High-purity indium and preparation method thereof

Abstract

The invention belongs to the technical field of metal purification, and discloses high-purity indium and a preparation method thereof.The preparation method comprises the following steps that 1, an indium ingot is smelted to remove impurities; 2, casting the indium ingot subjected to impurity removal in the step 1 into an anode plate, and carrying out electrolytic impurity removal to obtain compact indium metal; 3, compact indium metal is melted and cast into ingots, and reduction zone smelting is carried out under the condition that hydrogen is continuously introduced; 4, after reduction zone smelting is completed, zone smelting impurity removal is conducted under inert gas protection, and high-purity indium is obtained; wherein the introduction flow of the hydrogen in the step 3 is 4-6L / min, the zone melting temperature is 300-400 DEG C, and the reaction is performed for 3-4 hours. According to the preparation method of the high-purity indium provided by the invention, the impurity removal efficiency of the high-purity indium prepared by the method is high, and impurities among crystal lattices deeply hidden in indium ingots can be discharged and removed, so that the purity of the indium is further improved.

Description

Technical Field

[0001] The invention relates to the technical field of metal purification, and in particular to high-purity indium and a preparation method thereof. Background Art

[0002] Indium is a rare and associated metal located in the IIIA group of the fifth period of the periodic table. It is a silvery white metal with a slightly blue luster. It has good ductility and plasticity, good photoelectric properties, excellent physical and chemical properties such as corrosion resistance, and is widely used in photovoltaic industry, display target industry, military industry, aerospace and other high-tech fields of modern electronic information industry. The purity of the metal directly affects the physical and chemical properties of the corresponding metal products. As the purity of the metal increases, it is beneficial to further improve the performance of its metal products. However, the current methods for purifying metallic indium have many problems such as high energy consumption and low metal purification efficiency.

[0003] Prior art 1: Chinese patent application 2014103260458 discloses a method for removing thallium and cadmium in the production of high-purity indium. Its background technology records: "Currently, the main method for removing impurities and producing refined indium is electrolysis. Since the potential of cadmium and thallium is very different from that of indium, they cannot be effectively removed during the electrolysis process." Therefore, the prior art has made technical improvements based on this.

[0004] Prior art 1 discloses a technical solution of using ammonium chloride, zinc chloride, glycerol and indium to smelt and remove thallium, and using potassium iodide, iodine, glycerol and indium to smelt and remove cadmium. This technology can effectively remove thallium and cadmium that are difficult to remove by electrolysis; it is a good impurity removal solution.

[0005] Similarly, prior art 2 also has a similar idea to prior art 1, and further purifies indium. Prior art 2: Chinese patent 2012103587901 discloses a method for preparing high-purity indium, and its specification states: "It includes the following steps: (1) acid leaching, the raw material enters dilute sulfuric acid to remove surface oxides; (2) determination; (3) smelting and impurity removal, removing impurities such as thallium, tin, and cadmium; further, the raw material indium of step 3 is placed in a crucible, and a glycerol solution of potassium iodide with a concentration of 5% is added, and the mixture is heated to 180°C and smelted for 30 minutes to remove the impurity cadmium... (also including the step of removing thallium and tin); (4) primary electrolysis; (5) secondary electrolysis".

[0006] Prior art 2 uses a combination of smelting and impurity removal and electrolysis to prepare high-purity indium, and can produce 5N-level high-purity indium.

[0007] However, for some high-end products, 5N-level high-purity indium cannot meet their application requirements, and too many impurities will affect the quality of high-end products. Therefore, it is necessary to find a method for preparing high-purity indium with higher purity, so as to meet the needs of high-end products in the high-tech fields of modern electronic information industries such as photovoltaic industry, display target industry, military industry and aerospace. Summary of the invention

[0008] One of the purposes of the present invention is to provide a method for preparing high-purity indium to solve the problem that the high-purity indium prepared by the prior art is not of sufficient purity and is difficult to meet customer needs; through the method for preparing high-purity indium, 7N grade high-purity indium can be prepared.

[0009] Another object of the present invention is to provide a high-purity indium, the purity of which reaches 7N level, which can meet the production needs of many products in the high-tech fields of modern electronic information industries such as photovoltaic industry, display target industry, military industry and aerospace.

[0010] To achieve the above object, the present invention provides a method for preparing high-purity indium, comprising the following steps:

[0011] Step 1: Smelting and removing impurities from the indium ingot;

[0012] Step 2: Cast the indium ingot after impurity removal in step 1 into an anode plate, and perform electrolytic de-impurification to obtain dense indium metal;

[0013] Step 3: Melt the dense indium metal into an ingot and perform reduction zone smelting under continuous hydrogen flow;

[0014] Step 4: After the reduction zone smelting is completed, the zone smelting is carried out under the protection of inert gas to remove impurities and obtain high-purity indium;

[0015] The hydrogen flow rate in step 3 is 4-6 L / min, the zone melting temperature is 300-400° C., and the reaction time is 3-4 hours.

[0016] The molten salt purification principle of the present invention is to use the halogen element to have a greater affinity for Cd and Tl, which can effectively remove impurities Cd and Tl under certain conditions, Cd + I2 = CdI2, CdI2 + 2KI = K2CdI4, Tl + +I - =TlI, TlI+I2=TlI3.

[0017] Electrolytic refining utilizes the fact that impurity metals such as Pb, Sn, Bi, Sb have a more positive potential than In metal and exist in the form of anode mud, thereby achieving the purpose of purification.

[0018] Hydrogenation reduction is the process of removing interstitial elements (O, P, S, etc.) in gaseous form by reacting them with hydrogen at high temperatures.

[0019] Zone smelting utilizes the different solubility of impurity metals in the solid and liquid indium metal, K=Cs / CL, K>1, the impurities remain at the head of the ingot, K<1, the impurities are enriched at the tail of the ingot. The above method can effectively purify 5N indium ingots to 7N and above ultra-high purity indium.

[0020] For high-purity indium with a purity level of 5N, the remaining impurities are difficult to remove. The reason is that the impurities are deeply hidden in the lattice gaps inside the indium, and the gaps are occupied by some O elements, S elements, etc., resulting in the remaining impurities being discharged through zone melting; therefore, hydrogen reduction is a key step in the scheme of the present invention. The purpose of introducing hydrogen is to remove the interstitial elements O, S, N, P, etc., to enlarge the space in the indium ingot lattice, and to increase the directional mobility of the metal elements, thereby improving the impurity removal efficiency. If hydrogen reduction is not added, the number of zone melting times will increase, and at the same time, the impurity removal rate will not be significantly improved, and energy consumption will increase.

[0021] Preferably, the specific operation of step 1 is: placing the indium ingot, potassium chloride and glycerol in a mass ratio of 100:5:30 in a heating furnace and heating to 180-220°C, then stirring and smelting for 10-30 minutes, continuously dripping I2 during the stirring and smelting process until the solution turns reddish brown, and then taking out the indium ingot for acid washing to obtain an indium ingot with impurities removed.

[0022] Preferably, the specific operation of step 2 is: casting the indium ingot after impurity removal in step 1 into an anode plate, and then configuring 3+ 80-100g / L, NaCl 100-120g / L, gelatin 0.2-0.5g / L, thiourea 0.1-0.3g / L electrolyte, cell voltage 0.2-0.3V, current density 60-100A / m 2 , at a temperature of 20-30°C, the electrolysis reaction lasts for 7 days, and indium ions are precipitated on the cathode plate as dense indium metal.

[0023] Preferably, the specific operation of step 3 is: melt the dense indium metal ingot, place it in a zone furnace, use inert gas to evacuate the air in the zone furnace so that the zone furnace is in an inert gas protective atmosphere, and then introduce hydrogen at a flow rate of 4-6L / min to react at 300-400°C for 3-4h.

[0024] Preferably, the specific operation of step 4 is: after the reduction zone smelting is completed, the inert gas is continuously introduced at a flow rate of 6-8L / min, the zone smelting is performed twice at a temperature of 600-650°C and a moving rate of 120mm / h, and then the temperature is adjusted to 400-500°C, and the zone smelting is performed four times at a moving rate of 100mm / h.

[0025] It should be noted that, in the specific operation of the above step 4, the number of zone melting can be adjusted according to the purity of the indium ingot in step 1; when the purity of the indium ingot in step 1 is at the 3N level, the number of zone melting at 600-650°C is 4 times, and the number of zone melting at 400-500°C is 7 times; when the purity of the indium ingot in step 1 is at the 4N level, the number of zone melting at 600-650°C is 3 times, and the number of zone melting at 400-500°C is 6 times; when the purity of the indium ingot in step 1 is at the 5N level, the number of zone melting at 600-650°C is 2 times, and the number of zone melting at 400-500°C is 4 times.

[0026] The present invention also provides high-purity indium, which is prepared by using the above-mentioned method for preparing high-purity indium.

[0027] Preferably, the indium ingot in step 1 is an indium ingot with a purity level of 5N. By using an indium ingot with a purity level of 5N to be processed according to the preparation method of the present invention, it can be further purified more quickly, thereby enabling mass production.

[0028] Beneficial Effects

[0029] Compared with the prior art, the present invention provides a method for preparing high-purity indium. The high-purity indium prepared by the method has high impurity removal efficiency and can remove impurities hidden between the crystal lattices inside the indium ingot, thereby further improving the purity of indium. DETAILED DESCRIPTION

[0030] The present invention will be further described below in conjunction with the embodiments, but it does not constitute any limitation to the present invention. Any limited number of modifications made within the scope of the claims of the present invention are still within the scope of the claims of the present invention.

[0031] In order to explain the technical content of the present invention in detail, further description is given below in conjunction with the implementation modes.

[0032] Example 1

[0033] A high-purity indium is prepared by the following steps:

[0034] Step 1: Place an indium ingot with a purity of 99.999%, potassium chloride and glycerol in a mass ratio of 100:5:30 in a heating furnace and heat to 200°C, then stir and smelt for 20 minutes, continuously drip I2 during the stirring and smelting process until the solution turns reddish brown, then take out the indium ingot and acid wash it to obtain an indium ingot with impurities removed;

[0035] Step 2: Cast the indium ingot after impurity removal in step 1 into an anode plate, and then configure the indium 3+100g / L, NaCl110g / L, gelatin 0.4g / L, thiourea 0.2g / L electrolyte, at a cell voltage of 0.25V and a current density of 80A / m 2 , at a temperature of 25±5℃, the electrolysis reaction lasts for 7 days, and the indium ions are precipitated as dense indium metal on the cathode plate;

[0036] Step 3: melt the dense indium metal ingot, place it in a zone furnace, use inert gas to evacuate the air in the zone furnace so that the zone furnace is in an inert gas protection atmosphere, and then introduce hydrogen at a flow rate of 4-6L / min to react at 300-400°C for 3-4h;

[0037] Step 4: After the reduction zone smelting is completed, inert gas is continuously introduced at a flow rate of 6-8L / min, and the zone smelting is performed twice at a temperature of 600-650°C and a moving speed of 120mm / h. Then the temperature is adjusted to 400-500°C, and the zone smelting is performed four times at a moving speed of 100mm / h to obtain high-purity indium.

[0038] Example 2

[0039] It is generally the same as Example 1, except that step 1 uses an indium ingot with a purity of 99.99%, and step 4 is changed to: after the reduction zone smelting is completed, an inert gas is continuously introduced at a flow rate of 6-8L / min, and the zone is smelted 3 times at a temperature of 600-650°C and a moving rate of 120mm / h, and then the temperature is adjusted to 400-500°C, and the zone is smelted 6 times at a moving rate of 100mm / h to obtain high-purity indium.

[0040] Example 3

[0041] It is generally the same as Example 1, except that step 1 uses an indium ingot with a purity of 99.9%, and step 4 is changed to: after the reduction zone smelting is completed, an inert gas is continuously introduced at a flow rate of 6-8L / min, and the zone is smelted 4 times at a temperature of 600-650°C and a moving speed of 120mm / h, and then the temperature is adjusted to 400-500°C, and the zone is smelted 7 times at a moving speed of 100mm / h to obtain high-purity indium.

[0042] Comparative Example 1

[0043] A high-purity indium is prepared by the following steps:

[0044] Step 1: Place an indium ingot with a purity of 99.999%, potassium chloride and glycerol in a mass ratio of 100:5:30 in a heating furnace and heat to 200°C, then stir and smelt for 20 minutes, continuously drip I2 during the stirring and smelting process until the solution turns reddish brown, then take out the indium ingot and acid wash it to obtain an indium ingot with impurities removed;

[0045] Step 2: Cast the indium ingot after impurity removal in step 1 into an anode plate, and then configure the indium 3+ The electrolyte is 100g / L, NaCl 110g / L, gelatin 0.4g / L, thiourea 0.2g / L, at a cell voltage of 0.25V and a current density of 80A / m 2 , at a temperature of 25±5℃, the electrolysis reaction lasts for 7 days, and the indium ions are precipitated as dense indium metal on the cathode plate;

[0046] Step 3: melt the dense indium metal ingot, place it in a zone furnace, continuously introduce inert gas at a flow rate of 6-8L / min, perform zone melting twice at a temperature of 600-650°C and a moving speed of 120mm / h, then adjust the temperature to 400-500°C, perform zone melting four times at a moving speed of 100mm / h to obtain high-purity indium.

[0047] Comparative Example 2

[0048] A high-purity indium is prepared by the following steps:

[0049] Step 1: placing an indium ingot with a purity of 99.999% in a zone furnace, exhausting the air in the zone furnace with an inert gas so that the zone furnace is in an inert gas protection atmosphere, and then introducing hydrogen at a flow rate of 4-6L / min to react at 300-400°C for 3-4h;

[0050] Step 2: placing the indium ingot obtained in step 1, potassium chloride and glycerol in a mass ratio of 100:5:30 in a heating furnace and heating to 200°C, then stirring and smelting for 20 minutes, continuously dripping I2 during the stirring and smelting process until the solution turns reddish brown, then taking out the indium ingot and pickling it to obtain an indium ingot with impurities removed;

[0051] Step 3: Cast the indium ingot after impurity removal in step 1 into an anode plate, and then configure the indium 3+ 100g / L, NaCl110g / L, gelatin 0.4g / L, thiourea 0.2g / L electrolyte, at a cell voltage of 0.25V and a current density of 80A / m 2 , at a temperature of 25±5℃, the electrolysis reaction lasts for 7 days, and the indium ions are precipitated as dense indium metal on the cathode plate;

[0052] Step 4: melt the dense indium metal ingot, place it in a zone furnace, continuously introduce inert gas at a flow rate of 6-8L / min, perform zone melting twice at a temperature of 600-650°C and a moving speed of 120mm / h, then adjust the temperature to 400-500°C, perform zone melting four times at a moving speed of 100mm / h to obtain high-purity indium.

[0053] The high-purity indium obtained in Example 1-3 and Comparative Example 1-2 was tested by GDMS / ICP-MS. The results are shown in Table 1.

[0054] Table 1 Purity of high-purity indium in Examples 1-3 and Comparative Examples 1-2

[0055] High purity indium Example 1 99.99999％ Example 2 99.9999％ Example 3 99.9999％ Comparative Example 1 99.99995％ Comparative Example 2 99.99995％

[0056] According to the results in Table 1, we can see that:

[0057] According to the data comparison between Example 1 and Comparative Examples 1 and 2, it can be seen that the hydrogen reduction step of the present application is the key factor that enables high-purity indium to reach the 7N level;

[0058] Although comparative example 1 can obtain 6N grade high-purity indium without using hydrogen reduction, it does not clean the lattice space inside the indium ingot, making it difficult to remove some impurities;

[0059] Although Comparative Example 2 adopts a hydrogen reduction step, since most of the impurities are removed after hydrogen reduction, although the impurity removal efficiency is improved to a certain extent, it cannot achieve the effect of cleaning the indium ingot lattice space and improving the impurity removal rate;

[0060] The present application first removes most of the impurities through a smelting step and an electrolysis step, and then removes the interstitial elements O, S, N, P, etc. in the lattice space inside the indium ingot through hydrogen reduction, so that the space in the indium ingot lattice becomes larger, and the directional mobility of the metal elements is increased, thereby improving the impurity removal efficiency and impurity removal ability.

[0061] The embodiments presented herein are only embodiments selected according to the combination of all possible embodiments. The appended claims should not be limited by the embodiments describing the present invention. Some numerical ranges used in the claims include sub-ranges therein, and the changes in these ranges should also be covered by the appended claims.

Claims

1. A method for preparing high-purity indium, characterized in that: The steps include: Step 1: Smelting and removing impurities from the indium ingot; Step 2: Cast the indium ingot after impurity removal in step 1 into an anode plate, and perform electrolytic de-impurification to obtain dense indium metal; Step 3: Melt the dense indium metal into an ingot and perform reduction zone smelting under continuous hydrogen flow; Step 4: After the reduction zone smelting is completed, the zone smelting is carried out under the protection of inert gas to remove impurities and obtain high-purity indium; The hydrogen flow rate in step 3 is 4-6 L / min, the zone melting temperature is 300-400° C., and the reaction time is 3-4 hours.

2. The method for preparing high-purity indium according to claim 1, characterized in that: The specific operation of step 1 is: placing the indium ingot, potassium chloride and glycerol in a mass ratio of 100:5:30 in a heating furnace and heating to 180-220° C., then stirring and smelting for 10-30 minutes, continuously dripping I2 during the stirring and smelting process until the solution turns reddish brown, and then taking out the indium ingot for pickling to obtain the indium ingot after impurities are removed.

3. The method for preparing high-purity indium according to claim 1, characterized in that: The specific operation of step 2 is: casting the indium ingot after impurity removal in step 1 into an anode plate, and then configuring 3+ 80-100g / L, NaCl 100-120g / L, gelatin 0.2-0.5g / L, thiourea 0.1-0.3g / L electrolyte, cell voltage 0.2-0.3V, current density 60-100A / m 2 , at a temperature of 20-30°C, the electrolysis reaction lasts for 7 days, and indium ions are precipitated on the cathode plate as dense indium metal.

4. The method for preparing high-purity indium according to claim 1, characterized in that: The specific operation of step 3 is: melt the dense indium metal ingot, place it in a zone furnace, use inert gas to evacuate the air in the zone furnace so that the zone furnace is in an inert gas protection atmosphere, and then introduce hydrogen at a flow rate of 4-6L / min to react at 300-400°C for 3-4h.

5. The method for preparing high-purity indium according to claim 1, characterized in that: The specific operation of step 4 is: after the reduction zone smelting is completed, the inert gas is continuously introduced at a flow rate of 6-8L / min, the zone smelting is performed twice at a temperature of 600-650°C and a moving speed of 120mm / h, and then the temperature is adjusted to 400-500°C, and the zone smelting is performed four times at a moving speed of 100mm / h.

6. A high-purity indium, characterized in that: The high-purity indium is prepared by the preparation method of any one of claims 1 to 5.

7. The high-purity indium according to claim 6, characterized in that: The indium ingot in step 1 is an indium ingot with a purity level of 5N.