CN114808036B - A method for recycling high-purity tin-indium alloy from ITO target waste - Google Patents

Abstract

A method for recycling high-purity tin-indium alloy from ITO target scraps is to take the ITO target scraps as anode plates, and comprises the following steps: (1) dissolving; (2) primary purification; (3) secondary purification. According to the invention, a small current is added to the large-size anode plate and the small-size cathode plate to form a weak nonuniform electric field, under the nonuniform electric field, indium tin in ITO target waste is firstly rapidly dissolved into electrolyte to form pure indium tin solution, and then the indium tin solution is used as electrolyte for secondary microcurrent electrolysis, so that the indium tin alloy cannot drift to cathode deposition due to nonuniform electric field, but rapidly sinks to the bottom of an electrolytic tank, and cathode-anode short-circuiting is avoided; under the method, the recovery rate of the indium-tin alloy is improved to more than 80 percent.

Description

A method for recycling high-purity tin-indium alloy from ITO target waste

Technical field

The invention belongs to the field of ITO powder production, and specifically relates to a method for recovering high-purity tin-indium alloy from ITO target waste.

Background technique

With the rapid development of electronic information technology, liquid crystal displays have been widely used, and the consumption of ITO targets, which are raw materials for producing indium tin oxide films, has also increased significantly. The utilization rate of ITO targets in the production of ITO films is low, and about 70% of ITO targets become waste and need to be recycled. The composition of ITO targets is generally indium oxide and tin oxide with a mass ratio of 9:1. The content of metallic indium in the waste target is about 74.40%, and the content of metallic tin is about 7.88%. Both indium and tin metals are precious metals. The content of indium in the earth's crust is 1×10-5%, and it is relatively dispersed. No rich ore has been found so far. Although there are 5 independent mineral species identified, such as copper sulfide indium (CuInS ₂ ), sulfide indium iron ore (FeInS ₄ ), hydroindium ore [In(OH) ₃ ], etc., these minerals are also rare in nature. Indium It mainly exists in isomorphous iron sphalerite (indium content is 0.0001% to 0.1%), hematite, galena and other polymetallic sulfide ores. In addition, tin ore, wolframite, and common hornblende also contain indium. Indium is therefore classified as a rare metal. The global estimated indium reserves are only 50,000 tons, of which 50% can be mined. Tin is one of the rare metals in the world, with a content of 0.004% in the earth's crust. The global tin reserves are about 4.8 million tons, and the basic reserves are about 11 million tons. Therefore, realizing green and efficient recycling of metal indium tin in waste targets is a major technical need for the development of the ITO industry. It is also of extremely important significance for the protection and rational utilization of metal resources. For the current recovery of indium tin from ITO waste targets, we found patent document CN200780039782.8 which discloses a method of recovering indium-tin alloy by electrolysis of ITO waste. This method uses sulfuric acid, hydrochloric acid, and alkali as the electrolyte, and adds ammonium sulfate, sodium chloride, sodium sulfate, etc. as the electrolyte, ITO as the anode, carbon and other corrosion-resistant electrodes as the cathode motherboard, and the electrolysis temperature is controlled at 20 to 50 ℃, the current density is preferably adjusted appropriately according to the type of raw material, and electrolysis is performed under conditions. This method takes a long time to electrolyze, and the highest recovery rate of indium tin alloy is only 75%.

Contents of the invention

The purpose of the present invention is to solve the above technical problems and provide a method for recovering high-purity tin-indium alloy from ITO target waste that can increase the recovery rate of indium-tin alloy and has high product purity.

In order to achieve the above objects, the technical solution of the present invention is:

A method of recycling high-purity tin-indium alloy from ITO target waste is to use ITO target waste as an anode plate. The steps include:

(1) Dissolution: Place the anode plate and titanium cathode plate in the first electrolytic tank, use sulfuric acid solution as the electrolyte, and perform the first microcurrent electrolysis to obtain an indium tin solution;

(2) Primary purification: Place the anode plate and titanium cathode plate in the second electrolytic tank, use the indium tin solution as the electrolyte, and perform the second microcurrent electrolysis;

(3) Secondary purification: Filter out the water from the indium-tin alloy precipitate at the bottom of the second electrolytic tank, put it into a suspension equipment for vacuum and high-temperature melting, and obtain a high-purity indium-tin alloy.

As a further technical solution, the length ratio of the above-mentioned anode plate and cathode plate is (1.4-1.6):1, and the ratio of the width is (1.4-1.6):1.

As a further technical solution, the length, width and thickness of the above-mentioned anode plate are 19.80cm~20.20cm, 13.80cm~14.20cm, 0.90cm~1.10cm; the length, width and thickness of the cathode plate are 12.38cm~14.42cm, 8.63 cm～10.15cm, 0.20cm～0.30cm.

As a further technical solution, the current density of the first microcurrent electrolysis mentioned above is 40A/m ² to 50A/m ² , the temperature is 20 to 60°C, and the electrolysis time is 120 to 180 minutes.

As a further technical solution, the current density of the second microcurrent electrolysis mentioned above is 51A/m ² to 70A/m ² , the temperature is 20 to 60°C, and the electrolysis time is 100 to 150 minutes.

As a further technical solution, for the above-mentioned vacuum high-temperature smelting in the suspension equipment, the precipitate at the bottom of the second electrolytic tank is placed in a graphite crucible, and then placed in the suspension equipment that has been pre-passed with high-purity Ar, and vacuumed. Heat to a molten state, then increase the temperature to 2500-3000°C, and keep it for 1 hour. After the insulation is completed, cool the material to room temperature under the protection of high-purity Ar.

As a further technical solution, the above-mentioned vacuum degree is ≥0.08Mpa.

As a further technical solution, the above-mentioned ITO target waste is ultrasonically cleaned with acetone, crushed, and then pressed into anode plates.

As a further technical solution, the above-mentioned drying temperature is 100-110°C and the time is 30-60 minutes.

As a further technical solution, the concentration of the above sulfuric acid solution is 800g/l.

Compared with the prior art, the beneficial effects of the present invention are:

1. The large-sized anode plate and small-sized cathode plate of the present invention, coupled with a small current, form a weak non-uniform electric field. Under this non-uniform electric field, the indium tin in the ITO target waste material first quickly dissolves into the electrolyte, A pure indium tin solution is formed, and then the indium tin solution is used as the electrolyte for secondary microcurrent electrolysis. Due to the uneven electric field, the indium tin alloy will not drift to the cathode for deposition, but will quickly sink to the bottom of the electrolytic tank to avoid negative and positive effects. Extreme short circuit; under this method, the recovery rate of the indium tin alloy of the present invention is increased to more than 80%.

2. The present invention uses suspension purification. The principle is to increase the melting temperature of the indium tin crude alloy to increase the gap between the saturated vapor pressure and temperature relationship curves of oxygen, nitrogen, hydrogen and the indium tin crude alloy, thereby making the indium tin crude alloy and the indium tin crude alloy. Oxygen, nitrogen and hydrogen are separated to obtain high-purity tin-indium alloy with N content ≤0.001%, H content ≤0.001% and O content ≤0.001%.

Detailed ways

The present invention will be described in further detail below with reference to the examples, but the implementation of the present invention is not limited to the scope represented by the examples.

The ITO target waste selected in this example comes from an indium tin target factory in Guangxi, and its composition is tested as shown in Table 1:

Table 1

chemical composition In Sn N O H Content /% 74.40 7.81 0.005 17.70 0.005

Clean the ITO target waste with acetone, wipe off the acetone, clean it with ultrasonic waves in pure water medium for 30 minutes, put it into the jaw crusher and crush it into pieces less than 5 mm, and then press it into an anode plate. Each anode Boards are limited to 2kg.

The dimensions of the anode plate and the cathode plate used in Example 1, Example 2 and Example 3 are: the length, width and thickness of the anode plate are 19.80cm, 13.80cm, 0.90cm; the length, width and thickness of the cathode plate are 12.38cm, 8.63cm cm, 0.20cm.

The dimensions of the anode plate and cathode plate used in Examples 4 and 5 are: the length, width and thickness of the anode plate are 20.20cm, 14.20cm, and 1.10cm in order; the length, width and thickness of the cathode plate are 14.42cm, 10.15cm, and 0.30cm in order. .

Example 1:

(1) Dissolution: Place the anode plate and titanium cathode plate in the first electrolytic tank, use 800g/l sulfuric acid as the electrolyte, and perform the first microcurrent electrolysis. The current density of the first microcurrent electrolysis is 40A/m. ^2. The temperature is 20°C and the electrolysis time is 120 minutes. Take the indium tin solution in the first electrolytic tank;

(2) Primary purification: Place the anode plate and titanium cathode plate in the second electrolytic tank, use the indium tin solution as the electrolyte, and perform the second microcurrent electrolysis. The current density of the second microcurrent electrolysis is 50A/m ² , the temperature is 20, and the electrolysis time is 100min;

(3) Secondary purification: Filter out the water from the indium-tin alloy precipitate at the bottom of the second electrolytic tank and place it in a graphite crucible, then put it into the high-purity Ar suspension equipment that has been passed in for half an hour in advance, and then vacuum. The temperature is -0.08MPa, heat until the precipitate melts, then increase the temperature to 2500°C, and keep it for 1 hour. After the insulation is completed, add high-purity Ar protection and cool the material to room temperature. Vacuum high-temperature smelting in the suspension equipment produced 1.35kg of high-purity indium-tin alloy with a recovery rate of 81.82%.

Example 2:

(1) Dissolution: Place the anode plate and titanium cathode plate in the first electrolytic tank, use 800g/l sulfuric acid as the electrolyte, and perform the first microcurrent electrolysis. The current density of the first microcurrent electrolysis is 45A/m. ^2. The temperature is 40°C and the electrolysis time is 160 minutes. Take the indium tin solution in the first electrolytic tank;

(2) Primary purification: Place the anode plate and titanium cathode plate in the second electrolytic tank, use the indium tin solution as the electrolyte, and perform the second microcurrent electrolysis. The current density of the second microcurrent electrolysis is 60A/m ² , the temperature is 40°C, and the electrolysis time is 130min;

(3) Secondary purification: Filter out the water from the indium-tin alloy precipitate at the bottom of the second electrolytic tank and place it in a graphite crucible, then put it into the high-purity Ar suspension equipment that has been passed in for half an hour in advance, and then vacuum. The temperature is -0.08MPa, heat until the precipitate melts, then increase the temperature to 2500°C, and keep it for 1 hour. After the insulation is completed, add high-purity Ar protection and cool the material to room temperature. Vacuum high-temperature smelting in the suspension equipment produced 1.37kg of high-purity indium-tin alloy with a recovery rate of 83.03%.

Example 3:

(1) Dissolution: Place the anode plate and titanium cathode plate in the first electrolytic tank, use 800g/l sulfuric acid as the electrolyte, and perform the first microcurrent electrolysis. The current density of the first microcurrent electrolysis is 50A/m. ^2. The temperature is 60°C and the electrolysis time is 180 minutes. Take the indium tin solution in the first electrolytic tank;

(2) Primary purification: Place the anode plate and titanium cathode plate in the second electrolytic tank, use the indium tin solution as the electrolyte, and perform the second microcurrent electrolysis. The current density of the second microcurrent electrolysis is 70A/m ² , the temperature is 60°C, and the electrolysis time is 150min;

(3) Secondary purification: Filter out the water from the indium-tin alloy precipitate at the bottom of the second electrolytic tank and place it in a graphite crucible, then put it into the high-purity Ar suspension equipment that has been passed in for half an hour in advance, and then vacuum. The temperature is -0.08MPa, heat until the precipitate melts, then increase the temperature to 2500°C, and keep it for 1 hour. After the insulation is completed, add high-purity Ar protection and cool the material to room temperature. Vacuum high-temperature melting in the suspension equipment produced 1.38kg of high-purity indium-tin alloy with a recovery rate of 83.63%.

Example 4:

(1) Dissolution: Place the anode plate and titanium cathode plate in the first electrolytic tank, use 800g/l sulfuric acid as the electrolyte, and perform the first microcurrent electrolysis. The current density of the first microcurrent electrolysis is 42A/m. ^2. The temperature is 30°C and the electrolysis time is 130 minutes. Take the indium tin solution in the first electrolytic tank;

(2) Primary purification: Place the anode plate and titanium cathode plate in the second electrolytic tank, use the indium tin solution as the electrolyte, and perform the second microcurrent electrolysis. The current density of the second microcurrent electrolysis is 55A/m ² , the temperature is 30, and the electrolysis time is 100min;

(3) Secondary purification: Filter out the water from the indium-tin alloy precipitate at the bottom of the second electrolytic tank and place it in a graphite crucible, then put it into the high-purity Ar suspension equipment that has been passed in for half an hour in advance, and then vacuum. The temperature is -0.08MPa, heat until the precipitate melts, then increase the temperature to 2500°C, and keep it for 1 hour. After the insulation is completed, add high-purity Ar protection and cool the material to room temperature. Vacuum high-temperature smelting in the suspension equipment produced 1.36kg of high-purity indium-tin alloy with a recovery rate of 82.71%.

Example 5:

(1) Dissolution: Place the anode plate and titanium cathode plate in the first electrolytic tank, use 800g/l sulfuric acid as the electrolyte, and perform the first microcurrent electrolysis. The current density of the first microcurrent electrolysis is 48A/m. ^2. The temperature is 40℃, the electrolysis time is 170min, take the indium tin solution in the first electrolytic tank;

(2) Primary purification: Place the anode plate and titanium cathode plate in the second electrolytic tank, use the indium tin solution as the electrolyte, and perform the second microcurrent electrolysis. The current density of the second microcurrent electrolysis is 65A/m ² , the temperature is 50℃, and the electrolysis time is 130min;

(3) Secondary purification: Filter out the water from the indium-tin alloy precipitate at the bottom of the second electrolytic tank and place it in a graphite crucible, then put it into the high-purity Ar suspension equipment that has been passed in for half an hour in advance, and then vacuum. The temperature is -0.08MPa, heat until the precipitate melts, then increase the temperature to 2500°C, and keep it for 1 hour. After the insulation is completed, add high-purity Ar protection and cool the material to room temperature. Vacuum high-temperature smelting in the suspension equipment produced 1.39kg of high-purity indium-tin alloy with a recovery rate of 84.54%.

The test results of the high-purity indium tin alloy of Examples 1-5 are shown in Table 2:

Table 2

It can be seen from Table 2 that the N, O, and H contents of the high-purity indium tin alloy prepared in Examples 1-5 are all less than 0.001%, and the other impurity contents are ≤0.0020%.

Next, the present invention uses steps (1) and (2) of Example 1 to conduct a recovery rate comparison experiment.

(1) Use cathode and anode plates of the same size (excluding sides) for microcurrent electrolysis, that is, the length, width and thickness of the anode plate are 19.80cm, 13.80cm, 0.90cm, and the weight is 2kg; the length, width and thickness of the cathode plate are 19.80cm, 13.80cm, 0.25cm. The microcurrent electrolysis parameters are the same as those in Example 1, and finally 1.22kg of indium-tin alloy precipitate is obtained in the second electrolytic tank. ;

(2) High current electrolysis is used, the current density is 300A/m ² , the temperature is 20°C, the electrolysis time is 120 minutes, the sizes of the cathode and anode plates are the same as in Example 1, and finally 1.25kg of indium tin alloy precipitation is obtained in the second electrolytic tank things.

The recovery rate comparison experiment proves that the recovery rate of the indium tin alloy can be improved under the weak non-uniform electric field of the present invention.

Then, the present invention uses suspension purification comparative experiments. In this comparative experiment (3), steps (1) and (2) are the same as in Example 1. The purification method of step (3) adopts the vacuum distillation method commonly used in this field. The results are shown in Table 3.

table 3

As can be seen from Table 3, the content of N, O, H and other impurities in the indium tin alloy obtained in Comparative Experiment (3) without suspension purification is significantly higher than that in Experiment 1.

The above embodiments are only specific examples to further describe the purpose, technical solutions and beneficial effects of the present invention in detail, and the present invention is not limited thereto. Any modifications, equivalent substitutions, improvements, etc. made within the scope of the disclosure of the present invention are included in the protection scope of the present invention.

Claims (5)

1. A method for recycling high-purity tin-indium alloy from ITO target scraps is characterized by taking the ITO target scraps as anode plates and comprising the following steps:

(1) Dissolving: placing the anode plate and the titanium cathode plate in a first electrolytic tank, and carrying out first microcurrent electrolysis by taking sulfuric acid solution as electrolyte to obtain indium tin solution;

(2) Primary purification: placing the anode plate and the titanium cathode plate in a second electrolytic tank, and carrying out second microcurrent electrolysis by taking the indium tin solution as electrolyte;

(3) And (3) secondary purification: filtering out water from the indium tin alloy precipitate at the bottom of the second electrolytic tank, and placing the precipitate into suspension equipment for vacuum high-temperature smelting to obtain high-purity indium tin alloy;

the ratio of the lengths of the anode plate to the cathode plate is (1.4-1.6): 1, and the ratio of the widths is (1.4-1.6): 1;

the length and width of the anode plate are 19.80 cm-20.20 cm, 13.80 cm-14.20 cm and 0.90 cm-1.10 cm in sequence; the length and width of the cathode plate are 12.38 cm-14.42 cm, 8.63 cm-10.15 cm and 0.20 cm-0.30 cm in sequence;

the current density of the first micro-current electrolysis is 40A/m ² ～50A/m ² The temperature is 20-60 ℃, and the electrolysis time is 120-180 min;

the current density of the second micro-current electrolysis is 51A/m ² ～70A/m ² The temperature is 20-60 ℃, and the electrolysis time is 100-150 min.

2. The method for recovering high-purity tin-indium alloy from ITO target scrap as recited in claim 1, wherein: the vacuum high-temperature smelting in the suspension equipment is that the sediment at the bottom of the second electrolytic tank is placed in a graphite crucible, then placed in the suspension equipment which is filled with high-purity Ar in advance, vacuumized, heated to be in a molten state, then heated to 2500-3000 ℃, kept for 1 hour, and cooled to room temperature under the protection of the high-purity Ar after the heat preservation is finished.

3. The method for recycling high-purity tin-indium alloy from ITO target scrap according to claim 2, characterized in that: the vacuum degree is more than or equal to 0.08MPa.

4. The method for recovering high-purity tin-indium alloy from ITO target scrap as recited in claim 1, wherein: and ultrasonic cleaning is carried out on the ITO target scraps by adopting acetone, then crushing is carried out, and then the crushed ITO target scraps are pressed into anode plates.

5. The method for recovering high-purity tin-indium alloy from ITO target scrap as recited in claim 1, wherein: the concentration of the sulfuric acid solution was 800g/l.