JP4831408B2 - Method for producing plate-like electrolytic copper - Google Patents

Description

  The present invention relates to the production of metallic copper by electrowinning, and more specifically, relates to a method for producing plate-like electrolytic copper having a dense structure from a halogen-based solution.

The electrolytic collection method has been widely put into practical use as a method for producing metallic copper. The method currently used is, for example, SX-EW method, and mainly refined through various liquid purification processes such as leaching copper from raw copper ore using sulfuric acid and solvent extraction, mainly for oxide ore. -Metal copper is manufactured from the concentrated copper electrolyte, and the target liquid is a sulfuric acid-based solution. On the other hand, a technique for electrolytically collecting copper from a solution obtained by leaching copper using a halogen-based solution such as a chloride bath has been studied. (Patent No. 2857930: Patent Document 1)

Advantages of using halogen-based solutions include:
(1) The ability to leach low-reactivity sulfide ore by utilizing the strong oxidizability of simple chlorine, bromine or its compounds produced by anodic oxidation;
(2) Since copper dissolves stably in a monovalent state in a solution containing a high concentration of halogen salts, electrolysis as monovalent copper ions results in half the amount of electricity compared to divalent electrolysis in a sulfuric acid bath. That copper can be manufactured,
(3) Ion conductivity / exchange current density is high, and even at high current densities, current efficiency does not drop significantly, so productivity is high.
Etc.

However, in electrowinning from a halogen-based solution, the electrodeposited metal copper becomes dendritic powder or aggregated coarse particles. For this reason, the electrodeposited copper of SX-EW in a sulfuric acid bath can be taken out and sold as a plate-like electrodeposited cathode, whereas in the case of electrolytic extraction from a halogen-based solution, the copper is taken out from the battery case, washed, and product It takes time for handling such as casting. In addition, the copper powder easily oxidizes even after repeated cleaning, which has been a cause of product quality degradation.

In order to solve these problems, conditions for obtaining a smooth electrodeposit have been studied experimentally for monovalent copper electrolysis in a chloride bath.
Halogen-based solutions such as chloride baths tend to have dendritic electrodeposition compared to sulfuric acid baths. Additives that are effective in smoothing in sulfuric acid baths such as glue can be used for dense and smooth electrodeposition over long periods The practical conditions for producing copper were not known.
As a result of investigation for solving this problem, the inventor found that polyethylene glycol is an additive having an excellent smoothing effect in a halogenated bath, and invented a method for producing plate-like electrolytic copper using the same. . (Patent Document 2)
Patent No. 2857930 Japanese Patent Application No. 2005-147122

However, since the above-mentioned invention adds an additive to the electrolytic solution, there is no problem when the operation is considered in the electrolysis process alone, but the anolyte having a reduced copper concentration combined with the leaching process is repeatedly used for copper leaching from the ore. In some cases, there is a concern that even a trace amount of organic additive may interfere with the reaction in the leaching process, particularly in terms of ensuring stable operation when considering long-term behavior. It was.

The present invention takes advantage of power saving by monovalent electrolysis in copper electrowinning from a halogen-based solution, while on the other hand, a dense plate-like electrolytic copper excellent in handling properties such as removal from a battery case and product washing, The present invention proposes a technique that enables production without using an additive.

In general, in metal electrodeposition from a solution, it is known that the diffusion limit current density can be increased by stirring the liquid and promoting the supply of ions to the cathode, thereby forming a metal layer having a dense structure.
The inventors have found that, in copper electrodeposition from a halogen-based solution, the dendritic growth can be suppressed and the electrodeposited copper structure can be densified by flowing the liquid in the vicinity of the cathode at a high speed. It came to.
That is, the present invention
(1) In the copper electrowinning step in the method of recovering copper from the halogen-based copper electrolyte, the halogen-based electrolyte is passed through the cathode surface at a rate of 1 m / second to 6 m / second, and a cathode current density of 300 A A method for producing a plate-like electrolytic copper that produces a dense plate-like electrolytic copper by electrolysis at / m ² or more and 3000 A / m ² or less.
(2) In the above (1), a copper chloride and / or bromide is added to a solution containing 3 mol / L or more of an alkali metal chloride and / or bromide and / or a mixture thereof as a supporting salt. A method for producing plate-like electrolytic copper which is a dissolved solution.
(3) In the method of either (1) or (2) above, the copper electrodeposited on the cathode base plate is taken out from the electrolytic cell for each cathode, and the electrodeposited copper is separated and recovered. Production method.
It is.

According to the present invention,
(1) Since it is possible to produce electrodeposited copper having a dense structure from a halogen-based solution and in close contact with the mother board, it is easy to take out the product from the electrolytic cell.
(2) The electrodeposit has excellent detergency, has few problems of surface contamination and oxidation, and can provide a high-quality product similar to electrolytic copper obtained in a sulfuric acid bath.
Effects such as can be obtained.

In the present invention, electrolysis is carried out while flowing the halogen-based copper electrolyte near the cathode using, for example, a pump.
An example of the implementation method of the present invention is shown in FIG.
In order to prevent precipitation of basic salts and monovalent copper halides, the halogen-based electrolyte to be treated is stable in copper leachate under acidic conditions of pH = 1 to 3 and monovalent copper is stable as a complex halogen ion. In order to dissolve, a solution in which an alkali halide such as sodium chloride is dissolved in a high concentration as a supporting salt is used.
In order for the copper complex ions to be stable and have a sufficiently high solubility, the supporting salt is at least 3 mol / L or more, preferably 4 mol / L or more and less than the saturation solubility.

The electrolytic device for the monovalent copper solution only needs to have a structure in which the anode and the cathode face each other and the liquid flows between them. In practice, a device in which the anode chamber and the cathode chamber are separated by a filter cloth is used. A diaphragm electrolysis method is used.
In the cathode chamber, the liquid between the cathode and the diaphragm is flowed at a high speed by a pump to promote the supply of copper ions to the cathode surface.
The electrolyte in the cathode chamber circulates back to the tank. Since the copper concentration of the liquid is reduced by the amount of copper electrodeposited on the cathode, the high concentration copper leachate produced in the leaching process is replenished to the circulation system.
Part of the liquid in the cathode chamber passes through the diaphragm and flows into the anode chamber. In the anode chamber, the leaching ability of the liquid is restored by oxidation of the remaining monovalent copper to divalent copper and oxidation reaction of halogen, and then the liquid is discharged from the anode chamber and repeatedly used in the leaching process. The total liquid volume is balanced by balancing the supply volume of the cathode chamber circulation system and the discharge volume of the liquid from the anode chamber.

Titanium is used for the cathode in consideration of corrosion resistance. The flow condition of the liquid in the vicinity of the cathode is determined by the average linear velocity of the liquid in the flow path and the Reynolds number (Re) in the flow path corresponding to this. In order to promote ion supply, turbulent flow conditions (Re> 2300) are presupposed, but the liquid linear velocity has a stronger influence on the diffusion factor in the vicinity of the cathode, which affects the electrodeposition state.
If the linear velocity is low, the effect of dense electrolytic copper electrodeposition due to the stirring effect is hardly obtained. In order to electrodeposit dense copper closely adhered to the cathode base plate at a current density with practical productivity, for example, 300 to 1000 A / m ² , a linear velocity of at least 1 m / second is required.
As the linear velocity is increased, the upper limit of the current density at which dense electrolytic copper in close contact with the cathode is obtained increases, so that productivity is improved. On the other hand, as the linear velocity increases, the liquid flow rate increases and the required capacity of the pump for circulating the liquid increases. Therefore, the upper limit of the speed is restricted in terms of capital investment and operating power cost. Also, if the flow rate is high, the liquid feed pressure increases and pressure loss occurs in the flow path, making it difficult to isolate the liquid in the cathode chamber and the anode chamber using a diaphragm and prevent mixing. The upper limit of the liquid linear velocity is practically 5 to 6 m / sec.

The upper limit of the current density at which adhesion / dense electrodeposition is possible was 2000 A / m ² at a linear velocity of 2.5 m / sec and 3000 A / m ² at a linear velocity of 6 m / sec.
The cathode current density is limited by the thickness (or electrodeposition time) of the electrodeposited copper as well as the linear velocity of the electrolyte. The titanium cathode is electrodeposited with a dense structure of copper at first, but as electrodeposition progresses, it becomes a columnar structure oriented with priority over the growth direction and surface irregularities increase. The protrusion begins to grow.
In particular, under conditions where the current density is high, once the protrusions grow, the flow of the liquid is disturbed and the protrusion growth becomes violent and a short circuit with the anode tends to occur. For this reason, it is difficult to increase the current density and stably deposit thick plate-like copper over a long period of time even under conditions where the liquid speed is sufficiently increased.
Even in this case, since the adhesion between the dense copper layer electrodeposited first and the underlying titanium cathode is good, the electrodeposited copper can be easily taken out of the battery case together with the cathode base plate.
Therefore, in order to improve the handleability of electrodeposited copper, if the surface of the electrodeposited copper has some irregularities, it is possible to suppress the growth of the protrusions described above. Can be easily removed and cleaned. After washing, the electrodeposited copper is peeled off from the mother board and collected. The recovered electrodeposited copper can be cast into a form for external sales.

As described above, according to the present invention, from the halogen-based copper electrolyte, while taking advantage of power saving by monovalent electrolysis, it is a plate-like material that is dense and easy to clean and has excellent handling properties compared to powder. Electrodeposited copper can be manufactured.

Example 1
FIG. 2 shows the structure of an apparatus for investigating the relationship between the liquid flow rate and the dense and tight cathode current density in the present invention. In this device, no diaphragm was used, and copper was dissolved in the anode using a copper plate to prevent the composition change of the liquid in contact with the cathode. In this test, liquid replenishment for maintaining the copper concentration was omitted.
Table 1 shows the composition of the halogen-based copper electrolyte (concentration of alkali halide 5 mol / L, and after preparing the solution, add metal copper pieces, turn off the air, heat and stir at 60 ° C to remove the divalent copper in the solution. After reducing in advance, the pH is adjusted to 1) and electricity is passed through a rectangular channel with a cross section of 10mm x 5mm or 20mm x 10mm in width, and a titanium plate cathode (effective surface size 10 or 20 x 100mm) ) Copper was electrodeposited on top.

Electrolysis was performed by changing the current density and energization time while flowing catholyte at a flow rate of 0.5-6 m / sec. An example of the appearance of the obtained electrodeposited copper is shown in FIG. All of the electrodeposited copper was deposited in a plate shape in close contact with the titanium cathode. Electrodeposited copper is fragile and easily breaks when bent. It is also easily broken when peeled off from the cathode. It was possible.
As the current density increases, the surface irregularities increase, and bumps and protrusions tend to grow. The higher the flow rate, the higher the current density at which the bumps begin to grow. At a flow rate of 2.5 m / sec, irregularities start to appear at 2000 A / m ² . Concavity and convexity growth is suppressed at a flow rate of 6 m / sec, but bumps and protrusions occur frequently when it exceeds 3000 A / m ² . Conversely, when the flow velocity drops to 0.5 m / second, 1000
Even at A / m ² , it became difficult to suppress partial protrusion growth. In practice, even if some irregularities occur in the electrodeposited copper, the electrodeposited copper itself is in close contact with the cathode base plate, so there is no problem in removing it with the cathode and cleaning it. Electrolysis is not possible due to the occurrence of a short circuit.
The relationship between the electrodeposition state and the electrolysis conditions in Example 1 is shown in FIG.
(Example 2)

As in Example 1, electrolysis was performed at a catholyte flow rate of 2.7 m / sec, and electrolysis was performed at a current density of 1000 A / m ² capable of dense and smooth electrodeposition. As shown in FIG. As the length increased, the surface irregularities gradually increased, and bump-shaped protrusions grew. When such a hump grows, current concentrates on this part, and a protrusion grows and a short circuit is likely to occur, so that the energization time is limited.
(Comparative example)

A solution having the same composition as in Examples 1 and 2 was placed in an electrolytic cell with an acid-resistant filter cloth having the structure shown in FIG. 6 and kept at 57-60 ° C. A titanium plate cathode (effective surface 100 mm square) was placed in the cathode chamber of this electrolytic cell, and an insoluble anode (iridium compound baked and applied on a titanium plate, effective surface 100 mm square) was placed in the anode chamber.
The liquid on the cathode side is not forced to flow by a pump or the like, and argon gas is blown from the lower side of the cathode and constantly stirred to replenish the liquid in the tank while supplying a liquid with a copper concentration of 75 g / L to the cathode chamber. The current was 1.5 A (current density 150 A / m ² ) and 24 hours electrolysis was performed.
Despite the low current density, the electrodeposited copper had protrusions and depressions on the entire surface as shown in FIG. Since the electrodeposited copper was poorly washed and poorly adhered to the cathode base plate, it was easily crushed and peeled off when the cathode was pulled up.

Copper electrowinning method of the present invention Example of copper electrowinning in Examples Copper electrodeposition state in Example 1 (Copper electrodeposition state in Example (liquid linear velocity 0.5-6 m / sec)) Relationship between copper electrodeposition state and electrolysis conditions in Example 1 Change in copper electrodeposition state with energization time in Example 2 Copper electrowinning method in comparative examples Copper electrodeposition state in liquid quiescent state in comparative example (copper electrodeposition state in liquid quiescent condition in comparative example (150A / m ² × 24h))

Claims (3)

In the copper electrowinning process in the method of recovering copper from the halogen-based copper electrolyte,
The halogen-based electrolyte is passed through the cathode surface at a speed of 1 m / sec to 6 m / sec and electrolyzed at a cathode current density of 300 A / m ^{2 to} 3000 A / m ² to produce a dense plate-shaped electrolytic copper. A method for producing plate-like electrolytic copper, comprising: 2. The solution according to claim 1, wherein the halogen-based copper electrolyte is a solution in which copper chloride and / or bromide is dissolved in a solution containing 3 mol / L or more of an alkali metal chloride and / or bromide as a supporting salt and / or a mixture thereof. A method for producing plate-shaped electrolytic copper, which is characterized by the following. 3. The method according to claim 1, wherein the copper electrodeposited on the cathode base plate is taken out from the electrolytic cell for each cathode, and the electrodeposited copper is peeled off and collected. Production method.