JP2012167318A - Method for electrorefining copper, and method for producing electrolytic copper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for electrorefining copper which can suppress the production of suspended solids without damaging safety on an operation, and also, can improve electrolytic efficiency, and a method for producing electrolytic copper.SOLUTION: In the method for electrorefining copper using an anode electrode plate comprising crude copper, arsenic and antimony, electrorefining is performed at a current density of ≥290 A/musing the anode electrode plate controlled in such a manner that antimony is comprised by ≥50 ppm, and the mass ratio of arsenic/antimony reaches ≥5.0.

Description

  The present invention relates to a method for electrolytic purification of copper and a method for producing electrolytic copper.

  Conventionally, the presence of suspended solids (SS) in the electrolytic solution at the time of electrolytic refining of copper has been considered as one of the causes of degradation of electrolytic performance such as current efficiency and short-circuit rate. The generation mechanism of suspended solids has not been elucidated so far.

As an elucidating example of the generation mechanism of floating solids, for example, in Japanese Patent Application Laid-Open No. 2008-121066 (Patent Document 1), the main component of floating slime at the time of copper electrolytic purification is antimony (Sb), and dissolved oxygen in the electrolytic solution And Sb react to form diantimony pentoxide (Sb ₂ O ₅ ), and when Sb ₂ O ₅ entraps arsenic (As) and bismuth (Bi), a floating slime is formed. It is described that the quality of electrolytic copper is reduced by welding. In Patent Document 1, in order to suppress the formation of floating slime, electrolytic treatment at a high current density of 2.8 to 5.0 A / dm ² is performed to generate hydrogen from the cathode, and the generated hydrogen is contained in the electrolyte solution. Attempts have been made to reduce the dissolved oxygen concentration in the electrolyte by reacting with oxygen, to suppress the formation of Sb ₂ O ₅ and to improve the quality of electrolytic copper.

JP 2008-121066 A

However, even though it is a fact that hydrogen ions are present in the electrolytic solution during electrolytic purification, the current density is about 2.8 to 5.0 A / dm ² from the present inventors' previous knowledge. It is unlikely that copper is subjected to electrolytic purification under the above conditions, and hydrogen is newly generated by the electrolytic purification. If hydrogen is newly generated by electrolytic refining at a high current density, it may react with arsenic in the electrolytic solution to generate hydrogen arsenide, which is a harmful gas, which may impair safety during operation. It is done.

  In view of the above problems, the present invention provides a method for electrolytic purification of copper and a method for producing electrolytic copper that can suppress the generation of floating solids without impairing safety during operation and that can improve electrolytic efficiency.

  As a result of intensive studies to solve the above problems, the present inventor has a dominant mechanism for the formation of floating solids under high current density, as in Patent Document 1, the reaction between dissolved oxygen concentration in the electrolyte and antimony is dominant. Rather, it was found that the presence ratio of antimony and arsenic in the anode electrode plate affects the formation of floating solids and the electrolysis efficiency.

  Although the present invention is not limited by the following explanation, it is considered that the relationship between the ratio of antimony and arsenic in the anode electrode plate and the frequency of occurrence of suspended solids during electrolytic purification is due to the following mechanism. . At the time of electrolytic purification, impurities such as arsenic and antimony are eluted into the electrolytic solution from the interface of the anode electrode plate together with copper ions by the anode reaction (oxidation reaction). At this time, since arsenic eluted from the anode electrode plate at the anode interface has a higher affinity for oxygen than antimony, it reacts with dissolved oxygen near the anode electrode plate interface in preference to antimony to produce an oxide. Arsenic preferentially forms an oxide, thereby suppressing the generation of antimony oxide, which is the main component of the floating solid. That is, in the present invention, arsenic, which is an element having a higher affinity for oxygen than antimony, is positively mixed in the anode electrode plate, and the abundance ratio is controlled within an appropriate range, so that it can be used during electrolytic purification. This is an attempt to effectively suppress the generation of floating solids.

  Originally, arsenic has been treated as a poison and has been regarded as an element that must be removed as much as possible in the copper smelting process. For this reason, there has never been a report of positively adding such toxic arsenic to the anode electrode plate used for electrolytic purification, and it has contributed to the suppression of the generation of floating solids in electrolytic purification. There is no report that you will get.

The present invention completed on the basis of the above knowledge is, in one aspect, a copper electrolytic purification method using an anode electrode plate containing crude copper, arsenic and antimony, containing 50 ppm or more of antimony and an arsenic / antimony mass ratio of 5. This is a copper electrolytic purification method including performing electrolytic purification at a current density of 290 A / m ² or more using an anode electrode plate controlled to be 0 or more.

  In one embodiment of the copper electrolytic purification method according to the present invention, the anode electrode plate contains 50 ppm or more and less than 200 ppm of antimony.

  In another embodiment of the copper electrolytic purification method according to the present invention, the anode electrode plate contains 700 ppm to 1200 ppm of arsenic.

  In yet another embodiment, the copper electrolytic purification method according to the present invention includes circulating and filtering a part of the electrolytic solution in which the anode electrode plate is immersed.

  In yet another embodiment, the copper electrolytic purification method according to the present invention includes filtering a part of the electrolytic solution with an ultrafiltration membrane.

  In yet another embodiment, the copper electrolytic purification method according to the present invention includes performing electrolytic purification while maintaining the suspended solid concentration in the electrolytic solution at 0.6 mg / L or less.

According to another aspect of the present invention, there is provided a step of manufacturing an anode electrode plate containing crude copper, arsenic, and 50 ppm or more of antimony, and controlled to have an arsenic / antimony mass ratio of 5.0 or more, and an anode electrode plate And a step of performing electrolytic purification at a current density of 290 A / m ² or more using a copper.

  In one embodiment of the method for producing electrolytic copper of the present invention, the step of producing the anode electrode plate includes adding arsenic to the molten copper and controlling the mass ratio of arsenic / antimony.

  ADVANTAGE OF THE INVENTION According to this invention, the production | generation of floating solid can be suppressed without impairing the safety | security at the time of operation, and the electrolytic refining method of copper and the manufacturing method of electrolytic copper which can improve electrolytic efficiency can be provided.

It is a graph showing the example of the influence which As / Sb ratio has on SS density | concentration (SS generation amount) in electrolyte solution. It is a graph showing the example of the relationship between As / Sb ratio and current efficiency. FIG. 3A shows a transition of current efficiency when a part of the electrolytic solution is extracted in a batch, the extracted electrolytic solution is filtered, and electrolytic purification is performed while returning the filtered electrolytic solution to the electrolytic solution. It is a graph. FIG.3 (b) is a graph showing transition of SS density | concentration in electrolyte solution in the process of Fig.3 (a).

The copper electrolytic purification method according to an embodiment of the present invention is a copper electrolytic purification method using an anode electrode plate containing crude copper, arsenic and antimony, containing 50 ppm or more of antimony and an arsenic / antimony mass ratio of 5. Using an anode electrode plate controlled to be 0 or more, electrolytic purification is performed at a current density of 290 A / m ² or more.

  By controlling the arsenic / antimony mass ratio in the anode electrode plate to 5.0 or more, the anode reaction occurring in the vicinity of the interface of the anode electrode plate can be controlled. That is, the generation of floating solids in electrolytic purification is affected by the anode reaction near the anode electrode plate rather than the components of the electrolytic solution. Therefore, by controlling the mass ratio of the anode electrode plate and appropriately controlling the anode reaction, the suspended solid (SS) concentration in the electrolyte can be reduced, and the current efficiency is 94% or more, depending on the case, 96% or 98%. This can be improved. When the mass ratio of As / Sb is made smaller than 5.0, antimony may preferentially combine with dissolved oxygen in the electrolytic solution rather than arsenic due to the anodic reaction, thereby generating an oxide. The SS concentration becomes high, and the SS component adheres to the surface of the produced electric copper. As a result, bumps are generated or the copper quality is lowered, and it is difficult to keep the current efficiency high.

As the anode electrode plate, for example, an electrode plate of about 104 × 91 cm ² is used. In addition to crude copper, antimony (Sb), and arsenic (As), bismuth (Bi), nickel (Ni), lead (Pb), iron An impurity element such as (Fe) may be included. Although not limited to the following, as the anode electrode plate used in the present embodiment, the anode electrode plate adjusted so that the mass ratio of As / Sb is 5.0 or more, more preferably 5.5 or more. Is preferably used. The upper limit value of the mass ratio of As / Sb is not particularly limited, but the upper limit value of the mass ratio of As / Sb is preferably about 24.0, more preferably, due to the product characteristics of the anode electrode plate used for copper electrolytic purification. 14.0, more preferably about 8.0. In a high current density region where the current density is 290 A / m ² or more, SS tends to be generated when the Sb in the anode electrode plate is generally in a high concentration state of 150 ppm or more, so the mass ratio of As / Sb Control is particularly effective for SS reduction. Moreover, since generation | occurrence | production of SS will become remarkable when there is too much Sb content in an anode electrode plate, it is preferable that Sb contained in an anode electrode plate is less than 200 ppm. At this time, if arsenic in the anode electrode plate is contained at least 700 ppm or more, a desired effect can be obtained, and if it is less than 700 ppm, the effect of reducing the generation of SS becomes small. The upper limit of the arsenic content is not particularly limited. However, if the arsenic content is too large, there may be a problem in the safety of electrolytic operation. When the Sb concentration in the anode electrode plate is 150 ppm or less, the generation of SS is not affected if As is contained in the anode electrode plate at 700 ppm or more. The material of the cathode electrode plate is not particularly limited, and a general material such as stainless steel is used.

  As a method for controlling the As / Sb mass ratio of the anode electrode plate to 5.0 or more, adjustment of the raw material for the treatment in the copper smelting process is suitable. Specifically, crude copper is charged into a refining furnace, and based on the concentration values of As and Sb of the charged crude copper, the mass ratio of As / Sb is adjusted to be 5.0 or more. When the mass ratio of As / Sb in crude copper is less than 5.0, metal arsenic (gray arsenic) is charged into the refining furnace and controlled.

There is no particular restriction on the current density during the electrolytic refining operation, but in the operation smaller than the current density of 290 A / m ² , the moving speed of the substance between the anode electrode plate and the cathode electrode plate is low, and the floating solid is electrodeposited on the cathode electrode plate. Since it forms and precipitates with other metals such as lead and silver, which have heavy specific gravity, the quality of the electrodeposited copper electrodeposited on the cathode electrode plate is less affected. There arises a problem that productivity decreases. On the other hand, under a high current density of 350 A / m ² or more, the quality of the electrodeposited copper may be deteriorated by entrainment of the floating solid electrodeposited copper surface generated by electrolytic purification. Therefore, the current density is preferably 290 A / m ² or more, for example, 300 to 340 A / m ² , more preferably 310 to 330 A / m ² .

  In order to remove SS and the like that are precipitated in the electrolytic solution during the electrolytic purification operation, it is preferable to circulate and filter part of the electrolytic solution in which the anode electrode plate is immersed (circulated solution). When a part of the electrolytic solution is circulated and the circulating liquid is filtered, a continuous system in which a part of the electrolytic solution is always extracted and circulated may be used, or a part of the electrolytic solution may be circulated every predetermined time. It may be a batch system that extracts and circulates. Normally, as electrolytic purification progresses, impurity elements contained in the anode electrode plate are eluted into the electrolytic solution, and the impurity concentration in the electrolytic solution increases. However, by circulating the electrolytic solution, the electrolytic solution It becomes easy to control the impurity concentration within the predetermined range.

  As a filtration device attached in the circulation path, filtration using various membranes such as reverse osmosis (RO) membrane, ultrafiltration membrane (UF) membrane, microfiltration membrane (MF) membrane can be performed. In this embodiment, it is preferable to use a UF membrane. By using the UF film, SS floating in the electrolytic solution together with impurity elements such as As and Sb can be efficiently removed, and therefore, contamination of electrolytic copper during electrolytic purification due to adhesion or entrainment of SS is suppressed. In the embodiment of the present invention, a UF membrane is used as a filtration device, but the repair particle size of the UF membrane is about 5 to 10 μmφ, which is most suitable for the recovery of the SS component floating in the electrolytic solution. Furthermore, in order to recover SS with a fine particle size of 5 μm or less, it is conceivable to use a filter with a finer repair particle size, but the resistance when the electrolyte is passed increases, and the filtration processing time is increased. It becomes a long time, and the amount of filtration of the electrolytic solution decreases, making it unsuitable for operation.

  In order to improve the filtration capacity, it is considered effective to install multiple filtration devices and increase the filtration rate (filtration capacity) to a certain level. Optimal conditions are determined.

  According to the knowledge of the present inventors, in order to keep the SS concentration in the electrolyte solution low and improve the current efficiency to produce high quality electrolytic copper, the filtration rate is preferably 60% or more. More preferably, it was found to be 70% or more. If the filtration rate is lower than 60%, SS may not be sufficiently removed, resulting in a decrease in current efficiency, or current efficiency may not be maintained above a certain level.

  By setting the filtration rate to 60% or more, the suspended solid concentration in the electrolytic solution is reduced to a predetermined level or less. Specifically, the suspended solid concentration in the electrolytic solution can be maintained at 0.6 mg / less, more preferably at 0.1 mg / less. As a result, the current efficiency during electrolytic purification can be maintained at 94% or more. The “filtration rate” in this embodiment is defined as “filtration rate [%] = (filtration amount / circulating fluid amount) × 100”.

  During the electrolytic purification operation, the component concentration in the electrolytic solution may be monitored. For example, a detector that can constantly monitor the concentration in the electrolytic solution may be arranged in the electrolytic purification system, or the electrolytic solution is extracted at regular intervals and the components of the electrolytic solution are measured using an analyzer. Such a mode may be used.

  As described above, according to the copper electrolytic purification method and the electrolytic copper manufacturing method according to the present embodiment, the anode reaction during the electrolytic purification can be appropriately controlled by controlling the As / Sb ratio of the anode electrode plate. Therefore, the generation of floating solids can be suppressed and the electrolysis efficiency can be improved without deteriorating the safety during operation without generating hydrogen that can cause toxic gas generation.

  Examples of the present invention are shown below, but the present invention is not intended to be limited to the following examples.

(Influence of As / Sb ratio)
As shown in Table 1, anode electrode plates (Nos. 1 to 12) having different impurity element compositions are used, and the As / Sb ratio in the anode electrode plate gives the SS concentration (SS generation amount) in the electrolytic solution. The impact was evaluated. Cu: 40-50 g / L, H ₂ SO in an electrolytic cell in which 50 anode electrode plates with a surface area of 20,380 cm ² and 49 cathode electrode plates (SUS316L) were alternately installed at a distance of 27 mm between the anode and cathode electrode plates. ₄ : A 165 to 185 g / L sulfuric acid electrolyte solution was added, the electrolyte temperature was adjusted to 60 to 70 ° C., and the current density of the cathode electrode plate was adjusted to 290 A / m ^2, and electrolytic purification was performed for 9 hours. The amount of SS generated was measured with an electronic balance. The results are shown in FIG. As shown in FIG. 1, it can be seen that as the As / Sb ratio increases, the SS generation amount decreases, and when the As / Sb ratio is 5.0 or more, the SS generation amount can be stably reduced to 250 ppm or less. This is considered to be because when the As / Sb ratio is increased, the arsenic and oxygen products are preferentially generated over the Sb and oxygen products, the generation of Sb ₂ O ₅ is suppressed, and SS is less likely to occur. It is done.

(Relation between As / Sb ratio and current efficiency)
FIG. 2 summarizes the relationship between the As / Sb ratio in the anode used for electrolytic purification and the current efficiency during operation. As shown in FIG. 2, when the As / Sb ratio is smaller than 5.0, it was difficult to maintain a current efficiency of 98% or more. On the other hand, when the As / Sb ratio was 5.0 or more, the current efficiency could be improved to 98% or more.

(Relationship between current efficiency due to electrolyte circulation and SS concentration)
FIG. 3A and FIG. 3B show the relationship between the transition of current efficiency and the SS concentration during the electrolytic purification process. As shown in FIG. 3B, it can be seen that when the SS concentration in the circulating fluid increases, the current efficiency tends to decrease as shown in FIG. In addition, when the SS concentration is 0.6 mg / L or less, it can be seen that the current efficiency can be operated at a high efficiency of 96% or more. Conversely, when the SS concentration is high, the current efficiency is about 85%. It can be seen that it is depressed.

Claims (8)

In the method for electrolytic purification of copper using an anode electrode plate containing crude copper, arsenic and antimony,
A copper electrolytic purification method comprising electrolytic purification at an electric current density of 290 A / m ² or more using an anode electrode plate containing 50 ppm or more of antimony and controlled to have an arsenic / antimony mass ratio of 5.0 or more.   The copper electrolytic purification method according to claim 1, wherein the anode electrode plate contains 50 ppm or more and less than 200 ppm of antimony.   The copper electrolytic purification method according to claim 1 or 2, wherein the anode electrode plate contains 700 ppm to 1200 ppm of arsenic.   The method for electrolytic purification of copper according to any one of claims 1 to 3, comprising circulating and filtering a part of the electrolytic solution in which the anode electrode plate is immersed.   The method for electrolytic purification of copper according to claim 4, comprising filtering a part of the electrolytic solution with an ultrafiltration membrane.   The method for electrolytic purification of copper according to any one of claims 1 to 5, comprising carrying out electrolytic purification while maintaining a suspended solid concentration in the electrolytic solution at 0.6 mg / L or less. Producing an anode electrode plate comprising crude copper, arsenic, and 50 ppm or more antimony, and controlled to have a mass ratio of arsenic / antimony of 5.0 or more;
And a process of performing electrolytic purification at a current density of 290 A / m ² or more using the anode electrode plate.   The method for producing electrolytic copper according to claim 7, wherein the step of producing the anode electrode plate includes adding arsenic to the molten copper and controlling a mass ratio of arsenic / antimony.