Process for preparing high-purity gallium by acid pickling crystallization method

Abstract

The invention relates to the field of purification of high-purity gallium, in particular to high-purity gallium and a preparation method thereof, and particularly relates to a process for preparing the high-purity gallium through a low-loss and high-purity acid pickling crystallization method. According to the technical scheme, the gallium raw material subjected to acid pickling is subjected to multiple times of immersion cleaning by adopting a mixture of two acids, the immersion temperature of each time is gradually reduced, and finally directional crystallization is carried out. The mixture of the two acids can more effectively remove impurities in the gallium raw material, and the pickling efficiency and the cleaning effect are improved, so that the purity of gallium is improved. And secondly, the temperature is gradually reduced during each immersion, so that stress or damage on the surface of the gallium raw material caused by too fast temperature change can be avoided, and the integrity and quality stability of the raw material are ensured. The optimized pickling and crystallizing process is beneficial to reducing the loss of raw materials, improving the production efficiency, reducing the production cost and realizing the large-scale stable production of the high-purity gallium.

Description

Technical Field

[0001] This invention relates to the field of high-purity gallium purification, specifically to a high-purity gallium and its preparation method, particularly to a process for preparing high-purity gallium by acid washing and crystallization, and especially to a low-loss, high-purity acid washing and crystallization process for preparing high-purity gallium. Background Technology

[0002] Gallium is an important rare-dispersed metal with wide applications in semiconductors, electronics, and communications due to its unique physical and chemical properties. With the rapid development of technology, the demand for high-purity gallium is constantly increasing, and the requirements for its purity are also becoming more stringent.

[0003] Currently, the main methods for preparing high-purity gallium include electrolytic refining, zone melting, and acid leaching crystallization. While electrolytic refining can yield high-purity products, it suffers from high energy consumption and complex equipment, and is typically only suitable for further purification of already high-purity raw materials. Zone melting is effective at removing impurities from gallium raw materials, but it has low production efficiency, requires sophisticated equipment, and is difficult to implement for low-cost, large-scale production. In contrast, acid leaching crystallization offers advantages such as lower equipment requirements and suitability for large-scale continuous production.

[0004] However, traditional acid pickling and crystallization processes have some shortcomings. The acid pickling step typically employs a two-step method of hydrochloric acid-nitric acid pickling, followed directly by crystallization. Experimental observations revealed that after nitric acid pickling, the liquid gallium and acid solution exhibit a gray suspension on top and rice-grain-sized liquid gallium particles on the bottom. Related literature analysis indicates that this is due to the reaction of hot nitric acid with liquid gallium to form a Ga2O3 oxide film, which surrounds the liquid gallium. Under rapid stirring, the liquid gallium is broken into fine particles. The smaller particles are dispersed in the upper suspension, while the larger particles accumulate in the lower layer due to gravity. Traditional acid pickling methods discharge the upper suspension as waste, while the turbid liquid gallium in the lower layer is directly used as raw material in the next step. However, this rigid separation of the upper and lower liquid layers leads to a significant loss of the lower liquid, significantly increasing the loss rate of the acid pickling process. Incomplete separation will prevent impurities in the acid pickling waste liquid from being discharged, thus reducing the quality of the acid-washed product. Therefore, removing the Ga2O3 oxide film produced by nitric acid pickling and enriching the pickling product is an effective method to improve pickling purity and reduce loss rate.

[0005] Patent CN117778764A discloses an acid-washing purification method that purifies 2-3 N gallium metal to 7 N through a two-step acid washing process, followed by electrolysis and finally crystallization. However, this method has several problems: its current density is high (4000-5000 A / m). 2The patent suffers from several drawbacks: high energy consumption; expensive electrolytic devices (using platinum electrodes) leading to high costs; and long production time (the entire process, excluding the actual electrolysis time, requires at least 30 hours). Furthermore, a comparison of the main impurity element content listed in the patent's embodiments with national standards reveals that the product quality does not meet the ideal 7N standard, and the quality of each batch is inconsistent. More importantly, the patent fails to address the issue of raw material loss and recycling, while experiments have proven that such losses are real. Therefore, the patent's consideration of the issues is insufficient.

[0006] In conclusion, how to shorten production time, reduce production costs, minimize raw material loss, and output stable and qualified 7N standard products in the production of high-purity gallium remains an urgent problem to be solved.

[0007] Furthermore, on the one hand, there are differences in understanding among those skilled in the art; on the other hand, the inventors studied a large number of documents and patents when making this invention, but due to space limitations, not all details and contents were listed in detail. However, this does not mean that the present invention does not possess the features of these prior art. On the contrary, the present invention already possesses all the features of the prior art, and the applicant reserves the right to add relevant prior art to the background art. Summary of the Invention

[0008] To address the aforementioned technical problems, this invention provides a high-purity gallium and its preparation method, particularly relating to a low-loss, high-purity acid washing and crystallization process for preparing high-purity gallium.

[0009] A method for preparing high-purity gallium, comprising the following steps: S1 sequentially uses hydrochloric acid and nitric acid to acid-wash gallium raw materials; S2 involves adding a mixture of hydrochloric acid and acetic acid in a 1:1~2 ratio to the gallium raw material after the first acid wash, immersing the gallium raw material in this mixture, and performing a three-stage immersion reaction. The first immersion is at 46~50℃ and the mixture is mixed for no less than 5 minutes. The second immersion is at a temperature 2~6℃ lower than the temperature of the first immersion and the mixture is mixed for no less than 5 minutes. The third immersion is at a temperature 2~6℃ lower than the temperature of the second immersion and the mixture is mixed for no less than 5 minutes. S3 removes the supernatant and rinses with water; S4 directional crystallization was used to obtain purified metallic gallium.

[0010] According to a preferred embodiment, the immersion of the mixed acid specifically involves mixing at 48°C for at least 5 minutes, followed by mixing at temperature gradients of 43°C and 38°C for at least 5 minutes in sequence.

[0011] According to a preferred embodiment, the concentration of hydrochloric acid in S1 is 2-5 mol / L. Preferably, the concentration of hydrochloric acid in S1 is 2 mol / L.

[0012] According to a preferred embodiment, the concentration of nitric acid in S1 is 2-3 mol / L. Preferably, the concentration of nitric acid in S1 is 2 mol / L.

[0013] According to a preferred embodiment, the ratio of hydrochloric acid to acetic acid in S2 is 1:1.

[0014] According to a preferred embodiment, the third immersion reaction in S2 continues until the supernatant is colorless and transparent.

[0015] According to a preferred embodiment, directional crystallization includes the following steps: Directional crystallization is performed in a crystallizer with a cold end temperature of 17°C and an external hot end temperature of 50°C. Preferably, gallium that has undergone acid washing pretreatment is placed symmetrically with four seed crystals on the four sides of the crystallizer wall with a cold end temperature of 17°C and an external hot end temperature of 50°C, and directional crystallization is carried out under magnetic stirring. After crystallization to the point where 8% of the material remains, the material is extracted and stored. The temperature is then raised to 50°C again until the metallic gallium melts, and the crystallization process is repeated four times.

[0016] Another objective of this invention is to provide a high-purity gallium, which is prepared based on the above-described preparation method.

[0017] According to a preferred embodiment, the obtained high-purity gallium has a purity of 7 N.

[0018] According to a preferred embodiment, the obtained high-purity gallium contains Mg < 0.001 ppm, Al < 0.001 ppm, Ca < 0.005 ppm, Fe < 0.001 ppm, Ni < 0.005 ppm, Cu < 0.005 ppm, Zn < 0.003 ppm, Hg < 0.005 ppm, and Pb < 0.005 ppm. This quality meets the testing requirements and is superior to the 7N national standard GB / T 10118-2023 "High-Purity Gallium".

[0019] Another objective of this invention is to provide the application of the above-described preparation method in gallium purification.

[0020] The beneficial effects of this technical solution are: This patented technology involves multiple immersion cleanings of acid-washed gallium raw materials using a mixture of two acids, with the temperature of each immersion gradually decreasing, followed by directional crystallization. This invention significantly improves the purification efficiency and product stability of high-purity gallium by optimizing the acid washing process. It employs a mixed acid synergistic cleaning mechanism using hydrochloric acid and nitric acid. Nitric acid preferentially removes large-particle impurities from the gallium raw material surface, forming a controllable oxide film (Ga2O3). Hydrochloric acid directionally dissolves this oxide film and deeply removes micron-sized metal inclusions. The synergistic chemical effect of the dual acid washing significantly expands the impurity removal spectrum, improving washing efficiency compared to traditional single-acid cleaning. Furthermore, the surface smoothness of the gallium raw material is improved after cleaning, and the total amount of residual impurities is reduced to the ppm level.

[0021] By gradually lowering the solution temperature after each immersion operation (in a stepwise manner of 2-6°C), stress concentration and phase transformation microcracks on the liquid gallium surface caused by rapid cooling are effectively avoided, maintaining the structural integrity of the raw material. Simultaneously, the gradual cooling allows the acid solution to act continuously in a dynamically temperature-controlled environment, both suppressing gallium loss caused by excessive release of acid reactivity and enhancing the directional precipitation of impurity ions driven by the temperature gradient. This temperature control strategy improves the surface stability of the raw material, effectively removing impurities during the acid washing process through stirring and ensuring the orderly growth of the crystal lattice in subsequent directional crystallization.

[0022] The combined use of two technologies creates a synergistic effect of "deep chemical impurity removal - physical structure protection": As pickling progresses, the oxide film content in the raw material gradually decreases. Excess mixed acid will further react with excess raw material at the same high temperature, resulting in losses. By removing the oxide film through multi-step gradient cooling, lowering the pickling temperature in the later stages can effectively slow down the reaction rate between the mixed acid and the oxide film, thereby reducing the losses caused by the reaction between the mixed acid and the raw material, further reducing the loss rate of the pickled product, and achieving the technical goal of cost reduction and efficiency improvement.

[0023] Hybrid acid washing ensures efficient removal of impurities, while gradient cooling protects the intrinsic quality of raw materials. Together, they achieve a breakthrough optimization in the purity of crude gallium obtained from acid washing, laying a core foundation for the stable mass production of 7N-grade high-purity gallium, thereby enabling the large-scale and stable production of high-purity gallium.

[0024] The intermediate high-purity gallium obtained by the acid washing method provided in this technical solution has Mg<0.001 ppm, Al<0.001 ppm, Ca<0.005 ppm, Fe<0.001 ppm, Ni≦0.008 ppm, Cu≦0.008 ppm, Zn<0.005 ppm, Hg<0.005 ppm, and Pb≦0.003 ppm, which is better than the national standard of 6N. This effectively reduces the number of subsequent crystallization and purification steps and obtains high-purity gallium products of the same purity. Attached Figure Description

[0025] Figure 1 This is a flowchart of the pickling process involved in the present invention. Detailed Implementation

[0026] In the description of this invention, terminology is used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly defined.

[0027] Unless otherwise specified, the experimental methods used in the following examples are all conventional methods; the materials, reagents or instruments used, unless otherwise specified by the manufacturer, are all commercially available reagents and materials; the conditions not specified in the examples are all carried out according to conventional conditions or conditions recommended by the manufacturer. At the same time, the present invention does not limit the source of the raw materials used. Unless otherwise specified, the raw materials used in the present invention are all commercially available products in this technical field.

[0028] Example 1 This embodiment relates to a method for acid washing of cadmium, the method as follows: Figure 1 As shown.

[0029] First, 5 kg of 4N liquid gallium raw material was acid-washed at 48℃ with 600 mL of 2 mol / L hydrochloric acid and 750 mL of 2 mol / L nitric acid for 2 h each. After nitric acid washing, 100 mL of a 1:1 mixture of hydrochloric acid and acetic acid was added and stirred for 5 min to remove the oxide film. Subsequently, the temperature was lowered to 43℃ and then 38℃ for the same oxide film removal operation. Finally, a colorless and transparent supernatant and a bright lower layer of silvery-white liquid gallium were obtained from the acid washing. The supernatant waste liquid was extracted, followed by washing with pure water and stirring. After the washing was completed, the waste liquid was extracted. The acid washing product yield was 99.28%, and the purity of the acid washing product reached 6N.

[0030] Gallium that has undergone acid washing pretreatment is placed symmetrically with four seed crystals on the four sides of the wall of a crystallizer with a cold end temperature of 17°C and an external hot end temperature of 50°C. Directional crystallization is carried out under magnetic stirring. After crystallization to the point where 8% of the material remains, the material is extracted and stored. The temperature is then raised to 50°C again until the metallic gallium melts. The crystallization process is repeated four times, and the resulting gallium purity is 7N.

[0031] Comparative Example 1 First, 5 kg of 4N liquid gallium raw material was acid-washed at 48℃ with 600 mL of 2 mol / L hydrochloric acid and 750 mL of 2 mol / L nitric acid for 2 h each. After nitric acid washing, 300 mL of 3 mol / L hydrochloric acid was added and stirred for 15 min to remove the oxide film. Finally, a colorless and transparent supernatant and a bright lower layer of silvery-white liquid gallium were obtained. The supernatant waste liquid was extracted, followed by washing with pure water with stirring. After completion, the waste liquid was extracted. The acid-washed product yield was 97.76%, and the purity of the acid-washed product was 5N.

[0032] Gallium that has undergone acid washing pretreatment is placed symmetrically with four seed crystals on the four sides of the wall of a crystallizer with a cold end temperature of 17°C and an external hot end temperature of 50°C. Directional crystallization is carried out under magnetic stirring. After crystallization to the point where 8% of the material remains, the material is extracted and stored. The temperature is then raised to 50°C again until the metallic gallium melts. The crystallization process is repeated four times, and the resulting gallium purity is 6N.

[0033] Comparative Example 2 First, 5 kg of 4N liquid gallium raw material was acid-washed at 48℃ with 600 mL of 2 mol / L hydrochloric acid and 750 mL of 2 mol / L nitric acid for 2 h each. After nitric acid washing, 100 mL of 3 mol / L hydrochloric acid was added and stirred for 5 min to remove the oxide film. Subsequently, the temperature was successively reduced to 43℃ and 38℃ for the same oxide film removal operation. Finally, a colorless and transparent supernatant and a bright lower layer of silvery-white liquid gallium were obtained from the acid washing. The supernatant waste liquid was extracted, followed by pure water stirring and washing. After the washing was completed, the waste liquid was extracted. The acid washing product yield was 98.14%, and the purity of the acid washing product reached 6N.

[0034] Gallium that has undergone acid washing pretreatment is placed symmetrically with four seed crystals on the four sides of the wall of a crystallizer with a cold end temperature of 17°C and an external hot end temperature of 50°C. Directional crystallization is carried out under magnetic stirring. After crystallization to the point where 8% of the material remains, the material is extracted and stored. The temperature is then raised to 50°C again until the metallic gallium melts. The crystallization process is repeated four times, and the resulting gallium purity is 7N.

[0035] Comparative Example 3 First, 5 kg of 4N liquid gallium raw material was acid-washed at 48℃ with 600 mL of 2 mol / L hydrochloric acid and 750 mL of 2 mol / L nitric acid for 2 h each. After nitric acid washing, 300 mL of a 1:1 mixture of hydrochloric acid and acetic acid was added and stirred for 15 min to remove the oxide film. Finally, a colorless and transparent supernatant and a bright, silvery-white lower layer of liquid gallium were obtained. The supernatant waste liquid was extracted, followed by washing with pure water and stirring. After completion, the waste liquid was extracted. The acid-washed product yield was 98.46%, and the purity of the acid-washed product reached nearly 6N.

[0036] Gallium that has undergone acid washing pretreatment is placed symmetrically with four seed crystals on the four sides of the wall of a crystallizer with a cold end temperature of 17°C and an external hot end temperature of 50°C. Directional crystallization is carried out under magnetic stirring. After crystallization to the point where 8% of the material remains, the material is extracted and stored. The temperature is then raised to 50°C again until the metallic gallium melts. The crystallization process is repeated four times, and the resulting gallium purity is 7N.

[0037] Comparative Example 4 First, 5 kg of 4N liquid gallium raw material was acid-washed at 48℃ with 600 mL of 2 mol / L hydrochloric acid and 750 mL of 2 mol / L nitric acid for 2 h each. After nitric acid washing, 100 mL of a 1:2 mixture of hydrochloric acid and acetic acid was added and stirred for 5 min to remove the oxide film. Subsequently, the temperature was lowered to 43℃ and then 38℃ for the same oxide film removal operation. Finally, a colorless and transparent supernatant and a bright silvery-white lower layer of liquid gallium were obtained from the acid washing. The supernatant waste liquid was extracted, followed by pure water stirring and washing. After the washing was completed, the waste liquid was extracted. The acid washing product yield was 98.75%, and the purity of the acid washing product reached 5N.

[0038] Gallium that has undergone acid washing pretreatment is placed symmetrically with four seed crystals on the four sides of the wall of a crystallizer with a cold end temperature of 17°C and an external hot end temperature of 50°C. Directional crystallization is carried out under magnetic stirring. After crystallization to the point where 8% of the material remains, the material is extracted and stored. The temperature is then raised to 50°C again until the metallic gallium melts. The crystallization process is repeated four times, and the resulting gallium purity is 7N.

[0039] Comparative Example 5 First, 5 kg of 4N liquid gallium raw material was acid-washed at 48℃ with 600 mL of 2 mol / L hydrochloric acid and 750 mL of 2 mol / L nitric acid for 2 h each. After nitric acid washing, 100 mL of a 2:1 mixture of hydrochloric acid and acetic acid was added and stirred for 5 min to remove the oxide film. Subsequently, the temperature was lowered to 43℃ and then 38℃ for the same oxide film removal operation. Finally, a colorless and transparent supernatant and a bright lower layer of silvery-white liquid gallium were obtained from the acid washing. The supernatant waste liquid was extracted, followed by pure water stirring and washing. After the washing was completed, the waste liquid was extracted. The acid washing product yield was 98.69%, and the purity of the acid washing product reached 6N.

[0040] Gallium that has undergone acid washing pretreatment is placed symmetrically with four seed crystals on the four sides of the wall of a crystallizer with a cold end temperature of 17°C and an external hot end temperature of 50°C. Directional crystallization is carried out under magnetic stirring. After crystallization to the point where 8% of the material remains, the material is extracted and stored. The temperature is then raised to 50°C again until the metallic gallium melts. The crystallization process is repeated four times, and the resulting gallium purity is 7N.

[0041] The results of testing the purity and impurity content of gallium obtained in Example 1 and Comparative Examples 1-5 are shown in Table 1.

[0042] Table 1

[0043] The results show that, compared with comparative examples 1 to 5, the examples are the most effective in removing impurity elements.

[0044] It should be noted that the specific embodiments described above are exemplary, and those skilled in the art can devise various solutions inspired by the disclosure of this invention. These solutions all fall within the scope of this invention and its protection. Those skilled in the art should understand that this specification and its accompanying drawings are illustrative and not intended to limit the scope of the claims. The scope of protection of this invention is defined by the claims and their equivalents.

Claims

1. A method for producing high-purity gallium, characterized by comprising: The preparation method comprises the following steps: ​ S1: sequentially using hydrochloric acid and nitric acid to clean the gallium raw material; S2: adding a mixed acid with a hydrochloric acid to acetic acid ratio of 1:1-2 to the gallium raw material after the first cleaning, so that the gallium raw material is immersed, and performing three immersion reactions, wherein, the first immersion is mixed at 46-50 DEG C for no less than 5 min, the second immersion is mixed at a temperature 2-6 DEG C lower than the first immersion for no less than 5 min, and the third immersion is mixed at a temperature 2-6 DEG C lower than the second immersion for no less than 5 min; S3: removing the supernatant and adding water for cleaning; S4: directional crystallization to obtain the purified metal gallium.

2. The production method according to claim 1, characterized by, The concentration of the hydrochloric acid in S1 is 2-5 mol / L.

3. The preparation method according to claim 1, characterized in that, The concentration of the nitric acid in S1 is 2-3 mol / L.

4. The method of claim 1, wherein, The ratio of the hydrochloric acid to the acetic acid in S2 is 1:

1.

5. The preparation method according to claim 1, characterized in that, The third immersion reaction in S2 is performed until the supernatant is colorless and transparent.

6. The method of claim 1, wherein, The directional crystallization comprises the following steps: directional crystallization in a crystallizer with a cold end temperature of 17 DEG C and an external hot end temperature of 50 DEG C.

7. High purity gallium, characterized in that, The high-purity gallium is prepared based on the preparation method in any one of claims 1-6.

8. The high purity gallium according to claim 7, characterized by, The purity of the high-purity gallium is 7 N.

9. The high purity gallium according to claim 7, characterized by, In the high-purity gallium, Mg < 0.001 ppm, Al < 0.001 ppm, Ca < 0.005 ppm, Fe < 0.001 ppm, Ni < 0.005 ppm, Cu < 0.005 ppm, Zn < 0.003 ppm, Hg < 0.005 ppm, and Pb < 0.005 ppm.

10. A method for the production of high-purity gallium and the use thereof in the purification of gallium, characterized in that The preparation method of the high-purity gallium is the preparation method in any one of claims 1-6.

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