Preparation method of high-purity zinc

Abstract

The invention relates to the technical field of high-purity metal preparation, and discloses a preparation method of high-purity zinc. The invention provides a preparation method of high-purity zinc, which comprises the following steps: 1) putting zinc particles into a quartz test tube, and sealing; 2) hanging the sealed quartz test tube in the step 1) on a lifting rod in a lifting furnace; (3) heating the lifting furnace; and (4) after the pulling furnace reaches the preset temperature, firstly placing the quartz test tube in a high-temperature area in the pulling furnace, melting, then slowly descending the quartz test tube in the vertical direction, and growing crystals to obtain the high-purity zinc. The 6N-grade high-purity zinc single crystal prepared by the preparation method of the high-purity zinc, provided by the invention, has higher purity, shows more stable behavior in electrochemical reaction, can keep lower current density in a wider potential range, and reduces the corrosion rate.

Description

Technical Field

[0001] The present invention relates to the technical field of high-purity metal preparation, and in particular to a method for preparing high-purity zinc. Background Art

[0002] Metal corrosion is a core cause of global industrial losses, and innovation in its prevention and control technologies has become a key research direction in materials science. Zinc, due to its unique electrochemical properties and passivation ability, plays a key role in corrosion prevention. It is widely used to protect galvanized steel, marine engineering, and concrete structures through multiple mechanisms, including sacrificial anodic protection, self-passivation, and synergistic corrosion inhibition. However, issues such as accelerated corrosion of zinc-based materials in extremely acidic and alkaline / high-salt environments, as well as the galvanic effect of high-potential metals, continue to limit their long-term service performance.

[0003] As a core component of an electrochemical system, the stability and cost-effectiveness of the reference electrode directly impact the efficiency of corrosion monitoring and protection. Reference electrodes are essential components in electrochemical experiments and are widely used in various electrochemical measurements, analyses, and sensors. Their primary function is to provide a stable and known potential reference for comparison with the electrode under test, thereby obtaining accurate electrochemical data. In many electrochemical reactions, accurate measurement of electrode potential is crucial for understanding reaction mechanisms, optimizing experimental conditions, and developing new materials and sensors. Therefore, reference electrodes play a fundamental and critical role in corrosion research, battery design, and electrolysis processes. They are a core tool for achieving precise measurement and control of electrochemical reactions, and ensuring the reliability of experimental results. High-purity zinc reference electrodes are becoming a preferred alternative to traditional Ag / AgCl electrodes due to their unique advantages, such as dual-environment compatibility (seawater and soil media), low cost, and long service life.

[0004] However, current technology for producing high-purity zinc faces bottlenecks. The primary method for producing high-purity zinc is to produce zinc with purities of 4N5-4N7 through electrolysis, which is then refined to a purity of 6N or higher through vacuum distillation or zone melting. Vacuum distillation lowers the metal's boiling point in a low-pressure environment, selectively evaporating and separating impurities to achieve purification. Using 3N zinc as a starting material, researchers StAli et al. successfully produced high-purity zinc with a purity of up to 99.9999% by combining fractional distillation with double vacuum distillation. Researchers Gopala et al. extracted ultra-pure 6N5 zinc from 4N5 zinc raw material by combining fractional distillation with triple vacuum distillation. Vacuum distillation requires maintaining a certain vacuum level, which relies on vacuum pumps, consumes additional energy, and increases operating costs. From a safety perspective, glassware and equipment must be handled with care during vacuum work to prevent internal explosions. Safety measures, such as wrapping glassware with protective materials, are essential. On an industrial scale, vacuum distillation is more complex to implement and maintain, requiring specialized equipment, and managing the vacuum level also increases operational complexity. The zone melting method forms a moving molten zone through local heating and gradually purifies the metal by utilizing the impurity condensation effect, ultimately obtaining a high-purity material. Li Wenliang et al. studied the zone melting method for preparing high-purity zinc. Under the protection of a high-purity argon flow, the melting zone moved at a rate of 3 cm / h. -1 The melting zone length is 50 mm, and after 20 zones of smelting, a purity of 6N or higher is achieved. High-purification zinc in zone smelting furnaces is relatively slow, energy-intensive, and requires complex equipment, resulting in high costs. Consequently, impurity removal efficiency can be limited in some cases, and processing of large or complex samples can be difficult.

[0005] This makes regional smelting methods potentially uneconomical for large-scale production, although they still have advantages when pursuing extremely high-purity zinc products. In addition, the quality of the high-purity zinc in the product also affects the stability of the electrode potential. Its stability is synergistically affected by the medium and the chloride ion concentration at temperature. Its surface passivation film is easily damaged by organic matter / mechanical stress in contaminated sea areas, causing crack propagation and accelerating corrosion. Single crystal zinc significantly inhibits crack initiation by reducing the grain boundary density, while increasing the density of the passivation film and its resistance to Cl. - This provides the electrode with potential stability and resistance to stress corrosion in the dynamic marine environment. Therefore, the development of new, efficient, low-consumption, and safe high-purity zinc purification technologies has become an urgent need to break through the bottleneck of material performance and ensure the sustainable development of the marine engineering and clean energy industries. Summary of the Invention

[0006] The purpose of the present invention is to provide a method for preparing high-purity zinc.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] A method for preparing high-purity zinc comprises the following steps:

[0009] 1) Place zinc particles in a quartz test tube and seal it;

[0010] 2) Hanging the sealed quartz test tube in step 1) on a lifting rod in a pulling furnace;

[0011] 3) heating the pulling furnace;

[0012] 4) After the pulling furnace reaches a preset temperature, the quartz test tube is first placed in the high temperature zone of the pulling furnace to melt, and then the quartz test tube is slowly lowered in a vertical direction to allow crystal growth to obtain the high-purity zinc.

[0013] Furthermore, in step 1), the zinc particles are 4N grade zinc particles.

[0014] Furthermore, in step 1), the sealing is specifically performed by using a quartz cylinder as a sealing material and an oxyhydrogen flame machine to seal the quartz test tube.

[0015] Furthermore, in step 1), after the sealing, the interior of the quartz test tube needs to be evacuated to a vacuum state.

[0016] Furthermore, in step 2), the hanging is specifically: using an alloy wire to hang the quartz test tube on a pulling rod in the pulling furnace.

[0017] Furthermore, the alloy wire is a nickel-chromium alloy with a diameter of 0.6 mm.

[0018] Furthermore, in step 3), the heating is specifically as follows: controlling the temperature of the upper high temperature zone of the pulling furnace to 570°C, and reducing the temperature of the lower low temperature zone from 570°C to 380°C from top to bottom with a temperature gradient of 5°C / cm.

[0019] Furthermore, in step 4), the melting time is 3 hours.

[0020] Furthermore, in step 4), the slowly descending is specifically: slowly descending the quartz test tube in a vertical direction at a descending speed of 60 mm / h.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The 6N-grade high-purity zinc single crystal prepared by the high-purity zinc preparation method provided by the present invention has higher purity, exhibits more stable behavior in electrochemical reactions, can maintain a lower current density in a wider potential range, and reduces the corrosion rate.

[0023] The present invention provides a method for preparing high-purity zinc by innovatively introducing the Bridgeman method. Through the coordinated regulation of the axial temperature gradient and the solidification rate, dynamic exclusion of impurities is achieved on the basis of the solute coagulation effect, and 6N-grade high-purity zinc single crystals are successfully prepared. Compared with the zone melting process, the present invention provides a method for preparing high-purity zinc without the need for a high-frequency heating system in multiple melting zones, which simplifies the equipment structure and reduces the risk of thermal damage. The columnar crystal structure formed by directional solidification reduces grain boundary defects and significantly improves crack resistance and electrochemical stability. At the same time, constant solidification parameters ensure the fluctuation of the axial purity gradient, breaking through the limitation of poor batch consistency of traditional processes, and providing an efficient and reliable solution for the industrial production of high-precision zinc-based reference electrodes in marine engineering.

[0024] The method for preparing high-purity zinc provided by the present invention does not require repeated heating and cooling, thus avoiding the complex cyclic operations required by the zone smelting method. In addition, the method for preparing high-purity zinc provided by the present invention is suitable for large-scale production, can process metal samples of larger sizes, and can usually obtain high-purity metal in a shorter time. Therefore, it has certain advantages in production efficiency and energy consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiment below. The accompanying drawings are for illustration purposes only and are not to be considered as limiting the present invention. The same reference symbols are used throughout the drawings to represent the same components. In the drawings:

[0026] Figure 1 The XRD analysis results of 4N-grade zinc particles and 6N-grade high-purity zinc single crystals before and after corrosion, where (a) is the 4N-grade zinc particles before corrosion, (b) is the 4N-grade zinc particles after corrosion, (c) is the 6N-grade high-purity zinc single crystal before corrosion, and (d) is the 6N-grade high-purity zinc single crystal after corrosion;

[0027] Figure 2 The SEM analysis results of 4N-grade zinc particles and 6N-grade high-purity zinc single crystals before and after corrosion, among which (a) is the 4N-grade zinc particles before corrosion, (b) is the 4N-grade zinc particles after corrosion, (c) is the 6N-grade high-purity zinc single crystal before corrosion, (d) are all the 6N-grade high-purity zinc single crystals after corrosion, (e) is the 4N-grade zinc particle energy spectrum, and (f) is the 6N-grade high-purity zinc single crystal energy spectrum;

[0028] Figure 3 The AC impedance analysis results of 4N-grade zinc particles and 6N-grade high-purity zinc single crystals before and after corrosion, where (a) is the Nyquist diagram of 4N-grade zinc particles, (b) is the Bode diagram of 4N-grade zinc particles, (c) is the Nyquist diagram of 6N-grade high-purity zinc single crystals, and (d) is the Bode diagram of 6N-grade high-purity zinc single crystals. DETAILED DESCRIPTION

[0029] Various exemplary embodiments of the present invention are now described in detail. This detailed description should not be considered as a limitation of the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention. It should be understood that the terms used in the present invention are only for describing specific embodiments and are not intended to limit the present invention.

[0030] In addition, for numerical ranges in the present invention, it is understood that each intervening value between the upper and lower limits of the range is also specifically disclosed. Each smaller range between any stated value or intervening value in a stated range and any other stated value or intervening value in the stated range is also included in the present invention. The upper and lower limits of these smaller ranges may independently be included or excluded in the range.

[0031] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of any conflict with any incorporated document, the contents of this specification shall prevail.

[0032] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the description of the invention. The description and examples are intended to be exemplary only.

[0033] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0034] In the following examples, the purity of the 4N grade zinc particles is 99.993-99.997%.

[0035] In the following examples, a method for preparing high-purity zinc comprises the following steps:

[0036] 1) Place 4N grade zinc particles in a quartz test tube, use a quartz cylinder as a sealing material, seal the quartz test tube with an oxyhydrogen flame, and evacuate the interior of the quartz test tube to a vacuum state;

[0037] 2) Covering the sealed quartz test tube in step 1) with a nickel-chromium alloy sleeve having a diameter of 0.6 mm, and hanging the quartz test tube on a pulling rod in a pulling furnace;

[0038] 3) Turn on the heating system of the pulling furnace, control the temperature of the upper high-temperature zone of the pulling furnace to 570°C, and reduce the temperature of the lower low-temperature zone from 570°C to 380°C at a temperature gradient of 5°C / cm from top to bottom;

[0039] 4) After the pulling furnace reaches the preset temperature, the quartz test tube is first placed in the high temperature zone and melted for 3 hours. Thereafter, the quartz test tube is slowly lowered in the vertical direction at a descending speed of 60 mm / h to allow crystal growth. After the quartz test tube drops to the 380°C temperature zone, the pulling furnace heating system is turned off and cooled to room temperature to obtain the high-purity zinc.

[0040] Example 1

[0041] A method for preparing high-purity zinc

[0042] In this example, the 4N grade zinc particles described in Table 1 were used as raw materials to prepare high-purity zinc. The specific steps are as follows:

[0043] Table 1 Main elements and contents of N-grade zinc particles in Example 14

[0044]

[0045] 1) Place 4N grade zinc particles in a quartz test tube, use a quartz cylinder as a sealing material, seal the quartz test tube with an oxyhydrogen flame, and evacuate the interior of the quartz test tube to a vacuum state;

[0046] 2) Covering the sealed quartz test tube in step 1) with a nickel-chromium alloy sleeve having a diameter of 0.6 mm, and hanging the quartz test tube on a pulling rod in a pulling furnace;

[0047] 3) Turn on the heating system of the pulling furnace, control the temperature of the upper high-temperature zone of the pulling furnace to 570°C, and reduce the temperature of the lower low-temperature zone from 570°C to 380°C at a temperature gradient of 5°C / cm from top to bottom;

[0048] 4) After the pulling furnace reaches the preset temperature, the quartz test tube is first placed in the high temperature zone and melted for 3 hours. Thereafter, the quartz test tube is slowly lowered in the vertical direction at a descending speed of 60 mm / h to allow crystal growth. After the quartz test tube drops to the 380°C temperature zone, the pulling furnace heating system is turned off and cooled to room temperature to obtain the high-purity zinc.

[0049] The main elements and contents of the high-purity zinc prepared in Example 1 are shown in Table 2;

[0050] Table 2 Main elements and contents of high purity zinc in Example 1

[0051]

[0052] As can be seen from the data in Table 2, the method for preparing high-purity zinc provided by the present invention successfully prepared 6N-grade high-purity zinc single crystals using 4N-grade zinc particles as raw materials. In the prepared 6N-grade high-purity zinc single crystals, the content of impurities such as iron and lead was significantly reduced by two orders of magnitude compared to that of 4N-grade zinc particles.

[0053] The raw material 4N grade zinc particles and the prepared high purity zinc 6N grade high purity zinc single crystals of Example 1 were subjected to XRD analysis before and after corrosion. The XRD analysis results of the 4N grade zinc particles and the 6N grade high purity zinc single crystals before and after corrosion are shown as follows: Figure 1 As shown, (a) is before 4N grade zinc grain corrosion, (b) is after 4N grade zinc grain corrosion, (c) is before 6N grade high purity zinc single crystal corrosion, and (d) is after 6N grade high purity zinc single crystal corrosion;

[0054] The raw material 4N grade zinc particles and the prepared high purity zinc 6N grade high purity zinc single crystals of Example 1 were subjected to SEM analysis before and after corrosion. The SEM analysis results of the 4N grade zinc particles and the 6N grade high purity zinc single crystals before and after corrosion are shown as follows: Figure 2 As shown, (a) is before 4N-level zinc particle corrosion, (b) is after 4N-level zinc particle corrosion, (c) is before 6N-level high-purity zinc single crystal corrosion, (d) are after 6N-level high-purity zinc single crystal corrosion, (e) is the 4N-level zinc particle energy spectrum, and (f) is the 6N-level high-purity zinc single crystal energy spectrum;

[0055] Depend on Figure 1 and Figure 2 It can be seen that a dense and continuous Zn5(OH)8Cl2·H2O passivation film is formed on the surface of the 6N grade high-purity zinc single crystal, and its porosity is reduced by more than 80% compared with the 4N grade zinc particles, which effectively inhibits the penetration of chloride ions and the occurrence of localized corrosion.

[0056] The raw material 4N grade zinc particles and the prepared high purity zinc 6N grade high purity zinc single crystals of Example 1 were subjected to AC impedance analysis before and after corrosion. The AC impedance analysis results of the 4N grade zinc particles and the 6N grade high purity zinc single crystals before and after corrosion are shown as follows: Figure 3 As shown, (a) is the Nyquist diagram of 4N-grade zinc particles, (b) is the Bode diagram of 4N-grade zinc particles, (c) is the Nyquist diagram of 6N-grade high-purity zinc single crystal, and (d) is the Bode diagram of 6N-grade high-purity zinc single crystal;

[0057] Depend on Figure 3 It can be seen that the corrosion current density of 6N grade high-purity zinc single crystal is only 58% of that of 4N grade zinc particles, and the charge transfer resistance is increased by about 2 times, which has good electrochemical properties.

[0058] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered by the scope of protection of the claims of the present invention.

Claims

1. A method for preparing high-purity zinc, characterized in that: The following steps are involved: 1) Place zinc particles in a quartz test tube and seal it; 2) Hanging the sealed quartz test tube in step 1) on a lifting rod in a pulling furnace; 3) heating the pulling furnace; 4) After the pulling furnace reaches a preset temperature, the quartz test tube is first placed in the high temperature zone of the pulling furnace to melt, and then the quartz test tube is slowly lowered in a vertical direction to allow crystal growth to obtain the high-purity zinc.

2. The method for preparing high-purity zinc according to claim 1, wherein: In step 1), the zinc particles are 4N grade zinc particles.

3. The method for preparing high-purity zinc according to claim 1, wherein: In step 1), the sealing is specifically performed by using a quartz cylinder as a sealing material and an oxyhydrogen flame machine to seal the quartz test tube.

4. The method for preparing high-purity zinc according to claim 1, wherein: In step 1), after the sealing, the interior of the quartz tube needs to be evacuated to a vacuum state.

5. The method for preparing high-purity zinc according to claim 1, wherein: In step 2), the hanging is specifically: using an alloy wire to hang the quartz test tube on a pulling rod in the pulling furnace.

6. The method for preparing high-purity zinc according to claim 5, wherein: The alloy wire is a nickel-chromium alloy with a diameter of 0.6 mm.

7. The method for preparing high-purity zinc according to claim 1, wherein: In step 3), the heating is specifically as follows: controlling the temperature of the upper high temperature zone of the pulling furnace to 570°C, and decreasing the temperature of the lower low temperature zone from 570°C to 380°C from top to bottom with a temperature gradient of 5°C / cm.

8. The method for preparing high-purity zinc according to claim 1, wherein: In step 4), the melting time is 3 hours.

9. The method for preparing high-purity zinc according to claim 1, wherein: In step 4), the slow descent is specifically: slowly lowering the quartz test tube in a vertical direction at a descent speed of 60 mm / h.

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