Method and system for purifying metal gallium

Abstract

The invention provides a method and system for purifying metal gallium, the purity of the metal gallium is smaller than or equal to 4N, the method comprises the steps that part of the metal gallium is subjected to first electrolysis through electrolyte, and purified electrolyte with the set gallate ion content is obtained; the purified electrolyte containing the set gallate ion content is used for conducting second electrolysis on the remaining metal gallium, and electrolytic gallium is obtained; and carrying out gradient crystallization on the electrolytic gallium to remove impurity metals in the electrolytic gallium so as to obtain the high-purity metal gallium. According to the method, gallium metal is purified to the purity of 7N or above.

Description

Technical Field

[0001] The present application relates to the technical field of high-purity gallium purification, and in particular to a method and system for purifying metallic gallium. Background Art

[0002] Gallium is a rare metal with high boiling point and low melting point. Industrial production uses industrial-grade gallium as raw material, and further purifies it through electrolytic refining, crystallization, vacuum distillation, zone melting and other process methods to produce high-purity gallium. High-purity gallium is mainly used in wireless communications, optoelectronic semiconductors and solar cells in the form of compounds such as gallium arsenide, gallium phosphide and gallium nitride, 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 major harmful impurities such as Cu, Zn, Fe and Si; and semi-insulating gallium arsenide single crystals used to make integrated circuit (IC) substrates require the purity of high-purity gallium to reach 7N or above. The impurities in high-purity gallium are analyzed by glow discharge mass spectrometry (GDMS). Except for C, N, O and Ta, the content of major harmful impurities must be within 5×10 －7 %, and the contents of other impurities must be below the detection limit.

[0003] Due to the importance of high-purity gallium in applications and the complexity of its purification technology, how to purify and prepare high-purity gallium with a purity of 7N or above using metallic gallium as raw material has become a technical problem that urgently needs to be solved in this field. Summary of the invention

[0004] The present application provides a method and system for purifying metal gallium to solve the following technical problem: how to purify metal gallium to above 7N.

[0005] In a first aspect, the present application provides a method for purifying metallic gallium, wherein the purity of the metallic gallium is ≤4N, and the method comprises:

[0006] Using an electrolyte to perform a first electrolysis on a portion of the metal gallium to obtain a purified electrolyte containing a set gallate ion content;

[0007] Using the purified electrolyte containing a set gallate ion content to perform a second electrolysis on the remaining metal gallium to obtain electrolytic gallium;

[0008] The electrolytic gallium is subjected to gradient crystallization to remove impurity metals in the electrolytic gallium to obtain high-purity metallic gallium.

[0009] Optionally, the gallate ion content is set to be ≥30 g / L.

[0010] Optionally, the process parameters of the first electrolysis include: the concentration of the electrolyte is 150 g / L to 260 g / L, the current density is 130 A / m2 ~250A / m 2 The electrolysis time is 3 to 9 days, and the electrolysis temperature is above 30°C.

[0011] Optionally, the process parameters of the second electrolysis include: the concentration of the electrolyte is 150 g / L to 260 g / L, the current density is 130 A / m 2 ~250A / m 2 The electrolysis time is 12 to 25 days, and the electrolysis temperature is above 30°C.

[0012] Optionally, the step of subjecting the electrolytic gallium to gradient crystallization to remove impurity metals in the electrolytic gallium to obtain high-purity metallic gallium comprises:

[0013] The electrolytic gallium is placed in a crystallization region between the inner temperature region and the outer temperature region, and the electrolytic gallium is subjected to gradient crystallization to remove impurity metals in the electrolytic gallium to obtain high-purity metallic gallium; wherein,

[0014] 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.

[0015] Optionally, the temperature of the inner temperature area is 30°C to 40°C;

[0016] The temperature of the outer temperature area is 20°C to 29°C;

[0017] The initial temperature of the electrolytic gallium during the gradient crystallization is 30°C to 40°C.

[0018] Optionally, the process parameters of the gradient crystallization include: a single crystallization time of 4 hours to 10 hours, a single crystallization rate of 80% to 90%, a number of crystallizations of 3 to 7 times, and a cumulative crystallization time of 12 hours to 60 hours.

[0019] Optionally, the electrolytic gallium meets the following indicators: the purity of the electrolytic gallium is 6N, and the Fe content in the electrolytic gallium is less than 20 ppb.

[0020] In a second aspect, the present application provides a system for purifying metallic gallium, the system being adapted to the method described in any one of the embodiments of the first aspect, the system comprising an electrolytic cell 1 and a crystallization cell 2;

[0021] An electrolysis zone 11 is arranged inside the electrolytic cell 1. The height of the electrolysis zone 11 is lower than the depth of the electrolytic cell 1. The electrolysis zone 11 is immersed in the electrolyte. The electrolysis zone 11 includes an anode zone 111, a first cathode zone 112 and a second cathode zone 113.

[0022] The anode area 111 is arranged at the outermost layer of the electrolysis area 11; the first cathode area 112 is arranged at the innermost layer of the electrolysis area 11; the second cathode area 113 is arranged between the anode area 111 and the first cathode area 112; the discharge port of the electrolytic cell 1 is arranged at the second cathode area 113, the feed port of the electrolytic cell 1 is arranged at the anode area 111, and the discharge port of the electrolytic cell 1 is connected to the feed port of the crystallization cell 2.

[0023] Optionally, the crystallization tank 2 includes a heating zone 21, a crystallization zone 22 and a cooling zone 23; wherein the heating zone 21 is arranged at the innermost layer of the crystallization tank 2, the cooling zone 23 is arranged at the outermost layer of the crystallization tank 2, and the crystallization zone 22 is arranged between the heating zone 21 and the cooling zone 23;

[0024] The feed port of the crystallization tank 2 is arranged in the crystallization zone 22 .

[0025] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0026] The present application provides a method for purifying metallic gallium, wherein the purity of the metallic gallium is ≤4N, and the method comprises: using an electrolyte to perform a first electrolysis on a portion of the metallic gallium to obtain a purified electrolyte containing a set gallate ion content; using the purified electrolyte containing the set gallate ion content to perform a second electrolysis on the remaining metallic gallium to obtain electrolytic gallium; performing gradient crystallization on the electrolytic gallium to remove impurity metals in the electrolytic gallium to obtain high-purity metallic gallium. Using an electrolyte to perform a first electrolysis on a portion of the metallic gallium can obtain the set gallate ion content while removing impurity metals in the electrolyte with an electrode potential higher than gallium, thereby preventing the impurity metals from contaminating the electrolytic gallium purified by the electrolysis 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; using the purified electrolyte containing the set gallate ion content to perform a second electrolysis on the remaining metallic gallium, thereby fully reducing the gallate ions to 6N with a high purity. electrolytic gallium; the electrolytic gallium with high purity is subjected to gradient crystallization, and the gradient crystallization can better control the crystallization speed and crystallization rate of the electrolytic gallium, and the electrolytic gallium is repeatedly subjected to the gradient crystallization for multiple times, and the liquid-phase metal gallium with high impurity content is removed by each crystallization purification, and the purified solid-phase metal gallium is melted and then subjected to crystallization purification again, which can not only improve the effect of crystallization purification, but also achieve the purpose of reducing the crystallization speed, so as to better realize the slow crystallization of the electrolytic gallium, and then remove the impurity metals in the electrolytic gallium to a great extent, and finally obtain high-purity metal gallium with a purity of more than 7N. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0028] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0029] Figure 1 A schematic flow chart of a method for purifying metallic gallium provided in an embodiment of the present application;

[0030] Figure 2 A schematic diagram of the structure of a metal gallium crystal purification provided in an embodiment of the present application;

[0031] Figure 3 A schematic diagram of the structure of the electrolysis zone of an electrolytic cell of a system for purifying metallic gallium provided in an embodiment of the present application; wherein:

[0032] 1-electrolytic cell, 11-electrolytic zone, 111-anode zone, 112-first cathode zone, 113-second cathode zone, 2-crystallization cell, 21-heating zone, 22-crystallization zone, 23-cooling zone. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0034] Various embodiments of the present application may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity, and should not be understood as a rigid limitation on the scope of the present application; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numerical values ​​within the range. For example, the range description from 1 to 6 should be considered to have 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 numbers within the range, such as 1, 2, 3, 4, 5 and 6, which apply regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0035] In this document, the terms "upper", "lower", "left", "right", "front", "back", "top", "bottom", "inside", "outside", "vertical", "horizontal", "lateral", "longitudinal" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings. These terms are mainly used to better describe the present invention and its embodiments, and are not used to limit the indicated devices, elements or components to have a specific orientation, or to be constructed and operated in a specific orientation. In addition, in addition to being used to indicate an orientation or positional relationship, some of the above terms may also be used to indicate other meanings. For example, the term "upper" may also be used to indicate a certain dependency or connection relationship in some cases. For those of ordinary skill in the art, the specific meanings of these terms in the present invention can be understood according to the specific circumstances. In addition, the terms "installed", "set", "provided with", "connected", and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral structure; it can be a mechanical connection, or an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, or it can be internally connected between two devices, elements or components, or it can be not directly connected but only indicate the flow relationship between devices.

[0036] In addition, in the description of the present application, the terms "including", "comprising", etc. mean "including but not limited to". In this article, relational terms such as "first" and "second" are only used 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 these entities or operations. Unless otherwise specified, various raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0037] In a first aspect, the present application provides a method for purifying metallic gallium, wherein the purity of the metallic gallium is ≤4N. Figure 1 For a schematic diagram of a method for purifying gallium metal provided in an embodiment of the present application, see Figure 1 , the method comprising:

[0038] S1, using an electrolyte to perform a first electrolysis on a portion of the metal gallium to obtain a purified electrolyte containing a set gallate ion content;

[0039] In some embodiments, the gallate ions (GaO 2- ) content is ≥30g / L.

[0040] In the embodiment of the present application, the gallate ion content is set to be ≥30 g / L, which indicates that the electrolyte is used to perform a first electrolysis on a portion of the metal gallium to achieve a sufficient amount of GaO in the electrolyte. 2-, thereby ensuring the efficiency of the subsequent second electrolysis. 2- ) content can be 30g / L, 31g / L, 32g / L, 33g / L, 34g / L, 35g / L, etc.

[0041] In some embodiments, the process parameters of the first electrolysis include: the concentration of the electrolyte is 150 g / L to 260 g / L, the current density is 130 A / m 2 ~250A / m 2 The electrolysis time is 3 to 9 days, and the electrolysis temperature is above 30°C.

[0042] In the embodiment of the present application, in the electrolyte, metal gallium loses electrons at the anode to become gallate ions and enter the electrolyte, while at the cathode the gallate ions gain electrons and are reduced to metal gallium and precipitate at the cathode. Electrolysis mainly controls the relevant process parameters of electrolysis of metal gallium, including current density, electrolyte concentration, electrolysis time and electrolysis temperature. These process parameters affect the impurity control of electrolytic purification of metal gallium to a set degree. The first electrolysis represents pre-electrolysis, which can obtain the set gallate ion content while purifying the electrolyte; the concentration of the electrolyte can be 150g / L to 260g / L, which can avoid the rapid increase of impurity content such as Pb, Zn, Sn, Fe, etc. at the cathode of the first electrolysis due to the low concentration of the electrolyte and less than 150g / L, resulting in overflow of the electrolytic cell and pollution of the electrolysis process; and avoid the formation of crystals on the wall of the electrolytic cell due to the high concentration of the electrolyte and higher than 300g / L, causing the electrolysis environment to deteriorate, which is not conducive to electrolytic purification. The current density can be 130A / m 2 ~250A / m 2 , the first electrolysis can be fully realized while avoiding the current density being too high and exceeding 250A / m 2 This caused the impurity content of Pb, Zn, Sn, Fe, etc. in the cathode of the first electrolysis to increase rapidly, resulting in overflow of the electrolytic cell and contamination of the electrolysis process. In addition, the anode area caused GaO 2- If the concentration is too high, it is easy to have local oversaturated crystals covering the electrode, resulting in the precipitation of impurities. The electrolysis time of the first electrolysis can be 3 to 9 days. Sufficient electrolysis time of the first electrolysis can ensure that a sufficient amount of GaO is produced in the electrolyte. 2-, to ensure the efficiency of the subsequent second electrolysis; and if the electrolysis time is too long and exceeds 9 days, the metal gallium raw material may be lost, and the cathode produces too much gallium with high impurity concentration, which causes overflow of the electrolytic cell and pollutes the electrolysis process. The electrolysis temperature can be above 30°C. The melting point of metal gallium is 29.80°C. The electrolytic purification of metal gallium requires an electrolytic purification method in a molten state of metal gallium. In order to maintain the continuous electrolysis process of metal gallium, the electrolysis temperature should be kept higher than the melting point of metal gallium. Exemplarily, in the process parameters of the first electrolysis, the concentration of the electrolyte can be 150g / L, 160g / L, 170g / L, 180g / L, 190g / L, 200g / L, 210g / L, 220g / L, 230g / L, 240g / L, 250g / L, 260g / L, etc.; the current density can be 130A / m 2 , 150A / m 2 、170A / m 2 、190A / m 2 、210A / m 2 、230A / m 2 , 250A / m 2 etc.; 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°C, 31°C, 32°C, 33°C, 34°C, etc.

[0043] S2, using the purified electrolyte containing a set gallate ion content to perform a second electrolysis on the remaining metal gallium to obtain electrolytic gallium;

[0044] In some embodiments, the process parameters of the second electrolysis include: the concentration of the electrolyte is 150 g / L to 260 g / L, the current density is 130 A / m 2 ~250A / m 2 The electrolysis time is 12 to 25 days, and the electrolysis temperature is above 30°C.

[0045] In the embodiment of the present application, the second electrolysis is deep electrolysis to obtain electrolytic gallium. The concentration of the electrolyte, the current density and the electrolysis temperature control reasons in the second electrolysis are consistent with those in the first electrolysis. The electrolysis time in the second electrolysis can be 12 to 25 days, which can fully realize the second electrolysis. Since the impurities such as Pb, Zn, Sn, and Fe will increase significantly at the end of the second electrolysis, appropriately shortening the time of the second electrolysis is beneficial to improving the purity of the product. Exemplarily, in the process parameters of the second electrolysis, the concentration of the electrolyte can be 150g / L, 160g / L, 170g / L, 180g / L, 190g / L, 200g / L, 210g / L, 220g / L, 230g / L, 240g / L, 250g / L, 260g / L, etc.; the current density can be 130A / m 2 , 150A / m2 、170A / m 2 、190A / m 2 、210A / m 2 、230A / m 2 , 250A / m 2 etc.; 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°C, 31°C, 32°C, 33°C, 34°C, etc.

[0046] In addition, during the first electrolysis and the second electrolysis, the electrolysis voltage is kept stable by adjusting the concentration of the NaOH aqueous solution so that the positive and negative deviations do not exceed 5%.

[0047] The first electrolysis realizes the creation of a set content of GaO in the electrolyte solution. 2- Electrolytic solution is used to facilitate the subsequent electrolysis of metal gallium. At the same time, during the pre-electrolysis process, impurities (such as Cu, Zn, Sn, Fe, etc.) in the electrolyte solution are precipitated at the cathode to purify the electrolyte and create a pure electrolysis environment for the subsequent electrolysis. The first electrolysis and the second electrolysis work together to electropurify metal gallium below 4N to a purity level of 6N, further providing raw materials with low impurity content for subsequent crystallization purification, ensuring that after further crystallization purification, the purity of metal gallium can eventually be increased to above 7N.

[0048] S3, performing gradient crystallization on the electrolytic gallium to remove impurity metals in the electrolytic gallium to obtain high-purity metallic gallium.

[0049] In some embodiments, the step of subjecting the electrolytic gallium to gradient crystallization (repeated crystallization) to remove impurity metals in the electrolytic gallium to obtain high-purity metallic gallium comprises:

[0050] The electrolytic gallium is placed in a crystallization area between an inner temperature area and an outer temperature area to perform gradient crystallization on the electrolytic gallium to remove impurity metals in the electrolytic gallium and obtain high-purity metallic gallium; wherein the temperature of the inner temperature area is higher than the melting point of the metallic gallium, and the temperature of the outer temperature area is lower than the melting point of the metallic gallium.

[0051] In the embodiment of the present application, the electrolytic gallium is subjected to gradient crystallization according to the principle of metal segregation purification, that is, in the process of metal conversion from liquid phase to solid phase, the impurity elements in the metal will be redistributed in the solid and liquid phases of the metal during this conversion process, and this process is segregation. When the distribution in the solid phase is less than that in the liquid phase, the metal in the solid phase is purified. The crystallization and purification of metal gallium is based on this principle. In the process of converting liquid metal gallium into solid metal gallium, the distribution of impurity elements in the solid phase is reduced, thereby achieving the purification of metal gallium. This segregation purification process is affected by the speed and conversion ratio of the solid phase conversion, which is called the crystallization speed and crystallization rate. Therefore, it is necessary to regulate the crystallization speed to achieve sufficient impurity distribution and ensure the purification effect.

[0052] In some embodiments, the temperature of the internal temperature zone is 30°C to 40°C;

[0053] The temperature of the outer temperature area is 20°C to 29°C;

[0054] The initial temperature of the electrolytic gallium during the gradient crystallization is 30°C to 40°C.

[0055] In the embodiment of the present application, the electrolytic gallium crystallization purification temperature field is composed of two temperature environments, the inner and outer regions, and the metal gallium to be crystallized and purified is set in the middle of the two temperature fields. The outer temperature region provides a supercooled temperature environment below the melting point of the metal gallium, so that the metal gallium close to the outer temperature region solidifies and continues to crystallize inward through the effect of heat conduction; the inner temperature region provides a high temperature environment above the melting point of the metal gallium, so that the metal gallium close to the inner temperature region does not crystallize, and through the effect of temperature conduction, the metal gallium on the supercooled side is prevented from crystallizing inward.

[0056] The temperature of the inner temperature zone can be 30℃~40℃. The temperature of the inner temperature zone for metal gallium crystallization purification is set to a temperature higher than the melting point of metal gallium, in order to adjust the crystallization rate of electrolytic gallium; if the temperature of the inner temperature zone is too high and higher than 40℃, it may cause excessive heat release in the inner temperature zone, completely offsetting the low-temperature crystallization temperature field of the outer temperature, and electrolytic gallium is difficult to achieve the crystallization process; if the temperature of the inner temperature zone is too low and lower than 30℃, it may cause too little heat release in the inner temperature zone, making it difficult to adjust the crystallization rate of electrolytic gallium, causing the crystallization rate to be too fast, affecting the purification effect. Exemplarily, the temperature of the inner temperature zone can be 30℃, 32℃, 34℃, 36℃, 38℃, 40℃, etc. The temperature of the outer temperature zone can be 20℃~29℃, and the temperature of the outer temperature zone is adjusted to be lower than the temperature field of the melting point of metal gallium, so that the electrolytic gallium forms crystals on the side close to the outer temperature zone, and based on the principle of temperature conduction, the electrolytic gallium gradually crystallizes from the side close to the outer temperature field to the inside, and purification is achieved during the crystallization process. If the temperature of the outer temperature zone is too low and below 20°C, the crystallization speed will be too fast, affecting the crystallization purification effect. If the temperature of the outer temperature zone is too high and above 29°C, due to the synergistic effect with the internal high temperature temperature field, the crystallization is too slow or even no crystallization occurs, making it difficult to achieve the purpose of crystallization purification. Exemplarily, the temperature of the outer temperature zone can be 20°C, 22°C, 24°C, 26°C, 28°C, 29°C, etc. The initial temperature of electrolytic gallium during gradient crystallization can be 30°C to 40°C. In order to realize the transformation of electrolytic gallium from liquid phase to solid phase and realize purification in this process, it is necessary to ensure that the metal gallium is all liquid in the initial state of crystallization. Exemplarily, the initial temperature of electrolytic gallium during gradient crystallization can be 30°C, 32°C, 34°C, 36°C, 38°C, 40°C, etc.

[0057] In some embodiments, the process parameters of the gradient crystallization include: a single crystallization time of 4 hours to 10 hours, a single crystallization rate of 80% to 90%, 3 to 7 crystallization times, and a cumulative crystallization time of 12 hours to 60 hours.

[0058] In the embodiment of the present application, the crystallization purification of metal 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, the slower the crystallization speed and the lower the crystallization rate, the higher the purity of the crystallized solid phase metal gallium. However, due to the limitations of the implementation conditions of the internal and external temperature field control, it is difficult for the two internal and external temperature fields to achieve the ideal slow crystallization purpose, and it is difficult to purify the metal gallium to a purity of more than 7N after one crystallization purification. Therefore, the gradient crystallization (repeated crystallization) method is adopted. Each crystallization purification removes the liquid phase metal gallium with a high impurity content, and the purified solid phase metal gallium is melted and then crystallized and purified again. This can not only improve the effect of crystallization purification, but also make the temperature field control easy to achieve, and objectively achieve the purpose of reducing the crystallization speed. Electrolytic gallium with Fe impurity content less than 20ppb can be purified by repeated crystallization. The crystallization rate can be controlled at 40% to 50% to reach a purity level of 5ppb. Repeated crystallization can extend the crystallization time to more than 30 hours, so that the crystallization process is achieved at a slower crystallization speed. The crystallization purification effect of metal gallium can be purified to a purity level of 7N. With the goal of achieving a crystallization rate of 40% to 50%, the single crystallization rate needs to be controlled at 80% to 90%, which can be achieved after 3-7 repeated crystallizations. The single crystallization time is aimed at meeting the final crystallization purification requirements, thereby ensuring the crystallization speed and the efficiency of electrolytic gallium crystallization purification. Exemplarily, in the process parameters of repeated gradient crystallization, the single crystallization time can be 4h, 5h, 6h, 7h, 8h, 9h, 10h, etc., the single crystallization rate is 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, etc., the number of crystallizations is 3 times, 4 times, 5 times, 6 times, 7 times, etc., and the cumulative crystallization time is 12h, 14h, 16h, 18h, 20h, 25h, 30h, 35h, 40h, 45h, 50h, 55h, 60h, etc.

[0059] In some embodiments, the electrolytic gallium meets the following indicators: the purity of the electrolytic gallium is 6N, and the Fe content in the electrolytic gallium is less than 20 ppb.

[0060] In the embodiment of the present application, the purity of the metal gallium raw material can reach 6N level after the first electrolysis and the second electrolysis purification, the Fe content in the electrolytic gallium can be less than 20 ppb, and further through gradient crystallization, the purity of high-purity metal gallium can reach above 7N.

[0061] In a second aspect, the present application provides a system for purifying metallic gallium, wherein the system is adapted to the method described in any embodiment of the first aspect, Figure 2 A schematic diagram of the structure of a system for purifying gallium metal provided in an embodiment of the present application; see Figure 2The system comprises an electrolytic cell 1 and a crystallization cell 2. An electrolytic zone 11 is arranged inside the electrolytic cell 1. The height of the electrolytic zone 11 is lower than the depth of the electrolytic cell 1. The electrolytic zone 11 is immersed in the electrolyte. Figure 3 For a schematic diagram of the structure of the electrolysis zone of the electrolytic cell of a system for purifying gallium metal provided in an embodiment of the present application, please refer to Figure 3 ;

[0062] The electrolysis area 11 includes an anode area 111, a first cathode area 112 and a second cathode area 113; wherein the anode area 111 is disposed at the outermost layer of the electrolysis area 11; the first cathode area 112 is disposed at the innermost layer of the electrolysis area 11; and the second cathode area 113 is disposed between the anode area 111 and the first cathode area 112;

[0063] 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 connected to the feed port of the crystallization cell 2 .

[0064] In the embodiment of the present application, the first electrolysis and the second electrolysis are realized by the above-mentioned electrolytic cell 1, and a gallium electrolysis zone 11 is set inside the electrolytic cell 1, the height of the electrolysis zone 11 is lower than the depth of the electrolytic cell 1, and the electrolysis zone 11 is separated into an anode zone 111, a first cathode zone 112 and a second cathode zone 113 by an organic glass plate. The anode zone 111, the first cathode zone 112 and the second cathode zone 113 are completely isolated, and these areas are immersed in the electrolyte, and an electrolysis circuit is formed by the electrolyte. The electrolytic gallium with a high impurity content formed during the first electrolysis is isolated in the first cathode zone 112 to avoid contamination with the second cathode zone 113. At the same time, through the transfer of the cathode electrode (the first cathode zone 112 is transferred to the second cathode zone 113), the conversion from the first electrolysis to the second electrolysis is realized in the same electrolytic cell 1, and the material transfer during the conversion from the first electrolysis to the second electrolysis is avoided, which plays a positive role in the continuous stability of the gallium electrolysis purification process.

[0065] Gallium metal is electrolyzed. The gallium metal to be electrolyzed is added to the anode region 111 of the electrolysis zone 11 of the electrolysis cell 1 from the feed port, and then the electrolysis cell 1 is filled with electrolyte so that the electrolysis zone 11 is completely immersed in the electrolyte. The platinum electrode connected to the positive electrode is inserted into the gallium metal raw material in the anode region 111, and the other platinum electrode connected to the negative electrode is inserted into the first cathode region 112 to perform the first electrolysis. When the GaO 2-After the concentration reaches the set value, the platinum electrode of the first cathode region 112 is removed, and the gallium electrolyzed from the first cathode region 112 is removed, and the first electrolysis is completed. After the first electrolysis is completed, the platinum electrode of the first cathode region 112 is wiped clean and inserted into the second cathode region 113 for the second electrolysis. After the second electrolysis is completed, the electrolytic gallium purified by electrolysis is collected from the discharge port. Furthermore, a small amount of high-purity gallium with a purity of 6N or above can be added to the second cathode region 113 to effectively contact the platinum electrode, thereby increasing the cathode electrolysis area.

[0066] In some embodiments, the crystallization tank 2 includes a heating zone 21, a crystallization zone 22 and a cooling zone 23; wherein the heating zone 21 is disposed at the innermost layer of the crystallization tank 2, the cooling zone 23 is disposed at the outermost layer of the crystallization tank 2, and the crystallization zone 22 is disposed between the heating zone 21 and the cooling zone 23;

[0067] The feed port of the crystallization tank 2 is arranged in the crystallization zone 22 .

[0068] In the embodiment of the present application, the crystallization tank 2 includes a heating zone 21, a crystallization zone 22 and a cooling zone 23. The crystallization zone 22 is arranged between the crystallization zone 22 and the cooling zone 23, and a directional temperature field can be formed. The cooling zone 23 provides a temperature zone below the melting point of the metal gallium, corresponding to the above-mentioned external temperature zone, so that the liquid metal gallium below the melting point of the metal gallium solidifies; the heating zone 21 provides a temperature zone above the melting point of the metal gallium, corresponding to the above-mentioned internal temperature zone, so that the heating zone 21 and the cooling zone 23 offset each other in the solid-liquid phase transformation process of the metal gallium, and the crystallization speed is controlled. When the crystallization rate reaches a single crystallization rate, the current crystallization is ended, the liquid metal gallium containing impurities is removed, and the remaining solid metal gallium is melted and the crystallization process is repeated until the purity of the solid metal gallium reaches the requirement. Further, the heating zone 21 can be a barreled device filled with water, and there is a heating element in the device to meet the requirements of the temperature field. At the same time, the barrel-shaped device can achieve up and down disturbances through a mechanical device connected thereto, which plays a stirring role, and better assists in controlling the crystallization speed and crystallization time of electrolytic gallium.

[0069] The system for purifying metal gallium is implemented based on the above-mentioned method for purifying metal gallium. The specific steps of the method for purifying metal gallium can refer to the above-mentioned embodiment. Since the system for purifying metal gallium adopts part or all of the technical solutions of the above-mentioned embodiment, it has at least all the beneficial effects brought by the technical solutions of the above-mentioned embodiment, which will not be described one by one here.

[0070] The present application will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are intended only to illustrate the present application and are not intended to limit the scope of the present application. The experimental methods for which specific conditions are not specified in the following examples are usually measured according to industry standards. If there is no corresponding industry standard, then the conditions recommended by the manufacturer are followed.

[0071] Example 1

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

[0073] S11, using an electrolyte to perform a first electrolysis on a portion of the metal gallium to obtain a purified electrolyte containing a set gallate ion content; wherein the electrolyte is a 220 g / L NaOH electrolyte, the electrolysis temperature is 30° C., and the current density is 210 A / m 2 , the electrolysis time is 6 days;

[0074] S21, using a purified electrolyte containing a set gallate ion content to perform a second electrolysis on the remaining metal gallium to obtain electrolytic gallium; wherein the electrolysis temperature is 30° C. and the current density is 210 A / m 2 , the electrolysis time is 18 days; the purity of electrolytic gallium is 6N, and the Fe content is 9ppb;

[0075] S31. Gradient crystallization of electrolytic gallium to remove impurity metals in the electrolytic gallium to obtain high-purity metallic gallium; specifically comprising: placing the electrolytic gallium between an inner temperature zone and an outer temperature zone to gradient crystallize the electrolytic gallium to remove impurity metals in the electrolytic gallium to obtain high-purity metallic gallium; wherein the temperature of the inner temperature zone is higher than the melting point of metallic gallium, and the temperature of the outer temperature zone is lower than the melting point of metallic gallium; the temperature of the inner temperature zone is 32°C; the temperature of the outer temperature zone 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 repeated crystallizations is 36 hours, and the final yield of solid gallium is 40.9%.

[0076] Example 2

[0077] A method for purifying metallic gallium, wherein the purity of the raw metallic gallium is 4N, comprising the following steps:

[0078] S12, using an electrolyte to perform a first electrolysis on a portion of the metal gallium to obtain a purified electrolyte containing a set gallate ion content; wherein the electrolyte is a 240 g / L NaOH electrolyte, the electrolysis temperature is 30° C., and the current density is 180 A / m 2 , the electrolysis time is 5 days;

[0079] S22, using a purified electrolyte containing a set gallate ion content to perform a second electrolysis on the remaining metal gallium to obtain electrolytic gallium; wherein the electrolysis temperature is 30° C. and the current density is 180 A / m 2 , the electrolysis time is 16 days; the purity of electrolytic gallium is 6N, and the Fe content is 12ppb;

[0080] S32, subjecting the electrolytic gallium to gradient crystallization to remove impurity metals in the electrolytic gallium to obtain high-purity metallic gallium; specifically comprising: placing the electrolytic gallium between an inner temperature zone and an outer temperature zone to subject the electrolytic gallium to gradient crystallization to remove impurity metals in the electrolytic gallium to obtain high-purity metallic gallium; wherein the temperature of the inner temperature zone is higher than the melting point of metallic gallium, and the temperature of the outer temperature zone is lower than the melting point of metallic gallium; the temperature of the inner temperature zone is 31°C; the temperature of the outer temperature zone is 28°C; the initial temperature of the electrolytic gallium during 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 yield of solid gallium is 47%.

[0081] Example 3

[0082] A method for purifying metallic gallium, wherein the purity of the raw metallic gallium is 4N, comprising the following steps:

[0083] S13, using an electrolyte to perform a first electrolysis on a portion of the metal gallium to obtain a purified electrolyte containing a set gallate ion content; wherein the electrolyte is a 200 g / L NaOH electrolyte, the electrolysis temperature is 30° C., and the current density is 160 A / m 2 , the electrolysis time is 8 days;

[0084] S23, using a purified electrolyte containing a set gallate ion content to perform a second electrolysis on the remaining metal gallium to obtain electrolytic gallium; wherein the electrolysis temperature is 30° C. and the current density is 160 A / m 2 , the electrolysis time is 23 days; the purity of electrolytic gallium is 6N, and the Fe content is 16ppb;

[0085] S33, subjecting the electrolytic gallium to gradient crystallization to remove impurity metals in the electrolytic gallium to obtain high-purity metallic gallium; specifically comprising: placing the electrolytic gallium between an inner temperature zone and an outer temperature zone to subject the electrolytic gallium to gradient crystallization to remove impurity metals in the electrolytic gallium to obtain high-purity metallic gallium; wherein the temperature of the inner temperature zone is higher than the melting point of metallic gallium, and the temperature of the outer temperature zone is lower than the melting point of metallic gallium; the temperature of the inner temperature zone is 32°C; the temperature of the outer temperature zone is 24°C; the initial temperature of the electrolytic gallium during gradient crystallization is 40°C; the single crystallization time is 8.5 hours, the single crystallization rate is 82%, the cumulative crystallization time corresponding to 4 repeated crystallizations is 34 hours, and the final yield of solid gallium is 45.2%.

[0086] Example 4

[0087] A method for purifying metallic gallium, wherein the purity of the raw metallic gallium is 4N, comprising the following steps:

[0088] S14, using an electrolyte to perform a first electrolysis on a portion of the metal gallium to obtain a purified electrolyte containing a set gallate ion content; wherein the electrolyte is a 220 g / L NaOH electrolyte, the electrolysis temperature is 30° C., and the current density is 240 A / m 2 , the electrolysis time is 4 days;

[0089] S24, using a purified electrolyte containing a set gallate ion content to perform a second electrolysis on the remaining metal gallium to obtain electrolytic gallium; wherein the electrolyte is a NaOH electrolyte, the electrolysis temperature is 30°C, and the current density is 240A / m 2 , the electrolysis time is 14 days; the purity of electrolytic gallium is 6N, and the Fe content is 14ppb;

[0090] S34, subjecting the electrolytic gallium to gradient crystallization to remove impurity metals in the electrolytic gallium to obtain high-purity metallic gallium; specifically comprising: placing the electrolytic gallium between an inner temperature zone and an outer temperature zone to subject the electrolytic gallium to gradient crystallization to remove impurity metals in the electrolytic gallium to obtain high-purity metallic gallium; wherein the temperature of the inner temperature zone is higher than the melting point of metallic gallium, and the temperature of the outer temperature zone is lower than the melting point of metallic gallium; the temperature of the inner temperature zone is 33°C; the temperature of the outer temperature zone is 25°C; the initial temperature of the electrolytic gallium during gradient crystallization is 40°C; the single crystallization time is 8.5 hours, the single crystallization rate is 85%, the cumulative crystallization time corresponding to 5 repeated crystallizations is 42 hours, and the final yield of solid gallium is 44.4%.

[0091] Example 5

[0092] Based on Example 1, a system for purifying metallic gallium includes an electrolytic cell 1 and a crystallization cell 2, wherein an electrolytic zone 11 is arranged inside the electrolytic cell 1, wherein the height of the electrolytic zone 11 is lower than the depth of the electrolytic cell 1, and the electrolytic zone 11 is immersed in an electrolyte; the electrolytic zone 11 includes an anode zone 111, a first cathode zone 112 and a second cathode zone 113; wherein the anode zone 111 is arranged at the outermost layer of the electrolytic zone 11; the first cathode zone 112 is arranged at the innermost layer of the electrolytic 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 at the second cathode zone 113, the feed port of the electrolytic cell 1 is arranged at the anode zone 111, and the discharge port of the electrolytic cell 1 is connected to the feed port of the crystallization cell 2. The crystallization tank 2 includes a heating zone 21, a crystallization zone 22 and a cooling zone 23; wherein the heating zone 21 is arranged at the innermost layer of the crystallization tank 2, the cooling zone 23 is arranged at the outermost layer of the crystallization tank 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 at the crystallization zone 22. The method of Example 1 is implemented using this system as follows: First electrolysis: Arrange the raw metal gallium in the anode area 111 from the feed port of the electrolytic tank 1, insert the anode electrode and the cathode electrode into the metal gallium in the anode area 111 and the first cathode area 112 respectively, add 220g / L of NaOH electrolyte, connect direct current to start electrolysis, and maintain the electrolysis temperature at 30°C, and the current density is 210A / m 2 The first electrolysis time is 6 days. After the first electrolysis, the cathode electrode is removed, and the electrolytic material in the first cathode area 112 is extracted with a clean straw; the second electrolysis: keep the state of the anode area 111 and the electrolyte unchanged, arrange a set amount of high-purity gallium in the second cathode area 113, insert the cleaned cathode electrode into the high-purity gallium in the second cathode area 113, connect direct current to start electrolysis, maintain the electrolysis temperature at 30°C, and the current density is 210A / m 2 The deep electrolysis time is 18 days. After the deep electrolysis is completed, the electrolytic gallium after electrolysis purification is collected from the material taking port; gradient crystallization: the electrolytic gallium is placed in the crystallization tank 2, the initial temperature of the electrolytic gallium is 40°C, and the surface of the gallium is covered with a dilute hydrochloric acid solution to reduce the introduction of impurities from the environment. The temperature of the heating zone 21 is 32°C, and the temperature of the cooling zone 23 (cooling water) is 27°C. The cumulative crystallization time corresponding to 4 repeated crystallizations is 36 hours.

[0093] Comparative Example 1

[0094] A method for purifying metallic gallium, wherein the purity of the raw metallic gallium is 4N, comprising the following steps:

[0095] S51, using an electrolyte to perform a first electrolysis on a portion of the metal gallium to obtain a purified electrolyte containing a set gallate ion content; wherein the electrolyte is a 220 g / L NaOH electrolyte, the electrolysis temperature is 30° C., and the current density is 210 A / m 2, the electrolysis time is 24 days; the purity of electrolytic gallium is 6N, and the Fe content is 33ppb;

[0096] S52, subjecting the electrolytic gallium to gradient crystallization to remove impurity metals in the electrolytic gallium to obtain high-purity metallic gallium; specifically comprising: placing the electrolytic gallium between an inner temperature zone and an outer temperature zone to subject the electrolytic gallium to gradient crystallization to remove impurity metals in the electrolytic gallium to obtain high-purity metallic gallium; wherein the temperature of the inner temperature zone is higher than the melting point of metallic gallium, and the temperature of the outer temperature zone is lower than the melting point of metallic gallium; the temperature of the inner temperature zone is 32°C; the temperature of the outer temperature zone 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 repeated crystallizations is 36 hours.

[0097] The purity of the solid gallium finally obtained in Examples 1 to 5 and Comparative Example 1 was detected by glow discharge mass spectrometry (GDMS), and the main element Ga = 99.99999+%, wherein the contents of 19 impurity elements specified for 7N high-purity gallium in the current national standard GB / T 10118-2023 are shown in Table 1. It can be seen that the purity of the solid gallium obtained in Examples 1 to 4 all reached 7N, which met the national standard, while the purity of the solid gallium obtained in Comparative Example 1 did not reach 7N.

[0098] Table 1 Impurity element content in solid gallium obtained in Examples 1 to 4 (unit: ppb)

[0099]

[0100] In addition, one or more technical solutions in the embodiments of the present application have at least the following technical effects or advantages:

[0101] (1) During the electrolysis process, completely isolated first and second cathode regions are set up, and the impurity-rich materials precipitated in the first electrolysis stage will not pollute the electrolytic purification cathode materials in the second electrolysis stage, thereby achieving the effect of purifying the electrolyte during the first electrolysis liquid preparation period while preventing impurities precipitated from the cathode from contaminating the electrolysis process.

[0102] (2) During the crystallization process, a directional temperature field is established to gradually crystallize electrolytic gallium from the crystallization area to the central area, which has strong controllability over the crystallization speed and crystallization rate. At the same time, the mechanical device connected thereto realizes relative disturbance between the liquid phase gallium and the solid phase gallium, which plays a stirring role, and better assists in controlling the crystallization speed and crystallization time of electrolytic gallium. It can also solve the problem of impurities retained in the dendrite crystals at the front of the crystallization surface, and further improve the crystal purity;

[0103] (3) By rationally controlling the relevant process parameters of the first electrolysis, the second electrolysis and the gradient crystallization, the gradient purification of metallic gallium is achieved, and high-purity gallium products with a purity of more than 7N are stably prepared.

[0104] The above description is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features applied for herein.

Claims

1. A method for purifying metallic gallium, characterized in that: The purity of the metal gallium is ≤4N, and the method comprises: Using an electrolyte to perform a first electrolysis on a portion of the metal gallium to obtain a purified electrolyte containing a set gallate ion content; Using the purified electrolyte containing a set gallate ion content to perform a second electrolysis on the remaining metal gallium to obtain electrolytic gallium; The electrolytic gallium is subjected to gradient crystallization to remove impurity metals in the electrolytic gallium to obtain high-purity metallic gallium.

2. The method according to claim 1, characterized in that The gallate ion content is set to be ≥30 g / L.

3. The method according to claim 1, characterized in that The process parameters of the first electrolysis include: the concentration of the electrolyte is 150g / L to 260g / L, the current density is 130A / m 2 ~250A / m 2 The electrolysis time is 3 to 9 days, and the electrolysis temperature is above 30°C.

4. The method according to claim 1, characterized in that: The process parameters of the second electrolysis include: the concentration of the electrolyte is 150g / L to 260g / L, the current density is 130A / m 2 ~250A / m 2 The electrolysis time is 12 to 25 days, and the electrolysis temperature is above 30°C.

5. The method according to claim 1, characterized in that The electrolytic gallium meets the following indicators: the purity of the electrolytic gallium is 6N, and the Fe content in the electrolytic gallium is less than 20 ppb.

6. The method according to claim 1, characterized in that The step of subjecting the electrolytic gallium to gradient crystallization to remove impurity metals in the electrolytic gallium to obtain high-purity metallic gallium comprises: The electrolytic gallium is placed in a crystallization region between an inner temperature region and an outer temperature region, and the electrolytic gallium is subjected to gradient crystallization 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.

7. The method according to claim 6, characterized in that The temperature of the inner temperature area is 30°C to 40°C; The temperature of the outer temperature area is 20°C to 29°C; The initial temperature of the electrolytic gallium during the gradient crystallization is 30°C to 40°C.

8. The method according to claim 6, characterized in that The process parameters of the gradient crystallization include: a single crystallization time of 4 hours to 10 hours, a single crystallization rate of 80% to 90%, a crystallization number of 3 to 7 times, and a cumulative crystallization time of 12 hours to 60 hours.

9. A system for purifying metallic gallium, characterized in that: The system is adapted to the method described in any one of claims 1 to 8, and the system comprises an electrolytic cell (1) and a crystallization cell (2); An electrolysis zone (11) is arranged inside the electrolysis tank (1), the height of the electrolysis zone (11) is lower than the depth of the electrolysis tank (1), and the electrolysis zone (11) is immersed in the electrolyte; The electrolysis zone (11) comprises an anode zone (111), a first cathode zone (112) and a second cathode zone (113); wherein 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); and 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 region (113), the feed port of the electrolytic cell (1) is arranged in the anode region (111), and the discharge port of the electrolytic cell (1) is connected to the feed port of the crystallization cell (2).

10. The system according to claim 9, characterized in that The crystallization tank (2) comprises a heating zone (21), a crystallization zone (22) and a cooling zone (23); wherein the heating zone (21) is arranged at the innermost layer of the crystallization tank (2), the cooling zone (23) is arranged at the outermost layer of the crystallization tank (2), and the crystallization zone (22) is arranged between the heating zone (21) and the cooling zone (23); and the feed port of the crystallization tank (2) is arranged at the crystallization zone (22).

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