A process and leaching reagent for selectively leaching, enriching and recovering precious metals from waste precious metal coating materials

Abstract

The present invention discloses a process for selectively leaching, enriching, and recovering precious metals from waste precious metal coating materials. The process utilizes a leaching agent comprising a precious metal chelating agent, a metal complexing agent, an oxidant, a pH regulator, and a accelerator to selectively leach the precious metal coating from the material. The leached precious metal is then enriched and recovered by electrowinning, and the solution after electrowinning is recycled for preparing the leaching agent. This process improves the production efficiency and actual recovery rate of precious metals, and the entire process is mild and has minimal environmental pollution. The present invention also provides a leaching agent for selectively leaching, enriching, and recovering precious metals from waste precious metal coating materials.

Description

Technical Field

[0001] The present invention belongs to the field of solid waste resource utilization, and in particular relates to a process and a leaching reagent for selectively leaching, enriching and recovering precious metals from waste precious metal plating materials. Background Art

[0002] Precious metal plating is widely used in industrial and consumer products, such as printed circuit boards (PCBs), electronic connectors, electronic components, precious metal-plated anodes, and decorative craft pieces like luggage zippers. With the rapid development of the electronics industry, the amount of electronic waste, including PCBs, electronic connectors, and electronic components, as well as scrap and waste generated during production processes, has increased significantly. According to statistics, my country processes over 500,000 tons of waste PCBs annually. This electronic waste contains a large amount of valuable metals, making it a high-quality "urban mineral" resource and a significant source of precious metal recycling. For example, printed circuit boards (PCBs) are composed of 40% metal. PCBs requiring high connection reliability, such as communications PCBs, are typically treated with electroless nickel-gold plating, electroless nickel-gold plating, electroless silver plating, palladium plating, and silver tarnish prevention processes. Consequently, these waste PCBs contain significant amounts of precious metals and have high recycling value. Used mobile phone PCBs are a particularly representative example of this type of waste. Precious and non-ferrous metals account for approximately 30% of a mobile phone's total weight, primarily gold, palladium, silver, copper, tin, and nickel. Taking gold as an example, tests have shown that the gold content of gold-plated circuit boards is approximately 300 grams per ton, while the average grade of gold ore is only 5 grams per ton. This means that the gold content of scrap circuit boards is 20 to 40 times that of gold ore. This demonstrates the enormous economic potential inherent in recycling precious metals and other valuable metals. The key to their reuse is efficient and low-pollution recovery.

[0003] Currently, the domestic recycling of valuable metals from scrap circuit boards (PCBs) is primarily done through physical crushing and sorting, as well as pyrometallurgical smelting. Physical crushing and sorting involves breaking the boards into particles of a specific size through impact, shear, and extrusion. Metals and non-metals are then separated based on the physical properties of the individual particles through gravity, magnetic, eddy current, and electrostatic separation. The separated metals primarily consist of base metals such as copper, tin, lead, nickel, and iron, as well as precious metal and polymetallic powders, primarily gold, and a small amount of unseparated epoxy resin organics. The non-metallics consist of epoxy resin powder, glass fiber powder, and a small amount of unseparated metals. The metal fraction is primarily copper powder, which is smelted through pyrometallurgical smelting to produce copper ingots. The refined copper is then recovered through electrolysis, and the precious metals are concentrated in anode mud. Nitric acid is then used to remove residual impurities such as copper, nickel, tin, and lead from the mud. Aqua regia or hydrochloric acid combined with chlorine is then used to dissolve, purify, and recover the precious metals. Pyrometallurgy is the process of using a copper smelting furnace to pyrometallurgically enrich the copper in waste circuit boards, smelting it into copper ingots, separating the impurity metals such as tin, lead, and iron into slag, and then recovering the refined copper through an electrolytic process, and enriching the precious metals in the anode mud. The residual copper, nickel, tin, lead and other impurity metals in the anode mud are then removed with nitric acid or sulfuric acid, and the precious metals are dissolved, purified, separated and recovered using methods such as aqua regia or hydrochloric acid + chlorine.

[0004] The main problem with pyrometallurgy is that during the pyrometallurgical treatment process, the epoxy resin and halogen-containing flame retardants in the waste circuit boards produce difficult-to-treat carcinogens such as dioxins during combustion. Furthermore, the use of aqua regia, chlorine, nitric acid, sulfuric acid, and hydrochloric acid creates wastewater, exhaust gas, and residue that are difficult to handle, causing severe environmental pollution. Physical crushing and sorting, by comparison, is a more environmentally friendly treatment method, but it requires a lengthy process. Existing physical crushing and sorting processes involve physical sorting, pyrometallurgy, copper ingot electrolytic refining, anode mud pickling to remove impurity metals, and precious metal leaching and reduction to enrich and separate precious metals. The extraction and separation cycle for precious metals takes at least 15-20 days, resulting in long recovery times. Precious metals circulate excessively during the production process, leading to significant capital backlogs. Furthermore, some residual metallic powder containing precious metals remains in the resulting non-metallic powder, and the smelting slag produced during the pyrometallurgical process also contains small amounts of precious metals. These steps result in low actual precious metal yields. Summary of the Invention

[0005] One of the purposes of the present invention is to provide a process for selectively leaching, enriching and recovering precious metals from waste precious metal coating materials. The process first selectively leaches the precious metal coating in the material, and then uses an electrolytic method to enrich and recover the leached precious metals, thereby improving the production efficiency and actual recovery rate of precious metals. In addition, the entire process has a mild reaction and low environmental pollution.

[0006] A second object of the present invention is to provide a leaching reagent for selectively leaching, enriching and recovering precious metals from waste precious metal coating materials in response to the current industry status. The leaching reagent is environmentally friendly, has a short process, a mild reaction, and is selective for leaching nickel, tin, lead and iron. Environmental friendliness means that the leaching reagent has low toxicity and is weakly alkaline, and the leaching reaction does not volatilize any toxic waste gas and has low corrosion to equipment; leaching selectivity means that the leaching reagent can leach precious metal coatings such as gold, silver, platinum, palladium and rhodium at room temperature, and basically does not leach the underlying nickel and the tin-lead solder thereon.

[0007] In order to achieve the first object of the invention, the following technical solutions are adopted:

[0008] A process for selectively leaching, enriching and recovering precious metals from waste precious metal coating materials comprises the following steps:

[0009] (1) preparing a leaching agent; the leaching agent comprises a noble metal chelating agent, a metal complexing agent, an oxidant, a pH regulator, a accelerator, and water, wherein the noble metal chelating agent comprises polycyanate;

[0010] The pH value of the leaching agent is controlled in the range of 9 to 11;

[0011] (2) Leaching process: The waste precious metal coating material is placed in a leaching reagent to carry out a leaching reaction, wherein the precious metal coating is leached to form precious metal chelate ions and metal complex ions through oxidation chelation, and the precious metal is dissolved into the solution to obtain a precious metal leaching solution;

[0012] (3) Electrolytic process: The precious metal leaching solution is placed in an electrolytic cell and energized for electrolytic deposition, so that the precious metal ions in the solution are precipitated and enriched on the cathode. In the electrolytic process, a ruthenium-iridium-titanium alloy mesh is used as the anode and a stainless steel plate is used as the cathode. The electrolytic cell voltage is 1.5-3.0V and the current density is 10-30A / m 2 ;

[0013] (4) Extraction of precious metals: When the precious metal ion content in the solution is less than 0.5 ppm, the electrolysis is terminated, the cathode is removed from the cell, and the precious metals are then extracted;

[0014] (5) Recycling of the post-electrolysis solution: The post-electrolysis solution obtained after the completion of the electrolysis is recycled for the preparation of the leaching reagent in step (1); when the impurities in the post-electrolysis solution accumulate to the point where they affect the leaching effect, it is vacuum-decompressed and concentrated, and the condensed water generated is recovered for the preparation of the leaching reagent, thus realizing a closed-loop circulation of the waste liquid.

[0015] In fact, if the electrolysis time is long enough, the content of precious metal ions can be less than 0.1ppm. In order to ensure production efficiency, it is defined as less than 0.5ppm during actual operation.

[0016] In the leaching reagent of the present invention, the main function of the noble metal chelating agent is to chelate noble metal ions to form noble metal complex ions; the main function of the metal complexing agent is to complex the leached base metal ions to prevent them from forming a passivation layer on the surface of the noble metal and affecting the leaching effect of the noble metal; the oxidizing agent is used to oxidize the noble metal so that it combines with the metal chelating agent to form soluble noble metal complex ions; the accelerator can prevent the noble metal layer from being passivated during dissolution, resulting in incomplete dissolution of the noble metal or even cessation of the dissolution reaction, thereby accelerating the dissolution reaction; and the main function of the pH buffer is to keep the leaching solution within an optimal pH value range so that the pH value does not change due to the extension of the leaching time and does not affect the leaching reaction.

[0017] The leaching reagent of the present invention can be recycled after the leaching process and the electrolysis process. According to the inventor's test, the electrolysis liquid in step (5) can be recycled multiple times. Finally, the electrolysis liquid that cannot be reused is vacuum-decompressed and concentrated to recover the generated condensed water, thereby achieving the purpose of zero wastewater discharge and greatly reducing the generation of waste residue.

[0018] Furthermore, the leaching reagent used in the present invention includes 12-55 g / L of noble metal chelating agent; 3-10 g / L of metal complexing agent; 8-15 g / L of oxidant; 1-10 g / L of pH regulator; and 1-2 g / L of promoter.

[0019] When the scrap metal coating material contains metallic copper, the leaching agent may also include 0.5 to 1 g / L of a copper corrosion inhibitor to inhibit the dissolution of metallic copper during the leaching reaction, thereby preventing the leaching agent from affecting the leaching effect on precious metals and ensuring production efficiency. The copper corrosion inhibitor is one or more of benzotriazole, tolyltriazole, or mercaptobenzothiazole sodium salt.

[0020] The noble metal chelating agent further comprises one or more of glycine, alanine, aspartic acid, phenylalanine and lysine. The polycyanate ion and the above components are compounded to produce a synergistic effect, thereby further improving the efficiency of noble metal dissolution.

[0021] The metal complexing agent is selected from one or more of sodium edetate, sodium gluconate, potassium sodium tartrate, ammonium succinate, ammonium citrate, sodium citrate and sodium nitrilotriacetate.

[0022] The oxidant is selected from one or more of hydrogen peroxide, sodium peroxide, calcium peroxide, sodium percarbonate, sodium perborate, calcium peroxide, sodium persulfate, potassium permanganate and the like.

[0023] The pH regulator is one or more of citric acid, disodium hydrogen phosphate, aminoacetic acid, ammonium chloride, boric acid and sodium hydroxide.

[0024] The accelerator is selected from one or more inorganic salts such as cerium sulfate, cerium nitrate, ammonium cerium nitrate, cerium chloride, and cerium acetate.

[0025] Furthermore, the present invention also includes a cleaning step; the cleaning step specifically comprises: subjecting the waste precious metal coating material treated in step (2) to a three-stage countercurrent cleaning, and reusing the third-stage relatively concentrated cleaning water for the preparation of the leaching reagent in step (1). This step can avoid the loss of precious metal and leaching reagent caused by removing the waste precious metal coating material. The cleaning step can use the condensed water from step (5).

[0026] The operation of extracting the precious metal in step (4) is as follows: scraping the precious metal powder electrodeposited on the stainless steel plate with a scraper, and then washing, filtering and drying to obtain a precious metal-enriched product.

[0027] The precious metals that can be enriched and recovered by the method of the present invention are one or more of gold, silver, platinum, palladium and rhodium.

[0028] The method of the invention can enrich and recycle precious metals in the metal plating layers of waste printed circuit boards, electronic connectors, electronic components, decorative craft parts, locks, and luggage zippers.

[0029] The present invention also provides a leaching agent for selectively leaching, enriching and recovering precious metals from waste precious metal coating materials, which contains water and is characterized by comprising 12 to 55 g / L of a precious metal chelating agent; 3 to 10 g / L of a metal complexing agent; 8 to 15 g / L of an oxidizing agent; 1 to 10 g / L of a pH regulator; and 1 to 2 g / L of a promoter; wherein the pH value of the leaching agent is 9 to 11;

[0030] The precious metal chelating agent polycyanate;

[0031] When the waste metal plating material contains metallic copper, it also includes 0.5 to 1 g / L of copper corrosion inhibitor.

[0032] The polycyanate of the present invention is prepared by the following steps: adding urea into a reaction kettle and heating it to carry out a condensation reaction to generate cyanuric acid; then adding sodium carbonate and ferrous sulfate to form a polycyanate chelate, wherein the polycyanate ions have a chelating effect on precious metals such as gold to form chelated ions of the precious metals.

[0033] Furthermore, the noble metal chelating agent further comprises one or more of glycine, alanine, aspartic acid, phenylalanine, and lysine.

[0034] The metal complexing agent is selected from one or more of sodium edetate, sodium gluconate, potassium sodium tartrate, ammonium succinate, ammonium citrate, sodium citrate and sodium nitrilotriacetate.

[0035] The oxidant is selected from one or more of hydrogen peroxide, sodium peroxide, calcium peroxide, sodium percarbonate, sodium perborate, calcium peroxide, sodium persulfate, potassium permanganate and the like.

[0036] The pH regulator is one or more of citric acid, disodium hydrogen phosphate, aminoacetic acid, ammonium chloride, boric acid and sodium hydroxide.

[0037] The accelerator is selected from one or more of cerium sulfate, cerium nitrate, ammonium cerium nitrate, cerium chloride and cerium acetate.

[0038] The copper corrosion inhibitor is one or more of benzotriazole, toluenetriazole or mercaptobenzothiazole sodium salt.

[0039] The present invention has the following beneficial effects:

[0040] (1) The method of the present invention can effectively separate and enrich precious metals such as gold, silver, platinum, palladium, and rhodium from waste precious metal plating materials through leaching and electrowinning processes. It can separate and enrich single gold, silver, platinum, palladium, or rhodium, as well as mixtures of any of the aforementioned precious metals. The method of the present invention has a high precious metal recovery rate, reaching over 97%. In particular, it improves the precious metal recovery efficiency of mixed waste materials with low platinum and rhodium contents compared to existing technologies.

[0041] (2) The present invention only requires two steps, leaching and electrowinning, to enrich and recover precious metals, thus shortening the production process and increasing production efficiency. Furthermore, for precious metal coatings ranging from the thinnest decorative luggage accessories to the thickest wear-resistant precious metal coatings for electronic connectors, as well as for various types of precious metal coatings (particularly the more inert rhodium), the present invention can leach the precious metals in the leaching process in just 5 to 60 minutes.

[0042] After the process of the present invention completes the recovery of precious metals, the materials are physically crushed and sorted to recover and process other valuable metals such as copper, which not only ensures the recovery efficiency of precious metals but also effectively recovers other metals.

[0043] Moreover, compared with the existing pyrometallurgical smelting and physical crushing and sorting treatment processes, the present invention first selectively leaches the higher-value precious metal coating on the waste precious metal coating material, and then adopts the electrolytic method to enrich and recover the leached precious metal, which changes the extraction order of precious metals in the existing process, improves the actual recovery rate of precious metals and the production efficiency of precious metals. From feeding to outputting qualified precious metals, the process of the present invention only takes 2 to 3 days to complete the recovery of precious metals.

[0044] (3) The leaching reagent used in the present invention does not contain highly toxic substances such as sodium cyanide, potassium cyanide, and aqua regia. The entire process is safe and reliable, with little pollution to the environment. At the same time, the precious metals are extracted by electrolysis without the need to add any other reducing agents. The solution after electrolysis can be recycled multiple times, and the waste liquid is vacuum-decompressed and concentrated to recover the condensed water, thereby avoiding wastewater discharge and achieving the goal of zero wastewater discharge.

[0045] (4) The leaching reagent of the present invention is weakly alkaline and has mild reaction conditions. It can react at 25-50°C, that is, it can react at room temperature. Moreover, it does not emit irritating or corrosive gases, thus avoiding harm to the human body and the environment and corrosion to equipment.

[0046] At the same time, the leaching reagent used in the present invention is selective for base metals such as nickel, iron, tin, and lead. The so-called selectivity means that under the same process conditions, the leaching rate of base metals such as nickel, iron, tin, and lead is extremely low. In other words, base metals such as nickel, tin-lead solder, and iron commonly found on waste electronic devices are basically not leached. The copper substrates of most waste circuit boards and other materials are covered with nickel and tin plating layers, and there is very little exposed copper. In addition, the present invention reduces the amount of copper leaching by adding a copper corrosion inhibitor.

[0047] In summary, the process of the present invention has mild process conditions, high production efficiency, and small equipment investment, is suitable for industrial production, and has significant economic and social benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 The process flow for recovering gold from the nickel-gold layer of chip substrate production waste in Example 4;

[0049] Figure 2 This is a comparison chart of the before and after effects of recovering gold from the nickel-gold layer of chip substrate production waste. DETAILED DESCRIPTION

[0050] The following examples are only used to illustrate the present invention, and the scope of protection of the present invention is not limited to the following examples. Those skilled in the art can achieve the purpose of the present invention based on the above disclosure of the present invention and the ranges of various parameters.

[0051] The preparation method of the polycyanate in the embodiment of the present invention is as follows: urea is added to a reactor and heated to perform a condensation reaction to generate cyanuric acid, and then sodium carbonate and ferrous sulfate are added to form the polycyanate, which is then cooled to room temperature and then crushed and sieved.

[0052] In the embodiment of the present invention, a ruthenium-iridium-titanium alloy mesh is used as an anode and a 304 stainless steel polishing plate is used as a cathode in the electrowinning process.

[0053] Example 1

[0054] Gold recovery from the nickel-gold plating of INTEL computer CPU LGA package contact points:

[0055] (1) Prepare the leaching reagent for precious metals. The composition of the leaching reagent is shown in the following table. After adding each component into water and stirring to dissolve completely, adjust the pH value.

[0056]

[0057] (2) Leaching: First, weigh 1.2 kg (50 CPUs) of Intel desktop computer CPUs, then clean them with water and place them in the leaching reagent; the solid-liquid ratio of the leaching process is determined to be 1 kg:5 L based on the volume of the leached workpiece, that is, the volume of the leaching reagent is 1.2 x 5 = 6 L;

[0058] The gold on the surface of the CPU is leached by mechanical stirring at room temperature. The color of the plating layer changes from gold to a bright white nickel layer, which can be clearly observed by the naked eye. The gold plating layer can be dissolved after 10 minutes to obtain a precious metal leaching solution. The waste computer CPU is then taken out and placed in a clean water tank for three-stage countercurrent cleaning. The third-stage relatively concentrated cleaning water is reused for the preparation of the leaching reagent in step (1). The function is to clean the precious metal leaching solution brought out by the computer CPU and prevent the loss of precious metals and leaching reagents. After cleaning, the computer CPU is taken out, washed and dried.

[0059] (3) Electrolysis: Place the precious metal leaching solution into the electrolysis tank and connect the power supply for electrolysis; the anode is a ruthenium-iridium-titanium alloy mesh, the cathode is a 304 stainless steel polished plate, the tank voltage is 2.5V, and the cathode current density is 15A / m 2 ;

[0060] After 24 hours of electrolysis, the gold chelate ion content in the solution is measured using an ICP-AES inductively coupled atomic emission spectrometer. If the content is less than 0.5 ppm, the electrolysis is terminated. The cathode is removed, the reduced and enriched gold powder on it is scraped off, and a small amount of dilute sulfuric acid and hydrogen peroxide are added to remove the base metals. The solution is then washed, dried and enriched with deionized water to obtain pure sponge gold powder.

[0061] After the electrodeposition is complete, the post-electrodeposition liquid is recycled for the preparation of the next round of leaching reagent production. Because impurity accumulation can affect the leaching effect, a sodium ion meter is used to measure the sodium ion concentration in the post-electrodeposition liquid. When the impurity accumulation reaches approximately 150 g / L, the post-electrodeposition liquid is evaporated and condensed. The resulting condensed water can be used to prepare leaching reagents or in the cleaning process, achieving "zero wastewater discharge" and centrally treating the small amount of waste residue generated. In this embodiment, the post-electrodeposition liquid was recycled five times.

[0062] (4) Determination of gold recovery rate: Due to the wide variety of types of waste devices, the gold content of the surface plating in the devices cannot be accurately determined during batch processing. Therefore, in actual operation, the method to determine whether the gold layer is completely dissolved is to observe the change in the color of the plating with the naked eye. Because the underlying metal of almost all precious metal plating is bright or semi-bright nickel plating, it is easy to determine whether the gold plating on the plating is completely dissolved. In order to ensure complete dissolution, the leaching time is extended by 2 minutes on this basis to ensure complete dissolution. Then, the gold chelate ion content in the precious metal leaching solution was measured by ICP-AES inductively coupled atomic emission spectrometer, which was 85.05ppm, that is, 85.05mg / L. The residual concentration of gold chelate ions in the solution after electrolysis was measured to be 0.5ppm. The concentration was multiplied by the respective volumes 85.05mg / L×6L=510.3mg=0.510g, and the gold content on the surface of 1.2kg of waste computer CPU was calculated to be 0.51g. 0.5mg / L×6L=3mg=0.003g, and the residual gold content in the solution after electrolysis was calculated, that is, the lost gold content was 0.003g. The theoretical recovery rate of gold = (0.510-0.003) / 0.510=99.4%. The pure sponge gold powder obtained in the above step (3) was weighed using a precision electronic balance to be 0.502g, and the actual recovery rate was 0.502 / 0.510=98.4%.

[0063] Example 2

[0064] Recovering gold from the nickel-gold plating of AMD computer CPU PGA package pin arrays:

[0065] (1) Prepare the leaching reagent for precious metals. The composition of the leaching reagent is shown in the following table. After adding each component into water and stirring to dissolve completely, adjust the pH value.

[0066]

[0067]

[0068] (2) Leaching: First, weigh 1.0 kg (25 CPUs) of AMD desktop computer CPUs, then clean them with water and place them in the leaching reagent; the solid-liquid ratio of the leaching process is determined to be 1 kg:5 L based on the volume of the leached workpiece, that is, the volume of the leaching reagent is 1.0 x 5 = 5 L;

[0069] The gold-plated layer can be dissolved by mechanical stirring at room temperature for 8 minutes to obtain a precious metal leaching solution. The waste computer CPU is then taken out and placed in a clean water tank for three-stage countercurrent cleaning. The more concentrated cleaning water of the third stage is reused for the preparation of the leaching reagent in step (1). The function is to clean the precious metal leaching solution brought out by the computer CPU and prevent the loss of precious metals and leaching reagents. Finally, the computer CPU is taken out, washed and dried.

[0070] (3) Electrolysis: Place the precious metal leaching solution into the electrolysis tank and connect the power supply for electrolysis; the anode is a ruthenium-iridium-titanium alloy mesh, the cathode is a 304 stainless steel polished plate, the tank voltage is 3.0V, and the cathode current density is 15A / m 2 ;

[0071] After 24 hours of electrolysis, the gold chelate ion content in the solution is measured using an ICP-AES inductively coupled atomic emission spectrometer. If the content is less than 0.5 ppm, the electrolysis is completed. The cathode is removed, the reduced and enriched gold powder on it is scraped off, and a small amount of dilute sulfuric acid and hydrogen peroxide are added to remove the base metals. The solution is then washed, dried and enriched with deionized water to obtain pure sponge gold powder.

[0072] After the completion of electrolysis, the post-electrolysis liquid is recycled for the preparation of the next round of leaching reagents. Since the accumulation of impurities will affect the leaching effect, a sodium ion meter is used to measure the concentration of sodium ions in the post-electrolysis liquid. When the impurity accumulation reaches about 150g / L, the post-electrolysis liquid is evaporated and condensed. The condensed water obtained can be used for the preparation of leaching reagents or cleaning processes, which can achieve "zero discharge" of wastewater and the small amount of waste residue generated is centrally treated.

[0073] (4) Determination of gold recovery rate: Due to the wide variety of types of waste devices, the gold content of the surface coating in the device cannot be accurately determined during batch processing. Therefore, in actual operation, the method to determine whether the gold layer is completely dissolved is to observe the color change of the coating with the naked eye. Because the underlying metal of almost all precious metal coatings is bright or semi-bright nickel coating, it is easy to determine whether the gold coating on the coating is completely dissolved. In order to ensure complete dissolution, the leaching time is extended by 2 minutes on this basis to ensure complete dissolution. Then, the gold chelate ion content in the precious metal leaching solution is measured by ICP-AES inductively coupled atomic emission spectrometer, which is 40.21 mg / L. The gold chelate ion in the solution after electrolysis is measured. The residual concentration is 0.5 mg / L, and the concentration is multiplied by the respective volumes 40.21 mg / L x 5 L = 210.05 mg = 0.210 g, which means that the gold content on the surface of 1.0 kg of waste computer CPU is 0.21 g. 0.5 mg / L x 5 L = 2.5 mg = 0.0025 g, which means that the gold content remaining in the liquid after electrolysis can be calculated, that is, the gold content lost is 0.003 g. The theoretical recovery rate of gold = (0.210-0.0025) / 0.210 = 98.8%. The pure sponge gold powder obtained in the above step (3) is weighed using a precision electronic balance to be 0.206 g, and the actual recovery rate is 0.206 / 0.210 = 98.1%.

[0074] Example 3

[0075] Recovering gold from the chemical nickel-gold protective layer on the surface of mobile phone circuit boards:

[0076] (1) Prepare the leaching reagent for precious metals. The composition of the leaching reagent is shown in the following table. After adding each component into water and stirring to dissolve completely, adjust the pH value.

[0077]

[0078] (2) Leaching: First, weigh 1.0 kg of waste mobile phone circuit boards, clean them with water, and place them in the leaching reagent; the solid-liquid ratio of the leaching process is determined to be 1 kg:3 L based on the volume of the leached workpiece, that is, the volume of the leaching reagent is 1.0 x 3 = 3 L;

[0079] Since the chemical nickel-plated gold layer on the waste mobile phone circuit board is relatively thin, the gold-plated layer can be dissolved by mechanical stirring at room temperature for 5 minutes to obtain a precious metal leaching solution; then the waste mobile phone circuit board is taken out and placed in a clean water tank for three-level countercurrent cleaning, and the third-level relatively concentrated cleaning water is reused for the preparation of the leaching reagent in step (1), so as to clean the precious metal leaching solution brought out by the waste mobile phone circuit board and prevent the loss of precious metals and leaching reagents. Finally, the waste mobile phone circuit board is taken out, washed and dried.

[0080] (3) Electrolysis: Place the precious metal leaching solution into the electrolysis tank and connect the power supply for electrolysis; the anode is a ruthenium-iridium-titanium alloy mesh, the cathode is a 304 stainless steel polished plate, the tank voltage is 2.0V, and the cathode current density is 10A / m 2 ;

[0081] After 24 hours of electrolysis, the gold chelate ion content in the solution is measured using an ICP-AES inductively coupled atomic emission spectrometer. If the content is less than 0.5 ppm, the electrolysis is terminated. The cathode is removed, the reduced and enriched gold powder on it is scraped off, and a small amount of dilute sulfuric acid and hydrogen peroxide are added to remove the base metals. The solution is then washed, dried and enriched with deionized water to obtain pure sponge gold powder.

[0082] After the completion of electrolysis, the post-electrolysis liquid is recycled for the preparation of the next round of leaching reagents. Since the accumulation of impurities will affect the leaching effect, a sodium ion meter is used to measure the concentration of sodium ions in the post-electrolysis liquid. When the impurity accumulation reaches about 150g / L, the post-electrolysis liquid is evaporated and condensed. The condensed water obtained can be used for the preparation of leaching reagents or cleaning processes, which can achieve "zero discharge" of wastewater and the small amount of waste residue generated is centrally treated.

[0083] (4) Determination of gold recovery rate: Due to the wide variety of types of waste devices, the gold content of the surface coating of the device cannot be accurately determined during batch processing. Therefore, in actual operation, the method to determine whether the gold layer is completely dissolved is to observe the color change of the coating with the naked eye. Because the underlying metal of almost all precious metal coatings is bright or semi-bright nickel coating, it is easy to determine whether the gold coating on the coating is completely dissolved. In order to ensure complete dissolution, the leaching time is extended by 2 minutes on this basis to ensure complete dissolution; then the gold chelate ion content in the precious metal leaching solution is measured by ICP-AES inductively coupled atomic emission spectrometer, which is 35.50 mg / L. Then the gold chelate ion content in the solution after electrolysis is measured. The residual concentration is 0.5 mg / L, and the concentration is multiplied by the respective volumes 35.50 mg / L×3L=106.5 mg=0.107 g, from which it can be calculated that the gold content on the surface of 1.0 kg of waste mobile phone circuit boards is 0.107 g. 0.5 mg / L×3L=1.5 mg=0.0015 g, and the gold content remaining in the liquid after electrolysis can be calculated, that is, the lost gold content is 0.0015 g. The theoretical recovery rate of gold = (0.107-0.0015) / 0.107=98.6%. The pure sponge gold powder obtained in the above step (3) is weighed using a precision electronic balance to be 0.104 g, and the actual recovery rate is 0.104 / 0.107=97.2%.

[0084] Example 4

[0085] Gold recovery from nickel-gold protective layer of chip substrate production waste:

[0086] (1) Prepare the leaching reagent for precious metals. The composition of the leaching reagent is shown in the following table. After adding each component into water and stirring to dissolve completely, adjust the pH value.

[0087]

[0088] (2) Leaching: First, weigh 1.0 kg of chip substrate production waste, then clean it with water and put it into the leaching reagent. The solid-liquid ratio of the leaching process is determined to be 1 kg:2 L based on the volume of the leached workpiece, that is, the volume of the leaching reagent is 1.0 x 2 = 2 L;

[0089] Since the electroplated nickel-gold layer of the chip substrate production waste is slightly thick, the gold-plated layer is dissolved by mechanical stirring at room temperature for 10 minutes to obtain a precious metal leaching solution; then the chip substrate production waste is taken out and placed in a clean water tank for three-level countercurrent washing, and the third-level relatively concentrated washing water is reused for the preparation of the leaching reagent in step (1), so as to clean the precious metal leaching solution brought out by the chip substrate production waste and prevent the loss of precious metals and leaching reagents. Finally, the chip substrate production waste is taken out, washed and dried.

[0090] like Figure 2 As shown, Figure 2 a is the chip substrate production waste after the leaching process, Figure 2 b is the original chip substrate production waste, and the two are clearly visible. Figure 2 a. The metal coating on the surface of chip substrate production waste has been completely dissolved.

[0091] (3) Electrolysis: Place the precious metal leaching solution into the electrolysis tank and connect the power supply for electrolysis; the anode is a ruthenium-iridium-titanium alloy mesh, the cathode is a 304 stainless steel polished plate, the tank voltage is 3.0V, and the cathode current density is 20A / m 2 ;

[0092] After 24 hours of electrolysis, the gold chelate ion content in the electrolysis solution is measured using an ICP-AES inductively coupled atomic emission spectrometer. If the content is less than 0.5 ppm, the electrolysis is terminated. The cathode is removed, the reduced and enriched gold powder on it is scraped off, and a small amount of dilute sulfuric acid and hydrogen peroxide are added to remove the base metals. The solution is then washed, dried and enriched with deionized water to obtain pure sponge gold powder.

[0093] After the completion of electrolysis, the post-electrolysis liquid is recycled for the preparation of the next round of leaching reagents. Since the accumulation of impurities will affect the leaching effect, a sodium ion meter is used to measure the concentration of sodium ions in the post-electrolysis liquid. When the impurity accumulation reaches about 150g / L, the post-electrolysis liquid is evaporated and condensed. The condensed water obtained can be used for the preparation of leaching reagents or cleaning processes, which can achieve "zero discharge" of wastewater and the small amount of waste residue generated is centrally treated.

[0094] (4) Determination of gold recovery rate: Due to the wide variety of types of waste devices, the gold content of the surface coating in the devices cannot be accurately determined during batch processing. Therefore, in actual operation, the method to determine whether the gold layer is completely dissolved is to observe the color change of the coating with the naked eye. Because the underlying metal of almost all precious metal coatings is bright or semi-bright nickel coating, it is easy to determine whether the gold coating on the coating is completely dissolved. In order to ensure complete dissolution, the leaching time is extended by 2 minutes on this basis to ensure complete dissolution; then the gold chelate ion content in the precious metal leaching solution is measured by ICP-AES inductively coupled atomic emission spectrometer, which is 600.58 mg / L. Then the gold chelate ion content in the solution after electrolysis is measured. The residual concentration is 0.5 mg / L, and the concentration is multiplied by the respective volumes 600.58 mg / L x 2 L = 1201.16 mg = 1.201 g, which means that the surface gold content of 1.0 kg of chip substrate production waste is 1.201 g. 0.5 mg / L x 2 L = 1.0 mg = 0.001 g, which means that the residual gold content in the liquid after electrolysis can be calculated, that is, the lost gold content is 0.001 g. The theoretical recovery rate of gold = (1.201-0.001) / 1.201 = 99.9%. The pure sponge gold powder obtained in the above step (3) is weighed using a precision electronic balance to be 1.189 g, and the actual recovery rate is 1.189 / 1.201 = 99.0%.

[0095] Example 5

[0096] Recycling of thin bright gold plating on the surface of luggage decoration parts production waste:

[0097] (1) Prepare the leaching reagent for precious metals. The composition of the leaching reagent is shown in the following table. After adding each component into water and stirring to dissolve completely, adjust the pH value.

[0098]

[0099] (2) Leaching: First, weigh 5.0 kg of luggage decoration parts production waste, then wash it with water and put it into the leaching reagent. The solid-liquid ratio of the leaching process is determined to be 5 kg:1 L based on the volume of the leached workpiece, that is, the volume of the leaching reagent is 1.0 L;

[0100] Since the gold-plated layer on the surface of the luggage and bag decoration production waste is relatively thin, the gold-plated layer can be dissolved by mechanical stirring at room temperature for 2 minutes to obtain a precious metal leaching solution; then the luggage and bag decoration production waste is taken out and placed in a clean water tank for three-level countercurrent washing, and the third-level relatively concentrated washing water is reused for the preparation of the leaching reagent in step (1), so as to clean the precious metal-containing leaching reagent brought out by the luggage and bag decoration production waste and prevent the loss of the precious metal-containing leaching reagent; finally, the luggage and bag decoration production waste is taken out, washed and dried.

[0101] (3) Electrolysis: Place the precious metal leaching solution into the electrolysis tank and connect the power supply for electrolysis; the anode is a ruthenium-iridium-titanium alloy mesh, the cathode is a 304 stainless steel polished plate, the tank voltage is 2.0V, and the cathode current density is 10A / m 2 ;

[0102] After 24 hours of electrolysis, the gold chelate ion content in the electrolysis solution is measured using an ICP-AES inductively coupled atomic emission spectrometer. If the content is less than 0.5 ppm, the electrolysis is terminated. The cathode is removed, the reduced and enriched gold powder on it is scraped off, and a small amount of dilute sulfuric acid and hydrogen peroxide are added to remove the base metals. The solution is then washed, dried and enriched with deionized water to obtain pure sponge gold powder.

[0103] After the completion of electrolysis, the post-electrolysis liquid is recycled for the preparation of the next round of leaching reagents. Since the accumulation of impurities will affect the leaching effect, a sodium ion meter is used to measure the concentration of sodium ions in the post-electrolysis liquid. When the impurity accumulation reaches about 150g / L, the post-electrolysis liquid is evaporated and condensed. The condensed water obtained can be used for the preparation of leaching reagents or cleaning processes, which can achieve "zero discharge" of wastewater and the small amount of waste residue generated is centrally treated.

[0104] (4) Determination of gold recovery rate: In the actual operation process, the method to judge whether the gold layer is completely dissolved is to observe the color change of the coating with the naked eye. Because the underlying metal of almost all precious metal coatings is bright or semi-bright nickel coating, it is easy to judge whether the gold coating on the coating is completely dissolved. In order to ensure complete dissolution, the leaching time is extended by 2 minutes on this basis to ensure complete dissolution. Then, the gold chelate ion content in the precious metal leaching solution is measured by ICP-AES inductively coupled atomic emission spectrometer, which is 100.2 mg / L. The residual concentration of gold chelate ions in the solution after electrolysis is measured to be 0.5 mg / L. The concentration is multiplied by the value of each Since the volume of 100.2mg / L×1L=100.2mg=0.100g, it can be calculated that the surface gold content of 5.0kg of luggage decoration parts production waste is 0.100g, 0.5mg / L×1L=0.5mg=0.0005g, the gold content remaining in the liquid after electrolysis can be calculated, that is, the lost gold content is 0.0005g, the theoretical recovery rate of gold = (0.100-0.0005) / 0.100=99.5%. A precision electronic balance is used to weigh 0.097g of the pure sponge gold powder obtained in the above step (3), and the actual recovery rate is 0.097 / 0.100=97%.

[0105] Example 6

[0106] Recovery of platinum from waste platinum-coated titanium anode mesh:

[0107] (1) Prepare a precious metal leaching reagent. The composition of the leaching reagent is shown in the following table. After each component is added to water and stirred to dissolve completely, the pH value is adjusted. Since the waste platinum-plated titanium anode mesh does not contain copper, no copper corrosion inhibitor is added to the leaching reagent in this example.

[0108]

[0109] (2) Leaching: First, weigh 1.0 kg of waste platinum-coated titanium anode mesh, then clean it with water and put it into the leaching reagent. The solid-liquid ratio of the leaching process is determined to be 1 kg:1 L according to the volume of the leached workpiece, that is, the volume of the leaching reagent is 1.0 L;

[0110] The leaching agent is mechanically stirred at 40°C for 60 minutes to dissolve the thin platinum coating on the surface to obtain a precious metal leaching solution. The waste platinum-plated titanium anode mesh is then taken out and placed in a clean water tank for three-stage countercurrent cleaning. The third-stage relatively concentrated cleaning water is reused for the preparation of the leaching agent in step (1). The function is to clean the precious metal-containing leaching agent brought out by the waste platinum-plated titanium anode mesh and prevent the loss of the precious metal-containing leaching agent. Finally, the waste platinum-plated titanium anode mesh is taken out, washed and dried.

[0111] (3) Electrolysis: The concentration of platinum chelate ions in the precious metal leaching solution was measured by ICP-AES inductively coupled atomic emission spectrometer, which was 10.5 mg / L. The solution was then placed in an electrolysis tank and powered on for electrolysis. The anode was a ruthenium-iridium-titanium alloy mesh, the cathode was a 304 stainless steel polished plate, the tank voltage was 2.0 V, and the cathode current density was 10 A / m 2 ;

[0112] After 24 hours of electrolysis, the gold chelate ion content in the electrolysis solution was measured using an ICP-AES inductively coupled atomic emission spectrometer. If the content was less than 0.5 ppm, the electrolysis was terminated. The cathode was removed and the reduced and enriched platinum powder on it was scraped off.

[0113] Since the substrate of the waste platinum-plated titanium anode is metallic titanium, there are no other metal ions in the leaching reagent, but it is still better to add some oxidizing acid for cooking, and then use deionized water to wash, dry and enrich to obtain pure sponge platinum powder.

[0114] After the completion of electrolysis, the post-electrolysis liquid is recycled for the preparation of the next round of leaching reagents. Since the accumulation of impurities will affect the leaching effect, a sodium ion meter is used to measure the concentration of sodium ions in the post-electrolysis liquid. When the impurity accumulation reaches about 150g / L, the post-electrolysis liquid is evaporated and condensed. The condensed water obtained can be used for the preparation of leaching reagents or cleaning processes, which can achieve "zero discharge" of wastewater and the small amount of waste residue generated is centrally treated.

[0115] (4) Determination of platinum recovery rate: The platinum chelate ion content in the precious metal leaching solution was measured by ICP-AES inductively coupled atomic emission spectrometry and was found to be 120.5 mg / L. The platinum content on the surface of the waste platinum-plated titanium anode mesh was 120.5 mg / ⅹ1 L = 120.5 mg = 0.121 g. 0.118 g of the pure sponge platinum powder obtained in step (3) above was weighed using a precision electronic balance. The actual recovery rate was 0.118 / 0.121 = 97.5%.

[0116] Example 7

[0117] Recycling rhodium from scrapped military instrument plug-in components:

[0118] (1) Prepare the leaching reagent for precious metals. The composition of the leaching reagent is shown in the following table. After adding each component into water and stirring to dissolve completely, adjust the pH value.

[0119]

[0120] (2) Leaching: First, weigh 500g of waste plug-in components, then clean them with water and place them in the leaching reagent; the solid-liquid ratio of the leaching process is determined to be 1kg:1L based on the volume of the leached workpiece, that is, the volume of the leaching reagent is 0.5L;

[0121] The leaching agent is mechanically stirred at 40° C. for 60 minutes to dissolve the thin rhodium-plated layer above to obtain a precious metal leaching solution. The waste plug-in components are then removed and placed in a clean water tank for three-stage countercurrent cleaning. The third-stage relatively concentrated cleaning water is reused for the preparation of the leaching agent in step (1). The function is to clean the precious metal leaching solution brought out by the waste plug-in components and prevent the loss of precious metals and leaching agents. Finally, the waste plug-in components are removed, washed and dried.

[0122] (3) Electrolysis: The rhodium chelate ion concentration in the precious metal leaching solution was measured by ICP-AES inductively coupled atomic emission spectrometry and was found to be 10.5 mg / L. This concentration was relatively low, and the actual recovery rate was reduced due to the low concentration. Therefore, two methods were used to increase the rhodium recovery rate: one was to concentrate the leachate by vacuum evaporation, reducing its volume from 1 L to 0.5 L; the other was to extend the electrolysis time and reduce the residual rhodium ion concentration in the leachate after electrolysis to 0.2 ppm.

[0123] The precious metal leaching solution was placed in the electrolytic cell and the power was turned on for electrolytic deposition. The anode was a ruthenium-iridium-titanium alloy mesh, the cathode was a 304 stainless steel polished plate, the cell voltage was 2.0V, and the cathode current density was 10A / m 2 ;

[0124] After 40 hours of electrolysis, the rhodium chelate ion content in the electrolysis solution is measured using an ICP-AES inductively coupled atomic emission spectrometer. If the content is less than 0.2 ppm, the electrolysis is terminated. The cathode is removed, the reduced and enriched rhodium powder on it is scraped off, sulfuric acid and an oxidant are added for cooking, and the solution is washed, dried and enriched with deionized water to obtain pure sponge rhodium powder.

[0125] After the completion of electrolysis, the post-electrolysis liquid is recycled for the preparation of the next round of leaching reagents. Since the accumulation of impurities will affect the leaching effect, a sodium ion meter is used to measure the concentration of sodium ions in the post-electrolysis liquid. When the impurity accumulation reaches about 150g / L, the post-electrolysis liquid is evaporated and condensed. The condensed water obtained can be used for the preparation of leaching reagents or cleaning processes, which can achieve "zero discharge" of wastewater and the small amount of waste residue generated is centrally treated.

[0126] (4) Determination of rhodium recovery: The rhodium chelate ion content in the precious metal leaching solution was measured by ICP-AES inductively coupled atomic emission spectrometry and was found to be 40.8 mg / L. The rhodium content on the surface of the plug-in components of the scrapped military instrument was 40.8 mg / L x 0.5 L = mg = 20.4 mg. 0.0202 g of the pure sponge platinum powder obtained in step (3) above was weighed using a precision electronic balance. The actual recovery rate was 0.020 / 0.0204 = 98.0%.

[0127] Example 8

[0128] Recovering palladium from the surface coating of scrap palladium-plated IC bonding copper wire:

[0129] (1) Prepare the leaching reagent for precious metals. The composition of the leaching reagent is shown in the following table. After adding each component into water and stirring to dissolve completely, adjust the pH value.

[0130]

[0131]

[0132] (2) Leaching: First, weigh 1.0 kg of palladium-plated copper wire, then clean it with water and put it into the leaching reagent. The solid-liquid ratio of the leaching process is determined to be 1 kg:1 L according to the volume of the leached workpiece, that is, the volume of the leaching reagent is 1 L;

[0133] The palladium-plated layer can be dissolved by mechanical stirring at room temperature for 60 minutes to obtain a precious metal leaching solution, and then the waste palladium-plated IC bonding copper wire is taken out and placed in a clean water tank for three-level countercurrent cleaning. The third-level relatively concentrated cleaning water is reused for the preparation of the leaching reagent in step (1), so as to clean the precious metal leaching solution brought out by the waste palladium-plated IC bonding copper wire and prevent the loss of precious metals and leaching reagents. Finally, the waste palladium-plated IC bonding copper wire is taken out, washed and dried.

[0134] (3) Electrolysis: Place the precious metal leaching solution into the electrolysis tank and connect the power supply for electrolysis. The anode is a ruthenium-iridium-titanium alloy mesh, the cathode is a 304 stainless steel polished plate, the tank voltage is 3.0V, and the cathode current density is 25A / m 2 ;

[0135] After 24 hours of electrolysis, the palladium chelate ion content in the electrolysis solution is measured using an ICP-AES inductively coupled atomic emission spectrometer. If the content is less than 0.5 ppm, the electrolysis is terminated. The cathode is removed, the reduced and enriched palladium powder on it is scraped off, and a small amount of dilute sulfuric acid and hydrogen peroxide are added to remove the base metals. The solution is then washed, dried and enriched with deionized water to obtain pure sponge palladium powder.

[0136] The post-electrodeposition liquid can be recycled as a leaching reagent after multiple cycles of failure. After evaporation and condensation treatment, the condensed water can be reused to prepare the leaching reagent, which can achieve "zero discharge" of wastewater and the small amount of waste residue generated can be centrally treated.

[0137] (4) Determination of palladium recovery: The palladium chelate ion content in the precious metal leaching solution was measured using an ICP-AES inductively coupled atomic emission spectrometer and was found to be 210.4 mg / L. The palladium content on the surface of the waste palladium-plated IC bonding copper wire was 210.4 mg / L x 1 L = mg = 210.4 mg. 0.205 g of the pure sponge platinum powder obtained in step (3) above was weighed using a precision electronic balance. The actual recovery rate was 0.205 / 0.210 = 97.6%.

[0138] Example 9

[0139] Recovering silver from the surface coating of waste silver-plated plugs:

[0140] (1) Prepare the leaching reagent for precious metals. The composition of the leaching reagent is shown in the following table. After adding each component into water and stirring to dissolve completely, adjust the pH value.

[0141]

[0142] (2) Leaching: First, weigh 2.0 kg of waste silver-plated plugs, clean them with water, and place them in the leaching reagent. The solid-liquid ratio of the leaching process is determined to be 2 kg:2 L based on the volume of the leached workpiece, that is, the volume of the leaching reagent is 2 L;

[0143] The silver-plated layer can be dissolved by mechanical stirring at room temperature for 60 minutes to obtain a precious metal leaching solution. The waste silver-plated plug is then taken out and placed in a clean water tank for three-stage countercurrent cleaning. The third-stage relatively concentrated cleaning water is reused for the preparation of the leaching reagent in step (1). The function is to clean the precious metal leaching solution brought out by the waste silver-plated plug and prevent the loss of precious metals and leaching reagents. Finally, the waste silver-plated plug is taken out, washed and dried.

[0144] (3) Electrolysis: Place the precious metal leaching solution into the electrolysis tank and connect the power supply for electrolysis. The anode is a ruthenium-iridium-titanium alloy mesh, the cathode is a 304 stainless steel polished plate, the tank voltage is 3.0V, and the cathode current density is 30A / m 2 ;

[0145] After 24 hours of electrolysis, the palladium chelate ion content in the electrolysis solution is measured using an ICP-AES inductively coupled atomic emission spectrometer. If the content is less than 0.5 ppm, the electrolysis is terminated. The cathode is removed, the reduced and enriched silver powder on it is scraped off, and a small amount of dilute sulfuric acid and hydrogen peroxide are added to remove the base metals. The solution is then washed, dried and enriched with deionized water to obtain pure sponge silver powder.

[0146] After the completion of electrolysis, the post-electrolysis liquid is recycled for the preparation of the next round of leaching reagents. Since the accumulation of impurities will affect the leaching effect, a sodium ion meter is used to measure the concentration of sodium ions in the post-electrolysis liquid. When the impurity accumulation reaches about 150g / L, the post-electrolysis liquid is evaporated and condensed. The condensed water obtained can be used for the preparation of leaching reagents or cleaning processes, which can achieve "zero discharge" of wastewater and the small amount of waste residue generated is centrally treated.

[0147] (4) Determination of silver recovery: The silver chelate ion content in the precious metal leaching solution was measured using an ICP-AES inductively coupled atomic emission spectrometer and was found to be 150.6 mg / L. The palladium content on the surface of the waste palladium-plated IC bonding copper wire was 150.6 mg / L x 2 L = mg = 301.2 mg = 0.301 g. 0.205 g of the pure sponge platinum powder obtained in step (3) above was weighed using a precision electronic balance. The actual recovery rate was 0.293 / 0.301 = 97.3%.

[0148] The present invention may be summarized in other specific forms that do not violate the spirit or main features of the present invention. The above embodiments of the present invention are only to be considered as illustrative and not restrictive of the present invention. Therefore, any minor modifications, equivalent variations, and modifications made to the above embodiments based on the essential technology of the present invention are within the scope of the technical solution of the present invention.

Claims

1. A process for selectively leaching, enriching and recovering precious metals from waste precious metal coating materials, characterized in that: The following steps are involved: (1) Preparation of leaching reagents; The leaching reagent includes 12-55 g / L of a noble metal chelating agent, 3-10 g / L of a metal complexing agent, 8-15 g / L of an oxidant, 1-10 g / L of a pH regulator, 1-2 g / L of a promoter, and water, and its pH value is controlled at 9-11; The noble metal chelating agent includes polycyanate and one or more of glycine, alanine, aspartic acid, phenylalanine and lysine; The metal complexing agent is selected from one or more of sodium edetate, sodium gluconate, potassium sodium tartrate, ammonium succinate, ammonium citrate, sodium citrate, and sodium nitrilotriacetate; The oxidant is selected from one or more of hydrogen peroxide, sodium peroxide, calcium peroxide, sodium percarbonate, sodium perborate, calcium peroxide, sodium persulfate, and potassium permanganate; The accelerator is selected from one or more of cerium sulfate, cerium nitrate, ammonium cerium nitrate, cerium chloride, and cerium acetate; (2) Leaching process: The waste precious metal coating material is placed in a leaching reagent for leaching reaction, wherein the precious metal coating is leached through oxidation chelation to form precious metal chelate ions and metal complex ions, and the precious metal is dissolved into the solution to obtain a precious metal leaching solution; (3) Electrolytic process: The precious metal leaching solution is placed in an electrolytic cell and energized for electrolytic deposition, so that the precious metal ions in the solution are precipitated and enriched on the cathode. In the electrolytic process, a ruthenium-iridium-titanium alloy mesh is used as the anode and a stainless steel plate is used as the cathode. The electrolytic cell voltage is 1.5~3.0V and the current density is 10~30A / m 2 ; (4) Extraction of precious metals: When the precious metal ion content in the solution is less than 0.5 ppm, the electrolysis ends, the cathode is removed from the tank, and the precious metals are extracted; (5) Recycling of the post-electrolysis solution: The post-electrolysis solution obtained after the completion of the electrolysis is recycled for the preparation of the leaching reagent in step (1); when the impurities in the post-electrolysis solution accumulate to the point where they affect the leaching effect, it is vacuum-decompressed and concentrated, and the condensed water generated is recovered and used for the preparation of the leaching reagent, thus realizing a closed-loop circulation of the waste liquid.

2. The process for selectively leaching, enriching and recovering precious metals from waste precious metal coating materials according to claim 1, characterized in that: When the waste metal plating material contains metallic copper, the leaching reagent also includes 0.5-1 g / L of a copper corrosion inhibitor; the copper corrosion inhibitor is one or more of benzotriazole, tolyltriazole or mercaptobenzothiazole sodium salt.

3. The process for selectively leaching, enriching and recovering precious metals from waste precious metal coating materials according to claim 2, wherein: The pH regulator is one or more of citric acid, disodium hydrogen phosphate, aminoacetic acid, ammonium chloride, boric acid and sodium hydroxide.

4. The process for selectively leaching, enriching and recovering precious metals from waste precious metal coating materials according to any one of claims 1 to 3, characterized in that: The method further includes a cleaning process; the cleaning process specifically comprises: performing three-stage countercurrent cleaning on the waste precious metal coating material after treatment in step (2), and reusing the concentrated cleaning water of the third stage for the preparation of the leaching reagent in step (1). This process can avoid the loss of precious metals and leaching reagents caused by removing the waste precious metal coating material; the cleaning process uses the condensed water of step (5).

5. The process for selectively leaching, enriching and recovering precious metals from waste precious metal coating materials according to claim 4, wherein: The precious metal is one or more of gold, silver, platinum, palladium and rhodium; the waste precious metal coating material is waste printed circuit boards, electronic connectors, electronic components, decorative craft parts, locks, and luggage zippers containing precious metal coatings.

6. A leaching agent for selectively leaching, enriching and recovering precious metals from waste precious metal coating materials, comprising water, characterized in that: The invention comprises 12-55 g / L of noble metal chelating agent, 3-10 g / L of metal complexing agent, 8-15 g / L of oxidizing agent, 1-10 g / L of pH adjusting agent, and 1-2 g / L of accelerator; the pH value of the leaching agent is 9-11; The noble metal chelating agent includes polycyanate and one or more of glycine, alanine, aspartic acid, phenylalanine and lysine; The metal complexing agent is selected from one or more of sodium edetate, sodium gluconate, potassium sodium tartrate, ammonium succinate, ammonium citrate, sodium citrate, and sodium nitrilotriacetate; The oxidant is selected from one or more of hydrogen peroxide, sodium peroxide, calcium peroxide, sodium percarbonate, sodium perborate, calcium peroxide, sodium persulfate, and potassium permanganate; The accelerator is selected from one or more of cerium sulfate, cerium nitrate, ammonium cerium nitrate, cerium chloride, and cerium acetate; When the scrap metal plating material contains metallic copper, it also includes 0.5~1g / L of copper corrosion inhibitor.

7. The leaching agent for selectively leaching, enriching and recovering precious metals from waste precious metal coating materials according to claim 6, characterized in that: The pH regulator is one or more of citric acid, disodium hydrogen phosphate, aminoacetic acid, ammonium chloride, boric acid and sodium hydroxide; the copper corrosion inhibitor is one or more of benzotriazole, toluenetriazole or mercaptobenzothiazole sodium salt.

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