JP4524248B2 - Copper collection method - Google Patents

Description

The present invention relates to a copper collection method that can be used in a process of collecting or recovering copper by electrolysis from a liquid and can prevent a short-circuit accident between an anode and a cathode.

In the field of electrolytic copper refining, copper ore as a raw material is melted at a high temperature of about 1300 ° C and then injected into a mold to perform the electrolysis using the formed crude copper as the anode, and at that time, the copper eluted from the anode is deposited on the cathode thin plate As a result, high-purity copper is produced. However, since copper elutes from the anode more than the amount of electricity added, it is necessary to remove extra eluted copper by separate electrolysis. This electrolysis is generally called copper removal electrolysis or copper electrowinning.
Conventionally, lead has been used in this copper removal electrolysis as an anode other than copper. When copper removal electrolysis is performed using a lead plate as an anode, it is inevitable that lead peeled off from the surface of the anode lead is mixed into the copper collected at the cathode. Since copper mixed with lead has low commercial value, it is often re-dissolved as a copper raw material.

Further, as a general problem of the lead anode, in addition to being heavy, it is difficult to handle it, and the lead anode is easily consumed in a non-uniform manner. Furthermore, in the case of the hard lead anode such as Pb-Sb, the electrode plate itself is thick and it is difficult to increase the distance between the electrodes. In addition, the lead electrode is easily deformed during electrolysis, and a short-circuit accident with the cathode has been a problem. .
Thus, in recent years, insoluble metal electrodes (dimension-stable electrodes) in which titanium is used as a film-forming metal substrate and the surface thereof is coated with an active coating containing iridium oxide have been used. The electrode is generally known by the name of DSA (Dimensionally Stable Anode) or DSE (Dimensionally Stable Electrode).
DSE is also attracting attention as an anode for the SX-EW method, which is being developed in the field of copper refining. In the SX-EW method, which does not use crude copper as the anode, but directly refining copper from a copper sulfate solution, Expectations for DSE, an insoluble electrode, are high.

  When DSE is used for copper removal electrolysis, it has often been confirmed that non-conductive substances such as antimony adhere to the surface of DSE. However, even in a DSE in which antimony or the like is confirmed to adhere to the surface in a pull-up inspection after electrolysis, although the initial voltage is high, the voltage drops with energization, so there is no problem with normal energization. This is because non-conducting substances such as antimony adhere to the electrode surface depending on conditions in the electrolytic solution when electrolysis is stopped, but the adhering antimony and other substances are presumed to peel off due to electrolysis. It is not expected to occur.

  However, in the copper removal electrolysis, in order to collect the deposited copper, the cathode is frequently taken in and out of the electrolytic cell. When the cathode is extracted and the electrolyte level is low, the antimony in the electrolyte is deposited on the anode surface, and then the cathode is returned to its original position for operation. When the surface becomes higher, there are a portion where the non-conductive substance is deposited and a portion where it is not deposited on the surface of the anode immersed in the electrolytic solution. When electrolysis is started in this state and electricity flows, current concentrates in the area where the non-conducting material on the upper part of the anode is not deposited, and copper grows significantly in that part, generating dendrite. There is a risk of a short accident.

This will be described with reference to FIGS. 2a to 2d.
In the copper removal electrolysis tank 1, flat or porous anodes 2 and flat cathodes 3 are alternately installed, and the anode material 4 is located on the anode 2 up to a position higher than the liquid level 6 of the electrolytic solution 5. Almost uniform coating. When electricity is passed between both electrodes of the electrolytic cell 1, copper ions in the electrolytic solution 5 are reduced and deposited as metallic copper 7 on the surface of the cathode 3 (FIG. 2a).

The cathode 3 on which a predetermined amount of metallic copper 7 is deposited is pulled up from the electrolytic cell 1 for replacement after the energization is stopped. When the cathode 3 is taken out of the electrolytic cell 1 in this way, the liquid level of the electrolytic solution is lowered by the volume, and the distance “d” from the liquid level 6 at the time of electrolysis to the liquid level 6a at the time of taking out the cathode. ”(FIG. 2b). In the anode 2 in this state, the anode material 4 is mostly immersed in the electrolytic solution 5, but the upper part is not immersed in the electrolytic solution 5.
As described above, antimony is present in the electrolytic solution of copper removal electrolysis in addition to copper ions to be collected, and this antimony is deposited on the surface of the anode material 4 of the anode 2 as a nonconductive material 8 (FIG. 2b). However, the part of the anode surface that is not immersed in the electrolytic solution 5 at the time of taking out the cathode in FIG. 2b, that is, the part that has not been immersed in the electrolytic solution 5 from the beginning, and the original liquid level 6 of the electrolytic solution 5 and after the cathode is taken out. The non-conductive substance 8 does not deposit on the surface of the anode 2 corresponding to the distance (d) with respect to the liquid surface 6a of the electrolytic solution 5.

In this state, when a new cathode 3a is re-installed in the electrolytic cell 1 in order to restart the operation of copper removal electrolysis (FIG. 2c), the liquid surface 6a of the electrolyte 5 is a distance (d) by the volume of the cathode 3a. And returns to the original liquid level 6 (the volume of metallic copper deposited on the cathode surface is ignored). In this state, as shown in the enlarged view of FIG. 2 c, the surface of the anode material 4 of the anode 2 corresponding to the distance (d) between the old liquid surface 6 a and the new liquid surface 6 in the electrolytic solution 5 is formed on the surface of the nonconductive material 8. There is no precipitation, and the anode material 4 which is a conductive material is exposed to the electrolytic solution 5.
When the operation is resumed by energizing in this state, the non-conductive substance 8 is deposited on the anode material 4 below the old liquid level 6a and becomes non-conductive, whereas the old liquid level 6a and the new liquid level There is no deposit in the anode material 4 between 6 and there is a danger that a current will concentrate on the anode material 4 in this range (d) and a short accident will occur due to the dendrite 9 (FIG. 2d).

  This short-circuit accident due to dendrites may occur not only for copper removal electrolysis but also for other metal extraction or recovery for the same reason. When this short accident occurs, the anode and the cathode are damaged and need to be replaced, which takes a lot of labor and cost.

An object of this invention is to provide the method for preventing the short-circuit between both poles by the current concentration at the time of the resumption of operation in copper extraction including copper removal electrolysis.

In the present invention, a dimensionally stable anode and a copper cathode coated with an anode material are immersed in an electrolytic solution in which copper ions are dissolved, and the copper ions are reduced by being energized between both electrodes to be deposited on the copper cathode as metallic copper. in copper metal collection method for collecting by, as the anode, a copper collection side, characterized by using an anode coated with the anode material only on the surface which is located below the electrolytic surface when immersed in the electrolyte Is the law.

The present invention will be described in detail below.
The inventors of the present invention have a short-circuit at the time of resuming energization in copper extraction electrolysis such as conventional copper removal electrolysis due to uneven deposition of a non-conductive material on the anode material surface of the anode at the time of de-energization such as cathode replacement. It has been found that the present invention has been reached.
In other words, when the cathode on which copper is deposited is taken out of the electrolytic cell after the energization is stopped, the liquid level of the electrolytic solution in the electrolytic cell is lowered, and the anode material immersed in the electrolytic solution during electrolysis appears outside the electrolytic solution. The impurities therein are deposited as a non-conductive material only on the surface of the anode material present in the electrolytic solution, and the non-conductive material is not deposited on the anode material outside the electrolytic solution.
Thereafter, when the cathode on which copper is not deposited is returned to the original position for restarting the operation, the liquid level of the electrolytic solution rises and returns to the original liquid level. Then, the anode material on which the non-conducting material is not deposited is immersed in the electrolyte solution, and the anode surface in the electrolyte solution has a portion coated with the upper anode material and the anode material on which the lower non-conducting material is deposited. Will do.
When energization is performed in this state, the current does not flow in the lower part of the anode due to the insulating property of the non-conductive substance, and the current concentrates on the anode material covering part on the upper part of the anode, causing a short circuit.

Precipitation of the nonconductive material occurs selectively on the surface of the anode material present in the electrolyte when the energization is stopped, and it does not occur or hardly occurs on the non-conductive or low-conductive anode substrate. A short accident occurs in a conventional copper removal electrolytic cell, etc., when non-conducting material is deposited only on part of the anode material when energization is stopped, and a conductive surface and non-conducting surface are formed on the anode surface, and energization starts. This is because current sometimes concentrates on conductivity.
Accordingly, the present invention presupposes the use of an electrolytic cell in which the cathode for depositing copper is taken out of the electrolytic cell, and the anode material on the anode surface is coated only below the surface of the electrolytic solution when the cathode is removed. Like that. Although the upper edge of the anode material and the liquid surface of the electrolyte solution may coincide, the electrode effective area is slightly reduced, but for safety, the upper edge of the anode material is slightly lower than the liquid surface of the electrolyte solution. It is desirable to keep it.

When such a configuration is adopted, the anode material on the anode surface is always in contact with the electrolytic solution both when energized and when the energization is stopped, and even when the nonconductive material is deposited on the anode material when energization is stopped, It is deposited to become non-conductive and does not form a conductive surface and non-conductive surface on the anode.
Therefore, current concentration does not occur even when energization is started, and non-conducting substances such as antimony gradually fall off from the anode due to the supplied current, and energization to the anode material occurs and copper is collected as usual. Can do.
In the method of the present invention, since the anode material covering area is smaller than that of the conventional one, the voltage rises accordingly, but it is possible to reliably prevent a short accident due to dendrites.

Using the DSE is used as an anode in the method of the present invention, prior to being prevented from an electrical short circuit due as dendrites mentioned high purity of the metal is a merit of the metal collected electrolyte by DSE use, improvement in workability and improvement of environmental The effect becomes obvious.
In order to cover only a part of the anode with the anode material, masking is performed in advance and the coating is applied to a portion other than masking. After the anode material is coated on the entire anode, a part of the anode material is removed mechanically or chemically. However, it is not limited to these methods.
Metal serving as collection subject according to the invention Dodea is, application is possible to such SX-EW process in addition to copper smelting field of decoppered electrolysis pre mentioned.

As described above, according to the copper sampling method of the present invention, when the nonconductive material in the electrolytic solution is deposited on the surface of all anode materials when the cathode is taken out when the energization is stopped, the cathode is returned to the original position. The anode surface is all made non-conductive by coating with a non-conductive material. Therefore, even if energization is started as it is, current does not flow, and therefore a short circuit accident due to current concentration does not occur.

An example of collecting metal (copper) by the method of the present invention will be described with reference to the accompanying drawings.
1a to 1d are schematic views showing a series of steps of copper collection according to the method of the present invention.
As shown in FIG. 1 a, a flat or porous anode 12 and a flat cathode 13 are alternately installed in a copper removal electrolytic cell 11, and the anode 12 is coated with an anode material 14. The anode material 14 is formed on the surface of the anode 12 corresponding to the length “D” downward from the liquid surface 16 of the electrolytic solution 15 when the cathode 13 is immersed in the electrolytic cell 11 as shown in FIG. Not covered.
When electricity is passed between both electrodes of the electrolytic cell 11, the copper ions in the electrolytic solution 15 are reduced and deposited as metallic copper 17 on the surface of the cathode 13 (FIG. 1a).

In this type of metal collecting electrolytic cell 11 in which the anode 12 and the cathode 13 are alternately arranged in a comb shape, a crane or the like is periodically used to collect the metal copper 17 deposited on the surface of the cathode 13 from the surface of the cathode 13. Is removed from the electrolytic cell 11 (FIG. 1b). When the cathode 13 is taken out of the electrolytic cell 11 in this way, the liquid level of the electrolytic solution is lowered by the volume, and the height “from the liquid level 16 at the time of electrolysis described above to the liquid level 16a at the time of taking out the cathode“ It decreases by “D”. In this state, the upper edge of the anode material 14 of the anode 12 substantially coincides with the electrolyte surface 16a.
As described above, in addition to the copper ions to be collected, antimony is present in the electrolytic solution of the copper removal electrolysis, and this antimony is deposited on the surface of the anode material 14 of the anode 12 as the nonconductive material 18 when the energization is stopped (Fig. 1b). In this example, since the upper edge of the anode material 14 and the liquid surface 16a of the electrolytic solution 15 coincide with each other, the nonconductive material 18 is deposited only on the surface of the anode material 14.

In this state, when a new cathode 13a is reinstalled in the electrolytic cell 11 in order to resume the copper removal electrolysis operation (FIG. 1c), the liquid level 16a of the electrolyte 15 is a distance (D) by the volume of the cathode 13a. And returns to the original liquid level 16 (ignoring the volume of metallic copper deposited on the cathode surface).
In this state, as shown in the enlarged view of FIG. 1c, the non-conductive material 18 is coated only on the anode material 14 below the old liquid surface 16a in the electrolytic solution 15, and the old liquid surface 16a and the new liquid surface 16 are covered. On the surface of the anode 12 corresponding to the distance (D), there is no deposition of the non-conductive substance 18, and the anode (a non-conductive or low-conductive anode substrate) 12 is exposed to the electrolytic solution 15.

In this state, the non-conductive substance 18 is deposited on the anode material 14 below the old liquid level 16a and becomes non-conductive, and deposits are also formed on the surface of the anode 12 between the old liquid level 16a and the new liquid level 16. There is no electrical conductivity. Therefore, the anode 12 as a whole is made non-conductive, and even if the operation is resumed by energization, the current is concentrated and a short circuit accident due to dendrite does not occur.
When energization is continued, the non-conductive material 18 on the surface of the anode material 14 is peeled off and deposited as a piece 18a on the bottom plate, the anode material 14 comes into contact with the electrolytic solution 15 and electrolysis is started, and metal copper is deposited on the surface of the cathode 13a. 17 precipitates out.

  Next, although the Example and comparative example of metal extraction which concern on this invention are described, these do not limit this invention.

[Reference Example 1]
Uses an electrolytic cell for decoppering electrolysis (actual tank) in which 20 lead anodes (vertical 1100 mm, horizontal 1000 mm, thickness 25 mm) and 19 copper cathodes are alternately arranged per tank, where copper is electrolyzed electrolytically. did. The inner diameter of the actual tank was 2600 mm long, 1200 mm wide, and 1400 mm deep.
The actual distance between the anode surface and the cathode surface of the electrolytic cell was 117.5 mm, and the distance between the electrode centers was 130 mm. The weight of one lead electrode was about 310 kg.
Among the lead anodes, two lead anodes adjacent to each other with the cathode interposed therebetween were replaced with a DSE anode having the same shape as the lead anode (manufactured by Permerek Electrode Co., Ltd.), and an energization test was performed under the following conditions. In the DSE, the anode material was coated on the entire length of 1100 mm, and from the upper edge portion to the lower 120 mm was not immersed in the electrolyte solution, and from the lower edge to the height of 980 mm was immersed in the electrolyte solution.

The electrolytic solution has a copper ion concentration of 50 to 55 g / liter and a copper-containing solution after electrolytic copper refining containing 150 g / liter of antimony, and this electrolytic solution is circulated to the electrolytic cell at 28 to 30 liter / minute to form copper ions. The decrease was replenished as appropriate. Other electrolysis conditions were a current density of 2.55 A / dm ² and an electrolysis temperature of 60 to 65 ° C.
The operation was performed for 10 days under these conditions, and when the surface was observed by pulling up the DSE, antimony was deposited in a thickness of about 50 μm. This thickness corresponded to about 10 times the thickness of the active coating (anode material) of DSE used. I tried to measure the monopolar potential using this DSE, but because of the voltage rise. The current could not flow.

  As a result of placing the antimony-attached DSE in the electrolytic bath for copper removal electrolysis again and energizing under the same conditions, no abnormality was observed, and the copper deposited on the cathode also grew normally. This is because the DSE voltage was high at the beginning of energization, and there was a possibility that some energization failure occurred, but antimony peeled off from the DSE simultaneously with the start of electrolysis, and as a result, the DSE returned to a normal state. I was able to estimate.

[Comparative Example 1]
Replace all lead anodes in the electrolytic cell for copper removal electrolysis used in Reference Example 1 with the same DSE as in Reference Example 1, energize for 10 days under the same conditions as in Reference Example 1, use the crane after stopping energization All 19 copper cathodes were pulled up. On the surface of the copper cathode, metallic copper was deposited with a thickness of about 10 mm.
After 180 minutes, 19 copper cathodes of the same size were reinstalled in their original positions. When energization was started under the same conditions as in Reference Example 1, dendrite abnormally grew on the DSE surface, and a severe short circuit occurred between adjacent DSEs with the cathode interposed therebetween.

[Example 1]
When the distance from the upper edge of the DSE contacting the uppermost liquid surface of the electrolytic solution at the start of energization in Comparative Example 1 (the copper cathode was immersed in the electrolytic solution) and at the time of pulling up the copper cathode was measured, 120 mm and 180 mm, respectively. Met.
When coating DSE, masking was performed from the upper edge to 196 mm, and the anode material was coated only on the surface other than this masking. Except for using these 20 DSEs, electricity was applied for 10 days under the same conditions as in Comparative Example 1, and after stopping energization, all 19 lead cathodes were pulled up using a crane. On the surface of the copper cathode, metallic copper was deposited with a thickness of about 10 mm.
After 180 minutes, 19 copper cathodes of the same size were reinstalled in their original positions. While energization was started under the same conditions as in Reference Example 1, no short circuit occurred due to abnormal dendrite growth.
The current was applied for 10 days under the same conditions as it was, and after replacing the copper cathode, the current supply was resumed under the same conditions, but no short circuit occurred.

1a to 1d are schematic views showing a series of steps of copper collection according to the method of the present invention. 2a to 2d are schematic views showing a series of steps of copper collection by a conventional method.

Explanation of symbols

11 Electrolysis tank
12 Anode
13 Cathode
14 Anode material
15 Electrolyte
16, 16 a Liquid level
17 Copper metal
18, 18 a Non-conductive material

Claims (1)

A dimensionally stable anode and a copper cathode coated with an anode material are immersed in an electrolytic solution in which copper ions are dissolved, and the copper ions are reduced by being energized between the two electrodes to be deposited on the copper cathode as metallic copper and collected. in copper metal sampling method, as the anode, a copper collection how, characterized by using an anode coated with the anode material only on the surface which is located below the electrolytic surface when immersed in the electrolyte.

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