Preparation method of 6N high-purity copper

Abstract

The invention belongs to the technical field of hydrometallurgy, and particularly relates to a preparation method of 6N high-purity copper. It is worth mentioning that the additive adopted in the method also has remarkable applicability in the aspect of reducing the silver content in the 4-6N high-purity copper. Drilling a hole in the copper anode plate for hanging a copper hook, then cleaning, and simultaneously cleaning the filter bag and the cathode plate; putting the copper anode plate and the copper cathode plate which are respectively sleeved with the filter bags into an electrolytic cell, preparing electrolyte, adding the electrolyte into an electrolysis system, and starting circulation at the same time; an additive is added, the additive is any halogen simple substance of bromine water or iodine, electrolyte circulation is started, the electrolyte enters the electrolytic bath from the lower part and flows out of the electrolytic bath from the upper part, after circulation is uniform, a direct-current power source is turned on, the current is adjusted to 80-150 A / m < 2 >, and electrolysis is conducted at the temperature of 20-60 DEG C; and in the whole electrolysis process, the circulation speed is maintained, a proper amount of additives, ultrapure water and acid are continuously supplemented into a circulation tank, electrolyte components are maintained to be stable, and cathode copper, namely the 6N high-purity copper, is obtained. The high-purity copper prepared through the method is low in impurity content, especially the minimum Ag content can reach 0.008 ppm, and the silver reduction effect is remarkable.

Description

Technical Field

[0002] This invention belongs to the field of hydrometallurgical technology and relates to a method for preparing 6N high-purity copper. Background Technology

[0004] High-purity copper of 6N and above (≥99.9999wt%) is a core basic material for strategic emerging industries such as electronic information, new energy, and high-end manufacturing. Breakthroughs in its preparation technology are crucial for the high-quality development of the industrial chain. Currently, the preparation of this level of high-purity copper is mainly divided into two categories: hydrometallurgical and pyrometallurgical processes. Although pyrometallurgical processes are highly efficient and have simple procedures, their ability to remove impurities (oxygen, sulfur, Fe, Ni, Pb, etc.) is insufficient, making it difficult to meet the requirements for ultra-high purity. Electrolytic refining technology in the hydrometallurgical process has become the mainstream industrial application path due to its high impurity separation efficiency, strong purity controllability, and stable process. Based on the electrolyte system, it can be divided into sulfuric acid system and nitric acid system.

[0005] Sulfuric acid electrolyte is stable, low-cost, environmentally friendly and easy to treat, and has been successfully applied in the preparation of mid-to-high-end copper materials. However, a variety of additives are required during the preparation process to ensure that the content of trace precious metals such as Ag and Au and non-metallic impurities in the electrolyte is at a low level. Multiple additives can easily introduce impurities from outside the system, making it difficult to stably produce products with 6N and above.

[0006] Nitric acid systems, with their strong oxidizing and complexing properties, offer significant advantages in the deep removal of metallic impurities and the improvement of cathode surface morphology, making them a key research area for the preparation of 6N and higher purity copper. However, traditional nitric acid systems suffer from a core drawback: bubbles are generated on the cathode surface during electrolysis, potentially due to NO3. ～ The reduction process produces harmful gases such as NO and NO2, which causes defects such as "loose copper" to appear on the cathode plate.

[0007] Therefore, developing a new generation of electrolytic refining technology with high impurity removal efficiency and system stability is the key to breaking through the bottleneck in the preparation of 6N and above high-purity copper. Summary of the Invention

[0009] The purpose of this invention is to provide a method for preparing 6N high-purity copper, so as to solve the problems of low purity and surface defects of cathode copper produced by existing sulfuric acid and nitric acid electrolysis methods.

[0010] To address the above challenges, this invention provides a method for preparing 6N high-purity copper, comprising the following steps:

[0011] a. Punch holes in the 4N copper anode plate for suspension with copper hooks, then clean it, while also cleaning the filter bag and cathode plate.

[0012] b. Place the copper anode plate and cathode plate, each covered with a filter bag, into the electrolytic cell, prepare the electrolyte, add the electrolyte to the electrolysis system and start the circulation simultaneously;

[0013] c. Add additives, using any halogen element from bromine water or iodine. Start electrolyte circulation, with the electrolyte entering from the bottom and exiting from the top of the electrolytic cell. After uniform circulation, turn on the DC power supply and adjust the current to 80–150 A / m. 2 Electrolysis is performed at 20–60°C.

[0014] d. Throughout the electrolysis process, maintain electrolyte circulation and continuously replenish appropriate amounts of additives, ultrapure water, and nitric acid to the circulation tank to maintain the stability of the electrolyte composition and obtain cathode copper, which is 6N high-purity copper.

[0015] e. Clean, treat with antioxidants, dry and package the cathode copper.

[0016] In step a, the hole diameter of the copper anode plate is estimated based on the anode weight, and generally two holes are used. The filter bag is typically selected with a 400-mesh pore size, mainly to prevent anode sludge from entering the electrolyte and becoming trapped on the cathode. The cathode plate can be pure titanium, titanium-clad copper, 316L stainless steel, or 316L copper-clad stainless steel.

[0017] In step b, the electrolyte can be either a sulfuric acid system or a nitric acid system; that is, the electrolyte can be analytical grade copper sulfate pentahydrate + superior grade sulfuric acid, or copper nitrate trihydrate + superior grade nitric acid. Preferably, the electrolyte is prepared with a copper ion concentration of 40–80 g / L, for example, 40 g / L, 50 g / L, 60 g / L, 70 g / L, or 80 g / L. The acidity is 1 g / L–80 g / L based on the total volume of the electrolyte.

[0018] Preferably, the same pole spacing in step b is 70-200mm, for example, it can be 70mm, 80mm, 90mm, 100mm, 110mm, 120mm, 130mm, 140mm, 150mm, 160mm, 170mm, 180mm, 190mm, or 200mm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0019] In step c, to ensure uniform electrolyte circulation, at least one cycle is required. For example, if the circulation rate is 10L / h and the total electrolyte volume is 10L, then one cycle is completed in 1 hour.

[0020] In step c, the additive works on the following principle: halogen elements dissolve in the electrolyte and undergo a disproportionation reaction (X2 + H2O → HX + HXO). The generated hydrohalic acid (HX) reacts with Ag in the electrolyte. +The ionic reaction forms a sparingly soluble AgX precipitate, thus achieving efficient precipitation removal. Simultaneously, the generated hypohalous acid (HXO) possesses strong oxidizing properties, capable of directionally oxidizing reducing impurities in the electrolyte (such as certain low-valence metal ions or organic substances). Through these dual effects, this single additive system significantly reduces impurity content, thereby effectively improving the stability of the electrolysis process.

[0021] Preferably, the amount of additive added in step c is 0.001 to 0.3 g / L based on the total volume of the electrolyte, for example, it can be 0.01 g / L, 0.1 g / L, 0.2 g / L, or 0.3 g / L.

[0022] Preferably, the DC current density in step c is 80–150 A / m. 2 For example, it could be 80A / m 2 90A / m 2 100A / m 2 110A / m 2 120A / m 2 130A / m 2 140A / m 2 150A / m 2 However, this does not apply to all values ​​listed; other unlisted values ​​within the same range also apply.

[0023] Preferably, the electrolyte circulation rate in step d is 30-50 mL / min, for example, 30 mL / min, 40 mL / min, or 50 mL / min, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0024] Preferably, the cleaning of raw materials and finished products in steps a and e includes acid washing and water washing. The acid washing is prepared with a 1-5 wt% nitric acid or sulfuric acid solution, for example, it can be 1 wt%, 2 wt%, 3 wt%, 4 wt%, or 5 wt%, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0025] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] This invention provides a method for preparing high-purity copper through electrolytic refining. The core of this method lies in the fact that only a trace additive is needed to significantly reduce the content of Ag and other impurities, achieving a synergistic purification effect of "one agent, multiple effects" in different systems: on the one hand, it specifically precipitates silver (Ag). + On the one hand, it oxidizes ions, and on the other hand, it simultaneously oxidizes other reducing metal ions and organic impurities. Especially in nitric acid systems, its function can completely replace the traditional hydrogen peroxide, fundamentally avoiding the generation of harmful gases such as NO and NO2. Through this technology, electrolyte impurities can be reduced to the greatest extent, with the content of the key impurity silver being stably reduced to below 0.008 ppm, thereby effectively improving the purity of raw copper from 4N to 6N and above. The entire preparation process is characterized by its simplicity, ease of operation, and low cost. Detailed Implementation

[0029] Using 4N grade cathode copper as the anode plate, cleaned filter bags were placed on the anode and cathode plates respectively. The anode and cathode, wrapped with filter bags, were then placed in the electrolyte and electrolyzed at room temperature. During the electrolysis process, a fixed amount of additives were added daily, and acid and water were replenished every 3 hours according to the state of the electrolyte to keep the acidity and copper ion concentration of the electrolyte within the controlled range. After electrolysis, the copper was washed, peeled off, washed, and dried in sequence to obtain 6N high-purity copper.

[0030] Example 1

[0031] This embodiment provides a method for preparing 6N high-purity copper, specifically including the following steps:

[0032] (1) Using 4N cathode copper as the anode plate, the copper plate is processed into 100mm×150mm by wire cutting method. Then, two holes with a diameter of φ8 are drilled in the width using a bench drill. In order to remove impurities from the surface of the copper plate, it is placed in an ultrasonic cleaning tank and completely immersed in 1-5wt% nitric acid solution for acid washing, and then washed with water.

[0033] (2) The pure titanium cathode plate is acid-washed in a 1-5 wt% nitric acid solution, and then washed with water;

[0034] (3) The anode, which is covered by the filter bag, is hung on a copper hook in the electrolytic cell. A pure titanium plate with a size of 100mm×150mm is used as the cathode plate. The filter bag is also covered on the cathode plate. The cathode plate is connected to the copper busbar on the electrolytic cell using pure titanium screws. A nitric acid electrolyte system with an acidity of 1g / L and a copper ion concentration of 80g / L is prepared. The current density is 120A / m 2 Electrolysis was carried out at 20℃, with 0.02 g / L of elemental iodine added daily.

[0035] (4) To ensure that the concentration of copper ions and acidity in the electrolyte remain constant, the electrolyte is tested every 3 hours and water and acid are added accordingly. At the same time, to maintain a consistent liquid level, the electrolyte level is marked, and water is added by dripping using a peristaltic pump. The electrolysis cycle is 7 days, and 6N high-purity copper is prepared.

[0036] (5) The cathode plate was cleaned with deionized water in an ultrasonic cleaning tank for 30 min. After peeling, acid washing, water washing, and anti-oxidation treatment, the high-purity copper was obtained. The specific chemical composition is shown in Table 1.

[0037] Table 1. Results of Glow Discharge Mass Spectrometry (GDMS) Analysis of High-Purity Copper

[0038]

[0039] Example 2

[0040] This embodiment provides a method for preparing 6N high-purity copper, specifically including the following steps:

[0041] (1) Using 4N grade cathode copper as the anode plate, the copper plate is processed into 100mm×150mm by wire cutting method. Then, two holes with a diameter of φ8 are drilled in the width using a bench drill. In order to remove impurities from the surface of the copper plate, it is placed in an ultrasonic cleaning tank and completely immersed in 1-5wt% sulfuric acid solution for acid washing, and then washed with water.

[0042] (2) The titanium-clad copper cathode plate is acid-washed in a 1-5 wt% sulfuric acid solution, and then washed with water;

[0043] (3) The anode, which is covered by the filter bag, is hung on a copper hook in the electrolytic cell. A 100mm×150mm titanium-clad copper plate is used as the cathode plate, which is also covered with a bag. It is connected to the copper busbar on the electrolytic cell using pure titanium screws. A sulfuric acid electrolyte system with a copper ion concentration of 40g / L and an acidity of 80g / L is prepared. The current density is 150A / m 2 Electrolysis was carried out at a temperature of 60℃, with 0.001 g / L of elemental iodine added daily;

[0044] (4) To ensure that the concentration of copper ions and acidity in the electrolyte remain constant, the electrolyte is tested every 3 hours and water and acid are added accordingly. At the same time, to maintain a consistent liquid level, the electrolyte level is marked, and water is added by dripping using a peristaltic pump. The electrolysis cycle is 7 days, and 6N high-purity copper is prepared.

[0045] (5) The cathode plate was cleaned with deionized water in an ultrasonic cleaning tank for 30 minutes. After peeling, acid washing, water washing, and anti-oxidation treatment, the high-purity copper was obtained. The specific chemical composition is shown in Table 2.

[0046] Table 2. Results of Glow Discharge Mass Spectrometry (GDMS) Analysis of High-Purity Copper

[0047]

[0048] Example 3

[0049] This embodiment provides a method for preparing 6N high-purity copper, except that the temperature in step (3) of Example 1 is changed to 20℃ and the current density is changed to 80A / m. 2 The remaining steps and conditions are the same as in Example 1, and therefore will not be repeated here. Glow discharge mass spectrometry was used for analysis, and the specific chemical composition is shown in Table 3.

[0050] Table 3. Results of Glow Discharge Mass Spectrometry (GDMS) Analysis of High-Purity Copper

[0051]

[0052] Example 4

[0053] This embodiment provides a method for preparing 6N high-purity copper. Except that the additive in step (3) of Example 1 is replaced with bromine water, and the amount added is 0.03 g / L, the other steps and conditions are the same as in Example 1, so they will not be described in detail here. The specific chemical composition is shown in Table 4 by glow discharge mass spectrometry.

[0054] Table 4. Results of Glow Discharge Mass Spectrometry (GDMS) Analysis of High-Purity Copper

[0055]

[0056] Control group 1

[0057] In this embodiment, the electrolysis temperature in step (3) of Example 1 is changed to 20°C and the current density is changed to 100A / m. 2 The additives were changed to hydrochloric acid and hydrogen peroxide, with the amount of hydrochloric acid added being 0.02 ml / L and the amount of hydrogen peroxide added being 0.006 ml / L; the remaining steps and conditions were the same as in Example 1, so they will not be repeated here. Glow discharge mass spectrometry was used for analysis, and the specific chemical composition is shown in Table 4.

[0058] Table 3. Results of Glow Discharge Mass Spectrometry (GDMS) Analysis of High-Purity Copper

[0059]

[0060] Therefore, this invention provides a method for preparing high-purity copper applicable to various electrolytic systems. Its core advantage lies in achieving synergistic purification using only one trace additive: it can deeply precipitate silver ions (making Ag...) +The concentration is stably reduced to below 0.008 ppm, and it can also oxidize other reducing impurities. This method can replace hydrogen peroxide in nitric acid systems, fundamentally avoiding the generation of harmful gases such as NO and NO2. With this simple process, 4N copper can be efficiently purified to 6N and above, and the entire process is characterized by its ease of operation and low cost.

[0061] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing 6N high-purity copper, characterized in that, Includes the following steps: a. Drill holes in the 4N copper anode plate for copper hook suspension, then clean it, while cleaning the filter bag and cathode plate at the same time; b. Place the copper anode plate and cathode plate, each covered with a filter bag, into the electrolytic cell, prepare the electrolyte, add the electrolyte to the electrolysis system and start the circulation at the same time; c. Add additives, using any halogen element from bromine water or iodine. Start electrolyte circulation, with the electrolyte entering from the bottom and exiting from the top of the electrolytic cell. After uniform circulation, turn on the DC power supply and adjust the current to 80–150 A / m. 2 Electrolysis is performed at 20–60°C. d. Throughout the electrolysis process, maintain electrolyte circulation and continuously replenish appropriate amounts of additives, ultrapure water, and nitric acid or sulfuric acid to the circulation tank to maintain the stability of electrolyte composition and obtain cathode copper, which is 6N high-purity copper. e. Clean, treat with antioxidants, dry and package the cathode copper.

2. The preparation method according to claim 1, characterized in that, In step a, two holes are drilled in the copper anode plate, and a filter bag with a 400-mesh aperture is selected to prevent anode mud from entering the electrolyte and getting trapped on the cathode.

3. The preparation method according to claim 1, characterized in that, In step a, the cathode plate is made of pure titanium, titanium-clad copper, 316L stainless steel, or 316L copper-clad stainless steel.

4. The preparation method according to claim 1, characterized in that, In step b, the electrolyte is either analytical grade copper sulfate pentahydrate + superior grade sulfuric acid, or copper nitrate trihydrate + superior grade nitric acid.

5. The preparation method according to claim 4, characterized in that, In step b, the electrolyte is prepared with a copper ion concentration of 40–80 g / L and an acidity of 1–80 g / L based on the total volume of the electrolyte.

6. The preparation method according to claim 1, characterized in that, The pole spacing mentioned in step b is 70-200 mm.

7. The preparation method according to claim 1, characterized in that, The amount of additive added in step c is 0.001 to 0.3 g / L based on the total volume of the electrolyte.

8. The preparation method according to claim 1, characterized in that, The electrolyte circulation rate in step d is 30-50 mL / min.

9. The preparation method according to claim 1, characterized in that, The cleaning of raw materials and finished products described in steps a and e includes acid washing and water washing. The acid washing is prepared by preparing a 1-5 wt% nitric acid or sulfuric acid solution.

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