KR102185807B1 - In-situ microwave-assisted leaching process with selective separation of gold and copper from waste PCBs - Google Patents

Abstract

The present invention relates to a leaching method in which leaching of precious metals and non-precious metals from a waste printed circuit board and selective separation by a hydrophobic ionic liquid are continuously performed.
Compared with the conventional leaching process, the present invention can improve the leaching speed and efficiency of precious metals and non-precious metals by pulverizing the waste printed circuit board by applying microwaves to the leachate.

Description

In-situ microwave-assisted leaching process with selective separation of gold and copper from waste PCBs, which allows simultaneous leaching and selective separation of gold and copper from waste printed circuit boards.

The present invention relates to a microwave-assisted leaching method, and more particularly, to a leaching process in which leaching and solvent extraction times are reduced by continuously leaching and separating precious metals and non-precious metals from a waste printed circuit board, while increasing efficiency. will be.

As the demand for electronic products increases rapidly, various waste electronic products are discharged as garbage along with industrial wastewater generated during the electronic product manufacturing process. Industrial wastewater and waste electronic products are also the main culprit for polluting the environment, but they contain valuable metals such as gold, silver, and copper, so they are highly recyclable.

To cope with the recent crisis of resource depletion, the problem of recycling resources is a global issue. The discovery of new resources is gradually reaching its limit, and there is a great need to devise fundamental solutions such as the use of alternative materials or waste resources in order to cope with the crisis of resource depletion.

Since Korea relies on imports for 99.3% of natural ore, recycling of metal resources through urban mining is essential. In terms of urban mining, waste PCBs are a valuable resource containing more copper and rare metals than ore.

The hydrosmelting method for recovering gold and copper from such a substrate consists of the steps of crushing/selecting resources-acid leaching-copper recovery-acid leaching-gold recovery. Existing processes require a large amount of leachate and various chemicals in the step of crushing/selecting resources and extracting metals, and as a result, there is a problem that a large amount of waste acid and sludge are generated to extract metals.

Korean Patent Registration No. 10-1749869 discloses an environmentally friendly method of separating platinum group metals using an ionic liquid. The Korean registered patent includes preparing a platinum group-containing aqueous solution by dissolving waste in a first acid solution, and solvent extraction of a platinum group metal by mixing an ionic liquid with the platinum group-containing aqueous solution. Referring to the example of the registered patent, the registered patent takes only 5 hours to extract the solvent, and if the time to prepare an aqueous solution containing a platinum group (leaching step, usually takes 2 to 5 hours or more) is included, leaching and extraction are less than 5 hours. It seems that it will take a much longer time.

The present invention is to provide a method for selective separation and to increase leaching speed and efficiency in leaching precious metals and non-precious metals from a waste printed circuit board.

The present invention

Adding precious metal-containing waste, hydrophobic ionic liquid and leachate to the reactor;

A leaching and selective separation step of leaching noble metals and non-precious metals by applying microwaves to the leachate, and moving the noble metals into the ionic liquid; And

It relates to the recovery of noble and non-precious metals comprising the step of separating leachate and ionic liquid.

In the method of the present invention, the precious metal-containing waste (waste printed circuit board) is physically separated from the ionic liquid in the reactor, but mixed in the leachate, and microwaves are applied to leach the non-precious metal and the precious metal, and the leached precious metal ions are ions. It is transferred to the ionic liquid through solvent extraction at the interface between the soluble liquid and the leachate.

As described above, in the present invention, since solvent extraction (optional separation step) can also be performed during the leaching process in the reactor (a separate solvent extraction process and time are not required), the leaching and solvent extraction time can be significantly reduced. have.

In addition, the present invention can increase the extraction efficiency by 45% or more compared to the same extraction time by powdering waste by applying microwaves to the leachate.

1 and 2 show a reactor.
3 is a comparison of the extraction concentrations of gold and copper in the aquatic layer.
4 is a photograph taken by collecting the pulverized printed circuit board after maintaining the temperature of the leachate at 80° C., 130° C., and 180° C. for 3 hours by adjusting the irradiation time with the microwave in Example 1, and FIG. 5 Is a graph showing the amount of (a) gold and (b) copper per 1 g of a waste printed circuit board according to temperature.
6 is a graph examining changes in the concentration of gold and copper in a two-phase (aqueous phase/ionic liquid phase).
7 is a graph in which acidic thiourea was added to the ionic liquid separated in Example 1 to recover gold as an aqueous phase, and the recovered concentration was measured.

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

The method for leaching and selectively separating noble metals and non-precious metals from the waste printed circuit board of the present invention includes the steps of putting noble metal-containing waste (1), hydrophobic ionic liquid (2) and leachate (3) into the reactor 100, microwave ( 200) is added to the leachate to leach noble metals and non-precious metals, and leaching and selective separation of moving the noble metal to the ionic liquid, and separating the leachate from the ionic liquid.

1 and 2 illustrate a separator. 1 and 2, the reactor 100 includes a separation layer 110 or a separation means 120 therein.

The separating layer or separating means separates the waste from the ionic liquid, but has a hole or a space through which fluid or ions can move.

Referring to FIG. 1, the separation layer 110 is a plate in which a plurality of holes 111 is formed, and may be installed inside the separation layer. The hole 111 is a passage through which ionic liquid or ions move, and may have a diameter of 0.5-1 mm.

Referring to FIG. 2, the separating means may be a plurality of separating objects filled to a predetermined height from the bottom. The separated object may be a bead, packing, or a particulate object having a predetermined volume, which is higher in density than the ionic liquid. The ionic liquid may settle and be filled between the separating objects.

In the above method, the amount of the ionic liquid may be adjusted such that the ionic liquid is positioned under the separating means or the separating layer, and the leachate is positioned above the separating means or the separating layer.

In the above method, the height of the separation means can be adjusted by adjusting the input amount of the separation means or by changing the position (cradle, 112) mounted inside the reactor of the separation layer.

In the above method, the reactor 100, the hydrophobic ionic liquid (2), the noble metal-containing waste (1) and the leachate (3) may be introduced into the reactor 100 simultaneously or sequentially. In this case, the dense ionic liquid precipitates under the leachate and is layered, and the waste is located in a separating layer or in the leachate layer above the separating means.

For example, the precious metal-containing waste 1 may be a PCB board cut into a number of 3×3×1-13×10×2 mm.

The present invention can use a hydrophobic ionic liquid. An ionic liquid refers to a liquid composed of cations and anions, and is generally composed of large cations including nitrogen and smaller anions.

The ionic liquid may be prepared by referring to a known technique (Korean Publication 10-2004-65550), and commercially available ionic liquids (eg, Basionic ST 80, BASF) may be used.

The ionic liquid may contain 5%, preferably 1% or less of water or a nitrogen-containing base. The ionic liquid may be composed of cations and anions containing a single 5- or 6-membered ring that is not fused with other ring structures.

Looking specifically for the ionic liquid, pyridinium, imidazolium, pyrrolidinium, ammonium, phosphonium, pyrazolium, oxazolium, 1,2,3-triazolium or 1,2,4-triazolium and It may be a cation selected from the group of sulfonium and an acetate, halogen, pseudohalogen, or C1-6 carboxylate anion.

More preferably, the ionic liquid is a liquid at room temperature,

1-Methyl-3-octylimidazoliumbis(trifluoromethylsulfonyl)imide)([C8min][Tf2N]), 1-ethyl-3-methylimidazolium, 1-butyl-3-methylimidazolium, 1-hexyl-3-methyl It may be imidazolium or 1-decyl3-methylimidazolium.

As the leachate, an acid solution known to leach metal ions may be used without limitation. For example, the leachate may be hydrochloric acid, nitric acid, or a mixture thereof (aqua regia). As the leachate, aqua regia (aqua regia, hydrochloric acid: nitric acid = 3:1), which is highly corrosive and chemically unstable, can be used. In the above method, the ionic liquid may be added in a range of 2% to 10% relative to the leachate.

The selective separation step is a step in which the leaching step proceeds and the leached noble metal ions are solvent-extracted into the ionic liquid. In the present invention, the leaching step and solvent extraction may be continuously performed in the reactor.

That is, the leaching and selective separation step may include the step of dissolving the noble metal and the non-precious metal of the waste by reacting with the leachate, and the step of moving the noble metal ions into the ionic liquid phase by reacting with the ionic liquid.

The noble metal may be gold, silver or a platinum group element, preferably gold.

The non-precious metal may be copper, zinc, aluminum, or lead, preferably copper.

In the leaching and selective separation step, microwave 200 is added to the leachate. Due to the microwave, the leachate may pulverize the waste printed circuit board due to an increase or fluctuation in temperature and pressure, thereby increasing the contact surface area with the leachate, thereby increasing leaching efficiency.

There is no particular limitation on the output condition of the microwave. For example, the method may adjust the microwave output in the range of 500 to 2000W, preferably 500 to 1000W.

In the above method, microwaves may be applied for 1 to 5 hours, preferably 1 to 3 hours under the output condition.

In the above method, the temperature of the leachate may be maintained at 50 to 250°C, preferably 80 to 250°C, and the pressure applied to the leachate at 5 to 40 atm for the reaction time by applying microwave to the leachate.

The leaching and selective separation step includes a solvent extraction step of moving the leached noble metal ions into the ionic liquid.

For example, AuCl ₄ ^- produced by reacting gold ions leached from waste printed circuit boards with aqua regia and ionic liquid anions ([Tf ₂ N] ^- ) at the hydrophobic ionic liquid interface and ion exchange reactions and cations ( [C ₈ min]) and can move to the ionic liquid phase by forming an ion pair. On the other hand, Cu(NO ₃ ) ₂ produced by the reaction of copper ions leached from the waste printed circuit board and aqua regia does not react with the ionic liquid and remains in the aqueous phase.

In the present invention, since metal leaching and solvent extraction are continuously performed in one reactor (solvent extraction can be performed continuously after leaching), a method of separately performing solvent extraction by adding an ionic liquid to the leachate after the conventional leaching process Compared to the process time can be shortened.

The present invention can separate the leachate from the aqueous solution and the ionic liquid by known methods (separating funnel, centrifuge, etc.).

The present invention can recover non-precious metals and noble metals from leachate and ionic liquids, respectively.

For example, the noble metal recovery method may recover the noble metal as an aqueous solution by adding an aqueous complexing agent to the ionic liquid. The complexing agent may be an acidic thiourea having a strong binding force with a noble metal in an ionic liquid.

Gold ions recovered in the aqueous phase by reaction with the complexing agent aqueous solution are recovered as pure gold (Au(0)) through various methods such as electrospinning, flotation, adsorption, and precipitation. I can.

In addition, non-precious metals such as copper remaining in the aqua regia can be recovered as pure copper through a known method.

In another aspect the present invention relates to a selective reactor of noble and non-precious metals. 1 and 2, the optional reactor includes a separator 100 and a microwave generator 200.

The separator has a separating means therein, an ionic liquid layer under the separating means, and a leachate layer above the separating means.

The microwave generator 200 irradiates microwaves to the leachate layer of the reactor.

The separating means may be a plurality of separating objects filled to a predetermined height from the bottom, or may be a separating layer having a plurality of holes.

The waste printed circuit board is placed on the leachate layer.

The microwave generator may pulverize (pulverize) the waste printed circuit board by increasing the temperature and pressure of the leachate in the reactor.

In the reactor, leaching in which noble metals and non-precious metals of the waste printed circuit board react with leachate and eluted, and solvent extraction in which the eluted noble metal ions react with the ionic liquid and move to the ionic liquid phase under the separation means are continuously performed.

For the selective reactor, reference may be made to the method for selectively separating the noble metal and the non-precious metal described above.

Hereinafter, the present invention will be described in more detail through examples, but the present invention is not limited to these examples.

Example 1

1 g of unprocessed waste printed circuit board (3× 3× 1 mm-13× 10× 2 mm) was mixed with 0.1 mL of hydrophobic ionic liquid (1-Methyl-3-octylimidazoliumbis(trifluoromethylsulfonyl)imide)([C8min][ TNf ₂ ], 5 mL of aqua regia (hydrochloric acid: nitric acid = 3:1) and glass beads were placed in a microwave reactor After separating into an aquatic layer and an ionic liquid layer, microwave (800W) was irradiated on the aquatic layer. Thus, the temperature of the aquatic layer was raised to 180° C. (At this time, the pressure applied to the aquatic layer was 16.8 atm.) Leaching and solvent extraction were performed while controlling the microwave exposure time from 30 minutes to 3 hours.

The aquatic layer and the ionic liquid layer were separated using a centrifuge or a separatory funnel.

Comparative Example 1

It was carried out in the same manner as in Example 1 except that an ionic liquid was not used (aqua regia and microwave application).

Comparative Example 2

Gold and copper were extracted in the same manner as in Example 1 using only aqua regia (no ionic liquid and microwave applied).

3 is a comparison of the leaching concentrations of gold and copper in the aquatic layer. Referring to FIG. 3, in the case of Example 1 (aqua regia, ionic liquid, microwave), it can be confirmed that the gold concentration in the aqua regia layer becomes constant after 30 minutes elapsed (3a). That is, after 30 minutes, gold ions migrated to the ionic liquid through solvent extraction with the ionic liquid. On the other hand, in the case of copper, the concentration of leached copper continues to increase with time (leaching time increases), because copper ions do not migrate to the ionic liquid and are present in aqua regia (3b).

4 is a photograph taken by collecting the pulverized printed circuit board after maintaining the temperature of the leachate at 80° C., 130° C., and 180° C. for 3 hours by adjusting the irradiation time with the microwave in Example 1, and FIG. 5 Is a graph showing the amount of (a) gold and (b) copper per 1 g of a waste printed circuit board according to temperature.

Referring to FIG. 4, it can be seen that as the temperature increases, the size of the waste printed circuit board gradually decreases and becomes powdered (powdered).

Referring to FIG. 5, in the case of gold and copper, it can be seen that the amount of gold extracted increases with increasing temperature.

6 is a graph examining changes in the concentration of gold and copper in a two-phase (aqueous phase/ionic liquid phase). The initial concentration of the gold trivalent solution of 47.55 mg/L decreased by about 95.50% to 2.14 mg/L in reaction with the ionic liquid (FIG. 6A). On the other hand, in the case of copper, after the reaction with the ionic liquid at an initial concentration of 39.61 mg/L, it decreased by about 3.58% to 38.19 mg/L (Fig. 6b). Referring to FIG. 6, it was confirmed that gold and copper ions can be selectively separated with a small amount of hydrophobic ionic liquid. A similar trend was also observed in the mixed solution of gold and copper (Fig. 6c). 6D is a photograph showing that yellow gold ions have moved to the ionic liquid phase. Table 1 shows the change in the concentration of gold ions in phase 2 (a mixed solution of gold and copper/ionic liquid phase).

Initial state Final state Water (5 mL) 47.55 ppm = 0.24 mg/5 mL 2.14 ppm = 0.01 mg/5 mL Ionic liquid phase (0.1 mL) 0 ppm = 0 mg/0.1 mL 2300 ppm = 0.23 mg/0.1 mL

FIG. 7 shows the concentration of gold by putting thiourea having a strong binding force with gold ions into the ionic liquid separated in Example 1 to recover pure gold as an aqueous phase.

The initial concentration of the gold trivalent solution decreased 92.34% from 53.03 mg/L to 4.06 mg/L after 30 minutes after contact with 0.1 mL ionic liquid (FIGS. 7a and 7b). Thereafter, a 0.1 M hydrochloric acid-0.01 M thiourea solution was brought into contact with a highly concentrated ionic liquid. The concentration of gold recovered as an aqueous phase by the hydrochloric acid-thiourea solution was 48.24 mg/L, showing a high recovery rate of 98.51% (Fig. 7c).

So far, specific embodiments of the present invention have been looked at. Those of ordinary skill in the art to which the present invention pertains will be able to understand that the present invention may be implemented in a modified form without departing from its essential characteristics. The scope of the present invention is shown in the claims rather than the foregoing description, and all differences within the scope equivalent thereto should be construed as being included in the present invention.

Claims (13)

Placing precious metal-containing waste, hydrophobic ionic liquid and leachate into a reactor;
A leaching and selective separation step of leaching noble metals and non-precious metals by applying microwaves to the leachate, and moving the noble metals into the ionic liquid;
Separating the leachate from the ionic liquid;
A method for selectively separating noble metals and non-precious metals comprising the step of recovering gold as an aqueous solution by adding an aqueous complex solution to the ionic liquid separated from the leachate. The method of claim 1, wherein the reactor includes a plurality of separating objects filled to a predetermined height from the bottom or a separating layer having a plurality of holes. The method of claim 1, wherein the ionic liquid is settled in the lower part of the reactor and separated from the leachate, and the waste is located in the upper leachate. In claim 1, wherein the leaching and selective separation step comprises the step of dissolving the noble and non-precious metals of the waste by reacting with the leachate, and moving the noble metal ions into the ionic liquid phase by reacting with the ionic liquid. Method for selective separation of precious and non-precious metals. The method of claim 1, wherein the method maintains the temperature of the leachate at 50°C to 250°C. delete In claim 1, wherein the ionic liquid is 1-Methyl-3-octylimidazolium bis(trifluoromethylsulfonyl)imide)([C ₈ min][Tf ₂ N]), 1-ethyl-3-methylimidazolium, 1-butyl -3-methylimidazolium, 1-hexyl-3-methylimidazolium, or 1-decyl3-methylimidazolium. The method of claim 1, wherein the aqueous complex solution is an acidic thiourea. delete The method of claim 1, wherein the method comprises adding the ionic liquid in the range of 2% to 10% relative to the leachate. A reactor (100) having a separation means therein, in which an ionic liquid layer is formed below the separation means, and a leachate layer is formed above the separation means;
Including a microwave generator 200 for irradiating microwaves to the leachate layer of the reactor,
The separating means is a plurality of separating objects filled to a predetermined height from the bottom or a separating layer having a plurality of holes,
The precious metal-containing waste is located in the leachate layer,
The microwave generator is a reactor for selectively separating noble metals and non-precious metals to powder (pulverize) the noble metal-containing waste by increasing the temperature and pressure of the leachate in the reactor. The method of claim 11, wherein the reactor comprises leaching in which noble metals and non-precious metals of the noble metal-containing waste react with the leachate, and the eluted noble metal ions react with the ionic liquid to move to the ionic liquid phase below the separation means. A reactor for selective separation of noble metals and non-precious metals, characterized in that it is continuously generated. [13] The reactor of claim 11, wherein the noble metal of the noble metal-containing waste is gold, silver or a platinum group element, and the base metal is copper, zinc, aluminum, or lead.

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