Method for producing electrolytic copper

Abstract

Provided is a method for producing electrolytic copper, which has good production efficiency even if the nickel concentration in crude copper used as an anode is high. The method for producing electrolytic copper includes a step in which Ni-containing crude copper is used as an anode and electrolysis is performed under conditions in which the Ni concentration in an electrolyte solution is maintained at 15 g / L or less.

Description

[0001] This application is a divisional application of PCT / JP2018 / 043288 with an application number of 201880034523.4, a filing date of November 22, 2018, and an invention title of "Method for Producing Electrolytic Copper". Technical Field

[0002] The present invention relates to a method for producing electrolytic copper. Background Art

[0003] Generally, electrolytic extraction of copper forms electrolytic copper through copper electrolytic refining. This copper electrolytic refining involves leaching copper from raw materials such as ores into a solution and reducing it to a metal through electrolysis. More specifically, raw materials such as ores are refined to produce blister copper, which is used as an anode for electrolytic refining in an electrolyte solution.

[0004] In recent years, there has been an increasing demand for recovering copper from recycled products (mainly scrap copper) such as those from electronic devices as raw materials for electrolytic extraction of copper (Patent Document 1).

[0005] Prior Art Documents

[0006] Patent Documents

[0007] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2009-287096 Summary of the Invention

[0008] Generally, blister copper used as an anode in copper electrolytic refining contains impurities such as arsenic, bismuth, antimony, and nickel, and these impurities dissolve into the electrolyte solution.

[0009] Among the impurities, the electrodeposition potential of nickel is extremely low compared to that of copper, and it is particularly likely to be concentrated in the electrolyte solution. If the nickel concentration in the electrolyte solution increases, the voltage rises due to an increase in the liquid resistance of the electrolyte solution, resulting in problems such as increased power consumption and reduced manufacturing efficiency of electrolytic copper. In addition, if the nickel concentration in the electrolyte solution rises excessively, a sludge layer is formed on the anode surface, causing so-called passivation, which hinders the dissolution of copper ions and becomes a cause of reduced manufacturing efficiency of electrolytic copper.

[0010] Especially in the case of using recycled products as raw materials, since the nickel concentration in the blister copper used as an anode tends to be high, the reduction in the manufacturing efficiency of electrolytic copper as described above becomes a more serious problem, particularly in operations in regions with high current density.

[0011] Therefore, the problem to be solved by the present invention is to provide a method for producing electrolytic copper with good manufacturing efficiency even when the nickel concentration in the blister copper used as an anode is high.

[0012] The inventors of the present invention conducted repeated studies to solve the above problems, and as a result, it was found that by controlling the nickel concentration in the electrolyte during copper electrorefining, even if the nickel concentration in the blister copper used as the anode is high, the manufacturing efficiency of electrolytic copper is good.

[0013] The present invention completed based on the above insights is, on the one hand, a method for manufacturing electrolytic copper including a step of electrolyzing using blister copper containing Ni as the anode under the condition of maintaining the Ni concentration in the electrolyte at 15 g / L or less.

[0014] In one embodiment of the method for manufacturing electrolytic copper of the present invention, the Ni concentration in the anode is 1800 ppm or more.

[0015] In another embodiment of the method for manufacturing electrolytic copper of the present invention, in the step of performing the electrolysis, the Ni concentration maintained in the electrolyte is 12 g / L or less.

[0016] In still another embodiment of the method for manufacturing electrolytic copper of the present invention, the electrolyte is an aqueous solution of copper sulfate.

[0017] In still another embodiment of the method for manufacturing electrolytic copper of the present invention, the current efficiency defined by the following formula in the electrolysis is 96% or more.

[0018] Current efficiency (%) = (amount of electrolytic copper produced / theoretical amount of electrolytic copper) × 100

[0019] Advantages of the Invention

[0020] According to the present invention, a method for manufacturing electrolytic copper can be provided, in which even if the nickel concentration in the blister copper used as the anode is high, the manufacturing efficiency is good. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a coordinate diagram of current efficiency - Ni content in the anode of Example 1.

[0022] Figure 2 It is a coordinate diagram of current efficiency - Ni content in the anode of Example 2.

[0023] Figure 3 It is a coordinate diagram of current efficiency - Ni content in the anode of Example 3.

[0024] Figure 4 It is a coordinate diagram of current efficiency - Ni content in the anode of Example 4.

[0025] Figure 5 It is a coordinate diagram of current efficiency - Ni content in the anode of Comparative Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0026] Hereinafter, embodiments of the method for manufacturing electrolytic copper of the present invention will be described in detail.

[0027] <Anode>

[0028] Typically, the anode used in the electrolytic refining in the method for manufacturing electrolytic copper of the present invention is an anode obtained by subjecting blister copper having a copper grade of about 93% to 99% by mass or 97% to 99% by mass obtained in the converter process to oxidative refining and reduction treatment and then casting it, usually in the form of a plate.

[0029] The blister copper of this anode contains Ni as an impurity. In the method for manufacturing electrolytic copper of the present invention, even if the Ni concentration in the blister copper is high, the manufacturing efficiency of electrolytic copper is good. Therefore, the Ni concentration in the blister copper can be, for example, 1800 ppm or more, 2400 ppm or more, or 3000 ppm or more. In addition, the blister copper may also contain impurities such as As, Bi, and Sb.

[0030] <Cathode>

[0031] The cathode used in the electrolytic refining in the method for manufacturing electrolytic copper of the present invention is not limited. In addition to the method of using starter sheets, a method called the permanent cathode method (PC method) in which copper is electrodeposited on the surface of a stainless steel plate can also be cited. As the material of the permanent cathode, there is no particular limitation. However, since it is insoluble in the electrolyte solution, titanium or stainless steel is usually used. From the perspective of low cost, stainless steel is preferably used. As the stainless steel, there is no particular limitation, and any one of martensitic stainless steel, ferritic stainless steel, austenitic stainless steel, austenitic-ferritic duplex stainless steel, and precipitation hardening stainless steel can be used.

[0032] <Electrolyte solution>

[0033] In the method for manufacturing electrolytic copper of the present invention, in order to perform electrolytic refining of copper, a sulfuric acid-based electrolyte solution can be used. For example, an aqueous copper sulfate solution is preferably used as the electrolyte solution. Generally, the sulfuric acid concentration is in the range of 120 g / L to 220 g / L, and the Cu ion concentration is in the range of 40 g / L to 60 g / L, but it is not limited thereto. Typically, the sulfuric acid concentration is in the range of 160 g / L to 180 g / L, and the Cu ion concentration is in the range of 45 g / L to 55 g / L.

[0034] In the case of electrolytic refining of copper, additives are usually added to the electrolyte. The additives are used to improve the precipitation state of copper in the cathode plate and the like. For example, as organic additives, additives that form protective colloids such as glue, gelatin, and lignin (pulp waste liquid) can be used in common, and organic substances having functional groups such as thiourea or aloin can also be used. Generally, the activation polarization during precipitation increases according to the additive, and by increasing the polarization, the uniform electrodeposition property is improved. Therefore, a dense and surface-uniform precipitated metal can be obtained.

[0035] <Electrolytic refining>

[0036] In an industrial electrolytic copper manufacturing process, a plurality of electrolytic cells equipped with a plurality of cathodes and anodes (for example, 40 to 60 pieces each) are provided, and the copper electrolyte is continuously supplied to the electrolytic cells and continuously discharged by overflow.

[0037] In the method for manufacturing electrolytic copper of the present invention, in electrolytic refining, electrolysis is carried out under the condition that the Ni concentration in the electrolyte is maintained at 15 g / L or less. By maintaining the Ni concentration in the electrolyte at 15 g / L or less in this way, an increase in voltage caused by an increase in the liquid resistance of the electrolyte can be suppressed, power consumption can be reduced, and the manufacturing efficiency of electrolytic copper can be improved. In addition, the occurrence of passivation forming a slag layer on the anode surface can be suppressed, the dissolution of copper ions is not hindered, and the manufacturing efficiency of electrolytic copper becomes good.

[0038] In particular, when it is necessary to increase the current density to a higher level than usual for the purpose of increasing production, if the recycled raw material increases, the Ni grade becomes higher and the current efficiency deteriorates. However, according to the present invention, since electrolysis is carried out under the condition that the Ni concentration in the electrolyte is maintained at 15 g / L or less, the manufacturing efficiency of electrolytic copper is good even through electrolysis under such conditions.

[0039] In the method for manufacturing electrolytic copper of the present invention, in electrolytic refining, it is preferable to carry out electrolysis under the condition that the Ni concentration in the electrolyte is maintained at 14 g / L or less, more preferably under the condition of maintaining at 13 g / L or less, and further preferably under the condition of maintaining at 12 g / L or less. In particular, by carrying out electrolysis under the condition that the Ni concentration in the electrolyte is maintained at 12 g / L, the current efficiency in the subsequent electrolysis can be controlled at 97% or more. It should be noted that considering the crystallization and discharge in the form of nickel sulfate by overcooling in the subsequent process, the lower the Ni concentration in the electrolyte is not necessarily better.

[0040] In the method for manufacturing electrolytic copper of the present invention, in electrolytic refining, the current density is not particularly limited. For example, it can be set to 300 A / m 2 ~360 A / m 2 .

[0041] As a method for controlling the Ni concentration in the electrolyte in electrolytic refining, conventional methods for removing impurities from the electrolyte can be used. As an illustration, the control of the Ni concentration using the freeze crystallization method will be described. Specifically, first, the electrolyte is stored in a freeze crystallization tank or the like, cooled to about -15°C to crystallize it, then dewatered using a centrifuge, and further dried using a dryer, thereby obtaining crystals containing Ni. When an aqueous copper sulfate solution is used as the electrolyte, the crystals containing Ni are NiSO4·6H2O (nickel sulfate hexahydrate). Next, the dewatered liquid obtained using the above centrifuge can be used as the electrolyte after removing Ni and used as the electrolyte in the electrolytic refining in the method for producing electrolytic copper of the present invention. The Ni concentration of the electrolyte during electrolysis is monitored in advance, and if necessary, Ni is removed as described above, whereby electrolysis can be carried out under the condition of maintaining the Ni concentration in the electrolyte at 15 g / L or less.

[0042] In the method for producing electrolytic copper of the present invention, the current efficiency defined by the following formula during electrolysis is preferably 96% or more.

[0043] Current efficiency (%) = (amount of electrolytic copper produced / theoretical amount of electrolytic copper) × 100

[0044] With such a configuration, even when electrolysis is carried out at a high current density with a high concentration of Ni of 1800 ppm or more in the blister copper used as the anode, the production efficiency of electrolytic copper becomes better. In addition, even if the tolerance of the copper raw material to be processed is increased (i.e., the allowable amount of Ni, an element that hinders the production of electrolytic copper, contained in the copper raw material), it is possible to increase the production of electrolytic copper that matches the demand for copper. This current efficiency is more preferably 96% or more, further preferably 96.5% or more, and even more preferably 97% or more.

[0045] Examples

[0046] Hereinafter, examples and comparative examples of the present invention are shown together. These examples are provided to better understand the present invention and its advantages and do not mean that the invention is limited.

[0047] (Example 1)

[0048] Using sheet blister copper with a copper grade of 99% by mass as the anode and a stainless steel sheet as the cathode, electrolytic decomposition was carried out in the electrolyte under the following conditions.

[0049] · Ni concentration (Ni grade) in the anode blister copper: 900 ppm to 2000 ppm

[0050] · Composition of the electrolyte: copper: 40 g / L to 60 g / L, nickel: 14.1 g / L to 14.6 g / L, sulfuric acid: 120 g / L to 220 g / L, arsenic: 3 g / L to 10 g / L, antimony: 0.1 g / L to 0.5 g / L, bismuth: 0.1 g / L to 0.5 g / L

[0051] · Current density: 322 A / m 2

[0052] Pre-monitor the Ni concentration in the electrolyte and control it in such a way that the Ni concentration always remains below 14.5 g / L during electrolysis. Specifically, when necessary, take out the electrolyte, remove the Ni component by the freeze crystallization method described in the implementation method, and reuse the electrolyte with reduced Ni concentration. Thus, control it in such a way that the Ni concentration of the electrolyte remains below 14.5 g / L.

[0053] In addition, extract the electrolytic copper generated at the cathode by electrolysis and calculate the current efficiency (%) based on the following formula.

[0054] Current efficiency (%) = (amount of electrolytic copper generated / theoretical amount of electrolytic copper) × 100

[0055] (Example 2)

[0056] Use plate-shaped blister copper with a copper grade of 99% by mass as the anode and a stainless steel plate as the cathode, and perform electrolytic decomposition in the electrolyte under the following conditions.

[0057] · Ni concentration (Ni grade) in the anode blister copper: 1000 ppm to 2100 ppm

[0058] · Composition of the electrolyte: copper: 40 g / L to 60 g / L, nickel: 13.6 g / L to 14.0 g / L, sulfuric acid: 120 g / L to 220 g / L, arsenic: 3 g / L to 10 g / L, antimony: 0.1 g / L to 0.5 g / L, bismuth: 0.1 g / L to 0.5 g / L

[0059] · Current density: 322 A / m 2

[0060] Pre-monitor the Ni concentration in the electrolyte and control it in such a way that the Ni concentration always remains below 14.0 g / L during electrolysis. Specifically, when necessary, take out the electrolyte, remove the Ni component by the freeze crystallization method described in the implementation method, and reuse the electrolyte with reduced Ni concentration. Thus, control it in such a way that the Ni concentration of the electrolyte remains below 14.0 g / L.

[0061] In addition, calculate the current efficiency in the same way as in Example 1.

[0062] (Example 3)

[0063] Using sheet-shaped blister copper with a copper grade of 99% by mass as the anode and a stainless steel sheet as the cathode, electrolytic decomposition is carried out in an electrolytic solution under the following conditions.

[0064] · Ni concentration (Ni grade) in the anode blister copper: 1100 ppm to 1900 ppm

[0065] · Composition of the electrolytic solution: copper: 40 g / L to 60 g / L, nickel: 13.2 g / L to 13.5 g / L, sulfuric acid: 120 g / L to 220 g / L, arsenic: 3 g / L to 10 g / L, antimony: 0.1 g / L to 0.5 g / L, bismuth: 0.1 g / L to 0.5 g / L

[0066] · Current density: 322 A / m 2

[0067] Pre-monitor the Ni concentration in the electrolytic solution and control it in such a way that the Ni concentration always remains below 13.4 g / L during electrolysis. Specifically, when necessary, take out the electrolytic solution, remove the Ni component by the freeze crystallization method described in the implementation manner, and reuse the electrolytic solution with a reduced Ni concentration. Thus, control is carried out in such a way that the Ni concentration of the electrolytic solution remains below 13.5 g / L.

[0068] In addition, calculate the current efficiency in the same manner as in Example 1.

[0069] (Example 4)

[0070] Using sheet-shaped blister copper with a copper grade of 99% by mass as the anode and a stainless steel sheet as the cathode, electrolytic decomposition is carried out in an electrolytic solution under the following conditions.

[0071] · Ni concentration (Ni grade) in the anode blister copper: 1100 ppm to 1900 ppm

[0072] · Composition of the electrolytic solution: copper: 40 g / L to 60 g / L, nickel: 11.0 g / L to 12.0 g / L, sulfuric acid: 120 g / L to 220 g / L, arsenic: 3 g / L to 10 g / L, antimony: 0.1 g / L to 0.5 g / L, bismuth: 0.1 g / L to 0.5 g / L

[0073] · Current density: 322 A / m 2

[0074] Pre-monitor the Ni concentration in the electrolyte and control it in such a way that the Ni concentration during electrolysis always remains below 12.0 g / L. Specifically, when necessary, take out the electrolyte, remove the Ni component by the freeze crystallization method described in the embodiments, and reuse the electrolyte with a reduced Ni concentration. Thus, control it in such a way that the Ni concentration of the electrolyte remains below 12.0 g / L.

[0075] In addition, calculate the current efficiency in the same manner as in Example 1.

[0076] (Comparative Example 1)

[0077] Use plate-shaped blister copper with a copper grade of 99% by mass as the anode and a stainless steel plate as the cathode, and perform electrolytic decomposition in the electrolyte under the following conditions.

[0078] · Ni concentration (Ni grade) in the anode blister copper: 1400 ppm to 2400 ppm

[0079] · Composition of the electrolyte: copper: 40 g / L to 60 g / L, nickel: 15.5 g / L to 17.0 g / L, sulfuric acid: 120 g / L to 220 g / L, arsenic: 3 g / L to 10 g / L, antimony: 0.1 g / L to 0.5 g / L, bismuth: 0.1 g / L to 0.5 g / L

[0080] · Current density: 322 A / m 2

[0081] Pre-monitor the Ni concentration in the electrolyte and control it in such a way that the Ni concentration during electrolysis always remains above 15.5 g / L.

[0082] In addition, calculate the current efficiency in the same manner as in Example 1.

[0083] Show the evaluation results of Examples 1 to 4 and Comparative Example 1 in Figures 1 to 5 . Figure 1 It is a coordinate diagram of current efficiency - Ni grade in the anode when the Ni concentration in the electrolyte of Example 1 is 14.1 g / L to 14.6 g / L. Figure 2 It is a coordinate diagram of current efficiency - Ni grade in the anode when the Ni concentration in the electrolyte of Example 2 is 13.6 g / L to 14.0 g / L. Figure 3 It is a coordinate diagram of current efficiency - Ni grade in the anode when the Ni concentration in the electrolyte of Example 3 is 13.2 g / L to 13.5 g / L. Figure 4 It is a coordinate diagram of current efficiency - Ni grade in the anode when the Ni concentration in the electrolyte of Example 4 is 11.0 g / L to 12.0 g / L. Figure 5It is a coordinate diagram of current efficiency - Ni grade in the anode at a Ni concentration of 15.5 g / L to 17.0 g / L in the electrolyte of Comparative Example 1.

[0084] Thus, in Examples 1 to 3, by using blister copper containing Ni as the anode and performing electrolysis under the condition of keeping the Ni concentration in the electrolyte below 15 g / L, even when the Ni grade in the anode is as high as 1800 ppm or more, the current efficiency is all good, being 96% or more.

[0085] In addition, in Example 4, blister copper containing Ni was used as the anode and electrolysis was carried out under the condition of keeping the Ni concentration in the electrolyte below 12 g / L. Thus, even when the Ni grade in the anode is as high as 1800 ppm or more, the current efficiency is all good, being 97% or more.

[0086] In contrast, in Comparative Example 1, blister copper containing Ni was used as the anode and electrolysis was carried out under the condition of keeping the Ni concentration in the electrolyte exceeding 15 g / L. Therefore, especially when the Ni grade in the anode is as high as 1800 ppm or more, the current efficiency is lower than 96%.

Claims

1. A method for manufacturing electrolytic copper, comprising: Using crude copper containing Ni as the anode and a stainless steel plate as the cathode, electrolysis is carried out at a current density of 322 to 360 A / m 2 under the condition that the Ni concentration in the electrolyte is maintained at 13.2 g / L or more and 15 g / L or less. Among them, The Ni-containing crude copper is cast after oxidative refining and reduction treatment of crude copper with a copper grade of 93% to 99% by mass obtained in the converter process. The Ni concentration in the anode is 1800 ppm or more. Ni is removed by crystallizing Ni in the electrolyte in the form of nickel sulfate by using the freeze crystallization method.

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