A method for recovering indium fluoride and tin oxide from waste ITO targets

Abstract

This invention provides a method for recovering indium fluoride and tin oxide from waste ITO targets, belonging to the field of indium tin oxide waste target recycling technology. The method includes: acid leaching of powdered ITO waste targets with hydrofluoric acid to obtain an acid leaching slurry containing indium fluoride and tin oxide; vacuum distilling the acid leaching slurry to obtain indium fluoride gas and tin oxide solid, respectively; the vacuum distillation temperature is 1000–1100°C; the vacuum degree of the vacuum distillation is 5–20 Pa; the indium fluoride gas is vacuum condensed to obtain indium fluoride solid; the condensation temperature is 700–800°C; the purity of the tin oxide solid is >99.999%; and the purity of the indium fluoride obtained by vacuum condensation is >99.99%. The method provided by this invention has low energy consumption, no carbon emissions, low cost, and high added value, enabling the conversion and recycling of waste materials into high-value materials.

Description

Technical Field

[0001] This invention belongs to the field of indium tin oxide waste target recycling technology, specifically relating to a method for recovering indium fluoride and tin oxide from ITO waste targets. Background Technology

[0002] Indium tin oxide (ITO) sputtering targets are compound targets composed of tin, indium, and oxygen, typically containing approximately 90% indium oxide and 10% tin oxide. Due to their excellent conductivity, transparency, and chemical stability, they are widely used in display devices such as LCDs, PDPs, and OLEDs. With the rapid development of smartphones, tablets, and other mobile devices, as well as emerging fields like smart homes and smart mobility, the demand and waste of ITO sputtering targets are constantly increasing. Indium used for ITO sputtering accounts for more than 80% of total indium consumption annually, making it the primary raw material for the secondary resource recovery of the rare and dispersed metal indium.

[0003] Currently, the main methods for recovering ITO waste targets are vacuum reduction and wet electrolysis. Vacuum reduction includes carbothermal reduction and hydrogen reduction. Generally, the carbothermal reduction temperature reaches 1200-1700℃, which consumes a lot of energy, requires sophisticated equipment, and produces carbon dioxide, which is not in line with my country's carbon emission reduction goals. Hydrogen reduction has the problem of high cost. The crude indium (2N) recovered by wet electrolysis does not meet industrial requirements. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide a method for recovering indium fluoride and tin oxide from waste ITO targets. The method provided by this invention has low energy consumption, no carbon emissions, low cost, and the recovered indium fluoride and tin oxide have high purity.

[0005] To achieve the above objectives, the present invention provides the following solution:

[0006] This invention provides a method for recovering indium fluoride and tin oxide from spent ITO targets, comprising the following steps:

[0007] ITO waste target powder is acid-leached with hydrofluoric acid to obtain an acid leaching slurry containing indium fluoride and tin oxide;

[0008] The acid leaching slurry was subjected to vacuum distillation to obtain indium fluoride gas and tin oxide solid, respectively; the temperature of the vacuum distillation was 1000-1100℃; and the vacuum degree of the vacuum distillation was 5-20 Pa.

[0009] The indium fluoride gas was vacuum condensed to obtain indium fluoride solid; the condensation temperature was 700-800℃.

[0010] The purity of the tin oxide solid is >99.999%; the purity of the indium fluoride obtained by vacuum condensation is >99.99%.

[0011] Preferably, the mass concentration of the hydrofluoric acid is 40-50%.

[0012] Preferably, the mass ratio of the ITO waste target powder to the volume ratio of hydrofluoric acid is 1g:(10-15)mL.

[0013] Preferably, the acid leaching temperature is 65-75°C and the time is 1.5-2.5 hours.

[0014] Preferably, the powder of the ITO waste target has a mesh size of 100 to 200 mesh.

[0015] Preferably, the composition of the ITO waste target is 89.4% In₂O₃, 9.9% SnO₂, 0.6% Ca, and 0.1% Mg.

[0016] Preferably, the heat preservation time for vacuum distillation is 1 to 2 hours.

[0017] Preferably, the heat preservation time for vacuum condensation is 1 to 2 hours.

[0018] Preferably, the vacuum degree of the vacuum condensation is 5 to 20 Pa.

[0019] Preferably, the heating rate to the temperature of the vacuum distillation is 10°C / min.

[0020] This invention provides a method for recovering indium fluoride and tin oxide from waste ITO targets, comprising the following steps: leaching powdered ITO target with hydrofluoric acid to obtain an acid leaching slurry containing indium fluoride and tin oxide; subjecting the acid leaching slurry to vacuum distillation to obtain indium fluoride gas and tin oxide solid, respectively; the vacuum distillation temperature is 1000–1100°C; the vacuum degree of the vacuum distillation is 5–20 Pa; the indium fluoride gas is vacuum condensed to obtain indium fluoride; the condensation temperature is 700–800°C; the purity of the tin oxide solid is >99.999%; and the purity of the indium fluoride obtained by vacuum condensation is >99.99%. The method provided by this invention can simultaneously separate and purify indium and tin in ITO waste targets, recovering indium in the form of high-purity indium fluoride and tin in the form of high-purity tin oxide, with tin oxide purity >5N (99.999%) and indium fluoride >4N (99.99%). The method provided by this invention has low energy consumption, no carbon emissions, low cost, and high added value, and can realize the conversion and recycling of waste into high-value materials. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of an ITO waste target recovery device; where 1-high-purity argon gas generator, 2-quartz tube, 3-first temperature-controlled tubular vacuum furnace, 4-second temperature-controlled tubular vacuum furnace, 5-tail gas absorption device, and 6-vacuum pump. Detailed Implementation

[0023] This invention provides a method for recovering indium fluoride and tin oxide from spent ITO targets, comprising the following steps:

[0024] ITO waste target powder is acid-leached with hydrofluoric acid to obtain an acid leaching slurry containing indium fluoride and tin oxide;

[0025] The acid leaching slurry was subjected to vacuum distillation to obtain indium fluoride gas and tin oxide solid, respectively; the temperature of the vacuum distillation was 1000-1100℃; and the vacuum degree of the vacuum distillation was 5-20 Pa.

[0026] The indium fluoride gas was vacuum condensed to obtain indium fluoride; the condensation temperature was 700–800°C.

[0027] The purity of the tin oxide solid is >99.999%; the purity of the indium fluoride obtained by vacuum condensation is >99.99%.

[0028] Unless otherwise specified, all materials and equipment used in this invention are commercially available products.

[0029] ITO waste target powder is acid-leached with hydrofluoric acid to obtain an acid leaching slurry containing indium fluoride and tin oxide.

[0030] In this invention, the composition of the ITO waste target is preferably 89.4% In₂O₃, 9.9% SnO₂, 0.6% Ca, and 0.1% Mg. In this invention, the ITO waste target is waste and defective products generated during the ITO preparation process; the powder of the ITO waste target is preferably obtained by mechanically crushing the ITO waste target.

[0031] In this invention, the powder of the ITO waste target is preferably 100 to 200 mesh. In the embodiments of this invention, it can be 100 mesh, 150 mesh or 200 mesh.

[0032] In this invention, the mass concentration of the hydrofluoric acid is preferably 40-50%, and in specific embodiments, it can be 40%, 42%, 45%, 48%, or 50%. The mass ratio of the ITO waste target powder to the volume ratio of the hydrofluoric acid is preferably 1g:(10-15)mL, and in specific embodiments, it can be 1g:10mL, 1g:12mL, or 1g:15mL. In this invention, the acid leaching temperature is preferably 65-75℃, and in specific embodiments, it can be 65, 70, 72, or 75℃. The acid leaching time is preferably 1.5-2.5h, and in specific embodiments, it can be 1.5h, 2.0h, 2.2h, or 2.5h.

[0033] In the acid leaching process of this invention, indium oxide in the waste ITO target reacts with hydrofluoric acid to generate indium fluoride, while tin oxide does not react. The reaction equation is as follows:

[0034] In2O3+6HF(l)=2InF3+3H2O(g);

[0035] After obtaining the acid leaching slurry, the present invention performs vacuum distillation on the acid leaching slurry to obtain indium fluoride gas and tin oxide solid, respectively.

[0036] In this invention, the vacuum degree of the vacuum distillation is 5–20 Pa, and in specific embodiments, it can be 5 Pa, 8 Pa, 10 Pa, 12 Pa, 15 Pa, or 20 Pa. In this invention, the temperature of the vacuum distillation is 1000–1100 °C, and in specific embodiments, it can be 1000 °C, 1030 °C, 1050 °C, 1060 °C, 1080 °C, 1090 °C, or 1100 °C. The holding time for the vacuum distillation is preferably 1–2 hours, and in specific embodiments, it can be 1 hour, 1.5 hours, or 2 hours. Preferably, the temperature is increased from room temperature to the vacuum distillation temperature, and the heating rate to the vacuum distillation temperature is preferably 10 °C / min.

[0037] In the vacuum distillation process of the present invention, the indium fluoride, water, calcium and magnesium impurities in the acid leaching slurry are completely vaporized and separated from tin oxide.

[0038] After obtaining the indium fluoride gas, the present invention performs vacuum condensation on the indium fluoride gas to obtain indium fluoride solid.

[0039] In this invention, the vacuum degree of the vacuum condensation is preferably 5-20 Pa, and in specific embodiments, it can be 5 Pa, 8 Pa, 10 Pa, 12 Pa, 15 Pa, or 20 Pa. In this invention, the vacuum condensation temperature is 700-800℃, and in specific embodiments, it can be 700℃, 720℃, 740℃, 750℃, 780℃, or 800℃. The holding time for the vacuum condensation is preferably 1-2 hours, and in specific embodiments, it can be 1 hour, 1.5 hours, or 2 hours. Preferably, the temperature is increased from room temperature to the vacuum condensation temperature, and the heating rate is preferably 10℃ / min.

[0040] This invention controls the temperature of vacuum condensation at 700-800℃, which can condense indium fluoride and prevent impurities such as calcium, magnesium and water from cooling, thereby further purifying and drying the condensed indium fluoride product.

[0041] In this invention, the vacuum distillation and vacuum condensation are preferably carried out in a tubular vacuum furnace (referred to as the first temperature-controlled tubular vacuum furnace and the second temperature-controlled tubular vacuum furnace, respectively). Figure 1 The diagram shown is a schematic of the ITO waste target recycling device of the present invention.

[0042] Before the vacuum distillation, the first and second temperature-controlled tubular vacuum furnaces are preferably cleaned and the air is removed.

[0043] The present invention preferably lays graphite paper on the inner wall of the quartz tube of the second temperature-controlled tubular vacuum furnace for the condensation of indium fluoride gas.

[0044] The present invention preferably employs a tail gas absorption device to absorb hydrogen fluoride gas, water, and calcium and magnesium impurities during the reaction process (calcium and magnesium impurities may also condense at low temperatures, such as the inner wall of the unheated quartz tube outside the two temperature-controlled tubular vacuum furnaces).

[0045] To further illustrate the present invention, a method for recovering indium fluoride and tin oxide from waste ITO targets provided by the present invention will be described in detail below with reference to the accompanying drawings and embodiments, but these should not be construed as limiting the scope of protection of the present invention.

[0046] Example 1

[0047] The waste ITO target was mechanically crushed to 100-200 mesh to obtain ITO waste target powder; the composition of the waste ITO target was 89.4% In2O3, 9.9% SnO2, 0.6% Ca, and 0.1% Mg.

[0048] The powder of the ITO waste target was placed into a polyethylene beaker, and hydrofluoric acid with a mass concentration of 40% was added to the beaker. The mass ratio of the ITO waste target powder to the volume of hydrofluoric acid was 1g:10mL. The resulting mixture was heated to 70°C in a water bath for acid leaching for 2 hours (the indium oxide in the ITO waste target reacts with the hydrofluoric acid to form indium fluoride, while tin oxide does not react), resulting in an acid leaching slurry containing indium fluoride and tin oxide.

[0049] The acid leaching slurry is poured into a graphite boat, and graphite paper is laid on the inner wall of the quartz tubes of the first and second temperature-controlled tubular vacuum furnaces for the condensation of indium fluoride gas.

[0050] A schematic diagram of the ITO waste target recovery device of the present invention is shown below. Figure 1 As shown, the temperature control program for the tubular vacuum furnace is set as follows: First temperature control tubular vacuum furnace: start heating from room temperature, heating rate 10℃ / min, target temperature 1100℃, holding time 2h;

[0051] The second temperature-controlled tubular vacuum furnace starts at room temperature with a heating rate of 10℃ / min, a target temperature of 700℃, and a holding time of 2 hours. It is used to condense indium fluoride gas. This temperature is set to prevent calcium, magnesium, and water from cooling, and further serves to purify and dry the condensed indium fluoride product.

[0052] Place the graphite boat (open) in the first temperature-controlled tubular vacuum furnace, seal the temperature control device, turn on the vacuum pump, wait for the pressure to drop to 5 Pa, introduce pure argon gas for 5 minutes to purge, turn off the argon gas, and keep the vacuum pump on.

[0053] Simultaneously turn on the heating systems of two temperature-controlled tubular vacuum furnaces. After the temperature rises to the target temperature, keep it at that temperature for 2 hours to allow the indium fluoride, water, and calcium and magnesium impurities in the acid leaching slurry to completely vaporize and separate from the tin oxide. At this time, the system pressure is 5 Pa.

[0054] After the vacuum distillation stage is completed, the system cools down naturally. Indium fluoride solid is recovered from the graphite paper surface of the second temperature-controlled tubular vacuum furnace, and tin oxide solid is recovered from the graphite boat.

[0055] The purity of tin oxide solid was >5N (99.999%), the purity of indium fluoride solid was >4N (99.99%), the direct recovery rate of tin oxide solid was 99.8%, and the direct recovery rate of indium fluoride solid was 95%.

[0056] Example 2

[0057] Using the method and apparatus of Example 1, indium fluoride and tin oxide materials were prepared from waste ITO targets. The difference was that the mass ratio of the waste ITO target powder to the volume ratio of hydrofluoric acid was reduced to 1 g: 8 mL, while the other conditions were the same as in Example 1.

[0058] The results showed that the purity of the tin oxide solid obtained in Example 2 was 92%, because the indium oxide was not completely fluorinated and remained in the residue along with the tin oxide. The purity of the indium fluoride solid was >4N (99.99%), the direct recovery rate of the tin oxide solid was 98%, and the direct recovery rate of the indium fluoride solid was 95%.

[0059] Example 3

[0060] Using the method and apparatus of Example 1, indium fluoride and tin oxide materials were prepared using ITO waste targets. The difference was that the temperature of the first temperature-controlled tubular vacuum furnace (i.e., the high-temperature distillation separation zone) was set to 1000°C, while the other conditions were the same as in Example 1.

[0061] The results showed that indium fluoride in the residue obtained in Example 3 was not completely vaporized and separated, indium fluoride accounted for about 10% in the tin oxide solid, the purity of indium fluoride solid in the condensation zone was >4N (99.992%), the recovery rate of tin oxide solid was 98%, and the direct recovery rate of indium fluoride solid decreased to 89%.

[0062] Example 4

[0063] Using the method and apparatus of Example 1, indium fluoride and tin oxide materials were prepared using ITO waste targets. The difference was that the temperature of the second temperature-controlled tubular vacuum furnace (i.e., the indium fluoride condensation temperature) was set to 800°C, while the other conditions were the same as in Example 1.

[0064] The results showed that the purity of the tin oxide solid obtained in Example 4 was >5N (99.999%), the purity of the indium fluoride solid was >4N (99.992%), the direct recovery rate of the tin oxide solid was 98%, and the direct recovery rate of the indium fluoride solid dropped to 85%, because the condensation temperature was too high, which hindered the condensation of indium fluoride.

[0065] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. People can obtain other embodiments based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for recovering indium fluoride and tin oxide from waste ITO targets, comprising the following steps: ITO waste target powder is acid-leached with hydrofluoric acid to obtain an acid leaching slurry containing indium fluoride and tin oxide; The acid leaching slurry was subjected to vacuum distillation to obtain indium fluoride gas and tin oxide solid, respectively; the temperature of the vacuum distillation was 1000-1100℃; and the vacuum degree of the vacuum distillation was 5-20 Pa. The indium fluoride gas was vacuum condensed to obtain indium fluoride solid; the condensation temperature was 700-800℃. The purity of the tin oxide solid is >99.999%; the purity of the indium fluoride obtained by vacuum condensation is >99.99%.

2. The method according to claim 1, characterized in that, The hydrofluoric acid has a mass concentration of 40-50%.

3. The method according to claim 1 or 2, characterized in that, The mass ratio of the ITO waste target powder to the volume ratio of hydrofluoric acid is 1g:(10-15)mL.

4. The method according to claim 1 or 2, characterized in that, The acid leaching temperature is 65–75°C, and the time is 1.5–2.5 h.

5. The method according to claim 1 or 2, characterized in that, The powder from the ITO waste target has a mesh size of 100 to 200 mesh.

6. The method according to claim 1 or 2, characterized in that, The composition of the ITO waste target is 89.4% In₂O₃, 9.9% SnO₂, 0.6% Ca, and 0.1% Mg.

7. The method according to claim 1, characterized in that, The vacuum distillation process is carried out for 1 to 2 hours.

8. The method according to claim 1, characterized in that, The vacuum condensation holding time is 1 to 2 hours.

9. The method according to claim 1 or 8, characterized in that, The vacuum degree of the vacuum condensation is 5-20 Pa.

10. The method according to claim 1 or 7, characterized in that, The heating rate to the vacuum distillation temperature is 10 °C / min.

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