Method for preparing indium-silver alloy powder from waste ITO and waste silver scraps

Abstract

The invention discloses a method for preparing indium-silver alloy powder by using waste ITO (indium tin oxide) and waste silver scraps, which comprises the following steps of: 1, selecting the waste ITO and the waste silver scraps to carry out acid leaching treatment, and filtering to obtain a solution A; 2, adjusting the pH value of the solution A with ammonia water, and filtering to obtain a solution B; 3, adding citric acid into the solution B, adjusting the pH and the total concentration of metal ions by using deionized water and ammonia water, and filtering to obtain a solution C; 4, gradually adding a reducing agent into the solution C, continuously stirring until the reducing agent is completely added, and then continuously stirring at constant temperature until the reduction reaction is complete to obtain a precipitate D; and 5, separating and washing the precipitate D, and carrying out vacuum drying to obtain the indium-silver alloy powder. According to the method, the waste ITO and the waste silver scraps serve as raw materials, impurity elements are removed through the wet process, the indium-silver alloy powder is obtained through the reduction process, the process is simple, the flow is short, energy consumption is low, the utilization rate of valuable metal is high, the added value of products is high, and the method is suitable for the field of microelectronic packaging and low-temperature brazing.

Description

Technical Field

[0001] This invention belongs to the field of metallurgical recycling and preparation technology, specifically relating to a method for preparing indium-silver alloy powder using waste ITO and waste silver scrap. Background Technology

[0002] Indium tin oxide (ITO) is mainly used as a target material in liquid crystal display panels, electronic devices, and other fields. Global refined indium consumption is projected to exceed 2,000 tons by 2025, while the annual generation of waste target materials exceeds 1,200 tons. ITO has a low primary utilization rate in electronic product manufacturing, generating a large amount of waste after molding and use. Currently, the domestic indium recovery rate is less than 30%, resulting in resource waste. Recycling indium while simultaneously manufacturing high-value-added products is an effective measure to improve the indium recovery rate.

[0003] Indium-silver alloys, due to their high electrical and thermal conductivity, low melting point, good ductility and plasticity, and excellent weldability, are widely used in electronic semiconductor chip packaging, low-temperature welding, defense and military industries, printed electronics, and solar cells. They are an irreplaceable choice in fields with stringent requirements for performance, reliability, and process temperature. Currently, indium-silver alloys are mainly prepared using a vacuum melting pyrometallurgical process, which places high demands on equipment, energy consumption, and raw materials. Developing low-cost, low-energy-consumption, and readily adaptable wet processing methods is an effective measure to promote industry progress.

[0004] There are currently no reports on the preparation of indium-silver alloy powder using waste ITO and waste silver scrap as raw materials. Therefore, it is necessary to find a wet process that can effectively promote the recycling of waste ITO, develop a wet process for preparing indium-silver alloy powder using waste materials, and reduce the high equipment and energy consumption requirements of traditional processes. Summary of the Invention

[0005] The technical problem to be solved by this invention is to address the shortcomings of the prior art by providing a method for preparing indium-silver alloy powder using waste ITO and waste silver scrap. This invention achieves the removal of impurity elements and the wet preparation of indium-silver alloy powder through co-leaching, impurity removal, and co-reduction of valuable elements in the raw materials, waste ITO and waste silver scrap. This improves the utilization rate of indium and silver in the waste, reduces raw material costs, and yields high-value-added products, solving problems such as low waste ITO recovery rate, complex recycling processes, and long recycling procedures.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: a method for preparing indium-silver alloy powder using waste ITO and waste silver scrap, characterized in that the method includes the following steps: Step 1: Select waste ITO and waste silver scraps according to the composition of the target product, indium silver alloy powder, and perform acid leaching treatment. After filtration, solution A is obtained. Step 2: Adjust the pH of solution A from step 1 using ammonia, and remove the precipitate by filtration to obtain solution B; Step 3: Add citric acid to solution B from step 2 and stir well. Then adjust the pH and total metal ion concentration with deionized water and ammonia. Filter to remove the precipitate and obtain solution C. Step 4: Gradually add the reducing agent to solution C from step 3, stirring continuously throughout the process until all the reducing agent is added. Then continue stirring at a constant temperature until the reduction reaction is complete, yielding precipitate D. Step 5: After separating and washing the precipitate D from Step 4, vacuum dry it to obtain indium silver alloy powder.

[0007] This invention uses waste ITO and waste silver scrap as raw materials and employs a wet process to prepare indium-silver alloy powder. Since indium oxide accounts for up to 90% of the metal mass in waste ITO, and the main impurity element is tin, the waste ITO and waste silver scraps are first acid-leached (usually with nitric acid) to dissolve them. This allows indium and silver to enter the solution almost entirely in ionic form, while most of the tin precipitates out as stannic acid and remains in the solid phase. This is then removed by filtration, achieving initial separation of tin. The resulting solution A mainly contains indium, silver, and tin. Ammonia is used to adjust the pH of solution A, causing tin ions to precipitate first, effectively separating tin from indium and silver, resulting in solution B. Citric acid is then added to solution B to complex indium ions, preventing further hydrolysis and instability of the solution composition. This also ensures a uniform distribution of indium ions in the solution. Deionized water and ammonia are then used to adjust the pH and total metal ion concentration, and to complex silver ions, making the solution alkaline and ensuring uniform composition. After filtration to remove a small amount of precipitated impurities, a reducing agent is used for reduction, generating an indium-silver alloy. After separation, washing, and drying, indium-silver alloy powder is obtained.

[0008] The above-mentioned method for preparing indium-silver alloy powder using waste ITO and waste silver scrap is characterized in that, in step one, the waste ITO is waste ITO scrap and powder after dismantling, cleaning, impurity removal, and crushing; the acid leaching process uses a nitric acid solution with a concentration of 5mol / L to 15mol / L for leaching, a leaching time of 2h to 7h, a leaching temperature of 80℃ to 95℃, and a leaching liquid-to-solid ratio of 5 to 10:1. The method described above for preparing indium-silver alloy powder using waste ITO and waste silver scrap is characterized in that, in step two, the pH of solution A is adjusted to 2-3.5. By adjusting the pH of solution A to 2-3.5, tin is ensured to precipitate first, thereby removing residual tin and achieving the separation of tin from indium and silver.

[0009] The method described above for preparing indium-silver alloy powder using waste ITO and waste silver scrap is characterized in that the molar ratio of citric acid added in step three to the molar ratio of indium in the waste ITO in step one is 1.5~5:1, the pH is adjusted to 8.5~11 using deionized water and ammonia, and the total concentration of metal ions is 6g / L~20g / L. By adjusting the pH to the range of 8.5~11, the reducing power of the reducing agent is further released, ensuring that the reducing agent exhibits strong reducing properties and is more likely to form indium-silver alloy.

[0010] The method for preparing indium-silver alloy powder using waste ITO and waste silver scrap is characterized in that the reducing agent in step four is hydrazine hydrate, and the amount of reducing agent added is 1.5 to 4 times the theoretical amount, and the temperature of the reduction reaction is 30℃ to 70℃. Since silver ions are more easily reduced than indium ions, hydrazine hydrate, a strong reducing agent, is chosen to avoid incomplete reduction of indium during the reduction process, ensuring the formation of indium-silver alloy and improving the utilization rate of indium in the waste.

[0011] Compared with the prior art, the present invention has the following advantages: 1. Compared with the indium and tin separation process in traditional ITO recycling, this invention achieves the removal of impurity elements and wet preparation of indium-silver alloy powder by co-leaching, impurity removal and co-reduction of valuable elements in raw material waste ITO and waste silver scraps. This improves the utilization rate of indium and silver in waste materials, while avoiding specific indium and tin separation processes, shortening and simplifying the process flow.

[0012] 2. Compared with the high equipment, raw material, and energy consumption requirements of traditional pyrometallurgical processes for preparing indium-silver alloys, the wet preparation process of this invention is simple, has a short process, and low energy consumption. It solves the problems of low waste ITO recovery rate, complex recycling process, and long recycling process, and achieves an effective replacement for the pyrometallurgical process with high equipment, energy consumption, and raw material requirements.

[0013] 3. This invention uses waste ITO and waste silver scrap as raw materials to prepare high-value-added indium-silver alloy powder, which improves the utilization rate of valuable metal indium and increases the added value of the product.

[0014] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0015] Figure 1 This is a scanning electron microscope image of the indium-silver alloy powder prepared in Example 1 of the present invention.

[0016] Figure 2 This is an elemental surface distribution diagram of the indium-silver alloy powder prepared in Example 1 of the present invention.

[0017] Figure 3This is a scanning electron microscope image of the indium-silver alloy powder prepared in Example 2 of the present invention.

[0018] Figure 4 This is an elemental surface distribution diagram of the indium-silver alloy powder prepared in Example 2 of the present invention.

[0019] Figure 5 This is a scanning electron microscope image of the indium-silver alloy powder prepared in Example 3 of the present invention.

[0020] Figure 6 This is an elemental surface distribution diagram of the indium-silver alloy powder prepared in Example 3 of the present invention. Detailed Implementation

[0021] Example 1 This embodiment includes the following steps: Step 1: According to the composition In93Ag7 of the target product In-silver alloy powder, weigh 126g of the disassembled, cleaned and crushed waste ITO scrap and 7g of waste silver scrap and add them together to 680mL of 15mol / L nitric acid solution for leaching. The leaching liquid-solid ratio is 5:1, the leaching temperature is 80℃, the leaching time is 2h, and the solution A is obtained after filtration. Step 2: Adjust the pH of solution A from Step 1 to 2 using ammonia, stir thoroughly, let stand, and filter out the precipitate to obtain solution B; Step 3: Add 1.2 mol of citric acid to solution B from step 2 and stir until homogeneous. The molar ratio of the added citric acid to the molar amount of indium in the waste ITO scrap from step 1 is 1.5:1. Then, adjust the pH to 8.5 and the total metal ion concentration to 20 g / L using deionized water and ammonia. Filter to remove the precipitate and obtain solution C. Step 4: Gradually add 60 mL of 80% hydrazine hydrate solution to solution C from step 3. The amount of hydrazine hydrate added is 1.5 times the theoretical amount. The entire process is stirred continuously until the hydrazine hydrate solution is completely added. Then, continue stirring at a constant temperature of 70°C until no more bubbles are generated in the reduction reaction. After aging for 1 hour, the reduction reaction is ended, yielding precipitate D and the reaction liquid. Step 5: After separating the precipitate D from Step 4, wash it with pure water and then vacuum dry it to obtain indium silver alloy powder.

[0022] Figure 1 This is a scanning electron microscope image of the indium-silver alloy powder prepared in this embodiment. Figure 1 It can be seen that the indium-silver alloy powder is distributed in a porous dendritic structure.

[0023] Figure 2 This is an elemental surface distribution diagram of the indium-silver alloy powder prepared in this embodiment, from... Figure 2It can be seen that indium and silver are uniformly distributed in the indium-silver alloy powder, indicating that indium and silver are uniformly distributed in the microstructure and exhibit an alloy structure.

[0024] Example 2 This embodiment includes the following steps: Step 1: According to the composition of the target product, indium silver alloy powder In10Ag90, weigh 13.5g of waste ITO scrap and 90g of waste silver scrap and add them together to 1035mL of 5mol / L nitric acid solution for leaching. The leaching liquid-solid ratio is 10:1, the leaching temperature is 95℃, and the leaching time is 7h. After filtration, solution A is obtained. Step 2: Adjust the pH of solution A from Step 1 to 3.5 using ammonia, stir thoroughly, let stand, and filter out the precipitate to obtain solution B; Step 3: Add 0.43 mol of citric acid to solution B from step 2 and stir until homogeneous. The ratio of the molar amount of citric acid added to the molar amount of indium in the waste ITO scrap from step 1 is 5:1. Then, adjust the pH to 11 and the total concentration of metal ions to 6 g / L using deionized water and ammonia. Filter to remove the precipitate and obtain solution C. Step 4: Gradually add 135 mL of 80% hydrazine hydrate solution to solution C from step 3. The amount of hydrazine hydrate added is 4 times the theoretical amount. The entire process is stirred continuously until the hydrazine hydrate solution is completely added. Then, continue stirring at a constant temperature of 30°C until no more bubbles are generated in the reduction reaction. After aging for 1 hour, the reduction reaction is ended, and precipitate D and the reaction liquid are obtained. Step 5: After separating the precipitate D from Step 4, wash it with pure water and then vacuum dry it to obtain indium silver alloy powder.

[0025] Figure 3 This is a scanning electron microscope image of the indium-silver alloy powder prepared in this embodiment. Figure 3 It can be seen that the indium-silver alloy powder is distributed in a porous dendritic structure.

[0026] Figure 4 This is an elemental surface distribution diagram of the indium-silver alloy powder prepared in this embodiment, from... Figure 4 It can be seen that indium and silver are uniformly distributed in the indium-silver alloy powder, indicating that indium and silver are uniformly distributed in the microstructure and exhibit an alloy structure.

[0027] Example 3 This embodiment includes the following steps: Step 1: According to the composition In70Ag30 of the target product In-silver alloy powder, weigh 95g of waste ITO scrap and 30g of waste silver scrap and add them together to 880mL of 10mol / L nitric acid solution for leaching. The leaching liquid-solid ratio is 7:1, the leaching temperature is 92℃, and the leaching time is 4.5h. After filtration, solution A is obtained. Step 2: Adjust the pH of solution A from Step 1 to 3 using ammonia, stir thoroughly, let stand, and filter out the precipitate to obtain solution B; Step 3: Add 1.5 mol of citric acid to solution B from step 2 and stir until homogeneous. The ratio of the molar amount of citric acid added to the molar amount of indium in the waste ITO scrap from step 1 is 2.5:1. Then, adjust the pH to 10 and the total concentration of metal ions to 10 g / L using deionized water and ammonia. Filter to remove the precipitate and obtain solution C. Step 4: Gradually add 85 mL of 80% hydrazine hydrate solution to solution C from step 3. The amount of hydrazine hydrate added is 2.5 times the theoretical amount. The entire process is stirred continuously until the hydrazine hydrate solution is completely added. Then, continue stirring at a constant temperature of 50°C until no more bubbles are generated in the reduction reaction. After aging for 1 hour, the reduction reaction is ended, yielding precipitate D and the reaction liquid. Step 5: After separating the precipitate D from Step 4, wash it with pure water and then vacuum dry it to obtain indium silver alloy powder.

[0028] Figure 5 This is a scanning electron microscope image of the indium-silver alloy powder prepared in this embodiment. Figure 5 It can be seen that the indium-silver alloy powder is distributed in a porous dendritic structure.

[0029] Figure 6 This is an elemental surface distribution diagram of the indium-silver alloy powder prepared in this embodiment, from... Figure 6 It can be seen that indium and silver are uniformly distributed in the indium-silver alloy powder, indicating that indium and silver are uniformly distributed in the microstructure and exhibit an alloy structure.

[0030] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any way. Any simple modifications, alterations, and equivalent changes made to the above embodiments based on the inventive essence shall still fall within the protection scope of the present invention.

Claims

1. A method for preparing indium-silver alloy powder using waste ITO and waste silver scrap, characterized by, The method comprises the following steps: Step one, according to the composition of the target product indium-silver alloy powder, waste ITO and waste silver scrap are selected and subjected to acid leaching treatment, and after filtration, solution A is obtained; Step two, the pH of solution A in step one is adjusted by using ammonia water, and the generated precipitate is removed by filtration to obtain solution B; Step three, citric acid is added to solution B in step two and stirred uniformly, and then deionized water and ammonia water are used to adjust the pH and the total concentration of metal ions, and the precipitate is removed by filtration to obtain solution C; Step four, a reducing agent is gradually added to solution C in step three, and the whole process is continuously stirred until the reducing agent is completely added, and then constant temperature stirring is continued until the reduction reaction is completed to obtain precipitate D; Step five, precipitate D in step four is separated, washed and vacuum dried to obtain indium-silver alloy powder.

2. The method for preparing indium-silver alloy powder from waste ITO and waste silver scrap according to claim 1, characterized in that, The waste ITO in step one is waste ITO scrap and powder material after disassembly, cleaning, impurity removal and crushing; the acid leaching treatment process uses a nitric acid solution with a concentration of 5 mol / L to 15 mol / L for leaching, the leaching time is 2 h to 7 h, the leaching temperature is 80℃ to 95℃, and the solid-liquid ratio of the leaching solution is 5 to 10:

1.

3. The method for preparing indium-silver alloy powder from waste ITO and waste silver scrap according to claim 1, characterized in that, In step two, the pH of solution A is adjusted to 2 to 3.

5.

4. The method for preparing indium-silver alloy powder from waste ITO and waste silver scrap according to claim 1, characterized in that, In step three, the ratio of the added amount of citric acid to the molar amount of indium in the waste ITO in step one is 1.5 to 5:1, deionized water and ammonia water are used to adjust the pH to 8.5 to 11, and the total concentration of metal ions is 6 g / L to 20 g / L.

5. The method for preparing indium-silver alloy powder from waste ITO and waste silver scrap according to claim 1, characterized in that, In step four, the reducing agent is hydrazine hydrate, and the amount of the reducing agent added is 1.5 to 4 times the theoretical amount, and the temperature of the reduction reaction is 30℃ to 70℃.

Images