JP3097824B2 - Long-period pulse electrolysis operation method in copper electrorefining - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to copper electrolysis, and more particularly to a method for operating copper electrorefining.

[0002]

2. Description of the Related Art In copper electrorefining, usually 40 to 4 times is used.
An electrolytic solution containing 7 g / l of copper is used, blister copper is used as an anode, and a pure copper plate is used as a cathode. However, with the same electrolytic cell scale, the higher the current density, the higher the productivity. However, in the operation of high current density (300 A / m ² or more) employed for improving productivity, the defect rate of the product cathode plate increases due to the generation of particles, bumps and needle-like electrodeposition on the cathode side, and short-circuiting occurs. There is a technical problem in that the increase in the number of particles and the occurrence of passivation on the anode side occur. On the other hand, the passivation phenomenon is also affected by impurities in the anode, copper concentration in the electrolytic solution, surface smoothing agent concentration, etc., but is greatly affected by the current density. 3
When it is more than 00 A / m ² , it is often seen. As a method for solving these problems, the energization method includes a pulse method in which the current is periodically stopped for a short time, and a periodic inversion current electrolysis (PRC) method in which the direction of the current is periodically inverted for a short time. It is effective to be.
However, the occurrence of particles, bumps, and needle-like electrodeposition becomes remarkable as the current density increases, and at a current density of 300 A / m ² or more,
Even when ordinary pulse electrolysis is applied, deterioration of the electrodeposition state on the surface cannot be avoided.

[0003] Further, with respect to the passivation time and the cycle of the pulse electrolysis, the purpose of the passivation prevention can be achieved without deteriorating the cycle efficiency even by the conventional pulse electrolysis. However, conventional pulse electrolysis is insufficient to maintain the surface condition of the cathode in a good condition. here,
The cycle efficiency (%) is defined as E _C = 100 × (T / (T + T ′)) where T is the energizing time in the positive direction in pulse electrolysis, T ′ is the power outage time, and T + T ′ is one cycle. . Further, in the conventional pulse electrolysis, T ′ = 0.1 to 9 seconds and 1
It is a short cycle method with a short cycle.
In the case of pulse electrolysis, a long-time blackout occurs, which causes problems such as a decrease in cycle efficiency and an economical problem. Regarding prevention of short circuit,
A surface smoothing agent such as glue or thiourea is added to the electrolyte to prevent current from concentrating on a specific portion of the cathode. However, when these surface smoothing agents are used, there is a disadvantage that the components are electrodeposited on the cathode together with copper, and the purity of electrolytic copper is reduced. It is also known that the use of excess surface smoothing agent often increases shorts. By properly controlling the amount of the surface smoothing agent, the surface condition of the cathode is improved and short-circuit can be prevented. However, analysis of surface smoothers is generally difficult, and as a result, it is difficult to accurately determine the effective amount.
Therefore, the addition amount of the surface smoothing agent must be adjusted while observing the surface of the cathode, and there is a limit in use, and the effect has not always been sufficiently exerted.

[0004]

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to reduce the defective product rate by improving the energization method in pulse electrolytic refining of copper.

[0005]

According to the present invention, 300 A / m
^In the electrolytic refining of copper at a high current density of ² or more, a pulse energization method of periodically stopping the current for a certain period of time is employed. For at least 30 seconds. Specifically, the energizing time in the positive direction is T, the power outage time is T ', and T + T' is one cycle, and the cycle efficiency E _C (%) in pulse electrolysis is E _C = 10.
When defined as 0 × (T / (T + T ′)), the current stop time is maintained for 30 seconds or more, and the cycle per hour is 4
By making the number of times equal to or less than the number of times, the cycle efficiency is increased to 95% or more, and the productivity is increased without deteriorating the quality of the product cathode plate.

[0006]

DETAILED DESCRIPTION OF THE INVENTION In the present invention, in the electrolytic refining of copper at a high current density, the current is periodically stopped for a certain period of time, that is, in the so-called pulse electrolysis, the operation method is used to determine the surface condition of the cathode. Is maintained well. FIG. 1 shows that when the power outage time is changed in electrolytic refining at a high current density of, for example, 300 A / m ² or more, the potential change from the start of the positive current supply until the potential reaches a steady state, that is, the potential difference and the power outage time Shows the relationship. From FIG. 1, it can be seen that the potential difference converges to a constant value during a power outage time of about 30 to 40 seconds. That is, if there is a power outage of 30 seconds or more, it is considered that the surface state of the cathode is in the same state as at the start of energization. In other words, with the power outage of 30 seconds or more, the surface smoothing agents such as thiourea, glue, and chloride ion, which are usually used in the electrolytic refining of copper, are reproduced in a state in which they are adsorbed on the cathode surface in the same way as when power was turned on. It is thought that it is done. on the other hand,
If the power outage time exceeds 100 seconds, it will be in a steady state,
It only reduces production efficiency. Generally, the surface smoothing agent is
Usually, it is interpreted that the particles are adsorbed on the granular portion of the surface and the grain growth is suppressed by reducing the electrodeposition rate of the portion. On the other hand, when the current density increases, the concentration of the current on the granules and the promotion of the decomposition of the surface smoothing agent adsorbed on the granules promote the deposition of the surface smoothing agent on the electrode surface with respect to the electrodeposition rate of copper on the electrode. It is considered that the relative decrease in the supply rate causes the concentration of the adsorbed material on the electrode surface to decrease, and as a result, the cathode surface electrodeposition becomes granular.

According to the present invention, even in an operation at a high current density of 300 A / m ² or more, the surface smoothing agent is re-adsorbed due to a power outage for a relatively long time, and the surface smoothing agent lacking on the electrode surface. , Good electrodeposition can be obtained. On the other hand, the reason why the cycle is short in ordinary pulse electrolysis is that it has been pointed out that the growth of the diffusion layer on the electrode surface increases as the energization time increases. However, in industrial electrolysis such as copper electrorefining, a large circulating flow exists on the electrode surface, and the growth of the diffusion layer, which is usually considered, is greatly increased by the upward flow due to the circulating flow on the cathode surface and the downward flow due to natural convection on the anode surface. Has been suppressed. Therefore 1
It is considered that passivation due to an increase in the diffusion layer of the anode can be prevented even with one or two pulse outages per time. Based on the above theory, in the present invention, by configuring a cycle of pulse power failure, specifically, the pulse power failure is performed about 1 to 4 times per hour, and the power failure time at that time is preferably 30 times. By securing for more than a second, passivation of the anode can be prevented even during operation at a high current density, and a smooth product cathode plate having a good electrodeposition state can be obtained. Furthermore, according to the present invention, if the power is cut off 1 to 4 times / hr, the cycle efficiency is also maintained at 95% or more, and an economically advantageous improvement in productivity can be achieved.

[0008]

【Example】

[Example 1] The appearance evaluation point of the product cathode plate when the number of cycles per hour was changed was examined. Table 1 shows the results. The energization conditions are as follows. Also,
Appearance evaluation points are obtained by dividing both surfaces of the product cathode plate into nine parts, and visually giving the worst one point and the best one five points.
The points are the total points when a five-point evaluation is performed (9
0 points). (Electrification conditions) Current density: 328 (A / m ² ) Copper concentration: 52 (g / l) Sulfuric acid concentration: 188 (g / l) Glue concentration: 1.4 (mg / l) Chloride ion concentration: 33 ( mg / l) Thiourea concentration: 1.1 (mg / l) Liquid temperature: 62 (° C) Anode: 1015 x 1015 x 36 (mm) Cathode: 1050 x 1070 x 0.7 (mm) Number of cathodes: 23 ( Electrolyzer: 3000 × 1250 × 1360 (mm)

[0009]

[Table 1] Cycle configuration Energization Power failure Cycle efficiency Cycles Appearance evaluation point 59 (min) 1 (min) 98 (%) 1 (times / hr) 69.5 59.5 (min) 0.5 (min) 99 (%) 1 (times) (hr) 69.5 201 (s) 15 (s) 93 (%) 17 (times / hr) 59.5

From Table 1, it can be seen that the number of cycles is 30 times / hr.
Those that adopt the so-called long-period pulse method with a power outage time of seconds or more have higher appearance evaluation points than those that adopt the so-called short-period pulse method with a cycle time of 17 times / hr and a shorter power outage time. I understand. This is considered to be because, as described above, the surface smoothing agent was re-adsorbed due to a long-time power failure, and the surface smoothing agent was sufficiently supplied to the electrode surface. Since the management pass criterion for the appearance evaluation point is usually 63 points, it is possible to achieve the management pass criterion by adopting the long-period pulse method.
In the case of the long-period pulse method, a cycle efficiency of 95% or more is ensured, and it is considered that there is no problem economically. On the other hand, in all cases, passivation of the anode was completely prevented.

[Embodiment 2] The energization conditions are changed from those in Embodiment 1 so that the number of cycles per hour is 1, 2 and 4.
The appearance evaluation point of the product cathode plate when the number of times was changed was examined. Table 2 shows the results. The energization conditions are as follows. (Electrification conditions) Current density: 319 to 324 (A / m ² ) Copper concentration: 47 to 53 (g / l) Sulfuric acid concentration: 187 to 191 (g / l) Mold concentration: 1.4 (mg / l) Chloride Substance ion concentration: 50 (mg / l) Thiourea concentration: 2.2 (mg / l) Liquid temperature: 63.1-63.6 (° C.) Anode: 1015 × 1015 × 36 (mm) Cathode: 1050 × 1070 × 0.7 (mm) Number of cathodes: 25 to 27 (sheets) Electrolyzer: 3000 × 1250 × 1360 (mm)

[0012]

[Table 2] Cycle configuration Energization Power failure Cycle efficiency Cycles Appearance evaluation point 59 (min) 1 (min) 98 (%) 1 (times / hr) 71.5 29.4 ( min ) 34 (s) 98 (%) 2 (times) (hr) 71.5 14.7 (min) 16 (s) 98 (%) 4 (times / hr) 69.5

According to Table 2, the number of cycles is 1 to 4 times / hr.
In the long-period pulse method with
It can be seen that the evaluation criteria for the appearance evaluation point are satisfied. However, in the case of the cycle number of 4 times / hr in which the power outage time is 30 seconds or less, it can be seen that the appearance evaluation score is slightly reduced. This is considered to be because the surface smoothing agent was not sufficiently supplied to the electrode surface during the power failure because the power failure time was short. In the case of the cycle number of 4 times / hr, for example, when the cycle efficiency is set to 95%, the power outage time is secured about 45 seconds, and it is considered that the appearance evaluation point can be further improved. Also in Example 2, passivation of the anode was completely prevented.

[0014]

According to the present invention, in the electrolytic refining of copper at a high current density, an energizing method of periodically stopping the current for a fixed time is adopted, the energizing time in the positive direction is set to T, and the power outage time is set to T. ', T + T' is defined as one cycle, and the cycle efficiency E _C (%) in pulse electrolysis is E _C = 100 × (T / (T +
T ')), the current stop time is preferably 30
By keeping the cycle for at least 4 seconds and the cycle per hour at 4 times or less, and maintaining the cycle efficiency at 95% or more,
It is possible to increase the productivity without deteriorating the quality of the product cathode plate.

[Brief description of the drawings]

FIG. 1 is a graph showing a relationship between a potential difference and a power outage time from the start of positive current supply to a cathode until the potential reaches a steady state.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) C25C 1/00-7/08

Claims (2)

(57) [Claims] 1. In a copper electrolytic refining having a current density of 300 A / m ² or more, a pulse blackout is performed 1 to 4 times per hour.
A long-period pulse electrolysis operation method, wherein one pulse power outage is performed for 30 seconds or more. ^{2. In} a copper electrorefining method having a current density of 300 A / m ² or more, an energization cycle method in which current is periodically stopped for a certain period of time is adopted, the energization time in the positive direction is T, and the outage time is T ′, T + T ′ is defined as one cycle, and the cycle efficiency E _C (%) in pulse electrolysis is E _C = 100 × (T /
(T + T ')), wherein the cycle efficiency is maintained at 95% or more, the cycle per hour is set to four or less, and the current stop time of 30 seconds or more is maintained. Operation method.