Method for recycling precious metal by electrochemically dissolving semiconductor lining plate

Abstract

The invention discloses a method for recovering precious metal by electrochemically dissolving a semiconductor lining plate, and belongs to the technical field of precious metal recovery, and the method is characterized by comprising the following steps: cleaning the lining plate; the lining plate is used as an anode, the titanium plate is used as a cathode, an electrochemical dissolving solution of the anode is an acidic mixed solution containing chloride ions, an electrochemical dissolving solution of the cathode is a hydrochloric acid solution, a cation exchange membrane is arranged between the cathode and the anode, the current density is 5-40A / m < 2 >, and the dissolving temperature is 30-60 DEG C; the electrochemical dissolution gold reduction is repeated to obtain gold powder, and the reduction potential is monitored to be larger than or equal to 720 mV; oxidizing bivalent platinum ions in the residual anode electrochemical dissolving solution into tetravalent platinum ions, and then adding ammonium chloride to react to generate ammonium chloroplatinate precipitate; and filtering and washing the ammonium chloroplatinate, and then carrying out reduction treatment to obtain platinum powder. By controlling the electrochemical dissolution temperature and the current density, the gold and platinum plating layers on the surface of the semiconductor lining plate are subjected to oxidation dissolution reaction, so that the substrate of the lining plate is not damaged and can be used for the second time.

Description

Technical Field

[0001] This invention relates to the field of precious metal recycling technology, and in particular to a method for recovering precious metals by electrochemically dissolving semiconductor substrates. Background Technology

[0002] Semiconductor substrates serve as a support carrier for evaporating materials, ensuring the material's morphological stability during high-temperature evaporation, preventing collapse or displacement, and providing a flat, clean surface to reduce contamination and guarantee the uniformity and purity of the film deposited on the semiconductor substrate. After a period of use, the residual gold and platinum on the surface of the semiconductor substrate needs to be recovered. Current methods for recovering gold and platinum from substrates mainly include: First, physical methods such as high-pressure water jetting, manual scraping, grinding, and sandblasting are used to remove the gold and platinum coating. This method is characterized by high labor intensity and high loss of precious metals. Second, chemical methods are used, employing chemical reagents such as aqua regia, cyanide, or thiourea to dissolve the gold and platinum on the substrate surface. The aqua regia method has drawbacks such as high corrosivity and the generation of nitrogen oxides; the cyanide method is restricted due to its high toxicity; and the thiourea method suffers from problems such as easy decomposition of thiourea and low gold stripping efficiency. Summary of the Invention

[0003] To address the problems in the prior art, this invention provides a method for recovering precious metals from semiconductor substrates through electrochemical dissolution. This application achieves anodic oxidation dissolution of the gold and platinum plating on the surface of the semiconductor substrate by precisely controlling the electrochemical dissolution temperature, current density, and electrochemical dissolution system. This results in the substrate being undamaged and reusable, reducing production costs and achieving resource recycling.

[0004] This invention provides a method for recovering precious metals from semiconductor substrates through electrochemical dissolution, employing the following technical solution: A method for recovering precious metals, specifically gold and platinum, from a semiconductor substrate via electrochemical dissolution includes the following steps: S1. Liner cleaning; S2. Electrochemical Dissolution: The liner serves as the anode, and the passivated titanium plate serves as the cathode. The anode electrochemical dissolution solution is an acidic mixed solution containing chloride ions, and the cathode electrochemical dissolution solution is a hydrochloric acid solution. A cation exchange membrane is placed between the cathode and anode. The current density is 5-40 A / m. 2 The electrochemical dissolution temperature is 30-60℃; S3. Noble metal ion enrichment: Repeat the above electrochemical dissolution to enrich noble metal ions in the anodic electrochemical solution after multiple dissolutions until the reduction requirements are met. S4. Gold Reduction: Gold ions in the anolyte enriched with precious metal ions are reduced to obtain gold powder. The amount of reducing agent added is 1.2-1.5 times the theoretical mass of gold. The reduction potential of the anolyte is monitored to be ≥720mV. S5, Platinum precipitation: Oxidize the divalent platinum ions in the remaining anodic electrochemical solution obtained in step S4 into tetravalent platinum ions, and then add ammonium chloride to react and generate ammonium chloroplatinate precipitate. S6. After filtering and washing ammonium chloroplatinate, platinum powder is obtained through reduction treatment.

[0005] By employing the above technical solution, this application achieves anodic oxidation and dissolution of the gold and platinum plating on the semiconductor substrate surface through precise control of the electrochemical dissolution temperature, current density, and composition of the anodic electrochemical dissolution solution system. Simultaneously controlling the current density and electrochemical dissolution temperature not only oxidizes the precious metals into metal ions but also prevents corrosion of the substrate, allowing for undamaged reuse, reducing production costs, and achieving resource recycling. Furthermore, the dissolved gold and platinum ions can rapidly form stable chloride complex ions (AuCl4) with chloride ions in the solution. ﹣ and PtCl6 2﹣ This method avoids the situation where precious metal ions pass through the cation exchange membrane and are reduced and deposited on the cathode plate. Therefore, compared with traditional chemical dissolution methods, the electrochemical dissolution method of this application has the advantages of high selectivity and strong reaction controllability. At the same time, combined with the subsequent stepwise reduction steps, control of the reduction potential of the anolyte electrochemical dissolution solution and the amount of reducing agent added, the gold ions in the solution can be fully reduced to elemental gold, while other metal ions are not reduced to elemental gold at this reduction potential. As a result, the purity of the gold powder obtained by this application can reach 99.99%, and the gold powder recovery rate can reach more than 97%. Through the platinum precipitation and reduction steps, the purity of platinum can reach more than 99.95%, and the platinum recovery rate can reach more than 98%, which meets the application requirements of high-purity precious metals.

[0006] In a preferred embodiment, the cation exchange membrane is a perfluorosulfonic acid-modified cation exchange membrane or an aromatic resin-modified cation exchange membrane with a thickness of 50-150 μm.

[0007] By adopting the above technical solutions, when the thickness of the cation exchange membrane is within this range, the migration rate of cations can be guaranteed to be within a certain range, ensuring the stability of membrane operation and the migration rate of cations. In addition, perfluorosulfonic acid modified cation exchange membranes or aromatic resin-based modified cation exchange membranes have good corrosion resistance, ensuring the continuity of the process.

[0008] In a preferred embodiment, the chloride ion concentration in the anodic electrochemical solution is 2-6 mol / L, and the anodic electrochemical solution comprises water, hydrochloric acid, and additives in a mass ratio of 1:(0.5-2):(0.1-0.5).

[0009] In a preferred embodiment, the additive is one or more of sodium chloride, sodium chlorate, and hydrogen peroxide.

[0010] By adopting the above technical solution, sodium chlorate and hydrogen peroxide, as oxidants, can produce a synergistic effect with electrochemical oxidation, accelerating the dissolution of precious metals on the liner and improving the dissolution efficiency of precious metals; while the addition of sodium chloride can not only provide chloride ions, but also improve the dissolution efficiency of precious metals due to the conductivity of sodium chloride in water.

[0011] In a preferred embodiment, in step S3, after each electrochemical dissolution, hydrochloric acid solution is added to the anolyte electrochemical dissolution solution until the chloride ion concentration in the anolyte electrochemical dissolution solution is 2-6 mol / L.

[0012] By adopting the above technical solution, this application continuously adds hydrochloric acid to the anodic electrochemical solution, which not only ensures sufficient chloride ions in the anodic electrochemical solution to complex noble metal ions, but also keeps the pH of the anodic electrochemical solution low, thus avoiding the adsorption or encapsulation of noble metal ions during the hydrolysis of base metal ions to form precipitates or flocs, and reducing its impact on the reduction of noble metal ions.

[0013] Further preferred methods involve 8-40 electrochemical dissolutions.

[0014] By adopting the above technical solution, and by supplementing the anolyte with hydrochloric acid solution, there are always enough chloride ions in the solution to react with noble metal ions to generate chloride complex ions, thereby maintaining the ion concentration balance and reactivity of the electrochemical solution system. At the same time, by adopting a recycling mode of repeated electrochemical dissolution and incremental replenishment of new electrochemical solution, the high efficiency of electrochemical solution resources and the significant reduction of waste liquid discharge are achieved.

[0015] In a preferred embodiment, the temperature of the gold ion reduction reaction in step S4 is 40-60°C. More preferably, the reduction treatment refers to adding 8-15% nitric acid or sulfuric acid solution to the crude gold powder obtained by reduction with sodium sulfite, controlling the temperature at 80-100°C and the stirring rate at 150-250 r / min, and boiling the powder in acid for 1.5-2 hours, and then washing it with water to obtain high-purity gold powder.

[0016] In a preferred embodiment, in step S4, when the reduction potential of the anolyte is >750mV, the dropping rate of the reducing agent is 4-5L / min; when the reduction potential of the anolyte is between 730-750mV, the dropping rate of the reducing agent is 0.9-1.1L / min; when the reduction potential of the anolyte is ≤730mV, the dropping is stopped; and the reaction ends when the fluctuation range of the reduction potential of the anolyte is ≤10mV.

[0017] Since the reduction potential of platinum ions is lower than that of gold ions, the reduction potential of the anodic electrochemical solution and the dropping rate of the reducing agent solution are monitored to ensure that platinum ions are not reduced during the gold reduction process. When the reduction potential is lower than 720mV, it indicates that the reducing agent is in excess, and at this time, platinum ions may be reduced to platinum. Therefore, controlling the reduction potential of the solution above 720mV in this application can improve the purity of gold and platinum.

[0018] In a preferred embodiment, the amount of ammonium chloride added in step S5 is 1.0-2.5 times the mass of platinum in the solution, the reaction temperature is 25-55℃, and the reaction time is 0.5-2h.

[0019] In a preferred embodiment, hydrazine hydrate is used as a reducing agent in step S6, and the amount of hydrazine hydrate added is 0.14-0.30 times the mass of ammonium chloroplatinate. The reaction temperature is 60-80℃ and the reaction time is 1.0-1.5h.

[0020] In a preferred embodiment, the impurity removal and cleaning agent used in step S1 is one or a combination of organic acid and disodium EDTA, hydrogen peroxide, and polyethylene glycol. More preferably, the organic acid is one of citric acid, oxalic acid, tartaric acid, malic acid, and succinic acid.

[0021] In a preferred embodiment, the cleaning temperature in step S1 is 35-55°C and the cleaning time is 15-40 minutes.

[0022] In summary, the present invention has the following beneficial effects: By synergistically optimizing the electrochemical dissolution parameters, the precious metal ion enrichment process, and the stepwise reduction steps, this application constructs a highly efficient precious metal recovery system. On the one hand, the electrochemical dissolution process uses a low-concentration hydrochloric acid and chloride salt mixed system to replace the highly corrosive reagents such as high-concentration aqua regia in traditional processes, reducing the generation of toxic gases. On the other hand, the electrochemical dissolution process uses a low current density, which can effectively reduce energy consumption and avoid corrosion of the substrate. At the same time, the electrolysis temperature is controlled at 30-60℃, and the temperature can be maintained using low-power heating equipment, eliminating the need for high-power heating devices. Furthermore, the precious metal ion enrichment process achieves precious metal ion enrichment through repeated electrolysis, eliminating the need for additional evaporation equipment for precious metal ion enrichment, further reducing energy consumption and saving costs. Attached Figure Description

[0023] Figure 1 This is a process flow diagram of precious metal recovery from semiconductor substrates in Embodiments 1-5 of this application. Detailed Implementation

[0024] The following combination Figure 1The present invention will be further described in detail below. All reagents, unless otherwise specified, are commercially available conventional reagent products.

[0025] The following embodiments of this application describe the recovery of precious metals from gold and platinum-coated substrates. The substrate is stainless steel with an aluminum layer and a gold and platinum coating. To ensure the substrate substrate is not corroded and the precious metals can be effectively recovered, this application employs low current density and low electrochemical dissolution temperature. During this process, the gold and platinum in the coating are effectively oxidized into metal ions, while also effectively preventing corrosion of the stainless steel substrate during electrochemical dissolution. After each dissolution, the undissolved substrate is replaced. Hydrochloric acid is added to the electrolyte to control the chloride ion content, allowing the electrolyte to be recycled 8-40 times, effectively reducing wastewater discharge, ensuring the stainless steel substrate is not corroded, and enabling secondary use.

[0026] The specific production process flow diagrams for Examples 1-5 are as follows: Figure 1 As shown.

[0027] Example 1

[0028] A method for recovering precious metals from semiconductor substrates by electrochemical dissolution, wherein the precious metals are gold and platinum, includes the following steps: S1. Impurity removal and cleaning: The semiconductor substrate is placed in a composite agent composed of citric acid and EDTA-disodium in a mass ratio of 3:1 and immersed and cleaned at a temperature of 40℃ for 25 minutes. After cleaning, there are no corrosion marks on the substrate. S2. Electrochemical Dissolution: The impurity-removed liner is placed in the anode basket as the anode. The surface of the anode basket is coated with a 5μm thick tantalum-iridium coating. The titanium plate, after passivation treatment by immersion in 10% nitric acid solution for 30 minutes, serves as the cathode. The anode electrochemical dissolution solution is a mixed solution containing 2mol / L chloride ions, and the cathode electrochemical dissolution solution is a 1.2mol / L hydrochloric acid solution. An 80μm thick fluoropolymer-modified cation exchange membrane (DuPont NaFion) is placed between the cathode and anode. TM (Model N-117), with a control current density of 20A / m 2 The electrochemical dissolution temperature is 45℃, and the electrochemical dissolution time is 6 hours. The ionic reaction equation for this process is: Anode: Au + 4Cl ﹣ -3e ﹣ = AuCl4 ﹣ Pt + 6Cl ﹣ -4e ﹣ = PtCl6 2﹣ Cathode: 2H + +2e﹣ =H2↑ The mixed solution consists of water, hydrochloric acid, and sodium chloride in a mass ratio of 1:0.5:0.1; S3. Noble Metal Ion Enrichment: After each dissolution, replace the liner and repeat the electrochemical dissolution process eight times. After each dissolution, add a small amount of hydrochloric acid solution to ensure the chloride ion concentration in the anolyte reaches 2 mol / L before reuse. Enrich the anolyte with noble metal ions (Au) after multiple dissolutions. 3＋ The concentration reaches 10 g / L, which meets the reduction requirements; S4. Gold Reduction: The pH of the anolyte after enrichment of precious metal ions was 1. Sodium sulfite, a reducing agent, was added at a concentration 1.3 times the theoretical mass of gold. The sodium sulfite solution was prepared as a 20% solution and added dropwise to the anolyte. The reduction potential of the solution was monitored during the addition. When the reduction potential was greater than 750 mV, the dropping rate was 4 L / min; when the reduction potential was between 730-750 mV, the dropping rate was 1 L / min; when the reduction potential was ≤730 mV, the dropping was stopped. When the change in reduction potential was 5 mV within 5 minutes (Note: a change in reduction potential ≤10 mV within 5 minutes indicates complete reduction of surface gold ions), the gold ions in the solution were completely reduced, and the reaction was stopped. Stirring was maintained throughout the process, and the reduction reaction temperature was controlled at 50℃. After the reaction, the resulting coarse gold powder was collected by filtration. The ionic equation for this process is: 2AuCl4 ﹣ + 3SO3 2﹣ + 3H₂O = 2Au↓ + 3SO₄ 2﹣ +6H + + 8Cl ﹣ S5. Acid boiling: Transfer the crude gold powder to the reaction vessel, add a 10% nitric acid solution, heat to 85°C, maintain this temperature for 2 hours of acid boiling. After the acid boiling is completed, stop heating and allow it to cool naturally to room temperature. Separate the gold powder and acid solution by vacuum filtration, then wash the gold powder with deionized water until the pH of the washing solution is 6, and dry to obtain high-purity gold powder. S6. Platinum Precipitation: The remaining anolyte solution from step S4 is heated to boiling, and hydrogen peroxide (30% concentration, 0.4 times the mass of platinum) is added for oxidation. This oxidizes all divalent platinum ions in the electrolyte to tetravalent platinum ions. Ammonium chloride is then added to react and form ammonium chloroplatinate precipitate. The reaction temperature is controlled at 40℃, the stirring rate at 100 r / min, and the reaction time at 1 h. The amount of ammonium chloride added is 1.5 times the mass of platinum in the solution. After the reaction, a pale yellow ammonium chloroplatinate precipitate is formed. The ionic equation for this process is: PtCl6 2- + 2NH4 + = (NH4)2PtCl6↓ S7. Filtration: The ammonium chloroplatinate precipitate is separated by vacuum filtration to obtain solid ammonium chloroplatinate. After washing five times with ammonium chloride solution, the filter cake is slurried with water at a mass ratio of ammonium chloroplatinate solid to water of 1:15. Then, sodium hydroxide solution is added to adjust the pH of the system to 8.5. S8. Add 0.14 times the mass of ammonium chloroplatinate to the ammonium chloroplatinate solution, control the reaction temperature at 70℃, and the reaction time at 1.2h. After the reaction is complete, filter and collect the generated platinum powder, wash it three times with pure water, and dry it at 80℃ for 2h to obtain high-purity platinum powder. The ionic equation for this reaction process is as follows: 2PtCl6 2- + 3N2H4 = 2Pt↓ + 3N2↑ + 12Cl - +8H + .

[0029] Example 2

[0030] The difference from Example 1 lies in the adjustment of parameters in each step, as detailed below: A method for recovering precious metals from semiconductor substrates by electrochemical dissolution, wherein the precious metals are gold and platinum, includes the following steps: S1. Cleaning: The semiconductor substrate is placed in a composite agent composed of oxalic acid and hydrogen peroxide in a mass ratio of 4:1 and immersed at a temperature of 50°C for 35 minutes. After cleaning, there are no corrosion marks on the substrate. S2. Electrochemical Dissolution: The impurity-removed liner is placed in the anode basket as the anode. The surface of the anode basket is coated with an 8μm thick tantalum-iridium coating. The titanium plate, after passivation treatment by immersion in 15% nitric acid solution for 25 minutes, serves as the cathode. The anode electrochemical dissolution solution is a mixed solution containing 3 mol / L chloride ions, and the cathode electrochemical dissolution solution is a 1.8 mol / L hydrochloric acid solution. A 120μm thick fluoropolymer-modified cation exchange membrane (DuPont NaFion brand) is placed between the cathode and anode. TM (Model N-117), with a control current density of 10A / m 2 The electrochemical dissolution temperature is 55℃, and the electrochemical dissolution time is 7h. The mixed solution consists of water, hydrochloric acid, and sodium chlorate in a mass ratio of 1:1.2:0.2; S3. Noble Metal Ion Enrichment: After each dissolution, replace the liner and repeat the electrochemical dissolution process 15 times. After each dissolution, add a small amount of hydrochloric acid solution to ensure that the chloride ion concentration in the anolyte reaches 3 mol / L. Then, enrich the anolyte with noble metal ions up to Au using the repeated dissolutions. 3＋ The concentration reached 15.8 g / L, which met the reduction requirements; S4. Gold Reduction: The pH of the anodic electrochemical solution enriched with precious metal ions was 0.8. Sodium sulfite, a reducing agent, was added. The amount of sodium sulfite added was 1.5 times the theoretical mass of gold. The sodium sulfite was prepared as a 20% sodium sulfite solution and added dropwise to the anodic electrochemical solution. During the dropwise addition, the reduction potential of the solution was monitored. When the reduction potential was greater than 750 mV, the dropwise addition rate was 4.2 L / min. When the reduction potential was between 730-750 mV, the dropwise addition rate was 0.9 L / min. When the reduction potential was ≤730 mV, the dropwise addition was stopped. When the change in reduction potential within 5 min was 2 mV, it indicated that the gold ions in the solution had been completely reduced, and the reaction was stopped. The entire process was stirred, and the reduction reaction temperature was controlled at 55℃. After the reaction was completed, the crude gold powder generated was collected by filtration. S5. Acid boiling: Transfer the crude gold powder to the reaction vessel, add a 12% nitric acid solution, heat to 90°C, maintain this temperature for 1.5 hours of acid boiling. After the acid boiling is completed, stop heating and allow it to cool naturally to room temperature. Separate the gold powder and acid solution by vacuum filtration, then wash the gold powder with deionized water until the pH of the washing solution is 7, and dry to obtain high-purity gold powder. S6, Platinum precipitation: The remaining anolyte solution from step S4 is heated to boiling, and hydrogen peroxide is added for oxidation. The concentration of hydrogen peroxide is 20%, and the amount added is 0.8 times the mass of platinum. This oxidizes all divalent platinum ions in the electrolyte to tetravalent platinum ions. Then, ammonium chloride is added to react and generate ammonium chloroplatinate precipitate. The reaction temperature is controlled at 50℃, the stirring rate is 120 r / min, the reaction time is 1.5 h, and the amount of ammonium chloride added is 2.2 times the mass of platinum in the solution. After the reaction is completed, a pale yellow ammonium chloroplatinate precipitate is generated. S7. Filtration: The ammonium chloroplatinate precipitate is separated by vacuum filtration to obtain solid ammonium chloroplatinate. After washing five times with ammonium chloride solution, the filter cake is slurried with water at a mass ratio of ammonium chloroplatinate solid to water of 1:15. Then, sodium hydroxide solution is added to adjust the pH of the system to 9.0. S8. Add 0.18 times the mass of ammonium chloroplatinate to the ammonium chloroplatinate solution, control the reaction temperature at 75℃, and the reaction time at 1.4h. After the reaction is completed, filter and collect the generated platinum powder, wash it three times with pure water, and dry it at 80℃ for 2h to obtain high-purity platinum powder.

[0031] Example 3

[0032] The difference from Example 1 lies in the adjustment of parameters in each step, as detailed below: A method for recovering precious metals from semiconductor substrates by electrochemical dissolution, wherein the precious metals are gold and platinum, includes the following steps: S1. Cleaning: The semiconductor substrate is placed in a composite agent composed of tartaric acid and polyethylene glycol in a mass ratio of 2:1 and immersed in the solution at a temperature of 35°C for 15 minutes. After cleaning, there are no corrosion marks on the substrate. S2. Electrochemical Dissolution: The impurity-removed liner is placed in the anode basket as the anode. The surface of the anode basket is coated with a 3μm thick tantalum-iridium coating. The titanium plate, after passivation treatment by immersion in 8% nitric acid solution for 35 minutes, serves as the cathode. The anode electrochemical dissolution solution is a mixed solution with a chloride ion concentration of 4mol / L, and the cathode electrochemical dissolution solution is a 0.5mol / L hydrochloric acid solution. A 50μm thick fluoropolymer-modified cation exchange membrane (DuPont NaFion) is placed between the cathode and anode. TM (Model N-117), with a control current density of 5A / m 2 The electrochemical dissolution temperature is 30℃, and the electrochemical dissolution time is 4h. The mixed solution consists of water, hydrochloric acid, and hydrogen peroxide in a mass ratio of 1:2:0.5; S3. Noble Metal Ion Enrichment: After each dissolution, replace the liner and repeat the electrochemical dissolution process 40 times. After each dissolution, add a small amount of hydrochloric acid solution to ensure that the chloride ion concentration in the anolyte reaches 4 mol / L. Then, enrich the anolyte with noble metal ions up to Au using the repeated dissolutions. 3＋ The concentration reaches 30 g / L, which meets the reduction requirements; S4. Gold Reduction: The pH of the anolyte after enrichment of precious metal ions was 0.5. Sodium sulfite, a reducing agent, was added at a concentration 1.2 times the theoretical mass of gold. The sodium sulfite solution was prepared as a 20% solution and added dropwise to the anolyte. The reduction potential of the solution was monitored during the dropwise addition. When the reduction potential was greater than 750 mV, the dropwise addition rate was 4.4 L / min. When the reduction potential was between 730 and 750 mV, the dropwise addition rate was 0.95 L / min. When the reduction potential was ≤730 mV, the dropwise addition was stopped. When the change in reduction potential was 6 mV within 5 minutes, it indicated that the gold ions in the solution had been completely reduced, and the reaction was stopped. The entire process was stirred, and the reduction reaction temperature was controlled at 40℃. After the reaction was completed, the crude gold powder generated was collected by filtration. S5. Acid boiling: Transfer the crude gold powder to the reaction vessel, add an 8% nitric acid solution, heat to 80°C, maintain this temperature for 2.5 hours of acid boiling. After the acid boiling is completed, stop heating and allow it to cool naturally to room temperature. Separate the gold powder and acid solution by vacuum filtration, then wash the gold powder with deionized water until the pH of the washing solution is 7, and dry to obtain high-purity gold powder. S6, Platinum precipitation: The remaining anolyte solution from step S4 is heated to boiling, and hydrogen peroxide is added for oxidation. The concentration of hydrogen peroxide is 15%, and the amount added is 1 times the mass of platinum, so that all divalent platinum ions in the electrolyte are oxidized to tetravalent platinum ions. Then ammonium chloride is added to react and generate ammonium chloroplatinate precipitate. The reaction temperature is controlled at 25℃, the stirring rate is 80r / min, the reaction time is 0.5h, and the amount of ammonium chloride added is 1.2 times the mass of platinum in the solution. After the reaction is completed, a pale yellow ammonium chloroplatinate precipitate is generated. S7. Filtration: The ammonium chloroplatinate precipitate is separated by vacuum filtration to obtain solid ammonium chloroplatinate. After washing five times with ammonium chloride solution, the filter cake is slurried with water at a mass ratio of ammonium chloroplatinate solid to water of 1:15. Then, sodium hydroxide solution is added to adjust the pH of the system to 8.5. S8. Add 0.22 times the mass of ammonium chloroplatinate to the ammonium chloroplatinate solution, control the reaction temperature at 60℃ and the reaction time at 1h. After the reaction is completed, filter and collect the generated platinum powder, wash it three times with pure water, and dry it at 80℃ for 2h to obtain high-purity platinum powder.

[0033] Example 4

[0034] The difference from Example 1 lies in the adjustment of parameters in each step, as detailed below: A method for recovering precious metals from semiconductor substrates by electrochemical dissolution, wherein the precious metals are gold and platinum, includes the following steps: S1. Impurity removal and cleaning: The semiconductor substrate is placed in a composite agent composed of malic acid and EDTA-disodium in a mass ratio of 3:2 and immersed and cleaned at a temperature of 45℃ for 30 minutes. After cleaning, there are no corrosion marks on the substrate. S2. Electrochemical Dissolution: The impurity-removed liner is placed in the anode basket as the anode. The surface of the anode basket is coated with a 7μm thick tantalum-iridium coating. The titanium plate, after passivation treatment by immersion in 12% nitric acid solution for 32 minutes, serves as the cathode. The anode electrochemical dissolution solution is a mixed solution with a chloride ion concentration of 5mol / L, and the cathode electrochemical dissolution solution is a 1.5mol / L hydrochloric acid solution. A 100μm thick fluoropolymer-modified cation exchange membrane (DuPont NaFion) is placed between the cathode and anode. TM (Model N-117), with a control current density of 30A / m 2 The electrochemical dissolution temperature is 50℃, and the electrochemical dissolution time is 5h. The mixed solution consists of water, hydrochloric acid, and sodium chloride in a mass ratio of 1:1.8:0.3; S3. Noble Metal Ion Enrichment: After each dissolution, replace the liner and repeat the electrochemical dissolution process 30 times. After each dissolution, add a small amount of hydrochloric acid solution to ensure that the chloride ion concentration in the anolyte reaches 5 mol / L. Then, enrich the anolyte with noble metal ions up to Au using the repeated dissolutions. 3＋ The concentration reaches 25 g / L, which meets the reduction requirements; S4. Gold Reduction: The pH of the anolyte after enrichment of precious metal ions was 0.9. Sodium sulfite, a reducing agent, was added at a concentration 1.4 times the theoretical mass of gold. The sodium sulfite solution was prepared as a 20% solution and added dropwise to the anolyte. The reduction potential of the solution was monitored during the dropwise addition. When the reduction potential was greater than 750 mV, the dropwise addition rate was 4.7 L / min. When the reduction potential was between 730 and 750 mV, the dropwise addition rate was 0.9 L / min. When the reduction potential was ≤730 mV, the dropwise addition was stopped. If the change in reduction potential was 7 mV within 5 minutes, it indicated that the gold ions in the solution had been completely reduced, and the reaction was stopped. The entire process was stirred, and the reduction reaction temperature was controlled at 48℃. After the reaction was completed, the crude gold powder generated was collected by filtration. S5. Acid boiling: Transfer the crude gold powder to the reaction vessel, add a 15% nitric acid solution, heat to 88°C, maintain this temperature for 1.8 hours of acid boiling. After the acid boiling is completed, stop heating and allow it to cool naturally to room temperature. Separate the gold powder and acid solution by vacuum filtration, then wash the gold powder with deionized water until the pH of the washing solution is 7, and dry to obtain high-purity gold powder. S6, Platinum precipitation: The remaining anolyte solution from step S4 is heated to boiling, and hydrogen peroxide is added for oxidation. The concentration of hydrogen peroxide is 20%, and the amount added is 0.6 times the mass of platinum, so that all divalent platinum ions in the electrolyte are oxidized to tetravalent platinum ions. Then ammonium chloride is added to react and generate ammonium chloroplatinate precipitate. The reaction temperature is controlled at 45℃, the stirring rate is 95r / min, the reaction time is 1.2h, and the amount of ammonium chloride added is 2.5 times the mass of platinum in the solution. After the reaction is completed, a pale yellow ammonium chloroplatinate precipitate is generated. S7. Filtration: The ammonium chloroplatinate precipitate is separated by vacuum filtration to obtain solid ammonium chloroplatinate. After washing five times with ammonium chloride solution, the filter cake is slurried with water at a mass ratio of ammonium chloroplatinate solid to water of 1:15. Then, sodium hydroxide solution is added to adjust the pH of the system to 8.5. S8. Add 0.26 times the mass of ammonium chloroplatinate to the ammonium chloroplatinate solution, control the reaction temperature at 72℃, and the reaction time at 1.3h. After the reaction is completed, filter and collect the generated platinum powder, wash it three times with pure water, and dry it at 80℃ for 2h to obtain high-purity platinum powder.

[0035] Example 5

[0036] The difference from Example 1 lies in the adjustment of parameters in each step, as detailed below: A method for recovering precious metals from semiconductor substrates by electrochemical dissolution, wherein the precious metals are gold and platinum, includes the following steps: S1. Impurity removal and cleaning: The semiconductor substrate is placed in a composite agent composed of succinic acid and EDTA-disodium in a mass ratio of 5:1 and immersed and cleaned at a temperature of 55℃ for 40 minutes. After cleaning, there are no corrosion marks on the substrate. S2. Electrochemical Dissolution: The impurity-removed liner is placed in the anode basket as the anode. The surface of the anode basket is coated with a 3μm thick tantalum-iridium coating. The titanium plate, after passivation treatment by immersion in 14% nitric acid solution for 28 minutes, serves as the cathode. The anode electrochemical dissolution solution is a mixed solution with a chloride ion concentration of 6 mol / L, and the cathode electrochemical dissolution solution is a 2.0 mol / L hydrochloric acid solution. A 150μm thick fluoropolymer-modified cation exchange membrane (DuPont NaFion) is placed between the cathode and anode. TM (Model N-117), with a control current density of 40A / m 2 The electrochemical dissolution temperature is 60℃, and the electrochemical dissolution time is 4h. The mixed solution consists of water, hydrochloric acid, and sodium chloride in a mass ratio of 1:1.4:0.4; S3. Noble Metal Ion Enrichment: After each dissolution, replace the liner and repeat the electrochemical dissolution process 25 times. After each dissolution, add a small amount of hydrochloric acid solution to ensure that the chloride ion concentration in the anolyte reaches 6 mol / L. Then, enrich the anolyte with noble metal ions up to Au using the repeated dissolutions. 3＋ The concentration reaches 30 g / L, which meets the reduction requirements; S4. Gold Reduction: After adjusting the pH to 1.2 by adding hydrochloric acid to the anolyte enriched with precious metal ions, sodium sulfite, a reducing agent, is added. The amount of sodium sulfite added is 1.5 times the theoretical mass of gold. The sodium sulfite is prepared as a 20% sodium sulfite solution and added dropwise to the anolyte. During the dropwise addition, the reduction potential of the solution is monitored. When the reduction potential is greater than 750mV, the dropwise addition rate is 5L / min. When the reduction potential is between 730-750mV, the dropwise addition rate is 0.9L / min. When the reduction potential is ≤730mV, the dropwise addition is stopped. When the change in reduction potential is 3mV within 5 minutes, it indicates that the gold ions in the solution have been completely reduced, and the reaction is stopped. The entire process is stirred, and the reduction reaction temperature is controlled at 60℃. After the reaction is completed, the crude gold powder generated is collected by filtration. S5. Acid Boiling: Transfer the crude gold powder to a reaction vessel, add an 11% nitric acid solution, heat to 92°C, maintain this temperature for 1.6 hours of acid boiling. After the acid boiling is completed, stop heating and allow it to cool naturally to room temperature. Separate the gold powder and acid solution by vacuum filtration, then wash the gold powder with deionized water until the pH of the washing solution is 6.5, and dry to obtain high-purity gold powder. S6, Platinum precipitation: The remaining anolyte solution from step S4 is heated to boiling, and hydrogen peroxide is added for oxidation. The concentration of hydrogen peroxide is 25%, and the amount added is 0.5 times the mass of platinum, so that all divalent platinum ions in the electrolyte are oxidized to tetravalent platinum ions. Then ammonium chloride is added to react and generate ammonium chloroplatinate precipitate. The reaction temperature is controlled at 55℃, the stirring rate is 120r / min, the reaction time is 2h, and the amount of ammonium chloride added is 2.3 times the mass of platinum in the solution. After the reaction is completed, a pale yellow ammonium chloroplatinate precipitate is generated. S7. Filtration: The ammonium chloroplatinate precipitate is separated by vacuum filtration to obtain solid ammonium chloroplatinate. After washing five times with ammonium chloride solution, the filter cake is slurried with water at a mass ratio of ammonium chloroplatinate solid to water of 1:15. Then, sodium hydroxide solution is added to adjust the pH of the system to 8.5. S8. Add 0.30 times the mass of ammonium chloroplatinate to the ammonium chloroplatinate solution, control the reaction temperature at 80℃, and the reaction time at 1.6h. After the reaction is completed, filter and collect the generated platinum powder, wash it three times with pure water, and dry it at 80℃ for 2h to obtain high-purity platinum powder.

[0037] Comparative Example 1

[0038] A method for recovering precious metals by electrochemically dissolving semiconductor substrates, differing from Example 1 in that, in step S2, the current density is 60 A / m. 2The electrochemical dissolution temperature was 80°C, the electrochemical dissolution time was 6 hours, and the other steps were the same as in Example 1. After 6 hours of dissolution, obvious pitting corrosion appeared on the surface of the semiconductor substrate.

[0039] Comparative Example 2

[0040] A method for recovering precious metals by electrochemically dissolving a semiconductor substrate differs from Example 1 in that, in step S2, the chloride ion concentration in the anolyte electrochemical dissolution solution is 8 mol / L, while the other steps are the same as in Example 1. After 6 hours of dissolution, obvious pitting corrosion appears on the surface of the semiconductor substrate.

[0041] Comparative Example 3

[0042] A method for recovering precious metals by electrochemically dissolving semiconductor substrates differs from Example 1 in that the dropping rate of sodium sulfite solution in step S4 is different, specifically as follows: when the reduction potential is >750mV, the dropping rate of sodium sulfite solution is 8L / min; when the reduction potential is between 730-750mV, the dropping rate is 3L / min; when the reduction potential is ≤730mV, the dropping is stopped, and the crude gold powder is directly filtered and collected. All other steps are the same as in Example 1.

[0043] Comparative Example 4

[0044] A method for recovering precious metals by electrochemically dissolving semiconductor substrates differs from Example 1 in that the reduction potential in step S4 is different. Specifically, when the reduction potential is above 700mV, the dropping rate of sodium sulfite solution is 4L / min; when the reduction potential is between 680-700mV, the dropping rate is 1L / min; and when the reduction potential is ≤680mV, the dropping is stopped, and the crude gold powder is directly filtered and collected. All other steps are the same as in Example 1.

[0045] The purity and recovery rate of the gold powder and platinum powder obtained in the above embodiments and comparative examples are shown in Table 1.

[0046] Table 1. Results of Gold and Platinum Recycling project Gold powder recovery rate % Gold powder purity % Platinum recovery rate % Platinum purity % Example 1 98.6 99.995 97.6 99.956 Example 2 96.7 99.992 98.7 99.954 Example 3 99.1 99.993 98.3 99.956 Example 4 98.7 99.996 97.6 99.957 Example 5 97.8 99.993 98.6 99.954 Comparative Example 1 99.4 99.991 97.2 99.893 Comparative Example 2 98.9 99.993 96.7 99.912 Comparative Example 3 98.2 95.794 94.6 99.943 Comparative Example 4 99.1 95.978 95.1 99.958 Based on the precious metal recycling data in Table 1: The recovery rate obtained in Examples 1-5 of this application is above 98%, the purity is above 99.99%, the platinum recovery rate is above 97%, and the platinum purity is above 99.9%. This indicates that the gold and platinum obtained in this application are not only of high purity, but the method of this application also effectively improves the yield of platinum and gold.

[0047] When the current density, dissolution temperature, and chloride ion concentration in the anolyte of Comparative Examples 1 and 2 exceeded the limits of this application during electrochemical dissolution, the semiconductor substrates of Comparative Examples 1 and 2 showed corrosion after electrochemical dissolution, which would affect the secondary use of the substrates.

[0048] Compared with Example 1, Comparative Example 3 shows that when the dropping speed of the reducing agent is too fast, there will be an excess of sodium sulfite in some areas. As a result, platinum ions will also be reduced. Especially when the reduction potential is between 730-750mV, the dropping speed is too fast and the reduction potential drops rapidly. When the reduction potential drops to 720mV, there is already an excess of reducing agent, and platinum ions are also reduced, which leads to a decrease in the purity of gold powder and a decrease in the yield of platinum.

[0049] Compared with Example 1, in Comparative Example 4, the sodium sulfite solution was added at a faster rate when the reduction potential was above 700mV. The addition rate decreased when the reduction potential was between 680-700mV. The addition was stopped when the reduction potential was below 680mV. However, the purity of the gold powder and the recovery rate of platinum both decreased in the end. This was because platinum ions were also reduced during the gold reduction process, resulting in a decrease in gold purity and a decrease in platinum recovery rate.

[0050] The embodiments described herein are preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, all equivalent changes made in accordance with the structure, shape, and principle of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for recovering precious metals from a semiconductor substrate by electrochemical dissolution, wherein the precious metals are gold and platinum, characterized in that, Includes the following steps: S1. Liner cleaning; S2. Electrochemical Dissolution: The liner serves as the anode, and the passivated titanium plate serves as the cathode. The anode electrochemical dissolution solution is an acidic mixed solution containing chloride ions, and the cathode electrochemical dissolution solution is a hydrochloric acid solution. A cation exchange membrane is placed between the cathode and anode. The current density is 5-40 A / m. 2 The electrochemical dissolution temperature is 30-60℃; S3. Noble metal ion enrichment: Repeat the above electrochemical dissolution to enrich noble metal ions in the anodic electrochemical solution after multiple dissolutions until the reduction requirements are met. S4. Gold Reduction: Gold ions in the anolyte enriched with precious metal ions are reduced to obtain gold powder. A reducing agent is added dropwise, with the amount of reducing agent being 1.2-1.5 times the theoretical mass of gold. The reduction potential of the anolyte is monitored to be ≥720mV. S5, Platinum precipitation: Oxidize the divalent platinum ions in the remaining anodic electrochemical solution obtained in step S4 into tetravalent platinum ions, and then add ammonium chloride to react and generate ammonium chloroplatinate precipitate. S6. After filtering and washing ammonium chloroplatinate, platinum powder is obtained through reduction treatment.

2. The method for recovering precious metals by electrochemically dissolving semiconductor substrates according to claim 1, characterized in that: The cation exchange membrane is a perfluorosulfonic acid-modified cation exchange membrane or an aromatic resin-based modified cation exchange membrane with a thickness of 50-150 μm.

3. The method for recovering precious metals by electrochemically dissolving semiconductor substrates according to claim 1, characterized in that: The chloride ion concentration in the anodic electrochemical solution is 2-6 mol / L, and the anodic electrochemical solution comprises water, hydrochloric acid and additives in a mass ratio of 1:(0.5-2):(0.1-0.5).

4. The method for recovering precious metals by electrochemically dissolving a semiconductor substrate according to claim 3, characterized in that: The additive is one or more of sodium chloride, sodium chlorate, and hydrogen peroxide.

5. The method for recovering precious metals by electrochemically dissolving a semiconductor substrate according to claim 1, characterized in that: In step S3, after each electrochemical dissolution, hydrochloric acid solution is added to the anolyte electrochemical dissolution solution until the chloride ion concentration in the anolyte electrochemical dissolution solution is 2-6 mol / L.

6. The method for recovering precious metals by electrochemically dissolving semiconductor substrates according to claim 1, characterized in that: The temperature of the gold ion reduction reaction in step S4 is 40-60℃.

7. The method for recovering precious metals by electrochemically dissolving semiconductor substrates according to claim 1, characterized in that: In step S4, when the reduction potential of the anolyte is >750mV, the dropping rate of the reducing agent is 4-5L / min; when the reduction potential of the anolyte is between 730-750mV, the dropping rate of the reducing agent is 0.9-1.1L / min; when the reduction potential of the anolyte is ≤730mV, the dropping is stopped; and the reaction ends when the fluctuation range of the reduction potential of the anolyte is ≤10mV.

8. The method for recovering precious metals by electrochemically dissolving semiconductor substrates according to claim 1, characterized in that: In step S5, the amount of ammonium chloride added is 1.0-2.5 times the mass of platinum in the solution, the reaction temperature is 25-55℃, and the reaction time is 0.5-2h.

9. The method for recovering precious metals by electrochemically dissolving semiconductor substrates according to claim 1, characterized in that: In step S6, hydrazine hydrate is used as a reducing agent. The amount of hydrazine hydrate added is 0.14-0.30 times the mass of ammonium chloroplatinate. The reaction temperature is 60-80℃ and the reaction time is 1.0-1.5h.

10. The method for recovering precious metals by electrochemically dissolving a semiconductor substrate according to claim 1, characterized in that: In step S1, the cleaning agent used for impurity removal is one or a combination of organic acid and disodium EDTA, hydrogen peroxide, and polyethylene glycol. The cleaning temperature is 35-55℃ and the cleaning time is 15-40 minutes.

Images