JP7089862B2 - Copper electrorefining method - Google Patents

Description

Application of Article 30, Paragraph 2 of the Patent Law 1. 2017 Special Study Group, Rare Metal Study Group, Donation Unit Special Symposium, "Symposium on Minor Metals in Non-Iron Smelting" sponsored by the Institute of Industrial Science, JX Metals Co., Ltd. Technology Development Center Hidenori Okamoto Organizer: Institute of Industrial Science, University of Tokyo Non-ferrous Metal Resources Recycling Engineering Donation Research Division (JX Metal Donation Unit) Date: November 10, 2017 Venue: Institute of Industrial Science, University of Tokyo

The present invention relates to a copper electrorefining method, and relates to a copper electrorefining method using a copper anode containing a large amount of impurities.

Standards have been established for the impurity grade of copper anodes used in copper electrorefining, and the components have been adjusted so that the impurity content does not exceed the standard. However, the impurity grade in the copper anode has continued to rise due to the recent rise in the impurity grade in the ore and the increase treatment of recycled raw materials including substrate waste, and in the future, the copper anode with the impurity grade higher than the current standard will be treated. It is foreseen that we will have to do it. In particular, as the amount of recycled raw material processed increases, the quality of Sb and Ni mixed in the copper anode increases.

As the quality of impurities in the copper anode increases, naturally, the amount of impurities dissolved in the electrolytic solution also increases, and if left as it is, there is a high possibility that the electrolytic performance and the quality of electrolytic copper will deteriorate. In addition, among the impurities, the copper anode with high grade of Sb and Ni contains insoluble NiO and Cu, Sb, and Ni crystals called copper-nickel-antimon-oxide (Kupferglimmer) existing in the copper anode. It is thought that there are many of these crystals, and when these crystals increase in the burial mound, the diffusion of Cu ions near the anode is inhibited and passivation is promoted.

Passivation is a phenomenon in which the Cu concentration continues to increase near the copper anode and non-conductive CuSO _{4.5H 2 O} crystals are deposited, making it impossible to energize. At the operation site, in order to prevent passivation, the Cu concentration, sulfuric acid concentration, liquid temperature, etc. of the electrolytic solution are controlled, but if there is a sign of passivation, copper sulfate crystals are deposited. We have taken measures by changing the liquid composition and liquid temperature so as not to cause it. However, there is no systematic regulation for the response to the occurrence of passivation, and it is only implemented based on the experience so far, and there is no knowledge about the response when using a copper anode containing a large amount of impurities. ..

As a method for suppressing passivation, JP-A-2000-54181 (Patent Document 1) uses a relational expression consisting of Cu grade, oxygen grade, Se grade, Ag grade, and As grade of the anode to perform passivation. A method of using an anode adjusted to a suppressable grade is disclosed.

Japanese Unexamined Patent Publication No. 2000-54181

However, the method described in Patent Document 1 is to suppress the phenomenon that monovalent Cu ions become Cu powder in an electric substance and inhibit the diffusion of Cu ions as a cause of the occurrence of the passivation phenomenon. However, only a method of adjusting the composition of the copper anode to suppress the generation of monovalent Cu ions has been proposed, and it is said that the root cause of the passivation phenomenon of increasing the Cu concentration near the electrode can be sufficiently solved. I can't say.

Further, the method described in Patent Document 1 describes only an example of adjusting the impurity grade in the copper anode by focusing on the Cu, Ag, and As grades. Therefore, when a copper anode with high grade of Sb or Ni, which is considered to have many insoluble NiO or Kupferglimmer that inhibits the diffusion of the liquid, is used, electrolytic refining can be efficiently performed with high current efficiency while suppressing passivation. It is unknown whether or not.

In view of the above problems, the present invention provides copper electrorefining capable of efficiently performing electrolytic refining with high current efficiency while suppressing passivation even when a copper anode having high grades of Sb and Ni is used. A purification method is provided.

As a result of diligent studies to solve the above problems, the present inventor has found that it is effective to control the SO ₄ concentration in the electrolytic solution to a predetermined value or less.

In one aspect, the present invention completed based on the above findings is electrolyzed in copper electrorefining using a copper anode containing 0.030 to 0.040% by mass of Sb and 0.20 to 0.30% by mass of Ni. Provided is a copper electrorefining method characterized by performing copper electrorefining at an SO ₄ concentration of 268 g / L or less in a liquid.

In one embodiment, the copper electrorefining method according to the present invention performs copper electrorefining at a cathode current density of 300 to 350 A / m ² .

In still another embodiment of the copper electrorefining method according to the present invention, the copper anode contains 0.05 to 0.24% by mass of As and 0.01 to 0.027% by mass of Bi.

In still another embodiment of the copper electrorefining method according to the present invention, the liquid temperature of the electrolytic solution is 65 ° C. or higher.

According to the present invention, there is a copper electrorefining method capable of efficiently performing electrolytic refining with high current efficiency while suppressing passivation even when a copper anode having high grades of Sb and Ni is used. Can be provided.

It is a graph showing an example of the relationship between the anode current density (passivation DA) and the SO ₄ concentration in the electrolytic solution when passivation occurs.

Hereinafter, embodiments of the present invention will be described. The copper electrorefining method according to the embodiment of the present invention uses a copper anode containing 0.030 to 0.040% by mass of Sb and 0.20 to 0.30% by mass of Ni.

The Sb concentration in the copper anode is more typically 0.030 to 0.038% by weight, and even more typically 0.035 to 0.038% by weight. The Ni concentration in the copper anode is more typically 0.20 to 0.28% by mass, and even more typically 0.20 to 0.25% by mass. The copper anode according to this embodiment contains 0.05 to 0.24% by mass of As and 0.01 to 0.027% by mass of Bi in addition to Sb and Ni, and has a copper grade of 99.3 to 99.4. It can be about% by mass.

The cause of the passivation is the precipitation of copper sulfate crystals near the electrodes. In particular, when the Sb concentration in the copper anode is high as in the copper anode used in the present embodiment, floating slime is generated and the SB (V) of Sb (III) is oxidized at the anode-electrolyte solution boundary. Causes the problem of causing the formation of a gel-like film on the surface of the insoluble and sticky anode. In particular, when both the Sb concentration and the Ni concentration in the copper anode are high, insoluble crystals such as kupferglimmer are generated, which hinders liquid diffusion and promotes passivation.

In the copper electrolytic purification according to the present embodiment, a copper anode having a high impurity concentration containing 0.030 to 0.040% by mass of Sb and 0.20 to 0.30% by mass of Ni is used, and SO ₄ in the electrolytic solution is used. When the anodic current density at which immobilization occurs by changing the concentration (hereinafter referred to as "immobilized DA") was investigated, the difference between the anodic current density and the SO ₄ concentration in the electrolytic solution was investigated. , Found to have the relationship as shown in FIG. That is, it was found that the lower the SO ₄ concentration, the less likely the passivation occurs even if the anode current density is increased.

"Passivation DA" indicates the value of the anode current density at the time of passivation. A high passivation DA indicates that electrolysis proceeded without passivation, indicating that it is highly effective as a passivation countermeasure. Here, the "SO ₄ concentration" represents the total value of the SO ₄ ion concentration calculated by adding up the substances having sulfate roots in the electrolytic solution. Specifically, the SO ₄ concentration is calculated by the following formula (A).
{(Concentration of copper with sulfate root in electrolytic solution ÷ Atomic weight of copper 63.5) +
(Concentration of nickel with sulfate root in electrolytic solution ÷ Atomic weight of nickel 58.7) +
(Concentration of free sulfuric acid ÷ Molecular weight of sulfuric acid 98)} × Molecular weight of SO ₄ 96 ・ ・ ・ (A)

Further, from the relationship of FIG. 1, the concentration of the substance having a sulfate root in the electrolytic solution is adjusted by using the relationship based on the relationship of the formula (1) as the passivation suppression index for suppressing the passivation. be able to. As a result, it is possible to suppress the precipitation of copper sulfate crystals in the vicinity of the electrode and efficiently proceed with electrolytic refining with high current efficiency while suppressing passivation.

The passivation suppression index is the following formula (1).
Y = -13.37X + 4147 ... (1)
Can be represented by.
Here, Y indicates passivation DA (A / m ² ), and X indicates SO ₄ concentration (g / L).

Furthermore, in order to carry out the copper electrolysis purification process with higher efficiency, for the passivation DA targeted in actual operation, a plurality of samples when the target cathode current density DK is about 350 A / m ² When calculated from the variation, it was found that the target passivation DA was 560 A / m ² .

When calculated according to the passivation suppression index of the formula (1) based on the target passivation DA, the SO ₄ concentration is about 268 g / L. Therefore, in the present embodiment, the SO ₄ concentration in the electrolytic solution is Copper electrorefining shall be performed so as to be 268 g / L or less. As a result, even when a copper anode with a high content of Sb and Ni is used and the cathode current density DK is increased to about 350 A / m ² , the increase in Cu concentration near the electrodes is suppressed and immobilization is suppressed. At the same time, electrolytic purification can be efficiently advanced with high current efficiency.

On the other hand, if the SO ₄ concentration in the electrolytic solution, especially the free acid concentration (free sulfate ion concentration) that has a large effect on the SO ₄ concentration, is too low, the solubility of Sb ₂ O ₃ and As ₂ O ₅ decreases. The viscosity of the object increases, which may hinder the diffusion of the liquid near the electrode and promote immobilization. Therefore, the free acid concentration in the electrolytic solution is preferably 150 g / L or more, more preferably 160 g / L or more, and typically 160 to 180 g / L. The SO ₄ concentration at that time is preferably 244 g / L or more, more preferably 254 g / L or more, further preferably 264 g / L or more, and typically 254 to 268 g / L. ..

The temperature of the electrolytic solution in the copper electrorefining step according to the present embodiment is preferably 60 ° C. or higher, more preferably 65 ° C. or higher, because the passivation DA can be increased as the temperature is raised. In one embodiment, the temperature is 65 to 70 ° C.

Examples of the present invention are shown below together with comparative examples, but these examples are provided for a better understanding of the present invention and its advantages, and are not intended to limit the invention.

(Evaluation of the relationship between the passivation DA and the SO ₄ concentration in the electrolytic solution (passivation suppression index))
When copper electrolytic purification was carried out using a copper anode (Samples 1 to 13) containing 0.037 to 0.040% by mass of Sb and 0.23 to 0.27% of Ni, and passivation occurred. The value of the anode current density (passivation DA) was measured. The copper anode contained As: 0.09 to 0.11% and Bi: 0.012 to 0.016% as other impurities. The liquid temperature of the electrolytic solution was 63 to 65 ° C. or higher. The cathode current density DK of Samples 1 to 9 was 322 to 350 A / m ² .

For samples 10 to 13, a copper anode smaller than that of samples 1 to 9 was used in order to evaluate the passivation DA targeted in the actual operation. That is, in the samples 10 to 13, the cathode current density DK was set to 33 to 50 A / m ² so that the anode current density DA at the start of the test was 400 A / m ² , and the passivation DA was evaluated.

The liquid composition of Samples 1 to 13 was changed as shown in Table 1 and tested. For "SO ₄ concentration" in Table 1, the total value calculated from the Cu, Ni, and free sulfuric acid concentrations represented by the above relational expression (A) was used. The results are shown in FIG.

As shown in FIG. 1, there was a relationship between the SO ₄ concentration in the liquid and the passivated DA, regardless of the cathode current density DK, as the passivated DA increased as the SO ₄ concentration decreased. Moreover, the relationship of the formula (1) was obtained as an index for suppressing passivation from the relationship of the samples 1 to 13. In addition, the target passivation DA was calculated based on the samples 10 to 13. When the cathode current density DK was operated at 350 A / m ² , the anode current density DA at the end of the operation was 460 A / m ² on average. The current flowing through the electrodes varies even in the electrodes in the same electrolytic cell due to variations in contact resistance and suspension properties of the electrodes. Therefore, assuming that the variation of the measured current distribution follows the normal distribution, the anode current density DA is estimated to be 560 A / m ² at the maximum, considering the normal distribution of 3σ. From this result, the target passivation DA was 560 A / m ² . As a result of introducing the target passivation DA into the formula (1) and calculating the target SO ₄ concentration, it was found that the concentration should be 268 g / L or less.

(Relationship between passivation DA and liquid temperature)
Sb is 0.034 to 0.036% by mass, Ni is 0.24 to 0.26% by mass, and other elements include As: 0.07 to 0.10% and Bi: 0.010 to 0.013%. Using a copper anode, the cathode DK was set to 322-350 A / m ² and the liquid temperature was varied between 68-70 ° C. to investigate the effect on immobilized DA. The results are shown in Table 2.

From the results in Tables 1 and 2, it was obtained that the passivation DA could be increased by raising the liquid temperature to 65 ° C. or higher with respect to the electrolytic solution.

Claims (3)

Calculated by adding up substances with sulfuric acid roots in the electrolytic solution in copper electrolytic purification using a copper anode containing 0.030 to 0.040% by mass of Sb and 0.20 to 0.30% by mass of Ni. The SO ₄ concentration, which is the total concentration of SO ₄ ions, was set to 244 to 268 g / L, and copper electrolytic purification was performed at a cathode current density of 322 to 350 A / m ² .
The SO ₄ concentration is based on the demobilization suppression index calculated based on the relationship between the mobilized anode current density at which demobilization occurs at the cathode current density and the SO ₄ concentration in the copper electrolytic purification. Including adjusting
The derivatization suppression index is the following equation (1):
Y = -13.37X + 4147 ... (1)
(Here, Y represents the deconducted anode current density (A / m ² ), and X represents the SO ₄ concentration (g / L)).
A copper electrorefining method characterized by being based on . The copper electrorefining method according to claim 1, wherein the copper anode contains 0.05 to 0.24% by mass of As and 0.01 to 0.027% by mass of Bi. The copper electrorefining method according to claim 1 or 2, wherein the temperature of the electrolytic solution is 65 ° C. or higher.

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