Method for separating and purifying high-cadmium crude indium

Abstract

The invention discloses a method for separating and purifying high-cadmium crude indium, which comprises the following steps: heating and melting the high-cadmium crude indium into a molten liquid under the coverage of glycerol, adding ammonium bromide at the temperature of 180-230 DEG C under an ultrasonic strengthening condition to refine the molten salt to obtain refined indium, and separating and purifying the high-cadmium crude indium along with the proceeding of the reaction. Cadmium and thallium in the crude indium react with ammonium bromide to generate bromide, and the bromide is transferred into a glycerol solution, so that purification and separation of impurities and indium are realized. Smelting refined indium particles obtained by the reaction into metal indium ingots under the protection of glycerol, so as to obtain a high-purity indium product; and in addition, direct current deposition is carried out on glycerin obtained after molten salt refining, indium and cadmium in the glycerin are recycled, crude indium is obtained, and the molten salt refining step is returned. According to the method, ammonium bromide is adopted as a cadmium and thallium removal agent, an ultrasonic strengthening mode is additionally adopted, the impurity removal reaction is completed within a short time, the indium loss is small, the process is simple, the reaction period is short, the reaction is easy to control, industrial production is easy to achieve, and the method has good industrial application prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of metal purification, and particularly relates to a method for separating and purifying high-cadmium crude indium. Background Art

[0002] Indium is a metal with a silvery-white luster and weak radioactivity. It has relatively stable chemical properties and can remain stable in air at 100 °C without being oxidized. The melting point of indium is 156.6 °C. At the same time, indium is soft in texture and has a high viscosity, and it is easy to adhere to other substances. As a rare metal, indium is often used in liquid crystal display devices of various electronic devices, indium tin oxide (ITO target materials), copper indium gallium selenide (CIGS) solar cells, indium Sb infrared detectors, indium P power device semiconductors, etc. The performance of these optoelectronic material devices has extremely high requirements for the impurity purity of the materials. For example, the purity requirement of indium in the preparation of CIGS is above 99.999%. For the above reasons, the purification of indium and the separation of impurities are of great significance.

[0003] The separation and purification of indium include electrolytic refining, vacuum distillation, molten salt refining, and crystallization methods. The electrolytic refining method is simple in operation, low in cost, small in pollution, and is commonly used in the industrial production of 4N-grade indium. However, when the cadmium and thallium contents in the raw materials are too high, the raw materials need to be pretreated because the electrode potentials of cadmium and thallium are close to that of indium, and it is difficult to remove cadmium and thallium through electrolytic refining. The melting point of indium is only 156 °C, but the boiling point is as high as 2100 °C. Using this characteristic, some impurities with high saturated vapor pressures are volatilized and removed through vacuum distillation. This method has an ideal removal effect on cadmium and Zn, but the loss rate of indium is relatively high. The crystallization method utilizes the different distribution behaviors of impurities in the liquid phase and the solid phase, and achieves the deep separation effect of impurities through multiple crystallizations. The crystallization method is often used in the process of preparing ultra-high-purity indium at the backend.

[0004] In the case of specific elements cadmium and thallium, molten salt refining has its unique advantages, and the separation and purification effect is achieved by the higher affinity of cadmium and thallium with halogen elements than that of indium. In the traditional molten salt refining process, glycerol, iodine, potassium iodide are commonly used to react with cadmium and thallium in crude indium. The separation efficiency of cadmium and thallium is high, and the loss rate of indium is about 1%. However, the easy volatility and high price of iodine limit its wide application.

[0005] In summary, it is of great significance to develop a process that can quickly and effectively remove impurities cadmium and thallium in crude indium and prepare high-purity indium. Summary of the Invention

[0006] The purpose of the present application is to provide a method for separating and purifying high-cadmium crude indium, which can quickly and effectively remove impurities cadmium and thallium in crude indium and prepare high-purity indium.

[0007] To solve the above technical problems, the present application provides a method for separating and purifying high-cadmium crude indium, including:

[0008] Under the coverage of glycerol, heat the high-cadmium crude indium to melt it into a molten liquid state, and add ammonium bromide under ultrasonic strengthening conditions to refine the molten salt to obtain refined indium. Among them, the refining temperature is 180 - 230 °C, the refining reaction time is 1 - 10 min, the addition amount of ammonium bromide is expressed by the excess coefficient of ammonium bromide after the complete reaction of cadmium and thallium in the high-cadmium crude indium, the excess coefficient is 1 - 4, the addition amount of glycerol and the liquid-solid ratio of the high-cadmium crude indium is 4:1 - 8:1, the stirring speed during the refining process is 50 - 300 rpm, the ultrasonic frequency is 20 - 200 kHz, and the ultrasonic power is 10 - 200 W;

[0009] Wash the refined indium to obtain refined indium particles with a particle size range of 0.2 - 0.5 cm, and recover the indium and cadmium dissolved in the glycerol solution by direct current electrodeposition to obtain crude indium and then return it to the step of adding ammonium bromide to refine the molten salt under ultrasonic strengthening conditions. Among them, the conditions of the direct current electrodeposition are that the current density is 100 - 200 A / m 2 , the temperature is 25 - 50 °C, the electrode spacing is 1 - 4 cm, and the anode and cathode plates are high-purity titanium plates;

[0010] Melt the refined indium particles into metal indium ingots under the coverage of glycerol, wash the metal indium ingots several times with deionized water, and then wash them several times with alcohol, and dry them in a vacuum drying oven to obtain high-purity indium.

[0011] As a preferred embodiment, a method for separating and purifying high-cadmium crude indium, the liquid-solid ratio is 4:1 - 6:1, the refining temperature is 180 - 190 °C, the refining reaction time is 2 - 8 min, and the excess coefficient is 1 - 2.

[0012] It should be detailed in the solution that, a method for separating and purifying high-cadmium crude indium, the stirring speed is 50 - 200 rpm, the ultrasonic frequency is 50 - 100 kHz, and the ultrasonic power is 50 - 150 W.

[0013] It should be detailed in the solution that, a method for separating and purifying high-cadmium crude indium, the current density is 100 - 150 A / m 2 , the temperature is 30 - 40 °C, and the electrode spacing is 2 - 3 cm.

[0014] As a preferred embodiment, a method for separating and purifying high-cadmium crude indium, when the refined indium particles are melted into metal indium ingots under the coverage of glycerol, the temperature is 180 - 230 °C, and the holding time is 10 min.

[0015] Compared with the prior art, the present invention provides a method for separating and purifying high-cadmium crude indium. The high-cadmium crude indium is heated and melted into a molten liquid under the cover of glycerol, and ammonium bromide is added to refine the molten salt under a temperature of 180-230°C and ultrasonic enhancement conditions to obtain refined indium. As the reaction proceeds, the cadmium and thallium in the crude indium react with the ammonium bromide to generate bromides that are transferred to the glycerol solution, thereby achieving the purification and separation of impurities and indium. The refined indium particles obtained by the reaction are smelted into a metal indium ingot under the protection of glycerol, that is, a high-purity indium product is obtained; in addition, the glycerol after molten salt refining is subjected to direct current electrodeposition, and the indium and cadmium in the glycerol are recovered to obtain crude indium, and the molten salt refining step is returned. The present invention uses ammonium bromide as a cadmium and thallium removal agent, and an ultrasonic enhancement method is added to complete the impurity removal reaction in a shorter time and with less indium loss. The temperature, time and amount of ammonium bromide required by the present invention are smaller, and the effect of removing cadmium and thallium is obvious. The glycerol containing cadmium and indium produced in the refining process can be recovered by electrodeposition. The process is simple, the reaction cycle is short, the reaction is easy to control, and industrial production is easy to achieve. It has good industrial application prospects and is of great significance for the preparation of high-purity indium and energy saving and consumption reduction. By adopting this separation and purification method, the cadmium content in high-cadmium crude indium can be removed from 0.7%-0.2% to 0.0091% and 0.003%, and the thallium content can be removed from 0.007%-0.003% to 0.0008%-0.0005%. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solution of the present application, the following briefly introduces the drawings required for use in the embodiments. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without inventiveness.

[0017] Figure 1 A flow chart of a method for separating and purifying high-cadmium crude indium provided in an embodiment of the present application. DETAILED DESCRIPTION

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

[0019] The core of this application is to provide a method for separating and purifying high-cadmium crude indium, which can quickly and effectively remove the impurities cadmium and thallium in the crude indium and prepare high-purity indium.

[0020] Figure 1 A flow chart of a method for separating and purifying high-cadmium crude indium provided in the embodiment of the present application is shown in FIG. Figure 1 shown.

[0021] The preparation technology of high-purity indium is of great significance to the development of traditional industries, semiconductor industries, electronic industries and other fields. The purification of indium often requires selecting appropriate methods for treatment according to the content levels of different impurities in the raw materials. The purification from 2N indium to 4N indium mainly relies on electrolysis. When the content of cadmium and thallium impurities in the raw materials to be treated is relatively high, the results of the electrolysis method are often not ideal. Aiming at the deficiencies of the above existing technologies, the purpose of this solution is to provide a method for separating and purifying crude indium to prepare high-purity indium by using molten salt refining under ultrasonic intensification.

[0022] A method for separating and purifying high-cadmium crude indium, comprising the following steps:

[0023] Step S1: Heat the high-cadmium crude indium to melt it into a molten liquid under the coverage of glycerol, and add ammonium bromide to refine the molten salt under ultrasonic intensification conditions to obtain refined indium. Among them, the refining temperature is 180 - 230 °C, the refining reaction time is 1 - 10 min, the addition amount of ammonium bromide is expressed by the excess coefficient of ammonium bromide after the complete reaction of cadmium and thallium in the high-cadmium crude indium, the excess coefficient is 1 - 4, the addition amount of glycerol and the liquid-solid ratio of the high-cadmium crude indium is 4:1 - 8:1, the stirring speed during the refining process is 50 - 300 rpm, the ultrasonic frequency is 20 - 200 kHz, and the ultrasonic power is 10 - 200 W;

[0024] Step S2: Wash the refined indium to obtain refined indium particles with a particle size range of 0.2 - 0.5 cm, and recover the indium and cadmium dissolved in the glycerol solution by direct current electrodeposition to obtain crude indium, which is then returned to the step of adding ammonium bromide to refine the molten salt under ultrasonic intensification conditions. Among them, the conditions for direct current electrodeposition are a current density of 100 - 200 A / m 2 , a temperature of 25 - 50 °C, a pole distance of 1 - 4 cm, and the anode and cathode plates are high-purity titanium plates;

[0025] Step S3: Melt the refined indium particles into metal indium ingots under the coverage of glycerol, wash the metal indium ingots several times with deionized water, then wash them several times with alcohol, and dry them in a vacuum drying oven to obtain high-purity indium.

[0026] As a preferred embodiment, in a method for separating and purifying high-cadmium crude indium, the liquid-solid ratio is 4:1 - 6:1, the refining temperature is 180 - 190 °C, the refining reaction time is 2 - 8 min, and the excess coefficient is 1 - 2.

[0027] As a preferred embodiment, in a method for separating and purifying high-cadmium crude indium, the stirring speed is 50 - 200 rpm, the ultrasonic frequency is 50 - 100 kHz, and the ultrasonic power is 50 - 150 W.

[0028] As a preferred embodiment, in a method for separating and purifying high-cadmium crude indium, the current density is 100 - 150 A / m 2, the temperature is 30 - 40°C, and the electrode distance is 2 - 3 cm.

[0029] As a preferred embodiment, in a method for separating and purifying high-cadmium crude indium, when refined indium particles are melted into indium ingots under the coverage of glycerol, the temperature is 180 - 230°C, and the heat preservation time is 10 min.

[0030] Taking 99% In (0.68% cadmium and 0.007% thallium) prepared by a zinc smelting enterprise as an example, the reaction principle of the technological process of the present invention is as follows:

[0031] 2NH4Br + Cd = CdBr2 + 2NH3 + H2

[0032] 2NH4Br + 2Tl = 2TlBr + 2NH3 + H2.

[0033] To enable those skilled in the art to better understand this solution, the following uses specific examples to elaborate on this solution in detail:

[0034] Example 1

[0035] The purity of the crude indium is 99.3%, and the main impurities are 0.6696% cadmium, 0.007% thallium, 0.015% arsenic, 0.008% antimony, and 0.007% lead. The refining conditions are as follows: 10 g of crude indium, temperature 180°C, liquid-solid ratio 5:1, excess coefficient of NH4Br is 1, reaction time is 3 min, stirring speed is 50 rpm, ultrasonic frequency is 100 kHz, and ultrasonic power is 100 W. After the reaction, refined indium particles with a particle size range of 0.2 - 0.5 cm and glycerol containing cadmium and indium are obtained. The refined indium particles are melted into indium ingots at 180°C under the protection of glycerol, and high-purity indium products are obtained after being washed with deionized water and alcohol. In addition, glycerol is electro-deposited under the conditions of a current density of 100 A / m 2 , temperature 30°C, and electrode distance 2 cm for 6 h to obtain crude indium.

[0036] After chemical detection and calculation, the direct recovery rate of indium is 99.5%, the cadmium removal rate and thallium removal rate are 98.4% and 96.2% respectively, and the purity of the refined indium is 99.94%. In addition, the current efficiency of electro-deposition is 87%, and the purity of the crude indium is 88.2%.

[0037] Example 2

[0038] The purity of crude indium is 99.3%, and the main impurities are cadmium 0.6696%, thallium 0.007%, arsenic 0.015%, antimony 0.008%, and lead 0.007%. The refining conditions are as follows: 10 g of crude indium, a temperature of 200 °C, a liquid-solid ratio of 6:1, an excess coefficient of NH4Br of 2, a reaction time of 3 min, a stirring speed of 50 rpm, an ultrasonic frequency of 100 kHz, and an ultrasonic power of 100 W. After the reaction, refined indium particles with a particle size range of 0.2 - 0.5 cm and glycerol containing cadmium and indium are obtained. The refined indium particles are melted into indium ingots at a temperature of 180 °C under the protection of glycerol, and high-purity indium products are obtained after washing with deionized water and alcohol. In addition, glycerol is electro-deposited under the conditions of a current density of 100 A / m 2 and a temperature of 30 °C and a pole pitch of 2 cm. Crude indium is obtained after 6 h of electro-deposition.

[0039] After chemical detection and calculation, the direct recovery rate of indium is 99.6%, the cadmium removal rate and thallium removal rate are 98.5% and 96.5% respectively, and the purity of refined indium is 99.95%. In addition, the current efficiency of electro-deposition is 86%, and the purity of crude indium is 87.6%.

[0040] Example 3

[0041] The purity of crude indium is 99.5%, and the main impurities are cadmium 0.2656 ωt.%, arsenic 0.086 ωt.%, antimony 0.008 ωt.%, and lead 0.037 ωt.%. The refining conditions are as follows: 10 g of crude indium, a temperature of 200 °C, a liquid-solid ratio of 6:1, an excess coefficient of NH4Br of 2, a reaction time of 3 min, a stirring speed of 50 rpm, an ultrasonic frequency of 100 kHz, and an ultrasonic power of 100 W. After the reaction, refined indium particles with a particle size range of 0.2 - 0.5 cm and glycerol containing cadmium and indium are obtained. The refined indium particles are melted into indium ingots at a temperature of 180 °C under the protection of glycerol, and high-purity indium products are obtained after washing with deionized water and alcohol. In addition, glycerol is electro-deposited under the conditions of a current density of 100 A / m 2 and a temperature of 30 °C and a pole pitch of 2 cm. Crude indium is obtained after 6 h of electro-deposition.

[0042] After chemical detection and calculation, the direct recovery rate of indium is 99.6%, the cadmium removal rate is 97.8%, and the purity of refined indium is 99.95%. In addition, the current efficiency of electro-deposition is 88%, and the purity of crude indium is 88.2%.

[0043] Example 4

[0044] The purity of crude indium is 99.5%, and the main impurities are cadmium 0.2656%, arsenic 0.086%, antimony 0.008%, and lead 0.037%. The refining conditions are as follows: 10 g of crude indium, temperature 180 °C, liquid-solid ratio 6:1, excess coefficient of NH4Br is 2, reaction time is 3 min, stirring speed is 50 rpm, ultrasonic frequency is 100 kHz, and ultrasonic power is 150 W. After the reaction, refined indium particles with a particle size range of 0.2 - 0.5 cm and glycerol containing cadmium and indium are obtained. The refined indium particles are melted into indium ingots at a temperature of 180 °C under the protection of glycerol, and high-purity indium products are obtained after washing with deionized water and alcohol. In addition, glycerol is electro-deposited under the conditions of a current density of 100 A / m 2 , temperature 30 °C, and electrode spacing 3 cm for 6 h to obtain crude indium.

[0045] After chemical detection and calculation, the direct recovery rate of indium is 99.5%, the cadmium removal rate is 97.3%, and the purity of refined indium is 99.93%. In addition, the current efficiency of electro-deposition is 86%, and the purity of crude indium is 87.8%.

[0046] Comparative Example 1 (without ultrasonic enhancement)

[0047] Other conditions are the same as those in Example 1 above, except that ultrasonic waves are not used to assist the reaction process.

[0048] After chemical detection and calculation, the direct recovery rate of indium is 99.2%, the cadmium removal rate and thallium removal rate are 92.1% and 88.2% respectively, and the purity of refined indium is 99.91%. In addition, the current efficiency of electro-deposition is 81%, and the purity of crude indium is 86.5%.

[0049] The present embodiment provides a method for separating and purifying high-cadmium crude indium, wherein the high-cadmium crude indium is heated and melted into a molten liquid under the cover of glycerol, and ammonium bromide is added to the molten salt under a temperature of 180-230°C and ultrasonic enhancement conditions to refine the molten salt to obtain refined indium. As the reaction proceeds, the cadmium and thallium in the crude indium react with the ammonium bromide to generate bromides that are transferred to the glycerol solution, thereby achieving the purification and separation of impurities and indium. The refined indium particles obtained by the reaction are smelted into a metallic indium ingot under the protection of glycerol, i.e., a high-purity indium product is obtained; in addition, the glycerol after the molten salt refinement is subjected to direct current electrodeposition, and the indium and cadmium in the glycerol are recovered to obtain crude indium, and the molten salt refining step is returned. The present invention uses ammonium bromide as a cadmium and thallium removal agent, and an ultrasonic enhancement method is added to complete the impurity removal reaction in a shorter time and with less indium loss. The temperature, time and amount of ammonium bromide required by the present invention are smaller, and the effect of removing cadmium and thallium is obvious. The glycerol containing cadmium and indium produced in the refining process can be recovered by electrodeposition. The process is simple, the reaction cycle is short, the reaction is easy to control, and industrial production is easy to achieve. It has good industrial application prospects and is of great significance for the preparation of high-purity indium and energy saving and consumption reduction. By adopting this separation and purification method, the cadmium content in high-cadmium crude indium can be removed from 0.7%-0.2% to 0.0091% and 0.003%, and the thallium content can be removed from 0.007%-0.003% to 0.0008%-0.0005%.

[0050] Those skilled in the art will readily appreciate other embodiments of the present application after considering the specification and practicing the application disclosed herein. The present application is intended to cover any variations, uses or adaptations of the present application, which follow the general principles of the present application and include common knowledge or customary technical means in the art disclosed in the present application. The specification and examples are to be regarded as exemplary only, and the true scope of the present application is indicated by the claims.

[0051] It should be understood that the present application is not limited to the precise structure described above and shown in the drawings, and various modifications and changes can be made without departing from its scope. The above-described embodiments of the present application do not constitute a limitation on the scope of protection of the present application.

Claims

1. A method for separating and purifying high-cadmium crude indium, characterized in that: include: Under the cover of glycerol, the high-cadmium crude indium is heated and melted into a molten liquid state, and ammonium bromide is added under ultrasonic enhancement conditions to refine the molten salt to obtain refined indium, wherein the refining temperature is 180-230° C., the refining reaction time is 1-10 min, the amount of ammonium bromide added is represented by the excess coefficient of the ammonium bromide after the cadmium and thallium in the high-cadmium crude indium are completely reacted, the excess coefficient is 1-4, the liquid-solid ratio of the glycerol addition amount to the high-cadmium crude indium is 4:1-8:1, and the stirring speed is 50-300 rpm, the ultrasonic frequency is 20-200 kHz, and the ultrasonic power is 10-200 W during the refining process; The refined indium is washed to obtain refined indium particles with a particle size range of 0.2-0.5 cm, and the indium and cadmium dissolved in the glycerol solution are recovered by direct current deposition to obtain crude indium, which is then returned to the step of adding ammonium bromide to refine the molten salt under ultrasonic enhancement conditions, wherein the direct current deposition condition is a current density of 100-200 A / m 2 , the temperature is 25-50℃, the inter-electrode distance is 1-4cm, and the cathode and anode plates are high-purity titanium plates; The refined indium particles are smelted into metal indium ingots under the cover of glycerol, the metal indium ingots are washed several times with deionized water, and then washed several times with alcohol, and dried in a vacuum drying oven to obtain high-purity indium.

2. The method for separating and purifying high-cadmium crude indium according to claim 1, characterized in that: The liquid-to-solid ratio is 4:1-6:1, the refining temperature is 180-190°C, the refining reaction time is 2-8min, and the excess coefficient is 1-2.

3. The method for separating and purifying high-cadmium crude indium according to claim 2, characterized in that: The stirring speed is 50-200 rpm, the ultrasonic frequency is 50-100 kHz, and the ultrasonic power is 50-150 W.

4. The method for separating and purifying high-cadmium crude indium according to claim 1, characterized in that: The current density is 100-150A / m 2 , the temperature is 30-40°C, and the inter-electrode distance is 2-3cm.

5. The method for separating and purifying high-cadmium crude indium according to claim 1, characterized in that: The temperature of the refined indium particles when smelted into metal indium ingots under the cover of glycerol is 180-230° C., and the heat preservation time is 10 minutes.

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