Low-silver-content cathode copper and preparation method thereof

Abstract

The invention belongs to the field of electrode materials, and particularly relates to low-silver-content cathode copper and a preparation method thereof. The method comprises the following steps: 1) preparing a bromine-containing copper electrolyte; and 2) performing electrolytic refining by taking pyrometallurgy anode copper as an anode, an inert material as a cathode and the copper electrolyte obtained in the step 1) as electrolyte to obtain the low-silver-content cathode copper. According to the invention, the original Cl <-> additive is replaced by the bromine salt additive, and the concentration of the novel additive is controlled, so that the concentration of free Ag < + > in the copper electrolyte is greatly reduced, a long-term stable effect can be formed, and the copper electrolyte is suitable for industrial electrolytic copper material production; compared with a conventional process, the silver content in the prepared electrolytic copper material can be greatly reduced, and the quality of the electrolytic copper material is improved.

Description

Technical Field

[0001] The invention belongs to the field of electrode materials, and in particular relates to cathode copper with low silver content and a preparation method thereof. Background Art

[0002] The pyrometallurgical process of copper sulfide ore produces most of the world's crude copper. However, since the matte produced during the smelting process and the crude copper obtained after blowing are both excellent Ag capture agents, Ag is easily dissolved in copper sulfide and metallic copper, which also leads to the presence of a large amount of precious metal Ag in the crude copper produced by pyrometallurgy. The Ag in crude copper mainly exists in the form of solid solution. During the copper electrolytic refining process where it serves as the anode, as the copper is electrochemically dissolved, the silver in the crude copper may also dissolve into the electrolyte. Most of the Ag will enter the anode mud in the form of complex oxides such as Cu-Ag-Se-Te-Pb-O, and a small part will be in the form of Ag. + dissolves into the electrolyte in the form of Ag + The reduction potential is much higher than that of Cu 2+ , this part of Ag + Under the action of the electric field and flow field, it will eventually discharge and precipitate on the cathode copper surface, and then enter the cathode copper.

[0003] As a precious metal, Ag is 100 times more expensive than copper. However, the silver in cathode copper cannot be included in the pricing, which will cause huge economic losses to copper production companies. At the same time, as a precious metal, silver becomes a harmful impurity in cathode copper, so the amount of silver content is also one of the important indicators for judging the quality of cathode copper. Therefore, the silver content in cathode copper should be reduced as much as possible in copper electrolysis production. During copper electrolysis, the silver in the electrolyte mainly enters the cathode copper in the form of free Ag+ reduction and mechanical inclusions of Ag-containing particles. According to a study by FENG W, CAO H, SHEN Y, et al. Migration regularity and control of silver inclusions during copper electrodefining process[J]. Transactions of Nonferrous Metals Society of China, 2023, 33(9): 2853-2865., more than 60% of the total Ag content in cathode copper is composed of free Ag+. +reduction. At present, some materials have reported methods of reducing impurity Ag in cathode copper by using specific additives. For example, on March 8, 2022, the China Patent Office disclosed an invention patent application for a method for reducing the silver content in cathode copper, and the application publication number is CN114150349A. It mainly changes the way the electrolyte circulates, filters and separates the Ag-containing suspension, reduces the mechanical adhesion of silver-containing particles in the cathode copper, and thus effectively reduces the Ag content. Obviously, when the above processes are applied, they can only solve the effect of Ag-containing particles on the Ag content of cathode copper, but for Ag + Discharge reduction at the cathode still has no obvious effect.

[0004] To reduce the free Ag in the electrolyte + concentration, inhibiting its reduction at the cathode discharge. In industry, Cl - However, Cl - When used as an additive, its actual utilization rate is low. Most of the Cl - With Cu 2+ Combined, and because the solubility product of AgCl is large, in order to make free Ag + Concentrations below which it can take precedence over Cu 2+ The minimum concentration for reduction to occur requires the addition of a large amount of Cl - , which is unbearable for copper electrolysis systems.

[0005] Among the many silver salt precipitates with smaller solubility products, the solubility product of AgBr is 4.9×10 -13 , than the solubility product of AgCl (1.8×10 -10 ) is several orders of magnitude smaller. Zhang P, Wei Y, Ou M, et al. Behind the role of bromide ions in the synthesis of ultrathin silver nanowires[J]. Materials Letters, 2018, 213: 23-26. A study showed that AgBr complex is more stable than AgCl in solution and it is more difficult to release Ag. + . Combining the data of complex equilibrium constant, it can also be found that Br - With Ag + The stable complex constant of the reaction of combining to form AgBr is significantly greater than that of Cl - With Ag + The stable complex constant for the reaction to form AgCl; in other words, relative to Cl - ,Br - Ag + The affinity of+ The reaction limit is larger, and the solubility product of the precipitated species formed is smaller. In addition, Br and Cl are elements of the same family. Adding Br to the copper electrolyte - The impact on the existing copper electrolytic refining process is also small. Therefore, the present invention proposes to use Br - Replace Cl - As an additive in the copper electrolytic refining process, it can effectively reduce the Ag content in cathode copper products. Summary of the invention

[0006] In order to solve the problem of Cl - Additives can reduce free Ag in electrolyte + The concentration effect is limited, resulting in the problem that the silver content of cathode copper is still too high. The present invention provides a cathode copper with low silver content and a preparation method of the cathode copper. The method can effectively inhibit the doping of silver ions in the cathode copper, reduce harmful impurities and facilitate the recovery of silver.

[0007] The objects of the present invention are: 1. Reduce the content of impurity silver in cathode copper and improve its purity and quality; 2. It is suitable for industrial copper electrolysis production, adapts to the existing electrolysis process, and the current efficiency reaches more than 95%; 3. The continuous control of Ag content in cathode copper is effective under long-term electrolysis.

[0008] To achieve the above object, the present invention adopts the following scheme.

[0009] A method for preparing cathode copper with low silver content, The method comprises: 1) Prepare bromine-containing copper electrolyte; 2) Using pyrometallurgical anode copper as the anode and inert material as the cathode, and using the copper electrolyte obtained in step 1) as the electrolyte for electrolytic refining, thus obtaining cathode copper with low silver content.

[0010] As a preference, Step 1) The copper electrolyte contains 10-100 mg / L of bromine salt; After the bromine salt is added, the mixture is stirred at a constant temperature of 50 to 70° C. for 5 to 10 minutes.

[0011] As a preference, The cations in the bromide salt are alkali metal cations and / or cations with a reduction potential ≤ the reduction potential of copper ions.

[0012] As a preference, Step 1) The copper electrolyte contains Cu 2+ Ion concentration is 30-60 g / L; Step 1) The concentration of sulfuric acid in the copper electrolyte is 150-250 g / L.

[0013] As a preference, Step 2) During the electrolytic refining process: Control the current density to 150~350 mA / cm 2 The distance between the cathode and the anode is 6 to 8 cm, and the electrolytic refining process is carried out at 50 to 70 °C.

[0014] A low silver content copper cathode.

[0015] For the technical solution of the present invention, the bromine salt additive is used to replace the original Cl - Additives, using it with Ag + The stronger complexing ability makes the free Ag in the electrolyte + More AgBr precipitation is formed to reduce the residual free Ag in the electrolyte + Concentration. According to the Nernst equation, Ag + The reduction potential of Br also decreases, and the difficulty of discharge reduction at the cathode increases, which significantly reduces the Ag content in the cathode copper. - With Cu 2+ Smaller complex constant, CuBr + The amount of copper-containing complex phases produced is also small, and the use of additives is more efficient. On the other hand, the regular electrolyte circulation replenishment and anode copper dissolution in the industrial copper electrolytic refining production process will continuously introduce impurities Ag into the electrolyte. Therefore, the ability of additives to continuously produce effects is also the key to industrial implementation. The bromine salt additive used in the present invention, due to Br - With Cu 2+ The smaller the complex constant, the more efficient the use of additives. With regular small-scale replenishment, the bromide salt additive in the electrolyte system can be stably maintained at the required concentration, and the effect of continuous precipitation of Ag is better.

[0016] However, at the same time, it is also necessary to pay attention to the influence of cations in the bromide salt on the technical solution of the present invention. When the cations have a greater reduction tendency, new impurities will be further introduced. For the solution of the present invention, the preparation of cathode copper with low silver content is mainly based on electrochemical reaction. Therefore, by selecting and controlling the cations in the bromide salt to have a smaller reduction potential, the generation of new impurities can be relatively effectively avoided.

[0017] In addition, the amount of bromine salt additives used also needs to be strictly controlled. - According to the law of equilibrium and the law of conservation of mass, in addition to free Ag + In addition, free Cu in the electrolyte2+ Can also be with Br - Forms various complexes, such as CuBr + These positively charged ions are easily transferred to the cathode surface under the action of the electric field, which may lead to more Br inclusions in the cathode copper.

[0018] In addition, since the impurity silver content in the cathode copper is reduced by Ag + With Br - The complex reaction is achieved, which is accompanied by the precipitation of AgBr. Therefore, the temperature, time and solution state during electrolysis also have a significant impact. In the temperature range of 55-65 ℃, too low temperature will have a greater impact on the solubility of copper sulfate, making the Cu in the solution 2+ The decrease in concentration can easily lead to the appearance of concentration polarization, which affects the current efficiency of the electrolysis process and makes Ag + As the temperature rises, the viscosity of the electrolyte decreases, and the small amount of AgBr in the electrolyte is more likely to diffuse to the cathode surface with the floating anode mud, resulting in an increase in the Ag content of the cathode copper. The optimal electrolysis temperature is 60 ℃.

[0019] Generally speaking, the free Ag in the copper electrolyte after the bromine salt is added + The concentration is lower than 0.1 mg / L, and the lowest Ag content in cathode copper can reach 6 ppm. - The Ag content in the cathode copper obtained by adding the additive is reduced by more than 50%.

[0020] After being treated by the process of the present invention, the free silver in the copper electrolyte is mainly converted into AgBr and precipitated into the anode mud. Compared with the cathode copper-silver content of the original Cl-additive (about 12-15 ppm), the cathode copper-silver content obtained by electrolysis of the copper electrolyte with the addition of bromine / salt additives is significantly reduced.

[0021] For the electrolytic refining process, at high current density, Cu 2+ The reduction rate is faster, and Cu is more likely to appear on the cathode surface. 2+ depleted micro-regions, but the resulting high current density freed Ag + It is easier to move to the cathode surface, which makes Ag + The possibility of discharge reduction is greater, and as Cu 2+ The deposits are mixed with the copper deposit layer. However, too low current density also leads to reduced production efficiency of the copper electrolysis process. Therefore, it is necessary to control and form a relatively optimal current density range to effectively reduce copper ions while minimizing the movement of free silver ions to the cathode surface. The optimal current density is 300 A / m 2 .

[0022] In addition, during the electrolytic refining process, the solution circulation rate is 1 to 6 L / h.

[0023] At high cycle rates, free Ag + The mass transfer rate is accelerated, making it easier to reach the cathode surface for discharge reduction. However, for the AgBr particles mixed on the cathode surface, they will be taken away from the electrode surface by the electrolyte with a faster flow rate and cannot be mixed in the cathode copper. Under the combined effect of the above two factors, the Ag content in the cathode copper obtained by the two electrolytes shows a trend of first decreasing and then increasing with the increase of the electrolyte circulation rate. The optimal circulation rate is 5 L / h.

[0024] The silver content in the cathode copper prepared by the present invention can be lower than 6 ppm, and can even be lower than 1 ppm at the lowest, thus having an extremely good use effect.

[0025] The beneficial effects of the present invention are: The present invention converts the original Cl - The additive was replaced with a bromide salt additive, and the concentration of the new additive was controlled, which greatly reduced the free Ag in the copper electrolyte. + The concentration can be reduced and a long-term and stable effect can be formed, which is suitable for the industrial production of electrolytic copper materials. The silver content in the prepared electrolytic copper materials can be greatly reduced compared with the conventional process, thereby improving the quality of the electrolytic copper materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A schematic diagram of an electrolysis device used in an embodiment of the present invention; Figure 2 The optical photograph and SEM image of the cathode copper prepared by electrolysis in Example 1 of the present invention; Figure 3 This is the XRD diagram of the anode mud obtained by electrolysis of the purified electrolyte used in Example 1 of the present invention. DETAILED DESCRIPTION

[0027] The present invention is further described in detail below in conjunction with specific embodiments and the accompanying drawings. A person of ordinary skill in the art will be able to implement the present invention based on these descriptions. In addition, the embodiments of the present invention involved in the following description are generally only embodiments of a part of the present invention, rather than all embodiments. Therefore, based on the embodiments of the present invention, all other embodiments obtained by a person of ordinary skill in the art without making creative work should fall within the scope of protection of the present invention.

[0028] Unless otherwise specified, the raw materials used in the examples of the present invention are all commercially available or available to those skilled in the art; unless otherwise specified, the methods used in the examples of the present invention are all methods known to those skilled in the art.

[0029] Unless otherwise specified, the implementation of the methods of the embodiments of the present invention is based on the following Figure 1 The equipment shown is carried out.

[0030] Unless otherwise specified, the present invention simulates the industrial production environment in a laboratory environment, so a conventional industrial electrolyte after long-term electrolysis is used as the initial copper electrolyte, and a certain concentration of KBr is added as a bromine salt additive to replace the original Cl - The anode crude copper used is the same batch of commercially available crude copper.

[0031] Unless otherwise specified, the copper ion concentration of the initial copper electrolyte was measured by iodine titration. The characterization results showed that Cu 2+ The ion concentration is about 42-43 g / L, and the sulfuric acid concentration converted to sulfate ion is about 220-228 g / L. The copper ion and sulfuric acid concentrations are maintained at the initial set values ​​by supplementing CuSO4·5H2O and dilute sulfuric acid.

[0032] Example 1 A method for preparing cathode copper with low silver content, the method comprising: 1) Add KBr (based on the mass of Br) to the initial copper electrolyte at a solid-liquid ratio of 20 mg:1 L, and stir at 60°C for 10 min to mix thoroughly; 2) Using crude copper as the anode and stainless steel as the cathode, electrolytic refining is performed in the copper electrolyte obtained in step 1) at a temperature of 60 °C and a current density of 250 A / m 2 The electrolyte circulation flow rate of the electrolytic cell is 5 L / h, the total electrolysis time is 100 h, and KBr is regularly added to make Br in the electrolyte - Maintained at 20 mg / L. After electrolysis is completed, electrolytic copper material, i.e. cathode copper, is recovered.

[0033] The cathode copper prepared in this embodiment was characterized by optical photographs and SEM. The characterization results are as follows: Figure 2 As shown, it can be seen from the optical photographs that the surface of the cathode copper prepared by the present invention is smooth and flat, without defects such as dendrite nodules, which also shows that the use of bromine salt additives will not have a significant effect on the surface state and quality of the cathode copper.

[0034] The distribution of Ag in the copper electrolyte and cathode copper in steps 1) and 2) of this embodiment is shown in the following table. Group Initial copper electrolyte Bromine electrolyte Cathode copper obtained by electrolysis of initial electrolyte Cathode copper obtained by electrolysis with bromide electrolyte Silver content 0.20 mg / L 0.07 mg / L 16 ppm 6.0 ppm

[0035] First, it can be seen that the method of the present invention can effectively reduce the free Ag in the copper electrolyte. +In addition, the anode mud obtained by filtration after electrolysis of the initial copper electrolyte and the copper electrolyte with bromine salt additive was characterized by XRD. The characterization results are as follows: Figure 3 As shown, from Figure 3 It can be clearly seen that the original Cl - Free Ag in copper electrolyte with additives + It mainly precipitates into the anode mud in the form of AgCl, while adding Br - Afterwards, the precipitation is mainly converted into AgBr. The electrolytic copper material in the preparation process is continuously sampled and characterized. The results of continuous sampling and characterization are shown in the following table. Sampling time (h) 5 h 10 h 20 h 30 h 50 h 70 h 100 h Mean Silver content (ppm) 5.7 5.9 6.0 6.1 6.0 6.2 6.0 6.0

[0036] From the results of long-term electrolysis, it can be seen that as the electrolysis progresses, the copper-silver content of the cathode fluctuates overall. This may be because the addition of Br- is periodic. As the electrolysis progresses, the Br in the electrolyte - The concentration fluctuated to a certain extent, resulting in free Ag in the electrolyte. + However, for the technical solution of the present invention, the silver content of the copper material obtained after 100 h of electrolytic refining is only about 0.3 ppm higher than that after 5 h, indicating that the copper electrolyte with bromide as an additive has a good long-term effect of reducing the Ag content in cathode copper.

[0037] Comparative Example 1 A method for electrolytic refining of copper material, the method comprising: Using crude copper as anode and stainless steel as cathode, electrolytic refining is carried out in the initial copper electrolyte (Cl - The concentration is about 50 mg / L), the temperature during electrolytic refining is 60 °C, and the current density is 250 A / m 2 The electrolyte circulation flow rate of the electrolytic cell is 5L / h, and the total electrolysis time is 200 h. After completion, the electrolytic copper material, i.e. cathode copper, is recovered.

[0038] The electrolytic copper material in the preparation process was continuously sampled and characterized. The results of the continuous sampling and characterization are shown in the following table. Sampling time (h) 5 h 10 h 20 h 30 h 50 h 70 h 100 h Mean Silver content (ppm) 15.3 15.5 15.5 15.7 15.8 16.0 16.0 15.7

[0039] It can be seen from the above characterization results that as the electrolysis process proceeds, the silver content increases significantly, and compared with Example 1, the average silver content of the cathode copper has more than doubled. - The copper electrolyte as an additive has limited effect on reducing the silver content in the cathode copper. The results of this comparative example also show that the process of the present invention has the effect of maintaining the stability of the quality of the electrolytic copper material and achieving a long-term stable low silver content in the cathode copper.

[0040] Example 2 A method for preparing cathode copper with low silver content, the method comprising: 1) Add KBr (based on the mass of Br) to the initial copper electrolyte at a solid-liquid ratio of 10 mg: 1 L, and stir at 60°C for 10 min to mix thoroughly; 2) Using crude copper as the anode and stainless steel as the cathode, electrolytic refining is performed in the copper electrolyte obtained in step 1) at a temperature of 60 °C and a current density of 250 A / m 2 The electrolyte circulation flow rate of the electrolytic cell is 5 L / h, the total electrolysis time is 100 h, and KBr is regularly added to make Br in the electrolyte - Maintained at 10 mg / L. After completion, electrolytic copper material, i.e. cathode copper, is recovered.

[0041] Among them, in steps 1) and 2) of this embodiment, Ag in the copper electrolyte and cathode copper + The distribution of is shown in the following table. Group Initial copper electrolyte Bromine electrolyte Cathode copper obtained by electrolysis of initial electrolyte Cathode copper obtained by electrolysis with bromide electrolyte Silver content 0.2 mg / L 0.09 mg / L 16 ppm 6.8 ppm

[0042] It can be seen from the table that the method of the present invention can effectively reduce the free Ag in the copper electrolyte + Add 10 mg / L Br - This can reduce the copper-silver content in the cathode and the free Ag in the electrolyte. + The content is significantly reduced compared with Comparative Example 1. However, compared with Example 1, it is found that when Br - When the concentration is lower than 20 mg / L, due to the addition of Br - The amount of free Ag in the electrolyte cannot be fully + It precipitates as AgBr, resulting in some free Ag + Discharge at the cathode, therefore adding 20 ppm Br - The silver content in the cathode copper obtained by electrolysis of copper electrolyte is slightly higher.

[0043] Example 3 A method for reducing the silver content in cathode copper, the method comprising: 1) Add KBr (based on the mass of Br) to the initial copper electrolyte at a solid-liquid ratio of 50 mg:1 L, and stir the reaction at a constant temperature of 60°C for 10 min to fully mix; 2) Using crude copper as an anode and stainless steel as a cathode, electrolytic refining is performed in the copper electrolyte containing bromine salt additive obtained in step 1), the temperature during electrolytic refining is 60 °C, and the current density is 250 A / m 2 The electrolyte circulation flow rate of the electrolytic cell is 5 L / h, the total electrolysis time is 100 h, and KBr is regularly added to make Br in the electrolyte- Maintained at 50 mg / L. After completion, electrolytic copper material, i.e. cathode copper, is recovered.

[0044] Among them, in the steps 1) and 2) of this embodiment, Ag in the copper electrolyte and cathode copper + The distribution of is shown in the following table. Group Initial copper electrolyte Bromine electrolyte Cathode copper obtained by electrolysis of initial electrolyte Cathode copper obtained by electrolysis with bromide electrolyte Silver content 0.20 mg / L 0.06 mg / L 16 ppm 6.5 ppm

[0045] It can be seen that compared with Comparative Example 1, adding 50 ppm of Br - It can reduce the copper-silver content of the cathode and the free Ag in the electrolyte. + The content dropped significantly.

[0046] From the above characterization results, it can be seen that the actual value of the Ag content in the cathode copper of the copper electrolyte obtained by adding 50 mg / L bromine salt additive in this example is slightly higher than that in Example 1. This is because the higher Br - The concentration will lead to a significant increase in the AgBr concentration in the electrolyte, and the probability of these AgBr particles being mixed on the cathode surface will also increase greatly. Therefore, it can be seen that for the technical solution of the present invention, it is not the case that the more bromine salt additive is used, the better, but rather that a moderate amount is used to build a corresponding stable system in the copper electrolyte.

[0047] Continue to conduct continuous sampling and characterization of the electrolytic copper materials in the preparation process. The continuous sampling and characterization results are shown in the following table. Sampling time (h) 5 h 10 h 20 h 30 h 50 h 70 h 100 h Mean Silver content (ppm) 6.1 6.2 5.9 6.1 6.3 6.4 6.5 6.2

[0048] From the results of long-term electrolysis, it can be seen that as the electrolysis progresses, the copper-silver content of the cathode fluctuates overall. This may be because the addition of Br- is periodic. As the electrolysis progresses, the Br in the electrolyte - The concentration fluctuated to a certain extent, resulting in free Ag in the electrolyte. + However, for the technical solution of the present invention, the silver content of the copper material obtained after 100 hours of electrolytic refining is only about 0.4 ppm higher than that after 5 hours, indicating that the copper electrolyte with bromide as an additive has a good long-term effect of reducing the Ag content in cathode copper.

[0049] Example 4 A method for reducing the silver content in cathode copper, the method comprising: 1) Add KBr (based on the mass of Br) to the initial copper electrolyte at a solid-liquid ratio of 20 mg:1 L, and stir at 56°C for 10 min to fully mix; 2) Using crude copper as an anode and stainless steel as a cathode, electrolytic refining is performed in the copper electrolyte containing bromine salt additive obtained in step 1), the temperature during electrolytic refining is 56 °C, and the current density is 250 A / m2 The electrolyte circulation flow rate of the electrolytic cell is 5 L / h, the total electrolysis time is 100 h, and KBr is regularly added to make Br in the electrolyte - Maintained at 20 mg / L. After completion, electrolytic copper material, i.e. cathode copper, is recovered.

[0050] Among them, in steps 1) and 2) of this embodiment, Ag in the copper electrolyte and cathode copper + The distribution of is shown in the following table. Group Initial copper electrolyte Bromine electrolyte Cathode copper obtained by electrolysis of initial electrolyte Cathode copper obtained by electrolysis with bromide electrolyte Silver content 0.20 mg / L 0.07 mg / L 16 ppm 6.2 ppm

[0051] It can be seen that the method of the present invention can reduce the copper-silver content of the cathode and the free Ag in the electrolyte. + At the same time, the cathode copper Ag content in this example is slightly higher than that in Example 1. This is because as the temperature increases, according to the Nernst equation and the thermodynamic calculation of species equilibrium, the free Ag + The difference between the critical concentration of reduction and its actual concentration will decrease, that is, the amount of free Ag+ reduced in the electrolyte will decrease, so the Ag content in the cathode copper will decrease.

[0052] Continue to conduct continuous sampling and characterization of the electrolytic copper materials in the preparation process. The continuous sampling and characterization results are shown in the following table. Sampling time (h) 5 h 10 h 20 h 30 h 50 h 70 h 100 h Mean Silver content (ppm) 6.0 5.9 5.8 6.1 6.3 6.3 6.2 6.1

[0053] From the long-term electrolysis results, it can be seen that as the electrolysis progresses, the cathode copper and silver content fluctuates slightly overall, which may be due to Br - The addition of Br in the electrolyte is periodic. As the electrolysis proceeds, - The concentration fluctuated to a certain extent, resulting in free Ag in the electrolyte. + However, for the technical solution of the present invention, the silver content of the copper material obtained after 100 hours of electrolytic refining is only about 0.2 ppm higher than that after 5 hours, indicating that the copper electrolyte with bromide as an additive has a good long-term effect of reducing the Ag content in cathode copper.

[0054] Example 5 A method for reducing the silver content in cathode copper, the method comprising: 1) Add KBr (based on the mass of Br) to the initial copper electrolyte at a solid-liquid ratio of 20 mg:1 L, stir at 64°C for 10 min, and then mix thoroughly; 2) Using crude copper as the anode and stainless steel as the cathode, electrolytic refining is performed in the copper electrolyte obtained in step 1) at a temperature of 64 °C and a current density of 250 A / m 2 The electrolyte circulation flow rate of the electrolytic cell is 5 L / h, the total electrolysis time is 100 h, and KBr is regularly added to make Br in the electrolyte- Maintained at 20 mg / L. After completion, electrolytic copper material, i.e. cathode copper, is recovered.

[0055] Among them, in the steps 1) and 2) of this embodiment, Ag in the copper electrolyte and cathode copper + The distribution of is shown in the following table. Group Initial copper electrolyte Bromine electrolyte Cathode copper obtained by electrolysis of initial electrolyte Cathode copper obtained by electrolysis with bromide electrolyte Silver content 0.20 mg / L 0.07 mg / L 16 ppm 6.4 ppm

[0056] It can be seen that the method of the present invention can reduce the copper-silver content of the cathode and the free Ag in the electrolyte. + At the same time, the Ag content of the cathode copper in this example is slightly higher than that in Example 1. This is because the amount of floating anode mud in the electrolyte increases rapidly at a higher temperature, and the viscosity of the electrolyte decreases with increasing temperature, which makes it easier for AgBr and other Ag-containing particles to diffuse to the cathode surface with the floating anode mud and be mixed in the cathode copper, causing the Ag content of the cathode copper to increase.

[0057] Continue to conduct continuous sampling and characterization of the electrolytic copper materials in the preparation process. The continuous sampling and characterization results are shown in the following table. Sampling time (h) 5 h 10 h 20 h 30 h 50 h 70 h 100 h Mean Silver content (ppm) 6.1 6.4 6.1 6.0 6.4 6.3 6.4 6.2

[0058] From the long-term electrolysis results, it can be seen that as the electrolysis progresses, the cathode copper and silver content fluctuates slightly overall, which may be due to Br - The addition of Br in the electrolyte is periodic. As the electrolysis proceeds, - The concentration fluctuated to a certain extent, resulting in free Ag in the electrolyte. + However, for the technical solution of the present invention, the silver content of the copper material obtained after 100 hours of electrolytic refining is only about 0.3 ppm higher than that after 5 hours, indicating that the copper electrolyte with bromide as an additive has a good long-term effect of reducing the Ag content in cathode copper.

[0059] Example 6 A method for reducing the silver content in cathode copper, the method comprising: 1) Add KBr (based on the mass of Br) to the initial copper electrolyte at a solid-liquid ratio of 20 mg:1 L, and stir the reaction at 60°C for 10 min to fully mix; 2) Using crude copper as the anode and stainless steel as the cathode, electrolytic refining is performed in the copper electrolyte obtained in step 1) at a temperature of 60 °C and a current density of 250 A / m 2 The electrolyte circulation flow rate of the electrolytic cell is 4 L / h, the total electrolysis time is 100 h, and KBr is regularly added to make Br in the electrolyte - Maintained at 20 mg / L. After completion, electrolytic copper material, i.e. cathode copper, is recovered.

[0060] Among them, in the steps 1) and 2) of this embodiment, Ag in the copper electrolyte and cathode copper + The distribution of is shown in the following table. Group Initial copper electrolyte Bromine electrolyte Cathode copper obtained by electrolysis of initial electrolyte Cathode copper obtained by electrolysis with bromide electrolyte Silver content 0.2 mg / L 0.07 mg / L 16 ppm 6.2 ppm

[0061] It can be seen that the method of the present invention can reduce the copper-silver content of the cathode and the free Ag in the electrolyte. + At the same time, the cathode copper Ag content in this example is slightly higher than that in Example 1, because Br - The addition of free Ag in the electrolyte + The concentration is very low, that is, the inclusion amount of AgBr and Ag-containing colloid particles plays a key role in the Ag content of cathode copper. According to the analysis of the reasons for the influence of electrolyte circulation flow rate on the Ag content of cathode copper in Chapter 3, the increase in flow rate will make the inclusion of AgBr and Ag-containing colloid particles difficult, so the Ag content of cathode copper prepared in this embodiment at a smaller flow rate is higher than that in Example 1.

[0062] Continue to conduct continuous sampling and characterization of the electrolytic copper materials in the preparation process. The continuous sampling and characterization results are shown in the following table. Sampling time (h) 5 h 10 h 20 h 30 h 50 h 70 h 100 h Mean Silver content (ppm 6.1 6.4 6.1 6.0 6.4 6.3 6.4 6.2

[0063] From the long-term electrolysis results, it can be seen that as the electrolysis progresses, the cathode copper and silver content fluctuates slightly overall, which may be due to Br - The addition of Br in the electrolyte is periodic. As the electrolysis proceeds, - The concentration fluctuated to a certain extent, resulting in free Ag in the electrolyte. + However, for the technical solution of the present invention, the silver content of the copper material obtained after 100 hours of electrolytic refining is only about 0.3 ppm higher than that after 5 hours, indicating that the copper electrolyte with bromide as an additive has a good long-term effect of reducing the Ag content in cathode copper.

[0064] Example 7 A method for reducing the silver content in cathode copper, the method comprising: 1) Add NaBr (based on the mass of Br) to the initial copper electrolyte at a solid-liquid ratio of 20 mg:1 L, and stir the reaction at a constant temperature of 60°C for 10 min to fully mix; 2) Using crude copper as the anode and stainless steel as the cathode, electrolytic refining is performed in the copper electrolyte obtained in step 1) at a temperature of 60 °C and a current density of 250 A / m 2 The electrolyte circulation flow rate of the electrolytic cell is 5 L / h, the total electrolysis time is 100 h, and NaBr solution is regularly added to make the Br in the electrolyte - Maintained at 20 mg / L. After completion, electrolytic copper material, i.e. cathode copper, is recovered.

[0065] Among them, in the steps 1) and 2) of this embodiment, Ag in the copper electrolyte and cathode copper + The distribution of is shown in the following table. Group Initial copper electrolyte Bromine electrolyte Cathode copper obtained by electrolysis of initial electrolyte Cathode copper obtained by electrolysis with bromide electrolyte Silver content 0.2 mg / L 0.07 mg / L 16 ppm 6.2 ppm

[0066] It can be seen that the method of the present invention can reduce the copper-silver content of the cathode and the free Ag in the electrolyte. + The control effect of using HBr solution and KBr solid on the Ag content in cathode copper is basically the same.

[0067] Continue to conduct continuous sampling and characterization of the electrolytic copper materials in the preparation process. The continuous sampling and characterization results are shown in the following table. Sampling time (h) 5 h 10 h 20 h 30 h 50 h 70 h 100 h Mean Silver content (ppm) 6.0 5.9 6.1 6.3 6.1 6.3 6.2 6.1

[0068] From the long-term electrolysis results, it can be seen that as the electrolysis progresses, the cathode copper and silver content fluctuates slightly overall, which may be due to Br - The addition of Br in the electrolyte is periodic. As the electrolysis proceeds, - The concentration fluctuated to a certain extent, resulting in free Ag in the electrolyte. + However, for the technical solution of the present invention, the silver content of the copper material obtained after 100 h of electrolytic refining is only about 0.2 ppm higher than that after 5 h, indicating that the copper electrolyte with NaBr as an additive also has a good long-term effect of reducing the Ag content in cathode copper.

Claims

1. A method for preparing cathode copper with low silver content, characterized in that: The method comprises: 1) Prepare bromine-containing copper electrolyte; 2) Using pyrometallurgical anode copper as the anode and inert material as the cathode, and using the copper electrolyte obtained in step 1) as the electrolyte for electrolytic refining, thus obtaining cathode copper with low silver content.

2. The method for preparing cathode copper with low silver content according to claim 1, characterized in that: Step 1) The copper electrolyte contains 10-100 mg / L of bromine salt; After the bromine salt is added, the mixture is stirred at a constant temperature of 50 to 70° C. for 5 to 10 minutes.

3. The method for preparing cathode copper with low silver content according to claim 2, characterized in that: The cations in the bromide salt are alkali metal cations and / or cations with a reduction potential ≤ the reduction potential of copper ions.

4. The method for preparing a low-silver content cathode copper according to claim 1, 2 or 3, characterized in that: Step 1) The copper electrolyte contains Cu 2+ Ion concentration is 30-60 g / L; Step 1) The concentration of sulfuric acid in the copper electrolyte is 150-250 g / L.

5. The method for preparing cathode copper with low silver content according to claim 1, characterized in that: Step 2) During the electrolytic refining process: Control the current density to 150~350 mA / cm 2 The distance between the cathode and the anode is 6 to 8 cm, and the electrolytic refining process is carried out at 50 to 70 °C.

6. A cathode copper with low silver content obtained by the method according to any one of claims 1 to 5.

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