Method for separating and recycling precious metal in waste platinum group metal catalyst

Abstract

The invention discloses a method for separating and recycling precious metal in a waste platinum group metal catalyst, and belongs to the technical field of waste treatment and resource utilization. According to the method, the characteristics of uniform heating, high heating rate and high heating efficiency of microwave heat treatment are fully utilized, the required temperature can be reached in a short time, the choline chloride / p-toluenesulfonic acid eutectic solvent (DES) is rapidly synthesized, and metal in the waste catalyst is leached by utilizing the eutectic solvent; platinum and palladium enrichment is efficiently and rapidly achieved through DES hydrophilic phase-quaternary ammonium phosphorus salt ionic liquid hydrophobic phase liquid-liquid extraction, palladium is stripped through thiourea and hydrochloric acid, platinum is stripped through nitric acid, and platinum and palladium products are selectively obtained. According to the method, high-pressure (6000 kPa), high-temperature (250 DEG C) and necessary high-temperature (800 DEG C) thermal pretreatment steps and great acid consumption in the traditional hydrometallurgy waste catalyst recovery process are avoided.

Description

Technical Field

[0001] The invention belongs to the technical field of waste treatment and resource utilization, and specifically relates to a method for separating and recovering precious metals in waste platinum group metal catalysts. Background Art

[0002] Platinum group metals (PGMs) are indispensable strategic metal resources in the fields of automobiles, petrochemicals, energy, and national defense equipment. They have unique physical and chemical properties, such as excellent catalytic activity, high conductivity, and chemical stability. Due to these properties, platinum group metals occupy a vital position in many modern industrial and technological applications, including catalysts, electronic products, petroleum refining, and medical applications. Among them, platinum, palladium, and rhodium are particularly important in the fields of automobile exhaust catalytic treatment and petrochemicals.

[0003] At present, PGMs mineral resources are extremely scarce. In 2023, the demand for Pt, Pd, and Rh will increase, but the shortage of supply will further widen the gap between supply and demand. Since 2019, the global production of recycled PGMs has been decreasing year by year. Since catalysts are the most important application area of ​​PGMs, waste catalysts have become the most critical secondary resource type for PGMs. Compared with the average grade of PGMs of about 0.4g / t in the original ore, the PGMs content in waste catalysts is extremely high (100-3000g / t), making it an important strategic material. However, in my country, the recovery of PGMs in waste catalysts accounts for less than 40%, and it is urgent to break through key processing technologies to improve the recycling level of PGMs waste catalysts.

[0004] At present, platinum enrichment from spent PGMs catalysts is mainly achieved through two methods: pyrometallurgy and hydrometallurgy. Pyrometallurgy is a mature metallurgical technology used to extract metals from primary ores as well as various waste materials. After initial physical separation, the waste is mixed with flux (SiO2, CaO, etc.), reducing agent and metal collector (Cu, Fe, etc.) for smelting, and then the precious metals (PGMs) are melted and collected in the concentrate. The PGMs carrier (ceramic, alumina, etc.) is transferred to the slag, and the collector content is less than 0.2%. The concentrate containing PGMs is then cast into anodes for further electrorefining with a recovery rate of up to 99%. However, pyrometallurgy requires continuous and large amounts of waste input to make its operation profitable, and the capital investment of the smelter is high. The presence of high energy consumption, significant emission gases and flux consumption are the main environmental issues for the use of pyrometallurgy for PGMs recovery. Future research should focus on making its operation more sustainable, by reducing energy consumption, waste generation and flux consumption to minimize environmental impact. Hydrometallurgy is another common method for extracting precious metals (PGMs) from spent PGMs catalysts, which has the advantages of low energy consumption and high efficiency. The most commonly used leaching system combines high concentrations of hydrochloric acid and oxidants such as nitric acid, hydrogen peroxide or sodium chlorate, because PGM-chloride complexes are very stable in acidic environments. Hydrometallurgy can be used to extract directly from spent PGMs and recover PGMs in the leachate through solution separation and purification technology. Compared with pyrometallurgy, the advantages of hydrometallurgy include low operating temperature and high extraction efficiency, thereby reducing energy consumption and carbon emissions. In addition, the capital investment in equipment and infrastructure for hydrometallurgy is significantly lower than that for pyrometallurgy. However, hydrometallurgy also has limitations such as chemical reagent consumption and wastewater discharge, which can be reduced by selecting cheap and renewable reagents and applying appropriate wastewater treatment processes. In summary, the total recovery rate of spent PGMs catalysts in my country is low, and the existing pyrometallurgy and hydrometallurgy have certain limitations. A green, efficient and short-process method is urgently needed to achieve PGMs recovery. Summary of the invention

[0005] In view of the above-mentioned shortcomings of the prior art, the present invention provides a method for separating and recovering precious metals in waste platinum group metal catalysts.

[0006] To achieve the above object, the technical solution adopted by the present invention is:

[0007] A method for separating and recovering precious metals from waste platinum group metal catalysts comprises the following steps:

[0008] (1) crushing and grinding the waste platinum group metal catalyst and dissolving it in an HCl solution to obtain a waste catalyst solution;

[0009] (2) then subjecting choline chloride and p-toluenesulfonic acid to a microwave reaction to prepare a deep eutectic solvent;

[0010] (3) mixing a low eutectic solvent, nitric acid, a waste catalyst solution and water, and then subjecting the mixture to microwave reaction, solid-liquid separation, and obtaining an enriched liquid and slag;

[0011] (4) dissolving a quaternary ammonium phosphonium salt (trihexyl (tetradecyl) phosphonium chloride) in toluene to obtain a quaternary ammonium phosphonium salt (trihexyl (tetradecyl) phosphonium chloride solution;

[0012] (5) mixing the enriched liquid and a quaternary ammonium phosphate (trihexyl (tetradecyl) phosphine chloride solution and stirring to extract, and obtaining a hydrophilic phase and a hydrophobic phase after solid-liquid separation;

[0013] (6) adding water to the hydrophobic phase, then adding hydrochloric acid and thiourea to separate palladium, and then adding water and nitric acid to separate platinum, and the final liquid is the hydrophobic phase ionic liquid residue;

[0014] (7) Adding hydrochloric acid to the residual ionic liquid of the hydrophobic phase of step (6) and the hydrophilic phase obtained in step (5) to remove the remaining impurity metals, and washing and purifying them with water for recycling.

[0015] The hydrophilic phase in step (7) of the present invention can be recycled in step (3) after impurities removal to replace the low eutectic solvent in step (3) without affecting the leaching rate and recovery rate of platinum and palladium.

[0016] The residual liquid of the hydrophobic phase ionic liquid in step (7) of the present invention can be recycled in step (5) after impurities are removed to replace the quaternary ammonium phosphonium salt (trihexyl (tetradecyl) phosphine chloride solution in step (5), and will not affect the extraction rate and recovery rate of platinum and palladium.

[0017] As a preferred embodiment of the present invention, the concentration of the HCl solution is 1-9 mol / L; the mass volume ratio of the waste platinum group metal catalyst to the HCl solution is 1 g: (3-5) ml.

[0018] As a preferred embodiment of the present invention, the molar ratio of choline chloride to p-toluenesulfonic acid is 1:1.8.

[0019] As a preferred embodiment of the present invention, in the step (2), the microwave power is 800 W, the temperature is 80° C., the time is 10-30 min, and the rotation speed is 300 rpm.

[0020] The present invention adopts the microwave method to prepare the deep eutectic solvent, which can reduce the generation time and quickly synthesize the deep eutectic solvent. If an ordinary water bath is used, the deep eutectic solvent cannot be generated at the same temperature and time as the microwave, and the time needs to be extended by more than 6 times to achieve the generation of the deep eutectic solvent.

[0021] As a preferred embodiment of the present invention, the volume ratio of the low eutectic solvent, nitric acid and spent catalyst solution is 5:1:1, and the volume ratio of the total volume of the low eutectic solvent, nitric acid and spent catalyst solution to water is 1:1-5.

[0022] As a preferred embodiment of the present invention, in the step (3), the microwave power is 800 W, the temperature is 80° C., and the time is 90-120 min.

[0023] As a preferred embodiment of the present invention, the molar concentration of the quaternary ammonium phosphonium salt (trihexyl (tetradecyl) phosphine chloride in toluene is 0.005-0.05 mol / L, and more preferably, the molar concentration of the quaternary ammonium phosphonium salt (trihexyl (tetradecyl) phosphine chloride in toluene is 0.02 mol / L.

[0024] As a preferred embodiment of the present invention, the concentration ratio of the quaternary ammonium phosphate (trihexyl (tetradecyl) phosphine chloride solution and the enriched solution is 1:1-2.

[0025] As a preferred embodiment of the present invention, in the step (6), the volume ratio of the platinum-palladium metal-enriched hydrophobic phase to water is 1:1; the concentrations of hydrochloric acid and thiourea are 0.5 mol / L and 0.1 mol / L respectively; and the concentration of nitric acid is 1 mol / L.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention adopts DES hydrophilic phase-quaternary ammonium phosphate ionic liquid hydrophobic phase liquid-liquid extraction to efficiently and quickly achieve platinum and palladium enrichment and separation of rhodium, and finally strips palladium by thiourea and hydrochloric acid, and strips platinum by nitric acid, and selectively obtains platinum and palladium products. This method also avoids the high pressure (6000kPa) and high temperature (250°C) and necessary high temperature (800°C) thermal pretreatment steps required in the traditional hydrometallurgical waste catalyst recovery process, as well as the need to consume a large amount of acid. In addition, the low eutectic solvent and ionic liquid used in the present invention can be recycled, avoiding the discharge of a large amount of waste liquid in the traditional wet process. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 A schematic diagram of a method for separating and recovering precious metals from waste platinum group metal catalysts. DETAILED DESCRIPTION

[0028] In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0029] Example 1

[0030] like Figure 1 As shown, a method for separating and recovering precious metals from waste platinum group metal catalysts comprises the following steps:

[0031] (1) Commercially available platinum group metal waste catalysts were crushed, ground into 200 meshes, and dissolved in a 1 mol / L HCl solution to obtain a waste catalyst solution, wherein the solid-liquid ratio of the platinum group metal waste catalyst to the HCl solution was 1 g:3 ml.

[0032] (2) Choline chloride and p-toluenesulfonic acid in a molar ratio of 1:1.8 were mixed in a 100 ml round-bottom flask, and placed in a microwave reactor for reaction at 800 W, 80° C., 300 rpm, and 10 min to obtain a deep eutectic solvent (DES).

[0033] (3) DES, nitric acid, and waste catalyst solution are mixed in a volume ratio of 5:1:1 to obtain a hydrophilic DES phase, and then water is added to obtain a diluted hydrophilic DES phase, wherein the volume ratio of the hydrophilic DES phase to water is 1:2.

[0034] (4) The diluted hydrophilic DES phase was placed in a microwave reactor and mixed at 80°C, 800W, and 120min. The solution system was placed in a microwave reactor for platinum group metal leaching and enrichment. The centrifugal speed was 4000rpm. After centrifugation for 10min, an enriched solution and slag were obtained. The platinum and palladium leaching rates in the enriched solution were 96.45% and 98.94%, respectively.

[0035] (5) Dissolve 0.02 mol / L trihexyl (tetradecyl) phosphine chloride in toluene.

[0036] (6) The enriched liquid and trihexyl (tetradecyl) phosphine chloride solution were mixed, stirred at a stirring rate of 300 rpm for 20 min for extraction, and centrifuged at a centrifugal speed of 4000 rpm for 10 min for solid-liquid separation to obtain a hydrophilic DES phase and a hydrophobic phase. Platinum and palladium were in the hydrophobic ionic liquid phase, and the extraction rates of platinum and palladium were 94.89% and 95.91%, respectively.

[0037] (7) An equal volume of water was added to the hydrophobic phase, and then 0.5 mol / L hydrochloric acid and 0.1 mol / L thiourea were added to strip the palladium and filtrate. An equal volume of water and 1 mol / L nitric acid were added to the filtrate to strip the platinum and ionic liquid. The stripping rates of platinum and palladium were 98.85% and 98.69%, respectively.

[0038] (8) The residual liquid of the hydrophilic and hydrophobic phases is purified by centrifugation with water and 5 mol / L HCl and then recycled.

[0039] In Example 1, the recovery rates of platinum and palladium were 95.34% and 94.65%, respectively.

[0040] Table 1 Chemical composition of spent PGMs catalysts

[0041]

[0042] (*Unit is g / t)

[0043] Example 2

[0044] like Figure 1 As shown, a method for separating and recovering precious metals from waste platinum group metal catalysts comprises the following steps:

[0045] (1) A waste platinum group metal catalyst (chemical composition is shown in Table 1) was crushed, ground into 200 meshes, and dissolved in a 1 mol / L HCl solution to obtain a waste catalyst solution, wherein the solid-liquid ratio of the waste platinum group metal catalyst to the HCl solution was 1 g:5 ml.

[0046] (2) Choline chloride and p-toluenesulfonic acid in a molar ratio of 1:1.8 were mixed in a 100 ml round-bottom flask, and placed in a microwave reactor for reaction at 800 W, 80° C., 300 rpm, and 10 min to obtain a deep eutectic solvent (DES).

[0047] (3) DES, nitric acid, and waste catalyst solution are mixed in a volume ratio of 5:1:1 to obtain a hydrophilic DES phase, and then water is added to obtain a diluted hydrophilic DES phase, wherein the volume ratio of the hydrophilic DES phase to water is 1:1.

[0048] (4) The diluted hydrophilic DES phase was placed in a microwave reactor and mixed at 80°C, 800W, and 120min. The solution system was placed in a microwave reactor for platinum group metal leaching and enrichment. The centrifugal speed was 4000rpm. After centrifugation for 10min, an enriched solution and slag were obtained. The platinum and palladium leaching rates in the enriched solution were 94.64% and 98.92%, respectively.

[0049] (5) Dissolve 0.02 mol / L trihexyl (tetradecyl) phosphine chloride in toluene.

[0050] (6) The enriched liquid and trihexyl (tetradecyl) phosphine chloride solution were mixed, stirred at a stirring rate of 300 rpm for 20 min for extraction, and centrifuged at a centrifugal speed of 4000 rpm for 10 min for solid-liquid separation to obtain a hydrophilic DES phase and a hydrophobic phase. Platinum and palladium were in the hydrophobic ionic liquid phase, and the extraction rates of platinum and palladium were 98.98% and 99.03%, respectively.

[0051] (7) An equal volume of water was added to the hydrophobic phase, and then 0.5 mol / L hydrochloric acid and 0.1 mol / L thiourea were added to strip the palladium and filtrate. An equal volume of water and 1 mol / L nitric acid were added to the filtrate to strip the platinum and liquid. The stripping rates of platinum and palladium were 98.97% and 98.94%, respectively.

[0052] In Example 2, the recovery rates of platinum and palladium are 97.96% and 98.34%, respectively.

[0053] Example 3

[0054] like Figure 1 As shown, a method for separating and recovering precious metals from waste platinum group metal catalysts comprises the following steps:

[0055] (1) A waste platinum group metal catalyst (chemical composition is shown in Table 1) was crushed, ground into 200 meshes, and dissolved in a 1 mol / L HCl solution to obtain a waste catalyst solution, wherein the solid-liquid ratio of the waste platinum group metal catalyst to the HCl solution was 1 g:4 ml.

[0056] (2) Choline chloride and p-toluenesulfonic acid in a molar ratio of 1:1.8 were mixed in a 100 ml round-bottom flask, and placed in a microwave reactor for reaction at 800 W, 80° C., 300 rpm, and 10 min to obtain a deep eutectic solvent (DES).

[0057] (3) DES, nitric acid, and waste catalyst solution are mixed in a volume ratio of 5:1:1 to obtain a hydrophilic DES phase, and then water is added to obtain a diluted hydrophilic DES phase, wherein the volume ratio of the hydrophilic DES phase to water is 1:2.

[0058] (4) The diluted hydrophilic DES phase was placed in a microwave reactor and mixed at 80°C, 800W, and 120min. The solution system was placed in a microwave reactor for platinum group metal leaching and enrichment. The centrifugal speed was 4000rpm. After centrifugation for 10min, an enriched solution and slag were obtained. The leaching rates of platinum and palladium in the enriched solution were 94.45% and 99.31%, respectively.

[0059] (5) Dissolve 0.05 mol / L trihexyl (tetradecyl) phosphine chloride in toluene.

[0060] (6) The enriched liquid and trihexyl (tetradecyl)phosphine chloride solution were mixed, stirred at a stirring rate of 300 rpm for 15 minutes for extraction, and centrifuged at a centrifugal speed of 4000 rpm for 10 minutes for solid-liquid separation to obtain a hydrophilic DES phase and a hydrophobic phase. Platinum and palladium were in the hydrophobic ionic liquid phase, and the extraction rates of platinum and palladium were 91.35% and 82.77%, respectively.

[0061] (7) An equal volume of water was added to the hydrophobic phase, and then 0.5 mol / L hydrochloric acid and 0.1 mol / L thiourea were added to strip the palladium and filtrate. An equal volume of water and 1 mol / L nitric acid were added to the filtrate to strip the platinum and liquid. The stripping rates of platinum and palladium were 99.25% and 98.72%, respectively.

[0062] In Example 3, the recovery rates of platinum and palladium are 93.74% and 98.03%, respectively.

[0063] Example 4

[0064] The method for separating and recovering precious metals from waste platinum group metal catalysts described in this embodiment is different from that in embodiment 1 in that: the DES in step (3) is replaced by the hydrophilic DES phase obtained in step (6) in embodiment 1 which has been used once;

[0065] The trihexyl (tetradecyl)phosphine chloride solution in step (6) used once is replaced with the ionic liquid obtained in step (7) in Example 1;

[0066] In step (4), the leaching rates of platinum and palladium in the enriched solution are 94.45% and 98.31%, respectively.

[0067] In step (6), the extraction rates of platinum and palladium are 91.37% and 94.68%, respectively.

[0068] In step (7), the stripping rates of platinum and palladium are 99.27% ​​and 99.33%, respectively.

[0069] In Example 2, the recovery rates of platinum and palladium are 84.69% and 92.64%, respectively.

[0070] Example 5

[0071] The method for separating and recovering precious metals from waste platinum group metal catalysts described in this embodiment is different from that in embodiment 1 in that: the DES in step (3) is replaced by the hydrophilic DES phase obtained in step (6) of embodiment 1 which is reused 4 times;

[0072] The trihexyl (tetradecyl)phosphine chloride solution in step (6) is replaced by the liquid obtained in step (7) in Example 1 which is reused 4 times;

[0073] In step (4), the leaching rates of platinum and palladium in the enriched solution are 93.88% and 96.79%, respectively.

[0074] In step (6), the extraction rates of platinum and palladium are 94.65% and 93.98%, respectively.

[0075] In step (7), the stripping rates of platinum and palladium are 98.91% and 99.14%, respectively.

[0076] In Example 2, the recovery rates of platinum and palladium are 87.88% and 90.18%, respectively.

[0077] By comparing Examples 4 and 5 with Examples 1-3, it can be seen that the recycled hydrophilic DES phase - trihexyl (tetradecyl) phosphine chloride solution has little effect on the liquid-liquid extraction rate, leaching rate, stripping rate and recovery rate of platinum and palladium.

[0078] Comparative Example 1

[0079] The only difference between the method for separating and recovering precious metals from waste platinum group metal catalysts in this comparative example and that in Example 1 is that the concentration of the HCl solution in step (1) is different, and the concentration of the HCl solution is 0.1 mol / L.

[0080] In step (4), the leaching rates of platinum and palladium in the enriched solution are 30.53% and 38.69%, respectively.

[0081] In step (6), the extraction rates of platinum and palladium are 96.78% and 98.44%, respectively.

[0082] In step (7), the stripping rates of platinum and palladium are 98.63% and 98.47%, respectively.

[0083] In Comparative Example 1, the recovery rates of platinum and palladium were 28.17% and 37.50%, respectively.

[0084] Comparative Example 2

[0085] The only difference between the method for separating and recovering precious metals from waste platinum group metal catalysts in this comparative example and that in Example 1 is that the concentration of the HCl solution in step (1) is different, and the concentration of the HCl solution is 2 mol / L.

[0086] In step (4), the leaching rates of platinum and palladium in the enriched solution are 95.73% and 98.29%, respectively.

[0087] In step (6), the extraction rates of platinum and palladium are 90.28% and 92.65%, respectively.

[0088] In step (7), the stripping rates of platinum and palladium are 98.79% and 98.66%, respectively.

[0089] In Comparative Example 2, the recovery rates of platinum and palladium were 85.37% and 88.30%, respectively.

[0090] By comparing Comparative Examples 1 and 2 with Example 1, it can be seen that the HCl concentration has a certain influence on the microwave leaching and extraction of platinum and palladium. Too low HCl concentration will greatly reduce the leaching rate of platinum and palladium, resulting in a great reduction in the recovery rate of platinum and palladium. Too high HCl concentration will reduce the extraction rate of platinum and palladium, resulting in a reduction in the recovery rate of platinum and palladium.

[0091] Comparative Example 3

[0092] The only difference between the method for separating and recovering precious metals from waste platinum group metal catalysts in this comparative example and that in Example 1 is that in step (4), the leaching reactor is different. The leaching reactor in this comparative example is a muffle furnace, and platinum group metal leaching and enrichment are carried out at 80°C for 120 min, the centrifugal speed is 4000 rpm, and the centrifugation is carried out for 10 min.

[0093] In step (4), the leaching rates of platinum and palladium in the enriched solution are 60.75% and 64.31%, respectively.

[0094] In step (6), the extraction rates of platinum and palladium are 95.27% and 95.88%, respectively.

[0095] In step (7), the stripping rates of platinum and palladium are 99.34% and 99.17%, respectively.

[0096] In Comparative Example 3, the recovery rates of platinum and palladium are 57.49% and 61.14%, respectively.

[0097] By comparing Example 1 and Comparative Example 3, it can be seen that compared with the conventional reactor, the microwave reactor has a greatly improved platinum and palladium leaching rate and a greatly improved recovery rate under the same reaction time, temperature and other conditions through a microwave-enhanced leaching process.

[0098] Comparative Example 4

[0099] The only difference between the method for separating and recovering precious metals from waste platinum group metal catalysts in this comparative example and that in Example 1 is that the low eutectic solvents in steps (2) and (3) are different. In this comparative example, the low eutectic solvent is prepared by mixing trioctylphosphine oxide and 1-butyric acid in a concentration ratio of 1:1 in a 100 ml round-bottom flask, placing the mixture in a microwave reactor and reacting at 800 W, 80 ° C, 300 rpm, and 10 min to obtain a low eutectic solvent (DES).

[0100] In step (4), the leaching rates of platinum and palladium in the enriched solution are 86.19% and 85.56%, respectively.

[0101] In step (6), the extraction rates of platinum and palladium are 92.85% and 95.02%, respectively.

[0102] In step (7), the stripping rates of platinum and palladium are 99.27% ​​and 99.35%, respectively.

[0103] In Comparative Example 4, the recovery rates of platinum and palladium were 79.44% and 80.77%, respectively.

[0104] Comparative Example 5

[0105] The only difference between the method for separating and recovering precious metals from waste platinum group metal catalysts in this comparative example and that in Example 1 is that the trihexyl (tetradecyl) phosphine chloride in step (5) is replaced with an equal concentration of trihexyl (tetradecyl) phosphonium bromide.

[0106] In step (4), the leaching rates of platinum and palladium in the enriched solution are 94.31% and 97.94%, respectively.

[0107] In step (6), the extraction rates of platinum and palladium are 81.23% and 84.09%, respectively.

[0108] In step (7), the stripping rates of platinum and palladium are 99.09% and 99.14%, respectively.

[0109] In Comparative Example 5, the recovery rates of platinum and palladium were 75.91% and 81.64%, respectively.

[0110] By comparing Example 1 with Comparative Examples 4 and 5, it can be seen that the highest recovery rate of platinum and palladium can be obtained by synergistically carrying out platinum and palladium leaching, extraction and stripping with choline chloride-p-toluenesulfonic acid and trihexyl (tetradecyl) phosphonium chloride.

[0111] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A method for separating and recovering precious metals from waste platinum group metal catalysts, characterized in that: The steps include: (1) crushing and grinding the waste platinum group metal catalyst and dissolving it in an HCl solution to obtain a waste catalyst solution; (2) then subjecting choline chloride and p-toluenesulfonic acid to a microwave reaction to prepare a deep eutectic solvent; (3) mixing a low eutectic solvent, nitric acid, a waste catalyst solution and water, and then subjecting the mixture to microwave reaction, solid-liquid separation, and obtaining an enriched liquid and slag; (4) dissolving a quaternary ammonium phosphonium salt (trihexyl (tetradecyl) phosphonium chloride) in toluene to obtain a quaternary ammonium phosphonium salt (trihexyl (tetradecyl) phosphonium chloride solution; (5) mixing the enriched liquid and a quaternary ammonium phosphate (trihexyl (tetradecyl) phosphine chloride solution and stirring to extract, and obtaining a hydrophilic phase and a hydrophobic phase after solid-liquid separation; (6) adding water to the hydrophobic phase, then adding hydrochloric acid and thiourea to separate palladium, and then adding water and nitric acid to separate platinum, and finally obtaining a liquid as a hydrophobic phase ionic liquid residue; (7) Adding hydrochloric acid to the residual ionic liquid of the hydrophobic phase of step (6) and the hydrophilic phase obtained in step (5) to remove the remaining impurity metals, and washing and purifying them with water for recycling.

2. The method for separating and recovering precious metals from waste platinum group metal catalysts is characterized by: The concentration of the HCl solution is 1-9 mol / L; the solid-liquid ratio of the waste platinum group metal catalyst to the HCl solution is 1 g: (3-5) ml.

3. The method for separating and recovering precious metals from waste platinum group metal catalysts according to claim 1, characterized in that: The molar ratio of the choline chloride to p-toluenesulfonic acid is 1:1.5-2.

4. The method for separating and recovering precious metals from waste platinum group metal catalysts according to claim 1, characterized in that: In the step (2), the microwave power is 800 W, the temperature is 80° C., the time is 10-30 min, and the rotation speed is 300 rpm.

5. The method for separating and recovering precious metals from waste platinum group metal catalysts according to claim 1, characterized in that: The volume ratio of the low eutectic solvent, nitric acid and the spent catalyst solution is 5:1:1, and the volume ratio of the total volume of the low eutectic solvent, nitric acid and the spent catalyst solution to water is 1:1-5.

6. The method for separating and recovering precious metals from waste platinum group metal catalysts according to claim 1, characterized in that: In the step (3), the microwave power is 800 W, the temperature is 80° C., and the time is 90-120 min.

7. The method for separating and recovering precious metals from waste platinum group metal catalysts according to claim 1, characterized in that: The molar concentration of the quaternary ammonium phosphonium salt (trihexyl (tetradecyl) phosphine chloride) dissolved in toluene is 0.005-0.05 mol / L.

8. The method for separating and recovering precious metals from waste platinum group metal catalysts according to claim 1, characterized in that: The volume ratio of the quaternary ammonium phosphate (trihexyl (tetradecyl) phosphine chloride solution to the enriched solution is 1:1-2.

9. The method for separating and recovering precious metals from waste platinum group metal catalysts according to claim 1, characterized in that: In the step (6), the volume ratio of the platinum-palladium metal-enriched hydrophobic phase to water is 1:1; the concentrations of hydrochloric acid and thiourea are 0.5 mol / L and 0.1 mol / L, respectively; and the concentration of nitric acid is 1 mol / L.

10. The method for separating and recovering precious metals from waste platinum group metal catalysts according to claim 1, characterized in that: In the step (7), the molar concentration of HCl is 3-5 mol / L.

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