Method for preparing high-purity indium from indium-containing dross

Abstract

The invention discloses the technical field of non-ferrous metal smelting, and belongs to the technical field of non-ferrous metal smelting, indium-containing scum reacts with aluminum powder and carbon powder under compressed air, the aluminum powder and the carbon powder can promote antimony, arsenic, tin and the like to form metal oxide alloy under the oxygen-enriched condition, the density of the metal oxide alloy is smaller than that of indium metal, and the metal oxide alloy is not prone to being damaged. Therefore, the indium floating on the surface of the metal liquid effectively prevents loss of indium metal. Hydrogen is introduced for heat treatment and reaction with metal oxides, and elements such as phosphorus, oxygen and sulfur are taken away; through two steps of distillation treatment, low-boiling-point substances (Zn, Cd, As and the like) with relatively high saturated vapor pressure are evaporated and removed in the first step of distillation, and indium metal is volatilized in the second step of distillation, so that high-boiling-point impurities (Sn, Fe, Ni and the like) are remained in a crucible; and finally, molten salt electrolysis is carried out, the anhydrous chloride forms electrolyte, indium ions move towards the cathode to be separated out, and therefore indium metal is purified.

Description

Technical Field

[0001] The present invention relates to the technical field of non-ferrous metal smelting, and particularly relates to a method for preparing high-purity indium by using indium-containing dross. Background Art

[0002] Indium has wide applications in the fields of photovoltaic materials, low-temperature welding materials, catalysts, anti-wear, anti-corrosion coatings, ITO targets, etc. The higher the purity of indium metal, the better the performance of its products.

[0003] At present, indium metal is purified by vacuum distillation, electrolytic refining, zone melting, etc. For some specific impurities such as thallium, cadmium, lead, antimony, bismuth, etc., a combined process is required for directional removal in order to produce indium ingots with higher purity. During the purification of indium, smelting is usually required. During the smelting process, indium is generated together with the by-products of metal smelting and enriched in the dross. These drosses usually contain a high grade of indium and are an important raw material source for indium extraction.

[0004] As a by-product, indium-containing dross contains a high grade of indium and has great recycling value. However, the traditional indium extraction methods have problems such as complex process flow, high energy consumption, high cost, low metal recovery rate, etc., and it is difficult to meet the current industrial production demand for high-purity indium. Summary of the Invention

[0005] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a method for preparing high-purity indium by using indium-containing dross, which can effectively recover indium from indium-containing dross and prepare high-purity indium.

[0006] To achieve the above purpose, the present application provides a method for preparing high-purity indium by using indium-containing dross, including the following steps:

[0007] (1) Put the indium-containing dross into an intermediate-frequency induction furnace, heat it up to 200 - 300 °C, introduce compressed air, add aluminum powder, react, then add carbon powder, react, cool down, and skim the surface dross to obtain indium metal ingots;

[0008] (2) Put the indium metal ingots into a tubular furnace, introduce hydrogen, and perform heat treatment to obtain reduced indium ingots;

[0009] (3) Distill the reduced indium ingots to obtain distilled indium ingots;

[0010] (4) Distill the distilled indium ingots again to obtain refined indium ingots;

[0011] (5) Use the refined indium ingots as anodes, 5N pure indium as cathodes, and anhydrous chloride salts as electrolytes for molten salt electrolysis to obtain high-purity indium.

[0012] As an embodiment of the present application, the introduction amount of the compressed air is 2-4 L / min.

[0013] As an embodiment of the present application, the mass ratio of the indium-containing dross, aluminum powder, and carbon powder is 1:(0.05-0.1):(0.005-0.01).

[0014] As an embodiment of the present application, the introduction amount of the hydrogen gas is 4-6 L / min.

[0015] As an embodiment of the present application, the temperature of the heat treatment is 500-600 °C, and the time is 4-6 h.

[0016] As an embodiment of the present application, the vacuum degree of the distillation in step (3) is 1-5 Pa, the temperature is 850-980 °C, and the time is 3-4 h.

[0017] As an embodiment of the present application, the vacuum degree of the distillation in step (3) is 0.5-1 Pa, the temperature is 1050-1100 °C, and the time is 4-6 h.

[0018] As an embodiment of the present application, the anhydrous chloride includes at least one of anhydrous indium chloride, anhydrous sodium chloride, and anhydrous zinc chloride.

[0019] As an embodiment of the present application, the electrolysis temperature is 250-300 °C, the current density is 20-25 A / dm 2 , and the electrolysis time is 12-24 h.

[0020] As an embodiment of the present application, the indium-containing dross mainly contains the following elements in mass percentages: In 80-85%, Bi 0.06-1%, Pb 1.78-2.61%, Sb 1.06-1.36%, Sn 3.07-6.5%, Zn 0.057-1.25%, As 0.03-0.06%.

[0021] The beneficial effects of the present invention are as follows: The present invention reacts the indium-containing dross with aluminum powder and carbon powder under compressed air. Among them, aluminum powder and carbon powder can promote the formation of metal oxide alloys of antimony, arsenic, tin, etc. under oxygen-rich conditions, and the density is less than that of indium metal, so it floats on the surface of the metal liquid, effectively preventing the loss of indium metal; introducing hydrogen for heat treatment to react with metal oxides to remove elements such as phosphorus, oxygen, and sulfur; through two-step distillation treatment, the first distillation evaporates and removes low-boiling substances (such as Zn, Cd, As, etc.) with a large saturated vapor pressure, and the second distillation volatilizes indium metal and leaves high-boiling impurities such as Sn, Fe, and Ni in the crucible; finally, through molten salt electrolysis, anhydrous chloride forms an electrolyte, and indium ions move to the cathode and precipitate, thereby purifying indium metal. Specific Embodiments

[0022] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the following will clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the described embodiments are some, but not all, of the embodiments of this application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in this application without making creative efforts fall within the scope of protection of this application.

[0023] In this application, among the technically characterized described in an open-ended manner, there are included closed technical solutions composed of the listed features, as well as open technical solutions containing the listed features.

[0024] In this application, regarding numerical ranges, unless otherwise specified, the above numerical ranges are considered continuous and include the minimum and maximum values of the range, as well as each value between such minimum and maximum values. Further, when the range refers to integers, it includes each integer between the minimum and maximum values of the range. In addition, when multiple ranges are provided to describe features or characteristics, the ranges can be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all sub-ranges subsumed therein.

[0025] In this application, there are no particular restrictions on the specific dispersion and stirring treatment methods.

[0026] Unless otherwise specified, the component raw materials or instruments used in each embodiment and comparative example of the present invention are all commercially available raw materials or instruments, and the component raw materials used in each parallel experiment are of the same type.

[0027] The embodiments of this application provide a method for preparing high-purity indium using indium-containing dross, which includes the following steps:

[0028] (1) Put the indium-containing dross into an intermediate-frequency induction furnace, heat it up to 200 - 300 °C, introduce compressed air, add aluminum powder, react (for 30 - 45 minutes), then add carbon powder, react (for 5 - 10 minutes), cool down, and skim the surface dross to obtain indium metal ingots;

[0029] (2) Put the indium metal ingots into a tubular furnace, introduce hydrogen, and perform heat treatment to obtain reduced indium ingots;

[0030] (3) Distill the reduced indium ingots to obtain distilled indium ingots;

[0031] (4) Distill the distilled indium ingots again to obtain refined indium ingots;

[0032] (5) Use the refined indium ingots as anodes, 5N purity indium as cathodes, and anhydrous chloride salts as electrolytes for molten salt electrolysis to obtain high-purity indium.

[0033] In the present invention, indium-containing dross reacts with aluminum powder and carbon powder under compressed air. Among them, aluminum powder and carbon powder can promote the formation of metal oxide alloys of antimony, arsenic, tin, etc. under oxygen-rich conditions, and their density is less than that of indium metal, so they float on the surface of the molten metal, effectively preventing the loss of indium metal. Hydrogen is introduced for heat treatment to react with metal oxides, removing elements such as phosphorus, oxygen, and sulfur. After two-step distillation treatment, in the first distillation, low-boiling substances (such as Zn, Cd, As, etc.) with relatively high saturated vapor pressures are evaporated and removed, and in the second distillation, indium metal volatilizes while high-boiling impurities such as Sn, Fe, Ni, etc. remain in the crucible. Finally, through molten salt electrolysis, anhydrous chloride forms an electrolyte, and indium ions move to the cathode and precipitate, thereby purifying indium metal.

[0034] In one embodiment, the flow rate of the compressed air is 2 - 4 L / min.

[0035] In one embodiment, the mass ratio of the indium-containing dross, aluminum powder, and carbon powder is 1:(0.05 - 0.1):(0.005 - 0.01). Especially when the dosage ratio of the three is within this range, the recovery rate of indium metal can be further improved, and the purity of indium can be increased.

[0036] In one embodiment, the flow rate of the hydrogen is 4 - 6 L / min.

[0037] In one embodiment, the temperature of the heat treatment is 500 - 600 °C, and the time is 4 - 6 h.

[0038] In one embodiment, the vacuum degree of the distillation in step (3) is 1 - 5 Pa, the temperature is 850 - 980 °C, and the time is 3 - 4 h. Especially when the temperature is within this range, low-boiling substances (such as Zn, Cd, As, etc.) can be removed more effectively.

[0039] In one embodiment, the vacuum degree of the distillation in step (3) is 0.5 - 1 Pa, the temperature is 1050 - 1100 °C, and the time is 4 - 6 h. Especially when the temperature is within this range, high-boiling impurities such as Sn, Fe, Ni, etc. can be more effectively retained in the crucible.

[0040] In one embodiment, the anhydrous chloride salt includes at least one of anhydrous indium chloride, anhydrous sodium chloride, and anhydrous zinc chloride.

[0041] In one embodiment, the electrolysis temperature is 250 - 300 °C, the current density is 20 - 25 A / dm 2 , and the electrolysis time is 12 - 24 h.

[0042] In one of the embodiments, the indium-containing dross mainly contains the following elements in mass percentage: In 80-85%, Bi 0.06-1%, Pb 1.78-2.61%, Sb 1.06-1.36%, Sn 3.07-6.5%, Zn 0.057-1.25%, As 0.03-0.06%.

[0043] It should be noted that the molten salt electrolysis is carried out in a conventional molten salt electrolysis furnace in the art. For example, it can be carried out in the molten salt electrolysis furnace disclosed in CN202310790108.4.

[0044] The following further elaborates on this application with specific examples:

[0045] Example 1

[0046] A method for preparing high-purity indium from indium-containing dross includes the following steps:

[0047] (1) Put the indium-containing dross into an induction medium-frequency furnace, heat it up to 300 °C, introduce compressed air with a pressure of 0.2 MPa at a flow rate of 3 L / min, add aluminum powder, stir and react for 30 min, then add carbon powder, stir and react for 10 min, cool down to 150 °C, and fish out the surface dross to obtain indium metal ingots;

[0048] The mass ratio of the indium-containing dross, aluminum powder, and carbon powder is 1:0.05:0.01.

[0049] The indium-containing dross mainly contains the following elements in mass percentage: In 83.87%, Bi 0.07%, Pb 2.08%, Sb 1.27%, Sn 5.96%, Zn 0.92%, As 0.04%.

[0050] (2) Load the indium metal ingots into a graphite boat, and then put it into a tube furnace, introduce hydrogen at a flow rate of 5 L / min, and heat-treat at 500 °C for 6 h to obtain reduced indium ingots;

[0051] (3) Load the reduced indium ingots into a graphite boat, and then place it in a vacuum distillation furnace, evacuate to a vacuum degree of 2 Pa, and react at 980 °C for 3 h to obtain distilled indium ingots;

[0052] (4) Load the distilled indium ingots into a graphite boat, and then place it in a vacuum distillation furnace, evacuate to a vacuum degree of 1 Pa, and react at 1050 °C for 4 h to obtain refined indium ingots;

[0053] (5) Use the refined indium ingots as anodes, 5N purity indium as cathodes, and anhydrous indium chloride as the electrolyte for molten salt electrolysis to obtain high-purity indium.

[0054] The electrolysis temperature is 300 °C, the current density is 20 A / dm 2 , and the electrolysis time is 20 h.

[0055] Example 2

[0056] A method for preparing high-purity indium from indium-containing dross, comprising the following steps:

[0057] (1) Put the indium-containing dross into an intermediate frequency induction furnace, heat it up to 300 °C, introduce compressed air with a pressure of 0.2 MPa at a flow rate of 3 L / min, add aluminum powder, stir and react for 30 min, then add carbon powder, stir and react for 10 min, cool down to 150 °C, and skim the surface dross to obtain indium metal ingots;

[0058] The mass ratio of the indium-containing dross, aluminum powder, and carbon powder is 1:0.1:0.005.

[0059] The indium-containing dross mainly contains the following elements by mass percentage: In 83.87%, Bi 0.07%, Pb 2.08%, Sb 1.27%, Sn 5.96%, Zn 0.92%, As 0.04%.

[0060] (2) Load the indium metal ingots into a graphite boat, and then put them into a tube furnace, introduce hydrogen at a flow rate of 5 L / min, and heat-treat at 500 °C for 6 h to obtain reduced indium ingots;

[0061] (3) Load the reduced indium ingots into a graphite boat, and then place them in a vacuum distillation furnace, evacuate to a vacuum degree of 2 Pa, and react at 980 °C for 3 h to obtain distilled indium ingots;

[0062] (4) Load the distilled indium ingots into a graphite boat, and then place them in a vacuum distillation furnace, evacuate to a vacuum degree of 1 Pa, and react at 1050 °C for 4 h to obtain refined indium ingots;

[0063] (5) Use the refined indium ingots as the anode, 5N pure indium as the cathode, and anhydrous indium chloride as the electrolyte for molten salt electrolysis to obtain high-purity indium.

[0064] The electrolysis temperature is 300 °C, the current density is 20 A / dm 2 , and the electrolysis time is 20 h.

[0065] Example 3

[0066] A method for preparing high-purity indium from indium-containing dross, comprising the following steps:

[0067] (1) Put the indium-containing dross into an intermediate frequency induction furnace, heat it up to 300 °C, introduce compressed air with a pressure of 0.2 MPa at a flow rate of 3 L / min, add aluminum powder, stir and react for 30 min, then add carbon powder, stir and react for 10 min, cool down to 150 °C, and skim the surface dross to obtain indium metal ingots;

[0068] The mass ratio of the indium-containing dross, aluminum powder, and carbon powder is 1:0.05:0.01.

[0069] The indium-containing dross mainly contains the following elements by mass percentage: In 83.87%, Bi 0.07%, Pb 2.08%, Sb 1.27%, Sn 5.96%, Zn 0.92%, As 0.04%.

[0070] (2) Load the indium metal ingots into a graphite boat, then put it into a tube furnace, introduce hydrogen at a flow rate of 5 L / min, and heat-treat at 500 °C for 6 h to obtain reduced indium ingots;

[0071] (3) Load the reduced indium ingots into a graphite boat, then place it in a vacuum distillation furnace, evacuate to a vacuum degree of 2 Pa, and react at 850 °C for 4 h to obtain distilled indium ingots;

[0072] (4) Load the distilled indium ingots into a graphite boat, then place it in a vacuum distillation furnace, evacuate to a vacuum degree of 1 Pa, and react at 1100 °C for 6 h to obtain refined indium ingots;

[0073] (5) Use the refined indium ingots as the anode, 5N purity indium as the cathode, and anhydrous indium chloride as the electrolyte for molten salt electrolysis to obtain high-purity indium.

[0074] The electrolysis temperature is 300 °C, the current density is 20 A / dm 2 , and the electrolysis time is 20 h.

[0075] Example 4

[0076] A method for preparing high-purity indium from indium-containing dross, comprising the following steps:

[0077] (1) Put the indium-containing dross into an intermediate frequency induction furnace, heat it up to 300 °C, introduce compressed air with a pressure of 0.2 MPa at a flow rate of 3 L / min, add aluminum powder, stir and react for 30 min, then add carbon powder, stir and react for 10 min, cool down to 150 °C, and skim the surface dross to obtain indium metal ingots;

[0078] The mass ratio of the indium-containing dross, aluminum powder, and carbon powder is 1:0.05:0.01.

[0079] The indium-containing dross mainly contains the following elements by mass percentage: In 83.87%, Bi 0.07%, Pb 2.08%, Sb 1.27%, Sn 5.96%, Zn 0.92%, As 0.04%.

[0080] (2) Load the indium metal ingot into a graphite boat, and then place it in a tube furnace. Pass hydrogen at a flow rate of 5 L / min and heat-treat at 500 °C for 6 h to obtain a reduced indium ingot;

[0081] (3) Load the reduced indium ingot into a graphite boat, and then place it in a vacuum distillation furnace. Evacuate to a vacuum degree of 2 Pa and react at 980 °C for 3 h to obtain a distilled indium ingot;

[0082] (4) Load the distilled indium ingot into a graphite boat, and then place it in a vacuum distillation furnace. Evacuate to a vacuum degree of 1 Pa and react at 1050 °C for 4 h to obtain a refined indium ingot;

[0083] (5) Use the refined indium ingot as the anode, 5N purity indium as the cathode, and anhydrous indium chloride as the electrolyte for molten salt electrolysis to obtain high-purity indium.

[0084] The electrolysis temperature is 250 °C, the current density is 25 A / dm 2 , and the electrolysis time is 20 h.

[0085] Comparative Example 1

[0086] A method for preparing high-purity indium from indium-containing dross, comprising the following steps:

[0087] (1) Put the indium-containing dross into an induction medium-frequency furnace, heat up to 300 °C, pass compressed air with a pressure of 0.2 MPa at a flow rate of 3 L / min, stir and react for 40 min, fish out the surface dross to obtain an indium metal ingot;

[0088] The indium-containing dross mainly contains the following elements by mass percentage: In 83.87%, Bi 0.07%, Pb 2.08%, Sb 1.27%, Sn 5.96%, Zn 0.92%, As 0.04%.

[0089] (2) Load the indium metal ingot into a graphite boat, and then place it in a tube furnace. Pass hydrogen at a flow rate of 5 L / min and heat-treat at 500 °C for 6 h to obtain a reduced indium ingot;

[0090] (3) Load the reduced indium ingot into a graphite boat, and then place it in a vacuum distillation furnace. Evacuate to a vacuum degree of 2 Pa and react at 980 °C for 3 h to obtain a distilled indium ingot;

[0091] (4) Load the distilled indium ingot into a graphite boat, then place it in a vacuum distillation furnace, evacuate to a vacuum degree of 1 Pa, and react at 1050 °C for 4 h to obtain refined indium ingots;

[0092] (5) Use the refined indium ingot as the anode, 5N purity indium as the cathode, and anhydrous indium chloride as the electrolyte for molten salt electrolysis to obtain high-purity indium.

[0093] The electrolysis temperature is 300 °C, the current density is 20 A / dm 2 , and the electrolysis time is 20 h.

[0094] Comparative Example 2

[0095] A method for preparing high-purity indium from indium-containing dross, comprising the following steps:

[0096] (1) Put the indium-containing dross into an induction medium-frequency furnace, heat up to 300 °C, introduce compressed air with a pressure of 0.2 MPa at a flow rate of 3 L / min, add aluminum powder, stir and react for 10 min, then add carbon powder, stir and react for 10 min, cool down to 150 °C, and skim the surface dross to obtain indium metal ingots;

[0097] The mass ratio of the indium-containing dross, aluminum powder, and carbon powder is 1:0.02:0.02.

[0098] The indium-containing dross mainly contains the following elements by mass percentage: In 83.87%, Bi 0.07%, Pb 2.08%, Sb 1.27%, Sn 5.96%, Zn 0.92%, As 0.04%.

[0099] (2) Load the indium metal ingots into a graphite boat, then place it in a tube furnace, introduce hydrogen at a flow rate of 5 L / min, and heat-treat at 500 °C for 6 h to obtain reduced indium ingots;

[0100] (3) Load the reduced indium ingots into a graphite boat, then place it in a vacuum distillation furnace, evacuate to a vacuum degree of 2 Pa, and react at 980 °C for 3 h to obtain distilled indium ingots;

[0101] (4) Load the distilled indium ingots into a graphite boat, then place it in a vacuum distillation furnace, evacuate to a vacuum degree of 1 Pa, and react at 1050 °C for 4 h to obtain refined indium ingots;

[0102] (5) Use the refined indium ingot as the anode, 5N purity indium as the cathode, and anhydrous indium chloride as the electrolyte for molten salt electrolysis to obtain high-purity indium.

[0103] The electrolysis temperature is 300 °C, the current density is 20 A / dm 2 , and the electrolysis time is 20 h.

[0104] Comparative Example 3

[0105] A method for preparing high-purity indium from indium-containing dross, comprising the following steps:

[0106] (1) Put the indium-containing dross into an induction medium-frequency furnace, heat it up to 300 °C, introduce compressed air with a pressure of 0.2 MPa at a flow rate of 3 L / min, add aluminum powder, stir and react for 10 min, then add carbon powder, stir and react for 10 min, cool down to 150 °C, and skim the surface dross to obtain an indium metal ingot;

[0107] The mass ratio of the indium-containing dross, aluminum powder, and carbon powder is 1:0.2:0.002.

[0108] The indium-containing dross mainly contains the following elements in mass percentage: In 83.87%, Bi 0.07%, Pb 2.08%, Sb 1.27%, Sn 5.96%, Zn 0.92%, As 0.04%.

[0109] (2) Load the indium metal ingot into a graphite boat, then put it into a tube furnace, introduce hydrogen at a flow rate of 5 L / min, and perform heat treatment at 500 °C for 6 h to obtain a reduced indium ingot;

[0110] (3) Load the reduced indium ingot into a graphite boat, then place it in a vacuum distillation furnace, evacuate to a vacuum degree of 2 Pa, and react at 980 °C for 3 h to obtain a distilled indium ingot;

[0111] (4) Load the distilled indium ingot into a graphite boat, then place it in a vacuum distillation furnace, evacuate to a vacuum degree of 1 Pa, and react at 1050 °C for 4 h to obtain a refined indium ingot;

[0112] (5) Use the refined indium ingot as the anode, 5N pure indium as the cathode, and anhydrous indium chloride as the electrolyte for molten salt electrolysis to obtain high-purity indium.

[0113] The electrolysis temperature is 300 °C, the current density is 20 A / dm 2 , and the electrolysis time is 20 h.

[0114] Comparative Example 4

[0115] A method for preparing high-purity indium from indium-containing dross, comprising the following steps:

[0116] (1) Put the indium-containing dross into an induction medium-frequency furnace, heat it up to 300 °C, introduce compressed air with a pressure of 0.2 MPa at a flow rate of 3 L / min, add aluminum powder, stir and react for 10 min, then add carbon powder, stir and react for 10 min, cool down to 150 °C, and skim the surface dross to obtain an indium metal ingot;

[0117] The mass ratio of the indium-containing dross, aluminum powder, and carbon powder is 1:0.05:0.01.

[0118] The indium-containing dross mainly contains the following elements by mass percentage: In 83.87%, Bi 0.07%, Pb 2.08%, Sb 1.27%, Sn 5.96%, Zn 0.92%, As 0.04%.

[0119] (2) Load the indium metal ingot into a graphite boat, then place it in a tube furnace, introduce hydrogen at a flow rate of 5 L / min, and perform heat treatment at 500 °C for 6 h to obtain a reduced indium ingot;

[0120] (3) Load the reduced indium ingot into a graphite boat, place it in a vacuum distillation furnace, evacuate to a vacuum degree of 1 Pa, and react at 1050 °C for 4 h to obtain a refined indium ingot;

[0121] (4) Use the refined indium ingot as the anode, 5N purity indium as the cathode, and anhydrous indium chloride as the electrolyte for molten salt electrolysis to obtain high-purity indium.

[0122] The electrolysis temperature is 300 °C, the current density is 20 A / dm 2 , and the electrolysis time is 20 h.

[0123] Comparative Example 5

[0124] A method for preparing high-purity indium from indium-containing dross includes the following steps:

[0125] (1) Put the indium-containing dross into an induction medium-frequency furnace, heat it up to 300 °C, introduce compressed air with a pressure of 0.2 MPa at a flow rate of 3 L / min, add aluminum powder, stir and react for 10 min, then add carbon powder, stir and react for 10 min, cool down to 150 °C, and skim the surface dross to obtain an indium metal ingot;

[0126] The mass ratio of the indium-containing dross, aluminum powder, and carbon powder is 1:0.05:0.01.

[0127] The indium-containing dross mainly contains the following elements by mass percentage: In 83.87%, Bi 0.07%, Pb 2.08%, Sb 1.27%, Sn 5.96%, Zn 0.92%, As 0.04%.

[0128] (2) Load the indium metal ingot into a graphite boat, then place it in a tube furnace, introduce hydrogen at a flow rate of 5 L / min, and perform heat treatment at 500 °C for 6 h to obtain a reduced indium ingot;

[0129] (3) Load the reduced indium ingot into a graphite boat, then place it in a vacuum distillation furnace, evacuate to a vacuum degree of 2 Pa, and react at 980 °C for 3 h to obtain a distilled indium ingot;

[0130] (4) Using indium ingot obtained by distillation as the anode, indium with 5N purity as the cathode, and anhydrous indium chloride as the electrolyte for molten salt electrolysis to obtain high-purity indium.

[0131] The electrolysis temperature is 300 °C, the current density is 20 A / dm 2 , and the electrolysis time is 20 h.

[0132] Comparative Example 6

[0133] A method for preparing high-purity indium from indium-containing dross, comprising the following steps:

[0134] (1) Put the indium-containing dross into an induction medium-frequency furnace, heat up to 300 °C, introduce compressed air with a pressure of 0.2 MPa at a flow rate of 3 L / min, add aluminum powder, stir and react for 10 min, then add carbon powder, stir and react for 10 min, cool down to 150 °C, and skim the surface dross to obtain indium metal ingots;

[0135] The mass ratio of the indium-containing dross, aluminum powder, and carbon powder is 1:0.05:0.01.

[0136] The indium-containing dross mainly contains the following elements in mass percentage: In 83.87%, Bi 0.07%, Pb 2.08%, Sb 1.27%, Sn 5.96%, Zn 0.92%, As 0.04%.

[0137] (2) Load the indium metal ingots into a graphite boat, then put it into a tube furnace, introduce hydrogen at a flow rate of 5 L / min, and heat-treat at 500 °C for 6 h to obtain reduced indium ingots;

[0138] (3) Load the reduced indium ingots into a graphite boat, then place it in a vacuum distillation furnace, evacuate to a vacuum degree of 2 Pa, and react at 700 °C for 3 h to obtain distilled indium ingots;

[0139] (4) Load the distilled indium ingots into a graphite boat, then place it in a vacuum distillation furnace, evacuate to a vacuum degree of 1 Pa, and react at 1250 °C for 4 h to obtain refined indium ingots;

[0140] (5) Using the refined indium ingots as the anode, indium with 5N purity as the cathode, and anhydrous indium chloride as the electrolyte for molten salt electrolysis to obtain high-purity indium.

[0141] The electrolysis temperature is 300 °C, the current density is 20 A / dm 2 , and the electrolysis time is 20 h.

[0142] Comparative Example 7

[0143] A method for preparing high-purity indium from indium-containing dross, comprising the following steps:

[0144] (1) Put the indium-containing dross into an intermediate frequency induction furnace, heat it up to 300 °C, introduce compressed air with a pressure of 0.2 MPa at a flow rate of 3 L / min, add aluminum powder, stir and react for 10 min, then add carbon powder, stir and react for 10 min, cool down to 150 °C, and skim the surface dross to obtain indium metal ingots;

[0145] The mass ratio of the indium-containing dross, aluminum powder, and carbon powder is 1:0.05:0.01.

[0146] The indium-containing dross mainly contains the following elements by mass percentage: In 83.87%, Bi 0.07%, Pb 2.08%, Sb 1.27%, Sn 5.96%, Zn 0.92%, As 0.04%.

[0147] (2) Load the indium metal ingots into a graphite boat, then put it into a tube furnace, introduce hydrogen at a flow rate of 5 L / min, and heat-treat at 500 °C for 6 h to obtain reduced indium ingots;

[0148] (3) Load the reduced indium ingots into a graphite boat, then place it in a vacuum distillation furnace, evacuate to a vacuum degree of 2 Pa, and react at 1200 °C for 3 h to obtain distilled indium ingots;

[0149] (4) Load the distilled indium ingots into a graphite boat, then place it in a vacuum distillation furnace, evacuate to a vacuum degree of 1 Pa, and react at 700 °C for 4 h to obtain refined indium ingots;

[0150] (5) Use the refined indium ingots as the anode, 5N purity indium as the cathode, and anhydrous indium chloride as the electrolyte for molten salt electrolysis to obtain high-purity indium.

[0151] The electrolysis temperature is 300 °C, the current density is 20 A / dm 2 , and the electrolysis time is 20 h.

[0152] Test Example

[0153] Among them, the high-purity indium and recovery rates of the examples and comparative examples are shown in Table 1.

[0154] Table 1

[0155] Purity of high-purity indium Recovery rate / % Example 1 5N(99.999) 99 Example 2 5N(99.999) 98 Example 3 5N(99.999) 97 Example 4 5N(99.999) 95 Comparative Example 1 3.5N(99.95) 87 Comparative Example 2 4N(99.99) 80 Comparative Example 3 4.5N(99.995) 78 Comparative Example 4 4N(99.99) 90 Comparative Example 5 3.5N(99.95) 85 Comparative Example 6 4N(99.99) 70 Comparative Example 7 4N(99.99) 65

[0156] As can be seen from Table 1, in the present invention, indium-containing dross reacts with aluminum powder and carbon powder under compressed air. Among them, aluminum powder and carbon powder can promote the formation of metal oxide alloys of antimony, arsenic, tin, etc. under oxygen-rich conditions, and their density is less than that of indium metal, so they float on the surface of the metal liquid, effectively preventing the loss of indium metal. Hydrogen is introduced for heat treatment to react with metal oxides to remove elements such as phosphorus, oxygen, and sulfur. After two-step distillation treatment, in the first distillation, low-boiling substances with relatively high saturated vapor pressures (such as Zn, Cd, As, etc.) are evaporated and removed. In the second distillation, indium metal volatilizes while high-boiling impurities such as Sn, Fe, and Ni remain in the crucible. Finally, through molten salt electrolysis, anhydrous chloride forms an electrolyte, and indium ions move to the cathode and precipitate, thereby purifying indium metal, and the purity of the prepared indium metal reaches the 5N level.

[0157] Comparing Example 1 with Comparative Examples 1 to 3, it can be seen that in the present invention, by introducing and adding carbon powder and aluminum powder and controlling the mass ratio of the three to be 1:(0.05 - 0.1):(0.005 - 0.01), the recovery rate of indium metal can be effectively increased and the purity of indium can be improved.

[0158] Comparing Example 1 with Comparative Examples 4 to 7, it can be seen that in the present invention, by adopting two-step distillation and strictly controlling the temperatures of the two-step distillation, the recovery rate of indium metal can be effectively increased and the purity of indium can be improved.

[0159] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the protection scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing high-purity indium using indium-containing dross, characterized in that, It includes the following steps: (1) Put indium-containing dross into an intermediate frequency induction furnace, heat it up to 200 - 300 °C, introduce compressed air, add aluminum powder, react, then add carbon powder, react, cool down, and skim the surface dross to obtain indium metal ingots; (2) Put the indium metal ingots into a tubular furnace, introduce hydrogen, and conduct heat treatment to obtain reduced indium ingots; (3) Distill the reduced indium ingots to obtain distilled indium ingots; (4) Distill the distilled indium ingots again to obtain refined indium ingots; (5) Use the refined indium ingots as the anode, 5N purity indium as the cathode, and anhydrous chloride salt as the electrolyte for molten salt electrolysis to obtain high-purity indium.

2. The method for preparing high-purity indium using indium-containing dross according to claim 1, characterized in that, The flow rate of the introduced compressed air is 2 - 4 L / min.

3. The method for preparing high-purity indium by using indium-containing dross according to claim 1, characterized in that, The mass ratio of the indium-containing dross, aluminum powder, and carbon powder is 1:(0.05 - 0.1):(0.005 - 0.01).

4. The method for preparing high-purity indium by using indium-containing dross according to claim 1, characterized in that, The flow rate of the introduced hydrogen is 4 - 6 L / min.

5. The method for preparing high-purity indium by using indium-containing dross according to claim 1, characterized in that, The temperature of the heat treatment is 500 - 600 °C, and the time is 4 - 6 h.

6. The method for preparing high-purity indium by using indium-containing dross according to claim 1, characterized in that, For the distillation in step (3), the vacuum degree is 1 - 5 Pa, the temperature is 850 - 980 °C, and the time is 3 - 4 h.

7. The method for preparing high-purity indium by using indium-containing dross according to claim 1, characterized in that, For the distillation in step (3), the vacuum degree is 0.5 - 1 Pa, the temperature is 1050 - 1100 °C, and the time is 4 - 6 h.

8. The method for preparing high-purity indium by using indium-containing dross according to claim 1, characterized in that, The anhydrous chloride salt includes at least one of anhydrous indium chloride, anhydrous sodium chloride, and anhydrous zinc chloride.

9. The method for preparing high-purity indium by using indium-containing dross according to claim 1, characterized in that, The electrolysis temperature is 250 to 300 °C, the current density is 20 to 25 A / dm 2 , and the electrolysis time is 12 to 24 h.

10. The method for preparing high-purity indium by using indium-containing dross according to claim 1, wherein The indium-containing dross mainly contains the following elements with mass percentages: In 80 - 85%, Bi 0.06 - 1%, Pb 1.78 - 2.61%, Sb 1.06 - 1.36%, Sn 3.07 - 6.5%, Zn 0.057 - 1.25%, As 0.03 - 0.06%.