JP7272147B2 - Electrolytic refining method for non-ferrous metals - Google Patents

Description

The present invention relates to a method for electrolytic refining of non-ferrous metals such as copper and nickel, in particular, by energizing between an anode and a cathode immersed in an electrolytic solution to remove target metals such as copper and nickel dissolved in the electrolytic solution. It relates to a method for electrorefining non-ferrous metals by electrodepositing them on a cathode surface.

In the refining of non-ferrous metals such as copper (Cu) and nickel (Ni), the crude metal processed into a plate is used as an anode (anode), electrolysis is performed using an aqueous solution of the metal salt as an electrolyte, and the purity is applied to the cathode (cathode). Electrolytic refining is carried out to deposit metals with high volatility.

For example, in electrolytic refining of copper, refined blister copper having a purity of about 99.5% obtained by subjecting blister copper to oxidation refining and reduction treatment in a refining furnace is cast into a plate, and the copper plate is used as an anode.

Regarding the cathode, there are a permanent cathode (PC) method using a permanent cathode made of a thin plate of stainless steel, titanium, etc., and a conventional (seed plate) method using a seed plate made of a thin plate of a high-purity target metal.

The anode and cathode are alternately immersed in an electrolytic solution stored in an electrolytic bath. In this state, a voltage is applied between the anode and cathode to electrodeposit the target metal on the surface of the cathode. In the conventional method, the target metal is shipped as a product in the state of the cathode plate as it is. On the other hand, in the permanent cathode method, when the target metal is electrodeposited to a predetermined thickness, the target metal is peeled off from the cathode to obtain a product, and the cathode is reused.

In the permanent cathode method, as shown in FIG. 1, the electrorefining step includes, as shown in FIG. After the process, the cathode on which the target metal is electrodeposited is transferred to a traverse conveyor by a transfer machine, and subjected to a stripping step of stripping off the target metal from the cathode. After the stripping step, the cathodes are subjected to a strain measurement step to measure their strain, the cathodes with strain within the allowable range are repeated to the electrolysis step, and the cathodes with strain exceeding the allowable range are ejected from the above step. Then, it is transferred to the distortion correction process and returned to the above process after the distortion correction.

In the stripping step of stripping off the target metal from the cathode, for example, as described in Japanese Unexamined Patent Application Publication No. 2008-231501, first, the cathode on which the target metal is electrodeposited is supported upright on a traverse conveyor. The cathode is elastically bent (flexing) by alternately pressing both surfaces of the cathode with a pressing tool. At this time, the target metal electrodeposited on the surface of the cathode is also deformed, but a difference occurs between the amount of deformation of the cathode and the amount of deformation of the target metal. Next, by inserting a chisel through the upper opening of this gap and lowering it, the amount of stripped target metal from the surface of the cathode is increased (chiseling). By laying it on its side, it completely separates from the surface of the cathode (down-ender).

The permanent cathode system has the advantage that the permanent cathode can be reused, thus reducing production costs and increasing the overall production efficiency of the operation. Permanent cathodes also have the advantage of having better verticality in the electrolytic cell compared to seed plate cathodes.

Maintaining the verticality of the cathode is extremely important in electrorefining. That is, when a cathode with good verticality, in which the entire cathode is in a flat state without bending or warping, and the cathode surface is in a flat state with little unevenness, is suspended in the electrolytic cell, the cathode is suspended adjacently. Variation in the distance from the anode is reduced. Therefore, it is possible to operate with a small distance between the cathode and the anode, and the productivity per unit area is improved. In addition, even if the current density is increased, the current short circuit between the cathode and the anode is less likely to occur, the current loss can be reduced (current efficiency is improved), and the production volume per unit time can be increased. From this point of view, the permanent cathode system is widely applied in the refining of non-ferrous metals.

The verticality of the cathode is evaluated by the distortion of the cathode. The distortion of the cathode is quantitatively represented by a numerical value that indicates the degree of bending or warping of the cathode. The absolute value of the distance difference, that is, the distortion of the cathode=|maximum measured distance−minimum measured distance|.

At the cathode, the process from charging to stripping of the target metal is repeated due to collision during charging into the electrolytic cell, heat during electrolytic refining, and bending during stripping of the electrodeposited target metal. Distortions such as bending and warping occur during the operation. For this reason, the cathode has very good verticality while the number of times of repeated use is relatively small. , the verticality of the cathode gradually deteriorates.

For example, in a cathode having a size of about 1200 mm long×1200 mm wide×3 mm thick, distortion occurs in the thickness direction due to repeated use. The distortion is within 5 mm at the beginning of use, but if the distortion exceeds the standard value of 13 mm due to repeated use, a decrease in production volume (decrease in current efficiency) due to the occurrence of a current short circuit between the cathode and the anode is avoided. To do so, it is necessary to correct the distortion of the cathode. This reference value is a value that varies depending on the insertion positions of the cathode and anode in the electrolytic cell and the magnitude of the applied current.

The strain of all cathodes after stripping the electrodeposited metal is measured, and the cathodes whose strain exceeds a predetermined value (for example, 10 mm) are discharged from the above process and transferred to the strain correction process. be. In the distortion correction step, the distortion of the cathode is mechanically corrected by a correction device disclosed in JP-A-2010-007106 and JP-A-2012-207273. For example, the correction device of Japanese Patent Application Laid-Open No. 2012-207273 includes a fixed wall having a vertical surface, a hanger portion projecting from the upper portion of the fixed wall and suspending the cathode beam of the cathode, and a surface of the suspended cathode. Pushing means for applying a static load from the side of the convex portion of the strain, a pressing member provided at the tip of the pushing means, a receiving member attached to the fixed wall for receiving the back surface of the cathode, and installed on the back surface side of the cathode. equipped with a distance measuring device to the cathode.

In addition, as a means for correcting the distortion of the cathode, a hammer, a pressing machine for full or partial pressing, a leveler, or the like can be used.

Japanese Patent Application Laid-Open No. 2008-231501 JP 2010-007106 A JP 2012-207273 A

In the permanent cathode system, from the viewpoint of reducing the man-hours and equipment costs required for correcting the distortion of the cathode, it is preferable that the distortion of the cathode be as small as possible. The present inventors considered that the deformation caused by the force when bending the cathode in the flexing in the peeling process is not perfect elastic deformation, and thought that it was important to reduce the strain due to flexing. However, if the amount of pressure applied to both surfaces of the cathode by the pressing tool is reduced in order to strip off the target metal electrodeposited on the surface of the cathode, the distortion occurring in the cathode can be reduced. The resulting gap may become so small that the chisel cannot be inserted, making it difficult to automatically strip the target metal.

In view of the circumstances as described above, the present invention provides a non-ferrous metal that can suppress the distortion caused in the cathode, particularly the distortion of the cathode caused by pressing both sides of the cathode in the flexing in the peeling process, with a pressing tool. It is an object of the present invention to provide an electrorefining method for

As a result of intensive research conducted by the present inventors in order to solve the above-mentioned problems, the present inventors found that, in order to strip off the target metal electrodeposited on the surface of the cathode, pressing the surface when pressing both surfaces of the cathode alternately with a pressing tool It was found that the order affects the distortion (curvature) that occurs in the cathode. The present invention has been completed based on this finding.

The electrorefining method for non-ferrous metals of the present invention comprises:
An electrolysis step of electrodepositing a target metal onto a cathode in an electrolytic cell, a cleaning step of pulling up the cathode electrodeposited with the target metal from the electrolytic cell and cleaning it, and stripping the target metal from the cathode electrodeposited with the target metal. and a strain measurement step of measuring the strain of the cathode from which the target metal has been stripped,
said cathode is repeated to said electrolysis step if said strain is within a predetermined value in said strain measurement step;
The peeling step includes
While the cathode on which the target metal is electrodeposited is supported upright, both surfaces of the cathode are alternately pressed to elastically bend the cathode, thereby peeling off the target metal from at least an upper end portion of the cathode. a flexing step to create a gap;
a chiseling step of inserting a chisel through the upper opening of the gap and further lowering it to increase the amount of stripping of the target metal from the surface of the cathode;
a down-ending step of laying down the stripped target metal with the lower end portion as a fulcrum;
and
In the flexing step, which side of the cathode is to be pressed first is switched every time the target metal is stripped off a predetermined number of times (a predetermined number of life cycles).
It is characterized by

It is preferable that the predetermined number of times is once. That is, it is preferable to switch the surface to be pressed first among both surfaces of the cathode each time the cathode is subjected to the flexing process (each life cycle).

In the flexing step, the central position in the vertical direction of both surfaces of the cathode or its vicinity can be alternately pressed once each.

According to the electrorefining method for non-ferrous metals of the present invention, the distortion occurring in the cathode can be kept small.

FIG. 1 is a flow chart showing a method for electrolytic refining of non-ferrous metals. FIG. 2(A) is a side view showing a cathode electrodeposited with a target metal, FIG. 2(B) is a cross-sectional view taken along the line XX of FIG. 2(A), and FIG. 2(B) is an enlarged view of the Y portion. 3(A) to 3(E) are cross-sectional views for explaining the procedure for stripping the target metal from the cathode. FIG. 4 is a diagram showing changes over time in the distortion of the cathode when the order in which both surfaces of the cathode are pressed is changed once each. FIG. 5 is a diagram showing changes over time in distortion of the cathode when the order of pressing both surfaces of the cathode is not changed.

The inventors of the present invention have extensively studied the cause of the deterioration of the verticality of the cathode, and found that both surfaces of the cathode are repeatedly pressed alternately from the same side in order to strip off the target metal electrodeposited on the cathode. was found to be the main factor of the distortion (curvature) that occurs in the cathode. The present invention has been completed based on this finding.

The method for electrolytic refining of non-ferrous metals of the present invention comprises, as shown in FIG. It comprises a cleaning step of removing the target metal from the electrolytic cell and cleaning it, a stripping step of stripping the target metal from the cathode on which the target metal is electrodeposited, and a strain measuring step of measuring strain of the cathode stripped of the target metal. . The cathode is cycled to the electrolysis step if the strain is within a predetermined value in the strain measurement step, transferred to a strain correction step if the strain exceeds a predetermined value, and returned to the step after strain correction. be Descriptions of these steps are omitted because they are the same as in the conventional art.

In addition, the stripping step in the electrolytic refining method for non-ferrous metals of the present invention is the same as in the prior art,
While the cathode on which the target metal is electrodeposited is supported upright, both sides of the cathode are pressed alternately to elastically bend the cathode, thereby peeling off the target metal from at least the upper end of the cathode. a flexing step to create a gap;
a chiseling step of inserting a chisel through the upper opening of the gap and further lowering it to increase the amount of stripping of the target metal from the surface of the cathode;
a down-endering step of laying down the peeled target metal with the lower end portion as a fulcrum;
Prepare.

In particular, the non-ferrous metal electrolytic refining method of the present invention is
In the flexing step, which side of the cathode is pressed first is switched every time the target metal is stripped off a predetermined number of times.
It is characterized by

Each step constituting the peeling step will be described below.

(1) Flexing step In the flexing step, while the cathode on which the target metal is electrodeposited is supported upright, both sides of the cathode are alternately pressed to elastically bend the cathode, thereby bending the cathode. It is a step of peeling off the target metal from at least the upper end to form a gap.

A plurality of anodes and cathodes are alternately immersed in parallel in an electrolytic solution containing target metals such as copper (Cu) and nickel (Ni), and energized for a predetermined period (about 5 to 10 days). As shown in 2(A) to 2(C), the target metal 2 is electrodeposited on the surface of the mother plate of the cathode 1 . The number and size of the anode and cathode can be arbitrarily set according to the size of the electrolytic cell storing the electrolytic solution. For example, the cathode 1 can have a length (height) of 800 mm to 1300 mm, a width (width) of 800 mm to 1300 mm, and a thickness of 2 mm to 40 mm.

The cathode 1 with the target metal 2 electrodeposited thereon is pulled up from the electrolytic bath, washed, and as shown in FIG. is transferred to the flexing process.

The flexing process can basically be performed by the same method as the conventional technique described in JP-A-2008-231501. That is, in the flexing step, as shown in FIG. 3B, while the lower end of the cathode 1 is supported by the fixture 3, both sides of the cathode 1 (left and right sides in FIG. 3B) are flexed in the vertical direction. The central position or its vicinity is alternately pressed by a pair of rod-shaped pressing tools 4 to elastically bend the cathode 1 . By elastically bending the cathode 1, the target metal 2 electrodeposited on the surface of the cathode 1 is also deformed. The target metal 2 is peeled off from the gap to form a gap.

Each of the pushers 4 can have a length dimension substantially equal to or greater than the width dimension of the cathode 1 (horizontal dimension in FIG. 2(A)). That is, each of the pressing tools 4 presses both surfaces of the cathode 1 in the width direction. The cathode 1 is pressed by about 50 mm to 200 mm at a position about 30% to 70% of the height from the upper end. If the pressed position in the height direction of the cathode 1 is out of the above range, or if the pressed amount is less than 50 mm, the target metal 2 may not be peeled off from the surface of the cathode 1 . On the other hand, if the pressing amount of the cathode 1 is larger than 200 mm, the cathode 1 is plastically deformed, and even if the pressing tool 4 is retracted, the cathode 1 may not be elastically restored.

The number of times each of the two surfaces of the cathode 1 is pressed is not particularly limited as long as both surfaces of the cathode 1 are pressed alternately. For the purpose of peeling off, it is sufficient to press once.

In particular, in the electrolytic refining method for non-ferrous metals of the present invention, which side of the cathode is pressed first is switched every time the target metal is stripped off a predetermined number of times. That is, of the two surfaces of the cathode 1, the first surface (for example, the left side in FIG. 3B) is first pressed to perform the flexing process, and then the chiseling process and the down-ending process are performed. Metal 2 is stripped. The cathode 1 from which the target metal 2 has been stripped is transported to the measurement process, strain is measured, and is returned to the electrolysis process through the strain correction process as necessary. In the electrolysis process, the cathode 1 with the target metal 2 electrodeposited thereon is subjected to the flexing process again (second time, third time, . . . ). After being subjected to the flexing process a predetermined number of times, in the next flexing process, the second surface (for example, the right side in FIG. 3(B)) of the two surfaces of the cathode 1 is pressed first.

For example, according to the examination of actual operation by the present inventors, the cathode 1 is a permanent cathode made of stainless steel, the size of the cathode 1 is 1200 mm in length (height), 1200 mm in width (width), and the thickness of the plate When the thickness is 3 mm, in the flexing process for each cathode life, of the two surfaces of the cathode 1, the first surface is always pressed first, then the second surface is pressed, and both surfaces are pressed once. When the flexing process is performed one by one, the distortion of the cathode 1 tends to increase as the flexing process is repeated. When the flexing process of pressing and the flexing process of pressing the second surface first were performed alternately, the distortion of the cathode 1 hardly increased, but rather tended to decrease. For example, if the number of cathodes 1 to be repeatedly used is 55, the surface to be pressed first is always In the same case, the average strain value after the flexing process is about 6.4 mm, but when the surface to be pressed first is alternately changed, the average strain value after the flexing process is about 6.0 mm. Got. By pressing the same surface first, the tendency of the cathode 1 to bend tends to increase, whereas by alternately changing the surface to be pressed first, the curvature of the cathode 1 tends to increase. This is considered to be due to the tendency to decrease.

In the present invention, the surface to be pressed first in the flexing process is preferably switched every time the cathode 1 is subjected to the flexing process one to seven times, and each time the cathode 1 is subjected to the flexing process once. , ie every time. By switching the surface to be pressed first in the repeated flexing process every time the cathode 1 is subjected to the flexing process 1 to 7 times, the cathode 1 can be made less likely to be distorted (curved). . In the repeated flexing process, if the same surface is pressed first eight times or more, the cathode 1 may be distorted (curved). The surface to be pressed first can be switched by switching the pressing tool 4 that moves first toward the surface of the cathode 1 among the pair of pressing tools 4, or by manually or automatically turning over the cathode 1. can also be done with

The timing of pressing the second surface of the cathode 1 with the other pressing tool 4 after pressing the first surface of the cathode 1 with one pressing tool 4 is not particularly limited. For example, depending on the operating speed and stop time of the pusher 4, after the surface to be pushed first (the first surface or the second surface) is pushed, the cathode 1 is in a neutral state as shown in FIG. It is also possible to press the surface to be pressed later (the second surface or the first surface) while the cathode 1 is in a deformed state without going through. Specifically, for example, after pressing the surface to be pressed first with one of the pressing tools 4, the front end of the one pressing tool 4 is pressed first without being retracted from the surface to be pressed first. The surface to be pressed later can be pressed by the other pressing tool 4 while keeping contact with the surface. Alternatively, one pressing tool 4 may be used to press the surface to be pressed first, and after the tip of the one pressing tool 4 is retracted from the first pressing surface, the elastic deformation of the cathode 1 may be completely subsided. In the waving state, the other pressing tool 4 can press the surface to be pressed later. In this way, after pressing the surface to be pressed first, if the surface to be pressed later is pressed while the cathode 1 is in a deformed state without going through the neutral state, the cathode 1 will not be affected by pressing the surface to be pressed first. The difference between the influence on the deformation of the cathode 1 and the influence on the deformation of the cathode 1 by pressing the surface to be pressed later becomes remarkable. Therefore, as in the present invention, in the flexing process, the effect of switching which side of the cathode 1 is pressed first each time the cathode 1 is subjected to the flexing process a predetermined number of times. can be obtained remarkably.

(2) Chiseling Step In the chiseling step, a chisel is inserted through the upper opening of the gap formed in the flexing step and further lowered to increase the peeling amount of the target metal from the surface of the cathode.

The chiseling step can be performed by the same method as in the prior art described in Japanese Unexamined Patent Application Publication No. 2008-231501.

In the chiseling process, as shown in FIG. 3C, the cathode 1 and the target metal 2 are separated from the surface of the cathode 1 with the pushing tool 4 retracted and the cathode beam 5 suspended from the suspending tool 6. A cutting edge 8 provided at the tip (lower end) of the chisel 7 is inserted into a wedge-shaped gap with an open top formed between the two. The thickness of the cutting edge 8 decreases toward the bottom. At this time, the cathode 1 is in an elastically restored state and is in the shape of a vertical plate. Therefore, as shown in FIGS. It increases the peeling amount of the target metal 2 from the surface of the cathode 1 .

The chisel 7 can have a width dimension that is smaller than the width dimension of the cathode 1 . When the cutting edge 8 of such a chisel 7 is inserted into the center of the width direction of the gap between the cathode 1 and the target metal 2 and further lowered, the center stripped off by the cutting edge 8 is removed, and the central part is removed. The portions existing on both sides are also pulled off from the cathode 1 by being pulled by the central portion. Alternatively, a pair of chisels can be inserted at two locations across the width of the gap between the cathode and the target metal.

(3) Down-Ender Process In the down-ender process, the target metal stripped from the cathode surface is laid down with its lower end as a fulcrum.

The down-endering process can be performed by a method similar to the conventional technique described in Japanese Patent Application Laid-Open No. 2008-231501.

The downendering process is started after the chiseling process or slightly later in conjunction with the chiseling process. In the down-ending process, first, as shown in FIG. 3C, the target metal 2 separated from the cathode 1 by the flexing process and the chiseling process is held by a holder 9 such as a vacuum pad. Next, as shown in FIGS. 3(C) to 3(E), the target metal 2 is pulled by the holder 9 in a direction in which the target metal 2 is tilted with the lower end as a fulcrum, so that the target metal 2 is completely removed from the cathode 1. tear off. In addition, as shown in FIG. 2(C), a V-shaped groove 10 is provided in the lower end surface of the cathode 1 in the width direction. Therefore, when the target metal 2 is pulled by the holder 9, the target metal 2 covers the lower end of the cathode 1 and falls down with the part bent at an acute angle as a fulcrum. Completely stripped from 1.

The target metal 2 separated from the cathode 1 is loaded and shipped.

On the other hand, the cathode 1 from which the target metal 2 has been stripped is transported to a measurement step for measuring strain. If the measured distortion of the cathode 1 is within the allowable range (predetermined value, eg, 10 mm), the cathode 1 is returned to the electrolysis step and used repeatedly. If the distortion of the cathode 1 exceeds the allowable range (predetermined value, for example, 10 mm), the cathode 1 is sent to the distortion correction process, and the distortion is corrected to within the appropriate value (for example, 6 mm). , is returned to the electrolysis step. The measurement process and the distortion correction process can be performed by methods similar to the conventional techniques described in JP-A-2010-007106 and JP-A-2012-207273.

The present invention will be further described with reference to examples and comparative examples below. However, the present invention is not limited by these examples.

[Example 1]
Fifty-five cathodes 1 consisting of permanent cathodes made of stainless steel were repeatedly used in copper electrorefining. For each cathode life, as in the conventional case, all the cathodes 1 are subjected to the distortion measurement process, and if the distortion exceeds 10 mm, they are transferred to the distortion correction process and corrected so that the distortion is within 6.0 mm. After application, the electrolysis step was repeated.

The present invention was applied to the cathode 1 on which the target metal (copper) 2 was electrodeposited, and the target metal 2 was peeled off from the cathode 1 . The cathode 1 had a length (height) of 1200 mm, a width (width) of 1200 mm, and a plate thickness of 3 mm.

Fifty-six anodes and fifty-five cathodes 1 were alternately immersed in a 1 mol/L copper sulfate aqueous solution stored in an electrolytic bath, and a current of 800 A/sheet was applied between the anodes and cathodes 1 for 7-8 times. The target metal 2 was electrodeposited on the surface of the cathode 1 by flowing for days.

The cathode 1 with the target metal 2 electrodeposited thereon is lifted from the electrolytic cell and washed. The surface was alternately pressed once by a pair of pressing tools 4 . The pressing position of the pressing tool 4 was set to the central position in the height direction of the cathode 1, and the amount of pressing was set to 100 mm.

Next, the cathode 1 is transferred to the chiseling process, and the chisel 7 is inserted into the wedge-shaped gap created between the cathode 1 and the target metal 2 with the cathode beam 5 suspended from the suspension tool 6 . By inserting the cutting edge 8 provided at the tip and further lowering the chisel 7, the peeling amount of the target metal 2 from the surface of the cathode 1 was increased. A little after the chiseling process, the down-endering process is started, the target metal 2 stripped from the cathode 1 is held by the holder 9, and the target metal 2 is pulled by the holder 9 in the direction of tilting the lower end portion as a fulcrum. By doing so, the target metal 2 was completely stripped from the cathode 1 .

The cathode 1 from which the target metal 2 was stripped was transferred to the strain measurement step, and the strain was measured. Specifically, while the cathode 1 is suspended, a laser sensor (IL300 manufactured by Keyence) is used to measure the distance from an arbitrary vertical surface of the cathode 1, and the closest place from the vertical surface and the most The absolute value of the distance difference from the distant place, that is, the distortion of the cathode 1=|maximum value of measured distance−minimum value of measured distance| was obtained. After that, if necessary, some of the cathodes 1 were transferred to the strain correction process, and the shortfall was replenished, and the 55 cathodes 1 were returned to the electrolysis process. Such an electrolysis process was repeated seven times. However, in Example 1, in the flexing process, the surface of the cathode 1 to be pressed first by the pressing tool 4 was switched each time the cathode 1 was subjected to the flexing process.

FIG. 4 shows the measurement results of the distortion of the cathode 1 from the first measurement process to the final (seventh) measurement process. In Example 1, the average value of the strain after the stripping step from the first electrolysis step to the final electrolysis step (7 life cycles) of the distortion of the 55 cathodes 1 was 6.16 mm, and the standard The deviation was 0.06 mm.

[Comparative Example 1]
In the flexing step, the same procedure as in Example 1 was carried out, except that, of the two surfaces of the cathode 1, the surface to be pressed first by the pressing tool 4 was the same each time. FIG. 5 shows the measurement results of the distortion of the cathode 1 from the first measurement process to the final measurement process. In Comparative Example 1, the average strain after the stripping step from the first electrolysis step to the final electrolysis step (7 life cycles) of the distortion of the 55 cathodes 1 was 6.31 mm. The deviation was 0.14 mm.

In Example 1, in comparison with Comparative Example 1, it is understood that the generation of distortion due to the flexing process is suppressed in the cathode 1 as a whole, that is, it is difficult to cause bending tendency. Regarding Example 1 and Comparative Example 1, the significance level A two-tailed t-test at 5% gave a t-value of 11 and a p-value of less than 1%, demonstrating the effect of the present invention.

REFERENCE SIGNS LIST 1 cathode 2 target metal 3 fixture 4 pushing tool 5 cathode beam 6 suspension tool 7 chisel 8 cutting edge 9 holder 10 groove

Claims (4)

A stripping step of stripping the target metal from the cathode on which the target metal is electrodeposited ,
The peeling step includes
While the cathode on which the target metal is electrodeposited is supported upright, both surfaces of the cathode are alternately pressed to elastically bend the cathode, thereby peeling off the target metal from at least an upper end portion of the cathode. a flexing step to create a gap;
a chiseling step of inserting a chisel through the upper opening of the gap and further lowering it to increase the amount of stripping of the target metal from the surface of the cathode;
a down-endering step of laying down the peeled target metal with the lower end portion as a fulcrum;
and
In the flexing step, which side of the cathode is pressed first is switched every time the target metal is stripped off a predetermined number of times.
Electrolytic refining method for non-ferrous metals. 2. The electrorefining method for non-ferrous metals according to claim 1, wherein said predetermined number of times is once. 3. The method for electrolytic refining of non-ferrous metals according to claim 1 or 2, wherein in said flexing step, the center position in the vertical direction of said cathode or its vicinity is alternately pressed once from both sides. Before the stripping step, the target metal is electrodeposited on the cathode in an electrolytic cell to obtain a cathode electrodeposited with the target metal, and the cathode electrodeposited with the target metal is removed from the electrolytic cell and washed. A strain measurement step of measuring the strain of the cathode from which the target metal has been stripped after the stripping step,
the cathode is cycled through the electrolysis step if the strain in the strain measurement step is within a predetermined value;
The electrorefining method for nonferrous metals according to any one of claims 1 to 3.

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