Method for purifying metallic gallium

Abstract

The application provides a method for purifying metallic gallium. The method comprises the following steps: first melting an industrial gallium raw material to obtain a liquid gallium raw material; wherein the liquid gallium raw material contains difficult-to-remove impurities; mixing the liquid gallium raw material with an easy-to-remove metal and performing second melting to make the difficult-to-remove impurities and the easy-to-remove metal form impurity alloying clusters in the molten liquid, thereby obtaining a molten mixture; and sequentially performing cooling and crystallization on the molten mixture to obtain metallic gallium crystals; wherein the difficult-to-remove impurities include one or more of iron, nickel and calcium; and the easy-to-remove metal includes an easy-to-remove metal element, and the easy-to-remove metal element includes one or more of aluminum, magnesium, tin, silver and cobalt. By introducing the above-mentioned easy-to-remove metal into the metallic gallium raw material, the above-mentioned difficult-to-remove impurities are made to have strong interaction to form alloying clusters, thereby significantly improving the migration ability of the difficult-to-remove impurities from the solid phase to the liquid phase during the crystallization process, and the effective separation of the difficult-to-remove impurities is realized.

Description

Technical Field

[0001] This invention relates to the field of metal purification technology, and more specifically, to a method for purifying gallium. Background Technology

[0002] Gallium is an important rare and dispersed metal and a core raw material for preparing advanced compound semiconductor functional materials such as gallium antimonide, gallium oxide, and gallium nitride. The purity level of high-purity gallium directly determines the performance stability and yield of high-end electronic components, infrared detectors, and optoelectronic devices. Currently, the mainstream industrial processes for preparing high-purity gallium mainly include chemical extraction, electrolytic refining, vacuum distillation, zone melting, directional crystallization, and multi-process coupling purification. However, industrial gallium raw materials contain various metallic impurities such as iron (Fe), nickel (Ni), and calcium (Ca). These impurities have similar physicochemical properties to gallium and their equilibrium distribution coefficient in gallium tends to be close to or greater than 1, making it difficult to achieve deep removal using the aforementioned traditional purification processes.

[0003] Furthermore, existing technologies also employ methods such as increasing the number of purification cycles and repeated purification through multiple process combinations. While these methods can reduce the total amount of impurities to some extent, they suffer from poor selectivity in impurity removal and still lack effective means to separate difficult-to-remove impurities with equilibrium distribution coefficients close to or greater than 1. Simply increasing the number of purification cycles is insufficient to break through purity limits and achieve efficient purification. Simultaneously, the process chain is excessively long, requiring multiple processes and repeated purification to achieve the target purity, resulting in long production cycles and complex operations.

[0004] Therefore, how to develop a simple, efficient, and low-cost method to purify high-purity gallium, especially how to effectively control and separate difficult-to-remove impurity elements, has become a technical problem that urgently needs to be solved in this field.

[0005] Chinese patent application CN103031450A discloses a method for purifying metallic gallium, including steps such as pre-purification, freeze crystallization, acid washing, and packaging. This method uses a combination of ultrasonic vibration and freeze crystallization to initially separate sponge gallium impurities from liquid metallic gallium, and then separates the metallic gallium from the sponge gallium through acid washing. Patent CN104099485B provides a method for preparing high-purity gallium, including steps such as acid extraction, electrolytic purification, and partial crystallization. This method uses acid extraction to extract impurities from crude gallium solution into an acidic solution, separating them from the metallic gallium solution, and then electrolytically purifies the metallic gallium solution. Finally, partial crystallization is used to crystallize the purified gallium solution to obtain high-purity gallium. However, none of the above crystallization purification methods address the effective separation of difficult-to-remove impurities in gallium, limiting the purification effect of high-purity gallium. Summary of the Invention

[0006] The main objective of this invention is to provide a method for purifying metallic gallium, thereby solving the problem that impurities in industrial gallium raw materials are difficult to separate, resulting in low purity of metallic gallium.

[0007] To achieve the above objectives, according to one aspect of the present invention, a method for purifying metallic gallium is provided, comprising the following steps: Step S1, first melting an industrial gallium raw material to obtain a liquid gallium raw material; wherein the liquid gallium raw material contains impurities that are difficult to remove; Step S2, mixing the liquid gallium raw material with an easily removable metal and performing a second melting, such that the impurities that are difficult to remove and the easily removable metal form impurity alloying clusters in the molten liquid, to obtain a molten mixture; Step S3, sequentially cooling and crystallizing the molten mixture to obtain metallic gallium crystals; wherein the impurities that are difficult to remove include one or more of iron, nickel, and calcium; the easily removable metal includes easily removable elemental metals, which include one or more of aluminum, magnesium, tin, silver, and cobalt.

[0008] Furthermore, the temperature of the first melt is less than the temperature of the second melt, with a difference of 15~90℃.

[0009] Furthermore, the crystallization temperature is less than the first melting temperature, with a difference of 2 to 18.5°C.

[0010] Furthermore, in step S1, the purity of the industrial gallium raw material is 3N~5N.

[0011] Furthermore, in step S1, the temperature of the first melting is 30~45℃, and the time is 1~2h.

[0012] Further, in step S2, the purity of the easily removable metal is 4N~5N; and / or, the weight ratio of the easily removable metal to the liquid gallium raw material is (0.1~2):100.

[0013] Further, in step S2, the temperature of the second melting is 60~120℃, the time is 6~24h, and the stirring rate is 50~150r / min; and / or, the second melting is carried out in a protective atmosphere, which includes nitrogen and / or argon.

[0014] Furthermore, in step S3, the cooling rate is 0.1~1.0℃ / min; and / or the crystallization temperature is 25~29℃, and the time is 1~24h.

[0015] Furthermore, in step S3, when crystals appear in the molten mixture, cooling is stopped and crystallization is carried out.

[0016] Furthermore, when the weight ratio of the easily removable metal to the liquid gallium raw material is (0.3~0.5):100, the crystallization temperature is 26.5~27℃.

[0017] By introducing a specific type of easily removable metal into gallium raw materials, a strong interaction is achieved between this metal and a specific type of difficult-to-remove impurities, forming alloyed impurity clusters. This disrupts the original distribution equilibrium of difficult-to-remove impurities in the solid-liquid phases of gallium. When the easily removable metal accumulates in the liquid phase, it can carry the difficult-to-remove impurities into the liquid phase in the form of alloy clusters. This significantly enhances the diffusion and migration ability of difficult-to-remove impurities from the solid phase to the liquid phase during crystallization, achieving effective separation of these impurities. This invention eliminates the need for multiple purification processes or complex setups, achieving efficient removal with a single crystallization. It significantly shortens the process flow, effectively reducing energy consumption and operational complexity, making it particularly suitable for the low-cost and large-scale preparation of high-purity gallium. Attached Figure Description

[0018] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0019] Figure 1 A schematic flowchart of a gallium purification method according to Embodiment 1 of the present invention is shown. Detailed Implementation

[0020] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0021] Terminology Explanation:

[0022] Equilibrium partition coefficient: During the crystallization process of liquid gallium containing a certain non-gallium metal towards equilibrium, pure gallium metal will form a solid phase, while the remaining part will still be a liquid phase. The equilibrium partition coefficient of this metal is the ratio of the concentration of this metal in the solid phase to the concentration of this metal in the liquid phase.

[0023] As described in the background section of this invention, existing technologies suffer from the problem of difficult-to-separate impurities in industrial gallium raw materials, resulting in low purity of metallic gallium. To address this problem, in a typical embodiment of this invention, a method for purifying metallic gallium is provided, comprising the following steps: Step S1, first melting industrial gallium raw material to obtain liquid gallium raw material; Step S2, mixing the liquid gallium raw material with an easily removable metal and performing a second melting, causing difficult-to-remove impurities and the easily removable metal to form impurity alloy clusters in the molten liquid, obtaining a molten mixture; Step S3, sequentially cooling and crystallizing the molten mixture to obtain metallic gallium crystals; wherein, the difficult-to-remove impurities include one or more of iron, nickel, and calcium; the easily removable metal includes easily removable elemental metals, which include one or more of aluminum, magnesium, tin, silver, and cobalt.

[0024] First, industrial gallium raw materials are heated above their melting point to completely melt them, forming a homogeneous liquid gallium raw material. During this process, the aforementioned types of difficult-to-remove impurities present in the raw material are dispersed in the liquid gallium matrix. Because these difficult-to-remove impurities have similar physicochemical properties to metallic gallium, their equilibrium distribution coefficient tends to be close to or greater than 1. That is, during the crystallization process of liquid gallium containing these impurities towards equilibrium, the impurities tend to remain in the solid phase and are difficult to separate from the metallic gallium, which also crystallizes into a solid phase.

[0025] Then, an easily removable metal is added to the liquid gallium raw material, and a second melting process is performed to ensure thorough mixing and thermal diffusion between the liquid gallium raw material and the easily removable metal. A strong interaction occurs between the easily removable metal element and the difficult-to-remove impurities, inducing the formation of stable impurity alloy clusters. These easily removable metals themselves possess good solubility in the liquid gallium raw material and an equilibrium partition coefficient less than 1, effectively binding the difficult-to-remove impurities within the cluster structure. This promotes the uniform diffusion of the difficult-to-remove impurities from the solid phase to the liquid phase, resulting in an equilibrium partition coefficient for the difficult-to-remove impurities significantly less than 1.

[0026] Finally, the molten mixture containing impurity alloy clusters is cooled. As the temperature decreases, pure gallium preferentially precipitates from the liquid phase to form solid-phase crystals. The easily removable metals with an equilibrium distribution coefficient less than 1 tend to accumulate in the liquid phase. During this process, due to the strong interaction with the difficult-to-remove impurities, the difficult-to-remove impurities can migrate into the liquid phase together. In the crystallization step, the easily removable metal element added in this invention has a strong interaction with the difficult-to-remove element (forming alloy clusters). Therefore, when the easily removable metal accumulates in the liquid phase, it can carry the difficult-to-remove impurities into the liquid phase in the form of alloy clusters, making the equilibrium distribution coefficient of the difficult-to-remove impurities less than 1. The difficult-to-remove impurities flow with the liquid phase and accumulate in the unsolidified molten metal, separating from the solidified gallium. Finally, high-purity gallium crystals with reduced impurity content are obtained by separating the liquid phase.

[0027] This invention introduces easily removable metals into gallium raw materials, causing them to interact strongly with difficult-to-remove impurities whose equilibrium partition coefficient is close to or greater than 1. This interaction forms alloyed impurity clusters, significantly enhancing the diffusion and migration ability of these impurities from the solid phase to the liquid phase during crystallization, thus achieving effective separation of these impurities. This invention eliminates the need for multiple purification processes or complex setups, achieving efficient removal with a single crystallization step. It significantly shortens the process flow, effectively reducing energy consumption and operational complexity, making it particularly suitable for the low-cost and large-scale preparation of high-purity gallium.

[0028] To further promote the uniform diffusion of gallium raw materials and added metal elements in the liquid phase, and to further promote the full and positive progress of the alloying process, in a preferred embodiment, the temperature of the first melting point is lower than the temperature of the second melting point, with a difference of 15~90°C. In some embodiments, the temperature of the first melting point is lower than the temperature of the second melting point, with a difference of 25~75°C.

[0029] In a preferred embodiment, the crystallization temperature is lower than the first melting temperature, with a difference of 2 to 18.5°C. When the crystallization temperature is lower than the first melting temperature and the difference is within the above range, it is more beneficial to control the stability of the solid-liquid interface, making the crystallization process more stable, thereby improving the separation efficiency of difficult-to-remove impurities during the crystallization process. In some embodiments, the crystallization temperature is lower than the first melting temperature, with a difference of 8.5 to 18.5°C.

[0030] In a preferred embodiment, in step S1, the purity of the gallium raw material is 3N to 5N; and / or, the first melting temperature is 30 to 45°C, and the time is 1 to 2 hours. Using gallium raw materials with the above-mentioned purity can effectively reduce the content of impurity elements in the raw material, reducing the burden on subsequent purification processes. The first melting operation within the above-mentioned temperature and time range can further promote the complete melting of the raw material and the homogenization of its initial state, making it easier for subsequently added easily removable metals to fully contact the liquid gallium raw material and initiate the diffusion process. Here, 3N indicates that the mass fraction of gallium is not less than 99.9%, and the total impurity content is not more than 0.1%; 5N indicates that the mass fraction of gallium is not less than 99.999%, and the total impurity content is not more than 0.001%. In some embodiments, the first melting temperature is 35 to 45°C, and the time is 1 to 1.5 hours.

[0031] To further reduce the risk of introducing new impurities, more easily control the impurity content in the matrix, and improve purification efficiency, in a preferred embodiment, in step S2, the purity of the easily removable metal is 4N~5N; and / or, the weight ratio of the easily removable metal to the liquid gallium raw material is (0.1~2):100. Controlling the weight ratio of the easily removable metal to the liquid gallium raw material within the above range facilitates the melting of the easily removable metal and gallium, effectively inducing cluster formation, and making the purification process both efficient and economical. Here, 4N indicates that the mass fraction of metallic gallium is not less than 99.99%, and the total impurity content is not higher than 0.01%.

[0032] In a preferred embodiment, in step S2, the second melting temperature is 60-120°C, the time is 6-24 hours, and the stirring rate is 50-150 r / min; and / or, the second melting is carried out in a protective atmosphere, including nitrogen and / or argon. Performing the second melting at the above-mentioned temperature, time, and stirring rate can further promote mass transfer within the molten system, making the alloying reaction more complete and more conducive to the formation of stable alloy clusters. Conducting the second melting in a protective atmosphere containing the above-mentioned elements can further prevent the oxidation and volatilization of gallium and easily removable metals at high temperatures, making the reaction system more stable and thus making it easier to obtain intermediate products with controllable impurity content. In some embodiments, the stirring rate of the second melting is 50-100 r / min.

[0033] To further control the crystal growth rate, make the grain structure denser, and facilitate the removal of difficult-to-remove impurities into the liquid phase, in a preferred embodiment, in step S3, the cooling rate is 0.1~1.0℃ / min; and / or, the crystallization temperature is 25~29℃, and the time is 1~24h. In a preferred embodiment, in step S3, when crystals appear in the molten mixture, cooling is stopped, and crystallization is carried out to further improve the crystal quality and facilitate the full diffusion and separation of impurity elements between the gallium solid-liquid phase. In some embodiments, the cooling rate is 0.1~0.5℃ / min; and / or, the crystallization temperature is 26.5~27℃, and the time is 1~2h; and / or, during the cooling process, when the temperature of the material drops to the crystallization temperature, cooling is stopped, and crystallization is carried out.

[0034] In a preferred embodiment, in step S2, when the weight ratio of the easily removable metal to the liquid gallium material is (0.3~0.5):100, the crystallization temperature is 26.5~27°C. When the weight ratio of the easily removable metal to the liquid gallium material is within the above range, the crystallization temperature is more easily and stably controlled within the above range, making the crystallization process easier to operate and significantly improving repeatability.

[0035] Typical, but not limiting, temperature differences between the second melting point and the first melting point are within the range of 15°C, 25°C, 35°C, 45°C, 55°C, 65°C, 75°C, 90°C, or any two of these values. Temperature differences between the first melting point and the crystallization point are within the range of 2°C, 4°C, 6.5°C, 8.5°C, 9°C, 10.5°C, 12.5°C, 15°C, 16.5°C, 18°C, 18.5°C, or any two of these values. The weight ratio of the easily removable metal to the liquid gallium feedstock is 0.1:100, 0.3:100, 0.5:100, 0.7:100, 0.9:100, 1.2:100, 1.4:100, 1.6:100, 1.8:100, 2.0:100, or any two of these values.

[0036] Typical, but not limiting, temperatures for the first melting point are 30°C, 32°C, 34°C, 36°C, 38°C, 40°C, 42°C, 44°C, 45°C, or any two of these values. Melting times for the first melting point are 1 hour, 1.2 hours, 1.4 hours, 1.6 hours, 1.8 hours, 2 hours, or any two of these values. Temperatures for the second melting point are 60°C, 70°C, 80°C, 90°C, 100°C, 110°C, 120°C, or any two of these values. Melting times for the second melting point are 6 hours, 9 hours, 12 hours, 15 hours, 18 hours, 21 hours, 24 hours, or any two of these values. Stirring rates for the second melting point are 50 rpm, 70 rpm, 90 rpm, 110 rpm, 130 rpm, 150 rpm, or any two of these values.

[0037] Typical, but not limiting, cooling rates are 0.1℃ / min, 0.2℃ / min, 0.3℃ / min, 0.4℃ / min, 0.5℃ / min, 0.6℃ / min, 0.7℃ / min, 0.8℃ / min, 0.9℃ / min, 1.0℃ / min, or any two of these values. Crystallization temperatures are 25℃, 26℃, 27℃, 28℃, 29℃, or any two of these values. Crystallization times are 1h, 4h, 7h, 10h, 13h, 16h, 19h, 22h, 24h, or any two of these values.

[0038] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0039] Example 1

[0040] A schematic diagram of the gallium purification method in Example 1 is shown below. Figure 1The parameters of raw materials and additives in the preparation method are shown in Table 1, and the parameters of each step are shown in Table 2.

[0041] Step S1: Place 99.4g of industrial gallium raw material with a purity of 4N (impurities include iron, nickel and calcium) into a melting container, heat to 45°C, keep warm and stir until the gallium raw material is completely melted, and keep warm at this temperature for 1 hour to complete the first melting and form a uniform liquid gallium raw material;

[0042] Step S2: Add an easily removable metal to the liquid gallium raw material, heat to 90°C under a nitrogen atmosphere, stir at 100 r / min, and keep warm for 12 h to complete the second melting and obtain a molten mixture; wherein, the type, purity and amount of the easily removable metal are shown in Table 1;

[0043] In step S3, the molten mixture is cooled at a rate of 0.5℃ / min. When the system temperature drops to 26.5℃, solid phase crystallization is observed to begin in the container. The mixture is kept at this temperature to allow natural crystallization and purification. After keeping it at this temperature for 2 hours, crystallization is stopped. Metallic gallium crystals are obtained in the liquid phase of the molten mixture. The remaining liquid phase is removed, and the solid metallic gallium after crystallization is collected.

[0044] Example 2

[0045] The parameters of raw materials and additives in the preparation method are shown in Table 1, and the parameters of each step are shown in Table 2.

[0046] Step S1: Place 101.5g of industrial gallium raw material with a purity of 4N (impurities include iron, nickel and calcium) into a melting container, heat to 45°C, keep warm and stir until the gallium raw material is completely melted, and keep warm at this temperature for 1 hour to complete the first melting and form a uniform liquid gallium raw material.

[0047] Step S2: Add an easily removable metal to the liquid gallium raw material, heat to 110°C under a nitrogen atmosphere, stir at 100 r / min, and keep warm for 12 h to complete the second melting and obtain a molten mixture; wherein the easily removable metal is magnesium with a purity of 4N5, and its weight ratio with the liquid gallium raw material is 0.3:100.

[0048] In step S3, the molten mixture is cooled at a rate of 0.5℃ / min. When the system temperature drops to 27℃, solid phase crystallization is observed to begin to appear in the container. The mixture is kept at this temperature to allow natural crystallization and purification. After keeping it at this temperature for 2 hours, crystallization is stopped. Metallic gallium crystals are obtained in the liquid phase of the molten mixture. The remaining liquid phase is removed, and the solid metallic gallium after crystallization is collected.

[0049] Example 3

[0050] The parameters of raw materials and additives in the preparation method are shown in Table 1, and the parameters of each step are shown in Table 2.

[0051] Step S1: Place 104.8g of industrial gallium raw material with a purity of 4N (impurities include iron, nickel and calcium) into a melting container, heat to 45°C, keep warm and stir until the gallium raw material is completely melted, and keep warm at this temperature for 1 hour to complete the first melting and form a uniform liquid gallium raw material.

[0052] Step S2: Add an easily removable metal to the liquid gallium raw material, heat to 100°C under a nitrogen atmosphere, stir at 100 r / min, and keep warm for 6 hours to complete the second melting and obtain a molten mixture; wherein the easily removable metal is tin with a purity of 5N, and its weight ratio with the liquid gallium raw material is 0.5:100.

[0053] In step S3, the molten mixture is cooled at a rate of 0.5℃ / min. When the system temperature drops to 27℃, solid phase crystallization is observed to begin to appear in the container. The mixture is kept at this temperature to allow natural crystallization and purification. After keeping it at this temperature for 2 hours, crystallization is stopped. Metallic gallium crystals are obtained in the liquid phase of the molten mixture. The remaining liquid phase is removed, and the solid metallic gallium after crystallization is collected.

[0054] Example 4

[0055] The parameters of raw materials and additives in the preparation method are shown in Table 1, and the parameters of each step are shown in Table 2.

[0056] Step S1: Place 99.4g of industrial gallium raw material with a purity of 4N (impurities include iron, nickel and calcium) into a melting container, heat to 35°C, keep warm and stir until the gallium raw material is completely melted, and keep warm at this temperature for 1.5h to complete the first melting and form a uniform liquid gallium raw material;

[0057] Step S2: Add an easily removable metal to the liquid gallium raw material, heat to 60°C under a nitrogen atmosphere, stir at 50 r / min, and keep warm for 10 h to complete the second melting and obtain a molten mixture; wherein the easily removable metal is aluminum with a purity of 5N, and its weight ratio with the liquid gallium raw material is 0.1:100.

[0058] In step S3, the molten mixture is cooled at a rate of 0.1℃ / min. When the system temperature drops to 26.5℃, solid phase crystallization is observed to begin in the container. The mixture is kept at this temperature to allow natural crystallization and purification. After keeping it at this temperature for 1 hour, crystallization is stopped. Metallic gallium crystals are obtained in the liquid phase of the molten mixture. The remaining liquid phase is removed, and the solid metallic gallium after crystallization is collected.

[0059] Example 5

[0060] The parameters of raw materials and additives in the preparation method are shown in Table 1, and the parameters of each step are shown in Table 2.

[0061] Step S1: Place 99.4g of industrial gallium raw material with a purity of 4N (impurities include iron, nickel and calcium) into a melting container, heat to 45°C, keep warm and stir until the gallium raw material is completely melted, and keep warm at this temperature for 1 hour to complete the first melting and form a uniform liquid gallium raw material;

[0062] Step S2: Add an easily removable metal to the liquid gallium raw material, heat to 120°C under a nitrogen atmosphere, stir at 100 r / min, and keep warm for 24 hours to complete the second melting and obtain a molten mixture; wherein, the easily removable metal is aluminum with a purity of 5N, and its weight ratio with the liquid gallium raw material is 2:100.

[0063] Step S3: Cool the molten mixture at a rate of 0.1℃ / min. When the system temperature drops to 27℃, solid phase crystallization is observed to begin to appear in the container. Keep the mixture at this temperature to allow it to crystallize and purify naturally. Stop crystallization after keeping the mixture at this temperature for 2 hours. Metallic gallium crystals are obtained in the liquid phase of the molten mixture. Remove the remaining liquid phase and collect the solid metallic gallium after crystallization.

[0064] Example 6

[0065] The parameters of raw materials and additives in the preparation method are shown in Table 1, and the parameters of each step are shown in Table 2.

[0066] Step S1: Place 99.4g of industrial gallium raw material with a purity of 3N (impurities include iron, nickel and calcium) into a melting container, heat to 45°C, keep warm and stir until the gallium raw material is completely melted, and keep warm at this temperature for 1 hour to complete the first melting and form a uniform liquid gallium raw material.

[0067] Step S2: Add an easily removable metal to the liquid gallium raw material, heat to 110°C under a nitrogen atmosphere, stir at 100 r / min, and keep warm for 10 h to complete the second melting and obtain a molten mixture; wherein the easily removable metal is silver with a purity of 5N, and its weight ratio with the liquid gallium raw material is 0.3:100.

[0068] Step S3: Cool the molten mixture at a rate of 0.5℃ / min. When the system temperature drops to 27℃, solid phase crystallization is observed to begin to appear in the container. Keep the mixture at this temperature to allow it to crystallize and purify naturally. Stop crystallization after keeping the mixture at this temperature for 1 hour. Metallic gallium crystals are obtained in the liquid phase of the molten mixture. Remove the remaining liquid phase and collect the solid metallic gallium after crystallization.

[0069] Example 7

[0070] The parameters of raw materials and additives in the preparation method are shown in Table 1, and the parameters of each step are shown in Table 2.

[0071] Step S1: Place 99.4g of industrial gallium raw material with a purity of 5N (impurities include iron, nickel and calcium) into a melting container, heat to 45°C, keep warm and stir until the gallium raw material is completely melted, and keep warm at this temperature for 1 hour to complete the first melting and form a uniform liquid gallium raw material.

[0072] Step S2: Add an easily removable metal to the liquid gallium raw material, heat to 100°C under a nitrogen atmosphere, stir at 100 r / min, and keep warm for 12 h to complete the second melting and obtain a molten mixture; wherein the easily removable metal is cobalt with a purity of 5N, and its weight ratio with the liquid gallium raw material is 0.3:100.

[0073] In step S3, the molten mixture is cooled at a rate of 0.5℃ / min. When the system temperature drops to 26.5℃, solid phase crystallization is observed to begin in the container. The mixture is kept at this temperature to allow natural crystallization and purification. After keeping it at this temperature for 1 hour, crystallization is stopped. Metallic gallium crystals are obtained in the liquid phase of the molten mixture. The remaining liquid phase is removed, and the solid metallic gallium after crystallization is collected.

[0074] Comparative Example 1

[0075] Step S1: Place 99.4g of industrial gallium raw material with a purity of 4N (impurities include iron, nickel and calcium, with a total weight content of 1ppm) into a melting container, heat to 45°C, keep warm and stir until the gallium raw material is completely melted, and keep warm at this temperature for 1 hour to complete the first melting and form a uniform liquid gallium raw material.

[0076] Step S2: The liquid gallium raw material is heated to 90°C under a nitrogen atmosphere, stirred at 100 r / min, and kept at this temperature for 12 h to complete the second melting and obtain a molten mixture.

[0077] In step S3, the molten mixture is cooled at a rate of 0.5℃ / min. When the system temperature drops to 28℃, solid phase crystallization is observed to begin to appear in the container. The mixture is kept at this temperature to allow natural crystallization and purification. After keeping it at this temperature for 2 hours, crystallization is stopped. Metallic gallium crystals are obtained in the liquid phase of the molten mixture. The remaining liquid phase is removed, and the solid metallic gallium after crystallization is collected.

[0078] Performance testing:

[0079] The gallium crystals obtained in the above examples and comparative examples were analyzed and tested as follows, and the results are shown in Table 3.

[0080] Elemental content: Detected using glow discharge mass spectrometry (GDMS).

[0081] Table 1

[0082]

[0083] Table 2

[0084]

[0085] Table 3

[0086]

[0087] As can be seen from the comparative examples and Comparative Example 1, by adding easily removable metals Al, Mg, and Sn to induce the formation of alloyed clusters before crystallization and purification, the content of various metal impurities in crystalline gallium is significantly reduced, with particularly noticeable separation and removal of the core, difficult-to-remove impurity Ni. In Comparative Example 1, without the introduction of easily removable metals for crystallization and purification, the separation and removal of Fe, Ni, and Ca impurities is far less effective than that of the embodiments of the present invention. This demonstrates that the present invention, by adding easily removable metal elements (Al, Mg, Sn) to induce the formation of alloyed clusters, can effectively separate and remove the difficult-to-remove impurities Fe, Ni, and Ca from metallic gallium, which is beneficial for the efficient crystallization and purification of metallic gallium. This breakthrough overcomes the purity bottleneck of existing processes and meets the demand for ultra-high purity gallium in high-end applications.

[0088] In practical applications, depending on the amount of easily removable metal added, the gallium crystal obtained after separating the difficult-to-remove impurities may still contain trace amounts (≤10 ppm) of easily removable metal. Since the equilibrium distribution coefficient of easily removable metal is less than 1, it readily transfers from the solid phase to the liquid phase during crystallization. Therefore, after removing the difficult-to-remove impurities using the method of this invention, conventional crystallization operations can be further performed to separate the remaining easily removable metal in the gallium crystal until the content of each impurity metal in the gallium crystal decreases to the required level.

[0089] Furthermore, it can be seen that the overall effect is better when all process parameters are within the preferred range of the present invention.

[0090] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for purifying metallic gallium, characterized in that, Includes the following steps: Step S1: The industrial gallium raw material is first melted to obtain liquid gallium raw material; wherein, the liquid gallium raw material contains impurities that are difficult to remove; Step S2: The liquid gallium raw material is mixed with an easily removable metal and then melted for the second time, so that the difficult-to-remove impurities and the easily removable metal form impurity alloying clusters in the molten liquid to obtain a molten mixture; Step S3: The molten mixture is cooled and crystallized sequentially to obtain metallic gallium crystals; The difficult-to-remove impurities include one or more of iron, nickel, and calcium; the easily removable metals include easily removable elemental metals, which include one or more of aluminum, magnesium, tin, silver, and cobalt.

2. The method for purifying metallic gallium according to claim 1, characterized in that, The temperature of the first melt is less than the temperature of the second melt, with a difference of 15~90℃.

3. The method for purifying metallic gallium according to claim 1 or 2, characterized in that, The temperature of crystallization is less than the temperature of the first melting point, with a difference of 2 to 18.5°C.

4. The method for purifying metallic gallium according to claim 1 or 2, characterized in that, In step S1, the purity of the industrial gallium raw material is 3N~5N.

5. The method for purifying metallic gallium according to claim 1 or 2, characterized in that, In step S1, the temperature of the first melt is 30~45℃ and the time is 1~2h.

6. The method for purifying metallic gallium according to claim 1 or 2, characterized in that, In step S2 The purity of the easily removable metal is 4N~5N; and / or, The weight ratio of the easily removable metal to the liquid gallium raw material is (0.1~2):

100.

7. The method for purifying metallic gallium according to claim 1 or 2, characterized in that, In step S2 The second melting temperature is 60~120℃, the time is 6~24h, and the stirring rate is 50~150r / min; and / or, The second melting is carried out in a protective atmosphere, which includes nitrogen and / or argon.

8. The method for purifying metallic gallium according to claim 1 or 2, characterized in that, In step S3 The cooling rate is 0.1~1.0℃ / min; and / or, The crystallization temperature is 25~29℃, and the time is 1~24h.

9. The method for purifying metallic gallium according to claim 1 or 2, characterized in that, In step S3, when crystals appear in the molten mixture, the cooling is stopped and the crystallization process is carried out.

10. The method for purifying metallic gallium according to claim 1 or 2, characterized in that, When the weight ratio of the easily removable metal to the liquid gallium raw material is (0.3~0.5):100, the crystallization temperature is 26.5~27℃.

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