Method and system for purifying metal gallium

Abstract

Disclosed herein is a method for purifying metal gallium. The purity of metal gallium is less than or equal to 4 N. The method comprises: subjecting a portion of metal gallium to first electrolysis by using an electrolyte, so as to obtain a purified electrolyte containing a set content of gallate ions; subjecting the remaining metal gallium to second electrolysis by using the purified electrolyte containing the set content of gallate ions, so as to obtain electrolytic gallium; and subjecting the electrolytic gallium to gradient crystallization to remove impurity metals from the electrolytic gallium, so as to obtain high-purity metal gallium.

Description

Method and system for purifying metallic gallium Cross-reference to related applications

[0001] This application claims priority to Chinese Patent Application No. 202411330611.2, filed September 24, 2024, the entire contents of which are incorporated herein by reference. TECHNICAL FIELD

[0002] The present disclosure relates to the technical field of high-purity gallium purification, and in particular to a method and system for purifying metallic gallium. BACKGROUND

[0003] Gallium is a rare metal with high boiling point and low melting point. Industrial production uses industrial-grade metallic gallium as raw material, which is further purified by electrolytic refining, crystallization, vacuum distillation, zone melting, and other process methods to produce high-purity gallium. High-purity gallium is mainly used in the form of compounds such as gallium arsenide, gallium phosphide, and gallium nitride in wireless communication, optoelectronic semiconductors, and solar cells, and other fields, becoming an irreplaceable high-performance and high-demand material. These application fields not only require the purity of high-purity gallium to reach 6N, but also have strict requirements on the content of main harmful impurities such as Cu, Zn, Fe, and Si; and semi-insulating gallium arsenide single crystals used for making integrated circuit (IC) substrates require the purity of high-purity gallium to be above 7N. By using glow discharge mass spectrometry (GDMS) to analyze impurities in high-purity gallium, the content of main harmful impurities must be below 5x10 -7 % except C, N, O, and Ta, and the content of the remaining impurities must be below the detection limit.

[0004] Due to the importance of high-purity gallium in applications and the complexity of purification technology, how to purify metallic gallium to prepare high-purity gallium with a purity of above 7N has become a technical problem to be solved in the field. SUMMARY

[0005] The technical problem of how to purify metallic gallium to above 7N is solved by using one or more embodiments of the present disclosure.

[0006] In a first aspect, a method for purifying metallic gallium according to some embodiments of the present disclosure, the purity of the metallic gallium is ≤4N, comprising: using an electrolyte to perform first electrolysis on part of the metallic gallium to obtain a purified electrolyte containing a set content of gallate ions; using the purified electrolyte containing the set content of gallate ions to perform second electrolysis on the remaining metallic gallium to obtain electrolytic gallium; and performing gradient crystallization on the electrolytic gallium to remove impurity metals in the electrolytic gallium to obtain high-purity metallic gallium.

[0007] In a second aspect, a system for purifying metallic gallium according to some embodiments of the present disclosure is adapted to the method for purifying metallic gallium according to any of the embodiments of the first aspect. The system comprises an electrolytic cell 1 and a crystallization cell 2. The electrolytic cell 1 is internally provided with an electrolysis zone 11, the height of the electrolysis zone 11 being lower than the depth of the electrolytic cell 1, and the electrolysis zone 11 being immersed in an electrolyte. The electrolysis zone 11 comprises an anode zone 111, a first cathode zone 112, and a second cathode zone 113. The anode zone 111 is disposed at the outermost layer of the electrolysis zone 11. The first cathode zone 112 is disposed at the innermost layer of the electrolysis zone 11. The second cathode zone 113 is disposed between the anode zone 111 and the first cathode zone 112. The discharge port of the electrolytic cell 1 is disposed at the second cathode zone 113, and the feed port of the electrolytic cell 1 is disposed at the anode zone 111. The discharge port of the electrolytic cell 1 is in communication with the feed port of the crystallization cell 2. BRIEF DESCRIPTION OF DRAWINGS

[0008] The accompanying drawings, which are incorporated herein and constitute part of the specification, illustrate embodiments consistent with the present disclosure and serve to explain the principles of the present disclosure together with the specification.

[0009] In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure or the related art, the accompanying drawings needed to be used in the embodiments or the related art description will be briefly introduced. Obviously, those skilled in the art can obtain other drawings from these drawings without any creative effort.

[0010] FIG. 1 shows a flowchart of a method for purifying metallic gallium according to some embodiments of the present disclosure.

[0011] FIG. 2 shows a structural diagram of a system for purifying metallic gallium according to some embodiments of the present disclosure.

[0012] FIG. 3 shows a structural diagram of an electrolysis zone of an electrolytic cell of a system for purifying metallic gallium according to some embodiments of the present disclosure. In the figure, 1 represents an electrolytic cell, 11 represents an electrolysis zone, 111 represents an anode zone, 112 represents a first cathode zone, 113 represents a second cathode zone, 2 represents a crystallization cell, 21 represents a heating zone, 22 represents a crystallization zone, and 23 represents a cooling zone. DETAILED DESCRIPTION

[0013] In order to make the objects, technical solutions, and advantages of the embodiments of the present disclosure clearer, the technical solutions in the embodiments of the present disclosure will be described clearly and completely below with reference to the drawings in the embodiments of the present disclosure. Obviously, the described embodiments are some, but not all of the embodiments of the present disclosure. Based on the embodiments in the present disclosure, all other embodiments obtained by those of ordinary skill in the art without any creative effort belong to the scope of protection of the present disclosure.

[0014] Various embodiments of the present disclosure can exist in a range of forms; it should be understood that the description in a range form is merely for the convenience and brevity, and should not be understood as a hard limitation on the scope of the present disclosure; therefore, it should be considered that all possible sub-ranges and single values within the range have been specifically disclosed. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single values such as 1, 2, 3, 4, 5, and 6 within the range, which applies to any range. In addition, whenever a numerical range is indicated herein, it refers to any cited number (fraction or integer) within the indicated range.

[0015] In this document, the terms "upper", "lower", "left", "right", "front", "back", "top", "bottom", "inner", "outer", "vertical", "horizontal", "lateral", "longitudinal", and similar terms, indicate the orientation or positional relationship as shown in the drawings. These terms are mainly used for better description of the present application and its embodiments, and are not used to limit the indicated devices, elements or components to necessarily have a specific orientation, or to be constructed and operated in a specific orientation. In addition, in addition to indicating the orientation or positional relationship, the above-mentioned terms can also be used to indicate other meanings, for example, the term "upper" can also be used to indicate a certain dependent relationship or connection relationship in some cases. For those skilled in the art, the specific meaning of these terms in the present application can be understood according to the specific circumstances. In addition, the terms "mount", "set", "provided with", "communicate", "connected" should be understood broadly. For example, it can be fixedly connected, detachably connected, or integrally constructed; it can be mechanically connected, or electrically connected; it can be directly connected, or indirectly connected through an intermediate medium, or it can be internal communication between two devices, elements or components, or it can be a relationship between devices indicating flow direction without direct communication.

[0016] In addition, in the description of the present disclosure, the terms "include", "contain" and the like mean "include but not limited to". In this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between the entities or operations. Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present disclosure can be purchased on the market or can be prepared by existing methods.

[0017] In addition, in the description of the present disclosure, the terms "include", "contain" and the like mean "include but not limited to". In this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between the entities or operations. Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present disclosure can be purchased on the market or can be prepared by existing methods.

[0018] In a first aspect, a method for purifying metallic gallium with a purity of ≤4N according to some embodiments of the present disclosure is provided. FIG. 1 shows a flowchart of a method for purifying metallic gallium according to some embodiments of the present disclosure. As shown in FIG. 1, the method comprises:

[0019] S1, performing first electrolysis on part of the metallic gallium using an electrolyte to obtain a purified electrolyte containing a set amount of gallate ions;

[0020] S2, performing second electrolysis on the remaining metallic gallium using the purified electrolyte containing the set amount of gallate ions to obtain electrolytic gallium; and

[0021] S3, performing gradient crystallization on the electrolytic gallium to remove impurity metals in the electrolytic gallium to obtain high-purity metallic gallium.

[0022] In some embodiments, the set amount of gallate ions (GaO 2- ) is ≥30g / L.

[0023] In some embodiments of the present disclosure, the set amount of gallate ions is ≥30g / L, which means that the first electrolysis on part of the metallic gallium using the electrolyte can generate sufficient GaO 2– in the electrolyte, thereby ensuring the efficiency of the subsequent second electrolysis. For example, the set amount of gallate ions (GaO 2- ) can be 30g / L, 31g / L, 32g / L, 33g / L, 34g / L, 35g / L, etc.

[0024] In some embodiments, the process parameters of the first electrolysis include: the concentration of the electrolyte is 150g / L-260g / L, the current density is 130A / m 2 -250A / m 2 , the electrolysis time is 3-9 days, and the electrolysis temperature is above 30°C.

[0025] In some embodiments of the present disclosure, in the electrolyte, the metallic gallium loses electrons at the anode to become gallate ions and enters the electrolyte, and the gallate ions are reduced to metallic gallium at the cathode and can be deposited at the cathode. The process parameters of the first electrolysis mainly control the electrolysis of metallic gallium, including current density, electrolyte concentration, electrolysis time, and electrolysis temperature. These process parameters can have certain effects on the control of impurities in the electrolysis of metallic gallium to a certain extent. The first electrolysis represents pre-electrolysis, which can obtain a purified electrolyte containing a set amount of gallate ions and also purify the electrolyte.

[0026] In some embodiments of this disclosure, the concentration of the electrolyte in the first electrolysis can be 150 g / L to 260 g / L. On the one hand, this can prevent the content of impurities such as Pb, Zn, Sn and Fe at the cathode of the first electrolysis from rapidly increasing and overflowing from the electrolytic cell due to the electrolyte concentration being too low and below 150 g / L, thus contaminating the electrolysis process. On the other hand, it can also prevent the formation of crystals on the electrolytic cell wall due to the electrolyte concentration being too high and above 300 g / L, which would deteriorate the electrolysis environment and be detrimental to electrolytic purification.

[0027] In some embodiments of this disclosure, the current density of the first electrolysis can be 130 A / m. 2 ~250A / m 2 This allows for full realization of the first electrolysis while avoiding excessively high current densities exceeding 250 A / m. 2 This causes a rapid increase in the content of impurities such as Pb, Zn, Sn, and Fe at the cathode during the first electrolysis, leading to their overflow from the electrolytic cell and contamination of the electrolysis process; simultaneously, it can prevent GaO from forming in the anode region due to excessively high current density. 2– The higher concentration helps to avoid the precipitation of impurities caused by localized oversaturation of crystals covering the electrode.

[0028] In some embodiments of this disclosure, the electrolysis time of the first electrolysis can be 3 to 9 days. Sufficient electrolysis time in the first electrolysis can ensure the generation of a sufficient amount of GaO in the electrolyte. 2– This ensures the efficiency of the subsequent second electrolysis; however, if the electrolysis time is too long and exceeds 9 days, on the one hand, it may result in the loss of metallic gallium raw materials, and on the other hand, it may lead to the generation of too much gallium with high impurity concentration at the cathode, which may overflow the electrolytic cell and contaminate the electrolysis process.

[0029] In some embodiments of this disclosure, the electrolysis temperature of the first electrolysis can be above 30°C. The melting point of gallium is 29.80°C. Electrolytic purification of gallium needs to be carried out when gallium is in a molten state. In order to maintain the continuous progress of the gallium electrolysis process, the electrolysis temperature of the first electrolysis should be kept higher than the melting point of gallium.

[0030] For example, in the process parameters of the first electrolysis, the concentration of the electrolyte can be 150 g / L, 160 g / L, 170 g / L, 180 g / L, 190 g / L, 200 g / L, 210 g / L, 220 g / L, 230 g / L, 240 g / L, 250 g / L, 260 g / L, etc.; the current density can be 130 A / m 2 150A / m 2 170A / m 2 190A / m 2 210A / m 2 230A / m 2250A / m 2 The electrolysis time can be 3 days, 4 days, 5 days, 6 days, 7 days, 8 days, 9 days, etc.; the electrolysis temperature can be 30℃, 31℃, 32℃, 33℃, 34℃, etc.

[0031] In some embodiments, the process parameters for the second electrolysis include: an electrolyte concentration of 150 g / L to 260 g / L and a current density of 130 A / m. 2 ~250A / m 2 The electrolysis time is 12 to 25 days, and the electrolysis temperature is above 30℃.

[0032] In some embodiments of this disclosure, the second electrolysis is a deep electrolysis to obtain electrolytic gallium. The reasons for controlling the concentration of the electrolyte, the current density, and the electrolysis temperature in the second electrolysis are the same as those for the first electrolysis, and will not be repeated here. The electrolysis time in the second electrolysis can be 12 to 25 days, which can fully realize the second electrolysis. Since impurities such as Pb, Zn, Sn, and Fe will significantly increase at the end of the second electrolysis, appropriately shortening the second electrolysis time is beneficial to improving the purity of the product.

[0033] For example, in the process parameters of the second electrolysis, the concentration of the electrolyte can be 150 g / L, 160 g / L, 170 g / L, 180 g / L, 190 g / L, 200 g / L, 210 g / L, 220 g / L, 230 g / L, 240 g / L, 250 g / L, 260 g / L, etc.; the current density can be 130 A / m 2 150A / m 2 170A / m 2 190A / m 2 210A / m 2 230A / m 2 250A / m 2 The electrolysis time can be 12 days, 14 days, 16 days, 18 days, 20 days, 22 days, 24 days, 25 days, etc.; the electrolysis temperature can be 30℃, 31℃, 32℃, 33℃, 34℃, etc.

[0034] In some embodiments of this disclosure, during the first and second electrolysis processes, the voltage stability of the electrolysis process can be maintained by adjusting the concentration of the NaOH aqueous solution, so that its positive and negative deviations do not exceed 5%.

[0035] In some embodiments of this disclosure, the first electrolysis achieves the creation of a predetermined amount of GaO in the electrolyte solution. 2–The purpose of the electrolytic solution is to facilitate the second electrolysis of the later-stage metal gallium, and at the same time, impurities (such as Cu, Zn, Sn, and Fe, etc.) in the electrolyte solution can be deposited at the cathode in the first electrolysis process, so as to play a purifying effect on the electrolyte and create a pure electrolysis environment for the later-stage second electrolysis. The first electrolysis and the second electrolysis cooperatively purify the metal gallium below 4N to a purity level of 6N, and further provide raw materials with lower impurity content for the subsequent crystallization purification of the electrolytic gallium, so as to ensure that the purity of the metal gallium can be finally improved to above 7N through further crystallization purification.

[0036] In some embodiments, the gradient crystallization of the electrolytic gallium (multiple repeated crystallization) is performed to remove the impurity metals in the electrolytic gallium, and high-purity metal gallium is obtained, including:

[0037] The electrolytic gallium is placed in a crystallization region between an inner temperature region and an outer temperature region, so as to perform gradient crystallization on the electrolytic gallium to remove the impurity metals in the electrolytic gallium, and obtain high-purity metal gallium; wherein the temperature of the inner temperature region is higher than the melting point of the metal gallium, and the temperature of the outer temperature region is lower than the melting point of the metal gallium.

[0038] In some embodiments of the present disclosure, the gradient crystallization of the electrolytic gallium is based on the principle of metal segregation purification, that is, in the process of conversion of metal from liquid phase to solid phase, the impurity elements in the metal will be redistributed in the solid and liquid phases in this conversion process, which is called segregation. When the distribution of metal in the solid phase is less than that in the liquid phase, the solid phase metal is purified. The crystallization purification of metal gallium is based on this principle, that is, in the process of conversion of liquid metal gallium to solid metal gallium, the distribution of impurity elements in the solid phase is reduced, so as to realize the purification of metal gallium. This segregation purification process is affected by the speed and proportion of solid phase conversion. The speed of solid phase conversion can be called crystallization speed, and the proportion of solid phase conversion can be called crystallization rate. Therefore, the crystallization speed and crystallization rate need to be regulated to realize the sufficient distribution of impurities and ensure the purification effect.

[0039] In some embodiments, the temperature of the inner temperature region is 30-40°C;

[0040] The temperature of the outer temperature region is 20-29°C;

[0041] The initial temperature of the electrolytic gallium during the gradient crystallization is 30-40°C.

[0042] In some embodiments of the present disclosure, the temperature field of the electrolytic gallium for gradient crystallization purification is composed of an inner temperature region and an outer temperature region, and the gradient crystallization purified gallium is arranged between the two temperature fields. The outer temperature region provides a supercooled temperature environment lower than the melting point of the gallium, so that the gallium near the outer temperature region side solidifies and continuously crystallizes inward by the effect of heat conduction; the inner temperature region provides a high-temperature temperature environment higher than the melting point of the gallium, so that the gallium near the inner temperature region side does not crystallize, and the crystallization of the gallium near the supercooled side is prevented by the effect of temperature conduction.

[0043] In some embodiments of the present disclosure, the temperature of the inner temperature region can be 30-40°C, and the temperature of the inner temperature region for gradient crystallization purification of the gallium is set to be higher than the melting point of the gallium, so as to adjust the crystallization speed of the electrolytic gallium; if the temperature of the inner temperature region is too high and higher than 40°C, the heat released by the inner temperature region can be too much to offset the low-temperature crystallization temperature field of the outer temperature region, so that the electrolytic gallium is difficult to realize the crystallization process, thereby causing the electrolytic gallium to be unable to perform crystallization purification; if the temperature of the inner temperature region is too low and lower than 30°C, the heat released by the inner temperature region can be too little to adjust the crystallization speed of the electrolytic gallium, which can cause the crystallization speed of the gallium to be too fast and affect the purification effect of the gallium.

[0044] For example, the temperature of the inner temperature region can be 30°C, 32°C, 34°C, 36°C, 38°C, 40°C, etc.

[0045] In some embodiments of the present disclosure, the temperature of the outer temperature region can be 20-29°C, and the temperature of the outer temperature region is adjusted to be lower than the melting point of the gallium, so that the electrolytic gallium near the outer temperature region side forms crystals, and based on the principle of temperature conduction, the electrolytic gallium gradually crystallizes inward from the side near the outer temperature field, and purification is realized in the process of crystallization. If the temperature of the outer temperature region is too low and lower than 20°C, the crystallization speed of the gallium can be too fast, which can affect the crystallization purification effect of the gallium. If the temperature of the outer temperature region is too high and higher than 29°C, the crystallization of the gallium can be too slow or even not occur due to the synergistic effect with the high-temperature temperature field inside, which can make it difficult to realize the purpose of crystallization purification.

[0046] For example, the temperature of the outer temperature region can be 20°C, 22°C, 24°C, 26°C, 28°C, 29°C, etc.

[0047] In some embodiments of the present disclosure, the initial temperature of the electrolytic gallium during gradient crystallization can be 30-40°C, and in order to realize the conversion of the electrolytic gallium from liquid phase to solid phase and achieve purification in the process, it is necessary to ensure that the initial state of the crystallization of the gallium is completely liquid.

[0048] Exemplarily, the initial temperature of the gradient crystallization of the electrolytic gallium can be 30℃, 32℃, 34℃, 36℃, 38℃, 40℃, etc.

[0049] In some embodiments, the process parameters of the gradient crystallization include: a single crystallization time of 4h-10h, a single crystallization rate of 80%-90%, a crystallization number of 3-7 times, and a cumulative crystallization time of 12h-60h.

[0050] In some embodiments of the present disclosure, the crystallization purification of metallic gallium is closely related to the crystallization speed and the final crystallization rate (the weight ratio of the crystallized solid phase to the raw material). In theory, slowing down the crystallization speed and controlling a lower crystallization rate can make the purity of the obtained crystallized solid phase metallic gallium higher. However, due to the implementation conditions of the internal and external temperature field control, it is difficult to achieve the ideal slow crystallization purpose in the internal and external temperature fields, and it is difficult to purify the metallic gallium to more than 7N purity through one crystallization purification. Therefore, the gradient crystallization (multiple repeated crystallization and a crystallization number of 3-7 times) method can be used. Each time, the liquid phase metallic gallium with high impurity content is removed, and the purified solid phase metallic gallium is melted and then crystallized again. The gradient crystallization not only improves the crystallization purification effect and makes the control of the temperature field easy to achieve, but also objectively achieves the purpose of reducing the crystallization speed. Taking the electrolytic gallium with Fe impurity content less than 20ppb as an example, through multiple repeated crystallization purification, while the cumulative crystallization rate is controlled at 40%-50%, the obtained high-purity metallic gallium can reach the purity level of 5ppb. The multiple repeated crystallization can prolong the crystallization time to more than 30 hours, so that the crystallization process is realized at a slower crystallization speed, and the crystallization purification effect of the metallic gallium can be purified to the purity level of 7N. In order to achieve the cumulative crystallization rate of 40%-50%, the single crystallization rate needs to be controlled at 80%-90%, and the repeated crystallization for 3-7 times can be realized. The single crystallization time of 4h-10h is targeted at meeting the final crystallization purification requirement, so as to ensure the crystallization speed and the efficiency of the electrolytic gallium crystallization purification.

[0051] Exemplarily, in the process parameters of the repeated multiple gradient crystallization, the single crystallization time can be 4h, 5h, 6h, 7h, 8h, 9h, 10h, etc., the single crystallization rate can be 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, etc., the crystallization number can be 3 times, 4 times, 5 times, 6 times, 7 times, etc., and the cumulative crystallization time can be 12h, 14h, 16h, 18h, 20h, 25h, 30h, 35h, 40h, 45h, 50h, 55h, 60h, etc.

[0052] In some embodiments, the electrolytic gallium meets the following indexes: the purity of the electrolytic gallium is 6N, and the Fe content in the electrolytic gallium is less than 20ppb.

[0053] In some embodiments of the present disclosure, the purity of the gallium raw material can reach 6N level after the first and second electrolysis, and the Fe content in the electrolytic gallium can be less than 20 ppb. Further, through gradient crystallization, the purity of the high-purity gallium can reach more than 7N.

[0054] In a second aspect, a system for purifying gallium according to some embodiments of the present disclosure is adapted to the method of any one of the preceding embodiments. FIG. 2 shows a structural schematic diagram of a system for purifying gallium according to some embodiments of the present disclosure. As shown in FIG. 2, the system includes an electrolytic tank 1 and a crystallization tank 2. The electrolytic tank 1 is internally provided with an electrolysis zone 11. The height of the electrolysis zone 11 is lower than the depth of the electrolytic tank 1, and the electrolysis zone 11 is immersed in an electrolyte. FIG. 3 shows a structural schematic diagram of the electrolysis zone of the electrolytic tank of the system for purifying gallium according to some embodiments of the present disclosure. As shown in FIG. 3, the electrolysis zone 11 includes an anode zone 111, a first cathode zone 112, and a second cathode zone 113. The anode zone 111 is disposed at the outermost layer of the electrolysis zone 11. The first cathode zone 112 is disposed at the innermost layer of the electrolysis zone 11. The second cathode zone 113 is disposed between the anode zone 111 and the first cathode zone 112. The discharge port of the electrolytic tank 1 is disposed in the second cathode zone 113, the feed port of the electrolytic tank 1 is disposed in the anode zone 111, and the discharge port of the electrolytic tank 1 is in communication with the feed port of the crystallization tank 2.

[0055] In some embodiments of the present disclosure, the first and second electrolysis is achieved by the electrolytic tank 1 described above. The electrolysis zone 11 of gallium is internally provided in the electrolytic tank 1. The height of the electrolysis zone 11 is lower than the depth of the electrolytic tank 1. The electrolysis zone 11 can be isolated into the anode zone 111, the first cathode zone 112, and the second cathode zone 113 by the organic glass plate. The anode zone 111, the first cathode zone 112, and the second cathode zone 113 can be completely isolated by the organic glass plate, and at the same time, these zones are immersed in the electrolyte (i.e., the height of the added electrolyte is higher than the height of the electrolysis zone 11), and an electrolytic loop is formed by the electrolyte. The high-impurity-content electrolytic gallium precipitated during the first electrolysis is isolated in the first cathode zone 112, avoiding contamination of the second cathode zone 113. At the same time, the purified electrolyte containing a set of gallate ions obtained by the first electrolysis can be transferred by the action of the cathode electrode (i.e., the purified electrolyte containing a set of gallate ions obtained by the first electrolysis is transferred from the first cathode zone 112 to the second cathode zone 113), realizing the conversion from the first electrolysis to the second electrolysis in the same electrolytic tank 1, avoiding the material transfer in the conversion process from the first electrolysis to the second electrolysis, and playing a positive role in the continuous and stable process of gallium electrolytic purification.

[0056] The metal gallium is electrolyzed, the metal gallium to be electrolyzed is added into the anode area 111 of the electrolysis area 11 of the electrolytic tank 1 through the feeding port, and then the electrolyte is filled into the electrolytic tank 1 to make the electrolysis area 11 completely immersed in the electrolyte. The platinum-gold electrode connected to the positive electrode is inserted into the metal gallium raw material of the anode area 111, and the other platinum-gold electrode connected to the negative electrode is inserted into the first cathode area 112 to perform the first electrolysis. When the GaO2- concentration in the electrolyte reaches a set value, the platinum-gold electrode of the first cathode area 112 is taken out, and the high-impurity-content electrolytic gallium electrolyzed in the first cathode area 112 is removed, and the first electrolysis is completed. After the first electrolysis is completed, the platinum-gold electrode of the first cathode area 112 is cleaned and inserted into the second cathode area 113 to perform the second electrolysis. After the second electrolysis is completed, the electrolytic gallium after electrolysis and purification is collected from the discharge port. Further, a small amount of high-purity gallium with a purity of 6N or above can be added to the second cathode area 113 to make it effectively contact with the platinum-gold electrode, thereby increasing the cathode electrolysis area.

[0057] In some embodiments, the crystallization tank 2 comprises a heating area 21, a crystallization area 22 and a cooling area 23; the heating area 21 is arranged in the innermost layer of the crystallization tank 2, the cooling area 23 is arranged in the outermost layer of the crystallization tank 2, and the crystallization area 22 is arranged between the heating area 21 and the cooling area 23; the feeding port of the crystallization tank 2 is arranged in the crystallization area 22.

[0058] In some embodiments of the present disclosure, the crystallization tank 2 comprises a heating area 21, a crystallization area 22 and a cooling area 23, the crystallization area 22 is arranged between the crystallization area 22 and the cooling area 23, a directional temperature field can be formed, the cooling area 23 provides a temperature area lower than the melting point of metal gallium, corresponding to the outer temperature area described above, so that the liquid metal gallium lower than the melting point of metal gallium solidifies; the heating area 21 provides a temperature area higher than the melting point of metal gallium, corresponding to the inner temperature area described above, thereby controlling the crystallization rate through the mutual offset of the heating area 21 and the cooling area 23 in the solid-liquid phase state transformation process of metal gallium, ending the crystallization at a single crystallization rate, removing the liquid-phase metal gallium containing impurities, and continuing to repeat the crystallization process after melting the remaining solid-phase metal gallium until the purity of the solid-phase metal gallium reaches the requirement. Further, the heating area 21 can be a barrel-shaped device filled with water, which has a heating element inside to meet the requirements of the temperature field, and the barrel-shaped device can be stirred up and down through a mechanical device connected thereto to play a stirring role, thereby better assisting in controlling the crystallization rate and crystallization time of the electrolytic gallium.

[0059] In some embodiments of the present disclosure, the system for purifying metal gallium is implemented based on the method for purifying metal gallium described above. The specific steps of the method for purifying metal gallium can refer to the above-mentioned embodiments. Since the system for purifying metal gallium adopts part or all of the technical solutions of the above-mentioned embodiments, it at least has all the beneficial effects brought by the technical solutions of the above-mentioned embodiments, and will not be described here.

[0060] The present disclosure will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present disclosure and not to limit the scope of the present disclosure. The experimental methods not specified in the following examples are generally determined according to the industry standard. If there is no corresponding industry standard, it is determined according to the general international standard, the conventional condition, or according to the condition suggested by the manufacturer.

[0061] Embodiment 1

[0062] A method for purifying metal gallium, the purity of the raw material metal gallium is 4N, comprising the following steps:

[0063] S1, using an electrolyte to perform first electrolysis on part of the metal gallium to obtain a purified electrolyte containing a set amount of gallate ions; wherein the process parameters of the first electrolysis are as follows: the electrolyte is 220 g / L NaOH electrolyte, the electrolysis temperature is 30°C, the current density is 210 A / m 2 , and the electrolysis time is 6 days;

[0064] S2, using the purified electrolyte containing a set amount of gallate ions to perform second electrolysis on the remaining metal gallium to obtain electrolytic gallium; wherein the process parameters of the second electrolysis are as follows: the electrolysis temperature is 30°C, the current density is 210 A / m 2 , and the electrolysis time is 18 days; the purity of the electrolytic gallium is 6N, and the Fe content is 9 ppb;

[0065] S3, performing gradient crystallization on the electrolytic gallium to remove impurity metals in the electrolytic gallium to obtain high-purity metal gallium; the gradient crystallization step can include: placing the electrolytic gallium between an inner temperature region and an outer temperature region to perform gradient crystallization on the electrolytic gallium to remove impurity metals in the electrolytic gallium to obtain high-purity metal gallium; wherein the temperature of the inner temperature region is higher than the melting point of the metal gallium, and the temperature of the outer temperature region is lower than the melting point of the metal gallium; the temperature of the inner temperature region is 32°C; the temperature of the outer temperature region is 27°C; the initial temperature of the electrolytic gallium during gradient crystallization is 40°C; the single crystallization time is 9 hours, the single crystallization rate is 80%, the cumulative crystallization time corresponding to 4 times of repeated crystallization is 36 hours, and the final yield of solid gallium is 40.9%.

[0066] Embodiment 2

[0067] A method for purifying metal gallium, the purity of the raw material metal gallium is 4N, comprising the following steps:

[0068] S1, using an electrolyte to perform first electrolysis on part of the metallic gallium to obtain a purified electrolyte containing a set gallate ion content; wherein the process parameters of the first electrolysis are as follows: the electrolyte is a 240 g / L NaOH electrolyte, the electrolysis temperature is 30°C, the current density is 180 A / m 2 , and the electrolysis time is 5 days;

[0069] S2, using the purified electrolyte containing the set gallate ion content to perform second electrolysis on the remaining metallic gallium to obtain electrolytic gallium; wherein the process parameters of the second electrolysis are as follows: the electrolysis temperature is 30°C, the current density is 180 A / m 2 , and the electrolysis time is 16 days; the purity of the electrolytic gallium is 6N, and the Fe content is 12 ppb;

[0070] S3, performing gradient crystallization on the electrolytic gallium to remove impurity metals in the electrolytic gallium to obtain high-purity metallic gallium; the gradient crystallization step can include: placing the electrolytic gallium between an inner temperature region and an outer temperature region to perform gradient crystallization on the electrolytic gallium to remove impurity metals in the electrolytic gallium to obtain high-purity metallic gallium; wherein the temperature of the inner temperature region is higher than the melting point of the metallic gallium, and the temperature of the outer temperature region is lower than the melting point of the metallic gallium; the temperature of the inner temperature region is 31°C; the temperature of the outer temperature region is 28°C; the initial temperature of the electrolytic gallium during the gradient crystallization is 40°C; the single crystallization time is 8 hours, the single crystallization rate is 86%, the cumulative crystallization time corresponding to 5 repeated crystallizations is 40 hours, and the final solid gallium yield is 47%.

[0071] Example 3

[0072] A method for purifying metallic gallium, the purity of the raw material metallic gallium being 4N, comprising the following steps:

[0073] S1, using an electrolyte to perform first electrolysis on part of the metallic gallium to obtain a purified electrolyte containing a set gallate ion content; wherein the process parameters of the first electrolysis are as follows: the electrolyte is a 240 g / L NaOH electrolyte, the electrolysis temperature is 30°C, the current density is 180 A / m 2 , and the electrolysis time is 5 days;

[0074] S2, using the purified electrolyte containing the set gallate ion content to perform second electrolysis on the remaining metallic gallium to obtain electrolytic gallium; wherein the process parameters of the second electrolysis are as follows: the electrolysis temperature is 30°C, the current density is 180 A / m 2 , and the electrolysis time is 16 days; the purity of the electrolytic gallium is 6N, and the Fe content is 12 ppb;

[0075] S3, gradient crystallization is performed on the electrolytic gallium to remove impurity metals in the electrolytic gallium, and high-purity metal gallium is obtained; the gradient crystallization step can include: placing the electrolytic gallium between an inner temperature region and an outer temperature region to perform gradient crystallization on the electrolytic gallium to remove impurity metals in the electrolytic gallium, and obtain high-purity metal gallium; wherein the temperature of the inner temperature region is higher than the melting point of metal gallium, and the temperature of the outer temperature region is lower than the melting point of metal gallium; the temperature of the inner temperature region is 32℃; the temperature of the outer temperature region is 24℃; the initial temperature of the electrolytic gallium during gradient crystallization is 40℃; the single crystallization time is 8.5 hours, the single crystallization rate is 82%, the cumulative crystallization time corresponding to 4 times of repeated crystallization is 34 hours, and the final yield of solid gallium is 45.2%.

[0076] Example 4

[0077] A method for purifying metal gallium, the purity of the raw material metal gallium being 4N, comprising the following steps:

[0078] S1, a first electrolysis is performed on part of the metal gallium using an electrolyte to obtain a purified electrolyte containing a set amount of gallate ions; wherein the process parameters of the first electrolysis are as follows: the electrolyte is a 220g / L NaOH electrolyte, the electrolysis temperature is 30℃, the current density is 240A / m 2 , and the electrolysis time is 4 days;

[0079] S2, a second electrolysis is performed on the remaining metal gallium using the purified electrolyte containing a set amount of gallate ions to obtain electrolytic gallium; wherein the process parameters of the second electrolysis are as follows: the electrolyte is a NaOH electrolyte, the electrolysis temperature is 30℃, the current density is 240A / m 2 , and the electrolysis time is 14 days; the purity of the electrolytic gallium is 6N, and the Fe content is 14ppb;

[0080] S3, gradient crystallization is performed on the electrolytic gallium to remove impurity metals in the electrolytic gallium, and high-purity metal gallium is obtained; the gradient crystallization step can include: placing the electrolytic gallium between an inner temperature region and an outer temperature region to perform gradient crystallization on the electrolytic gallium to remove impurity metals in the electrolytic gallium, and obtain high-purity metal gallium; wherein the temperature of the inner temperature region is higher than the melting point of metal gallium, and the temperature of the outer temperature region is lower than the melting point of metal gallium; the temperature of the inner temperature region is 33℃; the temperature of the outer temperature region is 25℃; the initial temperature of the electrolytic gallium during gradient crystallization is 40℃; the single crystallization time is 8.5 hours, the single crystallization rate is 85%, the cumulative crystallization time corresponding to 5 times of repeated crystallization is 42 hours, and the final yield of solid gallium is 44.4%.

[0081] Example 5

[0082] Based on example 1, a system for purifying metal gallium includes an electrolytic cell 1 and a crystallization cell 2. The electrolytic cell 1 has an electrolysis zone 11 inside, the height of the electrolysis zone 11 is lower than the depth of the electrolytic cell 1, and the electrolysis zone 11 can be immersed in the electrolyte after adding the electrolyte. The electrolysis zone 11 includes an anode zone 111, a first cathode zone 112, and a second cathode zone 113. The anode zone 111 is arranged at the outermost layer of the electrolysis zone 11. The first cathode zone 112 is arranged at the innermost layer of the electrolysis zone 11. The second cathode zone 113 is arranged between the anode zone 111 and the first cathode zone 112. The discharge port of the electrolytic cell 1 is arranged in the second cathode zone 113, the feed port of the electrolytic cell 1 is arranged in the anode zone 111, and the discharge port of the electrolytic cell 1 is in communication with the feed port of the crystallization cell 2. The crystallization cell 2 includes a heating zone 21, a crystallization zone 22, and a cooling zone 23. The heating zone 21 is arranged at the innermost layer of the crystallization cell 2, the cooling zone 23 is arranged at the outermost layer of the crystallization cell 2, and the crystallization zone 22 is arranged between the heating zone 21 and the cooling zone 23. The feed port of the crystallization zone 22 is arranged in the crystallization zone 22. The system is used to implement the method of example 1, which includes the following steps:

[0083] First electrolysis: The raw material metal gallium is arranged in the anode zone 111 from the feed port of the electrolytic cell 1, the anode electrode and the cathode electrode are respectively inserted into the metal gallium in the anode zone 111 and the first cathode zone 112, the electrolyte of 220 g / L NaOH is added, and then the direct current is connected to start electrolysis. The electrolysis temperature is maintained at 30℃, the current density is 210A / m 2 , the first electrolysis time is 6 days, the cathode electrode is removed after the first electrolysis is completed, and the electrolytic material in the first cathode zone 112 is extracted with a clean suction tube.

[0084] Second electrolysis: The state of the anode zone 111 and the electrolyte is maintained unchanged, a certain amount of high-purity gallium is arranged in the second cathode zone 113, the cleaned cathode electrode is inserted into the high-purity gallium in the second cathode zone 113, the direct current is connected to start electrolysis, the electrolysis temperature is maintained at 30℃, and the current density is 210A / m 2 , the depth of the electrolysis is 18 days, and the electrolytic gallium after purification is collected from the discharge port after the depth of the electrolysis is completed.

[0085] Gradient crystallization: The electrolytic gallium is placed in the crystallization cell 2, the initial temperature of the electrolytic gallium is 40℃, the surface of the gallium is covered with dilute hydrochloric acid solution to reduce the introduction of impurities in the environment, the temperature of the heating zone 21 is 32℃, the temperature of the cooling zone 23 (cooling water) is 27℃, and the cumulative crystallization time of 4 times of repeated crystallization is 36 hours.

[0086] Comparative example 1

[0087] A method for purifying metal gallium, the purity of the raw material metal gallium is 4N, including the following steps:

[0088] Part of the metal gallium is subjected to first electrolysis using an electrolyte to obtain a purified electrolyte containing a set gallate ion content; wherein the process parameters of the first electrolysis are as follows: the electrolyte is 220 g / L of NaOH electrolyte, the electrolysis temperature is 30°C, the current density is 210 A / m2, and the electrolysis time is 24 days; the purity of the electrolytic gallium is 6N, and the Fe content is 33 ppb;

[0089] The electrolytic gallium is subjected to gradient crystallization to remove impurity metals in the electrolytic gallium to obtain high-purity metal gallium; the gradient crystallization step includes: placing the electrolytic gallium between an inner temperature region and an outer temperature region to perform gradient crystallization on the electrolytic gallium to remove impurity metals in the electrolytic gallium to obtain high-purity metal gallium; wherein the temperature of the inner temperature region is higher than the melting point of metal gallium, and the temperature of the outer temperature region is lower than the melting point of metal gallium; the temperature of the inner temperature region is 32°C; the temperature of the outer temperature region is 25°C; the initial temperature of the electrolytic gallium during gradient crystallization is 40°C; the single crystallization time is 9 hours, the secondary crystallization rate is 82%, and the cumulative crystallization time corresponding to 4 times of repeated crystallization is 36 hours.

[0090] The solid gallium finally obtained in Examples 1-5 and Comparative Example 1 is subjected to purity detection by glow discharge mass spectrometry (GDMS), and the main element Ga is 99.99999+%; the detection results of the contents of 19 kinds of impurity elements of 7N high-purity gallium as specified in the test method in the current national standard GB / T 10118-2023 are shown in Table 1, and it can be seen that the purity of the solid gallium obtained in Examples 1-4 all reaches 7N, which meets the national standard, while the purity of the solid gallium obtained in Comparative Example 1 does not reach 7N.

[0091] Table 1: Impurity element contents in the solid gallium obtained in Examples 1-4 and Comparative Example 1 (unit: ppb)

[0092] The method and system for purifying metal gallium according to some embodiments of the present disclosure at least have the following technical effects or advantages:

[0093] (1) A completely isolated first cathode region and a second cathode region are established during the electrolysis process, and the impurity-rich material precipitated in the first electrolysis stage will not contaminate the electrolytic purification cathode material in the second electrolysis stage, achieving the effect of purifying the electrolyte during the first electrolysis and avoiding contamination of the electrolysis process by impurities precipitated in the cathode.

[0094] (2) In the crystallization process, the electrolytic gallium is gradually directionally crystallized from the crystallization zone to the central region by establishing a directional temperature field, and the controllability of the crystallization speed and the crystallization rate is strong. At the same time, the relative disturbance of the liquid phase gallium and the solid phase gallium is realized through the mechanical device connected thereto, which plays a stirring role and better assists in realizing the control of the crystallization speed and the crystallization time of the electrolytic gallium. In addition, the problem of impurities remaining in the branch-shaped crystals in the front of the crystallization surface can be solved, and the crystallization purity is further improved.

[0095] (3) The gradient purification of the metal gallium is realized by reasonably controlling the related process parameters of the first electrolysis, the second electrolysis and the gradient crystallization, and the high-purity gallium product with a purity of 7N or more is stably prepared.

[0096] In summary, the method and system for purifying metal gallium according to some embodiments of the present disclosure have the following advantages compared with related technologies:

[0097] The method for purifying metal gallium disclosed herein, the purity of the metal gallium is ≤4N, the method comprises: using an electrolyte to perform first electrolysis on part of the metal gallium to obtain a purified electrolyte containing a set gallate ion content; using the purified electrolyte containing the set gallate ion content to perform second electrolysis on the remaining metal gallium to obtain electrolytic gallium; and performing gradient crystallization on the electrolytic gallium to remove impurity metals in the electrolytic gallium and obtain high-purity metal gallium. In the purification process, part of the metal gallium is first electrolyzed using an electrolyte, which can obtain a set gallate ion content while removing impurity metals in the electrolyte with a higher electrode potential than gallium, thereby avoiding pollution of the electrolytic purification of the electrolytic gallium in the second electrolysis stage, thereby achieving the purpose of purifying the electrolyte while generating gallate ions in the first electrolysis, thereby obtaining a purified electrolyte containing a set gallate ion content. The remaining metal gallium is second electrolyzed using the purified electrolyte containing the set gallate ion content, which fully reduces the gallate ion to electrolytic gallium with a higher purity of 6N. The electrolytic gallium with a higher purity is subjected to gradient crystallization, which can better control the crystallization speed and crystallization rate of the electrolytic gallium, and the electrolytic gallium is repeatedly subjected to the gradient crystallization. Each crystallization purification removes liquid phase metal gallium with high impurity content, and the purified solid phase metal gallium is melted and then subjected to crystallization purification again, which not only improves the crystallization purification effect, but also achieves the purpose of reducing the crystallization speed, thereby better realizing slow crystallization of the electrolytic gallium, and greatly removing impurity metals in the electrolytic gallium, and finally obtaining high-purity metal gallium with a purity of 7N or more.

[0098] The foregoing is merely illustrative of the various implementations of the present disclosure and the general principles thereof. Numerous modifications can be made to these illustrations, and equivalents can be substituted therefor, without departing from the scope of the present disclosure. The specific embodiments commensurate with the specific application are intended to be illustrative only and not limiting of the scope of the application as set forth in the following claims.

Claims

1. A method for purifying metallic gallium with a purity of ≤4N, comprising: performing first electrolysis on part of the metallic gallium using an electrolyte to obtain a purified electrolyte containing a set gallate ion content; performing second electrolysis on the remaining metallic gallium using the purified electrolyte containing the set gallate ion content to obtain electrolytic gallium; and performing gradient crystallization on the electrolytic gallium to remove impurity metals in the electrolytic gallium to obtain high-purity metallic gallium. The set gallate ion content is ≥30g / L. The electrolytic gallium meets the following indexes: the purity of the electrolytic gallium is 6N, and the Fe content in the electrolytic gallium is ≤20ppb. The performing gradient crystallization on the electrolytic gallium to remove impurity metals in the electrolytic gallium to obtain high-purity metallic gallium comprises: placing the electrolytic gallium in a crystallization region between an inner temperature region and an outer temperature region, and performing gradient crystallization on the electrolytic gallium to remove impurity metals in the electrolytic gallium to obtain high-purity metallic gallium; wherein the temperature of the inner temperature region is higher than the melting point of the metallic gallium, and the temperature of the outer temperature region is lower than the melting point of the metallic gallium. The temperature of the inner temperature region is 30-40℃.

2. The method of claim 1, wherein, The temperature of the outer temperature region is 20-29℃.

3. The method of claim 1, wherein, The process parameters of the first electrolysis include: the concentration of electrolyte is 150g / L-260g / L, the current density is 130A / m 2 ~250A / m 2 , the electrolysis time is 3 days-9 days, and the electrolysis temperature is above 30℃.

4. The method of claim 1, wherein, The process parameters of the second electrolysis include: the concentration of electrolyte is 150g / L-260g / L, the current density is 130A / m 2 -250A / m 2 , the electrolysis time is 12 days-25 days, and the electrolysis temperature is above 30℃.

5. The method of claim 1, wherein, The initial temperature of the electrolytic gallium during the gradient crystallization is 30-40℃.

6. The method of claim 1, wherein, The process parameters of the gradient crystallization include: a single crystallization time of 4-10h, a single crystallization rate of 80-90%, a crystallization number of 3-7, and a cumulative crystallization time of 12-60h. 9.A system for purifying metallic gallium, adapted to the method of any one of claims 1-8, comprising an electrolytic cell (1) and a crystallization cell (2).

7. The method of claim 6, wherein, The electrolytic cell (1) is internally provided with an electrolysis region (11) with a height lower than the depth of the electrolytic cell (1), and the electrolysis region (11) is immersed in an electrolyte. The anode region (111) is arranged at the outermost layer of the electrolysis region (11), the first cathode region (112) is arranged at the innermost layer of the electrolysis region (11), and the second cathode region (113) is arranged between the anode region (111) and the first cathode region (112). The discharge port of the electrolytic cell (1) is arranged at the second cathode region (113), the feed port of the electrolytic cell (1) is arranged at the anode region (111), and the discharge port of the electrolytic cell (1) is in communication with the feed port of the crystallization cell (2).

8. The method of claim 6, wherein, The crystallization cell (2) comprises a heating region (21), a crystallization region (22), and a cooling region (23); wherein the heating region (21) is arranged at the innermost layer of the crystallization cell (2), the cooling region (23) is arranged at the outermost layer of the crystallization cell (2), the crystallization region (22) is arranged between the heating region (21) and the cooling region (23), and the feed port of the crystallization cell (2) is arranged at the crystallization region (22). ​ ​ The electrolysis zone (11) comprises an anode zone (111), a first cathode zone (112), and a second cathode zone (113); wherein, ​ ​ 10. The system of claim 9, wherein, ​

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