JPS6332872B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to an electrolytic refining method for copper using an acidic copper sulfate solution as an electrolyte, and is particularly applicable to reducing electric power consumption and producing electrolytic copper with a smooth and dense surface and low sulfur content. It is for the purpose of [Prior art] For electrolytic refining of copper, an acidic copper sulfate solution containing 40 to 55 g of copper and 100 to 220 g of free sulfuric acid is usually used as an electrolyte, and blister copper with a purity of about 99% is used as an anode.
Using a thin plate of pure copper, titanium or stainless steel as the cathode, liquid temperature 40-70℃, current density 1-5A/d.
A method of purification is used by electrolyzing with m ² and depositing electrolytic copper on the cathode. In such electrolytic refining of copper, various improvements and innovations have been made in order to obtain high-quality electrolytic copper with high productivity. One of the most important issues is to make the copper crystals deposited on the cathode finer and create electrolytic copper with a smooth and beautiful surface. In coarse crystals, electrolyte remains at the grain boundaries, degrading the quality of electrolytic copper. If this is particularly severe, bumps and resin-like protrusions occur, and when they reach the anode surface, they cause electrical short circuits and reduce the power supply. Not only does this cause loss, but it also captures slime that falls from the anode surface, causing a significant deterioration in the quality of electrolytic copper. To prevent this,
Various organic substances are added to the electrolyte in order to make the precipitated crystals finer. For example, by adding one or more of thiourea, polyvinyl alcohol, and aliphatic sulfonated substances, especially both glue and thiourea, together with glue and its similar substances such as casein and gelatin to an acidic copper sulfate solution, the surface manufactures smooth and beautiful electrolytic copper. [Problem to be solved by the invention] During various processing, electrolytic copper was melted in a reverberatory furnace with a desulfurizing effect, but recently electric furnaces, shaft furnaces, etc. have been used instead of reverberatory furnaces. The amount of sulfur contained in electrolytic copper has become a problem. Furthermore, in view of recent energy conservation efforts, it is desired to reduce power consumption. The eutectoid of sulfur into electrolytic copper is caused by contamination of precipitated grain boundaries with sulfuric acid radicals in the electrolyte;
The other one is due to the sulfidation of precipitated copper due to the reduction of thiourea, one of the additives. In electrolytic copper, which has a smooth and dense surface, contamination by the former is several ppm, but in the latter, it depends on the amount added, but it is usually as high as around 10 ppm, which does not meet the requirement for low sulfur, for example 5 ppm.
Reducing the amount of thiourea added is effective in reducing the amount of sulfur contained, but it not only causes deterioration in the appearance of electrolytic copper, but also
In severe cases, a short circuit occurs between the anode and the cathode as described above, resulting in an increase in power consumption due to a decrease in current efficiency. On the other hand, it is well known that many additives significantly increase electrode polarization, especially cathode polarization, during electrolysis, and when glue and thiourea are used together, the voltage often reaches 20-30% of the cell voltage, which reduces power consumption. This improvement is desired from above. [Means for Solving the Problems] In view of this, the present invention has developed, as a result of various studies, an electrolytic refining method for copper that can reduce power consumption and obtain electrolytic copper with a smooth and dense surface and a low content of sulfur. In the electrolytic refining of copper, in which pure copper is deposited on the cathode by electrolyzing blister copper as an anode in an acidic copper sulfate solution, an aqueous aromatic azo compound is added to the acidic copper sulfate solution together with glue or glue and thiourea. It is characterized in that it is added and electrolyzed. That is, the present invention adds glue (casein, which is a similar substance,
A water-soluble aromatic azo compound is added to an acidic copper sulfate solution containing thiourea (containing gelatin, etc.) or glue, and copper is electrolyzed. A part of the ring is azo-bonded, and the aromatic ring may be a benzene ring or a naphthalene ring, and is a water-soluble compound substituted with a hydroxyl group, an amino group, a sulfonic acid, a carboxylic acid, etc. Generally, it is often used as a dye because it has a unique color. For example, basic dyes such as Bismarck Brown, Jenas Brown, Cachilon Pink, Diamond Green, Aniline Yellow, and Jenas Thread, acidic dyes such as Methyl Orange,
Metanyl Yellow, Fast Stretched, Victoria Blue Black, Naphthol Blue Black, etc.
There are mordants such as Diamond Black and Eriochrome Black T, direct dyes such as Congo Red, Diamine Black, and Brilliant Yellow, and even food-grade dyes. However, disperse dyes, which are insoluble dyes, are not included. [Function] When added to the conventionally used acidic copper sulfate solution, any of these water-soluble aromatic azo compounds exhibits a smoothing effect on deposited copper, making it possible to obtain electrolytic copper with a smooth and dense surface. Not only that, but the sulfur content is reduced to 5 ppm or less, and the polarization during electrolysis is reduced to 15 to 20 m.
V, it is possible to reduce the cell voltage by nearly 10%.
The amount added to the acidic copper sulfate solution is based on the concentration in the solution.
The amount is 0.1 to 100 ppm, preferably 0.5 to 5 ppm, and should be added at a rate of 5 to 100 g, preferably 15 to 50 g per 1 ton of deposited copper. Even if the amount added is increased, the effect will be saturated. In particular, when a water-soluble aromatic azo compound is added to an acidic copper sulfate solution to which conventional glue or its similar substances such as casein, gelatin, etc. or glue and thiourea have been added, it exhibits a better smoothing effect on deposited copper. The increase in cathode polarization caused by the addition of conventional additives such as glue does not occur at all, and on the contrary, the above-mentioned polarization lowering effect is maintained. Although the mechanism of this unique effect caused by the addition of water-soluble aromatic azo compounds is only a matter of speculation, the azo group in the molecule interacts with the copper ions on the copper surface and near the electrode, resulting in the formation of dense copper. It is thought that this makes it possible to precipitate in a depolarized manner. In addition, this compound does not contain sulfur, especially the active and easily reducible form of sulfur, in its molecule.
Not only does it not become a source of sulfur contamination like conventional thiourea, but it is thought that even if a small amount of active sulfur compounds such as thiourea coexist, the depolarization effect can effectively suppress the contamination and eutectoid. . Examples of the present invention will be described below. Example 1 Approximately 40 electrolytic cells were filled with 40 g of copper and free sulfuric acid.
An acidic copper sulfate solution with a concentration of 180 g/min and a liquid temperature of 60°C was refluxed at a rate of about 2.5/min, and
Three blister copper plates with a length of 300 mm and four pure copper thin plates of the same size are arranged alternately at a pitch of 100 mm, the blister copper plate is used as an anode, the pure copper thin plate is used as a cathode, and the current density is 2 A/dm ² at the cathode base. It was electrolyzed. The electrolysis process was repeated twice by removing the cathode (electrolytic copper) every 10 days and replacing it with a pure copper thin plate. When electrolyzing, add 50% glue per deposited copper.
g/T and the predetermined amounts of additives shown in Table 1 were added continuously. The results are shown in Table 2.

【table】

【table】

〔Effect of the invention〕

As described above, according to the present invention, in the electrolytic refining of copper, electrolytic copper with a smooth and dense surface and low sulfur content can be easily obtained, and power consumption can be reduced, resulting in a remarkable industrial effect. It is.

Claims (1)

[Claims] 1 In electrolytic refining of copper, in which pure copper is deposited on the cathode by electrolyzing blister copper as an anode in an acidic copper sulfate solution, a water-soluble aromatic azo compound is added to the acidic copper sulfate solution along with glue or glue and thiourea. A copper electrolytic refining method characterized by electrolysis.