JP2002105684A - Electrolytic method, and electrolytic tank used therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrolytic method of preventing anodic passivation by eliminating any high concentration area of metal subjected to electrolysis such as copper which is locally or globally generated in the vicinity of an anode surface to unify the whole concentration distribution between both electrode plates for the electrolyte between anodes and cathodes, and to provide an electrolytic tank used therefor. SOLUTION: In this electrolytic method and the electrolytic tank, a large number of anodes and cathodes are disposed in the electrolytic tank 1 facing each other, the anodes and cathodes are energized in parallel, the electrolyte is discharged from an electrolyte feed port 3 to an electrolyte discharge port 4 in a bottom part parallel to an electrolytic surface of an electrode plate and diagonally therebelow between the adjacent electrode plates, and the electrolyte in the electrolytic tank is agitated and replaced, and waste electrolyte is discharged from the electrolyte discharge port 4 in the bottom part and the electrolyte discharge port 4 in an upper part of a sidewall of the electrolytic tank.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anode and a cathode which are alternately arranged in an electrolytic cell and are energized in parallel in electrolysis such as electrolytic refining of copper (both are called electrode plates).
Efficient electrolysis method for preventing the passivation of the anode, etc. by forcibly passing the electrolytic solution between the electrodes to promote the homogenization of the concentration of the electrolytic solution between the electrode plates and the replacement of the liquid, and the use in this method The present invention relates to an electrolytic cell to be used.

[0002]

2. Description of the Related Art In electrolysis, for example, electrolytic refining of copper, an anode containing copper as an electrolysis target metal as a main component and containing impurities, and a cathode for electrodepositing copper are alternately arranged in an electrolytic cell. And electrically connected in parallel, filled with an electrolytic solution, and passed a direct current, thereby dissolving the copper in the anode and the more noble elements in the electrolytic solution, Electrodeposit more noble elements on the cathode.
At this time, the electrolytic solution near the anode surface has a high copper concentration, so that the specific gravity of the solution is large, and the electrolytic solution near the cathode surface has a low copper concentration, and the specific gravity of the electrolytic solution is small, so that the concentration is increased. Cause As a result, an electrolytic solution having a high copper concentration exists near the anode surface and at the bottom of the electrolytic cell.
Also, the temperature of the electrolytic solution tends to decrease at the bottom of the electrolytic cell due to heat dissipation from the bottom surface.

[0003] An anode in an electrolytic solution under such a bad condition that the copper concentration is high and the liquid temperature is low is easily passivated. In other words, the concentration of copper in the electrolyte near the anode surface becomes supersaturated, and copper sulfate and the like precipitate on the anode surface and the slime layer in contact with the anode to form a solid film, so that copper cannot be eluted from the anode. It is considered that The concentration of the target metal in the electrolytic solution in the electrolytic refining is highest on the anode surface and lowest on the cathode surface. Generally, there is a sharp concentration change in the region very close to the surface of the bipolar, during which the concentration gradient of the liquid phase is very slow. Here, when the anode passivation is caused by the anode (for example, when the anode contains a large amount of impurities),
There are cases where it is caused by electrolysis conditions (for example, high current density electrolysis) and cases where it is caused by the electrolytic solution. By the flow, the concentration of copper dissolved in the electrolytic solution on the anode surface or in the slime layer becomes supersaturated, and copper sulfate or the like precipitates, forming a thin film on the surface,
It is considered that the elution of copper from the anode does not proceed. As a measure to prevent such passivation of the anode,
Proposals have been made to raise the temperature of the electrolytic solution, lower the copper concentration in the electrolytic solution, and increase the flow rate.

[0004] However, an increase in the heating cost is inevitable for raising the temperature of the electrolytic solution, and if the concentration of copper in the electrolytic solution is reduced in the electrolytic refining of copper, the electrodeposition structure at the cathode becomes coarse and the electrolytic solution in the electrolytic solution is reduced. Therefore, it is desired that the copper concentration of the electrolytic solution be kept high especially in high current density electrolysis because the impurities are easily involved and the quality is easily deteriorated. Further, an increase in the flow rate induces a slime entrainment phenomenon which causes a deterioration in the quality of the electrodeposited metal, and thus there is a limit to the increase in the flow rate. In addition, regarding the measures to increase the flow rate of the electrolyte on the electrode surface, focusing on the reflux of the electrolyte, the supply and discharge of the liquid is performed so as not to obstruct the flow generated around the electrode due to electrolysis in the electrolytic cell. JP-A-10-183 with the position of the mouth determined
Although there is an example of No. 389, it does not reliably and forcibly flow the electrolyte between each electrode plate, and also substantially discloses the suppression of uneven copper concentration affecting passivation. There is no. Conventionally, a side recirculation method in which an electrolytic solution is passed in a direction parallel to the electrode plates has also been implemented. However, these are basically laminar flows between the electrodes and act on the concentration convection described above. It did not cause agitation to a moderate degree, and was insufficient as a measure for preventing passivation.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to eliminate the high concentration region of an electrolytic object metal such as copper which is locally or entirely generated in the vicinity of the anode surface with respect to the electrolyte between the anode and the cathode. It is an object of the present invention to provide an electrolysis method for homogenizing the concentration distribution across the both electrode plates to prevent the passivation of the anode, and to provide an electrolytic cell used for the electrolysis method.

[0006]

Means for Solving the Problems An artificial flow is caused in the electrolyte between the plates, and the electrolyte between the plates is mechanically agitated. As a result of various investigations to eliminate the unevenness of the concentration of dissolved components, particularly the concentration of the metal for the purpose of electrolysis, and to prevent passivation of the anode, the present invention was achieved.

That is, the present invention firstly provides that a plurality of anodes and a plurality of cathodes are alternately arranged in an electrolytic cell, and that a plane Secondly, the electrolytic solution is discharged by passing an electrolytic solution in a direction parallel to the direction of the electrolytic solution, and secondly, from the portion between the upper portion of one side surface and the lower portion of the other side surface between the adjacent electrode plates. A first electrolytic method in which an electrolytic solution is discharged toward a portion between the first and second electrolytic cells to allow the electrolytic solution to pass therethrough for electrolysis, and thirdly, the first or second electrolytic method in which the discharge speed of the electrolytic solution is 0.2 m / sec or more. Fourth, any one of the first to third electrolysis methods, wherein the electrolysis is electrolytic refining of copper. Fifth, a plurality of anodes and a plurality of cathodes are alternately opposed in an electrolytic cell. Parallel to the plane of the plates between the plates, which are arranged in parallel and are energized in parallel. A liquid supply port for discharging an electrolytic solution is provided in the electrolytic cell, and sixthly, the liquid supply port is provided between adjacent two electrode plates at a portion between upper portions of one side surface and near an upper portion thereof. , Is a liquid supply port that discharges the electrolyte toward a liquid discharge port disposed at a portion between the lower portion and the vicinity of the other side surface,
Seventh, a seventh electrolytic cell, wherein the drainage port is integrated or divided in the lower part of the side wall of the electrolytic cell opposite to the liquid supply port so as to face the entire number of the liquid supply ports, and is disposed in the cell. Done, sixth
Eighth, any one of Fifth to Seventh electrolysis tanks in which a drain port is provided at one or more locations on the upper side wall of the electrolysis tank. Ninth, the electrolysis tank is made of copper. The electrolytic cell for electrolytic refining of any one of the fifth to eighth electrolytic cells.

In the present specification, the term “parallel direction” with respect to the plane of the electrode plate from which the electrolyte is discharged is not only a “strictly geometrically parallel direction” but also a “substantially parallel direction”. It is a concept that also encompasses the bipolar plates, preferably until the center line in the discharge direction of the electrolyte from the portion between the upper portions of the one side surface of the opposing bipolar plates reaches the portion between the lower portions of the other side surface. It means the case that does not cross any of them. It is preferable to provide one or more liquid supply ports between each electrode plate. Also,
The drainage port is preferably provided at one or more places in the electrolyte opposite to the liquid supply port between each electrode plate (especially at the lower end level of the electrode plate or less, and (It is preferable to be integrated or divided so as to face all the liquid supply ports, and to be arranged at the lower part of the inner wall of the electrolytic cell facing the liquid supply ports), (2)
It is also preferable to dispose the electrolytic solution near the liquid surface of the electrolytic bath between the electrode plates at the upper part of the side wall of the electrolytic bath opposite to or adjacent to the liquid supply port. (3) More preferably, (1) and ( 2) should be added. In the present specification, the case of electrolytic refining of copper is described in Examples and the like, but this is one example of the present invention, and the present invention is not limited to these. It encompasses a wide range of electrolysis such as electrolytic refining of metals such as lead, bismuth, gold, and silver, electrowinning of metals such as zinc dissolved in a liquid, and plating.

The direction of discharge of the electrolyte discharged in a plane parallel to the plane of the electrode plate may be any of a horizontal direction, an upward direction, a downward direction, an obliquely upward direction, and an obliquely downward direction. Discharge is preferably performed at an angle of 30 to 75 degrees downward from the portion near the upper portion of the side surface to the lower portion on the other side, and more preferably, obliquely downward (downward) from the portion near the upper portion of one side to the portion near the lower portion of the other side. By discharging in the diagonal direction), the electrolyte between the electrode plates can be discharged most effectively and replaced with a new electrolyte. Regarding the discharge speed of the electrolyte from the liquid supply port, in order to eliminate the stagnation of the electrolyte between each electrode plate and to ensure the replacement of the electrolyte,
A discharge speed of 0.2 m / sec or more is necessary in order to generate a stirring flow in the electrolyte between the electrode plates to eliminate and homogenize the electrolyte concentration unevenness. At a discharge speed of less than 0.2 m / sec, stirring cannot be performed over the entire area between the electrodes, so that the purpose of homogenizing the concentration of the electrolyte between the electrodes cannot be achieved. Cleaning is also difficult.

[0010]

Next, the present invention will be further described with reference to examples.

[Example 1] First, in designing an electrolytic cell,
As a basic condition that the electrolyte solution between the electrode plates can be efficiently stirred and the separation and settling of the anode slime is promoted, a recirculation method in which the electrolyte solution is discharged in a diagonal direction in which the electrolyte is discharged upward and downward is adopted. Next, the vertical 18
Create a water tank made of transparent acrylic plate of 00 mm, 900 mm in width and 30 mm in width. In the tank, various liquid supply ports are installed on the upper side of one side, and the drainage port is installed on the lower side of the other side. A transparent solution is placed in the water tank in advance, and the black semi-transparent liquid of the same specific gravity is changed in the liquid supply direction and discharge speed for each test, and the liquid is supplied at a constant speed and the liquid exchange is observed in chronological order. did. One example of such a situation is shown in FIG. That is, this is a case where a straight pipe nozzle having a diameter of 10 mm is discharged obliquely downward at an angle of 60 degrees at a discharge speed of 0.3 m / sec, and a, b, c, and d in FIG. It is a state in which the liquid is replaced at each point in time after one second, one minute, and two minutes. From these tests, it was found that the installation angle of the liquid supply port is more preferably 30 to 75 degrees obliquely downward with respect to the horizontal direction, and more preferably the liquid supply port is directed to a drain port provided diagonally downward. That is, the oblique downward direction 30
When the temperature is less than 75 degrees or more than 75 degrees, a region where the liquid stays locally occurs, and the time required for the replacement of the solution is significantly longer than that in the case of 30 degrees or more and 75 degrees or less. In addition, the discharge angle
Specific numerical values such as the speed vary depending on the shape of the electrolytic cell and the electrode. However, in the test electrolytic cell having the above-described gap between the electrodes, the discharge speed is set to 0.
2 m / sec or more, preferably 0.3 to 1.0 m / sec is required. From the viewpoint of preventing entrainment of settling slime and supply / drainage equipment in an actual electrolytic process, the discharge speed is 0.3 m / sec.
Seconds were found to be the most efficient overall.

An electrolytic cell determined in this way is prepared, and in the actual electrolysis process, the same supply of copper having a concentration of 46 g / l is supplied to the electrolytic cell by the conventional reflux method (conventional cell) and the test tank according to the reflux method of the present invention. Using the reference point at the upper part of the electrolytic cell (120
mm), the copper concentration distribution in the electrolyte in the plane direction between the plates near the cathode surface was measured at three points at 400 mm, 800 mm, and 1200 mm below, one point immediately below the liquid surface, and one point immediately below the cathode. The results are shown in Tables 1 and 2, respectively. The conventional tank used here is as shown in FIG.
A liquid supply port is provided at the lower part of one central part of the side wall of the electrolytic cell parallel to the plane of the electrode plate, and a liquid discharge port is provided at the upper part of the other central part. As shown in FIG. 3, a liquid supply port is provided between adjacent adjacent electrode plates at a portion between the upper portions of one side surface of the two electrode plates, and a liquid discharge port is provided at a portion between the lower portions of the other side surface (provided that they are provided). All drains are integrated). Regarding the copper concentration distribution of the electrolytic solution, the average value at 9 points between the electrode plates in the conventional tank was 48.3 g / l and the universal standard deviation was 0.76 g / l, while the electrode plate in the test tank of the present invention was The average value of 9 points was 51.1 g / l, and the universal standard deviation was 0.
When compared with the Cp value obtained by dividing the universal standard deviation, which is a measure of variation, by the average value, the former was 1.g / l.
57% and 0.57% for the latter, and the test tank of the present invention was able to significantly reduce the unevenness of the copper concentration as compared with the conventional tank. In addition, regarding the homogenization of the electrolyte concentration, it was found that the test tank was closer to the 9-point average value just below the gap between the electrodes, and that the stirring effect was extended to a position near the bottom just below the gap between the electrodes. . Regarding the quality of silver which is a typical impurity with respect to the quality of electrodeposition by the test tank of the present invention, 5 g / g
t, which is improved from 10 g / t in the conventional tank (the silver grade in the copper anode was 7000 g / t).
same as below).

[0013]

[Table 1]

[0014]

[Table 2]

It should be noted that the average value of the electrolytic copper concentration between the electrode plates is 2 g / l in the conventional tank and 5 in the test tank as compared with the supply liquid concentration.
g / l higher. This is because, as described above, in the conventional tank, the copper component eluted from the anode forms a downward flow near the anode and the slime layer remaining on the surface of the anode, whereas in the test layer, artificial stirring occurs. Thus, it is estimated that the gas was diffused from the vicinity of the anode to the vicinity of the cathode.

Example 2 In Tables 1 and 2, the copper concentration near the surface layer of the electrolytic cell was lower in the test tank, but the specific gravity of the electrolytic solution having a reduced copper concentration near the cathode became smaller. As a result, it was found that the solution gathered in the vicinity of the surface of the electrolyte and remained because the extraction of the electrolyte was insufficient. Since the decrease in the copper concentration causes the electrodeposition property at the cathode to be roughened, as shown in FIG. 4, the liquid near the electrolyte surface flows out into the test tank of Example 1 (FIG. 3). If a drain outlet is also installed on the upper part of the side wall of the electrolytic cell, specifically, on the upper part of one central part of the electrolytic cell wall parallel to the plane of the electrode plate as in the conventional cell, the copper concentration distribution of the electrolytic solution is shown. As shown in FIG. The electrodeposition quality was 4 g / t for a typical impurity silver.

[0017]

[Table 3]

Example 3 Since the improvement of the copper concentration distribution of the electrolytic solution in the electrolytic cell and the maintenance of the electrodeposition quality were confirmed, the possibility of passivation was evaluated. 13 per current density of 230 A / m ² per anode
When the electrolysis is performed twice a day, the test tank (the test tank of Example 2 shown in FIG. 4) and the conventional tank (Example 1 shown in FIG. 2)
The current density was 340 in the second electrolysis
When the electrolysis was performed for 9 days at a rate of up to A / m ² , in the conventional cell, anode passivation progressed on the 8th day, and in order to continue electrolysis, measures had to be taken to reduce the current density. In contrast, the test tank did not passivate,
Electrolysis could be performed at A / m ² for 9 days. Table 4 shows the transition of the second tank voltage. The second electrodeposition quality of silver was 16 g / t in the conventional tank and 5 g / t in the test tank.

[0019]

[Table 4]

[0020]

By employing the electrolysis method and the electrolytic cell of the present invention, it is possible to forcibly flow the electrolyte between the respective electrodes, and to prevent unevenness in the flow between the electrodes. Compared to the reflux method from the longitudinal direction or the side, the concentration distribution of the target metal for electrolysis between the electrode plates can be homogenized, and the copper concentration in the liquid near the anode can be reduced. Even when a contained anode is used or in the case of high current density electrolysis, a high purity electrodeposited metal can be obtained without passivating the anode. In addition to electrolysis metal,
In particular, in the electrolytic refining of a copper anode containing a large amount of a noble metal such as silver, passivation is of particular concern, so far it has been necessary to reduce the current density and perform electrolysis. It has become possible to increase the current density and increase operation. Furthermore, electrolysis of a copper anode containing a higher concentration of impurities such as silver has become possible.

[Brief description of the drawings]

FIG. 1 is a diagram of a discharge test performed to determine a liquid supply method.

FIG. 2 is a view showing the entire conventional tank used in Example 1 and the positional relationship between a liquid supply port and a liquid discharge port thereof.

FIG. 3 is a view showing the entire test tank used in Example 1 and the positional relationship between a liquid supply port and a liquid discharge port thereof according to the present invention.

FIG. 4 is a view showing the entire test tank used in Example 2 and the positional relationship between a liquid supply port and a liquid discharge port thereof according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electrolyzer 2 Electrode plate 3 Supply port 4 Drain port

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takeshi Watanabe 1-8-2 Marunouchi, Chiyoda-ku, Tokyo Dowa Mining Co., Ltd. (72) Inventor Atsushi Honda 1-8-2 Marunouchi, Chiyoda-ku, Tokyo Same as above (72) Inventor Takayuki Kimura 1-8-2 Marunouchi, Chiyoda-ku, Tokyo Kosaka Smelting Co., Ltd. F-term (reference) 4K058 AA07 AA11 BA21 BB03 FA30

Claims (9)

[Claims] 1. A plurality of anodes and a plurality of cathodes are alternately arranged in an electrolytic cell so as to face each other, and an electrolytic solution is discharged in a direction parallel to the plane of the plates between the plates which are energized in parallel. An electrolytic method characterized in that the solution is passed through and electrolyzed. 2. The electrolysis according to claim 1, wherein an electrolytic solution is discharged from a portion between the vicinity of the upper portion of one side surface to a portion between the vicinity of the lower portion of the other side surface between the adjacent two electrode plates, and the electrolytic solution is allowed to flow therethrough for electrolysis. Method. 3. The electrolysis method according to claim 1, wherein the discharge speed of the electrolytic solution is 0.2 m / sec or more. 4. The method according to claim 1, wherein the electrolysis is copper electrorefining.
3. The electrolysis method according to any one of 3. 5. A plurality of anodes and a plurality of cathodes are alternately arranged in an electrolytic cell so as to be opposed to each other, and an electrolytic solution is discharged in a direction parallel to the plane of the plates between the plates which are energized in parallel. An electrolytic cell characterized in that a liquid supply port is provided. 6. The liquid supply port is configured such that the electrolyte is supplied to a drain port provided between a portion near an upper portion of one side surface between two adjacent electrode plates and a portion between a portion near a lower portion of the other side surface. The electrolytic cell according to claim 5, which is a liquid supply port for discharging. 7. The liquid discharge port is integrated or divided in the lower part of the side wall of the electrolytic cell opposite to the liquid supply port so as to face the entire number of the liquid supply ports, and is disposed in the cell. Electrolytic cell. 8. The electrolytic cell according to claim 5, wherein a drain port is provided at one or more locations on the upper side wall of the electrolytic cell. 9. The electrolytic cell is an electrolytic cell for electrolytic refining of copper.
The electrolytic cell according to claim 5.