Method for recovering copper from circuit board for preparing copper rod

Abstract

The invention relates to the field of copper recovery, and discloses a method for recovering copper from a circuit board for preparing a copper rod, which comprises the following steps: physical separation; performing enzymolysis on organic matters; iron and zinc are removed through acid leaching; aluminum is removed through alkaline leaching; tin and lead are jointly removed; deep purification; the invention provides a physical separation, enzymolysis and chemical leaching deep purification forming purification method, which comprises the steps of physical separation, enzymolysis removal of organic impurities, acid-base chemical treatment, enzymatic reaction, extraction technology, electrolytic treatment and the like, and gradually removes the impurities in the circuit board. And finally, high-purity copper elementary substance is provided for manufacturing of the copper rod.

Description

Technical Field

[0001] This invention relates to the field of copper recycling, and in particular to a method for recovering copper from circuit boards for the preparation of copper rods. Background Technology

[0002] Circuit boards (PCBs) are among the most copper-rich components in electronic waste, accounting for 15% to 20% of their total mass. For example, 1 ton of waste PCBs can yield 150 to 200 kilograms of copper. PCBs are a composite of metals and non-metals, containing not only copper but also resins, glass fibers, lead, tin, gold, silver, palladium, and other substances, making separation and purification challenging. For instance, in the pretreatment stage, the multi-layered structure of the PCB, with its tightly bonded copper foil, resin, and glass fibers, makes mechanical crushing prone to encapsulating the copper foil with non-metallic powder, hindering complete separation by physical methods such as magnetic and electrostatic separation. In the chemical treatment stage, while acid leaching can dissolve copper, it also dissolves lead, tin, and other metals, resulting in an excessive amount of impurities in the copper solution.

[0003] It is evident that existing technologies still need improvement and enhancement. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the purpose of this invention is to provide a method for recovering copper from circuit boards for the preparation of copper rods, aiming to solve the problems of low copper recovery rate and insufficient purity.

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

[0006] A method for recovering copper from circuit boards for the manufacture of copper rods includes the following steps:

[0007] S1. Physical separation: The circuit board is crushed and separated to separate resin, glass fiber, copper, and other metal particles; magnetic separation is used to adsorb magnetic metals from copper and other metal particles; light metals are then separated by sorting, and the remaining material consists of copper particles, organic matter, tin, and lead.

[0008] S2. Enzymatic hydrolysis of organic matter: Add enzymes to the remaining material to hydrolyze the organic matter and obtain copper particles;

[0009] S3. Acid leaching to remove iron and zinc: Add acid solution to copper particles, stir to dissolve iron and zinc, and filter to obtain filter residue;

[0010] S4. Alkaline leaching to remove aluminum: Add an alkaline solution to the filter residue, stir to dissolve the aluminum, and then filter to obtain the filter residue;

[0011] S5. Combined removal of tin and lead: First, add tin ion reductase to the filter residue, then add acid solution to remove tin, then add lead chelate enzyme to remove lead, and after filtration, crude copper particles are obtained.

[0012] S6. Deep purification: Dissolve crude copper particles in sulfuric acid and hydrogen peroxide to obtain copper sulfate solution; extract with an extractant to obtain pure copper sulfate solution; add enzyme to copper sulfate solution to enzymatically dissolve residual flux grease and protein binder; use electrolytic refining to produce electrolytic copper at the cathode;

[0013] S7. Preparation of copper rods: Electrolytic copper is smelted and then continuously drawn into copper rods.

[0014] The method for recovering copper from circuit boards for preparing copper rods includes the following steps: in step 1, the circuit board is crushed into 5-10 mm pieces, then ball-milled into 0.5-2 mm pieces, sieved to 1-2 mm particles, and air-separated to separate the light components of resin and glass fiber from the heavy components of copper and other metal particles.

[0015] The method for recovering copper from circuit boards for preparing copper rods includes step 1, in which the magnetic metals are iron, nickel, and cobalt; and the light metals aluminum and zinc are separated by an eddy current separator.

[0016] The method for recovering copper from circuit boards for preparing copper rods includes the following steps: In step 2, the organic matter includes epoxy resin in the solder resist layer and phenolic resin in the ink layer; enzymatic hydrolysis is performed using an enzymatic hydrolysate containing 2-4% epoxy resin depolymerase, 1-3% laccase, and 0.5-1% octyl glucoside dissolved in phosphate; the hydrolysis temperature is 40-50°C, and the mixture is stirred for 30-60 minutes.

[0017] The method for recovering copper from circuit boards for preparing copper rods, wherein in step 3, the acid solution is one or both of dilute hydrochloric acid and dilute sulfuric acid with a concentration of 3-5%; the stirring conditions are: stirring at room temperature for 30-40 minutes.

[0018] The method for recovering copper from circuit boards for preparing copper rods, wherein in step 4, the alkaline solution is one or both of sodium hydroxide and potassium hydroxide with a concentration of 10-15%; the stirring conditions are: stirring at 70-90°C for 30-40 minutes.

[0019] The method for recovering copper from circuit boards for preparing copper rods includes the following steps: Step 5, which involves the combined removal of tin and lead, is as follows: 0.5-1% tin ion reductase is added to the filter residue and reacted at 30-40°C for 10-20 minutes; then 3-5% dilute sulfuric acid solution is added to remove tin; then 1-2% lead chelating enzyme is added to remove lead, and crude copper particles are obtained after filtration.

[0020] The method for recovering copper from circuit boards for preparing copper rods includes the following steps: in step 6, the concentration of sulfuric acid is 3-5% and the concentration of hydrogen peroxide is 3-5%; extraction is performed under pH 2-3 conditions to separate copper ions from nickel and cobalt ions, resulting in a pure copper sulfate solution.

[0021] The method for recovering copper from circuit boards for preparing copper rods includes step 6, in which 1-2% salt-tolerant lipase and 0.5-1.5% alkaline protease are added to a copper sulfate solution, and the reaction is carried out at a temperature of 30-40°C for 20-30 minutes.

[0022] The method for recovering copper from circuit boards for preparing copper rods includes step 7, which involves preparing copper rods by: electrolyzing copper in a vacuum induction furnace with a vacuum degree ≤1Pa and a temperature of 1150~1200℃ and introducing argon gas for protection, and melting it into copper liquid; the copper liquid flows into a water-cooled crystallizer and is continuously drawn into copper rods.

[0023] Beneficial effects:

[0024] This invention provides a method for recovering copper from circuit boards for preparing copper rods, which has the following advantages: First, high purity; through multi-stage impurity removal and deep purification, the final copper rod purity can reach over 99.95%, meeting the needs of high-end applications. Second, excellent environmental friendliness; the introduction of bio-enzymes reduces the amount of strong acids and alkalis used, reducing wastewater pollution, and the recovery of precious metals maximizes resource utilization. Third, a balance between efficiency and economy; physical separation combined with enzymatic hydrolysis and chemical methods shortens the processing cycle, while reagent recycling and by-product recovery reduce overall costs. Fourth, stable and reliable process; each step is precisely designed for the characteristics of circuit board impurities, with an impurity removal rate consistently above 99%, suitable for large-scale production, providing an efficient and green technical path for the resource recovery of waste copper from circuit boards. Detailed Implementation

[0025] This invention provides a method for recovering copper from circuit boards for the preparation of copper rods. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the following embodiments are provided for further detailed explanation. It should be understood that the specific embodiments described herein are only for explaining this invention and are not intended to limit the scope of protection of this invention.

[0026] This invention provides a method for recovering copper from circuit boards for the preparation of copper rods, comprising the following steps:

[0027] S1. Physical separation:

[0028] The circuit board is first crushed into 5-10mm pieces by jaw crusher, then further ground into 0.5-2mm pieces by ball milling. A vibrating screen is used to screen particles of 1-2mm, and air separation is employed to separate the light components (resin and glass fiber) from the heavy components (copper and other metal particles). The circuit board is a composite structure of copper foil, resin, glass fiber, and metal solder joints, with each component tightly bound by adhesives. The crushing and shearing action of the moving and fixed jaws breaks the entire circuit board into 5-10mm block particles. This stage primarily disrupts the macroscopic structure of the circuit board, initially separating the copper foil from the substrate composed of resin and glass fiber. However, some copper foil remains adhered to the substrate due to the adhesive. The crushed particles then enter a ball mill, where the impact and grinding action of steel balls further refines them to 0.5-2mm. The brittle resin and glass fiber are easily pulverized into fine particles during grinding, while copper, due to its high toughness, is mostly retained in flake or granular form, and its bonding with non-metallic materials is completely destroyed, creating conditions for subsequent separation. A vibrating screen (with 1mm and 2mm mesh sizes) was used to classify the finely crushed material, screening out particles of 1-2mm. Among these 1-2mm particles, copper showed the highest separation degree from non-metals, with copper particles concentrated in this size range. By controlling the airflow velocity, the density difference of the material was utilized to separate non-metallic impurities from metallic particles.

[0029] Magnetic separation is used to adsorb magnetic metals such as iron, nickel, and cobalt from copper and other metal particles. The magnetic separator generates a strong magnetic field using electromagnets, utilizing the differences in magnetic properties to achieve separation. Metals such as iron, nickel, and cobalt are ferromagnetic and are magnetized in the magnetic field, attracting them to the magnetic material collection area along with the magnetic rollers. Copper, aluminum, zinc, tin, lead, and organic matter are non-magnetic or weakly magnetic and are unaffected by the magnetic force, falling to the non-magnetic material area under the influence of gravity, thus achieving the separation of magnetic metals from other components.

[0030] The material is then separated into light metals such as aluminum and zinc using an eddy current separator. The remaining material consists of copper particles, organic matter, tin, and lead. The eddy current separator uses a high-frequency alternating magnetic field. Non-ferrous metals like aluminum and zinc are good conductors; when they enter the alternating magnetic field, eddy currents are induced. The magnetic field generated by these eddy currents repels the original magnetic field, causing the aluminum and zinc particles to receive lateral thrust, deviating from their falling trajectory and entering the light metal collection area. Copper, tin, lead, and organic matter experience weak or no repulsive force from the eddy currents and fall along the direction of gravity to the remaining material area. Ultimately, copper particles, tin, lead, and a small amount of organic matter remain.

[0031] S2. Enzymatic hydrolysis of organic matter: The organic matter in the remaining material includes epoxy resin in the solder resist layer and phenolic resin in the ink layer. Add 2-4% epoxy resin depolymerizing enzyme, 1-3% laccase, and 0.5-1% octyl glucoside to the remaining material, dissolved in a phosphoric acid hydrolysate solution for enzymatic hydrolysis. The hydrolysis temperature is 40-50℃, and the mixture is stirred for 30-60 minutes to hydrolyze the organic matter, yielding copper particles. Epoxy resin depolymerizing enzyme, as a specific biocatalyst, can recognize the ether bond structure of epoxy resin and catalyze its breakage, depolymerizing the poorly soluble epoxy resin in the solder resist layer into small organic molecules, allowing them to detach from the copper surface and dissolve in the hydrolysate. Specifically, epoxy resin depolymerizing enzymes can be derived from Pseudomonas and Actinomycetes. Laccase catalyzes the degradation of phenolic resin through a redox reaction, destroying its aromatic ring structure and converting large phenolic resin molecules into soluble oxidation products, removing ink residues adhering to the surface of the copper particles. Specifically, laccase mainly originates from white-rot fungi. Octyl glucoside is a surfactant that reduces the surface tension of the enzymatic hydrolysate, enhances the contact efficiency between the enzyme and organic impurities, and helps dissolve the degraded small organic molecules, preventing them from re-adsorbing onto the copper particle surface. A phosphate buffer system is used to maintain a stable pH in the hydrolysate, typically slightly acidic, providing a suitable catalytic environment for both enzymes, ensuring their activity, and improving degradation efficiency.

[0032] S3. Acid leaching to remove iron and zinc: Add an acid solution (one or both of dilute hydrochloric acid and dilute sulfuric acid with a concentration of 3-5%) to the copper particles and stir at room temperature for 30-40 minutes to dissolve the iron and zinc. After filtration, the residue is obtained. Iron and zinc are active metals and can undergo a displacement reaction with dilute hydrochloric acid or dilute sulfuric acid to produce soluble salts and hydrogen gas, thus dissolving in the acid solution. Copper, however, has moderate metallic activity and does not react with dilute hydrochloric acid or dilute sulfuric acid, remaining as solid particles. Stirring at room temperature promotes the complete reaction. After filtration, iron and zinc enter the filtrate as soluble salts, and the residue is the copper particles after iron and zinc removal. However, the copper particles still contain residual tin, lead, etc.

[0033] S4. Alkali leaching for aluminum removal: Add an alkaline solution (10-15% sodium hydroxide or potassium hydroxide, or one or both) to the filter residue. Stir at 70-90°C for 30-40 minutes to dissolve the aluminum. Filter to obtain the filter residue. Aluminum reacts with both acids and the aforementioned strong alkalis under heating conditions to form soluble aluminates and water. The copper, tin, lead, and other metals in the filter residue do not react with the strong alkalis and remain in solid form. Heating and stirring accelerate the reaction, ensuring complete dissolution of the aluminum. After filtration, the aluminum enters the filtrate as aluminates, while the filter residue consists of mixed particles of copper, tin, lead, etc., after aluminum removal.

[0034] S5. Combined removal of tin and lead: Add 0.5-1% tin ion reductase to the filter residue and react at 30-40℃ for 10-20 minutes. Tin often forms a dense alloy phase with copper. Tin ion reductase can specifically recognize and catalyze the reduction of tin ions to loose elemental tin, destroying the alloy phase structure and causing tin to detach from the copper surface into easily soluble particles. The above temperature is the optimal temperature range for the enzyme, and structural dissociation is completed in 10-20 minutes. Specifically, tin ion reductase can be derived from Pseudomonas aeruginosa or Escherichia coli genetically engineered strains. Then, add a 3-5% dilute sulfuric acid solution to remove tin. After enzyme pretreatment, the loose elemental tin readily reacts with the 3-5% dilute sulfuric acid to generate soluble tin sulfate, which enters the solution, achieving the separation of tin and copper. Finally, add a 1-2% lead chelate enzyme to remove lead, and after filtration, crude copper particles are obtained. Lead often remains in elemental or compound form. The active site of lead chelating enzymes can specifically bind lead ions to form a stable, water-soluble enzyme-lead complex, which can then be completely removed from copper particles through filtration. Lead chelating enzymes can be derived from Saccharomyces cerevisiae and Pseudomonas putida.

[0035] S6. Deep purification:

[0036] Crude copper particles are dissolved in a 3-5% sulfuric acid solution and a 3-5% hydrogen peroxide solution to form a copper sulfate solution. Under acidic conditions, the elemental copper in the crude copper undergoes an oxidation-dissolution reaction with hydrogen peroxide as the oxidant, producing copper sulfate and water. The reaction can proceed efficiently at room temperature or under slight heating conditions, and the copper in the crude copper is almost completely dissolved. Some insoluble impurities, such as precious metals like gold and silver, do not participate in the reaction and can be initially separated by filtration.

[0037] Extraction is performed using an extractant at pH 2–3 to separate copper ions from nickel and cobalt ions, yielding a pure copper sulfate solution. Hydroxyoxime extractants such as the LIX series and N902 can be used; their molecular structure contains hydroxyl and oxime groups that can form stable chelates with metal ions. However, their binding ability for copper ions is much stronger than that for nickel and cobalt ions, especially at pH 2–3, where the selectivity difference is significantly more pronounced. Under acidic conditions at pH 2–3, the chelation reaction between copper ions and the extractant proceeds more readily, and the resulting chelate is soluble in the organic phase; while nickel and cobalt ions have extremely weak binding ability with the extractant within this pH range and remain in the aqueous phase in ionic form.

[0038] Adding 1-2% salt-tolerant lipase and 0.5-1.5% alkaline protease to a copper sulfate solution and reacting at 30-40°C for 20-30 minutes enzymatically hydrolyzes residual flux grease and protein adhesives. Flux contains greases such as mineral oil and synthetic esters, which are ester compounds. Salt-tolerant lipase can specifically catalyze the cleavage of ester bonds in grease molecules at 30-40°C, hydrolyzing them into water-soluble glycerol and fatty acids. Because the reaction system is a copper sulfate solution containing a certain amount of salt, the salt-tolerant lipase can maintain its activity in the salt environment, ensuring efficient degradation of the grease. Specifically, salt-tolerant lipase can be derived from *Halobacterium* or *Halobacter* species. Residual animal glue, protein glue, and other protein adhesives are composed of amino acids linked by peptide bonds. Alkaline protease can specifically cleave these peptide bonds in a weakly alkaline to neutral environment, decomposing them into small peptide fragments or amino acids. These products are water-soluble, avoiding interference with subsequent copper purification. Specifically, alkaline protease is produced by Bacillus fermentation. A temperature of 30–40°C ensures stable activity of both enzymes while accelerating the dissolution and degradation of fats and proteins; a reaction time of 20–30 minutes ensures complete enzymatic hydrolysis of impurities. Ultimately, the fat and protein binders are converted into water-soluble small molecules, which can be removed through subsequent filtration or precipitation steps, further purifying the copper sulfate solution.

[0039] Electrolytic refining is employed, with a pure copper sheet as the cathode, serving as the substrate for copper deposition and ensuring the purity of the deposited copper. The anode is crude copper residue, which consists of copper-containing solid impurities enriched after pretreatment throughout the purification process, primarily originating from crude copper particles. If the crude copper particles are not completely dissolved during the dissolution process into copper sulfate solution using sulfuric acid and hydrogen peroxide, the remaining small amount of insoluble matter containing copper and more difficult-to-dissolve precious metal impurities also constitutes crude copper residue. The role of crude copper residue is to provide the copper source and impurities to be purified. The electrolyte is a purified copper sulfate solution.

[0040] Specifically, the electrolysis conditions are a temperature of 50–60°C, which reduces electrolyte viscosity, increases copper ion migration rate, reduces concentration polarization, and results in more uniform copper deposition; and a current density of 250 A / m. 2This density controls the copper deposition rate, preventing excessive current from causing impurity co-deposition or a rough cathode surface. The cell voltage is 0.25V. Electrolysis lasts 48 hours to ensure complete dissolution of the crude copper residue at the anode and sufficient high-purity copper deposition at the cathode. During electrolysis, the cathode produces high-purity electrolytic copper, and the anode sludge contains gold, silver, and selenium, which can be used for subsequent recovery. Elemental copper in the crude copper residue is oxidized to copper ions and enters the electrolyte. Simultaneously, impurities more reactive than copper, such as iron and zinc, will preferentially oxidize to ions if any remain in the crude copper residue; while impurities less reactive than copper, such as gold, silver, and selenium, do not oxidize and detach from the anode, forming anode sludge deposited at the bottom of the cell. Copper ions in the electrolyte are reduced to elemental copper and deposited on the surface of pure copper sheets. Because the reduction potential of copper ions is higher than that of other residual metal ions such as iron and zinc ions, only copper ions will preferentially deposit at the cathode, ensuring product purity.

[0041] S7. Preparation of copper rods: Electrolytic copper is melted into copper liquid in a vacuum induction furnace with a vacuum degree ≤1Pa and a temperature of 1150~1200℃ under argon protection. This effectively removes trace gases such as oxygen, hydrogen, and nitrogen remaining in the electrolytic copper, avoiding defects such as porosity and looseness inside the copper rod. The copper liquid flows into a water-cooled crystallizer for rapid cooling and solidification. It is then continuously drawn into copper rods by a traction device to ensure purity and mechanical properties.

[0042] This invention relates to the preparation of copper rods from recycled copper from circuit boards. It provides a purification method involving physical separation, enzymatic hydrolysis, chemical leaching, and deep purification. The method primarily utilizes physical methods such as crushing, sieving, air separation, magnetic separation, and eddy current separation, leveraging differences in particle size, density, magnetic properties, and conductivity to achieve initial separation of non-metallic impurities from metallic particles. A composite system of epoxy resin depolymerase, laccase, and octyl glucoside is employed to directionally degrade the epoxy resin in the solder resist layer and the phenolic resin in the ink under mild conditions, efficiently removing organic impurities. A combination of acid leaching, alkaline leaching, and enzymatic reactions is used to specifically remove metallic impurities such as iron, zinc, aluminum, tin, and lead. The combined process of tin ion reductase pretreatment with dilute sulfuric acid and lead chelate specific chelation significantly reduces copper matrix loss. Copper ions are separated from trace impurities such as nickel and cobalt through solvent extraction, followed by electrolytic refining to obtain high-purity electrolytic copper, while simultaneously recovering precious metals such as gold, silver, and selenium from the anode mud. Finally, copper rods are produced using vacuum induction melting and continuous casting processes, ensuring product purity and performance.

[0043] Example 1

[0044] A method for recovering copper from circuit boards for the manufacture of copper rods includes the following steps:

[0045] S1. Physical Separation: The circuit board is jaw-crushed to 5-10mm, then ball-milled to 0.5-2mm. A vibrating screen is used to screen particles to 1-2mm. Air separation is used to separate the light components of resin and glass fiber from the heavy components of copper and other metal particles. Magnetic separation is used to adsorb magnetic metals such as iron, nickel, and cobalt from the copper and other metal particles. A light metal such as aluminum and zinc is then separated using an eddy current separator. The remaining material consists of copper particles, organic matter, tin, and lead.

[0046] S2. Enzymatic hydrolysis of organic matter: Add 4% epoxy resin depolymerase, 1% laccase, and 1% octyl glucoside to the remaining material, dissolve them in phosphate hydrolysate, and carry out enzymatic hydrolysis at 40℃ for 60 minutes to obtain copper particles.

[0047] S3. Acid leaching to remove iron and zinc: Add an acid solution (5% dilute hydrochloric acid) to the copper particles, stir at room temperature for 30 minutes to dissolve the iron and zinc, and then filter to obtain the filter residue.

[0048] S4. Alkali leaching to remove aluminum: Add an alkaline solution (10% sodium hydroxide) to the filter residue, stir at 90°C for 35 minutes to dissolve the aluminum, and then filter to obtain the filter residue.

[0049] S5. Combined removal of tin and lead: Add 0.7% tin ion reductase to the filter residue and react at 30℃ for 20 minutes. Then add 3% dilute sulfuric acid solution to remove tin. Next, add 2% lead chelate enzyme to remove lead. After filtration, crude copper particles are obtained.

[0050] S6. Deep Purification: Crude copper particles are dissolved in a 4% sulfuric acid solution and a 5% hydrogen peroxide solution to obtain a copper sulfate solution. Extraction is performed using an extractant at pH 2-3 to separate copper ions from nickel and cobalt ions, yielding a pure copper sulfate solution. A 1% salt-tolerant lipase and a 1.5% alkaline protease are added to the copper sulfate solution, and the reaction is carried out at 35°C for 20 minutes to enzymatically hydrolyze residual flux grease and protein binders. Electrolytic refining is then performed at 60°C and a current density of 250 A / m. 2 The cell voltage is 0.25V; after 48 hours of electrolysis, high-purity electrolytic copper is produced at the cathode.

[0051] S7. Preparation of copper rods: Electrolytic copper is melted into copper liquid in a vacuum induction furnace with a vacuum degree ≤1Pa and a temperature of 1150℃ under argon protection. The copper liquid flows into a water-cooled crystallizer and is continuously drawn into copper rods by a traction device.

[0052] Example 2

[0053] A method for recovering copper from circuit boards for the manufacture of copper rods includes the following steps:

[0054] S1. Physical separation: Same as Example 1.

[0055] S2. Enzymatic hydrolysis of organic matter: Add 2% epoxy resin depolymerase, 3% laccase, and 0.5% octyl glucoside to the remaining material, dissolve them in a phosphoric acid hydrolysate, and carry out enzymatic hydrolysis at 50°C for 30 minutes to obtain copper particles.

[0056] S3. Acid leaching to remove iron and zinc: Add an acid solution (4% dilute sulfuric acid) to the copper particles, stir at room temperature for 40 minutes to dissolve the iron and zinc, and then filter to obtain the filter residue.

[0057] S4. Alkali leaching to remove aluminum: Add an alkaline solution (15% potassium hydroxide) to the filter residue, stir at 70°C for 30 minutes to dissolve the aluminum, and then filter to obtain the filter residue.

[0058] S5. Combined removal of tin and lead: Add 1% tin ion reductase to the filter residue and react at 35℃ for 10 minutes. Then add 5% dilute sulfuric acid solution to remove tin. Next, add 1% lead chelate enzyme to remove lead. After filtration, crude copper particles are obtained.

[0059] S6. Deep Purification: Crude copper particles are dissolved in a 5% sulfuric acid solution and a 3% hydrogen peroxide solution to obtain a copper sulfate solution. Extraction is performed using an extractant at pH 2-3 to separate copper ions from nickel and cobalt ions, yielding a pure copper sulfate solution. A 2% salt-tolerant lipase and a 0.5% alkaline protease solution are added to the copper sulfate solution, and the reaction is carried out at 40°C for 30 minutes to enzymatically hydrolyze residual flux grease and protein binders. Electrolytic refining is then performed at 50°C and a current density of 250 A / m. 2 The cell voltage is 0.25V; after 48 hours of electrolysis, high-purity electrolytic copper is produced at the cathode.

[0060] S7. Preparation of copper rods: Electrolytic copper is melted into copper liquid in a vacuum induction furnace with a vacuum degree ≤1Pa and a temperature of 1200℃ under argon protection. The copper liquid flows into a water-cooled crystallizer and is continuously drawn into copper rods by a traction device.

[0061] Example 3

[0062] A method for recovering copper from circuit boards for the manufacture of copper rods includes the following steps:

[0063] S1. Physical separation: Same as Example 1.

[0064] S2. Enzymatic hydrolysis of organic matter: Add 3% epoxy resin depolymerase, 2% laccase, and 0.7% octyl glucoside to the remaining material, dissolve them in a phosphoric acid hydrolysate, and carry out enzymatic hydrolysis at 45°C for 45 minutes to obtain copper particles.

[0065] S3. Acid leaching to remove iron and zinc: Add an acid solution (5% dilute hydrochloric acid and dilute sulfuric acid mixed in a mass ratio of 1:1) to the copper particles, stir at room temperature for 35 minutes to dissolve the iron and zinc, and then filter to obtain the filter residue.

[0066] S4. Alkali leaching to remove aluminum: Add an alkaline solution (12% sodium hydroxide and potassium hydroxide mixed in a mass ratio of 1:1) to the filter residue, stir at 80°C for 40 minutes to dissolve the aluminum, and then filter to obtain the filter residue.

[0067] S5. Combined removal of tin and lead: Add 0.5% tin ion reductase to the filter residue and react at 40℃ for 15 minutes. Then add 4% dilute sulfuric acid solution to remove tin. Next, add 1.5% lead chelate enzyme to remove lead. After filtration, crude copper particles are obtained.

[0068] S6. Deep Purification: Crude copper particles are dissolved in a 3% sulfuric acid solution and a 4% hydrogen peroxide solution to obtain a copper sulfate solution. Extraction is performed using an extractant at pH 2-3 to separate copper ions from nickel and cobalt ions, yielding a pure copper sulfate solution. A 1.5% salt-tolerant lipase and a 1% alkaline protease solution are added to the copper sulfate solution, and the reaction is carried out at 30°C for 25 minutes to enzymatically dissolve residual flux grease and protein binders. Electrolytic refining is then performed at 55°C and a current density of 250 A / m. 2 The cell voltage is 0.25V; after 48 hours of electrolysis, high-purity electrolytic copper is produced at the cathode.

[0069] S7. Preparation of copper rods: Electrolytic copper is smelted into liquid copper in a vacuum induction furnace with a vacuum degree ≤1Pa and a temperature of 1170℃ under argon protection. The liquid copper flows into a water-cooled crystallizer and is continuously drawn into copper rods by a traction device.

[0070] Performance testing:

[0071] 1. Copper recovery rate (%): Recovery rate = (Target copper amount / Initial copper amount × 100%)

[0072] 2. Key impurity removal rate (%): The content of each impurity (Fe, Zn, Al, Sn, Pb, Ni, Co) before and after treatment was detected by ICP-OES, and the removal rate was calculated as ((initial amount - residual amount) / initial amount × 100%).

[0073] 3. Organic impurity residue rate (%) and wastewater COD: The organic impurity residue rate was calculated using the ignition weight loss method (residual organic matter was ignited at 550℃ to constant weight, and the residue rate was calculated), combined with high performance liquid chromatography (HPLC) to detect soluble small organic molecules. The wastewater COD value was determined according to the potassium dichromate method.

[0074] 4. Performance of copper rods: Compliant with GB / T 4423 "Drawn Copper and Copper Alloy Rods", YS / T 759, and YS / T 648 standards.

[0075] Table 1 Copper Recovery Rate

[0076]

[0077] Table 2 Removal rate of key impurities

[0078] impurities Example 1 Example 2 Example 3 Fe (after acid leaching) 99.1 99.5 99.6 Zn (after acid leaching) 98.9 99.4 99.5 Al (after alkali leaching) 99.4 99.7 99.8 Sn (after joint processing) 99.2 99.5 99.7 Pb (after combined treatment) 99.6 99.8 99.9 Ni, Co (after extraction) 98.8 99.2 99.3

[0079] Table 3 Organic impurity residue rate (%) and wastewater COD

[0080]

[0081] Table 4 Properties of Copper Rods

[0082] project Example 1 Example 2 Example 3 purity(%) 99.95 99.97 99.98 Conductivity (%IACS) 97.8 98.5 98.8 Brinell hardness (HB) 64 66 67

[0083] It is understood that those skilled in the art can make equivalent substitutions or changes to the technical solution and inventive concept of the present invention, and all such changes or substitutions should fall within the protection scope of the present invention.

Claims

1. A method for recovering copper from circuit boards for the preparation of copper rods, characterized in that, Includes the following steps: S1. Physical separation: The circuit board is crushed and separated to separate resin, glass fiber, copper, and other metal particles; magnetic separation is used to adsorb magnetic metals from copper and other metal particles; light metals are then separated by sorting, and the remaining material consists of copper particles, organic matter, tin, and lead. S2. Enzymatic hydrolysis of organic matter: Add enzymes to the remaining material to hydrolyze the organic matter and obtain copper particles; S3. Acid leaching to remove iron and zinc: Add acid solution to copper particles, stir to dissolve iron and zinc, and filter to obtain filter residue; S4. Alkaline leaching to remove aluminum: Add an alkaline solution to the filter residue, stir to dissolve the aluminum, and then filter to obtain the filter residue; S5. Combined removal of tin and lead: First, add tin ion reductase to the filter residue, then add acid solution to remove tin, then add lead chelate enzyme to remove lead, and after filtration, crude copper particles are obtained. S6. Deep purification: Dissolve crude copper particles in sulfuric acid and hydrogen peroxide to obtain copper sulfate solution; extract with an extractant to obtain pure copper sulfate solution; add enzyme to copper sulfate solution to enzymatically dissolve residual flux grease and protein binder; use electrolytic refining to produce electrolytic copper at the cathode; S7. Preparation of copper rods: Electrolytic copper is smelted and then continuously drawn into copper rods.

2. The method for recovering copper from circuit boards for preparing copper rods according to claim 1, characterized in that, In step 1, the circuit board is crushed into 5-10mm pieces and then finely crushed into 0.5-2mm pieces using a ball mill. The 1-2mm particles are then screened, and the light components of resin and glass fiber and the heavy components of copper and other metal particles are separated by air separation.

3. The method for recovering copper from circuit boards for preparing copper rods according to claim 1, characterized in that, In step 1, the magnetic metals are iron, nickel, and cobalt; light metals such as aluminum and zinc are separated by an eddy current separator.

4. The method for recovering copper from circuit boards for preparing copper rods according to claim 1, characterized in that, In step 2, the organic matter includes the epoxy resin in the solder resist layer and the phenolic resin in the ink layer. Enzymatic hydrolysis is carried out using an enzymatic hydrolysate containing 2-4% epoxy resin depolymerase, 1-3% laccase, and 0.5-1% octyl glucoside dissolved in phosphate. The hydrolysis temperature is 40-50℃, and the mixture is stirred for 30-60 minutes.

5. The method for recovering copper from circuit boards for preparing copper rods according to claim 1, characterized in that, In step 3, the acid solution is one or both of dilute hydrochloric acid and dilute sulfuric acid with a concentration of 3-5%; the stirring conditions are: stirring at room temperature for 30-40 minutes.

6. The method for recovering copper from circuit boards for preparing copper rods according to claim 1, characterized in that, In step 4, the alkaline solution is one or both of sodium hydroxide and potassium hydroxide with a concentration of 10-15%; the stirring conditions are: stirring at 70-90℃ for 30-40 minutes.

7. The method for recovering copper from circuit boards for preparing copper rods according to claim 1, characterized in that, The specific operation for the combined removal of tin and lead in step 5 is as follows: add tin ion reductase with a concentration of 0.5-1% to the filter residue and react at a temperature of 30-40℃ for 10-20 minutes; then add dilute sulfuric acid solution with a concentration of 3-5% to remove tin; then add lead chelating enzyme with a concentration of 1-2% to remove lead, and obtain crude copper particles after filtration.

8. The method for recovering copper from circuit boards for preparing copper rods according to claim 1, characterized in that, In step 6, the concentration of sulfuric acid is 3-5% and the concentration of hydrogen peroxide is 3-5%. Extraction is performed under pH 2-3 conditions to separate copper ions from nickel and cobalt ions, resulting in a pure copper sulfate solution.

9. The method for recovering copper from circuit boards for preparing copper rods according to claim 1, characterized in that, In step 6, 1-2% salt-tolerant lipase and 0.5-1.5% alkaline protease are added to the copper sulfate solution, and the reaction is carried out at 30-40°C for 20-30 minutes.

10. The method for recovering copper from circuit boards for preparing copper rods according to claim 1, characterized in that, The specific operation for preparing copper rods in step 7 is as follows: electrolytic copper is smelted into copper liquid by introducing argon gas into a vacuum induction furnace with a vacuum degree ≤1Pa and a temperature of 1150~1200℃; the copper liquid flows into a water-cooled crystallizer and is continuously drawn into copper rods.

Images