JP2003073878A - Treatment method of waste copper sulfate solution by electrolysis - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a waste copper sulfate liquid containing copper, sulfuric acid and hydrogen peroxide as main components under a simple facility and with an efficient method for a hydrogen peroxide contained in the liquid. Decomposition and recovery of metallic copper are performed simultaneously. SOLUTION: An electrolytic cell is divided into an anode side and a cathode side by a diaphragm, a copper sulfate solution containing hydrogen peroxide is supplied to the anode side, and a copper sulfate solution containing no hydrogen peroxide is supplied to the cathode side. By electrolysis, decomposition of hydrogen peroxide is performed at the anode, and metal copper is recovered at the cathode.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method of decomposing hydrogen peroxide from a waste copper sulfate solution discharged in sulfuric acid / hydrogen peroxide etching which is a manufacturing process of a printed circuit board, and electrolytically recovering copper to remove the waste. The present invention relates to a method for treating a copper sulfate solution.

[0002]

2. Description of the Related Art In the process of manufacturing a printed circuit board, unnecessary parts of copper are dissolved and removed by a chemical reaction with an etching solution to form a desired electric circuit pattern. When this etching process is performed, the copper concentration in the etching solution gradually increases and the etching performance decreases, so an etching solution with a copper concentration exceeding a certain value is replaced with a new etching solution to continue etching. Must be replaced. For this reason, the exchanged etching liquid becomes a waste liquid, and in the past, it was the actual situation that a waste liquid treatment company was requested to perform the treatment.

In order to remove the copper component in the sulfuric acid solution, there is known a neutralization coagulation method in which an alkali is added to convert copper into hydroxide, which is precipitated with a coagulant and separated by filtration. However, a large amount of chemical liquid is consumed and copper cannot be recovered as a resource.

When copper is electrolyzed to recover copper, electricity is used to deposit copper at the cathode, but when hydrogen peroxide coexists, it is higher than copper deposition, depending on the concentration of each component on the cathode side. Since the decomposition of hydrogen oxide occurs at a noble potential, the current efficiency of copper deposition at the cathode is reduced. On the other hand, at the anode, electricity is used to generate oxygen by electrolysis of water, which is useless in the process. Further, since hydrogen peroxide contained in the sulfuric acid / hydrogen peroxide etching solution becomes unstable in the presence of copper, a decomposition inhibitor of hydrogen peroxide called a stabilizer is usually added. Therefore, decomposition of hydrogen peroxide in the copper sulfate solution by aeration or addition of chemicals takes time and is difficult.

[0005]

Therefore, the present invention is directed to copper,
A method for simultaneously decomposing hydrogen peroxide contained in the waste copper sulfate liquid containing sulfuric acid and hydrogen peroxide as a main component and efficiently recovering the copper metal under simple equipment and with an efficient method The challenge is to provide.

[0006]

[Means for Solving the Problems] When a copper sulfate solution containing hydrogen peroxide is electrolyzed in an electrolytic cell that does not use a diaphragm, it depends on the concentration of each component on the cathode side, but peroxidation rather than copper precipitation. Since the decomposition of hydrogen occurs at a noble potential, the decomposition of hydrogen peroxide occurs first. Further, hydrogen peroxide also acts as a reducing agent, so that it decomposes even on the anode side. When copper is used as an electrode material in a copper sulfate solution containing hydrogen peroxide, a trace amount of the electrode itself or the deposited copper is dissolved.

After the decomposition of hydrogen peroxide, the deposition of copper starts at the cathode. At that time, electricity is wasted at the anode to generate oxygen by electrolysis of water. In order to solve the above problems, the electrolytic cell is divided into the anode side and the cathode side with a diaphragm, the copper sulfate solution containing hydrogen peroxide is supplied to the anode side, and the copper sulfate solution containing no hydrogen peroxide is supplied to the cathode side. The present invention has been completed by discovering that hydrogen peroxide can be decomposed at the anode and metallic copper can be recovered at the cathode at the same time by supplying and electrolyzing.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below in detail based on specific examples. Copper sulfate waste liquid containing hydrogen peroxide 22
5 liters was received in the anolyte tank 1, and the anolyte supply pump 2 was intermittently operated to supply it to the anode side 6 of the electrolytic cell 3 partitioned by the diaphragm 4. The liquid supplied to the anode side of the electrolytic cell is returned to the anolyte tank 1 via the anolyte overflow line 7, and the liquid is always circulating. Cu, SO ₄ , H in the copper sulfate waste liquid on the anode side
The initial concentrations of ₂ O ₂ are 23.1, 167, and 25.7 g, respectively.
/ Liter.

On the other hand, 225 liters of copper sulfate solution containing no hydrogen peroxide is stored in the catholyte tank 9, and is supplied to the cathode side 12 of the electrolytic cell 3 by intermittently operating the catholyte supply pump 10. . Similarly, the liquid supplied to the cathode side of the electrolytic cell is also returned to the catholyte tank 9 through the catholyte overflow line 13, and the liquid is always circulating. The initial concentrations of Cu and SO ₄ in the copper sulfate solution on the cathode side were 24.9 and 239 g / liter, respectively.

An insoluble electrode in which titanium is coated with iridium was used as the anode 5, and a copper electrode was used as the cathode 11. While circulating the liquid of both electrodes, a current of 500 A was applied to the anode 5 and the cathode 11 by the rectifier 14 to perform electrolysis.
Immediately after the start of electrolysis, decomposition of hydrogen peroxide occurs at the anode,
The hydrogen peroxide concentration on the anode side gradually decreases. on the other hand,
In the cathode, copper contained on the cathode side and copper, which is a trace amount and moves from the anode side through the diaphragm, are deposited as metallic copper on the cathode, whereby the copper concentration on the cathode side gradually decreases. Go. Further, since the precipitation of copper occurs from the start of electrolysis, the copper electrode was not dissolved.

During the electrolysis, the temperature of the liquid is detected by the temperature sensors 15, 16
The liquid temperature was kept below 50 ° C. by operating a cooler (not shown) when the liquid temperature exceeded 50 ° C.

On the anode side, 99.9% of the hydrogen peroxide contained in the liquid initially received was decomposed 14 hours after the start of electrolysis. The final Cu, SO ₄ , and H ₂ O ₂ concentrations on the anode side were 23.5, 185, and 0.01 g / liter, respectively.

On the cathode side, 14 hours after the start of electrolysis, 99.5% of the copper contained in the initial catholyte tank liquid was recovered. The current efficiency of copper deposition during this period was 67.6% on average because the efficiency was lower than that of copper concentration of about 1 g / liter or less. The final Cu and SO ₄ concentrations on the cathode side are each 0.1
It was 27,228 g / liter. It took 11 hours from the start of electrolysis to reduce the copper concentration on the cathode side to 1.29 g / liter, and the current efficiency was about 81.6% on average.

The sulfuric acid solution on the cathode side after decoppering can be used as sulfuric acid for the etching step, and can be used in other than the etching step. The liquid on the anode side is sent to the catholyte tank 9 and the cathode side 12 by switching the valve 8 and receives a new copper sulfate waste liquid, whereby the same electrolytic treatment as described above can be performed.

In the above-mentioned embodiment, the method according to the invention is carried out by electrolysis of a flat plate, but it is not particularly limited as long as it is an electrolytic mode in which the cathode side and the anode side can be separated by a diaphragm. It is particularly preferable to use a so-called barrel electrolysis cell in which a flowing cathode pellet is contained in a rotating barrel body and electrolytically collected as shown.

[Brief description of drawings]

1 is a schematic diagram of an installation for implementing the method according to the invention.

FIG. 2 is a schematic view of a barrel electrolyzer.

[Explanation of symbols]

1 Anolyte tank 2 Anolyte delivery pump 3 electrolysis tank 4 diaphragm 5 anode 6 Anode side 7 Anolyte overflow line 8 switching valve 9 Catholyte tank 10 Catholyte delivery pump 11 cathode 12 cathode side 13 Catholyte overflow line 14 Rectifier 15, 16 Temperature sensor

Claims (4)

[Claims] 1. An aqueous solution containing copper, sulfuric acid, and hydrogen peroxide as main components on the anode side of an electrolytic cell having a diaphragm, and copper on the cathode side.
A method for treating a waste copper sulfate solution, characterized in that an aqueous solution containing sulfuric acid as a main component is supplied for electrolysis to decompose hydrogen peroxide on the anode side and recover copper on the cathode side at the same time. 2. The treatment method according to claim 1, wherein copper is recovered by supplying a liquid obtained by decomposing hydrogen peroxide on the anode side to the cathode side. 3. The processing method according to claim 1, wherein a copper electrode is used as the cathode material. 4. The treatment method according to claim 1, wherein an electrolytic cell of a type in which a cathode is put in a rotary container and electrolyzed is used as the electrolytic cell.