KR20030006792A - Method for recovering high-value metals from waste printed circuit boards - Google Patents

Abstract

PURPOSE: A method for recovering valuable metals from waste printed circuit boards is provided to separately recover the valuable metals and rare metals by physically pretreating and chemically treating the waste printed circuit boards to recycle the waste printed circuit boards. CONSTITUTION: The method for recovering valuable metals from waste printed circuit boards comprises the processes of (i) crushing the waste printed circuit boards; (ii) separating the crushed material into a low specific gravity materials and a high specific gravity materials by wind separation; (iii) separating the high specific gravity materials into conductive materials and nonconductive materials by electrostatic separation; (iv) separating the conductive materials into magnetic materials and non-magnetic materials by magnetic separation; and (v) chemical treating the non-magnetic materials, wherein the chemical treating process comprises the steps of (a) melting and separating Cu, Fe, Zn, Ni and Al from the non-magnetic materials by adding a mixture of sulfuric acid and hydrogen peroxide to the non-magnetic materials so that they are reacted with each other; (b) melting and separating gold and silver by adding insoluble residue of the step (a) to a mixed solvent comprising (NH4)2S2O3, CuSO4 and NH4OH in mole ratios of 0.2, 0.02 and 0.4 respectively so that they are reacted with each other; (c) melting and separating lead from the residue by adding brine to the residue of the step (b) so that they are reacted with each other; and (d) reacting the residue of the step (c) with aqua regia, thereby melting and separating palladium from the residue.

Description

Recovery of valuable metals from waste printed circuit boards {METHOD FOR RECOVERING HIGH-VALUE METALS FROM WASTE PRINTED CIRCUIT BOARDS}

The present invention relates to a method for recovering metals from discarded printed circuit boards (PCBs). More specifically, the present invention relates to a method for separating and recovering valuable metals and rare metals by physical pretreatment and chemical treatment in order to recycle waste printed circuit boards.

In general, printed circuit board assemblies have a complex structure, which is a significant problem of recycling. In the case of printed circuit board assemblies, valuable metals and contaminants are very close to each other, so use or processing must be carried out separately. Metals such as copper, iron, tin and lead are attracting attention as valuable metals found in printed circuit board assemblies. In addition, precious metals such as gold, silver and palladium are found in significant amounts, particularly in high quality printed circuit board assemblies.

At home and abroad, research on the recovery of valuable metals, including gold, silver, and copper, from electronic waste has been conducted for a long time, and a factory for commercially recovering them is currently in operation. As a commercial method for recovering valuable metals from electronic waste, a wet method and a dry method are generally used in combination.

The dry method includes a chlorination reaction and a method of dissolving an electronic waste in a plasma, an electric arc furnace, or the like to recover a crude metal, and chemically treating the crude metal to obtain a metal. This dry method has the advantage of being able to handle all types of scrap, which is not limited by physical properties, while causing air pollution and reducing the recovery of valuable metals due to the increase of slag during treatment. In particular, the recovery of non-ferrous metals such as zinc, aluminum, lead and tin is impossible.

A wet method in order to recover the precious metals from electronic waste, cyanide solution leaching method, can be chlorinated Leaching and caustic dissolution method is mainly used, in recent years, has become the treatment by S ₂ O ₃ studies. The wet method has the advantage of generating less environmental pollution and recovering the main components of the scrap separately than the dry method, but it is impossible to process complex scraps, requires pretreatment, and has a large volume of leachate and corrosiveness. It is strong and has the disadvantage of being toxic. Therefore, in recent years, recovery methods by electrochemical methods and biochemical treatments have been studied, but they are not useful economically.

From the above, the present inventors treated the printed circuit board in parallel with physical and chemical methods, and pulverized it to selectively separate metals and nonmetals, and treated the recovered metal-containing material with a solvent, thereby producing oil value from the mixed solution. It has led to the development of environmentally friendly and simplified recycling methods for the extraction of metals and rare metals.

An object of the present invention is to selectively and efficiently recover valuable metals such as gold, silver, copper, and zinc and rare metals such as palladium from waste printed circuit boards, while recovering most of the metals contained therein. The present invention provides a method of recovering metals that can recycle resources by overcoming the environmental pollution problem caused by the disposal of waste home appliances and minimizing environmental pollution generated during recovery.

1 is a process chart for recovering metal from a waste printed circuit board according to the present invention,

2 is a graph showing the recovery rate of metals (copper, nickel, aluminum, iron, zinc) according to reaction time with sulfuric acid as a leaching solvent in the extraction step of the recovery process according to the present invention;

Figure 3 is a graph showing the recovery rate of the metal (gold, silver, copper, nickel, iron, zinc, lead) according to the concentration of sulfuric acid as a leaching solvent in the extraction step of the recovery process according to the present invention;

4 is a graph showing the recovery rate of gold and silver with reaction time from the mixed solvent ((NH ₃ ) ₂ S ₂ O ₃ , CuSO ₄ and NH ₄ OH) in the extraction step of the recovery process according to the present invention.

In order to achieve the above object, a method for recovering valuable metals from the waste printed circuit board of the present invention

(1) grinding the waste printed circuit board;

(2) separating the pulverized product into a portion having a light specific gravity and a portion having a high specific gravity by wind screening;

(3) separating the heavy portion into a conductor and an insulator by electrostatic screening;

(4) separating the conductor portion into magnetic and nonmagnetic materials by magnetic screening;

(5) chemically treating the nonmagnetic portion,

The chemical treatment step

(a) adding a mixture of sulfuric acid and hydrogen peroxide to the nonmagnetic portion to react, dissolving and separating the copper, iron, zinc, nickel and aluminum components from the nonmagnetic portion;

(b) adding a mixed solvent containing (NH ₄ ) ₂ S ₂ O ₃ , CuSO ₄ and NH ₄ OH to the poorly soluble residue of step (a) to dissolve and separate gold and silver from the residue. ;

(c) reacting the residue of step (b) by adding brine to dissolve and separate lead from the residue;

(d) reacting the residue of step (c) with aqua regia to dissolve and separate the palladium from the residue.

Hereinafter, the present invention will be described in more detail.

A waste printed circuit board that can be used in particular in the present invention is a printed circuit board for computer-embedded that is discarded after being used, and can be used separately from the computer body without considering the shape or characteristics of the substrate. The general composition of the printed circuit board is composed of 30% metal compound, 30% plastic material and 40% poorly soluble compound. The metal compound comprises a general metal (29%) and a noble metal (1%), the general metal is copper (10%), iron (8%), nickel (2%), tin (4%), lead ( 2%), aluminum (2%), zinc (1%) and the like, the precious metals include gold (0.08%), silver (1.7%), palladium (0.005%) and the like. The plastic material can be: ① 25% or more of CHO polymers (e.g., polyester and phenolformaldehyde), ② 5% or less of halogenated polymers (e.g., PVC, tracer PTFE and polybromo compounds), and ③ nitrogen-containing polymers ( Nylon and polyurethane) for example 1% or less. The poorly soluble compounds also include silica (15%), alkali and alkaline earth oxides (6%), alumina (6%), and other oxides (13%).

A schematic recovery process diagram of a metal from a closed printed circuit board according to the method of the present invention is shown in FIG. 1, which is described as follows:

Discarded computer printed circuit boards after use are ground using a grinder, for example a shredder. By passing the pulverized product through a screen capable of controlling the size of the particles, it is preferable to recover a product of about 1 mm or less, and to re-mill the further particles to obtain a uniform pulverized product.

The pulverized product is separated into a light portion and a heavy portion by, for example, a wind screening method, and then the heavy portion is separated into a conductor and a non-conductor by an electrostatic separation method. When separating the conductor and the non-conductor by the electrostatic screening, it is preferable to maintain the intensity of the constant current in the range of 500 to 3,000 W, particularly about 1,500 W. At this time, the recovery rate of the conductor, the non-conductor, and the intermediate conductor as the intermediate product of the conductor and the non-conductor is about 12%, about 72% and about 16%, respectively. The conductor mainly comprises a metal component, and the insulator includes a plastic material.

Subsequently, the conductors and the intermediate conductors except the non-conductors are separated into magnetic bodies and non-magnetic bodies according to the strength of the magnetic force by the magnetic force selection method. At this time, the strength of the magnetic force is preferably changed to 3,000 to 12,000 gauss, particularly about 8,000 gauss. The content of magnetic material and nonmagnetic material separated by magnetic screening is about 42% and about 58%, respectively. When the strength of the magnetic force is 8,000 gauss, the magnetic substance is mostly separated and removed, and the non-magnetic substance mainly containing the valuable metal is put in a continuous valuable material extraction process to recover the valuable metal.

In the valuable metal extraction process, sulfuric acid is used as a starting leach solvent and hydrogen peroxide water is used as an oxidation promoter. The sulfuric acid solvent to which the hydrogen peroxide solution is added can dissolve the copper, iron, zinc and nickel components contained in the waste printed circuit board. The solution in which the metal components are leached in the sulfuric acid solvent is separated and removed for each metal extraction, and the residues which are poorly soluble in the leaching solvent are separated by filtration for use in the subsequent leaching process. In this sulfuric acid leaching process, the reaction temperature is preferably carried out at 75 to 85 ℃, particularly about 85 ℃. The concentration of sulfuric acid used is preferably in the range of 1.0 to 2.0 M, with about 2.0 M being particularly preferred. The amount of hydrogen peroxide added is preferably in the range of 0.1 to 0.2 M, particularly preferably about 0.2 M. Leaching reactions of copper, iron, zinc and nickel metals with sulfuric acid are represented by the following schemes 1, 2, 3 and 4, respectively:

Cu + H ₂ SO ₄ + H ₂ O ₂ ↔ CuSO ₄ + 2H ₂ O

Zn + H ₂ SO ₄ + H ₂ O ₂ ↔ ZnSO ₄ + 2H ₂ O

Fe + H ₂ SO ₄ + H ₂ O ₂ ↔ FeSO ₄ + 2H ₂ O

Ni + H ₂ SO ₄ + H ₂ O ₂ ↔ NiSO ₄ + 2H ₂ O

Cu metal is recovered from the sulfuric acid leaching solution produced by the reaction schemes 1 to 4 by electrolysis, and ZnSO _4, FeSO ₄ and NiSO ₄ are recovered from the precipitation method (T. Tran, Hydrometallurgy -Theory & Practice, Chem. Eng). & Ind. Chem. , UNSW, 2000)

Subsequently, gold and silver are selectively extracted from the poorly soluble residue of the sulfuric acid leaching process, wherein (NH ₃ ) ₂ S ₂ O ₃ , CuSO ₄ and NH ₃ OH are used as molar ratios of 0.2, 0.02 and 0.4, respectively. Configured mixed solvents are used. The leaching reactions of gold and silver using mixed solvents are shown in Schemes 5 and 6, respectively:

Au + 5S ₂ O ₃ ^2- + Cu (NH ₃ ) ₄ ²⁺ → Au (S ₂ O ₃ ) ₂ ^3- + Cu (S ₂ O ₃ ) ₃ ^5- + 4NH ₃

Ag + 5S ₂ O ₃ ^2- + Cu (NH ₃ ) ₄ ²⁺ → Ag (S ₂ O ₃ ) ₂ ^3- + Cu (S ₂ O ₃ ) ₃ ^5- + 4NH ₃

Au and Ag metals from the resulting leaching solution are recovered by known cementation (T. Tran, Hydrometallurgy-Theory & Practice, Chem. Eng. & Ind. Chem. , UNSW, 2000).

Subsequently, the residue was reacted with brine such as a NaCl solution to selectively separate Pb and Sn from the leach residue remaining without leaching into the mixed solvent [(NH ₄ ) ₂ S ₂ O ₃ + CuSO ₄ + NH ₄ OH]. Let's do it. The leaching reaction of Pb with NaCl solution is represented by the following scheme 7:

PbSO ₄ + 2NaCl ↔ PbCl ₂ + Na ₂ SO ₄

The Pb metal is recovered from the produced leaching solution by the usual precipitation method, respectively.

In order to separate the palladium from the final residue remaining in the brine leaching process, aqua regia (HCl: HNO ₃ = 3: 1) is used as the leaching solvent. The leaching reaction of palladium and aqua regia is shown in Scheme 8 below:

Pd + 8HCl + 2HNO ₃ → H ₂ PdCl ₆ + 4H ₂ O + 2NOCl

Recovery of the palladium metal from the extraction solution generated in Scheme 8 is carried out by precipitation after obtaining the concentrate by solvent extraction (T. Tran, Hydrometallurgy-Theory & Practice, Chem. Eng. & Ind. Chem. , UNSW) . , 2000).

According to the metal recovery method of the present invention as described above, 95% or more of metals including valuable metals and rare metals can be recovered from a waste printed circuit board as a starting material. In addition, by first separating the metal part and the nonmetal part from the starting material, not only the metal but also the non-metal part plastic can be recovered, and particularly, expensive gold and silver can be recovered with a high purity of almost 100%. Since S ₂ O ₃ is used as the solvent, the method of the present invention is environmentally friendly, simple and economical.

The invention can be better understood by the following examples, which are intended for the purpose of illustration of the invention and are not intended to limit the scope of protection defined by the appended claims. As used herein,% is by weight unless otherwise indicated.

In addition, in the embodiment of the present invention, the component analysis of the sample used AAS (Atomic Adsorption Spectrometer-Spectra 220, Varian, Australia) and ICP (Inductively Coupled Plasma-Atomic Emission Spectrometer-JY 38Plus, Jobin Yvon, France).

Example

Example 1 Separation of Lightweight Part from Heavy Part by Windscreen

The waste printed circuit board was introduced into a shredder (Sambo Precision Industries), which was pulverized to a particle size of 1 mm or less, and put into a wind separator at a speed of 100 Kg / hr to separate plastics with light gravity and heavy metals. . Table 1 shows the content of metals classified in each cyclone.

Stage 1 2 steps 3 steps % Of metal 84.4 25.3 4.1

Example 2 Separation of Conductor and Non-Conductor by Electrostatic Screening

A sample containing a metal component separated by wind screening was put into an electrostatic separator (Dings Magnetic group Co.) to conduct an experiment to separate the conductor and the insulator. As the experimental condition of the electrostatic screening, 300 g of the sample was treated per hour with the strength of the current of 500 to 3,000 W, and the results are shown in Table 2.

Constant current intensity (W) 500 1000 1500 2000 3000 Conductor (wt%) 5.66 9.45 12.00 13.35 13.68 Intermediate (wt%) 13.82 13.50 16.23 15.15 15.00 Insulator (% by weight) 80.52 77.05 72.77 71.50 71.32

From Table 2, it can be seen that the separation efficiency is the highest when the intensity of the constant current is 1,500 W.

Example 3 Separation of Magnetic and Nonmagnetic Materials by Magnetic Separation

Among the parts separated in Example 2, except for the non-conductor mainly containing the plastic material, the conductor and the intermediate conductor were put into the following magnetic separator (Dings Magnetic Group Company) apparatus, and the magnetic and nonmagnetic materials were separated by magnetic separation. The experiment was performed to separate. At this time, a dry magnetic separator was used for magnetic separation, and 1,000 g of sample was processed per hour while changing the strength of the magnetic force to 3,000 to 12,000 gauss. The results are shown in Table 3.

Gauss 3000 6000 8000 12000 Magnetic material (% by weight) 28.35 36.50 41.61 42.05 Nonmagnetic material (% by weight) 71.65 63.0 58.39 57.95

From Table 3, it can be seen that the magnetic material and the nonmagnetic material are mostly separated when the magnetic force is 8,000 Gauss. Table 4 shows the results of component analysis of the separated and recovered nonmagnetic material at 8,000 gauss.

Au Ag Pd Cu Ni Fe Zn Pb Al Sn content mg / g 0.227 1.097 0.099 589.0 0.915 4.29 2.1 15.1 25.1 1.56 % 0.0227 0.1097 0.0099 58.9 0.00915 0.429 0.21 1.51 2.51 0.156

From Table 4, it can be seen that the gold and silver contents are 0.227 mg / g and 1.097 mg / g, respectively, indicating high separation efficiency. The nonmagnetic material recovered from the magnetic screening was used as a sample in the next valuables extraction process.

Example 4 Extraction of Valuable Metals Using Sulfuric Acid

The nonmagnetic material obtained in Example 3 was used as a sample for valuable metal extraction, and sulfuric acid to which hydrogen peroxide solution, an oxidation promoter was added, was added as a starting leach solvent. The leaching process using the sulfuric acid solvent is to dissolve the Cu, Fe, Zn and Ni components that are easily leached among the components contained in the printed circuit board. The leached solution was separated and removed for each metal extraction, and the residue which was poorly soluble in the leaching solvent was filtered and used in the subsequent leaching process. In leaching sulfuric acid, the leaching conditions were carried out at 65, 75 and 85 ° C., respectively, and the concentration of sulfuric acid was changed in the range of 1.0 to 2.0 M, and the amount of hydrogen peroxide added was in the range of 0.025 to 0.2 M. The amount of the sample used was 5 g / l, and the stirring speed was fixed at 350 rpm.

In the sulfuric acid leaching reaction, leaching was carried out at a reaction temperature of 85 ° C. at a concentration of 2.0 M sulfuric acid and 0.2 M hydrogen peroxide. Cu and Zn leached 100% within 8 hours, while Fe, Ni and Al leached over 90% after 24 hours reaction. 2 shows the recovery of the metal according to the reaction time at the reaction temperature of 85 ℃ using sulfuric acid, Figure 3 shows the recovery of each metal by sulfuric acid concentration.

Example 5 Selective Separation of Gold and Silver Using Mixed Solvents

To selectively extract gold and silver from poorly soluble residues after sulfuric acid leaching, mixed solvents (NH ₄ ) ₂ S ₂ O ₃ + CuSO ₄ + NH ₄ OH were used as concentrations of 0.2 M, 0.02 M, and 0.4 M, respectively. . The reaction was carried out at a reaction temperature of 40 ° C. using a sample having a concentration of 5 g / l. Silver leached 100% within 24 hours and gold leached 100% after 48 hours. Dissolution rates of gold and silver according to the reaction time are shown in FIG. 4.

Example 6: Selective Separation of Lead by NaCl Solution

NaCl solution was used to selectively separate Pb from the leaching residue produced in Example 5. As the leaching conditions, the concentration of NaCl was changed in the range of 0.5 to 1 M, and the sample was used at a concentration of 10 g / l, and the experiment was conducted under a stirring condition of 300 rpm at room temperature. When the leaching residue was reacted with 1 M NaCl solution for 2 hours, the precipitate of PbCl ₂ could be separated and extracted 98%.

Example 7 Selective Extraction of Palladium by Aqua Solution

To the final residue resulting from Example 6 was added aqua regia as a leaching solvent. The aqua regia was prepared in the ratio of HCl: HNO ₃ = 3: 1. After reacting at room temperature for 60 minutes using a concentration of 10 g / l of sample, palladium was completely leached into the solution. These metals were able to recover 95% or more by the substitution method.

The metal recovery method of the present invention can recover valuable resources including valuable metals from the waste printed circuit board with high efficiency by using physical and chemical methods, and pre-separates metal and non-metal parts using physical methods. In addition, plastics can be recovered, valuable metals such as gold and silver can be recovered with high purity, and palladium, a rare metal, can be separated, and in particular, S ₂ O ₃ is contained as a solvent in the recovery of gold and silver. By using a solvent, it has an environmentally friendly and economic effect.

Simple modifications or changes of the present invention can be easily carried out by those skilled in the art, and all such modifications or changes can be seen to be included in the scope of the present invention.

Claims (3)

(1) grinding the waste printed circuit board; (2) separating the pulverized product into a portion having a light specific gravity and a portion having a high specific gravity by wind screening; (3) separating the heavy portion into a conductor and an insulator by electrostatic screening; (4) separating the conductor portion into magnetic and nonmagnetic materials by magnetic screening; (5) chemically treating the nonmagnetic portion, The chemical treatment step (a) adding a mixture of sulfuric acid and hydrogen peroxide to the nonmagnetic portion to react, dissolving and separating the copper, iron, zinc, nickel and aluminum components from the nonmagnetic portion; (b) reacting the poorly soluble residue of step (a) by adding (NH ₄ ) ₂ S ₂ O ₃ , CuSO ₄ and NH ₄ OH to a mixed solvent having a molar ratio of 0.2, 0.02 and 0.4, respectively, And dissolving silver; (c) reacting the residue of step (b) by adding brine to dissolve and separate lead from the residue; (d) reacting the residue of step (c) with aqua regia to dissolve and separate the palladium from the residue, A method for recovering valuable metals from waste printed circuit boards. The method of claim 1, Wherein copper is recovered by electrolysis, zinc by precipitation, gold, silver and palladium by cementation, and lead by solvent extraction. The method of claim 1, In the sulfuric acid leaching step (a), the concentration of sulfuric acid is 1.0 to 2.0 M, the hydrogen peroxide content is 0.1 to 0.2 M, the reaction time is 20 to 24 hours, and the reaction temperature is performed at 80 to 85 ° C. How to feature.