A method for preparing 6N high-purity zinc

Abstract

The invention discloses a method for preparing 6N high-purity zinc, comprising the following steps: S1, alkali dissolution: dissolving electro zinc with sodium hydroxide, filtering after the reaction is completed; S2, acidification: adding hydrochloric acid to the filtered solution for acidification; S3, evaporation concentration: putting the acidified solution into an evaporating kettle for evaporation concentration; S4, freezing crystallization: filtering and drying the concentrated solution after cooling in a freezing tank; S5, secondary dissolution: dissolving the dried zinc chloride solid in an ether solution at room temperature, filtering; S6, vacuum distillation: putting the filtered ether solution into a vacuum distillation device, S7, heating and decomposing; S8, vacuum distillation. This method can achieve the purpose of preparing 6N high-purity zinc from electro zinc, and realize the low-cost recycling of zinc resources; at the same time, the alkali dissolution-acidification-ether secondary dissolution process can be used to effectively separate metals such as cadmium with a segregation coefficient close to 1 in zinc, which is convenient for the rear-end pyrometallurgical method to purify 6N high-purity zinc.

Description

Technical Field

[0001] The invention relates to the technical field of high-purity metal preparation, and in particular to a method for preparing 6N high-purity zinc. Background Art

[0002] Zinc, as a deep-processing product of metallic zinc, is a new type of multi-purpose functional material, which is widely used in the preparation of semiconductor compounds, fluorescent materials, reducing agents or alloys, functional ceramic materials, precision castings, electronic refrigeration components, cosolvents, and reactor liquid cooling carriers. At present, the zinc preparation technology commonly used in industry is electrolytic deposition, which specifically uses rolled aluminum plates as cathodes and lead-silver alloys as anodes to produce electrolytic zinc from zinc sulfate electrolytes by electrolytic deposition, and then produces zinc ingots after slagging by pyrometallurgical casting. This traditional zinc production process has the defects of long process flow, high requirements for electrolyte composition control, and the impurity removal process is very troublesome and is subject to the characteristics of the process. It cannot break through the quality standards of high-purity zinc above 5N. At present, the mainstream processes used to produce 6N and above high-purity zinc are vacuum distillation, regional smelting, and heavy distillation, etc., and these processes inevitably have the problem of raw material oxidation, resulting in the problem of product direct yield. Therefore, this application provides a method for preparing 6N high-purity zinc to meet the demand. Summary of the invention

[0003] The purpose of the present application is to provide a method for preparing 6N high-purity zinc. This process is simple to operate and solves the shortcomings of the traditional zinc production process, such as long process flow, high requirements for electrolyte composition control, and a very troublesome impurity removal process. Due to the characteristics of the process, it is still unable to break through the shortcomings of high-purity zinc above 5N. This method can efficiently utilize electrolytic zinc to obtain 6N zinc products.

[0004] To achieve the above object, the present application provides the following technical solution: A method for preparing 6N high-purity zinc, characterized in that it comprises the following steps: S1. Alkaline dissolution: dissolve the electrolytic zinc with sodium hydroxide, filter after the reaction is completed, and separate the undissolved heavy metals such as copper, cadmium and manganese; S2. Acidification: gradually add hydrochloric acid to the filtered solution for acidification. When the pH reaches 6-7, stop adding hydrochloric acid. The concentration of hydrochloric acid is 3-10 mol / L. S3, evaporation concentration: the acidified solution is placed in an evaporator for evaporation concentration, and when the volume is reduced to one fifth to one tenth of the original volume, it is immediately transferred to a freezing tank; When the volume is reduced to one fifth to one tenth of the original volume, it is immediately transported to the freezing tank. On the one hand, the crystallization rate of zinc chloride can be controlled. If the crystallization rate of zinc chloride is too low, the product production efficiency is low. If the crystallization rate of zinc chloride is too high, it is easy to cause metals such as aluminum and lead in the solution to crystallize into the zinc chloride product, resulting in low purity of the zinc chloride product. On the other hand, it can prevent excessive saturation in a local area during subsequent freezing crystallization, avoid the formation of excessively large zinc chloride crystals or too many crystal nuclei, thereby entraining more impurities and causing the product purity to decrease. At the same time, the evaporated solution is immediately transported to the freezing tank in a hot state. Direct freezing crystallization in a hot state can greatly shorten the crystallization time, improve the zinc chloride crystallization efficiency, and the particle size of the crystallized zinc chloride product is controllable.

[0005] S4, freezing crystallization: the concentrated solution is fully cooled in a freezing tank, filtered and dried to obtain a high purity zinc chloride solid; Freezing in a freezing tank can achieve cooling crystallization of zinc chloride. Due to freezing, the zinc chloride concentrate can be directly frozen and crystallized in a hot state, which can greatly shorten the crystallization time and improve the zinc chloride crystallization efficiency. The particle size of the crystallized zinc chloride product is controllable. When the temperature of the zinc chloride solution drops to 0-10°C (it is filtered and dried after reaching this temperature), within the temperature range, the product purity requirements can be met and a higher crystallization rate can be achieved.

[0006] S5. Secondary dissolution: dissolving the dried zinc chloride solid in ether solution at room temperature, filtering, and separating a small amount of lead chloride, bismuth chloride, cadmium chloride, selenium chloride and other metals mixed in the zinc chloride; S6, vacuum distillation: placing the filtered ether solution into a vacuum distillation apparatus to distill and recover all the ether to obtain high-purity zinc chloride solid; S7, heating decomposition: put high-purity zinc chloride solid into a tube furnace, first evacuate and then introduce nitrogen, and start heating after the nitrogen is introduced stably for 10 minutes; S8. Vacuum distillation: After the heating decomposition is completed, start cooling. When the temperature of the tubular furnace reaches 450~550℃, turn off the nitrogen, start the vacuum unit, and evacuate the vacuum degree in the tubular furnace to within 0~10Pa. The distillation time is 1~5h. When the distillation is completed, 6N high-purity zinc is obtained on the quartz tube wall.

[0007] Under this vacuum degree, the boiling and evaporation temperature of tin is 1350℃, the boiling and evaporation temperature of aluminum is 1250℃, the boiling and evaporation temperature of lead is 760℃, the boiling and evaporation temperature of zinc is 450℃, and the boiling and evaporation temperature of cadmium is 350℃. Therefore, the temperature of the heating zone is 450~550℃, and zinc is easily converted from liquid to gas and enriched at the cold end of the high-purity quartz tube, thereby realizing the preparation of high-purity zinc.

[0008] As a preferred implementation in this embodiment, in S1, the reaction temperature is 50-90° C., the reaction time is 1-5 h, and the sodium hydroxide concentration is 50-200 g / L.

[0009] Under this reaction condition, electrolytic zinc can be dissolved quickly, while the micro-dissolution of heavy metals such as copper, cadmium and manganese can be avoided, thereby improving the purity of zinc in the solution.

[0010] As a preferred implementation in this embodiment, in S6, the vacuum degree is 0-100 Pa, and the heating temperature is 50-90°C.

[0011] The vacuum degree is 0~100Pa and the heating temperature is 50~90℃, which can not only fully volatilize the ether and avoid the introduction of flammable and explosive gases in the back-end pyrometallurgical process, but also under this condition, the ether volatilization rate is high and the production cycle is short, which can effectively improve production efficiency.

[0012] As a preferred implementation in this embodiment, in S7, the heating temperature is 500-600° C., the reaction time is 1-5 h, and the nitrogen flow rate is 0.1-3 L / min.

[0013] Under this temperature and time condition, zinc chloride can be fully decomposed and converted into metallic zinc. At the same time, the introduction of nitrogen can safely bring out the gas generated during the decomposition of zinc chloride to the absorption tower at the rear end of the tubular furnace to avoid production accidents.

[0014] As a preferred implementation manner in this example, the diethyl ether is analytically pure diethyl ether.

[0015] As a preferred implementation in this embodiment, the tube tube of the tube furnace is made of high-purity quartz.

[0016] In summary, the technical effects and advantages of the present invention are as follows: The invention has a reasonable structure, and the method can achieve the purpose of preparing 6N high-purity zinc by electro-zincification, and realize the low-cost recycling of zinc resources; at the same time, the alkali dissolution-acidification-ether secondary dissolution process can be used to effectively separate metals such as cadmium with a segregation coefficient close to 1 in zinc, which is convenient for the rear-end pyrometallurgical method to purify 6N high-purity zinc; the invention is simple and reasonable, economical and practical, and easy to use. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without paying any creative work.

[0018] Figure 1is a process flow chart of the present invention; Figure 2 A composition analysis table of 6N high purity zinc was prepared for each example and comparative example. DETAILED DESCRIPTION

[0019] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Example

[0020] Dissolve the electrolytic zinc with 100g / L sodium hydroxide at 60°C, filter after the reaction is completed, and separate the undissolved heavy metals such as copper, cadmium and manganese; gradually add 4mol / L hydrochloric acid to the filtered solution for acidification, and stop adding hydrochloric acid when the pH reaches 6-7; put the acidified solution into an evaporator for evaporation and concentration, and immediately transfer it to a freezing tank for sufficient cooling when the volume is reduced to one-fourth of the original volume, filter and dry to obtain a high-purity zinc chloride solid; dissolve the dried zinc chloride solid in ether solution at room temperature, filter, and separate a small amount of lead chloride, bismuth chloride, and chlorine chloride mixed in the zinc chloride. Cadmium, selenium chloride and other metals; the filtered ether solution is placed in a vacuum distillation device to distill and recover all the ether to obtain high-purity zinc chloride solid; the high-purity zinc chloride solid is placed in a tubular furnace, first evacuated and then nitrogen is introduced, and heating is started after the nitrogen is introduced stably for 10 minutes, the heating temperature is 550°C, the reaction time is 3 hours, and the nitrogen flow rate is 0.5L / min; after the heating and decomposition are completed, the temperature is lowered, and when the temperature of the tubular furnace is about to reach 500°C, the nitrogen is turned off, and the vacuum unit is started, and the vacuum degree in the tubular furnace is evacuated to less than 10Pa, the distillation time is 2 hours, and 6N high-purity zinc is obtained on the quartz tube wall after the distillation is completed. The test results are shown in Figure 2 . Example

[0021] Dissolve the electrolytic zinc with 130g / L sodium hydroxide at 60°C, filter after the reaction to separate undissolved heavy metals such as copper, cadmium and manganese; gradually add 6mol / L hydrochloric acid to the filtered solution for acidification, and stop adding hydrochloric acid when the pH reaches 6-7; put the acidified solution into an evaporator for evaporation and concentration, and immediately transfer it to a freezing tank for sufficient cooling when the volume is reduced to one-fifth of the original volume, filter and dry to obtain a high-purity zinc chloride solid; dissolve the dried zinc chloride solid in ether solution at room temperature, filter and separate a small amount of lead chloride, bismuth chloride and chloride mixed in the zinc chloride. The filtered ether solution was placed in a vacuum distillation device to distill and recover all the ether to obtain high-purity zinc chloride solid; the high-purity zinc chloride solid was placed in a tubular furnace, first evacuated and then nitrogen was introduced, and heating was started after the nitrogen was introduced stably for 10 minutes, the heating temperature was 570°C, the reaction time was 2.5 hours, and the nitrogen flow rate was 0.4L / min; after the heating decomposition was completed, the temperature began to decrease, and when the temperature of the tubular furnace was about to reach 500°C, the nitrogen was turned off, and the vacuum unit was started, and the vacuum degree in the tubular furnace was evacuated to 8Pa, the distillation time was 2 hours, and 6N high-purity zinc was obtained on the quartz tube wall after the distillation was completed. The test results are shown in Figure 2 . Example

[0022] Dissolve the electrolytic zinc with 110g / L sodium hydroxide at 70°C, filter after the reaction is completed, and separate the undissolved heavy metals such as copper, cadmium and manganese; gradually add 3mol / L hydrochloric acid to the filtered solution for acidification, and stop adding hydrochloric acid when the pH reaches 6-7; put the acidified solution into an evaporator for evaporation and concentration, and immediately transfer it to a freezing tank for sufficient cooling when the volume is reduced to one-seventh of the original volume, filter and dry to obtain a high-purity zinc chloride solid; dissolve the dried zinc chloride solid in ether solution at room temperature, filter, and separate a small amount of lead chloride, bismuth chloride, and Cadmium chloride, selenium chloride and other metals; put the filtered ether solution into a vacuum distillation device to distill and recover all the ether to obtain high-purity zinc chloride solid; put the high-purity zinc chloride solid into a tubular furnace, first evacuate and then introduce nitrogen, and start heating after the nitrogen is introduced stably for 10 minutes, the heating temperature is 580℃, the reaction time is 4h, and the nitrogen flow rate is 0.2L / min; after the heating decomposition is completed, start cooling, when the temperature of the tubular furnace is about to reach 520℃, turn off the nitrogen, start the vacuum unit, and evacuate the vacuum degree in the tubular furnace to less than 7, the distillation time is 2h, and 6N high-purity zinc is obtained on the quartz tube wall after the distillation is completed. The test results are shown in Figure 2 . Example

[0023] Dissolve the electrolytic zinc with 110g / L sodium hydroxide at 80°C, filter after the reaction is completed, and separate the undissolved heavy metals such as copper, cadmium and manganese; gradually add 3mol / L hydrochloric acid to the filtered solution for acidification, and stop adding hydrochloric acid when the pH reaches 6-7; put the acidified solution into an evaporator for evaporation and concentration, and immediately transfer it to a freezing tank for sufficient cooling when the volume is reduced to one tenth of the original volume, filter and dry to obtain a high-purity zinc chloride solid; dissolve the dried zinc chloride solid in ether solution at room temperature, filter, and separate a small amount of lead chloride, bismuth chloride, and Cadmium chloride, selenium chloride and other metals; put the filtered ether solution into a vacuum distillation device to distill and recover all the ether to obtain high-purity zinc chloride solid; put the high-purity zinc chloride solid into a tubular furnace, first evacuate and then introduce nitrogen, and start heating after the nitrogen is introduced stably for 10 minutes, the heating temperature is 580℃, the reaction time is 4h, and the nitrogen flow rate is 0.2L / min; after the heating decomposition is completed, start cooling, when the temperature of the tubular furnace is about to reach 520℃, turn off the nitrogen, start the vacuum unit, and evacuate the vacuum degree in the tubular furnace to less than 7, the distillation time is 2h, and 6N high-purity zinc is obtained on the quartz tube wall after the distillation is completed. The test results are shown in Figure 2 . Example

[0024] Dissolve the electrolytic zinc with 120g / L sodium hydroxide at 90°C, filter after the reaction is completed, and separate the undissolved heavy metals such as copper, cadmium and manganese; gradually add 6mol / L hydrochloric acid to the filtered solution for acidification, and stop adding hydrochloric acid when the pH reaches 6-7; put the acidified solution into an evaporator for evaporation and concentration, and immediately transfer it to a freezing tank for sufficient cooling when the volume is reduced to one eleventh of the original volume, filter and dry to obtain a high-purity zinc chloride solid; dissolve the dried zinc chloride solid in ether solution at room temperature, filter, and separate a small amount of lead chloride, bismuth chloride, and chloride mixed in the zinc chloride. The filtered ether solution was placed in a vacuum distillation device to distill and recover all the ether to obtain high-purity zinc chloride solid; the high-purity zinc chloride solid was placed in a tubular furnace, first evacuated and then nitrogen was introduced, and heating was started after the nitrogen was introduced stably for 10 minutes, the heating temperature was 570°C, the reaction time was 2.5 hours, and the nitrogen flow rate was 0.4L / min; after the heating decomposition was completed, the temperature began to decrease, and when the temperature of the tubular furnace was about to reach 500°C, the nitrogen was turned off, and the vacuum unit was started, and the vacuum degree in the tubular furnace was evacuated to 8Pa, the distillation time was 2 hours, and 6N high-purity zinc was obtained on the quartz tube wall after the distillation was completed. The test results are shown in Figure 2 .

[0025] Comparative Example 1 Dissolve the electrolytic zinc with 100g / L sodium hydroxide at 60°C, filter after the reaction to separate undissolved heavy metals such as copper, cadmium and manganese; gradually add 4mol / L hydrochloric acid to the filtered solution for acidification, and stop adding hydrochloric acid when the pH reaches 6-7; put the acidified solution into an evaporator for evaporation and concentration to obtain a high-purity zinc chloride solid; dissolve the dried zinc chloride solid in ether solution at room temperature, filter to separate a small amount of lead chloride, bismuth chloride, cadmium chloride, selenium chloride and other metals mixed in the zinc chloride; The liquid was placed in a vacuum distillation device to distill and recover all the ether to obtain high-purity zinc chloride solid; the high-purity zinc chloride solid was placed in a tubular furnace, first evacuated and then nitrogen was introduced, and heating began after the nitrogen was introduced stably for 10 minutes, the heating temperature was 550°C, the reaction time was 3 hours, and the nitrogen flow rate was 0.5L / min; after the heating decomposition was completed, the temperature began to be lowered, and when the temperature of the tubular furnace was about to reach 500°C, the nitrogen was turned off, and the vacuum unit was started, and the vacuum degree in the tubular furnace was evacuated to less than 10Pa, the distillation time was 2 hours, and 6N high-purity zinc was obtained on the quartz tube wall after the distillation was completed. The test results are shown in Figure 2 .

[0026] It can be seen from Examples 1-5 and Comparative Example 1 (which is compared with Example 1) that when the volume is reduced to one fifth to one tenth of the original volume, it is immediately transported to the freezing tank, which is beneficial to improving the purity of subsequent products, and 6N high-purity zinc can be prepared using this method.

[0027] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing 6N high-purity zinc, characterized in that: The steps include: S1. Alkaline dissolution: dissolve the electrolytic zinc with sodium hydroxide, filter after the reaction is completed, and separate the undissolved heavy metals such as copper, cadmium and manganese; S2. Acidification: gradually add hydrochloric acid to the filtered solution for acidification. When the pH reaches 6-7, stop adding hydrochloric acid. The concentration of hydrochloric acid is 3-10 mol / L. S3, evaporation concentration: the acidified solution is placed in an evaporator for evaporation concentration, and when the volume is reduced to one fifth to one tenth of the original volume, it is immediately transferred to a freezing tank; S4, freezing crystallization: the concentrated solution is fully cooled in a freezing tank, filtered and dried to obtain a high purity zinc chloride solid; S5. Secondary dissolution: dissolving the dried zinc chloride solid in ether solution at room temperature, filtering, and separating a small amount of lead chloride, bismuth chloride, cadmium chloride, selenium chloride and other metals mixed in the zinc chloride; S6, vacuum distillation: placing the filtered ether solution into a vacuum distillation apparatus to distill and recover all the ether to obtain high-purity zinc chloride solid; S7, heating decomposition: put high-purity zinc chloride solid into a tube furnace, first evacuate and then introduce nitrogen, and start heating after the nitrogen is introduced stably for 10 minutes; S8. Vacuum distillation: After the heating decomposition is completed, start cooling. When the temperature of the tubular furnace reaches 450~550℃, turn off the nitrogen, start the vacuum unit, and draw the vacuum degree in the tubular furnace to 0~10Pa. The distillation time is 1~5h. When the distillation is completed, 6N high-purity zinc is obtained on the quartz tube wall.

2. A method for preparing 6N high-purity zinc according to claim 1, characterized in that: In the S1, the reaction temperature is 50-90° C., the reaction time is 1-5 hours, and the sodium hydroxide concentration is 50-200 g / L.

3. A method for preparing 6N high-purity zinc according to claim 1, characterized in that: In S6, the vacuum degree is 0-100 Pa, and the heating temperature is 50-90°C.

4. A method for preparing 6N high-purity zinc according to claim 1, characterized in that: In S7, the heating temperature is 500-600°C, the reaction time is 1-5h, and the nitrogen flow rate is 0.1-3L / min.

5. A method for preparing 6N high-purity zinc according to claim 1, characterized in that: The diethyl ether is analytically pure diethyl ether.

6. A method for preparing 6N high purity zinc according to any one of claims 1 to 5, characterized in that: The tube of the tubular furnace is made of high-purity quartz.

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