Method for preparing high-purity nano zinc oxide by electrochemically dissolving zinc

Abstract

The invention relates to a method for preparing high-purity nano zinc oxide by electrochemically dissolving zinc, and belongs to the technical field of powder material preparation. Comprising the following steps: (1) electrochemically dissolving zinc, and preparing a zinc-containing solution under the action of direct current; (2) solution adjustment: adding a neutralizer into the zinc-containing solution to adjust the pH value to 4.0-6.0, and diluting the zinc ion concentration to 0.1-0.3 mol / L; (3) hydro-thermal synthesis: transferring the adjusted solution into a high-pressure reaction kettle, adding a slow-release weak base and a surfactant, and reacting at 120-150 DEG C for 4-8 hours to obtain a zinc hydroxide precipitate; and (4) calcining treatment: calcining the zinc hydroxide to obtain the high-purity nano zinc oxide. The method is green, environment-friendly, simple and convenient in process, low in energy consumption and suitable for large-scale preparation.

Description

Technical Field

[0001] This application relates to the field of powder material preparation technology, and in particular to a method for preparing high-purity nano zinc oxide by electrochemical zinc dissolution. Background Technology

[0002] Zinc oxide, as an indispensable metal compound raw material in modern industry, has a wide range of applications. Its main application areas include glass, animal feed, ceramics, dyes, paints, papermaking, and rubber industries. In recent years, with the rapid development of high-end industries and emerging application fields, industries such as pharmaceuticals, cosmetics, and food have placed higher demands on the purity (≥4N) and low content of harmful impurities in zinc oxide to ensure its reliability and stability in terms of safety and functional performance.

[0003] Currently, the main methods for preparing zinc oxide include physical methods, gas-phase methods, and liquid-phase methods. Physical methods are further divided into direct and indirect methods: the direct method involves reducing zinc ore or zinc-containing waste at high temperatures, reducing and vaporizing the zinc metal, and then reacting it with oxygen to produce zinc oxide. This method has advantages such as low cost and wide availability of raw materials, but the purity is relatively low (99.0%, national standard GB / T 3494-2012). The indirect method involves vaporizing high-purity metallic zinc at high temperatures and then reacting it with oxygen to produce zinc oxide, yielding a product with higher purity (99.5%, national standard GB / T 3185-2016), but its disadvantages include high energy consumption and high production costs. The gas-phase method is limited in application due to its difficulty in large-scale industrial production. The liquid-phase method typically involves reacting zinc salts with alkoxides, precipitants, or alkaline solutions to generate precursors such as colloids or precipitates, which are then thermally decomposed or dehydrated to prepare zinc oxide. Because the liquid-phase process conditions are relatively mild, and the reaction rate and morphology are easily controlled, nano-zinc oxide with small and uniform particle sizes can be obtained. However, impurities can be easily introduced during the reaction process, such as impurities in the reaction reagents or by-products, which can lead to a decrease in the purity of the final product.

[0004] The patent application CN109133150A, titled "A Method for Preparing High-Purity Nano Zinc Oxide," describes a method where zinc sulfate and potassium carbonate are reacted in an apple extract environment to obtain a white precipitate. This precipitate is then mixed with a modifier and ball-milled. Following this, the mixture is subjected to microwave irradiation, magnetic stirring under nitrogen protection, and electric field treatment. Finally, it is calcined under an inert atmosphere to obtain nano zinc oxide with a purity of over 99.9%. The problems with this method are that it involves numerous raw materials and extremely complex steps, making it unsuitable for industrial application. Furthermore, the purity of the obtained nano zinc oxide still has significant room for improvement.

[0005] Therefore, how to improve the purity of nano zinc oxide and simplify the preparation process to facilitate its industrial application has always been a technical problem that needs to be solved by those skilled in the art. Summary of the Invention

[0006] To address or partially address the problems existing in related technologies, this application provides a method for preparing high-purity nano-zinc oxide through electrochemical zinc dissolution. This method not only yields nano-zinc oxide with a purity of 4N, but also an average particle size below 100 nm. Simultaneously, when using a more inexpensive micro-dissolution electrode as the cathode, by isolating the anode and cathode chambers with an anion exchange membrane, nano-zinc oxide with a purity of 4N and an average particle size below 100 nm can also be obtained.

[0007] This application discloses a method for preparing high-purity nano-zinc oxide through electrochemical zinc dissolution, comprising the following steps: (1) In an electrolytic cell, metallic zinc with a purity ≥ 99.0% is used as the anode, and an inert electrode or a slightly soluble electrode under acidic conditions is used as the cathode. The electrolyte is a sulfuric acid solution or an acetic acid solution. Electrolysis is carried out under the action of direct current to obtain a zinc-containing solution with a zinc ion concentration of 0.1 mol / L ~ 2.0 mol / L. When a slightly soluble electrode is used as the cathode, an anion exchange membrane is set to isolate the anode chamber from the cathode chamber. (2) Add a neutralizing agent to the zinc-containing solution obtained in step (1) to neutralize the acid and add an appropriate amount of water to dilute the zinc ion concentration, so that the final pH of the zinc-containing solution is 4.0~6.0 and the zinc ion concentration is 0.1 mol / L~0.3 mol / L; (3) The zinc-containing solution, weak base and surfactant obtained in step (2) are added to a high-pressure reactor for hydrothermal reaction. The molar ratio of the amount of weak base added to zinc ions is 2:1 to 12:1. The reaction temperature is 120 ℃ to 150 ℃ and the reaction time is 4 h to 8 h. After the reaction is completed, the precipitate is washed and dried to obtain zinc hydroxide. (4) The zinc hydroxide is calcined to obtain high-purity nano zinc oxide with a purity ≥99.99% and a particle size <100 nm.

[0008] Furthermore, in step (1), the temperature of the electrolyte during electrolysis is 20 ℃~85 ℃, the current density is 1000A / m2~2000A / m2, and the acid concentration is 0.1 mol / L~3.0 mol / L.

[0009] Furthermore, in step (1), when the electrolyte is an acetic acid solution, a supporting electrolyte is added to improve conductivity. The supporting electrolyte is selected from one or more of lithium chloride, sodium chloride, potassium chloride, and ammonium chloride, and the amount added is 0.1 mol / L to 3.0 mol / L.

[0010] Furthermore, the inert electrode is selected from Pt, Ru noble metal coated electrodes, graphite, or carbon rods.

[0011] Furthermore, the microsoluble electrode is a copper sheet.

[0012] Furthermore, the neutralizing agent in step (2) is one or more of ammonia, sodium hydroxide, potassium hydroxide, ammonium bicarbonate, and calcium carbonate.

[0013] Furthermore, the weak base in step (3) is a slow-release base source, including one or more of urea, hexamethylenetetramine, or acetamide.

[0014] Further, the surfactant in step (3) includes one or more of sodium dodecyl sulfate, Tween 80, and polyvinylpyrrolidone, and the molar ratio of the amount of surfactant added to zinc ions is 0.01:1 to 0.2:1.

[0015] Furthermore, in step (4), the calcination temperature is 400 ℃~900 ℃, the holding time is 2 h~6 h, and the calcination atmosphere is air, oxygen or inert gas atmosphere.

[0016] The present invention has the following technical effects: 1. This invention employs an electrochemical method to dissolve zinc to prepare a zinc-containing solution. The zinc dissolution rate is fast and efficient, and the process can be carried out under mild conditions. This method has low environmental pollution, low energy consumption, and minimal emissions, meeting the requirements of green production. The obtained zinc oxide has a purity ≥99.99% and a particle size ≤100 nm, meeting the high purity requirements of the pharmaceutical, cosmetic, and food industries. Compared with existing methods, this invention provides a green, efficient, low-energy-consumption, and easily scalable process for preparing high-purity nano-zinc oxide.

[0017] 2. This invention uses a more inexpensive micro-dissolution electrode as the cathode. By isolating the anode and cathode chambers with an anion exchange membrane, nano-zinc oxide with a purity of 4N and an average particle size of less than 100 nm can be obtained. This method is easy to scale up and industrialize, and is of great significance to enterprises. Attached Figure Description

[0018] The above and other objects, features and advantages of this application will become more apparent from the more detailed description of exemplary embodiments thereof in conjunction with the accompanying drawings, wherein the same reference numerals generally represent the same components in the exemplary embodiments thereof.

[0019] Figure 1 This is a process flow diagram of the present invention.

[0020] Figure 2 The X-ray diffraction pattern of the high-purity nano zinc oxide prepared in Example 1 of this invention; Figure 3 and Figure 4These are SEM images of the high-purity nano-zinc oxide prepared in Example 1 of this invention at different magnifications. Figure 5 This is a SEM image of zinc oxide prepared in Comparative Example 3 of this invention; Figure 6 This is a SEM image of the zinc oxide prepared in Comparative Example 4 of this invention; Figure 7 This is a SEM image of the zinc oxide prepared in Comparative Example 5 of this invention. Detailed Implementation

[0021] The embodiments of this application will now be described in more detail with reference to the examples. While embodiments of this application are shown in the examples, it should be understood that this application can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to make this application more thorough and complete, and to fully convey the scope of this application to those skilled in the art.

[0022] Example 1 A method for preparing high-purity nano-zinc oxide by electrochemical zinc dissolution, the process flow is as follows: Figure 1 As shown, it includes the following steps: (1) Electrochemical dissolution of zinc: In the electrolytic cell, metallic zinc with a purity of 99.99% is used as the anode (anode area 21.6 cm²). 2 The cathode is a copper sheet, and an anion exchange membrane separates the anode and cathode chambers. A 1.0 mol / L sulfuric acid solution is used as the electrolyte, and the operation is performed at 25 °C and a current density of 2000 A / m³. 2 Electrolysis for 6 hours under the specified conditions yielded a zinc sulfate solution with a zinc ion concentration of 1.0 mol / L, and the dissolution rate of metallic zinc was 1252 g / m³. 2 h.

[0023] (2) Solution adjustment: Add an appropriate amount of ammonia to the zinc sulfate solution in step (1) to neutralize the excess acidic components, adjust the final pH to 6.0, and dilute with water to a zinc ion concentration of 0.1 mol / L; (3) Hydrothermal synthesis: The solution adjusted in step (2) was transferred to a high-pressure reactor, and urea (molar ratio of 12:1) and CTAB (molar ratio of 0.1:1) were added to adjust the morphology of the product. The hydrothermal reaction was carried out at a temperature of 120 °C for 6 h. After the reaction was completed, the precipitate was washed and dried to obtain zinc hydroxide. (4) Calcination treatment: The zinc hydroxide was calcined at 600℃ for 3 h in air atmosphere to obtain high-purity nano zinc oxide. The purity of the product was 4N and the particle size was <100 nm, as determined by inductively coupled plasma mass spectrometry (ICP-MS). Figures 2 to 4 ).

[0024] Example 2 A method for preparing high-purity nano-zinc oxide by electrochemical zinc dissolution includes the following steps: (1) Electrochemical dissolution of zinc: In the electrolytic cell, metallic zinc with a purity of 99.99% is used as the anode (anode area 21.6 cm²). 2 Using a titanium-coated Pt electrode as the cathode, and a 0.5 mol / L sulfuric acid solution as the electrolyte, the operation was carried out at a temperature of 25℃ and a current density of 1500 A / m. 2 Electrolysis for 6 hours under the specified conditions yielded a zinc sulfate solution with a zinc ion concentration of 0.75 mol / L, and the dissolution rate of metallic zinc was 1878 g / m³. 2 h.

[0025] (2) Solution adjustment: Add an appropriate amount of ammonia to the zinc sulfate solution in step (1) to neutralize the excess acidic components, adjust the final pH to 5.5, and dilute with water to a zinc ion concentration of 0.2 mol / L; (3) Hydrothermal synthesis: The solution adjusted in step (2) was transferred to a high-pressure reactor, and urea (molar ratio of 6:1) and CTAB (molar ratio of 0.05:1) were added to adjust the morphology of the product. The hydrothermal reaction was carried out at a temperature of 120 °C for 6 h. After the reaction was completed, the precipitate was washed and dried to obtain zinc hydroxide. (4) Calcination treatment: The zinc hydroxide was calcined at 600°C for 3 h in air atmosphere to obtain high-purity nano zinc oxide. The purity of the product was 4N and the particle size was <100 nm by inductively coupled plasma mass spectrometry (ICP-MS).

[0026] Example 3 A method for preparing high-purity nano-zinc oxide by electrochemical zinc dissolution includes the following steps: (1) Electrochemical dissolution of zinc: In the electrolytic cell, 99.99% pure metallic zinc was used as the anode (anode area 21.6 cm2), and a titanium-coated Pt electrode was used as the cathode. A 2.0 mol / L acetic acid solution was used as the electrolyte, and 2.0 mol / L potassium chloride was added to the electrolyte as a supporting electrolyte to increase the conductivity of the electrolyte. The electrolytic cell was operated at a temperature of 40 ℃ and a current density of 1000 A / m. 2 Electrolysis for 3 hours under the specified conditions yielded a zinc acetate solution with a zinc ion concentration of 0.5 mol / L, and the dissolution rate of metallic zinc was 2516 g / m³. 2 h.

[0027] (2) Solution adjustment: Add an appropriate amount of ammonia to the zinc acetate solution in step (1) to neutralize the excess acidic components, adjust the final pH to 6.0, and dilute with water to a zinc ion concentration of 0.2 mol / L; (3) Hydrothermal synthesis: The solution adjusted in step (2) was transferred to a high-pressure reactor, and urea (molar ratio of 6:1) and CTAB (molar ratio of 0.05:1) were added to adjust the morphology of the product. The hydrothermal reaction was carried out at a temperature of 120 °C for 6 h. After the reaction was completed, the precipitate was washed and dried to obtain zinc hydroxide. (4) Calcination treatment: The zinc hydroxide was calcined at 600°C for 3 h in air atmosphere to obtain high-purity nano zinc oxide. The purity of the product was 4N and the particle size was <100 nm by inductively coupled plasma mass spectrometry (ICP-MS).

[0028] Example 4 A method for preparing high-purity nano-zinc oxide by electrochemical zinc dissolution includes the following steps: (1) Electrochemical dissolution of zinc: In the electrolytic cell, 99.99% pure zinc metal was used as the anode (anode area 21.6 cm2), and a copper sheet was used as the cathode. An anion exchange membrane was installed to separate the anode chamber and the cathode chamber. A 1.0 mol / L sulfuric acid solution was used as the electrolyte, and the electrolytic cell was operated at a temperature of 25 ℃ and a current density of 2000 A / m. 2 Electrolysis for 6 hours under the specified conditions yielded a zinc sulfate solution with a zinc ion concentration of 1.0 mol / L, and the dissolution rate of metallic zinc was 1252 g / m³. 2 h.

[0029] (2) Solution adjustment: Add an appropriate amount of ammonia to the zinc sulfate solution in step (1) to neutralize the excess acidic components, adjust the final pH to 6.0, and dilute with water to a zinc ion concentration of 0.1 mol / L; (3) Hydrothermal synthesis: The solution adjusted in step (2) was transferred to a high-pressure reactor, and urea (molar ratio of 12:1) and sodium dodecyl sulfate (SDS) (molar ratio of 0.1:1) were added to adjust the morphology of the product. The hydrothermal reaction was carried out at a temperature of 150 °C for 4 h. After the reaction was completed, the precipitate was washed and dried to obtain zinc hydroxide. (4) Calcination treatment: The zinc hydroxide was calcined at 800°C for 3 h in air atmosphere to obtain high-purity nano zinc oxide. The purity of the product was 4N and the particle size was <100 nm by inductively coupled plasma mass spectrometry (ICP-MS).

[0030] Comparative Example 1 The parameters are the same as in Example 1, but the electrolyzer is not separated by anion exchange membranes. The specific process is as follows: (1) Electrochemical dissolution of zinc: In the electrolytic cell, metallic zinc with a purity of 99.99% is used as the anode (anode area 21.6 cm²). 2The cathode was a copper sheet. A 1.0 mol / L sulfuric acid solution was used as the electrolyte, and the electrolyte was applied at a temperature of 25 °C and a current density of 2000 A / m. 2 Electrolysis for 6 hours under the specified conditions yielded a zinc sulfate solution with a zinc ion concentration of 0.65 mol / L. At the same time, a large amount of zinc metal was deposited on the cathode surface, accounting for 38% of the actual zinc dissolution.

[0031] (2) Solution adjustment: Add an appropriate amount of ammonia to the zinc sulfate solution in step (1) to neutralize the excess acidic components, adjust the final pH to 6.0, and dilute with water to a zinc ion concentration of 0.1 mol / L; (3) Hydrothermal synthesis: The solution adjusted in step (2) was transferred to a high-pressure reactor, and urea (molar ratio of 12:1) and CTAB (molar ratio of 0.1:1) were added to adjust the morphology of the product. The hydrothermal reaction was carried out at a temperature of 120 °C for 6 h. After the reaction was completed, the precipitate was washed and dried to obtain zinc hydroxide. (4) Calcination treatment: The zinc hydroxide was calcined at 600°C for 3 h in air atmosphere to obtain high-purity nano zinc oxide. The purity of the product was only 4N and the particle size was <100 nm by inductively coupled plasma mass spectrometry (ICP-MS).

[0032] Comparative Example 2 A 1.5 mol / L sulfuric acid solution (200 mL volume) was added to a 500 mL beaker. A 4 cm × 5 cm high-purity zinc plate was placed in the solution and heated at 40 °C to dissolve. After 45 hours, a total of 15.63 g of zinc dissolved, yielding a zinc sulfate solution with a zinc ion concentration of 0.48 mol / L and a zinc dissolution rate of 86.83 g / mL. 2 h. In contrast, the dissolution rate of Example 1 (1252 g / m³) 2 The dissolution rate of Example 3 (2516 g / m³) was approximately 14 times that of Comparative Example 2. 2 h) is approximately 28 times that of Comparative Example 2.

[0033] Comparative Example 3 (compared to Example 1, except that the zinc ion concentration was 1.0 mol / L and undiluted) A zinc-containing solution was prepared using the same electrochemical method as in Example 1, followed by the precipitation method to prepare zinc hydroxide. The calcination process was also consistent with that in Example 1. That is, steps (1) and (4) were the same as in Example 1. The specific operation is as follows: (1) Electrochemical dissolution of zinc: In the electrolytic cell, 99.99% pure zinc metal was used as the anode (anode area 21.6 cm2), and a copper sheet was used as the cathode. An anion exchange membrane was installed to separate the anode chamber and the cathode chamber. A 1.0 mol / L sulfuric acid solution was used as the electrolyte, and the electrolytic cell was operated at a temperature of 25 ℃ and a current density of 2000 A / m. 2 Electrolysis for 6 hours under the specified conditions yielded a zinc sulfate solution with a zinc ion concentration of 1.0 mol / L, and the dissolution rate of metallic zinc was 1252 g / m³. 2 h.

[0034] (2) Preparation of zinc hydroxide by precipitation method: Add an appropriate amount of ammonia to the zinc sulfate solution in step (1) to carry out the precipitation reaction. At the same time, add sodium dodecyl sulfate (SDS) as a surfactant to adjust the pH value of the solution to 8-9 to form zinc hydroxide precipitate, and let it stand for 6 hours. Filter, wash and dry the precipitate to obtain solid zinc hydroxide.

[0035] (3) Calcination treatment: The zinc hydroxide was calcined at 600°C for 3 h in air atmosphere to obtain zinc oxide with an irregular morphology and a particle size of 100 nm to 500 nm. Figure 5 ).

[0036] Comparative Example 4 The difference between the comparative example and Example 1 is that no water is added to dilute the zinc-containing solution in step (2), but the rest are the same.

[0037] The obtained zinc oxide has a purity of 4N, a particle size of 0.5μm~2.0μm, and is as follows: Figure 6 As shown, its morphology is irregular and it is severely aggregated.

[0038] Comparative Example 5 The difference between the comparative example and Example 1 is that a strong base is used instead of a weak base in step (3), while the rest are the same.

[0039] The obtained zinc oxide has a purity of 4N, a particle size of 0.5μm~2.0μm, and is as follows: Figure 7 As shown, its particles aggregate into lamellar structures, with individual lamellar structures ranging from 1.0 μm to 3.0 μm.

[0040] The various embodiments of this application have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or improvement of the technology in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A method for preparing high-purity nano-zinc oxide by electrochemical zinc dissolution, characterized in that, Includes the following steps: (1) In an electrolytic cell, metallic zinc with a purity ≥ 99.0% is used as the anode, and an inert electrode or a slightly soluble electrode under acidic conditions is used as the cathode. The electrolyte is a sulfuric acid solution or an acetic acid solution. Electrolysis is carried out under the action of direct current to obtain a zinc-containing solution with a zinc ion concentration of 0.1 mol / L ~ 2.0 mol / L. When a slightly soluble electrode is used as the cathode, an anion exchange membrane is set to isolate the anode chamber from the cathode chamber. (2) Add a neutralizing agent to the zinc-containing solution obtained in step (1) to neutralize the acid and add an appropriate amount of water to dilute the zinc ion concentration, so that the final pH of the zinc-containing solution is 4.0~6.0 and the zinc ion concentration is 0.1 mol / L~0.3 mol / L; (3) The zinc-containing solution, weak base and surfactant obtained in step (2) are added to a high-pressure reactor for hydrothermal reaction. The molar ratio of the amount of weak base added to zinc ions is 2:1 to 12:

1. The reaction temperature is 120 ℃ to 150 ℃ and the reaction time is 4 h to 8 h. After the reaction is completed, the precipitate is washed and dried to obtain zinc hydroxide. (4) The zinc hydroxide is calcined to obtain high-purity nano zinc oxide with a purity ≥99.99% and a particle size <100 nm.

2. The method according to claim 1, characterized in that, In step (1), the electrolyte temperature during electrolysis is 20 ℃~85 ℃, and the current density is 1000 A / m. 2 ~2000A / m 2 The acid concentration ranges from 0.1 mol / L to 3.0 mol / L.

3. The method according to claim 1, characterized in that, In step (1), when the electrolyte is an acetic acid solution, a supporting electrolyte is added to improve conductivity. The supporting electrolyte is selected from one or more of lithium chloride, sodium chloride, potassium chloride, and ammonium chloride, and the amount added is 0.1 mol / L to 3.0 mol / L.

4. The method according to claim 1, characterized in that, The inert electrode is selected from Pt, Ru noble metal coated electrodes, graphite or carbon rods.

5. The method according to claim 1, characterized in that, The microsoluble electrode is a copper sheet.

6. The method according to claim 1, characterized in that, The neutralizing agent in step (2) is one or more of ammonia, sodium hydroxide, potassium hydroxide, ammonium bicarbonate and calcium carbonate.

7. The method according to claim 1, characterized in that, The weak base in step (3) is a slow-release base source, including one or more of urea, hexamethylenetetramine or acetamide.

8. The method according to claim 1, characterized in that, The surfactant in step (3) includes one or more of sodium dodecyl sulfate, Tween 80, and polyvinylpyrrolidone, and the molar ratio of the amount of surfactant added to zinc ions is 0.01:1 to 0.2:

1.

9. The method according to claim 1, characterized in that, In step (4), the calcination temperature is 400℃~900℃, the holding time is 2h~6h, and the calcination atmosphere is air, oxygen or inert gas atmosphere.

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