A method for recovering three-way catalyst by wet method

Abstract

The present invention discloses a wet-process recovery method for a three-way catalyst, belonging to the technical field of precious metal catalyst recovery. The method comprises crushing, calcining, and alkaline hydrolyzing the three-way catalyst to obtain a reduced residue, which is then dissolved and precipitated to obtain palladium and platinum. The remaining rhodium-containing insoluble residue after dissolution is subjected to high-temperature annealing and acid hydrolysis to precipitate rhodium. A dedicated precipitant is used for the precipitation of platinum, palladium, and rhodium. The method utilizes a step-by-step leaching and recovery process to recover rhodium, platinum, and palladium, respectively, thereby improving the leaching rate and recovery rate of the three metals.

Description

Technical Field

[0001] The invention belongs to the technical field of precious metal catalyst recovery, and particularly relates to a method for recovering a three-way catalyst by a wet process. Background Art

[0002] The three-way catalytic converter is the most important off-board purification device installed in automobile exhaust. It converts harmful gases such as CO, HC, and NOx into harmless carbon dioxide, water, and nitrogen through oxidation and reduction. When high-temperature automobile exhaust passes through the three-way catalytic converter, the purifier inside the converter enhances the activity of CO, HC, and NOx, prompting them to undergo specific oxidation-reduction chemical reactions. At high temperatures, CO is oxidized into colorless, non-toxic carbon dioxide; HC compounds are oxidized into water (H2O) and carbon dioxide; and NOx is reduced into nitrogen and oxygen. These three harmful gases are converted into harmless gases, purifying automobile exhaust. The carrier component of the three-way catalytic converter is a porous ceramic material coated with a layer of precious metals such as platinum, rhodium, and palladium, as well as rare earth elements, to purify exhaust gas. Similar to a muffler, the three-way catalytic converter is cylindrical in shape, constructed from a double layer of stainless steel sheets. Between these sheets lies an insulating material, asbestos fiber felt. Inside, a purifier is placed between mesh partitions. A purifier consists of a carrier and a catalyst. The carrier is typically made of aluminum oxide and can be spherical, polygonal, or have a mesh-like shape. The purifier is the catalyst, also known as the catalyst. The catalyst is made of metals like platinum, rhodium, or palladium, which are sprayed onto the carrier to form the purifier.

[0003] The methods for recovering platinum group metals from three-way catalysts can be summarized into the following treatment processes: (1) Carrier complete dissolution method: This method is used to treat early granular and columnar catalysts composed of γ-alumina. First, the catalyst is ground to 200 mesh, and then the carrier is dissolved with sulfuric acid. The insoluble residue is added with hydrochloric acid and chlorine to leach the platinum group metals. The platinum group metals in the leachate are recovered by precipitation with sulfur dioxide. The recovery rates of this method are 88-94% for platinum, 88-96% for palladium, and 84-88% for rhodium. (2) Carrier insolubility method: This method is used to recover platinum group metals from catalysts with cordierite as the carrier. It only dissolves the alumina coating containing the catalyst, while the cordierite carrier is basically not corroded. First, the catalyst is broken into one-inch pieces, and the γ-Al2O3 on the carrier surface is dissolved with dilute sulfuric acid. Then, it is washed by decantation. Three-stage decantation washing can quantitatively recover the dissolved platinum group metals. Then, sulfur dioxide is used as a reducing precipitant and Te is used as a collector. The recovery rates of this method are: 85-92% for platinum, 85-93% for palladium, and 78-85% for rhodium. (3) Plasma enrichment method: The high temperature generated by the plasma can reach over 2000°C. Alumina and cordierite are directly melted without adding flux, and the platinum group metals enter the high-silicon ferroalloy slag. After the ferrosilicon alloy is spray-granulated, sulfuric acid and air are used to dissolve impurities to produce a leaching slag containing platinum group metals; the platinum group metals are then recovered from this slag. This method has the problem of lead pollution, high power consumption, and difficulty in dissolving the alloy, resulting in a low metal recovery rate and high costs. (4) Copper smelting synergistic recovery method: During the pyrometallurgical copper smelting process, a catalyst is added to it to allow PGMS to enter the matte and crude copper. During the electrolysis of crude copper, PGMS enters the copper anode mud, and then PGMS is recovered from the copper anode mud. Therefore, the copper recovery rate in the smelting process determines the yield of PGMS. Generally speaking, the recovery rates of platinum, palladium and rhodium are relatively high, above 90%, but the production cycle is long and must be handled in cooperation with copper smelting enterprises. Summary of the Invention

[0004] In response to the above technical problems, the present invention provides a method for wet recovery of a three-way catalyst, which adopts a step-by-step leaching and recovery method to respectively recover rhodium, platinum and palladium, thereby improving the leaching rate and recovery rate of the three metals.

[0005] In order to achieve the above object, the present invention provides a method for wet recovery of a three-way catalyst, comprising the following steps:

[0006] (1) Crushing the three-way catalytic converter, calcining at 600-800℃ for 3-5h, and ball milling to obtain the material;

[0007] (2) Alkaline water is used to remove impurities and the reduction residue is retained after reduction treatment;

[0008] (3) dissolving the reduced slag in aqua regia to separate the rhodium-containing insoluble slag and solution;

[0009] (4) adding a palladium precipitant and a platinum precipitant to the solution in sequence to obtain elemental palladium and elemental platinum;

[0010] (5) The rhodium-containing insoluble slag is mixed with base metals and then annealed at high temperature, and the base metals are acidified to obtain rhodium-containing slag;

[0011] (6) After the rhodium-containing slag is dissolved in aqua regia, a rhodium precipitant is added to obtain rhodium precipitate;

[0012] (7) The rhodium precipitate is mixed with a reducing agent and reduced to obtain elemental rhodium.

[0013] Preferably, the particle size of the material in step (1) is 80-120 mesh.

[0014] Preferably, the alkaline hydrolysis in step (2) is to mix the material with alkaline solution, stir at 90-100 rpm / min, heat to 80-95° C., and then hydrolyze for 0.5-2 h.

[0015] Further preferably, the alkali solution is a sodium hydroxide solution with a mass concentration of 8-15%, and the mass ratio of the material to the alkali solution is 1:5-6.

[0016] Preferably, the reduction treatment in step (2) is to add a reducing agent to the solution after impurities are removed and boil it for 0.3-1h.

[0017] Further preferably, the reducing agent is hydrazine hydrate; the amount of the reducing agent is 25-35% of the total mass of all metals in the solution.

[0018] Preferably, the mass ratio of the reducing slag to aqua regia in step (3) is 1:7-9.

[0019] Preferably, the palladium precipitant in step (4) is dimethylglyoxime; the platinum precipitant is ammonium chloride; the amount of the palladium precipitant is such that the molar ratio of palladium in the solution is 1.1-1.3:1, and the amount of the platinum precipitant is such that the molar ratio of platinum in the solution is 1.1-1.3:1.

[0020] Preferably, the mass ratio of the rhodium-containing insoluble slag to the base metal in step (5) is 1:3.5-4, and the high-temperature annealing conditions are 800-850°C for 5-8h; the acid used in the acid removal of the base metal is a 5-8M hydrochloric acid solution.

[0021] More preferably, the base metal is any one of zinc powder, aluminum powder, magnesium powder and aluminum-zinc mixed powder.

[0022] More preferably, the particle size of the zinc powder, aluminum powder, magnesium powder and aluminum-zinc mixed powder is 200-300 mesh.

[0023] Preferably, the mass ratio of the rhodium-containing slag to aqua regia in step (6) is 1:7-9.

[0024] Preferably, the rhodium precipitant in step (6) is diethylenetriamine; and the molar ratio of the rhodium precipitant to the rhodium in the solution is 1.1-1.3:1.

[0025] Preferably, the reducing agent in step (7) is hydrazine hydrate; the molar ratio of the reducing agent to the rhodium in the rhodium precipitate is 1.1-1.3:1.

[0026] The beneficial effects of the present invention are: rhodium, platinum and palladium are recovered separately by adopting a step-by-step leaching and recovery method, thereby improving the leaching rate (laboratory leaching rate is about 100%) and recovery rate of the three metals, so that the recovery rate of palladium and platinum in the three-way catalytic converter reaches more than 98%, the recovery rate of rhodium reaches more than 95%, and the product purity reaches 99.95%, thereby improving its economic value and facilitating subsequent use.

[0027] Palladium is precipitated using dimethylglyoxime. In an acidic solution, palladium ions can form a chelate precipitate with dimethylglyoxime. This reaction is based on the fact that palladium belongs to a weakly alkaline medium. Dimethylglyoxime, as an organic precipitant, can react with palladium to form a bright yellow precipitate. Therefore, only palladium can be quantitatively precipitated without affecting other metal ions, which has good selectivity.

[0028] Diethylenetriamine is used as a precipitant for rhodium. Under specific conditions, it forms a water-insoluble complex with rhodium, effectively separating rhodium from other metals. It has the advantages of low cost, environmental friendliness, simple operation, and easy control.

[0029] The method adopted by the present invention has low equipment investment cost and production cost, short process and high yield, and can be widely used in the recovery of platinum, palladium and rhodium metals in automobile exhaust three-way catalytic converters. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION

[0031] The technical solutions of the present invention are further explained below with reference to the accompanying drawings and specific embodiments. It is worth noting that the following embodiments are only preferred embodiments of the present invention and should not be construed as limiting the present invention. The scope of protection of the present invention shall be determined by the claims. Any modifications or substitutions made to the technical solutions of the present invention by those skilled in the art without creative effort shall fall within the scope of protection of the present invention.

[0032] Example 1

[0033] (1) The automobile exhaust three-way catalytic converter was sheared and crushed, and then calcined at 700 °C for 4 h to remove organic matter and carbon, and then ball-milled to 100 mesh to obtain the material;

[0034] (2) The material was mixed with a 10% sodium hydroxide solution at a mass ratio of 1:5.5, stirred at 90 rpm / min and heated to 90 °C, and continued stirring for 1 h to complete the impurity removal;

[0035] (3) Add 100 mL of hydrazine hydrate solution (50% by mass) while stirring, so that the mass of hydrazine hydrate is 30% of the total mass of metal in the solution, heat to boiling, cook for 0.5 h, and then cool to 40 ° C. Separate the solid and liquid and retain the reduced slag;

[0036] (4) mixing the reduced slag with aqua regia in a mass ratio of 1:8, stirring and dissolving, and then adding potassium nitrate solution to drive out the nitrate. After the nitrate is driven out, solid-liquid separation is performed to obtain a palladium-platinum solution and an insoluble slag containing rhodium;

[0037] (5) directly adding dimethylglyoxime (wherein the molar ratio of palladium to dimethylglyoxime is 1:1.2) as a precipitant to the palladium-platinum solution, stirring and mixing uniformly to precipitate, and separating the solid and liquid after no new precipitate appears to obtain a palladium precipitate and a platinum solution;

[0038] (6) directly adding ammonium chloride (wherein the molar ratio of platinum to ammonium chloride is 1:1.2) as a precipitant to the platinum solution, stirring and mixing uniformly, and then precipitating. When there is no new precipitate, solid-liquid separation occurs to obtain platinum precipitate;

[0039] (7) The palladium precipitate is complexed with ammonia water to make the pH value of the solution 7.5 (complexation temperature is 65°C), and after dissolution, the solid-liquid separation is performed. Then, hydrochloric acid solution is slowly added to the filtrate to adjust the pH value of the solution to 1.5, and acidification precipitation is performed. After no new precipitate is generated, the solid-liquid separation is performed to obtain palladium precipitate; repeat three times to obtain purified sponge palladium;

[0040] (8) The platinum precipitate is mixed and dissolved with aqua regia, and then the solid and liquid are separated. Ammonium chloride is added to the filtrate as a precipitant, and the mixture is stirred and mixed evenly before precipitation. When no new precipitate appears, the solid and liquid are separated to obtain a platinum precipitate. This process is repeated three times to obtain purified sponge platinum. The molar ratio of platinum to ammonium chloride in the filtrate is 1:1.2.

[0041] (9) The rhodium-containing insoluble slag and zinc powder were mixed in a mass ratio of 1:4 and then annealed at 820°C for 6 h. The annealed product was then mixed and dissolved with a 6M hydrochloric acid solution, excess zinc powder was removed, and solid-liquid separation was performed to obtain the rhodium-containing slag;

[0042] (10) The rhodium-containing slag and aqua regia are mixed in a mass ratio of 1:8, stirred and dissolved, and then the solid and liquid are separated to obtain a rhodium-containing solution. Diethylenetriamine is added to the rhodium-containing solution as a precipitant, stirred and reacted until no new precipitate appears, and then the solid and liquid are separated. The solid product is mixed and dissolved with aqua regia again, and precipitated again. This is repeated three times to obtain a purified rhodium-containing solution. Then, a reducing agent, hydrazine hydrate solution (mass fraction of 50%), is added to the purified rhodium-containing solution, stirred and reacted, and then the solid and liquid are separated to obtain elemental rhodium, wherein the mass ratio of rhodium to diethylenetriamine in the rhodium-containing solution is 2:1, and the mass ratio of rhodium to hydrazine hydrate in the purified rhodium-containing solution is 1:2.

[0043] The yield of platinum is 99% and the purity is 99.95%; the yield of palladium is 98.5% and the purity is 99.95%; the yield of rhodium is 95% and the purity is 99.95%.

[0044] Example 2

[0045] (1) The automobile exhaust three-way catalytic converter was sheared and crushed by a machine, calcined at 600 °C for 5 h, and then ball-milled to 80 mesh as the material;

[0046] (2) The material was mixed with 8% sodium hydroxide solution at a mass ratio of 1:5, and then heated to 80°C at 100 rpm / min. After stirring for 1 hour, 50 mL of hydrazine hydrate solution (50% by mass) was added while stirring, so that the mass of hydrazine hydrate was 25% of the total mass of all metals in the solution. The temperature was raised to boiling, boiled for 1 hour, and then cooled to 40°C. The solid-liquid separation was performed to retain the reduced slag;

[0047] (3) mixing the reduced slag with aqua regia in a mass ratio of 1:7, stirring and dissolving, and then separating the solid and liquid to obtain a palladium-platinum solution and rhodium-containing insoluble slag;

[0048] (4) adding dimethylglyoxime (wherein the molar ratio of palladium to dimethylglyoxime is 1:1.1) as a precipitant to the palladium-platinum solution, stirring and mixing to uniformly carry out precipitation, and performing solid-liquid separation when no new precipitate is generated after half an hour to obtain a palladium precipitate and a platinum solution;

[0049] (5) adding ammonium chloride (wherein the molar ratio of platinum to ammonium chloride is 1:1.1) as a reducing agent to the platinum solution, stirring and mixing until uniform, and then precipitating. After half an hour, when no new precipitate is generated, solid-liquid separation is performed to obtain platinum precipitate;

[0050] (6) The palladium precipitate is mixed with ammonia water to make the pH value of the solution 7 (complexation temperature is 70 ° C), and the solid-liquid separation is carried out after dissolution. Then, hydrochloric acid solution is slowly added to the filtrate to adjust the pH value of the solution to 1.5, and acidification precipitation is carried out. After no new precipitate is generated, the solid-liquid separation is carried out to obtain palladium precipitate; repeat three times to obtain purified sponge palladium;

[0051] (7) The platinum precipitate is mixed and dissolved with aqua regia, and then the solid and liquid are separated. Ammonium chloride is added to the filtrate as a precipitant, and the mixture is stirred and mixed evenly before precipitation. When no new precipitate appears, the solid and liquid are separated to obtain a platinum precipitate. This process is repeated three times to obtain purified sponge platinum. The molar ratio of platinum to ammonium chloride in the filtrate is 1:1.2.

[0052] (8) The rhodium-containing insoluble slag and zinc powder were mixed in a mass ratio of 1:3 and annealed at 800°C for 8 hours. The annealed product was then mixed and dissolved with a 6M hydrochloric acid solution, excess zinc powder was removed, and solid-liquid separation was performed to obtain the rhodium-containing slag;

[0053] (9) The rhodium-containing slag and aqua regia are mixed in a mass ratio of 1:7, stirred and dissolved, and then the solid-liquid separation is performed to obtain a rhodium-containing solution. Diethylenetriamine is added to the rhodium-containing solution as a precipitant, stirred and reacted until no new precipitate appears, and then the solid-liquid separation is performed. The solid product is mixed and dissolved with aqua regia again, and precipitation is added again. This is repeated three times to obtain a purified rhodium-containing solution. Hydrazine hydrate solution (mass fraction of 50%) is added to the purified rhodium-containing solution as a reducing agent, stirred and reacted, and then the solid-liquid separation is performed to obtain elemental rhodium, wherein the mass ratio of rhodium to diethylenetriamine in the rhodium-containing solution is 2:1, and the mass ratio of rhodium to hydrazine hydrate in the purified rhodium-containing solution is 1:2.

[0054] The yield of platinum is 98% and the purity is 99.93%; the yield of palladium is 98% and the purity is 99.92%; the yield of rhodium is 92% and the purity is 99.9%.

[0055] Example 3

[0056] (1) The automobile exhaust three-way catalytic converter was sheared and crushed by a machine, calcined at 800 °C for 3 h, and then ball-milled to 80 mesh as the material;

[0057] (2) The material was mixed with a 15% sodium hydroxide solution at a mass ratio of 1:6, and then heated to 95°C at 100 rpm / min. After stirring for 1 hour, 200 mL of hydrazine hydrate solution (50% by mass) was added while stirring to make the mass of hydrazine hydrate 35% of the metal amount. The temperature was raised to boiling, boiled for 0.3 hours, and then cooled to 40°C. The solid-liquid separation was performed to retain the reduced slag.

[0058] (3) mixing the reduced slag with aqua regia in a mass ratio of 1:9, stirring and dissolving, and then separating the solid and liquid to obtain a palladium-platinum solution and rhodium-containing insoluble slag;

[0059] (4) adding dimethylglyoxime (wherein the molar ratio of palladium to dimethylglyoxime is 1:1.3) as a precipitant to the palladium-platinum solution, stirring and mixing to uniformly carry out precipitation, and when no new precipitate is generated after half an hour, performing solid-liquid separation to obtain palladium precipitate and platinum solution;

[0060] (5) adding ammonium chloride (wherein the molar ratio of platinum to ammonium chloride is 1:1.3) as a reducing agent to the platinum solution, stirring and mixing until uniform, and then precipitating. When no new precipitate is generated after half an hour, solid-liquid separation is performed to obtain platinum precipitate;

[0061] (6) The palladium precipitate is complexed with ammonia water to make the pH value of the solution 8 (complexation temperature is 65℃), and the solid-liquid separation is carried out after dissolution. Then, hydrochloric acid solution is slowly added to the filtrate to adjust the pH value of the solution to 1, and acidification precipitation is carried out. After no new precipitate is generated, the solid-liquid separation is carried out to obtain palladium precipitate; repeat three times to obtain purified sponge palladium.

[0062] (7) The platinum precipitate is mixed and dissolved with aqua regia, and then the solid and liquid are separated. Ammonium chloride is added to the filtrate as a precipitant, and the mixture is stirred and mixed evenly before precipitation. When no new precipitate appears, the solid and liquid are separated to obtain a platinum precipitate. This process is repeated three times to obtain purified sponge platinum. The molar ratio of platinum to ammonium chloride in the filtrate is 1:1.2.

[0063] (8) The rhodium-containing insoluble slag and aluminum powder were mixed in a mass ratio of 1:3 and annealed at 850°C for 5 h. The annealed product was then mixed and dissolved with 8M hydrochloric acid solution, excess zinc powder was removed, and solid-liquid separation was performed to obtain the rhodium-containing slag;

[0064] (9) The rhodium-containing slag and aqua regia are mixed in a mass ratio of 1:9, stirred and dissolved, and then the solid and liquid are separated to obtain a rhodium-containing solution. Diethylenetriamine is added to the rhodium-containing solution as a precipitant, stirred and reacted until no new precipitate appears, and then the solid and liquid are separated. The solid product is mixed and dissolved with aqua regia again, and precipitated again. This is repeated three times to obtain a purified rhodium-containing solution. Hydrazine hydrate solution (mass fraction of 50%) is added to the purified rhodium-containing solution as a reducing agent, stirred and reacted, and then the solid and liquid are separated to obtain elemental rhodium, wherein the mass ratio of rhodium to diethylenetriamine in the rhodium-containing solution is 2:1, and the mass ratio of rhodium to hydrazine hydrate in the purified rhodium-containing solution is 1:2.

[0065] The yield of platinum is 98.5% and the purity is 99.95%; the yield of palladium is 98.3% and the purity is 99.95%; the yield of rhodium is 94% and the purity is 99.95%.

[0066] Comparative Example 1

[0067] The method and steps are the same as those in Example 1, except that step (3) is omitted. After the impurity removal is completed, the temperature is directly raised to boiling and the solution is cooked for 0.5 h. Then, the solution is cooled to 40° C. and solid-liquid separation is performed to obtain a solid residue. After subsequent treatment, elemental platinum, elemental palladium and elemental rhodium are obtained, wherein the yield of platinum is 98.5% and the purity is 99.95%; the yield of palladium is 60% and the purity is 99.95%; and the yield of rhodium is 93% and the purity is 99.95%.

[0068] The results show that omitting the initial reduction with hydrazine hydrate solution in step (3) seriously affects the yield of palladium, reducing the yield of palladium from 98.5% to 60%, resulting in serious waste of resources.

[0069] Comparative Example 2

[0070] The method and steps are the same as those in Example 1, except that the amount of hydrazine hydrate in step (3) is changed to 250 mL. Elemental platinum, elemental palladium and elemental rhodium are recovered, wherein the yield of platinum is 98.6% and the purity is 99.95%; the yield of palladium is 80% and the purity is 99.95%; and the yield of rhodium is 93.2% and the purity is 99.95%.

[0071] Compared with Example 1, increasing the amount of hydrazine hydrate has no effect on the purity of the product, but the yields of platinum, palladium and rhodium all decrease, among which the yield of palladium decreases the most, by 18.5%, because palladium oxide is difficult to dissolve.

[0072] Comparative Example 3

[0073] The method and steps are the same as those in Example 1, except that hydrazine hydrate in step (3) is replaced by formic acid, and elemental platinum, elemental palladium and elemental rhodium are recovered. The yield of platinum is 98.8% and the purity is 99.95%; the yield of palladium is 97.5% and the purity is 99.95%; and the yield of rhodium is 90% and the purity is 99.95%.

[0074] Comparative Example 4

[0075] The method and steps are the same as those in Example 1, except that the mass ratio of the reducing slag to aqua regia in step (4) is changed to 1:5, and elemental platinum, elemental palladium and elemental rhodium are recovered. The yield of platinum is 93% and the purity is 99.93%; the yield of palladium is 90% and the purity is 99.90%; and the yield of rhodium is 89% and the purity is 99.89%.

[0076] The results show that, compared with Example 1, reducing the amount of aqua regia in step (4) has a lower impact on the recovery purity of platinum, palladium and rhodium, but the yield decreases significantly. This shows that the minimum mass ratio of reducing slag to aqua regia should be 1:7, otherwise it will affect the yield of platinum, palladium and rhodium.

[0077] Comparative Example 5

[0078] The method and steps are the same as those in Example 1, except that the mass ratio of the reducing slag to aqua regia in step (4) is changed to 1:10, and elemental platinum, elemental palladium and elemental rhodium are recovered, wherein the yield of platinum is 99% and the purity is 99.95%; the yield of palladium is 98.5% and the purity is 99.95%; and the yield of rhodium is 95% and the purity is 99.95%.

[0079] The results show that, compared with Example 1, increasing the amount of aqua regia in step (4) does not significantly change the yield and purity of platinum, palladium and rhodium. This shows that further increasing the amount of aqua regia will not further improve the recovery of platinum, palladium and rhodium. For cost considerations, the mass ratio of reducing slag to aqua regia is controlled between 1:7-9, which can achieve high purity and high yield recovery of platinum, palladium and rhodium and control economic costs.

Claims

1. A method for recovering a three-way catalyst by a wet process, characterized in that: The steps include: (1) Crushing the three-way catalytic converter, calcining at 600-800°C, and ball milling to obtain the material; (2) Alkaline water is used to remove impurities and the reduction residue is retained after reduction treatment; (3) dissolving the reduced slag in aqua regia to separate the rhodium-containing insoluble slag and solution; (4) adding a palladium precipitant and a platinum precipitant to the solution in sequence to obtain a palladium precipitate and a platinum precipitate; (5) The rhodium-containing insoluble slag is mixed with base metals and then annealed at high temperature, and the base metals are acidified to obtain rhodium-containing slag; (6) After the rhodium-containing slag is dissolved in aqua regia, a rhodium precipitant is added to obtain rhodium precipitate; (7) After rhodium precipitation and aqua regia are mixed and dissolved, a rhodium precipitant is added, and the precipitation is purified three times. A reducing agent is added to the purified rhodium-containing solution and mixed and reduced to obtain elemental rhodium; The reducing agent in step (2) is hydrazine hydrate; The palladium precipitant in step (4) is dimethylglyoxime, and the amount of the palladium precipitant is such that the molar ratio of palladium in the solution is 1.1-1.3:

1.

2. The method for wet recovery of a three-way catalyst according to claim 1, characterized in that: The particle size of the material described in step (1) is 80-120 mesh.

3. The method for wet recovery of a three-way catalyst according to claim 1, characterized in that: The alkaline hydrolysis in step (2) is to mix the material with alkaline solution, stir, heat to 80-95°C and then hydrolyze for 0.5-2h.

4. The method for wet recovery of a three-way catalyst according to claim 3, characterized in that: The alkali solution is a sodium hydroxide solution with a mass concentration of 8-15%, and the mass ratio of the material to the alkali solution is 1:5-6.

5. The method for wet recovery of a three-way catalyst according to claim 1, characterized in that: The reduction treatment in step (2) is to add a reducing agent to the solution after impurities are removed and boil it for 0.3-1h.

6. The method for wet recovery of a three-way catalyst according to claim 5, characterized in that: The amount of the reducing agent used is 25-35% of the total metal mass in the solution.

7. The method for wet recovery of a three-way catalyst according to claim 1, characterized in that: The platinum precipitant in step (4) is ammonium chloride.

8. The method for wet recovery of a three-way catalyst according to claim 1, characterized in that: The mass ratio of the rhodium-containing insoluble slag to the base metal in step (5) is 1:3.5-4, and the high-temperature annealing conditions are 800-850°C annealing for 5-8h; the base metal is any one of zinc powder, aluminum powder, magnesium powder and aluminum-zinc mixed powder.

9. The method for wet recovery of a three-way catalyst according to claim 1, characterized in that: The rhodium precipitant in step (6) is diethylenetriamine.

10. The method for wet recovery of a three-way catalyst according to claim 1, characterized in that: The reducing agent in step (7) is hydrazine hydrate.

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