A method for removing cobalt ions from zinc sulfate electrolyte

Abstract

The application relates to a method for removing impurity cobalt ions in zinc sulfate electrolyte, and belongs to the technical field of zinc electrodeposition and cobalt recovery. 2+ and Sb 3+ are added into the zinc sulfate electrolyte containing cobalt ions; a reducing agent zinc powder is added into the zinc sulfate electrolyte, and a replacement reaction is carried out for 50-70 min under ultrasonic strengthening conditions, so that purified slag and zinc sulfate purified liquid are obtained through solid-liquid separation. 2+ and Sb 3+ are used as activators, Sb-Cu-Co alloy is formed with Co 2+ in the zinc sulfate electrolyte, so that the hydrogen evolution is inhibited, in addition, the Sb-Cu-Co alloy can effectively reduce the Co precipitation potential, the thermodynamics of the reaction between the reducing agent zinc powder and Co 2+ is optimized, the ultrasonic wave strengthens the reaction, the reaction kinetics is improved, the production of zinc powder wrapping and agglomeration is reduced, the particle size of the purified slag is reduced, and the utilization rate of the reducing agent zinc powder is improved.

Description

Technical Field

[0001] This invention relates to a method for removing cobalt ions, an impurity, from zinc sulfate electrolyte, belonging to the fields of zinc electrowinning and cobalt metal recovery technology. Background Technology

[0002] Zinc is one of the most important non-ferrous metals, playing a vital role in modern industrial production. Due to its low melting point, good melt flowability, and high corrosion resistance, zinc alloys are used in machinery manufacturing, such as automotive, aerospace, electronics, instrumentation, and galvanizing. Currently, the main method for zinc production is hydrometallurgical zinc refining, which includes roasting, leaching, purification, and electrowinning processes. The purification process is crucial for eliminating or reducing impurities such as copper, cadmium, and cobalt that appear during leaching. Cobalt impurities combine with the zinc surface to create micro-batteries, causing zinc to dissolve as the anode of these micro-batteries. Additionally, hydrogen evolution occurs on the zinc surface, causing the precipitated zinc to redissolve, ultimately leading to black spots or pores in the zinc deposit. This adversely affects the quality of the zinc product, reduces current efficiency, and increases power consumption. Therefore, purification processes are essential for producing high-quality zinc. Furthermore, cobalt poses a serious threat to human health, as ingestion can lead to neurological disorders, genotoxicity, and cancer. Its release into the environment causes serious environmental problems. Therefore, from the perspectives of industrial production, human health, and environmental impact, it is imperative to remove Co from zinc sulfate solutions. 2+ Currently, the main methods for removing cobalt from zinc sulfate electrolyte are organic reagent purification and zinc powder replacement. Organic reagent purification has poor overall impurity removal capabilities, the reagents are expensive, and the introduction of organic matter may have a detrimental effect on subsequent electrowinning. Therefore, zinc powder replacement remains the standard process for removing cobalt from zinc sulfate electrolyte. According to equation (1), the impurity Co in the solution... 2+ Replaced by zinc powder with Co:

[0003] Co 2+ +Zn=Co+Zn 2+ (1)

[0004] Currently, the high zinc powder consumption caused by zinc powder agglomeration and coating on the zinc powder surface is the most perplexing problem in zinc powder impurity removal. The reasons for low zinc powder utilization include: (1) the cobalt generated by displacement lowers the overpotential of the hydrogen evolution reaction, while H... + The depletion of zinc leads to an increase in pH around the zinc powder, promoting the concentration of Zn in the solution. 2+ (1) Ions generate alkaline zinc sulfate or zinc hydroxide, which then deposit on the surface of zinc powder; (2) Newly generated Zn 2+ Ions aggregate around the zinc powder, attracting anions (SO4) from the solution. 2- and OH -(3) Cobalt generated by zinc powder displacement covers the reaction surface of zinc powder; and (4) The low mass transfer coefficient causes zinc powder to agglomerate, reducing the reaction surface area of ​​zinc powder.

[0005] Therefore, it is necessary to develop a method that can disrupt the surface coating and inhibit zinc powder agglomeration, which can reduce the amount of zinc powder used and accelerate the purification process. Summary of the Invention

[0006] To address the problems of severe zinc powder agglomeration and encapsulation, high processing costs, large zinc powder consumption, long processing cycles, and high energy consumption in the removal of cobalt from zinc sulfate electrolyte, this invention proposes a method for removing cobalt ions from zinc sulfate electrolyte. This method utilizes the more negatively charged zinc to reduce cobalt ions (which are more electronegative than zinc) from the zinc sulfate solution, and the resulting Zn... 2+ It will not affect the zinc sulfate solution; utilizing Cu 2+ Using Sb₂O₃ as an activator, it reacts with Co in the zinc sulfate electrolyte. 2+ The formation of an Sb-Cu-Co alloy suppresses hydrogen evolution. Furthermore, the Sb-Cu-Co alloy effectively reduces the potential for Co deposition, optimizing the interaction between zinc powder and Co. 2+ Thermodynamics of the reaction. The cavitation and mechanical effects generated by ultrasound synergistically enhance the removal efficiency of cobalt ions by zinc powder, greatly reducing the amount of zinc powder used and the time required for the leaching process, thus lowering production costs, and the operation is simple.

[0007] A method for removing cobalt ions, an impurity, from zinc sulfate electrolyte comprises the following steps:

[0008] (1) Activator Cu 2+ and Sb 3+ Added to zinc sulfate electrolyte containing cobalt ions;

[0009] (2) Add zinc powder as a reducing agent to zinc sulfate electrolyte and perform a displacement reaction for 50-70 minutes under ultrasonic enhancement conditions. The solid and liquid are separated to obtain purified residue and zinc sulfate purified solution.

[0010] In step (1), the concentration of cobalt ions in the zinc sulfate electrolyte is 20-40 mg / L, and the concentration of zinc ions is 120-130 g / L.

[0011] The activator Cu in step (1) 2+ The addition amount is 40-60 mg / L, activator Sb 3+ The dosage is 20-30 mg / L.

[0012] In step (2), the solid-liquid ratio of zinc powder reducing agent to zinc sulfate electrolyte is 2-4:500 (g:mL).

[0013] In step (2), the ultrasonic power density is 100-300W / L and the ultrasonic frequency is 19.63-19.73kHz.

[0014] The principle of this invention for removing cobalt ions, an impurity, from zinc sulfate electrolyte is as follows: Cobalt ions, which are more electronegative than zinc, are reduced from the zinc sulfate solution using zinc, which is more positively electronegative than zinc; Cu... 2+ and Sb 3+ As an activator, it reacts with Co in the zinc sulfate electrolyte. 2+ The formation of an Sb-Cu-Co alloy suppresses hydrogen evolution. This Sb-Cu-Co alloy effectively reduces the potential for Co deposition, optimizing the interaction between zinc powder and Co. 2+ Thermodynamics of the reaction; the specific principle of Sb-Cu-Co alloy formation is: in the presence of zinc powder, as Sb... 3+ HSbO2 and SbO2 of hydrates - It is converted into metallic antimony and forms the intermetallic compound CoSb with the precipitated cobalt, as shown in reactions (2) and (3). CoSb has a larger stability region and a higher standard reduction electrode potential than Co, thus significantly improving the thermodynamic trend of cobalt removal using zinc powder. In the process of removing cobalt ions by zinc powder replacement in zinc hydrometallurgy, Sb2O3 and Cu are added simultaneously. 2+ The reaction that occurs is shown in reaction formula (4). The formation of the ternary alloy Sb-Cu-Co is accompanied by the release of energy, thus providing additional energy compensation for the displacement reaction; the general consensus among researchers regarding the mechanism by which antimony promotes the removal of cobalt ions is based on electrochemistry, that is, the formation of intermetallic compounds between antimony and cobalt under the action of zinc-antimony micro-batteries, thereby increasing the thermodynamic driving force for the removal of cobalt by zinc powder displacement. It is believed that cobalt has a small overvoltage on antimony, so under chemical action, zinc is dissolved while cobalt precipitates on antimony with a small overvoltage and precipitates around antimony, which has a good affinity for cobalt. In this way, antimony makes zinc dissolve faster and provides electrons, while cobalt ions accept electrons and become metals and precipitate.

[0015] Co 2+ +SbO 2- +4H + +Zn+2e → CoSb+Zn 2+ +2H₂O, (2)

[0016] Co 2+ +HSbO2+3H + +5 / 2Zn → CoSb+5 / 2Zn 2+ +2H2O, (3)

[0017] Co 2+ +2HSbO2+6H + +Cu 2++Zn+8e → Co-Cu-Sb (alloy)+Zn 2+ +4H2O. (4)

[0018] The cavitation and mechanical effects of ultrasound are utilized to increase the mass transfer and displacement capacity of zinc powder, thereby improving the direct reaction rate of the mineral and the oxidation process of intermediate products. Ultrasound can dissociate inclusions on the surface of zinc powder, exposing unreacted zinc powder to zinc sulfate solution, allowing the zinc powder and cobalt ions to react fully.

[0019] The beneficial effects of this invention are:

[0020] (1) This invention utilizes zinc powder as a reducing agent, Cu 2+ and Sb 3+ (Added in the form of Sb2O3) as an activator, and with the assistance of ultrasound, the zinc powder removes cobalt ions from the zinc sulfate electrolyte. Compared with the traditional zinc powder replacement method, the method of the present invention has a high removal rate of cobalt ions, a short leaching time, low zinc powder consumption, and a low required temperature.

[0021] (2) This invention utilizes the mechanical and cavitation effects generated during ultrasonic treatment of the solution. During the breaking of cavitation bubbles, the reaction zone composed of the soluble metal layer also breaks, generating an acoustic flow effect that disturbs the original steady-state diffusion, thereby improving the removal rate of cobalt ions; the micro-jets generated by ultrasound cause the coating layer on the surface of zinc powder to fall off, and acoustic cavitation provides a special local high-temperature and high-pressure material environment for the displacement reaction, thereby improving the removal rate of cobalt ions; the mechanical effect produces a mechanical stirring effect, promoting solid-liquid two-phase contact, which is beneficial to interfacial chemical reactions and improves the removal efficiency of cobalt ions;

[0022] (3) This invention uses zinc powder as a reducing agent, without introducing impurities, and the Zn produced by the reaction... 2+ It will not affect the zinc sulfate solution; activator Cu 2+ After the reaction, Sb2O3 enters the purification residue without introducing other impurities. Attached Figure Description

[0023] Figure 1 This is a particle size distribution diagram of the purified residue from Example 1;

[0024] Figure 2 This is a SEM image of the purified residue from Example 1. Detailed Implementation

[0025] The present invention will be further described in detail below with reference to specific embodiments, but the scope of protection of the present invention is not limited to the content described.

[0026] Example 1: A method for removing cobalt ions, an impurity, from zinc sulfate electrolyte, comprising the following specific steps:

[0027] (1) Activator Cu 2+ (Added in CuSO4 form) and Sb 3+ (Added in the form of Sb₂O₃) to a zinc sulfate electrolyte containing cobalt ions; wherein the concentration of cobalt ions in the zinc sulfate electrolyte is 20 mg / L, the concentration of zinc ions is 120 g / L, and the activator is Cu. 2+ The addition amount is 40 mg / L, activator Sb 3+ The addition amount is 20 mg / L;

[0028] (2) Add zinc powder reducing agent to zinc sulfate electrolyte and perform ultrasonic enhanced displacement reaction for 50 min at a temperature of 60℃ and a stirring rate of 350 rpm. Solid-liquid separation is performed to obtain purification residue and zinc sulfate purification solution. The solid-liquid ratio of zinc powder reducing agent to zinc sulfate electrolyte is 2:500 g:mL, the ultrasonic power density is 100W / L, and the ultrasonic frequency is 19.63kHz.

[0029] The purification residue was dried and ground, and its composition and particle size were determined. The concentration of residual cobalt ions in the zinc sulfate purification solution was also detected.

[0030] A control example was prepared without ultrasound, with all other conditions identical to this embodiment. The particle size distribution diagrams of the purified residue from both examples are shown below. Figure 1 SEM image of the purified residue is shown below. Figure 2 ,from Figure 1 and Figure 2 It can be seen that ultrasound significantly pulverizes slag particles into irregularly distributed fine particles. The purified slag under conventional experiments exhibits a larger particle size, indicating greater agglomeration of zinc powder in conventional experiments. The particle size distribution of the purified slag was further determined using a Malvern particle size analyzer; the zinc powder particle size was mainly in the range of 14-32 μm, with an average diameter (da) of 116.98 μm. In conventional experiments, due to inclusions and agglomeration of zinc powder, the particle size of the purified slag was mainly in the range of 0.28-252 μm, with an average diameter of 136.22 μm. The mechanical action of ultrasound significantly reduced the particle size of the slag; the average diameter of the purified slag under ultrasound experiments was 19.81 μm. This result indicates that the encapsulated slag is kneaded, thereby significantly improving the utilization rate of zinc powder.

[0031] In this embodiment, the purified residue is composed of Zn, Co, Cu and Sb. The residual cobalt ion concentration in the zinc sulfate purification solution is 0.78 mg / L, and the removal rate of cobalt ions is 96.1%.

[0032] Example 2: A method for removing cobalt ions, an impurity, from zinc sulfate electrolyte, comprising the following specific steps:

[0033] (1) Activator Cu 2+ (Added in CuSO4 form) and Sb 3+(Added in the form of Sb₂O₃) to a zinc sulfate electrolyte containing cobalt ions; wherein the concentration of cobalt ions in the zinc sulfate electrolyte is 25 mg / L, the concentration of zinc ions is 122 g / L, and the activator is Cu. 2+ The addition amount was 44 mg / L, and the activator Sb 3+ The addition amount was 22 mg / L;

[0034] (2) Add zinc powder reducing agent to zinc sulfate electrolyte and perform ultrasonic enhanced displacement reaction for 55 min at a temperature of 65℃ and a stirring rate of 350 rpm. Solid-liquid separation is performed to obtain purification residue and zinc sulfate purification solution. The solid-liquid ratio of zinc powder reducing agent to zinc sulfate electrolyte is 2:500 g:mL, the ultrasonic power density is 150 W / L, and the ultrasonic frequency is 19.65 kHz.

[0035] The purification residue was dried and ground, and its composition and particle size were determined. The concentration of residual cobalt ions in the zinc sulfate purification solution was also detected.

[0036] In this embodiment, the purification residue is composed of Zn, Co, Cu and Sb. The residual cobalt ion concentration in the zinc sulfate purification solution is 0.55 mg / L, and the cobalt ion removal rate is 97.8%.

[0037] Example 3: A method for removing cobalt ions, an impurity, from zinc sulfate electrolyte, comprising the following steps:

[0038] (1) Activator Cu 2+ (Added in CuSO4 form) and Sb 3+ (Added in the form of Sb₂O₃) to a zinc sulfate electrolyte containing cobalt ions; wherein the concentration of cobalt ions in the zinc sulfate electrolyte is 30 mg / L, the concentration of zinc ions is 124 g / L, and the activator is Cu. 2+ The addition amount was 48 mg / L, and the activator Sb 3+ The addition amount was 24 mg / L;

[0039] (2) Add zinc powder reducing agent to zinc sulfate electrolyte and perform ultrasonic enhanced displacement reaction for 60 min at a temperature of 70℃ and a stirring rate of 400 rpm. Solid-liquid separation is performed to obtain purification residue and zinc sulfate purification solution. The solid-liquid ratio of zinc powder reducing agent to zinc sulfate electrolyte is 3:500 g:mL, the ultrasonic power density is 200 W / L, and the ultrasonic frequency is 19.67 kHz.

[0040] The purification residue was dried and ground, and its composition and particle size were determined. The concentration of residual cobalt ions in the zinc sulfate purification solution was also detected.

[0041] In this embodiment, the purification residue is composed of Zn, Co, Cu and Sb. The residual cobalt ion concentration in the zinc sulfate purification solution is 0.36 mg / L, and the cobalt ion removal rate is 98.8%.

[0042] Example 4: A method for removing cobalt ions, an impurity, from zinc sulfate electrolyte, comprising the following steps:

[0043] (1) Activator Cu 2+ (Added in CuSO4 form) and Sb 3+ (Added in the form of Sb₂O₃) to a zinc sulfate electrolyte containing cobalt ions; wherein the concentration of cobalt ions in the zinc sulfate electrolyte is 35 mg / L, the concentration of zinc ions is 126 g / L, and the activator is Cu. 2+ The addition amount was 52 mg / L, and the activator Sb 3+ The addition amount was 26 mg / L;

[0044] (2) Add zinc powder reducing agent to zinc sulfate electrolyte and perform ultrasonic enhanced displacement reaction for 60 min at a temperature of 75℃ and a stirring rate of 300 rpm. Solid-liquid separation is performed to obtain purification residue and zinc sulfate purification solution. The solid-liquid ratio of zinc powder reducing agent to zinc sulfate electrolyte is 3.5:500 g:mL, the ultrasonic power density is 250 W / L, and the ultrasonic frequency is 19.69 kHz.

[0045] The purification residue was dried and ground, and its composition and particle size were determined. The concentration of residual cobalt ions in the zinc sulfate purification solution was also detected.

[0046] In this embodiment, the purification residue is composed of Zn, Co, Cu and Sb. The residual cobalt ion concentration in the zinc sulfate purification solution is 0.48 mg / L, and the cobalt ion removal rate is 97.6%.

[0047] Example 5: A method for removing cobalt ions, an impurity, from zinc sulfate electrolyte, comprising the following steps:

[0048] (1) Activator Cu 2+ (Added in CuSO4 form) and Sb 3+ (Added in the form of Sb₂O₃) to a zinc sulfate electrolyte containing cobalt ions; wherein the cobalt ion concentration in the zinc sulfate electrolyte is 40 mg / L, the zinc ion concentration is 128 g / L, and the activator is Cu. 2+ The addition amount was 56 mg / L, and the activator Sb 3+ The addition amount was 28 mg / L;

[0049] (2) Add zinc powder reducing agent to zinc sulfate electrolyte and perform ultrasonic enhanced displacement reaction at 80℃ and 400rpm for 70min. Solid-liquid separation is performed to obtain purification residue and zinc sulfate purification solution. The solid-liquid ratio of zinc powder reducing agent to zinc sulfate electrolyte is 4:500 g:mL, the ultrasonic power density is 300W / L, and the ultrasonic frequency is 19.71kHz.

[0050] The purification residue was dried and ground, and its composition and particle size were determined. The concentration of residual cobalt ions in the zinc sulfate purification solution was also detected.

[0051] In this embodiment, the purification residue is composed of Zn, Co, Cu and Sb. The residual cobalt ion concentration in the zinc sulfate purification solution is 1.24 mg / L, and the cobalt ion removal rate is 96.9%.

[0052] The specific embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A method for removing cobalt ions, an impurity, from zinc sulfate electrolyte, characterized in that, The specific steps are as follows: (1) Add activator Cu 2+ and Sb 3+ Added to a zinc sulfate electrolyte containing cobalt ions; the activator Cu 2+ The addition amount is 40-60 mg / L, activator Sb 3+ The addition amount is 20-30 mg / L; (2) Add zinc powder as a reducing agent to zinc sulfate electrolyte and perform a displacement reaction under ultrasonic enhancement for 50-70 min. Separate the solid and liquid to obtain purified residue and purified zinc sulfate solution. The ultrasonic power density is 100-300 W / L and the ultrasonic frequency is 19.63-19.73 kHz.

2. The method for removing cobalt ions from zinc sulfate electrolyte according to claim 1, characterized in that: Step (1) The concentration of cobalt ions in the zinc sulfate electrolyte is 20~30 mg / L and the concentration of zinc ions is 120~130 g / L.

3. The method for removing cobalt ions from zinc sulfate electrolyte according to claim 1, characterized in that: Step (2) The solid-liquid ratio of reducing agent zinc powder to zinc sulfate electrolyte is 2-4:500 g:mL.

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