Method for preferentially stripping gold-plated layer of waste circuit board based on controlled potential erosion method

Abstract

The invention provides a method for preferentially stripping a gold-plated layer of a waste circuit board based on a controlled potential erosion method, which comprises the following steps of: placing the waste circuit board in a solution, and carrying out erosion reaction under ultrasonic reinforcement to obtain a crude gold foil, a solution containing copper and nickel and a degolded substrate; based on the electrode potential difference of the noble metal layer and the base metal layer in the same medium system, the gold-plated layer on the waste circuit board is efficiently cleaned and extracted by utilizing the gain of ultrasonic waves on physical and chemical levels.

Description

Technical Field

[0001] The present invention relates to the technical field of resource recycling, and more specifically, to resource utilization and harmless disposal of waste circuit boards. Background Art

[0002] The gold in the waste circuit board is attached to the copper-nickel metal substrate by electroplating or chemical plating. According to this mechanism, if the copper and nickel plating layers under the gold plating layer are slightly corroded and dissolved, the surface gold plating layer can be directly stripped from the waste circuit board to obtain rough gold foil. In recent years, researchers have conducted a lot of research on the stripping method to recover gold from electronic waste and verified its feasibility. Syed et al. used a strong oxidant potassium persulfate to selectively dissolve copper, nickel and other common metals in the circuit board. The precious metals were recovered by filtration, and pure gold could be directly recovered by melting. The gold recovery efficiency was similar to that of the cyanidation method, but it was simpler and more cost-effective than the cyanidation method. Alzate et al. proposed the use of ammonium persulfate and oxygen to strip gold from waste computer chips, and the gold recovery rate reached more than 98%. Based on the research of Alzate et al., Lu Yan et al. proposed a method for recovering unleached gold from memory sticks using ammonium persulfate and hydrogen peroxide. The gold stripping rate reached 98.95% and the recovered gold purity reached 93.11%. Patent CN200710020408.5 discloses a method for recovering gold and copper from gold-plated printed circuit board waste, using hydrogen peroxide and sulfuric acid as reaction reagents to recover gold and copper from gold-plated printed circuit board waste; Patent application CN202310338603.1 discloses a green and efficient stripping method for gold-plated surface of circuit board scraps, using persulfate and strong oxidant to strip the gold-plated layer; Patent application CN202010058345.8 discloses a wet harmless extraction process for heavy metals from waste mobile phone circuit boards, using sulfuric acid, sodium chlorate and hydrogen peroxide to strip the gold-plated layer. However, the above methods have poor stripping efficiency and effect, consume more reagents, and are limited to the selection of reagents in the field of hydrometallurgy. In addition, since the contact area between the circuit board substrate and the solution is small, and the reaction process is not suitable for stirring. Therefore, patent application CN202010058345.8 first crushes the circuit board into powder and then dissolves it, but ~60% of the waste circuit boards are non-metallic materials such as resin powder. Crushing them into powder will increase the processing volume and reduce the leaching effect and efficiency.

[0003] Therefore, it is urgent to develop a new method for preferentially stripping the gold-plated layer of waste circuit boards and strengthen the stripping means to improve the stripping efficiency and effect of the gold-plated layer. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a method for preferentially stripping the gold-plated layer of waste circuit boards based on a controlled potential corrosion method. The method places the waste circuit boards directly in a solution and strengthens the gold-plated layer stripping process through ultrasonic waves, thereby achieving preferential and efficient stripping of the gold-plated layer of the waste circuit boards, and greatly improving the stripping rate and efficiency of the gold-plated layer.

[0005] In order to achieve the above object, the technical solution of the present invention is as follows:

[0006] A method for preferentially stripping the gold-plated layer of waste circuit boards based on a controlled potential erosion method, comprising the following steps:

[0007] The waste circuit board is placed in a solution and subjected to an erosion reaction under ultrasonic enhancement to obtain a rough gold foil, a copper-nickel-containing solution and a gold-removed substrate;

[0008] The solution is controlled to have a potential range of 1.3 to 1.5 V and a pH value of ≤2 by adding acid-base reagents and oxidants.

[0009] In some embodiments, the ultrasonic power is 400-900W; the reaction temperature is 20-90°C.

[0010] In some embodiments, the liquid-to-solid ratio of the solution to the waste circuit boards is 1-10 mL: 1 g; and the reaction time is 10-60 min.

[0011] In some embodiments, the acidic reagent includes at least one of sulfuric acid, hydrochloric acid, nitric acid, and citric acid, and the alkaline reagent includes at least one of sodium hydroxide, sodium carbonate, and ammonia water.

[0012] In some embodiments, the oxidant is at least one of potassium permanganate, chlorine, sodium hypochlorite, hydrogen peroxide, ozone, chlorate, oxygen, ammonium persulfate, and potassium persulfate.

[0013] In some embodiments, the method comprises the following steps:

[0014] The waste circuit board is placed in a solution and subjected to an erosion reaction under ultrasonic enhancement to obtain a rough gold foil, a copper-nickel-containing solution and a gold-removed substrate;

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0016] The present invention innovatively develops a technology for directional stripping of gold-plated layers on waste circuit boards by coupling potential control and ultrasonic enhancement. First, based on the difference in electrode potential between the noble metal layer and the base metal layer in the same dielectric system (such as Figure 1As shown in the figure, base metals such as copper and nickel are separated from waste circuit boards by corrosion, while precious metal gold does not participate in the corrosion reaction due to its high potential and naturally falls off from the surface of the circuit board, thereby achieving preferential and selective extraction of gold from waste circuit boards. In addition, the gain of ultrasound at the physical and chemical levels is used to increase the probability of solid-liquid contact during the reaction process, strengthen fluid movement and mass and heat transfer, improve stripping efficiency, and achieve efficient and clean extraction of the gold-plated layer on waste circuit boards. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a mechanism diagram of the present invention. DETAILED DESCRIPTION

[0018] Many specific details are set forth in the following description to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways than those described herein, and those skilled in the art can make similar modifications without violating the connotation of the present invention, so the present invention is not limited to the specific implementation disclosed below.

[0019] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0020] Example 1

[0021] A method for preferentially stripping the gold-plated layer of waste circuit boards based on a controlled potential erosion method, comprising the following steps:

[0022] The waste circuit board is placed in a solution, and ultrasonic intensification is used to perform corrosion reaction to obtain a rough gold foil, a copper-nickel solution and a gold-removed substrate; wherein the liquid-to-solid ratio of the solution to the waste circuit board is 1 mL:1 g; sulfuric acid and hydrogen peroxide are slowly added to the solution through a peristaltic pump, and the pH and potential of the solution are monitored in real time using a thunder magnetic potentiostat-pH ​​meter to maintain the solution potential at 0.3 V and pH ≤ 2; the ultrasonic power is 500 W, and the corrosion reaction time is 20 min.

[0023] After the reaction was completed under this condition, the Au stripping rate was 0.56%.

[0024] Example 2

[0025] A method for preferentially stripping the gold-plated layer of waste circuit boards based on a controlled potential erosion method, comprising the following steps:

[0026] The waste circuit board is placed in a solution, and ultrasonic intensification is used to perform corrosion reaction to obtain a rough gold foil, a copper-nickel solution and a de-golded substrate; wherein the liquid-to-solid ratio of the solution to the waste circuit board is 1 mL:1 g; sulfuric acid and potassium permanganate solution are slowly added to the solution through a peristaltic pump, and the pH and potential of the solution are monitored in real time using a thunder magnetic potentiostat-pH ​​meter to maintain the solution potential at 0.5 V and pH ≤ 2; the ultrasonic power is 500 W, and the corrosion reaction time is 20 min.

[0027] After the reaction was completed under this condition, the Au stripping rate was 20.85%.

[0028] Example 3

[0029] A method for preferentially stripping the gold-plated layer of waste circuit boards based on a controlled potential erosion method, comprising the following steps:

[0030] The waste circuit board is placed in a solution, and ultrasonic intensification is used to perform corrosion reaction to obtain a rough gold foil, a copper-nickel solution and a de-golded substrate; wherein the liquid-to-solid ratio of the solution to the waste circuit board is 1 mL:1 g; nitric acid and oxygen are slowly added to the solution through a peristaltic pump, and the pH and potential of the solution are monitored in real time using a thunder magnetic potentiostat-pH ​​meter to maintain the solution potential at 1.0 V and pH ≤ 2; the ultrasonic power is 500 W, and the corrosion reaction time is 20 min.

[0031] After the reaction was completed under this condition, the Au stripping rate was 81.37%.

[0032] Example 4

[0033] A method for preferentially stripping the gold-plated layer of waste circuit boards based on a controlled potential erosion method, comprising the following steps:

[0034] The waste circuit board is placed in a solution, and ultrasonic intensification is used to perform corrosion reaction to obtain a rough gold foil, a copper-nickel solution and a gold-removed substrate; wherein the liquid-to-solid ratio of the solution to the waste circuit board is 1mL:1g; sulfuric acid and hydrogen peroxide are slowly added to the solution through a peristaltic pump, and the pH and potential of the solution are monitored in real time using a thunder magnetic potentiostat-pH ​​meter to maintain the solution potential at 1.5V and pH≤2; the ultrasonic power is 500W, and the corrosion reaction time is 20min.

[0035] After the reaction was completed under this condition, the Au stripping rate was 99.28%.

[0036] Example 5

[0037] A method for preferentially stripping the gold-plated layer of waste circuit boards based on a controlled potential erosion method, comprising the following steps:

[0038] The waste circuit board is placed in a solution, and ultrasonic intensification is used to perform corrosion reaction to obtain a rough gold foil, a copper-nickel solution and a gold-removed substrate; wherein the liquid-to-solid ratio of the solution to the waste circuit board is 1 mL:1 g; sulfuric acid, sodium hydroxide solution and hydrogen peroxide are slowly added to the solution through a peristaltic pump, and the pH and potential of the solution are monitored in real time using a thunder magnetic potentiostat-pH ​​meter to maintain the solution potential in a controlled potential range of 1.5 V and pH = 3; the ultrasonic power is 500 W, and the corrosion reaction time is 20 min.

[0039] After the reaction was completed under this condition, the Au stripping rate was 24.08%.

[0040] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0041] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for preferentially stripping the gold-plated layer of waste circuit boards based on a controlled potential erosion method, characterized in that: The following steps are involved: The waste circuit board is placed in a solution and subjected to an erosion reaction under ultrasonic enhancement to obtain a rough gold foil, a copper-nickel-containing solution and a gold-removed substrate; The solution is controlled to have a potential range of 1.3 to 1.5 V and a pH value of ≤2 by adding an acid-base reagent and an oxidant.

2. The method for preferentially stripping the gold-plated layer of waste circuit boards based on the controlled potential corrosion method according to claim 1, characterized in that: The ultrasonic power is 400-900W; the reaction temperature is 20-90°C.

3. The method for preferentially stripping the gold-plated layer of waste circuit boards based on the controlled potential corrosion method according to claim 1, characterized in that: The liquid-to-solid ratio of the solution to the waste circuit board is 1-10 mL: 1 g; and the reaction time is 10-60 min.

4. The method for preferentially stripping the gold-plated layer of waste circuit boards based on the controlled potential corrosion method according to claim 1, characterized in that: The acidic reagent includes at least one of sulfuric acid, hydrochloric acid, nitric acid and citric acid, and the alkaline reagent includes at least one of sodium hydroxide, sodium carbonate and ammonia water.

5. The method for preferentially stripping the gold-plated layer of waste circuit boards based on the controlled potential corrosion method according to claim 1, characterized in that: The oxidant is at least one of potassium permanganate, chlorine, sodium hypochlorite, hydrogen peroxide, ozone, chlorate, oxygen, ammonium persulfate and potassium persulfate.

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