JP3158684B2 - Copper electrorefining method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for electrolytically refining copper, and more particularly to a method for producing electrolytic copper having few pinholes.

[0002]

2. Description of the Related Art A pinhole made of electrolytic copper means that bubbles generated by air in a liquid or gas during electrolysis adhere to the cathode surface, and copper is electrodeposited directly around the cathode. Without electrodeposition, about 3 mm in diameter as shown in FIG. 1,
A hole having a depth of about 10 mm is left. Since the electrolytic solution remains in the pinholes to increase the sulfur content of the electrolytic copper and deteriorate the appearance of the product, it is desirable that the electrolytic solution be as small as possible.

[0003] It is considered that the cause of the formation of bubbles that cause this pinhole is mainly due to the circulation pump of the electrolyte or the entrainment of air in the circulation tank, but it has not been clearly determined, and the pump may be adjusted from time to time. , Adjustment of liquid supply, supply,
Various measures such as adjustment of the drainage temperature were performed. In particular, in electrolysis at a high current density of 240 amperes / m ² or more, the copper concentration in the electrolyte must be increased in order to prevent the supply of copper ions on the cathode surface from being insufficient. As a result, the viscosity of the electrolytic solution was increased, bubbles attached to the cathode surface were hardly separated, and pinholes of electrolytic copper tended to increase.

[0004] In general, it has been proposed to add a special organic additive to smooth the surface of electrolytic copper (for example, Japanese Patent Publication No. 61-33918), but the problem is that the organic additive is expensive. There was a point.

[0005]

SUMMARY OF THE INVENTION The present invention relates to a copper electrolysis method in which pinholes are generated on the surface of electrolytic copper particularly under electrolytic conditions having a high current density, and thereby the S content of the electrolytic copper is not significantly increased. The aim is to propose a purification method.

[0006]

The copper electrorefining method according to the present invention is a copper electrolysis method having a current density of 240 amperes / m ² or more, in which the electrolytic temperature and the amount of organic additives are kept constant and the copper concentration of the electrolytic solution is kept constant. , Sulfuric acid concentration and nickel concentration are adjusted so that the specific gravity of the electrolyte is 1.250 to 1.
263.

[0007]

As described above, the pinhole of electrolytic copper occurs because bubbles in the electrolytic solution are unlikely to separate from the cathode surface, and thus the viscosity of the electrolytic solution is considered to have a large effect. It is difficult to measure the current continuously and with high accuracy.
At 60 amps / m ² , the electrolyte temperature (61.5 ° C.) and the organic additives (paste 80 g / electrodeposited copper ton, thiourea 7
0g / copper ton and 20g of avidone / copper ton) were measured under a constant electrolysis condition, and the relationship with the pinhole occurrence rate was investigated. Invented the invention.

If the specific gravity of the electrolytic solution exceeds 1.263, the pinhole occurrence rate of electrolytic copper increases, and
If the value is less than 50, the specific gravity of the electrolytic solution must be considerably adjusted in order to reduce the specific gravity of the electrolytic solution, which is not economical. Therefore, the specific gravity of the electrolytic solution must be 1.250 to 1.263. is there.

If the electrolysis temperature and the type and amount of the organic additive are changed during the operation, the relationship shown in FIG. 2 is greatly deviated. Therefore, it is necessary to keep the electrolysis temperature and the organic additive amount constant.

The electrolysis temperature and the type and amount of the organic additive may be selected so as not to cause a problem in ordinary electrolysis, but appropriate values are as follows: electrolysis temperature of 60 to 65 ° C., glue of 50 to 100 g / electrodeposition. Copper ton, thiourea 50-10
0 g / ton of electrodeposited copper and 10 to 30 g of Aviton / ton of electrodeposited copper.

The specific gravity of the electrolytic solution is adjusted by changing the copper concentration, sulfuric acid concentration, and nickel concentration of the electrolytic solution. The copper concentration of the electrolytic solution is determined by removing excessively chemically soluble copper from the anode. The degree of removal from the electrolytic solution is adjusted by an electrolytic method or the like. The nickel concentration of the electrolytic solution is adjusted so as to remove nickel from the electrolytic solution as nickel sulfate by an electric evaporation method or the like. The concentration of sulfuric acid in the electrolyte is adjusted by adjusting the amount of sulfuric acid to be added.

The specific gravity of the electrolytic solution may be adjusted by adjusting any of the copper concentration, sulfuric acid concentration and nickel concentration of the electrolytic solution.
It is preferable to select the conditions that are usually performed so as not to deteriorate the state of electrolysis. The copper concentration of the electrolytic solution is desirably 47 to 51 g / l in electrolysis at a high current density as in the present invention. A higher sulfuric acid concentration in the electrolytic solution is preferable because the bath resistance of the electrolytic solution is reduced. However, an excessively high concentration may cause passivation of the anode or deteriorate the quality of electrolytic copper, and is therefore preferably 150 to 210 g / l. The higher the nickel concentration of the electrolyte, the higher the bath resistance of the electrolyte and the risk of crystallization of nickel sulfate crystals, which may cause problems such as scaling. The lower the better, the better. The target anode quality, the purification cost and the like are not clear because they vary depending on each electrolysis facility, but 17 to 23 g / l is desirable.

[0013]

EXAMPLE An electrolysis was performed under the following conditions using an anode obtained by casting in a refining furnace and casting on a turntable and a cathode obtained by seed plate electrolysis. In each test (the test period is one month each), the concentration of copper, sulfuric acid, and nickel in the electrolyte were adjusted so that the electrolysis temperature and the type and amount of the organic additive were constant and the specific gravity of the electrolyte was the target value. Was adjusted. Table 1 shows the results of the composition of the electrolytic solution, the specific gravity (all are average values for one month), and the pinhole occurrence rate of electrolytic copper.

Electrolysis conditions Electrolysis temperature 61.5 ° C. ± 0.5 ° C. Organic additive addition amount 80 g / electrodeposited copper ton thiourea 70 g / electrodeposited copper ton Aviton 20 g / electrodeposited copper ton Current density 260 amps / m ² Electrolytic cell dimensions 5.6m × 1.25m × 1.4m Number of cells 256 Anode number 50 / cell Grade Cu 99.2%, Ni 0.1 ~ 0.3% Dimensions 1.04m × 1.03m × 35cm Weight 370kg Number 51 sheets / bath Cathode dimensions 1.07m × 1.03m × 0.7cm Weight 6.6kg Electrolytic copper output 6000 tons / month Distance between poles 105mm

[0015]

[Table 1]

In Table 1, the specific gravity is a value measured at a temperature of 57 to 62 ° C. by using a floating-type hydrometer, and the pinhole generation rate means that 10 or more pinholes are generated in one piece of electrolytic copper. It shows the ratio of the total number of sheets.

For comparison, Table 1 shows the results of a test in which the specific gravity of the electrolytic solution was outside the scope of the claims of the present invention under the same electrolytic conditions as in the examples.

From the results shown in Table 1, it can be seen that when the specific gravity of the electrolytic solution is outside the scope of the present invention, the pinhole occurrence rate of electrolytic copper is high.

[0019]

As described above, according to the present invention, the number of pinholes in electrolytic copper is drastically reduced, electrolytic copper without pinholes can be stably produced, and the quality of electrolytic copper can be improved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an electrolytic copper showing a state of a pinhole of the electrolytic copper.

FIG. 2 is a graph showing the relationship between the specific gravity of an electrolytic solution and the incidence of pinholes.

[Explanation of symbols]

 1. Electroplated copper 2. Seed plate 3. Pinhole

Claims (1)

(57) [Claims] In a copper electrolysis method having a current density of 240 amps / m ² or more, the electrolysis temperature and the amount of organic additives added are kept constant, and one or more of the copper concentration, sulfuric acid concentration and nickel concentration of the electrolytic solution are adjusted. The specific gravity of the electrolyte is 1.25
A copper electrorefining method characterized by being 0 to 1.263.