JPH01159392A - Production of high purity electrolytic copper - Google Patents

Abstract

PURPOSE:To produce high purity electrolytic copper without requiring a troublesome process by adding and dispersing copper-montmorillonite in an electrolytic soln. acidified with nitric acid, filtering the electrolytic soln. to remove impurities in the soln. and electrolytically refining copper in the resulting electrolytic soln. CONSTITUTION:Copper-montmorillonite is added and dispersed in an electrolytic soln. acidified with nitric acid. After impurity cations in the soln. are adsorbed between the montmorillonite layers, the electrolytic soln. is filtered. The impurity cations in the soln. are efficiently removed and a purified electrolytic soln. is obtd. Copper is electrolytically refined in the purified electrolytic soln. to produce high purity electrolytic copper. The pref. average particle size of the copper-montmorillonite is <=about 10mum and the copper-montmorillonite is desirably added by such an amt. that it has >=about 10mg equiv. cation exchange capacity per 1l electrolytic soln.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing high-purity electrolytic copper, which produces high-purity copper by electrolytic refining.

[Prior Art] Conventionally, electrolytic copper has generally been produced using a sulfuric acid acid bath, and its purity has been at most 99.99 ml. Incidentally, recently, there has been an increasing demand for high-purity copper having a purity of 99.999% by weight or more for applications such as connection conductors for semiconductor devices or source materials for vapor deposition.

In electrolytic refining using a sulfuric acid acid bath, contamination due to sulfur in the electrolyte is unavoidable, so a nitric acid acid bath is often used in the production of high-purity electrolytic copper.

However, similar to the sulfuric acid acid bath, the nitric acid acid bath, as well as the sulfuric acid acid bath, have a tendency to contain cations (Na"), which have a greater ionization tendency than Cu, in the electrolytic solution as the amount of electrolytic copper collected increases through repeated electrolytic refining.
, AJI'', Fe20, etc.) or slime suspended as fine particles.

This increase in impurities in the electrolyte is a major factor that hinders the high purity of electrolytic copper, so either add new electrolyte to prevent the amount of impurities from exceeding a certain concentration, or adjust the amount of impurities in the electrolyte. It is necessary to remove impurities.

However, the method of adjusting the impurity concentration by adding new electrolytic solution has a problem in that waste liquid is generated in proportion to the amount of new electrolyte added, and the treatment of this waste liquid is complicated. Furthermore, since it is necessary to constantly prepare and replenish a considerable amount of new electrolyte, there is also the problem that the replenishment process for this electrolyte is complicated.

On the other hand, as a method for removing impurities in an electrolytic solution, there is a conventional solution purification method whose flow of the electrolytic solution is shown in FIG.

In other words, as shown in FIG. 3, first, the electrolytic solution transferred from the electrolytic bath 1 to the circulating bath 2 is subjected to decopper removal electrolytic treatment 3, and then impurity cations are removed by purified liquid electrolytic treatment 4. . The cleaning liquid 5 is then returned to the circulation bath 2 and further supplied to the electrolytic bath 1.

[Problems to be solved by the invention] However, in this conventional method, impurity cations are removed by electrowinning (purifying solution electrolysis treatment 4), but at this time, copper precipitates before impurities. ,
It becomes necessary to lower the copper concentration in advance (copper removal electrolytic treatment 3). Therefore, the clean electrolyte 5 after the liquid purification treatment has a lower copper concentration and contains excess free nitric acid than the electrolyte in the electrolytic bath 1 or the circulating bath 2.

This free nitric acid has the problem of eluting electrolytic copper deposited on the cathode. In order to avoid such problems, the concentration of free nitric acid should be adjusted and the P of the clean electrolyte should be adjusted.
Since it is necessary to make H the same level as the pH of the circulating bath liquid, complicated processing is required.

Furthermore, since slime suspended as an impurity is conventionally removed by a filter, there is a problem in that slime particles smaller than the opening of the filter are not removed and continue to remain in the electrolyte.

The present invention has been made in view of such problems, and includes:
Purity is 99.999 by electrolytic refining using nitric acid bath.
It is an object of the present invention to provide a method for producing high-purity electrolytic copper, which can produce high-purity electrolytic copper of % by weight or more without requiring complicated steps.

[Means for Solving the Problems] The method for producing high-purity electrolytic copper according to the present invention includes adding and dispersing Cu-montmorillonite in a nitric acid acidic electrolyte, and then filtering the electrolyte. It is characterized by removing impurities in the electrolyte and then electrolytically refining copper.

[Function] In the present invention, impurity cations in the electrolyte are adsorbed between the montmorillonite layers by adding and dispersing Cu-montmorillonite in a nitric acidic electrolyte. Next, when this electrolytic solution is filtered, impurities in the electrolytic solution are removed, and an extremely clean electrolytic solution can be easily obtained. By electrolytically refining copper using this electrolytic solution, high purity electrolytic copper with a purity of 99.999% by weight or more can be obtained.

[Example] Hereinafter, an example of the present invention will be specifically described with reference to the accompanying drawings.

FIG. 1 is a process flow diagram showing an example method of the present invention, and arrows indicate the flow of the electrolyte. The electrolytic solution is circulated between an electrolytic bath 1 and a circulating bath 2, and a part of the electrolytic solution is supplied from the circulating bath 2 to the Cu-montmorillonite addition and dispersion treatment 6. In this process 6, Cu-montmorillonite is added and dispersed in the electrolytic solution, and impurities are adsorbed in the Cu-montmorillonite. Next, the electrolyte is subjected to filtration treatment 7.
The cleaning liquid 5 is filtered to remove impurities together with Cu-montmorillonite, and the cleaning liquid 5 is returned to the circulation bath 2. In this way, a certain amount of the electrolyte is always extracted from the circulating bath 2 and subjected to cleaning treatment, so the impurity concentration of the electrolyte in the electrolyte bath 1 does not rise above a certain amount, and this electrolyte is By using this method, high purity electrolytic copper having a purity of 99.999% by weight or more can be repeatedly produced.

Cu-montmorillonite has a chemical structure shown in the chemical formula (1) below, and has the exchangeable cation in the layered structure shown in FIG. 2 replaced with Cu and 2+.

[(○I() 4 S ia (A!29,4Mgo
, 66) 020] 066-・Cu” o, 33-
- (1) In Figure 2, A is hydroxyl group, B is silicon,
C is oxygen, D is aluminum (partially magnesium), and E is an exchangeable cation. The position of this exchangeable cation E between the eyebrows is not necessarily fixed.

In this Cu-montmorillonite, even in an acidic aqueous solution, Cu 2+ between the eyebrows has the ability to exchange with other cations. Therefore, the impurity cations M''(Na'', A
11'', Fe 2+, etc.), the cation exchange reaction shown in the following formula (2) occurs.

[(OH) 4 S is (Aj?3.34Mgo
, 66) 020] "66- ・cuo, 332+ +
o, 66M”-[(OH)4S is (
A-R3,s4Mgo,6a)020] ”66-・
Mo, 66"+0.33Cu" (2) Through this cation exchange reaction, many impurity cations are adsorbed between the montmorillonite layers.

Therefore, when this electrolytic solution is filtered, impurities in the electrolytic solution are removed together with montmorillonite, and the electrolytic solution is purified.

Furthermore, since this reaction is an exchange reaction between cations and there is no change in the number of cation equivalents in the electrolyte, no new free nitric acid is generated by the cation exchange reaction. Therefore, there is virtually no change in pH.

Since Cu-montmorillonite is colloidally dispersed as fine particles in an acidic aqueous solution, it has a large specific surface area and can physically adsorb fine slime whose particle size is even smaller than Cu-montmorillonite itself. When this Cu-montmorillonite is recovered from the electrolytic solution by filtration treatment, this fine slime is also removed.

The Cu-montmorillonite particle size is preferably 10 μm or less. If this particle size is larger than 10 μm,
The specific surface area of Cu-montmorillonite dispersed in the electrolytic solution becomes small, and the adsorption function of impurity cations and fine slime decreases.

The amount of Cu-montmorillonite added is 1 part of electrolyte (1 part per part)
It is preferable to use one having a cation exchange capacity of 0 mg equivalent or more. This is because if the cation exchange capacity is lower than 10 mg equivalent, the ability to adsorb impurity cations is small and a desired clean electrolyte solution cannot be obtained.

Next, Examples 1 to 6 in which high-purity electrolytic steel was manufactured by cleaning the electrolyte by the method of the present invention will be described together with Comparative Examples 1 and 2. Table 1 below shows the composition of the nitric acid acid bath electrolyte after repeated electrolytic refining. To this electrolytic solution, under the conditions shown in Table 2 above, Cu-montmorillonite having a cation exchange capacity of 1 (milliequivalent/g) was added and dispersed, and then filtered to remove impurity cations. .

Table 1, Table 2, and Table 3 below show the amount of impurity cations contained in the electrolyte after this treatment. Then, using the electrolytic solution after this cleaning treatment, copper was electrolytically refined under conditions of a current density of 0.7 A/dm2 and an electrolytic time of 100 hours. The measurement results of the residual resistance ratio (RRR) of the obtained electrolytic copper are also shown in Table 3 above.

Table 3 RRR shows the ratio of the electrical resistivity ρ4.2 of 4.2 to the electrical resistivity ρ293 of 293. It is expressed as /ρ4.2 and is used as a comprehensive indicator of purity in boat fishing. The larger the value of this RRR, the higher the purity;
When R exceeds 1000, it can be considered to have a purity of 99.999% by weight class.

As can be seen from Table 3, in Examples 1 to 6, the content of impurity cations in the electrolytic solution is extremely small, and the removal effect is remarkable. Therefore, highly pure electrolytic copper can be obtained by electrolytic refining.

In particular, as in Examples 1 to 4, the average particle diameter of Cu montmorillonite is 10 μm or less, and the amount added is 10 g #
or more (one that can obtain a cation exchange capacity of 10 mg equivalent or more), an extremely high RRR value of 1400 or more can be obtained.

As described above, according to the present invention, high purity copper of 99.999% by weight or more can be obtained through a simple process. On the other hand, in the case of Comparative Examples 1 and 2, the RRR is low and high purity electrolytic copper cannot be obtained.

[Effects of the Invention] As explained above, according to the present invention, preferably Cu-
Montmorillonite is added to obtain cation exchange of 10 mg equivalent or more, and this Cu-montmorillonite is dispersed and then filtered, so impurity cations in the electrolyte can be removed with high efficiency, resulting in a clean solution. An electrolyte can be obtained. Therefore, by electrolytically refining in this electrolytic solution, high purity electrolytic copper having a purity of 99.999% by weight or more can be repeatedly produced.

[Brief explanation of the drawing]

- Figure 1 is a process flow diagram showing an example method of the present invention,
Figure 2 shows the structure of Cu-montmorillonite, Figure 3
The figure is a process flow diagram showing a conventional method.

Claims (3)

[Claims] (1) After Cu-montmorillonite is added and dispersed in a nitric acid acidic electrolyte, impurities in the electrolyte are removed by filtering the electrolyte, and then copper is electrolytically refined. A method for producing high-purity electrolytic copper. (2) The average particle diameter of the Cu-montmorillonite is 1
Claim 1 characterized in that it is 0 μm or less
A method for producing high-purity electrolytic copper as described in . (3) The amount of Cu-montmorillonite added is 1 liter of electrolyte.
2. The method for producing high-purity electrolytic copper according to claim 1, which has a cation exchange capacity of 10 mg equivalent or more per copper.