A method for preparing 6N ultra-high purity copper based on combination of alkali-acid two-stage electrolysis
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SOUTHWEAT UNIV OF SCI & TECH
- Filing Date
- 2026-04-24
- Publication Date
- 2026-06-16
Smart Images
Figure CN122214973A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the fields of non-ferrous metal smelting, electronic waste resource utilization and high-purity material preparation technology, and in particular to a method for preparing 6N ultra-high purity copper based on a two-stage alkali-acid electrolysis process. Background Technology
[0002] With the rapid development of 5G communication, artificial intelligence, semiconductor integrated circuits and superconducting technology, ultra-high purity copper (purity ≥99.9999%, i.e. 6N and above) has become a core basic material for manufacturing cutting-edge products such as electronic bonding wires, semiconductor sputtering targets, ultra-high frequency cables and superconducting material matrices due to its excellent electrical and thermal conductivity, superior processing performance and extremely low resistivity.
[0003] Currently, the preparation of high-purity copper mainly relies on the traditional acidic sulfate system for electrolytic refining. However, due to the extremely complex composition of impurities in secondary resources such as waste circuit boards and scrap copper (containing large amounts of silver, lead, tin, antimony, arsenic, silicon, aluminum, iron, zinc, etc.), the single acidic electrolytic system has significant limitations in deep purification: First, impurities with relatively positive potentials, such as silver (Ag), are prone to co-deposition at the cathode, making it difficult to achieve high purity; second, impurities such as lead (Pb), tin (Sn), and antimony (Sb) are prone to forming anode mud or undergoing hydrolysis under acidic conditions, and the resulting fine particles are easily mechanically embedded on the cathode surface, seriously affecting the purity of copper; in addition, in order to obtain a smooth cathode morphology, traditional processes often require the addition of organic additives such as gelatin and thiourea, which not only increases the difficulty of electrolyte maintenance but also introduces non-metallic impurities such as carbon, sulfur, and nitrogen into the copper lattice, making it difficult to meet the stringent requirements of extremely low content of all elements for 6N grade ultra-high purity copper.
[0004] Although some alkaline leaching processes can achieve preliminary copper recovery, the purity of the resulting cathode copper is usually only at the 3N-4N level, making it difficult to directly apply to the high-end semiconductor industry.
[0005] Therefore, it is of great significance to develop a high-purity copper preparation process that has broad applicability of raw materials, is environmentally friendly, does not rely on organic additives, and can achieve deep stripping of impurities from all components. Summary of the Invention
[0006] Addressing the challenge of balancing impurity removal efficiency with extremely high purity in processing complex copper sources using existing purification technologies, this invention provides a method for deep impurity removal from copper-containing raw materials to prepare 6N ultra-high purity copper using a two-stage alkaline-acid electrolysis process. This invention leverages the selective purification mechanism of an alkaline ammonia complex system for specific impurities, and the potential shielding and additive-free crystallization control of an acidic sulfate system during the deep refining stage. Through the coupling of two electrolysis processes with different chemical environments, it achieves gradient stripping and efficient interception of impurities across all components, providing a new process for the high-value utilization of copper resources from electronic waste and low-purity cathode copper.
[0007] To achieve the above objectives, the present invention provides the following solution: This invention provides a method for preparing 6N ultra-high purity copper based on a two-stage alkali-acid electrolysis, comprising the following steps: Step 1: Place the copper-containing raw material in an alkaline amino complex electrolyte system for a first-stage electrolysis to obtain copper intermediate cathode; Step 2: Using the intermediate cathode copper as the anode, a two-stage electrolysis is performed in an acidic sulfate electrolyte system to obtain 6N grade ultra-high purity copper; Both the first-stage and second-stage electrolysis are carried out at natural temperatures without the addition of organic additives or external heating.
[0008] In a preferred embodiment of the present invention, the copper-containing raw material is at least one of waste circuit boards, scrap copper, crude copper, black copper, electrolytic copper powder, and low-purity cathode copper.
[0009] In a preferred embodiment of the present invention, the alkaline amino complex electrolyte contains Cu. 2+ 20-30 g / L, NH4Cl 0.5-1 mol / L, NH3·H2O 3-5 mol / L and NaCl 0.1-1.0 mol / L, with deionized water as the solvent.
[0010] In a preferred embodiment of the present invention, the current density of the electrolysis stage is 200-400 A / m. 2 The electrode spacing is 5-10 cm, and the electrolysis time is 6-24 hours. Optionally, the current density for one stage of electrolysis is 200 A / m. 2 300 A / m 2 400 A / m 2 Or any value between the two aforementioned values; the electrode spacing of a single electrolysis stage is 5 cm, 6 cm, 7 cm, 8 cm, 9 cm, 10 cm or any value between the two aforementioned values; the electrolysis time of a single electrolysis stage is 6 h, 10 h, 12 h, 20 h, 24 h or any value between the two aforementioned values.
[0011] After the electrolysis is completed, the process also includes cleaning and polishing the resulting intermediate cathode copper. Furthermore, the grinding process includes a shaping step; the shaping method is either casting or pressing. That is, after grinding, the material can be directly used as an anode for two-stage electrolysis, or it can be shaped and then used as an anode for two-stage electrolysis.
[0012] In a preferred embodiment of the present invention, the anode chamber and the cathode chamber are separated in the electrolytic cell of the electrolysis section by a physical barrier (such as a diaphragm); the anode is an insoluble anode, specifically a titanium-based ruthenium-iridium coated electrode (DSA); the cathode is a titanium plate or a stainless steel plate; and the copper-containing raw material is placed in the anode chamber (anode area).
[0013] In a preferred embodiment of the present invention, the acidic sulfate electrolyte system contains Cu. 2+ 30-50 g / L, sulfuric acid 20-150 g / L, ultrapure water as solvent. Optionally, the Cu in the electrolyte of the acidic sulfate system... 2+ The concentration of sulfuric acid in the electrolyte of the acidic sulfate system is 30 g / L, 40 g / L, 50 g / L or any value between the two aforementioned values; the concentration of sulfuric acid in the electrolyte of the acidic sulfate system is 20 g / L, 50 g / L, 100 g / L, 150 g / L or any value between the two aforementioned values.
[0014] The total content of characteristic impurity elements in the electrolyte of the acidic sulfate system is less than 1 mg / L. Characteristic impurity elements refer to elements listed in the national standard GB / T 26017-2020.
[0015] In a preferred embodiment of the present invention, the current density of the two-stage electrolysis is 20-200 A / m. 2 The electrode spacing is 2-10 cm, and the electrolysis time is 12-48 hours. Optionally, the current density of the two-stage electrolysis is 20 A / m. 2 50 A / m 2 100 A / m 2 150 A / m 2 200 A / m 2 Or any value between the two aforementioned values; the electrode spacing of the two-stage electrolysis is 2cm, 4cm, 6cm, 8cm, 10cm or any value between the two aforementioned values; the electrolysis time of the two-stage electrolysis is 12h, 24h, 48h or any value between the two aforementioned values.
[0016] In a preferred embodiment of the present invention, the cathode of the two-stage electrolysis is a high-purity titanium plate or an ultra-high-purity copper plate.
[0017] In a preferred embodiment of the present invention, the natural temperature is 15-40 °C, maintained by the ambient temperature and heat generated during the electrolysis process, without the need for external heating or cooling.
[0018] In this invention, two-stage electrolysis achieves deep stripping of impurities by adjusting electrochemical refining parameters, and obtains 6N ultra-high purity copper at the cathode.
[0019] The 6N ultra-high purity copper prepared by the method of this invention has a copper content of ≥99.9999% and a total amount of impurity elements Ag, Si, Al, Pb, Fe and Zn of less than 0.5 ppm.
[0020] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention is the first to employ a two-stage combined process of an alkaline ammonia complexation system and an acidic sulfate system. By utilizing the complementary impurity removal capabilities of the two electrolytic environments, alkaline insoluble impurities such as lead (Pb), tin (Sn), and antimony (Sb) are efficiently removed in the first stage of electrolysis through complexation equilibrium and solubility product differences. In the second stage of electrolysis, trace residual impurities such as silver (Ag), silicon (Si), aluminum (Al), arsenic (As), and boron (B) are deeply stripped away through potential shielding and interfacial behavior regulation. This achieves gradient removal of impurities from all components and ensures the stable preparation of 6N-grade (purity ≥99.9999%) ultra-high purity copper.
[0021] 2. This invention has extremely broad applicability of raw materials and can directly process secondary resources such as waste circuit boards and scrap copper with complex compositions. It breaks through the dependence of traditional processes on the purity of raw materials and transforms low-end copper sources into electronic-grade ultra-high purity materials, which has significant economic value and resource recycling significance.
[0022] 3. This invention eliminates the need for organic additives such as gelatin and thiourea in the two-stage refining process, effectively preventing the introduction of non-metallic impurities such as C, S, and N into the crystal lattice, thus reducing electrolyte maintenance difficulty and environmental pollution risks. Furthermore, both stages of the process can operate at ambient temperature without additional heating, significantly reducing production energy consumption and costs. Attached Figure Description
[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0024] Figure 1 This is a process flow diagram of the preparation of 6N ultra-high purity copper based on the combined use of alkali-acid two-stage electrolysis according to the present invention.
[0025] Figure 2This is a schematic diagram of the alkaline selective electrolysis device used in the first stage of the method for preparing 6N ultra-high purity copper based on the combined use of alkali and acid two-stage electrolysis in this invention.
[0026] Figure 3 This is a schematic diagram of the acidic deep refining electrolysis device used in the second stage of the method for preparing 6N ultra-high purity copper based on the combined use of alkali and acid two-stage electrolysis in this invention. Detailed Implementation
[0027] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.
[0028] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.
[0029] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.
[0030] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.
[0031] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.
[0032] Unless otherwise specified, the technical solutions described in this invention are all conventional solutions in the field, and the reagents or raw materials used are all purchased from commercial channels or are publicly available unless otherwise specified.
[0033] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.
[0034] The process flow for preparing 6N ultra-high purity copper based on the combined alkali-acid two-stage electrolysis of this invention is as follows: Figure 1 As shown.
[0035] The waste printed circuit boards (WPCBs) used in the following examples were all collected from an electronic waste recycling station. First, pretreatment was performed: the solder on the waste PCBs was melted using a hot air gun, components were removed, and bare substrates were obtained (the main components of the bare substrates were: copper (approximately 20%-30%), non-metallic substrates such as glass fiber and epoxy resin (approximately 60%-70%), and small amounts of impurity metals such as iron, aluminum, lead, tin, and silver). The bare substrates were then pulverized to 10-50 mesh to obtain circuit board substrate powder.
[0036] The natural temperature mentioned in this invention refers to the equilibrium temperature of the electrolyte maintained by the ambient temperature and the heat generated during the electrolysis process without external auxiliary heating or cooling, which is usually 15-40 ℃.
[0037] Preparation Example 1 (single-stage electrolysis, the schematic diagram of the electrolysis apparatus is shown below) Figure 2 (as shown) (1) The pulverized circuit board substrate powder is placed in the anode area of a section of an electrolytic cell, and a titanium-based ruthenium-iridium coated electrode (DSA) is used as the anode, a titanium plate as the cathode, and a nylon filter cloth as the diaphragm.
[0038] (2) Preparation of alkaline amino complex electrolyte: its components are Cu 2+ The concentration is 25 g / L, NH4Cl 0.5 mol / L, NH3∙H2O 4 mol / L, and NaCl 0.5 mol / L (prepared by dissolving CuSO4·5H2O, NH4Cl, NH3·H2O and NaCl in deionized water).
[0039] (3) At a current density of 200 A / m 2 Electrolysis was performed for 12 hours at a time with a plate spacing of 10 cm and at ambient temperature.
[0040] (4) The cathode copper was removed, and after ultrasonic cleaning with deionized water and surface polishing, the intermediate cathode copper was obtained. The purity was detected by glow discharge mass spectrometry (GD-MS) and was approximately 4N level. The contents of the main impurities are shown in Table 1.
[0041] Table 1
[0042] Note: Total impurities and copper purity are calculated according to national standard GB / T 26017-2020. Example 1 (Two-stage electrolysis, the schematic diagram of the electrolysis device is shown below) Figure 3 (As shown) (1) The intermediate cathode copper in the previous preparation example 1 was used as the anode and the high-purity titanium plate was used as the cathode.
[0043] (2) Preparation of high-purity acidic sulfate electrolyte: its components are Cu 2+ (CuSO4·5H2O) 40 g / L, sulfuric acid mass concentration 100 g / L, without any added organic additives (prepared by dissolving CuSO4·5H2O and sulfuric acid in ultrapure water).
[0044] (3) Control process parameters: current density is 50 A / m 2 The temperature is at ambient temperature, and the electrode spacing is 4 cm.
[0045] (4) The cathode was removed after 24 hours of electrolysis. GD-MS analysis showed that the total impurity content in the copper cathode was 0.85 ppm and the copper purity reached 99.999972% (6N7, Table 2).
[0046] Table 2
[0047] Note: Total impurities and copper purity were calculated according to the national standard GB / T 26017-2020; the test results were provided by National Standard (Beijing) Inspection and Certification Co., Ltd. / National Nonferrous Metals and Electronic Materials Analysis and Testing Center.
[0048] Example 2 The only difference from Example 1 is that the current density in the process control parameters is changed to 20 A / m. 2 The remaining steps and parameters are the same as in Example 1. The copper purity of the cathode product obtained in this example is 99.99979% (5N).
[0049] Example 3 The only difference from Example 1 is that the current density in the process control parameters is changed to 30 A / m. 2 The remaining steps and parameters are the same as in Example 1. The copper purity of the cathode product obtained in this example is 99.99986% (5N).
[0050] Example 4 The only difference from Example 1 is that the current density in the process control parameters is changed to 100 A / m. 2 The remaining steps and parameters are the same as in Example 1. The copper purity of the cathode product obtained in this example is 99.99992% (6N2).
[0051] Example 5 The only difference from Example 1 is that the current density in the process control parameters is changed to 150 A / m.2 The remaining steps and parameters are the same as in Example 1. The copper purity of the cathode product obtained in this example is 99.99994% (6N4).
[0052] Example 6 The only difference from Example 1 is that the sulfuric acid concentration in the high-purity acidic sulfate electrolyte system is 20 g / L; all other steps and parameters are the same as in Example 1. The cathode product obtained in this example has a copper purity of 99.99994% (6N4).
[0053] Example 7 The only difference from Example 1 is that the sulfuric acid concentration in the high-purity acidic sulfate electrolyte system is 50 g / L; all other steps and parameters are the same as in Example 1. The cathode product obtained in this example has a copper purity of 99.99993% (6N3).
[0054] Example 8 The only difference from Example 1 is that the sulfuric acid concentration in the high-purity acidic sulfate electrolyte system is 150 g / L; all other steps and parameters are the same as in Example 1. The cathode product obtained in this example has a copper purity of 99.99995% (6N5).
[0055] Example 9 The only difference from Example 1 is that the sulfuric acid concentration in the high-purity acidic sulfate electrolyte system is 200 g / L; all other steps and parameters are the same as in Example 1. The cathode product obtained in this example has a copper purity of 99.99985% (5N).
[0056] Example 10 The only difference from Example 1 is that the Cu in the high-purity acidic sulfate electrolyte system is different. 2+ The concentration of (CuSO4·5H2O) was 20 g / L, and the remaining steps and parameters were the same as in Example 1. The copper purity of the cathode product obtained in this example was 99.99983% (5N).
[0057] Example 11 The only difference from Example 1 is that the Cu in the high-purity acidic sulfate electrolyte system is different. 2+ The concentration of (CuSO4·5H2O) was 30 g / L, and the remaining steps and parameters were the same as in Example 1. The copper purity of the cathode product obtained in this example was 99.99995% (6N5).
[0058] Example 12 The only difference from Example 1 is that the Cu in the high-purity acidic sulfate electrolyte system is different. 2+The concentration of (CuSO4·5H2O) was 50 g / L, and the remaining steps and parameters were the same as in Example 1. The copper purity of the cathode product obtained in this example was 99.99985% (5N).
[0059] Example 13 The only difference from Example 1 is that the Cu in the high-purity acidic sulfate electrolyte system is different. 2+ The concentration of (CuSO4·5H2O) was 60 g / L, and the remaining steps and parameters were the same as in Example 1. The copper purity of the cathode product obtained in this example was 99.99985% (5N).
[0060] Example 14 The only difference from Example 1 is that the electrode spacing in the process parameters is changed to 2 cm; all other steps and parameters are the same as in Example 1. The cathode product obtained in this example has a copper purity of 99.99975% (5N).
[0061] Example 15 The only difference from Example 1 is that the electrode spacing in the process parameters is changed to 6 cm; all other steps and parameters are the same as in Example 1. The cathode product obtained in this example has a copper purity of 99.99976% (5N).
[0062] Example 16 The only difference from Example 1 is that the electrode spacing in the process parameters is changed to 8 cm; all other steps and parameters are the same as in Example 1. The cathode product obtained in this example has a copper purity of 99.99973% (5N).
[0063] Example 17 The only difference from Example 1 is that the electrode spacing in the process parameters is changed to 10 cm; all other steps and parameters are the same as in Example 1. The cathode product obtained in this example has a copper purity of 99.99963% (5N).
[0064] As can be seen from the above embodiments, this invention utilizes a synergistic deep purification mechanism of alkaline-acid two-stage electrolysis. Through a first-stage alkaline amino complexation system, it effectively intercepts impurities such as Pb, Sn, and Sb that are easily precipitated or insoluble under alkaline conditions. Based on this, it achieves deep stripping of trace residual impurities such as Ag, Si, and Al in a second-stage acidic sulfate system. The core advantage of this process is that it avoids the dependence on sulfur- and chlorine-containing additives in traditional refining, eliminating the introduction of non-metallic impurities at the source and ensuring extremely high product purity. Experiments have shown that, without external heating, this invention successfully purified complex waste circuit boards to 99.999972% (6N7). This method is simple, uses widely applicable raw materials, and has low energy consumption, providing an efficient technical solution for the resource utilization and production of electronic-grade ultra-high purity copper.
[0065] Comparative Example 1 (Nitric Acid System) The intermediate cathode copper (4N grade) obtained in Example 1 was used as the anode, and a high-purity titanium plate was used as the cathode. The electrolyte was a nitric acid system with the following composition: Cu 2+ The concentration was 80 g / L (Cu(NO3)2·3H2O), the pH value was 1.0, the amount of H2O2 added was 0.10 mL / 100 mL, and the current density was 120 A / m. 2 The electrode spacing is 4 cm, and the electrolysis time is 24 h.
[0066] Comparative Example 2 The only difference from Example 1 is that the sulfuric acid in the electrolyte of the high-purity acidic sulfate system is replaced with nitric acid of the same mass concentration; all other steps and parameters are the same as in Example 1.
[0067] The cathode copper products of Example 1, Comparative Examples 1 and 2 were analyzed by GD-MS and their physicochemical properties were compared. The results are shown in Table 3. Table 3
[0068] In summary, the two-stage deep refining process using a sulfuric acid system with specific parameters is a key technological choice for achieving a leap in copper purity from 4N to 6N.
[0069] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.
Claims
1. A method for preparing 6N ultra-high purity copper based on a two-stage alkali-acid electrolysis process, characterized in that, Includes the following steps: Step 1: Place the copper-containing raw material in an alkaline amino complex electrolyte system for a first-stage electrolysis to obtain copper intermediate cathode; Step 2: Using the intermediate cathode copper as the anode, a two-stage electrolysis is performed in an acidic sulfate electrolyte system to obtain 6N grade ultra-high purity copper; Both the first-stage and second-stage electrolysis are carried out at natural temperatures without the addition of organic additives or external heating.
2. The method according to claim 1, characterized in that, The copper-containing raw material is at least one of the following: waste circuit boards, scrap copper, crude copper, black copper, electrolytic copper powder, and low-purity cathode copper.
3. The method according to claim 1, characterized in that, The alkaline amino complex electrolyte contains Cu. 2+ 20-30 g / L, NH4Cl 0.5-1 mol / L, NH3·H2O 3-5 mol / L and NaCl 0.1-1.0 mol / L, with deionized water as the solvent.
4. The method according to claim 1, characterized in that, The current density of the electrolysis section is 200-400 A / m. 2 The electrode spacing is 5-10 cm, and the electrolysis time is 6-24 hours.
5. The method according to claim 1, characterized in that, In the electrolytic cell of the aforementioned electrolysis section, the anode chamber and the cathode chamber are separated by physical barriers; the anode is an insoluble anode; the cathode is a titanium plate or a stainless steel plate; and the copper-containing raw material is placed in the anode chamber.
6. The method according to claim 1, characterized in that, The electrolyte in the acidic sulfate system contains Cu. 2+ 30-50 g / L, sulfuric acid 20-150 g / L, solvent is ultrapure water.
7. The method according to claim 1, characterized in that, The current density of the two-stage electrolysis is 20-200 A / m. 2 The electrode spacing is 2-10 cm, and the electrolysis time is 12-48 hours.
8. The method according to claim 1, characterized in that, The cathode of the two-stage electrolysis is a high-purity titanium plate or an ultra-high-purity copper plate.
9. The method according to claim 1, characterized in that, The natural temperature is 15-40 ℃, maintained by the ambient temperature and heat generated during the electrolysis process, requiring no external heating or cooling.