Method for recovering gold from waste circuit board
By stripping, crushing, sorting, and electrolyzing waste circuit boards, combined with the reaction of gold separation solution and composite reduction solution, the problems of high energy consumption and environmental pollution in existing technologies are solved, achieving efficient and environmentally friendly gold recovery.
Patent Information
- Application Number
- CN202610077088.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-01-21
- Publication Date
- 2026-05-12
AI Technical Summary
Existing technologies for recovering gold from waste circuit boards involve high energy consumption and environmental pollution. In particular, pyrometallurgy produces dioxins and hydrometallurgy uses toxic and harmful reagents, resulting in high environmental costs and significant safety hazards.
After stripping electronic components, the metal is crushed, sorted, and cast into metal plates. Copper is then separated through electrolytic copper removal. Pure gold particles are generated by reacting the gold separation solution and composite reduction solution. Low-temperature crushing and selective dissolution methods are used to avoid the generation of toxic and harmful substances during high-temperature processes.
This improved the gold recovery rate, reduced the generation of toxic and harmful waste liquids and gases, and achieved an environmentally friendly and efficient gold recovery process.
Smart Images
Figure SMS_1
Abstract
Description
Technical Field
[0001] This invention relates to the field of resource recycling technology, and in particular to a method for recovering gold from waste circuit boards. Background Technology
[0002] With the continuous development of the global economy, resource issues are becoming increasingly severe. Currently, the electronics and information industry is experiencing rapid growth, and the pace of product upgrades is accelerating, generating a large amount of electronic waste. Waste circuit boards, which constitute a major component of electronic waste, have a high metal content and enormous potential for resource recovery, making them a key focus of resource recycling. In terms of composition, waste circuit boards are a composite of metallic and non-metallic materials. The metallic components mainly include basic metals such as copper, lead, and tin, as well as precious metals such as gold and silver, with the gold grade far exceeding that of primary ore.
[0003] Currently, there are two main methods for recovering gold from waste circuit boards: pyrometallurgy and hydrometallurgy. Pyrometallurgy relies on existing copper and lead smelting systems, using waste circuit boards as raw materials to co-process with primary ore. The circuit boards are smelted at high temperatures to induce base metals such as copper to form a molten phase, while precious metals are enriched in the molten metal. Finally, different metals are obtained through separate purification. This metallurgical method has a large processing capacity and a high gold recovery rate. Hydrometallurgy, on the other hand, uses chemical reagents to selectively dissolve gold. For example, the strong complexing ability of cyanide and aqua regia can be used to leach gold particles.
[0004] However, pyrometallurgy consumes a lot of energy, and the non-metallic components in the circuit board are prone to producing highly toxic substances such as dioxins during high-temperature processes, which greatly increases environmental protection costs. Hydrometallurgy, on the other hand, requires the use of more toxic and harmful reagents, which poses significant safety hazards. Furthermore, the post-treatment process for waste liquid is quite complex and generates a large amount of cyanide-containing wastewater or nitrogen oxide waste gas, which also increases environmental risks. Therefore, there is an urgent need to provide a solution to improve the above problems. Summary of the Invention
[0005] The purpose of this invention is to provide a method for recovering gold from waste circuit boards, which can improve the gold recovery rate from waste circuit boards and does not generate toxic or harmful waste liquids or gases during the recovery process.
[0006] This invention provides a method for recovering gold from waste circuit boards, comprising: stripping electronic components from the waste circuit board, crushing, sorting, and casting to obtain a metal plate; electrolyzing the metal plate to separate copper and obtain copper-removing sludge; mixing and reacting the copper-removing sludge in a gold-separating solution and then separating the gold-containing solution; mixing the gold-containing solution with a composite reducing solution and then carrying out a reduction reaction to generate pure gold particles; wherein: the gold-separating solution contains: 1 mol / L-3 mol / L NaCl, 2 mol / L-3 mol / L H2SO4, 0.1 mol / L-0.2 mol / L NaClO3, 0.05 mol / L-0.1 mol / L H2O2, and 10 g / L-20 g / L silane activator.
[0007] Optionally, the electronic components can be stripped after the waste circuit board is preheated at 200℃-250℃.
[0008] Optionally, the electronic components can be stripped and recycled.
[0009] Optionally, the electronic components are stripped from the waste circuit board, then sheared, crushed, and cryogenically pulverized.
[0010] Optionally, the crushed product can be passed through a 1mm-3mm sieve.
[0011] Optionally, the sorting includes at least one of gravity sorting, electrostatic sorting, and airflow sorting.
[0012] Optionally, after sorting, metal particles and non-metal particles are obtained, and the metal particles are melted and cast to obtain a metal plate.
[0013] Optionally, after sorting, the metal plates are melted and cast at 1200℃-1500℃ to obtain metal plates.
[0014] Optionally, after sorting, the material can be pre-calcined at 400℃-600℃ and then melted and cast.
[0015] Optionally, after sorting, the metal particles are mixed with flux at a mass ratio of 10:1 and then melted and cast.
[0016] Optionally, the flux includes borax.
[0017] Optionally, the metal plate is immersed in the electrolyte, and the metal plate is used as the anode and stainless steel as the cathode for electrolytic copper separation.
[0018] Optionally, the soluble substances in the electrolyte include: 1 mol / L-3 mol / L CuSO4, 0.5 mol / L-2 mol / L H2SO4, 0.2 mol / L-0.5 mol / L HCl, 0.01 mol / L-0.05 mol / L thiourea, 100 mg / L-200 mg / L gelatin, and 50 mg / L-100 mg / L bone glue.
[0019] Optionally, at 200A / m 2 -300A / m 2 Copper is separated by electrolysis at a current density of [value missing].
[0020] Optionally, copper electrolysis can be carried out at 50℃-60℃.
[0021] Optionally, after electrolytic copper separation, the anode mud is collected, and the anode mud is reacted with manganese dioxide in dilute sulfuric acid and then separated into solid and liquid materials to obtain mud material.
[0022] Optionally, the dilute sulfuric acid contains 0.2 mol / L to 0.5 mol / L of sulfuric acid and 0.1 mol / L to 0.3 mol / L of sodium chloride, and the mass ratio of the anode mud to the manganese dioxide is 1:(0.1-0.2).
[0023] Optionally, the copper-removing sludge is mixed and reacted in a gold-separating solution at 50°C-80°C.
[0024] Optionally, the mixture is reacted in the gold separation solution for 3-5 hours.
[0025] Optionally, an ultrasonic mixing reaction can be carried out in the gold separation solution.
[0026] Optionally, the copper removal sludge is pre-washed and dried with anhydrous ethanol before being mixed and reacted with the gold separation solution.
[0027] Optionally, the solid-liquid mass ratio of the copper removal sludge to the gold separation solution is 1:(10-30).
[0028] Optionally, the silane activator includes Tegopren-5885.
[0029] Optionally, the composite reducing solution contains: 1 mol / L-2 mol / L Na2SO3, 0.5 mol / L-1 mol / L ascorbic acid, 0.1 mol / L-0.3 mol / L EDTA, and 3 g / L-8 g / L polyvinylpyrrolidone.
[0030] Optionally, the pH of the composite reducing solution is 1-3.
[0031] Optionally, the gold-containing solution is desolventized to obtain gold-containing mud, and the gold-containing mud is mixed and dispersed in a composite reducing solution, wherein the solid-liquid mass ratio of the gold-containing mud to the composite reducing solution is 1:(10-30).
[0032] Optionally, the gold-containing solution is mixed with the composite reducing solution and then the reduction reaction is carried out at 30℃-50℃.
[0033] Optionally, the gold-containing solution is mixed with the composite reducing solution and then subjected to a reduction reaction for 2-5 hours.
[0034] Optionally, the gold-containing solution and the composite reducing solution are ultrasonically mixed.
[0035] Optionally, after the reduction reaction, the gold particles are separated by filtration and washed with anhydrous ethanol and deionized water in a cycle to obtain pure gold particles. Detailed Implementation
[0036] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Unless otherwise defined, the technical or scientific terms used herein should have the ordinary meaning understood by those skilled in the art to which this invention pertains.
[0037] This invention provides a method for recovering gold from waste circuit boards, comprising the following steps: S1. After stripping the electronic components off the waste circuit board, crush, sort and cast the metal plate. S2. After electrolytic copper separation of the metal plate, copper-removing sludge is obtained; S3. After mixing and reacting the copper-removing mud in the gold separation solution, separate the gold-containing solution. S4. After mixing the gold-containing solution with the composite reducing solution, a reduction reaction is carried out to generate pure gold particles.
[0038] In fact, this invention efficiently separates the metal and non-metal components (resin, glass fiber, etc.) from the waste circuit board by peeling off the electronic components and crushing and sorting them in step S1, increasing the metal concentration and casting it into a metal plate. This facilitates the electrolytic treatment in step S2, enabling the production of high-purity electrolytic copper products at the cathode and the acquisition of copper-removing sludge containing gold. In step S3, the gold in the copper-removing sludge is selectively reacted to separate a gold-containing solution, and in step S4, the gold in the gold-containing solution is reduced to obtain elemental gold particles.
[0039] In some embodiments, the waste circuit board can be preheated at 200°C-250°C before the electronic components are peeled off during step S1. In fact, the high temperature melts the metal solder between the waste circuit board and the electronic components, facilitating the peeling off of the electronic components. Furthermore, high-value and intact electronic components can be recovered after peeling. Specifically, in step S1, the waste circuit board can be subjected to vibration or mechanical scraping to peel off the electronic components from its surface.
[0040] In some embodiments, during step S1, the waste circuit boards stripped of electronic components are sheared, crushed, and cryogenically pulverized. In practice, shearing and crushing the waste circuit boards initially reduces their size, and then, during cryogenic pulverization, the brittle change between metallic and non-metallic components is utilized to pulverize the non-metallic components and separate them from the metallic components. Simultaneously, cryogenic pulverization avoids the pyrolysis of non-metallic components during high-temperature processes, preventing the generation of toxic and harmful gases.
[0041] Furthermore, the sheared and crushed waste circuit boards can be cryogenically pulverized in a liquid nitrogen environment and passed through a 1mm-3mm sieve. Specifically, the shearing, crushing, and cryogenic pulverization processes can be repeated to effectively reduce the particle size of the obtained particles, which helps to effectively distinguish between metal and non-metal particles and obtain high-purity metal particles for melting and casting. Further, the sorting can employ at least one of gravity sorting, electrostatic sorting, or airflow sorting. In addition, a combination of sorting technologies can be used for comprehensive processing to improve the differentiation between non-metallic and metallic particles.
[0042] In some embodiments, during step S1, the sorted metal particles are pre-calcined at 400℃-600℃ for 1-2 hours, then transferred to an environment of 1200℃-1500℃ to melt and cast to obtain a metal plate. In practice, during melting and casting, flux can be evenly spread on the surface of the preheated metal particles, and the temperature is raised for melting and casting. Specifically, the mass ratio of flux to metal particles used is 1:10, and the flux can be borax.
[0043] In some embodiments, during step S2, the metal plate is immersed in the electrolyte, using the metal plate as the anode and stainless steel as the cathode for electrolytic copper separation. In fact, electrochemical methods can precisely extract copper from the metal plate and enrich and recover it at the cathode, while other metallic components (gold, silver, tin, lead, etc.) are enriched in the anode mud, thus achieving the separation and recovery of copper components from the metal plate.
[0044] In some embodiments, the soluble substances in the electrolyte used in step S2 may include: 1 mol / L-3 mol / L CuSO4, 0.5 mol / L-2 mol / L H2SO4, 0.2 mol / L-0.5 mol / L HCl, 0.01 mol / L-0.05 mol / L thiourea, 100 mg / L-200 mg / L gelatin, and 50 mg / L-100 mg / L bone glue. Specifically, the metal plate can be subjected to 200 A / m 2 -300A / m 2 Copper is separated by electrolysis in an electrolyte at a current density of 50℃-60℃. After the copper is separated by electrolysis, the anode mud is collected. The anode mud is then reacted with manganese dioxide in dilute sulfuric acid and the solid and liquid are separated to obtain mud material.
[0045] In some embodiments, when anode mud is mixed with dilute sulfuric acid and then manganese dioxide is added and stirred, the oxidizing property of manganese dioxide promotes the reaction of residual copper in the anode mud with dilute sulfuric acid to form copper sulfate, which enters the mixed solution. The copper in the resulting mixed solution is then recovered. Furthermore, this process can further reduce the copper content in the mud, which is beneficial for subsequent separation and purification of precious metal components. In practice, the dilute sulfuric acid contains 0.2 mol / L-0.5 mol / L of sulfuric acid and 0.1 mol / L-0.3 mol / L of sodium chloride, and the mass ratio of anode mud to manganese dioxide is 1:(0.1-0.2).
[0046] Specifically, the gold separation solution used in step S3 contains 1 mol / L-3 mol / L NaCl, 2 mol / L-3 mol / L H2SO4, 0.1 mol / L-0.2 mol / L NaClO3, 0.05 mol / L-0.1 mol / L H2O2, and 10 g / L-20 g / L silane activator. Further, the copper-removing sludge can be mixed and reacted in the gold separation solution at 50℃-80℃ for 3-5 hours to promote the full dissolution of gold from the copper-removing sludge. Simultaneously, ultrasonic or mechanical mixing can be used to promote rapid dispersion of the copper-removing sludge in the gold-removing solution and improve its dispersion uniformity.
[0047] In some embodiments, the copper-removing sludge can be pre-washed and dried with anhydrous ethanol before being mixed with the gold separation solution in step S3. Furthermore, the solid-liquid mass ratio of the copper-removing sludge to the gold separation solution is 1:(10-30), and the silane activator used includes Tegopren-5885. In fact, adding a silane activator to the gold separation solution can effectively improve the dispersion stability of the copper-removing sludge in the solution, thereby increasing the gold yield.
[0048] In some embodiments, the composite reducing solution used in step S4 contains dissolved Na₂SO₃ (1 mol / L-2 mol / L), ascorbic acid (0.5 mol / L-1 mol / L), EDTA (0.1 mol / L-0.3 mol / L), and polyvinylpyrrolidone (3 g / L-8 g / L). In practice, the gold-containing solution can be pre-treated to obtain gold-containing mud, which is then mixed and dispersed in a composite reducing solution with a pH of 1-3. The solid-liquid mass ratio of the gold-containing mud to the composite reducing solution can be 1:(10-30).
[0049] In some embodiments, when performing step S4, the gold-containing solution and the composite reducing solution can be mixed and reacted at 30°C-50°C under ultrasonic conditions for 2-5 hours. After separation by filtration, pure gold particles are obtained by circulating rinsing with anhydrous ethanol and deionized water. Example 1
[0050] This embodiment 1 provides a method for recovering gold from waste circuit boards, including the following steps: S1. After pre-cleaning the surface of the waste circuit board, it is preheated at 230℃ for 30 minutes and the surface electronic components are peeled off and recycled. The waste circuit board with the surface electronic components peeled off is mechanically crushed by a shearing shredder, transferred to a liquid nitrogen environment for freezing and grinding, and then passed through a 3mm sieve. The sieved material is collected and sorted by gravity to obtain metal particles. The metal particles are filled into a crucible and preheated at 500℃ for 2 hours. Then, 10% borax is evenly spread on the surface of the metal particles and the temperature is raised to 1400℃ to melt and pour into a mold to form a metal plate. S2. Transfer the metal plate into the electrolytic cell, using the metal plate as the anode and the stainless steel plate as the cathode, at 250 A / m. 2 After electrolysis at a current density of 60℃, the anode mud was collected and mixed with dilute sulfuric acid (containing 0.3 mol / L sulfuric acid and 0.2 mol / L sodium chloride). After stirring and mixing, manganese dioxide was added and stirred until the reaction was complete. After solid-liquid separation, copper-removed mud was obtained. The mass ratio of anode mud to manganese dioxide was 1:0.15. The electrolyte contained 2 mol / L CuSO4, 1 mol / L H2SO4, 0.3 mol / L HCl, 0.03 mol / L thiourea, 150 mg / L gelatin, and 80 mg / L bone glue. S3. The copper-removing sludge was added to the gold-removing solution at a solid-liquid mass ratio of 1:20 and ultrasonically mixed. After ultrasonic reaction at 60℃ for 4 hours, the mixture was filtered to obtain a gold-containing solution. The gold-containing solution was then concentrated under reduced pressure to obtain gold-containing sludge. The gold-removing solution contained the following dissolved components: 2 mol / L NaCl, 2 mol / L H2SO4, 0.15 mol / L NaClO3, 0.08 mol / L H2O2, and 15 g / L Tegopren-5885 (purchased from Evonik). S4. The gold-containing mud was added to a composite reducing solution with pH=2 at a solid-liquid ratio of 1:20 and ultrasonically mixed. The mixture was then heated to 40℃ and ultrasonically reacted for 3 hours. After separation by filtration, pure gold particles were obtained by circulating rinsing with anhydrous ethanol and deionized water. The composite reducing solution contained: 1.5 mol / L Na2SO3, 0.8 mol / L ascorbic acid, 0.2 mol / L EDTA, and 5 g / L polyvinylpyrrolidone (PVP K30; purchased from Jinan Zhengkang Chemical Co., Ltd.). Example 2
[0051] This embodiment 2 provides a method for recovering gold from waste circuit boards, including the following steps: S1. After pre-cleaning the surface of the waste circuit board, it is preheated at 230℃ for 30 minutes and the surface electronic components are peeled off and recycled. The waste circuit board with the surface electronic components peeled off is mechanically crushed by a shearing shredder, transferred to a liquid nitrogen environment for freezing and grinding, and then passed through a 3mm sieve. The sieved material is collected and sorted by gravity to obtain metal particles. The metal particles are filled into a crucible and preheated at 500℃ for 2 hours. Then, 10% borax is evenly spread on the surface of the metal particles and the temperature is raised to 1400℃ to melt and pour into a mold to form a metal plate. S2. Transfer the metal plate into the electrolytic cell, using the metal plate as the anode and the stainless steel plate as the cathode, at 210 A / m. 2 After electrolysis at a current density of 60℃, the anode mud was collected and mixed with dilute sulfuric acid (containing 0.2 mol / L sulfuric acid and 0.1 mol / L sodium chloride). After stirring and mixing, manganese dioxide was added and stirred until the reaction was complete. After solid-liquid separation, copper-removed mud was obtained. The mass ratio of anode mud to manganese dioxide was 1:0.2. The electrolyte contained 2.2 mol / L CuSO4, 1 mol / L H2SO4, 0.4 mol / L HCl, 0.05 mol / L thiourea, 160 mg / L gelatin, and 60 mg / L bone glue. S3. The copper-removing sludge was added to the gold-removing solution at a solid-liquid mass ratio of 1:20 and ultrasonically mixed. After ultrasonic reaction at 60℃ for 4 hours, the mixture was filtered to obtain a gold-containing solution. The gold-containing solution was then concentrated under reduced pressure to obtain gold-containing sludge. The gold-removing solution contained the following dissolved components: 2.5 mol / L NaCl, 2.3 mol / L H2SO4, 0.12 mol / L NaClO3, 0.06 mol / L H2O2, and 13 g / L Tegopren-5885 (purchased from Evonik). S4. The gold-containing mud was added to a composite reducing solution with pH=2 at a solid-liquid ratio of 1:20 and ultrasonically mixed. The mixture was then heated to 40℃ and ultrasonically reacted for 3 hours. After separation by filtration, pure gold particles were obtained by circulating rinsing with anhydrous ethanol and deionized water. The composite reducing solution contained: 1.3 mol / L Na2SO3, 0.7 mol / L ascorbic acid, 0.1 mol / L EDTA, and 4 g / L polyvinylpyrrolidone (PVP K30; purchased from Jinan Zhengkang Chemical Co., Ltd.).
[0052] Comparative Example 1 Comparative Example 1 provides a method for recovering gold from waste circuit boards, comprising the following steps: D1. After pre-cleaning the surface of the waste circuit board, preheat it at 230℃ for 30 minutes, peel off and recycle the surface electronic components. After the waste circuit board with the surface electronic components peeled off is mechanically crushed by a shearing shredder, it is transferred to a liquid nitrogen environment to freeze and grind into powder. After passing through a 3mm sieve, the sieved material is collected and sorted by gravity to obtain metal particles. The metal particles are filled into a crucible and preheated at 500℃ for 2 hours. Then, 10% borax is evenly spread on the surface of the metal particles and the temperature is raised to 1400℃ to melt. After melting, it is poured into a mold to form a metal plate. D2. Transfer the metal plate into the electrolytic cell, using the metal plate as the anode and the stainless steel plate as the cathode, at 250 A / m. 2 After electrolysis at a current density of 60℃, the anode mud was collected and mixed with dilute sulfuric acid (containing 0.3 mol / L sulfuric acid and 0.2 mol / L sodium chloride). After stirring and mixing, manganese dioxide was added and stirred until the reaction was complete. After solid-liquid separation, copper-removed mud was obtained. The mass ratio of anode mud to manganese dioxide was 1:0.15. The electrolyte contained 2 mol / L CuSO4, 1 mol / L H2SO4, 0.3 mol / L HCl, 0.03 mol / L thiourea, 150 mg / L gelatin, and 80 mg / L bone glue. D3. The copper-removing sludge was added to the gold-removing solution at a solid-liquid mass ratio of 1:20 and ultrasonically mixed. After ultrasonic reaction at 60℃ for 4 hours, the mixture was filtered to obtain a gold-containing solution. The gold-containing solution was concentrated under reduced pressure to obtain gold-containing sludge. The gold-removing solution contained: 2 mol / L NaCl, 2 mol / L H2SO4, 0.15 mol / L NaClO3, and 0.08 mol / L H2O2. D4. The gold-containing mud was added to a composite reducing solution with pH=2 at a solid-liquid ratio of 1:20 and ultrasonically mixed. The mixture was then heated to 40℃ and ultrasonically reacted for 3 hours. After filtration and separation, pure gold particles were obtained by circulating rinsing with anhydrous ethanol and deionized water. The composite reducing solution contained: 1.5 mol / L Na2SO3, 0.8 mol / L ascorbic acid, 0.2 mol / L EDTA, and 5 g / L polyvinylpyrrolidone (PVP K30; purchased from Jinan Zhengkang Chemical Co., Ltd.).
[0053] Comparative Example 2 Comparative Example 2 provides a method for recovering gold from waste circuit boards, comprising the following steps: D1. After pre-cleaning the surface of the waste circuit board, preheat it at 230℃ for 30 minutes, peel off and recycle the surface electronic components. After the waste circuit board with the surface electronic components peeled off is mechanically crushed by a shearing shredder, it is transferred to a liquid nitrogen environment to freeze and grind into powder. After passing through a 3mm sieve, the sieved material is collected and sorted by gravity to obtain metal particles. The metal particles are filled into a crucible and preheated at 500℃ for 2 hours. Then, 10% borax is evenly spread on the surface of the metal particles and the temperature is raised to 1400℃ to melt. After melting, it is poured into a mold to form a metal plate. D2. Transfer the metal plate into the electrolytic cell, using the metal plate as the anode and the stainless steel plate as the cathode, at 250 A / m. 2 After electrolysis at a current density of 60℃, the anode mud was collected and mixed with dilute sulfuric acid (containing 0.3 mol / L sulfuric acid and 0.2 mol / L sodium chloride). After stirring and mixing, manganese dioxide was added and stirred until the reaction was complete. After solid-liquid separation, copper-removed mud was obtained. The mass ratio of anode mud to manganese dioxide was 1:0.15. The electrolyte contained 2 mol / L CuSO4, 1 mol / L H2SO4, 0.3 mol / L HCl, 0.03 mol / L thiourea, 150 mg / L gelatin, and 80 mg / L bone glue. D3. The copper-removing sludge was added to the gold-removing solution at a solid-liquid mass ratio of 1:20 and ultrasonically mixed. After ultrasonic reaction at 60℃ for 4 hours, the mixture was filtered to obtain a gold-containing solution. The gold-containing solution was then concentrated under reduced pressure to obtain gold-containing sludge. The gold-removing solution contained the following dissolved components: 2 mol / L NaCl, 2 mol / L H2SO4, 0.15 mol / L NaClO3, 0.08 mol / L H2O2, and 15 g / L Tegopren-5885 (purchased from Evonik). D4. The gold-containing mud was added to a composite reducing solution with pH=2 at a solid-liquid ratio of 1:20 and ultrasonically mixed. The mixture was then heated to 40℃ and ultrasonically reacted for 3 hours. After separation by filtration, pure gold particles were obtained by circulating rinsing with anhydrous ethanol and deionized water. The composite reducing solution contained 1.5 mol / L Na2SO3, 0.8 mol / L ascorbic acid, and 0.2 mol / L EDTA.
[0054] Comparative Example 3 Comparative Example 3 provides a method for recovering gold from waste circuit boards, comprising the following steps: D1. After pre-cleaning the surface of the waste circuit board, preheat it at 230℃ for 30 minutes, peel off and recycle the surface electronic components. After the waste circuit board with the surface electronic components peeled off is mechanically crushed by a shearing shredder, it is transferred to a liquid nitrogen environment to freeze and grind into powder. After passing through a 3mm sieve, the sieved material is collected and sorted by gravity to obtain metal particles. The metal particles are filled into a crucible and preheated at 500℃ for 2 hours. Then, 10% borax is evenly spread on the surface of the metal particles and the temperature is raised to 1400℃ to melt. After melting, it is poured into a mold to form a metal plate. D2. Transfer the metal plate into the electrolytic cell, using the metal plate as the anode and the stainless steel plate as the cathode, at 250 A / m. 2 After electrolysis at a current density of 60℃, the anode mud was collected and mixed with dilute sulfuric acid (containing 0.3 mol / L sulfuric acid and 0.2 mol / L sodium chloride). After stirring and mixing, manganese dioxide was added and stirred until the reaction was complete. After solid-liquid separation, copper-removed mud was obtained. The mass ratio of anode mud to manganese dioxide was 1:0.15. The electrolyte contained 2 mol / L CuSO4, 1 mol / L H2SO4, 0.3 mol / L HCl, 0.03 mol / L thiourea, 150 mg / L gelatin, and 80 mg / L bone glue. D3. The copper-removing sludge was added to the gold-removing solution at a solid-liquid mass ratio of 1:20 and ultrasonically mixed. After ultrasonic reaction at 60℃ for 4 hours, the mixture was filtered to obtain a gold-containing solution. The gold-containing solution was concentrated under reduced pressure to obtain gold-containing sludge. The gold-removing solution contained: 2 mol / L NaCl, 2 mol / L H2SO4, 0.15 mol / L NaClO3, and 0.08 mol / L H2O2. D4. The gold-containing mud was added to a composite reducing solution with pH=2 at a solid-liquid ratio of 1:20 and ultrasonically mixed. The mixture was then heated to 40℃ and ultrasonically reacted for 3 hours. After separation by filtration, pure gold particles were obtained by circulating rinsing with anhydrous ethanol and deionized water. The composite reducing solution contained 1.5 mol / L Na2SO3, 0.8 mol / L ascorbic acid, and 0.2 mol / L EDTA.
[0055] The gold recovery rates in Examples 1 to 2 and Comparative Examples 1 to 3 are shown in Table 1 below.
[0056] Table 1 Gold recovery rate
[0057] While embodiments of the present invention have been described in detail above, it will be apparent to those skilled in the art that various modifications and variations can be made to these embodiments. However, it should be understood that such modifications and variations fall within the scope and spirit of the invention as set forth in the claims. Furthermore, the invention described herein may have other embodiments and can be implemented or carried out in various ways.
Claims
1. A method for recovering gold from waste circuit boards, characterized in that, include: After stripping electronic components from waste circuit boards, they are crushed, sorted, and cast to obtain metal plates. Copper-free sludge is obtained by electrolytic separation of copper from metal plates; The copper-removing sludge is mixed and reacted in a gold-separating solution, and then the gold-containing solution is separated. The gold-containing solution is mixed with a composite reducing solution and then subjected to a reduction reaction to generate pure gold particles. The gold-separating solution contains: 1 mol / L-3 mol / L NaCl, 2 mol / L-3 mol / L H2SO4, 0.1 mol / L-0.2 mol / L NaClO3, 0.05 mol / L-0.1 mol / L H2O2, and 10 g / L-20 g / L silane activator.
2. The method according to claim 1, characterized in that: The electronic components are stripped off after the waste circuit board is preheated at 200℃-250℃; and / or the electronic components are stripped off and recycled; and / or the electronic components are stripped off, sheared, crushed and pulverized at low temperature; and / or the crushed components are passed through a 1mm-3mm sieve; and / or the sorting includes at least one of gravity sorting, electrostatic sorting and airflow sorting.
3. The method according to claim 1, characterized in that: After sorting, metal particles and non-metal particles are obtained. The metal particles are melted and cast to obtain a metal plate; and / or, after sorting, the metal particles are melted and cast at 1200℃-1500℃ to obtain a metal plate; and / or, after sorting, the metal particles are pre-calcined at 400℃-600℃ and then melted and cast; and / or, after sorting, the metal particles are mixed with a flux at a mass ratio of 10:1 and then melted and cast. Preferably, the flux includes borax.
4. The method according to claim 1, characterized in that: A metal plate is immersed in an electrolyte, and copper is separated by electrolysis using the metal plate as the anode and stainless steel as the cathode. The soluble substances in the electrolyte include: 1 mol / L-3 mol / L CuSO4, 0.5 mol / L-2 mol / L H2SO4, 0.2 mol / L-0.5 mol / L HCl, 0.01 mol / L-0.05 mol / L thiourea, 100 mg / L-200 mg / L gelatin, and 50 mg / L-100 mg / L bone glue.
5. The method according to claim 1 or 4, characterized in that: At 200A / m 2 -300A / m 2 Electrolytic copper separation is performed at a current density of 50℃-60℃; and / or, electrolytic copper separation is performed at 50℃-60℃; and / or, after electrolytic copper separation, anode mud is collected, and the anode mud is reacted with manganese dioxide in dilute sulfuric acid and then separated into solid and liquid materials to obtain mud material; wherein, the dilute sulfuric acid contains 0.2mol / L-0.5mol / L sulfuric acid and 0.1mol / L-0.3mol / L sodium chloride, and the mass ratio of the anode mud to the manganese dioxide is 1:(0.1-0.2).
6. The method according to claim 1, characterized in that: The copper-removing sludge is mixed and reacted in a gold separation solution at 50℃-80℃; and / or, mixed and reacted in the gold separation solution for 3h-5h; and / or, ultrasonically mixed and reacted in the gold separation solution; and / or, the copper-removing sludge is pre-washed and dried with anhydrous ethanol before being mixed and reacted with the gold separation solution; and / or, the solid-liquid mass ratio of the copper-removing sludge to the gold separation solution is 1:(10-30); and / or, the silane activator includes Tegopren-5885.
7. The method according to claim 1, characterized in that: The composite reducing solution contains: 1 mol / L-2 mol / L Na2SO3, 0.5 mol / L-1 mol / L ascorbic acid, 0.1 mol / L-0.3 mol / L EDTA, and 3 g / L-8 g / L polyvinylpyrrolidone; and / or, the pH of the composite reducing solution is 1-3; and / or, the gold-containing solution is desolventized to obtain gold-containing mud, and the gold-containing mud is mixed and dispersed in the composite reducing solution, wherein the solid-liquid mass ratio of the gold-containing mud to the composite reducing solution is 1:(10-30).
8. The method according to claim 1, characterized in that: The gold-containing solution is mixed with the composite reducing solution and then subjected to a reduction reaction at 30℃-50℃; or, the gold-containing solution is mixed with the composite reducing solution and then subjected to a reduction reaction for 2h-5h; or, the gold-containing solution is ultrasonically mixed with the composite reducing solution; or, after the reduction reaction, the gold particles are separated by filtration and then washed with anhydrous ethanol and deionized water in a circulating cycle to obtain pure gold particles.