving the Problems The present inventors have made intensive studies to achieve the above object, and as a result, have reached the present invention. That is, the present invention relates to (1) introducing sulfurous acid into a solution containing sulfuric acid and hydrogen peroxide, reacting the hydrogen peroxide with sulfurous acid to decompose hydrogen peroxide and generate sulfuric acid; A method for detecting the end point of the reaction from a sudden change in the measured oxidation-reduction potential at the end of the reaction by a reduction potential electrode, and (2) introducing sulfurous acid into a waste liquid containing sulfuric acid and hydrogen peroxide, With sulfurous acid,
A method for recovering sulfuric acid from a waste liquid containing sulfuric acid and hydrogen peroxide, wherein hydrogen peroxide is decomposed and sulfuric acid is generated, and the end point of the reaction is measured by the method described in (1) above. is there.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In addition to sulfuric acid and hydrogen peroxide, inorganic substances such as heavy metal ions and inorganic salts, and organic substances such as organic acid salts are contained in the aqueous solution and wastewater containing sulfuric acid and hydrogen peroxide which are the object of the present invention. There is no problem if they coexist. The concentration of sulfuric acid in the aqueous solution containing sulfuric acid and hydrogen peroxide and the wastewater is not particularly limited, but is preferably 30% or more. The concentration of hydrogen peroxide in the aqueous solution containing sulfuric acid and hydrogen peroxide and the wastewater is not limited. Examples of the sulfurous acid that can be used in the present invention include sulfurous acid gas, liquid sulfurous acid, and an aqueous solution of sulfurous acid.
The reaction temperature for carrying out the present invention is not particularly limited, but is preferably 0 to 290 ° C. According to the present invention,
Only the hydrogen peroxide in the sulfuric acid and hydrogen peroxide-containing waste liquid can be decomposed and removed, and the treated solution can be reused as a sulfuric acid solution or used for pH adjustment of wastewater treatment. Next, the present invention will be described with reference to examples, but the present invention is not limited thereto.

[0008]

【Example】

Example 1 Liquid temperature 22 ° C., hydrogen peroxide concentration 2.5%, sulfuric acid concentration 85.
100 ml of 0% sulfuric acid and hydrogen peroxide-containing waste liquid is placed in a closed container, and sulfurous acid gas is introduced from the bottom at a flow rate of 100 ml / min, and the residual hydrogen peroxide concentration, sulfuric acid concentration, OR
The P value was measured. Also, the sulfite ion concentration in the solution was measured as necessary. The liquid temperature at the end of the reaction was 47 ° C. The result is shown in FIG.

[0009]

According to the method of the present invention for recovering sulfuric acid from a waste liquid containing sulfuric acid and hydrogen peroxide utilizing the control of sulfurous acid based on the measured ORP value, the waste liquid containing sulfuric acid and hydrogen peroxide which could not be effectively used conventionally. Only hydrogen peroxide in the solution is removed, and the treated solution can be reused as a sulfuric acid solution or effectively used as a pH adjuster for wastewater treatment.

[0010]

[Brief description of the drawings]

FIG. 1 shows the ORP potential and hydrogen peroxide concentration of a solution in which sulfurous acid is introduced into a waste liquid containing sulfuric acid and hydrogen peroxide, the hydrogen peroxide reacts with sulfurous acid to decompose hydrogen peroxide and generate sulfuric acid. Shows the change over time.

Claims (2)

[Claims] 1. An oxidation-reduction potential electrode immersed in a solution containing sulfuric acid and hydrogen peroxide when the sulfuric acid is introduced into the solution and the hydrogen peroxide reacts with the sulfurous acid to decompose the hydrogen peroxide and generate sulfuric acid. A method of detecting the end point of the reaction from a sudden change in the measured value of the oxidation-reduction potential at the end of the reaction. 2. The method according to claim 1, wherein sulfurous acid is introduced into a waste liquid containing sulfuric acid and hydrogen peroxide, and the hydrogen peroxide and sulfurous acid are reacted to decompose hydrogen peroxide and generate sulfuric acid. A method for recovering sulfuric acid from a waste liquid containing sulfuric acid and hydrogen peroxide, which is measured by a method.