Method for photocatalytic efficient recovery of platinum group metals from spent catalysts and use thereof

Abstract

This invention belongs to the field of precious metal recycling technology and provides a method for efficient photocatalytic recovery of platinum group metals from catalysts and its application. The method includes the following steps: mixing spent catalyst pulverizer and metal powder, performing mechanochemical treatment, and then adding an acid solution for reaction to obtain a modified spent catalyst; mixing the modified spent catalyst with a leaching solution to obtain a suspension, then irradiating the suspension with ultraviolet-visible light for photocatalytic reaction and filtering to obtain a platinum group metal leaching solution and leaching residue; adjusting the pH of the platinum group metal leaching solution, adding an oxidant, and then using an extractant to extract and separate transition metal chlorides to obtain a platinum group metal solution. This invention employs mechanochemical activation while simultaneously regulating the platinum group metal particles to generate a plasma resonance effect. This invention utilizes the strongly redox active species generated by the photocatalyst under light conditions, which are then converted into soluble compounds through complexation, achieving efficient leaching and recovery.

Description

Technical Field

[0001] This invention relates to the field of precious metal recycling technology, and in particular to a method for the efficient photocatalytic recovery of platinum group metals from waste catalysts and its application. Background Technology

[0002] With the rapid development of modern industry, the use of catalysts containing platinum group metals is increasing year by year. Waste catalysts contain a large amount of platinum group metals (platinum, palladium, and rhodium). However, traditional recycling methods (such as pyrometallurgy and hydrometallurgy) have problems such as high energy consumption, high pollution, and low recovery rate, making it difficult to meet the dual requirements of environmental protection and economic benefits.

[0003] Photocatalysis, as an emerging green chemistry technology, is commonly used in environmental remediation and organic synthesis, but its application in resource recycling is relatively limited. Its principle is to utilize photocatalysts to generate highly oxidizing reactive species (such as hydroxyl radicals, superoxide radicals, and chlorine radicals) under light irradiation, thereby achieving efficient oxidative dissolution of target substances. This invention modifies spent catalysts and then combines them with green leaching solutions to achieve a photocatalytic leaching recovery process for platinum group metals, aiming to provide an efficient and environmentally friendly recycling method.

[0004] Li et al. proposed using benzaldehyde as a photoinitiator to generate ·OH radicals, which in turn generate ·CN radicals from CH3CN, achieving photochemical cyanation of gold (J. Am. Chem. Soc., 2012, 134, 18286-18294). This method is the first to use photocatalytic radical oxidation for gold recovery, which is undoubtedly a very environmentally friendly approach. Bian et al. (Nat. Sustain., 2021, 14, 618-626.) developed a TiO2 / MeCN / DCM leaching system that generates ·O radicals under ultraviolet light excitation. 2- The leaching of Pt / Pd / Rh from spent automotive catalysts (SAC) was achieved using CH2Cl· radicals, with leaching rates of 100%, 90%, and 85% (24h), respectively. However, this system still has the following three limitations: (i) Limited by the band gap of TiO2 (~3.2eV), the photoresponse range only covers the ultraviolet region (λ<387nm), and the light utilization rate is less than 5%; (ii) Both TiO2 and spent catalyst are solid phases, and there is interfacial mass transfer and diffusion between solid (TiO2)-liquid (MeCN / DCM)-solid (SAC)-liquid (MeCN / DCM). The interfacial mass transfer resistance is large, which leads to sluggish reaction kinetics and requires a high dose of TiO2 (mass ratio w(TiO2) / w(SAC) = 1:1); (iii) Due to the band gap structure of TiO2, highly volatile and toxic organic solvents (MeCN+DCM) must be used, which brings the risk of volatile organic compound (VOC) emissions.

[0005] Patent CN113088689B discloses a method for the selective dissolution of precious metals via photocatalysis. It primarily uses TiO2 as a photocatalyst to photocatalytically recover precious metals such as gold and palladium in an aqueous solution of inorganic bromine or iodine salts. This method involves the oxidation of elemental precious metals and uses a solid photocatalyst; the subsequent separation of the catalyst from the residue increases operational costs. Patent CN115717198B discloses a method for leaching platinum group metals from spent catalysts using ultraviolet-visible light. This method uses an ferric oxalate complex / hydrogen peroxide-chloride salt leaching system to dissolve platinum group metals under ultraviolet-visible light conditions (average dissolution rate >90%). However, this method exogenously supplements the hydrogen peroxide hydroxide, and the introduction of ferric oxalate increases the complexity of the process. The patent with publication number CN117821760 uses organic iron acid to replace iron oxalate and persulfate to replace hydrogen peroxide and sodium chloride, which efficiently leaches Pt, Pd and Rh from waste catalysts, with a leaching rate of 95%. However, it requires the addition of a large amount of organic iron acid and persulfate, generating a large amount of secondary solid waste.

[0006] While the photocatalytic technology disclosed in the above scheme can achieve the leaching of platinum group metals, it still suffers from problems such as solvent toxicity, poor reagent recycling and noble metal selectivity, limited oxidation capacity, and weak ligand binding. Therefore, it is currently essential to find a green and efficient photocatalytic recovery method. Summary of the Invention

[0007] The purpose of this invention is to provide a method for the efficient recovery of platinum group metals from waste catalysts via photocatalysis and its application, which solves the problems of high energy consumption, high pollution and low recovery rate in existing recovery methods, and achieves efficient and green recovery of platinum group metals.

[0008] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0009] This invention provides a method for the efficient photocatalytic recovery of platinum group metals from waste catalysts, comprising the following steps:

[0010] (1) Pretreatment: The waste catalyst pulverized material and metal powder are mixed and subjected to mechanical and chemical treatment, and then an acid solution is added to react to obtain the modified waste catalyst;

[0011] (2) Photocatalytic leaching: The modified waste catalyst and the leaching solution are mixed to obtain a suspension. The suspension is then irradiated with ultraviolet-visible light to carry out a photocatalytic reaction and filtered to obtain platinum group metal leaching solution and leaching residue.

[0012] (3) Platinum group metal separation: Adjust the pH of the platinum group metal leaching solution, add an amount of oxidant, and then use an extractant to extract and separate transition metal chlorides to obtain a platinum group metal solution.

[0013] As a metal, the spent catalyst in step (1) is a catalyst containing platinum group metals supported on cordierite, SiO2 or Al2O3.

[0014] Preferably, in step (1), the mass ratio of waste catalyst pulverizer to metal powder is 100-1000:0.1-10;

[0015] In step (1), the metal powder is one or more of Mg powder, Fe powder, Cu powder, Bi powder, Al powder and Ce powder.

[0016] Preferably, the time for the mechanochemical pretreatment in step (1) is 0.5 to 6 hours.

[0017] Preferably, the acid solution in step (1) is one or more of hydrochloric acid solution, nitric acid solution and sulfuric acid solution;

[0018] The concentration of the acid solution in step (1) is 0.5–6 mol / L;

[0019] The reaction time of the acid solution in step (1) is 3 to 7 hours.

[0020] Preferably, the leaching solution in step (2) includes a transition metal chloride, a chlorine source, and a green solvent;

[0021] The transition metal chloride is one or more of FeCl3, CuCl2, NiCl2, CeCl3, CoCl2, MoCl5, WCl6, and VCl4; the chlorine source is one or more of NH4Cl, NaCl, LiCl, KCl, CaCl2, MgCl2, and seawater; and the green solvent is one or two of water or ethanol.

[0022] Preferably, the concentration of transition metal chloride in the leaching solution is 0.1–5 mol / L;

[0023] The concentration of the chlorine source in the leaching solution is 0.1 to 8 times the concentration of the transition metal chloride;

[0024] The volume ratio of water to ethanol in the green solvent is 1:1 to 1:10.

[0025] Preferably, the solid-liquid ratio of the modified waste catalyst and the leaching solution in step (2) is 1:5 to 1:200;

[0026] The photocatalytic reaction in step (2) takes 0.5 to 6 hours.

[0027] Preferably, the pH in step (3) is 0.1 to 2.

[0028] The present invention has the following beneficial effects:

[0029] The present invention has the following advantages over the prior art:

[0030] (1) The recycling method of the present invention enables the waste catalyst to be transformed into a photocatalyst through in-situ mechanochemical function, and has the ability of self-catalytic leaching;

[0031] (2) The present invention employs mechanochemical pretreatment activation and simultaneously regulates platinum group metal particles to generate a plasma resonance effect, and can itself act as an electron acceptor to promote its own oxidation leaching.

[0032] (3) The LSPR effect can enhance light absorption efficiency and promote the separation of photogenerated electron-hole pairs, thereby increasing the redox reaction activity and accelerating the dissolution of platinum group metals. Adding an acid solution after pretreatment can further remove excess metal powder and activate the carrier surface to form a porous structure, increasing the contact area with the leaching solution.

[0033] (4) The present invention uses pure water or water + ethanol as a green solvent, which avoids the use of acid and toxic and harmful organic solvents, and the operating conditions are mild and the energy consumption is low.

[0034] (5) The photocatalyst prepared by waste conversion during the photocatalytic leaching process of this invention works synergistically with the transition metal chloride to promote the separation and transfer of photogenerated electrons and holes, promote the generation of active oxidizing species, and recover platinum group metals through photocatalytic technology. This effectively avoids the traditional methods of high-temperature roasting, high-temperature acid leaching or alkali dissolution, significantly reducing energy consumption and negative impacts on the environment.

[0035] (6) This invention utilizes photocatalysts to generate highly reactive redox species (such as hydroxyl radicals, superoxide radicals, etc.) under light conditions, and converts them into soluble compounds through complexation, thereby achieving efficient leaching and recovery. This method is not only mild in operation and low in energy consumption, but also environmentally friendly and has a high recovery rate, providing an innovative and sustainable solution for the green recovery of platinum group metals. Attached Figure Description

[0036] Figure 1 The UV-Vis diffuse reflectance spectra of the waste catalyst of the present invention before and after pretreatment and photocatalytic leaching;

[0037] Figure 2 This is a band structure diagram of the modified waste catalyst of the present invention. Detailed Implementation

[0038] This invention provides a method for the efficient photocatalytic recovery of platinum group metals from waste catalysts, comprising the following steps:

[0039] (1) Pretreatment: The waste catalyst pulverized material and metal powder are mixed and subjected to mechanical and chemical treatment, and then an acid solution is added to react to obtain the modified waste catalyst;

[0040] (2) Photocatalytic leaching: The modified waste catalyst and the leaching solution are mixed to obtain a suspension. The suspension is then irradiated with ultraviolet-visible light to carry out a photocatalytic reaction and filtered to obtain platinum group metal leaching solution and leaching residue.

[0041] (3) Platinum group metal separation: Adjust the pH of the platinum group metal leachate, add an oxidant, and use an extractant to extract and separate transition metal chlorides to obtain a platinum group metal solution.

[0042] In this invention, the spent catalyst in step (1) is preferably a catalyst containing platinum group metals with cordierite, SiO2 or Al2O3 as a support.

[0043] In this invention, the mass ratio of waste catalyst pulverizer and metal powder in step (1) is preferably 100-1000:0.1-10, more preferably 100:1-10, and even more preferably 100:3-7.

[0044] In this invention, the metal powder in step (1) is preferably one or more of Mg powder, Fe powder, Cu powder, Bi powder, Al powder and Ce powder.

[0045] In this invention, the time for the mechanochemical pretreatment in step (1) is preferably 0.5 to 6 hours, more preferably 1 to 5 hours, and even more preferably 1.5 to 3 hours.

[0046] In this invention, the mechanochemical pretreatment in step (1) involves uniformly mixing the waste catalyst pulverized material and the metal powder ductile iron.

[0047] In this invention, the acid solution in step (1) is preferably one or more of hydrochloric acid solution, nitric acid solution and sulfuric acid solution.

[0048] In this invention, the concentration of the acid solution in step (1) is preferably 0.5 to 6 mol / L, more preferably 0.5 to 3 mol / L, and even more preferably 0.5 to 1.5 mol / L.

[0049] In this invention, the reaction time of the acid solution in step (1) is preferably 3 to 7 hours, more preferably 3.5 to 6.5 hours, and even more preferably 4 to 6 hours.

[0050] In this invention, after reacting with acid solution in step (1), filtration can remove excess metal. The filtered solid is then dried to obtain the modified waste catalyst.

[0051] In this invention, the leaching solution in step (2) preferably includes a transition metal chloride, a chlorine source, and a green solvent.

[0052] In this invention, the transition metal chloride is preferably one or more of FeCl3, CuCl2, NiCl2, CeCl3, CoCl2, MoCl5, WCl6 and VCl4, the chlorine source is preferably one or more of NH4Cl, NaCl, LiCl, KCl, CaCl2, MgCl2 and seawater, and the green solvent is preferably one or two of water or ethanol.

[0053] In this invention, the concentration of transition metal chloride in the leaching solution is preferably 0.1 to 5 mol / L, more preferably 0.1 to 3 mol / L, and even more preferably 0.1 to 1.5 mol / L.

[0054] In this invention, the concentration of the chlorine source in the leaching solution is preferably 0.1 to 8 times the concentration of the transition metal chloride, more preferably 1 to 7 times, and even more preferably 2 to 5 times.

[0055] In this invention, the volume ratio of water to ethanol in the green solvent is preferably 1:1 to 1:10, more preferably 1:2 to 1:8, and even more preferably 1:3 to 1:5.

[0056] In this invention, the solid-liquid ratio of the modified waste catalyst and the leaching solution in step (2) is preferably 1:5 to 1:200, more preferably 1:5 to 1:80, and even more preferably 1:5 to 1:50.

[0057] In this invention, the light source in step (2) is a xenon lamp.

[0058] In this invention, the photocatalytic reaction time in step (2) is preferably 0.5 to 6 hours, more preferably 1 to 5 hours, and even more preferably 1.3 to 3 hours.

[0059] In this invention, the pH in step (3) is preferably 0.1 to 2, more preferably 0.5 to 1.5, and even more preferably 0.7 to 1.2.

[0060] Figure 1 The UV-Vis diffuse reflectance spectra of the waste catalyst of the present invention before and after pretreatment and photocatalytic leaching are shown.

[0061] like Figure 1 As shown, the waste catalyst of the present invention, through metal-assisted mechanochemical treatment, exhibits good light absorption in the range of 200–800 nm, and thus possesses photocatalytic performance.

[0062] Figure 2 This is a band structure diagram of the modified waste catalyst of the present invention.

[0063] like Figure 2 As shown, mechanical activation reduces the particle size of platinum group metals (PGMs) and generates a strong plasmon resonance effect. Furthermore, due to the synergistic effect between transition metal chlorides and photocatalysis, the generation of oxidizing active species is effectively promoted, thus accelerating the oxidative dissolution of PGMs. The Cl- ions in the chlorine source can form water-soluble PGM complexes with PGMs, further promoting their leaching.

[0064] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0065] The waste catalyst used in this embodiment of the invention is derived from cordierite-type scrap automotive exhaust catalyst pulverized material provided by a company in Jiangxi Province. Its main components are 2MgO2·Al2O3·5SiO2, with Pd, Pt and Rh contents of 1590.0 g / T, 345.0 g / T and 157.0 g / T, respectively.

[0066] Example 1

[0067] A certain amount of spent catalyst powder was weighed and mixed with Mg powder, with a mass ratio of spent catalyst powder to metal of 100:8. The mixture was mechanically and chemically treated for 2 hours. A slightly excess of 1.0 mol / L hydrochloric acid solution was added to the treated solid, and the mixture was allowed to react completely for 5 hours. After filtration to remove excess metal, the filtered solid was dried to obtain the modified catalyst. The modified catalyst and a leaching solution (0.5 mol / L CuCl₂ + 2.5 mol / L NaCl + water + ethanol, with a water-to-ethanol volume ratio of 1:3) were mixed at a solid-liquid ratio of 1:100 to obtain a suspension. The suspension was irradiated under a xenon lamp for 3 hours for photocatalytic oxidation and then filtered to obtain a platinum group metal leaching solution and leaching residue. The pH of the platinum group metal leaching solution was adjusted to 1.0, and an appropriate amount of oxidant was added. Transition metal chlorides were extracted and separated using an extractant to obtain a platinum group metal solution. The leaching rates of the platinum group metals in the solution were determined: Pd 96%, Pt 19%, Rh 60%.

[0068] Example 2

[0069] A certain amount of spent catalyst pulverized material was weighed and mixed with Bi powder, wherein the mass ratio of spent catalyst pulverized material to metal was 100:5. The mixture was mechanically and chemically treated for 2 hours. A slightly excess of 1.0 mol / L nitric acid solution was added to the treated solid, and the mixture was allowed to react fully for 5 hours. After filtration to remove excess metal, the filtered solid was dried to obtain the modified catalyst. The modified catalyst and a leaching solution (0.1 mol / L CuCl₂ + 0.5 mol / L NaCl + water + ethanol, with a water-to-ethanol volume ratio of 1:1) were mixed at a solid-liquid ratio of 1:100 to obtain a suspension. The suspension was irradiated under a xenon lamp for 2 hours for photocatalytic oxidation and then filtered to obtain a platinum group metal leaching solution and leaching residue. The pH of the platinum group metal leaching solution was adjusted to 2, and an appropriate amount of oxidant was added. Transition metal chlorides were extracted and separated using an extractant to obtain a platinum group metal solution. The leaching rates of the platinum group metals in the platinum group metal solution were determined: Pd 93%, Pt 43%, Rh 53%.

[0070] Example 3

[0071] A certain amount of spent catalyst pulverized material was weighed and mixed with Cu powder, wherein the mass ratio of spent catalyst pulverized material to metal was 100:10. The mixture was mechanically and chemically treated for 2 hours. A slightly excess of 1.5 mol / L nitric acid solution was added to the treated solid, and the mixture was allowed to react completely for 6 hours. After filtration to remove excess metal, the filtered solid was dried to obtain the modified catalyst. The modified catalyst and a leaching solution (0.5 mol / L FeCl3 + 1 mol / L NaCl + water + ethanol, with a water-to-ethanol volume ratio of 1:2) were mixed at a solid-liquid ratio of 1:100 to obtain a suspension. The suspension was irradiated under a xenon lamp for 3 hours for photocatalytic oxidation and then filtered to obtain a platinum group metal leaching solution and leaching residue. The pH of the platinum group metal leaching solution was adjusted to 0.5, and an appropriate amount of oxidant was added. Transition metal chlorides were extracted and separated using an extractant to obtain a platinum group metal solution. The leaching rates of the platinum group metals in the platinum group metal solution were determined: Pd 96%, Pt 65%, Rh 68%.

[0072] Example 4

[0073] A certain amount of spent catalyst powder was weighed and mixed with Mg powder and Bi powder, wherein the mass ratio of spent catalyst powder to metal was 100:10. The mixture was mechanically and chemically treated for 2 hours. A slightly excess of 1.0 mol / L nitric acid solution was added to the treated solid, and the mixture was allowed to react completely for 7 hours. After filtration to remove excess metal, the filtered solid was dried to obtain the modified catalyst. The modified catalyst and a leaching solution (0.5 mol / L CuCl₂ + 1 mol / L NaCl + water + ethanol, with a water-to-ethanol volume ratio of 1:1) were mixed at a solid-liquid ratio of 1:100 to obtain a suspension. The suspension was irradiated under a xenon lamp for 2 hours for photocatalytic oxidation and then filtered to obtain a platinum group metal leaching solution and leaching residue. The pH of the platinum group metal leaching solution was adjusted to 1.0, and an appropriate amount of oxidant was added. Transition metal chlorides were extracted and separated using an extractant to obtain a platinum group metal solution. The leaching rates of the platinum group metals in the platinum group metal solution were determined: Pd 98%, Pt 78%, Rh 55%.

[0074] Example 5

[0075] A certain amount of spent catalyst pulverized material was weighed and mixed with Mg powder and Cu powder, wherein the mass ratio of spent catalyst pulverized material to metal was 100:5. The mixture was mechanically and chemically treated for 2 hours. A slightly excess of 1.0 mol / L nitric acid solution was added to the treated solid, and the mixture was allowed to react fully for 5 hours. After filtration to remove excess metal, the filtered solid was dried to obtain the modified catalyst. The modified catalyst and a leaching solution (0.1 mol / L FeCl3 + 0.5 mol / L NaCl + water + ethanol, with a water-to-ethanol volume ratio of 1:3) were mixed at a solid-liquid ratio of 1:100 to obtain a suspension. The suspension was irradiated under a xenon lamp for 3 hours for photocatalytic oxidation and then filtered to obtain a platinum group metal leaching solution and leaching residue. The pH of the platinum group metal leaching solution was adjusted to 1.5, and an appropriate amount of oxidant was added to allow the extractant to extract and separate transition metal chlorides, obtaining a platinum group metal solution. The leaching rates of platinum group metals in the platinum group metal solution were determined as follows: Pd 100%, Pt 99%, Rh 98%.

[0076] Example 6

[0077] A certain amount of spent catalyst pulverized material was weighed and mixed with Mg powder and Fe powder, wherein the mass ratio of spent catalyst pulverized material to metal was 100:10. The mixture was mechanically and chemically treated for 2 hours. A slightly excess of 1.0 mol / L nitric acid solution was added to the treated solid, and the mixture was allowed to react fully for 6 hours. After filtration to remove excess metal, the filtered solid was dried to obtain the modified catalyst. The modified catalyst and a leaching solution (0.5 mol / L CuCl2 + 2.5 mol / L CaCl2 + water + ethanol, with a water-to-ethanol volume ratio of 1:1) were mixed at a solid-liquid ratio of 1:200 to obtain a suspension. The suspension was irradiated under a xenon lamp for 3 hours for photocatalytic oxidation and then filtered to obtain a platinum group metal leaching solution and leaching residue. The pH of the platinum group metal leaching solution was adjusted to 2.0, and an appropriate amount of oxidant was added to allow the extractant to extract and separate transition metal chlorides, obtaining a platinum group metal solution. The leaching rates of platinum group metals in the platinum group metal solution were determined as follows: Pd 94%, Pt 39%, Rh 89%.

[0078] Example 7

[0079] A certain amount of spent catalyst powder was weighed and mixed with Mg powder and Cu powder, wherein the mass ratio of spent catalyst powder to metal was 100:10. The mixture was mechanically and chemically treated for 2 hours. A slightly excess of 1.0 mol / L nitric acid solution was added to the treated solid, and the mixture was allowed to react fully for 6 hours. After filtration to remove excess metal, the filtered solid was dried to obtain the modified catalyst. The modified catalyst and a leaching solution (0.5 mol / L CuCl₂ + 2.5 mol / L NaCl + water + ethanol, with a water-to-ethanol volume ratio of 1:2) were mixed at a solid-liquid ratio of 1:50 to obtain a suspension. The suspension was irradiated under a xenon lamp for 3 hours for photocatalytic oxidation and then filtered to obtain a platinum group metal leaching solution and leaching residue. The pH of the platinum group metal leaching solution was adjusted to 1.5, and an appropriate amount of oxidant was added to allow the extractant to extract and separate transition metal chlorides, obtaining a platinum group metal solution. The leaching rates of platinum group metals in the platinum group metal solution were determined as follows: Pd 100%, Pt 98%, Rh 97%.

[0080] Example 8

[0081] A certain amount of spent catalyst powder was weighed and mixed with Mg powder and Al powder, wherein the mass ratio of spent catalyst powder to metal was 100:10. The mixture was mechanically and chemically treated for 2 hours. A slightly excess of 1.5 mol / L hydrochloric acid solution was added to the treated solid, and the mixture was allowed to react completely for 5 hours. After filtration to remove excess metal, the filtered solid was dried to obtain the modified catalyst. The modified catalyst and a leaching solution (0.5 mol / L FeCl3 + 2.0 mol / L LiCl + water + ethanol, with a water-to-ethanol volume ratio of 1:2) were mixed at a solid-liquid ratio of 1:50 to obtain a suspension. The suspension was irradiated under a xenon lamp for 3 hours for photocatalytic oxidation and then filtered to obtain a platinum group metal leaching solution and leaching residue. The pH of the platinum group metal leaching solution was adjusted to 2.0, and an appropriate amount of oxidant was added to allow the extractant to extract and separate transition metal chlorides, obtaining a platinum group metal solution. Metal chlorides were separated by resin adsorption and then filtered to obtain the platinum group metal solution. The leaching rates of platinum group metals in the platinum group metal solution were determined as follows: Pd 89%, Pt 53%, Rh 65%.

[0082] Example 9

[0083] A certain amount of spent catalyst pulverized material was weighed and mixed with Mg powder and Bi powder, wherein the mass ratio of spent catalyst pulverized material to metal was 100:10. The mixture was mechanically and chemically treated for 1 hour. A slightly excess of 1.0 mol / L hydrochloric acid solution was added to the treated solid, and the mixture was allowed to react fully for 3 hours. After filtration to remove excess metal, the filtered solid was dried to obtain the modified catalyst. The modified catalyst and a leaching solution (0.5 mol / L CuCl2 + 2.5 mol / L seawater + water + ethanol, with a water-to-ethanol volume ratio of 1:2) were mixed at a solid-liquid ratio of 1:100 to obtain a suspension. The suspension was irradiated under a xenon lamp for 2 hours for photocatalytic oxidation and then filtered to obtain a platinum group metal leaching solution and leaching residue. The pH of the platinum group metal leaching solution was adjusted to 1.5, and an appropriate amount of oxidant was added to allow the extractant to extract and separate transition metal chlorides, obtaining a platinum group metal solution. The leaching rates of platinum group metals in the platinum group metal solution were determined as follows: Pd 97%, Pt 86%, Rh 95%.

[0084] Example 10

[0085] A certain amount of spent catalyst powder was weighed and mixed with Mg powder and Ce powder, wherein the mass ratio of spent catalyst powder to metal was 100:8. The mixture was mechanically and chemically treated for 1 hour. A slightly excess of 1.0 mol / L hydrochloric acid solution was added to the treated solid, and the mixture was allowed to react completely for 4 hours. After filtration to remove excess metal, the filtered solid was dried to obtain the modified catalyst. The modified catalyst and a leaching solution (1.0 mol / L CeCl3 + 2.0 mol / L seawater + water + ethanol, with a water-to-ethanol volume ratio of 1:2) were mixed at a solid-liquid ratio of 1:50 to obtain a suspension. The suspension was irradiated under a xenon lamp for 3 hours for photocatalytic oxidation and then filtered to obtain a platinum group metal leaching solution and leaching residue. The pH of the platinum group metal leaching solution was adjusted to 2.0, and an appropriate amount of oxidant was added to allow the extractant to extract and separate transition metal chlorides, obtaining a platinum group metal solution. The leaching rates of the platinum group metals in the platinum group metal solution were determined: Pd 92%, Pt 79%, Rh 63%.

[0086] Example 11

[0087] A certain amount of spent catalyst powder was weighed and mixed with Mg powder and Al powder, wherein the mass ratio of spent catalyst powder to metal was 100:5. The mixture was mechanically and chemically treated for 2 hours. A slightly excess of 1.0 mol / L nitric acid solution was added to the treated solid, and the mixture was allowed to react fully for 4 hours. After filtration to remove excess metal, the filtered solid was dried to obtain the modified catalyst. The modified catalyst and a leaching solution (0.5 mol / L CuCl2 + 2.5 mol / L MgCl2 + water + ethanol, with a water-to-ethanol volume ratio of 1:3) were mixed at a solid-liquid ratio of 1:50 to obtain a suspension. The suspension was irradiated under a xenon lamp for 3 hours for photocatalytic oxidation and then filtered to obtain a platinum group metal leaching solution and leaching residue. The pH of the platinum group metal leaching solution was adjusted to 2.0, and an appropriate amount of oxidant was added to allow the extractant to extract and separate transition metal chlorides, obtaining a platinum group metal solution. The leaching rates of the platinum group metals in the solution were determined: Pd 100%, Pt 91%, Rh 72%.

[0088] Example 12

[0089] A certain amount of spent catalyst pulverized material was weighed and mixed with Mg powder and Fe powder, wherein the mass ratio of spent catalyst pulverized material to metal was 100:8. The mixture was mechanically and chemically treated for 1 hour. A slightly excess of 1.0 mol / L hydrochloric acid solution was added to the treated solid, and the mixture was allowed to react fully for 5 hours. After filtration to remove excess metal, the filtered solid was dried to obtain the modified catalyst. The modified catalyst and leaching solution (0.5 mol / L FeCl3 + 2.0 mol / L NH4Cl + water + ethanol, with a water-to-ethanol volume ratio of 1:1) were mixed at a solid-liquid ratio of 1:50 to obtain a suspension. The suspension was irradiated under a xenon lamp for 3 hours for photocatalytic oxidation and then filtered to obtain a platinum group metal leaching solution and leaching residue. The pH of the platinum group metal leaching solution was adjusted to 2.0. The leaching rates of the platinum group metals in the solution were determined: Pd 100%, Pt 95%, Rh 82%.

[0090] Example 13

[0091] A certain amount of spent catalyst pulverized material was weighed and mechanically treated for 3 hours. A slightly excess of 1.0 mol / L hydrochloric acid solution was added to the treated solid, and the reaction was allowed to proceed for 5 hours. Afterward, the excess metal was removed by filtration, and the filtered solid was dried to obtain the modified catalyst. The modified catalyst and leaching solution (2.5 mol / L CuCl2 + water + ethanol, with a water-to-ethanol volume ratio of 1:2) were mixed at a solid-liquid ratio of 1:200 to obtain a suspension. The suspension was irradiated under a xenon lamp for 3 hours for photocatalytic oxidation and then filtered to obtain a platinum group metal leaching solution and leaching residue. The pH of the platinum group metal leaching solution was adjusted to 2.0, and an appropriate amount of oxidant was added to allow the extractant to extract and separate transition metal chlorides, obtaining a platinum group metal solution. The leaching rates of the platinum group metals in the solution were determined: Pd 50%, Pt 36%, Rh 22%.

[0092] As can be seen from the above embodiments, the present invention provides a method for efficient photocatalytic recovery of platinum group metals from a catalyst and its application, comprising the following steps: pretreatment: mixing the spent catalyst pulverized material and metal powder, performing mechanical and chemical treatment, and then adding an acid solution to react, to obtain a modified spent catalyst; photocatalytic leaching: mixing the modified spent catalyst and leaching solution to obtain a suspension, then irradiating the suspension with ultraviolet-visible light to perform a photocatalytic reaction and filtering, to obtain a platinum group metal leaching solution and leaching residue; platinum group metal separation: adjusting the pH of the platinum group metal leaching solution, adding an oxidant, and using an extractant to extract and separate transition metal chlorides to obtain a platinum group metal solution. The recycling method of this invention transforms waste catalysts into photocatalysts through in-situ mechanochemical transformation, enabling them to undergo autocatalytic leaching. This invention employs mechanochemical pretreatment activation while simultaneously regulating platinum group metal particles to induce a plasma resonance effect, allowing them to act as electron acceptors and promote their own oxidative leaching. This invention uses pure water or water + ethanol as a green solvent, avoiding the use of acids and toxic organic solvents, resulting in mild operating conditions and low energy consumption. During the photocatalytic leaching process, the photocatalyst synergistically interacts with transition metal chlorides, promoting the separation and transfer of photogenerated electrons and holes, and fostering the generation of active oxidizing species. Photocatalytic technology for recovering platinum group metals effectively avoids traditional methods such as high-temperature roasting, high-temperature acid leaching, or alkaline dissolution, significantly reducing energy consumption and negative environmental impact. This invention utilizes the strong redox active species (such as hydroxyl radicals and superoxide radicals) generated by the photocatalyst under light conditions, simultaneously converting them into soluble compounds through complexation, thereby achieving efficient leaching and recovery. This method not only features mild operating conditions and low energy consumption but also boasts environmental friendliness and high recovery rates, providing an innovative and sustainable solution for the green recovery of platinum group metals.

[0093] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for efficiently recovering platinum group metals from waste catalysts via photocatalysis, characterized in that, Includes the following steps: (1) Pretreatment: The waste catalyst pulverized material and metal powder are mixed and subjected to mechanical and chemical treatment, and then an acid solution is added to react to obtain the modified waste catalyst; (2) Photocatalytic leaching: The modified waste catalyst and the leaching solution are mixed to obtain a suspension. The suspension is then irradiated with ultraviolet-visible light to carry out a photocatalytic reaction and filtered to obtain platinum group metal leaching solution and leaching residue. (3) Platinum group metal separation: Adjust the pH of the platinum group metal leaching solution, add an amount of oxidant, and then use an extractant to extract and separate transition metal chlorides to obtain a platinum group metal solution; The leaching solution in step (2) includes transition metal chloride, chlorine source and green solvent; The transition metal chloride is one or more of FeCl3, CuCl2, NiCl2, CeCl3, CoCl2, MoCl5, WCl6, and VCl4; the chlorine source is one or more of NH4Cl, NaCl, LiCl, KCl, CaCl2, MgCl2, and seawater; and the green solvent is one or two of water or ethanol.

2. The method for efficient photocatalytic recovery of platinum group metals from waste catalysts according to claim 1, characterized in that, In step (1), the spent catalyst is a catalyst containing platinum group metals supported by cordierite, SiO2 or Al2O3.

3. The method for efficient photocatalytic recovery of platinum group metals from waste catalysts according to claim 1, characterized in that, In step (1), the mass ratio of waste catalyst pulverizer to metal powder is 100~1000:0.1~10; In step (1), the metal powder is one or more of Mg powder, Fe powder, Cu powder, Bi powder, Al powder and Ce powder.

4. The method for efficient photocatalytic recovery of platinum group metals from waste catalysts according to claim 1, characterized in that, The mechanochemical treatment in step (1) takes 0.5 to 6 hours.

5. The method for efficient photocatalytic recovery of platinum group metals from waste catalysts according to claim 1, characterized in that, In step (1), the acid solution is one or more of hydrochloric acid solution, nitric acid solution and sulfuric acid solution; The concentration of the acid solution in step (1) is 0.5~6 mol / L; The reaction time of the acid solution in step (1) is 3~7h.

6. The method for efficient photocatalytic recovery of platinum group metals from waste catalysts according to claim 1, characterized in that, The concentration of transition metal chlorides in the leaching solution is 0.1~5 mol / L; The concentration of the chlorine source in the leaching solution is 0.1 to 8 times the concentration of the transition metal chloride; The volume ratio of water to ethanol in the green solvent is 1:1 to 1:

10.

7. The method for efficient photocatalytic recovery of platinum group metals from waste catalysts according to claim 1, characterized in that, In step (2), the solid-liquid ratio of the modified waste catalyst and the leaching solution is 1:5 to 1:200; The photocatalytic reaction in step (2) takes 0.5 to 6 hours.

8. The method for efficient photocatalytic recovery of platinum group metals from waste catalysts according to claim 1, characterized in that, In step (3), the pH is 0.1~2.

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