JPH11229172A - Method and apparatus for producing high-purity copper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the method and apparatus for electrolytically refining copper by suppressing the deposition of the metals other than copper in the electrolytic copper refining and electrodepositing only high-purity copper. SOLUTION: Copper is dissolved in an aq. hydrochloric acid soln. in an oxidizing atmosphere, the precipitate is filtered off, the soln. is sent to an anode compartment of the two-compartment electrolytic cell with a cation-exchange membrane as the diaphragm, the copper ion is electrolytically sent to the cathode compartment and electrolytically reduced by the cathode through which an oxygen-contg. gas is passed to deposit copper on the cathode, and high-purity copper is produced. This high-purity copper producing apparatus is provided with a means for dissolving copper in hydrochloric acid and adjusting the concn., a means for filtering the filtered copper chloride soln., a means for introducing the filtered soln. into an electrolytic cell divided by a cation-exchange membrane into an anode compartment and a cathode compartment and a means for supplying gaseous oxygen on the cathode surface, and electrolytic copper is formed on the cathode surface. A microfilter is preferably used for the filtration.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for producing ultra-high-purity metals used in fields requiring ultra-high-purity metals, mainly for the field of electronic processing, such as target materials.

[0002]

2. Description of the Related Art Conventionally, copper has been produced in a high purity by producing blister copper by a thermochemical reaction and subjecting it to electrolytic refining. As a result, the purity of wrought copper differs from other metals, at least from 99.9% to 99.99%.
A product of a degree of purity was produced, and the highest-purity metal was conventionally obtained. This has been done because the electrical conductivity of copper, which is a major application field of copper, varies greatly depending on the purity of copper, so that the purity is as high as possible. Since such high purity can be obtained easily, it is necessary to prepare it even when special high purity is required, and to extract high purity parts from it by analysis. A method for easily obtaining a large amount of pure copper has hardly been considered.

However, the use of copper in the field of electronics, wiring for electronic devices, and the like has become conceivable, and it has become necessary to use copper of high purity. In other words, for a target used for PVD, etc., 99.9
Ultra-high purity copper of 99% or more is required. For this purpose, methods such as electrorefining copper that has been electrorefined have been performed, but it has been difficult to achieve high purity. Volatile substances have been removed from electrolytic copper by electron beam melting or the like. However, even with this method, it has been almost impossible to remove impurities such as silver contained in copper.

[0004]

DISCLOSURE OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to suppress the deposition of metals other than copper in the electrolytic refining of copper, and to use only high-purity copper. The purpose of the present invention is to provide an electrolytic copper refining method and a refining apparatus for electrodepositing.

[0005]

SUMMARY OF THE INVENTION In order to electrolytically refine copper, the present invention removes silver deposited at a high potential with hydrochloric acid before dissolving copper in a base metal in an acid, and reduces the electrolytic potential to zero. By holding as described above, it is possible to obtain only high-purity copper by suppressing precipitation of metals such as nickel and iron. That is, the present invention has solved the above-mentioned problems by the following means. (1) After dissolving copper in an aqueous hydrochloric acid solution in an oxidizing atmosphere,
The precipitate is removed by filtration and sent to the anode chamber of a two-chamber electrolytic cell using a cation exchange membrane as a diaphragm, and copper ions are electrolytically sent to the cathode chamber side, and electrolytically reduced at the cathode through an oxygen-containing gas. And depositing copper on the cathode. (2) The method for producing high-purity copper according to (1), wherein the concentration of the aqueous hydrochloric acid solution is 1 to 5 mol.

(3) A means for adjusting the copper concentration by dissolving copper in hydrochloric acid, a means for filtering a copper chloride solution produced by the dissolution, and an anode chamber and a cathode chamber using the filtered copper chloride solution with a cation exchange membrane. A high-purity copper producing apparatus, comprising: means for feeding to a separated electrolytic cell; means for supplying oxygen gas to the cathode surface of the electrolytic cell; and forming electrolytic copper on the cathode surface by electrolysis. . (4) The apparatus for producing high-purity copper according to (3), wherein the dissolution of copper is by contact with chlorine gas. (5) The production of high-purity copper as described in (3) or (4) above, wherein hydrochloric acid is circulated in the anode chamber of the electrolytic cell, and chlorine generated by the electrolysis is sent to a copper dissolving tank. apparatus. (6) The apparatus for producing high-purity copper according to the above (3), wherein the copper is dissolved electrolytically in a hydrochloric acid aqueous solution using a copper ingot as an anode. (7) The apparatus for producing high-purity copper as described in (3) above, wherein the material dissolved in the dissolving tank and converted into copper chloride is passed through a microfilter and then supplied to the anode chamber side of the electrolytic tank. .

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
The potential at which copper is electrolytically deposited is Cu at 25 ° C standard conditions.
²⁺ / Cu (E ₀ = 0.345 V) and Cu ⁺ / Cu
(E ₀ = 0.522 V). In this manner, the metal deposited at the positive potential is bismuth, silver, a platinum group metal, gold, and the like in addition to the copper shown here. Bismuth is Bi ³⁺ / Bi (E ₀ = 0.2 V), and silver is Ag ⁺ / Ag (E ₀ = 0.799 V). To deposit copper by ordinary electrolysis, a cathode potential of 0.345 V
In practice, when there are sufficient copper ions, the potential is maintained at about 0.2 to 0.25 V, although it varies depending on the applied current density, electrolyte conditions, and the like. At this potential, it is conceivable that bismuth deposition and a metal such as silver having a very high deposition potential may occur simultaneously. The present invention has been devised in the electrolysis method so that the electrolysis voltage is automatically maintained at the deposition potential of copper by conducting an actual electrolysis experiment in consideration of these phenomena. As a result, deposition of metals other than copper was substantially eliminated, and only extremely high-purity copper was obtained.

That is, raw copper such as copper ingot is dissolved in hydrochloric acid as a solvent. Hydrochloric acid is reducing and thus hardly dissolves, but by adding chlorine as an oxidizing agent, it can dissolve metals almost stoichiometrically. In the dissolved metal, silver precipitates as insoluble silver chloride, which is removed by a microfilter. When the hydrochloric acid concentration is about 5 mol or less, it is known that bismuth, gold, and other platinum group metals are not formed as bare ions but formed as complex ions. That is, in the ion state, the ions are not positive but negative ions. For this reason, in the liquid containing this complex ion, if a cation exchange membrane is used, the complex ion hardly passes, and has the characteristic that it can be separated from the cation.
If the potential does not go to the negative side, no other metal is deposited. In order not to bring the potential to the negative side, it is sufficient that enough copper ions exist,
In addition, as a countermeasure against the occurrence of a side reaction other than the precipitation of copper, oxygen was reduced so that the potential was not lowered.

That is, reduction of oxygen O ₂ + 2H ₂ O + 4
e ⁻ → 4OH ⁻ (E ₀ = 0.401 V) was used. This reaction is generally known to have a large overvoltage, and apparently has a voltage of about 0.4 V at a practical current density of 10 A / dm ² or more. In addition, it is about 0.2 V at 0.1 to 1 A / dm ² . If this is used, the cathode potential does not fall below zero, so that precipitation of other metals does not occur, so that only high-purity copper can be obtained. Here we use all these properties,
We succeeded in obtaining copper with a high purity of 99.9999% or more.

First, a copper ingot is placed in 3 to 5 mol of hydrochloric acid, and chlorine gas is added to the solution. Then, after the liquid has a slight yellow tint, copper dissolves as copper ions almost stoichiometrically in accordance with the chlorine injection amount. At this time, some of the other metals contained in the base metal precipitate without being dissolved. In addition, silver becomes silver chloride, but the solubility of silver chloride is almost zero, and also precipitates as silver chloride. Bismuth is formed as bismuth chloride ions and partly as undissolved precipitate. Ruthenium, iridium, platinum and the like are also partially converted into precipitates and partially converted into chloride ions.
These chloride ions naturally have a negative charge. Other metals, such as iron, cobalt, and nickel, which are present in small amounts, exist as negative ions as they are, but have a negative deposition potential.

In addition, when dissolving copper, it is possible to electrolytically dissolve copper using a metal as an anode. Also, it goes without saying that dissolution by chlorine and dissolution by electrolysis may be combined. In this way, the hydrochloric acid solution in which the metal mainly composed of copper is dissolved is firstly filtered to remove the precipitate, and then sent to the anode chamber side of the electrolytic cell divided into an anode chamber and a cathode chamber by a cation exchange membrane. Here, the cations move to the cathode chamber side through the cation exchange membrane with energization. Those forming complex ions such as platinum group metals remain in the anode compartment. The anode chamber has an anode. As the anode, an electrode called DSE or DSA in which a so-called valve metal surface such as titanium is coated with a platinum group metal oxide is used.
These electrodes are known to have little dissolution of the electrode material.However, even if they dissolve, they become anions as shown above, so their movement to the cathode compartment is blocked by the cation exchange membrane. In the cathode chamber, almost no metal ions are deposited on the positive potential side. Of course, if it is known in advance that there is no such anion in the electrolyte and that copper of the desired purity can be obtained even if it exists, the electrolyte from the dissolution tank is supplied directly to the cathode chamber. You may. Even in this case, it is necessary to minimize the influence of the elution of the anode by using a cation exchange membrane divided into an anode and a cathode compartment.

Although it is standard to use a pure copper plate as the cathode on the cathode side, a non-metallic gas diffusion electrode can also be used. That is, a semi-hydrophobic gas diffusion electrode made of ordinary carbon and PTFE resin may be used. However, if a metal is used as the electrode material, it causes impurities, so that no metal is used, and at most copper or only carbon is used as the electrode material. When electrolysis is performed while flowing oxygen to the gas diffusion electrode or blowing oxygen to the surface of the copper electrode, the cathode potential is maintained at approximately 0.15 to 0.25 V, and copper is deposited on the surface of the cathode. When metallic copper is used as the cathode, needle-like copper precipitates on the copper surface, and copper deposited on the surface of the gas diffusion electrode accumulates as a precipitate in a lower portion near the electrode. The electrolysis is continued while removing these metals. The precipitate obtained here is 99.999
% Of metallic copper.

In this way, ultra-high-purity metallic copper is deposited.
Sent electrolyte to the adjustment tank again, where the copper concentration is adjusted
At the same time, remove excess chloride complex ions
The solution is sent again to the electrolytic cell. This electrolysis
May be batch or continuous, but the electrolytic current density
Setting too high may entrap other metal ions in the copper metal.
And the current density is 40 A / dm ^TwoBelow,
Flow density 1A / dm^TwoIn the following, the function of the gas diffusion electrode is excellent.
The deposition efficiency of copper may be extremely poor
Therefore, it is necessary to select the current optimally. In addition, acid
Current density of 10 A / dm without supply of element^TwoDo more
And depending on the purity of the electrolyte, slightly
Contamination may occur. This is to supply oxygen
Can be completely prevented. The electrolysis temperature is usually 40
It is not particularly specified that the temperature is in the range of about 80 ° C. to about 80 ° C.

[0014]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited thereto.

Example 1 As a copper ingot, based on electrolytic copper, 1000 pp
An electron beam melted alloy was prepared by adding silver, nickel, cobalt, and iron equivalent to m. The apparent particle size of this metal is 1m
m particles were placed in a titanium basket and placed in a 3 molar aqueous hydrochloric acid solution. This was heated to 40 ° C., and chlorine gas was sent from the bottom of the basket to dissolve the metal. This gives 100
An aqueous hydrochloric acid solution containing g / liter of copper was obtained. Since a black precipitate was formed in the aqueous solution, the black precipitate was opened.
2μm micro filter (membrane filter)
And filtered through. This solution was used as an electrolytic solution and sent to an anode chamber of an electrolytic cell using a cation exchange membrane as a diaphragm. This electrolytic cell is made of PTFE, and is made of Dupont as an ion exchange membrane.
Nafion 115 manufactured by Company t was used. An electrode having a trade name of DSE in which a composite oxide film having a weight ratio of ruthenium oxide and titanium oxide of 45 (ruthenium): 55 (titanium) was formed on an expanded mesh of titanium as an anode so as to be in close contact with the electrode. A punched plate having an apparent aperture ratio of a copper plate of 70% was prepared for the cathode, and oxygen gas was sent to the surface on the side of the ion exchange membrane.

The above-mentioned electrolytic solution was sent to the anode chamber of the electrolytic cell. When electrolysis was performed at a current density of ² A / dm ² , nothing was deposited on the cathode at first, but after the initial electrolysis for about 15 minutes, the catholyte became green and the precipitation of copper started. The deposition was performed in a plate shape containing dendrite-like crystals, and the adhesion to the cathode was not very strong. Although chlorine was generated on the anode side, this chlorine gas was sent to a copper dissolving tank. Further, since the generated chlorine alone is insufficient for dissolving the metal, the shortage was compensated for by chlorine from a small-sized hydrochloric acid electrolyzer. After the metal thus deposited was sufficiently washed with pure water and analyzed, it was found that the metal content was 99.9999% of copper.

Example 2 In the same manner as in Example 1, electrolysis was performed using copper ingot, dissolving the ingot, using it as an anode, and using carbon solidified with PTFE resin as a binder as a cathode. Dissolution of the metal was performed. The current density was 1 A / dm ² on the cathode side. The solution obtained by the above-mentioned dissolution is treated with a 0.2 μm mesh P
After filtration with a TFE resin filter, the mixture was sent to the cathode chamber of the electrolytic cell to perform electrolysis. The current density in the electrolysis was 10 A / dm ² on the cathode surface. The cathode used was a porous gas diffusion electrode composed of carbon black and PTFE resin. The core material of the gas diffusion electrode was a mesh made of high-purity copper, and oxygen gas was supplied from the opposite side of the gas diffusion electrode. When electrolysis was performed in this manner, metal particles were deposited on the surface of the gas diffusion electrode and deposited near the electrode. The metal deposited near this electrode is taken out, washed with pure water,
Further, the resultant was washed with ultrapure water, and was analyzed.
It turned out that it was high purity copper at 999% or more.

[0018]

According to the present invention, the following effects can be obtained. (1) 99.999% easily with relatively simple operation
The above high purity copper is obtained. (2) The production of ordinary high-purity copper required that the copper ingot be already of high purity. In the present invention, however, ordinary copper ingot can provide sufficiently pure copper. (3) Electrolytic deposition occurs, but the current density is relatively high, so the deposition rate is high, and a large amount of high-purity copper can be obtained with a small device. (4) Since the range of electrolysis conditions is wide, high-purity copper can be easily produced.

Claims (7)

[Claims] After dissolving copper in an aqueous hydrochloric acid solution in an oxidizing atmosphere, a precipitate is removed by filtration, and the solution is sent to an anode chamber of a two-chamber electrolytic cell having a cation exchange membrane as a membrane, and the copper ion is electrolyzed. A high purity copper is deposited on the cathode while electrolytic reduction is carried out by feeding the oxygen to the cathode chamber side and electrolytically reducing at the cathode through an oxygen-containing gas. 2. The method according to claim 1, wherein the concentration of the aqueous hydrochloric acid solution is 1 to 5 mol. 3. A means for adjusting the copper concentration by dissolving copper in hydrochloric acid, a means for filtering a copper chloride solution formed by the dissolution, and a step of applying the filtered copper chloride solution to an anode chamber and a cathode chamber with a cation exchange membrane. An apparatus for producing high-purity copper, comprising: means for feeding to a separated electrolytic cell; and means for supplying oxygen gas to the cathode surface of the electrolytic cell, wherein electrolytic copper is formed on the cathode surface by electrolysis. 4. The apparatus for producing high-purity copper according to claim 3, wherein the copper is dissolved by contact with chlorine gas. 5. The high-purity copper as claimed in claim 3, wherein hydrochloric acid is circulated in the anode chamber of the electrolytic cell and chlorine generated by electrolysis is sent to a copper dissolving tank. Manufacturing equipment. 6. The apparatus for producing high-purity copper according to claim 3, wherein the copper is dissolved in a hydrochloric acid aqueous solution using the copper ingot as an anode. 7. The production of high-purity copper according to claim 3, characterized in that the copper chloride dissolved in the dissolving tank is supplied to the anode chamber side of the electrolytic tank after passing through a microfilter. apparatus.