Method for preparing 6N indium by taking 4N indium as raw material

Abstract

The invention discloses a method for preparing 6N indium by taking 4N indium as a raw material, which comprises the following steps: S1, preparing an anode plate and an indium sulfate electrolyte by taking 4N indium as a raw material; s2, taking the electrolyte in the step S1 and an anode plate as raw materials, placing the raw materials in a diaphragm electrolytic cell, and carrying out a pulse pre-electrolysis process; and S3, after the step S2 is finished, a negative plate of the diaphragm electrolytic cell is replaced, a bidirectional pulse electrolysis process is carried out, and 6N indium is prepared from the negative electrode. By adopting the anion exchange membrane, low-potential impurities and high-potential metal impurity ions dissolved in the anode can be only retained in the anode liquid and cannot penetrate through the anion exchange membrane to enter the cathode chamber, so that the impurity ions are prevented from being separated out at the cathode to influence the purity of indium. The invention innovatively provides a technology for preparing 6N indium through pulse preelectrolysis impurity removal-bidirectional pulse electrolysis by utilizing the characteristics of pulse electrolysis. The technology is advanced and reliable in process, low in cost and high in efficiency, and has great application potential and popularization value.

Description

Technical Field

[0001] This invention belongs to the field of metallurgy and chemical engineering, and specifically relates to a method for preparing 6N high-purity indium using 4N indium as a raw material. Background Technology

[0002] Indium is an important non-ferrous metal with wide applications in photoelectric conversion, biopharmaceuticals, and the manufacture of low-melting-point alloys. Indium is not found as a standalone mineral; it is often found as an associated mineral in other non-ferrous minerals and is enriched in smelting fumes. The process of obtaining metallic indium from indium-containing smelting fumes typically involves wet leaching, solvent extraction, carbon reduction, and electrolytic refining. However, the purity of the indium obtained by this process is often only 99.99%, requiring further purification to meet the purity requirements of industrial production.

[0003] Currently, high-purity indium is often prepared using methods such as chlorination purification (CN 202410542917.8), vacuum separation (CN202410341222.3), and zone melting (CN 202310255330.4). While these methods yield high-purity indium, they also suffer from drawbacks such as long processes, high energy consumption, and high costs. Aqueous solution electrolytic refining is another method for preparing high-purity metals, but deep purification of impurity ions in aqueous solutions is difficult. Conventional electrolytic refining can only yield indium with a purity of 4N-5N. Preparing 6N indium requires improvements to conventional electrolytic refining to enhance the removal of impurity ions. Therefore, we propose a method for preparing 6N indium using 4N indium as a raw material to address these issues. Summary of the Invention

[0004] This application provides a method for preparing 6N indium from 4N indium as a raw material, which solves the problems of long process, high energy consumption and high cost of traditional purification methods.

[0005] This application provides a method for preparing 6N indium from 4N indium, comprising the following steps: S1, using 4N indium as raw material, prepares an anode plate and indium sulfate electrolyte; S2, using the electrolyte and anode plate from step S1 as raw materials, place them in a diaphragm electrolytic cell to carry out pulse pre-electrolysis process; S3. After step S2 is completed, the cathode plate of the diaphragm electrolytic cell is replaced, and a bidirectional pulse electrolysis process is carried out to prepare 6N indium cathode.

[0006] Preferably, the anode plate and the indium sulfate electrolyte in S1 are prepared by casting and dissolving in sulfuric acid, respectively.

[0007] Preferably, the sulfuric acid used in S1 to prepare the indium sulfate electrolyte is electronic grade sulfuric acid, and the concentration of indium in the indium sulfate electrolyte is 60-120 g / L, and the pH is 2-4.

[0008] Preferably, the diaphragm electrolyzer in S2 is an anion exchange membrane electrolyzer, which has an ion selectivity of more than 95%.

[0009] Preferably, the pulse current in the pulse pre-electrolysis process in S2 is a unidirectional pulse.

[0010] Preferably, the duty cycle of the pulse current in the pulse pre-electrolysis process in S2 is 1-99%, the current density of the pulse electrolysis in the pulse pre-electrolysis process is 1-500 A / m 2 , and the pulse electrolysis time in the pulse pre-electrolysis process is 4-100 h.

[0011] Preferably, the duty cycle of the pulse current in the pulse pre-electrolysis process in S2 is 20-40%, the current density of the pulse electrolysis in the pulse pre-electrolysis process is 5-20 A / m 2 , and the pulse electrolysis time in the pulse pre-electrolysis process is 8-12 h.

[0012] Preferably, the duty cycle of the current in the forward pulse cycle in the bidirectional pulse electrolysis process in S3 is 1-99%, the duty cycle of the current in the reverse pulse cycle is 1-99%, the current density of the forward pulse cycle in the bidirectional pulse electrolysis process is 1-500 A / m 2 , the current density of the reverse pulse cycle is 1-500 A / m 2 , the pulse electrolysis time in the bidirectional pulse electrolysis process is 4-100 h, and the pulse electrolysis temperature is 25-60℃.

[0013] Preferably, the duty cycle of the current in the forward pulse cycle in the bidirectional pulse electrolysis process in S3 is 60-90%, the duty cycle of the current in the reverse pulse cycle is 10-30%, the current density of the forward pulse cycle in the bidirectional pulse electrolysis process is 10-50 A / m 2 , the current density of the reverse pulse cycle is 5-10 A / m 2 , the pulse electrolysis time in the bidirectional pulse electrolysis process is 20-40 h, and the pulse electrolysis temperature is 25-60℃.

[0014] Preferably, the cathode plate material in S2 and S3 is one of a stainless steel plate and a ruthenium-plated titanium plate.

[0015] From the above technical solutions, the application provides a method for preparing 6N indium from 4N indium as raw material. In the preparation process, when the cathode is powered, the metal ions near the cathode rapidly discharge at the cathode, and the concentration of metal ions near the cathode decreases. The diffusion of metal ions in the solution is slow, and the diffusion speed is much lower than the electrode reaction speed, resulting in cathode polarization. The pulse electrolysis technology is a special electrolysis technology. After the power is turned off, the metal ions in the solution diffuse to the electrode, increasing the ion concentration near the electrode. In the pre-electrolysis process, the application of pulse current can effectively improve the impurity removal effect of high-potential impurity ions; in the formal electrolysis process, the reverse pulse current can make the impurity ions precipitated at the cathode in the forward electrolysis process dissolve and return to the electrolyte, thereby improving the purity of indium. It should be noted that impurity ions will also be released during the anode dissolution process and enter the electrolyte. The anion exchange membrane used in the application can only retain the low-potential impurity ions and high-potential metal impurity ions in the anode liquid, and cannot pass through the anion exchange membrane into the cathode chamber, thereby avoiding the precipitation of impurity ions at the cathode and affecting the purity of indium. The application utilizes the characteristics of pulse electrolysis and innovatively proposes a pulse pre-electrolysis impurity removal-bidirectional pulse electrolysis method for preparing 6N indium. The method can reliably, low-cost and efficiently prepare 6N indium, and has great application potential and promotion value. BRIEF DESCRIPTION OF DRAWINGS

[0016] In order to more clearly illustrate the technical solutions of the application, the following will briefly introduce the drawings needed in the implementation examples. Obviously, for those skilled in the art, other drawings can also be obtained without creative labor.

[0017] Figure 1 A process flow chart of a method for preparing 6N indium from 4N indium as raw material according to the application; Figure 2 High-purity indium XRD obtained by a method for preparing 6N indium from 4N indium as raw material according to the application; DETAILED DESCRIPTION

[0018] In order to enable those skilled in the art to better understand the technical solutions in the application, the technical solutions in the embodiments of the application will be described clearly and completely below with reference to the drawings.

[0019] In the drawings, Figure 1 A process flow chart of a method for preparing 6N indium from 4N indium as raw material according to the application, Figure 2 High-purity indium XRD obtained by a method for preparing 6N indium from 4N indium as raw material according to the application.

[0020] A method for preparing 6N indium from 4N indium as raw material, the application obtains 6N indium from 4N indium purchased by anion exchange membrane, and specifically comprises the following steps: S1, using 4N indium as raw material, respectively using ingot casting and sulfuric acid dissolution method, anode plate and indium sulfate electrolyte are prepared, wherein the sulfuric acid for preparing the indium sulfate electrolyte is electronic grade sulfuric acid, the concentration of indium in the indium sulfate electrolyte is 60-120g / L, and the pH is 2-4; S2, using the electrolyte and anode plate in step S1 as raw materials, placing them in a diaphragm electrolytic cell, and carrying out pulse pre-electrolysis process, wherein the diaphragm electrolytic cell is a cation exchange membrane electrolytic cell, the membrane therein is a cation exchange membrane, and the ion selectivity thereof needs to be greater than 95%, the pulse current of the pulse pre-electrolysis process is unidirectional pulse, the duty cycle of the pulse current of the pulse pre-electrolysis process is 1-99%, the current density of the pulse electrolysis of the pulse pre-electrolysis process is 1-500 A / m 2 , the pulse electrolysis time of the pulse pre-electrolysis process is 4-100h, the duty cycle of the current of the forward pulse period of the bidirectional pulse electrolysis process is 1-99%, the duty cycle of the current of the reverse pulse period is 1-99%, the current density of the forward pulse period of the bidirectional pulse electrolysis process is 1-500 A / m 2 , the current density of the reverse pulse period is 1-500 A / m 2 , the pulse electrolysis time of the bidirectional pulse electrolysis process is 4-100h, and the pulse electrolysis temperature is 25-60℃; S3, after step S2 is completed, the cathode plate of the diaphragm electrolytic cell is replaced, and bidirectional pulse electrolysis process is carried out, and 6N indium is prepared at the cathode, and in this application, the cathode plate material is one of stainless steel plate and ruthenium-plated titanium plate.

[0021] In this application, further, the duty cycle of the pulse current of the pulse pre-electrolysis process in S2 is 20-40%, the current density of the pulse electrolysis of the pulse pre-electrolysis process is 5-20 A / m 2 , and the pulse electrolysis time of the pulse pre-electrolysis process is 8-12h.

[0022] In this application, further, the duty cycle of the current of the forward pulse period of the bidirectional pulse electrolysis process in S3 is 60-90%, the duty cycle of the current of the reverse pulse period is 10-30%, the current density of the forward pulse period of the bidirectional pulse electrolysis process is 10-50 A / m 2 , the current density of the reverse pulse period is 5-10 A / m 2 , the pulse electrolysis time of the bidirectional pulse electrolysis process is 20-40h, and the pulse electrolysis temperature is 25-60℃.

[0023] The following examples are intended to further illustrate the present application, but not to limit the present application.

[0024] Example 1 The 4N metal indium purchased from the market was dissolved in electronic grade concentrated sulfuric acid to prepare an indium-containing electrolyte. The concentration of indium in the electrolyte was 101.08 g / L, and the pH of the electrolyte was 2.46. The indium-containing electrolyte obtained above was added to an anion exchange membrane electrolytic cell, and 4N metal indium was used as the anode and a ruthenium-titanium plated plate was used as the cathode. The current density was set to 5 A / m 2 at 30°C. Pulsed electrodeposition was carried out at a duty cycle of 40% for 8h. After the pulsed electrodeposition was completed, the cathode plate was removed. On the basis of the above-mentioned anion exchange membrane electrolytic cell, a new ruthenium-titanium plated plate was placed as the cathode, and a forward current with a duty cycle of 80% was applied at a current density of 10 A / m 2 at 30°C. At the same time, after each forward pulse current ended, a reverse pulse current with a duty cycle of 25% was applied at a current density of 5 A / m 2 . The electrolysis time was controlled to be 40h.

[0025] Example 2 The 4N metal indium purchased from the market was dissolved in electronic grade concentrated sulfuric acid to prepare an indium-containing electrolyte. The concentration of indium in the electrolyte was 80.43 g / L, and the pH of the electrolyte was 3.69.

[0026] The indium-containing electrolyte obtained above was added to an anion exchange membrane electrolytic cell, and 4N metal indium was used as the anode and a ruthenium-titanium plated plate was used as the cathode. The current density was set to 20 A / m 2 at 55°C. Pulsed electrodeposition was carried out at a duty cycle of 20% for 10h. After the pulsed electrodeposition was completed, the cathode plate was removed.

[0027] On the basis of the above-mentioned anion exchange membrane electrolytic cell, a new ruthenium-titanium plated plate was placed as the cathode, and a forward current with a duty cycle of 90% was applied at a current density of 50 A / m 2 at 55°C. At the same time, after each forward pulse current ended, a reverse pulse current with a duty cycle of 30% was applied at a current density of 10 A / m 2 . The electrolysis time was controlled to be 20h.

[0028] After the electrolysis was completed, GD-MS was used to analyze the purity of the cathode indium. The test results showed that the purity of the cathode indium was 99.99994%, and the content of impurity ions was less than 0.1 ppm, meeting the national standard requirements.

[0029] Example 3 The 4N metal indium purchased from the market was dissolved in electronic grade concentrated sulfuric acid to prepare an indium-containing electrolyte. The concentration of indium in the electrolyte was 115.97 g / L, and the pH of the electrolyte was 3.03.

[0030] The above obtained electrolyte containing indium was added into an anion exchange membrane electrolytic cell, 4N metallic indium was used as anode, and a plated ruthenium-titanium plate was used as cathode, at 50°C, a current density of 10 A / m 2 was set, and pulse electrodeposition was carried out for 12 h at a duty ratio of 35%. After the pulse electrodeposition, the cathode plate was taken out.

[0031] On the basis of the above step, a new plated ruthenium-titanium plate was put in as cathode, at 50°C, a forward current of 40 A / m 2 was applied, and at the same time, a reverse pulse current of 5 A / m 2 was applied at a duty ratio of 15% after each forward pulse current was ended. The electrolysis time was controlled to be 30 h.

[0032] After the electrolysis, GD-MS was used to analyze the purity of the cathode indium. The test results showed that the purity of the cathode indium was 99.99993%, and the content of impurity ions was all lower than 0.1 ppm, reaching the national standard requirements.

[0033] Comparative Example 1 (without using diaphragm electrolysis) Comparative Example 1 was basically the same as Example 1, except that the only difference was that Comparative Example 1 did not use diaphragm electrolysis technology. After the electrolysis, the purity of the cathode indium was only 99.9992%, and the content of Sn, Pb and As was 2 ppm, 3 ppm and 1 ppm respectively, which failed to reach the requirements of national standard 6N indium.

[0034] Comparative Example 2 (without using pulse electrolysis technology in pre-electrolysis process) Comparative Example 2 was basically the same as Example 1, except that the only difference was that Comparative Example 2 did not use pulse electrolysis technology in the pre-electrolysis process. After the electrolysis, the purity of the cathode indium was only 99.999%, and the content of Sn, Sb and Pb was 2 ppm, 3 ppm and 2 ppm respectively, which failed to reach the requirements of national standard 6N indium.

[0035] Comparative Example 3 (without using bidirectional pulse electrolysis technology to prepare high-purity indium) Comparative Example 3 was basically the same as Example 1, except that the only difference was that Comparative Example 3 did not use bidirectional pulse electrolysis technology when preparing high-purity indium by electrolysis. After the electrolysis, the purity of the cathode indium was only 99.9984%, and the content of Zn, Cd, Sn, Sb and Pb was 0.2 ppm, 0.2 ppm, 4 ppm, 6 ppm and 2 ppm respectively, which failed to reach the requirements of national standard 6N indium.

[0036] From the above technical solutions, it can be seen that the metal ions near the cathode rapidly discharge at the cathode when power is on, and the concentration of metal ions near the cathode is reduced. The metal ions in the solution diffuse slowly, and the diffusion speed is much lower than the electrode reaction speed, resulting in cathode polarization. The pulse electrolysis technology is a special electrolysis technology, after the power is turned off, the metal ions in the solution diffuse to the electrode, and the ion concentration near the electrode is increased. In the pre-electrolysis process, the application of pulse current can effectively improve the impurity removal effect of high potential impurity ions; in the formal electrolysis process, the reverse pulse current can make the impurity ions precipitated at the cathode in the forward electrolysis process discharge and dissolve, return to the electrolyte, and thus improve the purity of indium. It should be noted that impurity ions will also be released in the anode dissolution process and enter the electrolyte. The anion exchange membrane used in the present application can make the low potential impurity and high potential metal impurity ions dissolved at the anode remain in the anode liquid and cannot pass through the anion exchange membrane into the cathode chamber, avoiding the precipitation of impurity ions at the cathode affecting the purity of indium. The present application utilizes the characteristics of pulse electrolysis and innovatively proposes a pulse pre-electrolysis impurity removal-bidirectional pulse electrolysis technology for preparing 6N indium. The present application can reliably, low-cost and efficiently prepare 6N indium.

[0037] Other embodiments of the application will be apparent to those skilled in the art from consideration of the specification and practice of the application disclosed herein. It is intended that the specification and examples be considered as exemplary only, with the true scope of the application being indicated by the following claims.

[0038] It should be understood that the application is not limited to the precise construction that has been described above and illustrated in the accompanying drawings, and that various modifications and changes can be made by those skilled in the art without departing from the scope of the application. The embodiments of the application described above are not intended to be limiting of the scope of the application.

Claims

1. A method for preparing 6N indium using 4N indium as a raw material, characterized in that, Includes the following steps: S1, using 4N indium as raw material, prepares an anode plate and indium sulfate electrolyte; S2, using the electrolyte and anode plate from step S1 as raw materials, place them in a diaphragm electrolytic cell to carry out pulse pre-electrolysis process; S3. After step S2 is completed, the cathode plate of the diaphragm electrolytic cell is replaced, and a bidirectional pulse electrolysis process is carried out to prepare 6N indium cathode.

2. The method for preparing 6N indium from 4N indium according to claim 1, characterized in that, The anode plate and the indium sulfate electrolyte in S1 are prepared by casting and dissolving in sulfuric acid, respectively.

3. The method for preparing 6N indium using 4N indium as a raw material according to claim 1, characterized in that, The sulfuric acid used in S1 to prepare the indium sulfate electrolyte is electronic grade sulfuric acid, and the concentration of indium in the indium sulfate electrolyte is 60-120 g / L, and the pH is 2-4.

4. The method for preparing 6N indium from 4N indium according to claim 1, characterized in that, The membrane electrolyzer described in S2 is an anion exchange membrane electrolyzer, and its ion selectivity must be greater than 95%.

5. The method for preparing 6N indium from 4N indium according to claim 1, characterized in that, The pulse current in the pulse pre-electrolysis process described in S2 is a unidirectional pulse.

6. The method for preparing 6N indium from 4N indium according to claim 1, characterized in that, The duty cycle of the pulse current in the pulse pre-electrolysis process described in S2 is 1-99%, and the pulse electrolysis current density is 1-500 A / m. 2 The pulse electrolysis time in the pulse pre-electrolysis process is 4-100h.

7. The method for preparing 6N indium from 4N indium according to claim 6, characterized in that, The duty cycle of the pulse current in the pulse pre-electrolysis process described in S2 is 20-40%, and the pulse electrolysis current density of the pulse pre-electrolysis process is 5-20 A / m. 2 The pulse electrolysis time in the pulse pre-electrolysis process is 8-12 hours.

8. The method for preparing 6N indium from 4N indium according to claim 1, characterized in that, In the bidirectional pulse electrolysis process described in S3, the duty cycle of the current in the forward pulse cycle is 1-99%, the duty cycle of the current in the reverse pulse cycle is 1-99%, and the current density of the forward pulse cycle in the bidirectional pulse electrolysis process is 1-500 A / m. 2 The current density during the reverse pulse period is 1-500 A / m. 2 The pulse electrolysis time of the bidirectional pulse electrolysis process is 4-100h, and the pulse electrolysis temperature is 25-60℃.

9. A method for preparing 6N indium from 4N indium as claimed in claim 8, characterized in that, In the bidirectional pulse electrolysis process described in S3, the duty cycle of the current in the forward pulse cycle is 60-90%, and the duty cycle of the current in the reverse pulse cycle is 10-30%. The current density of the forward pulse cycle in the bidirectional pulse electrolysis process is 10-50 A / m. 2 The current density during the reverse pulse period is 5-10 A / m. 2 The pulse electrolysis time of the bidirectional pulse electrolysis process is 20-40 hours, and the pulse electrolysis temperature is 25-60℃.

10. A method for preparing 6N indium from 4N indium as claimed in claim 1, characterized in that, In S2 and S3, the cathode plate is made of either stainless steel or ruthenium-plated titanium.

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