JP2003183869A - Electrolyte purification method - Google Patents

Abstract

(57) [Abstract] [Problem] To provide a method for purifying an electrolytic solution that can increase the amount of impurities removed without requiring a significant equipment remodeling. SOLUTION: A part of the electrolytic solution is withdrawn from a general electrolytic cell for performing copper electrolytic refining, sent to a deconducting solution tank, the amount of copper in the solution is reduced by electrolytic sampling, and then sent to a clean electrolytic cell as a clean supply solution to perform electrolytic sampling. In the method for purifying an electrolytic solution which removes impurities in the solution and returns it to the general electrolytic cell as a clean tail solution, the Cu concentration of the clean tail solution is controlled in the range of 0.8 to 3.0 g / L. It is preferable to stir the electrolytic solution that has been subjected to electrowinning in at least the upstream portion of the clean electrolytic cell.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for purifying an electrolytic solution used for electrolytic refining of copper.

[0002]

2. Description of the Related Art In a copper electrolytic refining process, crude copper produced in a smelting furnace such as a converter → refining furnace is used as an anode, and a copper seed plate produced in a seed plate tank is used as a cathode in an electrolytic solution in a general electrolytic cell. It is charged into and charged with electricity to elute copper from crude copper and electrodeposit it on a copper seed plate to produce product electric copper with a purity of 99.99%. At this time, impurities (A
s, Sb, Bi) elutes. If the concentration of these impurities exceeds a certain level in the electrolytic solution, the appearance of the product is deteriorated (roughness of the surface, generation of grains and bumps) and the product quality is deteriorated.

Therefore, a part of the electrolytic solution is extracted from the general electrolytic cell and sent to a decoppering electrolytic cell, the amount of copper in the solution is reduced by electrolytic sampling, and then sent to a clean electrolytic cell, and impurities are removed (that is, sent by electrolytic sampling). After purifying (purifying) the electrolytic solution, it is returned to the general electrolytic cell. An insoluble anode (usually a Pb anode) is used in the electrowinning. The electrolytic solution sent to the clean electrolytic cell is called "clean feed solution (or copper removal tail solution)", and the electrolytic solution returned to the general electrolytic cell is called "clean tail solution (or tail solution)".

In the above-mentioned cleaning step, excess eluted Cu is first electrodeposited, and the Cu concentration is lowered to some extent before the As, S
b and Bi are electrodeposited and recovered and removed. In the normal purification method,
By reducing the Cu concentration in the tail fluid to less than about 0.8 g / L, about 90% of all impurities can be removed. According to this method, the one having a high concentration in the liquid to be treated is often taken. By returning the solution in which the impurities are reduced to the general electrolytic cell to keep the impurity concentration in the electrolytic solution at a certain value or less, it is possible to produce a product electrolytic copper having no problem in appearance and quality.

[0005]

By the way, in recent years, Sb,
Copper ores of the type containing a relatively large amount of Bi tend to be used. Crude copper produced from this type of copper ore has a higher Sb and Bi content. When this crude copper is used as the anode of a general electrolytic cell, the elution amount of Sb and Bi into the electrolytic solution increases. Therefore, unless the amount of impurities removed in the purifying step is increased, the impurity concentration of the electrolytic solution in the general electrolytic cell may increase, and the appearance and quality of the product electrolytic copper may deteriorate.

In order to increase the amount of impurities removed in the cleaning process, the capacity of the clean electrolytic cell should be increased.
To do so would require a major remodeling of the equipment, and the amount of equipment investment would be enormous, which is not realistic. It is an object of the present invention to solve the above-mentioned problems of the prior art and to provide a method for purifying an electrolytic solution that can increase the amount of impurities, particularly Bi and Sb, removed without requiring major equipment modification.

[0007]

According to the present invention, a part of an electrolytic solution is extracted from a general electrolytic cell for electrolytically refining copper and sent to a decoppered electrolytic cell, and the amount of copper in the solution is reduced by electrolytic extraction. As a clean tail solution to remove impurities in the solution by electrolytic collection and return to the general electrolytic cell as a clean tail solution, the Cu concentration of the clean tail solution is 0.8 to 3.0 g.
/ L is a method for purifying an electrolytic solution. In the present invention, it is preferable to stir the electrolytic solution electrolytically collected in at least the upstream side portion of the clean electrolytic cell.
In the present invention, the impurities to be removed are As, Sb, Bi.
In the case of removing more As than the other, the Cu concentration of the clean tail solution is set to less than 0.8 g / L, and in the case of removing more Sb and Bi than others, the Cu concentration of the clean tail solution is 0.8 g / L. It is preferably set to ~ 3.0 g / L.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION In the electrolytic solution purification step, the electrolytic solution having a higher theoretical electrolytic potential is electrolyzed earlier. The theoretical electrolysis potential is Cu>Bi>Sb> As, so first Cu is deposited, then
Bi, Sb, As are deposited in this order. Bi is a simple substance, and Sb and As are precipitated in the form of intermetallic compounds (Cu ₃ Sb, Cu ₃ As) with Cu. However, their detailed quantitative relationship was unknown. Therefore, the present inventors analyzed and investigated the component composition of tail fluid under various electrolytic extraction conditions, and as a result,
It was found that there is a relationship as shown in Fig. 1 between the As, Sb, Bi and Cu concentrations in the tail fluid. The impurity concentration of the supply liquid is As: 8 g / L, Sb: 0.45 g / L, Bi: 0.15 g / L.

According to the relationship shown in FIG. 1, the tail solution has a Cu concentration of 0.5 g.
When electrowinning is performed under the condition that / L, the tail solution impurity concentration becomes As: 1.0 g / L, Sb: 0.01 g / L, Bi: 0.01 g / L (the lower limit of Bi analysis is 0.01g / L), the impurity removal rate (= 1-tail solution impurity concentration / feed solution impurity concentration)
Are As: 87.5%, Sb: 97.8%, Bi: 93.3%. Here, the liquid supply flow rate is 140 m ³ / day, and the amount of impurities removed (=
Liquid supply flow rate × liquid supply impurity concentration × impurity removal rate) is As: 98
0kg / day, Sb: 61.6kg / day, Bi: 19.6kg / day. Since the impurity removal rate is substantially determined by the facility capacity of the clean electrolytic cell, in order to increase the amount of removed impurities (removed amount = electrolytic extraction amount), it is necessary to increase the concentration of the supplied liquid impurities or the flow rate of the supplied liquid. However, the concentration of impurities in the liquid supply cannot be increased due to the upper limit regulation on the side of the general electrolytic cell. In addition, when the feed fluid flow rate is increased, the tail fluid Cu concentration becomes 0.8 g / L or more from the relationship between the feed fluid flow rate and the tail fluid Cu concentration as shown in FIG. As long as it is less than 0.8 g / L, the liquid supply flow rate cannot be increased.

On the other hand, in the present invention, the Cu concentration in the tail fluid is set to 0.
It was controlled within the range of 8 to 3.0 g / L. FIG. 3 shows FIG.
3 is a graph showing the relationship between the tail solution Cu concentration derived from FIG. 2 and the amount of removed impurities. In Fig. 3, the amount of impurities removed on the vertical axis is 100 compared to the conventional value when the Cu concentration in tail fluid = 0.7 g / L.
It is shown by the relative value multiplied. As shown in FIG. 3, by controlling the tail solution Cu concentration to 0.8 to 3.0 g / L, preferably 1.2 to 2.5 g / L, the feed solution flow rate was increased to remove Sb and Bi (electrolytic extraction). Amount) can be increased. Therefore, it is possible to adapt to the increase in the Sb and Bi concentrations of the crude copper anode without remodeling the equipment. For example, even if the Bi concentration of the crude copper anode rises from 78ppm to 87ppm, the appearance of the product electrolytic copper deteriorates (eg, surface roughness, generation of grains and bumps) and quality (eg, LME standard (As ≦ 5ppm, Sb). ≦ 4ppm, Bi ≦ 2.0p
It becomes possible to remove impurities in the electrolytic solution to a level that does not cause pm) detachment. The amount of As removed is reduced to about 70% of the conventional amount, but since the concentration of As in the liquid is below a certain value, it does not affect the appearance and quality of the product electrolytic copper.

By the way, the tail water Cu concentration control value is 0.8 g compared with the conventional value.
When increasing from less than / L to 0.8 to 3.0 g / L of the present invention, the Cu concentration of the electrolytic solution is increased in the height (depth) direction, especially in the upstream side, in the normally used series cascade coupling type clean electrolytic cell. Segregation is likely to occur, and for example, a concentration difference of 10 g / L or more may occur. If this happens, the concentration of Cu in the tail fluid will vary, and the electrodeposition state of electrowinning copper will deteriorate (particles or bumps will be formed on the cathode and enlarge), resulting in a short circuit, which will reduce electrowinning efficiency. In order to eliminate such a problem, it is preferable to stir the electrolytic solution electrolyzed at least in the upstream portion of the clean electrolytic bath, that is, in the clean electrolytic bath portion having a high Cu concentration (for example, 5 g / L or more). As means for performing this stirring, liquid circulation by a pump, air bubbling and the like can be preferably used. As a result, the Cu concentration distribution in the depth direction of the electrolytic solution can be made uniform (concentration difference of 1 g / L or less) in the upstream clean electrolytic cell.
The Cu concentration control accuracy can be secured at a sufficiently high level, and the electrodeposition state of electrowinning copper can be maintained in a good condition.

[0012]

[Example] The present invention is applied to a purification process for removing impurities in a feed liquid by electrolytic extraction using a clean electrolytic bath in which six electrolytic baths each having a total area of cathode electrodeposition of 38 m ² are cascade-connected in series. did. In this purification process, the impurity grade of the crude copper anode used in the general electrolytic cell of the liquid supply source (the tail liquid return destination) is As ≤ 1350ppm, Sb ≤ 220ppm, Bi
It was operated so that the Cu concentration in tail fluid would be less than 0.8 g / L in conformity with ≤78 ppm. Under this condition, the upper limit of the supply flow rate (= tail flow rate) is 140 m ³ / day, and the amount of impurities removed is
As: 980kg / day, Sb: 61.6kg / day, Bi: 19.6kg / day.

However, from a certain time, the impurity grade of the crude copper anode was changed to As≤1250ppm, Sb≤240ppm, Bi≤87ppm, and accordingly, the Bi, Sb removal capacity of the purification step was about 10%. It became necessary to increase the above. Otherwise, it has been experimentally confirmed that grains and bumps frequently occur on the surface of the product electrolytic copper produced in the general electrolytic cell, and that the Bi quality of the product electrolytic copper exceeds the LME standard upper limit of 2.0 ppm. There is.

Therefore, according to the present invention, the control value of the tail fluid Cu concentration was changed to 2.0 g / L. As a result, it was possible to increase the liquid supply flow rate to about 180 m ³ (see Fig. 2) and to increase the Bi removal capacity by 20% or more (see Fig. 3) without the need to reinforce the clean electrolytic cell. As a result, in the liquid in a general electrolytic cell
It was possible to suppress the increase in Bi and Sb concentrations. In the beginning of the present invention, segregation of Cu concentration in the depth direction (maximum concentration difference of about 10 g / L) was observed in the upstream electrolytic bath, and the current efficiency was slightly lower than that of the conventional one. Therefore, according to the preferred embodiment of the present invention, when the aeration pipes were installed inside the first to fifth tanks on the upstream side and air bubbling was performed to stir the electrolytic solution in the same tank, the segregation was concentrated. Most of the difference is less than 1g / L, current efficiency is 60
It has remained stable at a high level of ~ 70%.

[0015]

EFFECTS OF THE INVENTION According to the present invention, it is possible to increase the electrolytic extraction amount (removal amount) of Sb and Bi in the liquid supply without significantly modifying the purification equipment. .

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between As, Sb, Bi concentrations and Cu concentrations in tail fluid.

FIG. 2 is a graph showing the relationship between the supply liquid flow rate and the tail liquid Cu concentration.

FIG. 3 is a graph showing the relationship between the tail solution Cu concentration and the amount of impurities removed.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Noboru Nakamura             6-1-1 Hibi, Tamano City, Okayama Prefecture Mitsui Metal Ore             Business Hibiki refinery (72) Inventor Yasushige Araki             6-1-1 Hibi, Tamano City, Okayama Prefecture Mitsui Metal Ore             Business Hibiki refinery F term (reference) 4K058 AA11 BA21 BB03 FC05 FC22

Claims (3)

[Claims] 1. An electrolytic solution is partially withdrawn from a general electrolytic cell for electrolytically refining copper and sent to a decoppered electrolytic cell. After electrolytic copper extraction, the amount of copper in the electrolytic solution is reduced, and the electrolytic solution is sent to a clean electrolytic cell as a clean feed solution for electrolysis. In the method of purifying the electrolytic solution by removing impurities in the solution by collecting and returning it to the general electrolytic cell as a clean tail solution, the electrolytic solution is characterized in that the Cu concentration of the clean tail solution is 0.8 to 3.0 g / L. Liquid purification method. 2. The method for purifying an electrolytic solution according to claim 1, wherein the electrolytic solution electrolyzed is stirred in at least an upstream side portion of the clean electrolytic cell. 3. The impurities to be removed include As, Sb, and Bi, and when As is removed more than others, the Cu concentration of the clean tail solution is set to less than 0.8 g / L and Sb and Bi are removed. The method for purifying an electrolytic solution according to claim 1 or 2, wherein the Cu concentration of the clean tail solution is 0.8 to 3.0 g / l in the case of removing more than that.