Method for recovering platinum group metal by activating platinum group waste catalyst and ILs through zinc steam

Abstract

The invention discloses a method for recovering platinum group metal by activating a platinum group waste catalyst and ILs through zinc steam, and belongs to the field of metallurgical solid waste resource utilization. According to the method, zinc steam activation roasting pretreatment and microwave acid leaching enrichment of the platinum group metal are adopted, the platinum group metal is subjected to two-stage extraction through trihexyl (tetradecyl) phosphonium chloride and bis (2-ethylhexyl) phosphate ionic liquid IL extraction, and then extraction and separation of the platinum group metal are achieved through sodium sulfite, hydrogen chloride, thiourea, nitric acid and sulfuric acid in sequence. According to the method, efficient separation of platinum, palladium and rhodium is achieved through reusable ILs extraction, platinum, palladium and rhodium with the purity as high as 98% are obtained, a new green and environment-friendly way is provided for the platinum, palladium and rhodium waste catalyst, and the method has very high application value.

Description

Technical Field

[0001] The present invention belongs to the technical field of resource utilization of waste treatment agents, and more specifically relates to a method for activating platinum group catalysts with zinc vapor and extracting and separating platinum group metals with ionic liquids. Background Art

[0002] Platinum group metals (PGMs) are a group of metals with low abundance in the Earth's crust but high market value. Their unique properties make them indispensable for industrial applications. PGMs not only possess typical transition metal properties such as catalytic activity, paramagnetism, and an exotropic tendency to form complexes, but also possess high melting points, low vapor pressures, and resistance to thermal corrosion. To date, researchers have discovered over 120 PGM minerals, but the average grade among these minerals is relatively low, at 0.4 gt. -1 Platinum group metal minerals are widely used in various fields, among which the automotive and petroleum industries are the main consumption areas for the reduction of carbon oxides, nitrogen oxides and reduction, reforming, hydroisomerization and conversion processes respectively.

[0003] Currently, the primary technologies for recovering platinum group metals (PGMs) from end-of-life materials such as automotive catalysts and electrical and electronic equipment rely on pyrometallurgical and hydrometallurgical processes. The pyrometallurgical process involves smelting the catalyst support or ceramic material in a reducing atmosphere at high temperatures in a specialized furnace. The addition of a flux reduces the metal compounds to their metallic form and induces vitrification of the substrate at a lower temperature. The PGMs are recovered from the support material slag as particulate matter and further enriched using collector metals with a strong affinity for the PGMs, such as Cu, Fe, Ni, or Pb. High-purity PGMs are ultimately obtained through electrolytic refining and other methods. Pyrometallurgical processes employing copper collectors offer rapid processing, high recovery rates, and even higher rhodium recovery rates. However, precious metal purification is a complex process that generates significant amounts of wastewater, resulting in secondary environmental impacts, and copper is expensive. Iron is an inexpensive collector, and the significant density difference between platinum group metals (PGMs) and slag allows for easy separation of PGMs. However, higher temperatures are required within the system, and there is a potential for SiO2 reduction to Si and subsequent formation of iron-silicon alloys. This makes acid hydrolysis difficult, hindering PGM recovery. Pyrometallurgical methods have numerous drawbacks, including high energy consumption and the production of large quantities of volatile and toxic combustion products. Hydrometallurgical methods, on the other hand, do not require high temperatures and offer relatively low costs at both small and large scales, while maintaining high efficiency and manageable processes. Hydrometallurgy requires pretreatment to maximize precious metal (PGM) leaching capacity, followed by selective dissolution using mineral acids with the addition of oxidants, extraction using extractants (alkylamines, alkyl sulfoxides, organophosphorus compounds, or pyridine derivatives), and finally, selective stripping of PGMs using chemicals such as mineral acids, ammonia, and thiourea. However, traditional hydrometallurgy also presents limitations, including high chemical reagent consumption and wastewater discharge. Therefore, the total recovery rate of waste PGMs catalysts in my country is low, and the existing pyrometallurgy and hydrometallurgy both have certain limitations. There is an urgent need for a green, efficient, and short-process method to achieve PGMs recovery.

[0004] Cyphos IL 101 and Aliquat 336 ionic liquids are increasingly being used to extract platinum group metals from aqueous solutions. Ionic liquids are known as "green solvents" due to their low volatility, non-flammability, and renewability. Furthermore, their ability to dissolve a wide range of substances has led to their application in organic synthesis, pharmaceutical production, catalysis, liquid chromatography, and electrochemistry. While ionic liquids are increasingly popular due to their high market availability and structural diversity, classic ionic liquids do not always exhibit selectivity for specific PGM complexes. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for recovering platinum group metals by zinc vapor activation of waste platinum group catalysts and ILs, so as to solve the problems existing in the above-mentioned prior art and provide a greener, more efficient and simple method for recovering waste PGMs catalysts, thereby achieving the enrichment and separation of platinum, palladium and rhodium in waste PGMs catalysts. The charged particles in the prepared ionic liquid ILs provide stronger interaction between the active ligands in the organic phase and the PGM molecules in the aqueous phase, thereby achieving efficient separation of platinum group chloride complexes.

[0006] A method for recovering platinum group metals by activating waste platinum group catalysts and ILs using zinc vapor comprises the following steps: (1) The spent PGMs catalyst and zinc powder are mixed and ball-milled, and then calcined. The calcined solid phase is further ball-milled, and a mixed solution of HCl and H2O2 is added for acid leaching, and centrifuged to obtain a PGMs supernatant; (2) Trihexyl (tetradecyl) phosphine chloride and bis (2-ethylhexyl) phosphate are mixed and then added with a solvent to react to obtain ionic liquids ILs; (3) The PGMs supernatant in step (1) is mixed with ionic liquid ILs, extracted, and centrifuged to obtain platinum group enriched ionic liquid ILs, and then passed through Na2SO3, HCl and thiourea, HNO3, and H2SO4 in sequence to strip metal Fe, Pd, Pt, copper, and zinc in sequence; (4) Zinc powder was added to the copper-zinc mixed liquid to separate Cu, Zn and residual Rh liquid; the residual Rh liquid was extracted by microwave by mixing ionic liquid ILs and hydrochloric acid solution. After solid-liquid separation, Na2SO3 and HCl were added to the liquid phase in sequence to separate and strip Fe and Rh, respectively.

[0007] Preferably, in step (1), the weight ratio of the waste platinum group catalyst to the zinc powder is (2-1):1, the microwave power is 800W, the calcination temperature is 500-700°C, and the calcination time is 2-4 hours. More preferably, the calcination time is 2 hours and the calcination temperature is 600°C.

[0008] Preferably, in the step (1), the solid phase material after the waste PGMs catalyst and zinc powder are mixed and calcined is ball-milled to a size of 200 mesh.

[0009] Preferably, in step (1), the molar concentration of HCl in the mixed solution of HCl and H2O2 is 1-2 mol / L, and the mass percentage of H2O2 is 1-5%. The solid-liquid ratio of the calcined solid phase added to the mixed solution of HCl and H2O2 is 1 g:5 ml.

[0010] Preferably, the microwave acid leaching temperature in step (1) is 70° C., the microwave power is 600 W, and the microwave acid leaching time is 1-4 hours. More preferably, the microwave acid leaching time is 2 hours.

[0011] Changing only the microwave-assisted leaching phase and the reaction time of the prepared ILs had little effect on the recovery of platinum, palladium, and rhodium. However, the duration of the secondary extraction (i.e., microwave extraction of the residual Rh solution using a mixture of ionic liquid ILs and hydrochloric acid) significantly affected rhodium recovery. This is because rhodium is more difficult to extract than platinum and palladium, so a longer extraction time is beneficial for its extraction.

[0012] Preferably, in step (2), the mass ratio of bis(2-ethylhexyl) phosphate to trihexyl(tetradecyl)phosphine chloride is 1:(0.7-1); and the solvent is a mixed solution of water and ethanol in a volume ratio of 1:1.

[0013] Because Cyphos IL 101 or Aliquat 336 ionic liquids cannot selectively separate the precious metals from the spent PGMs catalysts described in the present invention, the present invention creatively combines the leaching of spent PGMs catalysts with an ionic liquid prepared from trihexyl(tetradecyl)phosphine chloride and bis(2-ethylhexyl)phosphate, along with zinc vapor activation and microwave acid leaching, to synergistically achieve the separation of precious metals, resulting in significantly higher recovery and purity of the precious metals.

[0014] Preferably, in step (3), the volume ratio of the PGMs supernatant to the ionic liquid ILs is (2-1):1, the speed of microwave extraction is 100-300 rpm, the reaction time is 20-40 min, the power is 500-100 W, and the speed is 300 rpm.

[0015] Preferably, in step (3), the concentration of Na2SO3 is 0.5-1 mol / L, the concentration of HCl is 0.5-2 mol / L, the concentration of thiourea is 0.1-0.5 mol / L, the concentration of HNO3 is 1-10 mol / L, and the concentration of H2SO4 is 1-5 mol / L.

[0016] Preferably, in step (4), 1-5% by mass of zinc powder is added to the copper-zinc mixed liquid.

[0017] Preferably, in step (4), the volume ratio of the residual Rh solution to the ionic liquid ILs is (2-1):1, the ionic liquid ILs and the hydrochloric acid solution are mixed to a hydrochloric acid concentration of 1-2 mol / L, the microwave extraction temperature is 20±2°C, the time is 2h, the power is 300-600W, and the speed is 300rpm.

[0018] The present invention adopts zinc vapor activation roasting pretreatment and microwave acid leaching to enrich platinum group metals, prepares trihexyl (tetradecyl) phosphine chloride (P[6,6,6,14]Cl) and bis (2-ethylhexyl) phosphate (B2EHP) ionic liquids ILs, and extracts platinum group metals twice through ionic liquid ILs. Finally, the platinum group metals are extracted and stripped by using chemicals such as sodium sulfite, HCl, thiourea, HNO3, and H2SO4.

[0019] The preparation method of the present invention can reach the required temperature in a short time, strengthen the microwave roasting and microwave acid leaching processes, and quickly synthesize trihexyl (tetradecyl) phosphine chloride (P[6,6,6,14]Cl) and bis (2-ethylhexyl) phosphate (B2EHP) ionic liquids ILs.

[0020] The method for activating waste platinum group catalysts using zinc vapor and recovering platinum group metals using ILs according to the present invention can reuse ILs for extraction, thereby achieving efficient separation of platinum, palladium, and rhodium and obtaining a recovered solution of platinum, palladium, and rhodium with a purity higher than 98%.

[0021] Compared with the prior art, the present invention has the following advantages: (1) The present invention ball-mills zinc powder and waste platinum group waste catalysts, thereby achieving enhanced zinc vapor roasting pretreatment and microwave acid leaching of waste platinum catalysts in a short period of time, thereby increasing the rhodium recovery rate to more than 64%.

[0022] (2) The present invention provides a greener, more efficient and shorter process for the recovery of waste PGMs catalysts by preparing ionic liquids ILs for secondary extraction of waste PGMs catalysts. The charged particle active ligands of the ionic liquids ILs in the organic phase provide stronger interactions with the PGM molecules in the aqueous phase, thereby achieving efficient separation of platinum group chloride complexes and realizing the enrichment and separation of platinum, palladium and rhodium in the platinum group chloride complexes of the waste PGMs catalysts.

[0023] (3) The present invention improves the recovery rate of platinum group metals platinum, palladium and rhodium after the synergistic effect of zinc vapor activation, microwave acid leaching and ionic liquid. The recovery rate of palladium is as high as over 90%, the recovery rate of platinum is as high as over 94%, and the recovery rate of rhodium is increased by 20% (compared with the direct use of ionic liquid leaching-extraction process without zinc vapor activation). The purity of the separated platinum, palladium and rhodium exceeds 98%, 98% and 99%, respectively. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The present invention is a process flow chart of a method for recovering platinum group metals by activating spent platinum group catalysts and ILs using zinc vapor. DETAILED DESCRIPTION

[0025] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0026] It should be understood that the terms described herein are intended only to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges herein, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. The intermediate value within any stated value or stated range, and each smaller range between any other stated value or intermediate value within the stated range, is also encompassed within the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0027] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of any conflict with any incorporated document, the contents of this specification shall prevail.

[0028] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the description of the invention. The description and examples are intended to be illustrative only.

[0029] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0030] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments, but the protection scope of the present invention is not limited to the contents described above. Example 1

[0031] A method for recovering platinum group metals by activating waste platinum group catalysts and ILs using zinc vapor comprises the following steps: (1) Commercially available waste PGMs catalyst (composition see Table 1) and zinc powder were mixed in a mass ratio of 1:1 and calcined at 600°C for 2 h in an 800 W microwave reactor to obtain a pretreated solid phase; the pretreated solid phase was mixed with a mixed solution of 1 mol / L HCl and 1% mass percentage H2O2 at a solid ratio of 1 g:5 mL, then placed in a 600 W microwave reactor and microwave-leached at 70°C for 2 h, and then centrifuged at 3000 rpm for 5 min for solid-liquid separation to obtain a microwave acid-leached liquid phase and a microwave acid-leached solid phase.

[0032] (2) Dissolve 50 g of trihexyl (tetradecyl) phosphine chloride and 35 g of bis (2-ethylhexyl) phosphate (B2EHP) in a mixed solution of 50 mL of water and 50 mL of ethanol, place it in a microwave reactor and react at 70 ° C for 15 min to obtain light yellow viscous ionic liquid ILs.

[0033] (3) The microwave acid extraction liquid phase and the light yellow viscous ionic liquid ILs were mixed in a volume ratio of 2:1 and placed in a microwave reactor. The reaction extraction was carried out at a power of 300 W, a speed of 300 rpm / min, and 20±2°C for 20 min. Then, the mixture was centrifuged at a speed of 3500 rpm for 5 min, and solid-liquid separation was performed to obtain ILs enriched with PGMs.

[0034] (4) The PGMs-enriched ILs were sequentially stripped of Fe using 1 mol / L Na2SO3 solution, Pd using a mixed solution of 0.5 mol / L hydrochloric acid and 0.1 mol / L thiourea, Pt using 5 mol / L nitric acid solution, and Cu-Zn mixed liquid using 3 mol / L sulfuric acid solution. 2% by mass of zinc powder was added to the Cu-Zn mixed liquid for replacement separation to obtain copper, zinc, and residual Rh-containing liquid.

[0035] (5) The residual Rh-containing liquid and unused ILs were placed in a reactor at a volume ratio of 2:1, and then HCl solution was added to dilute the HCl concentration to 2 mol / L. The mixture was subjected to microwave extraction at 20±2°C, a speed of 300 rpm, and a power of 600 W for 2 h. After extraction, the mixture was centrifuged at 3500 rpm for 5 min for solid-liquid separation to obtain Rh-rich liquid ILs. The Rh-rich liquid ILs were then subjected to 1 mol / L Na2SO3 and 5 mol / L HCl to separate iron and rhodium, respectively. The final liquid was liquid ILs.

[0036] In this embodiment, the final recovery rates of platinum, palladium and rhodium are 94.95%, 90.36% and 64.89%, respectively. After stripping, the purities of platinum, palladium and rhodium are 98%, 98% and 99%, respectively.

[0037] Table 1 Chemical composition of spent PGMs catalysts Example 2

[0038] A method for recovering platinum group metals by activating waste platinum group catalysts and ILs using zinc vapor comprises the following steps: (1) Waste PGMs catalyst (composition see Table 1) and zinc powder were mixed in a mass ratio of 1:1 and calcined at 600°C for 2 h in an 800 W microwave reactor to obtain a pretreated solid phase; the pretreated solid phase was mixed with a mixed solution of 2 mol / L HCl and 1% by mass of H2O2 at a solid ratio of 1 g:5 mL, then placed in a 600 W microwave reactor and microwave-leached at 70°C for 2 h, and then centrifuged at 3000 rpm for 5 min for solid-liquid separation to obtain a microwave acid-leached liquid phase and a microwave acid-leached solid phase.

[0039] (2) Dissolve 50 g of trihexyl (tetradecyl) phosphine chloride and 35 g of bis (2-ethylhexyl) phosphate (B2EHP) in a mixed solution of 50 mL of water and 50 mL of ethanol, place it in a microwave reactor and react at 70 ° C for 15 min to obtain light yellow viscous ionic liquid ILs.

[0040] (3) The microwave acid extraction liquid phase and the light yellow viscous ionic liquid ILs were mixed in a volume ratio of 2:1 and placed in a microwave reactor. The reaction extraction was carried out at a power of 300 W, a speed of 300 rpm / min, and 20±2°C for 20 min. Then, the mixture was centrifuged at a speed of 3500 rpm for 5 min, and solid-liquid separation was performed to obtain ILs enriched with PGMs.

[0041] (4) The PGMs-enriched ILs were sequentially stripped of Fe using 1 mol / L Na2SO3 solution, Pd using a mixed solution of 0.5 mol / L hydrochloric acid and 0.1 mol / L thiourea, Pt using 5 mol / L nitric acid solution, and Cu-Zn mixed liquid using 3 mol / L sulfuric acid solution. 2% by mass of zinc powder was added to the Cu-Zn mixed liquid for replacement separation to obtain copper, zinc, and residual Rh-containing liquid.

[0042] (5) The residual Rh-containing liquid and unused ILs were placed in a reactor at a volume ratio of 2:1, and then HCl solution was added to dilute the concentration to 2 mol / L. The mixture was subjected to microwave extraction at 20±2°C, a speed of 300 rpm, and a power of 600 W for 2 h. After extraction, the mixture was centrifuged at 3500 rpm for 5 min for solid-liquid separation to obtain Rh-rich liquid ILs. The Rh-rich liquid ILs were then subjected to 1 mol / L Na2SO3 and 5 mol / L HCl to separate iron and rhodium, respectively. The final liquid was liquid ILs.

[0043] In this embodiment, the final recovery rates of platinum, palladium and rhodium are 86.68%, 89.19% and 62.49%, respectively. After stripping, the purities of platinum, palladium and rhodium are 95%, 96% and 93%, respectively. Example 3

[0044] A method for recovering platinum group metals by activating waste platinum group catalysts and ILs using zinc vapor comprises the following steps: (1) Waste PGMs catalyst (composition see Table 1) and zinc powder were mixed in a mass ratio of 1:1 and calcined at 700°C for 2 h in an 800 W microwave reactor to obtain a pretreated solid phase; the pretreated solid phase was mixed with a mixed solution of 1 mol / L HCl and 5% by mass H2O2 at a solid ratio of 1 g:5 mL, then placed in a 600 W microwave reactor and microwave-leached at 70°C for 2 h, and then centrifuged at 3000 rpm for 5 min for solid-liquid separation to obtain a microwave acid-leached liquid phase and a microwave acid-leached solid phase.

[0045] (2) Dissolve 50 g of trihexyl (tetradecyl) phosphine chloride and 50 g of bis (2-ethylhexyl) phosphate (B2EHP) in a mixed solution of 50 mL of water and 50 mL of ethanol, place it in a microwave reactor and react at 70 ° C for 15 min to obtain light yellow viscous ionic liquid ILs.

[0046] (3) The microwave acid extraction liquid phase and the light yellow viscous ionic liquid ILs were mixed in a volume ratio of 1:1 and placed in a microwave reactor. The reaction extraction was carried out at a power of 100 W, a speed of 300 rpm / min, and 20±2°C for 40 min. Then, the mixture was centrifuged at a speed of 3500 rpm for 5 min, and the PGMs-enriched ILs were obtained by solid-liquid separation.

[0047] (4) The PGMs-enriched ILs were sequentially stripped of Fe using 0.5 mol / L Na2SO3 solution, stripped of Pd using a mixed solution of 2 mol / L hydrochloric acid and 0.5 mol / L thiourea, stripped of Pt using 1 mol / L nitric acid solution, and stripped of the copper-zinc mixed liquid using 5 mol / L sulfuric acid solution. 5% by mass of zinc powder was added to the copper-zinc mixed liquid for replacement separation to obtain copper, zinc, and a liquid containing residual Rh.

[0048] (5) The residual Rh-containing liquid and unused ILs were placed in a reactor at a volume ratio of 1:1, and then HCl solution was added to dilute the concentration to 1 mol / L. The mixture was subjected to microwave extraction at 20±2°C, a speed of 300 rpm, and a power of 600 W for 2 h. After extraction, the mixture was centrifuged at 3500 rpm for 5 min for solid-liquid separation to obtain Rh-rich liquid ILs. The Rh-rich liquid ILs were then subjected to 1 mol / L Na2SO3 and 5 mol / L HCl to separate iron and rhodium, respectively. The final liquid was liquid ILs.

[0049] In this embodiment, the final recovery rates of platinum, palladium and rhodium are 94.58%, 90.06% and 63.71%, respectively. After stripping, the purities of platinum, palladium and rhodium are 98%, 98% and 99%, respectively. Example 4

[0050] A method for recovering platinum group metals by activating waste platinum group catalysts and ILs using zinc vapor comprises the following steps: (1) Waste PGMs catalyst (composition see Table 1) and zinc powder were mixed in a mass ratio of 2:1 and calcined at 500°C for 4 h in an 800 W microwave reactor to obtain a pretreated solid phase; the pretreated solid phase was mixed with a mixed solution of 1 mol / L HCl and 1% mass percentage H2O2 at a solid ratio of 1 g:5 mL, then placed in a 600 W microwave reactor and microwave-leached at 70°C for 2 h, and then centrifuged at 3000 rpm for 5 min for solid-liquid separation to obtain a microwave acid-leached liquid phase and a microwave acid-leached solid phase.

[0051] (2) Dissolve 50 g of trihexyl (tetradecyl) phosphine chloride and 35 g of bis (2-ethylhexyl) phosphate (B2EHP) in a mixed solution of 50 mL of water and 50 mL of ethanol, place it in a microwave reactor and react at 70 ° C for 15 min to obtain light yellow viscous ionic liquid ILs.

[0052] (3) The microwave acid extraction liquid phase and the light yellow viscous ionic liquid ILs were mixed in a volume ratio of 1:1 and placed in a microwave reactor. The reaction extraction was carried out at a power of 500 W, a speed of 300 rpm / min, and 20±2°C for 20 min. Then, the mixture was centrifuged at a speed of 3500 rpm for 5 min, and the PGMs-enriched ILs were obtained by solid-liquid separation.

[0053] (4) The PGMs-enriched ILs were sequentially stripped of Fe by 0.6 mol / L Na2SO3 solution, stripped of Pd by a mixed solution of 1 mol / L hydrochloric acid and 0.3 mol / L thiourea, stripped of Pt by 10 mol / L nitric acid solution, and stripped of the copper-zinc mixed liquid by 5 mol / L sulfuric acid solution. 1% by mass of zinc powder was added to the copper-zinc mixed liquid for replacement separation to obtain copper, zinc, and residual Rh-containing liquid.

[0054] (5) The residual Rh-containing liquid and unused ILs were placed in a reactor at a volume ratio of 1:1, and then HCl solution was added to dilute the concentration to 2 mol / L. The mixture was subjected to microwave extraction at 20±2°C, a speed of 300 rpm, and a power of 300 W for 2 h. After extraction, the mixture was centrifuged at 3500 rpm for 5 min for solid-liquid separation to obtain Rh-rich liquid ILs. The Rh-rich liquid ILs were sequentially subjected to 1 mol / L Na2SO3 and 5 mol / L HCl to strip off iron and rhodium, respectively. The final liquid was liquid ILs.

[0055] In this embodiment, the final recovery rates of platinum, palladium and rhodium are 94.86%, 92.29% and 64.94%, respectively. After stripping, the purities of platinum, palladium and rhodium are 98%, 98% and 99%, respectively.

[0056] Comparative Example 1 The method for activating waste PGM catalysts and ILs to recover PGMs using zinc vapor in this comparative example differs from that in Example 1 only in that, in step (1), the microwave reaction of waste PGMs catalysts (composition shown in Table 1) and zinc powder is replaced by conventional calcination in a muffle furnace at a temperature of 600°C for 2 h.

[0057] In this comparative example, the final recovery rates of platinum, palladium and rhodium were 76.59%, 80.72% and 45.67% respectively. After stripping, the purities of platinum, palladium and rhodium were 93%, 92% and 93% respectively.

[0058] Comparative Example 2 The method for recovering platinum group metals by zinc vapor activation of waste platinum group catalysts and ILs in this comparative example is different from that in Example 1 only in that: in step (1), the pretreated solid phase is mixed with a mixed solution of 5 mol / L HCl and 1% by mass of H2O2 at a solid ratio of 1 g:5 mL, and then leached at 50°C for 2 h, and then centrifuged at a speed of 3000 rpm for 5 min for solid-liquid separation to obtain a microwave acid leaching liquid phase and a microwave acid leaching solid phase.

[0059] In this comparative example, the final recovery rates of platinum, palladium and rhodium were 69.95%, 71.67% and 49.73% respectively. After stripping, the purities of platinum, palladium and rhodium were 83%, 86% and 65% respectively.

[0060] Comparative Example 3 The method for activating waste platinum group catalysts and ILs to recover platinum group metals using zinc vapor in this comparative example is different from that in Example 1 only in that the calcination temperature in step (1) is 800°C.

[0061] In this comparative example, the final recovery rates of platinum, palladium and rhodium were 26.38%, 48.86% and 59.76% respectively. After stripping, the purities of platinum, palladium and rhodium were 90%, 91% and 87% respectively.

[0062] Comparative Example 4 The method for activating waste platinum group catalysts and ILs to recover platinum group metals using zinc vapor in this comparative example is different from that in Example 1 only in that, in step (1), the microwave reaction temperature of the pretreated solid phase and the mixed solution of 1 mol / L HCl and 1% by mass H2O2 is 20°C.

[0063] In this comparative example, the final recovery rates of platinum, palladium and rhodium were 1.29%, 5.67% and 8.36%, respectively.

[0064] Comparative Example 5 The method for zinc vapor activation of waste PGMs catalyst and ILs recovery of PGMs described in this comparative example is different from that in Example 1 only in that the waste PGMs catalyst is not pretreated with zinc vapor activation and calcination.

[0065] In this comparative example, the final recovery rates of platinum, palladium and rhodium were 93.49%, 91.81% and 40.23% respectively. After stripping, the purities of platinum, palladium and rhodium were 98%, 98% and 98% respectively.

[0066] Comparative Example 6 The method for zinc vapor activation of platinum group waste catalysts and ILs for recovering platinum group metals described in this comparative example is different from that in Example 1 only in that in steps (3) and (5), the ionic liquids are trihexyl (tetradecyl) phosphine bromide and bis (2-ethylhexyl) phosphate.

[0067] In this comparative example, the final recovery rates of platinum, palladium and rhodium were 85.76%, 93.55% and 35.67%, respectively. After stripping, the purities of platinum, palladium and rhodium were 98%, 99% and 97%, respectively.

[0068] Comparative Example 7 The method for activating waste platinum group catalysts and ILs to recover platinum group metals using zinc vapor in this comparative example is different from that in Example 1 only in that in steps (3) and (5), the ionic liquids are trihexyl (tetradecyl) phosphine bromide and dicyanamide.

[0069] In this comparative example, the final recovery rates of platinum, palladium and rhodium were 81.37%, 73.2% and 43.13%, respectively. After stripping, the purities of platinum, palladium and rhodium were 93%, 93% and 95%, respectively.

[0070] Comparison of Examples 1-4 with Comparative Examples 1 and 2 Comparing Examples 1-4 with Comparative Examples 1 and 2, microwave roasting and microwave acid leaching enhanced the leaching process and increased the PGM leaching rate compared to conventional acid leaching or conventional roasting. During microwave leaching, only the HCl concentration was varied; lowering the HCl concentration improved the PGM leaching rate and PGM recovery. Increasing the HCl concentration significantly reduced the platinum and palladium leaching rate, resulting in lower recovery rates.

[0071] Comparing Examples 1-4 with Comparative Example 3, the zinc vapor roasting pretreatment temperature significantly impacted the PGM recovery rate. An activation temperature of 600°C was optimal, achieving the highest PGM recovery rate, reaching 94.95% for platinum, 90.36% for palladium, and 64.89% for rhodium. When the zinc vapor roasting pretreatment temperature was increased to 800°C, the overall PGM recovery rate decreased significantly. During the high-temperature (600-700°C) microwave roasting stage, the solubility of PGMs, particularly rhodium, was enhanced by the formation of intermetallic compounds between PGMs and Zn. This is attributed to the higher specific surface area and lower crystallinity of the PGMs resulting from the intermetallic alloying. However, at 800°C, the excessively high temperature reduced the specific surface area of ​​the intermetallic compounds formed compared to those at 600 / 700°C, increased crystallinity, and decreased the PGM leaching rate, ultimately resulting in a PGM recovery rate far lower than that of Examples 1-4.

[0072] According to Examples 1-4 and Comparative Example 4, microwave leaching temperature significantly affects the PGM recovery rate. Under microwave acid leaching conditions at 20°C, the PGM leaching rate is extremely low, with virtually no leaching occurring. Increasing the temperature increases the diffusion coefficient and rate constant of the leaching process. Compared to microwave acid leaching at 20°C, the leaching rate at 80°C is much higher, resulting in a significantly higher PGM recovery rate.

[0073] According to the comparison between Example 1 and Comparative Example 5, the zinc vapor activation roasting pretreatment mainly enhances the recovery rate of rhodium. When the zinc vapor activation roasting pretreatment is not performed, the recovery rate of rhodium decreases from 64.89% to 40.23%.

[0074] It can be seen from Comparative Examples 6 and 7 that, compared with trihexyl (tetradecyl) phosphine chloride and bis (2-ethylhexyl) phosphate, the ionic liquid is trihexyl (tetradecyl) phosphine bromide and bis (2-ethylhexyl) phosphate, and the ionic liquid has a high association efficiency for palladium, but a low platinum-rhodium, and a low extraction rate of platinum-rhodium, resulting in a low recovery rate of platinum-rhodium; when the ionic liquid is trihexyl (tetradecyl) phosphine bromide and bis (2-ethylhexyl) phosphate, the association efficiency of platinum, palladium and rhodium is low, and the extraction rate is also low, resulting in a low recovery rate.

[0075] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for recovering platinum group metals by zinc vapor activation of spent platinum group catalysts and ILs, characterized in that: The steps include: (1) The spent PGMs catalyst and zinc powder are mixed and ball-milled and then calcined. The calcined solid phase is further ball-milled and then added to a mixed solution of HCl and H2O2 for microwave acid leaching and centrifugation to obtain a PGMs supernatant; (2) trihexyl (tetradecyl) phosphine chloride and bis (2-ethylhexyl) phosphate were mixed and added to a solvent for microwave reaction to obtain ionic liquids ILs; (3) The PGMs supernatant in step (1) is mixed with ionic liquid ILs, and then subjected to microwave extraction and centrifugation to obtain platinum group enriched ionic liquid ILs, and then Na2SO3, HCl and thiourea, HNO3, and H2SO4 are added in sequence to strip Fe, Pd, Pt, and copper and zinc respectively; (4) Zinc powder is added to the copper-zinc mixed liquid to separate Cu, Zn and residual Rh liquid; the residual Rh liquid is extracted by microwave by mixing ionic liquid ILs and hydrochloric acid solution. After solid-liquid separation, Na2SO3 and HCl are added to the liquid phase in sequence to strip Fe and Rh, respectively.

2. The method for recovering platinum group metals by zinc vapor activation of waste platinum group catalysts and ILs according to claim 1, characterized in that: The mass ratio of the waste PGMs catalyst to the zinc powder is (2-1):1, the calcination temperature is 500-700°C, and the calcination time is 2-4h.

3. The method for recovering platinum group metals by zinc vapor activation of waste platinum group catalysts and ILs according to claim 1, characterized in that: The molar concentration of HCl in the mixed solution of HCl and H2O2 is 1-2 mol / L, and the mass percentage of H2O2 is 1-5 mol / L; the solid-liquid ratio of the calcined solid phase to the mixed solution of HCl and H2O2 is 1 g:5 ml.

4. The method for recovering platinum group metals by zinc vapor activation of waste platinum group catalysts and ILs according to claim 1, characterized in that: In the step (1), the temperature of microwave acid leaching is 70° C., the time is 1-4 h, and the power is 600 W.

5. The method for recovering platinum group metals by zinc vapor activation of waste platinum group catalysts and ILs according to claim 1, characterized in that: The mass ratio of the bis(2-ethylhexyl) phosphate to trihexyl(tetradecyl)phosphine chloride is 1:(0.7-1); and the solvent is a mixed solution of water and ethanol in a volume ratio of 1:

1.

6. The method for recovering platinum group metals by zinc vapor activation of waste platinum group catalysts and ILs according to claim 1, characterized in that: In the step (2), the temperature of the microwave reaction is 70° C., the time is 5-15 min, and the power is 500-1500 W.

7. The method for recovering platinum group metals by zinc vapor activation of waste platinum group catalysts and ILs according to claim 1, characterized in that: In the step (3), the volume ratio of the PGMs supernatant to the ionic liquid ILs is (2-1):1; the temperature of the microwave extraction is 20±2°C, the time is 20-40min, the power is 500-1000W, and the rotation speed is 300rpm.

8. The method for recovering platinum group metals by zinc vapor activation of waste platinum group catalysts and ILs according to claim 1, characterized in that: In the step (3), the concentration of Na2SO3 is 0.5-1 mol / L, the concentration of HCl is 0.5-2 mol / L, the concentration of thiourea is 0.1-0.5 mol / L, the concentration of HNO3 is 1-10 mol / L, and the concentration of H2SO4 is 1-5 mol / L.

9. The method for recovering platinum group metals by zinc vapor activation of waste platinum group catalysts and ILs according to claim 1, characterized in that: In the step (4), 1-5% by mass of zinc powder is added to the copper-zinc mixed liquid.

10. The method for recovering platinum group metals by zinc vapor activation of waste platinum group catalysts and ILs according to claim 1, characterized in that: In the step (4), the volume ratio of the residual Rh solution to the ionic liquid ILs is (2-1):1, the ionic liquid ILs and the hydrochloric acid solution are mixed to a hydrochloric acid concentration of 1-2 mol / L, the microwave extraction temperature is 20±2°C, the time is 2h, the power is 300-600W, and the rotation speed is 300rpm.

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